FN Thomson Reuters Web of Science™ VR 1.0 PT J AU Winther, JG Hall, DK AF Winther, JG Hall, DK TI Satellite-derived snow coverage related to hydropower production in Norway: present and future SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article ID THEMATIC MAPPER; REFLECTANCE; ALBEDO; GLACIER; INSITU; MODEL AB Hydropower derived from snow-melt runoff is a major source of electricity in Norway. Therefore, amount of snow-melt runoff is key to the prediction of available water. The prediction of water quantity may be accomplished through the use of hydrological models. These models, which may be run for individual basins, use satellite-derived snow-covered area in combination with snow-cover depletion curves. While it is known that snow albedo information would increase the accuracy of the models, large-scale albedo measurements have not yet been obtained from satellites on a regular basis. This paper presents Landsat-5 Thematic Mapper (TM) reflectances recorded in May 1989 from a mountainous catchment at Kvikne, Norway. Satellite-derived albedo values are analysed, and compared with simultaneously measured in situ albedo. The satellite-derived shortwave snow albedo is comparable with bare ground albedo and values as low as 0.19 were found in areas where the snow was highly metamorphosed and heavily blackened by organic material. To map snow-covered areas, the contrast between snow and snow-free areas can be improved by using a normalized TM Band 2-5 difference image. While TM Band 2 alone shows varying degrees of snow surface contamination within the study area, the normalized difference snow index (NDSI) is not affected by impurities. This paper also discusses the use of NASA's EOS (Earth Observing System) Moderate Resolution Imaging Spectroradiometer (MODIS) sensor, which is planned to be launched in the summer of 1999 for mapping of large-scale geophysical parameters including snow-cover. MODIS will enable snow cover and albedo to be mapped in Norway on a daily basis, and should enhance our ability to estimate snow coverage and thus manage hydropower production. C1 Norwegian Polar Inst, N-9296 Tromso, Norway. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Winther, JG (reprint author), Norwegian Polar Inst, N-9296 Tromso, Norway. RI Hall, Dorothy/D-5562-2012 NR 26 TC 21 Z9 21 U1 2 U2 7 PU TAYLOR & FRANCIS LTD PI LONDON PA ONE GUNPOWDER SQUARE, LONDON EC4A 3DE, ENGLAND SN 0143-1161 J9 INT J REMOTE SENS JI Int. J. Remote Sens. PD OCT 15 PY 1999 VL 20 IS 15-16 BP 2991 EP 3008 DI 10.1080/014311699211570 PG 18 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA 239LC UT WOS:000082768800006 ER PT J AU Bingham, AW Rees, WG AF Bingham, AW Rees, WG TI Construction of a high-resolution DEM of an Arctic ice cap using shape-from-shading SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article ID RADAR INTERFEROMETRY; SHEET; TOPOGRAPHY; NORDAUSTLANDET; GREENLAND; SVALBARD; MODEL AB Digital elevation models (DEMs) of ice sheets and ice caps are usually constructed from elevation data acquired from airborne or satellite-borne altimetric systems. Consequently, the DEMs have a spatial resolution of about 1 km which limits their use for most glaciological and remote sensing studies. In this paper we investigated the possibility of using a shape-from-shading technique, applied to a Landsat MSS image, to create a high spatial resolution DEM of Austfonna, an ice cap in Svalbard. A high correlation (coefficient of determination = 0.85) was observed between Landsat pixel brightness values, acquired during winter, and the surface slope component parallel to the solar azimuth. This relationship was used to create a DEM by calculating surface elevation profiles across the ice cap, using low spatial resolution radio echo sounding data as tie points. The resulting DEM had an estimated rms error of about 14 m, with the error occurring mostly at low spatial frequencies. Shape-from-shading produces less accurate DEMs than interferometric SAR (InSAR) techniques. Nevertheless, in scenarios for which InSAR cannot be used to construct a DEM, shape-from-shading provides an acceptable alternative. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Cambridge, Scott Polar Res Inst, Cambridge CB2 1ER, England. RP Bingham, AW (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 24 TC 4 Z9 4 U1 2 U2 7 PU TAYLOR & FRANCIS LTD PI LONDON PA ONE GUNPOWDER SQUARE, LONDON EC4A 3DE, ENGLAND SN 0143-1161 J9 INT J REMOTE SENS JI Int. J. Remote Sens. PD OCT 15 PY 1999 VL 20 IS 15-16 BP 3231 EP 3242 DI 10.1080/014311699211723 PG 12 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA 239LC UT WOS:000082768800021 ER PT J AU Manderson, JP Phelan, BA Bejda, AJ Stehlik, LL Stoner, AW AF Manderson, JP Phelan, BA Bejda, AJ Stehlik, LL Stoner, AW TI Predation by striped searobin (Prionotus evolans, Triglidae) on young-of-the-year winter flounder (Pseudopleuronectes americanus, Walbaum): examining prey size selection and prey choice using field observations and laboratory experiments SO JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY LA English DT Article DE predator-prey; prey choice; size selection; trigilid; flatfish predator ID NEW-YORK BIGHT; PLEURONECTES-PLATESSA; SCOPHTHALMUS-MAXIMUS; SEDIMENT PREFERENCE; 0-GROUP FLATFISHES; JUVENILE PLAICE; SHRIMP; RECRUITMENT; SUBSTRATUM; SETTLEMENT AB Laboratory experiments and field observations in shallow water habitats in the Navesink River/Sandy Hook Bay estuarine system (NSHES), New Jersey, USA, were used to examine the predator-prey relationship between the striped searobin (Prionotus evolans: Linnaeus) and young-of-the-year (YOY) winter flounder (Pseudopleuronectes americanus: Walbaum). Striped sea robins (121-367 mm total length [TL]) were present in Sandy Hook Bay but absent from the Navesink River in biweekly gillnet surveys conducted from May through October, 1998. However, juvenile winter flounder were present throughout the estuary during periodic beam trawl surveys. Although mysids and sand shrimp (Crangon septemspinosa, Say: 10-49 mm TL) were the numerically predominant prey of searobins, winter flounder (15-57 mm TL) accounted for an average of 17% (+/-3) of prey by weight and were found in the diets of 69% of predators collected in June. In the laboratory, searobins (212-319 mm TL) presented with a range of winter flounder sizes (30-114 mm TL) selected prey < 70 mm TL (24% of predator TL) and maximum prey size appeared to be constrained by predator esophageal width. When winter flounder (40-60 mm TL) and sand shrimp (30-50 mm TL) were offered at different densities to searobins, the predators fed opportunistically, consuming the prey in proportions similar to initial relative abundances. Laboratory observations showed that searobins rely on modified pectoral finrays to detect, flush, and occasionally excavate buried winter flounder. Our field and laboratory observations indicate that striped searobins consume large numbers of winter flounder in vulnerable size classes (15-70 mm TL) in habitats where the two species co-occur. Patterns in the distribution of the two species in the NSHES suggest that predation probably varies spatially in the estuary, with flounder more at risk in nurseries in Sandy Hook Bay than in the Navesink River, which may serve as a spatial refuge for winter flounder from searobin predation during some years. (C) 1999 Elsevier Science B.V. All rights reserved. C1 James J Howard Marine Sci Lab, Behav Ecol Branch NOAA, Natl Marine Fisheries Serv, Highlands, NJ 07732 USA. RP Manderson, JP (reprint author), James J Howard Marine Sci Lab, Behav Ecol Branch NOAA, Natl Marine Fisheries Serv, Highlands, NJ 07732 USA. EM john.manderson@noaa.gov NR 51 TC 37 Z9 37 U1 1 U2 4 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 OCT 15 PY 1999 VL 242 IS 2 BP 211 EP 231 DI 10.1016/S0022-0981(99)00105-7 PG 21 WC Ecology; Marine & Freshwater Biology SC Environmental Sciences & Ecology; Marine & Freshwater Biology GA 243MP UT WOS:000083002100004 ER PT J AU Wang, LP Koblinsky, C Howden, S Huang, N AF Wang, LP Koblinsky, C Howden, S Huang, N TI Interannual variability in the South China Sea from expendable bathythermograph data SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID WESTERN BOUNDARY; PACIFIC-OCEAN; NORTH PACIFIC; TEMPERATURE; KUROSHIO; WATER AB Using 29 years of expendable bathythermograph data, we studied the interannual temperature variability in the upper 300 m of the South China Sea (SCS). It is found that the temperature field has significant quasi-penta-annual variability throughout the 29 years. The interannual variability has a large decadal modulation. Although outside the SCS, in the Kuroshio, significant interannual variability extends to a much deeper layer beyond the 300 m depth, inside the SCS, especially in the central SCS, strong interannual variability is located near the 100 m depth and is capped by a surface layer of much weaker interannual variability. Similarities and differences in the temporal characteristics between the interannual variability inside and outside the SCS suggest that the interannual variability inside the SCS is primarily generated locally inside the SCS. In addition to the strong interannual variability, there exist strong decadal variability and a linear trend, which are also stronger in the subsurface than near the surface. It is found that below 100 m, the SCS has been cooling (linear trend) at a rate of similar to 0.4 degrees C per decade, decreasing from the eastern to the western basin. C1 Univ Maryland, Earth Syst Sci Interdisciplinary Ctr, College Pk, MD 20742 USA. NASA, Goddard Space Flight Ctr, Lab Hydropher Proc, Oceans & Ice Branch, Greenbelt, MD 20771 USA. RP Wang, LP (reprint author), Univ Maryland, Earth Syst Sci Interdisciplinary Ctr, College Pk, MD 20742 USA. NR 36 TC 7 Z9 7 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-OCEANS JI J. Geophys. Res.-Oceans PD OCT 15 PY 1999 VL 104 IS C10 BP 23509 EP 23523 DI 10.1029/1999JC900199 PG 15 WC Oceanography SC Oceanography GA 246KT UT WOS:000083163500016 ER PT J AU Huterer, D Turner, MS AF Huterer, D Turner, MS TI Prospects for probing the dark energy via supernova distance measurements SO PHYSICAL REVIEW D LA English DT Article ID STRING-DOMINATED UNIVERSE; COSMOLOGICAL CONSTANT; MODELS; COMPONENT AB Distance measurements to type Ia supernovae (SNe Ia) indicate that the Universe is accelerating and that two-thirds of the critical energy density exists in a dark-energy component with negative pressure. Distance measurements to SNe Ia can be used to distinguish between different possibilities for the dark energy, and if it is an evolving scalar field, to reconstruct the scalar-field potential. We derive the reconstruction equations and address the feasibility of this approach by Monte Carlo simulation. [S0556-2821(99)50118-5]. C1 Univ Chicago, Enrico Fermi Inst, Dept Phys, Chicago, IL 60637 USA. Univ Chicago, Enrico Fermi Inst, Dept Astron & Astrophys, Chicago, IL 60637 USA. Fermi Natl Accelerator Lab, NASA, Fermilab Astrophys Ctr, Batavia, IL 60510 USA. RP Huterer, D (reprint author), Univ Chicago, Enrico Fermi Inst, Dept Phys, Chicago, IL 60637 USA. NR 28 TC 225 Z9 225 U1 0 U2 2 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0556-2821 J9 PHYS REV D JI Phys. Rev. D PD OCT 15 PY 1999 VL 60 IS 8 AR 081301 DI 10.1103/PhysRevD.60.081301 PG 5 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA 247BN UT WOS:000083200900001 ER PT J AU Masso, E Toldra, R AF Masso, E Toldra, R TI Photon spectrum produced by the late decay of a cosmic neutrino background SO PHYSICAL REVIEW D LA English DT Article ID DARK-MATTER PROBLEM; MASSIVE OBJECTS; SN 1987A; LIMITS; NUCLEOSYNTHESIS; CONVERSION; PARTICLE; UNIVERSE; BOUNDS AB We obtain the photon spect;um induced by a cosmic background of unstable neutrinos. We study the spectrum in a variety of cosmological scenarios and also we allow for the neutrinos having a momentum distribution (only a critical matter dominated universe and neutrinos at rest have been considered until now). Our results can be helpful when extracting bounds on neutrino electric and magnetic moments from cosmic photon background observations: [S0556-2821(99)00118-6]. C1 Univ Autonoma Barcelona, Grp Fis Teor, Bellaterra 08193, Catalonia, Spain. Univ Autonoma Barcelona, Inst Fis Altes Energies, Bellaterra 08193, Catalonia, Spain. Fermi Natl Accelerator Lab, NASA, Fermilab Astrophys Grp, Batavia, IL 60510 USA. RP Masso, E (reprint author), Univ Autonoma Barcelona, Grp Fis Teor, Bellaterra 08193, Catalonia, Spain. NR 23 TC 15 Z9 15 U1 0 U2 0 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0556-2821 J9 PHYS REV D JI Phys. Rev. D PD OCT 15 PY 1999 VL 60 IS 8 AR 083503 DI 10.1103/PhysRevD.60.083503 PG 10 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA 247BN UT WOS:000083200900010 ER PT J AU Cabell, RH Fuller, CR AF Cabell, RH Fuller, CR TI A principal component algorithm for feedforward active noise and vibration control SO JOURNAL OF SOUND AND VIBRATION LA English DT Article ID CONTROL-SYSTEM; CYLINDRICAL-SHELL; LMS ALGORITHM; SOUND; PERFORMANCE; REGRESSION; FILTERS AB A principal component least-mean-square (PC-LMS) adaptive algorithm is described that is applicable to large control systems used for feedforward control of single-frequency disturbances. The algorithm is a transform domain version of the multiple-error LMS algorithm. A transformation given by the principal components (PCs) of the transfer function matrix between the sensors and actuators in a control system at a single frequency is used to rotate the control-filter coefficient axes to a more convenient co-ordinate system, where: (1) independent convergence factors can be used on each co-ordinate to accelerate convergence; (2) insignificant control co-ordinates can be eliminated from the controller; and (3) co-ordinates that require excessive control effort can be eliminated. The PC-LMS algorithm has lower computational requirements than the multiple-error LMS algorithm. The two algorithms were compared in an experiment involving active structural acoustic control of a tone inside a closed cylindrical shell using 12 control actuators and 48 error sensors. Both algorithms reduced the primary response by more than 20 dB, averaged across the 48 microphones. The control system was slightly ill-conditioned at the test frequency, but the PC-LMS algorithm demonstrated stable convergence to the optimal control solution. (C) 1999 Academic Press. C1 NASA, Langley Res Ctr, Struct Acoust Branch, Hampton, VA 23681 USA. Virginia Polytech Inst & State Univ, Vibrat & Acoust Labs, Dept Mech Engn, Blacksburg, VA 24061 USA. RP Cabell, RH (reprint author), NASA, Langley Res Ctr, Struct Acoust Branch, Mail Stop 463, Hampton, VA 23681 USA. NR 44 TC 22 Z9 23 U1 0 U2 7 PU ACADEMIC PRESS LTD PI LONDON PA 24-28 OVAL RD, LONDON NW1 7DX, ENGLAND SN 0022-460X J9 J SOUND VIB JI J. Sound Vibr. PD OCT 14 PY 1999 VL 227 IS 1 BP 159 EP 181 DI 10.1006/jsvi.1999.2338 PG 23 WC Acoustics; Engineering, Mechanical; Mechanics SC Acoustics; Engineering; Mechanics GA 245BR UT WOS:000083086800007 ER PT J AU Mather, JC AF Mather, JC TI Astronomy - Super photon counters SO NATURE LA English DT Editorial Material ID SINGLE C1 NASA, Goddard Space Flight Ctr, Infrared Astrophys Branch, Greenbelt, MD 20771 USA. RP Mather, JC (reprint author), NASA, Goddard Space Flight Ctr, Infrared Astrophys Branch, Greenbelt, MD 20771 USA. NR 8 TC 18 Z9 18 U1 0 U2 0 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON N1 9XW, ENGLAND SN 0028-0836 J9 NATURE JI Nature PD OCT 14 PY 1999 VL 401 IS 6754 BP 654 EP 655 DI 10.1038/44301 PG 2 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 247EJ UT WOS:000083207400037 ER PT J AU Keenan, FP Espey, BR Mathioudakis, M Aggarwal, KM Crawford, FL Feibelman, WA McKenna, FC AF Keenan, FP Espey, BR Mathioudakis, M Aggarwal, KM Crawford, FL Feibelman, WA McKenna, FC TI [Al II] in the ultraviolet spectrum of the symbiotic star RR Telescopii SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE atomic data; binaries : symbiotic; stars : individual : RR Tel; ultraviolet : stars ID EXCITATION RATE COEFFICIENTS; EMISSION-LINE STRENGTHS; OSCILLATOR-STRENGTHS; TRANSITIONS; PROGRAM; RATIOS AB An inspection of a GHRS/HST spectrum of the symbiotic star RR Telescopii reveals the presence of the [Al Pi] 3s(2) S-1 - 3s3p P-3(2) line at a vacuum wavelength of 2661.06 +/- 0.08 Angstrom, 8.89 +/- 0.08 Angstrom away from the Al II] 3s(2) S-1 - 3s3p P-3(1) intercombination transition at 2669.95 Angstrom, in good agreement with the theoretical prediction of Delta lambda = 8.80 Angstrom. We also find that the Al II] line profile is asymmetric, showing a strong low-density component with a weak high-density wing, redshifted by 30 km s(-1), in agreement with the findings of Schild & Schmid, which were based on optical observations. Our measurement of the emission-line ratio R = I(2661.06 Angstrom)/I(2669.95 Angstrom) = 0.027 +/- 0.003 implies log N-e = 5.8 +/- 0.2, in good agreement with the densities found from other ions, such as Si III. These results provide strong evidence that we have detected the [Al II] line, the first time (to our knowledge) that this feature has been reliably identified in an astrophysical or laboratory spectrum. C1 Queens Univ Belfast, Dept Pure & Appl Phys, Belfast BT7 1NN, Antrim, North Ireland. Space Telescope Sci Inst, Baltimore, MD 21218 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. Univ Delhi, Dept Phys & Astrophys, Delhi 110007, India. RP Keenan, FP (reprint author), Queens Univ Belfast, Dept Pure & Appl Phys, Belfast BT7 1NN, Antrim, North Ireland. OI Espey, Brian/0000-0002-2457-1380 NR 17 TC 3 Z9 3 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 OCT 11 PY 1999 VL 309 IS 1 BP 195 EP 198 DI 10.1046/j.1365-8711.1999.02823.x PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 247WJ UT WOS:000083243700019 ER PT J AU Srivastava, D Menon, M Cho, KJ AF Srivastava, D Menon, M Cho, KJ TI Nanoplasticity of single-wall carbon nanotubes under uniaxial compression SO PHYSICAL REVIEW LETTERS LA English DT Article ID FLEXIBILITY; DIAMETER; GROWTH AB Nanoplasticity of thin single-wall carbon nanotubes under uniaxial compression is investigated using generalized tight-binding molecular dynamics, and nb initio electronic structure methods. A novel mechanism of nanoplasticity of carbon nanotubes under uniaxial compression is observed in which bonding geometry collapses from a graphitic (sp(2)) to a localized diamondlike (sp(3)) reconstruction. The computed critical stress (approximate to 153 GPa) and the shape of the resulting plastic deformation is in good agreement with recent experimental observations. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Kentucky, Dept Phys & Astron, Lexington, KY 40506 USA. Univ Kentucky, Ctr Computat Sci, Lexington, KY 40506 USA. Stanford Univ, Dept Mech Engn, Stanford, CA 94305 USA. RP Srivastava, D (reprint author), NASA, Ames Res Ctr, MS T27A 1, Moffett Field, CA 94035 USA. NR 24 TC 193 Z9 199 U1 2 U2 18 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0031-9007 J9 PHYS REV LETT JI Phys. Rev. Lett. PD OCT 11 PY 1999 VL 83 IS 15 BP 2973 EP 2976 DI 10.1103/PhysRevLett.83.2973 PG 4 WC Physics, Multidisciplinary SC Physics GA 244FP UT WOS:000083041400027 ER PT J AU Briggs, MS Band, DL Kippen, RM Preece, RD Kouveliotou, C van Paradijs, J Share, GH Murphy, RJ Matz, SM Connors, A Winkler, C McConnell, ML Ryan, JM Williams, OR Young, CA Dingus, B Catelli, JR Wijers, RAMJ AF Briggs, MS Band, DL Kippen, RM Preece, RD Kouveliotou, C van Paradijs, J Share, GH Murphy, RJ Matz, SM Connors, A Winkler, C McConnell, ML Ryan, JM Williams, OR Young, CA Dingus, B Catelli, JR Wijers, RAMJ TI Observations of GRB 990123 by the Compton Gamma Ray Observatory SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays : bursts; X-rays : bursts ID BATSE OBSERVATIONS; BURST SPECTRA; OPTICAL COUNTERPART; AFTERGLOW; EMISSION; CONSTRAINTS; EVOLUTION; REDSHIFT AB GRB 990123 was the first burst from which simultaneous optical, X-ray, and gamma-ray emission was detected; its afterglow has been followed by an extensive set of radio, optical, and X-ray observations. We have studied the gamma-ray burst itself as observed by the Compton Gamma Ray Observatory detectors. We find that gamma-ray fluxes are not correlated with the simultaneous optical observations and that the gamma-ray spectra cannot be extrapolated simply to the optical fluxes. The burst is well fitted by the standard four-parameter GRB function, with the exception that excess emission compared with this function is observed below similar to 15 keV during some time intervals. The burst is characterized by the typical hard-to-soft and hardness-intensity correlation spectral evolution patterns. The energy of the peak of the upsilon f(upsilon) spectrum, E-p, reaches an unusually high value during the first intensity spike, 1470 +/- 110 keV, and then falls to similar to 300 keV during the tail of the burst. The high-energy spectrum above similar to 1 MeV is consistent with a power law with a photon index of about -3. By fluence, GRB 990123 is brighter than all but 0.4% of the GRBs observed with BATSE, clearly placing it on the - 3/2 power-law portion of the intensity distribution. However, the redshift measured for the afterglow is inconsistent with the Euclidean interpretation of the - 3/2 power law. Using the redshift value of greater than or equal to 1.61 and assuming isotropic emission, the gamma-ray energy exceeds 10(54) ergs. C1 Univ Alabama, Huntsville, AL 35812 USA. Univ Calif San Diego, Ctr Astrophys & Space Sci 0424, La Jolla, CA 92093 USA. Univ Space Res Assoc, Huntsville, AL 35800 USA. Univ Amsterdam, Amsterdam, Netherlands. NRL, Washington, DC 20375 USA. Northwestern Univ, Evanston, IL 60208 USA. Wellesley Coll, Wellesley, MA USA. Estec, ESA, Dept Space Sci, Div Astrophys, Noordwijk, Netherlands. Univ New Hampshire, Durham, NH 03824 USA. Univ Utah, Salt Lake City, UT 84102 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. SUNY Stony Brook, Dept Phys & Astron, Stony Brook, NY 11794 USA. RP Briggs, MS (reprint author), Univ Alabama, Huntsville, AL 35812 USA. OI Preece, Robert/0000-0003-1626-7335; Dingus, Brenda/0000-0001-8451-7450 NR 60 TC 101 Z9 105 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 OCT 10 PY 1999 VL 524 IS 1 BP 82 EP 91 DI 10.1086/307808 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 242TK UT WOS:000082957600008 ER PT J AU Hurley, K Li, P Boer, M Cline, T Fishman, GJ Meegan, C Kouveliotou, C Greiner, J Laros, J Luginbuhl, C Vrba, F Murakami, T Pedersen, H van Paradijs, J AF Hurley, K Li, P Boer, M Cline, T Fishman, GJ Meegan, C Kouveliotou, C Greiner, J Laros, J Luginbuhl, C Vrba, F Murakami, T Pedersen, H van Paradijs, J TI A ROSAT deep survey of four small gamma-ray burst error boxes SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : distances and redshifts; gamma rays : bursts; X-rays : galaxies ID ARRIVAL TIME LOCALIZATIONS; NEUTRON STAR MODELS; CONSTRAINTS; IDENTIFICATION; COUNTERPART; GALAXIES; REDSHIFT; ULYSSES; ORIGIN AB We have used the ROSAT High Resolution Imager to search for quiescent X-ray counterparts to four gamma-ray bursts (GRBs) which were localized to small (less than or equal to 10 arcmin(2)) error boxes with the Interplanetary Network. The observations took: place years after the bursts, and the effective exposure times for each target varied from similar to 16 to 23 ks. We have not found any X-ray sources inside any of the error boxes. The 0.1-2.4 keV 3 sigma flux upper limits range from around 5 x 10(-14) to 6 x 10(-13) ergs cm(-2) s(-1) depending on the burst and the assumed shape of the quiescent spectrum. Pie consider four types of X-ray-emitting galaxies (normal, active galactic nucleus, faint, and star forming) and use the flux upper limits to constrain their redshifts. We then use the GRB fluences to constrain the total energies of the bursts. C1 Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Ctr Etud Spatiale Rayonnements, F-31029 Toulouse, France. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. NASA, George C Marshall Space Flight Ctr, Univ Space Res Assoc, Huntsville, AL 35812 USA. MPE, D-85740 Garching, Germany. Univ Arizona, Dept Planetary Sci, Tucson, AZ 85721 USA. USN Observ, Flagstaff Stn, Flagstaff, AZ 86002 USA. Inst Space & Astronaut Sci, Kanagawa 229, Japan. Copenhagen Univ Observ, DK-1350 Copenhagen, Denmark. Univ Alabama, Huntsville, AL 35899 USA. RP Hurley, K (reprint author), Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. OI Boer, Michel/0000-0001-9157-4349 NR 38 TC 1 Z9 1 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 OCT 10 PY 1999 VL 524 IS 1 BP 92 EP 97 DI 10.1086/307812 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 242TK UT WOS:000082957600009 ER PT J AU Cox, DP Shelton, RL Maciejewski, W Smith, RK Plewa, T Pawl, A Rozyczka, M AF Cox, DP Shelton, RL Maciejewski, W Smith, RK Plewa, T Pawl, A Rozyczka, M TI Modeling W44 as a supernova remnant in a density gradient with a partially formed dense shell and thermal conduction in the hot interior. I. The analytical model SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM : general; ISM : individual (W44); radiative transfer; radio continuum : ISM; supernova remnants ID X-RAY; GALACTIC PLANE; MAGNETIC-FIELDS; PSR B1853+01; RADIO; EMISSION; PULSAR; SHOCK; W28; SUPPRESSION AB We show that many observations of W44, a supernova remnant in the Galactic plane at a distance of about 2500 pc, are remarkably consistent with the simplest realistic model. The model remnant is evolving in a smooth ambient medium of fairly high density, about 6 cm(-3) on average, with a substantial density gradient. At the observed time it has an age of about 20,000 yr, consistent with the age of the associated pulsar, and a radius of 11-13 pc. Over most of the outer surface, radiative cooling has become important in the postshock gas; on the denser end there has been sufficient compression of the cooled gas to develop a very thin dense half-shell of about 450 M., supported against further compression by nonthermal pressure. The half-shell has an expansion velocity of about 150 km s(-1) and is bounded on the outer surface by a radiative shock with that speed. The deep interior of the remnant has a substantial and fairly uniform pressure, as expected from even highly idealized adiabatic models; our model, however, is never adiabatic. Thermal conduction, while the remnant is young and hot, reduces the need for expansion cooling and prevents formation of the intensely vacuous cavity characteristic of adiabatic evolution. It radically alters the interior structure from what tone might expect from familiarity with the Sedov solution. At the time of observation, the temperature in the center is about 6 x 10(6) K, the density about 1 cm(-3). The temperature decreases gradually away from the center, while the density rises. Farther out, where cooling is becoming important, the pressure drops precipitously, and the temperature in the denser gas there is quite low. We provide several analytic tools for the assembly of models of this type. We review the early evolution and shell formation analyses and their generalizations to evolution in a density gradient. We also calculate the density and temperature that should be present in the hot interior of a remnant with thermal conduction. We supply the van der Laan mechanism in a particularly useful form for the calculation of radio continuum from radiative remnants. Finally, we estimate the optical emission that should be present from fluorescence of UV light, emitted by the forming shell and the radiative shock and absorbed in the cold shell and the ambient medium, and the associated 63 mu m [O I] emission. Both are in agreement with the intensity and spatial structures found in recent observations. Neither requires interaction with a dense molecular cloud for its generation. We calculate the gamma rays that should be emitted by cosmic-ray electrons and ions in the shell, interacting with the cold material, and find each capable of generating about 25% of the flux reported by EGRET for the vicinity. C1 Univ Wisconsin, Dept Phys, Madison, WI 53711 USA. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA. Univ Wisconsin, Dept Astron, Madison, WI 53711 USA. Max Planck Inst Astron, D-69117 Heidelberg, Germany. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. Max Planck Inst Astrophys, D-85740 Garching, Germany. Nicolaus Copernicus Astron Ctr, PL-00716 Warsaw, Poland. RP Univ Wisconsin, Dept Phys, 1150 Univ Ave, Madison, WI 53711 USA. EM cox@wisp.physics.wisc.edu; shelton@pha.jhu.edu; witold@mpia-hd.mpg.de; rsmith@kracko.harvard.edu; tomek@camk.edu.pl; mnr@camk.edu.pl RI Plewa, Tomasz/C-1470-2010 OI Plewa, Tomasz/0000-0002-1762-2565 NR 57 TC 99 Z9 101 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD OCT 10 PY 1999 VL 524 IS 1 BP 179 EP 191 DI 10.1086/307781 PN 1 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 242TK UT WOS:000082957600016 ER PT J AU Shelton, RL Cox, DP Maciejewski, W Smith, RK Plewa, T Pawl, A Rozyczka, M AF Shelton, RL Cox, DP Maciejewski, W Smith, RK Plewa, T Pawl, A Rozyczka, M TI Modeling W44 as a supernova remnant in a density gradient, with a partially formed dense shell and thermal conduction in the hot interior. II. The hydrodynamic models SO ASTROPHYSICAL JOURNAL LA English DT Article DE hydrodynamics; ISM : individual (W44); ISM : structure; methods : numerical; radio continuum : ISM; supernova remnants ID X-RAY-SPECTRUM; MOLECULAR CLOUDS; EVOLUTION; EMISSION; RADIO; PLASMAS; SHOCK; YOUNG; W28; GAS AB In a previous paper, we presented the analytical background for a new model for W44; in this paper, we report hydrocode experiments verifying many of the details. Our model remnant is evolving in a moderately dense (similar to 6 cm(-3)), ambient medium having a substantial density gradient. At the observed age (similar to 20,000 yr), the shock is radiative over much of the surface, with expansion speeds of only similar to 130-200 km s(-1) for the dense and rare ends, respectively. With these speeds, the remnant has a cool periphery and does not produce a limb-brightened X-ray image. It has thermal conduction within its hot interior, resulting in a nonnegligible density there, and its center is X-ray luminous. The combined effect creates a "center-filled" X-ray image. A thin, very dense cool shell has formed over the denser half of the remnant's surface, and its radio synchrotron emission derives from the highly compressed cosmic rays and swept up magnetic field, producing the usual "shell-type" image associated with radiative remnants. This combination of emission patterns results in the remnant being characterized as having a "thermal composite morphology." Our previous paper demonstrated that the intensities and qualitative distributions of the anticipated optical, IR line, X-ray, radio synchrotron, and gamma-ray emissions from the model are comparable to those actually observed in W44. In this paper we first use a two-dimensional hydrocode to follow the remnant evolution in a density gradient, verifying that the spatial and velocity structure of the H I shell are a good match to the observations, without the complications suggested by Koo & Heiles, and demonstrating that the remnant's asymmetry does not substantially affect the distribution of X-ray emitting material. We also calculate the distribution of radio-continuum emission expected from the compression of the ambient magnetic field and cosmic rays into the dense shell (the van der Laan mechanism) and examine the role of surface crinkling in generating filamentation. The results are in good agreement with observations, though the density of ambient cosmic-ray electrons required to match the observed flux is about 4 times greater than that estimated for the solar neighborhood. A one-dimensional hydrocode model was then used to explore the effects of nonequilibrium ionization on the X-ray spectrum and intensity. Our model is similar to but more comprehensive than the recent one by Harrus et at, and, because their model lacked thermal conduction, ours is more successful in providing the thermal X-rays from the hot interior, including a better match to the spectrum. Neither provides the sharpness of the central peaking of the X-ray distribution without further complications. (For that matter, however, the earlier models with evaporating clouds did no better.) The paper closes with a discussion of the OH masers associated with W44, proposing a specific site for their origin, in the dense trailing edge of the cooling region following the radiative shock. C1 Univ Wisconsin, Dept Phys, Madison, WI 53711 USA. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA. Max Planck Inst Astron, D-69117 Heidelberg, Germany. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. Max Planck Inst Astrophys, D-85740 Garching, Germany. Nicolaus Copernicus Astron Ctr, PL-00716 Warsaw, Poland. RP Shelton, RL (reprint author), Univ Wisconsin, Dept Phys, 1150 Univ Ave, Madison, WI 53711 USA. RI Plewa, Tomasz/C-1470-2010 OI Plewa, Tomasz/0000-0002-1762-2565 NR 53 TC 67 Z9 68 U1 0 U2 3 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 OCT 10 PY 1999 VL 524 IS 1 BP 192 EP 212 DI 10.1086/307799 PN 1 PG 21 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 242TK UT WOS:000082957600017 ER PT J AU Grundahl, F Catelan, M Landsman, WB Stetson, PB Andersen, MI AF Grundahl, F Catelan, M Landsman, WB Stetson, PB Andersen, MI TI Hot horizontal-branch stars: The ubiquitous nature of the "jump" in stromgren u, low gravities, and the role of radiative levitation of metals SO ASTROPHYSICAL JOURNAL LA English DT Review DE diffusion; stars : abundances; stars : atmospheres; stars : evolution; stars : horizontal-branch; stars : Population II ID RED GIANT STARS; GLOBULAR-CLUSTER GIANTS; PROTON CAPTURE CHAINS; ULTRAVIOLET IMAGING TELESCOPE; HYDROGEN-RICH SUBDWARFS; PALOMAR-GREEN SURVEY; POOR HALO FIELD; OXYGEN ABUNDANCES; ELLIPTIC GALAXIES; OMEGA-CENTAURI AB A "jump" in the blue horizontal-branch (HB) distribution in the (V, u-y) color-magnitude diagram has recently been detected in the globular cluster (GC) M13 (NGC 6205) by Grundahl and coworkers. Such an effect is morphologically best characterized as a discontinuity in the (u, u-y) locus, with stars in the range 11,500 K less than or similar to T-eff less than or similar to 20,000 K deviating systematically from (in the sense of appearing brighter and/or hotter than) canonical zero-age HE models. In this article, we present Stromgren u, y photometry of 14 GCs obtained with three different telescopes (ESO Danish, Nordic Optical Telescope, and the Hubble Space Telescope) and demonstrate that the jump in Stromgren u is present in every GC whose HE extends beyond T-eff greater than or similar to 11,500 K, irrespective of metallicity, mixing history on the red giant branch (RGB), or any known parameter characterizing our sample of GCs. We thus suggest that the tk jump is a ubiquitous feature, intrinsic to all WE stars hotter than T-eff similar or equal to 11,500 K. We draw a parallel between the ubiquitous nature of the u jump and the well-known problem of low measured gravities among blue HE stars in GCs and in the held. We note that the "gravity jump" occurs over the same temperature range as the u jump and also that it occurs in every metal-poor cluster for which gravities have been determine-again irrespective of metallicity, mixing history on the RGB, or any known parameter characterizing the surveyed GCs. Furthermore, we demonstrate that the u jump and the gravity jump are connected on a star-by-star basis. We thus suggest that the two most likely are different manifestations of one and the same physical phenomenon. We present an interpretative framework which may be capable of simultaneously accounting for both the u jump and the gravity jump. Reviewing spectroscopic data for several held blue HE stars, as well as two blue HE stars in NGC 6752, we find evidence that radiative levitation of elements heavier than carbon and nitrogen takes place at T-eff greater than or similar to 11,500 K, dramatically enhancing the abundances of such heavy elements in the atmospheres of blue HE stars in the "critical" temperature region. We argue that model atmospheres which take diffusion effects into account are badly needed and will likely lead to better overall agreement between canonical evolutionary theory and the observations for these stars. C1 Dominion Astrophys Observ, Herzberg Inst Astrophys, Natl Res Council, Victoria, BC V8X 4M6, Canada. Univ Victoria, Dept Phys & Astron, Victoria, BC V8W 3P7, Canada. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Raytheon ITSS, Greenbelt, MD 20771 USA. RP Dominion Astrophys Observ, Herzberg Inst Astrophys, Natl Res Council, 5071 W Saanich Rd, Victoria, BC V8X 4M6, Canada. EM Frank.Grundahl@hia.nrc.ca; catelan@stars.gsfc.nasa.gov; landsman@mpb.gsfc.nasa.gov; Peter.Stetson@hia.nrc.ca; andersen@not.iac.es NR 195 TC 151 Z9 151 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD OCT 10 PY 1999 VL 524 IS 1 BP 242 EP 261 DI 10.1086/307807 PN 1 PG 20 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 242TK UT WOS:000082957600021 ER PT J AU Canuto, VM AF Canuto, VM TI Turbulence in stars. III. Unified treatment of diffusion, convection, semiconvection, salt fingers, and differential rotation SO ASTROPHYSICAL JOURNAL LA English DT Article DE diffusion; stars : interiors; stars : rotation; turbulence ID REYNOLDS STRESS APPROACH; LARGE-EDDY SIMULATION; MIXING-LENGTH THEORY; STELLAR EVOLUTION; MASSIVE STARS; MERIDIONAL CIRCULATION; FLUX MEASUREMENTS; MAIN-SEQUENCE; MODELS; TRANSPORT AB The goal of this paper is to propose a unified treatment of diffusion, convection, semiconvection, salt fingers, overshooting, and rotational mixing. The detection of SN 1987A has served, among other things, to highlight the incompleteness of our understanding of such phenomena. Moreover, the variety of solutions proposed thus far to deal with each phenomenon separately, the uncertainty about the Ledoux-Schwarzschild criteria, the extent of overshooting, the effect of a CL gradient, the role of differential rotational mixing, etc., have added further urgency to the need of a unified, rather than a case-by-case, treatment of these processes. Since at the root of these difficulties lies the fact that we are dealing with a highly nonlinear, turbulent regime under the action of three gradients VT (temperature), VC (concentration), and VU (mean how), it is not surprising that such difficulties have arisen. In this paper we propose a unified treatment based on a turbulence model. A key difference with previous models is that we do not employ heuristic arguments to determine the five basic timescales that enter the problem and that entail a corresponding number of adjustable constants. These timescales are computed using renormalization group (RNG) techniques. The model comes in three flavors: (a) all the turbulent variables are treated nonlocally; (b) the turbulent kinetic energy K and its rate of dissipation epsilon are nonlocal, while the remaining turbulence variables (fluxes, Reynolds stresses, etc.) are treated locally; and (c) all turbulence variables are local. In the latter case, one must specify a mixing length. Some of the results are as follows: 1. The local model entails the solution of two algebraic equations, one being the flux conservation law. By solving them, we obtain the desired del - del(ad) versus del(mu) relations for semiconvection and salt fingers. We also derive other variables of interest, turbulent diffusivities, Peclet number, turbulent velocity, etc. 2. Schwarzschild and Ledoux criteria for instability are replaced by a new criterion that is physically equivalent to the requirement that turbulent mixing can exist only so long as the turbulent kinetic energy is positive. In addition to del, del(ad), and del(mu), the new criterion depends on the turbulent diffusivities for temperature and concentration that only a turbulence model can provide. 3. We derive the dynamic equations necessary to quantify the extent of overshooting OV in the presence of a mu barrier. 4. We prove that OV(del mu) < OV(mu = const.). Although this result is physically understandable, no direct proof has been available as yet. 5. We derive the turbulent diffusivity for a passive scalar, one that does not affect a preexisting turbulence, e.g., a sedimentation of He. We show that it differs from that of an active scalar, e.g., a mu held causing semiconvection and/or salt fingers. Such diffusivity is a function of the temperature gradient (stable/unstable) and shear (rotational mixing). 6. We show that the turbulent diffusivities of momentum (entering the angular momentum equation), of heat (entering the model of convection), and concentration (entering the diffusion equation and/or semiconvection and salt fingers) are different from. one another and should not be taken to be the same, as has been done thus far. 7. We consider the effect of shear. We solve the local turbulence problem analytically and derive the turbulent diffusivities for momentum, heat, and concentration in terms of the three gradients of the mean fields, VT, VC, and VU. Since shear is itself a source of turbulent mixing, one could expect it to enhance the diffusivities. However, its interaction with salt fingers and semiconvection is a subtle one, and the opposite may occur, a phenomenon for which we offer a physical interpretation and a validation with laboratory data. 8. A comparison is made with previous models. C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Columbia Univ, Dept Appl Phys, New York, NY 10027 USA. RP Canuto, VM (reprint author), NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. NR 89 TC 39 Z9 39 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 OCT 10 PY 1999 VL 524 IS 1 BP 311 EP 340 DI 10.1086/307783 PN 1 PG 30 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 242TK UT WOS:000082957600025 ER PT J AU Rastatter, L Schindler, K AF Rastatter, L Schindler, K TI Magnetized accreting stars: Studies of the inner accretion-disk edge by a magnetohydrodynamic approach. II. Ideal instabilities of the inner disk edge SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; instabilities; MHD; pulsars : general; stars : neutron ID LOCAL SHEAR INSTABILITY; NEUTRON STARS; INTERCHANGE INSTABILITY; RAPID BURSTER; MAGNETOSPHERE; EVOLUTION AB The interaction between an accretion disk and the magnetosphere of a rotating compact star is studied in two- and three-dimensional simulations to address the role of ideal (nonresistive) magnetohydrodynamic instabilities of the differentially rotating plasma. Two-dimensional simulations show the dominance of the gravitationally driven Rayleigh-Taylor instability over the shear-flow-driven Kelvin-Helmholtz instability. Three-dimensional simulations starting from the full equilibria obtained by a numerical magnetofrictional method rather than a radial cut at z = 0 generally show smaller growth rates and larger mode wavelengths due to magnetic line-tying. Thus growth rates of instability that cannot be calculated analytically because of the complicated magnetic field and plasma model can now be computed using numerical magnetohydrodynamic simulations. Variations of the accretion rate of a pulsar can be explained in terms of fast gravitational instability of the inner accretion disk edge and slow reloading of disk plasma. C1 NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. Ruhr Univ Bochum, D-44780 Bochum, Germany. RP Rastatter, L (reprint author), NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RI Rastaetter, Lutz/D-4715-2012 OI Rastaetter, Lutz/0000-0002-7343-4147 NR 20 TC 11 Z9 11 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 OCT 10 PY 1999 VL 524 IS 1 BP 361 EP 372 DI 10.1086/307801 PN 1 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 242TK UT WOS:000082957600027 ER PT J AU Strickman, MS Harding, AK de Jager, OC AF Strickman, MS Harding, AK de Jager, OC TI A Rossi X-Ray Timing Explorer observation of the vela pulsar: Filling in the X-ray gap SO ASTROPHYSICAL JOURNAL LA English DT Article DE pulsars : individual (Vela pulsar); X-rays : stars ID EMISSION AB We have detected pulsed emission from the Vela pulsar at 2-30 keV during a 93 ks observation with the Rossi X-Ray Timing Explorer (RXTE). The RXTE pulse profile shows two peaks, which are roughly in phase with the EGRET peaks, but does not show any significant interpeak emission. The phase of peak 2 is energy dependent, moving to higher phase with increasing energy in the RXTE band, in phase alignment with the second optical pulse in the lowest energy band (2-8 keV) and in phase alignment with the second EGRET pulse in the highest energy band (16-30 keV). The average pulse spectrum joins smoothly to the high-energy spectrum of OSSE, COMPTEL, and EGRET, although the spectrum of peak 1 is significantly harder than that of peak 2. A break or turnover in the spectrum around 50 keV, previously suggested by OSSE data, is now clearly defined. The RXTE spectrum falls several orders of magnitude below the ROSAT emission in the 0.1-2 keV band, suggesting a thermal origin for the ROSAT pulse. C1 USN, Res Lab, Washington, DC 20375 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Potchefstroom Univ Christian Higher Educ, ZA-2520 Potchefstroom, South Africa. RP USN, Res Lab, Washington, DC 20375 USA. EM strickman@osse.nrl.navy.mil RI Harding, Alice/D-3160-2012 NR 18 TC 28 Z9 28 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD OCT 10 PY 1999 VL 524 IS 1 BP 373 EP 378 DI 10.1086/307802 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 242TK UT WOS:000082957600028 ER PT J AU Evans, NR Carpenter, K Robinson, R Massa, D Wahlgren, GM Vinko, J Szabados, L AF Evans, NR Carpenter, K Robinson, R Massa, D Wahlgren, GM Vinko, J Szabados, L TI Toward an orbit for the high-luminosity cepheid T monocerotis SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries : spectroscopic; Cepheids; stars : chemically peculiar stars : fundamental parameters; stars : individual (T Monocerotis) ultraviolet : stars ID EFFECTIVE TEMPERATURES; BOLOMETRIC CORRECTIONS; CLASSICAL CEPHEIDS; NORTHERN CEPHEIDS; RADIAL-VELOCITIES; BRIGHT CEPHEIDS; METALLIC-LINE; NORMAL STARS; AP STARS; AM STARS AB We have obtained new velocities of the long-period Cepheid T Mon from the ground and velocities of its hot companion with the Hubble Space Telescope (HST) and the International Ultraviolet Explorer (IUE). Although observations do not cover a full orbit, both the maximum and minimum orbital velocities have now been obtained. We present a preliminary orbit and discuss the uncertainties in the orbital parameters. The velocities for the companion appear to be inconsistent with binary orbital motion, and it is likely that the companion is itself a binary in a short-period orbit. The HST spectrum of the companion shows that it is a chemically peculiar star, probably magnetic. Because it is coupled with the more massive Cepheid, it must be very close to the zero-age main sequence. The well-determined mass function from the preliminary orbit implies that the inclination of the long-period system is close to 90 degrees. C1 Smithsonian Astrophys Observ, Cambridge, MA 02138 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Comp Sci Corp, Astron Programs, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Raytheon STX Corp, Greenbelt, MD 20771 USA. Univ Lund, Dept Phys, S-22362 Lund, Sweden. JATE Univ, Dept Opt, H-6720 Szeged, Hungary. Konkoly Observ Budapest, H-1525 Budapest, Hungary. RP Evans, NR (reprint author), Smithsonian Astrophys Observ, 60 Garden St,Ms 4, Cambridge, MA 02138 USA. RI Carpenter, Kenneth/D-4740-2012; OI Vinko, Jozsef/0000-0001-8764-7832 NR 76 TC 13 Z9 13 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 OCT 10 PY 1999 VL 524 IS 1 BP 379 EP 393 DI 10.1086/307810 PN 1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 242TK UT WOS:000082957600029 ER PT J AU Giblin, TW van Paradijs, J Kouveliotou, C Connaughton, V Wijers, RAMJ Briggs, MS Preece, RD Fishman, GJ AF Giblin, TW van Paradijs, J Kouveliotou, C Connaughton, V Wijers, RAMJ Briggs, MS Preece, RD Fishman, GJ TI Evidence for an early high-energy afterglow observed with BATSE from GRB 980923 SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays : bursts ID GAMMA-RAY BURST; SPECTRA; SEARCH AB In this Letter, we present the first evidence in the BATSE data for a prompt high-energy (25-300 keV) afterglow component from a gamma-ray burst, GRB 980923. The event consists of rapid variability lasting similar to 40 a followed by a smooth power-law emission tail lasting similar to 400 s. An abrupt change in spectral shape is found when the tail becomes noticeable. Our analysis reveals that the spectral evolution in the tail of the burst mimics that of a cooling synchrotron spectrum, similar to the spectral evolution of the low-energy afterglows for gamma-ray bursts. This evidence for a separate emission component is consistent with the internal-external shock scenario in the relativistic fireball picture. In particular, it illustrates that the external shocks can be generated during the gamma-ray emission phase, as in the case of GRB 990123. 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, Ctr High Energy Astrophys, NL-1098 SJ Amsterdam, Netherlands. NASA, George C Marshall Space Flight Ctr, Natl Res Council, Huntsville, AL 35812 USA. SUNY Stony Brook, Dept Phys & Astron, Stony Brook, NY 11794 USA. RP Giblin, TW (reprint author), Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. NR 22 TC 54 Z9 54 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 OCT 10 PY 1999 VL 524 IS 1 BP L47 EP L50 DI 10.1086/312285 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 242TN UT WOS:000082957900012 ER PT J AU Woods, PM Kouveliotou, C van Paradijs, J Finger, MH Thompson, C Duncan, RC Hurley, K Strohmayer, T Swank, J Murakami, T AF Woods, PM Kouveliotou, C van Paradijs, J Finger, MH Thompson, C Duncan, RC Hurley, K Strohmayer, T Swank, J Murakami, T TI Variable spin-down in the soft gamma repeater SGR 1900+14 and correlations with burst activity SO ASTROPHYSICAL JOURNAL LA English DT Article DE pulsars : general; stars : individual (SGR 1900+14); X-rays : bursts ID X-RAY PULSAR; MAGNETIZED NEUTRON-STARS AB we have analyzed Rossi X-ray Timing Explorer Proportional Counter Array observations of the pulsed emission from SGR 1900+14 during 1996 September, 1998 June-October; and early 1999. Using these measurements and results reported elsewhere, we construct a period history of dais source for 2.5 yr. We find significant deviations from a steady spin-down trend during quiescence and the hurst active interval Burst and Transient Source Experiment observations of the burst emission are presented and correlations between the burst and Transient and spin-down Tate of SGR 1900+14 are discussed We find an 80 day interval during the summer of 1998 when the average spin-down rate is larger than the rate elsewhere by a factor similar to 2.3. This enhanced spin-down may be the result of a discontinuous spin-down event or "braking glitch" at the time of the giant flare on 1998 August 27. Furthermore, we find a large discrepancy between the pulsar period and average spin-down rate in X-rays as compared to radio observations for 1998 December and 1999 January. 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 N Carolina, Dept Phys & Astron, Chapel Hill, NC 27599 USA. Univ Texas, Dept Astron, Austin, TX 78712 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Inst Space & Astronaut Sci, Sagamihara, Kanagawa 229, Japan. RP Woods, PM (reprint author), Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. RI Swank, Jean/F-2693-2012 NR 28 TC 89 Z9 90 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 OCT 10 PY 1999 VL 524 IS 1 BP L55 EP L58 DI 10.1086/312297 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 242TN UT WOS:000082957900014 ER PT J AU Jacqmin, D AF Jacqmin, D TI Calculation of two-phase Navier-Stokes flows using phase-field modeling SO JOURNAL OF COMPUTATIONAL PHYSICS LA English DT Article ID 2-PHASE FLUID; DYNAMICS AB Phase-field models provide a way to model fluid interfaces as having finite thickness. This can allow the computation of interface movement and deformation on fixed grids. This paper applies phase-held modeling to the computation of two-phase incompressible Navier-Stokes flows. The Navier-Stokes equations are modified by the addition of the continuum forcing - C<(del)over bar>phi, where C is the composition variable and phi is C's chemical potential. The equation for interface advection is replaced by a continuum advective-diffusion equation, with diffusion driven by C's chemical potential gradients. The paper discusses how solutions to these equations approach those of the original sharp-interface Navier-Stokes equations as the interface thick ness epsilon-and the diffusivity both go to zero. The basic flow-physics of phase-field interfaces is discussed. Straining flows can thin or thicken an interface and this must be resisted by a high enough diffusion. On the other hand, too large a diffusion will overly damp the flow. These two constraints result in an upper bound for the diffusivity of O(epsilon) and a lower bound of O (epsilon(2)). Within these two bounds, the phase-field Navier-Stokes equations appear to generate an O(epsilon) error relative to the exact sharp-interface equations. An O(h(2)/epsilon(2)) numerical method is introduced that is energy conserving in the sense that creation of interface energy by convection is always balanced by an equal decrease in kinetic energy caused by surface tension forcing. An O (h(4)/epsilon(4)) compact scheme is introduced that takes advantage of the asymptotic, comparatively smooth, behavior of the chemical potential. For O(epsilon) accurate phase-field models the optimum path to convergence for this scheme appears to be epsilon proportional to h(4/5). The asymptotic rate of convergence corresponding to this is O(h(4/5)) but results at practical resolutions show that the practical convergence of the method is generally considerably faster than linear. Extensive analysis and computations show that this scheme is very effective and accurate. It allows the accurate calculation of two-phase flows with interfaces only two cells wide. Computational results are given for linear capillary waves and for Rayleigh-Taylor instabilities. The first set of computations is compared to exact solutions of the diffuse-interface equations and of the original sharp-interface equations. The Rayleigh-Taylor computations test the ability of the method to compute highly deforming flows. These flows include near-singular phenomena such as interface coalescences and breakups, contact line movement, and the formation and breakup of thin wall-films. Grid-refinement studies are made and rapid convergence is found for macroscopic flow features such as instability growth rate and propagation speed, wavelength, and the general physical characteristics of the instability and mass transfer rates. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Jacqmin, D (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 24 TC 499 Z9 514 U1 10 U2 115 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0021-9991 J9 J COMPUT PHYS JI J. Comput. Phys. PD OCT 10 PY 1999 VL 155 IS 1 BP 96 EP 127 DI 10.1006/jcph.1999.6332 PG 32 WC Computer Science, Interdisciplinary Applications; Physics, Mathematical SC Computer Science; Physics GA 244DE UT WOS:000083035900005 ER PT J AU Gotoh, T Rogallo, RS AF Gotoh, T Rogallo, RS TI Intermittency and scaling of pressure at small scales in forced isotropic turbulence SO JOURNAL OF FLUID MECHANICS LA English DT Article ID FULLY-DEVELOPED TURBULENCE; HOMOGENEOUS TURBULENCE; REYNOLDS-NUMBERS; STATISTICS; SIMULATIONS; EXPONENT; SPECTRA; MODELS; FLOW AB The intermittency of pressure and pressure gradient in stationary isotropic turbulence at low to moderate Reynolds numbers is studied by direct numerical simulation (DNS) and theoretically. The energy spectra scale in Kolmogorov units as required by the universal-equilibrium hypothesis, but the pressure spectra do not. It is found that the variances of the pressure and pressure gradient are larger than those computed using the Gaussian approximation for the fourth-order moments of velocity, and that the variance of the pressure gradient, normalized by Kolmogorov units, increases roughly as R-lambda(1/2), where R-lambda is the Taylor microscale Reynolds number. A theoretical explanation of the Reynolds number dependence is presented which assumes that the small-scale pressure field is driven by coherent small-scale vorticity-strain domains. The variance of the pressure gradient given by the model is the product of the variance of u(i,j)u(j,i), the source term of the Poisson equation for pressure, and the square of an effective length of the small-scale coherent vorticity-strain structures. This length can be expressed in terms of the Taylor and Kolmogorov microscales, and the ratio between them gives the observed Reynolds number dependence. Formal asymptotic matching of the spectral scaling observed at small scales in the DNS with the classical scaling at large scales suggests that at high Reynolds numbers the pressure spectrum in these forced flows consists of three scaling ranges which are joined by two inertial ranges, the classical k(-7/3) range and a k(-5/3) range at smaller scale. It is not possible, within the classical Kolmogorov theory, to determine the length scale at which the inertial range transition occurs because information beyond the energy dissipation rate is required. C1 Nagoya Inst Technol, Dept Syst Engn, Showa Ku, Nagoya, Aichi 466, Japan. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Gotoh, T (reprint author), Nagoya Inst Technol, Dept Syst Engn, Showa Ku, Nagoya, Aichi 466, Japan. NR 46 TC 42 Z9 42 U1 0 U2 2 PU CAMBRIDGE UNIV PRESS PI NEW YORK PA 40 WEST 20TH STREET, NEW YORK, NY 10011-4211 USA SN 0022-1120 J9 J FLUID MECH JI J. Fluid Mech. PD OCT 10 PY 1999 VL 396 BP 257 EP 285 DI 10.1017/S0022112099005972 PG 29 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 244BE UT WOS:000083031300009 ER PT J AU Peltzer, G Crampe, F King, G AF Peltzer, G Crampe, F King, G TI Evidence of nonlinear elasticity of the crust from the Mw7.6 Manyi (Tibet) earthquake SO SCIENCE LA English DT Article ID DIFFERENTIAL RADAR INTERFEROMETRY; PORE FLUID-FLOW; LANDERS EARTHQUAKE; SOUTHERN-CALIFORNIA; DEFORMATION; SEQUENCE; AFTERSHOCKS; DISPLACEMENTS; FAULTS AB Satellite synthetic aperture radar (SAR) interferometry shows that the magnitude 7.6 Manyi earthquake of 8 November 1997 produced a 170-kilometer-long surface break with up to 7 meters of Left-Lateral slip, reactivating a N76 degrees E quaternary fault in western Tibet. The radar interferometric map reveals asymmetric, along-strike displacement profiles between the two sides of the surface rupture, a pattern that cannot be explained with linear elastic theory. This observation suggests that the elastic moduli of the crust in tension and in compression are different because of the presence of cracks in the crust at shallow depth. A model indicates that a ratio of 2 between compressive and tensile elastic moduli can account for the observed asymmetry, a ratio that is consistent with Laboratory and borehole measurements. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Inst Phys Globe, Paris, France. RP Peltzer, G (reprint author), CALTECH, Jet Prop Lab, MS 300-233,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 32 TC 154 Z9 186 U1 1 U2 7 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 OCT 8 PY 1999 VL 286 IS 5438 BP 272 EP 276 DI 10.1126/science.286.5438.272 PG 5 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 243YE UT WOS:000083024400039 ER PT J AU Joughin, I Gray, L Bindschadler, R Price, S Morse, D Hulbe, C Mattar, K Werner, C AF Joughin, I Gray, L Bindschadler, R Price, S Morse, D Hulbe, C Mattar, K Werner, C TI Tributaries of West Antarctic Ice streams revealed by RADARSAT interferometry SO SCIENCE LA English DT Article ID SUBGLACIAL GEOLOGY; SATELLITE IMAGERY; SHEET; STAGNATION; GLACIER; ONSET; FLOW AB lnterferometric RADARSAT data are used to map ice motion in the source areas of four West Antarctic ice streams. The data reveal that tributaries, coincident with subglacial valleys, provide a spatially extensive transition between slow inland flow and rapid ice stream flow and that adjacent ice streams draw from shared source regions. Two tributaries flow into the stagnant ice stream C, creating an extensive region that is thickening at an average rate of 0.49 meters per year. This is one of the Largest rates of thickening ever reported in Antarctica. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Canada Ctr Remote Sensing, Applicat Div, Ottawa, ON K1A 0Y7, Canada. NASA, Oceans & Ice Branch, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. SAIC Gen Sci Corp, Beltsville, MD 20705 USA. Univ Texas, Inst Geophys, Austin, TX 78759 USA. RP Joughin, I (reprint author), CALTECH, Jet Prop Lab, M-S 300-235,4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM ian@radar-sci.jpl.nasa.gov RI Joughin, Ian/A-2998-2008; Price, Stephen /E-1568-2013 OI Joughin, Ian/0000-0001-6229-679X; Price, Stephen /0000-0001-6878-2553 NR 37 TC 136 Z9 137 U1 1 U2 19 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 OCT 8 PY 1999 VL 286 IS 5438 BP 283 EP 286 DI 10.1126/science.286.5438.283 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 243YE UT WOS:000083024400042 ER PT J AU Merline, WJ Close, LM Dumas, C Chapman, CR Roddier, F Menard, F Slater, DC Duvert, G Shelton, C Morgan, T AF Merline, WJ Close, LM Dumas, C Chapman, CR Roddier, F Menard, F Slater, DC Duvert, G Shelton, C Morgan, T TI Discovery of a moon orbiting the asteroid 45 Eugenia SO NATURE LA English DT Article ID ADAPTIVE OPTICS; SATELLITES; 253-MATHILDE; 243-IDA; DACTYL; SYSTEM; FLYBY AB Evidence for asteroidal satellites (moons) has been sought for decades, because the relative frequency of such satellites will bear on the collisional history of the asteroid belt and the Solar System, yet only one has been detected unambiguously(1-3). Here we report the discovery of a satellite of the asteroid 45 Eugenia, using an adaptive optics system on a ground-based telescope. The satellite has a diameter of about 13 km, and an orbital period of about 4.7 days with a separation of 1,190 km from Eugenia. Using a previously determined(4) diameter for Eugenia, we estimate that its bulk density is about 1.2 g cm(-3), which is similar to that of the C-type asteroid Mathilde(5,6). This implies that Eugenia, also a low-albedo C-type asteroid, may be a rubble pile, or composed of primitive, icy materials of low bulk density. C1 SW Res Inst, Boulder, CO 80302 USA. European So Observ, D-85748 Garching, Germany. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Hawaii, Inst Astron, Honolulu, HI 96822 USA. Canada France Hawaii Telescope Corp, Kamuela, HI 96743 USA. SW Res Inst, San Antonio, TX 78228 USA. Lab Astrophys Grenoble, F-38041 Grenoble 9, France. WM Keck Observ, Kamuela, HI 96743 USA. NASA Headquarters, Washington, DC 20546 USA. RP Merline, WJ (reprint author), SW Res Inst, Boulder, CO 80302 USA. NR 35 TC 79 Z9 80 U1 0 U2 4 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON N1 9XW, ENGLAND SN 0028-0836 J9 NATURE JI Nature PD OCT 7 PY 1999 VL 401 IS 6753 BP 565 EP 568 DI 10.1038/44089 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 244MG UT WOS:000083054900043 ER PT J AU Files, BS Mayeaux, BM AF Files, BS Mayeaux, BM TI Carbon nanotubes SO ADVANCED MATERIALS & PROCESSES LA English DT Article AB Carbon nanotubes have potential for a multitude of applications because of their high strength, low density, high electrical conductivity, and high thermal conductivity. C1 NASA, Lyndon B Johnson Space Ctr, Mat & Processes Technol Branch, Houston, TX 77058 USA. RP Files, BS (reprint author), NASA, Lyndon B Johnson Space Ctr, Mat & Processes Technol Branch, Mail Code EM2, Houston, TX 77058 USA. NR 5 TC 27 Z9 30 U1 1 U2 1 PU ASM INTERNATIONAL PI MATERIALS PARK PA SUBSCRIPTIONS SPECIALIST CUSTOMER SERVICE, MATERIALS PARK, OH 44073-0002 USA SN 0026-0665 J9 ADV MATER PROCESS JI Adv. Mater. Process. PD OCT PY 1999 VL 156 IS 4 BP 47 EP 49 PG 3 WC Materials Science, Multidisciplinary SC Materials Science GA 246ZY UT WOS:000083197200004 ER PT J AU Wissink, AM Lyrintzis, AS Chronopoulos, AT AF Wissink, AM Lyrintzis, AS Chronopoulos, AT TI Parallel Newton-Krylov method for rotary-wing flowfield calculations SO AIAA JOURNAL LA English DT Article ID NONSYMMETRIC LINEAR-SYSTEMS; NAVIER-STOKES EQUATIONS; MINIMAL RESIDUAL ALGORITHM; ITERATIVE METHODS; HELICOPTER ROTORS; SOLVER; PREDICTIONS; SCHEMES; FLOWS; HOVER AB The use of Krylov subspace iterative methods for the implicit solution of rotary-wing flowfields on parallel computers is explored. A Newton-Krylov scheme is proposed that couples conjugate-gradient-like iterative methods within the baseline structured-grid Euler/Navier-Stokes flow solver, transonic unsteady rotor Navier/Stokes. Two Krylov methods are studied, generalized minimum residual and orthogonal s-step orthomin. Preconditioning is performed with a parallelized form of the lower-upper symmetric Gauss-Seidel operator. The scheme is implemented on the IBM SP2 multiprocessor and applied td three-dimensional computations of a rotor in forward flight. The Newton-Krylov scheme is found to be more robust and to attain a higher level of time accuracy in implicit time stepping, increasing the allowable time step. The method yields approximately a 20% reduction in solution time with the same level of accuracy in time-accurate calculations but requires more memory than do more traditional implicit techniqes. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Purdue Univ, Sch Aeronaut & Astronaut, W Lafayette, IN 47907 USA. Univ Texas, Div Comp Sci, San Antonio, TX USA. RI Chronopoulos, Anthony/M-8720-2013 OI Chronopoulos, Anthony/0000-0002-8804-0773 NR 33 TC 6 Z9 6 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0001-1452 J9 AIAA J JI AIAA J. PD OCT PY 1999 VL 37 IS 10 BP 1213 EP 1221 PG 9 WC Engineering, Aerospace SC Engineering GA 243BR UT WOS:000082977700009 ER PT J AU Mavriplis, DJ AF Mavriplis, DJ TI Directional agglomeration multigrid techniques for high-Reynolds-number viscous flows SO AIAA JOURNAL LA English DT Article; Proceedings Paper CT AIAA 36th Aerospace Sciences Meeting CY JAN 12-15, 1998 CL RENO, NV SP Amer Inst Aeronaut & Astronaut ID NAVIER-STOKES EQUATIONS; SOLVER; MESHES AB A preconditioned directional-implicit agglomeration multigrid algorithm is developed for solving two- and three-dimensional viscous flows an highly anisotropic unstructured meshes of mixed-element types. The multigrid smoother consists of a preconditioned point- or line-implicit solver that operates on lines constructed in the unstructured mesh using a weighted graph algorithm. Directional coarsening or agglomeration is achieved using a similar weighted graph algorithm. A tight coupling of the line construction and directional agglomeration algorithms enables the use of aggressive coarsening ratios in the multigrid algorithm, which in turn reduces the cost of a multigrid cycle. Convergence rates that ape independent of the degree of grid stretching are demonstrated In both two and three dimensions. Further improvement of the three-dimensional convergence rates through a Generalized Minimum Residual (GMRES) technique is also demonstrated. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Mavriplis, DJ (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 36 TC 32 Z9 32 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091-4344 USA SN 0001-1452 J9 AIAA J JI AIAA J. PD OCT PY 1999 VL 37 IS 10 BP 1222 EP 1230 DI 10.2514/2.590 PG 9 WC Engineering, Aerospace SC Engineering GA 243BR UT WOS:000082977700010 ER PT J AU Brown, AM Ferri, AA AF Brown, AM Ferri, AA TI Application of the probabilistic dynamic synthesis method to realistic structures SO AIAA JOURNAL LA English DT Article ID RELIABILITY AB The probabilistic dynamic synthesis (PDS) method is a technique for obtaining the statistics of a desired response engineering quantity for a structure with nondeterministic parameters. The method uses measured data from modal testing of the structure as the input random variables, rather than more primitive quantities like geometry or material variation. This modal information is much more comprehensive and easily measured than the primitive information. The probabilistic analysis is carried out using either response surface reliability methods or Monte Carlo simulation. In previous work the feasibility of the PDS method applied to a simple seven-degree-of-freedom spring-mass system was verified. In this paper extensive issues involved with applying the method to a realistic three-substructure system are examined, and free- and forced-response analyses are performed. The results from using the method are promising, especially when the lack of alternatives for obtaining quantitative output for probabilistic structures is considered. C1 NASA, George C Marshall Space Flight Ctr, Struct Anal Div, Struct Dynam & Loads Branch, Huntsville, AL 35812 USA. Georgia Inst Technol, George W Woodruff Sch Mech Engn, Atlanta, GA 30332 USA. RP Brown, AM (reprint author), NASA, George C Marshall Space Flight Ctr, Struct Anal Div, Struct Dynam & Loads Branch, Huntsville, AL 35812 USA. NR 17 TC 0 Z9 0 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0001-1452 J9 AIAA J JI AIAA J. PD OCT PY 1999 VL 37 IS 10 BP 1292 EP 1297 PG 6 WC Engineering, Aerospace SC Engineering GA 243BR UT WOS:000082977700018 ER PT J AU Saxton, PC Moran, AL Rutledge, SK AF Saxton, PC Moran, AL Rutledge, SK TI Emissivity measurement comparison SO AMERICAN CERAMIC SOCIETY BULLETIN LA English DT Article AB Emissivity measurements generated by two different methods were compared for selected candidate materials. The system used by NASA Glenn Research Center is a useful tool for rapid screening of candidate emitter materials. C1 USN Acad, Annapolis, MD 21402 USA. NASA, Glenn Res Ctr, Cleveland, OH USA. RP Saxton, PC (reprint author), USN Acad, Annapolis, MD 21402 USA. NR 0 TC 0 Z9 0 U1 0 U2 1 PU AMER CERAMIC SOC PI WESTERVILLE PA 735 CERAMIC PLACE, PO BOX 6136, WESTERVILLE, OH 43081-6136 USA SN 0002-7812 J9 AM CERAM SOC BULL JI Am. Ceram. Soc. Bull. PD OCT PY 1999 VL 78 IS 10 BP 55 EP 58 PG 4 WC Materials Science, Ceramics SC Materials Science GA 291WR UT WOS:000085762800005 ER PT J AU West, SJ Frant, MS Wen, XW Geis, R Herdan, J Gillette, T Hecht, MH Schubert, W Grannan, S Kounaves, SP AF West, SJ Frant, MS Wen, XW Geis, R Herdan, J Gillette, T Hecht, MH Schubert, W Grannan, S Kounaves, SP TI Electrochemistry on Mars SO AMERICAN LABORATORY LA English DT Article AB The Mars Surveyor 2001 Lander is scheduled to carry the Mars Environmental Compatibility Assessment (MECA) that is being developed by the Jet Propulsion Laboratory of the California Institute of Technology. This article describes the Wet Chemistry Laboratory (WCL), which is a key component of the MECA. Through use of an array of electrochemical sensors, the WCL is designed to determine the extent of the hazard that the Martian soil will present to human explorers and equipment. C1 Orion Res Inc, Beverly, MA 01915 USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. Tufts Univ, Dept Chem, Medford, MA 02155 USA. RP West, SJ (reprint author), Orion Res Inc, 500 Cummings Ctr, Beverly, MA 01915 USA. OI Kounaves, Samuel/0000-0002-2629-4831 NR 4 TC 8 Z9 8 U1 0 U2 6 PU INT SCIENTIFIC COMMUN INC PI SHELTON PA PO BOX 870, 30 CONTROLS DRIVE, SHELTON, CT 06484-0870 USA SN 0044-7749 J9 AM LAB JI Am. Lab. PD OCT PY 1999 VL 31 IS 20 BP 48 EP + PG 7 WC Chemistry, Analytical; Instruments & Instrumentation SC Chemistry; Instruments & Instrumentation GA 246GJ UT WOS:000083155800006 PM 11543343 ER PT J AU Borisov, A Jones, JH AF Borisov, A Jones, JH TI An evaluation of Re, as an alternative to Pt, for the 1 bar loop technique: An experimental study at 1400 degrees C SO AMERICAN MINERALOGIST LA English DT Article ID MELTING EXPERIMENTS; IRON LOSS; CRYSTALLIZATION AB Previous investigators have shown that, at high pressure, Re is a good capsule material and that Fe loss to Re under these conditions is minimal (e.g., Herzberg and Zhang 1997). We present here the first systematic low-pressure study of Re loop stability and of Fe loss from silicate melts to Re loops as a function of f(o2). Experiments were performed ar 1400 degrees C and one bar pressure over a range of f(o2). For f(o2) values as low as QFM-2, Fe loss was found to be negligibly small, even for a charge/loop ratio of only about 2. According to our calculations, for the same conditions, Fe loss to a Pt loop could reach 70% of the initial FeO content. We have also estimated the diffusion coefficient of Fe in Re and found it to be very small (approximate to 10(-12) cm(2)/s), which is an additional factor in preventing Fe loss. At values of f(o2) near QFM, Re metal reacts to form volatile Re oxides. But at f(o2) below QFM-1.7, Re loops were found to be stable for any reasonable experimental run duration at 1400 OC. At lower temperatures Re may be stable to even higher values of f(o2). These conditions are similar to or slightly more reducing than the accepted redox states far the mantles of the Earth and Mars. Consequently, for many experiments, Re may be a more convenient loop material than Pt. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Borisov, A (reprint author), NASA, Lyndon B Johnson Space Ctr, SN2, Houston, TX 77058 USA. NR 26 TC 35 Z9 35 U1 0 U2 4 PU MINERALOGICAL SOC AMER PI WASHINGTON PA 1015 EIGHTEENTH ST, NW SUITE 601, WASHINGTON, DC 20036 USA SN 0003-004X J9 AM MINERAL JI Am. Miner. PD OCT PY 1999 VL 84 IS 10 BP 1528 EP 1534 PG 7 WC Geochemistry & Geophysics; Mineralogy SC Geochemistry & Geophysics; Mineralogy GA 244YT UT WOS:000083078900006 ER PT J AU Lepidi, S Francia, P Villante, U Meloni, A Lazarus, AJ Lepping, RP AF Lepidi, S Francia, P Villante, U Meloni, A Lazarus, AJ Lepping, RP TI The Earth's passage of the April 11, 1997 coronel ejecta: geomagnetic field fluctuations at high and low latitude during northward interplanetary magnetic field conditions SO ANNALES GEOPHYSICAE-ATMOSPHERES HYDROSPHERES AND SPACE SCIENCES LA English DT Article DE magnetospheric physics (MHD waves and; instabilities, solar wind-magnetosphere interactions) ID SUDDEN IMPULSES; MAGNETOSPHERE; CLOUD AB An analysis of the low frequency geomagnetic field fluctuations at an Antarctic (Terra Nova Bay) and a low latitude (L'Aquila, Italy) station during the Earth's passage of a coronal ejecta on April 11, 1997 shows that major solar wind pressure variations were followed at both stations by a high fluctuation level. During northward interplanetary magnetic field conditions and when Terra Nova Bay is close to the local geomagnetic noon, coherent fluctuations, at the same frequency (3.6 mHz) and with polarization characteristics indicating an antisunward propagation, were observed simultaneously at the two stations. An analysis of simultaneous measurements from geosynchronous satellites shows evidence for pulsations at approximately the same frequencies also in the magnetospheric field. The observed waves might then be interpreted as oscillation modes, triggered by an external stimulation, extending to a major portion of the Earth's magnetosphere. C1 Univ Aquila, Dipartimento Fis, I-67100 Laquila, Italy. Ist Nazl Geofis, I-00161 Rome, Italy. MIT, Ctr Space Res, Cambridge, MA 02139 USA. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RP Lepidi, S (reprint author), Univ Aquila, Dipartimento Fis, I-67100 Laquila, Italy. NR 19 TC 14 Z9 14 U1 0 U2 0 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0992-7689 J9 ANN GEOPHYS-ATM HYDR JI Ann. Geophys.-Atmos. Hydrospheres Space Sci. PD OCT PY 1999 VL 17 IS 10 BP 1245 EP 1250 DI 10.1007/s005850050850 PG 6 WC Astronomy & Astrophysics; Geosciences, Multidisciplinary; Meteorology & Atmospheric Sciences SC Astronomy & Astrophysics; Geology; Meteorology & Atmospheric Sciences GA 249BD UT WOS:000083311500001 ER PT J AU Vander Wal, RL Ticich, TM West, JR Householder, PA AF Vander Wal, RL Ticich, TM West, JR Householder, PA TI Trace metal detection by laser-induced breakdown spectroscopy SO APPLIED SPECTROSCOPY LA English DT Article DE LIBS; heavy metal; liquid; analysis; ablation ID TIME-INTEGRATED EMISSION; INDUCED PLASMA EMISSIONS; SHOCK-WAVE PLASMA; SPECTROCHEMICAL ANALYSIS; ELEMENTAL ANALYSIS; ATMOSPHERIC-PRESSURE; AQUEOUS-SOLUTIONS; LIQUID AEROSOLS; BUFFER GASES; ABLATION AB Laser-induced breakdown spectroscopy (LIBS) has been widely pursued for trace elemental determination in gases, solids, and liquids. Application to liquids has proved problematic due to high spatial confinement of the LIES plasma and rapid quenching of the excited-state emission. This work presents an alternative approach to trace metal determination in liquids in which 1.0 mL of liquid is deposited onto a carbon planchet and then evaporated, thus transforming the liquid analysis to a solid surface analysis. Using optimized excitation and detection conditions, we have identified spectral regions for sensitive detection of 15 metals (Mg, Al, Si, Ca, Ti, Cr, Fe, Co, Ni, Cu, Zn, As, Cd, Hg, Ph). The limit of detection (LOD) for the technique ranged from 10 ppb to 10 ppm for these elements. A 100 ppb LOD represents detection of 130 picograms of metal (approximately 2 picomoles) in a single measurement calculated from the laser spot size on the sample. Scanning electron microscopy (SEM) images and energy-dispersive X-ray (EDX) spectra of the samples provide insight into the observed reproducibility and linearity of the technique for several of the metals studied. C1 NASA, Lewis Res Ctr, NCMR, Cleveland, OH 44135 USA. Centenary Coll Louisiana, Dept Chem, Shreveport, LA 71134 USA. RP Vander Wal, RL (reprint author), NASA, Lewis Res Ctr, NCMR, MS 110-3,21000 Brookpk Rd, Cleveland, OH 44135 USA. NR 39 TC 58 Z9 59 U1 3 U2 31 PU SOC APPLIED SPECTROSCOPY PI FREDERICK PA 201B BROADWAY ST, FREDERICK, MD 21701 USA SN 0003-7028 J9 APPL SPECTROSC JI Appl. Spectrosc. PD OCT PY 1999 VL 53 IS 10 BP 1226 EP 1236 PG 11 WC Instruments & Instrumentation; Spectroscopy SC Instruments & Instrumentation; Spectroscopy GA 249BT UT WOS:000083312800012 ER PT J AU Vander Wal, RL Householder, PA Wright, TW AF Vander Wal, RL Householder, PA Wright, TW TI Phosphor thermometry in combustion applications SO APPLIED SPECTROSCOPY LA English DT Article DE phosphor; temperature; spectra fitting; luminescence; combustion ID LASER-INDUCED FLUORESCENCE; THERMOGRAPHIC PHOSPHORS; FLAME SPREAD; TEMPERATURE-MEASUREMENTS; FIBER; MICROGRAVITY; RESOLUTION; SENSOR; FUEL; SOOT AB A new approach for phosphor-based temperature determination is presented. This method is based on comparison between the spectrally resolved phosphorescent emission and a database of spectra collected at a series of temperatures. Applications of two phosphor materials, Gd2O2S:Tb and Mg-4(F)GeO6:Mn, possessing different and complementary temperature sensitivities are illustrated. Efficient and accurate comparison is demonstrated between application and calibration spectra with the use of a custom program featuring a general regression neural net algorithm. With this approach, single laser-pulse, spatially resolved measurements are demonstrated. Applications of the technique reported here include measurements of the surface temperature of a thermophoretic sampling probe, the surface temperature of a porous burning solid, wick surface temperatures of supported diffusion flames of acetone, heptane, and decane, and the cellulose pyrolysis and char oxidation temperatures associated with flame spread across a thermally thin fuel at 300 and 700 Torr air pressure. C1 NASA, Lewis Res Ctr, NCMR, Cleveland, OH 44135 USA. RP Vander Wal, RL (reprint author), NASA, Lewis Res Ctr, NCMR, MS 110-3,21000 Brookpk Rd, Cleveland, OH 44135 USA. NR 32 TC 12 Z9 12 U1 1 U2 8 PU SOC APPLIED SPECTROSCOPY PI FREDERICK PA 201B BROADWAY ST, FREDERICK, MD 21701 USA SN 0003-7028 J9 APPL SPECTROSC JI Appl. Spectrosc. PD OCT PY 1999 VL 53 IS 10 BP 1251 EP 1258 PG 8 WC Instruments & Instrumentation; Spectroscopy SC Instruments & Instrumentation; Spectroscopy GA 249BT UT WOS:000083312800015 ER PT J AU Chien, S Rabideau, G Willis, J Mann, T AF Chien, S Rabideau, G Willis, J Mann, T TI Automating planning and scheduling of shuttle payload operations SO ARTIFICIAL INTELLIGENCE LA English DT Article DE scheduling; planning; iterative repair; space operations; local search; autonomous spacecraft AB This paper describes the DATA-CHASER Automated Planner/Scheduler (DCAPS) system for automated generation and repair of command sequences for the DATA-CHASER shuttle payload. DCAPS uses general Artificial Intelligence (AI) heuristic search techniques, including an iterative repair framework in which the system iteratively resolves conflicts with the state, resource, and temporal constraints of the payload activities. DCAPS was used in the operations of the shuttle payload for the STS-85 shuttle flight in August 1997 and enabled a 80% reduction in mission operations effort and a 40% increase in science return, (C) 1999 Published by Elsevier B.V. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Chien, S (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,MS 126-347, Pasadena, CA 91109 USA. NR 15 TC 13 Z9 15 U1 0 U2 4 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0004-3702 J9 ARTIF INTELL JI Artif. Intell. PD OCT PY 1999 VL 114 IS 1-2 BP 239 EP 255 DI 10.1016/S0004-3702(99)00069-7 PG 17 WC Computer Science, Artificial Intelligence SC Computer Science GA 263XZ UT WOS:000084151700008 ER PT J AU Cole, AA Tolstoy, E Gallagher, JS Hoessel, JG Mould, JR Holtzman, JA Saha, A Ballester, GE Burrows, CJ Clarke, JT Crisp, D Griffiths, RE Grillmair, CJ Hester, JJ Krist, JE Meadows, V Scowen, PA Stapelfeldt, KR Trauger, JT Watson, AM Westphal, JR AF Cole, AA Tolstoy, E Gallagher, JS Hoessel, JG Mould, JR Holtzman, JA Saha, A Ballester, GE Burrows, CJ Clarke, JT Crisp, D Griffiths, RE Grillmair, CJ Hester, JJ Krist, JE Meadows, V Scowen, PA Stapelfeldt, KR Trauger, JT Watson, AM Westphal, JR TI Stellar populations at the center of IC 1613 SO ASTRONOMICAL JOURNAL LA English DT Article DE color-magnitude diagrams; galaxies : individual (IC 1613); galaxies : irregular; galaxies : stellar content; Local Group ID RED CLUMP STARS; LOCAL GROUP GALAXIES; GIANT BRANCH; IRREGULAR GALAXIES; MAGELLANIC CLOUDS; GLOBULAR-CLUSTERS; NEARBY GALAXIES; CCD PHOTOMETRY; SEXTANS-A; IC-1613 AB We have observed the center of the Local Group dwarf irregular galaxy IC 1613 with the WFPC2 aboard the Hubble Space Telescope in the F439W, F555W, and F814W filters. We analyze the resulting color-magnitude diagrams (CMDs) using the main-sequence and giant-branch luminosity functions and comparisons with theoretical stellar models to derive a preliminary star formation history for this galaxy. We find a dominant old stellar population (age approximate to 7 Gyr), identifiable by the strong red giant branch (RGB) and red dump populations. From the (V - I) color of the RGB, we estimate a mean metallicity of the intermediate-age stellar population [Fe/H] = -1.38 +/- 0.31. We confirm a distance of 715 +/- 40 kpc using the I magnitude of the RGB tip. The main-sequence luminosity function down to I approximate to 25 provides evidence for a roughly constant star formation rate (SFR) of approximately 3.5 x 10(-4) M. yr(-1) across the WFPC2 field of view (0.22 kpc(2)) during the past 250-350 Myr. Structure in the blue loop luminosity function implies that the SFR was approximate to 50% higher 400-900 Myr ago than today. The mean heavy-element abundance of these young stars is around one-tenth solar. The best explanation for a red spur on the main sequence at I approximate to 24.7 is the blue horizontal branch component of a very old stellar population at the center of IC 1613. We have also imaged a broader area of IC 1613 using the 3.5 m WIYN telescope under excellent seeing conditions. The WIYN CMD reveals a prominent sequence of asymptotic giant branch stars and red supergiants that is less prominent in the WFPC2 CMD because of the smaller field of view. The asymptotic giant branch star luminosity function is consistent with a period of continuous star formation over at least the age range 2-10 Gyr. We present an approximate age-metallicity relation for IC 1613, which appears to be similar to that of the Small Magellanic Cloud. We compare the Hess diagram of IC 1613 with similar data for three other Local Group dwarf galaxies and find that IC 1613 most closely resembles the nearby, transition-type dwarf galaxy Pegasus (DDO 216). C1 Univ Massachusetts, Dept Phys & Astron, Amherst, MA 01003 USA. European So Observ, D-8046 Garching, Germany. Australian Natl Univ, Mt Stromlo & Siding Spring Observ, Weston, ACT 2611, Australia. New Mexico State Univ, Dept Astron, Las Cruces, NM 88003 USA. Natl Opt Astron Observ, Tucson, AZ 85726 USA. Univ Michigan, Dept Atmospher & Ocean Sci, Ann Arbor, MI 48109 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. European Space Agcy, Dept Space Sci, Div Astrophys, F-75738 Paris 15, France. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Carnegie Mellon Univ, Dept Phys, Pittsburgh, PA 15213 USA. CALTECH, SIRTF Sci Ctr, Pasadena, CA 91125 USA. Arizona State Univ, Dept Phys & Astron, Tempe, AZ 85287 USA. Univ Nacl Autonoma Mexico, Inst Astron, Morelia 58090, Michoacan, Mexico. CALTECH, Div Geol & Planetary Sci, Pasadena, CA 91125 USA. RP Cole, AA (reprint author), Univ Massachusetts, Dept Phys & Astron, Amherst, MA 01003 USA. EM cole@astro.wisc.edu; etolstoy@eso.org; jsg@tiger.astro.wisc.edu; hoessel@astro.wisc.edu RI Stapelfeldt, Karl/D-2721-2012; Clarke, John/C-8644-2013; OI Cole, Andrew/0000-0003-0303-3855 NR 81 TC 67 Z9 67 U1 0 U2 2 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0004-6256 J9 ASTRON J JI Astron. J. PD OCT PY 1999 VL 118 IS 4 BP 1657 EP 1670 DI 10.1086/301042 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 251CR UT WOS:000083427500016 ER PT J AU Davidson, K Gull, TR Humphreys, RM Ishibashi, K Whitelock, P Berdnikov, L McGregor, PJ Metcalfe, TS Polomski, E Hamuy, M AF Davidson, K Gull, TR Humphreys, RM Ishibashi, K Whitelock, P Berdnikov, L McGregor, PJ Metcalfe, TS Polomski, E Hamuy, M TI An unusual brightening of eta Carinae SO ASTRONOMICAL JOURNAL LA English DT Article DE circumstellar matter; ISM : jets and outflows; stars : activity; stars : individual (eta Carinae); stars : peculiar; stars : winds, outflows ID STANDARD STARS; SPECTROSCOPY; VARIABILITY; BINARY AB HST/Space Telescope Imaging Spectrograph data show that the apparent near-UV, visual-wavelength, and near-IR brightness of eta Car increased by a factor of two during 1998. Meanwhile its Homunculus ejecta nebula brightened by about 30%, the largest fluctuation of this type in the past 40 years. These developments were quite unexpected and are not easy to explain. Some dust has probably been destroyed, while the star's luminosity may have increased even though it was already close to the Eddington limit. Such a rapid luminosity change would be a truly remarkable phenomenon, not predicted by existing models. C1 Univ Minnesota, Dept Astron, Minneapolis, MN 55455 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. S African Astron Observ, ZA-7935 W Cape, South Africa. Moscow MV Lomonosov State Univ, Sternberg Astron Inst, Moscow 119899, Russia. Australian Natl Observ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia. Univ Texas, Dept Astron, Austin, TX 78712 USA. Univ Florida, Dept Astron, Gainesville, FL 32611 USA. Univ Arizona, Steward Observ, Tucson, AZ 85721 USA. RP Davidson, K (reprint author), Univ Minnesota, Dept Astron, 116 Church St SE, Minneapolis, MN 55455 USA. RI Metcalfe, Travis/A-9388-2008; Gull, Theodore/D-2753-2012; Hamuy, Mario/G-7541-2016 OI Metcalfe, Travis/0000-0003-4034-0416; Gull, Theodore/0000-0002-6851-5380; NR 28 TC 61 Z9 61 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-6256 J9 ASTRON J JI Astron. J. PD OCT PY 1999 VL 118 IS 4 BP 1777 EP 1783 DI 10.1086/301063 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 251CR UT WOS:000083427500026 ER PT J AU Vink, JS de Koter, A Lamers, HJGLM AF Vink, JS de Koter, A Lamers, HJGLM TI On the nature of the bi-stability jump in the winds of early-type supergiants SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE radiative transfer; stars : early-type; stars : mass-loss; stars : supergiants; stars : winds, outflows ID RADIATION-DRIVEN WINDS; LUMINOUS BLUE VARIABLES; STELLAR WINDS; MULTILINE TRANSFER; STARS; MODELS; ATMOSPHERES; DYNAMICS AB We study the origin of the bi-stability jump in the terminal velocity of the winds of supergiants near spectral tg pe B1. Observations show that here the ratio v(infinity)/v(esc) drops steeply from about 2.6 at types earlier than B1 to a value of v(infinity)/v(esc) = 1.3 at types later than B2. To this purpose, we have calculated wind models and mass-loss rates for early-type supergiants in a T-eff grid covering the range between T-eff = 12 500 and 40 000 K. These models show the existence of a jump in mass loss around T-eff = 25 000 K for normal supergiants, with (M) over dot increasing by about a factor five from T-eff similar or equal to 27 500 to 22 500 K for constant luminosity. The wind efficiency number eta = (M) over dotv(infinity)/(L*/c) also increases drastically by a factor of 2 - 3 near that temperature. We argue that the jump in mass loss is accompanied by a decrease of the ratio v(infinity)/v(esc), which is the observed bi-stability jump in terminal velocity. Using self-consistent models for two values of T-eff, we have derived v(infinity)/v(esc) = 2.4 for T-eff = 30 000 K and v(infinity)/v(esc) = 1.2 for T-eff = 17 500 K. This is within 10 percent of the observed values around the jump. Up to now, a theoretical explanation of the observed bistability jump was not yet provided by radiation driven wind theory. To understand the origin of the bi-stability jump, we have investigated the line acceleration for models around the jump in detail. These models demonstrate that (M) over dot increases around the bi-stability jump due to an increase in the line acceleration of Fe III below the sonic point. This shows that the mass-loss rate of B-type supergiants is very sensitive to the abundance and the ionization balance of iron. Furthermore, we show that the elements C, N and O are important line drivers in the supersonic part of the wind, The subsonic part of the wind is dominated by the line acceleration due to Fe. Therefore, CNO-processing is expected not to have a large impact on (M) over dot but it might have impact on the terminal velocities. Finally, we discuss the possible role of the bi-stability jump on the mass loss during typical variations of Luminous Blue Variable stars. C1 Univ Utrecht, Inst Astron, NL-3508 TA Utrecht, Netherlands. Univ Amsterdam, Astron Inst Anton Pannekoek, NL-1098 SJ Amsterdam, Netherlands. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Vink, JS (reprint author), Univ Utrecht, Inst Astron, POB 80000, NL-3508 TA Utrecht, Netherlands. EM j.s.vink@astro.uu.nl NR 30 TC 109 Z9 109 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD OCT PY 1999 VL 350 IS 1 BP 181 EP 196 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 248QZ UT WOS:000083288000021 ER PT J AU Ehrenfreund, P Kerkhof, O Schutte, WA Boogert, ACA Gerakines, PA Dartois, E d'Hendecourt, L Tielens, AGGM van Dishoeck, EF Whittet, DCB AF Ehrenfreund, P Kerkhof, O Schutte, WA Boogert, ACA Gerakines, PA Dartois, E d'Hendecourt, L Tielens, AGGM van Dishoeck, EF Whittet, DCB TI Laboratory studies of thermally processed H2O-CH3OH-CO2 ice mixtures and their astrophysical implications SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE methods : laboratory; ISM : abundances; ISM : dust, extinction; ISM : evolution; ISM : molecules; infrared : ISM : lines and bands ID INFRARED SPECTRAL PROPERTIES; CARBONYL SULFIDE OCS; MOLECULAR CLOUDS; GRAIN MANTLES; ANALOGS; CO2; DIOXIDE; DESORPTION; NITROGEN; METHANOL AB Data of the Infrared Space Observatory ISO have strongly influenced the current view of interstellar ice chemistry. ISO and ground-based results have confirmed that the most abundant ice species in warm regions close to massive protostars are H2O, CO2, and CH3OH. Ice segregation in those environments reflects the extensive thermal processing of grains over the Lifetime of protostars. We present here a systematic set of laboratory infrared spectra of ice mixtures dominated by H2O, CO2 and CH3OH which have been exposed to thermal and UV irradiation processing. It is shown that the infrared bands of CO2 and of CH3OH are particularly sensitive to the ice composition, temperature and applied UV irradiation. The laboratory data suggest partial crystallization of interstellar ices in the protostellar environment. We present a detailed laboratory study of the CO2 bending mode at 15.2 mu m. The observed multipeak structure of the CO2 bending mode is a result of thermal processing and can not be produced by UV irradiation in the laboratory. Laboratory results show that annealed CO2 ice has a lower stability against UV irradiation than cold amorphous CO2 ice. Annealed ice mixtures containing H2O, CO2 and CH3OH show that the multipeak structure of the CO2 bending mode is not destroyed by UV fluxes of less than or similar to 10(18) photons.cm(-2). Detailed analysis of H2O, CO2 and CH3OH bands show that their profiles can be effectively used to trace the Line of sight conditions and the origin and evolution of the ice composition in dense clouds. The datafiles discussed in this paper can be retrieved from the Leiden observatory database (www.strw.leidenuniv.nl/similar to lab/isodb). C1 Leiden Observ, Raymond & Beverly Sackler Lab Astrophys, NL-2300 RA Leiden, Netherlands. Rensselaer Polytech Inst, Dept Phys Appl Phys & Astron, Troy, NY 12180 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Inst Astrophys Spatiale, F-91405 Orsay, France. Kapteyn Astron Inst, NL-9700 AV Groningen, Netherlands. RP Ehrenfreund, P (reprint author), Leiden Observ, Raymond & Beverly Sackler Lab Astrophys, POB 9513, NL-2300 RA Leiden, Netherlands. RI Gerakines, Perry/B-9705-2009; Appourchaux, Thierry/F-4692-2010; Gerakines, Perry/D-2226-2012 OI Gerakines, Perry/0000-0002-9667-5904 NR 49 TC 92 Z9 93 U1 0 U2 5 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD OCT PY 1999 VL 350 IS 1 BP 240 EP 253 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 248QZ UT WOS:000083288000025 ER PT J AU de Martino, D Silvotti, R Buckley, DAH Gansicke, BT Mouchet, M Mukai, K Rosen, SR AF de Martino, D Silvotti, R Buckley, DAH Gansicke, BT Mouchet, M Mukai, K Rosen, SR TI Time-resolved HST and IUE UV spectroscopy of the intermediate polar FO Aqr SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE accretion, accretion disks; stars : binaries : close; stars : individual : FO Aqr; ultraviolet : stars; X-rays : stars ID HUBBLE-SPACE-TELESCOPE; VARIABLE AE-AQUARII; DQ HERCULIS STARS; X-RAY; CATACLYSMIC VARIABLES; SPIN EPHEMERIDES; LIGHT CURVES; ULTRAVIOLET; H2215-086; LINE AB Time resolved spectroscopy of the Intermediate Polar FO Aqr reveals the presence of multiple periodicities in the UV range. A strong orbital modulation dominates both continuum and emission line flux variabilities, while line velocity motions are only detected at the rotational frequency. A prominent orbital periodicity is also observed in coordinated optical photometry, where FO Aqr was previously found to be spin dominated. The spectral dependence of the main periodicities shows the presence of multi-temperature components in FO Aqr and for the first time a hot and a cool component in the rotational modulation. From a comparison with previous UV and optical data obtained in 1990, no spectral variations in the orbital and rotational variabilities are detected, indicating no significant changes in the effects of X-ray illumination but rather a shrinking of the accretion curtain accompained by an increase in size of the thickened part of the accretion disc. These observations, consistent with the recently discovered long term trend in the X-ray pulsation amplitudes, independently confirm a change in the accretion mode in FO Aqr, which switched from a disc-fed into a disc-overflow state, likely triggered by mass accretion variations. C1 Osservatorio Astron Capodimonte, I-80131 Naples, Italy. S African Astron Observ, ZA-7935 Cape Town, South Africa. Univ Sternwarte Gottingen, D-37083 Gottingen, Germany. Observ Paris, DAEC, Sect Meudon, F-92195 Meudon, France. NASA, Goddard Space Flight Ctr, High Energy Phys Lab, Greenbelt, MD 20771 USA. Univ Leicester, Dept Phys & Astron, Leicester LE1 7RH, Leics, England. RP de Martino, D (reprint author), Osservatorio Astron Capodimonte, Via Moiariello 16, I-80131 Naples, Italy. EM demartin@na.astro.it RI Gaensicke, Boris/A-9421-2012 OI Gaensicke, Boris/0000-0002-2761-3005 NR 38 TC 14 Z9 14 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD OCT PY 1999 VL 350 IS 2 BP 517 EP 528 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 250LM UT WOS:000083389900021 ER PT J AU Clark, LL Dolan, JF AF Clark, LL Dolan, JF TI The distance to eight X-ray sources derived from Hipparcos observations SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE astrometry; stars : distances; stars : kinematics; X-rays : stars ID WAVELENGTH DEPENDENCE; STATISTICAL BEHAVIOR; LINEAR-POLARIZATION; POSITION ANGLE; SOLAR MOTION; BINARIES; PARAMETERS; SYSTEMS; PULSARS; CATALOG AB The parallaxes of eight galactic X-ray sources measured by Hipparcos are consistent with zero in all but two cases, 4U1145-619 (= Cen X-5) and HZ43. The parallax and proper motion measured for each of the others, including the Be/neutron star binaries X Per and A0535+26 and the massive X-ray binaries 4U0900-40, 4U1700-37, and Cyg XR-1, are consistent with their spectroscopic parallaxes. These results provide no evidence that visible stars in X-ray binaries have a luminosity that is abnormal for their spectral type. C1 NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. San Diego State Univ, Dept Astron, San Diego, CA 92182 USA. RP Dolan, JF (reprint author), NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. EM clark@vega.sdsu.edu; tejfd@splvin.gsfc.nasa.gov NR 39 TC 7 Z9 7 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD OCT PY 1999 VL 350 IS 3 BP 1085 EP 1088 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 257UV UT WOS:000083801100045 ER PT J AU Schulz, B Encrenaz, T Bezard, B Romani, PN Lellouch, E Atreya, SK AF Schulz, B Encrenaz, T Bezard, B Romani, PN Lellouch, E Atreya, SK TI Detection of C2H4 in Neptune from ISO/PHT-S observations SO ASTRONOMY & ASTROPHYSICS LA English DT Letter DE planets and satellites : general; planets and satellites : individual; : Neptune; infared : solar system ID RATE-CONSTANT; 121.6 NM; METHANE; JUPITER; PHOTOCHEMISTRY; RECOMBINATION; HYDROCARBONS; TEMPERATURE; ISOPHOT; SATURN AB The 6-12 mu m spectrum of Neptune has been recorded with the PHT-S instrument of the Infrared Space Observatory (ISO) at a resolution of 0.095 mu m. In addition to the emissions of CH4, CH3D and C2H6 previously identified, the spectrum shows the first firm identification of ethylene C2H4. The inferred column density above the 0.2-mbar level is in the range (1.1-3)x10(14) molecules cm(-2). To produce this low amount, previous photochemical models invoked rapid mixing between the source and sink regions of C2H4. We show that this requirement can be relaxed if recent laboratory measurements of CH4 photolysis branching ratios at Lyman alpha are used. C1 ESA, ISO Data Ctr, E-28080 Madrid, Spain. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Michigan, Ann Arbor, MI 48109 USA. RP Schulz, B (reprint author), ESA, ISO Data Ctr, POB 50727, E-28080 Madrid, Spain. EM bschulz@iso.vilspa.esa.es RI Romani, Paul/D-2729-2012 NR 29 TC 50 Z9 50 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 OCT PY 1999 VL 350 IS 1 BP L13 EP L17 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 248QZ UT WOS:000083288000004 ER PT J AU Crawford, FL McKenna, FC Keenan, FP Aller, LH Feibelman, WA Ryan, SG AF Crawford, FL McKenna, FC Keenan, FP Aller, LH Feibelman, WA Ryan, SG TI Line identifications and intensities for the optical spectrum of RR Telescopii between 3180 and 9455 angstrom SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article DE binaries : symbiotic; line : identifications; stars : individual (RR Tel) ID SYMBIOTIC STARS; HYDROGENIC IONS; COMPONENTS AB The symbiotic nova RR Telescopii has been observed with the 3.9 m telescope at the Angle-Australian Observatory (AAO), using the University College London Echelle Spectrograph (UCLES) in conjunction with a Tek CCD. It displays a rich emission line spectrum, ranging in excitation from NI to [NiVIII]. We present a list of 811 measured lines, with their suggested identifications and absolute line intensities, covering a wavelength range from 3180 Angstrom to 9455 Angstrom(1). The absolute line intensities have been derived by comparing the high resolution data with a flux-calibrated low resolution spectrum taken with the Australian National University 2.3 m telescope. All of the lines have been successfully identified. Comparing our results with those of previous studies indicates that the RR Tel system is advancing to-wards higher degrees of ionisation. C1 Queens Univ Belfast, Dept Pure & Appl Phys, Belfast BT7 1NN, Antrim, North Ireland. Univ Calif Los Angeles, Los Angeles, CA 90024 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Anglo Australian Observ, Epping, NSW 2121, Australia. RP Crawford, FL (reprint author), Queens Univ Belfast, Dept Pure & Appl Phys, Belfast BT7 1NN, Antrim, North Ireland. NR 19 TC 22 Z9 22 U1 0 U2 0 PU E D P SCIENCES PI LES ULIS CEDEXA PA 7, AVE DU HOGGAR, PARC D ACTIVITES COURTABOEUF, BP 112, F-91944 LES ULIS CEDEXA, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD OCT PY 1999 VL 139 IS 1 BP 135 EP 140 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 249BG UT WOS:000083311800013 ER PT J AU Mazets, EP Cline, TL Aptekar, RL Butterworth, PS Frederiks, DD Golenetskii, SV Il'inskii, VN Pal'shin, VD AF Mazets, EP Cline, TL Aptekar, RL Butterworth, PS Frederiks, DD Golenetskii, SV Il'inskii, VN Pal'shin, VD TI Activity of the soft gamma repeater SGR 1900+14 in 1998 from Konus-Wind observations: 1. Short recurrent bursts SO ASTRONOMY LETTERS-A JOURNAL OF ASTRONOMY AND SPACE ASTROPHYSICS LA English DT Article ID MAGNETIZED NEUTRON-STARS; X-RAY PULSAR; SGR1806-20; IDENTIFICATION; SGR-1900+14; COINCIDENT; TRANSIENT AB Observations of the soft gamma repeater SGR 1900+14 with a gamma-ray-burst spectrometer onboard the Wind spacecraft during the source reactivation from May 1998 through January 1999 are reported. Individual characteristics of recurrent bursts, such as their time histories, energy spectra, and maximum fluxes and fluences, are considered. Some statistical distributions and relations are also presented. The close similarity of these events to the recurrent bursts from other SGRs underlines a common emission mechanism. C1 Russian Acad Sci, AF Ioffe Phys Tech Inst, St Petersburg 194021, Russia. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Mazets, EP (reprint author), Russian Acad Sci, AF Ioffe Phys Tech Inst, St Petersburg 194021, Russia. RI Frederiks, Dmitry/C-7612-2014; Pal'shin, Valentin/F-3973-2014; Aptekar, Raphail/B-3456-2015; Golenetskii, Sergey/B-3818-2015; OI Frederiks, Dmitry/0000-0002-1153-6340 NR 34 TC 12 Z9 12 U1 0 U2 0 PU MAIK NAUKA/INTERPERIODICA PUBL PI WOODBURY PA C/O AMERICAN INST PHYSICS, 500 SUNNYSIDE BLVD, MEMBER SUBSCRIBER SERVICES, WOODBURY, NY 11797-2999 USA SN 1063-7737 J9 ASTRON LETT+ JI Astron. Lett.-J. Astron. Space Astrophys. PD OCT PY 1999 VL 25 IS 10 BP 628 EP 634 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 251VT UT WOS:000083467600002 ER PT J AU Mazets, EP Cline, TL Aptekar, RL Butterworth, PS Frederiks, DD Golenetskii, SV Il'inskii, VN Pal'shin, VD AF Mazets, EP Cline, TL Aptekar, RL Butterworth, PS Frederiks, DD Golenetskii, SV Il'inskii, VN Pal'shin, VD TI Activity of the soft gamma repeater SGR 1900+14 in 1998 from Konus-Wind observations: 2. The giant August 27 outburst SO ASTRONOMY LETTERS-A JOURNAL OF ASTRONOMY AND SPACE ASTROPHYSICS LA English DT Article ID RAY BURST AB Observations of the giant outburst in SGR 1900+14 on August 27, 1998, are presented. The two extremely intense events on August 27, 1998, and March 5, 1979, are compared. The striking similarity between the outbursts underlines their common nature. The occurrence of two giant outbursts in different sources within twenty years most likely suggests that such events occur in most SGRs once every 50-100 years. C1 Russian Acad Sci, AF Ioffe Phys Tech Inst, St Petersburg 194021, Russia. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Mazets, EP (reprint author), Russian Acad Sci, AF Ioffe Phys Tech Inst, St Petersburg 194021, Russia. RI Frederiks, Dmitry/C-7612-2014; Pal'shin, Valentin/F-3973-2014; Aptekar, Raphail/B-3456-2015; Golenetskii, Sergey/B-3818-2015; OI Frederiks, Dmitry/0000-0002-1153-6340 NR 18 TC 81 Z9 81 U1 0 U2 0 PU MAIK NAUKA/INTERPERIODICA PUBL PI WOODBURY PA C/O AMERICAN INST PHYSICS, 500 SUNNYSIDE BLVD, MEMBER SUBSCRIBER SERVICES, WOODBURY, NY 11797-2999 USA SN 1063-7737 J9 ASTRON LETT+ JI Astron. Lett.-J. Astron. Space Astrophys. PD OCT PY 1999 VL 25 IS 10 BP 635 EP 648 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 251VT UT WOS:000083467600003 ER PT J AU Newman, JA Zepf, SE Davis, M Freedman, WL Madore, BF Stetson, PB Silbermann, N Phelps, R AF Newman, JA Zepf, SE Davis, M Freedman, WL Madore, BF Stetson, PB Silbermann, N Phelps, R TI A Cepheid distance to NGC 4603 in Centaurus SO ASTROPHYSICAL JOURNAL LA English DT Article DE Cepheids; galaxies : clusters : individual (Centaurus); galaxies : distances and redshifts; galaxies : individual (NGC 4603) large-scale structure of universe ID HUBBLE-SPACE-TELESCOPE; SCALE KEY PROJECT; ELLIPTICAL GALAXIES; VELOCITY STRUCTURE; LIGHT-CURVE; PHOTOMETRY; DISCOVERY; CLUSTER; METALLICITY; SPECTROSCOPY AB In an attempt to use Cepheid variables to determine the distance to the Centaurus cluster, we have obtained images of NGC 4603 with the Hubble Space Telescope for 9 epochs (totalling 24 orbits) over 14 months in the F555W filter and 2 epochs (totalling six orbits) in the F814W filter. This galaxy has been suggested to lie within the "Cen 30" portion of the Centaurus cluster, which is concentrated around a heliocentric redshift of approximate to 3000 km s(-1) and is the most distant object for which this method has been attempted. Previous distance estimates for Cen 30 have varied significantly, and some have presented disagreements with the peculiar velocity predicted on the basis of full-sky redshift surveys of galaxies, motivating our investigation. Using our WFPC2 observations, we have found 61 candidate Cepheid variable stars with well-determined oscillation periods and mean magnitudes; however, a significant fraction of these candidates are likely to be nonvariable stars whose magnitude measurement errors happen to fit a Cepheid light curve of significant amplitude for some choice of period and phase. Through a maximum likelihood technique, we determine that we have observed 43 +/- 7 real Cepheids (with zero excluded at greater than 9 sigma) and that NGC 4603 has a distance modulus of 32.61(-0.10)(+0.11) (random, 1 sigma)(-0.25)(+0.24) (systematic, adding in quadrature), corresponding to a distance of 33.3(-1.5)(+1.7) (random, 1 sigma)(-3.7)(+3.8) (systematic) Mpc. This result is consistent with a number of recent estimates of the distance to NGC 4603 or Cen 30 and implies a small peculiar velocity consistent with predictions from the IRAS 1.2 Jy redshift survey if the galaxy lies in the foreground of the cluster. C1 Univ Calif Berkeley, Dept Astron, Berkeley, CA 94720 USA. Yale Univ, Dept Astron, New Haven, CT 06520 USA. Carnegie Inst Washington Observ, Pasadena, CA 91101 USA. CALTECH, Jet Prop Lab, NASA IPAC Extragalact Database Infrared Proc & An, Pasadena, CA 91125 USA. Dominion Astrophys Observ, Victoria, BC V8X 4M6, Canada. RP Newman, JA (reprint author), Univ Calif Berkeley, Dept Astron, 601 Campbell Hall, Berkeley, CA 94720 USA. EM jnewman@astro.berkeley.edu; zepf@astro.yale.edu; marc@astro.berkeley.edu; wendy@ociw.edu; barry@ipac.caltech.edu; Peter.Stetson@hia.nrc.ca; nancys@ipac.caltech.edu; rphelps@physics.oberlin.edu NR 48 TC 19 Z9 19 U1 0 U2 3 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD OCT 1 PY 1999 VL 523 IS 2 BP 506 EP 520 DI 10.1086/307764 PN 1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 239MG UT WOS:000082771500004 ER PT J AU Sakai, S Ferrarese, L Kennicutt, RC Grahm, JA Silbermann, NA Mould, JR Freedman, WL Bresolin, F Ford, HC Gibson, BK Han, MS Harding, P Hoessel, JG Huchra, JP Hughes, SM Illingworth, GD Kelson, D Macri, L Madore, BF Phelps, RL Saha, A Sebo, KM Setson, PB Turner, A AF Sakai, S Ferrarese, L Kennicutt, RC Grahm, JA Silbermann, NA Mould, JR Freedman, WL Bresolin, F Ford, HC Gibson, BK Han, MS Harding, P Hoessel, JG Huchra, JP Hughes, SM Illingworth, GD Kelson, D Macri, L Madore, BF Phelps, RL Saha, A Sebo, KM Setson, PB Turner, A TI The Hubble Space Telescope Extragalactic Distance Scale Key Project. XXIII. The discovery of Cepheids in NGC 3319 SO ASTROPHYSICAL JOURNAL LA English DT Article DE Cepheids; galaxies : distances and redshifts; galaxies : individual (NGC 3319) ID SPIRAL GALAXIES; EXTINCTION; PHOTOMETRY; STARS AB The distance to NGC 3319 has been determined from Cepheid variable stars as part of the Hubble Space Telescope Key Project on the Extragalactic Distance Scale. Thirteen and four epochs of observations, using filters F555W (V) and F814W (I), respectively, were made with the Wide Field Planetary Camera 2. Thirty-three Cepheid variables between periods of 8 and 47 days were discovered. Adopting a Large Magellanic Cloud distance modulus of 18.50 +/- 0.10 mag and extinction of E(V-I) = 0.13 mag, a true reddening-corrected distance modulus (based on an analysis employing the ALLFRAME software package) of 30.78 +/- 0.14 (random) +/-0.10 (systematic) mag and the extinction of EV-I) = 0.06 mag were determined for NGC 3319. This galaxy is the last galaxy observed for the HST H-o Key Project. C1 Kitt Peak Natl Observ, Natl Opt Astron Observ, Tucson, AZ 85726 USA. CALTECH, Jet Prop Lab, Ctr Infrared Proc & Anal, Pasadena, CA 91125 USA. Univ Arizona, Steward Observ, Tucson, AZ 85721 USA. Carnegie Inst Washington, Dept Terr Magnetism, Washington, DC 20015 USA. Australian Natl Univ, Mt Stromlo & Siding Spring Observ, Weston Creek, ACT 2611, Australia. Carnegie Inst Washington Observ, Pasadena, CA 91101 USA. European So Observ, D-85748 Garching, Germany. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Univ Colorado, Dept Astrophys & Planetary Sci, Ctr Astrophys & Space Astron, Boulder, CO 80309 USA. Avanti Corp, Fremont, CA 94538 USA. Univ Wisconsin, Dept Astron, Madison, WI 53706 USA. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England. Univ Calif Santa Cruz, Lick Observ, Santa Cruz, CA 95064 USA. Natl Res Council Canada, Herzberg Inst Astrophys, Dominion Astrophys Observ, Victoria, BC V8X 4M6, Canada. RP Sakai, S (reprint author), Kitt Peak Natl Observ, Natl Opt Astron Observ, POB 26732, Tucson, AZ 85726 USA. RI Gibson, Brad/M-3592-2015; OI Gibson, Brad/0000-0003-4446-3130; Macri, Lucas/0000-0002-1775-4859 NR 28 TC 22 Z9 22 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 OCT 1 PY 1999 VL 523 IS 2 BP 540 EP 558 DI 10.1086/307776 PN 1 PG 19 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 239MG UT WOS:000082771500006 ER PT J AU Beichman, C Helou, G Van Buren, D Ganga, K Desert, FX AF Beichman, C Helou, G Van Buren, D Ganga, K Desert, FX TI An Infrared Space Observatory upper limit to the low-mass star halo in the edge-on galaxy NGC 4565 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : halos; galaxies : individual (NGC 4565); galaxies : stellar content; infrared : galaxies ID LARGE-MAGELLANIC-CLOUD; DARK-MATTER; ROTATION CURVES; SPIRAL GALAXIES; MACHO PROJECT; BROWN DWARFS; V-BAND; NGC-4565; UNIVERSE; NGC-5907 AB We present deep ISOCAM observations taken at 4.5 mu m (LW1) in search of a faint halo surrounding the edge-on spiral galaxy NGC 4565. Such a halo might exist if the massive halo that is needed to explain the flat rotation curve of this galaxy were attributable to a population of faint, red objects. The upper limit, 5.4 kJy sr(-1) (3 sigma) at 20 kpc, reported here excludes a halo consisting of late-M dwarfs distributed in a spherical halo but not of lower luminosity brown dwarf stars. C1 CALTECH, Jet Prop Lab, Ctr Infrared Proc & Anal, Pasadena, CA 91109 USA. Observ Grenoble, Astrophys Lab, Grenoble, France. RP Beichman, C (reprint author), CALTECH, Jet Prop Lab, Ctr Infrared Proc & Anal, Pasadena, CA 91109 USA. NR 40 TC 4 Z9 4 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 OCT 1 PY 1999 VL 523 IS 2 BP 559 EP 565 DI 10.1086/307751 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 239MG UT WOS:000082771500007 ER PT J AU Lehnert, MD Heckman, TM Weaver, KA AF Lehnert, MD Heckman, TM Weaver, KA TI Very extended X-ray and H alpha emission in M82: Implications for the superwind phenomenon SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : active; galaxies : individual (M82); galaxies : ISM; galaxies : nuclei; galaxies : starburst ID STARBURST GALAXY M82; IONIZED-GAS; INTERSTELLAR CLOUDS; GALACTIC SUPERWINDS; DISK; WIND; HALO; SUPERNOVAE; TELESCOPE; CONTINUUM AB We discuss the properties and implications of the recently discovered 3.'5 x 0.'9 (3.7 x 0.9 kpc) region of spatially coincident X-ray and Her emission about 11' (11.6 kpc) to the north of the prototypical starburst/superwind galaxy M82. The total H alpha flux from this ridge of emission is 1.5 x 10(-13) ergs s(-1) cm(-2), or about 0.3% of the total M82 H alpha flux. The implied H alpha luminosity of this region is 2.4 x 10(38) ergs s(-1). Diffuse soft X-ray emission is seen over the same region by the ROSAT PSPC and HRI. The PSPC X-ray spectrum is fitted by thermal plasma absorbed by only the Galactic foreground column density (N-H = 3.7 x 10(20) cm(-2)) and having a temperature of kT = 0.80 +/- 0.17 keV. The total unabsorbed flux from the ridge is 1.4 x 10(-13) ergs cm(-2) s(-1) (similar to 2.2 x 10(38) ergs s(-1)), comprising about 0.7% of the total X-ray emission from M82. We evaluate the relationship of the X-ray/H alpha ridge to the M82 superwind. The H alpha emission could be excited by ionizing radiation from the starburst that propagates into the galactic halo along the cavity carved by the superwind. However, the main properties of the X-ray emission can all be explained as being due to shock heating driven as the superwind encounters a massive ionized cloud in the halo of M82 (possibly related to the tidal debris seen in H I in the interacting M81/M82/NGC 3077 system). This encounter drives a slow shock into the cloud, which contributes to the excitation of the observed H alpha emission. At the same time, a fast bow shock develops in the superwind just upstream of the cloud, and this produces the observed X-ray emission. This interpretation would imply that the superwind has an outflow speed of roughly 800 km s(-1), consistent with indirect estimates based on its general X-ray properties and the kinematics of the inner kiloparsec-scale region of H alpha filaments. The alternative, in which a much faster and more tenuous wind drives a fast radiative shock into a cloud that then produces both the X-ray and H alpha emission, is ruled out by the long radiative cooling times and the relatively quiescent Ha kinematics in this region. We suggest that wind-cloud interactions may be an important mechanism for generating X-ray and optical line emission in the halos of starbursts. Such interactions can establish that the wind has propagated out to substantially greater radii than could otherwise be surmised. This has potentially interesting implications for the fate of the outflowing metal-enriched material, and bears on the role of superwinds in the metal enrichment and heating of galactic halos and the intergalactic medium. In particular, the gas in the M82 ridge is roughly 2 orders of magnitude hotter than the minimum "escape temperature" at this radius, so this gas will not be retained by M82. C1 Max Planck Inst Extraterr Phys, D-85740 Garching, Germany. Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Lehnert, MD (reprint author), Max Planck Inst Extraterr Phys, Postfach 1603, D-85740 Garching, Germany. NR 62 TC 118 Z9 118 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 OCT 1 PY 1999 VL 523 IS 2 BP 575 EP 584 DI 10.1086/307762 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 239MG UT WOS:000082771500009 ER PT J AU Mitrofanov, IG Litvak, ML Briggs, MS Paciesas, WS Pendleton, GN Preece, RD Meegan, CA AF Mitrofanov, IG Litvak, ML Briggs, MS Paciesas, WS Pendleton, GN Preece, RD Meegan, CA TI Average emissivity curve of BATSE gamma-ray bursts with different intensities SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays : bursts; methods : statistical ID TIME DILATION AB Six intensity groups with similar to 150 BATSE gamma-ray bursts each are compared using average emissivity curves. Time stretch factors for each of the dimmer groups are estimated with respect to the brightest group, which serves as the reference, taking into account the systematics of counts-produced noise effects and choice statistics. A stretching/intensity anticorrelation is found with good statistical significance during the average back slopes of bursts. A stretch factor similar to 2 is found between the 150 dimmest bursts, with peak flux less than 0.45 photons cm(-2) s(-1), and the 147 brightest bursts, with peak flux greater than 4.1 photons cm(-2) s(-1). On the other hand, while a trend of increasing stretching factor may exist for rise fronts for bursts with decreasing peak flux from greater than 4.1 photons cm(-2) s(-1) down to 0.7 photons cm(-2) s(-1), the magnitude of the stretching factor is less than similar to 1.4 and is therefore inconsistent with stretching factor of back slope. C1 Moscow Space Res Inst, Moscow 117810, Russia. Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Mitrofanov, IG (reprint author), Moscow Space Res Inst, Profsojuznaya St 84-32, Moscow 117810, Russia. OI Preece, Robert/0000-0003-1626-7335 NR 19 TC 8 Z9 8 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 OCT 1 PY 1999 VL 523 IS 2 BP 610 EP 616 DI 10.1086/307749 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 239MG UT WOS:000082771500013 ER PT J AU Rood, RT Carretta, E Paltrinieri, B Ferraro, FR Pecci, FF Dorman, B Chieffi, A Straniero, O Buonanno, R AF Rood, RT Carretta, E Paltrinieri, B Ferraro, FR Pecci, FF Dorman, B Chieffi, A Straniero, O Buonanno, R TI The luminosity function of M3 SO ASTROPHYSICAL JOURNAL LA English DT Article DE globular clusters : individual (M3); stars : evolution; stars : late-type; stars : luminosity function, mass function ID HUBBLE-SPACE-TELESCOPE; GLOBULAR-CLUSTER SYSTEM; MASS SEGREGATION; PHOTOGRAPHIC PHOTOMETRY; SUBGIANT-BRANCH; BLUE STRAGGLERS; MAIN-SEQUENCE; RR LYRAE; STARS; AGES AB We present a high-precision, large-sample luminosity function (LF) for the Galactic globular duster M3. With a combination of ground-based and Hubble Space Telescope data we cover the entire radial extent of the cluster. The observed LF is well fitted by canonical standard stellar models from the red giant branch (RGB) tip to below the main-sequence turnoff point. Specifically, neither the RGB LF bump nor subgiant branch LF indicate any breakdown in the standard models. On the main sequence we find evidence for a flat initial mass function and for mass segregation due to the dynamical evolution of the cluster. C1 Univ Virginia, Dept Astron, Charlottesville, VA 22903 USA. Osserv Astron Padova, I-35122 Padua, Italy. Univ Roma La Sapienza, Ist Astron, I-00161 Rome, Italy. European So Observ, D-85748 Garching, Germany. Osservatorio Astron Bologna, I-40126 Bologna, Italy. Staz Astron Cagliari, I-09012 Capoterra, Italy. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. CNR, Ist Astrofis Spaziale, I-00044 Frascati, Italy. Osservatorio Astron Collurania, I-64100 Teramo, Italy. Osserv Astron Roma, I-00040 Monte Porzio Catone, Italy. RP Univ Virginia, Dept Astron, POB 3818, Charlottesville, VA 22903 USA. EM rtr@virginia.edu; carretta@astrpd.pd.astro.it; barbara@coma.mporzio.astro.it; ferraro@astbo3.bo.astro.it; flavio@astbo3.bo.astro.it; dorman@veris.gsfc.nasa.gov; alessandro@altachiara.ias.rm.cnr.it; straniero@astrte.te.astro.it; buonanno@coma.mporzio.astro.it RI Carretta, Eugenio/O-9476-2015; OI Carretta, Eugenio/0000-0002-1569-1911; Chieffi, Alessandro/0000-0002-3589-3203 NR 61 TC 38 Z9 38 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD OCT 1 PY 1999 VL 523 IS 2 BP 752 EP 762 DI 10.1086/307767 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 239MG UT WOS:000082771500026 ER PT J AU Kopeikin, SM Ozernoy, LM AF Kopeikin, SM Ozernoy, LM TI Post-Newtonian theory for precision Doppler measurements of binary star orbits SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries : general; gravitation; pulsars : general; relativity; techniques : interferometric ID RELATIVISTIC CELESTIAL MECHANICS; GENERAL-RELATIVITY; REFERENCE SYSTEMS; APSIDAL MOTION; GRAVITY; PULSARS; PARAMETERS; EQUATIONS; FIELD; TESTS AB The determination of velocities of stars from precise Doppler measurements is described here using a relativistic theory of astronomical reference frames to determine the Keplerian and post-Keplerian parameters of binary systems. Seven reference frames are introduced: (1) the proper frame of a particle emitting light, (2) the star-centered reference frame, (3) the barycentric frame of the binary, (4) the barycentric frame of the Galaxy, (5) the barycentric frame of the solar system, (6) the geocentric frame, and (7) the topocentric frame of observer at the Earth. We apply successive Lorentz transformations and the relativistic equation of light propagation to establish the exact treatment of Doppler effect in binary systems both in special and general relativity theories. As a result, the Doppler shift is a sum of (1) linear in c-l terms, which include the ordinary Doppler effect and its variation due to the secular radial acceleration of the binary with respect to observer; (2) terms proportional to c(-2), which include the contributions from the quadratic Doppler effect caused by the relative motion of binary star with respect to the solar system, the motion of the particle emitting light and diurnal rotational motion of observer, orbital motion of the star around the binary's barycenter, and the orbital motion of the Earth; and (3) terms proportional to c-2, which include the contributions from redshifts due to gravitational fields of the star, the star's companion, the Galaxy, the solar system, and the Earth. After parameterization of the binary's orbit, we find that the presence of periodically changing terms in the Doppler shift enables us to disentangle different terms and measure, along with the well-known Keplerian parameters of the binary, four additional post-Keplerian parameters, which characterize (1) the relativistic advance of the periastron; (2) a combination of the quadratic Doppler and gravitational shifts associated with the orbital motion of the primary relative to the binary's barycenter and the companion's gravitational field, respectively; (3) the amplitude of the "gravitational lensing" contribution to the Doppler shift; and (4) the usual inclination angle of the binary's orbit, i. We briefly discuss the feasibility of practical implementation of these theoretical results, which crucially depends on further progress in the technique of precision Doppler measurements. C1 Univ Jena, Inst Theoret Phys, D-07743 Jena, Germany. George Mason Univ, Dept Phys & Astron, Fairfax, VA 22030 USA. George Mason Univ, Inst Computat Sci & Informat, Fairfax, VA 22030 USA. NASA, Astron & Solar Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Univ Jena, Inst Theoret Phys, D-07743 Jena, Germany. EM smk@tpi.uni-jena.de; ozemoy@science.gmu.edu RI Kopeikin, Sergei/A-8857-2009 OI Kopeikin, Sergei/0000-0002-4866-1532 NR 44 TC 20 Z9 20 U1 1 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD OCT 1 PY 1999 VL 523 IS 2 BP 771 EP 785 DI 10.1086/307759 PN 1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 239MG UT WOS:000082771500028 ER PT J AU Diaz, MP Hubeny, I AF Diaz, MP Hubeny, I TI The eclipsing cataclysmic variable V347 Puppis revisited SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; binaries : close; novae, cataclysmic variables; stars : individual (V347 Puppis) ID X-RAY BINARIES; ACCRETION DISKS; EMISSION-LINES; RADIAL-VELOCITY; Z-CHAMAELEONTIS; SECONDARY STAR; URSAE-MAJORIS; DWARF NOVAE; SPECTRA; TELESCOPE AB An observational study of the nova-like cataclysmic binary V347 Pup (LB 1800) is presented. An analysis of optical and UV spectroscopy is made with the aim of defining the physical properties of the binary system and of the accretion disk. The study of the line profile behavior and the determination of the primary radial velocity are pursued using a variety of methods. We also present the detection of secondary spectral signatures that were used to derive the object's radial velocity curve. A tentative companion spectral classification and spectroscopic parallax are also given. A Doppler tomography study of Balmer and He II lines lead us to an estimate of the average surface brightness distribution of these lines in the accretion disk. Exploratory modeling of the accretion disk in V347 Pup and comparison with UV observations is carried on using the system parameters constrained by the radial velocity study. C1 Univ Sao Paulo, Inst Astron & Geofis, Sao Paulo, Brazil. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Diaz, MP (reprint author), Univ Sao Paulo, Inst Astron & Geofis, CP3386, Sao Paulo, Brazil. RI diaz, marcos/I-7233-2013 NR 53 TC 10 Z9 10 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 OCT 1 PY 1999 VL 523 IS 2 BP 786 EP 796 DI 10.1086/307745 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 239MG UT WOS:000082771500029 ER PT J AU Sittler, EC Guhathakurta, M AF Sittler, EC Guhathakurta, M TI Semiempirical two-dimensional magnetohydrodynamic model of the solar corona and interplanetary medium SO ASTROPHYSICAL JOURNAL LA English DT Article DE interplanetary medium; MHD; solar wind; Sun : corona; Sun : magnetic fields ID ULYSSES OBSERVATIONS; DENSITY STRUCTURE; ALFVEN WAVES; WIND; HOLE; ACCELERATION; FLOW; AU; DISCONTINUITIES; CONSTRAINTS AB We have developed a two-dimensional semiempirical MHD model of the solar corona and solar wind. The model uses empirically derived electron density profiles from white-light coronagraph data measured during the Skylab period and an empirically derived model of the magnetic field which is fitted to observed streamer topologies, which also come from the white-light coronagraph data. The electron density model comes from that developed by Guhathakurta and coworkers. The electron density model is extended into interplanetary space by using electron densities derived from the Ulysses plasma instrument. The model also requires an estimate of the solar wind velocity as a function of heliographic latitude and radial component of the magnetic field at 1 AU, both of which can be provided by the Ulysses spacecraft. The model makes estimates as a function of radial distance and latitude of various fluid parameters of the plasma such as flow velocity V, effective temperature T-eff, and effective heat flux q(eff), which are derived from the equations of conservation of mass, momentum, and energy, respectively. The term "effective" indicates that wave contributions could be present. The model naturally provides the spiral pattern of the magnetic field far from the Sun and an estimate of the large-scale surface magnetic field at the Sun, which we estimate to be similar to 12-15 G. The magnetic field model shows that the large-scale surface magnetic field is dominated by an octupole term. The model is a steady state calculation which makes the assumption of azimuthal symmetry and solves the various conservation equations in the rotating frame of the Sun. The conservation equations are integrated along the magnetic field direction in the rotating frame of the Sun, thus providing a nearly self-consistent calculation of the fluid parameters. The model makes a minimum number of assumptions about the physics of the solar corona and solar wind and should provide a very accurate empirical description of the solar corona and solar wind. Once estimates of mass density rho, flow velocity V, effective temperature T-eff, effective heat flux q(eff), and magnetic field B are computed from the model and waves are assumed unimportant, all other plasma parameters such as Mach number, Alfven speed, gyrofrequency, etc. can be derived as a function of radial distance and latitude from the Sun. The model can be used as a planning tool for such missions as Solar Probe and provide an empirical framework for theoretical models of the solar corona and solar wind. The model will be used to construct a semiempirical MHD description of the steady state solar corona and solar wind using the SOHO Large Angle Spectrometric Coronagraph (LASCO) polarized brightness white-light coronagraph data, SOHO Extreme Ultraviolet Imaging Telescope data, and Ulysses plasma data. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Catholic Univ Amer, Dept Phys, Washington, DC 20064 USA. RP Sittler, EC (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 40 TC 89 Z9 91 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 OCT 1 PY 1999 VL 523 IS 2 BP 812 EP 826 PN 1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 239MG UT WOS:000082771500032 ER PT J AU Buti, B Galinski, VL Shevchenko, VI Lakhina, GS Tsurutani, BT Goldstein, BE Diamond, P Medvedev, MV AF Buti, B Galinski, VL Shevchenko, VI Lakhina, GS Tsurutani, BT Goldstein, BE Diamond, P Medvedev, MV TI Evolution of nonlinear Alfven waves in streaming inhomogeneous plasmas SO ASTROPHYSICAL JOURNAL LA English DT Article DE MHD; plasmas; solar-terrestrial relations; solar wind; waves ID SOLAR-WIND; MAGNETOHYDRODYNAMIC TURBULENCE; FLUID MODELS; BETA PLASMA; SOLITONS; PARALLEL; FLUCTUATIONS; EQUATION; SYSTEMS; CHAOS AB A nonlinear evolution equation for Alfven waves, propagating in streaming plasmas with nonuniform densities and inhomogeneous magnetic fields, is obtained by using the reductive perturbation technique. The governing equation is a modified derivative nonlinear Schrodinger (MDNLS) equation. The numerical solution of this equation shows that inhomogeneities exhibit their presence as an effective dissipation. The spatiotemporal evolution of long-wavelength Alfvenic fluctuations shows that the wave steepens as it propagates. High-frequency radiation is also observed in our simulations. Unlike coherent Alfven waves in homogeneous plasmas, which can become noncoherent/chaotic only in the presence of a driver, MDNLS evolves into noncoherent/turbulent state without any driver simply because of inhomogeneities. This clearly indicates that the integrability property of the derivative nonlinear Schrodinger equation, which allows coherent solitary solutions, is destroyed by inhomogeneities. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Calif San Diego, Scripps Inst Oceanog, La Jolla, CA 92093 USA. Univ Calif San Diego, Dept Elect & Comp Engn, La Jolla, CA 92093 USA. Univ Calif San Diego, Dept Phys, La Jolla, CA 92093 USA. RP Buti, B (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM bbuti@jplsp.jpl.nasa.gov RI Lakhina, Gurbax /C-9295-2012; OI Lakhina, Gurbax /0000-0002-8956-486X NR 44 TC 37 Z9 37 U1 1 U2 7 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD OCT 1 PY 1999 VL 523 IS 2 BP 849 EP 854 DI 10.1086/307743 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 239MG UT WOS:000082771500035 ER PT J AU Grady, CA Woodgate, B Bruhweiler, FC Boggess, A Plait, P Lindler, DJ Clampin, M Kalas, P AF Grady, CA Woodgate, B Bruhweiler, FC Boggess, A Plait, P Lindler, DJ Clampin, M Kalas, P TI Hubble Space Telescope space telescope imaging spectrograph coronagraphic imaging of the Herbig Ae star Ab Aurigae SO ASTROPHYSICAL JOURNAL LA English DT Article DE circumstellar matter; planetary systems; stars : individual (AB Aurigae); stars : pre-main-sequence ID MODEL SCATTERING ENVELOPES; YOUNG STELLAR OBJECTS; CIRCUMSTELLAR DISKS; DUST AB We present the first broadband, coronagraphic Hubble Space Telescope images of the bright, optically visible, isolated Herbig Ae star AB Aurigae. The Space Telescope Imaging Spectrograph (STIS) images reveal extended circumstellar nebulosity (r approximate to 1300 AU) covering the region of the millimeter continuum and CO disk. The structure is observed in the disk on spatial scales down to 0." 1 (14 AU) and exhibits a north-south asymmetry. A comparison of the STIS data with scattering models for flared disks or disks + envelopes suggests that the disk inclination is i less than or equal to 45 degrees from the plane of the sky. C1 NOAO STIS, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. Catholic Univ Amer, Inst Astrophys & Computat Sci, Washington, DC 20064 USA. Adv Comp Cincepts Inc, Potomac, MD 20854 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. RP Grady, CA (reprint author), NOAO STIS, Goddard Space Flight Ctr, Code 681, Greenbelt, MD 20771 USA. RI Clampin, mark/D-2738-2012 NR 19 TC 104 Z9 104 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 OCT 1 PY 1999 VL 523 IS 2 BP L151 EP L154 DI 10.1086/312270 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 239MJ UT WOS:000082771700013 ER PT J AU Sahu, MS Landsman, W Bruhweiler, FC Gull, TR Bowers, CA Lindler, D Feggans, K Barstow, MA Hubeny, I Holberg, JB AF Sahu, MS Landsman, W Bruhweiler, FC Gull, TR Bowers, CA Lindler, D Feggans, K Barstow, MA Hubeny, I Holberg, JB TI The D/H ratio in interstellar gas toward G191-B2B SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM : abundances; ultraviolet : ISM; white dwarfs ID SPATIAL VARIATIONS; DEUTERIUM; SIGHT; CAPELLA; LINES AB Recent analysis of Goddard High-Resolution Spectrograph (GHRS) echelle spectra suggests similar to 30% variations in the D/H abundance ratio along the line of sight to the nearby (69 pc) hot white dwarf (WD) G191-B2B (Vidal-Madjar et al.). Variations in the D/H ratio on such short length scales imply nonuniform production/destruction of deuterium and an inefficient mixing of gas in the local interstellar medium (LISM). We reinvestigate the question of the spatial variation of the local D/H abundance using both archival GHRS spectra and new echelle spectra of G191-B2B obtained with the Space Telescope Imaging Spectrograph (STIS) aboard the Hubble Space Telescope. The STIS spectra were obtained in the high-resolution (E140H) mode and cover the wavelength region ranging from 1140 to 1700 Angstrom. Our analysis uses stratified line-blanketed non-LTE model atmosphere calculations to determine the shape of the intrinsic WD Ly alpha profile and to estimate the WD photospheric contamination of the interstellar lines. Although three velocity components were reported previously toward G191-B2B, we deduce only two velocity components. The first component is at v(hel) similar to 8.6 km s(,)(-1) and the second is at v(hel) similar to 19.3 km s(-1) which we identify with the local interstellar cloud (LIC). From the STIS data, we derive D/H = 1.60(+0.27)(+0.39) x 10(-5) for the LIC component and D/H s 1.26 x 10(-5) for the 8.6 km s(-1) component (uncatainties denote 2 sigma or 95% confidence limits). The derived D/H values in both components are consistent with (D/H)(LIC) = (1.5 +/- 0.1) x 10(-5), which was determined by Linsky in 1998. The STIS data provide no evidence for local or component-to-component variation in the D/H ratio. Our reanalysis of the GHRS data gives essentially the same results as Vidal-Madjar et al., despite using two velocity components for the profile fitting (vs. three by Vidal-Madjar et al.) and a more physically realistic WD Ly alpha profile for G191-B2B. The GHRS data indicate a component-to-component variation as well as a variation of the D/H ratio in the LISM, neither of which are supported by the newer STIS data, The D I absorption in the GHRS spectrum is shallower than in the STIS spectrum. The most probable cause for this difference in the two data sets is the characterization of the background due to scattered light in the GHRS and STIS spectrographs. The D/H ratios derived are sensitive to the background-subtraction procedures employed. The two-dimensional MAMA detectors of STIS measure both the spatial and wavelength dependences of scattered light, allowing more accurate scattered-light corrections than was possible with GHRS. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Natl Opt Astron Observ, Tucson, AZ 85726 USA. Raytheon Informat Technol & Sci Serv, Lanham, MD 20706 USA. Catholic Univ Amer, Dept Phys, Inst Astrophys & Computat Sci, Washington, DC 20064 USA. Adv Comp Concepts Inc, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Leicester, Dept Phys & Astron, Leicester LE1 RH, Leics, England. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. RP Sahu, MS (reprint author), NASA, Goddard Space Flight Ctr, Code 681, Greenbelt, MD 20771 USA. RI Gull, Theodore/D-2753-2012 OI Gull, Theodore/0000-0002-6851-5380 NR 25 TC 14 Z9 14 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 OCT 1 PY 1999 VL 523 IS 2 BP L159 EP L163 DI 10.1086/312278 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 239MJ UT WOS:000082771700015 ER PT J AU Sturrock, PA Scargle, JD Walther, G Wheatland, MS AF Sturrock, PA Scargle, JD Walther, G Wheatland, MS TI Rotational signature and possible r-mode signature in the GALLEX solar neutrino data SO ASTROPHYSICAL JOURNAL LA English DT Article DE elementary particles; methods : statistical; Sun : interior; Sun : particle emission ID RESONANT AMPLIFICATION; SUNSPOT NUMBER; SPACED DATA; FLUX; OSCILLATIONS; PERIODICITY; MATTER; SUN; PRECESSION; MODULATION AB Recent analysis of the Homestake data has yielded evidence that the solar neutrino flux varies in time-more specifically, that it exhibits a periodic variation that may be attributed to rotational modulation occurring deep in the solar interior, either in the tachocline or in the radiative zone. Here we present a spectral analysis of the GALLEX data that yields supporting evidence for this rotational modulation. The most prominent peak in the power spectrum occurs at the synodic frequency of 13.08 yr(-1) (cycles per year) and is estimated to be significant at the 0.1% level. It appears that the most likely interpretation of this modulation is that the electron neutrinos have nonzero magnetic moment, so that they oscillate between left-hand (detectable) and right-hand (nondetectable) chiralities as they traverse the Sun's internal magnetic field. This oscillation could account for the neutrino deficit. The second strongest peak in the GALLEX spectrum has a period of 52 days, and this period occurs in other solar data as well. We suggest that this periodicity and also the Rieger 154 day periodicity, which shows up in many solar parameters and in the Homestake data, are due to r-mode oscillations. C1 Stanford Univ, Ctr Space Sci & Astrophys, Stanford, CA 94305 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Stanford Univ, Dept Stat, Stanford, CA 94305 USA. Univ Sydney, Sch Phys, Special Res Ctr Theoret Astrophys, Sydney, NSW 2006, Australia. RP Stanford Univ, Ctr Space Sci & Astrophys, Varian 302G, Stanford, CA 94305 USA. RI Wheatland, Michael/G-1958-2016 OI Wheatland, Michael/0000-0001-5100-2354 NR 45 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 EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD OCT 1 PY 1999 VL 523 IS 2 BP L177 EP L180 DI 10.1086/312269 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 239MJ UT WOS:000082771700018 ER PT J AU Pattinson, TJ Gibson, CR Manuel, FK Bishop, SL March, WF AF Pattinson, TJ Gibson, CR Manuel, FK Bishop, SL March, WF TI The effects of betaxolol hydrochloride ophthalmic solution on intraocular pressures during transient microgravity SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Article DE betaxolol; glaucoma; weightlessness; weightlessness simulation ID TONO-PEN; BETA-BLOCKERS; GLAUCOMA; TIMOLOL; TONOMETER AB Background: Intraocular pressure (IOP) has been found to increase during microgravity. After peaking in the first few hours of orbital flight, IOP slowly decreases to a level that is slightly elevated above baseline IOP's. These modest elevations in IOP do not require treatment. just as in 1-G, a clinically significant elevation of IOP that occurred during spaceflight would require treatment. We are not aware of previous studies of the efficacy of IOP lowering agents under conditions of microgravity. Methods: This double-masked, placebo-controlled study measured the IOP's of 11 adult subjects (22 eyes) at baseline, preflight, and zero-gravity aboard the NASA KC-135 aircraft, and postflight. One eye of each of the subjects was treated with betaxolol hydrochloride ophthalmic solution 0.5%, while the contralateral eye was treated With normal saline placebo, for 7 d prior to parabolic flight. IOP's were measured by the Tone-Pen 2, a gravity independent tonometer. Results: A modest, but statistically significant reduction of 2.4 mmHg in mean IOP was noted in betaxolol treated eyes at the time of preflight measurement. During zero-C, the mean IOP's of both betaxolol treated eyes and placebo treated eyes increased approximately 20% over preflight levels. Postflight IOP's were similar to preflight IOP's. Conclusions: The effect of betaxolol on the IOP of eyes treated with for 1 wk prior to exposure to microgravity was statistically significant, but may lack clinical significance in normal eyes. Further research needs to be done to determine the efficacy during microgravity of betaxolol and other agents, in subjects who have upper normal to slightly elevated IOP's at 1 G. C1 Univ Texas, Med Branch, Galveston, TX 77550 USA. NASA, Lyndon B Johnson Space Ctr, Med Operat Branch, Houston, TX 77058 USA. Univ Texas, Med Branch, Dept Prevent Med & Community Hlth, Galveston, TX 77550 USA. Univ Texas, Med Branch, Dept Ophthalmol, Galveston, TX 77550 USA. RP Pattinson, TJ (reprint author), Lyndon B Johnson Space Ctr, SD-2,2101 NASA Rd 1, Houston, TX 77058 USA. NR 23 TC 1 Z9 2 U1 1 U2 1 PU AEROSPACE MEDICAL ASSOC PI ALEXANDRIA PA 320 S HENRY ST, ALEXANDRIA, VA 22314-3579 USA SN 0095-6562 J9 AVIAT SPACE ENVIR MD JI Aviat. Space Environ. Med. PD OCT PY 1999 VL 70 IS 10 BP 1012 EP 1017 PG 6 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA 241ZP UT WOS:000082914000010 PM 10519481 ER PT J AU Fagette, S Somody, L Bouzeghrane, F Eward, K Briggs, R Viso, M Gallo-Bon, N Gharib, C Gauquelin, G AF Fagette, S Somody, L Bouzeghrane, F Eward, K Briggs, R Viso, M Gallo-Bon, N Gharib, C Gauquelin, G TI Biochemical characteristics of beta-adrenoceptors in rats after an 18-day spaceflight (LMS-STS78) SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Article DE microgravity; beta-adrenoceptors; affinity constant; maximal binding capacity; corticosteroids ID WEIGHTLESSNESS AB Background: To ascertain whether there was autonomic adaptation with the development of adrenoceptor hypersensitivity under microgravity, the biochemical properties of the beta-adrenoceptors were determined using (I-125)iodocyanopindolol (ICYP) binding in rats flown for 18 d onboard the space shuttle. Methods: This study was performed on heart and kidneys of 3 groups of 12 animals: the flight and 2 ground control (vivarium and AEM) groups. To distinguish the possible role of the corticosteroids, half of each animal group was bilaterally adrenalectomized (ADX rats) with an aldosterone and corticosterone supplementation while the other half was SHAM operated. Results: The Scatchard analysis of the ICYP-binding in both organs revealed no significant alterations in the dissociation constant (Kd) and in the maximal binding capacity (Bmax) between SHAM flight and control groups. The Kd of the beta-adrenoceptors in the cardiac atria of the SHAM flight rats (74 +/- 5 pm) was significantly higher (p < 0.05) than in those of the ADX flight rats (60 +/- 3 pm) while the Bmax was nonsignificantly higher (1925 +/- 370 in SHAM flight rats vs. 1482 +/- 283 fmol.mg(-1) protein in ADX flight rats). No significant change was determined for the Bmax and Kd values in the kidneys of the ADX and SHAM flight rats. Conclusions: This work performed on animals did not show any obvious effect of microgravity on the beta-adrenergic function in the heart and kidneys. Inflight rodent sacrifice protocols should definitely ensure assessment of the influence of microgravity on the animals. C1 Fac Med Lyon Grange Blanche, Environm Physiol Lab, F-69373 Lyon 08, France. Ctr Natl Etud Spatiales, Paris, France. Florida Tech, Div Cellular & Mol Biol, Melbourne, FL USA. NASA, Ames Res Ctr, Lockheed Martin, Moffett Field, CA 94035 USA. RP Fagette, S (reprint author), Fac Med Lyon Grange Blanche, Environm Physiol Lab, 8 Ave Rockefeller, F-69373 Lyon 08, France. NR 11 TC 5 Z9 5 U1 0 U2 0 PU AEROSPACE MEDICAL ASSOC PI ALEXANDRIA PA 320 S HENRY ST, ALEXANDRIA, VA 22314-3579 USA SN 0095-6562 J9 AVIAT SPACE ENVIR MD JI Aviat. Space Environ. Med. PD OCT PY 1999 VL 70 IS 10 BP 1025 EP 1028 PG 4 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA 241ZP UT WOS:000082914000012 PM 10519483 ER PT J AU Potter, CS AF Potter, CS TI Terrestrial biomass and the effects of deforestation on the global carbon cycle - Results from a model of primary production using satellite observations SO BIOSCIENCE LA English DT Article ID NET PRIMARY PRODUCTION; NDVI DATA SET; INTERANNUAL VARIATION; ECOSYSTEM PRODUCTION; CLIMATE VARIABILITY; SOLAR-RADIATION; NITROGEN; FOREST; ALLOCATION; EXCHANGE 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 54 TC 87 Z9 97 U1 3 U2 27 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 OCT PY 1999 VL 49 IS 10 BP 769 EP 778 DI 10.2307/1313568 PG 10 WC Biology SC Life Sciences & Biomedicine - Other Topics GA 241PD UT WOS:000082891000005 ER PT J AU Entekhabi, D Asrar, GR Betts, AK Beven, KJ Bras, RL Duffy, CJ Dunne, T Koster, RD Lettenmaier, DP McLaughlin, DB Shuttleworth, WJ van Genuchten, MT Wei, MY Wood, EF AF Entekhabi, D Asrar, GR Betts, AK Beven, KJ Bras, RL Duffy, CJ Dunne, T Koster, RD Lettenmaier, DP McLaughlin, DB Shuttleworth, WJ van Genuchten, MT Wei, MY Wood, EF TI An agenda for land surface hydrology research and a call for the second international hydrological decade SO BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY LA English DT Article ID SOIL AB Hydrologic research at the interface between the atmosphere and land surface is undergoing a dramatic change in focus, driven by new societal priorities, emerging technologies, and better understanding of the earth system. In this paper an agenda for land surface hydrology research is proposed in order to open the debate for more comprehensive prioritization of science and application activities in the hydrologic sciences. Sets of priority science questions are posed and research strategies for achieving progress are identified. The proposed research agenda is also coupled with ongoing international data collection programs. The driving science questions and related research agenda lead to a call for the second International Hydrologic Decade. This activity will help to ensure that hydrology starts the new millennium as a coherent and vital discipline. C1 MIT, Cambridge, MA 02139 USA. NASA Headquarters, Washington, DC USA. Atmospher Res, Pittsford, VT USA. Univ Lancaster, Lancaster, England. Penn State Univ, University Pk, PA 16802 USA. Univ Calif Santa Barbara, Santa Barbara, CA 93106 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Washington, Seattle, WA 98195 USA. Univ Arizona, Tucson, AZ USA. USDA, US Salin Lab, Riverside, CA USA. Princeton Univ, Princeton, NJ 08544 USA. RP Entekhabi, D (reprint author), MIT, 48-331, Cambridge, MA 02139 USA. RI Beven, Keith/F-8707-2011; Betts, Alan/H-5282-2011; Koster, Randal/F-5881-2012; van Genuchten, Martinus/K-6892-2013; lettenmaier, dennis/F-8780-2011; Dunne, Thomas/B-6374-2014; OI Koster, Randal/0000-0001-6418-6383; van Genuchten, Martinus/0000-0003-1654-8858; lettenmaier, dennis/0000-0003-3317-1327; Dunne, Thomas/0000-0002-5281-6517; Wood, Eric/0000-0001-7037-9675 NR 10 TC 128 Z9 141 U1 2 U2 18 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 OCT PY 1999 VL 80 IS 10 BP 2043 EP 2058 DI 10.1175/1520-0477(1999)080<2043:AAFLSH>2.0.CO;2 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 239UJ UT WOS:000082787800005 ER PT J AU Curry, JA Clayson, CA Rossow, WB Reeder, R Zhang, YC Webster, PJ Liu, G Sheu, RS AF Curry, JA Clayson, CA Rossow, WB Reeder, R Zhang, YC Webster, PJ Liu, G Sheu, RS TI High-resolution satellite-derived dataset of the surface fluxes of heat, freshwater, and momentum for the TOGA COARE IOP SO BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY LA English DT Article ID ATMOSPHERE RESPONSE EXPERIMENT; PACIFIC WARM POOL; WESTERN EQUATORIAL PACIFIC; AIR-SEA FLUXES; TEMPERATURE DIFFERENCE; WATER-VAPOR; OCEAN; RADIATION; RAINFALL; BUDGETS AB An integrated approach is presented for determining from several different satellite datasets all of the components of the tropical sea surface fluxes of heat, freshwater, and momentum. The methodology for obtaining the surface turbulent and radiative fluxes uses physical properties of the atmosphere and surface retrieved from satellite observations as inputs into models of the surface turbulent and radiative flux processes. The precipitation retrieval combines analysis of satellite microwave brightness temperatures with a statistical model employing satellite observations of visible/infrared radiances. A high-resolution dataset has been prepared for the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE) intensive observation period (TOP), with a spatial resolution of 50 lan and temporal resolution of 3 h. The high spatial resolution is needed to resolve the diurnal and mesoscale storm-related variations of the fluxes. The fidelity of the satellite-derived surface fluxes is examined by comparing them with in situ measurements obtained from ships and aircraft during the TOGA. COARE IOP and from vertically integrated budgets of heat and freshwater for the atmosphere and ocean. The root-mean-square differences between the satellite-derived and in situ fluxes are dominated by limitations in the satellite sampling; these are reduced when some averaging is done, particularly for the precipitation (which is from a statistical algorithm) and the surface solar radiation (which uses spatially sampled satellite pixels). Nevertheless, the fluxes are determined with a useful accuracy, even at the highest temporal and spatial resolution. By compiling the fluxes at such high resolution, users of the dataset can decide whether and how to average for particular purposes. For example, over time, space, or similar weather events. C1 Univ Colorado, Dept Aerosp Engn Sci, Program Atmospher & Ocean Sci, Ctr Engn, Boulder, CO 80309 USA. Purdue Univ, Dept Earth & Atmospher Sci, W Lafayette, IN 47907 USA. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Columbia Univ, Dept Appl Phys, New York, NY 10027 USA. Florida State Univ, Dept Meteorol, Tallahassee, FL 32306 USA. Natl Ctr Atmospher Res, Boulder, CO 80307 USA. RP Curry, JA (reprint author), Univ Colorado, Dept Aerosp Engn Sci, Program Atmospher & Ocean Sci, Ctr Engn, Campus Box 429, Boulder, CO 80309 USA. RI Liu, Guosheng/D-3479-2011; Rossow, William/F-3138-2015 OI Liu, Guosheng/0000-0001-7899-6125; NR 54 TC 39 Z9 41 U1 2 U2 5 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 OCT PY 1999 VL 80 IS 10 BP 2059 EP 2080 DI 10.1175/1520-0477(1999)080<2059:HRSDDO>2.0.CO;2 PG 22 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 239UJ UT WOS:000082787800006 ER PT J AU Zak, M AF Zak, M TI Quantum computing - Introduction SO CHAOS SOLITONS & FRACTALS LA English DT Editorial Material C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Zak, M (reprint author), CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NR 0 TC 1 Z9 1 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0960-0779 J9 CHAOS SOLITON FRACT JI Chaos Solitons Fractals PD OCT PY 1999 VL 10 IS 10 BP XI EP XII PG 2 WC Mathematics, Interdisciplinary Applications; Physics, Multidisciplinary; Physics, Mathematical SC Mathematics; Physics GA 200XD UT WOS:000080564700002 ER PT J AU Zak, M AF Zak, M TI Quantum analog computing SO CHAOS SOLITONS & FRACTALS LA English DT Article AB Quantum analog computing is based upon similarity between mathematical formalism of quantum mechanics and phenomena to be computed. It exploits a dynamical convergence of several competing phenomena to an attractor which can represent an extremum of a function, an image, a solution to a system of ODE, or a stochastic process. In this paper, a quantum version of recurrent neural nets (QRN) as an analog computing device is discussed. This concept is introduced by incorporating classical feedback loops into conventional quantum networks. It is shown that the dynamical evolution of such networks, which interleave quantum evolution with measurement and reset operations, exhibit novel dynamical properties. Moreover, decoherence in quantum recurrent networks is less problematic than in conventional quantum network architectures due to the modest phase coherence times needed for network operation. Application of QRN to simulation of chaos, turbulence, NP-problems, as well as data compression demonstrate computational speedup and exponential increase of information capacity. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 CALTECH, Jet Prop Lab, Ultracomp Grp, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. RP Zak, M (reprint author), CALTECH, Jet Prop Lab, Ultracomp Grp, Ctr Space Microelect Technol, Mail Stop 126-347, Pasadena, CA 91109 USA. NR 13 TC 13 Z9 13 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0960-0779 J9 CHAOS SOLITON FRACT JI Chaos Solitons Fractals PD OCT PY 1999 VL 10 IS 10 BP 1583 EP 1620 DI 10.1016/S0960-0779(98)00215-X PG 38 WC Mathematics, Interdisciplinary Applications; Physics, Multidisciplinary; Physics, Mathematical SC Mathematics; Physics GA 200XD UT WOS:000080564700003 ER PT J AU Zhang, RH Rothstein, LM Busalacchi, AJ AF Zhang, RH Rothstein, LM Busalacchi, AJ TI Interannual and decadal variability of the subsurface thermal structure in the Pacific Ocean: 1961-90 SO CLIMATE DYNAMICS LA English DT Article ID SEA-SURFACE TEMPERATURE; EL-NINO; NORTH PACIFIC; CLIMATE VARIABILITY; SOUTHERN OSCILLATION; INTERDECADAL VARIABILITY; ATMOSPHERE SYSTEM; MODEL; CIRCULATIONS; PATTERNS AB Heat content anomalies are analyzed to understand subsurface variability on both interannual and decadal time scales in the Pacific ocean, with a particular focus on the evolving basinwide patterns and oceanic connections between the extratropics and tropics. Various analyses indicate two distinct modes, one interannual and the other decadal, that involve the tropics and the North Pacific subtropical gyre, respectively. Interannual variability is associated with Fl Nino in the tropics, with a prominent "see-saw" pattern alternately on and off the equator and in the east and west, respectively. The interannual cycle features a coherent propagation of subsurface signals around the tropical Pacific, eastward along the equator but westward off the equator at 10-15 degrees N. Decadal signals are dominant in the subtropics and midlatitudes but also have a tropical component that appears to be independent of interannual variations. An oceanic connection can be seen between subsurface anomalies in the midlatitudes, in the subtropics and tropics on decadal time scales. Subsurface thermal anomalies associated with midlatitude decadal variability can propagate through the subtropics into the tropics, which may modulate the intensity of interannual variability in the tropics. For example, in the middle and late 1970s, a significant warm temperature anomaly appeared to penetrate into the western and central tropics at depth, warming the tropical upper ocean and depressing the thermocline. During the development of El Nino, therefore, an extratropically preconditioned subsurface state (e.g., an enhanced positive heat content anomaly) in the western and central tropical Pacific would favor a warmer sea surface temperature anomaly in the eastern equatorial Pacific, potentially increasing the intensity of ocean-atmosphere coupling. These changes in the thermocline structure and possibly in the coupling strength can further alter the very character of tropical air-sea interactions. This may help to explain decadal variability of El Nine evolution in the tropical Pacific as observed in the 1980s. Our subsurface variability analysis presents observational evidence for the detailed space-time structure of decadal oceanic links between the extra-tropics and the tropics. C1 Univ Rhode Isl, Grad Sch Oceanog, Narragansett, RI 02882 USA. NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. RP Zhang, RH (reprint author), Univ Rhode Isl, Grad Sch Oceanog, Narragansett, RI 02882 USA. NR 49 TC 20 Z9 23 U1 0 U2 3 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 OCT PY 1999 VL 15 IS 10 BP 703 EP 717 DI 10.1007/s003820050311 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 245ZL UT WOS:000083138600001 ER PT J AU Yang, S Lau, KM Schopf, PS AF Yang, S Lau, KM Schopf, PS TI Sensitivity of the tropical Pacific Ocean to precipitation induced freshwater flux SO CLIMATE DYNAMICS LA English DT Article ID ATMOSPHERE RESPONSE EXPERIMENT; SEA-SURFACE TEMPERATURE; MIXED-LAYER; EQUATORIAL PACIFIC; TOGA-COARE; WARM POOL; WATER FLUX; SALINITY; MODEL; CIRCULATION AB We have performed experiments using an ocean model to study the sensitivity of tropical Pacific Ocean to variations in precipitation induced freshwater fluxes. Variations in these fluxes arise from natural causes on all time scales. In addition, estimates of these fluxes are uncertain because of differences among measurement techniques. The model used is a quasi-isopycnal model, covering the Pacific from 40 degrees S to 40 degrees N. The surface forcing is constructed from observed wind stress, evaporation, precipitation, and sea surface temperature (SST) fields. The heat flux is produced with an iterative technique so as to maintain the model close to the observed climatology, but with only a weak damping to that climatology. Climatological estimates of evaporation are combined with various estimates of precipitation to determine the net surface freshwater flux. Results indicate that increased freshwater input decreases salinity as expected, but increases temperatures in the upper ocean. Using the freshwater flux estimated from the Microwave Sounding Unit leads to a warming of up to 0.6 degrees C in the western Pacific over a case with zero net freshwater flux. SST is sensitive to the discrepancies among different precipitation observations, with root-mean-square differences in SST on the order of 0.2-0.3 degrees C. The change in SST is more pronounced in the eastern Pacific, with difference of over 1 degrees C found among the various precipitation products. Interannual variation in precipitation during El Nino events leads to increased warming. During the winter of 1982-83, freshwater flux accounts for about 0.4 degrees C (approximately 10-15% of the maximum warming) of the surface warming in the central-eastern Pacific. Thus, the error of SST caused by the discrepancies in precipitation products is more than half of the SST anomaly produced by the interannual variability of observed precipitation. Further experiments, in which freshwater flux anomalies are imposed in the western, central, and eastern Pacific, show that the influence of net freshwater flux is also spatially dependent. The imposition of freshwater flux in the far western Pacific leads to a trapping of salinity anomalies to the surface layers near the equator. An identical flux imposed in the central Pacific produces deeper and off-equatorial salinity anomalies. The contrast between these two simulations is consistent with other simulations of the western Pacific barrier layer formation. C1 NASA, Goddard Space Flight Ctr, Atmospheres Lab, Climate & Radiat Branch, Greenbelt, MD 20771 USA. SAIC Gen Sci Corp, Beltsville, MD USA. George Mason Univ, Inst Computat Sci & Informat, Fairfax, VA 22030 USA. RP Yang, S (reprint author), NASA, Goddard Space Flight Ctr, Atmospheres Lab, Climate & Radiat Branch, Greenbelt, MD 20771 USA. RI Yang, Song/B-4952-2009; Lau, William /E-1510-2012 OI Lau, William /0000-0002-3587-3691 NR 36 TC 37 Z9 37 U1 0 U2 1 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 OCT PY 1999 VL 15 IS 10 BP 737 EP 750 DI 10.1007/s003820050313 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 245ZL UT WOS:000083138600003 ER PT J AU Arthur, JD Groner, MK Hayhurst, KJ Holloway, CM AF Arthur, JD Groner, MK Hayhurst, KJ Holloway, CM TI Evaluating the effectiveness of independent verification and validation SO COMPUTER LA English DT Article AB The authors are among the first to test whether independent verification and validation have a measurable beneficial effect on the development process. C1 Virginia Tech, Blacksburg, VA 24061 USA. NASA, Langley Res Ctr, Hampton, VA 23665 USA. RP Arthur, JD (reprint author), Virginia Tech, Blacksburg, VA 24061 USA. NR 7 TC 9 Z9 9 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 0018-9162 J9 COMPUTER JI Computer PD OCT PY 1999 VL 32 IS 10 BP 79 EP + DI 10.1109/2.796141 PG 6 WC Computer Science, Hardware & Architecture; Computer Science, Software Engineering SC Computer Science GA 242RW UT WOS:000082956300024 ER PT J AU Noor, AK AF Noor, AK TI Computational structures technology: leap frogging into the twenty-first century SO COMPUTERS & STRUCTURES LA English DT Article; Proceedings Paper CT 3rd International Conference in Computational Structures Technology CY AUG 21-23, 1996 CL BUDAPEST, HUNGARY ID SUPERCONVERGENT PATCH RECOVERY; FINITE-ELEMENT METHOD; THERMOELECTROELASTIC MULTILAYERED PLATES; DISTRIBUTED-MEMORY COMPUTERS; POSTERIORI ERROR ESTIMATOR; SENSITIVITY ANALYSIS; COMPOSITE PANELS; AUTOMATIC DIFFERENTIATION; POSTBUCKLING RESPONSES; 3-DIMENSIONAL SOLUTIONS AB The history, recent developments and trends in computational structures technology (CST) are summarized. Discussion focuses on development of CST software and goals of CST activities, Some recent advances in a number of CST areas are described, including discretization techniques and element technology; computational material modeling; modeling of composite, sandwich and smart structures; computational tools and methodologies for life management, transient response analysis; numerical simulation of frictional contact/impact response; articulated structural dynamics; non-deterministic modeling and analysis methods; qualitative analysis and simulation; neuro-structural computing; hybrid techniques; error estimation and adaptive improvement strategies; strategies for solution of coupled problems; sensitivity analysis; integrated analysis and design; strategies and numerical algorithms for new computing systems; model generation facilities; and application of object-oriented technology. Research areas in CST that have high potential for meeting the future technological needs are identified. Published by Elsevier Science Ltd. C1 Univ Virginia, Ctr Adv Computat Technol, NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Noor, AK (reprint author), Univ Virginia, Ctr Adv Computat Technol, NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 208 TC 9 Z9 10 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0045-7949 J9 COMPUT STRUCT JI Comput. Struct. PD OCT-DEC PY 1999 VL 73 IS 1-5 BP 1 EP 31 DI 10.1016/S0045-7949(99)00075-9 PG 31 WC Computer Science, Interdisciplinary Applications; Engineering, Civil SC Computer Science; Engineering GA 240TW UT WOS:000082842100002 ER PT J AU Buchanan, PC Koeberl, C Reimold, WU AF Buchanan, PC Koeberl, C Reimold, WU TI Petrogenesis of the Dullstroom Formation, Bushveld Magmatic Province, South Africa SO CONTRIBUTIONS TO MINERALOGY AND PETROLOGY LA English DT Article ID CHEMICAL CLASSIFICATION; BASALT GEOCHEMISTRY; VOLCANIC-ROCKS; COMPLEX; MANTLE; EMPLACEMENT; ORIGIN; EARTH; AREA AB The Precambrian Dullstroom Formation of South Africa, which is predominantly composed of basaltic andesites interbedded with subordinate sedimentary and felsic volcanic strata, represents the first phase of an extended period of magmatism that was responsible for the Bushveld Magmatic Province, including the extrusive Rooiberg Group and the intrusive Bushveld Complex. New geochemical and isotopic data for the Dullstroom Formation are presented in an effort to elucidate the petrogenetic processes operative during the initiation of this magmatic episode. The volcanic units of the central:portion of the Dullstroom Formation have been subdivided into at least three interbedded compositional groups: low Ti mafic to intermediate units, high-Ti mafic to intermediate units, and high Mg felsic units, High Ti and low Ti volcanic units are similar in some compositional characteristics to basalts of the nearby northern and southern provinces, respectively, of the Mesozoic Karoo continental flood basalts. Isotopic and compositional data for low Ti Dullstroom strata are consistent with bulk assimilation into a melt similar in composition to a southern Karoo basalt of 20% upper continental crust accompanied by 20% fractional crystallization of pyroxene and plagioclase. Isotopic and compositional data for high Ti Dullstroom strata are consistent with magma mixing of 30% northern Karoo K-rich basalt and 70% southern Karoo basalt followed by 20% assimilation of upper continental crust and 20% fractional crystallization of pyroxene and plagioclase, Compositions of high Mg felsic volcanic strata are consistent with 25% assimilation of a mixture of silica-rich sedimentary rock and upper continental crust into a melt similar in composition to low Ti volcanic units with 25% fractional crystallization of pyroxene and plagioclase. However, it has been suggested that compositions of these high M felsic strata may also be consistent with interaction of a crustal melt. Assimilation, fractional crystallization, and magma mixing that apparently affected these Dullstroom Formation volcanic strata may have occurred in a series of shallow magma chambers. These data are consistent with the suggestion that Dullstroom Formation volcanic rocks are the result of a mantle plume. Mantle plume origin also is suggested by the large volume of intrusive and extrusive strata associated with this magmatic episode. These data do not support the hypothesis that the Bushveld Complex and the Rooiberg Group formed by impacts of a cluster of comets or asteroids. C1 Univ Witwatersrand, Dept Geochem, ZA-2050 Wits, Johannesburg, South Africa. Univ Vienna, Inst Geochem, A-1090 Vienna, Austria. RP Buchanan, PC (reprint author), NASA, Lyndon B Johnson Space Ctr, SN2, Houston, TX 77058 USA. NR 39 TC 19 Z9 22 U1 0 U2 4 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0010-7999 J9 CONTRIB MINERAL PETR JI Contrib. Mineral. Petrol. PD OCT PY 1999 VL 137 IS 1-2 BP 133 EP 146 DI 10.1007/s004100050587 PG 14 WC Geochemistry & Geophysics; Mineralogy SC Geochemistry & Geophysics; Mineralogy GA 250UD UT WOS:000083405800010 ER PT J AU Conley, CA Fowler, VM AF Conley, CA Fowler, VM TI Localization of the human 64kD autoantigen D1 to myofibrils in a subset of extraocular muscle fibers SO CURRENT EYE RESEARCH LA English DT Article DE 64kDa autoantigen D1; extraocular muscles; slow myosin; thyroid-associated orbitopathy; tropomodulin ID THYROID-ASSOCIATED OPHTHALMOPATHY; ACTIN FILAMENT LENGTH; EYE MUSCLE; GRAVES HYPERTHYROIDISM; MEMBRANE-PROTEIN; STRIATED-MUSCLE; ANTIBODIES; TISSUE; TROPOMODULIN; DISEASE AB Purpose. To evaluate the tissue-specific expression pattern of the 64kD human autoantigen D1, a tropomodulin-related protein that may be involved in thyroid-associated ophthalmopathy. Methods. Recombinant 64kD human autoantigen D1 was generated in a bacterial expression system and used to immunize rabbits. Specific antibodies were affinity-purified and used for Western blots on normal and hyperthyroid rat and rabbit tissue, and immunofluorescence localization on cryosections of rat tissue. Results. Anti-64kD human autoantigen D1 antibodies recognize specifically a similar to 70kD polypeptide in western blots of extraocular muscle, sternothyroid muscle, and smooth muscle. Immunofluorescence staining demonstrates that the 64kD human autoantigen D1 localizes to myofibrils in slow fibers from rat extraocular and sternothyroid muscle. The level of this protein is not altered in extraocular muscles from hyperthyroid rabbits. Conclusions. The 64kD human autoantigen D1 is expressed in slow fibers of extraocular and sternothyroid muscles as a component of myofibrils, and is not upregulated in conditions of hyperthyroidism. C1 Scripps Res Inst, Dept Cell Biol, La Jolla, CA 92037 USA. RP Conley, CA (reprint author), NASA, Ames Res Ctr, 239-11, Moffett Field, CA 94035 USA. FU NIGMS NIH HHS [GM34225] NR 36 TC 7 Z9 9 U1 0 U2 1 PU SWETS ZEITLINGER PUBLISHERS PI LISSE PA P O BOX 825, 2160 SZ LISSE, NETHERLANDS SN 0271-3683 J9 CURR EYE RES JI Curr. Eye Res. PD OCT PY 1999 VL 19 IS 4 BP 313 EP 322 DI 10.1076/ceyr.19.4.313.5304 PG 10 WC Ophthalmology SC Ophthalmology GA 250DJ UT WOS:000083373500004 PM 10520227 ER PT J AU Evans, DL AF Evans, DL TI Applications of imaging radar data in earth science investigations SO ELECTRONICS & COMMUNICATION ENGINEERING JOURNAL LA English DT Article ID SYNTHETIC-APERTURE RADAR; SAR; INTERFEROMETRY; FOREST; ICE AB Synthetic aperture radar (SAR) data provide unique information about the earth's surface and biodiversity, including critical data for natural hazards and resource assessments. The ability to calculate the cross-section of a scatterer for any transmit and receive polarisation combination provides detailed information about vegetation for assessing changes in land cover, biomass and forest regrowth. Unique SAR interferometric measurements, predominantly large-scale surface change at fine resolution, are used to generate topographic data sets, monitor surface topographic change, and measure glacier ice velocity. The LightSAR Mission, planned for launch in 2002 will be optimised for polarimetric and interferometric data acquisition in order to provide long-term observations of the earth's changing conditions. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Evans, DL (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 20 TC 4 Z9 4 U1 0 U2 2 PU IEE-INST ELEC ENG PI HERTFORD PA MICHAEL FARADAY HOUSE SIX HILLS WAY STEVENAGE, HERTFORD SG1 2AY, ENGLAND SN 0954-0695 J9 ELECTRON COMMUN ENG JI Electron. Commun. Eng. J. PD OCT PY 1999 VL 11 IS 5 BP 227 EP 234 DI 10.1049/ecej:19990504 PG 8 WC Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA 253GP UT WOS:000083548700004 ER PT J AU Deng, XM Newman, JC AF Deng, XM Newman, JC TI A study of some issues in stable tearing crack growth simulations SO ENGINEERING FRACTURE MECHANICS LA English DT Article DE stable crack growth; CTOD; finite element; numerical simulation; large rotation AB This paper investigates several issues in stable crack growth simulations relevant to the application of a particular crack-growth criterion based on the crack-tip opening displacement (CTOD). Specifically, the effects of finite element size, CTOD location, and large rotation on the performance of the CTOD criterion are examined. Finite element simulations of actual crack growth tests on Arcan specimens are carried out under plane stress and Mode-I conditions using a custom code ZIP2DL. With regard to finite element predictions for the load-crack-extension curve, the results of the simulations suggest the following. First, when elements are small enough along the crack growth path to produce converged crack-tip opening displacement (not necessarily converged crack-tip stresses and strains), the size of the elements has negligible effect, Second, the fixed distance between the CTOD location and the current crack-tip should be chosen so that it is consistent with the choice of the element size along the crack path and of the critical CTOD value. Third, the effect of large specimen rotation can be dealt with by performing both the CTOD calibration and its application under small-deformation conditions. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 Univ S Carolina, Dept Mech Engn, Columbia, SC 29208 USA. NASA, Langley Res Ctr, Hampton, VA 23665 USA. RP Deng, XM (reprint author), Univ S Carolina, Dept Mech Engn, Columbia, SC 29208 USA. NR 19 TC 19 Z9 20 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0013-7944 J9 ENG FRACT MECH JI Eng. Fract. Mech. PD OCT PY 1999 VL 64 IS 3 BP 291 EP 304 DI 10.1016/S0013-7944(99)00081-8 PG 14 WC Mechanics SC Mechanics GA 264HL UT WOS:000084174700002 ER PT J AU Buckel, JA Fogarty, MJ Conover, DO AF Buckel, JA Fogarty, MJ Conover, DO TI Foraging habits of bluefish, Pomatomus saltatrix, on the US east coast continental shelf SO FISHERY BULLETIN LA English DT Article ID THE-YEAR BLUEFISH; EARLY-LIFE-HISTORY; NEW-YORK BIGHT; JUVENILE BLUEFISH; BAY ANCHOVY; GROWTH; SIZE; PREY; ABUNDANCE; RATES AB After spending summer months in estuaries, spring- and summer-spawned young-of-the-year (YOY) bluefish, Pomatomus saltatrix, migrate out to continental shelf waters of the Mid-Atlantic Eight in early autumn. Adult bluefish are found on the continental shelf throughout summer and fall. Both juveniles and adults have high food consumption rates and are generally piscivorous. To determine principal prey types on the shelf, dietary analyses were performed on YOY and adult bluefish collected from National Marine Fisheries Service autumn bottom trawl surveys in 1994 and 1995. Both spring- and summer-spawned YOY bluefish diets were dominated by bay anchovy. However, the significantly larger size of the spring-spawned cohort was associated with the consumption of other prey species such as squid, butterfish, striped anchovy, and round herring. Summer-spawned bluefish were significantly smaller in 1995 than in 1994; diet and prey size comparisons suggest that body size had a dramatic influence on the amount of piscivorous feeding in the summer-spawned cohort. Adult bluefish diet was dominated by schooling species such as squid, butterfish, and clupeids. Cannibalism was virtually nonexistent. Daily ration estimates of YOY bluefish on the shelf(4-12% body wt/d) were similar to estuarine estimates in late summer. It is estimated that during the month of September, YOY bluefish in aggregate consumed 6.0 to 6.8 billion bay anchovies in 1994 and from 2.2 to 5.3 billion in 1995. The effect of this predatory loss on population dynamics of bay anchovy and the fish community on the continental shelf is unknown. C1 SUNY Stony Brook, Marine Sci Res Ctr, Stony Brook, NY 11794 USA. NOAA, Natl Marine Fisheries Serv, NE Fisheries Sci Ctr, Woods Hole, MA 02543 USA. RP Buckel, JA (reprint author), NOAA, Natl Marine Fisheries Serv, James J Howard Marine Sci Lab, 74 Magruder Rd, Highlands, NJ 07732 USA. EM jbuckel@sh.nmfs.gov NR 40 TC 53 Z9 56 U1 1 U2 10 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 EI 1937-4518 J9 FISH B-NOAA JI Fish. Bull. PD OCT PY 1999 VL 97 IS 4 BP 758 EP 775 PG 18 WC Fisheries SC Fisheries GA 256XX UT WOS:000083752700003 ER PT J AU Buckel, JA Fogarty, MJ Conover, DO AF Buckel, JA Fogarty, MJ Conover, DO TI Mutual prey of fish and humans: a comparison of biomass consumed by bluefish, Pomatomus saltatrix, with that harvested by fisheries SO FISHERY BULLETIN LA English DT Article ID THE-YEAR BLUEFISH; BIOENERGETICS MODELS; FOOD-CONSUMPTION; GROWTH; POPULATIONS; ENERGETICS; CONVERSION AB The bluefish, Pomatomus saltatrix, has long been considered a key predator on U.S. east coast fish species. Many of its prey species are also landed by humans, but no comparison of prey biomass harvested by bluefish versus fishermen has been attempted previously. We used data an growth, mortality, gross growth efficiency, and abundance to model the total prey consumption rate by bluefish at the population level. This estimate and previously published information on diet were used to calculate the biomass of individual resource species "harvested" by bluefish. The prey biomass consumed by bluefish annually along the U.S. Atlantic coast is equal to eight times the biomass of the bluefish population. Bluefish consume a much higher biomass of squid and butterfish than is currently harvested by commercial fisheries for these species. Bluefish consumption of Atlantic menhaden, however, was below the current fisheries landings for this species. For resource species that are shared with bluefish, our findings highlight the need for multi-species assessment and management. C1 SUNY Stony Brook, Marine Sci Res Ctr, Stony Brook, NY 11794 USA. NOAA, Natl Marine Fisheries Serv, NE Fisheries Sci Ctr, Woods Hole, MA 02543 USA. RP Buckel, JA (reprint author), NOAA, Natl Marine Fisheries Serv, James J Howard Marine Sci Lab, 74 Magruder Rd, Highlands, NJ 07732 USA. NR 26 TC 15 Z9 16 U1 0 U2 4 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 OCT PY 1999 VL 97 IS 4 BP 776 EP 785 PG 10 WC Fisheries SC Fisheries GA 256XX UT WOS:000083752700004 ER PT J AU Stoner, AW Bejda, AJ Manderson, JP Phelan, BA Stehlik, LL Pessutti, JP AF Stoner, AW Bejda, AJ Manderson, JP Phelan, BA Stehlik, LL Pessutti, JP TI Behavior of winter flounder, Pseudopleuronectes americanus, during the reproductive season: laboratory and field observations on spawning, feeding, and locomotion SO FISHERY BULLETIN LA English DT Article ID NEW-YORK BIGHT; PLEURONECTES-PLATESSA L; HIPPOGLOSSOIDES-PLATESSOIDES; NORTH-SEA; BAY; MATURATION; OCELLATUS; FISHES; DIETS; POND AB Continuous observations in a large research aquarium (121 kL) over a 14-week period were combined with field collection in the Navesink River estuary, New Jersey, to explore the behavior of winter flounder (Pseudo-pleuronectes americanus) during and after the spawning season. Ten males and ten females held in the aquarium spawned over a 60-day period, with an average of 40 spawns per female and 147 spawns per male. Males initiated all observed spawning events, which occurred throughout the night, but primarily between sunset and midnight. Spawning by one pair frequently elicited sudden convergence and spawning by secondary males (up to six individuals); consequently, strictly paired spawning was uncommon (22% of events). Males and females were almost entirely nocturnal during the reproductive season but became increasingly diurnal during the postspawning season. C1 NOAA, Natl Marine Fisheries Serv, NE Fisheries Sci Ctr, Highlands, NJ 07732 USA. RP Stoner, AW (reprint author), NOAA, Natl Marine Fisheries Serv, NE Fisheries Sci Ctr, 74 Magruder Rd, Highlands, NJ 07732 USA. NR 41 TC 48 Z9 49 U1 0 U2 5 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 OCT PY 1999 VL 97 IS 4 BP 999 EP 1016 PG 18 WC Fisheries SC Fisheries GA 256XX UT WOS:000083752700021 ER PT J AU Slavin, JA Hesse, M Owen, CJ Taguchi, S Fairfield, DH Lepping, RP Kokuban, S Mukai, T Lui, ATY Anderson, RR Matsumoto, H Sutcliffe, PR AF Slavin, JA Hesse, M Owen, CJ Taguchi, S Fairfield, DH Lepping, RP Kokuban, S Mukai, T Lui, ATY Anderson, RR Matsumoto, H Sutcliffe, PR TI Dual spacecraft observations of lobe magnetic field perturbations before, during and after plasmoid release SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID TRAVELING COMPRESSION REGIONS; GEOTAIL OBSERVATIONS; ISEE-3; MAGNETOTAIL; EVOLUTION AB This study examines a data set returned by IMP 8 and Geotail on January 29, 1995 during a substorm which resulted in the ejection of a plasmoid. The two spacecraft (sic) were situated in the north lobe of the tail and both observed a traveling compression region (TCR). We show that in this instance dual s/c measurements can be used to model all three dimensions of the underlying plasmoid and to estimate its rate of expansion. For this event plasmoid dimensions of Delta X similar to 18, Delta Y similar to 30, and Delta Z similar to 10 R-e are determined from the IMP 8 and Geotail observations. Furthermore, a factor of similar to 2 increase in the amplitude of the TCR occurred in the 1.5 min it took to move from IMP 8 to Geotail. Modeled using conservation of magnetic flux, this increase in lobe compression implies that the underlying plasmoid was expanding at a rate of similar to 140 km/s. Finally, a reconfiguration of the lobe magnetic field followed plasmoid ejection which moved magnetic flux tubes into the wake behind the plasmoid where they would become available to feed the reconnection region. C1 NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. Queen Mary Univ London, Astron Unit, London E1 4NS, England. Univ Electrocommun, Dept Elect Engn, Chofu, Tokyo 182, Japan. Nagoya Univ, Solar Terr Environm Lab, Nagoya, Aichi, Japan. Inst Space & Astronaut Sci, Kanagawa 2290022, Japan. Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA. Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA. Kyoto Univ, Ctr Radio Atmospher Sci, Gokanosho, Japan. Hermanus Magnet Observ, ZA-7200 Hermanus, South Africa. RP NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. EM james.a.slavin@gsfc.nasa.gov; c.j.owen@qmu.ac.uk; taguchi@ee.uec.ac.jp; mukai@stp.isas.ac.jp; lui@merritt.jhuapl.edu; anderson@iowave.uiowa.edu; matsumot@kursac.kyoto-u.ac.jp; psutclif@csir.co.za RI Owen, Christopher/C-2999-2008; Hesse, Michael/D-2031-2012; Slavin, James/H-3170-2012; Sutcliffe, Peter/E-8124-2014 OI Owen, Christopher/0000-0002-5982-4667; Slavin, James/0000-0002-9206-724X; NR 6 TC 21 Z9 22 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 EI 1944-8007 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD OCT 1 PY 1999 VL 26 IS 19 BP 2897 EP 2900 DI 10.1029/1999GL003606 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 242UU UT WOS:000082960700001 ER PT J AU Guhathakurta, M Sittler, E Fisher, R McComas, D Thompson, B AF Guhathakurta, M Sittler, E Fisher, R McComas, D Thompson, B TI Coronal magnetic field topology and source of fast solar wind SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID DENSITY STRUCTURE; HOLE AB We have developed a steady state, 2D semiempirical MHD model of the solar corona and the solar wind with many surprising results. This model for the first time shows, that the boundary between the fast and the slow solar wind as observed by Ulysses beyond 1 AU, is established in the low corona. The fastest wind observed by Ulysses (680-780 km/s) originates from the polar coronal holes at 70 degrees-90 degrees latitude at the Sun. Rapidly diverging magnetic field geometry accounts for the fast wind reaching down to a latitude of +/-30 degrees at the orbit of Earth. The gradual increase in the fast wind observed by Ulysses, with latitude, can be explained by an increasing field strength towards the poles, which causes Alfven wave energy flux to increase towards the poles. Empirically there is a direct relationship between this gradual increase in wind speed and the expansion factor, f, computed at r > 20 R.. This relationship is inverse if f is computed very close to the Sun. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM USA. Catholic Univ Amer, NASA HQ, Washington, DC 20064 USA. RP Guhathakurta, M (reprint author), NASA, Goddard Space Flight Ctr, Code 682, Greenbelt, MD 20771 USA. RI Thompson, Barbara/C-9429-2012 NR 16 TC 8 Z9 8 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD OCT 1 PY 1999 VL 26 IS 19 BP 2901 EP 2904 DI 10.1029/1999GL010662 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 242UU UT WOS:000082960700002 ER PT J AU Takalo, J Timonen, J Klimas, AJ Valdivia, JA Vassiliadis, D AF Takalo, J Timonen, J Klimas, AJ Valdivia, JA Vassiliadis, D TI A coupled-map model for the magnetotail current sheet SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB A magnetic field model of the magnetotail current sheet in the form of a coupled-map lattice (CML) is presented. It is a continuously driven and based on the MHD diffusion equation. Solar wind vB(S) data (solar wind speed multiplied by the southward component of IMF) are used for driving the model, and it is shown to exhibit perturbations (avalanches) with power-law scalings in their distributions of duration and size. Such distributions may indicate self-organized critical (SOC) behavior. Furthermore, it is shown that the power spectra of the model outputs are of bicolor power-law form with different slopes for high and low frequencies. The model parameters determine the frequency of the break points of the spectra, and the slopes of their low and high frequency regimes. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Jyvaskyla, Dept Phys, FIN-40351 Jyvaskyla, Finland. RP Takalo, J (reprint author), NASA, Goddard Space Flight Ctr, Code 690-2, Greenbelt, MD 20771 USA. RI Valdivia, Juan/A-3631-2008 OI Valdivia, Juan/0000-0003-3381-9904 NR 24 TC 23 Z9 23 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 OCT 1 PY 1999 VL 26 IS 19 BP 2913 EP 2916 DI 10.1029/1999GL003616 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 242UU UT WOS:000082960700005 ER PT J AU Meziane, K Lin, RP Parks, GK Larson, DE Bale, SD Mason, GM Dwyer, JR Lepping, RP AF Meziane, K Lin, RP Parks, GK Larson, DE Bale, SD Mason, GM Dwyer, JR Lepping, RP TI Evidence for acceleration of ions to similar to 1 MeV by adiabatic-like reflection at the quasi-perpendicular Earth's bow shock SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID WIND SPACECRAFT; ENERGETIC IONS; HEAVY-IONS; UPSTREAM; PLASMA; ELECTRONS; EVENTS; ENERGIZATION AB On December 6, 1994, during a CIR (Corotating Interaction Region) event, the WIND 3D-Plasma and energetic particle experiment observed a burst (less than or equal to 24 s) of 238-676 keV protons close to the electron foreshock boundary, followed by a 156-236 keV, 101-156 keV and 33-101 keV proton bursts about similar to 40 s, 65 s and 85 s later, respectively. Similar dispersed bursts of helium with energies between similar to 50 keV and similar to 1 MeV followed the proton bursts. During this time, the IMF direction varied slowly with an almost monotonic decrease in theta(Bn). The proton energy spectrum is initially peaked at similar to 350 keV, and progresses to lower energies with time. The proton 3D angular distributions are peaked at similar to 30 degrees pitch-angle, propagating away from the shock, but they are non-gyrotropic. Finally, we show that the proton energy-spectra as well as the pitch angle distribution agree quantitatively with a model of a single adiabatic reflection of the incident energetic interplanetary ions by the quasi-perpendicular shock. C1 Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Univ Washington, Geophys Program, Seattle, WA 98195 USA. Univ Maryland, Dept Phys, College Pk, MD 20742 USA. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RP Meziane, K (reprint author), Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. RI Bale, Stuart/E-7533-2011 OI Bale, Stuart/0000-0002-1989-3596 NR 24 TC 13 Z9 14 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD OCT 1 PY 1999 VL 26 IS 19 BP 2925 EP 2928 DI 10.1029/1999GL900603 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 242UU UT WOS:000082960700008 ER PT J AU Wilson, RM AF Wilson, RM TI Statistical aspects of major (intense) hurricanes in the Atlantic basin during the past 49 hurricane seasons (1950-1998): Implications for the current season SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SAHELIAN MONSOON RAINFALL; TROPICAL CYCLONE ACTIVITY; WEST-AFRICAN RAINFALL; UNITED-STATES; DOWNWARD TRENDS; 5 DECADES; STRONG ASSOCIATION; EL-NINO; FREQUENCY AB Statistical aspects of major (intense) hurricanes, those of category 3 or higher on the Saffir-Simpson scale (e.g., having a maximum sustained wind speed of greater than or equal to 50 m s(-1)), in the Atlantic basin during the interval of 1950-1998 are investigated in relation to the El Nino-Southern Oscillation cycle and to the postulated "more" versus "less" activity modes for intense hurricane activity. Based on Poisson statistics, when the hurricane season is simply classified as "non-El Nino-related" (NENR), the probability of having three or more intense hurricanes is approximate to 53%, while it is only approximate to 14% when it is classified as "El Nino-related" (ENR). including the activity levels ("more" versus "less"), the probability of having three or more intense hurricanes is computed to be approximate to 71% for the "more-NENR" season, 30% for the "less-NENR" season, 17% for the "more-ENR" season, and 12% for the "less-ENR" season. Because the 1999 hurricane season is believed to be a "more-NENR" season, the number of intense hurricanes forming in the Atlantic basin should be above average in number, probably about 4 +/- 1 or higher. C1 NASA, George C Marshall Space Flight Ctr, Sci Directorate, Huntsville, AL 35812 USA. RP Wilson, RM (reprint author), NASA, George C Marshall Space Flight Ctr, Sci Directorate, SD50, Huntsville, AL 35812 USA. NR 24 TC 21 Z9 21 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 OCT 1 PY 1999 VL 26 IS 19 BP 2957 EP 2960 DI 10.1029/1999GL004904 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 242UU UT WOS:000082960700016 ER PT J AU Garcia-Gorriz, E Carr, ME AF Garcia-Gorriz, E Carr, ME TI The climatological annual cycle of satellite-derived phytoplankton pigments in the Alboran Sea SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID ANTICYCLONIC GYRES AB The circulation and upwelling processes that control the phytoplankton distribution in the Alboran Sea (western Mediterranean) are examined from a climatological perspective for the first time. To characterize the annual cycle of the near-surface phytoplankton patterns, we analyze the monthly distributions of pigments from the Coastal Zone Color Scanner (CZCS). Two regimes occur: a fall-to-winter bloom (November-March) and a non-bloom period (May-September). These regimes differentiate the basin from other parts of the western Mediterranean, where a significant spring bloom occurs. The newest ocean color data sets available today from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) and the Ocean Color and Temperature Scanner (OCTS) fall within this annual progression. The combined interaction of seasonal stratification, coastal and gyre-induced upwelling, and horizontal advection control the near-surface pigment distribution in Alboran, while light availability does not determine the seasonal cycle of pigments. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Garcia-Gorriz, E (reprint author), CALTECH, Jet Prop Lab, MS 300-323,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 9 TC 37 Z9 38 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 OCT 1 PY 1999 VL 26 IS 19 BP 2985 EP 2988 DI 10.1029/1999GL900529 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 242UU UT WOS:000082960700023 ER PT J AU Bills, BG Ray, RD AF Bills, BG Ray, RD TI Lunar orbital evolution: A synthesis of recent results SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID EARTH-MOON SYSTEM; TIDAL RHYTHMITES; DISSIPATION; ROTATION; OCEAN; TIDES; DYNAMICS; ESTUARY; LAMINAE; HISTORY AB The present rate of tidal dissipation in the Earth-Moon system is known to be anomalously high, in the sense that the implied age of the lunar orbit is only 1.5 x 10(9) years, though other evidence suggests an age closer to 4 x 10(9) years. To assess how long the anomalous dissipation has persisted, we use published estimates of lunar orbital configurations derived from (a) fine grained sediments containing tidal laminations and (b) numerical ocean models averaged over varying ocean geometries. The implied histories of the lunar semimajor axis are surprisingly consistent over the past 10(9) years. The ocean models imply, on average, reduced dissipation in the past because of a spatial mismatch between tidal forcing and oceanic normal modes of higher frequencies. Webb's ocean model suggests that the "anomalous" oceanic dissipation began about 10(9) years ago and has been increasing since then. C1 Univ Calif San Diego, Scripps Inst Oceanog, Inst Geophys & Planetary Phys, La Jolla, CA 92093 USA. NASA, Goddard Space Flight Ctr, Space Geodesy Branch, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Geodynam Branch, Greenbelt, MD 20771 USA. RP Bills, BG (reprint author), Univ Calif San Diego, Scripps Inst Oceanog, Inst Geophys & Planetary Phys, La Jolla, CA 92093 USA. RI Bills, Bruce/C-1156-2008; Ray, Richard/D-1034-2012 NR 40 TC 33 Z9 34 U1 1 U2 18 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD OCT 1 PY 1999 VL 26 IS 19 BP 3045 EP 3048 DI 10.1029/1999GL008348 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 242UU UT WOS:000082960700038 ER PT J AU Friedlingstein, P Joel, G Field, CB Fung, IY AF Friedlingstein, P Joel, G Field, CB Fung, IY TI Toward an allocation scheme for global terrestrial carbon models SO GLOBAL CHANGE BIOLOGY LA English DT Review DE carbon allocation; primary productivity; root : shoot ratio ID NET PRIMARY PRODUCTION; LONG-TERM ELEVATION; INTERNAL NITROGEN CONCENTRATION; SURFACE PARAMETERIZATION SIB2; ATMOSPHERIC CO2 CONCENTRATION; BIOSPHERE MODEL; SHOOT RATIOS; BIOMASS ALLOCATION; PARTITIONING MODEL; PLANT-RESPONSES AB The distribution of assimilated carbon among the plant parts has a profound effect on plant growth, and at a larger scale, on terrestrial biogeochemistry. Although important progress has been made in modelling photosynthesis, less effort has been spent on understanding the carbon allocation, especially at large spatial scales. Whereas several individual-level models of plant growth include an allocation scheme, most global terrestrial models still assume constant allocation of net primary production (NPP) among plant parts, without any environmental coupling. Here, we use the CASA biosphere model as a platform for exploring a new global allocation scheme that estimates allocation of photosynthesis products among leaves, stems, and roots depending on resource availability. The philosophy underlying the model is that-allocation patterns result from evolved responses that adjust carbon investments to facilitate capture of the most limiting resources, i.e. light, water, and mineral nitrogen. In addition, we allow allocation of NPP to vary in response to changes in atmospheric CO2. The relative magnitudes of changes in NPP and resource-use efficiency control the response of root:shoot allocation. For ambient CO2, the model produces realistic changes in above-ground allocation along productivity gradients. In comparison to the CASA standard estimate using fixed allocation ratios, the new allocation scheme tends to favour root allocation, leading to a 10% lower global biomass. Elevated CO2, which alters the balance between growth and available resources, generally leads to reduced water stress and consequently, decreased root:shoot ratio. The major exception is forest ecosystems, where increased nitrogen stress induces a larger root allocation. C1 Columbia Univ, Goddard Inst Space Studies, New York, NY 10025 USA. Ctr Etud Saclay, Lab Sci Climat & Environm, F-91191 Gif Sur Yvette, France. Carnegie Inst Washington, Stanford, CA 94305 USA. Univ Victoria, Sch Earth & Ocean Sci, Victoria, BC V8W 2Y2, Canada. RP Friedlingstein, P (reprint author), Columbia Univ, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. RI Friedlingstein, Pierre/H-2700-2014 NR 101 TC 164 Z9 180 U1 2 U2 40 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 1354-1013 J9 GLOB CHANGE BIOL JI Glob. Change Biol. PD OCT PY 1999 VL 5 IS 7 BP 755 EP 770 DI 10.1046/j.1365-2486.1999.00269.x PG 16 WC Biodiversity Conservation; Ecology; Environmental Sciences SC Biodiversity & Conservation; Environmental Sciences & Ecology GA 237GH UT WOS:000082646900002 ER PT J AU Khaoustov, VI Murry, D Pellis, NR Yoffe, B Risin, D Soriano, U AF Khaoustov, VI Murry, D Pellis, NR Yoffe, B Risin, D Soriano, U TI Induction of three-dimensional growth of human liver cells in simulated microgravity SO HEPATOLOGY LA English DT Meeting Abstract C1 Baylor Coll Med, Houston, TX 77030 USA. Purdue Univ, Indianapolis, IN USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Wyle Lab, Houston, TX USA. Northwestern Univ, Chicago, IL 60611 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 0270-9139 J9 HEPATOLOGY JI Hepatology PD OCT PY 1999 VL 30 IS 4 SU S MA 1389 BP 508A EP 508A PN 2 PG 1 WC Gastroenterology & Hepatology SC Gastroenterology & Hepatology GA 239XE UT WOS:000082794701387 ER PT J AU Barlow, NG Allen, RA Vilas, F AF Barlow, NG Allen, RA Vilas, F TI Mercurian impact craters: Implications for polar ground ice SO ICARUS LA English DT Article DE Mercury; cratering; surfaces; planets; ices; Mars ID WATER ICE; MARS; RADAR; STABILITY; VOLATILES; VOLCANISM; POLES; MOON; TOPOGRAPHY; ANOMALIES AB Recent radar observations of Mercury have detected strong depolarized echoes from the north and south polar regions which have been interpreted by some as ice deposits in the floors of permanently shadowed impact craters. We have used the experience from Mars, where subsurface ice lowers the depth-to-diameter ratio (d/D) of impact craters, to test for subsurface ice deposits on Mercury. This analysis determines the d/D ratios for 170 impact craters in the Borealis (north polar), Tolstoj (equatorial), Kuiper (equatorial), and Each (south polar) quadrangles of the planet. Possible effects from sun angle and terrain were eliminated. To test whether d/D differences could be detected at Mariner 10 resolutions (similar to 1 km/pixel), we perform a similar analysis using Mariner 9 images of Mars which have similar resolutions. We demonstrate that d/D differences due to terrain softening can be detected between craters in the martian polar regions and the equatorial regions at the Mariner 9 resolutions. Although our initial results indicate that the south polar Each Quadrangle has a statistically lower d/D than the north polar (Borealis) or two equatorial (Tolstoj and Kuiper) quadrangles, further investigation reveals that this finding is most likely the result of the filtering which was applied to the images of the Each quadrangle by JPL. Thus, no unequivocal evidence exists that the possible ice deposits in craters at Mercury's north and south poles are the exposed portions of more extensive subsurface ice caps. Combined with the temporal constraint imposed by the fact that the proposed ice deposits are found only in USGS Class 4 craters, this suggests a large, rapidly emplaced exogenic source of water to Mercury during the Mansurian period. We suggest that the source was multiple impacts from a fragmented comet or a comet shower. (C) 1999 Academic Press. C1 Dickinson Coll, Dept Geol, Carlisle, PA 17013 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Barlow, NG (reprint author), Dickinson Coll, Dept Geol, Carlisle, PA 17013 USA. NR 56 TC 16 Z9 16 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 OCT PY 1999 VL 141 IS 2 BP 194 EP 204 DI 10.1006/icar.1999.6165 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 253ER UT WOS:000083544100002 ER PT J AU Hillier, JK Buratti, BJ Hill, K AF Hillier, JK Buratti, BJ Hill, K TI Multispectral photometry of the moon and absolute calibration of the clementine UV/Vis camera SO ICARUS LA English DT Article DE Moon; Moon, surface; photometry ID BIDIRECTIONAL REFLECTANCE SPECTROSCOPY; OUTER PLANET SATELLITES; COHERENT BACKSCATTER; POLARIZED-LIGHT; SURFACE; PARTICLES AB We present a multispectral photometric study of the Moon between solar phase angles of 0 and 85 degrees, Using Clementine images obtained between 0.4 and 1.0 mu m, we produce a comprehensive study of the lunar surface containing the following results: (1) empirical photometric functions for the spectral range and viewing and illumination geometries mentioned, (2) photometric modeling that derives the physical properties of the upper regolith and includes a detailed study of the causes for the lunar opposition surge, (3) an absolute calibration of the Clementine UV/Vis camera. The calibration procedure given on the Clementine calibration web site produces reflectances relative to a halon standard and further appear significantly higher than those seen in groundbased observations. By comparing Clementine observations with prior groundbased observations of 15 sites on the Moon we have determined a good absolute calibration of the Clementine UV/Vis camera. A correction factor of 0.532 has been determined to convert the web site (www.planetary.brown.edu/clementine/calibration.html) reflectances to absolute values. From the calibrated data, we calculate empirical phase functions useful for performing photometric corrections to observations of the Moon between solar phase angles of 0 and 85 degrees and in the spectral range 0.4 to 1.0 mu m Finally the calibrated data is used to fit a version of Hapke's photometric model modified to incorporate a new formulation, developed in this paper, of the lunar opposition surge which includes coherent backscatter. Recent studies of the lunar opposition effect have yielded contradictory results as to the mechanism responsible: shadow hiding, coherent backscatter, or both. We find that most of the surge can be explained by shadow hiding with a halfwidth of similar to 8 degrees. However, for the brightest regions (the highlands at 0.75-1.0 mu m) a small additional. narrow component (halfwidth of <2 degrees) of total amplitude similar to 1/6 to 1/4 that of the shadow hiding surge is observed, which may be attributed to coherent backscatter. Interestingly, no evidence for the narrow component is seen in the maria or in the highlands at 0.415 mu m. A natural explanation for this is that these regions are too dark to exhibit enough multiple scattering for the effects of coherent backscatter to be seen. Finally, because the Moon is the only celestial body for which we have "ground truth" measurements, our results provide an important test for the robustness of photometric models of remote sensing observations. (C) 1999 Academic Press. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Hillier, JK (reprint author), CALTECH, Jet Prop Lab, MS 183-501,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 38 TC 77 Z9 81 U1 1 U2 6 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 OCT PY 1999 VL 141 IS 2 BP 205 EP 225 DI 10.1006/icar.1999.6184 PG 21 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 253ER UT WOS:000083544100003 ER PT J AU Satoh, T Connerney, JEP AF Satoh, T Connerney, JEP TI Jupiter's H-3(+) emissions viewed in corrected jovimagnetic coordinates SO ICARUS LA English DT Article DE Jupiter, magnetosphere; aurorae; magnetic fields; ionospheres; infrared observations ID HUBBLE-SPACE-TELESCOPE; IO FLUX TUBE; INNER MAGNETOSPHERE; UPPER-ATMOSPHERE; MAGNETIC-FIELD; JOVIAN H-3(+); ULTRAVIOLET; AURORA; H-3+; THERMOSPHERE AB The distribution of H-3(+) emissions in Jupiter's polar region is interpreted in terms of the corresponding source regions and the energetic in the magnetosphere by reference to corrected jovimagnetic coordinates based on the VIP4 magnetic field model of J. E. P. Connerney etal. (1998, J. Geophys. Res. 103, 11929-11939). Two sets of 3.43-mu m auroral images, acquired on May 31/June 1, 1996, and on July 8/July 9, 1996, using NSFCAM at NASA IRTF, were analyzed. Model images were generated for observed rotation phases, and the generalized inverse methodology of T. Satoh et al. (1996, Icarus 122, 1-23) is applied to pixel-by-pixel comparison of intensities to constrain the parameters of the emission source model. The most intense emissions are found between the 12-R-j (jovian radii) and 30-R-j ovals, representing the main auroral emissions. The System-III longitudes (lambda(III)) of peak brightness in this zone, lambda(III) similar to 260 degrees in the north and similar to 130 degrees in the south, coincide well with those of the minimum surface field magnitudes according to the VIP4 model. Between the 8-R-j and the 12-R-j ovals, the peak brightness occurs at lambda(III) similar to 215 degrees in the north and at similar to 25 degrees in the south, consistent with the Satoh ef al. (1996) System-m anomalies. These enhancements may originate from the "windshield wiper" effects of drifting electrons, caused by pitch angle scattering of varying efficiency from the inner to the distant magnetosphere. The total power emitted from the entire auroral region by the H-3(+) ion at all re-vibrational levels is estimated as 2.1 x 10(12) W in the north, and 1.2 x 10(12) W in the south. Relative contributions from the individual zones are similar to 10% from the 6- to 8-Rj zone, similar to 20% from the 8- to 12-R-j zone, similar to 25% from the 12- to 30-R-j zone, and similar to 45% from the polar-cap emission, respectively. (C) 1999 Academic Press. C1 Sci Univ Tokyo, Frontier Res Ctr Computat Sci, Noda, Chiba 2788510, Japan. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RP Satoh, T (reprint author), Sci Univ Tokyo, Frontier Res Ctr Computat Sci, 2641 Yamazaki, Noda, Chiba 2788510, Japan. RI connerney, john/I-5127-2013 NR 48 TC 38 Z9 38 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 OCT PY 1999 VL 141 IS 2 BP 236 EP 252 DI 10.1006/icar.1999.6173 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 253ER UT WOS:000083544100005 ER PT J AU Meier, R Smith, BA Owen, TC Becklin, EE Terrile, RJ AF Meier, R Smith, BA Owen, TC Becklin, EE Terrile, RJ TI Near infrared photometry of the jovian ring and Adrastea SO ICARUS LA English DT Article DE planetary rings; Jupiter; satellites of Jupiter; Adrastea; photometry; infrared observations ID INNER SATELLITES; JUPITERS RING; SYSTEM; DISCOVERY; ORIGIN AB The near IR spectral reflectance of the Jupiter dust ring is poorly known because of problems with scattered light from the planet, Here we report colors for the jovian ring and one of the two ring satellites, Adrastea, using observations from the near-IR camera NICMOS on the Hubble Space Telescope. Near the time when the Earth crossed the jovian ring plane in the fall of 1997, we recorded broad-band images at similar to 1.1 (F110W), similar to 1.6 (F160W), and similar to 2.05 mu m (F205W) and derived a single-pass, in radial direction measured ring brightness of 19.19 +/- 0.07, 18.76 +/- 0.06, and 18.49 +/- 0.04 mag linear arcsec-l, respectively. These single-pass radial ring brightnesses were derived from the observable part of the ring at a projected distance of >1.2 R-J using a model to remove projection effects. The corresponding apparent magnitudes for Adrastea are 18.30 +/- 0.10 (F110W), 17.73 +/- 0.09 (F160W), and 17.57 +/- 0.07 mag (F205W), obtained at a phase angle of phi = 11.3 degrees. The relative spectral reflectance of the ring and that of Adrastea turn out to be nearly identical, slightly reddish with a slope of about 15-20% between 1 and 2 mu m. No evidence for transient ice crystals to be present in the main ring is seen, Our data are also in reasonable agreement with earlier ground-based measurements by Neugebauer et al. (1981), if we take their relatively large errors into account. The similarities of the colors of all inner satellites, including Io, are striking. The measured ring color provides evidence that the backscattered light from the ring is due to grains with mean particle sizes in excess of several micrometers, We were also able to infer a spatial particle distribution for the main ring. Its radial surface-density profile peaks sharply near the outer edge of the ring at the orbit of Adrastea, suggesting a strong dynamical relationship between the satellite and the ring particles. Our radial profile of the main ring is in excellent agreement with the results from Voyager images in backscattered light at visible wavelengths, except that we could not resolve any fine structures. The halo above and below the ring plane with a peak brightness near the inner edge of the ring appears to have a blue color compared to the main ring, but due to the low surface brightness of the halo the statistical significance of this color trend is only marginal. Such a color trend would be consistent with a dust population dominated by particles smaller than those in the main ring. (C) 1999 Academic Press. C1 Univ Hawaii, Inst Astron, Honolulu, HI 96822 USA. Univ Hawaii, Inst Astron, Napoopoo, HI 96704 USA. Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Meier, R (reprint author), Univ Hawaii, Inst Astron, 2680 Woodlawn Dr, Honolulu, HI 96822 USA. NR 39 TC 7 Z9 7 U1 0 U2 0 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD OCT PY 1999 VL 141 IS 2 BP 253 EP 262 DI 10.1006/icar.1999.6172 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 253ER UT WOS:000083544100006 ER PT J AU Lisse, CM Christian, D Denneel, K Englhauser, J Trumper, J Desch, M Marshall, FE Petre, R Snowden, S AF Lisse, CM Christian, D Denneel, K Englhauser, J Trumper, J Desch, M Marshall, FE Petre, R Snowden, S TI X-ray and extreme ultraviolet emission from comet P/Encke 1997 SO ICARUS LA English DT Article DE comets; atmospheres; coma; solar wind; spectrometry, X-rays ID C/1996 B2 HYAKUTAKE; SOLAR-WIND; OUTGASSING ASYMMETRY; DUST PARTICLES; P/HALLEY; ENCKE; GENERATION; NUCLEUS; WATER; IONS AB In an effort to understand the newly discovered phenomenon of cometary X-ray emission, we have obtained observations of the short period (3.3 years), well-studied comet 2P/Encke (Encke) during its July 1997 close approach to Earth. Extended, variable emission on the sunward side of the nucleus was found in the Rontgen X-ray satellite High Resolution Imager (HRI) at 0.090-0.75 keV and in the Extreme Ultraviolet Explorer (EUVE) scanner telescopes' Lexan B 0.090- to 0.28-keV and Al/Ti/C 0.050- to 0.16-keV bandpasses; useful upper limits were found in the Ti/Sb/Al 0.020- to 0.040-eV bandpass. Similar to our results for C/Hyakutake. the emission morphology was roughly symmetric with respect to a vector from the comet's nucleus toward the Sun, with a light curve consisting of a slowly varying baseline emission and a large impulsive event on 7 July 1997 with a time scale of similar to 3 h and an amplitude of similar to 3 times the baseline. A count rate of similar to 0.17 counts s(-1) in the HRI was measured for the slowly varying emission, corresponding to a total luminosity L(x) of 4 x 10(14) erg s(-1). Unlike Hyahutake, however the bulk of the emission clearly originates outside the comet's bow-shock, arguing against the magnetic reconnection and plasma dust emission models. The comet's lightcurve does not correlate with the solar X-ray lightcurve, ruling out scattering of solar X-rays as the emission mechanism. The multiwavelength HRI/EUVE photometry is inconsistent with the Haberli et al. (1997, Science 276, 939-942) charge transfer, plasma dust, and attogram dust models of cometary X-ray emission and is consistent with the Wegmann et al. (1988, Planet. Space Sci. 46, 603-612) charge exchange, 0.15- to 0.45-keV thermal bremsstrahlung, and photon index 1.6-2.0 power law models. While the impulsive event correlates very well with the passage of a solar magnetic field boundary at the Earth and an increase in the solar wind particle flux, it is not coincident, according to current models of the solar wind magnetic current sheet, with the passage of the sector boundary by the comet, suggesting that new models of the current sheet are necessary. (C) 1999 Academic Press. C1 Univ Maryland, Dept Astron, College Pk, MD 20742 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Univ Calif Berkeley, Ctr Extreme Ultraviolet Astrophys, Berkeley, CA 94720 USA. Max Planck Inst Extraterr Phys, D-85740 Garching, Germany. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Lisse, CM (reprint author), Univ Maryland, Dept Astron, College Pk, MD 20742 USA. EM lisse@stsci.edu RI Snowden, Steven/D-5292-2012; Lisse, Carey/B-7772-2016; OI Lisse, Carey/0000-0002-9548-1526; Christian, Damian/0000-0003-1746-3020 NR 45 TC 48 Z9 48 U1 0 U2 0 PU ACADEMIC PRESS INC ELSEVIER SCIENCE PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD OCT PY 1999 VL 141 IS 2 BP 316 EP 330 DI 10.1006/icar.1999.6176 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 253ER UT WOS:000083544100011 ER PT J AU Fink, U Hicks, MP Fevig, RA AF Fink, U Hicks, MP Fevig, RA TI Production rates for the Stardust mission target: 81P/Wild 2 SO ICARUS LA English DT Article DE comets; composition; 81 P/wild2; spectroscopy; spectrophotometry ID COMET; SPECTROSCOPY AB We observed 81P/Wild 2 from February 01 to June 01, 1997, during five observing runs spaced roughly 1 month apart straddling perihelion 1997 May 06.6. A considerable volume of spectroscopic data was collected and is analyzed in the present paper. In units of 10(25) molecules/s the following gas production rates were measured: H2O, 1500; CN, 3.3; NH2, 4.0; C-2, less than or equal to 0.9. Emissions by C-2 appear to be present in our data but this is not certain. The gas production stayed relatively constant throughout our observation period but the dust production as measured by Afp dropped from 564 to 311 cm. Comparison with other comets in our sample shows that Wild 2 is a Borrelly-type comet depleted in C-2, but with average to slightly high NH2 abundance. Our imaging data indicate noticeable coma activity around February 01 followed by relatively constant outgassing. Our V + R magnitudes are compared with visual data and their different behavior is discussed and explained. The comet's visual magnitude brightness dependence shows a steep 25 log r(H) dependence, indicating a mature crust. (C) 1999 Academic Press. C1 Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Fink, U (reprint author), Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. NR 16 TC 38 Z9 38 U1 0 U2 2 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 OCT PY 1999 VL 141 IS 2 BP 331 EP 340 DI 10.1006/icar.1999.6182 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 253ER UT WOS:000083544100012 ER PT J AU Cockell, CS AF Cockell, CS TI Carbon biochemistry and the ultraviolet radiation environments of F, G, and K main sequence stars SO ICARUS LA English DT Article ID EARTHS EARLY ATMOSPHERE; UV-RADIATION; DEINOCOCCUS-RADIODURANS; DIOXIDE CONCENTRATIONS; YOUNG SUN; EVOLUTION; OXYGEN; SENSITIVITY; PRESSURE; OZONE AB The ultraviolet radiation environment of main sequence stars might be a factor in determining the suitability of extrasolar planets for biological evolution and the subsequent radiation of life in exposed habitats. Assuming the validity of the carbon-water chauvinism, the absorbance of DNA in the UV region of the spectrum is used as a theoretical biological dosimeter to elucidate in more detail the photobiological parameter space of anoxic planets orbiting F, G, and K main sequence stars. Planets within the habitable zones of K main sequence stars have particularly favorable UV environments, with biochemically effective irradiances an order of magnitude lower than those believed to have existed on the surface of Archean Earth. Even using the UV shielding and repair habits of present-day terrestrial organisms, the survivability of the photobiological environment of anoxic K star planets can be demonstrated. The biochemically effective irradiances received in the F star radiation environment are more severe, being 6 to 27 times higher than on Archean Earth. Nevertheless, a combination of UV mitigation strategies seen on the present-day Earth suggest that UV radiation is not a constraint on life even in the inner region of the habitable zone. Life in an ocean on an F-star planet could experience a UV radiation regime similar even to that for present-day Earth. These calculations, although limited by our assumptions on the course of biochemical evolution and the UV absorbance of complex extraterrestrial molecules, suggest that life can survive the UV radiation environments of most extrasolar planets. (C) 1999 Academic Press. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Cockell, CS (reprint author), NASA, Ames Res Ctr, MIS 239-20, Moffett Field, CA 94035 USA. NR 47 TC 31 Z9 31 U1 0 U2 2 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 OCT PY 1999 VL 141 IS 2 BP 399 EP 407 DI 10.1006/icar.1999.6167 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 253ER UT WOS:000083544100017 ER PT J AU Hicks, MD Buratti, BJ Rabinowitz, DL AF Hicks, MD Buratti, BJ Rabinowitz, DL TI The lightcurve and geometric albedo of 433 Eros during the 1998 apparition SO ICARUS LA English DT Article DE asteroids; rotation; Eros ID ASTEROID 433-EROS; MU-M; PHOTOMETRY; STARS AB We obtained R-band photometry of 433 Eros at the Table Mountain 0.6-m telescope during its 1998 apparition. Our five nights of photometry yields a rotational period P-sid = 5.27048 +/- 0.00064 h and visual geometric albedo for 433 Eros of 0.27(-0.06)(+0.03), high, but within the range of S-type asteroids, Utilizing lightcurve data from the 1974/1975 apparition we solved for rotational pole position (RA = 00:46.9, DEC = +19:30.5; J2000) and axial ratios of 1.0:0.388:0.375, which are both significantly different from previously derived values. (C) 1999 Academic Press. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Pasadena City Coll, Dept Phys, Pasadena, CA 91106 USA. RP Hicks, MD (reprint author), CALTECH, Jet Prop Lab, MS 183-501,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 28 TC 2 Z9 2 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 OCT PY 1999 VL 141 IS 2 BP 411 EP 414 DI 10.1006/icar.1999.6178 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 253ER UT WOS:000083544100019 ER PT J AU Komisarek, KS Wang, NN Dominek, AK Hann, R AF Komisarek, KS Wang, NN Dominek, AK Hann, R TI An investigation of new FETD/ABC methods of computation of scattering from three-dimensional material objects SO IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION LA English DT Article ID ABSORBING BOUNDARY-CONDITIONS; FINITE-ELEMENT METHODS; MAXWELLS EQUATIONS; WAVES AB Finite-element time-domain (FETD) and absorbing boundary condition (ABC) methods for computation of scattering from three-dimensional (3-D) material objects are developed and investigated. The methods involve discrete-time FETD solution of the time-domain Helmholtz equation in a region that comprises the 3-D scatterer and its immediate vicinity. Coupling of the solution to the surrounding infinite space is achieved through the ABC. This FETD/ABC formulation is examined for a number of various geometries: sphere, plate, and ogive. C1 Ohio State Univ, Dept Elect Engn, Electrosci Lab, Columbus, OH 43212 USA. NASA, Computat Mat Lab, Div Mat, Cleveland, OH 44111 USA. RP Komisarek, KS (reprint author), Raytheon Syst Co, Radar Design Ctr, Sudbury, MA 01776 USA. NR 23 TC 14 Z9 16 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-926X J9 IEEE T ANTENN PROPAG JI IEEE Trans. Antennas Propag. PD OCT PY 1999 VL 47 IS 10 BP 1579 EP 1585 DI 10.1109/8.805903 PG 7 WC Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA 258VN UT WOS:000083860100013 ER PT J AU Jacob, JC Lee, SY AF Jacob, JC Lee, SY TI Task spreading and shrinking on multiprocessor systems and networks of workstations SO IEEE TRANSACTIONS ON PARALLEL AND DISTRIBUTED SYSTEMS LA English DT Article DE processor allocation; dynamic mapping; network of workstations; load balancing; task modeling ID LOAD AB In this paper, we describe how our computational model can be used for the problems of processor allocation and task mapping. The intended applications for this model include the dynamic mapping problems of shrinking or spreading an existing mapping when the available pool of processors changes during execution of the problem. The concept of problem edge class and other features of our model are developed to realistically and efficiently support task partitioning and merging for static and dynamic mapping. The model dictates realistic changes in the computation and communication characteristics of a problem when the problem partitioning is modified dynamically. This model forms the basis of our algorithms for shrinking and spreading, and yields realistic results for a variety of problems mapped onto real systems. An emulation program running on a network of workstations under PVM is used to measure execution times for the mapping solutions found by the algorithms. The results indicate that the problem edge class is a crucial consideration for processor allocation and task mapping. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Auburn Univ, Dept Elect Engn, Auburn, AL 36849 USA. RP Jacob, JC (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM joseph.jacob@jpl.nasa.gov; sylee@eng.auburn.edu NR 21 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 1045-9219 EI 1558-2183 J9 IEEE T PARALL DISTR JI IEEE Trans. Parallel Distrib. Syst. PD OCT PY 1999 VL 10 IS 10 BP 1082 EP 1101 DI 10.1109/71.808157 PG 20 WC Computer Science, Theory & Methods; Engineering, Electrical & Electronic SC Computer Science; Engineering GA 257YV UT WOS:000083811600011 ER PT J AU Stone, HS Le Moigne, J McGuire, M AF Stone, HS Le Moigne, J McGuire, M TI The translation sensitivity of wavelet-based registration SO IEEE TRANSACTIONS ON PATTERN ANALYSIS AND MACHINE INTELLIGENCE LA English DT Article DE image registration; image search; wavelet transform; correlation; low-pass filter; high-pass filter; Haar wavelet; Daubechies wavelet; multiresolution search ID TRANSFORM; IMAGERY AB This paper studies the effects of image translation on wavelet-based image registration. The main result is that the normalized correlation coefficients of low-pass Haar and Daubechies wavelet subbands are essentially insensitive to translations for features larger than twice the wavelet blocksize. The third-level low-pass subbands produce a correlation peak that varies with translation from 0.7 and 1.0 with an average in excess of 0.9. Translation sensitivity is limited to the high-pass subband and even this subband is potentially useful. The correlation peak for high-pass subbands derived from first and second-level low-pass subbands ranges from about 0.0 to 1.0 with an average of about 0.5 for Daubechies and 0.7 for Haar. We use a mathematical model to develop these results, and confirm them on real data. C1 NEC Res Inst, Princeton, NJ 08540 USA. NASA, Goddard Space Flight Ctr, Appl Informat SCi Branch CS, Greenbelt, MD 20771 USA. MIT, Cambridge, MA 02139 USA. RP Stone, HS (reprint author), NEC Res Inst, 4 Independence Way, Princeton, NJ 08540 USA. NR 27 TC 33 Z9 41 U1 0 U2 3 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1314 USA SN 0162-8828 J9 IEEE T PATTERN ANAL JI IEEE Trans. Pattern Anal. Mach. Intell. PD OCT PY 1999 VL 21 IS 10 BP 1074 EP 1081 DI 10.1109/34.799911 PG 8 WC Computer Science, Artificial Intelligence; Engineering, Electrical & Electronic SC Computer Science; Engineering GA 248DB UT WOS:000083259100008 ER PT J AU Meyyappan, M Economou, DJ Makabe, T AF Meyyappan, M Economou, DJ Makabe, T TI Special issue on the modeling of collisional or near-collisionless low-temperature plasmas SO IEEE TRANSACTIONS ON PLASMA SCIENCE LA English DT Editorial Material C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Houston, Dept Chem Engn, Houston, TX 77204 USA. Keio Univ, Dept Elect & Elect Engn, Yokohama, Kanagawa 2338522, Japan. RP Meyyappan, M (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0093-3813 J9 IEEE T PLASMA SCI JI IEEE Trans. Plasma Sci. PD OCT PY 1999 VL 27 IS 5 BP 1223 EP 1224 DI 10.1109/TPS.1999.799797 PG 2 WC Physics, Fluids & Plasmas SC Physics GA 251PA UT WOS:000083453000001 ER PT J AU Huo, WM Kim, YK AF Huo, WM Kim, YK TI Electron collision cross-section data for plasma modeling SO IEEE TRANSACTIONS ON PLASMA SCIENCE LA English DT Review DE chemistry; collision processes; database reliability; electrons; impact ionization; plasma properties ID LOW-ENERGY ELECTRONS; IMPACT IONIZATION; VIBRATIONAL-EXCITATION; FREE-RADICALS; DISSOCIATIVE ATTACHMENT; ELASTIC-SCATTERING; NEUTRAL RADICALS; INTERMEDIATE LIFETIMES; METHANE SCATTERING; DECAY ENERGETICS AB An overview of the current status in electron collision cross section databases for plasma modeling is presented, Emphasis is on dissociation, ionization, and dissociative ionization, The effect of the operating conditions on the relative importance of different collision mechanisms is discussed. For high density plasmas with low gas pressure, a second collision with electrons becomes likely and metastable states may play a role in the dissociation and ionization processes, A number of outstanding theoretical and experimental issues in the cross-section data are discussed. For the total ionization cross section, a four-parameter fitting formula is found to represent the numerical data well and the parameters for some molecules used in plasma modeling are presented. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Natl Inst Stand & Technol, Gaithersburg, MD 20899 USA. RP NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. EM huo@pegasus.arc.nasa.gov; yong-ki.kim@nist.gov NR 148 TC 26 Z9 26 U1 0 U2 12 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA SN 0093-3813 EI 1939-9375 J9 IEEE T PLASMA SCI JI IEEE Trans. Plasma Sci. PD OCT PY 1999 VL 27 IS 5 BP 1225 EP 1240 DI 10.1109/27.799798 PG 16 WC Physics, Fluids & Plasmas SC Physics GA 251PA UT WOS:000083453000002 ER PT J AU Khaoustov, VI Darlington, GJ Soriano, HE Krishnan, B Risin, D Pellis, NR Yoffe, B AF Khaoustov, VI Darlington, GJ Soriano, HE Krishnan, B Risin, D Pellis, NR Yoffe, B TI Induction of three-dimensional assembly of human liver cells by simulated microgravity SO IN VITRO CELLULAR & DEVELOPMENTAL BIOLOGY-ANIMAL LA English DT Article DE human hepatocytes; microgravity; bioreactor; biodegradable scaffolds; cell cultures ID HEPATOCYTE CULTURE; TISSUE; DIFFERENTIATION; ANGIOGENESIS; SYSTEMS; GROWTH; EGF AB The establishment of long-term cultures of functional primary human liver cells (PHLC) is formidable. Developed at NASA, the Rotary Cell Culture System (RCCS) allows the creation of the unique microgravity environment of low shear force, high-mass transfer, and 3-dimensional cell culture of dissimilar cell types. The aim of our study was to establish long-term hepatocyte cultures in simulated microgravity;. PHLC were harvested from human livers by collagenase perfusion and were cultured in RCCS. PHLC aggregates were readily formed and increased up to 1 cm long. The expansion of PHLC in bioreactors was further evaluated with microcarriers and biodegradable scaffolds. While microcarriers were not conducive to formation of spheroids, PHLC cultured with biodegradable scaffolds formed aggregates up to 3 cm long. Analyses of PHLC spheroids revealed tissue-like structures composed of hepatocytes, biliary epithelial cells, and/or progenitor liver cells that were arranged as bile duct-like structures along nascent vascular sprouts. Electron microscopy revealed groups of cohesive hepatocytes surrounded by complex stromal structures and reticulin fibers, bile canaliculi with multiple microvilli, and tight cellular junctions. Albumin mRNA was expressed throughout the 60-d culture. A simulated microgravity environment is conducive to maintaining long-term cultures of functional hepatocytes. This model system will assist in developing improved protocols for autologous hepatocyte transplantation, gene therapy and liver assist devices, and facilitate studies of liver regeneration and cell-to-cell interactions that occur in vivo. C1 Baylor Coll Med, Vet Affairs Med Ctr, Dept Med, Houston, TX 77030 USA. Baylor Coll Med, Vet Affairs Med Ctr, Dept Pathol, Houston, TX 77030 USA. Baylor Coll Med, Vet Affairs Med Ctr, Dept Pediat, Houston, TX 77030 USA. NASA, Biotechnol Program, Houston, TX 77058 USA. RP Yoffe, B (reprint author), Baylor Coll Med, Vet Affairs Med Ctr, Dept Med, 151B,2002 Holcombe Blvd, Houston, TX 77030 USA. NR 22 TC 70 Z9 72 U1 2 U2 11 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 OCT PY 1999 VL 35 IS 9 BP 501 EP 509 PG 9 WC Cell Biology; Developmental Biology SC Cell Biology; Developmental Biology GA 249GM UT WOS:000083325000004 PM 10548431 ER PT J AU Whittenberger, JD Raj, SV Locci, IE Salem, JA AF Whittenberger, JD Raj, SV Locci, IE Salem, JA TI Effect of growth rate on elevated temperature plastic flow and room temperature fracture toughness of directionally solidified NiAl-31Cr-3Mo SO INTERMETALLICS LA English DT Article DE nickel aluminides, based on NiAl; fracture toughness; mechanical properties at high temperatures ID ROD-PLATE TRANSITION; EUTECTIC NIAL-CR; CREEP-BEHAVIOR; COMPOSITES; ALLOYS; PHASE AB The eutectic system Ni-33Al-31Cr-3Mo was directionally solidified at rates ranging from 7.6 to 508 mm/h. Samples were examined for microstructure and alloy chemistry, compression tested at 1200 and 1300 K, and subjected to room temperature fracture toughness measurements. Lamellar eutectic grains were formed at 12.7 mm/h; however, cellular structures with a radial eutectic pattern developed at faster growth rates. Elevated temperature compression testing between 10(-4) to 10(-7) s(-1) did not reveal an optimum growth condition, nor did any single growth condition result in a significant fracture toughness advantage. The mechanical behavior, taken together, suggests that Ni-33Al-31Cr-3Mo grown at rates from 25.4 to 254 mm/h will have nominally equivalent properties (C) 1999 Elsevier Science Ltd. All rights reserved. C1 NASA, Glenn Res Ctr Lewis Field, Cleveland, OH 44135 USA. Case Western Reserve Univ, GRC, Cleveland, OH 44135 USA. RP Whittenberger, JD (reprint author), NASA, Glenn Res Ctr Lewis Field, Cleveland, OH 44135 USA. EM John.D.Whittenberger@grc.nasa.gov NR 29 TC 33 Z9 33 U1 0 U2 5 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND SN 0966-9795 EI 1879-0216 J9 INTERMETALLICS JI Intermetallics PD OCT PY 1999 VL 7 IS 10 BP 1159 EP 1168 DI 10.1016/S0966-9795(99)00023-0 PG 10 WC Chemistry, Physical; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Chemistry; Materials Science; Metallurgy & Metallurgical Engineering GA 232LW UT WOS:000082373100011 ER PT J AU Darolia, R Walston, WS Noebe, R Garg, A Oliver, BF AF Darolia, R Walston, WS Noebe, R Garg, A Oliver, BF TI Mechanical properties of high purity single crystal NiAl SO INTERMETALLICS LA English DT Article DE fracture toughness ID TEMPERATURE TENSILE DUCTILITY; COMPRESSIVE BEHAVIOR; ADDITIONS; ALLOYS; TI AB This paper describes the results of a study carried out to determine the role of impurities on the mechanical behavior of NiAl. Tensile, compression and toughness tests were carried out on high purity single crystal NiAl of the stoichiometric composition. The test results were compared with the results obtained with the conventional purity NiAl. The high purity NiAl specimens did not exhibit any improvement in room temperature ductility and toughness. The deformation behavior at room temperature of the high purity single crystals was found to be similar to that of the conventional purity NiAl single crystals. However, the high purity NiAl single crystals showed an absence of strain aging and much lower yield strength compared to the conventional purity NiAl. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 GE Aircraft Engines, Cincinnati, OH 45215 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. Univ Tennessee, Knoxville, TN 37996 USA. RP Darolia, R (reprint author), GE Aircraft Engines, 1 Neumann Way, Cincinnati, OH 45215 USA. NR 24 TC 24 Z9 25 U1 0 U2 5 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND SN 0966-9795 J9 INTERMETALLICS JI Intermetallics PD OCT PY 1999 VL 7 IS 10 BP 1195 EP 1202 DI 10.1016/S0966-9795(99)00043-6 PG 8 WC Chemistry, Physical; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Chemistry; Materials Science; Metallurgy & Metallurgical Engineering GA 232LW UT WOS:000082373100015 ER PT J AU Menzies, T Van Harmelen, F AF Menzies, T Van Harmelen, F TI Editorial: Evaluating knowledge engineering techniques SO INTERNATIONAL JOURNAL OF HUMAN-COMPUTER STUDIES LA English DT Editorial Material ID PROBLEM-SOLVING METHODS; ARTIFICIAL-INTELLIGENCE; SYSTEMS; ACQUISITION; LOGIC; REPRESENTATION; COMPUTER; SPACE C1 NASA WVU IV&V Facil, Fairmont, WV 26554 USA. Vrije Univ Amsterdam, Fac Sci, Dept AI, Amsterdam, Netherlands. RP Menzies, T (reprint author), NASA WVU IV&V Facil, 100 Univ Dr, Fairmont, WV 26554 USA. NR 78 TC 9 Z9 9 U1 2 U2 3 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 OCT PY 1999 VL 51 IS 4 BP 715 EP 727 DI 10.1006/ijhc.1999.0336 PG 13 WC Computer Science, Cybernetics; Ergonomics; Psychology, Multidisciplinary SC Computer Science; Engineering; Psychology GA 250PX UT WOS:000083397700001 ER PT J AU Menzies, T AF Menzies, T TI Critical success metrics: evaluation at the business level SO INTERNATIONAL JOURNAL OF HUMAN-COMPUTER STUDIES LA English DT Article ID ABDUCTION AB If we lack an objective human expert oracle who can assess a system, and if we lack a library of known or desired behavior, how can we assess an expert system? One method for doing so is a critical success metric (CSM). A CSM is an assessment of a running program which reflects the business concerns that prompted the creation of that program. Given Pre-disaster knowledge, a CSM can be used while the expert system is in routine use, without compromising the operation of the system. A general CSM experiment is defined using pre-disaster points which can compare (e.g.) human to expert system performance. Examples of using CSMs are given from the domains of farm management and process control. (C) 1999 Academic Press. C1 NASA WVU IV&V Facil, Fairmont, WV 26554 USA. RP Menzies, T (reprint author), NASA WVU IV&V Facil, 100 Univ Dr, Fairmont, WV 26554 USA. NR 42 TC 2 Z9 2 U1 0 U2 0 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 OCT PY 1999 VL 51 IS 4 BP 783 EP 799 DI 10.1006/ijhc.1999.0329 PG 17 WC Computer Science, Cybernetics; Ergonomics; Psychology, Multidisciplinary SC Computer Science; Engineering; Psychology GA 250PX UT WOS:000083397700004 ER PT J AU Leonardo, MR Moser, DP Barbieri, E Brantner, CA MacGregor, BJ Paster, BJ Stackebrandt, E Nealson, KH AF Leonardo, MR Moser, DP Barbieri, E Brantner, CA MacGregor, BJ Paster, BJ Stackebrandt, E Nealson, KH TI Shewanella pealeana sp nov., a member of the microbial community associated with the accessory nidamental gland of the squid Loligo pealei SO INTERNATIONAL JOURNAL OF SYSTEMATIC BACTERIOLOGY LA English DT Article DE Shewanella pealeana; Loligo pealei; sulfur reducer; choline ID PERFORMANCE LIQUID-CHROMATOGRAPHY; DNA HYBRIDIZATION; GLYCINE BETAINE; ALTEROMONAS-PUTREFACIENS; FACULTATIVE ANAEROBE; FORBESI CEPHALOPODA; RENATURATION RATES; TEICHOIC-ACID; REDUCTION; CHOLINE AB A new, mesophillic, facultatively anaerobic, psychrotolerant bacterium, strain ANG-SQ1(T) (T = type strain), was isolated from a microbial community colonizing the accessory nidamental gland of the squid Loligo pealei. It was selected from the community on the basis of its ability to reduce elemental sulfur. The cells are motile, Gram-negative rods (2.0-3.0 mu m long, 0.4-0.6 mu m wide). ANG-SQ1T grows optimally over the temperature range of 25-30 degrees C and a ph range of 6.5-7.5 degrees C in media containing 0.5 M NaCl. 16S rRNA sequence analysis revealed that this organism belongs to the gamma-3 subclass of the Proteobacteria. The closest relative of ANG-SQ1(T) is Shewanella gelidimarina, with a 16S rRNA sequence similarity of 97.0%. Growth occurs with glucose, lactate, acetate, pyruvate, glutamate, citrate, succinate, Casamino acids, yeast extract or peptone as sole energy source under aerobic conditions. The isolate grows anaerobically by the reduction of iron, manganese, nitrate, fumarate, trimethylamine-N-oxide, thiosulfate or elemental sulfur as terminal electron acceptor with lactate. Growth of ANG-SQ1(T) was enhanced by the addition of choline chloride to growth media lacking Casamino acids. The addition of leucine or valine also enhanced growth in minimal growth media supplemented with choline. The results of both phenotypic and genetic characterization indicate that ANG-SQ1T is a Shewanella species. Thus it is proposed that this new isolate be assigned to the genus Shewanella and that it should be named Shewanella pealeana sp. nov., in recognition of its association with L. pealei. C1 Univ Wisconsin, Ctr Great Lakes Studies, Milwaukee, WI 53204 USA. Univ Urbino, Ist Sci Tossicog Ingienst & Ambientali, I-61029 Urbino, Italy. Univ Wisconsin, Dept Biol Sci, Milwaukee, WI 53211 USA. Northwestern Univ, Dept Civil Engn, Evanston, IL 60208 USA. Forsyth Inst, Dept Mol Genet, Boston, MA 02115 USA. Deutsch Sammlung Mikroorganismen & Zellkulturen G, D-38124 Braunschweig, Germany. CALTECH, Jet Prop Labs, Pasadena, CA 91109 USA. RP Leonardo, MR (reprint author), Univ Alabama, Dept Biol Sci, Box 870206, Tuscaloosa, AL 35487 USA. RI MacGregor, Barbara/D-9911-2013; OI MacGregor, Barbara/0000-0003-1238-5799; Brantner, Christine/0000-0001-8172-901X; Barbieri, Elena/0000-0002-3480-7983 NR 60 TC 49 Z9 51 U1 3 U2 13 PU SOC GENERAL MICROBIOLOGY PI READING PA MARLBOROUGH HOUSE, BASINGSTOKE RD, SPENCERS WOODS, READING, BERKS, ENGLAND RG7 1AE SN 0020-7713 J9 INT J SYST BACTERIOL JI Int. J. Syst. Bacteriol. PD OCT PY 1999 VL 49 BP 1341 EP 1351 PN 4 PG 11 WC Microbiology SC Microbiology GA 251NB UT WOS:000083450800002 PM 10555311 ER PT J AU Kulikov, I AF Kulikov, I TI Scalar lambda phi(4) model with nontrivial topology SO INTERNATIONAL JOURNAL OF THEORETICAL PHYSICS LA English DT Article ID NON-MINKOWSKIAN SPACETIMES; QUANTUM-FIELD-THEORY; FINITE-TEMPERATURE; RENORMALIZATION-GROUP; SYMMETRY-BREAKING; COLLECTIVE PHENOMENA; MASS GENERATION; GAUGE THEORIES AB Effects of nontrivial topology S-1 x R-3 of space-time for a scalar self-interacting lambda phi(4) model in the perturbative regime are discussed. Asymptotic properties of the coupling constant for untwisted and twisted field configurations are investigated. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Kulikov, I (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 32 TC 0 Z9 0 U1 0 U2 0 PU KLUWER ACADEMIC/PLENUM PUBL PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 0020-7748 J9 INT J THEOR PHYS JI Int. J. Theor. Phys. PD OCT PY 1999 VL 38 IS 10 BP 2511 EP 2533 DI 10.1023/A:1026601108554 PG 23 WC Physics, Multidisciplinary SC Physics GA 258ZD UT WOS:000083868800003 ER PT J AU Chamis, CC Gotsis, PK AF Chamis, CC Gotsis, PK TI Infrastructure retrofit using design composite mechanics SO JOURNAL OF ADVANCED MATERIALS LA English DT Article AB Selected applications are described to illustrate the concept for retrofitting reinforced concrete structures with fiber reinforced plastic laminates. The concept is first illustrated by using an axially loaded reinforced concrete column. A reinforced concrete arch and a dome are then used to illustrate the versatility of the concept. Advanced methods such as finite element structural analysis and progressive structural fracture are then used to evaluate the retrofitting laminate adequacy. Results obtained show that retrofits can be designed to double and even triple the "as-designed" load of the selected reinforced concrete structures. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Chamis, CC (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 8 TC 0 Z9 0 U1 0 U2 0 PU SAMPE PUBLISHERS PI COVINA PA 1161 PARKVIEW DRIVE, COVINA, CA 91722 USA SN 1070-9789 J9 J ADV MATER JI J. Adv. Mater. PD OCT PY 1999 VL 31 IS 4 BP 33 EP 36 PG 4 WC Materials Science, Multidisciplinary SC Materials Science GA 244DR UT WOS:000083037000007 ER PT J AU Carli, B Ade, PAR Cortesi, U Dickinson, P Epifani, M Gannaway, FC Gignoli, A Keim, C Lee, C Meny, C Leotin, J Mencaraglia, F Murray, AG Nolt, IG Ridolfi, M AF Carli, B Ade, PAR Cortesi, U Dickinson, P Epifani, M Gannaway, FC Gignoli, A Keim, C Lee, C Meny, C Leotin, J Mencaraglia, F Murray, AG Nolt, IG Ridolfi, M TI SAFIRE-A: Spectroscopy of the atmosphere using far-infrared emission/airborne SO JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY LA English DT Article ID RESOLUTION FOURIER SPECTROMETER AB A new instrument named SAFIRE-A (Spectroscopy of the Atmosphere using Far-Infrared Emission/Airborne), which can operate on high-altitude platforms, has been developed for the study of the atmospheric composition through limb-scanning emission measurements. The instrument is a polarizing Fourier transform spectrometer that operates in the far infrared with a resolution of 0.004 cm(-1). SAFIRE-A uses efficient photon noise limited detectors and a novel optical configuration, which provide a cold pupil and field stop as well as cold narrow bandpass filters to enhance its sensitivity. The instrument was successfully operated on an M-55 stratospheric research aircraft in the polar regions during the winter 1996-97 Airborne Polar Experiment. The instrument design, aircraft integration, and performances attained in the field campaign are described and discussed. The atmospheric emission spectrum is measured with an rms noise accuracy of 0.5 K (measured in brightness temperature) in each spectral element near 20 cm(-1) with a 30-s measurement time. C1 CNR, Ist Ric Onde Elettromagnet, Nello Carrara, I-50127 Florence, Italy. QMW, London, England. FZK, IMK, Karlsruhe, Germany. RAL, Didcot, Oxon, England. SNCMP, Toulouse, France. NASA, Langley Res Ctr, Hampton, VA 23665 USA. RP Carli, B (reprint author), CNR, Ist Ric Onde Elettromagnet, Nello Carrara, Via Panciatichi 64, I-50127 Florence, Italy. RI Cortesi, Ugo/D-2704-2012 OI Cortesi, Ugo/0000-0002-2827-5239 NR 16 TC 20 Z9 20 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 OCT PY 1999 VL 16 IS 10 BP 1313 EP 1328 DI 10.1175/1520-0426(1999)016<1313:SASOTA>2.0.CO;2 PG 16 WC Engineering, Ocean; Meteorology & Atmospheric Sciences SC Engineering; Meteorology & Atmospheric Sciences GA 242TV UT WOS:000082958500004 ER PT J AU Ma, Q Tipping, RH AF Ma, Q Tipping, RH TI The averaged density matrix in the coordinate representation: Application to the calculation of the far-wing line shapes for H2O SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID WATER CONTINUUM ABSORPTION; ROTATIONAL BANDS; VAPOR; REGION AB The far-wing line shape theory within the binary collision and quasistatic framework developed previously for linear molecules using the coordinate representation has been generalized to symmetric- and asymmetric-top molecular systems. However, due to more variables needed to specify the orientation of these complicated molecules, one has to evaluate multidimensional integrals with higher dimensionality and this would be intractable for practical calculations. In cases where the anisotropic interaction contains cyclic coordinates, one can carry out the integration of the density matrix over these coordinates analytically and obtain the "averaged" density matrix. This reduces the dimensionality of the multidimensional integrals and thus dramatically reduces the computational time necessary to obtain converged results. In addition, a new interpolation method that enables one to treat more realistic potential models has been formulated. Using these results, calculations for the band-average far-wing line shapes and corresponding absorption coefficients in the spectral range 300-1100 cm(-1) have been carried out for H2O-H2O and H2O-N-2 pairs for a few temperatures. These results improve the agreement with experimental data over previous calculations that were limited in the number of states that could be included and in the sophistication of the anisotropic interaction potential model that was used. <(C)> 1999 American Institute of Physics. [S0021-9606(99)00935-6]. C1 Columbia Univ, Dept Appl Phys, New York, NY 10025 USA. NASA, Goddard Space Flight Ctr, Inst Space Studies, New York, NY 10025 USA. Univ Alabama, Dept Phys & Astron, Tuscaloosa, AL 35487 USA. RP Ma, Q (reprint author), Columbia Univ, Dept Appl Phys, 2880 Broadway, New York, NY 10025 USA. NR 22 TC 32 Z9 35 U1 0 U2 1 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0021-9606 J9 J CHEM PHYS JI J. Chem. Phys. PD OCT 1 PY 1999 VL 111 IS 13 BP 5909 EP 5921 DI 10.1063/1.479886 PG 13 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 238UW UT WOS:000082732100029 ER PT J AU Chen, MH Rood, RB Joiner, J AF Chen, MH Rood, RB Joiner, J TI Assimilating TOVS humidity into the GEOS-2 data assimilation system SO JOURNAL OF CLIMATE LA English DT Article ID GENERAL-CIRCULATION MODELS; TROPOSPHERIC WATER-VAPOR; VARIATIONAL ANALYSIS; UARS MLS; CLIMATE; INFORMATION; REANALYSIS; PREDICTION; PROJECT; IMPACT AB The humidity data retrieved from the TIROS Operational Vertical Sounder (TOVS) measurements is assimilated into the Goddard Earth Observing System (GEOS) data assimilation system. The study focuses on the impact of the TOVS humidity on assimilated humidity, precipitation, clouds, and radiation. The GEOS assimilation system utilizes the TOVS humidity effectively at levels below 300 mb, while the net impact on the 300-mb humidity is much less. It has been demonstrated that the impact results from direct and indirect effects. The direct effect is the analysis increment introduced by the humidity data, which draws the assimilated humidity toward the data. The indirect effect is realized through the interactions of humidity with physical processes, mainly with moist convection. The indirect effect is often opposite to the direct effect in the current assimilation system. The direct effect is dominant in the lower and middle troposphere while in the upper troposphere the indirect effect is more important. The impact of the TOVS humidity on the GEOS precipitation, clouds, and radiation is also significant due to strong interactions with convection and other physical processes. There is clear evidence indicating that tuning of physical parameterizations explicitly in the data assimilation mode is necessary for optimal use of the TOVS data in the assimilation system. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Chen, MH (reprint author), NASA, Goddard Space Flight Ctr, Code 910-3, Greenbelt, MD 20771 USA. RI Joiner, Joanna/D-6264-2012; Rood, Richard/C-5611-2008 OI Rood, Richard/0000-0002-2310-4262 NR 42 TC 5 Z9 5 U1 0 U2 1 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0894-8755 J9 J CLIMATE JI J. Clim. PD OCT PY 1999 VL 12 IS 10 BP 2983 EP 2995 DI 10.1175/1520-0442(1999)012<2983:ATHITG>2.0.CO;2 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 246KQ UT WOS:000083163300004 ER PT J AU Jadaan, OM Powers, LM Gyekenyesi, JP AF Jadaan, OM Powers, LM Gyekenyesi, JP TI Multixial creep life prediction of ceramic structures using continuum damage mechanics and the finite element method SO JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER-TRANSACTIONS OF THE ASME LA English DT Article; Proceedings Paper CT International Gas Turbine and Aeroengine Congress and Exhibition CY JUN 02-05, 1998 CL STOCKHOLM, SWEDEN ID SILICON-NITRIDE; RUPTURE; COMPONENTS; BEHAVIOR AB High temperature and long duration applications of monolithic ceramics can place their failure mode in the creep rupture regime. A previous model advanced by the authors described a methodology by which the creep rupture life of a loaded component can be predicted. That model was based on the life fraction damage accumulation rule in association with the modified Monkman-Grant creep rupture criterion. However, that model did not rake into account the deteriorating state of the material due to creep damage (e.g., cavitation) as time elapsed. In addition, the material creep parameters used in that life prediction methodology, were based on uniaxial creep curves displaying primary and secondary creep behavior, with no tertiary regime. The objective of this paper is to present a creep life prediction methodology based on a modified form of the Kachanov-Rabotnov continuum damage mechanics (CDM) theory. In this theory, the uniaxial creep rate is described in terms of stress, temperature, time, and the current state of material damage. This scalar damage state parameter is basically art abstract measure of the current state of material damage due to creep deformation. The damage rate is assumed to vary with stress, temperature, time, and the current state of damage itself Multiaxial creep and creep rupture formulations of the CDM approach are presented in this paper. Parameter estimation methodologies based on nonlinear regression analysis are also described for both, isothermal constant stress states and anisothermal variable stress conditions. This creep life prediction methodology was preliminarily added to the integrated design code named Ceramics Analysis and Reliability Evaluation of Structures/Creep (CARES/Creep), which is a postprocessor program to commercially available finite element analysis (FEA) packages. Two examples, showing comparisons between experimental and predicted creep lives of ceramic specimens, are used to demonstrate the viability of this methodology and the CARES/Creep program. C1 Univ Wisconsin, Coll Engn, Platteville, WI 53818 USA. Case Western Reserve Univ, Cleveland, OH 44106 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Jadaan, OM (reprint author), Univ Wisconsin, Coll Engn, Platteville, WI 53818 USA. NR 34 TC 0 Z9 0 U1 1 U2 3 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 USA SN 0742-4795 J9 J ENG GAS TURB POWER JI J. Eng. Gas. Turbines Power-Trans. ASME PD OCT PY 1999 VL 121 IS 4 BP 577 EP 585 DI 10.1115/1.2818511 PG 9 WC Engineering, Mechanical SC Engineering GA 250ZH UT WOS:000083419800001 ER PT J AU Van Selst, M Ruthruff, E Johnston, JC AF Van Selst, M Ruthruff, E Johnston, JC TI Can practice eliminate the psychological refractory period effect? SO JOURNAL OF EXPERIMENTAL PSYCHOLOGY-HUMAN PERCEPTION AND PERFORMANCE LA English DT Article ID DUAL-TASK INTERFERENCE; OVERLAPPING MENTAL OPERATIONS; CHRONOMETRIC EVIDENCE; SERIAL PERFORMANCE; 2 THINGS; ATTENTION; BOTTLENECK; MOVEMENTS; CAPACITY; PREVIEW AB Can people learn to perform two tasks at the same time without interference? To answer this question, the authors trained 6 participants for 36 sessions in a Psychological Refractory Period (PRP) experiment, where Task I required a speeded vocal response to an auditory stimulus and Task 2 required a speeded manual response to a visual stimulus. The large PRP effect found initially (353 ms in Session 1) shrank to only about 40 ms over the course of practice, disappearing entirely for 1 of the 6 participants. This reduction in the PRP effect with practice is considerably larger than has been previously reported. The obtained pattern of factor interactions between stimulus onset asynchrony and each of three task difficulty manipulations (Task 1 judgment difficulty, Task 2 stimulus contrast, and Task 2 mapping compatibility) supports a postponement (bottleneck) account of dual-task interference, both before and after practice. C1 San Jose State Univ, Dept Psychol 0120, San Jose, CA 95192 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Van Selst, M (reprint author), San Jose State Univ, Dept Psychol 0120, 1 Washington Sq, San Jose, CA 95192 USA. NR 69 TC 124 Z9 124 U1 1 U2 6 PU AMER PSYCHOLOGICAL ASSOC PI WASHINGTON PA 750 FIRST ST NE, WASHINGTON, DC 20002-4242 USA SN 0096-1523 J9 J EXP PSYCHOL HUMAN JI J. Exp. Psychol.-Hum. Percept. Perform. PD OCT PY 1999 VL 25 IS 5 BP 1268 EP 1283 DI 10.1037/0096-1523.25.5.1268 PG 16 WC Psychology; Psychology, Experimental SC Psychology GA 243RG UT WOS:000083010600006 PM 10531663 ER PT J AU Hathaway, DH Wilson, RM Reichmann, EJ AF Hathaway, DH Wilson, RM Reichmann, EJ TI A synthesis of solar cycle prediction techniques SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID SIZE; AMPLITUDE AB A number of techniques currently in use for predicting solar activity on a solar cycle timescale are tested with historical data. Some techniques, e.g., regression and curve fitting, work well as solar activity approaches maximum and provide a month-by-month description of future activity, while others, e.g., geomagnetic precursors, work well near solar minimum but only provide an estimate of the amplitude of the cycle. A synthesis of different techniques is shown to provide a more accurate and useful forecast of solar cycle activity levels. A combination of two uncorrelated geomagnetic precursor techniques provides a, more accurate prediction for the amplitude of a solar activity cycle at a time well before activity minimum. This combined precursor method gives a smoothed sunspot number maximum of 154 +/- 21 at the 95% level of confidence for the next cycle maximum. A mathematical function dependent on the time of cycle initiation and the cycle amplitude is used to describe the level of solar activity month by month for the next cycle. As the time of cycle maximum approaches a better estimate of the cycle activity is obtained by Including the fit between previous activity levels and this function. This Combined Solar Cycle Activity Forecast gives, as of January 1999, a smoothed sunspot maximum of 146 +/- 20 at the 95% level of confidence for the next cycle maximum. C1 NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Hathaway, DH (reprint author), NASA, George C Marshall Space Flight Ctr, Mail Code SD50, Huntsville, AL 35812 USA. EM david.hathaway@msfc.nasa.gov; robert.wilson@msfc.nasa.gov; ed.reichmann@msfc.nasa.gov NR 30 TC 123 Z9 125 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9380 EI 2169-9402 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD OCT 1 PY 1999 VL 104 IS A10 BP 22375 EP 22388 DI 10.1029/1999JA900313 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 240YV UT WOS:000082855100005 ER PT J AU Ogilvie, KW Burlaga, LF Chornay, DJ Fitzenreiter, RJ AF Ogilvie, KW Burlaga, LF Chornay, DJ Fitzenreiter, RJ TI Sources of the solar wind electron strahl in 1995 SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID VELOCITY DISTRIBUTION-FUNCTIONS; STREAM INTERFACES AB The electron "strahl" is a narrow beam of electrons formed along the interplanetary magnetic field in the solar wind, associated with coronal holes. Observations of this feature, covering the energy range 10-1000 eV, are being made continuously by a specially designed part of the Solar Wind Experiment (SWE) instrument on the Wind spacecraft. During 1995, when corotating streams were regularly observed, the strahl flux was always observed to increase to a maximum following the stream interface marking the separation of the interacting flows. It was not seen before a stream interface, meaning that the strahl does not cross the stream interface. The strahl is associated with corotating streams and their sources rather than with the magnetic sectors. The source of the strahl observed by Wind was the southern coronal hole during the first half of the year and the northern coronal hole during the last half, as indicated by the polarity of the magnetic field. C1 NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RP Ogilvie, KW (reprint author), NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. NR 15 TC 11 Z9 11 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 OCT 1 PY 1999 VL 104 IS A10 BP 22389 EP 22393 DI 10.1029/1999JA900294 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 240YV UT WOS:000082855100006 ER PT J AU Roberts, DA Ghosh, S AF Roberts, DA Ghosh, S TI A kinematic analysis of the role of velocity shear in expanding plasmas SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID SOLAR-WIND TURBULENCE; RADIAL EVOLUTION; MHD TURBULENCE; CROSS-HELICITY; MAGNETIC-FIELD; ALFVEN WAVES; FLUCTUATIONS; ORIGIN; SPECTRA; STREAMS AB We present a kinematic analysis of the effects on waves of the shear due to variations in radial flow and field-aligned propagation speeds in an expanding medium. We show that although the expansion limits the extent to which wave vectors transverse to the shear flow are produced, shear can be very effective at turning wave vectors and producing off-radial fluctuations. Any initial wave vector spectrum will become spread in wave vector space with no change in spectral index. For typical spectra of the sheared radial speeds, the small-scale variability in the speed is more important than the large-scale in the sense of effectively turning the wave vectors. Radial spectra will be unchanged by stream or microstream sheer, and although field-aligned Alfven speed changes will produce some observable effects, nonlinear processes are still needed to fully explain observations. This work suggests a model for near-Sun solar wind turbulence in which modes are "driven" nonlocally at all scales rather than the Kolmogoroff model, in which only large-scale driving is important; this is consistent with well-developed turbulence spectra in highly structured regions farther out in the wind. C1 NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. SM&A Corp, Largo, MD USA. RP Roberts, DA (reprint author), NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Code 692, Greenbelt, MD 20771 USA. EM roberts@vayu.gsfc.nasa.gov; sanjoy.ghosh@gsfc.nasa.gov RI Roberts, Dana/D-4625-2012 NR 29 TC 18 Z9 18 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 OCT 1 PY 1999 VL 104 IS A10 BP 22395 EP 22399 DI 10.1029/1999JA900272 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 240YV UT WOS:000082855100007 ER PT J AU Kahler, SW Cane, HV Hudson, HS Kurt, VG Gotselyuk, YV MacDowall, RJ Bothmer, V AF Kahler, SW Cane, HV Hudson, HS Kurt, VG Gotselyuk, YV MacDowall, RJ Bothmer, V TI Comment on "The solar energetic particle event of April 14, 1994, as a probe of shock formation and particle acceleration" by S. W. Kahler, H. V. Cane, H. S. Hudson, V. G. Kurt, Y. V. Gotselyuk, R. J. MacDowall, and V. Bothmer - Reply SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Editorial Material ID 3-DIMENSIONAL MHD SIMULATION; CORONAL MASS EJECTIONS; MAGNETIC-FIELD CHANGES; INTERPLANETARY; PROPAGATION; DECREASES; WIND; AU C1 Hanscom AFB, AFRL, VSBS, Bedford, MA 01731 USA. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Solar Phys Res Corp, Inst Space & Astronaut Sci, Sagamihara, Kanagawa, Japan. Moscow MV Lomonosov State Univ, Inst Nucl Phys, Moscow, Russia. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD USA. Univ Kiel, Inst Reine & Angew Kernphys, D-2300 Kiel, Germany. RP Kahler, SW (reprint author), Hanscom AFB, AFRL, VSBS, 29 Randolph Rd, Bedford, MA 01731 USA. EM kahler@plh.af.mil; cane@ncf.gsfc.nasa.gov; hudson@isass1.solar.isas.ac.jp; vgk@srdlan.npi.msu.su; juvg@srdlan.npi.msu.su; xrrjm@leprjm.gsfc.nasa.gov; bothmer@kernphysik.uni-kiel.de RI MacDowall, Robert/D-2773-2012 NR 25 TC 0 Z9 0 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD OCT 1 PY 1999 VL 104 IS A10 BP 22411 EP 22415 DI 10.1029/1999JA900235 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 240YV UT WOS:000082855100010 ER PT J AU Chandler, MO Fuselier, SA Lockwood, M Moore, TE AF Chandler, MO Fuselier, SA Lockwood, M Moore, TE TI Evidence of component merging equatorward of the cusp SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID MAGNETOPAUSE; RECONNECTION; SIGNATURES; TOPOLOGY AB The Polar spacecraft passed through a region near the dayside magnetopause on May 29, 1996, at a geocentric distance of similar to 8 R-E and high, northern magnetic latitudes. The interplanetary magnetic field (IMF) was northward during the pass. Data from the Thermal Ion Dynamics Experiment revealed the existence of low-speed (similar to 50 km s(-1)) ion D-shaped distributions mixed with cold ions (similar to 2 eV) over a period of 2.5 hours. These ions were traveling parallel to the magnetic field toward the Northern Hemisphere ionosphere and were convecting primarily eastward. The D-shaped distributions are distinct from a convecting Maxwellian and, along with the magnetic field direction, are taken as evidence that the spacecraft was inside the magnetosphere and not in the magnetosheath. Furthermore, the absence of ions in the antiparallel direction is taken as evidence that low-shear merging was occurring at a location southward of the spacecraft and equatorward of the Southern Hemisphere cusp. The cold ions were of ionospheric origin, with initially slow field-aligned speeds, which were accelerated upon reflection from the magnetopause. These observations provide significant new evidence consistent with component magnetic merging sites equatorward of the cusp for northward IMF. C1 NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. Lockheed Martin Palo Alto Res Lab, Palo Alto, CA 94304 USA. Rutherford Appleton Lab, Didcot OX11 0QX, Oxon, England. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RP Chandler, MO (reprint author), NASA, George C Marshall Space Flight Ctr, Space Sci Lab, NS ES-83, Huntsville, AL 35812 USA. RI Moore, Thomas/D-4675-2012; Lockwood, Mike/G-1030-2011 OI Moore, Thomas/0000-0002-3150-1137; Lockwood, Mike/0000-0002-7397-2172 NR 11 TC 53 Z9 55 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD OCT 1 PY 1999 VL 104 IS A10 BP 22623 EP 22633 DI 10.1029/1999JA900175 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 240YV UT WOS:000082855100028 ER PT J AU Sakaguchi, T Doke, T Hasebe, N Kikuchi, J Kono, S Takagi, T Takahashi, K Nagaoka, S Nakano, T Takahashi, S Badhwar, GD AF Sakaguchi, T Doke, T Hasebe, N Kikuchi, J Kono, S Takagi, T Takahashi, K Nagaoka, S Nakano, T Takahashi, S Badhwar, GD TI Measurement of the directional distribution of incident particles in the Shuttle-Mir mission orbit SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID PROTON AB The measurement of the directional distribution of incident particles was made by using the Realtime Radiation Monitoring Device (RRMD)-III placed inside the Space Shuttle STS-84 cruised at an altitude of 400 km and an inclination angle of 51.6 degrees, which are the same as the cruising orbit of the International Space Station (ISS). The directional distributions of incident particles were evaluated over the observed linear energy transfer (LET) range (1-100 keV/mu m). The pitch angle distribution is also obtained using the geomagnetic model of IGRF-95. The result is roughly in good agreement with the distribution obtained by the VF1-MIN anisotropy model calculation within the present experimental errors, if the shielding distribution is assumed to be uniform. C1 Waseda Univ, Adv Res Inst Sci & Engn, Shinjuku Ku, Tokyo 1698555, Japan. Natl Space Dev Agcy Japan, Tsukuba Space Ctr, Ibaragi, Japan. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Sakaguchi, T (reprint author), Waseda Univ, Adv Res Inst Sci & Engn, Shinjuku Ku, 3-4-1 Okubo, Tokyo 1698555, Japan. NR 6 TC 5 Z9 5 U1 2 U2 9 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 OCT 1 PY 1999 VL 104 IS A10 BP 22793 EP 22799 DI 10.1029/1999JA900231 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 240YV UT WOS:000082855100041 PM 11543495 ER PT J AU Schoener, DF Olsen, MA Cummings, PG Basic, C AF Schoener, DF Olsen, MA Cummings, PG Basic, C TI Electrospray ionization of neutral metal dithiocarbamate complexes using in-source oxidation SO JOURNAL OF MASS SPECTROMETRY LA English DT Article DE electrospray; mass spectrometry; metal dithiocarbamates ID MASS-SPECTROMETRY; TRIS(DITHIOCARBAMATO) COMPLEXES; CRYSTAL-STRUCTURE; ALKALINE-EARTH; ELECTROCHEMISTRY; COBALT(III); DERIVATIVES; NICKEL(II); CHEMISTRY; IRON(III) AB An electrospray ionization (ESI) mass spectral characterization of eight substituted tris(dithiocarbamato)iron(III) complexes (Fe(III)(dtc)(3)) and of the diethyldithiocarbamate (et(2)dtc)(-), complexes of Mn(III), Cu(II), Ni(II), and Co(III) is presented. Use is made of the inherent electrochemical potential of the ESI source to oxidize the neutral metal complexes and in-source collision-induced dissociation (CID) to characterize the resulting ions. The mass spectra obtained at low source offset voltages all show molecular ions of the oxidized complexes, in addition to ions due to the loss of a dithiocarbamate, (dtc)(-), ligand. Three of the Fe(III)(dtc)(3) complexes also show ions due to fragmentation of the (dtc)(-) ligands. Ions corresponding to the thiuram disulfide formed following the oxidation of excess (dtc)(-) in solution are also seen. In-source CID studies of the Fe(III), Mn(III), Cu(II), Ni(II) and Co(III) (et(2)dtc)(-) complexes all show [M(I)(et(2)dtc)+H](+) ions attributed to proton transfer from a protonated solvent ion to a M(I)(et(2)dtc) neutral formed upon following CID in the high-pressure region of the ion source. The results of the present in-source oxidation studies are compared with those obtained in previous ESI studies in which external oxidizing agents were added to the metal complex solutions prior to analysis. Copyright (C) 1999 John Wiley & Sons, Ltd. C1 Villanova Univ, Dept Chem, Villanova, PA 19085 USA. SmithKline Beecham Pharmaceut, King Of Prussia, PA 19046 USA. RP Basic, C (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 42 TC 18 Z9 18 U1 1 U2 10 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX PO19 1UD, ENGLAND SN 1076-5174 J9 J MASS SPECTROM JI J. Mass Spectrom. PD OCT PY 1999 VL 34 IS 10 BP 1069 EP 1078 DI 10.1002/(SICI)1096-9888(199910)34:10<1069::AID-JMS868>3.0.CO;2-Q PG 10 WC Biophysics; Chemistry, Organic; Spectroscopy SC Biophysics; Chemistry; Spectroscopy GA 245TL UT WOS:000083124200009 ER PT J AU Wolfenden, A Proffitt, CB Singh, M AF Wolfenden, A Proffitt, CB Singh, M TI Dynamic elastic modulus and vibration damping behavior of porous silicon carbide ceramics at elevated temperatures SO JOURNAL OF MATERIALS ENGINEERING AND PERFORMANCE LA English DT Article DE ceramics; damping; high temperature; silicon carbide; Young's modulus ID ANELASTIC PROPERTIES; DIFFUSION AB The piezoelectric ultrasonic composite oscillator technique (PUCOT) has been used to measure the Young's modulus, epsilon, the mechanical damping, Q(-1), and the strain amplitude, E, of a sintered silicon carbide containing pores (Hexoloy-SP). The silicon carbide material used in this study had at least 14 vol% porosity. Young's modulus was found to have a linear temperature dependence from room temperature to 740 degrees C. The damping was near 10(-4) and was independent of strain amplitude above room temperature. C1 Texas A&M Univ, Dept Mech Engn, College Stn, TX 77843 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Wolfenden, A (reprint author), Texas A&M Univ, Dept Mech Engn, College Stn, TX 77843 USA. NR 11 TC 4 Z9 4 U1 1 U2 6 PU ASM INTERNATIONAL PI MATERIALS PARK PA SUBSCRIPTIONS SPECIALIST CUSTOMER SERVICE, MATERIALS PARK, OH 44073-0002 USA SN 1059-9495 J9 J MATER ENG PERFORM JI J. Mater. Eng. Perform. PD OCT PY 1999 VL 8 IS 5 BP 598 EP 600 DI 10.1361/105994999770346657 PG 3 WC Materials Science, Multidisciplinary SC Materials Science GA 243RM UT WOS:000083011100016 ER PT J AU Olive, JR Hofmeister, WH Bayuzick, RJ Vlasse, M AF Olive, JR Hofmeister, WH Bayuzick, RJ Vlasse, M TI High-temperature phase relationships for YxNd1-xBa2Cu3Oy (0.7 <= x <= 1.0) superconductors via containerless processing SO JOURNAL OF MATERIALS RESEARCH LA English DT Article ID SYSTEM; DIAGRAM AB Drop-tube experiments have been performed on YxNd1-xBa2Cu3Oy (0.7 less than or equal to x less than or equal to 1.0) to understand the effects of partial substitutions of Nd for Y on the phase relationships in these systems at elevated temperatures. Powders 50-100 mu m in diameter were processed in pure O-2 at furnace temperatures of 1575-1800 degrees C, every 25 degrees C. The resulting samples were examined microstructurally by scanning electron microscopy, energy dispersive spectroscopy, and optical microscopy. Powder x-ray diffraction was performed for phase identification. It was found that Nd substitution alters phase selection by introducing at least one new phase and allowing for solidification of the superconducting composition directly from the melt via undercooling to below the peritectic transformation temperature. A decreasing trend in the overall melting temperature with increasing Nd was also identified. C1 Vanderbilt Univ, Dept Chem Engn, Nashville, TN 37235 USA. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. RP Olive, JR (reprint author), Vanderbilt Univ, Dept Chem Engn, Nashville, TN 37235 USA. OI Hofmeister, William/0000-0002-4145-7061 NR 20 TC 4 Z9 4 U1 0 U2 0 PU MATERIALS RESEARCH SOCIETY PI WARRENDALE PA 506 KEYSTONE DR, WARRENDALE, PA 15086 USA SN 0884-2914 J9 J MATER RES JI J. Mater. Res. PD OCT PY 1999 VL 14 IS 10 BP 3843 EP 3850 DI 10.1557/JMR.1999.0519 PG 8 WC Materials Science, Multidisciplinary SC Materials Science GA 246KV UT WOS:000083163700005 ER PT J AU Olive, JR Hofmeister, WH Bayuzick, RJ Vlasse, M AF Olive, JR Hofmeister, WH Bayuzick, RJ Vlasse, M TI High-temperature phase relationships for YxNd1-xBa2Cu3O (0 <= x <= 0.5) superconductors via containerless processing SO JOURNAL OF MATERIALS RESEARCH LA English DT Article AB This paper presents the results of drop-tube experiments performed on YxNd1-xBa2Cu3Oy (0 less than or equal to x less than or equal to 0.5) to understand some of the effects of partial substitutions of Nd for Y on the phase relationships in these systems at elevated temperatures. Powders from 50 to 100 mu m in diameter were processed in pure O-2 at furnace temperatures from 1400 to 1800 degrees C, every 25 degrees C, The resulting samples were examined microstructurally using scanning electron microscopy, energy dispersive spectroscopy, and optical microscopy. Powder x-ray diffraction was performed for phase identification. It was verified that Nd substitution alters phase selection by introducing at least one new phase and allowing for solidification of the superconducting composition directly from the melt via undercooling to below the peritectic transformation temperature. In addition, solidification pathways are altered for samples processed at temperatures just below the liquidus temperature. Microstructural and x-ray diffraction evidence was used to map the liquidus with increasing Nd substitution. It was found that a minimum in this liquidus occurs at or near the composition Y0.1Nd0.9Ba2Cu3Ox and at a temperature of 1500 degrees C (+/-25 degrees C). C1 Vanderbilt Univ, Dept Chem Engn, Nashville, TN 37235 USA. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. RP Olive, JR (reprint author), Vanderbilt Univ, Dept Chem Engn, Nashville, TN 37235 USA. NR 4 TC 4 Z9 4 U1 0 U2 0 PU MATERIALS RESEARCH SOCIETY PI WARRENDALE PA 506 KEYSTONE DR, WARRENDALE, PA 15086 USA SN 0884-2914 J9 J MATER RES JI J. Mater. Res. PD OCT PY 1999 VL 14 IS 10 BP 3851 EP 3858 DI 10.1557/JMR.1999.0520 PG 8 WC Materials Science, Multidisciplinary SC Materials Science GA 246KV UT WOS:000083163700006 ER PT J AU Toth, RA AF Toth, RA TI Line positions and strengths of N2O between 3515 and 7800 cm(-1) SO JOURNAL OF MOLECULAR SPECTROSCOPY LA English DT Article ID VIBRATION-ROTATION BANDS; FREQUENCY MEASUREMENTS; MU-M; REGION AB The line positions and strengths of N2O were measured from absorption spectra obtained at high spectral resolution (0.011 cm(-1)) in the region between 3515 and 7800 cm(-1). Measurements include line frequencies and strengths of several N2O isotopes, a few of which are reported for the first time, to my knowledge. Also in this category are two pi-pi bands, six Delta-Delta bands, and five Sigma-Sigma bands of (N2O)-N-14-O-16. Measurements also include eight (N2O)-N-14-O-16 bands of which several transitions of each band were perturbed due to resonance interactions with transitions of a perturbing band. For most cases, the positions and strengths of the strongest interacting transitions of the Perturbing bands were measured. (C) 1999 Academic Press. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Toth, RA (reprint author), CALTECH, Jet Prop Lab, Mail Stop 183-301, Pasadena, CA 91109 USA. NR 9 TC 48 Z9 49 U1 0 U2 8 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0022-2852 J9 J MOL SPECTROSC JI J. Mol. Spectrosc. PD OCT PY 1999 VL 197 IS 2 BP 158 EP 187 DI 10.1006/jmsp.1999.7907 PG 30 WC Physics, Atomic, Molecular & Chemical; Spectroscopy SC Physics; Spectroscopy GA 238ZD UT WOS:000082743900004 ER PT J AU Povitsky, A AF Povitsky, A TI Parallelization of pipelined algorithms for sets of linear banded systems SO JOURNAL OF PARALLEL AND DISTRIBUTED COMPUTING LA English DT Article DE Thomas Algorithm; linear banded systems; pipelined algorithms; parallel computations; implicit numerical methods; MIMD computer AB Solution of independent sets of linear banded systems is a core part of implicit numerical algorithms. In this study we propose a novel pipelined Thomas algorithm with low parallelization penalty. We introduce two-step pipelined algorithms (PAs) formally and show that the idle processor time is invariant with respect to the order of backward and forward steps, Therefore. the parallelization efficiency of the PA cannot be improved directly. However. the processor idle time can be used if some Lines have been computed by the time processors become idle. We develop the immediate backward pipelined Thomas algorithm (IB-PTA). The backward step is computed immediately after the forward step has been completed for the first portion of lines. The advantage of the IB-PTA over the basic PTA is the presence of solved lines, which are available for other computations, by the time processors become idle. Implementation of the IB-PTA is based on a proposed static processor schedule that switches between forward and backward computations and controls communication between processors, Computations are performed on the Gray T3E MIMD computer. Combination of the proposed IB-PTA with the "burn from two ends" algorithm shows low; parallelization penalty. (C) 1999 Academic Press. C1 NASA, Langley Res Ctr, ICASE, Hampton, VA 23681 USA. RP Povitsky, A (reprint author), NASA, Langley Res Ctr, ICASE, Hampton, VA 23681 USA. NR 22 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 0743-7315 J9 J PARALLEL DISTR COM JI J. Parallel Distrib. Comput. PD OCT PY 1999 VL 59 IS 1 BP 68 EP 97 DI 10.1006/jpdc.1999.1568 PG 30 WC Computer Science, Theory & Methods SC Computer Science GA 245CL UT WOS:000083088600005 ER PT J AU Sun, S Bleck, R Rooth, C Dukowicz, J Chassignet, E Killworth, P AF Sun, S Bleck, R Rooth, C Dukowicz, J Chassignet, E Killworth, P TI Inclusion of thermobaricity in isopycnic-coordinate ocean models SO JOURNAL OF PHYSICAL OCEANOGRAPHY LA English DT Article ID POTENTIAL VORTICITY; NEUTRAL SURFACES; WORLDS OCEANS; ATLANTIC AB Buoyancy anomalies caused by thermobaricity, that is, the modulation of seawater compressibility by potential temperature anomalies, underlie a long-standing argument against the use of potential-density-framed numerical models for realistic circulation studies. The authors show that this problem can be overcome by relaxing the strict correspondence between buoyancy and potential density in isopycnic-coordinate models. A parametric representation of the difference between the two variables is introduced in the form of a "virtual potential density," which can be viewed as the potential density that would be computed from the in situ conditions using the compressibility coefficient for seawater of a fixed (but representative) salinity and potential temperature. This variable is used as a basis for effective dynamic height computations in the dynamic equations, while the traditionally defined potential density may be retained as model coordinate. The conservation properties of the latter assure that adiabatic transport processes in a compressibility-compliant model can still be represented as exactly two-dimensional. Consistent with its dynamic significance, the distribution of virtual potential density is found to determine both the local static stability and, to a lesser degree, the orientation of neutrally buoyant mixing surfaces. The paper closes with a brief discussion of the pros and cons of replacing potential density by virtual potential density as vertical model coordinate. C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Univ Miami, Miami, FL 33152 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM USA. Southampton Oceanog Ctr, Southampton, Hants, England. RP Sun, S (reprint author), NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. RI Sun, Shan/H-2318-2015 NR 20 TC 52 Z9 52 U1 0 U2 0 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0022-3670 J9 J PHYS OCEANOGR JI J. Phys. Oceanogr. PD OCT PY 1999 VL 29 IS 10 BP 2719 EP 2729 DI 10.1175/1520-0485(1999)029<2719:IOTIIC>2.0.CO;2 PG 11 WC Oceanography SC Oceanography GA 250HG UT WOS:000083382500015 ER PT J AU Smith, JD Staehelin, LA Todd, P AF Smith, JD Staehelin, LA Todd, P TI Early root cap development and graviresponse in white clover (Trifolium repens) grown in space and on a two-axis clinostat SO JOURNAL OF PLANT PHYSIOLOGY LA English DT Article DE clover; statocyte; clinostat; gravitropism; microgravity; root cap; trifolium ID PLANT-CELLS; MICROGRAVITY; GRAVITY; STATOCYTES; GRAVITROPISM; AMYLOPLASTS; POLARITY; MISSION AB White clover (Trifolium repens) was germinated and grown in microgravity aboard the Space Shuttle (STS-60, 1994; STS-GS, 1995), on Earth in stationary racks and in a slow-rotating two-axis clinostat. The objective of this study was to determine if normal root cap development and early plant gravity responses were dependent on gravitational cues. Seedlings were germinated in space and chemically fixed in orbit after 21, 40, and 72 h. Seedlings 96 h old were returned viable to earth. Germination and total seedling length were not dependent on gravity treatment. In space-flown seedlings, the number of cell stories in the root cap and the geometry of central columella cells did not differ from those of the Earth-grown seedlings. The root cap structure of clinorotated plants appeared similar to that of seedlings from microgravity, with the exception of three-day rotated plants, which displayed significant cellular damage in the columella region. Nuclear polarity did not depend on gravity; however, the positions of amyloplasts in the central columella cells were dependent on both the gravity treatment and the age of the seedlings. Seedlings;from space, returned viable to earth, responded to horizontal stimulation as did 1 g controls, but seedlings rotated on the clinostat for the same duration had a reduced curvature response. This study demonstrates that initial root cap development is insensitive to either chronic clinorotation or microgravity. Soon after differentiation, however, clinorotation leads to loss of normal root cap structure and plant graviresponse while microgravity does not. C1 NASA, Ames Res Ctr, Space Life Sci Res Branch, Moffett Field, CA 94035 USA. Univ Colorado, Dept Mol Cellular & Dev Biol, Boulder, CO 80309 USA. Univ Colorado, Dept Chem Engn, Boulder, CO 80309 USA. RP Smith, JD (reprint author), NASA, Ames Res Ctr, Space Life Sci Res Branch, Moffett Field, CA 94035 USA. NR 32 TC 11 Z9 11 U1 0 U2 2 PU ELSEVIER GMBH, URBAN & FISCHER VERLAG PI JENA PA OFFICE JENA, P O BOX 100537, 07705 JENA, GERMANY SN 0176-1617 EI 1618-1328 J9 J PLANT PHYSIOL JI J. Plant Physiol. PD OCT PY 1999 VL 155 IS 4-5 BP 543 EP 550 PG 8 WC Plant Sciences SC Plant Sciences GA 257BP UT WOS:000083762000016 PM 11543182 ER PT J AU Cvitkovich, MK Jackson, WC AF Cvitkovich, MK Jackson, WC TI Compressive failure mechanisms in composite sandwich structures SO JOURNAL OF THE AMERICAN HELICOPTER SOCIETY LA English DT Article; Proceedings Paper CT American-Helicopter-Society 54th Annual Forum CY MAY 22-24, 1998 CL WASHINGTON, D.C. SP Amer Helicopter Soc AB The objective of this work was to investigate the compressive failure response of composite sandwich structures of four different configurations designed to produce different failure modes. Specimens were tested with no damage, with 0.25-inch-diameter open holes, and with three levels of impact damage. The facesheets consisted of two, three, or four layers of carbon/epoxy plain-weave fabric. Nomex and aluminum honeycomb were used as core materials, Strain gages were used to monitor the in-plane strain distribution around the damaged area. Out of-plane displacements were recorded using shadow moire interferometry to monitor initial signs of facesheet instability. After compression testing, representative specimens were sectioned to document the internal damage. The influence of damage state was documented for each specimen configuration. For Nomex-core specimens, the effects of facesheet thickness on strength and strains were investigated. The effect of core material was studied for the four-layer facesheet specimens. Strain distributions around the damage and the load carried by the damaged region were examined as a function of applied stress level. Depending on core material and damage type, different responses were identified. Two distinct compressive failure mechanisms, inward and outward buckling of the impacted facesheet, were identified that were functions of facesheet thickness and damage type, The experimental observations of these failure mechanisms were related to current damage tolerance analysis methodologies. Wrinkling analysis appeared to model the correct undamaged failure mechanisms but needs to be improved to more accurately predict the influence of facesheet thickness and core materials on strength. For open holes, the point stress/strain and average stress/strain criteria may not be appropriate as they are not sensitive to facesheet thickness or core stiffness. Modeling impact damage as an initial facesheet indentation on a damaged core appeared to be a suitable analysis for the inward-type buckling failure mechanism. C1 NASA, Langley Res Ctr, Div Mat,Mech Mat Branch, USA,REs Lab,Vehicle Technol Ctr, Hampton, VA 23665 USA. RP Cvitkovich, MK (reprint author), NASA, Langley Res Ctr, Div Mat,Mech Mat Branch, USA,REs Lab,Vehicle Technol Ctr, Hampton, VA 23665 USA. NR 7 TC 12 Z9 13 U1 0 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 OCT PY 1999 VL 44 IS 4 BP 260 EP 268 PG 9 WC Engineering, Aerospace SC Engineering GA 254GZ UT WOS:000083604700001 ER PT J AU Wang, KM Yang, DZ Danai, K Lewicki, DG AF Wang, KM Yang, DZ Danai, K Lewicki, DG TI Model-based selection of accelerometer locations for helicopter gearbox monitoring SO JOURNAL OF THE AMERICAN HELICOPTER SOCIETY LA English DT Article ID CONNECTIONIST NETWORK; FAULT-DIAGNOSIS; BOXES AB A novel method is introduced to quantify, based on the structure of the gearbox, the monitoring effectiveness of accelerometer locations on the housing. In this method, monitoring effectiveness of sets of accelerometer locations is defined in terms of two indices: the coverage index and the overlap index. The coverage index is obtained from an influence matrix defining the level of effect of component faults on accelerometer readings. The overlap index denotes the level of overlap between pairs of accelerometers in coverage of components. The effectiveness of the proposed method is verified experimentally based on measurement-fault data obtained from an OH-58A main rotor gearbox. The estimated rankings of various sets of accelerometer locations based on the estimated values of their monitoring effectiveness agree closely with those obtained empirically. C1 NASA, Glenn Res Ctr, USA, Res Lab,Vehicle Technol Ctr, Cleveland, OH 44135 USA. Univ Massachusetts, Dept Mech & Ind Engn, Amherst, MA 01003 USA. RP Danai, K (reprint author), NASA, Glenn Res Ctr, USA, Res Lab,Vehicle Technol Ctr, Cleveland, OH 44135 USA. NR 20 TC 0 Z9 0 U1 0 U2 0 PU AMER HELICOPTER SOC INC PI ALEXANDRIA PA 217 N WASHINGTON ST, ALEXANDRIA, VA 22314 USA SN 0002-8711 J9 J AM HELICOPTER SOC JI J. Am. Helicopter Soc. PD OCT PY 1999 VL 44 IS 4 BP 269 EP 275 PG 7 WC Engineering, Aerospace SC Engineering GA 254GZ UT WOS:000083604700002 ER PT J AU Lyle, KH Burley, CL Prichard, DS AF Lyle, KH Burley, CL Prichard, DS TI A comparison of measured and predicted XV-15 tiltrotor surface acoustic pressures SO JOURNAL OF THE AMERICAN HELICOPTER SOCIETY LA English DT Article; Proceedings Paper CT American-Helicopter-Society-Technical-Specialists Meeting for Rotorcraft Acoustics and Aerodynamics CY OCT 28-30, 1997 CL WILLIAMSBURG, VIRGINIA SP Amer Helicopter Soc, Tech Specialists AB Predicted XV-15 exterior surface acoustic pressures are compared with previously published experimental data, Surface acoustic pressure transducers were concentrated near the tip-path-plane of the rotor in airplane mode. The comparison emphasized cruise conditions which are of interest for tiltrotor interior noise-level flight for speeds ranging from 72 m/s to 113 m/s, The predictions were produced by components of the NASA Langley Tiltrotor Aeroacoustic Code (TRAC) system of computer codes, Comparisons between measurements and predictions were made in both the time and frequency domains, as well as overall sound pressure levels, In general, the predictions replicated the measured data well, Discrepancies between measurements and predictions were noted. Some of the discrepancies were due to poor correlation of the measured data with the rotor tach signal. In other cases limitations of the predictive methodology have been indicated. C1 USA, Vehicle Technol Ctr, Hampton, VA USA. NASA, Langley Res Ctr, Hampton, VA 23665 USA. Lockheed Martin Engn & Sci Corp, Hampton, VA USA. RP Lyle, KH (reprint author), USA, Vehicle Technol Ctr, Hampton, VA USA. NR 8 TC 0 Z9 0 U1 0 U2 0 PU AMER HELICOPTER SOC INC PI ALEXANDRIA PA 217 N WASHINGTON ST, ALEXANDRIA, VA 22314 USA SN 0002-8711 J9 J AM HELICOPTER SOC JI J. Am. Helicopter Soc. PD OCT PY 1999 VL 44 IS 4 BP 285 EP 292 PG 8 WC Engineering, Aerospace SC Engineering GA 254GZ UT WOS:000083604700004 ER PT J AU Wadcock, AJ Yamauchi, GK Driver, DM AF Wadcock, AJ Yamauchi, GK Driver, DM TI Skin friction measurements on a hovering full-scale tilt rotor SO JOURNAL OF THE AMERICAN HELICOPTER SOCIETY LA English DT Article; Proceedings Paper CT American-Helicopter-Society-Technical-Specialists Meeting for Rotorcraft Acoustics and Aerodynamics CY OCT 28-30, 1997 CL WILLIAMSBURG, VIRGINIA SP Amer Helicopter Soc, Tech Specialists AB The oil-film interferometric skin friction technique is described and applied to an isolated full-scale XV-15 rotor in hover. This is the first time that this technique has been applied to a rotary wing. The chordwise component of skin friction is presented for both low and high thrust cases. The technique is shown to be capable of revealing the presence of natural transition, leading edge laminar separation followed by turbulent reattachment, and the presence of reversed flow. An extensive region of laminar flow is shown to exist at 3 degrees collective. Transition is shown to move close to the blade leading edge at 10 degrees collective. The high-thrust case, corresponding to 1-g hover, is surprising in that reverse-how is shown to exist over a significant fraction of the chord at the 28% radial station. C1 Aerosp Comp Inc, Los Altos, CA USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Wadcock, AJ (reprint author), Aerosp Comp Inc, Los Altos, CA USA. NR 14 TC 12 Z9 14 U1 1 U2 4 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 OCT PY 1999 VL 44 IS 4 BP 312 EP 319 PG 8 WC Engineering, Aerospace SC Engineering GA 254GZ UT WOS:000083604700007 ER PT J AU Braun, SA Rotunno, R Klemp, JB AF Braun, SA Rotunno, R Klemp, JB TI Effects of coastal orography on landfalling cold fronts. Part II: Effects of surface friction SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID BOUNDARY-LAYER; SIERRA-NEVADA; MODEL; ROUGHNESS; MOUNTAINS; RIDGE; STORM AB The role of surface friction in modifying cord fronts as they make landfall in regions of steep coastal orography is examined by means of idealized simulations. Both the effects of the surface-roughness change at the coast in the absence of orography and the effects of orography are considered. Flow over a large and abrupt change in surface roughness generates an inertia-gravity wave above the boundary layer with characteristics similar to that associated with how over a plateau. Deceleration of the cross-coast flow occurs over land, as well as for a short distance upstream, and causes retardation of frontal motion. A prescribed northerly postfrontal jet weakens rapidly after landfall. Maximum vertical motions are several centimeters per second; however, only small rainfall enhancement is expected since the updraft is very narrow and produces only small vertical displacements. Friction modifies the flaw over the orography by increasing the upstream flow deceleration and reducing the magnitude of the barrier jet. The reduction of the barrier-jet strength (when compared to inviscid simulations) by surface friction becomes more pronounced as the mountain forcing of the jet increases. With surface friction, frontal-motion retardation by the orography is strong and upstream frontogenesis is enhanced. The frontal updraft is strongest at the coast and remains strong far a short distance inland along the lower portion of the windward slope. The coastal enhancement of the frontal updraft results from the combined effects of the orography and the surface-roughness change, but large parcel displacements are due mainly to the orographic forcing. Along-coast winds in the coastal zone during frontal passage are approximately determined by a superposition of the southerly barrier jet and the frontal jets. C1 Natl Ctr Atmospher Res, Boulder, CO 80307 USA. RP NASA, Goddard Space Flight Ctr, Mesoscale Atmospher Proc Branch, Code 912, Greenbelt, MD 20771 USA. EM braun@gilbert.gsfc.nasa.gov NR 29 TC 17 Z9 17 U1 0 U2 5 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0022-4928 EI 1520-0469 J9 J ATMOS SCI JI J. Atmos. Sci. PD OCT 1 PY 1999 VL 56 IS 19 BP 3366 EP 3384 DI 10.1175/1520-0469(1999)056<3366:EOCOOL>2.0.CO;2 PG 19 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 244NC UT WOS:000083056800002 ER PT J AU DelSole, T Hou, AY AF DelSole, T Hou, AY TI Empirical stochastic models for the dominant climate statistics of a general circulation model SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID QUASI-GEOSTROPHIC TURBULENCE; BAROCLINIC WAVES; ATMOSPHERE AB Two Markov models with different dynamics and forcing are used to model the transient eddy statistics of an idealized general circulation model (GCM). The first Markov model employs a physically based dynamical operator composed of the linearized primitive equations plus spatially uniform damping. This model, when driven by spatially uncorrelated forcing, failed to produce reasonable fluxes and variances, despite tuning of the damping and forcing coefficients. This result contrasts with previous studies that have used the linearized quasigeostrophic equations to model extratropical eddy statistics. The second Markov model is constructed empirically from the time-lagged covariances of the GCM time series. This empirical Markov model could reproduce the dominant covariances over a range of time lags, provided it contained a sufficiently large number of degrees of freedom. it could not, however reproduce the time-lag evolution of the trailing EOFs contained in the model. The errors in the trailing EOFs displayed a systematic behavior that could be explained by assuming that the "effective noise" -the noise required to reproduce the full covariances-is correlated over timescales comparable to the smallest e-folding time of the eigenmodes. Under this assumption, the effective noise is not white, but, for sufficiently large model dimension, the dominant disturbances still can be modeled appropriately by a Markov model because their associated decorrelation;rates are small compared to the decorrelation rate of noise. This explanation is illustrated using a three-variable Markov model. These results suggest the following criteria for Markov model estimation: the lag and number of EOFs should be chosen such that the least damped modes show little or no dependence on lag and that none of the imaginary eigenvalues are aliased (in a sense defined in the paper). The resulting Markov model for the dominant disturbances is not sensitive to EOF truncation or choice of time lag, except for the structure of the singular vectors and adjoints, and the ordering of the eigenmodes. The sensitivity in singular vectors and adjoints is a plausible consequence of nonnormality, as nonnormality of the underlying physical system leads to singular vectors differing considerably from the normal modes and EOFs. The stable eigenmodes resemble the leading EOFs used to construct the empirical model, but differ considerably from the unstable eigenmodes of the linearized GCM. This difference is attributed to nonlinear processes implicitly represented in the Markov model. The dissipation and stochastic forcing were concentrated in the Tropics and subtropics, in contrast to the eddy variance and fluxes, which were concentrated in subtropics and midlatitudes. The associated singular vectors also were localized initially in the Tropics and subtropics, but eventually develop into robust extratropical disturbances. Interestingly, the dominant singular vectors undergo a growth and decay life cycle characteristic of the classic nonlinear life cycle, with time-averaged fluxes in close agreement with those diagnosed from the GCM climatology The fact that the forcing, dissipation, and initial singular vectors are concentrated in the same vicinity suggests a dynamical feedback between Tropics and subtropics. C1 NASA, Goddard Space Flight Ctr, Data Assimilat Off, Greenbelt, MD 20771 USA. RP DelSole, T (reprint author), Ctr Ocean Land Atmosphere Studies, Suite 302,4041 Powder Mill Rd, Calverton, MD 20705 USA. RI Hou, Arthur/D-8578-2012 NR 17 TC 25 Z9 25 U1 0 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 OCT 1 PY 1999 VL 56 IS 19 BP 3436 EP 3456 DI 10.1175/1520-0469(1999)056<3436:ESMFTD>2.0.CO;2 PG 21 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 244NC UT WOS:000083056800006 ER PT J AU Begault, DR AF Begault, DR TI Virtual acoustic displays for teleconferencing: Intelligibility advantage for "telephone-grade" audio SO JOURNAL OF THE AUDIO ENGINEERING SOCIETY LA English DT Article; Proceedings Paper CT 98th Convention of the Audio-Engineering-Society CY FEB 25-28, 1995 CL PARIS, FRANCE SP Audio Engn Soc ID SPEECH AB Speech intelligibility was evaluated using a virtual acoustic (3-D audio) display using the method specified by ANSI (S3.2-1989). Ten subjects were evaluated with stimuli either unfiltered or low-pass filtered at 4-kHz. Results show that virtual acoustic techniques are advantageous for both full-bandwidth (44.1-kHz sampling rate) and low-bandwidth (8-kHz sampling rate) "telephone-grade" teleconferencing systems. C1 NASA, Ames Res Ctr, San Jose State Univ, Human Factors Res & Technol Div, Moffett Field, CA 94035 USA. RP Begault, DR (reprint author), NASA, Ames Res Ctr, San Jose State Univ, Human Factors Res & Technol Div, Moffett Field, CA 94035 USA. NR 13 TC 4 Z9 4 U1 0 U2 0 PU AUDIO ENGINEERING SOC PI NEW YORK PA 60 E 42ND ST, NEW YORK, NY 10165-2520 USA SN 0004-7554 J9 J AUDIO ENG SOC JI J. Audio Eng. Soc. PD OCT PY 1999 VL 47 IS 10 BP 824 EP 828 PG 5 WC Acoustics; Engineering, Multidisciplinary SC Acoustics; Engineering GA 253LX UT WOS:000083559000004 ER PT J AU Olejniczak, J Candler, GV Wright, MJ Leyva, I Hornung, HG AF Olejniczak, J Candler, GV Wright, MJ Leyva, I Hornung, HG TI Experimental and computational study of high enthalpy double-wedge flows SO JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER LA English DT Article; Proceedings Paper CT AIAA 19th Advanced Measurement and Ground Testing Technology Conference CY JUN 17-20, 1996 CL NEW ORLEANS, LOUISIANA SP Amer Inst Aeronaut & Astronaut ID NAVIER-STOKES EQUATIONS; RELAXATION AB A series of experiments designed to study reacting nitrogen flow over double-wedge geometries was conducted in the T5 shock tunnel at the California Institute of Technology. These experiments were designed using computational fluid dynamics to test nonequilibrium chemistry models. Surface heat transfer rate measurements were made, and holographic Mach-Zehnder interferometry was used to visualize the flow Analysis of the data shows that computations using standard thermochemical models cannot reproduce the experimental results. The computed separation zones are smaller than the experiments indicate. However, the computed heat transfer values match the experimental data in the separation zone, and on the second wedge the computed heat transfer distribution matches the shape and heights of the experimental distribution but is shifted due to the difference In the size of the separation zones, The most likely reasons for failure of the computations to reproduce the experimental data are uncertainties in the equilibrium and nonequilibrium nitrogen dissociation rates, non-Boltzmann vibrational energy distributions in the freestream, and possible noncontinuum effects at the model leading edge and in the shock interaction region. C1 Univ Minnesota, Minneapolis, MN 55455 USA. CALTECH, Grad Aeronaut Labs, Pasadena, CA 91125 USA. RP Olejniczak, J (reprint author), NASA, Ames Res Ctr, Mail Stop 230-2, Moffett Field, CA 94035 USA. NR 26 TC 12 Z9 12 U1 0 U2 6 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 OCT-DEC PY 1999 VL 13 IS 4 BP 431 EP 440 DI 10.2514/2.6481 PG 10 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA 251KH UT WOS:000083444500004 ER PT J AU Park, C AF Park, C TI Interaction of spalled particles with shock layer flow SO JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER 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 influence of the solid particles injected into the shock layer by the spallation of a carbonaceous ablating heatshield on the shock layer flow is investigated theoretically. The equation of motion of a solid particle is integrated using a polynomial expansion. Assuming a Gaussian distribution for the initial masses and velocities of the particles, the rates of production of CO, CN, C-3, and turbulence energy are calculated by integrating those production rates for one particle over the mass and velocity distributions. The results for the environment of Stardust Earth reentry show that these production rates decay approximately exponentially in the normal direction from the ablating wall. Correlation formulas for the magnitudes and slopes of this decay pattern are derived. The lower limits of particle size and initial velocity are estimated for a carbon-phenolic material from a spectroscopic result obtained in an arcjet wind-tunnel test. C1 NASA, Ames Res Ctr, Thermosci Inst, Moffett Field, CA 94035 USA. RP Park, C (reprint author), NASA, Ames Res Ctr, Thermosci Inst, Mail Stop 229-1, Moffett Field, CA 94035 USA. NR 19 TC 14 Z9 14 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0887-8722 J9 J THERMOPHYS HEAT TR JI J. Thermophys. Heat Transf. PD OCT-DEC PY 1999 VL 13 IS 4 BP 441 EP 449 DI 10.2514/2.6482 PG 9 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA 251KH UT WOS:000083444500005 ER PT J AU Ameri, AA Steinthorsson, E Rigby, DL AF Ameri, AA Steinthorsson, E Rigby, DL TI Effects of tip clearance and casing recess on heat transfer and stage efficiency in axial turbines SO JOURNAL OF TURBOMACHINERY-TRANSACTIONS OF THE ASME LA English DT Article AB Calculations were performed to assess the effect of the tip leakage flow on the rate of heat transfer to blade, blade tip, and casing. The effect on exit angle and efficiency was also examined. Passage geometries with and without casing recess were considered The geometry and rite flow conditions of the GE-E-3 first-stage turbine, which represents a modern gas turbine blade, were used for the analysis. Clearance heights of 0, 1, 1.5, and 3 percent of the passage height were considered. For the two largest clearance heights considered, different recess depths were studied. There was an increase in the thermal load on all the heat transfer surfaces considered due to enlargement of the clearance gap. Introduction of recessed casing resulted in a drop in the rate of heat transfer on the pressure side, bur the picture on the suction side was found to be more complex for the smaller tip clearance height considered. For the larger tip clearance height, the effect of casing recess was an orderly reduction in the suction side heat transfer as the casing recess height was increased There was a marked reduction of heat load and peak values on the blade tip upon introduction of casing recess; however, only a small reduction was observed on the casing itself: It was reconfirmed that there is a linear relationship between the efficiency and the tip gap height. It was also observed that the recess casing has a small effect on the efficiency but can have a moderating effect on the flow underturning at smaller tip clearances. C1 AYT Corp, Brook Pk, OH 44142 USA. NASA, Lewis Res Ctr, Inst Computat Mech Prop, ICOMP, Cleveland, OH 44135 USA. NYMA Inc, NASA, Lewis Grp, Cleveland, OH 44135 USA. RP Ameri, AA (reprint author), AYT Corp, Brook Pk, OH 44142 USA. NR 23 TC 50 Z9 51 U1 0 U2 0 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 USA SN 0889-504X J9 J TURBOMACH JI J. Turbomach.-Trans. ASME PD OCT PY 1999 VL 121 IS 4 BP 683 EP 693 PG 11 WC Engineering, Mechanical SC Engineering GA 246LR UT WOS:000083165700006 ER PT J AU Boyle, RJ Simon, FF AF Boyle, RJ Simon, FF TI Mach number effects on turbine blade transition length prediction SO JOURNAL OF TURBOMACHINERY-TRANSACTIONS OF THE ASME LA English DT Article ID BOUNDARY-LAYER-TRANSITION; FLOWS; TURBOMACHINERY; TURBULENCE AB The effect of a Mach number correction on a model for predicting the length of transition was investigated The transition length decreases as the turbulent spot production rate increases. Many of the data for predicting the spot production rate come from low-speed flaw experiments. Recent data and analysis showed that the spot production rate is affected by Mach number. The degree of agreement between analysis and data for turbine blade heat transfer without film cooling is strongly dependent on accurately predicting the length of transition. Consequently turbine blade heat transfer darn sets were used to validate a transition length turbulence model. A method for modifying models Sor the length of transition to account for Mach number effects is presented. The modification was made to two transition length models. The modified models were incorporated into the two-dimensional Navier-Stokes code, RVCQ3D. Comparisons were made between pre dieted and measured midspan surface heat transfer for stator and rotor turbine blades. The results showed that accounting for Mach number effects significantly improved the agreement with the experimental data. C1 NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. RP Boyle, RJ (reprint author), NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. NR 38 TC 14 Z9 14 U1 0 U2 1 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 USA SN 0889-504X J9 J TURBOMACH JI J. Turbomach.-Trans. ASME PD OCT PY 1999 VL 121 IS 4 BP 694 EP 702 PG 9 WC Engineering, Mechanical SC Engineering GA 246LR UT WOS:000083165700007 ER PT J AU Bright, MM Qammar, HK Wang, LZ AF Bright, MM Qammar, HK Wang, LZ TI Investigation of pre-stall mode and pip inception in high-speed compressors through the use of correlation integral SO JOURNAL OF TURBOMACHINERY-TRANSACTIONS OF THE ASME LA English DT Article ID CHAOTIC TIME-SERIES; AXIAL COMPRESSOR; ROTATING STALL; DYNAMICS AB Five high-speed compressor configurations are used to identify, pre-stall pressure signal activity under clean and distorted inlet conditions, and under steady injection and controlled injection conditions. Through the use of a nonlinear statistic called correlation integral, variations in the compressor dynamics are identified fr om the pre-stall pressure activity far before variations (,nodal or pip) are observed visually in the wall static pressure measurements. The correlation integral not only discerns changing dynamics of these compressors prior to stall, but is now? used to measure the strength of the tip flow field for these five high-speed compressors. Results show that correlation integral value changes dramatically when the stall inception is modal; and it changes less severely when the stall inception is through pip disturbances. This algorithm call therefore distinguish from the pre-stall pressure traces when a machine is more likely to stall due to pips versus modes. When used irt this manner, the correlation integral thus provides a measure of tip flow strength. The algorithm requires no predisposition about the expected behavior of the data in order to detect changing dynamics in the compressor; thus, no pre-filtering is necessary. However, by band-pass filtering the data, one can monitor changing dynamics in the tip flow field for various frequency regimes. An outcome of this is to associate changes in correlation integral value directly with frequency specific events occurring in the compressor, i.e., blade length scale events versus long length scale acoustic events. The correlation integral provides a potential advantage over linear spectral techniques because a single sensor is used for detection and analysis of the instabilities. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. Univ Akron, Akron, OH 44325 USA. RP Bright, MM (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 22 TC 15 Z9 15 U1 0 U2 2 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 USA SN 0889-504X J9 J TURBOMACH JI J. Turbomach.-Trans. ASME PD OCT PY 1999 VL 121 IS 4 BP 743 EP 750 PG 8 WC Engineering, Mechanical SC Engineering GA 246LR UT WOS:000083165700013 ER PT J AU Cox, DE Gibbs, GP Clark, RL Vipperman, JS AF Cox, DE Gibbs, GP Clark, RL Vipperman, JS TI Experimental robust control of structural acoustic radiation SO JOURNAL OF VIBRATION AND ACOUSTICS-TRANSACTIONS OF THE ASME LA English DT Article AB This work addresses the design and application of robust controllers for structural acoustic control. Both simulation and experimental results are presented. H-infinity and mu-synthesis design methods were used to design feedback controllers which minimize power radiated from a panel while avoiding instability due to unmodeled dynamics. Specifically, high-order structural modes which couple strongly to the actuator-sensor path were poorly modeled. This model error was analytically, bounded with an uncertainty model which allowed controllers to be designed without artificial limits on control effort. It is found that robust control methods provide the control designer with physically meaningful parameters with which to tune control designs and can be very useful in determining limits of performance. However, experimental results also showed poor robustness properties for control designs with ad-hoc uncertainty models. The importance of quantifying and bounding model errors is discussed. C1 NASA, Langley Res Ctr, Hampton, VA 23661 USA. RP Cox, DE (reprint author), NASA, Langley Res Ctr, Hampton, VA 23661 USA. NR 15 TC 9 Z9 9 U1 1 U2 4 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 USA SN 1048-9002 J9 J VIB ACOUST JI J. Vib. Acoust.-Trans. ASME PD OCT PY 1999 VL 121 IS 4 BP 433 EP 439 DI 10.1115/1.2893999 PG 7 WC Acoustics; Engineering, Mechanical; Mechanics SC Acoustics; Engineering; Mechanics GA 250DB UT WOS:000083372800002 ER PT J AU Work, TM Balazs, GH AF Work, TM Balazs, GH TI Relating tumor score to hematology in green turtles with fibropapillomatosis in Hawaii SO JOURNAL OF WILDLIFE DISEASES LA English DT Article DE Chelonia mydas; fibropapillomatosis; field monitoring techniques; green turtle; hematology ID CHELONIA-MYDAS; BLOOD; SPIRORCHIDAE; ISLANDS AB The relationship between hematologic status and severity of tumor affliction in green turtles (Chelonia mydas) with fibropapillomatosis (FP) was examined. During 1 wk periods in July 1997 and July 1998, we bled 108 free-ranging green turtles from Pala'au (Molokai, Hawaii, USA) where FP is endemic. Blood was analyzed for hematocrit, estimated total solids, total white blood cell (WBC) count and differential WBC count. Each turtle was assigned a subjective tumor score ranging from a (no visible external tumors) to 3 (heavily tumored) that indicated the severity of FP. There was a progressive increase in monocytes and a decrease in all other hematologic parameters except heterophils and total numbers of white blood cells as tumor score increased. These data indicate that tumor score can relate to physiologic status of green turtles afflicted with FP, and that tumor score is a useful field monitor of severity of FP in this species. C1 US Geol Survey, Natl Wildlife Hlth Ctr, Biol Resource Div, Honolulu Field Stn, Honolulu, HI 96850 USA. NOAA, Natl Marine Fisheries Serv, SW Fisheries Sci Ctr, Honolulu Lab, Honolulu, HI 96822 USA. RP Work, TM (reprint author), US Geol Survey, Natl Wildlife Hlth Ctr, Biol Resource Div, Honolulu Field Stn, POB 50167, Honolulu, HI 96850 USA. RI Work, Thierry/F-1550-2015 OI Work, Thierry/0000-0002-4426-9090 NR 21 TC 50 Z9 56 U1 0 U2 4 PU WILDLIFE DISEASE ASSN, INC PI LAWRENCE PA 810 EAST 10TH ST, LAWRENCE, KS 66044-8897 USA SN 0090-3558 J9 J WILDLIFE DIS JI J. Wildl. Dis. PD OCT PY 1999 VL 35 IS 4 BP 804 EP 807 PG 4 WC Veterinary Sciences SC Veterinary Sciences GA 321VL UT WOS:000087475300025 PM 10574546 ER PT J AU Greenberg, PS Weiland, KJ Vander Wal, RL AF Greenberg, PS Weiland, KJ Vander Wal, RL TI Microgravity combustion diagnostics: the path to the International Space Station SO MEASUREMENT SCIENCE AND TECHNOLOGY LA English DT Article DE combustion diagnostics; species concentration measurements; velocity measurements; soot measurements; International Space Station; laser spectroscopy; quantitative imaging; laser Doppler velocimeter; microgravity science ID RAINBOW SCHLIEREN DEFLECTOMETRY; SOOT-VOLUME FRACTION AB The Combustion Integrated Rack component of the Fluids and Combustion Facility (FCF), a multi-user, on-orbit International Space Station facility for the study of fluid physics and combustion science, is currently under development. The envelope of measurement requirements for the baselined combustion science experiments is presented, with a description of the basic diagnostic capabilities provided by the facility. An overview of instrumentation development supporting the FCF and conducted under the microgravity combustion research programme at the NASA Glenn Research Center is provided. The resulting advanced diagnostics capabilities serve as potential upgrades to this experimental facility. C1 NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. Natl Ctr Micrograv Res, Cleveland, OH 44135 USA. RP NASA, Glenn Res Ctr, 21000 Brookpk Rd,Mail Stop 110-3, Cleveland, OH 44135 USA. NR 19 TC 1 Z9 1 U1 0 U2 3 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0957-0233 EI 1361-6501 J9 MEAS SCI TECHNOL JI Meas. Sci. Technol. PD OCT PY 1999 VL 10 IS 10 BP 831 EP 835 DI 10.1088/0957-0233/10/10/301 PG 5 WC Engineering, Multidisciplinary; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA 246HJ UT WOS:000083158100002 ER PT J AU Mackey, JR Das, KK Anna, SL McKinley, GH AF Mackey, JR Das, KK Anna, SL McKinley, GH TI A compact dual-crystal modulated birefringence-measurement system for microgravity applications SO MEASUREMENT SCIENCE AND TECHNOLOGY LA English DT Article DE birefringence; polarization; modulation; electro-optical; Mueller matrix; rheology ID POLYMER-SOLUTIONS; FOURIER-ANALYSIS; MUELLER MATRIX; LIGHT; POLARIZATION; ELEMENTS; FLOW AB A compact modulated birefringence-measurement system has been developed for use in microgravity fluid physics applications with non-Newtonian fluids such as polymer solutions. This instrument uses a dual-crystal transverse electro-optical modulator capable of modulation frequencies in excess of 100 MHz. The two crystals are modulated 180 degrees out of phase from each other. The theoretical framework governing the development of this instrument using the Mueller-Stokes polarization matrices is discussed. Several ground-based experiments are performed to compare this system with the theoretical results. Results from this transverse electro-optical modulator-based birefringence-measurement system agree well with the theory. The instrument is also very stable and robust, making it suitable for the extreme acceleration environment to be encountered in a NASA Black Brandt sounding rocket. C1 NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. MIT, Dept Mech Engn, Cambridge, MA 02139 USA. RP Analex Corp, NASA, Glen Grp, 3001 Aerosp Pkwy, Cleveland, OH 44142 USA. EM jmackey@grc.nasa.gov RI McKinley, Gareth/G-4872-2011; Anna, Shelley/D-4270-2009 OI McKinley, Gareth/0000-0001-8323-2779; Anna, Shelley/0000-0003-2750-4754 NR 32 TC 25 Z9 25 U1 0 U2 4 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0957-0233 EI 1361-6501 J9 MEAS SCI TECHNOL JI Meas. Sci. Technol. PD OCT PY 1999 VL 10 IS 10 BP 946 EP 955 DI 10.1088/0957-0233/10/10/315 PG 10 WC Engineering, Multidisciplinary; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA 246HJ UT WOS:000083158100016 ER PT J AU Ting, DZY AF Ting, DZY TI Multiband and multidimensional quantum transport SO MICROELECTRONICS JOURNAL LA English DT Article DE three-dimensional quantum transport; realistic band structure; hole mixing; Gamma-X mixing; interband tunneling; interface roughness ID DOUBLE-BARRIER HETEROSTRUCTURES; INTERBAND TUNNEL STRUCTURES; TIGHT-BINDING MODEL; INTERFACE ROUGHNESS; SUPERLATTICES; SPECTROSCOPY; IMPURITIES; DIODES; DOT AB We give an overview of a numerically stable and efficient method for computing transmission coefficients in semiconductor heterostructures using multiband band structure models. The multiband quantum transmitting boundary method (MQTBM) has been successfully implemented for the empirical tight-binding model, the effective bond orbital, the k.p model, and the pseudopotential method. It has been used extensively in the investigation of band structure effects such as valley mixing and band mixing. We use a GaAs/AlAs double barrier heterostructure and an InAs/GaSb/AlSb interband tunnel device to illustrate the applications of this method to the phenomena of X-point tunneling, hole tunneling, and interband magneto-tunneling. We then review a closely related method,the open-boundary planar supercell stack method (OPSSM), as a means fdr treating 3D quantum transport in mesoscopic tunnel structures. The flexibility of the method allows us to examine a variety of physical phenomena relevant to quantum transport, including alloy disorder, interface roughness, defect impurities, and 0D, 1D, and 2D quantum confinement, in device geometries ranging from double barrier heterostructures to quantum wire electron waveguides. As examples, we examine double barrier structures with interface roughness, resonant tunneling through self-organized InAs quantum dots, and MOS tunnel structures with non-uniform ultra-thin oxide layers. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 CALTECH, Thomas J Watson Sr Lab Appl Phys, Pasadena, CA 91109 USA. Natl Tsing Hua Univ, Dept Phys, Hsinchu 30043, Taiwan. RP Ting, DZY (reprint author), CALTECH, Jet Prop Lab, M-S 302-306, Pasadena, CA 91109 USA. NR 45 TC 13 Z9 13 U1 0 U2 5 PU ELSEVIER ADVANCED TECHNOLOGY PI OXFORD PA OXFORD FULFILLMENT CENTRE THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND SN 0026-2692 J9 MICROELECTR J JI Microelectron. J. PD OCT PY 1999 VL 30 IS 10 BP 985 EP 1000 DI 10.1016/S0026-2692(99)00065-8 PG 16 WC Engineering, Electrical & Electronic; Nanoscience & Nanotechnology SC Engineering; Science & Technology - Other Topics GA 227BN UT WOS:000082058300006 ER PT J AU Gunapala, SD Bandara, SV AF Gunapala, SD Bandara, SV TI Significance of the first excited state position in quantum well infrared photodetectors SO MICROELECTRONICS JOURNAL LA English DT Article DE quantum wells; intersubband absorption; infrared detectors ID PHOTOCONDUCTIVE GAIN; MU-M; INTERSUBBAND ABSORPTION; DARK CURRENT; DETECTORS; WAVELENGTH; PERFORMANCE; CAMERA; SUPERLATTICES; RESPONSIVITY AB Exceptionally rapid progress has been made during the last few years in the performance of GaAs/AlGaAs based quantum well infrared photodetectors (QWIPs), starting from bound-to-bound which has relatively lower sensitivity, and culminating in high performance bound-to-quasibound QWIPs. In this article, we discuss and compare the dependence of absorption, responsivity, dark current, and detectivity of QWIPs with the position of the first excited state in the quantum well. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. RP Gunapala, SD (reprint author), CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. NR 35 TC 9 Z9 10 U1 0 U2 1 PU ELSEVIER ADVANCED TECHNOLOGY PI OXFORD PA OXFORD FULFILLMENT CENTRE THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND SN 0026-2692 J9 MICROELECTR J JI Microelectron. J. PD OCT PY 1999 VL 30 IS 10 BP 1057 EP 1065 DI 10.1016/S0026-2692(99)00056-7 PG 9 WC Engineering, Electrical & Electronic; Nanoscience & Nanotechnology SC Engineering; Science & Technology - Other Topics GA 227BN UT WOS:000082058300012 ER PT J AU Yang, Y Navon, IM Todling, R Yang, WY AF Yang, Y Navon, IM Todling, R Yang, WY TI Sensitivity to large-scale environmental fields of the relaxed Arakawa-Schubert parameterization in the NASA GEOS-1 GCM SO MONTHLY WEATHER REVIEW LA English DT Article ID NON-LINEAR SYSTEMS; ADJOINT SENSITIVITY; ASSIMILATION; MODEL AB An adjoint sensitivity analysis of the relaxed Arakawa-Schubert scheme in the National Aeronautics and Space Administration GEOS-1 GCM with respect to perturbations in large-scale environmental fields was conducted. The response functions were defined as measures of the strength of convective cloud precipitation, the cloud-induced heating and drying (moistening) in both the instantaneous and time-integrated sense. The roles of different variables in producing variations on the response functions were evaluated and the most sensitive vertical levels of the perturbations were identified with the gradient provided by the adjoint model. It was found that the potential temperature perturbations had significant impact on ail the response functionals analyzed, especially on the convective precipitation. The perturbations at subcloud layers and at midtroposphere from 500 to 600 hPa were found to be the most influential. The impact from the moisture fields was most significant on cloud heating and drying effects and the strongest influence came from the subcloud layers. The moisture perturbations at midtroposphere also significantly influenced the cloud drying (moistening) effect. On the other hand, the cloud-induced heating and drying at levels between 400 and 600 hPa felt the strongest impact from perturbations in large-scale fields. The influence of the perturbations in the wind field was weaker but still provided reasonable sensitivity patterns. The time-integrated and instantaneous sensitivities for the same response differ only in magnitude but not in the general distributions. The impact of large-scale condensation and reevaporation on the sensitivity was also evaluated. Their effect was significant at the midtropospheric level and they enhanced the model sensitivity to perturbations in temperature and moisture fields. The sensitivity analysis results obtained indicated that accurate gridscale vertical profile of temperature and moisture, especially at subcloud layers and midtroposphere between 500 and 600 hPa were essential for the accurate evaluation of the cumulus cloud effects. The implications of the results of this work for variational data assimilation were also discussed. C1 Florida State Univ, Supercomp Computat Res Inst, Dept Math, Tallahassee, FL 32306 USA. NASA, DAO, Greenbelt, MD USA. Gen Sci Corp, Greenbelt, MD USA. NCEP, Environm Modeling Ctr, Camp Springs, MD USA. UCAR, Camp Springs, MD USA. RP Navon, IM (reprint author), Florida State Univ, Supercomp Computat Res Inst, Dept Math, Tallahassee, FL 32306 USA. RI Navon, Ionel/A-5173-2008 OI Navon, Ionel/0000-0001-7830-7094 NR 19 TC 3 Z9 3 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 OCT PY 1999 VL 127 IS 10 BP 2359 EP 2378 DI 10.1175/1520-0493(1999)127<2359:STLSEF>2.0.CO;2 PG 20 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 243PT UT WOS:000083007000009 ER PT J AU Wang, JH Rossow, WB Uttal, T Rozendaal, M AF Wang, JH Rossow, WB Uttal, T Rozendaal, M TI Variability of cloud vertical structure during ASTEX observed from a combination of rawinsonde, radar, ceilometer, and satellite SO MONTHLY WEATHER REVIEW LA English DT Article ID UPPER-AIR OBSERVATIONS; MARINE STRATOCUMULUS; LIQUID WATER; FIRE-II; ALBEDO; LAYER; PHYSICS; SURFACE; ISLAND AB The macroscale cloud vertical structure (CVS), including cloud-base and -top heights and layer thickness, and characteristics of multilayered clouds, is studied at Porto Santo Island during the Atlantic Stratocumulus Transition Experiment (ASTEX) by using rawinsonde, radar, ceilometer, and satellite data. The comparisons of CVS parameters obtained from four different approaches show that 1) by using the method developed by Wang and Rossow rawinsonde observations (raob's) can sample all low clouds and determine their boundaries accurately, but oversample low clouds by about 10%, mistaking clear moist layers for clouds; 2) cloud-base heights less than 200 m in the radar data are ambiguous, but can be replaced by the values measured by ceilometer; and 3) the practical limit on the accuracy of marine boundary layer cloud-top heights retrieved from satellites appears to be about 150-300 m mainly due to errors in specifying the atmospheric temperature and humidity in the inversion layer above the cloud. The vertical distribution of clouds at Porto Santo during ASTEX is dominated by low clouds below 3 km, a cloud-free Layer between 3 and 4 km, and similar to 20% high clouds with a peak occurrence around 7-8 km. tow clouds have mean base and top heights of 1.0 km and 1.4 km, respectively, and occur as single layers 90% of the time. For double-layered low clouds, the tops of the uppermost layers and the bases of the lowermost layers have similar distributions as those of single-layered clouds. The temporal variations of low clouds during ASTEX are apparently dominated by advecting mesoscale (20-200 km) horizontal variations. Coherent time variations are predominately synoptic (timescale 4.5-6.8 days) and diurnal variability. On the diurnal timescale, all cloud properties show maxims in the early morning (around 0530 LST) decreasing to minima in the late afternoon. Diurnal variations appear to be altered when high clouds are present above low clouds. The general characteristics of CVS in three ASTEX and the First ISCCP Regional Experiment (FIRE87) regions derived from a 20-yr rawinsonde dataset are also presented. The results suggest that CVS characteristics obtained from data collected at Porto Santo during ASTEX (June 1992) are not representative of other marine stratiform cloud regions. C1 Univ Colorado, Program Atmospher & Ocean Sci, Boulder, CO 80309 USA. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. NOAA, ERL, Environm Technol Lab, Boulder, CO 80303 USA. Columbia Univ, Dept Earth & Environm Sci, New York, NY USA. RP Natl Ctr Atmospher Res, SSSF, POB 3000, Boulder, CO 80307 USA. EM junhong@ucar.edu RI Rossow, William/F-3138-2015 NR 36 TC 51 Z9 54 U1 0 U2 6 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0027-0644 EI 1520-0493 J9 MON WEATHER REV JI Mon. Weather Rev. PD OCT PY 1999 VL 127 IS 10 BP 2484 EP 2502 DI 10.1175/1520-0493(1999)127<2484:VOCVSD>2.0.CO;2 PG 19 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 243PT UT WOS:000083007000017 ER PT J AU Chao, TH Daud, T Thakoor, A AF Chao, TH Daud, T Thakoor, A TI HONORS: Advanced miniature processing hardware for ATR applications SO NEUROCOMPUTING LA English DT Article DE object recognition; optical correlator; parallel neural 3-D processor ID OPTICAL WAVELET PROCESSOR; CORRELATION FILTERS AB The hybrid optoelectronic neural object recognition system (HONORS), underway at the jet propulsion laboratory (JPL), consists of two major building blocks: (1) an advanced grayscale optical correlator (OC) and (2) a massively parallel, neural 3-D processor (N3DP). The OC, with its inherent advantages in parallel processing and shift invariance, will be used for target of interest (TOI) detection and segmentation. The N3DP,with its robust neural learning capability, will be used for target classification and identification. HONORS, with its powerful combination of optical processing and neural networks, will enable real-time, large frame, automatic target recognition (ATR). This paper presents the system architecture and processing algorithms. We provide the results from simulations and experiments, including the detection, classification, and tracking of tanks and aircraft. We will also discuss the potential application of using HONORS for real-time digital palomar observatory survey system (DPOSS). (C) 1999 Published by Elsevier Science B.V. All rights reserved. C1 CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. RP Chao, TH (reprint author), CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 14 TC 1 Z9 3 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0925-2312 J9 NEUROCOMPUTING JI Neurocomputing PD OCT PY 1999 VL 28 BP 233 EP 244 DI 10.1016/S0925-2312(98)00126-X PG 12 WC Computer Science, Artificial Intelligence SC Computer Science GA 237PN UT WOS:000082665400017 ER PT J AU Bever, SJ Hovenac, EA AF Bever, SJ Hovenac, EA TI Reticle for verification of the correct operation of the phase Doppler particle analyzer SO OPTICAL ENGINEERING LA English DT Article DE phase Doppler particle analyzer; microlenses; optical testing ID VELOCITY; SIZE AB A reticle for the verification of the correct operation of the phase Doppler particle analyzer (PDPA) is presented. As an alternative to common calibration devices such as a droplet generator or reticles, we introduce a new reticle that consists of a single polymer microlens affixed to a glass substrate. The microlens reticle, when placed in the measurement Volume of the PDPA, scatters light in a manner similar to that of a droplet. We report on results from tests performed using three microlens reticles of the same diameter and two models of the PDPA. (C) 1999 Society of Photo-Optical Instrumentation Engineers. [S0091-3286(99)00810-7]. C1 Wabash Coll, Dept Phys, Crawfordsville, IN 47933 USA. NASA, Lewis Res Ctr, Dynac Engn Co Inc, Cleveland, OH 44142 USA. RP Bever, SJ (reprint author), Wabash Coll, Dept Phys, Crawfordsville, IN 47933 USA. NR 9 TC 0 Z9 0 U1 0 U2 0 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 OCT PY 1999 VL 38 IS 10 BP 1730 EP 1734 DI 10.1117/1.602225 PG 5 WC Optics SC Optics GA 243YG UT WOS:000083024600018 ER PT J AU Clark, BC Baker, AL Cheng, AF Clemett, SJ McKay, D McSween, HY Pieters, CM Thomas, P Zolensky, M AF Clark, BC Baker, AL Cheng, AF Clemett, SJ McKay, D McSween, HY Pieters, CM Thomas, P Zolensky, M TI Survival of life on asteroids, comets and other small bodies SO ORIGINS OF LIFE AND EVOLUTION OF BIOSPHERES LA English DT Article ID CARBONACEOUS CHONDRITES; BACTERIAL-SPORES; SOLAR-SYSTEM; ANCIENT DNA; EVOLUTION; ORIGIN; METEORITES; AMBER; DUST; MICROORGANISMS AB The ability of living organisms to survive on the smaller bodies in our solar system is examined. The three most significant sterilizing effects include ionizing radiation, prolonged extreme vacuum, and relentless thermal inactivation. Each could be effectively lethal, and even more so in combination, if organisms at some time resided in the surfaces of airless small bodies located near or in the inner solar system. Deep within volatile-rich bodies, certain environments theoretically might provide protection of dormant organisms against these sterilizing factors. Sterility of surface materials to tens or hundreds of centimeters of depth appears inevitable, and to greater depths for bodies which have resided for long periods sunward of about 2 A.U. C1 Lockheed Martin Astronaut, Adv Planetary Studies Grp, Denver, CO USA. Lockheed Martin Astronaut, Planetary Protect Lab, Denver, CO USA. Johns Hopkins Univ, Appl Phys Lab, Laurel, MD USA. Stanford Univ, Dept Chem, Stanford, CA 94305 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Univ Tennessee, Dept Geol Sci, Knoxville, TN 37996 USA. Brown Univ, Dept Geol Sci, Providence, RI 02912 USA. Cornell Univ, Ithaca, NY USA. RP Clark, BC (reprint author), Lockheed Martin Astronaut, Adv Planetary Studies Grp, Denver, CO USA. NR 75 TC 26 Z9 26 U1 0 U2 7 PU SPRINGER PI DORDRECHT PA VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS SN 0169-6149 J9 ORIGINS LIFE EVOL B JI Orig. Life Evol. Biosph. PD OCT PY 1999 VL 29 IS 5 BP 521 EP 545 DI 10.1023/A:1006589213075 PG 25 WC Biology SC Life Sciences & Biomedicine - Other Topics GA 240HK UT WOS:000082819700007 PM 10573692 ER PT J AU Freund, F Gupta, AD Kumar, D AF Freund, F Gupta, AD Kumar, D TI Carboxylic and dicarboxylic acids extracted from crushed magnesium oxide single crystals SO ORIGINS OF LIFE AND EVOLUTION OF THE BIOSPHERE LA English DT Article ID TERT-BUTYLDIMETHYLSILYL DERIVATIVES; INFRARED-SPECTRUM; CARBON; WATER; MINERALS; HYDROGEN; YBA2CU3O7-DELTA; SILICATES; OLIVINE; SILICON AB Carboxylic and dicarboxylic acids (glycolic, oxalic, malonic and succinic) have been extracted with tetrahydrofuran (THF) and H2O from large synthetic MgO crystals, crushed to a medium fine powder. The extracts were characterized by infrared spectroscopy and H-1-NMR. The THF extracts were derivatized with tert-butyldimethylsilyl (t-BDMS) for GC-MS analysis. A single crystal separated from the extract was used for an x-ray structure analysis, giving the monoclinic unit cell, space group P2(1)/c with a(o) = 5.543 Angstrom, b(o) = 8.845 Angstrom, c(o) = 5.086 Angstrom, and beta = 91.9 degrees, consistent with beta-succinic acid, HOOC(CH2)COOH. The amount of extracted acids is estimated to be of the order of 0.1 to 0.5 mg g(-1) MgO. The MgO crystals from which these organic acids were extracted grew from the 2860 degrees C hot melt, saturated with CO/CO2 and H2O, thereby incorporating small amounts of the gaseous components to form a solid solution (ss) with MgO. Upon cooling, the ss becomes supersaturated, causing solute carbon and other solute species to segregate not only to the surface but also internally, to dislocations and subgrain boundaries. The organic acids extracted from the MgO crystals after crushing appear to derive from these segregated solutes that formed C-C, C-H and C-O bonds along dislocations and other defects in the MgO structure, leading to entities that can generically be described as (HxCyOz)(n-). The processes underlying the formation of these precursors are fundamental in nature and expected to be operational in any minerals, preferentially those with dense structures, that crystallized in H2O-CO2-laden environments. This opens the possibility that common magmatic and metamorphic rocks when weathering at the surface of a tectonically active planet like Earth may be an important source of abiogenically formed complex organic compounds. C1 NASA, Ames Res Ctr, SETI Inst, Moffett Field, CA 94035 USA. San Jose State Univ, Dept Phys, San Jose, CA 95192 USA. SETI Inst, Mt View, CA 94043 USA. RP Freund, F (reprint author), NASA, Ames Res Ctr, SETI Inst, Moffett Field, CA 94035 USA. NR 36 TC 6 Z9 6 U1 0 U2 1 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0169-6149 J9 ORIGINS LIFE EVOL B JI Orig. Life Evol. Biosph. PD OCT PY 1999 VL 29 IS 5 BP 489 EP 509 DI 10.1023/A:1006698710710 PG 21 WC Biology SC Life Sciences & Biomedicine - Other Topics GA 240HK UT WOS:000082819700005 PM 10573690 ER PT J AU Lowman, PD AF Lowman, PD TI Landsat and Apollo: The forgotten legacy SO PHOTOGRAMMETRIC ENGINEERING AND REMOTE SENSING LA English DT Article AB This paper demonstrates that Landsat was fundamentally a result of the Apollo Program. The U.S. Geological Survey's EROS proposal of 1966, which eventually led to Landsat, was stimulated largely by the demonstrated utility of 1100 orbital photographs from the Gemini missions, Gemini being solely preparation for Apollo. In addition, Earth-oriented remote sensing research sponsored by NASA in the mid-1960s, primarily support for Apollo lunar missions, included studies of Earth resource applications as well. Finally, the extensive series of airborne remote sensing studies carried out by the NASA Manned Spacecraft Center was Apollo-derived in that the primary mission of MSC was to accomplish a lunar landing. It is concluded that, had it not been for the Apollo Program, Landsat or its equivalent would have been delayed by 10 years or more. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Lowman, PD (reprint author), NASA, Goddard Space Flight Ctr, Code 921, Greenbelt, MD 20771 USA. NR 27 TC 6 Z9 6 U1 0 U2 2 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 OCT PY 1999 VL 65 IS 10 BP 1143 EP 1147 PG 5 WC Geography, Physical; Geosciences, Multidisciplinary; Remote Sensing; Imaging Science & Photographic Technology SC Physical Geography; Geology; Remote Sensing; Imaging Science & Photographic Technology GA 244YU UT WOS:000083079000007 ER PT J AU Ustin, SL Roberts, DA Green, RO Zomer, RJ Garcia, M AF Ustin, SL Roberts, DA Green, RO Zomer, RJ Garcia, M TI Remote sensing methods monitor natural resources SO PHOTONICS SPECTRA LA English DT Article C1 Univ Calif Davis, Dept Land Air & Water Resources, Davis, CA 95616 USA. Univ Calif Santa Barbara, Santa Barbara, CA 93106 USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. RP Ustin, SL (reprint author), Univ Calif Davis, Dept Land Air & Water Resources, Davis, CA 95616 USA. NR 0 TC 4 Z9 9 U1 1 U2 4 PU LAURIN PUBL CO INC PI PITTSFIELD PA BERKSHIRE COMMON PO BOX 1146, PITTSFIELD, MA 01202 USA SN 0731-1230 J9 PHOTON SPECTRA JI Photon. Spect. PD OCT PY 1999 VL 33 IS 10 BP 108 EP + PG 5 WC Optics SC Optics GA 244FR UT WOS:000083041600044 ER PT J AU Bhatia, AK Drachman, RJ AF Bhatia, AK Drachman, RJ TI Energy levels of triply ionized carbon (CIV): Polarization method SO PHYSICAL REVIEW A LA English DT Article ID RYDBERG STATES; MICROWAVE SPECTROSCOPY; C-IV; HELIUM; LITHIUM AB In a previous publication [Can. J. Phys. 75, 11 (1997)] we calculated the generalized polarizabilities up to multipole order 3 as well as certain higher-order hyperpolarizabilities for two-electron atoms and ions of Z = 2-6 and 10. In this paper we apply some of these results to calculate excited-state energies in three times ionized (lithiumlike) carbon. For states with angular momentum L>3 accurate results are obtained using an asymptotic polarizability expansion that includes nonadiabatic effects. Comparison is made with recent optical measurements, and a critical discussion of the correct form of the expansion is given. In addition, the possibility of very accurate measurements of the fine-structure splitting encourages us to present a table of such splittings to very high accuracy. An appendix contains similar results for lithiumlike oxygen and neon ions. [S1050-2947(99)07610-6]. C1 NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Bhatia, AK (reprint author), NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. NR 22 TC 4 Z9 4 U1 0 U2 0 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 1050-2947 J9 PHYS REV A JI Phys. Rev. A PD OCT PY 1999 VL 60 IS 4 BP 2848 EP 2852 DI 10.1103/PhysRevA.60.2848 PG 5 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA 247BP UT WOS:000083201000043 ER PT J AU Yeh, NC Vasquez, RP Fu, CC Samoilov, AV Li, Y Vakili, K AF Yeh, NC Vasquez, RP Fu, CC Samoilov, AV Li, Y Vakili, K TI Nonequilibrium superconductivity under spin-polarized quasiparticle currents in perovskite ferromagnet-insulator-superconductor heterostructures SO PHYSICAL REVIEW B LA English DT Article ID PAIRING SYMMETRY; SINGLE-CRYSTALS; TRANSPORT; YBA2CU3O7-DELTA; INTERFACE; INJECTION; SYSTEM AB We report phenomena manifesting nonequilibrium superconductivity induced by spin-polarized quasiparticles in perovskite ferromagnet-insulator-superconductor (F-I-S) heterostructures. Measurements of the critical current J(c), using a pulsed current technique to minimize Joule heating, reveal a monotonic increase with increasing insulator thickness, and for F-I-S with thin insulating barriers, a slight increase in J(c) is observed under small injection currents I-m from the ferromagnet, followed by a strong suppression of J(c) under large I-m. In contrast, no effect of injection on J(c) can be detected in the N-I-S control sample (N: nonmagnetic metal). The spin diffusion time and length in cuprate superconductors are also estimated and compared with our experimental results. [S0163-1829(99)05638-6]. C1 CALTECH, Dept Phys, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. RP Yeh, NC (reprint author), CALTECH, Dept Phys, Pasadena, CA 91125 USA. NR 27 TC 135 Z9 136 U1 0 U2 6 PU AMER PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 1098-0121 EI 1550-235X J9 PHYS REV B JI Phys. Rev. B PD OCT 1 PY 1999 VL 60 IS 14 BP 10522 EP 10526 DI 10.1103/PhysRevB.60.10522 PG 5 WC Physics, Condensed Matter SC Physics GA 244VE UT WOS:000083070800088 ER PT J AU Balasubramaniam, R Subramanian, RS AF Balasubramaniam, R Subramanian, RS TI Axisymmetric thermal wake interaction of two bubbles in a uniform temperature gradient at large Reynolds and Marangoni numbers SO PHYSICS OF FLUIDS LA English DT Article ID THERMOCAPILLARY MIGRATION; DROPLET INTERACTIONS; 2 BUBBLES; MOTION; LINE AB An analysis is performed on the thermocapillary motion of two bubbles in a continuous phase in which a linear temperature field is imposed in the undisturbed state. The bubbles are moving in the direction of the temperature gradient and are assumed to interact axisymmetrically via the influence of the thermal wake of the leading bubble on the trailing bubble. The flow-field interaction of the bubbles is neglected. The Reynolds number of the motion is assumed to be sufficiently large that a potential flow field prevails around each bubble. The energy equation for the temperature field around the trailing bubble is solved by matched asymptotic expansions for large values of the Marangoni number. It is shown that the thermal wake of the leading bubble induces a nonmonotonic temperature field on the surface of the trailing bubble. The effective temperature gradient on the trailing bubble is weakened. Hence its migration speed is reduced compared to the case when it is isolated. This result is in qualitative agreement with experimental results for a pair of interacting drops obtained from a space flight experiment that has been reported in the literature. (C) 1999 American Institute of Physics. [S1070-6631(99)03010-X]. C1 NASA, Natl Ctr Micrograv Res Fluids & Combust, Glenn Res Ctr, Cleveland, OH 44135 USA. Clarkson Univ, Dept Chem Engn, Potsdam, NY 13699 USA. RP Balasubramaniam, R (reprint author), NASA, Natl Ctr Micrograv Res Fluids & Combust, Glenn Res Ctr, Mail Stop 110-3, Cleveland, OH 44135 USA. NR 23 TC 10 Z9 11 U1 0 U2 0 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 1070-6631 J9 PHYS FLUIDS JI Phys. Fluids PD OCT PY 1999 VL 11 IS 10 BP 2856 EP 2864 DI 10.1063/1.870144 PG 9 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 233BH UT WOS:000082405300008 ER PT J AU Khazanov, GV Krivorutsky, EN Gallagher, DL AF Khazanov, GV Krivorutsky, EN Gallagher, DL TI Whistler solitons in plasma with anisotropic hot electron admixture SO PHYSICS OF PLASMAS LA English DT Article ID WAVES AB The longitudinal and transverse modulation instability of whistler waves in plasma, with a small admixture of hot anisotropic electrons, is discussed. If the hot particles temperature anisotropy is positive, it is found that, in such plasma, longitudinal perturbations can lead to soliton formation for frequencies forbidden in cold plasma. The soliton is enriched by hot particles. The frequency region unstable to transverse modulation in cold plasma in the presence of hot electrons is divided by stable domains. For both cases the role of hot electrons is more significant for whistlers with smaller frequencies. (C) 1999 American Institute of Physics. [S1070-664X(99)00310-9]. C1 Univ Alaska Fairbanks, Inst Geophys, Fairbanks, AK 99775 USA. Univ Alaska Fairbanks, Dept Phys, Fairbanks, AK 99775 USA. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. RP Khazanov, GV (reprint author), Univ Alaska Fairbanks, Inst Geophys, Fairbanks, AK 99775 USA. NR 15 TC 0 Z9 0 U1 0 U2 0 PU AMER INST PHYSICS PI MELVILLE PA CIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USA SN 1070-664X J9 PHYS PLASMAS JI Phys. Plasmas PD OCT PY 1999 VL 6 IS 10 BP 3794 EP 3798 DI 10.1063/1.873643 PG 5 WC Physics, Fluids & Plasmas SC Physics GA 238PY UT WOS:000082719700010 ER PT J AU Atreya, SK Wong, MH Owen, TC Mahaffy, PR Niemann, HB de Pater, I Drossart, P Encrenaz, T AF Atreya, SK Wong, MH Owen, TC Mahaffy, PR Niemann, HB de Pater, I Drossart, P Encrenaz, T TI A comparison of the atmospheres of Jupiter and Saturn: deep atmospheric composition, cloud structure, vertical mixing, and origin SO PLANETARY AND SPACE SCIENCE LA English DT Article; Proceedings Paper CT Symposium on the Jovian System after Galileo/The Saturnian System before Cassini-Huygens CY MAY 11-15, 1998 CL NANTES, FRANCE SP European Union, European Space Agcy, CNES, French Minist Educ Natl, CNRS, City Nantes, Univ Nantes, Reg Pays Loire, COSPAR ID TROPOSPHERIC GAS-COMPOSITION; NORTH EQUATORIAL BELT; VOYAGER IRIS SPECTRA; FAR-INFRARED-SPECTRA; D/H ISOTOPIC RATIO; GIANT PLANETS; LABORATORY MEASUREMENTS; MU-M; SOLAR-SYSTEM; WATER ICE AB We present our current understanding of the composition, vertical mixing, cloud structure and the origin of the atmospheres of Jupiter and Saturn. Available observations point to a much more vigorous vertical mixing in Saturn's middle-upper atmosphere than in Jupiter's. The nearly cloud- free nature of the Galileo probe entry site, a 5-micron hotspot, is consistent with the depletion of condensible volatiles to great depths, which is attributed to local meteorology. Somewhat similar depletion of water may be present in the 5-micron bright regions of Saturn also. The supersolar abundances of heavy elements, particularly C and S in Jupiter's atmosphere and C in Saturn's, as well as the progressive increase of C from Jupiter to Saturn and beyond, tend to support the icy planetesimal model of the formation of the giant planets and their atmospheres. However, much work remains to be done, especially in the area of laboratory studies, including identification of possible new microwave absorbers and modelling, in order to resolve the controversy surrounding the large discrepancy between Jupiter's global ammonia abundance, hence the nitrogen elemental ratio, derived from the earth-based microwave observations and that inferred from the analysis of the Galileo probe-orbiter radio attenuation data for the hotspot. We look forward to the observations from Cassini-Huygens spacecraft which are expected to result not only in a rich harvest of information for Saturn, but a better understanding of the formation of the giant planets and their atmospheres when these data are combined with those that exist for Jupiter. (C) 1999 Elsevier Science Ltd, All rights reserved. C1 Univ Michigan, Dept Atmospher Ocean & Space Sci, Ann Arbor, MI 48109 USA. Univ Hawaii, Inst Astron, Honolulu, HI 96822 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Calif Berkeley, Dept Astron, Berkeley, CA 94720 USA. Observ Paris, DESPA, F-92195 Meudon, France. RP Atreya, SK (reprint author), Univ Michigan, Dept Atmospher Ocean & Space Sci, Ann Arbor, MI 48109 USA. EM atreya@umich.edu RI Mahaffy, Paul/E-4609-2012 NR 119 TC 133 Z9 133 U1 0 U2 9 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD OCT-NOV PY 1999 VL 47 IS 10-11 BP 1243 EP 1262 DI 10.1016/S0032-0633(99)00047-1 PG 20 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 263XV UT WOS:000084151300007 PM 11543193 ER PT J AU Kiefer, RL Herring, K Wylie, BJ Orwoll, RA Thibeault, SA AF Kiefer, RL Herring, K Wylie, BJ Orwoll, RA Thibeault, SA TI The effects of UV radiation on several high-performance polyimide composites SO POLYMER INTERNATIONAL LA English DT Article; Proceedings Paper CT 37th International Symposium on Macromolecules - Radiation Chemistry of Polymers and Polymer Education (IUPAC) CY JUL 12-17, 1998 CL GOLD COAST, AUSTRALIA SP Int Union Pure & Appl Chem DE polyimide; ultraviolet radiation; XPS; thermal analysis AB Three high-performance polyimides were exposed at 177 degrees C to ultraviolet radiation at three different intensities and for three different times so that the product of intensity and time was a constant. Intensities of 1, 2 and 3 suns, and times of 500, 250 and 167 h were used. One sun is the power in space at one earth-sun distance and is 0.135 J s(-1) cm(-2). The polyimides were LARCO(TM)-8515, PETI-5 and K3B. Samples were analysed by XPS, TGA, TMA and DMA. Thermal analyses by TGA, TMA and DMA, which measure bulk properties, showed essentially no difference between samples exposed to heat and UV radiation, and control samples. Surface analysis by XPS showed an apparent decrease in carbonyl on the surface of some exposed samples. This could be correlated for the PETI-5 and LARC(TM)-8515 samples to surface contamination by a silicone-containing material. (C) 1999 Society of Chemical Industry. C1 Coll William & Mary, Dept Chem, Williamsburg, VA 23187 USA. NASA, Langley Res Ctr, Div Mat, Hampton, VA 23665 USA. RP Kiefer, RL (reprint author), Coll William & Mary, Dept Chem, POB 8795, Williamsburg, VA 23187 USA. NR 3 TC 1 Z9 1 U1 2 U2 3 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX PO19 1UD, ENGLAND SN 0959-8103 J9 POLYM INT JI Polym. Int. PD OCT PY 1999 VL 48 IS 10 BP 1042 EP 1045 PG 4 WC Polymer Science SC Polymer Science GA 241DF UT WOS:000082866500018 ER PT J AU Backes, PG Tso, KS Tharp, GK AF Backes, PG Tso, KS Tharp, GK TI The Web interface for telescience SO PRESENCE-TELEOPERATORS AND VIRTUAL ENVIRONMENTS LA English DT Article AB The Web Interface for Telescience (WITS) is an Internet-based tool that enables members of geographically distributed science teams to participate in daily planetary lander and rover mission planning. WITS enables the viewing of down-linked images and results in various ways, terrain-feature measurement and annotation, and the planning of daily mission activities. WITS is written in the Java language and is accessible by mission scientists and the general public via a Web browser. The public can use WITS to plan and simulate their own rover missions. WITS was used during the 1997 Mars Pathfinder mission primarily for public outreach and was evaluated as a science operations tool at the Jet Propulsion Laboratory (JPL). WITS will be used as an operations tool in the 1998 lander mission, which will land on Mars in December 1999, and in the 2001 and 2003 lander-rover missions to Mars. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. IA Tech Inc, Los Angeles, CA USA. RP CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91125 USA. EM Paul.G.Backes@jpl.nasa.gov NR 11 TC 8 Z9 8 U1 0 U2 0 PU MIT PRESS PI CAMBRIDGE PA ONE ROGERS ST, CAMBRIDGE, MA 02142-1209 USA SN 1054-7460 EI 1531-3263 J9 PRESENCE-TELEOP VIRT JI Presence-Teleoper. Virtual Env. PD OCT PY 1999 VL 8 IS 5 BP 531 EP 539 DI 10.1162/105474699566440 PG 9 WC Computer Science, Cybernetics; Computer Science, Software Engineering SC Computer Science GA 245MY UT WOS:000083113800004 ER PT J AU Welch, RB AF Welch, RB TI How can we determine if the sense of presence affects task performance? SO PRESENCE-TELEOPERATORS AND VIRTUAL ENVIRONMENTS LA English DT Article ID VIRTUAL ENVIRONMENTS AB The question of whether the sense of presence in virtual environments (or telepresence with respect to teleoperator systems) is causally related to task performance remains unanswered because the appropriate studies have yet to be carried out. In this brief report, the author describes a strategy for resolving this issue and the results of a pilot study in which this strategy was implemented. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Welch, RB (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 12 TC 26 Z9 27 U1 1 U2 1 PU M I T PRESS PI CAMBRIDGE PA FIVE CAMBRIDGE CENTER, CAMBRIDGE, MA 02142 USA SN 1054-7460 J9 PRESENCE-TELEOP VIRT JI Presence-Teleoper. Virtual Env. PD OCT PY 1999 VL 8 IS 5 BP 574 EP 577 DI 10.1162/105474699566387 PG 4 WC Computer Science, Cybernetics; Computer Science, Software Engineering SC Computer Science GA 245MY UT WOS:000083113800009 PM 11543209 ER PT J AU Soderberg, AM Pilachowski, CA Barden, SC Willmarth, D Sneden, C AF Soderberg, AM Pilachowski, CA Barden, SC Willmarth, D Sneden, C TI Radial velocities of giant stars in globular clusters SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC LA English DT Article ID INDIVIDUAL STARS; BINARY STARS; M13; M3; M92 AB We report radial velocities for 303 giant stars in the globular clusters M3, M13, M15, and M92. Spectra were obtained using the 4 m Mayall and 3.5 m WIYN telescopes and the Hydra fiber positioner between 1993 and 1997; most spectra were provided by the NOAO WIYN Queue Program. Observations spanned times from a few days to several months. The uncertainties in the velocity measurements are typically 1 km s(-1) or less. Several stars show velocity variations which may result from binary companions or atmospheric motions. Mean cluster velocities were measured to be -147.0 +/- 0.3, -245.5 +/- 1.0, -106.2 +/- 0.3, and -120.3 +/- 0.3 km s(-1), for M3, M13, M15, and M92, respectively. Radial velocity observations for the photometric variable V73 (vZ 1406) in M3 confirm that the star varies with a period of 0.67 days. C1 Natl Opt Astron Observ, Lewiston, ME 04240 USA. Bates Coll, Dept Phys & Astron, Lewiston, ME 04240 USA. Natl Opt Astron Observ, Tucson, AZ 85726 USA. Univ Texas, McDonald Observ, Austin, TX 78712 USA. Univ Texas, Dept Astron, Austin, TX 78712 USA. RP Soderberg, AM (reprint author), Natl Opt Astron Observ, Box 628, Lewiston, ME 04240 USA. NR 45 TC 8 Z9 8 U1 0 U2 0 PU ASTRONOMICAL SOC PACIFIC PI SAN FRANCISCO PA 390 ASHTON AVE, SAN FRANCISCO, CA 94112 USA SN 0004-6280 J9 PUBL ASTRON SOC PAC JI Publ. Astron. Soc. Pac. PD OCT PY 1999 VL 111 IS 764 BP 1233 EP 1247 DI 10.1086/316439 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 248FP UT WOS:000083264700003 ER PT J AU O'Dell, CR Doi, T AF O'Dell, CR Doi, T TI Calibration of Hubble Space Telescope WFPC2 emission-line filters SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC LA English DT Article ID ORION NEBULA AB The results of calibration of the primary emission-line filters of the Hubble Space Telescope WFPC2 are presented in a form which allows observers to easily calculate emission-line surface brightnesses for H alpha, H beta, [O III] lambda 5007, and [N II] lambda 6583. The H alpha and [N II] filters pass both lines in such a way that observations in both are necessary to obtain good isolation of either line. We establish that determination of the strength of the underlying continuum can be important, especially in H II regions. We express cautionary notes against overly simple interpretations of the signal from filters selected to isolate lines at 4363, 6300, and 6717 + 6731 Angstrom. Finally, we use this calibration to recommend guidelines for the selection of emission-line filters on future HST instruments. C1 Rice Univ, Dept Space Phys & Astron, Houston, TX 77251 USA. NASA, Johnson Space Ctr, MC CB, Houston, TX 77058 USA. RP O'Dell, CR (reprint author), Rice Univ, Dept Space Phys & Astron, MS-108,POB 1892, Houston, TX 77251 USA. NR 10 TC 35 Z9 35 U1 0 U2 0 PU ASTRONOMICAL SOC PACIFIC PI SAN FRANCISCO PA 390 ASHTON AVE, SAN FRANCISCO, CA 94112 USA SN 0004-6280 J9 PUBL ASTRON SOC PAC JI Publ. Astron. Soc. Pac. PD OCT PY 1999 VL 111 IS 764 BP 1316 EP 1320 DI 10.1086/316443 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 248FP UT WOS:000083264700012 ER PT J AU Prigent, C Rossow, WR AF Prigent, C Rossow, WR TI Retrieval of surface and atmospheric parameters over land from SSM/I: Potential and limitations SO QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY LA English DT Article DE microwave; radiative transfer; variational inversion ID CLOUD LIQUID-WATER; SNOW COVER; SATELLITE MEASUREMENTS; MICROWAVE; ISCCP; ASSIMILATION; EMISSIVITIES; PREDICTION; INVERSION; RADIANCES AB The potential to retrieve surface temperature, water vapour content and cloud liquid water path from the Special Sensor Microwave/Imager (SSM/I) observations over land is examined, using a variational inversion scheme. The method relies upon prior estimates of the monthly mean land surface microwave emissivities and exploits a priori information on the atmospheric situation (International Satellite Cloud Climatology Project (ISCCP) data and National Center for Environmental Prediction analysis). The accuracy of the surface temperature retrieval is of the order of 1 K, does not strongly depend on surface type and is not very sensitive to the presence of thin clouds. The sensitivity to the water vapour is very low except in the most arid areas. With an accuracy of similar to 0.1 kg m(-2), the SSM/I retrieval does not properly characterize thin clouds, but the major cloud structures are well delineated and qualitative agreement is observed between the SSM/I and ISCCP estimations. This inversion process also has some ability to detect rain events. C1 Columbia Univ, NASA, Goddard Inst Space Studies, New York, NY 10025 USA. RP Prigent, C (reprint author), Columbia Univ, NASA, Goddard Inst Space Studies, New York, NY 10025 USA. RI Rossow, William/F-3138-2015 NR 35 TC 21 Z9 22 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 OCT PY 1999 VL 125 IS 559 BP 2379 EP 2400 DI 10.1256/smsqj.55902 PN A PG 22 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 246MT UT WOS:000083168100002 ER PT J AU Pu, ZX Kalnay, E AF Pu, ZX Kalnay, E TI Targeting observations with the quasi-inverse linear and adjoint NCEP global models: Performance during FASTEX SO QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY LA English DT Article DE adjoint Fronts and Atlantic Storm-Track EXperiment (FASTEX); quasi-inverse linear; targeted observations ID INITIAL CONDITIONS; SINGULAR VECTORS; FORECAST ERRORS; SENSITIVITY AB This note gives a brief summary of the targeting results obtained with both adjoint and quasi-inverse linear NCEP global spectral models during the Fronts and Atlantic Storm-Track EXperiment (FASTEX). Questions concerning the feasibility of the methods and related issues about targeting observations are briefly discussed. C1 Univ Space Res Assoc, NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Natl Ctr Environm Predict, Camp Springs, MD USA. RP Pu, ZX (reprint author), Univ Space Res Assoc, NASA, Goddard Space Flight Ctr, Mail Code 912, Greenbelt, MD 20771 USA. RI Kalnay, Eugenia/F-4393-2010; OI Kalnay, Eugenia/0000-0002-9984-9906 NR 13 TC 32 Z9 40 U1 0 U2 2 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 OCT PY 1999 VL 125 IS 561 BP 3329 EP 3337 DI 10.1256/smsqj.56108 PN C PG 9 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 285LB UT WOS:000085389600009 ER PT J AU Davis, C Low-Nam, S Shapiro, MA Zou, XL Krueger, AJ AF Davis, C Low-Nam, S Shapiro, MA Zou, XL Krueger, AJ TI Direct retrieval of wind from total ozone mapping spectrometer (TOMS) data: Examples from FASTEX SO QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY LA English DT Article DE potential-vorticity inversion; upper-tropospheric analysis ID POTENTIAL-VORTICITY; CLIMATOLOGY AB The quantitative relationship between ozone and potential vorticity, and hence balanced wind and temperature, is examined using observations collected for a one-month period by the total ozone mapping spectrometer (TOMS). Ozone data are compared with Ertel potential vorticity (PV) integrated vertically from 500 to 50 mb, obtained from the NCEP/NCAR (National Centers for Environmental Prediction/National Center for Atmospheric Research) reanalysis archive. By performing a simple time filtering we isolate synoptic-scale transients in the ozone and PV. We show that the previously reported high correlation between PV and ozone is actually variable from day to day. The correlation also shows strong latitudinal dependence, with essentially no correlation in the tropics and high correlation in middle latitudes. A method is introduced to derive a three-dimensional PV representation from ozone data and a background field taken from the reanalysis data. PV-inversion methods are then used to recover balanced winds and temperatures and geopotential heights which may be compared to the analysed fields. Results suggest that many of the upper-tropospheric synoptic-scale wind perturbations may be recovered from the ozone data. A systematic error in the retrieval method used here is the underestimation of the strength of upper-level ridges, corresponding to an excess of vertically integrated ozone compared with integrated PV. We discuss reasons for this difference. C1 Natl Ctr Atmospher Res, Mesoscale & Microscale Meteorol Div, Boulder, CO 80307 USA. NOAA, Boulder, CO USA. Florida State Univ, Tallahassee, FL 32306 USA. NASA, Goddard Space Flight Ctr, Huntsville, AL 35812 USA. RP Davis, C (reprint author), Natl Ctr Atmospher Res, Mesoscale & Microscale Meteorol Div, POB 3000, Boulder, CO 80307 USA. NR 23 TC 10 Z9 12 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 OCT PY 1999 VL 125 IS 561 BP 3375 EP 3391 DI 10.1256/smsqj.56111 PN C PG 17 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 285LB UT WOS:000085389600012 ER PT J AU Friedel, RHW Reeves, G Belian, D Cayton, T Mouikis, C Korth, A Blake, B Fennell, J Selesnick, R Baker, D Onsager, T Kanekal, S AF Friedel, RHW Reeves, G Belian, D Cayton, T Mouikis, C Korth, A Blake, B Fennell, J Selesnick, R Baker, D Onsager, T Kanekal, S TI A multi-spacecraft synthesis of relativistic electrons in the inner magnetosphere using LANL, GOES, GPS, SAMPEX, HEO and POLAR SO RADIATION MEASUREMENTS LA English DT Article; Proceedings Paper CT Conference on Space Radiation Environment Modeling: New Phenomena and Approaches CY OCT 07-09, 1997 CL MOSCOW, RUSSIA SP Moscow State Univ, Skobeltsyn Inst Nucl Phys, Moscow State Univ, Russian Acad Sci, Russian Space Agcy, Russian Fdn Basic Res, COSPAR ID RADIATION BELT; PARTICLE; SOLAR AB One of the Brussels Radiation Belt Workshop recommendation was the establishment of a near-real-time data driven model of the inner magnetospheric energetic particle population (L < 8). Although the "ideal" missions and data sets for such a model do not exist at present, more spacecraft than ever before are currently sampling the inner magnetosphere. We attempt here in a case study of the 10 January, 1997 magnetic cloud event to construct such a model with the energetic electron data available from 5 geosynchronous and 6 elliptically orbiting satellites. We examine the constraints and difficulties of putting together a large number of datasets which are measured near-simultaneously at very different locations in the inner magnetosphere. First results indicate that we can achieve a time resolution of about 3 h for a given "snapshot" of the inner magnetosphere, and that large azimuthal asymmetries of the energetic electron population can be observed during large storms. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87544 USA. Max Planck Inst Aeron, Katlenburg Lindau, Germany. Aerospace Corp, El Segundo, CA 90245 USA. LASP, Boulder, CO USA. NOAA, SEC, Boulder, CO USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Friedel, RHW (reprint author), Univ Calif Los Alamos Natl Lab, POB 1663, Los Alamos, NM 87544 USA. RI Friedel, Reiner/D-1410-2012; Reeves, Geoffrey/E-8101-2011 OI Friedel, Reiner/0000-0002-5228-0281; Reeves, Geoffrey/0000-0002-7985-8098 NR 15 TC 2 Z9 2 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1350-4487 J9 RADIAT MEAS JI Radiat. Meas. PD OCT PY 1999 VL 30 IS 5 BP 589 EP 597 DI 10.1016/S1350-4487(99)00230-9 PG 9 WC Nuclear Science & Technology SC Nuclear Science & Technology GA 259MY UT WOS:000083898700011 ER PT J AU Fung, SF Tan, LC AF Fung, SF Tan, LC TI An alternative drift shell parameter for modeling trapped particles SO RADIATION MEASUREMENTS LA English DT Article; Proceedings Paper CT Conference on Space Radiation Environment Modeling: New Phenomena and Approaches CY OCT 07-09, 1997 CL MOSCOW, RUSSIA SP Moscow State Univ, Skobeltsyn Inst Nucl Phys, Moscow State Univ, Russian Acad Sci, Russian Space Agcy, Russian Fdn Basic Res, COSPAR AB The McIlwain L parameter has been widely used to label magnetic drift shells of trapped particles. In a dipolar magnetic field, L gives the equatorial radius of a drift shell. When the total magnetospheric magnetic field is significantly altered by the presence of external magnetospheric currents, particularly during geomagnetically active periods, L has to be calculated by using an appropriate magnetic field model that includes the external fields. Thus, an L value computed at a given local time does not always give the position of a drift shell in configuration (real) space, especially at high L values ( > 4). Since L is one of the magnetic coordinates typically used to organize trapped particle data, the external current effects on the L calculation need to be assessed. In this paper, we show that by conserving the second adiabatic invariant, I, in a model magnetospheric magnetic field given by the sum of the IGRF and the Tsyganenko T89c models, a configuration-space-based drift shell parameter can be defined. It has been found that for a given mirroring field strength B-m on a magnetic field Line, the quantity I is empirically related to the radial distance r, to the point of minimum field strength along that field line. By conserving I, r, measured in units of Earth radii (R-E) at any local time can be mapped to its equivalent value L-m at noon, and vice versa. We show that L-m can be used as a parameter to label drift shell in configuration space, analogous to the use of L in magnetic space. Published by Elsevier Science Ltd. C1 NASA, Goddard Space Flight Ctr, Space Phys Data Facil, Greenbelt, MD 20771 USA. RP Fung, SF (reprint author), NASA, Goddard Space Flight Ctr, Space Phys Data Facil, Code 632, Greenbelt, MD 20771 USA. RI Fung, Shing/F-5647-2012 NR 17 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 1350-4487 J9 RADIAT MEAS JI Radiat. Meas. PD OCT PY 1999 VL 30 IS 5 BP 609 EP 615 DI 10.1016/S1350-4487(99)00243-7 PG 7 WC Nuclear Science & Technology SC Nuclear Science & Technology GA 259MY UT WOS:000083898700013 ER PT J AU Ouaidrari, H Vermote, EF AF Ouaidrari, H Vermote, EF TI Operational atmospheric correction of Landsat TM data SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID AVHRR DATA; SATELLITE; RETRIEVAL; ALGORITHM; SENSOR; FIFE AB The recent algorithms developed for biophysical variables assessment require accurate surface reflectance measurements. This article describes algorithms used for atmospheric correction of Landsat Thematic Mapper (TM) data. Atmospheric corrections include Rayleigh scattering gaseous absorption, and aerosol scattering in three visible channels (480 nm, 560 nm, and 660 nm), and the near-infrared channel (830 nm). Atmospheric constituents such as water vapor and ozone are extracted from climatology data sets, while aerosol optical depths (AODs) are derived from the TM scene itself by adopting the dark target approach. The dark target pixels are identified, and their reflectances in the visible channels are estimated using TBI Channel 7 (2.1 mu m). Atmospheric transmittance and aerosol optical depth are derived for 16 grid points equally distributed over the scene, then interpolated to match the TM spatial resolution. This technique considerably reduces the computing time without decreasing the accuracy. These algorithms were tested using 11 TM scenes over a wide variety of sites, including forest, crop, ann semiarid areas. The AOD in the blue, green, and red channels retrieved using the dark target technique was validated using sunphotometer measurements. The absolute error associated with AOD assessment was less than 0.15. A statistical analysis teas also conducted to evaluate the atmospheric correction method. Based on data from the FIFE (First ISLSCP Field Experiment) experiment, the absolute error between ground measurements and TM reflectance was less than 0.015 in the visible channels, and less than 0.08 in the near-infrared channel. (C) Elsevier Science Inc., 1999. C1 Univ Maryland, Dept Geog, College Pk, MD 20742 USA. Univ Maryland, NASA, GSCF, Dept Geog, Greenbelt, MD USA. RP Ouaidrari, H (reprint author), Univ Maryland, Dept Geog, 2181 LeFrak Hall, College Pk, MD 20742 USA. RI Vermote, Eric/K-3733-2012 NR 21 TC 91 Z9 98 U1 3 U2 15 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 OCT PY 1999 VL 70 IS 1 BP 4 EP 15 DI 10.1016/S0034-4257(99)00054-1 PG 12 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA 241LJ UT WOS:000082884500002 ER PT J AU Friedl, RR AF Friedl, RR TI Atmospheric chemistry - Unraveling aircraft impacts SO SCIENCE LA English DT Editorial Material C1 NASA, Div Earth & Space Sci, Jet Prop Lab, Pasadena, CA 91109 USA. RP Friedl, RR (reprint author), NASA, Div Earth & Space Sci, Jet Prop Lab, Bldg 183,Room 906,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 12 TC 0 Z9 0 U1 0 U2 0 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 OCT 1 PY 1999 VL 286 IS 5437 BP 57 EP 58 DI 10.1126/science.286.5437.57 PG 2 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 241WT UT WOS:000082907400029 ER PT J AU Borg, LE Connelly, JN Nyquist, LE Shih, CY Wiesmann, H Reese, Y AF Borg, LE Connelly, JN Nyquist, LE Shih, CY Wiesmann, H Reese, Y TI The age of the carbonates in martian meteorite ALH84001 SO SCIENCE LA English DT Article ID PETROLOGIC EVIDENCE; SM-ND; MARS; ORIGIN; DIFFERENTIATION; TEMPERATURE; CHRONOLOGY; RB; SR AB The age of secondary carbonate mineralization in the martian meteorite ALH84001 was determined to be 3.90 +/- 0.04 billion years by rubidium-strontium (Rb-Sr) dating and 4.04 +/- 0.10 billion years by Lead-Lead (Pb-Pb) dating. The Rb-Sr and Pb-Pb isochrons are defined by Leachates of a mixture of high-graded carbonate (visually estimated as similar to 5 percent). whitlockite (trace), and orthopyroxene (similar to 95 percent). The carbonate formation age is contemporaneous with a period in martian history when the surface is thought to have had flowing water, but also was undergoing heavy bombardment by meteorites. Therefore, this age does not distinguish between aqueous and impact origins for the carbonates. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Univ Texas, Dept Geol Sci, Austin, TX 78713 USA. Lockheed Engn & Sci Co, Houston, TX 77258 USA. RP Borg, LE (reprint author), Univ New Mexico, Inst Meteorit, Albuquerque, NM 87131 USA. RI Connelly, James /O-7996-2015 NR 32 TC 96 Z9 99 U1 3 U2 15 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 OCT 1 PY 1999 VL 286 IS 5437 BP 90 EP 94 DI 10.1126/science.286.5437.90 PG 5 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 241WT UT WOS:000082907400039 PM 10506566 ER PT J AU Smith, DE Sjogren, WL Tyler, GL Balmino, G Lemoine, FG Konopliv, AS AF Smith, DE Sjogren, WL Tyler, GL Balmino, G Lemoine, FG Konopliv, AS TI The gravity field of Mars: Results from Mars global surveyor SO SCIENCE LA English DT Article ID ORBITER LASER ALTIMETER; IMPACT BASINS; GIANT IMPACT; TOPOGRAPHY; DICHOTOMY; MISSION; MODEL; MOON AB Observations of the gravity field of Mars reveal a planet that has responded differently in its northern and southern hemispheres to major impacts and volcanic processes. The rough, elevated southern hemisphere has a relatively featureless gravitational signature indicating a state of near-isostatic compensation, whereas the smooth, Low northern plains display a wider range of gravitational anomalies that indicates a thinner but stronger surface Layer than in the south. The northern hemisphere shows evidence for buried impact basins, although none large enough to explain the hemispheric elevation difference. The gravitational potential signature of Tharsis is approximately axisymmetric and contains the Tharsis Montes but not the Olympus Mons or Alba Patera volcanoes. The gravity signature of Valles Marineris extends into Chryse and provides an estimate of material removed by early fluvial activity. C1 NASA, Terr Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Stanford Univ, Ctr Radio Astron, Stanford, CA 94305 USA. Grp Rech Geodesie Spatiales, Toulouse, France. RP Smith, DE (reprint author), NASA, Terr Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RI Lemoine, Frank/D-1215-2013 NR 37 TC 95 Z9 98 U1 0 U2 6 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD OCT 1 PY 1999 VL 286 IS 5437 BP 94 EP 97 DI 10.1126/science.286.5437.94 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 241WT UT WOS:000082907400040 PM 10506567 ER PT J AU Carlson, RW Johnson, RE Anderson, MS AF Carlson, RW Johnson, RE Anderson, MS TI Sulfuric acid on Europa and the radiolytic sulfur cycle SO SCIENCE LA English DT Article ID MAGNETOSPHERIC ION-BOMBARDMENT; ICY GALILEAN SATELLITES; IRRADIATION EXPERIMENTS; REFLECTANCE SPECTRA; SURFACE-COMPOSITION; SPECTROSCOPY; OXYGEN; SYSTEM AB A comparison of laboratory spectra with Galileo data indicates that hydrated sulfuric acid is present and is a major component of Europa's surface. In addition, this moon's visually dark surface material, which spatially correlates with the sulfuric acid concentration, is identified as radiolytically altered sulfur polymers. Radiolysis of the surface: by magnetospheric plasma bombardment continuously cycles sulfur between three forms: sulfuric acid, sulfur dioxide, and sulfur polymers, with sulfuric acid being about 50 times as abundant as the other forms. Enhanced sulfuric acid concentrations are found in Europa's geologically young terrains, suggesting that low-temperature, liquid sulfuric acid may influence geological processes. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Virginia, Sch Engn & Appl Sci, Charlottesville, VA 22903 USA. RP Carlson, RW (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM rcarlson@lively.jpl.nasa.gov NR 42 TC 195 Z9 196 U1 1 U2 17 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 EI 1095-9203 J9 SCIENCE JI Science PD OCT 1 PY 1999 VL 286 IS 5437 BP 97 EP 99 DI 10.1126/science.286.5437.97 PG 5 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 241WT UT WOS:000082907400041 PM 10506568 ER PT J AU Carsey, FD Horvath, JC AF Carsey, FD Horvath, JC TI The lake that time forgot SO SCIENTIFIC AMERICAN LA English DT Editorial Material C1 CALTECH, Jet Prop Lab, Europa Lake Vostok Initiat, Pasadena, CA 91125 USA. RP Carsey, FD (reprint author), CALTECH, Jet Prop Lab, Europa Lake Vostok Initiat, Pasadena, CA 91125 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 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 OCT PY 1999 VL 281 IS 4 BP 62 EP 62 PG 1 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 236YU UT WOS:000082627500021 ER PT J AU Vianna, ML Servain, JM Busalacchi, AJ AF Vianna, ML Servain, JM Busalacchi, AJ TI The PIRATA Program: Monitoring tropical Atlantic waters SO SEA TECHNOLOGY LA English DT Article C1 Inst Nacl Pesquisas Espaciais, BR-12201 Sao Jose Dos Campos, Brazil. NASA, Goddard Space Flight Ctr, Lab Hydrosperh Proc, Greenbelt, MD 20771 USA. RP Vianna, ML (reprint author), Inst Nacl Pesquisas Espaciais, BR-12201 Sao Jose Dos Campos, Brazil. NR 1 TC 2 Z9 2 U1 0 U2 1 PU COMPASS PUBL INC PI ARLINGTON PA SUITE 1000 1117 N 19 ST, ARLINGTON, VA 22209 USA SN 0093-3651 J9 SEA TECHNOL JI Sea Technol. PD OCT PY 1999 VL 40 IS 10 BP 10 EP 15 PG 6 WC Engineering, Ocean SC Engineering GA 252ZY UT WOS:000083533200002 ER PT J AU Reder, LJ Takahashi, G AF Reder, LJ Takahashi, G TI Implementation of Intranet scene preview for feature animation SO SMPTE JOURNAL LA English DT Article; Proceedings Paper CT 140th SMPTE Technical Conference CY OCT 28-31, 1998 CL PASADENA, CALIFORNIA SP SMPTE AB This paper describes the development of an Intranet scene preview capability within Warner Bros. Feature Animation. This capability was developed so all members of the production staff could easily view production material as it was being animated. The animation production process as it pertains to the preview capabilities is presented and the organization of the server is reviewed. A discussion of HyperText MarkUp Language (HTML) along with the structure and function of the custom software developed is given. Performance and enhancements of QuickTime downloading and playback is also discussed. C1 Warner Bros, Feature Animat, Glendale, CA USA. RP Reder, LJ (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91125 USA. NR 6 TC 0 Z9 0 U1 0 U2 0 PU SOC MOTION PICTURE TV ENG INC PI WHITE PLAINS PA 595 WEST HARTSDALE AVE, WHITE PLAINS, NY 10607 USA SN 0036-1682 J9 SMPTE J JI SMPTE J. PD OCT PY 1999 VL 108 IS 10 BP 696 EP 709 PG 14 WC Engineering, Electrical & Electronic; Instruments & Instrumentation; Imaging Science & Photographic Technology; Telecommunications SC Engineering; Instruments & Instrumentation; Imaging Science & Photographic Technology; Telecommunications GA 244EF UT WOS:000083038300003 ER PT J AU Hagyard, MJ Pevtsov, AA AF Hagyard, MJ Pevtsov, AA TI Studies of solar helicity using vector magnetograms SO SOLAR PHYSICS LA English DT Article ID PHOTOSPHERIC MAGNETIC-FIELDS; ELECTRIC CURRENTS; SHEAR; CONFIGURATION; ATMOSPHERE; FILAMENTS; ANGLE AB Observations of photospheric magnetic fields made with vector magnetographs have been used recently to study helicity on the Sun. In this paper we indicate what can and cannot be derived from vector magnetograms, and point out some potential problems in these data that could affect the calculations of 'helicity'. Among these problems are magnetic saturation, Faraday rotation, low spectral resolution, and the method of resolving the ambiguity in the azimuth. C1 NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. Montana State Univ, Dept Phys, Bozeman, MT 59717 USA. RP Hagyard, MJ (reprint author), NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. OI Pevtsov, Alexei/0000-0003-0489-0920 NR 42 TC 32 Z9 32 U1 0 U2 0 PU SPRINGER PI DORDRECHT PA VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS SN 0038-0938 J9 SOL PHYS JI Sol. Phys. PD OCT PY 1999 VL 189 IS 1 BP 25 EP 43 DI 10.1023/A:1005215001514 PG 19 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 276EA UT WOS:000084861600002 ER PT J AU Caillat, T Fleurial, JP Snyder, GJ AF Caillat, T Fleurial, JP Snyder, GJ TI Potential of Chevrel phases for thermoelectric applications SO SOLID STATE SCIENCES LA English DT Article AB A low lattice thermal conductivity is one of the requirements to achieve high thermoelectric figures of merit. Several low thermal conductivity materials were identified and developed over the past few years at the Jet Propulsion Laboratory (JPL), including filled skutterudites and Zn4Sb3-based materials. A. study of the mechanisms responsible for the high phonon scattering rates in these compounds has demonstrated that materials with structures that can accommodate additional atoms in their lattice are likely to possess low lattice thermal conductivity values. Chevrel phases (Mo6Se8-type) are just such materials and are currently being investigated at JPL for thermoelectric applications. The crystal structures of the Chevrel phases present cavities which can greatly vary in size and can contain a large variety of atoms ranging from large ones such as Ph to small ones such as Cu. In these materials, small inserted atoms usually show large thermal parameters which indicate that they move around and can significantly scatter the phonons. The electronic and thermal properties of these materials can potentially be controlled by a careful selection of the filling element(s). We have synthesized (Cu, Cu/Fe, Ti)(x)Mo6Se8 samples and report in this paper on their thermoelectric properties. Approaches to optimize the properties of these materials for thermoelectric applications are discussed. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Caillat, T (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,MS 277-207, Pasadena, CA 91109 USA. EM thierry.caillat@jpl.nasa.gov RI Snyder, G. Jeffrey/E-4453-2011; Snyder, G/I-2263-2015 OI Snyder, G. Jeffrey/0000-0003-1414-8682; NR 20 TC 47 Z9 47 U1 0 U2 19 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 1293-2558 EI 1873-3085 J9 SOLID STATE SCI JI Solid State Sci. PD OCT-NOV PY 1999 VL 1 IS 7-8 BP 535 EP 544 DI 10.1016/S1293-2558(00)80105-3 PG 10 WC Chemistry, Inorganic & Nuclear; Chemistry, Physical; Physics, Condensed Matter SC Chemistry; Physics GA 271MM UT WOS:000084597800008 ER PT J AU Bernstein, MP Sandford, SA AF Bernstein, MP Sandford, SA TI Variations in the strength of the infrared forbidden 2328.2 cm(-1) fundamental of solid N(2) in binary mixtures SO SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY LA English DT Article DE nitrogen; carbon dioxide; water; infrared spectroscopy; interstellar ices; matrix isolation ID CARBON-DIOXIDE; ICE ANALOGS; SPECTRAL PROPERTIES; SPECTROSCOPY; NITROGEN; SURFACE; CO2; ABSORPTION; MATRICES; TRITON AB We present the 2335-2325 cm(-1) infrared spectra and band positions, profiles and strengths (A values) of solid nitrogen and binary mixtures of N(2) with other molecules at 12 K. The data demonstrate that the strength of the infrared forbidden N(2) fundamental near 2328 cm(-1) is moderately enhanced in the presence of NH(3), strongly enhanced in the presence of H(2)O and very strongly enhanced (by over a factor of 1000) in the presence of CO(2), but is not significantly affected by CO, CH(4), or O(2). The mechanisms for the enhancements in N(2)-NH(3) and N(2)-H(2)O mixtures are fundamentally different from those proposed for N(2)-CO(2) mixtures. In the first case, interactions involving hydrogen-bonding are likely the cause. In the latter, a resonant exchange between the N(2) stretching fundamental and the (18)O = (12)C asymmetric stretch of (18)O(12)C(16)O is indicated. The implications of these results for several astrophysical issues are briefly discussed. (C) 1999 Elsevier Science B.V. All rights reserved. C1 NASA, Ames Res Ctr, Astrophys Branch, Moffett Field, CA 94035 USA. RP Bernstein, MP (reprint author), NASA, Ames Res Ctr, Astrophys Branch, Mail Stop 245-6, Moffett Field, CA 94035 USA. EM mbernstein@mail.arc.nasa.gov NR 29 TC 15 Z9 15 U1 1 U2 3 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1386-1425 J9 SPECTROCHIM ACTA A JI Spectroc. Acta Pt. A-Molec. Biomolec. Spectr. PD OCT PY 1999 VL 55 IS 12 BP 2455 EP 2466 DI 10.1016/S1386-1425(99)00038-4 PG 12 WC Spectroscopy SC Spectroscopy GA 240XX UT WOS:000082853300011 PM 11543545 ER PT J AU Shogrin, BA Jones, WR Herrera-Fierro, P Lin, TY Kawa, H AF Shogrin, BA Jones, WR Herrera-Fierro, P Lin, TY Kawa, H TI Evaluation of boundary-enhancement additives for perfluoropolyethers SO TRIBOLOGY TRANSACTIONS LA English DT Article; Proceedings Paper CT 1997 World Tribology Congress CY SEP 08-12, 1997 CL LONDON, ENGLAND SP Soc Tribologists & Lubricat Engineers DE perfluoropolyethers; boundary lubrication; additives ID LUBRICATION PERFORMANCE; SOLUBLE ADDITIVES; HIGH-VACUUM; WEAR; SURFACES; HUMIDITY; FRICTION; STEEL; FLUID AB Six additives were synthesized and evaluated as boundary lubrication enhancers for perfluoropolyalkylethers. These additives included a phosphate, a thiophosphate, a beta-diketone, a benzothiazole, an amide/thiol and a sulfite. These additives were evaluated in a vacuum four-ball apparatus, at a one weight percent concentration ill a perfluoropolyalkylether based on hexafluroopropene oxide. Tests were performed in vacuum (< 6.7x 10(-4) Pa), at room temperature (similar to 23 degrees C), at an initial Hertzian stress of 3.5 GPa (200N load), and a sliding velocity of 28.8 mm/sec (100 rpm), Infrared (IR) and Raman spectroscopies were used to analyze the steel (AISI 52100) specimens after testing. Wear rates for each formulation were determined from the slope of wear volume as a function of sliding distance. All additives yielded reductions in mean wear rates of at least 50 percent, with the exception of the benzothiazole which had no effect. Two of the additives, an amide/thiol and a sulfite, reduced the mean,wear rate by at least 80 percent. IR and Raman analysis indicated the severity of wear call be correlated to rite amount of surface fluorinated polymeric ic acid species (R(f)COOH) and graphitic amorphous carbon, in and around the wear scar. C1 Case Western Reserve Univ, Cleveland, OH 44106 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. Ohio Aerosp Inst, Brookpark, OH 44142 USA. Exfluor Res Corp, Round Rock, TX 78664 USA. RP Shogrin, BA (reprint author), Case Western Reserve Univ, Cleveland, OH 44106 USA. NR 32 TC 3 Z9 3 U1 1 U2 2 PU TAYLOR & FRANCIS INC PI PHILADELPHIA PA 325 CHESTNUT ST, SUITE 800, PHILADELPHIA, PA 19106 USA SN 1040-2004 J9 TRIBOL T JI Tribol. Trans. PD OCT PY 1999 VL 42 IS 4 BP 747 EP 754 DI 10.1080/10402009908982278 PG 8 WC Engineering, Mechanical SC Engineering GA 243MN UT WOS:000083002000008 ER PT J AU Howard, SA AF Howard, SA TI Preliminary development of characterization methods for compliant air 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 AB Developing a system for dynamic stiffness and damping measurements for foil bearings is crucial for future advancements in the design and use of oil-free bearing technology. This paper addresses some of the preliminary issues involved in developing such a measurement system. Steady-state stiffness measurements are taken and used as a learning tool for the use and development of a fiber optic displacement probe system. The problems encountered with these probes and the problems expected in their use at high temperature are addressed. Some possible solutions for these issues are also discussed. From this effort it appears that it is feasible to experimentally characterize foil bearings at high speeds and temperatures. C1 Case Western Reserve Univ, NASA, Lewis Res Ctr, Cleveland, OH 44106 USA. RP Howard, SA (reprint author), Case Western Reserve Univ, NASA, Lewis Res Ctr, Cleveland, OH 44106 USA. NR 7 TC 13 Z9 14 U1 0 U2 0 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 OCT PY 1999 VL 42 IS 4 BP 789 EP 794 DI 10.1080/10402009908982284 PG 6 WC Engineering, Mechanical SC Engineering GA 243MN UT WOS:000083002000014 ER PT J AU Fajardo-Acosta, S AF Fajardo-Acosta, S TI Planetary systems - Ageing dust fades away SO NATURE LA English DT Editorial Material ID BETA-PICTORIS; DISK C1 CALTECH, Jet Prop Lab, IPAC, Pasadena, CA 91125 USA. RP Fajardo-Acosta, S (reprint author), CALTECH, Jet Prop Lab, IPAC, Mail Stop 100-22, Pasadena, CA 91125 USA. NR 10 TC 1 Z9 1 U1 0 U2 1 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON N1 9XW, ENGLAND SN 0028-0836 J9 NATURE JI Nature PD SEP 30 PY 1999 VL 401 IS 6752 BP 439 EP 440 DI 10.1038/46710 PG 2 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 243DF UT WOS:000082981200036 ER PT J AU Folkins, I Loewenstein, M Podolske, J Oltmans, SJ Proffitt, M AF Folkins, I Loewenstein, M Podolske, J Oltmans, SJ Proffitt, M TI A barrier to vertical mixing at 14 km in the tropics: Evidence from ozonesondes and aircraft measurements SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID UPPER TROPOSPHERE; OZONE; TROPOPAUSE; STRATOSPHERE; CONVECTION; TRANSPORT; PACIFIC; WAVE; AIR AB We use ozonesondes launched from Samoa (14 degrees S) during the Pacific Exploratory Mission (PEM) Tropics A to show that O-3 mixing ratios usually start increasing toward stratospheric values near 14 km. This is well below the tropical tropopause las defined either in terms of lapse rate or cold point), which usually occurs between 16 and 17 km. We argue that the main reason for this discrepancy in height between the chemopause and tropopause is that there is very little convective detrainment of ozone-depleted marine boundary layer air above 14 km. We conjecture that the top of the Hadley circulation occurs at roughly 14 km, that convective penetration above this altitude is rare, and that air that is injected above this height subsequently participates in a slow vertical ascent into the stratosphere. The observed dependence of ozone on potential temperature in the transitional zone between the 14-km chemopause and the tropical tropopause is consistent with what would be expected from this hypothesis given calculated clear-sky heating rates and typical in situ ozone production rates in this region. An observed anticorrelation between ozone and equivalent potential temperature below 14 km is consistent with what would be expected from an overturning Hadley circulation, with some transport of high O-3/low theta(e) air from midlatitudes. We also argue that the positive correlations between O-3 and N2O in the transitional zone obtained during the 1994 Airborne Southern Hemisphere Ozone Experiment/Measurements for Assessing the Effects of Stratospheric Aircraft) (ASHOE/MAESA) campaign support the notion that air in this region does have trace elements of Stratospheric air las conjectured previously), so that some of the ozone in the transitional zone does originate from the stratosphere rather than being entirely produced in situ. C1 Dalhousie Univ, Dept Oceanog, Atmospher Sci Program, Halifax, NS B3H 4J1, Canada. Dalhousie Univ, Dept Phys, Atmospher Sci Program, Halifax, NS B3H 4J1, Canada. NASA, Div Earth Sci, Ames Res Ctr, Moffett Field, CA 94035 USA. NOAA, Climate Monitoring & Diagnost Aeron Lab, Boulder, CO 80303 USA. NOAA, Aeron Lab, Boulder, CO 80303 USA. RP Folkins, I (reprint author), Dalhousie Univ, Dept Oceanog, Atmospher Sci Program, Halifax, NS B3H 4J1, Canada. EM Ian.Folkins@dal.ca; mloewenstein@mail.src.nasa.gov; soltmans@cmdl.noaa.gov; proffitt@al.noaa.gov NR 19 TC 155 Z9 155 U1 2 U2 11 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD SEP 27 PY 1999 VL 104 IS D18 BP 22095 EP 22102 DI 10.1029/1999JD900404 PG 8 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 239UZ UT WOS:000082789200003 ER PT J AU Guerra, DV Schwemmer, GK Wooten, AD Chaudhuri, SS Wilkerson, ND AF Guerra, DV Schwemmer, GK Wooten, AD Chaudhuri, SS Wilkerson, ND TI Prototype holographic atmospheric scanner for environmental remote sensing SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID BOUNDARY-LAYER; LIDAR AB A ground-based atmospheric lidar system that utilizes a holographic optical telescope and scanner has been developed and successfully operated to obtain atmospheric backscatter profiles. The Prototype Holographic Atmospheric Scanner for Environmental Remote Sensing is built around a volume phase reflection holographic optical element (HOE). This single optical element both directs and collimates the outgoing laser beam as well as collects, focuses, and filters the atmospheric laser backscatter while offering significant weight savings over existing telescope mirror technology. Conical scanning is accomplished as the HOE rotates on a turntable sweeping the 1.2 mrad field of view around a 42 degrees cone. During this technology demonstration, atmospheric aerosol and cloud return signals have been received in both stationary and scanning modes. The success of this program has led to the further development of this technology for integration into airborne and eventually satellite Earth-observing scanning lidar telescopes. C1 St Anselm Coll, Dept Phys, Manchester, NH 03102 USA. NASA, Atmospheres Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Western Maryland Coll, Dept Phys, Westminster, MD 21157 USA. Utah State Univ, Ctr Atmospher & Space Sci, Logan, UT 84322 USA. RP Guerra, DV (reprint author), St Anselm Coll, Dept Phys, 100 St Anselm Dr, Manchester, NH 03102 USA. EM dguerra@anselm.edu; geary@virl.gsfc.nasa.gov; tdw@sdl.usu.edu NR 13 TC 9 Z9 9 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD SEP 27 PY 1999 VL 104 IS D18 BP 22287 EP 22292 DI 10.1029/1999JD900324 PG 6 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 239UZ UT WOS:000082789200017 ER PT J AU Dowling, JP Williams, CP Franson, JD AF Dowling, JP Williams, CP Franson, JD TI Maxwell duality, Lorentz invariance, and topological phase SO PHYSICAL REVIEW LETTERS LA English DT Article ID AHARONOV-CASHER PHASE; QUANTUM PHASE; MOVING DIPOLE; MAGNETIC-FIELD; NEUTRAL PARTICLES; ATOMIC SYSTEM; MOMENT AB We discuss the Maxwell electromagnetic duality relations between the Aharonov-Bohm, Aharonov-Casher, and He-McKellar-Wilkens topological phases, which allow a unified description of all three phenomena. We also elucidate Lorentz transformations which allow these effects to be understood in an intuitive fashion in the rest frame of the moving quantum particle. Finally, we propose two experimental schemes for measuring the He-McKellar-Wilkens phase. C1 CALTECH, Jet Prop Lab, Quantum Comp Technol Grp, Pasadena, CA 91109 USA. Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA. RP Dowling, JP (reprint author), CALTECH, Jet Prop Lab, Quantum Comp Technol Grp, Mail Stop 126-347,4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI DOWLING, JONATHAN/L-2749-2013 NR 30 TC 72 Z9 72 U1 0 U2 7 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0031-9007 J9 PHYS REV LETT JI Phys. Rev. Lett. PD SEP 27 PY 1999 VL 83 IS 13 BP 2486 EP 2489 DI 10.1103/PhysRevLett.83.2486 PG 4 WC Physics, Multidisciplinary SC Physics GA 238HV UT WOS:000082705600002 ER PT J AU Canuto, VM Dubovikov, MS AF Canuto, VM Dubovikov, MS TI Comment on "Two scaling regimes for rotating Rayleigh-Benard convection" - Reply SO PHYSICAL REVIEW LETTERS LA English DT Article ID STATES C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. RP Canuto, VM (reprint author), NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. NR 8 TC 0 Z9 0 U1 1 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 SEP 27 PY 1999 VL 83 IS 13 BP 2679 EP 2679 DI 10.1103/PhysRevLett.83.2679 PG 1 WC Physics, Multidisciplinary SC Physics GA 238HV UT WOS:000082705600053 ER PT J AU Moore, JM Bullock, MA AF Moore, JM Bullock, MA TI Experimental studies of Mars-analog brines SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID DISSOLUTION KINETICS; ALTERATION PRODUCTS; SATURATION STATE; CLIMATIC-CHANGE; CARBON-DIOXIDE; SNC METEORITES; LIQUID WATER; EVOLUTION; MINERALS; ATMOSPHERE AB Evaporite deposits may represent significant sinks of mobile cations (e.g., those of Ca, N, Mg, and Fe) and anions (e.g., those of C, N, S, and Cl) among the materials composing the Martian surface and upper crust. Carbon and nitrogen are especially interesting because of their role as atmospheric gases which can become incorporated into crustal rocks. However, the nature of evaporite precursor brines formed under Martian conditions is poorly understood. To date, only a very limited number of laboratory investigations have been reported which have any bearing on a better understanding of various processes related to brine or evaporite formation on Mars. Here we report on preliminary laboratory experiments that exposed igneous minerals analogous to those in Martian (Shergottites, Nakhlites, and Chassigny (SNC) group) meteorites to a simulated Martian atmosphere and pure, deoxygenated water. Analysis of the water over intervals of time approaching 1 year showed that atmospheric gases dissolved to form carbonate and nitrate ions while minerals dissolved to form sulfate and chloride along with various cations. On an annual basis, ion formation gave a carbonate/sulfate ratio that is comparable to the ratio found among salts in SNC meteorites. The sulfate/chloride ratio of the experimental brines is higher than in SNC meteorites but lower than in surface soils measured at the Viking and Pathfinder landing sites. C1 NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. SW Res Inst, Dept Space Studies, Boulder, CO 80302 USA. RP Moore, JM (reprint author), NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. NR 63 TC 13 Z9 14 U1 1 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD SEP 25 PY 1999 VL 104 IS E9 BP 21925 EP 21934 DI 10.1029/1999JE001040 PG 10 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 239EL UT WOS:000082755800003 ER PT J AU Krasnopolsky, VA Cruikshank, DP AF Krasnopolsky, VA Cruikshank, DP TI Photochemistry of Pluto's atmosphere and ionosphere near perihelion SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Review ID EVALUATED KINETIC DATA; TEMPERATURE-DEPENDENCE; RATE CONSTANTS; PLANETARY-ATMOSPHERES; PRESSURE-DEPENDENCE; TRITONS ATMOSPHERE; TITANS ATMOSPHERE; RADICAL REACTIONS; THERMAL STRUCTURE; RATE COEFFICIENTS AB We consider Pluto's photochemistry using a background model for a hydrodynamically escaping atmosphere by Krasnopolsky [1999], Some adjustments are made in the basic continuity equation and in the boundary conditions to account for hydrodynamic flow in the atmosphere. We model the photochemistry for 44 neutral and 23 ion species. Because of the high methane mixing ratio, Pluto's photochemistry is more similar to that of Titan than that of Triton. Charge exchange between N(2)(+), and CH, significantly reduces the production of atomic nitrogen. The most abundant photochemical products are C(2)H(2) (3x10(17)), C(4)H(2) (10(17)), HCN (6x10(16)), H(2) (4x10(16)), C(2)H(4) (4x10(16)), HC(3)N (3.4x10(16)), C(2)H(6) (2x10(16)), C(3)H(2) (9x10(15)), and C(3)H(4) (8x10(15), all in cm(-2)). In addition to the parent N(2), CH(4), and CO molecules which absorb photons with lambda<145 nm, these products absorb almost completely photons with lambda<185 nm, therefore significantly increasing the number of dissociation events. Photochemical losses of the parent species are much smaller than their escape. Precipitation rates are the highest for C(2)H(2), C(4)H(2), HC(3)N, HCN, C(2)H(6), and C(2)H(4) (65, 58, 23, 14, 9, and 6 g cm(-2) Byr(-1), respectively, reduced by a factor of 3 to account for seasonal variations). Escape of photochemical products is highest for H(2), H, C(2)H(2), C(2)H(4), HCN, and N (2x10(26), 1.4x10(26), 6x10(24), 3.6x10(24), 2.3x10(24), and 1.8x10(24) s(-1), respectively). The electron density reaches a maximum of 800 cm(-3) at 2250 km. The most abundant ions are HCNH(+), C(3)H(3)(+), and C(3)H(5)(+). Some of the photochemical products might be detected using the technique of UV solar occultation spectroscopy from a spacecraft flyby. C1 Catholic Univ Amer, Dept Phys, Washington, DC 20064 USA. NASA, Ames Res Ctr, Astrophys Branch, Moffett Field, CA 94035 USA. RP Krasnopolsky, VA (reprint author), Catholic Univ Amer, Dept Phys, Washington, DC 20064 USA. EM vladimir.krasnopolsky@gte.net RI Krasnopolsky, Vladimir/L-5085-2013 NR 108 TC 59 Z9 59 U1 1 U2 5 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD SEP 25 PY 1999 VL 104 IS E9 BP 21979 EP 21996 DI 10.1029/1999JE001038 PG 18 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 239EL UT WOS:000082755800007 ER PT J AU Horz, F Cintala, MJ Rochelle, WC Kirk, B AF Horz, F Cintala, MJ Rochelle, WC Kirk, B TI Collisionally processed rocks on Mars SO SCIENCE LA English DT Article ID PATHFINDER AB The Pathfinder Landing site on Mars has boulders that may be cratered (Stimpy), split (Chimp), fragmented (Book End and Flat Top), or otherwise partly destroyed (Yogi and Frog) by collisional processes. Atmospheric-entry calculations show that centimeter-sized projectiles survive passage through the martian atmosphere and encounter the surface of Mars at velocities of a few kilometers per second. Craters Less than 1 meter in diameter may contribute to the evolution of the martian surface and its soils. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Lockheed Martin, Houston, TX 77058 USA. RP Horz, F (reprint author), NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 23 TC 12 Z9 12 U1 0 U2 0 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD SEP 24 PY 1999 VL 285 IS 5436 BP 2105 EP 2107 DI 10.1126/science.285.5436.2105 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 238VF UT WOS:000082734300035 ER PT J AU Bauschlicher, CW Martin, JML Taylor, PR AF Bauschlicher, CW Martin, JML Taylor, PR TI Boron heat of formation revisited: Relativistic effects on the BF3 atomization energy SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID BASIS-SET LIMIT; WAVE-FUNCTIONS AB The one-electron Douglas-Kroll approach, and perturbation theory including only the mass-velocity and Darwin terms, are used to compute the scalar relativistic contribution to the atomization energies of BS. Both approaches predict an approximately 0.7 kcal/mol reduction in the atomization energy. In combination with improved one-particle extrapolation techniques, this leads to a revised estimate for the heat of formation of gaseous boron, Delta H(f,0)degrees[B(g)] = 135.1 kcal/mol and Delta H(f,298)degrees[B(g)] = 136.3 kcal/mol, with error bars +/-0.75 kcal/mol or less. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Weizmann Inst Sci, Dept Organ Chem, IL-76100 Rehovot, Israel. Univ Calif San Diego, San Diego Supercomp Ctr, La Jolla, CA 92093 USA. Univ Calif San Diego, Dept Chem & Biochem MC0505, La Jolla, CA 92093 USA. RP Bauschlicher, CW (reprint author), NASA, Ames Res Ctr, Mail Stop 230-3, Moffett Field, CA 94035 USA. RI Martin, Jan/A-7457-2008 OI Martin, Jan/0000-0002-0005-5074 NR 36 TC 26 Z9 26 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 SEP 23 PY 1999 VL 103 IS 38 BP 7715 EP 7718 DI 10.1021/jp991713a PG 4 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 239RF UT WOS:000082782900023 ER PT J AU Maoz, E Newman, JA Ferrarese, L Stetson, PB Zepf, SE Davis, M Freedman, WL Madore, BF AF Maoz, E Newman, JA Ferrarese, L Stetson, PB Zepf, SE Davis, M Freedman, WL Madore, BF TI A distance to the galaxy NGC4258 from observations of Cepheid variable stars SO NATURE LA English DT Article ID KEY PROJECT; SCALE; DISCOVERY AB Cepheid variable stars pulsate in a way that is correlated with their intrinsic luminosity, making them useful as 'standard candles' for determining distances to galaxies; the potential systematic uncertainties in the resulting distances have been estimated(1) to be only 8-10%. They have played a crucial role in establishing the extragalactic distance scale and hence the value of the Hubble constant. Here we report observations of Cepheids in the nearby galaxy NGC4258; the distance calculated from the Cepheids is 8.1 +/- 0.4 Mpc, where the uncertainty does not include possible systematic errors. There is an independently determined geometric distance to this galaxy of 7.2 +/- 0.5 Mpc, based on the observed proper motions of water masers orbiting the central black hole(2); the distances differ by 1.3 sigma. If the maser-based distance is adopted and the Cepheid distance scale revised accordingly, the derived value of the Hubble constant would increase by 12 +/- 9%, while the expansion age of the Universe would decrease by the same amount. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Calif Berkeley, Dept Astron, Berkeley, CA 94720 USA. CALTECH, Pasadena, CA 91125 USA. Dominion Astrophys Observ, Victoria, BC V8X 4M6, Canada. Yale Univ, Dept Astron, New Haven, CT 06520 USA. Carnegie Inst Washington Observ, Pasadena, CA 91101 USA. CALTECH, Jet Prop Lab, NASA IPAC Extragalact Database, Infrared Proc & Anal Ctr, Pasadena, CA 91125 USA. RP Maoz, E (reprint author), NASA, Ames Res Ctr, MS 245-3, Moffett Field, CA 94035 USA. NR 32 TC 36 Z9 36 U1 0 U2 1 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON N1 9XW, ENGLAND SN 0028-0836 J9 NATURE JI Nature PD SEP 23 PY 1999 VL 401 IS 6751 BP 351 EP 354 DI 10.1038/43838 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 240JJ UT WOS:000082822600043 PM 16862105 ER PT J AU Gregg, WW Patt, FS Esalas, WE AF Gregg, WW Patt, FS Esalas, WE TI Initial analysis of ocean color data from the ocean color and temperature scanner. II. Geometric and radiometric analysis SO APPLIED OPTICS LA English DT Article ID EARTH SURVEY SENSORS; ALGORITHM; RADIANCE; WATER AB We assessed the geometric and radiometric performance of the ocean color and temperature scanner (OCTS) using data acquired over the United States. Initial results indicated a geometric offset in the along-track direction of 4-5 pixels that was attributed to a tilt bias. OCTS radiometric data appeared to suffer from near-held and possibly far-field scatter effects. Analysis of radiometric stability was inconclusive because of daily variability and the absence of a full seasonal cycle. Comparison of OCTS-computed water-leaving radiances with colocated in situ measurements showed that the prelaunch. calibration required adjustment from -2% to + 13%. Minor modification of OCTS data processing based on these results and avoidance of near-field scatter effects can enable improved and more-reliable OCTS data for quantitative scientific analyses. (C) 1999 Optical Society of America. OCIS codes: 010.4450, 280.0280, 110.2960, 110.3000. C1 NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. Gen Sci Corp, Laurel, MD 20707 USA. RP Gregg, WW (reprint author), NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Code 971, Greenbelt, MD 20771 USA. EM gregg@cabin.gsfc.nasa.gov NR 17 TC 5 Z9 5 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 SEP 20 PY 1999 VL 38 IS 27 BP 5692 EP 5702 DI 10.1364/AO.38.005692 PG 11 WC Optics SC Optics GA 239PX UT WOS:000082779600002 PM 18324080 ER PT J AU Vander Wal, RL Ticich, TM West, JR AF Vander Wal, RL Ticich, TM West, JR TI Laser-induced incandescence applied to metal nanostructures SO APPLIED OPTICS LA English DT Article ID SOOT-VOLUME FRACTION; FLICKERING METHANE; DIFFUSION FLAMES; POROUS SILICON; PARTICLES; VISUALIZATION; LUMINESCENCE; SPECTROSCOPY; DIAGNOSTICS; TEMPERATURE AB Laser-induced incandescence is both characterized and demonstrated for the measurement of metal nanoparticle concentration. Reported are the results of an initial characterization of the spectral and temporal signature of the laser+induced incandescence as a function of the excitation laser fluence and wavelength. Validation of the incandescence as a measure of the concentration is demonstrated by absorption measurements. Fluence dependence measurements are also presented. Double-pulse measurements determine the fluence for the onset of vaporization-induced mass loss. Comparisons between the present observations and those for carbon nanostructures are also made. Metals tested include (in order of increasing vaporization temperature) Fe, Ti, Mo, and W. OCIS codes: 280.1100, 280.2490, 300.6280, 290.2200, 280.1120, 280.1740. C1 NASA, Natl Ctr Micrograv Res, Lewis Res Ctr, Cleveland, OH 44135 USA. Centenary Coll Louisiana, Dept Chem, Shreveport, LA 71134 USA. RP Vander Wal, RL (reprint author), NASA, Natl Ctr Micrograv Res, Lewis Res Ctr, MS 110-3,21000 Brookpk Rd, Cleveland, OH 44135 USA. EM randy@rvander.lerc.nasa.gov NR 45 TC 28 Z9 28 U1 0 U2 3 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 SEP 20 PY 1999 VL 38 IS 27 BP 5867 EP 5879 DI 10.1364/AO.38.005867 PG 13 WC Optics SC Optics GA 239PX UT WOS:000082779600024 PM 18324102 ER PT J AU Freudling, W Zehavi, I da Costa, LN Dekel, A Eldar, A Giovanelli, R Haynes, MP Salzer, JJ Wegner, G Zaroubi, S AF Freudling, W Zehavi, I da Costa, LN Dekel, A Eldar, A Giovanelli, R Haynes, MP Salzer, JJ Wegner, G Zaroubi, S TI Large-scale power spectrum and cosmological parameters from SFI peculiar velocities SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmology : observations; cosmology : theory; dark matter; galaxies : clusters : general; galaxies : distances and redshifts; large-scale structure of universe ID TULLY-FISHER RELATION; SPIRAL GALAXIES; DENSITY FIELDS; HUBBLE FLOW; JY SURVEY; EVOLUTION; IRAS; FLUCTUATIONS; CLUSTERS; SAMPLES AB We estimate the power spectrum of mass density fluctuations from peculiar velocities of galaxies by applying an improved maximum likelihood technique to the new all-sky SFI catalog. Parametric models are used for the power spectrum and the errors, and the free parameters are determined by assuming Gaussian velocity fields and errors and maximizing the probability of the data given the model. It has been applied to generalized cold dark matter (CDM) models with and without COBE normalization. The method has been carefully tested using artificial SFI catalogs. The most likely distance errors are found to be similar to the original error estimates in the SFI data. The general result that is not very sensitive to the prior model used is a relatively high amplitude of the power spectrum. For example, at k = 0.1 h Mpc(-1) we find P(k)Omega(1.2) = (4.4 +/- 1.7) x 10(3)(h(-1) Mpc)(3). An integral over the power spectrum yields sigma(8)Omega(0.6) = 0.82 +/- 0.12. Model-dependent constraints on the cosmological parameters are obtained for families of CDM models. For example, for COBE-normalized ACDM models (scalar fluctuations only), the maximum likelihood result can be approximated by Omega n(2)h(60)(1.3) = 0.58 +/- 0.11. The formal random errors quoted correspond to the 90% confidence level. The total uncertainty, including systematic errors associated with nonlinear effects, may be larger by a factor of similar to 2. These results are in agreement with an application of a similar method to other data (Mark III). C1 European So Observ, Space Telescope European Coordinating Facil, D-85748 Garching, Germany. Hebrew Univ Jerusalem, Racah Inst Phys, IL-91904 Jerusalem, Israel. Fermi Natl Accelerator Lab, NASA, Fermilab Astrophys Grp, Batavia, IL 60510 USA. Observ Nacl, Rio De Janeiro, Brazil. Cornell Univ, Ctr Radiophys & Space Res, Ithaca, NY 14953 USA. Cornell Univ, Natl Astron & Ionosphere Ctr, Ithaca, NY 14953 USA. Wesleyan Univ, Dept Astron, Middletown, CT 06457 USA. Dartmouth Coll, Dept Phys & Astron, Hanover, NH 03755 USA. Max Planck Inst Astrophys, D-85740 Garching, Germany. RP Freudling, W (reprint author), European So Observ, Space Telescope European Coordinating Facil, Karl Schwarzschild Str 2, D-85748 Garching, Germany. NR 52 TC 44 Z9 44 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 SEP 20 PY 1999 VL 523 IS 1 BP 1 EP 15 DI 10.1086/307707 PN 1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 237TZ UT WOS:000082673300001 ER PT J AU Molnar, SM Birkinshaw, M AF Molnar, SM Birkinshaw, M TI Inverse Compton scattering in mildly relativistic plasma SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmic microwave background; galaxies : clusters : general; methods : numerical; plasmas; relativity; scattering ID MICROWAVE BACKGROUND-RADIATION; X-RAY; HUBBLE CONSTANT; CLUSTERS; GAS AB We investigated the effect of inverse Compton scattering in mildly relativistic static and moving plasmas with low optical depth using Monte Carlo simulations, and we calculated the Sunyaev-Zeldovich effect in the cosmic background radiation. Our semianalytic method is based on a separation of photon diffusion in frequency and real space. We use a Monte Carlo simulation to derive the intensity and frequency of the scattered photons for a monochromatic incoming radiation. The outgoing spectrum is determined by integrating over the spectrum of the incoming radiation using the intensity to determine the correct weight. This method makes it possible to study the emerging radiation as a function of frequency and direction. As a first application we have studied the effects of finite optical depth and gas infall on the Sunyaev-Zeldovich effect (not possible with the extended Kompaneets equation), and we discuss the parameter range in which the Boltzmann equation and its expansions can be used. For high-temperature clusters (k(B) T-e greater than or similar to 15 keV) relativistic corrections based on a fifth-order expansion of the extended Kompaneets equation seriously underestimate the Sunyaev-Zeldovich effect at high frequencies. The contribution from plasma infall is less important for reasonable velocities. We give a convenient analytical expression for the dependence of the crossover frequency on temperature, optical depth, and gas infall speed. Optical depth effects are often more important than relativistic corrections and should be taken into account for high-precision work, but they are smaller than the typical kinematic effect from cluster radial velocities. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Bristol, Dept Phys, Bristol BS8 1TL, Avon, England. Ctr Astrophys, Cambridge, MA 02138 USA. RP Molnar, SM (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 662, Greenbelt, MD 20771 USA. NR 34 TC 27 Z9 27 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 SEP 20 PY 1999 VL 523 IS 1 BP 78 EP 86 DI 10.1086/307718 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 237TZ UT WOS:000082673300008 ER PT J AU Vreeswijk, PM Galama, TJ Owens, A Oosterbroek, T Geballe, TR van Paradijs, J Groot, PJ Kouveliotou, C Koshut, T Tanvir, N Wijers, RAMJ Pian, E Palazzi, E Frontera, F Masetti, N Robinson, C Briggs, M Zand, JJMI Heise, J Piro, L Costa, E Feroci, M Antonelli, LA Hurley, K Greiner, J Smith, DA Levine, AM Lipkin, Y Leibowitz, E Lidman, C Pizzella, A Bohnhardt, H Doublier, V Chaty, S Smail, I Blain, A Hough, JH Young, S Suntzeff, N AF Vreeswijk, PM Galama, TJ Owens, A Oosterbroek, T Geballe, TR van Paradijs, J Groot, PJ Kouveliotou, C Koshut, T Tanvir, N Wijers, RAMJ Pian, E Palazzi, E Frontera, F Masetti, N Robinson, C Briggs, M Zand, JJMI Heise, J Piro, L Costa, E Feroci, M Antonelli, LA Hurley, K Greiner, J Smith, DA Levine, AM Lipkin, Y Leibowitz, E Lidman, C Pizzella, A Bohnhardt, H Doublier, V Chaty, S Smail, I Blain, A Hough, JH Young, S Suntzeff, N TI The X-ray, optical, and infrared counterpart to GRB 980703 SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays : bursts; infrared : galaxies; radiation mechanisms : nonthermal; X-rays : galaxies ID BURST; PHOTOMETRY; EMISSION AB We report on X-ray, optical, and infrared follow-up observations of GRB 980703. We detect a previously unknown X-ray source in the GRB error box; assuming a power-law decline, we find for its decay index alpha < -0.91 (3 sigma). We invoke host-galaxy extinction to match the observed spectral slope with the slope expected from "fireball" models. We find no evidence for a spectral break in the infrared to X-ray spectral range on 1998 July 4.4, and determine a lower limit of the cooling break frequency, v(c) > 1.3 x 10(17) Hz. For this epoch we obtain an extinction of A(V) = 1.50 +/- 0.11. From the X-ray data we estimate the optical extinction to be A(V) = 20.2(-7.3)(+12.3), inconsistent with the former value. Our optical spectra confirm the redshift of z = 0.966. We compare the afterglow of GRB 980703 with that of GRB 970508 and find that the fraction of the energy in the magnetic field, epsilon(B) < 6 x 10(-5), is much lower in the case of GRB 980703, as a consequence of the high frequency of the cooling break. C1 Univ Amsterdam, Astron Inst Anton Pannekoek, Amsterdam, Netherlands. Ctr High Energy Astrophys, NL-1098 SJ Amsterdam, Netherlands. European Space Technol Ctr, Dept Space Sci, ESA, Div Astrophys, NL-2200 AG Noordwijk, Netherlands. Joint Astron Ctr, Hilo, HI 96720 USA. Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. Univ Space Res Assoc, Washington, DC USA. NASA, Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England. SUNY Stony Brook, Dept Earth & Space Sci, Astron Program, Stony Brook, NY 11794 USA. CNR, TESRE, I-40129 Bologna, Italy. Univ Ferrara, Dipartimento Fis, I-44100 Ferrara, Italy. SRON, NL-3584 CA Utrecht, Netherlands. CNR, Ist Astrofis Spaziale, I-00133 Rome, Italy. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Inst Astrophys, D-14482 Potsdam, Germany. MIT, Cambridge, MA 02139 USA. Tel Aviv Univ, Wise Observ, IL-69978 Tel Aviv, Israel. European So Observ, Santiago 19, Chile. CEA Saclay, DAPNIA, Serv Astrophys, F-91191 Gif Sur Yvette, France. Ctr Etud Spatiale Rayonnements, F-31028 Toulouse 4, France. Univ Durham, Durham DH1 3LE, England. Univ Cambridge, Cavendish Lab, Cambridge CB3 0HE, England. Univ Hertfordshire, Hatfield AL10 9AB, Herts, England. Cerro Tololo Interamer Observ, La Serena, Chile. RP Vreeswijk, PM (reprint author), Univ Amsterdam, Astron Inst Anton Pannekoek, Kruislaan 403, Amsterdam, Netherlands. RI Galama, Titus/D-1429-2014; Smail, Ian/M-5161-2013; PIRO, LUIGI/E-4954-2013; Palazzi, Eliana/N-4746-2015; Groot, Paul/K-4391-2016; OI Galama, Titus/0000-0002-1036-396X; Smail, Ian/0000-0003-3037-257X; PIRO, LUIGI/0000-0003-4159-3984; Groot, Paul/0000-0002-4488-726X; Costa, Enrico/0000-0003-4925-8523; Feroci, Marco/0000-0002-7617-3421; Palazzi, Eliana/0000-0002-8691-7666; Chaty, Sylvain/0000-0002-5769-8601; Pian, Elena/0000-0001-8646-4858 NR 35 TC 67 Z9 69 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 SEP 20 PY 1999 VL 523 IS 1 BP 171 EP 176 DI 10.1086/307740 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 237TZ UT WOS:000082673300017 ER PT J AU Mitrofanov, IG Anfimov, DS Litvak, ML Briggs, MS Paciesas, WS Pendleton, GN Preece, RD Meegan, CA AF Mitrofanov, IG Anfimov, DS Litvak, ML Briggs, MS Paciesas, WS Pendleton, GN Preece, RD Meegan, CA TI Average cosmological invariant parameters of cosmic gamma-ray bursts SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays : bursts; methods : statistical ID BATSE; REDSHIFT AB Average cosmological invariant parameters (ACIPs) are calculated for six groups of BATSE cosmic gamma-ray bursts selected by their peak fluxes on the 1.024 s timescale. The ACIPs represent: the average temporal and spectral properties of these events equally in the observer frame of reference and in the comoving frames of outbursting emitters. The parameters are determined separately for rise fronts and for back slopes of bursts, defined as the time profiles before and after the main peaks, respectively. The ACIPs for the rise fronts are found to be different for different intensity groups, while the ACIPs for the back slopes show no significant dependence on intensity. We conclude that emitters of bursts manifest standard average properties only during the back slopes of bursts. C1 Moscow Space Res Inst, Moscow 117810, Russia. Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. NASA, Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Mitrofanov, IG (reprint author), Moscow Space Res Inst, Profsojuznaya Str 84-32, Moscow 117810, Russia. OI Preece, Robert/0000-0003-1626-7335 NR 22 TC 4 Z9 4 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 20 PY 1999 VL 523 IS 1 BP 192 EP 196 DI 10.1086/307709 PN 1 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 237TZ UT WOS:000082673300020 ER PT J AU Subramanian, P Becker, PA Kazanas, D AF Subramanian, P Becker, PA Kazanas, D TI Formation of relativistic outflows in shearing black hole accretion coronae SO ASTROPHYSICAL JOURNAL LA English DT Article DE acceleration of particles; accretion, accretion disks; gamma rays : theory; radiation mechanisms : nonthermal ID ACTIVE GALACTIC NUCLEI; MAGNETOHYDRODYNAMIC SIMULATIONS; PARTICLE-ACCELERATION; MAGNETIC-FIELDS; GAMMA-RAYS; DISKS; JETS; QUASARS; VISCOSITY; ORIGIN AB We examine the possibility that the relativistic jets observed in many active galactic nuclei may be powered by the Fermi acceleration of protons in a tenuous corona above a two-temperature accretion disk. In this picture the acceleration arises as a consequence of the shearing motion of the magnetic field in the corona, which is anchored in the underlying Keplerian disk. The protons in the corona have a power-law distribution because the density there is too low for proton-proton collisions to thermalize the energy supplied via Fermi acceleration. The same shear acceleration mechanism also operates in the disk itself; however, there the density is high enough for thermalization to occur and consequently the disk protons have a Maxwellian distribution. Particle acceleration in the corona leads to the development of a pressure-driven wind that passes through a critical point and subsequently transforms into a relativistic jet at large distances from the black hole. We combine the critical conditions for the wind with the structure equations for the disk and the corona to obtain a coupled disk-corona-wind model. Using the coupled model, we compute the asymptotic Lorentz factor Gamma(infinity) of the jet as a function of the cylindrical starting radius at the base of the outflow, in the corona. Our results suggest that Gamma(infinity) less than or similar to 10, which is consistent with observations of superluminal motion in blazars. We show that collisions between the jet and broad-line emission clouds can produce high-energy radiation with a luminosity sufficient to power the gamma-rays observed from blazars. C1 George Mason Univ, Inst Computat Sci & Informat, Ctr Earth Observing & Space Res, Fairfax, VA 22030 USA. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. George Mason Univ, Dept Phys & Astron, Fairfax, VA 22030 USA. RP Subramanian, P (reprint author), George Mason Univ, Inst Computat Sci & Informat, Ctr Earth Observing & Space Res, Fairfax, VA 22030 USA. EM psubrama@mahanadi.nrl.navy.mil; kazanas@milkyway.gsfc.nasa.gov NR 51 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 SEP 20 PY 1999 VL 523 IS 1 BP 203 EP 222 DI 10.1086/307703 PN 1 PG 20 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 237TZ UT WOS:000082673300022 ER PT J AU Varosi, F Dwek, E AF Varosi, F Dwek, E TI Analytical approximations for calculating the escape and absorption of radiation in clumpy dusty environments SO ASTROPHYSICAL JOURNAL LA English DT Article DE dust, extinction; ISM : structure; methods : analytical; radiative transfer ID INTERSTELLAR-MEDIUM; MOLECULAR CLOUDS; FILLING FACTOR; MASS-SPECTRUM; MODELS; GALAXIES; CIRRUS; GRAINS AB We present analytical approximations for calculating the scattering, absorption, and escape of non-ionizing photons from a spherically symmetric two-phase clumpy medium, with either a central point source of isotropic radiation, a uniform distribution of isotropic emitters, or uniformly illuminated by external sources. The analytical approximations are based on the mega-grains model of two-phase clumpy media, as proposed by Hobson & Padman, combined with escape and absorption probability formulae for homogeneous media. The accuracy of the approximations is examined by comparison with three-dimensional Monte Carlo simulations of radiative transfer, including multiple scattering. Our studies show that the combined mega-grains and escape/absorption probability formulae provide a good approximation of the escaping and absorbed radiation fractions for a wide range of parameters characterizing the clumpiness and optical properties of the medium. A realistic test of the analytic approximations is performed by modeling the absorption of a starlike source of radiation by interstellar dust in a clumpy medium and by calculating the resulting equilibrium dust temperatures and infrared emission spectrum of both the clumps and the interclump medium. In particular, we find that the temperature of dust in clumps is lower than in the interclump medium if the clumps are optically thick at wavelengths at which most of the absorption occurs. Comparison with Monte Carlo simulations of radiative transfer in the same environment shows that the analytic model yields a good approximation of dust temperatures and the emerging UV-FIR spectrum of radiation for all three types of source distributions mentioned above. Our analytical model provides a numerically expedient way to estimate radiative transfer in a variety of interstellar conditions and can be applied to a wide range of astrophysical environments, from clumpy star-forming regions to stal;burst galaxies. C1 NASA, Goddard Space Flight Ctr, Raytheon Informat Technol & Sci Serv, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Varosi, F (reprint author), NASA, Goddard Space Flight Ctr, Raytheon Informat Technol & Sci Serv, Code 685, Greenbelt, MD 20771 USA. EM varosi@gsfc.nasa.gov; edwek@stars.gsfc.nasa.gov NR 42 TC 49 Z9 49 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 20 PY 1999 VL 523 IS 1 BP 265 EP 305 DI 10.1086/307729 PN 1 PG 41 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 237TZ UT WOS:000082673300026 ER PT J AU Mastrodemos, N Morris, M AF Mastrodemos, N Morris, M TI Bipolar pre-planetary nebulae: Hydrodynamics of dusty winds in binary systems. II. Morphology of the circumstellar envelopes SO ASTROPHYSICAL JOURNAL LA English DT Article DE circumstellar matter; hydrodynamics; stars : winds, outflows ID DOUBLE-CORE EVOLUTION; ASYMPTOTIC GIANT BRANCH; SMOOTHED PARTICLE HYDRODYNAMICS; HUBBLE-SPACE-TELESCOPE; SOLAR-TYPE STARS; MASS-LOSS; COMMON ENVELOPE; MOLECULAR GAS; RED-RECTANGLE; DRIVEN WINDS AB We have constructed three-dimensional smoothed particle hydrodynamics models to examine the influence of a detached binary companion on the dusty winds from red giants and asymptotic giant branch (AGB) stars and the degree to which this model can reproduce some of the observable characteristics of axisymmetric or bipolar pre-planetary nebulae. In this second paper in the series, we focus our attention on the morphology of the circumstellar envelopes. The parameter space of our models includes wind outflow velocities in the range 10-26 km s(-1), circular orbits with binary separations 3.6-50 AU, and binary companions having masses in the range 0.25-2 M.. By varying these parameters, we find a continuous range of envelope geometries and density contrasts that correspond well to observational classifications of planetary and pre-planetary nebulae: bipolar, with density contrasts from 10 to >200 between the equatorial plane and the polar direction; elliptical, with intermediate contrasts of 5-10; and quasi-spherical, with very low density contrasts. This last category manifests a hitherto unknown type of hydrodynamic solution, in which a spiral shock is formed, covering most of the solid angle around the binary. The cross sections of these shocks, and to a lesser extent the two-dimensional projections of the quasi-spherical envelopes, appear as a series of rings in the wind. We discuss the observational implications of that type of wind solution. The quasi-spherical geometry is the prevailing type in parameter space. From binary statistics we estimate that similar to 34%-40% of detached binaries will give rise to bipolars for a 10 km s(-1) outflow. We present a classification scheme of the envelope geometries based on a combination of binary and wind parameters. We also find that the mass accretion rates onto the secondary are systematically lower than is predicted by the Bondi-Hoyle theory. C1 Univ Calif Los Angeles, Dept Astron, Los Angeles, CA 90095 USA. RP Mastrodemos, N (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 85 TC 197 Z9 197 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 SEP 20 PY 1999 VL 523 IS 1 BP 357 EP 380 DI 10.1086/307717 PN 1 PG 24 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 237TZ UT WOS:000082673300032 ER PT J AU Schmelz, JT Saba, JLR Strong, KT Winter, HD Brosius, JW AF Schmelz, JT Saba, JLR Strong, KT Winter, HD Brosius, JW TI Emission measure distribution for an active region using coordinated SERTS and Yohkoh SXT observations SO ASTROPHYSICAL JOURNAL LA English DT Article DE sun : activity; sun : X-rays, gamma rays ID ELEMENTAL ABUNDANCES; CORONAL PLASMA AB Often the derived temperature of an active region reflects the method and the nature of the instrument used in its measurement. The emission measure (i.e., the amount of emitting material) derived from spectroscopic observations usually depends on assumptions about the absolute elemental abundances and ionization fractions of the emitting ions. Yet establishing the distribution of emission measure with temperature is the first step needed to proceed with most of the interesting physics of active regions-including heating processes, cooling timescales, and loop stability. Accurately characterizing the thermal distribution of the coronal plasma requires data which can resolve multithermal features and constrain both low- and high-temperature emission. To model the temperature distribution of NOAA Active Region 7563, we have combined broadband filter data from the Yohkoh Soft X-Ray Telescope (SXT) with simultaneous spectral line data from the Goddard Solar EUV Rocket Telescope and Spectrograph (SERTS) taken during its flight on 1993 August 17. We have used a forward-folding technique to determine the emission measure distribution of the active region loops. We have found that (1) the SXT response functions are sensitive to both the elemental abundances and the ionization fractions assumed to compute the solar spectrum that is folded through the instrument effective area; (2) the relative calibration between the SERTS and the SXT instruments must be adjusted by a factor of 2 (a value consistent with the absolute measurement uncertainty of the 1993 SERTS flight) no matter which abundances or iron ionization fractions are used; (3) the two-peaked differential emission measure previously determined using SERTS data alone is not consistent with the SXT data: including the SXT data as a high-temperature constraint in the analysis requires that the emission above about 3 MK drop off steeply rather than extending out to 6 MK. The sensitivity of the SXT filter response functions to elemental abundance and iron ionization fraction could have a major impact on many routine analyses of SXT data. The emission measures can be greatly affected (up to a factor of 7) and temperatures derived from filter ratios can be significantly altered (up to at least 40%) by adopting different sets of commonly used elemental and ionic abundances. The results of our multithermal analysis imply that using broadband SXT data or a comparable high-temperature constraint in conjunction with high-resolution spectra covering a wide lower temperature range to study solar active regions can significantly improve the information derived from either data set alone. In this study, the revised multithermal distribution reduces the thermal energy content of the region by about a factor of 2 and the required heating by about a factor of 5, which in turn relaxes some constraints on possible heating models. C1 Univ Memphis, Dept Phys, Memphis, TN 38152 USA. NASA, Goddard Space Flight Ctr, Lockheed Martin Solar & Astrophys Lab, Greenbelt, MD 20771 USA. Lockheed Martin Solar & Astrophys Lab, Palo Alto, CA 94304 USA. NASA, Goddard Space Flight Ctr, Raytheon ITSS, Greenbelt, MD 20771 USA. RP Schmelz, JT (reprint author), Univ Memphis, Dept Phys, Memphis, TN 38152 USA. NR 19 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 SEP 20 PY 1999 VL 523 IS 1 BP 432 EP 443 DI 10.1086/307736 PN 1 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 237TZ UT WOS:000082673300037 ER PT J AU Hurley, K Kouveliotou, C Cline, T Mazets, E Golenetskii, S Frederiks, DD van Paradijs, J AF Hurley, K Kouveliotou, C Cline, T Mazets, E Golenetskii, S Frederiks, DD van Paradijs, J TI Where is SGR 1806-20? SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays : bursts; stars : neutron; supernova remnants; X-rays : stars ID GAMMA-RAY REPEATER; HIGH-ENERGY TRANSIENT; STAR ETA-CARINAE; RADIO OUTBURST; SGR-1806-20; IDENTIFICATION; SGR1806-20 AB We apply a statistical method to derive very precise locations for soft gamma repeaters using data from the interplanetary network. We demonstrate the validity of the method by deriving a 600 arcsec(2) error ellipse for SGR 1900+14 whose center agrees well with the VLA source position. We then apply it to SGR 1806-20, for which we obtain a 230 arcsec(2) error ellipse, the smallest burst error box to date. We find that the most likely position of the source has a small but significant displacement from that of the nonthermal core of the radio supernova remnant G10.0-0.3, which was previously thought to be the position of the repeater. We propose a different model to explain the changing supernova remnant morphology and the positions of the luminous blue variable and the bursting source. C1 Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. NASA, George C Marshall Space Flight Ctr, Univ Space Res Assoc, Huntsville, AL 35812 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Russian Acad Sci, AF Ioffe Phys Tech Inst, St Petersburg 194021, Russia. Univ Alabama, Huntsville, AL 35899 USA. Univ Amsterdam, Astron Inst Anton Pannekoek, NL-1098 SJ Amsterdam, Netherlands. RP Hurley, K (reprint author), Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. RI Frederiks, Dmitry/C-7612-2014; Golenetskii, Sergey/B-3818-2015 NR 23 TC 43 Z9 43 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 SEP 20 PY 1999 VL 523 IS 1 BP L37 EP L40 DI 10.1086/312256 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 237UB UT WOS:000082673500009 ER PT J AU Nandra, K George, IM Mushotzky, RF Turner, TJ Yaqoob, T AF Nandra, K George, IM Mushotzky, RF Turner, TJ Yaqoob, T TI The properties of the relativistic iron K-line in NGC 3516 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : active; galaxies : individual (NGC 3516); galaxies : nuclei; X-rays : galaxies ID ACTIVE GALAXY MCG-6-30-15; SEYFERT-1 GALAXIES; BLACK-HOLE; ASCA OBSERVATIONS; GALACTIC NUCLEI; EMISSION-LINE; DISK; PROFILES AB We present an analysis of the relativistic iron K alpha line in the Seyfert 1 galaxy NGC 3516, based on a continuous, 5 day ASCA observation. The broad profile which has been found in several other active galactic nuclei is confirmed in NGC 3516 with unprecedented signal-to-noise ratio. Disk-line models with either a Kerr or Schwarzschild metric fit the integrated profile, but both require emission very strongly concentrated in the inner disk. We find tentative evidence for the line signatures of Ni K alpha and/or Fe K beta. The continuum flux varied by similar to 50% during the observation and time-resolved analysis shows that the line also changes. The line core seems to follow the continuum, but the blue wing is unrelated and shows a greater amplitude (factor similar to 2) of variability. The red wing is formally consistent with a constant but appears to be correlated with the blue wing. We interpret this as evidence for independent variability of the broadest parts of the line. There also appears to be an absorption feature in the profile, consistent with resonance scattering in infalling material. This variable feature may be the signature of material being accreted by the central black hole. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Space Res Assoc, Greenbelt, MD USA. Univ Maryland Baltimore Cty, Baltimore, MD 21228 USA. RP Nandra, K (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Codes 660-2 & 662, Greenbelt, MD 20771 USA. NR 22 TC 92 Z9 93 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 SEP 20 PY 1999 VL 523 IS 1 BP L17 EP L20 DI 10.1086/312252 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 237UB UT WOS:000082673500004 ER PT J AU Osherovich, V Titarchuk, L AF Osherovich, V Titarchuk, L TI Interpretation of similar to 35 Hz QPO in the atoll source 4U 1702-42 as a low branch of the Keplerian oscillations under the influence of the Coriolis force SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; stars : individual (4U 1702-42; Scorpius X-1); stars : neutron; X-rays : bursts ID QUASI-PERIODIC OSCILLATIONS; NEUTRON-STAR; MILLISECOND AB The recent model of quasi-periodic oscillations in neutron star binaries has suggested the existence of two branches of QPOs due to the influence of Coriolis force on the linear Keplerian oscillator: one branch with frequencies similar to 400-1200 Hz and another branch with frequencies an order of magnitude lower. The frequencies of the high branch nu(h) hold a hybrid frequency relation with the Keplerian frequency nu(K): nu(h)(2) = nu(K)(2) + Omega(2)/pi(2), where Omega is the rotational frequency of the star's magnetosphere. The frequency of the low branch is nu(L) = (Omega/pi)(nu(K)/nu(h)) sin delta, where delta is a small angle between Omega and the vector normal to the plane of Keplerian oscillations. The observations of the source 4U 1702-42 have shown that the centroid of the similar to 35 Hz QPO tracks the frequency of the kilohertz oscillations. We interpret the similar to 35 Hz oscillations as nu(L) and find delta = 3.degrees 9 +/- 0.degrees 2. Our results make 4U 1702-42 the second source (after Sco X-1) for which the theoretically derived lower branch is identified (within our model) and delta is calculated. The inferred angle delta stays approximately the same over the significant range of nu(K) (650-900 Hz), as expected from the model. Based on our model, we present a classification of QPO frequencies in the source 4U 1702-42 observed above and below nu(L). C1 NASA, Goddard Space Flight Ctr, RITSS, Greenbelt, MD 20771 USA. George Mason Univ, CSI, Fairfax, VA 22030 USA. RP Osherovich, V (reprint author), NASA, Goddard Space Flight Ctr, RITSS, Greenbelt, MD 20771 USA. NR 15 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 SEP 20 PY 1999 VL 523 IS 1 BP L73 EP L76 DI 10.1086/312254 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 237UB UT WOS:000082673500017 ER PT J AU Perlman, ES Madejski, G Stocke, JT Rector, TA AF Perlman, ES Madejski, G Stocke, JT Rector, TA TI X-ray spectral variability of PKS 2005-489 during the spectacular 1998 November flare SO ASTROPHYSICAL JOURNAL LA English DT Article DE BL Lacertae objects : individual (PKS 2005-489); galaxies : active; X-rays : galaxies ID BL-LACERTAE OBJECTS; TIMING EXPLORER; PERFORMANCE; BLAZARS; JETS AB We report on monitoring of the BL Lac object PKS 2005-489 by the Rossi X-Ray Timing Explorer (RXTE) in 1998 October-December. During these months, the source umderwent a spectacular flare; at its peak on November 10, its 2-10 keV flux was 3.35 x 10(-10) ergs cm(-2) s(-1), over 30 times brighter than in quiescence. During the rising phase, the X-ray spectrum of PKS 2005-489 hardened considerably, reaching alpha = 1.32 (F-nu proportional to nu(-alpha)) near maximum. During the declining phase, the X-ray spectrum steepened rapidly, reaching alpha = 1.82, then became somewhat harder toward the end of December (alpha similar to 1.6). While such behavior has been seen before, the simplicity, magnitude, and duration of this flare allowed us to study it in great detail. We argue that this flare was caused by either the injection of particles into the jet or in situ particle acceleration and that the spectral steepening which followed the flare maximum was the result of synchrotron cooling. Contrary to other recently observed blazar flares (e.g., Mrk 501, 3C 279, PKS 2155-304), our results do not imply a major shift in the location of the synchrotron peak during this flare. C1 Space Telescope Sci Inst, Baltimore, MD 21218 USA. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. Univ Colorado, Ctr Astrophys & Space Astron, Boulder, CO 80309 USA. Natl Opt Astron Observ, Tucson, AZ 85719 USA. RP Perlman, ES (reprint author), Space Telescope Sci Inst, 3700 San Martin Dr, Baltimore, MD 21218 USA. OI Perlman, Eric/0000-0002-3099-1664 NR 37 TC 24 Z9 24 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 SEP 20 PY 1999 VL 523 IS 1 BP L11 EP L15 DI 10.1086/312260 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 237UB UT WOS:000082673500003 ER PT J AU Strohmayer, TE AF Strohmayer, TE TI Spin-down of pulsations in the cooling tail of an X-ray burst from 4U 1636-53 SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars : individual (4U 1636-53); stars : neutron; stars : rotation; X-rays : bursts ID ACCRETING NEUTRON-STARS; AQUILA X-1; EMISSION; MODEL AB With the proportional counter array on board the Rossi X-ray Timing Explorer, we report the discovery of a decrease in the frequency of X-ray brightness oscillations in the cooling tail of an X-ray burst from 4U 1636-53. This is the first direct evidence for a spin-down of the pulsations seen during thermonuclear bursts. We find that the spin-down episode is correlated with the appearance in this bm:st of an extended tail of emission with a decay timescale much longer than is seen in other bursts from 4U 1636-53 in the same set of observations. We present both time-resolved energy and variability spectra during this burst and compare them with results from a second burst that shows neither a spin-down episode nor an extended tail. A spectral evolution study of the "spin-down" burst reveals a secondary signature of weak radius expansion, which is not seen in other bursts and is correlated with the spin-down episode; this may indicate a secondary thermonuclear energy release. We interpret the spin-down episode in the context of an angular momentum-conserving shell, which is reexpanded and therefore spun down by an additional thermonuclear energy release that could also explain the extended X-ray tail. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Strohmayer, TE (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. EM stroh@clarence.gsfc.nasa.gov NR 17 TC 24 Z9 24 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 20 PY 1999 VL 523 IS 1 BP L51 EP L55 DI 10.1086/312258 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 237UB UT WOS:000082673500012 ER PT J AU Wiedenbeck, ME Binns, WR Christian, ER Cummings, AC Dougherty, BL Hink, PL Klarmann, J Leske, RA Lijowski, M Mewaldt, RA Stone, EC Thayer, MR von Rosenvinge, TT Yanasak, NE AF Wiedenbeck, ME Binns, WR Christian, ER Cummings, AC Dougherty, BL Hink, PL Klarmann, J Leske, RA Lijowski, M Mewaldt, RA Stone, EC Thayer, MR von Rosenvinge, TT Yanasak, NE TI Constraints on the time delay between nucleosynthesis and cosmic-ray acceleration from observations of Ni-59 and Co-59 SO ASTROPHYSICAL JOURNAL LA English DT Article DE acceleration of particles; cosmic rays; nuclear reactions, nucleosynthesis, abundances supernovae : general ID PARTIAL CROSS-SECTIONS; ISOTOPIC COMPOSITION; NUCLEI; ABUNDANCES; SOLAR; FE; NI AB Measurements of the abundances of cosmic-ray Ni-59 and Co-59 are reported from the Cosmic-Ray Isotope Spectrometer (CRIS) on the Advanced Composition Explorer. These nuclides form a parent-daughter pair in a radioactive decay which can occur only by electron capture. This decay cannot occur once the nuclei are accelerated to high energies and stripped of their electrons. The CRTS data indicate that the decay of Ni-59 to Co-59 has occurred, leading to the conclusion that a time longer than the 7.6 x 10(4) yr half-life of Ni-59 elapsed before the particles were accelerated. Such long delays indicate the acceleration of old, stellar or interstellar material rather than fresh supernova ejecta. For cosmic-ray source material to have the composition of supernova ejecta would require that these ejecta not undergo significant mixing with normal interstellar gas before similar to 10(5) yr has elapsed. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Washington Univ, St Louis, MO 63130 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. CALTECH, Pasadena, CA 91125 USA. RP Wiedenbeck, ME (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Christian, Eric/D-4974-2012 OI Christian, Eric/0000-0003-2134-3937 NR 18 TC 58 Z9 58 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 SEP 20 PY 1999 VL 523 IS 1 BP L61 EP L64 DI 10.1086/312242 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 237UB UT WOS:000082673500014 ER PT J AU Wijers, RAMJ Vreeswijk, PM Galama, TJ Rol, E van Paradijs, J Kouveliotou, C Giblin, T Masetti, N Palazzi, E Pian, E Frontera, F Nicastro, L Falomo, R Soffitta, P Piro, L AF Wijers, RAMJ Vreeswijk, PM Galama, TJ Rol, E van Paradijs, J Kouveliotou, C Giblin, T Masetti, N Palazzi, E Pian, E Frontera, F Nicastro, L Falomo, R Soffitta, P Piro, L TI Detection of polarization in the afterglow of GRB 990510 with the ESO very large telescope SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays : bursts; magnetic fields; polarization; radiation mechanisms : nonthermal ID GAMMA-RAY BURSTS; GRB-970508; BATSE; SIZE AB Following a BeppoSAX alert and the discovery of the OT at SAAO, we observed GRB 990510 with the FORS instrument on ESO's VLT Unit 1 (Antu). The burst is unremarkable in gamma rays, but in optical is the first one to show good evidence for jetlike outflow. We report the detection of significant linear polarization in the afterglow: it is 1.6 +/- 0.2% 0.86 days after trigger, and after 1.81 days is consistent with that same value, but much more uncertain. The polarization angle is constant on a timescale of hours and may be constant over one day. We conclude that the polarization is intrinsic to the source and due to the synchrotron nature of the emission, and discuss the random and ordered field geometries that may be responsible for it. C1 SUNY Stony Brook, Dept Phys & Astron, Stony Brook, NY 11794 USA. Univ Amsterdam, Astron Inst Anton Pannekoek, NL-1098 SJ Amsterdam, Netherlands. Ctr High Energy Astrophys, NL-1098 SJ Amsterdam, Netherlands. Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. Univ Space Res Assoc, Greenbelt, MD USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. CNR, Ist Tecnol & Studio Radiaz Extraterr, I-40129 Bologna, Italy. Univ Ferrara, Dept Phys, I-44100 Ferrara, Italy. CNR, IFCAI, I-90146 Palermo, Italy. Osserv Astron Padova, I-35122 Padua, Italy. CNR, Ist Astrofis Spaziale, I-00133 Rome, Italy. RP Wijers, RAMJ (reprint author), SUNY Stony Brook, Dept Phys & Astron, Stony Brook, NY 11794 USA. RI Galama, Titus/D-1429-2014; PIRO, LUIGI/E-4954-2013; Nicastro, Luciano/F-5866-2015; Palazzi, Eliana/N-4746-2015; OI Galama, Titus/0000-0002-1036-396X; PIRO, LUIGI/0000-0003-4159-3984; Nicastro, Luciano/0000-0001-8534-6788; Wijers, Ralph/0000-0002-3101-1808; Palazzi, Eliana/0000-0002-8691-7666; Masetti, Nicola/0000-0001-9487-7740 NR 51 TC 80 Z9 81 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 SEP 20 PY 1999 VL 523 IS 1 BP L33 EP L36 DI 10.1086/312262 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 237UB UT WOS:000082673500008 ER PT J AU Morisette, JT Khorram, S Mace, T AF Morisette, JT Khorram, S Mace, T TI Land-cover change detection enhanced with generalized linear models SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article ID LOGISTIC MULTIPLE-REGRESSION; TASSELED CAP; GIS AB This paper explores the use of generalized linear models (GLMs) for enhancing standard methods of satellite-based land-cover change detection. It starts by generalizing satellite-based change-detection algorithms in a modelling context and then gives an overview of GLMs. It goes onto describe how GLMs can fit into the context of existing change-detection methods. By way of example, using a change detection over two locations in North Carolina, USA, using Landsat Thematic Mapper data, it shows how the models provide a quantitative approach to image-based change detection. The application of GLMs requires special consideration of the spatial correlation of geographical data and how this effects the use of GLMs. The paper describes the use of preliminary variogram analysis on the image data for initial sampling considerations. For the binary response (change/no-change) derived from the reference data, a 'joint-count' test is used to assess their independence. Finally, the model error term is checked through the empirical variogram of the residuals. It is concluded that GLMs can be helpful in examining different change metrics and useful by applying the resulting model throughout the image to get a probability of change estimate as well as pixel-specific estimates of the variability of change estimate. However, as presented here, this application should respect the assumption of independent response data used for the modelling. C1 Univ Maryland, NASA, GSFC, Dept Geog, Greenbelt, MD 20771 USA. N Carolina State Univ, Ctr Earth Observat, Raleigh, NC 27695 USA. US EPA, Res Triangle Pk, NC 27711 USA. RP Morisette, JT (reprint author), Univ Maryland, NASA, GSFC, Dept Geog, Code 923, Greenbelt, MD 20771 USA. NR 28 TC 27 Z9 30 U1 1 U2 3 PU TAYLOR & FRANCIS LTD PI LONDON PA ONE GUNPOWDER SQUARE, LONDON EC4A 3DE, ENGLAND SN 0143-1161 J9 INT J REMOTE SENS JI Int. J. Remote Sens. PD SEP 20 PY 1999 VL 20 IS 14 BP 2703 EP 2721 DI 10.1080/014311699211750 PG 19 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA 234VN UT WOS:000082505200002 ER PT J AU Ziemke, JR Chandra, S AF Ziemke, JR Chandra, S TI Seasonal and interannual variabilities in tropical tropospheric ozone SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID COLUMN OZONE; STRATOSPHERIC OZONE; GLOBAL SIMULATION; TOMS MEASUREMENTS; CHEMISTRY; SATELLITE; IMPACT; TRACE; MODEL AB This paper presents the first detailed characterization of seasonal and interannual variability in tropical tropospheric column ozone (TCO) to delineate the relative importance of biomass burning and large-scale transport. TCO time series are derived from 20 years (1979-1998) of total ozone mapping spectrometer (TOMS) data using the convective cloud differential (CCD) method. Our study identifies three regions in the tropics with distinctly different characteristics related to seasonal and interannual variability. These three regions are the eastern Pacific, Atlantic, and western Pacific. TCO in the Atlantic region peaks at about the same time (September-October) both north and south of the equator, while the annual-cycle amplitude in TCO varies from about 3 to 6 Dobson units (DU) from north to south of the equator. In comparison, annual cycles in both the eastern and western Pacific are generally weak, with the largest TCO amount occurring around March-April in the northern hemisphere and September-November in the southern hemisphere. Interannual variabilities in these three regions are also very different. The Atlantic region indicates a predominant quasi-biennial oscillation (QBO) in TCO which is out of phase with the QBO in stratospheric ozone. This behavior is consistent with a UV modulation of upper tropospheric photochemistry on a QBO timescale caused by the QBO in stratospheric ozone. However, photochemical models predict significantly smaller changes, and dynamical effects may be a critical factor. Interannual variability in TCO in the Atlantic also appears to have some influence from biomass burning, but our study indicates that it is of lesser significance. Interannual variability in the eastern and western Pacific is dominated by El Nino events. During an El Nino there is anomalously low TCO in the eastern Pacific and high values in the western Pacific. These signatures indicate combined effects of convectively driven transport and tropospheric ozone generated by intense biomass burning in the Indonesian region. Finally, a simplified tropospheric ozone residual (STOR) method which utilizes the small variability of TCO near the dateline is proposed in this study to derive high-resolution maps and extended time series of TCO. C1 Software Corp Amer, Beltsville, MD 20705 USA. NASA, Goddard Space Flight Ctr, Chem & Dynam Branch, Greenbelt, MD 20771 USA. RP Ziemke, JR (reprint author), Software Corp Amer, Beltsville, MD 20705 USA. EM ziemke@jwocky.gsfc.nasa.gov; chandra@chapman.gsfc.nasa.gov NR 37 TC 56 Z9 57 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD SEP 20 PY 1999 VL 104 IS D17 BP 21425 EP 21442 DI 10.1029/1999JD900277 PG 18 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 238BC UT WOS:000082690200015 ER PT J AU Reichle, HG Anderson, BE Connors, VS Denkins, TC Forbes, DA Gormsen, BB Langenfelds, RL Neil, DO Nolf, SR Novelli, PC Pougatchev, NS Roell, MM Steele, LP AF Reichle, HG Anderson, BE Connors, VS Denkins, TC Forbes, DA Gormsen, BB Langenfelds, RL Neil, DO Nolf, SR Novelli, PC Pougatchev, NS Roell, MM Steele, LP TI Space shuttle based global CO measurements during April and October 1994, MAPS instrument, data reduction, and data validation SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID CARBON-MONOXIDE; RETRIEVAL AB The Measurement of Air Pollution From Satellites (MAPS) experiment flew as a payload aboard the space shuttle during April and October 1994. The instrument and the data reduction procedure were modified from earlier flights in 1981 and 1984. The modifications to both are described, and selected portions of the data are compared to concurrent aircraft borne direct measurements that had been carefully intercalibrated. In addition, the data acquired in 1984 were reprocessed using the new data reduction procedure, and the reprocessed data were compared to aircraft data acquired in 1984. The results of these comparisons indicate that the large bias error in the 1984 MAPS data has been reduced to about 10%. C1 N Carolina State Univ, Dept Marine Earth & Atmospher Sci, Raleigh, NC 27606 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. SpaceTec Inc, Hampton, VA 23666 USA. Sci Applicat Int Corp, Hampton, VA 23666 USA. CSIRO, Div Atmospher Res, Aspendale, Vic 3195, Australia. CSC, Hampton, VA 23666 USA. NOAA, Climate Monitoring & Diagnost Lab, Boulder, CO 80303 USA. Christopher Newport Univ, Dept Phys Comp Sci & Engn, Newport News, VA 23606 USA. RP Reichle, HG (reprint author), N Carolina State Univ, Dept Marine Earth & Atmospher Sci, Box 8208, Raleigh, NC 27606 USA. EM henry_reichle@ncsu.edu; s.r.nolf@larc.nasa.gov; pnovelli@cmdl.noaa.gov; n.s.pougatchev@larc.nasa.gov RI Steele, Paul/B-3185-2009; Langenfelds, Raymond/B-5381-2012 OI Steele, Paul/0000-0002-8234-3730; NR 20 TC 39 Z9 41 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 SEP 20 PY 1999 VL 104 IS D17 BP 21443 EP 21454 DI 10.1029/97JD03299 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 238BC UT WOS:000082690200016 ER PT J AU Newell, RE Zhu, Y Connors, VS Reichle, HG Novelli, PC Gormsen, BB AF Newell, RE Zhu, Y Connors, VS Reichle, HG Novelli, PC Gormsen, BB TI Atmospheric processes influencing measured carbon monoxide in the NASA Measurement of Air Pollution From Satellites (MAPS) experiment SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID CHEMISTRY; APRIL; OZONE; CO AB The Measurement of Air Pollution From Satellites (MAPS) experiment measured global distributions of carbon monoxide (CO) while on board the space shuttle during April 9-19 and September 30 to October 11, 1994. This paper examines selected examples of the meteorological processes that contributed to the observed signals. We first examine and relate the mean distribution of MAPS-measured CO, surface station-measured CO, streamlines, and divergent winds averaged over the two missions. Tropical high CO values were associated with boundary layer convergence regions, particularly in October, that enable CO associated with biomass burning to reach the free troposphere where it can be detected by the nadir viewing gas filter 4.7 mu m radiometer. CO values over northern middle latitudes show evidence of fossil fuel pollution especially in April. Southern middle and high latitudes in April suggest photochemical control, while in October these regions are strongly influenced by the tropical biomass burning. Next, we consider events on 1 day near the center of each mission and show that in one of these cases, low CO measurements are associated with high potential vorticity, which suggests that the air samples originated from the stratosphere. Finally, we modify the two mean patterns, both within 23 days of the equinox, to illustrate the possible separation of the natural photochemical CO pattern from the CO pollution patterns. This procedure brings out the intercontinental and transcontinental transport of pollution in April northern hemisphere middle and high latitudes as well as, less markedly, in the October maps. It also accentuates the biomass burning contribution in October and shows pollution to extend southeastward from South America into the South Atlantic and also from Australia into the South Pacific. The separation is made possible by having CO measurements with global coverage. C1 MIT, Dept Earth Atmospher & Planetary Sci, Cambridge, MA 02139 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. NOAA, Climate Monitoring & Diagnost Lab, Boulder, CO 80303 USA. N Carolina State Univ, Dept Marine Earth & Atmospher Sci, Raleigh, NC 27695 USA. Sci Applicat Int Corp, Hampton, VA USA. RP Newell, RE (reprint author), MIT, Dept Earth Atmospher & Planetary Sci, Cambridge, MA 02139 USA. EM newell@newell1.mit.edu NR 22 TC 2 Z9 2 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD SEP 20 PY 1999 VL 104 IS D17 BP 21487 EP 21501 DI 10.1029/1999JD900394 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 238BC UT WOS:000082690200019 ER PT J AU Cho, JYN Newell, RE Bui, TP Browell, EV Fenn, MA Mahoney, MJ Gregory, GL Sachse, GW Vay, SA Kucsera, TL Thompson, AR AF Cho, JYN Newell, RE Bui, TP Browell, EV Fenn, MA Mahoney, MJ Gregory, GL Sachse, GW Vay, SA Kucsera, TL Thompson, AR TI Observations of convective and dynamical instabilities in tropopause folds and their contribution to stratosphere-troposphere exchange SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID GRAVITY-WAVE SATURATION; INSITU MEASUREMENTS; CARBON-MONOXIDE; TURBULENCE; OZONE; SYSTEM; CONSTITUENTS; BREAKING; AIRCRAFT; MODEL AB With aircraft-mounted in situ and remote sensing instruments for dynamical, thermal, and chemical measurements we studied two cases of tropopause folding. In both folds we found Kelvin-Helmholtz billows with horizontal wavelength of similar to 900 m and thickness of similar to 120 m. In one case the instability was effectively mixing the bottomside of the fold, leading to the transfer of stratospheric air into the troposphere. Also, we discovered in both cases small-scale secondary ozone maxima shortly after the aircraft ascended past the topside of the fold that corresponded to regions of convective instability. We interpreted this phenomenon as convectively breaking gravity waves. Therefore we posit that convectively breaking gravity waves acting on tropopause folds must be added to the list of important irreversible mixing mechanisms leading to stratosphere-troposphere exchange. C1 MIT, Dept Earth Atmospher & Planetary Sci, Cambridge, MA 02139 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Sci Applicat Int Corp, Hampton, VA 23666 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. CALTECH, Jet Prop Lab, NASA, Pasadena, CA 91109 USA. RP Cho, JYN (reprint author), MIT, Dept Earth Atmospher & Planetary Sci, 77 Massachusetts Ave,54-1823, Cambridge, MA 02139 USA. EM jcho@pemtropics.mit.edu; newell@newell1.mit.edu; bui@mms.arc.nasa.gov; e.v.browell@larc.nasa.gov; m.a.fenn@larc.nasa.gov; michael.j.mahoney@jpl.nasa.gov; g.l.gregory@larc.nasa.gov; g.w.sachse@larc.nasa.gov; s.a.vay@larc.nasa.gov; tlk@croc.gsfc.nasa.gov; thompson@gator1.gsfc.nasa.gov RI Thompson, Anne /C-3649-2014 OI Thompson, Anne /0000-0002-7829-0920 NR 44 TC 26 Z9 26 U1 1 U2 7 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD SEP 20 PY 1999 VL 104 IS D17 BP 21549 EP 21568 DI 10.1029/1999JD900430 PG 20 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 238BC UT WOS:000082690200023 ER PT J AU Torres, O Bhartia, PK AF Torres, O Bhartia, PK TI Impact of tropospheric aerosol absorption on ozone retrieval from backscattered ultraviolet measurements SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID MOUNT-PINATUBO AEROSOLS; MAPPING SPECTROMETER AB The impact of tropospheric aerosols on the retrieval of column ozone amounts using space-borne measurements of backscattered ultraviolet radiation is examined. Using radiative transfer calculations, we show that the radiative effects of UV-absorbing aerosols produce spurious ozone column reductions. The magnitude of the total ozone underestimation depends on the aerosol type, optical depth, and aerosol layer height. Desert dust can produce errors as large as 10%. Smaller errors are produced by carbonaceous aerosols that result from biomass burning. Ozone retrieval errors associated with nonabsorbing aerosols are typically +/-1% of the total ozone amount depending on aerosol optical depth and viewing geometry. Though the error is produced by complex interactions between ozone absorption (both stratospheric and tropospheric), aerosol scattering, and aerosol absorption, a surprisingly simple correction procedure reduces the error to similar to 1% for a variety of aerosols and for a wide range of aerosol loading. Comparison of the corrected Total Ozone Mapping Spectrometer (TOMS) data with operational data indicates that though the zonal mean total ozone derived from TOMS is not significantly affected by these errors, localized effects in the tropics can be large enough to affect seriously the studies of tropospheric ozone that are currently undergoing using the TOMS data. C1 NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. Univ Maryland, Joint Ctr Earth Sci Technol, Baltimore, MD 21201 USA. RP Torres, O (reprint author), NASA, Goddard Space Flight Ctr, Atmospheres Lab, Code 916, Greenbelt, MD 20771 USA. EM torres@tparty.gsfc.nasa.gov RI Torres, Omar/G-4929-2013; Bhartia, Pawan/A-4209-2016 OI Bhartia, Pawan/0000-0001-8307-9137 NR 22 TC 45 Z9 47 U1 1 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD SEP 20 PY 1999 VL 104 IS D17 BP 21569 EP 21577 DI 10.1029/1999JD900410 PG 9 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 238BC UT WOS:000082690200024 ER PT J AU Johnson, DG Jucks, KW Traub, WA Chance, KV Toon, GC Russell, JM McCormick, MP AF Johnson, DG Jucks, KW Traub, WA Chance, KV Toon, GC Russell, JM McCormick, MP TI Stratospheric age spectra derived from observations of water vapor and methane SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID UARS HALOE DATA; TRANSPORT; CONVECTION; BUDGET; H2O; CH4 AB The stratospheric age spectrum is useful both as a diagnostic for testing models of stratospheric transport and as a tool for calculating the response of the stratosphere to changes in tropospheric composition. Although the age spectrum of an individual air parcel is not an observable quantity, it is possible to estimate a zonal mean age spectrum from long-term observations of a conserved tracer with sufficient temporal variability. We have constructed a conserved tracer by combining satellite and balloon-borne observations of water vapor and methane from 1986 to 1998. After discussing the possible roles of tropical sea surface temperatures and the quasi-biennial oscillation in determining stratospheric humidity, we use the observations to estimate the zonal mean age spectrum in the tropics and northern midlatitudes. The estimated age spectrum peaks at progressively greater lag times as the altitude increases above the tropopause, in agreement with model calculations. The mean age of air calculated from the derived age spectrum in the lower stratosphere is in good agreement with ages calculated from measurements of SF6, but the satellite record is still too short to calculate reliable ages from the age spectrum in the middle and upper stratosphere. C1 Smithsonian Astrophys Observ, Cambridge, MA 02138 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Hampton Univ, Dept Phys, Hampton, VA 23668 USA. RP Johnson, DG (reprint author), Smithsonian Astrophys Observ, 60 Garden St, Cambridge, MA 02138 USA. EM dgj@cfa.harvard.edu; kjucks@cfa.harvard.edu; wtraub@cfa.harvard.edu; kchance@cfa.harvard.edu; toon@mark4sun.jpl.nasa.gov; jmr@hamptonu.edu; mcc@hamptonu.edu RI Johnson, David/F-2376-2015; OI Johnson, David/0000-0003-4399-5653; Chance, Kelly/0000-0002-7339-7577 NR 28 TC 12 Z9 12 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD SEP 20 PY 1999 VL 104 IS D17 BP 21595 EP 21602 DI 10.1029/1999JD900363 PG 8 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 238BC UT WOS:000082690200027 ER PT J AU Wang, HJ Cunnold, DM Froidevaux, L Russell, JM AF Wang, HJ Cunnold, DM Froidevaux, L Russell, JM TI A reference model for middle atmosphere ozone in 1992-1993 SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID HALOGEN OCCULTATION EXPERIMENT; STRATOSPHERIC AEROSOL; POLAR VORTEX; TRENDS; VALIDATION; UARS; WAVES AB An ozone climatology for the period April 1992 to March 1993 and covering pressures from 0.1 to 100 hPa and from 80 degrees N to 80 degrees S is derived from satellite-based measurements by the Stratospheric Aerosol and Gas Experiment (SAGE), the Halogen Occultation Experiment (HALOE), and the Microwave Limb Sounder (MLS). At pressures <1 hPa, separate distributions are given for daytime and nighttime conditions. From 0.46 to 32 hPa the accuracy of the distribution is estimated to be 5%, and the precision is also similar to 5%. Estimates of atmospheric variability are provided on the basis of standard deviations of the measurements within months. Distributions of ozone monthly means and standard deviations are also given in a potential temperature, equivalent latitude coordinate system. This data set is included in the UARS reference atmosphere, and it is accessible through that web site. C1 Georgia Inst Technol, Sch Earth & Atmospher Sci, Atlanta, GA 30332 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Hampton Univ, Dept Phys, Ctr Atmospher Sci, Hampton, VA 23668 USA. RP Wang, HJ (reprint author), Georgia Inst Technol, Sch Earth & Atmospher Sci, Atlanta, GA 30332 USA. EM raywang@eas.gatech.edu; cunnold@eas.gatech.edu; lucien@nenc.jpl.nasa.gov; jmr@hamptonu.edu NR 41 TC 16 Z9 16 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD SEP 20 PY 1999 VL 104 IS D17 BP 21629 EP 21643 DI 10.1029/1999JD900412 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 238BC UT WOS:000082690200031 ER PT J AU Beard, BL Johnson, CM Cox, L Sun, H Nealson, KH Aguilar, C AF Beard, BL Johnson, CM Cox, L Sun, H Nealson, KH Aguilar, C TI Iron isotope biosignatures SO SCIENCE LA English DT Article AB The Fe-56/Fe-54 of Fe-bearing phases precipitated in sedimentary environments varies by 2.5 per mil (delta(56)Fe values of +0.9 to -1.6 per mil). In contrast, the Fe-56/Fe-54 of Fe-bearing phases in igneous rocks from Earth and the moon does not vary measurably (delta(56)Fe = 0.0 +/- 0.3 per mil). Experiments with dissimilatory Fe-reducing bacteria of the genus Shewanella algae grown on a ferrihydrite substrate indicate that the delta(56)Fe of ferrous Fe in solution is isotopically Lighter than the ferrihydrite substrate by 1.3 per mil. Therefore, the range in delta(56)Fe values of sedimentary rocks may reflect biogenic fractionation, and the isotopic composition of Fe may be used to trace the distribution of microorganisms in modern and ancient Earth. C1 Univ Wisconsin, Dept Geol & Geophys, Madison, WI 53706 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Wisconsin, Inst Great Lakes Study, Milwaukee, WI 53204 USA. RP Beard, BL (reprint author), Univ Wisconsin, Dept Geol & Geophys, 1215 W Dayton St, Madison, WI 53706 USA. NR 16 TC 231 Z9 257 U1 12 U2 81 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD SEP 17 PY 1999 VL 285 IS 5435 BP 1889 EP 1892 DI 10.1126/science.285.5435.1889 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 237CT UT WOS:000082638300042 PM 10489362 ER PT J AU Wang, JJ Keyser, LF AF Wang, JJ Keyser, LF TI Kinetics of the Cl(p-2(J)+CH4 reaction: Effects of secondary chemistry below 300 K SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID EXCITED CHLORINE ATOMS; CL+CH4->HCL+CH3 REACTION; REACTION CL+CH4->CH3+HCL; ANTARCTIC STRATOSPHERE; ATMOSPHERIC GASES; REACTION CH4+CL; ETHYL RADICALS; METHANE; METHYL; PRESSURE AB Absolute rate data for the Cl(P-2(J)) + CH4 --> HCl + CH3 reaction have been obtained from 218 to 298 K by using the discharge flow resonance fluorescence technique in helium at 1 Torr total pressure. The result at 298 K is (10.1 +/- 0.6) x 10(-14) cm(3) molecule(-1) s(-1). The temperature dependence in Arrhenius form is (6.5 +/- 0.9) x 10(-12) exp[(-1235 +/- 34)/T]. The errors given are one standard deviation; overall experimental error is estimated at +/-15%. Because of the relatively large disagreement among earlier measurements at low temperatures, the results were examined for possible effects of non-Boltzmann spin distribution and vibrational excitation of CH4, secondary chemistry of CH3 radicals, and impurities in the Cl atom and CH4 sources. There was no significant change in the observed rate constant when an efficient spin quencher, CF4, was added, and estimates indicate that vibrational partitioning in CH4 should be at the ambient reactor temperature before the start of the reaction. The results were also independent of the source of Cl atoms (microwave discharge or thermal decomposition of Cl-2) and whether CH4, was purified in situ. However, the observed rate constant did depend on initial Cl atom concentrations and to a lesser extent on CH4 concentrations. Numerical simulations were used to assess the importance of secondary chemistry over a range of reactant concentrations. C1 CALTECH, Jet Prop Lab, Atmospher Chem element Earth & Space Sci Div, Pasadena, CA 91109 USA. RP Keyser, LF (reprint author), CALTECH, Jet Prop Lab, Atmospher Chem element Earth & Space Sci Div, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 52 TC 20 Z9 20 U1 0 U2 4 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 1089-5639 J9 J PHYS CHEM A JI J. Phys. Chem. A PD SEP 16 PY 1999 VL 103 IS 37 BP 7460 EP 7469 DI 10.1021/jp9913259 PG 10 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 238JH UT WOS:000082706800011 ER PT J AU Zehavi, I Dekel, A AF Zehavi, I Dekel, A TI Evidence for a positive cosmological constant from flows of galaxies and distant supernovae SO NATURE LA English DT Article ID DENSITY FIELDS; OMEGA; VELOCITY; LIGHT AB Recent observations(1,2) of high-redshift supernovae seem to suggest that the global geometry of the Universe may be affected by a 'cosmological constant: which acts to accelerate the expansion rate with time. But these data by themselves still permit an open universe of low mass density and no cosmological constant. Here we derive an independent constraint on the lower bound to the mass density, based on deviations of galaxy velocities from a smooth universal expansion(3-7). This constraint rules out a low-density open universe with a vanishing cosmological constant, and together the two favour a nearly flat universe in which the contributions from mass density and the cosmological constant are comparable. This type of universe, however, seems to require a degree of fine tuning of the initial conditions that is in apparent conflict with 'common wisdom'. C1 Hebrew Univ Jerusalem, Racah Inst Phys, IL-91904 Jerusalem, Israel. NASA, Fermilab Astrophys Grp, Fermi Natl Accelerator Lab, Batavia, IL 60510 USA. RP Zehavi, I (reprint author), Hebrew Univ Jerusalem, Racah Inst Phys, IL-91904 Jerusalem, Israel. NR 34 TC 63 Z9 63 U1 0 U2 0 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON N1 9XW, ENGLAND SN 0028-0836 J9 NATURE JI Nature PD SEP 16 PY 1999 VL 401 IS 6750 BP 252 EP 254 DI 10.1038/45748 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 237VZ UT WOS:000082678400045 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 Dust devil vortices seen by the Mars Pathfinder camera SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SURFACE; LANDER AB Discovery of dust devil vortices in Mars Pathfinder (MPF) images reveals a dust entrainment mechanism at work on Mars. Scattering of visible light by dust in the Martian atmosphere creates a pronounced haze, preventing conventional image processing from displaying dust plumes. Spectral differencing techniques have enhanced five localized dust plumes from the general haze in images acquired near midday, which we determine to be dust devils. Processing of 440 nm images highlights dust devils as distinct occultation features against the horizon. The dust devils are interpreted to be 14-79 m wide, 46-350 m tall, travel at 0.5-4.6 mis, with dust loading of 7E-5 kg m-3, relative to the general haze of 9E-8 kg m-3, and total particulate transport of 2.2 - 700 kg. The vortices match predictions from terrestrial analog studies. 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, MS 172, 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 106 Z9 107 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 SEP 15 PY 1999 VL 26 IS 18 BP 2781 EP 2784 DI 10.1029/1999GL008341 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 237WV UT WOS:000082680300001 ER PT J AU Wohlfrom, KH Hauler, T Arnold, F Singh, H AF Wohlfrom, KH Hauler, T Arnold, F Singh, H TI Acetone in the free troposphere and lower stratosphere: Aircraft-based CIMS and GC measurements over the North Atlantic and a first comparison SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID HYDROCARBONS; CHEMISTRY; ION AB Acetone was measured in the free troposphere and lower stratosphere over the North Atlantic by aircraft-based CIMS (Chemical Ionization Mass Spectrometry) and GC (Cas Chromatography) instruments in fall 1997 within the framework of the POLINAT-2/SONEX campaigns. The measurements included 28 flights covering altitudes from 2.4 to 12.5 km, and geographic latitudes from 20 to 69 degrees N. The data are the most extensive measurements of acetone in the free troposphere and lower stratosphere published to date. A first comparison of the CIMS and the GC method is presented. The acetone data obtained by both instruments in the same air masses agree within 50% which is consistent with the uncertainty limits quoted. An inspection of all flights reveals upper tropospheric acetone to vary very substantially between 200 and 2200 pptv with a mean value of about 600 pptv. By contrast, in the lower stratosphere the acetone abundance is much less variable and is mostly around 100 to 200 pptv. Acetone rich air masses with volume mixing ratios exceeding 1000 pptv and reaching up to 2200 pptv were surprisingly frequently encountered in the upper troposphere. Probably these air masses had recent contact with the continental planetary boundary layer where they took up acetone and/or acetone precursor gases from ground-level sources. C1 MPIK Heidelberg, Atmospher Phys Div, D-69029 Heidelberg, Germany. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Wohlfrom, KH (reprint author), MPIK Heidelberg, Atmospher Phys Div, POB 103980, D-69029 Heidelberg, Germany. NR 18 TC 29 Z9 29 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 SEP 15 PY 1999 VL 26 IS 18 BP 2849 EP 2852 DI 10.1029/1999GL900597 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 237WV UT WOS:000082680300018 ER PT J AU Zhang, RH Busalacchi, AJ AF Zhang, RH Busalacchi, AJ TI A possible link between off-equatorial warm anomalies propagating along the NECC path and the onset of the 1997-98 El Nino SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID MODEL; ENSO AB By examining sea surface height (SSH) from the TOPEX/Poseidon (T/P) altimeter and upper-ocean temperature/current data from the NCEP reanalysis product, a well-defined, shallow pathway has been identified of subsurface temperature anomalies along the Pacific North Equatorial Countercurrent (NECC). A physical picture is developed to demonstrate how oceanic-atmospheric anomalies leading to the 1997-98 El Nino may be generated in the tropical Pacific climate system. Prior to its onset, a preconditioned oceanic state is set in the west during 1995-96, characterized by elevated sea level, depressed thermocline and warm temperature anomalies in the western boundary along 6-10 degrees N. With the seasonal intensification of the NECC in the fall, the warm anomalies propagated coherently eastward along the relatively shallow NECC subsurface pathways (centered about 100 m), from the western boundary in mid-1996 to near the date line in late 1996 and early 1997. As the thermocline shoals eastward and upward along the NECC, the subsurface anomalies were exposed to the surface near the date line, likely initiating warm sea surface temperature (SST) anomalies north of the equator in late 1996, Due to the convergence of mean subsurface circulation onto the equator, the equatorward flows helped move these initially subsurface-produced SST anomalies southward onto the equator, which would induce westerly wind anomalies. C1 Columbia Univ, Lamont Doherty Earth Observ, IRI, Palisades, NY 10964 USA. NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. RP Zhang, RH (reprint author), Columbia Univ, Lamont Doherty Earth Observ, IRI, Palisades, NY 10964 USA. NR 12 TC 9 Z9 10 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD SEP 15 PY 1999 VL 26 IS 18 BP 2873 EP 2876 DI 10.1029/1999GL002315 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 237WV UT WOS:000082680300024 ER PT J AU Frink, NT Pirzadeh, SZ AF Frink, NT Pirzadeh, SZ TI Tetrahedral finite-volume solutions to the Navier-Stokes equations on complex configurations SO INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS LA English DT Article; Proceedings Paper CT 10th International Conference on Finite Elements in Fluids CY JAN 05-08, 1998 CL TUCSON, ARIZONA DE finite-volume; Navier-Stokes; complex configurations ID ADVANCING-LAYERS METHOD; UNSTRUCTURED GRIDS; GENERATION; FLOWS AB A review of the algorithmic features and capabilities of the unstructured-grid flow solver USM3Dns is presented. This code, along with the tetrahedral grid generator, VGRIDns, is being extensively used throughout the USA for solving the Euler and Navier-Stokes equations on complex aerodynamic problems. Spatial discretization is accomplished by a tetrahedral cell-centered finite-volume formulation using Roe's upwind flux difference splitting. The fluxes are limited by either a Superbee or MinMod limiter. Solution reconstruction within the tetrahedral cells is accomplished with a simple, but novel, multidimensional analytical formula. Time is advanced by an implicit backward-Euler time-stepping scheme. Flow turbulence effects are modeled by the Spalart-Allmaras one-equation model, which is coupled with a wall function to reduce the number of cells in the near-wall region of the boundary layer. The issues of accuracy and robustness of USM3Dns Navier-Stokes capabilities are addressed for a flat-plate boundary layer, and a full F-16 aircraft with external stores at transonic speed. C1 NASA, Langley Res Ctr, Configurat Aerodynam Br, Hampton, VA 23681 USA. RP Frink, NT (reprint author), NASA, Langley Res Ctr, Configurat Aerodynam Br, Mail Stop 499, Hampton, VA 23681 USA. NR 26 TC 7 Z9 7 U1 0 U2 0 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX PO19 1UD, ENGLAND SN 0271-2091 J9 INT J NUMER METH FL JI Int. J. Numer. Methods Fluids PD SEP 15 PY 1999 VL 31 IS 1 BP 175 EP 187 DI 10.1002/(SICI)1097-0363(19990915)31:1<175::AID-FLD962>3.0.CO;2-V PG 13 WC Computer Science, Interdisciplinary Applications; Mathematics, Interdisciplinary Applications; Mechanics; Physics, Fluids & Plasmas SC Computer Science; Mathematics; Mechanics; Physics GA 242NE UT WOS:000082946500012 ER PT J AU Carswell, JR Donnelly, WJ McIntosh, RE Donelan, MA Vandemark, DC AF Carswell, JR Donnelly, WJ McIntosh, RE Donelan, MA Vandemark, DC TI Analysis of C and Ku band ocean backscatter measurements under low-wind conditions SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID RADAR CROSS-SECTION; SPEED; SEA; SCATTEROMETERS; SPECTRA; WAVES AB Airborne ocean backscatter measurements at C and Ku band wavelengths obtained in low to moderate-wind conditions are presented. The differences between the low-wind backscatter data and the CMOD4 and SASS-II models are reported. The measurements show that the upwind/crosswind backscatter ratio is greater than predicted. These large upwind/crosswind backscatter ratios are attributed to a rapid decrease in the crosswind backscatter at low winds. Qualitative agreement with the composite surface model proposed by Donelan and Pierson suggests the rapid decrease in the crosswind backscatter may be caused by viscous dampening of the Bragg-resonant capillary-gravity waves. We show that for larger antenna footprints typical of satellite-based scatterometers, the variability in the observed wind field smooths out the backscatter response such that the rapid decrease in the crosswind direction is not observed. C1 Univ Massachusetts, Microwave Remote Sensing Lab, Amherst, MA 01003 USA. Univ Miami, Rosenstiel Sch Marine & Atmospher Sci, Div Appl Marine Phys, Miami, FL 33149 USA. NASA, Goddard Space Flight Ctr, Wallops Island, VA 23337 USA. RP Carswell, JR (reprint author), Univ Massachusetts, Microwave Remote Sensing Lab, Amherst, MA 01003 USA. NR 20 TC 9 Z9 9 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-OCEANS JI J. Geophys. Res.-Oceans PD SEP 15 PY 1999 VL 104 IS C9 BP 20687 EP 20701 DI 10.1029/1999JC900140 PG 15 WC Oceanography SC Oceanography GA 251YD UT WOS:000083473200014 ER PT J AU Lin, B Katzberg, SJ Garrison, JL Wielicki, BA AF Lin, B Katzberg, SJ Garrison, JL Wielicki, BA TI Relationship between GPS signals reflected from sea surfaces and surface winds: Modeling results and comparisons with aircraft measurements SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID OCEAN SURFACE; BACKSCATTERING; DEPENDENCE; PARAMETERS; SYSTEM; BAND AB Theoretical calculations of global positioning system (GPS) signals reflected from rough sea surfaces are discussed and compared with the aircraft measurements. The theoretical model is based on the assumption that rough sea surfaces are composed of facets, and the reflection of GPS signals from the facets can be calculated on the basis of geometric optics. Ln-order to determine the slopes of the sea surface facets, the statistical model of Cox and Munk [1954] for ocean surface slopes is used. Since much of the sea surface roughness observed is at scales much less than the GPS wavelength, the dependence of the mean square slopes on frequency is taken into consideration. Model results agree well with aircraft measurements: the differences between model results and observations are within the level of experimental errors. For calm sea surfaces (near-sea-surface wind speeds < 1 m s(-1)), the correlation powers of the GPS signals are narrow functions of time delay with peak values of similar to 0 - -3 dB. In stronger wind cases (wind speeds > 7 m s(-1)), the correlation powers decrease their peak values to similar to -4 - -8 dB, significantly widen time delay responses, and shift toward the delays corresponding to path lengths longer than those of specular points. Sensitivity tests show that there is considerable potential for current or advanced GPS receiving systems to estimate Pear-sea-surface wind speeds: the errors in the wind speed estimates could be smaller than 2 m s(-1). For near-sea-surface wind directions, the maximum changes in the correlation powers of the GPS signals as a function of azimuth appear to be similar to 0.5 dB for current GPS receiving systems, which may be too small for wind direction estimation. New designs of the GPS receivers or a higher signal-to-noise ratio than that of current aircraft receivers may be needed. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Hampton Univ, Ctr Atmospher Sci, Hampton, VA 23668 USA. RP NASA, Langley Res Ctr, MS 420, Hampton, VA 23681 USA. EM bing@front.larc.nasa.gov NR 24 TC 19 Z9 21 U1 0 U2 7 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9275 EI 2169-9291 J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD SEP 15 PY 1999 VL 104 IS C9 BP 20713 EP 20727 DI 10.1029/1999JC900176 PG 15 WC Oceanography SC Oceanography GA 251YD UT WOS:000083473200016 ER PT J AU Gloersen, P Parkinson, CL Cavalieri, DJ Comiso, JC Zwally, HJ AF Gloersen, P Parkinson, CL Cavalieri, DJ Comiso, JC Zwally, HJ TI Spatial distribution of trends and seasonality in the hemispheric sea ice covers: 1978-1996 SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article AB We extend earlier analyses of a 8.8-year sea ice data set that described the local seasonal variations and trends in each of the hemispheric sea ice covers to the recently merged 18.2-year sea ice record from four satellite instruments. The seasonal cycle characteristics remain essentially the same as for the shorter time series, but the local trends are markedly different, in some cases reversing sign. The sign reversal reflects the lack of a consistent long-term trend and could be the result of localized long-term oscillations in the hemispheric sea ice covers. By combining the separate hemispheric sea ice records into a global one, we have shown that there are statistically significant net decreases in the sea ice coverage on a global scale. The change in the global sea ice extent is -0.01 +/- 0.003 x 10(6) km(2) per decade. The decrease in the areal coverage of the sea ice is only slightly smaller, so that the difference in the two, the ice-free areas within the packs, has no statistically significant change. C1 NASA, Goddard Space Flight Ctr, Oceans & Ice Branch, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. RP Gloersen, P (reprint author), NASA, Goddard Space Flight Ctr, Oceans & Ice Branch, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. RI Parkinson, Claire/E-1747-2012 OI Parkinson, Claire/0000-0001-6730-4197 NR 21 TC 35 Z9 38 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-OCEANS JI J. Geophys. Res.-Oceans PD SEP 15 PY 1999 VL 104 IS C9 BP 20827 EP 20835 DI 10.1029/1999JC900121 PG 9 WC Oceanography SC Oceanography GA 251YD UT WOS:000083473200022 ER PT J AU Parkinson, CL Cavalieri, DJ Gloersen, P Zwally, HJ Comiso, JC AF Parkinson, CL Cavalieri, DJ Gloersen, P Zwally, HJ Comiso, JC TI Arctic sea ice extents, areas, and trends, 1978-1996 SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID NORTH-ATLANTIC OSCILLATION; INTERANNUAL VARIABILITY; AIR-TEMPERATURE; ATMOSPHERIC CIRCULATION; COVER; FLUCTUATIONS; OCEAN; ANOMALIES; SYSTEM AB Satellite passive-microwave data for November 1978 through December 1996 reveal marked seasonal, regional, and interannual variabilities, with an overall decreasing trend of -34,300 +/- 3700 km(2)/yr (-2.8%/decade) in Arctic sea ice extents over the 18.2-year period. Decreases occur in all seasons and on a yearly average basis, although they are largest in spring and smallest in autumn. Regionally, the Kara and Barents Seas have the largest decreases, at -15,200 +/- 1900 km2(/)yr (-10.5%/decade), followed by the Seas of Okhotsk and Japan, the Arctic Ocean, Greenland Sea, Hudson Bay, and Canadian Archipelago. The yearly average trends for the total, the Kara and Barents Seas, and the Seas of Okhotsk and Japan all have high statistical significance, with the null hypothesis of a 0 slope being rejected at a 99% confidence level. Regions showing increasing yearly average ice extents are Baffin Bay/Labrador Sea, the Gulf of St. Lawrence, and the Bering Sea, with only the increases in the Gulf of St. Lawrence being statistically significant at the 99% level. Hemispheric results for sea ice areas exhibit the same -2.8%/decade decrease as for ice extents and hence a lower absolute decrease (-29,500 +/- 3800 km(2)/yr), with the ice-free area within the ice pack correspondingly decreasing at -4800 +/- 1600 km(2)/yr. Confidence levels for the trends in ice areas and ice-free water areas exceed 99% and 95%, respectively. Nonetheless, interannual variability is high, and, for instance, the Arctic Ocean ice extents have a positive trend 1990-1996, in spite of their negative trend for the time period as a whole. C1 NASA, Goddard Space Flight Ctr, Oceans & Ice Branch, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. RP Parkinson, CL (reprint author), NASA, Goddard Space Flight Ctr, Oceans & Ice Branch, Lab Hydrospher Proc, Code 971, Greenbelt, MD 20771 USA. RI Parkinson, Claire/E-1747-2012 OI Parkinson, Claire/0000-0001-6730-4197 NR 43 TC 397 Z9 437 U1 5 U2 39 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 SEP 15 PY 1999 VL 104 IS C9 BP 20837 EP 20856 DI 10.1029/1999JC900082 PG 20 WC Oceanography SC Oceanography GA 251YD UT WOS:000083473200023 ER PT J AU Sud, YC Walker, GK AF Sud, YC Walker, GK TI Microphysics of Clouds with the Relaxed Arakawa-Schubert Scheme (McRAS). Part I: Design and evaluation with GATE Phase III data SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID GENERAL-CIRCULATION MODELS; LARGE-SCALE ENVIRONMENT; CUMULUS PARAMETERIZATION; CLIMATE MODELS; ENSEMBLE MODELS; PREDICTION; ENTRAINMENT; CLOUDINESS; BUDGET; LIQUID AB A prognostic cloud scheme named McRAS (Microphysics of Clouds with Relaxed Arakawa-Schubert Scheme) has been designed and developed with the aim of improving moist processes, microphysics of clouds, and cloud-radiation interactions in GCMs. McRAS distinguishes three types of clouds: convective, stratiform, and boundary layer. The convective clouds transform and merge into stratiform clouds on an hourly timescale, while the boundary layer clouds merge into the stratiform clouds instantly. The cloud condensate converts into precipitation following the autoconversion equations of Sundqvist that contain a parametric adaptation for the Berperon-Findeisen process of ice crystal growth and collection of cloud condensate by precipitation. All clouds convect, advect, as well as diffuse both horizontally and vertically with a fully interactive cloud microphysics throughout the life cycle of the cloud, while the optical properties of clouds are derived from the statistical distribution of hydrometeors and idealized cloud geometry. An evaluation of McRAS in a single-column model (SCM) with the Global Atmospheric Research Program Atlantic Tropical Experiment (GATE) Phase III data has shown that, together with the rest of the model physics, McRAS can simulate the observed temperature, humidity, and precipitation without discernible systematic errors. The time history and time mean in-cloud water and ice distribution, fractional cloudiness, cloud optical thickness, origin of precipitation in the convective anvils and towers, and the convective updraft and downdraft velocities and mass fluxes all simulate a realistic behavior. Some of these diagnostics are not verifiable with data on hand. These SCM sensitivity tests show that (i) without clouds the simulated GATE-SCM atmosphere is cooler than observed; (ii) the model's convective scheme, RAS, is an important subparameterization of McRAS; and (iii) advection of cloud water substance is helpful in simulating better cloud distribution and cloud-radiation interaction. An evaluation of the performance of McRAS in the Goddard Earth Observing System II GCM is given in a companion paper (Part II). C1 NASA, Goddard Space Flight Ctr, Atmospheres Lab, Climate & Radiat Branch, Greenbelt, MD 20771 USA. RP Sud, YC (reprint author), NASA, Goddard Space Flight Ctr, Atmospheres Lab, Climate & Radiat Branch, Greenbelt, MD 20771 USA. NR 69 TC 78 Z9 79 U1 0 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 SEP 15 PY 1999 VL 56 IS 18 BP 3196 EP 3220 DI 10.1175/1520-0469(1999)056<3196:MOCWTR>2.0.CO;2 PG 25 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 241YZ UT WOS:000082912600002 ER PT J AU Sud, YC Walker, GK AF Sud, YC Walker, GK TI Microphysics of Clouds with the Relaxed Arakawa-Schubert Scheme (McRAS). Part II: Implementation and performance in GEOS II GCM SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID GENERAL-CIRCULATION MODEL; RADIATION BUDGET EXPERIMENT; LARGE-SCALE ENVIRONMENT; MICROWAVE IMAGER SSM/I; GLA GCM; CUMULUS PARAMETERIZATION; GLOBAL CLIMATE; LIQUID WATER; ENSEMBLE; PRECIPITATION AB A prognostic cloud scheme named the Microphysics of Clouds with the Relaxed Arakawa-Schubert Scheme (McRAS) and the Simple Biosphere Model have been implemented in a version of the Goddard Earth Observing System (CEOS) II GCM at a 4 degrees latitude x 5 degrees longitude x 20 sigma-layer resolution. The McRAS GCM was integrated for 50 months. The integration was initialized with the European Centre for Medium-Range Weather Forecasts analysis of observations for 1 January 1987 and was forced with the observed sea surface temperatures and sea-ice distribution; on land, the permanent ice and vegetation properties (biomes and soils) were climatological, while the soil moisture and snow cover were prognostic. The simulation shows that the McRAS GCM yields realistic structures of in-cloud water and ice, and cloud-radiative forcing (CRF) even though the cloudiness has some discernible systematic errors. The simulated intertropical convergence zone (ITCZ) has a realistic time mean structure and seasonal cycle. The simulated CRF is sensitive to vertical distribution of cloud water, which can be affected hugely with the choice of minimum in-cloud water for the onset of autoconversion or critical cloud water amount that regulates the autoconversion itself The generation of prognostic cloud water is accompanied by reduced global precipitation and interactive CRE These feedbacks have a profound effect on the ITCZ. Even though somewhat weaker than observed, the McRAS GCM simulation produces robust 30-60-day oscillations in the 200-hPa velocity potential. Comparisons of CRFs and precipitation produced in a parallel simulation with the GEOS II GCM are included. Several seasonal simulations were performed with the McRAS-GEOS II GCM for the summer (June-July-August) and winter (December-January-February) periods to determine how the simulated clouds and CRFs would be affected by (i) advection of clouds, (ii) cloud-top entrainment instability, (iii) cloud water inhomogeneity correction, and (iv) cloud production and dissipation in different cloud processes. The results show that each of these processes contributes to the simulated cloud fraction and CRE Because inclusion of these processes helps to improve the simulated CRE it is inferred that they would be useful to include in other cloud microphysics schemes as wall. Two ensembles of four summer (July-August-September) simulations, one each for 1987 and 1888, were produced with the earlier 17-layer GEOS I GCM with McRAS. The differences show that the model simulates realistic and statistically significant precipitation differences over India, Central America, and tropical Africa. These findings were also confirmed in the new 20-layer GEOS II GCM; with McRAS in the 1987 minus 1988 differences. C1 NASA, Goddard Space Flight Ctr, Atmospheres Lab, Climate & Radiat Branch, Greenbelt, MD 20771 USA. RP NASA, Goddard Space Flight Ctr, Atmospheres Lab, Climate & Radiat Branch, Greenbelt, MD 20771 USA. EM sud@climate.gsfc.nasa.gov NR 54 TC 29 Z9 30 U1 0 U2 3 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0022-4928 EI 1520-0469 J9 J ATMOS SCI JI J. Atmos. Sci. PD SEP 15 PY 1999 VL 56 IS 18 BP 3221 EP 3240 DI 10.1175/1520-0469(1999)056<3221:MOCWTR>2.0.CO;2 PG 20 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 241YZ UT WOS:000082912600003 ER PT J AU Arneodo, A Manneville, S Muzy, JF Roux, SG AF Arneodo, A Manneville, S Muzy, JF Roux, SG TI Revealing a lognormal cascading process in turbulent velocity statistics with wavelet analysis SO PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES LA English DT Article DE turbulence; wavelet analysis; intermittency; self-similarity; cascade models; multifractals ID FULLY-DEVELOPED TURBULENCE; REYNOLDS-NUMBER TURBULENCE; EXTENDED SELF-SIMILARITY; PROBABILITY DENSITY-FUNCTIONS; LOG-POISSON STATISTICS; MULTIFRACTAL FORMALISM; DISSIPATION RANGE; FRACTAL SIGNALS; DYNAMICAL MODEL; FLOWS AB We use the continuous wavelet transform to extract a cascading process from experimental turbulent velocity signals. We mainly investigate various statistical quantities such as the singularity spectrum, the self-similarity kernel and space-scale correlation functions, which together provide information about the possible existence and nature of the underlying multiplicative structure. We show that, at the highest accessible Reynolds numbers, the experimental data do not allow us to distinguish various phenomenological cascade models recently proposed to account for intermittency from their lognormal approximation. In addition, we report evidence that velocity fluctuations are not scale-invariant but possess more complex self-similarity properties, which are likely to depend on the Reynolds number. We comment on the possible asymptotic validity of the multifractal description. C1 Ctr Rech Paul Pascal, F-33600 Pessac, France. ESPCI, Lab Ondes & Acoust, F-75005 Paris, France. NASA, Goddard Space Flight Ctr, Climate & Radiat Branch, Greenbelt, MD 20771 USA. RP Ctr Rech Paul Pascal, Ave A Schweitzer, F-33600 Pessac, France. NR 64 TC 36 Z9 36 U1 2 U2 7 PU ROYAL SOC PI LONDON PA 6-9 CARLTON HOUSE TERRACE, LONDON SW1Y 5AG, ENGLAND SN 1364-503X EI 1471-2962 J9 PHILOS T R SOC A JI Philos. Trans. R. Soc. A-Math. Phys. Eng. Sci. PD SEP 15 PY 1999 VL 357 IS 1760 BP 2415 EP 2438 PG 24 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 243LL UT WOS:000082998700003 ER PT J AU Avishai, Y Band, Y Brown, D AF Avishai, Y Band, Y Brown, D TI Conductance distribution between Hall plateaus SO PHYSICAL REVIEW B LA English DT Article ID QUANTUM; FLUCTUATIONS; TRANSITION; EDGE AB Mesoscopic fluctuations of two-port conductance and four-port resistance between Hall plateaus an studied within a realistic model for a two-dimensional electron gas in a perpendicular magnetic field and a smooth disordered potential. The two-port conductance distribution P(g) is concave between g=0 and g=1 and is nearly flat between g=0.2 and g=0.8. These characteristics are consistent with recent observations. The distribution is found to be sharply peaked near the end points g=0 and g=1. The distribution functions for the three independent resistances in a four-port Hall bar geometry are, on the ether hand, characterized by a central peak and a relatively large width. C1 Ben Gurion Univ Negev, Dept Phys, IL-84105 Beer Sheva, Israel. NTT, Basic Res Labs, Atsugi, Kanagawa, Japan. Ben Gurion Univ Negev, Dept Chem, IL-84105 Beer Sheva, Israel. Goddard Inst Space Studies, New York, NY 10025 USA. RP Avishai, Y (reprint author), Ben Gurion Univ Negev, Dept Phys, IL-84105 Beer Sheva, Israel. NR 22 TC 7 Z9 7 U1 0 U2 0 PU AMER PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 1098-0121 EI 1550-235X J9 PHYS REV B JI Phys. Rev. B PD SEP 15 PY 1999 VL 60 IS 12 BP 8992 EP 8998 DI 10.1103/PhysRevB.60.8992 PG 7 WC Physics, Condensed Matter SC Physics GA 241EB UT WOS:000082868800090 ER PT J AU Leon, R Marcinkevicius, S Liao, XZ Zou, J Cockayne, DJH Fafard, S AF Leon, R Marcinkevicius, S Liao, XZ Zou, J Cockayne, DJH Fafard, S TI Ensemble interactions in strained semiconductor quantum dots SO PHYSICAL REVIEW B LA English DT Article ID VISIBLE LUMINESCENCE; ISLAND FORMATION; EXCITED-STATES; INAS ISLANDS; GROWTH; NUCLEATION; GAAS; TRANSFORMATION; EQUILIBRIUM; TRANSITIONS AB Large variations in InxGa1-xAs quantum dot concentrations were obtained with simultaneous growths on vicinal GaAs [001] substrates with different surface step densities. It was found that decreasing dot-dot separation blueshifts all levels, narrows intersublevel transition energies, shortens luminescence decay times for excited states, and increases inhomogeneous photoluminescence broadening. These changes in optical properties are attributed to a progressive strain deformation of the confining potentials and to the increasing effects of positional disorder in denser dot ensembles. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91009 USA. Royal Inst Technol, Dept Phys Opt 2, S-10044 Stockholm, Sweden. Univ Sydney, Australian Key Ctr Microscopy & Microanal, Sydney, NSW 2006, Australia. Natl Res Council Canada, Inst Microstruct Sci, Ottawa, ON K1A 0R6, Canada. RP Leon, R (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91009 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 39 TC 37 Z9 37 U1 0 U2 3 PU AMER PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 1098-0121 EI 1550-235X J9 PHYS REV B JI Phys. Rev. B PD SEP 15 PY 1999 VL 60 IS 12 BP R8517 EP R8520 DI 10.1103/PhysRevB.60.R8517 PG 4 WC Physics, Condensed Matter SC Physics GA 241EB UT WOS:000082868800026 ER PT J AU Vanlandingham, KM Starrfield, S Shore, SN Sonneborn, G AF Vanlandingham, KM Starrfield, S Shore, SN Sonneborn, G TI Elemental abundances for Nova LMC 1990#1 SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE stars, individual, Nova LMC 1990 1; novae, cataclysmic variables; ultraviolet, stars ID LARGE MAGELLANIC CLOUD; HERCULIS 1991; EXTINCTION; EVOLUTION; DUST; GAS AB We present our analysis of the UV spectra of the fast ONeMg Nova LMC 1990#1, Observations with the IUE began on 1990 January 18 and continued through to 1990 March 15, We have analysed these spectra; and determined line fluxes and physical parameters as a function of time, Using both He II lines and the Balmer decrement, we find the reddening for the nova to be E(B - V) similar or equal to 0.22, Using the photoionization code CLOUDY 90.03b and the minimization routine MINUIT, We derive elemental abundances for the ejecta, We find the following abundances, relative to solar material: He = 1, C = 8, N = 109, O = 20, Ne = 62, Mg = 16, Al = 257 and Si = 41. These results are based on independent fits to different data sets acquired three weeks apart. These abundances are extremely similar to those found for V693 Corona Austrinae 1981, Given the position of V693 CrA in the Galaxy and the range of distances found for it, the similar abundances imply that the V693 CrA outburst took place on an older population white dwarf. The high N/O ratio implies an outburst on a massive white dwarf. C1 Arizona State Univ, Dept Phys & Astron, Tempe, AZ 85287 USA. Indiana Univ, Dept Phys & Astron, South Bend, IN 46634 USA. NASA, Astron & Solar Phys Lab, GSFC, Greenbelt, MD 20771 USA. RP Vanlandingham, KM (reprint author), Arizona State Univ, Dept Phys & Astron, Tempe, AZ 85287 USA. NR 25 TC 23 Z9 23 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 SEP 11 PY 1999 VL 308 IS 2 BP 577 EP 587 DI 10.1046/j.1365-8711.1999.02731.x PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 240GR UT WOS:000082818000023 ER PT J AU Meier, DL AF Meier, DL TI A magnetically switched, rotating black hole model for the production of extragalactic radio jets and the Fanaroff and Riley class division SO ASTROPHYSICAL JOURNAL LA English DT Article DE black hole physics; galaxies : jets; hydrodynamics; MHD; relativity; stars : rotation ID ACTIVE GALACTIC NUCLEI; ACCRETION DISKS; RELATIVISTIC JETS; MAGNETOHYDRODYNAMIC SIMULATIONS; SURFACE PHOTOMETRY; GALAXIES; DRIVEN; LUMINOSITY; APPEARANCE; EVOLUTION AB A model is presented in which both Fanaroff and Riley (FR) class I and II extragalactic jets are produced by magnetized accretion disk coronae in the ergospheres of rotating black holes. It employs a hybrid version of the Blandford-Payne and Blandford-Znajek magnetohydrodynamic mechanisms (similar to the Punsly-Coroniti model, with the addition of a metric shear-driven dynamo) and a generalized form of the magnetic switch, which is shown to be the MHD analog of the Eddington luminosity. While the jets are produced in the ergospheric accretion disk itself, the output power still is an increasing function of the black hole angular momentum. For high enough spin, the black hole triggers the magnetic switch, producing highly relativistic, kinetic energy-dominated jets instead of magnetic energy-dominated jets for lower spin. The coronal mass densities needed to trigger the switch at the observed FR break power are quite small (similar to 10(-15) g cm(-3)), implying that the source of the jet material may be either a pair plasma or very tenuous electron-proton corona, not the main accretion disk itself. The model explains the differences in morphology and Mach number between FR I and II sources and the observed trend for massive galaxies (which contain more massive black holes) to undergo the FR I/II transition at higher radio power. It also is consistent with the energy content of extended radio lobes and explains why, because of black hole spin-down, the space density of FR II sources should evolve more rapidly than that of FR I sources. A specific observational test is proposed to distinguish between models like this one, in which the FR I/II division arises from processes near the black hole, and models like Bicknell's, in which the difference is produced by processes in the host galaxy's interstellar medium. If the present model is correct, then the ensemble average speed of parsec-scale jets in sources distinguished by their FR I morphology, (not luminosity) should be distinctly slower than that for sources with FR II morphology. The model also suggests the existence of a population of high-redshift, sub-mJy FR I and II radio sources associated with spiral or prespiral galaxies that flared once when their black holes were formed but were never again rekindled by mergers. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Meier, DL (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 62 TC 158 Z9 159 U1 0 U2 2 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 10 PY 1999 VL 522 IS 2 BP 753 EP 766 DI 10.1086/307671 PN 1 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 232FL UT WOS:000082360200014 ER PT J AU Stothers, RB Chin, CW AF Stothers, RB Chin, CW TI The brightest supergiants predicted by theory SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars : evolution; stars : interiors; stars : mass loss; stars : oscillations; supergiants ID WOLF-RAYET STARS; MASS-LOSS RATES; LUMINOUS BLUE VARIABLES; HERTZSPRUNG-RUSSELL DIAGRAM; MAGELLANIC-CLOUDS; STELLAR EVOLUTION; AG-CARINAE; O-STARS; GALAXY; MODELS AB The distribution of the brightest Galactic supergiants on the Hertzsprung-Russell diagram is studied here with the help of new theoretical evolutionary tracks for very massive stars. The shapes of the new tracks are determined largely by stellar wind mass loss during the main-sequence phase. In contrast to earlier theoretical work, the tracks for stars with the highest initial masses point down the main sequence and converge to essentially the same unique end product, which then evolves toward the region of red supergiants. Enhanced mass loss due to ionization-induced dynamical instability in the star's outer envelope eventually terminates the redward movement. In these two ways, mass loss imposes upper limits on the predicted luminosities for extreme OB supergiants, yellow hypergiants, and red supergiants. By adopting standard mass-loss rates for main-sequence stars, the new evolutionary tracks are found to account satisfactorily for the empirical supergiant luminosity limits determined by Humphreys & Davidson and by de Jager. Success is somewhat more mixed when main-sequence mass-loss rates 3 times larger (as suggested by some recent observational studies) are adopted. C1 NASA, Goddard Space Flight Ctr, Inst Space Studies, New York, NY 10025 USA. RP Stothers, RB (reprint author), NASA, Goddard Space Flight Ctr, Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. NR 38 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 SEP 10 PY 1999 VL 522 IS 2 BP 960 EP 964 DI 10.1086/307680 PN 1 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 232FL UT WOS:000082360200030 ER PT J AU Ferraro, FR Paltrinieri, B Rood, RT Dorman, B AF Ferraro, FR Paltrinieri, B Rood, RT Dorman, B TI Blue straggler stars: The spectacular population in M80 SO ASTROPHYSICAL JOURNAL LA English DT Article DE blue stragglers; globular clusters : individual (M80); stars : evolution; ultraviolet : stars ID GALACTIC GLOBULAR-CLUSTERS; CCD PHOTOMETRY; CORE; 47-TUCANAE; DIAGRAMS AB Using Hubble Space Telescope WFPC2 observations in two ultraviolet (UV) filters (F225W and F336W) of the central region of the high-density Galactic globular cluster (GGC) M80, we have identified 305 blue straggler stars (BSS), which represents the largest and most concentrated population of BSS ever observed in a GGC. We also identify the largest clean sample of evolved BSS yet found. The high stellar density alone cannot explain the BSS, and we suggest that in M80 we are witnessing a transient dynamical state, during which stellar interactions are delaying the core-collapse process leading to an exceptionally large population of collisional BSS. C1 European So Observ, D-85748 Garching, Germany. Osservatorio Astron Bologna, I-40127 Bologna, Italy. Univ La Sapienza, Inst Astron, I-00185 Rome, Italy. Univ Virginia, Dept Astron, Charlottesville, VA 22903 USA. Raytheon STX, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Ferraro, FR (reprint author), European So Observ, Karl Schwarzschild Str 2, D-85748 Garching, Germany. NR 28 TC 94 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 SEP 10 PY 1999 VL 522 IS 2 BP 983 EP 990 DI 10.1086/307700 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 232FL UT WOS:000082360200033 ER PT J AU Albrow, MD Beaulieu, JP Caldwell, JAR Dominik, M Greenhill, J Hill, K Kane, S Martin, R Menzies, J Naber, RM Pel, JW Pollard, K Sackett, PD Sahu, KC Vermaak, P Watson, R Williams, A Sahu, MS AF Albrow, MD Beaulieu, JP Caldwell, JAR Dominik, M Greenhill, J Hill, K Kane, S Martin, R Menzies, J Naber, RM Pel, JW Pollard, K Sackett, PD Sahu, KC Vermaak, P Watson, R Williams, A Sahu, MS CA PLANET Collaboration TI Limb darkening of a K giant in the galactic bulge: Planet photometry of MACHO 97-BLG-28 SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries : visual; gravitational lensing; stars : fundamental parameters; stars : late-type ID BINARY MICROLENSING EVENT; FINITE SOURCE SIZES; ANGULAR DIAMETER; LIGHT CURVES; EFFECTIVE TEMPERATURES; ALPHA-ORIONIS; STARS; COEFFICIENTS; RADII; SUPERGIANTS AB We present the PLANET photometric data set(10) for the binary-lens microlensing event MACHO 97-BLG-28, consisting of 696 I- and V-band measurements, and analyze it to determine the radial surface brightness profile of the Galactic bulge source star. The microlensed source, demonstrated to be a K giant by our independent spectroscopy, crossed an isolated cusp of the central caustic of the lensing binary, generating a sharp peak in the light curve that was well-resolved by dense (3-30 minute) and continuous monitoring from PLANET sites in Chile, South Africa, and Australia. This is the first time that such a cusp crossing has been observed. Analysis of the PLANET data set has produced a measurement of the square-root limb-darkening coefficients of the source star in the I and V bands; the resulting stellar profiles are in excellent agreement with those predicted by stellar atmospheric models for K giants. The limb-darkening coefficients presented here are the first derived from microlensing. They are also among the first found for normal giants by any technique and the first for any star as distant as the Galactic bulge. Modeling of our light curve for MACHO 97-BLG-28 indicates that the lensing binary has a mass ratio q = 0.23 and an (instantaneous) separation in units of the angular Einstein ring radius of d = 0.69. For a lens in the Galactic bulge, this corresponds to a typical stellar binary with a projected separation between 1 and 2 AU. If the lens lies closer (i.e., in the Galactic disk), the separation is smaller, and one or both of the lens objects is in the brown dwarf regime. Assuming that the source is a bulge K2 giant at 8 kpc, the relative lens-source proper motion is mu = 19.4 +/- 2.6 km s(-1) kpc(-1), consistent with a disk or bulge lens. If the nonlensed blended light is due to a single star, it is likely to be a young white dwarf in the bulge, consistent with the blended light coming from the lens itself. C1 S African Astron Observ, ZA-7935 Cape Town, South Africa. Univ Canterbury, Dept Phys & Astron, Christchurch 1, New Zealand. Kapteyn Astron Inst, NL-9700 AV Groningen, Netherlands. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Univ Dortmund, Inst Phys, D-44221 Dortmund, Germany. Univ Tasmania, Dept Phys, Hobart, Tas 7001, Australia. Perth Observ, Perth, WA 6076, Australia. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Natl Opt Astron Observ, Tucson, AZ 85719 USA. RP Albrow, MD (reprint author), S African Astron Observ, POB 9, ZA-7935 Cape Town, South Africa. RI Kane, Stephen/B-4798-2013; Greenhill, John/C-8367-2013; Williams, Andrew/K-2931-2013 OI Williams, Andrew/0000-0001-9080-0105 NR 65 TC 80 Z9 80 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 SEP 10 PY 1999 VL 522 IS 2 BP 1011 EP 1021 DI 10.1086/307681 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 232FL UT WOS:000082360200035 ER PT J AU Mitrofanov, IG Anfimov, DS Litvak, ML Sanin, AB Saevich, YY Briggs, MS Paciesas, WS Pendleton, GN Preece, RD Koshut, TM Fishman, GJ Meegan, CA Lestrade, JP AF Mitrofanov, IG Anfimov, DS Litvak, ML Sanin, AB Saevich, YY Briggs, MS Paciesas, WS Pendleton, GN Preece, RD Koshut, TM Fishman, GJ Meegan, CA Lestrade, JP TI The emission time of gamma-ray bursts SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays : bursts AB The concept of emission time tau(N) is suggested as a temporal parameter which is complementary to the classical parameters of duration times T-50 and T-90. The emission time is defined as the time of emission of N% of the total fluence. The definition adds the time bins of high fluence in decreasing fluence rank until N% of the fluence has been reached. The emission time interval excludes low-emission intervals of bursts, and so the emission time characterizes the state of high-power emission. The distribution of this new parameter is found to be bimodal for bright bursts. The distributions of emission time tau(30) and tau(50), for groups based on burst intensity, are also compared. C1 Moscow Space Res Inst, Moscow 117810, Russia. Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Mississippi State Univ, Dept Phys, Mississippi State, MS USA. RP Mitrofanov, IG (reprint author), Moscow Space Res Inst, Profsojuznaya St 84-32, Moscow 117810, Russia. OI Preece, Robert/0000-0003-1626-7335 NR 7 TC 26 Z9 26 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 SEP 10 PY 1999 VL 522 IS 2 BP 1069 EP 1078 DI 10.1086/307688 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 232FL UT WOS:000082360200040 ER PT J AU Osherovich, V Titarchuk, L AF Osherovich, V Titarchuk, L TI Kilohertz quasi-periodic oscillations in neutron star binaries modeled as Keplerian oscillations in a rotating frame of reference SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; radiation mechanisms : thermal; stars : neutron; X-rays : general ID MINIMUM AB Since the discovery of kHz quasi-periodic oscillations (QPOs) in neutron star binaries, the difference between peak frequencies of two modes in the upper part of the spectrum, i.e., Delta omega = omega(h) - omega(K) has been studied extensively. The idea that Delta omega is constant and (as a beat frequency) is related to the rotational frequency of the neutron star has been tested previously. The observed decrease of Delta omega when omega(h) and omega(K) increase has weakened the beat frequency interpretation. We put forward a different paradigm: a Keplerian oscillator under the influence of the Coriolis force. For such an oscillator, omega(h) and the assumed Keplerian frequency omega(K) hold an upper hybrid frequency relation: omega(h)(2) - omega(K)(2) = 4 Omega(2), where Omega is the rotational frequency of the star's magnetosphere near the equatorial plane. For three sources (Sco X-1, 4U 1608-52, and 4U 1702-429), we demonstrate that the solid-body rotation Omega = Omega(0) = const. is a good first order approximation. Within the second-order approximation, the slow variation of Omega as a function of omega(K) reveals the structure of the magnetospheric differential rotation. For Sco X-1, the QPOs have frequencies similar to 45 and 90 Hz which we interpret as the first and second harmonics of the lower branch of the Keplerian oscillations for the rotator with Omega not aligned with the normal of the disk: omega(L)/2 pi = (Omega/pi)(omega(K)/omega(h)) sin delta, where delta is the angle between Omega and the vector normal to the disk. C1 NASA, Goddard Space Flight Ctr, RITSS, Greenbelt, MD 20771 USA. George Mason Univ, CSI, Fairfax, VA 22030 USA. RP Osherovich, V (reprint author), NASA, Goddard Space Flight Ctr, RITSS, Greenbelt, MD 20771 USA. NR 23 TC 76 Z9 77 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 SEP 10 PY 1999 VL 522 IS 2 BP L113 EP L116 DI 10.1086/312225 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 232FN UT WOS:000082360400009 ER PT J AU Xu, RX Qiao, GJ Zhang, B AF Xu, RX Qiao, GJ Zhang, B TI PSR 0943+10: A bare strange star? SO ASTROPHYSICAL JOURNAL LA English DT Article DE elementary particles; pulsars : general; pulsars : individual (PSR 0943+10); stars : neutron ID STRONG MAGNETIC-FIELDS; INVERSE COMPTON-SCATTERING; BOUND PAIR CREATION; PULSAR POLAR CAPS; VARIATIONAL CALCULATION; CONDENSED MATTER; EMPIRICAL-THEORY; EMISSION; GAPS; RADIATION AB Recent work by Rankin & Deshpande strongly suggests that there exist strong "microstorms" rotating around the magnetic axis of the 1.1 s pulsar PSR 0943+10. Such a feature hints that most probably the large-voltage vacuum gap proposed by Ruderman & Sutherland (RS) does exist in the pulsar polar cap. However, there are severe arguments against the formation of the RS-type gap in pulsars, since the binding energies of both the Fe-56 ions and the electrons in a neutron star's surface layer are too small to prevent thermionic ejection of the particles from the surface. Here we propose that PSR 0943+10 (and probably also all of the other "drifting" pulsars) might be bare strange stars rather than normal neutron stars, in which the "binding energy" at the surface is merely infinity for the case of either a "pulsar" or an "antipulsar." It is further proposed that identifying a drifting pulsar as an antipulsar is the key criterion for distinguishing strange stars from neutron stars. C1 Chinese Acad Sci, Beijing Astron Observ, Beijing 100012, Peoples R China. Chinese Acad Sci, Natl Astron Observ, Beijing 100012, Peoples R China. Peking Univ, CAS, Beijing Astrophys Ctr, Beijing 100871, Peoples R China. Peking Univ, Dept Astron, Beijing 100871, Peoples R China. China Ctr Adv Sci & Technol, World Lab, Beijing 100080, Peoples R China. NASA, High Energy Astrophys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Xu, RX (reprint author), Chinese Acad Sci, Beijing Astron Observ, Beijing 100012, Peoples R China. NR 43 TC 64 Z9 65 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 SEP 10 PY 1999 VL 522 IS 2 BP L109 EP L112 DI 10.1086/312226 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 232FN UT WOS:000082360400008 ER PT J AU Usher, JM Fernandes, KJ AF Usher, JM Fernandes, KJ TI An object-oriented application of tool selection in dynamic process planning SO INTERNATIONAL JOURNAL OF PRODUCTION RESEARCH LA English DT Article ID SYSTEMS; INTEGRATION; DESIGN; MODEL; CAPP AB Tool selection is a vital function within any process planning system. This paper presents an approach to computer-aided tool selection that has the ability to generate and rank all alternative tool sets for a process plan. This approach has been used to develop the OATS (Object-oriented Application of Tool Selection) system. OATS is designed for use as a module within a dynamic process planning system and has been tested as a part of the dynamic planning system, PARIS (Process planning Architecture for Integration with Scheduling) (Usher and Fernandes 1996a, b). The necessary input data for this system are taken from a product model based on the ISQ STEP application protocol, AP224. Two alternative plans for a single part are used as examples to illustrate the approach and demonstrate the ability of the system to generate and rank all the viable alternative tool sets. C1 Mississippi State Univ, Dept Ind Engn, Mississippi State, MS 39762 USA. NASA, John C Stennis Space Ctr, Boeing N Amer Inc, Stennis Space Ctr, MS 39529 USA. RP Usher, JM (reprint author), Mississippi State Univ, Dept Ind Engn, 125 McCain Bldg,Box 9542, Mississippi State, MS 39762 USA. RI Usher, John/E-7762-2013 OI Usher, John/0000-0002-4762-6989 NR 30 TC 7 Z9 7 U1 0 U2 0 PU TAYLOR & FRANCIS LTD PI LONDON PA ONE GUNPOWDER SQUARE, LONDON EC4A 3DE, ENGLAND SN 0020-7543 J9 INT J PROD RES JI Int. J. Prod. Res. PD SEP 10 PY 1999 VL 37 IS 13 BP 2879 EP 2894 DI 10.1080/002075499190329 PG 16 WC Engineering, Industrial; Engineering, Manufacturing; Operations Research & Management Science SC Engineering; Operations Research & Management Science GA 227XY UT WOS:000082106300001 ER PT J AU Concus, P Finn, R Weislogel, M AF Concus, P Finn, R Weislogel, M TI Capillary surfaces in an exotic container: results from Space experiments SO JOURNAL OF FLUID MECHANICS LA English DT Article AB Experimental results from the Interface Configuration Experiment (ICE) performed aboard the Space Shuttle and the Mir Space Station are reported. The experiment concerns fluid interfaces in certain 'exotic' containers in a low-gravity environment. These containers are rotationally symmetric and have the property that for given contact angle and liquid volume, a continuum of distinct rotationally symmetric equilibrium configurations can appear, all of which have the same mechanical energy. These symmetric equilibrium configurations are unstable, in that deformations that are not rotationally symmetric can be shown mathematically to yield configurations with lower energy. It is found experimentally, in confirmation of mathematical results and of numerical computations, that distinct locally stable configurations can form that are not rotationally symmetric and have differing dynamic characteristics. It is found that this intriguing phenomenon of asymmetric local energy minimizers can occur even if conditions for an exotic container are not entirely met. 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 14 TC 9 Z9 9 U1 0 U2 4 PU CAMBRIDGE UNIV PRESS PI NEW YORK PA 40 WEST 20TH STREET, NEW YORK, NY 10011-4211 USA SN 0022-1120 J9 J FLUID MECH JI J. Fluid Mech. PD SEP 10 PY 1999 VL 394 BP 119 EP 135 DI 10.1017/S0022112099005789 PG 17 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 238AW UT WOS:000082689600006 ER PT J AU Randel, WJ Stolarski, RS Cunnold, DM Logan, JA Newchurch, MJ Zawodny, JM AF Randel, WJ Stolarski, RS Cunnold, DM Logan, JA Newchurch, MJ Zawodny, JM TI Atmosphere - Trends in the vertical distribution of ozone SO SCIENCE LA English DT Review AB Analyses of satellite, ground-based, and balloon measurements allow updated estimates of trends in the vertical profile of ozone since 1979. The results show overall consistency among several independent measurement systems, particularly for northern hemisphere midlatitudes where most balloon and ground-based measurements are made. Combined trend estimates over these Latitudes for the period 1979-96 show statistically significant negative trends at all altitudes between 10 and 45 km, with two Local extremes: -7.4 +/- 2.0% per decade at 40 km and -7.3 +/- 4.6% per decade at 15 km altitude. There is a strong seasonal variation in trends over northern midlatitudes in the altitude range of 10 to 18 km, with the Largest ozone loss during winter and spring. The profile trends are in quantitative agreement with independently measured trends in column ozone, the amount of ozone in a column above the surface. The vertical profiles of ozone trends provide a fingerprint for the mechanisms of ozone depletion over the last two decades. C1 Natl Ctr Atmospher Res, Boulder, CO 80307 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Georgia Inst Technol, Atlanta, GA 30332 USA. Harvard Univ, Cambridge, MA 02138 USA. Univ Alabama, Huntsville, AL 35899 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Randel, WJ (reprint author), Natl Ctr Atmospher Res, POB 3000, Boulder, CO 80307 USA. RI Stolarski, Richard/B-8499-2013; Randel, William/K-3267-2016 OI Stolarski, Richard/0000-0001-8722-4012; Randel, William/0000-0002-5999-7162 NR 11 TC 79 Z9 85 U1 0 U2 10 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD SEP 10 PY 1999 VL 285 IS 5434 BP 1689 EP 1692 DI 10.1126/science.285.5434.1689 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 234EY UT WOS:000082472600025 ER PT J AU Bradley, JP Keller, LP Snow, TP Hanner, MS Flynn, GJ Gezo, JC Clemett, SJ Brownlee, DE Bowey, JE AF Bradley, JP Keller, LP Snow, TP Hanner, MS Flynn, GJ Gezo, JC Clemett, SJ Brownlee, DE Bowey, JE TI An infrared spectral match between GEMS and interstellar grains SO SCIENCE LA English DT Article ID INTERPLANETARY DUST PARTICLES; SILICATE MINERALOGY; FEATURES; CLOUD; STEPS; STARS AB Infrared spectral properties of silicate grains in interplanetary dust particles (IDPs) were compared with those of astronomical silicates. The similar to 10-micrometer silicon-oxygen stretch bands of IDPs containing enstatite (MgSiO3), forsterite (Mg2SiO4), and glass with embedded metal and sulfides (GEMS) exhibit fine structure and bandwidths similar to those of solar system comets and some pre-main sequence Herbig Ae/Be stars. Some GEMS exhibit a broad, featureless silicon-oxygen stretch band similar to those observed in interstellar molecular clouds and young stellar objects. These GEMS provide a spectral match to astronomical "amorphous" silicates, one of the fundamental building blocks from which the solar system is presumed to have formed. C1 MVA Inc, Norcross, GA 30093 USA. Georgia Inst Technol, Sch Mat Sci & Engn, Atlanta, GA 30332 USA. Univ Colorado, Ctr Astrophys & Space Astron, Boulder, CO 80309 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Washington, Dept Astron, Seattle, WA 98195 USA. SUNY Coll Plattsburgh, Plattsburgh, NY 12901 USA. Univ London Queen Mary & Westfield Coll, Dept Phys, London E1 4NS, England. RP Bradley, JP (reprint author), MVA Inc, Norcross, GA 30093 USA. NR 60 TC 154 Z9 155 U1 0 U2 4 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD SEP 10 PY 1999 VL 285 IS 5434 BP 1716 EP 1718 DI 10.1126/science.285.5434.1716 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 234EY UT WOS:000082472600030 PM 10481004 ER PT J AU Gupta, KK Lawson, CL AF Gupta, KK Lawson, CL TI Structural vibration analysis by a progressive simultaneous iteration method SO PROCEEDINGS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES LA English DT Article DE structural vibrations; progressive simultaneous iteration; finite-element method; eigenvalue problem; mass orthonormalization; Lanczos method ID LANCZOS-ALGORITHM AB This paper provides details of a newly developed structural eigenproblem solution technique that effects simultaneous convergence of a set of desired roots and associated vectors in an accurate and efficient fashion. The procedure is based on a progressive simultaneous iteration method that enables effective computation of either the first few or a specified number of intermediate roots and associated vectors without having to compute any other. Numerical results pertaining to some practical problems are also presented that testify to the superior convergence characteristics of the present procedure when compared with other existing ones. C1 NASA, Dryden Flight Res Ctr, Edwards, CA 93523 USA. RP Gupta, KK (reprint author), NASA, Dryden Flight Res Ctr, POB 273, Edwards, CA 93523 USA. NR 6 TC 3 Z9 3 U1 0 U2 0 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 SEP 8 PY 1999 VL 455 IS 1989 BP 3415 EP 3423 PG 9 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 237KH UT WOS:000082654900013 ER PT J AU Draper, DS Brandon, AD Becker, H AF Draper, DS Brandon, AD Becker, H TI Interactions between slab and sub-are mantle: Dehydration, melting and element transport in subduction zones SO CHEMICAL GEOLOGY LA English DT Editorial Material C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Univ Maryland, Dept Geol, College Pk, MD 20742 USA. RP Draper, DS (reprint author), NASA, Lyndon B Johnson Space Ctr, Mail Code SN, Houston, TX 77058 USA. NR 0 TC 3 Z9 4 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0009-2541 J9 CHEM GEOL JI Chem. Geol. PD SEP 2 PY 1999 VL 160 IS 4 BP 251 EP 253 PG 3 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 233XM UT WOS:000082452500001 ER PT J AU Abdel-Tawab, K Noor, AK AF Abdel-Tawab, K Noor, AK TI Uncertainty analysis of welding residual stress fields SO COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING LA English DT Article ID PHASE-TRANSFORMATION; MODEL AB A fuzzy-set approach is applied in conjunction with a finite element procedure to study the effect of uncertainty in material properties on welding residual stress fields. The study focuses on steels that undergo martensitic transformations during the cool-down part of the weld thermal cycle. Uncoupled thermo-mechanical analysis is performed. Filler metal deposition, various convective-radiative energy losses, and latent heat generation are included in modeling of the welding process. A rate-independent thermo-elasto-plastic material model with nonlinear kinematic hardening is adopted in the study. Account is taken of the metallurgical transformations that occur during the entire weld thermal cycle. The material model is validated by comparing its predictions with existing experimental measurements of the welding residual mechanical fields. Fuzzy logic is then used to study the variability in the residual stress field due to pre-selected ranges of variation in material parameters associated with the martensitic transformations. It is found that the variations in material parameters considered have a significant effect on the welding residual stress held. Published by Elsevier Science S.A. C1 Univ Virginia, NASA Langley Res Ctr, Ctr Adv Computat Technol, Hampton, VA 23681 USA. GE, Corp Res & Dev, Mech Engn Lab, Schenectady, NY 12301 USA. RP Noor, AK (reprint author), Univ Virginia, NASA Langley Res Ctr, Ctr Adv Computat Technol, Mail Stop 201, Hampton, VA 23681 USA. NR 27 TC 11 Z9 13 U1 0 U2 4 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0045-7825 J9 COMPUT METHOD APPL M JI Comput. Meth. Appl. Mech. Eng. PD SEP 2 PY 1999 VL 179 IS 3-4 BP 327 EP 344 DI 10.1016/S0045-7825(99)00045-6 PG 18 WC Engineering, Multidisciplinary; Mathematics, Interdisciplinary Applications; Mechanics SC Engineering; Mathematics; Mechanics GA 247HA UT WOS:000083214300006 ER PT J AU Ji, Y Yao, XS Maleki, L AF Ji, Y Yao, XS Maleki, L TI Compact optoelectronic oscillator with ultralow phase noise performance SO ELECTRONICS LETTERS LA English DT Article AB A compact optoelectronic oscillator (OEO) is presented which is using constructed using a DFB laser. a semiconductor Mach-Zehnder modulator, and a dielectric resonator based RF filter. The achieved phase noise is -50dBc/Hz at 10Hz and -130dBc/Hz at 10kHz from a 10GHz oscillation frequency, a performance comparable to that of an OEO constructed with a diode-pumped YAG laser and an LiNbO3 modulator. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Ji, Y (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 4 TC 34 Z9 35 U1 1 U2 6 PU IEE-INST ELEC ENG PI HERTFORD PA MICHAEL FARADAY HOUSE SIX HILLS WAY STEVENAGE, HERTFORD SG1 2AY, ENGLAND SN 0013-5194 J9 ELECTRON LETT JI Electron. Lett. PD SEP 2 PY 1999 VL 35 IS 18 BP 1554 EP 1555 DI 10.1049/el:19991027 PG 2 WC Engineering, Electrical & Electronic SC Engineering GA 240AM UT WOS:000082803500040 ER PT J AU Karpova, EA Meehan, E Pusey, ML Chen, LQ AF Karpova, EA Meehan, E Pusey, ML Chen, LQ TI Crystallization and preliminary X-ray diffraction analysis of restriction endonuclease EcoRII SO ACTA CRYSTALLOGRAPHICA SECTION D-BIOLOGICAL CRYSTALLOGRAPHY LA English DT Article ID DNA RECOGNITION SITES; REFRACTORY DNA; DUPLEXES; SEQUENCE AB Crystals of the restriction endonuclease EcoRII have been obtained by the vapor-diffusion technique in the presence of ammonium sulfate or polyethylene glycol. The best crystals were grown with ammonium sulfate as a precipitant. Crystals with dimensions of up to 0.6 x 0.6 x 0.6 mm have been observed. The crystals diffract to about 4.0 Angstrom resolution at a cryo-temperature of 100 It using a rotating-anode X-ray source and. a Rigaku R-AXIS IV imaging-plate detector. The space group has been determined to be either I23 or I2(1)3, with unit-cell parameters a = b = c = 160.3 Angstrom, alpha = beta = gamma = 90 degrees. The crystal asymmetric unit contains two protein molecules, and self-rotation function analysis shows a pseudo-twofold symmetry relating the two monomers. Attempts to improve the resolution of crystal diffraction and to search for heavy-atom derivatives are under way. C1 NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Univ Alabama, Struct Biol Lab, Dept Chem, Huntsville, AL 35899 USA. Univ Alabama, Mat Sci Program, Huntsville, AL 35899 USA. RP Chen, LQ (reprint author), NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. NR 13 TC 2 Z9 2 U1 0 U2 0 PU MUNKSGAARD INT PUBL LTD PI COPENHAGEN PA 35 NORRE SOGADE, PO BOX 2148, DK-1016 COPENHAGEN, DENMARK SN 0907-4449 J9 ACTA CRYSTALLOGR D JI Acta Crystallogr. Sect. D-Biol. Crystallogr. PD SEP PY 1999 VL 55 BP 1604 EP 1605 DI 10.1107/S090744499900863X PN 9 PG 2 WC Biochemical Research Methods; Biochemistry & Molecular Biology; Biophysics; Crystallography SC Biochemistry & Molecular Biology; Biophysics; Crystallography GA 238TK UT WOS:000082727800019 PM 10489460 ER PT J AU Seifert, A Pack, LG AF Seifert, A Pack, LG TI Oscillatory control of separation at high Reynolds numbers SO AIAA JOURNAL 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 PERIODIC EXCITATION; AIRFOIL; DELAY AB An experiment conducted in a pressurized, cryogenic wind tunnel demonstrates that unsteady flow control using oscillatory blowing (with essentially zero mass flux) can effectively delay Row separation and reattach separated Row on an airfoil at chord Reynolds numbers as high as 38 X 10(6), Oscillatory blowing at frequencies that generate one to three vortices over the controlled region at all times are effective over the entire Reynolds number range, in accordance with previous low-Reynolds-number tests. Stall is delayed and poststall characteristics are improved when oscillatory blowing is applied from the leading edge region of the airfoil, whereas flap effectiveness is increased when control is applied at the Bap shoulder Similar gains in airfoil performance require steady blowing with a momentum coefficient that is two orders of magnitude greater. A detailed experimental and theoretical investigation was undertaken to characterize the oscillatory blowing disturbance, in the absence of external flow, and to estimate the oscillatory blowing momentum coefficient used in the cryogenic wind tunnel experiment. Possible approaches toward closed-loop active separation control are also presented. Based on the Endings of the present investigation, the application of active separation control at incompressible Eight Reynolds number is within reach. C1 NASA, Langley Res Ctr, Flow Modeling & Control Branch, Hampton, VA 23681 USA. RP Seifert, A (reprint author), NASA, Langley Res Ctr, Flow Modeling & Control Branch, Hampton, VA 23681 USA. NR 21 TC 94 Z9 95 U1 1 U2 6 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0001-1452 J9 AIAA J JI AIAA J. PD SEP PY 1999 VL 37 IS 9 BP 1062 EP 1071 DI 10.2514/2.834 PG 10 WC Engineering, Aerospace SC Engineering GA 231DH UT WOS:000082292500006 ER PT J AU Carpenter, MH Casper, JH AF Carpenter, MH Casper, JH TI Accuracy of shock capturing in two spatial dimensions SO AIAA JOURNAL LA English DT Article; Proceedings Paper CT AIAA 13th Computational Fluid Dynamics Conference CY JUN 29-JUL 02, 1997 CL SNOWMASS VILLAGE, COLORADO SP Amer Inst Aeronaut & Astronaut ID HYPERBOLIC EQUATIONS; DIFFERENCE-SCHEMES AB An assessment of the accuracy of shock-capturing schemes is made for two-dimensional steady flow around a cylindrical projectile. Both a linear fourth-order method and a nonlinear third-order method are used in this study. This study shows, contrary to conventional wisdom, that captured two-dimensional shocks are asymptotically first order, regardless of the design accuracy of the numerical method. The practical implications of this finding are discussed in the context of the efficacy of high-order numerical methods for discontinuous flows. C1 NASA, Langley Res Ctr, Aerodynam & Acoust Methods Branch, Hampton, VA 23681 USA. Old Dominion Univ, Norfolk, VA 23529 USA. RP Carpenter, MH (reprint author), NASA, Langley Res Ctr, Aerodynam & Acoust Methods Branch, MS 128, Hampton, VA 23681 USA. NR 15 TC 41 Z9 42 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 SEP PY 1999 VL 37 IS 9 BP 1072 EP 1079 DI 10.2514/2.835 PG 8 WC Engineering, Aerospace SC Engineering GA 231DH UT WOS:000082292500007 ER PT J AU Seifert, A Hodson, HP AF Seifert, A Hodson, HP TI Periodic turbulent strips and calmed regions in a transitional boundary layer SO AIAA JOURNAL LA English DT Article C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Univ Cambridge, Dept Engn, Cambridge CB3 0DY, England. RP Seifert, A (reprint author), NASA, Langley Res Ctr, MS 170, Hampton, VA 23681 USA. NR 10 TC 0 Z9 0 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0001-1452 J9 AIAA J JI AIAA J. PD SEP PY 1999 VL 37 IS 9 BP 1127 EP 1129 DI 10.2514/2.824 PG 3 WC Engineering, Aerospace SC Engineering GA 231DH UT WOS:000082292500015 ER PT J AU Ku, YTE Montgomery, LD Wenzel, KC Webbon, BW Burks, JS AF Ku, YTE Montgomery, LD Wenzel, KC Webbon, BW Burks, JS TI Physiologic and thermal responses of male and female patients with multiple sclerosis to head and neck cooling SO AMERICAN JOURNAL OF PHYSICAL MEDICINE & REHABILITATION LA English DT Article DE multiple sclerosis; cooling therapy; thermal stress; rehabilitation ID TEMPERATURE AB Personal cooling systems are used to alleviate symptoms of multiple sclerosis and to prevent increased core temperature during daily activities. The objective of this study was to determine the thermal and physiologic responses of patients with multiple sclerosis to short-term maximal head and neck cooling. A Life Support Systems, Inc. Mark VII portable cooling system and a liquid cooling helmet were used to cool the head and neck regions of 24 female and 26 male patients with multiple sclerosis in this study. The subjects, seated in an upright position at normal room temperature (similar to 22 degrees C), were cooled for 30 min by the liquid cooling garment, which was operated at its maximum cooling capacity. Oral, right, and left ear temperatures and cooling system parameters were logged manually every 5 min. Forearm, calf, chest, and rectal temperatures, heart rate, and respiration rate were recorded continuously on a U.F.I., Inc. Biolog ambulatory monitor. This protocol was performed during the winter and summer to investigate the seasonal differences in the way patients with multiple sclerosis respond to head and neck cooling. No significant differences were found between the male and female subject group's mean rectal or oral temperature responses during any phase of the experiment. The mean oral temperature decreased significantly (P < 0.05) for both groups similar to 0.3 degrees C after 30 min of cooling and continued to decrease further (similar to 0.1-0.2 degrees C) for a period of similar to 15 min after removal of the cooling helmet. The mean rectal temperatures decreased significantly (P < 0.05) in both male and female subjects in the winter studies (similar to 0.2-0.3 degrees C) and for the male subjects during the summer test (similar to 0.2 degrees C). However, the rectal temperature of the female subjects did not change significantly during any phase of the summer test. These data indicate that head and neck cooling may, in general, be used to reduce the oral and body temperatures of both male and female patients with multiple sclerosis by the approximate amount needed for symptomatic relief as shown by other researchers. However, thermal response of patients with multiple sclerosis may be affected by gender and seasonal factors, which should be considered in the use of liquid cooling therapy. C1 NASA, Lockheed Martin Engn & Sci, Ames Res Ctr, Moffett Field, CA 94035 USA. Rocky Mt MS Ctr, Adult Day Enrichment Program, Denver, CO USA. Ayarbe & Assoc, Aurora, CO USA. RP Ku, YTE (reprint author), NASA, Lockheed Martin Engn & Sci, Ames Res Ctr, Mail Stop 239-15, Moffett Field, CA 94035 USA. NR 15 TC 10 Z9 10 U1 0 U2 5 PU LIPPINCOTT WILLIAMS & WILKINS PI PHILADELPHIA PA 530 WALNUT ST, PHILADELPHIA, PA 19106-3621 USA SN 0894-9115 J9 AM J PHYS MED REHAB JI Am. J. Phys. Med. Rehabil. PD SEP-OCT PY 1999 VL 78 IS 5 BP 447 EP 456 DI 10.1097/00002060-199909000-00007 PG 10 WC Rehabilitation; Sport Sciences SC Rehabilitation; Sport Sciences GA 235RK UT WOS:000082556200006 PM 10493455 ER PT J AU Freudenreich, H AF Freudenreich, H TI Deconstructing the Milky Way Galaxy SO AMERICAN SCIENTIST LA English DT Article ID GALACTIC BULGE; DISK; STARS; DUST C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Freudenreich, H (reprint author), NASA, Goddard Space Flight Ctr, Code 696, Greenbelt, MD 20771 USA. NR 11 TC 0 Z9 0 U1 0 U2 0 PU SIGMA XI-SCI RES SOC PI RES TRIANGLE PK PA PO BOX 13975, RES TRIANGLE PK, NC 27709 USA SN 0003-0996 J9 AM SCI JI Am. Scientist PD SEP-OCT PY 1999 VL 87 IS 5 BP 418 EP 427 PG 10 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 226DX UT WOS:000082006000013 ER PT J AU Buchman, A Bryant, RG AF Buchman, A Bryant, RG TI Molded carbon-carbon composites based on microcomposite technology SO APPLIED COMPOSITE MATERIALS LA English DT Article DE carbon-carbon; microcomposites; polyimide resin; pyrolysis; graphite molding compounds ID CARBONIZATION; FIBER AB A one-step, cost-effective processing methodology based on compression molding of a mixture of graphite particles and short fibers, both coated with a soluble polyimide adhesive was developed. This technique shows a considerable potential in decreasing the complexity of the current carbon-carbon fabrication procedures. The new process eliminates additional infiltration and densification steps following the initial carbonization, which reduces the processing time from 5 weeks to 3-5 days and saves energy. The structure and properties of the new carbon-carbon composites were characterized using optical and electronic microscopy, thermal analysis, density and porosity measurements, and mechanical properties (hardness and flexural strength). The flexural strengths ranged from 20-45 MPa. The densities ranged from 1.9 to 2.2 g/cc (which is close to pure graphite) while the porosity was as low as 3%. The CTE was approximately +/- 1 ppm/degrees C (R.T. to 550 degrees C). The thermal stability of the carbonized and graphitized specimens when heated in flowing air up to 500 degrees C and flowing nitrogen up to 1000 degrees C showed no observable weight loss. There are numerous applications for these materials which include: optical mirrors, medical implants, thermal radiators and parts for rotating equipment, etc. A car piston was successfully molded using a mixture of polymer coated graphite powder, flakes and chopped fibers. C1 Old Dominion Univ, Norfolk, VA 23527 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 11 TC 3 Z9 6 U1 0 U2 3 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0929-189X J9 APPL COMPOS MATER JI Appl. Compos. Mater. PD SEP PY 1999 VL 6 IS 5 BP 309 EP 326 DI 10.1023/A:1008993507288 PG 18 WC Materials Science, Composites SC Materials Science GA 239NP UT WOS:000082775300003 ER PT J AU Papadopoulos, P Venkatapathy, E Prabhu, D Loomis, MP Olynick, D AF Papadopoulos, P Venkatapathy, E Prabhu, D Loomis, MP Olynick, D TI Current grid-generation strategies and future requirements in hypersonic vehicle design, analysis and testing SO APPLIED MATHEMATICAL MODELLING LA English DT Article AB Recent advances in computational power enable computational fluid dynamic modeling of increasingly complex configurations. A review of grid-generation methodologies implemented in support of the computational work per formed for the X-38 (Experimental Crew Return Vehicle) and X-33 hypersonic vehicles are presented. In strategizing topological constructs and blocking structures, the factors considered are geometric configuration, optimal grid size, numerical algorithms, accuracy requirements, physics of the problem at hand, computational expense and available computer hardware. Also addressed are grid-refinement strategies, the effect of wall spacing and convergence. The significance of grids is demonstrated through a comparison of computational and experimental results of the aero-heating environment experienced by the X-38 vehicle. Special topics on grid-generation strategies are also addressed to model control surface deflections and material mapping. (C) 1999 Elsevier Science Inc. All rights reserved. C1 NASA, Ames Res Ctr, Thermosci Inst, Moffett Field, CA 94035 USA. RP Papadopoulos, P (reprint author), NASA, Ames Res Ctr, Thermosci Inst, MS-230-2, Moffett Field, CA 94035 USA. NR 18 TC 13 Z9 14 U1 0 U2 1 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA SN 0307-904X J9 APPL MATH MODEL JI Appl. Math. Model. PD SEP PY 1999 VL 23 IS 9 BP 705 EP 735 DI 10.1016/S0307-904X(99)00007-4 PG 31 WC Engineering, Multidisciplinary; Mathematics, Interdisciplinary Applications; Mechanics SC Engineering; Mathematics; Mechanics GA 219RF UT WOS:000081620200003 ER PT J AU Tornikoski, M Tingay, SJ Mucke, A Chen, A Connaughton, V Jauncey, DL Johnston-Hollitt, M Kemp, J King, EA McGee, P Rantakyro, F Rayner, D Reimer, O Tzioumis, AK AF Tornikoski, M Tingay, SJ Mucke, A Chen, A Connaughton, V Jauncey, DL Johnston-Hollitt, M Kemp, J King, EA McGee, P Rantakyro, F Rayner, D Reimer, O Tzioumis, AK TI Multiwavelength observations of PKS 2255-282 SO ASTRONOMICAL JOURNAL LA English DT Article DE quasars : general; quasars : individual (PKS 2255-282) ID EXTRAGALACTIC RADIO-SOURCES; MILLIMETER CONTINUUM MEASUREMENTS; ACTIVE GALACTIC NUCLEI; GAMMA-RAY EMISSION; REFERENCE FRAME; BLAZARS; RADIATION; CATALOG; SAMPLE; QSOS AB During high radio frequency active galactic nucleus monitoring, we observed a major millimeter wave outburst from PKS 2255-282 in 1997 and initiated a campaign for multifrequency radio monitoring and VLBI imaging of the source. In 1998 January the EGRET instrument on board the Compton Gamma Ray Observatory detected a bright high-energy gamma-ray outburst from its direction. Thus, we had the unique opportunity to monitor the source in detail at various radio frequencies already before the detection of the gamma-ray outburst. We also initiated multiwavelength follow-up observations. In this paper we present multiwavelength data for PKS 2255-282 before and after the gamma-ray outburst. Further, based on the observations, we estimate some physical parameters for this source and discuss the various emission mechanisms possibly involved during this outburst. C1 Metsahovi Radio Observ, FIN-02540 Kylmala, Finland. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Adelaide, Dept Phys & Math Phys, Adelaide, SA 5005, Australia. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Australia Telescope Natl Facil, Epping, NSW 2121, Australia. Columbia Univ, Biosphere 2 Ctr, Oracle, AZ 85623 USA. European So Observ, SEST, Santiago 19, Chile. Univ Tasmania, Dept Phys, Hobart, Tas 7001, Australia. Max Planck Inst Extraterr Phys, D-85740 Garching, Germany. RP Tornikoski, M (reprint author), Metsahovi Radio Observ, Metsahovintie 114, FIN-02540 Kylmala, Finland. RI Johnston-Hollitt, Melanie/B-1803-2013; Tingay, Steven/B-5271-2013; King, Edward/A-1473-2012; Reimer, Olaf/A-3117-2013; Rayner, David/A-6414-2011 OI King, Edward/0000-0002-6898-2130; Reimer, Olaf/0000-0001-6953-1385; Rayner, David/0000-0003-0545-3634 NR 45 TC 13 Z9 13 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 SEP PY 1999 VL 118 IS 3 BP 1161 EP 1168 DI 10.1086/301019 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 241ZR UT WOS:000082914200003 ER PT J AU Harker, DE Woodward, CE Wooden, DH Witteborn, FC Meyer, AW AF Harker, DE Woodward, CE Wooden, DH Witteborn, FC Meyer, AW TI The 10 micron silicate feature of comet C/1996 Q1 (Tabur) SO ASTRONOMICAL JOURNAL LA English DT Article DE comets, general; comets, individual (C/1996 Q1 (Tabur), C/1998 K5 (LINEAR)); infrared radiation ID HALE-BOPP C/1995-O1; SPECTRA; SPECTROPHOTOMETRY; GRAINS; BAND; PHOTOMETRY; SIMULATION; AIRBORNE; P/HALLEY; OLIVINE AB We present 7.6-13.2 mu m infrared spectrophotometry (R similar or equal to 120) of the inner coma of comet C/1996 Q1 (Tabur), obtained 1996 October 8-10 UT. At this epoch, the comet was at a heliocentric distance of r(h) = 0.96 AU. The local 10 mu m continuum is fitted with a 300 +/- 10 K blackbody, revealing a weak silicate feature. Our analysis suggests that comet Tabur most likely contains large grains of radii a approximate to 1-3 pm. Synthetic spectra derived from laboratory measurements of amorphous pyroxene and amorphous and crystalline olivine of grain sizes (radii) between 1 and 5 pm are fitted to Tabur's silicate emission feature. A mixture of crystalline olivine (1 mu m radii) and amorphous pyroxene (3 mu m radii) grains provides the best model fit to the observed 10 mu m spectrum. We also compare the spectra of Tabur with the mid-IR spectra of C/1995 O1 (Hale-Bopp) and other comets with and without silicate features. In particular, we discuss the mid-IR spectrum of comet C/1998 K5 (LINEAR) obtained on 1998 June 2830 UT with the same instrument and spectral resolution. In contrast to comet Tabur, the spectrum of comet K5 LINEAR does not exhibit 10 mu m silicate emission in excess of a featureless continuum characterized by a 310 +/- 10 K blackbody. C1 Univ Wyoming, Dept Phys & Astron, Wyoming Infrared Observ, Laramie, WY 82071 USA. NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. RP Harker, DE (reprint author), Univ Wyoming, Dept Phys & Astron, Wyoming Infrared Observ, Laramie, WY 82071 USA. OI Harker, David/0000-0001-6397-9082 NR 39 TC 25 Z9 25 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 SEP PY 1999 VL 118 IS 3 BP 1423 EP 1429 DI 10.1086/301011 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 241ZR UT WOS:000082914200028 ER PT J AU Sutaria, FK Ray, A Sheikh, JA Ring, P AF Sutaria, FK Ray, A Sheikh, JA Ring, P TI Nuclear properties in early stages of stellar collapse SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE stars : supernovae : general; equation of state; nuclear reactions, nucleosynthesis, abundances ID MEAN-FIELD-THEORY; GROUND-STATE; GRAVITATIONAL COLLAPSE; ELECTRON-CAPTURE; HIGH-DENSITIES; FINITE NUCLEI; DENSE MATTER; EQUATION; SUPERNOVAE; STARS AB The spectroscopy of electron capture neutrinos emitted from nearby pre-supernova collapsing stars before the neutrino trapping sets in, can yield useful information on the physical conditions and on the nuclear composition of the core. The neutrino spectrum depends on the thermodynamic conditions of the core, the nuclear abundances, the lepton fractions and relevant nuclear properties. In the pre-trapping core, the density ranges from 0.1-100 10(10) g/cm(3) and the temperature from 0.2-1.5 MeV. The nuclear abundances can be obtained under the assumption of Nuclear Statistical Equilibrium (NSE). The nuclear abundances as well as the electron capture rates are thus determined, among other things, by the nuclear binding energies and the free nucleon chemical potentials. Because shell and pairing effects persist strongly up to temperatures of similar or equal to 0.5 MeV, any equation of state (EOS) relevant to this phase of the collapse must reproduce well the zero temperature nuclear properties and it must show a smooth transition to the known high temperature and high density limits. In this work we use the microscopic Relativistic Mean Field (RMF) theory based on a Lagrangian with non-linear self-interactions of the sigma-field for the neutron-rich nuclei of interest in the f - p shell to determine nuclear chemical potentials. We compare these results with those computed from an EOS calculated with the macroscopic liquid drop model. We also discuss extensions to finite temperature and we incorporate nuclear lattice effects into the microscopic calculations. C1 Tata Inst Fundamental Res, Mumbai 400005, India. Inter Univ Ctr Astron & Astrophys, Poona 411007, Maharashtra, India. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Tech Univ Munich, Dept Phys, D-85747 Garching, Germany. RP Ray, A (reprint author), Tata Inst Fundamental Res, Mumbai 400005, India. EM akr@tifr.res.in RI Ring, Peter/O-1638-2015 NR 45 TC 8 Z9 8 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD SEP PY 1999 VL 349 IS 1 BP 135 EP 150 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 241YY UT WOS:000082912500022 ER PT J AU Fishman, GJ AF Fishman, GJ TI Observed properties of gamma-ray bursts SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT Workshop on Gamma-Ray Bursts in the Afterglow Era CY NOV 03-06, 1998 CL CNR HEADQUARTERS, ROME, ITALY HO CNR HEADQUARTERS DE gamma-rays : bursts ID BATSE OBSERVATIONS; IDENTIFICATION; SPECTRA AB The observed temporal and spectral characteristics and the spatial distribution of gamma-ray bursts (GRBs) are summarized, primarily from data obtained with the BATSE experiment on the Compton Observatory. The availability of these data and the prospects for continued observations are also described. C1 NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. RP Fishman, GJ (reprint author), NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. NR 21 TC 9 Z9 11 U1 0 U2 0 PU E D P SCIENCES PI LES ULIS CEDEXA PA 7, AVE DU HOGGAR, PARC D ACTIVITES COURTABOEUF, BP 112, F-91944 LES ULIS CEDEXA, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD SEP PY 1999 VL 138 IS 3 BP 395 EP 398 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 246GM UT WOS:000083156100002 ER PT J AU Vreeswijk, PM Galama, TJ Owens, AN Oosterbroek, T Geballe, T van Paradijs, J Kouveliotou, C Tanvir, N Pian, E Palazzi, E Frontera, F Masetti, N AF Vreeswijk, PM Galama, TJ Owens, AN Oosterbroek, T Geballe, T van Paradijs, J Kouveliotou, C Tanvir, N Pian, E Palazzi, E Frontera, F Masetti, N TI The X-ray, optical and infrared counterpart to GRB 980703 SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT Workshop on Gamma-Ray Bursts in the Afterglow Era CY NOV 03-06, 1998 CL CNR HEADQUARTERS, ROME, ITALY HO CNR HEADQUARTERS DE gamma-rays : bursts; radiation mechanisms : non-thermal ID BURST AB We report on X-ray, optical and infrared followup observations of GRB 980703. We detect a previously unknown X-ray source in the GRB error box assuming a power law decline we find for its decay index alpha < -0.91(3 sigma). We invoke host galaxy extinction to match the observed spectral slope with the slope expected from "fire-ball" models. We find no evidence for a spectral break in the infrared to X-ray spectral range on 1998 July 4.4, and determine a lower limit of the cooling break frequency: nu(c) > 1.3 10(17) Hz. For this epoch we obtain an extinction of A(v) = 1.50 +/- 0.11. From the X-ray data ave estimate the optical extinction to be Av = 20.2(-7.3)(+12.3), inconsistent with the former value. Following Wijers & Galama (1998), we determine intrinsic fireball properties for this burst. C1 Univ Amsterdam, Astron Inst Anton Pannekoek, NL-1098 SJ Amsterdam, Netherlands. Natl Inst Nucl & High Energy Phys, Ctr High Energy Astrophys, NL-1098 SJ Amsterdam, Netherlands. European Space Agcy, European Space Res & Technol Ctr, Dept Space Sci, Div Astrophys, NL-2200 AG Noordwijk, Netherlands. Joint Astron Ctr, Hilo, HI 96720 USA. Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. Univ Space Res Assoc, Washington, DC USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England. CNR, Ist TESRE, I-40129 Bologna, Italy. RP Vreeswijk, PM (reprint author), Univ Amsterdam, Astron Inst Anton Pannekoek, Kruislaan 403, NL-1098 SJ Amsterdam, Netherlands. RI Galama, Titus/D-1429-2014; Palazzi, Eliana/N-4746-2015; OI Galama, Titus/0000-0002-1036-396X; Palazzi, Eliana/0000-0002-8691-7666; Masetti, Nicola/0000-0001-9487-7740; Pian, Elena/0000-0001-8646-4858 NR 16 TC 3 Z9 3 U1 0 U2 1 PU E D P SCIENCES PI LES ULIS CEDEXA PA 7, AVE DU HOGGAR, PARC D ACTIVITES COURTABOEUF, BP 112, F-91944 LES ULIS CEDEXA, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD SEP PY 1999 VL 138 IS 3 BP 447 EP 448 PG 2 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 246GM UT WOS:000083156100024 ER PT J AU Galama, TJ Wijers, RAMJ Vreeswijk, PM Groot, PJ Van Paradijs, J Kouveliotou, C Robinson, C Bremer, M Strom, RG Tanvir, N AF Galama, TJ Wijers, RAMJ Vreeswijk, PM Groot, PJ Van Paradijs, J Kouveliotou, C Robinson, C Bremer, M Strom, RG Tanvir, N TI Physical parameters of GRB 970508 from its afterglow synchrotron emission SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT Workshop on Gamma-Ray Bursts in the Afterglow Era CY NOV 03-06, 1998 CL CNR HEADQUARTERS, ROME, ITALY HO CNR HEADQUARTERS DE gamma-rays : bursts; radiation mechanisms : non-thermal AB For the case of an adiabatically expanding blast wave, which is applicable to observed gamma-ray burst (GRB) afterglows at late times, we give expressions to infer the physical properties of the afterglow from the measured spectral features. We show that enough data exist for GRB 970508 to compute unambiguously the ambient density, n = 0.03 cm(-3): and the blast wave energy per unit solid angle, epsilon = 4 10(52) erg/4 pi sr. We also compute the energy density in electrons and magnetic field. We find that they are 12% and 9%, respectively, of the nucleon energy density. C1 Univ Amsterdam, Astron Inst Anton Pannekoek, CHEAF, NL-1098 SJ Amsterdam, Netherlands. SUNY Stony Brook, Dept Phys & Astron, Stony Brook, NY 11794 USA. Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. NASA, George C Marshall Space Flight Ctr, Univ Space Res Assoc, Huntsville, AL 35812 USA. Inst Radio Astron Millimetr, F-38406 St Martin Dheres, France. Netherlands Fdn Res Astron, NL-7990 AA Dwingeloo, Netherlands. Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England. RP Galama, TJ (reprint author), Univ Amsterdam, Astron Inst Anton Pannekoek, CHEAF, Kruislaan 403, NL-1098 SJ Amsterdam, Netherlands. RI Galama, Titus/D-1429-2014; Groot, Paul/K-4391-2016 OI Galama, Titus/0000-0002-1036-396X; Groot, Paul/0000-0002-4488-726X NR 5 TC 5 Z9 5 U1 0 U2 0 PU E D P SCIENCES PI LES ULIS CEDEXA PA 7, AVE DU HOGGAR, PARC D ACTIVITES COURTABOEUF, BP 112, F-91944 LES ULIS CEDEXA, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD SEP PY 1999 VL 138 IS 3 BP 451 EP 452 PG 2 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 246GM UT WOS:000083156100026 ER PT J AU Hanlon, L Metcalfe, L Delaney, M Laureijs, R McBreen, B Smith, N Altieri, B Castro-Tirado, A Costa, E Feroci, M Frontera, F Galama, T Gorosabel, J Groot, P Heise, J Kouveliotou, C Palazzi, E van Paradijs, J Piro, L Kessler, M AF Hanlon, L Metcalfe, L Delaney, M Laureijs, R McBreen, B Smith, N Altieri, B Castro-Tirado, A Costa, E Feroci, M Frontera, F Galama, T Gorosabel, J Groot, P Heise, J Kouveliotou, C Palazzi, E van Paradijs, J Piro, L Kessler, M TI Observations of GRBs with the Infrared Space Observatory SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT Workshop on Gamma-Ray Bursts in the Afterglow Era CY NOV 03-06, 1998 CL CNR HEADQUARTERS, ROME, ITALY HO CNR HEADQUARTERS DE gamma-ray bursts ID GAMMA-RAY BURST; 28 FEBRUARY 1997; ERROR BOX; GRB-970508; AFTERGLOW AB We present results from the Target of Opportunity (TOO) program to observe GRB locations with the CAM and PHOT instruments aboard the Infrared Space Observatory (ISO). Four BeppoSAX GRB error circles were observed by ISO on timescales ranging from days to months after the GRB events. These observations represent the first prompt GRB counterpart searches at far-infrared wavelengths. A list of observations made in this TOO program, along with results of CAM follow-up observations of GRB 970508, are presented. A marginal CAM (12 mu m) detection of a source, consistent with the position of the optical transient of GRB 970508, is reported. C1 Natl Univ Ireland Univ Coll Dublin, Dept Expt Phys, Dublin 4, Ireland. ESA, Dept Space Sci, Div Astrophys, ISO Sci Operat Ctr, Villafranca Dasti, Italy. Cork Inst Technol, Cork, Ireland. LAEFF, Madrid 28080, Spain. CNR, Ist Astrofis Spaziale, I-00133 Rome, Italy. Univ Amsterdam, Astron Inst Anton Pannekoek, NL-1012 WX Amsterdam, Netherlands. SRON, Utrecht, Netherlands. NASA, USRA, MSFC, Huntsville, AL USA. CNR, ITESRE, Bologna, Italy. Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. Stockholm Observ, SE-13336 Saltsjobaden, Sweden. CSIC, IAA, Granada 18080, Spain. RP Hanlon, L (reprint author), Natl Univ Ireland Univ Coll Dublin, Dept Expt Phys, Stillorgan Rd, Dublin 4, Ireland. RI Galama, Titus/D-1429-2014; PIRO, LUIGI/E-4954-2013; Palazzi, Eliana/N-4746-2015; Groot, Paul/K-4391-2016; OI Galama, Titus/0000-0002-1036-396X; PIRO, LUIGI/0000-0003-4159-3984; Groot, Paul/0000-0002-4488-726X; Costa, Enrico/0000-0003-4925-8523; Feroci, Marco/0000-0002-7617-3421; Palazzi, Eliana/0000-0002-8691-7666; Castro-Tirado, A. J./0000-0003-2999-3563; Altieri, Bruno/0000-0003-3936-0284 NR 17 TC 4 Z9 4 U1 0 U2 1 PU E D P SCIENCES PI LES ULIS CEDEXA PA 7, AVE DU HOGGAR, PARC D ACTIVITES COURTABOEUF, BP 112, F-91944 LES ULIS CEDEXA, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD SEP PY 1999 VL 138 IS 3 BP 459 EP 460 PG 2 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 246GM UT WOS:000083156100030 ER PT J AU Galama, TJ Vreeswijk, PM van Paradijs, J Kouveliotou, C Augusteijn, T Patat, F Heise, J 't Zand, JI Groot, PJ Wijers, RAMJ Pian, E Palazzi, E Frontera, F Masetti, N AF Galama, TJ Vreeswijk, PM van Paradijs, J Kouveliotou, C Augusteijn, T Patat, F Heise, J 't Zand, JI Groot, PJ Wijers, RAMJ Pian, E Palazzi, E Frontera, F Masetti, N TI On the possible association of SN 1998bw and GRB 980425 SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT Workshop on Gamma-Ray Bursts in the Afterglow Era CY NOV 03-06, 1998 CL CNR HEADQUARTERS, ROME, ITALY HO CNR HEADQUARTERS DE gamma-rays : bursts; (stars :) supernovae : individual : SN 1998bw ID GAMMA-RAY BURST; 25 APRIL 1998; UNUSUAL SUPERNOVA AB We here discuss the possibility that the peculiar supernova SN 1998bw and the Gamma-Ray Burst GRB 980425 are associated. If the two are related, the energy radiated in gamma rays is at least four orders of magnitude less than in other GRBs, although its appearance is otherwise unremarkable: this suggests that very different mechanisms may give rise to GRBs. C1 Univ Amsterdam, Astron Inst Anton Pannekoek, CHEAF, NL-1098 SJ Amsterdam, Netherlands. UAH, Dept Phys, Huntsville, AL 35899 USA. Univ Space Res Assoc, Washington, DC USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. ESO, Santiago 19, Chile. SRON, Space Res Lab, NL-3584 CA Utrecht, Netherlands. SUNY Stony Brook, Dept Phys & Astron, Stony Brook, NY 11794 USA. CNR, Ist Tecnol & Studio Radiaz Extraterr, Bologna, Italy. RP Galama, TJ (reprint author), Univ Amsterdam, Astron Inst Anton Pannekoek, CHEAF, Kruislaan 403, NL-1098 SJ Amsterdam, Netherlands. RI Galama, Titus/D-1429-2014; Palazzi, Eliana/N-4746-2015; Groot, Paul/K-4391-2016; OI Galama, Titus/0000-0002-1036-396X; Groot, Paul/0000-0002-4488-726X; Palazzi, Eliana/0000-0002-8691-7666; Masetti, Nicola/0000-0001-9487-7740; Pian, Elena/0000-0001-8646-4858 NR 10 TC 30 Z9 30 U1 0 U2 2 PU E D P SCIENCES PI LES ULIS CEDEXA PA 7, AVE DU HOGGAR, PARC D ACTIVITES COURTABOEUF, BP 112, F-91944 LES ULIS CEDEXA, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD SEP PY 1999 VL 138 IS 3 BP 465 EP 466 PG 2 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 246GM UT WOS:000083156100033 ER PT J AU Bonnell, J Norris, J Watanabe, K AF Bonnell, J Norris, J Watanabe, K TI Chasing the association of single-pulse gamma-ray bursts and supernovae SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT Workshop on Gamma-Ray Bursts in the Afterglow Era CY NOV 03-06, 1998 CL CNR HEADQUARTERS, ROME, ITALY HO CNR HEADQUARTERS DE gamma-rays : bursts; stars : supernovae, general AB We explore the hypothesis, similar to one recently suggested by Bloom and colleagues, that some nearby supernovae are associated with smooth, single-pulse gamma-ray bursts, possibly having no emission above 300 keV. We examine BATSE bursts with durations longer than 2 s, fitting those which can be visually characterized as single-pulse events with a lognormal pulse model. The fraction of events that can be reliably ascertained to be temporally and spectrally similar to the exemplar, GRB 980425 - possibly associated with SN 1998bw - is 4/1573 or 0.25%. This fraction could be as high as 8/1573 (0.5%) if the dimmest bursts are included. Approximately 2% of bursts are morphologically similar to GRB 980425 but have emission above 300 keV. A search of supernova catalogs containing 630 detections during BATSE's lifetime reveals only one burst (GRB 980425) within a 3-month time window and within the total 3 sigma BATSE error radius that could be associated with a type Ib/c supernova. Thus we find no further evidence to support a single-pulse GRB and SN Ib/c connection. We also find no tendency for any set of single-pulse GRBs to fall near the Supergalactic Plane, whereas SNe of type Ib/c do show this tendency evidence that the tyro phenomena are not related. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20770 USA. Univ Space Res Assoc, Washington, DC USA. RP Bonnell, J (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20770 USA. NR 15 TC 1 Z9 1 U1 0 U2 0 PU E D P SCIENCES PI LES ULIS CEDEXA PA 7, AVE DU HOGGAR, PARC D ACTIVITES COURTABOEUF, BP 112, F-91944 LES ULIS CEDEXA, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD SEP PY 1999 VL 138 IS 3 BP 471 EP 472 PG 2 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 246GM UT WOS:000083156100036 ER PT J AU Cline, TL Barthelmy, S Butterworth, P Marshall, F McClanahan, T Palmer, D Trombka, J Hurley, K Gold, R Aptekar, R Frederiks, D Golenetskii, S Il'Inskii, V Mazets, E Fishman, G Kouveliotou, C Meegan, C AF Cline, TL Barthelmy, S Butterworth, P Marshall, F McClanahan, T Palmer, D Trombka, J Hurley, K Gold, R Aptekar, R Frederiks, D Golenetskii, S Il'Inskii, V Mazets, E Fishman, G Kouveliotou, C Meegan, C TI Precise GRB source locations from the renewed interplanetary network SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT Workshop on Gamma-Ray Bursts in the Afterglow Era CY NOV 03-06, 1998 CL CNR HEADQUARTERS, ROME, ITALY HO CNR HEADQUARTERS DE gamma-rays : bursts; instrumentation : miscellaneous AB A new interplanetary network (IPN) is made possible by the modification of the NEAR mission, now at 2 AU distance. With Ulysses and the near-Earth GRB monitors, this fully long-baseline network will produce GRB localizations at a rate of about one per week, with accuracies varying from several to tens of are minutes. Given the delays inherent in the collection of deep space data, high-precision alerts with delays under one day should be possible at a rate of one to several per month. An automatic analysis system is being developed to optimize the process. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. APL, Laurel, MD 20723 USA. AF Ioffe Phys Tech Inst, St Petersburg 194021, Russia. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Cline, TL (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RI McClanahan, Timothy/C-8164-2012; Barthelmy, Scott/D-2943-2012; Frederiks, Dmitry/C-7612-2014; Aptekar, Raphail/B-3456-2015; Golenetskii, Sergey/B-3818-2015; OI Frederiks, Dmitry/0000-0002-1153-6340 NR 2 TC 8 Z9 8 U1 0 U2 0 PU E D P SCIENCES PI LES ULIS CEDEXA PA 7, AVE DU HOGGAR, PARC D ACTIVITES COURTABOEUF, BP 112, F-91944 LES ULIS CEDEXA, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD SEP PY 1999 VL 138 IS 3 BP 557 EP 558 PG 2 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 246GM UT WOS:000083156100073 ER PT J AU Park, HS Porrata, RA Williams, GG Ables, E Band, DL Barthelmy, SD Bionta, RM Cline, TL Fishman, GJ Gehrels, N Hartmann, D Hurley, K Kouveliotou, C Meegan, CA AF Park, HS Porrata, RA Williams, GG Ables, E Band, DL Barthelmy, SD Bionta, RM Cline, TL Fishman, GJ Gehrels, N Hartmann, D Hurley, K Kouveliotou, C Meegan, CA TI LOTIS: GRB follow-up observations at early times SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT Workshop on Gamma-Ray Bursts in the Afterglow Era CY NOV 03-06, 1998 CL CNR HEADQUARTERS, ROME, ITALY HO CNR HEADQUARTERS DE gamma-rays : bursts ID GAMMA-RAY BURST; 28 FEBRUARY 1997; OPTICAL-EMISSION; AFTERGLOW AB LOTIS is an automated wide field-of-view telescope system capable of responding to GRB events as early as 10 s after a trigger from the GCN which rapidly distributes coordinates from the BeppoSAX, BATSE and RXTE instruments. Measurements of optical activity at these early times will provide important clues to the GRB production mechanism. In over two year's of operation, LOTIS has responded to 40 GCN triggers including GRB 971227 within 10 s and GRB 980703 within 5 hours. We report results from these events and constraints on simultaneous optical signals during these GRBs. C1 Univ Calif Lawrence Livermore Natl Lab, Livermore, CA 94550 USA. Clemson Univ, Dept Phys & Astron, Clemson, SC 29634 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Univ Calif San Diego, La Jolla, CA 92093 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Univ Space Res Assoc, Washington, DC USA. RP Park, HS (reprint author), Univ Calif Lawrence Livermore Natl Lab, Livermore, CA 94550 USA. RI Barthelmy, Scott/D-2943-2012 NR 10 TC 13 Z9 13 U1 0 U2 1 PU E D P SCIENCES PI LES ULIS CEDEXA PA 7, AVE DU HOGGAR, PARC D ACTIVITES COURTABOEUF, BP 112, F-91944 LES ULIS CEDEXA, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD SEP PY 1999 VL 138 IS 3 BP 577 EP 578 PG 2 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 246GM UT WOS:000083156100083 ER PT J AU Sulkanen, ME AF Sulkanen, ME TI Galaxy cluster shapes and systematic errors in H-0 measured by the Sunyaev-Zeldovich effect SO ASTROPHYSICAL JOURNAL LA English DT Article DE distance scale; galaxies : clusters : general; X-rays : galaxies ID X-RAY MORPHOLOGIES; HUBBLE-CONSTANT; ABELL CLUSTERS; CONSTRAINTS; SAMPLE AB Imaging of the Sunyaev-Zeldovich (SZ) effect in galaxy clusters combined with cluster plasma X-ray diagnostics can measure the cosmic distance scale to high redshift. However, projecting the inverse Compton scattering and X-ray emission along the cluster line of sight introduces systematic errors in the Hubble constant, H-0 because the true shape of the cluster is not known. In this paper, I present a study of the systematic errors in the value of H-0 as determined by the X-ray and SZ properties of theoretical samples of triaxial isothermal "beta" model clusters, caused by projection effects and observer orientation relative to the model clusters' principal axes. I calculate three estimates for H-0 for each cluster based on their large and small apparent angular core radii and their arithmetic mean. I demonstrate that the estimates for H-0 for a sample of 25 clusters have limited systematic error: the 99.7% confidence intervals for the mean estimated H-0 analyzing the clusters using either their large or mean angular core radius are within similar or equal to 14% of the "true" (assumed) value of H-0 (and enclose it), for a triaxial beta model cluster sample possessing a distribution of apparent X-ray cluster ellipticities consistent with that of observed X-ray clusters. This limit on the systematic error in H-0 caused by cluster shape assumes that each sample beta model cluster has a fixed shape; deviations from constant shape within the dusters may introduce additional uncertainty or bias into this result. C1 NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Xray Astron Grp, Huntsville, AL 35812 USA. RP Sulkanen, ME (reprint author), Univ Michigan, Dept Astron, Ann Arbor, MI 48109 USA. NR 27 TC 26 Z9 27 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 SEP 1 PY 1999 VL 522 IS 1 BP 59 EP 65 DI 10.1086/307615 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 228HJ UT WOS:000082130800004 ER PT J AU Giannakopoulou-Creighton, J Fich, M Wilson, CD AF Giannakopoulou-Creighton, J Fich, M Wilson, CD TI Star formation in the giant HII regions of M101 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : individual (M101); galaxies : ISM; ISM : clouds; radio lines : ISM; stars : formation ID H-II-REGIONS; MOLECULAR CLOUDS; IRREGULAR GALAXIES; OB ASSOCIATIONS; CO; M33; CALIBRATION; DENSITY; M-101; DISK AB The molecular components of three giant H II regions (NGC 5461, NGC 5462, and NGC 5471) in the galaxy M101 are investigated with new observations from single-dish telescopes (James Clerk Maxwell Telescope and the NRAO 12 m) and from the Owens Valley Radio Observatory millimeter array. Of the three H II regions, only NGC 5461 had previously been detected in CO emission. We calculate preliminary values for the molecular mass of the GMCs in NGC 5461 by assuming a CO-to-H, factor (X factor) and then comparing these values with the virial masses. We found that the appropriate X factor is 5 times smaller than the X factor in the Milky Way despite the lower metallicity of M101. We conclude that the data in this paper demonstrate for the first time that the value of X may decrease in regions with intense star formation. The molecular mass for the association of clouds in NGC 5461 is approximately 3 x 10(7) M. and is accompanied by 1-2 times as much atomic mass. The observed CO emission in NGC 5461 is an order of magnitude stronger than in NGC 5462, but it was not possible to detect molecular gas toward NGC 5471 with the James Clerk Maxwell Telescope. An even larger ratio of atomic to molecular gas in NGC 5471 was observed, which might be attributed to efficient conversion of molecular to atomic gas. The masses of the individual clouds in NGC 5461, which are gravitationally bound, cover a range of (2-8) x 10(5) M., comparable with the masses of Galactic giant molecular clouds. Higher star-forming efficiencies, and not massive clouds, appear to be the prerequisite for the formation of the large number of stars whose radiation is required to produce the giant H II regions in M101. C1 Univ Waterloo, Dept Phys, Waterloo, ON N2L 3G1, Canada. CALTECH, Jet Prop Lab, Ctr Infrared Proc & Anal, Pasadena, CA 91125 USA. McMaster Univ, Dept Phys & Astron, Hamilton, ON L8S 4M1, Canada. RP Giannakopoulou-Creighton, J (reprint author), Univ Waterloo, Dept Phys, Waterloo, ON N2L 3G1, Canada. NR 48 TC 7 Z9 7 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 SEP 1 PY 1999 VL 522 IS 1 BP 238 EP 249 PN 1 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 228HJ UT WOS:000082130800020 ER PT J AU Sandage, A Bell, RA Tripicco, MJ AF Sandage, A Bell, RA Tripicco, MJ TI On the sensitivity of the cepheid period-luminosity relation to variations of metallicity SO ASTROPHYSICAL JOURNAL LA English DT Review DE cepheids; Magellanic Clouds; stars : abundances; stars : atmospheres-stars : distances; stars : oscillations ID RR-LYRAE STARS; GALACTIC GLOBULAR-CLUSTERS; SMALL MAGELLANIC CLOUD; BLUE FUNDAMENTAL EDGE; STELLAR MODELS; EVOLUTIONARY SEQUENCES; INSTABILITY STRIP; VARIABLE-STARS; DISTANCE SCALE; RADIATIVE OPACITIES AB Predictions are made of the effect of variations in the [Fe/H] metallicity on the zero point of the Cepheid period-luminosity relation in bolometric, B, V, and I magnitudes. Theoretical evolutionary tracks in the H-R diagram, computed by three independent groups at Geneva, Padua, and Basel, are combined with the positions of the blue and red edges of the instability strip in the relevant H-R diagrams to give the predicted P-L relations for [Fe/H] metallicities of 0.0, -0.4, -0.7, -1.3, and -1.7. The predictions are based on the pulsation equation, P(M, L, T-e, Z, Y), calculated at the points where the tracks of a given mass for each metallicity intersect the instability strip in the H-R diagrams. New model atmospheres and synthetic spectra are computed giving sets of grids of the bolometric corrections and B-V, V-R, R-I, and V-I colors for temperatures between 7500 and 5000 It, gravities between log g = 3.0 and log g = 0.75, and metallicities between [Fe/H] = 0.0 and [Fe/H] = -1.7. Interpolation in the grids at the relevant temperatures, gravities, and metallicities of the Cepheid instability strip give theoretical P-L relations on the Cape Cousins BVI photometric system at the blue and red edges of the strip. The metallicity dependence of the P-L relations, read at P = 10 days, are dM/d[Fe/H] = 0.00 mag dex(-1) in M(bol), +0.03 mag dex(-1) in B, -0.08 mag dex(-1) in V, and -0.10 mag dex(-1) in I in the sense that lower metallicities mean brighter magnitudes in B and fainter ones in V and I. Similar dependencies are found at P = 31.6 days. Confirmation that the zero points of the Cepheid P-L relations are not steeper functions of [Fe/H] than the theoretical values derived here is found by comparing the distance moduli of the LMC, the SMC, and IC 1613 based on the P-L relation for Galactic Cepheids ([[Fe/H]] = 0) with the distance moduli determined for these galaxies using RR Lyrae variables with the steep absolute magnitude-metallicity calibration of M,(RR)= 0.30[Fe/H] + 0.94. Applying this bright calibration, based on the Oosterhoff-Arp-Preston (OAP) metallicity effect, to the RR Lyrae variables in the LMC, the SMC, and IC 1613 gives individual distance moduli that agree to within 0.10 mag with the Cepheid distance moduli for [Fe/H] = 0 for each galaxy, confirming that no metallicity dependence of the Cepheid P-L relation can be detected at this level with the present observational data if the bright RR Lyrae hi ([Fe/H]) calibration is used. Using the stated calibrations with the Cepheid data from the literature gives the distance modulus of the LMC to be (m - M)(0) = 18.57. The modulus for the SMC, corrected for the mild metallicity effect derived here, reconciles the deviant individual B, V, and I moduli to within +/-0.01 mag, giving (m - M)(0) = 18.94 for the SMC. C1 Carnegie Inst Washington Observ, Pasadena, CA 91101 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. NASA, Goddard Space Flight Ctr, Raytheon STX Corp, Greenbelt, MD 20771 USA. RP Sandage, A (reprint author), Carnegie Inst Washington Observ, 813 Santa Barbara St, Pasadena, CA 91101 USA. NR 116 TC 63 Z9 63 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 SEP 1 PY 1999 VL 522 IS 1 BP 250 EP 275 DI 10.1086/307617 PN 1 PG 26 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 228HJ UT WOS:000082130800021 ER PT J AU Hollis, JM Vogel, SN Van Buren, D Strong, JP Lyon, RG Dorband, JE AF Hollis, JM Vogel, SN Van Buren, D Strong, JP Lyon, RG Dorband, JE TI The [N II] kinematics of R Aquarii SO ASTROPHYSICAL JOURNAL LA English DT Article DE circumstellar matter; ISM : jets and outflows; stars : individual (R Aquarii); techniques : interferometric ID BINARY-SYSTEM; JET; RESOLUTION AB We report a kinematic study of the symbiotic star system R Aqr derived from [N II] lambda 6584 emission observations with a Fabry-Perot imaging spectrometer. The [N II] spatial structure of the R Aqr jet, first observed circa 1977, and surrounding hourglass-shaped nebulosity, due to an explosion similar to 660 yr ago, are derived from 41 velocity planes spaced at similar to 12 km s(-1) intervals. Fabry-Perot imagery shows that the elliptical nebulosity making up the waist of the hourglass shell is consistent with a circular ring expanding radially at 55 km s(-1) as seen at an inclination angle i similar to 70 degrees. With respect to the position of R Aqr, at optical and radio wavelengths the jet is made up of a northeast component and a less intense, more amorphous southwest component. The CN nl Fabry-Perot data cube demonstrates that the two jet components possess quite different intensity-velocity structures which represent collimated how in opposite directions. We offer an idealized schematic model for the R Aqr jet motion which results in a small-scale helical structure forming around a larger scale helical path. The implications of such a jet model are discussed. We present a movie showing a side-by-side comparison of the spatial structure of the model and the data as a function of the 41 velocity planes. C1 NASA, Goddard Space Flight Ctr, Earth & Space Data Comp Div, Greenbelt, MD 20771 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. CALTECH, Ctr Infrared Proc & Anal, Pasadena, CA 91125 USA. Univ Maryland, Ctr Excellence Space Data & Informat Sci, NASA, Goddard Space Flight Ctr, Greenbelt, MD USA. NASA, Goddard Space Flight Ctr, Appl Informat Sci Branch, Greenbelt, MD 20771 USA. RP Hollis, JM (reprint author), NASA, Goddard Space Flight Ctr, Earth & Space Data Comp Div, Code 930, Greenbelt, MD 20771 USA. RI Lyon, Richard/D-5022-2012 NR 21 TC 13 Z9 13 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 SEP 1 PY 1999 VL 522 IS 1 BP 297 EP 304 DI 10.1086/307631 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 228HJ UT WOS:000082130800024 ER PT J AU Gerakines, PA Whittet, DCB Ehrenfreund, P Boogert, ACA Tielens, AGGM Schutte, WA Chiar, JE van Dishoeck, EF Prusti, T Helmich, FP de Graauw, T AF Gerakines, PA Whittet, DCB Ehrenfreund, P Boogert, ACA Tielens, AGGM Schutte, WA Chiar, JE van Dishoeck, EF Prusti, T Helmich, FP de Graauw, T TI Infrared Space Observatory with the observations of solid carbon dioxide in molecular clouds SO ASTROPHYSICAL JOURNAL LA English DT Article DE dust, extinction; infrared : ISM : lines and bands; ISM : molecules; stars : pre-main-sequence ID H-II REGIONS; SHORT-WAVELENGTH SPECTROMETER; 1.3MM CONTINUUM OBSERVATIONS; DEEPLY EMBEDDED PROTOSTARS; DENSE INTERSTELLAR CLOUDS; ASTROPHYSICAL ICE ANALOGS; TIME-DEPENDENT CHEMISTRY; GRAIN SURFACE-REACTIONS; TAURUS DARK CLOUD; GALACTIC-CENTER AB Spectra of interstellar CO2 ice absorption features at a resolving power of lambda/Delta lambda approximate to 1500-2000 are presented for 14 lines of sight. The observations were made with the Short-Wavelength Spectrometer (SWS) of the Infrared Space Observatory (ISO). Spectral coverage includes the primary stretching mode of CO2 near 4.27 mu m in all sources; the bending mode near 15.2 mu m is also detected in 12 of them. The selected sources include massive protostars (Elias 29 [in rho Oph], GL 490, GL 2136, GL 2591, GL 4176, NGC 7538 IRS 1, NCC 7538 IRS 9, S140, W3 IRS 5, and W33 A), sources associated with the Galactic Center (Sgr A*, GCS 3 I, and GCS 4), and a background star behind a quiescent dark cloud in Taurus (Elias 16); they thus probe a diverse range of environments. Column densities of interstellar CO2 ice relative to H2O ice fall in the range 10%-23%: this ratio displays remarkably little variation for such a physically diverse sample. Comparison of the observed profiles with laboratory data for CO2-bearing ice mixtures indicates that CO2 generally exists in at least two phases, one polar (H2O dominant) and one nonpolar (CO2 dominant). The observed CO2 profiles may also be reproduced when the nonpolar components are replaced with thermally annealed ices. Formation and evolutionary scenarios for CO2 and implications for grain mantle chemistry are discussed. Our results support the conclusion that thermal annealing, rather than energetic processing due to UV photons or cosmic rays, dominates the evolution of CO2-bearing ices. C1 Rensselaer Polytech Inst, Dept Phys Appl Phys & Astron, Troy, NY 12180 USA. Leiden Observ, NL-2300 RA Leiden, Netherlands. Kapteyn Astron Inst, NL-9700 AV Groningen, Netherlands. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. European Space Agcy, Infrared Space Observ, Sci Operat Ctr, Div Astrophys, Madrid 28080, Spain. SRON, NL-3584 CA Utrecht, Netherlands. Stichting Ruimte Onderzoek Nederland, NL-9700 AV Groningen, Netherlands. RP Gerakines, PA (reprint author), NASA, Goddard Space Flight Ctr, Code 691, Greenbelt, MD 20771 USA. RI Gerakines, Perry/B-9705-2009; Gerakines, Perry/D-2226-2012 OI Gerakines, Perry/0000-0002-9667-5904 NR 70 TC 230 Z9 231 U1 0 U2 4 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 SEP 1 PY 1999 VL 522 IS 1 BP 357 EP 377 DI 10.1086/307611 PN 1 PG 21 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 228HJ UT WOS:000082130800029 ER PT J AU Harris, MJ Naya, JE Teegarden, BJ Cline, TL Gehrels, N Palmer, DM Ramaty, R Seifert, H AF Harris, MJ Naya, JE Teegarden, BJ Cline, TL Gehrels, N Palmer, DM Ramaty, R Seifert, H TI Transient gamma ray spectrometer observations of gamma-ray lines from novae. I. Limits on the positron annihilation line in five individual novae SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays : observations; novae, cataclysmic variables; nuclear reactions, nucleosynthesis, abundances; white dwarfs ID CLASSICAL NOVAE; EMISSION; ASTRONOMY; SEARCH; BE-7 AB The Transient Gamma Ray Spectrometer (TGRS) on board the Wind spacecraft has spent most of the interval 1995-1997 in a high-altitude orbit where gamma-ray backgrounds are low. Its high-resolution Ge spectrometer is thus able to detect weak lines that are slightly offset from stronger background features. One such line is predicted from nucleosynthesis in classical novae, where beta decays on a timescale of a few hours in an expanding envelope produce positrons that annihilate to generate a line that is blueshifted by a few keV away from the background annihilation line at 511 keV. The broad TGRS field of view contained five known Galactic novae during 1995 January-1997 June, and we have searched the spectra taken around the times of these events for the blueshifted nova annihilation line. Although no definite detections were made, the method is shown to be sensitive enough to detect novae occurring on ONeMg-rich white dwarfs out to about 2.5 kpc. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RI Gehrels, Neil/D-2971-2012 NR 37 TC 46 Z9 46 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 SEP 1 PY 1999 VL 522 IS 1 BP 424 EP 432 DI 10.1086/307625 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 228HJ UT WOS:000082130800035 ER PT J AU Patt, BL Ulmer, MP Zhang, W Cordes, JM Arzoumanian, Z AF Patt, BL Ulmer, MP Zhang, W Cordes, JM Arzoumanian, Z TI A search for pulse-to-pulse variability of the Crab pulsar SO ASTROPHYSICAL JOURNAL LA English DT Article DE plasmas; pulsars : individual (Crab); stars : magnetic fields; stars : neutron ID RAPIDLY SPINNING PULSARS; GAMMA-RAY; ENERGETIC RADIATION; EMISSION AB We report the analysis of 1 hour's worth of RXTE data in which it was possible to detect individual pulses from the Crab pulsar. These data demonstrate that the Crab pulsar X-ray pulses are steady at the level of 7%, and we suggest that the emitting region is likely to come from a region where the magnetic field is "stiff." C1 Northwestern Univ, Dept Phys & Astron, Evanston, IL 60208 USA. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Cornell Univ, Dept Astron, Ithaca, NY 14853 USA. Cornell Univ, Natl Astron & Ionosphere Ctr, Ithaca, NY 14853 USA. RP Patt, BL (reprint author), Northwestern Univ, Dept Phys & Astron, Evanston, IL 60208 USA. NR 17 TC 7 Z9 7 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 SEP 1 PY 1999 VL 522 IS 1 BP 440 EP 443 DI 10.1086/307620 PN 1 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 228HJ UT WOS:000082130800037 ER PT J AU Burgasser, AJ Kirkpatrick, JD Brown, ME Reid, IN Gizis, JE Dahn, CC Monet, DG Beichman, CA Liebert, J Cutri, RM Skrutskie, MF AF Burgasser, AJ Kirkpatrick, JD Brown, ME Reid, IN Gizis, JE Dahn, CC Monet, DG Beichman, CA Liebert, J Cutri, RM Skrutskie, MF TI Discovery of four field methane (T-type) dwarfs with the Two Micron All-Sky Survey SO ASTROPHYSICAL JOURNAL LA English DT Article DE infrared : stars; stars : fundamental parameters; stars : individual (2MASSI J1047539+212423, 2MASSW J1217111-031113, 2MASSW; J1225543-273947, 2MASSW J1237392+652615, 2MASSW J1346464-003150); stars : low-mass, brown dwarfs ID BROWN DWARF; STAR AB We report the discovery of four field methane ("T"-type) brown dwarfs using Two Micron All-Sky Survey (2MASS) data. One additional methane dwarf, previously discovered by the Sloan Digital Sky Survey, was also identified. Near-infrared spectra clearly show the 1.6 and 2.2 pm CH, absorption bands characteristic of objects with T(eff) less than or similar to 1300 K as well as broadened H(2)O bands at 1.4 and 1.9 mu m. Comparing the spectra of these objects with that of Gl 229B, we propose that all new 2MASS T dwarfs are warmer than 950 K, in order from warmest to coolest: 2MASS J1217-03, 2MASS J1225-27, 2MASS J1047+21, and 2MASS J1237+65. Based on this preliminary sample, we find a warm T dwarf surface density of 0.0022 T dwarfs deg(-2), or similar to 90 warm T dwarfs over the whole sky detectable to J < 16. The resulting space density upper limit, 0.01 T dwarfs pc(-3), is comparable to that of the first L dwarf sample from Kirkpatrick et al. C1 CALTECH, Div Phys, Pasadena, CA 91125 USA. CALTECH, Ctr Infrared Proc & Anal, Pasadena, CA 91125 USA. CALTECH, Div Geol & Planetary Sci, Pasadena, CA 91125 USA. Univ Penn, Dept Phys & Astron, Philadelphia, PA 19104 USA. Univ Massachusetts, Five Coll Radio Astron Observ, Dept Phys & Astron, Dept Astron, Amherst, MA 01003 USA. USN Observ, Flagstaff, AZ 86002 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Arizona, Steward Observ, Tucson, AZ 85721 USA. RP Burgasser, AJ (reprint author), CALTECH, Div Phys, M-S 103-33, Pasadena, CA 91125 USA. EM diver@cco.caltech.edu OI Gizis, John/0000-0002-8916-1972 NR 33 TC 158 Z9 158 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 1 PY 1999 VL 522 IS 1 BP L65 EP L68 DI 10.1086/312221 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 228HL UT WOS:000082131000016 ER PT J AU Gotthelf, EV Vasisht, G Dotani, T AF Gotthelf, EV Vasisht, G Dotani, T TI On the spin history of the X-ray pulsar in Kes 73: Further evidence for an ultramagnetized neutron star SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars : individual (Kes 73, 1E 1841-045); stars : neutron; supernova remnants; X-rays : stars ID SUPERNOVA REMNANT G27.4+0.0 AB In previous papers, we presented the discovery of a 12 s X-ray pulsar in the supernova remnant Kes 73, providing the first direct evidence for an ultramagnetized neutron star, a magnetar, with an equivalent dipole field of nearly 20 times the quantum critical magnetic field (m(e)(2)c(3)/e(h) over bar). Our conclusions were based on two epochs of the measurement of the spin, along with an age estimate of the host supernova remnant. Herein, we present a spin chronology of the pulsar using additional Ginga, ASCA, RXTE, and BeppoSAX data sets spanning over a decade. The timing and spectral analyses confirm our initial results and severely Limit an accretion origin for the observed flux. Over the 10 yr baseline, the pulsar is found to undergo a rapid, constant spin-down while maintaining a steady flux and an invariant pulse profile. Within the measurement uncertainties, no systematic departures from a linear spin-down are found-departures as in the case of glitches or simply stochastic fluctuations in the pulse times of arrival (e.g,, red timing noise). We suggest that this pulsar is akin to the soft gamma-ray repeaters; however, it is remarkably stable and has yet to display similar outbursts. Future gamma-ray activity from this object is likely. C1 Columbia Univ, Columbia Astrophys Lab, New York, NY 10027 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Inst Space & Astronaut Sci, Sagamihara, Kanagawa 229, Japan. RP Gotthelf, EV (reprint author), Columbia Univ, Columbia Astrophys Lab, Mail Code 5247,Pupin Hall,550 W 120th St, New York, NY 10027 USA. NR 23 TC 61 Z9 62 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 SEP 1 PY 1999 VL 522 IS 1 BP L49 EP L52 DI 10.1086/312220 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 228HL UT WOS:000082131000012 ER PT J AU Judge, RA Jacobs, RS Frazier, T Snell, EH Pusey, ML AF Judge, RA Jacobs, RS Frazier, T Snell, EH Pusey, ML TI The effect of temperature and solution pH on the nucleation of tetragonal lysozyme crystals SO BIOPHYSICAL JOURNAL LA English DT Article ID EGG-WHITE LYSOZYME; DYNAMIC LIGHT-SCATTERING; PROTEIN CRYSTALLIZATION; TITRATION CURVE; HEN LYSOZYME; X-RAY; GROWTH; IMPURITIES; PURIFICATION; RESOLUTION AB Part of the challenge of macromolecular crystal growth for structure determination is obtaining crystals with a volume suitable for x-ray analysis. In this respect an understanding of the effect of solution conditions on macromolecule nucleation rates is advantageous. This study investigated the effects of supersaturation, temperature, and pH on the nucleation rate of tetragonal lysozyme crystals. Batch crystallization plates were prepared at given solution concentrations and incubated at set temperatures over 1 week. The number of crystals per well with their size and axial ratios were recorded and correlated with solution conditions. Crystal numbers were found to increase with increasing supersaturation and temperature. The most significant variable, however, was pH; crystal numbers changed by two orders of magnitude over the pH range 4.0-5.2. Crystal size also varied with solution conditions, with the largest crystals obtained at pH 5.2. Having optimized the crystallization conditions, we prepared a batch of crystals under the same initial conditions, and 50 of these crystals were analyzed by x-ray diffraction techniques. The results indicate that even under the same crystallization conditions, a marked variation in crystal properties exists. C1 NASA, George C Marshall Space Flight Ctr, Alliance Micrograv Mat Sci & Applicat, Huntsville, AL 35812 USA. Univ Alabama, Dept Chem Engn, Huntsville, AL 35899 USA. Michigan State Univ, Dept Biochem, E Lansing, MI 48825 USA. RP Pusey, ML (reprint author), NASA, George C Marshall Space Flight Ctr, Alliance Micrograv Mat Sci & Applicat, Huntsville, AL 35812 USA. NR 40 TC 51 Z9 52 U1 2 U2 25 PU BIOPHYSICAL SOCIETY PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0006-3495 J9 BIOPHYS J JI Biophys. J. PD SEP PY 1999 VL 77 IS 3 BP 1585 EP 1593 DI 10.1016/S0006-3495(99)77006-2 PG 9 WC Biophysics SC Biophysics GA 232AL UT WOS:000082343500037 PM 10465769 ER PT J AU Pitman, AJ Henderson-Sellers, A Desborough, CE Yang, ZL Abramopoulos, F Boone, A Dickinson, RE Gedney, N Koster, R Kowalczyk, E Lettenmaier, D Liang, X Mahfouf, JF Noilhan, J Polcher, J Qu, W Robock, A Rosenzweig, C Schlosser, CA Shmakin, AB Smith, J Suarez, M Verseghy, D Wetzel, P Wood, E Xue, Y AF Pitman, AJ Henderson-Sellers, A Desborough, CE Yang, ZL Abramopoulos, F Boone, A Dickinson, RE Gedney, N Koster, R Kowalczyk, E Lettenmaier, D Liang, X Mahfouf, JF Noilhan, J Polcher, J Qu, W Robock, A Rosenzweig, C Schlosser, CA Shmakin, AB Smith, J Suarez, M Verseghy, D Wetzel, P Wood, E Xue, Y TI Key results and implications from phase 1(c) of the Project for Intercomparison of Land-Surface Parametrization Schemes SO CLIMATE DYNAMICS LA English DT Article ID GENERAL-CIRCULATION MODELS; SOIL-MOISTURE; BIOSPHERE MODEL; PARAMETERIZATION; TRANSPIRATION; PREDICTION; BOUNDARY; CLIMATE; GCMS AB Using atmospheric forcing data generated from a general circulation climate model, sixteen land surface schemes participating in the Project for the Intercomparison of Land-surface Parametrization Schemes (PILPS) were run off-line to equilibrium using forcing data from a GCM representative of a tropical forest and a mid-latitude grassland grid point. The values for each land surface parameter (roughness length, minimum stomatal resistance, soil depth etc.) were provided. Results were quality controlled and analyzed, focusing on the scatter simulated amongst the models. There were large differences in how the models' partitioned available energy between sensible and latent heat. Annually averaged, simulations for the tropical forest ranged by 79 W m(-2) for the sensible heat flux and 80 W m(-2) for the latent heat flux. For the grassland, simulations ranged by 34 W m(-2) for the sensible heat flux and 27 W m(-2) for the latent heat flux. Similarly large differences were found for simulated runoff and soil moisture and at the monthly time scale. The models' simulation of annually averaged effective radiative temperature varied with a range, between all the models, of 1.4 K for tropical forest and 2.2 K for the grassland. The simulation of latent and sensible heat fluxes by a standard 'bucket' models was anomalous although this could be corrected by an additional resistance term. These results imply that the current land surface models do not agree on the land surface climate when the atmospheric forcing and surface parameters are prescribed. The nature of the experimental design, it being offline and with artificial forcing, generally precludes judgements concerning the relative quality of any specific model. Although these results were produced de-coupled from a host model, they do cast doubt on the reliability of land surface schemes. It is therefore a priority to resolve the disparity in the simulations, understand the reasons behind the scatter and to determine whether this lack of agreement in decoupled tests is reproduced in coupled experiments. C1 Macquarie Univ, Dept Phys Geog, N Ryde, NSW 2109, Australia. Australian Nucl Sci & Technol Org, Sydney, NSW, Australia. Univ Arizona, Inst Atmospher Phys, Tucson, AZ 85721 USA. Sci Syst & Applicat Inc, New York, NY USA. Metro France, Toulouse, France. Hadley Ctr, Bracknell, Berks, England. NASA, Goddard Space Flight Ctr, Hydrol Sci Branch, Greenbelt, MD 20771 USA. CSIRO, Div Atmospher Res, Aspendale, Vic, Australia. Univ Washington, Dept Civil Engn, Seattle, WA 98195 USA. Princeton Univ, Princeton, NJ 08544 USA. ECMWF, Reading, Berks, England. CNRS, Meteorol Dynam Lab, Paris, France. RMIT, Melbourne, Vic, Australia. Rutgers State Univ, New Brunswick, NJ 08903 USA. COLA, Calverton, MD USA. Inst Geog, Moscow, ID USA. Atmospher Environm Serv, Climate Res Branch, Downsview, ON, Canada. NASA, Goddard Space Flight Ctr, Mesoscale Dynam & Precipitat Branch, Greenbelt, MD 20771 USA. Univ Maryland, Dept Geog, College Pk, MD 20742 USA. RP Pitman, AJ (reprint author), Macquarie Univ, Dept Phys Geog, N Ryde, NSW 2109, Australia. EM apitman@penman.es.mq.edu.au RI Yang, Zong-Liang/B-4916-2011; Pitman, Andrew/A-7353-2011; Henderson-Sellers, Ann/H-5323-2011; Koster, Randal/F-5881-2012; lettenmaier, dennis/F-8780-2011; Robock, Alan/B-6385-2016; OI Pitman, Andrew/0000-0003-0604-3274; Koster, Randal/0000-0001-6418-6383; lettenmaier, dennis/0000-0003-3317-1327; Wood, Eric/0000-0001-7037-9675 NR 34 TC 76 Z9 78 U1 2 U2 9 PU SPRINGER PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 0930-7575 EI 1432-0894 J9 CLIM DYNAM JI Clim. Dyn. PD SEP PY 1999 VL 15 IS 9 BP 673 EP 684 DI 10.1007/s003820050309 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 236WK UT WOS:000082622100005 ER PT J AU Guattery, S Leighton, T Miller, GL AF Guattery, S Leighton, T Miller, GL TI The path resistance method for bounding the smallest nontrivial eigenvalue of a Laplacian SO COMBINATORICS PROBABILITY & COMPUTING LA English DT Article ID MATRICES; GRAPHS; EIGENVECTORS AB We introduce the path resistance method for lower bounds on the smallest nontrivial eigenvalue of the Laplacian matrix of a graph. The method is based on viewing the graph in terms of electrical circuits: it uses clique embeddings to produce lower bounds on lambda(2) and star embeddings to produce lower bounds on the smallest Rayleigh quotient when there is a zero Dirichlet boundary condition. The method assigns priorities to the paths in the embedding; we show that, for an unweighted tree T, using uniform priorities for a clique embedding produces a lower bound on lambda(2) that is off by at most an O(log diameter(T)) factor. We show that the best bounds this method can produce for clique embeddings are the same as for a related method that uses clique embeddings and edge lengths to produce bounds. C1 NASA, Langley Res Ctr, ICASE, Hampton, VA 23681 USA. MIT, Dept Math, Cambridge, MA 02139 USA. Carnegie Mellon Univ, Sch Comp Sci, Pittsburgh, PA 15213 USA. RP Guattery, S (reprint author), NASA, Langley Res Ctr, ICASE, Mail Stop 403, Hampton, VA 23681 USA. NR 21 TC 5 Z9 5 U1 0 U2 0 PU CAMBRIDGE UNIV PRESS PI NEW YORK PA 40 WEST 20TH STREET, NEW YORK, NY 10011-4211 USA SN 0963-5483 J9 COMB PROBAB COMPUT JI Comb. Probab. Comput. PD SEP PY 1999 VL 8 IS 5 BP 441 EP 460 DI 10.1017/S0963548399003958 PG 20 WC Computer Science, Theory & Methods; Mathematics; Statistics & Probability SC Computer Science; Mathematics GA 273DD UT WOS:000084691500005 ER PT J AU Konsur, B Megaridis, CM Griffin, DW AF Konsur, B Megaridis, CM Griffin, DW TI Soot aerosol properties in laminar soot-emitting microgravity nonpremixed flames SO COMBUSTION AND FLAME LA English DT Article ID ETHYLENE DIFFUSION FLAMES; PARTICLES; GROWTH; MORPHOLOGY; TRANSPORT AB The spatial distributions and morphological properties of the soot aerosol are examined experimentally in a series of 0-g laminar gas-jet nonpremixed flames. The methodology deploys round jet diffusion flames of nitrogen-diluted acetylene fuel burning in quiescent air at atmospheric pressure. Full-field laser-light extinction is utilized to determine transient soot spatial distributions within the flames. Thermophoretic sampling is employed in conjunction with transmission electron microscopy to define soot microstructure within the seat-emitting 0-g flames. The microgravity tests indicate that the 0-g flames attain a quasi-steady state roughly 0.7 s after ignition, and sustain their annular structure even beyond their luminous flame tip. The measured peak soot volume fractions show a complex dependence on burner exit conditions, and decrease in a nonlinear fashion with decreasing characteristic flow residence times. Fuel preheat by similar to 140 K appears to accelerate the formation of soot near the flame axis via enhanced fuel pyrolysis rates. The increased soot presence caused by the elevated fuel injection temperatures triggers higher flame radiative losses, which may account for the premature suppression of soot growth observed along the annular region of preheated-fuel flames. Electron micrographs of soot aggregates collected in 0-g reveal the presence of soot precursor particles near the symmetry axis at midflame height. The observations also verify that soot primary particle sizes are nearly uniform among aggregates present at the same flame location, but vary considerably with radius at a fixed distance from the burner. The maximum primary size in 0-g is found to be by 40% larger than in I-g, under the same burner exit conditions. Estimates of the number concentration of primary particles and surface area of soot particulate phase per unit volume of the combustion gases are also made for selected in-flame locations. (C) 1999 by The Combustion Institute. C1 Univ Illinois, Dept Mech Engn MC 251, Chicago, IL 60607 USA. NASA, Lewis Res Ctr, Micrograv Fluid Phys Branch, Cleveland, OH 44135 USA. RP Megaridis, CM (reprint author), Univ Illinois, Dept Mech Engn MC 251, 842 W Taylor St, Chicago, IL 60607 USA. OI Megaridis, Constantine/0000-0002-6339-6933 NR 26 TC 18 Z9 19 U1 0 U2 4 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA SN 0010-2180 J9 COMBUST FLAME JI Combust. Flame PD SEP PY 1999 VL 118 IS 4 BP 509 EP 520 DI 10.1016/S0010-2180(99)00021-8 PG 12 WC Thermodynamics; Energy & Fuels; Engineering, Multidisciplinary; Engineering, Chemical; Engineering, Mechanical SC Thermodynamics; Energy & Fuels; Engineering GA 219UN UT WOS:000081625600001 ER PT J AU Arian, E Ta'asan, S AF Arian, E Ta'asan, S TI Analysis of the Hessian for aerodynamic optimization: inviscid flow SO COMPUTERS & FLUIDS LA English DT Article DE aerodynamic optimization; optimal shape; full potential equation; Euler equations; Hessian; preconditioning; regularization ID DESIGN AB In this paper, we analyze inviscid aerodynamic shape optimization problems governed by the full potential and the Euler equations in two and three dimensions. The analysis indicates that minimization of pressure-dependent cost functions results in Hessians whose eigenvalue distributions are identical for the full potential and the Euler equations. However, the optimization problems in two and three dimensions are inherently different. While the two-dimensional optimization problems are well posed, the three dimensional ones are ill-posed. Oscillations in the shape up to the smallest scale allowed by the design space can develop in the direction perpendicular to the flow, implying that a regularization is required. The analysis also gives an estimate of the Hessian's condition number which implies that the problems at hand are ill-conditioned. Infinite dimensional approximations for the Hessians are constructed and preconditioners for gradient-based methods are derived from these approximate Hessians. Numerical results are given for the small disturbance potential equation in two and in three space dimensions. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 Carnegie Mellon Univ, Dept Math Sci, Pittsburgh, PA 15213 USA. NASA, Langley Res Ctr, Inst Comp Applicat Sci & Engn, Hampton, VA 23681 USA. RP Ta'asan, S (reprint author), Carnegie Mellon Univ, Dept Math Sci, Pittsburgh, PA 15213 USA. RI Ta'asan, Shlomo/B-8366-2017 OI Ta'asan, Shlomo/0000-0002-6085-7124 NR 18 TC 17 Z9 17 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 SEP PY 1999 VL 28 IS 7 BP 853 EP 877 DI 10.1016/S0045-7930(98)00060-7 PG 25 WC Computer Science, Interdisciplinary Applications; Mechanics SC Computer Science; Mechanics GA 211NG UT WOS:000081166700002 ER PT J AU Sams, CF Crucian, BE Clift, VL Meinelt, EM AF Sams, CF Crucian, BE Clift, VL Meinelt, EM TI Development of a whole blood staining device for use during space shuttle flights SO CYTOMETRY LA English DT Article DE flow cytometry; microgravity; Space Shuttle; immunology; immunophenotyping AB Background: Exposure to microgravity during space flight results in profound physiologic changes. Numerous studies have shown changes in circulating populations of peripheral blood immune cells immediately after space flight. It is currently unknown if these changes result from exposure to microgravity or are caused by the stress of reentry and readaptation to gravity. Methods: We have developed the whole blood staining device (WBSD) as a system for the staining of whole blood collected during space flight for subsequent flow cytometric analysis. This device contains all liquids to address safety issues concerned with space flight and also moves the cells through the staining, lyse/fixation, and dilution steps. Results: Data from now cytometric analysis of samples stained in the WBSD was found to be comparable to data from samples stained by the conventional methods. Cells stained with the WBSD remain stable in the device for up to 14 days. The necessary manipulations required to use the device were tested on the KC-135 aircraft during the reduced gravity segment of parabolic flight. Conclusions: With the WBSD immunophenotype analysis can be performed at various time points for the duration of an entire Shuttle flight. In addition, this device has significant terrestrial applications for rapid and easy immunofluorescence labeling of whole blood in remote and isolated locations where immediate access to specialized equipment and skilled laboratory personnel may not be available. The WBSD provides a simple mechanism to design specific immunophenotyping tests for use by nontechnical personnel at bedside or in field locations. Published 1999 Wiley-Liss, Inc.(dagger). C1 NASA, Lyndon B Johnson Space Ctr, Life Sci Res Labs, Houston, TX 77058 USA. Wyle Labs, Houston, TX USA. DBCD Inc, Houston, TX USA. Becton Dickinson Immunocytometry Syst, San Jose, CA 95131 USA. RP Sams, CF (reprint author), NASA, Lyndon B Johnson Space Ctr, Life Sci Res Labs, Mail Code SD3, Houston, TX 77058 USA. NR 3 TC 10 Z9 10 U1 0 U2 0 PU WILEY-LISS PI NEW YORK PA DIV JOHN WILEY & SONS INC, 605 THIRD AVE, NEW YORK, NY 10158-0012 USA SN 0196-4763 J9 CYTOMETRY JI Cytometry PD SEP 1 PY 1999 VL 37 IS 1 BP 74 EP 80 DI 10.1002/(SICI)1097-0320(19990901)37:1<74::AID-CYTO9>3.0.CO;2-H PG 7 WC Biochemical Research Methods; Cell Biology SC Biochemistry & Molecular Biology; Cell Biology GA 229CD UT WOS:000082175200009 PM 10451509 ER PT J AU Olson, SL T'ein, JS AF Olson, SL T'ein, JS TI Near-surface vapour bubble layers in buoyant low stretch burning of polymethylmethacrylate SO FIRE AND MATERIALS LA English DT Article ID LIQUID AB Large-scale buoyant low stretch stagnation point diffusion flames over a solid fuel (polymethylmethacrylate) were studied for a range of aerodynamic stretch rates of 2-12 s(-1) which are of the same order as spacecraft ventilation induced stretch in a microgravity environment. An extensive layer of polymer material above the glass transition temperature,vas observed. Unique phenomena associated with this extensive glass layer included substantial swelling of the burning surface, in-depth bubble formation, and migration and/or elongation of the bubbles normal to the hot surface. The bubble layer acted to insulate the polymer surface by reducing the effective conductivity of the solid. The reduced in-depth conduction stabilized the dame for longer than expected from theory neglecting the bubble layer. While buoyancy acts to move the bubbles deeper into the molten polymer, thermocapillary forces and surface regression both act to bring the bubbles to the burning surface. Bubble layers may thus be very important in low gravity (low stretch) burning materials, As bubbles reached the burning surface, monomer fuel vapours jetted from the surface, enhancing burning by entraining ambient air flow. Popping of these bubbles at the surface can expel burning droplets of the molten material, which may increase the fire propagation hazards at low stretch rates. Published in 1999 by John Wiley & Sons, Ltd. C1 NASA, Glenn Res Ctr, Cleveland, OH 44145 USA. Case Western Reserve Univ, Cleveland, OH 44106 USA. RP Olson, SL (reprint author), NASA, Glenn Res Ctr, Mail Stop 500-115, Cleveland, OH 44145 USA. NR 26 TC 5 Z9 5 U1 2 U2 3 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX PO19 1UD, ENGLAND SN 0308-0501 J9 FIRE MATER JI Fire Mater. PD SEP-OCT PY 1999 VL 23 IS 5 BP 227 EP 237 DI 10.1002/(SICI)1099-1018(199909/10)23:5<227::AID-FAM689>3.0.CO;2-2 PG 11 WC Materials Science, Multidisciplinary SC Materials Science GA 274EP UT WOS:000084751000005 ER PT J AU Bigelow, KA Boggs, CH He, X AF Bigelow, KA Boggs, CH He, X TI Environmental effects on swordfish and blue shark catch rates in the US North Pacific longline fishery SO FISHERIES OCEANOGRAPHY LA English DT Article DE blue shark; fishery oceanography; generalized additive models; longline fishery; North Pacific; remote sensing; swordfish ID SUB-TROPICAL FRONT; TUNA CATCH; SOUND-VELOCITY; BERING SEA; GULF; MEXICO; ASSOCIATION; TEMPERATURE; MOVEMENTS; YELLOWFIN AB Generalized additive models (GAMs) were applied to examine the relative influence of various factors on fishery performance, defined as nominal catch- per-unit-effort (CPUE) of swordfish (Xiphias gladius) and blue shark (Prionace glauca) in the Hawaii-based swordfish fishery. Commercial fisheries data for the analysis consisted of a 5 year (1991-1995) time series of 27 901 longline sets. Mesoscale relationships were analysed for seven physical variables (latitude, longitude, SST, SST frontal energy, temporal changes in SST (Delta SST), SST frontal energy (Delta SST frontal energy) and bathymetry), all of which may affect the availability of swordfish and blue shark to the fishery, and three variables (number of lightsticks per hook, lunar index, and wind velocity) which may relate to the effectiveness of the fishing gear. Longline CPUE data were analysed in relation to SST data on three spatiotemporal scales (18 km weekly, 1 degrees-weekly, 1 degrees-monthly). Depending on the scale of SST data, GAM analysis accounted for 39-42% and 44-45% of the variance in nominal CPUE for swordfish and blue shark, respectively. Stepwise GAM building revealed the relative importance of the variables in explaining the variance in CPUE. For swordfish, by decreasing importance, the variables ranked: (1) latitude, (2) time, (3) longitude, (4) lunar index, (5) lightsticks per hook, (6) SST, (7) Delta SST frontal energy, (8) wind velocity, (9) SST frontal energy, (10) bathymetry, and (11) Delta SST. For blue shark, the variables ranked: (1) latitude, (2) longitude, (3) time, (4) SST, (5) lightsticks per hook, (6) Delta SST, (7) Delta SST frontal energy, (8) SST frontal energy, (9) wind velocity, (10) lunar index, and (11) bathymetry. Swordfish CPUE increased with latitude to peak at 35-40 degrees N and increased in the vicinity of temperature fronts and during the full moon. Shark CPUE also increased with latitude up to 40 degrees N, and increased westward, but declined abruptly at SSTs colder than 16 degrees C. As a comparison with modelling fishery performance in relation to specific environmental and fishery operational effects, fishery performance was also modelled as a function of categorical time (month) and area (2 degrees squares) variables using a generalized linear model (GLM) approach. The variance accounted for by the GLMs was approximate to 1-3% lower than the variance explained by the GAMs. Time series of swordfish and blue shark CPUE standardized for the environmental and operational variables quantified in the GAM and for the time-area effects in the GLM are presented. For swordfish, both nominal and standardized time series indicate a decline in CPUE, whereas the opposite trend was seen for blue shark. C1 Univ Hawaii, Joint Inst Marine & Atmospher Res, Pelag Fisheries Res Program, Honolulu, HI 96822 USA. NOAA, Natl Marine Fisheries Serv, SW Fisheries Sci Ctr, Honolulu Lab, Honolulu, HI 96822 USA. RP Bigelow, KA (reprint author), Ocean Fisheries Programme, SPC, BP D5, Noumea 98848, New Caledonia. NR 64 TC 142 Z9 167 U1 4 U2 28 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 SEP PY 1999 VL 8 IS 3 BP 178 EP 198 DI 10.1046/j.1365-2419.1999.00105.x PG 21 WC Fisheries; Oceanography SC Fisheries; Oceanography GA 262UH UT WOS:000084084500002 ER PT J AU Borg, L Norman, M Nyquist, L Bogard, D Snyder, G Taylor, L Lindstrom, M AF Borg, L Norman, M Nyquist, L Bogard, D Snyder, G Taylor, L Lindstrom, M TI Isotopic studies of ferroan anorthosite 62236: A young lunar crustal rock from a light rare-earth-element-depleted source SO GEOCHIMICA ET COSMOCHIMICA ACTA LA English DT Article ID RB-SR; SM-ND; IMBRIUM BASIN; MELT ROCKS; MOON; AGE; EVOLUTION; PETROGENESIS; CONSTRAINTS; CHRONOLOGY AB Isotopic analyses of mineral fractions and whole rocks from the ferroan anorthosite 62236 yield a Sm-Nd isochron with an age of 4.29 +/- 0.06 Ga and an initial epsilon(Nd)(143) value of +3.1 +/- 0.9. We have also measured epsilon(Nd)(142) anomalies of +0.25 on two fractions of 62236. These values are higher than the value of -0.1 predicted if 62236 was derived from a chondritic source at 4.29 Ga, but are consistent with the positive initial epsilon(Nd)(143) value. The Sm-Nd isotopic composition of 62236 has been modified by the capture of thermal neutrons such that the Sm-147/Nd-144, Nd-143/Nd-144, and Nd-142/Nd-144 ratios measured on the mineral fractions and whole rocks must be corrected. The corrections do not significantly alter the Sm-Nd isotopic results determined on 62236, Despite the fact that the Ar-Ar and Rb-Sr isotopic systematics of 62236 have been reset by impact metamorphism at 3.93 +/- 0.04 Ga, the Sm-Nd systematics appear to have been unaffected. The Sm-Nd isotopic systematics of 62236 provide several constrains on models of lunar crustal differentiation provided they have not been reset since crystallization. First, the relatively young age of 62236, as well as the old ages determined on several crustal plutonic rocks of the Mg-suite, require multiple sources of magmas on the Moon very early in its history. Second, positive epsilon(Nd)(143) values determined on all analyzed ferroan anorthosites suggest that they were derived from sources depleted in light rare earth elements. And third, models based on initial epsilon(Nd)(143) and present-day epsilon(Nd)(143) values suggest that the source of 62236 was depleted in light rare earth elements at similar to 4.46 Ga. In order to reconcile these observations with the lunar magma ocean model (1) the magma ocean must have existed for a very short period of time, and may have had a sub-chondritic Nd/Sm ratio, and (2) the youngest ferroan anorthosites, such as 62236, cannot be cumulates from the magma ocean, but must form by other processes. Copyright (C) 1999 Elsevier Science Ltd. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Macquarie Univ, Sch Earth Sci, ARC Natl Key Ctr Geochem Evolut & Metallogeny Con, Sydney, NSW 2109, Australia. Univ Tennessee, Dept Geol Sci, Knoxville, TN 37996 USA. RP Borg, L (reprint author), Univ New Mexico, Dept Earth & Planetary Sci, Inst Meteorit, Albuquerque, NM 87131 USA. NR 70 TC 62 Z9 66 U1 2 U2 4 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0016-7037 J9 GEOCHIM COSMOCHIM AC JI Geochim. Cosmochim. Acta PD SEP PY 1999 VL 63 IS 17 BP 2679 EP 2691 DI 10.1016/S0016-7037(99)00130-1 PG 13 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 242NX UT WOS:000082948100014 ER PT J AU Ivins, ER James, TS AF Ivins, ER James, TS TI Simple models for late Holocene and present-day Patagonian glacier fluctuations and predictions of a geodetically detectable isostatic response SO GEOPHYSICAL JOURNAL INTERNATIONAL LA English DT Article DE crustal deformation; geodesy; glacial rebound; hydrology; mantle rheology ID SURFACE AIR-TEMPERATURE; MAXWELL HALF-SPACE; SOUTH-AMERICA; UPPER-MANTLE; MAGELLAN-STRAIT; TRIPLE JUNCTION; HIGH-RESOLUTION; TREE-RING; ICE-AGE; EARTH AB The late Holocene glacial moraine chronology in the southernmost South American Andes includes four (14)C dated Neoglacial advances and retreats. These are used as proxy information to characterize mass fluctuation of the Patagonian icefields during the last 5000 years. Modelled ice loads force a phase-lagged viscoelastic gravitational deformation of the solid Earth. The ancient glacier fluctuations may, therefore, drive present-day crustal motion even in the absence of present-day ice mass imbalance. Numerical models show that such rates of present-day uplift and subsidence are larger than those driven by the viscous memory of late Pleistocene deglaciation. Both spherical and flat-earth models are employed, the latter being used to study exhaustively the effects of glacial load history on the predicted vertical crustal velocity. Recent assessment of net mass balance from 1944 to 1985 indicates that the Southern Patagonian icefield has significantly deteriorated due to snout retreat and thinning. Volume loss rates are estimated at about 3.4-9.3 km(3) yr(-1). The predicted vertical isostatic response to this recession and to the modelled Holocene Neoglaciations is at a marginally detectable level (approximate to 1 mm yr(-1)) if the mantle/asthenosphere beneath Patagonia has a viscosity of about 10(21) p, S. However, for reduced mantle viscosities, the younger Holocene glacial load histories predict larger signatures. In fact, if the viscosity is about 2 x 10(20) Pa s, or lower, then geodetically detectable vertical motion may be driven by a regional Little Ice Age (LIA) (1400-1750 AD) glacier advance and subsequent 20th century retreat. Although this value for mantle viscosity is lower than thought typical of continental shield mantle (approximate to 10(21) Pa s), it is consistent with inversions for post-seismic relaxation time constants in island are environments and in regions with significant Neogene continental tectonism. In the viscosity regime of 5 x 10(18)-2 X 10(19) Pa s, the predicted rates of vertical crustal motion are similar to those presently occurring in Fennoscandia and Hudson Bay (5-10 mm yr(-1)). Geodetic data may be sensitive to the time-integrated growth and subsequent retreat of Patagonian glacier ice mass over the last 600 years. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Geol Survey Canada, Pacific Geosci Ctr, Sidney, BC V8L 4B2, Canada. RP Ivins, ER (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM eri@fryxell.jpl.nasa.gov RI James, Thomas/D-9301-2013 OI James, Thomas/0000-0001-7321-047X NR 82 TC 42 Z9 43 U1 3 U2 9 PU WILEY-BLACKWELL PI MALDEN PA COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA SN 0956-540X J9 GEOPHYS J INT JI Geophys. J. Int. PD SEP PY 1999 VL 138 IS 3 BP 601 EP 624 DI 10.1046/j.1365-246x.1999.00899.x PG 24 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 235KY UT WOS:000082541900001 ER PT J AU Zatman, S Bloxham, J AF Zatman, S Bloxham, J TI On the dynamical implications of models of B(s) in the Earth's core SO GEOPHYSICAL JOURNAL INTERNATIONAL LA English DT Article DE core flows; dynamo theory; geomagnetism ID ANGULAR-MOMENTUM; MAGNETIC-FIELD; INNER-CORE; MANTLE; SURFACE; MOTIONS; FLOW; ROTATION AB Recent work has shown that the zonal, equatorially symmetric, time-varying part of a model of the flow at the surface of the Earth's core can be well explained by only two standing waves, and that by making certain assumptions these waves may be inverted for rms B(s) (the component of field pointing away from the rotation axis) and a quantity parametrizing friction or excitation (F) of the waves. Here, we discuss the two-wave fit, and describe the implications of models of rms B(s) and friction/excitation for the dynamic state of the core, for the torque balance on axial cylinders, and for recent numerical simulations of the geodynamo. We find several possible explanations for why only two standing waves are needed to fit the data, including the possibility that it is due to the resolution of the core flow model rather than conditions within the core itself. We find that the fits of rms B(s) and F suggest that the role of inertia should not be discounted in the core, and that care should be taken in constructing geodynamo simulations so that the effective friction at the core-mantle boundary does not swamp the inertial term. A ratio of the magnitude of the two appears to be O(1) in the Earth's core: we believe that, ideally, a numerical model of the Earth's core should reproduce this result. C1 NASA, USRA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Harvard Univ, Dept Earth & Planetary Sci, Cambridge, MA 02138 USA. RP Zatman, S (reprint author), Univ Calif Berkeley, Dept Geol & Geophys, Berkeley, CA 94720 USA. EM zatman@seismo.berkeley.edu NR 31 TC 17 Z9 17 U1 1 U2 1 PU WILEY-BLACKWELL PI MALDEN PA COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA SN 0956-540X J9 GEOPHYS J INT JI Geophys. J. Int. PD SEP PY 1999 VL 138 IS 3 BP 679 EP 686 DI 10.1046/j.1365-246x.1999.00909.x PG 8 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 235KY UT WOS:000082541900006 ER PT J AU Cloutier, PA Law, CC Crider, DH Walker, PW Chen, Y Acuna, MH Connerney, JEP Lin, RP Anderson, KA Mitchell, DL Carlson, CW McFadden, J Brain, DA Reme, H Mazelle, C Sauvaud, JA d'Uston, C Vignes, D Bauer, SJ Ness, NF AF Cloutier, PA Law, CC Crider, DH Walker, PW Chen, Y Acuna, MH Connerney, JEP Lin, RP Anderson, KA Mitchell, DL Carlson, CW McFadden, J Brain, DA Reme, H Mazelle, C Sauvaud, JA d'Uston, C Vignes, D Bauer, SJ Ness, NF TI Venus-like interaction of the solar wind with Mars SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID MAGNETIC-FLUX ROPES; IONOSPHERE; FIELD AB The magnetometer and electron reflectometer experiment (MAG/ER) on the Mars Global Surveyor (MGS) spacecraft has obtained magnetic field and electron data which indicates that the solar wind interaction with Mars is primarily an ionospheric-atmospheric interaction similar to that at Venus. However, the global-scale electric currents and resulting magnetic fields due to the interaction at Mars are locally interrupted or perturbed over distance scales of several hundred kilometers by the effects of paleomagnetic fields due to crustal remanence. In this paper we compare the Mars-solar wind interaction with the Venus-solar wind interaction by selecting MGS orbits which do not show significant magnetic perturbations due to crustal magnetic anomalies, and demonstrate that a number of phenomena characteristic of the Venus-solar wind interaction are also observable at Mars. C1 Rice Univ, Dept Space Phys & Astron, Houston, TX 77251 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA. Ctr Etud Spatiale Rayonnements, Toulouse, France. Graz Univ, Graz, Austria. Inst Space Res, Graz, Austria. Univ Delaware, Bartol Res Inst, Newark, DE 19716 USA. RP Cloutier, PA (reprint author), Rice Univ, Dept Space Phys & Astron, POB 1892, Houston, TX 77251 USA. RI connerney, john/I-5127-2013; Hurley, Dana/F-4488-2015; OI Hurley, Dana/0000-0003-1052-1494; Bauer, Siegfried/0000-0003-4213-2047 NR 12 TC 80 Z9 81 U1 2 U2 7 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD SEP 1 PY 1999 VL 26 IS 17 BP 2685 EP 2688 DI 10.1029/1999GL900591 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 232VR UT WOS:000082391100012 ER PT J AU Leske, RA Mewaldt, RA Cohen, CMS Cummings, AC Stone, EC Wiedenbeck, ME Christian, ER von Rosenvinge, TT AF Leske, RA Mewaldt, RA Cohen, CMS Cummings, AC Stone, EC Wiedenbeck, ME Christian, ER von Rosenvinge, TT TI Event-to-event variations in the isotopic composition of neon in solar energetic particle events SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID IONIC CHARGE; ABUNDANCES; FLARES; NUCLEI AB Using the Solar Isotope Spectrometer on the Advanced Composition Explorer, we have measured the isotopic composition of neon at 24-72 MeV/nucleon in nine solar energetic particle events between 4 November 1997 and 16 November 1998. The Ne-22/Ne-20 ratio varies from similar to 0.7 to similar to 2 times the solar wind value from event to event, indicating significant mass fractionation in the acceleration and/or transport of these particles. The mass fractionation is strongly correlated with the Fe/O and Na/Mg element abundance ratios, suggesting that elemental and isotopic fractionation are both governed by the ionic charge to mass ratio. C1 CALTECH, Downs Lab 220 47, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Leske, RA (reprint author), CALTECH, Downs Lab 220 47, Pasadena, CA 91125 USA. RI Christian, Eric/D-4974-2012 OI Christian, Eric/0000-0003-2134-3937 NR 30 TC 21 Z9 21 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD SEP 1 PY 1999 VL 26 IS 17 BP 2693 EP 2696 DI 10.1029/1999GL900561 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 232VR UT WOS:000082391100014 ER PT J AU Cohen, CMS Mewaldt, RA Leske, RA Cummings, AC Stone, EC Wiedenbeck, ME Christian, ER von Rosenvinge, TT AF Cohen, CMS Mewaldt, RA Leske, RA Cummings, AC Stone, EC Wiedenbeck, ME Christian, ER von Rosenvinge, TT TI New observations of heavy-ion-rich solar particle events from ACE SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID ENERGETIC PARTICLES; ABUNDANCES; FLARES; CHARGE AB Following launch of the Advanced Composition Explorer in August 1997, the Solar Isotope Spectrometer measured the composition of nine solar energetic particle events. We have used isotopic measurements of Ne to determine the degree of charge-to-mass-dependent fractionation and infer the charge states of C - Ni in the four most heavy-ion-rich of the nine events. The results indicate a source temperature of similar to 4 x 10(6) K; this and the measured abundances suggest that these four events are more characteristic of impulsive events than gradual. Although the He-3/He-4 ratios are not enhanced to the level commonly ascribed to impulsive events, there are sizable enhancements over typical solar wind values measured in three of the events. C1 CALTECH, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Cohen, CMS (reprint author), CALTECH, MC 220-47, Pasadena, CA 91125 USA. RI Christian, Eric/D-4974-2012 OI Christian, Eric/0000-0003-2134-3937 NR 27 TC 78 Z9 78 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD SEP 1 PY 1999 VL 26 IS 17 BP 2697 EP 2700 DI 10.1029/1999GL900560 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 232VR UT WOS:000082391100015 ER PT J AU Schmid, B Michalsky, J Halthore, R Beauharnois, M Harrison, L Livingston, J Russell, P Holben, B Eck, T Smirnov, A AF Schmid, B Michalsky, J Halthore, R Beauharnois, M Harrison, L Livingston, J Russell, P Holben, B Eck, T Smirnov, A TI Comparison of aerosol optical depth from four solar radiometers during the Fall 1997 ARM Intensive Observation Period SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SCATTERING; INSTRUMENT AB In the Fall of 1997 the Atmospheric Radiation Measurement (ARM) program conducted an Intensive Observation Period (IOP) to study aerosols. Five sun-tracking radiometers were present to measure the total column aerosol optical depth. This comparison performed on the Southern Great Plains (SGP) demonstrates the capabilities and limitations of modern tracking sunphotometers at a location typical of where aerosol measurements are required. The key result was agreement in aerosol optical depth measured by 4 of the 5 instruments within 0.015 (rms). The key to this level of agreement was meticulous care in the calibrations of the instruments. C1 Bay Area Environm Res Inst, San Francisco, CA 94122 USA. SUNY Albany, Atmospher Sci Res Ctr, Albany, NY 12203 USA. Brookhaven Natl Lab, Upton, NY 11973 USA. SRI Int, Menlo Park, CA 94025 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Raytheon ITSS Corp, Lanham, MD USA. Sci Syst & Applicat Inc, Lanham, MD USA. RP Schmid, B (reprint author), Bay Area Environm Res Inst, 3430 Noriega St, San Francisco, CA 94122 USA. RI Smirnov, Alexander/C-2121-2009; ECK, THOMAS/D-7407-2012 OI Smirnov, Alexander/0000-0002-8208-1304; NR 12 TC 83 Z9 84 U1 1 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD SEP 1 PY 1999 VL 26 IS 17 BP 2725 EP 2728 DI 10.1029/1999GL900513 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 232VR UT WOS:000082391100022 ER PT J AU Manney, GL Lahoz, WA Swinbank, R O'Neill, A Connew, PM Zurek, RW AF Manney, GL Lahoz, WA Swinbank, R O'Neill, A Connew, PM Zurek, RW TI Simulation of the December 1998 stratospheric major warming SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID POLAR VORTEX; EVOLUTION; MODEL AB An atypically early major stratospheric sudden warming in mid-Dec 1998 resulted in an abnormally warm and weak polar vortex through most of the 1998-99 winter. The first major warming in nearly 8 years, it was only the second major warming observed before the end of Dec, and strongly resembled the previous Dec 1987 major warming in several characteristics atypical of major warmings later in winter. 3D mechanistic model simulations reproduced most characteristics of the Dec 1998 major warming, including the magnitudes of zonal mean easterlies and temperature increases and the 3D evolution of the flow, paving the way for more detailed future studies of the mechanisms involved in this unusual event. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. UK Meteorol Off, Bracknell RG12 2SZ, Berks, England. Univ Reading, CGAM, Reading RG6 6BB, Berks, England. NASA, Goddard Space Flight Ctr, USRA, Greenbelt, MD 20771 USA. RP Manney, GL (reprint author), CALTECH, Jet Prop Lab, MS 183-701, Pasadena, CA 91109 USA. NR 10 TC 38 Z9 38 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 SEP 1 PY 1999 VL 26 IS 17 BP 2733 EP 2736 DI 10.1029/1999GL900516 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 232VR UT WOS:000082391100024 ER PT J AU Dessler, AE AF Dessler, AE TI Comment on "A reexamination of the 'stratospheric fountain' hypothesis" by A. E. Dessler - Reply SO GEOPHYSICAL RESEARCH LETTERS LA English DT Editorial Material C1 Univ Maryland, Dept Meteorol, College Pk, MD 20742 USA. Univ Maryland, Earth Syst Sci Interdisciplinary Ctr, College Pk, MD 20742 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Dessler, AE (reprint author), Univ Maryland, Dept Meteorol, College Pk, MD 20742 USA. RI Dessler, Andrew/G-8852-2012 OI Dessler, Andrew/0000-0003-3939-4820 NR 2 TC 4 Z9 4 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD SEP 1 PY 1999 VL 26 IS 17 BP 2739 EP 2739 DI 10.1029/1999GL900594 PG 1 WC Geosciences, Multidisciplinary SC Geology GA 232VR UT WOS:000082391100026 ER PT J AU Nevison, CD Keim, ER Solomon, S Fahey, DW Elkins, JW Loewenstein, M Podolske, JR AF Nevison, CD Keim, ER Solomon, S Fahey, DW Elkins, JW Loewenstein, M Podolske, JR TI Constraints on N2O sinks inferred from observed tracer correlations in the lower stratosphere SO GLOBAL BIOGEOCHEMICAL CYCLES LA English DT Article ID WINTER POLAR STRATOSPHERES; NITROUS-OXIDE; 3-DIMENSIONAL MODEL; ATMOSPHERIC N2O; DENITRIFICATION; RATIOS; TRANSPORT; EMISSIONS; AIRCRAFT; ABOARD AB Recent isotopic studies have suggested that the trace gas N2O has a missing stratospheric sink of potentially major significance. While these studies have raised interesting questions, the constraints on N2O photochemistry imposed by correlations between N2O, total reactive nitrogen, and other tracers measured in situ in the lower stratosphere also should be considered. Measured tracer correlations, when compared to the results of models using standard photochemistry, provide evidence in support of conventional N2O sinks. Stratospheric tracer correlations, however, cannot be used to preclude a new atmospheric source of N2O in the troposphere or to argue against an undiscovered stratospheric sink that contributes less than similar to 20% of the total sink. C1 NOAA, Aeron Lab, Boulder, CO 80303 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NOAA, Environm Res Lab, Boulder, CO 80303 USA. Univ Colorado, Cooperat Inst Res Environm Sci, Boulder, CO 80309 USA. RP Nevison, CD (reprint author), Natl Ctr Atmospher Res, POB 3000, Boulder, CO 80307 USA. RI Fahey, David/G-4499-2013 OI Fahey, David/0000-0003-1720-0634 NR 42 TC 6 Z9 6 U1 0 U2 2 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 SEP PY 1999 VL 13 IS 3 BP 737 EP 742 DI 10.1029/1999GB900018 PG 6 WC Environmental Sciences; Geosciences, Multidisciplinary; Meteorology & Atmospheric Sciences SC Environmental Sciences & Ecology; Geology; Meteorology & Atmospheric Sciences GA 232HK UT WOS:000082365000004 ER PT J AU DeFries, RS Field, CB Fung, I Collatz, GJ Bounoua, L AF DeFries, RS Field, CB Fung, I Collatz, GJ Bounoua, L TI Combining satellite data and biogeochemical models to estimate global effects of human-induced land cover change on carbon emissions and primary productivity SO GLOBAL BIOGEOCHEMICAL CYCLES LA English DT Article ID TROPICAL DEFORESTATION; TERRESTRIAL ECOSYSTEMS; AMAZON DEFORESTATION; SPATIAL-RESOLUTION; CLIMATE CHANGE; CO2; STORAGE; POOLS; CYCLE; CLASSIFICATIONS AB This study uses a global terrestrial carbon cycle model (the Carnegie-Ames-Stanford Approach (CASA) model), a satellite-derived map of existing vegetation, and global maps of natural vegetation to estimate the effects of human-induced land cover change on carbon emissions to the atmosphere and net primary production. We derived two maps approximating global land cover that would exist for current climate in the absence of human disturbance of the landscape, using a procedure that minimizes disagreements between maps of existing and natural vegetation that represent artifacts in the data. Similarly, we simulated monthly fields of the Normalized Difference Vegetation Index, required as input to CASA, for the undisturbed land cover case. Model results estimate total carbon losses from human-induced land cover changes of 182, and 199 Pg for the two simulations, compared with an estimate of 124 Pg for total flux between 1850 and 1990 [Houghton, 1999], suggesting that land cover change prior to 1850 accounted for approximately one-third of total carbon emissions from land use change. Estimates of global carbon loss from the two independent methods, the modeling approach used in this paper and the accounting approach of Houghton [1999], are comparable taking into account carbon losses from agricultural expansion prior to 1850 estimated at 48-57 Pg. However, estimates of regional carbon losses vary considerably, notably in temperate midlatitudes where our estimates indicate higher cumulative carbon loss. Overall, land cover changes reduced global annual net primary productivity (NPP) by approximately 5%, with large regional variations. High-input agriculture in North America and Europe display higher annual NPP than the natural vegetation that would exist in the absence of cropland. However, NPP has been depleted in localized areas in South Asia and Africa by up to 90%. These results provide initial crude estimates, limited by the spatial resolution of the data sets used as input to the model and by the lack of information about transient changes in land cover. The results suggest that a modeling approach can be used to estimate spatially-explicit effects of land cover change on biosphere-atmosphere interactions. C1 Univ Maryland, Dept Geog, College Pk, MD 20742 USA. Univ Maryland, Dept Meteorol, College Pk, MD 20742 USA. Univ Calif Berkeley, Ctr Atmospher Sci, Berkeley, CA 94720 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP DeFries, RS (reprint author), Univ Maryland, Dept Geog, College Pk, MD 20742 USA. RI collatz, george/D-5381-2012 NR 56 TC 174 Z9 206 U1 5 U2 84 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 SEP PY 1999 VL 13 IS 3 BP 803 EP 815 DI 10.1029/1999GB900037 PG 13 WC Environmental Sciences; Geosciences, Multidisciplinary; Meteorology & Atmospheric Sciences SC Environmental Sciences & Ecology; Geology; Meteorology & Atmospheric Sciences GA 232HK UT WOS:000082365000011 ER PT J AU Broedling, LA AF Broedling, LA TI Applying a systems approach to human resource management SO HUMAN RESOURCE MANAGEMENT LA English DT Article AB One reason why organizational improvement efforts often fall short of expectations is that they are rarely systematic. This article describes both the theory and practice of improving human resource management (HRM) using an example from McDonnell Douglas Corporation, in which an integrated systems approach was applied. A model of various, specific HRM initiatives is presented. The plan for undertaking these initiatives is also described. A hey factor in the success of this approach is in changing the mental model that executives hold regarding hour organizations really function. A major part of this shift is appreciating that organizational improvement initiatives are not additive but interactive. (C) 1999 John Wiley & Sons, Inc. C1 McDonnell Douglas Corp, Human Resources & Qual, St Louis, MO 63166 USA. NASA, Washington, DC 20546 USA. US Dept Def, Washington, DC 20305 USA. USN, Washington, DC USA. RP Broedling, LA (reprint author), McDonnell Douglas Corp, Human Resources & Qual, St Louis, MO 63166 USA. NR 9 TC 2 Z9 2 U1 0 U2 1 PU JOHN WILEY & SONS INC PI NEW YORK PA 605 THIRD AVE, NEW YORK, NY 10158-0012 USA SN 0090-4848 J9 HUM RESOURCE MANAGE JI Hum. Resour. Manage. PD FAL PY 1999 VL 38 IS 3 BP 269 EP 277 DI 10.1002/(SICI)1099-050X(199923)38:3<269::AID-HRM9>3.0.CO;2-0 PG 9 WC Psychology, Applied; Management SC Psychology; Business & Economics GA 235DH UT WOS:000082524400009 ER PT J AU Liou, JC Zook, HA Jackson, AA AF Liou, JC Zook, HA Jackson, AA TI Orbital evolution of retrograde interplanetary dust particles and their distribution in the solar system SO ICARUS LA English DT Article DE interplanetary dust; meteoroids; resonances ID SHORT-PERIOD COMETS; KUIPER BELT; INTERSTELLAR DUST; DYNAMICAL EVOLUTION; BODY PROBLEM; ULYSSES; DISCOVERY; PLANETARY; COMPLEX; IMPACTS AB The orbital evolution of interplanetary dust particles (IDPs) from both retrograde and prograde Halley-type comets is numerically simulated. It is found that dust particles nearly always get trapped into one or more mean motion resonances (MMRs) with giant planets while in retrograde orbits. Of the 1000 retrograde particles simulated 116 are trapped in MMRs that last longer than 100,000 years, and the MMRs are typically exterior MMRs of the type p:1 with Jupiter where p ranges from 1 to 12. We present a simple analysis of the physical processes involved when an IDP is in a resonance. A quasistable resonance is maintained by the combined effect of the direct perturbation from the planet as well as the indirect perturbation that arises because the Sun is moving around the Sun-planet barycenter. The direct and indirect perturbations are often of comparable magnitudes, although one or the other can be dominant. Of the 1000 retrograde particles simulated, 45 of them evolved to prograde orbits while in MMRs with a giant planet. Although the overall distribution in eccentricity and inclination of 10(-7) g dust particles from Halley-type comets is consistent with D. H. Humes' (1980, J. Geophys. Res. 85, 5841-5852) interpretation of the Pioneer 10 and 11 data, the spatial density variation is not. Instead of the constant spatial density derived by Humes, the spatial density of Halley-type comet dust varies as r(-gamma) with heliocentric distance r, where gamma ranges from 1.5 to 1.8. Additional sources of interplanetary dust particles are needed to account for the discrepancy. (C) 1999 Academic Press. C1 GB Tech Lockheed Martin, Houston, TX 77058 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Lunar & Planetary Inst, Houston, TX 77058 USA. RP Liou, JC (reprint author), GB Tech Lockheed Martin, Mail Code C104,2400 NASA Rd 1, Houston, TX 77058 USA. NR 48 TC 17 Z9 17 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 SEP PY 1999 VL 141 IS 1 BP 13 EP 28 DI 10.1006/icar.1999.6170 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 239EM UT WOS:000082755900002 ER PT J AU Doyle, R Montemerlo, M Nakatani, I Piedboeuf, JC Putz, P AF Doyle, R Montemerlo, M Nakatani, I Piedboeuf, JC Putz, P TI An international forum for space AI and robotics SO IEEE INTELLIGENT SYSTEMS & THEIR APPLICATIONS LA English DT Article C1 NASA, Jet Prop Lab, Washington, DC 20546 USA. Inst Space & Astronaut Sci, Tokyo 153, Japan. European Space Agcy, Estec, F-75738 Paris, France. RP Doyle, R (reprint author), NASA, Jet Prop Lab, Washington, DC 20546 USA. NR 20 TC 0 Z9 0 U1 0 U2 0 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1314 USA SN 1094-7167 J9 IEEE INTELL SYST APP JI IEEE Intell. Syst. Appl. PD SEP-OCT PY 1999 VL 14 IS 5 BP 8 EP 13 PG 6 WC Computer Science, Artificial Intelligence; Engineering, Electrical & Electronic SC Computer Science; Engineering GA 242MH UT WOS:000082944500006 ER PT J AU Filman, R AF Filman, R TI Dazzle me SO IEEE INTERNET COMPUTING LA English DT Editorial Material C1 NASA, Ames Res Ctr, Caelum Res Corp, Moffett Field, CA 94035 USA. RP Filman, R (reprint author), NASA, Ames Res Ctr, Caelum Res Corp, Moffett Field, CA 94035 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1314 USA SN 1089-7801 J9 IEEE INTERNET COMPUT JI IEEE Internet Comput. PD SEP-OCT PY 1999 VL 3 IS 5 BP 70 EP 71 DI 10.1109/MIC.1999.793462 PG 2 WC Computer Science, Software Engineering SC Computer Science GA 239FM UT WOS:000082758200016 ER PT J AU Mensa, D Pullela, R Lee, Q Guthrie, J Martin, SC Smith, RP Jaganathan, S Mathew, T Agarwal, B Long, SI Rodwell, M AF Mensa, D Pullela, R Lee, Q Guthrie, J Martin, SC Smith, RP Jaganathan, S Mathew, T Agarwal, B Long, SI Rodwell, M TI 48-GHz digital IC's and 85-GHz baseband amplifiers using transferred-substrate HBT's SO IEEE JOURNAL OF SOLID-STATE CIRCUITS LA English DT Article; Proceedings Paper CT 20th Annual IEEE GaAs IC Symposium CY NOV 01-04, 1998 CL ATLANTA, GEORGIA SP IEEE DE baseband amplifier; heterojunction bipolar transistor (HBT); static frequency divider; substrate transfer AB Using substrate transfer processes, we have fabricated heterojunction bipolar transistors with submicrometer emitter-base and collector-base junctions, minimizing RC parasitics and increasing f(max) to 500 GHz, The process also provides a microstrip wiring environment on a low-epsilon(r) dielectric substrate, First design iterations of emitter-coupled-logic master-slave flip-flops exhibit 48 GHz maximum clock frequency when connected as static frequency dividers. Baseband amplifiers have been demonstrated with bandwidths up to 85 GHz. C1 Univ Calif Santa Barbara, Dept Elect & Comp Engn, Santa Barbara, CA 93106 USA. Lucent Technol, Murray Hill, NJ USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. Conexant, Newport Beach, CA USA. RP Mensa, D (reprint author), Univ Calif Santa Barbara, Dept Elect & Comp Engn, Santa Barbara, CA 93106 USA. NR 15 TC 8 Z9 8 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9200 J9 IEEE J SOLID-ST CIRC JI IEEE J. Solid-State Circuit PD SEP PY 1999 VL 34 IS 9 BP 1196 EP 1203 DI 10.1109/4.782076 PG 8 WC Engineering, Electrical & Electronic SC Engineering GA 228ZQ UT WOS:000082167800004 ER PT J AU Pobanz, CW Matloubian, M Lui, M Sun, HC Case, M Ngo, CM Janke, P Gaier, T Samoska, L AF Pobanz, CW Matloubian, M Lui, M Sun, HC Case, M Ngo, CM Janke, P Gaier, T Samoska, L TI A high-gain monolithic D-band InPHEMT amplifier SO IEEE JOURNAL OF SOLID-STATE CIRCUITS LA English DT Article; Proceedings Paper CT 20th Annual IEEE GaAs IC Symposium CY NOV 01-04, 1998 CL ATLANTA, GEORGIA SP IEEE DE coplanar waveguides; III-V semiconductors; indium compounds; integrated circuit design; millimeter-wave amplifiers; millimeter-wave measurements; modulation doped field effect transistor (MODFET); monolithic microwave integrated circuit (MMIC) ID HEMT AB This paper describes a three-stage monolithic amplifier that exhibits a small-signal gain of 30 dB at 140 GHz, The amplifier employs AlInAs/GaInAs/InP high electron mobility transistor devices with 0.1 x 150 mu m(2) gate periphery, is implemented with coplanar waveguide circuitry fabricated on an InP substrate, and occupies a total area of 2 mm(2), Gain exceeding 10 dB was measured on-wafer from 129 to 157 GHz, This is the highest reported gain per stage for a transistor amplifier operating at these frequencies. C1 Hughes Res Labs, Microelect Lab, Malibu, CA 90265 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Pobanz, CW (reprint author), Hughes Res Labs, Microelect Lab, Malibu, CA 90265 USA. NR 11 TC 13 Z9 13 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 0018-9200 J9 IEEE J SOLID-ST CIRC JI IEEE J. Solid-State Circuit PD SEP PY 1999 VL 34 IS 9 BP 1219 EP 1224 DI 10.1109/4.782079 PG 6 WC Engineering, Electrical & Electronic SC Engineering GA 228ZQ UT WOS:000082167800007 ER PT J AU Teitelbaum, B Hares, S Dunn, L Neilson, R Narayan, V Reichmeyer, F AF Teitelbaum, B Hares, S Dunn, L Neilson, R Narayan, V Reichmeyer, F TI Internet2 QBone: Building a testbed for differentiated services SO IEEE NETWORK LA English DT Article AB The Internet2 project is a partnership of over 130 U.S. universities, 40 corporations, and 30 other organizations. Since its inception, one of the primary technical objectives of Internet2 has been to engineer scalable, interoperable, and administrable interdomain QoS to support an evolving set of new advanced networked applications. Applications like distance learning, remote instrument access and control, advanced scientific visualization, and networked collaboratories will allow universities to fulfill their research and education missions into the future, but only if the network QoS these applications require can be ensured. To meet this challenge, the Internet2 QBone initiative [1] has brought together a dedicated group of U.S. university and Federal agency networks, international research networks, engineers, researchers, and applications developers to build a testbed for interdomain IP differentiated services. This article presents the engineering motivations behind DiffServ and its adoption by Internet2, provides an overview of the QBone architecture, and describes its anticipated deployment, including plans for a trial interdomain bandwidth brokering architecture. C1 British Columbia Inst Technol, Burnaby, BC, Canada. NASA, Raytheon Co, ITSS, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 18 TC 46 Z9 47 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 0890-8044 J9 IEEE NETWORK JI IEEE Netw. PD SEP-OCT PY 1999 VL 13 IS 5 BP 8 EP 16 DI 10.1109/65.793686 PG 9 WC Computer Science, Hardware & Architecture; Computer Science, Information Systems; Engineering, Electrical & Electronic; Telecommunications SC Computer Science; Engineering; Telecommunications GA 239TY UT WOS:000082786800003 ER PT J AU Weisbin, CR Blitch, J Lavery, D Krotkov, E Shoemaker, C Matthies, L Rodriguez, G AF Weisbin, CR Blitch, J Lavery, D Krotkov, E Shoemaker, C Matthies, L Rodriguez, G TI Miniature robots for space and military missions SO IEEE ROBOTICS & AUTOMATION MAGAZINE LA English DT Article DE minitaure robots; space telerobotics; tactical mobile robotics; urban terrain; planetary surface exploration ID TECHNOLOGY AB Addressing the Challenges of Future Space Exploration and National Security Through Collaborative Technology Development in There Two Areas. C1 NASA, Jet Prop Lab, Cross Enterprise Technol Dev Program, Pasadena, CA 91109 USA. RP Weisbin, CR (reprint author), NASA, Jet Prop Lab, Cross Enterprise Technol Dev Program, Mail Stop 179-224, Pasadena, CA 91109 USA. NR 21 TC 24 Z9 28 U1 0 U2 6 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 1070-9932 J9 IEEE ROBOT AUTOM MAG JI IEEE Robot. Autom. Mag. PD SEP PY 1999 VL 6 IS 3 BP 9 EP 18 DI 10.1109/100.793696 PG 10 WC Automation & Control Systems; Robotics SC Automation & Control Systems; Robotics GA 240EM UT WOS:000082813000005 ER PT J AU Mili, A Yacoub, S Addy, E Mili, H AF Mili, A Yacoub, S Addy, E Mili, H TI Toward an engineering discipline of software reuse SO IEEE SOFTWARE LA English DT Article AB This article stems from participation in a panel session at the 1997 Symposium on 5 Software Reusability, and discusses open research issues, classified by goal and by approach. C1 Inst Software Res, Fairmont, WV 26554 USA. W Virginia Univ, Morgantown, WV 26506 USA. NASA, Software Independent Verification & Validat Facil, NASA WVU Software Res Lab, Morgantown, WV USA. Univ Quebec, Montreal, PQ H3C 3P8, Canada. RP Inst Software Res, 1000 Technol Dr, Fairmont, WV 26554 USA. EM amili@softwareresearch.org; syacoub@softwareresearch.org; eaddy@csee.wvu.edu; mili@info.uqam.ca NR 11 TC 21 Z9 21 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 0740-7459 EI 1937-4194 J9 IEEE SOFTWARE JI IEEE Softw. PD SEP-OCT PY 1999 VL 16 IS 5 BP 22 EP 31 DI 10.1109/52.795098 PG 10 WC Computer Science, Software Engineering SC Computer Science GA 240WX UT WOS:000082851000011 ER PT J AU Bhatia, R Krattiger, H Bonanini, A Schafer, D Inge, JT Sydnor, GH AF Bhatia, R Krattiger, H Bonanini, A Schafer, D Inge, JT Sydnor, GH TI Adjustable speed drive using a single 135,000 HP synchronous motor SO IEEE TRANSACTIONS ON ENERGY CONVERSION LA English DT Article AB Windtunnels utilize some of the largest drives in the world. The current NASA - NTF windtunnel project, by replacing its aging fan drive system with a new Adjustable Speed Drive (ASD) using a single 135,000 HP synchronous motor, will employ the largest adjustable speed drive system in the world. High Voltage DC Transmission and traditional ASD technology, and utilization of large rotating:machinery design and manufacturing techniques, makes this system possible. C1 ABB Ind Syst, New Berlin, WI 53151 USA. ABB Power Generat Ltd, ABB Ind AG, Baden, Switzerland. NASA, Langley Res Ctr, Hampton, VA 23665 USA. RP Bhatia, R (reprint author), ABB Ind Syst, New Berlin, WI 53151 USA. NR 4 TC 14 Z9 14 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 0885-8969 J9 IEEE T ENERGY CONVER JI IEEE Trans. Energy Convers. PD SEP PY 1999 VL 14 IS 3 BP 571 EP 576 DI 10.1109/60.790916 PG 6 WC Energy & Fuels; Engineering, Electrical & Electronic SC Energy & Fuels; Engineering GA 235WC UT WOS:000082564700048 ER PT J AU Lohn, JD Colombano, SP AF Lohn, JD Colombano, SP TI A circuit representation technique for automated circuit design SO IEEE TRANSACTIONS ON EVOLUTIONARY COMPUTATION LA English DT Article; Proceedings Paper CT 2nd International Conference on Evolvable Systems - From Biology to Hardware (ICES 98) CY SEP 23-25, 1998 CL LAUSANNE, SWITZERLAND SP Int Latsis Fdn, Swiss Nat Sci Fdn, Swiss Fed Inst Technol DE analog circuit synthesis; automated design; circuit representation; genetic algorithms AB We present a method of automatically generating circuit designs using evolutionary search and a set of circuit-constructing primitives arranged in a linear sequence, This representation has the desirable property that virtually all sets of circuit-constructing primitives result in valid circuit graphs. While this representation excludes certain circuit topologies, it is capable of generating a rich set of them including many of the useful topologies seen in hand-designed circuits. Our system allows circuit size (number of devices), circuit topology, and device values to be evolved. Using a parallel genetic algorithm and circuit simulation software, we present experimental results as applied to three analog filter and two amplifier design tasks. In all tasks, our system is able to generate circuits that achieve the target specifications. Although the evolved circuits exist as software models, detailed examinations of each suggest that they are electrically well behaved and thus suitable for physical implementation. The modest computational requirements suggest that the ability to evolve complex analog circuit representations in software is becoming more approachable on a single engineering workstation. C1 Caelum Res Corp, Moffett Field, CA 94035 USA. NASA, Ames Res Ctr, Div Computat Sci, Moffett Field, CA 94035 USA. RP Lohn, JD (reprint author), Caelum Res Corp, Moffett Field, CA 94035 USA. NR 17 TC 92 Z9 105 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 1089-778X J9 IEEE T EVOLUT COMPUT JI IEEE Trans. Evol. Comput. PD SEP PY 1999 VL 3 IS 3 BP 205 EP 219 DI 10.1109/4235.788491 PG 15 WC Computer Science, Artificial Intelligence; Computer Science, Theory & Methods SC Computer Science GA 238UA UT WOS:000082729500004 ER PT J AU Jackson, TJ Le Vine, DM Hsu, AY Oldak, A Starks, PJ Swift, CT Isham, JD Haken, M AF Jackson, TJ Le Vine, DM Hsu, AY Oldak, A Starks, PJ Swift, CT Isham, JD Haken, M TI Soil moisture mapping at regional scales using microwave radiometry: The Southern Great Plains Hydrology Experiment SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article; Proceedings Paper CT International Geoscience and Remote Sensing Symposium (IGARSS 98) CY 1998 CL SEATTLE, WASHINGTON SP Int Geosci & Remote Sensing Soc DE hydrology; microwave; remote sensing; soil moisture ID EMISSION AB Surface soil moisture retrieval algorithms based on passive microwave observations, developed and verified at high spatial resolution, were evaluated in a regional scale experiment. Using previous investigations as a base, the Southern Great Plains Hydrology Experiment (SGP97) was designed and conducted to extend the algorithm to coarser resolutions, larger regions with more diverse conditions, and longer time periods. The L-band electronically scanned thinned array radiometer (ESTAR) was used for daily mapping of surface soil moisture over an area greater than 10 000 km(2) for a one month period. Results show that the soil moisture retrieval algorithm performed the same as in previous investigations, demonstrating consistency of both the retrieval and the instrument. Error levels were on the order of 3% for area integrated averages of sites used for validation. This result showed that for the coarser resolution used here that the theory and techniques employed in the algorithm apply at this scale. Spatial patterns observed in the Little Washita Watershed in previous investigations were also observed here. These results showed that soil texture dominated the spatial pattern at this scale. However, the regional soil moisture patterns were a reflection of the spatially variable rainfall and soil texture patterns were not as obvious. C1 USDA ARS, Hydrol Lab, Sci Syst & Applicat Inc, Beltsville, MD 20705 USA. NASA, Goddard Space Flight Ctr, Microwave Sensors Branch, Greenbelt, MD 20771 USA. USDA ARS, Grazinglands Res Lab, El Reno, OK 73036 USA. Univ Massachusetts, Dept Elect Engn, Microwave Res Lab, Amherst, MA 01001 USA. Raytheon Informat Technol & Sci Serv, Greenbelt, MD 20771 USA. RP Jackson, TJ (reprint author), USDA ARS, Hydrol Lab, Sci Syst & Applicat Inc, Beltsville, MD 20705 USA. NR 18 TC 411 Z9 437 U1 5 U2 52 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 SEP PY 1999 VL 37 IS 5 BP 2136 EP 2151 DI 10.1109/36.789610 PN 1 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 236YT UT WOS:000082627400002 ER PT J AU Bindschadler, R Fahnestock, M Sigmund, A AF Bindschadler, R Fahnestock, M Sigmund, A TI Comparison of Greenland ice sheet topography measured by TOPSAR and airborne laser altimetry SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE ice sheets; topography; synthetic aperture radar (SAR) ID RADAR INTERFEROMETRY AB A digital elevation model (DEM) produced from airborne interferometric synthetic aperture radar (TOPSAR) data of a 5 km x 65 km region of the Greenland Ice Sheet is compared with multiple airborne laser altimeter profiles of the same surface TOPSAR-derived elevation values were calculated on a 10 m x 10 m grid, Surface topography at wavelengths greater than one kilometer is accurately reproduced. A planar adjustment of -8 m with along-track and cross-track tilts of 0.17 and 2.4 m/km, respectively, is required to match the two elevation data sets, Residual noise of the TOPSAR data at subkilometer wavelengths is less than two meters, This study underscores the need for independent elevation data for controlling TOPSAR elevation surveys. C1 NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Oceans & Ice Branch, Greenbelt, MD 20771 USA. Univ Maryland, Earth Syst Sci Interdisciplinary Ctr, College Pk, MD 20740 USA. Gen Sci Corp, Laurel, MD 20727 USA. RP Bindschadler, R (reprint author), NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Oceans & Ice Branch, Greenbelt, MD 20771 USA. RI Fahnestock, Mark/N-2678-2013 NR 12 TC 7 Z9 7 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD SEP PY 1999 VL 37 IS 5 BP 2530 EP 2535 DI 10.1109/36.789648 PN 2 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 236ZA UT WOS:000082628100015 ER PT J AU Treuhaft, RN Cloude, SR AF Treuhaft, RN Cloude, SR TI The structure of oriented vegetation from polarimetric interferometry SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Letter DE polarimetric interferometry; radar interferometry; radar polarimetry; vegetation remote sensing ID IMAGING RADAR AB Polarimetric radar interferometry is much more sensitive to the distribution of oriented objects in a vegetated land surface than either polarimetry or interferometry alone, This paper shows that single-baseline polarimetric interferometry can be used to estimate the heights of oriented-vegetation volumes and underlying topography, while at least two baselines are needed fur randomly oriented volumes. Single-baseline, calculated vegetation-height accuracies are in the range of 2-8 m for reasonable levels of vegetation orientation in forest canopies. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Appl Electromagnet, St Andrews KY16 9UR, Fife, Scotland. RP Treuhaft, RN (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 16 TC 83 Z9 85 U1 4 U2 10 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 SEP PY 1999 VL 37 IS 5 BP 2620 EP 2624 DI 10.1109/36.789657 PN 2 PG 5 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA 236ZA UT WOS:000082628100024 ER PT J AU Huttenlocher, DP Lilien, RH Olson, CF AF Huttenlocher, DP Lilien, RH Olson, CF TI View-based recognition using an eigenspace approximation to the Hausdorff measure SO IEEE TRANSACTIONS ON PATTERN ANALYSIS AND MACHINE INTELLIGENCE LA English DT Article DE model-based recognition; Hausdorff matching; subspace methods; image matching ID PARTIALLY OCCLUDED OBJECTS AB View-based recognition methods, such as those using eigenspace techniques, have been successful for a number of recognition tasks. Such approaches, however, are somewhat limited in their ability to recognize objects that are partly hidden from view or occur against cluttered backgrounds. In order to address these limitations, we have developed a view matching technique based on an eigenspace approximation to the generalized Hausdorff measure. This method achieves the compact storage and fast indexing that are the main advantages of eigenspace view matching techniques, while also being tolerant of partial occlusion and background clutter. The method applies to binary feature maps, such as intensity edges, rather than directly to intensity images. C1 Cornell Univ, Dept Comp Sci, Ithaca, NY 14853 USA. Dartmouth Coll, Sudikoff Lab 6211, Hanover, NH 03755 USA. NASA, JPL, Pasadena, CA 91109 USA. RP Cornell Univ, Dept Comp Sci, Ithaca, NY 14853 USA. EM dph@cs.cornell.edu; ryan.h.lilien@dartmouth.edu; olson@robotics.jpl.nasa.gov NR 8 TC 33 Z9 35 U1 0 U2 1 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1314 USA SN 0162-8828 EI 1939-3539 J9 IEEE T PATTERN ANAL JI IEEE Trans. Pattern Anal. Mach. Intell. PD SEP PY 1999 VL 21 IS 9 BP 951 EP 955 DI 10.1109/34.790437 PG 5 WC Computer Science, Artificial Intelligence; Engineering, Electrical & Electronic SC Computer Science; Engineering GA 234TZ UT WOS:000082501600013 ER PT J AU Kalbarczyk, Z Iyer, RK Ries, GL Patel, JU Lee, MS Xiao, YX AF Kalbarczyk, Z Iyer, RK Ries, GL Patel, JU Lee, MS Xiao, YX TI Hierarchical simulation approach to accurate fault modeling for system dependability evaluation SO IEEE TRANSACTIONS ON SOFTWARE ENGINEERING LA English DT Article; Proceedings Paper CT 6th IFIP International Working Conference on Dependable Computing for Critical Applications (DCCA-6) CY MAR 05-07, 1997 CL GARMISCH PARTENKI, GERMANY SP IFIP DE hierarchical simulation; accurate fault modeling; fault dictionaries; dependability evaluation ID ENVIRONMENT AB This paper presents a hierarchical simulation methodology that enables accurate system evaluation under realistic faults and conditions. In this methodology, effects of low-level (i.e., transistor or circuit level) faults are propagated to higher levels (i.e., system level) using fault dictionaries. The primary fault models are obtained via simulation of the transistor-level effect of a radiation particle penetrating a device. The resulting current bursts constitute the first-level fault dictionary and are used in the circuit-level simulation to determine the impact on circuit latches and flip-flops. The latched outputs constitute the next level fault dictionary in the hierarchy and are applied in conducting fault injection simulation at the chip-level under selected workloads or application programs. Faults injected at the chip-level result in memory corruptions, which are used to form the next level fault dictionary for the system-level simulation of an application running on simulated hardware. When an application terminates, either normally or abnormally, the overall fault impact on the software behavior is quantified and analyzed. The system in this sense can be a single workstation or a network. The simulation method is demonstrated and validated in the case study of Myrinet (a commercial, high-speed network) based network system. The study shows that the method: 1) allows detailed simulation of faults at lower levels and effective fault propagation through the system to the user-visible higher levels using fault dictionaries, 2) links physical faults with effects that the user can observe at the higher levels and thus provides a foundation for realistic fault injection studies, 3) allows significant reduction in the number of simulations needed, due to the fault dictionary method, 4) offers a high confidence in the evaluation results because the system is analyzed in presence of realistic fault conditions, and 5) provides Valuable feedback for designing error recovery mechanisms to improve dependability. C1 Univ Illinois, Ctr Reliable & High Performance Comp, Urbana, IL 61801 USA. ATI Res Silicon Valley Inc, Santa Clara, CA 95051 USA. NASA, Jet Prop Lab, Pasadena, CA 91109 USA. Hewlett Packard Corp, Cupertino, CA 95014 USA. Strategy, Vienna, VA 22182 USA. RP Kalbarczyk, Z (reprint author), Univ Illinois, Ctr Reliable & High Performance Comp, 1308 W Main St, Urbana, IL 61801 USA. EM kalbar@crhc.uiuc.edu; iyer@crhc.uiuc.edu; ries@chromatic.com; jupatel@mail1.jpl.nas.gov; myeong_lee@cup.hp.com; yxiao@strategy.com NR 16 TC 14 Z9 14 U1 0 U2 6 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1314 USA SN 0098-5589 EI 1939-3520 J9 IEEE T SOFTWARE ENG JI IEEE Trans. Softw. Eng. PD SEP-OCT PY 1999 VL 25 IS 5 BP 619 EP 632 DI 10.1109/32.815322 PG 14 WC Computer Science, Software Engineering; Engineering, Electrical & Electronic SC Computer Science; Engineering GA 268RW UT WOS:000084430200003 ER PT J AU Leary, SP Pilgrim, SM AF Leary, SP Pilgrim, SM TI Determination of nonlinear electromechanical energy conversion and the field-dependent elastic modulus of Pb(Mg1/3Nb2/3) O-3-based electrostrictors SO IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL LA English DT Article ID PB(MG1/3NB2/3)O-3-PBTIO3-(BA,SR)TIO3 CERAMICS; POLARIZATION AB Energy conversion efficiency is a critical parameter for all electromechanical materials. Although excellent techniques are available for linear materials, nonlinearities complicate the determination of conversion efficiency in electrostrictive Pb(Mg1/3Nb2/3)O-3 (PMN). The field dependence of the elastic modulus presents additional problems. A technique combining pulse-echo ultrasound has been developed to approximate the change in the Youngs modulus with applied field. A 30% decrease was observed at 1 MV/m (from similar to 100 to similar to 70 GPa). The boundary condition for these measurements was a constant electric field as opposed to constant dielectric displacement. In combination with the results from harmonic analysis, the modulus data may be used to determine the electromechanical conversion efficiency. This has been accomplished using an energy balance criterion for a PMN-based composition (with and without de bias). The resulting longitudinal coupling values are >0.5 for practical electric fields (<1 MV/m peak). C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Alfred Univ, New York State Coll Ceram, Lab Elect Ceram, Alfred, NY 14802 USA. RP Leary, SP (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 35 TC 4 Z9 4 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0885-3010 J9 IEEE T ULTRASON FERR JI IEEE Trans. Ultrason. Ferroelectr. Freq. Control PD SEP PY 1999 VL 46 IS 5 BP 1155 EP 1163 DI 10.1109/58.796121 PG 9 WC Acoustics; Engineering, Electrical & Electronic SC Acoustics; Engineering GA 245RK UT WOS:000083121800011 PM 18244309 ER PT J AU Greenhall, CA Howe, DA Percival, DB AF Greenhall, CA Howe, DA Percival, DB TI Total variance, an estimator of long-term frequency stability SO IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL LA English DT Article AB Total variance is a statistical tool developed for improved estimates of frequency stability at averaging times up to one-half the test duration. As a descriptive statistic, total variance performs an exact decomposition of the sample variance of the frequency residuals into components associated with increasing averaging times. As an estimator of Allan variance, total variance has greater equivalent degrees of freedom and lesser mean square error than the standard unbiased estimator has. C1 CALTECH, Jet Prop Lab, CIT, Pasadena, CA 91109 USA. Natl Inst Stand & Technol, Div Time & Frequency, Boulder, CO 80303 USA. Univ Washington, Appl Phys Lab, Seattle, WA 98195 USA. MathSoft Inc, Seattle, WA 98195 USA. RP Greenhall, CA (reprint author), CALTECH, Jet Prop Lab, CIT, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 17 TC 54 Z9 58 U1 0 U2 5 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0885-3010 J9 IEEE T ULTRASON FERR JI IEEE Trans. Ultrason. Ferroelectr. Freq. Control PD SEP PY 1999 VL 46 IS 5 BP 1183 EP 1191 DI 10.1109/58.796124 PG 9 WC Acoustics; Engineering, Electrical & Electronic SC Acoustics; Engineering GA 245RK UT WOS:000083121800014 PM 18244312 ER PT J AU Singh, M AF Singh, M TI A new approach to joining of silicon carbide-based materials for high temperature applications SO INDUSTRIAL CERAMICS LA English DT Article ID CERAMICS AB Ceramic joining is recognized as one of the enabling technologies for the application of silicon carbide-based materials in a number of high temperature applications. An affordable, robust technique for the joining of silicon carbide-based ceramics has been developed. This technique is capable of producing joints with tailorable thickness and composition. Microstructure and mechanical properties of reaction formed joints in a reaction bonded silicon carbide have been reported. These joints maintain their mechanical strengths at high temperatures (up to 1350 degrees C) in air. This technique is capable of joining large and complex shaped ceramic components. C1 NASA, Lewis Res Ctr Grp, FDC NYMA Inc, Cleveland, OH 44135 USA. NR 15 TC 1 Z9 2 U1 0 U2 2 PU TECHNA SRL PI FAENZA PA PO BOX 174, 48018 FAENZA, ITALY SN 1121-7588 J9 IND CERAM JI Ind. Ceram. PD SEP-DEC PY 1999 VL 19 IS 3 BP 171 EP 172 PG 2 WC Materials Science, Ceramics SC Materials Science GA 284BR UT WOS:000085311300007 ER PT J AU Gotoh, E Kawata, T Durante, M AF Gotoh, E Kawata, T Durante, M TI Chromatid break rejoining and exchange aberration formation following gamma-ray exposure: analysis in G(2) human fibroblasts by chemically induced premature chromosome condensation SO INTERNATIONAL JOURNAL OF RADIATION BIOLOGY LA English DT Article ID FIELD GEL-ELECTROPHORESIS; DOUBLE-STRAND BREAKS; CELL-CYCLE; CHO CELLS; SACCHAROMYCES-CEREVISIAE; HYPERTONIC TREATMENT; HUMAN-LYMPHOCYTES; G2 BLOCK; DNA; KINETICS AB Purpose: To analyse the kinetics of chromatid break induction, rejoining, and misrejoining after gamma-irradiation in G(2) phase human cells using premature chromosome condensation induced by calyculin A. Materials and methods: Human fibroblast AG1522 cells were irradiated with gamma-rays and chromosomes were then prematurely condensed by calyculin A. The number of chromatid breaks and chromatid exchanges in G(2) chromosomes were scored, and fitted curves were calculated. Results: Calyculin A induced premature chromosome condensation in cells immediately after irradiation. Kinetics of rejoining of chromatid breaks demonstrated two exponential components with rapid and slow time constants. Within 5 min after irradiation, the number of chromatid breaks fell rapidly to about one-half, then gradually decreased. Chromatid exchanges were formed very quickly, reaching a plateau within 20 min from exposure. Conclusions: Chemically induced premature chromosome condensation technique allows a simple, rapid and precise analysis of chromatid breakage and rejoining. The rapid kinetic component was particularly well characterized. C1 Natl Inst Infect Dis, Div Genet Resources, Tokyo, Japan. NASA, Johnson Space Ctr, Radiat Biophys Lab, Houston, TX USA. Univ Naples Federico II, Dept Phys, Naples, Italy. RP Gotoh, E (reprint author), Natl Inst Infect Dis, Div Genet Resources, Tokyo, Japan. RI Durante, Marco/K-1315-2014 NR 43 TC 46 Z9 56 U1 0 U2 0 PU TAYLOR & FRANCIS LTD PI LONDON PA ONE GUNPOWDER SQUARE, LONDON EC4A 3DE, ENGLAND SN 0955-3002 J9 INT J RADIAT BIOL JI Int. J. Radiat. Biol. PD SEP PY 1999 VL 75 IS 9 BP 1129 EP 1135 PG 7 WC Biology; Nuclear Science & Technology; Radiology, Nuclear Medicine & Medical Imaging SC Life Sciences & Biomedicine - Other Topics; Nuclear Science & Technology; Radiology, Nuclear Medicine & Medical Imaging GA 237YT UT WOS:000082684700008 PM 10528921 ER PT J AU Allendorf, MD Melius, CF Bauschlicher, CW AF Allendorf, MD Melius, CF Bauschlicher, CW TI Heats of formation and bond energies in group III compounds SO JOURNAL DE PHYSIQUE IV LA English DT Article; Proceedings Paper CT 12th European Conference on Chemical Vapour Deposition CY SEP 05-10, 1999 CL BARCELONA, SPAIN SP Elect Soc, Gen Catalunya Dept Presidencia Comm Univ Recerca, ICMAB, CSIC, ISCAR New Line, INORGTECH, CND ID GAUSSIAN-BASIS SETS; CORRELATED MOLECULAR CALCULATIONS; VAPOR-PHASE EPITAXY; THERMAL-DECOMPOSITION; WAVE-FUNCTIONS; THERMOCHEMISTRY; APPROXIMATION; PREDICTIONS; EXCHANGE; GALLIUM AB We present heats of formation and bond energies for Group-III compounds obtained from calculations of molecular ground-state electronic energies. Data for compounds of the form MXn are presented, where M = B, Al, Ga, and In, X = H, CI, and CH3, and n = 1-3. Energies for the B, Al, and Ga compounds are obtained from G2 predictions, while those for the In compounds are obtained from CCSD(T)/CBS calculations; these are the most accurate calculations for indium-containing compounds published to date. In most cases, the calculated thermochemistry is in good agreement with published values derived from experiments for those species that have well-established heats of formation. Bond energies obtained from the heats of formation follow the expected trend (C1 >> CH3 similar to H). However. the CH3M-(CH3)(2) bond energies obtained for trimethylgallium and trimethylindium are considerably stronger (> 15 kcal mol(-1)) than currently accepted values. C1 Sandia Natl Labs, Livermore, CA 94551 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Allendorf, MD (reprint author), Sandia Natl Labs, Livermore, CA 94551 USA. NR 63 TC 13 Z9 13 U1 0 U2 1 PU E D P SCIENCES PI LES ULIS CEDEXA PA 7, AVE DU HOGGAR, PARC D ACTIVITES COURTABOEUF, BP 112, F-91944 LES ULIS CEDEXA, FRANCE SN 1155-4339 J9 J PHYS IV JI J. Phys. IV PD SEP PY 1999 VL 9 IS P8 BP 23 EP 31 DI 10.1051/jp4:1999803 PN 1 PG 9 WC Physics, Multidisciplinary SC Physics GA 235DM UT WOS:000082524800004 ER PT J AU Greenman, RM Roth, KR AF Greenman, RM Roth, KR TI Minimizing computational data requirements for multi-element airfoils using neural networks 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 ID NAVIER-STOKES EQUATIONS; UPWIND DIFFERENCING SCHEME; PREDICTION; LIFT AB Artificial neural networks were used to fill in a design space of computational data to optimize the flap position for maximum lift for a multi-element airfoil. Multiple-input, single-output networks were trained using NASA Ames Research Center's variation of the Levenberg-Marquardt algorithm. The computational data set was generated using an incompressible Navier-Stokes algorithm with the Spalart-Allmaras turbulence model. An empirically-based criteria, designated the "pressure difference rule," was applied to the training set because numerical inaccuracies for the computational method were identified near maximum lift. The neural networks were trained with only three values of the inputs: flap deflection, gap, and overlap at various angles of attack. The entire computational data set was thus sparse, and yet by using only 52-70% of the computed data, the trained neural networks predicted the aerodynamic coefficients within 1.7% of the maximum lift coefficient. In addition, a genetic algorithm and a gradient-based optimizer were integrated with the neural networks to optimize the high-lift rigging. This new optimization process had a higher fidelity and a reduction in CPU time when compared with an optimization procedure that excluded the genetic algorithm. C1 NASA, Ames Res Ctr, Integrated Syst Technol Branch, Moffett Field, CA 94035 USA. NASA, Ames Res Ctr, Chief Technol Off, Moffett Field, CA 94035 USA. RP Greenman, RM (reprint author), NASA, Ames Res Ctr, Integrated Syst Technol Branch, Moffett Field, CA 94035 USA. NR 32 TC 10 Z9 10 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0021-8669 J9 J AIRCRAFT JI J. Aircr. PD SEP-OCT PY 1999 VL 36 IS 5 BP 777 EP 784 DI 10.2514/2.2533 PG 8 WC Engineering, Aerospace SC Engineering GA 245NJ UT WOS:000083114800007 ER PT J AU Carr, GC Erzberger, H Neuman, F AF Carr, GC Erzberger, H Neuman, F TI Delay exchanges in arrival sequencing and scheduling SO JOURNAL OF AIRCRAFT LA English DT Article AB Air traffic management (ATM) must often place restrictions on arriving flights transitioning from en route airspace to highly congested terminal airspace. The restriction of arrival traffic, or arrival flow management, is performed without regard for the relative priority that airlines may be placing on individual flights. The development of new arrival how management techniques that consider priorities expressed by air carriers will reduce the economic impact of ATM restrictions and lead to increased airline economic efficiency by allowing airlines to have greater control over their individual arrival banks of aircraft. NASA is exploring the possibility of allowing airlines to express relative arrival priorities to ATM through the development of new sequencing and scheduling algorithms ;that take airline arrival preferences into account. This paper introduces the concept of "delay exchange" which is defined as a fair method of accommodating an airline request for an earlier arrival by advancing the landing time of one aircraft while simultaneously delaying another aircraft from the same airline. Fast-time simulation is used to evaluate the feasibility of scheduling these delay exchanges among individual arriving aircraft. Results show that the probability of successfully time advancing an aircraft is highest for an algorithm that allows delay exchange between aircraft arriving at any feeder fix. Results also show that the success of this algorithm varies with airport acceptance rate, indicating that the performance of this algorithm is a function of traffic density as well as the position of the aircraft within the traffic rush interval. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Raytheon STX Corp, Moffett Field, CA 94035 USA. RP Carr, GC (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 7 TC 13 Z9 14 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 SEP-OCT PY 1999 VL 36 IS 5 BP 785 EP 791 DI 10.2514/2.2534 PG 7 WC Engineering, Aerospace SC Engineering GA 245NJ UT WOS:000083114800008 ER PT J AU Poe, CC Dexter, HB Raju, IS AF Poe, CC Dexter, HB Raju, IS TI Review of the NASA textile composites research SO JOURNAL OF AIRCRAFT LA English DT Article; Proceedings Paper CT AIAA/ASME/ASCE/AHS/ASC 38th Structures, Structural Dynamics, and Materials Conference CY APR 07-10, 1997 CL KISSIMMEE, FLORIDA SP Amer Inst Aeronaut & Astronaut, ASME, ASCE, AHS, ASC AB During the past 15 years, NASA has taken the lead role in exploiting the benefits of textile reinforced composite materials for application to aircraft structures. The NASA advanced composites technology program was started in 1989 to develop composite primary structures for commercial transport airplanes with costs that are competitive with metal structures. As part of this program, several contractors investigated the cost, weight, and performance attributes of textile reinforced composites. Textile composites made using resin transfer molding-type processes were evaluated for numerous applications. Methods were also developed to predict resin infiltration end how in textile preforms and to predict and measure mechanical properties of the textile composites. The salient results of that program are described. C1 NASA, Langley Res Ctr, Mech Mat Branch, Hampton, VA 23681 USA. RP Poe, CC (reprint author), NASA, Langley Res Ctr, Mech Mat Branch, Hampton, VA 23681 USA. NR 17 TC 6 Z9 6 U1 3 U2 4 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 SEP-OCT PY 1999 VL 36 IS 5 BP 876 EP 884 DI 10.2514/2.2521 PG 9 WC Engineering, Aerospace SC Engineering GA 245NJ UT WOS:000083114800018 ER PT J AU Dukhan, N Masiulaniec, KC De Witt, KJ Van Fossen, GJ AF Dukhan, N Masiulaniec, KC De Witt, KJ Van Fossen, GJ TI Acceleration effect on the Stanton number for castings of ice-roughened surfaces SO JOURNAL OF AIRCRAFT LA English DT Article; Proceedings Paper CT AIAA 34th Aerospace Sciences Meeting and Exhibit CY JAN 15-19, 1996 CL RENO, NEVADA SP Amer Inst Aeronaut & Astronaut ID HEAT-TRANSFER C1 Univ Toledo, Dept Mech Ind & Mfg Engn, Toledo, OH 43606 USA. NASA, John H Glenn Res Ctr Lewis Field, Turbomachinery & Propuls Syst Div, Cleveland, OH 44135 USA. RP Dukhan, N (reprint author), RELTEC Corp, 4350 Weaver Pkwy, Warrenville, IL 60555 USA. NR 9 TC 2 Z9 2 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0021-8669 J9 J AIRCRAFT JI J. Aircr. PD SEP-OCT PY 1999 VL 36 IS 5 BP 896 EP 898 DI 10.2514/2.2527 PG 3 WC Engineering, Aerospace SC Engineering GA 245NJ UT WOS:000083114800023 ER PT J AU Burner, AW Liu, TS Garg, S Bell, JH Morgan, DG AF Burner, AW Liu, TS Garg, S Bell, JH Morgan, DG TI Unified model deformation and flow transition measurements SO JOURNAL OF AIRCRAFT LA English DT Article C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. High Technol Corp, Hampton, VA 23666 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Burner, AW (reprint author), NASA, Langley Res Ctr, MS 236, Hampton, VA 23681 USA. NR 6 TC 3 Z9 4 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0021-8669 J9 J AIRCRAFT JI J. Aircr. PD SEP-OCT PY 1999 VL 36 IS 5 BP 898 EP 901 DI 10.2514/2.2528 PG 4 WC Engineering, Aerospace SC Engineering GA 245NJ UT WOS:000083114800024 ER PT J AU Platt, CMR Winker, DM Vaughan, MA Miller, SD AF Platt, CMR Winker, DM Vaughan, MA Miller, SD TI Backscatter-to-extinction ratios in the top layers of tropical mesoscale convective systems and in isolated cirrus from LITE observations SO JOURNAL OF APPLIED METEOROLOGY LA English DT Article ID TECHNOLOGY EXPERIMENT LITE; MONTE-CARLO CALCULATIONS; HEXAGONAL ICE CRYSTALS; OPTICAL-PROPERTIES; LIGHT-SCATTERING; HIGH CLOUDS; RADIATIVE-TRANSFER; LIDAR; RETURNS; PHASE AB Cloud-integrated attenuated backscatter from observations with the Lidar In-Space Technology Experiment (LITE) was studied over a range of cirrus clouds capping some extensive mesoscale convective systems (MCSs) in the Tropical West Pacific. The integrated backscatter when the cloud is completely attenuating, and when corrected for multiple scattering, is a measure of the cloud particle backscatter phase function. Four different cases of MCS were studied. The first was very large, very intense, and fully attenuating, with cloud tops extending to 17 km and a maximum lidar pulse penetration of about 3 km. It also exhibited the highest integrated attenuated isotropic backscatter, with values in the 532-nm channel of up to 2.5 near the center of the system, falling to 0.6 near the edges. The second MCS had cloud tops that extended to 14.8 km. Although MCS2 was almost fully attenuating, the pulse penetration into the cloud was up to 7 km and the MCS2 had a more diffuse appearance than MCS1. The integrated backscatter values were much lower in this system but with some systematic variations between 0.44 and 0.75. The third MCS was Typhoon Melissa. Values of integrated backscatter in this case varied from 1.64 near the rye of the typhoon to between 0.44 and 1.0 in the areas of typhoon outflow and in the 532-nm channel. Mean pulse penetration through the cloud top was 2-3 km, the lowest penetration of any of the systems. The fourth MCS consisted of a region of outflow from Typhoon Melissa. The cloud was semitransparent for more than half of the image time. During that time, maximum cloud depth was about 7 km. The integrated backscatter varied from about 0.38 to 0.63 in the 532-nm channel when the cloud was fully attenuating. In some isolated cirrus between the main systems, a plot of integrated backscatter against one minus the two-way transmittance gave a linear dependence with a maximum value of 0.35 when the clouds were fully attenuating. The effective backscatter-to-extinction ratios. when allowing for different multiple-scattering factors from space, were often within the range of those observed with ground-based lidar. Exceptions occurred near the centers of the most intense convection, where values were measured that were considerably higher than those in cirrus observed from the surface. In this case, the values were more compatible with theoretical values for perfectly formed hexagonal columns or plates. The large range in theoretically calculated backscatter-to-extinction ratio and integrated multiple-scattering factor precluded a closer interpretation in terms of cloud microphysics. C1 CSIRO, Div Atmospher Res, Aspendale, Vic 3195, Australia. NASA, Langley Res Ctr, Hampton, VA 23665 USA. Sci Applicat Int Corp, Hampton, VA USA. Colorado State Univ, Dept Atmospher Sci, Ft Collins, CO 80523 USA. RP Platt, CMR (reprint author), Colorado State Univ, Dept Atmospher Sci, Ft Collins, CO 80523 USA. NR 37 TC 33 Z9 37 U1 0 U2 1 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0894-8763 J9 J APPL METEOROL JI J. Appl. Meteorol. PD SEP PY 1999 VL 38 IS 9 BP 1330 EP 1345 DI 10.1175/1520-0450(1999)038<1330:BTERIT>2.0.CO;2 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 240NY UT WOS:000082833100005 ER PT J AU Cahill, AT Parlange, MB Jackson, TJ O'Neill, P Schmugge, TJ AF Cahill, AT Parlange, MB Jackson, TJ O'Neill, P Schmugge, TJ TI Evaporation from nonvegetated surfaces: Surface aridity methods and passive microwave remote sensing SO JOURNAL OF APPLIED METEOROLOGY LA English DT Article ID BARE SOIL; PARAMETERIZING EVAPORATION; METEOROLOGICAL MODELS; SCHEMES; ENERGY AB The use of remotely sensed near-surface soil moisture for the estimation of evaporation is investigated. Two widely used parameterizations of evaporation, the so-called alpha and beta methods, which use near-surface soil moisture to reduce some measure of potential evaporation, are studied. The near-surface soil moisture is provided by a set of L- and S-band microwave radiometers, which were mounted 13 m above the surface. It is shown that soil moisture measured with a passive microwave sensor in combination with the beta method yields reliable estimates of evaporation, whereas the a method is not as robust. C1 Texas A&M Univ, Dept Civil & Environm Engn, College Stn, TX 77843 USA. Johns Hopkins Univ, Dept Geog & Environm Engn, Baltimore, MD 21218 USA. ARS, USDA, Hydrol Lab, Beltsville, MD USA. NASA, Goddard Space Flight Ctr, Hydrol Sci Branch, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. RP Cahill, AT (reprint author), Texas A&M Univ, Dept Civil & Environm Engn, College Stn, TX 77843 USA. RI O'Neill, Peggy/D-2904-2013; Parlange, Marc/A-3403-2015 NR 18 TC 17 Z9 17 U1 0 U2 2 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0894-8763 J9 J APPL METEOROL JI J. Appl. Meteorol. PD SEP PY 1999 VL 38 IS 9 BP 1346 EP 1351 DI 10.1175/1520-0450(1999)038<1346:EFNSSA>2.0.CO;2 PG 6 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 240NY UT WOS:000082833100006 ER PT J AU Cwik, T Yeh, C AF Cwik, T Yeh, C TI Highly sensitive quantum well infrared photodetectors SO JOURNAL OF APPLIED PHYSICS LA English DT Article ID PERFORMANCE; SCATTERING AB A fundamentally new method for light coupling in quantum well infrared photodetectors that provides a ten-fold improvement over an optimized grating coupler is presented. It is based on the prism-film coupler concept developed earlier for selective mode coupling into integrated optical circuits. In this article this concept is specifically used to turn the incident electric field from one that is polarized parallel to the quantum well layer to one that is mostly perpendicular to the layer, thereby increasing dramatically the sensitivity of the quantum well infrared photodetector. Detailed sample design and its computer simulation results are given and discussed. (C) 1999 American Institute of Physics. [S0021-8979(99)03517-3]. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Cwik, T (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 13 TC 1 Z9 1 U1 1 U2 2 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0021-8979 J9 J APPL PHYS JI J. Appl. Phys. PD SEP 1 PY 1999 VL 86 IS 5 BP 2779 EP 2784 DI 10.1063/1.371125 PG 6 WC Physics, Applied SC Physics GA 227GV UT WOS:000082073000064 ER PT J AU McCall, GE Goulet, C Roy, RR Grindeland, RE Boorman, GI Bigbee, AJ Hodgson, JA Greenisen, MC Edgerton, VR AF McCall, GE Goulet, C Roy, RR Grindeland, RE Boorman, GI Bigbee, AJ Hodgson, JA Greenisen, MC Edgerton, VR TI Spaceflight suppresses exercise-induced release of bioassayable growth hormone SO JOURNAL OF APPLIED PHYSIOLOGY LA English DT Article DE fatigue; human; maximum voluntary contraction; electromyography ID RAT PITUITARY AB We have reported that bed rest suppressed the release of bioassayable growth hormone (BGH) that normally occurs after an acute bout of unilateral plantar flexor exercise (G. E. McCall, C. Goulet, R. E. Grindeland, J. A. Hodgson, A. J. Bigbee, and V. R. Edgerton. J. AppL. Physiol. 83: 2086-2090, 1997). In the present study, the effects of spaceflight on the hormonal responses to this exercise protocol were examined. Four male astronauts on the National Aeronautics and Space Administration Shuttle Transport System (STS-78) mission completed the exercise protocol before, during, and after a 17-day spaceflight. The maximal voluntary contraction torque output at the onset of exercise was similar on all test days. Before spaceflight, plasma BGH increased 114-168% from pre- to postexercise. During spaceflight and after 2 days recovery at normal gravity (1 G;), the BGH response to exercise was absent. After 4 days of recovery, this response was restored. Plasma concentrations of immunoassayable growth hormone were similar at all time points. The preexercise plasma immunoassayable insulin-like growth factor I(IGF-I) levels were elevated after 12 or 13 days of microgravity, and a approximate to 7% postexercise IGF-I increase was independent of this spaceflight effect. The suppression of the BGH response to exercise during spaceflight indicates that some minimum level of chronic neuromuscular activity and/or loading is necessary to maintain a normal exercise-induced BGH release. Moreover, these results suggest that there is a muscle afferent-pituitary axis that can modulate BGH release. C1 Univ Calif Los Angeles, Dept Physiol Sci, Los Angeles, CA 90095 USA. Univ Calif Los Angeles, Brain Res Inst, Los Angeles, CA 90095 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Edgerton, VR (reprint author), Univ Calif Los Angeles, Dept Physiol Sci, 2301 Life Sci,621 Charles E Young Dr S, Los Angeles, CA 90095 USA. FU NIDCR NIH HHS [DE-07212] NR 25 TC 29 Z9 30 U1 0 U2 2 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 SEP PY 1999 VL 87 IS 3 BP 1207 EP 1212 PG 6 WC Physiology; Sport Sciences SC Physiology; Sport Sciences GA 233VM UT WOS:000082448000046 PM 10484597 ER PT J AU Landsberg, JH Balazs, GH Steidinger, KA Baden, DG Work, TM Russell, DJ AF Landsberg, JH Balazs, GH Steidinger, KA Baden, DG Work, TM Russell, DJ TI The potential role of natural tumor promoters in marine turtle fibropapillomatosis SO JOURNAL OF AQUATIC ANIMAL HEALTH LA English DT Article ID OKADAIC ACID CLASS; PROTEIN PHOSPHATASE INHIBITOR; CHELONIA-MYDAS L; GREEN TURTLE; HAWAIIAN-ISLANDS; CALYCULIN-A; MOUSE SKIN; CELL-TRANSFORMATION; CHEMICAL COFACTORS; PROROCENTRUM-LIMA AB Fibropapillomatosis (FP) in green turtles Chelonia mydas is a debilitating, neoplastic disease that has reached worldwide epizootic levels. The etiology of FP is unknown but has been linked to oncogenic viruses. Toxic benthic dinoflagellates (Prorocentrum spp.) are not typically considered tumorigenic agents, yet they have a worldwide distribution and produce a tumor promoter, okadaic acid (OA). Prorocentrum spp. are epiphytic on macroalgae and seagrasses that are normal components of green turtle diets. Here we show that green turtles in the Hawaiian Islands consume Prorocentrum and that high-risk FP areas are associated with areas where P. lima and P. concavum are both highly prevalent and abundant. The presence of presumptive OA in the tissues of Hawaiian green turtles further suggests exposure and a potential role for this tumor promoter in the etiology of FP. C1 Florida Marine Res Inst, Florida Fish & Wildlife Conservat Commiss, St Petersburg, FL 33701 USA. Natl Marine Fisheries Serv, Honolulu Lab, SW Fisheries Sci Ctr, Honolulu, HI 96822 USA. Univ Miami, Rosenstiel Sch Marine & Atmospher Sci, Marine & Freshwater Biomed Sci Ctr, Natl Inst Environm Hlth Sci, Miami, FL 33149 USA. US Geol Survey, Biol Resources Div, Natl Wildlife Hlth Ctr, Honolulu Field Stn, Honolulu, HI 96850 USA. Univ Alaska SE, Dept Biol, Juneau, AK 99801 USA. RP Landsberg, JH (reprint author), Florida Marine Res Inst, Florida Fish & Wildlife Conservat Commiss, 100 8th Ave SE, St Petersburg, FL 33701 USA. EM landsberg.j@epic7.dep.state.fl.us RI Work, Thierry/F-1550-2015 OI Work, Thierry/0000-0002-4426-9090 NR 90 TC 40 Z9 43 U1 0 U2 9 PU TAYLOR & FRANCIS INC PI PHILADELPHIA PA 325 CHESTNUT ST, SUITE 800, PHILADELPHIA, PA 19106 USA SN 0899-7659 J9 J AQUAT ANIM HEALTH JI J. Aquat. Anim. Health PD SEP PY 1999 VL 11 IS 3 BP 199 EP 210 DI 10.1577/1548-8667(1999)011<0199:TPRONT>2.0.CO;2 PG 12 WC Fisheries; Veterinary Sciences SC Fisheries; Veterinary Sciences GA 316TT UT WOS:000087184700001 ER PT J AU Aguirre, AA Spraker, TR Chaves, A Du Toit, L Eure, W Balazs, GH AF Aguirre, AA Spraker, TR Chaves, A Du Toit, L Eure, W Balazs, GH TI Pathology of fibropapillomatosis in Olive Ridley turtles Lepidochelys olivacea nesting in Costa Rica SO JOURNAL OF AQUATIC ANIMAL HEALTH LA English DT Article ID GREEN TURTLES; CHELONIA-MYDAS; HAWAIIAN-ISLANDS AB Fibropapillomatosis (FP) is a neoplastic disease that primarily affects green turtles Chelonia mydas in epidemic proportions worldwide. Although several infectious agents (herpesvirus, retrovirus, and papillomavirus) have been associated with the condition, the etiologic agent has not been isolated or characterized. Recently, FP has been reported in other sea turtle species including confirmed cases in loggerhead turtles Caretta caretta in Florida and field observations in olive ridley turtles Lepidochelys olivacea in the Pacific coasts elf Mexico and Costa Rica. Skin and tumor specimens were collected from 72 olive ridley turtles nesting in Ostional Wildlife Refuge, Costa Pica, between July and September 1997. In all, 50 tumor biopsies were examined from 25 of the affected turtles. In addition, six biopsies were examined from five turtles that did not have visible masses and served as controls. Grossly, masses were 25 mm or less in diameter, white to gray, smooth to verruciform, raised tumors of the integument of the neck and flippers. Histologically, 42 of 50 were diagnosed as fibropapillomas and eight were classified as chronic active dermatitis and not tumors. Twenty of 42 fibropapillomas were in stages of regression and 9 of the remaining 22 tumors had histological changes that suggested early degeneration within the tumor. During field surveys based cn gross lesions, prevalences of 1-10% have been reported in this nesting population. This is considered the first histopathologic confirmation of FP in olive ridley turtles. C1 Univ Hawaii, Joint Inst Marine & Atmospher Res, Honolulu, HI 96822 USA. Colorado State Univ, State Vet Diagnost Lab, Ft Collins, CO 80523 USA. Douglas Robinson Marine Turtle Res Ctr, Ostional, Costa Rica. Natl Marine Fisheries Serv, SW Fisheries Sci Ctr, Honolulu Lab, Honolulu, HI 96822 USA. RP Aguirre, AA (reprint author), Tufts Univ, Sch Vet Med, Wildlife Clin, 200 Westboro Rd, N Grafton, MA 01536 USA. NR 19 TC 10 Z9 11 U1 0 U2 9 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 SEP PY 1999 VL 11 IS 3 BP 283 EP 289 DI 10.1577/1548-8667(1999)011<0283:POFIOR>2.0.CO;2 PG 7 WC Fisheries; Veterinary Sciences SC Fisheries; Veterinary Sciences GA 316TT UT WOS:000087184700010 ER PT J AU Merceret, FJ AF Merceret, FJ TI The vertical resolution of the Kennedy Space Center 50-MHz wind profiler SO JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY LA English DT Article AB The effective vertical resolution of the Kennedy Space Center 50-MHz Doppler radar wind profiler is deter mined using vertical wavenumber spectra and temporal coherence. The resolution ranges from being Nyquist limited at 300 m to as coarse as 900 m. The average resolution is about 500 m. C1 NASA, Appl Meteorol Unit, Kennedy Space Ctr, FL 32899 USA. RP Merceret, FJ (reprint author), NASA, Appl Meteorol Unit, AA-C-1, Kennedy Space Ctr, FL 32899 USA. NR 4 TC 2 Z9 2 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 SEP PY 1999 VL 16 IS 9 BP 1273 EP 1278 DI 10.1175/1520-0426(1999)016<1273:TVROTK>2.0.CO;2 PG 6 WC Engineering, Ocean; Meteorology & Atmospheric Sciences SC Engineering; Meteorology & Atmospheric Sciences GA 236YC UT WOS:000082626000010 ER PT J AU Lin, C LeBlanc, AD Evans, HJ Shackelford, L Organov, V Driscoll, T Hedrick, T AF Lin, C LeBlanc, AD Evans, HJ Shackelford, L Organov, V Driscoll, T Hedrick, T TI Vertebra bone marrow changes in long-duration space flight and bed rest. SO JOURNAL OF BONE AND MINERAL RESEARCH LA English DT Meeting Abstract C1 Baylor Coll Med, Houston, TX 77030 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Moscow Biomed Problems Inst, Moscow, Russia. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER SOC BONE & MINERAL RES PI DURHAM PA PO BOX 2759, DURHAM, NC 27715-2759 USA SN 0884-0431 J9 J BONE MINER RES JI J. Bone Miner. Res. PD SEP PY 1999 VL 14 SU 1 MA F280 BP S265 EP S265 PG 1 WC Endocrinology & Metabolism SC Endocrinology & Metabolism GA 232CA UT WOS:000082347100528 ER PT J AU Rabkin, BA Szivek, JA Schonfeld, J Halloran, BP AF Rabkin, BA Szivek, JA Schonfeld, J Halloran, BP TI An in-vivo model for long term assessment of bone strains. SO JOURNAL OF BONE AND MINERAL RESEARCH LA English DT Meeting Abstract C1 Univ Calif San Francisco, San Francisco, CA 94143 USA. VAMC, Div Endocrinol, San Francisco, CA USA. NASA, Ames Res Ctr, BioMineralizat Res Lab, Moffett Field, CA 94035 USA. Univ Arizona, Dept Surg, Orthoped Res Lab, Tucson, AZ USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER SOC BONE & MINERAL RES PI DURHAM PA PO BOX 2759, DURHAM, NC 27715-2759 USA SN 0884-0431 J9 J BONE MINER RES JI J. Bone Miner. Res. PD SEP PY 1999 VL 14 SU 1 MA SA029 BP S316 EP S316 PG 1 WC Endocrinology & Metabolism SC Endocrinology & Metabolism GA 232CA UT WOS:000082347100731 ER PT J AU Rianon, NJ LeBlanc, AD Feeback, DL Driscoll, TB Shackelford, L AF Rianon, NJ LeBlanc, AD Feeback, DL Driscoll, TB Shackelford, L TI Analysis of sweat calcium using skin patches. SO JOURNAL OF BONE AND MINERAL RESEARCH LA English DT Meeting Abstract C1 Baylor Coll Med, Houston, TX 77030 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER SOC BONE & MINERAL RES PI DURHAM PA PO BOX 2759, DURHAM, NC 27715-2759 USA SN 0884-0431 J9 J BONE MINER RES JI J. Bone Miner. Res. PD SEP PY 1999 VL 14 SU 1 MA F311 BP S271 EP S271 PG 1 WC Endocrinology & Metabolism SC Endocrinology & Metabolism GA 232CA UT WOS:000082347100553 ER PT J AU Ruff, CB Beck, TJ LeBlanc, AD Evans, HJ Shackelford, L Oganov, V Schneider, VS AF Ruff, CB Beck, TJ LeBlanc, AD Evans, HJ Shackelford, L Oganov, V Schneider, VS TI Effects of prolonged weightlessness on hip structural geometry in Russian cosmonauts. SO JOURNAL OF BONE AND MINERAL RESEARCH LA English DT Meeting Abstract C1 Johns Hopkins Univ, Baltimore, MD USA. Baylor Coll Med, Houston, TX 77030 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Minist Publ Hlth Russia, Inst Biomed Problems, Moscow, Russia. NR 0 TC 1 Z9 1 U1 0 U2 0 PU AMER SOC BONE & MINERAL RES PI DURHAM PA PO BOX 2759, DURHAM, NC 27715-2759 USA SN 0884-0431 J9 J BONE MINER RES JI J. Bone Miner. Res. PD SEP PY 1999 VL 14 SU 1 MA T282 BP S205 EP S205 PG 1 WC Endocrinology & Metabolism SC Endocrinology & Metabolism GA 232CA UT WOS:000082347100292 ER PT J AU Shackelford, LC LeBlanc, AD Feiveson, AH Evans, HJ Driscoll, TB Rianon, NJ AF Shackelford, LC LeBlanc, AD Feiveson, AH Evans, HJ Driscoll, TB Rianon, NJ TI Countermeasures against disuse bone loss. SO JOURNAL OF BONE AND MINERAL RESEARCH LA English DT Meeting Abstract C1 NASA, Lyndon B Johnson Space Ctr, Life Sci Res Labs, Houston, TX 77058 USA. Baylor Coll Med, Houston, TX 77030 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER SOC BONE & MINERAL RES PI DURHAM PA PO BOX 2759, DURHAM, NC 27715-2759 USA SN 0884-0431 J9 J BONE MINER RES JI J. Bone Miner. Res. PD SEP PY 1999 VL 14 SU 1 MA F347 BP S279 EP S279 PG 1 WC Endocrinology & Metabolism SC Endocrinology & Metabolism GA 232CA UT WOS:000082347100584 ER PT J AU Mankbadi, RR Ali, AA AF Mankbadi, RR Ali, AA TI Evaluation of subsonic inflow treatments for unsteady jet flow SO JOURNAL OF COMPUTATIONAL ACOUSTICS LA English DT Article ID DEPENDENT BOUNDARY-CONDITIONS; HYPERBOLIC SYSTEMS AB Linearized Euler simulations of the unsteady flow of a subsonic jet and its associated acoustic held are presented in this paper. Various subsonic inflow treatments are evaluated. Some of these treatments have been found to produce reflections at the inflow while others are reflection-free. Results are then presented for the effect of Mach number on the radiated sound. It is shown that as the Mach number increases the source becomes noncompact and the directivity is characterized by a well-defined peak. By comparing the linear prediction to the experimental results, validity range of linear approximation for subsonic jet noise is assessed. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. Univ Notre Dame, Notre Dame, IN 46556 USA. RP Mankbadi, RR (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 12 TC 1 Z9 1 U1 0 U2 1 PU WORLD SCIENTIFIC PUBL CO PTE LTD PI SINGAPORE PA JOURNAL DEPT PO BOX 128 FARRER ROAD, SINGAPORE 912805, SINGAPORE SN 0218-396X J9 J COMPUT ACOUST JI J. Comput. Acoust. PD SEP PY 1999 VL 7 IS 3 BP 147 EP 160 DI 10.1142/S0218396X99000114 PG 14 WC Acoustics; Mathematics, Interdisciplinary Applications SC Acoustics; Mathematics GA 243WF UT WOS:000083019900001 ER PT J AU Kahn, R Braverman, A AF Kahn, R Braverman, A TI What shall we do with the data we are expecting from upcoming earth observation satellites? SO JOURNAL OF COMPUTATIONAL AND GRAPHICAL STATISTICS LA English DT Article DE combining information; global grids; massive datasets; sensitivity studies; visualization ID AEROSOL AB The community of researchers studying global climate change is preparing to launch the first Earth observing system (EOS) satellite, EOS Terra. The satellite will generate huge amounts of data, filling gaps in the information available to address critical questions about Earth's climate. But many data handling and data analysis problems must be solved if we are to make best use of the new measurements. In key areas, the experience and expertise of the statistics community could be of great help. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Calif Los Angeles, Dept Stat, Los Angeles, CA 90095 USA. RP Kahn, R (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,Mail Stop 169-237, Pasadena, CA 91109 USA. RI Kahn, Ralph/D-5371-2012 OI Kahn, Ralph/0000-0002-5234-6359 NR 18 TC 5 Z9 5 U1 0 U2 1 PU AMER STATISTICAL ASSOC PI ALEXANDRIA PA 1429 DUKE ST, ALEXANDRIA, VA 22314 USA SN 1061-8600 J9 J COMPUT GRAPH STAT JI J. Comput. Graph. Stat. PD SEP PY 1999 VL 8 IS 3 BP 575 EP 588 DI 10.2307/1390877 PG 14 WC Statistics & Probability SC Mathematics GA 245XQ UT WOS:000083134100015 ER PT J AU Fayyad, UM Smyth, P AF Fayyad, UM Smyth, P TI Cataloging and mining massive datasets for science data analysis SO JOURNAL OF COMPUTATIONAL AND GRAPHICAL STATISTICS LA English DT Article DE cataloging; classification; clustering; data mining; data reduction; massive datasets; science data analysis ID DIGITIZED POSS-II; SKY SURVEY; CLASSIFICATION; PALOMAR; VENUS AB With hardware advances in sensors, scientific instruments, and data storage techniques has come the inevitable flood of data that threatens to render traditional approaches to data analysis inadequate. The classic paradigm of a scientist manually and exhaustively going through a dataset is no longer feasible for many problems, ranging from remote sensing, astronomy, and atmospheric science to medicine, molecular biology, and biochemistry, This article presents our views as practitioners engaged in building computational systems to help scientists analyze and reduce massive datasets. We focus on what we view as challenges and shortcomings of the current state-of-the-art in data analysis in view of the massive datasets that are still awaiting analysis. The presentation focuses on recent and current scientific data analysis applications in astronomy, planetary sciences, solar physics, and atmospheric science that we have been involved with at the Jet Propulsion Laboratory (SPL). C1 Microsoft Res, Data Min & Explorat DMX Grp, Redmond, WA 98052 USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. Univ Calif Irvine, Irvine 92697, CA USA. RP Fayyad, UM (reprint author), Microsoft Res, Data Min & Explorat DMX Grp, Redmond, WA 98052 USA. NR 58 TC 4 Z9 4 U1 0 U2 2 PU AMER STATISTICAL ASSOC PI ALEXANDRIA PA 1429 DUKE ST, ALEXANDRIA, VA 22314 USA SN 1061-8600 J9 J COMPUT GRAPH STAT JI J. Comput. Graph. Stat. PD SEP PY 1999 VL 8 IS 3 BP 589 EP 610 DI 10.2307/1390878 PG 22 WC Statistics & Probability SC Mathematics GA 245XQ UT WOS:000083134100016 ER PT J AU Rothschild, LJ AF Rothschild, LJ TI The influence of UV radiation on protistan evolution SO JOURNAL OF EUKARYOTIC MICROBIOLOGY LA English DT Article DE DNA damage; DNA repair; photosynthesis; sex; ultraviolet radiation ID ULTRAVIOLET-B RADIATION; DNA-REPAIR; DEINOCOCCUS RADIODURANS; HAEMOPHILUS-INFLUENZAE; SOLAR ULTRAVIOLET; IRRADIATION; DAMAGE; MARS; LIFE; MICROORGANISMS AB Utraviolet radiation has provided an evolutionary challenge to life on Earth. Recent increases in surficial ultraviolet B fluxes have focused attention on the role of UV radiation in protistan ecology, cancer, and DNA damage. Exploiting this new wealth of data, I examine the possibility that ultraviolet radiation may have played a significant role in the evolution of the first eukaryotes, that is, protists. Protists probably arose well before the formation of a significant ozone shield, and thus were probably subjected to substantial ultraviolet A, ultraviolet B, and ultraviolet C fluxes early in their evolution. Evolution consists of the generation of heritable variations and the subsequent selection of these variants. Ultraviolet radiation has played a role both as a mutagen and as a selective agent. In its role as a mutagen, it may have been crucial in the origin of sex and as a driver for molecular evolution. As a selective agent, its influence has been broad. Discussed in this paper are the influence of ultraviolet radiation on biogeography, photosynthesis, and desiccation resistance. C1 NASA, Ames Res Ctr, Ecosyst Sci & Technol Branch MS 239 20, Moffett Field, CA 94035 USA. RP Rothschild, LJ (reprint author), NASA, Ames Res Ctr, Ecosyst Sci & Technol Branch MS 239 20, Moffett Field, CA 94035 USA. NR 85 TC 29 Z9 29 U1 0 U2 8 PU SOC PROTOZOOLOGISTS PI LAWRENCE PA 810 E 10TH ST, LAWRENCE, KS 66044 USA SN 1066-5234 J9 J EUKARYOT MICROBIOL JI J. Eukaryot. Microbiol. PD SEP-OCT PY 1999 VL 46 IS 5 BP 548 EP 555 DI 10.1111/j.1550-7408.1999.tb06074.x PG 8 WC Microbiology SC Microbiology GA 242TZ UT WOS:000082958900015 PM 11536924 ER PT J AU Peck, B Sigurdson, L AF Peck, B Sigurdson, L TI Geometry effects on free surface vorticity flux SO JOURNAL OF FLUIDS ENGINEERING-TRANSACTIONS OF THE ASME LA English DT Article ID DYNAMICS AB Effects of geometry on the flux of vorticity from a free surface are discussed. Special attention is paid to situations where curvature-dependent contributions to the vorticity flux can be neglected. The geometry of vortex lines embedded in the surface is discussed in this context. These results show that vortex lines can be straight and geometry-induced vorticity flux is produced; conversely vortex lines can be curved and no geometry-induced vorticity flux is produced. A convenient method for assessing vorticity flux from a steady surface based on Gaussian curvature is derived. C1 Univ Alberta, Dept Mech Engn, Edmonton, AB T6G 2G8, Canada. RP Peck, B (reprint author), NASA, Ames Res Ctr, Ctr Turbulence Res, Stanford, CA 94305 USA. NR 19 TC 3 Z9 3 U1 2 U2 2 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 SEP PY 1999 VL 121 IS 3 BP 678 EP 683 DI 10.1115/1.2823523 PG 6 WC Engineering, Mechanical SC Engineering GA 238JY UT WOS:000082708200025 ER PT J AU Whang, YC Lu, JY Burlaga, LF AF Whang, YC Lu, JY Burlaga, LF TI Evolution of a strong shock in the distant heliosphere SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID WIND TERMINATION SHOCK; PRESSURE-BALANCED STRUCTURES; MERGED INTERACTION REGIONS; ANOMALOUS COSMIC-RAYS; SOLAR-WIND; OUTER HELIOSPHERE; VOYAGER-2 OBSERVATIONS; PICKUP PROTONS; INTERPLANETARY SPACE; NEUTRAL HYDROGEN AB The 1991 global merged interaction region (GMIR) shock is a strong forward shock observed from Voyager 2 on day 146 of 1991 at 34.6 AU at the leading edge of the 1991 GMIR. This shock is the strongest shock ever identified from the Voyager data in the distant heliosphere. In this paper we study the evolution and propagation of the 1991 GMIR shock outside 34.6 AU in the upwind direction taking into account the influence of interstellar pickup protons. We calculate the time, location, and various variables of this shock in the subsequent 400 days. We use the shock interaction model to develop a R,t-simulation code to study this problem. The model treats the shock as a surface of discontinuity with zero thickness and uses the method of characteristics to study the evolution of the solar wind in the disturbed region. This model can accurately calculate the propagation speed and the strength of the shock. The numerical solution shows that as the GMIR shock propagates from 35 AU to 150 AU, the shock speed decreases monotonically from 543 km/s to 478 km/s and the density ratio decreases from 2.55 to 2.09. The solar wind proton temperature and the pickup proton temperature on two sides of the shock decrease monotonically with increasing heliocentric distance. Across the shock the solar wind proton temperature ratio is high, namely, similar to 22 at 35 AU and similar to 11.5 at 150 AU, while the pickup proton temperature ratio is an order of magnitude smaller: similar to 2.1 at 35 AU and similar to 1.8 at 150 AU. C1 Catholic Univ Amer, Dept Mech Engn, Washington, DC 20064 USA. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RP Whang, YC (reprint author), Catholic Univ Amer, Dept Mech Engn, Washington, DC 20064 USA. NR 47 TC 11 Z9 11 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 SEP 1 PY 1999 VL 104 IS A9 BP 19787 EP 19795 DI 10.1029/1999JA900210 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 232FK UT WOS:000082360100004 ER PT J AU Scudder, JD Puhl-Quinn, PA Mozer, FS Ogilvie, KW Russell, CT AF Scudder, JD Puhl-Quinn, PA Mozer, FS Ogilvie, KW Russell, CT TI Generalized Walen tests through Alfven waves and rotational discontinuities using electron flow velocities SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID SOLAR-WIND; EARTHS MAGNETOPAUSE; ANISOTROPIC PLASMA; MAGNETIC SHEAR; FIELD; RECONNECTION; COLLISIONLESS; LAYER AB A new formulation of the Walen test [Walen, 1944] to locate rotational discontinuities (RD) or Alfven wave trains is constructed that is more appropriate for use within and across the current-carrying layers of these structures, This generalized test is to be distinguished from the traditional rigorous jump condition that is only appropriate for connecting asymptotic, current free states on either side of the discontinuity or wave train. The generalized test is most simply formulated as a vector difference equation relating changes in the electron flow velocity vector and changes of the magnetic field vector, hU(e)(x) = alpha(e)Delta B(x) with a prescribed scalar constant of proportionality. For an electron proton plasma this paper shows that is precisely the same constant of the jump condition that has long been in use. Small corrections to alpha(e) are computed for minor helium populations. This new formulation is used with Polar plasma, E, and B measurements to search for rotational discontinuities at the: magnetopause. Of the 44 cases where electrons gave acceptable theoretical correlations and coefficients cu, predicted by the theory, nearly 95% of the simultaneous ion fits gave corresponding values of alpha(i) that were smaller in magnitude than implied by simple ideal MHD jump conditions. Possible explanations for this discrepancy are discussed. In addition, these data have been used to provide the first empirical evidence of the importance of the electron pressure gradient in these RD current layers and represent the first direct determination of the sizes E-n(HT) similar or equal to 0.3-5 mV/m of the deHoffmann-Teller electric field in RD current layers at the magnetopause. C1 Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20770 USA. Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90024 USA. RP Scudder, JD (reprint author), Univ Iowa, Dept Phys & Astron, Van Allen Hall,Room 203,Dubuque Jefferson St, Iowa City, IA 52242 USA. RI Scudder, Jack/D-8417-2013 OI Scudder, Jack/0000-0001-7975-5630 NR 31 TC 34 Z9 35 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 SEP 1 PY 1999 VL 104 IS A9 BP 19817 EP 19833 DI 10.1029/1999JA900146 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 232FK UT WOS:000082360100007 ER PT J AU Gary, SP Neagu, E Skoug, RM Goldstein, BE AF Gary, SP Neagu, E Skoug, RM Goldstein, BE TI Solar wind electrons: Parametric constraints SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID ULYSSES OBSERVATIONS; HEAT-FLUX; INSTABILITY; TEMPERATURE; ANISOTROPY; SPACECRAFT; WAVES; 1-AU AB Solar wind electrons are often observed to consist of two distinguishable components, a thermal, more dense core and a suprathermal, less dense halo. In this core/halo model linear Vlasov theory for the whistler heat flux instability predicts dimensionless heat flux thresholds which decrease as the electron core beta, <(beta)over tilde>parallel to(c), increases. It has been proposed that this theoretical threshold corresponds to an observable upper bound on the electron heat flux. Linear theory also predicts that there is a critical value of <(beta)over tilde>parallel to c below which the whistler heat flux instability does not have appreciable growth in the solar wind; there is another suggestion that this corresponds to an observable lower bound on <(beta)over tilde>parallel to(c). These two proposals are examined by comparison of linear theory and data from the initial in-ecliptic phase of the Ulysses mission. The instability threshold does provide a statistical constraint on observed solar wind heat fluxes, and the critical <(beta)over tilde>parallel to(c) Of theory is not inconsistent with a statistical lower bound on the observations of that parameter. C1 Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Gary, SP (reprint author), Univ Calif Los Alamos Natl Lab, MS D466, Los Alamos, NM 87545 USA. NR 28 TC 14 Z9 14 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 SEP 1 PY 1999 VL 104 IS A9 BP 19843 EP 19849 DI 10.1029/1999JA900244 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 232FK UT WOS:000082360100009 ER PT J AU Birn, J Hesse, M Haerendel, G Baumjohann, W Shiokawa, K AF Birn, J Hesse, M Haerendel, G Baumjohann, W Shiokawa, K TI Flow braking and the substorm current wedge SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID FIELD-ALIGNED CURRENTS; MAGNETOTAIL RECONNECTION; MAGNETOSPHERIC SUBSTORMS; CURRENT DISRUPTION; CURRENT SHEET; SIMULATIONS; DIVERSION; PHASE; TAIL AB Recent models of magnetotail activity have associated the braking of earthward flow with dipolarization and the reduction and diversion of cross-tail current, that is, the signatures of the substorm current wedge. Estimates of the magnitude of the diverted current by Haerendel [1992] and Shiokawa et al. [1997, 1998] tend to be lower than results from computer simulations of magnetotail reconnection and tail collapse [Birn and Hesse, 1996], despite similar underlying models. An analysis of the differences between these estimates on the basis of the simulations gives a more refined picture of the diversion of perpendicular into parallel currents. The inertial currents considered by Haerendel [1992] and Shiokawa et al. [1997] contribute to the initial current reduction and diversion, but the dominant and more permanent contribution stems from the pressure gradient terms, which change in connection with the field collapse and distortion. The major effect results form pressure gradients in the z direction, rather than from the azimuthal gradients [Shiokawa et al., 1998], combined with changes in B-y and B-x. The reduction of the current density near the equatorial plane is associated with a reduction of the curvature drift which overcompensates changes of the magnetization current and of the gradient B drift current. In contrast to the inertial current effects, the pressure gradient effects persist even after the burst of earthward flow ends. C1 Los Alamos Natl Lab, Los Alamos, NM 87545 USA. NASA, Goddard Space Flight Ctr, Electrodynam Branch, Greenbelt, MD 20771 USA. Max Planck Inst Extraterr Phys, D-85740 Garching, Germany. Nagoya Univ, Solar Terr Environm Lab, Nagoya, Aichi, Japan. RP Los Alamos Natl Lab, NIS-1,POB 1663,MS D466, Los Alamos, NM 87545 USA. EM jbirn@lanl.gov; hesse@gsfc.nasa.gov; hae@mpe-garching.mpg.de; bj@mpe.mpg.de; shiokawa@stelab.nagoya-u.ac.jp RI Hesse, Michael/D-2031-2012; Baumjohann, Wolfgang/A-1012-2010 OI Baumjohann, Wolfgang/0000-0001-6271-0110 NR 22 TC 145 Z9 146 U1 0 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9380 EI 2169-9402 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD SEP 1 PY 1999 VL 104 IS A9 BP 19895 EP 19903 DI 10.1029/1999JA900173 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 232FK UT WOS:000082360100015 ER PT J AU Kumar, CRA AF Kumar, CRA TI Linear quadratic optimality of infinite gain margin controllers SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article ID STATIC OUTPUT-FEEDBACK C1 N Carolina Agr & Technol State Univ, NASA, Ctr Aerosp Res, Greensboro, NC 27411 USA. RP Kumar, CRA (reprint author), N Carolina Agr & Technol State Univ, NASA, Ctr Aerosp Res, Box 1078, Greensboro, NC 27411 USA. NR 11 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 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD SEP-OCT PY 1999 VL 22 IS 5 BP 720 EP 722 DI 10.2514/2.4441 PG 3 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA 240MJ UT WOS:000082829500015 ER PT J AU Harman, RR Bar-Itzhack, IY AF Harman, RR Bar-Itzhack, IY TI Pseudolinear and state-dependent Riccati equation filters for angular rate estimation SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article C1 NASA, Goddard Space Flight Ctr, Flight Dynam Anal Branch, Greenbelt, MD 20771 USA. Technion Israel Inst Technol, Fac Aerosp Engn, IL-32000 Haifa, Israel. RP Harman, RR (reprint author), NASA, Goddard Space Flight Ctr, Flight Dynam Anal Branch, Code 572, Greenbelt, MD 20771 USA. NR 12 TC 26 Z9 27 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD SEP-OCT PY 1999 VL 22 IS 5 BP 723 EP 725 DI 10.2514/2.4442 PG 3 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA 240MJ UT WOS:000082829500016 ER PT J AU Clark, RL Cox, DE AF Clark, RL Cox, DE TI Band-limited actuator and sensor selection for disturbance rejection SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article ID FLEXIBLE STRUCTURES; PLACEMENT C1 Duke Univ, Dept Mech Engn & Mat Sci, Durham, NC 27708 USA. NASA, Langley Res Ctr, Flight Dynam & Control Div, Hampton, VA 23681 USA. RP Clark, RL (reprint author), Duke Univ, Dept Mech Engn & Mat Sci, Box 90300, Durham, NC 27708 USA. NR 7 TC 12 Z9 12 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD SEP-OCT PY 1999 VL 22 IS 5 BP 740 EP 743 DI 10.2514/2.4449 PG 4 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA 240MJ UT WOS:000082829500022 ER PT J AU Ardren, WR Borer, S Thrower, F Joyce, JE Kapuscinski, AR AF Ardren, WR Borer, S Thrower, F Joyce, JE Kapuscinski, AR TI Inheritance of 12 microsatellite loci in Oncorhynchus mykiss SO JOURNAL OF HEREDITY LA English DT Article ID RAINBOW-TROUT POPULATIONS; SALMON SALMO-SALAR; GENETIC-VARIATION; ALLELE FREQUENCY; LINKAGE MAP; NULL ALLELE; DNA MARKERS; MOLECULAR-BASIS; BROWN TROUT; ATLANTIC AB Four full-sib families of Oncorhynchus mykiss were used to study the inheritance of allelic variation at 12 microsatellite loci. The loci examined were previously characterized in six different species from the family Salmonidae, Of the 48 genotypic ratios observed (12 loci x 4 crosses), disomic segregation of codominant autosomal alleles was established in 24 of 31 informative tests, The seven tests that did not conform to Mendelian ratios can be explained by the presence of null alleles (One mu 14 and Omy77) and a locus (One mu 1) that may be tandemly duplicated. Three significant pairwise linkage associations were observed between One mu 1 and Omy207, Ssa85 and One mu 11, and the two loci amplified by One mu 1 primers, indicating these loci are not asserting independently. The presence of unexpected heteroduplex structures in One mu 11 electropherograms in one cross prompted the sequencing of similar microsatellite electromorphs. Sequence differences revealed size homoplasy, that is, the electromorphs were identical in state but they were not identical by descent. These results demonstrate the need to conduct comprehensive species-specific inheritance studies for microsatellite loci used in population genetic or kinship analyses. Discovery of these four attributes by examining a small number of loci in four families suggests that they are common across microsatellite loci overall. C1 Univ Minnesota, Dept Fisheries & Wildlife, AquaGen Lab, St Paul, MN 55108 USA. Natl Marine Fisheries Serv, Auke Bay Lab, Juneau, AK USA. RP Ardren, WR (reprint author), Luther Coll, Dept Biol, 700 Coll Dr, Decorah, IA 52101 USA. NR 58 TC 34 Z9 53 U1 0 U2 1 PU OXFORD UNIV PRESS INC PI CARY PA JOURNALS DEPT, 2001 EVANS RD, CARY, NC 27513 USA SN 0022-1503 J9 J HERED JI J. Hered. PD SEP-OCT PY 1999 VL 90 IS 5 BP 529 EP 536 DI 10.1093/jhered/90.5.529 PG 8 WC Evolutionary Biology; Genetics & Heredity SC Evolutionary Biology; Genetics & Heredity GA 248AX UT WOS:000083254100004 ER PT J AU Paradis, PF Rhim, WK AF Paradis, PF Rhim, WK TI Thermophysical properties of zirconium at high temperature SO JOURNAL OF MATERIALS RESEARCH LA English DT Article ID NONCONTACT MEASUREMENT TECHNIQUE; EMISSIVITY; NICKEL; HEAT AB Six thermophysical properties of both solid and liquid zirconium measured using the high-temperature electrostatic levitator at the Jet Propulsion Laboratory are presented. These properties are density, thermal expansion coefficient, constant pressure heat capacity, hemispherical total emissivity, surface tension, and viscosity. For the first time, we report the densities and the thermal expansion coefficients of both the solid as well as liquid Zr over wide ranges of temperatures. Over the 1700-2300 K temperature span, the liquid density can be expressed as rho(1)(T) = 6.24 x 10(3) - 0.29(T - T-m) kg/m(3) with T-m = 2128 K, and the corresponding volume expansion coefficient as alpha(1) = 4.6 x 10(-5) /K. Similarly, over the 1250-2100 K range, the measured density of the solid can be expressed as rho(s)(T) = 6.34 x 10(3) - 0.15(T - T-m), giving a volume expansion coefficient alpha(s) = 2.35 x 10(-5) /K. The constant pressure heat capacity of the liquid phase could be estimated as C-pl(T) = 39.72 - 7.42 x 10(-3) (T - T-m) J/(mol/K) if the hemispherical total emissivity of the liquid phase epsilon(T1) remains constant at 0.3 over the 1825-2200 K range. Over the 1400-2100 K temperature span, the hemispherical total emissivity of the solid phase could be rendered as epsilon(Ts)(T) = 0.29 - 9.91 x 10(3) (T - T-m). The measured surface tension and the viscosity of the molten zirconium over the 1850-2200 K range can be expressed as sigma(T) = 1.459 x 10(3) - 0.244 (T - T-m) mN/m and as eta(T) = 4.83 - 5.31 x 10(-3)(T - T-m) mPa s, respectively. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Paradis, PF (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 22 TC 43 Z9 43 U1 1 U2 12 PU MATERIALS RESEARCH SOCIETY PI WARRENDALE PA 506 KEYSTONE DR, WARRENDALE, PA 15086 USA SN 0884-2914 J9 J MATER RES JI J. Mater. Res. PD SEP PY 1999 VL 14 IS 9 BP 3713 EP 3719 DI 10.1557/JMR.1999.0501 PG 7 WC Materials Science, Multidisciplinary SC Materials Science GA 304RX UT WOS:000086498900032 ER PT J AU Prosser, WH Hamstad, MA Gary, J O'Gallagher, A AF Prosser, WH Hamstad, MA Gary, J O'Gallagher, A TI Finite element and plate theory modeling of acoustic emission waveforms SO JOURNAL OF NONDESTRUCTIVE EVALUATION LA English DT Article DE acoustic emission; plate theory; finite element modeling ID MATRIX CRACKING; WAVES AB A comparison was made between two approaches to predict acoustic emission waveforms in thin plates. A normal mode solution method for Mindlin plate theory was used to predict the response of the flexural plate mode to a point source, step-function load, applied on the plate surface. The second approach used a dynamic finite element method to model the problem using equations of motion based on exact linear elasticity. Calculations were made using properties for both isotropic (aluminum) and anisotropic (unidirectional graphite/epoxy composite) materials. For simulations of anisotropic plates, propagation along multiple directions was evaluated. in general, agreement between the two theoretical approaches was good. Discrepancies in the waveforms at longer times were caused by differences in reflections from the lateral plate boundaries. These differences resulted from the fact that the two methods used different boundary conditions. At shorter times in the signals, before reflections, the slight discrepancies in the waveforms were attributed to limitations of Mindlin plate theory, which is an approximate plate theory. The advantages of the finite element method are that it used the exact linear elasticity solutions, and that it can be used to model real source conditions and complicated, finite specimen geometries as well as thick plates. These advantages come at a cost of increased computational difficulty, requiring lengthy calculations on workstations or supercomputers. The Mindlin plate theory solutions, meanwhile, can be quickly generated on personal computers. Specimens with finite geometry can also be modeled. However, only limited simple geometries such as circular or rectangular plates can easily be accommodated with the normal mode solution technique. Likewise, very Limited source configurations can be modeled and plate theory is applicable only to thin plates. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Univ Denver, Denver, CO 80208 USA. Natl Inst Stand & Technol, Boulder, CO 80303 USA. RP NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 20 TC 33 Z9 33 U1 1 U2 11 PU SPRINGER/PLENUM PUBLISHERS PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 0195-9298 EI 1573-4862 J9 J NONDESTRUCT EVAL JI J. Nondestruct. Eval. PD SEP PY 1999 VL 18 IS 3 BP 83 EP 90 DI 10.1023/A:1021888009896 PG 8 WC Materials Science, Characterization & Testing SC Materials Science GA 270AQ UT WOS:000084513600001 ER PT J AU Ahumada, AJ Beard, BL AF Ahumada, AJ Beard, BL TI Template learning models for visual target detection in fixed and random noise SO JOURNAL OF OPTICAL TECHNOLOGY LA English DT Article ID SIGNAL-DETECTION; DISCRIMINATION; DETECTABILITY; MASKING AB Models for the detection of targets in random backgrounds usually include an observer template that approximately matches the target. When detection thresholds are measured in noise using a two-interval forced-choice paradigm, three randomization conditions have been used: fixed, twin, and random. In the fixed noise condition, a single noise sample is presented in both intervals of all trials. In the twin noise condition, the same noise sample is used in the two intervals of a trial, but a new sample is generated for each trial. In the random noise condition, a new sample is always used. Fixed noise conditions usually result in lower thresholds than twin noise, and twin noise usually results in lower thresholds than random noise. Our template learning models attribute the advantage of fixed over twin noise either (1) to the template learning process introducing more noise into the template in the twin noise condition, or (2) to templates reducing position uncertainty by incorporating the fixed noise. In our models the template learning process contributes to the accelerating nonlinear increase in performance with signal amplitude at low signal-to-noise ratios. (C) 1999 The Optical Society of America. [S1070-9762(99)00809-X]. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Ahumada, AJ (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 18 TC 0 Z9 0 U1 0 U2 1 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 1070-9762 J9 J OPT TECHNOL+ JI J. Opt. Technol. PD SEP PY 1999 VL 66 IS 9 BP 817 EP 821 PG 5 WC Optics SC Optics GA 244EM UT WOS:000083038900008 ER PT J AU Banner, ML Chen, W Walsh, EJ Jensen, JB Lee, S Fandry, C AF Banner, ML Chen, W Walsh, EJ Jensen, JB Lee, S Fandry, C TI The Southern Ocean Waves Experiment. Part I: Overview and mean results SO JOURNAL OF PHYSICAL OCEANOGRAPHY LA English DT Article ID SURFACE WIND STRESS; SEA-SURFACE; SQUARE SLOPE; HEAT-FLUX; NUMBER SPECTRA; WATER-SURFACE; COEFFICIENTS; ROUGHNESS; RADAR AB The Southern Ocean Waves Experiment (SOWEX) was an international collaborative air-sea interaction experiment in which a specially instrumented meteorological research aircraft simultaneously gathered atmospheric turbulence data in the marine boundary layer and sea surface topography data over the Southern Ocean for a wide range of wind speeds. The aim was to increase present knowledge of severe sea state air-sea interaction. This first paper presents an overview of the experiment and a detailed discussion of the methodology and mean results. A companion paper describes the findings on variability of the wind speed and wind stress and their relationship to variations in the underlying sea surface roughness. C1 Univ New S Wales, Sch Math, Sydney, NSW 2052, Australia. NASA, Goddard Space Flight Ctr, Observ Sci Branch, Wallops Island, VA 23337 USA. CSIRO, Mordialloc, Vic, Australia. CSIRO, Marine Labs, Hobart, Tas, Australia. RP Banner, ML (reprint author), Univ New S Wales, Sch Math, Sydney, NSW 2052, Australia. RI Jensen, Jorgen/C-9211-2009; OI Banner, Michael/0000-0002-0799-5341 NR 46 TC 44 Z9 48 U1 0 U2 2 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0022-3670 J9 J PHYS OCEANOGR JI J. Phys. Oceanogr. PD SEP PY 1999 VL 29 IS 9 BP 2130 EP 2145 DI 10.1175/1520-0485(1999)029<2130:TSOWEP>2.0.CO;2 PG 16 WC Oceanography SC Oceanography GA 246EC UT WOS:000083150600002 ER PT J AU Leong, MY Samuelsen, GS Holdeman, JD AF Leong, MY Samuelsen, GS Holdeman, JD TI Mixing of jet air with a fuel-rich, reacting crossflow SO JOURNAL OF PROPULSION AND POWER LA English DT Article ID MULTIPLE JETS; FLOW AB The mixing of jet air into hot, fuel-rich products of a gas-turbine primary zone is a critical step in staged combustion. Often referred to as quick quench, the mixing occurs instead with chemical conversion and substantial heat release. An experiment has been designed to simulate and study this process. The geometry is a crossflow confined in a cylindrical duct with a sidewall injection of jets issuing from round holes. A specially designed reactor, operating on propane, presents a uniform mixture to a module containing jet-air-injection orifices that can be varied in geometry. Temperature and species concentrations of O-2, CO2, CO, and HC are obtained upstream, downstream, and within orifice planes. From this information, penetration of the jet, the spatial extent of chemical reaction, and mixing can be deduced. Results are presented for a mixing module containing 10 round holes that is operated at a momentum-flux ratio of 57 and a jet-to-mainstream mass-flow ratio of 2.5. C1 Univ Calif Irvine, Combust Lab, Irvine, CA 92697 USA. NASA, John H Glenn Res Ctr, Combust Branch, Cleveland, OH 44135 USA. RP Leong, MY (reprint author), Univ Calif Irvine, Combust Lab, Irvine, CA 92697 USA. NR 13 TC 6 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 0748-4658 J9 J PROPUL POWER JI J. Propul. Power PD SEP-OCT PY 1999 VL 15 IS 5 BP 617 EP 622 DI 10.2514/2.5479 PG 6 WC Engineering, Aerospace SC Engineering GA 235YL UT WOS:000082571400001 ER PT J AU Larosiliere, LM Skoch, GJ Prahst, PS AF Larosiliere, LM Skoch, GJ Prahst, PS TI Aerodynamic synthesis of a centrifugal impeller using computational fluid dynamics and measurements SO JOURNAL OF PROPULSION AND POWER LA English DT Article; Proceedings Paper CT AIAA/ASME/SAE/ASEE 33rd Joint Propulsion Conference CY JUL 06-09, 1998 CL SEATTLE, WASHINGTON SP AIAA, ASME, SAE, ASEE AB The performance and flow structure in an unshrouded impeller of approximately 4:1 pressure ratio is synthesized from a detailed analysis of three-dimensional viscous computational fluid dynamics (CFD) results and aerodynamic measurements. A good data match was obtained between CFD and measurements using laser anemometry and pneumatic probes. This solidified the role of the CFD model as a reliable representation of the impeller internal flow structure and integrated performance. Results are presented showing the loss production and secondary flow structure in the impeller. The results indicate that, while the overall impeller efficiency is high, the impeller shroud static-pressure recovery potential is underdeveloped, leading to a performance degradation in the downstream diffusing element. Thus, a case is made for a follow-on impeller parametric design study to improve the flow quality. A strategy for aerodynamic performance enhancement Is outlined; and an estimate of the gain in overall impeller efficiency that might be realized through improvements to the relative diffusion process is provided. C1 NASA, John H Glenn Res Ctr, Cleveland, OH 44135 USA. NYMA Inc, Brook Pk, OH 44142 USA. RP Larosiliere, LM (reprint author), USA, Res Lab, Washington, DC 20310 USA. NR 16 TC 3 Z9 4 U1 0 U2 2 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 SEP-OCT PY 1999 VL 15 IS 5 BP 623 EP 632 DI 10.2514/2.5486 PG 10 WC Engineering, Aerospace SC Engineering GA 235YL UT WOS:000082571400002 ER PT J AU Melis, ME Zaretsky, EV August, R AF Melis, ME Zaretsky, EV August, R TI Probabilistic analysis of aircraft gas turbine disk life and reliability SO JOURNAL OF PROPULSION AND POWER LA English DT Article; Proceedings Paper CT AIAA/ASME/ASCE/AHS/ASC 38th Structures, Structural Dynamics, and Materials Conference CY APR 07-10, 1997 CL KISSIMMEE, FLORIDA SP Amer Inst Aeronaut & Astronaut, ASME, ASCE, AHS, ASC ID PREDICTION AB Two series of low-cycle-fatigue (LCF) test data for two different groups of aircraft gas turbine engine compressor-disk geometries were reanalyzed and compared by using Weibull statistics. Both groups of disks were manufactured from titanium (Ti-6Al-4V) alloy, A probabilistic computer code called Probable Cause was used to predict disk life and reliability. A material-life factor A was determined for the titanium (Ti-6Al-4V) alloy by using fatigue disk data and was applied to predict disk life as a function of speed. A comparison was made with results from the currently used life prediction method, which is based on crack growth rate. Applying an endurance limit to the computer code did not significantly affect the predicted lives under engine operating conditions. Failure location predictions correlated with experimentally observed failure locations in the LCF tests. A reasonable correlation was obtained between the disk lives predicted by using the Probable Cause code and those predicted by using a modified crack growth method. Both methods slightly overpredicted life for one disk group and significantly underpredicted it for the other. C1 NASA, John H Glenn Res Ctr, Struct & Acoust Div, Cleveland, OH 44135 USA. NYMA Inc, Brook Pk, OH 44142 USA. RP Melis, ME (reprint author), NASA, John H Glenn Res Ctr, Struct & Acoust Div, Lewis Field, Cleveland, OH 44135 USA. NR 25 TC 16 Z9 20 U1 0 U2 8 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 SEP-OCT PY 1999 VL 15 IS 5 BP 658 EP 666 DI 10.2514/2.5490 PG 9 WC Engineering, Aerospace SC Engineering GA 235YL UT WOS:000082571400006 ER PT J AU Mishchenko, MI Videen, G AF Mishchenko, MI Videen, G TI Single-expansion EBCM computations for osculating spheres SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article; Proceedings Paper CT Conference on Light Scattering by Nonspherical Particles - Theory, Measurements, and Applications CY SEP 29-OCT 01, 1998 CL GODDAARD INST SPACE STUDIES, NEW YORK, NY HO GODDAARD INST SPACE STUDIES ID LIGHT-SCATTERING; ELECTROMAGNETIC SCATTERING AB We show that the standard, single-expansion extended boundary condition method provides convergent scattering results for osculating dielectric spheres and discuss the implications of this result. Published by Elsevier Science Ltd. C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. USA, Res Lab, AMSRL IS EE, Adelphi, MD 20783 USA. RP NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. EM crmim@giss.nasa.gov RI Mishchenko, Michael/D-4426-2012 NR 16 TC 7 Z9 7 U1 0 U2 2 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0022-4073 EI 1879-1352 J9 J QUANT SPECTROSC RA JI J. Quant. Spectrosc. Radiat. Transf. PD SEP-DEC PY 1999 VL 63 IS 2-6 BP 231 EP 236 DI 10.1016/S0022-4073(99)00047-3 PG 6 WC Optics; Spectroscopy SC Optics; Spectroscopy GA 230VX UT WOS:000082273300009 ER PT J AU Mishchenko, MI Dlugach, JM Yanovitskij, EG Zakharova, NT AF Mishchenko, MI Dlugach, JM Yanovitskij, EG Zakharova, NT TI Bidirectional reflectance of flat, optically thick particulate layers: an efficient radiative transfer solution and applications to snow and soil surfaces SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article; Proceedings Paper CT Conference on Light Scattering by Nonspherical Particles - Theory, Measurements, and Applications CY SEP 29-OCT 01, 1998 CL GODDAARD INST SPACE STUDIES, NEW YORK, NY HO GODDAARD INST SPACE STUDIES ID LIGHT-SCATTERING; MULTIPLE-SCATTERING; POLARIZED-LIGHT; PHASE FUNCTIONS; COHERENT BACKSCATTERING; PLANETARY ATMOSPHERES; ASYMMETRY PARAMETERS; SPHERICAL-PARTICLES; SINGLE-SCATTERING; ICE CRYSTALS AB We describe a simple and highly efficient and accurate radiative transfer technique for computing bidirectional reflectance of a macroscopically flat scattering layer composed of nonabsorbing or weakly absorbing, arbitrarily shaped, randomly oriented and randomly distributed particles. The layer is assumed to be homogeneous and optically semi-infinite, and the bidirectional reflection function (BRF) is found by a simple iterative solution of the Ambartsumian's nonlinear integral equation. As an exact solution of the radiative transfer equation, the reflection function thus obtained fully obeys the fundamental physical laws of energy conservation and reciprocity. Since this technique bypasses the computation of the internal radiation held, it is by far the fastest numerical approach available and can be used as an ideal input for Monte Carlo procedures calculating BRFs of scattering layers with macroscopically rough surfaces. Although the effects of packing density and coherent backscattering are currently neglected, they can also be incorporated. The FORTRAN implementation of the technique is available on the World Wide Web at http://www.giss.nasa.gov/ similar to crmim/brf.html and can be applied to a wide range of remote sensing, engineering, and biophysical problems. We also examine the potential effect of ice crystal shape on the bidirectional reflectance of flat snow surfaces and the applicability of the Henyey-Greenstein phase function and the delta-Eddington approximation in calculations for soil surfaces, (C) 1999 Elsevier Science Ltd. All rights reserved. C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Ukrainian Acad Sci, Main Astron Observ, Lab Radiat Transfer Theory, UA-252650 Kiev 22, Ukraine. Sci Syst & Applicat Inc, New York, NY 10025 USA. RP NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. EM crmim@giss.nasa.gov RI Mishchenko, Michael/D-4426-2012 NR 102 TC 207 Z9 209 U1 3 U2 17 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0022-4073 EI 1879-1352 J9 J QUANT SPECTROSC RA JI J. Quant. Spectrosc. Radiat. Transf. PD SEP-DEC PY 1999 VL 63 IS 2-6 BP 409 EP 432 DI 10.1016/S0022-4073(99)00028-X PG 24 WC Optics; Spectroscopy SC Optics; Spectroscopy GA 230VX UT WOS:000082273300021 ER PT J AU Han, QY Rossow, WB Chou, J Kuo, KS Welch, RM AF Han, QY Rossow, WB Chou, J Kuo, KS Welch, RM TI The effects of aspect ratio and surface roughness on satellite retrievals of ice-cloud properties SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article; Proceedings Paper CT Conference on Light Scattering by Nonspherical Particles - Theory, Measurements, and Applications CY SEP 29-OCT 01, 1998 CL GODDAARD INST SPACE STUDIES, NEW YORK, NEW YORK HO GODDAARD INST SPACE STUDIES ID OPTICAL-THICKNESS; CIRRUS; PARAMETERIZATION; CLIMATE AB This study investigates the effects of non-sphericity on satellite retrievals of ice-cloud properties including optical thickness and particle sizes. Ray-tracing technique is used to calculate single scattering phase function and single scattering albedo for both smooth and rough surfaces of hexagonal columns and plates at visible and near-infrared wavelengths. Two parameters, aspect ratio and distortion parameter, are used to simulate different, randomly oriented, ice crystal shapes and surface roughnesses in the ray-tracing process. A wide range of aspect ratio and distortion parameter is explored in the calculations. The resultant phase functions and single scattering albedos are used to compute bidirectional reflection functions by a radiative transfer model with adding-doubling technique. The results show that in a direct backscattering regima (Theta > 150 degrees), if no information of particle shape is available, the uncertainties in the retrieved optical thickness (a factor of more than ten) would make the retrieval meaningless. For images with viewing geometry outside of this region, the typical range of uncertainty of retrieved optical thickness is less than a factor of about two. Using averaged phase function will cut this uncertainty in half. That is, the uncertainty in the retrieved optical thickness is about 40%. Sensitivity tests show that aspect ratios are critical in reducing the uncertainties of the retrieved optical thickness using satellite data. The uncertainties in the retrieved ice particle sizes are also estimated in a similar way. It is found that using an averaged aspect ratio and roughness, the uncertainty of retrieved particle size is about 30% for small particles and 10% for large particles at lambda = 3.7 mu m. The corresponding uncertainties are about 70% for small particles and 35% for large particles if data at lambda = 1.6 or 2.2 mu m are used in the retrieval. However, at lambda = 1.6 and 2.2 mu m, retrieval of particle size may encounter even larger uncertainties for thin ice-clouds ( tau < 3). (C) 1999 Elsevier Science Ltd. All rights reserved. C1 Univ Alabama, Dept Atmospher Sci, Huntsville, AL 35899 USA. NASA, Goddard Inst Space Studies, Greenbelt, MD USA. RP Han, QY (reprint author), Univ Alabama, Dept Atmospher Sci, 977 Explorer Blvd, Huntsville, AL 35899 USA. RI Rossow, William/F-3138-2015 NR 21 TC 17 Z9 17 U1 0 U2 4 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0022-4073 J9 J QUANT SPECTROSC RA JI J. Quant. Spectrosc. Radiat. Transf. PD SEP-DEC PY 1999 VL 63 IS 2-6 BP 559 EP 583 DI 10.1016/S0022-4073(99)00039-4 PG 25 WC Optics; Spectroscopy SC Optics; Spectroscopy GA 230VX UT WOS:000082273300031 ER PT J AU Krotkov, NA Flittner, DE Krueger, AJ Kostinski, A Riley, C Rose, W Torres, O AF Krotkov, NA Flittner, DE Krueger, AJ Kostinski, A Riley, C Rose, W Torres, O TI Effect of particle non-sphericity on satellite monitoring of drifting volcanic ash clouds SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article; Proceedings Paper CT Conference on Light Scattering by Nonspherical Particles - Theory, Measurements, and Applications CY SEP 29-OCT 01, 1998 CL GODDAARD INST SPACE STUDIES, NEW YORK, NY HO GODDAARD INST SPACE STUDIES ID OZONE MAPPING SPECTROMETER; TROPOSPHERIC AEROSOLS; LIGHT-SCATTERING; SULFUR-DIOXIDE; INDEX AB The NASA total ozone mapping spectrometer (TOMS) instruments aboard the Nimbus-7, Meteor3, ADEOS, and Earth Probe satellites have produced a unique data set of global S0(2) volcanic emissions since 1978. Besides S0(2), a new technique has been developed which uses the measured spectral contrast of the backscattered radiances in the 0.34-0.38 mu m spectral interval (where gaseous absorption is negligible) in conjunction with radiative transfer models to retrieve properties of ash clouds including the optical depth and effective particle radius, R-eff. Using the T-matrix method for computing the scattering properties of randomly oriented spheroids, we have tested the sensitivity of the TOMS volcanic ash retrievals to particle shape. For the case of the August 19, 1992 Mt. Spurr ash cloud and the TOMS observational geometry, modeling the ash as spherical particles causes the TOMS-retrieved R-eff to be underestimated for R-eff > 0.1 mu m by as much as 30%. On the other hand, the optical depth will be overestimated by as much as 25%. In terms of the total mass of the cloud, the compensating errors in R-eff and optical depth tend to produce a 5-20% underestimation. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 Raytheon ITSS Corp, Lanham, MD 20706 USA. Univ Arizona, Tucson, AZ 85721 USA. NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. Michigan Technol Univ, Houghton, MI 49931 USA. Univ Maryland Baltimore Cty, Joint Ctr Earth Syst Technol, Greenbelt, MD 20771 USA. RP Raytheon ITSS Corp, 4400 Forbes Blvd, Lanham, MD 20706 USA. EM krotkov@hoss.stx.com RI Krotkov, Nickolay/E-1541-2012; Torres, Omar/G-4929-2013 OI Krotkov, Nickolay/0000-0001-6170-6750; NR 27 TC 43 Z9 43 U1 2 U2 7 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0022-4073 EI 1879-1352 J9 J QUANT SPECTROSC RA JI J. Quant. Spectrosc. Radiat. Transf. PD SEP-DEC PY 1999 VL 63 IS 2-6 BP 613 EP 630 DI 10.1016/S0022-4073(99)00041-2 PG 18 WC Optics; Spectroscopy SC Optics; Spectroscopy GA 230VX UT WOS:000082273300034 ER PT J AU Konstantinov, PP Shelimova, LE Avilov, ES Kretova, MA Fleurial, JP AF Konstantinov, PP Shelimova, LE Avilov, ES Kretova, MA Fleurial, JP TI Transport phenomena in mixed layered tetradymite-like compounds in the GeTe-Bi2Te3 system SO JOURNAL OF SOLID STATE CHEMISTRY LA English DT Article ID HOMOLOGOUS SERIES; X-RAY AB The electrical transport properties of the GeBi2Te4-, Ge3Bi2Te6-, and GeBi4Te7-layered compounds were characterized as a function of temperature and for samples with various stoichiometric deviations. The Hall coefficient and electrical resistivity were measured from 77 to 800 K, and the Seebeck coefficient was determined in the 90-450 K temperature range, The onset of intrinsic conductivity behavior was observed in these ternary compounds at fairly low temperatures. On the basis of the variation of the electrical conductivity at elevated temperatures, energy gap values of 0.24, 0.20, and 0.22 eV were calculated at 0 K for the Ge3Bi2Te6, GeBi2Te4, and GeBi4Te7 compounds, respectively. To explain the carrier mobility temperature dependence, a mixed carrier scattering mechanism on acoustic phonons and point defects is proposed at low temperatures. It is found that the contribution of scattering by acoustic phonons increases with temperature. The analysis of experimental data for the GeBi4T7 compound in the 150-200 K temperature range demonstrated the need for an additional carrier scattering mechanism, probably connected to the order-disorder phenomena in the cation layers. An anomalous temperature dependence of the Hall coefficient was discovered for the "stoichiometric" GeBi2Te4 compound. It is explained by mixed carrier conduction effects due to fluctuations of the composition and the existence of p- and n-type conductivity domains in the GeBi2Te4 crystal. (C) 1999 Academic Press. C1 Russian Acad Sci, AA Baikov Met Inst, Moscow 117911, Russia. Russian Acad Sci, AF Ioffe Phys Tech Inst, St Petersburg 194021, Russia. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Shelimova, LE (reprint author), Russian Acad Sci, AA Baikov Met Inst, Leninskii Prospect 49, Moscow 117911, Russia. RI Konstantinov, Peter/G-1898-2014 NR 18 TC 15 Z9 15 U1 1 U2 15 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0022-4596 J9 J SOLID STATE CHEM JI J. Solid State Chem. PD SEP PY 1999 VL 146 IS 2 BP 305 EP 312 DI 10.1006/jssc.1999.8340 PG 8 WC Chemistry, Inorganic & Nuclear; Chemistry, Physical SC Chemistry GA 232DE UT WOS:000082349800003 ER PT J AU Wang, FY Karatekin, O Charbonnier, JM AF Wang, FY Karatekin, O Charbonnier, JM TI Low-speed aerodynamics of a planetary entry capsule SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article ID FLOW AB Results of an investigation of the global aerodynamic coefficients and flow characterization around an Apollo-style capsule model at low speed are presented. Flow features were ascertained quantitatively with laser Doppler velocimetry, digital particle image velocimetry, and hot-wire measurements, as well as qualitatively by how visualizations. The study revealed a meandering vortex ring around the capsule, well organized streamwise vortices whose maximum vorticity increased in the recirculating wake before decaying farther downstream, as well as a complex array of flow separation and reattachment features. A number of particularities in the flowfield have been identified as potential candidates for triggering the onset of vehicle instability. Based on these findings, a modeling approach is proposed. C1 Von Karman Inst Fluid Dynam, Aeronaut & Aerosp Dept, B-1640 Rhode St Genese, Belgium. RP Charbonnier, JM (reprint author), NASA, John H Glenn Res Ctr Lewis Field, Turbomachinery & Propuls Syst Div, Cleveland, OH 44135 USA. NR 21 TC 4 Z9 4 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD SEP-OCT PY 1999 VL 36 IS 5 BP 659 EP 667 DI 10.2514/2.3498 PG 9 WC Engineering, Aerospace SC Engineering GA 245VN UT WOS:000083129000006 ER PT J AU Hollis, BR Perkins, JN AF Hollis, BR Perkins, JN TI Transition effects on heating in the wake of a blunt body SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article ID HIGH-ENTHALPY AEROTHERMODYNAMICS; MARS ENTRY VEHICLE; GENERATION AB A series of aerodynamic heating tests was conducted on a 70-deg sphere cone planetary entry vehicle model in a Mach 10 perfect-gas wind tunnel at freestream Reynolds numbers based on model diameter of 8.23 x 10(4) to 3.15 x 10(5). Surface heating distributions were determined from temperature time histories measured on the model and on its support sting using thin-film resistance gauges. The experimental heating data were compared to computations performed using an axisymmetric/two-dimensional, laminar, perfect gas Navier-Stokes solver. On the forebody of the vehicle, as well as on the sting upstream of the free-shear-layer reattachment point, comparisons between the measured and computed heating distributions were within, or slightly greater than, the estimated uncertainty of the experimental data. However, the comparisons diverged after the reattachment point, with the experimental data becoming increasingly greater than the computations with distance downstream from the reattachment point. It was theorized that this disagreement was because of the transition of the wake free shear layer just upstream of the reattachment point on the sting. C1 NASA, Langley Res Ctr, Aerothermodynam Branch, Hampton, VA 23681 USA. N Carolina State Univ, Dept Mech & Aerosp Engn, Raleigh, NC 27695 USA. RP Hollis, BR (reprint author), NASA, Langley Res Ctr, Aerothermodynam Branch, Hampton, VA 23681 USA. NR 28 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 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD SEP-OCT PY 1999 VL 36 IS 5 BP 668 EP 674 DI 10.2514/2.3499 PG 7 WC Engineering, Aerospace SC Engineering GA 245VN UT WOS:000083129000007 ER PT J AU Sridharan, R Beavers, S Gaposchkin, EM Lambour, R Kansky, J Stansbery, E AF Sridharan, R Beavers, S Gaposchkin, EM Lambour, R Kansky, J Stansbery, E TI Radar and optical characterization of an anomalous orbital debris population SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB Analysis of orbital debris data collected by the Haystack radar have shown an anomalously high concentration of debris between the altitudes of 800 and 1000 km. Indications from the Haystack data are that the debris range in size from 8 mm to 2 cm and that they are spherical in shape. Previous work by NASA researchers has shown the likely origin to be the leaking of liquid coolant from the nuclear power sources of a now defunct Soviet space-based series of ocean surveillance satellites. We report on a project at Massachusetts Institute of Technology's Lincoln Laboratory to detect, track, and characterize a small sample of the anomalous debris using ground-based radars and telescopes. Our goal was to provide evidence supporting or refuting the NASA conclusions. We have determined that the size, shape, density, and surface properties of the debris are consistent with the hypothesis that it is liquid, eutectic sodium-potassium coolant like that used in the Soviet satellites. The techniques used to detect and track the debris are discussed. The radar and optical data used to characterize the debris are also presented. C1 MIT, Lincoln Lab, Seuveillance Tech Grp, Lexington, MA 02420 USA. NASA, Lyndon B Johnson Space Ctr, Orbital Debris Program Off, Earth Sci & Solar Syst Explorat Div, Houston, TX 77058 USA. RP Sridharan, R (reprint author), MIT, Lincoln Lab, Seuveillance Tech Grp, 244 Wood St, Lexington, MA 02420 USA. NR 18 TC 7 Z9 8 U1 1 U2 3 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 SEP-OCT PY 1999 VL 36 IS 5 BP 719 EP 725 DI 10.2514/2.3485 PG 7 WC Engineering, Aerospace SC Engineering GA 245VN UT WOS:000083129000015 ER PT J AU Lee, AY AF Lee, AY TI Model-based thruster leakage monitor for the Cassini spacecraft SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB The Cassini spacecraft uses thrusters to perform many spacecraft control functions: to detumble the spacecraft, to maintain three axis attitude control, to perform small trajectory correction burns, to desaturate the reaction wheels, and others. If one of the prime thrusters leaks, e.g., becomes stuck open, the opposing thrusters will he fired extra hard to maintain the commanded spacecraft pointing attitude. Obviously, the resultant draining of hydrazine and the excessive firings of thrusters cannot be allowed to persist indefinitely. A set of three model-based thruster leakage detection monitors has been designed, tested, and implemented in the Right software to protect Cassini against the occurrence of this highly unlikely event. Test results indicated that these monitors can detect thruster leaks of all sizes quickly and robustly. Once the leak is detected, the onboard fault protection logic will activate corrective actions, including the swapping of thruster branches. C1 CALTECH, Jet Prop Lab, Tech Staff, Avion Syst Engn Sect, Pasadena, CA 91109 USA. RP Lee, AY (reprint author), CALTECH, Jet Prop Lab, Tech Staff, Avion Syst Engn Sect, 4800 Oak Grove Dr,Mail Stop 198-235, Pasadena, CA 91109 USA. NR 5 TC 1 Z9 1 U1 0 U2 2 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 SEP-OCT PY 1999 VL 36 IS 5 BP 745 EP 749 DI 10.2514/2.3488 PG 5 WC Engineering, Aerospace SC Engineering GA 245VN UT WOS:000083129000018 ER PT J AU Wang, FY Charbonnier, JM Karatekin, O Paris, S AF Wang, FY Charbonnier, JM Karatekin, O Paris, S TI Utilization of low-speed experiments in transonic capsule stability research SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article C1 Von Karman Inst Fluid Dynam, Aeronaut & Aerosp Dept, B-1640 Rhode St Genese, Belgium. RP Wang, FY (reprint author), NASA, John H Glenn Res Ctr Lewis Field, Turbomachinery & Prop Syst Div, Cleveland, OH 44135 USA. NR 5 TC 2 Z9 2 U1 1 U2 2 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 SEP-OCT PY 1999 VL 36 IS 5 BP 774 EP 776 PG 3 WC Engineering, Aerospace SC Engineering GA 245VN UT WOS:000083129000023 ER PT J AU Gil, CM Lissenden, CJ Lerch, BA AF Gil, CM Lissenden, CJ Lerch, BA TI Yield of inconel 718 by axial-torsional loading at temperatures up to 649 degrees C SO JOURNAL OF TESTING AND EVALUATION LA English DT Article DE Inconel 718; offset yield loci; superalloy ID DEFORMATION-BEHAVIOR; SURFACES; PRESSURE; STEEL AB An experimental program has been implemented to determine small offset yield loci for the nickel-base superalloy Inconel 718 (IN718) under axial-torsional loading at elevated temperatures. Initial and subsequent yield loci were determined for solutioned IN718 at 23 and 454 degrees C and for aged (precipitation-hardened) IN718 at 23 and 649 degrees C. The shape of the initial yield loci fbr solutioned and aged IN718 agrees well with the von Mises prediction. However, in general, the centers of initial yield loci are eccentric to the origin due to a strength-differential (S-D) effect that increases with temperature. Subsequent yield loci exhibit kinematic and distortional hardening, and solutioned IN718 shows a weak cross effect. This work demonstrates that it is possible to determine yield surfaces for metallic materials at temperatures up to at least 649 degrees C using multiple probes of a single specimen. The experimental data are first of their kind for a superalloy at these temperatures and will enable a better understanding of multiaxial material response. C1 Penn State Univ, University Pk, PA 16802 USA. NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. RP Gil, CM (reprint author), Penn State Univ, University Pk, PA 16802 USA. NR 36 TC 13 Z9 13 U1 1 U2 3 PU AMER SOC TESTING MATERIALS PI W CONSHOHOCKEN PA 100 BARR HARBOR DR, W CONSHOHOCKEN, PA 19428-2959 USA SN 0090-3973 J9 J TEST EVAL JI J. Test. Eval. PD SEP PY 1999 VL 27 IS 5 BP 327 EP 336 PG 10 WC Materials Science, Characterization & Testing SC Materials Science GA 287YR UT WOS:000085535500004 ER PT J AU Seale, MD Madaras, EI AF Seale, MD Madaras, EI TI Lamb wave characterization of the effects of long-term thermal-mechanical aging on composite stiffness SO JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA LA English DT Article ID FATIGUE AB Lamb waves offer a promising method of evaluating damage in composite materials. The Lamb wave velocity is directly related to the material parameters, so an effective tool exists to monitor damage in composites by measuring the velocity of these waves. The Lamb Wave Imager(TM) (LWI) uses a pulse/receive technique that excites an antisymmetric Lamb mode and measures the time-of-flight over a wide frequency range. Given the material density and plate thickness, the bending and out-of-plane shear stiffnesses are calculated from a reconstruction of the dispersion curve. In this study, the time-of-flight as well as the elastic stiffnesses D(11), D(22), A(44), and A(55) for composite samples which have undergone combined thermal and mechanical aging are obtained. The samples examined include a baseline specimen with 0 cycles, specimens which have been aged 2350 and 3530 cycles at high strain levels, and one specimen aged 3530 cycles at low strain levels. (C) 1999 Acoustical Society of America. [S0001-4966(99)02309-7]. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Seale, MD (reprint author), NASA, Langley Res Ctr, Mail Stop 231, Hampton, VA 23681 USA. NR 22 TC 16 Z9 16 U1 0 U2 1 PU ACOUSTICAL SOC AMER AMER INST PHYSICS PI MELVILLE PA STE 1 NO 1, 2 HUNTINGTON QUADRANGLE, MELVILLE, NY 11747-4502 USA SN 0001-4966 J9 J ACOUST SOC AM JI J. Acoust. Soc. Am. PD SEP PY 1999 VL 106 IS 3 BP 1346 EP 1352 DI 10.1121/1.427168 PN 1 PG 7 WC Acoustics; Audiology & Speech-Language Pathology SC Acoustics; Audiology & Speech-Language Pathology GA 238EW UT WOS:000082698800017 PM 10489699 ER PT J AU Cassell, AM Franklin, NR Tombler, TW Chan, EM Han, J Dai, HJ AF Cassell, AM Franklin, NR Tombler, TW Chan, EM Han, J Dai, HJ TI Directed growth of free-standingsingle-walled carbon nanotubes SO JOURNAL OF THE AMERICAN CHEMICAL SOCIETY LA English DT Article ID OXIDES C1 Stanford Univ, Dept Chem, Stanford, CA 94350 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Dai, HJ (reprint author), Stanford Univ, Dept Chem, Stanford, CA 94350 USA. NR 15 TC 199 Z9 204 U1 3 U2 46 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0002-7863 J9 J AM CHEM SOC JI J. Am. Chem. Soc. PD SEP 1 PY 1999 VL 121 IS 34 BP 7975 EP 7976 DI 10.1021/ja992083t PG 2 WC Chemistry, Multidisciplinary SC Chemistry GA 234EG UT WOS:000082471100045 ER PT J AU Li, XF Sui, CH Lau, KM Chou, MD AF Li, XF Sui, CH Lau, KM Chou, MD TI Large-scale forcing and cloud-radiation interaction in the tropical deep convective regime SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID TOGA COARE; NUMERICAL EXPERIMENTS; MICROSCALE STRUCTURE; MESOSCALE PROCESSES; DIURNAL-VARIATIONS; FRONTAL RAINBANDS; SOLAR-RADIATION; CLIMATE MODELS; PHASE-III; PARAMETERIZATION AB The simulations of tropical convection and thermodynamic states in response to different imposed large-scale forcing are carried out by using a cloud-resolving model and are evaluated with the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment observation. The model is forced either with imposed large-scale vertical velocity and horizontal temperature and moisture advections (model I) or with imposed total temperature and moisture advections (model 2). The comparison of simulations with observations shows that bias in temperature and moisture simulations by model 1 is smaller than that by model 2. This indicates that the adjustment of the mean thermodynamic stability distribution by vertical advection in model 1 is responsible for better simulations. Model 1 is used to examine effects of different parameterized solar radiative and cloud microphysical processes. A revised parameterization scheme for cloud single scattering properties in solar radiation calculations is found to generate more solar heating in the upper troposphere and less heating in the middle and lower troposphere. The change in the vertical heating distribution is suggested to stabilize the environment and to cause less stratiform cloud that further induces stabilization through cloud-IR interaction. The revised scheme also causes a drier middle and lower troposphere by weakening vertical moisture flux convergence. Also tested is the effect of a revised parameterization scheme for cloud microphysical processes that tends to generate more ice clouds. The cloud-induced thermal effect in which less ice cloud leads to less infrared cooling at cloud top and more heating below cloud top is similar to the effect of no cloud-radiation interaction shown in a sensitivity experiment. However. the exclusion of cloud-radiation interaction causes drying by enhancing condensation, and the reduction of ice clouds by the microphysics scheme induces moistening by suppressing condensation. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Space Applicat Corp, Vienna, VA USA. RP Sui, CH (reprint author), NASA, Goddard Space Flight Ctr, Code 913, Greenbelt, MD 20771 USA. RI Li, Xiaofan/F-5605-2010; Li, Xiaofan/G-2094-2014; Lau, William /E-1510-2012; OI Lau, William /0000-0002-3587-3691; SUI, CHUNG-HSIUNG/0000-0003-2842-5660 NR 37 TC 128 Z9 139 U1 0 U2 9 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 SEP 1 PY 1999 VL 56 IS 17 BP 3028 EP 3042 DI 10.1175/1520-0469(1999)056<3028:LSFACR>2.0.CO;2 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 236UB UT WOS:000082616500004 ER PT J AU Tao, WK Simpson, J Sui, CH Shie, CL Zhou, B Lau, KM Moncrieff, M AF Tao, WK Simpson, J Sui, CH Shie, CL Zhou, B Lau, KM Moncrieff, M TI Equilibrium states simulated by cloud-resolving models SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID RADIATIVE-CONVECTIVE EQUILIBRIUM; CUMULUS ENSEMBLE MODEL; MESOSCALE PROCESSES; SQUALL LINES; TRANSPORT; MOMENTUM; SYSTEMS; WATER; TROPICS AB Recently, several cloud-resolving models (CRMs) were used to study the tropical water and energy cycles and their role in the climate system. They are typically run for several weeks until modeled temperature and water vapor fields reach a quasi-equilibrium state. However, two CRMs produced different quasi-equilibrium states (warm and humid versus cold and dry) even though both used similar initial thermodynamic profiles, horizontal wind, prescribed large-scale vertical velocity, and fixed sea surface temperature. Sensitivity tests were designed to identify the major physical processes that determine the equilibrium states for the different CRM simulations. Differences in the CRM simulated quasi-equilibrium state can be attributed to how the atmospheric horizontal wind was treated throughout the integration. The model that had stronger surface wind produced a warmer and more humid thermodynamic equilibrium state. The physical processes responsible for determining the modeled equilibrium states can be identified by examining the differences in the modeled water vapor, temperature, and moist static energy budget between warm/humid and cold/dry states. One of the major physical processes responsible for the warmer and more humid equilibrium state is larger latent hear fluxes From the ocean (due to stronger surface wind). The moist static energy budget further indicates that the large-scale forcing in water vapor is another major physical process responsible for producing the warmer and more humid thermodynamic equilibrium state. The model results also indicated that the advective forcing in temperature (cooling) and water vapor (moistening) by the imposed large-scale vertical velocity was larger (smaller) for the warm and humid (cold and dry) equilibrium state. This is because the domain mean thermodynamic stare is more unstable and has a stronger vertical gradient of water vapor for those experiments that produced a warmer and more humid climate. Specified minimum wind speed in the bulk aerodynamic formulas and initial soundings on the modeled thermodynamic equilibrium state are also discussed. C1 NASA, Goddard Space Flight Ctr, Mesoscale Atmospher Proc Branch, Atmospheres Lab, Greenbelt, MD 20771 USA. Sci Syst & Applicat Inc, Lanham, MD USA. Univ Space Res Assoc, Columbia, MD USA. Natl Ctr Atmospher Res, Boulder, CO 80307 USA. RP Tao, WK (reprint author), NASA, Goddard Space Flight Ctr, Mesoscale Atmospher Proc Branch, Atmospheres Lab, Code 912, Greenbelt, MD 20771 USA. EM tao@agnes.gsfc.nasa.gov RI Lau, William /E-1510-2012; OI Lau, William /0000-0002-3587-3691; SUI, CHUNG-HSIUNG/0000-0003-2842-5660 NR 34 TC 47 Z9 48 U1 2 U2 3 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0022-4928 EI 1520-0469 J9 J ATMOS SCI JI J. Atmos. Sci. PD SEP 1 PY 1999 VL 56 IS 17 BP 3128 EP 3139 DI 10.1175/1520-0469(1999)056<3128:ESSBCR>2.0.CO;2 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 236UB UT WOS:000082616500010 ER PT J AU Scharton, T Vujcich, M AF Scharton, T Vujcich, M TI Combined loads, vibration, and modal testing on the QuikSCAT spacecraft SO JOURNAL OF THE IEST LA English DT Article DE vibration testing; force; QuikSCAT AB Combining the quasi-static loads, workmanship verification, and model validation tests of aerospace hardware into a single vibration test sequence can reduce schedule and cost considerably. The enabling factor in the implementation of the combined dynamic testing approach is the measurement of the dynamic forces exerted on the test item by the shaker. The dynamic testing of the QuikSCAT spacecraft is discussed as an example of a successful combined loads, workmanship, and model validation test program. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. Ball Aerosp & Technol Corp, Commercial Space Operat Grp, Boulder, CO USA. RP Scharton, T (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91125 USA. NR 2 TC 0 Z9 1 U1 0 U2 2 PU INST ENVIRONMENTAL SCI TECHNOLOGY PI MT PROSPECT PA 940 E NORTHWEST HIGHWAY, MT PROSPECT, IL 60056 USA SN 1052-2883 J9 J IEST JI J. IEST PD SEP-OCT PY 1999 VL 42 IS 5 BP 36 EP 42 PG 7 WC Engineering, Environmental; Environmental Sciences; Instruments & Instrumentation SC Engineering; Environmental Sciences & Ecology; Instruments & Instrumentation GA 245TB UT WOS:000083123300004 ER PT J AU Gil, CM Lissenden, CJ Lerch, BA AF Gil, CM Lissenden, CJ Lerch, BA TI Unusual nonlinear response of some metallic materials SO MECHANICS OF MATERIALS LA English DT Article DE yield surface; plastic flow; tension test; compression test; stiffening; nonlinear elasticity; metal matrix composite; precipitation hardened alloy ID ELASTIC-PLASTIC BEHAVIOR; BORON ALUMINUM COMPOSITE; DOMINATED MODE; YIELD; SURFACES; STEEL AB An anomalous material response has been observed under the action of compressive loads in fibrous silicon carbide/titanium (both Ti-6242 and Ti-15-3 alloys) and the nickel-base alloy Inconel 718 in the aged (precipitation hardened) condition. The observed behavior is an increase, rather than a decrease, in the instantaneous Young's modulus with increasing load and is referred to as stiffening. This increase is small, but can be significant in yield surface tests where an equivalent offset strain on the order of 10 mu epsilon (10 X 10(-6) m/m) is being used. Stiffening has been quantified by calculating offset strains from the linear elastic loading line. The offset strains associated with stiffening during compressive loading are positive and of the same order as the target offset strains in yield surface tests. Stiffening appears to be nonlinear elastic and for SiC/Ti-15-3 decreases as the test temperature increases, suggesting a temperature-dependent mechanism. No stiffening occurred in SiC/Ti-15-3 above approximately 500 degrees C. In addition, the tensile response of aged Inconel 718 exhibits a nonlinear elastic response (not stiffening) prior to the initiation of plastic deformation. The nonlinear elastic response in both tension and compression agrees with a second order stress-strain relation. The higher order terms may be important due to constraint interactions associated with a strengthening second phase such as precipitates or fibers. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 Penn State Univ, Dept Engn Sci & Mech, University Pk, PA 16802 USA. NASA, Lewis Res Ctr, Life Predict Branch, Cleveland, OH 44135 USA. RP Lissenden, CJ (reprint author), Penn State Univ, Dept Engn Sci & Mech, University Pk, PA 16802 USA. NR 21 TC 9 Z9 9 U1 1 U2 7 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0167-6636 J9 MECH MATER JI Mech. Mater. PD SEP PY 1999 VL 31 IS 9 BP 565 EP 577 DI 10.1016/S0167-6636(99)00018-6 PG 13 WC Materials Science, Multidisciplinary; Mechanics SC Materials Science; Mechanics GA 229WR UT WOS:000082219200002 ER PT J AU McCoy, TJ Dickinson, TL Lofgren, GE AF McCoy, TJ Dickinson, TL Lofgren, GE TI Partial melting of the Indarch (EH4) meteorite: A textural, chemical, and phase relations view of melting and melt migration SO METEORITICS & PLANETARY SCIENCE LA English DT Article ID UNEQUILIBRATED ENSTATITE CHONDRITES; AUBRITE PARENT BODY; OLDHAMITE; ORIGIN; ACHONDRITES; EVOLUTION; METAL AB To test whether aubrites can be formed by melting of enstatite chondrites and to understand igneous processes at very low O fugacities, we have conducted partial melting experiments on the Indarch (EH4) chondrite at 1000-1500 C. Silicate melting begins at 1000 C, and Indarch is completely melted by 1500 C. The metal-sulfide component melts completely at 1000 degrees C. Substantial melt migration occurs at 1300-1400 C, and metal migrates out of the silicate charge at 1450 C and similar to 50% silicate partial melting. As a group, our experiments contain three immiscible metallic melts (Si-, P-, and C-rich), two immiscible sulfide melts (Fe- and FeMgMnCa-rich), and silicate melt. Our partial melting experiments on the Indarch (EH4) enstatite chondrite suggest that igneousprocesses at low fO(2) exhibit several unique features. The complete melting of sulfides at 1000 C suggests that aubritic sulfides are not relics. Aubritic oldhamite may have crystallized from Ca and S complexed in the silicate melt. Significant metal-sulfide melt migration might occur at relatively low degrees of silicate partial melting. Substantial elemental exchange occurredbetween different melts (e.g., S between sulfide and silicate, Si between silicate and metal), a feature not observed during experiments at higher fO(2). This exchange may help explain the formation of aubrites from known enstatite chondrites. C1 Smithsonian Inst, Natl Air & Space Museum, Dept Mineral Sci, Washington, DC 20560 USA. Catholic Univ Amer, Dept Phys, Washington, DC 20064 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP McCoy, TJ (reprint author), Smithsonian Inst, Natl Air & Space Museum, Dept Mineral Sci, Washington, DC 20560 USA. NR 39 TC 105 Z9 105 U1 0 U2 9 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 SEP PY 1999 VL 34 IS 5 BP 735 EP 746 PG 12 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 240XG UT WOS:000082851900007 ER PT J AU Dzegilenko, FN Srivastava, D Saini, S AF Dzegilenko, FN Srivastava, D Saini, S TI Nanoscale etching and indentation of a silicon(001) surface with carbon nanotube tips SO NANOTECHNOLOGY LA English DT Article; Proceedings Paper CT 6th Foresight Conference CY NOV 12-15, 1998 CL SANTA CLARA, CALIFORNIA ID SCANNING-TUNNELING-MICROSCOPY; MOLECULAR-DYNAMICS SIMULATIONS; INDIVIDUAL MOLECULES; ATOMIC-SCALE; NANOSTRUCTURES; MANIPULATION; MECHANISMS; ADHESION; FRACTURE; DIAMOND AB The possibility of nanoscale etching and indentation of a Si(001)(2 x 1) surface by (8, 0) and(10, 10) carbon nanotube tips is demonstrated, for the first time, by classical molecular dynamics simulations employing Tersoff's many-body potential for a mixed C/Si/Ge system. In the scenario with the nanotube tip barely touching the surface atomistic etching is observed, whereas in the nanoindentation scenario, the nanotube tip penetrates the surface without much hindrance. The results are explained in terms of the relative strength of the C-C, C-Si, and Si-Si bonds. C1 NASA, Ames Res Ctr, IT Modeling & Simulat Grp, NAS, Moffett Field, CA 94035 USA. RP Dzegilenko, FN (reprint author), NASA, Ames Res Ctr, IT Modeling & Simulat Grp, NAS, Mail Stop T27-A1, Moffett Field, CA 94035 USA. NR 33 TC 16 Z9 18 U1 1 U2 5 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0957-4484 J9 NANOTECHNOLOGY JI Nanotechnology PD SEP PY 1999 VL 10 IS 3 BP 253 EP 257 DI 10.1088/0957-4484/10/3/305 PG 5 WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Physics, Applied SC Science & Technology - Other Topics; Materials Science; Physics GA 236RW UT WOS:000082613200006 ER PT J AU Cagin, T Che, JW Gardos, MN Fijany, A Goddard, WA AF Cagin, T Che, JW Gardos, MN Fijany, A Goddard, WA TI Simulation and experiments on friction and wear of diamond: a material for MEMS and NEMS application SO NANOTECHNOLOGY LA English DT Article; Proceedings Paper CT 6th Foresight Conference CY NOV 12-15, 1998 CL SANTA CLARA, CALIFORNIA ID FILMS; CHIP AB To date most of the microelectromechanical system (MEMS) devices have been based on silicon. This is due to the technological know-how accumulated on the manipulation, machining and manufacturing of silicon. However, only very few devices involve moving parts. This is because of the rapid wear arising from high friction in these silicon-based systems. Recent tribometric experiments carried out by Gardos on silicon and polycrystalline diamond (PCD) show that this rapid wear is caused by a variety of factors, related both to surface chemistry and cohesive energy density of these likely MEMS bearing materials. In particular, the 1.8-times stronger C-C bond in diamond as opposed to the Si-Si bond in the bulk translates into a more than 10(4)-times difference in wear rates, even though the difference in flexural strength is only 20-times, in hardness 10-times and in fracture toughness 5-times. It also has been shown that the wear rates of silicon and PCD are controlled by high-friction-induced surface cracking, and the friction is controlled by the number of dangling, reconstructed or adsorbate-passivated surface bonds. Therefore, theoretical and tribological characterization of Si and PCD surfaces is essential prior to device fabrication to assure reliable MEMS operation under various atmospheric environments, especially at elevated temperatures. As a part of the rational design and manufacturing of MEMS devices containing moving mechanical assemblies (MEMS-MMA) and especially nanoelectromechanical devices (NEMS), theory and simulation can play an important role. Predicting system properties such as friction and wear, and materials properties such as thermal conductivity is of critical importance for materials and components to be used in MEMS-MMAs. In this paper, we present theoretical studies of friction and wear processes on diamond surfaces using a steady state molecular dynamics method. We studied the atomic friction of the diamond-(100) surface using an extended bond-order-dependent potential for hydrocarbon systems. Unlike traditional empirical potentials, bond order potentials can simulate bond breaking and formation processes. Therefore, it is a natural choice to study surface dynamics under friction and wear. In order to calculate the material properties correctly, we have established a consistent approach to incorporate non-bond interactions into the bond order potentials. We have also developed an easy-to-use software to evaluate the atomic-level friction coefficient for an arbitrary system, and interfaced it into a third-party graphical software. C1 CALTECH, Mat & Proc Simulat Ctr, Pasadena, CA 91125 USA. Raytheon Co, Commun Syst, El Segundo, CA 90245 USA. NASA, Jet Prop Lab, Pasadena, CA 91101 USA. RP Cagin, T (reprint author), CALTECH, Mat & Proc Simulat Ctr, 139-74, Pasadena, CA 91125 USA. NR 21 TC 39 Z9 39 U1 1 U2 14 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0957-4484 J9 NANOTECHNOLOGY JI Nanotechnology PD SEP PY 1999 VL 10 IS 3 BP 278 EP 284 PG 7 WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Physics, Applied SC Science & Technology - Other Topics; Materials Science; Physics GA 236RW UT WOS:000082613200011 ER PT J AU Globus, A Lawton, J Wipke, T AF Globus, A Lawton, J Wipke, T TI Automatic molecular design using evolutionary techniques SO NANOTECHNOLOGY LA English DT Article; Proceedings Paper CT 6th Foresight Conference CY NOV 12-15, 1998 CL SANTA CLARA, CALIFORNIA AB Molecular nanotechnology is the precise, three-dimensional control of materials and devices at the atomic scale. An important part of nanotechnology is the design of molecules for specific purposes. This paper describes early results using genetic software techniques to automatically design molecules under the control of a fitness function. The fitness function must be capable of determining which of two arbitrary molecules is better for a specific task. The software begins by generating a population of random molecules. The individual molecules in a population are then evolved towards greater fitness by randomly combining parts of the better existing molecules to create new molecules. These new molecules then replace some of the less fit molecules in the population. We apply a unique genetic crossover operator to molecules represented by graphs, i.e., sets of atoms and the bonds that connect them. We present evidence suggesting that crossover alone, operating on graphs, can evolve any possible molecule given an appropriate fitness function and a population containing both rings and chains. Most prior work evolved strings or trees that were subsequently processed to generate molecular graphs. In principle, genetic graph software should he able to evolve other graph-representable systems such as circuits, transportation networks, metabolic pathways, and computer networks. C1 NASA, Ames Res Ctr, MRJ Technol Solut Inc, Moffett Field, CA 94035 USA. Univ Calif Santa Cruz, Dept Chem, Santa Cruz, CA 95010 USA. RP Globus, A (reprint author), NASA, Ames Res Ctr, MRJ Technol Solut Inc, Moffett Field, CA 94035 USA. NR 21 TC 45 Z9 46 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0957-4484 J9 NANOTECHNOLOGY JI Nanotechnology PD SEP PY 1999 VL 10 IS 3 BP 290 EP 299 DI 10.1088/0957-4484/10/3/312 PG 10 WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Physics, Applied SC Science & Technology - Other Topics; Materials Science; Physics GA 236RW UT WOS:000082613200013 ER PT J AU Buti, B AF Buti, B TI Chaos in magnetoplasmas SO NONLINEAR PROCESSES IN GEOPHYSICS LA English DT Article ID NONLINEAR ALFVEN WAVES; COMET GIACOBINI-ZINNER; LOWER-HYBRID WAVES; SOLAR-WIND; STOCHASTIC ACCELERATION; INHOMOGENEOUS PLASMAS; BETA PLASMA; TURBULENCE; FLUCTUATIONS; SOLITONS AB A nonlinear wave, in general, is equivalent to a nonlinear dynamical system, which exhibits the phenomena of chaos. By means of techniques of nonlinear dynamical systems, we have investigated the conditions under which nonlinear Alfven waves and lower-hybrid waves can become chaotic. The role of heavy ions, in controlling the chaos in magnetoplasmas, is examined. Chaotic routes to Alfvenic turbulence, with k(-1) spectra, are observed in case of externally driven nonlinear Alfven waves. Anomalous heating and particle acceleration resulting from chaotic fields, generated by lower-hybrid waves, are briefly outlined. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Buti, B (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 61 TC 5 Z9 5 U1 0 U2 6 PU COPERNICUS GESELLSCHAFT MBH PI GOTTINGEN PA BAHNHOFSALLEE 1E, GOTTINGEN, 37081, GERMANY SN 1023-5809 J9 NONLINEAR PROC GEOPH JI Nonlinear Process Geophys. PD SEP-DEC PY 1999 VL 6 IS 3-4 BP 129 EP 143 PG 15 WC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences SC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences GA 306FR UT WOS:000086587100002 ER PT J AU Tsurutani, BT Lakhina, GS Smith, EJ Buti, B Moses, SL Coroniti, FV Brinca, AL Slavin, JA Zwickl, RD AF Tsurutani, BT Lakhina, GS Smith, EJ Buti, B Moses, SL Coroniti, FV Brinca, AL Slavin, JA Zwickl, RD TI Mirror mode structures and ELF plasma waves in the Giacobini-Zinner magnetosheath SO NONLINEAR PROCESSES IN GEOPHYSICS LA English DT Article ID LOWER-HYBRID WAVES; SOLAR-WIND PLASMA; LION ROARS; STOCHASTIC ACCELERATION; EARTHS MAGNETOSHEATH; MAGNETIC-FIELD; INSTABILITY; MECHANISM; ULYSSES; MAGNETOSPHERE AB We show evidence for mirror mode structures at comet Giacobini-Zinner. These are plasma structures with alternating high beta and low beta regions driven unstable when beta(perpendicular to)/beta(parallel to) > 1+1/beta(perpendicular to). These structures are detected in a region just adjacent to the magnetic tail and have scale sizes of similar to 12 H2O group ion cyclotron radii. Calculations are presented to show that mirror mode instability can occur due to the perpendicular pressure associated with H2O+ cometary pickup ions in the region of minor mode observation. Adjacent regions tin the magnetic tail and further in the sheath) are found to be stable to the mirror mode. Plasma waves are detected in relation with the mirror mode structures. Low frequency 56 to 100 Hz waves are present in the high beta portions, and high frequency, 311 Hz to 10 kHz, waves are present in low beta regions. These may be electromagnetic lion roar waves and electrostatic festoon-shaped waves, respectively, in analogy to plasma waves detected in the Earth's magnetosheath. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91103 USA. Indian Inst Geomagnetism, Bombay 400005, Maharashtra, India. TRW Syst, Redondo Beach, CA USA. Univ Tecn Lisboa, Inst Super Tecn, Ctr Fis Plasmas, Lisbon, Portugal. Goddard Space Flight Ctr, Greenbelt, MD USA. NOAA, Space Environm Lab, Boulder, CO 80303 USA. RP Tsurutani, BT (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91103 USA. RI Lakhina, Gurbax /C-9295-2012; Slavin, James/H-3170-2012; OI Slavin, James/0000-0002-9206-724X; Lakhina, Gurbax /0000-0002-8956-486X NR 44 TC 21 Z9 21 U1 0 U2 0 PU COPERNICUS GESELLSCHAFT MBH PI GOTTINGEN PA BAHNHOFSALLEE 1E, GOTTINGEN, 37081, GERMANY SN 1023-5809 J9 NONLINEAR PROC GEOPH JI Nonlinear Process Geophys. PD SEP-DEC PY 1999 VL 6 IS 3-4 BP 229 EP 234 PG 6 WC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences SC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences GA 306FR UT WOS:000086587100012 ER PT J AU Tsurutani, BT Lakhina, GS Winterhalter, D Arballo, JK Galvan, C Sakurai, R AF Tsurutani, BT Lakhina, GS Winterhalter, D Arballo, JK Galvan, C Sakurai, R TI Energetic particle cross-field diffusion: Interaction with Magnetic Decreases (MDs) SO NONLINEAR PROCESSES IN GEOPHYSICS LA English DT Article ID MIRROR-MODE STRUCTURES; SOLAR-WIND; ALFVEN WAVES; INTERPLANETARY DISCONTINUITIES; ULYSSES OBSERVATIONS; HOLES; SOUTH AB Magnetic field Decreases (MDs) are detected in the heliospheric polar regions. The MDs have minimum spatial scales sizes of 25 proton thermal gyroradii, and are typically bounded by tangential or rotational discontinuities. The distribution of the magnitudes of the decreases within MDs is a continuum, with the smallest decreases being most frequent in occurrence. The largest decreases can be similar to 80% of the ambient field. The thickness distribution is also a continuum, and is shown to be independent of the field magnitude decrease. Charged particle interactions with the MDs lead to particle guiding center displacements and hence particle cross-field diffusion. We develop a diffusion model to apply to energetic ion interactions with MDs using the MD properties described in this paper. One specific day of data is used to illustrate that the particle cross-field diffusion will be extremely rapid due to such interactions. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Indian Inst Geomagnetism, Bombay 400005, Maharashtra, India. RP CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Lakhina, Gurbax /C-9295-2012; OI Lakhina, Gurbax /0000-0002-8956-486X NR 23 TC 29 Z9 31 U1 0 U2 1 PU COPERNICUS GESELLSCHAFT MBH PI GOTTINGEN PA BAHNHOFSALLEE 1E, GOTTINGEN, 37081, GERMANY SN 1023-5809 J9 NONLINEAR PROC GEOPH JI Nonlinear Process Geophys. PD SEP-DEC PY 1999 VL 6 IS 3-4 BP 235 EP 242 PG 8 WC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences SC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences GA 306FR UT WOS:000086587100013 ER PT J AU Tripathi, RK Cucinotta, FA Wilson, JW AF Tripathi, RK Cucinotta, FA Wilson, JW TI Accurate universal parameterization of absorption cross sections III - light systems SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS LA English DT Article ID NUCLEI; PROTONS; HELIUM AB Our prior nuclear absorption cross sections model [R.K. Tripathi, F.A. Cucinotta, J.W. Wilson, Nucl. Instr. and Meth. B 117 (1996) 347; R.K. Tripathi, J.W. Wilson, F.A. Cucinotta, Nucl. Instr. and Meth. B 129 (1997) 11] is extended for light systems (A less than or equal to 4) where either both projectile and target are light particles or one is light particle and the other is medium or heavy nucleus. The agreement with experiment is excellent for these cases as well. Present work in combination with our original model provides a comprehensive picture of absorption cross sections for light, medium and heavy systems. As a result the extended model can reliably be used in all studies where there is a need for absorption cross sections. (C) 1999 Published by Elsevier Science B.V. All rights reserved. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Natl Res Council, Washington, DC 20418 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Tripathi, RK (reprint author), NASA, Langley Res Ctr, Mail Stop 188B, Hampton, VA 23681 USA. NR 18 TC 63 Z9 63 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-583X J9 NUCL INSTRUM METH B JI Nucl. Instrum. Methods Phys. Res. Sect. B-Beam Interact. Mater. Atoms PD SEP PY 1999 VL 155 IS 4 BP 349 EP 356 DI 10.1016/S0168-583X(99)00479-6 PG 8 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Atomic, Molecular & Chemical; Physics, Nuclear SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 233VX UT WOS:000082448800002 PM 11542770 ER PT J AU Orlin, PA Perkins, AL AF Orlin, PA Perkins, AL TI A frequency accurate r(th) order spatial derivative finite difference approximation SO NUMERICAL METHODS FOR PARTIAL DIFFERENTIAL EQUATIONS LA English DT Article DE frequency accurate methods; finite difference approximations ID SCHEMES; FLOW AB A method for the specification and design of finite difference spatial derivative approximations of general order r is presented. The method uses a difference polynomial with undetermined coefficients. Spatial frequency domain-based criteria, which include phase velocity, group velocity, and dissipation requirements at a priori selected spatial frequencies, are used to find the appropriate coefficient values. The method is formulated as an optimal design problem but is pursued heuristically. The general derivative approximation and the design method are suitable for use in more general design problems involving finite difference schemes for linear and nonlinear partial differential equations. (C) 1999 John Wiley & Sons, Inc. C1 USN, Oceanog Off, Stennis Space Ctr, MS 39522 USA. Univ So Mississippi, Stennis Space Ctr, MS 39529 USA. RP Orlin, PA (reprint author), USN, Oceanog Off, Stennis Space Ctr, MS39522,506 Jeff Davis Ave, Waveland, MS 39576 USA. NR 13 TC 0 Z9 0 U1 0 U2 1 PU JOHN WILEY & SONS INC PI NEW YORK PA 605 THIRD AVE, NEW YORK, NY 10158-0012 USA SN 0749-159X J9 NUMER METH PART D E JI Numer. Meth. Part Differ. Equ. PD SEP PY 1999 VL 15 IS 5 BP 569 EP 580 DI 10.1002/(SICI)1098-2426(199909)15:5<569::AID-NUM4>3.0.CO;2-3 PG 12 WC Mathematics, Applied SC Mathematics GA 229HT UT WOS:000082188900004 ER PT J AU DeFries, RS Los, SO AF DeFries, RS Los, SO TI Implications of land-cover misclassification for parameter estimates in global land-surface models: An example from the simple biosphere model (SiB2) SO PHOTOGRAMMETRIC ENGINEERING AND REMOTE SENSING LA English DT Article ID TERRESTRIAL BIOPHYSICAL PARAMETERS; CLASSIFICATIONS; GENERATION; SATELLITE; FIELDS; NDVI AB One of the primary applications of the global 1-km land-cover DISCover product is to derive biophysical and ecological parameters for a range of land-surface models, including biosphere-atmosphere, biogeochemical, and ecological models. The validation effort reported in this special issue enables a realistic assessment of the implications of misclassification errors for parameter estimates within the models. In most land-surface models, cover types are aggregated to coarser groupings than the 17 IGBP classes for estimating parameters, with aggregation schemes varying with individual models and individual parameters within each model. Misclassification errors are consequential only when they occur between cover types that are not aggregated by the model. We use examples of two biophysical parameters-leaf area index and surface roughness-as estimated for use in the Simple Biosphere Model (SiB2) and other modeling applications to quantify the effects of misclassification on parameter estimates. SiB2 relies on satellite data as well as land-cover information for estimating the biophysical parameters. Consequences of misclassification are likely to be greater for those models that do not use satellite data. Mean class accuracy based on those sites for which a majority of interpreters agreed (percentage of validation pixels classified correctly out of total number of validation pixels, averaged over all classes), adjusted by area of each cover type in the IGBP DISCover product, is 78.6 when all misclassification errors are included. By excluding misclassification errors when they are inconsequential for leaf area index and surface roughness length estimates, mean class accuracies are 90.2 and 87.8, respectively. The results illustrate that misclassification errors ore most meaningfully viewed in the context of the application of the land-cover information. C1 Univ Maryland, Dept Geog, Lab Global Remote Sensing Studies, College Pk, MD 20742 USA. Sci Syst & Applicat Inc, Biospher Sci Branch, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP DeFries, RS (reprint author), Univ Maryland, Dept Geog, Lab Global Remote Sensing Studies, College Pk, MD 20742 USA. RI Los, Sietse/G-8985-2012; OI Los, Sietse/0000-0002-1325-3555 NR 22 TC 45 Z9 46 U1 0 U2 6 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 SEP PY 1999 VL 65 IS 9 BP 1083 EP 1088 PG 6 WC Geography, Physical; Geosciences, Multidisciplinary; Remote Sensing; Imaging Science & Photographic Technology SC Physical Geography; Geology; Remote Sensing; Imaging Science & Photographic Technology GA 234LP UT WOS:000082486400013 ER PT J AU Sornborger, AT Stewart, ED AF Sornborger, AT Stewart, ED TI Higher-order methods for simulations on quantum computers SO PHYSICAL REVIEW A LA English DT Article ID MANY-BODY THEORIES; MECHANICS; PHYSICS; SYSTEMS AB To implement many-qubit gates for use in quantum simulations on quantum computers efficiently, we develop and present methods reexpressing exp[-i(H-1+H-2+...)Delta t] as a product of factors exp[-iH(1)Delta t], exp[-iH(2)Delta t],..., which is accurate to third or fourth order in Delta t. The methods we derive are an extended form of the symplectic method, and can also be used for an integration of classical Hamiltonians on classical computers. We derive both integral and irrational methods, and find the most efficient methods in both cases. [S1050-2947(99)07209-1]. C1 Fermi Natl Accelerator Lab, Fermilab Astrophys Grp, NASA, Batavia, IL 60510 USA. RP Sornborger, AT (reprint author), Fermi Natl Accelerator Lab, Fermilab Astrophys Grp, NASA, Box 500, Batavia, IL 60510 USA. RI Stewart, Ewan/C-1565-2011 NR 20 TC 36 Z9 36 U1 0 U2 0 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 1050-2947 J9 PHYS REV A JI Phys. Rev. A PD SEP PY 1999 VL 60 IS 3 BP 1956 EP 1965 DI 10.1103/PhysRevA.60.1956 PG 10 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA 235YF UT WOS:000082570900033 ER PT J AU Bellotti, R Cafagna, F Circella, M De Marzo, CN Golden, RL Stochaj, SJ De Pascale, MP Morselli, A Picozza, P Stephens, SA Hof, M Menn, W Simon, M Mitchell, JW Ormes, JF Streitmatter, RE Finetti, N Grimani, C Papini, P Piccardi, S Spillantini, P Basini, G Ricci, M AF Bellotti, R Cafagna, F Circella, M De Marzo, CN Golden, RL Stochaj, SJ De Pascale, MP Morselli, A Picozza, P Stephens, SA Hof, M Menn, W Simon, M Mitchell, JW Ormes, JF Streitmatter, RE Finetti, N Grimani, C Papini, P Piccardi, S Spillantini, P Basini, G Ricci, M TI Balloon measurements of cosmic ray muon spectra in the atmosphere along with those of primary protons and helium nuclei over midlatitude SO PHYSICAL REVIEW D LA English DT Article ID NEUTRINO FLUX; CHARGE RATIO; SEA-LEVEL; ELECTRONS; SPECTROMETER; PERFORMANCE; KAMIOKANDE; POSITRONS; ENERGIES AB We report here the measurements of the energy spectra of atmospheric muons and of the parent cosmic ray primary proton and helium nuclei in a single experiment. These were carried out using the MASS superconducting spectrometer in a balloon flight experiment in 1991. The relevance of these results to the atmospheric neutrino anomaly is emphasized. In particular, this approach allows uncertainties caused by the level of solar modulation, the geomagnetic cut-off of the primaries and possible experimental systematics, to be decoupled in the comparison of calculated fluxes of muons to measured muon fluxes. The muon observations cover the momentum and depth ranges of 0.3-40 GeV/c and 5-886 g/cm(2), respectively. A comparison of these results with those obtained in a previous experiment by the same collaboration using a similar apparatus allows us to search for differences due to the different experimental conditions at low energy and to check for the overall normalization between the two measurements. The proton and helium primary measurements cover the rigidity range from 3 to 100 GV, in which both the solar modulation and the geomagnetic cut-off affect the energy spectra at low energies. From the observed low-energy helium spectrum, the geomagnetic transmission function at mid-latitude has been determined. [S0556-2821(99)07513-X]. C1 Univ Bari, Dipartimento Fis, I-70126 Bari, Italy. Ist Nazl Fis Nucl, Sez Bari, I-70126 Bari, Italy. New Mexico State Univ, Particle Astrophys Lab, Las Cruces, NM 88003 USA. Univ Roma Tor Vergata, Dipartimento Fis, I-00173 Rome, Italy. Ist Nazl Fis Nucl, Sez Roma 2, I-00173 Rome, Italy. Tata Inst Fundamental Res, Bombay 400005, Maharashtra, India. Univ Gesamthsch Siegen, D-57068 Siegen, Germany. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. 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 Urbino, Dipartimento Fis, I-61029 Urbino, Italy. RP Bellotti, R (reprint author), Univ Bari, Dipartimento Fis, Via Amendola 173, I-70126 Bari, Italy. EM marco.circella@ba.infn.it; paolo.papini@fi.infn.it RI Morselli, Aldo/G-6769-2011; Cafagna, Francesco/A-9299-2010 OI Morselli, Aldo/0000-0002-7704-9553; Cafagna, Francesco/0000-0002-7450-4784 NR 56 TC 73 Z9 74 U1 0 U2 3 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0556-2821 J9 PHYS REV D JI Phys. Rev. D PD SEP 1 PY 1999 VL 60 IS 5 AR 052002 DI 10.1103/PhysRevD.60.052002 PG 15 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA 234DX UT WOS:000082470200006 ER PT J AU Thacker, WD Gatski, TB Grosch, CE AF Thacker, WD Gatski, TB Grosch, CE TI Analyzing mean transport equations of turbulence and linear disturbances in decaying flows SO PHYSICS OF FLUIDS LA English DT Article ID WALL AB The decay of laminar disturbances and turbulence in mean shear-free flows is studied. In laminar flows, such disturbances are linear superpositions of modes governed by the Orr-Sommerfeld equation. In turbulent flows, disturbances are described through transport equations for representative mean quantities. The link between a description based on a deterministic evolution equation and a probability-based mean transport equation is established. Because an uncertainty in initial conditions exists in the laminar as well as the turbulent regime, a probability distribution must be defined even in the laminar case. Using this probability distribution, it is shown that the exponential decay of the linear modes in the laminar regime can be related to a power law decay of both the (ensemble) mean disturbance kinetic energy and the dissipation rate. The evolution of these mean disturbance quantities is then described by transport equations similar to those for the corresponding turbulent decaying flow. (C) 1999 American Institute of Physics. [S1070-6631(99)00609-1]. C1 St Louis Univ, Dept Phys, Parks Coll, St Louis, MO 63156 USA. NASA, Langley Res Ctr, Aerodynam & Acoust Methods Branch, Hampton, VA 23681 USA. Old Dominion Univ, Dept Oceanog, Norfolk, VA 23529 USA. Old Dominion Univ, Dept Comp Sci, Norfolk, VA 23529 USA. RP Thacker, WD (reprint author), St Louis Univ, Dept Phys, Parks Coll, St Louis, MO 63156 USA. NR 14 TC 4 Z9 4 U1 0 U2 1 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 1070-6631 J9 PHYS FLUIDS JI Phys. Fluids PD SEP PY 1999 VL 11 IS 9 BP 2626 EP 2631 DI 10.1063/1.870124 PG 6 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 224NW UT WOS:000081906000019 ER PT J AU Adumitroaie, V Ristorcelli, JR Taulbee, DB AF Adumitroaie, V Ristorcelli, JR Taulbee, DB TI Progress in Favre-Reynolds stress closures for compressible flows SO PHYSICS OF FLUIDS LA English DT Article ID TURBULENT SHEAR-FLOW; RAPID-DISTORTION-THEORY; CONSTITUTIVE RELATION; MIXING LAYERS; MODEL; CONSISTENT; EXPLICIT; GROWTH AB A closure for the compressible portion of the pressure-strain covariance is developed. It is shown that, within the context of a pressure-strain closure assumption linear in the Reynolds stresses, an expression for the pressure-dilatation can be used to construct a representation for the pressure-strain. Additional closures for the unclosed terms in the Favre-Reynolds stress equations involving the mean acceleration are also constructed. The closures accommodate compressibility corrections depending on the magnitude of the turbulent Mach number, the mean density gradient, the mean pressure gradient, the mean dilatation, and, of course, the mean velocity gradients. The effects of the compressibility corrections on the Favre-Reynolds stresses are consistent with current DNS results. Using the compressible pressure-strain and mean acceleration closures in the Favre-Reynolds stress equations an algebraic closure for the Favre-Reynolds stresses is constructed. Noteworthy is the fact that, in the absence of mean velocity gradients, the mean density gradient produces Favre-Reynolds stresses in accelerating mean flows. Computations of the mixing layer using the compressible closures developed are described. Favre-Reynolds stress closure and two-equation algebraic models are compared to laboratory data for the mixing layer. Experimental data from diverse laboratories for the Favre-Reynolds stresses appears inconsistent and, as a consequence, comparison of the Reynolds stress predictions to the data is not conclusive. Reductions of the kinetic energy and the spread rate are consistent with the sizable decreases seen in these classes of flows. (C) 1999 American Institute of Physics. [S1070-6631(99)00809-0]. C1 SUNY Buffalo, Dept Mech & Aerosp Engn, Buffalo, NY 14260 USA. NASA, Langley Res Ctr, Inst Comp Applicat Sci & Engn, Hampton, VA 23681 USA. RP CFD Res Corp, 215 Wynn Dr, Huntsville, AL 35805 USA. EM va@cfdrc.com; jrrj@lanl.gov NR 65 TC 22 Z9 22 U1 0 U2 4 PU AMER INST PHYSICS PI MELVILLE PA 1305 WALT WHITMAN RD, STE 300, MELVILLE, NY 11747-4501 USA SN 1070-6631 EI 1089-7666 J9 PHYS FLUIDS JI Phys. Fluids PD SEP PY 1999 VL 11 IS 9 BP 2696 EP 2719 DI 10.1063/1.870130 PG 24 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 224NW UT WOS:000081906000025 ER PT J AU Myong, RS AF Myong, RS TI Thermodynamically consistent hydrodynamic computational models for high-Knudsen-number gas flows SO PHYSICS OF FLUIDS LA English DT Article ID CYLINDRICAL COUETTE-FLOW; LENNARD-JONES FLUIDS; GENERALIZED HYDRODYNAMICS; MOMENT CLOSURE; MONTE-CARLO; SIMULATION; EQUATIONS; SYSTEMS AB In high-Knudsen-number flows nonequilibrium effects become dominant and the use of Navier-Stokes-Fourier equations becomes questionable since they are based on small deviation from local thermodynamic equilibrium. In this paper new hydrodynamic computational models are proposed for modeling gases in the transition regime. They are based on Eu's generalized hydrodynamic equations and it turns out that they apply in all Mach numbers and satisfy the second law of thermodynamics to every order of approximation. In order to learn more about the new equations a model equation similar to the Burgers' equation is studied. From this analysis new insight into constitutive relations of various hydrodynamic equations has been gained. In addition, a convergent iterative method for solving the highly nonlinear constitutive equations is developed. Finally, the shock structure and slip flow problems are computed by using high resolution numerical schemes and issues of extending the one-dimensional solver to multidimensional problems are discussed. (C) 1999 American Institute of Physics. [S1070-6631(99)02909-8]. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Myong, RS (reprint author), Gyeongsang Natl Univ, Div Aerosp & Mech Engn, Gyeongnam 660701, South Korea. NR 39 TC 40 Z9 42 U1 0 U2 3 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 1070-6631 J9 PHYS FLUIDS JI Phys. Fluids PD SEP PY 1999 VL 11 IS 9 BP 2788 EP 2802 DI 10.1063/1.870137 PG 15 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 224NW UT WOS:000081906000032 ER PT J AU Cao, CD Wang, N Wei, BB de Groh, HC AF Cao, CD Wang, N Wei, BB de Groh, HC TI Rapid solidification of Ag-Si eutectic alloys in drop tube SO PROGRESS IN NATURAL SCIENCE LA English DT Article DE rapid solidification; Ag-Si; irregular eutectic growth; drop tube ID IRREGULAR EUTECTICS; GROWTH VELOCITY AB Rapid solidification has been investigated on Ag-2.5 % Si hypoeutectic, Ag-3.1 % Si eutectic, and Ag-5 % Si (weight percentage) hypereutectic alloys in a 3-m drop tube. The irregular eutectic microstructures vary with droplet size and composition. Grain refinement has occurred to primary Ag dendrites, and to primary and eutectic Si with the decrease of droplet diameter. The interphase spacing was measured experimentally and calculated theoretically based on the modified Jackson-Hunt and Trivedi-Magnin-Kurz eutectic growth models. The growth velocity was also predicted by these two models. The operating range parameter phi has been obtained approximately to be 2.614. It is presumed that Marangoni convection may be responsible for the central distribution of primary Si blocks in the hypereutectic alloy. Appearance of primary Ag phase in the eutectic alloy and a novel microstructure characterized by primary Ag grains with a few Si blocks distributing in the fine globular eutectic matrix in small droplets of Ag-5 % Si hypereutectic alloy is interpreted by the skewed-coupled zone. C1 Northwestern Polytech Univ, Dept Appl Phys, Lab Mat Sci Space, Xian 710072, Peoples R China. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Cao, CD (reprint author), Northwestern Polytech Univ, Dept Appl Phys, Lab Mat Sci Space, Xian 710072, Peoples R China. NR 14 TC 3 Z9 3 U1 1 U2 4 PU TAYLOR & FRANCIS LTD PI LONDON PA ONE GUNPOWDER SQUARE, LONDON EC4A 3DE, ENGLAND SN 1002-0071 J9 PROG NAT SCI JI Prog. Nat. Sci. PD SEP PY 1999 VL 9 IS 9 BP 687 EP 695 PG 9 WC Materials Science, Multidisciplinary; Multidisciplinary Sciences SC Materials Science; Science & Technology - Other Topics GA 235CX UT WOS:000082523300007 ER PT J AU Chipot, C Maigret, B Pohorille, A AF Chipot, C Maigret, B Pohorille, A TI Early events in the folding of an amphipathic peptide: A multinanosecond molecular dynamics study SO PROTEINS-STRUCTURE FUNCTION AND BIOINFORMATICS LA English DT Review DE molecular dynamics simulations; amphipathic peptides; aqueous interfaces; peptide folding; free energy calculations ID ALANINE-BASED PEPTIDES; HYDROPHOBIC TRANSMEMBRANE SEGMENTS; MAGNETIC-RESONANCE SPECTROSCOPY; 4-HELIX BUNDLE PROTEINS; WATER-HEXANE INTERFACE; PORE-FORMING STRUCTURE; ION-CHANNEL FORMATION; ALPHA-HELIX; LIPID BILAYERS; SECONDARY STRUCTURE AB Folding of the capped LQQLLQQLLQL peptide is investigated at the water-hexane interface by molecular dynamics simulations for 161.5 ns. Initially placed in the aqueous phase as a beta-strand, the peptide rapidly adsorbs to the interface, where it adopts an amphipathic conformation. The marginal presence of nonamphipathic structures throughout the complete trajectory indicates that the corresponding conformations are strongly disfavored at the interface. It is further suggestive that folding in an interfacial environment proceeds through a pathway of successive amphipathic intermediates. The energetic and entropic penalties involved in the conformational changes along this pathway markedly increase the folding time scales of LQQLLQQLLQL, explaining why the alpha-helix, the hypothesized lowest free energy structure for a sequence with a hydrophobic periodicity of 3.6, has not been reached yet. The formation of a type I beta-turn at the end of the simulation confirms the importance of such motifs as initiation sites allowing the peptide to coalesce towards a secondary structure. Proteins 1999;36:383-399. (C) 1999 Wiley-Liss, Inc. C1 Univ Nancy 1, Chim Theor Lab, CNRS, UMR 7565, F-54506 Vandoeuvre Les Nancy, France. NASA, Exobiol Branch, Ames Res Ctr, Moffett Field, CA USA. Univ Calif San Francisco, Dept Pharmaceut Chem, San Francisco, CA 94143 USA. RP Univ Nancy 1, Chim Theor Lab, CNRS, UMR 7565, BP 239, F-54506 Vandoeuvre Les Nancy, France. EM chipot@lctn.u-nancy.fr NR 117 TC 26 Z9 26 U1 0 U2 6 PU WILEY-BLACKWELL PI HOBOKEN PA 111 RIVER ST, HOBOKEN 07030-5774, NJ USA SN 0887-3585 EI 1097-0134 J9 PROTEINS JI Proteins PD SEP 1 PY 1999 VL 36 IS 4 BP 383 EP 399 PG 17 WC Biochemistry & Molecular Biology; Biophysics SC Biochemistry & Molecular Biology; Biophysics GA 225NQ UT WOS:000081968000002 PM 10450080 ER PT J AU Trent, J AF Trent, J TI Excursion to the kingdom of the Phoneyacious and the Confuzoaires SO RECHERCHE LA French DT Article ID 250-DEGREES-C; TEMPERATURES; BIOMOLECULES C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Trent, J (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 6 TC 0 Z9 0 U1 0 U2 0 PU SOC ED SCIENTIFIQUES PI PARIS 06 PA 57 RUE DE SEINE, 75280 PARIS 06, FRANCE SN 0029-5671 J9 RECHERCHE JI Recherche PD SEP PY 1999 IS 323 BP 73 EP 77 PG 5 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 233GN UT WOS:000082418400020 ER PT J AU Sandmeier, S Deering, DW AF Sandmeier, S Deering, DW TI Structure analysis and classification of boreal forests using airborne hyperspectral BRDF data from ASAS SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID CARBON-DIOXIDE; MULTIANGLE; SOUTHERN; AREA AB A new approach Is presented for deriving vegetation canopy structural characteristics from hyperspectral bidirectional reflectance distribution function (BRDF) data. The methodology is based on the relationship between spectral variability of BRDF effects and canopy geometry Tests with data acquired with the Advanced Solid-State Array Spectroradiometer (ASAS) over Canadian boreal forests during the BOREAS campaign show that vegetation structural characteristics can be derived from the spectral variability of BRDF effects. In addition, the incorporation of both BRDF effects and hyperspectral resolution data substantially improve the classification accuracy. Best classification results are obtained when hyperspectral resolution and BRDF data are combined, but the improvement is not consistent for all classes. For example, adding BRDF information to hyperspectral data increases the overall classification accuracy for a sirs-class fen site from 37.8% to 44.7%. The addition, however reduces the accuracy for the jack pine class from 43.6% to 28.8%. These new findings provide evidence for improved capabilities for applications of MISR and MODIS data. The spectral resolution of MODIS is expected to be sufficient to derive canopy structural information based on the spectral variability of BRDF effects, and for MISR a significant improvement of classification accuracies can be anticipated from the combination of nadir reflectance and off-nadir data. (C)Elsevier Science Inc., 1999. C1 NASA, Goddard Space Flight Ctr, Biospher Sci Branch, USRA, Greenbelt, MD 20771 USA. RP Sandmeier, S (reprint author), NASA, Goddard Space Flight Ctr, Biospher Sci Branch, USRA, Code 923, Greenbelt, MD 20771 USA. NR 27 TC 70 Z9 79 U1 1 U2 5 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 SEP PY 1999 VL 69 IS 3 BP 281 EP 295 DI 10.1016/S0034-4257(99)00032-2 PG 15 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA 237BP UT WOS:000082634000007 ER PT J AU Fenske, MT Barth, JL Didion, JR Mule, P AF Fenske, MT Barth, JL Didion, JR Mule, P TI The development of lightweight electronics enclosures for space applications SO SAMPE JOURNAL LA English DT Article AB This paper outlines the end-to-end effort to produce lightweight electronics enclosures for NASA GSFC electronics applications with the goal of presenting art array of lightweight box options for a flight opportunity. Topics including the development of requirements, design of three different boxes, utilization of advanced materials and processes, and analysis and test will be discussed. Three different boxes were developed independently and in parallel. A light-weight machined aluminum box, a cast aluminum box and a composite bore were designed, fabricated, and tested both mechanically and thermally. There were many: challenges encountered in meeting the requirements with a nonmetallic enclosure and the development of the composite box employed several innovative techniques. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Fenske, MT (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 5 TC 2 Z9 2 U1 1 U2 1 PU SAMPE PUBLISHERS PI COVINA PA 1161 PARKVIEW DRIVE, COVINA, CA 91722 USA SN 0091-1062 J9 SAMPE J JI Sampe J. PD SEP-OCT PY 1999 VL 35 IS 5 BP 25 EP 34 PG 10 WC Engineering, Multidisciplinary; Materials Science, Multidisciplinary SC Engineering; Materials Science GA 234PQ UT WOS:000082493600008 ER PT J AU Seth, A Lush, GB McClure, JC Singh, VP Flood, D AF Seth, A Lush, GB McClure, JC Singh, VP Flood, D TI Growth and characterization of CdTe by close spaced sublimation on metal substrates SO SOLAR ENERGY MATERIALS AND SOLAR CELLS LA English DT Article; Proceedings Paper CT 2nd International Symposium on New Materials for Solar, Hydrogen, Fuel Cell and Batteries - CANCUN 98 CY 1998 CL CANCUN, MEXICO DE CdS/CdTe solar cells; close spaced sublimation; grain size ID FILMS AB CdS/CdTe solar cells have long been recognized for their terrestrial applications. These cells are usually fabricated on soda-lime glass substrates, but the poor mechanical and thermal properties of glass make it difficult to incorporate it in continuous fabrication processes involving high temperatures, typically above 500 degrees C. In addition, prospective space power applications would benefit if a lighter flexible substrate can be used. With a view to making light-weight modules suitable for large-scale production, a new device structure on metal foils has been proposed. CdTe films have been deposited on light-weight molybdenum foils by the close spaced sublimation (CSS) technique. Firstly, the salient features of the CSS technique as well as the design and construction of a CSS system will be described. CdTe films were deposited using this CSS system. The source and substrate temperatures were varied in steps and the film thickness and grain sizes were studied. The films were characterized by SEM, EDS, XRD and AFM as well as contact resistance measurements between the CdTe and molybdenum substrate. Films deposited with source and substrate temperatures of 650 degrees C and 575 degrees C respectively, spaced 0.5 mm apart in helium ambient at 70 Torr yielded CdTe films of 4-5 mu m thickness. SEM studies showed CdTe films to be continuous and of uniform grain size. The grains are well faceted and the grain size is of the order of the film thickness. EDS studies indicated stoichiometric CdTe. XRD analysis showed a cubic phase with a preferred orientation in the (1 1 1) direction. A cadmium chloride dip followed by annealing treatment did not alter the grain size or the orientation of the film. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Univ Texas, Dept Met & Mat Engn, El Paso, TX 79968 USA. Univ Texas, Dept Elect & Comp Engn, El Paso, TX 79968 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP McClure, JC (reprint author), Univ Texas, Dept Met & Mat Engn, El Paso, TX 79968 USA. NR 10 TC 28 Z9 29 U1 0 U2 11 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0927-0248 J9 SOL ENERG MAT SOL C JI Sol. Energy Mater. Sol. Cells PD SEP PY 1999 VL 59 IS 1-2 BP 35 EP 49 DI 10.1016/S0927-0248(99)00029-X PG 15 WC Energy & Fuels; Materials Science, Multidisciplinary; Physics, Applied SC Energy & Fuels; Materials Science; Physics GA 233YV UT WOS:000082455500005 ER PT J AU Singh, VP McClure, JC Lush, GB Wang, W Wang, X Thompson, GW Clark, E AF Singh, VP McClure, JC Lush, GB Wang, W Wang, X Thompson, GW Clark, E TI Thin film CdTe-CdS heterojunction solar cells on lightweight metal substrates SO SOLAR ENERGY MATERIALS AND SOLAR CELLS LA English DT Article; Proceedings Paper CT 2nd International Symposium on New Materials for Solar, Hydrogen, Fuel Cell and Batteries - CANCUN 98 CY AUG 30-SEP 04, 1998 CL CANCUN, MEXICO SP Natl Autonomous Univ Mexico ID CADMIUM TELLURIDE; EFFICIENCY; CONTACTS; OXYGEN AB An unconventional thin film CdTe-CdS solar cell device configuration, in which the substrate is molybdenum foil and CdS is deposited on top of CdTe, was developed. A conducting contact between Mo and CdTe was achieved by using thin interlayers. The CdTe-CdS junction process development led to an open circuit voltage of 824 mV. CdCl(2) treatment followed by oxygen annealing greatly improved solar cell performance. An initial study of capacitance-voltage data has shown a depletion layer width of 4.62 mu m into CdTe in the dark, Cell efficiency of 5.3% was achieved. Higher cell efficiency is now being sought by improving the top contact to CdS and lowering series resistance. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Univ Texas, Dept Elect & Comp Engn, El Paso, TX 79968 USA. Univ Texas, Dept Met & Mat Engn, El Paso, TX 79968 USA. Univ Texas, Dept Mat Sci & Engn, El Paso, TX 79968 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Singh, VP (reprint author), Univ Texas, Dept Elect & Comp Engn, El Paso, TX 79968 USA. NR 28 TC 38 Z9 38 U1 1 U2 20 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0927-0248 J9 SOL ENERG MAT SOL C JI Sol. Energy Mater. Sol. Cells PD SEP PY 1999 VL 59 IS 1-2 BP 145 EP 161 DI 10.1016/S0927-0248(99)00039-2 PG 17 WC Energy & Fuels; Materials Science, Multidisciplinary; Physics, Applied SC Energy & Fuels; Materials Science; Physics GA 233YV UT WOS:000082455500015 ER PT J AU Choudhary, DP Gary, GA AF Choudhary, DP Gary, GA TI Magnetic field configuration of active region NOAA 6555 at the time of a long-duration flare on 23 March 1991 - An exception to standard flare reconnection model SO SOLAR PHYSICS LA English DT Article ID LOOPS AB The high-resolution H alpha images observed during the decay phase of a long-duration flare on 23 March 1991 are used to study the three-dimensional magnetic field configuration of the active region NOAA 6555. Whereas all the large flares in NOAA 6555 occurred at the location of high magnetic shear and flux emergence, this long-duration flare was observed in the region of low magnetic shear at the photosphere. The H alpha loops activity started soon after the maximum phase of the flare. There were a few long loop at the initial phase of the activity. Some of these were sheared in the chromosphere at an angle of about 45 degrees to the east-west axis. Gradually, an increasing number of shorter loops, oriented along the east-west axis, started appearing. The chromospheric Dopplergrams show blue shifts at the end points of the loops. By using different magnetic field models, we have extrapolated the photospheric magnetograms to chromospheric heights. The magnetic field lines computed by using the potential field model correspond to most of the observed H alpha loops. The height of the H alpha loops were derived by comparing them with the computed field lines. From the temporal evolution of the H alpha loop activity, we derive the negative rate of appearance of H alpha features as a function of height. It is found that the field lines oriented along one of the neutral lines were sheared and low lying. The higher field lines were mostly potential. The paper also outlines a possible scenario for describing the post-flare stage of the observed long-duration flare. C1 NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. RP Choudhary, DP (reprint author), NASA, George C Marshall Space Flight Ctr, Space Sci Lab, ES82, Huntsville, AL 35812 USA. NR 18 TC 7 Z9 7 U1 0 U2 0 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0038-0938 J9 SOL PHYS JI Sol. Phys. PD SEP PY 1999 VL 188 IS 2 BP 345 EP 364 DI 10.1023/A:1005165425964 PG 20 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 258HC UT WOS:000083832200010 ER PT J AU Halicioglu, T Srivastava, D AF Halicioglu, T Srivastava, D TI Energetics for bonding and detachment steps in etching of Si by Cl SO SURFACE SCIENCE LA English DT Letter DE adatoms; chlorine; computer simulations; etching; silicon; stepped single crystal surfaces; surface chemical reaction ID MOLECULAR-DYNAMICS SIMULATIONS; FIRST-PRINCIPLES; SURFACE; CHLORINE; SI(100); SILICON; SI(001); LAYER; MECHANISMS AB Simulation calculations were carried out to investigate the energetics of adsorption and desorption processes taking place during etching of the Si(100) surface by Cl atoms. Clean and fully chlorinated surfaces with step edges were taken into consideration. Attachment energies of Cl atoms at step edge sites and subsequent detachment (etching) energies of SiClx species were calculated. Configurational characteristics of Cl bonded regions were also investigated. Results provide a systematic description of Cl adsorption and etching processes. (C) 1999 Elsevier Science B.V. All rights reserved. C1 NASA, Thermosci Inst, Ames Res Ctr, Moffett Field, CA 94035 USA. NASA, Computat Nanotechnol, NAS MRJ Tech, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Halicioglu, T (reprint author), Stanford Univ, Dept Mat Sci & Engn, Stanford, CA 94305 USA. NR 21 TC 5 Z9 5 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0039-6028 J9 SURF SCI JI Surf. Sci. PD SEP 1 PY 1999 VL 437 IS 3 BP L773 EP L778 DI 10.1016/S0039-6028(99)00765-7 PG 6 WC Chemistry, Physical; Physics, Condensed Matter SC Chemistry; Physics GA 232VN UT WOS:000082390800003 ER PT J AU Lakhina, GS Tsurutani, BT AF Lakhina, GS Tsurutani, BT TI Broadband plasma waves in the magnetopause and polar cap boundary layers SO SURVEYS IN GEOPHYSICS LA English DT Review DE plasma waves; boundary layer waves; broadband waves ID HYBRID-DRIFT INSTABILITY; ELECTROSTATIC SOLITARY WAVES; ELECTRIC-FIELD STRUCTURES; DAYSIDE MAGNETOPAUSE; ION-BEAM; FREQUENCY INSTABILITIES; MAGNETOSPHERIC BOUNDARY; PARTICLE INTERACTIONS; MAGNETIC-FIELDS; SHEET BOUNDARY AB Boundary layers occurring in the magnetosphere can support a wide spectrum of plasma waves spanning a frequency range of a few mHz to tens of kHz and beyond. This review describes the main characteristics of the broadband plasma waves observed in the Earth's low-latitude magnetopause boundary layer (LLBL), in the polar cap boundary layer (PCBL), and the possible generation mechanisms. The broadband waves at the low-latitude boundary layer are sufficiently intense to cause the diffusion of the magnetosheath plasma across the closed magnetospheric field lines at a rate rapid enough to populate and maintain the boundary layer itself. The rapid pitch angle scattering of energetic particles via cyclotron resonant interactions with the waves can provide sufficient precipitation energy flux to the ionosphere to create the dayside aurora. In general, the broadband plasma waves may play an important part in the processes of local heating/acceleration of the boundary layer plasma. C1 Indian Inst Geomagnetism, Mumbai 400005, India. CALTECH, Jet Prop Lab, Pasadena, CA USA. RP Lakhina, GS (reprint author), Indian Inst Geomagnetism, Dr Nanabhai Moos Marg, Mumbai 400005, India. RI Lakhina, Gurbax /C-9295-2012; OI Lakhina, Gurbax /0000-0002-8956-486X NR 105 TC 6 Z9 6 U1 1 U2 1 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0169-3298 J9 SURV GEOPHYS JI Surv. Geophys. PD SEP PY 1999 VL 20 IS 5 BP 377 EP 414 DI 10.1023/A:1006603103116 PG 38 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 303FV UT WOS:000086412600001 ER PT J AU Chou, MD AF Chou, MD TI Atmospheric solar heating in minor absorption bands SO TERRESTRIAL ATMOSPHERIC AND OCEANIC SCIENCES LA English DT Article DE atmospheric solar heating; minor absorption bands; trace gases; climate modeling ID INHOMOGENEOUS ATMOSPHERES; MULTIPLE-SCATTERING; RADIATIVE-TRANSFER; WATER-VAPOR; PARAMETERIZATIONS; CLIMATE; MODEL; CO2 AB Solar radiation is the primary source of energy driving atmospheric and oceanic circulations. Concerned with the huge amount of time required for computing radiative transfer in weather and climate models, solar heating in minor absorption bands has often been neglected. The individual contributions of these minor bands to the atmospheric heating is small, but collectively they are not negligible. The solar heating in minor bands includes the absorption due to water vapor in the photosynthetically active radiation (PAR) spectral region from 14284 cm(-1) to 25000 cm(-1), the ozone absorption and Rayleigh scattering in the near infrared, as well as the O-2 and CO2 absorption in a number of weak bands. Detailed high spectral- and angular-resolution calculations show that the total effect of these minor absorption is to enhance the atmospheric solar heating by similar to 10%, Depending upon the strength of the absorption and the overlapping among gaseous absorption, different approaches are applied to parameterize these minor absorption. The parameterizations are accurate and require little extra time for computing radiative fluxes. They have been efficiently implemented in the various atmospheric models at NASA/Goddard Space Flight Center, including cloud ensemble, mesoscale, and climate models. C1 NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. RP Chou, MD (reprint author), NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. NR 19 TC 6 Z9 6 U1 0 U2 1 PU CHINESE GEOSCIENCE UNION PI TAIPEI PA PO BOX 23-59, TAIPEI 10764, TAIWAN SN 1017-0839 J9 TERR ATMOS OCEAN SCI JI Terr. Atmos. Ocean. Sci. PD SEP PY 1999 VL 10 IS 3 BP 511 EP 528 PG 18 WC Geosciences, Multidisciplinary; Meteorology & Atmospheric Sciences; Oceanography SC Geology; Meteorology & Atmospheric Sciences; Oceanography GA 244WD UT WOS:000083073000002 ER PT J AU Berejikian, BA Tezak, EP Schroder, SL Flagg, TA Knudsen, CM AF Berejikian, BA Tezak, EP Schroder, SL Flagg, TA Knudsen, CM TI Competitive differences between newly emerged offspring of captive-reared and wild coho salmon SO TRANSACTIONS OF THE AMERICAN FISHERIES SOCIETY LA English DT Article ID AGONISTIC BEHAVIOR; ONCORHYNCHUS-KISUTCH; ATLANTIC SALMON; BODY SIZE; DOMINANCE; HATCHERY; GROWTH; GAIRDNERI; POPULATIONS; EXPERIENCE AB We investigated competition among newly emerged fry from captive-reared and wild female coho salmon Oncorhynchus kisutch by conducting dominance challenges and growth and survival experiments in laboratory stream channels. Newly emerged fry from captive-reared females won a significant majority (72.7%) of dyadic dominance challenges against fry from wild females. In a growth and survival experiment conducted from emergence to 30 d postemergence. fewer captive brood fry died of apparent starvation when food was limited than wild fry. further suggesting a competitive advantage for the captive brood fry. All fry used in the study were paternal half-sibs, so observed differences between captive brood and wild fry were attributed to the maternal parent. We hypothesize that fry coloration resulting from differences in egg color between wild and captive-reared females may have influenced the observed competitive asymmetries. If so, such differences might be ameliorated by changes in husbandry practices such as providing more natural diets. C1 NW Fisheries Sci Ctr, Natl Marine Fisheries Serv, Manchester Marine Expt Stn, Manchester, WA 98353 USA. Washington Dept Fish & Wildlife, Olympia, WA 98501 USA. RP Berejikian, BA (reprint author), NW Fisheries Sci Ctr, Natl Marine Fisheries Serv, Manchester Marine Expt Stn, POB 130, Manchester, WA 98353 USA. EM barry.berejikian@noaa.gov NR 33 TC 23 Z9 23 U1 1 U2 8 PU TAYLOR & FRANCIS INC PI PHILADELPHIA PA 325 CHESTNUT ST, SUITE 800, PHILADELPHIA, PA 19106 USA SN 0002-8487 J9 T AM FISH SOC JI Trans. Am. Fish. Soc. PD SEP PY 1999 VL 128 IS 5 BP 832 EP 839 DI 10.1577/1548-8659(1999)128<0832:CDBNEO>2.0.CO;2 PG 8 WC Fisheries SC Fisheries GA 351XC UT WOS:000089183900005 ER PT J AU Murphy, ML Heintz, RA Short, JW Larsen, ML Rice, SD AF Murphy, ML Heintz, RA Short, JW Larsen, ML Rice, SD TI Recovery of pink salmon spawning areas after the Exxon Valdez oil spill SO TRANSACTIONS OF THE AMERICAN FISHERIES SOCIETY LA English DT Article ID PRINCE-WILLIAM-SOUND; AROMATIC-COMPOUNDS; SEDIMENTS; HYDROCARBONS; ENVIRONMENT; INDUCTION; TISSUES; DAMAGE; ALASKA AB Up to 70% of wild pink salmon Oncorhynchus gorbuscha in Prince William Sound, Alaska, spawn in intertidal stream areas, many of which were contaminated by the 1989 Exxon Valdez oil spill. To assess recovery of salmon habitat after the spill, we analyzed sediment samples from stream deltas throughout Prince William Sound from 1989 to 1991 and 1995. In 1989, petroleum hydrocarbon concentration at 172 stream deltas (1-8 samples each) was bimodally distributed: 85 deltas had no detectable petroleum hydrocarbons (detection limit, 2 mu g/g), whereas 87 deltas had a concentration of 2-90,000 mu g/g. In 1995, petroleum hydrocarbons were still detected at eight of nine oiled streams that we resampled, with mean concentration up to 242 mu g/g. The polynuclear aromatic hydrocarbon (PAH) fraction was also analyzed in 1995 to determine its origin, state of weathering, and toxic potential of the residual oil. The PAH fraction consisted mostly of the more toxic compounds with high molecular weight (e.g., phenanthrenes and chrysenes), and PAH composition was consistent with weathered Exxon Valdez oil. Total PAH concentration in 1995 averaged 0-1,300 ng/g, which was below the minimum sediment concentration (3,800 ng/g) shown to reduce salmon embryo survival in the laboratory. Interpolation between 1989 and 1995 indicated that residual PAH concentration exceeded 3,800 ng/g at some stream deltas through 1993, but all streams were below this level by 1994. We conclude that tidal leaching of PAH from weathered oil into incubation substrate could explain persistent elevated embryo mortality observed in pink salmon through 1993, and that spawning habitat had recovered to below lethal threshold by 1994. C1 NOAA, Auke Bay Lab, Alaska Fisheries Sci Ctr, Natl Marine Fisheries Serv, Juneau, AK 99801 USA. RP Murphy, ML (reprint author), NOAA, Auke Bay Lab, Alaska Fisheries Sci Ctr, Natl Marine Fisheries Serv, 11305 Glacier Highway, Juneau, AK 99801 USA. EM mike.murphy@noaa.gov NR 27 TC 16 Z9 17 U1 4 U2 20 PU TAYLOR & FRANCIS INC PI PHILADELPHIA PA 325 CHESTNUT ST, SUITE 800, PHILADELPHIA, PA 19106 USA SN 0002-8487 J9 T AM FISH SOC JI Trans. Am. Fish. Soc. PD SEP PY 1999 VL 128 IS 5 BP 909 EP 918 DI 10.1577/1548-8659(1999)128<0909:ROPSSA>2.0.CO;2 PG 10 WC Fisheries SC Fisheries GA 351XC UT WOS:000089183900013 ER PT J AU Breininger, DR Brugman, MA Stith, BM AF Breininger, DR Brugman, MA Stith, BM TI Influence of habitat quality, catastrophes, and population size on extinction risk of the Florida scrub-jay SO WILDLIFE SOCIETY BULLETIN LA English DT Article DE Aphelocoma coerculescens; extinction risk; fire management; habitat quality; population viability; scrub-jay ID DEMOGRAPHIC SUCCESS; VIABILITY; LANDSCAPES; DYNAMICS; IMPACT; FOREST AB Within the range of the Florida scrub-jay (Aphelocoma coerulescens), the only bird species endemic to Florida, there was a need for a population risk assessment that considered the impacts of declining habitat availability and declining fire frequency associated with rapid human population expansion. We developed a population risk model to examine influence of population size, catastrophes (epidemics and hurricanes), and habitat management scenarios on Florida scrub-jay populations. Extinction risk declined rapidly when initial population sizes increased from 20 to 100 breeding pairs. Hurricanes increased extinction risk for coastal populations by 10-30% compared to inland populations. Our results suggested that habitat in poor condition was unlikely to support a population for more than a few decades. Poor habitat quality conditions were common throughout the species' range because of fire suppression or inadequate fire management. Habitat management was more effective than habitat restoration because population recovery occurred slowly after restoration and only if habitat was restored to optimal conditions. Sensitivity analyses showed that fecundity and survival of experienced breeders without helpers (adult nonbreeders) were the most important model parameters. Slow recovery rates occurred because helpers were the only rapid source of colonists in restored habitat and because an absence of helpers reduced breeder survival and fecundity. Small population sizes and habitat degradation make the Florida scrub-jay vulnerable to rangewide decline and extinction unless habitat is protected, restored, and managed to maintain optimal conditions. C1 Dynamac Corp, DYN 2, NASA, Biomed Operat Off, Kennedy Space Ctr, FL 32899 USA. Univ Melbourne, Sch Bot, Parkville, Vic 3052, Australia. Univ Florida, Dept Wildlife Ecol & Conservat, Gainesville, FL 32611 USA. Archbold Biol Stn, Lake Placid, FL 33862 USA. RP Breininger, DR (reprint author), Dynamac Corp, DYN 2, NASA, Biomed Operat Off, Kennedy Space Ctr, FL 32899 USA. NR 54 TC 37 Z9 37 U1 2 U2 21 PU WILDLIFE SOC PI BETHESDA PA 5410 GROSVENOR LANE, BETHESDA, MD 20814-2197 USA SN 0091-7648 J9 WILDLIFE SOC B JI Wildl. Soc. Bull. PD FAL PY 1999 VL 27 IS 3 BP 810 EP 822 PG 13 WC Biodiversity Conservation SC Biodiversity & Conservation GA 264GZ UT WOS:000084173500036 ER PT J AU Liu, AS Ning, CZ AF Liu, AS Ning, CZ TI Terahertz optical gain based on intersubband transitions in optically pumped semiconductor quantum wells: Coherent pump-probe interactions SO APPLIED PHYSICS LETTERS LA English DT Article ID LASERS AB Terahertz optical gain due to intersubband transitions in optically pumped semiconductor quantum wells (QWs) is calculated nonperturbatively. We solve the pump-field-induced nonequilibrium distribution function for each subband of the QW system from a set of rate equations that include both intrasubband and intersubband relaxation processes. The gain arising from population inversion and stimulated Raman processes is calculated in a unified manner. We show that the coherent pump and signal wave interactions contribute significantly to the tetrahertz gain. Because of the optical Stark effect and pump-induced population redistribution, optical gain saturation at larger pump intensities is predicted. (C) 1999 American Institute of Physics. [S0003-6951(99)05035-4]. 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 T27A-1, Moffett Field, CA 94035 USA. RI Ning, C. Z./D-4699-2009 OI Ning, C. Z./0000-0003-4583-8889 NR 13 TC 31 Z9 32 U1 0 U2 4 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0003-6951 J9 APPL PHYS LETT JI Appl. Phys. Lett. PD AUG 30 PY 1999 VL 75 IS 9 BP 1207 EP 1209 DI 10.1063/1.124643 PG 3 WC Physics, Applied SC Physics GA 228BV UT WOS:000082117000007 ER PT J AU Boykin, TB Bowen, RC Klimeck, G Lear, KL AF Boykin, TB Bowen, RC Klimeck, G Lear, KL TI Resonant-tunneling diodes with emitter prewells SO APPLIED PHYSICS LETTERS LA English DT Article ID SIMULATION AB Resonant-tunneling diodes (RTDs) incorporating an emitter prewell structure are studied both theoretically and experimentally in order to investigate the utility of the emitter region as a device design parameter. The experiments show a tendency for peak bias, current, and the peak-to-valley ratio to increase for wider prewells, behavior likewise seen in both very simple and detailed calculations. Both the simple and more complete models point to interactions between states associated with the prewell and the main quantum well as the reasons for the increase in peak current. These results suggest design guidelines to affect peak bias, current, or the peak-to-valley ratio of RTDs. (C) 1999 American Institute of Physics. [S0003-6951(99)01435-7]. C1 Univ Alabama, Dept Elect & Comp Engn, Huntsville, AL 35899 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Colorado State Univ, Dept Elect & Comp Engn, Ft Collins, CO 80523 USA. RP Boykin, TB (reprint author), Univ Alabama, Dept Elect & Comp Engn, Huntsville, AL 35899 USA. RI Klimeck, Gerhard/A-1414-2012 OI Klimeck, Gerhard/0000-0001-7128-773X NR 9 TC 20 Z9 22 U1 0 U2 2 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0003-6951 J9 APPL PHYS LETT JI Appl. Phys. Lett. PD AUG 30 PY 1999 VL 75 IS 9 BP 1302 EP 1304 DI 10.1063/1.124675 PG 3 WC Physics, Applied SC Physics GA 228BV UT WOS:000082117000039 ER PT J AU Anderson, JD Laing, PA Lau, EL Liu, AS Nieto, MM Turyshev, SG AF Anderson, JD Laing, PA Lau, EL Liu, AS Nieto, MM Turyshev, SG TI Prosaic explanation for the anomalous accelerations seen in distant spacecraft - Reply SO PHYSICAL REVIEW LETTERS LA English DT Article C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Aerospace Corp, El Segundo, CA 90245 USA. Astrodynam Sci, Los Angeles, CA 90039 USA. Univ Calif Los Alamos Natl Lab, Div Theoret, Los Alamos, NM 87545 USA. RP Anderson, JD (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 4 TC 21 Z9 21 U1 1 U2 1 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0031-9007 J9 PHYS REV LETT JI Phys. Rev. Lett. PD AUG 30 PY 1999 VL 83 IS 9 BP 1891 EP 1891 DI 10.1103/PhysRevLett.83.1891 PG 1 WC Physics, Multidisciplinary SC Physics GA 230GC UT WOS:000082242600049 ER PT J AU Anderson, JD Laing, PA Lau, EL Liu, AS Nieto, MM Turyshev, SG AF Anderson, JD Laing, PA Lau, EL Liu, AS Nieto, MM Turyshev, SG TI Comment on "Indication, from Pioneer 10/11, Galileo, and Ulysses data, of an apparent anomalous, weak, long-range acceleration" - Reply SO PHYSICAL REVIEW LETTERS LA English DT Article C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Aerospace Corp, El Segundo, CA 90245 USA. Astrodynam Sci, Los Angeles, CA 90039 USA. Univ Calif Los Alamos Natl Lab, Div Theoret, Los Alamos, NM 87545 USA. Univ Ulm, Abt Quantenphys, D-86069 Ulm, Germany. RP Anderson, JD (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 5 TC 18 Z9 20 U1 2 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 AUG 30 PY 1999 VL 83 IS 9 BP 1893 EP 1893 DI 10.1103/PhysRevLett.83.1893 PG 1 WC Physics, Multidisciplinary SC Physics GA 230GC UT WOS:000082242600051 ER PT J AU Tarasova, TA Nobre, CA Holben, BN Eck, TF Setzer, A AF Tarasova, TA Nobre, CA Holben, BN Eck, TF Setzer, A TI Assessment of smoke aerosol impact on surface solar irradiance measured in the Rondonia region of Brazil during Smoke, Clouds, and Radiation - Brazil SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID DELTA-EDDINGTON APPROXIMATION; AMAZON BASIN; SIMULATION; GCM AB The impact of smoke aerosols on the surface solar irradiance in the Rondonia region of Brazil is examined. The climate of this region is subequatorial with two distinct seasons; There is a sharp decline of the precipitation and cloudiness during the dry season which lasts from June to September accompanied by anthropogenic burning of savanna and forest in August and September with the resultant strong emission of smoke into the troposphere. Thus the magnitude of the column aerosol optical depth increases in these months while both precipitable water and cloud amount decrease in accordance with the seasonal cycle of humidity. All these atmospheric constituents influence the magnitude of the solar irradiance at the surface. In order to assess the aerosol and gaseous effects on the surface irradiance as compared with impact of cloudiness, we performed the clear-sky radiative transfer model calculations by employing a broadband radiation code and both aerosol optical depth and precipitable water retrieved from Sun photometer measurements. Calculation results show that the elevated aerosol optical depth observed in Rondonia during August and September causes a negative trend in the daily mean clear-sky surface solar irradiance during this period. Since the daily mean solar irradiance measured at the surface under all-sky conditions demonstrates a similar negative trend, it can be explained by the aerosol influence while the effect of clouds appears in the daily variations of the irradiance. It was also shown that smoke aerosols cause a decrease of the monthly mean values of all-sky surface irradiance in August and September as compared with July and October. Corresponding decreases in the near surface air temperature due to the smoke aerosols were not found. C1 Ctr Previsao Tempo & Estudos Climaticos, Inst Nacl Pesquisas Espaciais, BR-12630000 Sao Paulo, Brazil. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Hughes STX Corp, Greenbelt, MD 20771 USA. Inst Nacl Pesquisas Espaciais, Sao Paulo, Brazil. RP Ctr Previsao Tempo & Estudos Climaticos, Inst Nacl Pesquisas Espaciais, Rodovia Presidente Dutra Km 40, BR-12630000 Sao Paulo, Brazil. EM tatiana@cptec.inpe.br; nobre@cptec.inpe.br; brent@spamer.gsfc.nasa.gov; tom@spamer.gsfc.nasa.gov; asetzer@ltid.inpe.br RI ECK, THOMAS/D-7407-2012 NR 24 TC 13 Z9 13 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD AUG 27 PY 1999 VL 104 IS D16 BP 19161 EP 19170 DI 10.1029/1999JD900258 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 230CY UT WOS:000082235300011 ER PT J AU Bosilovich, MG Sun, WY AF Bosilovich, MG Sun, WY TI Numerical simulation of the 1993 midwestern flood: Local and remote sources of water SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID LAND-SURFACE PARAMETERIZATION; LATENT-HEAT RELEASE; UNITED-STATES; 1988 DROUGHT; PRECIPITATION; SENSITIVITY; LAYER; MODEL AB Local and remote sources of water are estimated by removing the surface source of water vapor in a numerical simulation without significantly influencing the large-scale dynamical circulation. This is done by reducing the surface moisture flux in the model's hydrologic equations but maintaining latent heat in the surface energy balance and evaporation in the soil water budget. Simulations of the 1993 midwestern flood are used as test cases, Without the local surface source of water vapor, the flood region's atmospheric hydrology budget reduces to an approximate balance between precipitation and moisture flux convergence. Comparison with the control simulation hydrology approximated 12% and 20% of the precipitation with a local source for June and July 1993 respectively. The differences between the two months are reasonable considering that June is dominated by a transient synoptic-scale wave pattern, but July precipitation is largely related to mesoscale convective complexes. The southern Great Plains source influences the flood region precipitation slightly less than the local anomaly for each month. The differences between June and July are striking. A great deal of variability exists in the modeled interactions between the surface and atmosphere. This indicates that simply using any one month to generalize the interactions or feedback of water does not address the complete problem. C1 Purdue Univ, Dept Earth & Atmospher Sci, W Lafayette, IN 47907 USA. RP NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Code 910-3, Greenbelt, MD 20771 USA. EM mikeb@dao.gsfc.nasa.gov RI Bosilovich, Michael/F-8175-2012 NR 19 TC 12 Z9 12 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD AUG 27 PY 1999 VL 104 IS D16 BP 19415 EP 19423 DI 10.1029/1999JD900218 PG 9 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 230CY UT WOS:000082235300030 ER PT J AU Takle, ES Gutowski, WJ Arritt, RW Pan, ZT Anderson, CJ da Silva, RR Caya, D Chen, SC Giorgi, F Christensen, JH Hong, SY Juang, HMH Katzfey, J Lapenta, WM Laprise, R Liston, GE Lopez, P McGregor, J Pielke, RA Roads, JO AF Takle, ES Gutowski, WJ Arritt, RW Pan, ZT Anderson, CJ da Silva, RR Caya, D Chen, SC Giorgi, F Christensen, JH Hong, SY Juang, HMH Katzfey, J Lapenta, WM Laprise, R Liston, GE Lopez, P McGregor, J Pielke, RA Roads, JO TI Project to Intercompare Regional Climate Simulations (PIRCS): Description and initial results SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID AMERICAN MONSOON SYSTEM; UNITED-STATES; LAND-SURFACE; BOUNDARY-CONDITIONS; LATERAL BOUNDARY; SPECTRAL MODEL; 1988 DROUGHT; FIFE; PRECIPITATION; PARAMETERIZATION AB The first simulation experiment and output archives of the Project to Intercompare Regional Climate Simulations (PIRCS) is described. Initial results from simulations of the summer 1988 drought over the central United States indicate that limited-area models forced by large-scale information at the lateral boundaries reproduce bulk temporal and spatial characteristics of meteorological fields. In particular, the 500 hPa height field time average and temporal variability are generally well simulated by all participating models. Model simulations of precipitation episodes vary depending on the scale of the dynamical forcing. Organized synoptic-scale precipitation systems are simulated deterministically in that precipitation occurs at close to the same time and location as observed (although amounts may vary from observations). Episodes of mesoscale and convective precipitation are represented in a more stochastic sense, with less precise agreement in temporal and spatial patterns. Simulated surface energy fluxes show broad similarity with the First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE) observations in their temporal evolution and time average diurnal cycle. Intermodel differences in midday Bowen ratio tend to be closely associated with precipitation differences. Differences in daily maximum temperatures also are linked to Bowen ratio differences, indicating strong local, surface influence on this field. Although some models have bias with respect to FIFE observations, all tend to reproduce the synoptic variability of observed daily maximum and minimum temperatures. Results also reveal the advantage of an intercomparison in exposing common tendencies of models despite their differences in convective and surface parameterizations and different methods of assimilating lateral boundary conditions. C1 Iowa State Univ, Dept Agron, Ames, IA 50011 USA. Univ Quebec, Montreal, PQ H3C 3P8, Canada. Scripps Inst Oceanog, La Jolla, CA 92037 USA. Abdus Salam Int Ctr Theoret Phys, I-34100 Trieste, Italy. Danish Meteorol Inst, DK-2100 Copenhagen, Denmark. Natl Ctr Environm Predict, Camp Springs, MD 20031 USA. CSIRO, Aspendale, Vic 3195, Australia. Colorado State Univ, Dept Atmospher Sci, Ft Collins, CO 80521 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Iowa State Univ, Dept Agron, 3010 Agron, Ames, IA 50011 USA. EM gstakle@iastate.edu RI Pielke, Roger/A-5015-2009; McGregor, John/C-6646-2012; Pan, Zaitao/D-7846-2012; Hong, Song-You/I-3824-2012; Giorgi, Filippo/C-3169-2013; Christensen, Jens/C-4162-2013; Katzfey, Jack/K-1231-2012; Ramos-da-Silva, Renato/I-4759-2012 OI Christensen, Jens/0000-0002-9908-8203; Katzfey, Jack/0000-0002-0604-8860; NR 46 TC 120 Z9 124 U1 2 U2 9 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD AUG 27 PY 1999 VL 104 IS D16 BP 19443 EP 19461 DI 10.1029/1999JD900352 PG 19 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 230CY UT WOS:000082235300033 ER PT J AU Bosilovich, MG Yang, RH Houser, PR AF Bosilovich, MG Yang, RH Houser, PR TI River basin hydrology in a global off-line land-surface model SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SOIL-MOISTURE; CLIMATE MODELS; WATER-BALANCE; UNITED-STATES; PARAMETERIZATION; PRECIPITATION; GCMS AB Land-surface hydrology has been examined for the Off-line Land-surface GEOS Assimilation (OLGA) system and Goddard Earth Observing System (GEOS-1) data assimilation system using a river routing model, The GEOS-1 land-surface parameterization is very simple, using an energy balance prediction of surface temperature and prescribed soil water, OLGA uses atmospheric data from GEOS-1 to drive a more comprehensive parameterization of the land-surface processes. Using a global river routing model, OLGA's hydrology is evaluated against GEOS-1 (which serves as a control case) and observations. The river routing model moves monthly mean climatologic source runoff: through river networks to simulate the river discharge from many river basins around the world, which can be compared to observed climatologic river discharge. Because of the soil hydrology, the OLGA system shows a general improvement in the simulation of river discharge, compared to the GEOS-1, by slowing the discharge of water. Snowmelt processes included in OLGA also have a positive effect on the annual cycle of river discharge and source runoff. The timing of the snowmelt in river discharge, however, still needs improvement in the annual cycle. Preliminary tests of a coupled land-atmosphere model indicate improvements to the hydrologic cycle compared to the uncoupled system. The river routing model has provided a useful tool in the evaluation of the GCM hydrologic cycle and has helped quantify the influence of the more advanced land-surface model. C1 NASA, Univ Space Res Assoc, Data Assimilat Off, GSFC, Greenbelt, MD 20771 USA. NASA, Gen Sci Corp, Data Assimiliat Off, Greenbelt, MD USA. NASA, Goddard Space Flight Ctr, Hydrol Sci Branch, Greenbelt, MD 20771 USA. RP NASA, Univ Space Res Assoc, Data Assimilat Off, GSFC, Code 910-3, Greenbelt, MD 20771 USA. EM mikeb@dao.sfc.nasa.gov RI Bosilovich, Michael/F-8175-2012; Houser, Paul/J-9515-2013 OI Houser, Paul/0000-0002-2991-0441 NR 31 TC 6 Z9 6 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD AUG 27 PY 1999 VL 104 IS D16 BP 19661 EP 19673 DI 10.1029/1999JD900346 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 230CY UT WOS:000082235300050 ER PT J AU Owe, M Van de Griend, AA de Jeu, R de Vries, JJ Seyhan, E Engman, ET AF Owe, M Van de Griend, AA de Jeu, R de Vries, JJ Seyhan, E Engman, ET TI Estimating soil moisture from satellite microwave observations: Past and ongoing projects, and relevance to GCIP SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID VEGETATION OPTICAL DEPTH; SURFACE MOISTURE; WATER-CONTENT; EMISSION; MODEL; POLARIZATION; SCATTERING; CANOPIES; CLIMATE; AREA AB On the basis of a series of studies conducted in Botswana and preliminary results from an ongoing study in Spain, developments in microwave remote sensing by satellite, which can be used to monitor near-real-time surface moisture and also study long-term soil moisture climatology, are described. A progression of methodologies beginning with single-polarization studies and leading to both dual polarization and multiple frequency techniques are described. Continuing analysis of a 9 year data set of satellite-derived surface moisture in Spain is ongoing. Preliminary results from this study appear to provide some evidence of long-term desertification in certain parts of this region. The methodologies developed during these investigations can be applied easily to other regions such as the GCIP area and could provide useful databases for simulation and validation studies. Additionally, they have strong potential for global applications such as climate change studies. C1 NASA, Goddard Space Flight Ctr, Hydrol Sci Branch, Greenbelt, MD 20771 USA. Vrije Univ Amsterdam, Fac Earth Sci, NL-1081 HV Amsterdam, Netherlands. RP NASA, Goddard Space Flight Ctr, Hydrol Sci Branch, Mail Code 974, Greenbelt, MD 20771 USA. EM owe@hydro4.gsfc.nasa.gov NR 22 TC 22 Z9 22 U1 0 U2 6 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD AUG 27 PY 1999 VL 104 IS D16 BP 19735 EP 19742 DI 10.1029/1999JD900107 PG 8 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 230CY UT WOS:000082235300055 ER PT J AU Cruikshank, DP de Bergh, C Doute, S Geballe, TR Owen, TC Quirico, E Roush, TL Schmitt, B AF Cruikshank, DP de Bergh, C Doute, S Geballe, TR Owen, TC Quirico, E Roush, TL Schmitt, B TI Ethane on Pluto? SO SCIENCE LA English DT Letter C1 NASA, Planetary Syst Branch, Ames Res Ctr, Moffett Field, CA 94035 USA. Observ Paris, Sect Astrophys, F-92195 Meudon, France. Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90095 USA. Gemini Observ, Hilo, HI 96720 USA. Univ Hawaii, Inst Astron, Honolulu, HI 96822 USA. Univ Paris 11, Inst Astrophys Spatiale, F-91405 Orsay, France. CNRS, Lab Planetol Grenoble, F-38402 St Martin Dheres, France. RP Cruikshank, DP (reprint author), NASA, Planetary Syst Branch, Ames Res Ctr, Moffett Field, CA 94035 USA. EM dale@ssa1.arc.nasa.gov; Catherine.deBergh@obspm.fr; sdoute@igpp.ucla.edu; tgeballe@gemini.edu; owen@hubble.ifa.hawaii.edu; troush@mail.arc.nasa.gov; schmitt@glaciog.ujf-grenoble.tr RI Schmitt, Bernard/A-1064-2009; quirico, eric/K-9650-2013 OI Schmitt, Bernard/0000-0002-1230-6627; quirico, eric/0000-0003-2768-0694 NR 7 TC 1 Z9 1 U1 0 U2 1 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD AUG 27 PY 1999 VL 285 IS 5432 BP 1355 EP 1355 PG 1 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 230CD UT WOS:000082233500017 ER PT J AU Zolensky, ME Bodnar, RJ Gibson, EK Nyquist, LE Reese, Y Shih, CY Wiesmann, H AF Zolensky, ME Bodnar, RJ Gibson, EK Nyquist, LE Reese, Y Shih, CY Wiesmann, H TI Asteroidal water within fluid inclusion-bearing halite in an H5 chondrite, Monahans (1998) SO SCIENCE LA English DT Article ID CARBONACEOUS CHONDRITES; AQUEOUS ALTERATION; CONSTRAINTS; MINERALOGY; AGE AB Crystals of halite and sylvite within the Monahans (1998) H5 chondrite contain aqueous fluid inclusions. The fluids are dominantly sodium chloride-potassium chloride brines. but they also contain divalent cations such as iron, magnesium, or calcium. Two possible origins for the brines are indigenous fluids flowing within the asteroid and exogenous fluids delivered into the asteroid surface from a salt-containing icy object. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Virginia Tech, Dept Geol Sci, Blacksburg, VA 24061 USA. Lockheed Martin Space Operat Co, Houston, TX 77058 USA. RP Zolensky, ME (reprint author), NASA, Lyndon B Johnson Space Ctr, Mail Code SN2, Houston, TX 77058 USA. RI Bodnar, Robert/A-1916-2009 NR 29 TC 112 Z9 118 U1 1 U2 20 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD AUG 27 PY 1999 VL 285 IS 5432 BP 1377 EP 1379 DI 10.1126/science.285.5432.1377 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 230CD UT WOS:000082233500035 PM 10464091 ER PT J AU Kriens, BJ Shoemaker, EM Herkenhoff, KE AF Kriens, BJ Shoemaker, EM Herkenhoff, KE TI Geology of the upheaval dome impact structure, southeast Utah SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID SHOCK METAMORPHISM; QUARTZ; BASIN; COMET AB Two vastly different phenomena, impact and salt diapirism, have been proposed for the origin of Upheaval Dome, a spectacular scenic feature in southeast Utah. Detailed geologic mapping and seismic refraction data indicate that the dome originated by collapse of a transient cavity formed by impact. Evidence is as follows: (I)sedimentary strata in the center of the structure are pervasively imbricated by top-toward-the-center thrust faulting and are complexly folded as well; (2) top-toward-the-center normal faults are found at the perimeter of the structure; (3) clastic dikes are widespread; (4) the top of the underlying salt horizon is at least 500 m below the surface at the center of the dome, and there are no exposures of salt or associated rocks of the Paradox Formation in the dome to support the possibility that a salt diapir has ascended through it; and (5) planar microstructures in quartz grains, fan-tailed fracture surfaces (shatter surfaces), and rare shatter cones are present near the center of the structure. We show that the dome formed mainly by centerward motion of rock units along listric faults. Outcrop-scale folding and upturning of beds, especially common in the center, are largely a consequence of this motion. We have also detected some centerward motion of fault-bounded wedges resulting from displacements on subhorizontal faults that conjoin and die out within horizontal bedding near the perimeter of the structure. The observed deformation corresponds to the central uplift and the encircling ring structural depression seen in complex impact craters. C1 US Geol Survey, Flagstaff, AZ 86001 USA. Calif State Univ Dominguez Hills, Dept Earth Sci, Carson, CA 90747 USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. RP Herkenhoff, KE (reprint author), US Geol Survey, 2255 N Gemini Dr, Flagstaff, AZ 86001 USA. NR 55 TC 39 Z9 39 U1 3 U2 12 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 AUG 25 PY 1999 VL 104 IS E8 BP 18867 EP 18887 DI 10.1029/1998JE000587 PG 21 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 229KG UT WOS:000082193300001 ER PT J AU Glaze, LS AF Glaze, LS TI Transport of SO2 by explosive volcanism on Venus SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID PLINIAN ERUPTION COLUMNS; NUMERICAL-MODELS; DYNAMICS; EMISSIVITY; INJECTION; HEIGHTS; EARTH; MARS; ASH AB Observations by the Pioneer Venus orbiter and many different types of analyses have suggested the possibility of contemporary explosive volcanism on Venus. The rise of volcanic eruption plumes on Venus is reexamined using recent improvements in buoyant plume modeling. The first-order model applied to Venus by previous authors features nonphysical discontinuous solutions for all of the model parameters and lacks internal consistency in the formulation of the governing equations. This makes it difficult to assess the validity of the Venus applications and conclusions derived from these models. The model used here contains several improvements including two corrections to the formulation and a change in the criterion for the transition of the plume from the jet region to the buoyancy-driven region. The model used in earlier works assumed a discontinuous transition between these two regions, resulting in an overestimate of the transition height as well as the maximum plume height. The effect of the transition criterion is magnified on Venus! where the continuous solution appears to have very little dependence on initial vent size. In contrast, the discontinuous solution shows a very strong dependence on initial vent size. The continuous solution used here indicates that plumes on Venus become dominated by buoyancy effects almost immediately above the vent. Use of the discontinuous solution, however, suggests that jets up to 10 km above the vent are possible for the boundary conditions considered. The combined effect of using the older mod :I for conditions on Venus is a 5-8% overestimate of the maximum plume height for vent radii ranging from 20 to 250 m. The influence of latitude and elevation are also explored. For large eruptions on Venus, plumes rising in the Northern Highlands would rise much higher than plumes with identical boundary conditions erupted in the equatorial Lowlands. This is due to the greater stability of the upper atmosphere at higher latitudes and the sharp decrease in atmospheric pressure as a function of altitude. To examine the net effect of all the model assumptions and ambient influences, eruptions are simulated for a range of conditions at Maat Mons and compared with results in the literature. These simulations indicate that for small mass fluxes, the new model predicts smaller plumes than the older model. For larger mass fluxes, however, the new model predicts larger plumes than the older model. Because the Maat Mons summit elevation is already more than 9 km above the mean planetary radius, the reduced atmospheric pressure results in a plume with enough buoyancy to more than compensate for all of the model effects. These results continue to support the possibility that explosive eruptions on Venus may be capable of producing plumes that rise buoyantly to heights detected by the Pioneer Venus orbiter. C1 NASA, Goddard Space Flight Ctr, Proxemy Res, Greenbelt, MD 20771 USA. RP Glaze, LS (reprint author), NASA, Goddard Space Flight Ctr, Proxemy Res, Mail Code 921,7335 Hanover Pkwy,Suite C, Greenbelt, MD 20771 USA. RI Glaze, Lori/D-1314-2012 NR 40 TC 13 Z9 13 U1 1 U2 9 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 AUG 25 PY 1999 VL 104 IS E8 BP 18899 EP 18906 DI 10.1029/1998JE000619 PG 8 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 229KG UT WOS:000082193300003 ER PT J AU Weitz, CM Head, JW AF Weitz, CM Head, JW TI Spectral properties of the Marius Hills volcanic complex and implications for the formation of lunar domes and cones SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID STATE IMAGING DATA; MOON; REGION; EMPLACEMENT; CLASSIFICATION; STRATIGRAPHY; DEPOSITS; ERUPTION; GEOLOGY; HISTORY AB We have used multispectral data from the Clementine UV-visible camera to study the volcanic features of the Marius Hills complex and their comparison to other lunar domes and cones. There are several mare units identified in the complex, each with a unique Ti content, as indicated by their 415/750 nm value, The domes in Marius Hills are spectrally identical to the mare plains of the complex, supporting similar compositions. In contrast, most of the volcanic cones. of the complex are lower in reflectance, bluer in color, and have weaker mafic absorptions than the mare and domes. The spectral characteristics of the cones can best be explained by fine-grainad crystallization in the spatter that compose the cones. Other lunar cones, such as Mons Esam in northern Tranquillitatis, have spectral properties similar to those at Marius Hills. The Rima Parry cones and their associated dark mantle deposit appear redder with a stronger mafic absorption than the Marius Hills cones. The cones Isis and Osiris in southern Mare Serenitatis, the domes of Rumker Hills, and several domes in northern Mare Tranquillitatis are spectrally similar to adjacent mare units. The Mairan and Gruithuisen domes in northern Oceanus Procellarum have a feldspathic signature characteristic of highland material although they are redder and brighter than adjacent highland soils. They appear to represent highland material that resembles domes rather than actual mare domes, like those at Marius and Rumker Hills. The diversity of lunar volcanic features can best be explained by differences in accumulation rates and cooling of ejected clasts from various eruption styles. Mare domes may have formed at lower effusion rates, thereby allowing lava to construct small shields with slopes <3 degrees. The steeper domes at Marius Hills require higher viscosities resulting from even lower effusion rates and enhanced crystallization in the magmas during the terminal stages of earlier eruptions that emplaced the mare. Cones like Mons Esam, Rima Parry, Isis, and Osiris are aligned along linear rilles and are interpreted to result from degassing of near-surface dikes. In contrast, the cones of Marius Hills show no linear alignment and may result from strombolian eruptions at the terminal stages of earlier effusive eruptions that emplaced the domes and mare in the complex. C1 CNR, Jet Prop Lab, Pasadena, CA 91109 USA. Brown Univ, Dept Geol Sci, Providence, RI 02912 USA. RP Weitz, CM (reprint author), CNR, Jet Prop Lab, MS 183-335,4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM cweitz@jpl.nasa.gov NR 76 TC 31 Z9 32 U1 0 U2 8 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 AUG 25 PY 1999 VL 104 IS E8 BP 18933 EP 18956 DI 10.1029/1998JE000630 PG 24 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 229KG UT WOS:000082193300006 ER PT J AU Anderson, FS Greeley, R Xu, P Lo, E Blumberg, DG Haberle, RM Murphy, JR AF Anderson, FS Greeley, R Xu, P Lo, E Blumberg, DG Haberle, RM Murphy, JR TI Assessing the Martian surface distribution of aeolian sand using a Mars general circulation model SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID GLOBAL SURVEYOR; SALTATION THRESHOLD; MOJAVE DESERT; KELSO DUNES; DUST STORMS; DEPOSITS; SPECTROMETER; SIMULATIONS; ATMOSPHERE; CALIFORNIA AB A sand transport model using White's [1979] sand flux equation and the Mars general circulation model [Pollack et al., 1990] was developed to understand the erosional sources, transport pathways, and depositional sinks of windblown sand on Mars. An initially uniform distribution of sand (4 mm over the entire surface) is regionally transported based on wind stress, saltation threshold, and percentage of topographic trapping. Results are consistent with the observed polar and Hellespontus dunes and Christensen's [1986] modeled block size distribution, but only for an extremely low saltation threshold (0.024 N/m(2)). Low thresholds generally result in transport of sand-sized particles originating in the northern mid latitudes to the north pole, and transport from the northern lower latitudes to the southern hemisphere, Our results indicate that the polar dune fields could form in 50,000 years, consistent with the active polar dunes and lack of longitudinal dunes observed on the surface of Mars. C1 Arizona State Univ, Dept Geol, Tempe, AZ 85287 USA. Ben Gurion Univ Negev, IL-84105 Beer Sheva, Israel. NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. RP Anderson, FS (reprint author), CALTECH, Jet Prop Lab, M-S 183-501,4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI BLUMBERG, DAN/F-1285-2012 OI BLUMBERG, DAN/0000-0001-9337-1617 NR 57 TC 23 Z9 24 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-PLANET JI J. Geophys. Res.-Planets PD AUG 25 PY 1999 VL 104 IS E8 BP 18991 EP 19002 DI 10.1029/1999JE900024 PG 12 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 229KG UT WOS:000082193300009 ER PT J AU Cyr, KE Sharp, CM Lunine, JI AF Cyr, KE Sharp, CM Lunine, JI TI Effects of the redistribution of water in the solar nebula on nebular chemistry SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID CONDENSATION; ABUNDANCES; SYSTEM; ATMOSPHERES; EQUILIBRIUM; METEORITES; ELEMENTS; RATIOS; CARBON; VAPOR AB We quantify the effects on solar nebula chemistry of variations in the C to O ratio brought on by diffusive and advective redistribution of water vapor. The SOLGASMIX chemical equilibrium code was used to compute abundances of nebular elements and major molecular species, C, N, S and others, for a variety of water-depleted nebular settings produced by the water distribution models, and for low- and high-pressure (10(-5) and 10(-3) atm) nebulae. Both relatively oxidizing and reducing nebular conditions can occur across 0.1-5 AU, varying over time. This variety of conditions may help explain the variation in oxidation state of meteorites. Additionally, abundances of organics increase over what would be expected to form from a solar composition gas. Modest increases occur in a relatively oxidizing nebula assuming a solar C/O ratio of 0.42, while large increases of several orders of magnitude occur in a more reducing nebula with solar C/O of 0.6. The increase in organics in the inner nebula could, have allowed local accretion of organics to the terrestrial planets, and perhaps supplied organics to the Jovian planetesimal formation region and beyond via outward mixing processes. Lastly, nebular water could have been directly supplied to Earth and the other terrestrial planets via icy body drift and scattering. C1 CALTECH, Jet Prop Lab, Pasadena, CA USA. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. Univ Arizona, Steward Observ, Tucson, AZ 85721 USA. RP Cyr, KE (reprint author), NASA, Lyndon B Johnson Space Ctr, Planetary Sci Branch, SN2, Houston, TX 77058 USA. NR 48 TC 16 Z9 16 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD AUG 25 PY 1999 VL 104 IS E8 BP 19003 EP 19014 DI 10.1029/1998JE000617 PG 12 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 229KG UT WOS:000082193300010 ER PT J AU Meador, MAB Johnston, JC Frimer, AA Gilinsky-Sharon, P AF Meador, MAB Johnston, JC Frimer, AA Gilinsky-Sharon, P TI On the oxidative degradation of nadic end-capped polyimides. 3. Synthesis and characterization of model compounds for end-cap degradation products SO MACROMOLECULES LA English DT Article ID POLYMERS AB The oxidative degradation of PMR (for polymerization of monomeric reactants) polyimides at elevated temperatures was followed by cross-polarized magic angle spinning (CP-MAS) NMR. Labeling of selected sites in the polymers with C-13 allowed for direct observation of the transformations arising from oxidation processes. The formation of several degradation products has been proposed to be occurring in the cross-links derived from the nadic end caps on oxidation. Model compounds have been synthesized and characterized by CPMAS NMR with both normal and delayed decoupling to distinguish between protonated and unprotonated carbons. Comparison of these spectra to predicted chemical shifts of proposed products for the aged polymer provides further insight to degradation occurring in the cross-linked moieties. C1 NASA, Glenn Res Ctr, Div Mat, Cleveland, OH 44135 USA. Bar Ilan Univ, Dept Chem, IL-52900 Ramat Gan, Israel. RP Meador, MAB (reprint author), NASA, Glenn Res Ctr, Div Mat, 21000 Brookpk Rd, Cleveland, OH 44135 USA. OI Meador, Mary Ann/0000-0003-2513-7372 NR 10 TC 17 Z9 19 U1 0 U2 1 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0024-9297 J9 MACROMOLECULES JI Macromolecules PD AUG 24 PY 1999 VL 32 IS 17 BP 5532 EP 5538 DI 10.1021/ma990081n PG 7 WC Polymer Science SC Polymer Science GA 229WN UT WOS:000082218900010 ER PT J AU Aydil, ES Maroudas, D Ramalingam, S Marra, DC Hanyaloglu, BF Kessels, WMM Mahalingam, P Walch, SP AF Aydil, ES Maroudas, D Ramalingam, S Marra, DC Hanyaloglu, BF Kessels, WMM Mahalingam, P Walch, SP TI Combined experimental and theoretical study of the radical-surface interactions during plasma-enhanced chemical vapor deposition of Si films from silane/hydrogen discharges. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 Univ Calif Santa Barbara, Dept Chem Engn, Santa Barbara, CA 93106 USA. Eindhoven Univ Technol, Dept Appl Phys, NL-5600 MB Eindhoven, Netherlands. NASA, Ames Res Ctr, Thermosci Inst, 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 AUG 22 PY 1999 VL 218 MA 195-COLL BP U455 EP U456 PN 1 PG 2 WC Chemistry, Multidisciplinary SC Chemistry GA 226QZ UT WOS:000082033901388 ER PT J AU Gariepy, CA Eby, RK Meador, MA AF Gariepy, CA Eby, RK Meador, MA TI Approach to processable PMR 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, Polymers Branch, 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 AUG 22 PY 1999 VL 218 MA 75-POLY BP U420 EP U420 PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 226RA UT WOS:000082034001219 ER PT J AU Geiger, CL Clausen, CA Prasad, V Pettey, L Ofori, E Quinn, J AF Geiger, CL Clausen, CA Prasad, V Pettey, L Ofori, E Quinn, J TI Study of three variables involved in the electrokinetic remediation of lead-contaminated soil: Flow rate ano concentration of conditioning fluid and voltage. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 Univ Cent Florida, Dept Chem, Orlando, FL 32816 USA. NASA, Kennedy Space Ctr, FL 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 AUG 22 PY 1999 VL 218 MA 109-ENVR BP U575 EP U575 PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 226QZ UT WOS:000082033901748 ER PT J AU Guidry, JL Fowler, PS Clausen, CA Allen, N AF Guidry, JL Fowler, PS Clausen, CA Allen, N TI Novel single-unit analyzers for nonvolatile residue test of space flight hardware. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 Florida State Univ, Dept Chem, Tallahassee, FL 32306 USA. Univ Cent Florida, Dept Chem, Orlando, FL 32816 USA. NASA, Kennedy Space Ctr, Kennedy Space Ctr, FL 32889 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 AUG 22 PY 1999 VL 218 MA 88-ANYL BP U154 EP U154 PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 226QZ UT WOS:000082033900405 ER PT J AU Hack, MD Jasper, AW Volobuev, YL Topaler, MS Schwenke, DW Truhlar, DG AF Hack, MD Jasper, AW Volobuev, YL Topaler, MS Schwenke, DW Truhlar, DG TI Comparison of semiclassical trajectory methods with quantum mechanics for a variety of electronically nonadiabatic systems. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 Univ Minnesota, Dept Chem, Minneapolis, MN 55455 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RI Jasper, Ahren/A-5292-2011; schwenke, david/I-3564-2013; Truhlar, Donald/G-7076-2015 OI Truhlar, Donald/0000-0002-7742-7294 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 AUG 22 PY 1999 VL 218 MA 64-PHYS BP U292 EP U292 PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 226RA UT WOS:000082034000797 ER PT J AU Kojiro, DR Carle, GC Stratton, DM Valentin, JR AF Kojiro, DR Carle, GC Stratton, DM Valentin, JR TI Sample acquisition techniques for exobiology flight experiments. 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. SETI Inst, Mt View, CA 94043 USA. Canada Coll, Redwood City, CA 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 AUG 22 PY 1999 VL 218 MA 49-ANYL BP U142 EP U142 PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 226QZ UT WOS:000082033900368 ER PT J AU Nguyen, BN Eby, RK Meador, MA AF Nguyen, BN Eby, RK Meador, MA TI Development of processable pmr-type polyimides with star-branched structures. 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, Polymers Branch, Cleveland, OH 44132 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 AUG 22 PY 1999 VL 218 MA 76-POLY BP U421 EP U421 PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 226RA UT WOS:000082034001220 ER PT J AU Park, C Lowther, SE Smith, JG AF Park, C Lowther, SE Smith, JG TI Organic-inorganic hybrids using novel phenylethynyl imide silanes. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA, Langley Res Ctr, Composites & Polymers Branch, Larc, Hampton, VA 23681 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 AUG 22 PY 1999 VL 218 MA 130-PMSE BP U639 EP U639 PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 226RA UT WOS:000082034001926 ER PT J AU Pilcher, CB AF Pilcher, CB TI Future of NASA's space science program. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA, Off Space Sci, Washington, DC 20546 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 AUG 22 PY 1999 VL 218 MA 208-NUCL BP U1090 EP U1090 PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 226QZ UT WOS:000082033903273 ER PT J AU Rao, MN AF Rao, MN TI Solar Cosmic-Ray (SEP) interactions in regolith breccias and carbonaceous chondrites. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 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 AUG 22 PY 1999 VL 218 MA 173-NUCL BP U1079 EP U1079 PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 226QZ UT WOS:000082033903238 ER PT J AU Srivastava, D AF Srivastava, D TI Generalized tight-binding molecular dynamics simulations of CxByNz nanotube-based electronics and electromechanics. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA, Ames Res Ctr, MRJ, Computat Nanotechnol NAS, 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 AUG 22 PY 1999 VL 218 MA 149-COMP BP U519 EP U519 PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 226QZ UT WOS:000082033901584 ER PT J AU Wood, GM Farmer, FH AF Wood, GM Farmer, FH TI STC catalysts, Inc: An example of how technology transfer can work for you. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 STC Catalysts Inc, Hampton, VA 23666 USA. NASA, Technol Applicat Grp, 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 AUG 22 PY 1999 VL 218 MA 19-SCHB BP U698 EP U698 PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 226RA UT WOS:000082034002127 ER PT J AU Barlow, S Henling, LM Day, MW Marder, SR AF Barlow, S Henling, LM Day, MW Marder, SR TI Effect of the end-groups upon delocalisation in polymethines: the first crystallographically characterised bond-alternated cyanine SO CHEMICAL COMMUNICATIONS LA English DT Article ID MOLECULAR-STRUCTURE; CRYSTAL-STRUCTURE; COMPLEXES; CATIONS; DYE AB The reorganisation energy associated with the end groups may be used to influence the localisation behaviour of cyanines; thus, the 1,3-bis(ruthenocenyl)allylium cation is markedly unsymmetrical in the crystal structure of its hexafluorophosphate salt, with the positive charge localised on one ruthenium, whereas the analogous iron species is delocalised and has approximate C-5 symmetry. C1 CALTECH, Beckman Inst, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Arizona, Dept Chem, Tucson, AZ 85721 USA. RP Marder, SR (reprint author), CALTECH, Beckman Inst, 139-74, Pasadena, CA 91125 USA. RI Barlow, Stephen/E-9754-2010 NR 21 TC 13 Z9 13 U1 1 U2 4 PU ROYAL SOC CHEMISTRY PI CAMBRIDGE PA THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD,, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND SN 1359-7345 J9 CHEM COMMUN JI Chem. Commun. PD AUG 21 PY 1999 IS 16 BP 1567 EP 1568 DI 10.1039/a903868j PG 2 WC Chemistry, Multidisciplinary SC Chemistry GA 222BT UT WOS:000081764000059 ER PT J AU Georgantopoulos, I Papadakis, I Warwick, RS Smith, DA Stewart, GC Griffiths, RG AF Georgantopoulos, I Papadakis, I Warwick, RS Smith, DA Stewart, GC Griffiths, RG TI RXTE monitoring observations of Markarian 3 SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE galaxies : active; galaxies : individual : Markarian 3; galaxies : Seyfert; X-rays : galaxies ID ACTIVE GALACTIC NUCLEI; X-RAY REFLECTION; SEYFERT-GALAXIES; COLD MATTER; SPECTRUM AB We present Rossi X-ray Timing Explorer monitoring observations of the type 2 Seyfert galaxy Markarian 3 spanning a 200-d period during which time the source flux varied by a factor of similar to 2 in the 4-20keV bandpass, In broad agreement with earlier Ginga results, the average spectrum can be represented in terms of a simple spectral model consisting of a very hard power-law continuum (Gamma approximate to 1.1) modified below similar to 6 keV by a high absorbing column (N-H similar to 6 x 10(23) cm(-2)) together with a high equivalent width Fe K emission feature at 6.4 keV. The abnormally flat spectral index is probably the signature of a strong reflection component and we consider two models incorporating such emission. In the first the reflected signal suffers the same absorption as the intrinsic continuum, whereas in the second the reflection is treated as an unabsorbed spectral component, In the former case, we require a very strong reflection signal (R less than or similar to 3) in order to match the data; in addition variability of both the intrinsic power-law and the reflection components is required. The unabsorbed reflection model requires a somewhat higher line-of-sight column density to the nuclear source (similar to 10(24) cm(-2)), but in this case the reflected signal remains constant whilst the level of the intrinsic continuum varies. The latter description is consistent with the reflection originating from the illuminated far inner wall of a molecular torus, the near side of which screens our direct view of the central continuum source. C1 Natl Observ Athens, Astron Inst, Athens 15236, Greece. Univ Crete, Dept Phys, Heraklion, Greece. Univ Leicester, Dept Phys & Astron, Leicester LE1 7RH, Leics, England. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. RP Georgantopoulos, I (reprint author), Natl Observ Athens, Astron Inst, Athens 15236, Greece. RI Papadakis, Iossif/C-3235-2011; Georgantopoulos, Ioannis/L-3687-2013 NR 22 TC 13 Z9 13 U1 0 U2 0 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD AUG 21 PY 1999 VL 307 IS 4 BP 815 EP 820 DI 10.1046/j.1365-8711.1999.02658.x PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 229WM UT WOS:000082218800013 ER PT J AU Barstow, MA Hubeny, I Holberg, JB AF Barstow, MA Hubeny, I Holberg, JB TI Evidence for the stratification of Fe in the photosphere of G191-B2B SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE stars : abundances; stars : atmospheres; stars : individual : G191-B2B; white dwarfs; ultraviolet : stars; X-rays : stars ID DA WHITE-DWARFS; MODEL STELLAR ATMOSPHERES; RADIATIVE LEVITATION; EXTREME-ULTRAVIOLET; INTERSTELLAR-MEDIUM; HOT; HELIUM; ELEMENTS; ROSAT; IRON AB The presence of heavy elements in the atmospheres of the hottest H-rich DA white dwarfs has been the subject of considerable interest. While theoretical calculations can demonstrate that radiative forces, counteracting the effects of gravitational settling, can explain the detections of individual species, the predicted abundances do not accord well with observation. However, accurate abundance measurements can only be based on a thorough understanding of the physical structure of the white dwarf photospheres, which has proved elusive. Recently, the availability of new non-local thermodynamic equilibrium model atmospheres with improved atomic data has allowed self-consistent analysis of the extreme ultraviolet (EUV), far UV and optical spectra of the prototypical object G191-B2B, Even so, the predicted and observed stellar fluxes remain in serious disagreement at the shortest wavelengths (below approximate to 190 Angstrom), while the inferred abundances remain largely unaltered. We show here that the complete spectrum of G191-B2B can be explained by a model atmosphere where Fe is stratified, with increasing abundance at greater depth. This abundance profile may explain the difficulties in matching observed photospheric abundances, usually obtained by analyses using homogeneous model atmospheres, to the detailed radiative levitation predictions, particularly as the latter are only strictly valid for regions deeper than where the EUV/far UV lines and continua are formed. Furthermore, the relative depletion of Fe in the outer layers of the atmosphere may be evidence for radiatively driven mass-loss in G191-B2B. C1 Univ Leicester, Dept Phys & Astron, Leicester LE1 7RH, Leics, England. NASA, Astron & Solar Phys Lab, GSFC, Greenbelt, MD 20711 USA. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. RP Barstow, MA (reprint author), Univ Leicester, Dept Phys & Astron, Univ Rd, Leicester LE1 7RH, Leics, England. EM mab@star.le.ac.uk NR 36 TC 33 Z9 33 U1 0 U2 0 PU WILEY-BLACKWELL PI MALDEN PA COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD AUG 21 PY 1999 VL 307 IS 4 BP 884 EP 894 DI 10.1046/j.1365-8711.1999.02661.x PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 229WM UT WOS:000082218800020 ER PT J AU Halpern, JP Turner, TJ George, IM AF Halpern, JP Turner, TJ George, IM TI Are there any type 2 QSOs? The case of AXJ0341.4-4453 SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE galaxies : active; galaxies : individual : AXJ0341.4-4453; quasars : general; X-rays : general ID X-RAY; SPECTROSCOPY; GALAXIES AB The X-ray source AXJ0341.4-4453 was described by Boyle et al. as a Type 2 active galactic nucleus (AGN) at z = 0.672 based on the absence of broad emission lines in the observed wavelength range 4000-7000 Angstrom. We obtained a new spectrum of AXJ0341.4-4453 extending to 9600 Angstrom which reveals broad Balmer lines and other characteristics of Seyfert 1 galaxies. The FWHM of broad H beta is at least 1600 kms(-1), while [O III] lambda 5007 has FWHM = 730 km s(-1). The flux ratio [O III] lambda 5007/H beta = 1. Thus, AXJ0341.4-4453 is by definition a narrow-line Seyfert 1 galaxy, or perhaps a moderately reddened Seyfert 1 galaxy, but it is not a Type 2 QSO, Although examples of the latter have long been sought, particularly in connection with the problem of the X-ray background, there is still virtually no evidence for the existence of any Type 2 QSO among X-ray selected samples. C1 Columbia Univ, Columbia Astrophys Lab, New York, NY 10027 USA. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. Univ Space Res Assoc, Columbia, MD 21044 USA. RP Halpern, JP (reprint author), Columbia Univ, Columbia Astrophys Lab, 550 W 120th St, New York, NY 10027 USA. NR 19 TC 32 Z9 32 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 AUG 21 PY 1999 VL 307 IS 4 BP L47 EP L50 DI 10.1046/j.1365-8711.1999.02874.x PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 229WM UT WOS:000082218800004 ER PT J AU Peskov, V Silin, E Sokolova, T Radionov, I AF Peskov, V Silin, E Sokolova, T Radionov, I TI First attempts to combine capillary tubes with photocathodes SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article; Proceedings Paper CT 3rd International Workshop on Ring Imaging Cherenkov Detectors (RICH98) CY NOV 15-20, 1998 CL EN GEDI, ISRAEL SP Israel Sci Fdn, Weizmann Inst Sci ID GASEOUS DETECTORS; GAS AB We describe our efforts to combine glass capillary plates, operating as a gas amplification structure at similar to 1 atm, with photocathodes sensitive to visible light. Such capillary tubes are a by-product of the manufacture of Microchannel Plates and are commercially available. Preliminary tests indicate that gas gains >10(3) could be achieved without photon feedback. With two capillary plates in tandem (double-step multiplication) overall gains up to 10(5) were possible at counting rate <100 Hz/mm(2). This approach may open new possibilities for detection of visible photons by gaseous detectors. Potential advantages are: high gains, large sensitive area, high granularity, and insensitivity to magnetic fields. (C) 1999 Elsevier Science B.V. All rights reserved. C1 NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Russian Acad Sci, Inst Appl Mech, Moscow, Russia. Univ Friendship Nat, Moscow, Russia. Reagent Res & Dev Ctr, Moscow, Russia. RP Peskov, V (reprint author), Royal Inst Technol, Phys Dept Frescati, Frescativagen 24, S-10405 Stockholm, Sweden. NR 30 TC 51 Z9 51 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-9002 J9 NUCL INSTRUM METH A JI Nucl. Instrum. Methods Phys. Res. Sect. A-Accel. Spectrom. Dect. Assoc. Equip. PD AUG 21 PY 1999 VL 433 IS 1-2 BP 492 EP 501 DI 10.1016/S0168-9002(99)00346-0 PG 10 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 229MW UT WOS:000082199200071 ER PT J AU Fonte, P Ferreira-Marques, R Peskov, V Policarpo, A AF Fonte, P Ferreira-Marques, R Peskov, V Policarpo, A TI Single-electron pulse-height spectra in thin-gap parallel-plate chambers SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article; Proceedings Paper CT 3rd International Workshop on Ring Imaging Cherenkov Detectors (RICH98) CY NOV 15-20, 1998 CL EN GEDI, ISRAEL SP Israel Sci Fdn, Weizmann Inst Sci DE single-electron pulse-height spectra; parallel-plate chambers ID BREAKDOWN AB Single-electron pulse-height spectra were measured in 0.6 and 1.2 mm parallel-plate chambers developed for the TOF system of the ALICE/LHC-HI experiment. Mixtures of Ar with ethane, isobutane, and SF, were studied. The observed spectrum shows a clear peak for all gases, suggesting efficient single-electron detection in thin parallel-plate structures. The pulse-height spectrum can be described by the weighted sum of an exponential and a Polya distribution, the Polya contribution becoming more important at higher gains. Additionally, it was found that the maximum gain, above 10(6), is limited by the appearance of streamers and depends weakly on the gas composition. The suitability of each mixture for single-electron detection is also quantitatively assessed. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Inst Super Engn Coimbra, Coimbra, Portugal. Univ Coimbra, Dept Fis, P-3000 Coimbra, Portugal. LIP Lab Instrumentacao & Fis Expt Particulas, Coimbra, Portugal. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Fonte, P (reprint author), CERN, European Lab Particle Phys, CH-1211 Geneva 23, Switzerland. RI Fonte, Paulo/B-1842-2008; OI Fonte, Paulo/0000-0002-2275-9099; Marques, Rui/0000-0003-3549-8198 NR 8 TC 7 Z9 7 U1 1 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 AUG 21 PY 1999 VL 433 IS 1-2 BP 513 EP 517 DI 10.1016/S0168-9002(99)00309-5 PG 5 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 229MW UT WOS:000082199200074 ER PT J AU Crenshaw, DM Kraemer, SB AF Crenshaw, DM Kraemer, SB TI Intrinsic absorption lines in the Seyfert 1 galaxy NGC 5548: Ultraviolet echelle spectra from the space telescope imaging spectrograph SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : individual (NGC 5548); galaxies : kinematics and dynamics; galaxies : Seyfert; ultraviolet : galaxies ID C-IV; NGC-5548; MODELS AB We present the first observations of a Seyfert galaxy with the echelle gratings on the Space Telescope Imaging Spectrograph (STIS), which provide high-resolution (lambda/Delta lambda approximate to 40,000) coverage of the intrinsic UV absorption lines in NGC 5548. We confirm the presence of five kinematic components of absorption in Ly alpha, C IV, and N V at radial velocities of -160 to -1060 km s(-1) with respect to the emission lines, and find an additional Lya component near the systemic velocity, which probably arises in the interstellar medium of the host galaxy. Compared to Goddard High-Resolution Spectrograph spectra of the N V and C IV absorption obtained similar to 2 yr earlier, the kinematic components have not changed in radial velocity, but the ionic column densities for two components have decreased. We attribute these variations to changes in the total column of gas, but for one component we cannot rule out changes in the ionization of the gas. We have calculated photoionization models to match the UV column densities from each of the five components associated with the nucleus. In four of the components, the ionization parameters (U = 0.15-0.80) and effective hydrogen column densities (N-eff = 6.0 x 10(18) to 2.8 x 10(20) cm(-2)) cannot produce the O VII and O VIII absorption edges seen in the X-ray-warm absorber. The remaining component is more highly ionized (U = 2.4, N-eff = 6.5 x 10(21) cm(-2)), and our model matches the previously observed X-ray absorption columns. This component is therefore likely to be responsible for the X-ray-warm absorber. It also has the highest outflow velocity and showed the largest variations in column density. 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, Code 681, Greenbelt, MD 20771 USA. NR 17 TC 58 Z9 58 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 AUG 20 PY 1999 VL 521 IS 2 BP 572 EP 576 DI 10.1086/307586 PN 1 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 226JX UT WOS:000082017800010 ER PT J AU Drake, JJ Swartz, DA Beiersdorfer, P Brown, GV Kahn, SM AF Drake, JJ Swartz, DA Beiersdorfer, P Brown, GV Kahn, SM TI On photospheric fluorescence and the nature of the 17.62 angstrom feature in solar X-ray spectra SO ASTROPHYSICAL JOURNAL LA English DT Article DE atomic processes; line : formation; line : identification; Sun : corona; Sun : X-rays, gamma rays ID PHOTOIONIZATION CROSS-SECTIONS; ABUNDANCE; FLARE; IRON; SPECTROMETER; SUN AB The identification of the emission-line feature at 17.62 Angstrom, in solar X-ray spectra is reexamined. Using a Monte Carlo technique, we compute a realistic theoretical upper limit to the observed Fe L alpha photospheric fluorescent line strength caused by irradiation from an overlying corona. These calculations demonstrate that the photospheric Fe L alpha characteristic line is much too weak to account for the observed 17.62 Angstrom, line flux. Instead, we identify this line with the configuration interaction 2s(2)2p(4)3p P-2(3/2)-2s2p(6) S-2(1/2) transition in Fe XVIII seen in Electron Beam Ion Trap spectra and predicted in earlier theoretical work on the Fe XVIII X-ray spectrum. This line should be easily resolved and detected in stellar coronae by the spectrographs on the upcoming Chandra X-ray Observatory, and X-ray Multi-mirror Mission. C1 Harvard Smithsonian Ctr Astrophys, Chandra Xray Ctr, Cambridge, MA 02138 USA. NASA, George C Marshall Space Flight Ctr, Univ Space Res Assoc, Huntsville, AL 35812 USA. Lawrence Livermore Natl Lab, Livermore, CA 94551 USA. Columbia Univ, Dept Phys, New York, NY 10027 USA. Columbia Univ, Columbia Astrophys Lab, New York, NY 10027 USA. RP Harvard Smithsonian Ctr Astrophys, Chandra Xray Ctr, MS-3,60 Garden St, Cambridge, MA 02138 USA. EM jdrake@cfa.harvard.edu; swartz@avalon.msfc.nasa.gov; beiersdorfer@llnl.gov; brown86@llnl.gov; skahn@astro.columbia.edu NR 28 TC 19 Z9 21 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 AUG 20 PY 1999 VL 521 IS 2 BP 839 EP 843 DI 10.1086/307593 PN 1 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 226JX UT WOS:000082017800035 ER PT J AU Cadavid, AC Lawrence, JK Ruzmaikin, AA AF Cadavid, AC Lawrence, JK Ruzmaikin, AA TI Anomalous diffusion of solar magnetic elements SO ASTROPHYSICAL JOURNAL LA English DT Article DE diffusion; Sun : granulation; Sun : magnetic fields ID PERCOLATION THEORY; LARGE-SCALE; SURFACE; GEOMETRY; PATTERNS; MOTION; MODELS; FIELD; PLAGE; FLOW AB The diffusion properties of photospheric bright points associated with magnetic elements (magnetic bright points) in the granulation network are analyzed. We find that the transport is subdiffusive for times less than 20 minutes but normal for times larger than 25 minutes. The subdiffusive transport is caused by the walkers being trapped at stagnation points in the intercellular pattern. We find that the distribution of waiting times at the trap sites obeys a truncated Levy type (power-law) distribution. The fractal dimension of the pattern of sites available to the random walk is less than 2 for the subdiffusive range and tends to 2 in the normal diffusion range. We show how the continuous time random walk formalism can give an analytical explanation of the observations. We simulate this random walk by using a version of a phenomenological model of renewing cells introduced originally for supergranules by Simon, Title, & Weiss. We find that the traps that cause the subdiffusive transport arise when the renewed convection cell pattern is neither fixed nor totally uncorrelated from the old pattern, as required in Leighton's model, but in some intermediate state between these extremes. C1 Calif State Univ Northridge, Dept Phys & Astron, Northridge, CA 91330 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Cadavid, AC (reprint author), Calif State Univ Northridge, Dept Phys & Astron, Northridge, CA 91330 USA. NR 32 TC 48 Z9 49 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 AUG 20 PY 1999 VL 521 IS 2 BP 844 EP 850 DI 10.1086/307573 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 226JX UT WOS:000082017800036 ER PT J AU Frieman, JA Gaztanaga, E AF Frieman, JA Gaztanaga, E TI The projected three-point correlation function: Theory and observations SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmology : observations; cosmology : theory; large-scale structure of universe; methods : analytical; methods : numerical ID 3-POINT CORRELATION-FUNCTION; LARGE-SCALE STRUCTURE; APM GALAXY SURVEY; GAUSSIAN INITIAL CONDITIONS; HIGHER-ORDER STATISTICS; SHANE-WIRTANEN CATALOG; QUASI-LINEAR REGIME; POWER SPECTRUM; COSMOLOGICAL PERTURBATIONS; GRAVITATIONAL-INSTABILITY AB We report results for the angular three-point galaxy correlation function in the APM Galaxy Survey and compare them with theoretical expectations. For the first time, these measurements extend to sufficiently large scales to probe the weakly nonlinear regime. On large scales, the results are in good agreement with the predictions of nonlinear cosmological perturbation theory for a model with initially Gaussian fluctuations and linear power spectrum P(k) consistent with that inferred from the APM survey. These results reinforce the conclusion that large-scale structure is driven by nonlinear gravitational instability and that APM galaxies are relatively unbiased tracers of the mass on large scales; they also provide stringent constraints upon models with non-Gaussian initial conditions and strongly exclude the standard cold dark matter model. C1 NASA, Fermilab Astrophys Ctr, Fermi Natl Accelerator Lab, Batavia, IL 60510 USA. Univ Chicago, Dept Astron & Astrophys, Chicago, IL 60637 USA. CSIC, Inst Estudis Espacials Catalunya, IEEC, Barcelona 08034, Spain. RP Frieman, JA (reprint author), NASA, Fermilab Astrophys Ctr, Fermi Natl Accelerator Lab, POB 500, Batavia, IL 60510 USA. NR 38 TC 56 Z9 58 U1 1 U2 3 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 AUG 20 PY 1999 VL 521 IS 2 BP L83 EP L86 DI 10.1086/312195 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 226KA UT WOS:000082018100002 ER PT J AU Shrader, CR Titarchuk, L AF Shrader, CR Titarchuk, L TI Mass determination of black holes in LMC X-1 and Nova Muscae 1991 from their high-energy spectra SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; black hole physics; radiation mechanisms : nonthermal relativity; stars : individual (LMC X-1, Nova Muscae 1991) ID ACCRETION DISKS; EVOLUTION AB We offer a brief description of the bulk motion Comptonization (BMC) model for accretion onto black holes, illustrated by its application to observational data for LMC X-l and Nova Muscae 1991. We then extract some physical parameters of these systems from observables within the context of the BMC model, drawing from results on GRO J1655-40, for which we presented extensive analysis previously. We derive estimates of the mass, (16 +/- 1) M. x [0.5/ cos (i)](1/2), and mass accretion rate in the disk in Eddington units ((m) over dot (d) similar or equal to 2) for LMC X-l and (24 +/- 1) M. x [0.5/ cos(i)](1/2)d(5.5) and ((m) over dot (d) similar or equal to 3) for Nova Muscae 1991, where cos(i) and d(5.5) are the inclination angle cosine and distance in 5.5 kpc units, respectively. Differences between these estimates and previous estimates based on dynamical studies are discussed. It is further shown that the disk inner radius increases with the high-to-low-state transition in Nova Muscae 1991. Specifically, our analysis suggests that the inner disk radius increases to r(in) similar or equal to 17 Scwarzschild radii as the transition to the low-hard state occurs. C1 Univ Space Res Assoc, Lanham, MD 20703 USA. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Shrader, CR (reprint author), Univ Space Res Assoc, Lanham, MD 20703 USA. NR 23 TC 36 Z9 36 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 AUG 20 PY 1999 VL 521 IS 2 BP L121 EP L124 DI 10.1086/312194 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 226KA UT WOS:000082018100011 ER PT J AU Perrin, A Rinsland, CP Goldman, A AF Perrin, A Rinsland, CP Goldman, A TI Spectral parameters for the nu(6) region of HCOOH and its measurement in the infrared tropospheric spectrum SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID FORMIC-ACID; SPECTROSCOPY; BAND AB New spectral parameters (line positions and intensities) have been generated for the nu(6) band of HCOOH, which agree well with 0.002 cm(-1) resolution infrared laboratory spectra. The line positions were derived from previously published spectroscopic constants [Bumgarner et al., 1988]. New relative intensities were derived from the analysis of A type and B type transitions. The new line parameters allow improved quantitative analysis of atmospheric spectra from the 1105 cm(-1) Q branch, provided that the previously neglected HDO strong tropospheric absorption in this region is taken into account. C1 Univ Paris 11, Photophys Mol Lab, F-91405 Orsay, France. Univ Denver, Dept Phys, Denver, CO 80208 USA. NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. RP Perrin, A (reprint author), Univ Paris 11, Photophys Mol Lab, Bat 210, F-91405 Orsay, France. EM goldman@du.edu NR 26 TC 21 Z9 21 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 AUG 20 PY 1999 VL 104 IS D15 BP 18661 EP 18666 DI 10.1029/1999JD900358 PG 6 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 228GJ UT WOS:000082128500012 ER PT J AU Rinsland, CP Goldman, A Murcray, FJ Stephen, TM Pougatchev, NS Fishman, J David, SJ Blatherwick, RD Novelli, PC Jones, NB Connor, BJ AF Rinsland, CP Goldman, A Murcray, FJ Stephen, TM Pougatchev, NS Fishman, J David, SJ Blatherwick, RD Novelli, PC Jones, NB Connor, BJ TI Infrared solar spectroscopic measurements of free tropospheric CO, C2H6, and HCN above Mauna Loa, Hawaii: Seasonal variations and evidence for enhanced emissions from the Southeast Asian tropical fires of 1997-1998 SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Review ID VERTICAL COLUMN ABUNDANCES; CARBON-MONOXIDE; ATMOSPHERIC GASES; HYDROGEN-CYANIDE; TRACE GASES; KITT PEAK; OZONE; ETHANE; SCALE; DISTRIBUTIONS AB High spectral resolution (0.003 cm(-1)) infrared solar absorption measurements of CO, C2H6, and HCN have been recorded at the Network for the Detection of Stratospheric Change station on Mauna Loa, Hawaii, (19.5 degrees N, 155.6 degrees W, altitude 3.4 km). The observations were obtained on over 250 days between August 1995 and February 1998. Column measurements are reported for the 3.4-16 km altitude region, which corresponds approximately to the free troposphere above the station. average CO mixing ratios computed for this layer have been compared with flask sampling CO measurements obtained in situ at the station during the same time period. Both show asymmetrical seasonal cycles superimposed on significant variability. The first 2 years of observations exhibit a broad January-April maximum and a sharper CO minimum during late summer. The C2H6 and CO 3.4-16 km columns were highly correlated throughout the observing period with the C2H6/CO slope intermediate between higher and lower values derived from similar infrared spectroscopic measurements at 32 degrees N and 45 degrees S latitude, respectively. Variable enhancements in CO, C2H6, and particularly HCN were observed beginning in about September 1997. The maximum HCN free tropospheric monthly mean column observed in November 1997 corresponds to an average 3.4-16 fim mixing ratio of 0.7 ppbv (1 ppbv = 10(-9) per unit volume), more than a factor of 3 above the background level. The HCN enhancements continued through the end of the observational series. Back-trajectory calculations suggest that the emissions originated at low northern latitudes in southeast Asia. Surface CO mixing ratios and the C2H6 tropospheric columns measured during the same time also showed anomalous autumn 1997 maxima. The intense and widespread tropical wild fires that burned during the strong El Nino warm phase of 1997-1998 are the likely source of the elevated emission products. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Univ Denver, Dept Phys, Denver, CO 80208 USA. NIWA Climate, Lauder 9182, New Zealand. NOAA, Climate Monitoring & Diagnost Lab, Boulder, CO 80303 USA. Christopher Newport Univ, Dept Phys, Newport News, VA 23606 USA. RP Rinsland, CP (reprint author), NASA, Langley Res Ctr, Mail Stop 401A, Hampton, VA 23681 USA. RI Jones, Nicholas/G-5575-2011 OI Jones, Nicholas/0000-0002-0111-2368 NR 70 TC 60 Z9 60 U1 2 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 AUG 20 PY 1999 VL 104 IS D15 BP 18667 EP 18680 DI 10.1029/1999JD900366 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 228GJ UT WOS:000082128500013 ER PT J AU Khattatov, BV Gille, JC Lyjak, LV Brasseur, GP Dvortsov, VL Roche, AE Waters, JW AF Khattatov, BV Gille, JC Lyjak, LV Brasseur, GP Dvortsov, VL Roche, AE Waters, JW TI Assimilation of photochemically active species and a case analysis of UARS data SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID VARIATIONAL DATA ASSIMILATION; WEATHER-PREDICTION; SATELLITE; VORTICITY; ADJOINT; MODELS; RATES AB We present a short overview of applications of estimation theory in atmospheric chemistry and discuss some common methods of gridding and mapping of irregular satellite observations of chemical constituents. It is shown that these methods are unable to produce truly synoptic maps of short-lived photochemically active species due to insufficient temporal and spatial density of satellite observations. The only way to overcome this limitation is to supplement observations with prior independent information given, for instance, by atmospheric numerical models and/or climatologies. Objective approaches to combining such prior information with observations are commonly referred to as data assimilation. Mathematical basis of data assimilation known as optimal estimation equations is presented following Lorenc [1986]. Two particular techniques of data assimilation, the variational method and the extended Kalman filter, are briefly described, and their applications to time-dependent numerical photochemical models are discussed. We investigate validity of the linear approximation which is utilized in both methods, present time evolution of the linearization and covariance matrices, and discuss some of their properties. On the basis of ideas of Fisher and Lary [1995] we then employ a trajectory model and a photochemical box model for assimilation and mapping of the Upper Atmosphere Research Satellite (UARS) measurements of chemical species. The assimilation is performed using the variational technique and the extended Kalman filter, and results of bo th methods are presented and discussed. C1 Natl Ctr Atmospher Res, Boulder, CO 80307 USA. NOAA, Aeron Lab, Boulder, CO 80303 USA. Lockheed Res Lab, Palo Alto, CA 94304 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Colorado, Cooperat Inst Res Environm Sci, Boulder, CO 80309 USA. RP Khattatov, BV (reprint author), Natl Ctr Atmospher Res, POB 3000, Boulder, CO 80307 USA. EM boris@ucar.edu NR 28 TC 56 Z9 58 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 AUG 20 PY 1999 VL 104 IS D15 BP 18715 EP 18737 DI 10.1029/1999JD900225 PG 23 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 228GJ UT WOS:000082128500017 ER PT J AU Douglass, AR Kawa, SR AF Douglass, AR Kawa, SR TI Contrast between 1992 and 1997 high-latitude spring Halogen Occultation Experiment observations of lower stratospheric HCl SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Review ID ARCTIC POLAR VORTEX; ETALON SPECTROMETER CLAES; CHEMICAL OZONE DEPLETION; INTERHEMISPHERIC DIFFERENCES; 3-DIMENSIONAL SIMULATION; REACTIVE NITROGEN; WINTER; CHLORINE; UARS; HNO3 AB HCl measurements from the Halogen Occultation Experiment (HALOE) in the northern hemisphere during mid-May 1997 revealed vortex fragments in which the chlorine reservoir partitioning was strongly pushed toward HCl (similar to 90% HCl, similar to 10% ClONO2), similar to partitioning previously observed in the Antarctic vortex region. In contrast, observations of ClONO2 and HCl in the northern polar spring, 1992, and in other years, show these species established the balance typical for gas phase photochemical reactions in this region (similar to 60% HCl, similar to 40% ClONO2). Annually, chlorine reservoirs in the winter lower stratosphere polar vortex are converted to chlorine radicals via heterogeneous reactions on particle surfaces at very cold temperatures (less than about 200 K). As temperatures warm in spring, the heterogeneous processes become insignificant compared with gas phase reactions, and the chlorine reservoirs are reformed. Measurements through the northern winter/spring in 1992 show rapid formation of ClONO2, followed by steady loss of ClONO2 and increasing HCl. Although ClONO2 measurements are not available for 1997, the HCl increase in 1997 is observed to be much more rapid, and the eventual HCl mixing ratio is about 50% greater than that of 1992. The observations are examined through comparison with the Goddard three-dimensional chemistry and transport model. This model utilizes winds and temperatures from the Goddard Earth Observing System Data Assimilation System and a complete integration scheme for stratospheric photochemistry. Analysis of the evolution of HCl and ClONO2 shows that the observed difference in the overall rate of HCl formation is explained by the sensitivity of the gas-phase chemistry to the ozone mixing ratio and the temperature. The results show that the model accurately simulates HCl and ClONO2 evolution during these two winters. Model validity is further supported by comparisons with O-3 and reactive nitrogen species NO and NO2. This analysis provides a sensitive test of the lower stratospheric chlorine photochemistry, particularly because the analysis considers constituent evolution at a time when the HCl and ClONO2 are far from a photochemical stationary state. C1 NASA, Goddard Space Flight Ctr, Atmospher Chem & Dynam Branch, Greenbelt, MD 20771 USA. RP Douglass, AR (reprint author), NASA, Goddard Space Flight Ctr, Atmospher Chem & Dynam Branch, Greenbelt, MD 20771 USA. EM douglass@persephone.gsfc.nasa.gov RI Douglass, Anne/D-4655-2012; Kawa, Stephan/E-9040-2012 NR 57 TC 31 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 AUG 20 PY 1999 VL 104 IS D15 BP 18739 EP 18754 DI 10.1029/1999JD900281 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 228GJ UT WOS:000082128500018 ER PT J AU Woyke, T Muller, R Stroh, F McKenna, DS Engel, A Margitan, JJ Rex, M Carslaw, KS AF Woyke, T Muller, R Stroh, F McKenna, DS Engel, A Margitan, JJ Rex, M Carslaw, KS TI A test of our understanding of the ozone chemistry in the Arctic polar vortex based on in situ measurements of ClO, BrO, and O-3 in the 1994/1995 winter SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID VISIBLE ABSORPTION-SPECTRA; ANTARCTIC OZONE; 3-DIMENSIONAL MODEL; STRATOSPHERIC OZONE; INSITU OBSERVATIONS; ATMOS MEASUREMENTS; REACTIVE NITROGEN; 1994-95 WINTER; DEPLETION; CHLORINE AB We present an analysis of in situ measurements of ClO, BrO, O-3, and long-lived tracers obtained on a balloon flight in the Arctic polar vortex launched from Kiruna, Sweden, 68 degrees N, on February 3, 1995. Using the method of tracer correlations, we deduce that the air masses sampled at an altitude of 21 km (480 K potential temperature), where a layer of enhanced ClO mixing ratios of up to 1150 parts per trillion by volume was observed, experienced a cumulative chemical ozone loss of 1.0+/-0.3 ppmv between late November 1994 and early February 1995, This estimate of chemical ozone loss can be confirmed using independent data sets and independent methods. Calculations using a trajectory box model show that the simulations underestimate the cumulative ozone loss by approximately a factor of 2, although observed ClO and BrO mixing ratios are well reproduced by the model. Employing additional simulations of ozone loss rates for idealized conditions, we conclude that the known chlorine and bromine catalytic cycles destroying odd oxygen with the known rate constants and absorption cross sections do not quantitatively account for the early winter ozone losses infered for air masses observed at 21 km. C1 Forschungszentrum Julich, Inst Stratosphar Chem, D-52425 Julich, Germany. Goethe Univ Frankfurt, Inst Meteorol & Geophys, D-60325 Frankfurt, Germany. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Alfred Wegener Inst Polar & Marine Res, Potsdam, Germany. Max Planck Inst Chem, D-55128 Mainz, Germany. RP Woyke, T (reprint author), Forschungszentrum Julich, Inst Stratosphar Chem, Postfach 1913, D-52425 Julich, Germany. EM t.woyke@fz-juelich.de RI Rex, Markus/A-6054-2009; Stroh, Fred/A-6505-2009; Muller, Rolf/A-6669-2013; Carslaw, Ken/C-8514-2009; McKenna, Daniel/E-7806-2014; Engel, Andreas/E-3100-2014 OI Rex, Markus/0000-0001-7847-8221; Stroh, Fred/0000-0002-4492-2977; Muller, Rolf/0000-0002-5024-9977; Carslaw, Ken/0000-0002-6800-154X; McKenna, Daniel/0000-0002-4360-4782; Engel, Andreas/0000-0003-0557-3935 NR 65 TC 37 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 AUG 20 PY 1999 VL 104 IS D15 BP 18755 EP 18768 DI 10.1029/1999JD900287 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 228GJ UT WOS:000082128500019 ER PT J AU Hall, TM Waugh, DW Boering, KA Plumb, RA AF Hall, TM Waugh, DW Boering, KA Plumb, RA TI Evaluation of transport in stratospheric models SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Review ID MIDLATITUDE LOWER STRATOSPHERE; GENERAL-CIRCULATION MODEL; MIDDLE ATMOSPHERE; 2-DIMENSIONAL MODEL; CARBON-DIOXIDE; ANNUAL CYCLE; SULFUR-HEXAFLUORIDE; DATA ASSIMILATION; TRACER TRANSPORT; NITROUS-OXIDE AB We evaluate transport characteristics of two- and three-dimensional chemical transport models of the stratosphere by comparing their simulations of the mean age of stratospheric air and the propagation of annually periodic oscillations in tracer mixing ratio at the tropical tropopause into the stratosphere to inferences from in situ and satellite observations of CO2, SF6, and water vapor. The models, participants in the recent NASA "Models and Measurements II" study, display a wide range of performance. Most models propagate annual oscillations too rapidly in the vertical and overattenuate the signal. Most models also significantly underestimate mean age throughout the stratosphere, and most have at least one of several unrealistic features in their mean age contour shapes. In the lower stratosphere, model-to-model variation in N2O, NOy, and Cl-y is well correlated with variation in mean age, and the magnitude of NOy and Cl-y variation is large. We conclude that model transport inaccuracies significantly affect simulations of important long-lived chemical species in the lower stratosphere. C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Univ Calif Berkeley, Dept Chem, Berkeley, CA 94720 USA. MIT, Dept Earth Atmospher & Planetary Sci, Cambridge, MA 02139 USA. Johns Hopkins Univ, Dept Earth & Planetary Sci, Baltimore, MD 21218 USA. Univ Calif Berkeley, Dept Geol & Geophys, Berkeley, CA 94720 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; boering@cchem.berkeley.edu; rap@rossby.mit.edu RI Waugh, Darryn/K-3688-2016 OI Waugh, Darryn/0000-0001-7692-2798 NR 63 TC 132 Z9 132 U1 2 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 AUG 20 PY 1999 VL 104 IS D15 BP 18815 EP 18839 DI 10.1029/1999JD900226 PG 25 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 228GJ UT WOS:000082128500023 ER PT J AU Manney, GL Michelsen, HA Santee, ML Gunson, MR Irion, FW Roche, AE Livesey, NJ AF Manney, GL Michelsen, HA Santee, ML Gunson, MR Irion, FW Roche, AE Livesey, NJ TI Polar vortex dynamics during spring and fall diagnosed using trace gas observations from the Atmospheric Trace Molecule Spectroscopy instrument SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Review ID SOLAR OCCULTATION SPECTRA; LOW-OZONE POCKETS; ATMOS MEASUREMENTS; WATER-VAPOR; ATMOS/ATLAS-3 MEASUREMENTS; LOWER STRATOSPHERE; NOVEMBER 1994; INTERANNUAL VARIABILITY; TRAJECTORY CALCULATIONS; ANTARCTIC STRATOSPHERE AB Trace gases measured by the Atmospheric Trace Molecule Spectroscopy (ATMOS) instrument during three Atmospheric Laboratory for Applications and Science (ATLAS) space-shuttle missions, in March/April 1992 (AT-1), April 1993 (AT-2), and November 1994 (AT-3) have been mapped into equivalent latitude/potential temperature (EqL/theta) coordinates. The asymmetry of the spring vortices results in coverage of subtropical to polar EqLs, EqL/theta fields of long-lived tracers in spring in both hemispheres show the net effects of descent at high EqL throughout the winter, reflecting strong descent in the upper stratosphere, decreasing descent at lower altitudes, and evidence of greater descent at the edge of the lower stratospheric vortex than in the vortex center; these results are consistent with trajectory calculations examining the history of the air measured by ATMOS in the month prior to each mission. EqL/theta tracer fields, the derived fields CH4-CH4* (CH4* is the expected CH4 calculated from a prescribed relationship with N2O for fall) and NOy-NOy* (analogous to CH4*), and parcel histories all indicate regions of strong mixing in the 1994 Southern Hemisphere (SH) spring vortex above 500 K, with the strongest mixing confined to the vortex edge region between 500 and 700 K, and mixing throughout the Northern Hemisphere (NH) spring vortex in 1993 below about 850 K. Parcel histories indicate mixing of extravortex air with air near the vortex edge below 500 K in the SH but not with air in the vortex core; they show extravortex air mixing well into the vortex above similar to 450 K in the NH and in to the vortex edge region below. The effects of severe denitrification are apparent in EqL/theta HNO3 in the SH lower stratospheric spring vortex. The morphology of HNO3 in the Arctic spring lower stratospheric vortex is consistent with the effects of descent. EqL/theta fields of ATMOS NOy-NOy* show decreases consistent with the effects of mixing throughout the NH lower stratospheric vortex. The EqL/theta-mapped ATMOS data thus indicate no significant denitrification during the 1992-1993 NH winter. Examination of H2O+2CH(4) shows that dehydration in SH spring 1994 extended up to similar to 600 K; it also suggests the possibility of a small amount of dehydration in the NH 1993 spring vortex below similar to 465 K. Ozone depletion is evident in the spring vortices in both hemispheres. Differences in autumn EqL/theta tracer fields between the missions reflect the fact that each succeeding mission took place similar to 2 weeks later in the season, when the vortex had developed further. There was greater average descent and greater isolation of air in the developing vortex during each succeeding mission, consistent with progressively larger downward excursions of long-lived tracer contours observed in the upper stratosphere at high EqL. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Atmospher & Environm Res Inc, San Ramon, CA 94583 USA. Lockheed Martin Adv Technol Ctr, Palo Alto, CA 94304 USA. RP Manney, GL (reprint author), CALTECH, Jet Prop Lab, Mail Stop 183-701, Pasadena, CA 91109 USA. EM manney@mls.jpl.nasa.gov NR 76 TC 52 Z9 54 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD AUG 20 PY 1999 VL 104 IS D15 BP 18841 EP 18866 DI 10.1029/1999JD900317 PG 26 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 228GJ UT WOS:000082128500024 ER PT J AU Wolfenden, A Anthony, AC Singh, M AF Wolfenden, A Anthony, AC Singh, M TI Measurement of Young's modulus and damping for hexoloy SG silicon carbide SO SCRIPTA MATERIALIA LA English DT Article DE elastic modulus; damping; ceramics; silicon carbide; temperature C1 Texas A&M Univ, Dept Mech Engn, College Stn, TX 77843 USA. NASA, Dynacs Engn Co, John H Glenn Res Ctr, Cleveland, OH 44135 USA. RP Wolfenden, A (reprint author), Texas A&M Univ, Dept Mech Engn, College Stn, TX 77843 USA. NR 5 TC 5 Z9 5 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1359-6462 J9 SCRIPTA MATER JI Scr. Mater. PD AUG 20 PY 1999 VL 41 IS 6 BP 611 EP 615 DI 10.1016/S1359-6462(99)00198-0 PG 5 WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Science & Technology - Other Topics; Materials Science; Metallurgy & Metallurgical Engineering GA 230TE UT WOS:000082265800007 ER PT J AU Andrews, L Zhou, MF Chertihin, GV Bauschlicher, CW AF Andrews, L Zhou, MF Chertihin, GV Bauschlicher, CW TI Reactions of laser-ablated Y and La atoms, cations and electrons with O-2. Infrared spectra and density functional calculations of the MO, MO+, MO2, MO2+, and MO2- species in solid argon SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID MICROWAVE ROTATIONAL SPECTRUM; OXYGEN MOLECULES; CONDENSING ARGON; METAL-OXIDES; IRON ATOMS; DIOXYGEN; SCO; SPECTROSCOPY; DIOXIDES; MONOXIDE AB Laser-ablated Y and La condensed with O-2 in excess argon formed small metal oxides, cations, and anions, which were identified from isotopic substitution and density functional frequency calculations. In accord with gas phase thermochemistry, the OYO and OLaO molecules are more weakly bound than YO and LaO, on the basis of vibrational frequencies, and their symmetric stretching modes are unusually intense. The bent OYO- and OLaO- anions, the cyclic Y(O-2)(+) and La(O-2)(+), and linear OLaO+ cation isomers are characterized. The (O-2)MO and MO3 isomers are also observed. C1 Univ Virginia, Dept Chem, Charlottesville, VA 22901 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Andrews, L (reprint author), Univ Virginia, Dept Chem, Mccormick Rd, Charlottesville, VA 22901 USA. NR 48 TC 42 Z9 43 U1 0 U2 8 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 AUG 19 PY 1999 VL 103 IS 33 BP 6525 EP 6532 DI 10.1021/jp991024z PG 8 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 231WW UT WOS:000082335200005 ER PT J AU Dumas, C Terrile, RJ Smith, BA Schneider, G Becklin, EE AF Dumas, C Terrile, RJ Smith, BA Schneider, G Becklin, EE TI Stability of Neptune's ring arcs in question SO NATURE LA English DT Article ID OCCULTATION AB Although all four of the gas-giant planets in the Solar System have ring systems, only Neptune exhibits 'ring arcs'-stable dumps of dust that are discontinuous from each other(1). Two basic mechanisms for confining the dust to these arcs have been proposed. The first(2) relies on orbital resonances with two shepherding satellites, while the second(3) invokes a single satellite (later suggested to be Galatea(4)) to produce the observed ring are structures. Here we report observations of the ring arcs and Galatea, which show that there is a mismatch between the locations of the arcs and the site of Galatea's co-rotation inclined resonance. This result calls into question Galatea's sole role in confining the arcs. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Hawaii, Inst Astron, Napoopoo, HI 96704 USA. Univ Arizona, Steward Observ, Tucson, AZ 85721 USA. Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA. RP Dumas, C (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,MS 183-501, Pasadena, CA 91109 USA. NR 13 TC 25 Z9 26 U1 0 U2 1 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON N1 9XW, ENGLAND SN 0028-0836 J9 NATURE JI Nature PD AUG 19 PY 1999 VL 400 IS 6746 BP 733 EP 735 DI 10.1038/23414 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 228HM UT WOS:000082131100040 ER PT J AU Osborne, BP AF Osborne, BP TI Maintain visibility SO AVIATION WEEK & SPACE TECHNOLOGY LA English DT Letter C1 NASA, Aeronaut Advisory Comm, Palm Desert, CA 92211 USA. RP Osborne, BP (reprint author), NASA, Aeronaut Advisory Comm, Palm Desert, CA 92211 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU MCGRAW HILL INC PI NEW YORK PA 1221 AVENUE OF THE AMERICAS, NEW YORK, NY 10020 USA SN 0005-2175 J9 AVIAT WEEK SPACE TEC JI Aviat. Week Space Technol. PD AUG 16 PY 1999 VL 151 IS 7 BP 6 EP 6 PG 1 WC Engineering, Aerospace SC Engineering GA 226RW UT WOS:000082036300004 ER PT J AU Goldin, DS AF Goldin, DS TI Viewpoint SO AVIATION WEEK & SPACE TECHNOLOGY LA English DT Editorial Material 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 MCGRAW HILL INC PI NEW YORK PA 1221 AVENUE OF THE AMERICAS, NEW YORK, NY 10020 USA SN 0005-2175 J9 AVIAT WEEK SPACE TEC JI Aviat. Week Space Technol. PD AUG 16 PY 1999 VL 151 IS 7 BP 90 EP 90 PG 1 WC Engineering, Aerospace SC Engineering GA 226RW UT WOS:000082036300041 ER PT J AU Nakajima, T Higurashi, A Takeuchi, N Herman, JR AF Nakajima, T Higurashi, A Takeuchi, N Herman, JR TI Satellite and ground-based study of optical properties of 1997 Indonesian forest fire aerosols SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID BIOMASS; AIRBORNE; SMOKE AB Optical properties of biomass burning aerosols in the event of Indonesian forest fires in 1997 were studied by groundbased sky radiometry and satellite remote sensing with AVHRR and TOMS radiometers. The AVHRR-derived optical thickness distribution agreed with the distribution of TOMS-derived UV-absorbing aerosol index and with the optical thickness measured by sky radiometry and sunphotometry. The single scattering albedo of aerosols was fairly constant as 0.9 in the September-October period. Relationship between Angstrom turbidity factor and exponent supported the polydispersion consisted of aged small particles. This observation was consistent with the fact that the retrieved volume size distribution by sky radiometry has a distinct accumulation mode with a peak radius of 0.25 mu m. Those optical properties of smoke aerosols seem to reflect the specific chemical structure of Indonesian forest fire aerosols, i. e,, a mixture of carbonaceous and sulfate particles. C1 Univ Tokyo, Ctr Climate Syst Res, Meguro Ku, Tokyo 1538904, Japan. Chiba Univ, Ctr Environm Remote Sensing, Chiba 2608502, Japan. NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. RP Nakajima, T (reprint author), Univ Tokyo, Ctr Climate Syst Res, Meguro Ku, 4-6-1 Komaba, Tokyo 1538904, Japan. RI Nakajima, Teruyuki/H-2370-2013; OI Nakajima, Teruyuki/0000-0002-9042-504X; Herman, Jay/0000-0002-9146-1632 NR 16 TC 53 Z9 53 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD AUG 15 PY 1999 VL 26 IS 16 BP 2421 EP 2424 DI 10.1029/1999GL900208 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 226GD UT WOS:000082011200004 ER PT J AU Ou, SC Liou, KN AF Ou, SC Liou, KN TI Remote sensing of cirrus cloud parameters eased on a 0.63-3.7 mu m radiance correlation technique applied to AVHRR data SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID FIRE-II-IFO; 3.7-MU-M AB Using the data gathered from the Advanced Very High Resolution Radiometer (AVHRR) 0.63 and 3.7 mu m channels, an algorithm for the inference of cirrus cloud optical depth and mean effective size has been developed for the first time. This scheme is based on the correlation between the 3.7 mu m (total) and 0.63 mu m radiances that is constructed from radiative transfer calculations involving ice crystal clouds. Application of the algorithm to AVHRR channels has been performed by using data sets that were collected during the First ISCCP Regional Experiment, Phase II, Cirrus Intensive Field Observation (FIRE-II-IFO; November-December 1991) at Coffeyville, Kansas. For validation, the in-situ data collected by the balloon-borne replicator and airborne 2-D probes that were collocated with AVHRR pixels were carefully analyzed for five cases involving single and multiple cirrus cloud layers. We demonstrate that the retrieved cirrus cloud optical depths and mean effective sizes compare reasonably well with those determined from the insitu analyses. C1 Univ Calif Los Angeles, Dept Atmospher Sci, Los Angeles, CA 90095 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Ou, SC (reprint author), Univ Calif Los Angeles, Dept Atmospher Sci, Los Angeles, CA 90095 USA. RI King, Michael/C-7153-2011 OI King, Michael/0000-0003-2645-7298 NR 11 TC 13 Z9 15 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 AUG 15 PY 1999 VL 26 IS 16 BP 2437 EP 2440 DI 10.1029/1999GL900554 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 226GD UT WOS:000082011200008 ER PT J AU Liu, SC Yu, H Ridley, B Wang, Y Davis, DD Kondo, Y Koike, M Anderson, BE Vay, SA Sachse, GW Gregory, GL Fuelburg, H Thompson, A Singh, H AF Liu, SC Yu, H Ridley, B Wang, Y Davis, DD Kondo, Y Koike, M Anderson, BE Vay, SA Sachse, GW Gregory, GL Fuelburg, H Thompson, A Singh, H TI Sources of reactive nitrogen in the upper troposphere during SONEX SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID OZONE AB The relationship among NOy, O-3, N2O, ultra-fine condensation nuclei (CN), and other trace gases in the upper troposphere (UT) and lower stratosphere (LS) observed during SONEX are analyzed with the goal to identify and quantify the sources of NOy in the UT. We use N2O to separate upper tropospheric air from stratospheric influenced air and focus our analysis to the former. The distributions of NOy and O-3 show remarkable similarity when they are plotted as a function of N2O. The only difference between NOy and O-3 is found in upper tropospheric air where a large number of data points have high values of both NOy and the NOy/O-3 ratio. Major sources contributing to these high NOy values are found to be emissions from lightning and surface sources transported to the UT by convection. C1 Georgia Inst Technol, Sch Earth & Atmospher Sci, Atlanta, GA 30332 USA. Natl Ctr Atmospher Res, Boulder, CO 80303 USA. Nagoya Univ, Solar Terr Environm Lab, Aichi 442, Japan. NASA, Div Atmospher Sci, Langley Res Ctr, Hampton, VA 23681 USA. Florida State Univ, Dept Meteorol, Tallahassee, FL 32306 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Liu, SC (reprint author), Georgia Inst Technol, Sch Earth & Atmospher Sci, Atlanta, GA 30332 USA. RI Yu, Hongbin/C-6485-2008; Koike, Makoto/F-4366-2011; Kondo, Yutaka/D-1459-2012; Wang, Yuhang/B-5578-2014; Thompson, Anne /C-3649-2014 OI Yu, Hongbin/0000-0003-4706-1575; Thompson, Anne /0000-0002-7829-0920 NR 20 TC 11 Z9 11 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 AUG 15 PY 1999 VL 26 IS 16 BP 2441 EP 2444 DI 10.1029/1999GL900532 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 226GD UT WOS:000082011200009 ER PT J AU Dickey, JO Gegout, P Marcus, SL AF Dickey, JO Gegout, P Marcus, SL TI Earth-atmosphere angular momentum exchange and ENSO: The rotational signature of the 1997-98 event SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID EL-NINO; SOUTHERN OSCILLATION; INTERANNUAL FLUCTUATIONS; VARIABILITY; CIRCULATION; LENGTH; MODEL AB The impact of the 1997-1998 ENSO event is presented in context of axial Earth-atmosphere angular momentum exchange utilizing length of day (LOD), Southern Oscillation Index (SOI) and atmospheric angular momentum (AAM) data from 1970 to 1998; comparisons are made with previous events. The analysis of equal-area latitudinally belted AAM from the NCEP reanalysis (1958-98) reveals slow global coherent poleward propagation of angular momentum. These structures originate in the equatorial regions, penetrate into high latitudes and are bimodal in nature with variations centered at low-frequency (LF similar to 4.7 yr) and quasi-biennial (QB similar to 2.4 yr) periods. Analyses utilize both a recursive filter and multichannel singular spectrum analysis (M-SSA). C1 CALTECH, Jet Prop Lab, Space Geodet Sci & Applicat Grp, Pasadena, CA 91109 USA. Ecole & Observ Sci Terre, Lab Dynam Globale, F-67084 Strasbourg, France. RP Dickey, JO (reprint author), CALTECH, Jet Prop Lab, Space Geodet Sci & Applicat Grp, 4800 Oak Grove Dr,Mail Stop 238-332, Pasadena, CA 91109 USA. OI Marcus, Steven/0000-0002-5763-6961 NR 20 TC 14 Z9 15 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD AUG 15 PY 1999 VL 26 IS 16 BP 2477 EP 2480 DI 10.1029/1999GL900449 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 226GD UT WOS:000082011200018 ER PT J AU Wadhams, P Comiso, JC AF Wadhams, P Comiso, JC TI Two modes of appearance of the Odden ice tongue in the Greenland Sea SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID COVER; BASIN AB The Odden ice tongue of the Greenland Sea normally forms locally in winter as frazil-pancake ice allowing for high positive salt fluxes during freezing that leads to open ocean convection. We report that another type of Odden can develop usually late in the season and is composed of old ice advected through the East Greenland Current and by the Jan Mayen Current. This type causes the introduction of more meltwater that stabilizes the water column, enhances productivity, and affects the carbon cycle in the region. The history of Oddens is reviewed and our results indicate that from 1978 through 1997, the first type occurred almost every year except in 1984, 1994, and 1995, while the second type has been observed to occur in 1987 and 1996. C1 Univ Cambridge, Scott Polar Res Inst, Cambridge CB2 1ER, England. NASA, Lab Hydrospher Proc, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Wadhams, P (reprint author), Univ Cambridge, Scott Polar Res Inst, Cambridge CB2 1ER, England. NR 21 TC 9 Z9 9 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 AUG 15 PY 1999 VL 26 IS 16 BP 2497 EP 2500 DI 10.1029/1999GL900502 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 226GD UT WOS:000082011200023 ER PT J AU Blair, JB Hofton, MA AF Blair, JB Hofton, MA TI Modeling laser altimeter return waveforms over complex vegetation using high-resolution elevation data SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SCANNER DATA; SYSTEM AB The upcoming generation of laser altimeters record the interaction of emitted laser radiation with terrestrial surfaces in the form of a digitized waveform. We model these laser altimeter return waveforms as the sum of the reflections from individual surfaces within laser footprints, accounting for instrument-specific properties. We compare over 1000 modeled and recorded waveform pairs using the Pearson correlation. We show that we reliably synthesize the vertical structure information for vegetation canopies contained in a medium-large diameter laser footprint from a high-resolution elevation data set. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Maryland, Dept Geog, College Pk, MD 20742 USA. RP Blair, JB (reprint author), NASA, Goddard Space Flight Ctr, Code 924, Greenbelt, MD 20771 USA. RI Blair, James/D-3881-2013; Beckley, Matthew/D-4547-2013 NR 10 TC 95 Z9 99 U1 4 U2 12 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 AUG 15 PY 1999 VL 26 IS 16 BP 2509 EP 2512 DI 10.1029/1999GL010484 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 226GD UT WOS:000082011200026 ER PT J AU Osherovich, VA Fainberg, J Stone, RG AF Osherovich, VA Fainberg, J Stone, RG TI Solar wind quasi-invariant as a new index of solar activity SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID INTERPLANETARY MAGNETIC-FIELD AB Solar wind parameters, such as magnetic field strength B, plasma density rho and bulk speed v correlate with solar cycle measured by sunspot numbers SSN. Using hourly data in the solar wind near the Earth. we show that the energy density ratio QI = (B-2/8 pi)/(rho v(2)/2) has a correlation coefficient (cc) with SSN which is appreciably higher than for each of B, rho and v taken separately. The proposed quasi-invariant is related to magnetic Mach number M-A (QI = M-A(-2)). The yearly median QI for the last 28 years holds a linear relation with SSN with high cc = 0.98, which makes it the best index of solar activity derived from solar wind parameters so far. C1 NASA, Goddard Space Flight Ctr, RITSS, Greenbelt, MD 20771 USA. RP Osherovich, VA (reprint author), NASA, Goddard Space Flight Ctr, RITSS, Code 690-2, Greenbelt, MD 20771 USA. NR 6 TC 33 Z9 33 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 AUG 15 PY 1999 VL 26 IS 16 BP 2597 EP 2600 DI 10.1029/1999GL900583 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 226GD UT WOS:000082011200048 ER PT J AU Farrell, WM Kaiser, ML Desch, MD AF Farrell, WM Kaiser, ML Desch, MD TI A model of the lightning discharge at Jupiter SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID RADIO; RADIATION; VOYAGER-2; SPRITES; STROKES AB Based on the lightning waveform and spectra observed by the Galileo Atmospheric Probe, we present a discharge, radiation, and propagation model of the Jovian lightning that explains the absence of detectable HF spherics along with the measurement of ELF whistler emissions by the Voyager radio and plasma wave instruments. We find that although there is signal attenuation in the ionosphere, the controlling factor in determining lightning detectability at Jupiter is the intrinsically slow nature of the lightning discharge itself. The proposed discharge model is not unique, but matches the observed spectrum which spans several frequency decades and provides a basis for comparing lightning discharge models for other planets. C1 NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Planetary Magnetospheres Branch, Greenbelt, MD 20771 USA. RP Farrell, WM (reprint author), NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Planetary Magnetospheres Branch, Greenbelt, MD 20771 USA. RI Farrell, William/I-4865-2013 NR 19 TC 19 Z9 19 U1 1 U2 5 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 AUG 15 PY 1999 VL 26 IS 16 BP 2601 EP 2604 DI 10.1029/1999GL900527 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 226GD UT WOS:000082011200049 ER PT J AU Feldman, WC Skoug, RM Gosling, JT McComas, DJ Tokar, RL Burlaga, LF Ness, NF Smith, CW AF Feldman, WC Skoug, RM Gosling, JT McComas, DJ Tokar, RL Burlaga, LF Ness, NF Smith, CW TI Observations of suprathermal electron conics in an interplanetary coronal mass ejection SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID HELIOS PLASMA-EXPERIMENT; SOLAR-WIND ELECTRON; INTER-PLANETARY SHOCK; DISTRIBUTIONS; EVENTS AB Solar wind suprathermal electron velocity distributions measured by the SWEPAM experiment aboard ACE were studied to determine the internal magnetic structure of the coronal mass ejection (CME) that passed 1 AU on 4-5 February, 1998. Pitch-angle distributions range from symmetric counter-streaming to complex distributions that include conics. Identification of suprathermal electron conics in interplanetary CMEs (ICMEs) is reported here for the first time. The origin of these conics is highly uncertain. We suggest, however, that the conics may originate in transient electron heating associated with magnetic reconnection within the magnetic legs of the CMEs. Such reconnection generates large, complex magnetic loops that have enhanced anti-solar electric fields at their solar edge to maintain charge neutrality. This field must be sufficiently strong to bind electrons with high pitch angles to the bottom of the loops as they propagate away from the Sun. C1 Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87544 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Delaware, Bartol Res Inst, Newark, DE 19716 USA. RP Feldman, WC (reprint author), Univ Calif Los Alamos Natl Lab, MS D466, Los Alamos, NM 87544 USA. NR 16 TC 10 Z9 10 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 AUG 15 PY 1999 VL 26 IS 16 BP 2613 EP 2616 DI 10.1029/1999GL900460 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 226GD UT WOS:000082011200052 ER PT J AU Dorsey, KD Desai, P Abhiraman, AS Hinkley, JA St Clair, TL AF Dorsey, KD Desai, P Abhiraman, AS Hinkley, JA St Clair, TL TI Structure and properties of melt-extruded LaRC-IA (3,4 '-ODA 4,4 '-ODPA) polyimide fibers SO JOURNAL OF APPLIED POLYMER SCIENCE LA English DT Article DE LaRC-IA polyimide fibers; melt extrusion; crystallization AB LaRC-IA polyimide fibers were extruded from the melt and drawn. The fibers were characterized by sonic pulse propagation, polarized optical microscopy, calorimetric analysis, X-ray diffraction, and tensile testing. When the amorphous, essentially isotropic, as-extruded filaments were heated slowly in a calorimeter, no "cold" crystallization could be detected. However, when these filaments were drawn at temperatures above the T-g of the polymer, they crystallized rapidly to produce oriented semicrystalline structures. The consequent increases in modulus and strength were significant, with the properties reaching the levels of commercial fibers of intermediate tenacity. (C) 1999 Jokn Wiley & Sons, Inc. C1 Georgia Inst Technol, Sch Chem Engn, Polymer Educ & Res Ctr, Atlanta, GA 30332 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Abhiraman, AS (reprint author), Georgia Inst Technol, Sch Chem Engn, Polymer Educ & Res Ctr, Atlanta, GA 30332 USA. NR 13 TC 8 Z9 10 U1 0 U2 11 PU JOHN WILEY & SONS INC PI NEW YORK PA 605 THIRD AVE, NEW YORK, NY 10158-0012 USA SN 0021-8995 J9 J APPL POLYM SCI JI J. Appl. Polym. Sci. PD AUG 15 PY 1999 VL 73 IS 7 BP 1215 EP 1222 DI 10.1002/(SICI)1097-4628(19990815)73:7<1215::AID-APP15>3.0.CO;2-1 PG 8 WC Polymer Science SC Polymer Science GA 200QG UT WOS:000080550900016 ER PT J AU Halpern, D Woiceshyn, PM AF Halpern, D Woiceshyn, PM TI Onset of the Somali Jet in the Arabian Sea during June 1997 SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID TROPICAL INDIAN-OCEAN; SCATTEROMETER; MONSOON AB The National Aeronautics and Space Administration scatterometer surface wind vectors are used to describe the rapid onset of the Somali Jet throughout the Arabian Sea. In June 1997 the time of Somali Jet onset varied over the Arabian Sea, with June 17-18 the average time. The Somali Jet appeared first in the western Arabian Sea, expanded over 2 weeks to encompass the Arabian Sea, and produced a threefold increase in surface wind convergence in the eastern Arabian Sea. The onset time of the 12 m s(-1) isotach preceded by 3-4 days the onset of monsoon rainfall in Goa. For Somali Jet wind speeds above 10 m s(-1) the 2 day 1 degrees x 1 degrees sea surface temperature decreased 0.5 degrees C per 1 m s(-1) increase in collocated wind speed. The Somali Jet created a north-south distribution of Ekman pumping and suction in the central Arabian Sea to enhance the eastward surface current by 0.1 m s(-1). The Somali Jet doubled the southward Ekman transport across the southern boundary of the Arabian Sea. In June 1997, when the most intense El Nino episode of the century was in its onset phase, the southward Ekman transport across the southern boundary of the Arabian Sea was one half that observed since 1992. C1 CALTECH, Jet Prop Lab, Div Earth & Space Sci, Pasadena, CA 91109 USA. RP Halpern, D (reprint author), CALTECH, Jet Prop Lab, Div Earth & Space Sci, Pasadena, CA 91109 USA. NR 21 TC 23 Z9 25 U1 2 U2 3 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 AUG 15 PY 1999 VL 104 IS C8 BP 18041 EP 18046 DI 10.1029/1999JC900141 PG 6 WC Oceanography SC Oceanography GA 226VL UT WOS:000082043100001 ER PT J AU McClain, CR Murtugudde, R Signorini, S AF McClain, CR Murtugudde, R Signorini, S TI A simulation of biological processes in the equatorial Pacific Warm Pool at 165 degrees E SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID SEA-SURFACE TEMPERATURE; MIXED-LAYER MODEL; TROPICAL PACIFIC; SOLAR IRRADIANCE; HEAT-BUDGET; OCEAN MODEL; TOGA-COARE; EL-NINO; PHYTOPLANKTON; CARBON AB A 9-year simulation (1984-1992) of biological processes in the equatorial Pacific Warm Pool is presented. A modified version of the four-component (phytoplankton, zooplankton, nitrate, and ammonium) ecosystem model by McClain et al. [1996] is used. Modifications include use of a spectral model for computation of photosynthetically available radiation and inclusion of fecal pellet remineralization and ammonium nitrification. The physical parameters (horizontal and vertical velocities and temperature) required by the ecosystem model were derived from an improved version of the Gent and Cane [1990] ocean general circulation model [Murtugudde and Busalacchi, 1998], Surface downwelling spectral irradiance was estimated using the clear-sky models of Frouin et al. [1989] and Gregg and Carder [1990] and cloud cover information from the International Satellite Cloud Climatology Project. The simulations indicate considerable variability on interannual timescales in all four ecosystem components. In particular, surface chlorophyll concentrations varied by an order of magnitude with maximum values exceeding 0.30 mg m(-3) in 1988, 1989, and 1990 and pronounced minima during 1987 and 1992. The deep chlorophyll maximum (DCM) ranged between 75 and 125 m with values occasionally exceeding 0.40 mg m(-3). With the exception of periods during 1984 and 1988, surface nitrate was always near depletion. Ammonium exhibited a subsurface maximum just below the DCM with concentrations as high as 0.5 mg-atN m(-3), where "at" is atoms. Total integrated annual primary Production varied between 40 and 250 gC m(-2) yr(-1) with an annual average of 140 gC m(-2) yr(-1). Finally, the model is used to estimate the mean irradiance at the base of the mixed layer, i.e., the penetration irradiance, which was 18 W m(-2) over the 9-year period or about 8% of the incident total irradiance. The average mixed layer depth was 42 m. C1 NASA, SeaWiFS Project Off, Lab Hydrospher Proc, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Maryland, Joint Ctr Earth Syst Sci, College Pk, MD 20742 USA. Gen Sci Corp, Sci Applicat Int Corp, Laurel, MD 20707 USA. RP McClain, CR (reprint author), NASA, SeaWiFS Project Off, Lab Hydrospher Proc, Goddard Space Flight Ctr, Code 970-2, Greenbelt, MD 20771 USA. NR 64 TC 15 Z9 15 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-OCEANS JI J. Geophys. Res.-Oceans PD AUG 15 PY 1999 VL 104 IS C8 BP 18305 EP 18322 DI 10.1029/1999JC900087 PG 18 WC Oceanography SC Oceanography GA 226VL UT WOS:000082043100018 ER PT J AU Murtugudde, RG Signorini, SR Christian, JR Busalacchi, AJ McClain, CR Picaut, J AF Murtugudde, RG Signorini, SR Christian, JR Busalacchi, AJ McClain, CR Picaut, J TI Ocean color variability of the tropical Indo-Pacific basin observed by SeaWiFS during 1997-1998 SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID WESTERN EQUATORIAL PACIFIC; MIXED-LAYER MODEL; ARABIAN SEA; INDIAN-OCEAN; EL-NINO; SURFACE-LAYER; WIND STRESS; PHYTOPLANKTON; SIMULATION; CIRCULATION AB High-quality ocean color data (chlorophyll) provided by the Sea-viewing Wide Field of view Sensor (SeaWiFS) satellite were analyzed for the first complete year of coverage (October 1997 to September 1998) in the tropical Indo-Pacific basin. This period coincides with the peak of one of the strongest Fl Nino events during December 1997 and the La Nina of 1998 that appeared dramatically in less than a month as a sea surface temperature (SST) change of over 6 degrees C in the central equatorial Pacific during June 1998, The tropical Indian Ocean also underwent a highly anomalous series of events with negative SST anomalies (SSTA) of over 3 degrees C in the eastern equatorial and coastal regions during October-December 1997 and warm SSTA in the west that peaked at over 2 degrees C during February 1998. The ocean color variability is interpreted using other satellite data such as sea level from TOPEX/Poseidon and also in terms of the dynamics and thermodynamics of the region from simulations with an ocean general circulation model, The El Nino-related reductions in equatorial production and the off-equatorial increase in biological activity, and their basin scale evolution is clearly seen for the first time. Persistent northerly wind anomalies resulted in a northward shift of the equatorial divergence and the upwelling Kelvin wave which signalled the end of the 1997-1998 El Nino. The anomalous surface chlorophyll associated with this Kelvin wave was also clearly shifted north of the equator by nearly 300 km and appeared more than a month before the negative sea level anomalies seen by TOPEX/Poseidon. On the equator near 165 degrees E, the disappearance of the barrier layer appeared to coincide with a localized bloom that occurred in response to the easterly wind bursts over the western Pacific that lasted from December 1997 through the boreal summer. The ecosystem response to the cold La Nina conditions is clearly seen as elevated chlorophyll during the boreal summer of 1998 in the equatorial Pacific cold tongue region. In the Indian Ocean, an anomalous phytoplankton bloom was observed by SeaWiFS during October-December 1997 coincident with the anomalous upwelling in the eastern equatorial region and off the coast of Sumatra, A stronger than normal northeast monsoon is seen as higher than climatological values of surface chlorophyll. The open ocean Ekman pumping and the shoaling of the thermocline near 60 degrees E and 10 degrees S and the eastward extension of mixed layer entrainment in the same latitude band is seen as a region of higher biological activity during the boreal summer. C1 Univ Maryland, Earth Syst Sci Interdisciplinary Ctr, College Pk, MD 20742 USA. NASA, Lab Hydrospher Proc, Goddard Space Flight Ctr, SeaWiFS Project, Greenbelt, MD 20771 USA. Gen Sci Corp, SAIC, Laurel, MD USA. NASA, Univ Space Res Assoc, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Murtugudde, RG (reprint author), Univ Maryland, Earth Syst Sci Interdisciplinary Ctr, College Pk, MD 20742 USA. NR 50 TC 168 Z9 170 U1 1 U2 15 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 AUG 15 PY 1999 VL 104 IS C8 BP 18351 EP 18366 DI 10.1029/1999JC900135 PG 16 WC Oceanography SC Oceanography GA 226VL UT WOS:000082043100021 ER PT J AU Signorini, SR Murtugudde, RG McClain, CR Christian, JR Picaut, J Busalacchi, AJ AF Signorini, SR Murtugudde, RG McClain, CR Christian, JR Picaut, J Busalacchi, AJ TI Biological and physical signatures in the tropical and subtropical Atlantic SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID NORTH-ATLANTIC; THERMAL DOMES; OCEAN; SEA; ALGORITHMS; SIMULATION; MODEL; CYCLE AB The variability of sea surface chlorophyll concentration in the tropical and subtropical Atlantic during the first year of Sea-viewing Wide Field-of-view Sensor (SeaWiFS) imagery is examined. An Ocean General Circulation Model (OGCM) is used, along with TOPEX/Poseidon dynamic height observations and global gridded wind stress data sets, to explain the physical forcing of surface ocean color signals. Regions of high surface chlorophyll are strongly correlated with mesoscale and large-scale physical processes such as the strong upwelling off the west coast of Africa, the relatively high oceanic production within the Guinea Dome region, and the generation and propagation of large anticyclonic eddies along the coast of South America, north of the equator. The major river outflows (Amazon, Orinoco, and Congo) have strong signatures with plumes of apparently high Chi a in excess of 10 mg m(-3) near their deltas. The fall bloom in the eastern tropical Atlantic observed by the Coastal Zone Color Scanner (CZCS) was absent in 1997, whereas a bloom was observed in this region in July-September 1998, which was not observed by the CZCS, We attribute these apparent anomalies to the projection of the 1997-1998 El Nine event into the tropical Atlantic basin; these signals are correlated with sea surface temperature anomalies known to be associated with ENSO, The SeaWiFS images show that there are seasonal blooms within the hydrographic provinces of the Guinea and Angola domes. These hydrographic provinces are characterized by the dynamic uplift of the thermocline at the North Equatorial Current southern boundary (Guinea Dome) and the Benguela Current eastern boundary (Angola Dome). Within these domes, the Ekman pumping and transport are significant due to the strong trade winds at the surface. The Ekman drift plays a major role in the spreading of surface blooms, The spreading of the oceanic bloom at 12 degrees N, 30 degrees W, the Congo River plume, and the areal extent of the upwelling blooms off the coast of Africa, parallels the strength and extent of the Ekman surface drift. Upwelling, when broadly defined to include large scale vertical excursions of the thermocline, explains virtually all of the surface chlorophyll observations in excess of 0.5 mg m(-3), except in the river plumes. C1 Gen Sci Corp, SAIC, Beltsville, MD USA. NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, SeaWiFS Project, Greenbelt, MD 20771 USA. Univ Maryland, Earth Syst Sci Interdisciplinary Ctr, College Pk, MD 20742 USA. NASA, Univ Space Res Assoc, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. ORSTOM, IRD, Paris, France. RP Signorini, SR (reprint author), Gen Sci Corp, SAIC, Beltsville, MD USA. NR 30 TC 56 Z9 57 U1 1 U2 19 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 AUG 15 PY 1999 VL 104 IS C8 BP 18367 EP 18382 DI 10.1029/1999JC900134 PG 16 WC Oceanography SC Oceanography GA 226VL UT WOS:000082043100022 ER PT J AU Ferreira, RN Schubert, WH AF Ferreira, RN Schubert, WH TI The role of tropical cyclones in the formation of tropical upper-tropospheric troughs SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID TWO-DIMENSIONAL VORTEX; ROSSBY-WAVE BREAKING; OFF-LOW SYSTEMS; POTENTIAL VORTICITY; STRATOSPHERE; ATMOSPHERE; MODEL; FILAMENTATION; CIRCULATION; RESOLUTION AB Tropical upper-tropospheric troughs (TUTTs), also known as midoceanic troughs, are elongated troughs that appear in summer monthly averaged maps of the upper-tropospheric flow over the oceans. The transient part of these climatological features is composed of TUTT cells and their origin is the subject of this study. TUTT cells often occur to the east of tropical cyclones. A nonlinear shallow water model on the sphere was used in a simplified study of the interactions between tropical cyclones and the circumpolar vortex. Based on the results of these simulations and keeping in mind their limitations, it is proposed that dispersion of short Rossby wave energy is a possible mechanism to explain the formation of TUTT cells to the east of tropical cyclones. The model simulations suggest that two types of TUTT cells may form to the east of tropical cyclones. When embedded in cyclonic or weak anticyclonic shear, the trough to the east of the tropical cyclone may broaden, resulting in the formation of an intense TUTT cell that has a strong signature in the wind and mass fields. In the presence of stronger anticyclonic shear, the trough to the east of the tropical cyclone may become a thin and elongated TUTT cell that has a comparatively negligible signature in the mass and flow fields. Moreover, the model simulations indicate that the mode of evolution of TUTT cells that form to the east of a tropical cyclone is strongly dependent on the intensity and relative location of midlatitude waves. Wave-mean how interaction calculations indicated that tropical cyclones produced a westerly acceleration of the mean zonal flow in the latitudinal band through which they move and an easterly acceleration elsewhere. These calculations also indicated that broadening TUTT cells may cause an easterly acceleration of the zonal mean flow. C1 NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Atmospheres Lab, Greenbelt, MD 20771 USA. Colorado State Univ, Dept Atmospher Sci, Ft Collins, CO 80523 USA. RP Ferreira, RN (reprint author), NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Atmospheres Lab, Mailcode 913-0, Greenbelt, MD 20771 USA. NR 41 TC 25 Z9 26 U1 0 U2 2 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 AUG 15 PY 1999 VL 56 IS 16 BP 2891 EP 2907 DI 10.1175/1520-0469(1999)056<2891:TROTCI>2.0.CO;2 PG 17 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 230DW UT WOS:000082237400009 ER PT J AU Whittenberger, JD Locci, IE Darolia, R Bowman, R AF Whittenberger, JD Locci, IE Darolia, R Bowman, R TI 1300 K creep behavior of [001] oriented Ni-49Al-1Hf (at.%) single crystals SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING LA English DT Article DE creep; NiAL; Ni-49Al-1Hf; single crystals ID COMPRESSIVE PROPERTIES; DEFORMATION; PHASE; ALLOY; ZR AB A study of the 1300 K compressive and tensile creep properties of [001]-oriented NiAl-1Hf (D209) single crystals has been undertaken. Neither post homogenization cooling treatment, minor chemical variations within an ingot or from ingot-to-ingot, nor testing procedure had a significant effect on mechanical behavior; however a heat treatment which dissolved the initial G-phase precipitates and promoted formation of Heusler particles led to a strength reduction. Little primary creep was found utilizing direct measurement of strain, and a misorientation of 18 degrees from the [001] did not reduce the creep strength. The effects of heat treatments on properties and a comparison of the how stress-strain rate data to those predicted by the Jaswon-Cottrell solid solution hardening model indicate that the 1300 K strength in NiAl-1Hf single crystals is mainly due to precipitation hardening mechanisms. (C) 1999 Elsevier Science S.A. All rights reserved. C1 Case Western Reserve Univ, NASA, Glenn Res Ctr Lewis Field, Cleveland, OH 44106 USA. Gen Elect Aircraft Engines, Cincinnati, OH USA. RP Whittenberger, JD (reprint author), Case Western Reserve Univ, NASA, Glenn Res Ctr Lewis Field, Cleveland, OH 44106 USA. EM john.d.whittenberger@grc.nasa.gov NR 29 TC 36 Z9 38 U1 0 U2 4 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0921-5093 EI 1873-4936 J9 MAT SCI ENG A-STRUCT JI Mater. Sci. Eng. A-Struct. Mater. Prop. Microstruct. Process. PD AUG 15 PY 1999 VL 268 IS 1-2 BP 165 EP 183 DI 10.1016/S0921-5093(99)00071-4 PG 19 WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Science & Technology - Other Topics; Materials Science; Metallurgy & Metallurgical Engineering GA 211FK UT WOS:000081149700021 ER PT J AU Rangarajan, A Yuille, A Mjolsness, E AF Rangarajan, A Yuille, A Mjolsness, E TI Convergence properties of the softassign quadratic assignment algorithm SO NEURAL COMPUTATION LA English DT Article ID ANALOG NEURAL NETWORKS; STATISTICAL PHYSICS; DYNAMICS; STABILITY AB The softassign quadratic assignment algorithm is a discrete-time, continuous-state, synchronous updating optimizing neural network. While its effectiveness has been shown in the traveling salesman problem, graph matching, and graph partitioning in thousands of simulations, its convergence properties have not been studied. Here, we construct discrete-time Lyapunov functions for the cases of exact and approximate doubly stochastic constraint satisfaction, which show convergence to a fixed point. The combination of good convergence properties and experimental success makes the softassign algorithm an excellent choice for neural quadratic assignment optimization. C1 Yale Univ, Dept Diagnost Radiol, New Haven, CT 06520 USA. Yale Univ, Dept Elect Engn, New Haven, CT 06520 USA. Smith Kettlewell Eye Res Inst, San Francisco, CA 94115 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Rangarajan, A (reprint author), Yale Univ, Dept Diagnost Radiol, New Haven, CT 06520 USA. RI Rangarajan, Anand/A-8652-2009 OI Rangarajan, Anand/0000-0001-8695-8436 NR 29 TC 21 Z9 22 U1 0 U2 0 PU M I T PRESS PI CAMBRIDGE PA FIVE CAMBRIDGE CENTER, CAMBRIDGE, MA 02142 USA SN 0899-7667 J9 NEURAL COMPUT JI Neural Comput. PD AUG 15 PY 1999 VL 11 IS 6 BP 1455 EP 1474 DI 10.1162/089976699300016313 PG 20 WC Computer Science, Artificial Intelligence SC Computer Science GA 222VL UT WOS:000081806000009 PM 10423503 ER PT J AU Abdeldayem, HA Frazier, DO Penn, BG Smith, DD Banks, CE AF Abdeldayem, HA Frazier, DO Penn, BG Smith, DD Banks, CE TI Non-linear optothermal properties of metal-free phthalocyanine SO THIN SOLID FILMS LA English DT Article DE nonlinear optics; optical bistability; phthalocyanine; logic gate ID PHASE-CONJUGATION; LANGMUIR-BLODGETT; FILMS; PULSES AB The non-linear optical properties of metal-free phthalocyanine (MFPC) thin films were examined using the second harmonic at 532 nm from a pulsed Nd:YAG laser, and the continuous wave He-Ne and Ar+ lasers. The He-Ne laser transmission at fixed input intensity was found to increase temporally within a period of 12 h. The third-order non-linear susceptibilities (chi((3))) by four-wave mixing were measured for films of different thickness. The saturation intensity of MFPC, and its absorption cross-section, at 633 nm from a He-Ne laser, are reported. An optical bistability was recorded using a He-Ne laser. An AND logic gate was also demonstrated in the system. These phenomena in the system are attributed to refractive index modulation by thermal excitations. (C) 1999 Elsevier Science S.A. All rights reserved. C1 NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. OI banks, craig/0000-0002-0756-9764 NR 20 TC 28 Z9 28 U1 0 U2 7 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0040-6090 J9 THIN SOLID FILMS JI Thin Solid Films PD AUG 15 PY 1999 VL 350 IS 1-2 BP 245 EP 248 DI 10.1016/S0040-6090(98)01432-1 PG 4 WC Materials Science, Multidisciplinary; Materials Science, Coatings & Films; Physics, Applied; Physics, Condensed Matter SC Materials Science; Physics GA 226MH UT WOS:000082023400042 ER PT J AU Bhatt, HD Vedula, R Desu, SB Fralick, GC AF Bhatt, HD Vedula, R Desu, SB Fralick, GC TI La(1-x)SrxCoO3 for thin film thermocouple applications SO THIN SOLID FILMS LA English DT Article DE Lanthanum strontium cobalt oxide; thermocouples AB In this study, the LSCO (lanthanum strontium cobalt oxide) family has been investigated for thin film thermocouple applications. Thin films of La(1-x)SrxCoO3 (x = 0.3, 0.5, 0.7) were prepared on sapphire substrates by pulsed laser deposition. The films were annealed at different temperatures in air and characterized for phase, composition and microstructure to determine their thermal stability. From the phase and composition analyses, it is clear that as the Sr content in LSCO increases, the thermal stability decreases. Among the three compositions studied, x = 0.3 had the best phase and chemical stability, and microstructural properties. It was observed that La0.7Sr0.3CoO3 possesses excellent phase, composition and microstructural stability up to 1273 K. Above 1273 K,however, LSCO decomposes resulting in the loss of cobalt and formation of individual oxide phases. Electrical resistivity and Seebeck coefficients were measured in situ as a function of temperature in air up to 1023 K. The electrical and Seebeck coefficient properties were found to be stable for all the three compositions up to 1023 K and studies indicated that electrical conduction occurs through a small polaron hopping mechanism. In conclusion, LSCO possessed good thermal stability in air up to 1273 K and exhibits excellent potential in thin film thermocouple applications. (C) 1999 Elsevier Science S.A. All rights reserved. C1 Virginia Tech, Dept Mat Sci & Engn, Thin Films Lab, Blacksburg, VA 24061 USA. NASA, Lewis Res Ctr, Res Sensors Technol Branch, Cleveland, OH 44135 USA. RP Vedula, R (reprint author), Univ Massachusetts, Dept Elect & Comp Engn, 201 Marcus Hall, Amherst, MA 01003 USA. NR 14 TC 29 Z9 29 U1 2 U2 17 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0040-6090 J9 THIN SOLID FILMS JI Thin Solid Films PD AUG 15 PY 1999 VL 350 IS 1-2 BP 249 EP 257 DI 10.1016/S0040-6090(98)01442-4 PG 9 WC Materials Science, Multidisciplinary; Materials Science, Coatings & Films; Physics, Applied; Physics, Condensed Matter SC Materials Science; Physics GA 226MH UT WOS:000082023400043 ER PT J AU Abgrall, H Roueff, E Liu, XM Shemansky, DE James, GK AF Abgrall, H Roueff, E Liu, XM Shemansky, DE James, GK TI High-resolution far ultraviolet emission spectra of electron-excited molecular deuterium SO JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS LA English DT Article ID ENHANCED MULTIPHOTON IONIZATION; WERNER BAND SYSTEMS; ABINITIO CALCULATION; IMPACT EXCITATION; D2 MOLECULES; VACUUM ULTRAVIOLET; TRANSITION MOMENTS; HYDROGEN MOLECULE; RYDBERG SERIES; CROSS-SECTIONS AB The high-resolution (full width at half maximum Delta lambda = 0.11 Angstrom) emission spectrum of the deuterium molecule produced by electron-impact excitation at 100 eV has been measured in the wavelength range 1200-1660 Angstrom. In conjunction with the experimental measurement, transition probabilities of B (1)Sigma(u)(+)-X (1)Sigma(g)(+), C-1 Pi(u)-X (1)Sigma(g)(+), B' (1)Sigma(u)(+)-X (1)Sigma(g)(+) and D (1)Pi(u)-X (1)Sigma(g)(+) band systems are calculated. Synthetic spectra based on the calculated transition probabilities are in very good agreement with the optically thin experimental spectra. While centrifugal effects on the overall Lyman band emission intensity in D-2 and H-2 are similar, the effect of rotation-vibrational perturbations between the B (1)Sigma(u)(+) and C (1)Pi(u)(+) states on spectral intensities is found to be less significant in D-2. Excitations via isotropic (Delta J = 0) and anisotropic (Delta J = +/-2, and 0) interactions for the dipole forbidden E,F (1)Sigma(g)(+)-X (1)Sigma(g)(+) transition are inferred from the measured spectra. Excitation cross sections of the B (1)Sigma(u)(+)-X (1)Sigma(g)(+) and C (1)Pi(u)-X (1)Sigma(g)(+) bands, along with the estimated E, F (1)Sigma(g)(+)-B (1)Sigma(u)(+) cascade cross section, for D-2 are obtained. C1 Observ Paris, DAEC, Sect Meudon, F-92195 Meudon, France. CNRS, UMR 8631, F-92195 Meudon, France. Univ So Calif, Dept Aerosp & Mech Engn, Los Angeles, CA 90089 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Abgrall, H (reprint author), Observ Paris, DAEC, Sect Meudon, F-92195 Meudon, France. NR 57 TC 28 Z9 28 U1 0 U2 8 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0953-4075 J9 J PHYS B-AT MOL OPT JI J. Phys. B-At. Mol. Opt. Phys. PD AUG 14 PY 1999 VL 32 IS 15 BP 3813 EP 3838 DI 10.1088/0953-4075/32/15/313 PG 26 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA 230VW UT WOS:000082273200022 ER PT J AU Hack, MD Jasper, AW Volobuev, YL Schwenke, DW Truhlar, DG AF Hack, MD Jasper, AW Volobuev, YL Schwenke, DW Truhlar, DG TI Quantum mechanical and quasiclassical trajectory surface hopping studies of the electronically nonadiabatic predissociation of the (A)over-tilde state of NaH2 SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID VIBRATIONAL ENERGY-TRANSFER; MOLECULAR-DYNAMICS; CHEMICAL-REACTIONS; CROSS-SECTIONS; TRANSITIONS; DISSOCIATION; COLLISIONS; SCATTERING; SYSTEMS AB Fully coupled quantum mechanical scattering calculations and adiabatic uncoupled bound-state calculations are used to identify Feshbach funnel resonances that correspond to long-lived exciplexes in the (A) over tilde state of NaH2, and the scattering calculations are used to determine their partial and total widths. The total widths determine the lifetimes, and the partial widths determine the branching probabilities for competing decay mechanisms. We compare the quantum mechanical calculations of the resonance lifetimes and the average final vibrational and rotational quantum numbers of the decay product, H-2(nu', j'), to trajectory surface hopping calculations carried out by various prescriptions for the hopping event. Tully's fewest switches algorithm is used for the trajectory surface hopping calculations, and we present a new strategy for adaptive stepsize control that dramatically improves the convergence of the numerical propagation of the solution of the coupled classical and quantum mechanical differential equations. We performed the trajectory surface hopping calculations with four prescriptions for the hopping vector that is used for adjusting the momentum at hopping events. These include changing the momentum along the nonadiabatic coupling vector (d), along the gradient of the difference in the adiabatic energies of the two states (g), and along two new vectors that we describe as the rotated-d and the rotated-g vectors. We show that the dynamics obtained from the d and g prescriptions are significantly different from each other, and we show that the d prescription agrees better with the quantum results. The results of the rotated methods show systematic deviations from the nonrotated results, and in general, the error of the nonrotated methods is smaller. The nonrotated TFS-d method is thus the most accurate method for this system, which was selected for detailed study precisely because it is more sensitive to the choice of hopping vector than previously studied systems. C1 Univ Minnesota, Dept Chem, Minneapolis, MN 55455 USA. Univ Minnesota, Inst Supercomp, Minneapolis, MN 55455 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Truhlar, DG (reprint author), Univ Minnesota, Dept Chem, 207 Pleasant St SE, Minneapolis, MN 55455 USA. RI Jasper, Ahren/A-5292-2011; schwenke, david/I-3564-2013; Truhlar, Donald/G-7076-2015 OI Truhlar, Donald/0000-0002-7742-7294 NR 51 TC 58 Z9 58 U1 1 U2 7 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 AUG 12 PY 1999 VL 103 IS 32 BP 6309 EP 6326 DI 10.1021/jp9912049 PG 18 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 228AA UT WOS:000082111400005 ER PT J AU Bauschlicher, CW AF Bauschlicher, CW TI Accurate indium bond energies SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID GAUSSIAN-BASIS SETS; CORRELATED MOLECULAR CALCULATIONS; COUPLED-CLUSTER THEORY; IONIZATION-POTENTIALS; ELECTRON CORRELATION; WAVE-FUNCTIONS; APPROXIMATION; SPIN; EXCHANGE; STATES AB InXn atomization energies are computed for n = 1-3 and X = H, Cl, and CH3. The geometries and frequencies are determined using density functional theory. The atomization energies are computed at the coupled cluster level of theory. The complete basis set limit is obtained by extrapolation. The scalar relativistic effect is computed using the Douglas-Kroll approach. While the heats of formation for InH, InCl, and InCl3 are in good agreement with experiment, the current results show that the experimental value for In(CH3)(3) must be wrong. 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 39 TC 19 Z9 19 U1 0 U2 0 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 AUG 12 PY 1999 VL 103 IS 32 BP 6429 EP 6432 DI 10.1021/jp990967t PG 4 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 228AA UT WOS:000082111400021 ER PT J AU Boldt, E Ghosh, P AF Boldt, E Ghosh, P TI Cosmic rays from remnants of quasars? SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE acceleration of particles; black hole physics; cosmic rays; galaxies : nuclei ID SUPERMASSIVE BLACK-HOLES; ELECTROMAGNETIC EXTRACTION; GALACTIC NUCLEI; ENERGY; ACCRETION; EVOLUTION; SPECTRUM; LUMINOSITY; PHYSICS; CUTOFF AB Considerations of the collision losses for protons traversing the 2.7-K blackbody microwave radiation field have led to the conclusion that the highest energy cosmic rays, those observed at greater than or equal to 10(20) eV, must come from sources within the present epoch. In light of this constraint, it is hen suggested that these particles may be accelerated near the event horizons of spinning supermassive black holes associated with presently inactive quasar remnants. The required emf is generated by the black hole induced rotation of externally supplied magnetic field lines threading the horizon. Producing the observed flux of the highest energy cosmic rays would constitute a negligible drain on the black hole dynamo. Observations with upcoming air shower arrays and space missions may lead to the identification of candidate dormant galaxies that harbour such black holes. Although the highest energy events observed so far are accounted for within the context of this scenario, a spectral upper bound at similar to 10(21) eV is expected since the acceleration to higher energies appears to be precluded, on general grounds. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. EM boldt@lheavx.gsfc.nasa.gov; pranab@rufus.gsfc.nasa.gov NR 42 TC 66 Z9 66 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 AUG 11 PY 1999 VL 307 IS 3 BP 491 EP 494 DI 10.1046/j.1365-8711.1999.02600.x PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 227VV UT WOS:000082101400005 ER PT J AU Iwasawa, K Fabian, AC Nandra, K AF Iwasawa, K Fabian, AC Nandra, K TI ASCA and ROSAT observations of NGC 5548: discrepant spectral indices SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE galaxies : active; galaxies : individual : NGC 5548; galaxies : Seyfert; X-rays : galaxies ID ACTIVE GALACTIC NUCLEI; X-RAY-SPECTRUM; COLD MATTER; NGC-5548; VARIABILITY; REFLECTION; BEPPOSAX; 3C273; DISK AB We report on simultaneous ASCA and ROSAT observations of the Seyfert galaxy NGC 5548 made during the ASCA Performance Verification phase. Spectral features due to a warm absorber and reflection are clearly seen in the X-ray spectra. We find that the continuum spectral shape differs between the ASCA and ROSAT data sets. The photon-index obtained from the ROSAT PSPC exceeds that from the ASCA SIS Delta Gamma approximate to 0.4. The discrepancy is clear even in the 0.5-2 keV energy band over which both detectors are sensitive. The spectra cannot be made consistent by choosing a more complex model. The problem likely lies in the response curve (estimated effective area) of one, or both, detectors, There may be important consequences for a wide range of published results. C1 Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Iwasawa, K (reprint author), Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0HA, England. NR 29 TC 39 Z9 39 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 AUG 11 PY 1999 VL 307 IS 3 BP 611 EP 618 DI 10.1046/j.1365-8711.1999.02664.x PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 227VV UT WOS:000082101400015 ER PT J AU Pian, E Urry, CM Maraschi, L Madejski, G McHardy, IM Koratkar, A Treves, A Chiappetti, L Grandi, P Hartman, RC Kubo, H Leach, CM Pesce, JE Imhoff, C Thompson, R Wehrle, AE AF Pian, E Urry, CM Maraschi, L Madejski, G McHardy, IM Koratkar, A Treves, A Chiappetti, L Grandi, P Hartman, RC Kubo, H Leach, CM Pesce, JE Imhoff, C Thompson, R Wehrle, AE TI Ultraviolet and multiwavelength variability of the blazar 3C 279: Evidence for thermal emission SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : active; galaxies : individual (3C 279); gamma rays : observations; radiation mechanisms : nonthermal; ultraviolet : galaxies; X-rays : galaxies ID ACTIVE GALACTIC NUCLEI; X-RAY EXCESS; BL LACERTAE; GAMMA-RAY; QUASAR 3C-279; MULTIFREQUENCY OBSERVATIONS; SPECTRAL VARIABILITY; OPTICAL OBSERVATIONS; OBJECT PKS-2155-304; ACCRETION DISKS AB The gamma-ray blazar 3C 279 was monitored on a nearly daily basis with IUE, ROSAT, and EGRET for 3 weeks between 1992 December and 1993 January. During this period, the blazar was at a historical minimum at all wavelengths. Here we present the UV data obtained during this multiwavelength campaign. A maximum UV variation of similar to 50% is detected while during the same period the X-ray flux varied by no more than 13%. At the lowest UV flux level, the average spectrum in the 1230-2700 Angstrom interval is unusually flat for this object ([alpha(UV)] similar to 1). The flattening could represent the lo lowest energy tail of the inverse Compton component responsible for the X-ray emission, or it could be due to the presence of a thermal component at similar to 20,000 K, possibly associated with an accretion disk. The presence of an accretion disk in this blazar object, likely observable only in very low states and otherwise hidden by the beamed, variable synchrotron component, would be consistent with the scenario in which the seed photons for the inverse Compton mechanism producing the gamma-rays are external to the relativistic jet. We further discuss the long-term correlation of the UV flux with the X-ray and gamma-ray fluxes obtained at various epochs. All UV archival data are included in the analysis. Both the X-ray and gamma-ray fluxes are generally well correlated with the UV flux, with approximately square root and quadratic dependences, respectively. C1 Space Telescope Sci Inst, Baltimore, MD 21218 USA. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Southampton, Dept Phys, Southampton SO9 5NH, Hants, England. Univ Como, Dept Phys, I-22100 Como, Italy. CNR, Ist Fis Cosm & Tecnol Relat, I-20133 Milan, Italy. CNR, Ist Astrofis Spaziale, I-00133 Rome, Italy. Tokyo Inst Technol, Dept Phys, Meguro Ku, Tokyo 1528551, Japan. Comp Sci Corp, Sci Program, Laurel, MD 20707 USA. CALTECH, Jet Prop Lab, Infrared Proc Anal Ctr, Pasadena, CA 91125 USA. Osservatorio Astron Brera, I-20121 Milan, Italy. RP Pian, E (reprint author), CNR, Ist Tecnol & Studio Radiaz Extraterrestri, Via Gobetti 101, I-40129 Bologna, Italy. RI Urry, Claudia/G-7381-2011; OI Urry, Claudia/0000-0002-0745-9792; Chiappetti, Lucio/0000-0001-7857-7908; Pian, Elena/0000-0001-8646-4858 NR 67 TC 68 Z9 69 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 AUG 10 PY 1999 VL 521 IS 1 BP 112 EP 120 DI 10.1086/307548 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 223YC UT WOS:000081868300010 ER PT J AU Madejski, GM Sikora, M Jaffe, T Blazejowski, M Jahoda, K Moderski, R AF Madejski, GM Sikora, M Jaffe, T Blazejowski, M Jahoda, K Moderski, R TI X-ray observations of BL Lacertae during the 1997 outburst and association with quasar-like characteristics SO ASTROPHYSICAL JOURNAL LA English DT Article DE BL Lacertae objects : individual (BL Lacertae); galaxies : active; radiation mechanisms : nonthermal; X-rays : galaxies ID EXTRAGALACTIC RADIO-SOURCES; LOCAL INTERSTELLAR CO; RELATIVISTIC JETS; MULTIFREQUENCY OBSERVATIONS; TIMING EXPLORER; GAMMA-RAYS; BLAZARS; CLOUDS; PERFORMANCE; ABSORPTION AB This paper reports on the X-ray emission from BL Lacertae during its 1997 July outburst as observed with the Rossi X-Ray Timing Explorer (RXTE), compares the RXTE data with previous measurements, and interprets the overall electromagnetic emission in the context of the currently popular theoretical models. The source is bright and variable, with the 2-10 keV flux approximately 2-3.5 times higher than measured in 1995 November by ASCA. The spectrum is also harder, with power-law energy indices of similar to 0.4-0.6, compared with similar to 0.9 in 1995 November. Both in the optical band, where BL Lacertae now shows broad emission lines, and in the X-ray band, where the spectrum is hard, the overall electromagnetic distribution of BL Lacertae is similar to that observed in blazars associated with quasars rather than to that seen in the more common high-energy peaked BL Lac-type objects. We argue that the high-energy (X-ray and gamma-ray) emission from BL Lacertae consists of two spectral components: X-rays are produced by Comptonization of synchrotron radiation, while the gamma-rays are produced by Comptonization of the broad emission line flux. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. Copernicus Astron Ctr, PL-00716 Warsaw, Poland. Raytheon STX, Lexington, MA 02173 USA. Univ Colorado, Joint Inst Lab Astrophys, Boulder, CO 80309 USA. RP Madejski, GM (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RI Jahoda, Keith/D-5616-2012 NR 54 TC 53 Z9 53 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 AUG 10 PY 1999 VL 521 IS 1 BP 145 EP 154 DI 10.1086/307524 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 223YC UT WOS:000081868300013 ER PT J AU Macri, LM Huchra, JP Stetson, PB Silbermann, NA Freedman, WL Kennicutt, RC Mould, JR Madore, BF Bresolin, F Ferrarese, L Ford, HC Graham, JA Gibson, BK Han, M Harding, P Hill, RJ Hoessel, JG Hughes, SMG Kelson, DD Illingworth, GD Phelps, RL Prosser, CF Rawson, DM Saha, A Sakai, S Turner, A AF Macri, LM Huchra, JP Stetson, PB Silbermann, NA Freedman, WL Kennicutt, RC Mould, JR Madore, BF Bresolin, F Ferrarese, L Ford, HC Graham, JA Gibson, BK Han, M Harding, P Hill, RJ Hoessel, JG Hughes, SMG Kelson, DD Illingworth, GD Phelps, RL Prosser, CF Rawson, DM Saha, A Sakai, S Turner, A TI The extragalactic distance scale key project. XVIII. The discovery of Cepheids and a new distance to NGC 4535 using the Hubble Space Telescope SO ASTROPHYSICAL JOURNAL LA English DT Article DE Cepheids; distance scale; galaxies : distances and redshifts; galaxies : individual (NGC 4535) ID VIRGO-CLUSTER; SPIRAL GALAXIES; CALIBRATION; CONSTANT; PERFORMANCE; PHOTOMETRY; VARIABLES; WFPC2 AB We report on the discovery of Cepheids in the Virgo spiral galaxy NGC 4535, based on observations made with the Wide Field and Planetary Camera 2 on board the Hubble Space Telescope (HST). NGC 4535 is one of 18 galaxies observed as a part of The HST Key Project on the Extragalactic Distance Scale, which aims to measure the Hubble constant to 10% accuracy. NGC 4535 was observed over 13 epochs using the F555W filter, and over 9 epochs using the F814W filter. The HST F555W and F814W data were transformed to the Johnson V and Kron-Cousins I magnitude systems, respectively. Photometry was performed using two independent programs, DoPHOT and DAOPHOT II/ALLFRAME. Period-luminosity relations in the V and I bands were constructed using 39 high-quality Cepheids present in our set of 50 variable candidates. We obtain a distance modulus of 31.02 +/- 0.26 mag, corresponding kto a distance of 16.0 +/- 1.9 Mpc. Our distance estimate is based on values of mu(0) = 18.50 +/- 0.10 mag and E(V-I) = 0.13 mag for the distance modulus and reddening of the LMC, respectively. C1 Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. Dominion Astrophys Observ, Victoria, BC V8X 4M6, Canada. CALTECH, IPAC, Pasadena, CA 91125 USA. Carnegie Inst Washington Observ, Pasadena, CA 91101 USA. Univ Arizona, Steward Observ, Tucson, AZ 85721 USA. Australian Natl Univ, Mt Stromlo & Siding Spring Observ, Weston, ACT 2611, Australia. European So Observ, D-85478 Garching, Germany. CALTECH, Dept Astron, Pasadena, CA 91125 USA. Johns Hopkins Univ, Baltimore, MD 21218 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Carnegie Inst Washington, Dept Terr Magnetism, Washington, DC 20015 USA. Univ Colorado, Ctr Astrophys & Space Astron, Boulder, CO 80309 USA. Avanti Corp, Fremont, CA 94538 USA. Univ Wisconsin, Madison, WI 53706 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England. Univ Calif Santa Cruz, Lick Observ, Santa Cruz, CA 95064 USA. Natl Opt Astron Observ, Tucson, AZ 85726 USA. RP Macri, LM (reprint author), Harvard Smithsonian Ctr Astrophys, 60 Garden St, Cambridge, MA 02138 USA. RI Gibson, Brad/M-3592-2015; OI Gibson, Brad/0000-0003-4446-3130; Macri, Lucas/0000-0002-1775-4859 NR 39 TC 54 Z9 54 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 AUG 10 PY 1999 VL 521 IS 1 BP 155 EP 178 DI 10.1086/307541 PN 1 PG 24 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 223YC UT WOS:000081868300014 ER PT J AU Shelton, RL AF Shelton, RL TI Simulations of supernova remnants in diffuse media. II. Three remnants and their X-ray emission SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM : abundances; supernova remnants; X-rays : ISM ID INTERSTELLAR-MEDIUM; THIN PLASMAS; HOT GAS; ABSORPTION; SPECTRUM AB This paper provides detailed descriptions of the X-ray emission from supernova remnants (SNRs) evolving in warm, low-density, nonthermal pressure-dominated regions (T-0 = 10(4) K, n = 0.001 cm(-3), P-nt = 1800 or 7200 K cm-3). Nonequilibrium ionization hydrocode simulations are used to predict the high-resolution spectra, 1/4 and 3/4 keV ROSAT PSPC count rates, spatial appearance, color temperatures, and ratios of O VII to O VIII emission-line fluxes as a function of time. If undisturbed, the remnants are quite long lived, surviving for similar to 1.2 x 10(7) to similar to 1.6 x 10(7) yr. During their brief energy-conserving phases, the hot, highly pressurized gas behind their shock fronts copiously emits X-rays. Thus, their 1/4 keV surface brightnesses are thousands of ROSAT PSPC counts s(-1) arcmin(-2) and the remnants appear strongly edge brightened. The onset of the radiative phase heralds the end of the extreme X-ray luminosities but not the end of the X-ray emission. After the cool shell forms behind the shock front, the hot SNR bubble slowly radiates away the remaining energy, with a diminutive fraction released in the form of X-rays. Thus, the 1/4 keV surface brightnesses are tens to hundreds of ROSAT PSPC counts s(-1) arcmin(-2) and the remnants appear "centrally filled." The hot plasma within the remnant bubbles is always out of collisional ionizational equilibrium Early on, the ionization states are much lower than expected for such hot gas. Later on, the ionization states are higher. This paper also applies the standard observational analyses for determining the color temperature, electron density, and thermal pressure to ROSAT "observations" of one of the simulated remnants, thus providing a map between observational results and physical conditions. The paper reports the O+5, N+4, and C+3 column densities for the simulated remnants. The simulations may be of interest and are applied to studies of the Galactic halo and Local Bubble. They may also be of interest to studies of external galaxies and interarm regions of the Milky Way. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Shelton, RL (reprint author), Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA. NR 31 TC 28 Z9 28 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 AUG 10 PY 1999 VL 521 IS 1 BP 217 EP 233 DI 10.1086/307553 PN 1 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 223YC UT WOS:000081868300020 ER PT J AU Arendt, RG Dwek, E Moseley, SH AF Arendt, RG Dwek, E Moseley, SH TI Newly synthesized elements and pristine dust in the Cassiopeia A supernova remnant SO ASTROPHYSICAL JOURNAL LA English DT Article DE dust, extinction; infrared : ISM : continuum; infrared : ISM : lines and bands; ISM : individual (Cassiopeia A); supernova remnants ID FAST-MOVING KNOTS; INFRARED-EMISSION; A SUPERNOVA; X-RAY; PHYSICAL CONDITIONS; OPTICAL-PROPERTIES; ELECTRON-DENSITY; MASSIVE STARS; SPECTRA; EJECTA AB Spectroscopic observations at 2.4-45 mu m of the young supernova remnant Cas A with the Infrared Space Observatory (ISO) Short Wavelength Spectrometer reveal strong emission lines of O, Ne, Si, S, and Ar. These lines are observed at high velocities (several 10(3) km s(-1)) and are therefore associated with the supernova ejects known as the fast-moving knots (FMKs). Continuum emission from dust is also seen in the Cas A spectrum. The continuum strength is spatially well correlated with the O and Ar line strengths, which indicates that the dust emission also arises from the FMKs. The dust continuum has an emission feature at similar to 22 mu m which cannot be fitted by typical astronomical silicates but can be fitted with a particular class of silicate minerals. This suggests that the dust in Cas A is silicate material that has freshly condensed from the Cas A ejecta into a mineral form that is uncharacteristic of typical ISM dust grains. C1 NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Arendt, RG (reprint author), Raytheon ITSS, Lexington, MA 02173 USA. RI Moseley, Harvey/D-5069-2012 NR 52 TC 87 Z9 87 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 AUG 10 PY 1999 VL 521 IS 1 BP 234 EP 245 DI 10.1086/307545 PN 1 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 223YC UT WOS:000081868300021 ER PT J AU Szkody, P Linnell, A Honeycutt, K Robertson, J Silber, A Hoard, DW Pastwick, L Desai, V Hubeny, I Cannizzo, J Liller, W Zissell, R Walker, G AF Szkody, P Linnell, A Honeycutt, K Robertson, J Silber, A Hoard, DW Pastwick, L Desai, V Hubeny, I Cannizzo, J Liller, W Zissell, R Walker, G TI RXTE, ROSAT, EUVE, IUE, and optical observations through the 45 day supercycle of V1159 Orionis SO ASTROPHYSICAL JOURNAL LA English DT Article DE novae, cataclysmic variables; stars : individual (V1159 Orionis); ultraviolet : stars; X-rays : stars ID NOVA VW HYDRI; DWARF NOVA; SS-CYGNI; X-RAY; CATACLYSMIC VARIABLES; URSAE-MAJORIS; ACCRETION DISKS; Z-CHAMAELEONTIS; BINARY-SYSTEMS; OUTBURST CYCLE AB A complete 45 day supercycle of the cataclysmic variable V1159 Ori comprising a superoutburst and eight normal outbursts was observed. Coverage included ground-based optical observations as well as observations with RXTE for 38 days, ROSAT for 34 days, IUE for 27 days, and Extreme Ultraviolet Explorer (EUVE) for 10 days. The resulting light curves reveal that the optical and UV light variations are inversely correlated with the RXTE and ROSAT fluxes, with the largest change in intensity occurring in the ROSAT bandpass. There is no evidence for a strong EUV/soft X-ray component during outburst. An out flowing wind is evident from the C IV line profile during each brief outburst as well as the superoutburst. The transitions from outburst states of the disk to quiescent slates take place on timescales of hours. Accretion disk models can fit the UV line and continuum energy distributions near outburst only if the disk radial temperature profile is modified from the standard case to produce a hotter distribution in the outer annuli. The high mass transfer rate, the hot disk distribution, and the similarity of outbursts and superoutbursts argue for outside-in outbursts in this system. C1 Univ Washington, Dept Astron, Seattle, WA 98195 USA. Indiana Univ, Dept Astron, Bloomington, IN 47405 USA. Arkanas Tech Univ, Dept Phys Sci, Russellville, AR 72801 USA. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. Mt Holyoke Coll, S Hadley, MA 01075 USA. RP Szkody, P (reprint author), Univ Washington, Dept Astron, Box 351580, Seattle, WA 98195 USA. NR 44 TC 10 Z9 10 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 AUG 10 PY 1999 VL 521 IS 1 BP 362 EP 375 DI 10.1086/307550 PN 1 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 223YC UT WOS:000081868300035 ER PT J AU Carpenter, KG Robinson, RD Harper, GM Bennett, PD Brown, A Mullan, DJ AF Carpenter, KG Robinson, RD Harper, GM Bennett, PD Brown, A Mullan, DJ TI GHRS observations of cool, low-gravity stars. V. The outer atmosphere and wind of the nearby K supergiant lambda Velorum SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars : atmospheres; stars : chromospheres; stars : individual (lambda Velorum); stars : late-type; stars : mass loss; supergiants ID HUBBLE-SPACE-TELESCOPE; CHROMOSPHERIC HEATING MECHANISMS; H-R DIAGRAM; C-II; GIANT STARS; MASS-LOSS; EFFECTIVE TEMPERATURES; ULTRAVIOLET-SPECTRUM; ANGULAR DIAMETERS; RESONANCE LINES AB UV spectra of lambda Velorum taken with the Goddard High Resolution Spectrograph (GHRS) on the Hubble Space Telescope are used to probe the structure of the outer atmospheric layers and wind and to estimate the mass-loss rate from this K5 Ib-II supergiant. VLA radio observations at lambda = 3.6 cm are used to obtain an independent check on the wind velocity and mass-loss rate inferred from the UV observations. Parameters of the chromospheric structure are estimated from measurements of UV line widths, positions, and fluxes and from the UV continuum flux distribution. The ratios of optically thin C II] emission lines indicate a mean chromospheric electron density of log N-e approximate to 8.9 +/- 0.2 cm(-3). The profiles of these lines indicate a chromospheric turbulence (upsilon(0) approximate to 25-36 km s(-1)), which greatly exceeds that seen in either the photosphere or wind. The centroids of optically thin emission lines of Fe II and of the emission wings of self-reversed Fe II lines indicate that they are formed in plasma approximately at rest with respect to the photosphere of the star. This suggests that the acceleration of the wind occurs above the chromospheric regions in which these emission line photons are created. The UV continuum detected by the GHRS clearly traces the mean flux-formation temperature as it increases with height in the chromosphere from a well-defined temperature minimum of 3200 K up to about 4600 K. Emission seen in lines of C III] and Si III] provides evidence of material at higher than chromospheric temperatures in the outer atmosphere of this noncoronal star. The photon-scattering wind produces self-reversals in the strong chromospheric emission lines, which allow us to probe the velocity held of the wind. The velocities to which these self-absorptions extend increase with intrinsic line strength, and thus height in the wind, and therefore directly map the wind acceleration. The width and shape of these; self-absorptions reflect a wind turbulence of approximate to 9-21 km s(-1). We further characterize the wind by comparing the observations with synthetic profiles generated with the Lamers et al. Sobolev with Exact Integration (SEI) radiative transfer code, assuming simple models of the outer atmospheric structure. These comparisons indicate that the wind in 1994 can be described by a model with a wind acceleration parameter beta similar to 0.9, a terminal velocity of 29-33 km s(-1), and a mass-loss rate similar to 3 x 10(-9) M. yr(-1). Modeling of the 3.6 cm radio flux observed in 1997 suggests a more slowly accelerating wind (higher beta) and/or a higher mass-loss rate than inferred from the UV line profiles. These differences may be due to temporal variations in the wind or from limitations in one or both of the models. The discrepancy is currently under investigation. C1 NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. Catholic Univ Amer, NASA, Goddard Space Flight Ctr, Inst Astrophys & Computat Sci, Greenbelt, MD 20771 USA. Univ Colorado, Ctr Astrophys & Space Astron, Boulder, CO 80309 USA. Univ Delaware, Bartol Res Inst, Newark, DE 19716 USA. RP NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Code 681, Greenbelt, MD 20771 USA. EM kgc@stargate.gsfc.nasa.gov; robinson@opal.gsfc.nasa.gov; gmh@casa.colorado.edu; pbennett@casa.colorado.edu; ab@casa.colorado.edu RI Carpenter, Kenneth/D-4740-2012 NR 99 TC 23 Z9 23 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 AUG 10 PY 1999 VL 521 IS 1 BP 382 EP 406 DI 10.1086/307520 PN 1 PG 25 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 223YC UT WOS:000081868300037 ER PT J AU Haiman, Z Loeb, A AF Haiman, Z Loeb, A TI X-ray emission from the first quasars SO ASTROPHYSICAL JOURNAL LA English DT Article DE black hole physics; cosmology : theory; quasars : general ID HIGH-REDSHIFT GALAXIES; LUMINOSITY FUNCTION; EVOLUTION; UNIVERSE; DENSITY; NUCLEI AB It is currently unknown whether the universe was reionized by quasars or stars at z greater than or similar to 5. We point out that quasars can be best distinguished from stellar systems by their X-ray emission. Based on a simple hierarchical CDM model, we predict the number counts and X-ray fluxes of quasars at high redshifts. The model is consistent with available data on the luminosity function of high-redshift quasars in the optical and soft X-ray bands. The cumulative contribution of faint, undetected quasars in our model is consistent with the unresolved fraction of the X-ray background. We find that the Chandra X-ray Observatory might detect similar to 10(2) quasars from redshifts z greater than or similar to 5 per its 17' x 17' field of view at the flux threshold of similar to 2 x 10(-16) ergs s(-1) cm(-2). The redshifts of these faint point sources could be identified by follow-up infrared observations from the ground or with the Next Generation Space Telescope. C1 NASA, Fermilab Astrophys Ctr, Fermi Natl Accelerator Lab, Batavia, IL 60510 USA. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. RP Haiman, Z (reprint author), NASA, Fermilab Astrophys Ctr, Fermi Natl Accelerator Lab, Batavia, IL 60510 USA. NR 29 TC 33 Z9 33 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 AUG 10 PY 1999 VL 521 IS 1 BP L9 EP L12 DI 10.1086/312177 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 223YE UT WOS:000081868500003 ER PT J AU Xu, K AF Xu, K TI Gas-kinetic theory-based flux splitting method for ideal magnetohydrodynamics SO JOURNAL OF COMPUTATIONAL PHYSICS LA English DT Article DE magnetohydrodynamics; flux splitting; gas-kinetic scheme ID EQUATIONS; SCHEME; FLOW AB A gas-kinetic flux splitting method is developed for the ideal magnetohydrodynamics (MHD) equations. The new scheme is based on the direct splitting of the flux function of the MHD equations with the inclusion of "particle" collisions in the transport process. Consequently, the artificial dissipation in the new scheme is greatly reduced in comparison with the MHD flux vector splitting method. Numerical results from the current scheme are favorable compared with those from the well-developed Roe-type MHD solver. In the current paper, the general principle of splitting the macroscopic flux function based on the gas-kinetic theory is presented. The flux construction strategy may shed some light on the possible construction of accurate and robust hybrid schemes for the compressible flow simulations. (C) 1999 Academic Press. C1 Hong Kong Univ Sci & Technol, Dept Math, Kowloon, Peoples R China. NASA, Langley Res Ctr, Inst Comp Applicat Sci & Engn, Hampton, VA 23681 USA. RP Hong Kong Univ Sci & Technol, Dept Math, Clear Water Bay, Kowloon, Peoples R China. EM makxu@uxmail.ust.hk RI Xu, Kun/F-7627-2011 NR 35 TC 29 Z9 31 U1 1 U2 3 PU ACADEMIC PRESS INC ELSEVIER SCIENCE PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0021-9991 EI 1090-2716 J9 J COMPUT PHYS JI J. Comput. Phys. PD AUG 10 PY 1999 VL 153 IS 2 BP 334 EP 352 DI 10.1006/jcph.1999.6280 PG 19 WC Computer Science, Interdisciplinary Applications; Physics, Mathematical SC Computer Science; Physics GA 224NA UT WOS:000081904100004 ER PT J AU Wood, WA Kleb, WL AF Wood, WA Kleb, WL TI Diffusion characteristics of finite volume and fluctuation splitting schemes SO JOURNAL OF COMPUTATIONAL PHYSICS LA English DT Article DE finite volume; fluctuation splitting; artificial dissipation ID EULER EQUATIONS; GRIDS AB The diffusive characteristics of two upwind schemes, multi-dimensional fluctuation splitting and locally one-dimensional finite volume, are compared for scalar advection-diffusion problems. Algorithms for the two schemes are developed for node-based data representation on median-dual meshes associated with unstructured triangulations in two spatial dimensions. Four model equations are considered: Linear advection, non-linear advection, diffusion, and advection-diffusion, with cases chosen to mimic features present in compressible gas dynamics. Modular coding is employed to isolate the effects of the two approaches for upwind flux evaluation, allowing for head-to-head accuracy and efficiency comparisons. Both the stability of compressive limiters and the amount of artificial diffusion generated by the schemes are found to be grid-orientation dependent, with the fluctuation splitting scheme producing less artificial diffusion than the finite volume scheme. Convergence rates are compared for an advection-diffusion problem, with a speedup of 2.5 seen for fluctuation splitting versus finite volume when solved on the same mesh. However, accurate solutions to problems with small diffusion coefficients can be achieved on coarser meshes using fluctuation splitting rather than finite volume, so that when comparing convergence rates to reach a given accuracy, fluctuation splitting shows a speedup of 29 over finite volume for the test problem. (C) 1999 Academic Press. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Wood, WA (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 22 TC 5 Z9 6 U1 0 U2 0 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0021-9991 J9 J COMPUT PHYS JI J. Comput. Phys. PD AUG 10 PY 1999 VL 153 IS 2 BP 353 EP 377 DI 10.1006/jcph.1999.6281 PG 25 WC Computer Science, Interdisciplinary Applications; Physics, Mathematical SC Computer Science; Physics GA 224NA UT WOS:000081904100005 ER PT J AU Ray, RD Bills, BG Chao, BF AF Ray, RD Bills, BG Chao, BF TI Lunar and solar torques on the oceanic tides SO JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH LA English DT Article ID TIDAL DISSIPATION; ANGULAR-MOMENTUM; EARTH ROTATION; ALTIMETRY AB A general framework for calculating lunar and solar torques on the oceanic tides is developed in terms of harmonic constituents. Axial torques and their associated angular momentum and Earth rotation variations are deduced from recent satellite-altimeter and satellite-tracking tide solutions. Torques on the prograde components of the tide produce the familiar secular braking of the rotation rate. The estimated secular acceleration is approximately -1300 arcseconds/century(2) (less 4% after including atmospheric tides); the implied rate of change in the length of day is 2.28 milliseconds/century. Torques on the retrograde components of the tide produce periodic rotation variations at twice the tidal frequency. Interaction torques (for example, solar torques on lunar tides) generate a large suite of rotation-rate variations at sums and differences of the original tidal frequencies. These are estimated for periods from 18.6 years to 6 hours. At subdaily periods the angular momentum variations are 5 to 6 orders of magnitude smaller than the variations caused by ocean tidal currents. C1 NASA, Goddard Space Flight Ctr, Terr Phys Lab, Greenbelt, MD 20771 USA. Univ Calif San Diego, Scripps Inst Oceanog, Inst Geophys & Planetary Phys, La Jolla, CA 92093 USA. RP NASA, Goddard Space Flight Ctr, Terr Phys Lab, Code 926, Greenbelt, MD 20771 USA. EM richard.ray@gsfc.nasa.gov RI Bills, Bruce/C-1156-2008; Ray, Richard/D-1034-2012; Chao, Benjamin Fong/N-6156-2013 NR 36 TC 5 Z9 5 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9313 EI 2169-9356 J9 J GEOPHYS RES-SOL EA JI J. Geophys. Res.-Solid Earth PD AUG 10 PY 1999 VL 104 IS B8 BP 17653 EP 17659 DI 10.1029/1999JB900165 PG 7 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 224LL UT WOS:000081900500008 ER PT J AU Dudley, M Huang, XR Huang, W Powell, A Wang, S Neudeck, P Skowronski, M AF Dudley, M Huang, XR Huang, W Powell, A Wang, S Neudeck, P Skowronski, M TI The mechanism of micropipe nucleation at inclusions in silicon carbide SO APPLIED PHYSICS LETTERS LA English DT Article ID 6H-SIC SINGLE-CRYSTALS; SCREW DISLOCATIONS; GROWTH AB A model is presented for a possible mechanism of screw dislocation (including micropipe) nucleation in silicon carbide. The model is based on the observation of micropipe nucleation at the sites of foreign material inclusions using synchrotron white beam x-ray topography and transmission optical microscopy. It is shown that incorporation of the inclusion into the growing crystal can lead to deformation of the protruding ledge which constitutes the overgrowing layer. Accommodation of this deformation into the crystal lattice leads to the production of pairs of opposite sign screw dislocations which then propagate with the growing crystal. Evidence for the existence of such pairs of dislocations is presented. (C) 1999 American Institute of Physics. [S0003-6951(99)01332-7]. C1 SUNY Stony Brook, Dept Mat Sci & Engn, Stony Brook, NY 11794 USA. Adv Technol Mat Inc, Danbury, CT 06810 USA. NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. Carnegie Mellon Univ, Dept Mat Sci & Engn, Pittsburgh, PA 15213 USA. RP Dudley, M (reprint author), SUNY Stony Brook, Dept Mat Sci & Engn, Stony Brook, NY 11794 USA. RI Skowronski, Marek/A-8934-2011 OI Skowronski, Marek/0000-0002-2087-0068 NR 19 TC 79 Z9 82 U1 2 U2 25 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0003-6951 J9 APPL PHYS LETT JI Appl. Phys. Lett. PD AUG 9 PY 1999 VL 75 IS 6 BP 784 EP 786 DI 10.1063/1.124512 PG 3 WC Physics, Applied SC Physics GA 222FJ UT WOS:000081772600014 ER PT J AU Arneodo, A Decoster, N Roux, SG AF Arneodo, A Decoster, N Roux, SG TI Intermittency, log-normal statistics, and multifractal cascade process in high-resolution satellite images of cloud structure SO PHYSICAL REVIEW LETTERS LA English DT Article ID FULLY-DEVELOPED TURBULENCE; REYNOLDS-NUMBER TURBULENCE; MARINE STRATOCUMULUS; SCALE-INVARIANCE; WAVELETS; MODELS; RAIN AB We apply a wavelet based deconvolution method to LANDSAT satellite images of cloudy scenes. This method proves to be very efficient to disentangle the convective cell anisotropic texture from the isotropic scale invariant background radiance fluctuations. We show that the experimental data do not allow us to discriminate between various phenomenological cascade models that account for intermittency and their log-normal approximations. We comment on the multifractal properties of stratocumulus radius fields comparatively to fully developed turbulence data. C1 Ctr Rech Paul Pascal, F-33600 Pessac, France. NASA, Goddard Space Flight Ctr, Climate & Radiat Branch, Greenbelt, MD 20771 USA. RP Arneodo, A (reprint author), Ctr Rech Paul Pascal, Ave A Schweitzer, F-33600 Pessac, France. NR 23 TC 36 Z9 37 U1 0 U2 3 PU AMER 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 AUG 9 PY 1999 VL 83 IS 6 BP 1255 EP 1258 DI 10.1103/PhysRevLett.83.1255 PG 4 WC Physics, Multidisciplinary SC Physics GA 223ZL UT WOS:000081871400045 ER PT J AU Nakariakov, VM Ofman, L DeLuca, EE Roberts, B Davila, JM AF Nakariakov, VM Ofman, L DeLuca, EE Roberts, B Davila, JM TI TRACE observation of damped coronal loop oscillations: Implications for coronal heating SO SCIENCE LA English DT Article ID RESONANT ABSORPTION; ALFVEN WAVES; SOLAR CORONA; SCALING LAWS; DRIVEN AB The imaging telescope on board the Transition Region and Coronal Explorer (TRACE) spacecraft observed the decaying transversal oscillations of a Long [(130 +/- 6) x 10(6) meters], thin [diameter (2.0 +/- 0.36) x 10(6) meters], bright coronal Loop in the 171 angstrom Fe-IX emission line. The oscillations were excited by a solar flare in the adjacent active region. The decay time of the oscillations is 14.5 +/- 2.7 minutes for an oscillation with a frequency 3.90 +/- 0.13 millihertz, The coronal dissipation coefficient is estimated to be eight to nine orders of magnitude Larger than the theoretically predicted classical value. The larger dissipation coefficient may solve existing difficulties with wave heating and reconnection theories. C1 NASA, Goddard Space Flight Ctr, Raytheon ITSS, Greenbelt, MD 20771 USA. Univ St Andrews, Sch Math & Computat Sci, St Andrews KY16 9SS, Fife, Scotland. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. RP Ofman, L (reprint author), NASA, Goddard Space Flight Ctr, Raytheon ITSS, 682, Greenbelt, MD 20771 USA. RI Nakariakov, Valery/E-2375-2013; DeLuca, Edward/L-7534-2013 OI Nakariakov, Valery/0000-0001-6423-8286; DeLuca, Edward/0000-0001-7416-2895 NR 26 TC 566 Z9 572 U1 0 U2 8 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD AUG 6 PY 1999 VL 285 IS 5429 BP 862 EP 864 DI 10.1126/science.285.5429.862 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 223UX UT WOS:000081860900040 ER PT J AU Geissler, PE McEwen, AS Ip, W Belton, MJS Johnson, TV Smyth, WH Ingersoll, AP AF Geissler, PE McEwen, AS Ip, W Belton, MJS Johnson, TV Smyth, WH Ingersoll, AP TI Galileo imaging of atmospheric emissions from Io SO SCIENCE LA English DT Article ID PLASMA TORUS; ELECTRON-IMPACT; ULTRAVIOLET; JUPITER; TEMPERATURE; VOLCANISM; SO2 AB The Galileo spacecraft has detected diffuse optical emissions from to in high-resolution images acquired while the satellite was eclipsed by Jupiter. Three distinct components make up lo's visible emissions. Bright blue glows of more than 300 kilorayleighs emanate from volcanic plumes, probably due to electron impact on molecular sulfur dioxide. Weaker red emissions, possibly due to atomic oxygen, are seen along the Limbs, brighter on the pole closest to the plasma torus. A faint green glow appears concentrated on the night side of to, possibly produced by atomic sodium. to's disk-averaged emission diminishes with time after entering eclipse, whereas the localized blue glows brighten instead. C1 Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85711 USA. Natl Cent Univ, Astron Inst, Chungli 320, Taiwan. Natl Opt Astron Observ, Tucson, AZ 85719 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Atmospher & Environm Res Inc, Cambridge, MA 02139 USA. CALTECH, Div Geol & Planetary Sci, Pasadena, CA 91125 USA. RP Geissler, PE (reprint author), Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85711 USA. NR 38 TC 59 Z9 59 U1 0 U2 2 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD AUG 6 PY 1999 VL 285 IS 5429 BP 870 EP 874 DI 10.1126/science.285.5429.870 PG 5 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 223UX UT WOS:000081860900043 PM 10436151 ER PT J AU Cassell, AM Raymakers, JA Kong, J Dai, HJ AF Cassell, AM Raymakers, JA Kong, J Dai, HJ TI Large scale CVD synthesis of single-walled carbon nanotubes SO JOURNAL OF PHYSICAL CHEMISTRY B LA English DT Article ID FIELD-EMISSION; CATALYTIC GROWTH; CHEMISTRY; ALUMINA; FILAMENTS; PYROLYSIS; PARTICLES; METHANE; SULFATE; PROBES AB The synthesis of bulk amounts of high quality single-walled carbon nanotubes (SWNTs) is accomplished by optimizing the chemical compositions and textural properties of the catalyst material used in the chemical vapor deposition (CVD) of methane. A series of catalysts are derived by systematically varying the catalytic metal compounds and support materials. The optimized catalysts consist of Fe/Mo bimetallic species supported on a novel silica-alumina multicomponent material. The high SWNT yielding catalyst exhibits high surface-area and large mesopore volume at elevated temperatures. Gram quantities of SWNT materials have been synthesized in similar to 0.5 h using the optimized catalyst material. The nanotube material consists of individual and bundled SWNTs that are free of defects and amorphous carbon coating. This work represents a step forward toward obtaining kilogram scale perfect SWNT materials via simple CVD routes. C1 Stanford Univ, Dept Chem, Stanford, CA 94305 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Dai, HJ (reprint author), Stanford Univ, Dept Chem, Stanford, CA 94305 USA. NR 51 TC 664 Z9 688 U1 33 U2 369 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 1520-6106 J9 J PHYS CHEM B JI J. Phys. Chem. B PD AUG 5 PY 1999 VL 103 IS 31 BP 6484 EP 6492 DI 10.1021/jp990957s PG 9 WC Chemistry, Physical SC Chemistry GA 227UW UT WOS:000082099200014 ER PT J AU Summons, RE Jahnke, LL Hope, JM Logan, GA AF Summons, RE Jahnke, LL Hope, JM Logan, GA TI 2-Methylhopanoids as biomarkers for cyanobacterial oxygenic photosynthesis SO NATURE LA English DT Article ID PROKARYOTIC TRITERPENOIDS; METHYLOBACTERIUM-ORGANOPHILUM; HOPANE SERIES; 2-BETA-METHYLHOPANOIDS; LOCALIZATION; BIOSYNTHESIS; ANTIQUITY; ORIGIN AB Oxygenic photosynthesis is widely accepted as the most important bioenergetic process happening in Earth's surface environment(1). It is thought to have evolved within the cyanobacterial lineage, but it has been difficult to determine when it began. Evidence based on the occurrence and appearance of stromatolites(2) and microfossils' indicates that phototrophy occurred as long ago as 3,465 Myr although no definite physiological inferences can be he made from these objects. Carbon isotopes and other geological phenomena(4,5) provide clues but are also equivocal, Biomarkers are potentially useful because the three domains of extant life-Bacteria, Archaea and Eukarya-have signature membrane lipids with recalcitrant carbon skeletons. These lipids turn into hydrocarbons in sediments and can be found wherever the record is sufficiently well preserved. Here we show that 2-methylbacteriohopanepolyols occur in a high proportion of cultured cyanobacteria and cyanobacterial mats, Their 2-methylhopane hydrocarbon derivatives are abundant in organic-rich sediments as old as 2,500 Myr. These biomarkers may help constrain the age of the oldest cyanobacteria and the advent of oxygenic photosynthesis. They could also be used to quantify the ecological importance of cyanobacteria through geological time. C1 Australian Geol Survey Org, Canberra, ACT 2601, Australia. NASA, Ames Res Ctr, Exobiol Biol Branch, Moffett Field, CA 94035 USA. RP Summons, RE (reprint author), Australian Geol Survey Org, GPO Box 378, Canberra, ACT 2601, Australia. NR 28 TC 520 Z9 562 U1 7 U2 65 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON N1 9XW, ENGLAND SN 0028-0836 J9 NATURE JI Nature PD AUG 5 PY 1999 VL 400 IS 6744 BP 554 EP 557 DI 10.1038/23005 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 223RT UT WOS:000081854800052 PM 10448856 ER PT J AU Lemoine, M Audouze, J Ben Jaffel, L Feldman, P Ferlet, R Hebrard, G Jenkins, EB Mallouris, C Moos, W Sembach, K Sonneborn, G Vidal-Madjar, A York, DG AF Lemoine, M Audouze, J Ben Jaffel, L Feldman, P Ferlet, R Hebrard, G Jenkins, EB Mallouris, C Moos, W Sembach, K Sonneborn, G Vidal-Madjar, A York, DG TI Deuterium abundances SO NEW ASTRONOMY LA English DT Article DE ISM : abundances; cosmology : observations ID LOCAL INTERSTELLAR-MEDIUM; BIG-BANG NUCLEOSYNTHESIS; QSO ABSORPTION SYSTEMS; LYMAN LIMIT SYSTEMS; D/H RATIO; SPECTROGRAPH OBSERVATIONS; CHEMICAL EVOLUTION; GHRS OBSERVATIONS; LIGHT-ELEMENTS; HYDROGEN RATIO AB We discuss the measurements of deuterium abundances in high redshift quasar absorbers, in the solar system and in the interstellar medium. We present new results that indicate spatial variations of the deuterium abundance in the interstellar medium at the level of similar to 50% over scales possibly as small as similar to 10 pc, and discuss plausible causes for the origin of these variations. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Observ Paris, CNRS, UPR 176, DARC, F-92195 Meudon, France. Inst Astrophys, CNRS, F-75014 Paris, France. Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA. Princeton Univ Observ, Princeton, NJ 08544 USA. Univ Chicago, Dept Astron & Astrophys, Chicago, IL 60637 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Lemoine, M (reprint author), Observ Paris, CNRS, UPR 176, DARC, F-92195 Meudon, France. EM Martin.Lemoine@obspm.fr; audouze@iap.fr; bjaffel@iap.fr; pdf@rocket.pha.jhu.edu; ferlet@iap.fr; hebrard@pha.jhu.edu; ebj@astro.princeton.edu; chrism@oddjob.uchicago.edu; hwm@pha.jhu.edu; ken.sembach@pha.jhu.edu; sonneborn@fornax.gsfc.nasa.gov; alfred@iap.fr; don@oddjobuchicago.edu RI Jenkins, Edward/P-5684-2014; OI Jenkins, Edward/0000-0003-1892-4423; Lemoine, Martin/0000-0002-2395-7812 NR 100 TC 58 Z9 58 U1 1 U2 3 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 1384-1076 J9 NEW ASTRON JI New Astron. PD AUG 5 PY 1999 VL 4 IS 4 BP 231 EP 243 DI 10.1016/S1384-1076(99)00017-2 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 244VU UT WOS:000083072100002 ER PT J AU Noor, AK Malik, M AF Noor, AK Malik, M TI Accurate determination of transverse normal stresses in sandwich panels subjected to thermomechanical loadings SO COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING LA English DT Article ID LAMINATED COMPOSITE PLATES; HIGHER-ORDER THEORY AB A two-stage computational procedure is presented for the accurate determination of transverse normal stresses in sandwich panels subjected to thermomechanical loadings. The procedure involves the use of a first-order shear deformation model in the first stage, and an iterational process for successive improvement of the accuracy of the displacement and stress fields in the second stage. The effectiveness of the procedure is demonstrated by means of numerical studies of thin and moderately thick dat rectangular sandwich panels. Two sets of boundary conditions are considered; namely, one with all edges simply supported, and the other with two opposite edges simply supported and the remaining two clamped. The displacement components and the transverse shear and normal stresses obtained by the proposed computational procedure are found to be in close agreement with the solutions of the three-dimensional (3-D) continuum models. Published by Elsevier Science S.A. C1 Univ Virginia, NASA, Langley Res Ctr, Ctr Adv Computat Technol, Hampton, VA 23681 USA. RP Noor, AK (reprint author), Univ Virginia, NASA, Langley Res Ctr, Ctr Adv Computat Technol, Hampton, VA 23681 USA. NR 20 TC 13 Z9 15 U1 0 U2 2 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0045-7825 J9 COMPUT METHOD APPL M JI Comput. Meth. Appl. Mech. Eng. PD AUG 3 PY 1999 VL 178 IS 3-4 BP 431 EP 443 DI 10.1016/S0045-7825(99)00025-0 PG 13 WC Engineering, Multidisciplinary; Mathematics, Interdisciplinary Applications; Mechanics SC Engineering; Mathematics; Mechanics GA 239YN UT WOS:000082798300015 ER PT J AU Glavin, DP Bada, JL Brinton, KLF McDonald, GD AF Glavin, DP Bada, JL Brinton, KLF McDonald, GD TI Amino acids in the Martian meteorite Nakhla SO PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA LA English DT Article ID MURCHISON METEORITE; SEARCH; HYDROCARBONS; HYDROLYSIS; SEDIMENTS; ALH84001 AB A suite of protein and nonprotein amino acids were detected with high-performance liquid chromatography in the water- and acid-soluble components of an interior fragment of the Martian meteorite Nakhla, which fell in Egypt in 1911. Aspartic and glutamic acids, glycine, alanine, beta-alanine, and gamma-amino-n-butyric acid (gamma-ABA) were the most abundant amino acids detected and were found primarily in the 6 M HCl-hydrolyzed, hot water extract, The concentrations ranged from 20 to 330 parts per billion of bulk meteorite. The amino acid distribution in Nakhla, including the D/L ratios (values range from <0.1 to 0.5), is similar to what is found in bacterially degraded organic matter. The amino acids in Nakhla appear to be derived from terrestrial organic matter that infiltrated the meteorite soon after its fall to Earth, although it is possible that some of the amino acids are endogenous to the meteorite. The rapid amino acid contamination of Martian meteorites after direct exposure to the terrestrial environment has important implications for Mars sample-return missions and the curation of the samples from the time of their delivery to Earth. C1 Univ Calif San Diego, Scripps Inst Oceanog, La Jolla, CA 93093 USA. NASA, Jet Propuls Lab, Pasadena, CA 91109 USA. RP Bada, JL (reprint author), Univ Calif San Diego, Scripps Inst Oceanog, La Jolla, CA 93093 USA. RI Glavin, Daniel/D-6194-2012 OI Glavin, Daniel/0000-0001-7779-7765 NR 30 TC 58 Z9 58 U1 0 U2 9 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 AUG 3 PY 1999 VL 96 IS 16 BP 8835 EP 8838 DI 10.1073/pnas.96.16.8835 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 223HL UT WOS:000081835500014 PM 10430856 ER PT J AU Southward, RE Thompson, DW AF Southward, RE Thompson, DW TI Inverse CVD: A novel synthetic approach to metallized polymeric films SO ADVANCED MATERIALS LA English DT Article ID REFLECTIVE POLYIMIDE FILMS; CHEMICAL-VAPOR-DEPOSITION; SITU SILVER(I) REDUCTION C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Coll William & Mary, Dept Chem, Williamsburg, VA 23187 USA. RP Southward, RE (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 13 TC 33 Z9 35 U1 1 U2 10 PU WILEY-V C H VERLAG GMBH PI BERLIN PA MUHLENSTRASSE 33-34, D-13187 BERLIN, GERMANY SN 0935-9648 J9 ADV MATER JI Adv. Mater. PD AUG 2 PY 1999 VL 11 IS 12 BP 1043 EP 1047 DI 10.1002/(SICI)1521-4095(199908)11:12<1043::AID-ADMA1043>3.0.CO;2-C PG 5 WC Chemistry, Multidisciplinary; Chemistry, Physical; Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Physics, Applied; Physics, Condensed Matter SC Chemistry; Science & Technology - Other Topics; Materials Science; Physics GA 233PJ UT WOS:000082435000021 ER PT J AU Bettelheim, FA Ansari, R Cheng, QF Zigler, JS AF Bettelheim, FA Ansari, R Cheng, QF Zigler, JS TI The mode of chaperoning of dithiothreitol-denatured alpha-lactalbumin by alpha-crystallin SO BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS LA English DT Article ID HEAT-SHOCK PROTEINS; QUATERNARY STRUCTURE; MOLECULAR CHAPERONE; LENS CRYSTALLINS; SPECTROSCOPY; EXPRESSION; EVOLUTION; EXCHANGE AB Molecular chaperones prevent the aggregation of partially folded or misfolded forms of protein. alpha-crystallin performs such a function in the ocular lens. To gain insight into the mechanism of the anti-aggregation activity of alpha-crystallin, we performed dynamic light scattering(DLS) measurements investigating its interaction with partially denatured alpha-lactalbumin over a 24 hr period. Analyses were conducted as a function of the concentration of alpha-lactalbumin as well, as the bovine alpha-crystallin/alpha-lactalbumin ratio. Additional studies of the systems were performed by HPLC and SDS gel electrophoresis. The particle distribution patterns derived from the DLS data indicated that the chaperoned complex (lactalbumin plus crystallin) is a loose fluffy globular entity. After the complex becomes saturated with lactalbumin, it appears to release the partially denatured lactalbumin which may aggregate into high molecular weight moieties. These eventually may precipitate out of solution. On longer standing, 24hr and over, the chaperoned complex as well as the lactalbumin aggregates become more compact. The chaperoned complex (alpha-crystallin plus alpha-lactalbumin) is in dynamic equilibrium both with the monomeric and the aggregated alpha-lactalbumin population. (C) 1999 Academic Press. C1 Adelphi Univ, Dept Chem, Garden City, NY 11530 USA. NEI, Lab Mechanisms Ocular Dis, NIH, Bethesda, MD 20892 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Bettelheim, FA (reprint author), Adelphi Univ, Dept Chem, Garden City, NY 11530 USA. FU NEI NIH HHS [EY-12496-01] NR 34 TC 33 Z9 33 U1 0 U2 5 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0006-291X J9 BIOCHEM BIOPH RES CO JI Biochem. Biophys. Res. Commun. PD AUG 2 PY 1999 VL 261 IS 2 BP 292 EP 297 DI 10.1006/bbrc.1999.1031 PG 6 WC Biochemistry & Molecular Biology; Biophysics SC Biochemistry & Molecular Biology; Biophysics GA 226TC UT WOS:000082036900012 PM 10425180 ER PT J AU Agrawal, GP Ning, CZ Miguel, MS AF Agrawal, GP Ning, CZ Miguel, MS TI Introduction for the joint special issue on spatial and polarization dynamics of semiconductor lasers SO OPTICS EXPRESS LA English DT Editorial Material C1 Univ Rochester, Inst Opt, Rochester, NY 14627 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Illes Balears, Inst Mediterraneo Estudios Avanzados, E-07071 Palma de Mallorca, Spain. RP Agrawal, GP (reprint author), Univ Rochester, Inst Opt, Rochester, NY 14627 USA. RI Agrawal, Govind/D-5380-2013; San Miguel, Maxi/G-3224-2015 OI Agrawal, Govind/0000-0003-4486-8533; San Miguel, Maxi/0000-0001-6237-425X NR 0 TC 0 Z9 0 U1 0 U2 1 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 1094-4087 J9 OPT EXPRESS JI Opt. Express PD AUG 2 PY 1999 VL 5 IS 3 BP 28 EP 29 PG 2 WC Optics SC Optics GA 222KK UT WOS:000081783700001 PM 19399041 ER PT J AU Goorjian, PM Ning, CZ AF Goorjian, PM Ning, CZ TI Transverse mode dynamics of VCSELs through space-time domain simulation SO OPTICS EXPRESS LA English DT Article ID SURFACE-EMITTING LASERS; SEMICONDUCTOR-LASERS AB An approximation to the Maxwell-Semiconductor Bloch equations is used to model transverse mode dynamics of vertical-cavity surface-emitting lasers (VCSELs). The time-evolution of the spatial profiles of the laser field and carrier density is solved by a finite-difference algorithm. The algorithm is fairly general; it can handle devices of any shape, which are either gain or index guided or both. Also there is no a priori assumption about the type or number of modes. The physical modeling includes the nonlinear carrier dependence of the optical gain and refractive index and dispersion effects on the gain and the refractive index are also included. (C) 1998 Optical Society of America. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Goorjian, PM (reprint author), NASA, Ames Res Ctr, MS T27A-2, Moffett Field, CA 94035 USA. RI Ning, C. Z./D-4699-2009 OI Ning, C. Z./0000-0003-4583-8889 NR 17 TC 8 Z9 8 U1 0 U2 1 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 1094-4087 J9 OPT EXPRESS JI Opt. Express PD AUG 2 PY 1999 VL 5 IS 3 BP 55 EP 62 PG 8 WC Optics SC Optics GA 222KK UT WOS:000081783700005 PM 19399046 ER PT J AU Huntress, WT AF Huntress, WT TI The Discovery program SO ACTA ASTRONAUTICA LA English DT Article C1 NASA Headquarters, Off Space Sci, Washington, DC 20546 USA. RP Huntress, WT (reprint author), NASA Headquarters, Off Space Sci, Code S, Washington, DC 20546 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0094-5765 J9 ACTA ASTRONAUT JI Acta Astronaut. PD AUG-NOV PY 1999 VL 45 IS 4-9 BP 207 EP 213 DI 10.1016/S0094-5765(99)00138-1 PG 7 WC Engineering, Aerospace SC Engineering GA 263XT UT WOS:000084151100005 ER EF