FN Thomson Reuters Web of Science™ VR 1.0 PT J AU Smith, EJ Jokipii, JR Kota, J Lepping, RP Szabo, A AF Smith, EJ Jokipii, JR Kota, J Lepping, RP Szabo, A TI Evidence of a north-south asymmetry in the heliosphere associated with a southward displacement of the heliospheric current sheet SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmic rays; Sun : magnetic fields ID POLE-TO-POLE; MAGNETIC-FIELD; ULYSSES OBSERVATIONS; LATITUDE SCAN AB Evidence of a north-south asymmetry in the global heliosphere, first inferred from Ulysses cosmic-ray observations, is investigated using simultaneous Ulysses and Wind magnetic field observations. Such an asymmetry, presumably associated with a southward displacement of the heliospheric current sheet (HCS), is expected to produce significantly different magnitudes of the radial field component, /B-R/, in the Sun's north and south magnetic hemispheres or, alternatively, in the positive and negative magnetic sectors. Ulysses, while at high latitudes, spends time predominantly in first one and then the other hemisphere. As a consequence, measurements in the positive sector are obtained several months later than measurements made in the negative sector, making comparisons susceptible to temporal changes. To address this ambiguity, the fields in both sectors observed by the Wind spacecraft in the ecliptic were compared. A large difference in /B-R/ of approximate to 30% was observed at Wind between 1994 December and 1995 April, with /B-R/ larger in the south than in the north. Subsequent measurements show a gradual increase in the north (outward) radial component and a decrease in the south (inward) component, ending in only a small difference by 1995 June. Thus, the Wind observations are consistent with a southward displacement of the HCS of approximate to 10 degrees and with the energetic particle observations. The secular time variation, which occurred as the spacecraft transited from the south to the north hemisphere, explains why a significant north-south difference in /B-R/ was not evident in the Ulysses measurements. The current sheet configuration and various questions and implications associated with these results are also discussed. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RP Smith, EJ (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,Mail Stop 169-506, Pasadena, CA 91109 USA. NR 13 TC 48 Z9 49 U1 0 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 20 PY 2000 VL 533 IS 2 BP 1084 EP 1089 DI 10.1086/308685 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 313GA UT WOS:000086990900043 ER PT J AU Blasi, P Epstein, RI Olinto, AV AF Blasi, P Epstein, RI Olinto, AV TI Ultra-high-energy cosmic rays from young neutron star winds SO ASTROPHYSICAL JOURNAL LA English DT Article DE acceleration of particles; magnetic fields; MHD; plasmas ID PULSAR WINDS; MICROWAVE-RADIATION; SUPERNOVA-REMNANTS; CRAB-NEBULA; SPECTRUM; ACCELERATION; INSTABILITY; CUTOFF AB The long-held notion that the highest energy cosmic rays are of distant extragalactic origin is challenged by observations that events above similar to 10(20) eV do not exhibit the expected high-energy cutoff from photopion production off the cosmic microwave background. We suggest that these unexpected ultra-high-energy events are due to iron nuclei accelerated from young strongly magnetized neutron stars through relativistic MHD winds. We find that neutron stars whose initial spin periods are shorter than similar to 10 ms and whose surface magnetic fields are in the 10(12)-10(14) G range can accelerate iron cosmic rays to greater than similar to 10(20) eV. These ions can pass through the remnant of the supernova explosion that produced the neutron star without suffering significant spallation reactions or energy loss. For plausible models of the Galactic magnetic field, the trajectories of the iron ions curve sufficiently to be consistent with the observed, largely isotropic arrival directions of the highest energy events. C1 NASA, Fermilab Astrophys Grp, Fermi Natl Accelerator Lab, Batavia, IL 60510 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. Univ Chicago, Dept Astron & Astrophys, Chicago, IL 60637 USA. Univ Chicago, Enrico Fermi Inst, Chicago, IL 60637 USA. RP Blasi, P (reprint author), NASA, Fermilab Astrophys Grp, Fermi Natl Accelerator Lab, Box 500, Batavia, IL 60510 USA. RI Blasi, Pasquale/O-9345-2015 OI Blasi, Pasquale/0000-0003-2480-599X NR 47 TC 92 Z9 93 U1 0 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 20 PY 2000 VL 533 IS 2 BP L123 EP L126 DI 10.1086/312626 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 313GC UT WOS:000086991100013 ER PT J AU Greenwood, JB Williams, ID Smith, SJ Chutjian, A AF Greenwood, JB Williams, ID Smith, SJ Chutjian, A TI Measurement of charge exchange and X-ray emission cross sections for solar wind-comet interactions SO ASTROPHYSICAL JOURNAL LA English DT Article DE atomic processes; comets : general; X-rays : general ID ELECTRON-CAPTURE; IONS; COLLISIONS; H-2 AB X-ray emission from a comet was observed for the first time in 1996. One of the mechanisms believed to be contributing to this surprisingly strong emission is the interaction of highly charged solar wind ions with cometary gases. Reported herein are total absolute charge-exchange and normalized line-emission (X-ray) cross sections for collisions of high-charge state (+3 to +10) C, N, O, and Ne ions with the cometary species H(2)O and CO(2). It is found that in several cases the double charge-exchange cross sections can be large, and in the case of C(3+) they are equal to those for single charge exchange. Present results are compared to cross section values used in recent comet models. The importance of applying accurate cross sections, including double charge exchange, to obtain absolute line-emission intensities is emphasized. C1 Queens Univ Belfast, Dept Phys, Belfast BT7 1NN, Antrim, North Ireland. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Greenwood, JB (reprint author), Queens Univ Belfast, Dept Phys, Belfast BT7 1NN, Antrim, North Ireland. EM j.greenwood@qub.ac.uk; i.williams@qub.ac.uk; steven.j.smith@jpl.nasa.gov; ara.chutjian@jpl.nasa.gov RI Greenwood, Jason/L-4799-2014 NR 19 TC 66 Z9 67 U1 1 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 2000 VL 533 IS 2 BP L175 EP L178 DI 10.1086/312615 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 313GC UT WOS:000086991100026 ER PT J AU Mathur, S Green, PJ Arav, N Brotherton, M Crenshaw, M DeKool, M Elvis, M Goodrich, RW Hamann, F Hines, DC Kashyap, V Korista, K Peterson, BM Shields, JC Shlosman, I van Breugel, W Voit, M AF Mathur, S Green, PJ Arav, N Brotherton, M Crenshaw, M DeKool, M Elvis, M Goodrich, RW Hamann, F Hines, DC Kashyap, V Korista, K Peterson, BM Shields, JC Shlosman, I van Breugel, W Voit, M TI Thomson thick X-ray absorption in a broad absorption line quasar, PG 0946+301 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : active; quasars : absorption lines; quasars : individual (PG 0946+301); X-rays : galaxies ID ABUNDANCES; PHL-5200 AB We present a deep ASCA observation of a broad absorption line quasar (BALQSQ) PG 0946+301. The source was clearly detected in one of the gas imaging spectrometers, but not in any other detector. If BALQSOs have intrinsic X-ray spectra similar to normal radio-quiet quasars, our observations imply that there is Thomson thick X-ray absorption (N-H greater than or similar to 10(24) cm(-2)) toward PG 0946+301. This is the largest column density estimated so far toward a BALQSO. The absorber must be at least partially ionized and may be responsible for attenuation in the optical and UV. If the Thomson optical depth toward BALQSOs is close to 1, as inferred here, then spectroscopy in hard X-rays with large telescopes like XMM would be feasible. C1 Ohio State Univ, Columbus, OH 43220 USA. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. Univ Calif Berkeley, Berkeley, CA 94720 USA. Natl Opt Astron Observ, Tucson, AZ 85726 USA. Catholic Univ, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Australian Natl Univ, Res Sch Astron & Astrophys, Weston Creek, ACT 2611, Australia. WM Keck Observ, Kamuela, HI 96743 USA. Univ Florida, Gainesville, FL 32611 USA. Univ Arizona, Steward Observ, Tucson, AZ 85721 USA. Western Michigan Univ, Kalamazoo, MI 49008 USA. Ohio Univ, Athens, OH 45701 USA. Univ Kentucky, Lexington, KY 40506 USA. Univ Calif Lawrence Livermore Natl Lab, Livermore, CA 94550 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. RP Mathur, S (reprint author), Ohio State Univ, Columbus, OH 43220 USA. NR 22 TC 30 Z9 30 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 20 PY 2000 VL 533 IS 2 BP L79 EP L82 DI 10.1086/312617 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 313GC UT WOS:000086991100003 ER PT J AU Moriarty-Schieven, GH Powers, JA Butner, HM Wannier, PG Keene, J AF Moriarty-Schieven, GH Powers, JA Butner, HM Wannier, PG Keene, J TI L1551NE - Discovery of a binary companion SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries : general; ISM : individual (L1551NE)-; stars : formation ID STAR-FORMING REGIONS; IMAGING SURVEY; MOLECULAR OUTFLOW; MULTIPLICITY; TAURUS; OPHIUCHUS; EVOLUTION; OBJECTS; CLOUDS AB L1551NE is a very young (class 0 or I) low-mass protostar located close to the well-studied L1551 IRS 5. Here we present evidence, from 1.3 mm continuum interferometric observations at similar to 1 " resolution, for a binary companion to L1551NE. The companion, whose 1.3 mm flux density is -1/3 that of the primary component, is located 1." 43 (similar to 230 AU at 160 pc) to the southeast. The millimeter-wave emission from the primary component may have been just barely resolved, with a deconvolved size of similar to 0.'82 x 0.'70 (similar to 131 x 112 AU), The companion emission was unresolved (<100 AU), The pair is embedded within a flattened circumbinary envelope of size similar to 5.'4 x 2.'3 (similar to 860 x 370 AU). The masses of the three components (i.e., from the circumstellar material of the primary star and its companion and the envelope) are approximately 0.044, 0.014, and 0.023 M., respectively. C1 Joint Astron Ctr, Herzberg Inst Astrophys, Natl Res Council Canada, Hilo, HI 96720 USA. Univ Hawaii, Hilo, HI 96720 USA. Univ Arizona, Steward Observ, Submillimeter Telescope Observ, Tucson, AZ 85721 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. CALTECH, Pasadena, CA 91125 USA. RP Moriarty-Schieven, GH (reprint author), Joint Astron Ctr, Herzberg Inst Astrophys, Natl Res Council Canada, 660 N Aohoku Pl, Hilo, HI 96720 USA. NR 16 TC 19 Z9 19 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 20 PY 2000 VL 533 IS 2 BP L143 EP L145 DI 10.1086/312610 PN 2 PG 3 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 313GC UT WOS:000086991100018 ER PT J AU Stern, D Spinrad, H Eisenhardt, P Bunker, AJ Dawson, S Stanford, SA Elston, R AF Stern, D Spinrad, H Eisenhardt, P Bunker, AJ Dawson, S Stanford, SA Elston, R TI Discovery of a color-selected quasar at z=5.50 SO ASTROPHYSICAL JOURNAL LA English DT Article DE early universe; quasars : general; quasars : individual (RD J030117+002025) ID SPECTROSCOPIC CCD-SURVEYS; HIGH-REDSHIFT QUASARS; HUBBLE DEEP FIELD; LUMINOSITY FUNCTION; SKY SURVEY; GALAXIES; EVOLUTION; EMISSION AB We present observations of RD J030117+002025, a quasar at z = 5.50 discovered from deep, multicolor, ground-based observations covering 74 arcmin(2). This is the most distant quasar or active galaxy currently known. The object was targeted as an R-band dropout, with R-AB > 26.3 (3 sigma limit in a 3 " diameter region), I-AB = 23.8, and z(AB) = 23.4. The Kecknow-Resolution Imaging Spectrometer spectrum shows broad Ly alpha/N v lambda 1240 emission and sharp absorption decrements from the highly redshifted hydrogen forests. The fractional continuum depression due to the Ly alpha forest is D-A = 0.90. RD J030117+002025 is the least luminous high-redshift quasar known (M-B approximate to -22.7). C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Calif Berkeley, Dept Astron, Berkeley, CA 94720 USA. Inst Astron, Cambridge CB3 0HA, England. Univ Calif Davis, Dept Phys, Davis, CA 95616 USA. Univ Calif Lawrence Livermore Natl Lab, Davis, CA 95616 USA. Univ Florida, Dept Astron, Gainesville, FL 32611 USA. RP Stern, D (reprint author), CALTECH, Jet Prop Lab, Mail Stop 169-327, Pasadena, CA 91109 USA. NR 32 TC 46 Z9 46 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 20 PY 2000 VL 533 IS 2 BP L75 EP L78 DI 10.1086/312614 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 313GC UT WOS:000086991100002 ER PT J AU Kaur, I Pierson, DL AF Kaur, I Pierson, DL TI Effect of space flight on the functions of NK and LAK cells. SO FASEB JOURNAL LA English DT Meeting Abstract C1 Enterprise Advisory Serv Inc, Houston, TX 77058 USA. NASA, Lyndon B Johnson Space Ctr, Life Sci Res Labs, Houston, TX 77058 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD APR 20 PY 2000 VL 14 IS 6 SU S BP A1025 EP A1025 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 307FQ UT WOS:000086643100671 ER PT J AU Yazdani, AA Riggs, HR Tessler, A AF Yazdani, AA Riggs, HR Tessler, A TI Stress recovery and error estimation for shell structures SO INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING LA English DT Article DE stress recovery; shell structures; error estimation; finite element ID SUPERCONVERGENT PATCH RECOVERY; FINITE-ELEMENT METHOD; DERIVATIVE RECOVERY; VARIATIONAL METHOD; EQUILIBRIUM; SHEAR; REP AB The Penalized Discrete Least-Squares (PDLS) stress recovery (smoothing) technique developed for two-dimensional linear elliptic problems [1-3] is adapted here to three-dimensional shelf structures. The surfaces are restricted to those which have a 2-D parametric representation, or which can be built-up of such surfaces. The proposed strategy involves mapping the finite element results to the 2-D parametric space which describes the geometry, and smoothing is carried out in the parametric space using the PDLS-based Smoothing Element Analysis (SEA). Numerical results for two well-known shell problems are presented to illustrate the performance of SEA/PDLS for these problems. The recovered stresses are used in the Zienkiewicz-Zhu a posteriori error estimator. The estimated errors are used to demonstrate the performance of SEA-recovered stresses in automated adaptive mesh refinement of shell structures. The numerical results are encouraging. Further testing involving more complex, practical structures is necessary. Copyright (C) 2000 John Wiley & Sons, Ltd. C1 Univ Hawaii Manoa, Dept Civil Engn, Honolulu, HI 96822 USA. NASA, Langley Res Ctr, Computat Struct Branch, Hampton, VA 23681 USA. RP Riggs, HR (reprint author), Univ Hawaii Manoa, Dept Civil Engn, 2540 Dole St,Holmes Hall 383, Honolulu, HI 96822 USA. RI Tessler, Alexander/A-4729-2009 NR 42 TC 9 Z9 9 U1 0 U2 3 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX PO19 1UD, ENGLAND SN 0029-5981 J9 INT J NUMER METH ENG JI Int. J. Numer. Methods Eng. PD APR 20 PY 2000 VL 47 IS 11 BP 1825 EP 1840 PG 22 WC Engineering, Multidisciplinary; Mathematics, Interdisciplinary Applications SC Engineering; Mathematics GA 297UB UT WOS:000086100100002 ER PT J AU Yeomans, D AF Yeomans, D TI Small bodies of the solar system SO NATURE LA English DT Article ID 253-MATHILDE; FLYBY C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Yeomans, D (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 23 TC 10 Z9 11 U1 1 U2 2 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON N1 9XW, ENGLAND SN 0028-0836 J9 NATURE JI Nature PD APR 20 PY 2000 VL 404 IS 6780 BP 829 EP 832 DI 10.1038/35009193 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 306XY UT WOS:000086625000030 ER PT J AU Howe, PT Dai, HL AF Howe, PT Dai, HL TI Translational energy distribution in hot electron mediated photodesorption: a one-dimensional quantum mechanical calculation of NO/Pt(111) and SO2/Ag(111) SO SURFACE SCIENCE LA English DT Article; Proceedings Paper CT 8th International Workshop on Desorption Induced by Electronic Transitions CY SEP 27-OCT 01, 1999 CL LONG BRANCH, NEW JERSEY SP Army Res Off, Durham, Natl Sci Fdn, Ruters Lab Surface Modificat DE electron stimulated desorption (ESD); energy dissipation; nitrogen oxides; photon stimulated desorption (PSD); platinum; semi-empirical models and model calculations; silver; single crystal surfaces; sulphur dioxide ID PHOTON-STIMULATED DESORPTION; LASER-INDUCED DESORPTION; DESORBED MOLECULES; DIATOMIC-MOLECULES; WAVE-PACKET; DYNAMICS; NO; AG(111); PHOTOCHEMISTRY; SURFACES AB An one-dimensional (along the adsorbate-surface coordinate) quantum mechanical calculation within the framework of the Antoniewicz model has been performed for understanding the translational energy distribution in desorption of chemisorbed systems such as NO/Pt(111) and SO2/Ag(111). The potential energy curve of the ground state is constructed from known adsorption properties and that of the excited state is constructed by adding a Coulombic term for the image charge stabilization. For these model potentials, the one-dimensional Schrodinger equation is solved exactly using the Cooley-Numerov integrator. This enables one to follow the time evolution of the wavepacket while the excited state is allowed to decay exponentially with a mean lifetime. The translational energy distributions of the desorbed molecules are obtained by mapping out the Franck-Condon overlap of the final state wavefunction with the continuum states of the ground PES. The effects of the shape of the potential energy curves and the residence lifetime in the excited state are examined. It is found that the calculated average translational energies compare with those experimentally measured for both systems. It also appears that the translational temperature is hotter for adsorbates that are more strongly bonded to the substrates. (C) 2000 Published by Elsevier Science B.V. All rights reserved. C1 Univ Penn, Res Struct Matter Lab, Philadelphia, PA 19104 USA. RP Howe, PT (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 40 TC 13 Z9 13 U1 1 U2 4 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0039-6028 J9 SURF SCI JI Surf. Sci. PD APR 20 PY 2000 VL 451 IS 1-3 BP 12 EP 21 DI 10.1016/S0039-6028(00)00293-4 PG 10 WC Chemistry, Physical; Physics, Condensed Matter SC Chemistry; Physics GA 308ZG UT WOS:000086742300004 ER PT J AU Dodelson, S Knox, L AF Dodelson, S Knox, L TI Dark energy and the cosmic microwave background radiation SO PHYSICAL REVIEW LETTERS LA English DT Article ID GRAVITATIONAL LENS PG-1115+080; GALAXY CLUSTERS; ANISOTROPY; UNIVERSE; MODELS AB We find that current cosmic microwave background anisotropy data strongly constrain the mean spatial curvature of the Universe to be near zero, or, equivalently, the total energy density to be near critical-as predicted by inflation. This result is robust to editing of data sets, and variation of other cosmological parameters (totaling seven, including a cosmological constant). Other lines of argument indicate that the energy density of nonrelativistic matter is much less than critical. Together, these results are evidence, independent of supernovae data, for dark energy in the Universe. C1 Fermi Natl Accelerator Lab, NASA, Fermilab Astrophys Ctr, Batavia, IL 60510 USA. Univ Chicago, Dept Astron & Astrophys, Chicago, IL 60637 USA. RP Dodelson, S (reprint author), Fermi Natl Accelerator Lab, NASA, Fermilab Astrophys Ctr, Batavia, IL 60510 USA. NR 63 TC 92 Z9 92 U1 0 U2 3 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 17 PY 2000 VL 84 IS 16 BP 3523 EP 3526 DI 10.1103/PhysRevLett.84.3523 PG 4 WC Physics, Multidisciplinary SC Physics GA 304VH UT WOS:000086504500005 PM 11019136 ER PT J AU Mingo, N Makoshi, K AF Mingo, N Makoshi, K TI Calculation of the inelastic scanning tunneling image of acetylene on Cu(100) SO PHYSICAL REVIEW LETTERS LA English DT Article ID MICROSCOPY; EXCITATION; MOLECULE AB A Green function linear combination of atomic orbitals technique is used to theoretically calculate the "inelastic" scanning tunneling microscope image of a C2H2 molecule adsorbed on Cu(100) and explain previous experimental results. Our analysis of the inelastic scattering process in terms of the orbitals shows that a destructive interference occurs in the inelastic scattering by the C-H bending modes. This results in a much smaller inelastic fraction due to the bending modes as compared to the stretching ones, and explains why the former cannot be observed experimentally. C1 Himeji Inst Technol, Fac Sci, Kamigori, Hyogo 6781297, Japan. RP Mingo, N (reprint author), NASA, Ames Res Ctr, Mail Stop 27A-1, Moffett Field, CA 94035 USA. NR 16 TC 79 Z9 80 U1 0 U2 4 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 17 PY 2000 VL 84 IS 16 BP 3694 EP 3697 DI 10.1103/PhysRevLett.84.3694 PG 4 WC Physics, Multidisciplinary SC Physics GA 304VH UT WOS:000086504500048 ER PT J AU Houweling, S Dentener, F Lelieveld, J Walter, B Dlugokencky, E AF Houweling, S Dentener, F Lelieveld, J Walter, B Dlugokencky, E TI The modeling of tropospheric methane: How well can point measurements be reproduced by a global model? SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID 1,1,1-TRICHLOROETHANE METHYL CHLOROFORM; ATMOSPHERIC TRANSPORT MODEL; GROWTH-RATE; MAUNA-LOA; NORTHERN-HEMISPHERE; SULFUR-HEXAFLUORIDE; DRAMATIC DECREASE; EMISSIONS; CHEMISTRY; TRACER AB Global model simulations of tropospheric methane are presented, using state of the art representations of its terrestrial sources. Parameters critical for its tropospheric sink and transport have been evaluated using CH3CCl3 and SF6. We assess how well available methane measurements can be reproduced by the model, and how model and measurements can most efficiently be compared. Using European Centre for Medium-Range Weather Forecasts reanalyzed meteorological fields, direct comparisons between model results and flask or in situ measurements are presented, as opposed to comparing multiannual averaged seasonal cycles and trends as was done in previous studies. When comparing monthly means derived from weekly flask sampling and the model, the agreement at stations as Bermuda East and Mace Head is improved if, instead of sampling the model at each model time step, samples are taken at the same times as the measurements were taken. A method is presented to estimate the potential influence of subgrid variability using a marked tracer that is emitted in the vicinity of observational stations only. From the contribution of this tracer to the computed methane concentration at a particular station, the potential contribution of subgrid sources can be estimated. Radon 222 is used to select baseline conditions in the model to improve the comparability of model and measurements when a clean air sector is selected for sampling. Comparisons of model results and measurements, screened for local influences and artifacts of wind sector selection, indicate that the model has in particular difficulty reproducing seasonal cycles at higher latitude stations of the Northern Hemisphere. Sensitivity simulations show that the simulated annual variation at these stations is sensitive to the parameterization of wetland emissions. Also at the South China Sea, model simulations point to errors in the representation of methane sources. Marked tracer simulations indicate that this is most likely related to emissions from natural wetlands and rice paddies, in line with recent inverse modeling and up-scaling estimates. C1 Univ Utrecht, Inst Marine & Atmospher Res, NL-3584 CC Utrecht, Netherlands. Columbia Univ, NASA, Goddard Inst Space Studies, New York, NY 10025 USA. NOAA, Climate Monitoring & Diagnost Lab, Boulder, CO 80303 USA. RP Houweling, S (reprint author), Univ Utrecht, Inst Marine & Atmospher Res, Princetonplein 5, NL-3584 CC Utrecht, Netherlands. EM s.houweling@phys.uu.nl; f.j.dentener@phys.uu.nl; j.lelieveld@phys.uu.nl RI Pfister, Gabriele/A-9349-2008; Lelieveld, Johannes/A-1986-2013 NR 74 TC 53 Z9 55 U1 1 U2 12 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD APR 16 PY 2000 VL 105 IS D7 BP 8981 EP 9002 DI 10.1029/1999JD901149 PG 22 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 306FJ UT WOS:000086586400008 ER PT J AU Gettelman, A Holton, JR Douglass, AR AF Gettelman, A Holton, JR Douglass, AR TI Simulations of water vapor in the lower stratosphere and upper troposphere SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID LOWER TROPICAL STRATOSPHERE; VARYING BASIC STATE; DEHYDRATION MECHANISM; GENERAL-CIRCULATION; ANNUAL CYCLE; TRANSPORT; EXCHANGE; TEMPERATURES; TROPOPAUSE; CONVECTION AB A three-dimensional Chemical Tracer Model is used to simulate the distribution of water vapor in the upper troposphere (UT) and lower stratosphere (LS). The simulations include only the large scale advection of water vapor and the restriction that the sir be at or below saturation at all times. This simulation is used to help distinguish among those processes that control water vapor in the UT/LS. The exchange of water vapor across the tropopause is analyzed in detail. The simulation qualitatively reproduces the water vapor distribution given by satellite and radiosonde observations on both sides of the tropopause, confirming the importance of the global temperature distribution and advection in controlling the water vapor distribution. Quantitative differences with observations of water vapor are ascribed to input temperature biases. Water vapor enters the stratosphere at all longitudes in the tropics. Details of subgrid-scale dynamic and convective processes are not necessary to explain the entry of water vapor into the stratosphere, but these are found to be important for controlling the water vapor distribution in the upper troposphere. C1 NASA, Goddard Space Flight Ctr, Atmospher Chem & Dynam Branch, Greenbelt, MD 20771 USA. Univ Washington, Dept Atmospher Sci, Seattle, WA 98195 USA. RP Gettelman, A (reprint author), Natl Ctr Atmospher Res, Box 3000, Boulder, CO 80307 USA. EM andrew@ucar.edu; holton@atmos.washington.edu; douglass@persephone.gsfc.nasa.gov RI Douglass, Anne/D-4655-2012 NR 60 TC 35 Z9 37 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 16 PY 2000 VL 105 IS D7 BP 9003 EP 9023 DI 10.1029/1999JD901133 PG 21 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 306FJ UT WOS:000086586400009 ER PT J AU Feist, DG Aellig, CP Kampfer, N Solomon, PM Barrett, JW Zoonematkermani, S Hartogh, P Jarchow, C Waters, JW AF Feist, DG Aellig, CP Kampfer, N Solomon, PM Barrett, JW Zoonematkermani, S Hartogh, P Jarchow, C Waters, JW TI Validation of stratospheric ClO measurements from the Millimeter-wave Atmospheric Sounder (MAS) SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID IN-SITU MEASUREMENTS; MICROWAVE LIMB SOUNDER; CHLORINE MONOXIDE; ERROR ANALYSIS; LATITUDINAL DISTRIBUTION; RESEARCH SATELLITE; OZONE MEASUREMENTS; DIURNAL-VARIATION; ARCTIC WINTER; INSTRUMENT AB During three missions in 1992, 1993, and 1994, the Millimeter-wave Atmospheric Sounder (MAS) measured volume mixing ratio profiles of stratospheric chlorine monoxide (ClO) at 204 GHz from the space shuttle. Owing to the space shuttle orbit, measurements were restricted to tropical and midlatitudes. We compared zonal mean profiles to correlative ClO measurements by an airborne 649 GHz radiometer, a groundbased 278 GHz instrument on Mauna Kea, Hawaii, and Version 4 ClO profiles by the Microwave Limb Sounder (MLS) on the Upper Atmosphere Research Satellite (UARS). The agreement between MAS and all the other instruments was well within the combined error bars over a pressure range of 0.4-40 hPa. Further comparisons of MAS and MLS day-night difference profiles produced an agreement of typically better than 0.1 ppbv. A detailed analysis proved that this agreement was independent of the a priori information that was used for the retrieval of the different data sets. C1 Univ Bern, Inst Appl Phys, CH-3012 Bern, Switzerland. SUNY Stony Brook, Dept Earth & Space Sci, Stony Brook, NY 11794 USA. Max Planck Inst Aeron, D-37189 Katlenburg Lindau, Germany. Jet Prop Lab, Pasadena, CA 91109 USA. USN, Res Lab, Washington, DC 20375 USA. RP Feist, DG (reprint author), Univ Bern, Inst Appl Phys, Sidlerstr 5, CH-3012 Bern, Switzerland. EM dietrich.feist@mw.iap.unibe.ch; aellig.meli@bluewin.ch; niklaus.kaempfer@mw.iap.unibe.ch; philip.solomon@sunysb.edu; james.barrett@sunysb.edu; saeid.zoonematkermani@sunysb.edu; paul@chirp.mpae.gwdg.de; chris@chirp.mpae.gwdg.de; joe@mls.jpl.nasa.gov RI Feist, Dietrich/B-6489-2013 OI Feist, Dietrich/0000-0002-5890-6687 NR 41 TC 6 Z9 6 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 16 PY 2000 VL 105 IS D7 BP 9053 EP 9062 DI 10.1029/1999JD901175 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 306FJ UT WOS:000086586400012 ER PT J AU Lait, LR AF Lait, LR TI Effects of satellite scanning configurations on derived gridded fields SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID TIME-SPACE-INTERPOLATION; STRATOSPHERIC TEMPERATURE AB Various configurations of a scanning satellite instrument are simulated by sampling realistic fields of nitrous oxide. Synoptic grids are computed from the resulting simulated orbital data and compared to the original sampled data fields. Results are compared with those obtained by flying a simulated satellite over low-resolution fields and fields that are static in time. Although increasing the number of instrument scan positions does provide more information along an orbital. swath, using more than three to five scan positions does not significantly increase the accuracy of global synoptic grids using the gridding techniques described here. C1 Raytheon ITSS, Lanham, MD USA. RP Lait, LR (reprint author), NASA, Goddard Space Flight Ctr, Code 916, Greenbelt, MD 20071 USA. EM lrlait@code916.gsfc.nasa.gov NR 22 TC 3 Z9 3 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD APR 16 PY 2000 VL 105 IS D7 BP 9063 EP 9074 DI 10.1029/1999JD901078 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 306FJ UT WOS:000086586400013 ER PT J AU Nunnermacker, LJ Kleinman, LI Imre, D Daum, PH Lee, YN Lee, JH Springston, SR Newman, L Gillani, N AF Nunnermacker, LJ Kleinman, LI Imre, D Daum, PH Lee, YN Lee, JH Springston, SR Newman, L Gillani, N TI NOy lifetimes and O-3 production efficiencies in urban and power plant plumes: Analysis of field data SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID CHEMICALLY REACTIVE PLUME; 1995 SOUTHERN OXIDANTS; EASTERN-UNITED-STATES; DRY DEPOSITION; TROPOSPHERIC OZONE; RURAL OZONE; NASHVILLE; TURBULENCE; EMISSIONS; AIRCRAFT AB In an effort to describe and characterize power plant plumes in the Nashville region, emissions from a small power plant (Gallatin) and a large power plant (Paradise) were examined using data obtained on the Department of Energy G-1 airborne sampling platform. Observations made on July 3, 7, 15, 17, and 18, 1995, were compiled, and a kinetic analysis of the chemical evolution of the power plant plumes was performed. Analysis of the power plant plume data revealed a very active photochemistry, as had been determined previously for the urban plume. Ozone production efficiencies (OPE), defined as the number of molecules of O-3 formed per NOx molecule consumed, were found to be 3 for Gallatin and 2 for Paradise. Lifetimes for NOx (2.8 and 4.2 hours) and NOy (7.0 and 7.7 hours) were determined for Gallatin and Paradise, respectively. These NOx and NOy lifetimes imply rapid loss of NOz (NOz is assumed to be primarily HNO3). Lifetimes for NOz are calculated to be 3 and 2.5 hours for Gallatin and Paradise, respectively. A sensitivity analysis indicates that the Gallatin NOz lifetime could be as long as 5 hours, bringing it into agreement with the value determined for the Nashville urban plume. It is unlikely that the Paradise NOz lifetime is as long as 4 hours. If NOz loss is attributed to dry deposition, a 3 hour lifetime implies a deposition velocity greater than 10 cm s(-1), which is much faster than expected based on accepted theory. Possible reasons for this discrepancy are discussed. C1 Brookhaven Natl Lab, Dept Appl Sci, Environm Chem Div, Upton, NY 11973 USA. Univ Alabama, NASA, UAH Global Hydrol & Climate Ctr, Earth Syst Sci Lab, Huntsville, AL 35806 USA. RP Nunnermacker, LJ (reprint author), Brookhaven Natl Lab, Dept Appl Sci, Environm Chem Div, Upton, NY 11973 USA. EM lindan@bnl.gov NR 36 TC 31 Z9 33 U1 2 U2 13 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 APR 16 PY 2000 VL 105 IS D7 BP 9165 EP 9176 DI 10.1029/1999JD900753 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 306FJ UT WOS:000086586400021 ER PT J AU Detwiler, AG Johnson, LR Schauer, AG AF Detwiler, AG Johnson, LR Schauer, AG TI Exploratory analysis of the distribution of condensation nuclei in the Northern Hemisphere upper troposphere and lower stratosphere during the late 1970s SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID AIRCRAFT TURBINE-ENGINES; AEROSOL MEASUREMENTS; AIRBORNE OBSERVATIONS; CHEMICAL-COMPOSITION; EMISSION INDEXES; CARBON-MONOXIDE; EXHAUST; OZONE; SUCCESS; CRUISE AB Data obtained from the Global Atmospheric Sampling Program (GASP) during the late 1970s are used to evaluate the hypothesis that particulate emissions by aircraft are a significant source for the upper tropospheric/lower stratospheric fine and ultrafine aerosol. Measurements of condensation nuclei (CN) were acquired above 6 km mean sea level as part of GASP from October 1977 through June 1979, using automated packages on up to four commercial airliners simultaneously flying their normal daily routes. These routes spanned much of the midlatitude Northern Hemisphere, with the notable exceptions of the former Soviet Union and China. The GASP measurements are analyzed to determine the vertical, geographical, and seasonal distribution of upper tropospheric/lower stratospheric CN in clear air, spanning an altitude range from several kilometers above to several kilometers below the tropopause. The general lack of vertical gradients in median CN mixing ratio at altitudes in the troposphere suggests that CN in the clear troposphere are generally well mixed. CN mixing ratios decrease with distance above the tropopause, consistent with a tropospheric source for stratospheric CN. Median CN mixing ratios for selected regions were compared to the Northern Hemisphere median, by altitude and season. Regional median CN mixing ratios can differ from the hemispheric median by more than a factor of 2 but never an order of magnitude. The lack of vertical variation of CN concentrations in the troposphere is not at all consistent with the vertical variation of fuel consumed by aircraft, which peaks at altitudes near the tropopause. The observations of CN show some regional medians exceeding Northern Hemisphere medians in some seasons and not others, but the regions with the highest medians are not always those with the highest aircraft fuel consumption. We conclude that aircraft emissions are not a major component of the global clear air background CN measured during GASP. C1 S Dakota Sch Mines & Technol, Inst Atmospher Sci, Rapid City, SD 57701 USA. NASA, Wallops Flight Facil, Sci & Engn Serv Inc, Wallops Isl, VA 23336 USA. RP Detwiler, AG (reprint author), S Dakota Sch Mines & Technol, Inst Atmospher Sci, Rapid City, SD 57701 USA. EM andy@ias.sdsmt.edu NR 60 TC 2 Z9 2 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 16 PY 2000 VL 105 IS D7 BP 9265 EP 9282 DI 10.1029/2000JD900022 PG 18 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 306FJ UT WOS:000086586400029 ER PT J AU Wang, PH Kent, GS Powell, FA Yue, GK Poole, LR McCormick, MP AF Wang, PH Kent, GS Powell, FA Yue, GK Poole, LR McCormick, MP TI Properties of the 1979 SAM II Antarctic 1.0-mu m extinction coefficients: Implications of dehydration and seasonal evolution of the Antarctic polar vortex SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID STRATOSPHERIC AEROSOL; CORRELATIVE MEASUREMENTS; VOLCANIC AEROSOL; SATELLITE; SAGE; CLOUD; MODEL; DUSTSONDES; PARTICLES; GROWTH AB The present study investigates the 1.0-mu m extinction coefficient measurements obtained in the Antarctic region in 1979 from the Stratospheric Aerosol Measurement (SAM) II, with particular focus on the background aerosol properties. Correlative meteorological information from the National Centers for Environmental Prediction is incorporated in this investigation. The results indicate that the data frequency distribution of the background aerosol extinction coefficient in the local summer and fall can be adequately modeled by using a single-mode normal distribution, and that a binormal distribution is needed for modeling the distribution in the local winter and spring because of the different characteristics of the aerosols inside and outside the polar vortex. In general, the vertical distribution of the aerosol mean extinction coefficient exhibits two regions of different seasonal variation. Above 16 km the extinction coefficient is the highest during the local summer, and the lowest during the local, spring inside the polar vortex. Below 16 km the aerosol seasonal variation is more complex, but the winter enhancement of die aerosol extinction coefficient inside the Antarctic polar vortex is clearly evident. As the season changes from winter to spring, the results inside the Antarctic polar vortex also indicate a reduction in aerosol optical depth in the stratosphere, but no significant changes in the upper troposphere. The present study further indicates that the bottom of the winter polar vortex in Antarctica is located at an altitude as low as 8 to 9 km, which is about 4 to 5 km lower than the bottom of the Arctic polar vortex. This difference may be attributable to the different strengths of the winter polar vortex and the planetary wave activities between the two hemispheres. In summary, the properties of the Antarctic background aerosol are very consistent with the effect of polar stratospheric clouds on the aerosol vertical distribution through their formation, sedimention, and evaporation, and with the seasonal evolution of the polar vortex. Finally, the result of the present study provides valuable opportunities for fully utilizing the multiyear SAM II tropospheric and si stratospheric measurements to investigate the aerosol climatology and long-term variations in the Arctic and Antarctic regions. C1 Sci & Technol Corp, Hampton, VA 23666 USA. Hampton Univ, Ctr Atmospher Sci, Hampton, VA 23668 USA. NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. NASA, Langley Res Ctr, Sci Applicat Int Corp, Hampton, VA 23681 USA. RP Wang, PH (reprint author), Sci & Technol Corp, 10 Basil Sawyer Dr, Hampton, VA 23666 USA. EM p.wang@larc.nasa.gov NR 39 TC 2 Z9 2 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 16 PY 2000 VL 105 IS D7 BP 9407 EP 9420 DI 10.1029/1999JD901123 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 306FJ UT WOS:000086586400039 ER PT J AU Lohmann, U Tselioudis, G Tyler, C AF Lohmann, U Tselioudis, G Tyler, C TI Why is the cloud albedo-particle size relationship different in optically thick and optically thin clouds? SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB Recent studies have analyzed satellite data in terms of the relationship of cloud albedo with droplet size for warm clouds. It was found that for optically thick marine clouds (tau >15) the cloud albedo increases with decreasing cloud droplet effective radius (r(e)). For optically thinner marine clouds (tau < 15) cloud albedo increases with increasing r(e) as to be expected if the liquid water content is adiabatic. Hypotheses for the change in sign in the tau - r(e) relationship are deviations from an adiabatic liquid water content or the presence of single layer versus multi layer clouds. In this study, the ECHAM model, which exhibits this sign change in the tau- r(e) correlation for optically thin and thick marine clouds, is used to test these hypotheses. Probability density functions of tau - r(e) show that the change in sign of the correlation can be attributed to precipitating versus non-precipitating clouds, but not to the difference in single layer versus multi-layer clouds. C1 Dalhousie Univ, Dept Phys, Atmospher Sci Program, Halifax, NS B3H 3J5, Canada. Columbia Univ, NASA, GISS, New York, NY 10025 USA. RP Lohmann, U (reprint author), Dalhousie Univ, Dept Phys, Atmospher Sci Program, Halifax, NS B3H 3J5, Canada. RI Lohmann, Ulrike/B-6153-2009 OI Lohmann, Ulrike/0000-0001-8885-3785 NR 13 TC 17 Z9 17 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD APR 15 PY 2000 VL 27 IS 8 BP 1099 EP 1102 DI 10.1029/1999GL011098 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 305HW UT WOS:000086534700005 ER PT J AU Tabazadeh, A Martin, ST Lin, JS AF Tabazadeh, A Martin, ST Lin, JS TI The effect of particle size and nitric acid uptake on the homogeneous freezing of aqueous sulfuric acid particles SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID CIRRUS CLOUD FORMATION; UPPER TROPOSPHERE; NUCLEATION; ICE; AEROSOLS; MODEL; HNO3; TEMPERATURES; STRATOSPHERE; SIMULATIONS AB Recent laboratory data on ice freezing from aqueous H2SO4 solutions are used to update our homogeneous ice freezing nucleation algorithm. The effect of particle size on the ice freezing process is demonstrated by calculating and comparing ice freezing curves for different size particles ranging from 0.2 to 4 micron in radius. Using the ice nucleation model we show that liquid water saturation is required above -44 degrees C to activate submicron H2SO4 particles into cloud droplets. A thermodynamic model is used to show that the available laboratory data on ice freezing from ternary H2SO4/HNO3/H2O solutions are insufficient to adequately address the effect of HNO3 uptake on the homogeneous freezing of aqueous H2SO4 particles into ice. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ N Carolina, Dept Environm Sci & Engn, Chapel Hill, NC 27599 USA. Bay Area Environm Res Inst, San Francisco, CA USA. RP Tabazadeh, A (reprint author), NASA, Ames Res Ctr, MS 245-4, Moffett Field, CA 94035 USA. RI Martin, Scot/G-1094-2015 OI Martin, Scot/0000-0002-8996-7554 NR 25 TC 42 Z9 42 U1 0 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD APR 15 PY 2000 VL 27 IS 8 BP 1111 EP 1114 DI 10.1029/1999GL010966 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 305HW UT WOS:000086534700008 ER PT J AU Orsolini, YJ Grant, WB AF Orsolini, YJ Grant, WB TI Seasonal formation of nitrous oxide laminae in the mid and low latitude stratosphere SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID CIRCULATION; EVOLUTION; DYNAMICS; AEROSOL; VORTEX AB The seasonal and global distributions of laminae in nitrous oxide (N2O), a long-lived tropospheric source gas, are examined in a multi-year, three-dimensional model simulation. The frequency of laminae occurrences is described as a function of geographical location and season. Enhanced laminae occurrence is found in the midlatitude surf zones of both hemispheres, but there are zonal asymmetries, especially in the northern hemisphere. In boreal winter and spring, laminae intruding from mid-latitudes into the deep tropics are found across the Pacific Ocean, on the southern flank of the Aleutian High. A "quiet zone", free of laminae, lies on the summer side of the equator, and separates the winter from the summer stratosphere. It coincides in latitude with the location of the N2O low-latitude maximum. High laminae occurrences are again found in the extratropics of the summer hemisphere. C1 Norwegian Inst Air Res, N-2027 Kjeller, Norway. NASA, Langley Res Ctr, Hampton, VA 23665 USA. RP Orsolini, YJ (reprint author), Norwegian Inst Air Res, POB 100, N-2027 Kjeller, Norway. RI Grant, William/B-8311-2009 OI Grant, William/0000-0002-1439-3285 NR 16 TC 16 Z9 16 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD APR 15 PY 2000 VL 27 IS 8 BP 1119 EP 1122 DI 10.1029/1999GL011172 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 305HW UT WOS:000086534700010 ER PT J AU Taalas, P Kaurola, J Kylling, A Shindell, D Sausen, R Dameris, M Grewe, V Herman, J AF Taalas, P Kaurola, J Kylling, A Shindell, D Sausen, R Dameris, M Grewe, V Herman, J TI The impact of greenhouse gases and halogenated species on future solar UV radiation doses SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID OZONE DEPLETION; CLIMATE; HOLE AB The future development of stratospheric ozone layer depends on the concentration of chlorine and bromine containing species. The stratosphere is also expected to be affected by future enhanced concentrations of greenhouse gases. These result in a cooling of the winter polar stratosphere and to more stable polar vortices which leads to enhanced chemical depletion and reduced transport of ozone into high latitudes. One of the driving forces behind the interest in stratospheric ozone is the impact of ozone on solar UV-B radiation. In this study UV scenarios have been constructed based on ozone predictions from the chemistry-climate model runs carried out by GISS, UKMO and DLR. Since cloudiness, albedo and terrain height are also important factors, climatological values of these quantities are taken into account in the UV calculations. Relative to 1979-92 conditions, for the 2010-2020 time period the GISS model results indicate a springtime enhancement of erythemal UV doses of up to 90% in the 60-90 degrees N region and an enhancement of 100% in the 60-90 degrees S region. The corresponding maximum increases in the annual Northern Hemispheric UV doses are estimated to be 14 % in 2010-20, and 2 % in 2040-50. In the Southern Hemisphere 40 % enhancement is expected during 2010-20 and 27 % duping 2040-50. C1 Finnish Meteorol Inst, Helsinki 00101, Finland. Norwegian Inst Air Res, N-2007 Kjeller, Norway. Columbia Univ, NASA, GISS, New York, NY 10025 USA. DLR, Inst Phys, Oberpfaffenhofen, Germany. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Taalas, P (reprint author), Finnish Meteorol Inst, POB 503, Helsinki 00101, Finland. RI Shindell, Drew/D-4636-2012; Grewe, Volker/A-6147-2011; Kylling, Arve/B-1137-2017; OI Grewe, Volker/0000-0002-8012-6783; Kylling, Arve/0000-0003-1584-5033; Herman, Jay/0000-0002-9146-1632 NR 13 TC 95 Z9 108 U1 0 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD APR 15 PY 2000 VL 27 IS 8 BP 1127 EP 1130 DI 10.1029/1999GL010886 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 305HW UT WOS:000086534700012 ER PT J AU Miller, JR Russell, GL AF Miller, JR Russell, GL TI Projected impact of climate change on the freshwater and salt budgets of the Arctic Ocean by a global climate model SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID WATER AB The annual flux of freshwater into the Arctic Ocean by the atmosphere and rivers is balanced by the export of sea ice and oceanic freshwater. Two 150-year simulations of a global climate model are used to examine how this balance might change if atmospheric greenhouse gases (GHGs) increase Relative to the control, the last 50-year period of the GHG experiment indicates that the total inflow of water from the atmosphere and rivers increases by 10% primarily due to an increase in river discharge, the annual sea-ice export decreases by about half, the oceanic liquid water export increases,salinity decreases, sea-ice cover decreases, and the total mass and sea-surface height of the Arctic Ocean increase. The closed, compact, and multi-phased nature of the hydrologic cycle in the Arctic Ocean makes it an ideal test of water budgets that could be included in model intercomparisons. C1 Rutgers State Univ, Cook Coll, Dept Marine & Coastal Sci, New Brunswick, NJ 08901 USA. NASA, Goddard Space Flight Ctr, Inst Space Studies, New York, NY 10025 USA. RP Miller, JR (reprint author), Rutgers State Univ, Cook Coll, Dept Marine & Coastal Sci, 71 Dudley Rd, New Brunswick, NJ 08901 USA. NR 12 TC 35 Z9 35 U1 1 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD APR 15 PY 2000 VL 27 IS 8 BP 1183 EP 1186 DI 10.1029/1999GL007001 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 305HW UT WOS:000086534700026 ER PT J AU Chang, CWJ Chao, Y AF Chang, CWJ Chao, Y TI A comparison between the World Ocean Atlas and Hydrobase Climatology SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB The gridded 1/4 degrees World Ocean Atlas (WOA, Boyer and Levitus, 1998) is compared with the 1 degrees WOA (Levitus et al., 1994) over the North Atlantic Ocean. The temperature and salinity fields from both the 1/4 degrees and 1 degrees WOA are projected on two isopycnal surfaces and compared with the Hydrobase climatology (Lozier et al., 1995). Geostrophic current maps diagnosed from hydrographic temperature and salinity are also presented. Results show that the 1/4 degrees WOA, with a smaller smoothing radius, greatly improves the 1 degrees WOA in several important aspects. In particular, sharp frontal features associated with the western boundary current which are absent in the 1 degrees WOA are apparent in the 1/4 degrees WOA. The 1/4 degrees WOA describes similar small-scale mid-depth recirculation gyres reported by Lozier (1997) based on Hydrobase. However, "artifacts" in the property fields created by the isobaric averaging are still evident in the 1/4 degrees WOA. C1 Univ Calif Los Angeles, Dept Atmospher Sci, Los Angeles, CA 90095 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Chang, CWJ (reprint author), Univ Calif Los Angeles, Dept Atmospher Sci, 405 Hilgard Ave, Los Angeles, CA 90095 USA. NR 13 TC 4 Z9 4 U1 1 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD APR 15 PY 2000 VL 27 IS 8 BP 1191 EP 1194 DI 10.1029/1999GL002379 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 305HW UT WOS:000086534700028 ER PT J AU Saatchi, SS Nelson, B Podest, E Holt, J AF Saatchi, SS Nelson, B Podest, E Holt, J TI Mapping land cover types in the Amazon Basin using 1 km JERS-1 mosaic SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article ID SYNTHETIC-APERTURE RADAR; SATELLITE DATA; TROPICAL DEFORESTATION; SPATIAL-RESOLUTION; FOREST BIOMASS; SAR IMAGES; CLASSIFICATION; VEGETATION; BRAZIL; CLASSIFIERS AB During the Global Rain Forest Mapping (GRFM) project, the JERS-1 SAR (Synthetic Aperture Radar) satellite acquired wall-to-wall image coverage of the humid tropical forests of the world. The rationale for the project was to demonstrate the application of spaceborne L-band radar in tropical forest studies. In particular, the use of orbital radar data for mapping land cover types, estimating the area of floodplains, and monitoring deforestation and forest regeneration were of primary importance. In this paper we examine the information content of the JERS-1 SAR data for mapping land cover types in the Amazon basin. More than 1500 high-resolution (12.5 m pixel spacing) images acquired during the low flood period of the Amazon river were resampled to 100 m resolution and mosaicked into a seamless image of about 8 million km(2), including the entire Amazon basin. This image was used in a classifier to generate a 1 km resolution land cover map. The inputs to the classifier were 1 km resolution mean backscatter and seven first-order texture measures derived from the 100 m data by using a 10 x 10 independent sampling window. The classification approach included two interdependent stages. First, a supervised maximum a posteriori Baysian approach classified the mean backscatter image into five general cover categories: terra firme forest (including secondary forest), savanna, inundated vegetation, open deforested areas and open water. A hierarchical decision rule based on texture measures was then applied to attempt further discrimination of known subcategories of vegetation types based on taxonomic information and woody biomass levels. True distributions of the general categories were identified from the RADAMBRASIL project vegetation maps and several field studies. Training and validation test sites were chosen from the JERS-1 image by consulting the RADAM vegetation maps. After several iterations and combining land cover types, 14 vegetation classes were successfully separated at the 1 km scale. The accuracy of the classification methodology was estimated to be 78% when using the validation sites. The results were also verified by comparison with the RADAM- and AVHRR-based 1 km resolution land cover maps. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Inst Nacl Pesquisas Amazonia, BR-69011970 Manaus, Amazonas, Brazil. RP Saatchi, SS (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 43 TC 57 Z9 59 U1 1 U2 17 PU TAYLOR & FRANCIS LTD PI LONDON PA 11 NEW FETTER LANE, LONDON EC4P 4EE, ENGLAND SN 0143-1161 J9 INT J REMOTE SENS JI Int. J. Remote Sens. PD APR 15 PY 2000 VL 21 IS 6-7 BP 1201 EP 1234 DI 10.1080/014311600210146 PG 34 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA 302GQ UT WOS:000086357700007 ER PT J AU El Saleous, NZ Vermote, EF Justice, CO Townshend, JRG Tucker, CJ Goward, SN AF El Saleous, NZ Vermote, EF Justice, CO Townshend, JRG Tucker, CJ Goward, SN TI Improvements in the global biospheric record from the Advanced Very High Resolution Radiometer (AVHRR) SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article ID LAND DATA SET; NDVI DATA SET; ABSOLUTE CALIBRATION; INFRARED CHANNELS; SATELLITE; SCIENCE; MODIS; ALGORITHMS; PARAMETERS; CLIMATE AB Results are provided of a project to derive improved products from the National Oceanic and Atmospheric Administration (NOAA) Advanced Very High Resolution Radiometer (AVHRR) data record for land investigations. As part of this project, a prototype AVHRR processing system has been developed. This paper describes the different components of this system, which include radiometric in-flight vicarious calibration for the visible and near infrared channels, geometric correction and atmospheric correction as pre-processing steps. The processed data are then stored in a new intermediate data format, which enables flexible compositing approaches. The system generates surface reflectance and vegetation index products as well as new higher order products of reflectance at 3.75 mu m and active fires. A comparison of a significant sample of data with widely used precursor AVHRR products is presented to evaluate the processing chain and the improvements it provides. C1 Univ Maryland, Dept Geog, Lab Global Remote Sensing Syst, College Pk, MD 20942 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Virginia, Dept Environm Sci, Charlottesville, VA 22903 USA. Univ Maryland, Inst Adv Comp Studies, College Pk, MD 20742 USA. RP El Saleous, NZ (reprint author), Univ Maryland, Dept Geog, Lab Global Remote Sensing Syst, College Pk, MD 20942 USA. RI Vermote, Eric/K-3733-2012 NR 56 TC 46 Z9 46 U1 0 U2 4 PU TAYLOR & FRANCIS LTD PI LONDON PA 11 NEW FETTER LANE, LONDON EC4P 4EE, ENGLAND SN 0143-1161 J9 INT J REMOTE SENS JI Int. J. Remote Sens. PD APR 15 PY 2000 VL 21 IS 6-7 BP 1251 EP 1277 PG 27 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA 302GQ UT WOS:000086357700009 ER PT J AU Rosenqvist, A Shimada, M Chapman, B Freeman, A De Grandi, G Saatchi, S Rauste, Y AF Rosenqvist, A Shimada, M Chapman, B Freeman, A De Grandi, G Saatchi, S Rauste, Y TI The Global Rain Forest Mapping project - a review SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article AB The Global Rain Forest Mapping (GRFM) project is an international endeavour led by the National Space Development Agency of Japan (NASDA), with the aim of producing spatially and temporally contiguous Synthetic Aperture Radar (SAR) data sets over the tropical belt on the Earth by use of the JERS-1 L-band SAR, through the generation of semi-continental, 100 m resolution, image mosaics. The GRFM project relies on extensive collaboration with the National Aeronautics and Space Administration (NASA), the Joint Research Centre of the European Commission (JRC) and the Japanese Ministry of International Trade and Industry (MITI) for data acquisition, processing, validation and product generation. A science programme is underway in parallel with product generation. This involves the agencies mentioned above, as well as a large number of international organizations, universities and individuals to perform field activities and data analysis at different levels. The GRFM project was initiated in 1995 and, through a dedicated data acquisition policy by NASDA, data acquisitions could be completed within a 1.5-year period, resulting in a spatially and temporally homogeneous coverage to encompass the entire Amazon Basin from the Atlantic to the Pacific; Central America up to the Yucatan Peninsular in Mexico; equatorial Africa from Madagascar and Kenya in the east to Sierra Leone in the west; and south-east Asia, including Papua New Guinea and northern Australia. Over the Amazon and Congo river basins, the project aimed to provide complete cover at two different seasons, featuring the basins at high and low water. In total, the GRFM acquisitions comprise some 13 000 SAR scenes, which are currently in the course of being processed and compiled into image mosaics. In March 1999, SAR mosaics over the Amazon Basin tone out of two seasonal coverages) and equatorial Africa (both seasonal coverages) were completed; the data are available on CD-ROM and, at a coarser resolution, via the Internet. Coverage of the second-season Amazon and Central America will be completed during 1999, with the south-east Asian data sets following thereafter. All data are being provided free of charge to the international science community for research and educational purposes. C1 Commiss European Communities, Joint Res Ctr, Space Applicat Inst, Global Vegetat Monitoring Unit, I-21020 Ispra, VA, Italy. Natl Space Dev Agcy Japan, Earth Observat Res Ctr, Minato Ku, Tokyo 106, Japan. CALTECH, Jet Prop Lab, Radar Sci & Engn Grp, Pasadena, CA 91109 USA. RP Rosenqvist, A (reprint author), Commiss European Communities, Joint Res Ctr, Space Applicat Inst, Global Vegetat Monitoring Unit, I-21020 Ispra, VA, Italy. NR 22 TC 88 Z9 96 U1 1 U2 11 PU TAYLOR & FRANCIS LTD PI LONDON PA 11 NEW FETTER LANE, LONDON EC4P 4EE, ENGLAND SN 0143-1161 J9 INT J REMOTE SENS JI Int. J. Remote Sens. PD APR 15 PY 2000 VL 21 IS 6-7 BP 1375 EP 1387 DI 10.1080/014311600210227 PG 13 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA 302GQ UT WOS:000086357700015 ER PT J AU Tucker, CJ Townshend, JRG AF Tucker, CJ Townshend, JRG TI Strategies for monitoring tropical deforestation using satellite data SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article ID ATMOSPHERIC CARBON-DIOXIDE; FOREST AREA; AMAZON; VEGETATION; BRAZIL; AMERICA; IMAGERY; FUTURE; AVHRR AB Measuring the aerial extent of tropical deforestation for other than localized areas requires the use of satellite data. We present evidence to show that an accurate determination of tropical deforestation is very difficult to achieve by a 'random sampling' analysis of Landsat or similar high spatial resolution data unless a very high percentage of the area to be studied is sampled. Tn order to achieve a Landsat-derived deforestation estimate within +/-20% of the actual deforestation amount 90% of the time, 37 of 40 scenes, 55 of 61 scenes and 37 of 45 scenes were required for Bolivia, Colombia and Peru respectively. C1 NASA, Goddard Space Flight Ctr, Terr Phys Lab, Greenbelt, MD 20771 USA. Univ Maryland, Dept Geog, Lab Global Remote Sensing Studies, College Pk, MD 20742 USA. Univ Maryland, Inst Adv Comp Studies, College Pk, MD 20742 USA. RP Tucker, CJ (reprint author), NASA, Goddard Space Flight Ctr, Terr Phys Lab, Greenbelt, MD 20771 USA. NR 40 TC 114 Z9 121 U1 2 U2 25 PU TAYLOR & FRANCIS LTD PI LONDON PA 11 NEW FETTER LANE, LONDON EC4P 4EE, ENGLAND SN 0143-1161 J9 INT J REMOTE SENS JI Int. J. Remote Sens. PD APR 15 PY 2000 VL 21 IS 6-7 BP 1461 EP 1471 DI 10.1080/014311600210263 PG 11 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA 302GQ UT WOS:000086357700019 ER PT J AU Gourdeau, L Verron, J Delcroix, T Busalacchi, AJ Murtugudde, R AF Gourdeau, L Verron, J Delcroix, T Busalacchi, AJ Murtugudde, R TI Assimilation of TOPEX/Poseidon altimetric data in a primitive equation model of the tropical Pacific Ocean during the 1992-1996 El Nino-Southern Oscillation period SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID GENERAL-CIRCULATION MODELS; SEA-LEVEL; KALMAN FILTER; INTERANNUAL VARIABILITY; EQUATORIAL PACIFIC; REDUCED-GRAVITY; WIND STRESS; ENSO; SIMULATION; TEMPERATURE AB Four years of TOPEX/Poseidon data (October 1992 to October 1996) are assimilated into a high-resolution primitive equation model [Gent ann Cane, 1989] of the tropical Pacific Ocean. The assimilation method used is a degraded version of the Singular Evolutive Extended Kalman filter approach [Pham et al., 1998] in which the reduced order basis is fixed. The along-track TOPEX/Poseidon sea surface height residuals are introduced in the model every 3 days. Initialization of the model runs appears to be crucial. This is particularly true for the 1992-1996 period, which is characterized by several El Nino and La Nina events and exhibits quite anomalous climatological behavior. An in situ database dedicated to this period was built and used to initialize the model properly. The simulation results with and without assimilation were compared with expendable bathythermograph and Tropical Atmosphere-Ocean in situ observations. The impact of sea surface height assimilation is observed both on the surface and subsurface temperature and velocity fields. The deficiencies of the free model in terms of means and variability structures are significantly reduced. More importantly, the evolution of the model fields over time is considerably improved by the assimilation. These supposedly more realistic assimilated four-dimensional fields are used to investigate the mechanism responsible for the 1992-1996 warm pool replenishment and depletion. This approach provides insights into the combined role of zonal and meridional transports in balancing volume changes in the warm pool. C1 IRD, LEGOS, F-31401 Toulouse, France. CNRS, LEGI, UMR 5519, F-38041 Grenoble, France. IRD, Noumea 98848, New Caledonia. NASA, LHP, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Gourdeau, L (reprint author), IRD, LEGOS, 14 Av Ed Belin, F-31401 Toulouse, France. RI Delcroix, Thierry/I-6103-2016 OI Delcroix, Thierry/0000-0002-8850-4865 NR 49 TC 12 Z9 12 U1 1 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD APR 15 PY 2000 VL 105 IS C4 BP 8473 EP 8488 DI 10.1029/2000JC900011 PG 16 WC Oceanography SC Oceanography GA 305GX UT WOS:000086532000001 ER PT J AU Keppenne, CL Marcus, SL Kimoto, M Ghil, M AF Keppenne, CL Marcus, SL Kimoto, M Ghil, M TI Intraseasonal variability in a two-layer model and observations SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID ATMOSPHERIC ANGULAR-MOMENTUM; NORTHERN-HEMISPHERE WINTER; EXTRATROPICAL 40-DAY OSCILLATION; OUTGOING LONGWAVE RADIATION; GENERAL-CIRCULATION MODEL; MULTIPLE FLOW REGIMES; 40-50 DAY OSCILLATION; TIME-SERIES; PERSISTENT ANOMALIES; MARTIAN ATMOSPHERE AB A two-layer shallow-water model with R15 truncation and topographic forcing is used to study intraseasonal variability in the Northern Hemisphere's (NH's) extratropical atmosphere. The model's variability is dominated by oscillations with average periods near 65-70 and 40-50 days. These periods are also found in 13.5 years of daily upper-air data from January 1980 to July 1993. The spatial variability associated with these oscillations is examined by compositing the streamfunction-anomaly fields of the model and the observations. The model's 70-day oscillation is strongest in the Euro-Atlantic sector, where it bears a close resemblance to observed streamfunction composites of the North Atlantic oscillation. The observed 70-day mode exhibits similar features in che Euro-Atlantic sector: accompanied by a north-south "seesaw" over the Pacific and Eurasia. Previous authors, in their analyses of geopotential height observations. also found these features to be present in an empirical orthogonal function that contain?; aspects of both the North Pacific and North Atlantic oscillations. The 40-day oscillation is characterized, in both the model simulations and observed data, by a zonal wave-number-2 pattern anchored over the NH topography. This pattern undergoes a tilted-trough vacillation in both the model and observations. This midlatitude vacillation is strongest in the Pacific-North American sector, where it resembles a 30-day oscillation in the University of California, Los Angeles, general circulation model that is largely driven by mountain torques over the Rockies. Comparisons with observational data show a clear separation between a tropical 50-day oscillation, not present in the authors' model results, and a 40-day NH extratropical oscillation, which resembles the topographically induced oscillation that arises in their two-layer model. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Tokyo, Ctr Climate Syst Res, Tokyo, Japan. Univ Calif Los Angeles, Dept Atmospher Sci, Los Angeles, CA 90024 USA. Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90024 USA. RP Marcus, SL (reprint author), CALTECH, Jet Prop Lab, Mail Stop 238-332,4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM steven.marcus@jpl.nasa.gov RI kimoto, masahide/P-9077-2014; OI Marcus, Steven/0000-0002-5763-6961 NR 94 TC 12 Z9 12 U1 0 U2 1 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0022-4928 J9 J ATMOS SCI JI J. Atmos. Sci. PD APR 15 PY 2000 VL 57 IS 8 BP 1010 EP 1028 DI 10.1175/1520-0469(2000)057<1010:IVIATL>2.0.CO;2 PG 19 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 306HU UT WOS:000086591900002 ER PT J AU Anyamba, E Williams, E Susskind, J Fraser-Smith, A Fullekrug, M AF Anyamba, E Williams, E Susskind, J Fraser-Smith, A Fullekrug, M TI The manifestation of the Madden-Julian oscillation in global deep convection and in the Schumann resonance intensity SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID FREQUENCY INTRASEASONAL OSCILLATIONS; TROPICAL ATMOSPHERE; SURFACE-TEMPERATURE; WAVE DISTURBANCES; CLOUD; VARIABILITY; 40-50-DAY; DATASET; CIRCUIT; MODELS AB This study determines the relationship between intraseasonal oscillations observed in two independent measures of global lightning activity: a global mean convective index (a proxy for deep convection) derived from the Goddard Television Infrared Observational Satellite (TIROS) Operational Vertical Sounder (TOVS) Pathfinder infrared cloud observations, and Schumann resonance magnetic intensity recorded at Arrival Heights, Antarctica. The study was initiated when previous results indicated a possible link between intraseasonal variations in Schumann resonances and variability of sunspot numbers on the timescale of the solar rotation period. The authors used seven years (1989-95) of daily records, though the Schumann resonance record had a number of gaps. Results of cross-spectrum and composite analysis show that intraseasonal oscillations in deep convection modulate the global variations in the Schumann resonance intensity. In the Tropics, the intraseasonal wave in deep convection has a wavenumber-1 structure with the region from 120 degrees W to 60 degrees E having one phase, while the other hemisphere has the opposite phase. The Schumann resonances are enhanced when a maximum in deep convection lies in the former hemisphere that comprises the main lightning-producing regions of South America and Africa. Conversely, Schumann resonances are suppressed when the convection propagates eastward to the Indian Ocean and the western Pacific Ocean. This relationship between the deep convection and Schumann resonances was best defined during the Northern Hemisphere springs of 1990 and 1992 but was less evident in 1993 and 1994. C1 NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Greenbelt, MD 20771 USA. MIT, Ralph M Parsons Lab, Cambridge, MA 02139 USA. Stanford Univ, Star Lab, Stanford, CA 94305 USA. Univ Frankfurt, D-6000 Frankfurt, Germany. RP Anyamba, E (reprint author), NASA, Goddard Space Flight Ctr, Gen Sci Corp, Code 910-4, Greenbelt, MD 20771 USA. NR 57 TC 26 Z9 27 U1 1 U2 3 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0022-4928 J9 J ATMOS SCI JI J. Atmos. Sci. PD APR 15 PY 2000 VL 57 IS 8 BP 1029 EP 1044 DI 10.1175/1520-0469(2000)057<1029:TMOTMJ>2.0.CO;2 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 306HU UT WOS:000086591900003 ER PT J AU Bauer, P Khain, A Pokrovsky, A Meneghini, R Kummerow, C Marzano, F Baptista, JPVP AF Bauer, P Khain, A Pokrovsky, A Meneghini, R Kummerow, C Marzano, F Baptista, JPVP TI Combined cloud-microwave radiative transfer modeling of stratiform rainfall SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID ENSEMBLE MODEL; PRECIPITATION; SIMULATION; RADAR; RADIOMETER; SNOW AB The simulation of explicit particle spectra during cloud evolution by a two-dimensional spectral cloud model was used to investigate the response of microwave radiative transfer to particle spectra development with special focus on the radiative effects of melting particles below the freezing level. For this purpose, 1) a particle-melting model was implemented with increased vertical resolution: 2) several models of the dielectric permittivity for melting particles were compared; 3) the dependence on size-density distributions was evaluated; and 4) the influence on the results by the replacement of explicit by parameterized particle spectra was tested. Radiative transfer simulations over ocean background at frequencies between 10.7 and 85.5 GHz showed a considerable increase in brightness temperatures (T-n) once melting particles were included. The amounts were strongly dependent on the implemented permittivity model, the number concentrations of large frozen particles right above the freezing level, and the local cloud conditions. Assuming a random mixture of air, ice, and meltwater in the panicle, T(n)s increased by up to 30 K (at 37.0 GHz) in the stratiform cloud portion For nadir view. If the meltwater was taken to reside at the particle boundaries, unrealistic T-n changes were produced at ail frequencies. This led to the conclusion that for large tenuous snowflakes the random-mixture model seems most appropriate, while for small and dense particles a nonuniform water distribution may be realistic. The net melting effect on simulated T(n)s, however, depended strongly on attenuation by supercooled liquid water above the freezing level, which generally suppressed the signal at 85.5 GHz. Over land background, changes in T-n due to melting particles remained below 8 K, which would be difficult to identify compared to variations in surface emission and cloud profile heterogeneity. Replacement of the explicit particle spectra for rain, snow, and graupel by parameterized spectra there, in exponential form with a fixed intercept) produced reductions of the melting signature by up to 40% over ocean. It was found that exponential size distribution formulas tended to underestimate number concentrations of large particles and overestimated those of small particles at those cloud levels where sufficient particle sedimentation leads to collection, aggregation, and evaporation, respectively, Consequently, the strongest differences between explicit and parameterized spectra occurred right, above the freezing level for snow and graupel, and close to the surface for rain. Radiometrically, this resulted in an underestimation of scattering above the freezing level and an underestimation of emission by melting particles below the freezing level as well as by rain toward the surface. In the stratiform region, the net effect was a reduction of the melting signature: however, T-n's were still up to 15 K higher than from the no-melting case for the random-mixture permittivity model. C1 German Aerosp Ctr, German Remote Sensing Data Ctr, D-51147 Cologne, Germany. Hebrew Univ Jerusalem, Inst Earth Sci, IL-91904 Jerusalem, Israel. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Aquila, Dipartimento Ingn Elettr, I-67100 Laquila, Italy. European Space Agcy, ESTEC, Electromagnet Div, Noordwijk, Netherlands. RP Bauer, P (reprint author), German Aerosp Ctr, German Remote Sensing Data Ctr, Linder Hohe, D-51147 Cologne, Germany. NR 25 TC 37 Z9 37 U1 0 U2 0 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0022-4928 J9 J ATMOS SCI JI J. Atmos. Sci. PD APR 15 PY 2000 VL 57 IS 8 BP 1082 EP 1104 DI 10.1175/1520-0469(2000)057<1082:CCMRTM>2.0.CO;2 PG 23 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 306HU UT WOS:000086591900007 ER PT J AU Bhattacharyya, A Alam, JE Sarkar, S Roy, P Sinha, B Raha, S Bhattacharjee, P AF Bhattacharyya, A Alam, JE Sarkar, S Roy, P Sinha, B Raha, S Bhattacharjee, P TI Relics of the cosmological QCD phase transition SO PHYSICAL REVIEW D LA English DT Article ID EARLY UNIVERSE; PRIMORDIAL NUCLEOSYNTHESIS; STRANGE MATTER; COSMIC SEPARATION; QUARK NUGGETS; FLUCTUATIONS; EVAPORATION; INHOMOGENEITIES AB The abundance and size distribution of quark nuggets (QN's), formed a few microseconds after the big bang due to a first-order QCD phase transition in the early universe, has been estimated. It appears that stable QN's could be a viable candidate for cosmological dark matter. The evolution of baryon inhomogeneity due to evaporated (unstable) QN's is also examined. C1 Bhabha Atom Res Ctr, Ctr Variable Energy Cyclotron, Calcutta 700064, W Bengal, India. Saha Inst Nucl Phys, Calcutta 700064, W Bengal, India. Bose Inst, Dept Phys, Calcutta 700009, W Bengal, India. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Indian Inst Astrophys, Bangalore 560034, Karnataka, India. RP Bhattacharyya, A (reprint author), Bhabha Atom Res Ctr, Ctr Variable Energy Cyclotron, 1-AF Bidhan Nagar, Calcutta 700064, W Bengal, India. NR 30 TC 28 Z9 28 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 APR 15 PY 2000 VL 61 IS 8 AR 083509 DI 10.1103/PhysRevD.61.083509 PG 8 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA 305RM UT WOS:000086554100017 ER PT J AU New, MH Pohorille, A AF New, MH Pohorille, A TI An inherited efficiencies model of non-genomic evolution SO SIMULATION PRACTICE AND THEORY LA English DT Article DE origin of life; non-genomic evolution; autocatalytic peptides ID REPLICATING PEPTIDE; RIBOZYMES AB A model for the evolution of biological systems in the absence of a nucleic acid-like genome is proposed and applied to model the earliest living organisms - protocells composed of membrane encapsulated peptides. Assuming that the peptides can make and break bonds between amino acids, and bonds in non-functional peptides are more likely to be destroyed than in functional peptides, it is demonstrated that the catalytic capabilities of the system as a whole can increase. This increase is defined to be non-genomic evolution. The relationship between the proposed mechanism for evolution and recent experiments on self-replicating peptides is discussed. (C) 2000 Published by Elsevier Science B.V. All rights reserved. C1 NASA, Ames Res Ctr, Exobiol Branch, Moffett Field, CA 94035 USA. NASA, Ames Res Ctr, Evolutionary Cell Comp Grp, Moffett Field, CA 94035 USA. RP Pohorille, A (reprint author), NASA, Ames Res Ctr, Exobiol Branch, Mail Stop 239-4, Moffett Field, CA 94035 USA. NR 8 TC 8 Z9 9 U1 1 U2 3 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0928-4869 J9 SIMULAT PRACT THEORY JI Simul. Pract. Theory PD APR 15 PY 2000 VL 8 IS 1-2 BP 99 EP 108 DI 10.1016/S0928-4869(00)00002-1 PG 10 WC Computer Science, Interdisciplinary Applications; Computer Science, Software Engineering SC Computer Science GA 325DX UT WOS:000087662000008 ER PT J AU Branchini, E Zehavi, I Plionis, M Dekel, A AF Branchini, E Zehavi, I Plionis, M Dekel, A TI Cluster versus POTENT density and velocity fields: cluster biasing and Omega SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE galaxies : clusters : general; galaxies : kinematics and dynamics; cosmology : theory; large-scale structure of Universe ID PECULIAR VELOCITIES; IRAS-GALAXIES; RECONSTRUCTING POSITIONS; 25,000 KILOMETERS; OPTICAL GALAXIES; REDSHIFT SURVEY; RICH CLUSTERS; DIPOLE; MASS; CATALOGS AB The density and velocity fields as extracted from the Abell/ACO clusters are compared with the corresponding fields recovered by the POTENT method from the Mark III peculiar velocities of galaxies. In order to minimize non-linear effects and to deal with ill-sampled regions, we smooth both fields using a Gaussian window with radii ranging between 12 and 20 h(-1) Mpc. The density and velocity fields within 70 h(-1) Mpc exhibit similarities, qualitatively consistent with gravitational instability theory and a linear biasing relation between clusters and mass. The random and systematic errors are evaluated with the help of mock catalogues. Quantitative comparisons within a volume containing similar to 12 independent samples yield beta(c)=Omega(0.6)/b(c)=0.22 +/- 0.08, where b(c) is the cluster biasing parameter at 15 h(-1) Mpc. If b(c)similar to 4.5, as indicated by the cluster correlation function, our result is consistent with Omega similar to 1. C1 Univ Durham, Dept Phys, Durham DH1 3LE, England. Univ Groningen, Kapteyn Astron Inst, NL-9700 AV Groningen, Netherlands. Fermi Natl Accelerator Lab, NASA, Fermilab Astrophys Grp, Batavia, IL 60510 USA. Hebrew Univ Jerusalem, Racah Inst Phys, IL-91904 Jerusalem, Israel. Natl Observ Athens, Athens 18110, Greece. Sch Adv Int Studies, SISSA, I-34013 Trieste, Italy. RP Branchini, E (reprint author), Univ Durham, Dept Phys, South Rd, Durham DH1 3LE, England. RI Plionis, Manolis/K-4354-2013; OI Branchini, Enzo/0000-0002-0808-6908 NR 51 TC 18 Z9 18 U1 0 U2 0 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD APR 11 PY 2000 VL 313 IS 3 BP 491 EP 503 DI 10.1046/j.1365-8711.2000.03257.x PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 302WU UT WOS:000086390100006 ER PT J AU Blain, AW Frayer, DT Bock, JJ Scoville, NZ AF Blain, AW Frayer, DT Bock, JJ Scoville, NZ TI Millimetre/submillimetre-wave emission-line searches for high-redshift galaxies SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE ISM : molecules; galaxies : evolution; galaxies : formation; cosmology : observations; infrared : galaxies; radio lines : galaxies ID DEEP SUBMILLIMETER SURVEY; C-II LINE; MOLECULAR GAS; CARBON-MONOXIDE; GALACTIC-CENTER; STAR-FORMATION; IRAS GALAXIES; QUASAR; EVOLUTION; DUST AB The redshifted spectral line radiation emitted from both atomic fine-structure and molecular rotational transitions in the interstellar medium (ISM) of high-redshift galaxies can be detected in the centimetre, millimetre and submillimetre wavebands. Here we predict the counts of galaxies detectable in an array of molecular and atomic lines. This calculation requires a reasonable knowledge of both the surface density of these galaxies on the sky, and the physical conditions in their ISM. The surface density is constrained using the results of submillimetre-wave continuum surveys. Follow-up OVRO Millimeter Array observations of two of the galaxies detected in the dust continuum have provided direct measurements of CO rotational line emission at redshifts of 2.56 and 2.81. Based on these direct high-redshift observations and on models of the ISM that are constrained by observations of low-redshift ultraluminous infrared galaxies, we predict the surface density of line-emitting galaxies as a function of line flux density and observing frequency. We incorporate the sensitivities and mapping speeds of existing and future millimetre/submillimetre-wave telescopes and spectrographs, and so assess the prospects for blank-field surveys to detect this line emission from gas-rich high-redshift galaxies. C1 Univ Cambridge, Cavendish Lab, Cambridge CB3 0HE, England. CALTECH, Dept Astron, Pasadena, CA 91125 USA. Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Univ Cambridge, Cavendish Lab, Madingley Rd, Cambridge CB3 0HE, England. EM awb@ast.cam.ac.uk NR 80 TC 31 Z9 31 U1 0 U2 0 PU OXFORD UNIV PRESS PI OXFORD PA GREAT CLARENDON ST, OXFORD OX2 6DP, ENGLAND SN 0035-8711 EI 1365-2966 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD APR 11 PY 2000 VL 313 IS 3 BP 559 EP 570 DI 10.1046/j.1365-8711.2000.03287.x PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 302WU UT WOS:000086390100013 ER PT J AU Chervenak, JA Grossman, EN Irwin, KD Martinis, JM Reintsema, CD Allen, CA Bergman, DI Moseley, SH Shafer, R AF Chervenak, JA Grossman, EN Irwin, KD Martinis, JM Reintsema, CD Allen, CA Bergman, DI Moseley, SH Shafer, R TI Performance of multiplexed SQUID readout for Cryogenic Sensor Arrays SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article; Proceedings Paper CT 8th International Workshop on Low-Temperature Detectors (LTD-8) CY AUG 15-20, 1999 CL DALFSEN, NETHERLANDS SP Technol Fdn, European Space Technol Ctr, Space Res Org Netherlands AB We report on the implementation of a multiplexer that uses superconducting quantum interference devices (SQUIDs) to read out low-impedance cryogenic detectors. Using prototype chips, a circuit was built which interfaces eight input SQUID channels with a close-packed array of eight transition-edge sensor (TES) infrared bolometers. Circuit elements were measured and crosstalk specifications are reported. Digital feedback is employed to flux-lock a single element in the array of SQUIDs. Published by Elsevier Science B.V. C1 Natl Inst Stand & Technol, Boulder, CO 80303 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Chervenak, JA (reprint author), Natl Inst Stand & Technol, 325 Broadway, Boulder, CO 80303 USA. RI Moseley, Harvey/D-5069-2012 NR 3 TC 11 Z9 11 U1 0 U2 6 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 APR 11 PY 2000 VL 444 IS 1-2 BP 107 EP 110 DI 10.1016/S0168-9002(99)01339-X PG 4 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 310JU UT WOS:000086823400025 ER PT J AU Kelley, RL Audley, MD Boyce, KR Fujimoto, R Gendreau, KC Ishisaki, Y McCammon, D Mihara, T Mitsuda, K Moseley, SH Mott, DB Porter, FS Stahle, CK Szymkowiak, AE AF Kelley, RL Audley, MD Boyce, KR Fujimoto, R Gendreau, KC Ishisaki, Y McCammon, D Mihara, T Mitsuda, K Moseley, SH Mott, DB Porter, FS Stahle, CK Szymkowiak, AE TI The microcalorimeter spectrometer on the ASTRO-E X-ray observatory SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article; Proceedings Paper CT 8th International Workshop on Low-Temperature Detectors (LTD-8) CY AUG 15-20, 1999 CL DALFSEN, NETHERLANDS SP Technol Fdn, European Space Technol Ctr, Space Res Org Netherlands DE detectors; calorimeters; bolometers; X-ray; spectrometer; instruments; missions ID HELIUM CRYOSTAT; XRS; PERFORMANCE; DETECTOR; DESIGN; SYSTEM AB The Astro-E Observatory will employ a high-resolution X-ray spectrometer based on a 32 pixel array of microcalorimeters with an energy resolution of about 12 eV at 6 keV (the Fe-K region). This will provide spectral resolving power 10 times higher than any other non-dispersive X-ray spectrometer. The instrument incorporates a three-stage cooling system capable of maintaining the temperature of the detector stage at 60 mK for about two years in orbit with a 97% duty cycle. The array sits at the focus of a grazing incidence conical mirror. The quantum efficiency of the microcalorimeters and the reflectivity of the X-ray mirror system combine to give high throughput over the 0.3-12 keV energy band. This new capability will enable the study of a wide range of high-energy astrophysical sources with unprecedented spectral sensitivity. (C) 2000 Published by Elsevier Science B.V. All rights reserved. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Space Res Assoc, Columbia, MD 21044 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. Univ Wisconsin, Dept Phys, Madison, WI 53706 USA. Univ Wisconsin, Dept Phys, Madison, WI 53706 USA. Inst Space & Astronaut Sci, Tokyo, Japan. Tokyo Metropolitan Univ, Tokyo 158, Japan. RIKEN, Inst Phys & Chem Res, Wako, Saitama, Japan. RP Kelley, RL (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RI Mitsuda, Kazuhisa/C-2649-2008; Porter, Frederick/D-3501-2012; Moseley, Harvey/D-5069-2012; Kelley, Richard/K-4474-2012; Mihara, Tatehiro/C-5536-2017 OI Porter, Frederick/0000-0002-6374-1119; Mihara, Tatehiro/0000-0002-6337-7943 NR 11 TC 17 Z9 17 U1 2 U2 4 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 APR 11 PY 2000 VL 444 IS 1-2 BP 170 EP 174 DI 10.1016/S0168-9002(99)01358-3 PG 5 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 310JU UT WOS:000086823400038 ER PT J AU Porter, FS Almy, R Apodaca, E Figueroa-Feliciano, E Galeazzi, M Kelley, R McCammon, D Stahle, CK Szymkowiak, AE Sanders, WT AF Porter, FS Almy, R Apodaca, E Figueroa-Feliciano, E Galeazzi, M Kelley, R McCammon, D Stahle, CK Szymkowiak, AE Sanders, WT TI Observations of the soft X-ray background with the XQC microcalorimeter sounding rocket SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article; Proceedings Paper CT 8th International Workshop on Low-Temperature Detectors (LTD-8) CY AUG 15-20, 1999 CL DALFSEN, NETHERLANDS SP Technol Fdn, European Space Technol Ctr, Space Res Org Netherlands AB On March 28, 1999 the X-ray Quantum Calorimeter (XQC) sounding rocket instrument completed its third flight to observe the soft X-ray background in the 0.02-1.0 keV energy band. The detector system is a 36-pixel ion implanted microcalorimeter array with 0.5 x 2.0 mm HgTe absorbers that is operated at 60 mK with a single-stage adiabatic demagnetization refrigerator. The detector array, mounting system, thin film filters and dewar infrastructure have all undergone substantial improvements since the last Eight. The result is a scientifically successful observation of the diffuse soft X-ray background that reveals several emission lines from highly ionized elements in the interstellar medium. Preliminary results show strong emission from both O VII and O VIII. In this paper, we discuss problems and their solutions for this mature Low-Temperature Detector (LTD) instrument and recent astrophysical results. (C) 2000 Elsevier Science B.V. All rights reserved. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Wisconsin, Dept Phys, Madison, WI 53706 USA. Univ Genoa, Genoa, Italy. RP Porter, FS (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RI Porter, Frederick/D-3501-2012; Kelley, Richard/K-4474-2012 OI Porter, Frederick/0000-0002-6374-1119; NR 3 TC 16 Z9 16 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-9002 J9 NUCL INSTRUM METH A JI Nucl. Instrum. Methods Phys. Res. Sect. A-Accel. Spectrom. Dect. Assoc. Equip. PD APR 11 PY 2000 VL 444 IS 1-2 BP 175 EP 179 DI 10.1016/S0168-9002(99)01352-2 PG 5 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 310JU UT WOS:000086823400039 ER PT J AU Tralshawala, N Aslam, S Brekosky, RP Chen, TC Feliciano, EF Finkbeiner, FM Li, MJ Mott, DB Stahle, CK Stahle, CM AF Tralshawala, N Aslam, S Brekosky, RP Chen, TC Feliciano, EF Finkbeiner, FM Li, MJ Mott, DB Stahle, CK Stahle, CM TI Design and fabrication of superconducting transition edge X-ray calorimeters SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article; Proceedings Paper CT 8th International Workshop on Low-Temperature Detectors (LTD-8) CY AUG 15-20, 1999 CL DALFSEN, NETHERLANDS SP Technol Fdn, European Space Technol Ctr, Space Res Org Netherlands DE Constellation-X; low-temperature detector; microcalorimeter; superconducting transition edge sensors; silicon nitride membranes AB We report on progress made so far at NASA Goddard Space Flight Center towards the development of arrays of X-ray microcalorimeters as candidates for the high-resolution X-ray spectrometer on the Constellation-X mission. In the design concept presently under consideration, the microcalorimeter consists of(i) a Bi/Cu multilayer absorber for stopping and thermalizing the incident X-rays, (ii) an e-beam evaporated Mo/Au proximity bilayer with sputtered Nb leads for sensing the resultant temperature rise, and (iii) a silicon nitride membrane to provide a weak thermal link to the sink temperature so that the calorimeter can return to its equilibrium temperature. Fabrication details and preliminary results are reported. (C) 2000 Elsevier Science B.V. All rights reserved. C1 Raytheon ITSS, Lanham, MD USA. Swales Aerosp, Beltsville, MD USA. Global Sci & Technol Inc, Greenbelt, MD USA. Stanford Univ, Stanford, CA 94305 USA. Univ Maryland, College Pk, MD 20742 USA. NASA, Goddard Space Flight Ctr, Detector Syst Branch, Greenbelt, MD 20771 USA. RP Tralshawala, N (reprint author), Raytheon ITSS, Lanham, MD USA. RI Aslam, Shahid/D-1099-2012 NR 8 TC 28 Z9 28 U1 0 U2 4 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 APR 11 PY 2000 VL 444 IS 1-2 BP 188 EP 191 DI 10.1016/S0168-9002(99)01355-8 PG 4 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 310JU UT WOS:000086823400042 ER PT J AU Porter, FS Almy, R Apodaca, E Figueroa-Feliciano, E Galeazzi, M Kelley, R McCammon, D Stahle, CK Szymkowiak, AE Sanders, WT AF Porter, FS Almy, R Apodaca, E Figueroa-Feliciano, E Galeazzi, M Kelley, R McCammon, D Stahle, CK Szymkowiak, AE Sanders, WT TI The XQC microcalorimeter sounding rocket: a stable LTD platform 30 seconds after rocket motor burnout SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article; Proceedings Paper CT 8th International Workshop on Low-Temperature Detectors (LTD-8) CY AUG 15-20, 1999 CL DALFSEN, NETHERLANDS SP Technol Fdn, European Space Technol Ctr, Space Res Org Netherlands AB The XQC microcalorimeter sounding rocket experiment is designed to provide a stable thermal environment for an LTD detector system within 30 s of the burnout of its second stage rocket motor. The detector system used for this instrument is a 36-pixel microcalorimeter array operated at 60 mK with a single-stage adiabatic demagnetization refrigerator (ADR). The ADR is mounted on a space-pumped liquid helium tank with vapor cooled shields which is vibration isolated from the rocket structure. We present here some of the design and performance details of this mature LTD instrument, which has just completed its third suborbital flight. (C) 2000 Elsevier Science B.V. All rights reserved. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Wisconsin, Dept Phys, Madison, WI 53706 USA. Univ Genoa, Genoa, Italy. RP Porter, FS (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RI Porter, Frederick/D-3501-2012; Kelley, Richard/K-4474-2012 OI Porter, Frederick/0000-0002-6374-1119; NR 2 TC 12 Z9 12 U1 1 U2 2 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 APR 11 PY 2000 VL 444 IS 1-2 BP 220 EP 223 DI 10.1016/S0168-9002(99)01391-1 PG 4 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 310JU UT WOS:000086823400049 ER PT J AU Stahle, CK Finkbeiner, FM Boyce, KR Chen, T Feliciano, EF Gygax, JD Kelley, RL Li, M Mattson, BJ Mott, DB Porter, FS Stahle, CM Szymkowiak, AE Tralshawala, N AF Stahle, CK Finkbeiner, FM Boyce, KR Chen, T Feliciano, EF Gygax, JD Kelley, RL Li, M Mattson, BJ Mott, DB Porter, FS Stahle, CM Szymkowiak, AE Tralshawala, N TI First results from Mo/Au transition-edge sensor X-ray calorimeters SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article; Proceedings Paper CT 8th International Workshop on Low-Temperature Detectors (LTD-8) CY AUG 15-20, 1999 CL DALFSEN, NETHERLANDS SP Technol Fdn, European Space Technol Ctr, Space Res Org Netherlands DE microcalorimeter; transition-edge sensor; superconducting quantum interference devices AB Superconducting bilayers made of thin films of molybdenum and gold show promise as robust transition-edge sensor (TES) thermometers for calorimeters. We present our first X-ray results from experiments with Mo/Au TES calorimeters on silicon-nitride membranes. These results include analysis of the signal pulse shape and noise as functions of the bias point, which is varied through changing the bias voltage for operation at different places within the superconducting transition and changing the heat sink temperature relative to the transition temperature. Ultimately, we determined that the performance of our devices is limited by the slew rate of the SQUID amplifier used to measure the change in current, which restricts the choice of bias. The amplifier must be replaced before further device characterization and optimization can proceed. (C) 2000 Elsevier Science B.V. All rights reserved. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. Global Sci & Technol Inc, Greenbelt, MD 20770 USA. Stanford Univ, Dept Phys, Stanford, CA 94305 USA. Swales Aerosp, Beltsville, MD 20705 USA. Raytheon ITSS, Lanham, MD 20706 USA. RP Stahle, CK (reprint author), NASA, Goddard Space Flight Ctr, Code 662, Greenbelt, MD 20771 USA. RI Porter, Frederick/D-3501-2012; Kelley, Richard/K-4474-2012 OI Porter, Frederick/0000-0002-6374-1119; NR 7 TC 6 Z9 6 U1 0 U2 4 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 APR 11 PY 2000 VL 444 IS 1-2 BP 224 EP 227 DI 10.1016/S0168-9002(99)01363-7 PG 4 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 310JU UT WOS:000086823400050 ER PT J AU Li, L Frunzio, L Segall, K Wilson, CM Prober, DE Szymkowiak, AE Moseley, SH AF Li, L Frunzio, L Segall, K Wilson, CM Prober, DE Szymkowiak, AE Moseley, SH TI Single-photon 2-D imaging X-ray spectrometer employing trapping with four tunnel junctions SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article; Proceedings Paper CT 8th International Workshop on Low-Temperature Detectors (LTD-8) CY AUG 15-20, 1999 CL DALFSEN, NETHERLANDS SP Technol Fdn, European Space Technol Ctr, Space Res Org Netherlands AB We are developing single-photon 2-D imaging X-ray spectrometers for applications in X-ray astrophysics. The devices employing a Ta strip X-ray absorber with Al traps and a tunnel junction at each end have been tested. They achieve an energy resolution of 26 eV out of 5.9 keV over a limited length (Segall, IEEE Trans., in press) with a 1-D spatial resolution of about 2 mu m over the full 160 mu m length. By analytical and numerical simulations of the quasiparticle diffusion process. we study related devices with a square Ta absorber having four traps and attached junctions to provide 2-D imaging. The traps give charge division to the corners or to the edges of the square absorber. We find that these devices can give good 2-D spatial resolution. We discuss the operating principle and the factors which affect the spatial resolution. (C) 2000 Elsevier Science B.V. All rights reserved. C1 Yale Univ, Dept Appl Phys, New Haven, CT 06520 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Prober, DE (reprint author), Yale Univ, Dept Appl Phys, New Haven, CT 06520 USA. RI Wilson, Christopher/A-9676-2008; Moseley, Harvey/D-5069-2012; OI Frunzio, Luigi/0000-0002-0272-5481 NR 3 TC 4 Z9 4 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 APR 11 PY 2000 VL 444 IS 1-2 BP 228 EP 231 DI 10.1016/S0168-9002(99)01364-9 PG 4 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 310JU UT WOS:000086823400051 ER PT J AU Galeazzi, M Gatti, F Vitale, S McCammon, D Sanders, WT Porter, FS Szymkowiak, A AF Galeazzi, M Gatti, F Vitale, S McCammon, D Sanders, WT Porter, FS Szymkowiak, A TI The interstellar medium X-ray spectrometer (IMXS) SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article; Proceedings Paper CT 8th International Workshop on Low-Temperature Detectors (LTD-8) CY AUG 15-20, 1999 CL DALFSEN, NETHERLANDS SP Technol Fdn, European Space Technol Ctr, Space Res Org Netherlands AB The proposal for an experiment on the International Space Station that will perform an all sky survey of the soft X-ray background for interstellar and intergalactic medium studies has been submitted to the Italian Space Agency (AST). The goal of the experiment is to obtain spectroscopic information on the X-ray diffuse background in the energy range 30-1000 eV. This information will address many questions concerning the origin, composition, structure and evolution of the interstellar and intergalactic medium. The experiment will be installed on one of the outside mounting pallets of the Space Station looking at the local zenith with a field of view of 10 degrees. (C) 2000 Elsevier Science B.V. All rights reserved. C1 Univ Genoa, I-116146 Genoa, Italy. INFN Genoa, Dept Phys, I-116146 Genoa, Italy. Univ Wisconsin, Dept Phys, Madison, WI 53706 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Galeazzi, M (reprint author), Univ Genoa, Via Dodecaneso 33, I-116146 Genoa, Italy. RI Porter, Frederick/D-3501-2012; Gatti, Flavio/K-4568-2013 OI Porter, Frederick/0000-0002-6374-1119; NR 8 TC 2 Z9 2 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 APR 11 PY 2000 VL 444 IS 1-2 BP 268 EP 272 DI 10.1016/S0168-9002(99)01387-X PG 5 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 310JU UT WOS:000086823400061 ER PT J AU Sudiwala, RV Maffei, B Griffin, MJ Haynes, CV Ade, PAR Bhatia, RS Turner, AD Bock, JJ Lange, AE Beeman, JW AF Sudiwala, RV Maffei, B Griffin, MJ Haynes, CV Ade, PAR Bhatia, RS Turner, AD Bock, JJ Lange, AE Beeman, JW TI Evaluation of prototype 100 mK bolometric detector for Planck Surveyor SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article; Proceedings Paper CT 8th International Workshop on Low-Temperature Detectors (LTD-8) CY AUG 15-20, 1999 CL DALFSEN, NETHERLANDS SP Technol Fdn, European Space Technol Ctr, Space Res Org Netherlands DE spider web bolometer; Planck HFI ID NOISE AB The High-Frequency Instrument (HFI) for the Planck Surveyor mission will measure anisotropies of the Cosmic Microwave Background (CMB) down to scales of 6 arcmin and to an accuracy of Delta T/T = 2 x 10(-6). Channels ranging in frequency from 100 to 857 GHz will use 100 mK spider web bolometer detectors with NTD Ge thermistors, The detectors must be photon noise limited and fast enough to preserve signal information at the 1 r.p.m. scan rate of the satellite. The prime low-frequency CMB channels at 143 and 217 GHz are the most technically demanding owing to the lower background limited NEPs. For the 143 GHz channel the requirements are that the time constant tau < 5.7 ms and The NEPbol <1.53 x 10(-17) WHz(-1/2) including contribution from amplifier noise. We present here thermal, electrical and optical data on a prototype detector which, although optimised for the 100 GHz channel, satisfies most of the requirements of the more demanding 143 GHz channel. The measurements art: consistent with ideal thermal behaviour of the detector over the appropriate bias and temperature ranges for optimum performance. From optically blanked electrical measurements we determined the dependence of resistance and thermal conductance on temperature over a wide range, 70-200 mK. The optical responsivity and NEP were measured under photon background conditions similar to those expected in flight. Measurements of speed of response as a function of bias at different temperatures allowed us to determine the variation of total heat capacity with temperature. Extrapolation of these data show that in principal performance for all the Planck HFI channels can be met, (C) 2000 Elsevier Science B.V. All rights reserved. C1 Univ London Queen Mary & Westfield Coll, Dept Phys, London E1 4NS, England. CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. Univ Calif Berkeley, Lawrence Berkeley Lab, Berkeley, CA 94720 USA. RP Sudiwala, RV (reprint author), Univ London Queen Mary & Westfield Coll, Dept Phys, Mile End Rd, London E1 4NS, England. NR 9 TC 7 Z9 7 U1 1 U2 2 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 APR 11 PY 2000 VL 444 IS 1-2 BP 408 EP 412 DI 10.1016/S0168-9002(99)01410-2 PG 5 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 310JU UT WOS:000086823400091 ER PT J AU Hargrave, PC Maffei, B Hermoso, R Gannaway, G Griffin, MJ Ade, PAR Haynes, CV Tucker, CE Moseley, SH Bock, JJ Rodriguez, L AF Hargrave, PC Maffei, B Hermoso, R Gannaway, G Griffin, MJ Ade, PAR Haynes, CV Tucker, CE Moseley, SH Bock, JJ Rodriguez, L TI A low-background He-3 bolometer array test facility and its use in evaluating prototype arrays for FIRST-SPIRE SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article; Proceedings Paper CT 8th International Workshop on Low-Temperature Detectors (LTD-8) CY AUG 15-20, 1999 CL DALFSEN, NETHERLANDS SP Technol Fdn, European Space Technol Ctr, Space Res Org Netherlands DE FIRST; bolometers; astronomy AB We report on the imaging detector array test and evaluation program for the Spectral and Photometric Imaging REceiver (SPIRE) instrument for the Far InfraRed and Submillimetre Telescope (FIRST) satellite. Three candidate detector array technologies are under evaluation: (i) hexagonally close-packed arrays of 2 F lambda feedhorns with NTD germanium sensors; (Ii) filled absorber arrays with 0.5 F lambda square pixels with ion-implanted silicon sensors; and (iii) 0.5 F lambda filled arrays with transition-edge superconducting (TES) sensors. Detector arrays are required for SPIRE bands covering the 200-700 mu m range. To meet the SPIRE performance requirements, the detectors must be background limited by the thermal emission from the 80 K low-emissivity FIRST telescope, achieve a speed of response of 20 Hz, and be fabricated in sizes up to 32 x 32. A novel cryogenic array test facility has been built to enable a range of experiments to be carried out under low background to enable a comprehensive evaluation and calibration programme on prototype detector arrays with a minimum of disruptive warm-up/cool-down cycles. The facility will be used to compare the performance of the different array types prior to array technology selection for SPIRE. (C) 2000 Elsevier Science B.V. All rights reserved. C1 Univ London Queen Mary & Westfield Coll, Dept Phys, Astrophys Grp, London E1 4NS, England. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. CEA SAp, Saclay, France. RP Hargrave, PC (reprint author), Univ London Queen Mary & Westfield Coll, Dept Phys, Astrophys Grp, Mile End Rd, London E1 4NS, England. RI Moseley, Harvey/D-5069-2012 NR 8 TC 8 Z9 8 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 APR 11 PY 2000 VL 444 IS 1-2 BP 427 EP 431 DI 10.1016/S0168-9002(99)01416-3 PG 5 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 310JU UT WOS:000086823400095 ER PT J AU Wilson, CM Segall, K Frunzio, L Li, L Prober, DE Schiminovich, D Mazin, B Martin, C Vasquez, R AF Wilson, CM Segall, K Frunzio, L Li, L Prober, DE Schiminovich, D Mazin, B Martin, C Vasquez, R TI Optical/UV single-photon imaging spectrometers using superconducting tunnel junctions SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article; Proceedings Paper CT 8th International Workshop on Low-Temperature Detectors (LTD-8) CY AUG 15-20, 1999 CL DALFSEN, NETHERLANDS SP Technol Fdn, European Space Technol Ctr, Space Res Org Netherlands DE superconductivity; spectrometer; junction; imaging; detector ID DETECTORS AB We present preliminary test results of optical/UV single-photon imaging spectrometers using superconducting tunnel junctions. Our devices utilize a lateral trapping geometry. Photons are absorbed in a Ta thin film, creating excess quasiparticles. Quasiparticles diffuse and are trapped by Al/AlOx/Al tunnel junctions located on the sides of the absorber. The Ta/Al interface does not overlap the junction area. Imaging devices have tunnel junctions on two opposite sides of the absorber. Position information is obtained from the fraction of the to tal charge collected by each junction. We have fabricated high-quality junctions with a ratio of subgap resistance to normal state resistance greater than 100000 at 0.22 K. We have measured the single-photon response of our devices. For photon energies between 2 and 5 eV, we measure an energy resolution between 1 and 1.6 eV. We can estimate the number of pixels the device can resolve from the energy resolution. We find that these early devices have as many as 4 pixels per strip. (C) 2000 Published by Elsevier Science B.V. All rights reserved. C1 Yale Univ, New Haven, CT 06520 USA. CALTECH, Pasadena, CA 91125 USA. NASA, Jet Prop Lab, Pasadena, CA USA. RP Wilson, CM (reprint author), Yale Univ, New Haven, CT 06520 USA. RI Wilson, Christopher/A-9676-2008; Mazin, Ben/B-8704-2011; OI Mazin, Ben/0000-0003-0526-1114; Frunzio, Luigi/0000-0002-0272-5481 NR 9 TC 19 Z9 19 U1 1 U2 2 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 APR 11 PY 2000 VL 444 IS 1-2 BP 449 EP 452 DI 10.1016/S0168-9002(99)01421-7 PG 4 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 310JU UT WOS:000086823400099 ER PT J AU Figueroa-Feliciano, E Cabrera, B Miller, AJ Powell, SF Saab, T Walker, ABC AF Figueroa-Feliciano, E Cabrera, B Miller, AJ Powell, SF Saab, T Walker, ABC TI Optimal filter analysis of energy-dependent pulse shapes and its application to TES detectors SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article; Proceedings Paper CT 8th International Workshop on Low-Temperature Detectors (LTD-8) CY AUG 15-20, 1999 CL DALFSEN, NETHERLANDS SP Technol Fdn, European Space Technol Ctr, Space Res Org Netherlands AB We present a method for applying optimal filtering to data sets containing energy-dependent pulse shapes. This occurs frequently in transition edge sensors (TES) when dealing with signal energies that are close to the saturation point of the detector. Different filter templates are created which span the dynamic range desired for the TES. These filters are then used as templates to filter the data, using interpolation to bridge the gap between templates. The method has been demonstrated on our tungsten (W) TES. We present the latest results from heat-pulse data on a (125 mu m)(2) TES with resolutions of 3 eV FWHM at 42 eV and 4 eV FWHM at 1.42 keV with the same sensor demonstrating the wide band operation possible with this technique. (C) 2000 Elsevier Science B.V. All rights reserved. C1 Stanford Univ, Dept Phys, Stanford, CA 94305 USA. RP Figueroa-Feliciano, E (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 662, Greenbelt, MD 20771 USA. NR 5 TC 13 Z9 13 U1 0 U2 4 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 APR 11 PY 2000 VL 444 IS 1-2 BP 453 EP 456 DI 10.1016/S0168-9002(99)01434-5 PG 4 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 310JU UT WOS:000086823400100 ER PT J AU Bleile, A Egelhof, P Kluge, HJ Liebisch, U McCammon, D Meier, HJ Sebastian, O Stahle, CK Weber, M AF Bleile, A Egelhof, P Kluge, HJ Liebisch, U McCammon, D Meier, HJ Sebastian, O Stahle, CK Weber, M TI Low-temperature X-ray detectors for precise Lamb shift measurements on hydrogen-like heavy ions SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article; Proceedings Paper CT 8th International Workshop on Low-Temperature Detectors (LTD-8) CY AUG 15-20, 1999 CL DALFSEN, NETHERLANDS SP Technol Fdn, European Space Technol Ctr, Space Res Org Netherlands AB The precise determination of the Lamb shift in heavy hydrogen-like ions provides a sensitive test of quantum electrodynamics in very strong Coulomb fields, not accessible otherwise. For the investigation of the Lyman-alpha transitions in Pb-208(81+) Or U-238(91+) With sufficient accuracy a high resolving calorimetric detector for hard X-rays (E less than or equal to 100 keV) is presently developed. The detector modules consist of arrays of silicon thermistors and of X-ray absorbers made of high Z material to optimize the absorption efficiency. The detectors are housed in a specially designed He-3/He-4 dilution refrigerator with a side arm which fits to the geometry of the internal target of the storage ring ESR at GSI Darmstadt. The detector performance presently achieved is already close to fulfill the demands of the Lamb shift experiment. For a prototype detector pixel with a 0.3 mm(2) x 66 mu m Sn absorber an energy resolution of Delta E-FWHM = 75 eV is obtained for 60 keV X-rays. (C) 2000 Elsevier Science B.V. All rights reserved. C1 Gesell Schwerionenforsch Inst Darmstadt, D-64291 Darmstadt, Germany. Univ Mainz, Inst Phys, D-55099 Mainz, Germany. Univ Wisconsin, Dept Phys, Madison, WI 53706 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Egelhof, P (reprint author), Gesell Schwerionenforsch Inst Darmstadt, D-64291 Darmstadt, Germany. NR 3 TC 14 Z9 14 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-9002 J9 NUCL INSTRUM METH A JI Nucl. Instrum. Methods Phys. Res. Sect. A-Accel. Spectrom. Dect. Assoc. Equip. PD APR 11 PY 2000 VL 444 IS 1-2 BP 488 EP 491 DI 10.1016/S0168-9002(99)01429-1 PG 4 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 310JU UT WOS:000086823400108 ER PT J AU Zhou, ZJ Apte, SS Soininen, R Cao, RH Baaklini, GY Rauser, RW Wang, JM Cao, YH Tryggvason, K AF Zhou, ZJ Apte, SS Soininen, R Cao, RH Baaklini, GY Rauser, RW Wang, JM Cao, YH Tryggvason, K TI Impaired endochondral ossification and angiogenesis in mice deficient in membrane-type matrix metalloproteinase I SO PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA LA English DT Article ID INSITU HYBRIDIZATION; MESSENGER-RNA; GELATINASE-A; IDENTIFICATION; SURFACE; TISSUE; MMP; EMBRYOGENESIS; MECHANISMS; ACTIVATION AB Membrane-type matrix metalloproteinase I (MT1-MMP)-deficient mice were found to have severe defects in skeletal development and angiogenesis, The craniofacial, axial, and appendicular skeletons were severely affected, leading to a short and domed skull, marked deceleration of postnatal growth, and death by 3 wk of age. Shortening of bones is a consequence of decreased chondrocyte proliferation in the proliferative zone of the growth plates. Defective vascular invasion of cartilage leads to enlargement of hypertrophic zones of growth plates and delayed formation of secondary ossification centers in long bones. In an in vivo corneal angiogenesis assay, null mice did not have angiogenic response to implanted FGF-2, suggesting that the defect in angiogenesis is not restricted to cartilage alone. In tissues from null mice, activation of latent matrix metalloproteinase 2 was deficient, suggesting that MT1-MMP is essential for its activation in vivo. C1 Karolinska Hosp, Dept Mol Med, S-17176 Stockholm, Sweden. Karolinska Inst, Dept Med Biochem & Biophys, Div Matrix Biol, S-17177 Stockholm, Sweden. Cleveland Clin Fdn ND 20, Lerner Res Inst, Dept Biomed Engn, Cleveland, OH 44195 USA. Karolinska Inst, Ctr Microbiol & Tumor Biol, S-17177 Stockholm, Sweden. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Tryggvason, K (reprint author), Karolinska Hosp, Dept Mol Med, S-17176 Stockholm, Sweden. RI zhou, zhongjun/D-4818-2012 NR 25 TC 541 Z9 558 U1 4 U2 14 PU NATL ACAD SCIENCES PI WASHINGTON PA 2101 CONSTITUTION AVE NW, WASHINGTON, DC 20418 USA SN 0027-8424 J9 P NATL ACAD SCI USA JI Proc. Natl. Acad. Sci. U. S. A. PD APR 11 PY 2000 VL 97 IS 8 BP 4052 EP 4057 DI 10.1073/pnas.060037197 PG 6 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 304AV UT WOS:000086461100050 PM 10737763 ER PT J AU Huck, FO Fales, CL Davis, RE Alter-Gartenberg, R AF Huck, FO Fales, CL Davis, RE Alter-Gartenberg, R TI Visual communication with retinex coding SO APPLIED OPTICS LA English DT Article ID INFORMATION-THEORY; IMAGE; RESTORATION; ALGORITHMS; STATISTICS; LIGHTNESS; FILTER AB Visual communication with retinex coding seeks to suppress the spatial variation of the irradiance (e.g., shadows) across natural scenes and preserve only the spatial detail and the reflectance (or the lightness) of the surface itself. The separation of reflectance from irradiance begins with nonlinear retinex coding that sharply and clearly enhances edges and preserves their contrast, and it ends with a Wiener filter that restores images from this edge and contrast information. An approximate small-signal model of image gathering with retinex coding is found to consist of the familiar difference-of-Gaussian bandpass filter and a locally adaptive automatic-gain control. A linear representation of this model is used to develop expressions within the small-signal constraint for the information rate and the theoretical minimum data rate of the retinex-coded signal and for the maximum-realizable fidelity of the images restored from this signal. Extensive computations and simulations demonstrate that predictions based on these figures of merit correlate closely with perceptual and measured performance. Hence these predictions can serve as a general guide for the design of visual communication channels that produce images with a visual quality that consistently approaches the best possible sharpness, clarity, and reflectance constancy, even for nonuniform irradiances. The suppression of shadows in the restored image is found to be constrained inherently more by the sharpness of their penumbra than by their depth. (C) 2000 Optical Society of America OCIS codes: 100.0100, 110.0110, 150.0150, 250.0250, 330.0330. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Comp Sci Corp, Hampton, VA 23666 USA. RP Huck, FO (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. EM f.o.huck@larc.nasa.gov NR 47 TC 8 Z9 8 U1 0 U2 1 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 1559-128X EI 2155-3165 J9 APPL OPTICS JI Appl. Optics PD APR 10 PY 2000 VL 39 IS 11 BP 1711 EP 1730 DI 10.1364/AO.39.001711 PG 20 WC Optics SC Optics GA 302ZV UT WOS:000086397100004 PM 18345070 ER PT J AU Liu, AS Ning, CZ AF Liu, AS Ning, CZ TI Near-infrared laser pumped intersubband THz laser gain in InGaAs-AlAsSb-InP quantum wells SO APPLIED PHYSICS LETTERS LA English DT Article ID CASCADE LASERS AB We investigate the possibility of using InGaAs-AlAsSb-InP coupled quantum wells to generate THz radiation by means of intersubband optical pumping. We show that large conduction band offsets of these quantum wells make it possible to use conventional near-infrared diode lasers around 1.55 mu m as pump sources. Taking into account the pump-probe coherent interaction and the optical nonlinearity for the pump field, we calculate the THz gain of the quantum well structure. We show that resonant Raman scattering enhances the THz gain at low and moderate optical pumping levels. When the pump intensity is strong, the THz gain is reduced by pump-induced population redistribution and pump-probe coherent interactions. (C) 2000 American Institute of Physics. [S0003-6951(00)02015-5]. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Arizona State Univ, Dept Elect Engn, Tempe, AZ 85287 USA. RP Liu, AS (reprint author), NASA, Ames Res Ctr, M-S N229-1, Moffett Field, CA 94035 USA. RI Ning, C. Z./D-4699-2009 OI Ning, C. Z./0000-0003-4583-8889 NR 17 TC 15 Z9 16 U1 0 U2 2 PU AMER INST PHYSICS PI MELVILLE PA 2 HUNTINGTON QUADRANGLE, STE 1NO1, MELVILLE, NY 11747-4501 USA SN 0003-6951 J9 APPL PHYS LETT JI Appl. Phys. Lett. PD APR 10 PY 2000 VL 76 IS 15 BP 1984 EP 1986 DI 10.1063/1.126230 PG 3 WC Physics, Applied SC Physics GA 301ER UT WOS:000086296200006 ER PT J AU Leon, R Swift, GM Magness, B Taylor, WA Tang, YS Wang, KL Dowd, P Zhang, YH AF Leon, R Swift, GM Magness, B Taylor, WA Tang, YS Wang, KL Dowd, P Zhang, YH TI Changes in luminescence emission induced by proton irradiation: InGaAs/GaAs quantum wells and quantum dots SO APPLIED PHYSICS LETTERS LA English DT Article ID RADIATIVE RECOMBINATION; HETEROSTRUCTURES; TRANSFORMATION; MECHANISM; STATES AB The photoluminescence (PL) emission from InGaAs/GaAs quantum-well and quantum-dot (QD) structures are compared after controlled irradiation with 1.5 MeV proton fluxes. Results presented here show a significant enhancement in radiation tolerance with three-dimensional quantum confinement. Some additional radiation-induced changes in photocarrier recombination from QDs, which include a slight increase in PL emission with low and intermediate proton doses, are also examined. (C) 2000 American Institute of Physics. [S0003-6951(00)01615-6]. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Calif State Univ Los Angeles, Dept Phys & Astron, Los Angeles, CA 90032 USA. Univ Calif Los Angeles, Dept Elect Engn, Los Angeles, CA 90095 USA. Arizona State Univ, Dept Elect Engn, Tempe, AZ 85287 USA. Arizona State Univ, Ctr Solid State Elect Res, Tempe, AZ 85287 USA. RP Leon, R (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 22 TC 80 Z9 81 U1 2 U2 15 PU AMER INST PHYSICS PI MELVILLE PA 2 HUNTINGTON QUADRANGLE, STE 1NO1, MELVILLE, NY 11747-4501 USA SN 0003-6951 J9 APPL PHYS LETT JI Appl. Phys. Lett. PD APR 10 PY 2000 VL 76 IS 15 BP 2074 EP 2076 DI 10.1063/1.126259 PG 3 WC Physics, Applied SC Physics GA 301ER UT WOS:000086296200036 ER PT J AU Kawamura, J Miller, D Chen, J Zmuidzinas, J Bumble, B LeDuc, HG Stern, JA AF Kawamura, J Miller, D Chen, J Zmuidzinas, J Bumble, B LeDuc, HG Stern, JA TI Very high-current-density Nb/AlN/Nb tunnel junctions for low-noise submillimeter mixers SO APPLIED PHYSICS LETTERS LA English DT Article AB We have fabricated and tested submillimeter-wave superconductor-insulator-superconductor (SIS) mixers using very high-current-density Nb/AlN/Nb tunnel junctions (J(c) approximate to 30 kA cm(-2)). The junctions have low-resistance-area products (R(N)A approximate to 5.6 Ohm mu m(2)), good subgap-to-normal resistance ratios R-sg/R-N approximate to 10, and good run-to-run reproducibility. From Fourier transform spectrometer measurements, we infer that omega RNC = 1 at 270 GHz. This is a factor of 2.5 improvement over what is generally available with Nb/AlOx/Nb junctions suitable for low-noise mixers. The AlN-barrier junctions are indeed capable of low-noise operation: we measure an uncorrected double-sideband receiver noise temperature of T-RX = 110 K at 533 GHz for an unoptimized device. In addition to providing wider bandwidth operation at lower frequencies, the AlN-barrier junctions will considerably improve the performance of THz SIS mixers by reducing rf loss in the tuning circuits. (C) 2000 American Institute of Physics. [S0003-6951(00)04915-9]. C1 CALTECH, Pasadena, CA 91125 USA. Jet Prop Lab, Ctr Space Microelect Technol, San Marino, CA 91108 USA. RP Kawamura, J (reprint author), CALTECH, 320-47, Pasadena, CA 91125 USA. NR 12 TC 28 Z9 29 U1 0 U2 3 PU AMER INST PHYSICS PI MELVILLE PA 2 HUNTINGTON QUADRANGLE, STE 1NO1, MELVILLE, NY 11747-4501 USA SN 0003-6951 J9 APPL PHYS LETT JI Appl. Phys. Lett. PD APR 10 PY 2000 VL 76 IS 15 BP 2119 EP 2121 DI 10.1063/1.126272 PG 3 WC Physics, Applied SC Physics GA 301ER UT WOS:000086296200051 ER PT J AU Udry, S Mayor, M Naef, D Pepe, F Queloz, D Santos, NC Burnet, M Confino, B Melo, C AF Udry, S Mayor, M Naef, D Pepe, F Queloz, D Santos, NC Burnet, M Confino, B Melo, C TI The CORALIE survey for southern extra-solar planets II. The short-period planetary companions to HD 75289 and HD 130322 SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE techniques : radial velocities; binaries : spectroscopic; stars : individual : HD75289; stars : individual : HD 130322; stars : activity; planetary systems ID RADIAL-VELOCITY; ORBITAL MIGRATION; MAGNETIC ACTIVITY; GIANT PLANETS; COOL STARS; 51-PEGASI; SYSTEMS; PHOTOMETRY; BINARIES; DISK AB Doppler measurements from the high-resolution CORALIE spectrometer of the stars HD 75289 and HD 130322 reveal 2 new extra-solar giant planets. They are the second and third planetary candidates discovered with CORALIE in less than 1 year, since its installation on the 1.2-m Euler Swiss telescope at La Silla. The minimum mass of the planet around HD 75289 (m(2) sin i = 0.42 M-Jup) is the lightest found to date for a solar-type star companion. The orbital period is 3.5 days and the orbit is circular. The second candidate, a Jupiter-mass planet, orbits HD 130322 in 10.72 days, on an almost circular trajectory. Due to their small orbital periods, both planets belong to the hot Jupiter family, increasing thus the already large number of known Jupiter sized planets with orbits much smaller than in the solar system. C1 Observ Geneva, CH-1290 Sauverny, Switzerland. Jet Prop Lab, Pasadena, CA 91109 USA. St Luc Observ, CH-3961 St Luc, Switzerland. RP Udry, S (reprint author), Observ Geneva, 51 Ch Maillettes, CH-1290 Sauverny, Switzerland. EM stephane.udry@obs.unige.ch RI Santos, Nuno/E-9957-2011; Melo, Claudio/O-2797-2013 OI Santos, Nuno/0000-0003-4422-2919; NR 60 TC 172 Z9 172 U1 0 U2 2 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD APR 10 PY 2000 VL 356 IS 2 BP 590 EP 598 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 316RW UT WOS:000087182700024 ER PT J AU Santos, NC Mayor, M Naef, D Pepe, F Queloz, D Udry, S Burnet, M Revaz, Y AF Santos, NC Mayor, M Naef, D Pepe, F Queloz, D Udry, S Burnet, M Revaz, Y TI The CORALIE survey for Southern extra-solar planets III. A giant planet in orbit around HD 192263 SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE techniques : radial velocities; solar system : general; stars : individual : HD 192263; planetary systems ID MAGNETIC ACTIVITY; COOL STARS; VELOCITY; COLOR AB A new extra-solar planet has been discovered in the context of the CORALIE survey at La Silla Observatory. This new planetary candidate orbits the star HD 192263 in an almost circular orbit at a distance of 0.15 AU, producing a 24.13 day periodic radial-velocity variation, with a semi-amplitude of 62 ms(-1). The derived minimum mass of the planet is 0.73 M-Jup. C1 Observ Geneva, CH-1290 Sauverny, Switzerland. Jet Prop Lab, Pasadena, CA 91109 USA. RP Santos, NC (reprint author), Observ Geneva, 51 Ch Maillettes, CH-1290 Sauverny, Switzerland. EM Nuno.Santos@obs.unige.ch RI Santos, Nuno/E-9957-2011 OI Santos, Nuno/0000-0003-4422-2919 NR 23 TC 37 Z9 37 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 10 PY 2000 VL 356 IS 2 BP 599 EP 602 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 316RW UT WOS:000087182700025 ER PT J AU Reese, ED Mohr, JJ Carlstrom, JE Joy, M Grego, L Holder, GP Holzapfel, WL Hughes, JP Patel, SK Donahue, M AF Reese, ED Mohr, JJ Carlstrom, JE Joy, M Grego, L Holder, GP Holzapfel, WL Hughes, JP Patel, SK Donahue, M TI Sunyaev-Zeldovich effect-derived distances to the high-redshift clusters MS 0451.6-0305 and Cl 0016+16 SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmic microwave background; cosmology : observations; distance scale; galaxies : clusters : individual (MS 0451.6-0305, Cl 0016+16) techniques : interferometric ID X-RAY-PROPERTIES; RELATIVISTIC CORRECTIONS; HUBBLE-CONSTANT; THERMAL BREMSSTRAHLUNG; PECULIAR VELOCITIES; COOLING FLOWS; HOT PLASMA; GALAXIES; ROSAT; H-0 AB We determine the distances to the z similar or equal to 0.55 galaxy clusters MS 0451.6-0305 and Cl 0016+16 from a maximum-likelihood joint fit to interferometric Sunyaev-Zeldovich effect (SZE) and X-ray observations. We model the intracluster medium (ICM) using a spherical isothermal beta model. We quantify the statistical and systematic uncertainties inherent to these direct distance measurements, and we determine constraints on the Hubble parameter for three different cosmologies. For an Omega(M) = 0.3, Omega(A) = 0.7 cosmology, these distances imply a Hubble constant of 63(-9-21)(+12+21) km s(-1) Mpc(-1), where the uncertainties correspond to statistical followed by systematic at 68% confidence. The best-fit H-0 is 57 km s(-1) Mgc(-1) for an open (Omega(M) = 0.3) universe and 52 km s(-1) Mpc(-1) for a flat (Omega(M) = 1) universe. C1 Univ Chicago, Dept Astron & Astrophys, Chicago, IL 60637 USA. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. Univ Calif Berkeley, Dept Phys, Berkeley, CA 94720 USA. Rutgers State Univ, Dept Phys & Astron, Piscataway, NJ 08854 USA. CEA Saclay, Serv Astrophys, F-91191 Gif Sur Yvette, France. Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. RP Reese, ED (reprint author), Univ Chicago, Dept Astron & Astrophys, 5640 S Ellis Ave, Chicago, IL 60637 USA. RI Donahue, Megan/B-5361-2012; Holzapfel, William/I-4836-2015 NR 79 TC 74 Z9 74 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 10 PY 2000 VL 533 IS 1 BP 38 EP 49 DI 10.1086/308662 PN 1 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 309VL UT WOS:000086789900003 ER PT J AU Menn, W Hof, M Reimer, O Simon, M Davis, AJ Labrador, AE Mewaldt, RA Schindler, SM Barbier, LM Christian, ER Krombel, KE Krizmanic, JF Mitchell, JW Ormes, JF Streitmatter, RE Golden, RL Stochaj, SJ Webber, WR Rasmussen, IL AF Menn, W Hof, M Reimer, O Simon, M Davis, AJ Labrador, AE Mewaldt, RA Schindler, SM Barbier, LM Christian, ER Krombel, KE Krizmanic, JF Mitchell, JW Ormes, JF Streitmatter, RE Golden, RL Stochaj, SJ Webber, WR Rasmussen, IL TI The absolute flux of protons and helium at the top of the atmosphere using IMAX SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmic rays; elementary particles; ISM : abundances ID COSMIC-RAY PROTON; FRAGMENTATION CROSS-SECTIONS; RELATIVISTIC NUCLEI; CARBON TARGETS; SPECTRA; HYDROGEN; RATIO; SPECTROMETER; RADIATION; ANTIPROTONS AB The cosmic-ray proton and helium spectra from 0.2 GeV nucleon(-1) to about 200 GeV nucleon(-1) have been measured with the balloon-borne experiment Isotope Matter-Antimatter Experiment (IMAX) launched from Lynn Lake, Manitoba, Canada, in 1992. IMAX was designed to search for antiprotons and light isotopes using a superconducting magnet spectrometer together with scintillators, a time-of-flight system, and Cherenkov detectors. Using redundant detectors, an extensive examination of the instrument efficiency was carried out. We present here the absolute spectra of protons and helium corrected to the top of the atmosphere and to interstellar space. If demodulated with a solar modulation parameter of phi = 750 MV, the measured interstellar spectra between 20 and 200 GV can be represented by a power law in rigidity, with (1.42 +/- 0.21) x 10(4)R(-2.71+/-0.04) (m(2) GV s sr)(-1) for protons and (3.15 +/- 1.03) x 10(3)R(-2.79+/-0.08) (m(2) GV s sr)(-1) for helium. C1 Univ Siegen, D-57068 Siegen, Germany. CALTECH, Pasadena, CA 91125 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. New Mexico State Univ, Las Cruces, NM 88003 USA. Danish Space Res Inst, DK-2100 Copenhagen, Denmark. RP Menn, W (reprint author), Univ Siegen, D-57068 Siegen, Germany. RI Christian, Eric/D-4974-2012; Reimer, Olaf/A-3117-2013 OI Christian, Eric/0000-0003-2134-3937; Reimer, Olaf/0000-0001-6953-1385 NR 41 TC 118 Z9 119 U1 2 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 10 PY 2000 VL 533 IS 1 BP 281 EP 297 DI 10.1086/308645 PN 1 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 309VL UT WOS:000086789900025 ER PT J AU Mukai, K Smale, AP AF Mukai, K Smale, AP TI The low-mass X-ray binary X1832-330 in the globular cluster NGC 6652: A serendipitous ASCA observation SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries : close; X-rays : bursts; X-rays : stars ID NGC-6652; LUMINOSITY; DISCOVERY AB The low-mass X-ray binary (LMXB) X1832-330 in NGC 6652 is one of 12 bright, or transient, X-ray sources to have been discovered in globular clusters. We report on a serendipitous ASCA observation of this globular cluster LMXB, during which a type I burst was detected and the persistent, nonburst emission of the source was at its brightest level recorded to date. No orbital modulation was detected, which argues against a high inclination for the X1832-330 system. The spectrum of the persistent emission can be fitted with a power law plus a partial covering absorber, although other models are not ruled out. Our time-resolved spectral analysis through the burst shows, for the first time, clear evidence for spectral cooling from kT = 2.4 +/- 0.6 keV to kT = 1.0 +/- 0.1 keV during the decay. The measured peak flux during the burst is similar to 10% of the Eddington luminosity for a 1.4 M. neutron star. These quantities are characteristic of a type I burst, in the context of the relatively low quiescent luminosity of X1832-330. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Mukai, K (reprint author), NASA, Goddard Space Flight Ctr, Code 662, Greenbelt, MD 20771 USA. NR 15 TC 12 Z9 12 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 10 PY 2000 VL 533 IS 1 BP 352 EP 357 DI 10.1086/308648 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 309VL UT WOS:000086789900030 ER PT J AU Goodman, ML AF Goodman, ML TI On the mechanism of chromospheric network heating and the condition for its onset in the sun and other solar-type stars SO ASTROPHYSICAL JOURNAL LA English DT Article DE MHD; stars : chromospheres; Sun : chromosphere; Sun : magnetic fields waves ID MAGNETIC-FLUX TUBES; BRIGHT POINTS; CONVECTIVE COLLAPSE; QUIET SUN; K-GRAINS; FIELDS; OSCILLATIONS; ATMOSPHERE; FEATURES; GRANULES AB A mechanism for chromospheric network heating and a necessary and sufficient condition for its onset are presented. The heating mechanism consists of resistive dissipation of proton Pedersen currents, which flow orthogonal to the magnetic field in weakly ionized chromospheric plasma. The currents are driven by a convection electric field generated by velocity oscillations of linear, slow, longitudinal magnetoacoustic waves with frequencies nu less than or similar to 3.5 mHz in the lower chromosphere. The heating occurs in thin magnetic flux tubes and begins lower in the chromosphere in flux tubes with higher photospheric field strength. The lower chromosphere, which emits most of the net radiative loss in the network, is heated by flux tubes with photospheric field strengths similar to 700-1500 G. A typical field strength and core diameter for a flux tube in the lower chromosphere with a core heating rate of 10(7) ergs cm(-2) s(-1) are 170 G and 10 km. This core region is contained in a region with a diameter similar to 100 km in which the heating rate is an order of magnitude smaller. About N similar to 10(2) of these flux tubes distributed over the boundary region of a granule with a diameter similar to 10(3) km provide an average heating rate over the entire granule similar to 10(7) ergs cm(-2) s(-1). If the core heating rate is changed by a factor f; then N similar to f(-1/2)10(2). The condition for the onset of heating is that the ratio of the proton cyclotron frequency to the proton-hydrogen collision frequency equal unity. This ratio increases with height, and the condition is satisfied at a single height in a given flux tube. At this height, control of the proton dynamics begins to be dominated by the magnetic field rather than by collisions with hydrogen, and the anisotropic nature of the electrical conductivity begins to play a critical role in resistive dissipation. The protons become magnetized. Heating by dissipation of heavy ion and, to a lesser extent, proton Pedersen currents causes the temperature to start increasing. The heating increases hydrogen ionization. With increasing height, and hence proton magnetization, the Pedersen current density rapidly increases with hydrogen ionization via positive feedback, and the proton number density rapidly reaches and exceeds the heavy ion number density, resulting in an increase in heating rate by an order of magnitude over only 1 pressure scale height. During this process the protons rapidly dominate the Pedersen current. Heating by dissipation of magnetic field aligned currents is insignificant. Below the height in the atmosphere at which the onset condition is satisfied, any current orthogonal to the magnetic field must be primarily a Hall current, which is nondissipative. Heating by this mechanism must occur to some degree in the chromospheric network of all solar-type stars. It is proposed to be the dominant mechanism of chromospheric network heating, although viscous dissipation may also be important if the core heating rate is much larger than similar to 107 cm(-2) s(-1) or if the linear MHD waves studied here evolve into shock waves with increasing height. Flux tubes in the quiet chromosphere are predicted to have two possible core diameters: similar to 10 km, corresponding to flux tubes in which network heating occurs, and similar to 10(4)-10(5) km, perhaps corresponding to flux tubes in which active region heating might occur. The model has a singularity at the acoustic cutoff frequency, corresponding to periods near 3 minutes. Therefore, unless nonresistive damping mechanisms such as viscous dissipation and thermal conduction provide sufficiently strong damping, MHD oscillations with periods near 3 minutes in chromospheric magnetic flux tubes must be nonlinear. C1 Catholic Univ Amer, Dept Phys, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RP Catholic Univ Amer, Dept Phys, Code 695, Greenbelt, MD 20771 USA. EM goodman@spof02.gsfc.nasa.gov NR 51 TC 47 Z9 47 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 APR 10 PY 2000 VL 533 IS 1 BP 501 EP 522 DI 10.1086/308635 PN 1 PG 22 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 309VL UT WOS:000086789900042 ER PT J AU Chou, DY Duvall, TL AF Chou, DY Duvall, TL TI Phase time and envelope time in time-distance analysis and acoustic imaging SO ASTROPHYSICAL JOURNAL LA English DT Article DE Sun : oscillations; Sun : magnetic fields; sunspots ID HELIOSEISMIC TOMOGRAPHY; TRAVEL-TIME; SUNSPOTS AB Time-distance analysis and acoustic imaging are two related techniques for probing the local properties of the solar interior. In this study, we discuss the relation of phase time and envelope time between the two techniques. The location of the envelope peak of the cross-correlation function in time-distance analysis is identified as the travel time of the wave packet formed by modes with the same horizontal phase velocity. The phase time of the cross-correlation function provides information on the phase change accumulated along the wave path, including the phase change at the boundaries of the mode cavity. The acoustic signals constructed with the technique of acoustic imaging contain both phase and intensity information. The phase of constructed signals can be studied by computing the crosscorrelation function between time series constructed with ingoing and outgoing waves. We use a simple theory of wave packets to obtain two predictions about the cross-correlation function of constructed ingoing and outgoing time series. First, if the envelope time measured in time-distance analysis is used to construct signals in acoustic imaging, the envelope time of the cross-correlation is zero. Second, the phase time of the cross-correlation is twice the difference between the phase time and envelope time measured in time-distance analysis. In this study, we use data taken with the Taiwan Oscillation Network (TON) instrument and the Michelson Doppler Imager (MDI) instrument. The analysis is carried out for the quiet Sun. We use the relation of envelope time versus distance measured in time-distance analysis to construct the acoustic signals in acoustic imaging analysis. The phase time of the cross-correlation function of constructed ingoing and outgoing time series is twice the difference between phase time and envelope time in time-distance analysis, as predicted. The envelope peak of the crosscorrelation function between constructed ingoing and outgoing time series is located at zero time, as predicted for one-bounce results at 3 mHz for all four data sets and two-bounce results at 3 mHz for two TON data sets, but it is different from zero for other cases. The deviation of the envelope peak from zero has the same sign for all these cases. The cause is not known. C1 Natl Tsing Hua Univ, Dept Phys, Hsinchu 30043, Taiwan. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Chou, DY (reprint author), Natl Tsing Hua Univ, Dept Phys, Hsinchu 30043, Taiwan. RI Duvall, Thomas/C-9998-2012 NR 21 TC 19 Z9 19 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 10 PY 2000 VL 533 IS 1 BP 568 EP 573 DI 10.1086/308655 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 309VL UT WOS:000086789900047 ER PT J AU Colina, L Arribas, S Borne, KD Monreal, A AF Colina, L Arribas, S Borne, KD Monreal, A TI Detection and mapping of decoupled stellar and ionized gas structures in the ultraluminous infrared galaxy IRAS 12112+0305 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : active; galaxies : individual (IRAS 12112+0305); galaxies : interactions; galaxies : nuclei; galaxies : starburst ID STAR-FORMATION; LINERS; SPECTROSCOPY; REGIONS; SYSTEM; MODELS AB Integral field optical spectroscopy with the INTEGRAL fiber-fed system and Hubble Space Telescope optical imaging are used to map the complex stellar and warm ionized gas structure in the ultraluminous infrared galaxy IRAS 12112+0305. Images reconstructed from wavelength-delimited extractions of the integral field spectra reveal that the observed ionized gas distribution is decoupled from the stellar main body of the galaxy, with the dominant continuum and emission-line regions separated by projected distances of up to 7.5 kpc. The two optical nuclei are detected as apparently faint emission-line regions, and their optical properties are consistent with being dust-enshrouded weak [O (I)] LINERs. The brightest emission-line region is associated with a faint (m(I) = 20.4), giant H (II) region of 600 pc diameter, in which a young (similar to 5 Myr) massive cluster of about 2 x 10(7) M. dominates the ionization. Internal reddening toward the line-emitting regions and the optical nuclei ranges from 1 to 8 mag in the visual. Taking the reddening into account, the overall star formation in IRAS 12112+0305 is dominated by starbursts associated with the two nuclei and corresponds to a star formation rate of 80 M. yr(-1). C1 CSIC, Fac Ciencias, Inst Fis Cantabria, UC, Santander 39005, Spain. Inst Astrofis Canarias, La Laguna 38200, Tenerife, Spain. NASA, Goddard Space Flight Ctr, Raytheon Informat Technol & Sci Serv, Greenbelt, MD 20771 USA. RP Colina, L (reprint author), CSIC, Fac Ciencias, Inst Fis Cantabria, UC, Avenida Los Castros S-N, Santander 39005, Spain. NR 28 TC 18 Z9 18 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 10 PY 2000 VL 533 IS 1 BP L9 EP L12 DI 10.1086/312590 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 309VN UT WOS:000086790100003 ER PT J AU Figer, DF Becklin, EE McLean, IS Gilbert, AM Graham, JR Larkin, JE Levenson, NA Teplitz, HI Wilcox, MK Morris, M AF Figer, DF Becklin, EE McLean, IS Gilbert, AM Graham, JR Larkin, JE Levenson, NA Teplitz, HI Wilcox, MK Morris, M TI 2 micron spectroscopy within 0 ''.13 of Sagittarius A SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxy : center; infrared : stars; ISM : individual (Sagittarius A*); stars : formation; techniques : spectroscopic ID GALACTIC-CENTER; MASSIVE STARS; A-ASTERISK; BLACK-HOLE; GALAXY AB We present moderate- (R approximate to 2700) and high-resolution (R approximate to 22,400) 2.0-2.4 mu m spectroscopy of the central 0.1 arcsec(2) of the Galaxy obtained with the facility near-infrared spectrometer (NIRSPEC) for the Keek II telescope. The composite spectra do not have any features attributable to the brightest stars in the central cluster; i.e., after background subtraction, W12CO(2-0) < 2 Angstrom. This Stringent limit leads us to conclude that the majority, if not all, of the stars are hotter than typical red giants. Coupled with previously reported photometry, we conclude that the sources are likely OB main-sequence stars. In addition, the continuum slope in the composite spectrum is bluer than that of a red giant and is similar to that of the nearby hot star IRS 16NW. It is unlikely that they are late-type giants stripped of their outer envelopes because such sources would be much fainter than those observed. Given their inferred youth (tau(age) < 20 Myr), we suggest the possibility that the stars have formed within 0.1 pc of the supermassive black hole. We find a newly identified broad-line component (V-FWHM approximate to 1000 km s(-1)) toward the 2.2178 mu m [Fe III] line located within a few arcseconds of Sagittarius AX. A similar component is not seen in the Br gamma emission. C1 Space Telescope Sci Inst, Baltimore, MD 21218 USA. Univ Calif Los Angeles, Dept Phys & Astron, Div Astron & Astrophys, Los Angeles, CA 90095 USA. Univ Calif Berkeley, Dept Astron, Berkeley, CA 94720 USA. Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Figer, DF (reprint author), Space Telescope Sci Inst, 3700 San Martin Dr, Baltimore, MD 21218 USA. NR 20 TC 30 Z9 30 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 10 PY 2000 VL 533 IS 1 BP L49 EP L52 DI 10.1086/312596 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 309VN UT WOS:000086790100013 ER PT J AU Gilbert, AM Graham, JR McLean, IS Becklin, EE Figer, DF Larkin, JE Levenson, NA Teplitz, HI Wilcox, MK AF Gilbert, AM Graham, JR McLean, IS Becklin, EE Figer, DF Larkin, JE Levenson, NA Teplitz, HI Wilcox, MK TI Infrared spectroscopy of a massive obscured star cluster in the Antennae galaxies (NGC 4038/9) with NIRSPEC SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : individual (NGC 4038/9); galaxies : ISM; galaxies : starburst; galaxies : star clusters; HII regions; infrared : galaxies ID PHOTODISSOCIATION REGIONS; STARBURST GALAXIES; GAMMA-RATIO; EMISSION; NGC-4038/4039; TELESCOPE; HYDROGEN; MICRONS; HELIUM AB We present infrared spectroscopy of the Antennae galaxies (NCC 4038/9) with the near-infrared spectrometer (NIRSPEC) at the W. M. Keck Observatory. We imaged the star clusters in the vicinity of the southern nucleus (NGC 4039) with 0".39 seeing in the K band using NDRSPEC's slit-viewing camera. The brightest star cluster revealed in the near-IR [M-K(0) = 17.9] is insignificant optically but is coincident with the highest surface brightness peak in the mid-IR (12-18 mu m) Infrared Space Observatory image presented by Mirabel et al. We obtained high signal-to-noise ratio 2.03-2.45 mu m spectra of the nucleus and the obscured star cluster at R similar to 1900. The cluster is very young (similar to 4 Myr), massive (M similar to 16 x 10(6) M.), and compact (with a density of similar to 115 M. pc(-3) within a 32 pc half-light radius), assuming a Salpeter initial mass function (0.1-100 M.). Its hot stars have a radiation field characterized by T-eff similar to 39,000 K, and they ionize a compact H (II) region with n(e) similar to 10(4) cm(-3). The stars are deeply embedded in gas and dust (A(v) similar to 9-10 mag), and their strong far-ultraviolet field cm powers a clumpy photodissociation region with densities n(H) greater than or similar to 10(5) cm(-3) on scales of similar to 200 pc, radiating L-H2 (1-OS(1)) = 9600 L.. C1 Univ Calif Berkeley, Dept Astron, Berkeley, CA 94720 USA. Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Gilbert, AM (reprint author), Univ Calif Berkeley, Dept Astron, 601 Campbell Hall, Berkeley, CA 94720 USA. NR 26 TC 47 Z9 47 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 10 PY 2000 VL 533 IS 1 BP L57 EP L60 DI 10.1086/312599 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 309VN UT WOS:000086790100015 ER PT J AU Larkin, JE McLean, IS Graham, JR Becklin, EE Figer, DF Gilbert, AM Levenson, NA Teplitz, HI Wilcox, MK Glassman, TM AF Larkin, JE McLean, IS Graham, JR Becklin, EE Figer, DF Gilbert, AM Levenson, NA Teplitz, HI Wilcox, MK Glassman, TM TI Discovery of an obscured broad-line region in the high-redshift radio galaxy MRC 2025-218 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : active; galaxies : kinematics and dynamics; galaxies : structure; infrared : galaxies; quasars : general ID INFRARED-SPECTROSCOPY; STAR FORMATION; ALIGNMENT; QUASARS; GAS AB Letter presents infrared spectra taken with the newly commissioned near-infrared spectrometer (NIRSPEC) on the Keek II telescope of the high-redshift radio galaxy MRC 2025 - 218 (z = 2.63). These observations represent the deepest infrared spectra of a radio galaxy to date and have allowed for the detection of H beta, [O III] lambda lambda 4959, 5007, [O I] lambda 6300, H alpha, [N II] lambda lambda 6548, 6583, and [S II] lambda lambda 6716, 6713. The H alpha emission is very broad (FWHM = 9300 km s(-1)) and luminous (2.6 x 10(44) ergs s(-1)), and it is very comparable to the line widths and strengths of radio-loud quasars at the same redshift. This strongly supports active galactic nucleus unification models linking radio galaxies and quasars, although we discuss some of the outstanding differences. The line [O III] lambda 5007 is extremely strong and has extended emission with large relative velocities toward the nucleus. We also derive that if the extended emission is due to star formation, each knot has a star formation rate comparable to a Lyman-break galaxy at the same redshift. C1 Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA. Univ Calif Berkeley, Dept Astron, Berkeley, CA 94720 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Larkin, JE (reprint author), Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA. NR 29 TC 9 Z9 9 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 10 PY 2000 VL 533 IS 1 BP L61 EP L64 DI 10.1086/312598 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 309VN UT WOS:000086790100016 ER PT J AU Levenson, NA Graham, JR McLean, IS Becklin, EE Figer, DF Gilbert, AM Larkin, JE Teplitz, HI Wilcox, MK AF Levenson, NA Graham, JR McLean, IS Becklin, EE Figer, DF Gilbert, AM Larkin, JE Teplitz, HI Wilcox, MK TI Hot stars and cool clouds: The photodissociation region M16 SO ASTROPHYSICAL JOURNAL LA English DT Article DE infrared : ISM : lines and bands; ISM : individual (M16); molecular processes ID MOLECULAR-HYDROGEN; EAGLE NEBULA; PHOTOEVAPORATION; RADIATION; TELESCOPE; GALAXIES; FRONTS; GAS AB We present high-resolution spectroscopy and images of a photodissociation region (PDR) in M16 obtained during commissioning of the near-infrared spectrometer (NIRSPEC) on the Keck IT telescope. PDRs play a significant role in regulating star formation, and M16 offers the opportunity to examine the physical processes of a PDR in detail. We simultaneously observe both the molecular and ionized phases of the PDR and resolve the spatial and kinematic differences between them. The most prominent regions of the PDR are viewed edge-on. Fluorescent emission from nearby stars is the primary excitation source, although collisions also preferentially populate the lowest vibrational levels of H-2. Variations in density-sensitive emission-line ratios demonstrate that the molecular cloud is clumpy, with an average density n = 3 x 10(5) cm(-3). We measure the kinetic temperature of the molecular region directly and find that T-H2 = 930 K. The observed density, temperature, and UV flux imply a photoelectric heating efficiency of 4%. In the ionized region, n(i) = 5 x 10(3) cm(-3) and T-H II = 9500 K. In the brightest regions of the PDR, the recombination line widths include a nonthermal component, which we attribute to viewing geometry. C1 Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA. Univ Calif Berkeley, Dept Astron, Berkeley, CA 94720 USA. Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Levenson, NA (reprint author), Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA. OI Levenson, Nancy A./0000-0003-4209-639X NR 22 TC 20 Z9 20 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 10 PY 2000 VL 533 IS 1 BP L53 EP L56 DI 10.1086/312601 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 309VN UT WOS:000086790100014 ER PT J AU McLean, IS Wilcox, MK Becklin, EE Figer, DF Gilbert, AM Graham, JR Larkin, JE Levenson, NA Teplitz, HI Kirkpatrick, JD AF McLean, IS Wilcox, MK Becklin, EE Figer, DF Gilbert, AM Graham, JR Larkin, JE Levenson, NA Teplitz, HI Kirkpatrick, JD TI J-band infrared spectroscopy of a sample of brown dwarfs using NIRSPEC on Keck II SO ASTROPHYSICAL JOURNAL LA English DT Article DE infrared : stars; stars : atmospheres; stars : low-mass, brown dwarfs ID ATMOSPHERES; DENIS AB Near-infrared spectroscopic observations of a sample of very cool, low-mass objects are presented with higher spectral resolution than in any previous studies. Six of the objects are L dwarfs, ranging in spectral class from L2 to L8/9, and che seventh is a methane or T dwarf. These new observations were obtained during commissioning of the near-infrared spectrometer (NIRSPEC), the first high-resolution near-infrared cryogenic spectrograph for the Keck II 10 m telescope on Mauna Kea, Hawaii. Spectra with a resolving power of R approximate to 2500 from 1.135 to 1.360 mu m (approximately J band) are presented for each source. At this resolution, a rich spectral structure is revealed, much of which is due to blending of unresolved molecular transitions. Strong lines due to neutral potassium (K (I)) and bands due to iron hydride (FeH) and steam (H(2)O) change significantly throughout the L sequence. Iron hydride disappears between L5 and L8, the steam bands deepen, and the K (I) lines gradually become weaker but wider because of pressure broadening. An unidentified feature occurs at 1.22 mu m that has a temperature dependence like FeH but has no counterpart in the available FeH opacity data. Because these objects are 3-6 mag brighter in the near-infrared compared with the I band, spectral classification is efficient. One of the objects studied (2MASSW J1523 + 3014) is the coolest L dwarf discovered so far by the 2 Micron All-Sky Survey (2MASS), but its spectrum is still significantly different from the methane-dominated objects such as Gl 229B or SDSS 1624+0029. C1 Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Univ Calif Berkeley, Dept Astron, Berkeley, CA 94720 USA. Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. CALTECH, Ctr Infrared Proc & Anal, Pasadena, CA 91125 USA. RP McLean, IS (reprint author), Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA. NR 17 TC 44 Z9 44 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 10 PY 2000 VL 533 IS 1 BP L45 EP L48 DI 10.1086/312600 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 309VN UT WOS:000086790100012 ER PT J AU Teplitz, HI McLean, IS Becklin, EE Figer, DF Gilbert, AM Graham, JR Larkin, JE Levenson, NA Wilcox, MK AF Teplitz, HI McLean, IS Becklin, EE Figer, DF Gilbert, AM Graham, JR Larkin, JE Levenson, NA Wilcox, MK TI The rest-frame optical spectrum of MS 1512-cB58 SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmology : observations; galaxies : evolution; galaxies : individual (MS 1512-cB58) ID H-II REGIONS; STAR-FORMATION; SOUTHERN GALAXIES; CANDIDATE; EXTINCTION; ABUNDANCES; RATIOS; Z=2.72; CB58 AB Moderate-resolution, near-IR spectroscopy of MS 1512-cB58 is presented, obtained during commissioning of the near-infrared spectrometer (NIRSPEC) on the Reck II telescope. The strong lensing of this z = 2.72 galaxy by the foreground cluster MS 1512+36 makes it the best candidate for detailed study of the rest-frame optical properties of Lyman-break galaxies. In 80 minutes of on-source integration, we have detected H alpha, [N II] lambda lambda 6583, 6548, [O I] lambda 6300, He I lambda 5876, [O III] lambda lambda 5007, 4959, H beta, H gamma, [O II] lambda 3727, and a strong continuum signal in the range of 1.29-2.46 mu m. A redshift of z = 2.7290 +/- 0.0007 is inferred from the emission lines, in contrast to the z = 2.7233 calculated from UV observations of interstellar absorption lines. Using the Balmer line ratios, we find an extinction of E(B-V) = 0.27. Using the line strengths? we infer a star formation rate (SFR) of 620 +/- 18 M. yr(-1) (H-0 = 75, q(0) = 0.1, and Lambda = 0), which is a factor of 2 higher than that measured from narrowband imaging observations of the galaxy but is a factor of almost 4 lower than the SFR inferred from the UV continuum luminosity. The width of the Balmer lines yields a mass of M-vir = 1.2 x 10(10) M.. We find that the oxygen abundance is 1/3 solar, in good agreement with other estimates of the metallicity. However, we infer a high nitrogen abundance, which may argue for the presence of an older stellar population. C1 NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Univ Calif Berkeley, Dept Astron, Berkeley, CA 94720 USA. Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA. RP Teplitz, HI (reprint author), NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Code 681, Greenbelt, MD 20771 USA. NR 33 TC 109 Z9 109 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 10 PY 2000 VL 533 IS 1 BP L65 EP L68 DI 10.1086/312595 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 309VN UT WOS:000086790100017 ER PT J AU Laure, E Haines, M Mehrotra, P Zima, H AF Laure, E Haines, M Mehrotra, P Zima, H TI On the implementation of the Opus coordination language SO CONCURRENCY-PRACTICE AND EXPERIENCE LA English DT Article DE opus; task parallelism; data parallelism; coordination ID COMMUNICATION; PARALLELISM; SYSTEMS; TASK AB Opus is a new programming language designed to assist in coordinating the execution of multiple, independent program modules. With the help of Opus, coarse grained tush parallelism between data parallel modules can be expressed in a clean and structured way, In this paper we address the problems of how to build a compilation and runtime support system that can efficiently implement the Opus constructs, Our design considers the often-conflicting goals of efficiency and modular construction through software re-use, In particular, we present the system requirements for an efficient Opus implementation, the Opus runtime system, and describe how they work together to provide the underlying services that the Opus compiler needs for a broad class of machines, Copyright (C) 2000 John Wiley & Sons, Ltd. C1 Univ Vienna, Inst Software Technol & Parallel Syst, A-1090 Vienna, Austria. Univ Wyoming, Dept Comp Sci, Laramie, WY 82071 USA. NASA, Inst Comp Applicat Sci & Engn, Langley Res Ctr, Hampton, VA 23681 USA. RP Laure, E (reprint author), Univ Vienna, Inst Software Technol & Parallel Syst, Liechtensteinstr 22, A-1090 Vienna, Austria. NR 29 TC 2 Z9 2 U1 0 U2 0 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX PO19 1UD, ENGLAND SN 1040-3108 J9 CONCURRENCY-PRACT EX JI Concurrency-Pract. Exp. PD APR 10 PY 2000 VL 12 IS 4 BP 227 EP 249 DI 10.1002/(SICI)1096-9128(20000410)12:4<227::AID-CPE474>3.3.CO;2-8 PG 23 WC Computer Science, Software Engineering; Computer Science, Theory & Methods SC Computer Science GA 319BT UT WOS:000087320100002 ER PT J AU Pollitz, FF Peltzer, G Burgmann, R AF Pollitz, FF Peltzer, G Burgmann, R TI Mobility of continental mantle: Evidence from postseismic geodetic observations following the 1992 Landers earthquake SO JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH LA English DT Article ID SOUTHWESTERN UNITED-STATES; COMPOSITE LOWER CRUST; ANDREAS FAULT ZONE; 28 JUNE 1992; SOUTHERN CALIFORNIA; MOJAVE DESERT; STRESS DIFFUSION; HEAT-FLOW; NORTHERN CALIFORNIA; EASTERN CALIFORNIA AB The crust around the rupture zone of the 1992 Landers earthquake has continued to deform in the years following the earthquake at rates similar to 3 times greater than pre-earthquake rates. We use a combination of Global Positioning System (GPS) and synthetic aperture radar (InSAR) data collected during a similar to 3-year epoch following the earthquake in order to investigate postseismic mechanisms responsible for the high transient velocities. In order to maximize the potential signal from viscoelastic relaxation we evaluate and model postseismic relaxation following the first few months of documented accelerated deformation. The combination of GPS and InSAR data allows us to establish viscoelastic relaxation of the lower crust and upper mantle as the dominant postseismic process and to discriminate among possible viscoelastic models. The data particularly require the presence of a highly ductile uppermost mantle beneath the central Mojave Domain, with temperature between the wet and dry basalt solidus. This is consistent with independent seismic and geochemical inferences of a regionally warm uppermost mantle. Further consideration of seismic velocity variations in conjunction with faulting patterns within the Mojave Desert suggests that the primary faulting characteristics of the Mojave Desert, namely, the pervasive late Cenozoic deformation within the Eastern California Shear Zone versus the near absence of faults in the Western Mojave Domain, are controlled by the rheology of the uppermost mantle. C1 Univ Calif Davis, Dept Geol, Livermore, CA 95616 USA. Univ Calif Berkeley, Dept Geol & Geophys, Berkeley, CA 94720 USA. Jet Propuls Lab, Pasadena, CA 91109 USA. RP Pollitz, FF (reprint author), Univ Calif Davis, Dept Geol, 1 Shields Ave, Livermore, CA 95616 USA. EM pollitz@geology.ucdavis.edu NR 84 TC 149 Z9 157 U1 1 U2 11 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 2000 VL 105 IS B4 BP 8035 EP 8054 DI 10.1029/1999JB900380 PG 20 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 303RK UT WOS:000086437500015 ER PT J AU Sauber, J Plafker, G Molnia, BF Bryant, MA AF Sauber, J Plafker, G Molnia, BF Bryant, MA TI Crustal deformation associated with glacial fluctuations in the eastern Chugach Mountains, Alaska SO JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH LA English DT Article ID SOUTH CENTRAL ALASKA; BERING GLACIER; GEODETIC MEASUREMENT; 1987-1988 GULF; FINITE-ELEMENT; UPPER-MANTLE; SEA-LEVEL; EARTHQUAKE; SURGE; UPLIFT AB The changes of the solid Earth in south central Alaska in response to two major glacial fluctuations on different temporal and spatial scales have been estimated and we evaluated their influence on the stress state and ongoing tectonic deformation of the region. During the recent (1993-1995) Bering Glacier surge, a large transfer of ice from the Bagley Ice Field to the Bering Glacier terminus region occurred. We estimated the elastic displacement of the solid Earth due to ice mass redistribution from Global Positioning System (GPS) measurements at sites near the surging glacier. We can account for these displacements by transfer of an ice volume of about 14 km(3) from the surge reservoir area to the terminus region. We examined the background seismicity (M-L greater than or equal to 2.5) before, during, and after the surge. We found that the occurrence of small earthquakes (M-L less than or equal to 4.0) in the surge reservoir region increased during the surge time interval possibly in response to a decrease in ice mass. This suggests that a Small decrease in the vertical stress, sigma(3), could be enough to modulate the occurrence of small, shallow earthquakes in this dominantly thrust fault setting. During this century the southern Alaska coastal glaciers have been undergoing an overall decrease in volume. Based on our compilation of changes in the extent and thickness of the coastal glaciers between the Malaspina and Bering, we calculated surface displacements due to the Earth's viscoelastic response to annual thinning and to the cumulative retreat over the last 100 years. The uplift of the region due to an average annual thinning rate of 1-6 m/yr in the ablation region is 1-12 mm/yr. For our reference model with a viscosity of 5 x 10(19) Pa s for depths between approximate to 40 and 200 km the total viscoelastic response due to the retreat over the last century may be as much as a couple of meters within the coastal ablation zone near Icy Bay. The maximum decrease in sigma(V) between 0 and 10 km was approximate to 1.0 MPa, which is significant in relation to the stress drops in recent earthquakes (approximate to 2 to 10 MPa) but small in relation to the estimated tectonic stress magnitude. Therefore the occurrence of an earthquake such as the St. Elias (1979, M-S = 7.2) may have been advanced in time; however, most of the ongoing stress accumulation would be primarily due to tectonic forces. C1 NASA, Goddard Space Flight Ctr, Geodynam Branch, Greenbelt, MD 20771 USA. ASHTECH, Reston, VA 20191 USA. US Geol Survey, Reston, VA 20192 USA. US Geol Survey, Menlo Park, CA 94025 USA. RP Sauber, J (reprint author), NASA, Goddard Space Flight Ctr, Geodynam Branch, Code 921, Greenbelt, MD 20771 USA. EM jeanne@steller.gsfc.nasa.gov RI Sauber, Jeanne/D-7684-2012 NR 79 TC 32 Z9 32 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 2000 VL 105 IS B4 BP 8055 EP 8077 DI 10.1029/1999JB900433 PG 23 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 303RK UT WOS:000086437500016 ER PT J AU Freymueller, JT Cohen, SC Fletcher, HJ AF Freymueller, JT Cohen, SC Fletcher, HJ TI Spatial variations in present-day deformation, Kenai Peninsula, Alaska, and their implications SO JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH LA English DT Article ID WILLIAM-SOUND EARTHQUAKE; GLACIAL-ISOSTATIC-ADJUSTMENT; SUBDUCTION ZONES; HALF-SPACE; DISLOCATION MODEL; TENSILE FAULTS; UPLIFT; RELEASE; INVERSION; SHEAR AB From four years of Global Positioning System (GPS) measurements, we find significant spatial variations in present-day deformation between the eastern and western Kenai Peninsula, Alaska. Sites in the eastern Kenai Peninsula and Prince William Sound move to the NNW relative to North America, in the direction of Pacific-North America relative plate motion. Velocities decrease in magnitude from nearly the full plate rate in southern Prince William Sound to about 30 mm/yr at Seward and to about 5 mm/yr near Anchorage. In contrast, sites in the western Kenai Peninsula move to the SW, in a nearly trenchward direction, with a velocity of about 20 mm/yr. The data are consistent with the shallow plate interface offshore and beneath the eastern Kenai and Prince William Sound being completely locked or nearly so, with elastic strain accumulation resulting in rapid motion in the direction of relative plate motion of sites in the overriding plate. The velocities of sites in the western Kenai, along strike to the southwest, are opposite in sign with those predicted from elastic strain accumulation. These data are incompatible with a significant locked region in this segment of the plate boundary. Trenchward velocities are found also for some sites in the Anchorage area. We interpret the trenchward velocities as being caused by a continuing postseismic transient from the 1964 great Alaska earthquake. There may be significant along-strike differences in the long-term behavior of the plate interface between the western and eastern Kenai, based on roughly coincident boundaries in the coseismic slip distribution, cumulative postseismic uplift, present-day plate coupling, and stress field. The present postseismic response appears to generate purely trenchward motion, suggesting a creep process that is purely dip slip. Our observations suggest that postseismic processes after the largest earthquakes can influence patterns of deformation for decades after the event. C1 Univ Alaska Fairbanks, Inst Geophys, Fairbanks, AK 99775 USA. NASA, Goddard Space Flight Ctr, Geodynam Branch, Greenbelt, MD 20771 USA. RP Freymueller, JT (reprint author), Univ Alaska Fairbanks, Inst Geophys, POB 757320, Fairbanks, AK 99775 USA. EM jeff@giseis.alaska.edu NR 61 TC 63 Z9 63 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 2000 VL 105 IS B4 BP 8079 EP 8101 DI 10.1029/1999JB900388 PG 23 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 303RK UT WOS:000086437500017 ER PT J AU Younis, BA Gatski, TB Speziale, CG AF Younis, BA Gatski, TB Speziale, CG TI Towards a rational model for the triple velocity correlations of turbulence SO PROCEEDINGS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES LA English DT Article DE representation theorem; triple velocity correlations; turbulence ID REYNOLDS-STRESS; BOUNDARY-LAYER; FLOWS AB The purpose of this paper is to present a rational approach to modelling the triple velocity correlations that appear in the transport equations for the Reynolds stresses. All existing models of these correlations have largely been formulated on phenomenological grounds and are defective in one important aspect: they all neglect to allow for the dependence of these correlations on the local gradients of mean velocity. The mathematical necessity for this dependence will be demonstrated in the paper. The present contribution lies in the novel use of group representation theory to determine the most general tensorial form of these correlations in terms of all the second- and third-order tensor quantities which appear in the exact equations that govern their evolution. The requisite representation did not exist in the literature and had therefore to be developed specifically for this purpose. The outcome of this work is a mathematical framework for the construction of algebraic, explicit and rational models for the triple velocity correlations that are theoretically consistent and include all the correct dependencies. Previous models are reviewed, and all are shown to be incomplete subsets of this new representation, even to lowest order. C1 City Univ London, Dept Civil Engn, London EC1V 0HB, England. NASA, Langley Res Ctr, Aerodynam & Acoust Methods Branch, Hampton, VA USA. Boston Univ, Dept Aerosp & Mech Engn, Boston, MA 02215 USA. RP Younis, BA (reprint author), City Univ London, Dept Civil Engn, London EC1V 0HB, England. NR 17 TC 14 Z9 14 U1 0 U2 4 PU ROYAL SOC PI LONDON PA 6-9 CARLTON HOUSE TERRACE, LONDON SW1Y 5AG, ENGLAND SN 1364-5021 EI 1471-2946 J9 P ROY SOC A-MATH PHY JI Proc. R. Soc. A-Math. Phys. Eng. Sci. PD APR 8 PY 2000 VL 456 IS 1996 BP 909 EP 920 PG 12 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 305CW UT WOS:000086522300006 ER PT J AU Anbar, AD Roe, JE Barling, J Nealson, KH AF Anbar, AD Roe, JE Barling, J Nealson, KH TI Nonbiological fractionation of iron isotopes SO SCIENCE LA English DT Article ID CHLORIDE SOLUTIONS; COMPLEXES AB Laboratory experiments demonstrate that iron isotopes can be chemically fractionated in the absence of biology. Isotopic variations comparable to those seen during microbially mediated reduction of ferrihydrite are observed. Fractionation may occur in aqueous solution during equilibration between inorganic iron complexes. These findings provide insight into the mechanisms of iron isotope fractionation and suggest that nonbiological processes may contribute to iron isotope variations observed in sediments. C1 Univ Rochester, Dept Earth & Environm Sci, Rochester, NY 14627 USA. Univ Rochester, Dept Chem, Rochester, NY 14627 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91106 USA. RP Anbar, AD (reprint author), Univ Rochester, Dept Earth & Environm Sci, Rochester, NY 14627 USA. RI Barling, Jane/F-9443-2015; OI Barling, Jane/0000-0001-8535-5262 NR 23 TC 189 Z9 205 U1 5 U2 73 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD APR 7 PY 2000 VL 288 IS 5463 BP 126 EP 128 DI 10.1126/science.288.5463.126 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 302VT UT WOS:000086387700048 PM 10753114 ER PT J AU Yeh, C Shimabukuro, F Stanton, P Jamnejad, V Imbriale, W Manshadi, F AF Yeh, C Shimabukuro, F Stanton, P Jamnejad, V Imbriale, W Manshadi, F TI Communication at millimetre-submillimetre wavelengths using a ceramic ribbon SO NATURE LA English DT Article ID POLYMERS AB Following the discovery by Kao and Hockman(1-3) that ultra-low-loss optical fibres could be made from pure silica through the elimination of impurities, the ability to guide signals effectively at optical wavelengths has been assured. But there remains an important region of the spectrum-from 30 to 3,000 GHz (the millimetre-submillimetre band)-where low-loss waveguides are unknown. The main problem here in finding low-loss solids is no longer one of eliminating impurities, but is due to the presence of intrinsic vibration absorption bands(4-6). And the use of highly conducting materials is also precluded owing to high skin-depth losses(7,8) in this part of the spectrum. Here we show that a combination of material and waveguide geometry can circumvent these difficulties. We adopt a ribbon-like structure with an aspect ratio of 10:1, fabricated from ceramic alumina (Coors' 998 Alumina), and the resulting waveguide has an attenuation factor of less than 10 dB km(-1) in the millimetre-submillimetre band. This attenuation is more than 100 times smaller than that of a typical ceramic (or other dielectric) circular rod waveguide and is sufficient for immediate application. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Aerospace Corp, Los Angeles, CA 90009 USA. RP Yeh, C (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 17 TC 21 Z9 24 U1 2 U2 8 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON N1 9XW, ENGLAND SN 0028-0836 J9 NATURE JI Nature PD APR 6 PY 2000 VL 404 IS 6778 BP 584 EP + DI 10.1038/35007036 PG 5 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 303BC UT WOS:000086400100048 ER PT J AU Oshman, Y Markley, FL AF Oshman, Y Markley, FL TI Sequential gyroless attitude and attitude-rate estimation from vector observations SO ACTA ASTRONAUTICA LA English DT Article ID EQUATION AB A sequential nonlinear estimator is presented For satellite attitude and attitude-rate, which utilizes vector observations in a gyroless setting. The estimator is based on a recently introduced, third-order, minimal-parameter method for solving the attitude matrix kinematic equation. Possessing an extremely simple kinematics, the third-order parameters render the resulting estimator highly computationally efficient. Employing tracking theory concepts, the angular acceleration is modeled as an exponential autocorrelation stochastic process, thus avoiding the use of the uncertain spacecraft dynamic model. An attitude matrix orthogonalization procedure, built into the estimator's scheme, enhances its accuracy and robustness, yet retains reasonable simplicity. The estimator's performance is demonstrated via a Monte Carlo simulation study. (C) 2000 Elsevier Science Ltd. All rights reserved. C1 NASA, Goddard Space Flight Ctr, Guidance Naviagat & Control Ctr, Greenbelt, MD 20771 USA. RP Oshman, Y (reprint author), Technion Israel Inst Technol, Dept Aerosp Engn, IL-32000 Haifa, Israel. NR 12 TC 2 Z9 5 U1 2 U2 5 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0094-5765 J9 ACTA ASTRONAUT JI Acta Astronaut. PD APR PY 2000 VL 46 IS 7 BP 449 EP 463 DI 10.1016/S0094-5765(99)00184-8 PG 15 WC Engineering, Aerospace SC Engineering GA 303GB UT WOS:000086413200002 ER PT J AU Dunham, DW McAdams, JV Mosher, LE Helfrich, CE AF Dunham, DW McAdams, JV Mosher, LE Helfrich, CE TI Maneuver strategy for Near's rendezvous with 433 EROS I SO ACTA ASTRONAUTICA LA English DT Article; Proceedings Paper CT 48th International Astronautical Congress CY OCT 06-10, 1997 CL TURIN, ITALY ID 253-MATHILDE; MISSION; FLYBY AB On 17 February, 1996, a Delta-2 rocket placed NASA's Near-Earth Asteroid Rendezvous (NEAR) spacecraft into a 2-year Delta VEGA trajectory that will rendezvous with the large near-Earth asteroid, 433 Eros in early January 1999. This paper discusses the strategy for performing NEAR's two large deterministic Delta Vs, the Deep Space Maneuver (DSM; 269 m/s) 4 months after aphelion of the initial 2-year orbit and the rendezvous (RND; total 971 m/s) with Eros. The DSM was performed flawlessly on 3 July, 1997, 6 days after NEAR's flyby of the main-belt asteroid 253 Mathilde. But NEAR could have still gone into orbit about Eros even if there had been a delay of 8 weeks in performing the DSM. The RND maneuver will be much more time-critical than the DSM. The rendezvous will be split into four burns of decreasing size, the error for each of which will be successively decreased. The design can accommodate one-day and two-day delays. After that, NEAR will fly past Eros, necessitating longer delays and higher Delta V costs to orbit the asteroid. A strategy is shown that will allow the full Eros orbital phase to be performed with delays as long as 40 days in performing the first large rendezvous burn. If in the unlikely event the delay is even longer, NEAR could be aimed to swing by the Earth in January 2003, and from there it could encounter 4 Vesta and other interesting objects. (C) 1997 International Astronautical Federation. Published by Elsevier Science Ltd. All rights reserved. C1 Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Dunham, DW (reprint author), Johns Hopkins Univ, Appl Phys Lab, Johns Hopkins Rd, Laurel, MD 20723 USA. NR 10 TC 2 Z9 2 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0094-5765 J9 ACTA ASTRONAUT JI Acta Astronaut. PD APR PY 2000 VL 46 IS 8 BP 519 EP 529 DI 10.1016/S0094-5765(00)00013-8 PG 11 WC Engineering, Aerospace SC Engineering GA 319UV UT WOS:000087361700003 ER PT J AU Venneri, SL AF Venneri, SL TI A change in technology ... and in culture SO AEROSPACE AMERICA LA English DT Editorial Material C1 NASA, Washington, DC 20548 USA. RP Venneri, SL (reprint author), NASA, Washington, DC 20548 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0740-722X J9 AEROSPACE AM JI Aerosp. Am. PD APR PY 2000 VL 38 IS 4 BP 3 EP 3 PG 1 WC Engineering, Aerospace SC Engineering GA 303GH UT WOS:000086413800001 ER PT J AU Samimy, M Wernet, MP AF Samimy, M Wernet, MP TI Review of planar multiple-component velocimetry in high-speed flows SO AIAA JOURNAL LA English DT Review ID PARTICLE IMAGE VELOCIMETRY; SPECTRAL RESOLUTION LIDAR; TURBULENT BOUNDARY-LAYER; FREE SHEAR LAYERS; DOPPLER VELOCIMETRY; PASSIVE CONTROL; MIXING LAYERS; TRAILING-EDGE; VELOCITY; PIV AB High speed flows encountered in most applications typically have very high Reynolds numbers and are often highly turbulent. Even in a laboratory scale high subsonic or supersonic (high speed) flow, velocities could vary over 3 orders of magnitude, and the turbulence spatial and temporal scales could span over 4-5 orders of magnitude. Exploring detailed physics of such flows presents major challenges to both experimental and computational researchers. An ultimate velocimetry technique would provide detailed, accurate, volumetric, real-time velocity data in such flows. With that being the goal, currently there are two planar velocimetry techniques that are developing rapidly into very useful tools with the potential of providing accurate velocity information in high-speed flows. The techniques are planar Doppler velocimetry (PDV) and particle imaging velocimetry (PIV). Whereas PDV has been under development for a relatively short period of time and is becoming a powerful technique, more accurate in high-speed flows, PIV is an established technique in low-speed flows and is now breaking ground in high-speed flows. The purpose of this review is to provide detailed background on these two techniques, to discuss the strengths and constraints of each technique, and to outline the areas in need of further improvement and development. The aims are to assist the novice users in their proper usage and to help those who are in the process of deciding which technique is more appropriate in their specific applications. C1 Ohio State Univ, Columbus, OH 43210 USA. NASA, John H Glenn Res Ctr, Cleveland, OH 44135 USA. RP Samimy, M (reprint author), Ohio State Univ, Columbus, OH 43210 USA. NR 132 TC 48 Z9 49 U1 1 U2 8 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0001-1452 J9 AIAA J JI AIAA J. PD APR PY 2000 VL 38 IS 4 BP 553 EP 574 DI 10.2514/2.1004 PG 22 WC Engineering, Aerospace SC Engineering GA 299YH UT WOS:000086225700001 ER PT J AU Dahl, MD Papamoschou, D AF Dahl, MD Papamoschou, D TI Analytical predictions and measurements of the noise radiated from supersonic coaxial jets SO AIAA JOURNAL LA English DT Article ID HIGH-SPEED JETS; NORMAL-VELOCITY-PROFILE; INSTABILITY WAVES AB The noise radiated from perfectly expanded coaxial jets was measured in an anechoic chamber for operating conditions with the same total mass flow and thrust and with the same temperature ratio. The shape of the measured noise spectrum at different angles to the jet axis was found to agree with spectral shapes for single, axisymmetric jets. Based on these spectra, the sound was characterized as being generated by large-scale turbulent structures or fine-scale turbulence. Modeling the large-scale structures as instability waves, a stability analysis was conducted for the coaxial jets to identify the growing and decaying instability waves in each shear layer and to predict their noise radiation pattern outside the jet. When compared to measured directivity, the analysis identified the region downstream of the outer potential core, where the two shear layers were merging, as the source of the peak radiated noise where instability waves, with their origin in the inner shear layer, reach their maximum amplitude. The changes in the measured noise directivity that occurred when the operating conditions were changed, holding mass flow and thrust constant, followed the trend predicted by the instability wave analysis. C1 NASA, John H Glenn Res Ctr, Cleveland, OH 44135 USA. Univ Calif Irvine, Dept Mech & Aerosp Engn, Irvine, CA 92717 USA. RP Dahl, MD (reprint author), NASA, John H Glenn Res Ctr, Lewis Field, Cleveland, OH 44135 USA. NR 18 TC 16 Z9 16 U1 1 U2 4 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0001-1452 J9 AIAA J JI AIAA J. PD APR PY 2000 VL 38 IS 4 BP 584 EP 591 DI 10.2514/2.1026 PG 8 WC Engineering, Aerospace SC Engineering GA 299YH UT WOS:000086225700003 ER PT J AU Tam, CKW Zaman, KBMQ AF Tam, CKW Zaman, KBMQ TI Subsonic jet noise from nonaxisymmetric and tabbed nozzles SO AIAA JOURNAL LA English DT Article; Proceedings Paper CT AIAA 37th Aerospace Sciences Meeting CY JAN 11-14, 1999 CL RENO, NEVADA SP Amer Inst Aeronaut & Astronaut ID MIXING ENHANCEMENT; AXISYMMETRICAL JET; SUPERSONIC JET; TABS AB Subsonic jet noise from nonaxisymmetric and tabbed nozzles are investigated experimentally and theoretically It is shown that the noise spectra of these jets are in good agreement with the similarity spectra found empirically earlier by Tam et al. through a detailed analysis of supersonic jet noise data (Tam, C. K. W., Golebiowski, M., and Seiner, J. M., "On the Two Components of Turbulent Mixing Noise from Supersonic Jets," AIAA Paper 96-1716, 1996). Furthermore, the radiated noise fields of the jets under study, including elliptic and large-aspect-ratio rectangular jets, are found to be quite axisymmetric and are practically the same as that of a circular jet with the same exit area. These experimental results strongly suggest that nozzle geometry modification into elliptic or rectangular shapes is not an effective method for jet noise suppression. A lobed nozzle, on the other hand, is found to impart significantly the noise held. Noise from large-scale turbulent structures, radiating principally in the downstream direction, is effectively suppressed, Tabs also impact the noise field, primarily by shifting die spectral peak to a higher frequency. A jetlets model is developed to provide a basic understanding of the noise from tabbed jets. The model predicts that the noise spectrum from a jet with N tabs (N greater than or equal to 2) can be obtained from that of the original jet (no tab) by a simple frequency shift. The shifted frequency is obtained by multiplying the original frequency by N-1/2. This result is in fairly good agreement with experimental data. C1 Florida State Univ, Dept Math, Tallahassee, FL 32306 USA. NASA, John H Glenn Res Ctr, Nozzle Branch, Cleveland, OH 44135 USA. RP Tam, CKW (reprint author), Florida State Univ, Dept Math, Tallahassee, FL 32306 USA. NR 19 TC 39 Z9 39 U1 1 U2 9 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0001-1452 J9 AIAA J JI AIAA J. PD APR PY 2000 VL 38 IS 4 BP 592 EP 599 DI 10.2514/2.1029 PG 8 WC Engineering, Aerospace SC Engineering GA 299YH UT WOS:000086225700004 ER PT J AU Han, J Lin, YL Arya, SP Proctor, FH AF Han, J Lin, YL Arya, SP Proctor, FH TI Numerical study of wake vortex decay and descent in homogeneous atmospheric turbulence SO AIAA JOURNAL LA English DT Article ID AMBIENT TURBULENCE; TRAILING VORTICES; AIRCRAFT AB Numerical simulations are performed to isolate the effect of ambient turbulence on the wake vortex decay rate within a neutrally stratified atmosphere. Simulations are conducted for a range of turbulence intensities by injecting wake vortex pairs into an approximately homogeneous and isotropic turbulence field. Consistent with field observations, the decay rate of the vortex circulation increases clearly with increasing levels of ambient turbulence. Based on the results from the numerical simulations, simple decay models for the vortex pair are proposed as functions of nondimensional ambient turbulence intensity, nondimensional radial distance, and nondimensional time. For strong atmospheric turbulence, the model predictions are in reasonable agreement with the observational data. For weak turbulence with stable stratification, the model, based on turbulence dissipation alone, underestimates circulation decay with consistent overestimation of vortex descent, unless stratification effects are included. C1 N Carolina State Univ, Dept Marine Earth & Atmospher Sci, Raleigh, NC 27695 USA. NASA, Langley Res Ctr, Airborne Syst Competency, Hampton, VA 23681 USA. RP Han, J (reprint author), N Carolina State Univ, Dept Marine Earth & Atmospher Sci, Box 8208, Raleigh, NC 27695 USA. NR 41 TC 3 Z9 4 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0001-1452 J9 AIAA J JI AIAA J. PD APR PY 2000 VL 38 IS 4 BP 643 EP 656 DI 10.2514/2.1006 PG 14 WC Engineering, Aerospace SC Engineering GA 299YH UT WOS:000086225700011 ER PT J AU Wallin, S Girimaji, SS AF Wallin, S Girimaji, SS TI Evolution of an isolated turbulent trailing vortex SO AIAA JOURNAL LA English DT Article; Proceedings Paper CT AIAA 30th Fluid Dynamics Conference CY JUN 28-JUL 01, 1999 CL NORFOLK, VIRGINIA SP Amer Inst Aeronaut & Astronaut ID REYNOLDS STRESS MODEL; FLOWS; EXPLICIT; VORTICES AB The long-time development of an isolated wing-tip turbulent vortex has been studied by Reynolds-averaged Navier-Stokes computations. The vortex is assumed to extend to infinity and to be axisymmetric and homogeneous in the axial direction, and the axial velocity is assumed to be negligible. The validity of different turbulence models, ranging from Reynolds stress transport models to eddy-viscosity K-epsilon models, has been assessed and qualitative comparisons with field measurements are made. Reynolds stress transport models correctly predict strong suppression of the turbulence in the rotation-dominated vortex core and a reasonable decay rate of the vortex. Outside of the core, the different Reynolds stress models differ significantly. The standard eddy-viscosity K-epsilon model is insensitive to rotation and, thus, overpredicts the vortex decay rate. Computations using explicit algebraic Reynolds stress models that are strictly based on Reynolds stress transport models show that the algebraic form compares reasonably well with the full transport form. It is, however important that the curved dow algebraic assumption is invoked when deriving the explicit algebraic model. C1 Aeronaut Res Inst Sweden FFA, SE-16111 Bromma, Sweden. NASA, Langley Res Ctr, Inst Comp Applicat Sci & Engn, Hampton, VA 23681 USA. RP Wallin, S (reprint author), Aeronaut Res Inst Sweden FFA, Box 11021, SE-16111 Bromma, Sweden. NR 30 TC 7 Z9 7 U1 0 U2 2 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0001-1452 J9 AIAA J JI AIAA J. PD APR PY 2000 VL 38 IS 4 BP 657 EP 665 DI 10.2514/2.1007 PG 9 WC Engineering, Aerospace SC Engineering GA 299YH UT WOS:000086225700012 ER PT J AU Edwards, JR Thomas, JL AF Edwards, JR Thomas, JL TI Development of O(Nm(2)) preconditioned multigrid solvers for Euler and Navier-Stokes equations SO AIAA JOURNAL LA English DT Article; Proceedings Paper CT AIAA 14th Computational Fluid Dynamics Conference CY JUN 28-JUL 01, 1999 CL NORFOLK, VIRGINIA SP Amer Inst Aeronaut & Astronaut ID FLOWS C1 N Carolina State Univ, Dept Mech & Aerosp Engn, Raleigh, NC 27695 USA. NASA, Langley Res Ctr, Computat Modeling & Simulat Branch, Hampton, VA 23681 USA. RP Edwards, JR (reprint author), N Carolina State Univ, Dept Mech & Aerosp Engn, Campus Box 7910, Raleigh, NC 27695 USA. NR 14 TC 3 Z9 3 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0001-1452 J9 AIAA J JI AIAA J. PD APR PY 2000 VL 38 IS 4 BP 717 EP 720 DI 10.2514/2.1018 PG 4 WC Engineering, Aerospace SC Engineering GA 299YH UT WOS:000086225700022 ER PT J AU Larruquert, JI Keski-Kuha, RAM AF Larruquert, JI Keski-Kuha, RAM TI Optical properties of hot-pressed B4C in the extreme ultraviolet SO APPLIED OPTICS LA English DT Article ID BORON-CARBIDE COATINGS; SILICON-CARBIDE; REFLECTANCE AB Hot-pressed B4C is found to have a high normal reflectance in the extreme-UV spectral region above 49 nm. This reflectance is comparable with or higher than chemical-vapor-deposited Sic in the spectral region from 49 to 92 nm. Reflectance measurements as a function of the angle of incidence yielded the optical constants of B4C in the spectral range 49-121.6 nm. (C) 2000 Optical Society of America. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Larruquert, JI (reprint author), NASA, Goddard Space Flight Ctr, Code 551, Greenbelt, MD 20771 USA. EM larruquert@io.csic.es OI Larruquert, Juan/0000-0001-6356-9702 NR 10 TC 17 Z9 18 U1 0 U2 1 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 1559-128X EI 2155-3165 J9 APPL OPTICS JI Appl. Optics PD APR 1 PY 2000 VL 39 IS 10 BP 1537 EP 1540 DI 10.1364/AO.39.001537 PG 4 WC Optics SC Optics GA 299RD UT WOS:000086210900012 PM 18345048 ER PT J AU Hegner, SJ Mc Kevitt, P Norvig, P Wilensky, R AF Hegner, SJ Mc Kevitt, P Norvig, P Wilensky, R TI Intelligent help systems for UNIX: Computational models and systems SO ARTIFICIAL INTELLIGENCE REVIEW LA English DT Editorial Material C1 Umea Univ, S-90187 Umea, Sweden. Queens Univ Belfast, Belfast, Antrim, North Ireland. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Calif Berkeley, Berkeley, CA 94720 USA. RP Hegner, SJ (reprint author), Umea Univ, S-90187 Umea, Sweden. NR 4 TC 1 Z9 1 U1 0 U2 0 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0269-2821 J9 ARTIF INTELL REV JI Artif. Intell. Rev. PD APR PY 2000 VL 14 IS 1-2 BP 1 EP 4 PG 4 WC Computer Science, Artificial Intelligence SC Computer Science GA 375MW UT WOS:000165404600001 ER PT J AU Gorham, PW van Zee, L Unwin, SC Jacobs, C AF Gorham, PW van Zee, L Unwin, SC Jacobs, C TI Markarian 421's unusual satellite galaxy SO ASTRONOMICAL JOURNAL LA English DT Article DE BL Lacertae objects : individual (Markarian 421); galaxies : binary; galaxies : interactions ID BL LACERTAE OBJECTS; RADIO GALAXIES; ELLIPTICAL GALAXIES; EMISSION-LINES; MORPHOLOGY; APPEARANCE; CONTINUUM; SPECTRUM; SAMPLE; WFPC2 AB We present Hubble Space Telescope (HST) imagery and photometry of the active galaxy Markarian 421 and its companion galaxy 14 " to the east-northeast. The HST images indicate that the companion is a morphological spiral rather than elliptical, as previous ground-based imaging has concluded. The companion has a bright, compact nucleus, appearing unresolved in the HST images. This is suggestive of Seyfert activity, or possibly a highly luminous compact star cluster. We also report the results of high dynamic range long-slit spectroscopy with the slit placed to extend across both galaxies and nuclei. We detect no emission lines in the companion nucleus, though there is evidence for recent star formation. Velocities derived from a number of absorption lines visible in both galaxies indicate that the two systems are probably tidally bound and thus in close physical proximity. Using the measured relative velocities, we derive a lower limit on the Mrk 421 mass within the companion orbit (R similar to 10 kpc) of 5.9 x 10(11) solar masses, and a mass-to-light ratio of greater than or equal to 17. Our spectroscopy also shows for the first time the presence of H alpha and [N II] emission lines from the nucleus of Mrk 421, providing another example of the appearance of new emission features in the previously featureless spectrum of a classical BL Lac object. We see both broad and narrow line emission, with a velocity dispersion of several thousand kilometers per second evident in the broad lines. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Natl Radio Astron Observ, Socorro, NM 87801 USA. RP Gorham, PW (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 45 TC 6 Z9 6 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD APR PY 2000 VL 119 IS 4 BP 1677 EP 1686 DI 10.1086/301289 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 304WY UT WOS:000086508100012 ER PT J AU Tingay, SJ Jauncey, DL Reynolds, JE Tzioumis, AK McCulloch, PM Ellingsen, SP Costa, ME Lovell, JEJ Preston, RA Simkin, SM AF Tingay, SJ Jauncey, DL Reynolds, JE Tzioumis, AK McCulloch, PM Ellingsen, SP Costa, ME Lovell, JEJ Preston, RA Simkin, SM TI The parsec-scale structure and evolution of the nearby Fanaroff-Riley type II radio galaxy Pictor A SO ASTRONOMICAL JOURNAL LA English DT Article DE galaxies : active; galaxies : individual (Pictor A = PKS 0518-458); galaxies : jets; galaxies : nuclei; radio continuum; techniques : interferometric ID ACTIVE GALACTIC NUCLEI; CYGNUS-A; VLBI OBSERVATIONS; COMPLETE SAMPLE; QUASARS; JETS; SPECTROSCOPY; MECHANISM; MODELS; MOTION AB We present very long baseline interferometry (VLBI) images of the core emission from a nearby bright FR II radio galaxy, Pictor A, revealing its parsec-scale jet structure and evolution for the first time. These data constitute a significant addition to our knowledge of powerful radio galaxies on the smallest scales, effectively doubling the number studied at this resolution. The jet, 14 h(-1) pc in projected extent, is directed west of the core for the first 5 h(-1) pc and then appears to bend approximately 40 degrees to the north. Apparent motions for three of the five parsec-scale jet components have been estimated, 0.5 +/- 0.4, 1.1 +/- 0.5, and 0.4 +/- 0.7 h(-1)c, indicating that subluminal motion is likely. No parsec-scale counterjet has been detected, allowing only lower limits on the jet-to-counterjet surface brightness ratio to be estimated. Two models, one describing the apparent 40 degrees bend in the parsec-scale jet as an intrinsic deflection of the jet and one describing it as the effect of jet precession, may each be plausible and should be testable with future VLBI observations. By adopting the jet deflection model to describe the apparent 40 degrees bend, we estimate that the Pictor A jet is initially inclined to our line of sight by less than 51 degrees. Comparing this result with VLBI observations of Cygnus A suggests that, while the components in both jets are consistent with at least mildly relativistic speeds, the Pictor A jet lies significantly closer to our line of sight than the Cygnus A jet. This conclusion is consistent with both the parsec-scale radio structures and the kiloparsec-scale orientations of the host galaxies as well as the "unified model" interpretation of the optical spectra from these two objects. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. CSIRO, Australia Telescope Natl Facil, Epping, NSW 2121, Australia. Univ Tasmania, Dept Phys, Hobart, Tas 7001, Australia. Inst Space & Astronaut Sci, Kanagawa 229, Japan. Michigan State Univ, Dept Phys & Astron, E Lansing, MI 48824 USA. RP Tingay, SJ (reprint author), CSIRO, Australia Telescope Natl Facil, Paul Wild Observ, Locked Bag 194, Narrabri, NSW, Australia. RI Tingay, Steven/B-5271-2013; Ellingsen, Simon/J-7754-2014 OI Ellingsen, Simon/0000-0002-1363-5457 NR 37 TC 21 Z9 21 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD APR PY 2000 VL 119 IS 4 BP 1695 EP 1700 DI 10.1086/301283 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 304WY UT WOS:000086508100015 ER PT J AU Hartigan, P Morse, J Palunas, P Bally, J Devine, D AF Hartigan, P Morse, J Palunas, P Bally, J Devine, D TI Kinematics of Herbig-Haro objects in the protostellar outflow L1551 as mapped by Fabry-Perot spectroscopy SO ASTRONOMICAL JOURNAL LA English DT Article DE ISM : Herbig-Haro objects; ISM : individual (L1551); ISM : jets and outflows ID BOW SHOCK; MOLECULAR OUTFLOW; MACH DISK; BIPOLAR OUTFLOWS; YOUNG STARS; JETS; MODELS; CLOUD; ENTRAINMENT; REGION AB We present new velocity-resolved Fabry-Perot images in CS nl lambda 6731 and H alpha of the blueshifted portion of the protostellar outflow L1551. These new data isolate the line emission from the reflected continuum and make it possible to visualize the kinematics of the shock waves in the outflow clearly for the first time on large scales with subarcsecond spatial resolution. Velocity images of the L1551 jet confirm that a fainter, slower jet lies a few arcseconds below the main jet. Emission from the main jet decreases sharply in radial velocity and the emission-line width increases suddenly as the jet encounters bright knot 3, in agreement with bow shock models. This knot must move into previously ejected material to account for the observed radial velocities, supporting the idea that shocks in Herbig-Haro (HH) flows form as the result of variable velocity ejections from the embedded protostar. However, a velocity gradient observed along the entire edge of the bow shock is spatially larger than expected if the bow shock alone were responsible for all the Line emission. Deviations from the simple model are most easily explained if a Mach disk alters the emission and kinematics within the bow shock region, though a precursor to the bow shock is an alternate possibility. The spatial distribution of radial velocities and emission-line widths across HH 29 implies that this object is a slower portion of the outflow currently being overtaken by faster material. New proper-motion images of HH 29 independently confirm this result. The large-scale velocity structure of the L1551 outflow is complex but can generally be understood if faster material drives shock waves into slower material around the edge of a cavity. A striking circular feature whose center lies near the intersection of the axis of the bright jet and the cavity resembles similar structures in the Orion Nebula and could define a hole through which a fast jet has penetrated. The velocity structure along a string of HH objects to the southwest of HH 29 is consistent with the recent result of Devine et al. that L1551 NE drives this portion of the outflow. Linear features that cross the L1551 flow may be associated with separate, unrelated jets from the HH 30 region or elsewhere within L1551. C1 Rice Univ, Dept Space Phys & Astron, Houston, TX 77005 USA. Univ Colorado, Ctr Astrophys & Space Astron, Boulder, CO 80309 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Hartigan, P (reprint author), Rice Univ, Dept Space Phys & Astron, 6100 S Main, Houston, TX 77005 USA. NR 41 TC 31 Z9 31 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD APR PY 2000 VL 119 IS 4 BP 1872 EP 1880 DI 10.1086/301295 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 304WY UT WOS:000086508100029 ER PT J AU Clark, JS Miroshnichenko, AS Larionov, VM Lyuty, VM Hynes, RI Pooley, GG Coe, MJ McCollough, M Dieters, S Efimov, YS Fabregat, J Goranskii, VP Haswell, CA Metlova, NV Robinson, EL Roche, P Shenavrin, VI Welsh, WF AF Clark, JS Miroshnichenko, AS Larionov, VM Lyuty, VM Hynes, RI Pooley, GG Coe, MJ McCollough, M Dieters, S Efimov, YS Fabregat, J Goranskii, VP Haswell, CA Metlova, NV Robinson, EL Roche, P Shenavrin, VI Welsh, WF TI Photometric observations of the radio bright B[e]/X-ray binary CI Cam SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE stars : binaries : general; stars : circumstellar matter; stars : individual : CI Cam; stars : winds, outflows; X-rays : stars ID EMISSION-LINE STARS; MAGELLANIC CLOUDS; DUST; SPECTROSCOPY; OUTBURST; GRAINS AB We present multiwavelength (optical, IR, radio) observations of CI Cam, the optical counterpart to the transient X-ray source XTE J0421+560. Pre-outburst quiescent observations reveal the presence of a dusty envelope around the system. Pronounced short term variability is observed at all wavebands from U-K, but no indication of prior flaring of a similar magnitude to the 1998 April outburst is found in these data. Data obtained during the 1998 April X-ray flare reveal pronounced optical-radio flaring. The optical flux was observed to quickly return to quiescent levels, while the radio flare was of much longer duration. The optical component is likely to result from a combination of free-free/free-bound emission, emission line and thermal dust emission, caused by re-radiation of the X-ray flux, while the behaviour of the multiwavelength radio data is consistent with emission from expanding ejecta emitting via the synchrotron mechanism. Post-outburst (1998 August-1999 March) U-M broadband photometric observations reveal that while the optical (UBV) Bur remains at pre-outburst quiescent levels, near IR (JHKLM) fluxes exceed the pre-outburst fluxes by similar to 0.5 magnitudes. Modelling the pre- and post-outburst spectral energy distribution of CI Cam reveals that the structure and/or composition of the dusty component of the circumstellar envelope appears to have changed. Due to a lack of information on the precise chemical composition of the dust within the system several explanations for this behaviour are possible, such as the production of new dust at the inner edge of the envelope, or modification of the composition of the dust due to X-ray irradiation. C1 Univ Sussex, Ctr Astron, Brighton BN1 9QH, E Sussex, England. Pulkovo Observ, St Petersburg 196140, Russia. Univ Toledo, Dept Phys & Astron, Toledo, OH 43606 USA. St Petersburg State Univ, Astron Inst, St Petersburg 198904, Russia. Moscow State Univ, Crimean Lab, Sternberg Astron Inst, Moscow, Russia. Univ Southampton, Dept Phys & Astron, Southampton SO17 1BJ, Hants, England. Open Univ, Dept Phys, Milton Keynes MK7 6AA, Bucks, England. Univ Cambridge, Cavendish Lab, Mullard Radio Astron Observ, Cambridge CB3 0HE, England. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Crimean Astrophys Observ, UA-334413 Nauchnyi, Ukraine. Univ Valencia, Dept Astron, Valencia 46100, Spain. Univ Texas, Dept Astron, Austin, TX 78712 USA. NSSC, Leicester LE1 5FQ, Leics, England. RP Clark, JS (reprint author), Univ Sussex, Ctr Astron, Brighton BN1 9QH, E Sussex, England. EM jsc@star.cpes.susx.ac.uk RI Larionov, Valeri/H-1349-2013; Fabregat, Juan/F-9066-2016 OI Larionov, Valeri/0000-0002-4640-4356; Fabregat, Juan/0000-0002-5986-9347 NR 51 TC 38 Z9 39 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD APR PY 2000 VL 356 IS 1 BP 50 EP 62 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 311DJ UT WOS:000086869300014 ER PT J AU Negueruela, I Reig, P Finger, MH Roche, P AF Negueruela, I Reig, P Finger, MH Roche, P TI Detection of X-ray pulsations from the Be/X-ray transient A 0535+26 during a disc loss phase of the primary SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE stars : circumstellar matter; stars : emission-line, Be; stars : individual : A 0535+26; stars : binaries : close; stars : neutron; X-rays : stars ID NEUTRON-STAR; MU-CENTAURI; BINARIES; OUTBURSTS; OSCILLATIONS; A0535+262; ENVELOPES; STELLAR AB Using the RossiXTE experiment, we detect weak Xray emission from the recurrent Be/X-ray transient A 0535+26 at a time when the optical counterpart V725 Tau displayed Her in absorption, indicating the absence of a circumstellar disc. The X-ray radiation is strongly modulated at the 103.5-s pulse period of the neutron star, confirming that it originates from A 0535+26. The source is weaker than in previous quiescence detections by two orders of magnitude and should be in the centrifugal inhibition regime. We show that the X-ray luminosity cannot be due to accretion on to the magnetosphere of the neutron star. Therefore this detection represents a new state of the accreting pulsar. We speculate that the X-ray emission can be due to some matter leaking through the magnetospheric barrier or thermal radiation from the neutron star surface due to crustal heating. The observed luminosity is probably compatible with recent predictions of thermal radiation from X-ray transients in quiescence. The detection of the X-ray source in the inhibition regime implies a reduced density in the outflow from the Be companion during its disc-less phase. C1 Nuova Telespazio, ASI, SAX SDC, I-00131 Rome, Italy. Fdn Res & Technol Hellas, Heraklion 71110, Greece. Univ Crete, Dept Phys, Heraklion 71003, Greece. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, ES84, Huntsville, AL 35812 USA. Univ Leicester, Dept Phys & Astron, Leicester LE1 7RH, Leics, England. RP Negueruela, I (reprint author), Nuova Telespazio, ASI, SAX SDC, Via Corcolle 19, I-00131 Rome, Italy. EM ignacio@tocai.sdc.asi.it RI Reig, Pablo/A-1198-2014; Negueruela, Ignacio/L-5483-2014 OI Reig, Pablo/0000-0002-6446-3050; Negueruela, Ignacio/0000-0003-1952-3680 NR 35 TC 38 Z9 38 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD APR PY 2000 VL 356 IS 3 BP 1003 EP 1009 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 321GA UT WOS:000087446700027 ER PT J AU Hainaut, OR Delahodde, CE Boehnhardt, H Dotto, E Barucci, MA Meech, KJ Bauer, JM West, RM Doressoundiram, A AF Hainaut, OR Delahodde, CE Boehnhardt, H Dotto, E Barucci, MA Meech, KJ Bauer, JM West, RM Doressoundiram, A TI Physical properties of TNO 1996 TO(66) - Lightcurves and possible cometary activity SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE Kuiper belt, Oort cloud; planets and satellites : individual : 1996 TO66; solar system : formation ID KUIPER-BELT OBJECTS; SOUTHERN SPECTROPHOTOMETRIC STANDARDS; PLUTO-CHARON SYSTEM; TIME SCALES; EVOLUTION; SPECTRUM; CAMERA; 1993SC AB We describe observations of the Trans-Neptunian Object (TNO) 1996 TO(66) performed during three observing runs (August 1997, October 1997 and September 1998). They show significant brightness variations that indicate a rotation period of 6.25+/-0.03h. In the the 1997 data, the phased lightcurve displays a nearly symmetrical double peak with a peak-to-peak amplitude of 0.12 mag, while in the data of 1998, it shows a single maximum with a full amplitude of 0.33 mag. Possible causes for this change of shape are explored, the simplest explanation being that 1996 TO(66) experienced a phase of cometary activity during the interval between these observations. This hypothesis, if confirmed, could be of interest for the pending question of the observed color diversity of TNOs. The average magnitude (R = 21.15) was converted into a mean radius of 326+/-7 km (assuming albedo p = 0.04), making 1996 TO(66) the largest known TNO after Pluto and Charon. The object is among the bluest in the outer Solar System and the colour, as measured at different epochs, shows marginally significant changes. Deep, composite images, totaling 13,500s integration time with the NTT and 4500s with the UH 2.2m in the R filter, were searched for possible signatures of a faint coma. None were found and the photometric profile of 1996 TO(66) perfectly matches a stellar one, down to the 29 mag/sq.arcsec level. We also present an apparently featureless 8100s NTT +EMMI spectrum (6000-9100 Angstrom) with a neutral reflectivity in the 6000-7600 Angstrom, range, and with a marginally significant red gradient S' = 30 +/- 10%/1000 Angstrom in the 7600-9000 Angstrom range. C1 European So Observ, Santiago 19, Chile. Observ Paris, DESPA, F-92190 Meudon, France. Osserv Astron Torino, I-10025 Pino Torinese, TO, Italy. Astron Inst, Honolulu, HI 96822 USA. European So Observ, D-85748 Garching, Germany. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Hainaut, OR (reprint author), European So Observ, Casilla 19001, Santiago 19, Chile. OI Dotto, Elisabetta/0000-0002-9335-1656 NR 58 TC 80 Z9 80 U1 0 U2 1 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD APR PY 2000 VL 356 IS 3 BP 1076 EP 1088 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 321GA UT WOS:000087446700035 ER PT J AU Gurkan, MA Baykal, A Alpar, MA Ogelman, HB Strohmayer, T AF Gurkan, MA Baykal, A Alpar, MA Ogelman, HB Strohmayer, T TI Post-glitch RXTE-PCA observations of the Vela pulsar SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE radiation mechanisms : non-thermal; radiation mechanisms : thermal; stars : pulsars : individual : Vela ID NEUTRON-STAR AB We report the results of analysis of observations of the Vela Pulsar by PCA on RXTE. Our data consists of two parts. The first part contains observations at 1, 4, and 9 days after the glitch in 1996 and has 27000 sec, total exposure time. The second part of observations were performed three months after this glitch and have a total exposure time of 93000 sec. We found pulsations in both sets. The observed spectrum is a power-law with no apparent change in flux or count rate. The theoretical expectations of increase in flux due to internal heating after a glitch are smaller than the uncertainty of the observations. C1 Middle E Tech Univ, Dept Phys, TR-06531 Ankara, Turkey. Univ Wisconsin, Dept Phys, Madison, WI 53706 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Gurkan, MA (reprint author), Middle E Tech Univ, Dept Phys, TR-06531 Ankara, Turkey. EM ato@nwu.edu NR 18 TC 2 Z9 2 U1 0 U2 1 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD APR PY 2000 VL 356 IS 3 BP 1136 EP 1140 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 321GA UT WOS:000087446700039 ER PT J AU Haas, M Klaas, U Coulson, I Thommes, E Xu, C AF Haas, M Klaas, U Coulson, I Thommes, E Xu, C TI The cold dust concentrations in the colliding galaxies NGC 4038/39 SO ASTRONOMY & ASTROPHYSICS LA English DT Letter DE galaxies : fundamental parameters; galaxies : individual : galaxies : interactions; galaxies : photometry; infrared : galaxies ID EMISSION; ARP-244 AB SCUBA 450 and 850 mu m maps of the Antennae Galaxy resolve the nuclei of NGC 4038/39 and two prominent regions in the overlap area of the galaxy disks. They coincide excellently with bright emission peaks seen on 15 mu m, 6 cm and CO maps. ISOPHOT 60 and 100 mu m maps reveal that the overlap area and the NGC 4038 nucleus are also responsible for the bulk of the far-infrared emission. In addition to the prominent emission from dust at a temperature of about 30 K, typical for active starburst galaxies, cold dust at temperatures below 20 K is found like in quiescent,galaxies and dense cloud complexes. Thus, the observations suggest a common phenomenon for merging galaxies: besides the warm dust heated by active starbursts they possess simultaneously dense concentrations of cold dust which are presumably in a pre-starburst phase. The dust mass in the two overlap region knots is about 10(7) M. which comprises a considerable fraction of the typical dust content of a whole spiral galaxy. Such a high concentration could be explained by an initial inelastic collision of clouds which loose their angular momentum and serve as concentrating kernels into which the other clouds rotating in the disks are running. The two submm knots seem to comprise independent kernels, since they are too far separated to be mutually triggered. C1 Max Planck Inst Astron, D-69117 Heidelberg, Germany. Joint Astron Ctr, Hilo, HI 96720 USA. Royal Observ, Edinburgh EH9 3HJ, Midlothian, Scotland. CALTECH, Jet Prop Lab, Ctr Infrared Proc & Anal, Pasadena, CA 91125 USA. RP Haas, M (reprint author), Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany. EM haas@mpia-hd.mpg.de NR 19 TC 27 Z9 27 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD APR PY 2000 VL 356 IS 3 BP L83 EP L87 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 321GA UT WOS:000087446700006 ER PT J AU Hwang, U Petre, R Hughes, JP AF Hwang, U Petre, R Hughes, JP TI The X-ray line emission from the supernova remnant W49B SO ASTROPHYSICAL JOURNAL LA English DT Article DE supernova remnants; X-rays : ISM ID SPECTRUM; MODELS; RADIO AB The Galactic supernova remnant W49B has one of the most impressive X-ray emission-line spectra obtained with ASCA. We use both plasma line diagnostics and broadband model fits to show that the Si and S emission lines require multiple spectral components. The spectral data do not necessarily require individual elements to be spatially stratified, as suggested by earlier work, although when ASCA line images are considered, it is possible that Fe is stratified with respect to Si and S. Most of the X-ray emitting gas is from ejecta, based on the element abundances required, but is surprisingly close to being in collisional ionization equilibrium. A high ionization age implies a high internal density in a young remnant. The fitted emission measure for W49B indicates a minimum density of 2 cm(-3), with the true density likely to be significantly higher. W49B probably had a Type Ia progenitor, based on the relative element abundances, although a low-mass Type II progenitor is still possible. We find persuasive evidence for Cr and possibly Mn emission in the ASCA spectrum-the first detection of these elements in X-rays from a cosmic source. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. Rutgers State Univ, Dept Phys & Astron, Piscataway, NJ 08854 USA. RP NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. NR 24 TC 45 Z9 45 U1 0 U2 3 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 APR 1 PY 2000 VL 532 IS 2 BP 970 EP 979 DI 10.1086/308614 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 304DX UT WOS:000086468500016 ER PT J AU Zhang, B Harding, AK AF Zhang, B Harding, AK TI Full polar cap cascade scenario: Gamma-ray and X-ray luminosities from spin-powered pulsars SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays : theory; pulsars : general; radiation mechanisms : nonthermal; X-rays : stars ID STRONG MAGNETIC-FIELDS; INVERSE COMPTON-SCATTERING; NEUTRON-STARS; PAIR-PRODUCTION; ENERGETIC RADIATION; OUTER MAGNETOSPHERE; CONDENSED MATTER; VELA PULSAR; EMISSION; GAPS AB Canonical polar cap cascade models involve curvature radiation (CR) or inverse Compton scattering (ICS) of the primary particles and synchrotron radiation (SR) of the higher generation pairs. Here we modify such a cascade picture to include the ICS of the higher generation pairs. In such a "full-cascade" scenario, not only the perpendicular portion of the energy of the pairs goes to high-energy radiation via SR, but the parallel portion of the energy of the pairs can also contribute to high-energy emission via ICS with the soft thermal photons from either the full neutron star surface or the hot polar cap. The efficiency of converting particles' kinetic energy to radiation by ICS is very high if the scatterings occur in the "resonant" regime. As a result, almost 100% of the energy input from the pulsar inner accelerators could be converted to high-energy emission. An important output of such a scenario is that the soft tail of the ICS spectrum can naturally result in a nonthermal X-ray component that can contribute to the luminosities observed by ROSAT and ASCA. Here we present an analytic description of such a full polar cap cascade scenario using the recursion relationships between adjacent generations following the approach first proposed by Lu et al., but we develop it to be able to delineate the complex full-cascade process. The acceleration model we adopted is the space-charge-limited flow model proposed by Harding & Muslimov. We present the theoretical predictions of the gamma-ray luminosities, the thermal and nonthermal X-ray luminosities for the known spin-powered X-ray pulsars (eight of them are also gamma-ray pulsars) and compare them with the observations from CGRO, ROSAT, and ASCA. We estimate the nonthermal X-ray luminosity by including all the possible ICS branches contributing to a certain energy band and estimate both the full surface and hot polar cap thermal X-ray luminosities by adopting a standard neutron star cooling scenario, and by treating self-consistent polar cap heating in the Harding & Muslimov model, respectively. Our results show that the observed different dependences of the high-energy luminosities on the pulsar spin-down luminosities, i.e., L-gamma proportional to(L-sd)(1/2) and L-x similar to 10(-3)L(sd), are well reproduced. We found that, for normal pulsars, both the hard (ASCA band) and the soft (ROSAT band) X-ray luminosities are dominated by the nonthermal X-rays of ICS origin, although for some pulsars, thermal components due to either neutron star cooling or polar cap heating can have comparable luminosities so that they are detectable. For the millisecond pulsars, our predicted upper limits of the thermal luminosities due to polar cap heating are usually higher than the ICS-origin nonthermal components if there are no strong multipolar magnetic field components near the neutron star surface; thus, the pulsed soft X-rays in the ROSAT band from most of the millisecond pulsars might be of thermal origin. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Zhang, B (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RI Harding, Alice/D-3160-2012 NR 87 TC 145 Z9 146 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 1 PY 2000 VL 532 IS 2 BP 1150 EP 1171 DI 10.1086/308598 PN 1 PG 22 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 304DX UT WOS:000086468500032 ER PT J AU Buzasi, D Catanzarite, J Laher, R Conrow, T Shupe, D Gautier, TN Kreidl, T Everett, D AF Buzasi, D Catanzarite, J Laher, R Conrow, T Shupe, D Gautier, TN Kreidl, T Everett, D TI The detection of multimodal oscillations on alpha Ursae Majoris SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars : individual (alpha Ursae Majoris); stars : oscillations ID TIME-SERIES ANALYSIS; STARS; FREQUENCIES; PULSATIONS; GIANTS AB We have used the star camera on the Wide-Field Infrared Explorer satellite to observe the K0 III star alpha UMa, and we report the apparent detection of 10 oscillation modes. The lowest frequency mode is at 1.82 mu Hz, and it appears to be the fundamental mode. The mean spacing between the mode frequencies is 2.94 mu Hz, which implies that all detected modes are radial. The mode frequencies are consistent with the physical parameters of a K0 III star, if we assume that only radial modes are excited. Mode amplitudes are 100-400 mu mag, which is consistent with the scaling relation of Kjeldsen & Bedding. C1 Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. CALTECH, Ctr Infrared Proc & Anal, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. No Arizona Univ, Informat Technol Serv, Flagstaff, AZ 86011 USA. No Arizona Univ, Dept Phys & Astron, Flagstaff, AZ 86011 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Buzasi, D (reprint author), Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. NR 29 TC 54 Z9 54 U1 1 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 1 PY 2000 VL 532 IS 2 BP L133 EP L136 DI 10.1086/312573 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 304DZ UT WOS:000086468700013 ER PT J AU Crenshaw, DM Kraemer, SB AF Crenshaw, DM Kraemer, SB TI Resolved spectroscopy of the narrow-line region in NGC 1068: Kinematics of the ionized gas SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : individual (NGC 1068); galaxies : Seyfert ID ACTIVE GALACTIC NUCLEI; SEYFERT-GALAXIES; EMITTING REGIONS; NGC-1068; LOCATION; DYNAMICS; PROFILES; QUASARS; FIELD AB We have determined the radial velocities of the [O III]-emitting gas in the inner narrow-line region of the Seyfert 2 galaxy NGC 1068, along a slit at position angle 202 degrees, from STIS observations at a spatial resolution of 0."1 and a spectral resolving power of lambda/Delta lambda approximate to 1000. We use these data to investigate the kinematics of the narrow-line region within 6" (similar to 430 pc) of the nucleus. The emission-line knots show evidence for radial acceleration to a projected angular distance of 1."7 in most cases, followed by deceleration that approaches the systemic velocity at a projected distance of similar to 4". We find that a simple kinematic model of biconical radial outflow can match the general trend of observed radial velocities. In this model, the emitting material is evacuated along the bicone axis, and the axis is inclined 5 degrees out of the plane of the sky. The acceleration of the emission-line clouds provides support for dynamical models that invoke radiation and/or wind pressure. We suggest that the deceleration of the clouds is due to their collision with a patchy and anistropically distributed ambient medium. C1 Catholic Univ Amer, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Crenshaw, DM (reprint author), Catholic Univ Amer, Greenbelt, MD 20771 USA. NR 25 TC 93 Z9 94 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 1 PY 2000 VL 532 IS 2 BP L101 EP L104 DI 10.1086/312581 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 304DZ UT WOS:000086468700005 ER PT J AU Gogus, E Woods, PM Kouveliotou, C van Paradijs, J Briggs, MS Duncan, RC Thompson, C AF Gogus, E Woods, PM Kouveliotou, C van Paradijs, J Briggs, MS Duncan, RC Thompson, C TI Statistical properties of SGR 1806-20 bursts SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays : bursts; stars : individual (SGR 1806-20); X-rays : bursts ID MAGNETIZED NEUTRON-STARS; SELF-ORGANIZED CRITICALITY; HIGH-ENERGY TRANSIENT; SOFT GAMMA-REPEATERS; X-RAY PULSAR; BEHAVIOR AB We present statistics of SGR 1806-20 bursts, combining 290 events detected with the Rossi X-Ray Timing Explorer/Proportional Counter Array, 111 events detected with the Burst and Transient Source Experiment, and 134 events detected with the International Cometary Explorer. We find that the fluence distribution of bursts observed with each instrument are well described by power laws with indices 1.43, 1.76, and 1.67, respectively. The distribution of rime intervals between successive bursts from SGR 1806-20 is described by a lognormal function with a peak at 103 s. There is no correlation between the burst intensity and either the waiting times until the next burst or the time elapsed since the previous burst. In all these statistical properties, SGR 1806-20 bursts resemble a self-organized critical system, similar to earthquakes and solar flares. Our results thus support the hypothesis that the energy source for soft gamma repeater bursts is crustquakes due to the evolving, strong magnetic field of the neutron star, rather than any accretion or nuclear power. C1 Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Univ Amsterdam, Astron Inst Anton Pannekoek, NL-1098 SJ Amsterdam, Netherlands. Univ Texas, Dept Astron, Austin, TX 78712 USA. Univ N Carolina, Dept Phys & Astron, Chapel Hill, NC 27599 USA. RP Gogus, E (reprint author), Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. NR 32 TC 72 Z9 72 U1 0 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 1 PY 2000 VL 532 IS 2 BP L121 EP L124 DI 10.1086/312583 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 304DZ UT WOS:000086468700010 ER PT J AU Sambruna, RM Chartas, G Eracleous, M Mushotzky, RF Nousek, JA AF Sambruna, RM Chartas, G Eracleous, M Mushotzky, RF Nousek, JA TI Chandra uncovers a hidden low-luminosity active galactic nucleus in the radio galaxy Hydra A (3C 218) SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : active; galaxies : individual (Hydra A, 3C 218); X-rays : galaxies ID MASSIVE BLACK-HOLE; STAR-FORMATION; COOLING-FLOW; A CLUSTER; H-I; GAS; SEARCH; DISK AB We report the detection with Chandra of a low-luminosity active galactic nucleus (LLAGN) in the low-ionization nuclear emission-line region (LINER) hosted by Hydra A, a nearby (z = 0.0537) powerful FR I radio galaxy with complex radio and optical morphology. In a 20 ks ACIS-S exposure during the calibration phase of the instrument, a point source is detected at energies greater than or similar to 2 keV at the position of the compact radio core, embedded in diffuse thermal X-ray emission (kT similar to 1 keV) at softer energies. The spectrum of the point source is well fitted by a heavily absorbed power law with intrinsic column density N-H(int) similar to 3 x 10(22) cm(-2) and photon index Gamma similar to 1.7. The intrinsic (absorption-corrected) luminosity is L2-10 kev similar to 1.3 x 10(42) ergs s(-1). These results provide strong evidence that an obscured AGN is present in the nuclear region of Hydra A. We infer that the optical/UV emission of the AGN is mostly hidden by the heavy intrinsic reddening. In order to balance the photon budget of the nebula, we must either postulate that the ionizing spectrum includes a UV bump or invoke and additional power source (shocks in the cooling flow or interaction with the radio jets). Using an indirect estimate of the black hole mass and the X-ray luminosity, we infer that the accretion rate is low, suggesting that the accretion flow is advection dominated. Finally, our results support current unification schemes for radio-loud sources, in particular the presence of the putative molecular torus in FR I galaxies. These observations underscore the power of the X-rays and of Chandra in the quest for black holes. C1 Penn State Univ, Dept Astron & Astrophys, University Pk, PA 16802 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Sambruna, RM (reprint author), Penn State Univ, Dept Astron & Astrophys, 525 Davey Lab, University Pk, PA 16802 USA. NR 36 TC 18 Z9 18 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 1 PY 2000 VL 532 IS 2 BP L91 EP L94 DI 10.1086/312569 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 304DZ UT WOS:000086468700003 ER PT J AU Kane, J Arnett, D Remington, BA Glendinning, SG Bazan, G Drake, RP Fryxell, BA AF Kane, J Arnett, D Remington, BA Glendinning, SG Bazan, G Drake, RP Fryxell, BA TI Supernova experiments on the Nova laser SO ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 2nd International Workshop on Laboratory Astrophysics with Intense Lasers CY MAR 19-21, 1998 CL TUCSON, ARIZONA DE hydrodynamics; instabilities; ISM : bubbles; methods : laboratory; shock waves; supernovae : individual (SN 1987A) ID RAYLEIGH-TAYLOR INSTABILITY; LINE-PROFILES; SN-1987A; 1987A; PERTURBATIONS; HYDRODYNAMICS; SIMILARITY; SIMULATION; EVOLUTION; FRONTS AB Supernova (SN) 1987A focused attention on the critical role of hydrodynamic instabilities in the evolution of supernovae. To test the modeling of these instabilities, we are developing laboratory experiments of hydrodynamic mixing under conditions relevant to supernovae. Initial results were reported by Kane et al. in a recent paper. The Nova laser is used to generate a 10-15 Mbar shock at the interface of a two-layer planar target, which triggers perturbation growth, due to the Richtmeyer-Meshkov instability, and to the Rayleigh-Taylor instability as the interface decelerates. This resembles the hydrodynamics of the He-H interface of a Type II supernova at intermediate times, up to a few times 10(3) s. The experiment is modeled using the hydrodynamics codes HYADES and GALE, and the supernova code PROMETHEUS. Results of the experiments and simulations are presented. We also present new analysis of the bubble velocity, a study of two-dimensional versus three-dimensional difference in growth at the He-H interface of SN 1987A, and designs for two-dimensional versus three-dimensional hydro experiments. C1 Univ Arizona, Steward Observ, Tucson, AZ 85721 USA. Univ Calif Lawrence Livermore Natl Lab, Livermore, CA 94550 USA. Univ Michigan, Ann Arbor, MI 48109 USA. NASA, GFC, Greenbelt, MD 20771 USA. RP Kane, J (reprint author), Univ Arizona, Steward Observ, Mail Code L-411 LLNL, Tucson, AZ 85721 USA. RI Drake, R Paul/I-9218-2012 OI Drake, R Paul/0000-0002-5450-9844 NR 30 TC 11 Z9 11 U1 0 U2 4 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0067-0049 J9 ASTROPHYS J SUPPL S JI Astrophys. J. Suppl. Ser. PD APR PY 2000 VL 127 IS 2 BP 365 EP 369 DI 10.1086/313349 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 337FN UT WOS:000088346900025 ER PT J AU Potter, CS AF Potter, CS TI Shifting the carbon balance - Response from Potter SO BIOSCIENCE LA English DT Letter C1 NASA, Ames Res Ctr, Ecosyst Sci & Technol Branch, Moffett Field, CA 94035 USA. RP Potter, CS (reprint author), NASA, Ames Res Ctr, Ecosyst Sci & Technol Branch, Moffett Field, CA 94035 USA. NR 3 TC 0 Z9 0 U1 0 U2 1 PU AMER INST BIOLOGICAL SCI PI WASHINGTON PA 1444 EYE ST, NW, STE 200, WASHINGTON, DC 20005 USA SN 0006-3568 J9 BIOSCIENCE JI Bioscience PD APR PY 2000 VL 50 IS 4 BP 292 EP 293 PG 2 WC Biology SC Life Sciences & Biomedicine - Other Topics GA 300EL UT WOS:000086239800003 ER PT J AU Hufford, GL Salinas, LJ Simpson, JJ Barske, EG Pieri, DC AF Hufford, GL Salinas, LJ Simpson, JJ Barske, EG Pieri, DC TI Operational implications of airborne volcanic ash SO BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY LA English DT Article ID ERUPTION; REDOUBT AB Volcanic ash clouds pose a real threat to aircraft safety. The ash is abrasive and capable of causing serious damage to aircraft engines, control surfaces, windshields, and landing lights. In addition, ash can clog the pitot-static systems, which determine wind speed and altitude, and damage sensors used to fly the aircraft. To ensure aviation safety, a warning system should be capable of a 5-min response time once an eruption has been detected. Pilots are the last link in the chain of safety actions to avoid or mitigate encounters with volcanic ash. For the pilots to be effective, the warning and safety system must meet their needs. The ability to issue accurate and timely warnings, advisories, and forecasts re quires a rapid means to detect and continually track the ash cloud and smooth coordination between many agencies. The current operational ash detection technique uses satellite remote sensing. Potential problems with this technique and the potential impact of these problems on aircraft safety are discussed. C1 Natl Weather Serv, Anchorage, AK 99513 USA. United Airlines, World Headquarters, Chicago, IL USA. Univ Calif San Diego, Scripps Inst Oceanog, La Jolla, CA 92093 USA. Natl Weather Serv, Alaska Aviat Weather Unit, Anchorage, AK USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. RP Hufford, GL (reprint author), Natl Weather Serv, 222 W 7th Ave,23, Anchorage, AK 99513 USA. NR 25 TC 18 Z9 18 U1 0 U2 1 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0003-0007 J9 B AM METEOROL SOC JI Bull. Amer. Meteorol. Soc. PD APR PY 2000 VL 81 IS 4 BP 745 EP 755 DI 10.1175/1520-0477(2000)081<0745:OIOAVA>2.3.CO;2 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 300PY UT WOS:000086262400005 ER PT J AU Pawson, S Kodera, K Hamilton, K Shepherd, TG Beagley, SR Boville, BA Farrara, JD Fairlie, TDA Kitoh, A Lahoz, WA Langematz, U Manzini, E Rind, DH Scaife, AA Shibata, K Simon, P Swinbank, R Takacs, L Wilson, RJ Al-Saadi, JA Amodei, M Chiba, M Coy, L de Grandpre, J Eckman, RS Fiorino, M Grose, WL Koide, H Koshyk, JN Li, D Lerner, J Mahlman, JD McFarlane, NA Mechoso, CR Molod, A O'Neill, A Pierce, RB Randel, WJ Rood, RB Wu, F AF Pawson, S Kodera, K Hamilton, K Shepherd, TG Beagley, SR Boville, BA Farrara, JD Fairlie, TDA Kitoh, A Lahoz, WA Langematz, U Manzini, E Rind, DH Scaife, AA Shibata, K Simon, P Swinbank, R Takacs, L Wilson, RJ Al-Saadi, JA Amodei, M Chiba, M Coy, L de Grandpre, J Eckman, RS Fiorino, M Grose, WL Koide, H Koshyk, JN Li, D Lerner, J Mahlman, JD McFarlane, NA Mechoso, CR Molod, A O'Neill, A Pierce, RB Randel, WJ Rood, RB Wu, F TI The GCM-reality intercomparison project for SPARC (GRIPS): Scientific issues and initial results SO BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY LA English DT Article ID GENERAL-CIRCULATION MODEL; GRAVITY-WAVE DRAG; MIDDLE ATMOSPHERE MODEL; DOPPLER-SPREAD PARAMETERIZATION; STRATOSPHERE-MESOSPHERE GCM; NORTHERN-HEMISPHERE WINTER; ANNUAL CYCLE; INTERANNUAL VARIABILITY; METEOROLOGICAL-OFFICE; NUMERICAL FORECASTS AB To investigate the effects of the middle atmosphere on climate, the World Climate Research Programme is supporting the project "Stratospheric Processes and their Role in Climate" (SPARC). A central theme of SPARC, to examine model simulations of the coupled troposphere-middle atmosphere system, is being performed through the initiative called GRIPS (GCM-Reality Intercomparison Project for SPARC). In this paper, an overview of the objectives of GRIPS is given. Initial activities include an assessment of the performance of middle atmosphere climate models, and preliminary results from this evaluation are presented here. It is shown that although all 13 models evaluated represent most major features of the mean atmospheric state, there are deficiencies in the magnitude and location of the features, which cannot easily be traced to the formulation (resolution or the parameterizations included) of the models. Most models show a cold bias in all locations, apart from the tropical tropopause region where they can be either too warm or too cold. The strengths and locations of the major jets are often misrepresented in the models. Looking at three-dimensional fields reveals, for some models, more severe deficiencies in the magnitude and positioning of the dominant structures (such as the Aleutian high in the stratosphere), although undersampling might explain some of these differences from observations. All the models have shortcomings in their simulations of the present-day climate, which might limit the accuracy of predictions of the climate response to ozone change and other anomalous forcing. C1 NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Data Assimilat Off, Greenbelt, MD 20771 USA. Univ Space Res Assoc, Seabrook, MD USA. Free Univ Berlin, D-1000 Berlin, Germany. Meteorol Res Inst, Tsukuba, Ibaraki 305, Japan. NOAA, Geophys Fluid Dynam Lab, Princeton, NJ USA. Univ Toronto, Toronto, ON, Canada. York Univ, Toronto, ON M3J 2R7, Canada. NCAR, Boulder, CO USA. Univ Calif Los Angeles, Dept Atmospher Sci, Los Angeles, CA 90024 USA. Sci & Technol Corp, Hampton, VA 23666 USA. Univ Reading, Ctr Global Atmospher Modelling, Reading, Berks, England. Max Planck Inst Meteorol, Hamburg, Germany. NASA, Goddard Inst Space Studies, Palisades, NY USA. United Kingdom Meteorol Off, Bracknell, Berks, England. Meteo France, CNRM, Toulouse, France. Gen Sci Corp, Beltsville, MD USA. NASA, Langley Res Ctr, Hampton, VA 23665 USA. NIESDP, Tsukuba, Ibaraki, Japan. LLNI, PCMDI, Livermore, CA USA. European Ctr Medium Range Weather Forecasts, Reading RG2 9AX, Berks, England. AES, Victoria, BC, Canada. RP Pawson, S (reprint author), NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Data Assimilat Off, Code 910-3,Bldg 33, Greenbelt, MD 20771 USA. EM pawson@dao.gsfc.nasa.gov RI Pierce, Robert Bradley/F-5609-2010; Manzini, Elisa/H-5760-2011; Rood, Richard/C-5611-2008; Fiorino, Michael/N-4150-2014; Pawson, Steven/I-1865-2014; Randel, William/K-3267-2016 OI Pierce, Robert Bradley/0000-0002-2767-1643; Rood, Richard/0000-0002-2310-4262; Fiorino, Michael/0000-0002-2819-8157; Pawson, Steven/0000-0003-0200-717X; Randel, William/0000-0002-5999-7162 NR 62 TC 125 Z9 128 U1 1 U2 16 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 2000 VL 81 IS 4 BP 781 EP 796 DI 10.1175/1520-0477(2000)081<0781:TGIPFS>2.3.CO;2 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 300PY UT WOS:000086262400007 ER PT J AU Soden, B Tjemkes, S Schmetz, J Saunders, R Bates, J Ellingson, B Engelen, R Garand, L Jackson, D Jedlovec, G Kleespies, T Randel, D Rayer, P Salathe, E Schwarzkopf, D Scott, N Sohn, B de Souza-Machado, S Strow, L Tobin, D Turner, D van Delst, P Wehr, T AF Soden, B Tjemkes, S Schmetz, J Saunders, R Bates, J Ellingson, B Engelen, R Garand, L Jackson, D Jedlovec, G Kleespies, T Randel, D Rayer, P Salathe, E Schwarzkopf, D Scott, N Sohn, B de Souza-Machado, S Strow, L Tobin, D Turner, D van Delst, P Wehr, T TI An intercomparison of radiation codes for retrieving upper-tropospheric humidity in the 6.3-mu m band: A report from the first GVaP workshop SO BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY LA English DT Article ID WATER-VAPOR; MU-M; RADIANCES; ABSORPTION; ASSIMILATION; CLIMATOLOGY; CHANNEL; OZONE AB An intercomparison of radiation codes used in retrieving upper-tropospheric humidity (UTH) from observations in the v2 (6.3 mu m) water vapor absorption band was performed. This intercomparison is one part of a coordinated effort within the Global Energy and Water Cycle Experiment Water Vapor Project to assess our ability to monitor the distribution and variations of upper-tropospheric moisture from spaceborne sensors. A total of 23 different codes, ranging from detailed line-by-line (LBL) models, to coarser-resolution narrowband (NB) models, to highly parameterized single-band (SB) models participated in the study. Forward calculations were performed using a carefully selected set of temperature and moisture profiles chosen to be representative of a wide range of atmospheric conditions. The LBL model calculations exhibited the greatest consistency with each other, typically agreeing to within 0.5 K in terms of the equivalent blackbody brightness temperature (T-b). The majority of NE and SE models agreed to within +/-1 K of the LBL models, although a few older models exhibited systematic T-b biases in excess of 2 K. A discussion of the discrepancies between various models, their association with differences in model physics (e.g., continuum absorption), and their implications for UTH retrieval and radiance assimilation is presented. C1 NOAA, GFDL, Princeton, NJ USA. EUMETSAT, Darmstadt, Germany. ECMWF, Reading, Berks, England. NOAA, CDC, Boulder, CO USA. Univ Maryland, College Pk, MD 20742 USA. Colorado State Univ, Ft Collins, CO 80523 USA. AES, Dorval, PQ, Canada. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. NOAA, Natl Environm Satellite Data & Informat Serv, Washington, DC 20233 USA. CSU, CIRA, Ft Collins, CO USA. Meteorol Off, Bracknell RB12 2SZ, Berks, England. Univ Washington, Seattle, WA 98195 USA. Ecole Polytech, CNRS, LMD, F-91128 Palaiseau, France. Seoul Natl Univ, Seoul, South Korea. Univ Maryland Baltimore Cty, Baltimore, MD 21228 USA. Univ Wisconsin, Madison, WI USA. RP Soden, B (reprint author), Princeton Univ, Forrestal Campus,US Route 1,POB 308, Princeton, NJ 08542 USA. RI Kleespies, Thomas/F-5598-2010; Jackson, Darren/D-5506-2015; Bates, John/D-1012-2009 OI Jackson, Darren/0000-0001-5211-7866; Bates, John/0000-0002-8124-0406 NR 44 TC 42 Z9 42 U1 0 U2 3 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0003-0007 J9 B AM METEOROL SOC JI Bull. Amer. Meteorol. Soc. PD APR PY 2000 VL 81 IS 4 BP 797 EP 808 DI 10.1175/1520-0477(2000)081<0797:AIORCF>2.3.CO;2 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 300PY UT WOS:000086262400008 ER PT J AU Jones, C Waliser, DE Schemm, JKE Lau, WKM AF Jones, C Waliser, DE Schemm, JKE Lau, WKM TI Prediction skill of the Madden and Julian Oscillation in dynamical extended range forecasts SO CLIMATE DYNAMICS LA English DT Article ID OUTGOING LONGWAVE RADIATION; TROPICAL WESTERN PACIFIC; SEA-SURFACE TEMPERATURE; 40-50 DAY OSCILLATION; INTRASEASONAL OSCILLATION; SYSTEMATIC-ERRORS; HEAT FLUXES; MODEL; NMC; OCEAN AB The Madden and Julian Oscillation (MJO) is the most prominent mode of intraseasonal variations in the tropical region. It plays an important role in climate variability and has a significant influence on medium-to-extended ranges weather forecasting in the tropics. This study examines the forecast skill of the oscillation in a set of recent dynamical extended range forecasts (DERF) experiments performed by the National Centers for Environmental Prediction (NCEP). The present DERF experiments were done with the reanalysis version of the medium range forecast (MRF) model and include 50-day forecasts, initialized once-a-day (0Z) with reanalyses fields, for the period between 1 January, 1985, and 31 December, 1989. The MRF model shows large mean errors in representing intraseasonal variations of the large-scale circulation, especially over the equatorial eastern Pacific Ocean. A diagnostic analysis has considered the different phases of the MJO and the associated forecast skill of the MRF model. Anomaly correlations on the order of 0.3 to 0.4 indicate that skillful forecasts extend out to 5 to 7 days lead-time. Furthermore, the results show a slight increase in the forecast skill for periods when convective anomalies associated with the MJO ate intense. By removing the mean errors, the analysis shows systematic errors in the representation of the MJO with weaker than observed upper level zonal circulations. The examination of the climate run of the MRF model shows the existence of an intraseasonal oscillation, although less intense (50-70%) and with faster (nearly twice as fast) eastward propagation than the observed MJO. The results indicate that the MRF model likely has difficulty maintaining the MJO, which impacts its forecast. A discussion of future work to improve the representation of the MJO in dynamical models and assess its prediction is presented. C1 Univ Calif Santa Barbara, Inst Computat Earth Syst Sci, Santa Barbara, CA 93106 USA. SUNY Stony Brook, Inst Terr & Planetary Atmospheres, Stony Brook, NY 11794 USA. NOAA, NCEP, Climate Predict Ctr, Camp Springs, MD 20746 USA. NASA, Goddard Space Flight Ctr, Climate & Radiat Branch, Greenbelt, MD 20771 USA. RP Jones, C (reprint author), Univ Calif Santa Barbara, Inst Computat Earth Syst Sci, Santa Barbara, CA 93106 USA. RI Lau, William /E-1510-2012 OI Lau, William /0000-0002-3587-3691 NR 38 TC 65 Z9 76 U1 1 U2 6 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0930-7575 J9 CLIM DYNAM JI Clim. Dyn. PD APR PY 2000 VL 16 IS 4 BP 273 EP 289 DI 10.1007/s003820050327 PG 17 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 311JF UT WOS:000086880400003 ER PT J AU MacNeice, P Olson, KM Mobarry, C de Fainchtein, R Packer, C AF MacNeice, P Olson, KM Mobarry, C de Fainchtein, R Packer, C TI PARAMESH: A parallel adaptive mesh refinement community toolkit SO COMPUTER PHYSICS COMMUNICATIONS LA English DT Article ID EQUATIONS; SCHEME AB In this paper we describe a community toolkit which is designed to provide parallel support with adaptive mesh capability For a large and important class of computational models, those using structured, logically Cartesian meshes. The package of Fortran 90 subroutines, called PARAMESH, is designed to provide an application developer with an easy route to extend an existing serial code which uses a logically Cartesian structured mesh into a parallel code with adaptive mesh refinement. Alternatively, in its simplest use, and with minimal effort, it can operate as a domain decomposition tool for users who want to parallelize their serial codes, but who do not wish to use adaptivity. The package can provide them with an incremental evolutionary path for their code, converting it first to uniformly refined parallel code, and then later if they so desire, adding adaptivity. (C) 2000 Elsevier Science B.V. All rights reserved. C1 Drexel Univ, NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Chicago, Enrico Fermi Inst, Chicago, IL 60637 USA. Raytheon ITSS, Lanham, MD 20706 USA. RP MacNeice, P (reprint author), Drexel Univ, NASA, Goddard Space Flight Ctr, Code 931, Greenbelt, MD 20771 USA. NR 16 TC 343 Z9 346 U1 6 U2 19 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0010-4655 J9 COMPUT PHYS COMMUN JI Comput. Phys. Commun. PD APR PY 2000 VL 126 IS 3 BP 330 EP 354 DI 10.1016/S0010-4655(99)00501-9 PG 25 WC Computer Science, Interdisciplinary Applications; Physics, Mathematical SC Computer Science; Physics GA 312FP UT WOS:000086932800010 ER PT J AU Wang, LP Koblinsky, CJ Howden, S AF Wang, LP Koblinsky, CJ Howden, S TI Mesoscale variability in the South China Sea from the TOPEX/Poseidon altimetry data SO DEEP-SEA RESEARCH PART I-OCEANOGRAPHIC RESEARCH PAPERS LA English DT Article DE South China Sea; mesoscale variability; large-scale circulation ID LOW-FREQUENCY VARIABILITY; KUROSHIO EXTENSION; GEOSAT ALTIMETRY; SURFACE HEIGHT; PACIFIC-OCEAN; GULF-STREAM; CIRCULATION; DYNAMICS; REGION AB Using wavelet transform we studied the mesoscale variability in the South China Sea (SCS) by analyzing 5-yr (October 1992 to August 1997) TOPEX/Poseidon (T/P) altimetry data. Our analysis suggests that mesoscale variability inside the SCS is weaker than that outside the SCS in the Kuroshio. It is found that despite the large temporal variation in the mesoscale variability, there are two narrow bands of significant mesoscale variability north of 10 degrees N throughout much of the 5-yr period. The stronger one lies along the western boundary, while the weaker one is oriented in a southwest-to-northeast direction across the central SCS. In the rest of the SCS, the mesoscale variability is much weaker. In light of the numerical simulation by Metzger and Hurlburt (1996, Journal of Geophysical Research, 101, 12,331-12,352) and an XBT section along 15 degrees N, the broad characteristic structure of the mesoscale variability indicates that the large-scale mean circulation in the SCS is primarily a cyclonic gyre north of about 10 degrees N. In addition to the mesoscale variability, analysis of both the T/P and the XBT data indicates that there also exists significant intra-annual variability within similar geographic locations. The intra-annual variability is found to be primarily a subsurface feature with a very weak surface signature. (C) 2000 Elsevier Science Ltd. All rights reserved. C1 Univ Maryland, Earth Syst Sci Interdisciplinary Ctr, College Pk, MD 20742 USA. NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Oceans & Ice Branch, Greenbelt, MD 20771 USA. RP Wang, LP (reprint author), NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Oceans & Ice Branch, Code 971, Greenbelt, MD 20771 USA. NR 36 TC 47 Z9 61 U1 1 U2 14 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0967-0637 J9 DEEP-SEA RES PT I JI Deep-Sea Res. Part I-Oceanogr. Res. Pap. PD APR PY 2000 VL 47 IS 4 BP 681 EP 708 DI 10.1016/S0967-0637(99)00068-0 PG 28 WC Oceanography SC Oceanography GA 284NJ UT WOS:000085338200006 ER PT J AU Greatbatch, RJ Li, GQ AF Greatbatch, RJ Li, GQ TI Alongslope mean flow and an associated upslope bolus flux of tracer in a parameterization of mesoscale turbulence SO DEEP-SEA RESEARCH PART I-OCEANOGRAPHIC RESEARCH PAPERS LA English DT Article DE eddy parameterization; alongslope flow; climate models; coastal ocean processes ID OCEAN CIRCULATION MODELS; TOPOGRAPHIC STRESS; EDDY TRANSFER; GEOSTROPHIC EDDIES; CONTINENTAL-SHELF; RESIDUAL CURRENTS; MOMENTUM; TRANSPORT; SENSITIVITY; VARIABILITY AB We explore a parameterization for mesoscale turbulence, closely related to that of Gent and McWilliams, in which forcing terms proportional to the isopycnal flux of potential vorticity appear in the averaged momentum equations. We show that in the presence of variable bottom topography, the parameterization predicts alongslope mean flow and a corresponding upslope bolus (eddy) flux of tracer that is associated with an alongslope-directed bottom eddy stress. The upslope bolus flux is in qualitative agreement with observations of a cold dome over seamounts. The predicted alongslope flow corresponds to flow fields found in geostrophic turbulence experiments and has some similarity (although conceptually very different, as discussed in the text) to Holloway's prediction based on statistical mechanics. By considering continuous stratification as a limiting case of a multilayer model, we show how to treat the surface and bottom boundaries. Practical application of the parameterization is illustrated using a three-dimensional z-coordinate ocean circulation model that is very similar to the Bryan-Cox-Semtner model. The model-computed flow is consistent with observations of anticyclonic flow around a seamount. We show that the bottom eddy stress associated with the parameterization can be large, even compared to the annual mean surface wind stress, and hence could have important implications for the biology and water mass distribution of the coastal ocean as well as for the large-scale ocean circulation. From the climate modelling perspective, the approach adopted here provides a single formalism that combines the advantages of the Gent and McWilliams parameterization with alongslope mean flow similar to that suggested by Holloway. (C) 2000 Elsevier Science Ltd. All rights reserved. C1 Dalhousie Univ, Dept Oceanog, Halifax, NS B3H 4J1, Canada. NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Raytheon ITSS, Greenbelt, MD 20771 USA. RP Greatbatch, RJ (reprint author), Dalhousie Univ, Dept Oceanog, Halifax, NS B3H 4J1, Canada. NR 58 TC 20 Z9 21 U1 1 U2 3 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0967-0637 J9 DEEP-SEA RES PT I JI Deep-Sea Res. Part I-Oceanogr. Res. Pap. PD APR PY 2000 VL 47 IS 4 BP 709 EP 735 DI 10.1016/S0967-0637(99)00078-3 PG 27 WC Oceanography SC Oceanography GA 284NJ UT WOS:000085338200007 ER PT J AU Jackson, RB Schenk, HJ Jobbagy, EG Canadell, J Colello, GD Dickinson, RE Field, CB Friedlingstein, P Heimann, M Hibbard, K Kicklighter, DW Kleidon, A Neilson, RP Parton, WJ Sala, OE Sykes, MT AF Jackson, RB Schenk, HJ Jobbagy, EG Canadell, J Colello, GD Dickinson, RE Field, CB Friedlingstein, P Heimann, M Hibbard, K Kicklighter, DW Kleidon, A Neilson, RP Parton, WJ Sala, OE Sykes, MT TI Belowground consequences of vegetation change and their treatment in models SO ECOLOGICAL APPLICATIONS LA English DT Review DE belowground processes and global change; biogeochemistry; ecosystem models; global change; plant life forms; roots; shrub encroachment; soil carbon and nutrients; water balance ID MURRAY-DARLING BASIN; TERRESTRIAL BIOSPHERE MODEL; SOIL-WATER DYNAMICS; ECOHYDROLOGICAL CHANGES; ROOT DISTRIBUTIONS; EXPERIMENTAL CATCHMENTS; ECOSYSTEM PRODUCTION; EUCALYPTUS-GRANDIS; SATELLITE DATA; GLOBAL WATER AB The extent and consequences of global land-cover and land-use change are increasingly apparent. One consequence not so apparent is the altered structure of plants belowground. This paper examines such belowground changes, emphasizing the interaction of altered root distributions with other factors and their treatment in models. Shifts of woody and herbaceous vegetation with deforestation, afforestation, and woody plant encroachment typically alter the depth and distribution of plant rests, influencing soil nutrients, the water balance, and net primary productivity (NPP). For example, our analysis of global soil data sets shows that the major plant nutrients C, N, P, and K are more shallowly distributed than are Ca, Mg, and Na, but patterns for each element vary with the dominant vegetation type. After controlling for climate, soil C and N are distributed more deeply in arid shrublands than in arid grasslands, and subhumid forests have shallower nutrient distributions than do subhumid grasslands. Consequently, changes in vegetation may influence the distribution of soil carbon and nutrients over time (perhaps decades to centuries). Shifts in the water balance are typically much more rapid. Catchment studies indicate that the water yield decreases 25-40 mm for each 10% increase in tree cover, and increases in transpiration of water taken up by deep roots may account for as much as 50% of observed responses. Because models are increasingly important for predicting the consequences of vegetation change, we discuss the treatment of belowground processes and how different treatments affect model outputs. Whether models are parameterized by biome or plant life form (or neither), use single or multiple soil layers, or include N and water limitation will all affect predicted outcomes. Acknowledging and understanding such differences should help constrain predictions of vegetation change. C1 Duke Univ, Dept Bot, Durham, NC 27708 USA. Duke Univ, Nicholas Sch Environm, Durham, NC 27708 USA. Natl Ctr Ecol Anal & Synth, Santa Barbara, CA 93101 USA. CSIRO, Div Wildlife & Ecol, Lyneham, ACT 2602, Australia. Carnegie Inst Washington, Dept Plant Biol, Stanford, CA 94305 USA. Univ Arizona, Inst Atmospher Phys, Tucson, AZ 85721 USA. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Max Planck Inst Meteorol, D-20146 Hamburg, Germany. Univ New Hampshire, Climate Change Res Ctr, GAIM Task Force, Durham, NH 03824 USA. Marine Biol Lab, Ctr Ecosyst, Woods Hole, MA 02543 USA. US Forest Serv, USDA, Corvallis, OR 97331 USA. Colorado State Univ, Dept Rangeland Ecosyst Sci, Ft Collins, CO 80523 USA. Univ Buenos Aires, Fac Agron, Dept Ecol, RA-1417 Buenos Aires, DF, Argentina. Univ Lund, Global Syst Grp, S-22362 Lund, Sweden. RP Jackson, RB (reprint author), Duke Univ, Dept Bot, Durham, NC 27708 USA. RI Neilson, Ronald/A-8588-2009; Schenk, H./B-9651-2009; Canadell, Josep/E-9419-2010; Kleidon, Axel/O-7843-2014; Heimann, Martin/H-7807-2016; Friedlingstein, Pierre/H-2700-2014 OI Schenk, H./0000-0001-6261-2780; Canadell, Josep/0000-0002-8788-3218; Kleidon, Axel/0000-0002-3798-0730; Heimann, Martin/0000-0001-6296-5113; NR 121 TC 197 Z9 234 U1 19 U2 153 PU ECOLOGICAL SOC AMER PI WASHINGTON PA 1707 H ST NW, STE 400, WASHINGTON, DC 20006-3915 USA SN 1051-0761 J9 ECOL APPL JI Ecol. Appl. PD APR PY 2000 VL 10 IS 2 BP 470 EP 483 DI 10.2307/2641107 PG 14 WC Ecology; Environmental Sciences SC Environmental Sciences & Ecology GA 296DT UT WOS:000086008300013 ER PT J AU Spina, AP AF Spina, AP TI Habitat partitioning in a patchy environment: Considering the role of intraspecific competition SO ENVIRONMENTAL BIOLOGY OF FISHES LA English DT Article DE stream fish; headwater stream; biotic interaction; size specific habitat use; removal experiment ID TROUT SALMO-TRUTTA; STREAM FISHES; RAINBOW-TROUT; SIZE CLASSES; SELECTION; SEGREGATION; POSITIONS; RESPONSES; PREDATION; MINNOWS AB Coexistence of many size groups of conspecifics in habitat patches may complicate resource partitioning and increase intraspecific interactions. The objectives of my study were to determine partitioning of habitat among age groups of rainbow trout, Oncorhynchus mykiss, coexisting in pool habitat of a headwater stream, and to determine the role of intraspecific competition for such resource partitioning. The trout population showed size and age specific patterns of habitat use, and trout selected locations based on depth and longitudinal position. This habitat use pattern decreased intraspecific overlap among the trout age groups for use of pool space. I used a removal experiment to determine if two-year old trout constrained habitat use by the smaller conspecifics. Although the experimental results imply that recent intraspecific competition was not present, the absence of competitive exclusion was not clearly demonstrated because of low experimental power. While this study identified habitat partitioning among the trout age groups, it remains unclear whether biotic interactions or size specific requirements were causing the habitat use patterns. C1 Calif State Polytech Univ Pomona, Dept Biol Sci, Pomona, CA 91768 USA. RP Spina, AP (reprint author), Natl Marine Fisheries Serv, Habitat Conservat Div, SW Region,501 W Ocean Blvd,Suite 4200, Long Beach, CA 90802 USA. NR 33 TC 20 Z9 20 U1 0 U2 8 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0378-1909 J9 ENVIRON BIOL FISH JI Environ. Biol. Fishes PD APR PY 2000 VL 57 IS 4 BP 393 EP 400 DI 10.1023/A:1007682010268 PG 8 WC Ecology; Marine & Freshwater Biology SC Environmental Sciences & Ecology; Marine & Freshwater Biology GA 288EW UT WOS:000085550100005 ER PT J AU Mortensen, D Wertheimer, A Taylor, S Landingham, J AF Mortensen, D Wertheimer, A Taylor, S Landingham, J TI The relation between early marine growth of pink salmon, Oncorhynchus gorbuscha, and marine water temperature, secondary production, and survival to adulthood SO FISHERY BULLETIN LA English DT Article ID PRINCE-WILLIAM-SOUND; VALDEZ OIL-SPILL; CHUM SALMON; JUVENILE PINK; O-KETA; SELECTIVE PREDATION; BRITISH-COLUMBIA; PUGET SOUND; MORTALITY; KISUTCH AB Juvenile pink salmon, Oncorhynchus gorbuscha, from four consecutive brood years were tagged as they emigrated to the estuarine waters of Auke Bay, and information was obtained on the relationships between early marine growth, environmental conditions, and survival to adulthood. Juveniles that emigrated from Auke Creek later in the spring spent significantly less time in the estuary. Individual growth rates of tagged fish recovered in Auke Bay ranged from 3.1% to 7.1% per day. In all study years, juvenile pink salmon grew more slowly in early April than in late April and early May. Water temperature and growth were significantly correlated in all years, but growth did not consistently correlate with the biomass of epibenthic prey or zooplankton available to the fish. Comparisons of expected and observed growth rates suggested that low prey availability, as well as low temperatures, may have limited growth for early spring emigrants. Although early emigrants encountered poorer growth conditions, survivors were larger at a given date than later emigrants, their larger size possibly protecting them from size-selective predation. Early marine growth was significantly related to intra-annual cohort survival to adults (r(2)=0.65, P<0.05). Larger fish consistently survived better than their smaller cohorts for all years. Although early marine growth was an important determinate of survival within a cohort of pink salmon, other factors, such as predator abundance, contributed to the large interannual variability observed. C1 NOAA, Natl Marine Fisheries Serv, Alaska Fisheries Sci Ctr, Auke Bay Lab, Juneau, AK 99801 USA. RP Mortensen, D (reprint author), NOAA, Natl Marine Fisheries Serv, Alaska Fisheries Sci Ctr, Auke Bay Lab, 11305 Glacier Highway, Juneau, AK 99801 USA. EM don.mortensen@noaa.gov NR 44 TC 42 Z9 42 U1 1 U2 17 PU NATL MARINE FISHERIES SERVICE SCIENTIFIC PUBL OFFICE PI SEATTLE PA 7600 SAND POINT WAY NE BIN C15700, SEATTLE, WA 98115 USA SN 0090-0656 J9 FISH B-NOAA JI Fish. Bull. PD APR PY 2000 VL 98 IS 2 BP 319 EP 335 PG 17 WC Fisheries SC Fisheries GA 308BN UT WOS:000086688800008 ER PT J AU Pasley, JN Sumpter, JA Compadre, CM Breen, PR Ross, MD AF Pasley, JN Sumpter, JA Compadre, CM Breen, PR Ross, MD TI The virtual esophagus - Phase II. SO GASTROENTEROLOGY LA English DT Meeting Abstract C1 Univ Arkansas Med Sci, Little Rock, AR 72205 USA. NASA, Ames Ctr Bioinformat, Moffett Field, CA 94035 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU W B SAUNDERS CO PI PHILADELPHIA PA INDEPENDENCE SQUARE WEST CURTIS CENTER, STE 300, PHILADELPHIA, PA 19106-3399 USA SN 0016-5085 J9 GASTROENTEROLOGY JI Gastroenterology PD APR PY 2000 VL 118 IS 4 SU 2 MA 2527 BP A463 EP A463 PN 1 PG 1 WC Gastroenterology & Hepatology SC Gastroenterology & Hepatology GA 309RU UT WOS:000086783701894 ER PT J AU Rashed, HM Cowings, P Toscano, B El-Gammal, A Adl, D Abell, TL AF Rashed, HM Cowings, P Toscano, B El-Gammal, A Adl, D Abell, TL TI NASA biofeedback training as a potential treatment for patients with chronic GI symptoms. SO GASTROENTEROLOGY LA English DT Meeting Abstract C1 Univ Tennessee, Bowld Hosp, AFT Lab, Memphis, TN USA. NASA, Ames Res Ctr, Moffett Field, CA USA. Univ Calif Los Angeles, Dept Psychiat, Los Angeles, CA USA. Univ Tennessee, Dept Med, Memphis, TN 38104 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU W B SAUNDERS CO PI PHILADELPHIA PA INDEPENDENCE SQUARE WEST CURTIS CENTER, STE 300, PHILADELPHIA, PA 19106-3399 USA SN 0016-5085 J9 GASTROENTEROLOGY JI Gastroenterology PD APR PY 2000 VL 118 IS 4 SU 2 MA 3173 BP A618 EP A618 PN 1 PG 1 WC Gastroenterology & Hepatology SC Gastroenterology & Hepatology GA 309RU UT WOS:000086783702537 ER PT J AU Takeda, H Bogard, DD Mittlefehldt, DW Garrison, DH AF Takeda, H Bogard, DD Mittlefehldt, DW Garrison, DH TI Mineralogy, petrology, chemistry, and Ar-39-Ar-40 and exposure ages of the Caddo County IAB iron: Evidence for early partial melt segregation of a gabbro area rich in plagioclase-diopside SO GEOCHIMICA ET COSMOCHIMICA ACTA LA English DT Article ID ISOTOPIC COMPOSITION; PARENT BODY; NOBLE-GASES; METEORITES; ACHONDRITES; CHONDRITES; CLASSIFICATION; MESOSIDERITES; SILICATE; ORIGIN AB We describe coarse-grained gabbroic material rich in plagioclase and diopside in the Caddo County IAB iron meteorite. The gabbro is not a clast within a breccia, but rather is an area with transitional margins located mainly at silicate-metal boundaries only a few cm away from fine-grained, ultramafic silicates similar to winonaites. Medium-grained orthopyroxene and olivine are found in transitional areas and show no shock disturbance of their textures. A vein-like region, starting in an area of fine-grained ultramafic silicate, extends towards the gabbroic area with a gradual increase in abundance of plagioclase and diopside. These textures and mineralogies suggest that the gabbroic materials were formed by inhomogeneous segregation of partial melts from chondritic source materials. Compositional data on two mineralogically distinct samples of the gabbro-rich portion of the inclusion were obtained by INAA. Compared to an average of IAB silicate inclusions or winonaites, the Caddo County gabbro is enriched in the incompatible lithophile elements Na, Ca, Sc, REE and Hf, consistent with a melt origin for the gabbro. The cosmogenic space exposure age of Caddo County (5 +/- 1 Ma) is significantly younger than exposure ages of some other IAB meteorites. An Ar-39-Ar-40 age determination of the gabbroic material indicates a series of upward steps in age from 4.516 Ga to 4.523 Ga, with a few high temperature ages up to 4.54 Ga. The older age could approximate the primary recrystallization age of silicates. The stepped Ar age spectrum may indicate differences in Ar closure temperatures during slow cooling of similar to 2-20 degrees C/Myr in the parent body. Alternatively, the younger Ar-Ar ages may date a shock event which occurred while Caddo County was hot and which also created textures such as a linear metal vein with rounded zigzag walls in a diopside crystal and slightly misoriented rounded plagioclase domain. Copyright (C) 2000 Elsevier Science Ltd. C1 Univ Ryukyus, Fac Sci, Dept Phys & Earth Sci, Nishihara, Okinawa 9030213, Japan. Chiba Inst Technol, Inst Res, Narashino, Chiba 2750016, Japan. NASA, Lyndon B Johnson Space Ctr, Planetary Sci SN2, Houston, TX 77058 USA. Lockheed Martin SO, Houston, TX 77058 USA. RP Takeda, H (reprint author), Univ Ryukyus, Fac Sci, Dept Phys & Earth Sci, Nishihara, Okinawa 9030213, Japan. NR 71 TC 42 Z9 41 U1 0 U2 3 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0016-7037 J9 GEOCHIM COSMOCHIM AC JI Geochim. Cosmochim. Acta PD APR PY 2000 VL 64 IS 7 BP 1311 EP 1327 DI 10.1016/S0016-7037(99)00434-2 PG 17 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 297UM UT WOS:000086101100014 ER PT J AU Chen, JL Wilson, CR Chao, BF Shum, CK Tapley, BD AF Chen, JL Wilson, CR Chao, BF Shum, CK Tapley, BD TI Hydrological and oceanic excitations to polar motion and length-of-day variation SO GEOPHYSICAL JOURNAL INTERNATIONAL LA English DT Article DE length of day (LOD); ocean; polar motion; TOPEX/Poseidon; water ID ANGULAR-MOMENTUM; EARTHS ROTATION; WATER STORAGE AB Water mass redistributions in the global hydrosphere, including continental water storage change and non-steric sea level change, introduce variations in the hydrological angular momentum (HAM) and the oceanic angular momentum (OAM). Under the conservation of angular momentum, HAM and OAM variations are significant excitation sources of the Earth rotational variations at a wide range of timescales. In this paper, we estimate HAM and OAM variations and their excitations to polar motion and length-of-day variation using soil moisture and snow estimates andnon-steric sea level change determined by TOPEX/Poseidon satellite radar altimeter observations and a simplified steric sea level change model. The results are compared with the variations of polar motion and LOD that are not accounted for by the atmosphere. This study indicates that seasonal continental water storage change provides significant contributions to both polar motion and LOD variation, especially to polar motion X, and the non-steric sea level change is responsible for a major part of the remaining excitations at both seasonal scale and high frequencies, particularly in polar motion Y and LOD. The good correlation between OAM contributions and the remaining excitations shows that large-scale non-tidal mass variation exists in the oceans and can be detected by TOPEX/Poseidon altimeter observations. C1 Univ Texas, Space Res Ctr, Austin, TX 78759 USA. Univ Texas, Dept Geol Sci, Austin, TX 78712 USA. NASA Headquarters, Washington, DC USA. NASA, Goddard Space Flight Ctr, Space Geodesy Branch, Greenbelt, MD 20771 USA. Ohio State Univ, Dept Civil & Environm Engn & Geodet Sci, Columbus, OH 43210 USA. RP Chen, JL (reprint author), Univ Texas, Space Res Ctr, 3925 W Braker Lane,Suite 200, Austin, TX 78759 USA. RI Chao, Benjamin Fong/N-6156-2013 NR 27 TC 30 Z9 30 U1 0 U2 2 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 0956-540X J9 GEOPHYS J INT JI Geophys. J. Int. PD APR PY 2000 VL 141 IS 1 BP 149 EP 156 DI 10.1046/j.1365-246X.2000.00069.x PG 8 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 300YK UT WOS:000086281200011 ER PT J AU Cladis, JB Collin, HL Lennartsson, OW Moore, TE Peterson, WK Russell, CT AF Cladis, JB Collin, HL Lennartsson, OW Moore, TE Peterson, WK Russell, CT TI Observations of centrifugal acceleration during compression of magnetosphere SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID PLASMA SHEET; POLAR IONOSPHERE; IONS AB Centrifugal acceleration of escaping ionospheric plasma is one of the important and fundamental processes responsible for energizing and transporting ionospheric plasma to all regions of the magnetosphere. Normally this mechanism operates over extremely large distances. Because of this feature and limitations in particle instrumentation, it has not been possible to directly confirm from insitu plasma measurements the very specific predictions made by basic plasma theory about centrifugal acceleration. We report here data obtained near Polar satellite apogee over the northern polar cap during a magnetospheric compression event that occurred on September 24, 1998. Between 2345:18 and 2347:18 UT the magnetic field rotated by about 20 degrees and increased in intensity. The Toroidal Imaging Mass-Angle Spectrograph (TIMAS) instrument on Polar obtained bulk velocity moments of preexisting upflowing H+, O+, He+, and He++ ions with enough precision and resolution to directly demonstrate, together with computer simulation, that the magnitude and direction of changes in plasma motion during this event follow directly from the changes in the magnetic field configuration as predicted by the equations describing centrifugal acceleration. C1 Lockheed Martin Space Phys Lab, Palo Alto, CA 94304 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90095 USA. RP Cladis, JB (reprint author), Lockheed Martin Space Phys Lab, 3251 Hanover St, Palo Alto, CA 94304 USA. RI Moore, Thomas/D-4675-2012; Peterson, WK/A-8706-2009; OI Moore, Thomas/0000-0002-3150-1137; Peterson, WK/0000-0002-1513-6096; Russell, Christopher/0000-0003-1639-8298 NR 12 TC 23 Z9 23 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD APR 1 PY 2000 VL 27 IS 7 BP 915 EP 918 DI 10.1029/1999GL010737 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 299XV UT WOS:000086224500002 ER PT J AU Ji, Q Tsay, SC AF Ji, Q Tsay, SC TI On the dome effect of Eppley pyrgeometers and pyranometers SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID ABSORPTION AB Pyrgeometers and Pyranometers are fundamental instruments widely used for quantifying atmosphere-surface energetics in climate studies. The dome effect of these instruments can cause a measurement uncertainty larger than 10 W m(-2). Based on careful analysis, the dome factors of our two new pyrgeometers are found to lie in the range between 1.1 and 2.0. These values are far smaller than the value of 4.0 suggested by the World Meteorological Organization. The laboratory-determined dome factors fall within this range, if pyrgeometers approach equilibrium with the blackbody target during calibration cycles. From recent field campaigns, consistent results for the dome factors are also obtained by analyzing nighttime pyrgeometer measurements, which were regarded as approaching equilibrium state. Furthermore, we utilized an energy balance equation to describe the thermal dome effect of pyranometers that is commonly referred to as the nighttime negative outputs or the dark-offset. Lacking direct measurements of the dome and case temperatures of pyranometer, we used measurements from a pyrgeometer to derive and to account for the thermal dome effect of collocated pyranometers. This approximation revealed a reasonable agreement between calculations and measurements. C1 NASA, Goddard Space Flight Ctr, SSAI, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Atmospher Sci Lab, Greenbelt, MD 20771 USA. RP Ji, Q (reprint author), NASA, Goddard Space Flight Ctr, SSAI, Greenbelt, MD 20771 USA. RI Tsay, Si-Chee/J-1147-2014 NR 11 TC 26 Z9 26 U1 1 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD APR 1 PY 2000 VL 27 IS 7 BP 971 EP 974 DI 10.1029/1999GL011093 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 299XV UT WOS:000086224500016 ER PT J AU Heirtzler, JR AF Heirtzler, JR TI Another magnetic anomaly map SO GEOTIMES LA English DT Letter C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Heirtzler, JR (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER GEOLOGICAL INST PI ALEXANDRIA PA 4220 KING ST, ALEXANDRIA, VA 22302-1507 USA SN 0016-8556 J9 GEOTIMES JI Geotimes PD APR PY 2000 VL 45 IS 4 BP 4 EP 4 PG 1 WC Geosciences, Multidisciplinary SC Geology GA 303LM UT WOS:000086423400002 ER PT J AU Iglesias, A Rosenzweig, C Pereira, D AF Iglesias, A Rosenzweig, C Pereira, D TI Agricultural impacts of climate change in Spain: developing tools for a spatial analysis SO GLOBAL ENVIRONMENTAL CHANGE-HUMAN AND POLICY DIMENSIONS LA English DT Article DE agriculture; climate change; wheat; crop simulation models; spatial analysis; Spain ID SIMULATION-MODELS; CROP PRODUCTION; KANSAS AB CERES-Wheat, a dynamic process crop growth model, is specified and validated for seven sites in the major wheat-growing regions of Spain. Variables explaining a significant proportion of simulated yield Variance are crop water (sum of precipitation and irrigation) and temperature during the growing season. A multiple linear regression model is developed to represent simulated yield response to these variables. Seven agro-climatic regions are defined based on K-mean cluster analysis of temperature and precipitation data from 329 meteorological stations and provincial crop yield data. The yield functions derived from the validated crop model were then used with the gridded agro-climatic database to conduct a spatial analysis of climate change impacts on national wheat production. Climate change scenarios with and without sulfate aerosols developed from the Hadley Centre (HCGG and HCGS) and Canadian Climate Centre (CCGG and CCGC) are tested. (C) 2000 Published by Elsevier Science Ltd. C1 Univ Politecn Madrid, Escuela Tecn Super Ingn Agron, Dept Proyectos & Plantificat Rural, E-28040 Madrid, Spain. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. RP Iglesias, A (reprint author), Univ Politecn Madrid, Escuela Tecn Super Ingn Agron, Dept Proyectos & Plantificat Rural, E-28040 Madrid, Spain. NR 23 TC 67 Z9 75 U1 1 U2 22 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND SN 0959-3780 J9 GLOBAL ENVIRON CHANG JI Glob. Environ. Change-Human Policy Dimens. PD APR PY 2000 VL 10 IS 1 BP 69 EP 80 DI 10.1016/S0959-3780(00)00010-8 PG 12 WC Environmental Sciences; Environmental Studies; Geography SC Environmental Sciences & Ecology; Geography GA 344EB UT WOS:000088743700006 ER PT J AU Clifford, SM Crisp, D Fisher, DA Herkenhoff, KE Smrekar, SE Thomas, PC Wynn-Williams, DD Zurek, RW Barnes, JR Bills, BG Blake, EW Calvin, WM Cameron, JM Carr, MH Christensen, PR Clark, BC Clow, GD Cutts, JA DahlJensen, D Durham, WB Fanale, FP Farmer, JD Forget, F Gotto-Azuma, K Grard, R Haberle, RM Harrison, W Harvey, R Howard, AD Ingersoll, AP James, PB Kargel, JS Kieffer, HH Larsen, J Lepper, K Malin, MC McCleese, DJ Murray, B Nye, JF Paige, DA Platt, SR Plaut, JJ Reeh, N Rice, JW Smith, DE Stoker, CR Tanaka, KL Mosley-Thompson, E Thorsteinsson, T Wood, SE Zent, A Zuber, MT Zwally, HJ AF Clifford, SM Crisp, D Fisher, DA Herkenhoff, KE Smrekar, SE Thomas, PC Wynn-Williams, DD Zurek, RW Barnes, JR Bills, BG Blake, EW Calvin, WM Cameron, JM Carr, MH Christensen, PR Clark, BC Clow, GD Cutts, JA DahlJensen, D Durham, WB Fanale, FP Farmer, JD Forget, F Gotto-Azuma, K Grard, R Haberle, RM Harrison, W Harvey, R Howard, AD Ingersoll, AP James, PB Kargel, JS Kieffer, HH Larsen, J Lepper, K Malin, MC McCleese, DJ Murray, B Nye, JF Paige, DA Platt, SR Plaut, JJ Reeh, N Rice, JW Smith, DE Stoker, CR Tanaka, KL Mosley-Thompson, E Thorsteinsson, T Wood, SE Zent, A Zuber, MT Zwally, HJ TI The state and future of Mars polar science and exploration SO ICARUS LA English DT Article; Proceedings Paper CT 1st International Conference on Mars Polar Science and Exploration CY OCT 18-22, 1998 CL ALLEN, TX SP Lunar & Planetary Inst, Natl Aeronaut & Space Administrat Geolog, Int Glaciolog Soc DE Mars, surface; Mars, atmosphere; Mars, climate; ices; exobiology ID GENERAL-CIRCULATION MODEL; THERMAL MAPPER OBSERVATIONS; ORBITER-LASER-ALTIMETER; MARTIAN NORTHERN PLAINS; GROUND ICE INTERACTIONS; LAYERED DEPOSITS; ATMOSPHERIC DYNAMICS; WATER-VAPOR; CO2 ICE; SUMMER TEMPERATURES AB As the planet's principal cold traps, the martian polar regions have accumulated extensive mantles of ice and dust that cover individual areas of similar to 10(6) km(2) and total as much as 3-4 km thick. From the scarcity of superposed craters on their surface, these layered deposits are thought to be comparatively young-preserving a record of the seasonal and climatic cycling of atmospheric CO2, H2O, and dust over the past similar to 10(5)-10(8) years. For this reason, the martian polar deposits may serve as a Rosetta Stone for understanding the geologic and climatic history of the planet-documenting variations in insolation (due to quasiperiodic oscillations in the planet's obliquity and orbital elements), volatile mass balance, atmospheric composition, dust storm activity, volcanic eruptions, large impacts, catastrophic floods, solar luminosity, supernovae, and perhaps even a record of microbial life. Beyond their scientific value, the polar regions may soon prove important for another reason-providing a valuable and accessible reservoir of water to support the long-term human exploration of Mars. In this paper we assess the current state of Mars polar research, identify the key questions that motivate the exploration of the polar regions, discuss the extent to which current missions will address these questions, and speculate about what additional capabilities and investigations may be required to address the issues that remain outstanding. (C) 2000 Academic Press. C1 Lunar & Planetary Inst, Houston, TX 77058 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Geol Survey Canada, Terrain Sci Div, Ottawa, ON K1A 0E8, Canada. US Geol Survey, Flagstaff, AZ 86001 USA. Cornell Univ, Dept Astron, Ithaca, NY 14853 USA. British Antarctic Survey, NERC, Cambridge CB3 0ET, England. Oregon State Univ, Coll Ocean & Atmospher Sci, Corvallis, OR 97331 USA. NASA, Goddard Space Flight Ctr, Geodynam Branch, Greenbelt, MD 20771 USA. Icefield Instruments Inc, Whitehorse, YT Y1A 5H4, Canada. US Geol Survey, Menlo Pk, CA 94025 USA. Arizona State Univ, Dept Geol, Tempe, AZ 85287 USA. Lockheed Martin Astronaut, Denver, CO USA. US Geol Survey, Denver Fed Ctr, Denver, CO 80225 USA. Niels Bohr Inst Astron, Geofys Afdeling, DK-2100 Copenhagen, Denmark. Lawrence Livermore Natl Lab, Livermore, CA 94550 USA. Hawaii Inst Geophys & Planetol, Honolulu, HI 96822 USA. Univ Paris 06, CNRS, Meteorol Dynam Lab, F-75252 Paris 05, France. Nagaoka Inst Snow & Ice Studies, NIED, Nagaoka, Niigata 18716, Japan. European Space Agcy, Estec, NL-2200 AG Noordwijk, Netherlands. NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. Univ Alaska, Inst Geophys, Fairbanks, AK 99775 USA. Case Western Reserve Univ, Dept Geol Sci, Cleveland, OH 44106 USA. Univ Virginia, Dept Environm Sci, Charlottesville, VA 22903 USA. CALTECH, Div Geol & Planetary Sci, Pasadena, CA 91125 USA. Univ Toledo, Dept Phys & Astron, Toledo, OH 43606 USA. Oklahoma State Univ, Dept Phys, Environm Sci Program, Stillwater, OK 74078 USA. Malin Space Sci Syst Inc, San Diego, CA 92191 USA. Univ Bristol, Dept Phys, HH Wills Phys Lab, Bristol BS8 1TL, Avon, England. Univ Calif Los Angeles, Dept Earth & Space Sci, Los Angeles, CA 90095 USA. Univ Nebraska, Snow & Ice Res Grp, Lincoln, NE 68583 USA. Tech Univ Denmark, Danish Ctr Remote Sensing, DK-2800 Lyngby, Denmark. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. Ohio State Univ, Byrd Polar Res Ctr, Columbus, OH 43210 USA. Alfred Wegener Inst Polar & Marine Res, D-27568 Bremerhaven, Germany. Univ Washington, Dept Atmospher Sci, Seattle, WA 98195 USA. MIT, Dept Earth Atmospher & Planetary Sci, Cambridge, MA 02139 USA. RP Lunar & Planetary Inst, 3600 Bay Area Blvd, Houston, TX 77058 USA. EM clifford@lpl.jsc.nasa.gov RI Bills, Bruce/C-1156-2008; Larsen, Janus/I-7479-2013; Dahl-Jensen, Dorthe/N-4401-2016; Wood, Stephen/R-5592-2016; OI Dahl-Jensen, Dorthe/0000-0002-1474-1948; Wood, Stephen/0000-0002-9330-434X; Howard, Alan/0000-0002-5423-1600 NR 201 TC 71 Z9 71 U1 1 U2 19 PU ACADEMIC PRESS INC ELSEVIER SCIENCE PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 EI 1090-2643 J9 ICARUS JI Icarus PD APR PY 2000 VL 144 IS 2 BP 210 EP 242 DI 10.1006/icar.1999.6290 PG 33 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 304QB UT WOS:000086494000002 PM 11543391 ER PT J AU Herkenhoff, KE Plant, JJ AF Herkenhoff, KE Plant, JJ TI Surface ages and resurfacing rates of the polar layered deposits on Mars SO ICARUS LA English DT Article; Proceedings Paper CT 1st International Conference on Mars Polar Science and Exploration CY OCT 18-22, 1998 CL ALLEN, TEXAS SP Lunar & Planetary Inst, Natl Aeronaut & Space Administrat Geolog, Int Glaciolog Soc DE Mars, surface; cratering; Mars, climate ID ASTRONOMICAL THEORY; CHAOTIC OBLIQUITY; SNC METEORITES; CRATERING RATE; VIKING 2; REGION; HISTORY; ICE; DEBRIS; SCALE AB Interpretation of the polar stratigraphy of Mars in terms of global climate changes is complicated by the significant difference in surface ages between the north and south polar layered terrains inferred from crater statistics. We have reassessed the cratering record in both polar regions using Viking Orbiter and Mariner 9 images. No craters have been found in the north polar layered terrain, but the surface of most of the south polar layered deposits appears to have been stable for many of the orbital/axial cycles that are thought to have induced global climate changes on Mars. The inferred surface age of the south polar layered deposits (about 10 Ma) is two orders of magnitude greater than the surface age of the north polar layered deposits and residual cap (at most 100 ka), Similarly, modeled resurfacing rates are at least 20 times greater in the north than in the south, These results are consistent with the hypotheses that polar layered deposit resurfacing rates are highest in areas covered by perennial ice and that the differences in polar resurfacing rates result from the 6.4 km difference in elevation between the polar regions. Deposition on the portion of the south polar layered deposits that is not covered by the perennial ice cap may have ceased about 5 million years ago when the obliquity of Mars no longer exceeded 40 degrees, (C) 2000 Academic Press. C1 US Geol Survey, Astrogeol Team, Flagstaff, AZ 86001 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Herkenhoff, KE (reprint author), US Geol Survey, Astrogeol Team, 2255 N Gemini Dr, Flagstaff, AZ 86001 USA. NR 45 TC 91 Z9 91 U1 0 U2 4 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD APR PY 2000 VL 144 IS 2 BP 243 EP 253 DI 10.1006/icar.1999.6287 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 304QB UT WOS:000086494000003 ER PT J AU Johnson, CL Solomon, SC Head, JW Phillips, RJ Smith, DE Zuber, MT AF Johnson, CL Solomon, SC Head, JW Phillips, RJ Smith, DE Zuber, MT TI Lithospheric loading by the northern polar cap on Mars SO ICARUS LA English DT Article; Proceedings Paper CT 1st International Conference on Mars Polar Science and Exploration CY OCT 18-22, 1998 CL ALLEN, TX SP Lunar & Planetary Inst, Natl Aeronaut & Space Administrat Geolog, Int Glaciolog Soc DE Mars, ices; geophysics; Mars, climate; Mars, interior ID ORBITER LASER ALTIMETER; CLIMATE FRICTION; OBLIQUITY; TOPOGRAPHY AB New topography data for the northern polar region on Mars, returned by the the Mars Orbiter Laser Altimeter (MOLA) during the aerobraking hiatus and science phasing orbits, allow characterization of the topography of the present northern polar cap and its environs, Models for loading of an elastic shell by an axisymmetric load approximating the present polar cap geometry indicate that the maximum deflection of the subice basement is in the range 1200 to 400 m for an elastic lithosphere of thickness 40 to 200 km overlain by a cap of pure H2O ice. Corresponding model cap volumes increase from 1.5 to 1.8 x 10(6) km(3), as elastic lithosphere thickness decreases from 200 to 40 km. The presence of sediments in the polar cap increases the depth to basement and resulting cap volume for a given value of elastic lithosphere thickness, One-dimensional heat flow calculations indicate that the temperature at the base of the cap may approach the melting point of cap material if the lithosphere underlying the cap is thin. The basal temperature is 170 K for a 200-km-thick lithosphere overlain by pure ice but is as great as 234 K for a 40-km-thick lithosphere overlain by a cap with a high sediment/ice ratio. Constraints on elastic lithosphere thickness are weak, but geologic mapping and MOLA data suggest that a flexurally derived circumpolar depression filled with sediments is consistent with elastic lithosphere thickness values in the range 60-120 km, Gravity and topography over the whole cap are poorly correlated, possibly due to viscous relaxation of long-wavelength topography, but gravity and topography over the western portion of the main cap are consistent with an elastic lithosphere thickness of 120 km, for a crustal thickness of 50 km, Both MOLA data and geological information suggest a formerly larger northern polar cap. The relationship of time scales for changes in the polar cap volume and extent to time scales for viscous relaxation of topography has important implications for investigations of even present polar cap topography. Viscoelastic calculations show that the Maxwell time for an Earth-like mantle viscosity for Mars (10(21) Pa-s) is 10(5) yr. The Maxwell time scales directly with the martian mantle viscosity so that values as high as 10(7) yr are possible. Time scales for changes in polar cap volume are poorly constrained, but major changes in cap volume over periods of 10(6)-10(8) yr are consistent with current understanding of polar cap processes. (C) 2000 academic Press. C1 Carnegie Inst Sci, Dept Terr Magnetism, Washington, DC 20015 USA. Brown Univ, Dept Geol Sci, Providence, RI 02912 USA. Washington Univ, Dept Earth & Planetary Sci, St Louis, MO 63130 USA. NASA, Goddard Space Flight Ctr, Geodynam Branch, Greenbelt, MD 20771 USA. MIT, Dept Earth Atmospher & Planetary Sci, Cambridge, MA 02139 USA. RP Carnegie Inst Sci, Dept Terr Magnetism, 5241 Broad Branch Rd NW, Washington, DC 20015 USA. EM cjohnson@dtm.ciw.edu NR 39 TC 36 Z9 36 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 EI 1090-2643 J9 ICARUS JI Icarus PD APR PY 2000 VL 144 IS 2 BP 313 EP 328 DI 10.1006/icar.1999.6310 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 304QB UT WOS:000086494000009 ER PT J AU Garvin, JB Sakimoto, SEH Frawley, JJ Schnetzler, C AF Garvin, JB Sakimoto, SEH Frawley, JJ Schnetzler, C TI North polar region craterforms on Mars: Geometric characteristics from the Mars Orbiter Laser Altimeter SO ICARUS LA English DT Article; Proceedings Paper CT 1st International Conference on Mars Polar Science and Exploration CY OCT 18-22, 1998 CL ALLEN, TEXAS SP Lunar & Planetary Inst, Natl Aeronaut & Space Administrat Geolog, Int Glaciolog Soc DE Mars; impact craters; polar processes; ejecta; volcanism ID IMPACT CRATERS; DEPOSITS; EJECTA AB This study focuses on topographic characterization of ice-associated north polar region impact craters and several enigmatic polar craterforms using new information from the Mars Orbiter Laser Altimeter (MOLA), an instrument aboard the Mars Global Surveyor (MGS) orbiter. We find that, for ice-associated craters, the topography reveals several surprising results not previously apparent from orbital images alone. First, geometric properties for several impact craters associated with ice and frost deposits suggest that cavity infill is as high as 80% of reconstructed, preerosion levels. Second, craters associated with ice also demonstrate unique cavity geometries relative to their nonpolar counterparts. Finally, in some cases, ice-associated impact features are anomalously deep, on the basis of depths modeled from the best available seating laws. We suggest that burial of these impact features by either episodic advance of the polar cap margin or by continuous deposition at the highest rates previously estimated for the north polar region of Mars has occurred. Subsequent stripping has exhumed the features, leaving behind cavity infill deposits, and a few of these display topographic levels above the surrounding preimpact surface. In at least one case, cavity interior deposits show layering with a typical thickness of similar to 10 m, suggesting episodic deposition and ablation of materials as in the polar layered terrain. In addition to ice-associated craters, we investigated the topography of several enigmatic polar craterforms. In particular, a few craterforms within similar to 150 km of the permanent north polar cap appear to resemble simple, effusive lava shield volcanoes found on Earth. Their geometric properties cannot be reconciled with previous suggestions that they were manifestations of martian hydromagmatic processes (i.e., maar volcanism). MOLA's initial measurements of impact craters and other craterforms in the north polar latitudes of Mars support the concept of a geologically recent surface, with evidence of effusive volcanism and enhanced sedimentation. In addition, the measured impact crater depths for ice-associated craters suggest at least a few cases of enhanced excavation and thus a possibly weaker target relative to the typical northern hemisphere plains. (C) 2000 Academic Press. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. USRA, Greenbelt, MD 20771 USA. Raytheon STX, Herring Bay Geophys, Greenbelt, MD 20771 USA. SSAI, Greenbelt, MD 20771 USA. RP Garvin, JB (reprint author), NASA, Goddard Space Flight Ctr, Code 921, Greenbelt, MD 20771 USA. NR 32 TC 101 Z9 101 U1 1 U2 10 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD APR PY 2000 VL 144 IS 2 BP 329 EP 352 DI 10.1006/icar.1999.6298 PG 24 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 304QB UT WOS:000086494000010 ER PT J AU Nye, JF Durham, WB Schenk, PM Moore, JM AF Nye, JF Durham, WB Schenk, PM Moore, JM TI The instability of a south polar cap on Mars composed of carbon dioxide SO ICARUS LA English DT Article; Proceedings Paper CT 1st International Conference on Mars Polar Science and Exploration CY OCT 18-22, 1998 CL ALLEN, TX SP Lunar & Planetary Inst, Natl Aeronaut & Space Administrat Geolog, Int Glaciolog Soc DE Mars; Mars, surface; ices; geophysics AB If the martian south polar cap were composed of solid carbon dioxide, would it be sufficiently stable against collapse under its own weight? This question is examined in the light of new experiments on the creep of solid carbon dioxide and new high-resolution topographic mapping of the south polar cap. The conclusion from a simple model is that, with the strongest of three flow laws compatible with the measurements, CO2 is strong enough to support a cap of this material with thickness about 1800 m for 10(7) years or more, which is the age suggested by the cratering record. However, none of the three possible flow laws will allow a 3000-m cap, the thickness suggested by stereogrammetry, to survive for 10(7) years, indicating that the south polar ice cap is probably not composed of pure CO2 ice. (C) 2000 Academic Press. C1 Univ Bristol, HH Wills Phys Lab, Bristol BS8 1TL, Avon, England. Lawrence Livermore Natl Lab, Livermore, CA 94550 USA. Lunar & Planetary Inst, Houston, TX 77058 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Univ Bristol, HH Wills Phys Lab, Tyndall Ave, Bristol BS8 1TL, Avon, England. EM durham1@llnl.gov NR 18 TC 41 Z9 41 U1 0 U2 3 PU ACADEMIC PRESS INC ELSEVIER SCIENCE PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 EI 1090-2643 J9 ICARUS JI Icarus PD APR PY 2000 VL 144 IS 2 BP 449 EP 455 DI 10.1006/icar.1999.6306 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 304QB UT WOS:000086494000019 ER PT J AU de Winter, F Stapfer, G Medina, E AF de Winter, F Stapfer, G Medina, E TI The design of a nuclear power supply with a 50 year life expectancy: The JPL voyager's SiGe MHW RTG SO IEEE AEROSPACE AND ELECTRONIC SYSTEMS MAGAZINE LA English DT Article AB Between 25 and 30 years ago, the IECEC* Proceedings carried a series of papers by the present authors and other members of a JPL team on the problems and the desirable design features associated with the MHW RTGs to be used to power JPL's Voyager I and II spacecraft. The Voyager I and II spacecraft successfully completed their original 12 year missions 10 years ago and are at distances of over 55 AU and 70 AU from the sun, The power systems worked almost precisely as predicted, The Voyager spacecraft seem to have several decades of life left to make measurements outside the solar system. This paper gives a technical overview of the design process and problems. C1 Atlas Corp, Santa Cruz, CA 95060 USA. CALTECH, Jet Prop Lab, JPL Voyager Project, Pasadena, CA USA. RP de Winter, F (reprint author), Atlas Corp, 1401 Laurent St, Santa Cruz, CA 95060 USA. NR 71 TC 2 Z9 2 U1 1 U2 3 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0885-8985 J9 IEEE AERO EL SYS MAG JI IEEE Aerosp. Electron. Syst. Mag. PD APR PY 2000 VL 15 IS 4 BP 5 EP 12 DI 10.1109/62.839628 PG 8 WC Engineering, Aerospace; Engineering, Electrical & Electronic SC Engineering GA 311CW UT WOS:000086868100004 ER PT J AU Gawronski, W Baher, F Quintero, O AF Gawronski, W Baher, F Quintero, O TI Azimuth-track level compensation to reduce blind-pointing errors of the deep space network antennas SO IEEE ANTENNAS AND PROPAGATION MAGAZINE LA English DT Article DE space vehicle tracking; scanning antennas; pointing systems; antenna mechanical factors; antenna tolerance analysis; satellite communication; satellite tracking AB The 34-meter antennas of the NASA Deep Space Network are "wheel and track" antennas. The latter term refers to a set of wheels at the base of the structure, which roll on a circular steel track supported by a concrete foundation ring. The track is assumed flat, however, its level varies due to manufacturing imperfections, structural loads, non-uniformity of the soil, and temperature variations. It is specified that the deviations of the azimuth-track level shall not exceed +/- 0.5 mm. During tracking, this amplitude of deviations causes deformations of the antenna structure, resulting in pointing errors of +/- 2 mdeg, which exceed the required accuracy for 32-GHz (Ka-band) tracking. However, structural deformations caused by the azimuth track unevenness are repeatable; therefore, a look-up table can be created to improve the blind-pointing accuracy. This paper presents the process for creation of the look-up table, describes the instrumentation necessary for determining the pointing errors, and describes the processing of inclinometer data. It derives algorithms for the pointing-error estimation, and for the azimuth-axis tilt using the inclinometer data. It compares the error corrections based on the created look-up table and actual measurements of pointing errors using the conical scanning (conscan) technique. This comparison shows a satisfactory convergence that justifies the implementation of the approach in forthcoming NASA missions. C1 CALTECH, Jet Prop Lab, Commun Ground Syst Sect, Pasadena, CA 91109 USA. CALTECH, Jet Prop Lab, Space Instruments Implementat Sect, Pasadena, CA 91109 USA. RP Gawronski, W (reprint author), CALTECH, Jet Prop Lab, Commun Ground Syst Sect, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM wodek.k.gawronski@jpl.nasa.gov NR 0 TC 8 Z9 12 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA SN 1045-9243 EI 1558-4143 J9 IEEE ANTENN PROPAG M JI IEEE Antennas Propag. Mag. PD APR PY 2000 VL 42 IS 2 BP 28 EP 38 DI 10.1109/74.842123 PG 11 WC Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA 314XC UT WOS:000087082000003 ER PT J AU Subramanyam, G Miranda, FA Van Keuls, F Romanofsky, RR Canedy, CL Aggarwal, S Venkatesan, T Ramesh, R AF Subramanyam, G Miranda, FA Van Keuls, F Romanofsky, RR Canedy, CL Aggarwal, S Venkatesan, T Ramesh, R TI Performance of a K-band voltage-controlled Lange coupler using a ferroelectric tunable microstrip configuration SO IEEE MICROWAVE AND GUIDED WAVE LETTERS LA English DT Article DE BSTO ferroelectric thin-film; K-band frequencies; microstrip Lange coupler; voltage-controlled couplers AB We report for the first time on the performance of a Au/Ba0.6Sr0.4TiO3 (BSTO)/MgO two-layered microstrip voltage-controlled Lange coupler (VCLC) designed for Ku- and K-hand frequencies at room temperature. Tight coupling of 3 dB or higher was obtained over a frequency range of 14-19 GHz. At K-band frequencies, the coupling was voltage-controllable using the nonlinear de electric field dependence of the relative dielectric constant of BSTO (epsilon(rBSTO)). The coupling level was improved from -11.6 to -3.7 dB at 20 GHz with an applied de electric field of 16 kV/cm. The introduction of the ferroelectric tuning layer enhances the bandwidth of the VCLC in comparison with a Lange coupler with no ferroelectric layer. This work demonstrates another advantageous application for ferroelectric thin films in passive microwave components. C1 Univ Dayton, Dept Elect & Comp Engn, Dayton, OH 45469 USA. NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. Univ Maryland, College Pk, MD 20742 USA. RP Subramanyam, G (reprint author), Univ Dayton, Dept Elect & Comp Engn, Dayton, OH 45469 USA. RI Venkatesan, Thirumalai/E-1667-2013 NR 10 TC 7 Z9 8 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 1051-8207 J9 IEEE MICROW GUIDED W JI IEEE Microw. Guided Wave Lett. PD APR PY 2000 VL 10 IS 4 BP 136 EP 138 DI 10.1109/75.846924 PG 3 WC Engineering, Electrical & Electronic SC Engineering GA 327WG UT WOS:000087816700005 ER PT J AU Hamkins, J AF Hamkins, J TI An analytic technique to separate cochannel FM signals SO IEEE TRANSACTIONS ON COMMUNICATIONS LA English DT Article DE blind adaptation; cochannel interference; cochannel signal separation; FM; MMSE AB A new technique is presented to separate two cochannel frequency modulation signals. Two candidate solutions for the phases are analytically derived, and a sequence of phase solutions is chosen to match the expected power spectral density of each constituent signal. This is accomplished with a one-step linear predictor and a simple two-state Viterbi algorithm. Simulations on recorded radio frequency data indicate improved separation capability over other techniques such as the joint Viterbi algorithm and cross coupled phase-locked Loop. C1 CALTECH, Jet Propuls Lab, Pasadena, CA 91109 USA. RP Hamkins, J (reprint author), CALTECH, Jet Propuls Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM hamkins@jpl.nasa.gov NR 10 TC 9 Z9 9 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA SN 0090-6778 J9 IEEE T COMMUN JI IEEE Trans. Commun. PD APR PY 2000 VL 48 IS 4 BP 543 EP 546 DI 10.1109/26.843120 PG 4 WC Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA 314WU UT WOS:000087081200005 ER PT J AU Asenov, A Saini, S AF Asenov, A Saini, S TI Polysilicon gate enhancement of the random dopant induced threshold voltage fluctuations in sub-100 nm MOSFET's with ultrathin gate oxide SO IEEE TRANSACTIONS ON ELECTRON DEVICES LA English DT Article DE doping; fluctuations; MOSFET; semiconductor device simulation; silicon devices; threshold ID MOS-TRANSISTORS; MU-M; TECHNOLOGY; IMPACT AB In this paper, ne investigate various aspects of the polysilicon gate influence on the random dopant induced threshold voltage fluctuations in sub-100 nm MOSFET's with ultrathin gate oxides, The study is done by using an efficient statistical three-dimensional (3-D) "atomistic" simulation technique described elsewhere [1], MOSFET's with uniform channel doping and with tom doped epitaxial channels have been investigated, The simulations reveal that even in de rices with a single crystal gate the gate depletion and the random dopants in it are responsible for a substantial fraction of the threshold voltage fluctuations when the gate oxide is scaled to thickness in the range of 1-2 nm, Simulation experiments have been used in order to separate the enhancement in the threshold voltage fluctuations due to an effective increase in the oxide thickness associated with the gate depletion from the direct influence of the random dopants in the gate depletion layer The results of the experiments show that the both factors contribute to the enhancement of the threshold voltage fluctuations, but the effective increase in the oxide thickness has a dominant effect in the investigated range of devices, Simulations illustrating the effect of the polysilicon grain boundaries on the threshold voltage variation are also presented. C1 Univ Glasgow, Dept Elect & Elect Engn, Device Modeling Grp, Glasgow G12 8LT, Lanark, Scotland. NASA, Ames Res Ctr, Numer Aerosp Simulat Syst Div, Moffett Field, CA 94035 USA. RP Asenov, A (reprint author), Univ Glasgow, Dept Elect & Elect Engn, Device Modeling Grp, Glasgow G12 8LT, Lanark, Scotland. EM A.Asenov@erec.gla.ac.uk NR 27 TC 41 Z9 42 U1 0 U2 3 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA SN 0018-9383 EI 1557-9646 J9 IEEE T ELECTRON DEV JI IEEE Trans. Electron Devices PD APR PY 2000 VL 47 IS 4 BP 805 EP 812 DI 10.1109/16.830997 PG 8 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA 302GD UT WOS:000086356600021 ER PT J AU Welander, P Barmatz, M Hahn, I AF Welander, P Barmatz, M Hahn, I TI A new small nano-kelvin resolution thermometer for low-temperature experiments SO IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT LA English DT Article DE magnetic field measurement; magnetic susceptibility; SQUID magnetofilter; superconducting device; temperature measurement ID HEAT-CAPACITY; LAMBDA-POINT; HELIUM AB A small, high-resolution paramagnetic susceptibility thermometer was developed using a GdCl3 paramagnetic salt. The device uses a superconducting quantum interference device (SQUID) magnetometer to determine the temperature dependent magnetization of the salt in a magnetic field, The magnetic field is provided by a pair of small samarium cobalt permanent magnet disks situated inside the thermometer housing. This eliminates the need for a heavy, charging solenoid used in a conventional SQUID-based magnetic thermometer system. This thermometer can resolve approximately 10(-9) K near the liquid-gas critical point of He-3 (similar to 3.31 K). The drift rate of the thermometer was measured to be < 2 x 10(-13) K/s, This light weight thermometer (similar to 7 g) is a candidate fur use in future tow-temperature Space Shuttle and International Space Station experiments. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Welander, P (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 7 TC 10 Z9 10 U1 2 U2 6 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9456 J9 IEEE T INSTRUM MEAS JI IEEE Trans. Instrum. Meas. PD APR PY 2000 VL 49 IS 2 BP 253 EP 255 DI 10.1109/19.843058 PG 3 WC Engineering, Electrical & Electronic; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA 319EK UT WOS:000087328400008 ER PT J AU Hampton, RD Whorton, MS AF Hampton, RD Whorton, MS TI Frequency-weighting filter selection for H-2 control of microgravity isolation systems: A consideration of the "implicit frequency weighting" problem SO IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT LA English DT Article DE continuous time systems; control systems; feedback systems; linear-quadratic control; linear systems; optimal control ID VIBRATION ISOLATION; SPACE EXPERIMENTS AB Many space-science experiments need an active isolation system to provide them with the requisite microgravity environment. The isolation systems planned for use with the International Space Station (ISS) have been appropriately modeled using relative position, relative velocity, and acceleration states. In theory, frequency-weighting design filters can be applied to these state-space models, in order to develop optimal H-2 or mixed-norm controllers with desired stability and performance characteristics. In practice, however, since there is a kinematic relationship among the various states, any frequency weighting applied to one state will implicitly weight other states. These implicit frequency-weighting effects must be considered, for intelligent frequency-weighting filter assignment. This paper suggests a rational approach to the assignment of frequency-weighting design filters, in the presence of the kinematic coupling among states that exists in the microgravity vibration isolation problem. C1 Univ Alabama, MAE Dept, Huntsville, AL 35899 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Hampton, RD (reprint author), Univ Alabama, MAE Dept, Huntsville, AL 35899 USA. NR 12 TC 5 Z9 5 U1 1 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9456 J9 IEEE T INSTRUM MEAS JI IEEE Trans. Instrum. Meas. PD APR PY 2000 VL 49 IS 2 BP 265 EP 269 DI 10.1109/19.843061 PG 5 WC Engineering, Electrical & Electronic; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA 319EK UT WOS:000087328400011 ER PT J AU Subramanyam, G Van Keuls, FW Miranda, FA AF Subramanyam, G Van Keuls, FW Miranda, FA TI A K-band-frequency agile microstrip bandpass filter using a thin-film HTS/ferroelectric/dielectric multilayer configuration SO IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES LA English DT Article DE K-band frequencies; microstrip filters; STO ferroelectric thin films; tunable filters; YBCOHTS thin films AB In this paper, we report on YBa2CuO3O7-delta (YBCO) thin-film/SrTiO3 (STO) thin-film K-band tunable bandpass filters on LaAlO3 (LAO) dielectric substrates, The two-pole filter has a center frequency of 19 GHz and a 4% bandwidth. Tunability is achieved through the nonlinear de electric-field dependence of the relative dielectric constant of STO (epsilon(rSTO)) A large tunability (Delta f/f(o) = (f(V max) - f(o))/f(o), where f(o) is the center frequency of the biter at no bias and f(V max) is the center frequency of the filter at the maximum applied bias) of greater than 10% was obtained in YBCO/STO/LAO microstrip bandpass filters operating below 77 K, A center frequency shift of 2.3 GHz (i.e., a tunability factor of approximately 15%) was obtained at a 400-V bipolar de bias, and 30 K, with minimal degradation in the insertion loss of the filter. This paper addresses design, fabrication, and testing of tunable filters based on STO ferroelectric thin films, The performance of the YBCO/STO/LAO filters is compared to that of gold/STO/LAO counterparts. C1 Univ Dayton, Dept Elect & Comp Engn, Dayton, OH 45469 USA. NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. RP Subramanyam, G (reprint author), Univ Dayton, Dept Elect & Comp Engn, Dayton, OH 45469 USA. NR 19 TC 21 Z9 22 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9480 J9 IEEE T MICROW THEORY JI IEEE Trans. Microw. Theory Tech. PD APR PY 2000 VL 48 IS 4 BP 525 EP 530 DI 10.1109/22.842023 PN 1 PG 6 WC Engineering, Electrical & Electronic SC Engineering GA 310FJ UT WOS:000086815600006 ER PT J AU Gaidis, MC Pickett, HM Smith, CD Martin, SC Smith, RP Siegel, PH AF Gaidis, MC Pickett, HM Smith, CD Martin, SC Smith, RP Siegel, PH TI A 2.5-THz receiver front end for spaceborne applications SO IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES LA English DT Article DE antenna radiation patterns; atmospheric measurements; diplexers; heterodyning; horn antennas; membranes; micromachining; noise measurement; reliability; satellite applications; Schottky diode mixers; semiconductor device noise; space technology; submillimeter-wave receivers; terahertz ID GAAS AB The OH radical is an important player in known ozone depletion cycles; however, due to its location in the atmosphere, it must be studied from either a balloon or spaceborne platform. For long-term mapping over large portions of the earth, a spaceborne platform is the most desirable. NASA's Earth Observing System Microwave Limb Sounder instrument is slated to house a 2.5-THz Schottky-diode receiver for such measurements. In this paper, we describe the design, fabrication, and testing of the receiver front end. Measured double-sideband (DSB) receiver noise temperatures of better than 9000 K are reproducibly achieved with all devices of our best design. Estimated mixer noise is 3500-K DSB for optimal bias conditions and at room temperature. Selected components will be used in the first terahertz heterodyne receiver to be flown in space. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Swales Aerosp, Pasadena, CA 91107 USA. Cree Res, Durham, NC 27703 USA. RP Gaidis, MC (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Gaidis, Michael/D-3327-2013 NR 13 TC 51 Z9 55 U1 0 U2 7 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9480 J9 IEEE T MICROW THEORY JI IEEE Trans. Microw. Theory Tech. PD APR PY 2000 VL 48 IS 4 BP 733 EP 739 DI 10.1109/22.841966 PN 2 PG 7 WC Engineering, Electrical & Electronic SC Engineering GA 310FN UT WOS:000086816000016 ER PT J AU Carvajal, J Chen, GR Ogmen, H AF Carvajal, J Chen, GR Ogmen, H TI Fuzzy PID controller: Design, performance evaluation, and stability analysis SO INFORMATION SCIENCES LA English DT Article DE fuzzy control systems; PID controllers; stability analysis ID ROBOT ARM AB This paper presents a design for a new fuzzy logic proportional-integral-derivative (PID) controller. The main motivation for this design was to control some known nonlinear systems, such as robotic manipulators, which violate the conventional assumption of the linear PID controller. This controller is developed by first describing the discrete-time linear PID control law and then progressively deriving the steps necessary to incorporate a fuzzy logic control mechanism into the modifications of the PID structure. The final version of this new fuzzy PID controller is a computationally efficient analytic scheme suitable for implementation in a real-time closed-loop digital control. Numerous computer simulations are included to demonstrate the effectiveness of the controller for both linear and nonlinear systems. Finally, a brief analysis is presented to prove that the controller has bounded-input/bounded-output (BIBO) stability. (C) 2000 Elsevier Science Inc. All rights reserved. C1 Univ Houston, Dept Elect & Comp Engn, Houston, TX 77204 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Ogmen, H (reprint author), Univ Houston, Dept Elect & Comp Engn, Houston, TX 77204 USA. OI Chen, Guanrong/0000-0003-1381-7418 NR 12 TC 116 Z9 137 U1 3 U2 33 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA SN 0020-0255 J9 INFORM SCIENCES JI Inf. Sci. PD APR PY 2000 VL 123 IS 3-4 BP 249 EP 270 DI 10.1016/S0020-0255(99)00127-9 PG 22 WC Computer Science, Information Systems SC Computer Science GA 288YV UT WOS:000085593000007 ER PT J AU Mikata, Y AF Mikata, Y TI Determination of piezoelectric Eshelby tensor in transversely isotropic piezoelectric solids SO INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE LA English DT Article ID COMPOSITES; INCLUSION; INHOMOGENEITIES AB In this paper, by systematically treating the integrals involved in the piezoelectric inclusion problem, we have obtained explicit results for the piezoelectric Eshelby tensor for cylindrical inclusions aligned along the axes either parallel or perpendicular to the axis of the anisotropy in a transversely isotropic piezoelectric material. First, based on Deeg's result (W.F. Deeg, The analysis of dislocation, crack and inclusion problems in piezoelectric solids, Ph.D. Dissertation, Stanford University, 1980) the integral representation for the piezoelectric Eshelby tensor for a general ellipsoid in an anisotropic piezoelectric material is derived in a simple and straightforward manner. In this derivation, a key transformation for the area element has been used, and the complete proof of this transformation is provided in Appendix A. Next, by carefully examining the integrals involved in the problem, we have obtained a representation of the components of the piezoelectric Eshelby tensor in terms of certain integrals for a general ellipsoid in a transversely isotropic piezoelectric material. Explicit results for the piezoelectric Eshelby tensor are obtained for the transeversely isotropic piezoelectric materials when the elliptic cylindrical inclusion is aligned along the axis of the anisotropy. These results coincide with the results obtained by M.L. Dunn (Electroelastic Green's functions for transversely isotropic piezoelectric media and their applications to the solutions of inclusion and inhomogeneity problems, Int. J. Engineering Science 32 (1994) 119-131) as well as J.H. Huang, J.S. Yu (Electroelastic Eshelby tensors for an ellipsoidal piezoelectric inclusion, Composites Engineering 4(11) (1994) 1182). Similarly, explicit results for the piezoelectric Eshelby tensor are also obtained for the transeversely isotropic piezoelectric materials when the elliptic cylindrical inclusion is aligned along the axis perpendicular to the axis of the anisotropy. This latter configuration becomes important when we consider piezoelectric composites where the piezoelectric fibers are placed perpendicular to the polling direction. To the best of the author's knowledge, this is a totally new result. It is also found in this paper that all of the elliptic crack-like inclusions either normal or parallel to the axis of the anisotropy have the same piezoelectric Eshelby tensor regardless of their aspect ratios in their respective configurations. Finally, by examining the integrals involved in the expressions for the piezoelectric Eshelby tensor, a new type of constraints on the piezoelectric material properties are found. (C) 2000 Elsevier Science Ltd. All rights reserved. C1 NASA, Langley Res Ctr, Inst Computat & Appl Mech, Hampton, VA 23681 USA. RP Mikata, Y (reprint author), Bell Atlantic Network Serv, Project LiveWire, 13100 Columbia Pike,4th Floor, Silver Spring, MD 20904 USA. NR 17 TC 43 Z9 46 U1 0 U2 10 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0020-7225 J9 INT J ENG SCI JI Int. J. Eng. Sci. PD APR PY 2000 VL 38 IS 6 BP 605 EP 641 DI 10.1016/S0020-7225(99)00050-6 PG 37 WC Engineering, Multidisciplinary SC Engineering GA 287RK UT WOS:000085519600002 ER PT J AU Garg, VK AF Garg, VK TI Heat transfer on a film-cooled rotating blade SO INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW LA English DT Article DE film-cooling; rotating turbine blade; heat transfer; adiabatic effectiveness ID TURBINE-BLADES; TEMPERATURE AB A multi-block, three-dimensional Navier-Stokes code has been used to compute heat transfer coefficient on the blade, hub and shroud for a rotating high-pressure turbine blade with 172 film-cooling holes in eight rows. Film-cooling effectiveness is also computed on the adiabatic blade. Wilcox's k-omega model is used for modeling the turbulence. Of the eight rows of holes, three are staggered on the shower-head with compound-angled holes. The multi-block grid consists of 4818 elementary blocks which were merged into 280 super blocks. The viscous grid has nearly two million cells. Each hole-exit, in its true oval shape, has 80 cells within it so that coolant velocity, temperature, k and omega distributions can be specified at these hole-exits. For the given parameters, heat transfer coefficient on the cooled, isothermal blade is found to be high in the tip region, and in the leading edge region between the hub and blade mid-span. The effectiveness over the cooled, adiabatic blade is the lowest: in these regions. Results for an uncooled blade are also shown, providing a direct comparison with those for the cooled blade. The heat transfer coefficient is much higher on the blade tip and shroud as compared to that on the hub for both the cooled and the uncooled cases. Effect of gridding the tip clearance gap vs. use of a tip clearance model, as well as the effect of different orientation of coolant ejection from shower-head holes is found to be small as far as the heat transfer coefficient or the adiabatic effectiveness on the blade surface is concerned. (C) 2000 Elsevier Science Inc. All rights reserved. C1 NASA, Glenn Res Ctr, AYT Corp, Cleveland, OH 44135 USA. RP Garg, VK (reprint author), NASA, Glenn Res Ctr, AYT Corp, Mail Stop 5-11, Cleveland, OH 44135 USA. NR 24 TC 30 Z9 38 U1 2 U2 6 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA SN 0142-727X J9 INT J HEAT FLUID FL JI Int. J. Heat Fluid Flow PD APR PY 2000 VL 21 IS 2 BP 134 EP 145 DI 10.1016/S0142-727X(99)00072-7 PG 12 WC Thermodynamics; Engineering, Mechanical; Mechanics SC Thermodynamics; Engineering; Mechanics GA 300UN UT WOS:000086271400002 ER PT J AU Skitka, LJ Mosier, K Burdick, MD AF Skitka, LJ Mosier, K Burdick, MD TI Accountability and automation bias SO INTERNATIONAL JOURNAL OF HUMAN-COMPUTER STUDIES LA English DT Article; Proceedings Paper CT Annual Meeting of the American-Psychological-Society CY JUN, 1996 CL SAN FRANCISCO, CALIFORNIA SP Amer Psychol Soc DE automation; accountability; vigilance; decision making; bias ID JUDGMENT; STRATEGIES; COMPLEXITY; SYSTEM AB Although generally introduced to guard against human error, automated devices can fundamentally change how people approach their work, which in turn can lead to new and different kinds of error. The present study explored the extent to which errors of omission (failures to respond to system irregularities or events because automated devices fail to detect or indicate them) and commission (when people follow an automated directive despite contradictory information from other more reliable sources of information because they either fail to check or discount that information) can be reduced under conditions of social accountability. Results indicated that making participants accountable for either their overall performance or their decision accuracy led to lower rates of "automation bias". Errors of omission proved to be the result of cognitive vigilance decrements, whereas errors of commission proved to be the result of a combination of a failure to take into account information and a belief in the superior judgement of automated aids. (C) 2000 Academic Press. C1 Univ Illinois, Dept Psychol M C 285, Chicago, IL 60607 USA. San Francisco State Univ, Dept Psychol, San Francisco, CA 94132 USA. NASA, Ames Res Ctr, San Jose State Univ Fdn, Moffett Field, CA USA. RP Skitka, LJ (reprint author), Univ Illinois, Dept Psychol M C 285, 1009 BSB,1007 W Harrison St, Chicago, IL 60607 USA. OI Skitka, Linda/0000-0002-7078-0650 NR 32 TC 41 Z9 41 U1 0 U2 2 PU ACADEMIC PRESS LTD PI LONDON PA 24-28 OVAL RD, LONDON NW1 7DX, ENGLAND SN 1071-5819 J9 INT J HUM-COMPUT ST JI Int. J. Hum.-Comput. Stud. PD APR PY 2000 VL 52 IS 4 BP 701 EP 717 DI 10.1006/ijhc.1999.0349 PG 17 WC Computer Science, Cybernetics; Ergonomics; Psychology, Multidisciplinary SC Computer Science; Engineering; Psychology GA 304RU UT WOS:000086498600004 ER PT J AU Goldin, DS AF Goldin, DS TI Commercial benefits of international space stations SO INTERNATIONALE POLITIK LA German DT Article C1 NASA, Washington, DC 20546 USA. RP Goldin, DS (reprint author), NASA, Washington, DC 20546 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU VERLAG INT POLITIK GMBH PI BONN 1 PA POSTFACH 1529 BACHSTRASSE 32, D-53005 BONN 1, GERMANY SN 1430-175X J9 INT POLITIK JI Int. Polit. PD APR PY 2000 VL 55 IS 4 BP 9 EP 12 PG 4 WC International Relations; Political Science SC International Relations; Government & Law GA 314EH UT WOS:000087042000002 ER PT J AU Morey-Holton, ER Halloran, BP Garetto, LP Doty, SB AF Morey-Holton, ER Halloran, BP Garetto, LP Doty, SB TI Animal housing influences the response of bone to spaceflight in juvenile rats SO JOURNAL OF APPLIED PHYSIOLOGY LA English DT Article DE osteoporosis; weightlessness ID MESSENGER-RNA LEVELS; SPACE-FLIGHT; MATRIX PROTEINS; TRABECULAR BONE; CANCELLOUS BONE; GROWING RATS; WEIGHTLESSNESS; BIOCHEMISTRY; SKELETON; MODEL AB The rat has been used extensively as an animal model to study the effects of spaceflight on bone metabolism. The results of these studies have been inconsistent. On some missions, bone formation at the periosteal bone surface of weight-bearing bones is impaired and on others it is not, suggesting that experimental conditions may be an important determinant of bone responsiveness to spaceflight. To determine whether animal housing can affect the response of bone to spaceflight, we studied young growing (juvenile) rats group housed in the animal enclosure module and singly housed in the research animal holding facility under otherwise identical flight conditions (Spacelab Life Science 1). Spaceflight reduced periosteal bone formation by 30% (P < 0.001) and bone mass by 7% in single-housed animals but had Little or no effect on formation (-6%) or mass (-3%) in group-housed animals. Group housing reduced the response of bone to spaceflight by as much as 80%. The data suggest that housing can dramatically affect the skeletal response of juvenile rats to spaceflight. These observations explain many of the discrepancies in previous flight studies and emphasize the need to study more closely the effects of housing (physical-social interaction) on the response of bone to the weightlessness of space flight. C1 Vet Adm Med Ctr, Div Endocrinol, San Francisco, CA 94121 USA. NASA, Ames Res Ctr, Div Life Sci, Moffett Field, CA 94035 USA. Univ Calif San Francisco, Dept Med, San Francisco, CA 94121 USA. Indiana Univ, Sch Dent, Dept Oral Facial Dev, Indianapolis, IN 46202 USA. Indiana Univ, Sch Dent, Dept Physiol Biophys, Indianapolis, IN 46202 USA. Hosp Special Surg, Mineralized Tissues Res Sect, New York, NY 10021 USA. RP Halloran, BP (reprint author), Vet Adm Med Ctr, Div Endocrinol, 111N,4150 Clement St, San Francisco, CA 94121 USA. NR 40 TC 15 Z9 19 U1 0 U2 0 PU AMER PHYSIOLOGICAL SOC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 USA SN 8750-7587 J9 J APPL PHYSIOL JI J. Appl. Physiol. PD APR PY 2000 VL 88 IS 4 BP 1303 EP 1309 PG 7 WC Physiology; Sport Sciences SC Physiology; Sport Sciences GA 301MA UT WOS:000086312900022 PM 10749823 ER PT J AU Brooks, DP Nambi, P Laping, NJ Olson, BA Pullen, M Wade, CE AF Brooks, DP Nambi, P Laping, NJ Olson, BA Pullen, M Wade, CE TI Renal vasopressin receptor expression and function in rats following spaceflight SO JOURNAL OF APPLIED PHYSIOLOGY LA English DT Article DE microgravity; fluid balance; water metabolism; antidiuretic hormone AB It has been suggested there is a decreased renal responsiveness to vasopressin following spaceflight and that this may be the mechanism for the increased urine flow that is observed following return to normal gravity. In the present study, we have therefore measured vasopressin receptor expression and activity in kidneys taken from rats 1 and 14 days following spaceflight of 15 days duration. Measurements of renal vasopressin Vt and VI, receptor mRNA expression by quantitative RT-PCR demonstrated Little difference at either 1 day or at 14 days following return from space. Evaluation of H-3-labeled arginine vasopressin binding to membranes prepared from kidneys indicated that the majority of the vasopressin receptors were Vt receptors. Furthermore, the data suggested that binding to vasopressin V-2 or VI, receptors was unaltered at 1 day and 14 days following spaceflight. Similarly, the ability of vasopressin to stimulate adenylate cyclase suggested no change in vasopressin V2 receptor activity in these animals. These data suggest that, whatever changes in fluid and electrolyte metabolism are observed following spaceflight, they are not mediated by changes in vasopressin receptor number or vasopressin-induced stimulation of adenylate cyclase. C1 SmithKline Beecham Pharmaceut, Dept Renal Pharmacol, King Of Prussia, PA 19406 USA. NASA, Ames Res Ctr, Div Life Sci, Moffett Field, CA 94035 USA. RP Brooks, DP (reprint author), SmithKline Beecham Pharmaceut, Dept Renal Pharmacol, UW2521,709 Swedeland Rd,Box 1539, King Of Prussia, PA 19406 USA. NR 22 TC 3 Z9 4 U1 1 U2 1 PU AMER PHYSIOLOGICAL SOC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 USA SN 8750-7587 J9 J APPL PHYSIOL JI J. Appl. Physiol. PD APR PY 2000 VL 88 IS 4 BP 1316 EP 1320 PG 5 WC Physiology; Sport Sciences SC Physiology; Sport Sciences GA 301MA UT WOS:000086312900024 PM 10749825 ER PT J AU Lyu, CH Barnes, WL Barnes, RA AF Lyu, CH Barnes, WL Barnes, RA TI First results from the on-orbit calibrations of the visible and infrared scanner for the tropical rainfall measuring mission SO JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY LA English DT Article ID BIDIRECTIONAL REFLECTANCE SPECTROSCOPY; LUNAR; TRMM AB This work presents the first on-orbit calibration results using the Moon, the Sun, and cold deep space as inputs to the Visible and Infrared Scanner (VIRS) on board the Tropical Rainfall Measuring Mission (TRMM) satellite. The authors have developed lunar reflectance curves using VIRS data for phase angles ranging from 1.6 degrees to 82 degrees. Comparisons with modeled reflectance curves show that the VIRS lunar data are as predicted. Specifically, the six-parameter model of Helfenstein and Veverka provides a good description of the VIRS 0.62-mu m data. The lunar reflectance data will be used to discern long-term changes in VIRS response. Solar calibrations, performed using an onboard solar diffuser, show fluctuations of the VIRS responsivity of less than 1.3% and no indication of any systematic change during 11 months. Using the deep-space calibration implemented via a spacecraft maneuver on three different dates-7 January, 8 January, and 2 September 1998-the authors have measured the dependence of the scan mirror reflectance with angle of incidence for the VIRS thermal bands. These results have replaced the scan modulation curves adopted from the prelaunch measurements. From the on-orbit calibration results, it appears that the TRMM/VIRS is functioning as predicted by the prelaunch calibration and characterization tests and that there has been no discernable change in sensor performance during the first 11 months of operation. C1 NASA, Goddard Space Flight Ctr, Caelum Res Corp, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Lab Hydrospher Processes, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Gen Sci Corp, Beltsville, MD USA. RP Barnes, WL (reprint author), NASA, Goddard Space Flight Ctr, Lab Hydrospher Processes, Code 970, Greenbelt, MD 20771 USA. NR 18 TC 14 Z9 14 U1 0 U2 0 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0739-0572 J9 J ATMOS OCEAN TECH JI J. Atmos. Ocean. Technol. PD APR PY 2000 VL 17 IS 4 BP 385 EP 394 DI 10.1175/1520-0426(2000)017<0385:FRFTOO>2.0.CO;2 PG 10 WC Engineering, Ocean; Meteorology & Atmospheric Sciences SC Engineering; Meteorology & Atmospheric Sciences GA 307VN UT WOS:000086675000001 ER PT J AU Barnes, RA Barnes, WL Lyu, CH Gales, JM AF Barnes, RA Barnes, WL Lyu, CH Gales, JM TI An overview of the visible and infrared scanner radiometric calibration algorithm SO JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY LA English DT Article ID IMAGING SPECTRORADIOMETER MODIS; EOS-AM1 AB The Visible and Infrared Scanner (VIRS) is one of the principal instruments on board the Tropical Rainfall Measuring Mission (TRMM) satellite. VIRS measurements provide cloud-top temperatures and structures that complement the rainfall rates derived from other TRMM sensors. The VIRS radiometric calibration algorithm converts the digital data downlinked from the instrument into spectral radiances. VIRS has five bands: one in the visible, one in the shortwave infrared, and three in the thermal infrared. The calibration algorithm treats each band in the same manner except that the visible and shortwave infrared bands do not respond to the thermal radiation emitted by the instrument, and these bands do not have the nonlinear responses with input radiance found in the thermal bands. The calibration coefficients for the visible and shortwave infrared bands were determined in the laboratory before launch. VIRS carries a reference blackbody that is used to update the calibration coefficients for the thermal bands for each scan of the instrument on orbit. In addition, VIRS uses an onboard diffuser to view the Sun approximately once per month. The VIRS radiometric algorithm uses measurements of these reference sources to provide calibrated spectral radiances for each Earth pixel that it views. C1 Gen Sci Corp, Beltsville, MD USA. NASA, Goddard Space Flight Ctr, Lab Hydrospher Processes, Greenbelt, MD 20771 USA. Caelum Res Corp, Greenbelt, MD USA. George Mason Univ, Fairfax, VA 22030 USA. RP Barnes, WL (reprint author), NASA, Goddard Space Flight Ctr, Lab Hydrospher Processes, Code 970, Greenbelt, MD 20771 USA. NR 12 TC 29 Z9 29 U1 0 U2 2 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0739-0572 J9 J ATMOS OCEAN TECH JI J. Atmos. Ocean. Technol. PD APR PY 2000 VL 17 IS 4 BP 395 EP 405 DI 10.1175/1520-0426(2000)017<0395:AOOTVA>2.0.CO;2 PG 11 WC Engineering, Ocean; Meteorology & Atmospheric Sciences SC Engineering; Meteorology & Atmospheric Sciences GA 307VN UT WOS:000086675000002 ER PT J AU Boccippio, DJ Koshak, W Blakeslee, R Driscoll, K Mach, D Buechler, D Boeck, W Christian, HJ Goodman, SJ AF Boccippio, DJ Koshak, W Blakeslee, R Driscoll, K Mach, D Buechler, D Boeck, W Christian, HJ Goodman, SJ TI The Optical Transient Detector (OTD): Instrument characteristics and cross-sensor validation SO JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY LA English DT Article ID TIME STOCHASTIC-MODEL; TROPICAL RAINFALL; SAMPLING ERRORS; CLOUD AB Lightning data from the U.S. National Lightning Detection Network (NLDN) are used to perform preliminary validation of the satellite-based Optical Transient Detector (OTD). Sensor precision, accuracy, detection efficiency, and biases of the deployed instrument are considered. The sensor is estimated to have, on average, about 20-40-km spatial and better than 100-ms temporal accuracy. The detection efficiency for cloud-to-ground lightning is about 46%-69%. It is most likely slightly higher for intracloud lightning. There are only marginal day/night biases in the dataset, although 55- or 110-day averaging is required to remove the sampling-based diurnal lightning cycle bias. C1 NASA, George C Marshall Space Flight Ctr SD 60, Global Hydrol & Climate Ctr, Huntsville, AL 35806 USA. Univ Alabama, Huntsville, AL 35899 USA. Niagara Univ, Niagara Falls, NY USA. RP Boccippio, DJ (reprint author), NASA, George C Marshall Space Flight Ctr SD 60, Global Hydrol & Climate Ctr, 977 Explorer Blvd, Huntsville, AL 35806 USA. NR 29 TC 76 Z9 81 U1 0 U2 14 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0739-0572 J9 J ATMOS OCEAN TECH JI J. Atmos. Ocean. Technol. PD APR PY 2000 VL 17 IS 4 BP 441 EP 458 DI 10.1175/1520-0426(2000)017<0441:TOTDOI>2.0.CO;2 PG 18 WC Engineering, Ocean; Meteorology & Atmospheric Sciences SC Engineering; Meteorology & Atmospheric Sciences GA 307VN UT WOS:000086675000006 ER PT J AU Song, YT Chao, Y AF Song, YT Chao, Y TI An embedded bottom boundary layer formulation for z-coordinate ocean models SO JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY LA English DT Article ID SLOPING BOTTOM; DEEP-WATER; CIRCULATION; TOPOGRAPHY; DRIVEN; REPRESENTATION; EVOLUTION; SYSTEM; FLOW AB An embedded bottom boundary layer (EBBL) scheme is developed to improve the bottom topographic representation in z-coordinate ocean general circulation models. The EBBL scheme is based on the combined techniques of an embedded topography-following slab, an explicit turbulent bottom boundary layer (BBL), and a generalized pressure gradient formulation. The coupling between the interior z-level model and the EBBL model is achieved by exchanging entrainment/detrainment and pressure gradients at the bottom layer surface, which allows temporal and spatial variations. The EBBL is implemented into one of the most widely used z-coordinate models, the Modular Ocean Model (MOM). A test problem with a source of dense water on a slope is used. The new EBBL products significantly more realistic plume spreading than the existing BBL scheme of Killworth and Edwards and is comparable to the results from a topography-following coordinate model (SCRUM). which is believed to be more suitable for such a problem. Calculation of the momentum budget demonstrates that the improved representation of the downslope pressure gradient formulation plays an important role in the simulations of dense slope flows. Sensitivity experiments with different grid sizes, model parameters, and density contrast between the cold source water and the warm interior water are carried out to lest the robustness of the EBBL scheme. In contrast to the BBL model of Killworth and Edwards, which tends to diffuse too much dense water along isobaths. the EBBL model allows dense water to sink across isobaths through a very thin bottom layer into the deep ocean. Even in the coarser-resolution case (1/4 degrees and 15 levels) the EBBL produces more realistic deep water than the existing BBL with higher resolution (1/8 degrees and 30 levels), and at only one-eighth the computational cost. It is therefore concluded that the EBBL scheme presented here is cost effective and robust to model resolution and mixing parameters, and should be easily implemented in any nontopography-following coordinate ocean model. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Song, YT (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,M-S 300-323, Pasadena, CA 91109 USA. NR 33 TC 22 Z9 22 U1 0 U2 1 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0739-0572 J9 J ATMOS OCEAN TECH JI J. Atmos. Ocean. Technol. PD APR PY 2000 VL 17 IS 4 BP 546 EP 560 DI 10.1175/1520-0426(2000)017<0546:AEBBLF>2.0.CO;2 PG 15 WC Engineering, Ocean; Meteorology & Atmospheric Sciences SC Engineering; Meteorology & Atmospheric Sciences GA 307VN UT WOS:000086675000015 ER PT J AU Chappell, CR Giles, BL Moore, TE Delcourt, DC Craven, PD Chandler, MO AF Chappell, CR Giles, BL Moore, TE Delcourt, DC Craven, PD Chandler, MO TI The adequacy of the ionospheric source in supplying magnetospheric plasma SO JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS LA English DT Article ID POLAR WIND; MAGNETIC ACTIVITY; ION DYNAMICS; SHEET; OUTFLOW; FIELD; MAGNETOTAIL; INSTRUMENT; TRANSPORT; SATELLITE AB More than 30 years after the prediction of the polar wind outflow from the high latitude ionosphere, the exact magnitude and ultimate fate of the ionospheric plasma supply remains unknown. Estimates made more than a decade ago suggested that the polar ion outflow might well be of sufficient strength to populate the different regions of the Earth's magnetosphere. Direct measurements in the high altitude magnetosphere became possible only with the launch of the Polar spacecraft. The combination of the Thermal Ion Dynamics Experiment and the Plasma Source Instrument has revealed the presence of low energy (<10 eV) ions moving through the polar regions and into the lobes of the magnetotail, These ions would have been invisible to previous un-neutralized satellites because of the high positive spacecraft potentials. Through the use of a recently developed single particle trajectory and energization code, the movement and energy transformation of these measured particles can be estimated. They are found to move into the plasma sheet region and to be energized to typical plasma sheet energies. The magnitude of the flux of the highly variable out-flowing ions mapped to 1000 km altitude is 1 - 3 x 10(8) ion/cm(2) s in agreement with the original estimates. Future observations by the TIDE/PSI instruments will be required to determine the extent of the total ionospheric contribution. (C) 2000 Elsevier Science Ltd. All rights reserved. C1 Vanderbilt Univ, Dept Phys, Nashville, TN 37203 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Ctr Natl Etud Telecommun, Ctr Rech Phys Environm, St Maur Fosses, France. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Chappell, CR (reprint author), Vanderbilt Univ, Dept Phys, Nashville, TN 37203 USA. RI Moore, Thomas/D-4675-2012 OI Moore, Thomas/0000-0002-3150-1137 NR 27 TC 58 Z9 59 U1 1 U2 3 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1364-6826 J9 J ATMOS SOL-TERR PHY JI J. Atmos. Sol.-Terr. Phys. PD APR PY 2000 VL 62 IS 6 BP 421 EP 436 DI 10.1016/S1364-6826(00)00021-3 PG 16 WC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences SC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences GA 325KW UT WOS:000087675600003 ER PT J AU Liemohn, MW Kozyra, JU Khazanov, GV Craven, PD AF Liemohn, MW Kozyra, JU Khazanov, GV Craven, PD TI Effects of various transport processes on the streaming ion density during the first stage of plasmaspheric refilling SO JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS LA English DT Article DE plasmasphere; ionosphere-magnetosphere coupling; magnetic storms ID SUPERTHERMAL ELECTRONS; PLASMAPAUSE REGION; MODEL; FIELD; RECOVERY; FLOW AB The dependence of the first stage H+ plasmaspheric refilling density on various parameters is examined using a kinetic transport model. The first stage of refilling is defined as the time for the source cone to reach a quasi-steady-state level. Three influencing factors are examined in detail. The first two factors are actually studying numerical influences of physical phenomena. That is, the method of including these processes in the calculation is varied to determine the importance of calculational rigor. The two processes of interest are self-collisional feedback and the ambipolar electric field. The third influencing factor to be examined is the effect of coexistent energetic populations of the refilling rate. It is found that the results greatly depend on the method of incorporating self-collisions into the model, as the scattering and loss processes of the low-energy proton population interacting with itself has a significant influence on the early stage density. This interaction is particularly strong in the low-altitude region where the densities are high enough to substantially alter the distribution function. It is also found that the ambipolar electric field is the dominant force term, increasing the densities in the plasmasphere by accelerating the particles through the low-altitude scattering zone. The hot populations are found to have only a minor influence near the equatorial region, where they slow the H+ streams down and cause the density to slightly increase. The effects of hot ions are more pronounced in the streaming velocity and the temperature anistropy, but still confined to the equatorial region. (C) 2000 Elsevier Science Ltd. All rights reserved. C1 Univ Michigan, Space Phys Res Lab, Ann Arbor, MI 48109 USA. Univ Alaska, Inst Geophys, Fairbanks, AK 99775 USA. Univ Alaska, Dept Phys, Fairbanks, AK 99775 USA. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. RP Liemohn, MW (reprint author), Univ Michigan, Space Phys Res Lab, Ann Arbor, MI 48109 USA. RI Liemohn, Michael/H-8703-2012 OI Liemohn, Michael/0000-0002-7039-2631 NR 25 TC 2 Z9 2 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1364-6826 J9 J ATMOS SOL-TERR PHY JI J. Atmos. Sol.-Terr. Phys. PD APR PY 2000 VL 62 IS 6 BP 437 EP 447 DI 10.1016/S1364-6826(00)00018-3 PG 11 WC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences SC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences GA 325KW UT WOS:000087675600004 ER PT J AU Stevenson, BA Horwitz, JL Creel, B Elliott, HA Comfort, RH Moore, TE Craven, PD Su, YJ AF Stevenson, BA Horwitz, JL Creel, B Elliott, HA Comfort, RH Moore, TE Craven, PD Su, YJ TI Relationship of O+ field-aligned flows and densities to convection speed in the polar cap at 5000 km altitude SO JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS LA English DT Article ID CLEFT ION FOUNTAIN; WIND; DYNAMICS; REGION AB Measurements of thermal O+ ion number fluxes, densities, field-aligned velocities, and convection speeds from the Thermal Ion Dynamics Experiment (TIDE) on POLAR obtained near 5000 km altitude over the Southern hemisphere are examined. We find that the O+ parallel velocities, densities, and number fluxes are strongly related to the convection speeds. The polar cap densities decrease rapidly with convection speed, with a linear least square fit formula to bin averaged data giving the relationship log(NO+) = -0.33 * V-conv + 0.07, with a correlation coefficient of r = -0.96, The parallel bulk flow velocities are on average, slightly downward (0-2 km/s) for V-conv < 2.5 km/s, but tend to be upward (0-4 km/s) for average V-conv > 2 5 km/s. We also find that the downward number flux is strongly related to convection speed by log(Flux) = -0.54V(conv) + 5.14, with a correlation coefficient of r = -0.98, We interpret these relationships in terms of the Cleft Ion Fountain paradigm. The density decline with convection speed may result from increased spreading and resulting dilution from the restricted cleft source over the polar cap area with convection speed. The parallel velocities tend to be downward for low convection speeds because at such speeds, the ions fall earthward at shorter anti-sunward distances into the polar cap. At the higher convection speeds, the initially-upward flows are transported further into the polar cap and thus occupy a larger area of the polar cap. (C) 2000 Elsevier Science Ltd. All rights reserved. C1 Univ Alabama, Ctr Space Plasma & Aeronom Res, Huntsville, AL 35899 USA. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM USA. RP Stevenson, BA (reprint author), Univ Alabama, Ctr Space Plasma & Aeronom Res, S121-Tech Hall, Huntsville, AL 35899 USA. RI Moore, Thomas/D-4675-2012; OI Moore, Thomas/0000-0002-3150-1137; Stevenson, Benjamin/0000-0001-9918-1240 NR 18 TC 4 Z9 4 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1364-6826 J9 J ATMOS SOL-TERR PHY JI J. Atmos. Sol.-Terr. Phys. PD APR PY 2000 VL 62 IS 6 BP 495 EP 503 DI 10.1016/S1364-6826(00)00030-4 PG 9 WC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences SC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences GA 325KW UT WOS:000087675600009 ER PT J AU Moore, TE Giles, BL Delcourt, DC Fok, MC AF Moore, TE Giles, BL Delcourt, DC Fok, MC TI The plasma sheet source groove SO JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS LA English DT Article ID POLAR WIND; MAGNETOTAIL; ACCELERATION; IONS AB A test particle study of the ionospheric source of plasma in the Earth's plasma sheet has been performed, in an effort to understand an apparent inconsistency between the results of forward and backward (in time) test particle calculations. Most, if not all, forward calculations of polar wind ion outflows result in energetic plasma sheet ion populations; yet most, if not all, backward trajectory calculations from typical plasma sheet ion populations lead elsewhere than to low energy polar cap outflows. Using a trajectory discovered through forward calculation to connect these two regions, we found that the trajectory was only accurately reversible within an extremely narrow range of energy, pitch angle and gyrophase angle in the plasma sheet, referred to herein as 'the source groove'. This implies that ionospheric plasma tends to appear in the plasma sheet within narrow regions of velocity space, but is effectively diffused by fluctuations to form the observed more isotropic plasma sheet populations. The implications for backtracking test particle studies are discussed, and it is concluded that test particle backtracking from highly chaotic regions is impractical and should be supported by forward modeling of plasma flows up to the boundaries of such regions. (C) 2000 Elsevier Science Ltd. All rights reserved. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Ctr Etud Environm Terr & Planetaire, St Maur, France. Univ Space Res Assoc, Greenbelt, MD USA. RP Moore, TE (reprint author), NASA, Goddard Space Flight Ctr, 138 Mail Code 692, Greenbelt, MD 20771 USA. RI Moore, Thomas/D-4675-2012; Fok, Mei-Ching/D-1626-2012 OI Moore, Thomas/0000-0002-3150-1137; NR 17 TC 6 Z9 6 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1364-6826 J9 J ATMOS SOL-TERR PHY JI J. Atmos. Sol.-Terr. Phys. PD APR PY 2000 VL 62 IS 6 BP 505 EP 512 DI 10.1016/S1364-6826(00)00014-6 PG 8 WC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences SC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences GA 325KW UT WOS:000087675600010 ER PT J AU Loeb, NG Parol, F Buriez, JC Vanbauce, C AF Loeb, NG Parol, F Buriez, JC Vanbauce, C TI Top-of-atmosphere albedo estimation from angular distribution models using scene identification from satellite cloud property retrievals SO JOURNAL OF CLIMATE LA English DT Article ID EARTH RADIATION BUDGET; ENERGY SYSTEM CERES; EXPERIMENT ERBE; NIMBUS-7 ERB; CLIMATE; MISSION; POLDER; REFLECTANCES; VALIDATION; SCATTERING AB The next generation of earth radiation budget satellite instruments will routinely merge estimates of global top-of-atmosphere radiative fluxes with cloud properties. This information will offer many new opportunities for validating radiative transfer models and cloud parameterizations in climate models. In this study, five months of Polarization and Directionality of the Earth's Reflectances 670-nm radiance measurements are considered in order to examine how satellite cloud property retrievals can be used to define empirical angular distribution models (ADMs) for estimating top-of-atmosphere albedo. ADMs are defined for 19 scene types defined by satellite retrievals of cloud fraction and cloud optical depth. Two approaches are used to define the ADM scene types. The first assumes there are no biases in the retrieved cloud properties and defines ADMs for fixed discrete intervals of cloud fraction and cloud optical depth (fixed-tau approach). The second approach involves the same cloud fraction intervals, hut uses percentile intervals of cloud optical depth instead (percentile-tau approach). Albedos generated using these methods are compared with albedos inferred directly from the mean observed reflectance field. Aibedos based on ADMs that assume cloud properties are unbiased (fixed-tau approach) show a strong systematic dependence on viewing geometry. This dependence becomes more pronounced with increasing solar zenith angle, reaching approximate to 12% (relative) between near-nadir and oblique viewing zenith angles for solar zenith angles between 60 degrees and 70 degrees. The cause for this bias is shown to be due to biases in the cloud optical depth retrievals. In contrast, albedos based on ADMs built using percentile intervals of cloud optical depth (percentile-tau approach) show very little viewing zenith angle dependence and are in good agreement with albedos obtained by direct integration of the mean observed reflectance field (<1% relative error). When the ADMs are applied separately to populations consisting of only liquid water and ice clouds, significant biases in albedo with viewing geometry are observed (particularly at low sun elevations), highlighting the need to account for cloud phase both in cloud optical depth retrievals and in defining ADM scene types. ADM-derived monthly mean albedos determined for all 5 degrees x 5 degrees lat-long regions over ocean are in good agreement (regional rms relative errors <2%) with those obtained by direct integration when ADM albedos inferred from specific angular bins are averaged together. Albedos inferred from near-nadir and oblique viewing zenith angles are the least accurate, with regional rms errors reaching similar to 5%-10% (relative). Compared to an earlier study involving Earth Radiation Budget Experiment ADMs, regional mean albedos based on the 19 scene types considered here show a factor-of-4 reduction in bias error and a factor-of-3 reduction in rms error. C1 Hampton Univ, Ctr Atmospher Sci, Hampton, VA USA. Univ Sci & Technol, Opt Atmospher Lab, Lille, France. RP Loeb, NG (reprint author), NASA, Langley Res Ctr, Mail Stop 420, Hampton, VA 23681 USA. NR 39 TC 26 Z9 27 U1 1 U2 3 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 1 PY 2000 VL 13 IS 7 BP 1269 EP 1285 DI 10.1175/1520-0442(2000)013<1269:TOAAEF>2.0.CO;2 PG 17 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 300YG UT WOS:000086280900003 ER PT J AU Zhu, S Su, CH Lehoczky, SL Peters, P George, MA AF Zhu, S Su, CH Lehoczky, SL Peters, P George, MA TI Pressure effects in ZnO films using off-axis sputtering deposition SO JOURNAL OF CRYSTAL GROWTH LA English DT Article; Proceedings Paper CT 11th American Conference on Crystal Growth and Epitaxy CY AUG 01-06, 1999 CL TUCSON, ARIZONA SP Assoc Crystal Growth, NASA, Div Micrograv Sci & Applicat, Adv Ceram Corp, Adv Specialty Chem, Bicron Opt, Capen Simulat Inc, Cleveland Crystals Inc, Crystal Associates Inc, Crystal Photon Inc, Crystal Technol Inc, Engis Corp, Engelhard-Clal LP, INRAD Inc, Johnson Matthey, Div Electr, Johnson Matthey, Div Alfa Aesar, Johnson Matthey, Div Mfg Technol, Litton Airton Synopt, Lockheed Martin Sanders, OPTOVAC, PROCHEM, Quantum Technol Inc, Sawyer Res Prod, Sensors Unltd Inc, Thermcraft Inc, II-VI Inc, Zirmat Corp DE ZnO; photonic material; off-axis sputtering; morphology; growth mechanism AB ZnO films are deposited on (0 0 0 1) sapphire and quartz substrates using the off-axis reactive magnetron sputtering deposition. Based on film thickness measurements, three transport regions of sputtered particles are observed when films are deposited in the pressure regions of 5-150 mTorr, X-ray diffraction, scanning probes microscopy, and electrical measurements are also used to characterize these films. The full-width at half-maximum of theta-rocking curves for epitaxial films is less than 0.5 degrees. In textured films, it rises to several degrees. The epitaxial films deposited at high pressure reveal a flat surface with some hexagonal facets. The density of hexagonal facets decreases when the growth pressure is reduced. The resistivity of these epitaxial films also depends on the growth pressures. A relationship between the pressure effects and film properties are discussed. (C) 2000 Elsevier Science B.V. All rights reserved. C1 NASA, George C Marshall Space Flight Ctr, Space Sci Lab, USRA, Huntsville, AL 35812 USA. NASA, George C Marshall Space Flight Ctr, Sci Directory, Huntsville, AL 35812 USA. Univ Alabama, Dept Chem, Huntsville, AL 35899 USA. RP Zhu, S (reprint author), NASA, George C Marshall Space Flight Ctr, Space Sci Lab, USRA, SD47, Huntsville, AL 35812 USA. NR 12 TC 25 Z9 25 U1 0 U2 3 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 APR PY 2000 VL 211 IS 1-4 BP 106 EP 110 DI 10.1016/S0022-0248(99)00798-8 PG 5 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA 299LG UT WOS:000086199600020 ER PT J AU Thomas, BR Chernov, AA Vekilov, PG Carter, DC AF Thomas, BR Chernov, AA Vekilov, PG Carter, DC TI Distribution coefficients of protein impurities in ferritin and lysozyme crystals - Self-purification in microgravity SO JOURNAL OF CRYSTAL GROWTH LA English DT Article; Proceedings Paper CT 11th American Conference on Crystal Growth and Epitaxy CY AUG 01-06, 1999 CL TUCSON, AZ SP Assoc Crystal Growth, NASA, Div Micrograv Sci & Applicat, Adv Ceram Corp, Adv Specialty Chem, Bicron Opt, Capen Simulat Inc, Cleveland Crystals Inc, Crystal Associates Inc, Crystal Photon Inc, Crystal Technol Inc, Engis Corp, Engelhard-Clal LP, INRAD Inc, Johnson Matthey, Div Electr, Johnson Matthey, Div Alfa Aesar, Johnson Matthey, Div Mfg Technol, Litton Airton Synopt, Lockheed Martin Sanders, OPTOVAC, PROCHEM, Quantum Technol Inc, Sawyer Res Prod, Sensors Unltd Inc, Thermcraft Inc, II-VI Inc, Zirmat Corp ID GROWTH; CRYSTALLIZATION; TRANSPORT; KINETICS AB Ribonuclease, insulin, cytochrome C, myoglobin and ovalbumin were introduced into solutions from which ferritin and lysozyme crystals were grown. These measurements were also performed for the ferritin dimers trapped by growing ferritin crystals. The crystals were later dissolved in a pure solvent, the impurity concentrations were measured by high performance liquid chromatography and the effective impurity distribution coefficient, K, was evaluated relative to the initial concentrations of ferritin or lysozyme. The density of impurity species in crystal relative to its density in mother solution were used to calculate volumetric distribution coefficient, k. These distribution coefficients were found to exceed unity (k > 1) in terrestrial condition for all impurity species, except for insulin and cytochrome C lysozyme. For ferritin dimers, K = 4, k = 1.8 x 10(3). Crystals grown in space under the otherwise identical conditions incorporated lower amounts of all of these impurities, majority of them below the detection limit. The lower impurity incorporation obtained in stagnant solution may be partially due to more difficult impurity supply through the impurity depletion zone arising around the growing crystals at k > 1 in the absence of buoyancy driven convection or stirring. Analytical estimates of the depletion zone show reasonable agreement with measurements for ferritin dimers. Step bunching and other flow-dependent surface processes may also contribute to lower distribution coefficient. (C) 2000 Elsevier Science B.V. All rights reserved. C1 NASA, George C Marshall Space Flight Ctr, Univ Space Res Assoc, Huntsville, AL 35805 USA. Univ Alabama, Dept Chem, Huntsville, AL 35899 USA. Univ Alabama, Ctr Micrograv Mat Res, Huntsville, AL 35899 USA. New Century Pharmaceut, Huntsville, AL 35824 USA. RP Chernov, AA (reprint author), NASA, George C Marshall Space Flight Ctr, Univ Space Res Assoc, 4950 Corp Dr,Suite 100, Huntsville, AL 35805 USA. EM alex.chernov@msfc.nasa.gov NR 24 TC 54 Z9 57 U1 0 U2 7 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 APR PY 2000 VL 211 IS 1-4 BP 149 EP 156 DI 10.1016/S0022-0248(99)00813-1 PG 8 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA 299LG UT WOS:000086199600026 ER PT J AU Mauk, MG Shellenbarger, ZA Cox, JA Sulima, OV Bett, AW Mueller, RL Sims, PE McNeely, JB DiNetta, LC AF Mauk, MG Shellenbarger, ZA Cox, JA Sulima, OV Bett, AW Mueller, RL Sims, PE McNeely, JB DiNetta, LC TI Liquid-phase epitaxy of low-bandgap III-V antimonides for thermophotovoltaic devices SO JOURNAL OF CRYSTAL GROWTH LA English DT Article; Proceedings Paper CT 11th American Conference on Crystal Growth and Epitaxy CY AUG 01-06, 1999 CL TUCSON, ARIZONA SP Assoc Crystal Growth, NASA, Div Micrograv Sci & Applicat, Adv Ceram Corp, Adv Specialty Chem, Bicron Opt, Capen Simulat Inc, Cleveland Crystals Inc, Crystal Associates Inc, Crystal Photon Inc, Crystal Technol Inc, Engis Corp, Engelhard-Clal LP, INRAD Inc, Johnson Matthey, Div Electr, Johnson Matthey, Div Alfa Aesar, Johnson Matthey, Div Mfg Technol, Litton Airton Synopt, Lockheed Martin Sanders, OPTOVAC, PROCHEM, Quantum Technol Inc, Sawyer Res Prod, Sensors Unltd Inc, Thermcraft Inc, II-VI Inc, Zirmat Corp ID PHOTODETECTORS; GAINASSB AB Liquid-phase epitaxial (LPE) growth of low-bandgap III-V antimonides is developed for thermophotovoltaic and other optoelectronic device applications. Epitaxial layers of AlGaAsSb, InGaAsSb, and InAsSbP, with thicknesses up to 200 mu m, can be grown in a single LPE step. TPV devices based on InAsSbP extend the spectral response to a wavelength of 3500 nm. These single-epilayer structures are compatible with post-growth zinc diffusion processes that produce high-performance TPV devices. Thick epitaxial layers are also conducive for epilayer film transfer to surrogate substrates and subsequent removal of the GaSb and InAs seeding substrate. An insulating surrogate substrate facilitates isolation schemes for monolithic series-interconnected TPV arrays, and a reflective substrate acting as a backside mirror is used to effect photon recycling. (C) 2000 Elsevier Science B.V. All rights reserved. C1 AstroPower Inc, Newark, DE 19716 USA. Fraunhofer Inst Solar Energy Syst, D-79100 Freiburg, Germany. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Mauk, MG (reprint author), AstroPower Inc, Solar Pk, Newark, DE 19716 USA. RI Bett, Andreas/A-5888-2010 NR 16 TC 25 Z9 28 U1 0 U2 3 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 APR PY 2000 VL 211 IS 1-4 BP 189 EP 193 DI 10.1016/S0022-0248(99)00796-4 PG 5 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA 299LG UT WOS:000086199600033 ER PT J AU Zhu, S Banks, CE Frazier, DO Penn, B Abdeldayem, H Hicks, R Burns, HD Thompson, GW AF Zhu, S Banks, CE Frazier, DO Penn, B Abdeldayem, H Hicks, R Burns, HD Thompson, GW TI Structure and morphology of phthalocyanine films grown in electrical fields by vapor deposition SO JOURNAL OF CRYSTAL GROWTH LA English DT Article; Proceedings Paper CT 11th American Conference on Crystal Growth and Epitaxy CY AUG 01-06, 1999 CL TUCSON, ARIZONA SP Assoc Crystal Growth, NASA, Div Micrograv Sci & Applicat, Adv Ceram Corp, Adv Specialty Chem, Bicron Opt, Capen Simulat Inc, Cleveland Crystals Inc, Crystal Associates Inc, Crystal Photon Inc, Crystal Technol Inc, Engis Corp, Engelhard-Clal LP, INRAD Inc, Johnson Matthey, Div Electr, Johnson Matthey, Div Alfa Aesar, Johnson Matthey, Div Mfg Technol, Litton Airton Synopt, Lockheed Martin Sanders, OPTOVAC, PROCHEM, Quantum Technol Inc, Sawyer Res Prod, Sensors Unltd Inc, Thermcraft Inc, II-VI Inc, Zirmat Corp DE organic material; electrical field; phthalocyanine; non-linear optical material; vapor growth ID LANGMUIR-BLODGETT-FILMS; THIN-FILMS AB Phthalocyanine (Pc) films have been synthesized by vapor deposition on quartz substrates. some of which were coated with a very thin gold film before depositing the Pc films. Electrical fields up to 6200 V/cm between a mech electrode and the substrate are introduced during film growth. These films have been characterized by X-ray diffraction and scanning electron microscopy. The molecular orientations and surface morphology of Pc films were changed under the electrical fields. The surface of these films grown without an electrical field shows whisk-like morphology. When films are deposited under an electrical field. a dense film with a flat surface is obtained. (C) 2000 Elsevier Science B.V. All rights reserved. C1 NASA, George C Marshall Space Flight Ctr, Space Sci Lab, USRA, Huntsville, AL 35812 USA. NASA, George C Marshall Space Flight Ctr, Sci Directorate, Huntsville, AL 35812 USA. NASA, George C Marshall Space Flight Ctr, Engn Directorate, Huntsville, AL 35812 USA. Univ Alabama, Ctr Automat & Robot, Huntsville, AL 35899 USA. RP Zhu, S (reprint author), NASA, George C Marshall Space Flight Ctr, Space Sci Lab, USRA, Huntsville, AL 35812 USA. OI banks, craig/0000-0002-0756-9764 NR 12 TC 10 Z9 10 U1 0 U2 1 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 APR PY 2000 VL 211 IS 1-4 BP 308 EP 312 DI 10.1016/S0022-0248(99)00773-3 PG 5 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA 299LG UT WOS:000086199600055 ER PT J AU Yesilyurt, S Vjusic, L Motakef, S Szofran, FR Croell, A AF Yesilyurt, S Vjusic, L Motakef, S Szofran, FR Croell, A TI The influence of thermoelectromagnetic convection (TEMC) on the Bridgman growth of semiconductors SO JOURNAL OF CRYSTAL GROWTH LA English DT Article; Proceedings Paper CT 11th American Conference on Crystal Growth and Epitaxy CY AUG 01-06, 1999 CL TUCSON, ARIZONA SP Assoc Crystal Growth, NASA, Div Micrograv Sci & Applicat, Adv Ceram Corp, Adv Specialty Chem, Bicron Opt, Capen Simulat Inc, Cleveland Crystals Inc, Crystal Associates Inc, Crystal Photon Inc, Crystal Technol Inc, Engis Corp, Engelhard-Clal LP, INRAD Inc, Johnson Matthey, Div Electr, Johnson Matthey, Div Alfa Aesar, Johnson Matthey, Div Mfg Technol, Litton Airton Synopt, Lockheed Martin Sanders, OPTOVAC, PROCHEM, Quantum Technol Inc, Sawyer Res Prod, Sensors Unltd Inc, Thermcraft Inc, II-VI Inc, Zirmat Corp DE thermoelectromagnetic convection; vertical Bridgman growth ID METALLIC ALLOYS; MAGNETIC-FIELD; CRYSTAL-GROWTH; SOLIDIFICATION AB Application of a low-intensity axial magnetic field can promote significant convection Juring Bridgman growth of GeSi when resident thermoelectric currents at the growth interface are large due to the difference of thermoelectric powers of the melt and of the crystal and the tangential temperature gradient at the interface. Thermoelectromagnetic convection (TEMC) in the GeSi melt is characterized by a meridional flow driven by the rotation of the fluid due to the azimuthal Lorentz force from currents in the radial direction concentrated near the interface and an axial magnetic field. In this work. we developed a computational model to study convection of the GeSi melt in varying g and magnetic field intensity levels. (C) 2000 Elsevier Science B.V. All rights: reserved. C1 Cape Simulat Inc, Newton, MA 02458 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Univ Alabama, AMMSA, Huntsville, AL 35803 USA. RP Yesilyurt, S (reprint author), Cape Simulat Inc, 1 Bridge St, Newton, MA 02458 USA. RI Yesilyurt, Serhat/H-9546-2013; Croell, Arne/A-2480-2013 OI Yesilyurt, Serhat/0000-0001-5425-1532; Croell, Arne/0000-0002-8673-9994 NR 16 TC 3 Z9 3 U1 0 U2 4 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 APR PY 2000 VL 211 IS 1-4 BP 360 EP 364 DI 10.1016/S0022-0248(99)00808-8 PG 5 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA 299LG UT WOS:000086199600064 ER PT J AU Bune, AV Sen, S Mukherjee, S Catalina, A Stefanescu, DM AF Bune, AV Sen, S Mukherjee, S Catalina, A Stefanescu, DM TI Effect of melt convection at various gravity levels and orientations on the forces acting on a large spherical particle in the vicinity of a solidification interface SO JOURNAL OF CRYSTAL GROWTH LA English DT Article; Proceedings Paper CT 11th American Conference on Crystal Growth and Epitaxy CY AUG 01-06, 1999 CL TUCSON, ARIZONA SP Assoc Crystal Growth, NASA, Div Micrograv Sci & Applicat, Adv Ceram Corp, Adv Specialty Chem, Bicron Opt, Capen Simulat Inc, Cleveland Crystals Inc, Crystal Associates Inc, Crystal Photon Inc, Crystal Technol Inc, Engis Corp, Engelhard-Clal LP, INRAD Inc, Johnson Matthey, Div Electr, Johnson Matthey, Div Alfa Aesar, Johnson Matthey, Div Mfg Technol, Litton Airton Synopt, Lockheed Martin Sanders, OPTOVAC, PROCHEM, Quantum Technol Inc, Sawyer Res Prod, Sensors Unltd Inc, Thermcraft Inc, II-VI Inc, Zirmat Corp DE binary alloy; modeling; FIDAP; microgravity ID ENGULFMENT AB Numerical modeling was undertaken to analyze the influence of both radial and axial thermal gradients on convection patterns and velocities during solidification of pure Al and an Al-4 wt% Cu alloy. The objective of the numerical task was to predict the influence of convective velocity on an insoluble particle near a solid/liquid (s/l) interface. These predictions were then be used to define the minimum gravity level (g) required to investigate the fundamental physics of interactions between a particle and a s/l interface. This is an ongoing NASA funded flight experiment entitled "particle engulfment and pushing by solidifying interfaces (PEP)". Steady-state calculations were performed for different gravity levels and orientations with respect to the gravity vector. The furnace configuration used in this analysis is the quench module insert (QMI-1) proposed for the Material Science Research Facility (MSRF) on board the international Space Station (ISS). The general model of binary alloy solidification was based on the finite element code FIDAP. At a low g level of 10(-4)g(0) (g(0) = 9.8 m/s(2)) maximum melt convection was obtained for an orientation of 90 degrees. Calculations showed that even for this worst case orientation the dominant forces acting on the particle are the fundamental drag and interfacial forces. (C) 2000 Elsevier Science B.V. All rights reserved. C1 NASA, George C Marshall Space Flight Ctr, Univ Space Res Assoc, Huntsville, AL 35812 USA. Univ Alabama, Solidification Lab, Tuscaloosa, AL 35487 USA. RP Bune, AV (reprint author), NASA, George C Marshall Space Flight Ctr, Univ Space Res Assoc, SD 47, Huntsville, AL 35812 USA. RI Stefanescu, Doru/G-8101-2012; Mukherjee, Sundeep/N-5247-2014; OI Stefanescu, Doru M./0000-0001-5544-8396 NR 7 TC 10 Z9 10 U1 0 U2 4 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 APR PY 2000 VL 211 IS 1-4 BP 446 EP 451 DI 10.1016/S0022-0248(99)00785-X PG 6 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA 299LG UT WOS:000086199600079 ER PT J AU Hexmoor, H Kortenkamp, D AF Hexmoor, H Kortenkamp, D TI Introduction to autonomy control software SO JOURNAL OF EXPERIMENTAL & THEORETICAL ARTIFICIAL INTELLIGENCE LA English DT Editorial Material ID AI C1 Univ N Dakota, Dept Comp Sci, Grand Forks, ND 58202 USA. NASA, Lyndon B Johnson Space Ctr ER 2, Houston, TX 77058 USA. EM hexmoor@cs.und.edu; kortenkamp@jsc.nasa.gov NR 14 TC 2 Z9 2 U1 0 U2 0 PU TAYLOR & FRANCIS LTD PI ABINGDON PA 4 PARK SQUARE, MILTON PARK, ABINGDON OX14 4RN, OXON, ENGLAND SN 0952-813X J9 J EXP THEOR ARTIF IN JI J. Exp. Theor. Artif. Intell. PD APR-JUN PY 2000 VL 12 IS 2 BP 123 EP 127 DI 10.1080/095281300409784 PG 5 WC Computer Science, Artificial Intelligence SC Computer Science GA 338EJ UT WOS:000088404900001 ER PT J AU Pi, XQ Mendillo, M Hughes, WJ Buonsanto, MJ Sipler, DP Kelly, J Zhou, QH Lu, G Hughes, TJ AF Pi, XQ Mendillo, M Hughes, WJ Buonsanto, MJ Sipler, DP Kelly, J Zhou, QH Lu, G Hughes, TJ TI Dynamical effects of geomagnetic storms and substorms in the middle-latitude ionosphere: An observational campaign SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID F-REGION ELECTRODYNAMICS; AURORAL RED ARCS; ELECTRIC-FIELDS; INCOHERENT-SCATTER; MILLSTONE-HILL; NEUTRAL WINDS; SOLAR-CYCLE; DISTURBANCE DYNAMO; MAGNETIC STORM; MU RADAR AB An observational campaign was conducted in October 1992 for similar to 36 hours, at three high- to low-latitude sites near 75 degrees W longitude (Sondre Stromfjord, Millstone Hill, and Arecibo). Vector plasma drift velocities are obtained using the incoherent scatter radar technique at each site, Neutral winds were measured using a Fabry-Perot interferometer, and 6300 Angstrom airglow structures were imaged at the midlatitude site. Electric fields and meridional winds for the period were;perturbed when magnetic storms and substorms occurred on the day and night of the campaign. The penetration of magnetospheric electric field and the following interplays between ionospheric electrodynamics and thermospheric wind perturbations in the midlatitude ionosphere are assessed using the multidiagnostic measurements. Evidence for traveling atmospheric disturbances (TADs) and large-scale gravity waves induced by auroral heating effects upon the thermosphere is identified. Diffuse aurora and a stable aurora red (SAR) are were observed from Millstone Hill during the night of the campaign. The SAR are moved southward when there were westward electric field perturbations, indicating plasmasphere compression in the postmidnight sector under substorm conditions. The SAR are location was used to infer the motion of the magnetospheric shielding layer past the Millstone Hill site. Ionospheric F region disturbances in h(m)F(2), NmF2, and total electron content were driven by the observed dynamics, exhibiting a complex mix of wind and electric field perturbations. While standard model episodes of penetration and shielding/overshielding occurred during the daytime event, such unambiguous clarifications were far less obvious during the nighttime event. This is perhaps due to the prolonged period of moderate geomagnetic activity that served as the background conditions for the substorms that occurred during the campaign. C1 Boston Univ, Ctr Space Phys, Boston, MA 02215 USA. MIT, Haystack Observ, Atmospher Sci Grp, Westford, MA 01886 USA. Natl Res Council Canada, Herzberg Inst Astrophys, Ottawa, ON K1A 0R6, Canada. SRI Int, Menlo Park, CA 94025 USA. Natl Ctr Atmospher Res, High Altitude Observ, Boulder, CO 80307 USA. Natl Astron & Ionosphere Ctr, Arecibo Observ, Arecibo, PR 00613 USA. RP Pi, XQ (reprint author), CALTECH, Jet Prop Lab, MS 138-308,4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Lu, Gang/A-6669-2011; Mendillo, Michael /H-4397-2014 NR 53 TC 21 Z9 21 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD APR 1 PY 2000 VL 105 IS A4 BP 7403 EP 7417 DI 10.1029/1999JA900460 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 300FZ UT WOS:000086222800001 ER PT J AU Webb, DF Cliver, EW Crooker, NU Cyr, OCS Thompson, BJ AF Webb, DF Cliver, EW Crooker, NU Cyr, OCS Thompson, BJ TI Relationship of halo coronal mass ejections, magnetic clouds, and magnetic storms SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID EARTH CONNECTION EVENT; X-RAY EVENTS; GEOMAGNETIC-ACTIVITY; JANUARY 1997; SOLAR ORIGIN; CYCLE; CMES; WIND; TRANSIENTS; DISRUPTION AB Halo coronal mass ejections (CMEs) had been rarely reported in coronagraph observations of the Sun before the Solar and Heliospheric Observatory (SOHO) mission. Since mid-1996, however, the SOHO Large Angle Spectrometric Coronagraph (LASCO) instruments have observed many halo or partial-halo CMEs. A halo CME, especially when associated with solar activity near sun center, is important for space weather concerns because it suggests the launch of a potentially geoeffective disturbance toward Earth. During the post-solar minimum period from December 1996 to June 1997, we found that all six halo CMEs that were likely Earthward-directed were associated with shocks, magnetic clouds, and moderate geomagnetic storms at Earth 3-5 days later. The results imply that magnetic cloud-like structures are a general characteristic of CMEs. Most of the storms were driven by strong, sustained southward fields either in the magnetic clouds, in the post-shock region, or both. We discuss the characteristics of the halo events observed during this period, their associated signatures near the solar surface, and their usefulness as predictors of space weather at Earth. C1 Boston Coll, Inst Sci Res, Newton Ctr, MA USA. USAF, Res Lab, VSBS, Bedford, MA 01731 USA. Boston Univ, Ctr Space Phys, Boston, MA 02215 USA. NASA, Goddard Space Flight Ctr, CPI, USN,Res Lab, Greenbelt, MD 20771 USA. RP Boston Coll, Inst Sci Res, Newton Ctr, MA USA. EM webb@plh.af.mil RI Thompson, Barbara/C-9429-2012 NR 59 TC 221 Z9 228 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9380 EI 2169-9402 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD APR 1 PY 2000 VL 105 IS A4 BP 7491 EP 7508 DI 10.1029/1999JA000275 PG 18 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 300FZ UT WOS:000086222800009 ER PT J AU Cargill, PJ Schmidt, J Spicer, DS Zalesak, ST AF Cargill, PJ Schmidt, J Spicer, DS Zalesak, ST TI Magnetic structure of overexpanding coronal mass ejections: Numerical models SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID SOLAR-WIND; MAGNETOHYDRODYNAMIC SIMULATIONS; FLUX TUBES; CLOUDS; DRIVEN AB Numerical simulations are presented of the evolution of overexpanding coronal mass ejections (OCMEs), which are also magnetic clouds. The OCME is assumed to arise from the evolution of a magnetic flux rope with high plasma and magnetic pressure and high plasma density near the Sun in a high-speed solar wind. It is shown that the flux rope maintains its integrity from near the Sun to approximate to 5 AU, resisting hydrodynamic forces that tend to distort it. Thus OCMEs that are magnetic clouds at large heliocentric distances should have simply evolved from near-Sun flux ropes. It is shown that an initially circular flux rope is distorted into a hemispheric shape by its interaction with solar wind plasma hows. Forward and reverse shock pairs form with the forward shock being curved while the reverse shock is straight. The magnetic field properties at large distances are shown to depend on whether the initial flux rope undergoes overexpansion. A flux rope that is convected passively in the solar wind without overexpansion will ultimately have a magnetic field profile dominated by its toroidal component, so would not be observed as a magnetic cloud. The overexpanding flux ropes modeled here maintain an approximately equal ratio of toroidal to poloidal magnetic fields. The relative initial speed of the flux rope with respect to the solar wind does not influence the large-scale magnetic properties up to 5 AU, although it does affect the detailed field topology. C1 Univ London Imperial Coll Sci Technol & Med, Blackett Lab, London SW7 2BZ, England. NASA, Goddard Space Flight Ctr, Ctr Computat Sci, Greenbelt, MD 20771 USA. RP Cargill, PJ (reprint author), Univ London Imperial Coll Sci Technol & Med, Blackett Lab, Prince Consort Rd, London SW7 2BZ, England. OI Schmidt, Joachim/0000-0002-7927-0665 NR 25 TC 42 Z9 43 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 APR 1 PY 2000 VL 105 IS A4 BP 7509 EP 7519 DI 10.1029/1999JA900479 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 300FZ UT WOS:000086222800010 ER PT J AU Kuznetsova, MM Hesse, M Winske, D AF Kuznetsova, MM Hesse, M Winske, D TI Toward a transport model of collisionless magnetic reconnection SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID PARTICLE SIMULATION; CURRENT SHEETS; TEARING MODE; MAGNETOTAIL CONFIGURATION; HYBRID SIMULATIONS; MHD SIMULATIONS; X-LINE; DYNAMICS; FIELD; INSTABILITIES AB An absence of theoretical justification for the magnitude of resistivity is one of the major limitations of large-scale simulations of magnetic reconnection in collisionless magnetospheric plasma. We took advantage of the results of recent progress in kinetic modeling of collisionless dissipation in the vicinity of the magnetically neutral X point aiming to find ways to represent small-scale kinetic effects in large-scale models. The study was based on a combination of hybrid and particle methods and on analytical analysis. A comprehensive hybrid simulation code which incorporates the leading terms in electron dynamics responsible for breaking the frozen magnetic flux constraint (electron bulk flow inertia and nongyrotropic pressure effects) was utilized. The results of the comprehensive hybrid model were found to be in excellent quantitative agreement with the results of full particle simulations with similar setups. Both simulations demonstrated that the actual reconnection electric field is determined primarily by kinetic quasi-viscous effects and less by electron bulk flow inertia. An analytical expression for the quasi-viscous reconnection electric field averaged over the nongyrotropic region was obtained. Similar behavior of the evaluated quasi-viscous electric field and actual reconnection electric field taken from the simulations was demonstrated. Conventional hybrid simulations with simple nongyrotropic corrections to the electric field where also performed. The model was further reduced for utilization in MHD models. Analytical expressions for the time evolution of the reconnected flux evaluated from the MHD model modified by nongyrotropic corrections appeared to be in very good agreement with the results of comprehensive kinetic simulations. The evaluated averaged quasi-viscous electric field can be substituted into large-scale simulation models. C1 NASA, Goddard Space Flight Ctr, Electrodynam Branch, Greenbelt, MD 20771 USA. Univ Calif Los Alamos Natl Lab, Div Appl Theoret Phys, Los Alamos, NM 87545 USA. RP Kuznetsova, MM (reprint author), NASA, Goddard Space Flight Ctr, Electrodynam Branch, Greenbelt, MD 20771 USA. RI Hesse, Michael/D-2031-2012; Kuznetsova, Maria/F-6840-2012 NR 42 TC 36 Z9 36 U1 0 U2 4 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 2000 VL 105 IS A4 BP 7601 EP 7616 DI 10.1029/1999JA900396 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 300FZ UT WOS:000086222800018 ER PT J AU Farrugia, CJ Gratton, FT Contin, J Cocheci, CC Arnoldy, RL Ogilvie, KW Lepping, RP Zastenker, GN Nozdrachev, MN Fedorov, A Sauvaud, JA Steinberg, JT Rostoker, G AF Farrugia, CJ Gratton, FT Contin, J Cocheci, CC Arnoldy, RL Ogilvie, KW Lepping, RP Zastenker, GN Nozdrachev, MN Fedorov, A Sauvaud, JA Steinberg, JT Rostoker, G TI Coordinated Wind, Interball/tail, and ground observations of Kelvin-Helmholtz waves at the near-tail, equatorial magnetopause at dusk: January 11, 1997 SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID INTERPLANETARY MAGNETIC-FIELD; MAGNETOSPHERIC BOUNDARY; AMPTE/IRM OBSERVATIONS; DAYSIDE MAGNETOPAUSE; EARTHS MAGNETOPAUSE; HIGH-LATITUDE; MAGNETOSHEATH; INSTABILITY; DEPENDENCE; MOTIONS AB We analyze ground magnetograms and magnetic field, ion, and electron data from Interball/tail (IT) for the period 0030-0530 UT on January 11, 1997, focusing on waves at the near-tail (similar to-13 R(E)), duskside, equatorial flank, a locale whose physical and wave properties have not been as well studied as those on the dayside. Two major interplanetary features, monitored by Wind, are relevant to this work: The very high and variable dynamic pressure and the strongly northward and generally increasing magnetic field. In this paper, we report, first, on magnetosonic waves in the magnetosheath of frequency similar to 0.15 Hz, probably generated by the mirror instability, which are Doppler shifted with respect to similar waves on the dayside. Second, we discuss Kelvin-Helmholtz (KH) waves on the magnetopause, of wavelength similar to 13-14 R(E) and frequency similar to 3.6 mHz, i.e., in the Pc 5 range. At IT, these waves appear as an envelope modulation of the magnetosonics and are recorded on ground stations at dusk. We argue that the large magnetic shear across the magnetopause and a magnetosheath flow aligned almost normal to the field stabilized the magnetopause locally. Thus these waves were generated on the dayside and propagated to the flank. Third; we examine a low-latitude boundary layer (LLBL), whose tailward stretched field and average antisunward flow were perturbed quasi-periodically. This, together with the particle behavior, suggests a complex billowy structure where hot plasma sheet and cold magnetosheath populations wind around each other while drifting antisunward. A numerical calculation using IT parameters suggests that the inner edge of the LLBL was at this time KH unstable. Fourth, over the 5-hour period the power of the KH oscillations drifts to lower frequencies which we attribute to the progressive decrease in clock angle. Fifth, transients induced by dynamic pressure pulses include a 7.5-min single, free oscillation upon arrival of a fourfold pressure release. Sixth, the long-term effect on the magnetosphere of the increasing northward pointing magnetic field and the stepwise decreasing dynamic pressure is to make the shape of the cavity progressively less blunt. A conclusion of this work is that the equatorial magnetopause can be very oscillatory with various: distinct periodicities even when the interplanetary magnetic field is strongly north. The solar wind dynamic pressure, while responsible for some, cannot explain all of this wave activity. C1 Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA. Univ Buenos Aires, Fac Ciencias Exactas & Nat, RA-1428 Buenos Aires, DF, Argentina. Univ Buenos Aires, CONICET, Inst Fis Plasma, RA-1428 Buenos Aires, DF, Argentina. Russian Acad Sci, Space Res Inst, Moscow, Russia. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Alberta, Dept Phys, Edmonton, AB, Canada. Ctr Etud Spatiale Rayonnements, Toulouse, France. Los Alamos Natl Lab, Los Alamos, NM USA. RP Farrugia, CJ (reprint author), Univ New Hampshire, Ctr Space Sci, 39 Coll Rd, Durham, NH 03824 USA. NR 39 TC 45 Z9 45 U1 1 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD APR 1 PY 2000 VL 105 IS A4 BP 7639 EP 7667 DI 10.1029/1999JA000267 PG 29 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 300FZ UT WOS:000086222800021 ER PT J AU Cohen, CMS Garrard, TL Stone, EC Cooper, JF Murphy, N Gehrels, N AF Cohen, CMS Garrard, TL Stone, EC Cooper, JF Murphy, N Gehrels, N TI Io encounters past and present: A heavy ion comparison SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID JOVIAN MAGNETOSPHERE AB The heavy ion counter (HIC) on the Galileo spacecraft consists of two low-energy telescopes that were proof-test models of the telescopes used for the cosmic ray subsystem (CRS) on Voyager. The telescopes on HIC were improved to better withstand the intense radiation environment of the Jovian system and to measure higher-energy particles with greater sensitivity. The similarity of these two instruments makes it natural to compare the data in an effort to glean insight on the behavior of heavy ion fluxes at higher energies and how the inner Jovian magnetosphere has changed in the last 18 years. Inside L = 6, the oxygen spectrum suggests a spectral break at similar to 7500 MeV/Gauss, corresponding to ions with gyroradii of similar to 1.5 R-Io at L = 6. A comparison of the phase space densities show remarkable agreement between the two time periods outside of the Io orbit, with differential spectra consistent with gamma similar to -8 above similar to 6 MeV/nucleon. Near Io Galileo observed a large density gradient not apparent in the Voyager data that may be due to local time asymmetries or a decrease in the radial diffusion rate. C1 CALTECH, Space Radiat Lab, Pasadena, CA 91125 USA. NASA, Goddard Space Flight Ctr, Space Phys Data Facil, Hughes STX Corp, Greenbelt, MD 20771 USA. Jet Propuls Lab, Pasadena, CA 91109 USA. RP Cohen, CMS (reprint author), CALTECH, Space Radiat Lab, MC 220-47, Pasadena, CA 91125 USA. RI Gehrels, Neil/D-2971-2012; Cooper, John/D-4709-2012 NR 17 TC 5 Z9 5 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 APR 1 PY 2000 VL 105 IS A4 BP 7775 EP 7782 DI 10.1029/1999JA000021 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 300FZ UT WOS:000086222800030 ER PT J AU Dirmeyer, PA Zeng, FJ Ducharne, A Morrill, JC Koster, RD AF Dirmeyer, PA Zeng, FJ Ducharne, A Morrill, JC Koster, RD TI The sensitivity of surface fluxes to soil water content in three land surface schemes SO JOURNAL OF HYDROMETEOROLOGY LA English DT Article ID ATMOSPHERE TRANSFER SCHEME; SIMPLE BIOSPHERE MODEL; CLIMATE; CIRCULATION; PROJECT; PARAMETERIZATIONS; INTERCOMPARISONS; TRANSPIRATION; BOUNDARY; PHASE AB Evaporative fraction (EF; the ratio of latent heat flux to the sum of the latent plus sensible heat fluxes) can be measured in the field to an accuracy of about 10%. In this modeling study, the authors try to determine to what accuracy soil moisture must be known in order to simulate surface energy fluxes within this observational uncertainty and whether there is a firm relationship between the variabilities of soil moisture and surface turbulent energy fluxes. A relationship would provide information for planning the future measurement of soil moisture, the design of field experiments, and points of focus for soil model development The authors look for relationships in three different land surface schemes using results and ancillary integrations in the Global Soil Wetness Project. It is found that the variation of evaporative fraction as a function of soil moisture is consistent among the models and within subsets of vegetation type. In forested areas, there is high sensitivity of EF to soil moisture variations when soils are dry and there is little sensitivity in moderate to wet soils. Where vegetation is sparser, there is a more gradual decrease of EF sensitivity with a decrease in soil moisture. Bare soil desert areas behave similarly to sparsely vegetated areas but with lower peak EE Tundra regions have a unique behavior, probably because evaporation is limited more by a lack of radiant energy at high latitudes. The results suggest that accuracy in the measurement or model simulation of soil moisture is most critical within the drier portion of the range of variability of soil moisture. It also is more important over sparsely vegetated areas, for which evapotranspiration is dependent on moisture in a shallower column of soil. C1 NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. Univ Arizona, Dept Hydrol & Water Resources, Tucson, AZ 85721 USA. RP Dirmeyer, PA (reprint author), Ctr Ocean Land Atmosphere Studies, 4041 Powder Mill Rd,Suite 302, Calverton, MD 20705 USA. RI Koster, Randal/F-5881-2012; Dirmeyer, Paul/B-6553-2016 OI Koster, Randal/0000-0001-6418-6383; Dirmeyer, Paul/0000-0003-3158-1752 NR 38 TC 77 Z9 80 U1 2 U2 4 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 1525-755X J9 J HYDROMETEOROL JI J. Hydrometeorol. PD APR PY 2000 VL 1 IS 2 BP 121 EP 134 DI 10.1175/1525-7541(2000)001<0121:TSOSFT>2.0.CO;2 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 357DK UT WOS:000089483100002 ER PT J AU Los, SO Collatz, GJ Sellers, PJ Malmstrom, CM Pollack, NH DeFries, RS Bounoua, L Parris, MT Tucker, CJ Dazlich, DA AF Los, SO Collatz, GJ Sellers, PJ Malmstrom, CM Pollack, NH DeFries, RS Bounoua, L Parris, MT Tucker, CJ Dazlich, DA TI A global 9-yr biophysical land surface dataset from NOAA AVHRR data SO JOURNAL OF HYDROMETEOROLOGY LA English DT Article ID DIFFERENCE VEGETATION INDEX; LEAF-AREA INDEX; BOREAL CONIFER FORESTS; NET PRIMARY PRODUCTION; PARAMETERIZATION SIB2; ATMOSPHERIC CO2; COVER CLASSIFICATIONS; CANOPY ARCHITECTURE; SATELLITE DATA; NDVI DATA AB Global, monthly, 1 degrees by 1 degrees biophysical land surface datasets for 1982-90 were derived from data collected by the Advanced Very High Resolution Radiometer (AVHRR) on board the NOAA-7, -9, and -11 satellites. The AVHRR data are adjusted for sensor degradation, volcanic aerosol effects, cloud contamination, short-term atmospheric effects (e.g., water vapor and aerosol effects less than or equal to 2 months), solar zenith angle variations, and missing data. Interannual variation in the data is more realistic as a result. The following biophysical parameters are estimated: fraction of photosynthetically active radiation absorbed by vegetation, vegetation cover fraction, leaf area index, and fraction of green leaves. Biophysical retrieval algorithms are tested and updated with data from intensive remote sensing experiments. The multiyear vegetation datasets are consistent spatially and temporally and are useful for studying spatial, seasonal, and interannual variability in the biosphere related to the hydrological cycle, the energy balance, and biogeochemical cycles. The biophysical data are distributed via the Internet by the Goddard Distributed Active Archive Center as a precursor to the International Satellite Land Surface Climatology Project (ISLSCP) Initiative II. Release of more extensive, higher-resolution datasets (0.25 degrees by 0.25 degrees) over longer time periods (1982-97/98) is planned for ISLSCP Initiative II. C1 NASA, Goddard Space Flight Ctr, Biospher Sci Branch, Sci Syst & Applicat Inc, Greenbelt, MD 20771 USA. Lyndon B Johnson Space Ctr, Houston, TX USA. Michigan State Univ, Dept Bot & Plant Pathol, E Lansing, MI 48824 USA. Univ Maryland, Dept Geog, College Pk, MD 20742 USA. Univ Maryland, Dept Meteorol, College Pk, MD 20742 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Colorado State Univ, Dept Atmospher Sci, Ft Collins, CO 80523 USA. RP Los, SO (reprint author), NASA, Goddard Space Flight Ctr, Biospher Sci Branch, Sci Syst & Applicat Inc, Code 923, Greenbelt, MD 20771 USA. RI collatz, george/D-5381-2012; Los, Sietse/G-8985-2012; OI Los, Sietse/0000-0002-1325-3555 NR 65 TC 216 Z9 224 U1 3 U2 21 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 1525-755X J9 J HYDROMETEOROL JI J. Hydrometeorol. PD APR PY 2000 VL 1 IS 2 BP 183 EP 199 DI 10.1175/1525-7541(2000)001<0183:AGYBLS>2.0.CO;2 PG 17 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 357DK UT WOS:000089483100006 ER PT J AU Lara-Curzio, E Singh, M AF Lara-Curzio, E Singh, M TI High-temperature interlaminar shear strength of Hi-Nicalon (TM) fiber-reinforced MI-SiC matrix composites with BN/SiC fiber coating SO JOURNAL OF MATERIALS SCIENCE LETTERS LA English DT Article C1 Oak Ridge Natl Lab, Div Met & Ceram, Oak Ridge, TN 37831 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Lara-Curzio, E (reprint author), Oak Ridge Natl Lab, Div Met & Ceram, Oak Ridge, TN 37831 USA. NR 11 TC 1 Z9 2 U1 2 U2 4 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0261-8028 J9 J MATER SCI LETT JI J. Mater. Sci. Lett. PD APR PY 2000 VL 19 IS 8 BP 657 EP 661 DI 10.1023/A:1006702409475 PG 5 WC Materials Science, Multidisciplinary SC Materials Science GA 303HW UT WOS:000086417300009 ER PT J AU Launius, RD AF Launius, RD TI America's space sentinels: DSP satellites and national security SO JOURNAL OF MILITARY HISTORY LA English DT Book Review C1 NASA, Washington, DC 20546 USA. RP Launius, RD (reprint author), NASA, Washington, DC 20546 USA. NR 1 TC 0 Z9 0 U1 0 U2 0 PU SOC MILITARY HISTORY PI LEXINGTON PA C/O VIRGINIA MILITARY INST, GEORGE C MARSHALL LIBRARY, LEXINGTON, VA 24450-1600 USA SN 0899-3718 J9 J MILITARY HIST JI J. Mil. Hist. PD APR PY 2000 VL 64 IS 2 BP 607 EP 608 DI 10.2307/120321 PG 2 WC History SC History GA 297CD UT WOS:000086063200082 ER PT J AU Li, D Robinson, MB Rathz, TJ AF Li, D Robinson, MB Rathz, TJ TI Measurements of liquidus temperatures in the Cu-Nb and Cu-Cr systems SO JOURNAL OF PHASE EQUILIBRIA LA English DT Article ID MICROSTRUCTURAL EVOLUTION; THERMODYNAMIC ANALYSIS; THERMAL-STABILITY; ALLOYS AB The Cu-Nb and Cu-Cr alloys at compositions ranging from 5 to 86 wt% Nh (89 wt% Cr) were processed in a clean environment and solidified at relatively low cooling rates of 50 to 75 degrees C/s to determine liquidus temperatures. In this study, both temperature measurements and microstructural observations confirmed the equilibrium phase diagram having an S-shaped, nearly flat liquidus, rather than that with a monotectic reaction in the liquid state. However, a metastable liquid miscibility gap exists in the two systems. C1 Queens Univ, Dept Mat & Met Engn, Kingston, ON K7L 3N6, Canada. NASA, MSFC, Huntsville, AL USA. RP Li, D (reprint author), Queens Univ, Dept Mat & Met Engn, Kingston, ON K7L 3N6, Canada. NR 24 TC 12 Z9 12 U1 0 U2 3 PU ASM INTERNATIONAL PI MATERIALS PARK PA SUBSCRIPTIONS SPECIALIST CUSTOMER SERVICE, MATERIALS PARK, OH 44073-0002 USA SN 1054-9714 J9 J PHASE EQUILIB JI J. Phase Equilib. PD APR PY 2000 VL 21 IS 2 BP 136 EP 140 DI 10.1361/105497100770340183 PG 5 WC Chemistry, Physical; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Chemistry; Materials Science; Metallurgy & Metallurgical Engineering GA 325AK UT WOS:000087654000005 ER PT J AU Parusel, ABJ AF Parusel, ABJ TI A semiempirical study for the ground and excited states of free-base and zinc porphyrin-fullerene dyads SO JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY LA English DT Article DE semiempirical study; solvent effect; artificial photosynthesis; molecular dyad; electron transfer ID PHOTOINDUCED ELECTRON-TRANSFER; PHOTOSYNTHETIC REACTION CENTERS; CHARGE SEPARATION; SYSTEMS; ENERGY; C-60; PREDICTION; ABSORPTION; SPECTRA; MIMICRY AB The ground and excited states of a covalently linked porphyrin-fullerene dyad in both its free-base and zinc forms (D. Kuciauskas et al., J. Phys. Chem. 100 (1996) 15926) have been investigated by semiempirical methods. The excited-state properties are discussed by investigation of the character of the molecular orbitals. All frontier MOs are mainly localized on either the donor or the acceptor subunit. Thus, the absorption spectra of both systems are best described as the sum of the spectra of the single components. The experimentally observed spectra are well reproduced by the theoretical computations. Both molecules undergo efficient electron transfer in polar but not in apolar solvents. This experimental finding is explained theoretically by explicitly considering solvent effects. The tenth excited state in the gas phase is of charge-separated character where an electron is transferred from the porphyrin donor to the fullerene acceptor subunit. This state is stabilized in energy in polar solvents due to its large formal dipole moment. The stabilization energy for an apolar environment such as benzene is not sufficient to lower this state to become the first excited singlet state. Thus, no electron transfer is observed, in agreement with experiment. In a polar environment such as acetonitrile, the charge-separated state becomes the S-1 state and electron transfer takes place, as observed experimentally. The flexible single bond connecting both the donor and acceptor subunits allows free rotation by ca. +/- 30 degrees about the optimized ground-state conformation. For the charge-separated state this optimized geometry has a maximum dipole moment. The geometry of the charge-separated state thus does not change relatively to the ground-state conformation. The electron-donating properties of porphyrin are enhanced in the zinc derivative due to a reduced porphyrin HOMO-LUMO energy gap. This yields a lower energy for the charge-separated state compared to the free-base dyad. (C) 2000 Elsevier Science S.A. All rights reserved. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Inst Theoret Chem, Althanstr, A-1090 Vienna, Austria. EM andreas.parusel@univie.ac.at NR 20 TC 8 Z9 8 U1 0 U2 4 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 1011-1344 J9 J PHOTOCH PHOTOBIO B JI J. Photochem. Photobiol. B-Biol. PD APR-MAY PY 2000 VL 55 IS 2-3 BP 188 EP 195 DI 10.1016/S1011-1344(00)00048-8 PG 8 WC Biochemistry & Molecular Biology; Biophysics SC Biochemistry & Molecular Biology; Biophysics GA 334RF UT WOS:000088198900015 PM 10942085 ER PT J AU Lohrenz, SE AF Lohrenz, SE TI A novel theoretical approach to correct for pathlength amplification and variable sampling loading in measurements of particulate spectral absorption by the quantitative filter technique SO JOURNAL OF PLANKTON RESEARCH LA English DT Article ID GLASS-FIBER FILTERS; AQUATIC PARTICLES; PHYTOPLANKTON; LIGHT; COEFFICIENTS; SEA; PIGMENTS; MATTER AB A simple theoretical model is described that takes into account the combined effects of pathlength amplification and variable sample loading in measurements of particulate spectral absorption by the quantitative filter pad technique. The model differs from previous methods to correct for pathlength amplification by explicitly considering variability ill absorptance of sample material on the filter pad, A(fp), as a result of different degrees of particle loading on the tilter. Functional expressions were evaluated that describe the relationship between A(fp) and the product of a dimensionless path factor, rho, and pathlength amplification factor, beta. The path factor, rho, represented the product of the absorption coefficient of sample material on the filter and the geometric pathlength of the sample. A simple function was shown to adequately describe the relationship for varying filtration volumes with a variety of sample types, including phytoplankton cultures and coastal waters. Patterns predicted by the model are compared with previously published formulae developed for correction of filter pad absorption measurements. The functional form given here simplifies the approach for determining pathlength amplification. C1 Univ So Mississippi, Stennis Space Ctr, Dept Marine Sci, Stennis Space Ctr, MS 39529 USA. RP Lohrenz, SE (reprint author), Univ So Mississippi, Stennis Space Ctr, Dept Marine Sci, Stennis Space Ctr, MS 39529 USA. OI Lohrenz, Steven/0000-0003-3811-2975 NR 27 TC 41 Z9 42 U1 0 U2 4 PU OXFORD UNIV PRESS PI OXFORD PA GREAT CLARENDON ST, OXFORD OX2 6DP, ENGLAND SN 0142-7873 J9 J PLANKTON RES JI J. Plankton Res. PD APR PY 2000 VL 22 IS 4 BP 639 EP 657 DI 10.1093/plankt/22.4.639 PG 19 WC Marine & Freshwater Biology; Oceanography SC Marine & Freshwater Biology; Oceanography GA 302YL UT WOS:000086394000003 ER PT J AU Levinskikh, MA Sychev, VN Derendyaeva, TA Signalova, OB Salisbury, FB Campbell, WF Bingham, GE Bubenheim, DL Jahns, G AF Levinskikh, MA Sychev, VN Derendyaeva, TA Signalova, OB Salisbury, FB Campbell, WF Bingham, GE Bubenheim, DL Jahns, G TI Analysis of the spaceflight effects on growth and development of Super Dwarf wheat grown on the Space Station Mir SO JOURNAL OF PLANT PHYSIOLOGY LA English DT Article DE ethylene; floral development; gravitational biology; microgravity; morphometry; Mir-grown wheat; Triticum aestivum L. ID LIFE-SUPPORT; IN-SPACE; BARLEY; RESPONSES; ETHEPHON; FLIGHT; CULTIVARS; VULGARE; POLLEN; ETHREL AB The hypothesis being tested is that Super Dwarf wheat, Triticum aestivum L., plants in the Svet Greenhouse onboard the Russian Space Station Mir will complete a life cycle in spaceflight, providing that the environmental conditions necessary for adequate growth on Earth are supplied. Twenty six seeds of wheat were planted in each of 2 rows of 2 root compartments for a total of 104 seeds in Svet. Germination rate at 7d was 56 and 73% on Mir and 75 and 90% in ground-based controls. Plants were grown throughout the whole cycle of ontogenesis (123 d) with samples gathered at different times to validate the morphological and reproductive stages of the plants. Young plants showed vigorous early seedling growth, with large biomass production, including the formation of 280 floral spikes. Upon return to Earth, comparative analyses showed that the number of tillers and flowers per spikelet tt ere 63.2% and 40% greater, respectively, in Mir-grown plants than in the controls. By contrast, the stem length (52.4%), spike mass (49.2%) and length (23.1%), awn length (75.7%), number of spikelets per spike (42.8%) and number of seeds per spike (100% sterile) from Mir-grown plants were substantially less than the controls. Distribution of moisture and roots throughout the substrate was very good. All florets on Mir-grown spikes ceased development at the same stage of ontogeny. Lack of caryopses formation was attributed to male sterility occurring at different stages of staminal development. Anthers failed to dehisce and pollen grains were smaller and shriveled compared to the controls, suggesting a chronic stress had occurred in the Svet growth chamber. Recent ground-based studies indicated that ethylene, which was measured at 0.3 to 1.8 mg.kg(-1) in the Mir, almost certainly could have induced male sterility in the wheat plants grown on the Mir. C1 State Res Ctr Russian Federat, IBMP, Moscow, Russia. Utah State Univ, Logan, UT 84322 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Campbell, WF (reprint author), State Res Ctr Russian Federat, IBMP, Moscow, Russia. NR 43 TC 43 Z9 46 U1 0 U2 9 PU GUSTAV FISCHER VERLAG PI JENA PA VILLENGANG 2, D-07745 JENA, GERMANY SN 0176-1617 J9 J PLANT PHYSIOL JI J. Plant Physiol. PD APR PY 2000 VL 156 IS 4 BP 522 EP 529 PG 8 WC Plant Sciences SC Plant Sciences GA 316NV UT WOS:000087174600014 PM 11543345 ER PT J AU Brooks, TF Boyd, DD Burley, CL Jolly, JR AF Brooks, TF Boyd, DD Burley, CL Jolly, JR TI Aeroacoustic codes for rotor harmonic and BVI noise - CAMRAD.Mod1/HIRES SO JOURNAL OF THE AMERICAN HELICOPTER SOCIETY LA English DT Article; Proceedings Paper CT AIAA/CEAS 2nd Joint Aeroacoustics Conference CY MAY 06-08, 1996 CL STATE COLL, PENNSYLVANIA SP AIAA, CEAS AB This paper presents a status of non-CFD aeroacoustic codes at NASA Langley Research Center for the prediction of helicopter harmonic and Blade-Vortex Interaction (BVI) noise. The prediction approach incorporates three primary components: CAMRAD.Mod1-a substantially modified version of the performance/trim/wake code CAMRAD; HIRES-a high-resolution blade loads post-processor; and WOPWOP-an acoustic code. The functional capabilities and physical modeling in CAMRAD.Mod1/HIRES is summarized and illustrated. A new multi-core roll-up wake modeling approach is introduced and validated. Predictions of rotor wake and radiated noise are compared to the results of the HART program; a model BO-105 windtunnel test at the DNW in Europe. Additional comparisons are made to results from a DNW test of a contemporary design four-bladed rotor, as well as from a Langley test of a single proprotor (tiltrotor) three-bladed model configuration. The method is shown to help eliminate the necessity of guesswork in setting code parameters between different rotor configurations, and should prove useful as a rotor noise design tool. C1 NASA, Langley Res Ctr, Hampton, VA 23665 USA. Lockheed Engn & Sci Co, Hampton, VA 23666 USA. RP Brooks, TF (reprint author), Virginia Polytech Inst & State Univ, Blacksburg, VA 24061 USA. NR 39 TC 4 Z9 4 U1 0 U2 1 PU AMER HELICOPTER SOC INC PI ALEXANDRIA PA 217 N WASHINGTON ST, ALEXANDRIA, VA 22314 USA SN 0002-8711 J9 J AM HELICOPTER SOC JI J. Am. Helicopter Soc. PD APR PY 2000 VL 45 IS 2 BP 63 EP 79 PG 17 WC Engineering, Aerospace SC Engineering GA 311LD UT WOS:000086885000001 ER PT J AU Burley, CL Brooks, TF Marcolini, MM Brand, AG Conner, DA AF Burley, CL Brooks, TF Marcolini, MM Brand, AG Conner, DA TI Tiltrotor aeroacoustic code (TRAC) predictions and comparison with measurements SO JOURNAL OF THE AMERICAN HELICOPTER SOCIETY LA English DT Article; Proceedings Paper CT 52nd Annual Forum of the American-Helicopter-Society CY JUN 04-06, 1996 CL WASHINGTON, D.C. SP Amer Helicopter Soc AB A new rotor noise prediction system called the TiltRotor Aeroacoustic Code (TEUC) has been developed. This system couples the comprehensive rotorcraft code CAMRAD.Mod1 with either the high resolution sectional loads code HIRES or the full potential rotor code FPRBVI to predict unsteady blade loads, which are then input to the noise prediction program WOPWOP. In this paper using the HIRES option, predictions are compared to measured noise for an isolated proprotor (tiltrotor) operating over an extensive range of conditions. The measurements were acquired for a 15 percent scale JVX tiltrotor model in the 14- by 22-Foot Subsonic Tunnel at the NASA Langley Research Center. The effect of rotor angle and CT are examined for different equivalent flight conditions. Predicted tiltrotor wake geometries and wake cortex structure, employing the recently developed multi-core, roll-up wake model, provides insight into the physics of tiltrotor blade-vortex interactions. This provides an explanation to unique tiltrotor BVI noise trends. C1 NASA, Langley Res Ctr, Programs Off AFDD, Hampton, VA 23665 USA. Bell Helicopter Textron Inc, Ft Worth, TX USA. NR 35 TC 4 Z9 4 U1 1 U2 1 PU AMER HELICOPTER SOC INC PI ALEXANDRIA PA 217 N WASHINGTON ST, ALEXANDRIA, VA 22314 USA SN 0002-8711 J9 J AM HELICOPTER SOC JI J. Am. Helicopter Soc. PD APR PY 2000 VL 45 IS 2 BP 80 EP 89 PG 10 WC Engineering, Aerospace SC Engineering GA 311LD UT WOS:000086885000002 ER PT J AU Lewicki, DG Handschuh, RF Heath, GF Sheth, V AF Lewicki, DG Handschuh, RF Heath, GF Sheth, V TI Evaluation of carburized and ground face gears SO JOURNAL OF THE AMERICAN HELICOPTER SOCIETY LA English DT Article; Proceedings Paper CT 55th Annual Forum of the American-Helicopter-Society CY MAY 25-27, 1999 CL MONTREAL, CANADA SP Amer Helicopter Soc ID HELICOPTER TRANSMISSIONS; DRIVES; GEOMETRY AB Experimental durability tests were performed on carburized and ground AISI 9310 steel face gears. The tests were in support of a Defense Advanced Research Projects Agency (DARPA) Technology Reinvestment Program (TRP) to enhance face-gear technology. The tests were conducted in the NASA Glenn spiral-bevel-gear/face-gear test facility, Tests were run at 2300 rpm face gear speed and at loads of 64, 76, 88, 100, and 112-percent of the design torque of 377 N-m (3340 in.-lb.). The carburized and ground face gears demonstrated the required durability when run for ten-million cycles at each of the applied loads. proper installation was critical for the successful operation of the spur pinions and face gears. A large amount of backlash produced tooth contact patterns that approached the inner-diameter edge of the fate-gear tooth. Low backlash produced tooth contact patterns that approached the outer-diameter edge of the face-gear tooth. Measured backlashes in the range of 0.178 to 0.254 mm (0.007 to 0.010 in.) produced acceptable tooth contact patterns. C1 NASA, Glenn Res Ctr, USA, Res Lab, Cleveland, OH USA. Boeing Co, Mesa, AZ USA. RP Lewicki, DG (reprint author), NASA, Glenn Res Ctr, USA, Res Lab, Cleveland, OH USA. NR 17 TC 1 Z9 3 U1 1 U2 2 PU AMER HELICOPTER SOC INC PI ALEXANDRIA PA 217 N WASHINGTON ST, ALEXANDRIA, VA 22314 USA SN 0002-8711 J9 J AM HELICOPTER SOC JI J. Am. Helicopter Soc. PD APR PY 2000 VL 45 IS 2 BP 118 EP 124 PG 7 WC Engineering, Aerospace SC Engineering GA 311LD UT WOS:000086885000006 ER PT J AU Samuel, PD Pines, DJ Lewicki, DG AF Samuel, PD Pines, DJ Lewicki, DG TI A comparison of stationary and non-stationary metrics for detecting faults in helicopter gearboxes SO JOURNAL OF THE AMERICAN HELICOPTER SOCIETY LA English DT Article ID WAVELET ANALYSIS; VIBRATION; GEARS AB A comparison between stationary statistical fault indicators and the discrete harmonic wavelet packet transform (DHWPT) is investigated for accelerometer vibration data obtained from the OH-58A main rotor transmission. This transmission is comprised of two stages, a spiral bevel input stage and a planetary stage, resulting in an overall reduction of 17.44:1. Vibration data from a load-to-failure transmission test is used to evaluate the sensitivity of previously developed stationary fault metrics and a new non-stationary fault metric for early fault detection. The non-stationary fault indicator consists of a normalized energy metric which was developed to quantify the redistribution of sideband energy about the dominant mesh frequency and its harmonics in the presence of actual gearbox faults. This metric is used to qualitatively assess the presence, type and location of gearbox faults. Gearbox faults considered in this study include sun gear spalling and spiral bevel gear scoring. Results from the comparison suggest that the non-stationary normalized energy metric is capable of detecting damage at a rate that is comparable to the stationary statistical fault indicators. In addition, the normalized energy metric provides more information about the nature of a fault. C1 Univ Maryland, Dept Aerosp Engn, Alfred Gessow Rotorcraft Ctr, College Pk, MD 20742 USA. NASA, Glenn Res Ctr, USA, Res Lab, Cleveland, OH 44135 USA. RP Samuel, PD (reprint author), Univ Maryland, Dept Aerosp Engn, Alfred Gessow Rotorcraft Ctr, College Pk, MD 20742 USA. NR 41 TC 15 Z9 15 U1 2 U2 5 PU AMER HELICOPTER SOC INC PI ALEXANDRIA PA 217 N WASHINGTON ST, ALEXANDRIA, VA 22314 USA SN 0002-8711 J9 J AM HELICOPTER SOC JI J. Am. Helicopter Soc. PD APR PY 2000 VL 45 IS 2 BP 125 EP 136 PG 12 WC Engineering, Aerospace SC Engineering GA 311LD UT WOS:000086885000007 ER PT J AU Blake, R Khanbilvardi, R Rosenzweig, C AF Blake, R Khanbilvardi, R Rosenzweig, C TI Climate change impacts on New York City's water supply system SO JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION LA English DT Article DE climate change; PDSI; GCM; water supply; soil moisture; WatBal; New York ID DROUGHT SEVERITY INDEX AB It has been well established that the greenhouse gas loading of the atmosphere has been increasing since the mid 19th century. Consequently, shifts in the earth's radiative balance are expected with accompanying alterations to the earth's climate. With these anticipated, and perhaps already observable, changes in both global and regional climate, managers of regional water resources seek insight to the possible impacts climate change may have on their present and future water supplies. The types and degrees of impacts that climate change may have on New York City's water supply system were assessed in a study of a watershed at Allaben, New York. Hypothetical scenarios of future climate and climate change projections from three General Circulation Models (GCMs) were used in conjunction with the WatBal hydrological model and the Palmer Drought Severity Index (PDSI) to ascertain how runoff and soil moisture from this watershed may change in a warmer climate. For the worst case predictions, the results indicate that within the century of the 2000s, the watershed's air temperature may increase up to about 11 degrees F, while its precipitation and runoff may decrease by about 13 and 30 percent, respectively. If this watershed is typical of the others within the New York City water supply system, the system's managers should consider implementing mitigation and adaptation strategies in preparation for the worst of these possible future conditions. C1 CUNY City Coll, Ctr Water Resources & Environm Res, New York, NY 10031 USA. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. NR 10 TC 15 Z9 15 U1 0 U2 7 PU AMER WATER RESOURCES ASSOC PI MIDDLEBURG PA 4 WEST FEDERAL ST, PO BOX 1626, MIDDLEBURG, VA 20118-1626 USA SN 1093-474X J9 J AM WATER RESOUR AS JI J. Am. Water Resour. Assoc. PD APR PY 2000 VL 36 IS 2 BP 279 EP 292 DI 10.1111/j.1752-1688.2000.tb04267.x PG 14 WC Engineering, Environmental; Geosciences, Multidisciplinary; Water Resources SC Engineering; Geology; Water Resources GA 315LJ UT WOS:000087115000004 ER PT J AU Hughes, SP Hall, CD AF Hughes, SP Hall, CD TI Optimal configurations for rotating spacecraft formations SO JOURNAL OF THE ASTRONAUTICAL SCIENCES LA English DT Article; Proceedings Paper CT Richard H Battin Astrodynamics Symposium CY MAR 19-21, 2000 CL TEXAX A&M UNIV, COLLEGE STN, TEXAS SP Amer Astronaut Soc, Texas Eng Exptl Stn, Aerosp Engn Dept HO TEXAX A&M UNIV AB In this paper we introduce a new approach to the design of formations that maintain a constant shape as viewed from the Earth. An algorithm is developed to place n spacecraft in a formation spaced equally in time using orbital elements referenced to an intermediate reference frame, To first order, the dimensions of the formation are shown to be simple functions of orbit eccentricity and the relative inclination. The performance of the formation is investigated over a Keplerian orbit using a performance measure based on a weighted average of the angular separations between spacecraft in formation, Analytic approximations are developed that yield optimum configurations for different values of n. The analytic approximations are shown to be in excellent agreement eith the exact solutions. C1 NASA, Goddard Space Flight Ctr, Guidance Navigat & Control Ctr, Greenbelt, MD 20771 USA. Virginia Tech, Dept Aerosp & Ocean Engn, Blacksburg, VA USA. RP Hughes, SP (reprint author), NASA, Goddard Space Flight Ctr, Guidance Navigat & Control Ctr, Greenbelt, MD 20771 USA. NR 15 TC 16 Z9 16 U1 0 U2 3 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-SEP PY 2000 VL 48 IS 2-3 BP 225 EP 247 PG 23 WC Engineering, Aerospace SC Engineering GA 435WW UT WOS:000168906000008 ER PT J AU Ely, TA Bishop, RH Crain, TP AF Ely, TA Bishop, RH Crain, TP TI Adaptive interplanetary navigation using genetic algorithms SO JOURNAL OF THE ASTRONAUTICAL SCIENCES LA English DT Article; Proceedings Paper CT Richard H Battin Astrodynamics Symposium CY MAR 19-21, 2000 CL TEXAX A&M UNIV, COLLEGE STN, TEXAS SP Amer Astronaut Soc, Texas Eng Exptl Stn, Aerosp Engn Dept HO TEXAX A&M UNIV AB This study illustrates an automated approach for filter tuning (via model optimization) using a genetic algorithm (GA) coupled with an extended Kalman filter. In particular, the solar radiation pressure (SRP) model of the Mars Pathfinder (MPF) spacecraft is investigated using a three month span of tracking data during the cruise phase of the mission. The results obtained in this study are compared to the best model obtained by the MPF navigation team. The GA based approach does not require gradient information about neighboring model options, hence it is: capable of examining filter models of varying structure. The GA operates on a population of individuals that are selected (initially at random) from the design space. In this study, the selected design space includes 1.44E+17 possible SRP models. Each individual selected from the design space processes the tracking data set using the filter. The basis for the GA's fitness function is a normalized sample statistic of the output residual sequence. Using the fitness values computed for each individual, the GA selects the parent population via a tournament method. For crossover, several strategies are investigated to determine the best method for quick convergence of the GA to a near optimal solution. The results show that the GA is able to determine an SRP model with a fitness value that is similar to6% better than the model selected by the MPF navigation team, and produces predicted residuals that are more stable. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Texas, Dept Aerosp Engn & Engn Mech, Austin, TX 78712 USA. RP Ely, TA (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 12 TC 1 Z9 1 U1 0 U2 0 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-SEP PY 2000 VL 48 IS 2-3 BP 287 EP 303 PG 17 WC Engineering, Aerospace SC Engineering GA 435WW UT WOS:000168906000011 ER PT J AU Markley, FL Mortari, D AF Markley, FL Mortari, D TI Quaternion attitude estimation using vector observations SO JOURNAL OF THE ASTRONAUTICAL SCIENCES LA English DT Article; Proceedings Paper CT Richard H Battin Astrodynamics Symposium CY MAR 19-21, 2000 CL TEXAX A&M UNIV, COLLEGE STN, TEXAS SP Amer Astronaut Soc, Texas Eng Exptl Stn, Aerosp Engn Dept HO TEXAX A&M UNIV ID ALGORITHM AB This paper contains a critical comparison of estimators minimizing Wahba's loss function. Some new results are presented for the QUaternion ESTimater (QUEST) and EStimators of the Optimal Quaternion (ESOQ and ESOQ2) to avoid the computational burden of sequential rotations in these algorithms. None of these methods is as robust in principle as Davenport's q method or the Singular Value Decomposition (SVD) method, which are significantly slower. Robustness is only an issue for measurements with widely differing accuracies, so the fastest estimators, the modified ESOQ and ESOQ2, are well suited to sensors that track multiple stars with comparable accuracies. More robust forms of ESOQ and ESOQ2 are developed that are intermediate in speed. C1 NASA, Goddard Space Flight Ctr, Guidance Navigat & Control Ctr, Greenbelt, MD 20771 USA. Univ Rome La Sapienza, Sch Aerosp Engn, Rome, Italy. RP Markley, FL (reprint author), NASA, Goddard Space Flight Ctr, Guidance Navigat & Control Ctr, Greenbelt, MD 20771 USA. NR 27 TC 118 Z9 129 U1 1 U2 13 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-SEP PY 2000 VL 48 IS 2-3 BP 359 EP 380 PG 22 WC Engineering, Aerospace SC Engineering GA 435WW UT WOS:000168906000014 ER PT J AU Kim, HY Juang, JN Junkins, JL AF Kim, HY Juang, JN Junkins, JL TI Recursive attitude prediction SO JOURNAL OF THE ASTRONAUTICAL SCIENCES LA English DT Article; Proceedings Paper CT Richard H Battin Astrodynamics Symposium CY MAR 19-21, 2000 CL TEXAX A&M UNIV, COLLEGE STN, TEXAS SP Amer Astronaut Soc, Texas Eng Exptl Stn, Aerosp Engn Dept HO TEXAX A&M UNIV ID VECTOR OBSERVATIONS; SPACECRAFT ATTITUDE; ALGORITHM AB A new recursive attitude prediction method is derived for spacecraft equipped with attitude sensors, such as star cameras. The attitude predictor model is given in an autoregressive form (finite-difference model) and its model parameters are estimated by the prediction error approach with a quadratic norm. In this approach, concerns about system uncertainties (such as unknown external torque, inertia matrix, or initial conditions) are avoided by utilizing a kinematics-based model. Angular velocity is estimated as a by product of the attitude estimation algorithm. An example illustrates that the recursive attitude predictor estimates attitude trajectories accurately, for the case of a slowly rotating spacecraft, for a significant time interval without attitude measurements, which allows attitude to be predicted during intervals following occasional data dropout. C1 Texas A&M Univ, Dept Aerosp Engn, College Stn, TX 77843 USA. NASA, Langley Res Ctr, Struct Dynam Branch, Hampton, VA 23665 USA. RP Kim, HY (reprint author), Texas A&M Univ, Dept Aerosp Engn, College Stn, TX 77843 USA. NR 15 TC 1 Z9 1 U1 0 U2 0 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-SEP PY 2000 VL 48 IS 2-3 BP 409 EP 421 PG 13 WC Engineering, Aerospace SC Engineering GA 435WW UT WOS:000168906000017 ER PT J AU Campbell, AB French, JD Nair, SS Miles, JB Lin, CH AF Campbell, AB French, JD Nair, SS Miles, JB Lin, CH TI Thermal analysis and design of an advanced space suit SO JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER LA English DT Article AB The thermal dynamics and design of an advanced space suit are considered. A transient model of the advanced space suit design has been developed and implemented using MATLAB(R)/Simulink, to help with sizing, with design evaluation, and with the development of an automatic thermal comfort control strategy. The model is described and the thermal characteristics of the advanced space suit are investigated including various parametric design studies. The steady-state performance envelope for the advanced space suit is defined in terms of the thermal environment and human metabolic rate and the transient response of the human-suit-minimum consumables portable life support system is analyzed. C1 Univ Missouri, Dept Mech & Aerosp Engn, Columbia, MO 65211 USA. NASA, Lyndon B Johnson Space Ctr, Crew & Thermal Syst Div, Syst Design & Anal Branch, Houston, TX 77058 USA. RP Campbell, AB (reprint author), Univ Missouri, Dept Mech & Aerosp Engn, Columbia, MO 65211 USA. NR 14 TC 5 Z9 6 U1 1 U2 4 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0887-8722 J9 J THERMOPHYS HEAT TR JI J. Thermophys. Heat Transf. PD APR-JUN PY 2000 VL 14 IS 2 BP 151 EP 160 DI 10.2514/2.6526 PG 10 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA 306AN UT WOS:000086574100004 ER PT J AU Adamczyk, JJ AF Adamczyk, JJ TI Aerodynamic analysis of multistage turbomachinery flows in support of aerodynamic design SO JOURNAL OF TURBOMACHINERY-TRANSACTIONS OF THE ASME LA English DT Article; Proceedings Paper CT International Gas Turbine and Aeroengine Congress and Exhibition CY JUN 07-10, 1999 CL INDIANAPOLIS, INDIANA ID BLADE ROW INTERACTION; TURBINE; COMPRESSORS; WAKE AB This paper summarizes the state of 3D CFD based models of the time-averaged flow field within axial flow multistage turbomachines. Emphasis is placed on models that are compatible with the industrial design environment and those models that offer the potential of providing credible results at both design and off-design operating conditions. The need to develop models free of aerodynamic input from semiempirical design systems is stressed. The accuracy of such models is shown to be dependent upon their ability to account for the unsteady flow environment in multistage turbomachinery. The relevant flow physics associated with some of the unsteady flow processes present in axial pow multistage machinery are presented along with procedures that can be used to account for them in 3D CFD simulations. Sample results are presented for both axial flow compressors and axial flow turbines that help to illustrate the enhanced predictive capabilities afforded by including these procedures in 3D CFD simulations. Finally, suggestions are given for future work on the development of time-averaged flow models. [S0889-504X(00)02002-X]. C1 NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. RP Adamczyk, JJ (reprint author), NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. NR 86 TC 50 Z9 54 U1 0 U2 6 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA THREE PARK AVE, NEW YORK, NY 10016-5990 USA SN 0889-504X J9 J TURBOMACH JI J. Turbomach.-Trans. ASME PD APR PY 2000 VL 122 IS 2 BP 189 EP 217 DI 10.1115/1.555439 PG 29 WC Engineering, Mechanical SC Engineering GA 404NJ UT WOS:000167106400001 ER PT J AU Griffin, LW Dorney, DJ AF Griffin, LW Dorney, DJ TI Simulations of the unsteady flow through the Fastrac supersonic turbine SO JOURNAL OF TURBOMACHINERY-TRANSACTIONS OF THE ASME LA English DT Article; Proceedings Paper CT International Gas Turbine and Aeroengine Congress and Exhibition CY JUN 07-10, 1999 CL INDIANAPOLIS, INDIANA ID STAGE AB Analysis of the unsteady aerodynamic environment in the Fastrac supersonic turbine is presented. Model analysis of the turbine blades indicated possible resonance in crucial operating ranges of the turbopump. Unsteady computational fluid dynamics (CFD) analysis was conducted to support the aerodynamic and structural dynamic assessments of the turbine. Before beginning the analysis, two major problems with current unsteady analytical capabilities had to be addressed: modeling a straight centerline nozzle with the turbine blades and exit guide vanes (EGVs), and reducing run times significantly while maintaining physical accuracy. Modifications were made to the CFD code used in this study to allow the coupled nozzle/blade/EGV analysis and to incorporate Message Passing Interface (MPI) software. Because unsteadiness is a key issue for the Fastrac turbine [and future rocket engine turbines such as the Reusable Launch Vehicle (RLV)], calculations were performed for two nozzle-to-blade axial gaps. Calculations were also performed for the nozzle alone, and the results were imposed as an inlet boundary condition for a blade/EGV calculation for the large gap case. These results are compared to the nozzle/blade/EGV results. [S0889-504X(00)02902-0]. C1 NASA, Fluid Dynam Anal Branch, George C Marshall Space Flight Ctr, Marshall Space Flight Ce, AL 35802 USA. Virginia Commonwealth Univ, Dept Mech Engn, Richmond, VA 23113 USA. RP Griffin, LW (reprint author), NASA, Fluid Dynam Anal Branch, George C Marshall Space Flight Ctr, Marshall Space Flight Ce, AL 35802 USA. NR 10 TC 10 Z9 11 U1 1 U2 3 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA THREE PARK AVE, NEW YORK, NY 10016-5990 USA SN 0889-504X J9 J TURBOMACH JI J. Turbomach.-Trans. ASME PD APR PY 2000 VL 122 IS 2 BP 225 EP 233 DI 10.1115/1.555453 PG 9 WC Engineering, Mechanical SC Engineering GA 404NJ UT WOS:000167106400003 ER PT J AU Heidmann, JD Rigby, DL Ameri, AA AF Heidmann, JD Rigby, DL Ameri, AA TI A three-dimensional coupled internal/external simulation of a film-cooled turbine vane SO JOURNAL OF TURBOMACHINERY-TRANSACTIONS OF THE ASME LA English DT Article; Proceedings Paper CT International Gas Turbine and Aeroengine Congress and Exhibition CY JUN 07-10, 1999 CL INDIANAPOLIS, INDIANA AB A three-dimensional Navier-Stokes simulation has been performed for a realistic film-cooled turbine vane using the LeRC-HT code. The simulation includes the flow regions inside the coolant plena and film cooling holes in addition to the external flow. The vane is the subject of an upcoming NASA Lewis Research Center experiment and has both circular cross-sectional and shaped film cooling holes. This complex geometry is modeled using a multiblock grid, which accurately discretizes the actual vane geometry including shaped holes. The simulation matches operating conditions for the planned experiment and assumes periodicity in the spanwise direction on the scale of one pitch of the film cooling hole pattern. Two computations were performed for different isothermal wall temperatures, allowing independent determination of heat transfer coefficients and film effectiveness values. The results indicate separate localized regions of high heat flux in the showerhead region due to low film effectiveness and high hear transfer coefficient values, while the shaped holes provide a reduction in heat flux through both parameters. Hole exit data indicate rather simple skewed profiles for the round helps, but complex profiles for the shaped holes with mass fluxes skewed strongly toward their leading edges. [S0889-504X(00)02802-6]. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. Dynacs Engn Co Inc, Brookpark, OH 44142 USA. NASA, Lewis Res Grp, AYT Corp, Cleveland, OH 44135 USA. RP Heidmann, JD (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 23 TC 47 Z9 48 U1 0 U2 4 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA THREE PARK AVE, NEW YORK, NY 10016-5990 USA SN 0889-504X J9 J TURBOMACH JI J. Turbomach.-Trans. ASME PD APR PY 2000 VL 122 IS 2 BP 348 EP 359 DI 10.1115/1.555450 PG 12 WC Engineering, Mechanical SC Engineering GA 404NJ UT WOS:000167106400018 ER PT J AU Lu, YN Aguirre, AA Work, TM Balazs, GH Nerurkar, VR Yanagihara, R AF Lu, YN Aguirre, AA Work, TM Balazs, GH Nerurkar, VR Yanagihara, R TI Identification of a small, naked virus in tumor-like aggregates in cell lines derived from a green turtle, Chelonia mydas, with fibropapillomas SO JOURNAL OF VIROLOGICAL METHODS LA English DT Article DE green turtle fibropapilloma; Chelonia mydas; cell line; virus ID DNA AB Serial cultivation of cell lines derived from lung, testis, periorbital and tumor tissues of a green turtle (Chelonia mydas) with fibropapillomas resulted in the in vitro formation of tumor-like cell aggregates, ranging in size from 0.5 to 2.0 mm in diameter. Successful induction of tumor-like aggregates was achieved in a cell line derived from lung tissue of healthy green turtles, following inoculation with cell-free media from these tumor-bearing cell lines, suggesting the presence of a transmissible agent. Thin-section electron microscopy of the cell aggregates revealed massive collagen deposits and intranuclear naked viral particles, measuring 50 +/- 5 MI in diameter. These findings, together with the morphological similarity between these tumor-like cell aggregates and the naturally occurring tumor, suggest a possible association between this novel virus and the disease. Further characterization of this small naked virus will clarify its role in etiology of green turtle fibropapilloma. a life-threatening disease of this endangered marine species. (C) 2000 Published by Elsevier Science B.V. All rights reserved. C1 Univ Hawaii Manoa, Leahi Hosp, Pacific Biomed Res Ctr, Retrovirol Res Lab, Honolulu, HI 96816 USA. Tufts Univ, Sch Vet Med, Ctr Conservat Med, Wildlife Preservat Trust Int, N Grafton, MA 01536 USA. US Geol Survey, Biol Resource Div, Natl Wildlife Hlth Ctr, Honolulu Field Stn, Honolulu, HI 96850 USA. NOAA, Natl Marine Fisheries Serv, SW Fisheries Sci Ctr, Honolulu Lab, Honolulu, HI 96822 USA. RP Lu, YN (reprint author), Univ Hawaii Manoa, Leahi Hosp, Pacific Biomed Res Ctr, Retrovirol Res Lab, 3675 Kilauea Ave, Honolulu, HI 96816 USA. RI Work, Thierry/F-1550-2015 OI Work, Thierry/0000-0002-4426-9090 FU NCRR NIH HHS [G12RR/AI-03061] NR 25 TC 11 Z9 12 U1 1 U2 3 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0166-0934 J9 J VIROL METHODS JI J. Virol. Methods PD APR PY 2000 VL 86 IS 1 BP 25 EP 33 DI 10.1016/S0166-0934(99)00175-5 PG 9 WC Biochemical Research Methods; Biotechnology & Applied Microbiology; Virology SC Biochemistry & Molecular Biology; Biotechnology & Applied Microbiology; Virology GA 296ZP UT WOS:000086056900004 PM 10713373 ER PT J AU Parrish, FA Craig, MP Ragen, TJ Marshall, GJ Buhleier, BM AF Parrish, FA Craig, MP Ragen, TJ Marshall, GJ Buhleier, BM TI Identifying diurnal foraging habitat of endangered Hawaiian monk seals using a seal-mounted video camera SO MARINE MAMMAL SCIENCE LA English DT Article DE Hawaiian monk seal; Monachus schauinslandi; foraging habitat; CRITTERCAM; endangered species ID MONACHUS-SCHAUINSLANDI; FEEDING-HABITS; PHOCA-GROENLANDICA; MOVEMENTS; ISLANDS; REEF; DIET AB The Hawaiian monk seal (Monachus schauinslandi) is thought to be a foraging generalist, preying on numerous species in diverse habitats of the subtropical Northwestern Hawaiian Islands. Ac che atoll of French Frigate Shoals, recent evidence of emaciation and low survival in monk seals prompted a search for their specific prey communities and foraging habitat. A video camera (National Geographic Television's CRITTERCAM) fitted to 24 adult male seals documented benthic and demersal foraging on the deep slopes (50-80 m) of the atoll and neighboring banks. The number of bottom searches for prey was compared by year, time of day, type of bottom, individual seal, and length of bottom time. Analysis of variance identified a significant interaction of seal and bottom type, explaining 65% of the coral variance. Seals fed on communities of cryptic fauna (fish and large invertebrates) in transitional "ecotone" regions of low relief where consolidated substrate, rubble, and talus bordered areas of sand. Independent areal surveys of bottom types throughout the atoll and neighboring banks suggest that the type of bottom selected as foraging habitat represents a relatively small percentage of the total benthic area available. C1 NOAA, Natl Marine Fisheries Serv, SW Fisheries Sci Ctr, Honolulu Lab, Honolulu, HI 96822 USA. Univ Hawaii, Joint Inst Marine & Atmospher Res, Honolulu, HI 96822 USA. NOAA, NMFS, Juneau, AK 99801 USA. Natl Geog Televis, Washington, DC 20036 USA. RP Parrish, FA (reprint author), NOAA, Natl Marine Fisheries Serv, SW Fisheries Sci Ctr, Honolulu Lab, 2570 Dole St, Honolulu, HI 96822 USA. EM frank.parrish@noaa.gov NR 46 TC 47 Z9 54 U1 3 U2 16 PU WILEY-BLACKWELL PI HOBOKEN PA 111 RIVER ST, HOBOKEN 07030-5774, NJ USA SN 0824-0469 EI 1748-7692 J9 MAR MAMMAL SCI JI Mar. Mamm. Sci. PD APR PY 2000 VL 16 IS 2 BP 392 EP 412 DI 10.1111/j.1748-7692.2000.tb00932.x PG 21 WC Marine & Freshwater Biology; Zoology SC Marine & Freshwater Biology; Zoology GA 297WT UT WOS:000086106200009 ER PT J AU Roth, DJ Farmer, DA AF Roth, DJ Farmer, DA TI Thickness independent ultrasonic imaging applied to abrasive cut off wheels SO MATERIALS EVALUATION LA English DT Article DE ultrasonics; velocity; thickness; abrasives; wheels ID VELOCITY; ATTENUATION AB Abrasive cut off wheels are at times unintentionally manufactured with nonuniformity that is difficult to identify and sufficiently characterize without time consuming, destructive examination. One particular nonuniformity is a density variation condition occurring around the wheel circumference, along the radius, or both. This density variation, depending on its severity,can cause wheel warpage and wheel vibration resulting in unacceptable performance and perhaps premature failure of the wheel. Conventional nondestructive testing methods such as ultrasonic C-scan imaging and film radiography are inaccurate in their attempts at characterizing the density variation because a superimposing thickness variation exists as well in the wheel. In this article, the single transducer thickness independent ultrasonic imaging method, developed specifically to allow more accurate characterization of aerospace components, is shown to characterize the extent of the density variation in a cut off wheel having a superimposing thickness variation. The method thereby has potential as an effective quality control tool in the abrasives industry for the wheel manufacturer. C1 NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. Allison Abras Inc, Lancaster, KY 40444 USA. RP Roth, DJ (reprint author), NASA, Glenn Res Ctr, MS 6-1,21000 Brookpk Rd, Cleveland, OH 44135 USA. NR 18 TC 2 Z9 2 U1 0 U2 1 PU AMER SOC NON-DESTRUCTIVE TEST PI COLUMBUS PA 1711 ARLINGATE LANE PO BOX 28518, COLUMBUS, OH 43228-0518 USA SN 0025-5327 J9 MATER EVAL JI Mater. Eval. PD APR PY 2000 VL 58 IS 4 BP 551 EP 557 PG 7 WC Materials Science, Characterization & Testing SC Materials Science GA 304UJ UT WOS:000086502300005 ER PT J AU Fichter, WB AF Fichter, WB TI Transverse stress decay in a specially orthotropic strip under localized normal edge loading SO MECHANICS OF COMPOSITE MATERIALS AND STRUCTURES LA English DT Article AB Solutions are presented for the stresses in a specially orthotropic infinite strip which is subjected to localized uniform normal loading on one edge while the other edge is either restrained against normal displacement only, or completely fixed. The solutions are used to investigate the diffusion of load into the strip and in particular the decay of normal stress across the width of the strip. For orthotropic strips representative of a broad range of balanced and symmetric angle-ply composite laminates, minimum strip widths are found that ensure at least 90% decay of the normal stress across the strip. In addition, in a few cases where, on the fixed edge the peak shear stress exceeds the normal stress in magnitude, minimum strip widths that ensure 90% decay of both stresses are found. To help in putting these results into perspective, and to illustrate the influence of material properties on load diffusion in orthotropic materials, closed-form solutions for the stresses in similarly loaded orthotropic half-places are obtained. These solutions are used to generate illustrative stress contour plots for several representative laminates. Among the laminates, those composed of intermediate-angle plies, i.e., from about 30 degrees to 60 degrees, exhibit marked changes in normal stress contour shape with stress level. The stress contours are also used to find 90% decay distances in the half-planes. In all cases, the minimum strip widths for 90% decay of the normal stress exceed the 90% decay distances in the corresponding half-planes, in amounts ranging from only a few percent to about 50% of the half-plane decay distances. The 90% decay distances depend on both material properties and the boundary conditions on the supported edge. C1 NASA, Langley Res Ctr, Hampton, VA 23665 USA. RP Fichter, WB (reprint author), 113 Pierces Court, Williamsburg, VA 23185 USA. NR 6 TC 0 Z9 0 U1 0 U2 0 PU TAYLOR & FRANCIS LTD PI LONDON PA 11 NEW FETTER LANE, LONDON EC4P 4EE, ENGLAND SN 1075-9417 J9 MECH COMPOS MATER ST JI Mech. Compos. Mater. Struct. PD APR-JUN PY 2000 VL 7 IS 2 BP 153 EP 175 DI 10.1080/107594100305357 PG 23 WC Materials Science, Multidisciplinary; Materials Science, Characterization & Testing; Materials Science, Composites SC Materials Science GA 312FQ UT WOS:000086932900002 ER PT J AU MacDonald, AE Lee, JL Sun, S AF MacDonald, AE Lee, JL Sun, S TI QNH: Design and test of a quasi-nonhydrostatic model for mesoscale weather prediction SO MONTHLY WEATHER REVIEW LA English DT Article ID BAROCLINIC WAVES; PARAMETERIZATION; EQUATIONS; SCALES; FLOW AB A new mesoscale weather prediction model, called QNH, is described. It is characterized by a parameter that multiplies the hydrostatic terms in the vertical equation of motion. Models of this type are referred to generically as "quasi-nonhydrostatic." The quasi-nonhydrostatic parameter gives the model a character that is essentially nonhydrostatic, but with properties that are theoretically thought to result in smoother, more: accurate, and stable predictions. The model is unique in a number of other aspects, such as its treatment of lateral boundary conditions, the use of explicit calculation in the vertical direction, and the use of the hounded derivative theory for initialization This paper reports on the design and test of the QNH model, which represents the first time the applicability of this type of model has been demonstrated for full-physics, mesoscale weather prediction. The dynamic formulation, discretization, numerical formulation, and physics packages of the model are described. The results of a comprehensive validation of the model are presented. The validation includes barotropic baroclinic (Eady wave), mountain wave, tropical storm, and sea breeze tests. A simulation of a winter storm (with updated lateral boundary conditions) is presented, which shows that the model has significant skill in forecasting terrain-forced heavy precipitation. It is concluded that the QNH model may be valuable for mesoscale weather prediction. C1 NOAA, ERL, R E FS, Forecast Syst Lab, Boulder, CO 80523 USA. Colorado State Univ, CIRA, Ft Collins, CO 80523 USA. NASA, Goddard Inst, New York, NY USA. RP MacDonald, AE (reprint author), NOAA, ERL, R E FS, Forecast Syst Lab, 325 Broadway, Boulder, CO 80523 USA. RI Lee, JIN-LUEN/G-5364-2015; Sun, Shan/H-2318-2015 NR 34 TC 16 Z9 16 U1 0 U2 1 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0027-0644 J9 MON WEATHER REV JI Mon. Weather Rev. PD APR PY 2000 VL 128 IS 4 BP 1016 EP 1036 DI 10.1175/1520-0493(2000)128<1016:QDATOA>2.0.CO;2 PG 21 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 302ZG UT WOS:000086395900005 ER PT J AU Mukai, K AF Mukai, K TI X-ray observations of non-magnetic CVs in the ASCA era and beyond SO NEW ASTRONOMY REVIEWS LA English DT Article; Proceedings Paper CT Cataclysmic Variables: a 60th Birthday Symposium in Honour of Brian Warner CY APR 12-16, 1999 CL OXFORD UNIV, OXFORD, ENGLAND HO OXFORD UNIV ID NOVA HT-CASSIOPEIAE; OY CARINAE; OUTBURST; ECLIPSE; QUIESCENCE; DISCOVERY; FLUX AB Our ability to study the hard X-ray emission in non-magnetic CVs has improved dramatically within the last decade. We review the important results on X-ray eclipses and dips, the current state-of-the-art in the: modeling of X-ray spectra of CVs, then present some recent results on the hard X-ray emission from high accretion rate non-magnetic CVs. These results point to potential areas of conflict with accretion disk theories: the fate of the inner disk in quiescence, and the amount of material above the orbital plane. We conclude with some speculations on where near-future X-ray missions might take this field over the next decade. (C) 2000 Elsevier Science B.V. All rights reserved. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Space Res Assoc, Washington, DC USA. RP Mukai, K (reprint author), NASA, Goddard Space Flight Ctr, Code 662, Greenbelt, MD 20771 USA. NR 17 TC 5 Z9 5 U1 0 U2 0 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND SN 1387-6473 J9 NEW ASTRON REV JI New Astron. Rev. PD APR PY 2000 VL 44 IS 1-2 BP 9 EP 13 DI 10.1016/S1387-6473(00)00005-1 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 366RF UT WOS:000090017800003 ER PT J AU Cannizzo, JK AF Cannizzo, JK TI A brief overview of dwarf novae and X-ray novae SO NEW ASTRONOMY REVIEWS LA English DT Article; Proceedings Paper CT Cataclysmic Variables: a 60th Birthday Symposium in Honour of Brian Warner CY APR 12-16, 1999 CL OXFORD UNIV, OXFORD, ENGLAND HO OXFORD UNIV ID LIMIT-CYCLE MECHANISM; CATACLYSMIC VARIABLES; ULTRAVIOLET DELAY; ACCRETION DISKS; SS-CYGNI; UV DELAY; OUTBURSTS; INSTABILITY; DECAY; DISCS AB Dwarf novae and X-ray novae have proven to be important in advancing our knowledge of accretion disk physics, or at least of posing challenging questions. The myriad behavior of the various classes and subclasses, including aspects associated both with outburst and quiescence, are constantly providing stimulus to our efforts at modeling accretion disks. I will briefly review some of the main properties of these two classes of objects - including discussions of their outburst characteristics and physical differences. I will also try to point out areas in which we do not have a detailed understanding of the basic model within which to interpret the observations. (C) 2000 Elsevier Science B.V. All rights reserved. C1 NASA, Goddard Space Flight Ctr, LHEA, Greenbelt, MD 20771 USA. RP Cannizzo, JK (reprint author), Univ Space Res Assoc, Columbia, MD 21044 USA. NR 34 TC 2 Z9 2 U1 0 U2 0 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND SN 1387-6473 J9 NEW ASTRON REV JI New Astron. Rev. PD APR PY 2000 VL 44 IS 1-2 BP 41 EP 44 DI 10.1016/S1387-6473(00)00011-7 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 366RF UT WOS:000090017800009 ER PT J AU Plotnikov, YA Rajic, N Winfree, WP AF Plotnikov, YA Rajic, N Winfree, WP TI Means of eliminating background effects for defect detection and visualization in infrared thermography SO OPTICAL ENGINEERING LA English DT Article DE infrared thermography; image analysis; backgrounds; trend removal; defect detection; nondestructive testing AB Pulse infrared thermography is renowned as an effective and rapid method of nondestructive inspection. The primary difficulty in making useful interpretations of a Thermal image is the presence of extraneous effects such as thermal noise, optical distortion through the thermal imaging system, and of most concern, non-uniform heating through the uneven excitation of the surface. A means for removal of background trends caused by uneven illumination is presented. It is based on a polynomial fitting technique applied to a rectangular infrared image on a line-by-line basis in either horizontal or vertical directions. The polynomial coefficients are found by choosing three key pixels through a conditional iterative technique. The proposed algorithm enables improvements in flaw visibility and assists the effective application of additional image processing techniques. The procedure is found to remove trends without distorting real flaw indications as long as the indication spans less than 67% of the interval under examination. (C) 2000 Society of Photo-Optical Instrumentation Engineers. [S0091-3286(00)01904-8]. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Def Sci & Technol Org, Aeronaut & Maritime Res Lab, Melbourne, Vic 3001, Australia. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Plotnikov, YA (reprint author), NASA, Langley Res Ctr, MS 231, Hampton, VA 23681 USA. NR 6 TC 6 Z9 7 U1 1 U2 4 PU SPIE-INT SOCIETY OPTICAL ENGINEERING PI BELLINGHAM PA 1000 20TH ST, BELLINGHAM, WA 98225 USA SN 0091-3286 J9 OPT ENG JI Opt. Eng. PD APR PY 2000 VL 39 IS 4 BP 879 EP 884 DI 10.1117/1.602460 PG 6 WC Optics SC Optics GA 302QD UT WOS:000086375900005 ER PT J AU Martinez-Galarce, DS Walker, ABC Gore, DB Kankelborg, CC Hoover, RB Barbee, TW Boerner, PFX AF Martinez-Galarce, DS Walker, ABC Gore, DB Kankelborg, CC Hoover, RB Barbee, TW Boerner, PFX TI High resolution imaging with multilayer telescopes: resolution performance of the MSSTA II telescopes SO OPTICAL ENGINEERING LA English DT Article DE multilayer optics; space optics; solar chromosphere; solar corona; spectroheliograph; far ultraviolet to extreme ultraviolet imaging ID RAY BRIGHT POINTS; ARRAY-II; BLIND DECONVOLUTION; ENERGY-BALANCE; POLAR PLUMES; SOLAR CORONA; TEMPERATURE; COATINGS; MIRRORS AB The Multi-Spectral Solar Telescope Array (MSSTA) is a sounding rocket-borne observatory composed of a set of normal-incidence multilayer-coated telescopes that obtained selected bandpass spectroheliograms (44 to 1550 Angstrom) of the solar atmosphere. These spectroheliograms were recorded on specially fabricated XUV and FUV 70-mm Kodak film. Rocket launches of this instrument payload took place in 1991 (MSSTA I) and 1994 (MSSTA II) at the White Sands Missile Test Range in New Mexico, sponsored by the National Aeronautics and Space Administration (NASA) sounding rocket experiment program. Immediately prior to the 1994 launch, visible light focusing tests of each telescope were performed in situ using a 1951 standard Air Force high-resolution test target, to measure optical resolution performance. We determined that the MSSTA II telescopes performed at diffraction-limited resolutions down to 0.70 arcsec at visible wavelengths. Based on these measurements, we calculate an upper bound to the focusing errors that incorporate the sum of all uncorrelated system focus errors that affect resolution performance. Coupling these upper bound estimates with the in-band diffraction limits, surface scattering errors and payload pointing jitter, we demonstrate that 11 of 19 MSSTA II telescopes-having negligible figures of focus errors in comparison to the corresponding visible diffraction limits-performed at sub arcsecond resolution at their operational FUV/EUV/XUV wavelengths during flight. We estimate the in-band performance down to 0.14+/-0.08 arcsec. (C) 2000 Society of Photo-Optical Instrumentation Engineers. C1 Stanford Univ, W W Hansen Expt Phys Lab, Dept Elect Engn, Stanford, CA 94305 USA. Stanford Univ, Dept Phys, Dept Appl Phys, Stanford, CA 94305 USA. Univ Alabama, Dept Phys, Birmingham, AL 35294 USA. Montana State Univ, Dept Phys, Bozeman, MT 59717 USA. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. Univ Calif Lawrence Livermore Natl Lab, Livermore, CA 94550 USA. RP Martinez-Galarce, DS (reprint author), Stanford Univ, W W Hansen Expt Phys Lab, Dept Elect Engn, Stanford, CA 94305 USA. NR 49 TC 12 Z9 13 U1 0 U2 2 PU SPIE-INT SOCIETY OPTICAL ENGINEERING PI BELLINGHAM PA 1000 20TH ST, BELLINGHAM, WA 98225 USA SN 0091-3286 J9 OPT ENG JI Opt. Eng. PD APR PY 2000 VL 39 IS 4 BP 1063 EP 1079 PG 17 WC Optics SC Optics GA 302QD UT WOS:000086375900029 ER PT J AU Fischer, DG Ovryn, B AF Fischer, DG Ovryn, B TI Interfacial shape and contact-angle measurement of transparent samples with confocal interference microscopy SO OPTICS LETTERS LA English DT Article AB A model has been developed that predicts the effective optical path through a thick, refractive specimen on a reflective substrate, as measured with a scanning confocal interference microscope equipped with a high-numerical-aperture objective. Assuming that the effective pinhole of the confocal microscope has an infinitesimal diameter, only one ray in the illumination bundle (the magic ray) contributes to the differential optical path length (OPL). A pinhole with finite diameter, however, allows rays within a small angular cone centered on the magic ray to contribute to the OPL. The model was incorporated into an iterative algorithm that allows the measured phase to be corrected for refractive errors by use of an a priori estimate of the sample profile. The algorithm was validated with a reflected-light microscope equipped with a phase-shifting laser-feedback interferometer to measure the interface shape and the 68 degrees contact angle of a silicone-oil drop on a coated silicon wafer. (C) 2000 Optical Society of America. OCIS codes: 120.3180, 170.1790, 180.3170, 120.3940, 120.2830. C1 NASA, Natl Ctr Micrograv Res Fluids & Combust, Glenn Res Ctr, Cleveland, OH 44135 USA. Case Western Reserve Univ, Dept Mech & Aerosp Engn, Cleveland, OH 44106 USA. RP Fischer, DG (reprint author), NASA, Natl Ctr Micrograv Res Fluids & Combust, Glenn Res Ctr, MS 110-3,21000 Brookpk Rd, Cleveland, OH 44135 USA. NR 19 TC 13 Z9 13 U1 0 U2 4 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 0146-9592 J9 OPT LETT JI Opt. Lett. PD APR 1 PY 2000 VL 25 IS 7 BP 478 EP 480 DI 10.1364/OL.25.000478 PG 3 WC Optics SC Optics GA 298TW UT WOS:000086156100016 PM 18064085 ER PT J AU Bindschadler, R Vornberger, P AF Bindschadler, R Vornberger, P TI Detecting ice-sheet topography with AVHRR, RESURS-01, and landsat TM imagery SO PHOTOGRAMMETRIC ENGINEERING AND REMOTE SENSING LA English DT Article ID WEST ANTARCTICA; SOLAR-RADIATION; STREAM-B AB The ability of different visible-band satellite imagers to detect subtle ice-sheet topographic features is examined by both qualitative and quantitative comparisons. The AVHRR 10-bit sensor is shown to have the best radiometric resolution, but its poorer spatial resolution limits this sensor's ability to discriminate smaller scale topography. RESURS-01 is a less-well known 8-bit sensor, but this instrument's higher noise and poorer radiometric resolution restrict its utility for ice-sheet research. Landsat TM applies 8-bit quantization over a narrower radiometric range, causing it to saturate for some conditions. This limitation allows TM to achieve a radiometric resolution half that of AVHRR while retaining a much higher spatial resolution. No SPOT imagery was compared, but the sensor is shown to have less radiometric resolution than TM. However SPOT has better spatial resolution and is less likely to saturate. C1 NASA, Goddard Space Flight Ctr, Oceans & Ice Branch, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. SAIC Gen Sci Corp, Beltsville, MD 20705 USA. RP Bindschadler, R (reprint author), NASA, Goddard Space Flight Ctr, Oceans & Ice Branch, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. NR 15 TC 5 Z9 5 U1 0 U2 0 PU AMER SOC PHOTOGRAMMETRY PI BETHESDA PA 5410 GROSVENOR LANE SUITE 210, BETHESDA, MD 20814-2160 USA SN 0099-1112 J9 PHOTOGRAMM ENG REM S JI Photogramm. Eng. Remote Sens. PD APR PY 2000 VL 66 IS 4 BP 417 EP 422 PG 6 WC Geography, Physical; Geosciences, Multidisciplinary; Remote Sensing; Imaging Science & Photographic Technology SC Physical Geography; Geology; Remote Sensing; Imaging Science & Photographic Technology GA 301WM UT WOS:000086333500010 ER PT J AU Gunapala, SD Bandara, SV Singh, A Liu, JK Luong, EM Mumolo, JM LeVan, PD AF Gunapala, SD Bandara, SV Singh, A Liu, JK Luong, EM Mumolo, JM LeVan, PD TI Recent developments and applications of quantum well infrared photodetector focal plane arrays SO PHYSICA E LA English DT Article DE infrared photodetector; detectors; multi-color camera; arrays AB One of the simplest device realizations of the classic particle-in-the-box problem of basic quantum mechanics is the quantum well infrared photodetector (QWIP). In this paper we discuss the optimization of the detector design, material growth and processing that has culminated in realization of large format long-wavelength QWIP cameras, hording forth great promise for many applications in 6-25 mu m wavelength range in science, medicine, defense and industry. In addition, we present the recent developments in long-wavelength/very long-wavelength dualband QWIP imaging camera for various applications. (C) 2000 Published by Elsevier Science B.V. All rights reserved. C1 CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. USAF, Res Lab, Kirtland AFB, NM 87117 USA. RP Gunapala, SD (reprint author), CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, M-S 302-306, Pasadena, CA 91109 USA. NR 3 TC 11 Z9 12 U1 1 U2 4 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 1386-9477 J9 PHYSICA E JI Physica E PD APR PY 2000 VL 7 IS 1-2 BP 108 EP 111 DI 10.1016/S1386-9477(99)00286-6 PG 4 WC Nanoscience & Nanotechnology; Physics, Condensed Matter SC Science & Technology - Other Topics; Physics GA 297HL UT WOS:000086076800024 ER PT J AU Balasubramaniam, R Subramanian, RS AF Balasubramaniam, R Subramanian, RS TI The migration of a drop in a uniform temperature gradient at large Marangoni numbers SO PHYSICS OF FLUIDS LA English DT Article ID THERMOCAPILLARY BUBBLE MIGRATION; GAS BUBBLE; REYNOLDS; GRAVITY; MOTION AB The steady thermocapillary motion of a spherical drop in a uniform temperature gradient is treated in the situation where convective transport of energy is predominant in the drop phase as well as in the continuous phase, i.e., when the Marangoni numbers are large. It is assumed that the Reynolds numbers in both phases are large as well; to leading order, the velocity fields are given by a potential flow field in the continuous phase and Hill's vortex inside the drop. The migration velocity of the drop is obtained by equating the rate at which work is done by the thermocapillary stress to the rate of viscous dissipation of energy. The analysis deals with an asymptotic situation wherein convective transport of energy dominates with conduction playing a role only where essential. This leads to thin thermal boundary layers both outside and within the drop. The method of matched asymptotic expansions is employed to solve the conjugate heat transfer problem in the two phases. It is shown that the demand for energy within the drop, necessary to increase its temperature at a steady rate as it moves into warmer surroundings, results in a large temperature difference between the surface of the drop and its interior. The variation of temperature over the drop surface is large as well, and leads to a linear increase of the migration velocity of the drop with increasing Marangoni number. This result is strikingly different from that for the limiting case when the viscosity and thermal conductivity inside the drop become negligible compared to the corresponding properties in the continuous phase. This limit, which holds for a gas bubble, is recovered correctly from the analysis. (C) 2000 American Institute of Physics. [S1070-6631(00)01504-X]. C1 NASA, Glenn Res Ctr, Natl Ctr Micrograv Res Fluids & Combust, Cleveland, OH 44135 USA. Clarkson Univ, Dept Chem Engn, Potsdam, NY 13699 USA. RP Balasubramaniam, R (reprint author), NASA, Glenn Res Ctr, Natl Ctr Micrograv Res Fluids & Combust, Mail Stop 110-3, Cleveland, OH 44135 USA. NR 29 TC 40 Z9 42 U1 2 U2 11 PU AMER INST PHYSICS PI MELVILLE PA 2 HUNTINGTON QUADRANGLE, STE 1NO1, MELVILLE, NY 11747-4501 USA SN 1070-6631 J9 PHYS FLUIDS JI Phys. Fluids PD APR PY 2000 VL 12 IS 4 BP 733 EP 743 DI 10.1063/1.870330 PG 11 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 290RD UT WOS:000085689000001 ER PT J AU Lorenz, RD Moersch, JE Stone, JA Morgan, AR Smrekar, SE AF Lorenz, RD Moersch, JE Stone, JA Morgan, AR Smrekar, SE TI Penetration tests on the DS-2 Mars microprobes: penetration depth and impact accelerometry SO PLANETARY AND SPACE SCIENCE LA English DT Article; Proceedings Paper CT XXIVth General Assembly of the European-Geophysical-Society CY 1999 CL THE HAGUE, NETHERLANDS SP European Geophys Soc ID MISSION; EXPLORATION AB We describe the results of three separate sets of impact tests conducted during the development of the DS-2 Mars Microprobe mission, As well as indicating the promise of penetration to similar to 0.5 m depth on Mars, these tests show the utility of accelerometer data in determining the penetration depth, the hardness of the surface material and the existence of layers, and the presence of coarse-grained material. Various lessons learned in instrumentation and operation, airgun testing and target characterization, and penetrator design for reliable separation, are discussed. (C) 2000 Elsevier Science Ltd. All rights reserved. C1 Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. NASA, Ames Res Ctr, Natl Res Council, Moffett Field, CA 94043 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Lorenz, RD (reprint author), Univ Arizona, Lunar & Planetary Lab, 1629 E Univ Blvd, Tucson, AZ 85721 USA. RI Moersch, Jeffrey/F-7189-2010; Lorenz, Ralph/B-8759-2016 OI Lorenz, Ralph/0000-0001-8528-4644 NR 22 TC 21 Z9 21 U1 1 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD APR PY 2000 VL 48 IS 5 BP 419 EP 436 DI 10.1016/S0032-0633(00)00016-7 PG 18 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 322VK UT WOS:000087529800007 ER PT J AU Redelsperger, JL Brown, PRA Guichard, F Hoff, C Kawasima, M Lang, S Montmerle, T Nakamura, K Saito, K Seman, C Tao, WK Donner, LJ AF Redelsperger, JL Brown, PRA Guichard, F Hoff, C Kawasima, M Lang, S Montmerle, T Nakamura, K Saito, K Seman, C Tao, WK Donner, LJ TI A GCSS model intercomparison for a tropical squall line observed during TOGA-COARE. I: Cloud-resolving models SO QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY LA English DT Article DE cloud-resolving models; clouds; Doppler radar; GCSS ID MESOSCALE CONVECTIVE SYSTEM; DOPPLER RADAR DATA; 3-DIMENSIONAL SIMULATION; NUMERICAL-SIMULATION; LONGWAVE RADIATION; STRATIFORM REGION; EVOLUTION; SENSITIVITY; MOMENTUM; PARAMETERIZATION AB Results from eight cloud-resolving models are compared for the first time for the case of an oceanic tropicalsquall line observed during the Tropical Ocean/Global Atmosphere Coupled Ocean-Atmosphere Response Experiment. There is broad agreement between all the models in describing the overall structure and propagation of the squall line and some quantitative agreement in the evolution of rainfall. There is also a more qualitative agreement between the models in describing the vertical structure of the apparent heat and moisture sources. The three-dimensional (3D) experiments with an active ice phase and open lateral boundary conditions along the direction of the system propagation show good agreement for all parameters. The comparison of 3D simulated fields with those obtained from two different analyses of airborne Doppler radar data indicates that the 3D models are able to simulate the dynamical structure of the squall line, including the observed double-peaked updraughts. However, the second updraught peak at around 10 km in height is obtained only when the ice phase is represented. The 2D simulations with an ice-phase parametrization also exhibit this structure, although with a larger temporal variability. In the 3D simulations, the evolution of the mean wind profile is in the sense of decreasing the shear, but the 2D simulations are unable to reproduce this behaviour. C1 Inst Low Temp Sci, Tsukuba, Ibaraki, Japan. Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Ctr Etud Environm Terr & Planetaires, Velizy Villacoubl, France. Geophys Fluid Dynam Lab, Princeton, NJ USA. RP Redelsperger, JL (reprint author), CNRS, CNRM, GAME, 42 Av Coriolis, F-31057 Toulouse, France. RI Kawashima, Masayuki/D-9107-2012; Brown, Philip/D-9819-2013; Jean-Luc, Redelsperger/L-4021-2015 OI Brown, Philip/0000-0003-4643-4923; NR 48 TC 87 Z9 88 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 2000 VL 126 IS 564 BP 823 EP 863 DI 10.1256/smsqj.56403 PN A PG 41 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 314LT UT WOS:000087057900003 ER PT J AU Joiner, J Dee, DP AF Joiner, J Dee, DP TI An error analysis of radiance and suboptimal retrieval assimilation SO QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY LA English DT Article DE data assimilation; radiance; retrievals; TIROS (Television Infra-Red Operational Satellite) Operational Vertical Sounder (TOVS) ID TEMPERATURE; SOUNDER AB One of the outstanding problems in data assimilation has been, and continues to be, how best to utilize satellite data while balancing the trade-off between accuracy and computational cost. A number of weather-prediction centres have recently achieved remarkable success in improving their forecast skill by changing the method in which satellite data are assimilated into the forecast model from the traditional approach of assimilating retrieved products to the direct assimilation of radiances in a variational framework. Although there are clear theoretical advantages to the direct radiance-assimilation approach, it is not obvious at all to what extent the improvements that have been obtained so far can be attributed to the change in methodology or to various technical aspects of the implementation. The central question we address here is: how much improvement can we expect from assimilating radiances rather than retrievals, all other things being equal? We compare the two approaches in a simplified theoretical framework. Direct radiance analysis is optimal in this idealized context, while the traditional method of assimilating retrievals is suboptimal because it ignores the cross-covariances between background errors and retrieval errors. We show that interactive retrieval analysis (where the same background used for assimilation is also used in the retrieval step) is equivalent to direct assimilation of radiances with suboptimal analysis weights. We illustrate and extend these theoretical arguments with several one-dimensional analysis experiments, where we estimate vertical atmospheric profiles using simulated data from temperature sounding channels of both the High-resolution InfraRed Sounder 2 (HIRS2) and the future Atmospheric InfraRed Sounder (AIRS). In the case of non-interactive retrievals the results depend very much on the quality of the background information used for the retrieval step. In all cases, the impact of the choice of analysis method is dwarfed by the effect of changing some of the experimental parameters that control the simulated error characteristics of the data and the retrieval background. C1 NASA, Goddard Space Flight Ctr, Data Assimilat Off, Greenbelt, MD 20771 USA. Gen Sci Corp, Arlington, VA 22202 USA. RP Joiner, J (reprint author), NASA, Goddard Space Flight Ctr, Data Assimilat Off, Code 910-3, Greenbelt, MD 20771 USA. RI Joiner, Joanna/D-6264-2012 NR 20 TC 13 Z9 13 U1 0 U2 0 PU ROYAL METEOROLOGICAL SOC PI READING PA 104 OXFORD ROAD, READING, BERKS, ENGLAND RG1 7LJ SN 0035-9009 J9 Q J ROY METEOR SOC JI Q. J. R. Meteorol. Soc. PD APR PY 2000 VL 126 IS 565 BP 1495 EP 1514 DI 10.1256/smsqj.56513 PN B PG 20 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 322TH UT WOS:000087524500013 ER PT J AU Cucinotta, FA Nikjoo, H Goodhead, DT AF Cucinotta, FA Nikjoo, H Goodhead, DT TI Model for radial dependence of frequency distributions for energy imparted in nanometer volumes from HZE particles SO RADIATION RESEARCH LA English DT Article ID ULTRASOFT X-RAYS; TRACK STRUCTURE-ANALYSIS; LOW-LET RADIATIONS; HEAVY-IONS; ELECTRONS; CELL; INACTIVATION; SILICON; SPECTRA; EVENTS AB This paper develops a deterministic model of frequency distributions for energy imparted (total energy deposition) in small volumes similar to DNA molecules from high-energy ions of interest for space radiation protection and cancer therapy. Frequency distributions for energy imparted are useful for considering radiation quality and for modeling biological damage produced by ionizing radiation. For high-energy ions, secondary electron (delta-ray) tracks originating from a primary ion track make dominant contributions to energy deposition events in small volumes. Our method uses the distribution of electrons produced about an ion's path and incorporates results from Monte Carlo simulation of electron tracks to predict frequency distributions for ions, including their dependence on radial distance, The contribution from primary ion events is treated using an impact parameter formalism of spatially restricted linear energy transfer (LET) and energy-transfer straggling, We validate our model by comparing it directly to results from Monte Carlo simulations for proton acid or-particle tracks. We show for the first time frequency distributions of energy imparted in DNA structures by several high-energy ions such as cosmic-ray iron ions. Our comparison with results from Monte Carlo simulations at low energies indicates the accuracy of the method. (C) 2000 by Radiation Research Society. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. MRC, Radiat & Genome Stabil Unit, Didcot OX11 0RD, Oxon, England. RP Cucinotta, FA (reprint author), NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 36 TC 82 Z9 85 U1 0 U2 5 PU RADIATION RESEARCH SOC PI OAK BROOK PA 2021 SPRING RD, STE 600, OAK BROOK, IL 60521 USA SN 0033-7587 J9 RADIAT RES JI Radiat. Res. PD APR PY 2000 VL 153 IS 4 BP 459 EP 468 DI 10.1667/0033-7587(2000)153[0459:MFRDOF]2.0.CO;2 PG 10 WC Biology; Biophysics; Radiology, Nuclear Medicine & Medical Imaging SC Life Sciences & Biomedicine - Other Topics; Biophysics; Radiology, Nuclear Medicine & Medical Imaging GA 317BJ UT WOS:000087204100014 PM 10761008 ER PT J AU Tait, AB Hall, DK Foster, JL Armstrong, RL AF Tait, AB Hall, DK Foster, JL Armstrong, RL TI Utilizing multiple datasets for snow-cover mapping SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID MICROWAVE; VARIABILITY AB Snow-cover maps generated from surface data are based on direct measurements. However, they are prone to interpolation errors where climate stations are sparsely distributed. Snow cover is clearly discernible using satellite-obtained optical data because of the high albedo of snow, yet the surface is often obscured by cloud cover. Satellite-obtained passive microwave data, compared with optical data, is relatively unaffected by clouds; however, the snow-cover signature is significantly affected by melting snow and the microwaves may be transparent to thin snow (<3 cm). Both optical and microwave sensors have problems discerning snow beneath forest canopies. This paper describes a method that combines ground and satellite-derived optical and passive microwave data to produce a multiple-dataset snow-cover product. Comparisons with current snow-cover products show that the multiple-dataset product draws together the advantages of each of its component products while minimizing the potential errors. Improved estimates of the snow-covered area are derived through the addition of two snow-cover classes ("thin or patchy" and "high elevation" snow cover) and from the analysis of the climate station data within each class. The compatibility of this method for use with Moderate Resolution Imaging Spectroradiometer data, which will be available in 1999, and with Advanced Microwave Scanning Radiometer data, available in 2000, is also discussed. With the assimilation of these data, the resolution of the multiple-dataset product would be improved both spatially and temporally and the analysis would become completely automated. (C)Elsevier Science, Inc., 2000. C1 NASA, Goddard Space Flight Ctr, Hydrol Sci Branch, Greenbelt, MD 20771 USA. Univ Space Res Assoc, Lanham, MD USA. Univ Colorado, Natl Snow & Ice Data Ctr, Boulder, CO 80309 USA. RP Tait, AB (reprint author), NASA, Goddard Space Flight Ctr, Hydrol Sci Branch, Mail Code 974, Greenbelt, MD 20771 USA. RI Hall, Dorothy/D-5562-2012 NR 31 TC 20 Z9 23 U1 0 U2 9 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA SN 0034-4257 J9 REMOTE SENS ENVIRON JI Remote Sens. Environ. PD APR PY 2000 VL 72 IS 1 BP 111 EP 126 DI 10.1016/S0034-4257(99)00099-1 PG 16 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA 295CF UT WOS:000085947900008 ER PT J AU King, MD Herring, DD AF King, MD Herring, DD TI Monitoring Earth's vital signs SO SCIENTIFIC AMERICAN LA English DT Article C1 NASA, Earth Observing Syst, Greenbelt, MD 20771 USA. RP King, MD (reprint author), NASA, Earth Observing Syst, Greenbelt, MD 20771 USA. RI King, Michael/C-7153-2011 OI King, Michael/0000-0003-2645-7298 NR 3 TC 6 Z9 6 U1 1 U2 3 PU SCI AMERICAN INC PI NEW YORK PA 415 MADISON AVE, NEW YORK, NY 10017 USA SN 0036-8733 J9 SCI AM JI Sci.Am. PD APR PY 2000 VL 282 IS 4 BP 92 EP 97 PG 6 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 295VV UT WOS:000085989300027 PM 10789252 ER PT J AU Wood, K Brown, T Rogowski, R Jensen, B AF Wood, K Brown, T Rogowski, R Jensen, B TI Fiber optic sensors for health monitoring of morphing airframes: I. Bragg grating strain and temperature sensor SO SMART MATERIALS & STRUCTURES LA English DT Article ID DISTRIBUTED MEASUREMENT AB Fiber optic sensors are being developed for health monitoring of future aircraft. Aircraft health monitoring involves the use of strain, temperature, vibration and chemical sensors to infer integrity of the aircraft structure. Part I of this two part series describes sensors that will measure load and temperature signatures of these structures. In some cases a single fiber may be used for measuring these parameters. Part 2 will describe techniques for using optical fibers to monitor composite cure in real time during manufacture and to monitor in-service integrity of composite structures using a single fiber optic sensor capable of measuring multiple chemical and physical parameters. The facilities for fabricating optical fiber and associated sensors and the methods of demodulating Bragg gratings for strain measurement will be described. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Natl Res Council, Washington, DC 20418 USA. NR 11 TC 27 Z9 27 U1 0 U2 5 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0964-1726 J9 SMART MATER STRUCT JI Smart Mater. Struct. PD APR PY 2000 VL 9 IS 2 BP 163 EP 169 DI 10.1088/0964-1726/9/2/306 PG 7 WC Instruments & Instrumentation; Materials Science, Multidisciplinary SC Instruments & Instrumentation; Materials Science GA 309XP UT WOS:000086794900006 ER PT J AU Wood, K Brown, T Rogowski, R Jensen, B AF Wood, K Brown, T Rogowski, R Jensen, B TI Fiber optic sensors for health monitoring of morphing airframes: II. Chemical sensing using optical fibers with Bragg gratings SO SMART MATERIALS & STRUCTURES LA English DT Article ID WAVE ABSORPTION-SPECTROSCOPY; ALUMINUM HYDROXIDE; REMOTE DETECTION; CURE AB Part I of this two part series described the fabrication and calibration of Bragg gratings written into a single mode optical fiber for use in strain and temperature monitoring. Part II of the series describes the use of identical fibers and additional multimode fibers, both with and without Bragg gratings, to perform near infrared spectroscopy. The demodulation system being developed at NASA Langley Research Center currently requires the use of a single mode optical fiber. Attempts to use this single mode fiber for spectroscopic analysis are problematic given its small core diameter, resulting in low signal intensity. Nonetheless, we have conducted a preliminary investigation using a single mode fiber in conjunction with an infrared spectrometer to obtain spectra of a high-performance epoxy resin system. Spectra were obtained using single mode fibers that contained Bragg gratings; however, the peaks of interest were barely discernible above the noise. The goal of this research is to provide a multipurpose sensor in a single optical fiber capable of measuring a variety of chemical and physical properties. C1 Natl Res Council, Washington, DC 20418 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. Sandia Natl Labs, Albuquerque, NM 87185 USA. NR 9 TC 4 Z9 4 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0964-1726 J9 SMART MATER STRUCT JI Smart Mater. Struct. PD APR PY 2000 VL 9 IS 2 BP 170 EP 174 DI 10.1088/0964-1726/9/2/307 PG 5 WC Instruments & Instrumentation; Materials Science, Multidisciplinary SC Instruments & Instrumentation; Materials Science GA 309XP UT WOS:000086794900007 ER PT J AU Brosius, JW Thomas, RJ Davila, JM Thompson, WT AF Brosius, JW Thomas, RJ Davila, JM Thompson, WT TI SERTS-97 measurements of relative wavelength shifts in coronal emission lines across a solar active region SO SOLAR PHYSICS LA English DT Article ID EXTREME-ULTRAVIOLET-SPECTRA; DIAGNOSTIC SPECTROMETER CDS; TRANSITION REGION; QUIET-SUN; OBSERVED REDSHIFTS; FLOWS; SOHO; CHROMOSPHERE; DYNAMICS; ZONE AB We used slit spectra from the 18 November 1997 flight of Goddard Space Flight Center's Solar EUV Rocket Telescope and Spectrograph (SERTS-97) to measure relative wavelength shifts of coronal emission lines as a function of position across NOAA active region 8108. The shifts are measured relative to reference wavelengths derived from spectra of the region's nearby quiet surroundings (not necessarily at rest) because laboratory rest wavelengths for the coronal EUV lines have not been measured to sufficient accuracy for this work. An additional benefit to this approach is that any systematic uncertainties in the wavelength measurements are eliminated from the relative shifts by subtraction. We find statistically significant wavelength shifts between the spatially resolved active region slit spectra and the reference spectrum. For He ii 303.78 Angstrom the maximum measured relative red shift corresponds to a Doppler velocity similar to+13 km s(-1), and the maximum relative blue shift corresponds to a Doppler velocity similar to-3 km s(-1). For Si x 347.40 Angstrom, Si xi 303.32 Angstrom, Fe xiv 334.17 Angstrom, and Fe xvi 335.40 Angstrom the corresponding maximum relative Doppler velocities are similar to+19 and similar to-14, similar to+23 and similar to-7, similar to+10 and similar to-10, and similar to+13 and similar to-5 km s(-1), respectively. The active region appears to be divided into two different flow areas; hot coronal lines are predominantly red-shifted in the northern half and either blue-shifted or nearly un-shifted in the southern half. This may be evidence that material flows up from the southern part of the region, and down into the northern part. Qualitatively similar relative wavelength shifts and flow patterns are obtained with SOHO/CDS spectra. C1 NASA, Goddard Space Flight Ctr, Raytheon ITSS, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, SM&A, Greenbelt, MD 20771 USA. RP Brosius, JW (reprint author), NASA, Goddard Space Flight Ctr, Raytheon ITSS, Code 682, Greenbelt, MD 20771 USA. RI Thompson, William/D-7376-2012 NR 26 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 2000 VL 193 IS 1-2 BP 117 EP 129 DI 10.1023/A:1005200928518 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 354XV UT WOS:000089357300007 ER PT J AU Thompson, BJ Reynolds, B Aurass, H Gopalswamy, N Gurman, JB Hudson, HS Martin, SF St Cyr, OC AF Thompson, BJ Reynolds, B Aurass, H Gopalswamy, N Gurman, JB Hudson, HS Martin, SF St Cyr, OC TI Observations of the 24 September 1997 coronal flare waves SO SOLAR PHYSICS LA English DT Article ID II RADIO-BURSTS; MASS EJECTION; WIND SPACECRAFT; ORIGIN AB We report coincident observations of coronal and chromospheric 'flare wave' transients in association with a flare, large-scale coronal dimming, metric radio activity and a coronal mass ejection. The two separate eruptions occurring on 24 September 1997 originate in the same active region and display similar morphological features. The first wave transient was observed in EUV and H alpha data, corresponding to a wave disturbance in both the chromosphere and the solar corona, ranging from 250 to approaching 1000 km s(-1) at different times and locations along the wavefront. The sharp wavefront had a similar extent and location in both the EUV and H alpha data. The data did not show clear evidence of a driver, however. Both events display a coronal EUV dimming which is typically used as an indicator of a coronal mass ejection in the inner corona. White-light coronagraph observations indicate that the first event was accompanied by an observable coronal mass ejection while the second event did not have clear evidence of a CME. Both eruptions were accompanied by metric type II radio bursts propagating at speeds in the range of 500-750 km s(-1), and neither had accompanying interplanetary type II activity. The timing and location of the flare waves appear to indicate an origin with the flaring region, but several signatures associated with coronal mass ejections indicate that the development of the CME may occur in concert with the development of the flare wave. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Astrophys Inst Potsdam, Potsdam, Germany. Catholic Univ Amer, Washington, DC 20064 USA. Solar Phys Res Corp, Tucson, AZ USA. Helio Res, La Crescenta, CA USA. Computat Phys Inc, Fairfax, VA USA. RP Thompson, BJ (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RI Gopalswamy, Nat/D-3659-2012; Thompson, Barbara/C-9429-2012 NR 55 TC 106 Z9 107 U1 1 U2 1 PU SPRINGER PI DORDRECHT PA VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS SN 0038-0938 J9 SOL PHYS JI Sol. Phys. PD APR PY 2000 VL 193 IS 1-2 BP 161 EP 180 DI 10.1023/A:1005222123970 PG 20 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 354XV UT WOS:000089357300011 ER PT J AU Bromage, BJJ Alexander, D Breen, A Clegg, JR Del Zanna, G DeForest, C Dobrzycka, D Gopalswamy, N Thompson, B Browning, PK AF Bromage, BJJ Alexander, D Breen, A Clegg, JR Del Zanna, G DeForest, C Dobrzycka, D Gopalswamy, N Thompson, B Browning, PK TI Structure of a large low-latitude coronal hole SO SOLAR PHYSICS LA English DT Article ID WHOLE SUN MONTH; SOLAR-WIND; INTERPLANETARY SCINTILLATION; ELEPHANTS TRUNK; SOHO MISSION; SPECTROMETER; TELESCOPE; BOUNDARY; FIELD AB Coronal holes on the Sun are the source of high-speed solar wind streams that produce magnetic disturbances at the Earth. A series of multi-wavelength, multi-instrument observations obtained during the 1996 'Whole Sun Month' campaign examined a large coronal hole in greater detail than ever before. It appeared on the Sun in August, and extended from the north pole to a large active region in the southern hemisphere. Its physical and magnetic structure and subsequent evolution are described. C1 Univ Cent Lancashire, Ctr Astrophys, Preston PR1 2HE, Lancs, England. Lockheed Martin Solar & Astrophys Lab, Palo Alto, CA USA. Max Planck Inst Aeron, Katlenburg Lindau, Germany. NASA, Goddard Space Flight Ctr, SOHO SOI MDI, Greenbelt, MD 20771 USA. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. Catholic Univ Amer, NASA, GSFC, Greenbelt, MD USA. NASA, Goddard Space Flight Ctr, Space Applicat Corp, Greenbelt, MD 20771 USA. Univ Manchester, Inst Sci & Technol, Manchester M60 1QD, Lancs, England. RP Bromage, BJJ (reprint author), Univ Cent Lancashire, Ctr Astrophys, Preston PR1 2HE, Lancs, England. RI Gopalswamy, Nat/D-3659-2012; Thompson, Barbara/C-9429-2012 NR 29 TC 26 Z9 26 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 2000 VL 193 IS 1-2 BP 181 EP 193 DI 10.1023/A:1005209725885 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 354XV UT WOS:000089357300012 ER PT J AU Hathaway, DH Beck, JG Bogart, RS Bachmann, KT Khatri, G Petitto, JM Han, S Raymond, J AF Hathaway, DH Beck, JG Bogart, RS Bachmann, KT Khatri, G Petitto, JM Han, S Raymond, J TI The photospheric convection spectrum SO SOLAR PHYSICS LA English DT Article ID SPHERICAL HARMONIC-ANALYSIS; POWER SPECTRA; SOLAR CONVECTION; VELOCITY-FIELDS; GIANT-CELLS; SCALE; FLOWS; SUN; MESOGRANULES; GRANULATION AB Spectra of the cellular photospheric flows are determined from observations acquired by the MDI instrument on the SOHO spacecraft. Spherical harmonic spectra are obtained from the full-disk observations. Fourier spectra are obtained from the high-resolution observations. The p-mode oscillation signal and instrumental artifacts are reduced by temporal filtering of the Doppler data. The resulting spectra give power (kinetic energy) per wave number for effective spherical harmonic degrees from 1 to over 3000. Significant power is found at all wavenumbers, including the small wavenumbers representative of giant cells. The time evolution of the spectral coefficients indicates that these small wavenumber components rotate at the solar rotation rate and thus represent a component of the photospheric cellular flows. The spectra show distinct peaks representing granules and supergranules but no distinct features at wavenumbers representative of mesogranules or giant cells. The observed cellular patterns and spectra are well represented by a model that includes two distinct modes - granules and supergranules. C1 NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Stanford Univ, Stanford, CA 94305 USA. Birmingham So Coll, Birmingham, AL 35254 USA. Tennessee Technol Univ, Cookeville, TN 38505 USA. RP Hathaway, DH (reprint author), NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. NR 30 TC 94 Z9 94 U1 1 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 2000 VL 193 IS 1-2 BP 299 EP 312 DI 10.1023/A:1005200809766 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 354XV UT WOS:000089357300019 ER PT J AU Russell, PB Heintzenberg, J AF Russell, PB Heintzenberg, J TI An overview of the ACE-2 clear sky column closure experiment (CLEARCOLUMN) SO TELLUS SERIES B-CHEMICAL AND PHYSICAL METEOROLOGY LA English DT Article ID IN-SITU MEASUREMENTS; OPTICAL-PROPERTIES; AEROSOL; ABSORPTION; PARTICLES; ATLANTIC; HUMIDITY; SIZE AB As 1 of 6 focused ACE-2 activities, a clear sky column closure experiment (CLEARCOLUMN) took place in June/July 1997 at the southwest corner of Portugal, in the Canary Islands, and over the eastern Atlantic Ocean surrounding and linking those sites. Overdetermined sets of volumetric, vertical profile and columnar aerosol data were taken From the sea surface to similar to 5 km asl by samplers and sensors at land sites (20-3570 m asl), on a ship, and on 4 aircraft. In addition, 5 satellites measured upwelling radiances used to derive properties of the aerosol column. Measurements were made in a wide range of conditions and locations (e.g., the marine boundary layer with and without continental pollution, the free troposphere with and without African dust). Numerous tests of local and column closure, using unidisciplinary and multidisciplinary approaches, were conducted. This paper summarizes the methodological approach, the experiment sites and platforms, the types of measurements made on each, the types of analyses conducted, and selected key results, as a guide to the more complete results presented in other papers in this special issue and elsewhere. Example results include determinations of aerosol single scattering albedo by several techniques, measurements of hygroscopic effects on particle light scattering and size, and a wide range in the degree of agreement found in closure tests. In general, the smallest discrepancies were found in comparisons among (1) different techniques to measure an optical property of the ambient, unperturbed aerosol (e.g., optical depth, extinction, or backscatter by sunphotometer, lidar, and/or satellite) or (2) different techniques to measure an aerosol that had passed through a common sampling process (e.g., nephelometer and size spectrometer measurements with the same or similar inlets, humidities and temperatures). Typically, larger discrepancies were Found between techniques that measure the ambient, unperturbed aerosol and those that must reconstruct the ambient aerosol by accounting for (a) processes that occur during sampling (e.g., aerodynamic selection, evaporation of water and other volatile material) or (b) calibrations that depend on aerosol characteristics (e.g., size-dependent density or refractive index). A primary reason for the discrepancies in such cases is the lack of validated hygroscopic growth models covering the necessary range of particle sizes and compositions. Other common reasons include (1) using analysis or retrieval techniques that assume aerosol properties (e.g., density, single scattering albedo, shape) that do not apply in all cases and (2) using surface measurements to estimate column properties. Taken together, the ACE-2 CLEARCOLUMN data set provides a large collection of new information on the properties of the aerosol over the northeast Atlantic Ocean. CLEARCOLUMN studies have also pointed to improved techniques For analyzing current and future data sets (including satellite data sets) which will provide a more accurate and comprehensive description of the Atlantic-European-African aerosol. Thus they set the stage for an improved regional quantification of radiative forcing by anthropogenic aerosols. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Inst Tropospher Res, D-04318 Leipzig, Germany. RP Russell, PB (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 54 TC 76 Z9 76 U1 0 U2 5 PU MUNKSGAARD INT PUBL LTD PI COPENHAGEN PA 35 NORRE SOGADE, PO BOX 2148, DK-1016 COPENHAGEN, DENMARK SN 0280-6509 J9 TELLUS B JI Tellus Ser. B-Chem. Phys. Meteorol. PD APR PY 2000 VL 52 IS 2 BP 463 EP 483 DI 10.1034/j.1600-0889.2000.00013.x PG 21 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 316BR UT WOS:000087147900021 ER PT J AU Durkee, PA Nielsen, KE Smith, PJ Russell, PB Schmid, B Livingston, JM Holben, BN Tomasi, C Vitale, V Collins, D Flagan, RC Seinfeld, JH Noone, KJ Ostrom, E Gasso, S Hegg, D Russell, LM Bates, TS Quinn, PK AF Durkee, PA Nielsen, KE Smith, PJ Russell, PB Schmid, B Livingston, JM Holben, BN Tomasi, C Vitale, V Collins, D Flagan, RC Seinfeld, JH Noone, KJ Ostrom, E Gasso, S Hegg, D Russell, LM Bates, TS Quinn, PK TI Regional aerosol optical depth characteristics from satellite observations: ACE-1, TARFOX and ACE-2 results SO TELLUS SERIES B-CHEMICAL AND PHYSICAL METEOROLOGY LA English DT Article ID RADIANCES AB Analysis of the aerosol properties during 3 recent international field campaigns (ACE-1, TARFOX and ACE-2) are described using satellite retrievals from NOAA AVHRR data. Validation of the satellite retrieval procedure is performed with airborne, shipboard, and land-based sunphotometry during ACE-2. The intercomparison between satellite and surface optical depths has a correlation coefficient of 0.93 for 630 nm wavelength and 0.92 for 860 nm wave length. The standard error of estimate is 0.025 for 630 nm wavelength and 0.023 for 860 nm wavelength. Regional aerosol properties are examined in composite analysis of aerosol optical properties from the ACE-1, TARFOX and ACE-2 regions. ACE-1 and ACE-2 regions have strong modes in the distribution of optical depth around 0.1, but the ACE-2 tails toward higher values yielding an average of 0.16 consistent with pollution and dust aerosol intrusions. The TARFOX region has a noticeable mode of 0.2, but has significant spread of aerosol optical depth values consistent with the varied continental aerosol constituents off the eastern North American Coast. C1 USN, Postgrad Sch, Monterey, CA USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. SRI Int, Menlo Pk, CA 94025 USA. Bay Area Environm Res Inst, San Francisco, CA 94122 USA. CALTECH, Pasadena, CA 91125 USA. Stockholm Univ, S-10691 Stockholm, Sweden. Univ Washington, Seattle, WA 98195 USA. NOAA, Pacific Marine Environm Lab, Seattle, WA 98115 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Princeton Univ, Princeton, NJ 08544 USA. FISBAT, Bologna, Italy. RP Durkee, PA (reprint author), 589 Dyer Rd,Room 254, Monterey, CA 93943 USA. EM Durkee@nps.navy.mil RI Collins, Don/F-9617-2012; Gasso, Santiago/H-9571-2014; Bates, Timothy/L-6080-2016; Quinn, Patricia/R-1493-2016 OI Gasso, Santiago/0000-0002-6872-0018; Quinn, Patricia/0000-0003-0337-4895 NR 34 TC 19 Z9 19 U1 0 U2 4 PU WILEY-BLACKWELL PI MALDEN PA COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA SN 0280-6509 J9 TELLUS B JI Tellus Ser. B-Chem. Phys. Meteorol. PD APR PY 2000 VL 52 IS 2 BP 484 EP 497 DI 10.1034/j.1600-0889.2000.00040.x PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 316BR UT WOS:000087147900022 ER PT J AU Collins, DR Jonsson, HH Seinfeld, JH Flagan, RC Gasso, S Hegg, DA Russell, PB Schmid, B Livingston, JM Ostrom, E Noone, KJ Russell, LM Putaud, JP AF Collins, DR Jonsson, HH Seinfeld, JH Flagan, RC Gasso, S Hegg, DA Russell, PB Schmid, B Livingston, JM Ostrom, E Noone, KJ Russell, LM Putaud, JP TI In situ aerosol-size distributions and clear-column radiative closure during ACE-2 SO TELLUS SERIES B-CHEMICAL AND PHYSICAL METEOROLOGY LA English DT Article ID STRATOCUMULUS TRANSITION EXPERIMENT; MARINE BOUNDARY-LAYER; OPTICAL-PROPERTIES; GAS-EXCHANGE; ATLANTIC; NEPHELOMETER; TROPOSPHERE; ATMOSPHERE; PARTICLES AB As part of the second Aerosol Characterization Experiment (ACE-2) during June and July of 1997, aerosol-size distributions were measured on board the CIRPAS Pelican aircraft through the use of a DMA and 2 OPCs. During the campaign, the boundary-layer aerosol typically possessed characteristics representative of a background marine aerosol or a continentally influenced aerosol, while the free-tropospheric aerosol was characterized by the presence or absence of a Saharan dust layer. A range of radiative closure comparisons were made using the data obtained during vertical profiles flown on 4 missions. Of particular interest here are the comparisons made between the optical properties as determined through the use of measured aerosol-size distributions and those measured directly by an airborne 14-wavelength sunphotometer and 3 nephelometers. Variations in the relative humidity associated with each of the direct measurements required consideration of the hygroscopic properties of the aerosol for size-distribution-based calculations. Simultaneous comparison with such a wide range of directly-measured optical parameters not only offers evidence of the validity of the physicochemical description of the aerosol when closure is achieved, but also provides insight into potential sources of error when some or all of the comparisons result in disagreement. Agreement between the derived and directly-measured optical properties varied for different measurements and for different cases. Averaged over the 4 case studies, the derived extinction coefficient at 525 nm exceeded that measured by the sunphotometer by 2.5% in the clean boundary layer, but underestimated measurements by 13% during pollution events. For measurements within the free troposphere, the mean derived extinction coefficient was 3.3% and 17% less than that measured by the sunphotometer during dusty and non-dusty conditions, respectively. Likewise, averaged discrepancies between the derived and measured scattering coefficient were -9.6%, +4.7%, +17%, and -41% for measurements within the clean boundary layer, polluted boundary layer, free troposphere with a dust layer, and free troposphere without a dust layer, respectively. Each of these quantities, as well as the majority of the > 100 individual comparisons from which they were averaged, were within estimated uncertainties. C1 CALTECH, Pasadena, CA 91125 USA. USN, Postgrad Sch, Monterey, CA USA. Univ Washington, Seattle, WA 98195 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Bay Area Environm Res Inst, San Francisco, CA USA. SRI Int, Menlo Park, CA 94025 USA. Stockholm Univ, S-10691 Stockholm, Sweden. Princeton Univ, Princeton, NJ 08544 USA. Joint Res Ctr, Ispra, Italy. RP Seinfeld, JH (reprint author), CALTECH, 1200 E Calif Blvd,Mail Code 21-41, Pasadena, CA 91125 USA. RI Collins, Don/F-9617-2012; Gasso, Santiago/H-9571-2014 OI Gasso, Santiago/0000-0002-6872-0018 NR 36 TC 76 Z9 78 U1 0 U2 6 PU MUNKSGAARD INT PUBL LTD PI COPENHAGEN PA 35 NORRE SOGADE, PO BOX 2148, DK-1016 COPENHAGEN, DENMARK SN 0280-6509 J9 TELLUS B JI Tellus Ser. B-Chem. Phys. Meteorol. PD APR PY 2000 VL 52 IS 2 BP 498 EP 525 DI 10.1034/j.1600-0889.2000.00008.x PG 28 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 316BR UT WOS:000087147900023 ER PT J AU Gasso, S Hegg, DA Covert, DS Collins, D Noone, KJ Ostrom, E Schmid, B Russell, PB Livingston, JM Durkee, PA Jonsson, H AF Gasso, S Hegg, DA Covert, DS Collins, D Noone, KJ Ostrom, E Schmid, B Russell, PB Livingston, JM Durkee, PA Jonsson, H TI Influence of humidity on the aerosol scattering coefficient and its effect on the upwelling radiance during ACE-2 SO TELLUS SERIES B-CHEMICAL AND PHYSICAL METEOROLOGY LA English DT Article ID MARINE BOUNDARY-LAYER; RELATIVE-HUMIDITY; SIZE DISTRIBUTION; LIGHT-SCATTERING; SPECTRAL RADIANCES; OPTICAL DEPTH; SATELLITE; PARTICLES; OCEAN; MODIS AB Aerosol scattering coefficients (sigma(sp)) have been measured over the ocean at different relative humidities (RH) as a Function of altitude in the region surrounding the Canary Islands during the Second Aerosol Characterization Experiment (ACE-2) in June and July 1997. The data were collected by the University of Washington passive humidigraph (UWPH) mounted on the Pelican research aircraft. Concurrently, particle size distributions, absorption coefficients and aerosol optical depth were measured throughout 17 flights. A parameterization of sigma(sp) as a function of RH was utilized to assess the impact of aerosol hydration on the upwelling radiance (normalized to the solar constant and cosine of zenith angle). The top of the atmosphere radiance signal was simulated at wavelengths corresponding to visible and near-infrared bands of the EOS-AM ("Terra") detectors, MODIS and MISR. The UWPH measured sigma(sp) at 2 RHs, one below and the other above ambient conditions. Ambient sigma(sp) was obtained by interpolation of these 2 measurements. The data were stratified in terms of 3 types of aerosols: Saharan dust, clean marine (marine boundary layer background) and polluted marine aerosols (i.e., 2- or 1-day old polluted aerosols advected from Europe). An empirical relation for the dependence of sigma(sp) on RH, defined by sigma(sp) (RH) = k. (1 - RH/100)(-gamma), was used with the hygroscopic exponent gamma derived from the data. The following gamma values were obtained for the 3 aerosol types: gamma(dust) = 0.23 +/- 0.05, gamma(clean marine) = 0.69 +/- 0.06 and gamma(polluted marine) = 0.57 +/- 0.06. Based on the measured gamma's, the above equation was utilized to derive aerosol models with different hygroscopicities. The satellite simulation signal code 6S was used to compute the upwelling radiance corresponding to each of those aerosol models at several ambient humidities. For the prelaunch estimated precision of the sensors and the assumed viewing geometry of the instrument, the simulations suggest that the spectral and angular dependence of the reflectance measured by MISR is not sufficient to distinguish aerosol models with various different combinations of values for dry composition, gamma and ambient RH. A similar behavior is observed for MODIS at visible wavelengths. However, the 2100 nm band of MODIS appears to be able to differentiate between at least same aerosol models with different aerosol hygroscopicity given the MODIS calibration error requirements. This result suggests the possibility of retrieval of aerosol hygroscopicity by MODIS. C1 Univ Washington, Geophys Program, Seattle, WA 98195 USA. Univ Washington, Dept Atmospher Sci, Seattle, WA 98195 USA. CALTECH, Pasadena, CA 91125 USA. Stockholm Univ, Dept Meteorol, S-10691 Stockholm, Sweden. Bay Area Environm Res Inst, San Francisco, CA USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. SRI Int, Menlo Park, CA 94025 USA. USN, Postgrad Sch, Monterey, CA USA. RP Gasso, S (reprint author), Univ Washington, Geophys Program, Box 351650, Seattle, WA 98195 USA. RI Collins, Don/F-9617-2012; Gasso, Santiago/H-9571-2014 OI Gasso, Santiago/0000-0002-6872-0018 NR 51 TC 89 Z9 96 U1 1 U2 20 PU MUNKSGAARD INT PUBL LTD PI COPENHAGEN PA 35 NORRE SOGADE, PO BOX 2148, DK-1016 COPENHAGEN, DENMARK SN 0280-6509 J9 TELLUS B JI Tellus Ser. B-Chem. Phys. Meteorol. PD APR PY 2000 VL 52 IS 2 BP 546 EP 567 DI 10.1034/j.1600-0889.2000.00055.x PG 22 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 316BR UT WOS:000087147900025 ER PT J AU Schmid, B Livingston, JM Russell, PB Durkee, PA Jonsson, HH Collins, DR Flagan, RC Seinfeld, JH Gasso, S Hegg, DA Ostrom, E Noone, KJ Welton, EJ Voss, KJ Gordon, HR Formenti, P Andreae, MO AF Schmid, B Livingston, JM Russell, PB Durkee, PA Jonsson, HH Collins, DR Flagan, RC Seinfeld, JH Gasso, S Hegg, DA Ostrom, E Noone, KJ Welton, EJ Voss, KJ Gordon, HR Formenti, P Andreae, MO TI Clear-sky closure studies of lower tropospheric aerosol and water vapor during ACE-2 using airborne sunphotometer, airborne in-situ, space-borne, and ground-based measurements SO TELLUS SERIES B-CHEMICAL AND PHYSICAL METEOROLOGY LA English DT Article ID MID-ATLANTIC COAST; OPTICAL DEPTH; RADIATIVE CHARACTERISTICS; SIZE DISTRIBUTIONS; SAHARAN AEROSOLS; UNITED-STATES; SOLAR; DUST; SENSITIVITY; ABSORPTION AB We report on clear-sky column closure experiments (CLEARCOLUMN) performed in the Canary Islands during the second Aerosol Characterization Experiment (ACE-2) in June/July 1997. We present CLEARCOLUMN results obtained by combining airborne sunphotometer and in-situ (optical particle counter, nephelometer, and absorption photometer) measurements taken aboard the Pelican aircraft, space-borne NOAA/AVHRR data and ground-based lidar and sunphotometer measurements. During both days discussed here, vertical profiles flown in cloud-free air masses revealed 3 distinctly different layers: a marine boundary layer (MBL) with varying pollution levels, an elevated dust layer, and a very clean layer between the MBL and the dust layer. A key result of this study is the achievement of closure between extinction or layer aerosol optical depth (AOD) computed from continuous in-situ aerosol size-distributions and composition and those measured with the airborne sunphotometer. In the dust, the agreement in layer AOD (lambda = 380 1060 nm) is 3-8%. In the MBL there is a tendency for the in-situ results to be slightly lower than the sunphotometer measurements (10 17% at lambda = 525 nm), but those differences are within the combined error bars of the measurements and computations. C1 Bay Area Environm Res Inst, San Francisco, CA USA. SRI Int, Menlo Pk, CA 94025 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. USN, Postgrad Sch, Monterey, CA USA. CALTECH, Pasadena, CA 91125 USA. Univ Washington, Seattle, WA 98195 USA. Stockholm Univ, Inst Meteorol, S-10691 Stockholm, Sweden. Univ Miami, Miami, FL 33152 USA. Max Planck Inst Chem, D-55128 Mainz, Germany. RP Schmid, B (reprint author), NASA, Ames Res Ctr, MS-245, Moffett Field, CA 94035 USA. EM bschmid@mail.arc.nasa.gov RI Welton, Ellsworth/A-8362-2012; Collins, Don/F-9617-2012; Voss, Kenneth /A-5328-2013; Gasso, Santiago/H-9571-2014; Andreae, Meinrat/B-1068-2008 OI Voss, Kenneth /0000-0002-7860-5080; Gasso, Santiago/0000-0002-6872-0018; Andreae, Meinrat/0000-0003-1968-7925 NR 53 TC 72 Z9 72 U1 1 U2 9 PU CO-ACTION PUBLISHING PI JARFALLA PA RIPVAGEN 7, JARFALLA, SE-175 64, SWEDEN SN 0280-6509 J9 TELLUS B JI Tellus Ser. B-Chem. Phys. Meteorol. PD APR PY 2000 VL 52 IS 2 BP 568 EP 593 DI 10.1034/j.1600-0889.2000.00009.x PG 26 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 316BR UT WOS:000087147900026 ER PT J AU Livingston, JM Kapustin, VN Schmid, B Russell, PB Quinn, PK Bates, TS Durkee, PA Smith, PJ Freudenthaler, V Wiegner, M Covert, DS Gasso, S Hegg, D Collins, DR Flagan, RC Seinfeld, JH Vitale, V Tomasi, C AF Livingston, JM Kapustin, VN Schmid, B Russell, PB Quinn, PK Bates, TS Durkee, PA Smith, PJ Freudenthaler, V Wiegner, M Covert, DS Gasso, S Hegg, D Collins, DR Flagan, RC Seinfeld, JH Vitale, V Tomasi, C TI Shipboard sunphotometer measurements of aerosol optical depth spectra and columnar water vapor during ACE-2, and comparison with selected land, ship, aircraft, and satellite measurements SO TELLUS SERIES B-CHEMICAL AND PHYSICAL METEOROLOGY LA English DT Article ID MARINE BOUNDARY-LAYER; ATLANTIC; OCEANS AB Analyses of aerosol optical depth (AOD) and columnar water vapor (CWV) measurements acquired with NASA Ames Research Center's 6-channel Airborne Tracking Sunphotometer (AATS-6) operated aboard the R/V Professor Vodyanitskiy during the 2nd Aerosol Characterization Experiment (ACE-2) are discussed. Data are compared with various in situ and remote measurements for selected cases. The focus is on 10 July, when the Pelican airplane flew within 70 km of the ship near the time of a NOAA-14/AVHRR satellite overpass and AOD measurements with the 14-channel Ames Airborne Tracking Sunphotometer (AATS-14) above the marine boundary layer (MBL) permitted calculation of AOD within the MBL from the AATS-6 measurements. A detailed column closure test is performed for MBL AOD on 10 July by comparing the AATS-6 MBL AODs with corresponding values calculated by combining shipboard particle size distribution measurements with models of hygroscopic growth and radiosonde humidity profiles (plus assumptions on the vertical profile of the dry particle size distribution and composition). Large differences (30 80% in the mid-visible) between measured and reconstructed AODs are obtained, in large part because of the high sensitivity of the closure methodology to hygroscopic growth models, which vary considerably and have not been validated over the necessary range of particle size/composition distributions. The wavelength dependence of AATS-6 AODs is compared with the corresponding dependence of aerosol extinction calculated from shipboard measurements of aerosol size distribution and of total scattering measured by a shipboard integrating nephelometer for several days. Results are highly variable, illustrating further the great difficulty of deriving column values from point measurements. AATS-6 CWV values are shown to agree well with corresponding values derived from radiosonde measurements during 8 soundings on 7 days and also with values calculated from measurements taken on 10 July with the AATS-14 and the University of Washington Passive Humidigraph aboard the Pelican. C1 SRI Int, Menlo Pk, CA 94025 USA. Univ Hawaii, Dept Oceanog, Honolulu, HI 96822 USA. Bay Area Environm Res Inst, San Francisco, CA USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NOAA, Pacific Marine Environm Lab, Seattle, WA 98115 USA. USN, Postgrad Sch, Monterey, CA USA. Univ Munich, Munich, Germany. Univ Washington, Seattle, WA 98195 USA. CALTECH, Pasadena, CA 91125 USA. CNR, Ist Fisbat, I-40126 Bologna, Italy. RP Livingston, JM (reprint author), SRI Int, 333 Ravenswood Ave, Menlo Pk, CA 94025 USA. EM jlivingston@mail.arc.nasa.gov RI Collins, Don/F-9617-2012; Wiegner, Matthias/F-8484-2011; Gasso, Santiago/H-9571-2014; Bates, Timothy/L-6080-2016; Quinn, Patricia/R-1493-2016 OI Gasso, Santiago/0000-0002-6872-0018; Quinn, Patricia/0000-0003-0337-4895 NR 36 TC 17 Z9 17 U1 0 U2 3 PU CO-ACTION PUBLISHING PI JARFALLA PA RIPVAGEN 7, JARFALLA, SE-175 64, SWEDEN SN 0280-6509 EI 1600-0889 J9 TELLUS B JI Tellus Ser. B-Chem. Phys. Meteorol. PD APR PY 2000 VL 52 IS 2 BP 594 EP 619 DI 10.1034/j.1600-0889.2000.00045.x PG 26 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 316BR UT WOS:000087147900027 ER PT J AU Welton, EJ Voss, KJ Gordon, HR Maring, H Smirnov, A Holben, B Schmid, B Livingston, JM Russell, PB Durkee, PA Formenti, P Andreae, MO AF Welton, EJ Voss, KJ Gordon, HR Maring, H Smirnov, A Holben, B Schmid, B Livingston, JM Russell, PB Durkee, PA Formenti, P Andreae, MO TI Ground-based lidar measurements of aerosols during ACE-2: instrument description, results, and comparisons with other ground-based and airborne measurements SO TELLUS SERIES B-CHEMICAL AND PHYSICAL METEOROLOGY LA English DT Article ID EXTINCTION PROFILES; OPTICAL-PROPERTIES; FREE TROPOSPHERE; ATLANTIC; RATIOS; LAYER AB A micro-pulse lidar system (MPL) was used to measure the vertical and horizontal distribution of aerosols during the Aerosol Characterization Experiment 2 (ACE-2) in June and July of 1997. The MPL measurements were made at the Izana observatory (IZO), a weather station located on a mountain ridge (28 degrees 18'N, 16 degrees 30'W, 2367 m asl) near the center of the island of Tenerife, Canary Islands. The MPL was used to acquire aerosol backscatter, extinction, and optical depth profiles for normal background periods and periods influenced by Saharan dust from North Africa. System tests and calibration procedures are discussed, and an analysis of aerosol optical profiles acquired during ACE-2 is presented. MPL data taken during normal IZO conditions (no dust) showed that upslope aerosols appeared during the day and dissipated at night and that the layers were mostly confined to altitudes a few hundred meters above IZO. MPL data taken during a Saharan dust episode on 17 July showed that peak aerosol extinction values were an order of magnitude greater than molecular scattering over IZO, and that the dust layers extended to 5 km asl. The value of the dust backscatter-extinction ratio was determined to be 0.027 +/- 0.007 sr(-1). Comparisons of the MPL data with data from other co-located instruments showed good agreement during the dust episode. C1 Univ Miami, Dept Phys, Coral Gables, FL 33143 USA. Univ Miami, Rosenstiel Sch Marine & Atmospher Sci, MAC, Miami, FL 33149 USA. NASA, Goddard Space Flight Ctr, Sci Syst & Applicat Inc, Greenbelt, MD 20771 USA. NASA, Ames Res Ctr, Bay Area Environm Res Inst, Moffett Field, CA 94035 USA. NASA, Ames Res Ctr, SRI Int, Moffett Field, CA 94035 USA. USN, Postgrad Sch, Dept Meteorol, Monterey, CA 93943 USA. Max Planck Inst Chem, Biogeochem Dept, D-55020 Mainz, Germany. RP Welton, EJ (reprint author), NASA, Goddard Space Flight Ctr, Sci Syst & Applicat Inc, Code 912, Greenbelt, MD 20771 USA. RI Smirnov, Alexander/C-2121-2009; Welton, Ellsworth/A-8362-2012; Voss, Kenneth /A-5328-2013; Andreae, Meinrat/B-1068-2008 OI Smirnov, Alexander/0000-0002-8208-1304; Voss, Kenneth /0000-0002-7860-5080; Andreae, Meinrat/0000-0003-1968-7925 NR 21 TC 90 Z9 95 U1 2 U2 20 PU MUNKSGAARD INT PUBL LTD PI COPENHAGEN PA 35 NORRE SOGADE, PO BOX 2148, DK-1016 COPENHAGEN, DENMARK SN 0280-6509 J9 TELLUS B JI Tellus Ser. B-Chem. Phys. Meteorol. PD APR PY 2000 VL 52 IS 2 BP 636 EP 651 DI 10.1034/j.1600-0889.2000.00025.x PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 316BR UT WOS:000087147900029 ER PT J AU Powell, DM Reagan, JA Rubio, MA Erxleben, WH Spinhirne, JD AF Powell, DM Reagan, JA Rubio, MA Erxleben, WH Spinhirne, JD TI ACE-2 multiple angle micro-pulse lidar observations from Las Galletas, Tenerife, Canary Islands SO TELLUS SERIES B-CHEMICAL AND PHYSICAL METEOROLOGY LA English DT Article ID SAHARAN AB Multiple-angle micro-pulse lidar (MPL) observations were made at Las Galletas on Tenerife, Canary Islands during the Aerosol Characterization Experiment-2 (ACE-2) conducted June-July, 1997. A principal objective of the MPL observations was to characterize the temporal/spatial distributions of aerosols in the region, particularly to identify and profile elevated Saharan dust layers which occur intermittently during the June-July time period. Vertical and slant angle measurements taken 16 and 17 July characterize such an occurrence, providing aerosol backscatter, extinction, and optical depth profiles of the dust layer between 1 and 5 km above mean sea level (MSL). Additionally, horizontal measurements taken in Las Galletas throughout the 6-week period provide a time profile of the varying aerosol extinction at the surface. This profile exhibits the alternating periods of clean maritime air and pollution outbreaks that typified the region. Horizontal measurements also provide some evidence suggesting the possible influx of Saharan dust from the free troposphere to the surface. This paper presents estimates of aerosol optical properties retrieved from the multi-angle MPL measurements in addition to an outline of the methodologies employed to obtain these results. C1 Univ Arizona, Tucson, AZ 85721 USA. NASA, Goddard Space Flight Ctr, Tucson, AZ 85721 USA. RP Powell, DM (reprint author), Univ Arizona, Bldg 104, Tucson, AZ 85721 USA. NR 16 TC 21 Z9 22 U1 0 U2 5 PU MUNKSGAARD INT PUBL LTD PI COPENHAGEN PA 35 NORRE SOGADE, PO BOX 2148, DK-1016 COPENHAGEN, DENMARK SN 0280-6509 J9 TELLUS B JI Tellus Ser. B-Chem. Phys. Meteorol. PD APR PY 2000 VL 52 IS 2 BP 652 EP 661 DI 10.1034/j.1600-0889.2000.00059.x PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 316BR UT WOS:000087147900030 ER PT J AU Levin, E Stallcop, JR Partridge, H AF Levin, E Stallcop, JR Partridge, H TI Transport properties of boron and aluminum SO THEORETICAL CHEMISTRY ACCOUNTS LA English DT Article DE transport properties; cross sections; collision integrals; scaling relations; scattering ID MOLECULAR WAVE-FUNCTIONS; STATIC DIPOLE POLARIZABILITIES; GAUSSIAN-BASIS SETS; BENCHMARK CALCULATIONS; CROSS-SECTIONS; COLLISION INTEGRALS; DIATOMIC-MOLECULES; 1ST-ROW ATOMS; COEFFICIENTS; SPECTROSCOPY AB Transport cross sections and collision integrals are tabulated for a nide range of energies and temperatures for the interactions B-B and Al-Al. For aluminum, a semiclassical approximation was used to determine the scattering phase shifts from which the transport cross sections were calculated. For boron, the smaller reduced mass and the deep potential wells required the phase shifts at lower energies to be determined from a numerical solution of the time-independent Schroedinger equation; the semiclassical approximation was used at higher energies where the two methods agree. The variations of the collision integrals for viscosity and diffusion are presented graphically as a function of temperature. The results are applied to estimate the transport properties of gallium. C1 NASA, Thermosci Inst, Ames Res Ctr, Moffett Field, CA 94035 USA. NASA, Computat Chem Branch, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Levin, E (reprint author), NASA, Thermosci Inst, Ames Res Ctr, M-S 230-2, Moffett Field, CA 94035 USA. NR 36 TC 4 Z9 4 U1 1 U2 2 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 1432-881X J9 THEOR CHEM ACC JI Theor. Chem. Acc. PD APR PY 2000 VL 103 IS 6 BP 518 EP 523 DI 10.1007/s002149900085 PG 6 WC Chemistry, Physical SC Chemistry GA 314NC UT WOS:000087061300009 ER PT J AU Dellacorte, C AF Dellacorte, C TI The evaluation of a modified chrome oxide based high temperature solid lubricant coating for foil gas bearings SO TRIBOLOGY TRANSACTIONS LA English DT Article; Proceedings Paper CT 54th Annual Meeting of the Society-of-Tribologists-and-Lubrication-Engineers CY MAY 23-27, 1999 CL LAS VEGAS, NEVADA SP Soc Tribologists & Lubricat Engineers DE gas bearings; solid lubricants; high temperature ID COMPOSITE AB This paper describes the friction and wear performance of PS304, a modified chrome oxide based coating,for foil gas bearings. PS304 contains 60 Mit. % NiCr binder; 20 wt. % Cr2O3 hardener, and 10 wt. % each Ag and BaF2/CaF2 lubricants. For evaluation, the coating is plasma spray deposited onto test journals which are slid against a superalloy partial are foil bearing. The test load was 10 KPa (1.5 psi) and the bearings were I run under start/stop cyclic conditions. The data show good wear performance of the bearing especially at temperatures above 25 degrees C. Bearing friction was moderate (mu less than or equal to approximate to 0.4) over the entire temperature range. Based upon the results obtained, the PS304 coating has promise for high temperature, oil-free turbomachinery applications. C1 NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. RP Dellacorte, C (reprint author), NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. NR 11 TC 25 Z9 27 U1 2 U2 16 PU SOC TRIBOLOGISTS & LUBRICATION ENGINEERS PI PARK RIDGE PA 840 BUSSE HIGHWAY, PARK RIDGE, IL 60068 USA SN 1040-2004 J9 TRIBOL T JI Tribol. Trans. PD APR PY 2000 VL 43 IS 2 BP 257 EP 262 DI 10.1080/10402000008982337 PG 6 WC Engineering, Mechanical SC Engineering GA 307YL UT WOS:000086681700013 ER PT J AU Arepalli, S Scott, CD Nikolaev, P Smalley, RE AF Arepalli, S Scott, CD Nikolaev, P Smalley, RE TI Electronically excited C-2 from laser photodissociated C-60 SO CHEMICAL PHYSICS LETTERS LA English DT Article ID CARBON; REGION; GROWTH AB Spectral and transient emission measurements are made of radiation from products of laser excitation of buckminsterfullerene (C-60) vapor diluted in argon at 973 K. The principal radiation is from the Swan band system of C-2 and, at early times, also from a black-body continuum. Transient measurements indicate two characteristic periods of decay 2 and 50 mu s long, with characteristic decay times of similar to 0.3 and 5 mu s, respectively. The first period is thought to be associated with decomposition and radiative cooling of C-60 molecules or nano-sized carbon particles and the second period continues with decomposition products of laser excited C-60, C-58, C-56, etc. (C) 2000 Published by Elsevier Science B.V. All rights reserved. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Lockheed Martin, GB Tech, Houston, TX 77258 USA. Rice Univ, Ctr Nanoscale Sci & Technol, Houston, TX 77005 USA. RP Scott, CD (reprint author), NASA, Lyndon B Johnson Space Ctr, ES3, Houston, TX 77058 USA. RI Arepalli, Sivaram/A-5372-2010; Nikolaev, Pavel/B-9960-2009 NR 16 TC 25 Z9 25 U1 0 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0009-2614 J9 CHEM PHYS LETT JI Chem. Phys. Lett. PD MAR 31 PY 2000 VL 320 IS 1-2 BP 26 EP 34 DI 10.1016/S0009-2614(00)00193-7 PG 9 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 299RG UT WOS:000086211200006 ER PT J AU Nichol, CJ Huemmrich, KF Black, TA Jarvis, PG Walthall, CL Grace, J Hall, FG AF Nichol, CJ Huemmrich, KF Black, TA Jarvis, PG Walthall, CL Grace, J Hall, FG TI Remote sensing of photosynthetic-light-use efficiency of boreal forest SO AGRICULTURAL AND FOREST METEOROLOGY LA English DT Article DE xanthophyll cycle; AVIRIS; photochemical reflectance index; eddy covariance ID RADIATION-USE-EFFICIENCY; PHOTOCHEMICAL REFLECTANCE INDEX; XANTHOPHYLL CYCLE; VIOLAXANTHIN CYCLE; VEGETATION INDEX; CARBON-DIOXIDE; HIGHER-PLANTS; WATER-VAPOR; SAIL MODEL; SUN ANGLE AB Using a helicopter-mounted portable spectroradiometer and continuous eddy covariance data we were able to evaluate the photochemical reflectance index (PRI) as an indicator of canopy photosynthetic light-use efficiency (LUE) in four boreal forest species during the Boreal Ecosystem Atmosphere experiment (BOREAS). PRI was calculated from narrow waveband reflectance data and correlated with LUE calculated from eddy covariance data. Significant linear correlations were found between PRI and LUE when the four species were grouped together and when divided into functional type: coniferous and deciduous. Data from the helicopter-mounted spectroradiometer were then averaged to represent data generated by the Airborne Visible Infrared Imaging Spectrometer (AVIRIS). We calculated PRI from these data and relationships with canopy LUE were investigated. The relationship between PRI and LUE was weakened for deciduous species but strengthened for the coniferous species. The robust nature of this relationship suggests that relative photosynthetic rates may be derived from remotely-sensed reflectance measurements. (C) 2000 Elsevier Science B.V. All rights reserved. C1 Univ Edinburgh, Inst Ecol & Resource Management, Edinburgh EH9 3JU, Midlothian, Scotland. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ British Columbia, Dept Agr Sci, Vancouver, BC V6T 1Z4, Canada. US Agr Res Serv, Remote Sensing Lab, Laurel, MD 20707 USA. RP Nichol, CJ (reprint author), Univ Edinburgh, Inst Ecol & Resource Management, Edinburgh EH9 3JU, Midlothian, Scotland. EM caroline.nichol@ed.ac.uk; karl.huemmrich@gsfc.nasa.gov; ablack@interchange.ubc.ca; pjarvis@ed.ac.uk; cwalthal@asrr.arsuda.gov; jgrace@ed.ac.uk; fghall@ltpmail.nasa.gov NR 40 TC 128 Z9 136 U1 5 U2 28 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-1923 J9 AGR FOREST METEOROL JI Agric. For. Meteorol. PD MAR 30 PY 2000 VL 101 IS 2-3 BP 131 EP 142 DI 10.1016/S0168-1923(99)00167-7 PG 12 WC Agronomy; Forestry; Meteorology & Atmospheric Sciences SC Agriculture; Forestry; Meteorology & Atmospheric Sciences GA 293PF UT WOS:000085860800004 ER PT J AU Choudhury, BJ AF Choudhury, BJ TI A sensitivity analysis of the radiation use efficiency for gross photosynthesis and net carbon accumulation by wheat SO AGRICULTURAL AND FOREST METEOROLOGY LA English DT Article DE photosynthesis; respiration; radiation use efficiency; wheat ID DIOXIDE EXCHANGE-RATES; LEAF-AREA INDEX; WINTER-WHEAT; GAS-EXCHANGE; CANOPY PHOTOSYNTHESIS; NITROGEN DISTRIBUTION; NUTRIENT RELATIONS; TRITICUM-AESTIVUM; DIFFUSE-RADIATION; GROWTH-RATE AB Radiation use efficiency (RUE) provides a useful diagnostic approach for estimating carbon accumulation by terrestrial plant communities. A model for instantaneous gross photosynthesis by a canopy, considering sunlit and shaded leaves, variation of maximum rate of leaf photosynthesis within the canopy and a solution of the radiative transfer equation for propagation of direct and diffuse photosynthetically active radiation within the canopy, is numerically integrated in space (angular variation of radiances and depth within the canopy) and time (diurnal variation) to obtain daily total gross photosynthesis. Then, to obtain net carbon accumulation, growth and maintenance respiration at a prescribed temperature are calculated from nitrogen content of foliage, stem and root using field measurements for 27 canopies representing two cultivars of winter wheat and average data for five cultivars of spring wheat. The leaf area index (L-0) of these canopies varies between 0.5 and 5.2. The results show that for any given irradiance, the coefficient of variation of RUE for gross photosynthesis and net carbon accumulation due to changes in Lo is generally less than 10%. Strongly linear relationships are found between the RUE and diffuse fraction of the incident radiation, with slope varying with Lo. Temperature appears as an important factor determining RUE under predominantly cloudy conditions. The calculated RUE values are compared with observations. (C) 2000 Published by Elsevier Science B.V. C1 NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Hydrol Sci Branch, Greenbelt, MD 20771 USA. RP Choudhury, BJ (reprint author), NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Hydrol Sci Branch, Greenbelt, MD 20771 USA. NR 64 TC 37 Z9 48 U1 2 U2 24 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-1923 J9 AGR FOREST METEOROL JI Agric. For. Meteorol. PD MAR 30 PY 2000 VL 101 IS 2-3 BP 217 EP 234 DI 10.1016/S0168-1923(99)00156-2 PG 18 WC Agronomy; Forestry; Meteorology & Atmospheric Sciences SC Agriculture; Forestry; Meteorology & Atmospheric Sciences GA 293PF UT WOS:000085860800010 ER PT J AU Kletetschka, G Wasilewski, PJ Taylor, PT AF Kletetschka, G Wasilewski, PJ Taylor, PT TI Unique thermoremanent magnetization of multidomain sized hematite: Implications for magnetic anomalies SO EARTH AND PLANETARY SCIENCE LETTERS LA English DT Article DE hematite; multidomains; thermoremanent magnetization; magnetic anomalies; magnetic properties ID ROCK MAGNETISM; GRAIN-SIZE; TEMPERATURE; PARTICLES; BEHAVIOR AB Intense magnetic remanence (100-1000 A/m) associated with MD hematite and/or titanohematite and associated with high Koenigsberger ratios (40-1000) indicate that magnetic remanence may dominate the total magnetization if these minerals are volumetrically significant. Titanohematite behaves similarly to hematite and, thus, the grain size dependence of TRM acquisition in hematite is considered as a generalization. The transition between truly MD behavior and tendency towards SD behavior in hematite has been established to be between grain sizes of 0.1 and 0.05 mm. In contrast to magnetite and titanomagnetite, hematite exhibits inverse grain size dependence, with MD hematite acquiring a relatively intense TRM in the geomagnetic field, comparable to sub-micrometer sized magnetite and only an order of magnitude less than SD magnetite. Consequently MD hematite (and by analogy titanohematite) remanence may be of significance as a source of magnetic anomalies at all scales. MD hematite exhibits TRM weak field acquisition behavior that is different from all other magnetic minerals, being the only magnetic mineral having an REM (TRM/SIRM) value >> 0.1 for TRM acquisition in the geomagnetic field. The very different TRM behavior of MD hematite in contrast to magnetite is due to two factors. The first is the lesser influence of demagnetizing energy with respect to wall pinning energy, at temperatures almost up to the Curie temperature for hematite. The second is the greater importance of the magnetostatic energy in the applied field, which for hematite dominates the total energy at high temperatures. (C) 2000 Published by Elsevier Science B.V. All rights reserved. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Kletetschka, G (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RI Kletetschka, Gunther/C-9996-2011; Taylor, Patrick/D-4707-2012 OI Kletetschka, Gunther/0000-0002-0645-9037; Taylor, Patrick/0000-0002-1212-9384 NR 36 TC 42 Z9 43 U1 1 U2 12 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0012-821X J9 EARTH PLANET SC LETT JI Earth Planet. Sci. Lett. PD MAR 30 PY 2000 VL 176 IS 3-4 BP 469 EP 479 DI 10.1016/S0012-821X(00)00016-9 PG 11 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 298AV UT WOS:000086117900017 ER PT J AU Mushotzky, RF Cowie, LL Barger, AJ Arnaud, KA AF Mushotzky, RF Cowie, LL Barger, AJ Arnaud, KA TI Resolving the extragalactic hard X-ray background SO NATURE LA English DT Article ID ROSAT DEEP SURVEY; N-LOG S; FAINT GALAXIES; LOCKMAN FIELD; HIGH-REDSHIFT; RADIO-SOURCES; SPECTRUM; ASCA; IDENTIFICATION; SPECTROSCOPY AB The origin of the hard (2-10 keV) X-ray background has been a mystery for over 35 years. Most of the soft X-ray background has been resolved into individual sources (mainly quasars), but these sources do not have the spectral energy distribution required to match the spectrum of the X-ray background as a whole. Here we report the results of a deep survey, using the Chandra satellite, in which the detected hard X-ray sources account for at least 75 per cent of the hard X-ray background. The mean X-ray spectral energy distribution of these sources is in good agreement with that of the background. Moreover, most of those hard X-ray sources are associated unambiguously with either the nuclei of otherwise normal bright galaxies, or with optically faint sources. The latter could be active nuclei in dust-enshrouded galaxies or a population of quasars at extremely high redshift. C1 Univ Hawaii, Inst Astron, Honolulu, HI 96822 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. RP Cowie, LL (reprint author), Univ Hawaii, Inst Astron, 2680 Woodlawn Dr, Honolulu, HI 96822 USA. NR 44 TC 404 Z9 404 U1 0 U2 2 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON N1 9XW, ENGLAND SN 0028-0836 J9 NATURE JI Nature PD MAR 30 PY 2000 VL 404 IS 6777 BP 459 EP 464 DI 10.1038/35006564 PG 6 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 300MX UT WOS:000086257700037 ER PT J AU Becker, L Poreda, RJ Bunch, TE AF Becker, L Poreda, RJ Bunch, TE TI Fullerenes: An extraterrestrial carbon carrier phase for noble gases SO PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA LA English DT Article ID C-60; HELIUM; EXTRACTION; METEORITE; MOLECULES; CHEMISTRY; ATOMS AB In this work. we report on the discovery of naturally occurring fullerenes (C-60 to C-400) in the Allende and Murchison meteorites and some sediment samples from the 65 million-year-old Cretaceous/Tertiary boundary layer (KTB), Unlike the other pure forms of carbon (diamond and graphite), fullerenes are extractable in an organic solvent (e.g., tofuene or 1,2,4-trichlorobenzene). The recognition of this unique property led to the detection and isolation of the higher fullerenes in the Kratschmer/Huffmann are evaporated graphite soot and in the carbon material in the meteorite and impact deposits. By further exploiting the unique ability of the fullerene cage structure to encapsulate and retain noble gases, we have determined that both the Allende and Murchison fullerenes and the KTB fullerenes contain trapped noble gases with ratios that can only be described as extraterrestrial in origin. C1 Univ Hawaii, Sch Ocean & Earth Sci & Technol, Honolulu, HI 96822 USA. Univ Rochester, Dept Earth & Environm Sci, Rochester, NY 14627 USA. NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. RP Becker, L (reprint author), Univ Hawaii, Sch Ocean & Earth Sci & Technol, 1680 E West Rd,602C POST Bldg, Honolulu, HI 96822 USA. NR 28 TC 96 Z9 100 U1 0 U2 5 PU NATL ACAD SCIENCES PI WASHINGTON PA 2101 CONSTITUTION AVE NW, WASHINGTON, DC 20418 USA SN 0027-8424 J9 P NATL ACAD SCI USA JI Proc. Natl. Acad. Sci. U. S. A. PD MAR 28 PY 2000 VL 97 IS 7 BP 2979 EP 2983 DI 10.1073/pnas.050519397 PG 5 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 299JK UT WOS:000086195200006 PM 10725367 ER PT J AU Bell, LD Smith, RP McDermott, BT Gertner, ER Pittman, R Pierson, RL Sullivan, GJ AF Bell, LD Smith, RP McDermott, BT Gertner, ER Pittman, R Pierson, RL Sullivan, GJ TI Modification of GaN Schottky barrier interfaces probed by ballistic-electron-emission microscopy and spectroscopy SO APPLIED PHYSICS LETTERS LA English DT Article ID SURFACES AB Ballistic-electron-emission microscopy (BEEM) and spectroscopy have been used to investigate the properties of Au/GaN interfaces. The effects of in situ and ex situ annealing on the starting GaN surface were examined, with the aim of increasing the surprisingly low value of interface electron transmission observed in previous BEEM measurements. BEEM imaging and spectroscopy have demonstrated that much higher, more uniform transmission across the Au/GaN interface can be achieved. However, while methods were identified that increase transmission by more than an order of magnitude, BEEM spectroscopy indicates that annealing can substantially alter the Schottky barrier height. These barrier height changes at moderate temperatures are attributed to vacancy diffusion. (C) 2000 American Institute of Physics. [S0003-6951(00)03113-2]. C1 CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. Rockwell Int Sci Ctr, Thousand Oaks, CA 91360 USA. RP Bell, LD (reprint author), CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. NR 17 TC 10 Z9 10 U1 0 U2 3 PU AMER INST PHYSICS PI MELVILLE PA 2 HUNTINGTON QUADRANGLE, STE 1NO1, MELVILLE, NY 11747-4501 USA SN 0003-6951 J9 APPL PHYS LETT JI Appl. Phys. Lett. PD MAR 27 PY 2000 VL 76 IS 13 BP 1725 EP 1727 DI 10.1063/1.126148 PG 3 WC Physics, Applied SC Physics GA 295KH UT WOS:000085964900029 ER PT J AU Massie, ST Tie, XX Brasseur, GP Bevilacqua, RM Fromm, MD Santee, ML AF Massie, ST Tie, XX Brasseur, GP Bevilacqua, RM Fromm, MD Santee, ML TI Chlorine activation during the early 1995-1996 Arctic winter SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID POLAR STRATOSPHERIC CLOUDS; HALOGEN OCCULTATION EXPERIMENT; OZONE DEPLETION; SULFURIC-ACID; UARS; VORTEX; HCL; CLONO2; HNO3; TEMPERATURES AB The coupling of temperature, aerosol area density, and chlorine activation is studied by comparing values from a three-dimensional chemical transport model with observed temperature, aerosol area density, and ClO data in the Arctic for the time period December I, 1995, to January 9, 1996. The three-dimensional model uses United Kingdom Meteorological Office (UKMO) winds and temperatures, run on pressure surfaces between 316 and 0.31 hPa, and the model results are examined at 100, bs, 46, 31, and 21 hPa, Radiosonde values are compared to individual UKMO temperature values to assess the impact of model temperature errors upon heterogeneous chemistry reaction probabilities. Polar Ozone and Aerosol Measurement (POAM II) aerosol extinction values are transformed into area density values and compared to model daily averaged time trends. The model is run with gas phase chemistry only, gas phase plus sulfate aerosol chemistry, and the case where gas phase, sulfate aerosol, and polar stratospheric cloud reactions are active. Results from these calculations are used to examine the sensitivity of chlorine activation to temperature biases, area density uncertainties, and the effects of the reaction paths OH + ClO --> HCl + O-2 (4% yield) and HO2 + ClO --> HCl + O-3 (4% yield). Sulfate aerosol is demonstrated to be very effective in activating chlorine in the Arctic polar vortex. Time trends of five-day averages of model and Upper Atmosphere Research Satellite (UARS) Microwave Limb Sounder (MLS) version 4 ClO over extended regions inside and outside the vortex at 21 and 46 hPa agree within the experimental error. C1 Natl Ctr Atmospher Res, Boulder, CO 80307 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. USN, Res Lab, Washington, DC 20375 USA. RP Massie, ST (reprint author), Natl Ctr Atmospher Res, POB 3000, Boulder, CO 80307 USA. EM massie@ncar.ucar.edu RI Fromm, Michael/F-4639-2010 NR 52 TC 5 Z9 5 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAR 27 PY 2000 VL 105 IS D6 BP 7111 EP 7131 DI 10.1029/1999JD901035 PG 21 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 297QW UT WOS:000086095000005 ER PT J AU Chiapello, I Goloub, P Tanre, D Marchand, A Herman, J Torres, O AF Chiapello, I Goloub, P Tanre, D Marchand, A Herman, J Torres, O TI Aerosol detection by TOMS and POLDER over oceanic regions SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID METEOSAT ISCCP-B2 DATA; SAHARAN DUST LOAD; SATELLITE CLIMATOLOGY; TRANSPORT; ATLANTIC AB In this paper we investigate the aerosol content retrieved by Earth-Probe Total Ozone Mapping Spectrometer (TOMS) and ADEOS POLDER over oceanic regions for the period November 1996 to June 1997. We combine the aerosol index (AI) derived from TOMS corresponding to UV-absorbing aerosols (desert dust and biomass-burning particles) and the POLDER aerosol optical thickness (AOT) and Angstrom coefficients. The seasonal composited images from the two sensors show in general consistent spatial distributions of the aerosol over oceans, with the highest aerosol content retrieved over the north tropical and equatorial Atlantic. Over the different oceanic regions investigated (i.e., Atlantic Ocean, Mediterranean Sea, Indian Ocean, and Pacific Ocean), TOMS and POLDER show a good correspondence in the aerosol seasonal variability. At all sites with the exception of the region of the Sea of Japan, we show that during the time periods of maximum aerosol amounts, a linear correlation exists between the TOMS AI and POLDER AOT. For the Sea of Japan the influence of different aerosol types (i.e., desert dust and sulfates) is likely to complicate the TOMS detection. For the other oceanic regions, our results suggest a large variability in the relationship between the TOMS Al and the POLDER AOT, which is likely to be related to changes in aerosol composition and/or altitude. C1 Univ Lille 1, Opt Atmospher Lab, F-59655 Villeneuve Dascq, France. NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. RP Chiapello, I (reprint author), Univ Lille 1, Opt Atmospher Lab, Bat P5, F-59655 Villeneuve Dascq, France. EM chiapello@loa.univ-lille1.fr; goloub@loa.univ-lille1.fr; tanre@loa.univ-lille1.fr; marchand@loa.univ-lille1.fr; herman@tparty.gsfc.nasa.gov; torres@tparty.gsfc.nasa.gov RI Torres, Omar/G-4929-2013; OI Herman, Jay/0000-0002-9146-1632 NR 30 TC 32 Z9 33 U1 3 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 27 PY 2000 VL 105 IS D6 BP 7133 EP 7142 DI 10.1029/1999JD901048 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 297QW UT WOS:000086095000006 ER PT J AU Tegen, I Rind, D AF Tegen, I Rind, D TI Influence of the latitudinal temperature gradient on soil dust concentration and deposition in Greenland SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID GENERAL-CIRCULATION MODEL; ICE CORE RECORDS; CLIMATE-CHANGE; ASIA; VARIABILITY; AEROSOL; SUMMIT; DYE-3; AIR AB To investigate the effects of changes in the latitudinal temperature gradient and the global mean temperature on dust concentration in the Northern Hemisphere, experiments with the GISS GCM are performed. The dust concentration over Greenland is calculated from sources in central and eastern Asia, which are integrated on-line in the model. The results show that an increase in the latitudinal temperature gradient increases both the Asian dust source strength and the concentration over Greenland. The source increase is the result of increased surface winds, and to a minor extent, the increase in Greenland dust is also associated with increased northward transport. Cooling the climate in addition to this increased gradient leads to a decrease in precipitation scavenging, which helps produce a further (slight) increase in Greenland dust in this experiment. Reducing the latitudinal gradient reduces the surface wind and hence the dust source. with a subsequent reduction in Greenland dust concentrations. Warming the climate in addition to this reduced gradient leads to a further reduction in Greenland dust due to enhanced precipitation scavenging. These results can be used to evaluate the relationship of Greenland ice core temperature changes to changes in the latitudinal and global temperatures. C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Columbia Univ, Dept Appl Phys, New York, NY 10027 USA. RP Tegen, I (reprint author), Max Planck Inst Biogcochem, POB 10 01 64, D-07701 Jena, Germany. EM itegen@bgc-jena.mpg.de NR 35 TC 14 Z9 18 U1 1 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 MAR 27 PY 2000 VL 105 IS D6 BP 7199 EP 7212 DI 10.1029/1999JD901094 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 297QW UT WOS:000086095000011 ER PT J AU Druyan, LM Fulakeza, MB Thiaw, W AF Druyan, LM Fulakeza, MB Thiaw, W TI Regional model simulations of African wave disturbances SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SURFACE-TEMPERATURE; EASTERLY WAVES; PHASE III; SENSITIVITY; CLIMATE; PARAMETERIZATION; PRECIPITATION; CONVECTION; MOISTURE; RAINFALL AB A regional climate simulation model is run at 50 km horizontal resolution over West Africa to study synoptic systems, such as African wave disturbances (AWDs). The study examines the results of 18 simulations, the longest of them covering the period August 8-15, 1988. Simulations were initialized with European Center for Medium-Range Weather Forecasts (ECMWF) gridded analysis data which also supply the lateral boundary conditions. Daily means of 700 mbar circulation and other model diagnostics are compared with ECMWF and National Centers for Environmental Prediction analyses to assess the skill of the model in simulating the evolution of synoptic systems. Trajectories of AWDs are tracked on time-longitude cross sections of 700 mbar vorticity, lower tropospheric divergence and precipitation rates. Cloud clusters on satellite imagery relate rather well to synoptic features on observational analyses as well as to spatial patterns of rain gage measurements but not consistently to simulated precipitation, Movement of major AWDs and the generation of new waves are handled realistically by the model. Model dynamics and physics appear to be more important than lateral boundary conditions in determining the course of simulations. C1 Columbia Univ, Ctr Climate Syst Res, New York, NY 10025 USA. NOAA, Natl Ctr Environm Predict, Climate Predict Ctr, Camp Springs, MD 20746 USA. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Natl Acad Sci, Natl Res Council, Washington, DC 20418 USA. RP Druyan, LM (reprint author), Columbia Univ, Ctr Climate Syst Res, 2880 Broadway, New York, NY 10025 USA. EM ldruyan@giss.nasa.gov; mfulakeza@giss.nasa.gov; wd53wt@ncep.noaa.gov NR 29 TC 14 Z9 14 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAR 27 PY 2000 VL 105 IS D6 BP 7231 EP 7255 DI 10.1029/2000JD900017 PG 25 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 297QW UT WOS:000086095000013 ER PT J AU Ziemke, JR Chandra, S Herman, J Varotsos, C AF Ziemke, JR Chandra, S Herman, J Varotsos, C TI Erythemally weighted UV trends over northern latitudes derived from Nimbus 7 TOMS measurements SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID STRATOSPHERIC OZONE DEPLETION; ULTRAVIOLET-RADIATION; COLUMN OZONE; B RADIATION; IRRADIANCE; HEMISPHERE; WINTER; VARIABILITY AB This study examines the distribution of long-term trends in ground level erythemally weighted ultraviolet (UV) exposures in the northern latitudes for the period 1979-1991 using measurements from the Nimbus 7 Total Ozone Mapping Spectrometer (TOMS) instrument. A new erythemal UV data set (now available to the public via World Wide Web) was produced recently by NASA and has been tested by NASA at the Goddard Space Flight Center against a previous NASA erythemal UV product, which was used in a former study that included similar adjustments for aerosols and clouds but not aerosol absorption. Zonal mean erythemal UV data from both products show similar, similar to 3-7% per decade, increases in the midlatitudes to high latitudes. The detection of regional patterns in trends in erythemal UV favors summer months when surface UV is strongest and noise factors such as clouds and aerosols are not as influential. Analysis of the zonal patterns in trends around summer months indicates that most of the regional increases (exceeding 6% per decade) in the Northern Hemisphere in the latitude range 30 degrees N-40 degrees N originate from the Pacific and Atlantic oceanic regions. Increases (also exceeding 6% per decade) in latitudes 40 degrees-60 degrees N appear to originate from the North American and Asian continents and also central Europe. Trends over the east Asian continent in high latitudes indicate increases exceeding 10% per decade for May-August. The important conclusion is that positive trends in the northern subtropical latitudes originate mostly over oceanic regions, whereas positive trends at higher latitudes originate mostly over landmasses. Some of the increases in erythemal UV over central Europe and the east Asian continent in summer months can be attributed to decadal decreases in cloudiness for the 1979-1991 time period. C1 Software Corp Amer, Beltsville, MD USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Athens, Dept Phys, Athens 15784, Greece. RP Ziemke, JR (reprint author), Software Corp Amer, Beltsville, MD USA. EM ziemke@jwocky.gsfc.nasa.gov; chandra@chapman.gsfc.nasa.gov; herman@tparty.gsfc.nasa.gov; kvarots@atlas.uoa.gr RI Varotsos, Costas/H-6257-2013; OI Varotsos, Costas/0000-0001-7215-3610; Herman, Jay/0000-0002-9146-1632 NR 32 TC 71 Z9 73 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAR 27 PY 2000 VL 105 IS D6 BP 7373 EP 7382 DI 10.1029/1999JD901131 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 297QW UT WOS:000086095000022 ER PT J AU Choudhury, BJ AF Choudhury, BJ TI Seasonal and interannual variations of total evaporation and their relations with precipitation, net radiation, and net carbon accumulation for the Gediz basin area SO JOURNAL OF HYDROLOGY LA English DT Article DE evaporation; transpiration; carbon assimilation; net radiation; satellite observations ID SOIL-MOISTURE; VEGETATION; SATELLITE; DATASET; GROWTH; MODEL AB A model combining the rate of carbon assimilation with water and energy balance equations has been run using satellite and ancillary data for a period of 60 months (from January 1986 to December 1990) over the global land surface. Calculations for the Gediz basin area give mean annual total evaporation as 395 mm, which is composed of 45% transpiration, 42% soil evaporation and 13% interception. The coefficient of interannual variation of evaporation is found to be 6%, while that for precipitation and net radiation are, respectively, 16 and 2%, illustrating that net radiation has an important effect in modulating interannual variation of evaporation. The mean annual water use efficiency (i.e. the ratio of net carbon accumulation and total evaporation) is ca. 1 g m(-2) mm(-1), and has a coefficient of interannual variation of 5%. A comparison of the mean water use efficiency with field observations suggests that evaporation over the area is utilized well for biomass production. The reference crop evaporation for irrigated areas has annual mean and coefficient of variation as, respectively, 1176 mm and 3%. The total evaporation during three summer months of peak evaporation (June-August) is estimated to be about 575 mm for irrigated crops like maize and cotton. Seasonal variations of the fluxes are presented. Published by Elsevier Science B.V. C1 NASA, Goddard Space Flight Ctr, Hydrol Sci Branch, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. RP Choudhury, BJ (reprint author), NASA, Goddard Space Flight Ctr, Hydrol Sci Branch, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. NR 32 TC 14 Z9 16 U1 0 U2 5 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-1694 J9 J HYDROL JI J. Hydrol. PD MAR 27 PY 2000 VL 229 IS 1-2 BP 77 EP 86 DI 10.1016/S0022-1694(99)00201-2 PG 10 WC Engineering, Civil; Geosciences, Multidisciplinary; Water Resources SC Engineering; Geology; Water Resources GA 305GB UT WOS:000086530100009 ER PT J AU Rubinstein, R Zhou, Y AF Rubinstein, R Zhou, Y TI The frequency spectrum of sound radiated by isotropic turbulence SO PHYSICS LETTERS A LA English DT Article ID SWEEPING DECORRELATION AB The theory of turbulent time correlations is applied to compute the frequency spectrum of sound radiated by isotropic turbulence. Assuming the quasi-normality of the fourth-order velocity correlation generated by Lighthill's theory, it is argued that the frequency distribution of radiated acoustic energy is determined by the Eulerian space-time correlation function. The frequency spectrum of the sound radiated by isotropic turbulence is found to scale as omega(-4/3) at high frequencies. Dimensional analysis based on Kolmogorov scaling predicts the dependence omega(-7/2) instead. The discrepancy is explained by the dependence of Eulerian time correlations on an additional dimensional parameter: the sweeping velocity of the most energetic scales of motion. (C) 2000 Elsevier Science B.V. All rights reserved. C1 NASA, Inst Comp Applicat Sci & Engn, Langley Res Ctr, Hampton, VA 23681 USA. IBM Corp, Div Res, TJ Watson Res Ctr, Yorktown Heights, NY 10598 USA. RP Zhou, Y (reprint author), NASA, Inst Comp Applicat Sci & Engn, Langley Res Ctr, Hampton, VA 23681 USA. NR 11 TC 16 Z9 16 U1 0 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0375-9601 J9 PHYS LETT A JI Phys. Lett. A PD MAR 27 PY 2000 VL 267 IS 5-6 BP 379 EP 383 DI 10.1016/S0375-9601(00)00119-5 PG 5 WC Physics, Multidisciplinary SC Physics GA 308HH UT WOS:000086704100013 ER PT J AU Bloss, WJ Nickolaisen, SL Sander, SP AF Bloss, WJ Nickolaisen, SL Sander, SP TI Kinetics of formation and absorption cross section of the CIO dimer. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Calif State Univ Los Angeles, Dept Chem Biochem, Los Angeles, CA 90032 USA. RI Bloss, William/N-1305-2014 OI Bloss, William/0000-0002-3017-4461 NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 26 PY 2000 VL 219 MA 6-PHYS BP U268 EP U269 PN 2 PG 2 WC Chemistry, Multidisciplinary SC Chemistry GA 317UW UT WOS:000087246201465 ER PT J AU Brandon, EJ Wesseling, E Chery, H Ruiz, R Kolawa, E AF Brandon, EJ Wesseling, E Chery, H Ruiz, R Kolawa, E TI Electrodeposition of high-permeability magnetic films. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 CALTECH, Jet Prop Lab, Ctr Integrated Space Microsyst, Pasadena, CA 91109 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 26 PY 2000 VL 219 MA 179-INOR BP U798 EP U798 PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 317UV UT WOS:000087246104315 ER PT J AU Brinton, KLF Tsapin, AI McDonald, GD Gilichinsky, D AF Brinton, KLF Tsapin, AI McDonald, GD Gilichinsky, D TI Amino acid racemization in Siberian permafrost cores. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Russian Acad Sci, Inst Basic Biol Problems, Pushchino 142292, Moscow Region, Russia. NR 0 TC 0 Z9 0 U1 0 U2 1 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 26 PY 2000 VL 219 MA 45-GEOC BP U695 EP U695 PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 317UV UT WOS:000087246103763 ER PT J AU Brown, KG Burns, KS Upchurch, BT Wood, GM AF Brown, KG Burns, KS Upchurch, BT Wood, GM TI Polymerization in microgravity onboard STS-57, STS-63, and STS-77. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 Old Dominion Univ, Dept Chem & Biochem, Norfolk, VA 23529 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. STC Catalysts Inc, Hampton, VA 23666 USA. NR 0 TC 0 Z9 0 U1 0 U2 1 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 26 PY 2000 VL 219 MA 624-POLY BP U459 EP U460 PN 2 PG 2 WC Chemistry, Multidisciplinary SC Chemistry GA 317UW UT WOS:000087246202572 ER PT J AU Brown, KG Burns, KS Ingram, J Upchurch, BT Wood, GM AF Brown, KG Burns, KS Ingram, J Upchurch, BT Wood, GM TI Compositional characterization, by Raman spectroscopy, of polymers synthesized in microgravity onboard sts-57, sts-63, and sts-77. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 Old Dominion Univ, Dept Chem & Biochem, Norfolk, VA 23529 USA. NASA Langley, Hampton, VA 23681 USA. STC Catalysts Inc, Hampton, VA 23666 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 26 PY 2000 VL 219 MA 438-POLY BP U421 EP U421 PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 317UW UT WOS:000087246202386 ER PT J AU Carswell, WE Paley, MS Frazier, DO AF Carswell, WE Paley, MS Frazier, DO TI Polymer thin-film growth in microgravity. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 Univ Alabama, Huntsville, AL 35899 USA. NASA, George C Marshall Space Flight Ctr, Univ Space Res Assoc, Huntsville, AL 35812 USA. NR 0 TC 0 Z9 0 U1 0 U2 1 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 26 PY 2000 VL 219 MA 622-POLY BP U459 EP U459 PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 317UW UT WOS:000087246202570 ER PT J AU Curtis, V Ticich, TM Vander Wal, RL AF Curtis, V Ticich, TM Vander Wal, RL TI Growth mechanism of carbon nanotubes on supported substrates. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 Centenary Coll Louisiana, Dept Chem, Shreveport, LA 71134 USA. NASA, Glenn Res Ctr, Micrograv Combust Branch, NCMR, Cleveland, OH 44135 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 26 PY 2000 VL 219 MA 786-CHED BP U411 EP U411 PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 317UV UT WOS:000087246102177 ER PT J AU Downey, JP AF Downey, JP TI Effectively reducing acceleration to microgravity levels. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA, George C Marshall Space Flight Ctr, Micrograv Dept, Huntsville, AL 35812 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 26 PY 2000 VL 219 MA 588-POLY BP U454 EP U454 PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 317UW UT WOS:000087246202536 ER PT J AU Dworkin, JP Bernstien, MP Sandford, SA Allamandola, LJ AF Dworkin, JP Bernstien, MP Sandford, SA Allamandola, LJ TI Interstellar synthesis of naphthaquinones. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA, Ames Res Ctr, SETI INst, Astrochem Lab, Moffett Field, CA 94035 USA. RI Dworkin, Jason/C-9417-2012 OI Dworkin, Jason/0000-0002-3961-8997 NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 26 PY 2000 VL 219 MA 48-GEOC BP U695 EP U695 PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 317UV UT WOS:000087246103766 ER PT J AU Dyall, KG AF Dyall, KG TI Effective core potentials: How and why they work, or not. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA, Ames Res Ctr, Thermosci Inst, Moffett Field, CA 94035 USA. NR 0 TC 0 Z9 0 U1 0 U2 1 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 26 PY 2000 VL 219 MA 2-COMP BP U589 EP U589 PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 317UV UT WOS:000087246103169 ER PT J AU Farmer, FH Wood, GM AF Farmer, FH Wood, GM TI STC Catalysts Inc.: A small chemical business enabled through Technology Transfer. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA, Technol Appliat Grp, Langley Res Ctr, Hampton, VA 23681 USA. STC Catalysts Inc, Hampton, VA 23666 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 26 PY 2000 VL 219 MA 11-SCHB BP U515 EP U515 PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 317UW UT WOS:000087246202883 ER PT J AU Frazier, DO AF Frazier, DO TI Gravitational influences on the growth of polydiacetylene films by ultraviolet solution polymerization. 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 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 26 PY 2000 VL 219 MA 11-SOCED BP U557 EP U557 PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 317UW UT WOS:000087246203096 ER PT J AU Freund, F AF Freund, F TI Hydrogen in igneous rocks: Relation to early Earth and early life. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA, Ames Res Ctr, SETI Inst, Moffett Field, CA 94305 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 26 PY 2000 VL 219 MA 29-GEOC BP U692 EP U692 PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 317UV UT WOS:000087246103747 ER PT J AU Gariepy, CA Meador, MA Meador, MAB Eby, RK AF Gariepy, CA Meador, MA Meador, MAB Eby, RK TI Optimization of melt processable PMR-type polyimides. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 Univ Akron, Maurice Morton Inst Polymer Sci, Akron, OH 44325 USA. NASA, Glenn Res Ctr, Div Mat, Cleveland, OH 44135 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 26 PY 2000 VL 219 MA 219-POLY BP U388 EP U388 PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 317UW UT WOS:000087246202170 ER PT J AU Hockensmith, CM Goldsby, J Kacik, T AF Hockensmith, CM Goldsby, J Kacik, T TI Thermal studies of coordination compounds of indium-tin oxides as precursors to sensor materials for the detection of NOx. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 Austin Peay State Univ, Dept Chem, Clarksville, TN 37044 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 26 PY 2000 VL 219 MA 667-INOR BP U873 EP U873 PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 317UV UT WOS:000087246104800 ER PT J AU Jaffe, RL Han, J Yang, L Smith, GD AF Jaffe, RL Han, J Yang, L Smith, GD TI Potential energy functions for fluoropolymer modeling. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA, Ames Res Ctr, Computat Chem Branch, Moffett Field, CA 94035 USA. Univ Utah, Salt Lake City, UT 84112 USA. NR 0 TC 0 Z9 0 U1 1 U2 1 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 26 PY 2000 VL 219 MA 329-PHYS BP U327 EP U327 PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 317UW UT WOS:000087246201788 ER PT J AU Jenniskens, P AF Jenniskens, P TI Aerothermochemistry and the origin of life. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA, Ames Res Ctr, Moffett Field, CA 94305 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 26 PY 2000 VL 219 MA 26-GEOC BP U691 EP U691 PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 317UV UT WOS:000087246103744 ER PT J AU Kiefer, RL Weisman, JL Orwoll, RA Thibeault, SA AF Kiefer, RL Weisman, JL Orwoll, RA Thibeault, SA TI Polymer additives for reduced erosion by atomic oxygen. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 Coll William & Mary, Dept Chem, Williamsburg, VA 23187 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 26 PY 2000 VL 219 MA 198-POLY BP U385 EP U385 PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 317UW UT WOS:000087246202149 ER PT J AU Klemm, RB Thorn, RP Stief, LJ Buckley, TJ AF Klemm, RB Thorn, RP Stief, LJ Buckley, TJ TI Heat of formation of OBrO: An experimental photoionization study. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 Brookhaven Natl Lab, Dept Appl Sci, Upton, NY 11973 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Natl Inst Stand & Technol, Phys & Chem Properties Div, Gaithersburg, MD 20899 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 26 PY 2000 VL 219 MA 218-PHYS BP U310 EP U310 PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 317UW UT WOS:000087246201677 ER PT J AU Kojiro, D AF Kojiro, D TI Instrumentation developed for the Hummingbird comet nucleus analysis mission. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA, Ames Res Ctr, Div Space Sci, Exobiol Branch, Moffett Field, CA 94035 USA. NR 0 TC 0 Z9 0 U1 1 U2 1 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 26 PY 2000 VL 219 MA 228-ANYL BP U119 EP U119 PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 317UV UT WOS:000087246100543 ER PT J AU Kundu, KP Penko, PF AF Kundu, KP Penko, PF TI Numerical calculation of NOX formation in combustion of complex hydrocarbon fuels. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA, Glenn Res Ctr, Combust Branch, Cleveland, OH 44135 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 26 PY 2000 VL 219 MA 137-ENVR BP U640 EP U640 PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 317UV UT WOS:000087246103473 ER PT J AU Leu, MT Kane, SM Timonen, RS AF Leu, MT Kane, SM Timonen, RS TI Heterogeneous chemistry of acetone and methanol in sulfuric acid solutions: Implications for the upper troposphere. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 CALTECH, Jet Prop Lab, Div Earth & Space Sci, Pasadena, CA 91109 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 26 PY 2000 VL 219 MA 254-PHYS BP U316 EP U316 PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 317UW UT WOS:000087246201713 ER PT J AU Levine, LH Kwon, M Heyenga, AG Levine, HG Davin, LB Krikorian, AD Lewis, NG AF Levine, LH Kwon, M Heyenga, AG Levine, HG Davin, LB Krikorian, AD Lewis, NG TI Wheat cell-wall architecture and induced Douglas fir compression wood formation in a microgravity environment. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 Dynamac Corp, DYN 3, Kennedy Space Ctr, FL 32899 USA. Washington State Univ, Inst Biol Chem, Pullman, WA 99164 USA. NASA, Ames Res Ctr, Space Technol Div, Moffett Field, CA 94035 USA. SUNY Stony Brook, Dept Biochem & Cell Biol, Stony Brook, NY 11794 USA. NR 0 TC 0 Z9 0 U1 0 U2 1 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 26 PY 2000 VL 219 MA 55-CELL BP U265 EP U265 PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 317UV UT WOS:000087246101271 ER PT J AU Meador, MA Auping, JV Moeller, MN Yan, S AF Meador, MA Auping, JV Moeller, MN Yan, S TI Excited-state charge-transfer in donor/acceptor substituted benzofurans. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA, Glenn Res Ctr, Div Mat, Polymers Branch, Cleveland, OH 44135 USA. NASA, Glenn Res Ctr, Environm Durabil Branch, Div Mat, Cleveland, OH 44135 USA. USN, Undersea Warfare Ctr, Newport, RI 02841 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 26 PY 2000 VL 219 MA 853-ORGN BP U239 EP U239 PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 317UW UT WOS:000087246201331 ER PT J AU Meador, MAB Frimer, AA AF Meador, MAB Frimer, AA TI Approaches to new endcaps for addition polyimides for improved oxidation resistance. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA, Glenn Res Ctr, Div Mat, Cleveland, OH 44135 USA. Bar Ilan Univ, Act Oxygen Chem, IL-52900 Ramat Gan, Israel. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 26 PY 2000 VL 219 MA 176-POLY BP U381 EP U381 PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 317UW UT WOS:000087246202126 ER PT J AU Mecerreyes, D Pomposo, J Bemgoetxea, M Grande, H Nguyen, C AF Mecerreyes, D Pomposo, J Bemgoetxea, M Grande, H Nguyen, C TI Synthesis of polypyrrole-graft-polycaprolactone copolymers: New conductive nanocomposites. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 IBM Corp, Almaden Res Ctr, San Jose, CA 95120 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RI Mecerreyes, David/K-7541-2014 OI Mecerreyes, David/0000-0002-0788-7156 NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 26 PY 2000 VL 219 MA 82-POLY BP U368 EP U368 PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 317UW UT WOS:000087246202033 ER PT J AU Morris, KL AF Morris, KL TI Stratospheric Aerosol and Gas Experiment data available from the Langley Atmospheric Sciences Data Center. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 Comp Sci Corp, LaRC Atmospher Sci Data Ctr, User Serv, Hampton, VA 23666 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 26 PY 2000 VL 219 MA 237-PHYS BP U313 EP U313 PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 317UW UT WOS:000087246201696 ER PT J AU Navarro-Gonzalez, R McKay, CP Calva-Alejo, L Mvondo, DN AF Navarro-Gonzalez, R McKay, CP Calva-Alejo, L Mvondo, DN TI Nitrogen fixation by lightning on early Earth and Mars. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 Natl Autonomous Univ Mexico, Inst Ciencias Nucl, Mexico City 04510, DF, Mexico. NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. RI Gonzalez, Rafael/D-1748-2009 NR 0 TC 0 Z9 0 U1 0 U2 5 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 26 PY 2000 VL 219 MA 47-GEOC BP U695 EP U695 PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 317UV UT WOS:000087246103765 ER PT J AU Nguyen, BN Eby, RK Meador, MA AF Nguyen, BN Eby, RK Meador, MA TI High-temperature pmr-type polyimides with star-branched structure: Synthesis and characterization. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 Univ Akron, NASA, Glenn Res Ctr, Dept Polymer Sci,Polymers Branch, Akron, OH 44325 USA. NASA, Glenn Res Ctr, Div Mat, Inst Polymer Sci, Cleveland, OH 44135 USA. NASA, Glenn Res Ctr, Div Mat, Polymers Branch, Cleveland, OH 44135 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 26 PY 2000 VL 219 MA 145-POLY BP U377 EP U377 PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 317UW UT WOS:000087246202096 ER PT J AU Parusel, ABJ Grimme, S AF Parusel, ABJ Grimme, S TI Density functional theory based multireference configuration interaction calculations for excited states: Electronic absorption spectra of organic donor-acceptor systems and a series of porphyrin-type molecules including chlorophyll A. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 0 TC 0 Z9 0 U1 0 U2 1 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 26 PY 2000 VL 219 MA 34-COMP BP U593 EP U593 PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 317UV UT WOS:000087246103201 ER PT J AU Pizzarello, S Cooper, G AF Pizzarello, S Cooper, G TI Chiral amino acids in carbonaceous meteorites. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 Arizona State Univ, Dept Chem & Biochem, Tempe, AZ 85287 USA. NASA, Ames Res Ctr, Div Exobiol, Moffett Field, CA 94035 USA. NR 0 TC 1 Z9 1 U1 0 U2 1 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 26 PY 2000 VL 219 MA 27-GEOC BP U692 EP U692 PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 317UV UT WOS:000087246103745 ER PT J AU Schwenke, DW AF Schwenke, DW TI Modeling nonadiabatic effects in H2O. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RI schwenke, david/I-3564-2013 NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 26 PY 2000 VL 219 MA 417-PHYS BP U340 EP U340 PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 317UW UT WOS:000087246201876 ER PT J AU Snow, LA Smith, DD Sibille, L Cronise, RJ Hunt, AJ Ng, JD AF Snow, LA Smith, DD Sibille, L Cronise, RJ Hunt, AJ Ng, JD TI Determination of the effect of microgravity on silica sol-gels by electrophoretic porosimetry. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 Univ Alabama, Dept Chem, Huntsville, AL 35899 USA. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. NASA, George C Marshall Space Flight Ctr, Univ Space Res Assoc, Huntsville, AL 35812 USA. Univ Calif Berkeley, Lawrence Berkeley Natl Lab, Berkeley, CA 94720 USA. Univ Alabama, Dept Biol Sci, Huntsville, AL 35899 USA. NR 0 TC 0 Z9 0 U1 0 U2 1 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 26 PY 2000 VL 219 MA 594-POLY BP U455 EP U455 PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 317UW UT WOS:000087246202542 ER PT J AU Southward, R Dean, C Stoakley, D Thompson, D Chisholm-Brause, C AF Southward, R Dean, C Stoakley, D Thompson, D Chisholm-Brause, C TI Surface-metallized BPDA/ODA polyimide films via in situ thermal reduction of silver(I) beta-diketonate complexes. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Coll William & Mary, Dept Chem, Williamsburg, VA 23681 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 26 PY 2000 VL 219 MA 66-POLY BP U365 EP U365 PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 317UW UT WOS:000087246202017 ER PT J AU Southward, R Dean, C Thompson, D AF Southward, R Dean, C Thompson, D TI Synthesis of surface-metallized polyimide films via in situ reduction of silver(I) complexes: Ligand and polymer molecular weight and structural effects. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Coll William & Mary, Dept Chem, Williamsburg, VA 23681 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 26 PY 2000 VL 219 MA 266-INOR BP U811 EP U811 PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 317UV UT WOS:000087246104401 ER PT J AU Stark, S Gangl, S Hermann, D Parusel, A Grabner, G Koehler, G AF Stark, S Gangl, S Hermann, D Parusel, A Grabner, G Koehler, G TI Intramolecular charge transfer in a series of novel porphyrin-flavin dyads: Through bond versus through space mechanisms. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 Univ Vienna, Inst Theoret Chem & Struct Biol, A-1090 Vienna, Austria. Univ Munich, Inst Organ Chem, D-81377 Munich, Germany. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 26 PY 2000 VL 219 MA 45-PHYS BP U274 EP U274 PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 317UW UT WOS:000087246201504 ER PT J AU Watson, KA Bass, RG AF Watson, KA Bass, RG TI Synthesis and characterization of polyimides prepared via a Diels-Alder reaction between bisisobenzofurans and bisacetylenes. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA, Langley Res Ctr, Adv Mat & Proc Branch, Hampton, VA 23681 USA. Virginia Commonwealth Univ, Dept Chem, Richmond, VA 23284 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 26 PY 2000 VL 219 MA 119-POLY BP U373 EP U373 PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 317UW UT WOS:000087246202070 ER PT J AU Yan, JF AF Yan, JF TI Sequence analysis by a prime number code: Structure prediction for cellulose synthase. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 Dynamac Corp, DYN 3, Kennedy Space Ctr, FL 32899 USA. Washington State Univ, Inst Biol Chem, Pullman, WA 99164 USA. NASA, Ames Res Ctr, Space Technol Div, Moffett Field, CA 94035 USA. SUNY Stony Brook, Dept Biochem & Cell Biol, Stony Brook, NY 11794 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 26 PY 2000 VL 219 MA 56-CELL BP U265 EP U265 PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 317UV UT WOS:000087246101272 ER PT J AU Zhang, H Roehl, CM Wennberg, PO Sander, SP Blake, GA AF Zhang, H Roehl, CM Wennberg, PO Sander, SP Blake, GA TI Photodissociation of HNO4 in the near-IR. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 CALTECH, Div Geol & Planetary Sci, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RI Wennberg, Paul/A-5460-2012 NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 26 PY 2000 VL 219 MA 230-PHYS BP U312 EP U312 PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 317UW UT WOS:000087246201689 ER PT J AU Vasavada, AR Williams, JP Paige, DA Herkenhoff, KE Bridges, NT Greeley, R Murray, BC Bass, DS McBride, KS AF Vasavada, AR Williams, JP Paige, DA Herkenhoff, KE Bridges, NT Greeley, R Murray, BC Bass, DS McBride, KS TI Surface properties of Mars' polar layered deposits and polar landing sites SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID THERMAL MAPPER OBSERVATIONS; REGION; ALBEDO; ICE AB On December 3, 1999, the Mars Polar Lander and Mars Microprobes will land on the planet's south polar layered deposits near (76 degrees S, 195 degrees W) and conduct the first in situ studies of the planet's polar regions. The scientific goals of these missions address several poorly understood and globally significant issues, such as polar meteorology, the composition and volatile content of the layered deposits, the erosional state and mass balance of their surface, their possible relationship to climate cycles, and the nature of bright and dark aeolian material. Derived thermal inertias of the southern layered deposits are very low (50-100 J m(-2) s(-1/2) K-1), suggesting that the surface down to a depth of a few centimeters is generally fine grained or porous and free of an appreciable amount of rock or ice. The landing site region is smoother than typical cratered terrain on similar to 1 km pixel(-1) Viking Orbiter images but contains low-relief texture on similar to 5 to 100 m pixel(-1) Mariner 9 and Mars Global Surveyor images. The surface of the southern deposits is older than that of the northern deposits and appears to be modified by aeolian erosion or ablation of ground ice. C1 Univ Calif Los Angeles, Dept Earth & Space Sci, Los Angeles, CA 90095 USA. SW Res Inst, San Antonio, TX 78228 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Arizona State Univ, Dept Geol, Tempe, AZ 85287 USA. US Geol Survey, Flagstaff, AZ 86001 USA. CALTECH, Div Geol & Planetary Sci, Pasadena, CA 91125 USA. RP Vasavada, AR (reprint author), Univ Calif Los Angeles, Dept Earth & Space Sci, Los Angeles, CA 90095 USA. RI Williams, Jean-Pierre/C-3531-2009; Bridges, Nathan/D-6341-2016 OI Williams, Jean-Pierre/0000-0003-4163-2760; NR 40 TC 29 Z9 29 U1 0 U2 5 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD MAR 25 PY 2000 VL 105 IS E3 BP 6961 EP 6969 DI 10.1029/1999JE001108 PG 9 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 295PU UT WOS:000085977700002 ER PT J AU Huo, WM Kim, YK AF Huo, WM Kim, YK TI Use of relativistic effective core potentials in the calculation of total electron-impact ionization cross-sections SO CHEMICAL PHYSICS LETTERS LA English DT Article ID RARE-GAS ATOMS; WAVE-FUNCTIONS; BASIS-SETS; R-MATRIX; THRESHOLD; HYDROGEN; SCATTERING; MOLECULES; ENERGIES; DIPOLE AB The binary-encounter-Bethe (BEB) model of Kim and Rudd for total ionization cross-sections by electron impact is re-examined when the target is an atom with principal quantum number n greater than or equal to 3, or a molecule consisting of one or mon atoms with n greater than or equal to 3. It is shown that the use of relativistic effective core potential (RECP) for heavy atoms removes the need for the empirical scaling used previously. BEB cross-sections of Ar, Kr, Xe, Cl, Pr, I, and WF6 calculated using RECP are found to be in good agreement with available experimental data, especially in the low-energy region. (C) 2000 Published by Elsevier Science B.V. All rights reserved. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Natl Inst Stand & Technol, Gaithersburg, MD 20899 USA. RP Huo, WM (reprint author), NASA, Ames Res Ctr, Mail Stop 230-3, Moffett Field, CA 94035 USA. NR 31 TC 18 Z9 18 U1 0 U2 6 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 24 PY 2000 VL 319 IS 5-6 BP 576 EP 586 DI 10.1016/S0009-2614(00)00150-0 PG 11 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 298CL UT WOS:000086121700024 ER PT J AU Bauschlicher, CW AF Bauschlicher, CW TI The scalar relativistic contribution to the atomization energies of CF, CF4, and SiF4 SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID CORRELATED MOLECULAR CALCULATIONS; GAUSSIAN-BASIS SETS; WAVE-FUNCTIONS AB The one-electron Douglas Kroll (DK) approach and perturbation theory, accounting for the mass-velocity and Darwin (MVD) terms, are used to compute the scalar relativistic contribution to the atomization energies of CF, CF4, and SiF4. The difference between these two approaches is studied as a function of basis set and level of correlation treatment. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Bauschlicher, CW (reprint author), NASA, Ames Res Ctr, Mail Stop 230-3, Moffett Field, CA 94035 USA. NR 19 TC 20 Z9 20 U1 0 U2 2 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 1089-5639 J9 J PHYS CHEM A JI J. Phys. Chem. A PD MAR 23 PY 2000 VL 104 IS 11 BP 2281 EP 2283 DI 10.1021/jp992077j PG 3 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 296LF UT WOS:000086025300017 ER PT J AU Rogers, S Wang, DS Kuppermann, A Walch, S AF Rogers, S Wang, DS Kuppermann, A Walch, S TI Chemically accurate ab initio potential energy surfaces for the lowest (3)A ' and (3)A '' electronically adiabatic states of O(P-3)+H-2 SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID CONFIGURATION-INTERACTION CALCULATIONS; MOLECULAR WAVE-FUNCTIONS; COLLINEAR EXACT QUANTUM; BALANCED BASIS-SETS; REACTION DYNAMICS; RATE CONSTANTS; REACTION O(3P)+H2->OH+H; BENCHMARK CALCULATIONS; REACTION O+H2->OH+H; DISTORTED-WAVE AB The electronic energies of the lowest (3)A' and (3)A " states of the O(P-3) + H-2 system were calculated for 951 geometries using MOLPRO. The calculations were titled by a rotating Morse splint method and independently by a generalized London-Eyring-Polanyi-Sato (LEPS) doubie-polynomial method. A higher accuracy calculation for 112 of these geometries was also performed for both (3)A' and (3)A " to obtain correction potential energy surfaces (PESs) used to raise the accuracy of the original surfaces to about 0.3 kcal/mol. The resulting fitted PESs are presented and compared to each other and to a previous empirical LEPS surface. C1 CALTECH, Arthur Amos Noyes Lab Chem Phys, Div Chem & Chem Engn, Pasadena, CA 91125 USA. NASA, Ames Res Ctr, Thermosci Inst, Moffett Field, CA 94035 USA. RP Kuppermann, A (reprint author), CALTECH, Arthur Amos Noyes Lab Chem Phys, Div Chem & Chem Engn, Pasadena, CA 91125 USA. RI Walch, Susan/H-3858-2015 NR 89 TC 75 Z9 77 U1 2 U2 24 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 1089-5639 J9 J PHYS CHEM A JI J. Phys. Chem. A PD MAR 23 PY 2000 VL 104 IS 11 BP 2308 EP 2325 DI 10.1021/jp992985g PG 18 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 296LF UT WOS:000086025300022 ER PT J AU Parusel, ABJ Ghosh, A AF Parusel, ABJ Ghosh, A TI Density functional theory based configuration interaction calculations on the electronic spectra of free-base porphyrin, chlorin, bacteriochlorin, and cis- and trans-isobacteriochlorin SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID VALENCE IONIZATION-POTENTIALS; ABSORPTION-SPECTRA; COUPLED-CLUSTER; EXCITED-STATES; ABINITIO SCF; PORPHIN; PERFORMANCE AB Configuration interaction calculations with single excitations based on density Functional theory (DFT/SCI) provide a reasonably accurate description of the electronic spectra of prototype porphyrin-type molecules at modest computational cost, The calculations reproduce the experimentally observed Q-B energy splitting, differences in Q and B oscillator strengths, and the intensification, relative to porphyrin, of Q(x) bands of hydroporphyrins. In all cases, the DFT/SCI results are in comparable or better agreement with experiment, compared to recent nb initio CASPT2, SAC-CL, and STEOM-CCSD calculations. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Tromso, Fac Sci, Inst Chem, N-9037 Tromso, Norway. RP Parusel, ABJ (reprint author), NASA, Ames Res Ctr, MS 239-4, Moffett Field, CA 94035 USA. RI Ghosh, Abhik/G-8164-2016 OI Ghosh, Abhik/0000-0003-1161-6364 NR 27 TC 59 Z9 60 U1 3 U2 20 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 1089-5639 J9 J PHYS CHEM A JI J. Phys. Chem. A PD MAR 23 PY 2000 VL 104 IS 11 BP 2504 EP 2507 DI 10.1021/jp9921046 PG 4 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 296LF UT WOS:000086025300046 ER PT J AU Gehrels, N Macomb, DJ Bertsch, DL Thompson, DJ Hartman, RC AF Gehrels, N Macomb, DJ Bertsch, DL Thompson, DJ Hartman, RC TI Discovery of a new population of high-energy gamma-ray sources in the Milky Way SO NATURE LA English DT Article ID EGRET SOURCES; SUPERNOVA-REMNANTS; GALACTIC PLANE; GOULD BELT; EMISSION; PULSARS AB One of the great mysteries of the high-energy gamma-ray sky is the group of similar to 170 unidentified point sources(1,2) found along the Galactic plane. They are more numerous than all other high-energy gamma-ray sources combined and, despite 20 years of effort, no clear counterparts have been found at other wavelengths. Here we report a new population of such objects. A cluster of similar to 20 faint sources appears north of the Galactic Centre, which is part of a broader class of faint objects at mid-latitudes. In addition, we show in a model-independent way that the mid-latitude sources are distinct from the population of bright unidentified sources along the Galactic plane. The distribution on the sky indicates that the faint mid-latitude sources are associated with the Gould belt(3,4) of massive stars and gas clouds at similar to 600 light years distance, as has been previously suggested(5). C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Gehrels, N (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RI Thompson, David/D-2939-2012; Gehrels, Neil/D-2971-2012 OI Thompson, David/0000-0001-5217-9135; NR 25 TC 114 Z9 115 U1 0 U2 2 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON N1 9XW, ENGLAND SN 0028-0836 J9 NATURE JI Nature PD MAR 23 PY 2000 VL 404 IS 6776 BP 363 EP 365 DI 10.1038/35006001 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 298BG UT WOS:000086119000041 ER PT J AU Sylvester, RJ Mannings, V AF Sylvester, RJ Mannings, V TI Optical, infrared and millimetre-wave properties of Vega-like systems - IV. Observations of a new sample of candidate Vega-like sources SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE circumstellar matter; planetary systems; infrared : stars ID HERBIG AE/BE STARS; SPECTRAL IRRADIANCE CALIBRATION; INTERMEDIATE-MASS STARS; MAIN-SEQUENCE STARS; SOUTH-GALACTIC-CAP; T-TAURI STARS; MU-M SPECTRA; EFFECTIVE TEMPERATURE; NEARBY STARS; STANDARDS AB Photometric observations at optical and near-infrared wavelengths are presented for members of a new sample of candidate Vega-like systems, or main sequence stars with excess infrared emission due to circumstellar dust. The observations are combined with IRAS fluxes to define the spectral energy distributions of the sources. Most of the sources show only photospheric emission at near-IR wavelengths, indicating a lack of hot (similar to 1000 K) dust. Mid-infrared spectra are presented for four sources from the sample. One of them, HD 150193, shows strong silicate emission, while another, HD 176363, was not detected. The spectra of two stars from our previous sample of Vega-like sources both show UIR-band emission, attributed to hydrocarbon materials. Detailed comparisons of the optical and IRAS positions suggest that in some cases the IRAS source is not physically associated with the visible star. Alternative associations are suggested for several of these sources. Fractional. excess luminosities are derived from the observed spectral energy distributions. The values found are comparable to those measured previously for other Vega-like sources. C1 UCL, Dept Phys & Astron, London WC1E 6BT, England. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. SAAO, Cape Town, South Africa. RP Sylvester, RJ (reprint author), UCL, Dept Phys & Astron, Gower St, London WC1E 6BT, England. EM rjs@star.ucl.ac.uk NR 76 TC 41 Z9 41 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 MAR 21 PY 2000 VL 313 IS 1 BP 73 EP 86 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 300UV UT WOS:000086272200012 ER PT J AU LeBlanc, AG Murray, IS Hawkes, RL Worden, P Campbell, MD Brown, P Jenniskens, P Correll, RR Montague, T Babcock, DD AF LeBlanc, AG Murray, IS Hawkes, RL Worden, P Campbell, MD Brown, P Jenniskens, P Correll, RR Montague, T Babcock, DD TI Evidence for transverse spread in Leonid meteors SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE meteors; meteoroids AB We report here evidence for significant transverse spread of the light production region in bright Leonid meteors. One Leonid meteor has an apparent spread in the light production region of about 600 m perpendicular to the flight path for the meteor, that transverse spread persisting for at least 0.3 s. We have also detected short-duration, jet-like features emanating from a bright Leonid meteor recorded in 1998. These jet-like features have maximum spatial dimensions up to 1.9 km. While we cannot definitively rule out instrumental artefacts as a cause for these jet-like features, they may be evidence of motion contributing to the observed spatial spread in the light production region. C1 Mt Allison Univ, Dept Phys, Sackville, NB E4L 1E6, Canada. USAF, Washington, DC 20330 USA. Univ Western Ontario, Dept Phys & Astron, London, ON N6A 3K7, Canada. NASA, Ames Res Ctr, SETI Inst, Moffett Field, CA 94035 USA. Headquarters USAF Space Command, Washington, DC 20546 USA. NASA Headquarters, Washington, DC 20546 USA. USAF, Res Lab, Space Vehicles Directorate, Kirtland AFB, NM 87117 USA. York Univ, Ctr Res Earth & Space Sci, N York, ON M3J 1P3, Canada. RP LeBlanc, AG (reprint author), St Marys Univ, Dept Phys & Astron, Halifax, NS B3H 3C3, Canada. NR 24 TC 19 Z9 19 U1 0 U2 1 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD MAR 21 PY 2000 VL 313 IS 1 BP L9 EP L13 DI 10.1046/j.1365-8711.2000.03347.x PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 300UV UT WOS:000086272200003 ER PT J AU Leon, R Wellman, J Liao, XZ Zou, J Cockayne, DJH AF Leon, R Wellman, J Liao, XZ Zou, J Cockayne, DJH TI Adatom condensation and quantum dot sizes in InGaAs/GaAs (001) SO APPLIED PHYSICS LETTERS LA English DT Article AB The sizes and concentrations of capped and surface InGaAs/GaAs quantum dots (QDs) grown under the same conditions have been investigated. Comparisons obtained with transmission electron microscopy and scanning probe microscopy imaging show a significant enlargement in the sizes of surface QDs compared with capped QDs. This discrepancy in dot dimensions increases with decreasing island surface densities and can be partially explained by thermal adatom condensation during sample cooling. These findings suggest a technique to estimate adatom concentrations and their migration lengths in strained heteroepitaxy. (C) 2000 American Institute of Physics. [S0003-6951(00)03312-X]. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Sydney, Australian Key Ctr Microscopy & Microanal, Sydney, NSW 2006, Australia. Univ Oxford, Dept Mat, Oxford OX1 3PH, England. RP Leon, R (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Liao, Xiaozhou/B-3168-2009; Zou, Jin/B-3183-2009 OI Liao, Xiaozhou/0000-0001-8565-1758; Zou, Jin/0000-0001-9435-8043 NR 7 TC 20 Z9 20 U1 0 U2 3 PU AMER INST PHYSICS PI MELVILLE PA 2 HUNTINGTON QUADRANGLE, STE 1NO1, MELVILLE, NY 11747-4501 USA SN 0003-6951 J9 APPL PHYS LETT JI Appl. Phys. Lett. PD MAR 20 PY 2000 VL 76 IS 12 BP 1558 EP 1560 DI 10.1063/1.126095 PG 3 WC Physics, Applied SC Physics GA 293MU UT WOS:000085857100024 ER PT J AU Loewenstein, M AF Loewenstein, M TI Heating of intergalactic gas and cluster scaling relations SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmology : theory; galaxies : clusters : general; intergalactic medium; X-rays : galaxies ID INITIAL MASS FUNCTION; INTRACLUSTER MEDIUM; X-RAY; DARK-MATTER; POOR GROUPS; GALAXIES; ABUNDANCES; ENRICHMENT; ASCA AB X-ray observations of galaxy groups and clusters are inconsistent with the predictions of the simplest hierarchical clustering models, wherein nonbaryonic and baryonic components are assembled together under the sole influence of gravity. These departures are in the sense that the intergalactic medium is hotter and more extended than expected, and become increasingly strong for less massive systems. I model these effects by constructing baseline sequences of hydrostatic polytropic models normalized to observations of high-temperature clusters and numerical simulations, and then transforming them by adding proscribed amounts of heat per particle at the cluster center. I present sequences with a universal value of this heating parameter that simultaneously reproduce recently published observed (gas and total gravitational) mass-temperature and entropy-temperature relations. The required amount of energy injection is consistent with constraints on the number of supernovae needed to account for observed intracluster silicon abundances, provided that energy injection is centrally concentrated. I argue that most of the heating occurred during or after the assembly of the cluster, and not exclusively in precollapse proto-cluster fragments. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. RP Loewenstein, M (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 662, Greenbelt, MD 20771 USA. NR 47 TC 74 Z9 74 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAR 20 PY 2000 VL 532 IS 1 BP 17 EP 27 DI 10.1086/308542 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 301VF UT WOS:000086330400002 ER PT J AU Aguirre, A Haimi, Z AF Aguirre, A Haimi, Z TI Cosmological constant or intergalactic dust? Constraints from the cosmic far-infrared background SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmic microwave background; cosmology : observations; cosmology : theory; galaxies : evolution; galaxies : formation ID HUBBLE-DEEP-FIELD; OPTICAL-PROPERTIES; STAR-FORMATION; GRAINS; SUPERNOVAE; PARTICLES; GRAPHITE; UNIVERSE; GALAXIES AB Recent observations of Type Ia supernovae (SNe) at redshifts 0 < z < 1 reveal a progressive dimming that has been interpreted as evidence for a cosmological constant of Omega(A) similar to 0.7. An alternative explanation of the SN results is an open universe with Omega(A) = 0 and the presence of greater than or similar to 0.1 mu m dust grains with a mass density of Omega(dust) similar to a few x 10(-5) in the intergalactic (IG) medium. The same dust that dims the SNe absorbs the cosmic UV/optical background radiation around similar to 1 mu m, and reemits it at far-infrared (FIR) wavelengths. Here we compare the FIR emission from TG dust with observations of the cosmic microwave (CMB) and cosmic far-infrared backgrounds (FIRB) by the DIRBE/FIRAS instruments. We find that the emission would not lead to measurable distortion of the CMB, but would represent a substantial fraction (greater than or similar to 75%) of the measured value of the FIRE in the 300-1000 mu m range. This contribution would be marginally consistent with the present unresolved fraction of the observed FIRE in an open universe. However, we find that IG dust probably could not reconcile the standard Omega = 1 CDM model with the SN observations, even if the necessary quantity of dust existed. Future observations, capable of reliably resolving the FIRE to a flux limit of similar to 0.5 mJy, along with a more precise measure of the coarse-grained FIRE, will provide a definitive test of the IG dust hypothesis in all cosmologies. C1 Harvard Univ, Dept Astron, Cambridge, MA 02138 USA. Fermilab Natl Accelerator Lab, NASA, Fermilab Astrophys Ctr, Batavia, IL 60510 USA. RP Harvard Univ, Dept Astron, 60 Garden St, Cambridge, MA 02138 USA. EM aaguirre@cfa.harvard.edu; zoltan@fnal.gov NR 45 TC 46 Z9 46 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD MAR 20 PY 2000 VL 532 IS 1 BP 28 EP 36 DI 10.1086/308557 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 301VF UT WOS:000086330400003 ER PT J AU Leitch, EM Readhead, ACS Pearson, TJ Myers, ST Gulkis, S Lawrence, CR AF Leitch, EM Readhead, ACS Pearson, TJ Myers, ST Gulkis, S Lawrence, CR TI A measurement of anisotropy in the cosmic microwave background on 7 '-22 ' scales SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmic microwave background; cosmology : observations ID FLUX-DENSITY SCALE; POWER SPECTRUM; NORTHERN SKY; RADIATION; FLUCTUATIONS; EMISSION; LIMIT AB We report a measurement of anisotropy in the cosmic microwave background radiation (CMBR) on 7'-22' scales. Observations of 36 fields near the North Celestial Pole (NCP) were made at 31.7 and 14.5 GHz, using the 5.5 m and 40 m telescopes at the Owens Valley Radio Observatory (OVRO) from 1993 to 1996. Multiepoch VLA observations at 8.5 and 15 GHz allow removal of discrete source contamination. After point-source subtraction, we detected significant structure, which we identify with emission from a combination of a steep-spectrum foreground and the CMBR. The foreground component is found to correlate with IRAS 100 mu m dust emission. Lack of H alpha emission near the NCP suggests that this foreground is either high-temperature thermal bremsstrahlung (T-e greater than or similar to 10(6) K), hat-spectrum synchrotron, or an exotic component of dust emission. On the basis of low-frequency maps of the NCP, we can restrict the spectral index of the foreground to beta greater than or equal to -2.2. Although the foreground signal dominates at 14.5 GHz, the extracted CMBR component contributes 88% of the variance at 31.7 GHz, yielding an rms fluctuation amplitude of 82(-9.1)(+12.1) mu K, including 4.3% calibration uncertainty and 12% sample variance (68% confidence). In terms of the angular power spectrum, C-t = [\a(l)(m)\(2)], averaged over a range of multipoles l = 361-756, the detected broadband amplitude is delta T-le = [l(l + 1)C-l/(2 pi)](1/2) = 59(-6.5)(+8.6) mu K. This measurement, when combined with small angular scale upper limits obtained at the OVRO, indicates that the CMBR angular power spectrum decreases between l similar to 600 and l similar to 2000 and is consistent with hat cosmological models. C1 CALTECH, Pasadena, CA 91125 USA. Univ Penn, Philadelphia, PA 19104 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Leitch, EM (reprint author), CALTECH, 105-24, Pasadena, CA 91125 USA. RI Pearson, Timothy/N-2376-2015 OI Pearson, Timothy/0000-0001-5213-6231 NR 39 TC 30 Z9 30 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAR 20 PY 2000 VL 532 IS 1 BP 37 EP 56 DI 10.1086/308529 PN 1 PG 20 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 301VF UT WOS:000086330400004 ER PT J AU Wilson, GW Knox, L Dodelson, S Coble, K Cheng, ES Cottingham, DA Fixsen, DJ Goldin, AB Inman, CA Kowitt, MS Meyer, SS Page, LA Puchalla, JL Ruhl, JE Silverberg, RF AF Wilson, GW Knox, L Dodelson, S Coble, K Cheng, ES Cottingham, DA Fixsen, DJ Goldin, AB Inman, CA Kowitt, MS Meyer, SS Page, LA Puchalla, JL Ruhl, JE Silverberg, RF TI New cosmic microwave background power spectrum constraints from MSAM1 SO ASTROPHYSICAL JOURNAL LA English DT Article DE balloons; cosmic microwave background; cosmology : observations; infrared : ISM : continuum ID ANISOTROPY; MARS AB We present new cosmic microwave background (CMB) anisotropy results from the combined analysis of the three flights of the first Medium Scale Anisotropy Measurement (MSAM1). This balloon-borne bolometric instrument measured about 10 deg(2) of sky at half-degree resolution in four frequency bands from 5.2 to 20 cm(-1) with a high signal-to-noise ratio. Here we present an overview of our analysis methods, compare the results from the three flights, derive new constraints on the CMB power spectrum from the combined data, and reduce the data to total power Wiener-filtered maps of the CMB. A key feature of this new analysis is a determination of the amplitude of CMB fluctuations at l similar to 400. The analysis technique is described in a companion paper (L. Knox). C1 Univ Chicago, Chicago, IL 60637 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. Fermi Natl Accelerator Lab, Batavia, IL 60510 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Global Sci & Technol Inc, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Raytheon ITSS, Greenbelt, MD 20771 USA. Stanford Res Syst, Sunnyvale, CA 94089 USA. Princeton Univ, Princeton, NJ 08544 USA. Univ Penn, Dept Phys & Astron, Philadelphia, PA 19104 USA. Univ Calif Santa Barbara, Santa Barbara, CA 93106 USA. RP Wilson, GW (reprint author), Univ Chicago, 5640 S Ellis Ave, Chicago, IL 60637 USA. NR 21 TC 15 Z9 15 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAR 20 PY 2000 VL 532 IS 1 BP 57 EP 64 DI 10.1086/308535 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 301VF UT WOS:000086330400005 ER PT J AU Williger, GM Smette, A Hazard, C Baldwin, JA McMahon, RG AF Williger, GM Smette, A Hazard, C Baldwin, JA McMahon, RG TI Evidence for large-scale structure in the Ly alpha forest at z > 2.6 SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmology : observations; intergalactic medium; large-scale structure of universe; quasars : absorption lines ID ABSORPTION SYSTEMS; REDSHIFT EVOLUTION; GASEOUS EXTENT; CLOUDS; ABSORBERS; GALAXIES; SIZE; ORIGIN; LINES; SUPERCLUSTERS AB We present a search for spatial and redshift correlations in a 2 Angstrom, resolution spectroscopic survey of the Ly alpha forest at 2.15 < z < 3.37 toward 10 QSOs concentrated within a 1 degrees diameter field. We find a signal at 2.7 sigma significance for correlations of the Ly alpha absorption-line wavelengths between different lines of sight over the whole redshift range. The significance rises to 3.2 sigma if we restrict the redshift range to 2.60 < z < 3.37, and to 4.0 sigma if we further restrict the sample to lines with rest equivalent widths 0.1 less than or equal to W-0 < 0.9 Angstrom. We conclude that a significant fraction of the Ly alpha forest arises in structures whose correlation length extends at least over 30' (similar to 26 h(-1) comoving Mpc at z = 2.6 for H-0 = 100 h km s(-1) Mpc(-1), Omega = 1.0, Lambda = 0). We have also calculated the three-dimensional two-point correlation function for Ly alpha absorbers; we do not detect any significant signal in the data. However, we note that line blending prevents us from detecting the signal produced by a 100% overdensity of Ly alpha absorbers in simulated data. We find that the Ly alpha forest redshift distribution provides a more sensitive test for such clustering than the three-dimensional two-point correlation function. C1 Max Planck Inst Astron, D-69117 Heidelberg, Germany. NASA, Goddard Space Flight Ctr, NOAO, Greenbelt, MD 20771 USA. Kapteyn Lab, NL-9700 AV Groningen, Netherlands. Univ Pittsburgh, Dept Phys & Astron, Pittsburgh, PA 15260 USA. Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England. Cerro Tololo Interamer Observ, La Serena, Chile. RP Williger, GM (reprint author), Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany. NR 67 TC 24 Z9 25 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAR 20 PY 2000 VL 532 IS 1 BP 77 EP 87 DI 10.1086/308526 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 301VF UT WOS:000086330400007 ER PT J AU Lane, WM Briggs, FH Smette, A AF Lane, WM Briggs, FH Smette, A TI Detection of warm and cold phases of the neutral ISM in a damped Ly alpha absorber SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : ISM; quasars : absorption lines; quasars : individual (B30738+313) ID MG-II ABSORPTION; NEARBY DWARF GALAXIES; CENTIMETER ABSORPTION; INTERSTELLAR-MEDIUM; LYMAN-ALPHA; QSO SURVEY; H-I; SYSTEMS; REDSHIFT; SPECTRA AB present a detailed study of the HI 21 cm absorption system at z = 0.0912 toward the radio quasar B0738+313. The uncommonly narrow main absorption line and weak secondary line are resolved for the first time and have FWHM velocities of Delta v(1) = 3.7 and Delta v(2) = 2.2 km s(-1) (main and secondary components, respectively). In addition, we find it necessary to add a third, broader shallow component to obtain a good fit to the spectrum. Although the harmonic mean spin temperature calculated by comparison of the 21 cm lines to the damped Ly alpha line is [T-s] = 775 +/- 100 K, the thermal kinetic temperatures of the two narrow components, calculated from their widths, are much lower: T-k less than or equal to 297 +/- 3 and less than or equal to 103 +/- 10 K, respectively. This is the first case of a redshifted absorption system for which T-k is measured to be less than [T-s]. We discuss this result in the context of a two-phase gas model, in which the damped Ly alpha gas is sensitive to a significant neutral column density of warm-phase gas as well as the cold-phase gas of the narrow 21 cm lines. The third component is interpreted as representing the warm-phase gas with T-k less than or equal to 5050 +/- 950 K. The combined column density of the three 21 cm components is approximately equal to that derived from fits to the damped Ly alpha line. C1 Kapteyn Astron Inst, NL-9700 AV Groningen, Netherlands. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Lane, WM (reprint author), Kapteyn Astron Inst, Postbus 800, NL-9700 AV Groningen, Netherlands. NR 27 TC 48 Z9 48 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAR 20 PY 2000 VL 532 IS 1 BP 146 EP 151 DI 10.1086/308578 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 301VF UT WOS:000086330400012 ER PT J AU Crenshaw, DM Kraemer, SB AF Crenshaw, DM Kraemer, SB TI Resolved spectroscopy of the narrow-line region in NGC 1068. I. The nature of the continuum emission SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : individual (NGC 1068); galaxies : Seyfert ID ACTIVE GALACTIC NUCLEI; GALAXY NGC-1068; FE-II; ULTRAVIOLET; SPECTROPOLARIMETRY; SPECTRUM AB We present the first long-slit spectra of the Seyfert 2 galaxy NGC 1068 obtained by the Space Telescope Imaging Spectrograph (STIS); the spectra cover the wavelength range 1150-10270 Angstrom at a spatial resolution of 0 ".05-0 ".1 and a spectral resolving power of lambda/Delta lambda approximate to 1000. In this first paper, we concentrate on the far-UV to near-IR continuum emission from the continuum "hot spot" and surrounding regions extending out to +/-6 ".0 (+/-432 pc) at a position angle of 202 degrees. In addition to the broad emission lines detected by spectropolarimetry, the hot spot shows the "little blue bump" in the 2000-4000 Angstrom range, which is due to Fe II and Balmer continuum emission. The continuum shape of the hot spot is indistinguishable from that of NGC 4151 and other Seyfert 1 galaxies. Thus, the hot spot is reflected emission from the hidden nucleus, due to electron scattering (as opposed to wavelength-dependent dust scattering). The hot spot is similar to 0 ".3 in extent and accounts for 20% of the scattered light in the inner 500 pc. We are able to deconvolve the extended continuum emission in this region into two components: electron-scattered light from the hidden nucleus (which dominates in the UV) and stellar light (which dominates in the optical and near-IR). The scattered light is heavily concentrated toward the hot spot, is stronger in the northeast, and is enhanced in regions of strong narrow-line emission. The stellar component is more extended, concentrated southwest of the hot spot, is dominated by an old (greater than or equal to 2 x 10(9) yr) stellar population, and includes a nuclear stellar cluster that is similar to 200 pc in extent. C1 Catholic Univ Amer, NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Crenshaw, DM (reprint author), Catholic Univ Amer, NASA, Goddard Space Flight Ctr, Code 681, Greenbelt, MD 20771 USA. NR 32 TC 23 Z9 23 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAR 20 PY 2000 VL 532 IS 1 BP 247 EP 255 DI 10.1086/308570 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 301VF UT WOS:000086330400021 ER PT J AU Kraemer, SB Crenshaw, DM AF Kraemer, SB Crenshaw, DM TI Resolved spectroscopy of the narrow-line region in NGC 1068. II. Physical conditions near the NGC 1068 "hot spot" SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : active; galaxies : individual (NGC 1068); galaxies : nuclei; galaxies : Seyfert ID ACTIVE GALACTIC NUCLEI; X-RAY ABSORPTION; SEYFERT-GALAXIES; FORBIDDEN EMISSION; GAS-COMPOSITION; ORION NEBULA; NGC-1068; SPECTRUM; ULTRAVIOLET; ORIGIN AB The physical conditions near the optical continuum peak ("hot spot") in the inner narrow-line region of the Seyfert 2 galaxy NGC 1068 are examined using ultraviolet and optical spectra and photoionization models. The spectra were taken with the Hubble Space Telescope/Space Telescope Imaging Spectrograph (STIS) through the 0 ".1 x 52 ".0 slit, covering the full STIS 1200-10000 Angstrom waveband, and are from a region that includes the hot spot, extending 0 ".2, or similar to 14 pc (for H-0 = 75 km s(-1) Mpc(-1)), in the cross-dispersion direction. The spectra show emission lines from a wide range of ionization states for the most abundant elements, similar to archival Faint Object Spectrograph spectra of the same region. Perhaps the most striking feature of these spectra is the presence of strong coronal emission lines, including [S XII] lambda 7611, which has hitherto been identified only in spectra of the solar corona. There is an apparent correlation between ionization energy and velocity of the emission lines with respect to the systemic velocity of the host galaxy, with the coronal fines blueshifted, most other high-excitation lines near systemic, nd some of the low-ionization lines redshifted. From the results of our modeling, we find that the emission-line gas is photoionized and consists of three principal components: (1) one in which most of the strong emission lines, such as [O III] lambda 5007, [Ne V] lambda 3426, and C IV lambda 1550, arise; (2) a more tenuous, highly ionized component, which is the source of the coronal-line emission; and (3) a component, which is not coplanar with the other two, in which the low-ionization and neutral lines, such as [N II] lambda 6548 and [O I] lambda 6300, are formed. The first two components are directly ionized by the EUV-X-ray continuum emitted by the central source, while the low-ionization gas is ionized by a combination of highly absorbed continuum radiation and a small fraction of unabsorbed continuum scattered by free electrons associated with the hot spot. The combination of covering factor and Thomson optical depth of the high-ionization components is insufficient to scatter the observed fraction of continuum radiation into our fine of sight. Therefore, the scattering must occur in an additional component of hot plasma, which contributes little or no UV/optical line emission. C1 Catholic Univ Amer, NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Kraemer, SB (reprint author), Catholic Univ Amer, NASA, Goddard Space Flight Ctr, Code 681, Greenbelt, MD 20771 USA. NR 66 TC 57 Z9 57 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAR 20 PY 2000 VL 532 IS 1 BP 256 EP 266 DI 10.1086/308572 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 301VF UT WOS:000086330400022 ER PT J AU Brown, TM Bowers, CW Kimble, RA Sweigart, AV Ferguson, HC AF Brown, TM Bowers, CW Kimble, RA Sweigart, AV Ferguson, HC TI Detection and photometry of hot horizontal branch stars in the core of M32 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : abundances; galaxies : evolution; galaxies : stellar content; stars : evolution; ultraviolet : galaxies; ultraviolet : stars ID ASYMPTOTIC GIANT BRANCH; OLD STELLAR POPULATIONS; INTERMEDIATE-MASS STARS; EARLY-TYPE GALAXIES; ELLIPTIC GALAXIES; GLOBULAR-CLUSTERS; PLANETARY-NEBULAE; CALIBRATION; EVOLUTION; SPECTRA AB We present the deepest near-UV image of M32 to date, which for the first time resolves hot horizontal branch (HB) stars in an elliptical galaxy. Given the near-solar metallicity of M32, much larger than that of globular clusters, the existence of an extended horizontal branch is a striking example of the second parameter effect, and, most importantly, provides direct evidence that hot PIE stars and their progeny are the major contributors to the UV upturn phenomenon observed in elliptical galaxies. Our image, obtained with the Space Telescope Imaging Spectrograph (STIS), detects approximately 8000 stars in a 25 " x 25 " field, centered 7." 7 from the galaxy nucleus. These stars span a range of 21-28 mag in the STMAG system, and in the deepest parts of the image, our catalog is reasonably complete (>25%) to a magnitude of 27. The hot HE spans a magnitude range of 25-27 mag at effective temperatures hotter than 8500 K. We interpret this near-UV luminosity function with an extensive set of HE and post-MB evolutionary tracks. Although the W-to-optical flux ratio in M32 is weak enough to be explained solely by the presence of post-asymptotic giant branch (post-AGB) stars, our image conclusively demonstrates that it arises from a small fraction (less than or similar to 5%) of the population passing through the hot HE phase. The production of these hot HE stars does not appear to rely upon dynamical mechanisms-mechanisms that map play a role in the HE morphology of globular clusters. The majority of the population presumably evolves through the red HE and subsequent post-AGE phases; however, we see far fewer UV-bright stars than expected from the lifetimes of canonical hydrogen-burning low-mass post-AGE tracks. There are several possible explanations: (1) the transition from AGE to T-eff > 60,000 Ii could be much more rapid than previously thought; (2) the vast majority of the post-AGE stars could be evolving along helium-burning tracks; (3) the post-AGE stars could be surrounded by circumstellar dust during the transition from the AGE to T-eff > 60,000 K. C1 NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. RP NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Code 681, Greenbelt, MD 20771 USA. EM tbrown@pulsar.gsfc.nasa.gov; bowers@band2.gsfc.nasa.gov; kimble@ccd.gsfc.nasa.gov; sweigart@bach.gsfc.nasa.gov; ferguson@stsci.edu NR 61 TC 106 Z9 107 U1 0 U2 3 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD MAR 20 PY 2000 VL 532 IS 1 BP 308 EP 322 DI 10.1086/308566 PN 1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 301VF UT WOS:000086330400029 ER PT J AU Wilkin, FP AF Wilkin, FP TI Modeling nonaxisymmetric bow shocks: Solution method and exact analytic solutions SO ASTROPHYSICAL JOURNAL LA English DT Article DE HII regions; hydrodynamics; ISM : bubbles; shock waves; stars : mass loss ID KEPLER SUPERNOVA REMNANT; DYNAMICS; NEBULA AB A new solution method is presented for steady state, momentum-conserving nonaxisymmetric bow shocks and colliding winds in the thin-shell limit. This is a generalization of previous formulations to include a density gradient in the preshock ambient medium as well as anisotropy in the preshock wind. For cases where the wind is unaccelerated, the formalism yields exact, analytic solutions. Solutions are presented for two bow shock cases: (1) that due to a star moving supersonically with respect to an ambient medium with a density gradient perpendicular to the stellar velocity, and (2) that due to a star with a misaligned, axisymmetric wind moving in a uniform medium. It is also shown under quite general circumstances that the total rate of energy thermalization in the bow shock is independent of the details of the wind asymmetry, including the orientation of the nonaxisymmetric driving wind, provided the wind is nonaccelerating and point-symmetric. A typical feature of the solutions is that the region near the standoff point is tilted so that the star does not lie along the bisector of a parabolic fit to the standoff region. The principal use of this work is to infer the origin of bow shock asymmetries, whether due to the wind or ambient medium or both. C1 CALTECH, IPAC, Pasadena, CA 91125 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Wilkin, FP (reprint author), CALTECH, IPAC, MS 100-22, Pasadena, CA 91125 USA. NR 23 TC 36 Z9 36 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAR 20 PY 2000 VL 532 IS 1 BP 400 EP 414 DI 10.1086/308576 PN 1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 301VF UT WOS:000086330400036 ER PT J AU Pagano, I Linsky, JL Carkner, L Robinson, RD Woodgate, B Timothy, G AF Pagano, I Linsky, JL Carkner, L Robinson, RD Woodgate, B Timothy, G TI HST/STIS echelle spectra of the dM1e star AU Microscopii outside of flares SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars : chromospheres; stars : coronae; stars : hare; ultraviolet : stars ID HIGH-RESOLUTION SPECTROGRAPH; OBSERVING STELLAR CORONAE; RS-CANUM-VENATICORUM; TRANSITION REGION; OUTER ATMOSPHERES; QUIET REGIONS; SOLAR CORONA; AR-LACERTAE; COOL STARS; O-IV AB We report on observations of the dM1e flare star AU Microscopii obtained with the Space Telescope Imaging Spectrograph (STIS) on 1998 September 6. A total of 10,105 s of observations were obtained with the medium-resolution E140M grating. We report here on the 9200 s of "quiescent" data when the star did not obviously flare. In this data set, we identify 142 emission lines from 28 species, including low-temperature chromospheric lines (e.g., C I, O I), transition-region lines (e.g., C II-IV, N IV, O III-V, Si II-IV), and the coronal line Fe XXI 1354 Angstrom. There are a number of intersystem lines that are useful for measuring electron densities. We discuss line redshifts and the broad wings of transition-region lines that provide evidence of microflare heating. We derive the emission-measure distribution and compare it with the solar one. We also discuss the shape and formation mechanisms of the He II 1640 Angstrom lines. The analysis of the flare data and of the interstellar absorption features seen in the H I, D I, C II, and O I resonance lines will be published elsewhere. C1 Univ Colorado, Joint Inst Lab Astrophys, Boulder, CO 80309 USA. Univ Colorado, Natl Inst Stand & Technol, Boulder, CO 80309 USA. Catholic Univ Amer, Inst Astrophys & Computat Sci, Washington, DC 20034 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Nightsen Inc, Warwick, RI 02886 USA. Osserv Astrofis Catania, Catania, Italy. RP Univ Colorado, Joint Inst Lab Astrophys, Boulder, CO 80309 USA. EM ipagano@alpha4.ct.astro.it RI Pagano, Isabella/I-6934-2015 OI Pagano, Isabella/0000-0001-9573-4928 NR 61 TC 39 Z9 39 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD MAR 20 PY 2000 VL 532 IS 1 BP 497 EP 513 DI 10.1086/308559 PN 1 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 301VF UT WOS:000086330400045 ER PT J AU Lin, D Smith, IA Liang, EP Bridgman, T Smith, DM Marti, J Durouchoux, P Mirabel, IF Rodriguez, LF AF Lin, D Smith, IA Liang, EP Bridgman, T Smith, DM Marti, J Durouchoux, P Mirabel, IF Rodriguez, LF TI Simultaneous observations of GRS 1758-258 in 1997 by VLA, IRAM, SEST, RXTE, and OSSE: Spectroscopy and timing SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; black hole physics; gamma rays : observations; radio continuum : stars; stars : individual (GRS 1758-258); X-rays : stars ID X-RAY SOURCE; MOLECULAR CLOUD; GALACTIC-CENTER; COMPTONIZATION MODELS; SOURCE GRS-1758-258; TIME VARIATIONS; BLACK-HOLE; 1E-1740.7-2942; 1E1740.7-2942; COUNTERPART AB We report the results of our multiwavelength observations of GRS 1758-258 made in 1997 August. The energy bands include radio, millimeter, X-ray, and gamma-ray. The observations enable us to obtain a complete spectrum of the source over an energy range of 2-500 keV. The spectrum shows that GRS 1758-258 was in its hard state. It is well fit by the Sunyaev-Titarchuk (ST) Compton scattering model with a plasma temperature of 45 keV and a Thomson depth of 3.3. Taking relativistic effects into account, we get a little higher plasma temperature (52 keV) by using the improved version of the ST model (HT model) plus a soft blackbody component. The spectrum is also fit by a power law with an exponential cutoff (PLE) plus a soft blackbody component. The temperature of the soft components in both models is about 1.2 keV, and the energy flux is less than 1.5% of the total X-ray and gamma-ray flux. The deduced hydrogen column density is in the range of (0.93-2.0) x 10(22) cm(-2) NO significant iron lines are detected. The radio emission has a flat energy spectrum. The daily radio, X-ray, and gamma-ray light curves show that GRS 1758-258 was stable during the observation period but was highly variable on smaller timescales in X-rays and gamma rays. The power density spectra are typical for the low state, but we find the photon flux for the 5-10 keV band to be more variable than that in the other two energy bands (2-5 keV and 10-40 keV). Harmonically spaced quasi-periodic oscillations are observed in the power spectra. The phase lags between the hard photons and the soft photons have a hat distribution over a wide range of frequencies. A high coherence of about 1.0 (0.01-1 Hz) between the hard photons and the soft photons is also obtained in our observations. We compare these results with two variation models. Our millimeter observations did not reveal any conclusive signatures of an interaction between the jet from GRS 1758-258 and the molecular cloud that lies in the direction of GRS 1758-258. C1 Rice Univ, Dept Space Phys & Astron, Houston, TX 77005 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Univ Jaen, Dept Fis, Escuela Politecn Super, E-23071 Jaen, Spain. CEA, DSM, DAPNIA, Serv Astrophys, F-91191 Gif Sur Yvette, France. Inst Astron & Fis Espacio, RA-1428 Buenos Aires, DF, Argentina. Univ Nacl Autonoma Mexico, Inst Astron, Morelia 58090, Michoacan, Mexico. RP Rice Univ, Dept Space Phys & Astron, 6100 S Main, Houston, TX 77005 USA. EM lin@spacsun.rice.edu NR 48 TC 22 Z9 22 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD MAR 20 PY 2000 VL 532 IS 1 BP 548 EP 562 DI 10.1086/308553 PN 1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 301VF UT WOS:000086330400049 ER PT J AU Pereyra, NA Kallman, TR Blondin, JM AF Pereyra, NA Kallman, TR Blondin, JM TI Hydrodynamic models of line-driven accretion disk winds. II. Adiabatic winds from nonisothermal disks SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; hydrodynamics; novae, cataclysmic variables; stars : mass loss ID VARIABLE RW TRIANGULI; HIGH-VELOCITY WINDS; UX-URSAE-MAJORIS; X-RAY BINARIES; CATACLYSMIC VARIABLES; DWARF NOVA; SS CYGNI; ULTRAVIOLET-SPECTRUM; IUE OBSERVATIONS; EMISSION-LINES AB We present here numerical hydrodynamic simulations of line-driven accretion disk winds in cataclysmic variable systems. We calculate wind mass-loss rate, terminal velocities, and line profiles for C Iv (1550 Angstrom) for various viewing angles. The models are 2.5-dimensional, include an energy balance condition, and calculate the radiation held as a function of position near an optically thick accretion disk. The model results show that centrifugal forces produce collisions of streamlines in the disk wind that in turn generate an enhanced density region, underlining the necessity of two-dimensional calculations where these forces may be represented. For disk luminosity L-disk = L., white dwarf mass M-wd = 0.6 M., and white dwarf radii R-wd = 0.01 R., we obtain a wind mass-loss rate of (M) over dot(wind) = 8 x 10(-12) M. yr(-1), and a terminal velocity of similar to 3000 km s(-1). The line profiles we obtain are consistent with observations in their general form, in particular in the maximum absorption at roughly half the terminal velocity for the blueshifted component, in the magnitudes of the wind velocities implied by the absorption components, in the FWHM of the emission components, and in the strong dependence in inclination angle. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. N Carolina State Univ, Dept Phys, Raleigh, NC 27695 USA. RP Pereyra, NA (reprint author), Univ Maryland, Dept Astron, College Pk, MD 20742 USA. NR 65 TC 16 Z9 16 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAR 20 PY 2000 VL 532 IS 1 BP 563 EP 580 DI 10.1086/308527 PN 1 PG 18 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 301VF UT WOS:000086330400050 ER PT J AU Miesch, MS Elliott, JR Toomre, J Clune, TL Glatzmaier, GA Gilman, PA AF Miesch, MS Elliott, JR Toomre, J Clune, TL Glatzmaier, GA Gilman, PA TI Three-dimensional spherical simulations of solar convection. I. Differential rotation and pattern evolution achieved with laminar and turbulent states SO ASTROPHYSICAL JOURNAL LA English DT Article DE convection; hydrodynamics; stars : interiors; Sun : interior; Sun : rotation; turbulence ID LINEAR DYNAMOS DRIVEN; COMPRESSIBLE CONVECTION; NUMERICAL SIMULATIONS; HELIOSEISMIC CONSTRAINTS; SHELL; ZONE; SURFACE; TACHOCLINE; FLOWS; NONUNIFORM AB Rotationally constrained convection possesses velocity correlations that transport momentum and drive mean flows such as differential rotation. The nature of this transport can be very complex in turbulent flow regimes, where large-scale, coherent vorticity structures and mean flows can be established by smaller scale turbulence through inverse cascades. The dynamics of the highly turbulent solar convection zone therefore may be quite different than in early global-scale numerical models, which were limited by computational resources to nearly laminar flows. Recent progress in high-performance computing technology and ongoing helioseismic investigations of the dynamics of the solar interior have motivated us to develop more sophisticated numerical models of global-scale solar convection. Here we report three-dimensional simulations of compressible, penetrative convection in rotating spherical shells in both laminar and turbulent parameter regimes. The convective structure in the laminar case is dominated by "banana cells," but the turbulent case is much more complex, with an intricate, rapidly evolving downflow network in the upper convection zone and an intermittent, plume-dominated structure in the lower convection zone and overshoot region. Convective patterns generally propagate prograde at low latitudes and retrograde at high latitudes relative to the local rotation. The differential rotation profiles show some similarity with helioseismic determinations of the solar rotation but still exhibit significantly more cylindrical alignment. Strong, intermittent, vortical downflow lanes and plumes play an important dynamical role in turbulent flow regimes and are responsible for significant differences relative to laminar flows with regard to momentum and energy transport and to the structure of the overshoot region at the base of the convection zone. C1 Univ Cambridge, Dept Appl Math & Theoret Phys, Cambridge CB3 9EW, England. Univ Colorado, Joint Inst Lab Astrophys, Boulder, CO 80309 USA. NASA, Goddard Space Flight Ctr, SGI, Greenbelt, MD 20771 USA. Univ Calif Santa Cruz, Dept Earth Sci, Santa Cruz, CA 95064 USA. Natl Ctr Atmospher Res, High Altitude Observ, Boulder, CO 80307 USA. RP Univ Cambridge, Dept Appl Math & Theoret Phys, Silver St, Cambridge CB3 9EW, England. EM M.S.Miesch@damtp.cam.ac.uk RI Miesch, Mark/B-1104-2008; OI Miesch, Mark/0000-0003-1976-0811 NR 62 TC 215 Z9 218 U1 0 U2 6 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD MAR 20 PY 2000 VL 532 IS 1 BP 593 EP 615 DI 10.1086/308555 PN 1 PG 23 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 301VF UT WOS:000086330400052 ER PT J AU Sterling, AC Hudson, HS Thompson, BJ Zarro, DM AF Sterling, AC Hudson, HS Thompson, BJ Zarro, DM TI Yohkoh SXT and SOHO EIT observations of sigmoid-to-arcade evolution of structures associated with halo coronal mass ejections SO ASTROPHYSICAL JOURNAL LA English DT Article DE Sun : corona; Sun : flares; Sun : particle emission; Sun : UV radiation; Sun : X-rays, gamma rays ID EARTH CONNECTION EVENT; X-RAY TELESCOPE; MAGNETIC RECONNECTION; LASCO OBSERVATIONS; GEOMAGNETIC STORM; RADIO EMISSIONS; JANUARY 1997; SOLAR-FLARES; FILAMENT; DISTURBANCES AB A subset of the solar-disk counterparts to halo coronal mass ejections (CMEs) displays an evolution in soft X-rays (SXR) that is characterized by a preflare S-shaped structure, dubbed a "sigmoid," which evolves into a postflare cusp or arcade. We examine the morphological properties of the evolution of sigmoids into cusps and arcades for four such regions associated with SXR flares, using the Soft X-Ray Telescope (SXT) on the Yohkoh satellite and the EW Imaging Telescope (EIT) on the Solar and Heliospheric Observatory (SOHO) satellite. Most of our EIT observations are with the 1.5 MIG. 195 Angstrom Fe XII channel. At most, there is only a weak counterpart to the SXR sigmoid in the preflare 195 Angstrom EUV images, indicating that the preflare sigmoid has a temperature greater than 1.5 MK. While mon identifiable than in the 195 Angstrom channel, a clear preflare sigmoid is also not observed in the 2.0 ME: EIT 284 Angstrom Fe XV channel. During the time of the flare, however, an EUV sigmoid brightens near the location of the SXR preflare sigmoid. Initially the SXR sigmoid lies along a magnetic neutral line. As the SXR flare progresses, new held lines appear with orientation normal to the neutral line and with footpoints rooted in regions of opposite polarity; these footpoints are different from those of the preflare sigmoid. The cusp structures in SXRs develop from these newly ignited held lines. In EIT images, the EW sigmoid broadens as the flare progresses, forming an arcade beneath the SXR cusp. Our findings are consistent with a standard picture in which the origin of the hare and CME is caused by the eruption of a filament-like feature, with the stretching of held lines producing a cusp. We infer that the cusp-producing fields may be overlying the sigmoid fields in the preflare phase, but we do not directly observe such preflare overlying fields. C1 Computat Phys Inc, Fairfax, VA 22031 USA. USN, Res Lab, EO Hulburt Ctr Space Res, Washington, DC 20375 USA. Solar Phys Res Corp, Tucson, AZ 85718 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. SM&A, Syst Solut Grp, Greenbelt, MD 20771 USA. RP Sterling, AC (reprint author), NASA, George C Marshall Space Flight Ctr, Dept Space Sci, SD50, Huntsville, AL 35812 USA. RI Thompson, Barbara/C-9429-2012 NR 53 TC 120 Z9 123 U1 1 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAR 20 PY 2000 VL 532 IS 1 BP 628 EP 647 DI 10.1086/308554 PN 1 PG 20 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 301VF UT WOS:000086330400055 ER PT J AU Boezio, M Carlson, P Francke, T Weber, N Suffert, M Hof, M Menn, W Simon, M Stephens, SA Bellotti, R Cafagna, F Castellano, M Circella, M De Marzo, C Finetti, N Papini, P Piccardi, S Spillantini, P Ricci, M Casolino, M De Pascale, MP Morselli, A Picozza, P Sparvoli, R Barbiellini, G Bravar, U Schiavon, P Vacchi, A Zampa, N Grimani, C Mitchell, JW Ormes, JF Streitmatter, RE Golden, RL Stochaj, SJ AF Boezio, M Carlson, P Francke, T Weber, N Suffert, M Hof, M Menn, W Simon, M Stephens, SA Bellotti, R Cafagna, F Castellano, M Circella, M De Marzo, C Finetti, N Papini, P Piccardi, S Spillantini, P Ricci, M Casolino, M De Pascale, MP Morselli, A Picozza, P Sparvoli, R Barbiellini, G Bravar, U Schiavon, P Vacchi, A Zampa, N Grimani, C Mitchell, JW Ormes, JF Streitmatter, RE Golden, RL Stochaj, SJ TI The cosmic-ray electron and positron spectra measured at 1 Au during solar minimum activity SO ASTROPHYSICAL JOURNAL LA English DT Article DE balloons; cosmic rays; elementary particles; Sun : activity ID CAPRICE-RICH DETECTOR; IMAGING CALORIMETER; BALLOON FLIGHT; SPECTROMETER; PERFORMANCE; MODULATION; RADIATION; RATIO; FLUX AB We report on a new measurement of the cosmic-ray electron and positron spectra. The data were collected by the balloon-borne experiment CAPRICE94, which was flown from Lynn Lake, Canada, on 1994 August 8-9 at an altitude corresponding to 3.9 g cm(-2) of average residual atmosphere. The experiment used the NMSU-WIZARD/CAPRICE94 balloon-borne magnet spectrometer equipped with a solid radiator Ring Imaging Cerenkov (RICH) detector, a time-of-flight system, a tracking device consisting of drift chambers and multiwire proportional chambers, and a silicon-tungsten calorimeter. This was the first time a RICH detector was used together with an imaging calorimeter in a balloon-borne experiment. A total of 3211 electrons, with a rigidity at the spectrometer between 0.3 and 30 GV, and 734 positrons, between 0.3 and 10 GV, were identified with small backgrounds from other particles. The absolute energy spectra were determined in the energy region at the top of the atmosphere between 0.46 and 43.6 GeV for electrons and between 0.46 and 14.6 GeV for positrons. We found that the observed positron spectrum and the positron fraction are consistent with a pure secondary origin. A comparison of the theoretically predicted interstellar spectrum of electrons shows that the injection spectrum of primary electrons is steeper than that of the nucleonic components of cosmic rays. Furthermore, the observed electron and positron spectra can be reproduced from the interstellar spectra by a spherically symmetric model for solar modulation; hence, the modulation is independent of the sign of the particle charge. C1 Royal Inst Technol KTH, S-10405 Stockholm, Sweden. Ctr Rech Nucl, F-67037 Strasbourg, France. Univ Gesamthsch Siegen, D-57068 Siegen, Germany. Tata Inst Fundamental Res, Bombay 400005, Maharashtra, India. Univ Bari, Dipartmento Fis, I-70126 Bari, Italy. Ist Nazl Fis Nucl, Sez Bari, I-70126 Bari, Italy. Univ Florence, Dipartimento Fis, I-50125 Florence, Italy. Ist Nazl Fis Nucl, Sez Firenze, I-50125 Florence, Italy. Ist Nazl Fis Nucl, Lab Nazl Frascati, I-00044 Frascati, Italy. Univ Roma Tor Vergata, Dipartimento Fis, I-00133 Rome, Italy. Ist Nazl Fis Nucl, Sez Roma, I-00133 Rome, Italy. Univ Trieste, Dipartmento Fis, I-34147 Trieste, Italy. Ist Nazl Fis Nucl, Sez Trieste, I-34147 Trieste, Italy. Univ Urbino, Dipartimento Fis, I-61029 Urbino, Italy. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. New Mexico State Univ, PAL, Las Cruces, NM 88003 USA. RP Boezio, M (reprint author), Royal Inst Technol KTH, S-10405 Stockholm, Sweden. RI Morselli, Aldo/G-6769-2011; Castellano, Marcello/J-3428-2012; Cafagna, Francesco/A-9299-2010; Vacchi, Andrea/C-1291-2010; OI Morselli, Aldo/0000-0002-7704-9553; Castellano, Marcello/0000-0002-4211-2903; Cafagna, Francesco/0000-0002-7450-4784; Vacchi, Andrea/0000-0003-3855-5856; Bellotti, Roberto/0000-0003-3198-2708; casolino, marco/0000-0001-6067-5104; Sparvoli, Roberta/0000-0002-6314-6117; Picozza, Piergiorgio/0000-0002-7986-3321; Papini, Paolo/0000-0003-4718-2895; Boezio, Mirko/0000-0002-8015-2981 NR 53 TC 186 Z9 188 U1 1 U2 11 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAR 20 PY 2000 VL 532 IS 1 BP 653 EP 669 DI 10.1086/308545 PN 1 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 301VF UT WOS:000086330400057 ER PT J AU Akerlof, C Balsano, R Barthelmy, S Bloch, J Butterworth, P Casperson, D Cline, T Fletcher, S Frontera, F Gisler, G Heise, J Hills, J Hurley, K Kehoe, R Lee, B Marshall, S McKay, T Pawl, A Piro, L Szymanski, J Wren, J AF Akerlof, C Balsano, R Barthelmy, S Bloch, J Butterworth, P Casperson, D Cline, T Fletcher, S Frontera, F Gisler, G Heise, J Hills, J Hurley, K Kehoe, R Lee, B Marshall, S McKay, T Pawl, A Piro, L Szymanski, J Wren, J TI Prompt optical observations of gamma-ray bursts SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays : bursts; gamma rays : observations ID 28 FEBRUARY 1997; IDENTIFICATION AB The Robotic Optical Transient Search Experiment (ROTSE) seeks to measure simultaneous and early afterglow optical emission from gamma-ray bursts (GRBs). A search for optical counterparts to six GRBs with localization errors of 1 deg(2) or better produced no detections. The earliest limiting sensitivity is m(ROTSE) > 13.1 at 10.85 s (5 s exposure) after the gamma-ray rise, and the best limit is m(ROTSE) > 16.0 at 62 minutes (897 s exposure). These are the most stringent limits obtained for the GRB optical counterpart brightness in the first hour after the burst. Consideration of the gamma-ray fluence and peak flux for these bursts and for GRB 990123 indicates that there is not a strong positive correlation between optical flux and gamma-ray emission. C1 Univ Michigan, Dept Astron, Ann Arbor, MI 48109 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Ferrara, I-44100 Ferrara, Italy. Ruimteonderzoek, Space Res Org Netherlands, NL-3584 CA Utrecht, Netherlands. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Fermi Natl Accelerator Lab, Batavia, IL 60510 USA. Univ Calif Lawrence Livermore Natl Lab, Livermore, CA 94550 USA. CNR, Inst Astrofis Spaziale, Rome, Italy. RP Akerlof, C (reprint author), Univ Michigan, Dept Astron, 830 Dennison,501 E Univ Ave, Ann Arbor, MI 48109 USA. RI Barthelmy, Scott/D-2943-2012; McKay, Timothy/C-1501-2009; PIRO, LUIGI/E-4954-2013 OI McKay, Timothy/0000-0001-9036-6150; PIRO, LUIGI/0000-0003-4159-3984 NR 24 TC 36 Z9 36 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAR 20 PY 2000 VL 532 IS 1 BP L25 EP L28 DI 10.1086/312567 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 301VH UT WOS:000086330600007 ER PT J AU Blasi, P AF Blasi, P TI Stochastic acceleration and nonthermal radiation in clusters of galaxies SO ASTROPHYSICAL JOURNAL LA English DT Article DE acceleration of particles; galaxies : dusters : general; X-rays : galaxies ID COMA CLUSTER; MAGNETIC-FIELD; EMISSION AB We calculate the distribution of electrons in clusters of galaxies, which results from thermalization processes in the presence of stochastic acceleration due to plasma waves. We show that the electron distribution can deviate from a Maxwell-Boltzmann distribution because of the effect of the stochastic energy gain, provided that waves can be sustained against damping. The bremsstrahlung emission of the nonthermal tail of electrons can result in a flux of hard X-rays that is compatible with the ones recently detected in some clusters of galaxies. C1 NASA, Fermilab Astrophys Grp, Fermi Natl Accelerator Lab, Batavia, IL 60510 USA. RP Blasi, P (reprint author), NASA, Fermilab Astrophys Grp, Fermi Natl Accelerator Lab, Box 500,500 Wilson Rd, Batavia, IL 60510 USA. RI Blasi, Pasquale/O-9345-2015 OI Blasi, Pasquale/0000-0003-2480-599X NR 18 TC 51 Z9 51 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAR 20 PY 2000 VL 532 IS 1 BP L9 EP L12 DI 10.1086/312551 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 301VH UT WOS:000086330600003 ER PT J AU Castellano, T Jenkins, J Trilling, DE Doyle, L Koch, D AF Castellano, T Jenkins, J Trilling, DE Doyle, L Koch, D TI Detection of planetary transits of the star HD 209458 in the Hipparcos data set SO ASTROPHYSICAL JOURNAL LA English DT Article DE methods : data analysis; planetary systems; stars : individual (HD 209458) ID MISSION; KEPLER AB A search of the Hipparcos satellite photometry data for the star HD 209458 reveals evidence for a planetary transit signature consistent with the planetary properties reported by Henry et al. and Charbonneau et al. and allows further refinement of the planet's orbital period. The long time baseline (about 2926 days of 830 periods) from the best Hipparcos transit-like event to the latest transit reported by Henry et al, for the night of 1999 November 15 (UT) allows for an orbital period determination of 3.524736 days with an uncertainty of 0.000045 days (3.9 s). The transit events observed by Charbonneau et al. fall at the interim times expected to within the errors of this newly derived period. A series of statistical tests was performed to assess the likelihood of these events occurring by chance. This was crucial given the ill-conditioned problem presented by the sparse sampling of the light curve and the non-Gaussian distribution of the points. Monte Carlo simulations using bootstrap methods with the actual Hipparcos HD 209358 data set indicate that the transit-like signals of the depth observed would only be produced by chance in 21 out of 1 million trials. The transit durations and depths obtained from the Hipparcos data are also consistent with those determined by Charbonneau et al. and Henry et al. within the limitations of the sampling intervals and photometric precision of the Hipparcos data. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Calif Santa Cruz, Dept Astron & Astrophys, Santa Cruz, CA 95064 USA. SETI Inst, Mt View, CA 94043 USA. Univ Calif Santa Cruz, Lick Observ, UCO, Santa Cruz, CA 95064 USA. RP Castellano, T (reprint author), NASA, Ames Res Ctr, MS 245-6, Moffett Field, CA 94035 USA. NR 16 TC 32 Z9 32 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAR 20 PY 2000 VL 532 IS 1 BP L51 EP L53 DI 10.1086/312565 PN 2 PG 3 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 301VH UT WOS:000086330600013 ER PT J AU Helou, G Lu, NY Werner, MW Malhotra, S Silbermann, N AF Helou, G Lu, NY Werner, MW Malhotra, S Silbermann, N TI The mid-infrared spectra of normal galaxies SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : ISM; infrared : ISM : lines and bands ID SMALL GRAINS; SPECTROPHOTOMETRY; EMISSION; COLORS; ISOCAM; NGC-6946; VIRGO AB The mid-infrared spectra (2.5-5 and 5.7-11.6 mu m) obtained by ISOPHOT reveal the interstellar medium emission from galaxies powered by star formation to be strongly dominated by the aromatic features at 6.2, 7.7, 8.6, and 11.3 mu m. Additional emission appears in between the features, and an underlying continuum is clearly evident at 3-5 mu m. This continuum would contribute about a third of the luminosity in the 3-13 mu m range. The features together carry 5%-30% of the 40-120 mu m far-infrared (FIR) luminosity. The relative fluxes in individual features depend very weakly on galaxy parameters such as the far-infrared colors, direct evidence that the emitting particles are not in thermal equilibrium. The dip at 10 mu m is unlikely to result from silicate absorption since its shape is invariant among galaxies. The continuum component has a f(upsilon) proportional to upsilon(+0.65) shape between 3 and 5 mu m and carries 1%-4% of the FIR luminosity; its extrapolation to longer wavelengths falls well below the spectrum in the 6-12 mu m range. This continuum component is almost certainly of nonstellar origin and is probably due to fluctuating grains without aromatic features. The spectra reported here typify the integrated emission from the interstellar medium of the majority of star-forming galaxies and could thus be used to obtain redshifts of highly extincted galaxies up to z = 3 with SIRTF. C1 CALTECH, Ctr Infrared Proc & Anal, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Helou, G (reprint author), CALTECH, Ctr Infrared Proc & Anal, MS 100-22,770 S Wilson Ave, Pasadena, CA 91125 USA. NR 38 TC 81 Z9 81 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAR 20 PY 2000 VL 532 IS 1 BP L21 EP L24 DI 10.1086/312549 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 301VH UT WOS:000086330600006 ER PT J AU Carney, PS Fischer, DG Foley, JT Friberg, AT Shchegrov, AV Visser, TD Wolf, E AF Carney, PS Fischer, DG Foley, JT Friberg, AT Shchegrov, AV Visser, TD Wolf, E TI Comment - Evanescent waves do contribute to the far field SO JOURNAL OF MODERN OPTICS LA English DT Article C1 Univ Rochester, Dept Phys & Astron, Rochester, NY 14627 USA. Univ Rochester, Rochester Theory Ctr Opt Sci & Engn, Rochester, NY 14627 USA. NASA, Glenn Res Ctr, Natl Ctr Micrograv Res Fluids & Combust, Cleveland, OH 44135 USA. Mississippi State Univ, Dept Phys & Astron, Mississippi State, MS 39762 USA. Royal Inst Technol, Dept Phys Opt 2, S-10044 Stockholm, Sweden. Free Univ Amsterdam, Dept Phys & Astron, NL-1081 HV Amsterdam, Netherlands. RP Carney, PS (reprint author), Univ Rochester, Dept Phys & Astron, 601 Elmwood Ave, Rochester, NY 14627 USA. NR 6 TC 6 Z9 6 U1 0 U2 1 PU TAYLOR & FRANCIS LTD PI LONDON PA 11 NEW FETTER LANE, LONDON EC4P 4EE, ENGLAND SN 0950-0340 J9 J MOD OPTIC JI J. Mod. Opt. PD MAR 20 PY 2000 VL 47 IS 4 BP 757 EP 758 DI 10.1080/09500340008233395 PG 2 WC Optics SC Optics GA 293VN UT WOS:000085874200018 ER PT J AU Schultz, MG Jacob, DJ Bradshaw, JD Sandholm, ST Dibb, JE Talbot, RW Singh, HB AF Schultz, MG Jacob, DJ Bradshaw, JD Sandholm, ST Dibb, JE Talbot, RW Singh, HB TI Chemical NOx budget in the upper troposphere over the tropical South Pacific SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID REACTIVE NITROGEN; NITRIC-ACID; REMOTE TROPOSPHERE; GLOBAL SIMULATION; TRANSPORT MODEL; HNO3/NOX RATIO; OZONE BUDGET; ACETIC-ACIDS; AEROSOLS; CHEMISTRY AB The chemical NOx budget in the upper troposphere over the tropical South Pacific is analyzed using aircraft measurements made at 6-12 km altitude in September 1995 during the Global Tropospheric Experiment (GTE) Pacific Exploratory Mission (PEM) Tropics A campaign. Chemical loss and production rates of NOx along the aircraft flight tracks are calculated with a photochemical model constrained by observations. Calculations using a standard chemical mechanism show a large missing source for NOx; chemical loss exceeds chemical production by a factor of 2.4 on average. Similar or greater NOx budget imbalances have been reported in analyses of data from previous field studies. Ammonium aerosol concentrations in PEM-Tropics A generally exceeded sulfate on a charge equivalent basis, and relative humidities were low (median 25% relative to ice). This implies that the aerosol could be dry in which case N2O5 hydrolysis would be suppressed as a sink for NOx. Suppression of N2O5 hydrolysis and adoption of new measurements of the reaction rate constants for NO2 + OH + M and HNO3 + OH reduces the median chemical imbalance in the N-x budget for PEM-Tropics A from 2.4 to 1.9. The remaining imbalance cannot be easily explained from known chemistry or long-range transport of primary NOx and may imply a major gap in our understanding of the chemical cycling of NOx in the free troposphere. C1 Univ New Hampshire, Inst Study Earth Oceans & Space, Durham, NH 03824 USA. Harvard Univ, Div Engn & Appl Sci, Cambridge, MA 02139 USA. Harvard Univ, Dept Earth & Planetary Sci, Cambridge, MA 02139 USA. Georgia Inst Technol, Sch Earth & Atmospher Sci, Atlanta, GA 30332 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Schultz, MG (reprint author), Max Planck Inst Meteorol, Bundesstr 55, D-20146 Hamburg, Germany. EM martin.schultz@dkrz.de; djj@io.harvard.edu RI Schultz, Martin/I-9512-2012 OI Schultz, Martin/0000-0003-3455-774X NR 64 TC 17 Z9 17 U1 0 U2 12 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAR 16 PY 2000 VL 105 IS D5 BP 6669 EP 6679 DI 10.1029/1999JD900994 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 294KT UT WOS:000085911000005 ER PT J AU Talbot, RW Dibb, JE Scheuer, EM Bradshaw, JD Sandholm, ST Singh, HB Blake, DR Blake, NJ Atlas, E Flocke, F AF Talbot, RW Dibb, JE Scheuer, EM Bradshaw, JD Sandholm, ST Singh, HB Blake, DR Blake, NJ Atlas, E Flocke, F TI Tropospheric reactive odd nitrogen over the South Pacific in austral springtime SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID PEROXYACETYL NITRATE PAN; CHEMICAL CHARACTERISTICS; CONTINENTAL OUTFLOW; NOY; OZONE; OCEAN AB The distribution of reactive nitrogen species over the South Pacific during austral springtime appears to be dominated by biomass burning emissions and possibly lightning and stratospheric inputs. The absence of robust correlations of reactive nitrogen species with source-specific tracers (e.g., C2H2 [combustion], CH3Cl [biomass burning], C2Cl4, [industrial], Pb-210 [continental], and Be-7 [stratospheric]) suggests significant aging and processing of the sampled air parcels due to losses by surface deposition, OH attack, and dilution processes. Classification of the air parcels based on CO enhancements indicates that the greatest influence was found in plumes at 3-8 km altitude in the distributions of HNO3 and peroxyacetyl nitrate (PAN). Here mixing ratios of these species reached 600 parts per trillion by volume (pptv), values surprisingly large for a location several thousand kilometers removed from the nearest continental areas. The mixing ratio of total reactive nitrogen (the NOy sum), operationally defined in this paper as measured (NO + HNO3 + PAN + CH3ONO2 +C2H5ONO2) + modeled (NO2), had a median value of 285 pptv within these plumes compared with 120 pptv in nonplume air parcels. Particle NO3- was not included in this analysis of the NOy sum due to its 10- to 15-min sampling time resolution, but, in general, it was <10% of the NOy sum. Comparison of the (y)two air parcel classifications for NOx and alkyl nitrate distributions showed no perceivable plume influence, but recycling. of reactive nitrogen may have masked this direct effect. In the marine boundary layer, the NOy sum averaged 50 pptv in both air parcel classifications, being somewhat isolated from the polluted conditions above it by the trade wind inversion. In this region, however, alkyl nitrates appear to have an important marine source where they comprise 20-80% of the NOy sum in equatorial and high-latitude regions over the South Pacific. C1 Univ New Hampshire, Inst Study Earth Oceans & Space, Durham, NH 03824 USA. Georgia Inst Technol, Dept Earth & Atmospher Sci, Atlanta, GA 30322 USA. Natl Ctr Atmospher Res, Div Atmospher Chem, Boulder, CO 80303 USA. Univ Calif Irvine, Dept Chem, Irvine, CA 92697 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Talbot, RW (reprint author), Univ New Hampshire, Inst Study Earth Oceans & Space, Durham, NH 03824 USA. RI Atlas, Elliot/J-8171-2015 NR 34 TC 34 Z9 34 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 16 PY 2000 VL 105 IS D5 BP 6681 EP 6694 DI 10.1029/1999JD901114 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 294KT UT WOS:000085911000006 ER PT J AU Koike, M Kondo, Y Irie, H Murcray, FJ Williams, J Fogal, P Blatherwick, R Camy-Peyret, C Payan, S Oelhaf, H Wetzel, G Traub, W Johnson, D Jucks, K Toon, GC Sen, B Blavier, JF Schlager, H Ziereis, H Toriyama, N Danilin, MY Rodriguez, JM Kanzawa, H Sasano, Y AF Koike, M Kondo, Y Irie, H Murcray, FJ Williams, J Fogal, P Blatherwick, R Camy-Peyret, C Payan, S Oelhaf, H Wetzel, G Traub, W Johnson, D Jucks, K Toon, GC Sen, B Blavier, JF Schlager, H Ziereis, H Toriyama, N Danilin, MY Rodriguez, JM Kanzawa, H Sasano, Y TI A comparison of Arctic HNO3 profiles measured by the Improved Limb Atmospheric Spectrometer and balloon-borne sensors SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID FEBRUARY 1995; VORTEX; CAMPAIGN; STRATOSPHERE; SYSTEM AB The Improved Limb Atmospheric Spectrometer (ILAS), a solar occultation infrared satellite sensor, was launched in August 1996. The ILAS validation balloon campaigns were carried out from Kiruna, Sweden (68 degrees N, 21 degrees E), in February and March 1997 and Fairbanks, Alaska (65 degrees N, 148 degrees W), in April and May 1997. During these campaigns, measurements of nitric acid (HNO3) were made using infrared emission spectrometers (Cold Atmospheric Emission Spectral Radiometer, Michelson Interferometer for Passive Atmospheric Sounding-Balloon-Borne version 2, and far-infrared spectrometer) and infrared solar occultation spectrometers (Limb Profile Monitor of the Atmosphere and Mark IV interferometer). An in situ experiment (Chemiluminescence Detector) measured total reactive nitrogen (NOy), from which HNO3 mixing ratios in the lower stratosphere were calculated. In addition, an in situ NO, measurement was also made at 12 km altitude from the Deutsche Luft-und Raumfahrt Falcon aircraft in January 1997. The ILAS version 3.10 HNO3 mixing ratios obtained at the nearest location and averaged ILAS mixing ratios obtained within certain criteria were compared with the balloon data. The precision of the ILAS measurements was estimated from the random differences to be 0.8 parts per billion by volume (ppbv), corresponding to about 35% at 15 km and 10-15% at 20-35 km. While the absolute accuracy estimated from the systematic differences was as good as 0.5 ppbv (5%) at 20 km, the ILAS HNO3 mixing ratios were systematically lower than the balloon values by 1 ppbv (15-20%) at 25-30 km. The error in the altitude registration in the ILAS retrieval algorithm is a possible cause for the negative bias at higher altitudes. C1 Nagoya Univ, Solar Terr Environm Lab, Aichi 4428507, Japan. Univ Denver, Dept Phys, Denver, CO 80210 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. Univ Paris 06, Lab Phys Mol & Applicat, F-75252 Paris 05, France. CNRS, F-75252 Paris 05, France. Atmospher & Environm Res Inc, Cambridge, MA 02139 USA. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. Natl Inst Environm Studies, Tsukuba, Ibaraki 305, Japan. Forschungszentrum Karlsruhe, Inst Meteorol & Klimaforsch, D-76021 Karlsruhe, Germany. Deutsch Zentrum Luft & Raumfahrt, Inst Phys Atmosphare, D-82234 Wessling, Germany. Univ Miami, Rosenstiel Sch Marine & Atmospher Sci, Dept Marine & Atmospher Chem, Coral Gables, FL 33124 USA. RP Koike, M (reprint author), Nagoya Univ, Solar Terr Environm Lab, Aichi 4428507, Japan. EM koike@stelab.nagoya-u.ac.jp RI Sasano, Yasuhiro/C-2927-2009; Koike, Makoto/F-4366-2011; Kondo, Yutaka/D-1459-2012; Wetzel, Gerald/A-7065-2013; Oelhaf, Hermann/A-7895-2013; Rodriguez, Jose/G-3751-2013; Johnson, David/F-2376-2015 OI Sasano, Yasuhiro/0000-0001-7470-5642; Rodriguez, Jose/0000-0002-1902-4649; Johnson, David/0000-0003-4399-5653 NR 25 TC 33 Z9 33 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAR 16 PY 2000 VL 105 IS D5 BP 6761 EP 6771 DI 10.1029/1999JD901057 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 294KT UT WOS:000085911000012 ER PT J AU Hall, TM Waugh, DW AF Hall, TM Waugh, DW TI Stratospheric residence time and its relationship to mean age SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID MIDDLE ATMOSPHERE; TRACER TRANSPORT; NITROUS-OXIDE; SIMULATIONS; MODEL; CONSTITUENTS; SF6 AB Transport inaccuracies in stratospheric models are a major source of uncertainty in predicting the environmental impact of trace gases with stratospheric source, such as emissions from high-flying aircraft. Because there are no observed tracers of stratospheric aircraft emissions, a direct evaluation of the models' transport of the emissions is not possible. Here we examine the relationship between the stratospheric residence time tau(R) for tracers of midlatitude stratosphere source and the mean age Gamma, a transport diagnostic for which observations are available and have been used to evaluate stratospheric models. Employing a representation of the stratosphere that includes the basic kinematic features of the global circulation, we find that tau(R) and Gamma are correlated over a range of plausible circulations, but that the correlation is imperfect. A major (but not sole) limitation on Gamma as a proxy for tau(R) is the midlatitude tropopause height Z(M) Elevating Z(M) reduces tau(R) significantly, while Gamma is only weakly affected. The relationship between tau(R) and Gamma seen among the participants of a recent stratospheric model intercomparison is consistent with this analysis. C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Johns Hopkins Univ, Dept Earth & Planetary Sci, Baltimore, MD 21218 USA. RP Hall, TM (reprint author), NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. EM thall@giss.nasa.gov; waugh@jhu.edu RI Waugh, Darryn/K-3688-2016 OI Waugh, Darryn/0000-0001-7692-2798 NR 29 TC 25 Z9 25 U1 2 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 MAR 16 PY 2000 VL 105 IS D5 BP 6773 EP 6782 DI 10.1029/1999JD901096 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 294KT UT WOS:000085911000013 ER PT J AU Bergin, MH Schwartz, SE Halthore, RN Ogren, JA Hlavka, DL AF Bergin, MH Schwartz, SE Halthore, RN Ogren, JA Hlavka, DL TI Comparison of aerosol optical depth inferred from surface measurements with that determined by Sun photometry for cloud-free conditions at a continental US site SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID RAMAN LIDAR MEASUREMENTS; ANTHROPOGENIC AEROSOLS; HYGROSCOPIC GROWTH; AMMONIUM-NITRATE; LIGHT-SCATTERING; BOUNDARY-LAYER; CLIMATE; EXTINCTION; BACKSCATTERING; APPORTIONMENT AB Evaluation of the forcing of climate by aerosol scattering of shortwave radiation in cloud-free conditions(direct aerosol forcing) requires knowledge of aerosol optical properties on relevant spatial and temporal scales. It is convenient to measure these properties at the surface. However, before these measurements can be used to quantitatively estimate direct climate forcing, it is necessary to determine the extent to which these properties are representative of the entire atmospheric column. In this paper we compare aerosol optical depth (AOD) determined by Sun photometry at the Southern Great Plains (SGP) Atmospheric Radiation Measurement (ARM) site in north central Oklahoma for several cloud-free days with estimates of AOD based on two methods. First, the aerosol extinction measured at the surface (taken as the sum of the aerosol scattering and absorption coefficients at instrumental relative humidity of similar to 20%) is multiplied by the mixing height determined from temperature profiles from radiosonde measurements. Even under conditions of vigorous midday mixing this approach underestimates AOD by as much as 70% using dry aerosol measurements and by roughly 40% when hygroscopic growth of aerosol under ambient relative humidity is taken into account. This discrepancy is attributed primarily to underestimation of aerosol column extinction, as confirmed by examination of normalized aerosol backscatter profiles obtained from micropulse lidar (MPL), which show substantial contributions of aerosol loading above the atmospheric boundary layer. The second approach uses MPL profiles of normalized aerosol backscatter to estimate the vertical profile of aerosol extinction using surface values. The resulting AOD's are on average 30% less than measured values. This discrepancy is attributed to hygroscopic growth of aerosols in the atmospheric column. The results show that at the SGP site even under conditions of vigorous mixing in the atmospheric boundary layer the aerosol optical depth cannot be estimated with surface measurements of aerosol extinction unless information on the vertical profile of aerosol extinction is taken into account. C1 Brookhaven Natl Lab, Environm Chem Div, Upton, NY 11973 USA. NOAA, Climate Monitoring & Diagnost Lab, Boulder, CO 80303 USA. NASA, Goddard Space Flight Ctr, Sci Syst & Applicat Div, Greenbelt, MD 20771 USA. RP Bergin, MH (reprint author), Georgia Inst Technol, Sch Civil & Environm Engn, Atlanta, GA 30332 USA. EM mike.bergin@ce.gatech.edu RI Schwartz, Stephen/C-2729-2008; Ogren, John/M-8255-2015 OI Schwartz, Stephen/0000-0001-6288-310X; Ogren, John/0000-0002-7895-9583 NR 37 TC 30 Z9 31 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 16 PY 2000 VL 105 IS D5 BP 6807 EP 6816 DI 10.1029/1999JD900454 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 294KT UT WOS:000085911000016 ER PT J AU Clarke, MSF Bamman, MM Feeback, DL AF Clarke, MSF Bamman, MM Feeback, DL TI Sarcoplasmic reticulum cholesterol content during muscle unloading SO FASEB JOURNAL LA English DT Meeting Abstract C1 USRA, DSLS, Houston, TX 77058 USA. UAB, Birmingham, AL 35294 USA. NASA, JSC, Houston, TX 77058 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 15 PY 2000 VL 14 IS 4 BP A316 EP A316 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 294NV UT WOS:000085918101829 ER PT J AU Evans, JM Simonson, SR Knapp, CF Stocks, JM Biagini, HW Cowell, SA Bailey, KN Vener, JM Evetts, SN Moore, FB Stenger, MB Mcintosh, CM Greenleaf, JE AF Evans, JM Simonson, SR Knapp, CF Stocks, JM Biagini, HW Cowell, SA Bailey, KN Vener, JM Evetts, SN Moore, FB Stenger, MB Mcintosh, CM Greenleaf, JE TI Differences in acceleration training and exercise training on resting cardiovascular variables. SO FASEB JOURNAL LA English DT Meeting Abstract C1 NASA, Ames Res Ctr, Lab Human Environm Physiol, Moffett Field, CA 94035 USA. Univ Kentucky, Ctr Biomed Engn, Lexington, KY 40506 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 15 PY 2000 VL 14 IS 4 BP A616 EP A616 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 294NV UT WOS:000085918103565 ER PT J AU Girten, B Lee, M McPherson, S Day, K Omholt, P AF Girten, B Lee, M McPherson, S Day, K Omholt, P TI Differential effects of three melanocortin analogs on changes induced by hindlimb unloading in rats. SO FASEB JOURNAL LA English DT Meeting Abstract C1 Trega Biosci, San Diego, CA 92121 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 15 PY 2000 VL 14 IS 4 BP A622 EP A622 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 294NV UT WOS:000085918103596 ER PT J AU Greenleaf, JE Petersen, TW Gabrielsen, A Pump, B Bie, P Christensen, NJ Warberg, J Videbaeck, R Simonson, SR Norsk, P AF Greenleaf, JE Petersen, TW Gabrielsen, A Pump, B Bie, P Christensen, NJ Warberg, J Videbaeck, R Simonson, SR Norsk, P TI Low LBNP tolerance in men is associated with attenuated activation of the renin-angiotensin system. SO FASEB JOURNAL LA English DT Meeting Abstract C1 AS Rigshop 7805, DAMEC Res, DK-2200 Copenhagen, Denmark. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 15 PY 2000 VL 14 IS 4 BP A58 EP A58 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 294NV UT WOS:000085918100335 ER PT J AU Hurst, V Benavides, EW Westover, AR Fritsch-Yelle, JM AF Hurst, V Benavides, EW Westover, AR Fritsch-Yelle, JM TI Use of the Launch and Entry Suit increases heart rate and systolic pressure in astronauts. SO FASEB JOURNAL LA English DT Meeting Abstract C1 NASA, Lyndon B Johnson Space Ctr, Life Sci Res Labs, Houston, TX 77058 USA. Baylor Coll Med, Wyle Labs, Houston, TX 77058 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 15 PY 2000 VL 14 IS 4 BP A679 EP A679 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 294NV UT WOS:000085918103930 ER PT J AU Moran, MM Wade, CE Stein, TP Fuller, P Hoban-Higgins, TM Bennett, S Fuller, CA AF Moran, MM Wade, CE Stein, TP Fuller, P Hoban-Higgins, TM Bennett, S Fuller, CA TI Body composition in mature rats following centrifugation at 2 G. SO FASEB JOURNAL LA English DT Meeting Abstract C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Calif Davis, Davis, CA 95616 USA. Univ Med & Dent New Jersey, Stratford, NJ 08084 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 15 PY 2000 VL 14 IS 4 BP A623 EP A623 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 294NV UT WOS:000085918103602 ER PT J AU Ortiz, RM Wade, CE Ortiz, CL AF Ortiz, RM Wade, CE Ortiz, CL TI Effects of prolonged fasting on osmoregulatory and metabolic hormones in an adapted species. SO FASEB JOURNAL LA English DT Meeting Abstract C1 Univ Calif Santa Cruz, Santa Cruz, CA 95064 USA. NASA, Ames Res Ctr, Moffett Field, CA 94065 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 15 PY 2000 VL 14 IS 4 BP A45 EP A45 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 294NV UT WOS:000085918100259 ER PT J AU Reyes, C Hurst, V Fritsch-Yelle, J AF Reyes, C Hurst, V Fritsch-Yelle, J TI Cardiac baroreflex sensitivity during spontaneous arterial pressure ramps is not attenuated after long-duration spaceflight SO FASEB JOURNAL LA English DT Meeting Abstract C1 Baylor Coll Med, Life Sci Res Labs, Houston, TX 77058 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Wyle Labs, Houston, TX 77058 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 15 PY 2000 VL 14 IS 4 BP A679 EP A679 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 294NV UT WOS:000085918103928 ER PT J AU Smith, SM O'Brien, K Wastney, M Morukov, B Larina, I Abrams, S Lane, H Nillen, J Davis-Street, J Shackelford, L AF Smith, SM O'Brien, K Wastney, M Morukov, B Larina, I Abrams, S Lane, H Nillen, J Davis-Street, J Shackelford, L TI Calcium and bone homeostasis during 4-6 mos space flight. SO FASEB JOURNAL LA English DT Meeting Abstract C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Johns Hopkins Univ, Baltimore, MD 21218 USA. Georgetown Univ, Med Ctr, Washington, DC 20007 USA. Minist Publ Hlth Russia, Inst Biomed Problems, Moscow, Russia. Baylor Coll Med, Houston, TX 77030 USA. NR 0 TC 1 Z9 1 U1 1 U2 1 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 15 PY 2000 VL 14 IS 4 BP A39 EP A39 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 294NV UT WOS:000085918100227 ER PT J AU Tobin, BW Sams, CF Smith, MD Smith, SM AF Tobin, BW Sams, CF Smith, MD Smith, SM TI Increased arginine and ornithine flux in islets of Langerhans cultured in a microgravity model system. SO FASEB JOURNAL LA English DT Meeting Abstract C1 Mercer Univ, Sch Med, Macon, GA 31207 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 15 PY 2000 VL 14 IS 4 BP A745 EP A745 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 294NV UT WOS:000085918104309 ER PT J AU Waters, WW D'Aunno, DS Perez, SA Ziegler, MG Fritsch-Yelle, JM AF Waters, WW D'Aunno, DS Perez, SA Ziegler, MG Fritsch-Yelle, JM TI Menstrual cycle-related differences in cardiovascular responses to orthostatic stress. SO FASEB JOURNAL LA English DT Meeting Abstract C1 Baylor Coll Med, Houston, TX 77058 USA. Wyle Life Sci, Houston, TX 77058 USA. Univ Calif San Diego, San Diego, CA 92103 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Univ Texas, Galveston, TX 77555 USA. 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 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 15 PY 2000 VL 14 IS 4 BP A679 EP A679 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 294NV UT WOS:000085918103931 ER PT J AU Kwok, R AF Kwok, R TI Recent changes in Arctic Ocean sea ice motion associated with the North Atlantic Oscillation SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID CIRCULATION; IMAGERY AB Examination of a new ice motion dataset of the Arctic Ocean over a recent eighteen year period (1978-1996) reveals: patterns of variability that can be linked directly to the North Atlantic Oscillation. The intensity of the Icelandic Low, one of its centers of action, modulates the sea level pressure distribution over a broad region of the Arctic Ocean and the Greenland-Iceland-Norwegian and Barents Seas. Over the winters of 1988 through 1995, the Oscillation has remained in its positive phase contributing to coherent large-scale changes in the intensity and character of ice transport in the Arctic Ocean. The significant changes include: the weakening of the Beaufort Gyre; the increase in ice export through the Fram Strait; the increase in ice import from the Barents/Kara Seas; the enhanced eastward transport of sea ice from the Laptev Sea::the,weakening of the Transpolar Drift Stream; and, the reduction in ice extent in the Nordic Seas. All of these changes affect the regional and total sea ice mass balance of the Arctic Ocean. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Kwok, R (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Kwok, Ron/A-9762-2008 OI Kwok, Ron/0000-0003-4051-5896 NR 19 TC 67 Z9 73 U1 0 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD MAR 15 PY 2000 VL 27 IS 6 BP 775 EP 778 DI 10.1029/1999GL002382 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 293TC UT WOS:000085868600010 ER PT J AU Livesey, NJ Read, WG AF Livesey, NJ Read, WG TI Direct retrieval of line-of-sight atmospheric structure from limb sounding observations SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID REMOTE AB Optimal estimation of atmospheric temperature and composition from limb sounding observations is extended to the direct retrieval of line-of-sight atmospheric structure that can be obtained in certain limb viewing geometries. The approach is to divide the dataset into slightly overlapping chunks of several atmospheric profiles and retrieve estimates for all profiles concurrently. The method is made efficient due to the sparse nature of the matrices involved. In the case where the number of radiance measurements is significantly larger than the length of the state vector, the computational effort scales linearly with the number of profiles in the chunk. Prototype simulations, done for the EOS MLS experiment, show that application of this method can give significant improvements in accuracy. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Livesey, NJ (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 7 TC 30 Z9 31 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD MAR 15 PY 2000 VL 27 IS 6 BP 891 EP 894 DI 10.1029/1999GL010964 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 293TC UT WOS:000085868600039 ER PT J AU Ahumada, AJ Krebs, WK AF Ahumada, AJ Krebs, WK TI Signal detection in fixed pattern chromatic noise. SO INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE LA English DT Meeting Abstract C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. USN, Postgrad Sch, Monterey, CA USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU ASSOC RESEARCH VISION OPHTHALMOLOGY INC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0146-0404 J9 INVEST OPHTH VIS SCI JI Invest. Ophthalmol. Vis. Sci. PD MAR 15 PY 2000 VL 41 IS 4 SU S MA 3796B894 BP S713 EP S713 PG 1 WC Ophthalmology SC Ophthalmology GA 300HF UT WOS:000086246703865 ER PT J AU Ansari, RR Datiles, MB AF Ansari, RR Datiles, MB TI Clinical tests of a new instrument for the early detection of cataracts: Preliminary results. SO INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE LA English DT Meeting Abstract C1 NEI, NIH, Bethesda, MD 20892 USA. NASA, Glenn Res Ctr, NCMR, FC, Cleveland, OH 44135 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU ASSOC RESEARCH VISION OPHTHALMOLOGY INC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0146-0404 J9 INVEST OPHTH VIS SCI JI Invest. Ophthalmol. Vis. Sci. PD MAR 15 PY 2000 VL 41 IS 4 SU S MA 11B11 BP S3 EP S3 PG 1 WC Ophthalmology SC Ophthalmology GA 300HF UT WOS:000086246700012 ER PT J AU Arnoldussen, ME Chuck, RS Behrens, A Cohen, D Bearman, GH McDonnell, PJ Grundfest, WS AF Arnoldussen, ME Chuck, RS Behrens, A Cohen, D Bearman, GH McDonnell, PJ Grundfest, WS TI 193 NM excimer laser-induced fluorescence in diabetic human eye bank corneas SO INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE LA English DT Meeting Abstract C1 Cedars Sinai Med Ctr, Los Angeles, CA 90048 USA. Univ So Calif, Los Angeles, CA USA. Univ Calif Irvine, Dept Ophthalmol, Irvine, CA USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. Univ Calif Los Angeles, Dept Elect Engn, Los Angeles, CA 90024 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU ASSOC RESEARCH VISION OPHTHALMOLOGY INC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0146-0404 J9 INVEST OPHTH VIS SCI JI Invest. Ophthalmol. Vis. Sci. PD MAR 15 PY 2000 VL 41 IS 4 SU S MA 2437B683 BP S460 EP S460 PG 1 WC Ophthalmology SC Ophthalmology GA 300HF UT WOS:000086246702435 ER PT J AU Beard, BL Ahumada, AJ AF Beard, BL Ahumada, AJ TI Response classification images for parafoveal vernier acuity. SO INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE LA English DT Meeting Abstract C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 0 TC 5 Z9 5 U1 0 U2 0 PU ASSOC RESEARCH VISION OPHTHALMOLOGY INC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0146-0404 J9 INVEST OPHTH VIS SCI JI Invest. Ophthalmol. Vis. Sci. PD MAR 15 PY 2000 VL 41 IS 4 SU S MA 4267B214 BP S804 EP S804 PG 1 WC Ophthalmology SC Ophthalmology GA 300HF UT WOS:000086246704336 ER PT J AU Beutter, BR Eckstein, MP Stone, LS AF Beutter, BR Eckstein, MP Stone, LS TI Parallel differences in contrast-discrimination and detection performance for saccades and perception in visual search. SO INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE LA English DT Meeting Abstract C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Cedars Sinai Med Ctr, Los Angeles, CA 90048 USA. NR 0 TC 2 Z9 2 U1 0 U2 0 PU ASSOC RESEARCH VISION OPHTHALMOLOGY INC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0146-0404 J9 INVEST OPHTH VIS SCI JI Invest. Ophthalmol. Vis. Sci. PD MAR 15 PY 2000 VL 41 IS 4 SU S MA 2244B490 BP S424 EP S424 PG 1 WC Ophthalmology SC Ophthalmology GA 300HF UT WOS:000086246702242 ER PT J AU Chuck, RS Arnoldussen, ME Behrens, A Liaw, LH Cohen, D Bearman, GH McDonnell, PJ Berns, MW Grundfest, WS AF Chuck, RS Arnoldussen, ME Behrens, A Liaw, LH Cohen, D Bearman, GH McDonnell, PJ Berns, MW Grundfest, WS TI Laser-induced fluorescence during 193 NM excimer laser ablation of rabbit cornea damaged by hydrochloric acid SO INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE LA English DT Meeting Abstract C1 Univ Calif Irvine, Dept Ophthalmol, Irvine, CA USA. Cedars Sinai Med Ctr, Los Angeles, CA 90048 USA. Univ So Calif, Los Angeles, CA USA. Univ Calif Irvine, Beckman Laser Inst & Med Clin, Irvine, CA 92715 USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. Univ Calif Irvine, Dept Cell Biol, Irvine, CA USA. Univ Calif Irvine, Dept Surg, Irvine, CA USA. Univ Calif Los Angeles, Dept Elect Engn, Los Angeles, CA 90024 USA. NR 0 TC 2 Z9 2 U1 0 U2 0 PU ASSOC RESEARCH VISION OPHTHALMOLOGY INC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0146-0404 J9 INVEST OPHTH VIS SCI JI Invest. Ophthalmol. Vis. Sci. PD MAR 15 PY 2000 VL 41 IS 4 SU S MA 2436B682 BP S459 EP S459 PG 1 WC Ophthalmology SC Ophthalmology GA 300HF UT WOS:000086246702434 ER PT J AU DeLucia, PR Kaiser, MK Bush, JM Meyer, LE Sweet, BT AF DeLucia, PR Kaiser, MK Bush, JM Meyer, LE Sweet, BT TI Information integration in judgments about time to contact. SO INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE LA English DT Meeting Abstract C1 Texas Tech Univ, Lubbock, TX 79409 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU ASSOC RESEARCH VISION OPHTHALMOLOGY INC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0146-0404 J9 INVEST OPHTH VIS SCI JI Invest. Ophthalmol. Vis. Sci. PD MAR 15 PY 2000 VL 41 IS 4 SU S MA 4231B178 BP S798 EP S798 PG 1 WC Ophthalmology SC Ophthalmology GA 300HF UT WOS:000086246704300 ER PT J AU Eckstein, MP Beutter, BR Stone, LS AF Eckstein, MP Beutter, BR Stone, LS TI Task information increases from the first to the second saccade in visual search of a target among distractors. SO INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE LA English DT Meeting Abstract C1 Cedars Sinai Med Ctr, Los Angeles, CA 90048 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU ASSOC RESEARCH VISION OPHTHALMOLOGY INC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0146-0404 J9 INVEST OPHTH VIS SCI JI Invest. Ophthalmol. Vis. Sci. PD MAR 15 PY 2000 VL 41 IS 4 SU S MA 4027 BP S759 EP S759 PG 1 WC Ophthalmology SC Ophthalmology GA 300HF UT WOS:000086246704096 ER PT J AU Hirsch, J Silver, R Kleiner, S Rothman, L Barry, DT AF Hirsch, J Silver, R Kleiner, S Rothman, L Barry, DT TI The distributed functional neuroanatomy of human visually guided reach: An event-related fMRI study. SO INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE LA English DT Meeting Abstract C1 Cornell Univ, Weill Med Coll, New York, NY 10021 USA. Mem Sloan Kettering Canc Ctr, New York, NY 10021 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 1 TC 0 Z9 0 U1 0 U2 1 PU ASSOC RESEARCH VISION OPHTHALMOLOGY INC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0146-0404 J9 INVEST OPHTH VIS SCI JI Invest. Ophthalmol. Vis. Sci. PD MAR 15 PY 2000 VL 41 IS 4 SU S MA 4316B263 BP S813 EP S813 PG 1 WC Ophthalmology SC Ophthalmology GA 300HF UT WOS:000086246704385 ER PT J AU King, JF Chenault, VM Ansari, RR AF King, JF Chenault, VM Ansari, RR TI Detection of diabetic cataracts in psammomys obesus (sand rat) using Dynamic Light Scattering. SO INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE LA English DT Meeting Abstract C1 NASA, Glenn Res Ctr, NCMR, Cleveland, OH 44135 USA. US FDA, Rockville, MD 20857 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU ASSOC RESEARCH VISION OPHTHALMOLOGY INC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0146-0404 J9 INVEST OPHTH VIS SCI JI Invest. Ophthalmol. Vis. Sci. PD MAR 15 PY 2000 VL 41 IS 4 SU S MA 1120B495 BP S214 EP S214 PG 1 WC Ophthalmology SC Ophthalmology GA 300HF UT WOS:000086246701119 ER PT J AU McDonnell, PJ Chuck, RS Arnoldussen, ME Behrens, A Cohen, D Bearman, GH Grundfest, WS AF McDonnell, PJ Chuck, RS Arnoldussen, ME Behrens, A Cohen, D Bearman, GH Grundfest, WS TI 193 NM excimer laser-induced fluorescence in fresh cadaveric rabbit and human eye bank corneas: Spectral component analyses SO INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE LA English DT Meeting Abstract C1 Univ Calif Irvine, Dept Ophthalmol, Irvine, CA USA. Univ So Calif, Los Angeles, CA USA. Cedars Sinai Med Ctr, Los Angeles, CA 90048 USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. Univ Calif Los Angeles, Dept Elect Engn, Los Angeles, CA 90024 USA. NR 0 TC 1 Z9 1 U1 0 U2 0 PU ASSOC RESEARCH VISION OPHTHALMOLOGY INC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0146-0404 J9 INVEST OPHTH VIS SCI JI Invest. Ophthalmol. Vis. Sci. PD MAR 15 PY 2000 VL 41 IS 4 SU S MA 2435B681 BP S459 EP S459 PG 1 WC Ophthalmology SC Ophthalmology GA 300HF UT WOS:000086246702433 ER PT J AU Mulligan, JB AF Mulligan, JB TI Scan-path analysis of air traffic control displays. SO INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE LA English DT Meeting Abstract C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU ASSOC RESEARCH VISION OPHTHALMOLOGY INC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0146-0404 J9 INVEST OPHTH VIS SCI JI Invest. Ophthalmol. Vis. Sci. PD MAR 15 PY 2000 VL 41 IS 4 SU S MA 2239B485 BP S423 EP S423 PG 1 WC Ophthalmology SC Ophthalmology GA 300HF UT WOS:000086246702237 ER PT J AU Stone, LS Krauzlis, RJ AF Stone, LS Krauzlis, RJ TI Precision of the motion direction signals underlying pursuit eye-movements and perception in humans. SO INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE LA English DT Meeting Abstract C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Salk Inst, La Jolla, CA USA. NEI, Bethesda, MD 20892 USA. NR 0 TC 3 Z9 3 U1 0 U2 0 PU ASSOC RESEARCH VISION OPHTHALMOLOGY INC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0146-0404 J9 INVEST OPHTH VIS SCI JI Invest. Ophthalmol. Vis. Sci. PD MAR 15 PY 2000 VL 41 IS 4 SU S MA 1669 BP S316 EP S316 PG 1 WC Ophthalmology SC Ophthalmology GA 300HF UT WOS:000086246701668 ER PT J AU Watson, AB Ramirez, C AF Watson, AB Ramirez, C TI A standard observer for spatial vision. SO INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE LA English DT Meeting Abstract C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. De Anza Coll, Cupertino, CA USA. NR 0 TC 5 Z9 5 U1 0 U2 0 PU ASSOC RESEARCH VISION OPHTHALMOLOGY INC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0146-0404 J9 INVEST OPHTH VIS SCI JI Invest. Ophthalmol. Vis. Sci. PD MAR 15 PY 2000 VL 41 IS 4 SU S MA 3794B892 BP S713 EP S713 PG 1 WC Ophthalmology SC Ophthalmology GA 300HF UT WOS:000086246703863 ER PT J AU Hakkinen, S AF Hakkinen, S TI Decadal air-sea interaction in the North Atlantic based on observations and modeling results SO JOURNAL OF CLIMATE LA English DT Article ID GENERAL-CIRCULATION MODEL; SURFACE TEMPERATURE ANOMALIES; ICE-OCEAN SYSTEM; THERMOHALINE CIRCULATION; INTERDECADAL VARIABILITY; SST ANOMALIES; CLIMATE; OSCILLATION; LEVEL; HEMISPHERE AB The decadal, 12-14-yr cycle observed in the North Atlantic SST and tide gauge data was examined using the NCEP-NCAR reanalyses, the Comprehensive Ocean-Atmosphere Data Set, and an ocean model simulation. SST data are contrasted with tide gauge data, which shows that in SST the decadal mode is nonstationary with strong variability for the last 40-50 yr, but the sea level at the southeastern U.S. coast exhibits a robustly regular variability at this period for the last 75 yr. Thus, sea level variability gives credibility to the existence of a decadal mode. The main finding is that this 12-14-yr cycle can be constructed based on the leading mode of the surface heat Bur, which implicates the participation of the thermohaline circulation. This cycle has potential to be a coupled mode because three necessary aspects of a coupled mode are found: a positive feedback between the atmosphere and ocean in the subpolar gyre, a negative feedback of the overturning variability on itself, and a delayed adjustment through midlatitude Rossby waves to these processes. During the cycle, starting from the positive index phase of the North Atlantic oscillation (NAO), positive SST and oceanic heat content anomalies exist in the subtropics. The warm anomalies advect to the subpolar eyre where they are amplified by local heat flux, that is, a positive feedback between the atmosphere and ocean. At the same time the advection of warm anomalies to the subpolar gyre constitutes of a negative feedback of the thermohaline circulation on itself. The effect of this internal feedback of the ocean is amplified by the positive feedback between the atmosphere and ocean. Consequently the oceanic thermohaline circulation slows down and the opposite cycle starts. The adjustment to the changes in overturning is mediated by midlatitude Rossby waves. They are responsible for the subtropical heat content anomalies that later advect to the high latitudes. This analysis suggests that the two principal modes of heat flux variability, corresponding to patterns similar to the NAO and the Western Atlantic, are part of the same decadal cycle. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Hakkinen, S (reprint author), NASA, Goddard Space Flight Ctr, Code 971, Greenbelt, MD 20771 USA. RI Hakkinen, Sirpa/E-1461-2012 NR 54 TC 47 Z9 48 U1 2 U2 3 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 MAR 15 PY 2000 VL 13 IS 6 BP 1195 EP 1219 DI 10.1175/1520-0442(2000)013<1195:DASIIT>2.0.CO;2 PG 25 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 299LE UT WOS:000086199400008 ER PT J AU Hakkinen, S Geiger, CA AF Hakkinen, S Geiger, CA TI Simulated low-frequency modes of circulation in the Arctic Ocean SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID NORTH-ATLANTIC OSCILLATION; SOUTHERN CANADIAN BASIN; SEA-ICE VARIABILITY; LEVEL PRESSURE; HEMISPHERE; TEMPERATURES; GREENLAND; PATTERNS; WINTER; WATER AB The variability of the Arctic circulation is investigated for a 43 year period (1951-1993) from a coupled ice-ocean model. Empirical orthogonal function (EOF) analysis shows that the variability of the sea surface height (SSH) and vertically integrated transport is organized so that in the leading mode the whole Arctic operates as a single gyre. The mode is associated with the Arctic Oscillation (AO) [Thompson and Wallace, 1998], and it explains over 70% of the variance in the vertically integrated transport and 25% of the SSH variability. The physical interpretation of this mode is derived to arise from its close connection to the Atlantic inflow to the Arctic. The mode shows a major shift toward cyclonic circulation in the end of the 1980s which is associated with a large multiyear pulse of Atlantic water to the Arctic. Thus this event appears as the likely initiation of the Atlantic laver warming observed during the recent years [Carmack et al., 1995]. Overall, the first mode shows strong decadal variability as reported by Proshurinsky and Johnson [1997]. The second mode of the oceanic circulation, which explains 9% of the variance in the transport, contains mio gyres with opposing cyclonicity in the Eurasia and Canada basins. It projects onto the North Atlantic Oscillation (NAO) pattern and displays a 14 year cycle which is known to exist in the midlatitude North Atlantic surface temperatures [Deser and Blackmon, 1993]. A further examination reveals that this mode describes the variability of the flow through the Barents Sea, which is modulated by the water mass modification due to the local heat flux variability. The apparent NAO connection is provided by a simultaneous correlation between the time series of this second mode and the leading heat flux mode in the North Atlantic which is associated with NAG. C1 NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Greenbelt, MD 20771 USA. RP Hakkinen, S (reprint author), NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Code 971, Greenbelt, MD 20771 USA. RI Hakkinen, Sirpa/E-1461-2012 NR 50 TC 36 Z9 37 U1 0 U2 6 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD MAR 15 PY 2000 VL 105 IS C3 BP 6549 EP 6564 DI 10.1029/2000JC900003 PG 16 WC Oceanography SC Oceanography GA 293YG UT WOS:000085882400018 ER PT J AU Canham, JS AF Canham, JS TI DEHP concerns SO CHEMICAL & ENGINEERING NEWS LA English DT Letter C1 NASA, Greenbelt, MD 20771 USA. RP Canham, JS (reprint author), NASA, Greenbelt, MD 20771 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0009-2347 J9 CHEM ENG NEWS JI Chem. Eng. News PD MAR 13 PY 2000 VL 78 IS 11 BP 6 EP 6 PG 1 WC Chemistry, Multidisciplinary; Engineering, Chemical SC Chemistry; Engineering GA 292VZ UT WOS:000085817100004 ER PT J AU Dodelson, S Gaztanaga, E AF Dodelson, S Gaztanaga, E TI Inverting the angular correlation function SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE methods : numerical; large-scale structure of Universe ID APM GALAXY SURVEY; POWER SPECTRUM AB The two point angular correlation function is an excellent measure of structure in the Universe. To extract from it the three-dimensional power spectrum, one must invert Limber's equation. Here we perform this inversion using a Bayesian prior constraining the smoothness of the power spectrum. Among other virtues, this technique allows for the possibility that the estimates of the angular correlation function are correlated from bin to bin. The outputs of this technique are estimators for the binned power spectrum and a full covariance matrix. Angular correlations mix small and large scales but after the inversion, small-scale data can be trivially eliminated, thereby allowing for realistic constraints on theories of large-scale structure. We analyse the automated plate measurement (APM) catalogue as an example, comparing our results with previous results. As a by-product of these tests, we find - in rough agreement with previous work - that APM places stringent constraints on cold dark matter inspired models, with the shape parameter constrained to be 0.25 +/- 0.04 (using data with wavenumber k less than or equal to 0.1 h Mpc(-1)). This range of allowed values uses the full power spectrum covariance matrix, but assumes negligible covariance in the off-diagonal angular correlation error matrix, which is estimated with a large angular resolution of 0.5 degrees (in the range 0.5 degrees and 20 degrees). C1 Fermi Natl Accelerator Lab, NASA, Batavia, IL 60510 USA. Univ Chicago, Dept Astron & Astrophys, Chicago, IL 60637 USA. CSIC, Inst Estudis Espacials Catalunya, ES-08034 Barcelona, Spain. INAOE, Astrofis, Puebla 7200, Mexico. RP Dodelson, S (reprint author), Fermi Natl Accelerator Lab, NASA, POB 500, Batavia, IL 60510 USA. OI Gaztanaga, Enrique/0000-0001-9632-0815 NR 13 TC 21 Z9 21 U1 0 U2 1 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD MAR 11 PY 2000 VL 312 IS 4 BP 774 EP 780 DI 10.1046/j.1365-8711.2000.03186.x PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 302WB UT WOS:000086388500013 ER PT J AU Dickinson, M Hanley, C Elston, R Eisenhardt, PR Stanford, SA Adelberger, KL Shapley, A Steidel, CC Papovich, C Szalay, AS Bershady, MA Conselice, CJ Ferguson, HC Fruchter, AS AF Dickinson, M Hanley, C Elston, R Eisenhardt, PR Stanford, SA Adelberger, KL Shapley, A Steidel, CC Papovich, C Szalay, AS Bershady, MA Conselice, CJ Ferguson, HC Fruchter, AS TI The unusual infrared object HDF-N J123656.3+621322 SO ASTROPHYSICAL JOURNAL LA English DT Article DE early universe; galaxies : evolution; galaxies : photometry; infrared : galaxies ID HUBBLE DEEP FIELD; HIGH-REDSHIFT GALAXIES; STAR-FORMATION; LUMINOSITY FUNCTIONS; MAGELLANIC CLOUD; COLORS; SPECTROSCOPY; POPULATION; PHOTOMETRY; LIMIT AB We describe an object in the Hubble Deep Field North with very unusual near-infrared properties. It is readily visible in Hubble Space Telescope NICMOS images at 1.6 mu m and from the ground at 2.2 mu m, but it is undetected (with S/N less than or similar to 2) in very deep WFPC2 and NICMOS data from 0.3 to 1.1 mu m The f(v) flux density drops by a factor greater than or similar to 8.3 (97.7% confidence) from 1.6 to 1.1 mu m. The object is compact but may be slightly resolved in the NICMOS 1.6 mu m image. In a low-resolution, near-infrared spectrogram, we find a possible emission line at 1.643 mu m, but a reobservation at higher spectral resolution failed to confirm the line, leaving its reality in doubt. We consider various hypotheses for the nature of this object. Its colors are unlike those of known Galactic stars, except perhaps the most extreme carbon stars or Mira variables with thick circumstellar dust shells. It does not appear to be possible to explain its spectral energy distribution as that of a normal galaxy at any redshift without additional opacity from either dust or intergalactic neutral hydrogen. The colors can be matched by those of a dusty galaxy at z greater than or similar to 2, by a maximally old elliptical galaxy at z greater than or similar to 3 (perhaps with some additional reddening), or by an object at z greater than or similar to 10 whose optical and 1.1 mu m light have been suppressed by the intergalactic medium. Under the latter hypothesis, if the luminosity results from stars and not an AGN, the object would resemble a classical, unobscured protogalaxy, with a star formation rate greater than or similar to 100 M. yr(-1). Such UV-bright objects are evidently rare at 22.3.CO;2 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 305EB UT WOS:000086525500012 ER PT J AU Ziemke, JR Chandra, S Bhartia, PK AF Ziemke, JR Chandra, S Bhartia, PK TI A new NASA data product: Tropospheric and stratospheric column ozone in the tropics derived from TOMS measurements SO BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY LA English DT Editorial Material AB Tropospheric column ozone and stratospheric column ozone gridded data in the Tropics for 1979-present are now available from NASA Goddard Space Flight Center via either direct ftp, World Wide Web, or electronic mail. This paper provides a brief overview of the method used to derive the dataset including validation and adjustments. C1 Software Corp Amer, Beltsville, MD USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Ziemke, JR (reprint author), Software Corp Amer, Beltsville, MD USA. RI Bhartia, Pawan/A-4209-2016 OI Bhartia, Pawan/0000-0001-8307-9137 NR 8 TC 9 Z9 10 U1 0 U2 1 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0003-0007 J9 B AM METEOROL SOC JI Bull. Amer. Meteorol. Soc. PD MAR PY 2000 VL 81 IS 3 BP 580 EP 583 DI 10.1175/1520-0477(2000)081<0580:ANNDPT>2.3.CO;2 PG 4 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 305EB UT WOS:000086525500014 ER PT J AU Berejikian, BA Tezak, EP Flagg, TA LaRae, AL Kummerow, E Mahnken, CVW AF Berejikian, BA Tezak, EP Flagg, TA LaRae, AL Kummerow, E Mahnken, CVW TI Social dominance, growth, and habitat use of age-0 steelhead (Oncorhynchus mykiss) grown in enriched and conventional hatchery rearing environments SO CANADIAN JOURNAL OF FISHERIES AND AQUATIC SCIENCES LA English DT Article ID JUVENILE COHO SALMON; AGONISTIC BEHAVIOR; FOOD DISTRIBUTION; ATLANTIC SALMON; CHINOOK SALMON; TERRITORY SIZE; WILD ANCESTRY; BROWN TROUT; EXPERIENCE; GAIRDNERI AB This study investigated whether culturing age-0 steelhead (Oncorhynchus mykiss) in habitat-enriched rearing tanks, containing a combination of in-water structure, underwater feeders, and overhead cover, affected competitive ability and habitat use compared with juveniles cultured in more conventional vessels. In laboratory tests, steelhead juveniles grown in the enriched tanks socially dominated size-matched competitors grown in conventional tanks. When both treatments were introduced into separate sections of a quasi-natural stream, no differences in growth were found between them. However, when intermixed, fish reared in the enriched tanks grew at a higher rate than conventionally reared competitors, suggesting greater competitive ability of juveniles grown in the enriched tanks. Visual isolation and defensible food resources in combination in the enriched tanks were considered as the primary factors causing the observed competitive asymmetries. Steelhead juveniles from the two rearing environments exhibited very similar use of woody structure in the quasi-natural stream, both in the presence and in the absence of mutual competition. Rearing steelhead in more naturalistic environments could result in hatchery fish that behave and integrate into the postrelease (natural) environment in a manner more similar to wild fish. C1 Natl Marine Fisheries Serv, NW Fisheries Sci Ctr, Manchester Marine Expt Stn, Manchester, WA 98353 USA. RP Berejikian, BA (reprint author), Natl Marine Fisheries Serv, NW Fisheries Sci Ctr, Manchester Marine Expt Stn, POB 130, Manchester, WA 98353 USA. NR 41 TC 41 Z9 41 U1 1 U2 9 PU NATL RESEARCH COUNCIL CANADA PI OTTAWA PA RESEARCH JOURNALS, MONTREAL RD, OTTAWA, ONTARIO K1A 0R6, CANADA SN 0706-652X J9 CAN J FISH AQUAT SCI JI Can. J. Fish. Aquat. Sci. PD MAR PY 2000 VL 57 IS 3 BP 628 EP 636 PG 9 WC Fisheries; Marine & Freshwater Biology SC Fisheries; Marine & Freshwater Biology GA 296VA UT WOS:000086046400013 ER PT J AU Liou, WW Huang, G Shih, TH AF Liou, WW Huang, G Shih, TH TI Turbulence model assessment for shock wave/turbulent boundary-layer interaction in transonic and supersonic flows SO COMPUTERS & FLUIDS LA English DT Article AB Comparisons of the performance of several state-of-the-art low-Reynolds number turbulence models in the prediction of shock wave/turbulent boundary-layer interactions in transonic and supersonic flows are reported in this paper. The models include a realizable k-epsilon model, a k-epsilon/k-omega hybrid model, and a one-equation nu(t) model. Several flow experiments focused on the shock wave/turbulent boundary-layer interaction phenomena are chosen for model comparisons. The selected flows represent a range of flow conditions with the turbulent boundary layers being fully attached, incipiently separated, or displaying large region of flow separation. Care has been taken to obtain solutions on sufficiently refined grids in all calculations. The model predictions are compared with experimental data and with the results obtained using Chien's low-Reynolds number model. The results show that the models tested provide improvements over Chien's model in the predictions of shock wave/turbulent interactions. (C) 2000 Elsevier Science Ltd. All rights reserved. C1 Western Michigan Univ, Dept Mech & Aeronaut Engn, Kalamazoo, MI 49008 USA. Univ Kentucky, Dept Mech Engn, Lexington, KY 40506 USA. NASA, Ctr Modeling Turbulence & Transit, ICOMP, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Liou, WW (reprint author), Western Michigan Univ, Dept Mech & Aeronaut Engn, Kalamazoo, MI 49008 USA. NR 21 TC 21 Z9 28 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0045-7930 J9 COMPUT FLUIDS JI Comput. Fluids PD MAR PY 2000 VL 29 IS 3 BP 275 EP 299 DI 10.1016/S0045-7930(99)00010-9 PG 25 WC Computer Science, Interdisciplinary Applications; Mechanics SC Computer Science; Mechanics GA 285TE UT WOS:000085403500003 ER PT J AU Hsu, MK Liu, AK Liu, C AF Hsu, MK Liu, AK Liu, C TI A study of internal waves in the China Seas and Yellow Sea using SAR SO CONTINENTAL SHELF RESEARCH LA English DT Article DE internal waves; solitons; upwelling; wave-wave interaction; China Seas; Yellow Sea ID SULU SEA; NORTHEAST; EVOLUTION; KUROSHIO; TAIWAN; SHELF AB Synthetic aperture radar (SAR) images from ERS-1 and ERS-2 have been used to study the characteristics of internal waves in the East China Sea. Rank-ordered packets of nonlinear internal waves in the East China Sea are often observed in the SAR images, especially in the northeast Of Taiwan. Tn this region, the internal wave field is very complicated, and its generation mechanisms include the influence of the tide and the upwelling, which is induced by the intrusion of the Kuroshio across the continental shelf. The internal wave distributions in the East and South China Seas have been compiled based on the SAR observations from satellites. The Kortweg-deVries (KdV) type equation has been used to study the evolution of internal wave packets generated in the upwelling area. Depending on the mixed layer depth, both elevation and depression waves can be generated based on numerical simulations as observed in the SAR images. The merging of two wave packets from nonlinear wave-wave interaction in the Yellow Sea has been observed in the SAR image and is demonstrated by numerical results. (C) 2000 Elsevier Science Ltd. All rights reserved. C1 Natl Taiwan Ocean Univ, Dept Oceanog, Keelung, Taiwan. NASA, Goddard Space Flight Ctr, Oceans & Ice Branch, Greenbelt, MD 20771 USA. Chung Cheng Inst Technol, Dept Appl Phys, Tayuan, Taiwan. RP Hsu, MK (reprint author), Natl Taiwan Ocean Univ, Dept Oceanog, Keelung, Taiwan. NR 21 TC 106 Z9 127 U1 3 U2 14 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0278-4343 J9 CONT SHELF RES JI Cont. Shelf Res. PD MAR PY 2000 VL 20 IS 4-5 BP 389 EP 410 DI 10.1016/S0278-4343(99)00078-3 PG 22 WC Oceanography SC Oceanography GA 293JZ UT WOS:000085849600005 ER PT J AU Cockell, CS Blaustein, R AF Cockell, CS Blaustein, R TI "Ultraviolet spring" and the ecological consequences of catastrophic impacts SO ECOLOGY LETTERS LA English DT Article DE asteroid; comet; extinction; global change; impact events; UV radiation ID CRETACEOUS-TERTIARY EXTINCTIONS; UV-B PENETRATION; RADIATION; ACIDIFICATION; INHIBITION AB Asteroid and comet impacts cause ozone depletion. For the first time, we have quantified the photobiological characteristics of these events and speculate on some of the associated ecological consequences. Following the clearing of stratospheric dust after "impact winter", levels of damaging UVB radiation (280-315 nm) could increase by at least 100%, resulting in an "ultraviolet spring". Many of the taxa stressed by the cold and dark conditions of impact are the same that would be stressed by large increases in UVB radiation. Furthermore, depletion of dissolved organic carbon (DOC) by impact-induced acid rain would increase UVB penetrability into freshwater systems. Although an increase in UVB radiation is an attractive hypothesis for exacerbating the demise of land animals at the Cretaceous-Tertiary (K/T) boundary, e.g. dinosaurs, our calculations suggest the impact into rare sulphate-rich target rock may have prevented an ultraviolet spring in this case. If the K/T impact event had occurred in any other region on Earth, the stress to the biosphere would probably have been considerably greater. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Oregon State Univ, Dept Zool, Corvallis, OR 97331 USA. RP Cockell, CS (reprint author), British Antarctic Survey, High Cross,Madingley Rd, Cambridge CB3 0ET, England. NR 21 TC 7 Z9 8 U1 1 U2 8 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 1461-023X J9 ECOL LETT JI Ecol. Lett. PD MAR PY 2000 VL 3 IS 2 BP 77 EP 81 DI 10.1046/j.1461-0248.2000.00122.x PG 5 WC Ecology SC Environmental Sciences & Ecology GA 296JK UT WOS:000086021100002 ER PT J AU Narayanan, SR Valdez, TI Chun, W AF Narayanan, SR Valdez, TI Chun, W TI Design and operation of an electrochemical methanol concentration sensor for direct methanol fuel cell systems SO ELECTROCHEMICAL AND SOLID STATE LETTERS LA English DT Article AB The design and operation of a methanol concentration sensor suitable for use with direct methanol fuel cells is described. The sensing principle is based on the measurement of concentration-dependent oxidation currents for the electro-oxidation of methanol in a polymer electrolyte membrane cell at a platinum-ruthenium electrode. The device construction and properties are described. The sensor was integrated with an automatic fuel feed system, and was operated for several tens of hours. The results demonstrate that the sensor is robust and sensitive enough to meet the demands of concentration sensing and control in direct methanol fuel cell systems. (C) 2000 The Electrochemical Society. S1099-0062(99)09-073. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Narayanan, SR (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 10 TC 30 Z9 32 U1 0 U2 6 PU ELECTROCHEMICAL SOC INC PI PENNINGTON PA 65 SOUTH MAIN STREET, PENNINGTON, NJ 08534 USA SN 1099-0062 J9 ELECTROCHEM SOLID ST JI Electrochem. Solid State Lett. PD MAR PY 2000 VL 3 IS 3 BP 117 EP 120 PG 4 WC Electrochemistry; Materials Science, Multidisciplinary SC Electrochemistry; Materials Science GA 285BK UT WOS:000085368200002 ER PT J AU Wolpert, DH Wheeler, KR Tumer, K AF Wolpert, DH Wheeler, KR Tumer, K TI Collective intelligence for control of distributed dynamical systems SO EUROPHYSICS LETTERS LA English DT Article AB We consider the El Farol bar problem, also known as the minority game (W. B. Arthur, The American Economic Review, 84 (1994) 406; D. Challet and Y. C. Zhang, Physica A, 256 (1998) 514). We view it as an instance of the general problem of how to configure the nodal elements of a distributed dynamical system so that they do not "work at; cross purposes", in that, their collective dynamics avoids frustration and thereby achieves a provided global goal. We summarize a mathematical theory for such configuration applicable when (as in the bar problem) the global goal can be expressed as minimizing a global energy function and the nodes can be expressed as minimizers of local fi ee energy functions. We show that; a system designed with that theory performs nearly optimally for the bar problem. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 17 TC 16 Z9 17 U1 0 U2 1 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0295-5075 J9 EUROPHYS LETT JI Europhys. Lett. PD MAR PY 2000 VL 49 IS 6 BP 708 EP 714 DI 10.1209/epl/i2000-00208-x PG 7 WC Physics, Multidisciplinary SC Physics GA 296RD UT WOS:000086038800003 ER PT J AU Zebulum, RS Pacheco, MA Vellasco, M AF Zebulum, Ricardo S. Pacheco, Marco Aurelio Vellasco, Marley TI Variable Length Representation in Evolutionary Electronics SO EVOLUTIONARY COMPUTATION LA English DT Article DE VLR evolutionary algorithms; evolutionary electronics; genetic memory; digital circuits; analog filters AB This work investigates the application of variable length representation (VLR) evolutionary algorithms (EAs) in the field of Evolutionary Electronics. We propose a number of VLR methodologies that can cope with the main issues of variable length evolutionary systems. These issues include the search for efficient ways of sampling a genome space with varying dimensionalities, the task of balancing accuracy and parsimony of the solutions, and the manipulation of non-coding segments. We compare the performance of three proposed VLR approaches to sample the genome space: Increasing Length Genotypes, Oscillating Length Genotypes, and Uniformly Distributed Initial Population strategies. The advantages of reusing genetic material to replace non-coding segments are also emphasized in this work. It is shown, through examples in both analog and digital electronics, that the variable length genotype's representation is natural to this particular domain of application. A brief discussion on biological genome evolution is also provided. C1 [Zebulum, Ricardo S.] Univ Sussex, Sch Biol, CCNR, Brighton BN1 9QG, E Sussex, England. RP Zebulum, RS (reprint author), NASA, Jet Prop Lab, Washington, DC 20546 USA. EM ricardoz@cogs.susx.ac.uk; marco@ele.puc-rio.br; marley@ele.puc-rio.br RI Pacheco , Marco Aurelio /Q-3592-2016 FU CAPES Brazilian Federal Agency FX The authors wish to thank CAPES Brazilian Federal Agency for the financial support and Dr. Adrian Thompson, Dr. Inman Harvey, and Dr. David Nicholson from CCNR, Sussex, UK, for the collaboration. NR 48 TC 15 Z9 15 U1 0 U2 2 PU MIT PRESS PI CAMBRIDGE PA 55 HAYWARD STREET, CAMBRIDGE, MA 02142 USA SN 1063-6560 J9 EVOL COMPUT JI Evol. Comput. PD SPR PY 2000 VL 8 IS 1 BP 93 EP 120 DI 10.1162/106365600568112 PG 28 WC Computer Science, Artificial Intelligence; Computer Science, Theory & Methods SC Computer Science GA V20AY UT WOS:000208114100005 PM 10753232 ER PT J AU Ledyard, J Porter, D Wessen, R AF Ledyard, John Porter, David Wessen, Randii TI A Market-Based Mechanism for Allocating Space Shuttle Secondary Payload Priority SO EXPERIMENTAL ECONOMICS LA English DT Article DE mechanism design; auctions; scheduling AB This is an investigation into the design of a market-based process to replace NASA's current committee process for allocating Shuttle secondary payload resources (lockers, Watts and crew). The market-based process allocates budgets of tokens to NASA internal organizations that in turn use the budget to bid for priority for their middeck payloads. The scheduling algorithm selects payloads by priority class and maximizes the number of tokens bid to determine a manifest. The results of a number of controlled experiments show that such a system tends to allocate resources more efficiently by guiding participants to make resource and payload tradeoffs. Most participants were able to improve their position over NASA's current ranking system. Furthermore, those that are better off make large improvements while the few that do worse have relatively small losses. C1 [Ledyard, John] CALTECH, Div Humanities & Social Sci, Pasadena, CA 91125 USA. [Porter, David] Univ Arizona, Econ Sci Lab, Tucson, AZ 85721 USA. [Wessen, Randii] CALTECH, Jet Prop Lab, Syst Div, Pasadena, CA 91109 USA. RP Ledyard, J (reprint author), CALTECH, Div Humanities & Social Sci, Pasadena, CA 91125 USA. NR 14 TC 9 Z9 9 U1 0 U2 2 PU SPRINGER PI DORDRECHT PA VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS SN 1386-4157 J9 EXP ECON JI Exp. Econ. PD MAR PY 2000 VL 2 IS 3 BP 173 EP 195 PG 23 WC Economics SC Business & Economics GA V28FI UT WOS:000208666300001 ER PT J AU Concus, P Finn, R Weislogel, M AF Concus, P Finn, R Weislogel, M TI Measurement of critical contact angle in a microgravity space experiment SO EXPERIMENTS IN FLUIDS LA English DT Article AB Mathematical theory predicts that small changes in container shape or in contact angle can give rise to large shifts of liquid in a microgravity environment. This phenomenon was investigated in the Interface Configuration Experiment on board the NASA USML-2 Space Shuttle flight. The experiment's "double proboscis" containers were designed to strike a balance between conflicting requirements of sizable volume of liquid shift (for ease of observation) and abruptness of the shift (for accurate determination of critical contact angle). The experimental results support the classical concept of macroscopic contact angle and demonstrate the role of hysteresis in impeding orientation toward equilibrium. C1 Univ Calif Berkeley, Lawrence Berkeley Lab, Berkeley, CA 94720 USA. Univ Calif Berkeley, Dept Math, Berkeley, CA 94720 USA. Stanford Univ, Dept Math, Stanford, CA 94305 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Concus, P (reprint author), Univ Calif Berkeley, Lawrence Berkeley Lab, Berkeley, CA 94720 USA. NR 15 TC 18 Z9 19 U1 1 U2 11 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0723-4864 J9 EXP FLUIDS JI Exp. Fluids PD MAR PY 2000 VL 28 IS 3 BP 197 EP 205 DI 10.1007/s003480050379 PG 9 WC Engineering, Mechanical; Mechanics SC Engineering; Mechanics GA 304HG UT WOS:000086477200001 ER PT J AU Polovina, JJ Kobayashi, DR Parker, DM Seki, MP Balazs, GH AF Polovina, JJ Kobayashi, DR Parker, DM Seki, MP Balazs, GH TI Turtles on the edge: movement of loggerhead turtles (Caretta caretta) along oceanic fronts, spanning longline fishing grounds in the central North Pacific, 1997-1998 SO FISHERIES OCEANOGRAPHY LA English DT Article DE Caretta caretta; central North Pacific; loggerhead turtles; longline fishery; satellite remote sensing; subtropical front ID SEAWIFS; HAWAII AB Nine juvenile loggerhead sea turtles tracked during 1997 and 1998 in the central North Pacific by satellite telemetry all travelled westward, against prevailing currents, along two convergent fronts identified by satellite remotely sensed data on sea surface temperature (SST), chlorophyll and geostrophic currents. These fronts are characterized by gradients in sea surface height that produce an eastward geostrophic current, with gradients in surface chlorophyll and SST. Six of the turtles were associated with a front characterized by 17 degrees C SST, surface chlorophyll of about 0.2 mg m(-3), and eastward geostrophic current of about 4 cm s(-1), while the other three turtles were associated with a front with 20 degrees C SST, surface chlorophyll of about 0.1 mg m(-3), and eastward geostrophic flow of about 7 cm s(-1). These results appear to explain why incidental catch rates of loggerheads in the Hawaii longline fishery are highest when gear is set at 17 degrees C and 20 degrees C, SST. Further, from the seasonal distribution of longline effort relative to these fronts, it appears that the surface longline fishing ground lies largely between these two fronts during the first quarter and well to the south of the 17 degrees C front, but including the 20 degrees C front, in the second quarter. These findings suggest seasonal or area closures of the longline fishery that could be tested to reduce incidental catches of loggerheads. Finally, these results illustrate the insights which can be achieved by combining data on movement of pelagic animals with concurrent remotely sensed environmental data. C1 Natl Marine Fisheries Serv, Honolulu Lab, SW Fisheries Sci Ctr, NOAA, Honolulu, HI 96822 USA. Univ Hawaii, Joint Inst Marine & Atmospher Res, Honolulu, HI 96822 USA. RP Polovina, JJ (reprint author), Natl Marine Fisheries Serv, Honolulu Lab, SW Fisheries Sci Ctr, NOAA, 2570 Dole St, Honolulu, HI 96822 USA. NR 21 TC 158 Z9 169 U1 1 U2 23 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 1054-6006 J9 FISH OCEANOGR JI Fish Oceanogr. PD MAR PY 2000 VL 9 IS 1 BP 71 EP 82 DI 10.1046/j.1365-2419.2000.00123.x PG 12 WC Fisheries; Oceanography SC Fisheries; Oceanography GA 323FK UT WOS:000087552000006 ER PT J AU Ryer, CH Olla, BL AF Ryer, CH Olla, BL TI Avoidance of an approaching net by juvenile walleye pollock Theragra chalcogramma in the laboratory: the influence of light intensity SO FISHERIES RESEARCH LA English DT Article DE fish behavior; fishing gear; illumination; bycatch; gear selectivity; stress; walleye pollock; Theragra chalcogramma ID FISH; GEAR AB Fisheries management strategies often rely upon regulation of mesh sizes or the use of exclusion/escape structures to reduce the bycatch of undersize fish or non-target species. Design and evaluation of fishing gears to reduce bycatch should be based upon knowledge of fish behavior and sensory capabilities. The response of juvenile walleye pollock Theragra chalcogramma to an approaching panel made of 8 cm square mesh netting was compared under a range of laboratory illuminations, from <1 x 10(-8) (darkness) to 1.7 x 10(-3) mu moles photons m(-2)s(-1). Fish in darkness struck the net more frequently and swam closer to the net than fish at the highest illumination. These results, along with those of other laboratory and field studies, suggest that trawl bycatch reduction strategies which rely upon undersize or non-target fish using vision to guide them out of the net may be less effective at night or at depths where ambient light levels fall below critical levels. (C) 2000 Elsevier Science B.V. All rights reserved. C1 Oregon State Univ, Hatfield Marine Sci Ctr, Natl Marine Fisheries Serv, Alaska Fisheries Sci Ctr,Fisheries Behav Ecol Pro, Newport, OR 97365 USA. RP Ryer, CH (reprint author), Oregon State Univ, Hatfield Marine Sci Ctr, Natl Marine Fisheries Serv, Alaska Fisheries Sci Ctr,Fisheries Behav Ecol Pro, Newport, OR 97365 USA. NR 12 TC 24 Z9 25 U1 0 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0165-7836 J9 FISH RES JI Fish Res. PD MAR PY 2000 VL 45 IS 2 BP 195 EP 199 DI 10.1016/S0165-7836(99)00113-7 PG 5 WC Fisheries SC Fisheries GA 295VC UT WOS:000085987700009 ER PT J AU Grant, JA AF Grant, JA TI Valley formation in Margaritifer Sinus, Mars, by precipitation-recharged ground-water sapping SO GEOLOGY LA English DT Article DE Mars; valleys; precipitation; ground-water sapping ID TOPOGRAPHY; SURFACE; BASINS AB Drainage morphometry and geologic mapping place new constraints on valley origin in Margaritifer Sinus, Mars. Preserved valleys are constant width, typically head near divides, possess fourth-order trunk segments, and were formed from late Noachian into earliest Hesperian time. Relative to terrestrial systems, the Martian valleys have low densities (<0.1 km/km(2)), relief ratios (0.001-0.13), and ruggedness numbers (0.005-0.086), and the sediment volume in associated sinks exceeds the volume excavated by upstream segments. Valley characteristics are consistent with formation by precipitation-recharged ground-water sapping within a layered, permeable substrate. C1 SUNY Coll Buffalo, Dept Earth Sci, Buffalo, NY 14222 USA. RP Grant, JA (reprint author), NASA Headquarters, Code SR, Washington, DC 20546 USA. NR 24 TC 63 Z9 63 U1 1 U2 3 PU GEOLOGICAL SOC AMERICA, INC PI BOULDER PA PO BOX 9140, BOULDER, CO 80301-9140 USA SN 0091-7613 J9 GEOLOGY JI Geology PD MAR PY 2000 VL 28 IS 3 BP 223 EP 226 DI 10.1130/0091-7613(2000)28<223:VFIMSM>2.0.CO;2 PG 4 WC Geology SC Geology GA 288YE UT WOS:000085591400008 ER PT J AU Joshi, MM Hollingsworth, JL Haberle, RM Bridger, AFC AF Joshi, MM Hollingsworth, JL Haberle, RM Bridger, AFC TI An interpretation of Martian thermospheric waves based on analysis of a general circulation model SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID MARS GLOBAL SURVEYOR; ATMOSPHERE; TIDES AB Planetary-scale longitudinal variations in density observed by the Mars Global Surveyor accelerometer in the 125 km region can be qualitatively reproduced by the NASA Ames Mars general circulation model in the 80 km altitude region, but only when locations having specific local times are used in the analysis. If the model results are averaged over all local times, the high-altitude longitudinal variations nearly disappear, leaving only a small stationary wave 1 pattern, consistent with theory and previous modeling studies. This analysis suggests that the observed wavelike structures are a result of sampling tidal modes at a limited range of local times, rather than by topographically forced Rossby waves as previously suggested. C1 SETI Inst, Mt View, CA USA. RP Joshi, MM (reprint author), NASA, Ames Res Ctr, MS 245-3, Moffett Field, CA 94035 USA. RI Joshi, Manoj/C-1795-2008 OI Joshi, Manoj/0000-0002-2948-2811 NR 12 TC 13 Z9 13 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD MAR 1 PY 2000 VL 27 IS 5 BP 613 EP 616 DI 10.1029/1999GL010936 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 288YJ UT WOS:000085591800008 ER PT J AU Cummer, SA Vondrak, RR Ostgaard, N Stadsnes, J Bjordal, J Chenette, DL Brittnacher, MJ Parks, GK Sigwarth, JB Frank, LA AF Cummer, SA Vondrak, RR Ostgaard, N Stadsnes, J Bjordal, J Chenette, DL Brittnacher, MJ Parks, GK Sigwarth, JB Frank, LA TI Global multispectral auroral imaging of an isolated substorm SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID PRECIPITATION; ENERGY AB We analyze simultaneous visible, ultraviolet (UV), and X-ray auroral images of an isolated substorm on January 25, 1998. The total precipitating electron energy flux and mean energy extracted near substorm maximum from each of the imagers are in acceptable agreement. The expansion phase visible, UV, and Xray emissions are morphologically similar, with the brightest emissions coming from the auroral surge. However, during the recovery phase, there are regions of bright X-ray emissions near local midnight and dawn that do not correspond to obvious features in the visible and UV images. X-ray energy analysis in these regions reveals a high energy (similar to 30-100 keV) component of the precipitating electron population that contributes similar to 30% of the total electron energy flux. The temporal development of the X rays indicates that the dawn emissions originate in a drifting electron population, while the newly revealed midnight emissions originate in a continuous injection of energetic electrons in a narrow local time region. C1 Duke Univ, Dept Elect & Comp Engn, Durham, NC 27708 USA. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. Univ Bergen, Dept Phys, N-5007 Bergen, Norway. Lockheed Martin Adv Technol Ctr, Palo Alto, CA 94304 USA. Univ Washington, Dept Geophys, Seattle, WA 98195 USA. Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA. RP Cummer, SA (reprint author), Duke Univ, Dept Elect & Comp Engn, Durham, NC 27708 USA. RI Cummer, Steven/A-6118-2008 OI Cummer, Steven/0000-0002-0002-0613 NR 13 TC 3 Z9 4 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD MAR 1 PY 2000 VL 27 IS 5 BP 637 EP 640 DI 10.1029/1999GL003678 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 288YJ UT WOS:000085591800014 ER PT J AU Sassen, K Benson, RP Spinhirne, JD AF Sassen, K Benson, RP Spinhirne, JD TI Tropical cirrus cloud properties derived from TOGA/COARE airborne polarization lidar SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID OPTICAL-PROPERTIES; TROPOPAUSE; CLIMATE AB During the January-February 1993 TOGA/COARE intensive field program, airborne polarization lidar data were collected from cirrus clouds generated by thunderstorm anvils over the western Pacific Ocean. The cirrus cloud tops typically extended to near the 16.85 km average tropical tropopause. Average lidar linear depolarization ratios delta show a consistent increase with height, with the maximum delta approximate to 0.52 values found at the tropopause. This finding can be interpreted in terms of a fundamental dependence of ice crystal habit or axis ratio on temperature. Although similar delta trends have been observed elsewhere, a complication in this case is that the cirrus may have been affected by the Pinatubo volcanic aerosol, which midlatitude research indicates could alter ice crystal shapes. C1 Univ Utah, Dept Meteorol, Salt Lake City, UT 84112 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Sassen, K (reprint author), Univ Utah, Dept Meteorol, 135 S 1460 E 819 WBB, Salt Lake City, UT 84112 USA. NR 18 TC 23 Z9 23 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD MAR 1 PY 2000 VL 27 IS 5 BP 673 EP 676 DI 10.1029/1999GL010946 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 288YJ UT WOS:000085591800023 ER PT J AU Sherwood, SC AF Sherwood, SC TI A stratospheric "drain" over the maritime continent SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID AVERAGE VERTICAL MOTIONS; WIND PROFILERS AB Operational wind data are used to show that the time-averaged mass flux near the tropopause is downward over the maritime continent (Indonesia) region during both summer and winter. The air descends within a layer above the convective level of neutral buoyancy (despite mean upward motion below and above this layer) and must rise through the mean tropopause elsewhere, contradicting the common view that the entry occurs over strongly-convecting regions. Closing the energy budget in the sinking regions requires an energy sink; one possibility is that overshooting convective clouds are irreversibly injecting cold, heavy air at great heights. C1 Univ Space Res Assoc, Seabrook, MD USA. RP Sherwood, SC (reprint author), NASA, Goddard Space Flight Ctr, Mail Code 916, Greenbelt, MD 20771 USA. RI Sherwood, Steven/B-5673-2008 OI Sherwood, Steven/0000-0001-7420-8216 NR 21 TC 80 Z9 82 U1 1 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD MAR 1 PY 2000 VL 27 IS 5 BP 677 EP 680 DI 10.1029/1999GL010868 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 288YJ UT WOS:000085591800024 ER PT J AU Wang, LP Chao, Y Koblinsky, C Howden, S AF Wang, LP Chao, Y Koblinsky, C Howden, S TI Influence of lateral boundaries on mesoscale variability SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID KUROSHIO EXTENSION; GEOSAT ALTIMETRY; GULF-STREAM; ATLANTIC; ENERGY AB Using the Florida Strait as:a prototype, it is shown that lateral boundaries can have a significant dynamic influence on mesoscale variability, provided the distance between the lateral boundaries is very close to the critical width for baroclinic instability (D-c = pi L-r/root 2, L-r is the internal Rossby radius of deformation). As a result, the close relation between strong background currents and mesoscale variability found in open-ocean settings breaks down. In addition, straits that are narrow enough can very effectively block through-strait movement of strong mesoscale variability. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Maryland, ESSIC, College Pk, MD USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Wang, LP (reprint author), NASA, Goddard Space Flight Ctr, Code 971, Greenbelt, MD 20771 USA. NR 15 TC 0 Z9 0 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 2000 VL 27 IS 5 BP 709 EP 712 DI 10.1029/1999GL002361 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 288YJ UT WOS:000085591800032 ER PT J AU Wadhams, P Comiso, J AF Wadhams, P Comiso, J TI Two modes of appearance of the Odden ice tongue in the Greenland Sea (vol 26, pg 2497, 1999) SO GEOPHYSICAL RESEARCH LETTERS LA English DT Correction C1 Univ Cambridge, Scott Polar Res Inst, Cambridge CB2 1ER, England. NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. RP Wadhams, P (reprint author), Univ Cambridge, Scott Polar Res Inst, Cambridge CB2 1ER, England. NR 1 TC 0 Z9 0 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD MAR 1 PY 2000 VL 27 IS 5 BP 717 EP 717 DI 10.1029/2000GL000001 PG 1 WC Geosciences, Multidisciplinary SC Geology GA 288YJ UT WOS:000085591800034 ER PT J AU Fung, IY Meyn, SK Tegen, I Doney, SC John, JG Bishop, JKB AF Fung, IY Meyn, SK Tegen, I Doney, SC John, JG Bishop, JKB TI Iron supply and demand in the upper ocean SO GLOBAL BIOGEOCHEMICAL CYCLES LA English DT Article ID EQUATORIAL PACIFIC-OCEAN; SUB-ARCTIC PACIFIC; LIMITS PHYTOPLANKTON GROWTH; WORLD OCEAN; MARINE-PHYTOPLANKTON; SURFACE SEAWATER; SOUTHERN-OCEAN; LIMITATION; CIRCULATION; NITRATE AB Iron is hypothesized to be a limiting micronutrient for ocean primary production. This paper presents an analysis of the iron budget in the upper ocean. The global distribution of annual iron assimilation by phytoplankton was estimated from distributions of satellite-derived oceanic primary production and measured (Fe:C)(cellular) ratios. The distributions of iron supply by upwelling/mixing and aeolian deposition were obtained by applying (Fe:NO3)(dissolved) ratios to the nitrate supply and by assuming the soluble fraction of mineral aerosols. A lower bound on the rate of iron recycling in the photic zone was estimated as the difference between iron assimilation and supply. Global iron assimilation by phytoplankton for The open ocean was estimated to be 12x10(9) mol Fe yr(-1). Atmospheric deposition of total Fe is estimated to be 96x10(9) mol Fe yr(-1) in the open ocean, with the soluble Fe fraction ranging between 1 and 10% (or 1-10x10(9) mol Fe yr(-1)). By comparison, the upwelling/entrainment supply of dissolved Fe to the upper ocean is small, similar to 0.7x 10(9) mol Fe yr(-1). Uncertainties in the aeolian flux and assimilation may be as large as a factor of 5-10 but remain difficult to quantify, as information is limited about the form and transformation of iron from the soil to phytoplankton incorporation. An iron stress index, relating the (Fe:N) demand to the (Fe:N) supply, confirms the production in the high-nitrate low-chlorophyll regions is indeed limited by iron availability. C1 Univ Calif Berkeley, Ctr Atmospher Sci, Berkeley, CA 94720 USA. Univ Calif Berkeley, Lawrence Berkeley Lab, Berkeley, CA 94720 USA. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Natl Ctr Atmospher Res, Boulder, CO 80303 USA. Univ British Columbia, Dept Geog, Vancouver, BC V6T 1Z2, Canada. Univ Victoria, Victoria, BC V8W 2Y2, Canada. RP Fung, IY (reprint author), Univ Calif Berkeley, Ctr Atmospher Sci, 307 McCone Hall 4767, Berkeley, CA 94720 USA. RI Doney, Scott/F-9247-2010; John, Jasmin/F-8194-2012 OI Doney, Scott/0000-0002-3683-2437; John, Jasmin/0000-0003-2696-277X NR 75 TC 329 Z9 336 U1 8 U2 63 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0886-6236 J9 GLOBAL BIOGEOCHEM CY JI Glob. Biogeochem. Cycle PD MAR PY 2000 VL 14 IS 1 BP 281 EP 295 DI 10.1029/1999GB900059 PG 15 WC Environmental Sciences; Geosciences, Multidisciplinary; Meteorology & Atmospheric Sciences SC Environmental Sciences & Ecology; Geology; Meteorology & Atmospheric Sciences GA 292RM UT WOS:000085808900022 ER PT J AU Weiser, ES Johnson, TF St Clair, TL Echigo, Y Kaneshiro, H Grimsley, BW AF Weiser, ES Johnson, TF St Clair, TL Echigo, Y Kaneshiro, H Grimsley, BW TI Polyimide foams for aerospace vehicles SO HIGH PERFORMANCE POLYMERS LA English DT Article AB Due to a demand by the aerospace industry, NASA has begun developing the next generation of polyimide foams which could be utilized to reduce vehicle weight for the X-33 and Reusable Launch Vehicle (RLV) programmes. The activity at NASA Langley Research Center focuses on developing polyimide foam and foam structures which are made using monomeric solutions or salt solutions formed from the reaction of a dianhydride and diamine dissolved in a mixture of foaming agents and alkyl alcohols. This process can produce polyimide foams with varying properties from a large number of monomers and monomer blends. The specific densities of these foams can range from 0.008 g cc(-1) to 0.32 g cc(-1). Polyimide foams at densities of 0.032 g cc(-1) and 0.08 g cc(-1) were tested for a wide range of physical properties. The foams demonstrated excellent thermal stability at 321 degrees C, a good thermal conductivity at 25 degrees C of 0.03 W m(-1) K-1, compressive strengths as high as 0.84 MPa at 10% deflection and a limiting oxygen index of 51%. Thermomechanical cyclic testing was also performed on these materials for 50 cycles at temperatures from -253 degrees C to 204 degrees C. The foams survived the cyclic testing without debonding or cracking. Thermal forming of the 0.032 g cc(-1) foam was performed and a minimum radius curvature of 0.0711 m was achieved. The foams exhibited excellent properties overall and are shown to be viable for use as cryogenic insulation on the next generation RLV. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Unitika Ltd, Kyoto 611, Japan. Old Dominion Univ, Norfolk, VA 23529 USA. RP Weiser, ES (reprint author), NASA, Langley Res Ctr, 6A W Taylor St M-S 226, Hampton, VA 23681 USA. NR 9 TC 60 Z9 66 U1 7 U2 39 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0954-0083 J9 HIGH PERFORM POLYM JI High Perform. Polym. PD MAR PY 2000 VL 12 IS 1 BP 1 EP 12 PG 12 WC Polymer Science SC Polymer Science GA 300QG UT WOS:000086263200003 ER PT J AU Kim, MHY Thibeault, SA Wilson, JW Simonsen, LC Heilbronn, L Chang, K Kiefer, RL Weakley, JA Maahs, HG AF Kim, MHY Thibeault, SA Wilson, JW Simonsen, LC Heilbronn, L Chang, K Kiefer, RL Weakley, JA Maahs, HG TI Development and testing of in situ materials for human exploration of Mars SO HIGH PERFORMANCE POLYMERS LA English DT Article ID COSMIC-RAYS AB Interplanetary space radiation poses a serious health hazard in long-term manned space missions. Natural Martian surface materials are evaluated for their potential use as radiation shields for manned Mars missions. The modified radiation fluences behind various kinds of Martian rocks and regolith are determined by solving the Boltzmann equation using NASA Langley's HZETRN code along with the 1977 Solar Minimum galactic cosmic ray environmental model. To make structural shielding composite materials from constituents of the Martian atmosphere and from Martian regolith for Martian surface habitats, schemes for synthesizing polyimide from the Martian atmosphere and for processing Martian regolith/polyimide composites are proposed. Theoretical predictions of the shielding properties of these composites are computed to assess their shielding effectiveness. Adding high-performance polymer binders to Martian regolith to enhance the structural properties also enhances the shielding properties of these composites because of the added hydrogenous constituents. Laboratory testing of regolith simulant/polyimide composites is planned in order to validate this prediction and also to measure various structural properties. C1 Coll William & Mary, Williamsburg, VA 23187 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. Univ Calif Berkeley, Lawrence Berkeley Lab, Berkeley, CA 94720 USA. Christopher Newport Univ, Newport News, VA 23606 USA. RP Kim, MHY (reprint author), Coll William & Mary, Williamsburg, VA 23187 USA. EM m.y.kim@larc.nasa.gov RI Heilbronn, Lawrence/J-6998-2013 OI Heilbronn, Lawrence/0000-0002-8226-1057 NR 24 TC 8 Z9 8 U1 0 U2 5 PU SAGE PUBLICATIONS LTD PI LONDON PA 1 OLIVERS YARD, 55 CITY ROAD, LONDON EC1Y 1SP, ENGLAND SN 0954-0083 J9 HIGH PERFORM POLYM JI High Perform. Polym. PD MAR PY 2000 VL 12 IS 1 BP 13 EP 26 DI 10.1088/0954-0083/12/1/302 PG 14 WC Polymer Science SC Polymer Science GA 300QG UT WOS:000086263200004 ER PT J AU Connell, JW AF Connell, JW TI The effect of low Earth orbit atomic oxygen exposure on phenylphosphine oxide-containing polymers SO HIGH PERFORMANCE POLYMERS LA English DT Article ID POLY(ARYLENE ETHER HETEROCYCLE)S; CONTAINING POLYIMIDES; FILMS AB Thin films of phenylphosphine oxide-containing polymers were exposed to low Earth orbit aboard a space shuttle Eight (STS-85) as part of Right experiment designated Evaluation of Space Environment and Effects on Materials (ESEM). This flight experiment was a cooperative effort between the NASA Langley Research Center (LaRC) and the National Space Development Agency of Japan (NASDA). The thin-film samples described herein were part of an atomic oxygen exposure (AOE) experiment and were exposed to primarily atomic oxygen (similar to 1 x 10(19) atoms cm(-2)). The thin-film samples consisted of three phosphine oxide-containing polymers (arylene ether, benzimidazole and imide). Based on post-flight analyses using atomic force microscopy, x-ray photo-electron spectroscopy and weight loss data, it was found that the exposure of these materials to atomic oxygen (AO) produces a phosphorus oxide layer on the surface of the samples. Earlier work has shown that this layer provides a barrier towards further attack by AO. Consequently, these materials do not exhibit linear erosion rates which is in contrast with most organic polymers. Qualitatively, the results obtained from these analyses compare favourably with those obtained from samples exposed to AO and/or an oxygen plasma in ground-based exposure experiments. The results of the low Earth orbit AO exposure on these materials will be compared with those of ground-based exposure to AO. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Connell, JW (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 31 TC 27 Z9 31 U1 2 U2 9 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0954-0083 J9 HIGH PERFORM POLYM JI High Perform. Polym. PD MAR PY 2000 VL 12 IS 1 BP 43 EP 52 DI 10.1088/0954-0083/12/1/304 PG 10 WC Polymer Science SC Polymer Science GA 300QG UT WOS:000086263200006 ER PT J AU Harvey, GA Humes, DH Kinard, WH AF Harvey, GA Humes, DH Kinard, WH TI Shuttle and MIR special environmental effects and hardware cleanliness SO HIGH PERFORMANCE POLYMERS LA English DT Article AB The Evaluation of Space Environment and Effects on Materials (ESEM) experiments were developed, flown in-space on the STS-85 mission (August 1997), returned to Earth and analysed as one element of a collaboration between the National Space Development Agency (NASDA) of Japan and the National Aeronautics and Space Agency (NASA) of the United States. The primary objectives of the ESEM experiments were to investigate atomic oxygen effects on materials, cosmic dust and man-made debris, and Shuttle-induced contamination. In particular, the change in scattering of light from the 1/4 mil aluminized Kapton film due to atomic oxygen erosion and Shuttle-induced molecular contamination are discussed. The MIR environmental effects payload (MEEP) was attached to the docking module of the MIR space station for 18 months during calendar years 1996 and 1997 (March 1996, STS 76 to October 1997, STS 86). A solar panel array with more than 10 years space exposure was removed from the MIR core module in November 1997 and returned to Earth in January 1998, STS 89. MEEP and the returned solar array are part of the International Space Station (ISS) Risk Mitigation Program. This space Eight hardware has been inspected and studied by teams of space environmental effects (SEE) investigators for micrometeoroid and space debris effects, space exposure effects on materials and electrical performance. This paper reports changes in cleanliness of parts of MEEP and the solar array due to the space exposures. Special attention is given to the extensive water soluble residues deposited on some of the Eight hardware surfaces. Directionality of deposition and chemistry of these residues are discussed. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Harvey, GA (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 2 TC 0 Z9 0 U1 2 U2 8 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0954-0083 J9 HIGH PERFORM POLYM JI High Perform. Polym. PD MAR PY 2000 VL 12 IS 1 BP 65 EP 82 DI 10.1088/0954-0083/12/1/306 PG 18 WC Polymer Science SC Polymer Science GA 300QG UT WOS:000086263200008 ER PT J AU de Groh, KK Gaier, JR Hall, RL Espe, MP Cato, DR Sutter, JK Scheiman, DA AF de Groh, KK Gaier, JR Hall, RL Espe, MP Cato, DR Sutter, JK Scheiman, DA TI Insights into the damage mechanism of Teflon (R) FEP from the Hubble Space Telescope SO HIGH PERFORMANCE POLYMERS LA English DT Article AB Metallized Teflon(R) FEP (fluorinated ethylene propylene) thermal control material on the Hubble Space Telescope (HST) has been found to be degrading in the space environment. Teflon(R) FEP thermal control blankets (space-facing FEP) retrieved during the first servicing mission (SM1) were found to be embrittled on solar-facing surfaces and contained microscopic cracks. During the second servicing mission (SM2) astronauts noticed that the FEP outer layer of the multi-layer insulation (MLI) covering the telescope was cracked in many locations around the telescope. Large cracks were observed on the light shield, forward shell and equipment bays. A tightly curled piece of cracked FEP from the light shield was retrieved during SM2 and was severely embrittled, as witnessed by ground testing. A failure review board was organized to determine the mechanism causing the MLI degradation. Density, x-ray crystallinity and solid-state nuclear magnetic resonance (NMR) analyses of the FEP retrieved during SM1 were inconsistent with results of FEP retrieved during SM2. Because the retrieved SM2 material was curled while in space, it experienced a higher temperature extreme during thermal cycling, estimated at 200 degrees C, than the SM1 material, estimated at 50 degrees C, An investigation on the effects of heating pristine FEP and FEP retrieved from the HST was therefore conducted. Samples of pristine, SMI and SM2 FEP were heated to 200 degrees C and evaluated for changes in density and morphology. Elevated temperature exposure was found to have a major impact on the density of the retrieved materials. The characterization of the polymer morphology of the as-received and heated FEP by NMR provided results that were consistent with the density results. Differential scanning calorimetry (DSC) was conducted on pristine, SM1 and SM2 FEP DSC results provided evidence of chain scission and increased crystallinity in the space exposed FEP, which supported the density and NMR results. Samples exposed to simulated solar hare x-rays, thermal cycling and long-term thermal exposure provided information on the environmental contributions to degradation. These findings have provided insight into the damage mechanisms of FEP in the space environment. C1 NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. Ohio Aerosp Inst, Brook Pk, OH 44142 USA. Univ Akron, Dept Chem, Akron, OH 44325 USA. Dynacs Engn Inc, Brook Pk, OH 44142 USA. RP de Groh, KK (reprint author), NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. NR 27 TC 33 Z9 33 U1 0 U2 8 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0954-0083 J9 HIGH PERFORM POLYM JI High Perform. Polym. PD MAR PY 2000 VL 12 IS 1 BP 83 EP 104 PG 22 WC Polymer Science SC Polymer Science GA 300QG UT WOS:000086263200009 ER PT J AU Dever, JA de Groh, KK Banks, BA Townsend, JA Barth, JL Thomson, S Gregory, T Savage, W AF Dever, JA de Groh, KK Banks, BA Townsend, JA Barth, JL Thomson, S Gregory, T Savage, W TI Environmental exposure conditions for Teflon (R) fluorinated ethylene propylene on the Hubble Space Telescope SO HIGH PERFORMANCE POLYMERS LA English DT Article AB The outer layer of Teflon(R) fluorinated ethylene propylene (FEP) multi-layer insulation (MLI) on the Hubble Space Telescope (HST) was observed to be significantly cracked at the time of the Second HST Servicing Mission (SM2), 6.8 years after HST was launched into low Earth orbit (LEO). Comparatively minor embrittlement and cracking were also observed in the FEP materials retrieved from solar-facing surfaces on the HST at the time of the First Servicing Mission (3.6 years exposure). After SM2, a failure review board was convened to address the problem of degradation of MLI on the HST. In order for this board to determine possible degradation mechanisms, it was necessary to consider all environmental constituents to which the FEP MLI surfaces were exposed. Based on measurements and various models, the environmental exposure conditions for the FEP surfaces on the HST were estimated, including: the number and temperature ranges of thermal cycles; equivalent sun hours; fluence and absorbed radiation dose of x-rays, trapped protons and electrons and plasma electrons and protons: and atomic oxygen (AO) fluence. This paper presents the environmental exposure conditions for FEP on the HST, briefly describing the possible roles of the environmental factors in the observed FEP embrittlement and providing references to the published works which describe in detail testing and analysis related to FEP degradation on the HST. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Cleveland State Univ, Cleveland, OH 44115 USA. RP Dever, JA (reprint author), NASA, Lewis Res Ctr, 21000 Brookpk Rd, Cleveland, OH 44135 USA. NR 26 TC 41 Z9 42 U1 1 U2 6 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0954-0083 J9 HIGH PERFORM POLYM JI High Perform. Polym. PD MAR PY 2000 VL 12 IS 1 BP 125 EP 139 DI 10.1088/0954-0083/12/1/310 PG 15 WC Polymer Science SC Polymer Science GA 300QG UT WOS:000086263200012 ER PT J AU Smith, JG Connell, JW AF Smith, JG Connell, JW TI Chemistry and properties of imide oligomers from phenylethynyl-containing diamines SO HIGH PERFORMANCE POLYMERS LA English DT Article ID PENDENT; POLYIMIDES; ACID AB As an extension of work on pendent phenylethynyl-containing imide oligomers, three new diamines containing pendent phenylethynyl groups were prepared and characterized. These diamines were used to prepare pendent and pendent and terminal phenylethynyl imide oligomers via the amide acid route in N-methyl-2-pyrrolidinone at a calculated number average molecular weight of 5000 g mol(-1). The pendent phenylethynyl groups were randomly distributed along the oligomer backbone and provided a means of controlling the distance between reactive sites. The imide oligomers were characterized and thermally cured, and the cured polymers evaluated as thin films and compared with materials of similar composition prepared from 3,5-diamino-4'-phenylethynyibenzophenone. This work was performed as part of a continuing research effort to develop structural resins for potential aeronautical applications. C1 NASA, Langley Res Ctr, Adv Mat & Proc Branch, Hampton, VA 23681 USA. RP Smith, JG (reprint author), NASA, Langley Res Ctr, Adv Mat & Proc Branch, Hampton, VA 23681 USA. NR 33 TC 11 Z9 11 U1 1 U2 5 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0954-0083 J9 HIGH PERFORM POLYM JI High Perform. Polym. PD MAR PY 2000 VL 12 IS 1 BP 213 EP 223 DI 10.1088/0954-0083/12/1/318 PG 11 WC Polymer Science SC Polymer Science GA 300QG UT WOS:000086263200020 ER PT J AU Kelley, MS Gaffey, MJ AF Kelley, MS Gaffey, MJ TI 9 Metis and 113 Amalthea: A genetic asteroid pair SO ICARUS LA English DT Article DE asteroids; asteroids, composition; asteroids, Metis, Amalthea; spectrophotometry; surfaces, asteroids ID ACHONDRITE METEORITES; RADAR OBSERVATIONS; PARENT BODY; FAMILIES; VESTA; EVOLUTION; SEARCH AB Recent analyses of spectrophotometric data of asteroids 9 Metis and 113 Amalthea have revealed a probable genetic (compositional) link between these two objects. The nearly identical composition of the silicate components of these two asteroids is consistent with their derivation from a single parent body. Based on the present compositional and morphological interpretations of 9 Metis and 113 Amalthea, and using plausible (chondritic) starting compositions for the parent body, the original parent asteroid is estimated to have been between approximately 300 and 600 km in diameter. Thus Metis and Amalthea are the largest survivors of a highly evolved, genetic asteroid family from which 86-96% of the original mass has been lost. (C) 2000 Academic Press. C1 Rensselaer Polytech Inst, Planetary Sci Lab, Dept Earth & Environm Sci, Sci Ctr 1C25, Troy, NY 12180 USA. RP Kelley, MS (reprint author), NASA, Lyndon B Johnson Space Ctr, Mail Code SN2, Houston, TX 77058 USA. NR 65 TC 8 Z9 8 U1 0 U2 0 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD MAR PY 2000 VL 144 IS 1 BP 27 EP 38 DI 10.1006/icar.1999.6266 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 299VQ UT WOS:000086218900003 ER PT J AU Poulet, F Sicardy, B Nicholson, PD Karkoschka, E Caldwell, J AF Poulet, F Sicardy, B Nicholson, PD Karkoschka, E Caldwell, J TI Saturn's ring-plane crossings of August and November 1995: A model for the new F-ring objects SO ICARUS LA English DT Article DE planetary rings, Saturn; observation; dynamics ID ACCRETION; SATELLITES; EVOLUTION; SYSTEM AB We analyze observations made in August and November 1995 during the Earth and Sun crossings of Saturn's ring plane, respectively. The August 1995 observations combine data taken with the Adonis adaptive optics system at the European Southern Observatory (ESO) and images from the Hubble Space Telescope (HST), The November 1995 data are based on HST images only. We report here the detections of four new objects (three in August, one in November) orbiting near, or within, the F ring of Saturn. Two of the objects observed at ESO in August 1995 are most probably S/1995 S5 and S/1995 S6, reported by P. D. Nicholson et al, (1996, Science 272, 509-515) from the HST observations on August 10, 1995, The third object, S/1995 S20 cannot be clearly linked with any other objects reported by other observers, An elongated object, or are, is tracked in November 1995, acid can be connected to one of the arcs also reported by Nicholson et al. Our combined measurements improve the determination of the orbital parameters of S/1995 S5 and the are, indicating that these objects orbit, within the error bars (less than or similar to +/-140 km), in the F ring. We discuss the nature and origin of these F-ring features. We propose that they are clouds of regolith ejecta resulting from collisions between large particles, or "parent bodies," within the F ring. From the available constraints (brightness and lifetime of the objects), we show that the observations ate consistent with the presence of several hundred l-km-sized (and/or several thousand 100-m-sized) unseen parent bodies embedded in the F ring, each of which is covered by a regolith layer tens of centimeters to similar to 1 m in thickness (C) 2000 Academic Press. C1 Observ Paris, F-92195 Meudon, France. Observ Paris, Inst Univ France, F-92195 Meudon, France. Cornell Univ, Ctr Radiophys & Space Res, Ithaca, NY 14853 USA. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. York Univ, Dept Phys & Astron, N York, ON M3J 1P3, Canada. RP Poulet, F (reprint author), NASA, Ames Res Ctr, Mail Stop 245-3, Moffett Field, CA 94035 USA. NR 37 TC 37 Z9 37 U1 0 U2 1 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD MAR PY 2000 VL 144 IS 1 BP 135 EP 148 DI 10.1006/icar.2000.6267 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 299VQ UT WOS:000086218900011 ER PT J AU Mjolsness, E Tavormina, A AF Mjolsness, E Tavormina, A TI The synergy of biology, intelligent systems, and space exploration SO IEEE INTELLIGENT SYSTEMS & THEIR APPLICATIONS LA English DT Article C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Mjolsness, E (reprint author), CALTECH, Jet Prop Lab, MS 126-346,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 12 TC 2 Z9 2 U1 0 U2 0 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1314 USA SN 1094-7167 J9 IEEE INTELL SYST APP JI IEEE Intell. Syst. Appl. PD MAR-APR PY 2000 VL 15 IS 2 BP 20 EP + DI 10.1109/5254.850823 PG 6 WC Computer Science, Artificial Intelligence; Engineering, Electrical & Electronic SC Computer Science; Engineering GA 303DF UT WOS:000086405000009 ER PT J AU Simon, MK Alouini, MS AF Simon, MK Alouini, MS TI Exponential-type bounds on the generalized Marcum Q-function with application to error probability analysis over fading channels SO IEEE TRANSACTIONS ON COMMUNICATIONS LA English DT Article DE generalized Marcum Q-function; Nakagami fading; postdetection equal-gain combining AB Strict upper and lower bounds of exponential-type are derived for the generalized (mth order) Marcum Q-function which enable simple evaluation of a tight upper bound on the average bit-error probability performance of a wide class of noncoherent and differentially coherent communication systems operating over generalized fading channels. For the case of frequency-selective fading with arbitrary statistics per independent fading path, the resulting upper bound on performance is expressed in the form of a product of moment generating functions of the instantaneous power random variables that characterize these paths. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Minnesota, Dept Elect & Comp Engn, Minneapolis, MN 55455 USA. RP Simon, MK (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 18 TC 59 Z9 59 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0090-6778 J9 IEEE T COMMUN JI IEEE Trans. Commun. PD MAR PY 2000 VL 48 IS 3 BP 359 EP 366 DI 10.1109/26.837036 PG 8 WC Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA 301CG UT WOS:000086290100003 ER PT J AU Alouini, MS Simon, MK AF Alouini, MS Simon, MK TI An MGF-based performance analysis of generalized selection combining over Rayleigh fading channels SO IEEE TRANSACTIONS ON COMMUNICATIONS LA English DT Article; Proceedings Paper CT IEEE International Conference on Communications (ICC 99) CY JUN 06-10, 1999 CL VANCOUVER, CANADA SP IEEE DE generalized selection combining; hybrid SC/MRC; maximal ratio combining diversity; Rayleigh fading; selection combining ID MOBILE RADIO-COMMUNICATIONS; DIVERSITY; QAM; RECEPTION; INDOOR AB Using the notion of the "spacing" between ordered exponential random variables, a performance analysis of the generalized selection combining (GSC) diversity scheme over Rayleigh fading channels is presented and compared with that of the conventional maximal-ratio combining and selection combining schemes. Starting with the moment generating function of the GSC output signal-to-noise ratio (SNR), we derive closed-form expressions for the average combined SNR, outage probability, and average error probability of a wide variety of modulation schemes operating over independently, identically distributed (i.i.d.) diversity paths. Because of their simple form, these expressions readily allow numerical evaluation for cases of practical interest. The results are also extended to the case of non-i.i.d. diversity paths. C1 Univ Minnesota, Dept Elect & Comp Engn, Minneapolis, MN 55455 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Alouini, MS (reprint author), Univ Minnesota, Dept Elect & Comp Engn, Minneapolis, MN 55455 USA. EM alouini@ece.umn.edu; marvin.k.simon@jpl.nasa.gov NR 44 TC 281 Z9 283 U1 0 U2 2 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA SN 0090-6778 J9 IEEE T COMMUN JI IEEE Trans. Commun. PD MAR PY 2000 VL 48 IS 3 BP 401 EP 415 DI 10.1109/26.837044 PG 15 WC Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA 301CG UT WOS:000086290100011 ER PT J AU Kim, H White, AL Shin, KG AF Kim, H White, AL Shin, KG TI Effects of electromagnetic interference on controller-computer upsets and system stability SO IEEE TRANSACTIONS ON CONTROL SYSTEMS TECHNOLOGY LA English DT Article DE burst failure; controller upset; electromagnetic interference (EMI); stability; susceptibility AB Electromagnetic interference (EMI) causes controller upsets manifested as errors in control-law computation on a controller computer, or as disturbances in data transmission between sensors/actuators and the controller computer, which may be critical to system stability. In this paper, we compute the probability of these EMI-induced upsets in terms of the parameters governing EMI behaviors and the conditional probabilities of upsets in the presence of EMI, which is useful for the design and verification of the integrity of reliable controllers. The results are used to modify a system dynamic equation to examine asymptotical stability with probability one for the random sequences of the system states evolving according to the resultant dynamic equation, which are validated via a simple EMI experiment in a reverberation chamber. C1 Yonsei Univ, Dept Elect & Comp Engn, Seoul 120749, South Korea. NASA, Langley Res Ctr, Hampton, VA 23681 USA. Univ Michigan, Dept Elect Engn & Comp Sci, Ann Arbor, MI 48109 USA. RP Kim, H (reprint author), Yonsei Univ, Dept Elect & Comp Engn, Seoul 120749, South Korea. NR 9 TC 11 Z9 11 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 1063-6536 J9 IEEE T CONTR SYST T JI IEEE Trans. Control Syst. Technol. PD MAR PY 2000 VL 8 IS 2 BP 351 EP 357 DI 10.1109/87.826806 PG 7 WC Automation & Control Systems; Engineering, Electrical & Electronic SC Automation & Control Systems; Engineering GA 315DC UT WOS:000087096500015 ER PT J AU Saatchi, SS Moghaddam, M AF Saatchi, SS Moghaddam, M TI Estimation of crown and stem water content and biomass of boreal forest using polarimetric SAR imagery SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article; Proceedings Paper CT 2nd International Workshop on Retrieval of Bio and Geo Physical Parameters from SAR Data for Land Applications CY OCT 21-23, 1998 CL EUROPEAN RES & TECHNOL CTR, NOORDWIJK, NETHERLANDS HO EUROPEAN RES & TECHNOL CTR DE biomass; boreal; estimation; polarimetric SAR ID SYNTHETIC-APERTURE RADAR; BACKSCATTER; SENSITIVITY; MODEL AB Characterization of boreal forests in ecosystem models requires temporal and spatial distributions of water content and biomass over local and regional scales, In this paper, we report on the use of a semi-empirical algorithm for deriving these parameters from polarimetric synthetic aperture radar (SAR) measurements. The algorithm is based on a two layer radar backscatter model that stratifies the forest canopy into crown and stem layers and separates the structural and biometric attributes of forest stands. The structural parameters are estimated by training the model with SAR image data over dominant coniferous and deciduous stands in the boreal forest such as jack pine, black spruce, and aspen. The algorithm is then applied on AIRSAR images collected during the Boreal Ecosystem Atmospheric Study (BOREAS) over the boreal forest of Canada. The results are verified using biometry measurements during BOREAS-intensive held campaigns. Field data relating the water content of tree components to dry biomass are used to modify the coefficients of the algorithm for crown and stem biomass, The algorithm was then applied over the entire image generating biomass maps. A set of 18 test sites within the imaged area was used to assess the accuracy of the biomass maps. The accuracy of biomass estimation is also investigated by choosing different combinations of polarization and frequency channels of the AIRSAR system. It is shown that polarimetric data from P-band and L-band channels provide similar accuracy for estimating the above-ground biomass for boreal forest types, In general, the use of P-band channels can provide better estimates of stem biomass, while L-band channels can estimate the crown biomass more accurately, When AIRSAR images are also used to simulate the data from existing spaceborne radar systems, it was found that the combination of L-band HH polarization (JERS-1), C-band HH polarization (RADARSAT), and C-band VV polarization (ERS-1) had limited capacity for mapping boreal biomass (63% accuracy). C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Saatchi, SS (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 32 TC 73 Z9 76 U1 0 U2 13 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD MAR PY 2000 VL 38 IS 2 BP 697 EP 709 DI 10.1109/36.841999 PN 1 PG 13 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA 304TF UT WOS:000086499700008 ER PT J AU Wegmuller, U Strozzi, T Farr, T Werner, CL AF Wegmuller, U Strozzi, T Farr, T Werner, CL TI Arid land surface characterization with repeat-pass SAR interferometry SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article; Proceedings Paper CT 2nd International Workshop on Retrieval of Bio and Geo Physical Parameters from SAR Data for Land Applications CY OCT 21-23, 1998 CL EUROPEAN RES & TECHNOL CTR, NOORDWIJK, NETHERLANDS HO EUROPEAN RES & TECHNOL CTR DE classification; coherence; interferometry; vegetation density ID FOREST AB Repeat pass ERS SAR interferometry was used to map different surface types of the Death Valley Salt Pan. At this arid site, the surface roughness varies between extremely smooth (salt lakes, clay pan) and very rough (alluvial fans, eroded salt formations). The moisture varies from very dry (alluvial fans) to wet (wet clay, salt crust with water ponds) with seasonal changes in certain areas. While the surface geometry is stable for certain surface types (alluvial fans, thick salt crusts), it changes for others as a result of the changing water level and erosion by wind and rain. The changing surface roughness, moisture, and vegetation conditions cause large variations of the backscattering and coherence. This information is used to distinguish different surface types, Furthermore, interferometry was used to map the topographic height. In a second part of the study, the potential of the degree of coherence to retrieve information on the vegetation density and the surface erasion was evaluated. C1 GAMMA Remote Sensing, Bern, Switzerland. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Wegmuller, U (reprint author), GAMMA Remote Sensing, Bern, Switzerland. OI Farr, Thomas/0000-0001-5406-2096 NR 7 TC 15 Z9 17 U1 0 U2 2 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD MAR PY 2000 VL 38 IS 2 BP 776 EP 781 DI 10.1109/36.842006 PN 1 PG 6 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA 304TF UT WOS:000086499700015 ER PT J AU Metzger, SM Carr, JR Johnson, JR Parker, TJ Lemmon, MT AF Metzger, SM Carr, JR Johnson, JR Parker, TJ Lemmon, MT TI Techniques for identifying dust devils in Mars Pathfinder images SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE contrast stretching; difference images; dust devils; image processing; Mars pathfinder; principal components transformation; spectral ratios ID SURFACE AB Image processing methods used to identify and enhance dust devil features imaged by IMP (Imager for Mars Pathfinder) are reviewed. Spectral differences, visible red minus visible blue, were used for initial dust devil searches, driven by the observation that Martian dust has high red and low blue reflectance. The Martian sky proved to be more heavily dust-laden than pre-Pathfinder predictions, based on analysis of images from the Hubble Space Telescope. As a result, these initial spectral difference methods failed to contrast dust devils with background dust haze. Imager artifacts (dust motes on the camera lens, Bat-field effects caused by imperfections in the CCD, and projection onto a Bat sensor plane by a convex lens) further impeded the ability to resolve subtle dust devil features, Consequently, reference images containing sky with a minimal horizon were first subtracted from each spectral filter image to remove camera artifacts and reduce the background dust haze signal, Once the sky-flat preprocessing step was completed, the red-minus-blue spectral difference scheme was attempted again. Dust devils then were successfully identified as bright plumes, False-color ratios using calibrated IMP images were found useful for visualizing dust plumes, verifying initial discoveries as vortex-like features. Enhancement of monochromatic (especially blue filter) images revealed dust devils as silhouettes against brighter background sky. Experiments with principal components transformation identified dust devils in raw uncalibrated IMP images and further showed relative movement of dust devils across the Martian surface. A variety of methods therefore served qualitative and quantitative goals for dust plume identification and analysis in an environment where such features are obscure. C1 Univ Nevada, Dept Geol Sci, Reno, NV 89557 USA. US Geol Survey, Flagstaff, AZ 86001 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. RP Metzger, SM (reprint author), Univ Nevada, Dept Geol Sci, Reno, NV 89557 USA. RI Lemmon, Mark/E-9983-2010; Johnson, Jeffrey/F-3972-2015 OI Lemmon, Mark/0000-0002-4504-5136; NR 20 TC 8 Z9 8 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD MAR PY 2000 VL 38 IS 2 BP 870 EP 876 DI 10.1109/36.842015 PN 1 PG 7 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA 304TF UT WOS:000086499700024 ER PT J AU Montgomery, H Che, NZ Parker, K Bowser, J AF Montgomery, H Che, NZ Parker, K Bowser, J TI The algorithm for MODIS wavelength on-orbit calibration using the SRCA SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article ID SPATIAL CHARACTERISTICS; ASSEMBLY SRCA AB To the best of our knowledge, this is the first time that a monochromator is in orbit to monitor the spectral characteristics of a radiometer on-orbit. The Spectro-Radiometric Calibration Assembly (SRCA) provides on-orbit spectral calibration of the MODerate resolution Imaging Spectroradiometer (MODIS) reflected solar bands, and this paper describes how it is accomplished, On-orbit, the SRCA will measure the band center wavelength shifts over the whole mission, and will monitor the spectral response variations for some specific bands intraorbit, A unique feature of the SRCA spectral mode is its wavelength self-calibration capability. A stable didymium glass with known transmission peaks is equipped to establish the relationship between grating step and wavelength when the grating is located at a series of positions. The measured MODIS band/channel responses versus grating step number is then scaled to wavelengths, A reference silicon photo-diode (SiPD) is used to normalize the didymium signal as well as the MODIS response signals so that the affect of the light source spectrum can be eliminated, A series of prelaunch tests at different temperatures in a thermal vacuum (TV) chamber has been completed. The test results show that the SRCA is stable and is capable of detecting MODIS wavelength shifts on-orbit. C1 Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Swales Aerosp, Beltsville, MD 20705 USA. Res & Data Syst Co, Greenbelt, MD 20771 USA. Raytheon ITSS, Lanham, MD 20706 USA. RP Montgomery, H (reprint author), Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 10 TC 13 Z9 13 U1 1 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD MAR PY 2000 VL 38 IS 2 BP 877 EP 884 DI 10.1109/36.842016 PN 1 PG 8 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA 304TF UT WOS:000086499700025 ER PT J AU Nghiem, SV Li, FK Walsh, EJ Lou, SH AF Nghiem, SV Li, FK Walsh, EJ Lou, SH TI Radar backscatter across the Gulf Stream sea surface temperature front SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE Gulf Stream; Ku-band backscatter; scatterometer; sea surface temperature ID WAVE DYNAMICS EXPERIMENT; BOUNDARY-LAYER; MOMENTUM FLUX; WINDS; SATELLITE; SWADE AB Ku-band backscatter responses to frontal sea surface temperature (SST) changes are studied and applications of a high-resolution scatterometer to remote sensing of an SST front are suggested. Ocean backscatter signatures were measured with an airborne Ku-band scatterometer across the Gulf Stream SST front during the Surface Wave Dynamics Experiment. Oceanic and atmospheric parameters were measured bg buoys, bg the Scanning Radar Altimeter, and by the Advanced Very High Resolution Radiometer, and the surface current fields analyzed by the Fleet Numerical Meteorology and Oceanography Center were obtained, Vertical polarization backscatter difference across the SST front with an SST difference of 9 degrees C is more than 5 dB in several flight lines. Large horizontal polarization backscatter changes are also observed across the SST front with an SST difference approximately one-half of that in the vertical polarization backscatter case. Corresponding wind speed differences cannot account for the large backscatter changes in view of Seasat-A Satellite Scatterometer (SASS) geophysical model functions depending only on neutral wind velocity, For both polarizations, upwind backscatter on the cold side is smaller than or close to crosswind backscatter on the warm side for incidence angles larger than 20 degrees and smaller than 60 degrees. This suggests that the SST front can be detected with backscatter measured bg a spaceborne radar at a fixed azimuth angle even if wind directions are different over the cold and warm sides. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NASA, Goddard Space Flight Ctr, Observ Sci Branch, Lab Hydrospher Proc, Wallops Island, VA 23337 USA. RP Nghiem, SV (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 27 TC 4 Z9 5 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD MAR PY 2000 VL 38 IS 2 BP 926 EP 941 DI 10.1109/36.841975 PN 2 PG 16 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA 304TG UT WOS:000086499800004 ER PT J AU Margot, JL Campbell, DB Jurgens, RF Slade, MA AF Margot, JL Campbell, DB Jurgens, RF Slade, MA TI Digital elevation models of the moon from earth-based radar interferometry SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE interferometry; moon; radar; topography ID SYNTHETIC-APERTURE RADAR; LUNAR POLES; ICE AB Three-dimensional (3-D) maps of the nearside and polar regions of the Moon can be obtained with an Earth-based radar interferometer. This paper describes the theoretical background, experimental setup, and processing techniques for a sequence of observations performed with the Goldstone Solar System Radar in 1997. These data provide radar imagery and digital elevation models of the polar areas and other small regions at similar to 100 m spatial and similar to 50 m height resolutions. A geocoding procedure relying on the elevation measurements yields cartographically accurate products that are free of geometric distortions such as foreshortening. C1 Natl Astron & Ionosphere Ctr, Arecibo, PR 00612 USA. Cornell Univ, Dept Astron, Ithaca, NY 14853 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Margot, JL (reprint author), Natl Astron & Ionosphere Ctr, Arecibo, PR 00612 USA. RI Margot, Jean-Luc/A-6154-2012 OI Margot, Jean-Luc/0000-0001-9798-1797 NR 33 TC 11 Z9 11 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD MAR PY 2000 VL 38 IS 2 BP 1122 EP 1133 DI 10.1109/36.841991 PN 2 PG 12 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA 304TG UT WOS:000086499800020 ER PT J AU Rubaai, A Kotaru, R Kankam, MD AF Rubaai, A Kotaru, R Kankam, MD TI A continually online-trained neural network controller for brushless DC motor drives SO IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS LA English DT Article; Proceedings Paper CT Industry-Applications-Society Annual Meeting CY OCT 05-09, 1997 CL NEW ORLEANS, LOUISIANA SP Ind Applicat Soc DE adaptive learning; high-performance drives; neural network controller; online training ID IMPLEMENTATION; SYSTEMS; DESIGNS AB In this paper, a high-performance controller with simultaneous online identification and control is designed for brushless de motor drives, The dynamics of the motor/load are modeled "online," and controlled using two different neural network based identification and control schemes, as the system is in operation. In the first scheme, an attempt is made to control the rotor angular speed, utilizing a single three-hidden-layer network. The second scheme attempts to control the stator currents, using a predetermined control law as a function of the estimated states. This scheme incorporates three multilayered feedforward neural networks that are online trained, using the Levenburg-Marquadt training algorithm, The control of the direct and quadrature components of the stator current successfully tracked a wide variety of trajectories after relatively short online training periods, The control strategy adapts to the uncertainties of the motor/load dynamics and, in addition, learns their inherent nonlinearities. Simulation results illustrated that a neurocontroller used in conjunction with adaptive control schemes can result in a flexible control device which may be utilized in a wide range of environments. C1 Howard Univ, Dept Elect Engn, Washington, DC 20059 USA. NASA, John Glenn Res Ctr, Power & On Board Prop Technol Div, Cleveland, OH 44135 USA. RP Rubaai, A (reprint author), Howard Univ, Dept Elect Engn, Washington, DC 20059 USA. NR 26 TC 30 Z9 34 U1 1 U2 6 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0093-9994 J9 IEEE T IND APPL JI IEEE Trans. Ind. Appl. PD MAR-APR PY 2000 VL 36 IS 2 BP 475 EP 483 DI 10.1109/28.833764 PG 9 WC Engineering, Multidisciplinary; Engineering, Electrical & Electronic SC Engineering GA 304WL UT WOS:000086507000006 ER PT J AU Matsuura, S Chen, P Blake, GA Pearson, JC Pickett, HM AF Matsuura, S Chen, P Blake, GA Pearson, JC Pickett, HM TI A tunable cavity-locked diode laser source for terahertz photomixing SO IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES LA English DT Article DE calibration; diode lasers; photomixing; source; terahertz waves ID TEMPERATURE-GROWN GAAS; GENERATION; RADIATION; POWER AB An all solid-state approach to the precise frequency synthesis and control of widely tunable terahertz radiation bg differencing continuous-ware diode lasers at 850 nm is reported in this paper. The difference frequency is synthesized by three fiber-coupled external-cavity laser diodes. Two of the lasers are Pound-Drever-Hall locked to different orders of a Fabry-Perot (FP) cavity. and the third is offset-frequency locked to the second of the cavity-locked lasers using a tunable microwave oscillator. The first cavity-locked laser and the offset-locked laser produce the difference frequency whose value is accurately determined by the sum of an integer multiple of the free spectral range of the FP cavity and the offset frequency, The dual-frequency 850-nm output of the three laser system is amplified to 500 mW through two-frequency injection seeding of a single semiconductor tapered optical amplifier As proof of precision frequency synthesis and control of tunability the difference frequency is converted into a terahertz Hare bq optical-heterodyne photomixing in low-temperature-grown GaAs and used for the spectroscopy of simple molecules, The 3-dB spectral power bandwidth of the terahertz radiation is routinely observed to be less than or similar to 1 MHz. A simple, but highly accurate, method of obtaining an absolute frequency calibration is proposed and an absolute calibration of 10(-7) demonstrated using the known frequencies of carbon monoxide lines between 0.23-1.27 THz. C1 CALTECH, Div Geol & Planetary Sci, Pasadena, CA 91125 USA. CALTECH, Div Chem & Chem Engn, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Inst Space & Astronaut Sci, Infrared Astrophys, Kanagawa 2298510, Japan. EM matsuura@gps.caltech.edu RI Chen, Pin/B-1112-2008; Matsuura, Shuji/B-5658-2016 OI Chen, Pin/0000-0003-1195-9666; Matsuura, Shuji/0000-0002-5698-9634 NR 22 TC 37 Z9 37 U1 1 U2 7 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA SN 0018-9480 EI 1557-9670 J9 IEEE T MICROW THEORY JI IEEE Trans. Microw. Theory Tech. PD MAR PY 2000 VL 48 IS 3 BP 380 EP 387 DI 10.1109/22.826836 PG 8 WC Engineering, Electrical & Electronic SC Engineering GA 294LG UT WOS:000085912300007 ER PT J AU Adelstein, BD Ellis, SR AF Adelstein, BD Ellis, SR TI Rotation and direction judgment from visual images head-slaved in two and three degrees-of-freedom SO IEEE TRANSACTIONS ON SYSTEMS MAN AND CYBERNETICS PART A-SYSTEMS AND HUMANS LA English DT Article DE Fick gimbal; Listing's law; spatial situation awareness; telepresence; virtual environment ID ARM MOVEMENTS; LISTINGS LAW; EYE; ACCURACY AB The contribution to spatial awareness of adding a roll degree-of-freedom (DOF) to telepresence camera platform yaw and pitch was examined in an experiment where subjects judged direction and rotation of stationary target markers in a remote scene. Subjects viewed the scene via head-slaved camera images in a head-mounted display. Elimination of the roll DOF affected rotation judgment, but only at extreme yaw and pitch combinations, and did not affect azimuth and elevation judgement. Systematic azimuth overshoot occurred regardless of roll condition. Observed rotation misjudgments are explained by kinematic models for eye-head direction of gaze. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. EM bda@eos.arc.nasa.gov; silly@eos.arc.nasa.gov NR 24 TC 3 Z9 3 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA SN 1083-4427 EI 1558-2426 J9 IEEE T SYST MAN CY A JI IEEE Trans. Syst. Man Cybern. Paart A-Syst. Hum. PD MAR PY 2000 VL 30 IS 2 BP 165 EP 173 DI 10.1109/3468.833097 PG 9 WC Computer Science, Cybernetics; Computer Science, Theory & Methods SC Computer Science GA 302GJ UT WOS:000086357100008 PM 11727750 ER PT J AU Driscoll, M Maleki, L Parker, TE AF Driscoll, M Maleki, L Parker, TE TI Introduction to the special issue on frequency control and precision timing SO IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL LA English DT Editorial Material C1 Northrop Grumman Electr Sensors & Syst Sector, RF Signal Generat & Receive Syst Grp, Baltimore, MD USA. JPL, Time & Frequency Sci & Technol Grp, Pasadena, CA USA. RP Driscoll, M (reprint author), Northrop Grumman Electr Sensors & Syst Sector, RF Signal Generat & Receive Syst Grp, Baltimore, MD USA. NR 0 TC 0 Z9 0 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0885-3010 J9 IEEE T ULTRASON FERR JI IEEE Trans. Ultrason. Ferroelectr. Freq. Control PD MAR PY 2000 VL 47 IS 2 BP 315 EP 316 DI 10.1109/58.827415 PG 2 WC Acoustics; Engineering, Electrical & Electronic SC Acoustics; Engineering GA 294TL UT WOS:000085926400001 PM 18238545 ER PT J AU Young, RB Bridge, KY Strietzel, CJ AF Young, RB Bridge, KY Strietzel, CJ TI Effect of electrical stimulation on beta-adrenergic receptor population and cyclic AMP production in chicken and rat skeletal muscle cell cultures SO IN VITRO CELLULAR & DEVELOPMENTAL BIOLOGY-ANIMAL LA English DT Article DE myogenesis; cyclic AMP; adenylate cyclase; receptor desensitization ID MYOSIN HEAVY-CHAIN; FAST-TWITCH MUSCLE; CONTRACTILE ACTIVITY; FIBER-TYPE; BETA(1)-ADRENERGIC RECEPTOR; GENE-EXPRESSION; BREAST MUSCLE; PROTEIN; DIFFERENTIATION; PHOSPHORYLATION AB Expression of the beta-adrenergic receptor (beta AR) and its coupling to cyclic AMP (cAMP) synthesis are important components of the signaling system that controls muscle atrophy and hypertrophy, and the goal of this study was to determine if electrical stimulation in a pattern simulating slow muscle contraction would alter the beta AR response in primary cultures of avian and mammalian skeletal muscle cells. Specifically, chicken skeletal muscle cells and rat skeletal muscle cells that had been grown for 7 d in culture were subjected to electrical stimulation for an additional 2 d at a pulse frequency of 0.5 pulses/sec and a pulse duration of 200 msec. In chicken skeletal muscle cells, the beta AR population was not significantly affected by electrical stimulation; however, the ability of these cells to synthesize cyclic AMP was reduced by approximately one-half. In contrast, the beta AR population in rat muscle cells was increased slightly but not significantly by electrical stimulation, and the ability of these cells to synthesize cyclic AMP was increased by almost twofold. The basal levels of intracellular cyclic AMP in neither rat muscle cells nor chicken muscle cells were affected by electrical stimulation. C1 NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Univ Alabama, Dept Biol Sci, Huntsville, AL 35899 USA. RP Young, RB (reprint author), NASA, George C Marshall Space Flight Ctr, SD48,Bldg 4481, Huntsville, AL 35812 USA. NR 36 TC 4 Z9 4 U1 0 U2 0 PU SOC IN VITRO BIOLOGY PI LARGO PA 9315 LARGO DR WEST, STE 25, LARGO, MD 20774 USA SN 1071-2690 J9 IN VITRO CELL DEV-AN JI In Vitro Cell. Dev. Biol.-Anim. PD MAR PY 2000 VL 36 IS 3 BP 167 EP 173 PG 7 WC Cell Biology; Developmental Biology SC Cell Biology; Developmental Biology GA 302HN UT WOS:000086359800005 ER PT J AU Venkateswaran, K Dohmoto, N AF Venkateswaran, K Dohmoto, N TI Pseudoalteromonas peptidolytica sp nov., a novel marine mussel-thread-degrading bacterium isolated from the Sea of Japan SO INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY LA English DT Article DE Pseudoalteromonas peptidolytica; phylogeny; marine mussel thread; gyrB; 16S rDNA ID RIBOSOMAL-RNA SEQUENCES; PHYLOGENETIC ANALYSIS; FATTY-ACIDS; GYRB GENES; ALTEROMONAS; EVOLUTION; DISEASE; STRAINS; VIBRIO AB A new bacterial species belonging to the genus Pseudoalteromonas is described on the basis of phenotypic characterization, and sequence analysis of its 16S rRNA-coding and gyrase B (gyrB) genes, Ten strains, isolated from sea water of Yamato Island, Sea of Japan, were Gram-negative, yellow, motile, polarly flagellated. aerobic, rod-shaped eubacteria and had a G+C content of 42 mol%. Analysis of the 16S rDNA sequence revealed a clear affiliation between these strains and members of the gamma-Proteobacteria. High similarity values were found with members of the genus Pseudoalteromonas and this was supported by fatty acid profiles, The 16S rDNA sequence similarity between strain F12-50-A1(T) and Pseudoalteromonas piscicida was very high (99.1%). However, molecular characterizations employing small subunit 16S rDNA sequences were at the limits of resolution for the differentiation of species in this genus. As a result, DNA-DNA hybridization and sequence analyses of a more rapidly evolving gyrB gene were performed, Our assertion that this strain represents a distinct bacterial species within the genus Pseudoalteromonas was supported by both of these molecular analyses, Species-specific PCR probes were designed for the gyrB gene and used for the rapid screening of F12-50-A1(T)-like strains. thereby confirming the species, As these strains cleave complex protein compounds of the Mytilus edulis foot by secreting proteases, the name Pseudoalteromonas peptidolytica sp, nov. is proposed, with strain F12-50-A1T (= MBICC F1250A1(T)) as the type strain. C1 Nippon Suisan Kaisha Ltd, Cent Res Lab, Hachioji, Tokyo 192, Japan. RP Venkateswaran, K (reprint author), NASA, Jet Prop Lab, M-S 89-5,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 33 TC 21 Z9 25 U1 0 U2 2 PU SOC GENERAL MICROBIOLOGY PI READING PA MARLBOROUGH HOUSE, BASINGSTOKE RD, SPENCERS WOODS, READING RG7 1AE, BERKS, ENGLAND SN 1466-5026 J9 INT J SYST EVOL MICR JI Int. J. Syst. Evol. Microbiol. PD MAR PY 2000 VL 50 BP 565 EP 574 PN 2 PG 10 WC Microbiology SC Microbiology GA 298LX UT WOS:000086141800017 PM 10758862 ER PT J AU Rhim, WK Ishikawa, T AF Rhim, WK Ishikawa, T TI Thermophysical properties of molten germanium measured by a high-temperature electrostatic levitator SO INTERNATIONAL JOURNAL OF THERMOPHYSICS LA English DT Article; Proceedings Paper CT 5th Asian Thermophysical Properties Conference CY AUG 30-SEP 02, 1998 CL SEOUL, SOUTH KOREA DE density; electrical resistivity; electrostatic levitator; hemispherical total emissivity; molten germanium; specific heat; surface tension; thermal conductivity ID SILICON AB Thermophysical propel ties of molten germanium have been measured using the high-temperature electrostatic levitator at the Jet Propulsion Laboratory. Measured properties include the density, the thermal expansivity, the hemispherical total emissivity, the constant-pressure specific heat capacity, the surface tension, and the electrical resistivity. The measured density can be expressed by p(liq) = 5.67 x 10(3) - 0.542 (T - T-m) kg(.)m(-3) from 1150 to 1400 K with T-m= 1211.3 K. the volume expansion coefficient by alpha = 0.9656 x 10(-4) K-1, and the hemispherical total emissivity at the melting temperature by epsilon(T), (liq)( T-m)= 0.17. Assuming constant epsilon(T), (liq)(T) = 0.17 in the liquid range that has been investigated, the constant-pressure specific heat was evaluated as a function of temperature. The surface tension over the same temperature range can be expressed by sigma(T)= 583-0.08(T - T-m) mN(.)m(-1) and the temperature dependence of the electrical resistivity, when r(liq)( T-m) = 60 mu Omega(.)cm is used as a reference point, can be expressed by r(c, liq)(T) = 60 + 1.18 x 10(-2)(T - 1211.3) mu Omega(.)cm. The thermal conductivity, which was determined from the resistivity data using the Wiedemann-Franz-Lorenz law, is given by kappa(liq)(T) = 49.43 + 2.90 x 10(-2)(T - T-m) W(.)m(-1) K-1. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Rhim, WK (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 28 TC 25 Z9 25 U1 2 U2 9 PU KLUWER ACADEMIC/PLENUM PUBL PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 0195-928X J9 INT J THERMOPHYS JI Int. J. Thermophys. PD MAR PY 2000 VL 21 IS 2 BP 429 EP 443 DI 10.1023/A:1006639714415 PG 15 WC Thermodynamics; Chemistry, Physical; Mechanics; Physics, Applied SC Thermodynamics; Chemistry; Mechanics; Physics GA 310GT UT WOS:000086818700013 ER PT J AU Reehorst, A Chung, J Potapczuk, M Choo, Y AF Reehorst, A Chung, J Potapczuk, M Choo, Y TI Study of icing effects on performance and controllability of an accident aircraft SO JOURNAL OF AIRCRAFT LA English DT Article; Proceedings Paper CT AIAA 37th Aerospace Sciences Meeting CY JAN 11-14, 1999 CL RENO, NEVADA SP Amer Inst Aeronaut & Astronaut AB The activities at NASA John H. Glenn Research Center at Lewis Field in support of a National Transportation Safety Board accident investigation are described. An icing research tunnel (IRT) test was conducted in January 1998. Most conditions for the test were based on raw and derived data from the Eight data recorder recovered from the accident and on the current understanding of the meteorological conditions near the accident. Using a two-dimensional Navier-Stokes code, the flowfield and resultant lift and drag were calculated for the wing section with various ice shapes accreted in the IRT test. Before the final calculations could be performed extensive examinations of geometry smoothing and turbulence modeling were conducted, The most significant finding of this effort is that several of the 5-min ice accretions generated in the IRT were found by the Navier-Stokes analysis to produce severe lift and drag degradation. The information generated suggests a possible scenario for the kind of control upset recorded in the accident, Secondary findings were that the ice shapes accreted in the IRT were mostly limited to the protected pneumatic boot region of the wing and that during testing activation of the pneumatic boots cleared most of the ice. C1 NASA, John H Glenn Res Ctr, Icing Branch, Cleveland, OH 44135 USA. NASA, John H Glenn Res Ctr, Inst Computat Mech Propuls, Cleveland, OH 44135 USA. RP Reehorst, A (reprint author), NASA, John H Glenn Res Ctr, Icing Branch, Cleveland, OH 44135 USA. NR 10 TC 5 Z9 6 U1 1 U2 2 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0021-8669 J9 J AIRCRAFT JI J. Aircr. PD MAR-APR PY 2000 VL 37 IS 2 BP 253 EP 259 DI 10.2514/2.2588 PG 7 WC Engineering, Aerospace SC Engineering GA 302YP UT WOS:000086394300009 ER PT J AU Srinivasan, GR AF Srinivasan, GR TI Acoustics and unsteady flow of telescope cavity in an airplane SO JOURNAL OF AIRCRAFT LA English DT Article; Proceedings Paper CT AIAA 36th Aerospace Sciences Meeting CY JAN 12-15, 1998 CL RENO, NEVADA SP Amer Inst Aeronaut & Astronaut ID INFRARED ASTRONOMY; COMPUTATIONS; FLOWFIELD AB The Stratospheric Observatory for Infrared Astronomy consists of a 2.5-m aperture Cassegrain telescope housed in an open cavity onboard a Boeing 737-SP aircraft cruising at around 13 km altitude. The open cavity of this airborne observatory presents many acrodynamic and aeroacoustic challenges that are being resolved for its design using results from computational and experimental investigations. Results are reported from one such Navier-Stokes computational fluid dyanamics (CFD) investigation on an overset grid system at wind-tunnel and cruise flight conditions. Numerical results of sound pressure levels, spectra of unsteady pressures on the telescope and bulkheads, spectra of telescope moments, and time-averaged surface pressures on the empennage show fair comparisons with experiments. An acoustic tone at 440 Hz has been identified for this cavity from CFD calculations at sind-tunnel conditions, and this acoustic tone is in agreement with experimental observation. The good agreement of scaled wind-funnel results with computational results at cruise conditions indicates the scaling relations used are acc urate. The open cavity produces a drag increase of less than 2% of the aircraft drag and is found to have negligible effect on the aircraft controls in cruise flight. C1 NASA, Ames Res Ctr, Raytheon Syst Co, Moffett Field, CA 94035 USA. RP Srinivasan, GR (reprint author), NASA, Ames Res Ctr, Raytheon Syst Co, Moffett Field, CA 94035 USA. NR 47 TC 5 Z9 5 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0021-8669 J9 J AIRCRAFT JI J. Aircr. PD MAR-APR PY 2000 VL 37 IS 2 BP 274 EP 281 DI 10.2514/2.2591 PG 8 WC Engineering, Aerospace SC Engineering GA 302YP UT WOS:000086394300012 ER PT J AU Masseguin, C Corcoran, M Carcenac, C Daunton, NG Guell, A Verkman, AS Gabrion, J AF Masseguin, C Corcoran, M Carcenac, C Daunton, NG Guell, A Verkman, AS Gabrion, J TI Altered gravity downregulates aquaporin-1 protein expression in choroid plexus SO JOURNAL OF APPLIED PHYSIOLOGY LA English DT Article DE water transport; cerebrospinal fluid; spaceflight; hindlimb suspension; hypergravity; immunocytochemistry ID INTEGRAL MEMBRANE-PROTEIN; CHIP28 WATER CHANNELS; HEAD-DOWN TILT; TISSUE DISTRIBUTION; RATS; SPACEFLIGHT; VASOPRESSIN; HYBRIDIZATION; PURIFICATION; EPITHELIA AB Aquaporin-1 (AQP1) is a water channel expressed abundantly at the apical pole of choroidal epithelial cells. The protein expression was quantified by immunocytochemistry and confocal microscopy in adult rats adapted to altered gravity. AQP1 expression was decreased by 64% at the apical pole of choroidal cells in rats dissected 5.5-8 h after a 14-day spaceflight. AQP1 was significantly overexpressed in rats readapted for 2 days to Earth's gravity after an 11-day flight (48% overshoot, when compared with the value measured in control rats). In a ground-based model that simulates some effects of weightlessness and alters choroidal structures and functions, apical AQP1 expression was reduced by 44% in choroid plexus from rats suspended head down for 14 days and by 69% in rats suspended for 28 days. Apical AQP1 was rapidly enhanced in choroid plexus of rats dissected 6 h after a 14-day suspension (57% overshoot, in comparison with control rats) and restored to the control level when rats were dissected 2 days after the end of a 14-day suspension. Decreases in the apical expression of choroidal AQP1 were also noted in rats adapted to hypergravity in the NASA 24-ft centrifuge: AQP1 expression was reduced by 47% and 85% in rats adapted for 14 days to 2 G and 3 G, respectively. AQP1 is downregulated in the apical membrane of choroidal cells in response to altered gravity and is rapidly restored after readaptation to normal gravity. This suggests that water transport, which is partly involved in the choroidal production of cerebrospinal fluid, might be decreased during spaceflight and after chronic hypergravity. C1 Univ Paris 06, Inst Neurosci, CNRS, UMR 7624, F-75252 Paris 05, France. NASA, Ames Res Ctr, Moffett Field, CA 95034 USA. Ctr Natl Etud Spatiales, Direct Programmes, F-75001 Paris, France. Univ Calif San Francisco, Cardiovasc Res Inst, San Francisco, CA 94143 USA. RP Gabrion, J (reprint author), Univ Paris 06, Inst Neurosci, CNRS, UMR 7624, Boite 2,7 Quai St Bernard, F-75252 Paris 05, France. NR 34 TC 39 Z9 40 U1 0 U2 3 PU AMER PHYSIOLOGICAL SOC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 USA SN 8750-7587 J9 J APPL PHYSIOL JI J. Appl. Physiol. PD MAR PY 2000 VL 88 IS 3 BP 843 EP 850 PG 8 WC Physiology; Sport Sciences SC Physiology; Sport Sciences GA 291NC UT WOS:000085742100006 PM 10710377 ER PT J AU Lu, YN Yu, QG Zamzow, JP Wang, Y Losey, GS Balazs, GH Nerurkar, VRR Yanagihara, R AF Lu, YN Yu, QG Zamzow, JP Wang, Y Losey, GS Balazs, GH Nerurkar, VRR Yanagihara, R TI Detection of green turtle herpesviral sequence in saddleback wrasse Thalassoma duperrey: A possible mode of transmission of green turtle fibropapilloma SO JOURNAL OF AQUATIC ANIMAL HEALTH LA English DT Article ID CHELONIA-MYDAS; MARINE TURTLES AB Samples of DNA were prepared from various tissues and organs (including snout, gill, eye, brain, heart, liver, gut content, intestine, swim bladder, spleen, gallbladder, spinal cord, gonad, and muscle) of six healthy appearing reef cleaner fish. saddleback wrasses Thalassoma duperrey, captured from a cleaning station in North Kaneohe Bay, Oahu, Hawaii. The DNA samples were tested For evidence of green turtle herpesvirus infection by nested polymerase chain reaction (PCR). Green turtle herpesviral sequences were detected in snout (3/6), gill (2/6), and liver (1/6). All other tissues were negative. Except for a single nucleotide substitution (from A to G at position 48, resulting in a single amino acid change from isoleucine to methionine at position 16), the DNA sequences detected in the fish were identical to that of a newly reported green turtle herpesvirus. Although preliminary, these data represent the first evidence for an association of a herpesvirus with saddleback wrasse, suggesting that cleaner fish may serve as vectors or carriers for the transmission of the agent causing green turtle fibropapilloma. C1 Univ Hawaii, Pacific Biomed Res Ctr, Retrovirol Res Lab, Leahi Hosp, Honolulu, HI 96816 USA. Univ Hawaii Manoa, Dept Zool, Honolulu, HI 96822 USA. NOAA, Natl Marine Fisheries Serv, SW Fisheries Sci Ctr, Honolulu Lab, Honolulu, HI 96822 USA. RP Lu, YN (reprint author), Univ Hawaii, Pacific Biomed Res Ctr, Retrovirol Res Lab, Leahi Hosp, Atherton Bldg,3675 Kilauea Ave, Honolulu, HI 96816 USA. NR 21 TC 16 Z9 16 U1 1 U2 8 PU AMER FISHERIES SOC PI BETHESDA PA 5410 GROSVENOR LANE SUITE 110, BETHESDA, MD 20814-2199 USA SN 0899-7659 J9 J AQUAT ANIM HEALTH JI J. Aquat. Anim. Health PD MAR PY 2000 VL 12 IS 1 BP 58 EP 63 DI 10.1577/1548-8667(2000)012<0058:DOGTHS>2.0.CO;2 PG 6 WC Fisheries; Veterinary Sciences SC Fisheries; Veterinary Sciences GA 300UQ UT WOS:000086271700007 ER PT J AU Koshak, WJ Blakeslee, RJ Bailey, JC AF Koshak, WJ Blakeslee, RJ Bailey, JC TI Data retrieval algorithms for validating the optical transient detector and the lightning imaging sensor SO JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY LA English DT Article ID TOGA COARE; LOCATION; PROPAGATION AB A linear algebraic solution is provided for the problem of retrieving the location and time of occurrence of lightning ground strikes from an Advanced Lightning Direction Finder (ALDF) network. The ALDF network measures field strength, magnetic bearing, and arrival time of lightning radio emissions. Solutions for the plane (i.e., no earth curvature) are provided that implement all of these measurements. The accuracy of the retrieval method is tested using computer-simulated datasets, and the relative influence of bearing and arrival time data on the outcome of the final solution is formally demonstrated. The algorithm is sufficiently accurate to validate NASA's Optical Transient Detector and Lightning Imaging Sensor. A quadratic planar solution that is useful when only three arrival time measurements are available is also introduced. The algebra of the quadratic root results are examined in detail to clarify what portions of the analysis region lead to fundamental ambiguities in source location. Complex root results are shown to be associated with the presence of measurement errors when the lightning source lies near an outer sensor baseline of the ALDF network. For arbitrary noncollinear network geometries and in the absence of measurement errors, it is shown that the two quadratic roots are equivalent (no source location ambiguity) on the outer sensor baselines. The accuracy of the quadratic planar method is rested with computer-generated datasets, and the results are generally better than those obtained from the three-station linear planar method when bearing errors are about 2 degrees. C1 NASA, George C Marshall Space Flight Ctr, Global Hydrol & Climate Ctr, Raytheon STX, Huntsville, AL 35806 USA. RP Koshak, WJ (reprint author), NASA, George C Marshall Space Flight Ctr, Global Hydrol & Climate Ctr, Raytheon STX, MSFC-HR20,977 Explorer Blvd, Huntsville, AL 35806 USA. NR 18 TC 8 Z9 9 U1 0 U2 1 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0739-0572 J9 J ATMOS OCEAN TECH JI J. Atmos. Ocean. Technol. PD MAR PY 2000 VL 17 IS 3 BP 279 EP 297 DI 10.1175/1520-0426(2000)017<0279:DRAFVT>2.0.CO;2 PG 19 WC Engineering, Ocean; Meteorology & Atmospheric Sciences SC Engineering; Meteorology & Atmospheric Sciences GA 291FP UT WOS:000085723700002 ER PT J AU Liu, RB Cross, LE Knowles, G Bower, B Childers, B AF Liu, RB Cross, LE Knowles, G Bower, B Childers, B TI A stackable bonding-free flextensional piezoelectric actuator SO JOURNAL OF ELECTROCERAMICS LA English DT Article DE piezoelectric actuator; flextensional amplifier; optical fiber grating system AB A flextensional actuator was designed using commercial multilayer stacked actuator so as to produce large displacements at intermediate force levels. The simple design chosen eliminated the need for bonding the actuators into the frame and permitted easy series connection of multiple units. To satisfy the need for a fiber grating tuning device to interrogate an array of Bragg grating fiber optic stress sensors, a tuning device using four series connected units was constructed. The unit performs well, but the actual measured amplification is less than theoretical expectation. The problem was traced to unwanted flexing of the simple original frame and a hinged more robust flexing beam construction was shown to eliminate the problem. C1 Penn State Univ, Mat Res Lab 187, University Pk, PA 16802 USA. Qor TeK Inc, Williamsport, PA 17701 USA. NASA, NDE Branch MS 231, Langley Res Ctr, Hampton, VA 23665 USA. RP Liu, RB (reprint author), Penn State Univ, Mat Res Lab 187, University Pk, PA 16802 USA. NR 4 TC 3 Z9 3 U1 0 U2 2 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 1385-3449 J9 J ELECTROCERAM JI J. Electroceram. PD MAR PY 2000 VL 4 IS 1 BP 201 EP 206 DI 10.1023/A:1009980330174 PG 6 WC Materials Science, Ceramics SC Materials Science GA 317XY UT WOS:000087253300006 ER PT J AU Donohue, MJ Costa, DP Goebel, ME Baker, JD AF Donohue, MJ Costa, DP Goebel, ME Baker, JD TI The ontogeny of metabolic rate and thermoregulatory capabilities of northern fur seal, Callorhinus ursinus, pups in air and water SO JOURNAL OF EXPERIMENTAL BIOLOGY LA English DT Article DE metabolic rate; thermoregulation; thermal conductance; body composition; northern fur seal; Callorhinus ursinus ID HYDROGEN ISOTOPE-DILUTION; PHOCA-VITULINA-RICHARDI; ENERGY-METABOLISM; BODY SIZE; TEMPERATURE REGULATION; ARCTOCEPHALUS-GAZELLA; OXYGEN-CONSUMPTION; HARP SEAL; GROWTH; ENERGETICS AB Young pinnipeds, born on land, must eventually enter the water to feed independently. The aim of this study was to examine developmental factors that might influence this transition. The ontogeny of metabolic rate and thermoregulation in northern fur seal, Callorhinus ursinus, pups was investigated at two developmental stages in air and water using open-circuit respirometry. Mean in-air resting metabolic rate (RMR) increased significantly from 113+/-5 ml O-2 min(-1) (N=18) pre-molt to 160+/-4 ml O-2 min(-1) (N=16; means +/- S.E.M.) post-molt. In-water, whole-body metabolic rates did not differ pre- and post-molt and were 2.6 and 1.6 times in-air RMRs respectively. Mass-specific metabolic rates of pre-molt pups in water were 2.8 times in-air rates. Mean mass-specific metabolic rates of post-molt pups at 20 degrees C in water and air did not differ (16.1+/-1.7 ml O-2 min(-1) kg(-1); N=10). In-air mass-specific metabolic rates of post-molt pups were significantly lower than in-water rates at 5 degrees C (18.2+/-1.1 ml O-2 min(-1) kg(-1); N=10) and 10 degrees C (19.4+/-1.7 ml O-2 min(-1) kg(-1); N=10; means +/- S.E.M.). Northern fur seal pups have metabolic rates comparable with those of terrestrial mammalian young of similar body size. Thermal conductance was independent of air temperature, but increased with water temperature. In-water thermal conductance of pre-molt pups was approximately twice that of post-molt pups, In-water pre-molt pups matched the energy expenditure of larger post-molt pups while still failing to maintain body temperature. Pre-molt pups experience greater relative costs when entering the water regardless of temperature than do larger post-molt pups, This study demonstrates that the development of thermoregulatory capabilities plays a significant role in determining when northern fur seal pups enter the water. C1 Univ Calif Santa Cruz, Dept Biol, Santa Cruz, CA 95064 USA. Natl Marine Fisheries Serv, Honolulu Lab, Honolulu, HI 96822 USA. RP Donohue, MJ (reprint author), Univ Calif Santa Cruz, Dept Biol, Santa Cruz, CA 95064 USA. NR 87 TC 58 Z9 58 U1 3 U2 17 PU COMPANY OF BIOLOGISTS LTD PI CAMBRIDGE PA BIDDER BUILDING CAMBRIDGE COMMERCIAL PARK COWLEY RD, CAMBRIDGE CB4 4DL, CAMBS, ENGLAND SN 0022-0949 J9 J EXP BIOL JI J. Exp. Biol. PD MAR PY 2000 VL 203 IS 6 BP 1003 EP 1016 PG 14 WC Biology SC Life Sciences & Biomedicine - Other Topics GA 301GT UT WOS:000086302900004 PM 10683160 ER PT J AU Buckel, JA Stoner, AW AF Buckel, JA Stoner, AW TI Functional response and switching behavior of young-of-the-year piscivorous bluefish SO JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY LA English DT Article DE density-dependent; functional response; Morone saxatilis; Pomatomus saltatrix; seagrass; switching ID HUDSON RIVER ESTUARY; POMATOMUS-SALTATRIX; SELECTIVE PREDATION; CAPTURE SUCCESS; PREY; FISH; RECRUITMENT; POPULATION; ABUNDANCE; GROWTH AB Young-of-the-year (YOY) bluefish, Pomatomus saltatrix (L.) impose significant mortality on recently metamorphosed striped bass, Morone saxatilis (W.) in the Hudson River estuary. Field observations indicate that bluefish selectivity on striped bass increases with increasing striped bass density suggesting a density-dependent feeding response. Functional response and switching experiments were conducted to aid in determining the mechanism for this response. The type of functional response exhibited by bluefish under several prey treatments was examined. These were striped bass alone, Atlantic silversides, Menidia menidia (L.) alone, striped bass with a background density of alternative prey, and striped bass in the presence of eelgrass Zostera marina (L.). The functional response of bluefish to increasing prey density was more similar to a type I or II model than a type III model under all treatments. Switching was examined by providing bluefish both striped bass and silversides at five different ratios with and without a prey refuge, eelgrass. Bluefish did not exhibit a type III functional response or switching behavior suggesting that these mechanisms do not explain the observed density-dependent selectivity pattern in the field. Switching experiments did suggest that the presence of prey refuge can determine selectivity by YOY bluefish in the field. The abundance of submerged aquatic vegetation and other prey refuge may be important in controlling the predatory impact of bluefish on striped bass in the Hudson River. (C) 2000 Elsevier Science B.V. All rights reserved. C1 NOAA, Natl Marine Fisheries Serv, James J Howard Marine Sci Lab, Highlands, NJ 07732 USA. RP Buckel, JA (reprint author), Univ W Florida, Dept Biol, 11000 Univ Pkwy, Pensacola, FL 32514 USA. NR 36 TC 25 Z9 26 U1 1 U2 6 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-0981 J9 J EXP MAR BIOL ECOL JI J. Exp. Mar. Biol. Ecol. PD MAR 1 PY 2000 VL 245 IS 1 BP 25 EP 41 DI 10.1016/S0022-0981(99)00155-0 PG 17 WC Ecology; Marine & Freshwater Biology SC Environmental Sciences & Ecology; Marine & Freshwater Biology GA 285JX UT WOS:000085386900002 ER PT J AU Shyne, RJ Sohn, KH De Witt, KJ AF Shyne, RJ Sohn, KH De Witt, KJ TI Experimental investigation of boundary layer behavior in a simulated low pressure turbine SO JOURNAL OF FLUIDS ENGINEERING-TRANSACTIONS OF THE ASME LA English DT Article AB A detailed investigation of the flow physics occurring on the suction side of a simulated low pressure turbine (LPT) blade was performed. A contoured upper wall was designed to simulate the pressure distribution of an actual LPT blade onto a flat plate. The experiments were carried out at Reynolds number of 100,000 and 250,000 with three levels of freestream turbulence. The main emphasis in this paper is placed on flow field surveys performed at a Reynolds number of 100,000 with levels of freestream turbulence ranging from 0.8 percent to 8 percent. Smoke-wire flow visualization data were used to confirm that the boundary layer was separated and formed a bubble. The transition process over the separated flow region is observed to be similar to a laminar free shear layer flow with the formation of a large coherent eddy structure. For each condition, the locations defining the separation bubble were determined by careful examination of pressure and mean velocity profile data. Transition onset location and length determined from intermittency and height of the laminar separation bubble were observed to be inversely proportional to the levels of freestream turbulence. [S0098-2202(00)00701-X]. C1 NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. Univ Toledo, Toledo, OH 43606 USA. RP Shyne, RJ (reprint author), NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. NR 12 TC 7 Z9 7 U1 0 U2 0 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 USA SN 0098-2202 J9 J FLUID ENG-T ASME JI J. Fluids Eng.-Trans. ASME PD MAR PY 2000 VL 122 IS 1 BP 84 EP 89 DI 10.1115/1.483229 PG 6 WC Engineering, Mechanical SC Engineering GA 309HL UT WOS:000086762400013 ER PT J AU Luvall, JC Quattrochi, DA Rickman, D Estes, M AF Luvall, JC Quattrochi, DA Rickman, D Estes, M TI Assessment methods SO JOURNAL OF FORESTRY LA English DT Article C1 NASA, Global Hyrol & Climate Ctr, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Univ Space Res Assoc, Columbia, MD USA. RP Luvall, JC (reprint author), NASA, Global Hyrol & Climate Ctr, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. NR 0 TC 1 Z9 1 U1 0 U2 0 PU SOC AMER FORESTERS PI BETHESDA PA 5400 GROSVENOR LANE, BETHESDA, MD 20814 USA SN 0022-1201 J9 J FOREST JI J. For. PD MAR PY 2000 VL 98 IS 3 BP A1 EP A2 PG 2 WC Forestry SC Forestry GA 418NR UT WOS:000167898700008 ER PT J AU Zheng, D Chao, BF Zhou, Y Yu, N AF Zheng, D Chao, BF Zhou, Y Yu, N TI Improvement of edge effect of the wavelet time-frequency spectrum: application to the length-of-day series SO JOURNAL OF GEODESY LA English DT Article DE wavelet transform; edge effect; length of day ID EL-NINO; SOUTHERN OSCILLATION AB The edge effect in the wavelet time-frequency spectrum of a time series is treated. The time series is first extended on both ends by applying a non-linear model, namely the leap-step time series analysis (LSTSA) model: prior to the wavelet transform. The results of a series of simulation experiments and an application to the observed length-of-day (LOD) series demonstrate that the edge effect is effectively reduced this way. Thus, the application of the LSTSA model improves the wavelet time-frequency spectrum, especially enhancing the ability to detect the low-frequency signals. C1 Chinese Acad Sci, Shanghai Astron Observ, Shanghai 200030, Peoples R China. NASA, Goddard Space Flight Ctr, Space Geodesy Branch, Greenbelt, MD 20771 USA. RP Chinese Acad Sci, Shanghai Astron Observ, 80 Nandan Rd, Shanghai 200030, Peoples R China. EM zdw@center.shao.ac.cn RI Chao, Benjamin Fong/N-6156-2013 NR 16 TC 22 Z9 31 U1 0 U2 4 PU SPRINGER PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 0949-7714 EI 1432-1394 J9 J GEODESY JI J. Geodesy PD MAR PY 2000 VL 74 IS 2 BP 249 EP 254 DI 10.1007/s001900050283 PG 6 WC Geochemistry & Geophysics; Remote Sensing SC Geochemistry & Geophysics; Remote Sensing GA 307KC UT WOS:000086651600004 ER PT J AU Burlaga, LF Ness, NF AF Burlaga, LF Ness, NF TI Merged interaction regions observed by Voyagers 1 and 2 during 1998 SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID COSMIC-RAY MODULATION; HELIOSPHERIC SECTOR STRUCTURE; MAGNETIC-FIELD; DISTANT HELIOSPHERE; OUTER HELIOSPHERE; CURRENT SHEET; ULYSSES AB A broad region of relatively intense magnetic fields (a "merged interaction region" (MIR)) was observed by Voyager 2 (V2) from approximately calendar day (DOY) 264-313, 1998, at a distance of 56.1 +/- 0.2 AU and latitude -23.4 degrees. From the average speed of the material in the MIR at V2, 450 +/- 19 km/s, we estimate that the radial extent of the MIR was approximate to 13 AU. The average magnetic field strength B at V2 was (0.10 +/- 0.03) nT. A MIR was observed by Voyager 1 (V1) from approximate to DOY 257-302, 1998, when the heliocentric distance of V1 was R = 71.6 +/- 0.2 AU and its Ireliographic latitude was 33.4 degrees. The average magnetic field strength in this region at V1 was (0.05 +/- 0.01) nT. If the MIRs observed by V1 and V2 left the Sun at the same time, then the mean speed at V1 was similar to 1.3 times the mean speed at V2, i.e., similar to 600 km/s. The radial extent of the MIR at V1 was similar to 16 AU. The distribution of the azimuthal angles of the magnetic fields observed by V2 was double peaked, with both toward and away polarities, consistent with the location of V2 within the sector zone. The distribution of the azimuthal angles observed by V1 was single peaked with a positive polarity, consistent with the location of V1 above the sector zone. These distinctly different distributions of magnetic field directions suggests that V1 and V2 observed two related MIRs, rather than two parts of a single "global merged interaction region." C1 NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. Univ Delaware, Bartol Res Inst, Newark, DE 19716 USA. RP Burlaga, LF (reprint author), NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. NR 29 TC 13 Z9 13 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 2000 VL 105 IS A3 BP 5141 EP 5148 DI 10.1029/1999JA000379 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 288TY UT WOS:000085581600006 ER PT J AU Armstrong, JW Coles, WA Rickett, BJ AF Armstrong, JW Coles, WA Rickett, BJ TI Radio wave scattering in the outer heliosphere SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID SOLAR-WIND; SUN; DENSITY; EMISSION; CYCLE AB The Voyager 1 and 2 plasma wave instruments have observed low-frequency (1.5-4 kHz) radio waves apparently generated near the heliopause. The waves are found in two distinct bands. Power at the lower frequencies centered on 1.78 kHz shows no modulation when the spacecraft is rolled about the Earth-spacecraft line, indicating that the radiation is isotropic. Fewer in the higher band centered on 3.11 kHz shows roll modulation as high as 60%, indicating that the source of the radiation is quite compact, subtending an angle <1 rad at the spacecraft. Simple estimates of the scattering of 3.11 kHz radiation from electron density fluctuations indicate that, if the radiation had originated from the distance of the heliopause, the scattering would be so large that no roll modulation should be observed. Here we show that these earlier scattering estimates were too high because they ignored the latitude variation of scattering and the inner scale of the electron density fluctuation spectrum. With these two effects properly included, the expected scattering is consistent with the observations and the postulate that the radiation originates from near the nose of the heliosphere. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Calif San Diego, Dept Elect & Comp Engn, La Jolla, CA 92093 USA. RP Armstrong, JW (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,Mail Stn 238-725, Pasadena, CA 91109 USA. NR 21 TC 12 Z9 12 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 2000 VL 105 IS A3 BP 5149 EP 5156 DI 10.1029/1999JA900471 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 288TY UT WOS:000085581600007 ER PT J AU Maynard, NC Burke, WJ Pfaff, RF Weber, EJ Ober, DM Weimer, DR Moen, J Milan, S Maseide, K Sandholt, PE Egeland, A Soraas, F Lepping, R Bounds, S Acuna, MH Freudenreich, H Machuzak, JS Gentile, LC Clemmons, JH Lester, M Ning, P Hardy, DA Holtet, JA Stadsnes, J van Eyken, T AF Maynard, NC Burke, WJ Pfaff, RF Weber, EJ Ober, DM Weimer, DR Moen, J Milan, S Maseide, K Sandholt, PE Egeland, A Soraas, F Lepping, R Bounds, S Acuna, MH Freudenreich, H Machuzak, JS Gentile, LC Clemmons, JH Lester, M Ning, P Hardy, DA Holtet, JA Stadsnes, J van Eyken, T TI Driving dayside convection with northward IMF: Observations by a sounding rocket launched from Svalbard SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID INTERPLANETARY MAGNETIC-FIELD; POTENTIAL DISTRIBUTIONS; ION CONVECTION; BOUNDARY-LAYER; CUSP AURORA; MAGNETOSPHERE; MODEL; PLASMA; RECONNECTION; SOUTHWARD AB The first sounding rocket flight into the dayside cusp with dark ground and northward interplanetary magnetic field (IMF) conditions was launched from the new SvalRak range at Ny-Alesund in the Svalbard archipelago in early December 1997. Extensive ground observations of auroral emissions and radar backscatter provided contexts for in situ rocket measurements. Real-time interplanetary measurements from the Wind satellite aided launch selection with foreknowledge of impending conditions. NASA rocket flight 36.153 was launched near local magnetic noon while the IMF was dominated by positive B(X) and had lesser northward B(Z) and negative B(Y) components. The rocket's westward trajectory carried it toward auroral forms associated with morningside boundary layers. The rich set of vector de electric and magnetic fields, energetic particles, thermal plasma, plasma waves, and optical emissions gathered by the rocket reveal a complex electrodynamic picture of the cusp/boundary-layer region. Four factors were important in separating temporal and spatial effects: (1) Near the winter solstice the Earth's north magnetic pole tilts away from the Sun, (2) at the UT of the flight the dipole axis was rotated toward dawn, (3) the variability of solar wind driving was low, and (4) B(X) was the dominant IMF component. We conclude that no signatures of dayside merging in the Northern Hemisphere were detected in either the rocket or ground sensors. Electric field variations in the interplanetary medium directly correlate with those observed by the sounding rocket, with significantly shorter lag times than estimated for simple propagation between Wind and the ionosphere. The correlation requires that the observed Northern Hemisphere convection structures were stirred in part by merging of the IMF with closed field lines in the Southern Hemisphere, thereby adding open flux to the northern polar cap. Subsequent motions of adiaroic polar cap boundaries were detected in the rocket electric field measurements. The observations indicate that IMF B(X) significantly affected the location and timing of merging interactions. C1 Mission Res Corp, Nashua, NH 03062 USA. USAF, Res Lab, Bedford, MA 01731 USA. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. Univ Courses Svalbard, N-9170 Longyearbyen, Norway. Univ Leicester, Dept Phys, Leicester LE1 7RH, Leics, England. Univ Oslo, Dept Phys, N-0316 Oslo, Norway. Univ Bergen, Dept Phys, N-5007 Bergen, Norway. Boston Coll, Inst Sci Res, Chestnut Hill, MA 02467 USA. Aerosp Corp, Los Angeles, CA 90009 USA. Keo Consultants, Brookline, MA 02445 USA. Svalbard European Incoherent Scatter Radar, N-9170 Longyearbyen, Norway. RP Maynard, NC (reprint author), Mission Res Corp, 1 Tara Blvd,Suite 302, Nashua, NH 03062 USA. EM nmaynard@mrcnh.com RI Pfaff, Robert/F-5703-2012; OI Pfaff, Robert/0000-0002-4881-9715; Clemmons, James/0000-0002-5298-5222 NR 40 TC 19 Z9 19 U1 1 U2 4 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 2000 VL 105 IS A3 BP 5245 EP 5263 DI 10.1029/1999JA900462 PG 19 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 288TY UT WOS:000085581600015 ER PT J AU Lancaster, RS Waldrop, LS Kerr, RB Noto, J Solomon, SC Tepley, CA Garcia, R Friedman, J AF Lancaster, RS Waldrop, LS Kerr, RB Noto, J Solomon, SC Tepley, CA Garcia, R Friedman, J TI Brightness measurements of the nighttime OI 8446 angstrom airglow emission from the Millstone Hill and Arecibo Observatories SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID TROPICAL NIGHTGLOW; ATOMIC OXYGEN; SOLAR EUV; PHOTOELECTRON; RECOMBINATION; EXCITATION; TWILIGHT; STORM; MODEL AB Ground-based measurements of the O I 8446 Angstrom airglow brightness are made from the Millstone Hill and Arecibo Observatories. These measurements are made at various times throughout the year, and this paper reports those made between the years of 1993 and 1996. The maximum brightness of the 8446 Angstrom airglow emission is found to be less than about 35 Rayleighs during the nighttime at both these midlatitude sites. During the summer this emission is present for only a short time in the evening and morning. During the winter the emission can persist throughout the Eight. This observed behavior is in agreement with the calculations of current models that predict similar intensities from excitation by photoelectron impact on atomic oxygen. A close examination of these data, however, reveal that differences exist between the model predictions and the measured brightness. One difference is a persistence of the nighttime 8446 Angstrom brightness to times when the model predicts little or no emission from photoelectron production. A second difference is an occasional enhancement of the morning 8446 Angstrom brightness that is not predicted by the model. The former of these differences implies a shortcoming in current understanding of the 8446 Angstrom production mechanisms and must be resolved before atomic oxygen can be monitored from the ground using this emission. The latter may have important consequences fbr our understanding of upper atmosphere dynamics. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Boston Univ, Ctr Space Phys, Boston, MA 02215 USA. Sci Solut Inc, Chelmsford, MA USA. Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80309 USA. Cornell Univ, Arecibo Observ, Arecibo, PR 00613 USA. RP Lancaster, RS (reprint author), NASA, Goddard Space Flight Ctr, Code 912, Greenbelt, MD 20771 USA. RI Friedman, Jonathan/E-4985-2011; Solomon, Stanley/J-4847-2012 OI Friedman, Jonathan/0000-0002-9353-2377; Solomon, Stanley/0000-0002-5291-3034 NR 33 TC 9 Z9 9 U1 0 U2 4 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 2000 VL 105 IS A3 BP 5275 EP 5290 DI 10.1029/1999JA900410 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 288TY UT WOS:000085581600017 ER PT J AU Clemmons, JH Pfaff, RF Lennartsson, OW Mozer, FS Singer, HJ Peterson, WK Scudder, JD Kletzing, CA Chi, PJ Wallis, DD Larson, DE AF Clemmons, JH Pfaff, RF Lennartsson, OW Mozer, FS Singer, HJ Peterson, WK Scudder, JD Kletzing, CA Chi, PJ Wallis, DD Larson, DE TI Observations of traveling Pc5 waves and their relation to the magnetic cloud event of January 1997 SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID POTENTIAL MEASUREMENTS; PLASMA SHEET; INNER EDGE; SOLAR-WIND; ELECTRON; MAGNETOSPHERE; INSTRUMENT; SPACECRAFT; PROGRAM; MISSION AB Measurements of ULF waves in the Pc5 frequency range are presented and discussed. The waves were observed during the magnetic cloud event of January 1997 by instruments on the Polar satellite and ground instrumentation. These large-amplitude waves are best interpreted as traveling shear Alfven waves rather than in the usual standing-wave scenario. Characterization of the associated complex particle environment shows that the waves were largely confined to the plasma trough. Energetic protons modulated by the wave are shown to have caused modulated proton aurora. It is argued that the waves were caused by the interaction of a magnetic hole with the magnetosphere. C1 Aerospace Corp, Los Angeles, CA 90009 USA. Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90024 USA. Univ Iowa, Dept Phys & Astron, Iowa City, IA 52240 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Lockheed Martin Res Lab, Dept H1 11, Palo Alto, CA 94304 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NOAA, Space Environm Lab R E SE, Boulder, CO 80303 USA. Magnametr, Ottawa, ON K1H 7A9, Canada. RP Clemmons, JH (reprint author), Aerospace Corp, Mail Stop M2-260,POB 92957, Los Angeles, CA 90009 USA. RI Pfaff, Robert/F-5703-2012; Scudder, Jack/D-8417-2013; Peterson, WK/A-8706-2009; OI Pfaff, Robert/0000-0002-4881-9715; Scudder, Jack/0000-0001-7975-5630; Peterson, WK/0000-0002-1513-6096; Clemmons, James/0000-0002-5298-5222; Kletzing, Craig/0000-0002-4136-3348 NR 27 TC 12 Z9 13 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 2000 VL 105 IS A3 BP 5441 EP 5452 DI 10.1029/1999JA900418 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 288TY UT WOS:000085581600031 ER PT J AU Chang, SW Scudder, JD Fennell, JF Friedel, R Lepping, RP Russell, CT Trattner, KJ Fuselier, SA Peterson, WK Spence, HE AF Chang, SW Scudder, JD Fennell, JF Friedel, R Lepping, RP Russell, CT Trattner, KJ Fuselier, SA Peterson, WK Spence, HE TI Energetic magnetosheath ions connected to the Earth's bow shock: Possible source of cusp energetic ions SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID MAGNETIC-FIELD ORIENTATION; PLASMA DEPLETION LAYER; DIFFUSE IONS; SOLAR-WIND; DAYSIDE MAGNETOSHEATH; MAGNETOSPHERIC IONS; SUPRATHERMAL IONS; UPSTREAM; PARTICLE; ACCELERATION AB Plasma and magnetic field data detected by NASA GGS/Polar and Wind during the May 4, 1998, storm event are analyzed to demonstrate for the first time a causal relation between the magnetosheath energetic: ions and bow shock magnetic geometry. Intense magnetosheath energetic ions observed upstream from the cusp are from the quasi-parallel bow shock and show properties indicating that they are a possible source of cusp energetic ions. C1 Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA. Aerospace Corp, Los Angeles, CA 90009 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87544 USA. Lockheed Martin Adv Technol Ctr, Palo Alto, CA 94304 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90095 USA. Boston Univ, Dept Astron & Space Phys, Boston, MA 02215 USA. RP Chang, SW (reprint author), Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA. RI Friedel, Reiner/D-1410-2012; Scudder, Jack/D-8417-2013; Spence, Harlan/A-1942-2011; Peterson, WK/A-8706-2009; OI Friedel, Reiner/0000-0002-5228-0281; Scudder, Jack/0000-0001-7975-5630; Peterson, WK/0000-0002-1513-6096; Russell, Christopher/0000-0003-1639-8298; Spence, Harlan/0000-0002-2526-2205 NR 50 TC 29 Z9 29 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 2000 VL 105 IS A3 BP 5471 EP 5488 DI 10.1029/1999JA900468 PG 18 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 288TY UT WOS:000085581600034 ER PT J AU Tsyganenko, NA AF Tsyganenko, NA TI Solar wind control of the tail lobe magnetic field as deduced from Geotail, AMPTE/IRM, and ISEE 2 data SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID GEOMAGNETIC-FIELD; CURRENT SHEET; MAGNETOSPHERE; PARAMETERS; MODEL; MAGNETOMETER; MAGNETOTAIL; MISSION; DST; IRM AB A statistical study was made of the tail lobe field response to the dynamical pressure of the incoming solar wind and to the interplanetary magnetic field, as well as its relation to the concurrent level of the Dst field. The study covers a wide range of distances between 10 and 60R(E) and is based on a large set of tail lobe magnetic field data, compiled from three sources: (1) Geotail magnetometer and low-energy plasma instrument data for 1993-1997, (2) AMPTE/IRM magnetometer and plasma instrument data for 1985-1986, and (3) ISEE 2 magnetometer and fast plasma experiment data for 1978-1980. The tailward variation of the tail lobe field and of its response to the solar wind and interplanetary magnetic field (IMF) conditions was studied using a regression relationship, including various combinations of the interplanetary quantities, measured by IMP 8 and Wind spacecraft. An investigation of the role of the time lag effects was made by tagging each lobe field measurement by a "trail" of 12 consecutive 5-min average values of the solar wind parameters and finding best fit distributions of the lagged response amplitudes in the solar-wind and IMF-related regression terms. The goal of the work is to find a set of input variables providing the highest correlation between the observed and predicted magnitude of the tail lobe field, so that their combination could be used for parameterizing the strength of the cross-tail current in the data-based magnetospheric models. C1 NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. Raytheon ITSS Corp, Lanham, MD USA. RP Tsyganenko, NA (reprint author), NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RI Tsyganenko, Nikolai/J-7377-2012 OI Tsyganenko, Nikolai/0000-0002-5938-1579 NR 33 TC 20 Z9 21 U1 0 U2 4 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 2000 VL 105 IS A3 BP 5517 EP 5528 DI 10.1029/1999JA000375 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 288TY UT WOS:000085581600038 ER PT J AU Lim, KB Giesy, DP AF Lim, KB Giesy, DP TI Parameterization of model validating sets for uncertainty bound optimizations SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article; Proceedings Paper CT AIAA Guidance, Navigation, and Control Conference CY AUG 10-12, 1998 CL BOSTON, MASSACHUSETTS SP Amer Inst Aeronaut & Astronaut ID ROBUST-CONTROL AB Given measurement data, a nominal model, and a linear fractional transformation uncertainty structure with an allowance on unknown but bounded exogenous disturbances, easily computable tests for the existence of a model validating uncertainty. set are given. Under mild conditions, these tests are necessary and sufficient far the case of complex. nonrepeated, block-diagonal structure. For the more general case that includes repeated and/or real scalar uncertainties, the tests are only necessary but become sufficient if a collinearity condition is also satisfied. With the satisfaction of these tests, it is shown that a parameterization of all model validating sets of plant models is possible. The nea parameterization is used as a basis for a systematic way to construct or perform uncertainty tradeoff with model validating uncertainty sets that hare specific linear fractional transformation structure for use in robust control design and analysis. An illustrative example is given that includes a comparison of candidate model validating sets. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Lim, KB (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 14 TC 2 Z9 3 U1 0 U2 2 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD MAR-APR PY 2000 VL 23 IS 2 BP 222 EP 230 DI 10.2514/2.4544 PG 9 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA 294KC UT WOS:000085909600005 ER PT J AU Beard, RW McLain, TW Hadaegh, FY AF Beard, RW McLain, TW Hadaegh, FY TI Fuel optimization for constrained rotation of spacecraft formations SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article ID CONSTELLATION AB The problem of reorienting a constellation of spacecraft, such that the fuel distributed across the constellation is both conserved and expended uniformly, is considered. Results are derived for constellations with an arbitrary number of spacecraft, assuming that the constellation is in free space, that the spacecraft mass is time invariant, and that the thrusters can produce thrust in any direction. an open-loop control algorithm is derived by minimizing a cost function that trades off total fuel minimization and fuel equalization. The associated optimization problem is shown to be amenable to standard algorithms, simulation results using a four-spacecraft constellation are given. C1 Brigham Young Univ, Dept Elect & Comp Engn, Provo, UT 84602 USA. Brigham Young Univ, Dept Engn Mech, Provo, UT 84602 USA. CALTECH, Jet Propuls Lab, Automat & Control Sect, Pasadena, CA 91101 USA. RP Beard, RW (reprint author), Brigham Young Univ, Dept Elect & Comp Engn, Provo, UT 84602 USA. NR 17 TC 15 Z9 16 U1 0 U2 3 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD MAR-APR PY 2000 VL 23 IS 2 BP 339 EP 346 DI 10.2514/2.4528 PG 8 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA 294KC UT WOS:000085909600019 ER PT J AU Schaffner, G Newman, DJ Robinson, SK AF Schaffner, G Newman, DJ Robinson, SK TI Computational simulation of extravehicular activity dynamics during a satellite capture attempt SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article C1 MIT, Dept Aeronaut & Astronaut, Cambridge, MA 02139 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Schaffner, G (reprint author), MIT, Dept Aeronaut & Astronaut, Room 370219, Cambridge, MA 02139 USA. NR 4 TC 0 Z9 2 U1 0 U2 3 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD MAR-APR PY 2000 VL 23 IS 2 BP 367 EP 369 DI 10.2514/2.4533 PG 3 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA 294KC UT WOS:000085909600023 PM 11543562 ER PT J AU Lin, G Pister, KSJ Roos, KP AF Lin, G Pister, KSJ Roos, KP TI Surface micromachined polysilicon heart cell force transducer SO JOURNAL OF MICROELECTROMECHANICAL SYSTEMS LA English DT Article DE force transducer; heart cell; hinged microstructures; MEMS; micromechanical; surface micromachining ID CARDIAC MYOCYTES; STIFFNESS; TENSION AB A microelectromechanical systems (MEMS) force transducer system, with a volume less than 1 mm(3) millimeter, has been developed to measure forces generated by living heart muscle cells. Cell attachment and measurement of contractile forces have been demonstrated with a commercially fabricated surface-micromachined hinged polysilicon device, Two freestanding polysilicon clamps, each suspended by a pair of microbeams, hold each end of a heart cell. When the cell contracts, the beams bend and force is determined from the measured deflection and the spring constant in the beams. The average maximal force over seven contractile experiments using a calcium solution stimulus was F-max = 12.6 +/- 4.66 mu N. Normalizing to a cross-sectional area, F-max/area was 23.7 +/- 8.6 mN/mm(2). These force data were also correlated to optically imaged striation pattern periodicity. Intermediate forces were also measured in response to a calcium solution gradient and showed similar behavior to those measured in other laboratories. This MEMS force transducer demonstrates the feasibility of higher fidelity measurements from muscle cells and, thus, an improved understanding of the mechanisms of muscle contraction. [389]. C1 CALTECH, Jet Prop Lab, Microelectromech Technol Grp, Pasadena, CA 91109 USA. Univ Calif Berkeley, Berkeley Sensor & Actuator Ctr, Berkeley, CA 94720 USA. Univ Calif Los Angeles, Sch Med, Dept Physiol, Cardiovasc Res Lab, Los Angeles, CA 90095 USA. RP Lin, G (reprint author), CALTECH, Jet Prop Lab, Microelectromech Technol Grp, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 22 TC 81 Z9 83 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 1057-7157 J9 J MICROELECTROMECH S JI J. Microelectromech. Syst. PD MAR PY 2000 VL 9 IS 1 BP 9 EP 17 DI 10.1109/84.825771 PG 9 WC Engineering, Electrical & Electronic; Nanoscience & Nanotechnology; Instruments & Instrumentation; Physics, Applied SC Engineering; Science & Technology - Other Topics; Instruments & Instrumentation; Physics GA 293MY UT WOS:000085857600002 ER PT J AU Han, HS Chen, DR Pui, DYH Anderson, BE AF Han, Hee-Siew Chen, Da-Ren Pui, David Y. H. Anderson, Bruce E. TI A nanometer aerosol size analyzer (nASA) for rapid measurement of high-concentration size distributions SO JOURNAL OF NANOPARTICLE RESEARCH LA English DT Article DE nanometer particles; fast-response particle analyzer; jet-engine emissions; differential mobility analyzer (DMA); low-pressure measurement AB We have developed a fast-response nanometer aerosol size analyzer (nASA) that is capable of scanning 30 size channels between 3 and 100 nm in a total time of 3 s. The analyzer includes a bipolar charger (Po(210)), an extended-length nanometer differential mobility analyzer (Nano-DMA), and an electrometer (TSI 3068). This combination of components provides particle size spectra at a scan rate of 0.1 s per channel free of uncertainties caused by response-time-induced smearing. The nASA thus offers a fast response for aerosol size distribution measurements in high-concentration conditions and also eliminates the need for applying a de-smearing algorithm to resulting data. In addition, because of its thermodynamically stable means of particle detection, the nASA is useful for applications requiring measurements over a broad range of sample pressures and temperatures. Indeed, experimental transfer functions determined for the extended-length Nano-DMA using the tandem differential mobility analyzer (TDMA) technique indicate the nASA provides good size resolution at pressures as low as 200 Torr. Also, as was demonstrated in tests to characterize the soot emissions from the J85-GE engine of a T-38 aircraft, the broad dynamic concentration range of the nASA makes it particularly suitable for studies of combustion or particle formation processes. Further details of the nASA performance as well as results from calibrations, laboratory tests and field applications are presented below. C1 [Han, Hee-Siew; Chen, Da-Ren; Pui, David Y. H.] Univ Minnesota, Dept Mech Engn, Particle Technol Lab, Minneapolis, MN 55455 USA. [Anderson, Bruce E.] NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Pui, DYH (reprint author), Univ Minnesota, Dept Mech Engn, Particle Technol Lab, 111 Church St SE, Minneapolis, MN 55455 USA. EM dyhpui@maroon.tc.umn.edu FU NASA [NASA/NCC-1-311] FX We are grateful for the financial support provided by a grant from the NASA, Atmospheric Effect of Aviation Project (AEAP), NASA/NCC-1-311. NR 20 TC 10 Z9 10 U1 3 U2 8 PU SPRINGER PI DORDRECHT PA VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS SN 1388-0764 J9 J NANOPART RES JI J. Nanopart. Res. PD MAR PY 2000 VL 2 IS 1 BP 43 EP 52 DI 10.1023/A:1010014109495 PG 10 WC Chemistry, Multidisciplinary; Nanoscience & Nanotechnology; Materials Science, Multidisciplinary SC Chemistry; Science & Technology - Other Topics; Materials Science GA V19IW UT WOS:000208067100006 ER PT J AU Sato, OT Rossby, T AF Sato, OT Rossby, T TI Seasonal and low-frequency variability of the meridional heat flux at 36 degrees N in the North Atlantic SO JOURNAL OF PHYSICAL OCEANOGRAPHY LA English DT Article ID GULF-STREAM; ANNUAL CYCLE; OCEAN; TRANSPORT; CIRCULATION; 26.5-DEGREES-N; HEMISPHERE; ATMOSPHERE; MOTION AB Historical hydrographic sections are used to investigate the seasonal and interannual variability in the meridional heal flux at 36 degrees N in the North Atlantic. The data consist of ten transatlantic sections and sections from four sectors, which combined, cross the entire basin. These sectors are the slope water, the Gulf Stream, the Sargasso Sea, and the midocean. The data from the first three sectors actually come from sections that span all three regions, but their properties are examined individually. To improve estimates of the Gulf Stream contribution to the total heat flux, a tangent hyperbolic model of the current's temperature field is used to retain its structure in the temperature flux integrations even when only a few stations are available. The technique removes biases due to undersampling that averages about 0.3 PW. The temperature flux of the upper layer is estimated for the four sectors plus the climatologically forced Ekman layer. The annual mean is 1.4 +/- 0.3 PW with a range of 0.6 +/- 0.1 PW. The zero net mass flux across the transect can be accomplished by assuming that in the deep layer an equivalent amount of water to that estimated for the upper layer flows in the southward direction presumably via the deep western boundary current. The temperature flux of the deep layer. with its mean temperature of 2.3 degrees C, has an annual mean of -0.20 +/- 0.06 PW and a range of 0.05 +/- 0.02 PW. The net annual mean of the meridional heat flux is 1.2 +/- 0.3 PW and a range of 0.6 +/- 0.1 PW. Its phase is dominated by the annual cycle of the Ekman temperature flux. The heat flux residual is examined for evidence of long-term change in the poleward heat flux. While the database is very limited for a conclusive statement, it appears that the residual for the pentads 1935-39, 1970-74, and 1975-79 agreed to within 0.1 PW. The tightness of these estimates in the presence of a 0.6 PW annual range makes it clear how important it is to know the latter accurately before statements about long-term change can be made. To date, most individual transoceanic sections were taken during the summer and spring. The standard deviation of the heat flux estimates is 0.3 PW, much of it due to eddy variability, making it essential to obtain repeat sections preferably with a uniform distribution throughout the year. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Rhode Isl, Grad Sch Oceanog, Kingston, RI 02881 USA. RP Sato, OT (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,Mail Stop 300-323, Pasadena, CA 91109 USA. RI Sato, Olga/G-3656-2013 OI Sato, Olga/0000-0003-0751-4373 NR 36 TC 24 Z9 25 U1 0 U2 4 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0022-3670 J9 J PHYS OCEANOGR JI J. Phys. Oceanogr. PD MAR PY 2000 VL 30 IS 3 BP 606 EP 621 DI 10.1175/1520-0485(2000)030<0606:SALFVO>2.0.CO;2 PG 16 WC Oceanography SC Oceanography GA 292FA UT WOS:000085782400010 ER PT J AU Litchford, RJ Thompson, BR Lineberry, JT AF Litchford, RJ Thompson, BR Lineberry, JT TI Pulse detonation magnetohydrodynamic power SO JOURNAL OF PROPULSION AND POWER LA English DT Article AB A series of laboratory-scale experiments were conducted to investigate the basic engineering performance characteristics of a pulse detonation-driven magnetohydrodynamic electric power generator. In these experiments, stoichiometric oxy-acetylene mixtures seeded with a cesium-hydroxide/methanol spray were detonated at atmospheric pressure in a 1-m-long tube having an i.d, of 2.54 cm, Experiments with a plasma diagnostic channel attached to the end of the tube confirmed: the attainment of detonation conditions (p(2)/p(1) similar to 34 and D similar to 2400 m/s) and enabled the measurement of current density (similar to 2 A/cm(2)) and electrical conductivity (similar to 6 mho/m) behind the detonation wave front. In a second set of experiments, a 30-cm-long continuous electrode Faraday channel, having a height of 2.54 cm and a width of 2.0 cm, was attached to the end of the tube using an area transition duct. The Faraday channel was placed inside a permanent magnet assembly having a nominal magnetic induction of 0.6 T, and the electrodes were connected to an active loading circuit to characterize power-extraction dependence on load impedance while also simulating higher effective magnetic induction. The experiments Indicated peak power extraction at a load impedance between 5 and 10 Ohm. The measured peak electrical energy density ranged from 10 to 10(3) J/m(3) when the effective magnetic induction was varied from 0.6 to 4.2 T. These results were in reasonable agreement with a simple electrodynamic model incorporating a correction for near-electrode potential losses. By scaling-up to a practical-size device, limiting the near-electrode potential drop to 10% of the induced potential, and optimizing seed-atomization characteristics, we anticipate a five- to tenfold increase in attainable electrical energy density. C1 ERC Inc, Adv Dev Projects, Tullahoma, TN 37388 USA. ERC Inc, Res & Prod Dev Div, Tullahoma, TN 37388 USA. RP Litchford, RJ (reprint author), NASA, George C Marshall Space Flight Ctr, Propuls Lab, Huntsville, AL 35812 USA. NR 15 TC 5 Z9 5 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0748-4658 J9 J PROPUL POWER JI J. Propul. Power PD MAR-APR PY 2000 VL 16 IS 2 BP 251 EP 262 DI 10.2514/2.5563 PG 12 WC Engineering, Aerospace SC Engineering GA 295EV UT WOS:000085954500011 ER PT J AU Steinetz, BM Dunlap, PH AF Steinetz, BM Dunlap, PH TI Feasibility assessment of thermal barriers for extreme transient temperatures SO JOURNAL OF PROPULSION AND POWER LA English DT Article AB Assembly joints of modern solid rocket motor cases are generally sealed using conventional O-ring seals. The 5500 degrees F combustion gases produced by rocket motors are kept a safe distance away from the seals by thick layers of phenolic insulation. Special compounds are used to fill insulation gaps leading up to the seals to prevent a direct flowpath to them. Design criteria require that the seals should not experience torching or charring during operation, or their sealing ability would be compromised. On limited occasions, NASA has observed charring of the primary O-rings of the space shuttle solid rocket nozzle assembly joints because of parasitic leakage paths opening up in the gap-fill compounds during rocket operation. NASA is investigating different approaches for preventing torching or charring of the primary Q-rings. One approach is to implement a braided rope upstream of the primary O-ring to serve as a thermal barrier that prevents the hot gases from impinging on the O-ring seals. This paper presents flow, resiliency, and thermal resistance for several types of NASA thermal barriers braided out of carbon fibers. Burn tests were performed to determine the time to burn through each of the thermal barriers when exposed to the flame of an oxyacetylene torch (5500 degrees F), representative of the 5500 degrees F solid rocket motor combustion temperatures. Thermal barriers braided out of carbon fibers endured the flame for over six minutes, three times longer than the solid rocket motor burn time. Room and high temperature flow tests are presented for the thermal barriers for different amounts of linear compression. Room temperature compression tests were performed to assess resiliency and unit preloads as a function of compression. The thermal barrier was tested in a subscale rocket char motor test in which it served to impede hot gas Row through an intentionally oversized defect in the gap insulation. Temperature measurements indicated a 2200 degrees F temperature drop across the 1/4-in.-diam thermal barrier with no apparent signs of burning or charring. C1 NASA, John H Glenn Res Ctr, Mech Components Branch, Cleveland, OH 44135 USA. Modern Technol Corp, Middleburg Hts, OH 44130 USA. RP Steinetz, BM (reprint author), NASA, John H Glenn Res Ctr, Mech Components Branch, Lewis Field, Cleveland, OH 44135 USA. NR 11 TC 2 Z9 2 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0748-4658 J9 J PROPUL POWER JI J. Propul. Power PD MAR-APR PY 2000 VL 16 IS 2 BP 347 EP 356 DI 10.2514/2.5576 PG 10 WC Engineering, Aerospace SC Engineering GA 295EV UT WOS:000085954500023 ER PT J AU Dorney, DJ Griffin, LW Gundy-Burlet, KL AF Dorney, DJ Griffin, LW Gundy-Burlet, KL TI Simulations of the flow in supersonic turbines with straight centerline nozzles SO JOURNAL OF PROPULSION AND POWER LA English DT Article ID UNSTEADY C1 Virginia Commonwealth Univ, Dept Mech Engn, Richmond, VA 23284 USA. NASA, George C Marshall Space Flight Ctr, Fluid Dynam Anal Branch, Huntsville, AL 35812 USA. NASA, Ames Res Ctr, Computat Phys & Simulat Branch, Moffett Field, CA 94035 USA. RP Dorney, DJ (reprint author), Virginia Commonwealth Univ, Dept Mech Engn, Richmond, VA 23284 USA. NR 5 TC 3 Z9 4 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0748-4658 J9 J PROPUL POWER JI J. Propul. Power PD MAR-APR PY 2000 VL 16 IS 2 BP 370 EP 374 DI 10.2514/2.5580 PG 5 WC Engineering, Aerospace SC Engineering GA 295EV UT WOS:000085954500027 ER PT J AU Gamache, RR Lynch, R AF Gamache, RR Lynch, R TI Argon-induced halfwidths and line shifts of water vapor transitions SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article ID ROTATION-VIBRATION LINES; ASYMMETRIC-TOP MOLECULES; ROBERT-BONAMY FORMALISM; HALF-WIDTHS; BROADENING COEFFICIENTS; PERTURBER DEPENDENCES; NU(2) BAND; H2O LINES; 239 GHZ; TEMPERATURE AB Pressure-broadened halfwidths and pressure-induced line shifts are determined for water vapor transitions with argon as the perturbing gas. Calculations based on the complex Robert-Bonamy (CRB) formalism are made for a number of vibrational bands, for which there are experimental data to compare with. The intermolecular potential is taken as a sum of Lennard-Jones (6-12) atom-atom, isotropic induction, and dispersion components. The dynamics of the collision process are correct to second order in time. The calculations demonstrate that the atom-atom potential for this system should be expanded to 12th order. A new feature in the CRB approach is that the real and imaginary components of the Liouville S matrix affect both the halfwidth and the line shift. It is shown here that the imaginary parts of the S matrix strongly affect the calculated H2O-Ar halfwidths. The calculated values are compared with those obtained in a number of experimental studies. In general, good agreement is observed between the CRB calculations and the measured values for both halfwidths and line shifts. It is also clear that some parameters describing the intermolecular potential need to be better determined. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 Univ Massachusetts, Dept Environm Earth & Atmospher Sci, Lowell, MA 01854 USA. Columbia Univ, Goddard Inst Space Studies, New York, NY 10025 USA. RP Gamache, RR (reprint author), Univ Massachusetts, Dept Environm Earth & Atmospher Sci, 1 Univ Ave, Lowell, MA 01854 USA. NR 59 TC 12 Z9 13 U1 0 U2 3 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0022-4073 J9 J QUANT SPECTROSC RA JI J. Quant. Spectrosc. Radiat. Transf. PD MAR 1 PY 2000 VL 64 IS 5 BP 439 EP 456 DI 10.1016/S0022-4073(99)00101-6 PG 18 WC Optics; Spectroscopy SC Optics; Spectroscopy GA 266HD UT WOS:000084293800001 ER PT J AU Ustinov, EA AF Ustinov, EA TI A variational approach for computing weighting functions for remote sensing of the atmosphere in the thermal microwave spectral region SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article AB An approach is presented for the evaluation of weighting functions for temperature and mixing ratio retrievals based on the direct treatment of analytic expressions for the observed radiances using an evaluation of corresponding variational derivatives. The necessary mathematical and physical framework for variational derivatives of operators is also presented. (C) 1999 Published by Elsevier Science Ltd. All rights reserved. C1 Cornell Univ, Dept Astron, Ithaca, NY 14853 USA. RP Ustinov, EA (reprint author), CALTECH, Jet Prop Lab, Div Earth & Space Sci, Mail Stop 183-301,480 Oak Grove Dr, Pasadena, CA 91109 USA. RI Ustinov, Eugene/D-1350-2015 OI Ustinov, Eugene/0000-0003-0227-4286 NR 10 TC 4 Z9 4 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0022-4073 J9 J QUANT SPECTROSC RA JI J. Quant. Spectrosc. Radiat. Transf. PD MAR 1 PY 2000 VL 64 IS 5 BP 457 EP 465 DI 10.1016/S0022-4073(99)00124-7 PG 9 WC Optics; Spectroscopy SC Optics; Spectroscopy GA 266HD UT WOS:000084293800002 ER PT J AU Lorenzini, EC Cosmo, ML Kaiser, M Bangham, ME Vonderwell, DJ Johnson, L AF Lorenzini, EC Cosmo, ML Kaiser, M Bangham, ME Vonderwell, DJ Johnson, L TI Mission analysis of spinning systems for transfers from low orbits to geostationary SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB An analysis of the use of spaceborne spinning tethers for a reusable system to transfer payloads with a mass up to 4000 kg from low orbits to geostationary is presented. Results indicate that a two-stage system is lighter than a single-stage tethered system with present-day tether materials. A first stage in low orbit and a second stage in medium Earth orbit provide the required velocity increments for injecting the payload into geotransfer orbit with the final orbit circularization provided by the satellite kick motor. The orbits of the stages are resonant in order to provide periodic encounters and are optimized with the goal of reducing the overall system mass. The close-approach dynamics between the second stage and the payload released from the first stage is simulated to demonstrate the salient features of the rendezvous process. A total of 10 transfers over two years of operation without refueling is adopted for computing the propellant needed to reboost the stages, A preliminary analysis leads to the conclusion that a two-stage tethered system is more competitive, on a mass basis, than a chemical upper stage after two transfers. C1 Harvard Smithsonian Ctr Astrophys, Radio & Geoastron Div, Cambridge, MA 02138 USA. Tech Univ Munich, Inst Astron, D-8000 Munich, Germany. Boeing Co, Def & Space Grp, Huntsville, AL 35824 USA. NASA, George C Marshall Space Flight Ctr, Program Dev, Huntsville, AL 35812 USA. RP Lorenzini, EC (reprint author), Harvard Smithsonian Ctr Astrophys, Radio & Geoastron Div, MS80,60 Garden St, Cambridge, MA 02138 USA. NR 10 TC 18 Z9 21 U1 0 U2 4 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD MAR-APR PY 2000 VL 37 IS 2 BP 165 EP 172 DI 10.2514/2.3562 PG 8 WC Engineering, Aerospace SC Engineering GA 302XC UT WOS:000086390900003 ER PT J AU Johnson, L Estes, RD Lorenzini, E Martinez-Sanchez, M Sanmartin, J AF Johnson, L Estes, RD Lorenzini, E Martinez-Sanchez, M Sanmartin, J TI Propulsive Small Expendable Deployer System experiment SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB Relatively short electrodynamic tethers can extract orbital energy to "push" against a planetary magnetic field to achieve propulsion without the expenditure of propellant. The Propulsive Small Expendable Deployer System experiment will use the flight-proven Small Expendable Deployer System to deploy a 5-km bare aluminum tether from a Delta II upper stage to achieve approximate to 0.4-N drag thrust, thus lowering the altitude of the stage. The experiment will use a predominantly bare tether for current collection in lien of the endmass collector and insulated tether used on previous missions. The flight experiment is a precursor to a more ambitious electrodynamic tether upper-stage demonstration mission that will be capable of orbit-raising, -lowering, and inclination changes, all using electrodynamic thrust. The expected performance of the tether propulsion system during the experiment is described. C1 NASA, George C Marshall Space Flight Ctr, Adv Space Transportat Program, Huntsville, AL 35812 USA. Harvard Smithsonian Ctr Astrophys, Radio & Geoastron Div, Cambridge, MA 02138 USA. MIT, Cambridge, MA 02139 USA. Univ Politecn Madrid, Escuela Tecn Super Ingn Aeronaut, E-28040 Madrid, Spain. RP Johnson, L (reprint author), NASA, George C Marshall Space Flight Ctr, Adv Space Transportat Program, Mail Code TD15, Huntsville, AL 35812 USA. NR 7 TC 26 Z9 26 U1 0 U2 4 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD MAR-APR PY 2000 VL 37 IS 2 BP 173 EP 176 DI 10.2514/2.3563 PG 4 WC Engineering, Aerospace SC Engineering GA 302XC UT WOS:000086390900004 ER PT J AU Estes, RD Lorenzini, EC Sanmartin, J Pelaez, J Martinez-Sanchez, M Johnson, CL Vas, IE AF Estes, RD Lorenzini, EC Sanmartin, J Pelaez, J Martinez-Sanchez, M Johnson, CL Vas, IE TI Bare tethers for electrodynamic spacecraft propulsion SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article ID CURRENT COLLECTION; PRESHEATH; SATELLITE; PROBE; ORBIT AB Electrodynamic tether thrusters can use the power provided by solar panels to drive a current in the tether and then the Lorentz force to push against the Earth's magnetic field, thereby achieving propulsion without the expenditure of onboard energy sources or propellant. Practical tether propulsion depends critically on being able to extract multiamp electron currents from the ionosphere with relatively short tethers (10 km or less) and reasonably low power. We describe a new anodic design that uses an uninsulated portion of the metallic tether itself to collect electrons. Because of the efficient collection of this type of anode, electrodynamic thrusters for reboost of the International Space Station and for an upper stage capable of orbit raising, lowering, and inclination changes appear to be feasible. Specifically, a 10-km-long bare tether, utilizing 10 kW of the space station power could save most of the propellant required for the station reboost over its 10-year lifetime, The propulsive small expendable deployer system experiment is planned to test the bare-tether design in space in the year 2000 by deploying a 5-km bare aluminum tether from a Delta II upper stage to achieve up to 0.5-N drag thrust, thus deorbiting the stage. C1 Harvard Smithsonian Ctr Astrophys, Radio & Geoastron Div, Cambridge, MA 02138 USA. Univ Politecn Madrid, Escuela Super Ingn Aeronaut, E-28040 Madrid, Spain. MIT, Cambridge, MA 02139 USA. NASA, George C Marshall Space Flight Ctr, Adv Space Transportat Res Program, Huntsville, AL 35812 USA. Boeing Co, Huntsville, AL 35824 USA. RP Estes, RD (reprint author), Harvard Smithsonian Ctr Astrophys, Radio & Geoastron Div, MS 80,60 Garden St, Cambridge, MA 02138 USA. NR 24 TC 30 Z9 31 U1 2 U2 12 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD MAR-APR PY 2000 VL 37 IS 2 BP 205 EP 211 DI 10.2514/2.3567 PG 7 WC Engineering, Aerospace SC Engineering GA 302XC UT WOS:000086390900008 ER PT J AU Gupta, A Ruffin, SM Newfield, ME Yates, L AF Gupta, A Ruffin, SM Newfield, ME Yates, L TI Aerothermodynamic performance enhancement of sphere-cones using the artificially blunted leading-edge concept SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB Artificially blunted leading edges created by the use of a Bow-through channel sized to choke at supersonic conditions have been shown to be effective in significantly reducing drag in high-speed flow over blunted airfoils, Results of the work to apply the concept to blunted sphere-cones and the use of a channel at a leading edge to enhance lift are presented. This enhancement is caused: by the internal flow creating suction at the channel lip. Proof-of-concept numerical simulations on various sphere-cone configurations at different Eight conditions show the concept's effectiveness in reducing drag of axisymmetric bodies. Experimental data are used to validate the predicted drag reduction at alpha = 0 deg, Mach 2.25-2.5 range, and sea-level conditions, Direct correlations between the channel size and drag reduction, lip geometry and lift increment, as well as between the channel lip radius and peak heat-transfer rates, were established and characterized using an efficient concept evaluation method. These polynomial models for force coefficients and heat-transfer rates are used by a gradient-based optimizer to generate derivatives of a 10-deg sphere-cone with the concept for operation at Mach 7, 20 km altitude. These geometries had approximately 5% higher lift-to-drag ratio and similar peak heating rates as the baseline. To mitigate the potential system-level drawbacks caused by a straight channel, a cowl-like derivative with curved channels exhausting from the forebody was investigated and found to provide comparable performance enhancement. C1 Georgia Inst Technol, Sch Aerosp Engn, Atlanta, GA 30332 USA. NASA, Ames Res Ctr, Space Technol Div, Moffett Field, CA 94035 USA. Aerosp Comp Inc, Los Altos, CA 94022 USA. RP Gupta, A (reprint author), Georgia Inst Technol, Sch Aerosp Engn, Atlanta, GA 30332 USA. NR 18 TC 3 Z9 3 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD MAR-APR PY 2000 VL 37 IS 2 BP 235 EP 241 DI 10.2514/2.3551 PG 7 WC Engineering, Aerospace SC Engineering GA 302XC UT WOS:000086390900012 ER PT J AU Sokolov, P Ibrahim, M Kerslake, T AF Sokolov, P Ibrahim, M Kerslake, T TI Computational heat-transfer modeling of thermal energy storage canisters for space applications SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article; Proceedings Paper CT AIAA 36th Aerospace Sciences Meeting CY JAN 12-15, 1998 CL RENO, NEVADA SP Amer Inst Aeronaut & Astronaut ID PHASE-CHANGE; PACKED-BED AB A computer code has been developed for analyzing the phenomena occurring in cylindrical metal canisters containing a high-temperature phase change material. Such canisters are normally used as thermal storage elements in heat receivers of solar dynamic power systems for low-orbit space vehicles, The code is a useful canister design tool and able to predict the temperature distributions and the void behavior in the canisters. These in turn are used for the canister thermal stress analyses. The emphasis in the development of the code has been made on accurate descriptions of the solid-liquid phase change process, void dynamics and heat transfer, convective and radiative heat-transfer modes in the phase change:material. The abilities of the code include computations of three-dimensional and axisymmetric heat transfer and fluid mechanics phenomena inside the canisters. The code validation has been made based on the results of ground tests and two thermal energy storage flight experiments. The validated code has been used for canister analyses. The following features have been examined: 1) the location of hot spots in the canister, especially canister walls; 2) the void location and heat-transfer predictions; 3) the importance of radiative and convective heat-transfer modes in the void and liquid phase change material; and 4) the influence of three-dimensional vs axisymmetric boundary conditions on the canister performance. C1 Cleveland State Univ, Dept Mech Engn, Cleveland, OH 44115 USA. NASA, John H Glenn Res Ctr, Power & Propuls Off, Cleveland, OH 44135 USA. RP Sokolov, P (reprint author), Cleveland State Univ, Dept Mech Engn, Cleveland, OH 44115 USA. NR 21 TC 4 Z9 7 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD MAR-APR PY 2000 VL 37 IS 2 BP 265 EP 272 DI 10.2514/2.3555 PG 8 WC Engineering, Aerospace SC Engineering GA 302XC UT WOS:000086390900016 ER PT J AU Ohsaka, K Trinh, EH AF Ohsaka, K Trinh, EH TI A two-frequency acoustic technique for bubble resonant oscillation studies SO JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA LA English DT Article ID SHAPE OSCILLATIONS; DRIVEN; DYNAMICS; WATER AB A two-frequency acoustic apparatus has been developed to study the dynamics of a single gas or vapor bubble in water. An advantage of the apparatus is its capability of trapping a bubble by an ultrasonic standing wave while independently driving it into oscillations by a second lower frequency acoustic wave. For a preliminary application, the apparatus;is used to study resonant oscillations. First, near-resonant coupling between the volume and the n = 3 shape oscillation modes of air bubbles at room temperature is studied, where n is the mode number. The stability boundary, amplitude versus frequency, of the volume oscillation forms a wedge centered at the resonant frequency, which qualitatively agrees with a theoretical prediction based on a phase-space analysis. Next, the resonant volume oscillations of vapor bubbles are studied. The resonant radius of vapor bubbles at 80 degrees C driven at 1682 Hz is determined to be 0.7 mm, in agreement with a prediction obtained by numerical simulation. (C) 2000 Acoustical Society of America. [S0001-4966(00)03703-6]. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Ohsaka, K (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 13 TC 3 Z9 3 U1 1 U2 4 PU AMER INST PHYSICS PI MELVILLE PA 2 HUNTINGTON QUADRANGLE, STE 1NO1, MELVILLE, NY 11747-4501 USA SN 0001-4966 J9 J ACOUST SOC AM JI J. Acoust. Soc. Am. PD MAR PY 2000 VL 107 IS 3 BP 1346 EP 1351 DI 10.1121/1.428421 PG 6 WC Acoustics; Audiology & Speech-Language Pathology SC Acoustics; Audiology & Speech-Language Pathology GA 291YR UT WOS:000085767800024 ER PT J AU Kaplan, NR Nelson, ML AF Kaplan, NR Nelson, ML TI Determining the publication impact of a digital library SO JOURNAL OF THE AMERICAN SOCIETY FOR INFORMATION SCIENCE LA English DT Article ID USAGE STATISTICS; WEB AB We attempt to assess the publication impact of a digital library (DL) of aerospace scientific and technical information (STI). The Langley Technical Report Server (LTRS) is a digital library of over 1,400 electronic publications authored by NASA Langley Research Center personnel or contractors and has been available in its current World Wide Web (WWW) form since 1994. In this article, we examine calendar year 1997 usage statistics of LTRS and the Center for AeroSpace Information (CASI), a facility that archives and distributes hard copies of NASA and aerospace information. We also perform a citation analysis on some of the top publications distributed by LTRS. We find that although LTRS distributes over 71,000 copies of publications (compared with an estimated 24,000 copies from CASI), citation analysis indicates that LTRS has almost no measurable publication impact. We discuss the caveats of our investigation, speculate on possible different models of usage facilitated by DLs, and suggest "retrieval analysis" as a complementary metric to citation analysis. While our investigation failes to establish a relationship between LTRS and increased citations and raises at least as many questions as it answers, we hope it will serve as an invitation to, and guide for, further research in the use of DLs. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Kaplan, NR (reprint author), NASA, Langley Res Ctr, MS 158, Hampton, VA 23681 USA. OI Nelson, Michael/0000-0003-3749-8116 NR 29 TC 16 Z9 16 U1 0 U2 9 PU JOHN WILEY & SONS INC PI NEW YORK PA 605 THIRD AVE, NEW YORK, NY 10158-0012 USA SN 0002-8231 J9 J AM SOC INFORM SCI JI J. Am. Soc. Inf. Sci. PD MAR 1 PY 2000 VL 51 IS 4 BP 324 EP 339 DI 10.1002/(SICI)1097-4571(2000)51:4<324::AID-ASI3>3.0.CO;2-B PG 16 WC Computer Science, Information Systems; Information Science & Library Science SC Computer Science; Information Science & Library Science GA 282NK UT WOS:000085224800003 ER PT J AU Chao, WC AF Chao, WC TI Multiple quasi equilibria of the ITCZ and the origin of monsoon onset SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID HADLEY CIRCULATION; CONVECTION; ATMOSPHERE; NORTH; SST AB Supported by numerical experiment results, the abrupt change of the location of the intertropical convergence zone (ITCZ), from the equatorial trough how regime to the monsoon trough flow regime. or the monsoon onset, is interpreted as a subcritical instability. There are two balancing "forces" acting on the ITCZ. One toward the equator, or an equatorial latitude depending on the convection scheme, due to the earth's rotation, has a nonlinear latitudinal dependence; and the other toward a latitude close to the sea surface temperature peak has a relatively linear latitudinal dependence. The highly nonlinear latitudinal dependence of the first "force" is crucial for the existence of the multiple equilibria. This work pivots on the finding that the ITCZ and Hadley circulation can still exist without the pole-to-equator gradient of radiative-convective equilibrium temperature. The numerical experiments are done with an atmospheric general circulation model over an aquaplanet with zonally uniform sea surface temperature. The existence of the two flow regimes, the two "forces," and the abrupt transition are all demonstrated in the experiments. Experimental results show high dependence on the choice of cumulus parameterization scheme. especially during the equatorial trough circulation regime. Although the proposed interpretation is more suitable for explaining the monsoon trough onset in the western Pacific, it is hypothesized that the same basic mechanism is also at the core of monsoon onset in other parts of the Tropics. C1 NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. RP Chao, WC (reprint author), NASA, Goddard Space Flight Ctr, Atmospheres Lab, Mail Code 913, Greenbelt, MD 20771 USA. EM winston.chao@gsfc.nasa.gov NR 21 TC 40 Z9 44 U1 2 U2 11 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0022-4928 J9 J ATMOS SCI JI J. Atmos. Sci. PD MAR 1 PY 2000 VL 57 IS 5 BP 641 EP 651 DI 10.1175/1520-0469(2000)057<0641:MQEOTI>2.0.CO;2 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 301MT UT WOS:000086314500002 ER PT J AU Cairns, B Lacis, AA Carlson, BE AF Cairns, B Lacis, AA Carlson, BE TI Absorption within inhomogeneous clouds and its parameterization in general circulation models SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID STOCHASTIC RADIATIVE-TRANSFER; AVERAGED SOLAR FLUXES; MULTIPLE-SCATTERING; OPTICAL-CONSTANTS; LIGHT-SCATTERING; MEDIA; WATER; LOCALIZATION; ATMOSPHERE; TRANSPORT AB The effect on absorption in clouds of having an inhomogeneous distribution of droplets is shown to depend on whether one replaces a homogeneous cloud by an inhomogeneous cloud that has the same mean optical thickness, or one that has the same spherical albedo. For the purposes of general circulation models (GCMs) the more appropriate comparison is between homogeneous and inhomogeneous clouds that have the same spherical albeo. so that the radiation balance of the planet with space is maintained. In this ease it is found, using Monte Carlo and independent pixel approximation calculations, that inhomogeneous clouds can absorb more than homogeneous clouds. It is also found that because of the different effects of cloud inhomogeneity on absorption and on the transmission of the direct beam the absorption efficiency of an inhomogeneous cloud may be either greater (for low and high optical depths) or lesser (for intermediate optical depths) than that for a homogeneous cloud of the same mean optical depth. This effect is relevant both to in-cloud absorption and to absorption below clouds. In order to include these effects in GCMs a simple renormalization of the single-scattering parameters of radiative transfer theory is derived that allows the effects of cloud inhomogeneities to be included in plane-parallel calculations. This renormalization method is shown to give reasonable results when compared with Monte Carlo calculations, has the appropiate limits for conservative and completely absorbing cases, and provides a simple interpretation of the effects of cloud inhomogeneities that could readily be incorporated in a GCM. C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Columbia Univ, Dept Appl Phys, New York, NY 10027 USA. RP Cairns, B (reprint author), NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. RI Lacis, Andrew/D-4658-2012; Carlson, Barbara/D-8319-2012; OI Cairns, Brian/0000-0002-1980-1022 NR 72 TC 59 Z9 61 U1 1 U2 3 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0022-4928 J9 J ATMOS SCI JI J. Atmos. Sci. PD MAR 1 PY 2000 VL 57 IS 5 BP 700 EP 714 DI 10.1175/1520-0469(2000)057<0700:AWICAI>2.0.CO;2 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 301MT UT WOS:000086314500005 ER PT J AU Liu, AS Ning, CZ AF Liu, AS Ning, CZ TI Exciton absorption in semiconductor quantum wells driven by a strong intersubband pump field SO JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS LA English DT Article ID ELECTROMAGNETICALLY INDUCED TRANSPARENCY; POPULATION-INVERSION; LIGHT AMPLIFICATION; COHERENCE; INTERFERENCE; PULSES; GAIN AB Optical interband excitonic absorption of semiconductor quantum wells (QW's) driven by a coherent pump field is investigated on the basis of semiconductor Bloch equations. The pump field has a photon energy close to the intersubband spacing between the first two conduction subbands in the QW's. An external weak optical field probes the interband transition. The excitonic effects and pump-induced population redistribution within the conduction subbands in the QW system are included. When the density of the electron-hole pairs in the QW structure is low, the pump field induces an Autler-Townes splitting of the exciton absorption spectrum. The split size and the peak positions of the absorption doublet depend not only on the pump frequency and intensity but also on the carrier density. As the density of the electron-hole pairs is increased, the split contrast (the ratio between the maximum and the minimum values) is decreased, because the exciton effect is suppressed at higher densities owing to the many-body screening. (C) 2000 Optical Society of America [S0740-3224(00)01703-3] OCIS codes: 190.5970, 190.4720, 270.1670, 270.4180. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Arizona State Univ, Dept Elect Engn, Tempe, AZ 85287 USA. RP Liu, AS (reprint author), NASA, Ames Res Ctr, M-S N229-1, Moffett Field, CA 94035 USA. RI Ning, C. Z./D-4699-2009 OI Ning, C. Z./0000-0003-4583-8889 NR 21 TC 20 Z9 21 U1 0 U2 0 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 0740-3224 J9 J OPT SOC AM B JI J. Opt. Soc. Am. B-Opt. Phys. PD MAR PY 2000 VL 17 IS 3 BP 433 EP 439 DI 10.1364/JOSAB.17.000433 PG 7 WC Optics SC Optics GA 294MY UT WOS:000085916100012 ER PT J AU Launius, RD AF Launius, RD TI The road to Appomattox SO JOURNAL OF THE WEST LA English DT Book Review C1 NASA, Washington, DC 20546 USA. RP Launius, RD (reprint author), NASA, Washington, DC 20546 USA. NR 1 TC 0 Z9 0 U1 0 U2 0 PU J WEST INC PI MANHATTAN PA P O BOX 1009, MANHATTAN, KS 66505-1009 USA SN 0022-5169 J9 J WEST JI J. West PD SPR PY 2000 VL 39 IS 2 BP 81 EP 81 PG 1 WC History SC History GA 314JX UT WOS:000087053600044 ER PT J AU He, YR Lee, KN Tewari, S Miller, RA AF He, YR Lee, KN Tewari, S Miller, RA TI Development of refractory silicate-yttria-stabilized zirconia dual-layer thermal barrier coatings SO JOURNAL OF THERMAL SPRAY TECHNOLOGY LA English DT Article DE TBC; mullite; silicates; oxygen barrier; APS; sputtering; small particle plasma spray ID BOND COAT AB Development of advanced thermal barrier coatings (TBCs) is the most promising approach for increasing the efficiency and performance of gas turbine engines by enhancing the temperature capability of hot section metallic components. Spallation of the yttria-stabilized zirconia (YSZ) top coat, induced by the oxidation of the bond coat coupled with the thermal expansion mismatch strain, is considered to be the ultimate failure mode for current state-of-the-art TBCs. Enhanced oxidation resistance of TBCs can be achieved by reducing the oxygen conductance of TBCs below that of thermally grown oxide (TGO) alumina scale. One approach is incorporating an oxygen barrier having an oxygen conductance lower than that of alumina scale, Mullite, rare earth silicates, and glass ceramics have been selected as potential candidates for the oxygen barrier. This paper presents the results of cyclic oxidation studies of oxygen barrier/YSZ dual-layer TBCs. C1 Cleveland State Univ, Cleveland, OH 44115 USA. NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. RP He, YR (reprint author), Cleveland State Univ, Cleveland, OH 44115 USA. NR 19 TC 11 Z9 11 U1 0 U2 4 PU ASM INTERNATIONAL PI MATERIALS PARK PA SUBSCRIPTIONS SPECIALIST CUSTOMER SERVICE, MATERIALS PARK, OH 44073-0002 USA SN 1059-9630 J9 J THERM SPRAY TECHN JI J. Therm. Spray Technol. PD MAR PY 2000 VL 9 IS 1 BP 59 EP 67 DI 10.1361/105996300770350069 PG 9 WC Materials Science, Coatings & Films SC Materials Science GA 306FZ UT WOS:000086587800014 ER PT J AU Lee, KN Barrett, CA Smith, J AF Lee, KN Barrett, CA Smith, J TI Long-term cyclic oxidation behavior of uncoated and coated RE108 and IN939 at 980 and 870 degrees C SO JOURNAL OF THERMAL SPRAY TECHNOLOGY LA English DT Article DE cyclic oxidation; oxidative life; Re108; In939; VPA; SERMALOY J AB Very long-term cyclic oxidation behavior of Re108 and In939 with and without a protective coating was evaluated at 980 and 870 degrees C, respectively. Re108 and In939 without a protective coating began to show a rapid weight loss at 3000 h due to scale spallation, indicating the need for an oxidation protective coating for longer than thousands of hours of oxidative life. NiAl-base coatings of a vapor phase aluminide (VPA), a pack aluminide (CODEP), and a slurry paint aluminide (SERMALOY J) were applied on Re108 and In939, The VPA and CODEP on Re108 and all three coatings on In939 showed excellent cyclic oxidation resistance out to 10,000 h. Coated alloys were annealed in an inert atmosphere to determine the loss of Al from the coating into the alloy substrate through diffusion. The Al loss from the coating through diffusion was twice as great as the Al loss through oxidation after 10,000 h of cyclic exposure. The oxidation life of VPA-coated Re108 was estimated by calculating the amount of Al initially available for protective oxidation and the amount of Al lost through oxidation and diffusion. C1 Cleveland State Univ, Cleveland, OH 44135 USA. NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. Dynacs, Cleveland, OH 44135 USA. RP Lee, KN (reprint author), Cleveland State Univ, Cleveland, OH 44135 USA. NR 7 TC 3 Z9 3 U1 0 U2 3 PU ASM INTERNATIONAL PI MATERIALS PARK PA SUBSCRIPTIONS SPECIALIST CUSTOMER SERVICE, MATERIALS PARK, OH 44073-0002 USA SN 1059-9630 J9 J THERM SPRAY TECHN JI J. Therm. Spray Technol. PD MAR PY 2000 VL 9 IS 1 BP 121 EP 127 DI 10.1361/105996300770350159 PG 7 WC Materials Science, Coatings & Films SC Materials Science GA 306FZ UT WOS:000086587800023 ER PT J AU Perera, AGU Shen, WZ Ershov, M Liu, HC Buchanan, M Gunapala, SD Bandara, SV Liu, JK Ye, HH Schaff, WJ AF Perera, AGU Shen, WZ Ershov, M Liu, HC Buchanan, M Gunapala, SD Bandara, SV Liu, JK Ye, HH Schaff, WJ TI Effect of interface states on the performance of GaAs p(+)-i far-infrared detectors SO JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A-VACUUM SURFACES AND FILMS LA English DT Article; Proceedings Paper CT 9th Canadian Semiconductor Technology Conference (CSTC) CY AUG 10-13, 1999 CL OTTAWA, CANADA ID SI AB Interface states have been shown to have an appreciable effect on the performance of p-GaAs multilayer (p(+)-i-p(+)-i-...) homojunction interfacial work function internal photoemission (HIWIP) far-infrared detectors. In this article, a comparison of detector performance was made of p-GaAs HIWIP detectors with different interface state densities, with the emphasis on the detector's dark current, noise, and capacitance characteristics. (C) 2000 American Vacuum Society. [S0734-2101(oo)03502-8]. C1 Georgia State Univ, Dept Phys & Astron, Atlanta, GA 30303 USA. Natl Res Council Canada, Inst Microstruct Sci, Ottawa, ON K1A 0R6, Canada. CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. Cornell Univ, Sch Elect Engn, Ithaca, NY 14853 USA. RP Perera, AGU (reprint author), Georgia State Univ, Dept Phys & Astron, Atlanta, GA 30303 USA. NR 13 TC 0 Z9 0 U1 0 U2 2 PU AMER INST PHYSICS PI MELVILLE PA 2 HUNTINGTON QUADRANGLE, STE 1NO1, MELVILLE, NY 11747-4501 USA SN 0734-2101 J9 J VAC SCI TECHNOL A JI J. Vac. Sci. Technol. A-Vac. Surf. Films PD MAR-APR PY 2000 VL 18 IS 2 BP 597 EP 600 DI 10.1116/1.582233 PG 4 WC Materials Science, Coatings & Films; Physics, Applied SC Materials Science; Physics GA 293BG UT WOS:000085831200055 ER PT J AU Thuesen, LH Tolt, ZL Fink, RL Yaniv, Z Marrese, CM Bandy, S Nishimoto, C AF Thuesen, LH Tolt, ZL Fink, RL Yaniv, Z Marrese, CM Bandy, S Nishimoto, C TI Field emission carbon thin film and its lifetime and stability SO JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B LA English DT Article; Proceedings Paper CT 12th International Vaccum Microelectronics Conference (IVMC 99) CY JUL 06-09, 1999 CL DARMSTADT, GERMANY SP Amer Vacuum Soc, Darmstadt Univ Technol, Wroclaw Univ Technol, GMM VED VDI Gesell Mikroelektr, Mikro & Feinwerktech Frankfurt, Informat Techn Gesell, Verband Elektroteck Elektr, Informat Techn eV Frankfurt ID OXYGEN; PLASMA AB Tests were performed on FEPET, Inc. carbon thin film cathodes to characterize lifetime, resistance to environmental conditions, and performance stability. The cathodes were found to exhibit half lifetimes on the order of 7000 h in sealed glass envelopes. Operation in oxygen and water were found to degrade the cathode performance severely. Xenon had no effect on the cathode lifetime or stability, demonstrating its resistance to ion sputtering. During characterization in vacuum systems, initial turn on was quick and stable. Carbon thin films are suitable cathode materials for display, microelectronic, and ion propulsion uses. (C) 2000 American Vacuum Society. [S0734-211X(00)06902-X]. C1 FEPET Inc, Austin, TX 78758 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Varian Ginzton Res Ctr, Mt View, CA 94043 USA. RP Thuesen, LH (reprint author), FEPET Inc, Austin, TX 78758 USA. NR 6 TC 5 Z9 5 U1 0 U2 0 PU AMER INST PHYSICS PI MELVILLE PA 2 HUNTINGTON QUADRANGLE, STE 1NO1, MELVILLE, NY 11747-4501 USA SN 1071-1023 J9 J VAC SCI TECHNOL B JI J. Vac. Sci. Technol. B PD MAR-APR PY 2000 VL 18 IS 2 BP 968 EP 971 DI 10.1116/1.591308 PG 4 WC Engineering, Electrical & Electronic; Nanoscience & Nanotechnology; Physics, Applied SC Engineering; Science & Technology - Other Topics; Physics GA 306FQ UT WOS:000086587000065 ER PT J AU Smith, DE Frank, J Jonsson, AK AF Smith, DE Frank, J Jonsson, AK TI Bridging the gap between planning and scheduling SO KNOWLEDGE ENGINEERING REVIEW LA English DT Review ID CONSTRAINT SATISFACTION PROBLEMS; SEARCH; TIME; CONSISTENCY; ALGORITHMS; COMPLEXITY; FRAMEWORK; NETWORKS; GOALS AB Planning research in Artificial Intelligence (AI) has often focused on problems where there are cascading levels of action choice and complex interactions between actions. In contrast, scheduling research has focused on much larger problems where there is little action choice, but the resulting ordering problem is hard. In this paper, we give an overview of AI planning and scheduling techniques, focusing on their similarities, differences, and limitations. We also argue that many difficult practical problems lie somewhere between planning and scheduling, and that neither area has the right set of tools for solving these vexing problems. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP NASA, Ames Res Ctr, Mail Stop 269-2, Moffett Field, CA 94035 USA. EM de2smith@ptolemy.arc.nasa.gov; frank@ptolemy.arc.nasa.gov; jonsson@ptolemy.arc.nasa.gov NR 140 TC 43 Z9 46 U1 0 U2 5 PU CAMBRIDGE UNIV PRESS PI NEW YORK PA 32 AVENUE OF THE AMERICAS, NEW YORK, NY 10013-2473 USA SN 0269-8889 EI 1469-8005 J9 KNOWL ENG REV JI Knowl. Eng. Rev. PD MAR PY 2000 VL 15 IS 1 BP 47 EP 83 DI 10.1017/S0269888900001089 PG 37 WC Computer Science, Artificial Intelligence SC Computer Science GA 348AU UT WOS:000088962400004 ER PT J AU Kaminskii, AA Eichler, HJ Hulliger, J Haussuhl, S Chyba, T Temple, D Barnes, JC Dolbinina, VN Findeisen, J Wang, JY Menkai, L AF Kaminskii, AA Eichler, HJ Hulliger, J Haussuhl, S Chyba, T Temple, D Barnes, JC Dolbinina, VN Findeisen, J Wang, JY Menkai, L TI Multiple stokes and anti-stokes generation in triclinic gamma-KIO3 and hexagonal alpha-LiIO3 nonlinear crystals SO LASER PHYSICS LA English DT Article ID TEMPERATURE AB Efficient stimulated Raman scattering (SRS) in triclinic gamma-KIO3 and hexagonal alpha-LiIO3 crystals was observed under picosecond laser excitation. All scattering components were identified and connected with the SRS-active vibration modes of these iodates. We classify the gamma-KIO3 and alpha-LiIO3 acentric compounds as promising (chi((2)) + chi((3))) media for Raman laser shifters. C1 Russian Acad Sci, Inst Crystallog, Moscow 117333, Russia. Tech Univ Berlin, Inst Opt, D-10623 Berlin, Germany. Univ Bern, Dept Chem & Biochem, CH-3012 Bern, Switzerland. Univ Cologne, Inst Crystallog, D-50674 Cologne, Germany. Hampton Univ, Dept Phys, Hampton, VA 23688 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. Shandong Univ, State Key Lab Crystal Mat, Jinan 250100, Peoples R China. RP Kaminskii, AA (reprint author), Russian Acad Sci, Inst Crystallog, Moscow 117333, Russia. NR 15 TC 6 Z9 6 U1 0 U2 4 PU INTERPERIODICA PI BIRMINGHAM PA PO BOX 1831, BIRMINGHAM, AL 35201-1831 USA SN 1054-660X J9 LASER PHYS JI Laser Phys. PD MAR-APR PY 2000 VL 10 IS 2 BP 627 EP 632 PG 6 WC Optics; Physics, Applied SC Optics; Physics GA 305RQ UT WOS:000086554400040 ER PT J AU Berthon, JF Zibordi, G Hooker, SB AF Berthon, JF Zibordi, G Hooker, SB TI Marine optical measurements of a mucilage event in the northern Adriatic Sea SO LIMNOLOGY AND OCEANOGRAPHY LA English DT Article AB Optical measurements performed during the summer of 1997 from an off-shore oceanographic tower in the northern Adriatic Sea in the presence of mucilage matter are presented. These measurements include apparent (diffuse attenuation coefficient, reflectance) and inherent (absorption and beam attenuation coefficients) optical properties of the water column at several wavelengths. The presence of mucilage layers (which was confirmed by divers) was associated with unique, very sharp subsurface maxima in the vertical distribution of both apparent and inherent optical properties. These layers were characterized by very high values of the diffuse attenuation coefficient of upwelling radiance and the beam attenuation coefficient, as well as the ratio of the scattering-to-absorption coefficients at all wavelengths. The mucilage data were compared to nonmucilage observations and two situations came out regarding surface reflectance ratios: (a) When the mucilage was in (vertically narrow) subsurface layers, mucilage events could not be distinguished from nonmucilage situations; and (b) When the mucilage was more homogeneously distributed throughout the water column and, in particular, approaching the surface, there was a detectable difference with respect to nonmucilage water. However, the data set is small, and the detection capability is based on a small difference, so the variance in nonmucilage water properties may still mask the properties of the mucilage-contaminated water. C1 Commiss European Communities, Joint Res Ctr, Space Applicat Inst, Marine Environm Unit, I-21020 Ispra, Italy. NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. RP Berthon, JF (reprint author), Commiss European Communities, Joint Res Ctr, Space Applicat Inst, Marine Environm Unit, TP272, I-21020 Ispra, Italy. RI Hooker, Stanford/E-2162-2012 NR 12 TC 7 Z9 7 U1 0 U2 1 PU AMER SOC LIMNOLOGY OCEANOGRAPHY PI WACO PA 5400 BOSQUE BLVD, STE 680, WACO, TX 76710-4446 USA SN 0024-3590 J9 LIMNOL OCEANOGR JI Limnol. Oceanogr. PD MAR PY 2000 VL 45 IS 2 BP 322 EP 327 PG 6 WC Limnology; Oceanography SC Marine & Freshwater Biology; Oceanography GA 292YB UT WOS:000085822300007 ER PT J AU Aboudi, J Arnold, SM AF Aboudi, J Arnold, SM TI Micromechanical modeling of the finite deformation of thermoelastic multiphase composites SO MATHEMATICS AND MECHANICS OF SOLIDS LA English DT Article ID SPHERICAL-SHELLS; INFLATION; SOLIDS AB A micromechanical model is proposed for the prediction of nonlinearly thermoelastic, multiphase particulate, and/or continuous reinforced composites in which any or all constituents exhibit large strain (finite deformation). The analysis provides closed-form representations for the instantaneous mechanical and thermal concentration tensors, as well as the effective tangent mechanical and thermal properties of the composite. The micromechanical model predictions are assessed by a comparison with an analytical spherical composite model, valid for hydrostatic loadings only. Very good agreement between the two approaches was obtained. Similarly, results demonstrating the effects of nonlinearity are given for particulate and continuous fiber-reinforced S(i)C/Al composites. Finally, the nonlinear response of cellular solids idealized by open-cell and closed-cell structures are compared and contrasted. C1 Tel Aviv Univ, Fac Engn, IL-69978 Ramat Aviv, Israel. NASA, Life Predict Branch, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Aboudi, J (reprint author), Tel Aviv Univ, Fac Engn, IL-69978 Ramat Aviv, Israel. NR 26 TC 11 Z9 11 U1 0 U2 3 PU SAGE PUBLICATIONS LTD PI LONDON PA 1 OLIVERS YARD, 55 CITY ROAD, LONDON EC1Y 1SP, ENGLAND SN 1081-2865 J9 MATH MECH SOLIDS JI Math. Mech. Solids PD MAR PY 2000 VL 5 IS 1 BP 75 EP 99 DI 10.1177/108128650000500105 PG 25 WC Materials Science, Multidisciplinary; Mathematics, Interdisciplinary Applications; Mechanics SC Materials Science; Mathematics; Mechanics GA 283CL UT WOS:000085258500005 ER PT J AU Giddings, VL Beaupre, GS Whalen, RT Carter, DR AF Giddings, VL Beaupre, GS Whalen, RT Carter, DR TI Calcaneal loading during walking and running SO MEDICINE AND SCIENCE IN SPORTS AND EXERCISE LA English DT Article DE calcaneus; biomechanical model; foot; bone remodeling; finite element model; joint forces; bone forces; muscle forces; ground reaction force; bone adaptation ID GROUND REACTION FORCES; BONE-DENSITY; MUSCULOSKELETAL SYSTEM; ANKLE; BIOMECHANICS; MORPHOLOGY; LIGAMENTS; FRACTURE; ENERGY; STRESS AB Purpose: This study of the foot uses experimentally measured kinematic and kinetic data with a numerical model to evaluate in vivo calcaneal stresses during walking and running. Methods: External ground reaction forces (GRF) and kinematic data were measured during walking and running using cineradiography and force plate measurements. A contact-coupled finite element model of the foot was developed to assess the forces acting on the calcaneus during gait. Results: We found that the calculated force-time profiles of the joint contact, ligament, and Achilles tendon forces varied with the time-history curve of the moment about the ankle joint. The model predicted peak talocalcaneal and calcaneocuboid joint loads of 5.4 and 4.2 body weights (BW) during walking and 11.1 and 7.9 BW during running. The maximum predicted Achilles tendon forces were 3.9 and 7.7 BW for walking and running. Conclusions: Large magnitude forces and calcaneal stresses are generated late in the stance phase, with maximum loads occurring at similar to 70% of the stance phase during walking and at similar to 60% of the stance phase during running, for the gait velocities analyzed. The trajectories of the principal stresses, during both walking and running, corresponded to each other and qualitatively to the calcaneal trabecular architecture. C1 Stanford Univ, Dept Mech Engn, Biomech Engn Div, Stanford, CA 94305 USA. Vet Affairs Hlth Care Syst, Rehabil Res & Dev Ctr, Palo Alto, CA USA. NASA, Ames Res Ctr, Div Life Sci, Mt View, CA USA. RP Giddings, VL (reprint author), Exponent Failure Anal Associates, 149 Commonwealth Dr, Menlo Park, CA 94025 USA. OI Beaupre, Gary/0000-0002-6211-7621 NR 37 TC 98 Z9 103 U1 5 U2 31 PU LIPPINCOTT WILLIAMS & WILKINS PI PHILADELPHIA PA 530 WALNUT ST, PHILADELPHIA, PA 19106-3621 USA SN 0195-9131 J9 MED SCI SPORT EXER JI Med. Sci. Sports Exerc. PD MAR PY 2000 VL 32 IS 3 BP 627 EP 634 DI 10.1097/00005768-200003000-00012 PG 8 WC Sport Sciences SC Sport Sciences GA 294XD UT WOS:000085935000012 PM 10731005 ER PT J AU Raj, SV Ghosn, LJ AF Raj, SV Ghosn, LJ TI Effect of fiber volume fraction on the fracture behavior of Nb-1 Wt Pct Zr/218W composites at elevated temperatures SO METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE LA English DT Article; Proceedings Paper CT Symposium on Mechanisms and Mechanics of Composites Fracture held at the 1998 TMS Fall Meeting CY OCT 11-15, 1998 CL ROSEMONT, ILLINOIS SP TMS, SMD, ASM, MSCTS ID ALLOYS AB Nb-1 wt pet Zr/218W long-fiber composite monotapes, nominally containing 0 to 70 vol pet of 218 tungsten fibers, were fabricated by are spraying the Nb-1 pet Zr matrix onto the tungsten fibers. The monotapes were consolidated by hot pressing and hot isostatic pressing techniques. Tensile tests conducted between 1400 and 1600 K, under engineering strain rates varying between 1.5 x 10(-5) and 1.5 x 10(-3) s(-1), demonstrated that composites containing 70 vol pet of fibers had the highest strength-to-density ratio. Microstructural observations of specimens tested at 1400 It revealed that composites containing less than 50 vol pet of fibers showed extensive matrix cavitation, fiber-matrix debonding, and necking of the fibers. Above 50 vol pet, the composite matrix was less prone to cavitation, with an increasing tendency toward shear deformation of the fibers as the fiber volume fraction increased. No fiber damage was observed at 1400 K away from the fractured end, but significant fiber damage was observed at higher temperatures. A phenomenological model is presented to rationalize these observations. C1 NASA, Glenn Res Ctr Lewis Fields, Cleveland, OH 44136 USA. Cleveland State Univ, Cleveland, OH 44115 USA. Everready Battery Co, Westlake, OH 44145 USA. RP Raj, SV (reprint author), NASA, Glenn Res Ctr Lewis Fields, Cleveland, OH 44136 USA. NR 19 TC 0 Z9 0 U1 0 U2 1 PU MINERALS METALS MATERIALS SOC PI WARRENDALE PA 420 COMMONWEALTH DR, WARRENDALE, PA 15086 USA SN 1073-5623 J9 METALL MATER TRANS A JI Metall. Mater. Trans. A-Phys. Metall. Mater. Sci. PD MAR PY 2000 VL 31 IS 3A BP 873 EP 887 PG 15 WC Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Materials Science; Metallurgy & Metallurgical Engineering GA 297XC UT WOS:000086107100010 ER PT J AU Steele, A Goddard, DT Stapleton, D Toporski, JKW Peters, V Bassinger, V Sharples, G Wynn-Williams, DD McKay, DS AF Steele, A Goddard, DT Stapleton, D Toporski, JKW Peters, V Bassinger, V Sharples, G Wynn-Williams, DD McKay, DS TI Investigations into an unknown organism on the martian meteorite Allan Hills 84001 SO METEORITICS & PLANETARY SCIENCE LA English DT Article ID MICROBIAL COMMUNITIES; FORCE MICROSCOPY; ALH84001; ANTARCTICA; SEARCH; LIFE AB Examination of fracture surfaces near the fusion crust of the martian meteorite Allan Hills (ALH) 84001 have been conducted using scanning electron microscopy (SEM) and atomic force microscopy (AFM) and has revealed structures strongly resembling mycelium. These structures were compared with similar structures found in Antarctic cryptoendolithic communities. On morphology alone, we conclude that these features are not only terrestrial in origin but probably belong to a member of the Actinomycetales, which we consider was introduced during the Antarctic residency of this meteorite. If true, this is the first documented account of terrestrial microbial activity within a meteorite from the Antarctic blue ice fields. These structures, however, do not bear any resemblance to those postulated to be martian biota, although they are a probable source of the organic contaminants previously reported in this meteorite. C1 Univ Portsmouth, Sch Earth Environm & Phys Sci, Astrobiol Grp, Portsmouth PO1 2DT, Hants, England. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. BNFL, Preston PR7 1FU, Lancs, England. Liverpool John Moores Univ, Sch Biomol Sci, Liverpool L3 3AF, Merseyside, England. British Antarctic Survey, Cambridge CB3 0ET, England. RP Steele, A (reprint author), Univ Portsmouth, Sch Earth Environm & Phys Sci, Astrobiol Grp, Portsmouth PO1 2DT, Hants, England. NR 33 TC 32 Z9 32 U1 0 U2 5 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 USA SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD MAR PY 2000 VL 35 IS 2 BP 237 EP 241 PG 5 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 297WG UT WOS:000086105200003 PM 11542972 ER PT J AU Spurny, P Betlem, H van't Leven, J Jenniskens, P AF Spurny, P Betlem, H van't Leven, J Jenniskens, P TI Atmospheric behavior and extreme beginning heights of the thirteen brightest photographic Leonid meteors from the ground-based expedition to China SO METEORITICS & PLANETARY SCIENCE LA English DT Article ID FIREBALL AB Precise atmospheric trajectories including dynamic and photometric data on thirteen of the brightest Leonid fireballs have been determined from the double-station photographic observations of Leonid meteors during the ground-based expedition to China in 1998 November. The expedition was organized as a collaboration between the Dutch and Chinese Academy of Sciences and was supported by the Leonid multi-instrument aircraft campaign (MAC) program (Jenniskens and Butow, 1999). All data presented here were taken at Xinglong Observatory and at a remote station, Lin Ting Kou near Beijing, on the night of 1998 November 16/17. At the Xinglong station, photographic cameras were accompanied by an all-sky television camera equipped with an image intensifier and 15 mm fish-eye objective in order to obtain precise timings for all observed meteors up to magnitude +2. Whereas beginning heights of photographed meteors are all lower than 130 km, those observed by the all-shy television system are at similar to 160 km, and for three brightest events, even >180 km. Such high beginnings for meteors have never before been observed. We also obtained a precise dynamic single-body solution for the Leonid meteor 98003, including the ablation coefficient, which is an important material and structural quantity (0.16 s(2) km(-2)). From this and from known photometry, we derived a density of this meteoroid of 0.7 g/cm(3). Also, all PE coefficients indicate that these Leonid meteors belonged to the fireball group IIIB, which is typical for the most fragile and weak interplanetary bodies. From a photometric study of the meteor lightcurves, we found two typical shapes of light curves for these Leonid meteors. C1 Ondrejov Observ, Inst Astron, Ondrejov 25165, Czech Republic. Dutch Meteor Soc, NL-2318 NB Leiden, Netherlands. NASA, Ames Res Ctr, SETI Inst, Moffett Field, CA 94035 USA. RP Spurny, P (reprint author), Ondrejov Observ, Inst Astron, Ondrejov 25165, Czech Republic. RI Spurny, Pavel/G-9044-2014 NR 12 TC 44 Z9 44 U1 0 U2 2 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 USA SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD MAR PY 2000 VL 35 IS 2 BP 243 EP 249 PG 7 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 297WG UT WOS:000086105200004 ER PT J AU Paque, JM Lofgren, GE Le, L AF Paque, JM Lofgren, GE Le, L TI Crystallization of calcium-aluminum-rich inclusions: Experimental studies on the effects of repeated heating events SO METEORITICS & PLANETARY SCIENCE LA English DT Article ID ALLENDE; CA; SEQUENCES; MELILITE AB The observed textures and chemistry of calcium-aluminum-rich inclusions (CAIs) are presumed to be the culmination of a series of repeated heating and cooling events in the early history of the solar nebula. We have examined the effects of these heating/cooling cycles experimentally on a bulk composition representing an average Type B CAI composition by varying the nature of the starting material. Although the most recent and/or highest temperature event prior to incorporation into the parent body dominates the texture and chemistry of the CAI, prior events affect the phase compositions and texture. We have determined that a prior low-temperature event (simulated by heating the sample to 1275 degrees C and cooling slowly) increases the likelihood of anorthite crystallization in subsequent higher temperature events. A prior high-temperature event that produced dendritic melilite,(simulated by heating the sample to 1550 degrees C and cooling rapidly) results in melilite that shows evidence of rapid crystallization in subsequent lower temperature events. The addition of Pt powder to the starting material appears to enhance the ability of anorthite to nucleate from this composition and increases the number of melilite crystals present in samples that crystallize euhedral melilite. C1 NASA, Ames Res Ctr, SETI Inst, Moffett Field, CA 94035 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Lockheed Martin, Houston, TX 77058 USA. RP Paque, JM (reprint author), NASA, Ames Res Ctr, SETI Inst, Mail Stop 245-3, Moffett Field, CA 94035 USA. NR 21 TC 1 Z9 1 U1 1 U2 1 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 USA SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD MAR PY 2000 VL 35 IS 2 BP 363 EP 371 PG 9 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 297WG UT WOS:000086105200013 ER PT J AU Garrison, D Hamlin, S Bogard, D AF Garrison, D Hamlin, S Bogard, D TI Chlorine abundances in meteorites SO METEORITICS & PLANETARY SCIENCE LA English DT Article ID PARENT BODIES; CHONDRITES; HALOGENS; PETROLOGY; ORIGIN AB We used the nuclear reaction Cl-37 (n,gamma) Ar-38, achieved during neutron irradiation for dating meteorites by the Ar-39-Ar-40 technique, to calculate the elemental Cl concentration of 132 samples of 94 different meteorites (mostly finds) representing several different classes. Determined K and Ca concentrations are also reported. Total [Cl] varies considerably, both among meteorites of the same class and among different meteorite classes. The range in [Cl] is approximately 15-177 ppm for ordinary chondrites; approximately 24-650 ppm for enstatite chondrites; approximately 4-177 ppm for eucrites; approximately 7-128 ppm for mesosiderites; approximately 35-268 ppm for acapulcoites and lodranites; and approximately 12-507 ppm for winonaites and iron silicates. As expected, most differentiated meteorites have lower [Cl] compared to chondrites and iron silicates. Analyses of 11 interior samples (similar to 0.1 g each) of a large L6 chondrite varied over 68-129 ppm, which is a measure of the homogeneity of Cl distribution. By evaluating Ar release during stepwise sample degassing, we separated the Cl into low-temperature and high-temperature components, the former of which may consist of terrestrial contamination. Most samples show low-temperature Cl concentrations of <40 ppm, but for several samples terrestrial Cl contamination constitutes significant fractions of the total Cl. Among most differentiated meteorites, finds show considerably greater low-temperature [Cl] compared to falls. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Lockheed Martin Corp, Houston, TX 77058 USA. Earlham Coll, Richmond, IN 47374 USA. Lunar & Planetary Inst, Houston, TX 77058 USA. RP Bogard, D (reprint author), NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 29 TC 41 Z9 41 U1 2 U2 7 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 USA SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD MAR PY 2000 VL 35 IS 2 BP 419 EP 429 PG 11 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 297WG UT WOS:000086105200017 ER PT J AU Emardson, TR Derks, HJP AF Emardson, TR Derks, HJP TI On the relation between the wet delay and the integrated precipitable water vapour in the European atmosphere SO METEOROLOGICAL APPLICATIONS LA English DT Article ID GLOBAL POSITIONING SYSTEM; GPS METEOROLOGY AB A ground-based network of Global Positioning System (GPS) receivers can be used to determine the excess propagation path of the GPS signals. Using surface pressure data it is possible to derive the excess path caused by water vapour. This quantity, is often referred to as the wet delay. We have studied the relationship between the wet delay and the integrated precipitable water vapour (IPWV), based on more than 120 000 radiosonde profiles from 38 sites in Europe. We have studied four different models based on the surface temperature, the latitude of the site, and the time of the year in different combinations. The accuracies of the models have been evaluated and also compared with the accuracy resulting from the use of published model parameters derived from radiosonde data acquired in the United States. The models using the surface temperature data yielded the smallest relative root mean square errors of 1.14% and 1.15% respectively. We find that the accuracy can sometimes be further improved, typically down to 1.02%, by adjusting the values of the model parameters to the area or site of interest. C1 Chalmers Univ Technol, Onsala Space Observ, SE-43992 Onsala, Sweden. Royal Netherlands Meteorol Inst, NL-3730 AE De Bilt, Netherlands. RP Emardson, TR (reprint author), CALTECH, Jet Prop Lab, Mail Stop 238-600,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 5 TC 50 Z9 52 U1 0 U2 0 PU CAMBRIDGE UNIV PRESS PI NEW YORK PA 40 WEST 20TH STREET, NEW YORK, NY 10011-4211 USA SN 1350-4827 J9 METEOROL APPL JI Meteorol. Appl. PD MAR PY 2000 VL 7 IS 1 BP 61 EP 68 DI 10.1017/S1350482700001377 PG 8 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 308YD UT WOS:000086739700006 ER PT J AU Parsons-Wingerter, P Elliott, KE Farr, AG Radhakrishnan, K Clark, JI Sage, EH AF Parsons-Wingerter, P Elliott, KE Farr, AG Radhakrishnan, K Clark, JI Sage, EH TI Generational analysis reveals that TGF-beta 1 inhibits the rate of angiogenesis in vivo by selective decrease in the number of new vessels SO MICROVASCULAR RESEARCH LA English DT Article DE TGF-beta 1; angiogenesis; fractal; chorioallantoic membrane; CAM; quail; complexity; development ID TGF-BETA; CHORIOALLANTOIC MEMBRANE; STIMULATION; INVITRO AB Quantitative analysis of vascular generational branching demonstrated that transforming growth factor-beta 1 (TGF-beta 1), a multifunctional cytokine and angiogenic regulator, strongly inhibited angiogenesis in the arterial tree of the developing quail chorioallantoic membrane (CAM) by inhibition of the normal increase in the number of new, small vessels. The cytokine was applied uniformly in solution at embryonic day 7 (E7) to the CAMs of quail embryos cultured in petri dishes. After 24 h the rate of arterial growth was inhibited by as much as 105% as a function of increasing TGF-beta 1 concentration. Inhibition of the rate of angiogenesis in the arterial tree by TGF-beta 1 relative to controls was measured in digital images by three well-correlated, computerized methods. The first computerized method, direct measurement by the computer code VESGEN of vascular morphological parameters according to branching generations G(1) through G(greater than or equal to 5), revealed that TGF-beta 1 selectively inhibited the increase in the number density of small vessels, N-v greater than or equal to 5 (382 +/- 85 cm(-2) for specimens treated with 1 mu g TGF-beta 1/CAM for 24 h, compared to 583 +/- 99 cm(-2) for controls), but did not significantly affect other parameters such as average vessel length or vessel diameter. The second and third methods, the fractal dimension (D-f) and grid intersection (rho(v)), are statistical descriptors of spatial pattern and density. According to D-f and rho(v), arterial density increased in control specimens from 1.382 +/- 0.007 and 662 +/- 52 cm(-2) at E7 (0 h) to 1.439 +/- 0.013 and 884 +/- 55 cm(-2) at E8 (24 h), compared to 1.379 +/- 0.039 and 650 +/- 111 cm(-2) for specimens treated with 1 mu g TGF-beta 1/CAM for 24 h. TGF-beta 1 therefore regulates vascular pattern and the rate of angiogenesis in a unique "fingerprint" manner, as do other major angiogenic regulators that include VEGF, FGF-2 (bFGF), and angiostatin. TGF-beta 1 did not stimulate angiogenesis significantly at low cytokine concentrations, which suggests that this quail CAM model of angiogenesis is not associated with an inflammatory response. (C) 2000 Academic Press. C1 Univ Washington, Sch Med, Dept Biol Struct, Seattle, WA 98195 USA. 3Com Corp, Bellevue, WA 98006 USA. NASA, ICOMP, Glenn Res Ctr, Cleveland, OH 44135 USA. Hope Heart Inst, Dept Vasc Biol, Seattle, WA 98122 USA. RP Parsons-Wingerter, P (reprint author), Univ Washington, Sch Med, Dept Biol Struct, Seattle, WA 98195 USA. FU NEI NIH HHS [EY04542]; NIGMS NIH HHS [GM40711] NR 24 TC 22 Z9 22 U1 1 U2 5 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0026-2862 J9 MICROVASC RES JI Microvasc. Res. PD MAR PY 2000 VL 59 IS 2 BP 221 EP 232 DI 10.1006/mvre.1999.2213 PG 12 WC Peripheral Vascular Disease SC Cardiovascular System & Cardiology GA 292JA UT WOS:000085789700004 PM 10684728 ER PT J AU Hou, AY Ledvina, DV da Silva, AM Zhang, SQ Joiner, J Atlas, RM Huffman, GJ Kummerow, CD AF Hou, AY Ledvina, DV da Silva, AM Zhang, SQ Joiner, J Atlas, RM Huffman, GJ Kummerow, CD TI Assimilation of SSM/I-derived surface rainfall and total precipitable water for improving the GEOS analysis for climate studies SO MONTHLY WEATHER REVIEW LA English DT Article ID VARIATIONAL DATA ASSIMILATION; NUMERICAL WEATHER PREDICTION; SPECIAL SENSOR MICROWAVE/IMAGER; PHYSICAL INITIALIZATION; DIABATIC INITIALIZATION; TROPICAL RAINFALL; ARAKAWA-SCHUBERT; SATELLITE DATA; MODEL; FORECASTS AB This article describes a variational framework for assimilating the SSM/I-derived surface rain rate and total precipitable water (TPW) and examines their impact on the analysis produced by the Goddard Earth Observing System (GEOS) Data Assimilation System (DAS). The SSM/I observations consist of tropical rain rates retrieved using the Goddard Profiling Algorithm and tropical TPW estimates produced by Wentz. In a series of assimilation experiments for December 1992, results show that the SSM/I-derived rain rate, despite current uncertainty in its intensify, is better than the model-generated precipitation. Assimilating rainfall data improves cloud distributions and the cloudy-sky radiation, while assimilating TPW data reduces a moisture bias in the lower troposphere to improve the clear-sky radiation. Together, the two data types reduce the monthly mean spatial bias by 46% and the error standard deviation by 26% in the outgoing longwave radiation (OLR) averaged over the Tropics, as compared with the NOAA OLR observation product. The improved cloud distribution, in turn, improves the solar radiation at the surface. There is also evidence that the latent heating change associated with the improved precipitation improves the large-scale circulation in the Tropics. This is inferred from a comparison of the clear-sky brightness temperatures for TIROS Operational Vertical Sounder channel 12 computed from the GEOS analyses with the observed values, suggesting that rainfall assimilation reduces a prevailing moist bias in the upper-tropospheric humidity in the GEOS system through enhanced subsidence between the major convective centers. This work shows that assimilation of satellite-derived precipitation and TPW can reduce state-dependent systematic errors in the OLR, clouds, surface radiation, and the large-scale circulation in the assimilated dataset. The improved analysis also leads to better short-range forecasts, but the impact is modest compared with improvements in the time-averaged signals in the analysis. The study shows that, in the presence of biases and other errors of the forecast model, it is possible to improve the time-averaged "climate content" in the data without comparable improvements in forecast. The full impact of these data types on the analysis cannot be measured solely in terms of forecast skills. C1 NASA, Goddard Space Flight Ctr, Data Assimilat Off, Atmospheres Lab, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Mesoscale Atmospher Proc Branch, Atmospheres Lab, Greenbelt, MD 20771 USA. Gen Sci Corp, Beltsville, MD USA. Sci Syst & Applicat Inc, Lanham, MD USA. RP Hou, AY (reprint author), NASA, Goddard Space Flight Ctr, Data Assimilat Off, Atmospheres Lab, Code 910-3, Greenbelt, MD 20771 USA. RI Atlas, Robert/A-5963-2011; da Silva, Arlindo/D-6301-2012; Joiner, Joanna/D-6264-2012; Hou, Arthur/D-8578-2012; Huffman, George/F-4494-2014 OI Atlas, Robert/0000-0002-0706-3560; da Silva, Arlindo/0000-0002-3381-4030; Huffman, George/0000-0003-3858-8308 NR 60 TC 50 Z9 50 U1 1 U2 1 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0027-0644 J9 MON WEATHER REV JI Mon. Weather Rev. PD MAR PY 2000 VL 128 IS 3 BP 509 EP 537 DI 10.1175/1520-0493(2000)128<0509:AOSIDS>2.0.CO;2 PG 29 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 307AZ UT WOS:000086632400001 ER PT J AU Li, ZJ Navon, IM Zhu, YQ AF Li, ZJ Navon, IM Zhu, YQ TI Performance of 4D-Var with different strategies for the use of adjoint physics with the FSU global spectral model SO MONTHLY WEATHER REVIEW LA English DT Article ID VARIATIONAL DATA ASSIMILATION; NUMERICAL WEATHER PREDICTION; PRECIPITATION DATA; INCREMENTAL APPROACH; NEWTON ALGORITHMS; TROPICS; OPTIMIZATION; ATMOSPHERE; STORAGE; SYSTEM AB A set of four-dimensional variational data assimilation ( 4D-Var) experiments were conducted using both a standard method and an incremental method in an identical twin framework. The full physics adjoint model of the Florida State University global spectral model (FSUGSM) was used in the standard 4D-Var, while the adjoint of only a few selected physical parameterizations was used in the incremental method. The impact of physical processes on 4D-Var was examined in detail by comparing the results of these experiments. The inclusion of full physics turned out to be significantly beneficial in terms of assimilation error to the lower troposphere during the entire minimization process. The beneficial impact was found to be primarily related to boundary layer physics. The precipitation physics in the adjoint model also tended to have a beneficial impact after an intermediate number (50) of minimization iterations. Experiment results confirmed that the forecast From assimilation analyses with the full physics adjoint model displays a shorter precipitation spinup period. The beneficial impact on precipitation spinup did not result solely from the inclusion of the precipitation physics in the adjoint model, but rather from the combined impact of several physical processes, The inclusion of full physics in the adjoint model exhibited a detrimental impact on the rate of convergence at an early stage of the minimization process, but did not affect the final convergence. A truncated Newton-like incremental approach was introduced for examining the possibility of circumventing the detrimental aspects using the full physics in the adjoint model in 4D-Var but taking into account its positive aspects. This algorithm was based on the idea of the truncated Newton minimization method and the sequential cost Function incremental method introduced by Courtier et al., consisting of an inner loop and an outer loop. The inner loop comprised the incremental method, while the outer loop consisted of the standard 4D-Var method using the full physics adjoint. The limited-memory quasi-Newton minimization method (L-BFGS) was used for both inner and outer loops, while information on the Hessian of the cost function was jointly updated at every iteration in both loops, In an experiment with a two-cycle truncated Newton-like incremental approach, the assimilation analyses turned out to be better than those obtained from either the standard 4D-Var ol the incremental 4D-Var in all aspects examined. The CPU time required by this two-cycle approach was larger by 35% compared with that required by the incremental 4D-Var without almost any physics in the adjoint model, while the CPU time required by the standard 4D-Var with the full physics adjoint model was more than twice that required by the incremental 4D-Var. Finally, several hypotheses concerning the impact of using standard 4D-Var full physics on minimization convergence were advanced and discussed. C1 Florida State Univ, Dept Math, Tallahassee, FL 32306 USA. Florida State Univ, Supercomp Computat Res Inst, Tallahassee, FL 32306 USA. NASA, Gen Sci Corp, Data Assimilat Off, GSFC, Beltsville, MD USA. RP Navon, IM (reprint author), Florida State Univ, Dept Math, Tallahassee, FL 32306 USA. RI Navon, Ionel/A-5173-2008 OI Navon, Ionel/0000-0001-7830-7094 NR 50 TC 18 Z9 19 U1 0 U2 0 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0027-0644 J9 MON WEATHER REV JI Mon. Weather Rev. PD MAR PY 2000 VL 128 IS 3 BP 668 EP 688 DI 10.1175/1520-0493(2000)128<0668:POVWDS>2.0.CO;2 PG 21 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 307AZ UT WOS:000086632400007 ER PT J AU Menemenlis, D Chechelnitsky, M AF Menemenlis, D Chechelnitsky, M TI Error estimates for an ocean general circulation model from altimeter and acoustic tomography data SO MONTHLY WEATHER REVIEW LA English DT Article ID TROPICAL PACIFIC-OCEAN; ATMOSPHERIC DATA ASSIMILATION; KALMAN FILTER; SEA-LEVEL; COVARIANCE; RESOLUTION; ALGORITHM; SPACE AB An offline approach is proposed for the estimation of model and data error covariance matrices whereby covariance matrices of model data residuals are "matched" to their theoretical expectations using familiar least-squares methods. This covariance matching approach is both a powerful diagnostic tool for addressing theoretical questions and an efficient estimator for real data assimilation studies. Provided that model and data errors are independent, that error propagation is approximately linear, and that an observability condition is met, it is in theory possible to fully resolve covariance matrices for both model and data errors. In practice, however, due to large uncertainties in sample estimates of covariance matrices, the number of statistically significant parameters that can be estimated is two to three orders of magnitude smaller than the total number of independent observations. The covariance matching approach is applied in the North Pacific (5 degrees-60 degrees N, 132 degrees-252 degrees E) to TOPEX/Poseidon sea level anomaly data, acoustic tomography data from the Acoustic Thermometry of Ocean Climate Project, and a GCM. A reduced state linear model that describes large-scale internal (baroclinic) error dynamics is constructed. Twin experiments suggest that altimetric data are ill suited to estimating the statistics of the vertical GCM error structure, but that such estimates can in theory be obtained using acoustic data. The particular GCM integration exhibits a warming trend relative to TOPEX/Poseidon data of order 1 cm yr(-1) corresponding to a peak warming of up to 0.2 degrees C yr(-1) in the acoustic data at depths ranging from 50 to 200 m. At the annual cycle, GCM and TOPEX/Poseidon sea level anomaly are in phase, but GCM amplitude is 2 cm smaller, with the error confined above 200-m depth. After removal of trends and annual cycles, the low-frequency/wavenumber (periods >2 months, wavelengths >16 degrees) TOPEX/Poseidon sea level anomaly is order 6 cm(2). The GCM explains about 40% of that variance. By covariance matching, it is estimated that 60% of the GCM-TOPEX/Poseidon residual variance is consistent with the reduced state linear model. C1 MIT, Dept Earth Atmospher & Planetary Sci, Cambridge, MA USA. MIT Woods Hole Oceanog Inst Joint Program, Cambridge, MA USA. RP Menemenlis, D (reprint author), CALTECH, Jet Prop Lab, Mail Stop 300-323,4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM dimitri@pacific.jpl.nasa.gov NR 37 TC 13 Z9 13 U1 0 U2 0 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0027-0644 J9 MON WEATHER REV JI Mon. Weather Rev. PD MAR PY 2000 VL 128 IS 3 BP 763 EP 778 DI 10.1175/1520-0493(2000)128<0763:EEFAOG>2.0.CO;2 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 307AZ UT WOS:000086632400012 ER EF