FN Thomson Reuters Web of Science™
VR 1.0
PT J
AU Broadhurst, MK
Kennelly, SJ
Watson, JW
Workman, IK
AF Broadhurst, MK
Kennelly, SJ
Watson, JW
Workman, IK
TI Evaluations of the Nordmore grid and secondary bycatch-reducing devices
(BRD's) in the Hunter River prawn-trawl fishery, Australia
SO FISHERY BULLETIN
LA English
DT Article
ID BY-CATCH; REDUCTION
AB Several bycatch-reducing devices (BRD's) were compared for their effectiveness in reducing bycatch while maintaining catches of prawns in an estuarine prawn-trawl fishery in New South Wales (NSW), Australia. A solid separator-panel (the Nordmore grid), a soft separator panel (the commercially used blubber chute), and four secondary BRD's (the fisheye, extended mesh funnel, Allerio Brothers grid, and square-mesh panel) each attached to a Nordmore grid, were compared against each other in a series of paired comparisons in the Hunter River prawn-trawl. fishery. The results showed that the Nordmore grid and all secondary BRD's caught less bycatch and more prawns than the commercially used blubber chute. Most bycatch seemed to escape with use of the Nordmore grid, and there was no significant advantage in adding a secondary BRD to this design. The efficiency of the Nordmore grid has led to its voluntary adoption by many commercial prawn-trawl fishermen throughout NSW estuaries.
C1 MISSISSIPPI LABS,NATL MARINE FISHERIES SERV,PASCAGOULA FACIL,PASCAGOULA,MS 39568.
RP Broadhurst, MK (reprint author), NEW S WALES AGR & FISHERIES,FISHERIES RES INST,POB 21,CRONULLA,NSW 2230,AUSTRALIA.
RI Broadhurst, Matt/I-6783-2015
OI Broadhurst, Matt/0000-0003-0184-7249
NR 17
TC 9
Z9 10
U1 0
U2 1
PU NATL MARINE FISHERIES SERVICE SCIENTIFIC PUBL OFFICE
PI SEATTLE
PA 7600 SAND POINT WAY NE BIN C15700, SEATTLE, WA 98115
SN 0090-0656
J9 FISH B-NOAA
JI Fish. Bull.
PD APR
PY 1997
VL 95
IS 2
BP 209
EP 218
PG 10
WC Fisheries
SC Fisheries
GA WU782
UT WOS:A1997WU78200003
ER
PT J
AU Lutcavage, M
Kraus, S
Hoggard, W
AF Lutcavage, M
Kraus, S
Hoggard, W
TI Aerial survey of giant bluefin tuna, Thunnus thynnus, in the great
Bahama Bank, Straits of Florida, 1995
SO FISHERY BULLETIN
LA English
DT Article
AB Aerial surveys were conducted daily from 19 May to 9 June 1995 to document the apparent abundance and migration behavior of giant bluefin tuna, Thunnus thynnus, over the Great Bahama Bank region of the Straits of Florida. Our objectives mere to conduct an aerial assessment of giant bluefin tuna in this region and to compare our results with previous aerial surveys conducted in the 1950's and 1970's. Two professional bluefin spotter pilots flew 70-nmi transect surveys along ''Tuna Alley'' as well as surveys into adjacent areas in search of bluefin tuna. The present study area was broader than that surveyed in the 1970's, which consisted of repeated flight tracks, each 1 nmi, across Tuna Alley at a point just south of South Cat Cay. Spotter aircraft carried a data acquisition system consisting of a global positioning system (GPS), a laptop computer, and a 35-mm camera to photograph schools. A total of 839 giant bluefin tuna were documented, within range of totals counted in the 1974-76 surveys (368-3,125 bluefin tuna). Single fish and loosely aggregated schools of up to 100 fish were seen travelling steadily north along the western flank of the Great Bahama Bank. They did not engage in feeding, smashing, or cartwheeling behaviors that are exhibited in New England waters. AU bluefin tuna appeared to be ''large giants,'' weighing an estimated 227 kg and over. There is little information documenting the origins and previous locations of giant bluefin tuna travelling along the Great Bahama Bank; therefore the use of direct counts of bluefin tuna in this region as an index of spawning biomass would require further documentation.
C1 NOAA,NATL MARINE FISHERIES SERV,SE FISHERIES SCI CTR,PASCAGOULA,MS 39568.
RP Lutcavage, M (reprint author), NEW ENGLAND AQUARIUM,EDGERTON RES LAB,CENT WHARF,BOSTON,MA 02110, USA.
NR 6
TC 22
Z9 22
U1 0
U2 2
PU NATL MARINE FISHERIES SERVICE SCIENTIFIC PUBL OFFICE
PI SEATTLE
PA 7600 SAND POINT WAY NE BIN C15700, SEATTLE, WA 98115
SN 0090-0656
J9 FISH B-NOAA
JI Fish. Bull.
PD APR
PY 1997
VL 95
IS 2
BP 300
EP 310
PG 11
WC Fisheries
SC Fisheries
GA WU782
UT WOS:A1997WU78200010
ER
PT J
AU Liu, CX
Glitzenstein, JS
Harcombe, PA
Knox, RG
AF Liu, CX
Glitzenstein, JS
Harcombe, PA
Knox, RG
TI Tornado and fire effects on tree species composition in a savanna in the
Big Thicket National Preserve, southeast Texas, USA
SO FOREST ECOLOGY AND MANAGEMENT
LA English
DT Article
DE prescribed burning; ordination; disturbance; Pinus palustris mill;
vegetation change
ID TROPICAL RAIN-FOREST; HURRICANE HUGO; VEGETATION; DAMAGE; DISTURBANCES;
COMMUNITIES; WIND
AB Ordination showed that species composition in a savanna shifted toward mixed pine-hardwood types after the tornado damage in 1983. Of the twenty 250 m(2) study plots, one baygall plot remained unchanged in its position in ordination space, as did five mixed pine-hardwood plots and six savanna plots. However, eight savanna plots moved from the savanna space to the mixed pine-hardwood space after the tornado. Prescribed burns in 1986 and 1991 had a modest effect in reversing this trend: only four of the eight plots returned to the savanna ordination space by 1991.
The changes in species composition, summarized by movement of plots in ordination space, reflected the conflicting affects of the tornado and fire: the tornado tended to change savanna to mixed pine-hardwood by differentially removing pines and stimulating hardwood growth. Fires tended to reduce hardwood density. However, stand opening and increased fuel loads following the tornado did not result in fires intense enough to dramatically enhance savanna recovery.
C1 TALL TIMBERS RES STN,TALLAHASSEE,FL 32312.
RICE UNIV,DEPT ECOL & EVOLUT BIOL,HOUSTON,TX 77251.
NASA,GODDARD SPACE FLIGHT CTR,BIOSPHER SCI BRANCH,GREENBELT,MD 20771.
RP Liu, CX (reprint author), TEXAS PARKS & WILDLIFE DEPT,ENDANGERED RESOURCES BRANCH,3000 IH35 S,SUITE 100,AUSTIN,TX 78704, USA.
RI Knox, Robert/E-9657-2011
NR 39
TC 5
Z9 5
U1 2
U2 10
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0378-1127
J9 FOREST ECOL MANAG
JI For. Ecol. Manage.
PD APR
PY 1997
VL 91
IS 2-3
BP 279
EP 289
DI 10.1016/S0378-1127(96)03705-X
PG 11
WC Forestry
SC Forestry
GA WV908
UT WOS:A1997WV90800013
ER
PT J
AU Bhoyrul, S
Gantert, W
Johnston, R
Weiss, P
Tendick, F
Yamagata, S
Rangel, S
Zabelle, C
Patti, MG
Fletcher, D
Loftin, B
Way, LW
AF Bhoyrul, S
Gantert, W
Johnston, R
Weiss, P
Tendick, F
Yamagata, S
Rangel, S
Zabelle, C
Patti, MG
Fletcher, D
Loftin, B
Way, LW
TI Team dynamics in laparoscopic surgery
SO GASTROENTEROLOGY
LA English
DT Meeting Abstract
C1 UNIV CALIF SAN FRANCISCO, DEPT SURG, SAN FRANCISCO, CA 94143 USA.
UNIV HOUSTON, NASA, VIRTUAL REAL TECHNOL LAB, HOUSTON, TX 77004 USA.
NR 0
TC 0
Z9 0
U1 0
U2 0
PU W B SAUNDERS CO-ELSEVIER INC
PI PHILADELPHIA
PA 1600 JOHN F KENNEDY BOULEVARD, STE 1800, PHILADELPHIA, PA 19103-2899 USA
SN 0016-5085
J9 GASTROENTEROLOGY
JI Gastroenterology
PD APR
PY 1997
VL 112
IS 4
SU S
BP A1431
EP A1431
PG 1
WC Gastroenterology & Hepatology
SC Gastroenterology & Hepatology
GA WV419
UT WOS:A1997WV41905701
ER
PT J
AU Gantert, W
Bhoyrul, S
Johnston, R
Weiss, P
Tendick, F
Hayashi, E
Yamagata, S
Legha, P
Rangel, S
Patti, MG
Way, LW
AF Gantert, W
Bhoyrul, S
Johnston, R
Weiss, P
Tendick, F
Hayashi, E
Yamagata, S
Legha, P
Rangel, S
Patti, MG
Way, LW
TI Error analysis in laparoscopic surgery.
SO GASTROENTEROLOGY
LA English
DT Meeting Abstract
C1 UNIV CALIF SAN FRANCISCO, DEPT SURG, SAN FRANCISCO, CA 94143 USA.
UNIV HOUSTON, NASA, VIRTUAL REAL TECHNOL LAB, HOUSTON, TX USA.
NR 0
TC 0
Z9 0
U1 0
U2 0
PU W B SAUNDERS CO-ELSEVIER INC
PI PHILADELPHIA
PA 1600 JOHN F KENNEDY BOULEVARD, STE 1800, PHILADELPHIA, PA 19103-2899 USA
SN 0016-5085
J9 GASTROENTEROLOGY
JI Gastroenterology
PD APR
PY 1997
VL 112
IS 4
SU S
BP A1444
EP A1444
PG 1
WC Gastroenterology & Hepatology
SC Gastroenterology & Hepatology
GA WV419
UT WOS:A1997WV41905752
ER
PT J
AU Silaev, PK
Turyshev, SG
AF Silaev, PK
Turyshev, SG
TI Are the singularities stable?
SO GENERAL RELATIVITY AND GRAVITATION
LA English
DT Article
DE Einstein-Maxwell-scalar gravity; stability
ID STRING THEORY; BLACK-HOLES; GENERAL-RELATIVITY; SCALAR THEORIES; FIELD;
GRAVITY; EQUATIONS
AB The spacetime singularities play a useful role in gravitational theories by distinguishing physical solutions from non-physical ones. The problem, we are studying in this paper is whether these singularities are stable. To answer this question, we have analyzed the general problem of stability of the family of the static spherically symmetric solutions of the standard Einstein-Maxwell model coupled to an extra free massless scalar field. We have obtained the equations for the axial and polar perturbations. The stability against axial perturbations has been proven.
C1 MOSCOW MV LOMONOSOV STATE UNIV,BOGOLYUBOV INST THEORET MICROPHYS,MOSCOW 119899,RUSSIA.
CALTECH,JET PROP LAB,PASADENA,CA 91109.
RP Silaev, PK (reprint author), MOSCOW MV LOMONOSOV STATE UNIV,DEPT PHYS,MOSCOW 119899,RUSSIA.
NR 32
TC 2
Z9 2
U1 0
U2 0
PU PLENUM PUBL CORP
PI NEW YORK
PA 233 SPRING ST, NEW YORK, NY 10013
SN 0001-7701
J9 GEN RELAT GRAVIT
JI Gen. Relativ. Gravit.
PD APR
PY 1997
VL 29
IS 4
BP 417
EP 433
DI 10.1023/A:1018874414137
PG 17
WC Astronomy & Astrophysics; Physics, Multidisciplinary; Physics, Particles
& Fields
SC Astronomy & Astrophysics; Physics
GA WU554
UT WOS:A1997WU55400002
ER
PT J
AU Buchanan, PC
Zolensky, ME
Reid, AM
AF Buchanan, PC
Zolensky, ME
Reid, AM
TI Petrology of Allende dark inclusions
SO GEOCHIMICA ET COSMOCHIMICA ACTA
LA English
DT Article
ID AQUEOUS ALTERATION; CARBONACEOUS CHONDRITE; TRACE-ELEMENT; MATRIX;
PHYLLOSILICATES; MINERALOGY; XENOLITH; ORIGIN
AB Bulk compositions acquired by neutron activation analysis are reported for eight Allende dark inclusions (DIs) and compared with compositions of five DIs previously reported in the literature. Enrichments of the elements Na, K, Br, Ba, Au, and As are generally correlated with increased proportions of porous aggregates predominantly composed of fine-grained, platy to fibrous olivine. These aggregates have been interpreted by some workers as chondrules and inclusions that first were exposed to aqueous alteration, converting anhydrous silicates to phyllosilicates, and later were dehydrated by thermal metamorphism, converting phyllosilicates to olivine. Our data support this interpretation and suggest that the aqueous alteration was open system in character. Feldspathoid grains intergrown with platy to fibrous olivines in porous, olivine-rich aggregates and inclusions of sodalite, nepheline, pentlandite, ilmenite, and spinel in these olivines suggest that phyllosilicates produced during aqueous alteration could accommodate Na, K, Ni, S, etc and are most consistent with a mixture of both saponite and serpentine. Dehydration of saponite would require that the temperature of thermal metamorphism was higher than previously suggested and may have been as high as 800 degrees-900 degrees C. Nonporous rims containing Ca-rich minerals (andradite, hedenbergite) surrounding dark inclusions containing highest proportions of porous, olivine-rich aggregates and slight to moderate depletions of these clasts in Ca relative to bulk Allende suggest that these rims were also the result of redistribution of some elements during dehydration of these clasts caused by thermal metamorphism. Copyright (C) 1997 Elsevier Science Ltd.
C1 UNIV WITWATERSRAND,DEPT GEOL,ZA-2050 WITWATERSRAND,JOHANNESBURG,SOUTH AFRICA.
NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058.
UNIV HOUSTON,DEPT GEOSCI,HOUSTON,TX 77204.
NR 49
TC 29
Z9 30
U1 1
U2 3
PU PERGAMON-ELSEVIER SCIENCE LTD
PI OXFORD
PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB
SN 0016-7037
J9 GEOCHIM COSMOCHIM AC
JI Geochim. Cosmochim. Acta
PD APR
PY 1997
VL 61
IS 8
BP 1733
EP 1743
DI 10.1016/S0016-7037(97)00019-7
PG 11
WC Geochemistry & Geophysics
SC Geochemistry & Geophysics
GA WX767
UT WOS:A1997WX76700014
ER
PT J
AU Ivanov, AV
Migdisova, LF
Zolensky, ME
MacPherson, GJ
Kononkova, NN
AF Ivanov, AV
Migdisova, LF
Zolensky, ME
MacPherson, GJ
Kononkova, NN
TI The Kaidun meteorite: An enstatite chondrite fragment with unusual
inclusions in the metal
SO GEOKHIMIYA
LA Russian
DT Article
ID IRON; CHONDRULES; CHEMISTRY; HISTORY; BEARING; ORIGIN
AB A petrological and mineralogical description of fragment 01.3.06 of the polymict meteorite breccia Kaidun is presented. The fragment is classified with EH3-4. This is the third type of enstatite chondrite that was found in this unique meteorite. The fragment is rich in metal nodules, which can be subdivided into three textural types: (1) globular, (2) zoned, with massive cores and globular rims, and (3) having no internal structure. The sizes and compositions of kamacite globules in the nodules and kamacite grains in the matrix are identical. The nodules contain small, commonly less than 5 mu m, inclusions of widely ranging compositions: SiO2, albite glass, enstatite, roedderite, and a mixture of SiO2 and Na2S2. This is the first known occurrence of a simple alkalimetal sulfide in nature. The inclusions may have formed by condensation of material on the surface of metal grains. The nodules resulted from the agglomeration of individual metal grains and the simultaneous preservation, of condensates as inclusions. The processes of condensation and agglomeration of the metal grams were synchronous. The inclusions may have formed by the disequilibrium condensation of gas of solar composition or by equilibrium condensation of highly fractionated gas.
C1 NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058.
SMITHSONIAN INST,DEPT MINERAL,WASHINGTON,DC 20560.
RP Ivanov, AV (reprint author), VI VERNADSKII INST GEOCHEM & ANALYT CHEM,UL KOSYGINA 19,MOSCOW 117975,RUSSIA.
NR 38
TC 2
Z9 2
U1 3
U2 5
PU ROSSIISKAYA AKADEMIYA NAUK
PI MOSCOW
PA SAVELEVSKII PER., 13 OCTOZHENKA, 119034 MOSCOW, RUSSIA
SN 0016-7525
J9 GEOKHIMIYA+
JI Geokhimiya
PD APR
PY 1997
IS 4
BP 369
EP 379
PG 11
WC Geochemistry & Geophysics
SC Geochemistry & Geophysics
GA XF412
UT WOS:A1997XF41200002
ER
PT J
AU Mishchenko, MI
Wielaard, DJ
Carlson, BE
AF Mishchenko, MI
Wielaard, DJ
Carlson, BE
TI T-matrix computations of zenith-enhanced lidar backscatter from
horizontally oriented ice plates
SO GEOPHYSICAL RESEARCH LETTERS
LA English
DT Article
ID LIGHT-SCATTERING; CRYSTALS; CIRRUS
AB Zenith-enhanced backscattering (ZEE) of a lidar beam by cirrus clouds is a remarkable phenomenon usually explained in terms of specular reflection from large plane facets of horizontally oriented ice plates. Since the standard geometric optics approximation (GO) may be inapplicable in many cases, especially in analyzing infrared measurements, and ignores physical optics effects, we use the recently improved exact T-matrix method to compute the scattering of light by ice plates at visible and infrared wavelengths. Computations for horizontally and randomly oriented thin disks and oblate spheroids with size parameters up to 50 show that while all particles produce a strong Fraunhofer diffraction peak centered at exactly the forward-scattering direction, a strong and narrow ZEE peak can be produced only by horizontally oriented disks but not by horizontally oriented spheroids or particles in random orientation. This finding demonstrates that ZEE can be produced even by particles which are not in the GO domain of size parameters and supports the traditional interpretation of ZEE. Also, we have found that the angular width of the ZEE peak for horizontally oriented disks is equal tb half the width of the Fraunhofer diffraction peak. This result can be used in practice to derive a lower estimate of ice particle sizes from high angular resolution measurements of ZEE. We show that our exact T-matrix computations can explain the peculiar zenith-angle dependence of depolarization observed by Platt et al. [1978] in the visible and can be interpreted qualitatively in terms of the modified Kirchhoff approximation.
C1 SUNY STONY BROOK,NEW YORK,NY 10025.
COLUMBIA UNIV,NEW YORK,NY 10025.
RP Mishchenko, MI (reprint author), NASA,GODDARD INST SPACE STUDIES,2880 BROADWAY,NEW YORK,NY 10025, USA.
RI Carlson, Barbara/D-8319-2012; Mishchenko, Michael/D-4426-2012
NR 16
TC 31
Z9 30
U1 0
U2 5
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009
SN 0094-8276
J9 GEOPHYS RES LETT
JI Geophys. Res. Lett.
PD APR 1
PY 1997
VL 24
IS 7
BP 771
EP 774
DI 10.1029/97GL00545
PG 4
WC Geosciences, Multidisciplinary
SC Geology
GA WR211
UT WOS:A1997WR21100010
ER
PT J
AU Goswami, T
Halford, GR
Hoeppner, DW
AF Goswami, T
Halford, GR
Hoeppner, DW
TI Dwell sensitivity fatigue behavior of high temperature materials
SO HIGH TEMPERATURE MATERIALS AND PROCESSES
LA English
DT Article
DE dwell sensitivity; plastic and total strain ranges; cycles to failure;
normalized cycle ratio; isothermal and thermo-mechanical fatigue
AB The dwell sensitivity fatigue behavior of six high temperature materials is examined in this paper: two stainless steels, 304L and 304, two tantalum alloys, T-111 and ASTAR 811C, pure nickel Ni 201 and a single crystal nickel-base superalloy, PWA 1480. The stainless steel alloys were found to be tensile dwell sensitive; however, a saturation in dwell sensitivity was found with the increase in strain range for all materials examined. At lower strain ranges the dwell cycles were producing lower lives than at higher strains, as found in the case of AISI SS 304 and two tantalum based alloys, T-111 and ASTAR 811C. Trends in various normalized life curves were found to be strain dependent for ASTAR 811C, in which below 0.2% inelastic strain range, dwell effects were more deleterious than above it. Mechanistic aspects under different test conditions were summarized.
C1 WICHITA STATE UNIV,DEPT MECH ENGN,WICHITA,KS 67260.
NASA,LEWIS RES CTR,CLEVELAND,OH 44135.
NR 15
TC 3
Z9 3
U1 1
U2 3
PU FREUND PUBLISHING HOUSE
PI LONDON
PA STE 500, CHESHAM HOUSE, 150 REGENT ST, LONDON, ENGLAND W1R 5FA
SN 0334-6455
J9 HIGH TEMP MATER PROC
JI High Temp. Mater. Process.
PD APR-JUN
PY 1997
VL 16
IS 2
BP 87
EP 96
PG 10
WC Materials Science, Multidisciplinary
SC Materials Science
GA XC642
UT WOS:A1997XC64200002
ER
PT J
AU Pickett, BK
Durisen, RH
Link, R
AF Pickett, BK
Durisen, RH
Link, R
TI Rotating protostars and protostellar disks .1. Equilibrium models
SO ICARUS
LA English
DT Article
ID ECCENTRIC GRAVITATIONAL INSTABILITIES; INTERMEDIATE-MASS PROTOSTARS;
ACCRETION DISKS; SOLAR NEBULA; EVOLUTION; STAR; CLOUDS; POLYTROPES;
STABILITY; CORES
AB This paper is part of a series dealing with the structure and dynamic stability of rotating protostellar cores. As a first step in our study, we have generated numerical equilibrium models for isentropic, axisymmetric protostellar cores in rapid rotation. These models represent endstates for collapse from two different types of initial precollapse cloud conditions, chosen to be reasonable cases for the formation of low- or intermediate-mass stars on the basis of other theoretical or observational work. Specifically, we consider the equilibrium cores which would form from the collapse of uniformly rotating clouds with the density distributions of singular isothermal spheres and of truncated Gaussian spheres.
The major structural differences between the two sequences are largely due to their distinct angular momentum distributions. The protostellar cores which result from singular isothermal initial conditions can be readily interpreted as slowly rotating stars surrounded by massive, rotationally supported disks. A ''star'' and a ''disk'' are not easily distinguished for the Gaussian cases, but the outer regions of these models are typically in rapid, nearly Keplerian rotation. For reasonable assumptions about parameters, the most rapidly rotating protostellar cores that we can calculate accurately correspond to highly flattened disk or star/disk systems of roughly solar mass with equatorial radii of a few AUs or less. For the protostellar cores that result from the collapse of singular isothermal spheres, we find that a significant range in parameter space exists in which protostellar disks are much smaller than the typical dimensions usually considered for the solar nebula. These conditions may be conducive to the formation of relatively compact planetary systems such as 51 Pegasi. Our axisymmetric star/disk models are fully two-dimensional in the sense that both the vertical disk structure and the central starlike regions are resolved. These models will be used as a numerical laboratory for studies of various dynamic processes in protostellar disks. (C) 1997 Academic Press.
C1 INDIANA UNIV, DEPT ASTRON, BLOOMINGTON, IN 47405 USA.
RP NASA, AMES RES CTR, MS 245-3, MOFFETT FIELD, CA 94035 USA.
NR 70
TC 19
Z9 19
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
EI 1090-2643
J9 ICARUS
JI Icarus
PD APR
PY 1997
VL 126
IS 2
BP 243
EP 260
DI 10.1006/icar.1996.5657
PG 18
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WX524
UT WOS:A1997WX52400001
ER
PT J
AU Ward, WR
AF Ward, WR
TI Protoplanet migration by nebula tides
SO ICARUS
LA English
DT Article
ID PRIMORDIAL SOLAR NEBULA; DISK-SATELLITE INTERACTION; T-TAURI STARS;
X-RAY SOURCES; DENSITY WAVES; TIDAL INTERACTION; ORBITAL MIGRATION;
SATURNS RINGS; PLANETS; PLANETESIMALS
AB The tidal interaction of a protoplanet with a circumstellar gaseous disk results in mutual angular momentum exchange that modifies both the disk and the orbit of the secondary. There are two, conceptually distinct circumstances wherein nebula torques can cause a secular variation in a protoplanet's semimajor axis. (I) The net torque exerted on a secondary by an undisturbed disk is not, in general, zero. Although gradients in the disk density and temperature can contribute to this torque, it is mostly due to asymmetries in the disk/planet interaction that are inherent to a Keplerian disk. For a relatively thick disk, the differential torque can be a significant fraction of the torque from either its exterior or its interior portion. In this case, the protoplanet drifts relative to disk material on a time scale inversely proportional to its mass. (II) The protoplanet opens a gap in the disk that establishes a flow barrier to disk material. PL density discontinuity that locks the protoplanet into the disk's viscous evolution develops across the orbit. The protoplanet migrates on a time scale set by the disk's viscosity.
A unified model that clarifies the relationship between these migration types and reveals under what circumstances a given type is selected is presented. In both cases, orbital decay is the prevailing outcome, although type I migration rates can be between one and two orders of magnitudes faster than type II. Estimates of orbital lifetimes are given and are generally shorter than the expected lifetime of the disk. Some implications to the issue of planetary formation are discussed. (C) 1997 Academic Press.
C1 SAN JUAN CAPISTRANO RES INST, SAN JUAN CAPISTRANO, CA USA.
RP CALTECH, JET PROP LAB, 4800 OAK GROVE DR, PASADENA, CA 91109 USA.
NR 63
TC 572
Z9 575
U1 2
U2 3
PU ACADEMIC PRESS INC ELSEVIER SCIENCE
PI SAN DIEGO
PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA
SN 0019-1035
EI 1090-2643
J9 ICARUS
JI Icarus
PD APR
PY 1997
VL 126
IS 2
BP 261
EP 281
DI 10.1006/icar.1996.5647
PG 21
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WX524
UT WOS:A1997WX52400002
ER
PT J
AU Deming, D
Reuter, D
Jennings, D
Bjoraker, G
McCabe, G
Fast, K
Wiedemann, G
AF Deming, D
Reuter, D
Jennings, D
Bjoraker, G
McCabe, G
Fast, K
Wiedemann, G
TI Observations and analysis of longitudinal thermal waves on Jupiter
SO ICARUS
LA English
DT Article
ID SYSTEM; ATMOSPHERES; STABILITY; DYNAMICS; MOTION
AB We analyze the properties of wave-like longitudinal temperature variations in Jupiter's upper troposphere and stratosphere, as revealed using thermal infrared (IR) ground-based observations taken yearly during the 1989-1993 period, These thermal waves are apparently the same as the ''slowly moving thermal features'' identified in Voyager data, We conclude that they are ubiquitous at near-equatorial latitudes on Jupiter, and have a spatial scale which typically spans wavenumber approximate to 2 to approximate to 15. Their stratospheric (20 mbar) temperature amplitude, from 7.8 mu m data, is approximately a factor of 3 larger than their amplitude in the upper troposphere (approximate to 0.3 bars), as revealed using 18 mu m data. These amplitudes are consistent with the rho(-1/2) growth expected for a vertically propagating Rossby wave. The phase at the two levels is the same to within 5 degrees of longitude, The temperature wave is not advected by the zonal winds, having a phase velocity of approximate to 5 m sec(-1) in system III, but the temperature amplitude can decay on time scales approximate to 10(5) sec, Imaging of the thermal waves shows that they are extended in latitude to a greater extent than the belt/zone structure, or the zonal wind jets. An apparently related wave is seen in broad-bandwidth (7-13 mu m) IR observations which are sensitive to clouds and aerosols. This structure is advected by the zonal wind, indicating that some cloud or aerosol component shares the wave-like structure and spatial scale of the temperature wave,
We interpret these waves as stationary Rossby waves, represented by small latitude excursions in the streamlines of the zonal winds, The latitude excursions could be produced by either deep structure, or by the global effect of vortices such as the Great Red Spot. In either case, temperature fluctuations are produced via ''vortex stretching.'' We calculate the required magnitude of the latitude excursions in the zonal winds to be approximate to 1 degrees in order to produce the observed temperature amplitudes. This is a subarcsec scale for Earth-based observations, but might be detectable using observations from the Hubble space telescope. (C) 1997 Academic Press.
C1 HUGHES STX CORP,LANHAM,MD 20706.
UNIV MARYLAND,GODDARD SPACE FLIGHT CTR,COLLEGE PK,MD 20742.
UNIV MARYLAND,DEPT ASTRON,COLLEGE PK,MD 20742.
EUROPEAN SO OBSERV,D-8046 GARCHING,GERMANY.
RP Deming, D (reprint author), NASA,GODDARD SPACE FLIGHT CTR,PLANETARY SYST BRANCH,CODE 693,GREENBELT,MD 20771, USA.
RI Bjoraker, Gordon/D-5032-2012
NR 30
TC 19
Z9 19
U1 0
U2 1
PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS
PI SAN DIEGO
PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495
SN 0019-1035
J9 ICARUS
JI Icarus
PD APR
PY 1997
VL 126
IS 2
BP 301
EP 312
DI 10.1006/icar.1996.5658
PG 12
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WX524
UT WOS:A1997WX52400005
ER
PT J
AU Rappaport, N
Bertotti, B
Giampieri, G
Anderson, JD
AF Rappaport, N
Bertotti, B
Giampieri, G
Anderson, JD
TI Doppler measurements of the quadrupole moments of titan
SO ICARUS
LA English
DT Article
ID SURFACE; ATMOSPHERES; SEAS; N-2
AB Measurements of the Doppler frequency change in a microwave beam sent to and transponded back from an interplanetary spacecraft are very sensitive to the quadrupole gravitational field of a nearby natural satellite. This method will be used in Cassini's mission to the saturnian system in relation to Titan during some of the numerous flybys. The use of very stable coherent signals at X and Ka bands will allow an excellent determination of the quadrupole dimensionless coefficients, with absolute accuracy between 10(-8) and 10(-9). Titan's quadrupole deformation is due to its rotation and the saturnian tidal forces; the determination of the corresponding two parameters will greatly constrain the interior models, The measurement accuracy should be sufficient to determine also the variation of the tidal parameter with the orbital period, as a consequence of Titan's eccentricity; this will provide information on its rigidity and indicate whether it has an internal ocean of water and ammonia, The analysis of the complicated dependence on the geometry of Doppler measurements of the quadrupole can be done by means of an analytical expression of the covariance matrix. (C) 1997 Academic Press.
C1 UNIV PAVIA,DIPARTIMENTO FIS NUCL & TEOR,I-2700 PAVIA,ITALY.
UNIV LONDON QUEEN MARY & WESTFIELD COLL,ASTRON UNIT,LONDON E1 4NS,ENGLAND.
RP Rappaport, N (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA.
NR 35
TC 44
Z9 44
U1 0
U2 2
PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS
PI SAN DIEGO
PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495
SN 0019-1035
J9 ICARUS
JI Icarus
PD APR
PY 1997
VL 126
IS 2
BP 313
EP 323
DI 10.1006/icar.1996.5661
PG 11
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WX524
UT WOS:A1997WX52400006
ER
PT J
AU Noll, KS
Gilmore, D
Knacke, RF
Womack, M
Griffith, CA
Orton, G
AF Noll, KS
Gilmore, D
Knacke, RF
Womack, M
Griffith, CA
Orton, G
TI Carbon monoxide in Jupiter after Comet Shoemaker-Levy 9
SO ICARUS
LA English
DT Article
ID WATER-VAPOR; SPECTROSCOPIC OBSERVATIONS; COLLISION; STRATOSPHERE;
TROPOSPHERE; ATMOSPHERE; ABUNDANCE
AB Observations of the carbon monoxide fundamental vibration-rotation band near 4.7 mu m before and after the impacts of the fragments of Comet Shoemaker-Levy 9 showed no detectable changes in the R5 and R7 lines, with one possible exception, Observations of the G-impact site 21 hr after impact do not show CO emission, indicating that the heated portions of the stratosphere had cooled by that time, The large abundances of CO detected at the millibar pressure level by millimeter wave observations did not extend deeper in Jupiter's atmosphere. Predicted upwelling of shocked, O-rich material from below also did not occur, Combined with evidence for upwelling of N- and S-rich gas, our observations indicate that the comet fragments may not have penetrated to the H2O cloud, We find that CO concentrations in Jupiter's stratosphere may be higher than previously suspected, suggesting that some of the CO detected after the impacts may already have been present in Jupiter's stratosphere. (C) 1997 Academic Press.
C1 PENN STATE UNIV,ERIE,PA 16563.
NO ARIZONA UNIV,FLAGSTAFF,AZ 86011.
CALTECH,JET PROP LAB,PASADENA,CA 91109.
RP Noll, KS (reprint author), SPACE TELESCOPE SCI INST,3700 SAN MARTIN DR,BALTIMORE,MD 21218, USA.
RI Noll, Keith/C-8447-2012;
OI Womack, Maria/0000-0003-4659-8653
NR 39
TC 11
Z9 11
U1 0
U2 0
PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS
PI SAN DIEGO
PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495
SN 0019-1035
J9 ICARUS
JI Icarus
PD APR
PY 1997
VL 126
IS 2
BP 324
EP 335
DI 10.1006/icar.1996.5655
PG 12
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WX524
UT WOS:A1997WX52400007
ER
PT J
AU Wisniewski, WZ
Michalowski, TM
Harris, AW
McMillan, RS
AF Wisniewski, WZ
Michalowski, TM
Harris, AW
McMillan, RS
TI Photometric observations of 125 asteroids
SO ICARUS
LA English
DT Article
ID NEAR-EARTH ASTEROIDS; MAIN-BELT ASTEROIDS; LIGHTCURVE OBSERVATIONS;
PHOTOELECTRIC OBSERVATIONS; ROTATIONAL PROPERTIES; 1580 BETULIA;
OBJECTS; ALBEDO
AB We present observations of 125 asteroids taken by traditional photoelectric photometry as well as with CCD imaging systems, from 1985 to the end of 1993,just 2 months before the untimely death of the first author. From these observations, we derive rotation periods for 82 asteroids. Of these, 72 are for asteroids with no previously reported rotation period, and one is a significant revision of a period previously reported. We report V magnitudes for almost all of the objects and five-color observations (a subset of the eight-color asteroid system) for 35 of the asteroids. Most of the objects observed are small main-belt asteroids or near-Earth asteroids; thus this data set is a substantial addition to the known rotation periods and amplitudes of variations of those classes of asteroids. (C) 1997 Academic Press.
C1 CALTECH,JET PROP LAB,PASADENA,CA 91109.
UNIV ARIZONA,TUCSON,AZ 85721.
NR 50
TC 51
Z9 51
U1 0
U2 0
PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS
PI SAN DIEGO
PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495
SN 0019-1035
J9 ICARUS
JI Icarus
PD APR
PY 1997
VL 126
IS 2
BP 395
EP 449
DI 10.1006/icar.1996.5665
PG 55
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WX524
UT WOS:A1997WX52400013
ER
PT J
AU Harris, AW
Harris, AW
AF Harris, AW
Harris, AW
TI On the revision of radiometric albedos and diameters of asteroids
SO ICARUS
LA English
DT Article
AB A simple, approximate method is presented for the recalculation of asteroid diameters and geometric albedos given new, improved absolute visual magnitudes. This method avoids recourse to detailed models of an object's reflected and thermally emitted flux components. Its basis is the assumption that for small changes in absolute magnitude the quantity (1-A(v))D-2 can be considered invariant, where A(v) and D are the object's Bond albedo and diameter, respectively. The usefulness of the method for revising the diameters and albedos of asteroids, especially those covered by the IRAS Minor Planet Survey (E. F. Tedesco, Ed., 1992, Tech. Rep. PL-TR-92-2049, Phillips Laboratory, Hanscom AFB, MA), is demonstrated by applying it to a number of objects for which recently updated absolute magnitudes are available. (C) 1997 Academic Press.
C1 CALTECH, JET PROP LAB, PASADENA, CA 91109 USA.
RP Harris, AW (reprint author), DLR, INST PLANETENERKUNDUNG, RUDOWER CHAUSSEE 5, D-12489 BERLIN, GERMANY.
NR 8
TC 39
Z9 39
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 APR
PY 1997
VL 126
IS 2
BP 450
EP 454
DI 10.1006/icar.1996.5664
PG 5
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WX524
UT WOS:A1997WX52400014
ER
PT J
AU Bailey, D
AF Bailey, D
TI The 1997 Petaflops Algorithms Workshop
SO IEEE COMPUTATIONAL SCIENCE & ENGINEERING
LA English
DT Editorial Material
RP Bailey, D (reprint author), NASA,AMES RES CTR,MOFFETT FIELD,CA 94035, USA.
NR 0
TC 5
Z9 5
U1 0
U2 0
PU IEEE COMPUTER SOC
PI LOS ALAMITOS
PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1314
SN 1070-9924
J9 IEEE COMPUT SCI ENG
JI IEEE Comput. Sci. Eng.
PD APR-JUN
PY 1997
VL 4
IS 2
BP 82
EP 84
DI 10.1109/MCSE.1997.609838
PG 3
WC Computer Science, Theory & Methods; Engineering, Electrical &
Electronic; Mathematics, Applied
SC Computer Science; Engineering; Mathematics
GA XH888
UT WOS:A1997XH88800014
ER
PT J
AU Knopp, KJ
Christensen, DH
Hill, JR
AF Knopp, KJ
Christensen, DH
Hill, JR
TI Vertical-cavity surface-emitting lasers with low-ripple optical pumping
windows
SO IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS
LA English
DT Article; Proceedings Paper
CT 15th IEEE International Semiconductor Laser Conference (HAIFA 1996 ISLC)
CY OCT 13-18, 1996
CL HAIFA, ISRAEL
SP IEEE, Lasers & Electro Opt Soc, S Neaman Inst, ECI Telecom, Semiconductor Devices, Technion, Israel Inst Technol, Israeli Minist Sci & Arts
DE distributed Bragg reflector lasers; laser resonators; optical pumping;
thin-film devices; semiconductor lasers
ID DISTRIBUTED BRAGG REFLECTORS; MOLECULAR-BEAM EPITAXY; GROWTH
AB A general technique for numerically optimizing the optical admittances in vertical-cavity structures is used to suppress the interference ripple in the typical reflectance/transmittance spectra. This technique is applicable to any vertical-cavity device whose photonic properties at various wavelengths requires modification for specific applications. In this paper, we report the use of this optimization method to enhance the coupling of pump light into 850-nm vertical-cavity surface-emitting lasers (VCSEL's). We have designed and fabricated novel lasers which contain a wideband window of low reflectance amidst the typical interference fringe spectrum. The 750-800-nm region for the low-ripple design has an average reflectance of 5%; the peak-to-peak amplitude of the ripple is 0.25%. The sensitivity of these devices to temperature variations and layer-thickness manufacturing variations is also studied. The low-ripple pump window shifts at a rate of 0.036 nm/degrees C, the peak-to-peak ripple of the reflectance varies less than 2%, and the pump bandwidth remains constant, over temperatures ranging from 0 degrees C to 100 degrees C. The low-ripple structure substantially reduces the temperature and wavelength variation of the pump-field overlap by creating a window of nearly constant reflectance.
C1 NASA,LANGLEY RES CTR,HAMPTON,VA 23681.
UNIV COLORADO,DEPT ELECT & COMP ENGN,BOULDER,CO 80309.
RP Knopp, KJ (reprint author), NATL INST STAND & TECHNOL,325 BROADWAY,BOULDER,CO 80303, USA.
NR 20
TC 8
Z9 8
U1 0
U2 2
PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
PI NEW YORK
PA 345 E 47TH ST, NEW YORK, NY 10017-2394
SN 1077-260X
J9 IEEE J SEL TOP QUANT
JI IEEE J. Sel. Top. Quantum Electron.
PD APR
PY 1997
VL 3
IS 2
BP 366
EP 371
DI 10.1109/2944.605680
PG 6
WC Engineering, Electrical & Electronic; Optics; Physics, Applied
SC Engineering; Optics; Physics
GA XP732
UT WOS:A1997XP73200034
ER
PT J
AU Wells, BE
Ricks, KG
Weir, JM
AF Wells, BE
Ricks, KG
Weir, JM
TI Parallel simulation of a large-scale aerospace system in a multicomputer
environment
SO IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS
LA English
DT Article
AB This work describes the application of newly developed parallel processing techniques that exploit the irregularly-structured functional parallelism present within a test-bed aerospace system (i.e., a space shuttle main rocket engine simulation) utilizing a reduced complexity multicomputing architecture with an arbitrary topology, The methodologies are applicable to real time parallel simulation of large-scale dynamic systems and include deterministic model optimization and decomposition techniques, automated translation mechanisms, and a newly developed task allocation heuristic The effectiveness of these techniques are illustrated with performance being measured empirically for a wide range of topological configurations using a partially reconfigurable network of Transputers.
C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812.
RP Wells, BE (reprint author), UNIV ALABAMA,DEPT ELECT & COMP ENGN,HUNTSVILLE,AL 35899, USA.
NR 12
TC 2
Z9 2
U1 0
U2 0
PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
PI NEW YORK
PA 345 E 47TH ST, NEW YORK, NY 10017-2394
SN 0018-9251
J9 IEEE T AERO ELEC SYS
JI IEEE Trans. Aerosp. Electron. Syst.
PD APR
PY 1997
VL 33
IS 2
BP 507
EP 522
DI 10.1109/7.575890
PN 1
PG 16
WC Engineering, Aerospace; Engineering, Electrical & Electronic;
Telecommunications
SC Engineering; Telecommunications
GA WT379
UT WOS:A1997WT37900012
ER
PT J
AU Hogerheiden, J
Ciminera, M
Jue, G
AF Hogerheiden, J
Ciminera, M
Jue, G
TI Improved planar spiral transformer theory applied to a miniature lumped
element quadrature hybrid
SO IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES
LA English
DT Article
AB In this paper, an improved method of determining the primary-to-secondary coupling capacitance for planar spiral transformers (PST's) is presented, which enhances previous work. A more general monolithic microwave integrated circuit (MMIC) compatible lumped element multisection model is also presented based on symmetric-width uniformly coupled transmission lines. These techniques were developed to design a 90 degrees hybrid as a MMIC with a center frequency of 2.5 GHz. The design was frequency scaled to 0.5 GHz and fabricated in the microwave integrated circuit (MIG) for verification. Producibility is enhanced and coupling is effectively increased with the novel use of series capacitors which cancel some of the self-inductance of the transformers. Measured results are presented for both a quadrature hybrid and the individual PST used in the quadrature hybrid. The measured results show excellent agreement with the computer models.
C1 CALTECH,JET PROP LAB,PASADENA,CA 91109.
RP Hogerheiden, J (reprint author), AMER NUCLEON CORP,WESTLAKE VILLAGE,CA 91359, USA.
NR 8
TC 24
Z9 24
U1 0
U2 1
PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
PI NEW YORK
PA 345 E 47TH ST, NEW YORK, NY 10017-2394
SN 0018-9480
J9 IEEE T MICROW THEORY
JI IEEE Trans. Microw. Theory Tech.
PD APR
PY 1997
VL 45
IS 4
BP 543
EP 545
DI 10.1109/22.566635
PG 3
WC Engineering, Electrical & Electronic
SC Engineering
GA WR586
UT WOS:A1997WR58600011
ER
PT J
AU Rascoe, DL
Javadi, HHS
Bowen, JG
Romanofsky, RR
Chorey, CM
Bhasin, KB
Barner, JB
Chew, W
Foote, MC
Hunt, B
Vasquez, RP
AF Rascoe, DL
Javadi, HHS
Bowen, JG
Romanofsky, RR
Chorey, CM
Bhasin, KB
Barner, JB
Chew, W
Foote, MC
Hunt, B
Vasquez, RP
TI Jet Propulsion Laboratory NASA Lewis research center space qualified
hybrid high temperature superconducting/semiconducting 7.4 GHz low-noise
downconverter for NRL HTSSE-II program (vol 44, pg 1279, 1996)
SO IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES
LA English
DT Correction, Addition
RP Rascoe, DL (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA.
NR 1
TC 0
Z9 0
U1 0
U2 0
PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
PI NEW YORK
PA 345 E 47TH ST, NEW YORK, NY 10017-2394
SN 0018-9480
J9 IEEE T MICROW THEORY
JI IEEE Trans. Microw. Theory Tech.
PD APR
PY 1997
VL 45
IS 4
BP 560
EP 560
DI 10.1109/TMTT.1997.566641
PG 1
WC Engineering, Electrical & Electronic
SC Engineering
GA WR586
UT WOS:A1997WR58600017
ER
PT J
AU Miller, JA
Walch, SP
AF Miller, JA
Walch, SP
TI Prompt NO: Theoretical prediction of the high-temperature rate
coefficient for CH+N-2->HCN+N
SO INTERNATIONAL JOURNAL OF CHEMICAL KINETICS
LA English
DT Article
ID NITROGEN-OXIDE FORMATION; REACTION
CH(X2-PI)+N2(X1-SIGMA-G+)->HCN(X1-SIGMA+)+N(4S); NITRIC-OXIDE;
MECHANISM; FLAMES; PRESSURE; DEPENDENCE; N-2
AB With potential-energy-surface parameters provided by Walch's calculations of the reaction path, we have calculated the thermal rate coefficient for the reaction,
(R1) CH + N-2 <----> HCN + N.
The theory employed assumes that the change in the reaction of the electron spin has little or no effect on the rate coefficient. The resulting expression for k(1),
k(1) = 3.68 x 10(7) T-1.42 exp(-20723/RT) cm(3)/mole-sec.,
in the temperature range, 1000 K less than or equal to T less than or equal to 4000 K, is in remarkably good agreement with the limited amount of experimental data available, suggesting that the assumption is valid. The origins of the ''prompt-NO'' phenomenon, our analysis of reaction (RI), and comparison of the results with experiment are all discussed in detail. (C) 1997 John Wiley & Sons, Inc.
C1 NASA,AMES RES CTR,THERMOSCI INST,MOFFETT FIELD,CA 94035.
RP Miller, JA (reprint author), SANDIA NATL LABS,COMBUST RES FACIL,LIVERMORE,CA 94551, USA.
NR 35
TC 39
Z9 40
U1 1
U2 2
PU JOHN WILEY & SONS INC
PI NEW YORK
PA 605 THIRD AVE, NEW YORK, NY 10158-0012
SN 0538-8066
J9 INT J CHEM KINET
JI Int. J. Chem. Kinet.
PD APR
PY 1997
VL 29
IS 4
BP 253
EP 259
DI 10.1002/(SICI)1097-4601(1997)29:4<253::AID-KIN3>3.0.CO;2-T
PG 7
WC Chemistry, Physical
SC Chemistry
GA WQ883
UT WOS:A1997WQ88300003
ER
PT J
AU Fore, LB
Witte, LC
McQuillen, JB
AF Fore, LB
Witte, LC
McQuillen, JB
TI Heat transfer to two-phase slug flows under reduced-gravity conditions
SO INTERNATIONAL JOURNAL OF MULTIPHASE FLOW
LA English
DT Article
DE two-phase flow; slug flow; two-phase heat transfer; microgravity
AB New hydrodynamic and heat transfer measurements are presented for two-phase slug flows in a reduced gravity environment. Air and two liquids, water and 50% aqueous glycerine were used to obtain a range of liquid Reynolds numbers from 1000 to 20,000 in a 25.4 mm i.d. tube. The measurements include void fraction, pressure gradient, and heat transfer coefficient. The enhancement of the heat transfer coefficient over single-phase liquid flow increases with increasing void fraction and is somewhat larger for the 50% glycerine solution than for water. Based on a comparison to normal-gravity correlations, the heat transfer coefficients are smaller at reduced-gravity than at normal-gravity under the same flow conditions. This can be explained by smaller liquid-phase turbulence levels in the absence of buoyancy-induced slip between the gas and liquid. (C) 1997 Elsevier Science Ltd.
C1 UNIV HOUSTON,DEPT MECH ENGN,HOUSTON,TX 77204.
NASA,LEWIS RES CTR,CLEVELAND,OH 44135.
RP Fore, LB (reprint author), UNIV HOUSTON,DEPT CHEM ENGN,HOUSTON,TX 77204, USA.
NR 19
TC 6
Z9 6
U1 0
U2 3
PU PERGAMON-ELSEVIER SCIENCE LTD
PI OXFORD
PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB
SN 0301-9322
J9 INT J MULTIPHAS FLOW
JI Int. J. Multiph. Flow
PD APR
PY 1997
VL 23
IS 2
BP 301
EP 311
DI 10.1016/S0301-9322(96)00067-5
PG 11
WC Mechanics
SC Mechanics
GA WF587
UT WOS:A1997WF58700006
ER
PT J
AU Davis, JE
Fortney, SM
AF Davis, JE
Fortney, SM
TI Effect of fluid ingestion on orthostatic responses following acute
exercise
SO INTERNATIONAL JOURNAL OF SPORTS MEDICINE
LA English
DT Article
DE exercise; hydration state; orthostatic stress; cardiovascular responses
ID BAROREFLEX
AB Orthostatic tolerance is impaired following an acute bout of exercise. This study era mined the effect of fluid ingestion following treadmill exercise in restoring the cardiovascular responses to an orthostatic stress. Five men (age, 29.6 +/- 3.4 yrs) were exposed to a graded lower body negative (LBNP) pressure protocol (0 to -50 mmHg) during euhydration without exercise (C), 20 minutes after exercise dehydration (D), 20 minutes after exercise and fluid ingestion (FIZO), and 60 minutes after exercise and fluid ingestion (F160). Fluid ingestion (mean +/- SE) consisted of water ingestion equivalent to 50% of the body weight lost during exercise (520 +/- 15 ml). Exercise dehydration resulted in significantly higher heart rates (119 +/- 8 vs 82 +/- 7 bpm), lower systolic blood pressures (95 +/- 1.7 vs 108 +/- 2.3 mmHg), a smaller increase in leg circumference (3.7 +/- 4 vs 6.9 +/- 1.0 mm), and an attenuated increase in total peripheral resistance (2.58 +/- 1.2 vs 4.28 +/- 0.9 mmHg/L/min) at - 50 mmHg LBNP compared to the C condition. Fluid ingestion (both 20 and 60), partially restored the heart rate, systolic blood pressure, and total peripheral resistance responses to LBNP, but did not influence the change in leg circumference during LBNP (4 +/- 0.3 for R20 and 2.8 +/- 0.4 mm for R60). These data illustrate the effectiveness of fluid ingestion on improving orthostatic responses following exercise, and suggest that dehydration is a contributing factor to orthostatic intolerance following exercise.
C1 NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX.
RP Davis, JE (reprint author), ALMA COLL,DEPT EXERCISE & HLTH SCI,ALMA,MI 48801, USA.
NR 14
TC 22
Z9 23
U1 0
U2 2
PU GEORG THIEME VERLAG
PI STUTTGART
PA P O BOX 30 11 20, D-70451 STUTTGART, GERMANY
SN 0172-4622
J9 INT J SPORTS MED
JI Int. J. Sports Med.
PD APR
PY 1997
VL 18
IS 3
BP 174
EP 178
DI 10.1055/s-2007-972615
PG 5
WC Sport Sciences
SC Sport Sciences
GA XC064
UT WOS:A1997XC06400006
PM 9187970
ER
PT J
AU Shah, AR
Murthy, PLN
Chamis, CC
AF Shah, AR
Murthy, PLN
Chamis, CC
TI Reliability of thermomechanical fatigue in polymer matrix composites
SO JOURNAL OF ADVANCED MATERIALS
LA English
DT Article
AB A methodology to compute probabilistic fatigue life of polymer matrix laminated composites has been developed and demonstrated. Matrix degradation effects due to long term environmental exposure and mechanical/thermal cyclic loads are accounted for in the simulation process. A unified time-temperature-stress dependent multi-factor interaction relationship developed at NASA Lewis Research center has been used to model the degradation/aging of material properties due to cyclic loads. The fast probability integration method is used to compute probabilistic distribution of response. Sensitivity of fatigue Life reliability to uncertainties in the primitive random variables e.g. constituent properties, fiber volume ratio, void volume ratio, ply thickness, etc. are computed and their significance in the reliability based design for maximum Life is discussed. Effect of variation in the thermal cyclic loads on the fatigue reliability for a graphite/epoxy (0/+/-45/90)degrees(s) laminate with ply thickness 0.127 mm, with respect to impending failure modes has been studied. The results show that, at low mechanical cyclic loads and low thermal cyclic amplitudes, fatigue life for 0.999 reliability is most sensitive to matrix compressive strength, matrix modulus, thermal expansion coefficient, and ply thickness. Whereas at high mechanical cyclic loads and high thermal cyclic amplitudes, fatigue Life at 0.999 reliability is more sensitive to the shear strength of matrix, longitudinal fiber modulus, matrix modulus, and ply thickness.
C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135.
RP Shah, AR (reprint author), NYMA INC,BROOKPARK,OH, USA.
NR 7
TC 0
Z9 0
U1 0
U2 1
PU SAMPE PUBLISHERS
PI COVINA
PA 1161 PARKVIEW DRIVE, COVINA, CA 91722
SN 1070-9789
J9 J ADV MATER
JI J. Adv. Mater.
PD APR
PY 1997
VL 28
IS 3
BP 19
EP 28
PG 10
WC Materials Science, Multidisciplinary
SC Materials Science
GA XK445
UT WOS:A1997XK44500003
ER
PT J
AU Dutton, J
AF Dutton, J
TI Extravehicular activity hardware for international space station
SO JOURNAL OF AEROSPACE ENGINEERING
LA English
DT Article
AB The International Space Station (ISS) relies heavily on extravehicular activity (EVA) for assembly and maintenance. The ISS EVA system provides the translation aids, tools, and support hardware to allow the crew to assemble and maintain the U.S. portion of the ISS. The EVA hardware supports the three primary phases of an EVA: translation of crew and hardware to the worksite; worksite setup and restraint; and conducting the actual EVA task. The primary hardware items and the uses of the hardware are described. In addition, a brief overview of the Russian ISS EVA capability is provided along with plans for interoperability between U.S. and Russian EVA.
RP Dutton, J (reprint author), NASA,LYNDON B JOHNSON SPACE CTR,EVA PROJ OFF,EVA INTEGRAT & OPERAT,MAILCODE XA,HOUSTON,TX 77058, USA.
NR 1
TC 2
Z9 2
U1 1
U2 1
PU ASCE-AMER SOC CIVIL ENGINEERS
PI NEW YORK
PA 345 E 47TH ST, NEW YORK, NY 10017-2398
SN 0893-1321
J9 J AEROSPACE ENG
JI J. Aerosp. Eng.
PD APR
PY 1997
VL 10
IS 2
BP 91
EP 93
DI 10.1061/(ASCE)0893-1321(1997)10:2(91)
PG 3
WC Engineering, Aerospace; Engineering, Civil
SC Engineering
GA WX831
UT WOS:A1997WX83100006
ER
PT J
AU Boles, WW
Scott, WD
Connolly, JF
AF Boles, WW
Scott, WD
Connolly, JF
TI Excavation forces in reduced gravity environment
SO JOURNAL OF AEROSPACE ENGINEERING
LA English
DT Article
AB When we return to the moon we will likely do so on limited budgets that will necessitate small, low-cost missions. Since the cost of transportation to the moon consumes upwards of 50% of the cost of an entire mission, one way to reduce mission cost is to use lunar resources to the greatest extent practical. This will reduce the amount of material transported to the moon, translating directly and linearly into cost savings. The most obvious lunar resource is the lunar regolith. With the lunar regolith we can build blast barriers; provide radiation and micrometeorite protection for habitats; and provide feed stock for oxygen production processes. Excavation technology for the lunar environment is an important element that will enable these uses of lunar regolith and one that requires further investigation. The objective of this paper is to present the results of experiments that provide bounds to the problem. These bounds may be used for the design and construction of a realistic prototype for further testing and development.
C1 TEXAS A&M UNIV,DEPT IND ENGN,COLLEGE STN,TX 77843.
NASA,LYNDON B JOHNSON SPACE CTR,PLANETARY MISS & MAT OFC,HOUSTON,TX 77058.
RP Boles, WW (reprint author), EASTERN KENTUCKY UNIV,DEPT TECHNOL,RICHMOND,KY 40475, USA.
NR 4
TC 12
Z9 15
U1 0
U2 2
PU ASCE-AMER SOC CIVIL ENGINEERS
PI NEW YORK
PA 345 E 47TH ST, NEW YORK, NY 10017-2398
SN 0893-1321
J9 J AEROSPACE ENG
JI J. Aerosp. Eng.
PD APR
PY 1997
VL 10
IS 2
BP 99
EP 103
DI 10.1061/(ASCE)0893-1321(1997)10:2(99)
PG 5
WC Engineering, Aerospace; Engineering, Civil
SC Engineering
GA WX831
UT WOS:A1997WX83100008
ER
PT J
AU Ryzhkov, A
Zrnic, D
Atlas, D
AF Ryzhkov, A
Zrnic, D
Atlas, D
TI Polarimetrically tuned R(Z) relations and comparison of radar rainfall
methods
SO JOURNAL OF APPLIED METEOROLOGY
LA English
DT Article
ID PRECIPITATION
AB The following rainfall measurements are compared: 1) the reflectivity factor-rain rate or R(Z) relation, whereby the rain is estimated point by point for mapping or area integration; 2) use of a specific differential phase K-DP (between vertical and horizontal polarization) in a relation with rainfall rate for point-by-point mapping and subsequent integration over areas and time; 3) use of a R(K-DP) relation together with a relation between K-DP and Z to derive a polarimetrically tuned or matched R(Z) relation; and 4) use of empirical relations between the rainfall volume and the time integral of the storm area in which reflectivity is larger than a selected threshold. These methods are tested on five cases-two summer-type convections, one winter convective case, and two events of stratiform rain with embedded convection. Accumulations of rain in a dense gauge network in Oklahoma are used as a standard for comparison with radar measurements. In four of the five cases the rain totals obtained from the R(K-DP) relation agree very well with actual gauge accumulations. This is significantly better than the Marshall-Palmer R(Z) relation, which agrees well with gauges for only one event. Matching Z to K-DP brought the R(Z) derived rain total to better agreement with gauges in three more cases.
C1 UNIV OKLAHOMA,COOPERAT INST MESOSCALE METEOROL STUDIES,NORMAN,OK 73019.
NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771.
RP Ryzhkov, A (reprint author), NOAA,NATL SEVERE STORMS LAB,1313 HALLEY CIRCLE,NORMAN,OK 73069, USA.
NR 20
TC 13
Z9 13
U1 0
U2 1
PU AMER METEOROLOGICAL SOC
PI BOSTON
PA 45 BEACON ST, BOSTON, MA 02108-3693
SN 0894-8763
J9 J APPL METEOROL
JI J. Appl. Meteorol.
PD APR
PY 1997
VL 36
IS 4
BP 340
EP 349
DI 10.1175/1520-0450(1997)036<0340:PTRZRA>2.0.CO;2
PG 10
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA WV594
UT WOS:A1997WV59400006
ER
PT J
AU Cantrell, JH
Yost, WT
AF Cantrell, JH
Yost, WT
TI Effect of precipitate coherency strains on acoustic harmonic generation
SO JOURNAL OF APPLIED PHYSICS
LA English
DT Article
ID RADIATION STRESS; SOLIDS; NONLINEARITY
AB A model is presented of the dependence of acoustic harmonic generation in polycrystalline solids on the coherency strains resulting from the lattice mismatch at the interface between the matrix material and a precipitated second phase in the matrix material. The acoustic nonlinearity parameter (a quantitative measure of acoustic nonlinearity) is shown to depend on the second, third, and fourth order elastic constants of the material, the precipitate-matrix lattice misfit parameter, and the volume fraction of precipitates. The model is applied to the artificial aging of aluminum alloy 2024 from the T4 to the T6 temper. Experimental measurements on samples of Al 2024 taken at various heat treatment times not only confirm the predictions of the model but together with the model provide a basis for assessing the influence of precipitate phase transformations on the aging process.
RP Cantrell, JH (reprint author), NASA,LANGLEY RES CTR,MAIL STOP 231,HAMPTON,VA 23681, USA.
NR 19
TC 50
Z9 53
U1 0
U2 8
PU AMER INST PHYSICS
PI WOODBURY
PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999
SN 0021-8979
J9 J APPL PHYS
JI J. Appl. Phys.
PD APR 1
PY 1997
VL 81
IS 7
BP 2957
EP 2962
DI 10.1063/1.364327
PG 6
WC Physics, Applied
SC Physics
GA WT432
UT WOS:A1997WT43200006
ER
PT J
AU Mayr, HG
Harris, I
Herrero, FA
Varosi, F
AF Mayr, HG
Harris, I
Herrero, FA
Varosi, F
TI Winds and composition changes in the thermosphere using the transfer
function model
SO JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS
LA English
DT Article; Proceedings Paper
CT Symposium on Upper Atmosphere Structure, Dynamics and Electrodynamics,
at the IUGG General Assembly
CY JUL, 1995
CL BOULDER, CO
SP Int Assoc Geomagnetism & Aeron, Div II Aeron Phenomena
ID DISSIPATIVE MULTICONSTITUENT MEDIUM; ATMOSPHERIC GRAVITY-WAVES; EARTHS
THERMOSPHERE; GLOBAL EXCITATION; NEUTRAL COMPOSITION; MAGNETIC STORMS;
TEMPERATURE; DYNAMICS; PERTURBATIONS; PROPAGATION
AB Different theoretical formulations are used to describe the thermosphere, ranging from fully analytical, linear models based, in the case of gravity waves, on the work of C. O. Hines, to fully numerical, thermospheric general circulation models (TGCMs), which account for non-linear processes and coupling with the ionospheric plasma. The semi-analytical Transfer Function Model (TFM) describes perturbations in the wind field, temperature and composition, accounting in self-consistent form for the momentum transfer between species. The perturbations are driven by external energy and momentum sources associated with absorbed solar radiation and magnetospheric processes. Compared with TGCMs, the TFM is simplified mainly by its linear approximation. But the model is not limited in its spatial and temporal resolutions, and it describes acoustic gravity waves that are generated in the thermosphere and partially propagate through the lower atmosphere. Moreover, the model is semi-analytical, which helps in delineating and understanding the dynamical characteristics. Using expansions in terms of vector spherical harmonics and Fourier transformation, the transfer function of the atmosphere is obtained through numerical height integration, which is time consuming computationally but needs to be done only once. Once the transfer function is constructed, the thermospheric response is obtained virtually instantaneously, thus providing an efficient tool for numerical simulation and experimentation. After a review of the TFM, results are discussed, which describe a number of thermospheric phenomena covering a wide range of spatial and temporal scales. These include magnetic storm effects as well as gravity waves propagating in the thermosphere, which are partially reflected from the Earth's surface and ducted through the lower atmosphere. (C) 1997 Elsevier Science Ltd.
C1 HUGHES STX CO,GREENBELT,MD.
RP Mayr, HG (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA.
NR 54
TC 6
Z9 6
U1 0
U2 2
PU PERGAMON-ELSEVIER SCIENCE LTD
PI OXFORD
PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB
SN 1364-6826
J9 J ATMOS SOL-TERR PHY
JI J. Atmos. Sol.-Terr. Phys.
PD APR
PY 1997
VL 59
IS 6
BP 691
EP 709
DI 10.1016/S1364-6826(96)00100-9
PG 19
WC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences
SC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences
GA WM440
UT WOS:A1997WM44000008
ER
PT J
AU Scott, R
Entekhabi, D
Koster, R
Suarez, M
AF Scott, R
Entekhabi, D
Koster, R
Suarez, M
TI Timescales of land surface evapotranspiration response
SO JOURNAL OF CLIMATE
LA English
DT Article
ID CIRCULATION; RAINFALL; CLIMATE; MODEL
AB Soil and vegetation exert strong control over the evapotranspiration rate, which couples the land surface water and energy balances. A method is presented to quantify the timescale of this surface control using daily general circulation model (GCM) simulation values of evapotranspiration and precipitation. By equating the time history of evaporation efficiency (ratio of actual to potential evapotranspiration) to the convolution of precipitation and a unit kernel (temporal weighting function), response functions are generated that can be used to characterize the timescales of evapotranspiration response for the land surface model (LSM) component of GCMs. The technique is applied to the output of two multiyear simulations of a GCM, one using a Surface-Vegetation-Atmosphere-Transfer (SVAT) scheme and the other a Bucker LSM. The derived response functions show that the Bucket LSM's response is significantly slower than that of the SVAT across the globe. The analysis also shows how the timescales of interception reservoir evaporation, bare soil evaporation, and vegetation transpiration differ within the SVAT LSM.
C1 MIT, RALPH M PARSONS LAB, DEPT CIVIL & ENVIRONM ENGN 48331, CAMBRIDGE, MA 02139 USA.
USDA, ARS, TUCSON, AZ 85719 USA.
NASA, GODDARD SPACE FLIGHT CTR, HYDROL SCI BRANCH, LAB HYDROSPHER PROC, GREENBELT, MD 20771 USA.
NASA, GODDARD SPACE FLIGHT CTR, ATMOSPHERES LAB, CLIMATE & RADIAT BRANCH, GREENBELT, MD 20771 USA.
RI Koster, Randal/F-5881-2012
OI Koster, Randal/0000-0001-6418-6383
NR 14
TC 28
Z9 29
U1 0
U2 3
PU AMER METEOROLOGICAL SOC
PI BOSTON
PA 45 BEACON ST, BOSTON, MA 02108-3693 USA
SN 0894-8755
EI 1520-0442
J9 J CLIMATE
JI J. Clim.
PD APR
PY 1997
VL 10
IS 4
BP 559
EP 566
DI 10.1175/1520-0442(1997)010<0559:TOLSER>2.0.CO;2
PG 8
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA WV718
UT WOS:A1997WV71800002
ER
PT J
AU Chou, MD
Zhao, WZ
AF Chou, MD
Zhao, WZ
TI Estimation and model validation of surface solar radiation and cloud
radiative forcing using TOGA COARE measurements
SO JOURNAL OF CLIMATE
LA English
DT Article
ID ABSORPTION
AB The Tropical Ocean and Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE) radiation measurements in the western Pacific warm pool are used to estimate surface solar radiation budgets and to validate radiation model calculations. Clear-sky fluxes are identified from the measurements of direct and diffuse fluxes at the ARM (Atmospheric Radiation Measurements) site of Kavieng by simultaneously imposing conditions that I) the direct downward solar flux is a maximum, 2) the diffuse downward solar Aux is a minimum, and 3) the total flux varies smoothly with time. Averaged over the four TOGA COARE months, the clear-sky downward solar flux at Kavieng is 308 W m(-2), with a range of 302-317 W m(-2). The estimated clear-sky solar Aux, together with the temperature and humidity radiosondings, are then used to validate radiation model calculations. Using an inferred aerosol optical thickness of 0.12, results show that clear-sky surface solar fluxes can be reliably computed from a radiation model. The effect of clouds on surface solar radiation is found to be large. Averaged over the four TOGA COARE months and the seven radiation stations, the surface cloud radiative forcing is 99 W m(-2) with a range of 79-112 W m(-2). This result of the mean cloud radiative forcing is in agreement with other current studies.
C1 APPL RES CORP,LANDOVER,MD 20785.
RP Chou, MD (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ATMOSPHERES LAB,CODE 913,GREENBELT,MD 20771, USA.
NR 18
TC 41
Z9 41
U1 1
U2 1
PU AMER METEOROLOGICAL SOC
PI BOSTON
PA 45 BEACON ST, BOSTON, MA 02108-3693
SN 0894-8755
J9 J CLIMATE
JI J. Clim.
PD APR
PY 1997
VL 10
IS 4
BP 610
EP 620
DI 10.1175/1520-0442(1997)010<0610:EAMVOS>2.0.CO;2
PG 11
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA WV718
UT WOS:A1997WV71800006
ER
PT J
AU Jacobs, SS
Comiso, JC
AF Jacobs, SS
Comiso, JC
TI Climate variability in the Amundsen and Bellingshausen Seas
SO JOURNAL OF CLIMATE
LA English
DT Article
ID WINTER MIXED LAYER; ANTARCTIC PENINSULA; SOUTHERN-OCEAN; INTERANNUAL
VARIABILITY; AIR-TEMPERATURE; ANNUAL CYCLE; WEDDELL SEA; ICE EXTENT;
OSCILLATION; MODULATION
AB Satellite data reveal a 20% decline in sea ice extent in the Amundsen and Bellingshausen Seas in the two decades following 1973. This change is negatively correlated with surface air temperatures on the west side of the Antarctic Peninsula, which have increased similar to 0.5 degrees C decade(-1) since the mid-1940s. The recession was strongest during summer, when monthly average minima in 1991-92 removed much of the incipient multiyear ice over the continental shelf. This would have lowered the regional-mean ice thickness, impacting snow ice formation, brine production, and vertical heat flux. The northern ice edge contracted by similar to 1 degrees of latitude in all seasons from 1973-79 to 1987-93, returning toward mean conditions in 1993-95. The decline included multiyear cycles of several years in length, superimposed on high interannual variability. A review of atmospheric forcing shows winds consistent with mean and extreme ice extents, and suggests links to larger-scale circulation changes in the South Pacific. Historical ocean measurements are sparse in this sector, but mixed-layer depths and upper pycnoclines beneath the sea ice resemble those in the Weddell Sea. Weaker surface currents or changes in the upwelling of Circumpolar Deep water on the continental shelf could have contributed to the anomaly persistence.
C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771.
RP Jacobs, SS (reprint author), LAMONT DOHERTY EARTH OBSERV,POB 1000,PALISADES,NY 10964, USA.
NR 86
TC 144
Z9 150
U1 0
U2 13
PU AMER METEOROLOGICAL SOC
PI BOSTON
PA 45 BEACON ST, BOSTON, MA 02108-3693
SN 0894-8755
J9 J CLIMATE
JI J. Clim.
PD APR
PY 1997
VL 10
IS 4
BP 697
EP 709
DI 10.1175/1520-0442(1997)010<0697:CVITAA>2.0.CO;2
PG 13
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA WV718
UT WOS:A1997WV71800012
ER
PT J
AU Perigaud, C
Zebiak, SE
Melin, F
Boulanger, JP
Dewitte, B
AF Perigaud, C
Zebiak, SE
Melin, F
Boulanger, JP
Dewitte, B
TI On the role of meridional wind anomalies in a coupled model of ENSO
SO JOURNAL OF CLIMATE
LA English
DT Article
ID SEA-SURFACE TEMPERATURE; OCEAN-ATMOSPHERE INTERACTION; EL-NINO;
INTERANNUAL VARIABILITY; SOUTHERN OSCILLATION; EQUATORIAL PACIFIC;
TROPICAL OCEAN; UNIFIED VIEW; CIRCULATION; SYSTEM
AB The role of the meridional wind anomalies on the El Nino-Southern Oscillation as simulated by a simple coupled tropical Pacific ocean-atmosphere model is investigated. It is found that these anomalies play a key role in maintaining finite amplitude interannual variability in the coupled simulations. When the meridional wind stress anomalies are not allowed to feed back to the ocean, the simulated oscillations are damped out within a few years. This happens irrespective of initial conditions.
During a warm (cold) event, the simulated meridional wind stress anomalies drive convergent (divergent) surface currents in the equatorial east Pacific, inducing downwelling (upwelling) anomalies that act to strongly reinforce the SST and wind anomalies. This is in contrast to the model zonal wind stress anomalies, which due to the tendency to reverse sign in the eastern Pacific, induce upwelling (downwelling) anomalies in the east, and SST patterns with weaker net positive feedback.
Observed wind stress anomalies present some similarity with those simulated by the coupled model in the near-equatorial region. The zonal component reverses sign between the central and the eastern Pacific. There, the meridional component induces a vertical current anomaly of opposite sign and similar magnitude to that induced by the zonal one. These features suggest the importance of meridional wind stress anomalies in the real climate system.
C1 LAMONT DOHERTY EARTH OBSERV,PALISADES,NY 10964.
RP Perigaud, C (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,MAIL STOP 300-323,PASADENA,CA 91109, USA.
NR 48
TC 15
Z9 18
U1 0
U2 0
PU AMER METEOROLOGICAL SOC
PI BOSTON
PA 45 BEACON ST, BOSTON, MA 02108-3693
SN 0894-8755
J9 J CLIMATE
JI J. Clim.
PD APR
PY 1997
VL 10
IS 4
BP 761
EP 773
DI 10.1175/1520-0442(1997)010<0761:OTROMW>2.0.CO;2
PG 13
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA WV718
UT WOS:A1997WV71800016
ER
PT J
AU MacKay, RM
Ko, MKW
Shia, RL
Yang, YJ
Zhou, ST
Molnar, G
AF MacKay, RM
Ko, MKW
Shia, RL
Yang, YJ
Zhou, ST
Molnar, G
TI An estimation of the climatic effects of stratospheric ozone losses
during the 1980s
SO JOURNAL OF CLIMATE
LA English
DT Article
ID DYNAMICAL HEAT FLUXES; ENERGY-BALANCE; MODEL; ATMOSPHERE;
PARAMETERIZATION; SENSITIVITY; TEMPERATURE; OCEAN; CO2; O-3
AB In order to study the potential climatic effects of the ozone hole more directly and to assess the validity of previous lower resolution model results, the latest high spatial resolution version of the Atmospheric and Environmental Research, Inc., seasonal radiative dynamical climate model is used to simulate the climatic effects of ozone changes relative to the other greenhouse gases. The steady-state climatic effect of a sustained decrease in lower stratospheric ozone, similar in magnitude to the observed 1979-90 decrease, is estimated by comparing three steady-state climate simulations: I) 1979 greenhouse gas concentrations and 1979 ozone, II) 1990 greenhouse gas concentrations with 1979 ozone, and III) 1990 greenhouse gas concentrations with 1990 ozone. The simulated increase in surface air temperature resulting from nonozone greenhouse gases is 0.272 K. When changes in lower stratospheric ozone are included, the greenhouse warming is 0.165 K, which is approximately 39% lower than when ozone is fixed at the 1979 concentrations. Ozone perturbations at high latitudes result in a cooling of the surface-troposphere system that is greater (by a factor of 2.8) than that estimated from the change in radiative forcing resulting from ozone depletion and the model's 2 x CO2 climate sensitivity. The results suggest that changes in meridional heat transport from low to high latitudes combined with the decrease in the infrared opacity of the lower stratosphere are Very important in determining the steady-state response to high latitude ozone losses. The 39% compensation in greenhouse warming resulting from lower stratospheric ozone losses is also larger than the 28% compensation simulated previously by the lower resolution model. The higher resolution model is able to resolve the high latitude features of the assumed ozone perturbation, which are important in determining the overall climate sensitivity to these perturbations.
C1 ATMOSPHER & ENVIRONM RES INC,CAMBRIDGE,MA 02139.
NATL CTR ENVIRONM PREDICT,WASHINGTON,DC.
NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771.
RI Ko, Malcolm/D-5898-2015
NR 39
TC 11
Z9 11
U1 0
U2 1
PU AMER METEOROLOGICAL SOC
PI BOSTON
PA 45 BEACON ST, BOSTON, MA 02108-3693
SN 0894-8755
J9 J CLIMATE
JI J. Clim.
PD APR
PY 1997
VL 10
IS 4
BP 774
EP 788
DI 10.1175/1520-0442(1997)010<0774:AEOTCE>2.0.CO;2
PG 15
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA WV718
UT WOS:A1997WV71800017
ER
PT J
AU Minnetyan, L
Chamis, CC
AF Minnetyan, L
Chamis, CC
TI Progressive fracture of composite cylindrical shells subjected to
external pressure
SO JOURNAL OF COMPOSITES TECHNOLOGY & RESEARCH
LA English
DT Article
DE composites; composite structures; compression; damage; degradation;
durability; external pressure; fracture; laminates; simulation;
structural degradation
AB Progressive fractures of laminated graphite/epoxy composite cylindrical shells rue investigated under external hydrostatic pressure. An integrated computer code is used for the simulation of composite structural degradation under loading. Damage initiation, growth, accumulation, and propagation to structural fracture are included in the simulations. Results indicate that local defects do not have a significant effect on structural survivability under hydrostatic loading for thick composite shells. Influence of constituent material properties and the effects of residual stresses on damage initiation and progression under external pressure are evaluated Structural safety and damage tolerance characteristics of a prototype composite cylindrical shell are examined.
C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135.
RP Minnetyan, L (reprint author), CLARKSON UNIV,BOX 5710,POTSDAM,NY 13699, USA.
NR 11
TC 11
Z9 11
U1 0
U2 0
PU AMER SOC TESTING MATERIALS
PI W CONSHOHOCKEN
PA 100 BARR HARBOR DR, W CONSHOHOCKEN, PA 19428-2959
SN 0884-6804
J9 J COMPOS TECH RES
JI J. Compos. Technol. Res.
PD APR
PY 1997
VL 19
IS 2
BP 65
EP 71
PG 7
WC Materials Science, Composites; Polymer Science
SC Materials Science; Polymer Science
GA XB294
UT WOS:A1997XB29400002
ER
PT J
AU Matisak, BP
Zhao, AX
Narayanan, R
Fripp, AL
AF Matisak, BP
Zhao, AX
Narayanan, R
Fripp, AL
TI The microgravity environment: Its prediction, measurement, and
importance to materials processing
SO JOURNAL OF CRYSTAL GROWTH
LA English
DT Article; Proceedings Paper
CT 10th American Conference on Crystal Growth/9th International Conference
on Vapor Growth and Epitaxy
CY AUG 04-09, 1996
CL VAIL, CO
AB One of the primary benefits of conducting scientific research in space is to take advantage of the low acceleration environment. For experimenters conducting space research in the field of materials science the quality of the science return is contingent upon the extremely low frequency acceleration environment(much less than 1 Hz) aboard the spacecraft. Primary contributors to this low frequency acceleration environment (commonly referred to as the steady-state acceleration environment) include aerodynamic drag, gravity-gradient, and rotational effects. The space shuttle was used on the STS-75 mission as a microgravity platform for conducting a material science experiment in which a lead tin telluride alloy was melted and regrown in the Advanced Automated Directional Solidification Furnace under different steady-state acceleration environment conditions by placing the shuttle in particular fixed orientations during sample processing. The two different shuttle orientations employed during sample processing were a bay to Earth, tail into the velocity vector shuttle orientation and a tail to Earth, belly into the velocity vector shuttle orientation. Scientists have shown, through modeling techniques, the effects of various residual acceleration vector orientations to the micro-buoyant Bows during the growth of compound semiconductors. The signatures imposed by these temporally dependent hows are manifested in the axial and radial segregation or composition along the crystal.
C1 UNIV FLORIDA,GAINESVILLE,FL 32611.
NASA,LANGLEY RES CTR,HAMPTON,VA 23681.
RP Matisak, BP (reprint author), TELEDYNE BROWN ENGN INC,HUNTSVILLE,AL 35807, USA.
NR 8
TC 7
Z9 8
U1 1
U2 7
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0022-0248
J9 J CRYST GROWTH
JI J. Cryst. Growth
PD APR
PY 1997
VL 174
IS 1-4
BP 90
EP 95
DI 10.1016/S0022-0248(96)01083-4
PG 6
WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied
SC Crystallography; Materials Science; Physics
GA XJ186
UT WOS:A1997XJ18600014
ER
PT J
AU Gillies, DC
Lehoczky, SL
Szofran, FR
Watring, DA
Alexander, HA
Jerman, GA
AF Gillies, DC
Lehoczky, SL
Szofran, FR
Watring, DA
Alexander, HA
Jerman, GA
TI Effect of residual accelerations during microgravity directional
solidification of mercury cadmium telluride on the USMP-2 mission
SO JOURNAL OF CRYSTAL GROWTH
LA English
DT Article; Proceedings Paper
CT 10th American Conference on Crystal Growth/9th International Conference
on Vapor Growth and Epitaxy
CY AUG 04-09, 1996
CL VAIL, CO
DE microgravity; HgCdTe; solidification; fluid flow; furnace; crystal
growth
ID HGCDTE
AB Directional solidification of mercury cadmium telluride (MCT) requires that the temperature gradient to growth rate ratio be high to avoid constitutional supercooling. With the optimum gradient condition for solidifying MCT in NASA's advanced automated directional solidification furnace (AADSF), it is necessary to use translation rates as low as 0.2 mu m/s. The result is that any fluid flow with a velocity comparable to or higher than this will dominate the solidification characteristics, particularly the compositional distribution in an alloy such as this which has a large solidus-liquidus separation. In an effort to reduce fluid flow velocities a space experiment was performed. On the second United Slates Microgravity Payload Mission (USMP-2), the AADSF made its maiden flight and successfully completed growth of a MCT boule 16 cm long. The furnace was located approximately 3 m away from the center of gravity of the space shuttle, and this combined with the drag component of residual acceleration present during flight, resulted in quasisteady residual accelerations of the order of 1 mu g(0) where g(0) is the earth's natural gravity. Of more importance is that different orbiter attitudes during the mission produced significant differences in the resultant residual acceleration vector, in both magnitude and direction and that these differences caused large compositional variations both across the radii of the boule and along the surfaces of the boule. Comparison will be made with examples grown on the ground and in magnetic fields.
RP Gillies, DC (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,SPACE SCI LAB,ES75,HUNTSVILLE,AL 35812, USA.
NR 9
TC 19
Z9 20
U1 0
U2 3
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0022-0248
J9 J CRYST GROWTH
JI J. Cryst. Growth
PD APR
PY 1997
VL 174
IS 1-4
BP 101
EP 107
DI 10.1016/S0022-0248(97)01085-3
PG 7
WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied
SC Crystallography; Materials Science; Physics
GA XJ186
UT WOS:A1997XJ18600016
ER
PT J
AU Duval, WMB
Singh, NB
Glicksman, ME
AF Duval, WMB
Singh, NB
Glicksman, ME
TI Physical vapor transport of mercurous chloride crystals: Design of a
microgravity experiment
SO JOURNAL OF CRYSTAL GROWTH
LA English
DT Article; Proceedings Paper
CT 10th American Conference on Crystal Growth/9th International Conference
on Vapor Growth and Epitaxy
CY AUG 04-09, 1996
CL VAIL, CO
DE mercurous chloride; crystals; convection; microgravity; physical vapor
transport; dynamical state
ID CONVECTION; GROWTH; ENCLOSURES
AB Flow field characteristics predicted from a computational model show that the dynamical state of the flow, for practical crystal growth conditions of mercurous chloride, can range from steady to unsteady. Evidence that the flow field can be strongly dominated by convection for,ground-based conditions is provided by the prediction of asymmetric velocity profiles by the model which show reasonable agreement with laser Doppler velocimetry experiments in both magnitude and planform. Unsteady flow is shown to be correlated with a degradation of crystal quality as quantified by light scattering pattern measurements. A microgravity experiment is designed to show that an experiment performed with parameters which yield an unsteady Bow becomes steady (diffusive-advective) in a microgravity environment of 10(-3)g(0) as predicted by the model; and hence yields crystals with optimal quality.
C1 NORTHROP GRUMMAN SCI & TECHNOL CTR,PITTSBURGH,PA 15235.
RENSSELAER POLYTECH INST,TROY,NY 12180.
RP Duval, WMB (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA.
OI Glicksman, Martin/0000-0002-2675-2759
NR 19
TC 6
Z9 6
U1 0
U2 1
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0022-0248
J9 J CRYST GROWTH
JI J. Cryst. Growth
PD APR
PY 1997
VL 174
IS 1-4
BP 120
EP 129
DI 10.1016/S0022-0248(96)01088-3
PG 10
WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied
SC Crystallography; Materials Science; Physics
GA XJ186
UT WOS:A1997XJ18600019
ER
PT J
AU Rosch, WR
Fripp, AL
Debnam, WJ
Pendergrass, TK
AF Rosch, WR
Fripp, AL
Debnam, WJ
Pendergrass, TK
TI Performance testing of a vertical Bridgman furnace using experiments and
numerical modeling
SO JOURNAL OF CRYSTAL GROWTH
LA English
DT Article; Proceedings Paper
CT 10th American Conference on Crystal Growth/9th International Conference
on Vapor Growth and Epitaxy
CY AUG 04-09, 1996
CL VAIL, CO
ID CRYSTAL-GROWTH
AB This paper details a portion of the work performed in preparation for the growth of lead tin telluride crystals during a Space Shuttle flight. A coordinated effort of experimental measurements and numerical modeling tvas completed to determine the optimum growth parameters and the performance of the furnace. This work was done using NASA's Advanced Automated Directional Solidification Furnace, but the procedures used should be equally valid for other vertical Bridgman furnaces.
C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812.
RP Rosch, WR (reprint author), NASA,LANGLEY RES CTR,HAMPTON,VA 23681, USA.
NR 10
TC 4
Z9 4
U1 0
U2 0
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0022-0248
J9 J CRYST GROWTH
JI J. Cryst. Growth
PD APR
PY 1997
VL 174
IS 1-4
BP 139
EP 152
DI 10.1016/S0022-0248(96)01090-1
PG 14
WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied
SC Crystallography; Materials Science; Physics
GA XJ186
UT WOS:A1997XJ18600021
ER
PT J
AU Bly, JM
Kaforey, ML
Matthiesen, DH
Chait, A
AF Bly, JM
Kaforey, ML
Matthiesen, DH
Chait, A
TI Interface shape and growth rate analysis of Se/GaAs bulk crystals grown
in the NASA crystal growth furnace (CGF)
SO JOURNAL OF CRYSTAL GROWTH
LA English
DT Article; Proceedings Paper
CT 10th American Conference on Crystal Growth/9th International Conference
on Vapor Growth and Epitaxy
CY AUG 04-09, 1996
CL VAIL, CO
DE semiconductor; characterization; microgravity; gallium arsenide; peltier
effect; interface demarcation
ID SEGREGATION
AB Selenium-doped gallium arsenide, Se/GaAs, bulk crystals have been grown on earth using NASA's crystal growth furnace (CGF) in preparation for microgravity experimentation on the USML-2 spacelab mission. Peltier cooling pulses of 50 ms duration, 2040 A magnitude, and 0.0033 Hz frequency were used to successfully demark the melt-solid interface at known times during the crystal growth process. Post-growth characterization included interface shape measurement, growth rate calculation, and growth rate transient determinations. It was found that the interface shapes were always slightly concave into the solid, The curvature of the seeding interfaces was typically 1.5 mm for the 15 mm diameter samples. This was in agreement with the predicted interface shapes and positions relative to the furnace determined using a numerical model of the sample/ampoule/cartridge assembly (SAGA).
C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135.
RP Bly, JM (reprint author), CASE WESTERN RESERVE UNIV,CLEVELAND,OH 44106, USA.
NR 13
TC 0
Z9 0
U1 1
U2 1
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0022-0248
J9 J CRYST GROWTH
JI J. Cryst. Growth
PD APR
PY 1997
VL 174
IS 1-4
BP 220
EP 225
DI 10.1016/S0022-0248(96)01108-6
PG 6
WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied
SC Crystallography; Materials Science; Physics
GA XJ186
UT WOS:A1997XJ18600033
ER
PT J
AU Sha, YG
Su, CH
Alexander, HA
Lehoczky, SL
Wang, JC
AF Sha, YG
Su, CH
Alexander, HA
Lehoczky, SL
Wang, JC
TI Seeded growth of HgZnTe by directional solidification using an initial
composition profile simulating a ''diffusion-boundary'' layer
SO JOURNAL OF CRYSTAL GROWTH
LA English
DT Article; Proceedings Paper
CT 10th American Conference on Crystal Growth/9th International Conference
on Vapor Growth and Epitaxy
CY AUG 04-09, 1996
CL VAIL, CO
DE seeded growth; directional solidification; diffusion-boundary layer
AB Hg0.84Zn0.16Te crystals were grown vertically by back-melting a series of precast segments followed by directional solidification. The predetermined composition profiles of these segments simulate the distribution of a ''diffusion boundary'' layer in the melt ahead of the solid-melt interface during the directional solidification experiment. Composition analysis of the grown crystals confirm that steady-state growth were achieved from the beginning of the growth process.
C1 ALABAMA A&M UNIV,DEPT PHYS,NORMAL,AL 35762.
RP Sha, YG (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,SPACE SCI LAB,HUNTSVILLE,AL 35812, USA.
NR 11
TC 2
Z9 2
U1 0
U2 0
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0022-0248
J9 J CRYST GROWTH
JI J. Cryst. Growth
PD APR
PY 1997
VL 174
IS 1-4
BP 267
EP 271
DI 10.1016/S0022-0248(96)01156-6
PG 5
WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied
SC Crystallography; Materials Science; Physics
GA XJ186
UT WOS:A1997XJ18600041
ER
PT J
AU Chernov, AA
AF Chernov, AA
TI Protein versus conventional crystals: Creation of defects
SO JOURNAL OF CRYSTAL GROWTH
LA English
DT Article; Proceedings Paper
CT 10th American Conference on Crystal Growth/9th International Conference
on Vapor Growth and Epitaxy
CY AUG 04-09, 1996
CL VAIL, CO
DE kinetics of growth; solution growth; low temperature; superlattices
ID MORPHOLOGICAL STABILITY; VICINAL FACE; GROWTH; LYSOZYME;
CRYSTALLIZATION; PERFECTION; KINETICS; FLOW
AB Recent data on protein crystal growth are reviewed and analyzed with an emphasis to crystal perfection. Since relative supersaturation for protein crystal growth is typically much higher than unity, no considerable detachment of species is expected once joined to the crystal lattice at a kink. Selection of proper molecules and their precise orientation should occur mainly at the stage when they try to join kinks. Sectorial and zonal (striation) structures induced by impurities and other point defects may cause mosaicity even without creation of misfit dislocations. Critical crystal size is estimated al which the dislocation network may be thermodynamically favorable. Since the crystals have isometric shape, this critical size turns out to be about an order of magnitude higher than the critical thickness of a pseudomorphic epitaxial layer. X-ray diffraction rocking curves width of about 0.02 degrees for reflections equivalent to a misfit similar to 3 x 10(-4) should correspond to the critical crystal of ca 0.5 mm, As in epitaxy, if nucleation and spread of dislocations are hindered, the critical size may be essentially bigger or the crystal should crack. At high impurity concentrations, new misoriented blocks may appear by surface nucleation, similar to what should happen in inorganic crystals growing from solutions.
RP Chernov, AA (reprint author), NASA,MSFC,UNIV SPACE RES ASSOC,SUITE 100,4950 CORP DR,HUNTSVILLE,AL 35806, USA.
NR 66
TC 36
Z9 36
U1 1
U2 3
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0022-0248
J9 J CRYST GROWTH
JI J. Cryst. Growth
PD APR
PY 1997
VL 174
IS 1-4
BP 354
EP 361
DI 10.1016/S0022-0248(96)01129-3
PG 8
WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied
SC Crystallography; Materials Science; Physics
GA XJ186
UT WOS:A1997XJ18600057
ER
PT J
AU Lal, RB
Zhang, HW
Wang, WS
Aggarwal, MD
Lee, HWH
Penn, BG
AF Lal, RB
Zhang, HW
Wang, WS
Aggarwal, MD
Lee, HWH
Penn, BG
TI Crystal growth and optical properties of 4-aminobenzophenone crystals
for NLO applications
SO JOURNAL OF CRYSTAL GROWTH
LA English
DT Article; Proceedings Paper
CT 10th American Conference on Crystal Growth/9th International Conference
on Vapor Growth and Epitaxy
CY AUG 04-09, 1996
CL VAIL, CO
DE solution growth; Bridgman-Stockbarger growth; NLO materials;
4-aminobenzophenone ABP
ID 2ND-HARMONIC GENERATION; CZOCHRALSKI
AB Single crystals of 4-aminobenzophenone, a nonlinear optical(NLO) material have been grown successfully by a novel solution growth as well as modified Bridgman-Stockbarger techniques. The transmission spectrum (420-1400 nm) and SHG efficiencies were determined. 4-Aminobenzophenone crystals gave a lower limit on the second harmonic generation (SHG) efficiency of 10%. Laser damage threshold measurements conducted at the indicated wavelengths gave values of 1-2 GW/cm(2).
C1 LAWRENCE LIVERMORE NATL LAB,LIVERMORE,CA 94551.
NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812.
RP Lal, RB (reprint author), ALABAMA A&M UNIV,DEPT PHYS,NORMAL,AL 35762, USA.
NR 13
TC 11
Z9 12
U1 0
U2 0
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0022-0248
J9 J CRYST GROWTH
JI J. Cryst. Growth
PD APR
PY 1997
VL 174
IS 1-4
BP 393
EP 397
DI 10.1016/S0022-0248(96)01134-7
PG 5
WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied
SC Crystallography; Materials Science; Physics
GA XJ186
UT WOS:A1997XJ18600062
ER
PT J
AU Grasza, K
Trivedi, SB
Yu, ZC
Kutcher, SW
Palosz, W
Brost, GA
AF Grasza, K
Trivedi, SB
Yu, ZC
Kutcher, SW
Palosz, W
Brost, GA
TI Low supersaturation nucleation and ''contactless'' growth of
photorefractive ZnTe crystals
SO JOURNAL OF CRYSTAL GROWTH
LA English
DT Article; Proceedings Paper
CT 10th American Conference on Crystal Growth/9th International Conference
on Vapor Growth and Epitaxy
CY AUG 04-09, 1996
CL VAIL, CO
DE crystal growth from the vapor; low supersaturation nucleation; ZnTe;
photorefractive materials; doping by transition metals
ID CDTE
AB New photorefractive ZnTe crystals have been successfully grown by methods previously applied only for the growth of CdTe single crystals [K. Grasza, J. Crystal Growth 146 (1995) 65]. The main feature of this method lies in the novel procedure of self-seeding in conditions of permanently low supersaturation, growth with no contact between the crystal and ampoule wall, self-purification and improvement of stoichiometry of the source material during growth. Additionally, a new procedure of lowering the optimal growth temperature was applied and an optimal growth rate with stable growth conditions was investigated. The ZnTe crystals had resistivity exceeding 10(8) Omega.cm. Photorefractive characterization was performed using the two-beam mixing technique, and the photorefractive gain in the range 0.63-1.5 mu m was measured.
C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,SPACE SCI LAB,HUNTSVILLE,AL 35812.
ROME LAB,ROME,NY 13441.
RP Grasza, K (reprint author), BRIMROSE CORP AMER,5020 CAMPBELL BLVD,BALTIMORE,MD 21236, USA.
NR 15
TC 10
Z9 10
U1 0
U2 0
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0022-0248
J9 J CRYST GROWTH
JI J. Cryst. Growth
PD APR
PY 1997
VL 174
IS 1-4
BP 719
EP 725
DI 10.1016/S0022-0248(97)00026-2
PG 7
WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied
SC Crystallography; Materials Science; Physics
GA XJ186
UT WOS:A1997XJ18600110
ER
PT J
AU Palosz, W
George, MA
Collins, EE
Chen, KT
Zhang, Y
Hu, Z
Burger, A
AF Palosz, W
George, MA
Collins, EE
Chen, KT
Zhang, Y
Hu, Z
Burger, A
TI Seeded physical vapor transport of cadmium-zinc telluride crystals:
Growth and characterization
SO JOURNAL OF CRYSTAL GROWTH
LA English
DT Article; Proceedings Paper
CT 10th American Conference on Crystal Growth/9th International Conference
on Vapor Growth and Epitaxy
CY AUG 04-09, 1996
CL VAIL, CO
DE physics vapor transport; cadmium-zinc telluride
ID PHASE-SEPARATION; PHOTOLUMINESCENCE; ZNXCD1-XTE; CDTE; MICROSCOPY
AB Crystals of Cd1-xZnxTe with x = 0.2 and 40 g in weight were grown on monocrystalline cadmium-zinc telluride seeds by closed-ampoule physical vapor transport with or without excess (Cd + Zn) in the vapor phase. Two post-growth cool-down rates were used. The crystals were characterized using low temperature photoluminescence, atomic force microscopy, chemical etching, X-ray diffraction and electrical measurements. No formation of a second, ZnTe-rich phase was observed.
C1 FISK UNIV,DEPT PHYS,NASHVILLE,TN 37208.
RP Palosz, W (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,ES75,HUNTSVILLE,AL 35812, USA.
RI Hu, Zhiyu/J-7742-2013
NR 16
TC 6
Z9 6
U1 0
U2 2
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0022-0248
J9 J CRYST GROWTH
JI J. Cryst. Growth
PD APR
PY 1997
VL 174
IS 1-4
BP 733
EP 739
DI 10.1016/S0022-0248(97)00053-5
PG 7
WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied
SC Crystallography; Materials Science; Physics
GA XJ186
UT WOS:A1997XJ18600112
ER
PT J
AU Palosz, W
AF Palosz, W
TI Removal of oxygen from electronic materials by vapor-phase processes
SO JOURNAL OF CRYSTAL GROWTH
LA English
DT Article
AB Thermochemical analyses of equilibrium partial pressures over oxides with and without the presence of the respective element condensed phase, and hydrogen, chalcogens, hydrogen chalcogenides, and graphite are presented. Theoretical calculations are supplemented with experimental results on the rate of decomposition and/or sublimation/vaporization of the oxides under dynamic vacuum, and on the rate of reaction with hydrogen, graphite, and chalcogens. Procedures of removal of a number of oxides under different conditions are discussed.
RP Palosz, W (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,SPACE SCI LAB,ES75,HUNTSVILLE,AL 35812, USA.
NR 14
TC 7
Z9 7
U1 0
U2 0
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0022-0248
J9 J CRYST GROWTH
JI J. Cryst. Growth
PD APR
PY 1997
VL 173
IS 3-4
BP 427
EP 439
DI 10.1016/S0022-0248(96)00843-3
PG 13
WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied
SC Crystallography; Materials Science; Physics
GA XC981
UT WOS:A1997XC98100026
ER
PT J
AU Yao, MW
Chait, A
Fripp, AL
Debnam, WJ
AF Yao, MW
Chait, A
Fripp, AL
Debnam, WJ
TI Magnetically damped convection and segregation in Bridgman growth of
PbSnTe
SO JOURNAL OF CRYSTAL GROWTH
LA English
DT Article
DE finite element method; heat transfer; mass transfer; crystal growth;
Bridgman furnace; PbSnTe; magnetic damping; phase change; fluid dynamics
ID CZOCHRALSKI CRYSTAL PULLER; MELT MOTION; DIRECTIONAL SOLIDIFICATION;
BINARY ALLOY; FIELD; TRANSPORT; BUOYANCY; MODEL; HEAT; FLOW
AB The effects of an axially imposed magnetic field on convection and solute segregation during Bridgman growth of a non-dilute multicomponent system Pb0.8BSn0.2Te were studied using a finite-element model. The model considers heat and mass transport, fluid motion, solid/liquid-phase change and magnetic damping. The main objectives are to provide a quantitative understanding of the complex transport phenomena during solidification in a magnetic field, to provide estimates of the required magnetic field strength for low gravity growth, and to assess the role of magnetic damping for space and earth growth control. Numerical results for both vertical and horizontal growth configurations are presented. In addition to full-scale simulation, a revised scaling analysis is also presented.
C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135.
NASA,LANGLEY RES CTR,HAMPTON,VA 23665.
RP Yao, MW (reprint author), OHIO AEROSP INST,BROOKPARK,OH 44142, USA.
NR 40
TC 22
Z9 22
U1 1
U2 11
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0022-0248
J9 J CRYST GROWTH
JI J. Cryst. Growth
PD APR
PY 1997
VL 173
IS 3-4
BP 467
EP 480
DI 10.1016/S0022-0248(96)00844-5
PG 14
WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied
SC Crystallography; Materials Science; Physics
GA XC981
UT WOS:A1997XC98100031
ER
PT J
AU Yeoh, GH
Davis, GD
Leonardi, E
deGroh, HC
Yao, M
AF Yeoh, GH
Davis, GD
Leonardi, E
deGroh, HC
Yao, M
TI A numerical and experimental study of natural convection and interface
shape in crystal growth
SO JOURNAL OF CRYSTAL GROWTH
LA English
DT Article
ID SOLIDIFICATION; MELT
AB A numerical and experimental study has been conducted on the crystal growth of succinonitrile in a horizontal Bridgman apparatus. The shape of the solid-liquid interface was significantly influenced by three-dimensional natural convection in the liquid adjacent to the interface. The interface profile observed during experiments was compared with predictions from a two-dimensional (2D) finite element analysis and a three-dimensional (3D) finite difference approach. Good agreement was achieved between the experimental and predicted results. The computed velocities in the vicinity of the interface were found also to be in good agreement with the measured experimental velocities.
C1 UNIV NEW S WALES,SCH MECH & MFG ENGN,DEPT FLUID & THERMAL ENGN,SYDNEY,NSW 2052,AUSTRALIA.
NASA,LEWIS RES CTR,CLEVELAND,OH 44135.
OI Yeoh, Guan/0000-0003-3483-3759
NR 24
TC 19
Z9 21
U1 0
U2 0
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0022-0248
J9 J CRYST GROWTH
JI J. Cryst. Growth
PD APR
PY 1997
VL 173
IS 3-4
BP 492
EP 502
DI 10.1016/S0022-0248(96)00851-2
PG 11
WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied
SC Crystallography; Materials Science; Physics
GA XC981
UT WOS:A1997XC98100034
ER
PT J
AU Sen, S
Dhindaw, BK
Stefanescu, DM
Catalina, A
Curreri, PA
AF Sen, S
Dhindaw, BK
Stefanescu, DM
Catalina, A
Curreri, PA
TI Melt convection effects on the critical velocity of particle engulfment
SO JOURNAL OF CRYSTAL GROWTH
LA English
DT Article
DE convection; microgravity; directional solidification; composites;
solid/liquid interface velocity
ID METAL-MATRIX COMPOSITES; SOLID LIQUID INTERFACE; ANALYTICAL MODEL;
SOLIDIFICATION; BEHAVIOR
AB Liquid convection ahead of the solidifying interface alters particle behavior in the vicinity of the interface. This effect has not been quantified to date. Relevant directional solidification experiments were conducted using samples of varying thicknesses, as well as normal and low-gravity experiments. A mixture of transparent biphenyl matrix and spherical glass particles, as well as one of succinonitrile matrix with polystyrene particles were used, Two experimental setups were used: a horizontal gradient heating facility (HGF) for horizontal solidification, and a Bridgman-type furnace (BF) for vertical solidification. The convection level during solidification in the HGF was varied by changing the distance between the glass slides containing the composite sample. The BF was used on ground and during parabolic flights, and thus the convection level was changed by alternating low-gravity and high-gravity solidified regions. Tt was found that the convection level and/or particle buoyancy significantly influences the critical velocity for particle engulfment. At higher natural convection during solidification the critical velocity increases by up to 40%. At very high convection levels engulfment may become impossible because particles fail to interact with the interface, A systematic analysis of some theoretical models was performed in an attempt to evaluate the present level of theoretical understanding of the problem, Methods of evaluating the surface energies required for model validation are also presented.
C1 UNIV ALABAMA,SOLIDIFICAT LAB,TUSCALOOSA,AL 35487.
RP Sen, S (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,UNIV SPACE RES ASSOC,ES75,HUNTSVILLE,AL 35812, USA.
RI Stefanescu, Doru/G-8101-2012;
OI Stefanescu, Doru M./0000-0001-5544-8396; Dhindaw, Brij
Kumar/0000-0001-6991-9793
NR 24
TC 45
Z9 46
U1 1
U2 7
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0022-0248
J9 J CRYST GROWTH
JI J. Cryst. Growth
PD APR
PY 1997
VL 173
IS 3-4
BP 574
EP 584
DI 10.1016/S0022-0248(96)00802-0
PG 11
WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied
SC Crystallography; Materials Science; Physics
GA XC981
UT WOS:A1997XC98100041
ER
PT J
AU McElhaney, JM
Palazzolo, A
Kascak, A
AF McElhaney, JM
Palazzolo, A
Kascak, A
TI Modeling and simulation methods for MDOF structures and rotating
machinery with impact dampers
SO JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER-TRANSACTIONS OF THE
ASME
LA English
DT Article; Proceedings Paper
CT 40th International Gas Turbine and Aeroengine Congress and Exhibition
CY JUN 05-08, 1995
CL HOUSTON, TX
AB Previously published work on applied impact damping typically relates to SDOF models or simple MDOF models such as the classical cantilever beam. Structural models often require an extremely large number of DOF with mode shapes that are generally very complex. Dynamics simulation of these typically becomes both complicated and time consuming. The nonlinear behavior of impact dampers further complicates such simulation in that standard linear solutions are not possible. The primary objective in this research extends previous work by applying impact dampers to MDOF structures that are modeled with general three-dimensional ''beam'' finite elements. Modal-based models of the MDOF systems and efficient impact damper tracking algorithms were also developed that significantly reduced CPU time for simulation. Significant among the objectives was obtaining an impact damper design for the MDOF casing structure of the Space Shuttle Main Engine (SSME), High-Pressure Oxygen Turbo-Pump (HPOTP), subject to pump rotor shaft unbalance, Impact damper performance is based on suppression of vibration at casing critical frequencies for rotor speed ranges, at rotor full speed, and vert high unbalance to simulate a defect such as losing an impeller blade fragment or a cracked bearing [6]. Simulations show significant reductions in vibration at the casing critical-frequencies and very high unbalance levels while little or no improvement was observed off resonance. Additionally, the previous work with an experimental rotor bearing system (RBS) and impact damper was modeled using the developed modal-based methods. Simulation of the resulting model response shows remarkable agreement with the experimental. Finally, both the RES and the HPOTP were modeled and simulated as unstable systems with attached impact dampers. The simulations predict that the impact damper is an excellent stabilizing mechanism for a range of instability driver values. Simulation of the models in this research with the developed modal based algorithms were accomplished with excellent efficiency, and accurate results.
C1 NASA,LEWIS RES CTR,USA,CLEVELAND,OH 44135.
RP McElhaney, JM (reprint author), TEXAS A&M UNIV,DEPT MECH ENGN,COLLEGE STN,TX 77843, USA.
NR 2
TC 1
Z9 1
U1 0
U2 7
PU ASME-AMER SOC MECHANICAL ENG
PI NEW YORK
PA 345 E 47TH ST, NEW YORK, NY 10017
SN 0742-4795
J9 J ENG GAS TURB POWER
JI J. Eng. Gas. Turbines Power-Trans. ASME
PD APR
PY 1997
VL 119
IS 2
BP 436
EP 446
DI 10.1115/1.2815594
PG 11
WC Engineering, Mechanical
SC Engineering
GA WW751
UT WOS:A1997WW75100025
ER
PT J
AU Sawicki, JT
Gawronski, WK
AF Sawicki, JT
Gawronski, WK
TI Balanced model reduction and control of rotor-bearing systems
SO JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER-TRANSACTIONS OF THE
ASME
LA English
DT Article
ID FEEDBACK-CONTROL; LINEAR-SYSTEMS
AB An effective technique is applied to the suppression of vibrations in flexible rotor-bearing systems with small gyroscopic effects. A balanced linear-quadratic-Gaussian (LQG) controller design procedure is implemented. The size of the controller is reduced in two stages by using (i) a balanced model reduction, and (ii) an LQG balanced reduction. The condition for a gyroscopic matrix is developed that allows one to ignore the rotor gyroscopic effects in the process of the controller design, although they are included in the rotor dynamics. The approach is illustrated on a typical rotor-bearing system represented by a 48 degree-of freedom finite element model.
C1 CALTECH,JET PROP LAB,TECH STAFF,PASADENA,CA 91109.
RP Sawicki, JT (reprint author), CLEVELAND STATE UNIV,DEPT MECH ENGN,CLEVELAND,OH 44115, USA.
NR 29
TC 7
Z9 7
U1 1
U2 7
PU ASME-AMER SOC MECHANICAL ENG
PI NEW YORK
PA 345 E 47TH ST, NEW YORK, NY 10017
SN 0742-4795
J9 J ENG GAS TURB POWER
JI J. Eng. Gas. Turbines Power-Trans. ASME
PD APR
PY 1997
VL 119
IS 2
BP 456
EP 463
DI 10.1115/1.2815596
PG 8
WC Engineering, Mechanical
SC Engineering
GA WW751
UT WOS:A1997WW75100027
ER
PT J
AU Welch, GE
Jones, SM
Paxson, DE
AF Welch, GE
Jones, SM
Paxson, DE
TI Wave-rotor-enhanced gas turbine engines
SO JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER-TRANSACTIONS OF THE
ASME
LA English
DT Article
AB The benefits of wave rotor topping in small (300- to 500-kW [400- to 700-hp] class) and intermediate (2000- to 3000-kW [3000- to 4000-hp] class) turboshaft engines, and large (350- to 450-kN [80,000- to 100,000-lb(f)] class) high-bypass-ratio turbofan engines are evaluated. Wave rotor performance levels are calculated using a one-dimensional design/analysis code. Baseline and wave-rotor-enhanced engine perfor mance levels are obtained from a cycle deck in which the wave rotor is represented as a burner with pressure gain. Nave rotor topping is shown to enhance the specific fuel consumption and specific power of small- and intermediate-sized turboshaft engines significantly. The specific fuel consumption of the wave-rotor-enhanced large turbofan engine can be reduced while it operates at a significantly reduced turbine inlet temperature. The wave-rotor-enhanced engine is shown to behave off-design like a conventional engine. Discussion concerning the impact of the wave rotor/gas turbine engine integration identifies technical challenges.
C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135.
RP Welch, GE (reprint author), USA,RES LAB,WASHINGTON,DC, USA.
NR 24
TC 21
Z9 21
U1 0
U2 2
PU ASME-AMER SOC MECHANICAL ENG
PI NEW YORK
PA 345 E 47TH ST, NEW YORK, NY 10017
SN 0742-4795
J9 J ENG GAS TURB POWER
JI J. Eng. Gas. Turbines Power-Trans. ASME
PD APR
PY 1997
VL 119
IS 2
BP 469
EP 477
DI 10.1115/1.2815598
PG 9
WC Engineering, Mechanical
SC Engineering
GA WW751
UT WOS:A1997WW75100029
ER
PT J
AU Hexmoor, H
Kortenkamp, D
Horswill, I
AF Hexmoor, H
Kortenkamp, D
Horswill, I
TI Software architectures for hardware agents
SO JOURNAL OF EXPERIMENTAL & THEORETICAL ARTIFICIAL INTELLIGENCE
LA English
DT Article
DE architectures; mobile robotics; intelligent agents
ID COMPETITION
C1 SUNY BUFFALO, DEPT COMP SCI, BUFFALO, NY 14260 USA.
NASA, LYNDON B JOHNSON SPACE CTR,METRICA INC,ER2, ROBOT & AUTOMAT GRP, HOUSTON, TX 77058 USA.
NORTHWESTERN UNIV, INST LEARNING SCI, EVANSTON, IL 60201 USA.
RI Horswill, Ian/B-7175-2009
NR 38
TC 2
Z9 2
U1 0
U2 0
PU TAYLOR & FRANCIS LTD
PI ABINGDON
PA 2-4 PARK SQUARE, MILTON PARK, ABINGDON OR14 4RN, OXON, ENGLAND
SN 0952-813X
EI 1362-3079
J9 J EXP THEOR ARTIF IN
JI J. Exp. Theor. Artif. Intell.
PD APR-SEP
PY 1997
VL 9
IS 2-3
BP 147
EP 156
DI 10.1080/095281397147040
PG 10
WC Computer Science, Artificial Intelligence
SC Computer Science
GA XA328
UT WOS:A1997XA32800002
ER
PT J
AU Bonasso, RP
Firby, RJ
Gat, E
Kortenkamp, D
Miller, DP
Slack, MG
AF Bonasso, RP
Firby, RJ
Gat, E
Kortenkamp, D
Miller, DP
Slack, MG
TI Experiences with an architecture for intelligent, reactive agents
SO JOURNAL OF EXPERIMENTAL & THEORETICAL ARTIFICIAL INTELLIGENCE
LA English
DT Article
ID MOBILE-ROBOT; NAVIGATION
AB This paper describes an implementation of the 3T robot architecture which has been under development for the last eight years. The architecture uses three levels of abstraction and description languages which are compatible between levels. The makeup of the architecture helps to coordinate planful activities with real-time behaviours for dealing with dynamic environments. In recent years, other architectures have been created with similar attributes but two features distinguish the 3T architecture : (1) a variety of useful software tools have been created to help implement this architecture on multiple real robots; and (2) this architecture, or parts of it, have been implemented on a variety of very different robot systems using different processors, operating systems, effecters and sensor suites.
C1 NASA, LYNDON B JOHNSON SPACE CTR,METRICA INC, ROBOT & AUTOMAT GRP,ER4, HOUSTON, TX 77598 USA.
UNIV CHICAGO, DEPT COMP SCI, CHICAGO, IL 60637 USA.
JET PROPULS LAB, PASADENA, CA 91109 USA.
MITRE CORP, MCLEAN, VA 22102 USA.
NR 40
TC 130
Z9 130
U1 0
U2 5
PU TAYLOR & FRANCIS LTD
PI ABINGDON
PA 2-4 PARK SQUARE, MILTON PARK, ABINGDON OR14 4RN, OXON, ENGLAND
SN 0952-813X
EI 1362-3079
J9 J EXP THEOR ARTIF IN
JI J. Exp. Theor. Artif. Intell.
PD APR-SEP
PY 1997
VL 9
IS 2-3
BP 237
EP 256
DI 10.1080/095281397147103
PG 20
WC Computer Science, Artificial Intelligence
SC Computer Science
GA XA328
UT WOS:A1997XA32800008
ER
PT J
AU Cane, HV
Richardson, IG
Wibberenz, G
AF Cane, HV
Richardson, IG
Wibberenz, G
TI Helios 1 and 2 observations of particle decreases, ejecta, and magnetic
clouds
SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
LA English
DT Article
ID COSMIC-RAY DECREASES; CORONAL MASS EJECTIONS; INTERPLANETARY SHOCKS;
SOLAR-WIND; COMPOUND STREAMS; EVENTS
AB We have used >60 MeV/amu particle data from Hellos 1 and 2 to demonstrate the close association between ejecta (as defined, for example, by regions of depressed solar wind proton temperature) and short-term (<3 days duration) particle decreases. Of 84 short-term decreases of greater than or equal to 4%, we find that 88% were associated with an ejecta, and 70% of these were also associated with a shock. It is clear that the presence of a particle decrease is a robust signature for identifying ejecta in the ecliptic, at least within 1 AU. Conversely, ejecta are evidently important in the production of short-term cosmic ray depressions. The absence of a sample of well-defined ejecta without an associated particle decrease suggests that extended regions of open field geometry are rare inside ejecta, at least on the similar to 0.005 AU scale sizes probed by these particles. Sixty-three percent of the ejecta decreases were associated with smooth magnetic field rotations characteristic of magnetic clouds. Our results suggest that there is no fundamental difference in the particle response to ejecta with or without magnetic cloud signatures. We find that some ejecta observed at multiple spacecraft have a magnetic cloud signature at one spacecraft but not at another. The most likely explanation is that magnetic clouds are a substructure of ejecta and the field structure observed depends on where the ejecta is intercepted. We also find that ejecta probably typically extend much less in longitude than the 100 degrees inferred from single-spacecraft studies.
C1 NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771.
CHRISTIAN ALBRECHTS UNIV KIEL,INST REINE & ANGEW KERNPHYS,D-24118 KIEL,GERMANY.
UNIV MARYLAND,DEPT ASTRON,COLLEGE PK,MD 20742.
RP Cane, HV (reprint author), UNIV TASMANIA,DEPT PHYS,GPO BOX 252-21,HOBART,TAS 7001,AUSTRALIA.
OI Richardson, Ian/0000-0002-3855-3634
NR 35
TC 87
Z9 89
U1 0
U2 1
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009
J9 J GEOPHYS RES-SPACE
JI J. Geophys. Res-Space Phys.
PD APR 1
PY 1997
VL 102
IS A4
BP 7075
EP 7086
DI 10.1029/97JA00149
PG 12
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WR367
UT WOS:A1997WR36700006
ER
PT J
AU Farrugia, CJ
Erkaev, NV
Biernat, HE
Burlaga, LF
Lepping, RP
Osherovich, VA
AF Farrugia, CJ
Erkaev, NV
Biernat, HE
Burlaga, LF
Lepping, RP
Osherovich, VA
TI Possible plasma depletion layer ahead of an interplanetary ejecta
SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
LA English
DT Article
ID CORONAL MASS EJECTA; MAGNETIC CLOUDS; DAYSIDE MAGNETOPAUSE; FIELDS;
EVENTS
AB We present observations of a plasma depletion layer in front of an interplanetary magnetic cloud and analyze them quantitatively using a recent magnetohydrodynamic (MHD) theory of flow around magnetic clouds driving shocks. The magnetic field and plasma measurements were made by the ISEE 3 and IMP 8 on September 28-29, 1978. The magnetic cloud is expanding, and with a frontside boundary speed of approximate to 900 km s(-1) it is one of the fastest ever seen at Earth orbit. We find a simple variation of field and plasma parameters in the sheath region behind the shock. Along the spacecraft trajectory the sum of the gas and plasma pressures is approximately constant, with a plasma beta less than unity. As the frontside boundary of the magnetic cloud is approached, the magnetic field strength increases while the density and temperature simultaneously decrease. These are defining characteristics of a plasma depletion layer, similar to that often seen in the terrestrial magnetosheath adjacent to the magnetopause. This suggests that the underlying cause is the same: the stretching of interplanetary magnetic field lines around the ejecta. The plasma depletion layer extends throughout the sheath region for which data are available, that is, for approximately 3 out of 5.7 hours. The sheath terminates at a clear discontinuity at the cloud's surface. To compare the observations with MHD theory, we model the ejecta as a magnetic flux rope of locally straight cylindrical geometry. We consider two limiting cases separately: (1) bulk motion relative to the surrounding medium but without expansion and (2) expansion into the ambient medium but without bulk motion. The predictions of both these limiting theories yield good agreement with observed variations of plasma parameters and magnetic field strength across the sheath. This paper is intended as a first attempt at modeling plasma depletion layers associated with interplanetary magnetic clouds.
C1 AUSTRIAN ACAD SCI,SPACE RES INST,A-8042 GRAZ,AUSTRIA.
RUSSIAN ACAD SCI,CTR COMP,AKADEMGORODOK 660036,RUSSIA.
NASA,GODDARD SPACE FLIGHT CTR,EXTRATERR PHYS LAB,GREENBELT,MD 20771.
UNIV MALTA,DEPT MATH SCI & TECH EDUC,MSIDA,MALTA.
RP Farrugia, CJ (reprint author), UNIV NEW HAMPSHIRE,INST STUDY EARTH OCEANS & SPACE,DURHAM,NH 03824, USA.
RI Erkaev, Nikolai/M-1608-2013
OI Erkaev, Nikolai/0000-0001-8993-6400
NR 24
TC 13
Z9 13
U1 0
U2 0
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009
J9 J GEOPHYS RES-SPACE
JI J. Geophys. Res-Space Phys.
PD APR 1
PY 1997
VL 102
IS A4
BP 7087
EP 7093
DI 10.1029/96JA03822
PG 7
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WR367
UT WOS:A1997WR36700007
ER
PT J
AU Baker, DN
Pulkkinen, TI
Hesse, M
McPherron, RL
AF Baker, DN
Pulkkinen, TI
Hesse, M
McPherron, RL
TI A quantitative assessment of energy storage and release in the Earth's
magnetotail
SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
LA English
DT Article
ID SUBSTORM GROWTH-PHASE; GEOMAGNETIC-ACTIVITY; CURRENT SHEET; MODEL;
MAGNETOSPHERE; SATELLITE; CDAW-9; TAIL
AB Magnetospheric substorms represent a global interaction between the solar wind, the magnetosphere, and the ionosphere. Energy extracted from the solar wind is episodically stored in the magnetosphere, with large fraction of this energy being in the form of excess magnetic flux in the magnetotail lobes. The stored energy is periodically dissipated in an explosive instability that occurs in the near-Earth plasma sheet at substorm expansive phase onset. Methods are discussed to estimate the amount of energy transferred from the solar wind to the magnetosphere during substorm growth phases. Observational and modeling constraints are then used to assess quantitatively the total amount of energy stored in the plasma sheet and magnetotail lobes. Possible energy sources to drive substorm evolution are evaluated in one particularly well-observed case (May 3, 1986). By examining the major avenues of energy dissipation, the energy that is released in the form of plasma sheet heating, ionospheric Joule heating, etc, is assessed during the substorm. It is found that stored tail-lobe energy is sufficient (by a factor of 3 or more) to drive observed substorm dissipation processes. On the other hand, energy in the closed field lines of the plasma sheet is insufficient (by a substantial margin) to supply the substorm energy.
C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771.
UNIV CALIF LOS ANGELES,INST GEOPHYS & PLANETARY PHYS,LOS ANGELES,CA 90024.
FINNISH METEOROL INST,HELSINKI 500101,FINLAND.
RP Baker, DN (reprint author), UNIV COLORADO,ATMOSPHER & SPACE PHYS LAB,CAMPUS BOX 590,BOULDER,CO 80303, USA.
RI Hesse, Michael/D-2031-2012; Pulkkinen, Tuija/D-8403-2012
OI Pulkkinen, Tuija/0000-0002-6317-381X
NR 28
TC 59
Z9 60
U1 0
U2 4
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009
J9 J GEOPHYS RES-SPACE
JI J. Geophys. Res-Space Phys.
PD APR 1
PY 1997
VL 102
IS A4
BP 7159
EP 7168
DI 10.1029/96JA03961
PG 10
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WR367
UT WOS:A1997WR36700014
ER
PT J
AU Baker, DN
Klimas, AJ
Vassiliadis, D
Pulkkinen, TI
McPherron, RL
AF Baker, DN
Klimas, AJ
Vassiliadis, D
Pulkkinen, TI
McPherron, RL
TI Reexamination of driven and unloading aspects of magnetospheric
substorms
SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
LA English
DT Article
ID SOLAR-WIND CONTROL; GEOMAGNETIC-ACTIVITY; RECOVERY PHASE; MAGNETOTAIL;
PREDICTION; FILTERS; FIELD; MODEL
AB It is widely accepted that substorms consist of both directly driven and loading-unloading processes. However, a recent study has presented results which suggested that over 90% of the auroral electrojet (AE) variation was directly predictable from the solar wind variations alone. This would imply that only a small residual in the AE variability is due to internal magnetospheric dynamics. The present paper considers nonlinear dynamical models of the global solar wind-magnetosphere interaction and uses the observed, highly variable solar wind electric field (VBs) to drive the Faraday loop analogue model. It is found that it is critically important to include magnetotail unloading in the model in order to replicate the main features of geomagnetic activity: with just the driven response in the model, one does not obtain realistic time behavior of the model AL index. Thus these results show quite clearly that both driven and unloading processes must be included in a realistic model of geomagnetic activity.
C1 NASA,GODDARD SPACE FLIGHT CTR,EXTRATERR PHYS LAB,GREENBELT,MD 20771.
UNIV CALIF LOS ANGELES,INST GEOPHYS & PLANETARY PHYS,LOS ANGELES,CA 90024.
FINNISH METEOROL INST,SF-00101 HELSINKI,FINLAND.
RP Baker, DN (reprint author), UNIV COLORADO,ATMOSPHER & SPACE PHYS LAB,CAMPUS BOX 392,BOULDER,CO 80309, USA.
RI Pulkkinen, Tuija/D-8403-2012
OI Pulkkinen, Tuija/0000-0002-6317-381X
NR 38
TC 20
Z9 21
U1 1
U2 3
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009
J9 J GEOPHYS RES-SPACE
JI J. Geophys. Res-Space Phys.
PD APR 1
PY 1997
VL 102
IS A4
BP 7169
EP 7177
DI 10.1029/96JA02627
PG 9
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WR367
UT WOS:A1997WR36700015
ER
PT J
AU Richards, PG
Khazanov, GV
AF Richards, PG
Khazanov, GV
TI On the thermal electron energy balance in the ionosphere in January 1993
and June 1990
SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
LA English
DT Article
ID MILLSTONE HILL; DENSITY; MODEL; PHOTOELECTRON; WINDS; FLUX;
PLASMASPHERE; TEMPERATURE; ALGORITHM; HEIGHT
AB This paper examines the electron energy balance in the F region of the ionosphere at Millstone Hill in January 1993 by comparing model electron temperatures with measurements from the incoherent scatter radar. Initial modeling indicated three problem areas for the electron temperature at the height of the peak electron density. First, the nighttime temperature was much too low. Second, the afternoon temperature was a little lower than the measured temperature. Third, the model temperature was too high in the morning just after sunrise. A new algorithm is presented for using the measured topside electron temperature to determine the amount of plasmaspheric heating. It was found that the plasmaspheric heating from photoelectrons escaping the ionosphere must be doubled in order for the model to reproduce the observed topside temperature. With this increased plasmaspheric heat flux, the model temperature at the peak height was also much closer to the measured temperature at night. The low temperature in the afternoon could be easily explained by nominal errors in the model inputs or the radar measurements, but the high model temperatures in the morning remain unexplained. Examination of the cooling rates showed that ion cooling is the main cooling rate and is clearly dominant in the afternoon, while O fine structure cooling is equally important in the morning and at night in January 1993. In order to provide a reference, model-data comparisons were also for June 1990. In this case the agreement between model and data was excellent at all times without the need to adjust local heating and cooling rates. For these summer conditions, vibrationally excited N-2 and ion cooling were the two main cooling mechanisms. As was the case in January 1993, doubling of the plasmaspheric heating rate was also needed for the model to match the topside electron temperatures in June 1990. The daytime peak plasmaspheric heat flow deduced from the topside electron temperature showed little variation between June 1990 and January 1993 despite the different seasons and levels of solar activity.
C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,SPACE SCI LAB,HUNTSVILLE,AL 35812.
UNIV ALABAMA,CTR SPACE PLASMA AERONOM & ASTRON RES,HUNTSVILLE,AL 35899.
RP Richards, PG (reprint author), UNIV ALABAMA,DEPT COMP SCI,HUNTSVILLE,AL 35899, USA.
NR 28
TC 25
Z9 25
U1 0
U2 1
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009
J9 J GEOPHYS RES-SPACE
JI J. Geophys. Res-Space Phys.
PD APR 1
PY 1997
VL 102
IS A4
BP 7369
EP 7377
DI 10.1029/96JA03104
PG 9
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WR367
UT WOS:A1997WR36700032
ER
PT J
AU Khazanov, GV
Liemohn, MW
Moore, TE
AF Khazanov, GV
Liemohn, MW
Moore, TE
TI Photoelectron effects on the self-consistent potential in the
collisionless polar wind
SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
LA English
DT Article
ID ION-EXOSPHERE; PLASMASPHERE; IONOSPHERE; MODEL; ELECTRONS; VELOCITY
AB The presence of unthermalized photoelectrons in the sunlit polar cap leads to an enhanced ambipolar potential drop and enhanced upward ion acceleration. Observations in the topside ionosphere have led to the conclusion that large-scale electrostatic potential drops exist above the spacecraft along polar magnetic field lines connected to regions of photoelectron production. A kinetic approach is used for the O+, H+, and photoelectron (p) distributions, while a fluid approach is used to describe the thermal electrons (e) and self-consistent electric field (E(parallel to)). Thermal electrons are allowed to carry a flux that compensates for photoelectron escape, a critical assumption. Collisional processes are excluded, leading to easier escape of polar wind particles and therefore to the formation of the largest potential drop consistent with this general approach. We compute the steady state electric field enhancement and net potential drop expected in the polar wind due to the presence of photoelectrons as a function of the fractional photoelectron content and the thermal plasma characteristics. For a set of low-altitude boundary conditions typical of the polar wind ionosphere, including 0.1% photoelectron content, we found a potential drop from 500 km to 5 R(E) of 6.5 V and a maximum thermal electron temperature of 8800 K. The reasonable agreement of our results with the observed polar wind suggests that the assumptions of this approach are valid.
RP Khazanov, GV (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,SPACE SCI LAB,CODE ES-83,HUNTSVILLE,AL 35812, USA.
RI Moore, Thomas/D-4675-2012; Liemohn, Michael/H-8703-2012
OI Moore, Thomas/0000-0002-3150-1137; Liemohn, Michael/0000-0002-7039-2631
NR 30
TC 40
Z9 40
U1 0
U2 3
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009
J9 J GEOPHYS RES-SPACE
JI J. Geophys. Res-Space Phys.
PD APR 1
PY 1997
VL 102
IS A4
BP 7509
EP 7521
DI 10.1029/96JA03343
PG 13
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WR367
UT WOS:A1997WR36700046
ER
PT J
AU Liemohn, MW
Khazanov, GV
Moore, TE
Guiter, SM
AF Liemohn, MW
Khazanov, GV
Moore, TE
Guiter, SM
TI Self-consistent superthermal electron effects on plasmaspheric refilling
SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
LA English
DT Article
ID POLAR WIND; TEMPERATURE ANISOTROPY; PLASMA FLOWS; IONOSPHERE; FIELD;
MAGNETOSPHERE; SIMULATION; TRANSPORT; PARALLEL; MODEL
AB The effects of self-consistently including superthermal electrons in the definition of the ambipolar electric field are investigated for the case of plasmaspheric refilling after a geomagnetic storm. By using the total electron population in the hydrodynamic equations, a method for incorporating superthermal electron parameters in the electric field and electron temperature calculation is developed. Also, the ambipolar electric field is included in the kinetic equation for the superthermal electrons through a change of variables using the total energy and the first adiabatic invariant. Calculations based on these changes are performed by coupling time-dependent models of the thermal plasma and superthermal electrons. Results from this treatment of the electric field and the self-consistent development of the solution are discussed in detail. Specifically, there is a decreased thermal electron density in the plasmasphere during the first few minutes of refilling, a slightly accelerated proton shock front, and a decreased superthermal electron flux due to the deceleration by the electric field. The timescales of plasmaspheric refilling are discussed and determined to be somewhat shorter than previously calculated for the thermal plasma and superthermal electron population due to the effects of the field-aligned potential.
C1 UNIV ALABAMA,CTR SPACE PLASMA & AERON RES,HUNTSVILLE,AL 35899.
RP Liemohn, MW (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,SPACE SCI LAB,HUNTSVILLE,AL 35812, USA.
RI Moore, Thomas/D-4675-2012; Liemohn, Michael/H-8703-2012
OI Moore, Thomas/0000-0002-3150-1137; Liemohn, Michael/0000-0002-7039-2631
NR 34
TC 26
Z9 26
U1 0
U2 1
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009
J9 J GEOPHYS RES-SPACE
JI J. Geophys. Res-Space Phys.
PD APR 1
PY 1997
VL 102
IS A4
BP 7523
EP 7536
DI 10.1029/96JA03962
PG 14
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WR367
UT WOS:A1997WR36700047
ER
PT J
AU Hunley, JD
AF Hunley, JD
TI The Peenemuende wind tunnels: A memoir - Wegener,PP
SO JOURNAL OF MILITARY HISTORY
LA English
DT Book Review
RP Hunley, JD (reprint author), NASA DRYDEN FLIGHT RES CTR,TEHACHAPI,CA, USA.
NR 1
TC 0
Z9 0
U1 0
U2 0
PU SOC MILITARY HISTORY
PI LEXINGTON
PA C/O VIRGINIA MILITARY INST, GEORGE C MARSHALL LIBRARY, LEXINGTON, VA
24450-1600
SN 0899-3718
J9 J MILITARY HIST
JI J. Mil. Hist.
PD APR
PY 1997
VL 61
IS 2
BP 405
EP 406
DI 10.2307/2954011
PG 2
WC History
SC History
GA WT185
UT WOS:A1997WT18500052
ER
PT J
AU Weber, AL
AF Weber, AL
TI Energy from redox disproportionation of sugar carbon drives biotic and
abiotic synthesis
SO JOURNAL OF MOLECULAR EVOLUTION
LA English
DT Article
DE biosynthesis; fermentation; bioenergetics; origin of metabolism;
prebiotic synthesis; origin of life; molecular evolution; reduction;
oxidation; sugar chemistry; free energy
ID AQUEOUS-SOLUTION; GLYCERALDEHYDE
AB To identify the energy source that drives the biosynthesis of amino acids, lipids, and nucleotides from glucose, we calculated the free energy change due to redox disproportionation of the substrate carbon of (1) 26-carbon fermentation reactions and (2) the biosynthesis of amino acids and lipids of E. coli from glucose, The free energy (cal/mmol of carbon) of these reactions was plotted as a function of the degree of redox disproportionation of carbon (disproportionative electron transfers (mmol)/mmol of carbon). The zero intercept and proportionality between energy yield and degree of redox disproportionation exhibited by this plot demonstrate that redox disproportionation is the principal energy source of these redox reactions (slope of linear fit = -10.4 cal/mmol of disproportionative electron transfers). The energy and disproportionation values of E. coli amino acid and lipid biosynthesis from glucose lie near this linear curve fit with redox disproportionation accounting for 84% and 96% (and ATP only 6% and 1% of the total energy of amino acid and lipid biosynthesis, respectively. These observations establish that redox disproportionation of carbon, and not ATP, is the primary energy source driving amino acid and lipid biosynthesis from glucose. Ln contrast, we found that nucleotide biosynthesis involves very little redox disproportionation, and consequently depends almost entirely on ATP for energy. The function of sugar redox disproportionation as the major source of free energy for the biosynthesis of amino acids and lipids suggests that sugar disproportionation played a central role in the origin of metabolism, and probably the origin of life.
RP Weber, AL (reprint author), NASA,AMES RES CTR,SETI INST,MAIL STOP 239-4,MOFFETT FIELD,CA 94035, USA.
NR 26
TC 13
Z9 14
U1 0
U2 2
PU SPRINGER VERLAG
PI NEW YORK
PA 175 FIFTH AVE, NEW YORK, NY 10010
SN 0022-2844
J9 J MOL EVOL
JI J. Mol. Evol.
PD APR
PY 1997
VL 44
IS 4
BP 354
EP 360
DI 10.1007/PL00006154
PG 7
WC Biochemistry & Molecular Biology; Evolutionary Biology; Genetics &
Heredity
SC Biochemistry & Molecular Biology; Evolutionary Biology; Genetics &
Heredity
GA WR618
UT WOS:A1997WR61800002
PM 9089074
ER
PT J
AU Devi, VM
Benner, DC
Smith, MAH
Rinsland, CP
AF Devi, VM
Benner, DC
Smith, MAH
Rinsland, CP
TI Air-broadening and shift coefficients of O-3 lines in the nu(2) band and
their temperature dependence
SO JOURNAL OF MOLECULAR SPECTROSCOPY
LA English
DT Article
ID NU(3) ROVIBRATIONAL TRANSITIONS; OZONE LINES; 5-MU-M REGION; MU-M;
NITROGEN; HALFWIDTHS; OXYGEN; N2; O2; SPECTROSCOPY
AB Room temperature measurements of self- and air-broadening coefficients are reported for over 370 transitions covering a range of 0 less than or equal to J '' less than or equal to 45 and 1 less than or equal to K-a '' less than or equal to 12 for the nu(2) ozone band in the 630 to 800 cm(-1) spectral region. In addition, the temperature dependence of air-broadened halfwidth and air-induced pressure shift coefficients have been determined for over 350 spectral lines. A total of 29 O-3 absorption spectra (0.005-cm(-1) resolution) recorded at various temperatures (29 to -63 degrees C) with a Fourier transform spectrometer were used in the analysis. The spectral line parameters were deduced by analyzing all of the 29 spectra simultaneously using a nonlinear least-squares fitting technique. The results are compared with similar measurements obtained in the ozone nu(1) band. (C) 1997 Academic Press.
C1 NASA,LANGLEY RES CTR,DIV ATMOSPHER SCI,HAMPTON,VA 23681.
RP Devi, VM (reprint author), COLL WILLIAM & MARY,WILLIAMSBURG,VA 23187, USA.
NR 35
TC 17
Z9 20
U1 0
U2 1
PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS
PI SAN DIEGO
PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495
SN 0022-2852
J9 J MOL SPECTROSC
JI J. Mol. Spectrosc.
PD APR
PY 1997
VL 182
IS 2
BP 221
EP 238
DI 10.1006/jmsp.1996.7139
PG 18
WC Physics, Atomic, Molecular & Chemical; Spectroscopy
SC Physics; Spectroscopy
GA WT456
UT WOS:A1997WT45600001
ER
PT J
AU Smith, MAH
Devi, VM
Benner, DC
Rinsland, CP
AF Smith, MAH
Devi, VM
Benner, DC
Rinsland, CP
TI Temperature dependence of air-broadening and shift coefficients of O-3
lines in the nu(1) band
SO JOURNAL OF MOLECULAR SPECTROSCOPY
LA English
DT Article
ID NU(3) ROVIBRATIONAL TRANSITIONS; MILLIMETER-WAVE SPECTRUM; OZONE LINES;
5-MU-M REGION; MU-M; NITROGEN; INTENSITIES; OXYGEN; SPECTROSCOPY;
HALFWIDTHS
AB High-resolution Fourier transform absorption spectra of ozone broadened by dry air have been recorded at a number of temperatures from -63 degrees C to 29 degrees C. Using a multispectrum nonlinear least-squares procedure, we fit 29 of these spectra simultaneously to determine the air-broadening and shift coefficients and their temperature dependences for 450 lines in the 9-mu m region; most of these belong to the nu(1) band. Partial air-broadening results were obtained for 104 additional lines, and room-temperature self-broadening coefficients were also determined for most of the 554 lines measured. These results cover a wide range of rotational quantum numbers, particularly in the R branch, with J '' less than or equal to 55 and K-a '' less than or equal to 12. The variation of the retrieved broadening and shift parameters with the rotational quantum numbers has been examined; particularly interesting behavior of the broadening coefficients is noted as the value of K-a '' approaches that of J ''. The broadening and shift coefficients compare well with previous room-temperature measurements in the nu(1) and other bands. The temperature-dependence results are also consistent (within the stated uncertainties) with the few previous measurements of the temperature dependence of air- and N-2-broadening coefficients in other O-3 bands, but disagree with the mean value given in the HITRAN compilation. (C) 1997 Academic Press.
C1 COLL WILLIAM & MARY,DEPT PHYS,WILLIAMSBURG,VA 23187.
RP Smith, MAH (reprint author), NASA,LANGLEY RES CTR,DIV ATMOSPHER SCI,MAIL STOP 401A,HAMPTON,VA 23681, USA.
NR 37
TC 21
Z9 22
U1 0
U2 5
PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS
PI SAN DIEGO
PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495
SN 0022-2852
J9 J MOL SPECTROSC
JI J. Mol. Spectrosc.
PD APR
PY 1997
VL 182
IS 2
BP 239
EP 259
DI 10.1006/jmsp.1996.7232
PG 21
WC Physics, Atomic, Molecular & Chemical; Spectroscopy
SC Physics; Spectroscopy
GA WT456
UT WOS:A1997WT45600002
ER
PT J
AU Gamache, RR
Lynch, R
Plateaux, JJ
Barbe, A
AF Gamache, RR
Lynch, R
Plateaux, JJ
Barbe, A
TI Halfwidths and line shifts of water vapor broadened by CO2: Measurements
and complex Robert-Bonamy formalism calculations
SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER
LA English
DT Article
ID ROTATION-VIBRATION LINES; ASYMMETRIC-TOP MOLECULES; PERTURBER
DEPENDENCES; QUADRUPOLE-MOMENTS; H2O-CO2 MIXTURES; H2O; TEMPERATURE;
INTENSITIES; WIDTHS; OZONE
AB Measurements of CO2-broadened line shifts of 29 transitions belonging to the vl, 2 nu(2) and nu(3) bands of water vapor are made at T = 294.4 K. The halfwidths of 31 transitions were previously reported [R. R. Gamache et al (1995)]. Calculations of the halfwidth and line shifts based on a fully complex implementation of the formalism of Robert and Bonamy are made for these transitions. The calculations employ an electrostatic, Lennard-Jones (6-12) atom-atom, and isotropic induction and dispersion components of the potential and dynamics correct to second order in time. The results are compared with the measured values and very good agreement is observed for both halfwidths and line shifts. A new feature in this approach is that the real and imaginary components of the S matrix affect both the halfwidth and the line shift. It is shown here that the imaginary parts of the S matrix strongly affect the calculated H2O-CO2 halfwidths. (C) 1997 Elsevier Science Ltd.
C1 NASA,GODDARD INST SPACE STUDIES,NEW YORK,NY 10025.
UNIV REIMS,URA CNRS 1434,LAB SPECTROMETRIE MOL & ATMOSPHER,F-51062 REIMS,FRANCE.
RP Gamache, RR (reprint author), UNIV LOWELL,CTR ATMOSPHER RES,450 AIKEN ST,LOWELL,MA 01854, USA.
NR 47
TC 36
Z9 38
U1 0
U2 1
PU PERGAMON-ELSEVIER SCIENCE LTD
PI OXFORD
PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB
SN 0022-4073
J9 J QUANT SPECTROSC RA
JI J. Quant. Spectrosc. Radiat. Transf.
PD APR
PY 1997
VL 57
IS 4
BP 485
EP 496
DI 10.1016/S0022-4073(96)00148-3
PG 12
WC Optics; Spectroscopy
SC Optics; Spectroscopy
GA WR439
UT WOS:A1997WR43900006
ER
PT J
AU He, XY
Zou, QS
Luo, LS
Dembo, M
AF He, XY
Zou, QS
Luo, LS
Dembo, M
TI Analytic solutions of simple flows and analysis of nonslip boundary
conditions for the lattice Boltzmann BGK model
SO JOURNAL OF STATISTICAL PHYSICS
LA English
DT Article
DE lattice Boltzmann BGK equations; nonslip boundary conditions; analytic
solutions of simple flows
ID PARTICULATE SUSPENSIONS; NUMERICAL SIMULATIONS; GAS AUTOMATA; EQUATION
AB In this paper we analytically solve the velocity of the lattice Boltzman BGK equation (LBGK) for several simple flows. The analysis provides a framework to theoretically analyze various boundary conditions. In particular, the analysis is used to derive the slip velocities generated by various schemes for th nonslip boundary condition. We find that the slip velocity is zero as long as Sigma(alpha)f(alpha)e(alpha) = 0 at boundaries, no matter what combination of distributions is chosen. The schemes proposed by Noble ct al. and by Inamuro et al. yield the correct zero-slip velocity, while some other schemes, such as the bounce-back scheme and the equilibrium distribution scheme, would inevitably generate a nonzero slip velocity The bounce-back scheme with the wall located halfway between a now node and a bounce-back node is also studied for the simple flows considered and is shown to produce results of second-order accuracy. The momentum exchange at boundaries seems to be highly related to the slip velocity at boundaries. To be specific, the slip velocity is zero only when the momentum dissipated by boundaries is equal to the stress provided by fluids.
C1 LOS ALAMOS NATL LAB,THEORET BIOL & BIOPHYS GRP T10,DIV THEORET,LOS ALAMOS,NM 87545.
LOS ALAMOS NATL LAB,DIV THEORET,COMPLEX SYST GRP T13,LOS ALAMOS,NM 87545.
LOS ALAMOS NATL LAB,DIV X,COMPUTAT SCI METHODS GRP XCM,LOS ALAMOS,NM 87545.
KANSAS STATE UNIV,DEPT MATH,MANHATTAN,KS 66506.
NASA,LANGLEY RES CTR,ICASE,HAMPTON,VA 23681.
RP He, XY (reprint author), LOS ALAMOS NATL LAB,CTR NONLINEAR STUDIES,MS-B258,LOS ALAMOS,NM 87545, USA.
RI Dembo, Micah/C-2755-2013; Luo, Li-Shi/A-4561-2011
OI Luo, Li-Shi/0000-0003-1215-7892
NR 24
TC 325
Z9 349
U1 0
U2 42
PU PLENUM PUBL CORP
PI NEW YORK
PA 233 SPRING ST, NEW YORK, NY 10013
SN 0022-4715
J9 J STAT PHYS
JI J. Stat. Phys.
PD APR
PY 1997
VL 87
IS 1-2
BP 115
EP 136
DI 10.1007/BF02181482
PG 22
WC Physics, Mathematical
SC Physics
GA XE284
UT WOS:A1997XE28400005
ER
PT J
AU LeeGlauser, GJ
Ahmadi, G
Horta, LG
AF LeeGlauser, GJ
Ahmadi, G
Horta, LG
TI Integrated passive/active vibration absorber for multistory buildings
SO JOURNAL OF STRUCTURAL ENGINEERING-ASCE
LA English
DT Article
ID SYSTEMS
AB In this paper, a passive isolator, an active vibration absorber, and an integrated passive/active (hybrid) control are studied for their effectiveness in reducing structural vibration under seismic excitations. For the passive isolator, a laminated rubber bearing base isolator, which has been studied and used extensively by researchers and seismic designers, is studied. An active vibration absorber concept, which can provide guaranteed closed-loop stability with minimum knowledge of the controlled system, is used to reduce the passive isolator displacement and to suppress vibration. A three-story building model is used for the numerical simulation. The performance of an active vibration absorber and a hybrid vibration controller in reducing peak structural responses is compared with the passively isolated structural response under the NOOW component of the Fl Centro 1940 and N90W component of the Mexico City 1985 earthquake excitation records.
C1 CLARKSON UNIV,DEPT MECH & AERONAUT ENGN,POTSDAM,NY 13699.
NASA,LANGLEY RES CTR,STRUCT DYN BRANCH,HAMPTON,VA 23681.
RP LeeGlauser, GJ (reprint author), NASA,LANGLEY RES CTR,NRC RES ASSOC,MS 230,HAMPTON,VA 23681, USA.
NR 14
TC 36
Z9 36
U1 1
U2 4
PU ASCE-AMER SOC CIVIL ENGINEERS
PI NEW YORK
PA 345 E 47TH ST, NEW YORK, NY 10017-2398
SN 0733-9445
J9 J STRUCT ENG-ASCE
JI J. Struct. Eng.-ASCE
PD APR
PY 1997
VL 123
IS 4
BP 499
EP 504
DI 10.1061/(ASCE)0733-9445(1997)123:4(499)
PG 6
WC Construction & Building Technology; Engineering, Civil
SC Construction & Building Technology; Engineering
GA WP848
UT WOS:A1997WP84800014
ER
PT J
AU Opila, EJ
Fox, DS
Jacobson, NS
AF Opila, EJ
Fox, DS
Jacobson, NS
TI Mass spectrometric identification of Si-O-H(g) species from the reaction
of silica with water vapor at atmospheric pressure
SO JOURNAL OF THE AMERICAN CERAMIC SOCIETY
LA English
DT Article
AB A high-pressure sampling mass spectrometer was used to detect the volatile species formed from SiO2 at temperatures between 1200 degrees and 1400 degrees C in a flowing water vapor/oxygen gas mixture at 1 bar total pressure. The primary vapor species identified was Si(OH)(4). The fragment ion Si(OH)(3)(+) was observed in quantities 3 to 5 times larger than the parent ion Si(OH)(4)(+). The Si(OH)(3)(+) intensity was found to have a small temperature dependence and to increase with the water vapor partial pressure as expected. In addition, SiO(OH)+, believed to be a fragment of SiO(OH)(2), was observed. These mass spectral results were compared to the behavior of silicon halides.
C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135.
RI Jacobson, Nathan/A-9411-2009
NR 19
TC 83
Z9 85
U1 1
U2 6
PU AMER CERAMIC SOC
PI WESTERVILLE
PA 735 CERAMIC PLACE, PO BOX 6136, WESTERVILLE, OH 43081-6136
SN 0002-7820
J9 J AM CERAM SOC
JI J. Am. Ceram. Soc.
PD APR
PY 1997
VL 80
IS 4
BP 1009
EP 1012
PG 4
WC Materials Science, Ceramics
SC Materials Science
GA WV760
UT WOS:A1997WV76000025
ER
PT J
AU Zelenka, RE
Smith, PN
Coppenbarger, RA
Njaka, CE
Sridhar, B
AF Zelenka, RE
Smith, PN
Coppenbarger, RA
Njaka, CE
Sridhar, B
TI Results from the NASA automated Nap-of-the-Earth program
SO JOURNAL OF THE AMERICAN HELICOPTER SOCIETY
LA English
DT Article; Proceedings Paper
CT 52nd Annual Forum of the American-Helicopter-Society
CY JUN 04-06, 1996
CL WASHINGTON, D.C.
SP Amer Helicopter Soc
AB Military helicopter Nap-of-the-Earth (NOE) flight is one of the most demanding low-altitude, near terrain night operations, In NOE, the pilot is operating at or below tree-top levels, taking maximum advantage of the terrain and ground features for concealment. Such increased proximity to obstructions places heightened maneuverability requirements on the aircraft and extreme levels of workload on the pilot.
The basic issue being addressed in the NASA Automated Nap-of-the-Earth (ANOE) program is the intelligent use of environmental information such as knowledge of terrain, obstacles, and other external factors to enhance the flight path guidance of the vehicle, This is a major departure over contemporary guidance and control based on feedback of state variables such as vehicle attitudes, velocities, and accelerations, Although the immediate program has a military focus, the technological advances inherent for automating NOE flight have great benefit to the operation of a wide class of vehicles such as emergency medical helicopters, conventional and high-speed transports, unmanned aerial vehicles, and planetary vehicles,
This paper summarizes results to date of the NASA ANOE program in the areas of passive and active sensors, pilot displays, low-altitude manual trajectory guidance, and NOE automatic guidance, Each of these areas has been developed and evaluated in piloted, motion-based simulation or through flight test, These evaluations have demonstrated the feasibility of automating the NOE flight mission, and have generated additional spin-off applications of the technologies.
RP NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA.
NR 35
TC 2
Z9 2
U1 1
U2 1
PU AMER HELICOPTER SOC INC
PI ALEXANDRIA
PA 217 N WASHINGTON ST, ALEXANDRIA, VA 22314 USA
SN 0002-8711
EI 2161-6027
J9 J AM HELICOPTER SOC
JI J. Am. Helicopter Soc.
PD APR
PY 1997
VL 42
IS 2
BP 107
EP 115
PG 9
WC Engineering, Aerospace
SC Engineering
GA WX680
UT WOS:A1997WX68000001
ER
PT J
AU Jackson, KE
AF Jackson, KE
TI Analytical crash simulation of three composite fuselage concepts and
experimental correlation
SO JOURNAL OF THE AMERICAN HELICOPTER SOCIETY
LA English
DT Article; Proceedings Paper
CT 52nd Annual Forum of the American-Helicopter-Society
CY JUN 04-06, 1996
CL WASHINGTON, DC
SP Amer Helicopter Soc
AB The DYnamic Crash Analysis of STructures (DYCAST) crash analysis code was used to simulate the vertical impact response of two fuselage sections of the all-composite Lear Fan 2100 General Aviation aircraft. One fuselage section was tested in the unmodified condition, with the existing rigid subfloor in place. The second fuselage section was modified by replacing the rigid subfloor with an energy absorbing subfloor The DYCAST analysis results for both the unmodified and modified Lear Fan fuselage sections agreed well with the experimental data. The DYCAST analyses predicted the type and location of damage to the sections using a simple ultimate strain failure model. Experimental results from the Lear Fan testing program were used in the development of DYCAST models of three fuselage design concepts. The first fuselage concept is typical of conventional design and consists of a composite frame-reinforced fuselage shell with a stiff subfloor. The second fuselage concept is a retrofit of the previous design in which the rigid subfloor is replaced with a composite energy absorbing subfloor, The third fuselage concept is are innovative design which features a stiff ''inner'' fuselage intended to provide a protective shell surrounding the occupants, with a frangible ''outer'' shell which encapsulates an energy absorbing subfloor. The DYCAST models of the three fuselage concepts were analyzed for the same impact and loading conditions. A comparison of the response of the simulated occupant indicates a 25% reduction in vertical acceleration for the retrofit fuselage concept and a 50% reduction in vertical acceleration for the innovative third fuselage concept when compared with the conventional fuselage concept.
RP Jackson, KE (reprint author), USA,NASA,LANGLEY RES CTR,ARL,VEHICLE STRUCT DIRECTORATE,HAMPTON,VA 23681, USA.
NR 16
TC 8
Z9 10
U1 0
U2 1
PU AMER HELICOPTER SOC INC
PI ALEXANDRIA
PA 217 N WASHINGTON ST, ALEXANDRIA, VA 22314
SN 0002-8711
J9 J AM HELICOPTER SOC
JI J. Am. Helicopter Soc.
PD APR
PY 1997
VL 42
IS 2
BP 116
EP 125
PG 10
WC Engineering, Aerospace
SC Engineering
GA WX680
UT WOS:A1997WX68000002
ER
PT J
AU Popelka, D
Lindsay, D
Parham, T
Berry, V
Baker, DJ
AF Popelka, D
Lindsay, D
Parham, T
Berry, V
Baker, DJ
TI Results of an aeroelastic tailoring study for a composite tiltrotor wing
SO JOURNAL OF THE AMERICAN HELICOPTER SOCIETY
LA English
DT Article
AB The feasibility of a composite tailored wing for a high-speed civil tiltrotor is addressed using existing analytical methods. Composite tailoring is utilized to increase the proprotor aeroelastic stability margins for a thin wing (18% t/c) designed to improve high speed performance and productivity, Structural tailoring concepts are applied to the wing alone to improve the stability of the symmetric wing beamwise bending mode and the symmetric wing chordwise bending mode, which are the two most critical modes of instability. Skin laminate tailoring is shown to favorably influence the wing pitch/bending coupling and improve the stability of the wing beamwise mode. The wing chordwise mode stability is reduced by skin laminate tailoring due to a decrease in wing stiffness, but by tailoring the distribution of stringer and spar cap areas, the wing chard mode stability can be recovered, parametric studies show that the overall stability gains from composite tailoring can be limited because of conflicting structural design requirements imposed by the two critical modes of instability, and the necessity to balance the stability boundaries for bath modes. The parametric studies are used to define an 18% t/c tailored wing configuration that meets the stability goals with a minimum weight penalty.
C1 USA,LANGLEY RES CTR,RES LAB,VEHICLE STRUCT DIRECTORATE,HAMPTON,VA.
RP Popelka, D (reprint author), BELL HELICOPTER TEXTRON INC,FT WORTH,TX 76101, USA.
NR 10
TC 6
Z9 6
U1 2
U2 2
PU AMER HELICOPTER SOC INC
PI ALEXANDRIA
PA 217 N WASHINGTON ST, ALEXANDRIA, VA 22314
SN 0002-8711
J9 J AM HELICOPTER SOC
JI J. Am. Helicopter Soc.
PD APR
PY 1997
VL 42
IS 2
BP 126
EP 136
PG 11
WC Engineering, Aerospace
SC Engineering
GA WX680
UT WOS:A1997WX68000003
ER
PT J
AU Brentner, KS
Holland, PC
AF Brentner, KS
Holland, PC
TI An efficient and robust method for computing quadrupole noise
SO JOURNAL OF THE AMERICAN HELICOPTER SOCIETY
LA English
DT Article; Proceedings Paper
CT 1995 American-Helicopter-Society 2nd International Aeromechanics
Specialists Conference
CY OCT 11-13, 1995
CL BRIDGEPORT, CT
SP Amer Helicopter Soc
AB A new far-field approximation to the Ffowcs Williams-Hawkings quadrupole source, which is valid for an in-plane observer and utilizes preintegration in the direction normal to the rotor disk, is presented. This approximation is new and unique in that no further approximation of the quadrupole source strength is made and integrands with r(-2) and r(-3) dependence are retained, The far-field approximation leads to quadrupole integrals of the same form as thickness and loading noise, Quadrupole noise prediction is carried out in two parts: a preprocessing stage in which the previously computed flaw field is integrated in the direction normal to the rotor disk, and a noise computation stage in which quadrupole surface integrals are evaluated for a particular observer position. The predicted noise agrees well with both experimental data and Euler predictions for a hovering rotor up to a hover Mach number M-H = 0.9, even though only subsonic quadrupole sources are utilized in the present implementation, The method is robust and requires computer resources comparable to thickness and loading noise prediction.
C1 GEORGE WASHINGTON UNIV,JIAFS,HAMPTON,VA.
RP Brentner, KS (reprint author), NASA,LANGLEY RES CTR,HAMPTON,VA 23665, USA.
NR 20
TC 14
Z9 14
U1 0
U2 0
PU AMER HELICOPTER SOC INC
PI ALEXANDRIA
PA 217 N WASHINGTON ST, ALEXANDRIA, VA 22314
SN 0002-8711
J9 J AM HELICOPTER SOC
JI J. Am. Helicopter Soc.
PD APR
PY 1997
VL 42
IS 2
BP 172
EP 181
PG 10
WC Engineering, Aerospace
SC Engineering
GA WX680
UT WOS:A1997WX68000007
ER
PT J
AU Kontinos, D
AF Kontinos, D
TI Coupled thermal analysis method with application to metallic thermal
protection panels
SO JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER
LA English
DT Article
AB Metallic thermal protection systems are being considered for next-generation reusable launch vehicles. Experiments and numerical simulations show that heated metallic panels expand from the structure to create a quilt-like flow surface that alters the expected surface heating distribution. To model the thermal response of a metallic panel, this paper presents a two-dimensional boundary element procedure that is loosely coupled to a hypersonic computational fluid dynamics algorithm to solve coupled steady-state and transient heat conduction. First, the flowfield and internal temperature distribution of ceramic wing leading edge in a Mach 15 freestream is computed. Steady-state results are consistent with previous finite difference and finite element calculations. Transient computations show the peak temperature to occur at steady-state conditions. Second, the flowfield and resulting transient heat transfer is computed for convex and concave metallic panels. It is demonstrated that a transient conduction solution for a deformed metallic panel can be approximated by imposing the heat fluxes generated from a deformed surface now solution onto an undeformed panel.
RP Kontinos, D (reprint author), NASA,AMES RES CTR,THERMOSCI INST,M-S 230-2,MOFFETT FIELD,CA 94035, USA.
NR 25
TC 30
Z9 31
U1 0
U2 3
PU AMER INST AERONAUT ASTRONAUT
PI RESTON
PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091
SN 0887-8722
J9 J THERMOPHYS HEAT TR
JI J. Thermophys. Heat Transf.
PD APR-JUN
PY 1997
VL 11
IS 2
BP 173
EP 181
DI 10.2514/2.6249
PG 9
WC Thermodynamics; Engineering, Mechanical
SC Thermodynamics; Engineering
GA WU625
UT WOS:A1997WU62500007
ER
PT J
AU Lee, HS
Merte, H
Chiaramonte, F
AF Lee, HS
Merte, H
Chiaramonte, F
TI Pool boiling curve in microgravity
SO JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER
LA English
DT Article; Proceedings Paper
CT AIAA 34th Aerospace Sciences Meeting and Exhibit
CY JAN 15-19, 1996
CL RENO, NV
SP Amer Inst Aeronaut & Astronaut
ID SURFACE
AB Pool boiling experiments using R-113 were conducted in the microgravity of space on a flat heater, consisting of a semitransparent gold film sputtered on quartz substrate, 19.05 x 38.1 mm (0.75 x 1.50 in.), Transient measurements of both the mean heater surface temperature and input heat flux are used to compute the mean heat transfer coefficient at the heater wall, Steady-state pool boiling is achieved in microgravity under conditions in which a large vapor bubble somewhat removed from the heater surface is formed, which acts as a reservoir for the nucleating bubbles, The steady nucleate boiling heat transfer is enhanced materially in microgravity relative to that in Earth gravity, whereas the heat flux at which dryout occurs is considerably less, Using quasisteady data obtained during periods in which some significant portions of the heater surface were dried out, it was possible to construct two distinct composite approximate microgravity pool boiling curves for R-113, one for the higher level of subcooling and one for the lower level of subcooling. These are compared with a reference curve for pool boiling at a/g = +1, constructed from available data and correlations deemed to reasonably represent the circumstances present.
C1 NASA,LEWIS RES CTR,MICROGRAV FLUID PHYS BRANCH,CLEVELAND,OH 44135.
RP Lee, HS (reprint author), UNIV MICHIGAN,DEPT MECH ENGN & APPL MECH,ANN ARBOR,MI 48109, USA.
NR 17
TC 35
Z9 37
U1 0
U2 6
PU AMER INST AERONAUT ASTRONAUT
PI RESTON
PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091
SN 0887-8722
J9 J THERMOPHYS HEAT TR
JI J. Thermophys. Heat Transf.
PD APR-JUN
PY 1997
VL 11
IS 2
BP 216
EP 222
DI 10.2514/2.6225
PG 7
WC Thermodynamics; Engineering, Mechanical
SC Thermodynamics; Engineering
GA WU625
UT WOS:A1997WU62500013
ER
PT J
AU Liu, J
Shang, HM
Chen, YS
Wang, TS
AF Liu, J
Shang, HM
Chen, YS
Wang, TS
TI Analysis of discrete ordinates method with even parity formulation
SO JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER
LA English
DT Article
ID MULTIDIMENSIONAL GEOMETRIES; HEAT-TRANSFER; RADIATION; SYSTEMS
AB The even parity formulation (EPF) of the discrete ordinates method (DOM) is used to simulate radiative heat transfer in two-dimensional enclosures containing an absorbing-emitting and scattering medium. The discrete ordinates equations for the EPF are second-order differential equations and they are spatially discretized using a second-order central difference scheme. At the boundary, a higher-order upwind scheme is employed to prevent solution instability and minimize errors. The matrix solver of the discretized equations is based on a preconditioned conjugate gradients method. To investigate the accuracy and efficiency of the EPF of the DOM, several two-dimensional benchmark problems with an absorbing-emitting and scattering medium enclosed by gray walls are considered. By taking an appropriate numerical treatment, the numerical results from the EPF appear to compare Favorably with other available solutions. However, the even parity solution usually requires more CPU time and iterations to converge in comparison with the conventional DOM, especially for the case with a small optical thickness. This work indicates that the EPF of the DOM may be not as robust as the conventional DOM.
C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812.
RP Liu, J (reprint author), ENGN SCI INC,HUNTSVILLE,AL 35802, USA.
NR 20
TC 11
Z9 11
U1 0
U2 4
PU AMER INST AERONAUT ASTRONAUT
PI RESTON
PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091
SN 0887-8722
J9 J THERMOPHYS HEAT TR
JI J. Thermophys. Heat Transf.
PD APR-JUN
PY 1997
VL 11
IS 2
BP 253
EP 260
DI 10.2514/2.6230
PG 8
WC Thermodynamics; Engineering, Mechanical
SC Thermodynamics; Engineering
GA WU625
UT WOS:A1997WU62500018
ER
PT J
AU Gokcen, T
AF Gokcen, T
TI Effects of flowfield nonequilibrium on convective heat transfer to a
blunt body
SO JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER
LA English
DT Article; Proceedings Paper
CT AIAA 34th Aerospace Sciences Meeting and Exhibit
CY JAN 15-19, 1996
CL RENO, NV
SP Amer Inst Aeronaut & Astronaut
AB The axisymmetric Navier-Stokes equations are solved numerically for nonequilibrium airflows over a hemisphere. A formulation with a three-temperature thermochemical model has been employed to simulate vibrationally excited and partially dissociated airflow. A flow condition that has a total enthalpy of 25 MJ/kg and a surface pressure of 0.076 atm is studied. Computed stagnation point heat transfer using finite catalytic boundary conditions at the surface is compared with classical results. Departures from the classical heat transfer predictions caused by nonequilibrium effects are assessed for arcjet testing applications. A Damkohler number analysis is used to characterize the extent of flowfield nonequilibrium. It is shown that characterization of the thermodynamic state of the gas at the boundary-layer edge and within the boundary layer is needed to interpret the heat transfer measurements and to determine the surface catalytic efficiency.
RP Gokcen, T (reprint author), NASA,AMES RES CTR,THERMOSCI INST,MOFFETT FIELD,CA 94035, USA.
NR 14
TC 6
Z9 6
U1 0
U2 0
PU AMER INST AERONAUT ASTRONAUT
PI RESTON
PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091
SN 0887-8722
J9 J THERMOPHYS HEAT TR
JI J. Thermophys. Heat Transf.
PD APR-JUN
PY 1997
VL 11
IS 2
BP 289
EP 295
DI 10.2514/2.6236
PG 7
WC Thermodynamics; Engineering, Mechanical
SC Thermodynamics; Engineering
GA WU625
UT WOS:A1997WU62500023
ER
PT J
AU Nance, RP
Wilmoth, RG
Hassan, HA
AF Nance, RP
Wilmoth, RG
Hassan, HA
TI Comparison of grid-definition schemes for Monte Carlo simulations
SO JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER
LA English
DT Article; Proceedings Paper
CT AIAA 34th Aerospace Sciences Meeting and Exhibit
CY JAN 15-19, 1996
CL RENO, NV
SP Amer Inst Aeronaut & Astronaut
AB This paper examines spatial-discretization approaches for the direct simulation Monte Carlo method for axisymmetric and three-dimensional flows. Computations using three schemes, 1) a uniform Cartesian grid, 2) a structured body-fitted grid, and 3) an unstructured tetrahedral grid, are presented for the hypersonic flow past a blunted cone for two angles of attack, The results indicate that the approaches return very similar flowfield and surface results and that these results show fair agreement with available experimental data, Moreover, it will be demonstrated that the Cartesian scheme is significantly more efficient on a per-particle basis, but yields overall solution times significantly greater than those for the other two algorithms.
C1 NASA,LANGLEY RES CTR,AEROTHERMODYNAM BRANCH,GAS DYNAM DIV,HAMPTON,VA 23681.
RP Nance, RP (reprint author), N CAROLINA STATE UNIV,RALEIGH,NC 27695, USA.
NR 13
TC 0
Z9 0
U1 0
U2 0
PU AMER INST AERONAUT ASTRONAUT
PI RESTON
PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091
SN 0887-8722
J9 J THERMOPHYS HEAT TR
JI J. Thermophys. Heat Transf.
PD APR-JUN
PY 1997
VL 11
IS 2
BP 296
EP 303
PG 8
WC Thermodynamics; Engineering, Mechanical
SC Thermodynamics; Engineering
GA WU625
UT WOS:A1997WU62500024
ER
PT J
AU Siegel, R
AF Siegel, R
TI Green's function to determine temperature distribution in a
semitransparent thermal barrier coating
SO JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER
LA English
DT Article
RP Siegel, R (reprint author), NASA,LEWIS RES CTR,RES & TECHNOL DIRECTORATE,CLEVELAND,OH 44135, USA.
NR 7
TC 10
Z9 19
U1 0
U2 4
PU AMER INST AERONAUT ASTRONAUT
PI RESTON
PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091
SN 0887-8722
J9 J THERMOPHYS HEAT TR
JI J. Thermophys. Heat Transf.
PD APR-JUN
PY 1997
VL 11
IS 2
BP 315
EP 318
DI 10.2514/2.6242
PG 4
WC Thermodynamics; Engineering, Mechanical
SC Thermodynamics; Engineering
GA WU625
UT WOS:A1997WU62500029
ER
PT J
AU Kurkov, AP
Lucci, BL
AF Kurkov, AP
Lucci, BL
TI Measurement of gust response on a turbine cascade
SO JOURNAL OF TURBOMACHINERY-TRANSACTIONS OF THE ASME
LA English
DT Article; Proceedings Paper
CT 40th International Gas Turbine and Aeroengine Congress and Exhibition
CY JUN 05-08, 1995
CL HOUSTON, TX
ID UNSTEADY
AB The paper presents benchmark experimental data on a gust response of an annular turbine cascade. The experiment was particularly designed to provide data for comparison with the results of a typical linearized gust-response analysis. Reduced frequency, Mach number, and incidence were varied independently. Except for the lowest reduced frequency, the gust velocity distribution was nearly sinusoidal. For the high-inlet-velocity series of tests, the cascade was near choking. The mean flow was documented by measuring blade surface pressures and the cascade exit flow. High-response pressure transducers were used to measure the unsteady pressure distribution. Inlet-velocity components and turbulence parameters were measured using hot wire. In addition to the synchronous time-averaged pressure spectra, typical power spectra are included for several representative conditions.
RP Kurkov, AP (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA.
NR 8
TC 2
Z9 2
U1 0
U2 0
PU ASME-AMER SOC MECHANICAL ENG
PI NEW YORK
PA 345 E 47TH ST, NEW YORK, NY 10017
SN 0889-504X
J9 J TURBOMACH
JI J. Turbomach.-Trans. ASME
PD APR
PY 1997
VL 119
IS 2
BP 238
EP 246
PG 9
WC Engineering, Mechanical
SC Engineering
GA WW742
UT WOS:A1997WW74200009
ER
PT J
AU Damie, SV
Dang, TQ
Reddy, DR
AF Damie, SV
Dang, TQ
Reddy, DR
TI Throughflow method for turbomachines applicable for all flow regimes
SO JOURNAL OF TURBOMACHINERY-TRANSACTIONS OF THE ASME
LA English
DT Article; Proceedings Paper
CT 40th International Gas Turbine and Aeroengine Congress and Exhibition
CY JUN 05-08, 1995
CL HOUSTON, TX
AB A new axisymmetric throughflow method for analyzing and designing turbomachines is proposed. This method utilizes body-forte terms to represent blade forces and viscous losses. The resulting equations of motion, which include these body-force terms, are cast in terms of conservative variables and are solved using a finite-volume rime-stepping scheme. In the inverse mode, the swirl schedule in the bladed regions(i.e., the radius times the tangential velocity rV(theta)) is the primary specified flow quantity, and the corresponding blade shape is sought after, In the analysis mode, the blade geometry is specified and the flow solution is computed. The advantages of this throughflow method compared to the current family of streamline curvature and matrix methods are that the same code can be used for subsonic/transonic/supersonic throughflow velocities, and the proposed method has a shock capturing capability. This method is demonstrated for designing a supersonic throughflow fan stage and a transonic throughflow turbine stage.
C1 NASA,LEWIS RES CTR,INTERNAL FLUID MECH DIV,CLEVELAND,OH 44135.
RP Damie, SV (reprint author), SYRACUSE UNIV,DEPT MECH & AEROSP ENGN,SYRACUSE,NY 13244, USA.
NR 16
TC 2
Z9 2
U1 0
U2 3
PU ASME-AMER SOC MECHANICAL ENG
PI NEW YORK
PA 345 E 47TH ST, NEW YORK, NY 10017
SN 0889-504X
J9 J TURBOMACH
JI J. Turbomach.-Trans. ASME
PD APR
PY 1997
VL 119
IS 2
BP 256
EP 262
PG 7
WC Engineering, Mechanical
SC Engineering
GA WW742
UT WOS:A1997WW74200011
ER
PT J
AU Boyle, RJ
Jackson, R
AF Boyle, RJ
Jackson, R
TI Heat transfer predictions for two turbine nozzle geometries at high
Reynolds and Mach numbers
SO JOURNAL OF TURBOMACHINERY-TRANSACTIONS OF THE ASME
LA English
DT Article; Proceedings Paper
CT 40th International Gas Turbine and Aeroengine Congress and Exhibition
CY JUN 05-08, 1995
CL HOUSTON, TX
ID CASCADE FLOWS
AB Predictions of turbine vane and endwall heat transfer and pressure distributions are compared with experimental measurements for two vane geometries. The differences in geometries were due to differences in the hub profile, and both geometries were derived from the design of a high rim speed turbine (HRST). The experiments were conducted in the Isentropic Light Piston Facility (ILPF) at Pyestock at a Reynolds number of 5.3 x 10(6), a Mach number of 1.2, and a wall-to-gas temperature ratio of 0.66. Predictions are given for two different steady-state three-dimensional Navier-Stokes computational analyses. C-type meshes were used, and algebraic models were employed to calculate the turbulent eddy viscosity. The effects of different turbulence modeling assumptions on the predicted results are examined. Comparisons are also given between predicted and measured total pressure distributions behind the vane. The combination of realistic engine geometries and flow conditions proved to be quite demanding in terms of the convergence of the CFD solutions. An appropriate method of grid generation, which resulted in consistently converged CFD solutions, was identified.
C1 DRA PYESTOCK,FARNBOROUGH,HANTS,ENGLAND.
RP Boyle, RJ (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA.
NR 32
TC 4
Z9 4
U1 0
U2 1
PU ASME-AMER SOC MECHANICAL ENG
PI NEW YORK
PA 345 E 47TH ST, NEW YORK, NY 10017
SN 0889-504X
J9 J TURBOMACH
JI J. Turbomach.-Trans. ASME
PD APR
PY 1997
VL 119
IS 2
BP 270
EP 283
PG 14
WC Engineering, Mechanical
SC Engineering
GA WW742
UT WOS:A1997WW74200013
ER
PT J
AU Garg, VK
Gaugler, RE
AF Garg, VK
Gaugler, RE
TI Effect of velocity and temperature distribution at the hole exit on film
cooling of turbine blades
SO JOURNAL OF TURBOMACHINERY-TRANSACTIONS OF THE ASME
LA English
DT Article; Proceedings Paper
CT 40th International Gas Turbine and Aeroengine Congress and Exhibition
CY JUN 05-08, 1995
CL HOUSTON, TX
ID HEAT-TRANSFER; PREDICTION; GAS; HOT; ROW
AB An existing three-dimensional Navier-Stokes code (Arnone et al., 1991), modified to include film cooling considerations (Garg and Gaugler, 1994), has been used to study the effect of coolant velocity and temperature distribution at the hole exit on the heat transfer coefficient on three film-cooled turbine blades, namely, the C3X vane, the VKI rotor, and the ACE rotor. Results are also compared with the experimental data for all the blades. Moreover, Mayle's transition criterion (1991), Forest's model for augmentation of lending edge heat transfer due to free-stream turbulence (1977), and Crawford's model for augmentation of eddy viscosity due to film cooling (Crawford et al., 1980) are used. Use of Mayle's and Forest's models is relevant only for the ACE rotor due to the absence of showerhead cooling on this rotor. It is Sound that, in some cases, the effect of distribution of coolant velocity and temperature at the hole exit can be as much as 60 percent on the heat transfer coefficient at the blade suction surface, and 50 percent at the pressure surface. Also, different effects are observed on the pressure and suction surface depending upon the blade as well as upon the hole shape, conical or cylindrical.
C1 NASA,LEWIS RES CTR,TURBINE BRANCH,TURBOMACHINERY & PROP SYST DIV,CLEVELAND,OH 44135.
RP Garg, VK (reprint author), NASA,LEWIS RES CTR,AYT CORP,MAIL STOP 5-11,CLEVELAND,OH 44135, USA.
NR 39
TC 33
Z9 34
U1 1
U2 4
PU ASME-AMER SOC MECHANICAL ENG
PI NEW YORK
PA 345 E 47TH ST, NEW YORK, NY 10017
SN 0889-504X
J9 J TURBOMACH
JI J. Turbomach.-Trans. ASME
PD APR
PY 1997
VL 119
IS 2
BP 343
EP 351
PG 9
WC Engineering, Mechanical
SC Engineering
GA WW742
UT WOS:A1997WW74200020
ER
PT J
AU Kiper, JD
Howard, E
Ames, C
AF Kiper, JD
Howard, E
Ames, C
TI Criteria for evaluation of visual programming languages
SO JOURNAL OF VISUAL LANGUAGES AND COMPUTING
LA English
DT Article
AB Interest in visual programming languages has increased as graphic support in hardware and software has made display and manipulation of visual images, icons, diagrams and forms reasonable to consider. In this paper, we present a set of evaluation criteria and associated metrics to judge visual programming languages. The live criteria, visual nature, functionality, ease of comprehension, paradigm support and scalability, are intended to capture the essence of a general purpose visual programming language. These criteria are supplemented with a set of subjective metrics, resulting in an evaluation method that can be used to assess the quality of an individual visual programming language or to compare among elements of a set of such languages. (C) 1997 Academic Press Limited.
C1 CALTECH,JET PROP LAB,PASADENA,CA 91109.
RP Kiper, JD (reprint author), MIAMI UNIV,SYST ANAL DEPT,OXFORD,OH 45056, USA.
NR 39
TC 14
Z9 14
U1 1
U2 2
PU ACADEMIC PRESS LTD
PI LONDON
PA 24-28 OVAL RD, LONDON, ENGLAND NW1 7DX
SN 1045-926X
J9 J VISUAL LANG COMPUT
JI J. Vis. Lang. Comput.
PD APR
PY 1997
VL 8
IS 2
BP 175
EP 192
DI 10.1006/jvlc.1996.0034
PG 18
WC Computer Science, Software Engineering
SC Computer Science
GA XA945
UT WOS:A1997XA94500002
ER
PT J
AU Grugel, RN
Brush, LN
AF Grugel, RN
Brush, LN
TI Evaluation of the rodlike Cu6Sn5 phase in directionally solidified tin -
0.9 wt.% copper eutectic alloys
SO MATERIALS CHARACTERIZATION
LA English
DT Article
AB Sn - 0.9 wt.% Cu alloys were directionally solidified under controlled conditions after which diameters of the aligned and rodlike Cu6Sn5 eutectic phase were measured as a function of the imposed growth velocity. A rod diameter (d) and growth velocity (V) relation of d(2)V = constant was found, which is analogous to that established for eutectic phase spacings. A discussion is presented for using the fiber diameter, in lieu of or in addition to the interrod spacing, to evaluate the relation between solidification processing parameters and the observed microstructure. (C) Elsevier Science Inc., 1997.
C1 UNIV WASHINGTON,DEPT MAT SCI & ENGN,SEATTLE,WA 98195.
RP Grugel, RN (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,UNIV SPACE RES ASSOC,HUNTSVILLE,AL 35812, USA.
NR 20
TC 16
Z9 16
U1 0
U2 1
PU ELSEVIER SCIENCE INC
PI NEW YORK
PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010
SN 1044-5803
J9 MATER CHARACT
JI Mater. Charact.
PD APR-JUN
PY 1997
VL 38
IS 4-5
BP 211
EP 216
DI 10.1016/S1044-5803(97)00036-3
PG 6
WC Materials Science, Multidisciplinary; Metallurgy & Metallurgical
Engineering; Materials Science, Characterization & Testing
SC Materials Science; Metallurgy & Metallurgical Engineering
GA YC058
UT WOS:A1997YC05800003
ER
PT J
AU Bailey, D
Borwein, P
Plouffe, S
AF Bailey, D
Borwein, P
Plouffe, S
TI On the rapid computation of various polylogarithmic constants
SO MATHEMATICS OF COMPUTATION
LA English
DT Article
DE computation; digits; log; polylogarithms; SC; pi; algorithm
ID DIGITS; PI
AB We give algorithms for the computation of the d-th digit of certain transcendental numbers in various bases. These algorithms can be easily implemented (multiple precision arithmetic is not needed), require virtually no memory, and feature run times that scale nearly linearly with the order of the digit desired. They make it feasible to compute, for example, the billionth binary digit of log(2) or pi on a modest work station in a few hours run time.
We demonstrate this technique by computing the ten billionth hexadecimal digit of pi, the billionth hexadecimal digits of pi(2), log(2) and log(2)(2), and the ten billionth decimal digit of log(9/10).
These calculations rest on the observation that very special types of identities exist for certain numbers like pi, pi(2) log(2) and log(2)(2). These are essentially polylogarithmic ladders in an integer base. A number of these identities that we derive in this work appear to be new, for example the critical identity for pi:
[GRAPHICS]
C1 SIMON FRASER UNIV,DEPT MATH & STAT,BURNABY,BC V5A 1S6,CANADA.
RP Bailey, D (reprint author), NASA,AMES RES CTR,MAIL STOP T27A-1,MOFFETT FIELD,CA 94035, USA.
NR 21
TC 78
Z9 79
U1 0
U2 2
PU AMER MATHEMATICAL SOC
PI PROVIDENCE
PA 201 CHARLES ST, PROVIDENCE, RI 02940-2213
SN 0025-5718
J9 MATH COMPUT
JI Math. Comput.
PD APR
PY 1997
VL 66
IS 218
BP 903
EP 913
DI 10.1090/S0025-5718-97-00856-9
PG 11
WC Mathematics, Applied
SC Mathematics
GA WV771
UT WOS:A1997WV77100028
ER
PT J
AU Harris, BA
Billica, RD
Bishop, SL
Blackwell, T
Layne, CS
Harm, DL
Sandoz, GR
Rosenow, EC
AF Harris, BA
Billica, RD
Bishop, SL
Blackwell, T
Layne, CS
Harm, DL
Sandoz, GR
Rosenow, EC
TI Physical examination during space flight
SO MAYO CLINIC PROCEEDINGS
LA English
DT Article
AB Objective: To develop techniques for conducting a physical examination in microgravity and to describe and document the physiologic changes noted with use of a modified basic physical examination.
Design: On the basis of data gathered from physical examinations on KC-135 flights, three physical variables were assessed serially in astronauts during two shuttle missions (of 8- and 10-day duration, respectively), Preflight, in-flight, and postflight examinations were conducted by trained physician-astronauts or flight surgeons, who used this modified examination.
Material and Methods: Five male and two female crew members participated in the ''hands-on'' physical examination of all physiologic systems except the genitourinary system, Level of edema, intensity of bowel sounds, and peripheral reflexes were assessed and graded.
Results: This investigation identified unique elements of a physical examination performed during space night that will assist in the development of standard methods for conducting examinations of astronauts in weightlessness, In addition, demonstrable changes induced by microgravity were noted in most physiologic systems examined.
Conclusion: The data support the hypothesis that the microgravity examination differs from that conducted on earth or in a Ig environment, In addition, alterations in the physiologic response can be detected with use of a hands-on technique, These data are invaluable in the development of optimal medical care for humans in space.
C1 NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058.
UNIV TEXAS,MED BRANCH,DEPT INTERNAL MED,DEPT FAMILY MED,GALVESTON,TX 77550.
KRUG LIFE SCI INC,HOUSTON,TX.
MAYO CLIN & MAYO FDN,DIV PULM & CRIT CARE MED & INTERNAL MED,ROCHESTER,MN 55905.
NR 14
TC 12
Z9 12
U1 0
U2 0
PU MAYO CLINIC PROCEEDINGS
PI ROCHESTER
PA 660 SIEBENS BLDG MAYO CLINIC, ROCHESTER, MN 55905
SN 0025-6196
J9 MAYO CLIN PROC
JI Mayo Clin. Proc.
PD APR
PY 1997
VL 72
IS 4
BP 301
EP 308
PG 8
WC Medicine, General & Internal
SC General & Internal Medicine
GA XA018
UT WOS:A1997XA01800002
PM 9121174
ER
PT J
AU Breit, GA
Whalen, RT
AF Breit, GA
Whalen, RT
TI Prediction of human gait parameters from temporal measures of
foot-ground contact
SO MEDICINE AND SCIENCE IN SPORTS AND EXERCISE
LA English
DT Article
DE activity monitoring; musculoskeletal loading; ground reaction force;
skeletal adaptation
ID BONE-MINERAL DENSITY; PHYSICAL-ACTIVITY; REACTION FORCES; WALKING SPEED;
EXERCISE; ENERGY; MEN
AB Investigation of the influence of human physical activity on bone functional adaptation requires long-term histories of gait-related ground reaction force (GRF). Towards a simpler portable GRF measurement, we hypothesized that: 1) the reciprocal of foot-ground contact time (1/t(c)); or 2) the reciprocal of stride-period-normalized contact time (T/t(c)) predict peak vertical and horizontal GRF, loading rates, and horizontal speed juring gait. GRF data were collected from 24 subjects while they walked and ran at a variety of speeds. Linear regression and ANCOVA determined the dependence of gait parameters on 1/t(c) and T/t(c), and prediction SE. All parameters were significantly correlated to 1/t(c) and T/t(c). The closest pooled relationship existed between peak running vertical GRF and T/t(c) (r(2) = 0.896; SE = 3.6%) and improved with subject-specific regression (r(2) = 0.970; SE = 2.2%). We conclude that temporal measures can predict force parameters of gait and may represent an alternative to direct GRF measurements for determining daily histories of habitual lower limb loading quantities necessary to quantify a bone remodeling stimulus.
C1 NASA,AMES RES CTR,DIV LIFE SCI 239 11,MUSCULOSKELETAL BIOMECH LAB,MOFFETT FIELD,CA 94035.
NR 33
TC 20
Z9 21
U1 1
U2 6
PU WILLIAMS & WILKINS
PI BALTIMORE
PA 351 WEST CAMDEN ST, BALTIMORE, MD 21201-2436
SN 0195-9131
J9 MED SCI SPORT EXER
JI Med. Sci. Sports Exerc.
PD APR
PY 1997
VL 29
IS 4
BP 540
EP 547
DI 10.1097/00005768-199704000-00017
PG 8
WC Sport Sciences
SC Sport Sciences
GA WU062
UT WOS:A1997WU06200017
PM 9107638
ER
PT J
AU Miner, RV
AF Miner, RV
TI The effects of composition and gamma'/gamma lattice parameter mismatch
on the critical resolved shear stresses for octahedral and cube slip in
NiAlCrX alloys
SO METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND
MATERIALS SCIENCE
LA English
DT Article
ID TEMPERATURE-DEPENDENCE; MECHANICAL-PROPERTIES; SINGLE-CRYSTALS; VOLUME
FRACTION; ORIENTATION
AB Prototypical single-crystal NiAlCrX superalloys were studied to examine the effects of the common major alloying elements, Co, Mo, Nb, Ta, Ti, and W, on yielding behavior. The alloys contained about 10 at. pct Cr, 60 vol pet of the gamma' phase, and about 3 at. pct of X in the gamma'. The critical resolved shear stresses (CRSSs) for octahedral and primary cube slip were measured at 760 degrees C, which is about the peak strength temperature. The CRSSoct and CRSScube are discussed in relation to thoseof Ni-3 (Al, X) gamma' alloys taken from the literature and the gamma'/gamma lattice mismatch. The CRSSoct ofthe gamma + gamma' alloys reflected a similar compositional dependence to that of both the CRSScube of the gamma' phase and the gamma/gamma' lattice parameter mismatch. The CRSScube of the gamma + gamma' alloys also reflected the compositional dependence of the gamma'/gamma mismatch, but bore no similarity to that of CRSScube for gamma' alloys since it is controlled by the gamma matrix. The ratio of CRSScube/CRSSoct was decreased by all alloying elements except Co, which increased the ratio. The decrease in CRSScube/CRSSoct was related to the degree in which elements partition to ehe gamma' rather than the gamma phase.
RP Miner, RV (reprint author), NASA,LEWIS RES CTR,ADV ALLOYS BRANCH,CLEVELAND,OH 44135, USA.
NR 26
TC 6
Z9 6
U1 0
U2 2
PU MINERALS METALS MATERIALS SOC
PI WARRENDALE
PA 420 COMMONWEALTH DR, WARRENDALE, PA 15086
SN 1073-5623
J9 METALL MATER TRANS A
JI Metall. Mater. Trans. A-Phys. Metall. Mater. Sci.
PD APR
PY 1997
VL 28
IS 4
BP 1011
EP 1020
DI 10.1007/s11661-997-0231-2
PG 10
WC Materials Science, Multidisciplinary; Metallurgy & Metallurgical
Engineering
SC Materials Science; Metallurgy & Metallurgical Engineering
GA WV582
UT WOS:A1997WV58200011
ER
PT J
AU Steinberg, TA
Sircar, S
Wilson, DB
Stoltzfus, JM
AF Steinberg, TA
Sircar, S
Wilson, DB
Stoltzfus, JM
TI Multiphase oxidation of metals
SO METALLURGICAL AND MATERIALS TRANSACTIONS B-PROCESS METALLURGY AND
MATERIALS PROCESSING SCIENCE
LA English
DT Article
AB The burning of metals in enriched oxygen atmospheres includes multiple phases and, therefore, satisfies the definition of being a heterogeneous system. For a reaction to be considered heterogeneous, however, the site of the chemical transformation must be at an interface. While the Wagner theory of metal oxidation gives satisfactory mechanisms for this type of reaction for solid metals, no comparable theory is available for metal oxidation when the temperature is above the melting point of the metal. Similitude theory is applied to metal combustion under conditions of the NASA/ASTM flammability test system in order to identify rate-controlling regimes and conditions of heterogeneous reaction. Above 4 MPa, the observed burn rate for iron is proportional to the sample dimension, L, as L-0.7. Analysis shows that the heat transfer rate between the reaction surface and the solid rod is proportional to L-0.5 and may, therefore, be the rate-determining process for the system.
C1 REYNOLDS MET CO, CORP RES, RICHMOND, VA 23219 USA.
QUANTOS CONSULTING, MESILLA PK, NM 88047 USA.
NASA, LYNDON B JOHNSON SPACE CTR, WHITE SANDS TEST FACIL, LAS CRUCES, NM 88004 USA.
RP Steinberg, TA (reprint author), UNIV QUEENSLAND, DEPT MECH ENGN, ST LUCIA, QLD 4072, AUSTRALIA.
NR 27
TC 1
Z9 1
U1 0
U2 0
PU SPRINGER
PI NEW YORK
PA 233 SPRING ST, NEW YORK, NY 10013 USA
SN 1073-5615
J9 METALL MATER TRANS B
JI Metall. Mater. Trans. B-Proc. Metall. Mater. Proc. Sci.
PD APR
PY 1997
VL 28
IS 2
BP 209
EP 214
DI 10.1007/s11663-997-0086-3
PG 6
WC Materials Science, Multidisciplinary; Metallurgy & Metallurgical
Engineering
SC Materials Science; Metallurgy & Metallurgical Engineering
GA WV772
UT WOS:A1997WV77200004
ER
PT J
AU Johnston, R
Weiss, P
AF Johnston, R
Weiss, P
TI Analysis of virtual reality technology applied in education
SO MINIMALLY INVASIVE THERAPY & ALLIED TECHNOLOGIES
LA English
DT Article
DE task analyses; standard experimental designs; transfer of training;
transfer effectiveness ratio
AB The use of virtual reality (VR) technology in training and education is an extension of 50 years of flight simulation research. As virtual reality becomes integrated into medical practices, the same questions that confronted the developers of flight simulation also apply to those in the medical domain. Does this technology work for training and education? If so, how well does it work? How much does it cost? Is it less expensive than the alternative training methods? In order to answer these questions the authors have taken a look at the same problems in the history of military simulation. The four techniques used to assess the value of military simulation have been, and still are, task analyses (a detailed, timed description of the actual tasks), standard experimental designs (i.e. the pre-test, post-test control group design), transfer-of-training experiments (where the evaluation metric is the actual task) and various combinations of the three. At present the only evaluation technique being used for VR in medical education is the task analysis.
C1 UNIV HOUSTON,VIRTUAL ENVIRONM TECHNOL LAB,NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX.
NR 7
TC 7
Z9 7
U1 0
U2 1
PU BLACKWELL SCIENCE LTD
PI OXFORD
PA P O BOX 88, OSNEY MEAD, OXFORD, OXON, ENGLAND OX2 0NE
SN 0961-625X
J9 MINIM INVASIV THER
JI Minim. Invasive Ther. Allied Technol.
PD APR
PY 1997
VL 6
IS 2
BP 126
EP 127
DI 10.3109/13645709709152716
PG 2
WC Surgery
SC Surgery
GA XE769
UT WOS:A1997XE76900008
ER
PT J
AU Sui, CH
Li, X
Lau, KM
Adamec, D
AF Sui, CH
Li, X
Lau, KM
Adamec, D
TI Multiscale air-sea interactions during TOGA COARE
SO MONTHLY WEATHER REVIEW
LA English
DT Article
ID TROPICAL WESTERN PACIFIC; 1986-87 EL-NINO; SOUTHERN OSCILLATION;
MIXED-LAYER; HEAT-FLUX; OCEAN; TEMPERATURE; VARIABILITY; CONVECTION;
INTERFACE
AB Two distinct intraseasonal oscillations (ISO) are found in the tropical ocean atmosphere in the western Pacific region during Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE). The ISO is characterized by cycles of dry-wet phases in the atmosphere due to the passage of Madden-Julian oscillations, and corresponding warming/shoaling-cooling/deepening cycles in the ocean mixed layer (OML). During the wet phase, 2-3-day disturbances and diurnal variations in the atmosphere are pronounced. During the dry phase, diurnal cycles in sea surface temperature (SST) is much enhanced while the OML is shallow.
These multiscale coupled air-sea variations are further investigated with an ocean mixed-layer model forced by the observed surface heal, water, and momentum fluxes. The variations of ocean mixed layer are shown to be crucially dependent on the vertical distribution of solar radiation, that is, diurnal SST variability primarily determined by the absorbed solar radiation in the surface layer (similar to 1 m), and intraseasonal variations determined by penetrating solar radiation below the surface layer. Results further reveal that the accumulative effect of diurnal mixing cycles (solar hearing/nocturnal deepening) is essential to maintain a stable temperature stratification and a realistic evolution of mixed-layer depth and temperature at the intraseasonal scale. The nonlinear response of the ocean mixed layer to the surface heat and momentum fluxes indicates the need to resolve the high-frequency response including diurnal atmospheric radiative-convective processes and ocean mixing processes in a coupled model to simulate the whole spectrum of multiscale variations within ISOs.
C1 APPL RES CORP,LANDOVER,MD 20785.
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 39
TC 63
Z9 66
U1 0
U2 4
PU AMER METEOROLOGICAL SOC
PI BOSTON
PA 45 BEACON ST, BOSTON, MA 02108-3693
SN 0027-0644
J9 MON WEATHER REV
JI Mon. Weather Rev.
PD APR
PY 1997
VL 125
IS 4
BP 448
EP 462
DI 10.1175/1520-0493(1997)125<0448:MASIDT>2.0.CO;2
PG 15
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA WP480
UT WOS:A1997WP48000003
ER
PT J
AU Chao, WC
Deng, LT
AF Chao, WC
Deng, LT
TI Phase lag between deep cumulus convection and low-level convergence in
tropical synoptic-scale systems
SO MONTHLY WEATHER REVIEW
LA English
DT Article
ID INTRASEASONAL OSCILLATION; CLOUD CLUSTERS; WAVE-CISK; WESTERN PACIFIC;
DISTURBANCES; CIRCULATION; ORIGIN; MODEL
AB This study deals with the origin of the phase lag between deep cumulus convection and low-level convergence in tropical synoptic-scale systems, known since 1974. Several possible causes, including 1) propagation of the heating field, 2) beta, 3) vertical shear of the basic flow, and 4) vertical tilt of the heat source, are examined. The last one is found to be the reason for the phase lag. The vertical tilt of the heat source occurs as a result of evolution and propagation of mesoscale convective systems within the synoptic system. During this evolution the change of vertical heating profile results in the tilt of heating field. Previous efforts of incorporating such phase lag in wave-CISK studies are commented on.
C1 APPL RES CORP,LANDOVER,MD 20785.
RP Chao, WC (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ATMOSPHERES LAB,MAIL CODE 913,GREENBELT,MD 20771, USA.
NR 23
TC 5
Z9 5
U1 1
U2 1
PU AMER METEOROLOGICAL SOC
PI BOSTON
PA 45 BEACON ST, BOSTON, MA 02108-3693
SN 0027-0644
J9 MON WEATHER REV
JI Mon. Weather Rev.
PD APR
PY 1997
VL 125
IS 4
BP 549
EP 559
DI 10.1175/1520-0493(1997)125<0549:PLBDCC>2.0.CO;2
PG 11
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA WP480
UT WOS:A1997WP48000008
ER
PT J
AU Sienkiewicz, ME
Pfaendtner, J
AF Sienkiewicz, ME
Pfaendtner, J
TI Assimilation variability in the GEOS-1 data assimilation system
SO MONTHLY WEATHER REVIEW
LA English
DT Article
ID ERROR; CIRCULATION; PREDICTABILITY; PERTURBATIONS
AB Ensembles of assimilation runs were used to assess the sensitivity of the GEOS-1 (Goddard Earth Observing System-Version 1) data assimilation system to data gaps and changes in initial conditions. Perturbations from a ''control'' assimilation were induced by withholding data for periods ranging from 12 to 96 h. Data assimilation then proceeded with each ensemble member for periods up to one month, and ensemble members (''assimilations'') were examined for convergence to the control assimilation.
Experimental results show that this method is effective in identifying assimilation system weaknesses by determining where assimilations do not converge quickly. The methodology is also useful for determining assimilation ''spinup'' time. For the GEOS-1 system, convergence of the assimilation ensemble was slow near the poles and in the Southern Hemisphere. This slow convergence was largely due to the sparseness of data in the Southern Hemisphere and to strong polar filtering. The differences between assimilations were primarily differences in the location or intensity of small-scale waves in the larger-scale flow, which tracked eastward with the movement of the small-scale waves. A ''fixed'' quality control experiment showed that differences in quality control decisions contributed to maintaining differences between the ensemble members. The assimilation convergence was improved when a later version of the GEOS system, with weaker polar Altering, was used.
C1 SCI APPLICAT INT CORP,GEN SCI CORP,LAUREL,MD.
RP Sienkiewicz, ME (reprint author), NASA,GODDARD SPACE FLIGHT CTR,DATA ASSIMILAT OFF,CODE 9103,GREENBELT,MD 20771, USA.
RI Sienkiewicz, Meta/P-8168-2016
OI Sienkiewicz, Meta/0000-0002-9267-4568
NR 27
TC 0
Z9 0
U1 1
U2 1
PU AMER METEOROLOGICAL SOC
PI BOSTON
PA 45 BEACON ST, BOSTON, MA 02108-3693
SN 0027-0644
J9 MON WEATHER REV
JI Mon. Weather Rev.
PD APR
PY 1997
VL 125
IS 4
BP 560
EP 571
DI 10.1175/1520-0493(1997)125<0560:AVITGD>2.0.CO;2
PG 12
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA WP480
UT WOS:A1997WP48000009
ER
PT J
AU Vukovich, FM
Wayland, R
Toll, D
AF Vukovich, FM
Wayland, R
Toll, D
TI The surface heat flux as a function of ground cover for climate models
SO MONTHLY WEATHER REVIEW
LA English
DT Article
ID LAND-SURFACE; VEGETATION; SYSTEM; ENERGY; FIFE; TEMPERATURES;
CALIBRATION; REFLECTANCE; NOAA-7; NADIR
AB Surface heat fluxes were examined as a function of surface properties and meteorological conditions in a 100 km x 100 km grid square at 1-km spatial resolution centered at the location of the First ISLSCP (International Satellite Land Surface Climatology Project) Field Experiment (FIFE), the Forest Ecosystem Dynamics site in central Maine, and a semiarid rangeland site around Walnut Gulch, Arizona. This investigation treats the surface heat Aux variability within a GCM grid box to provide insight into methods for treating that variability in climate models. The heat fluxes were calculated using NOAA AVHRR and available meteorological data. The average heat fluxes that were estimated using the various area ground-cover representations were compared with the ensemble average heat fluxes for the entire area, which were assumed to be the best representation of the heal fluxes for the areas. Average heat fluxes were estimated for the entire 100 km x 100 km area based on a single ground-cover representation, and the mean error for the area sensible heat flux was about 10% and for the area latent heat flux, 21%. The estimation error was reduced, and in some cases significantly reduced, when the area heat fluxes were estimated by partitioning the area according to significant ground cover. The most significant effect of the partitioning was on the latent heat flux estimates.
C1 NASA, GODDARD SPACE FLIGHT CTR, NASA, GREENBELT, MD 20771 USA.
RP Vukovich, FM (reprint author), SCI APPLICAT INT CORP, 615 OBERLIN RD, SUITE 300, RALEIGH, NC 27605 USA.
NR 36
TC 3
Z9 3
U1 0
U2 1
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 APR
PY 1997
VL 125
IS 4
BP 572
EP 586
DI 10.1175/1520-0493(1997)125<0572:TSHFAA>2.0.CO;2
PG 15
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA WP480
UT WOS:A1997WP48000010
ER
PT J
AU Chai, JC
Moder, JP
AF Chai, JC
Moder, JP
TI Spatial-multiblock procedure for radiation heat transfer
SO NUMERICAL HEAT TRANSFER PART B-FUNDAMENTALS
LA English
DT Article
ID DISCRETE-ORDINATES METHOD; FINITE-VOLUME METHOD; RECTANGULAR ENCLOSURES;
CYLINDRICAL ENCLOSURES; MULTIDIMENSIONAL GEOMETRIES; ANISOTROPIC
SCATTERING; IRREGULAR GEOMETRIES; PARTICIPATING MEDIA; SURFACE RADIATION
AB A spatial-multiblock procedure for radiation heat transfer is presented in this article. The proposed procedure is applicable to isothermal or nonisothermal, absorbing, emitting and scattering or transparent media with black or reflecting walls. Although not shown in this article, the procedure is also applicable to nongray conditions. The proposed procedure can be used with the discrete-ordinates method and the finite-volume method. The heat transfer rate, net radiant power, and other full-range and half-range moments are conserved between spatial blocks by the proposed procedure. The utilities of the proposed procedure are shown using four sample problems. The solutions indicate that the multiblock procedure can reproduce the results of a single-block procedure even when very coarse spatial grids are used in the multiblock procedure.
C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135.
RP Chai, JC (reprint author), TENNESSEE TECHNOL UNIV,DEPT MECH ENGN,BOX 5014,COOKEVILLE,TN 38505, USA.
RI Chai, John/A-3764-2010
NR 28
TC 14
Z9 14
U1 0
U2 1
PU HEMISPHERE PUBL CORP
PI BRISTOL
PA 1900 FROST ROAD, SUITE 101, BRISTOL, PA 19007-1598
SN 1040-7790
J9 NUMER HEAT TR B-FUND
JI Numer Heat Tranf. B-Fundam.
PD APR-MAY
PY 1997
VL 31
IS 3
BP 277
EP 293
DI 10.1080/10407799708915110
PG 17
WC Thermodynamics; Mechanics
SC Thermodynamics; Mechanics
GA WW633
UT WOS:A1997WW63300002
ER
PT J
AU Barker, BC
Brockman, P
Koch, GJ
AF Barker, BC
Brockman, P
Koch, GJ
TI Laser radar watches the friendly skies
SO PHOTONICS SPECTRA
LA English
DT Article
RP Barker, BC (reprint author), NASA,LANGLEY RES CTR,HAMPTON,VA 23665, USA.
NR 4
TC 0
Z9 1
U1 0
U2 0
PU LAURIN PUBL CO INC
PI PITTSFIELD
PA BERKSHIRE COMMON PO BOX 1146, PITTSFIELD, MA 01202
SN 0731-1230
J9 PHOTON SPECTRA
JI Photon. Spect.
PD APR
PY 1997
VL 31
IS 4
BP 94
EP &
PG 4
WC Optics
SC Optics
GA WT869
UT WOS:A1997WT86900039
ER
PT J
AU Mohapatra, RN
Riotto, A
AF Mohapatra, RN
Riotto, A
TI Supersymmetric models with anomalous U(1) mediated supersymmetry
breaking
SO PHYSICAL REVIEW D
LA English
DT Article
ID CP-VIOLATION; FERMION MASSES; MIXING ANGLES; LIGHT GLUINO; SUPERGRAVITY;
SYMMETRIES; NEUTRON
AB We construct realistic supergravity models where supersymmetry breaking arises from the D terms of an anomalous U(1) gauge symmetry broken at the Planck scale. The effective action for these theories at sub-Planck energies (including higher dimensional terms in the superpotential) severely restricted by the U(1) symmetry and by the assumption, it arises from an underlying renormalizable theory at a higher scale. The phenomenological consequences of these models are studied. It is found that they have the attractive feature that the gaugino masses, the A and B terms, and the mass splittings between the like-charged squarks of the first two generations compared to their average masses can all be naturally suppressed. As a result, the electric dipole moment of the neutron as well as the flavor-changing neutral current effects are predicted to be naturally small. These models also predict the value of the mu term to be naturally small and have the potential to qualitatively explain the observed mass hierarchy among quarks and leptons. We then discuss examples of high scale renormalizable theories that can justify the choice of the the effective action from naturalness point of view.
C1 NASA,FERMILAB ASTROPHYS CTR,FERMI NATL ACCELERATOR LAB,BATAVIA,IL 60510.
RP Mohapatra, RN (reprint author), UNIV MARYLAND,DEPT PHYS & ASTRON,COLLEGE PK,MD 20742, USA.
NR 40
TC 54
Z9 54
U1 0
U2 1
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 0556-2821
J9 PHYS REV D
JI Phys. Rev. D
PD APR 1
PY 1997
VL 55
IS 7
BP 4262
EP 4267
DI 10.1103/PhysRevD.55.4262
PG 6
WC Astronomy & Astrophysics; Physics, Particles & Fields
SC Astronomy & Astrophysics; Physics
GA WY654
UT WOS:A1997WY65400031
ER
PT J
AU Girimaji, SS
AF Girimaji, SS
TI A Galilean invariant explicit algebraic Reynolds stress model for
turbulent curved flows
SO PHYSICS OF FLUIDS
LA English
DT Article
ID SURFACE CURVATURE; BOUNDARY-LAYERS
AB A Galilean invariant weak-equilibrium turbulence hypothesis that is sensitive to streamline curvature is proposed. The hypothesis leads to a fully explicit algebraic expression for Reynolds stress in terms of the mean velocity field and kinetic energy and dissipation of turbulence. The model is tested in curved homogeneous shear flow which is a homogeneous idealization of the circular streamline flow. The agreement is excellent with Reynolds stress closure model and adequate with available experimental data.
RP Girimaji, SS (reprint author), NASA,LANGLEY RES CTR,INST COMP APPL SCI & ENGN,HAMPTON,VA 23681, USA.
NR 18
TC 51
Z9 51
U1 0
U2 0
PU AMER INST PHYSICS
PI WOODBURY
PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999
SN 1070-6631
J9 PHYS FLUIDS
JI Phys. Fluids
PD APR
PY 1997
VL 9
IS 4
BP 1067
EP 1077
DI 10.1063/1.869200
PG 11
WC Mechanics; Physics, Fluids & Plasmas
SC Mechanics; Physics
GA WQ094
UT WOS:A1997WQ09400025
ER
PT J
AU Grosch, CE
Seiner, JM
Hussaini, MY
Jackson, TL
AF Grosch, CE
Seiner, JM
Hussaini, MY
Jackson, TL
TI Numerical simulation of mixing enhancement in a hot supersonic jet
SO PHYSICS OF FLUIDS
LA English
DT Article
ID AXISYMMETRICAL JET
AB Experimental observations show that the presence of small tabs on the edge of a hot, compressible jet exiting into a slower moving, colder ambient flow can increase the rate of spreading of the jet. This suggests that the rate of mixing of the jet and the ambient fluid is also increased. In order to elucidate the physical mechanism responsible for the increased spreading rate a set of calculations was carried out within the framework of the compressible three dimensional Navier-Stokes equations. A series of grid refinements were made to assess the accuracy of the results. We first simulated the flow without the tabs, obtaining reasonable agreement with experimental measurements of the velocity. We then simulated the flow, without tabs, over a range of values of the convective Mach number in order to determine the dependence of the mixing on this parameter. Simulations with modeled tabs were also carried out. In these calculations the effect of the tabs on the flow was modeled by pairs of counter-rotating vortices. The results of these calculations indeed show that the presence of the tabs increase the spreading rate of the jet. The basic physical mechanism responsible for the enhanced spreading rate is discussed and qualitative comparisons with flow visualizations are made. (C) 1997 American Institute of Physics.
C1 OLD DOMINION UNIV,DEPT COMP SCI,NORFOLK,VA 23529.
NASA,LANGLEY RES CTR,AEROACOUST BRANCH,HAMPTON,VA 23681.
FLORIDA STATE UNIV,PROGRAM COMPUTAT SCI & ENGN,TALLAHASSEE,FL 32306.
NASA,LANGLEY RES CTR,INST COMP APPL SCI & ENGN,HAMPTON,VA 23681.
RP Grosch, CE (reprint author), OLD DOMINION UNIV,DEPT OCEANOG,NORFOLK,VA 23529, USA.
NR 14
TC 15
Z9 16
U1 0
U2 2
PU AMER INST PHYSICS
PI WOODBURY
PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999
SN 1070-6631
J9 PHYS FLUIDS
JI Phys. Fluids
PD APR
PY 1997
VL 9
IS 4
BP 1125
EP 1143
DI 10.1063/1.869203
PG 19
WC Mechanics; Physics, Fluids & Plasmas
SC Mechanics; Physics
GA WQ094
UT WOS:A1997WQ09400029
ER
PT J
AU Li, JC
Jenniskens, P
AF Li, JC
Jenniskens, P
TI Inelastic neutron scattering study of high density amorphous water ice
SO PLANETARY AND SPACE SCIENCE
LA English
DT Article
ID SOLID WATER; IH; PRESSURE; IX; VI; TEMPERATURE; RELEASE; SPECTRA; GASES;
RANGE
AB The various forms of amorphous ices with trapped impurities play an important role in astrophysics. Such ices observed spectroscopically as frost on interstellar dust in dense molecular clouds and in comets require a detailed understanding of the spectroscopic properties in laboratory conditions. Using the neutron inelastic scattering technique on ISIS at Rutherford-Appleton Laboratory, the recovered high density amorphous ice is measured along with its subsequent high temperature metastable phases: low density amorphous ice, cubic and hexagonal ices under the same conditions in the energy transfer region from 2 to 500 meV (i.e. 16-4025 cm(-1)). The results show that the spectra of low density amorphous ice have similar features to cubic and hexagonal ices. However, the spectrum for the high density amorphous ice is significantly different from the others in the translational and librational regions (<150 meV). (C) 1997 Elsevier Science Ltd.
C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035.
RP Li, JC (reprint author), UMIST,DEPT PHYS,POB 88,MANCHESTER M60 1QD,LANCS,ENGLAND.
NR 28
TC 11
Z9 11
U1 2
U2 6
PU PERGAMON-ELSEVIER SCIENCE LTD
PI OXFORD
PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB
SN 0032-0633
J9 PLANET SPACE SCI
JI Planet Space Sci.
PD APR
PY 1997
VL 45
IS 4
BP 469
EP 473
DI 10.1016/S0032-0633(96)00131-6
PG 5
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WZ461
UT WOS:A1997WZ46100008
ER
PT J
AU Shiah, A
Hwang, KS
Wu, ST
Stone, NH
AF Shiah, A
Hwang, KS
Wu, ST
Stone, NH
TI Three-dimensional simulation of current collection in space
SO PLANETARY AND SPACE SCIENCE
LA English
DT Article
ID ELECTRON COLLECTION; MAGNETIC-FIELD; IONOSPHERE; SATELLITE; PLASMA
AB A three-dimensional, time-dependent, two species (i.e. electron and ion) particle simulation model gis developed for a better understanding of current collection by a charged body in space. The Low Earth Orbit (LEO) space environment is simulated by a super-particle simulation (SUPS) model to study the plasma transient response and its asymptotic behavior around a three-dimensional, highly biased satellite. The SUPS model is developed because the plasma particles in LEGS are so abundant that it is impossible to simulate each single particle in the study. Each simulation particle in this study represents a particle cloud. The potential distribution and the electric field are dependent on the density distribution of the particles. The simulation could apply to the spacecraft mission such as the first Tether Satellite System Re-fly (TSS-1R) mission for current collection analysis. Both positive and negative charged particles are considered in the study. The potential distribution surrounding the satellite is determined self-consistently by Poisson's equation. This study is both time dependent and space dependent simultaneously. Results indicate that when the satellite is charged to a highly positive potential, a plasma torus is formed in the plane perpendicular to the geomagnetic field. A dumbbell-shaped potential distribution is formed along the geomagnetic field lines and plasma oscillations are observed within the plasma sheath during the early stage of simulation. The effect of the local geomagnetic held on current collection is also presented. (C) 1997 Elsevier Science Ltd.
C1 UNIV ALABAMA,CTR SPACE PLASMA AERON & ASTROPHYS RES,HUNTSVILLE,AL 35899.
NASA,SPACE SCI LAB,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812.
NR 23
TC 4
Z9 5
U1 0
U2 0
PU PERGAMON-ELSEVIER SCIENCE LTD
PI OXFORD
PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB
SN 0032-0633
J9 PLANET SPACE SCI
JI Planet Space Sci.
PD APR
PY 1997
VL 45
IS 4
BP 475
EP 482
DI 10.1016/S0032-0633(96)00109-2
PG 8
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WZ461
UT WOS:A1997WZ46100009
ER
PT J
AU Orsolini, YJ
Hansen, G
Hoppe, UP
Manney, GL
Fricke, KH
AF Orsolini, YJ
Hansen, G
Hoppe, UP
Manney, GL
Fricke, KH
TI Dynamical modelling of wintertime lidar observations in the Arctic:
Ozone laminae and ozone depletion
SO QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY
LA English
DT Article
DE stratosphere; ozone; lidar; arctic polar vortex
ID LOWER STRATOSPHERE; TRANSPORT; TROPOSPHERE; BOUNDARY; VORTEX; SCALE;
WINDS
AB A series of lower stratospheric ozone profiles taken by a lidar during February 1995 in northern Norway are examined. The instrument location allowed continuous monitoring of rapidly evolving layered ozone structures, or laminae, near the polar vortex edge.
Observations under the vortex edge revealed laminae extending up to 20 Irm. Moreover, when the lidar was sampling vortex air, a thicker layer, characterized by unusually low mixing ratios, was also observed, thereby confirming satellite observations of Arctic ozone depletion during the winter 1994/95.
To unravel the respective role of dynamics and chemistry in generating these ozone-depleted layers requires better understanding of trace constituent lamination and filamentation through numerical modelling.
High-resolution modelled realistic transport of idealized tracers and satellite-derived ozone on many isentropes is therefore used to reconstruct fine-scale three-dimensional tracer fields. Tilted tracer or ozone sheets, peeled off near the vortex edge, lead to the formation of laminae in profiles. The model shows remarkable success in reproducing laminae intensification, thickening and lofting, analogous to the ones observed by the lidar over the course of a few hours.
C1 NORWEGIAN INST AIR RES,N-2001 LILLESTROM,NORWAY.
NORWEGIAN DEF RES ESTAB,N-2007 KJELLER,NORWAY.
CALTECH,JET PROP LAB,PASADENA,CA.
UNIV BONN,D-5300 BONN,GERMANY.
RP Orsolini, YJ (reprint author), METEO FRANCE,CNRM,42 AVE G CORIOLIS,F-31057 TOULOUSE,FRANCE.
NR 28
TC 39
Z9 39
U1 1
U2 1
PU ROYAL METEOROLOGICAL SOC
PI READING
PA 104 OXFORD ROAD, READING, BERKS, ENGLAND RG1 7LJ
SN 0035-9009
J9 Q J ROY METEOR SOC
JI Q. J. R. Meteorol. Soc.
PD APR
PY 1997
VL 123
IS 539
BP 785
EP 800
DI 10.1002/qj.49712353913
PN A
PG 16
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA WT663
UT WOS:A1997WT66300012
ER
PT J
AU Daughtry, CST
McMurtrey, JE
Kim, MS
Chappelle, EW
AF Daughtry, CST
McMurtrey, JE
Kim, MS
Chappelle, EW
TI Estimating crop residue cover by blue fluorescence imaging
SO REMOTE SENSING OF ENVIRONMENT
LA English
DT Article
ID SOIL; REFLECTANCE
AB Crop residues, the portion of the crop left in the field after harvest, can be an important management factor in controlling soil erosion. Current methods for quantifying crop residue cover use tedious manual sampling methods or visual comparisons with photographs. There is a need for new methods to quantify residue cover that are rapid, accurate, and objective. Scenes with known amounts of crop residue were illuminated in the lab with long-wave ultraviolet (UV) radiation and fluorescence images were measured and recorded with a video camera equipped with a mico-channel-plate image intensifier and fitted with a 453-488 nm bandpass filter. Six agricultural soils were used as backgrounds for the weathered soybean residue. Residue cover was determined from the proportion of the pixels in the image with fluorescence values greater than a threshold. Soil pixels gave the lowest fluorescence or brightness responses in the images and the residues the highest, so that brightness values of the scene spanned nearly the full range of the 8-bit video data. The images were classified in brightness categories that related to within 2% (absolute units) of measured residue cover regardless of the soil type or moisture condition (dry vs. wet). Therefore, fluorescence images can be used to provide percent residue cover in the lab, but portable equipment and procedures for use in the field still need to be developed. (C) Elsevier Science Inc., 1997.
C1 SCI SYST & APPLICAT INC,LANHAM,MD.
NASA,GODDARD SPACE FLIGHT CTR,TERR PHYS LAB,GREENBELT,MD 20771.
RP Daughtry, CST (reprint author), USDA ARS,REMOTE SENSING & MODELING LAB,BLDG 007,ROOM 008,BARC-W,10300 BALTIMORE AVE,BELTSVILLE,MD 20705, USA.
NR 25
TC 16
Z9 17
U1 0
U2 2
PU ELSEVIER SCIENCE INC
PI NEW YORK
PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010
SN 0034-4257
J9 REMOTE SENS ENVIRON
JI Remote Sens. Environ.
PD APR
PY 1997
VL 60
IS 1
BP 14
EP 21
DI 10.1016/S0034-4257(96)00118-6
PG 8
WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic
Technology
SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science &
Photographic Technology
GA WT709
UT WOS:A1997WT70900002
ER
PT J
AU Vierling, LA
Deering, DW
Eck, TF
AF Vierling, LA
Deering, DW
Eck, TF
TI Differences in arctic tundra vegetation type and phenology as seen using
bidirectional radiometry in the early growing season
SO REMOTE SENSING OF ENVIRONMENT
LA English
DT Article
ID CLIMATE-CHANGE; FIELD-MEASUREMENTS; DIURNAL PATTERNS; REFLECTANCE;
ECOSYSTEMS; BIOMASS; INDEXES; SPECTRORADIOMETERS; RADIANCE; PRAIRIE
AB Ground-based nadir and off-nadir radiometric measurements were collected on the North Slope of Alaska in early June to determine their utility in 1) differentiating arctic tundra vegetation community types through remote sensing, and 2) examining differences in structure and phenology of arctic tundra vegetation communities. We employed a PS-II (personal spectrometer II) portable field spectroradiometer to measure narrow-band spectra at nadir and the PARABOLA (portable apparatus for rapid acquisition of bidirectional observations of the land and atmosphere) three-channel radiometer to gather bidirectional radiometric data over almost the complete ground hemisphere. Measurements were taken at a lowland wet sedge site and at two tussock tundra sites containing different amounts of woody deciduous shrub cover. PS-II nadir measurements alone allowed spectral differentiation between the highly senescent wet sedge site and the two relatively greener tussock tundra sites but did not allow clear discrimination between tussock tundra sites. Off-nadir measurements, however, permitted good discrimination between the two tussock tundra sites. For example, the reflectance-based normalized difference vegetation index (NDVIrho) difference between the tussock tunda sites at a 75 degrees forward-scatter view angle averaged 26% over a range of solar zenith angles (Theta(s)s). Similarly, NDVI rho calculated from PARABOLA spectral hemispheric data averaged 6% higher in woody tussock tundra than in nonwoody tussock tundra. Differences between the tussock sites calculated by using NDVI based on hemispheric radiance (NDVIL) were greater than those calculated by using hemispheric NDVI rho by approximately a factor of two regardless of Theta(s). Measurements taken when Theta(s)=75 degrees generally exhibited the largest differences between NDVI at the two tussock tundra sites. Although nadir measurements exhibited minimal differences between tussock tundra types, bidirectional and hemispheric-based NDVI values revealed differences in tussock tundra woody vegetation cover because large view zenith angles were sensitive to the woody shrub foliage that extends above the hummocky tundra surface in early spring. These results may be useful for detecting changes in tundra woody cover through time. (C) Elsevier Science Inc., 1997.
C1 NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA.
HUGHES STX CORP, LANHAM, MD USA.
RP Vierling, LA (reprint author), UNIV COLORADO, DEPT ENVIRONM POPULAT & ORGAN BIOL, BOULDER, CO 80309 USA.
RI ECK, THOMAS/D-7407-2012; Vierling, Lee/E-6428-2010
OI Vierling, Lee/0000-0001-5344-1983
NR 40
TC 35
Z9 39
U1 2
U2 13
PU ELSEVIER SCIENCE INC
PI NEW YORK
PA 360 PARK AVE SOUTH, NEW YORK, NY 10010-1710 USA
SN 0034-4257
J9 REMOTE SENS ENVIRON
JI Remote Sens. Environ.
PD APR
PY 1997
VL 60
IS 1
BP 71
EP 82
DI 10.1016/S0034-4257(96)00139-3
PG 12
WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic
Technology
SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science &
Photographic Technology
GA WT709
UT WOS:A1997WT70900006
ER
PT J
AU Lidsey, JE
Liddle, AR
Kold, EW
Copeland, EJ
Barreiro, T
Abney, M
AF Lidsey, JE
Liddle, AR
Kold, EW
Copeland, EJ
Barreiro, T
Abney, M
TI Reconstructing the inflaton potential - An overview
SO REVIEWS OF MODERN PHYSICS
LA English
DT Review
ID PRIMORDIAL BLACK-HOLES; MICROWAVE BACKGROUND ANISOTROPIES; INFLATIONARY
UNIVERSE SCENARIO; BLUE PERTURBATION SPECTRA; BIG-BANG NUCLEOSYNTHESIS;
EINSTEIN-HILBERT ACTION; LARGE-SCALE STRUCTURE; GRAVITATIONAL-WAVES;
DARK-MATTER; COSMOLOGICAL PERTURBATIONS
AB The authors review the relation between the inflationary potential and the spectra of density waves (scalar perturbations) and gravitational waves (tensor perturbations) produced, with particular emphasis on the possibility of reconstructing the inflaton potential from observations. The spectra provide a potentially powerful test of the inflationary hypothesis; they are not independent but instead are linked by consistency relations reflecting their origin from a single inflationary potential. To lowest order in a perturbation expansion there is a single, now familiar, relation between the tensor spectral index and the relative amplitude of the spectra. The authors demonstrate that there is an infinite hierarchy of such consistency equations, though observational difficulties suggest only the first is ever likely to be useful. They also note that since observations are expected to yield much better information on the scalars than on the tensors, it is likely to be the next-order version of this consistency equation that will be appropriate, not the lowest-order one. If inflation passes the consistency test, one can then confidently use the remaining observational information to constrain the inflationary potential, and the authors survey the general perturbative scheme for carrying out this procedure. Explicit expressions valid to next-lowest order in the expansion are presented. The prospects for future observations' reaching the quality required are then briefly assessed and simulated data sets motivated by this outlook are considered.
C1 UNIV SUSSEX, CTR ASTRON, BRIGHTON BN1 9QH, E SUSSEX, ENGLAND.
FERMILAB NATL ACCELERATOR LAB, NASA, FERMILAB ASTROPHYS CTR, BATAVIA, IL 60510 USA.
UNIV CHICAGO, ENRICO FERMI INST, DEPT ASTRON & ASTROPHYS, CHICAGO, IL 60637 USA.
UNIV SUSSEX, CTR THEORET PHYS, BRIGHTON BN1 9QH, E SUSSEX, ENGLAND.
RP UNIV LONDON QUEEN MARY & WESTFIELD COLL, SCH MATH SCI, ASTRON UNIT, MILE END RD, LONDON E1 4NS, ENGLAND.
OI Barreiro, Tiago/0000-0001-8542-2066
NR 208
TC 520
Z9 520
U1 0
U2 13
PU AMER PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 0034-6861
EI 1539-0756
J9 REV MOD PHYS
JI Rev. Mod. Phys.
PD APR
PY 1997
VL 69
IS 2
BP 373
EP 410
DI 10.1103/RevModPhys.69.373
PG 38
WC Physics, Multidisciplinary
SC Physics
GA WU345
UT WOS:A1997WU34500002
ER
PT J
AU Bozzolo, G
Ferrante, J
Noebe, RD
Amador, C
AF Bozzolo, G
Ferrante, J
Noebe, RD
Amador, C
TI Zero temperature analysis of the defect structure of B2 FeAl alloys
SO SCRIPTA MATERIALIA
LA English
DT Article
ID INTERMETALLIC PHASES; POINT-DEFECTS; THERMODYNAMICS; COMPOUND
C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135.
NATL AUTONOMOUS UNIV MEXICO,FAC CIENCIAS,MEXICO CITY 04510,DF,MEXICO.
RP Bozzolo, G (reprint author), ANALEX CORP,3001 AEROSP PKWY,BROOK PARK,OH 44142, USA.
RI Amador-Bedolla, Carlos/E-7448-2010
OI Amador-Bedolla, Carlos/0000-0001-9590-2645
NR 22
TC 12
Z9 12
U1 1
U2 4
PU PERGAMON-ELSEVIER SCIENCE LTD
PI OXFORD
PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB
SN 1359-6462
J9 SCRIPTA MATER
JI Scr. Mater.
PD APR 1
PY 1997
VL 36
IS 7
BP 813
EP 819
DI 10.1016/S1359-6462(96)00447-2
PG 7
WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary;
Metallurgy & Metallurgical Engineering
SC Science & Technology - Other Topics; Materials Science; Metallurgy &
Metallurgical Engineering
GA WN941
UT WOS:A1997WN94100013
ER
PT J
AU Glenn, WE
Holton, CE
Dixon, GJ
Bos, PJ
AF Glenn, WE
Holton, CE
Dixon, GJ
Bos, PJ
TI High-efficiency light valve projectors and high-efficiency laser light
sources
SO SMPTE JOURNAL
LA English
DT Article; Proceedings Paper
CT 137th SMPTE Technical Conference
CY SEP 06-09, 1995
CL NEW ORLEANS, LA
SP SMPTE
AB The optical efficiency of an active matrix liquid crystal display (AMLCD) light valve projector is determined by the optical design, the method of modulation, and the efficiency of the light source. This paper describes a new projector with an efficient modulation technique, which can employ unpolarized light by using a unique diffraction grating formed in a liquid crystal panel. The technique uses a Schlieren optical system and has been tested with xenon arcs, metal halide arcs, and efficient solid-state laser light sources. The optical system reduces laser speckle significantly when highly coherent baser sources are used All source combinations exceeded 3 lm/W for white light projection performance, and the experimental results of the combinations are discussed. This modulation technique obtains a high contrast ratio with smaller panels than can be achieved with rotation-of-polarization light valve projectors.
C1 FLORIDA ATLANTIC UNIV,IMAGING SYST LAB,BOCA RATON,FL 33431.
VIRGINIA POLYTECH INST & STATE UNIV,FIBER & ELECTROOPT RES CTR,BLACKSBURG,VA 24061.
UNIV CENT FLORIDA,CREOL,ORLANDO,FL.
KENT STATE UNIV,KENT,OH 44242.
RP Glenn, WE (reprint author), FLORIDA ATLANTIC UNIV,NASA,SPACE COMMUN TECHNOL CTR,BOCA RATON,FL 33431, USA.
NR 5
TC 0
Z9 0
U1 0
U2 1
PU SOC MOTION PICTURE TV ENG INC
PI WHITE PLAINS
PA 595 WEST HARTSDALE AVE, WHITE PLAINS, NY 10607
SN 0036-1682
J9 SMPTE J
JI SMPTE J.
PD APR
PY 1997
VL 106
IS 4
BP 210
EP 216
PG 7
WC Engineering, Electrical & Electronic; Instruments & Instrumentation;
Imaging Science & Photographic Technology; Telecommunications
SC Engineering; Instruments & Instrumentation; Imaging Science &
Photographic Technology; Telecommunications
GA WQ981
UT WOS:A1997WQ98100003
ER
PT J
AU Ko, YK
Fisk, LA
Geiss, J
Gloeckler, G
Guhathakurta, M
AF Ko, YK
Fisk, LA
Geiss, J
Gloeckler, G
Guhathakurta, M
TI An empirical study of the electron temperature and heavy ion velocities
in the South polar coronal hole
SO SOLAR PHYSICS
LA English
DT Article
ID SOLAR-WIND; PHYSICAL-PROPERTIES; IRON IONIZATION; CHARGE STATES;
WHITE-LIGHT; MINOR IONS; ACCELERATION; FLOW; ULYSSES; SWICS
AB The solar wind ions flowing outward through the solar corona generally have their ionic fractions 'freeze-in' within 5 solar radii. The altitude where the freeze-in occurs depends on the competition between two time scales: the time over which the wind flows through a density scale height, and the time over which the ions achieve ionization equilibrium. Therefore, electron temperature, electron density, and the velocity of the ions are the three main physical quantities which determine the freeze-in process, and thus the solar wind ionic charge states. These physical quantities are determined by the heating and acceleration of the solar wind, as well as the geometry of the expansion. In this work, we present a parametric study of the electron temperature profile and velocities of the heavy ions in the inner solar corona. We use the ionic charge composition data observed by the SWICS experiment on Ulysses during the south polar pass to derive empirically the electron temperature profile in the south polar coronal hole. We find that the electron temperature profile in the solar inner corona is well constrained by the solar wind charge composition data. The data also indicate that the electron temperature profile must have a maximum within 2 solar radii. We also find that the velocities of heavy ions in their freeze-in regions are small (<100 km s(-1)) and different elements must flow at different velocities in the inner corona.
C1 UNIV MICHIGAN,DEPT ATMOSPHER OCEAN & SPACE SCI,ANN ARBOR,MI 48109.
INT SPACE SCI INST,BERN,SWITZERLAND.
UNIV MARYLAND,INST PHYS SCI & TECHNOL,COLLEGE PK,MD 20742.
NASA,GODDARD SPACE FLIGHT CTR,LAB SOLAR PHYS,GREENBELT,MD 20771.
UNIV MARYLAND,DEPT PHYS,SPACE PHYS GRP,COLLEGE PK,MD 20742.
NR 26
TC 133
Z9 133
U1 0
U2 0
PU KLUWER ACADEMIC PUBL
PI DORDRECHT
PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS
SN 0038-0938
J9 SOL PHYS
JI Sol. Phys.
PD APR
PY 1997
VL 171
IS 2
BP 345
EP 361
DI 10.1023/A:1004943213433
PG 17
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WT121
UT WOS:A1997WT12100009
ER
PT J
AU Horwitz, JL
Moore, TE
AF Horwitz, JL
Moore, TE
TI Four contemporary issues concerning ionospheric plasma flow to the
magnetosphere
SO SPACE SCIENCE REVIEWS
LA English
DT Review
DE magnetosphere; ionosphere; plasma; transport
ID CLEFT ION FOUNTAIN; SUPRATHERMAL O+ IONS; POLAR WIND;
ELECTRON-PRECIPITATION; HIGH-LATITUDES; AURORAL-ZONE; ACCELERATION;
SHEET; MAGNETOTAIL; SIGNATURE
AB In this review, we examine four specific questions/issues of contemporary interest within the overall topic of ionospheric plasma outflow into the magnetosphere. These four question areas are framed here as: (1) Are high-latitude F-region upflows predominantly driven by soft auroral electron precipitation?; (2) Is the O+ within the polar cap magnetosphere supplied primarily by the cleft ion fountain or a direct polar cap ionospheric source?; (3) Is centrifugal acceleration an important mechanism in the acceleration of ionospheric plasma outflows?; and (4) Are lobe ionospheric outflows captured by the plasma sheet?
C1 GEORGE C MARSHALL SPACE FLIGHT CTR, SPACE SCI LAB, SPACE PLASMA BRANCH, HUNTSVILLE, AL 35812 USA.
RP UNIV ALABAMA, CTR SPACE PLASMA & AERONOM RES, HUNTSVILLE, AL 35899 USA.
RI Moore, Thomas/D-4675-2012
OI Moore, Thomas/0000-0002-3150-1137
NR 55
TC 38
Z9 40
U1 0
U2 0
PU SPRINGER
PI DORDRECHT
PA VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS
SN 0038-6308
EI 1572-9672
J9 SPACE SCI REV
JI Space Sci. Rev.
PD APR
PY 1997
VL 80
IS 1-2
BP 49
EP 76
DI 10.1023/A:1004973603955
PG 28
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA XW668
UT WOS:A1997XW66800004
ER
PT J
AU Escoubet, CP
Schmidt, R
Goldstein, ML
AF Escoubet, CP
Schmidt, R
Goldstein, ML
TI Cluster-science and mission overview (vol 79, pg 11, 1997)
SO SPACE SCIENCE REVIEWS
LA English
DT Correction, Addition
C1 NASA,GODDARD SPACE FLIGHT CTR,EXTRATERR PHYS LAB,GREENBELT,MD 20771.
RP Escoubet, CP (reprint author), EUROPEAN SPACE AGCY,ESTEC,DEPT SPACE SCI,POB 299,NL-2200 AG NOORDWIJK,NETHERLANDS.
RI Goldstein, Melvyn/B-1724-2008
NR 1
TC 0
Z9 0
U1 0
U2 0
PU KLUWER ACADEMIC PUBL
PI DORDRECHT
PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS
SN 0038-6308
J9 SPACE SCI REV
JI Space Sci. Rev.
PD APR
PY 1997
VL 80
IS 1-2
BP 391
EP 391
PG 1
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA XW668
UT WOS:A1997XW66800018
ER
PT J
AU Ho, DT
Bliven, LF
Wanninkhof, R
Schlosser, P
AF Ho, DT
Bliven, LF
Wanninkhof, R
Schlosser, P
TI The effect of rain on air-water gas exchange
SO TELLUS SERIES B-CHEMICAL AND PHYSICAL METEOROLOGY
LA English
DT Article
ID WIND-SPEED; SULFUR-HEXAFLUORIDE; TRANSFER VELOCITIES; HUDSON ESTUARY;
LAKES; PARAMETERS; INTERFACE; SF6
AB The relationship between gas transfer velocity and rain rate was investigated at NASA's Rain-Sea Interaction Facility (RSIF) using several SF6 evasion experiments. During each experiment, a water tank below the rain simulator was supersaturated with SF6, a synthetic gas, and the gas transfer velocities were calculated from the measured decrease in SF6 concentration with time. The results from experiments with 18 different rain rates (7 to 110 mm h(-1)) and 1 of 2 dropsizes (2.8 or 4.2 mm diameter) confirm a significant and systematic enhancement of air-water gas exchange by rainfall. The gas transfer velocities derived from our experiment were related to the kinetic energy flux calculated from the rain rate and dropsize. The relationship obtained for mono-dropsize rain at the RSIF was extrapolated to natural rain using the kinetic energy flux of natural rain calculated from the Marshall-Palmer raindrop size distribution. Results of laboratory experiments at RSIF were compared to field observations made during a tropical rainstorm in Miami, Florida and show good agreement between laboratory and field data.
C1 COLUMBIA UNIV, DEPT EARTH & ENVIRONM SCI, PALISADES, NY 10964 USA.
NASA, GODDARD SPACE FLIGHT CTR, LAB HYDROSPHER PROC, WALLOPS ISL, VA 23337 USA.
NOAA, ATLANTIC OCEANOG & METEOROL LAB, OCEAN CHEM DIV, MIAMI, FL 33149 USA.
RP Ho, DT (reprint author), COLUMBIA UNIV, LAMONT DOHERTY EARTH OBSERV, PALISADES, NY 10964 USA.
RI Ho, David/A-3154-2011; Schlosser, Peter/C-6416-2012; bliven,
francis/E-1450-2012
OI Ho, David/0000-0002-0944-6952; Schlosser, Peter/0000-0002-6514-4203;
NR 29
TC 62
Z9 65
U1 0
U2 14
PU MUNKSGAARD INT PUBL LTD
PI COPENHAGEN
PA 35 NORRE SOGADE, PO BOX 2148, DK-1016 COPENHAGEN, DENMARK
SN 0280-6509
J9 TELLUS B
JI Tellus Ser. B-Chem. Phys. Meteorol.
PD APR
PY 1997
VL 49
IS 2
BP 149
EP 158
DI 10.1034/j.1600-0889.49.issue2.3.x
PG 10
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA WZ858
UT WOS:A1997WZ85800003
ER
PT J
AU Bauschlicher, CW
AF Bauschlicher, CW
TI Is the (c)over-tilde state of CH2 linear or bent?
SO THEORETICAL CHEMISTRY ACCOUNTS
LA English
DT Letter
DE structure or geometry; excited slate; electron correction
ID BASIS-SETS; ATOMS
AB The (c) over tilde state of CH2 is found to be bent at the highest levels of theory used in this work, but the energy difference between the linear and bent geometries is only about 10 cm(-1). Improving the basis set or correlation treatment favors the linear geometry over the bent, thus it is impossible to definitively determine if the (c) over tilde state has a barrier in its bending potential. If there is a barrier, it is clear that it will be so small that the (c) over tilde state will be quasilinear.
RP Bauschlicher, CW (reprint author), NASA,AMES RES CTR,STC 230 3,MOFFETT FIELD,CA 94035, USA.
NR 12
TC 6
Z9 6
U1 0
U2 0
PU SPRINGER VERLAG
PI NEW YORK
PA 175 FIFTH AVE, NEW YORK, NY 10010
SN 1432-881X
J9 THEOR CHEM ACC
JI Theor. Chem. Acc.
PD APR
PY 1997
VL 96
IS 1
BP 11
EP 13
DI 10.1007/s002140050197
PG 3
WC Chemistry, Physical
SC Chemistry
GA XF325
UT WOS:A1997XF32500003
ER
PT J
AU Jones, SP
Jansen, R
Fusaro, RL
AF Jones, SP
Jansen, R
Fusaro, RL
TI Preliminary investigation of neural network techniques to predict
tribological properties
SO TRIBOLOGY TRANSACTIONS
LA English
DT Article; Proceedings Paper
CT 51st Annual Meeting of the
Society-of-Tribologists-and-Lubrication-Engineers
CY MAY 19-23, 1996
CL CINCINNATI, OH
SP Soc Tribologists & Lubricat Engineers
DE engineering analysis and computing; maintenance; life prediction methods
AB A complete evaluation of the tribological characteristics of a given material/mechanical system is a time-consuming operation since the friction and wear process is extremely systems-sensitive. As a result, experimental designs, i.e., Latin Square and Taguchi, have been implemented in an attempt to not only reduce the total number of experimental combinations needed to fully characterize a material/mechanical system, but also to acquire life data for a system without having to perform an actual life test. Unfortunately, these experimental designs still require a great deal of experimental testing and the output does not always produce meaningful information. In order to further reduce the amount of experimental testing required, this study employs a computer neural network model to investigate different material/mechanical systems. The work focuses on the modeling of the wear behavior, while showing the feasibility of using neural networks to predict life data. The model is capable of defining which input variables will influence the tribological behavior of the particular material/mechanical system being studied based on the specifications of the overall system.
C1 OHIO AEROSP INST,CLEVELAND,OH 44135.
NASA,LEWIS RES CTR,CLEVELAND,OH 44135.
NR 19
TC 36
Z9 38
U1 0
U2 6
PU SOC TRIBOLOGISTS & LUBRICATION ENGINEERS
PI PARK RIDGE
PA 840 BUSSE HIGHWAY, PARK RIDGE, IL 60068
SN 0569-8197
J9 TRIBOL T
JI Tribol. Trans.
PD APR
PY 1997
VL 40
IS 2
BP 312
EP 320
DI 10.1080/10402009708983660
PG 9
WC Engineering, Mechanical
SC Engineering
GA WX394
UT WOS:A1997WX39400018
ER
PT J
AU Morales, W
Fusaro, RL
Siebert, M
Keith, T
Jansen, R
HerreraFierro, P
AF Morales, W
Fusaro, RL
Siebert, M
Keith, T
Jansen, R
HerreraFierro, P
TI A new antiwear additive surface pretreatment for PFPE liquid lubricants
SO TRIBOLOGY TRANSACTIONS
LA English
DT Article; Proceedings Paper
CT 50th Annual Meeting of the
Society-of-Tribologists-and-Lubrication-Engineers
CY MAY 14-19, 1995
CL CHICAGO, IL
SP Soc Tribologists & Lubricat Engineers
DE lubricants; antiwear additives; polyethers; surface analytical
techniques
ID PERFLUOROPOLYETHERS; TEMPERATURES; SPECTROSCOPY; ALUMINA
AB Pin-on-disk tribology experiments were conducted on a perfluoropolyalkylether (PFPE) liquid lubricant with and without a new PFPE lubricant antiwear additive material: a silane. It was found that the silane provided moderate improvement in the antiwear performance of the PFPE lubricant when applied to the metallic surface as a surface coating or when added to the PFPE as a dispersion (emulsion). Slightly better results were obtained by using the combination of a surface coating and an emulsion of the silane. The silane emulsions or coatings did not affect the friction properties of the lubricant. Micro-Fourier transformation infrared (mu FTIR) spectroscopy analysis was performed to study silane transfer films and the degradation of the PFPE. The silane was found to mitigate degradation of the PFPE which may have been the major reason for the improved antiwear performance observed.
C1 UNIV TOLEDO,TOLEDO,OH 43606.
OHIO AEROSP INST,CLEVELAND,OH 44135.
RP Morales, W (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA.
NR 18
TC 1
Z9 1
U1 1
U2 3
PU SOC TRIBOLOGISTS & LUBRICATION ENGINEERS
PI PARK RIDGE
PA 840 BUSSE HIGHWAY, PARK RIDGE, IL 60068
SN 0569-8197
J9 TRIBOL T
JI Tribol. Trans.
PD APR
PY 1997
VL 40
IS 2
BP 321
EP 329
DI 10.1080/10402009708983661
PG 9
WC Engineering, Mechanical
SC Engineering
GA WX394
UT WOS:A1997WX39400019
ER
PT J
AU Katul, G
Todd, P
Pataki, D
Kabala, ZJ
Oren, R
AF Katul, G
Todd, P
Pataki, D
Kabala, ZJ
Oren, R
TI Soil water depletion by oak trees and the influence of root water uptake
on the moisture content spatial statistics
SO WATER RESOURCES RESEARCH
LA English
DT Article
ID TIME DOMAIN REFLECTOMETRY; HYDRAULIC CONDUCTIVITY; VARIABILITY; TDR;
MODEL
AB The space-time statistical structure of soil water uptake by oak trees was investigated in a 3.1-m-diameter closed top chamber using a three-dimensional measurement grid of soil moisture and pressure, and measurements of tree transpiration. Using the time domain reflectometery (TDR) measured moisture content, resistance block measured soil water pressure, and a compact constant head permeameter measured saturated hydraulic conductivity, the soil hydraulic properties for the chamber were first estimated. Then, dimensionless statistical measures that utilize the soil water pressure were proposed and used to assess the relative importance of lateral to vertical flow. On the basis of the measured statistical properties of the soil-water pressure, it was found that the vertical flow is at least an order of magnitude larger than the lateral flow, and thus a one-dimensional flow approximation to continuity was utilized. Using continuity and a first-order Taylor series expansion of the Buckingham-Darcy vertical flux about the spatial mean moisture content state, an approximate relation for the time variation of the spatial mean moisture content was derived and tested with the TDR measurements, Despite a large spatial coefficient of variation in the TDR measured moisture content (which was also shown to be comparable to reported values from larger-scale field experiments), good agreement between mean moisture content predictions and measurements were found for two separate drying cycles. The approximate Taylor series flux expansion was utilized for deriving an analogous relation for the time variation of the spatial moisture content variance. The resultant variance budget was used to assess the role of root water uptake on the spatial variability of moisture content. It was found that the root uptake component, which resulted from a covariance between the root water uptake and moisture content spatial perturbations, is comparable to the contribution from soil hydraulic properties and soil water redistribution, One of the main findings in this study is that root water uptake is central to the moisture content spatial variance dissipation especially for dry soil moisture conditions. These results were further investigated using Monte-Carlo simulations.
C1 CALTECH,JET PROP LAB,DIV SCI,PASADENA,CA.
RP Katul, G (reprint author), DUKE UNIV,SCH ENVIRONM,DURHAM,NC 27708, USA.
RI Katul, Gabriel/A-7210-2008; Pataki, Diane/F-9732-2011
OI Katul, Gabriel/0000-0001-9768-3693;
NR 40
TC 50
Z9 53
U1 2
U2 16
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009
SN 0043-1397
J9 WATER RESOUR RES
JI Water Resour. Res.
PD APR
PY 1997
VL 33
IS 4
BP 611
EP 623
DI 10.1029/96WR03978
PG 13
WC Environmental Sciences; Limnology; Water Resources
SC Environmental Sciences & Ecology; Marine & Freshwater Biology; Water
Resources
GA WQ778
UT WOS:A1997WQ77800011
ER
PT J
AU Akapo, SO
AF Akapo, SO
TI Evaluation of transition metal complexes of
aminopropylsilyl-dithiooxamide bonded phases for gas chromatography
SO ANALYTICA CHIMICA ACTA
LA English
DT Article
DE gas chromatography; planetary atmospheres; light hydrocarbons;
aminopropylsilyl-dithiooxamide; cobalt(II) and copper(II) complexes
ID LOWER HYDROCARBONS; PERMANENT GASES; COPPER(II) COMPLEXES; TITANS
ATMOSPHERE; SOLID ADSORBENTS; SEPARATION; GC; NITRILES; OLEFINS; COLUMNS
AB Copper(II) and cobalt(II) complexes of dithiooxamide chemisorbed on aminopropyl bonded silicas were prepared and evaluated for the separation of light hydrocarbons (C-4 and below) by microcolumn gas chromatography (GC). All the columns appeared to be effective for the separation of C-1-C-4 saturates with reproducible retention times. In general, the sample components were retained longer on the metal-containing packings presumably due to specific solute-metal interactions. The cobalt(II) complex of aminopropylsilyl-dithiooxamide bonded phase showed better selectivity for the test solutes, particularly the C-2 hydrocarbons. This result, which reflects the higher capability of cobalt(II) to form pi-complexes with electron donor compounds than copper(II), showed a significant improvement in the separation of the C-2 hydrocarbons over molecular sieve 5A, alkyl bonded silicas and copper(II) complexes of cyano- or mercaptopropyl bonded phase where ethane and ethylene eluted as a single peak. Thermal stability test showed that the columns could be operated at temperatures up to 200 degrees C without any appreciable change in retention properties.
RP Akapo, SO (reprint author), NASA,AMES RES CTR,SETI INST,ECOBIOL BRANCH,MAIL STOP 239-12,MOFFETT FIELD,CA 94035, USA.
NR 25
TC 9
Z9 9
U1 0
U2 1
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0003-2670
J9 ANAL CHIM ACTA
JI Anal. Chim. Acta
PD MAR 31
PY 1997
VL 341
IS 1
BP 35
EP 42
DI 10.1016/S0003-2670(96)00569-7
PG 8
WC Chemistry, Analytical
SC Chemistry
GA WU641
UT WOS:A1997WU64100004
ER
PT J
AU Fleming, J
Brage, T
AF Fleming, J
Brage, T
TI Systematic CIV3 and MCDF calculations for the UV0.01 multiplet in O III
SO JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS
LA English
DT Article
ID INTERCOMBINATION LINE; OSCILLATOR-STRENGTHS; FORBIDDEN LINES;
RR-TELESCOPII; TRANSITIONS; SPECTRUM; SEQUENCE; PROGRAM; BREIT; LIST
AB We have carried out accurate, systematic calculations for the 2s2p(3 5)S(2)(o)-2s(2)2p(2 3)P(1,2) E1] lines at 1660.807 and 1666.153 Angstrom in O III. Uncertainty estimates for their A values and the lifetime of the S-5(2)o level have been determined from a set of quality criteria. A lifetime of 1.21 +/- 0.06 ms is recommended for this level, in excellent agreement with a recent experiment. The contributions to the branching ratios and lifetimes from different effects (e.g. core-valence correlation and Breit interaction) are discussed.
C1 NASA,GSFL,COMP SCI CORP,GREENBELT,MD 20771.
QUEENS UNIV BELFAST,DEPT APPL MATH & THEORET PHYS,BELFAST BT7 1NN,ANTRIM,NORTH IRELAND.
RP Fleming, J (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA.
OI Brage, Tomas/0000-0003-3985-767X
NR 33
TC 11
Z9 11
U1 0
U2 1
PU IOP PUBLISHING LTD
PI BRISTOL
PA DIRAC HOUSE, TEMPLE BACK, BRISTOL, ENGLAND BS1 6BE
SN 0953-4075
J9 J PHYS B-AT MOL OPT
JI J. Phys. B-At. Mol. Opt. Phys.
PD MAR 28
PY 1997
VL 30
IS 6
BP 1385
EP 1400
DI 10.1088/0953-4075/30/6/008
PG 16
WC Optics; Physics, Atomic, Molecular & Chemical
SC Optics; Physics
GA WT341
UT WOS:A1997WT34100008
ER
PT J
AU Cruikshank, DP
AF Cruikshank, DP
TI Comet Hale-Bopp - Stardust memories
SO SCIENCE
LA English
DT Editorial Material
ID INTERSTELLAR; DUST
RP Cruikshank, DP (reprint author), NASA,AMES RES CTR,MOFFETT FIELD,CA 94035, USA.
NR 19
TC 2
Z9 2
U1 0
U2 0
PU AMER ASSOC ADVANCEMENT SCIENCE
PI WASHINGTON
PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005
SN 0036-8075
J9 SCIENCE
JI Science
PD MAR 28
PY 1997
VL 275
IS 5308
BP 1895
EP 1896
DI 10.1126/science.275.5308.1895
PG 2
WC Multidisciplinary Sciences
SC Science & Technology - Other Topics
GA WQ513
UT WOS:A1997WQ51300030
PM 9122690
ER
PT J
AU Crovisier, J
Leech, K
BockeleeMorvan, D
Brooke, TY
Hanner, MS
Altieri, B
Keller, HU
Lellouch, E
AF Crovisier, J
Leech, K
BockeleeMorvan, D
Brooke, TY
Hanner, MS
Altieri, B
Keller, HU
Lellouch, E
TI The spectrum of comet Hale-Bopp (C/1995 O1) observed with the Infrared
Space Observatory at 2.9 astronomical units from the sun
SO SCIENCE
LA English
DT Article
ID INTERSTELLAR SILICATE MINERALOGY; AIRBORNE SPECTROPHOTOMETRY; EMISSION
FEATURES; WATER-VAPOR; P/HALLEY; MICRONS; SIMULATION; 2.8-MU-M; OLIVINE;
GRAINS
AB Comet Hale-Bopp (C/1995 O1) was observed at wavelengths from 2.4 to 195 micrometers with the Infrared Space Observatory when the comet was about 2.9 astronomical units (AU) from the sun, The main observed volatiles that sublimated from the nucleus ices were water, carbon monoxide, and carbon dioxide in a ratio (by number) of 10:6:2. These species are also the main observed constituents of ices in dense interstellar molecular clouds; this observation strengthens the links between cometary and interstellar material. Several broad emission features observed in the 7- to 45-micrometer region suggest the presence of silicates, particularly magnesium-rich crystalline olivine. These features are similar to those observed in the dust envelopes of Vega-type stars.
C1 EUROPEAN SPACE AGCY, DIV ASTROPHYS, ISO SCI OPERAT CTR, E-28080 VILLAFRANCA DASTI, SPAIN.
CALTECH, JET PROP LAB, PASADENA, CA 91109 USA.
MAX PLANCK INST AERON, D-37189 KATLENBURG DUHM, GERMANY.
RP Crovisier, J (reprint author), OBSERV PARIS, F-92195 MEUDON, FRANCE.
NR 46
TC 421
Z9 422
U1 1
U2 11
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 MAR 28
PY 1997
VL 275
IS 5308
BP 1904
EP 1907
DI 10.1126/science.275.5308.1904
PG 4
WC Multidisciplinary Sciences
SC Science & Technology - Other Topics
GA WQ513
UT WOS:A1997WQ51300035
PM 9072960
ER
PT J
AU Hayward, TL
Hanner, MS
AF Hayward, TL
Hanner, MS
TI Ground-based thermal infrared observations of comet Hale-Bopp (C/1995
O1) during 1996
SO SCIENCE
LA English
DT Article
ID EMISSION; GRAINS
AB Thermal infrared (IR) imaging and spectroscopy of comet Hale-Bopp (C/1995 O1) during June, August, and September 1996 traced the development of the dust coma several months before perihelion, Images revealed nightly variations in the brightness of the inner coma from 1 to 12 June that were correlated with the appearance of a northward-pointing jet. The central IR flux increased by a factor of 8 between 1 June and 30 September, and the September data showed IR jets that corresponded to similar structures that were visible in reflected sunlight at shorter wavelengths. At all epochs, 8- to 13-micrometer spectra of the central coma revealed a strong silicate emission feature, including an 11.2-micrometer feature indicative of crystalline olivine, even when the comet was at a heliocentric distance of 4.1 astronomical units.
C1 CALTECH,JET PROP LAB,PASADENA,CA 91109.
RP Hayward, TL (reprint author), CORNELL UNIV,CTR RADIOPHYS & SPACE RES,ITHACA,NY 14853, USA.
NR 10
TC 40
Z9 40
U1 0
U2 0
PU AMER ASSOC ADVANCEMENT SCIENCE
PI WASHINGTON
PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005
SN 0036-8075
J9 SCIENCE
JI Science
PD MAR 28
PY 1997
VL 275
IS 5308
BP 1907
EP 1909
DI 10.1126/science.275.5308.1907
PG 3
WC Multidisciplinary Sciences
SC Science & Technology - Other Topics
GA WQ513
UT WOS:A1997WQ51300036
PM 9072961
ER
PT J
AU Mo, KC
Dickey, JO
Marcus, SL
AF Mo, KC
Dickey, JO
Marcus, SL
TI Interannual fluctuations in atmospheric angular momentum simulated by
the national centers for environmental prediction medium range forecast
model
SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
LA English
DT Article
ID SOUTHERN OSCILLATION; HADLEY CIRCULATION; CLIMATE; SCALES; SYSTEM
AB An earlier study by Dickey et al. [1992] established the existence of globally coherent interannual fluctuations in atmospheric angular momentum (AAM), associated with the El Nino-Southern Oscillation (ENSO) cycle. In this paper, we pursue the origin and the structure of these fluctuations using an ensemble of experiments generated by the National Centers for Environmental Prediction, medium range forecast model version 9. In the control experiments, where the observed sea surface temperatures (SSTs) were used as the lower boundary conditions, the model captures the characteristic V-like structure in time-latitude plots of zonally averaged AAM found by Dickey et al., while experiments with climatological SSTs and those with either perpetual warm or cold ENSO conditions superimposed on the climatological SSTs failed to reproduce this structure. The numerical results indicate that these AAM structures are related to SST variations associated with transitions between different phases of the ENSO cycle and have both propagating and standing components. The largest zonal wind contribution from the levels studied (850, 500, and 200 hPa) is at 200 hPa, where the tropical convective outflow is the strongest. Composites of zonal wind and geopotential height show a clear relationship between the stages of the global AAM oscillation and the ENSO cycle. The strong similarity between the simulated and observed AAM series attests to the model's ability to realistically simulate the interannual response of the atmosphere to ENSO SST anomalies.
C1 CALTECH, JET PROP LAB, SPACE GEODET SCI & APPL GRP, PASADENA, CA 91109 USA.
RP Mo, KC (reprint author), NOAA, NATL WEATHER SERV, NCEP, CLIMATE PREDICT CTR, WASHINGTON, DC 20233 USA.
OI Marcus, Steven/0000-0002-5763-6961
NR 34
TC 11
Z9 12
U1 0
U2 0
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA
SN 2169-897X
J9 J GEOPHYS RES-ATMOS
JI J. Geophys. Res.-Atmos.
PD MAR 27
PY 1997
VL 102
IS D6
BP 6703
EP 6713
DI 10.1029/96JD02609
PG 11
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA WR433
UT WOS:A1997WR43300006
ER
PT J
AU Hansen, J
Ruedy, R
Lacis, A
Russell, G
Sato, M
Lerner, J
Rind, D
Stone, P
AF Hansen, J
Ruedy, R
Lacis, A
Russell, G
Sato, M
Lerner, J
Rind, D
Stone, P
TI Wonderland climate model
SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
LA English
DT Article
ID ATMOSPHERE; HEMISPHERE; ENERGY; CYCLE; OCEAN
AB We obtain a highly efficient global climate model by defining a sector version (120 degrees of longitude) of the coarse resolution Goddard Institute for Space Studies model II. The geography of Wonderland is chosen such that the amount of land as a function of latitude is the same as on Earth. We show that the zonal mean climate of the Wonderland model is very similar to that of the parent model II.
C1 MIT, CTR METEOROL & PHYS OCEANOG, CAMBRIDGE, MA 02139 USA.
RP Hansen, J (reprint author), NASA, GODDARD INST SPACE STUDIES, 2880 BROADWAY, NEW YORK, NY 10025 USA.
RI Lacis, Andrew/D-4658-2012
NR 12
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 MAR 27
PY 1997
VL 102
IS D6
BP 6823
EP 6830
DI 10.1029/96JD03435
PG 8
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA WR433
UT WOS:A1997WR43300014
ER
PT J
AU Hansen, J
Sato, M
Ruedy, R
AF Hansen, J
Sato, M
Ruedy, R
TI Radiative forcing and climate response
SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
LA English
DT Article
ID GENERAL CIRCULATION MODEL; STRATOSPHERIC OZONE; GREENHOUSE GASES;
SURFACE-TEMPERATURE; SULFATE AEROSOLS; AIR-TEMPERATURE; CARBON-DIOXIDE;
RELATIVE ROLES; BLACK CARBON; SOLAR-CYCLE
AB We examine the sensitivity of a climate model to a wide range of radiative forcings, including changes of solar irradiance, atmospheric CO2, O-3, CFCs, clouds, aerosols, surface albedo, and a ''ghost'' forcing introduced at arbitrary heights, latitudes, longitudes, seasons, and times of day. We show that, in general, the climate response, specifically the global mean temperature change, is sensitive to the altitude, latitude, and nature of the forcing; that is, the response to a given forcing can vary by 50% or more depending upon characteristics of the forcing other than its magnitude measured in watts per square meter, The consistency of the response among different forcings is higher, within 20% or better, for most of the globally distributed forcings suspected of influencing global mean temperature in the Fast century, but exceptions occur for certain changes of ozone or absorbing aerosols, for which the climate response is less well behaved. In all cases the physical basis for the variations of the response can be understood. The principal mechanisms involve alterations of lapse rate and decrease (increase) of large-scale cloud cover in layers that are preferentially heated (cooled). Although the magnitude of these effects must be model-dependent, the existence and sense of the mechanisms appear to be reasonable. Overall, we reaffirm the value of the radiative forcing concept for predicting climate response and for comparative studies of different forcings; indeed, the present results can help improve the accuracy of such analyses and define error estimates, Our results also emphasize the need for measurements having the specificity and precision needed to define poorly known forcings such as absorbing aerosols and ozone change. Available data on aerosol single scatter albedo imply that anthropogenic aerosols cause less cooling than has commonly been assumed. However, negative forcing due to the net ozone change since 1979 appears to have counterbalanced 30-50% of the positive forcing due to the increase of well-mixed greenhouse gases in the same period. As the net ozone change includes halogen-driven ozone depletion with negative radiative forcing and a tropospheric ozone increase with positive radiative forcing, it is possible that the halogen-driven ozone depletion has counterbalanced more than half of the radiative forcing due to well-mixed greenhouse gases since 1979.
RP Hansen, J (reprint author), NASA, GODDARD INST SPACE STUDIES, 2880 BROADWAY, NEW YORK, NY 10025 USA.
NR 85
TC 1054
Z9 1090
U1 65
U2 349
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA
SN 2169-897X
J9 J GEOPHYS RES-ATMOS
JI J. Geophys. Res.-Atmos.
PD MAR 27
PY 1997
VL 102
IS D6
BP 6831
EP 6864
DI 10.1029/96JD03436
PG 34
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA WR433
UT WOS:A1997WR43300015
ER
PT J
AU Bishop, JKB
Rossow, WB
Dutton, EG
AF Bishop, JKB
Rossow, WB
Dutton, EG
TI Surface solar irradiance from the International Satellite Cloud
Climatology Project 1983-1991
SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
LA English
DT Article
ID NORTH-ATLANTIC OCEAN; SHORTWAVE RADIATION; ISCCP; SEA; VARIABILITY;
TEMPERATURE; PRODUCTS; MODELS
AB An 8 year (July 1983 through June 1991) time series of daily and monthly mean surface solar irradiance has been produced for the globe using data from the International Satellite Cloud Climatology Project (ISCCP) and a revised Bishop and Rossow [1991] algorithm. We present a detailed validation analysis of the ISCCP solar irradiance fields with contemporaneous surface observations at buoys, at remote islands, and from the Global Energy Balance Archives (GEBA) [Ohmura et al., 1991]. The validation is hampered to some degree by the scale difference between the 280 km ISCCP product and the single-point measurements, some of which are affected by orographic clouds and other local meteorological effects. Our analysis suggests criteria for siting of island or coastal monitoring locations to minimize such biases. Particularly, eastward or poleward facing oceanic exposures are to be avoided. In addition, we suggest that deep sea buoys should be investigated for validation of oceanic surface fluxes. At open-ocean, clean-air sites, the ISCCP product is shown to be good to within 10 W m(-2) in the monthly mean. The high-frequency (daily) systematics of solar irradiance variability at the open-ocean sites are also well duplicated by the ISCCP product. An identifiable error in the revised solar irradiance product is the neglect of spatially and temporally varying aerosol extinction. This error, when translated into an equivalent aerosol extinction coefficient, can be as large as 0.6 in known polluted and mineral dust-affected regions. We cannot determine additional satellite sensor calibration errors beyond those already corrected in the ISCCP processing This uniquely long data set has been publicly available since 1994 at the National Center for Atmospheric Research. The data documents significant differences in solar fluxes received by the major oceans as well as significant flux variability on seasonal to interannual timescales.
C1 UNIV VICTORIA, SCH EARTH & OCEAN SCI, VICTORIA, BC, CANADA.
NOAA, CLIMATE MONITORING & DIAGNOST LAB, BOULDER, CO 80303 USA.
RP Bishop, JKB (reprint author), NASA, GODDARD SPACE FLIGHT CTR, INST SPACE STUDIES, NEW YORK, NY 10025 USA.
RI Rossow, William/F-3138-2015
NR 51
TC 69
Z9 70
U1 0
U2 8
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA
SN 2169-897X
J9 J GEOPHYS RES-ATMOS
JI J. Geophys. Res.-Atmos.
PD MAR 27
PY 1997
VL 102
IS D6
BP 6883
EP 6910
DI 10.1029/96JD03865
PG 28
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA WR433
UT WOS:A1997WR43300017
ER
PT J
AU Yamanouchi, T
Charlock, TP
AF Yamanouchi, T
Charlock, TP
TI Effects of clouds, ice sheet, and sea ice on the Earth radiation budget
in the Antarctic
SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
LA English
DT Article
ID SCENE IDENTIFICATION; CLIMATE-RESEARCH; MODEL; ALBEDO; SATELLITE;
SURFACE; REGIME; SNOW; ERBE; WIND
AB The effects of clouds, the continental ice sheet, and sea ice on the radiation budget in the Antarctic are examined by using Earth Radiation Budget Experiment, International Satellite Cloud Climatology Project, and special sensor microwave/imager data in 1987/1988. The continental ice sheet affects not only the albedo but also the surface temperature because of elevation and hence the outgoing longwave radiation (OLR). The high elevation of the Antarctic continent makes the radiation budget in both polar regions asymmetric. At elevations below 2 km the OLR is reduced at the rate of 5-10 W/m(2)/km; above 2 km the rate is about 20 W/m(2)/km. Sea ice. which is a critical climate feedback factor, appears to have less impact on radiation than do clouds. Between 60 degrees and 65 degrees S in October, sea ice increases the top of the atmosphere albedo by about 0.2 and reduces the OLR by 7-10 W/m(2); this seems smaller than the formal cloud forcing, which increases the albedo by 0.3 and reduces the OLR by 30-40 W/m(2). However, these numbers do not fully differentiate the independent effects of sea ice and cloudiness. A more detailed analysis shows that the independent effect of sea ice is as large as clouds, with clouds masking the radiative effect of sea ice by more than one half.
C1 NASA, LANGLEY RES CTR, HAMPTON, VA 23665 USA.
RP Yamanouchi, T (reprint author), NATL INST POLAR RES, TOKYO 173, JAPAN.
RI Yamanouchi, Takashi/P-2041-2015
NR 52
TC 9
Z9 9
U1 0
U2 1
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA
SN 2169-897X
J9 J GEOPHYS RES-ATMOS
JI J. Geophys. Res.-Atmos.
PD MAR 27
PY 1997
VL 102
IS D6
BP 6953
EP 6970
DI 10.1029/96JD02866
PG 18
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA WR433
UT WOS:A1997WR43300021
ER
PT J
AU Leroy, SS
AF Leroy, SS
TI Measurement of geopotential heights by GPS radio occultation
SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
LA English
DT Article
ID GRIDPOINT TEMPERATURE ANOMALIES; SOUTHERN-HEMISPHERE; ATMOSPHERE;
SATELLITE; PRECISION; VOYAGER-2; INTERPOLATION; VALIDATION; TRENDS;
WAVES
AB Geopotential heights of constant pressure surfaces are retrieved from global positioning system (GPS) radio occultation data. In order to assess accuracy a subset of data obtained by GPS/MET during spring 1995 and summer 1995 are compared to the output of the European Centre for Medium-Range Weather Forecasts (ECMWF) global model. The root-mean-square measurement error is 20 m throughout the upper troposphere and lower stratosphere. Furthermore, the ECMWF global model contains enhanced errors in the southeast Pacific. In probing the data for potential utility in climate studies, a Bayesian interpolation technique is used to map the geopotential height fields in the upper troposphere during the summer. Despite limitations of the GPS/MET data set the global average 300-mbar geopotential height over a 2-week period in summer 1995 is determined with an accuracy of 7 m. By obtaining greater coverage and partially resolving synoptic variability, a future constellation of 16 orbiting receivers could obtain global average geopotential height estimates in the upper troposphere with an accuracy of 1 m each day. Accuracy would be somewhat worse for regional studies, except in the tropics where synoptic variability is depressed.
RP Leroy, SS (reprint author), CALTECH, JET PROP LAB, DIV EARTH & SPACE SCI, PASADENA, CA 91109 USA.
NR 39
TC 64
Z9 68
U1 0
U2 0
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA
SN 2169-897X
J9 J GEOPHYS RES-ATMOS
JI J. Geophys. Res.-Atmos.
PD MAR 27
PY 1997
VL 102
IS D6
BP 6971
EP 6986
DI 10.1029/96JD03083
PG 16
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA WR433
UT WOS:A1997WR43300022
ER
PT J
AU Bauschlicher, CW
Langhoff, SR
Sandford, SA
Hudgins, DM
AF Bauschlicher, CW
Langhoff, SR
Sandford, SA
Hudgins, DM
TI Infrared spectra of perdeuterated naphthalene, phenanthrene, chrysene,
and pyrene
SO JOURNAL OF PHYSICAL CHEMISTRY A
LA English
DT Article
ID INTERPLANETARY DUST PARTICLES; AROMATIC HYDROCARBON CATIONS;
SOLAR-SYSTEM; SPECTROSCOPY; METEORITES; MOLECULES; HYDROGEN; MATTER;
CARBON
AB Calculations are carried out using density functional theory (DFT) to determine the harmonic frequencies and intensities of perdeuterated naphthalene, phenanthrene, pyrene, and chrysene. We also report matrix-isolation spectra for these four species. The theoretical and experimental frequencies and relative intensities for the perdeuterated species are in generally good agreement. The effect of perdeuteration is to reduce the sum of the integrated intensities by a factor of about 1.75. This reduction occurs for all vibrational motions, except for the weak low-frequency ring deformation modes. There is also a significant redistribution of the relative intensities between the out-of-plane C-D bands relative to those found for the out-of-plane C-H bands. The theoretical isotopic ratios provide an excellent diagnostic of the degree of C-H(C-D) involvement in the vibrational bands, allowing in most cases a clear distinction of the type of motion.
C1 ADRIAN COLL,DEPT CHEM,ADRIAN,MI 49221.
RP Bauschlicher, CW (reprint author), NASA,AMES RES CTR,MOFFETT FIELD,CA 94035, USA.
NR 26
TC 50
Z9 50
U1 1
U2 8
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036
SN 1089-5639
J9 J PHYS CHEM A
JI J. Phys. Chem. A
PD MAR 27
PY 1997
VL 101
IS 13
BP 2414
EP 2422
PG 9
WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical
SC Chemistry; Physics
GA WQ630
UT WOS:A1997WQ63000007
ER
PT J
AU Joshi, MM
Haberle, RM
Barnes, JR
Murphy, JR
Schaeffer, J
AF Joshi, MM
Haberle, RM
Barnes, JR
Murphy, JR
Schaeffer, J
TI Low-level jets in the NASA Ames Mars general circulation model
SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS
LA English
DT Article
ID ASIAN SUMMER MONSOON; DUST STORMS; ATMOSPHERIC DYNAMICS; MARTIAN
ATMOSPHERE; SIMULATIONS; WINDS
AB Previous simulations of the Martian atmosphere have shown how topography acts to confine the low-level Hadley cell flow into intense jets on the eastern flanks of Tharsis and Syrtis Major. We now conduct detailed studies of these jets using the NASA Ames Mars general circulation model (MGCM). The structure of the flow is found to be sensitive to local topography as well as large-scale diabatic heating patterns, consistent with terrestrial Studies, and MGCM studies carried out with simplified topography. The summer subtropical zonal winds associated with the Hadley circulation also form spatially confined intense jet cores. Diurnal variations in heating affect jet structure in three distinct ways. Global tides interact with the jets, resulting in effects such as the two reinforcing each other at the summer subtropics near midday, leading to high winds and surface stresses at this time. Slope winds act to, change the character of the jets during the course of a day, especially at Syrtis Major and the Hellas basin, where slopes are large. Vertical mixing acts to decrease low-level winds during the late afternoon. The sensitivity of the results to atmospheric dust loading is examined, We finally show how a decrease in boundary layer height due to dust loading actually augments mid-afternoon jet strength near the surface. The resulting increase in maximum surface stress indicates that this is a positive feedback to dust lifting.
C1 OREGON STATE UNIV,DEPT ATMOSPHER SCI,CORVALLIS,OR 97331.
SAN JOSE STATE UNIV FDN,SAN JOSE,CA.
STERLING SOFTWARE INC,PALO ALTO,CA.
RP Joshi, MM (reprint author), NASA,AMES RES CTR,DIV SPACE SCI,MOFFETT FIELD,CA 94035, USA.
RI Joshi, Manoj/C-1795-2008
OI Joshi, Manoj/0000-0002-2948-2811
NR 26
TC 19
Z9 19
U1 1
U2 6
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009
SN 0148-0227
J9 J GEOPHYS RES-PLANET
JI J. Geophys. Res.-Planets
PD MAR 25
PY 1997
VL 102
IS E3
BP 6511
EP 6523
DI 10.1029/96JE03765
PG 13
WC Geochemistry & Geophysics
SC Geochemistry & Geophysics
GA WR650
UT WOS:A1997WR65000001
ER
PT J
AU Krasnopolsky, VA
Bjoraker, GL
Mumma, MJ
Jennings, DE
AF Krasnopolsky, VA
Bjoraker, GL
Mumma, MJ
Jennings, DE
TI High-resolution spectroscopy of Mars at 3.7 and 8 mu m: A sensitive
search for H2O2, H2CO, HCl, and CH4, and detection of HDO
SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS
LA English
DT Article
ID MARTIAN ATMOSPHERE; WATER-VAPOR; MINOR CONSTITUENTS; THERMAL STRUCTURE;
GLOBAL BEHAVIOR; EVOLUTION; MARINER-9; ABUNDANCE; D/H; RATIOS
AB We report the first sensitive upper limits for H2O2, H2CO, and HCl, a sensitive upper limit for CH4, and a measured column abundance for HDO. A combination of the Kitt Peak National Observatory (KPNO) 4-m telescope and Fourier transform spectrometer with the Goddard Space Flight Center (GSFC) postdisperser was used to observe low-latitude regions of Mars in spectral ranges of 2650-2800 cm(-1) and 1229-1237 cm(-1) with resolving power nu/delta nu = 2.7 x 10(5) and 1.2 x 10(5), respectively. The main spectral features are lines of isotopic CO2 and HDO. A radiation transfer code has been developed which divides the atmosphere into 30 layers and the Voigt profile of each line in each layer into 60 intervals. This code couples the reflected solar and thermal radiations. A search for H2O2 at 1229-1237 cm(-1) results in a 2-sigma upper limit of 30 ppb, close to the predictions of recent photochemical models. Our 2-sigma upper limit for HCl (< 2 ppb) precludes any significant chlorine chemistry in the atmosphere. Our value for methane (70 +/- 50 ppb) is consistent with, but does not improve upon, earlier results from Mariner 9 infrared interferometer spectrometer (IRIS). Our 2-sigma upper limit for H2CO (3 ppb) is much smaller than recently claimed abundances. The observed HDO lines result in an abundance of (6.06 +/- 0.5) x 10(16) cm(-2), which, when compared with that of H2O measured by the Viking orbiters at the same season and latitudes, yields an enrichment in the D/H ratio of a factor of 5.5 +/- 2 relative to Earth. The given uncertainty is mainly caused by possible variations of Mars' atmospheric water abundance.
RP Krasnopolsky, VA (reprint author), NASA,GODDARD SPACE FLIGHT CTR,EXTRATERR PHYS LAB,MAIL CODE 693,GREENBELT,MD 20771, USA.
RI Bjoraker, Gordon/D-5032-2012; Jennings, Donald/D-7978-2012; mumma,
michael/I-2764-2013; Krasnopolsky, Vladimir/L-5085-2013
NR 42
TC 108
Z9 108
U1 0
U2 3
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009
SN 0148-0227
J9 J GEOPHYS RES-PLANET
JI J. Geophys. Res.-Planets
PD MAR 25
PY 1997
VL 102
IS E3
BP 6525
EP 6534
DI 10.1029/96JE03766
PG 10
WC Geochemistry & Geophysics
SC Geochemistry & Geophysics
GA WR650
UT WOS:A1997WR65000002
ER
PT J
AU Presley, MA
Christensen, PR
AF Presley, MA
Christensen, PR
TI Thermal conductivity measurements of particulate materials .1. A review
SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS
LA English
DT Review
AB Discussion of the thermal conductivity of particulate materials is dispersed over several decades and a wide range of disciplines. In addition, there is some disparity among the reported values. This paper presents a review of the methodology available for the study of thermal conductivity of particulate materials, with an emphasis on low atmospheric pressures, and an assessment of the dependability of the data previously reported. Both steady state and nonsteady state methods of thermal conductivity measurement are reviewed, delineating the advantages, disadvantages, and sources of error for each. Nonsteady state methods generally are simpler and more efficient. The transient hot wire and differentiated line-heat source are the preferred methods for the laboratory. These methods are better suited for small samples and short measurement times and are therefore the best methods to use for a series of comprehensive studies. Results of previous studies are presented, compared, and evaluated. A good way to assess the relative accuracy is to compare the values of thermal conductivity versus atmospheric pressure obtained from several experimenters. The lowest values of thermal conductivity at vacuum and very low atmospheric pressure, and the steepest slopes on the thermal conductivity versus atmospheric pressure curves, art indicative of the most accurate data. Previous thermal conductivity studies have shown that the thermal conductivity of particulate materials increases with increasing atmospheric pressure, with increasing particle size, and with increasing bulk density of the material. At vacuum, the thermal conductivity of particulate materials is proportional to the cube of the temperature. The temperature dependence of thermal conductivity is much less obvious at higher atmospheric pressures.
C1 ARIZONA STATE UNIV,DEPT GEOL,TEMPE,AZ 85287.
RP Presley, MA (reprint author), NASA,AMES RES CTR,MAIL STOP 239-14,MOFFETT FIELD,CA 94035, USA.
NR 61
TC 79
Z9 79
U1 2
U2 24
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009
SN 0148-0227
J9 J GEOPHYS RES-PLANET
JI J. Geophys. Res.-Planets
PD MAR 25
PY 1997
VL 102
IS E3
BP 6535
EP 6549
DI 10.1029/96JE03302
PG 15
WC Geochemistry & Geophysics
SC Geochemistry & Geophysics
GA WR650
UT WOS:A1997WR65000003
ER
PT J
AU Presley, MA
Christensen, PR
AF Presley, MA
Christensen, PR
TI Thermal conductivity measurements of particulate materials .2. Results
SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS
LA English
DT Article
ID PHYSICAL-PROPERTIES; MARS; INERTIA; FEATURES; SURFACE
AB A line-heat source apparatus was assembled for the purpose pf measuring thermal conductivities of particulate samples under low pressures of a carbon dioxide atmosphere. The primary result of this project is the compilation of the first comprehensive suite of measurements of the dependence of thermal conductivity on particle size. The thermal conductivity increases with increasing particle size and atmospheric pressure. In particular, over the range of Martian atmospheric pressures, from 1 to 7 torr, the thermal conductivity was found to be empirically related to approximately the square root of the particle diameter and the square of the cubed root of the atmospheric pressure. At the average pressure of the Martian surface (6 torr) the thermal conductivity varies from 0.011 W/m K, for particles less than 11 mu m in diameter, to 0.11 W/m K, for particles 900 mu m in diameter. These results differ significantly from the particle size dependence estimated for Mars from previous measurements, except for 200-mu m particles, whose thermal conductivity is 0.053 W/m K. The thermal conductivities of larger particles are lower than the previous estimate, by 40% at 900 mu m, and the thermal conductivities of smaller particles are higher than the previous estimate, by 60% at 11 mu m These newer estimates agree with other lines of evidence from Martian atmospheric and surficial processes and lead to improved particle size estimates for most of the planet's surface.
C1 ARIZONA STATE UNIV,DEPT GEOL,TEMPE,AZ 85287.
RP Presley, MA (reprint author), NASA,AMES RES CTR,MAIL STOP 239-14,MOFFETT FIELD,CA 94035, USA.
NR 48
TC 157
Z9 157
U1 1
U2 12
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009
SN 0148-0227
J9 J GEOPHYS RES-PLANET
JI J. Geophys. Res.-Planets
PD MAR 25
PY 1997
VL 102
IS E3
BP 6551
EP 6566
DI 10.1029/96JE03303
PG 16
WC Geochemistry & Geophysics
SC Geochemistry & Geophysics
GA WR650
UT WOS:A1997WR65000004
ER
PT J
AU Sakimoto, SEH
Crisp, J
Baloga, SM
AF Sakimoto, SEH
Crisp, J
Baloga, SM
TI Eruption constraints on tube-fed planetary lava flows
SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS
LA English
DT Article
ID ALBA-PATERA; FIELD-MEASUREMENTS; KILAUEA VOLCANO; MARS; EMPLACEMENT;
LIQUIDUS; HAWAII
AB We examine the role of pressure and gravity as driving forces in planetary lava tubes for Newtonian and power law theologies. The tubes are assumed to have been filled with lava that was emplaced in constant diameter circular tubes in the laminar flow regime and had constant density, heat capacity, thermal conductivity, and viscosity. Our model provides relationships between tube dimensions, driving forces, and effusion rates and rheology parameters. In general, the pressure term in the driving force dominates for very small slopes, but the gravity term eclipses the pressure term as the slope increases. Applying the model to Alba Patera tube flows suggests effusion rates somewhere between 2 and 10(5) m(3)/s and viscosities between 10(2) and 10(6) Pa s, with tighter constraints (2 to 4 orders of magnitude) for specific tube sizes and travel times. These effusion rate results are lower and the viscosity ranges are higher than those found in previous studies. This allows eruptions that are closer in style to terrestrial basaltic eruptions, although the flows are still considerably larger in scale than the Hawaiian tube flows. We find that very low lava viscosities are not essential for Alba Patera lava tubes and that tube formation may be a better indicator of the steadiness of the eruption and the presence of low slopes than it is of low viscosities (e.g., 10(2) Pa s). In addition, this analysis suggests that the tube systems on the steep flanks of Olympus Mons are fundamentally different from those at Alba Patera. The Olympus Mons flows could not have roofed over, been continuously full, or maintained a continuous lava tube transport system in the assumed full, steady, and fully developed conditions.
C1 PROXEMY RES INC,LAYTONSVILLE,MD 20882.
CALTECH,JET PROP LAB,PASADENA,CA 91109.
RP Sakimoto, SEH (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GEODYNAM BRANCH,CODE 921,GREENBELT,MD 20771, USA.
RI Crisp, Joy/H-8287-2016
OI Crisp, Joy/0000-0002-3202-4416
NR 32
TC 41
Z9 42
U1 1
U2 1
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009
SN 0148-0227
J9 J GEOPHYS RES-PLANET
JI J. Geophys. Res.-Planets
PD MAR 25
PY 1997
VL 102
IS E3
BP 6597
EP 6613
DI 10.1029/97JE00069
PG 17
WC Geochemistry & Geophysics
SC Geochemistry & Geophysics
GA WR650
UT WOS:A1997WR65000007
ER
PT J
AU Moeur, WA
Day, PK
Liu, FC
Boyd, STP
Adriaans, MJ
Duncan, RV
AF Moeur, WA
Day, PK
Liu, FC
Boyd, STP
Adriaans, MJ
Duncan, RV
TI Observation of self-organized criticality near the superfluid transition
in He-4
SO PHYSICAL REVIEW LETTERS
LA English
DT Article
ID HEAT CURRENT; THERMAL-CONDUCTIVITY; VAPOR-PRESSURE; BARS
AB We report on an experimental observation of self-organized criticality in He-4 very close to its superfluid transition. A constant temperature gradient, independent of the heat flux Q through the sample, is created along a vertical column of He-4 by applying heat to the top of the column. This constant temperature gradient equals the gravity-induced gradient in the superfluid transition temperature, indicating that the thermal conductivity of the sample has self-organized. The closeness to criticality in this state is the same throughout most of the sample, and it depends only on Q.
C1 CALTECH,JET PROP LAB,PASADENA,CA 91109.
SANDIA NATL LABS,ALBUQUERQUE,NM 87185.
RP Moeur, WA (reprint author), UNIV NEW MEXICO,DEPT PHYS & ASTRON,ALBUQUERQUE,NM 87131, USA.
NR 18
TC 42
Z9 42
U1 0
U2 2
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 MAR 24
PY 1997
VL 78
IS 12
BP 2421
EP 2424
DI 10.1103/PhysRevLett.78.2421
PG 4
WC Physics, Multidisciplinary
SC Physics
GA WP513
UT WOS:A1997WP51300037
ER
PT J
AU Barstow, MA
Dobbie, PD
Holberg, JB
Hubeny, I
Lanz, T
AF Barstow, MA
Dobbie, PD
Holberg, JB
Hubeny, I
Lanz, T
TI Interstellar and photospheric opacity from EUV spectroscopy of DA white
dwarfs
SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
LA English
DT Article
DE stars, atmospheres; white dwarfs; ISM, general; ultraviolet, stars;
X-rays, stars
ID EXTREME ULTRAVIOLET OBSERVATIONS; MODEL STELLAR ATMOSPHERES; RADIATIVE
LEVITATION; IONIZATION; HELIUM; ABUNDANCES; G191-B2B; IRON; TELESCOPE;
HYDROGEN
AB We present a derailed analysis of the extreme-ultraviolet (EUV) spectra of 13 hydrogen-rich DA white dwarfs, observed by the Extreme Ultraviolet Explorer (EWE) satellite, paying attention to the possible sources of absorbing material along the lines of sight both in the local interstellar medium (ISM) and in the photospheres of the stars themselves. The range of interstellar column densities seen are consistent with our previous understanding of the local distribution of material. Absorption from interstellar He II is found in the direction of five stars, allowing us to measure directly the He ionization fraction and estimate, indirectly, that of H. The weighted mean ionization fractions along these fines of sight are 0.27 +/- 0.04 and 0.35 +/- 0.1 respectively. Where Hen is directly detected, the observed ionization fractions are not correlated with direction or with the volume/column density of material along the line of sight. Furthermore, the limits on the amount of HeII established in all other directions completely encompass the range of observed values. Indeed, all the data can be consistent with more or less constant He and H ionization fractions throughout the local ISM, it is clear that there is little photospheric opacity, from either He or heavier elements, in the majority of the stars we have studied. This poses further difficulties in explaining the observed division of white dwarfs into H- and He-rich groups, the temperature gap in the He-rich sequence and the detailed spectral evolution of the H-rich DA white dwarfs as they cool, A striking observational result is that our spectroscopic evidence indicates that radiative levitation effects are only important at temperatures above 50 000 K, rather than the 40 000 K suggested by broad-band photometry. There is clearly an urgent need for further theoretical work on the mechanisms that determine the photospheric composition of white dwarf stars.
C1 UNIV ARIZONA, LUNAR & PLANETARY LAB, TUCSON, AZ 85721 USA.
NASA, GODDARD SPACE FLIGHT CTR, UNIV SPACE RES ASSOC, GREENBELT, MD 20771 USA.
RP Barstow, MA (reprint author), UNIV LEICESTER, DEPT PHYS & ASTRON, UNIV RD, LEICESTER LE1 7RH, LEICS, ENGLAND.
NR 48
TC 62
Z9 62
U1 0
U2 1
PU BLACKWELL SCIENCE LTD
PI OXFORD
PA P O BOX 88, OSNEY MEAD, OXFORD, OXON, ENGLAND OX2 0NE
SN 0035-8711
J9 MON NOT R ASTRON SOC
JI Mon. Not. Roy. Astron. Soc.
PD MAR 21
PY 1997
VL 286
IS 1
BP 58
EP 76
PG 19
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WR361
UT WOS:A1997WR36100009
ER
PT J
AU Atlas, D
AF Atlas, D
TI Budgetary foul weather
SO SCIENCE
LA English
DT Editorial Material
C1 AMER METEOROL SOC,BOSTON,MA 02108.
RP Atlas, D (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA.
NR 0
TC 0
Z9 0
U1 0
U2 0
PU AMER ASSOC ADVANCEMENT SCIENCE
PI WASHINGTON
PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005
SN 0036-8075
J9 SCIENCE
JI Science
PD MAR 21
PY 1997
VL 275
IS 5307
BP 1719
EP 1719
DI 10.1126/science.275.5307.1719
PG 1
WC Multidisciplinary Sciences
SC Science & Technology - Other Topics
GA WP056
UT WOS:A1997WP05600001
ER
PT J
AU Valero, FPJ
Collins, WD
Pilewskie, P
Bucholtz, A
Flatau, PJ
AF Valero, FPJ
Collins, WD
Pilewskie, P
Bucholtz, A
Flatau, PJ
TI Direct radiometric observations of the water vapor greenhouse effect
over the equatorial Pacific ocean
SO SCIENCE
LA English
DT Article
ID RADIATION BUDGET; TEMPERATURE; CLIMATE; SURFACE; TRENDS
AB Airborne radiometric measurements were used to determine tropospheric profiles of the clear sky greenhouse effect. At sea surface temperatures (SSTs) larger than 300 kelvin, the clear sky water vapor greenhouse effect was found to increase with SST at a rate of 13 to 15 watts per square meter per kelvin. Satellite measurements of infrared radiances and SSTs indicate that almost 52 percent of the tropical oceans between 20 degrees N and 20 degrees S are affected during all seasons. Current general circulation models suggest that the increase in the clear sky water vapor greenhouse effect with SST may have climatic effects an a planetary scale.
C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035.
RP Valero, FPJ (reprint author), UNIV CALIF SAN DIEGO,SCRIPPS INST OCEANOG,CTR ATMOSPHER SCI,ATMOSPHER RES LAB,9500 GILMAN DR,SAN DIEGO,CA 92093, USA.
RI Collins, William/J-3147-2014; Flatau, Piotr/E-2219-2011
OI Collins, William/0000-0002-4463-9848;
NR 22
TC 8
Z9 8
U1 0
U2 2
PU AMER ASSOC ADVANCEMENT SCIENCE
PI WASHINGTON
PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005
SN 0036-8075
J9 SCIENCE
JI Science
PD MAR 21
PY 1997
VL 275
IS 5307
BP 1773
EP 1776
DI 10.1126/science.275.5307.1773
PG 4
WC Multidisciplinary Sciences
SC Science & Technology - Other Topics
GA WP056
UT WOS:A1997WP05600035
ER
PT J
AU Sakai, S
Madore, BF
Freedman, WL
Lauer, TR
Ajhar, EA
Baum, WA
AF Sakai, S
Madore, BF
Freedman, WL
Lauer, TR
Ajhar, EA
Baum, WA
TI Detection of the tip of the red giant branch in NGC 3379 (M105) in the
Leo I Group using the Hubble Space Telescope
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE galaxies, distances and redshifts; galaxies, individual (M105);
galaxies, stellar constant; stars, AGB and post-AGB
ID SURFACE-BRIGHTNESS FLUCTUATIONS; MEASURING EXTRAGALACTIC DISTANCES;
ELLIPTICAL GALAXIES; GLOBULAR-CLUSTERS; PLANETARY-NEBULAE; RESOLVED
GALAXIES; STANDARD CANDLES; VIRGO CLUSTER; PHOTOMETRY; LUMINOSITY
AB We report the detection of individually resolved stars in the elliptical galaxy NGC 3379, a luminous member of the Leo I Group. The bright end of the stellar luminosity function has a logarithmic slope that is consistent with these stars being Population II red giants. An abrupt discontinuity in the apparent luminosity function at I = 26.30 +/- 0.09 mag is identified with the tip of the first-ascent red giant branch (TRGB). Adopting M(I)(TRGB)= -4.0 +/- 0.1 mag gives a distance modulus of 30.30 mag +/- 0.14 (random errors) +/- 0.23 (systematic errors) corresponding to a linear distance to NGC 3379 of 11.5 +/- 1.6 Mpc. The TRGB distance compares very well with the Cepheid distance of 11.9 +/- 0.9 Mpc (30.37 +/- 0.16 mag) to another group member M96 (= NGC 3368). The distance to NGC 3379 can be used in turn to calibrate the zero points of four other distance indicators: surface brightness fluctuations, planetary nebula luminosity functions, globular cluster luminosity functions and the D-n - sigma method. We apply two approaches to measuring the Hubble constant: (1) using a simple Virgocentric infall model and (2) stepping out from Leo I to the Coma cluster using the previously measured relative distance between the two clusters. These give values of the Hubble constant in the range H-0 = 60-68 km s(-1) Mpc(-1), each having a 20% uncertainty. The largest systematic errors could potentially increase this value to H-0 = 74 +/- 14 km s(-1) Mpc(-1).
C1 CALTECH,CTR INFRARED PROC & ANAL,NASA,IPAC EXTRAGALACT DATABASE,PASADENA,CA 91125.
OBSERV CARNEGIE INST WASHINGTON,PASADENA,CA 91101.
NATL OPT ASTRON OBSERV,TUCSON,AZ 85726.
UNIV WASHINGTON,DEPT ASTRON,SEATTLE,WA 98195.
RP Sakai, S (reprint author), CALTECH,JET PROP LAB,MS 100-22,PASADENA,CA 91125, USA.
NR 54
TC 36
Z9 36
U1 0
U2 0
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD MAR 20
PY 1997
VL 478
IS 1
BP 49
EP &
DI 10.1086/303768
PN 1
PG 10
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WN497
UT WOS:A1997WN49700006
ER
PT J
AU Pence, WD
Rots, AH
AF Pence, WD
Rots, AH
TI X-ray properties of the NGC 1961 group of galaxies
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE galaxies, clusters, individual (NGC 1961); galaxies, individual (NGC
1961); intergalactic medium; X-rays, galaxies
ID DARK-MATTER; ROSAT; EMISSION
AB We present an analysis of the ROSAT observations of the massive spiral galaxy NGC 1961 and surrounding small group of spiral galaxies. Contrary to the earlier Einstein observation which suggested that the X-ray emission comes mainly from an are-shaped region on one side of NGC 1961, the ROSAT observations show that the X-ray emission is fairly typical for a spiral galaxy and comes mainly from the starburst nucleus with some contribution from the surrounding spiral arm regions. The total X-ray flux of 5.1 x 10(40) ergs s(-1) is normal, but the spectrum has an unusually narrow peak at 0.9 keV that can only be fit by models that have high absorption and low characteristic temperatures. A nearby bright X-ray source (L(X) = 1.7 x 10(40) ergs s(-1)) at a projected distance of 44 kpc from NGC 1961 has no optical or radio counterpart and may be an example of the rare high-luminosity X-ray sources seen in a few other galaxies.
There is no detectable diffuse X-ray emission in this group or spiral galaxies, but this is not unexpected because recent statistical studies show that groups with a hot intragroup medium (IGM) tend to have a higher velocity dispersion and contain a large fraction of elliptical and SO galaxies. If there is a substantial IGM in this group, as is suggested by the head-tail distribution of H I gas around NGC 1961, then it must be cooler than approximate to 0.3 keV and thus invisible to the ROSAT detectors.
C1 NASA,GODDARD SPACE FLIGHT CTR,UNIV SPACE RES ASSOC,GREENBELT,MD 20771.
RP Pence, WD (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 662,GREENBELT,MD 20771, USA.
NR 26
TC 6
Z9 6
U1 0
U2 0
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD MAR 20
PY 1997
VL 478
IS 1
BP 107
EP 111
DI 10.1086/303758
PN 1
PG 5
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WN497
UT WOS:A1997WN49700013
ER
PT J
AU Hunter, DA
Light, RM
Holtzman, JA
Lynds, R
ONeil, EJ
Grillmair, CJ
AF Hunter, DA
Light, RM
Holtzman, JA
Lynds, R
ONeil, EJ
Grillmair, CJ
TI The intermediate-mass stellar population of the large magellanic cloud
cluster NGC 1818 and the universality of the stellar initial mass
function
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE galaxies, star clusters; Magellanic Clouds; stars, luminosity function,
mass function
ID STAR-CLUSTERS; OB ASSOCIATIONS; LMC CLUSTERS; AGE; LUMINOSITY; IMAGES
AB We present stellar photometry from Hubble Space Telescope images of NGC 1818, a young populous star cluster in the Large Magellanic Cloud. The cluster stars in both the core and the outlying regions are well resolved, and the photometry extends to a V magnitude of 26, corresponding approximately to a K4 V star. With the use of isochrones, we compute a stellar initial mass function (IMF) for stars from 0.85 to 9 M.. The slope of the mass function is -1.23 +/- 0.08, which is close to the Salpeter (1955) slope of -1.35. The NGC 1818 star cluster represents a star forming event intermediate between that of open clusters and of globular clusters in terms of the mass of stars formed and their spatial concentration. The products of the star forming event itself, as a diagnostic of the physical processes, indicate that star formation in NGC 1818 proceeded in a manner similar to that in events that are both less and more concentrated or rich in stars. We compare IMF slopes that have been measured from star counts in clusters and associations in Local Group galaxies, and we conclude that for young stellar clusters and associations the IMF is independent of the spatial concentration of the stars formed, the richness of stars formed, galactic characteristics including metallicity, and, at least down to 0.85 M., the stellar mass range.
C1 CALTECH,IPAC,PASADENA,CA 91125.
NEW MEXICO STATE UNIV,DEPT ASTRON,LAS CRUCES,NM 88003.
NATL OPT ASTRON OBSERV,KITT PEAK NATL OBSERV,TUCSON,AZ 85726.
CALTECH,JET PROP LAB,PASADENA,CA 91109.
RP Hunter, DA (reprint author), LOWELL OBSERV,1400 W MARS HILL RD,FLAGSTAFF,AZ 86001, USA.
NR 46
TC 60
Z9 60
U1 0
U2 0
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD MAR 20
PY 1997
VL 478
IS 1
BP 124
EP &
DI 10.1086/303790
PN 1
PG 12
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WN497
UT WOS:A1997WN49700015
ER
PT J
AU Afflerbach, A
Churchwell, E
Werner, MW
AF Afflerbach, A
Churchwell, E
Werner, MW
TI Galactic abundance gradients from infrared fine-structure lines in
compact H II regions
SO ASTROPHYSICAL JOURNAL
LA English
DT Review
DE Galaxy, abundances; H II regions; infrared, ISM, lines and bands; ISM,
abundances
ID GUIDE STAR CATALOG; CHEMICAL EVOLUTION; SPIRAL GALAXIES; CONTINUUM
OBSERVATIONS; ELECTRON TEMPERATURES; PHYSICAL-PROPERTIES; IONIZED-GAS;
O-III; VLA; EXCITATION
AB We present new observations of the [S III] 19 mu m, [O III] 52 and 88 mu m, and [N III] 57 mu m lines toward 18 compact and ultracompact (UC) H II regions. These data were combined with data from the literature and high-resolution radio continuum maps to construct detailed statistical equilibrium and ionization equilibrium models of 34 compact H II regions located at galactocentric distances (D-G) 0-12 kpc. Our models simultaneously fitted the observed IR fine-structure lines and high-resolution radio continuum maps. Abundance gradients are found of the form [S/H] = (-4.45 +/- 0.04) - (0.063 +/- 0.006) D-G (kpc), [N/H] = (- 3.58 +/- 0.04) - (0.072 +/- 0.006) D-G (kpc), and [O/H] = (-2.85 +/- 0.06) - (0.064 +/- 0.009) D-G (kpc), and we derive T-e = (4560 +/- 220) + (390 +/- 40) D-G (kpc). The T-e gradient is consistent with the T-e gradient determined independently via radio recombination lines (Afflerbach el at). We observe no dependence of S/O, N/O, or T-eff on D-G. Gradients in N++/O++ and O++/S++ fare observed in the sense of increasing ionization with increasing D-G. This is entirely consistent with the decreased line blanketing with increasing D-G required by the above abundance gradients. All three gradients are best fitted by a linear dependence on D-G. The abundances are consistent with production of sulfur, nitrogen, and oxygen by primary nucleosynthesis. Comparison with abundances in other galaxies implies a Hubble type between Sab and Sb for our Galaxy and an unbarred or mixed galactic structure (Vila-Costas & Edmunds). Our derived T-eff is 2000-10,000 K lower than T-eff expected from ZAMS stars of the same Lyman continuum flux (Panagia; Vacca et al.), probably owing to uncertainties in the UV flux of stellar models for E greater than or equal to 35.1 eV, uncertainties in the luminnosty-T-eff calibration, and/or ionization of H II regions by multiple stars in some sources.
C1 CALTECH,JET PROP LAB,PASADENA,CA 91109.
RP Afflerbach, A (reprint author), UNIV WISCONSIN,DEPT ASTRON,475 N CHARTER ST,MADISON,WI 53706, USA.
NR 103
TC 150
Z9 150
U1 0
U2 0
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD MAR 20
PY 1997
VL 478
IS 1
BP 190
EP 205
DI 10.1086/303771
PN 1
PG 16
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WN497
UT WOS:A1997WN49700021
ER
PT J
AU Mori, M
AF Mori, M
TI The Galactic diffuse gamma-ray spectrum from cosmic-ray proton
interactions
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE cosmic rays; diffuse radiation; gamma rays, theory; ISM, general
ID TOTAL CROSS-SECTIONS; HELIUM SPECTRA; GEV-C; ENERGY; PROPAGATION;
MODULATION; RADIATION; NEUTRINOS; GALAXY; MODEL
AB A new calculation of the Galactic diffuse gamma-ray spectrum from the decay of secondary particles produced by interactions of cosmic-ray protons with interstellar matter is presented. The calculation utilizes the modern Monte Carlo event generators, HADRIN, FRITIOF, and PYTHIA, which simulate high-energy proton-proton collisions and are widely used in studies of nuclear and particle physics, in addition to scaling calculation. This study is motivated by the result on the Galactic diffuse gamma-ray flux observed by the EGRET detector on the Compton Gamma-ray Observatory, which indicates an excess above about 1 GeV of the observed intensity compared with a model prediction. The prediction is based on cosmic-ray interactions with interstellar matter, in which secondary pion productions are treated by a simple model. With the improved interaction model used here, however, the diffuse gamma-ray flux agrees rather well with previous calculations within uncertainties, which mainly come from the unobservable demodulated cosmic-ray spectrum in interstellar space. As a possible solution to the excess flux, flatter spectra of cosmic-ray protons have been tested, and we found that the power-law spectrum with an index of about -(2.4 to 2.5) gives a better fit to the EGRET data, although the spectrum is not explained completely.
RP Mori, M (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771, USA.
NR 46
TC 111
Z9 111
U1 0
U2 0
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD MAR 20
PY 1997
VL 478
IS 1
BP 225
EP 232
DI 10.1086/303785
PN 1
PG 8
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WN497
UT WOS:A1997WN49700024
ER
PT J
AU SteimanCameron, TY
Haas, MR
Tielens, AGGM
Burton, MG
AF SteimanCameron, TY
Haas, MR
Tielens, AGGM
Burton, MG
TI Physical conditions in the photodissociation region of NGC 2023
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE infrared, ISM, lines and bands; ISM, individual (NGC 2023); ISM,
molecules; reflection nebulae
ID FLUORESCENT MOLECULAR-HYDROGEN; REFLECTION NEBULA NGC-2023; M17 NORTHERN
BAR; INTERSTELLAR GAS; LINE EMISSION; RESOLUTION OBSERVATIONS;
ULTRAVIOLET-RADIATION; MICRON EMISSION; CHEMICAL-MODELS; STAR FORMATION
AB Observations of the far-infrared fine-structure emission lines of [O I] (63, 146 mu m), [C II] (158 mu m), and [Si II] (35 mu m) and the adjacent continua were obtained for the reflection nebula NGC 2023 with the Cryogenic Grating Spectrometer aboard the Kuiper Airborne Observatory. These fine-structure lines originate from a warm, atomic photodissociation region (PDR), where gas has been heated by the illuminating star HD 37903. The measured line and continuum intensities were combined with [C II] and CO observations from the literature to estimate the density and temperature of the PDR. Simple analysis indicates densities of similar to 2 x 10(4) cm(-3) and temperatures around 400 K for the emitting gas.
Detailed models of the PDR in NGC 2023 have also been constructed. Comparisons between observed and predicted line strengths demonstrate that considerable density enhancements (clumps) exist throughout the PDR. A two-component model of dense (total hydrogen density = 10(5) cm(-3)) warm (approximate to 750 K) clumps with a beam area filling factor of 0.11 embedded in a diffuse (750 cm(-3)) cooler (approximate to 250 K) halo is in good agreement with the observations.
C1 UNIV NEW S WALES,SCH PHYS,SYDNEY,NSW 2052,AUSTRALIA.
RP SteimanCameron, TY (reprint author), NASA,AMES RES CTR,MS245-3,MOFFETT FIELD,CA 94035, USA.
OI Burton, Michael/0000-0001-7289-1998
NR 71
TC 34
Z9 34
U1 0
U2 0
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD MAR 20
PY 1997
VL 478
IS 1
BP 261
EP 270
PN 1
PG 10
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WN497
UT WOS:A1997WN49700027
ER
PT J
AU Canuto, VM
AF Canuto, VM
TI Sub-grid scale modeling: Correct models and others
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE convection; methods, numerical; stars, interiors; turbulence
ID CONVECTION; TURBULENCE; FLOWS
AB One approach to studying turbulent convection in stars is through the use of large computers with a technique called Large Eddy Simulation (LES). Since no computer presently available, or even projected in the foreseeable future, can resolve all of the scales that characterize a fully developed turbulent flow, the LES technique resolves the largest scales, while it models the ''unresolved'' scales with a sub-grid scale (SGS) model. In the astrophysical literature, two such models have been used.
It is the purpose of this paper to show that the first of the SGS models (1) contradicts Galilei invariance, (2) employs an incorrect timescale (Eulerian instead of Lagrangean), (3) contradicts the Kolmogorov inertial law and the Richardson diffusion law, (4) misinterprets dynamical and kinematic effects, and (5), from the numerical view point, gives rise to a turbulent viscosity much larger than it ought to be.
The second SGS model has none of the above problems, the only shortcoming being its incompleteness, since it was originally devised for shear rather than buoyancy dominated flows. Thus, it must be improved-a process that present knowledge of turbulence allows us to carry out quite systematically.
In conclusion, the first SGS should be avoided, while the second should be used and improved.
RP Canuto, VM (reprint author), NASA,GODDARD INST SPACE STUDIES,2880 BROADWAY,NEW YORK,NY 10025, USA.
NR 31
TC 10
Z9 10
U1 0
U2 1
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD MAR 20
PY 1997
VL 478
IS 1
BP 322
EP 325
DI 10.1086/303772
PN 1
PG 4
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WN497
UT WOS:A1997WN49700032
ER
PT J
AU Pasquali, A
Langer, N
Schmutz, W
Leitherer, C
Nota, A
Hubeny, I
Moffat, AFJ
AF Pasquali, A
Langer, N
Schmutz, W
Leitherer, C
Nota, A
Hubeny, I
Moffat, AFJ
TI O stars in transition .2. Fundamental properties and evolutionary status
of Ofpe/WN9 stars from Hubble Space Telescope ultraviolet observations
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE stars, early-type; stars, evolution; stars, mass loss; stars,
Wolf-Rayet; ultraviolet
ID WOLF-RAYET STARS; LARGE MAGELLANIC CLOUD; RADIATION-DRIVEN WINDS;
INTER-STELLAR EXTINCTION; EMISSION-LINE STARS; HOT LUMINOUS STARS;
MASS-LOSS RATES; INFRARED-SPECTROSCOPY; SPECTRAL ANALYSES;
GALACTIC-CENTER
AB We present new HST/FOS ultraviolet spectroscopic observations of seven LMC Ofpe/WN9 stars, We find that Ofpe/WN9) stars have slow winds with terminal velocities of about 400 ism s(-1) and high mass-loss rates of the order of 2-5 x 10(-5) M. yr(-1). Ofpe/WN9 stellar temperatures and radii are in the range 30,000-39,000 It, and 19-39 R., respectively. Stellar luminosities are between log (L/L.) = 5.6 and 6.3.
We study the Ofpe/WN9 stars winds and examine their evolutionary status. We find that Ofpe/WN9 stars are intermediate between O and W-R stars in terms of the wind momentum flux. We also find. that the stellar properties and wind momentum of the Ofpe/WN9 sample place them in the evolutionary sequence: O --> Of --> H-rich WNL --> Ofpe/WN9, for initial stellar masses less than similar to 100 M..
In view of persisting discrepancies of standard massive star models with observations, we compute massive main-sequence models according to three different evolutionary scenarios. We find that both higher mass-loss rate and enhanced mixing between core and envelope are required in order to yield models compatible with the derived stellar and wind properties of Ofpe/WN9 stars. The emerging picture may be consistent with earlier evidence of Ofpe/WN9 stars being quiescent luminous blue variables (LBVs). This idea is further strengthened by the highly reduced surface H mass fractions of the Ofpe/WN9 stars. We derive X(s) = 0.5 to 0.3, which still excludes Ofpe/WN9 stars from being core He-burning objects, but is almost identical to the X(s) values recently measured in LBVs.
C1 MAX PLANCK INST ASTROPHYS,D-85740 GARCHING,GERMANY.
ETH ZENTRUM,INST ASTRON,CH-8092 ZURICH,SWITZERLAND.
NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771.
UNIV MONTREAL,DEPT PHYS,MONTREAL,PQ H3C 3J7,CANADA.
EUROPEAN SPACE AGCY,DEPT SPACE SCI,DIV ASTROPHYS,F-75738 PARIS 15,FRANCE.
RP Pasquali, A (reprint author), SPACE TELESCOPE SCI INST,3700 SAN MARTIN DR,BALTIMORE,MD 21218, USA.
RI Schmutz, Werner/B-4153-2014
OI Schmutz, Werner/0000-0003-1159-5639
NR 86
TC 45
Z9 45
U1 0
U2 0
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD MAR 20
PY 1997
VL 478
IS 1
BP 340
EP 357
DI 10.1086/303767
PN 1
PG 18
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WN497
UT WOS:A1997WN49700035
ER
PT J
AU Brage, T
Hibbert, A
Leckrone, DS
AF Brage, T
Hibbert, A
Leckrone, DS
TI Transition rates of the intercombination UV0.01 multiplet in N II
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE atomic data
ID SINGLY-IONIZED NITROGEN; OSCILLATOR-STRENGTHS; ALLOWED TRANSITIONS;
FORBIDDEN LINES; C-III; O-III; SPECTRUM; PROBABILITIES; PROGRAM; RATIOS
AB The transition rates of the intercombination lines 2s2p(3 5)S(2)(0)-->2s(2)2p(2 3)P(1,2) are computed using a systematic configuration interaction method (SCIV3). The calculated lifetime of the upper S-5(2)o, level is in excellent agreement with a recent experiment. The branching ratio of the two lines is very different from earlier, less accurate theoretical values.
C1 QUEENS UNIV BELFAST,DEPT APPL MATH & THEORET PHYS,BELFAST BT7 1NN,ANTRIM,NORTH IRELAND.
NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771.
RP Brage, T (reprint author), NASA,GODDARD SPACE FLIGHT CTR,COMP SCI CORP,CODE 681,GREENBELT,MD 20771, USA.
OI Brage, Tomas/0000-0003-3985-767X
NR 37
TC 22
Z9 22
U1 0
U2 0
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD MAR 20
PY 1997
VL 478
IS 1
BP 423
EP 429
DI 10.1086/303777
PN 1
PG 7
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WN497
UT WOS:A1997WN49700043
ER
PT J
AU Inman, CA
Cheng, ES
Cottingham, DA
Fixsen, DJ
Kowitt, MS
Meyer, SS
Page, LA
Puchalla, JL
Ruhl, JE
Silverberg, RF
AF Inman, CA
Cheng, ES
Cottingham, DA
Fixsen, DJ
Kowitt, MS
Meyer, SS
Page, LA
Puchalla, JL
Ruhl, JE
Silverberg, RF
TI A cosmic microwave background radiation measurement reproduced: A
statistical comparison of MSAM1-94 to MSAM1-92
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE balloons; cosmic microwave background; cosmology, observations
ID ANISOTROPY
AB The goal of the second flight of the medium-scale anisotropy measurement (MSAM1-94) was to confirm the measurement of cosmic microwave background radiation (CMBR) anisotropy made in the first flight (MSAM1-92). The CMBR anisotropy and interstellar dust emission signals from the two flights are compared by forming the sum and difference of those portions of the data with the same pointings on the sky. The difference data are consistent with a null detection, while the summed data show significant signal. We conclude that MSAM1-92 and MSAM1-94 measured the same celestial signal.
C1 NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GLOBAL SCI & TECHNOL INC,GREENBELT,MD 20771.
NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,APPL RES CORP,GREENBELT,MD 20771.
PRINCETON UNIV,DEPT PHYS,PRINCETON,NJ 08544.
UNIV CALIF SANTA BARBARA,DEPT PHYS,SANTA BARBARA,CA 93106.
RP Inman, CA (reprint author), UNIV CHICAGO,5640 S ELLIS ST,CHICAGO,IL 60637, USA.
NR 12
TC 13
Z9 13
U1 0
U2 0
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD MAR 20
PY 1997
VL 478
IS 1
BP L1
EP L4
DI 10.1086/310537
PN 2
PG 4
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WN500
UT WOS:A1997WN50000001
ER
PT J
AU Chauhan, NS
AF Chauhan, NS
TI Soil moisture estimation under a vegetation cover: Combined active
passive microwave remote sensing approach
SO INTERNATIONAL JOURNAL OF REMOTE SENSING
LA English
DT Article
ID EMISSION; MODEL; PROPAGATION
AB Data gathered during the NASA sponsored Multisensor Aircraft Campaign Hydrology (MACHYDRO) experiment in central Pennsylvania (U.S.A.) in July, 1990 have been analysed to study the combined use of active and passive microwave sensors for estimating soil moisture from vegetated areas. These data sets were obtained during an eleven-day period with NASA's Airborne Synthetic Aperture Radar (AIRSAR), and Push-Broom Microwave Radiometer (PBMR) over an instrumented watershed, which included agricultural fields with a number of different crop covers. Simultaneous ground truth measurements were also made in order to characterize the state of vegetation and soil moisture under a variety of meteorological conditions. Various multi-sensor techniques are currently under investigation to improve the accuracy of remote sensing estimates of the soil moisture in the presence of vegetation and surface roughness conditions using these data sets. One such algorithm involving combination of active and passive microwave sensors is presented here, and is applied to representative corn fields in the Mahantango watershed that was the focus of study during the MACHYDRO experiment. In this algorithm, a simple emission model is inverted to obtain Fresnel reflectivity in terms of ground and vegetation parameters. Since Fresnel reflectivity depends on soil dielectric constant, soil moisture is determined from reflectivity using dielectric-soil moisture relations. The algorithm requires brightness temperature, vegetation and ground parameters as the input parameters. The former is measured by a passive microwave technique and the later two are estimated by using active microwave techniques. The soil moisture estimates obtained by this combined use of active and passive microwave remote sensing techniques, show an excellent agreement with the in situ soil moisture measurements made during the MACHYDRO experiment.
RP Chauhan, NS (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GWU,BIOSPHER SCI BRANCH,GREENBELT,MD 20771, USA.
NR 29
TC 26
Z9 29
U1 1
U2 4
PU TAYLOR & FRANCIS LTD
PI LONDON
PA ONE GUNPOWDER SQUARE, LONDON, ENGLAND EC4A 3DE
SN 0143-1161
J9 INT J REMOTE SENS
JI Int. J. Remote Sens.
PD MAR 20
PY 1997
VL 18
IS 5
BP 1079
EP 1097
DI 10.1080/014311697218584
PG 19
WC Remote Sensing; Imaging Science & Photographic Technology
SC Remote Sensing; Imaging Science & Photographic Technology
GA WN949
UT WOS:A1997WN94900006
ER
PT J
AU Ciais, P
Denning, AS
Tans, PP
Berry, JA
Randall, DA
Collatz, GJ
Sellers, PJ
White, JWC
Trolier, M
Meijer, HAJ
Francey, RJ
Monfray, P
Heimann, M
AF Ciais, P
Denning, AS
Tans, PP
Berry, JA
Randall, DA
Collatz, GJ
Sellers, PJ
White, JWC
Trolier, M
Meijer, HAJ
Francey, RJ
Monfray, P
Heimann, M
TI A three-dimensional synthesis study of delta O-18 in atmospheric CO2 .1.
Surface fluxes
SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
LA English
DT Article
ID GENERAL-CIRCULATION MODEL; ISOTOPIC COMPOSITION; BOUNDARY-LAYER;
STOMATAL CONDUCTANCE; SPATIAL VARIATION; CARBON-DIOXIDE; WATER-VAPOR;
OXYGEN; O-18; FRACTIONATION
AB The isotope O-18 in CO2 is of particular interest in studying the global carbon cycle because it is sensitive to the processes by which the global land biosphere absorbs and respires CO2. Carbon dioxide and water exchange isotopically both in leaves and in soils, and the O-18 character of atmospheric CO2 is strongly influenced by the land biota, which should constrain the gross primary productivity and total respiration of land ecosystems, In this study we calculate the global surface fluxes of O-18 for vegetation and soils using the SiB2 biosphere model coupled with the Colorado State University general circulation model. This approach makes it possible to use physiological variables that are consistently weighted by the carbon assimilation rate and integrated through the vegetation canopy, We also calculate the air-sea exchange of O-18 and the isotopic character of fossil emissions and biomass burning. Global mean values of the isotopic exchange with each reservoir are used to close the global budget of O-18 in CO2 results confirm the fact that the land biota exert a dominant control on the delta(18)O of the atmospheric reservoir, At the global scale, exchange with the canopy produces an isotopic enrichment of CO2, whereas exchange with soils has the opposite effect.
C1 CARNEGIE INST WASHINGTON, DEPT PLANT BIOL, STANFORD, CA 94305 USA.
NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA.
COLORADO STATE UNIV, DEPT ATMOSPHER SCI, FT COLLINS, CO 80523 USA.
CSIRO, DIV ATMOSPHER RES, MELBOURNE, VIC 3195, AUSTRALIA.
MAX PLANCK INST METEOROL, D-20146 HAMBURG, GERMANY.
UNIV GRONINGEN, CIO, NL-9722 JX GRONINGEN, NETHERLANDS.
CTR FAIBLES RADIOACT, LMCE, F-91191 GIF SUR YVETTE, FRANCE.
UNIV COLORADO, INST ARCTIC & ALPINE RES, BOULDER, CO 80303 USA.
NOAA, ERL 3, CLIMATE MONITORING & DIAGNOST LAB, BOULDER, CO 80303 USA.
RP Ciais, P (reprint author), CEA ORME MERISIERS, LMCE, COMMISSARIAT ENERGIE ATOM, BATIMENT 709, F-91191 GIF SUR YVETTE, FRANCE.
RI Berry, Joseph/B-8211-2009; White, James/A-7845-2009; Meijer,
Harro/A-5787-2012; collatz, george/D-5381-2012; Denning,
Scott/F-4974-2011; Randall, David/E-6113-2011; Heimann,
Martin/H-7807-2016
OI Berry, Joseph/0000-0002-5849-6438; White, James/0000-0001-6041-4684;
Denning, Scott/0000-0003-3032-7875; Randall, David/0000-0001-6935-4112;
Heimann, Martin/0000-0001-6296-5113
NR 64
TC 156
Z9 162
U1 4
U2 19
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA
SN 2169-897X
J9 J GEOPHYS RES-ATMOS
JI J. Geophys. Res.-Atmos.
PD MAR 20
PY 1997
VL 102
IS D5
BP 5857
EP 5872
DI 10.1029/96JD02360
PG 16
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA WQ021
UT WOS:A1997WQ02100001
ER
PT J
AU Ciais, P
Tans, PP
Denning, AS
Francey, RJ
Trolier, M
Meijer, HAJ
White, JWC
Berry, JA
Randall, DA
Collatz, GJ
Sellers, PJ
Monfray, P
Heimann, M
AF Ciais, P
Tans, PP
Denning, AS
Francey, RJ
Trolier, M
Meijer, HAJ
White, JWC
Berry, JA
Randall, DA
Collatz, GJ
Sellers, PJ
Monfray, P
Heimann, M
TI A three-dimensional synthesis study of delta O-18 in atmospheric CO2 .2.
Simulations with the TM2 transport model
SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
LA English
DT Article
ID CARBON-DIOXIDE; EXCHANGE
AB In this study, using a three-dimensional (3-D) tracer modeling approach, we simulate the delta(18)O of atmospheric CO2. In the atmospheric transport model TM2 we prescribe the surface fluxes of O-18 due to vegetation and soils, ocean exchange, fossil emissions, and biomass burning. The model simulations are first discussed for each reservoir separately, then all the reservoirs are combined to allow a comparison with the atmospheric delta(18)O measurements made by the National Oceanic and Atmospheric Administration-University of Colorado, Scripps Institution of Oceanography-Centrum Voor Isotopen Onderzoek (United States-Netherlands) and Commonwealth Scientific and Industrial Research Organisation (Australia) air sampling programs, Insights into the latitudinal differences and into the seasonal cycle of delta(18)O in CO2 are gained by looking at the contribution of each source, The isotopic exchange with soils induces a large isotopic depletion over the northern hemisphere continents, which overcomes the concurrent effect of isotopic enrichment due to leaf exchange, Compared to the land biota, the ocean fluxes and the anthropogenic CO2 source have a relatively minor influence, The shape of the latitudinal profile in delta(18)O appears determined primarily by the respiration of the land biota, which balances photosynthetic uptake over the course of a year, Additional information on the phasing of the terrestrial carbon exchange comes from the seasonal cycle of delta(18)O at high northern latitudes.
C1 CARNEGIE INST WASHINGTON, DEPT PLANT BIOL, STANFORD, CA 94305 USA.
NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA.
COLORADO STATE UNIV, DEPT ATMOSPHER SCI, FT COLLINS, CO 80523 USA.
CSIRO, DIV ATMOSPHER RES, MELBOURNE, VIC 3195, AUSTRALIA.
MAX PLANCK INST METEOROL, D-20146 HAMBURG, GERMANY.
UNIV GRONINGEN, CIO, NL-9722 JX GRONINGEN, NETHERLANDS.
CTR FAIBLES RADIOACT, LMCE, F-91191 GIF SUR YVETTE, FRANCE.
NOAA, ERL 3, CLIMATE MONITORING & DIAGNOST LAB, BOULDER, CO 80303 USA.
UNIV COLORADO, INST ARCTIC & ALPINE RES, BOULDER, CO 80303 USA.
RP Ciais, P (reprint author), CEA ORME MERISIERS, LMCE, BATIMENT 709, F-91191 GIF SUR YVETTE, FRANCE.
RI White, James/A-7845-2009; Meijer, Harro/A-5787-2012; Berry,
Joseph/B-8211-2009; collatz, george/D-5381-2012; Denning,
Scott/F-4974-2011; Randall, David/E-6113-2011; Heimann,
Martin/H-7807-2016
OI White, James/0000-0001-6041-4684; Berry, Joseph/0000-0002-5849-6438;
Denning, Scott/0000-0003-3032-7875; Randall, David/0000-0001-6935-4112;
Heimann, Martin/0000-0001-6296-5113
NR 24
TC 59
Z9 60
U1 1
U2 12
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA
SN 2169-897X
J9 J GEOPHYS RES-ATMOS
JI J. Geophys. Res.-Atmos.
PD MAR 20
PY 1997
VL 102
IS D5
BP 5873
EP 5883
DI 10.1029/96JD02361
PG 11
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA WQ021
UT WOS:A1997WQ02100002
ER
PT J
AU Jacob, DJ
Prather, MJ
Rasch, PJ
Shia, RL
Balkanski, YJ
Beagley, SR
Bergmann, DJ
Blackshear, WT
Brown, M
Chiba, M
Chipperfield, MP
deGrandpre, J
Dignon, JE
Feichter, J
Genthon, C
Grose, WL
Kasibhatla, PS
Kohler, I
Kritz, MA
Law, K
Penner, JE
Ramonet, M
Reeves, CE
Rotman, DA
Stockwell, DZ
VanVelthoven, PFJ
Verver, G
Wild, O
Yang, H
Zimmermann, P
AF Jacob, DJ
Prather, MJ
Rasch, PJ
Shia, RL
Balkanski, YJ
Beagley, SR
Bergmann, DJ
Blackshear, WT
Brown, M
Chiba, M
Chipperfield, MP
deGrandpre, J
Dignon, JE
Feichter, J
Genthon, C
Grose, WL
Kasibhatla, PS
Kohler, I
Kritz, MA
Law, K
Penner, JE
Ramonet, M
Reeves, CE
Rotman, DA
Stockwell, DZ
VanVelthoven, PFJ
Verver, G
Wild, O
Yang, H
Zimmermann, P
TI Evaluation and intercomparison of global atmospheric transport models
using Rn-222 and other short-lived tracers
SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
LA English
DT Review
ID GENERAL-CIRCULATION MODEL; ZONALLY AVERAGED CIRCULATION; TWO-DIMENSIONAL
MODEL; TROPOSPHERIC OZONE; ODD NITROGEN; 3-DIMENSIONAL SIMULATION;
NONGEOSTROPHIC THEORY; SEASONAL-VARIATION; MIDDLE ATMOSPHERE; CLIMATE
MODEL
AB Simulations of Rn-222 and other short-lived tracers are used to evaluate and intercompare the representations of convective and synoptic processes in 20 global atmospheric transport models. Results show that most established three-dimensional models simulate vertical mixing in the troposphere to within the constraints offered by the observed mean Rn-222 concentrations and that subgrid parameterization of convection is essential for this purpose. However, none of the models captures the observed variability of Rn-222 concentrations in the upper troposphere, and none reproduces the high Rn-222 concentrations measured at 200 hPa over Hawaii. The established three-dimensional models reproduce the frequency and magnitude of high- Rn-222 episodes observed at Crozet Island in the Indian Ocean, demonstrating that they can resolve the synoptic-scale transport of continental plumes with no significant numerical diffusion. Large differences between models are found in the rates of meridional transport in the upper troposphere (interhemispheric exchange, exchange between tropics and high latitudes). The four two-dimensional models which participated in the intercomparison tend to underestimate the rate of vertical transport from the lower to the upper troposphere but show concentrations of Rn-222 in the lower troposphere that are comparable to the zonal mean values in the three-dimensional models.
C1 HARVARD UNIV, DEPT EARTH & PLANETARY SCI, CAMBRIDGE, MA 02138 USA.
CEA, LAB MODELISAT CLIMAT ENVIRONNEMENT, F-91191 GIF SUR YVETTE, FRANCE.
YORK UNIV, N YORK, ON M3J 1P3, CANADA.
LAWRENCE LIVERMORE NATL LAB, LIVERMORE, CA 94550 USA.
NASA, LANGLEY RES CTR, HAMPTON, VA 23681 USA.
ACULIGHT CORP, BELLEVUE, WA 98005 USA.
METEOROL RES INST, LAB 2, DIV CLIMATE RES, TSUKUBA, IBARAKI 305, JAPAN.
UNIV CAMBRIDGE, DEPT CHEM, CAMBRIDGE CB2 1EW, ENGLAND.
MAX PLANCK INST METEOROL, D-20146 HAMBURG, GERMANY.
CNRS, LAB GLACIOL & GEOPHYS ENVIRONNEMENT, F-38402 ST MARTIN DHERES, FRANCE.
GEORGIA INST TECHNOL, SCH EARTH & ATMOSPHER SCI, ATLANTA, GA 30332 USA.
DLR OBERPFAFFENHOFEN, INST PHYS ATMOSPHARE, D-82234 WESSELING, GERMANY.
SUNY ALBANY, ATMOSPHER SCI RES CTR, ALBANY, NY 12222 USA.
UNIV CALIF IRVINE, DEPT GEOSCI, IRVINE, CA 92717 USA.
CEA, CNRS, CTR FAIBLES RADIOACTIV, F-91198 GIF SUR YVETTE, FRANCE.
NATL CTR ATMOSPHER RES, BOULDER, CO 80303 USA.
UNIV E ANGLIA, SCH ENVIRONM SCI, NORWICH NR4 7TJ, NORFOLK, ENGLAND.
ATMOSPHER & ENVIRONM RES INC, CAMBRIDGE, MA 02139 USA.
ROYAL NETHERLANDS METEOROL INST, NL-3730 AE DE BILT, NETHERLANDS.
UNIV WASHINGTON, DEPT APPL MATH, SEATTLE, WA 98195 USA.
MOGUNTIA GLOBAL MODELLING, D-65479 RAUNHEIM, GERMANY.
RP Jacob, DJ (reprint author), HARVARD UNIV, DIV APPL SCI, PIERCE HALL, 29 OXFORD ST, CAMBRIDGE, MA 02138 USA.
RI Wild, Oliver/A-4909-2009; Kasibhatla, Prasad/A-2574-2010; Bergmann,
Daniel/F-9801-2011; Chipperfield, Martyn/H-6359-2013; Penner,
Joyce/J-1719-2012; Balkanski, Yves/A-6616-2011
OI Wild, Oliver/0000-0002-6227-7035; Bergmann, Daniel/0000-0003-4357-6301;
Chipperfield, Martyn/0000-0002-6803-4149; Balkanski,
Yves/0000-0001-8241-2858
NR 121
TC 194
Z9 196
U1 2
U2 10
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA
SN 2169-897X
J9 J GEOPHYS RES-ATMOS
JI J. Geophys. Res.-Atmos.
PD MAR 20
PY 1997
VL 102
IS D5
BP 5953
EP 5970
DI 10.1029/96JD02955
PG 18
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA WQ021
UT WOS:A1997WQ02100009
ER
PT J
AU Olson, J
Prather, M
Berntsen, T
Carmichael, G
Chatfield, R
Connell, P
Derwent, R
Horowitz, L
Jin, SX
Kanakidou, M
Kasibhatla, P
Kotamarthi, R
Kuhn, M
Law, K
Penner, J
Perliski, L
Sillman, S
Stordal, F
Thompson, A
Wild, O
AF Olson, J
Prather, M
Berntsen, T
Carmichael, G
Chatfield, R
Connell, P
Derwent, R
Horowitz, L
Jin, SX
Kanakidou, M
Kasibhatla, P
Kotamarthi, R
Kuhn, M
Law, K
Penner, J
Perliski, L
Sillman, S
Stordal, F
Thompson, A
Wild, O
TI Results from the Intergovernmental Panel on Climatic Change
Photochemical Model Intercomparison (PhotoComp)
SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
LA English
DT Article
ID OH CONCENTRATIONS; OZONE PRODUCTION; ATMOSPHERE; MECHANISM; NITROGEN;
KINETICS; STRATOSPHERE; TROPOSPHERE; OXIDES; FIELD
AB Results from the Intergovernmental Panel on Climatic Change (IPCC) tropospheric photochemical model intercomparison (PhotoComp) are presented with a brief discussion of the factors that may contribute to differences in the modeled behaviors of HOx cycling and the accompanying O-3 tendencies. PhotoComp was a tightly controlled model experiment in which the IPCC 1994 assessment sought to determine the consistency among models that are used to predict changes in tropospheric ozone, an important greenhouse gas, Calculated tropospheric photodissociation rates displayed significant differences, with a root-mean-square (rms) error of the reported model results ranging from about +/-6-9% of the mean (for O-3 and NO2) to up to +/-15% (H2O2 and CH2O). Models using multistream methods in radiative transfer calculations showed distinctly higher rates for photodissociation of NO2 and CH2O compared to models using two-stream methods, and this difference accounted for up to one third of the rms error for these two rates, In general, some small but systematic differences between models were noted for the predicted chemical tendencies in cases that did not include reactions of nonmethane hydrocarbons (NMHC). These differences in modeled O-3 tendencies in some cases could be identified, for example, as being due to differences in photodissociation rates, but in others they could not and must be ascribed to unidentified errors. O-3 tendencies showed rms errors of about +/-10% in the moist, surface level cases with NOx concentrations equal to a few tens of parts per trillion by volume. Most of these model to model differences can be traced to differences in the destruction of O-3 due to reaction with HO2. Differences in HO2, in turn, are likely due to (1) inconsistent reaction rates used by the models for the conversion of HO2 to H2O2 and (2) differences in the model-calculated photolysis of H2O2 and CH2O. In the middle tropospheric ''polluted'' scenario with NOx concentrations larger than a few parts per billion by volume, O-3 tendencies showed rms errors of +/-10-30%. These model to model differences most likely stem from differences in the calculated rates of O-3 photolysis to O(D-1), which provides about 80% of the HOx source under these conditions. The introduction of hydrocarbons dramatically increased both the rate of NOx loss and its model to model differences, which, in turn, are reflected in an increased spread of predicted O-3. Including NMHC in the simulation approximately doubled the rms error for O-3 concentration.
C1 UNIV OSLO, N-1305 OSLO, NORWAY.
UNIV IOWA, IOWA CITY, IA 52240 USA.
NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA.
LAWRENCE LIVERMORE NATL LAB, LIVERMORE, CA 94550 USA.
METEOROL OFF, BRACKNELL RG12 2SZ, BERKS, ENGLAND.
HARVARD UNIV, CAMBRIDGE, MA 02138 USA.
NEW YORK STATE DEPT TRANSPORTAT, NEW YORK, NY 12232 USA.
CTR FAIBLES RADIOACT, GIF SUR YVETTE, FRANCE.
MCNC, ENVIRONM PROGRAMS, RES TRIANGLE PK, NC 27709 USA.
ATMOSPHER & ENVIRONM RES INC, CAMBRIDGE, MA 02139 USA.
FRAUNHOFER INST ATMOSPHAR UMWELTFORSCH, D-82467 GARMISCH PARTENKIRCHEN, GERMANY.
UNIV CAMBRIDGE, CAMBRIDGE CB2 1EW, ENGLAND.
NASA, LANGLEY RES CTR, HAMPTON, VA 23681 USA.
GEOPHYS FLUID DYNAM LAB, PRINCETON, NJ 08542 USA.
UNIV CALIF IRVINE, IRVINE, CA 92717 USA.
UNIV MICHIGAN, ANN ARBOR, MI 48109 USA.
NORWEGIAN INST AIR RES, N-2007 KJELLER, NORWAY.
NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA.
RP Olson, J (reprint author), NASA, LANGLEY RES CTR, HAMPTON, VA 23681 USA.
RI Wild, Oliver/A-4909-2009; Kasibhatla, Prasad/A-2574-2010; Kanakidou,
Maria/D-7882-2012; Horowitz, Larry/D-8048-2014; Garmisch-Pa,
Ifu/H-9902-2014; Thompson, Anne /C-3649-2014;
OI Wild, Oliver/0000-0002-6227-7035; Kanakidou, Maria/0000-0002-1724-9692;
Horowitz, Larry/0000-0002-5886-3314; Thompson, Anne
/0000-0002-7829-0920; Sillman, Sanford/0000-0001-6250-1191; Stordal,
Frode/0000-0002-5190-6473; Derwent, Richard/0000-0003-4498-645X;
Kasibhatla, Prasad/0000-0003-3562-3737
NR 34
TC 54
Z9 54
U1 1
U2 1
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA
SN 2169-897X
J9 J GEOPHYS RES-ATMOS
JI J. Geophys. Res.-Atmos.
PD MAR 20
PY 1997
VL 102
IS D5
BP 5979
EP 5991
DI 10.1029/96JD03380
PG 13
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA WQ021
UT WOS:A1997WQ02100011
ER
PT J
AU Glaze, LS
Baloga, SM
Wilson, L
AF Glaze, LS
Baloga, SM
Wilson, L
TI Transport of atmospheric water vapor by volcanic eruption columns
SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
LA English
DT Article
ID MOUNT ST-HELENS; EL-CHICHON; DYNAMICS; CLOUDS; STRATOSPHERE
AB Contrary to assumptions often made in the literature, explosive volcanic eruptions are capable of transporting significant amounts of water into the stratosphere. In addition to the magmatic water component, atmospheric water vapor is entrained by the column at lower levels. A theoretical model for the conservation of mass, momentum, and thermal energy of four separate components (dry air, water vapor, liquid condensates, and solid particles) is used to determine the extent of atmospheric water redistribution. We examine the effects of water vapor condensation on dynamical characteristics and ambient water vapor transport. A simple technique is presented for deriving canonical forms for the complex system of ordinary differential equations governing the column components. Solutions of this model are presented that show the influence of different volcanic boundary conditions and a range of ambient water vapor distributions on transport of the buoyant column. We show that the water component (vapor + liquid) of small eruption columns rising through a wet atmosphere is dominated by entrained water, whereas larger columns are dominated by the magmatic water. This is due, in part, to the proportionately smaller entrainment surface area in relation to the control volume for the larger columns. We also show that a maintained column with an initial mass flux of 2.7 x 10(8) kg s(-1) erupted into a wet atmosphere would inject 96 Mt of water vapor into the stratosphere over 24 hours, comparable to the annual input from methane oxidation or 100 midlatitude thunderstorms. This increase may accelerate the conversion of simultaneously erupted volcanic SO2 into sulfuric acid.
C1 UNIV LANCASTER, DIV ENVIRONM SCI, LANCASTER LA1 4YQ, ENGLAND.
PROXEMY RES INC, LAYTONSVILLE, MD USA.
RP Glaze, LS (reprint author), NASA, GODDARD SPACE FLIGHT CTR, GEODYNAM BRANCH, CODE 921, GREENBELT, MD 20771 USA.
RI Glaze, Lori/D-1314-2012
NR 42
TC 56
Z9 56
U1 0
U2 4
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA
SN 2169-897X
J9 J GEOPHYS RES-ATMOS
JI J. Geophys. Res.-Atmos.
PD MAR 20
PY 1997
VL 102
IS D5
BP 6099
EP 6108
DI 10.1029/96JD03125
PG 10
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA WQ021
UT WOS:A1997WQ02100020
ER
PT J
AU Ziemke, JR
Chandra, S
McPeters, RD
Newman, PA
AF Ziemke, JR
Chandra, S
McPeters, RD
Newman, PA
TI Dynamical proxies of column ozone with applications to global trend
models
SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
LA English
DT Article
ID QUASI-BIENNIAL OSCILLATION; TOMS DATA; STRATOSPHERE; TEMPERATURE;
CIRCULATION; DEPLETION; SPACE
AB Previous regression trend models for total column ozone have included only the quasi-biennial oscillation (QBO) winds and the El Nino Southern Oscillation (ENSO) ocean surface pressure as dynamical proxies, Trends derived from these regression models generally differ (are more negative) from two-dimensional (2-D) chemical transport trends by about 2-5% decade(-1) in midlatitudes during spring, The present study introduces additional dynamical proxies of total ozone in regression models in an effort to reduce errors in local ozone trends and reduce these model differences, Nimbus 7 total ozone mapping spectrometer (TOMS) version 7 total column ozone for 1979-1992 are used in conjunction with analyses from National Centers for Environmental Prediction (NCEP, formerly National Meteorological Center), Dynamical proxies investigated include winds (including diabatic winds), relative vorticity, potential vorticity, temperatures, and geopotential heights, Inclusion of additional dynamical proxies improves statistics by reducing residuals and uncertainty regions in both zonal mean and zonally asymmetric trend models. RMS reductions, relative to a trend model with only QBO, solar, and trend terms, are as large as 50% in 14-year means in the southern hemisphere, For zonal mean or zonally asymmetric global trend models with one optional surrogate, a favorable choice is prefiltered (at least deseasonalized and detrended) lower stratospheric temperatures. Relative vorticity, potential vorticity, and geopotential heights all exhibit similar relationships with total ozone, with highest correlative behavior near 200 hPa (midlatitudes year-round) and 10 hPa (high latitudes in winter-spring months), For models incorporating these latter proxies, combined 10- and 200-hPa (or similar) pressure levels are effective in reducing global residuals, ENSO, as a surrogate by itself or included with other dynamical proxies, has a comparatively small effect because of its episodic nature, Decadal variabilities in NCEP and microwave sounding unit channel 4 (MSU4) data as surrogates in trend models indicate maximal 1-3% decade(-1) reductions anywhere in TOMS trends, Total ozone trends derived from the Goddard 2-D heterogeneous chemistry and transport model agree favorably with trends in TOMS ozone, generally to within 2-3% decade(-1) in both hemispheres, Inclusion of possible decadal variabilities in dynamics may yield yet smaller differences.
C1 SOFTWARE CORP AMER, LANHAM, MD USA.
RP Ziemke, JR (reprint author), NASA, GODDARD SPACE FLIGHT CTR, NATL RES COUNCIL, CODE 916, GREENBELT, MD 20771 USA.
RI Newman, Paul/D-6208-2012; McPeters, Richard/G-4955-2013
OI Newman, Paul/0000-0003-1139-2508; McPeters, Richard/0000-0002-8926-8462
NR 34
TC 67
Z9 68
U1 0
U2 3
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA
SN 2169-897X
J9 J GEOPHYS RES-ATMOS
JI J. Geophys. Res.-Atmos.
PD MAR 20
PY 1997
VL 102
IS D5
BP 6117
EP 6129
DI 10.1029/96JD03783
PG 13
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA WQ021
UT WOS:A1997WQ02100022
ER
PT J
AU Stothers, RB
AF Stothers, RB
TI Stratospheric aerosol clouds due to very large volcanic eruptions of the
early twentieth century: Effective particle sizes and conversion from
pyrheliometric to visual optical depth
SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
LA English
DT Article
ID GAS EXPERIMENT-II; EL-CHICHON; PINATUBO AEROSOL; MOUNT-PINATUBO;
DISTRIBUTIONS; EVOLUTION; SATELLITE; PROFILES; LIDAR; RING
AB Spectral and pyrheliometric measurements of atmospheric transmission were made by staff members of the Astrophysical Observatory of the Smithsonian Institution at Washington, D. C., and at Mount Wilson, California, during the years 1901-1920. These valuable data are analyzed here with the help of a new inversion method to derive the effective, or area-weighted, radii of stratospheric aerosols formed after three very large volcanic eruptions in this period. After the great eruptions of Katmai (1912) and Santa Maria (1902), r(eff) remained close to 0.3 mu m for at least two years. This near constancy of r(eff) has been duplicated in modern times by the aerosols from El Chichon (1982). Following Ksudach's (1907) eruption, r(eff) grew from 0.2-0.3 mu m to 0.4-0.5 mu m in about 1 year. Pinatubo's (1991) aerosols grew similarly. Generally speaking, the pyrheliometric optical depth perturbation, as measured for the three early eruptions, is not equal to the visual optical depth perturbation, but in fact the latter is larger by a factor of about 1.6, at least for r(eff) = 0.25-0.45 mu m. Wider physical implications of the present results are discussed.
RP Stothers, RB (reprint author), NASA, GODDARD INST SPACE STUDIES, 2880 BROADWAY, NEW YORK, NY 10025 USA.
NR 72
TC 9
Z9 9
U1 0
U2 5
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA
SN 2169-897X
J9 J GEOPHYS RES-ATMOS
JI J. Geophys. Res.-Atmos.
PD MAR 20
PY 1997
VL 102
IS D5
BP 6143
EP 6151
DI 10.1029/96JD03985
PG 9
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA WQ021
UT WOS:A1997WQ02100024
ER
PT J
AU Ross, MD
AF Ross, MD
TI Morphological evidence for local microcircuits in rat vestibular maculae
SO JOURNAL OF COMPARATIVE NEUROLOGY
LA English
DT Article
DE hair cells; calyx; efferents; C synapse; 3-D reconstruction
ID COCHLEAR HAIR-CELLS; GUINEA-PIG; CHOLINE-ACETYLTRANSFERASE; NEUROACTIVE
SUBSTANCES; OLIVOCOCHLEAR NEURONS; CRISTAE-AMPULLARES; DENDRITIC SPINES;
PYRAMIDAL CELLS; SQUIRREL-MONKEY; LOCALIZATION
AB Previous studies suggested that intramacular, unmyelinated segments of vestibular afferent nerve fibers and their large afferent endings (calyces) on type I hair cells branch. Many of the branches (processes) contain vesicles and are presynaptic to type II hair cells, other processes, intramacular nerve fibers, and calyces. This study used serial section transmission electron microscopy and three-dimensional reconstruction methods to document the origins and distributions of presynaptic processes of afferents in the medial part of the adult rat utricular macula. The ultrastructural research focused on presynaptic processes whose origin and termination could be observed in a single micrograph. Results showed that calyces had 1) vesiculated, spine-like processes that invaginated type I cells and 2) other, elongate processes that ended on type II cells pre- as well as postsynaptically. Intramacular, unmyelinated segments of afferent nerve fibers gave origin to branches that were presynaptic to type II cells, calyces, calyceal processes, and other nerve fibers in the macula. Synapses with type II cells occurred opposite subsynaptic cisternae (C synapses); all other synapses were asymmetric. Vesicles were pleomorphic but were differentially distributed according to process origin. Small, clear-centered vesicles, similar to 40-60 nm in diameter, predominated in processes originating from afferent nerve fibers and basal parts of calyces. Larger vesicles similar to 70-120 nm in diameter having similar to 40-80 nm electron-opaque cores were dominant in processes originating from the necks of calyces. Results are interpreted to indicate the existence of a complex system of intrinsic feedforward (postsynaptic)-feedback (presynaptic) connections in a network of direct and local microcircuits. The morphological findings support the concept that maculae dynamically preprocess linear acceleratory information before its transmission to the central nervous system. (C) 1997 Wiley-Liss, Inc.
RP Ross, MD (reprint author), NASA,AMES RES CTR,BIOCOMPUTAT CTR,MAIL STOP 239-11,MOFFETT FIELD,CA 94035, USA.
FU NIMH NIH HHS [MH47305]
NR 81
TC 30
Z9 30
U1 0
U2 0
PU WILEY-LISS
PI NEW YORK
PA DIV JOHN WILEY & SONS INC, 605 THIRD AVE, NEW YORK, NY 10158-0012
SN 0021-9967
J9 J COMP NEUROL
JI J. Comp. Neurol.
PD MAR 17
PY 1997
VL 379
IS 3
BP 333
EP 346
DI 10.1002/(SICI)1096-9861(19970317)379:3<333::AID-CNE2>3.0.CO;2-4
PG 14
WC Neurosciences; Zoology
SC Neurosciences & Neurology; Zoology
GA WL659
UT WOS:A1997WL65900002
PM 9067828
ER
PT J
AU Kamionkowski, M
Kosowsky, A
Stebbins, A
AF Kamionkowski, M
Kosowsky, A
Stebbins, A
TI A probe of primordial gravity waves and vorticity
SO PHYSICAL REVIEW LETTERS
LA English
DT Article
ID MICROWAVE BACKGROUND-RADIATION; GRAVITATIONAL-WAVES; POLARIZATION;
INFLATION; COBE
AB A formalism for describing an all-sky map of the polarization of the cosmic microwave background is presented. The polarization pattern on the sky can be decomposed into two geometrically distinct components. One of these components is not coupled to density inhomogeneities. A nonzero amplitude for this component of polarization can only be caused by tensor or vector metric perturbations. This allows unambiguous identification of long-wavelength gravity waves or large-scale vortical flows at the time of last scattering.
C1 HARVARD SMITHSONIAN CTR ASTROPHYS,CAMBRIDGE,MA 02138.
HARVARD UNIV,LYMAN LAB,DEPT PHYS,CAMBRIDGE,MA 02138.
FERMILAB NATL ACCELERATOR LAB,NASA,FERMILAB ASTROPHYS CTR,BATAVIA,IL 60510.
RP Kamionkowski, M (reprint author), COLUMBIA UNIV,DEPT PHYS,538 W 120TH ST,NEW YORK,NY 10027, USA.
NR 28
TC 419
Z9 419
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 MAR 17
PY 1997
VL 78
IS 11
BP 2058
EP 2061
DI 10.1103/PhysRevLett.78.2058
PG 4
WC Physics, Multidisciplinary
SC Physics
GA WN079
UT WOS:A1997WN07900007
ER
PT J
AU Gates, E
Kamionkowski, M
Turner, MS
AF Gates, E
Kamionkowski, M
Turner, MS
TI Dispersion velocity of galactic dark matter particles - Comment
SO PHYSICAL REVIEW LETTERS
LA English
DT Article
ID KINEMATICS; GALAXY
C1 UNIV CHICAGO,ENRICO FERMI INST,DEPT ASTRON & ASTROPHYS,CHICAGO,IL 60637.
UNIV CHICAGO,ENRICO FERMI INST,DEPT PHYS,CHICAGO,IL 60637.
COLUMBIA UNIV,DEPT PHYS,NEW YORK,NY 10027.
RP Gates, E (reprint author), NASA,FERMI NATL ACCELERATOR LAB,FERMILAB THEORET ASTROPHYS CTR,BATAVIA,IL 60615, USA.
NR 6
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 0031-9007
J9 PHYS REV LETT
JI Phys. Rev. Lett.
PD MAR 17
PY 1997
VL 78
IS 11
BP 2261
EP 2261
DI 10.1103/PhysRevLett.78.2261
PG 1
WC Physics, Multidisciplinary
SC Physics
GA WN079
UT WOS:A1997WN07900058
ER
PT J
AU Morales, W
AF Morales, W
TI A semiempirical study on the interaction between BF3 and the compounds
dimethyl and perfluorodimethyl ether
SO THEOCHEM-JOURNAL OF MOLECULAR STRUCTURE
LA English
DT Article
DE perfluoropolyalkylether; surface Lewis acid site; catalytic
decomposition; liquid lubricant; metal oxide
ID THERMAL-DECOMPOSITION; CHEMISTRY; PERFLUOROPOLYETHERS; SURFACES; OXIDE
AB A semiempirical molecular orbital method (AM1) was used to study the interaction between BF3 (a Lewis acid) and the compounds dimethyl and perfluorodimethyl ether. The results indicated the existence of a Lewis acid-base interaction between the BF3 molecule and dimethyl ether but no interaction with the perfluorodimethyl ether, in agreement with experimental results. These results do not support the hypothesis that surface Lewis acid sites are responsible for the catalytic decomposition of perfluoropolyalkylethers.
RP Morales, W (reprint author), NASA,LEWIS RES CTR,21000 BROOKPK RD,CLEVELAND,OH 44135, USA.
NR 13
TC 1
Z9 1
U1 0
U2 0
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0166-1280
J9 THEOCHEM-J MOL STRUC
JI Theochem-J. Mol. Struct.
PD MAR 17
PY 1997
VL 391
IS 3
BP 225
EP 230
PG 6
WC Chemistry, Physical
SC Chemistry
GA WW444
UT WOS:A1997WW44400004
ER
PT J
AU Gazis, PR
AF Gazis, PR
TI The latitudinal structure of the solar wind in the vicinity of the solar
equator near solar minimum: 1986 and predictions for 1997
SO GEOPHYSICAL RESEARCH LETTERS
LA English
DT Article
ID PLASMA OBSERVATIONS
AB In situ observations by different spacecraft have shown that the heliospheric current sheet (HCS) is associated with a narrow band of low speed high density solar wind. The inclination of the HCS and the three-dimensional structure of solar wind streams is related to the inclination of the coronal neutral line. Observations from the Ulysses spacecraft during the descending phase of solar cycle 22, when Wilcox Solar Observatory coronal field models suggest that the inclination of the coronal neutral line was between 50 degrees and 70 degrees, showed that the inclination of the HCS was similar or equal to 20 degrees while solar wind streams were confined to heliographic latitudes less than 35 degrees. At higher latitudes, low and medium speed solar wind disappeared and the solar wind speed was uniformly high. Observations from the Pioneer 11-Voyager 2 spacecraft pair near the time of the 1986 solar minimum revealed a different structure. At that time the inclination of the coronal neutral line wits unusually low (<10 degrees-15 degrees). Solar wind streams vanished near the solar equator end may have disappeared at most heliographic latitudes in the outer heliosphere. This has implications for the forthcoming Ulysses equatorial pass at the end of 1997, when the inclination of the coronal neutral line and the HCS are again expected to be low. If the HCS is sufficiently flat, conditions may resemble those observed near the time of the 1986 solar minimum and the solar wind stream structure may disappear at Ulysses near the solar equator.
RP Gazis, PR (reprint author), NASA,AMES RES CTR,MS 245-3,MOFFETT FIELD,CA 94035, USA.
NR 14
TC 5
Z9 5
U1 0
U2 0
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009
SN 0094-8276
J9 GEOPHYS RES LETT
JI Geophys. Res. Lett.
PD MAR 15
PY 1997
VL 24
IS 6
BP 627
EP 630
DI 10.1029/97GL00540
PG 4
WC Geosciences, Multidisciplinary
SC Geology
GA WN972
UT WOS:A1997WN97200002
ER
PT J
AU Chandra, S
Jackman, CH
Fleming, EL
Russell, JM
AF Chandra, S
Jackman, CH
Fleming, EL
Russell, JM
TI The seasonal and long term changes in mesospheric water vapor
SO GEOPHYSICAL RESEARCH LETTERS
LA English
DT Article
ID GRAVITY-WAVE; MIDDLE ATMOSPHERE; MODEL; TRANSPORT; DIFFUSION
AB This study explores the feasibility of identifying long term changes in mesospheric water vapor as a result of increasing level of methane in the atmosphere and the solar cycle variation of Lyman alpha. The study is based on recent measurements of water vapor in the mesosphere and the solar Lyman alpha flux from the UARS (Upper Atmosphere Research Satellite) HALOE (Halogen Occultation Experiment) and the SOLSTICE (Solar Stellar Iradiance Comparison Experiment) instruments during the declining phase of the solar cycle 22. The solar activity during this period decreased from a near maximum to a near minimum level. The analysis of these data sets, in conjunction with the NASA/GSFC two dimensional chemistry and transport model suggests that on a seasonal time scale, the temporal changes in mesospheric water vapor are largely controlled by the vertical advection associated with the meridional circulation. On the time scale of a solar cycle, H2O may vary by about 30-40% near the mesopause height (similar to 80 km) to about 1-2% in the lower mesosphere (60-65 km) caused by the solar cycle modulation of Lyman alpha. In comparison, the secular increase in H2O related to methane increase in the atmosphere is about 0.4%/year at all heights in the mesosphere.
C1 APPL RES CORP,LANDOVER,MD 20785.
HAMPTON UNIV,DEPT PHYS,HAMPTON,VA 23668.
RP Chandra, S (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 916,GREENBELT,MD 20771, USA.
RI Jackman, Charles/D-4699-2012
NR 20
TC 50
Z9 50
U1 0
U2 1
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009
SN 0094-8276
J9 GEOPHYS RES LETT
JI Geophys. Res. Lett.
PD MAR 15
PY 1997
VL 24
IS 6
BP 639
EP 642
DI 10.1029/97GL00546
PG 4
WC Geosciences, Multidisciplinary
SC Geology
GA WN972
UT WOS:A1997WN97200005
ER
PT J
AU Yue, GK
Lu, J
Mohnen, VA
Wang, PH
Saxena, VK
Anderson, J
AF Yue, GK
Lu, J
Mohnen, VA
Wang, PH
Saxena, VK
Anderson, J
TI Retrieving aerosol optical properties from moments of the particle size
distribution
SO GEOPHYSICAL RESEARCH LETTERS
LA English
DT Article
ID STRATOSPHERIC AEROSOL; II SATELLITE; PINATUBO; ERUPTION
AB The randomized minimization search technique (RMST) is a powerful tool for retrieving aerosol size distribution from a set of aerosol extinction measurements. This technique is now extended to retrieve aerosol optical properties from a known moment sequence. The new usage of the RMST is demonstrated by using particle size distributions obtained from fits to in situ measurements conducted in the troposphere and stratosphere. Good agreements (with differences less than 5%) between some aerosol optical properties calculated from the moments and those calculated directly from the particle size distributions are obtained. Our results illustrate that the RMST can be applied to parameterize particle optical properties from the lower-order moments of an aerosol size distribution.
C1 SUNY ALBANY,ATMOSPHER SCI RES CTR,ALBANY,NY 12222.
SCI & TECHNOL CORP,HAMPTON,VA 23666.
N CAROLINA STATE UNIV,DEPT MARINE EARTH & ATMOSPHER SCI,RALEIGH,NC 27695.
RP Yue, GK (reprint author), NASA,LANGLEY RES CTR,DIV ATMOSPHER SCI,HAMPTON,VA 23681, USA.
NR 17
TC 13
Z9 13
U1 0
U2 0
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009
SN 0094-8276
J9 GEOPHYS RES LETT
JI Geophys. Res. Lett.
PD MAR 15
PY 1997
VL 24
IS 6
BP 651
EP 654
DI 10.1029/97GL00522
PG 4
WC Geosciences, Multidisciplinary
SC Geology
GA WN972
UT WOS:A1997WN97200008
ER
PT J
AU Melbourne, T
Carmichael, I
DeMets, C
Hudnut, K
Sanchez, O
Stock, J
Suarez, G
Webb, F
AF Melbourne, T
Carmichael, I
DeMets, C
Hudnut, K
Sanchez, O
Stock, J
Suarez, G
Webb, F
TI The geodetic signature of the M8.0 October 9, 1995, Jalisco subduction
earthquake
SO GEOPHYSICAL RESEARCH LETTERS
LA English
DT Article
ID MEXICO; RIVERA; DEFORMATION; PLATES; ZONE
AB The October, 1995 Mw 8.0 Jalisco subduction earthquake has provided a thorough geodetic observation of the coseismic subduction process. An 11 station regional GPS network located directly onshore of the rupture demonstrates consistent vertical subsidence verified by tide gauge data and southwest-directed extension, with measured displacements reaching 1 meter. Unusually shallow and non-uniform faulting is required to explain the displacements. We determine that up to 5 meters of slip occurred within the upper 15 km of the thrust fault zone and 2 meters possibly as shallow as 8 km, and that slip was likely distributed in two main patches. The paucity of continental sediments in this subduction zone could be responsible for the anomalously shallow faulting.
C1 UNIV CALIF BERKELEY, DEPT GEOL & GEOPHYS, BERKELEY, CA 94270 USA.
UNIV WISCONSIN, DEPT GEOL & GEOPHYS, MADISON, WI 53076 USA.
US GEOL SURVEY, PASADENA, CA 91106 USA.
NATL AUTONOMOUS UNIV MEXICO, INST GEOFIS, MEXICO CITY 04510, DF, MEXICO.
CALTECH, JET PROP LAB, PASADENA, CA 91109 USA.
RP CALTECH, SEISMOL LAB 252 21, PASADENA, CA 91125 USA.
RI Hudnut, Kenneth/B-1945-2009; Hudnut, Kenneth/G-5713-2010
OI Hudnut, Kenneth/0000-0002-3168-4797;
NR 23
TC 44
Z9 47
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 MAR 15
PY 1997
VL 24
IS 6
BP 715
EP 718
DI 10.1029/97GL00370
PG 4
WC Geosciences, Multidisciplinary
SC Geology
GA WN972
UT WOS:A1997WN97200024
ER
PT J
AU Watson, AB
Rosenholtz, R
AF Watson, AB
Rosenholtz, R
TI A Rorschach test for visual classification strategies
SO INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE
LA English
DT Meeting Abstract
C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035.
NR 0
TC 2
Z9 2
U1 0
U2 0
PU LIPPINCOTT-RAVEN PUBL
PI PHILADELPHIA
PA 227 EAST WASHINGTON SQ, PHILADELPHIA, PA 19106
SN 0146-0404
J9 INVEST OPHTH VIS SCI
JI Invest. Ophthalmol. Vis. Sci.
PD MAR 15
PY 1997
VL 38
IS 4
BP 2
EP 2
PN 1
PG 1
WC Ophthalmology
SC Ophthalmology
GA WN186
UT WOS:A1997WN18600002
ER
PT J
AU Ansari, RR
Suh, KI
Zigler, JS
Russell, P
AF Ansari, RR
Suh, KI
Zigler, JS
Russell, P
TI In vivo ''cataractograms'' of transgenic mice using a compact
backscatter dynamic light scattering (DLS) probe
SO INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE
LA English
DT Meeting Abstract
C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135.
NEI,NIH,BETHESDA,MD 20892.
NR 0
TC 0
Z9 0
U1 0
U2 0
PU LIPPINCOTT-RAVEN PUBL
PI PHILADELPHIA
PA 227 EAST WASHINGTON SQ, PHILADELPHIA, PA 19106
SN 0146-0404
J9 INVEST OPHTH VIS SCI
JI Invest. Ophthalmol. Vis. Sci.
PD MAR 15
PY 1997
VL 38
IS 4
BP 1611
EP 1611
PN 1
PG 1
WC Ophthalmology
SC Ophthalmology
GA WN186
UT WOS:A1997WN18601608
ER
PT J
AU Ahumada, AJ
Beard, BL
AF Ahumada, AJ
Beard, BL
TI Parafoveal target detectability reversal predicted by local luminance
and contrast gain control
SO INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE
LA English
DT Meeting Abstract
C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035.
UNIV CALIF BERKELEY,SCH OPTOMETRY,BERKELEY,CA 94720.
NR 0
TC 0
Z9 0
U1 0
U2 0
PU LIPPINCOTT-RAVEN PUBL
PI PHILADELPHIA
PA 227 EAST WASHINGTON SQ, PHILADELPHIA, PA 19106
SN 0146-0404
J9 INVEST OPHTH VIS SCI
JI Invest. Ophthalmol. Vis. Sci.
PD MAR 15
PY 1997
VL 38
IS 4
BP 1792
EP 1792
PN 1
PG 1
WC Ophthalmology
SC Ophthalmology
GA WN186
UT WOS:A1997WN18601787
ER
PT J
AU Bridgeman, B
Williams, JA
Welch, RB
AF Bridgeman, B
Williams, JA
Welch, RB
TI Adaptive generalization and dual adaptation in the human
vestibular-ocular reflex (VOR)
SO INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE
LA English
DT Meeting Abstract
C1 UNIV CALIF SANTA CRUZ,SANTA CRUZ,CA 95064.
NASA,AMES RES CTR,MOFFETT FIELD,CA 94035.
NR 0
TC 0
Z9 0
U1 0
U2 0
PU LIPPINCOTT-RAVEN PUBL
PI PHILADELPHIA
PA 227 EAST WASHINGTON SQ, PHILADELPHIA, PA 19106
SN 0146-0404
J9 INVEST OPHTH VIS SCI
JI Invest. Ophthalmol. Vis. Sci.
PD MAR 15
PY 1997
VL 38
IS 4
BP 3071
EP 3071
PN 1
PG 1
WC Ophthalmology
SC Ophthalmology
GA WN186
UT WOS:A1997WN18603061
ER
PT J
AU Williams, JA
Bridgeman, B
Welch, RB
Strain, V
AF Williams, JA
Bridgeman, B
Welch, RB
Strain, V
TI Frequency vs. acceleration specificity in human VOR adaptation
SO INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE
LA English
DT Meeting Abstract
C1 UNIV CALIF SANTA CRUZ,SANTA CRUZ,CA 95064.
NASA,AMES RES CTR,MOFFETT FIELD,CA 94035.
NR 0
TC 0
Z9 0
U1 0
U2 0
PU LIPPINCOTT-RAVEN PUBL
PI PHILADELPHIA
PA 227 EAST WASHINGTON SQ, PHILADELPHIA, PA 19106
SN 0146-0404
J9 INVEST OPHTH VIS SCI
JI Invest. Ophthalmol. Vis. Sci.
PD MAR 15
PY 1997
VL 38
IS 4
BP 3072
EP 3072
PN 1
PG 1
WC Ophthalmology
SC Ophthalmology
GA WN186
UT WOS:A1997WN18603062
ER
PT J
AU Sebag, J
Dunker, S
Suh, KI
Ansari, RR
AF Sebag, J
Dunker, S
Suh, KI
Ansari, RR
TI Dynamic light scattering measurements in vitreous
SO INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE
LA English
DT Meeting Abstract
C1 UNIV SO CALIF,DOHENY EYE INST,LOS ANGELES,CA.
NASA,LEWIS RES CTR,CLEVELAND,OH 44135.
NR 0
TC 0
Z9 0
U1 0
U2 2
PU LIPPINCOTT-RAVEN PUBL
PI PHILADELPHIA
PA 227 EAST WASHINGTON SQ, PHILADELPHIA, PA 19106
SN 0146-0404
J9 INVEST OPHTH VIS SCI
JI Invest. Ophthalmol. Vis. Sci.
PD MAR 15
PY 1997
VL 38
IS 4
BP 3100
EP 3100
PN 1
PG 1
WC Ophthalmology
SC Ophthalmology
GA WN186
UT WOS:A1997WN18603090
ER
PT J
AU Rosenholtz, R
AF Rosenholtz, R
TI Basic signal detection theory model for visual search does not predict
performance with heterogeneous distractors
SO INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE
LA English
DT Meeting Abstract
C1 NASA,AMES RES CTR,AMES,IA.
NR 0
TC 0
Z9 0
U1 0
U2 0
PU LIPPINCOTT-RAVEN PUBL
PI PHILADELPHIA
PA 227 EAST WASHINGTON SQ, PHILADELPHIA, PA 19106
SN 0146-0404
J9 INVEST OPHTH VIS SCI
JI Invest. Ophthalmol. Vis. Sci.
PD MAR 15
PY 1997
VL 38
IS 4
BP 3204
EP 3204
PN 2
PG 1
WC Ophthalmology
SC Ophthalmology
GA WN215
UT WOS:A1997WN21500029
ER
PT J
AU Beutter, BR
Stone, LS
AF Beutter, BR
Stone, LS
TI Pursuit and direction perception are driven by similar and largely
veridical object-motion signals.
SO INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE
LA English
DT Meeting Abstract
C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035.
NR 0
TC 0
Z9 0
U1 0
U2 0
PU LIPPINCOTT-RAVEN PUBL
PI PHILADELPHIA
PA 227 EAST WASHINGTON SQ, PHILADELPHIA, PA 19106
SN 0146-0404
J9 INVEST OPHTH VIS SCI
JI Invest. Ophthalmol. Vis. Sci.
PD MAR 15
PY 1997
VL 38
IS 4
BP 3228
EP 3228
PN 2
PG 1
WC Ophthalmology
SC Ophthalmology
GA WN215
UT WOS:A1997WN21500053
ER
PT J
AU Stone, LS
Beutter, BR
Lorenceau, JD
AF Stone, LS
Beutter, BR
Lorenceau, JD
TI Steady state pursuit is driven by object motion rather than the vector
average of local motions.
SO INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE
LA English
DT Meeting Abstract
C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035.
COLL FRANCE,LPPA,F-75231 PARIS 05,FRANCE.
NR 0
TC 0
Z9 0
U1 0
U2 0
PU LIPPINCOTT-RAVEN PUBL
PI PHILADELPHIA
PA 227 EAST WASHINGTON SQ, PHILADELPHIA, PA 19106
SN 0146-0404
J9 INVEST OPHTH VIS SCI
JI Invest. Ophthalmol. Vis. Sci.
PD MAR 15
PY 1997
VL 38
IS 4
BP 4357
EP 4357
PN 2
PG 1
WC Ophthalmology
SC Ophthalmology
GA WN215
UT WOS:A1997WN21501180
ER
PT J
AU Mulligan, JB
AF Mulligan, JB
TI Eye movements reveal hierarchical motion processing
SO INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE
LA English
DT Meeting Abstract
C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035.
NR 0
TC 0
Z9 0
U1 0
U2 0
PU LIPPINCOTT-RAVEN PUBL
PI PHILADELPHIA
PA 227 EAST WASHINGTON SQ, PHILADELPHIA, PA 19106
SN 0146-0404
J9 INVEST OPHTH VIS SCI
JI Invest. Ophthalmol. Vis. Sci.
PD MAR 15
PY 1997
VL 38
IS 4
BP 4359
EP 4359
PN 2
PG 1
WC Ophthalmology
SC Ophthalmology
GA WN215
UT WOS:A1997WN21501182
ER
PT J
AU Beard, BL
Ahumada, AJ
AF Beard, BL
Ahumada, AJ
TI Orientation tuning unchanged by vernier acuity practice
SO INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE
LA English
DT Meeting Abstract
C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035.
UNIV CALIF BERKELEY,SCH OPTOMETRY,BERKELEY,CA 94720.
NR 0
TC 0
Z9 0
U1 0
U2 0
PU LIPPINCOTT-RAVEN PUBL
PI PHILADELPHIA
PA 227 EAST WASHINGTON SQ, PHILADELPHIA, PA 19106
SN 0146-0404
J9 INVEST OPHTH VIS SCI
JI Invest. Ophthalmol. Vis. Sci.
PD MAR 15
PY 1997
VL 38
IS 4
BP 4458
EP 4458
PN 2
PG 1
WC Ophthalmology
SC Ophthalmology
GA WN215
UT WOS:A1997WN21501280
ER
PT J
AU Eckstein, MP
Beutter, BB
Stone, LS
AF Eckstein, MP
Beutter, BB
Stone, LS
TI The visual efficiency of eye movements during search
SO INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE
LA English
DT Meeting Abstract
C1 CEDARS SINAI MED CTR,DEPT MED PHYS & IMAGING,LOS ANGELES,CA 90048.
NASA,AMES RES CTR,MOFFETT FIELD,CA 94035.
NR 0
TC 0
Z9 0
U1 0
U2 1
PU LIPPINCOTT-RAVEN PUBL
PI PHILADELPHIA
PA 227 EAST WASHINGTON SQ, PHILADELPHIA, PA 19106
SN 0146-0404
J9 INVEST OPHTH VIS SCI
JI Invest. Ophthalmol. Vis. Sci.
PD MAR 15
PY 1997
VL 38
IS 4
BP 5384
EP 5384
PN 2
PG 1
WC Ophthalmology
SC Ophthalmology
GA WN215
UT WOS:A1997WN21502205
ER
PT J
AU Pool, FS
AF Pool, FS
TI Nitrogen plasma instabilities and the growth of silicon nitride by
electron cyclotron resonance microwave plasma chemical vapor deposition
SO JOURNAL OF APPLIED PHYSICS
LA English
DT Article
ID HYDROGEN CONTENT; ION-SOURCE; CVD METHOD; FILMS; FIELD; STABILITY
AB Nitrogen plasma instabilities have been identified through fluctuations in the ion current density and substrate floating potential. The behavior of the plasma instabilities was found to be confined to the pressure regime 0.9 mTorr
650 degrees C) carbonate precipitation and suggest non-equilibrium processes at low temperatures ( 0), (HCO+)-C-13 (J = 1, 0), and SiO (upsilon = 0, J = 2 --> 1) emission lines at similar to 2.5 '' resolution reveal both a flattened cloud of dense molecular gas similar to 1.1 pc in extent and a newly discovered inner torus similar to 0.5 pc in extent. The axis of the inner torus is tilted similar to 20 degrees with respect to the outer cloud. The inner torus surrounds a bright continuum source, associated with the origin of a bipolar ionized gas outflow, and has HCO+(J = 1-->0) optical depth greater than 14. Chemical abundances in the inner torus are azimuthally asymmetric, possibly due to differential impact of the ionized outflow on the inner region of the torus. Comparison with a kinematic radiative transfer model confirms that the torus is rotating and the rotation axis of the inner torus is aligned with the ionized outflow. While the cloud is not in solid body rotation, the rotational velocity of material in the cloud increases with radius.
We estimate molecular abundance ratios by comparison with high-resolution dust extinction maps previously obtained at the same spatial resolution. The abundance ratio [HCO+]/[H-2] = 3.9 x 10(-8) is enhanced and falls in the upper range of typically measured values for star formation regions. SiO is likewise enhanced relative to both H-2 and to HCO+. The ratio [SiO]/[H-2] = 3.9 x 10(-10) is within the range observed toward shock-excited regions. The cloud mass is estimated to be greater than or similar to 22600 M(.).
C1 UNIV MASSACHUSETTS,DEPT PHYS & ASTRON,LGRT,AMHERST,MA 01003.
JET PROPULS LAB,PASADENA,CA 91104.
RP Howard, EM (reprint author), UNIV ROCHESTER,DEPT PHYS & ASTRON,ROCHESTER,NY 14627, USA.
NR 41
TC 16
Z9 16
U1 0
U2 0
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD MAR 10
PY 1997
VL 477
IS 2
BP 738
EP &
DI 10.1086/303750
PN 1
PG 17
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WM090
UT WOS:A1997WM09000020
ER
PT J
AU deKoter, A
Heap, SR
Hubeny, I
AF deKoter, A
Heap, SR
Hubeny, I
TI On the evolutionary phase and mass loss of the Wolf-Rayet-like stars in
R136a
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE Magellanic Clouds; stars, early-type; stars, evolution; stars, mass
loss; stars, Wolf-Rayet; ultraviolet, stars
ID LARGE MAGELLANIC CLOUD; RADIATION-DRIVEN WINDS; EMISSION-LINE STARS; HOT
LUMINOUS STARS; O-TYPE STARS; STELLAR WINDS; NON-LTE; MULTILINE
TRANSFER; INDIVIDUAL STARS; MOLECULAR CLOUDS
AB We report on a systematic study of the most massive stars, in which we analyzed the spectra of four very luminous stars in the Large Magellanic Cloud. The stars lie in the 30 Doradus complex, three of which are located in the core of the compact cluster, R136a (R136a1, R136a3, and R136a5), and the fourth (Melnick 42), located about 8 '' north of R136a. Low-resolution spectra (<200 km s(-1)) of these four stars were obtained with the GHRS and FOS spectrographs on the Hubble Space Telescope. The GHRS spectra cover the spectral range from 1200 to 1750 Angstrom and the FOS spectra from 3200 to 6700 Angstrom We derived the fundamental parameters of these stars by fitting the observations by model spectra calculated with the ''ISA-WIND'' code of de Koter et al. We find that all four stars are very hot (similar to 45 kK), luminous, and rich in hydrogen. Their positions on the HR-diagram imply that they are stars with masses in the range 60-90 M. that are 2 million years old at most, and hence, they are O-type main-sequence stars still in the core H-burning phase of evolution. Nevertheless, the spectra of two of the stars (R136a1, R136a3) mimic those of Wolf-Rayet stars in showing very strong He II emission lines. According to our calculations, this emission is a natural consequence of a very high mass-loss rate.
We conjecture that the most massive stars in R136a-those with initial masses of similar to 100 M. or more-are born as WR-like stars and that the high mass loss may perhaps be connected to the actual stellar formation process. Because the observed mass-loss rates are up to 3 times higher than assumed by evolutionary models, the main-sequence and post-main-sequence tracks of these stars will be qualitatively different from current models. The mass-loss rate is 3.5-8 times that predicted by the analytical solutions for radiation-driven winds of Kudritzki et al. (1989). However, using sophisticated Monte Carlo calculations of radiative driving in unified model atmospheres, we show that-while we cannot say for sure what initiates the wind-radiation pressure is probably sufficient to accelerate the wind to its observed terminal velocity, if one accounts for the effects of multiple photon scattering in the dense winds of the investigated stars.
C1 NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771.
NASA,GODDARD SPACE FLIGHT CTR,UNIV SPACE RES ASSOC,GREENBELT,MD 20771.
RP deKoter, A (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ADV COMP CONCEPTS,CODE 681,GREENBELT,MD 20771, USA.
NR 60
TC 128
Z9 128
U1 4
U2 5
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD MAR 10
PY 1997
VL 477
IS 2
BP 792
EP 816
PN 1
PG 25
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WM090
UT WOS:A1997WM09000024
ER
PT J
AU Mauche, CW
Lee, YP
Kallman, TR
AF Mauche, CW
Lee, YP
Kallman, TR
TI Ultraviolet emission-line ratios of cataclysmic variables
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE atomic processes; line, formation; stars, novae, cataclysmic variables;
ultraviolet, stars
ID OLD-NOVA GK; DIELECTRONIC RECOMBINATION; ROSAT OBSERVATIONS; UV
SPECTROSCOPY; Z CHAMAELEONTIS; IUE SPECTRA; DWARF NOVAE; V-SAGITTAE;
OUTBURST; AM
AB We present a statistical analysis of the ultraviolet emission lines of cataclysmic variables (CVs) based on approximate to 430 ultraviolet spectra of 20 sources extracted from the International Ultraviolet Explorer Uniform Low Dispersion Archive. These spectra are used to measure the emission-line fluxes of N V, Si IV, C IV, and He II and to construct diagnostic flux ratio diagrams. We investigate the flux ratio parameter space populated by individual CVs and by various CV subclasses (e.g., AM Her stars, DQ Her stars, dwarf novae, nova-like variables). For most systems, these ratios are clustered within a range of similar to 1 decade for log Si IV/C IV approximate to 0.5 and log He II/C IV N approximate to-1.0 and similar to 1.5 decades for log N V/C IV approximate to-0.25. These ratios are compared to photoionization and collisional ionization models to constrain the excitation mechanism and the physical conditions of the line-emitting gas. We find that the collisional models do the poorest job of reproducing the data. The photoionization models reproduce the Si IV/C IV line ratios for some shapes of the ionizing spectrum, but the predicted N V/C IV line ratios are simultaneously too low by typically similar to 0.5 decades. Worse, for no parameters are any of the models able to reproduce the observed He II/C IV line ratios; this ratio is far too small in the collisional and scattering models and too large by typically similar to 0.5 decades in the photoionization models.
C1 UNIV CALIF DAVIS, DEPT PHYS, DAVIS, CA 95616 USA.
NASA, GODDARD SPACE FLIGHT CTR, HIGH ENERGY ASTROPHYS LAB, GREENBELT, MD 20771 USA.
RP Mauche, CW (reprint author), LAWRENCE LIVERMORE NATL LAB, L-41, POB 808, LIVERMORE, CA 94550 USA.
NR 45
TC 45
Z9 45
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 MAR 10
PY 1997
VL 477
IS 2
BP 832
EP 847
DI 10.1086/303717
PN 1
PG 16
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WM090
UT WOS:A1997WM09000027
ER
PT J
AU Sonneborn, G
Fransson, C
Lundqvist, P
Cassatella, A
Gilmozzi, R
Kirshner, RP
Panagia, N
Wamsteker, W
AF Sonneborn, G
Fransson, C
Lundqvist, P
Cassatella, A
Gilmozzi, R
Kirshner, RP
Panagia, N
Wamsteker, W
TI The evolution of ultraviolet emission lines from circumstellar material
surrounding SN 1987a
SO ASTROPHYSICAL JOURNAL
LA English
DT Review
DE circumstellar matter; supernovae, individual (SN 1987A); supernova
remnants; ultraviolet, ISM
ID LARGE MAGELLANIC CLOUD; ELECTRON-IMPACT EXCITATION; SUPERNOVA 1987A;
C-III; TRANSITION-PROBABILITIES; INTERSTELLAR EXTINCTION; LIGHT ECHOES;
N-III; SN-1987A; RING
AB The presence of narrow high-temperature emission lines from nitrogen-rich gas close to SN 1987A has been a principal observational constraint on the evolutionary status of the supernova's progenitor. A new analysis of the complete 5 year set of low- and high-resolution IUE ultraviolet spectra of SN 1987A (1987.2-1992.3) provides fluxes for the N V lambda 1240, N IV] lambda 1486, He II lambda 1640, O III] lambda 1665, N III] lambda 1751, and C III] lambda 1908 lines with significantly reduced random and systematic errors and reveals significant short-term fluctuations in the light curves. The N V N IV], and N III] lines turn on sequentially over 15-20 days and show a progression from high to low ionization potential, implying an ionization gradient in the emitting region. The line emission turns on suddenly at 83+/-4 days after the explosion, as defined by N IV]. The N III] line reaches peak luminosity at 399+/-15 days. A ring radius of (6.24+/-0.20)x10(17) cm and inclination of 41 degrees.0+/-3 degrees.9 is derived from these times, assuming a circular ring. The probable role of resonant scattering in the N V light curve introduces systematic errors that leads us to exclude this line from the timing analysis. A new nebular analysis yields improved CNO abundance ratios of N/C=6.1+/-1.1 and N/O=1.7+/-0.5, confirming the nitrogen enrichment found in our previous paper. From the late-time behavior of the light curves we find that the emission originates from progressively lower density gas and that the emitting region has a multicomponent density structure. We estimate the emitting mass near maximum (similar to 400 days) to be similar to 4.7x10(-2) M., assuming a filling factor of unity and an electron density of 2.6x10(4) cm(-3). These results are discussed in the context of current models for the emission and hydrodynamics of the ring.
C1 INST ASTROPHYS PARIS, F-75014 PARIS, FRANCE.
STOCKHOLM OBSERV, S-13336 SALTSJOBADEN, SWEDEN.
CNR, IST ASTROFIS SPAZIALE, I-00044 FRASCATI, ITALY.
EUROPEAN SO OBSERV, D-85748 GARCHING, GERMANY.
CTR ASTROPHYS, CAMBRIDGE, MA 02138 USA.
SPACE TELESCOPE SCI INST, BALTIMORE, MD 21218 USA.
ESA, VILSPA, IUE OBSERV, E-28080 MADRID, SPAIN.
ESA, SPACE SCI DEPT, ASTROPHYS DIV, F-75738 PARIS 15, FRANCE.
RP Sonneborn, G (reprint author), NASA, GODDARD SPACE FLIGHT CTR, ASTRON & SOLAR PHYS LAB, CODE 681, GREENBELT, MD 20771 USA.
NR 109
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 MAR 10
PY 1997
VL 477
IS 2
BP 848
EP 864
DI 10.1086/303720
PN 1
PG 17
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WM090
UT WOS:A1997WM09000028
ER
PT J
AU BohmVitense, E
Evans, NR
Carpenter, K
BeckWinchatz, B
Robinson, R
AF BohmVitense, E
Evans, NR
Carpenter, K
BeckWinchatz, B
Robinson, R
TI The mass of the classical Cepheid S Muscae
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE binaries, visual; Cepheids; stars, evolution; stars, fundamental
parameters; stars, individual (S Muscae); stars interiors
ID PERIOD-LUMINOSITY RELATIONS; AGE MAIN-SEQUENCE; STELLAR MODELS; OPACITY
TABLES; STARS; ATMOSPHERES; VARIABLES; COMPANIONS; EVOLUTION; BINARIES
AB A good determination of the mass-luminosity relation for evolved stars on blue loops can determine the degree of excess mixing in the interiors of their main-sequence companions. In this study we determine the dynamical mass of the Cepheid binary S Muscae. This can be combined with its known luminosity and be fitted on evolutionary tracks to determine the amount of mixing in the main-sequence progenitor.
Using the Goddard High Resolution Spectrograph on the Hubble Space Telescope we have measured the orbital radial velocity changes for the companion of the Cepheid S Mus. Spectra taken at minimum and maximum orbital velocities were cross-correlated. The velocity difference was measured to be 30.6+/-0.4 km s(-1). The difference for the orbital velocities of the Cepheid for the same phases was determined to be 26.9 km s(-1)+/-0.4 km s(-1). This gives a velocity ratio of 1.14+/-0.02, which gives us the mass ratio for the companions. Adding possible centering errors of the target in the entrance apertures the error limit would be increased to +/-0.06.
The derived spectral types of the companion S Mus B range from B3 V to B5 V depending on the criterion used to determine it, with an average spectral type B3.8 V. Using the average spectral type and the main-sequence mass-spectral type relation from Andersen & Harmanec we find for S Mus B a mass of 5.2+/-0.2 M.. With the newly determined mass ratio the mass for the Cepheid S Mus A comes out to be 5.9(-0.6)(+0.7) M..
Taking the mass of 5.9 M. at face value and adopting the absolute visual magnitude of M(upsilon)=-4.29 (log L/L.=3.62) for the Cepheid S Mus this indicates mixing in its main-sequence progenitor slightly in excess of the one assumed for the Maeder and Meynet evolutionary tracks. The present uncertainties in mass and luminosity prevent, however, a firm conclusion about the exact degree of mixing.
C1 HARVARD SMITHSONIAN CTR ASTROPHYS,CAMBRIDGE,MA 02138.
YORK UNIV,DEPT PHYS & ASTRON,N YORK,ON M3J 1P3,CANADA.
NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771.
COMP SCI CORP,GREENBELT,MD 20771.
RP BohmVitense, E (reprint author), UNIV WASHINGTON,DEPT ASTRON,SEATTLE,WA 98195, USA.
NR 52
TC 12
Z9 12
U1 0
U2 0
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD MAR 10
PY 1997
VL 477
IS 2
BP 916
EP 925
PN 1
PG 10
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WM090
UT WOS:A1997WM09000033
ER
PT J
AU Brosius, JW
Davila, JM
Thomas, RJ
Saba, JLR
Hara, H
MonsignoriFossi, BC
AF Brosius, JW
Davila, JM
Thomas, RJ
Saba, JLR
Hara, H
MonsignoriFossi, BC
TI The structure and properties of solar active regions and quiet-sun areas
observed in soft X-rays with Yohkoh/SXT and in the extreme-ultraviolet
with SERTS
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE Sun, activity; Sun, corona; Sun, X-rays, gamma rays; Sun, UV radiation
ID CORONAL EMISSION; CAMPAIGN; DIAGNOSTICS; PLASMA; SPECTROHELIOGRAMS;
SPECTROGRAPH; IONIZATION; RESOLUTION; ANGSTROMS; TELESCOPE
AB We observed two solar active regions (NOAA regions 7563 and 7565), quiet-Sun areas, and a coronal hole region simultaneously with Goddard Space Flight Center's Solar EUV Rocket Telescope and Spectrograph (SERTS) and with the Yohkoh Soft X-ray Telescope (SXT) on 1993 August 17. SERTS provided spatially resolved active region and quiet-Sun slit spectra in the 280 to 420 Angstrom, wavelength range, and images in the lines of He II lambda 303.8, Mg IX lambda 368.1, Fe XV lambda 284.1, and Fe XVI lambda lambda 335.4 and 360.8 SXT provided images through multiple broadband filters in both the full-frame imaging mode and the partial-frame imaging mode.
The SERTS images in Fe XV (log T-max=6.33, where T-max is the temperature which maximizes the fractional ion abundance in the available ionization equilibrium calculations, i.e., the formation temperature) and Fe XVI (log T-max=6.43) exhibit remarkable morphological similarity to the SXT images. Whereas the Fe XV and XVI images outline the loop structures seen with SXT, the cooler He II (log T-max=4.67) and Mg IX (log T-max=5.98) images outline loop footpoints. In addition, the Mg IX emission outlines other structures not necessarily associated with the hot loops; these may be cool (T less than or similar to 1x10(6) K) loops.
From the spatially resolved slit spectra, we obtained emission-line profiles for lines of He II lambda 303.8, Mg IX lambda 368.1, Fe XIII lambda 348.2, Fe XIV lambda 303.3, Fe XIV lambda 334.2, Fe XVI lambda 284.1, and Fe XVI lambda 335.4 for each spatial position. Based upon the spatial variations of the line intensities, active region 7563 systematically narrows when viewed with successively hotter lines, and appears narrowest in the broadband soft X-ray emission. The active region width (full width at half-maximum intensity) diminishes linearly with log T-max; the linear fit yields an extrapolated effective log T-max of 6.51+/-0.01 for the X-ray emission. The most intense, central core straddles the magnetic neutral line.
Active region and quiet-Sun one-dimensional temperature scans were derived from intensity ratios of spatially resolved SERTS slit spectral lines, and from coregistered SXT filter ratios. The highest plasma temperatures were measured in the most intense, central core of region 7563. The temperatures derived from Fe XVI lambda 335.4/Fe XV lambda 284.1 and Fe XVI lambda 335.4/Fe XIV lambda 334.2 vary significantly (based upon the measurement uncertainties) but not greatly (factors of less than 1.5) across the slit. The average log T values derived from the above two ratios for region 7563 are 6.39+/-0.04 and 6.32+/-0.02, respectively. Somewhat larger systematic variations were obtained from all available SXT filter ratios. The average active region log T values derived from the SXT AlMgMn/thin Al, thick Al/thin Al, and thick Al/AlMgMn filter ratios are 6.33+/-0.03, 6.45+/-0.02, and 6.49+/-0.03, respectively.
Active region and quiet-Sun one-dimensional density scans were derived from intensity ratios of spatially resolved SERTS slit spectral lines of Fe XIII and Fe XIV. The derived densities show neither systematic nor significant variations along the slit in either the active region or the quiet-Sun, despite the fact that the intensities themselves vary substantially. This indicates that the product of the volume filling factor and the path length (f Delta l) must be greater by factors of 3-5 in the active region core than in the outskirts. Furthermore, the derived active region densities are similar to 2 times the quiet-Sun densities. This density difference is adequate to explain the factor of similar to 4 intensity difference in Fe XII and Fe XIII between the active and quiet areas, but it is not adequate to explain the factor of similar to 8 intensity difference in Fe XIV between the active and quiet areas. We attribute the latter to a greater f Delta l in the active regions.
Statistically significant Doppler shifts are not detected in region 7563 or in the quiet-Sun with any of the EUV lines.
C1 NATL ASTRON OBSERV,MITAKA,TOKYO 181,JAPAN.
OSSERV ASTROFIS ARCETRI,I-50125 FLORENCE,ITALY.
HUGHES STX CORP,LANHAM,MD 20706.
LOCKHEED SOLAR & ASTROPHYS LAB,PALO ALTO,CA 94304.
RP Brosius, JW (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,CODE 682,GREENBELT,MD 20771, USA.
NR 40
TC 29
Z9 30
U1 0
U2 0
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD MAR 10
PY 1997
VL 477
IS 2
BP 969
EP &
DI 10.1086/303728
PN 1
PG 19
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WM090
UT WOS:A1997WM09000037
ER
PT J
AU Doschek, GA
Mariska, JT
Warren, HP
Wilhelm, K
Lemaire, P
Kucera, T
Schuhle, U
AF Doschek, GA
Mariska, JT
Warren, HP
Wilhelm, K
Lemaire, P
Kucera, T
Schuhle, U
TI Determination of the formation temperature of Si IV in the solar
transition region
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE sun, transition region; ultraviolet, stars
ID QUIET-SUN; AL-III
AB Using spectra obtained with the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer flown on the Solar and Heliospheric Observatory spacecraft, we deduce the temperature of formation of the Si IV ion in the solar transition region from the Si IV ultraviolet spectral line intensity ratio, 3p(2)P(3/2)-3d(2)D(3/2,5/2)/3s(2)S(1/2)-3p(2)P(1/2) and compare the result to the temperature predicted under the assumption of ionization equilibrium. The wavelengths are as follows: D-2(3/2,5/2), 1128.325, 1128.340 Angstrom; 2P(1/2), 1402.770 Angstrom. Ratios are derived for typical features of the quiet Sun, such as cell center and network, and are systematically higher than those predicted at the 6.3 x 10(4) K ionization equilibrium temperature of formation of Si IV. For most solar features the ratios imply a temperature of formation of about 8.5 x 10(4) K. The ratios for the faintest features imply a temperature of formation of up to 1.6 x 10(5) K. It is not clear, however, that all the discrepancies between the measured and theoretical ratios are due to a temperature effect. Accurate temperature measurements are important since a large discrepancy from ionization equilibrium has significant implications for the physics of the transition region, such as the possible presence of nonthermal electrons.
C1 MAX PLANCK INST AERON, D-37189 KATLENBURG DUHM, GERMANY.
UNIV PARIS 11, INST ASTROPHYS SPATIALE, UNITE MIXTE CNRS, F-91405 ORSAY, FRANCE.
NASA, GODDARD SPACE FLIGHT CTR, APPL RES CORP, GREENBELT, MD 20771 USA.
RP USN, RES LAB, EO HULBURT CTR SPACE RES, CODE 7670, 4555 OVERLOOK AVE SW, WASHINGTON, DC 20375 USA.
RI Kucera, Therese/C-9558-2012;
OI Kucera, Therese/0000-0001-9632-447X
NR 15
TC 19
Z9 19
U1 0
U2 0
PU IOP PUBLISHING LTD
PI BRISTOL
PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND
SN 0004-637X
EI 1538-4357
J9 ASTROPHYS J
JI Astrophys. J.
PD MAR 10
PY 1997
VL 477
IS 2
BP L119
EP +
DI 10.1086/310529
PN 2
PG 1
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WM091
UT WOS:A1997WM09100012
ER
PT J
AU Harmon, BA
Deal, KJ
Paciesas, WS
Zhang, SN
Robinson, CR
Gerard, E
Rodriguez, LF
Mirabel, IF
AF Harmon, BA
Deal, KJ
Paciesas, WS
Zhang, SN
Robinson, CR
Gerard, E
Rodriguez, LF
Mirabel, IF
TI Hard X-ray signature of plasma ejection in the galactic jet source GRS
1915+105
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE accretion, accretion disks; black hole physics; galaxies, jets; stars,
individual (GRS 1915+105)
ID RELATIVISTIC JETS; CYGNUS-X-3; WATCH
AB Since its discovery in 1992, GRS 1915+105 has undergone numerous X-ray outbursts with luminosities ranging from 10(37) to a few x10(38) ergs s(-1) (20-100 keV). The radio counterpart sometimes exhibits optically thin flares (0.1-1 Jy) in the GHz frequency range associated with superluminal ejection of radio-emitting plasma. Here we examine the temporal and spectral evolution of the hard X-ray and radio emission of GRS 1915+105. We find, during a 1993 December to 1994 April spring outburst, an exceptionally high level of activity in the GHz band coupled with the appearance of several ejection events when compared to other monitoring results. Within the derived uncertainty of the ejection times and the subsequent appearance of radio flares, there appear to be decreases or dips in the hard X-ray flux anticorrelated with increases in radio emission. These observations suggest an interaction between the hard X-ray emission region and jet production, and they imply the redirection of accretion material into jets on timescales of days or less. Although jet production may occur at high accretion rates, other factors must be important, i.e., at times, something must ''break'' the correlative nature of the radio and X-ray bands. We also search for long-term periodicities in the X-ray data for evidence of a binary signature in light of recent suggestions that GRS 1915+105 may be a high-mass system.
C1 UNIV ALABAMA, DEPT PHYS, HUNTSVILLE, AL 35899 USA.
NASA, MARSHALL SPACE FLIGHT CTR, UNIV SPACE RES ASSOC, HUNTSVILLE, AL 35812 USA.
OBSERV PARIS, DEPT ARPEGES, SECT MEUDON, F-92195 MEUDON, FRANCE.
NATL AUTONOMOUS UNIV MEXICO, INST ASTRON, MEXICO CITY 04510, DF, MEXICO.
CTR ETUD SACLAY, DAPNIA, CEA, SERV ASTROPHYS, DSM, F-91191 GIF SUR YVETTE, FRANCE.
RP Harmon, BA (reprint author), NASA, MARSHALL SPACE FLIGHT CTR, SPACE SCI LAB, ES84, HUNTSVILLE, AL 35812 USA.
NR 29
TC 48
Z9 48
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 MAR 10
PY 1997
VL 477
IS 2
BP L85
EP L89
DI 10.1086/310526
PN 2
PG 5
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WM091
UT WOS:A1997WM09100004
ER
PT J
AU Takashima, T
Doke, T
Hayashi, T
Kikuchi, J
Kobayashi, M
Shirai, H
Takehana, N
Ehara, M
Yamada, Y
Yanagita, S
Hasebe, N
Kashiwagi, T
Kato, C
Munakata, K
Kohno, T
Kondoh, K
Murakami, H
Nakamoto, A
Yanagimachi, T
Reames, DV
vonRosenvinge, TT
AF Takashima, T
Doke, T
Hayashi, T
Kikuchi, J
Kobayashi, M
Shirai, H
Takehana, N
Ehara, M
Yamada, Y
Yanagita, S
Hasebe, N
Kashiwagi, T
Kato, C
Munakata, K
Kohno, T
Kondoh, K
Murakami, H
Nakamoto, A
Yanagimachi, T
Reames, DV
vonRosenvinge, TT
TI The first observation of sulfur in anomalous cosmic rays by the Geotail
and the Wind spacecrafts
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE cosmic rays; ISM, general
ID SPECTRA; NUCLEI; OXYGEN
AB The Geotail high-energy particle instruments have observed cosmic-ray particles in the energy range from 3 MeV n(-1) to 150 MeV n(-1) at 1 AU during the period 1992 September-1995 August. A remarkable enhancement of anomalous cosmic-ray (ACR) N, O, Ne, and C is observed during the period. A measurable enhancement of the sulfur flux below about 20 MeV n(-1) was observed. This is the first evidence showing the existence of sulfur in the anomalous component. The flux increase of anomalous sulfur, with a first ionization potential (FIP) of 10.4 eV, is smaller than that of ACR carbon with an FIP of 11.3 eV and much smaller than those of high-FIP elements, which suggests that the fractions of neutral carbon and sulfur atoms are significantly low in the very local interstellar medium.
C1 IBARAKI UNIV,DEPT EARTH SCI,MITO,IBARAKI 310,JAPAN.
EHIME UNIV,DEPT COMP SCI,MATSUYAMA,EHIME 790,JAPAN.
KANAGAWA UNIV,FAC ENGN,YOKOHAMA,KANAGAWA 221,JAPAN.
SHINSHU UNIV,DEPT PHYS,MATSUMOTO,NAGANO 390,JAPAN.
RIKEN,INST PHYS & CHEM RES,WAKO,SAITAMA 35101,JAPAN.
EHIME UNIV,DEPT PHYS,MATSUYAMA,EHIME 790,JAPAN.
RIKKYO UNIV,DEPT PHYS,TOKYO 113,JAPAN.
NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771.
RP Takashima, T (reprint author), WASEDA UNIV,ADV RES INST SCI & ENGN,OKUBO 3-4-1,TOKYO 169,JAPAN.
NR 15
TC 11
Z9 11
U1 0
U2 0
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD MAR 10
PY 1997
VL 477
IS 2
BP L111
EP L113
DI 10.1086/310533
PN 2
PG 3
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WM091
UT WOS:A1997WM09100010
ER
PT J
AU Zhang, SN
Cui, W
Harmon, BA
Paciesas, WS
Remillard, RE
vanParadijs, J
AF Zhang, SN
Cui, W
Harmon, BA
Paciesas, WS
Remillard, RE
vanParadijs, J
TI The 1996 soft state transition of Cygnus X-1
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE accretion, accretion disks; black hole physics; stars, individual
(Cygnus X-1); X-rays, stars
ID X-RAY VARIABILITY; SPECTRA; GX-339-4
AB We report continuous monitoring of Cygnus X-1 in the 1.3-200 keV band using Ah-Sky Monitor/Rossi X-Ray Timing Explorer and BATSE/Compton Gamma Ray Observatory for about 200 days from 1996 February 21 to early September. During this period, Cygnus X-1 experienced a hard-to-soft and then a soft-to-hard state transition. The low-energy X-ray (1.3-12 keV) and high-energy X-ray (20-200 keV) fluxes are strongly anticorrelated during this period. During the state transitions, flux variations of about a factor of 5 and 15 were seen in the 1.3-3.0 keV and 100-200 keV bands, respectively, while the average 4.8-12 keV flux remains almost unchanged. The net effect of this pivoting is that the total 1.3-200 keV luminosity remained unchanged to within similar to 15%. The bolometric luminosity in the soft state may be as high as 50%-70% above the hard state luminosity, after color corrections for the luminosity below 1.3 keV. The blackbody component flux and temperature increase in the soft state are probably caused by a combination of the optically thick disk mass accretion rate increase and a decrease of the inner disk radius.
C1 UNIV SPACE RES ASSOC,COLUMBIA,MD.
MIT,CTR SPACE RES,CAMBRIDGE,MA 02139.
UNIV ALABAMA,HUNTSVILLE,AL 35899.
UNIV AMSTERDAM,STERRENKUNDIG INST ANTON PANNEKOEK,NL-1098 SJ AMSTERDAM,NETHERLANDS.
RP Zhang, SN (reprint author), NASA,MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812, USA.
NR 44
TC 110
Z9 112
U1 0
U2 0
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD MAR 10
PY 1997
VL 477
IS 2
BP L95
EP L98
DI 10.1086/310530
PN 2
PG 4
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WM091
UT WOS:A1997WM09100006
ER
PT J
AU Bawden, GW
Donnellan, A
Kellogg, LH
Dong, DN
Rundle, JB
AF Bawden, GW
Donnellan, A
Kellogg, LH
Dong, DN
Rundle, JB
TI Geodetic measurements of horizontal strain near the White Wolf fault,
Kern County, California, 1926-1993
SO JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
LA English
DT Article
ID SAN-ANDREAS FAULT; SOUTHERN-CALIFORNIA; CONTEMPORARY SEISMICITY; CRUSTAL
DEFORMATION; JOAQUIN VALLEY; EARTHQUAKE; ACCUMULATION
AB The White Wolf fault, located north of the Big Bend segment of the San Andreas fault, is the NE-SW trending, left lateral-oblique reverse fault responsible for the M(S)=7.8 1952 Kern County earthquake. We combined Global Positioning System (GPS) measurements with historical triangulation and trilateration data to determine changes in the strain rate over 7 decades (1926-1993). We reanalyzed the historical geodetic data and calculated an elevated preseismic (1926-1952) maximum shear strain rate (gamma over dot) of 0.62 +/- 0.16 mu strain/yr across the White Wolf fault. The maximum shear strain rate decreased with distance toward the Garlock fault to 0.09 +/- 0.08 mu strain/yr. In the decade following the earthquake (1952-1963), the near fault gamma over dot was high (0.85 +/-0.23 mu strain/yr), and decreased to 0.23+/-0.13 mu strain/yr across the Garlock fault. In 1993, we resurveyed many of the same monuments with GPS receivers to estimate fault-crossing and off-fault strain rates for the preceding 30 years. Across the White Wolf fault, the maximum shear strain rate (gamma over dot) dropped to 0.19+/-0.07 mu strain/yr. The azimuths of the maximum principal strain rates (phi) for the 1963-1993 epoch rotate from a fault normal orientation (-57 degrees+/-15 degrees) across the White Wolf fault to 11 degrees+/-3 degrees E across the Garlock fault.
C1 CALTECH, JET PROP LAB, PASADENA, CA 91109 USA.
UNIV COLORADO, CIRES, BOULDER, CO 80309 USA.
RP Bawden, GW (reprint author), LAWRENCE LIVERMORE NATL LAB, DEPT GEOL, DAVIS, CA 95616 USA.
RI Kellogg, Louise/J-2171-2012
OI Kellogg, Louise/0000-0001-5874-0472
NR 34
TC 20
Z9 20
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 MAR 10
PY 1997
VL 102
IS B3
BP 4957
EP 4967
DI 10.1029/96JB03554
PG 11
WC Geochemistry & Geophysics
SC Geochemistry & Geophysics
GA WM584
UT WOS:A1997WM58400002
ER
PT J
AU Zumberge, JF
Heflin, MB
Jefferson, DC
Watkins, MM
Webb, FH
AF Zumberge, JF
Heflin, MB
Jefferson, DC
Watkins, MM
Webb, FH
TI Precise point positioning for the efficient and robust analysis of GPS
data from large networks
SO JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
LA English
DT Article
ID LANDERS EARTHQUAKE SEQUENCE; CRUSTAL DEFORMATION; POLE POSITION; SYSTEM
AB Networks of dozens to hundreds of permanently operating precision Global Positioning System (GPS) receivers are emerging at spatial scales that range from 10(0) to 10(3) km. To keep the computational burden associated with the analysis of such data economically feasible, one approach is to first determine precise GPS satellite positions and clock corrections from a globally distributed network of GPS receivers. Then, data from the local network are analyzed by estimating receiver-specific parameters with receiver-specific data; satellite parameters are held fixed at their values determined in the global solution. This ''precise point positioning'' allows analysis of data from hundreds to thousands of sites every day with 40-Mflop computers, with results comparable in quality to the simultaneous analysis of all data. The reference frames for the global and network solutions can be free of distortion imposed by erroneous fiducial constraints on any sites.
RP Zumberge, JF (reprint author), CALTECH, JET PROP LAB, 4800 OAK GROVE DR, MS 238-600, PASADENA, CA 91109 USA.
NR 29
TC 1089
Z9 1204
U1 17
U2 87
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA
SN 2169-9313
EI 2169-9356
J9 J GEOPHYS RES-SOL EA
JI J. Geophys. Res.-Solid Earth
PD MAR 10
PY 1997
VL 102
IS B3
BP 5005
EP 5017
DI 10.1029/96JB03860
PG 13
WC Geochemistry & Geophysics
SC Geochemistry & Geophysics
GA WM584
UT WOS:A1997WM58400005
ER
PT J
AU Tornkvist, O
Schroder, E
AF Tornkvist, O
Schroder, E
TI Vortex dynamics in dissipative systems
SO PHYSICAL REVIEW LETTERS
LA English
DT Article
ID DEFECT-MEDIATED TURBULENCE; QUANTUM VORTICES; WAVES; FILAMENTS; MODEL
AB We derive the exact equation of motion for a vortex in two- and three-dimensional nonrelativistic systems governed by the Ginzburg-Landau equation with complex coefficients. The velocity is given in terms of local gradients of the magnitude and phase of the complex field and is exact also for arbitrarily small intervortex distances. The results for vortices in a superfluid or a superconductor are recovered.
C1 NIELS BOHR INST,DK-2100 COPENHAGEN O,DENMARK.
RP Tornkvist, O (reprint author), FERMILAB NATL ACCELERATOR LAB,NASA,FERMILAB ASTROPHYS CTR,MS209,POB 500,BATAVIA,IL 60510, USA.
RI Schroder, Elsebeth/A-2030-2011
OI Schroder, Elsebeth/0000-0003-4995-3585
NR 30
TC 20
Z9 20
U1 0
U2 1
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 0031-9007
J9 PHYS REV LETT
JI Phys. Rev. Lett.
PD MAR 10
PY 1997
VL 78
IS 10
BP 1908
EP 1911
DI 10.1103/PhysRevLett.78.1908
PG 4
WC Physics, Multidisciplinary
SC Physics
GA WM064
UT WOS:A1997WM06400020
ER
PT J
AU Apfel, RE
Tian, Y
Jankovsky, J
Shi, T
Chen, X
Holt, RG
Trinh, E
Croonquist, A
Thornton, KC
Sacco, A
Coleman, C
Leslie, FW
Matthiesen, DH
AF Apfel, RE
Tian, Y
Jankovsky, J
Shi, T
Chen, X
Holt, RG
Trinh, E
Croonquist, A
Thornton, KC
Sacco, A
Coleman, C
Leslie, FW
Matthiesen, DH
TI Free oscillations and surfactant studies of superdeformed drops in
microgravity
SO PHYSICAL REVIEW LETTERS
LA English
DT Article
ID DEFORMED LIQUID-DROP; SHAPE OSCILLATIONS; ACOUSTIC FIELD; RESONANCE;
TENSION
AB An unprecedented microgravity observation of maximal shape oscillations of a surfactant-bearing water drop the size of a ping-pong ball was observed during a mission of Space Shuttle Columbia. The goal of the research, of which this observation is a part, was to study the rheological properties of liquid drop surfaces on which are adsorbed surfactant molecules under conditions not possible at Ig. Numerical computation of the evolution of the shape of greatly deformed drops using the boundary integral method has successfully predicted the observed drop shapes over a complete cycle of oscillation, thereby permitting the calculation of the dynamic surface tension under these unique conditions.
C1 CALTECH,JET PROP LAB,PASADENA,CA 91109.
NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058.
THOMAS JEFFERSON UNIV,PHILADELPHIA,PA 19107.
RP Apfel, RE (reprint author), YALE UNIV,DEPT MECH ENGN,NEW HAVEN,CT 06520, USA.
RI Holt, Ray/G-5677-2010
NR 20
TC 59
Z9 61
U1 1
U2 11
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 MAR 10
PY 1997
VL 78
IS 10
BP 1912
EP 1915
DI 10.1103/PhysRevLett.78.1912
PG 4
WC Physics, Multidisciplinary
SC Physics
GA WM064
UT WOS:A1997WM06400021
ER
PT J
AU Schwenke, DW
AF Schwenke, DW
TI Exchange integrals for four-atom reactive-scattering calculations
SO JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS
LA English
DT Article
ID ABSORBING BOUNDARY-CONDITIONS; REACTION PROBABILITIES; QUANTUM
SCATTERING; 4-ATOM REACTIONS; STATE; H-2+CN->H+HCN; OH+H-2->H2O+H
AB We give the details required for evaluating the exchange integrals that arise when treating four-atom reactive scattering using variational basis set methods to solve the time-independent Schrodinger equation.
RP Schwenke, DW (reprint author), NASA,AMES RES CTR,MAIL STOP 230-3,MOFFETT FIELD,CA 94035, USA.
RI schwenke, david/I-3564-2013
NR 30
TC 0
Z9 0
U1 0
U2 0
PU ROYAL SOC CHEMISTRY
PI CAMBRIDGE
PA THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON ROAD, CAMBRIDGE, CAMBS,
ENGLAND CB4 4WF
SN 0956-5000
J9 J CHEM SOC FARADAY T
JI J. Chem. Soc.-Faraday Trans.
PD MAR 7
PY 1997
VL 93
IS 5
BP 811
EP 814
DI 10.1039/a606067f
PG 4
WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical
SC Chemistry; Physics
GA WP012
UT WOS:A1997WP01200018
ER
PT J
AU Allison, TC
Mielke, SL
Schwenke, DW
Truhlar, DG
AF Allison, TC
Mielke, SL
Schwenke, DW
Truhlar, DG
TI Funnel states as mediators of Born-Oppenheimer breakdown in reactions at
an avoided crossing
SO JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS
LA English
DT Review
ID POTENTIAL-ENERGY SURFACES; ELECTRONICALLY NONADIABATIC REACTION;
TRANSITION-STATE; MC-SCF; SCATTERING CALCULATIONS; QUANTUM
PHOTOCHEMISTRY; MOLECULAR-COLLISIONS; CHEMICAL-REACTION; APPROXIMATION;
SYSTEMS
AB Accurate quantum dynamics calculations are described for a series of three-body model systems exhibiting closely avoided crossings of potential energy surfaces in the vicinity of the reaction barrier. In particular, the surfaces show avoided crossings of bond-switching diabatic states in the vicinity of a saddle point. The dynamics calculations are carried out by linear algebraic variational methods with diabatic electronic basis functions. The coupling of electronically non-adiabatic effects to barrier crossings leads to qualitatively new kinds of quantum effects on the chemical reactivity. We nd strong non-adiabatic effects on reaction probabilities due to funnel resonances with weaker effects (typically 2-20%) off resonance.
C1 UNIV MINNESOTA,DEPT CHEM,MINNEAPOLIS,MN 55455.
UNIV MINNESOTA,INST SUPERCOMP,MINNEAPOLIS,MN 55455.
NASA,AMES RES CTR,MOFFETT FIELD,CA 94035.
RI Mielke, Steven/B-7533-2008; schwenke, david/I-3564-2013; Truhlar,
Donald/G-7076-2015
OI Mielke, Steven/0000-0002-1938-7503; Truhlar, Donald/0000-0002-7742-7294
NR 102
TC 20
Z9 20
U1 0
U2 5
PU ROYAL SOC CHEMISTRY
PI CAMBRIDGE
PA THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON ROAD, CAMBRIDGE, CAMBS,
ENGLAND CB4 4WF
SN 0956-5000
J9 J CHEM SOC FARADAY T
JI J. Chem. Soc.-Faraday Trans.
PD MAR 7
PY 1997
VL 93
IS 5
BP 825
EP 832
DI 10.1039/a606254g
PG 8
WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical
SC Chemistry; Physics
GA WP012
UT WOS:A1997WP01200021
ER
PT J
AU Gawronski, W
Sawicki, JT
AF Gawronski, W
Sawicki, JT
TI Response errors of non-proportionally lightly damped structures
SO JOURNAL OF SOUND AND VIBRATION
LA English
DT Letter
ID FREQUENCY-RESPONSE; LINEAR-SYSTEMS; EQUATIONS; BOUNDS; MOTION
C1 CLEVELAND STATE UNIV, DEPT MECH ENGN, CLEVELAND, OH 44115 USA.
RP Gawronski, W (reprint author), CALTECH, JET PROP LAB, 4800 OAK GROVE DR, PASADENA, CA 91109 USA.
NR 21
TC 27
Z9 27
U1 0
U2 2
PU ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
PI LONDON
PA 24-28 OVAL RD, LONDON NW1 7DX, ENGLAND
SN 0022-460X
EI 1095-8568
J9 J SOUND VIB
JI J. Sound Vibr.
PD MAR 6
PY 1997
VL 200
IS 4
BP 543
EP 550
DI 10.1006/jsvi.1996.0682
PG 8
WC Acoustics; Engineering, Mechanical; Mechanics
SC Acoustics; Engineering; Mechanics
GA WN365
UT WOS:A1997WN36500015
ER
PT J
AU Lissauer, JJ
AF Lissauer, JJ
TI Planetary systems - Growing up in a two-parent family?
SO NATURE
LA English
DT Editorial Material
ID BETA-PICTORIS; DISKS; STARS
RP Lissauer, JJ (reprint author), NASA, AMES RES CTR, DIV SPACE SCI, MOFFETT FIELD, CA 94035 USA.
NR 15
TC 6
Z9 6
U1 0
U2 0
PU NATURE PUBLISHING GROUP
PI LONDON
PA MACMILLAN BUILDING, 4 CRINAN ST, LONDON N1 9XW, ENGLAND
SN 0028-0836
J9 NATURE
JI Nature
PD MAR 6
PY 1997
VL 386
IS 6620
BP 18
EP 19
DI 10.1038/386018a0
PG 2
WC Multidisciplinary Sciences
SC Science & Technology - Other Topics
GA WL746
UT WOS:A1997WL74600024
ER
PT J
AU Bublitz, GU
Ortiz, R
Runser, C
Fort, A
Barzoukas, M
Marder, SR
Boxer, SG
AF Bublitz, GU
Ortiz, R
Runser, C
Fort, A
Barzoukas, M
Marder, SR
Boxer, SG
TI Stark spectroscopy of donor-acceptor polyenes: Correlation with
nonlinear optical measurements
SO JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
LA English
DT Article
ID BOND-LENGTH ALTERNATION; POLARIZABILITIES
C1 STANFORD UNIV, DEPT CHEM, STANFORD, CA 94305 USA.
CALTECH, BECKMAN INST, PASADENA, CA 91125 USA.
INST PHYS & CHIM MAT STRASBOURG, OPT NONLINEAIRE & OPTOELECT GRP, UMR 046 CNRS, F-67037 STRASBOURG, FRANCE.
CALTECH, JET PROP LAB, PASADENA, CA 91109 USA.
NR 13
TC 57
Z9 57
U1 0
U2 10
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 MAR 5
PY 1997
VL 119
IS 9
BP 2311
EP 2312
DI 10.1021/ja963672r
PG 2
WC Chemistry, Multidisciplinary
SC Chemistry
GA WL646
UT WOS:A1997WL64600040
ER
PT J
AU Rulison, AJ
Rhim, WK
Bayuzick, R
Hofmeister, W
Morton, C
AF Rulison, AJ
Rhim, WK
Bayuzick, R
Hofmeister, W
Morton, C
TI Containerless liquid to solid nucleation pathways in two representative
grades of commercially available zirconium
SO ACTA MATERIALIA
LA English
DT Article
ID SOLIDIFICATION
AB Experimental measurements were conducted to determine the solid metal nucleation pathways of radiatively cooling, molten zirconium spheres of two different commercially available purity grades in a high-vacuum, high-temperature electrostatic levitator. The ensemble distribution of maximum undercooling temperatures was interpreted using Poisson statistics to determine the temperature dependence of the solid metal nucleation rate. For a sample of nominally 99.95% pure zirconium, the results are consistent with heterogeneous solid metal nucleation either on static catalyst particles at least similar to 30 nm diameter or on a surface coating. For a sample of nominally 99% pure zirconium, however, it appears that heterogeneous solid metal nucleation occurred either on a polydispersion of similar to 10 nm (mean diameter) static catalyst particles or on dynamic catalyst particles that precipitated from a solution that became supersaturated as the melt cooled. Copyright (C) 1997 Acta Metallurgica Inc.
C1 CALTECH,JET PROP LAB,PASADENA,CA 91109.
VANDERBILT UNIV,NASHVILLE,TN 37235.
OI Hofmeister, William/0000-0002-4145-7061
NR 21
TC 4
Z9 4
U1 2
U2 2
PU PERGAMON-ELSEVIER SCIENCE LTD
PI OXFORD
PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB
SN 1359-6454
J9 ACTA MATER
JI Acta Mater.
PD MAR
PY 1997
VL 45
IS 3
BP 1237
EP 1245
DI 10.1016/S1359-6454(96)00237-6
PG 9
WC Materials Science, Multidisciplinary; Metallurgy & Metallurgical
Engineering
SC Materials Science; Metallurgy & Metallurgical Engineering
GA WK702
UT WOS:A1997WK70200031
ER
PT J
AU Chien, S
DeCoste, D
Doyle, R
Stolorz, P
AF Chien, S
DeCoste, D
Doyle, R
Stolorz, P
TI Making an impact - Artificial intelligence at the jet propulsion
laboratory
SO AI MAGAZINE
LA English
DT Article
AB The National Aeronautics and Space Administration (NASA) is being challenged to perform more frequent and intensive space-exploration missions at greatly reduced cost. Nowhere is this challenge more acute than among robotic planetary exploration missions that the Jet Propulsion Laboratory (JPL) conducts for NASA. This article describes recent and ongoing work on spacecraft autonomy and ground systems that builds on a legacy of existing success at JPL applying AI techniques to challenging computational problems in planning and scheduling, real-time monitoring and control, scientific data analysis, and design automation.
C1 CALTECH, JET PROP LAB, INFORMAT & COMP TECHNOL RES SECT, MONITORING & DIAGNOSIS TECHNOL GRP, PASADENA, CA 91125 USA.
CALTECH, JET PROP LAB, INFORMAT & COMP TECHNOL RES SECT, MACHINE LEARNING SYST GRP, PASADENA, CA 91125 USA.
RP Chien, S (reprint author), CALTECH, JET PROP LAB, INFORMAT & COMP TECHNOL RES SECT, ARTIFICIAL INTELLIGENCE GRP, PASADENA, CA 91125 USA.
NR 37
TC 7
Z9 9
U1 0
U2 1
PU AMER ASSOC ARTIFICIAL INTELL
PI MENLO PK
PA 445 BURGESS DRIVE, MENLO PK, CA 94025-3496 USA
SN 0738-4602
J9 AI MAG
JI AI Mag.
PD SPR
PY 1997
VL 18
IS 1
BP 103
EP 122
PG 20
WC Computer Science, Artificial Intelligence
SC Computer Science
GA WP604
UT WOS:A1997WP60400013
ER
PT J
AU Seiner, JM
Gilinsky, MM
AF Seiner, JM
Gilinsky, MM
TI Nozzle thrust optimization while reducing jet noise
SO AIAA JOURNAL
LA English
DT Article; Proceedings Paper
CT CEAS/AIAA Aeroacoustics Conference
CY JUN 12-15, 1995
CL MUNICH, GERMANY
SP CEAS, AIAA
AB A Bluebell nozzle design concept is proposed for jet noise reduction with minimal thrust loss or even thrust augmentation. A Bluebell nozzle has a sinusoidal lip-line edge (chevrons) and a sinusoidal cross-section shape with linear amplitude increasing downstream in the divergent nozzle part (corrugations). The experimental tests of several Bluebell nozzle designs have shown noise reduction relative to a convergent-divergent round nozzle with design exhaust Mach number M(e) = 1.5. The best design provides an acoustic benefit near 4 dB with about 1% thrust augmentation. For subsonic flow (M(e) = 0.6), the tests indicated that the present method of design for Bluebell nozzles produces increased levels of jet noise. The proposed designs incorporate analytical theory and two- and three-dimensional numerical simulations. Full Navier-Stokes and Euler solvers were utilized. Boundary layer effects were used. Several different designs were accounted for in the Euler applications.
C1 HAMPTON UNIV,HAMPTON,VA 23668.
RP Seiner, JM (reprint author), NASA,LANGLEY RES CTR,HAMPTON,VA 23681, USA.
NR 13
TC 4
Z9 6
U1 0
U2 1
PU AMER INST AERONAUT ASTRONAUT
PI RESTON
PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091
SN 0001-1452
J9 AIAA J
JI AIAA J.
PD MAR
PY 1997
VL 35
IS 3
BP 420
EP 427
DI 10.2514/2.130
PG 8
WC Engineering, Aerospace
SC Engineering
GA WM098
UT WOS:A1997WM09800002
ER
PT J
AU Doggett, GP
Chokani, N
Wilkinson, SP
AF Doggett, GP
Chokani, N
Wilkinson, SP
TI Effect of angle of attack on hypersonic boundary-layer stability
SO AIAA JOURNAL
LA English
DT Article
AB An experimental investigation of the effects of angle of attack on hypersonic boundary-layer stability on a flared-cone model was conducted in the low-disturbance Mach-6 Nozzle-Test-Chamber Facility at NASA Langley Research Center, Hot-wire anemometry diagnostics were applied to identify the boundary-layer instability mechanisms that lead to transition, The present results show that the boundary layer becomes more stable on the windward ray and less stable on the leeward ray relative to the zero-degree angle-of-attack case, The second-mode instability dominates the transition process at a 0-deg angle of attack; however, on the windward meridian at an angle of attack this mode was stabilized, On the leeward meridian the frequency of the dominant instability was higher than the estimated frequency of the second-mode disturbance; thus the dominant transition mechanism may be other than a second-mode disturbance. Nonlinear effects, such as growth saturation, harmonic generation, and spectral broadening, were observed in the transitional and turbulent flow regimes.
C1 NASA,LANGLEY RES CTR,FLOW MODELING & CONTROL BRANCH,FLUID MECH & ACOUST DIV,HAMPTON,VA 23681.
RP Doggett, GP (reprint author), N CAROLINA STATE UNIV,DEPT MECH & AEROSP ENGN,RALEIGH,NC 27695, USA.
NR 24
TC 17
Z9 21
U1 0
U2 1
PU AMER INST AERONAUT ASTRONAUT
PI RESTON
PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091
SN 0001-1452
J9 AIAA J
JI AIAA J.
PD MAR
PY 1997
VL 35
IS 3
BP 464
EP 470
DI 10.2514/2.152
PG 7
WC Engineering, Aerospace
SC Engineering
GA WM098
UT WOS:A1997WM09800008
ER
PT J
AU Weislogel, MM
AF Weislogel, MM
TI Spontaneous capillary flow in partially coated tubes
SO AICHE JOURNAL
LA English
DT Article
ID HETEROGENEOUS SURFACES; CONTACT LINE; SYSTEMS
AB A spontaneous, steady capillary flow is produced for a liquid index in a circular tube that is partially coated with a surface modifier to create a discontinuous wetting condition between upstream and downstream portions of the tube. As a means of demonstrating that the flow configuration may prove useful as a diagnostic tool in studies concerning capillarity and the physics associated with the moving contact line, average steady velocities are predicted and compared against a large experimental data set that includes the effects of tube dimensions and fluid properties. To access a wider range of tube diameters (0.516-9.88 mm), experiments are performed employing ''U-tubes'' tested in the low-gravity environment of a drop tower, in addition to straight capillary tubes tested horizontally in a laboratory. The sensitivity of the steady capillary flow to surface cleanliness is dramatic.
RP Weislogel, MM (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA.
NR 13
TC 28
Z9 29
U1 0
U2 11
PU AMER INST CHEMICAL ENGINEERS
PI NEW YORK
PA 345 E 47TH ST, NEW YORK, NY 10017
SN 0001-1541
J9 AICHE J
JI AICHE J.
PD MAR
PY 1997
VL 43
IS 3
BP 645
EP 654
DI 10.1002/aic.690430310
PG 10
WC Engineering, Chemical
SC Engineering
GA WM318
UT WOS:A1997WM31800009
ER
PT J
AU Sathaye, JA
Dixon, RK
Rosenzweig, C
AF Sathaye, JA
Dixon, RK
Rosenzweig, C
TI Climate change country studies
SO APPLIED ENERGY
LA English
DT Article; Proceedings Paper
CT International Workshop on Greenhouse Gas Mitigation Technologies and
Measures
CY NOV 12-15, 1996
CL BEIJING, PEOPLES R CHINA
SP US Country Studies Program, Environm Canada, German Fed Minist Econ Cooperat & dev, Netherlands Minist Foreign Affairs, Peoples Republic China, State Sci & Technol Commiss
ID EMISSIONS; ABATEMENT
AB Over the past three years, country studies have improved country-specific, and hence global, estimates of: (i) greenhouse gas (GHG) emissions and sequestration, and (ii) costs and benefits of mitigation options, and (iii) the vulnerability of natural habitats and human systems. The technical and financial support provided by the US and other country-study programs has enhanced the contribution of experts from developing and transition countries to their global scientific assessment. This paper presents a brief overview of work conducted in the context of the US Country Studies Program in the development of national GHG inventories, assessment of GHG mitigation options, and assessment of vulnerability to climate change and options for adaptation. Published by Elsevier Science Ltd.
C1 US COUNTRY STUDIES PROGRAM,WASHINGTON,DC.
COLUMBIA UNIV,NASA,GODDARD INST SPACE STUDIES,NEW YORK,NY.
RP Sathaye, JA (reprint author), LAWRENCE BERKELEY LAB,BERKELEY,CA 94720, USA.
NR 33
TC 8
Z9 8
U1 0
U2 1
PU ELSEVIER SCI LTD
PI OXFORD
PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB
SN 0306-2619
J9 APPL ENERG
JI Appl. Energy
PD MAR-APR
PY 1997
VL 56
IS 3-4
BP 225
EP 235
DI 10.1016/S0306-2619(97)0007X-4
PG 11
WC Energy & Fuels; Engineering, Chemical
SC Energy & Fuels; Engineering
GA XR663
UT WOS:A1997XR66300005
ER
PT J
AU Han, M
Hoessel, JG
Gallagher, JS
Holtzman, J
Stetson, PB
Trauger, J
Ballester, GE
Burrows, C
Clarke, J
Crisp, D
Griffiths, R
Grillmair, C
Hester, J
Krist, J
Mould, JR
Scowen, P
Stapelfeldt, K
Watson, A
Westphal, J
AF Han, M
Hoessel, JG
Gallagher, JS
Holtzman, J
Stetson, PB
Trauger, J
Ballester, GE
Burrows, C
Clarke, J
Crisp, D
Griffiths, R
Grillmair, C
Hester, J
Krist, J
Mould, JR
Scowen, P
Stapelfeldt, K
Watson, A
Westphal, J
TI Stellar populations in the dwarf elliptical galaxy NGC 147
SO ASTRONOMICAL JOURNAL
LA English
DT Article
ID ASYMPTOTIC GIANT BRANCH; LOCAL GROUP GALAXIES; GLOBULAR-CLUSTERS; STARS;
NGC-147; EVOLUTION; NGC-205; CLOUDS; AGE
AB Deep V and I CCD images in a central and an outer field of the Local Group dwarf elliptical galaxy NGC 147 have been obtained with the Wide Field and Planetary Camera-2 (WFPC2) on board of the Hubble Space Telescope. The color-magnitude diagram shows a number of interesting features, including a well defined red giant branch (RGB); a red horizontal branch (HB), a strong red clump, and a small number of extended asymptotic giant branch (EAGB) stars. A mean distance modulus of (m-M)(0)=24.39 is derived based on both the HB and the RGB tip brightness. The metallicity [Fe/H] as determined from the RGB color has a mean value of -0.91 in the central field, and -1.0 in the outer field; and the outer field shows a weak tendency of increasing metallicity with galactocentric radius. A metallicity dispersion is also present in the galaxy, and it shows a clear radial variation in the sense that a larger dispersion is seen at smaller radii. The small population of EAGB stars indicates the presence of intermediate-aged (several Gyr) stars in the galaxy, while the absence of the main sequence stars with M(V)<1 shows that star formation ceased at least 1 Gyr ago. The distribution of the EAGB stars indicates that the younger stars are more centrally concentrated than the majority of older stars. A similar age gradient is also implied by the relative distribution of the HB stars, which appear to be more populous at larger radii. These results are considered within the context of theoretical models for the evolution of dwarf elliptical galaxies. (C) 1997 American Astronomical Society.
C1 NEW MEXICO STATE UNIV,DEPT ASTRON,LAS CRUCES,NM 88003.
DOMINION ASTROPHYS OBSERV,VICTORIA,BC V8X 4M6,CANADA.
CALTECH,JET PROP LAB,PASADENA,CA 91109.
UNIV MICHIGAN,DEPT ATMOSPHER & OCEAN SCI,ANN ARBOR,MI 48109.
SPACE TELESCOPE SCI INST,BALTIMORE,MD 21218.
ARIZONA STATE UNIV,DEPT PHYS & ASTRON,TEMPE,AZ 85287.
AUSTRALIAN NATL UNIV,MT STROMLO & SIDING SPRING OBSERV,WESTON,ACT 2611,AUSTRALIA.
CALTECH,PASADENA,CA 91125.
RP Han, M (reprint author), UNIV WISCONSIN,DEPT ASTRON,MADISON,WI 53706, USA.
RI Stapelfeldt, Karl/D-2721-2012; Clarke, John/C-8644-2013
NR 43
TC 80
Z9 80
U1 0
U2 1
PU AMER INST PHYSICS
PI WOODBURY
PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999
SN 0004-6256
J9 ASTRON J
JI Astron. J.
PD MAR
PY 1997
VL 113
IS 3
BP 1001
EP &
DI 10.1086/118316
PG 12
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WK846
UT WOS:A1997WK84600009
ER
PT J
AU Cornett, RH
Greason, MR
Hill, JK
Parker, JW
Waller, WH
Bohlin, RC
Cheng, KP
Neff, SG
OConnell, RW
Roberts, MS
Smith, AM
Stecher, TP
AF Cornett, RH
Greason, MR
Hill, JK
Parker, JW
Waller, WH
Bohlin, RC
Cheng, KP
Neff, SG
OConnell, RW
Roberts, MS
Smith, AM
Stecher, TP
TI UIT: Ultraviolet observations of the Small Magellanic Cloud
SO ASTRONOMICAL JOURNAL
LA English
DT Article
ID IMAGING TELESCOPE; STARS
AB A mosaic of four UIT far-UV (FUV) (lambda(eff)=1620 Angstrom) images, with derived stellar and H II region photometry, is presented for most of the Bar of the SMC. The UV morphology of the SMC's Bar shows that recent star formation there has left striking features including: (a) four concentrations of UV-bright stars spread from northeast to southwest at nearly equal (similar to 30 arcmin=0.5 kpc) spacings; (b) one of the concentrations, near DEM 55, comprises a well-defined 8-arcmin diameter ring surrounded by a larger H alpha ring, suggestive of sequential star formation. FUV PSF photometry is obtained for 11,306 stars in the FUV images, resulting in magnitudes m(162). We present a FUV luminosity function for the SMC Bar, complete to m(162)similar to 14.5. Detected objects are well correlated with other SMC Population I material; of 711 H alpha emission-line stars and small nebulae within the UIT fields of view, 520 are identified with FUV sources. The FUV photometry is compared with available ground-based catalogs of supergiants, yielding 191 detections of 195 supergiants with spectral type earlier than F0 in the UIT fields. The (m(162)-V) color for supergiants is a sensitive measure of spectral type. The bluest observed colors for each type agree well with colors computed from unreddened Galactic spectral atlas stars for types earlier than about A0; for later spectral types the observed SMC stars range significantly bluer, as predicted by comparison of low-metallicity and Galactic-composition models. Redder colors for some stars of all spectral types are attributed to the strong FUV extinction arising from even small amounts of SMC dust. Internal SMC reddenings are determined for all catalog stars. All stars with E(B-V)>0.15 are within regions of visible H alpha emission. FUV photometry for 42 H alpha-selected H II regions in the SMC Bar is obtained for stars and for total emission (as measured in H II-region-sized apertures). The flux-weighted average ratio of total to stellar FUV flux is 2.15; consideration of the stellar FUV luminosity function indicates that most of the excess total flux is due to scattered FUV radiation, rather than stars fainter than m(162)=14.5. Both stellar and total emission are well correlated with H alpha fluxes measured by Kennicutt and Hodge [ApJ. 306, 130 (1986)], yielding FUV/H alpha flux ratios that are consistent with models of SMC metallicity, ages from 1-5 Myr, and moderate (E(B-V) = 0.0-0.1 mag) internal SMC extinction. (C) 1997 American Astronomical Society.
C1 SW RES INST, BOULDER, CO 80302 USA.
SPACE TELESCOPE SCI INST, BALTIMORE, MD 21218 USA.
CALIF STATE UNIV FULLERTON, DEPT PHYS, FULLERTON, CA 92634 USA.
NASA, GODDARD SPACE FLIGHT CTR, ASTRON & SOLAR PHYS LAB, GREENBELT, MD 20771 USA.
UNIV VIRGINIA, DEPT ASTRON, CHARLOTTESVILLE, VA 22903 USA.
NATL RADIO ASTRON OBSERV, CHARLOTTESVILLE, VA 22903 USA.
RP Cornett, RH (reprint author), HUGHES STX CORP, GODDARD SPACE FLIGHT CTR, CODE 681, GREENBELT, MD 20771 USA.
NR 33
TC 17
Z9 17
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 MAR
PY 1997
VL 113
IS 3
BP 1011
EP +
DI 10.1086/118317
PG 0
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WK846
UT WOS:A1997WK84600010
ER
PT J
AU Dulk, GA
Leblanc, Y
Sault, RJ
Ladreiter, HP
Connerney, JEP
AF Dulk, GA
Leblanc, Y
Sault, RJ
Ladreiter, HP
Connerney, JEP
TI The radiation belts of Jupiter at 13 and 22 cm .2. The asymmetries and
the magnetic field
SO ASTRONOMY & ASTROPHYSICS
LA English
DT Article
DE Jupiter; radio emission; magnetosphere; radiation belts
ID SYNCHROTRON RADIATION; MODEL-CALCULATIONS; RADIO DATA; IMAGES
AB Observations of Jupiter at 13 and 22 cm made with the Australia Telescope in July 1995, reported in Paper I (Leblanc et al. 1996), are interpreted by comparing with models of the magnetic field. The field models used are the O6 and a new, 4th degree and order model due to one of us (JEPC), denoted H4.
1) From our 3-D reconstruction we derive the variation with longitude lambda(III) of the latitude and radial distance of peak radio emissivity: -10 degrees less than or similar to lat less than or similar to + 13 degrees, and 1.45 R(J) R less than or similar to 1.75 R(J). These values are in good agreement with the location of the magnetic equator on a surface of constant total field \B\ approximate to 1 G.
2) We present the variation with lambda(III) of the latitude and radial distance of high-latitude peaks in linearly-polarized brightness from a similar 3-D reconstruction. Comparing with calculations from the H4 model, these ''mirror points'' are in good accord with calculated latitudinal and radial variations for electrons with pitch angle alpha(e) approximate to 27 degrees on L shell L approximate to 2.37 R(J).
3) The variations with lambda(III) (Paper I) of the brightness of legions traversing the east and west limbs (the east-west asymmetry) are compared with field model calculations that take into account the warp of the magnetic equator, i.e. the magnetic declination D-mag and the Earth's jovicentric declination D-E that was D-E = -2.9 degrees during our observations. The generally excellent agreement allows us to account for the brightness minimum near lambda(III) approximate to 120 degrees, the maximum near 200 degrees, and the fact that the bright spot near 200 degrees is fainter when crossing the west limb than when crossing the east limb.
4) From the results of (3) we are able to predict the form of the east-west asymmetry when the Earth is at other declinations, up to D-E = +2.9 degrees. Some published results substantiate the prediction.
The observations are in better agreement with model H4 than with O6. The discrepancies that remain can be used to improve the field models or further explore the properties of the synchrotron-emitting electrons.
C1 UNIV COLORADO, DEPT ASTROPHYS PLANETARY & ATMOSPHER SCI, BOULDER, CO 80309 USA.
CSIRO, AUSTRALIA TELESCOPE NATL FACIL, EPPING, NSW 2121, AUSTRALIA.
GRAZ UNIV, INST SPACE RES, A-8010 GRAZ, AUSTRIA.
NASA, GODDARD SPACE FLIGHT CTR, PLANETARY MAGNETOSPHERES BRANCH, GREENBELT, MD 20771 USA.
RP Dulk, GA (reprint author), OBSERV PARIS, CNRS URA 264, DEPT RECH SPATIALE, F-92195 MEUDON, FRANCE.
RI connerney, john/I-5127-2013
NR 13
TC 27
Z9 27
U1 0
U2 0
PU EDP SCIENCES S A
PI LES ULIS CEDEX A
PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A,
FRANCE
SN 0004-6361
J9 ASTRON ASTROPHYS
JI Astron. Astrophys.
PD MAR
PY 1997
VL 319
IS 1
BP 282
EP 289
PG 8
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WN717
UT WOS:A1997WN71700028
ER
PT J
AU Baykal, A
AF Baykal, A
TI The torque and X-ray flux changes of OAO 1657-415
SO ASTRONOMY & ASTROPHYSICS
LA English
DT Article
DE stars: OAO 1657-415; accretion; x-rays: stars; stars: neutron
ID MAGNETIC NEUTRON STARS; TIMING OBSERVATIONS; PERIOD VARIATIONS;
ACCRETION FLOW; SPIN-UP; VELA PULSAR; NOISE; DISCOVERY; MODEL; X-1
AB Combining previously published pulse frequencies and BATSE measurements, we estimate the noise strengths (or power density estimates) of angular accelerations by using the root mean square residuals of angular velocity time series of OAO 1657-415 and present the power spectra. The statistical interpretation of the angular velocity fluctuations is consistent with a random walk model. In order to investigate the short term angular velocity fluctuations in detail, a structure function analysis is applied for a two component neutron star model with a solid crust and a superfluid neutron core which is subjected to external white torque noise. No evidence for core-crust coupling on timescales longer than one day is found. The correlations between X-ray flux and angular acceleration (Omega over dot) fluctuations are investigated. These are compared with disk accretion theory (Ghosh & Lamb 1979 a,b) and wind accretion theory (Blondin et al., 1990). It is found that the most natural explanation of X ray flux and angular acceleration fluctuations is the formation of episodic accretion disks in the case of stellar wind accretion.
C1 MIDDLE E TECH UNIV, DEPT PHYS, TR-06531 ANKARA, TURKEY.
RP Baykal, A (reprint author), NASA, GODDARD SPACE FLIGHT CTR, HIGH ENERGY ASTROPHYS LAB, GREENBELT, MD 20771 USA.
NR 68
TC 16
Z9 16
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 MAR
PY 1997
VL 319
IS 2
BP 515
EP 524
PG 10
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WM894
UT WOS:A1997WM89400019
ER
PT J
AU Parmar, AN
Williams, OR
Kuulkers, E
Angelini, L
White, NE
AF Parmar, AN
Williams, OR
Kuulkers, E
Angelini, L
White, NE
TI Archival observations of the ultra-soft x-ray transient 4U 1630-47
SO ASTRONOMY & ASTROPHYSICS
LA English
DT Article
DE accretion; binaries: close; stars: individual (4U 1630-47); X-rays:
stars
ID ROSAT OBSERVATIONS; OUTBURST; QUIESCENCE; GINGA; VARIABILITY; SPECTRA;
TENMA
AB We report on archival observations of the ultra-soft X-ray transient 4U 1630-47. In 1979 February, 1989 March, and 1994 September, 4U 1630-47 was observed in outburst by the Einstein High Resolution Imager (HRI), the Ginga Large Area Counter (LAC) and the ASCA Gas Imaging Spectrometers, respectively In 1987 October, the Ginga LAC observed the region of sky containing 4U 1630-47 and a faint source was detected. While it is possible that this emission originates from another object within the LAC field of view, its properties are consistent with an observation towards the end of an outburst. The times of the Ginga outbursts are consistent with the known similar to 600 day ephemeris. However, the ASCA observation and observations of the subsequent outburst by the Rossi X-ray Timing Explorer, indicate that these outbursts started 100-150 days later than predicted. This delay confirms the occurrence of more complex outburst behavior from 4U 1630-47. Finally, an observation by the imaging Einstein HRI in 1980 February, approximately mid-way between expected outburst times, revealed a faint source at a position consistent with 4U 1630-47. The measured source intensity is higher than the previous best upper-limit. This implies that (a) the quiescent intensity is variable by a factor similar to 10, or (b) that the 1979 outburst had an extremely long duration, or (c) that the emission originates from previously undetected inter-outburst activity.
C1 NASA, GODDARD SPACE FLIGHT CTR, HIGH ENERGY ASTROPHYS LAB, GREENBELT, MD 20771 USA.
RP Parmar, AN (reprint author), EUROPEAN SPACE AGCY, DEPT SPACE SCI, DIV ASTROPHYS, NL-2200 AG NOORDWIJK, NETHERLANDS.
RI White, Nicholas/B-6428-2012
OI White, Nicholas/0000-0003-3853-3462
NR 49
TC 28
Z9 28
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 MAR
PY 1997
VL 319
IS 3
BP 855
EP 862
PG 8
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WR878
UT WOS:A1997WR87800019
ER
PT J
AU Smith, IA
Schultz, ASB
Hurley, K
vanParadijs, J
Waters, LBFM
AF Smith, IA
Schultz, ASB
Hurley, K
vanParadijs, J
Waters, LBFM
TI JCMT observations of Soft Gamma-Ray Repeaters
SO ASTRONOMY & ASTROPHYSICS
LA English
DT Article
DE gamma rays: bursts; radio continuum: stars; infrared: stars; supernovae:
general; stars: neutron
ID MILLIMETER; SGR1806-20; TELESCOPE; NEBULA
AB The spectra of the quiescent counterparts to the Soft Gamma-Ray Repeaters SGR 1900+14 and SGR 1806-20 peak in the infrared. Their infrared spectra appear to contain several components: the photospheric emission from star(s) dominates at shorter wavelengths, a bright point source dominates at 25 mu m, while an extended source dominates at 60 mu m. However, we show here that these counterparts were not detected by the James Clerk Maxwell Telescope at 450 mu m or 800 mu m. These observations are consistent with other millimeter studies, and are consistent with the detection of a point-like ''core'' to the radio nebula of SGR 1806-20. We show that monoenergetic synchrotron radiation and black body spectra are too broad to be consistent with both the infrared and submillimeter observations. However, simple dust models can explain the combined observations.
C1 NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA.
UNIV CALIF BERKELEY, SPACE SCI LAB, BERKELEY, CA 94720 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.
SRON, SPACE RES LAB, NL-9700 AV GRONINGEN, NETHERLANDS.
RP Smith, IA (reprint author), RICE UNIV, DEPT SPACE PHYS & ASTRON, POB 1892, HOUSTON, TX 77251 USA.
NR 31
TC 3
Z9 3
U1 0
U2 0
PU EDP SCIENCES S A
PI LES ULIS CEDEX A
PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A,
FRANCE
SN 0004-6361
J9 ASTRON ASTROPHYS
JI Astron. Astrophys.
PD MAR
PY 1997
VL 319
IS 3
BP 923
EP 927
PG 5
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WR878
UT WOS:A1997WR87800026
ER
PT J
AU Ruzmaikin, A
AF Ruzmaikin, A
TI On the origin of sunspots
SO ASTRONOMY & ASTROPHYSICS
LA English
DT Letter
DE sun: sunspots; sun: random magnetic fields
ID SOLAR CONVECTION ZONE; MAGNETIC-FLUX TUBES; DYNAMOS
AB It is proposed that sunspots (and other flux emergence phenomena) originate due to the presence of fluctuating magnetic fields in addition to the regular, mean field in the convection zone. The mean field predicted by dynamo theories is too weak by itself to emerge at the surface of the Sun. However, the same dynamo processes that produce the mean field also produce fluctuating fields. It is suggested here that magnetic fields emerge at the solar surface at those random times and places when the total magnetic field (mean field plus fluctuations) exceeds the threshold for buoyancy. In this way the mean field is responsible for observed regularities of the sunspot magnetic fields, such as the Hale's law and the 11-year periodicity, and the fluctuations are responsible for emergence of the magnetic field of individual sunspots. A simple illustrative model calculation of a series of ''sunspot cycles'' is presented. The model spectrum compares well with the observed spectrum of sunspots.
C1 CALIF STATE UNIV NORTHRIDGE, SAN FERNANDO OBSERV, NORTHRIDGE, CA 91330 USA.
RP Ruzmaikin, A (reprint author), CALTECH, JET PROP LAB, PASADENA, CA 91109 USA.
NR 16
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 MAR
PY 1997
VL 319
IS 3
BP L13
EP L16
PG 4
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WR878
UT WOS:A1997WR87800004
ER
PT J
AU Aptekar, RL
Butterworth, PS
Golenetskii, SV
Ilinskii, VN
Cline, TL
Mazets, EP
Stilwell, DE
Terekhov, MM
Frederiks, DD
AF Aptekar, RL
Butterworth, PS
Golenetskii, SV
Ilinskii, VN
Cline, TL
Mazets, EP
Stilwell, DE
Terekhov, MM
Frederiks, DD
TI Long-term activity of the bursting X-ray pulsar GRO J1744-28 from
Konus-Wind and Konus-A observations
SO ASTRONOMY LETTERS-A JOURNAL OF ASTRONOMY AND SPACE ASTROPHYSICS
LA English
DT Article
AB Konus-Wind and Konus-A observations of hard X-ray bursts from the source GRO J1744-28 are reported. The mean characteristics of the burst time profiles and energy spectra were obtained. The mean burst intensity rapidly rises, reaches its maximum on January 20, 1996, and then begins to decline. The observed burst rate was corrected for missing weak events. The mean time interval between bursts, (T) over bar = 29.6 min and sigma = 9.7 min, was found to be constant for the entire long period of observations. The time intervals between bursts are shown to constitute a random Markov sequence. The correlation coefficient for two successive intervals is rho = -0.13 +/- 0.03. A positive correlation of the burst intensity with the next interval and a negative correlation with the previous interval were revealed.
C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771.
RP Aptekar, RL (reprint author), RUSSIAN ACAD SCI,AF IOFFE PHYSICOTECH INST,POLITEKHNICHESKAYA UL 26,ST PETERSBURG 194021,RUSSIA.
RI Frederiks, Dmitry/C-7612-2014; Aptekar, Raphail/B-3456-2015;
Golenetskii, Sergey/B-3818-2015;
OI Frederiks, Dmitry/0000-0002-1153-6340
NR 10
TC 2
Z9 2
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
SN 1063-7737
J9 ASTRON LETT+
JI Astron. Lett.-J. Astron. Space Astrophys.
PD MAR-APR
PY 1997
VL 23
IS 2
BP 147
EP 154
PG 8
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WV571
UT WOS:A1997WV57100002
ER
PT J
AU Scharf, CA
Jones, LR
Ebeling, H
Perlman, E
Malkan, M
Wegner, G
AF Scharf, CA
Jones, LR
Ebeling, H
Perlman, E
Malkan, M
Wegner, G
TI The wide-angle ROSAT pointed X-ray survey of galaxies, groups, and
clusters .1. Method and first results
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE galaxies, clusters, general; methods, numerical; surveys; X-rays,
galaxies
ID MEDIUM-SENSITIVITY SURVEY; N-LOG-S; HYDRODYNAMIC SIMULATION;
HIGH-RESOLUTION; EVOLUTION; DEEP; UNIVERSE; EINSTEIN; DENSITY; SAMPLE
AB We have embarked on a survey of ROSAT PSPC archival data with the aim of detecting all significant surface brightness enhancements resulting from sources in the innermost R less than or equal to 15' of the PSPC field of view in the energy band 0.5-2.0 keV. This project is part of the Wide-Angle ROSAT Pointed Survey (WARPS), and it is designed primarily to measure the low-luminosity, high-redshift, X-ray luminosity function of galaxy clusters and groups. The approach we have chosen for source detection (Voronoi Tessellation and Percolation [VTP]) represents a significant advance over conventional methods, and it is particularly suited for the detection and accurate quantification of extended and/or low surface brightness emission that could otherwise be missed or wrongly interpreted. We also use energy-dependent exposure maps to estimate the fluxes of sources that can amount to corrections of as much as 15%. In an extensive optical follow-up program, we are identifying galaxies, groups, and clusters at redshifts ranging from z similar to 0.1 to z similar to 0.7.
In this paper, we present our method and its calibration using simulated and real data. We present first results for an initial 91 fields (17.2 deg(2)) at detected fluxes greater than 3.5 x 10(-14) ergs s(-1) cm(-2) (the WARPS-I survey). We find the sky density of extended objects to be in the range 2.8-4.0 (+/- 0.4) deg(-2). A comparison with a point-source detection algorithm demonstrates that our VTP approach typically finds 1-2 more objects deg(-2) to this detected flux limit, suggesting that the conventional method fails to detect a significant fraction of extended objects. The surface brightness limit of the WARPS cluster survey is similar to 1 x 10(-15) ergs s(-1) cm(-2) arcmin(-2), approximately 6 times lower than the Extended Medium Sensitivity Survey (EMSS). The WARPS Log N-Log S (which currently represents a lower limit) shows a significant excess over previous measurements for S greater than or similar to 8 x 10(-14) ergs s(-1) cm(-2). We attribute this mainly to a larger measured flux from extended sources as well as new detections of low surface brightness systems in the WARPS.
C1 UNIV CAMBRIDGE,INST ASTRON,CAMBRIDGE CB3 0HA,ENGLAND.
UNIV CALIF LOS ANGELES,DEPT ASTRON,LOS ANGELES,CA 90024.
DARTMOUTH COLL,DEPT PHYS & ASTRON,WILDER LAB 6127,HANOVER,NH 03755.
RP Scharf, CA (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,CODE 660,GREENBELT,MD 20771, USA.
NR 33
TC 127
Z9 127
U1 0
U2 1
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD MAR 1
PY 1997
VL 477
IS 1
BP 79
EP 92
DI 10.1086/303698
PN 1
PG 14
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WK037
UT WOS:A1997WK03700008
ER
PT J
AU Prestwich, AH
Joy, M
Luginbuhl, CB
Sulkanen, M
Newberry, M
AF Prestwich, AH
Joy, M
Luginbuhl, CB
Sulkanen, M
Newberry, M
TI A search for the cooling flow accretion population: Optical and
near-infrared imaging of NGC 1275
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE galaxies, clusters, individual (Perseus); galaxies, cooling flows;
galaxies, elliptical and lenticular, cD; galaxies, individual (NGC
1275); galaxies, photometry; X-rays, galaxies
ID SURFACE PHOTOMETRY; GALAXIES; CLUSTERS; EMISSION; MATTER
AB We present near-infrared and optical images of NGC 1275, the cD galaxy at the center of the Perseus cluster, and a well-known cooling how. Although cooling flows are common (perhaps occurring in > 50% of X-ray clusters) and the mass accreted over the lifetime of the cluster similar to 10(12) M., attempts to detect the cooled gas at wavelengths other than X-rays has met with limited success. In this paper, we measure the optical and near-infrared brightness profiles of NGC 1275, in an attempt to detect spatially extended low-mass stars that may have formed from the cooled gas. To measure the profiles to the required low flux levels, they have been corrected for overlapping galaxy halos and scattered light. We find that our profiles are inconsistent with models of low-mass star formation unless the initial mass function has an upper mass cutoff less than 0.1 M., or the mass of gas accumulated over the lifetime of the cluster is 1%-10% of that predicted from the X-ray mass accretion rate determined at the present epoch.
C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,SPACE SCI LAB,HUNTSVILLE,AL 35812.
USN OBSERV,FLAGSTAFF STN,FLAGSTAFF,AZ 86002.
AXIOM RES INC,TUCSON,AZ 85716.
RP Prestwich, AH (reprint author), SMITHSONIAN ASTROPHYS OBSERV,60 GARDEN ST,MS4,CAMBRIDGE,MA 02138, USA.
NR 26
TC 11
Z9 11
U1 0
U2 0
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD MAR 1
PY 1997
VL 477
IS 1
BP 144
EP 151
DI 10.1086/303693
PN 1
PG 8
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WK037
UT WOS:A1997WK03700013
ER
PT J
AU Wolkovitch, D
Langer, WD
Goldsmith, PF
Heyer, M
AF Wolkovitch, D
Langer, WD
Goldsmith, PF
Heyer, M
TI Physical conditions in quiescent dark cloud cores determined from
multitransition observations of CCS
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE ISM, clouds; ISM, individual (Taurus Molecular Cloud, L1498); ISM,
molecules; radio lines, ISM
ID ROTATIONALLY INELASTIC-COLLISIONS; DENSE INTERSTELLAR CLOUDS; MOLECULAR
CLOUDS; CHEMISTRY; LINE; TMC-1; HC3N; NH3; CO; CS
AB We have studied three transitions of the CCS molecule to determine physical conditions in L1498 and TMC-1D, two narrow-line dense cores in the Taurus region. We observed the N-J = 1(2) --> 0(1), 3(4) --> 2(3), and 7(8) --> 6(7) transitions at 22.3, 45.4, and 93.9 GHz, respectively, at 50 '' angular resolution. The intensities of the emission lines have been analyzed using statistical equilibrium calculations and collision rates calculated for the CCS-H-2 system. These were obtained from the Molscat scattering code together with inclusion of spin dependence in Hund's case (b) model. We find that the kinetic temperature in both sources is extremely low, between 7 and 10 K. The L1498 emission appears to originate in a single velocity component with mean hydrogen density 3-14 x 10(4) cm(-3). We analyzed three velocity components in TMC-1D separately, and find that the low-velocity component has a mean H-2 density of 6 x 10(3) cm(-3), while the two higher velocity components are denser by approximately a factor of 3. The L1498 core is close to virial equilibrium in that the magnitude of its gravitational energy is close to that of its kinetic energy. However, the cores corresponding to the three velocity components in TMC-1D are unbound by factors of 2-7.
We dedicate this paper to the memory of Sheldon Green, who passed away in 1995 December. Sheldon was an outstanding chemist who made many significant contributions to molecular astrophysics.
C1 CORNELL UNIV,NATL ASTRON & IONOSPHERE CTR,DEPT ASTRON,ITHACA,NY 14850.
CALTECH,JET PROP LAB,PASADENA,CA 91109.
UNIV MASSACHUSETTS,FIVE COLL RADIO ASTRON OBSERV,DEPT PHYS & ASTRON,AMHERST,MA 01003.
RI Goldsmith, Paul/H-3159-2016
NR 40
TC 40
Z9 41
U1 0
U2 0
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD MAR 1
PY 1997
VL 477
IS 1
BP 241
EP 264
DI 10.1086/303677
PN 1
PG 24
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WK037
UT WOS:A1997WK03700024
ER
PT J
AU Pereyra, NA
Kallman, TR
Blondin, JM
AF Pereyra, NA
Kallman, TR
Blondin, JM
TI Hydrodynamical models of line-driven accretion disk winds
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE accretion, accretion disks; hydrodynamics; novae, cataclysmic variables;
stars, mass loss
ID HIGH-VELOCITY WINDS; CATACLYSMIC VARIABLES; ROSAT OBSERVATIONS; IUE
OBSERVATIONS; STELLAR WINDS; DWARF NOVA; HOT STARS; SS CYGNI; OUTBURST;
EMISSION
AB We present here one-dimensional analytic hydrodynamic models and both one-dimensional and two-dimensional numerical hydrodynamic models for line-driven accretion disk winds from cataclysmic variable (CV) systems. Using the one-dimensional analytic models we explore the physical conditions necessary for the existence of a disk wind and study the dependence of wind speed and mass-loss rate on radius. The results of our two-dimensional model are consistent with the spectrum observed from CVs in the polar nature of the wind, the maximum absorption at roughly half the terminal speed of the P Cygni profiles, and the order of magnitude of the terminal speeds. For disk luminosity L(disk) = L., white dwarf mass M(wd) = 0.6 M., disk radius R(disk) = R., and sound speed a = 10 km s(-1) we obtain a wind mass-loss rate of M(wind) = 2 x 10(-14) M. yr(-1) and a terminal velocity of similar to 3000 km s(-1). The two-dimensional models show that centrifugal forces produce shocks in the disk wind. If these shocks were absent, the mass-loss rates obtained would be too low to produce the optical depths required to explain the P Cygni profile of CVs. The two-dimensional models demonstrate the importance of centrifugal forces in winds from accretion disks and thus the necessity of models where these forces may be represented.
C1 N CAROLINA STATE UNIV,DEPT PHYS,RALEIGH,NC 27695.
RP Pereyra, NA (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,CODE 662,GREENBELT,MD 20771, USA.
NR 33
TC 36
Z9 37
U1 0
U2 0
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD MAR 1
PY 1997
VL 477
IS 1
BP 368
EP 378
DI 10.1086/303671
PN 1
PG 11
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WK037
UT WOS:A1997WK03700032
ER
PT J
AU Chick, KM
Cassen, P
AF Chick, KM
Cassen, P
TI Thermal processing of interstellar dust grains in the primitive solar
environment
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE accretion, accretion disks; dust, extinction; meteors, meteoroids;
radiative transfer; solar system, formation; stars, pre-main-sequence
ID PROTOSTELLAR DISKS; NEBULA; EVOLUTION; ACCRETION; GRAPHITE; DIAMOND;
CLOUDS
AB The heating and vaporization of dust grains in the protosolar environment is modeled in order to assess the survivability of interstellar solids during the formation of the solar system. A multidimensional, discrete ordinate radiative transfer code is used to compute thermal transport in the collapsing protosolar cloud. The results are combined with estimates of heating at the shock where infalling material arrives at the surface of the solar nebula/accretion disk, and in the interior of the disk, to determine the distances at which various solid phases are vaporized. The thermal coupling between the envelope and the accretion disk (backheating) is treated self-consistently, so its effect on the disk's radial temperature profile is included. This treatment also permits evaluation of the effect of backheating on the observational inference of disk properties.
Calculations are performed for various values of cloud collapse rate, rotation rate, and disk accretion rate. The latter factor is the main determinant of the total luminosity, and we consider both ''low-luminosity'' cases, in which disk accretion is inefficient, and high-luminosity'' cases, in which disk accretion keeps pace with cloud collapse. We also examine situations in which a polar, optically thin cavity is swept clear by a protosolar wind.
We conclude that refractory grains, such as silicates, can generally survive the envelope and accretion shock, and enter the nebula at or within 1 AU. Inside the nebula, their vaporization distances are controlled by the disk accretion rate and optical depth. In contrast, the vaporization distances of volatiles such as water ice are sensitive to envelope conditions, which control the thermal state of the outer, optically thin regions of the disk. The ice vaporization distance lies between about 2 and 30 AU, depending on the total source luminosity and characteristics of the collapsing cloud. Moderately volatile organics (methanol, formaldehyde, and polymerized formaldehyde) may survive as solids in the terrestrial planet region; they generally are not vaporized outside of several AU, which supports the idea that comets inherit this material from the parent molecular cloud.
C1 UNIV CALIF SANTA CRUZ,SANTA CRUZ,CA 95064.
RP Chick, KM (reprint author), NASA,AMES RES CTR,DIV SPACE SCI,MS 245-3,MOFFETT FIELD,CA 94035, USA.
NR 32
TC 77
Z9 77
U1 0
U2 0
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD MAR 1
PY 1997
VL 477
IS 1
BP 398
EP 409
DI 10.1086/303700
PN 1
PG 12
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WK037
UT WOS:A1997WK03700035
ER
PT J
AU Christian, DJ
Smale, AP
Swank, JH
Serlemitsos, PJ
AF Christian, DJ
Smale, AP
Swank, JH
Serlemitsos, PJ
TI X-ray observations of X2127+119/AC 211 in the metal-poor globular
cluster M15: An X-ray measure of metallicity?
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE binaries, close; globular clusters, individual (M15); stars, abundances;
stars, individual (X2127+119); X-rays, stars
ID ENERGY-SPECTRA; SPECTROMETER; DISCOVERY; BINARIES; PERIOD; BURST; DIPS
AB We present results from observations of the 17.1 hr low-mass X-ray binary X2127+119 (AC 211) in M15 obtained with the broadband X-ray telescope (BBXRT) in 1990 December and observations obtained with the solid state spectrometer (SSS) together with the monitor proportional counter (MPG) on the Einstein Observatory in 1978 and 1979. The continuum can be well described with the two-component model of a blackbody (kT similar to 1 keV) and a power law that was found to fit the EXOSAT medium-energy data. Short-term variability observed by the SSS and MPC was related to changes in the intensities of both components in this description. The SSS and MPC observed factor of 10 differences in column density in observations separated by a few binary orbits. These observations confirm correlations between the steepness of the spectrum and the column density, and column density with phase. The percentage contribution of the blackbody is anticorrelated with the factor of 4 variations in the apparent luminosity, but other correlations are weak. A 1000 s observation by BBXRT at photometric phase 0.9 provides an upper limit of similar to 150 eV to narrow Fe K line emission. BBXRT spectra are generally inconsistent with the overall cluster metallicity of 1% of solar, although complex spectral models can be more consistent with the cluster metallicity. A model separating the absorption of H and He from the metals gives 1.25(-0.2)(+0.03) x 10(18) cm(-2) for the column density of metals in the absorbing gas associated with the binary system. The noted correlations between spectral parameters, luminosity, and their relation to orbital phase are consistent with a disk plus moderate-sized corona interpretation.
C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771.
RP Christian, DJ (reprint author), UNIV CALIF BERKELEY,CTR EUV ASTROPHYS,2150 KITTREDGE ST,BERKELEY,CA 94720, USA.
RI Swank, Jean/F-2693-2012
NR 34
TC 3
Z9 3
U1 0
U2 0
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD MAR 1
PY 1997
VL 477
IS 1
BP 424
EP 430
DI 10.1086/303678
PN 1
PG 7
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WK037
UT WOS:A1997WK03700037
ER
PT J
AU Schmelz, JT
Saba, JLR
Chauvin, JC
Strong, KT
AF Schmelz, JT
Saba, JLR
Chauvin, JC
Strong, KT
TI Investigating the effect of opacity in soft X-ray spectral lines emitted
by solar coronal active regions
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE line, formation; radiative transfer; Sun, activity; Sun, corona; Sun, UV
radiation; Sun, X-rays, gamma rays
ID FE-XVII; DOUBLET; RATIOS
AB Current literature suggests that several lines in the soft X-ray portion of the coronal spectrum may not be optically thin. Here, we wish to check this possibility for five of the brightest resonance lines in this part of the spectrum-O VIII at 18.97 Angstrom, Fe XVII at 15.25 Angstrom Fe XVII at 15.01 Angstrom Ne IX at 13.45 Angstrom and Mg XI at 9.17 Angstrom. A comparison is made between each of these resonance lines and an optically thin ''reference'' line produced by the same element in the same ionization state-O VIII at 16.01 Angstrom Fe XVII at 16.78 Angstrom Ne IX at 13.70 Angstrom, and Mg XI at 9.31 Angstrom. In the latter two cases, the comparison line is the forbidden line of the He-like triplet.
The spectra are from the Solar Maximum Mission Flat Crystal Spectrometer, which had a FWHM held of view of 15 '' and could scan the soft X-ray resonance lines of prominent ions in the 1.5-20.0 Angstrom portion of the spectrum. Here 33 spectra are analyzed, all of which were obtained from nonflaring, quasi-stable active regions.
For the quiescent regions selected, the data for the Fe XVII line at 15.01 Angstrom are clearly consistent with resonance scattering, with an increasing trend from Sun center to the limb. For the other lines tested, however, we find neither significant opacity effects nor center-to-limb variations.
C1 NASA,GODDARD SPACE FLIGHT CTR,LOCKHEED SOLAR & ASTROPHYS GRP,GREENBELT,MD 20771.
RHODES COLL,DEPT PHYS,MEMPHIS,TN 38112.
LOCKHEED SOLAR & ASTROPHYS GRP,PALO ALTO,CA 94304.
RP Schmelz, JT (reprint author), MEMPHIS STATE UNIV,DEPT PHYS,MEMPHIS,TN 38152, USA.
NR 27
TC 36
Z9 37
U1 0
U2 1
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD MAR 1
PY 1997
VL 477
IS 1
BP 509
EP 515
DI 10.1086/303689
PN 1
PG 7
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WK037
UT WOS:A1997WK03700045
ER
PT J
AU Borkowski, KJ
Szymkowiak, AE
AF Borkowski, KJ
Szymkowiak, AE
TI X-ray emission from dust in hot plasmas
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE dust, extinction; supernova remnants; X-rays, ISM
ID SUPERNOVA-REMNANTS
AB Energetic (few keV) thermal electrons easily penetrate interstellar dust grains immersed in hot plasmas. These electrons create K-shell vacancies in atoms locked in dust grains through the K-shell collisional ionization process. Heavy elements such as Fe and Ca produce fluorescent K alpha emission in the subsequent decay of the inner shell vacancy. We predict that this emission from Fe atoms in dust grains should be present in X-ray spectra emitted by dusty plasma, in addition to K alpha emission from highly ionized Fe ions. This affects the strength and shape of the Fe K alpha complex. We also predict a low ratio of L-shell/K alpha emission for dust grains, because of low fluorescent yields for L-shell transitions. These effects should be most pronounced in young supernova remnants (SNRs). We discuss observational evidence for the fluorescent Fe K alpha emission from dust in X-ray spectra of Tycho's, Kepler's, and Cassiopeia A SNRs, the three youngest remnants in our Galaxy.
C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771.
RP Borkowski, KJ (reprint author), N CAROLINA STATE UNIV,DEPT PHYS,RALEIGH,NC 27695, USA.
NR 19
TC 9
Z9 9
U1 0
U2 0
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD MAR 1
PY 1997
VL 477
IS 1
BP L49
EP L52
DI 10.1086/310522
PN 2
PG 4
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WK039
UT WOS:A1997WK03900013
ER
PT J
AU Chen, XM
Swank, JH
Taam, RE
AF Chen, XM
Swank, JH
Taam, RE
TI The pattern of correlated X-ray timing and spectral behavior in GRS
1915+105
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE accretion, accretion disks; binaries, close; black hole physics; stars,
individual (GRS 1915+105, GS 1124-68); X-rays, stars
ID QUASI-PERIODIC OSCILLATIONS; ACCRETION DISKS; NEUTRON-STARS;
BINARY-SYSTEMS; BLACK-HOLES; VARIABILITY; EVOLUTION; J1655-40
AB From data obtained from the proportional counter array in the 2-11 keV and 11-30.5 keV energy ranges, GRS 1915+105 is seen during Rossi X-Ray Timing Explorer observations between 1996 May and October on two separate branches in a hardness-intensity diagram. On the hard branch, GRS 1915+105 exhibits narrow quasi-periodic oscillations (QPOs) ranging from 0.5 to 6 Hz with Delta nu/nu similar to 0.2. The QPOs are observed over intensities ranging from about 6000 to 20,000 counts s(-1) in the 2-12.5 keV energy band, indicating a strong dependence on source intensity. Strong harmonics are seen, especially at lower frequencies. As the QPO frequency increases, the harmonic feature weakens and disappears. On the soft branch, narrow QPOs are absent and the low-frequency component of the power density spectrum is approximated by a power law, with index of about -1.25 for low count rates and -1.5 for high count rates (greater than or similar to 18,000 counts s(-1)). Occasionally, a broad, peaked feature in the 1-6 Hz frequency range is also observed on this branch. The source was probably in a very high state similar to those of other black hole candidates. Thermal-viscous instabilities in accretion disk models do not predict the correlation of the narrow QPO frequency and luminosity unless the fraction of luminosity from the disk decreases with the total luminosity.
C1 UNIV CALIF SANTA CRUZ,UNIV CALIF OBSERV,LICK OBSERV,SANTA CRUZ,CA 95064.
NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771.
RP Chen, XM (reprint author), NORTHWESTERN UNIV,DEPT PHYS & ASTRON,2131 SHERIDAN RD,EVANSTON,IL 60208, USA.
RI Swank, Jean/F-2693-2012
NR 40
TC 53
Z9 54
U1 0
U2 0
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD MAR 1
PY 1997
VL 477
IS 1
BP L41
EP L44
DI 10.1086/310515
PN 2
PG 4
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WK039
UT WOS:A1997WK03900011
ER
PT J
AU Wu, CC
Crenshaw, DM
Hamilton, AJS
Fesen, RA
Leventhal, M
Sarazin, CL
AF Wu, CC
Crenshaw, DM
Hamilton, AJS
Fesen, RA
Leventhal, M
Sarazin, CL
TI Far-ultraviolet absorption lines in the remnant of SN 1006
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE ISM, abundances; ISM, individual (SN 1006); supernova remnants
ID SPECTRA; SN-1006
AB We have obtained a far-ultraviolet spectrum (1150-1600 ii) of a hot subdwarf star behind the remnant of supernova 1006 with the Faint Object Spectrograph (FOS) on the Hubble Space Telescope. The high-quality spectrum is used to test previous identifications of the strong absorption features discovered with the International Ultraviolet Explorer. These features have FWHM = 4000 (+/-300) km s(-1) and are not at the rest wavelengths of known interstellar lines, as opposed to the broader (similar to 8000 km s(-1) FWHM) Fe II lines from the remnant centered at 0 km s(-1) in near-UV FOS spectra. We confirm that the broad absorption features are principally due to redshifted Si II, Si III, and Si Iv lines, which are centered at a radial velocity of 5100 (+/-200) km s(-1).
The Si II lambda 1260.4 profile is asymmetric, with a nearly flat core and sharp red wing, unlike the Si II lambda 1526.7 and Si IV lambda lambda 1393.8, 1402.8 profiles. One possible explanation is additional absorption from another species. Previous work has suggested that S II lambda lambda 1250.6, 1253.8, 1259.5 at a radial velocity of similar to 6000 km s(-1) is responsible, but this would require a sulfur-to-silicon abundance ratio that is at least a factor of 10 higher than expected. Another possible explanation is that the Si II and Si IV profiles are intrinsically different, but this does not explain the symmetric (albeit weaker) Si II lambda 1526.7 profile.
C1 COMP SCI CORP,NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771.
UNIV COLORADO,JOINT INST LAB ASTROPHYS,BOULDER,CO 80309.
DARTMOUTH COLL,DEPT PHYS & ASTRON,HANOVER,NH 03755.
UNIV MARYLAND,DEPT ASTRON,COLLEGE PK,MD 20742.
UNIV VIRGINIA,DEPT ASTRON,CHARLOTTESVILLE,VA 22903.
RP Wu, CC (reprint author), COMP SCI CORP,SPACE TELESCOPE SCI INST,3700 SAN MARTIN DR,BALTIMORE,MD 21218, USA.
NR 17
TC 12
Z9 12
U1 0
U2 0
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD MAR 1
PY 1997
VL 477
IS 1
BP L53
EP L56
DI 10.1086/310510
PN 2
PG 4
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WK039
UT WOS:A1997WK03900014
ER
PT J
AU Christian, DJ
Swank, JH
AF Christian, DJ
Swank, JH
TI The survey of low-mass X-ray binaries with the Einstein Observatory
solid-state spectrometer and monitor proportional counter
SO ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES
LA English
DT Review
ID K LINE EMISSION; ORBITAL PERIOD; SCORPIUS X-1; CYGNUS X-2;
MULTIWAVELENGTH CAMPAIGN; EDDINGTON LUMINOSITIES; EXOSAT OBSERVATIONS;
ACCRETION DISKS; CCD PHOTOMETRY; ENERGY-SPECTRA
AB The HEAO 2 or Einstein solid-state spectrometer (SSS; 0.5-4.5 keV) and monitor proportional counter (MPC; 1.2-20.0 keV) carried out an extensive survey of 49 low-mass X-ray binaries (LMXBs). Simultaneous SSS plus MPC spectra, selected on the basis of their intensity, were fitted with a set of simple and complex spectral models. For all the sources, including Eddington-limited bulge sources, bursters, dippers, the soft spectrum black hole candidates, and a few transients in decline, the spectra could be fitted acceptably with combinations of thermal bremsstrahlung and blackbody models or a Comptonized spectrum and a blackbody. The results rule out optically thick disk models for the bright (Z) sources and power-law models for the bursters. The SSS can confirm only the strongest of previously reported low-energy emission lines due to O VIII or Fe L transitions. Uncertainties in column densities are modest, and together with consideration of a disk distribution of gas and dust in the galaxy, the column densities provide distance estimates. These are the only measures yet available for eight sources. Several physical interpretations in terms of an optically thick component located on or very near the neutron star, an optically thin region farther in radius from the neutron star, and contribution of the accretion disk are possible. Assumptions required of the pulsar in a cocoon model are problematical. Correlations of spectral parameters with intensity observed in color-color diagrams are more complex than previously reported, although relating luminosity changes to the mass accretion rate is still tenable.
C1 NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771.
RI Swank, Jean/F-2693-2012
NR 106
TC 153
Z9 153
U1 0
U2 0
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0067-0049
J9 ASTROPHYS J SUPPL S
JI Astrophys. J. Suppl. Ser.
PD MAR
PY 1997
VL 109
IS 1
BP 177
EP 224
DI 10.1086/312970
PG 48
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WN498
UT WOS:A1997WN49800006
ER
PT J
AU McKenna, FC
Keenan, FP
Hambly, NC
Prieto, CA
Rolleston, WRJ
Aller, LH
Feibelman, WA
AF McKenna, FC
Keenan, FP
Hambly, NC
Prieto, CA
Rolleston, WRJ
Aller, LH
Feibelman, WA
TI The optical spectral line list of RR Telescopii
SO ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES
LA English
DT Article
DE binaries, symbiotic; line, identification; stars, individual (RR
Telescopii)
ID PLANETARY-NEBULA IC-4997; SYMBIOTIC STARS; EMISSION-LINES; ORION NEBULA;
ELEMENTS; TEL
AB The symbiotic nova RR Telescopii has been observed with the 1.5 m telescope of the Cerro Tololo Inter-American Observatory (CTIO), using the 1.5 m bench-mounted echelle spectrograph in conjunction with a Tektronix CCD. It displays a rich emission-line spectrum, ranging in excitation from O I to [Ni VIII]. We present a list of 491 measured lines, with their suggested identifications, covering a wavelength range from 3430 to 9320 Angstrom Of these, only nine are unidentified, and 70 lines are cataloged that were not given in the original line list of Thackeray. Absolute line intensities are also given, which have been derived by comparing the high-resolution data with a flux-calibrated low-resolution spectrum taken with the Cassegrain spectrograph on the 1.0 m telescope at CTIO.
C1 UNIV CALIF LOS ANGELES,DEPT ASTRON,LOS ANGELES,CA 90024.
NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771.
RP McKenna, FC (reprint author), QUEENS UNIV BELFAST,DEPT PURE & APPL PHYS,BELFAST BT7 1NN,ANTRIM,NORTH IRELAND.
NR 35
TC 38
Z9 38
U1 0
U2 0
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0067-0049
J9 ASTROPHYS J SUPPL S
JI Astrophys. J. Suppl. Ser.
PD MAR
PY 1997
VL 109
IS 1
BP 225
EP 239
DI 10.1086/312977
PG 15
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WN498
UT WOS:A1997WN49800007
ER
PT J
AU Kastner, SO
Bhatia, AK
AF Kastner, SO
Bhatia, AK
TI The neutral nitrogen spectrum: Term populations, multiplet intensities,
diagnostic diagrams, and comparisons with observations
SO ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES
LA English
DT Article
DE atomic data; atomic processes
ID EXCITATION CROSS-SECTIONS; TRANSITION-PROBABILITIES; ATOMIC NITROGEN;
ELECTRON-IMPACT; EMISSION-LINES; ULTRAVIOLET; NEBULA; RANGE;
SPECTROPHOTOMETRY; IDENTIFICATION
AB A spectroscopic model of the neutral nitrogen atom is constructed using published radiative rates and derived approximate collisional excitation rates, giving term populations and allowed and forbidden multiplet intensities for a range of electron temperatures and densities. Figures illustrate the predicted variations of the stronger UV and IR multiplet intensities, which are compared with laboratory- and solar-observed UV line intensities and with IR line intensities observed in a number of astrophysical sources. Reasonable agreement is found for all of the compared UV and IR lines, except for one anomalous solar line. Diagnostic diagrams of allowed/allowed, allowed/forbidden, and forbidden/forbidden line ratios in nitrogen are provided and are applied also to other published observations of nitrogen UV and IR lines.
C1 NASA, GODDARD SPACE FLIGHT CTR, ASTRON & SOLAR PHYS LAB, GREENBELT, MD 20771 USA.
NR 58
TC 2
Z9 2
U1 0
U2 2
PU IOP PUBLISHING LTD
PI BRISTOL
PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND
SN 0067-0049
J9 ASTROPHYS J SUPPL S
JI Astrophys. J. Suppl. Ser.
PD MAR
PY 1997
VL 109
IS 1
BP 241
EP 267
DI 10.1086/312974
PG 27
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WN498
UT WOS:A1997WN49800008
ER
PT J
AU Loftin, KC
Conkin, J
Powell, MR
AF Loftin, KC
Conkin, J
Powell, MR
TI Modeling the effects of exercise during 100% oxygen prebreathe on the
risk of hypobaric decompression sickness
SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE
LA English
DT Article
AB Background: Several previous studies indicated that exercise during prebreathe with 100% O-2 decreased the incidence of hypobaric decompression sickness (DCS). We report a meta-analysis of these investigations combined with a new study in our laboratory to develop a statistical model as a predictive tool for DCS. Hypothesis: Exercise during pre breathe increases N-2, elimination in a theoretical 360-min half-time compartment decreasing the incidence of DCS. Methods: A dose-response probability tissue ratio (TR) model with 95% confidence limits was created for two groups, prebreathe with exercise (n = 113) and resting prebreathe (n = 113), using nonlinear regression analysis with maximum likelihood optimization. Results: The model predicted that prebreathe exercise would reduce the residual N, in a 360-min half-time compart- ment to a level analogous to that in a 180-min compartment. This finding supported the hypothesis. The incidence of DCS for the exercise prebreathe group was significantly decreased (Chi-Square = 17.1, p < 0.0001) from the resting prebreathe group. Conclusions: The results suggested that exercise during prebreathe increases tissue perfusion and Nz elimination approximately 2-fold and markedly lowers the risk of DCS. Based on the model, the prebreathe duration may be reduced from 240 min to a predicted 91 min for the protocol in our study, but this remains to be verified. The model provides a useful planning tool to develop and test appropriate prebreathe exercise protocols and to predict DCS risks for astronauts.
C1 UNIV SPACE RES ASSOC,HOUSTON,TX.
NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058.
RP Loftin, KC (reprint author), KRUG LIFE SCI INC,1290 HERCULES DR,SUITE 120,HOUSTON,TX 77058, USA.
NR 23
TC 7
Z9 7
U1 0
U2 0
PU AEROSPACE MEDICAL ASSOC
PI ALEXANDRIA
PA 320 S HENRY ST, ALEXANDRIA, VA 22314-3579
SN 0095-6562
J9 AVIAT SPACE ENVIR MD
JI Aviat. Space Environ. Med.
PD MAR
PY 1997
VL 68
IS 3
BP 199
EP 204
PG 6
WC Public, Environmental & Occupational Health; Medicine, General &
Internal; Sport Sciences
SC Public, Environmental & Occupational Health; General & Internal
Medicine; Sport Sciences
GA WK695
UT WOS:A1997WK69500004
PM 9056027
ER
PT J
AU Atkinson, C
AF Atkinson, C
TI Regenerative systems - NASA tests composters for space
SO BIOCYCLE
LA English
DT Article
RP Atkinson, C (reprint author), NASA,KENNEDY SPACE CTR,FL 32899, USA.
NR 0
TC 1
Z9 1
U1 0
U2 0
PU JG PRESS, INC
PI EMMAUS
PA 419 STATE AVE, EMMAUS, PA 18049
SN 0276-5055
J9 BIOCYCLE
JI Biocycle
PD MAR
PY 1997
VL 38
IS 3
BP 47
EP 48
PG 2
WC Ecology; Soil Science
SC Environmental Sciences & Ecology; Agriculture
GA WN885
UT WOS:A1997WN88500044
PM 11540129
ER
PT J
AU Randall, DA
Wielicki, BA
AF Randall, DA
Wielicki, BA
TI Measurements, models, and hypotheses in the atmospheric sciences
SO BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY
LA English
DT Article; Proceedings Paper
CT Workshop on Cloud Measurements and Models
CY NOV, 1995
CL NATL OCEANOG & ATMOSPHER ADM, ENVIRONM TECHNOL LAB, BOULDER, CO
SP Natl Oceanog & Atmospher Adm, Environm Technol Lab, Colorado State Univ, Dept Atmospher Sci
HO NATL OCEANOG & ATMOSPHER ADM, ENVIRONM TECHNOL LAB
ID OPERATIONAL FORECASTING-MODEL; SYSTEMATIC-ERRORS; BOUNDARY-LAYER;
CLIMATE; ENTRAINMENT; INSTABILITY; SIMULATION; TURBULENCE; RADIATION;
CLOSURES
AB Measurements in atmospheric science sometimes determine universal functions, but more commonly data are collected in the form of case studies. Models are conceptual constructs that can be used to make predictions about the outcomes of measurements. Hypotheses can be expressed in terms of model results, and the best use of measurements is to falsify such hypotheses. Tuning of models should be avoided because it interferes with falsification. Comparison of models with data would be easier if the minimum data requirements for testing some types of models could be standardized.
C1 NASA,LANGLEY RES CTR,DIV ATMOSPHER SCI,RADIAT SCI BRANCH,HAMPTON,VA 23665.
RP Randall, DA (reprint author), COLORADO STATE UNIV,DEPT ATMOSPHER SCI,FT COLLINS,CO 80523, USA.
RI Randall, David/E-6113-2011
OI Randall, David/0000-0001-6935-4112
NR 26
TC 37
Z9 37
U1 0
U2 1
PU AMER METEOROLOGICAL SOC
PI BOSTON
PA 45 BEACON ST, BOSTON, MA 02108-3693
SN 0003-0007
J9 B AM METEOROL SOC
JI Bull. Amer. Meteorol. Soc.
PD MAR
PY 1997
VL 78
IS 3
BP 399
EP 406
DI 10.1175/1520-0477(1997)078<0399:MMOHIT>2.0.CO;2
PG 8
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA WW304
UT WOS:A1997WW30400002
ER
PT J
AU Kuo, YH
Bresch, JF
Cheng, MD
Kain, J
Parsons, DB
Tao, WK
Zhang, DL
AF Kuo, YH
Bresch, JF
Cheng, MD
Kain, J
Parsons, DB
Tao, WK
Zhang, DL
TI Summary of a mini workshop on cumulus parameterization for mesoscale
models
SO BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY
LA English
DT Editorial Material
ID MIDLATITUDE SQUALL LINE; EXPLOSIVE OCEANIC CYCLONE; 1985 PRE-STORM;
NUMERICAL-SIMULATION; ERICA IOP-5; CONVECTIVE PRECIPITATION; FRONTAL
STRUCTURE; MOMENTUM BUDGET; EARLY EVOLUTION; ENSEMBLE MODEL
AB Representing the effects of cumulus parameterization in numerical models, known as cumulus parameterization, is of fundamental importance in atmospheric sciences. Despite a significant amount of effort devoted to improving the understanding of the parameterization problem, a general theory of cumulus parameterization does not exist. The problem is particularly difficult for a mesoscale model with a grid size of 1-20 km because at such a resolution, a numerical model introduces an artificial spectral gap by splitting an organized mesoscale convective system into resolvable and subgrid scales of motions. To provide a forum for a focused discussion on the problem of cumulus parameterization for mesoscale models, the Mesoscale and Microscale Meteorology Division of NCAR conducted a mini workshop on 11-12 September 1995 in Boulder, Colorado. Approximately 50 scientists participated in this workshop. The workshop was organized into six sessions: 1) overview of the cumulus parameterization problem, 2) cloud model perspectives, 3) model sensitivity to convective parameterization, 4) mesoscale organization and momentum transport, 5) mesoscale observations and verification of schemes, and 6) summary and general discussion. The scientific presentations and the discussion are summarized from reports submitted by the session chairs.
C1 UNIV WASHINGTON, DEPT ATMOSPHER SCI, SEATTLE, WA 98195 USA.
CENT WEATHER BUR, DIV RES & DEV, TAIPEI, TAIWAN.
PENN STATE UNIV, DEPT METEOROL, STATE COLL, PA 16804 USA.
NATL CTR ATMOSPHER RES, ATMOSPHER TECHNOL DIV, BOULDER, CO 80307 USA.
NASA, GODDARD SPACE FLIGHT CTR, MESOSCALE ATMOSPHER PROC BRANCH, GREENBELT, MD 20771 USA.
UNIV MARYLAND, DEPT METEOROL, COLLEGE PK, MD 20742 USA.
RP NATL CTR ATMOSPHER RES, MESOSCALE & MICROSCALE METEOROL DIV, POB 3000, BOULDER, CO 80307 USA.
RI Zhang, Da-Lin/F-2634-2010
OI Zhang, Da-Lin/0000-0003-1725-283X
NR 56
TC 26
Z9 29
U1 0
U2 3
PU AMER METEOROLOGICAL SOC
PI BOSTON
PA 45 BEACON ST, BOSTON, MA 02108-3693 USA
SN 0003-0007
EI 1520-0477
J9 B AM METEOROL SOC
JI Bull. Amer. Meteorol. Soc.
PD MAR
PY 1997
VL 78
IS 3
BP 475
EP 491
PG 17
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA WW304
UT WOS:A1997WW30400011
ER
PT J
AU Hayes, DB
Brodziak, JKT
AF Hayes, DB
Brodziak, JKT
TI Efficiency and bias of estimators and sampling designs for determining
length-weight relationships of fish - Reply
SO CANADIAN JOURNAL OF FISHERIES AND AQUATIC SCIENCES
LA English
DT Editorial Material
C1 NATL MARINE FISHERIES SERV,NW FISHERY SCI CTR,HATFIELD MARINE SCI CTR,NEWPORT,OR 97365.
RP Hayes, DB (reprint author), MICHIGAN STATE UNIV,DEPT FISHERIES & WILDLIFE,PARTNERSHIP ECOSYST RES & MANAGEMENT,E LANSING,MI 48824, USA.
NR 6
TC 0
Z9 0
U1 0
U2 0
PU NATL RESEARCH COUNCIL CANADA
PI OTTAWA
PA RESEARCH JOURNALS, MONTREAL RD, OTTAWA ON K1A 0R6, CANADA
SN 0706-652X
J9 CAN J FISH AQUAT SCI
JI Can. J. Fish. Aquat. Sci.
PD MAR
PY 1997
VL 54
IS 3
BP 744
EP 745
DI 10.1139/cjfas-54-3-744
PG 2
WC Fisheries; Marine & Freshwater Biology
SC Fisheries; Marine & Freshwater Biology
GA XB788
UT WOS:A1997XB78800027
ER
PT J
AU Bryson, S
AF Bryson, S
TI Visualization '96 volume rendering shifts into high gear
SO COMPUTERS IN PHYSICS
LA English
DT Article
RP Bryson, S (reprint author), NASA,AMES RES CTR,MRJ INC,MOFFETT FIELD,CA 94035, USA.
NR 0
TC 0
Z9 0
U1 0
U2 0
PU AMER INST PHYSICS
PI WOODBURY
PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999
SN 0894-1866
J9 COMPUT PHYS
JI Comput. Phys.
PD MAR-APR
PY 1997
VL 11
IS 2
BP 174
EP 180
PG 7
WC Computer Science, Interdisciplinary Applications; Physics,
Multidisciplinary; Physics, Mathematical
SC Computer Science; Physics
GA WR042
UT WOS:A1997WR04200016
ER
PT J
AU Herrmann, DJ
Hillberry, BM
AF Herrmann, DJ
Hillberry, BM
TI A new approach to the analysis of unidirectional titanium matrix
composites with bridge and unbridged cracks
SO ENGINEERING FRACTURE MECHANICS
LA English
DT Article
ID FATIGUE CRACKING; FIBER COMPOSITES
AB An alternative method to the continuum approach for calculating the fiber stresses and crack opening displacements for a longitudinal laminae containing a crack that may be bridged by unbroken fibers is developed. The composite is modeled as discrete cells containing a fiber and the surrounding matrix material. Shear lag theory including the stiffness of the matrix material is used to formulate the stress-strain-displacement relations. The method allows for the implementation of different crack bridging laws for each composite cell including the presence of broken fibers among intact, bridging fibers.
Results are compared with results from the literature and finite element analysis. The capability of this method to model broken fibers among bridging fibers in the crack wake is demonstrated through an example. (C) 1997 Published by Elsevier Science Ltd. All rights reserved.
C1 PURDUE UNIV,SCH MECH ENGN,W LAFAYETTE,IN 47907.
RP Herrmann, DJ (reprint author), NASA,LANGLEY RES CTR,NATL RES COUNCIL,MS 188E,HAMPTON,VA 23681, USA.
NR 24
TC 4
Z9 6
U1 1
U2 2
PU PERGAMON-ELSEVIER SCIENCE LTD
PI OXFORD
PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB
SN 0013-7944
J9 ENG FRACT MECH
JI Eng. Fract. Mech.
PD MAR
PY 1997
VL 56
IS 5
BP 711
EP 726
DI 10.1016/0013-7944(95)00165-4
PG 16
WC Mechanics
SC Mechanics
GA WK647
UT WOS:A1997WK64700008
ER
PT J
AU Clarke, KC
Hoppen, S
Gaydos, L
AF Clarke, KC
Hoppen, S
Gaydos, L
TI A self-modifying cellular automaton model of historical urbanization in
the San Francisco Bay area
SO ENVIRONMENT AND PLANNING B-PLANNING & DESIGN
LA English
DT Article
ID CONTERMINOUS UNITED-STATES; LAND
AB In this paper we describe a cellular automaton (CA) simulation model developed to predict urban growth as part of a project for estimating the regional and broader impact of urbanization on the San Francisco Bay area's climate. The rules of the model are more complex than those of a typical CA and involve the use of multiple data sources, including topography, road networks, and existing settlement distributions, and their modification over time. In addition, the control parameters of the model are allowed to self-modify: that is, the CA adapts itself to the circumstances it generates, in particular, during periods of rapid growth or stagnation. In addition, the model was written to allow the accumulation of probabilistic estimates based on Monte Carlo methods. Calibration of the model has been accomplished by the use of historical maps to compare model predictions of urbanization, based solely upon the distribution in year 1900, with observed data for years 1940, 1954, 1962, 1974, and 1990. The complexity of this model has made calibration a particularly demanding step. Lessons learned about the methods, measures, and strategies developed to calibrate the model may be of use in other environmental modeling contexts. With the calibration complete, the model is being used to generate a set of future scenarios for the San Francisco Bay area along with their probabilities based on the Monte Carlo version of the model. Animated dynamic mapping of the simulations will be used to allow visualization of the impact of future urban growth.
C1 NASA,AMES RES CTR,US GEOL SURVEY,EROS,DATA CTR,MOFFETT FIELD,CA 94035.
RP Clarke, KC (reprint author), CUNY HUNTER COLL,DEPT GEOL & GEOG,GRAD SCH & UNIV CTR,695 PK AVE,NEW YORK,NY 10021, USA.
RI Clarke, Keith/E-1863-2011
OI Clarke, Keith/0000-0001-5805-6056
NR 28
TC 532
Z9 650
U1 8
U2 91
PU PION LTD
PI LONDON
PA 207 BRONDESBURY PARK, LONDON, ENGLAND NW2 5JN
SN 0265-8135
J9 ENVIRON PLANN B
JI Environ. Plan. B-Plan. Des.
PD MAR
PY 1997
VL 24
IS 2
BP 247
EP 261
DI 10.1068/b240247
PG 15
WC Environmental Studies
SC Environmental Sciences & Ecology
GA WP572
UT WOS:A1997WP57200008
ER
PT J
AU Rozas, LP
Minello, TJ
AF Rozas, LP
Minello, TJ
TI Estimating densities of small fishes and decapod crustaceans in shallow
estuarine habitats: A review of sampling design with focus on gear
selection
SO ESTUARIES
LA English
DT Review
ID CRABS CALLINECTES-SAPIDUS; SEAGRASS-COVERED BANKS; BEAM-TRAWL CATCHES;
BUOYANT POP NET; CAPE FEAR RIVER; SALT-MARSH; SOUTH-CAROLINA;
NORTH-CAROLINA; PENAEUS-AZTECUS; FRESH-WATER
AB Shallow estuarine habitats often support large populations of small nekton (fishes and decapod crustaceans), but unique characteristics of these habitats make sampling these nekton populations difficult. We discuss development of sampling designs and evaluate some commonly used devices for quantitatively sampling nekton populations. Important considerations of the sampling design include the size and number of samples, their distribution in time and space, and control of tide level. High, stable catch efficiency should be the most important gear characteristic considered when selecting a sampling device to quantify nekton densities. However, the most commonly used gears in studies of estuarine habitats (trawls and seines) have low, variable catch efficiency. Problems with consistently low catch efficiency can be corrected, but large unpredictable variations in this gear characteristic pose a much more difficult challenge. Study results may be biased if the variability in catch efficiency is related to the treatments or habitat characteristics being measured in the sampling design. Enclosure devices, such as throw traps and drop samplers, have fewer variables influencing catch efficiency than do towed nets (i.e., trawls and seines); and the catch efficiency of these enclosure samplers does not appear to vary substantially with habitat characteristics typical of shallow estuarine areas (e.g., presence of vegetation). The area enclosed by these samplers is often small, but increasing the sample number can generally compensate for this limitation. We recommend using enclosure samplers for estimating densities of small nekton in shallow estuarine habitats because these samplers provide the most reliable quantitative data, and the results of studies using these samplers should be comparable. Many kinds of enclosure samplers are now available, and specific requirements of a project will dictate which gear should be selected.
RP Rozas, LP (reprint author), NATL OCEAN & ATMOSPHER ADM,NATL MARINE FISHERIES SERV,SW FISHERIES SCI CTR,4700 AVE U,GALVESTON,TX 77551, USA.
NR 123
TC 224
Z9 235
U1 7
U2 50
PU ESTUARINE RES FEDERATION
PI LAWRENCE
PA PO BOX 368, LAWRENCE, KS 66044
SN 0160-8347
J9 ESTUARIES
JI Estuaries
PD MAR
PY 1997
VL 20
IS 1
BP 199
EP 213
DI 10.2307/1352731
PG 15
WC Environmental Sciences; Marine & Freshwater Biology
SC Environmental Sciences & Ecology; Marine & Freshwater Biology
GA WT784
UT WOS:A1997WT78400016
ER
PT J
AU Veazie, DR
Gates, TS
AF Veazie, DR
Gates, TS
TI Compressive creep of IM7/K3B composite and the effects of physical aging
on viscoelastic behavior
SO EXPERIMENTAL MECHANICS
LA English
DT Article
AB An experimental study was undertaken to establish the viscoelastic behavior of IM7/K3B composite in compression at elevated temperature. Creep compliance, strain recovery and the effects of physical aging on the time dependent response was measured for uniaxial loading at several isothermal conditions below the glass transition temperature (T-g). The IM7/K3B composite is a graphite-reinforced thermoplastic polyimide with a T-g of approximately 240 degrees C. In a composite, the two matrix-dominated compliance terms associated with time dependent behavior occur in the transverse and shear directions. Linear viscoelasticity was used to characterize the creep/recovery behavior, and superposition techniques were used to establish the physical aging related material constants. Creep strain was converted to compliance and measured as a function of test time and aging time. Results included creep compliance master curves, physical aging shift factors and shift rates, The description of the unique experimental techniques required for compressive testing is also given.
C1 NASA,LANGLEY RES CTR,HAMPTON,VA 23681.
RP Veazie, DR (reprint author), CLARK ATLANTA UNIV,ATLANTA,GA 30314, USA.
NR 13
TC 6
Z9 6
U1 0
U2 0
PU SAGE PUBLICATIONS INC
PI THOUSAND OAKS
PA 2455 TELLER RD, THOUSAND OAKS, CA 91320
SN 0014-4851
J9 EXP MECH
JI Exp. Mech.
PD MAR
PY 1997
VL 37
IS 1
BP 62
EP 68
DI 10.1007/BF02328751
PG 7
WC Materials Science, Multidisciplinary; Mechanics; Materials Science,
Characterization & Testing
SC Materials Science; Mechanics
GA WL455
UT WOS:A1997WL45500012
ER
PT J
AU Prabhakaran, R
Piascik, RS
AF Prabhakaran, R
Piascik, RS
TI A blunt notch extended compact tension (BN-ECT) specimen for the study
of short and long crack propagation
SO EXPERIMENTAL TECHNIQUES
LA English
DT Article
ID FATIGUE CRACKS
C1 NASA,LANGLEY RES CTR,MECH MAT BRANCH,HAMPTON,VA 23665.
RP Prabhakaran, R (reprint author), OLD DOMINION UNIV,DEPT MECH ENGN,NORFOLK,VA 23508, USA.
NR 15
TC 2
Z9 2
U1 0
U2 1
PU SOC EXPERIMENTAL MECHANICS
PI BETHEL
PA 7 SCHOOL STREET, BETHEL, CT 06801
SN 0732-8818
J9 EXP TECHNIQUES
JI Exp. Tech.
PD MAR-APR
PY 1997
VL 21
IS 2
BP 24
EP 26
DI 10.1111/j.1747-1567.1997.tb00504.x
PG 3
WC Engineering, Mechanical; Mechanics; Materials Science, Characterization
& Testing
SC Engineering; Mechanics; Materials Science
GA WR773
UT WOS:A1997WR77300005
ER
PT J
AU Ray, RD
Egbert, GD
AF Ray, RD
Egbert, GD
TI The flux of tidal energy across latitude 60 degrees S
SO GEOPHYSICAL RESEARCH LETTERS
LA English
DT Article
ID OCEAN TIDES; TOPEX/POSEIDON; ALTIMETRY
AB How and where the ocean tides dissipate their energy are longstanding questions with both oceanographic and astronomical implications. Two decades ago, Doake suggested that flexing of Antarctic ice shelves by the underlying ocean tide is an important energy sink, perhaps accounting for over half the global dissipation rate. Observational constraints on Antarctic dissipation have been scarce. Here two new and complementary ocean-tide models, both derived from Topex/Poseidon satellite altimeter measurements, are used to determine the flux of tidal energy across 60 degrees S toward the Antarctic coastline. Our results show relatively small fluxes and they therefore rule out Doake's suggestion: Antarctica is an insignificant sink in the global tidal energy budget.
C1 OREGON STATE UNIV,COLL OCEAN & ATMOSPHER SCI,CORVALLIS,OR 97331.
RP Ray, RD (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HUGHES STX,CODE 926,GREENBELT,MD 20771, USA.
RI Ray, Richard/D-1034-2012
NR 25
TC 4
Z9 4
U1 0
U2 2
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009
SN 0094-8276
J9 GEOPHYS RES LETT
JI Geophys. Res. Lett.
PD MAR 1
PY 1997
VL 24
IS 5
BP 543
EP 546
DI 10.1029/97GL50316
PG 4
WC Geosciences, Multidisciplinary
SC Geology
GA WL742
UT WOS:A1997WL74200013
ER
PT J
AU Carr, ME
Kearns, EJ
Rossby, HT
AF Carr, ME
Kearns, EJ
Rossby, HT
TI Isopycnal RAFOS floats as roving hydrographers in the North Atlantic
Current region
SO GEOPHYSICAL RESEARCH LETTERS
LA English
DT Article
AB The properties measured by isopycnal floats can be compiled to provide hydrographic information about the sampled surfaces. The height and temperature of two specific volume anomaly surfaces reported by 84 RAFOS floats deployed in the North Atlantic Current (NAC) region are compared here with the climatological hydrographic database. The mean pathway of the NAC and other prominent features of the region are similar in float-derived and climatological surfaces. The most striking difference between floats and climatology, an extended trough in the NAC path at 44 degrees N in the float-derived surface, reflects the sampling time scales. The baroclinic transport of the NAC estimated from RAFOS floats using the observed climatological relationship between the potential energy anomaly and the height of the specific volume anomaly surfaces was 42 Sv at 42 degrees N and 24 Sv at 47 degrees N, in reasondble agreement with climatological estimates.
C1 NATL DATA BUOY CTR,BAY ST LOUIS,MS 39529.
UNIV RHODE ISL,GRAD SCH OCEANOG,NARRAGANSETT,RI 02882.
RP Carr, ME (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,M-S 300-323,PASADENA,CA 91109, USA.
NR 11
TC 12
Z9 12
U1 0
U2 0
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009
SN 0094-8276
J9 GEOPHYS RES LETT
JI Geophys. Res. Lett.
PD MAR 1
PY 1997
VL 24
IS 5
BP 551
EP 554
DI 10.1029/97GL00156
PG 4
WC Geosciences, Multidisciplinary
SC Geology
GA WL742
UT WOS:A1997WL74200015
ER
PT J
AU Crisp, D
AF Crisp, D
TI Absorption of sunlight by water vapor in cloudy conditions: A partial
explanation for the cloud absorption anomaly
SO GEOPHYSICAL RESEARCH LETTERS
LA English
DT Article
ID SCATTERING; PHYSICS
AB The atmospheric radiative transfer algorithms used in most global general circulation models underestimate the globally-averaged solar energy absorbed by cloudy atmospheres by up to 25 W m(-2). The origin of this anomalous absorption is not yet known, but it has been attributed to a variety of sources including oversimplified or missing physical processes in these models, uncertainties in the input data, and even measurement errors. Here, a sophisticated atmospheric radiative transfer model was used to provide a more comprehensive description of the physical processes that contribute to the absorption of solar radiation by the Earth's atmosphere. We found that the amount of sunlight absorbed by a cloudy atmosphere is inversely proportional to the solar zenith angle and the cloud top height, and directly proportional to the cloud optical depth and the water vapor concentration within the clouds. Atmospheres with saturated, optically-thick, low clouds absorbed about 12 W m(-2) more than clear atmospheres. This accounts for about 1/2 to 1/3 of the anomalous absorption. Atmospheres with optically thick middle and high clouds usually absorb less than clear atmospheres. Because water vapor is concentrated within and below the cloud tops, this absorber is most effective at small solar zenith angles. An additional absorber that is distributed at or above the cloud tops is needed to produce the amplitude and zenith angle dependence of the observed anomalous absorption.
RP Crisp, D (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,MS 241-105,PASADENA,CA 91109, USA.
NR 16
TC 57
Z9 57
U1 0
U2 3
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009
SN 0094-8276
J9 GEOPHYS RES LETT
JI Geophys. Res. Lett.
PD MAR 1
PY 1997
VL 24
IS 5
BP 571
EP 574
DI 10.1029/97GL50245
PG 4
WC Geosciences, Multidisciplinary
SC Geology
GA WL742
UT WOS:A1997WL74200020
ER
PT J
AU Stolarski, RS
Labow, GJ
McPeters, RD
AF Stolarski, RS
Labow, GJ
McPeters, RD
TI Springtime Antarctic total ozone measurements in the early-1970s from
the BUV instrument on Nimbus 4
SO GEOPHYSICAL RESEARCH LETTERS
LA English
DT Article
ID BACKSCATTER ULTRAVIOLET
AB Data from the BUV instrument on the Nimbus 4 satellite have been used to construct maps of the measured total ozone field over the Antarctic region during the Austral springs of 1970 through 1973. These maps show an October mean ozone distribution similar to that measured in 1979 by the Nimbus 7 TOMS instrument. These ozone maps during the 1970s are very different from those measured during the late 1980s and early 1990s. The ozone distribution for each of the years during the early 1970s is characterized by a circumpolar, crescent-shaped maximum surrounding a shallow minimum centered near the pole. The total ozone amounts in the polar minimum region in the early 1970s average about 300 Dobson units, comparable to the amounts measured at that time over Halley Bay and Syowa by ground-based Dobson Spectrophotometers.
C1 HUGHES STX CORP,GREENBELT,MD 20770.
RP Stolarski, RS (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 916,GREENBELT,MD 20771, USA.
RI Stolarski, Richard/B-8499-2013; McPeters, Richard/G-4955-2013
OI Stolarski, Richard/0000-0001-8722-4012; McPeters,
Richard/0000-0002-8926-8462
NR 13
TC 22
Z9 23
U1 0
U2 0
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009
SN 0094-8276
J9 GEOPHYS RES LETT
JI Geophys. Res. Lett.
PD MAR 1
PY 1997
VL 24
IS 5
BP 591
EP 594
DI 10.1029/96GL04017
PG 4
WC Geosciences, Multidisciplinary
SC Geology
GA WL742
UT WOS:A1997WL74200025
ER
PT J
AU Massie, ST
Dye, JE
Baumgardner, D
Randel, WJ
Wu, F
Tie, XX
Pan, LW
Figarol, F
Brasseur, GP
Santee, ML
Read, WG
Grainger, RG
Lambert, A
Mergenthaler, JL
Tabazadeh, A
AF Massie, ST
Dye, JE
Baumgardner, D
Randel, WJ
Wu, F
Tie, XX
Pan, LW
Figarol, F
Brasseur, GP
Santee, ML
Read, WG
Grainger, RG
Lambert, A
Mergenthaler, JL
Tabazadeh, A
TI Simultaneous observations of Polar Stratospheric Clouds and HNO3 over
Scandinavia in January, 1992
SO GEOPHYSICAL RESEARCH LETTERS
LA English
DT Article
ID AEROSOL; GROWTH; WINTER; ACID
AB Simultaneous observations of Polar Stratospheric Cloud (PSC) aerosol extinction and HNO3 mixing ratios over Scandinavia are examined for January 9-10, 1992. Data measured by the Microwave Limb Sounder(MLS), Cryogenic Limb Array Etalon Spectrometer (CLAES), and Improved Stratospheric and Mesospheric Sounder (ISAMS) experiments on the Upper Atmosphere Research Satellite (UARS) are examined at locations adjacent to parcel trajectory positions. Regression coefficients, obtained from Mie calculations, are used to transform aerosol extinctions into aerosol volume densities. Graphs of volume density versus temperature, and importantly, HNO3 mixing ratio versus temperature, show volume increases and simultaneous loss of HNO3 as temperatures decrease. The data is consistent with initial PSC growth processes which transform sulfate droplets into ternary droplets or nitric acid dihydrate (NAD) particles.
C1 CALTECH,JET PROP LAB,PASADENA,CA 91109.
UNIV OXFORD,OXFORD,ENGLAND.
LOCKEED MARTIN PALO ALTO RES LAB,DEPT 91 20,PALO ALTO,CA 94304.
NASA,AMES RES CTR,MOFFETT FIELD,CA 94035.
RP Massie, ST (reprint author), NATL CTR ATMOSPHER RES,POB 3000,BOULDER,CO 80307, USA.
RI Pan, Laura/A-9296-2008; Grainger, Roy/E-8823-2011; Randel,
William/K-3267-2016
OI Pan, Laura/0000-0001-7377-2114; Grainger, Roy/0000-0003-0709-1315;
Randel, William/0000-0002-5999-7162
NR 22
TC 21
Z9 21
U1 0
U2 1
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009
SN 0094-8276
J9 GEOPHYS RES LETT
JI Geophys. Res. Lett.
PD MAR 1
PY 1997
VL 24
IS 5
BP 595
EP 598
DI 10.1029/97GL00315
PG 4
WC Geosciences, Multidisciplinary
SC Geology
GA WL742
UT WOS:A1997WL74200026
ER
PT J
AU Goodman, J
Verma, S
Pueschel, RF
Hamill, P
Ferry, GV
Webster, D
AF Goodman, J
Verma, S
Pueschel, RF
Hamill, P
Ferry, GV
Webster, D
TI New evidence of size and composition of polar stratospheric cloud
particles
SO GEOPHYSICAL RESEARCH LETTERS
LA English
DT Article
ID ICE PARTICLES; NITRIC-ACID; ANTARCTIC OZONE; NITRATE; DENITRIFICATION;
CONDENSATION; TEMPERATURE; CRYSTALS; CHLORIDE; AEROSOLS
AB A NASA Ames ER-2 aircraft encountered polar stratospheric cloud particles on July 28 and July 30, 1994 during the ASHOE/MAESA deployment. Stratospheric particles were collected by impaction techniques on specially treated Substrates. For the first time, Nitron- nitrate reaction spots were detected on the ice crystal replicas, indicating the presence of NO3- ions on/in ice. Because the reaction spots were detected only on very small crystals (r<1 mu m) and never on larger crystals, suggest that the amount of NO3- coating Sufficient to initiate reactions will accumulate during ice crystal evaporation in ice subsaturated air. This may slow down the evaporation rate and enable ice crystals to survive longer in subsaturated environment. That provides an explanation of why on both days ice crystals were replicated at temperatures avole the frost point, when their appearance and size suggest substantial evaporation.
C1 TMA NORCAL,RICHMOND,CA 94804.
NASA,AMES RES CTR,MOFFETT FIELD,CA 94035.
SAN JOSE STATE UNIV,DEPT PHYS,SAN JOSE,CA 95192.
RP Goodman, J (reprint author), SAN JOSE STATE UNIV,DEPT METEOROL,SAN JOSE,CA 95192, USA.
NR 29
TC 17
Z9 17
U1 0
U2 1
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009
SN 0094-8276
J9 GEOPHYS RES LETT
JI Geophys. Res. Lett.
PD MAR 1
PY 1997
VL 24
IS 5
BP 615
EP 618
DI 10.1029/97GL00256
PG 4
WC Geosciences, Multidisciplinary
SC Geology
GA WL742
UT WOS:A1997WL74200031
ER
PT J
AU Dovner, PO
Eriksson, AI
Bostrom, R
Holback, B
Waldemark, J
Eliasson, L
Boehm, M
AF Dovner, PO
Eriksson, AI
Bostrom, R
Holback, B
Waldemark, J
Eliasson, L
Boehm, M
TI The occurrence of lower hybrid cavities in the upper ionosphere
SO GEOPHYSICAL RESEARCH LETTERS
LA English
DT Article
ID TRANSVERSE ION-ACCELERATION; TOPSIDE AURORAL IONOSPHERE; FREJA; PLASMA;
WAVES
AB Lower hybrid cavities (LHC), i. e., small-scale density depletions coinciding with enhanced lower hybrid waves, are frequent in the upper ionosphere. It is found that they exist in all regions the Freja satellite has scanned, as long as lower hybrid waves are present. They are found most frequently at magnetic latitudes between 55 degrees to 65 degrees, preferably on the morning side. In the auroral oval, the LHCs do not occur as densely as at lower latitudes but they usually form larger structures.
C1 UMEA UNIV,DEPT APPL PHYS & ELECT,S-90187 UMEA,SWEDEN.
SWEDISH INST SPACE PHYS,S-98128 KIRUNA,SWEDEN.
CALTECH,JET PROP LAB,PASADENA,CA 91109.
RP Dovner, PO (reprint author), SWEDISH INST SPACE PHYS,S-75591 UPPSALA,SWEDEN.
RI Eriksson, Anders/C-2887-2009
NR 18
TC 27
Z9 27
U1 0
U2 0
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009
SN 0094-8276
J9 GEOPHYS RES LETT
JI Geophys. Res. Lett.
PD MAR 1
PY 1997
VL 24
IS 5
BP 619
EP 622
DI 10.1029/97GL00424
PG 4
WC Geosciences, Multidisciplinary
SC Geology
GA WL742
UT WOS:A1997WL74200032
ER
PT J
AU Macari, EJ
Parker, JK
Costes, NC
AF Macari, EJ
Parker, JK
Costes, NC
TI Measurement of volume changes in triaxial tests using digital imaging
techniques
SO GEOTECHNICAL TESTING JOURNAL
LA English
DT Article
DE triaxial testing; digital imaging; volume change
AB Conventional procedures for the determination of volume changes in triaxial tests are based on the amount of pore fluid changes into or out of the fully saturated cylindrical specimen. As a triaxial soil specimen shears, the total volume may increase or decrease depending on the soil density, current state of stress, and the stress history. The measurement of these changes in volume are of great importance in the characterization of the soil's mechanical properties. This paper presents an innovative or alternative technique that has been used for measuring the volumetric deformation that cylindrical specimens experience during the shearing stages of a triaxial test. This method incorporates digital imaging techniques and computer-aided analysis to assess the changes in volume throughout a test. A detailed description of the hardware and other equipment is provided along with the data analysis methodology used to simplify the operation. Comparisons are made between the observed results and those obtained from conventional measurement techniques.
C1 UNIV ALABAMA,DEPT MECH ENGN,TUSCALOOSA,AL 35487.
NASA,SPACE SCI LAB,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812.
RP Macari, EJ (reprint author), GEORGIA INST TECHNOL,SCH CIVIL ENGN,ATLANTA,GA 30332, USA.
NR 8
TC 36
Z9 38
U1 0
U2 2
PU AMER SOC TESTING MATERIALS
PI W CONSHOHOCKEN
PA 100 BARR HARBOR DR, W CONSHOHOCKEN, PA 19428-2959
SN 0149-6115
J9 GEOTECH TEST J
JI Geotech. Test. J.
PD MAR
PY 1997
VL 20
IS 1
BP 103
EP 109
PG 7
WC Engineering, Geological; Geosciences, Multidisciplinary
SC Engineering; Geology
GA XT613
UT WOS:A1997XT61300010
ER
PT J
AU Buratti, BJ
Goguen, JD
Mosher, JA
AF Buratti, BJ
Goguen, JD
Mosher, JA
TI No large brightness variations on nereid
SO ICARUS
LA English
DT Article
ID CHAOTIC ROTATION; HYPERION
AB Observations of Nereid with the 200-in. telescope on Palomar Mountain over three contiguous nights in July 1995 show no evidence for the large photometric variations seen by earlier observers. Total brightness variations within a single night are less than 10%. Our results suggest that Nereid may have a long rotational period, perhaps on the order of weeks. Our observations were not obtained close enough to Nereid's apoapsis to determine whether its rotation state is chaotic, as suggested by Dobrovolskis (1993, Icarus 118, 181-198). (C) 1997 Academic Press.
C1 CALTECH, PALOMAR OBSERV, PASADENA, CA 91109 USA.
RP Buratti, BJ (reprint author), CALTECH, JET PROP LAB, 4800 OAK GROVE DR 183-501, PASADENA, CA 91109 USA.
NR 13
TC 9
Z9 9
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
EI 1090-2643
J9 ICARUS
JI Icarus
PD MAR
PY 1997
VL 126
IS 1
BP 225
EP 228
DI 10.1006/icar.1996.5644
PG 4
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WT567
UT WOS:A1997WT56700016
ER
PT J
AU Hudson, RL
Moore, MH
AF Hudson, RL
Moore, MH
TI Hydrocarbon radiation chemistry in ices of cometary relevance
SO ICARUS
LA English
DT Article
ID INFRARED-SPECTROSCOPY; IRRADIATION
AB Recent discoveries of acetylene, methane, and ethane in Comet Hyakutake, C/1996 B2, have led us to investigate these and other hydrocarbons in irradiated ices of cometary relevance. Laboratory experiments showed that chemical reactions, particularly those involving H atoms, influence the C2H6:CH4 ratio in H2O + hydrocarbon mixtures, (C) 1997 Academic Press.
C1 NASA, GODDARD SPACE FLIGHT CTR, ASTROCHEM BRANCH, GREENBELT, MD 20771 USA.
RP Hudson, RL (reprint author), ECKERD COLL, DEPT CHEM, ST PETERSBURG, FL 33733 USA.
RI Hudson, Reggie/E-2335-2012
NR 18
TC 24
Z9 25
U1 0
U2 2
PU ACADEMIC PRESS INC ELSEVIER SCIENCE
PI SAN DIEGO
PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA
SN 0019-1035
J9 ICARUS
JI Icarus
PD MAR
PY 1997
VL 126
IS 1
BP 233
EP 235
DI 10.1006/icar.1997.5678
PG 3
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WT567
UT WOS:A1997WT56700018
ER
PT J
AU Neudeck, PG
Fazi, C
AF Neudeck, PG
Fazi, C
TI Positive temperature coefficient of breakdown voltage in 4H-SiC PN
junction rectifiers
SO IEEE ELECTRON DEVICE LETTERS
LA English
DT Article
ID FILMS; DEVICES; SI
AB It has been suggested that once silicon carbide (SIG) technology overcomes some crystal growth obstacles, superior SIC semiconductor devices would supplant silicon in many high-power applications. However, the property of positive temperature coefficient of breakdown voltage, a behavior crucial to realizing excellent power device reliability, has not been observed in 4H-SiC, which is presently the best-suited SiC polytype for power device implementation. This paper reports the first experimental measurements of stable positive temperature coefficient behavior observed in 4H-SiC pn junction rectifiers. This research indicates that robust 4H-SiC power devices with high breakdown reliability should be achievable after SIC foundries reduce material defects such as micropipes, dislocations, and deep level impurities.
C1 USA,RES LAB,ADELPHI,MD 20783.
RP Neudeck, PG (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA.
NR 17
TC 47
Z9 47
U1 0
U2 6
PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
PI NEW YORK
PA 345 E 47TH ST, NEW YORK, NY 10017-2394
SN 0741-3106
J9 IEEE ELECTR DEVICE L
JI IEEE Electron Device Lett.
PD MAR
PY 1997
VL 18
IS 3
BP 96
EP 98
DI 10.1109/55.556092
PG 3
WC Engineering, Electrical & Electronic
SC Engineering
GA WJ197
UT WOS:A1997WJ19700006
ER
PT J
AU Kim, M
Lubecke, VM
Martin, SC
Smith, RP
Siegel, PH
AF Kim, M
Lubecke, VM
Martin, SC
Smith, RP
Siegel, PH
TI A planar parabola-feed frequency multiplier
SO IEEE MICROWAVE AND GUIDED WAVE LETTERS
LA English
DT Article
DE dielectric-filled parabola; diode frequency multiplier; slot antenna
AB A novel quasi-optical all-planar frequency doubler that could provide an alternative approach to conventional waveguide circuits for millimeter- and submillimeter-wave signal generation is presented. The multiplier uses a quad-bridge diode configuration for inherent isolation between the input and output signals. Two pairs of double-slot antennas with orthogonal polarizations directly couple input and output signals to the diodes, without the need for hybrid couplers required in typical balanced circuits. The integrated quad-bridge-diode/slot-antenna circuit is mounted on a dielectric-filled parabola for coupling to quasioptical propagation systems, Measurement results for an X to K-band doubler show frequency conversion loss of 6.8 dB at the output frequency of 20.3 GHz.
RP Kim, M (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA.
NR 5
TC 5
Z9 5
U1 0
U2 0
PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
PI NEW YORK
PA 345 E 47TH ST, NEW YORK, NY 10017-2394
SN 1051-8207
J9 IEEE MICROW GUIDED W
JI IEEE Microw. Guided Wave Lett.
PD MAR
PY 1997
VL 7
IS 3
BP 60
EP 62
DI 10.1109/75.556032
PG 3
WC Engineering, Electrical & Electronic
SC Engineering
GA WK281
UT WOS:A1997WK28100002
ER
PT J
AU Bonitz, RG
Hsia, TC
AF Bonitz, RG
Hsia, TC
TI Calibrating a multi-manipulator robotic system
SO IEEE ROBOTICS & AUTOMATION MAGAZINE
LA English
DT Article
DE calibration; robot; multi-manipulator; multi-arm
AB A simple, but effective, method of calibrating a multi-manipulator robotic system is introduced, The algorithm uses precisely machined calibration plates which are inexpensive to manufacture and require no measuring instrumentation. The method is tested on a dual-arm system which resulted in an order of magnitude reduction in the pose error Coordinated dual-arm manipulation experiments are conducted using the calibrated kinematic model to validate the usefulness of the calibration process.
C1 UNIV CALIF DAVIS,DEPT ELECT & COMP ENGN,SYST CONTROL & ROBOT LAB,DAVIS,CA 95616.
RP Bonitz, RG (reprint author), CALTECH,JET PROP LAB,MS 198-219,4800 OAK GROVE DR,PASADENA,CA 91109, USA.
NR 9
TC 7
Z9 8
U1 0
U2 1
PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
PI NEW YORK
PA 345 E 47TH ST, NEW YORK, NY 10017-2394
SN 1070-9932
J9 IEEE ROBOT AUTOM MAG
JI IEEE Robot. Autom. Mag.
PD MAR
PY 1997
VL 4
IS 1
BP 18
EP 22
DI 10.1109/100.580975
PG 5
WC Automation & Control Systems; Robotics
SC Automation & Control Systems; Robotics
GA WW627
UT WOS:A1997WW62700003
ER
PT J
AU Cwik, T
Katz, DS
Patterson, J
AF Cwik, T
Katz, DS
Patterson, J
TI Scalable solutions to integral-equation and finite-element simulations
SO IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION
LA English
DT Article
DE finite-element methods; integral equations
ID LINEAR ALGEBRA SUBPROGRAMS; ELECTROMAGNETIC SCATTERING; COMPUTATION;
SYSTEMS; ALGORITHM; IMPLEMENTATION; MATRICES; OBJECTS; SET
AB When developing numerical methods, or applying them to the simulation and design of engineering components, it inevitably becomes necessary to examine the scaling of the method with a problem's electrical size, The scaling results from the original mathematical development; for example, a dense system of equations in the solution of integral equations, as well as the specific numerical implementation. Scaling of the numerical implementation depends upon many factors; far example, direct or iterative methods far solution of the linear system, as well as the computer architecture used in the simulation, In this paper, scalability will he divided into toro components-scalability of the numerical algorithm specifically on parallel computer systems and algorithm or sequential scalability, The sequential implementation and scaling is initially presented, with the parallel implementation following, This progression is meant to illustrate the differences in using current parallel platforms and sequential machines and the resulting savings. Time to solution (wall-clock time) for differing problem sizes are the key parameters plotted or tabulated, Sequential and parallel scalability of time harmonic surface integral equation forms and the finite-element solution to the partial differential equations are considered in detail.
RP Cwik, T (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA.
OI Katz, Daniel S./0000-0001-5934-7525
NR 55
TC 5
Z9 5
U1 0
U2 2
PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
PI NEW YORK
PA 345 E 47TH ST, NEW YORK, NY 10017-2394
SN 0018-926X
J9 IEEE T ANTENN PROPAG
JI IEEE Trans. Antennas Propag.
PD MAR
PY 1997
VL 45
IS 3
BP 544
EP 555
DI 10.1109/8.558670
PG 12
WC Engineering, Electrical & Electronic; Telecommunications
SC Engineering; Telecommunications
GA WN339
UT WOS:A1997WN33900023
ER
PT J
AU Evans, JW
Evans, JY
Yu, BK
AF Evans, JW
Evans, JY
Yu, BK
TI Designing and building-in reliability in advanced microelectronic
assemblies and structures
SO IEEE TRANSACTIONS ON COMPONENTS PACKAGING AND MANUFACTURING TECHNOLOGY
PART A
LA English
DT Article; Proceedings Paper
CT Second International Conference on Adhesive Joining and Coating
Technology in Electronics Manufacturing
CY JUN 03-05, 1996
CL STOCKHOLM, SWEDEN
SP ECA
DE electronic components; fatigue; modeling; Monte Carlo; multichip module;
reliability; simulation; via
AB New technologies in electronics require that product development embrace the paradigms of design for reliability and built-in reliability, These paradigms require effective measures to create robust designs and manufacturing processes, This objective must be achieved through modeling failure processes and taking proactive steps early in the development, Following an assessment of material properties, finite element models are built of key structures in the system, A statistical experimental design is then developed, This statistically designed ''virtual experiment'' will include the geometrical and materials' variables comprising the system and a damage model, such as a fatigue prediction model, Information for process development or improvement is derived from the virtual experiment, The statistical model is then embedded in a Monte Carlo simulation to assess the impact of uncertainty and variability, This process of stochastic physics of failure is the subject of this paper, The process will be described and an application of this systems engineering based approach to micro-via interconnect reliability, in a complex multichip module (MCM), will be presented.
C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771.
INST ADV ENGN,MFG TECHNOL LAB,SEOUL,SOUTH KOREA.
RP Evans, JW (reprint author), AJOU UNIV,INST ADV ENGN,DEPT SYST ENGN,SEOUL,SOUTH KOREA.
NR 9
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
SN 1070-9886
J9 IEEE T COMPON PACK A
JI IEEE Trans Compon. Packag. Manuf. Technol. Part A
PD MAR
PY 1997
VL 20
IS 1
BP 38
EP 45
DI 10.1109/95.558542
PG 8
WC Engineering, Manufacturing; Engineering, Electrical & Electronic;
Materials Science, Multidisciplinary
SC Engineering; Materials Science
GA WM720
UT WOS:A1997WM72000007
ER
PT J
AU Wang, JR
Racette, P
Chang, LA
AF Wang, JR
Racette, P
Chang, LA
TI MIR measurements of atmospheric water vapor profiles
SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING
LA English
DT Article
ID RAMAN LIDAR; RADIOMETRIC MEASUREMENTS; MICROWAVE RADIOMETRY; MOISTURE
PROFILES; OCEAN SURFACE; RETRIEVAL; CLEAR
AB Three subjects related to atmospheric water vapor profiling using the 183.3 GHz absorption line are discussed in this paper, First, data acquired by an airborne millimeter-wave imaging radiometer (MIR) over ocean surface in the western Pacific are used to estimate three-dimensional (3-D) distribution of atmospheric water vapor, The instrument's radiometric measurements with mixed vertical and horizontal polarizations require modifications to the retrieval algorithm used in the past, It is demonstrated that, after the modifications, the new algorithm can provide adequate retrieval of water vapor profiles, even though the measured data are of mixed polarizations, Next, the retrieved profiles, in terms of water vapor mixing ratio rho (g/kg), are compared with those measured in near concurrence by dropsondes from a research aircraft in the western Pacific and by a ground-based Raman lidar at Wallops Island, Virginia, The ratio of the standard deviation to the mean rho is found to be 0.12 at 0.25 km altitude and gradually degraded to 0.67 at the highest altitude of the retrieval of 10.25 km, Finally, the effect of the ''initial guess'' relative humidity profile on the final retrieved product is analyzed with respect to the condition for the convergent retrieval, It is found that the effect is minimal if the initial profile is not unrealistically different from the true one. If the initial profile is very different from the true one, the final retrieved product could be subject to a substantial error, Tightening of the convergent condition in the retrieval helped reduce magnitude of the error, but not remove it totally. It is concluded that an initial profile based on climatology is likely to provide most reliable retrieval results.
C1 FUTURETECH CORP,GAITHERSBURG,MD 20878.
RP Wang, JR (reprint author), NASA,GODDARD SPACE FLIGHT CTR,LAB HYDROSPHER PROC,GREENBELT,MD 20771, USA.
NR 19
TC 5
Z9 5
U1 0
U2 1
PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
PI NEW YORK
PA 345 E 47TH ST, NEW YORK, NY 10017-2394
SN 0196-2892
J9 IEEE T GEOSCI REMOTE
JI IEEE Trans. Geosci. Remote Sensing
PD MAR
PY 1997
VL 35
IS 2
BP 212
EP 223
DI 10.1109/36.563259
PG 12
WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote
Sensing; Imaging Science & Photographic Technology
SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science
& Photographic Technology
GA WN531
UT WOS:A1997WN53100002
ER
PT J
AU Gregg, WW
Patt, FS
Woodward, RH
AF Gregg, WW
Patt, FS
Woodward, RH
TI Development of a simulated data set for the SeaWiFS mission
SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING
LA English
DT Article
ID ZONE COLOR SCANNER; OCEAN COLOR; MODEL; IRRADIANCE; RADIANCE;
ATMOSPHERES; CHLOROPHYLL; ALGORITHM; SENSORS
AB A realistic simulated data set is essential for mission readiness preparations and can potentially assist in all phases of ground support for a future mission. Such a data set was created for the Sea-viewing Wide Field-of-view Sensor (SeaWiFS), a global ocean color mission due for launch in 1997. This data set incorporates a representation of virtually every known aspect of the flight mission. Thus, it provides a high fidelity data set for testing most phases of the ground system, including data processing, data transfers, calibration and validation, quality control, and mission operations. The data set is constructed for a seven-day period, March 25-31, 1994. Specific features of the data set: it includes Global Area Coverage (GAC), recorded Local Area Coverage (LAC), and real-time High Resolution Picture Transmission (HRPT) data for the seven-day period; it includes a realistic orbit which is propagated using a Brouwer-Lyddane model with drag; the data correspond to a command schedule based on the orbit for this seven-day period; it includes total (at satellite) radiances for ocean, land, clouds, and ice; it utilizes a high-resolution land/sea mask; it includes actual SeaWiFS spectral responses; it includes the actual sensor saturation responses; it is formatted according to current onboard data structures; and it includes corresponding telemetry (instrument and spacecraft) data. The methods are described and some examples of the output are given.
C1 GEN SCI CORP,LAUREL,MD 20707.
RP Gregg, WW (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 902,GREENBELT,MD 20771, USA.
NR 21
TC 3
Z9 3
U1 0
U2 0
PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
PI NEW YORK
PA 345 E 47TH ST, NEW YORK, NY 10017-2394
SN 0196-2892
J9 IEEE T GEOSCI REMOTE
JI IEEE Trans. Geosci. Remote Sensing
PD MAR
PY 1997
VL 35
IS 2
BP 421
EP 435
DI 10.1109/36.563281
PG 15
WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote
Sensing; Imaging Science & Photographic Technology
SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science
& Photographic Technology
GA WN531
UT WOS:A1997WN53100022
ER
PT J
AU Breon, FM
Vanderbilt, V
Leroy, M
Bicheron, P
Walthall, CL
Kalshoven, JE
AF Breon, FM
Vanderbilt, V
Leroy, M
Bicheron, P
Walthall, CL
Kalshoven, JE
TI Evidence of hot spot directional signature from airborne POLDER
measurements
SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING
LA English
DT Article
ID BIDIRECTIONAL REFLECTANCE; FOREST CANOPIES; VEGETATION CANOPIES;
PHYSICAL MODEL; LEAF CANOPIES; INVERSION; DISTRIBUTIONS; VALIDATION;
ASAS
AB The POLDER instrument was down during the BOREAS experiment over various sites and at various altitudes in the canadian boreal forest and other nearby targets. The instrument design permits the acquisition of the directional signature of any surface cover. In particular, the high directional resolution of POLDER allows it to measure, with an unprecedented accuracy, the hot spot signature of natural targets. In this paper we present some typical examples of such highly anisotropic reflectance directional signatures. The ratio of the maximum reflectance (hot spot direction) to the minimum reflectance (broad area in the forward scattering hemisphere) varies with wavelength and canopy. It can be as large as six in the visible and three in the near IR.
C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035.
CNRS,CNES,UMR,UPS,CTR ETUD SPATIALES BIOSPHERE,F-31055 TOULOUSE,FRANCE.
ARS,USDA,REMOTE SENSING & MODELING LAB,BELTSVILLE,MD 20705.
NASA,GODDARD SPACE FLIGHT CTR,TERR PHYS LAB 924,GREENBELT,MD 20771.
RP Breon, FM (reprint author), CEA,DSM,LMCE,LAB MODELIZAT CLIMAT & ENVIRONNEMENT,F-91191 GIF SUR YVETTE,FRANCE.
RI Breon, Francois-Marie/M-4639-2016
OI Breon, Francois-Marie/0000-0003-2128-739X
NR 31
TC 33
Z9 35
U1 1
U2 5
PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
PI NEW YORK
PA 345 E 47TH ST, NEW YORK, NY 10017-2394
SN 0196-2892
J9 IEEE T GEOSCI REMOTE
JI IEEE Trans. Geosci. Remote Sensing
PD MAR
PY 1997
VL 35
IS 2
BP 479
EP 484
DI 10.1109/36.563289
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 WN531
UT WOS:A1997WN53100030
ER
PT J
AU Jobson, DJ
Rahman, ZU
Woodell, GA
AF Jobson, DJ
Rahman, ZU
Woodell, GA
TI Properties and performance of a center/surround retinex
SO IEEE TRANSACTIONS ON IMAGE PROCESSING
LA English
DT Article
ID COLOR-VISION
AB The last version of Land's retinex model for human vision's lightness and color constancy has been implemented and tested in image processing experiments. Previous research has established the mathematical foundations of Land's retinex but has not subjected his lightness theory to extensive image processing experiments, We have sought to define a practical implementation of the retinex without particular concern for its validity as a model for human lightness and color perception, Here we describe the trade-off between rendition and dynamic range compression that is governed by the surround space constant, Further, unlike previous results, we find that the placement of the logarithmic function is important and produces best results when placed after the surround formation, Also unlike previous results, we find best rendition for a ''canonical'' gain/offset applied after the retinex operation. Various functional forms for the retinex surround are evaluated, and a Gaussian form found to perform better than the inverse square suggested by Land. Images that violate the gray world assumptions (implicit to this retinex) are investigated to provide insight into cases where this retinex fails to produce a good rendition.
C1 SCI & TECHNOL CORP,HAMPTON,VA 23666.
RP Jobson, DJ (reprint author), NASA,LANGLEY RES CTR,HAMPTON,VA 23681, USA.
NR 15
TC 506
Z9 636
U1 5
U2 54
PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
PI NEW YORK
PA 345 E 47TH ST, NEW YORK, NY 10017-2394
SN 1057-7149
J9 IEEE T IMAGE PROCESS
JI IEEE Trans. Image Process.
PD MAR
PY 1997
VL 6
IS 3
BP 451
EP 462
DI 10.1109/83.557356
PG 12
WC Computer Science, Artificial Intelligence; Engineering, Electrical &
Electronic
SC Computer Science; Engineering
GA WL075
UT WOS:A1997WL07500009
PM 18282940
ER
PT J
AU Deshpande, MD
Reddy, CJ
Tiemsin, PI
Cravey, R
AF Deshpande, MD
Reddy, CJ
Tiemsin, PI
Cravey, R
TI A new approach to estimate complex permittivity of dielectric materials
at microwave frequencies using waveguide measurements
SO IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES
LA English
DT Article
DE dielectric constant; finite-element method
AB In this paper, a simple waveguide measurement technique is presented to determine the complex dielectric constant of a dielectric material, The dielectric sample is loaded in a short-circuited rectangular waveguide, Using a network analyzer, the reflection coefficient of the waveguide is measured, Using the finite-element method (FEM) the exact reflection coefficient of this;configuration is determined as a function of the dielectric constant. The measured and calculated values of the reflection coefficient are then matched using the Newton-Raphson method to estimate the dielectric constant of a material, A comparison of estimated values of the dielectric constant obtained from simple waveguide modal theory and the FEM approach is presented, Numerical results for dielectric constants of Teflon and Plexiglas measured at the X- and Ku-bands are presented. Numerical inaccuracies in the estimate of the dielectric constant due to: 1) the presence of airgaps between sample and sample holder waveguide surfaces and 2) inaccuracy in the sample dimensions are also discussed.
C1 HAMPTON UNIV,HAMPTON,VA 23668.
NASA,LANGLEY RES CTR,ARMY CECOM,HAMPTON,VA 23681.
RP Deshpande, MD (reprint author), VIGYAN INC,HAMPTON,VA 23681, USA.
NR 8
TC 34
Z9 34
U1 0
U2 5
PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
PI NEW YORK
PA 345 E 47TH ST, NEW YORK, NY 10017-2394
SN 0018-9480
J9 IEEE T MICROW THEORY
JI IEEE Trans. Microw. Theory Tech.
PD MAR
PY 1997
VL 45
IS 3
BP 359
EP 366
DI 10.1109/22.563334
PG 8
WC Engineering, Electrical & Electronic
SC Engineering
GA WP281
UT WOS:A1997WP28100006
ER
PT J
AU Brasunas, JC
AF Brasunas, JC
TI Measuring and modeling the frequency response of infrared detectors
SO INFRARED PHYSICS & TECHNOLOGY
LA English
DT Article
AB It is shown that a light-emitting diode is a simple way of characterizing the frequency response of an infrared detector over several decades of frequency, since the diode has a linear relationship between input current and output radiant power. By normalizing a detector's output voltage to the diode input current, the detector frequency response can be measured as simply as one measures the transfer function of an electrical filter. This is advantageous in studying higher-order effects in a thermal-type detector response, where the detector deviates from the Lorentzian behavior predicted by a simple model of a lumped heat capacity connected to a thermal bath by a lumped thermal conductance path. An example is given of a thermoelectric detector with marked non-lorentzian behavior.
RP Brasunas, JC (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 693,GREENBELT,MD 20771, USA.
RI brasunas, john/I-2798-2013
NR 5
TC 5
Z9 5
U1 1
U2 2
PU PERGAMON-ELSEVIER SCIENCE LTD
PI OXFORD
PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB
SN 1350-4495
J9 INFRARED PHYS TECHN
JI Infrared Phys. Technol.
PD MAR
PY 1997
VL 38
IS 2
BP 69
EP 74
DI 10.1016/S1350-4495(96)00037-0
PG 6
WC Instruments & Instrumentation; Optics; Physics, Applied
SC Instruments & Instrumentation; Optics; Physics
GA WP144
UT WOS:A1997WP14400002
ER
PT J
AU Brasunas, JC
AF Brasunas, JC
TI Thallium-bromo-iodide as a far-infrared beamsplitter for Fourier
transform spectroscopy
SO INFRARED PHYSICS & TECHNOLOGY
LA English
DT Article
AB We show that room-temperature, thallium-bromo-iodide is a useful material for a beamsplitter for spectroscopy in the far-infrared, to near 50 mu m wavelength.
RP Brasunas, JC (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 693,GREENBELT,MD 20771, USA.
RI brasunas, john/I-2798-2013
NR 5
TC 0
Z9 0
U1 0
U2 0
PU PERGAMON-ELSEVIER SCIENCE LTD
PI OXFORD
PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB
SN 1350-4495
J9 INFRARED PHYS TECHN
JI Infrared Phys. Technol.
PD MAR
PY 1997
VL 38
IS 2
BP 75
EP 81
DI 10.1016/S1350-4495(96)00035-7
PG 7
WC Instruments & Instrumentation; Optics; Physics, Applied
SC Instruments & Instrumentation; Optics; Physics
GA WP144
UT WOS:A1997WP14400003
ER
PT J
AU Brown, GM
AF Brown, GM
TI Evaluation of vision correction alternatives for myopic adults
SO INTERFACES
LA English
DT Article
ID PHOTOREFRACTIVE KERATECTOMY; EXCIMER-LASER
AB Prior to 1980, eyeglasses and contact lenses were the only widely available corrective treatments for myopia, commonly known as nearsightedness. In recent years, surgical procedures such as radial keratotomy (RK) and photorefractive keratectomy (PRK) have become viable corrective alternatives for myopic adults. I developed a decision model that a myopic adult can use to periodically revisit his or her decision regarding vision correction, given the expected costs, benefits, and risks of the surgical and nonsurgical alternatives. I exercised this decision model using my own personal values, and found that although the expected outcomes of the surgeries are already preferable to the perpetual use of external corrective lenses, my best near-term decision was to delay surgery and give the surgeons a chance to further improve their success rates.
RP Brown, GM (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,MAIL STOP 198-235,PASADENA,CA 91109, USA.
NR 11
TC 2
Z9 2
U1 0
U2 1
PU INST OPERATIONS RESEARCH MANAGEMENT SCIENCES
PI LINTHICUM HTS
PA 901 ELKRIDGE LANDING RD, STE 400, LINTHICUM HTS, MD 21090-2909
SN 0092-2102
J9 INTERFACES
JI Interfaces
PD MAR-APR
PY 1997
VL 27
IS 2
BP 66
EP 84
DI 10.1287/inte.27.2.66
PG 19
WC Management; Operations Research & Management Science
SC Business & Economics; Operations Research & Management Science
GA XA247
UT WOS:A1997XA24700006
ER
PT J
AU Rhim, WK
Chung, SK
Rulison, AJ
Spjut, RE
AF Rhim, WK
Chung, SK
Rulison, AJ
Spjut, RE
TI Measurements of thermophysical properties of molten silicon by a
high-temperature electrostatic levitator
SO INTERNATIONAL JOURNAL OF THERMOPHYSICS
LA English
DT Article; Proceedings Paper
CT 4th Asian Thermophysical Properties Conference
CY SEP 05-08, 1995
CL KEIO UNIV, MITA CAMPUS, TOKYO, JAPAN
HO KEIO UNIV, MITA CAMPUS
DE density; electrostatic levitation; hemispherical total emissivity;
molten silicon; specific heat; surface tension
ID LIQUID
AB Several thermophysical properties of molten silicon measured by the high-temperature electrostatic levitator at JPL are presented. They are density, constant-pressure specific heat capacity, hemispherical total emissivity, and surface tension. Over the temperature range investigated (1350 < T-m < 1825 K), the measured liquid density (in g.cm(-3)) can be expressed by a quadratic function, rho(T) = rho(m) - 1.69 x 10(-4)(T - T-m) - 1.75 x 10(-7)(T - T-m)(2) with T-m and rho(m) being 1687 K and 2.56 g.cm(-3), respectively. The hemispherical total emissivity of molten silicon at the melting temperature was determined to be 0.18, and the constant-pressure specific heat was evaluated as a Function of temperature. The surface tension (in 10(-3) N.m(-1)) of molten silicon over a similar temperature range can be expressed by sigma(T) = 875 - 0.22(T - T-m).
C1 HARVEY MUDD COLL,DEPT ENGN,CLAREMONT,CA 91711.
RP Rhim, WK (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA.
NR 12
TC 57
Z9 57
U1 0
U2 5
PU PLENUM PUBL CORP
PI NEW YORK
PA 233 SPRING ST, NEW YORK, NY 10013
SN 0195-928X
J9 INT J THERMOPHYS
JI Int. J. Thermophys.
PD MAR
PY 1997
VL 18
IS 2
BP 459
EP 469
DI 10.1007/BF02575175
PG 11
WC Thermodynamics; Chemistry, Physical; Mechanics; Physics, Applied
SC Thermodynamics; Chemistry; Mechanics; Physics
GA WT230
UT WOS:A1997WT23000014
ER
PT J
AU Grugel, RN
Brush, LN
AF Grugel, RN
Brush, LN
TI Macrosegregation in directionally solidified dendritic alloys
SO JOM-JOURNAL OF THE MINERALS METALS & MATERIALS SOCIETY
LA English
DT Review
ID DOUBLE-DIFFUSIVE CONVECTION; AMMONIUM-CHLORIDE SOLUTION; NICKEL-BASE
SUPERALLOYS; PB-SN ALLOYS; THERMOSOLUTAL CONVECTION; BINARY ALLOY;
FLUID-FLOW; INTERDENDRITIC LIQUID; CHANNEL FORMATION; COMPOSITIONAL
CONVECTION
AB In this article, gravity-driven flow and its subsequent effect of promoting macrosegregation during unidirectional solidification of dendritic alloys is presented. Examples of macrosegregation that arise during the controlled directional solidification of hypo- and hypereutectic Pb-Sn alloys are shown, and a method of preventing macrosegregation is demonstrated. The experimental work is discussed in terms of how current knowledge of solute redistribution in a dendritic array can be promoted as well as how the processing technique might be applied to improve microstructural homogeneity during controlled directional solidification.
C1 UNIV WASHINGTON,SEATTLE,WA 98195.
RP Grugel, RN (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,UNIV SPACE RES ASSOC,MS-ES75,HUNTSVILLE,AL 35812, USA.
NR 139
TC 6
Z9 6
U1 1
U2 9
PU MINERALS METALS MATERIALS SOC
PI WARRENDALE
PA 420 COMMONWEALTH DR, WARRENDALE, PA 15086
SN 1047-4838
J9 JOM-J MIN MET MAT S
JI JOM-J. Miner. Met. Mater. Soc.
PD MAR
PY 1997
VL 49
IS 3
BP 26
EP 30
DI 10.1007/BF02914652
PG 5
WC Materials Science, Multidisciplinary; Metallurgy & Metallurgical
Engineering; Mineralogy; Mining & Mineral Processing
SC Materials Science; Metallurgy & Metallurgical Engineering; Mineralogy;
Mining & Mineral Processing
GA WN404
UT WOS:A1997WN40400007
ER
PT J
AU Roth, KR
AF Roth, KR
TI Comparison of computation with experiment for a geometrically simplified
powered-lift model
SO JOURNAL OF AIRCRAFT
LA English
DT Article; Proceedings Paper
CT AIAA 14th Applied Aerodynamics Conference
CY JUN 17-20, 1996
CL NEW ORLEANS, LA
SP Amer Inst Aeronaut & Astronaut
ID IMPLICIT
AB The performance of a representative short takeoff and vertical landing model during transition flight is investigated by comparison of experimental and numerical simulations. The model consists of a 60-deg cropped delta wing planform; a simple fuselage shape blended to the wing; and tandem, circular, high-pressure-air lift-jets that exit perpendicularly to the Bat lower surface. The configuration minimizes the geometric complexity while retaining the important flow physics of the lift-jet/aerodynamic surface interaction. Three-dimensional, laminar, and turbulent Navier-Stokes computations are made using a multiple, overset grid scheme, Results are presented for jet-off and powered-lift eases and compared with the measured forces and pressures for the model at a freestream Mach number of 0.146, a 10-deg angle of attack, and sonic lift-jets. Computational flow visualization illustrates the presence of primary and secondary wing leading-edge vortices and the deflection of the lift-jets by the freestream, Significantly, both computational fluid dynamics and experiment predict a jet-induced lift loss that is mostly a result of a reduction in the suction pressure at the wing leading edge.
RP Roth, KR (reprint author), NASA,AMES RES CTR,APP COMPUTAT AERODYNAM BRANCH,M-S 258-1,MOFFETT FIELD,CA 94035, USA.
NR 27
TC 0
Z9 0
U1 0
U2 1
PU AMER INST AERONAUT ASTRONAUT
PI RESTON
PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091
SN 0021-8669
J9 J AIRCRAFT
JI J. Aircr.
PD MAR-APR
PY 1997
VL 34
IS 2
BP 160
EP 167
DI 10.2514/2.2167
PG 8
WC Engineering, Aerospace
SC Engineering
GA WQ862
UT WOS:A1997WQ86200003
ER
PT J
AU Smith, SC
Kroo, IM
AF Smith, SC
Kroo, IM
TI Induced drag computations on wings with accurately modeled wakes
SO JOURNAL OF AIRCRAFT
LA English
DT Article
C1 STANFORD UNIV,STANFORD,CA 94305.
RP Smith, SC (reprint author), NASA,AMES RES CTR,HIGH SPEED AERODYNAM BRANCH,MOFFETT FIELD,CA 94035, USA.
NR 10
TC 4
Z9 4
U1 0
U2 0
PU AMER INST AERONAUT ASTRONAUT
PI RESTON
PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091
SN 0021-8669
J9 J AIRCRAFT
JI J. Aircr.
PD MAR-APR
PY 1997
VL 34
IS 2
BP 253
EP 255
DI 10.2514/2.7570
PG 3
WC Engineering, Aerospace
SC Engineering
GA WQ862
UT WOS:A1997WQ86200016
ER
PT J
AU Zelenka, RE
Almsted, LD
AF Zelenka, RE
Almsted, LD
TI Design and flight test of 35-GigaHertz radar for terrain and obstacle
avoidance+
SO JOURNAL OF AIRCRAFT
LA English
DT Article
C1 HONEYWELL MILITARY AVION,MINNEAPOLIS,MN 55413.
RP Zelenka, RE (reprint author), NASA,AMES RES CTR,FLIGHT DECK BRANCH,M-S 210-9,MOFFETT FIELD,CA 94035, USA.
NR 9
TC 3
Z9 3
U1 0
U2 0
PU AMER INST AERONAUT ASTRONAUT
PI RESTON
PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091
SN 0021-8669
J9 J AIRCRAFT
JI J. Aircr.
PD MAR-APR
PY 1997
VL 34
IS 2
BP 261
EP 263
DI 10.2514/2.7574
PG 3
WC Engineering, Aerospace
SC Engineering
GA WQ862
UT WOS:A1997WQ86200020
ER
PT J
AU Taylor, PT
Ravat, D
AF Taylor, PT
Ravat, D
TI An interpretation of the MAGSAT anomalies of Central Europe - Reply
SO JOURNAL OF APPLIED GEOPHYSICS
LA English
DT Editorial Material
RP Taylor, PT (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA.
RI Taylor, Patrick/D-4707-2012
OI Taylor, Patrick/0000-0002-1212-9384
NR 9
TC 2
Z9 2
U1 1
U2 1
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0926-9851
J9 J APPL GEOPHYS
JI J. Appl. Geophys.
PD MAR
PY 1997
VL 36
IS 4
BP 217
EP 219
DI 10.1016/S0926-9851(96)00041-9
PG 3
WC Geosciences, Multidisciplinary; Mining & Mineral Processing
SC Geology; Mining & Mineral Processing
GA WR026
UT WOS:A1997WR02600008
ER
PT J
AU Sha, YG
Su, CH
Lehoczky, SL
AF Sha, YG
Su, CH
Lehoczky, SL
TI Intrinsic carrier concentration and electron effective mass in
Hg1-xZnxTe
SO JOURNAL OF APPLIED PHYSICS
LA English
DT Article
ID N-TYPE HG1-XCDXTE; HGZNTE; GROWTH; SEMICONDUCTORS; MICROHARDNESS;
MOBILITY; ALLOYS; GAP
AB The intrinsic carrier concentrations, Fermi energies, and the electron effective masses are calculated for Hg1-xZnxTe with 02.0.CO;2
PG 12
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA WM904
UT WOS:A1997WM90400001
ER
PT J
AU Lau, KM
Sui, CH
AF Lau, KM
Sui, CH
TI Mechanisms of short-term sea surface temperature regulation:
Observations during TOGA COARE
SO JOURNAL OF CLIMATE
LA English
DT Article
ID SUPER CLOUD CLUSTERS; INTRASEASONAL OSCILLATIONS; TROPICAL ATMOSPHERE;
VARIABILITY; DYNAMICS
AB Analyses of ocean-atmosphere data from Tropical Oceans Global Atmosphere Coupled Ocean-Atmosphere Response Experiment indicate that short-term (weekly to monthly) fluctuations of SST in the western Pacific warm pool are closely linked to the alternation of wet and dry spells driven by the Madden-Julian oscillation (MJO). The dry phase is characterized by increased convection over the Indian Ocean, a prolonged period of atmospheric subsidence, and surface easterlies over the western Pacific warm pool. During this phase, increased surface shortwave radiation and reduced evaporation contribute about equally to the warming of the warm pool. Pronounced diurnal Variations in SST observed during the dry phase may be instrumental in leading to the prolonged warming. The dry phase is followed by the wet phase, in which the SST warming trend is arrested and a cooling trend initiated by a reduction in surface shortwave radiation accompanying the buildup of organized convection. Subsequently, the continued cooling of the upper ocean is accelerated by increased westerly surface wind leading to enhanced surface evaporation and increased entrainment of cold water from below the thermocline. At this stage, the increased surface shortwave radiation due to the diminished cloud cover from reduced convection opposes the cooling by evaporation. The cooling trend is reversed as soon as the westerly phase terminates and the dry phase is reinitiated by the establishment of new organized convection over the Indian Ocean.
The authors' results suggest that short-term SST variability in the western Pacific warm pool is closely linked to surface fluxes, which are strongly modulated by atmospheric low-frequency variability associated with the MIG. The implications of the present results on the dynamics of the MJO and the possible role of coupled SST in influencing the MJO variability are also discussed.
RP Lau, KM (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CLIMATE & RADIAT BRANCH,ATMOSPHERES LAB,CODE 913,GREENBELT,MD 20771, USA.
RI Lau, William /E-1510-2012;
OI Lau, William /0000-0002-3587-3691; SUI, CHUNG-HSIUNG/0000-0003-2842-5660
NR 18
TC 127
Z9 131
U1 1
U2 5
PU AMER METEOROLOGICAL SOC
PI BOSTON
PA 45 BEACON ST, BOSTON, MA 02108-3693
SN 0894-8755
J9 J CLIMATE
JI J. Clim.
PD MAR
PY 1997
VL 10
IS 3
BP 465
EP 472
DI 10.1175/1520-0442(1997)010<0465:MOSTSS>2.0.CO;2
PG 8
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA WM904
UT WOS:A1997WM90400007
ER
PT J
AU Seager, R
Murtugudde, R
AF Seager, R
Murtugudde, R
TI Ocean dynamics, thermocline adjustment, and regulation of tropical SST
SO JOURNAL OF CLIMATE
LA English
DT Article
ID NINO-SOUTHERN OSCILLATION; SURFACE-TEMPERATURE; CARBON-DIOXIDE;
INCREASED CO2; PACIFIC; MODEL; SIMULATION; GCM; ATMOSPHERE; CLIMATOLOGY
AB The role of tropical Pacific ocean dynamics in regulating the ocean response to thermodynamic forcing is investigated using an ocean general circulation model (GCM) coupled to a model of the atmospheric mixed layer. It is found that the basin mean sea surface temperature (SST) change is less in the presence of varying ocean heat transport than would be the case if the forcing was everywhere balanced by an equivalent change in the surface heat flux. This occurs because the thermal forcing in the eastern equatorial Pacific is partially compensated by an increase in heat flux divergence associated with the equatorial upwelling. This constitutes a validation of st previously identified ''ocean dynamical thermostat.''
A simple two-box model of subtropical-equatorial interaction shows that the SST regulation mechanism crucially depends on spatial variation in the sensitivity of the surface fluxes to SST perturbations. In the GCM, this sensitivity increases with latitude, largely a result of the wind speed dependence of the latent heat Aux, so that a uniform forcing can be balanced by a smaller SST change in the subtropics than in equatorial latitudes. The tropical ocean circulation moves heat to where the ocean more readily loses it to the atmosphere. Water that subducts in subtropical latitudes and returns to the equatorial thermocline therefore has a smaller temperature perturbation than the surface equatorial waters. The thermocline temperature adjusts on timescales of decades to the imposed forcing, but the adjustment is insufficient to cancel the thermostat mechanism. The results imply that an increase in the downward heat flux at the ocean surface, as happens with increasing concentrations of greenhouse gases, should be accompanied by a stronger equatorial SST gradient. This contradicts the results of coupled atmosphere-ocean GCMs. Various explanations are offered. None are conclusive, but the possibility that the discrepancy lies in the low resolution of the ocean GCMs typically used in the study of climate change is discussed.
C1 NASA,GODDARD SPACE FLIGHT CTR,UNIV SPACE RES ASSOC,LAB HYDROSPHER PROC,GREENBELT,MD 20771.
RP Seager, R (reprint author), COLUMBIA UNIV,LAMONT DOHERTY EARTH OBSERV,POB 1000,PALISADES,NY 10964, USA.
NR 28
TC 82
Z9 85
U1 0
U2 6
PU AMER METEOROLOGICAL SOC
PI BOSTON
PA 45 BEACON ST, BOSTON, MA 02108-3693
SN 0894-8755
J9 J CLIMATE
JI J. Clim.
PD MAR
PY 1997
VL 10
IS 3
BP 521
EP 534
DI 10.1175/1520-0442(1997)010<0521:ODTAAR>2.0.CO;2
PG 14
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA WM904
UT WOS:A1997WM90400011
ER
PT J
AU Sha, YG
Su, CH
Lehoczky, SL
AF Sha, YG
Su, CH
Lehoczky, SL
TI Growth of HgZnTe by directional solidification in a magnetic field
SO JOURNAL OF CRYSTAL GROWTH
LA English
DT Article
ID CRYSTAL-GROWTH; HGCDTE ALLOYS; SEGREGATION
AB Hg0.84Zn0.16Te crystals were grown vertically by directional solidification in a 5 T axial magnetic field. Growth in an identical thermal environment but without the presence of magnetic field was also performed. The ingots were partially grown and quenched to preserve the growth interface shapes. The effects of magnetic damping on the buoyancy-driven convective flows in the melt were investigated by examining the quenched-in interface shapes and by measuring the composition variations along the axial and radial directions of the grown ingots and comparing them with those of ingots grown without a field.
C1 UNIV SPACE RES ASSOC,HUNTSVILLE,AL 35806.
RP Sha, YG (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,SPACE SCI LAB,HUNTSVILLE,AL 35812, USA.
NR 26
TC 9
Z9 9
U1 0
U2 0
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0022-0248
J9 J CRYST GROWTH
JI J. Cryst. Growth
PD MAR
PY 1997
VL 173
IS 1-2
BP 88
EP 96
DI 10.1016/S0022-0248(96)00792-0
PG 9
WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied
SC Crystallography; Materials Science; Physics
GA WT163
UT WOS:A1997WT16300014
ER
PT J
AU Frazier, DO
Hung, RJ
Paley, MS
Long, YT
AF Frazier, DO
Hung, RJ
Paley, MS
Long, YT
TI Effects of convection during the photodeposition of polydiacetylene thin
films
SO JOURNAL OF CRYSTAL GROWTH
LA English
DT Article
ID OPTICAL-PROPERTIES; SINGLE-CRYSTALS; GROWTH; POLY(DIACETYLENES);
MICROGRAVITY; DIACETYLENE; DERIVATIVES; GRAVITY
AB In this work, we describe a preliminary investigation of buoyancy-driven heat transfer during the growth of thin films from solution following exposure to ultraviolet (UV) light. Irradiation of the growth cell occurs at various directions relative to gravitational acceleration. Through numerical computations, the steady-state flow and temperature profiles are simulated during the course of light exposure. Light-induced polymerization accompanies a heat transfer process through a fairly complicated recirculating flow pattern. A scaling analysis shows that buoyancy-driven velocities only reduce by a factor of 10 for gravity levels as low as 10(-2)g(0). Paley et al. observe what appears to be gravitationally sensitive particle development and inclusion in thin films using a photodeposition process. From this study, it is clear that production of homogeneous thin films would have to occur in the environment of a complicated flow pattern of recirculation with a nonuniform temperature distribution. Indeed, even when irradiation occurs from the top of the cell, the most stable stratified cell orientation, defects remain in our films due to the persistence of buoyancy-driven convection. To achieve homogeneity, minimal scattering centers, and possible molecular order, photodeposition of polymer films by UV light exposure must proceed in a reduced-convection environment. Fluid mechanics simulations are useful for establishing gravitational sensitivity to this recently discovered process (patent # 5,451,433) for preparing thin films having quite promising nonlinear optical characteristics.
C1 UNIV ALABAMA,DEPT MECH & AEROSP ENGN,HUNTSVILLE,AL 35899.
RP Frazier, DO (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,SPACE SCI LAB,UNIV SPACE RES ASSOC,HUNTSVILLE,AL 35812, USA.
NR 21
TC 9
Z9 9
U1 1
U2 1
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0022-0248
J9 J CRYST GROWTH
JI J. Cryst. Growth
PD MAR
PY 1997
VL 173
IS 1-2
BP 172
EP 181
DI 10.1016/S0022-0248(96)00800-7
PG 10
WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied
SC Crystallography; Materials Science; Physics
GA WT163
UT WOS:A1997WT16300025
ER
PT J
AU Arnold, WA
Matthiesen, D
Bennett, RJ
Jayne, DT
AF Arnold, WA
Matthiesen, D
Bennett, RJ
Jayne, DT
TI An innovative method for preparing semiconductor charges used in crystal
growth and shear cell diffusion experiments
SO JOURNAL OF CRYSTAL GROWTH
LA English
DT Article
AB An innovative technique for machining semiconductors has been developed. This technique was used to prepare semiconductor charges for crystal growth and shear cell diffusion experiments. The technique allows brittle semiconductor materials to be quickly and accurately machined. Lightly doping the semiconductor material increases the conductivity enough to allow the material to be shaped by an electrical discharge machine (EDM).
RP Arnold, WA (reprint author), CASE WESTERN RESERVE UNIV,NASA,LEWIS RES CTR,CLEVELAND,OH 44106, USA.
NR 4
TC 4
Z9 7
U1 0
U2 1
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0022-0248
J9 J CRYST GROWTH
JI J. Cryst. Growth
PD MAR
PY 1997
VL 172
IS 3-4
BP 450
EP 454
DI 10.1016/S0022-0248(96)00692-6
PG 5
WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied
SC Crystallography; Materials Science; Physics
GA WL653
UT WOS:A1997WL65300021
ER
PT J
AU Gawronski, WK
Sawicki, JT
AF Gawronski, WK
Sawicki, JT
TI Balanced dissipative controllers for flexible structures
SO JOURNAL OF DYNAMIC SYSTEMS MEASUREMENT AND CONTROL-TRANSACTIONS OF THE
ASME
LA English
DT Article
ID LARGE SPACE STRUCTURES; MODEL-REDUCTION; LINEAR-SYSTEMS; POSITIVITY
AB A balanced approach to shaping the closed-loop properties of the dissipative controllers for flexible structures is presented. In the balanced representation the properties of flexible structures are introduced, and a simple method of designing of the dissipative controllers is obtained It relates the controller gains with the closed-loop pole locations. The examples illustrate the accuracy of the design method.
C1 CLEVELAND STATE UNIV,CLEVELAND,OH 44115.
RP Gawronski, WK (reprint author), CALTECH,JET PROP LAB,TECH STAFF,PASADENA,CA 91109, USA.
NR 28
TC 0
Z9 0
U1 0
U2 1
PU ASME-AMER SOC MECHANICAL ENG
PI NEW YORK
PA 345 E 47TH ST, NEW YORK, NY 10017
SN 0022-0434
J9 J DYN SYST-T ASME
JI J. Dyn. Syst. Meas. Control-Trans. ASME
PD MAR
PY 1997
VL 119
IS 1
BP 5
EP 9
DI 10.1115/1.2801215
PG 5
WC Automation & Control Systems; Instruments & Instrumentation
SC Automation & Control Systems; Instruments & Instrumentation
GA WN866
UT WOS:A1997WN86600002
ER
PT J
AU Tang, PN
Palazzolo, AB
Kascak, AF
Montague, GT
AF Tang, PN
Palazzolo, AB
Kascak, AF
Montague, GT
TI Electromechanical modeling of hybrid piezohydraulic actuator system for
active vibration control
SO JOURNAL OF DYNAMIC SYSTEMS MEASUREMENT AND CONTROL-TRANSACTIONS OF THE
ASME
LA English
DT Article
AB Electromechanical modelling of a hybrid piezohydraulic actuator system for active vibration control was developed. The transfer function of piezoelectric actuator was derived from the electromechanical potential energy law. This transfer function represents the dynamic relationship between en input electric voltage and piezoelectric actuator displacement. The hydraulic actuator was characterized by impedance matching in which its transfer functions were experimentally determined. The transfer functions were transformed into a state-space representation, which is easily assembled into an active vibration control (AVC) closed-loop simulation. Good correlation of simulation and test was achieved for the hybrid system. A closed-loop dynamic simulation for imbalance response with/without AVC of a spinning rotor test rig at NASA Lewis was performed and showed excellent agreement with test results. The simulation couples the piezoelectric, hydraulic, and structural (rotor) components.
C1 NASA,LEWIS RES CTR,USA,CLEVELAND,OH 44135.
RP Tang, PN (reprint author), TEXAS A&M UNIV,COLLEGE STN,TX 77843, USA.
NR 11
TC 3
Z9 3
U1 0
U2 1
PU ASME-AMER SOC MECHANICAL ENG
PI NEW YORK
PA 345 E 47TH ST, NEW YORK, NY 10017
SN 0022-0434
J9 J DYN SYST-T ASME
JI J. Dyn. Syst. Meas. Control-Trans. ASME
PD MAR
PY 1997
VL 119
IS 1
BP 10
EP 18
DI 10.1115/1.2801199
PG 9
WC Automation & Control Systems; Instruments & Instrumentation
SC Automation & Control Systems; Instruments & Instrumentation
GA WN866
UT WOS:A1997WN86600003
ER
PT J
AU Huang, ZC
Mott, DB
Shu, PK
Chen, JC
Wickenden, DK
AF Huang, ZC
Mott, DB
Shu, PK
Chen, JC
Wickenden, DK
TI Improvement of metal-semiconductor-metal GaN photoconductors
SO JOURNAL OF ELECTRONIC MATERIALS
LA English
DT Article; Proceedings Paper
CT 38th Electronic Materials Conference (EMC)
CY JUN 26-28, 1996
CL UNIV OF CALIF AT SANTA BARBARA, SANTA BARBARA, CA
HO UNIV OF CALIF AT SANTA BARBARA
DE GaN; photoconductors; ultraviolet (UV) detector
ID LIGHT-EMITTING-DIODES
AB Metal-semiconductor-metal photoconductors made on GaN usually exhibit a slow response time and a low responsivity. We have carried out a systematic study on the performance of the photoconductors made from GaN grown by metalorganic chemical vapor deposition using different growth conditions and have found that both response time and responsivity of the GaN detector are improved when the material is grown using increased ammonia flow rates. The best GaN ultraviolet photoconductive detector shows a response time of 0.3 ms and a responsivity of 3200 A/W at 365 nm under an operation bias of 10 V. We attribute this improvement to the reduction of the point defects in GaN.
C1 UNIV MARYLAND,DEPT COMP SCI & ELECT ENGN,BALTIMORE,MD 21228.
JOHNS HOPKINS UNIV,APPL PHYS LAB,LAUREL,MD 20723.
RP Huang, ZC (reprint author), NASA,GODDARD SPACE FLIGHT CTR,SOLID STATE DEVICE DEV BRANCH,GREENBELT,MD 20771, USA.
NR 11
TC 20
Z9 20
U1 0
U2 2
PU MINERALS METALS MATERIALS SOC
PI WARRENDALE
PA 420 COMMONWEALTH DR, WARRENDALE, PA 15086
SN 0361-5235
J9 J ELECTRON MATER
JI J. Electron. Mater.
PD MAR
PY 1997
VL 26
IS 3
BP 330
EP 333
DI 10.1007/s11664-997-0173-x
PG 4
WC Engineering, Electrical & Electronic; Materials Science,
Multidisciplinary; Physics, Applied
SC Engineering; Materials Science; Physics
GA WN137
UT WOS:A1997WN13700041
ER
PT J
AU Stainback, PC
Nagabushana, KA
AF Stainback, PC
Nagabushana, KA
TI Review: Hot-wire anemometry in transonic and subsonic slip flows (Data
Bank contribution)
SO JOURNAL OF FLUIDS ENGINEERING-TRANSACTIONS OF THE ASME
LA English
DT Article
AB In the past, only a relatively small number of investigations were conducted using hot-wire anemometry in transonic and subsonic slip flows. This was due to the complexity of the applicable equations. Now it appears that the developments in electronics and computational methods have made it practical to reconsider this problem. A review of past work performed in these flow regimes using hot-wire anemometry will be made along with a description of recent efforts made to develop methods which might be used to make measurements in these flow regimes. A detailed version of this review article is available through the electronic JFE.
C1 OLD DOMINION UNIV RES FDN,NORFOLK,VA 23508.
ADV ENGN,YORKTOWN,VA 23693.
RP Stainback, PC (reprint author), NASA,LANGLEY RES CTR,HAMPTON,VA 23681, USA.
NR 27
TC 1
Z9 1
U1 1
U2 2
PU ASME-AMER SOC MECHANICAL ENG
PI NEW YORK
PA 345 E 47TH ST, NEW YORK, NY 10017
SN 0098-2202
J9 J FLUID ENG-T ASME
JI J. Fluids Eng.-Trans. ASME
PD MAR
PY 1997
VL 119
IS 1
BP 14
EP 18
DI 10.1115/1.2819101
PG 5
WC Engineering, Mechanical
SC Engineering
GA WT471
UT WOS:A1997WT47100003
ER
PT J
AU McDonald, FB
Ferrando, P
Heber, B
Kunow, H
McGuire, R
MullerMellin, R
Paizis, C
Raviart, A
Wibberenz, G
AF McDonald, FB
Ferrando, P
Heber, B
Kunow, H
McGuire, R
MullerMellin, R
Paizis, C
Raviart, A
Wibberenz, G
TI A comparative study of cosmic ray radial and latitudinal gradients in
the inner and outer heliosphere
SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
LA English
DT Article
ID MODULATION; ULYSSES; TRANSPORT; HYDROGEN; DRIFT
AB The radial and latitudinal intensity gradients of 145-255 MeV/nucleon He, 34-50 MeV/nucleon He and 30-69 MeV H are studied over an extensive range of heliocentric distances and latitudes for the 1993.0-1996.0 time period using data from cosmic ray experiments on the Ulysses, IMP 8, Voyager 1 and 2, and Pioneer 10 spacecraft. The radial gradients are found to decrease rapidly with increasing heliocentric distance and agree with those measured 20 years earlier at a similar phase of the heliomagnetic cycle. The latitudinal gradients measured in the inner and outer heliosphere are in reasonable agreement and positive albeit exceedingly small. In agreement with other Ulysses energetic particle experiments it is found that a shift of heliolatitude by -7 degrees to -10 degrees is necessary to get reasonable symmetry in the measurements at midlatitudes. From the Ulysses data it appears there is a significantly reduced latitudinal variation in the intensity of the three energetic particle components at (magnetic) heliolatitudes above about 50 degrees at this phase of the modulation cycle. Such a reduced entry of cosmic rays over such an extensive area above the solar poles implies a strong modification of the previously assumed cosmic ray transport processes at high latitudes, most probably a considerably increased rate of scattering combined with reduced particle gradient and curvature drifts. A significant higher intensity is observed over the north solar pole than over the south pole for the low-energy components after the corrections have been applied for the temporal changes at the 1-AU baseline.
C1 CENS,CEA,SERV ASTROPHYS,F-91191 GIF SUR YVETTE,FRANCE.
CHRISTIAN ALBRECHTS UNIV KIEL,INST KERNPHYS,KIEL,GERMANY.
NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771.
UNIV MILAN,IST FIS COSM,MILAN,ITALY.
RP McDonald, FB (reprint author), UNIV MARYLAND,INST PHYS SCI & TECHNOL,COMP & SPACE SCI BLDG 3245,COLLEGE PK,MD 20742, USA.
NR 28
TC 31
Z9 31
U1 0
U2 0
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009
J9 J GEOPHYS RES-SPACE
JI J. Geophys. Res-Space Phys.
PD MAR 1
PY 1997
VL 102
IS A3
BP 4643
EP 4651
DI 10.1029/96JA03673
PG 9
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WL464
UT WOS:A1997WL46400013
ER
PT J
AU Burlaga, LF
Ness, NF
Belcher, JW
AF Burlaga, LF
Ness, NF
Belcher, JW
TI Radial evolution of corotating merged interaction regions and flows
between approximate to 14 AU and approximate to 43 AU
SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
LA English
DT Article
ID WIND PLASMA OBSERVATIONS; SOLAR-WIND; OUTER HELIOSPHERE; LATITUDE SCAN;
ULYSSES; SHOCKS
AB During 1993 and 1994 the solar coronal holes and the heliospheric current sheet were relatively stationary, and recurrent streams and interaction regions with periods of the order of the solar rotation period were present within 5 AU. One expects that during 1994 Voyager 2 (V2) (located at approximate to 43 AU and at approximate to 12 degrees S latitude, in the sector zone) would have observed some evolutionary form of corotating streams and interaction regions. The ''sector zone'' is the latitude band in which a spacecraft observes both positive and negative sectors [Burlaga and Ness, 1996]. We present the observations of the magnetic field strength (B), the speed (V), density (N), and proton temperature (T) made by V2-94, and for reference we also discuss the observations made by V2 at approximate to 14 AU during 1983 (V2-83) a solar cycle earlier. Correlated, quasiperiodic variations in B and N with a period of approximate to 26 days (corotating merged interaction regions) were observed at approximate to 14 AU but not at approximate to 43 AU. The speed and temperature profiles were irregular at approximate to 14 AU but quasiperiodic at approximate to 43 AU. An f(-2) spectrum of the magnetic field strength B (indicating the dominance of shocks) was observed at approximate to 14 AU, but an f(-5/3) spectrum (indicating the dominance of Kolmogorov turbulence) was observed at approximate to 43 AU in the range (2.7 x 10(-6) to 2.3 x 10(-5))Hz. An f(-2.5) spectrum of the speed fluctuations was observed at approximate to 14 AU, but an f(-2) spectrum was observed at approximate to 43 AU in the range (8.8 x 10(-7) to 2.3 x 10(-5))Hz. We suggest the hypothesis that the qualitative differences between the observations at approximate to 14 AU and approximate to 43 AU represent a change in the state of the solar wind as it moves between these two positions. This change involves a transition from a quasiperiodic (ordered) state in B and N at approximate to 14 AU to a disordered state at approximate to 43 AU and from an aperiodic state in V and T at approximate to 14 AU to a quasiperiodic state at approximate to 43 AU. The standard MHD models for the radial evolution of corotating streams and interaction regions have not predicted such a transition. Our results suggest that it would be fruitful to develop a new MHD model of such flows, which should include (1) three-dimensional effects, (2) the intermediate-scale fluctuations, and (3) the interstellar pickup ion pressure.
C1 UNIV DELAWARE, BARTOL RES INST, NEWARK, DE 19716 USA.
MIT, DEPT PHYS, CAMBRIDGE, MA 02139 USA.
MIT, CTR SPACE RES, CAMBRIDGE, MA 02139 USA.
RP Burlaga, LF (reprint author), NASA, GODDARD SPACE FLIGHT CTR, EXTRATERR PHYS LAB, GREENBELT, MD 20771 USA.
NR 35
TC 36
Z9 36
U1 0
U2 1
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA
SN 0148-0227
J9 J GEOPHYS RES-SPACE
JI J. Geophys. Res-Space Phys.
PD MAR 1
PY 1997
VL 102
IS A3
BP 4661
EP 4671
DI 10.1029/96JA03629
PG 11
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WL464
UT WOS:A1997WL46400015
ER
PT J
AU Crooker, NU
Lazarus, AJ
Phillips, JL
Steinberg, JT
Szabo, A
Lepping, RP
Smith, EJ
AF Crooker, NU
Lazarus, AJ
Phillips, JL
Steinberg, JT
Szabo, A
Lepping, RP
Smith, EJ
TI Coronal streamer belt asymmetries and seasonal solar wind variations
deduced from Wind and Ulysses data
SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
LA English
DT Article
ID HELIOSPHERIC CURRENT SHEET; SPACECRAFT OBSERVATIONS; HELIOGRAPHIC
LATITUDES; SECTOR STRUCTURE; SPEED; PARAMETERS; MINIMUM; 1-AU; SCAN
AB Solar wind measurements from Wind during March 1995 are combined with those from Ulysses' fast latitude scan to construct a map of the streamer belt. On the timescale of coronal change, the map is nearly a snapshot view of solar wind speed contours threaded by the trace of the heliospheric current sheet (HCS) in the +/-30 degrees heliolatitude range. The combined set of HCS crossings agrees remarkably well with the neutral line on the corresponding classical source surface map. The neutral line is displaced slightly southward, with latitudinal excursions ranging from -22 degrees to +17 degrees. In contrast, a line running through the locus of minimum speed, although following the general trend of the neutral line, is confined to lower latitudes and displaced slightly northward, ranging from -4 degrees to +13 degrees. The separation between the minimum speed locus and the neutral line marking the HCS was unexpected. Possible interplanetary and solar origins are discussed. The deduced asymmetries as well as coronal change between December and March were responsible for solar wind variations at Earth that mimicked the previously reported seasonal variation in Wind data and would have masked it had the observations been taken during September equinox.
C1 MIT,CTR SPACE RES,CAMBRIDGE,MA 02139.
LOS ALAMOS NATL LAB,LOS ALAMOS,NM.
NASA,GODDARD SPACE FLIGHT CTR,EXTRATERR PHYS LAB,GREENBELT,MD 20771.
CALTECH,JET PROP LAB,PASADENA,CA.
RP Crooker, NU (reprint author), BOSTON UNIV,CTR SPACE PHYS,725 COMMONWEALTH AVE,BOSTON,MA 02215, USA.
NR 31
TC 38
Z9 38
U1 0
U2 0
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009
J9 J GEOPHYS RES-SPACE
JI J. Geophys. Res-Space Phys.
PD MAR 1
PY 1997
VL 102
IS A3
BP 4673
EP 4679
DI 10.1029/96JA03681
PG 7
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WL464
UT WOS:A1997WL46400016
ER
PT J
AU Richardson, IG
Farrugia, CJ
Cane, HV
AF Richardson, IG
Farrugia, CJ
Cane, HV
TI A statistical study of the behavior of the electron temperature in
ejecta
SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
LA English
DT Article
ID INTERPLANETARY MAGNETIC CLOUDS; SOLAR-WIND; PROTON TEMPERATURE; SHOCK;
EVENTS; IMP-8
AB Ejecta, which are the interplanetary manifestations of coronal mass ejections, are identified by various signatures. It was first reported over 20 years ago that ejecta are generally associated with low plasma electron temperatures (T-e). However, further case studies, in particular, recent studies of magnetic clouds (a subset of ejecta characterized by large rotations in the magnetic field direction), have shown that in some ejecta, T-e is enhanced, not depressed, after the forward boundary is crossed. To clarify the general behavior of T-e in ejecta, we have examined, in a statistical study, the behavior of T-e in 95 ejecta in the near-Earth solar wind. Of these ejecta, 13 were magnetic clouds. We find that the behavior of T-e in ejecta is variable. Most typically, T-e fluctuates and may be enhanced (relative to the temperature in the ambient (unshocked) solar wind) in one region of the ejecta sind depressed in another. This structure in T-e is often reflected in the electron density (n(e)), with variations in T-e being significantly anticorrelated with variations in n(e). The behavior of T-e contrasts with that of the proton temperature (T-p) in that T-p is depressed in most ejecta so that T-e/T-p >> 1 in virtually all events. In addition, T-p shows no correlation or anticorrelation with the plasma density. Our study suggests that a criterion according to which T-e/T-p > 2 is a more appropriate, though still not unique, indicator of an ejecta than one based on depressions in T-e.
C1 NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771.
UNIV MARYLAND,DEPT ASTRON,COLLEGE PK,MD 20742.
UNIV NEW HAMPSHIRE,INST STUDY EARTH OCEANS & SPACE,DURHAM,NH 03824.
UNIV TASMANIA,DEPT PHYS,HOBART,TAS 7001,AUSTRALIA.
OI Richardson, Ian/0000-0002-3855-3634
NR 27
TC 33
Z9 34
U1 0
U2 0
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009
J9 J GEOPHYS RES-SPACE
JI J. Geophys. Res-Space Phys.
PD MAR 1
PY 1997
VL 102
IS A3
BP 4691
EP 4699
DI 10.1029/96JA04001
PG 9
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WL464
UT WOS:A1997WL46400018
ER
PT J
AU Tsurutani, BT
Arballo, JK
Goldstein, BE
Ho, CM
Lakhina, GS
Smith, EJ
CornilleauWehrlin, N
Prange, R
Lin, N
Kellogg, P
Phillips, JL
Balogh, A
Krupp, N
Kane, M
AF Tsurutani, BT
Arballo, JK
Goldstein, BE
Ho, CM
Lakhina, GS
Smith, EJ
CornilleauWehrlin, N
Prange, R
Lin, N
Kellogg, P
Phillips, JL
Balogh, A
Krupp, N
Kane, M
TI Plasma wave characteristics of the Jovian magnetopause boundary layer:
Relationship to the Jovian aurora?
SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
LA English
DT Article
ID ION-CYCLOTRON INSTABILITY; HUBBLE-SPACE-TELESCOPE; DIFFUSION-PROCESSES;
ULYSSES ENCOUNTER; SOLAR-WIND; UV AURORA; JUPITER; MAGNETOSPHERE;
TURBULENCE; PRECIPITATION
AB The Jovian magnetopause boundary layer (BL) plasma wave spectra from 10(-3) to 10(2) Hz have been measured for the first time. For one intense event the magnetic (B') and electric (E') spectra were 2 x 10(-4) f(2.4) nT(2)/Hz and 4 x 10(-9) f(2.4) V-2/m(2) Hz, respectively. Although no measurable wave amplitudes were detected above the electron gyrofrequency, similar to 140 Hz, this finding may be due to the low signal strength characteristic of this region; The B'/E' ratio is relatively frequency independent. It is possible that waves are obliquely propagating whistler mode waves. The B' and E' spectra are broadband with no obvious spectral peaks. The waves are sufficiently intense to cause cross-field diffusion of magnetosheath plasma to create the BL itself. A Jovian BL thickness of 10,700 km is predicted, which is consistent with past in situ measurements. The Jovian boundary layer wave properties are quite similar to the BL waves at Earth (however, the Jovian waves are orders of magnitude less intense). It appears that the solar wind/magnetosphere dynamos at the two planets are similar enough to be consistent with a common wave generation mechanism. The predicted ionospheric latitudinal width of the BL of similar to 100-200 km is quite similar to the Jovian auroral high-latitude ring measured by Hubble. The location of the BL at and inside the foot point of the last closed field line may place the boundary layer and the aurora on approximately the same magnetic field lines. The Jovian BL waves are sufficiently intense to cause strong pitch angle diffusion for <5-keV electrons and 1-keV to 1-MeV protons. The estimated energy precipitation rate from this interaction <1 erg cm(-2) s(-1), sufficient for a weak high-latitude auroral ring. This intensity is 2 to 3 orders of magnitude too low to cause the main aurora ring, however. If it is found that this main aurora maps into the boundary layer, then other mechanisms such as (ionospheric) double layers must be responsible for the particle energization and precipitation.
C1 UNIV VERSAILLES,CTR ETUDE ENVIRONM TERRESTRE & PLANETAIRES,VERSAILLES,FRANCE.
UNIV PARIS 06,INST ASTROPHYS SPATIALE,ORSAY,FRANCE.
UNIV MINNESOTA,SCH PHYS & ASTRON,MINNEAPOLIS,MN.
LOS ALAMOS NATL LAB,LOS ALAMOS,NM.
UNIV LONDON IMPERIAL COLL SCI TECHNOL & MED,BLACKETT LAB,LONDON,ENGLAND.
MAX PLANCK INST AERON,KATLENBURG DUHM,GERMANY.
JOHNS HOPKINS UNIV,APPL PHYS LAB,LAUREL,MD.
RP Tsurutani, BT (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA.
RI Lakhina, Gurbax /C-9295-2012;
OI Lakhina, Gurbax /0000-0002-8956-486X
NR 49
TC 13
Z9 13
U1 0
U2 0
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009
J9 J GEOPHYS RES-SPACE
JI J. Geophys. Res-Space Phys.
PD MAR 1
PY 1997
VL 102
IS A3
BP 4751
EP 4764
DI 10.1029/96JA02785
PG 14
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WL464
UT WOS:A1997WL46400024
ER
PT J
AU Slattery, R
Zhao, YY
AF Slattery, R
Zhao, YY
TI Trajectory synthesis for air traffic automation
SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS
LA English
DT Article
ID FUEL; AIRCRAFT
AB Trajectory synthesis algorithms that are key to the center-terminal radar approach control automation system (CTAS) developed at NASA Ames Research Center for air traffic control automation are discussed. CTAS generates computer advisories based on synthesized trajectories that help controllers to produce a safe, efficient, and expeditious flow of traffic over the extended terminal area. Trajectories are synthesized from initial aircraft positions to a metering fix or runway, depending on airspace, The horizontal path is constructed first from specified waypoints using straight lines and constant-radius turns, The vertical trajectory is divided into a series of flight segments. Three types of flight profiles are defined by connecting selected segments in a predetermined order: fast, nominal, and slow. Each profile can produce a certain range of arrival times, A second-order Runge-Kutta scheme is used for integrating a set of simplified point-mass equations to generate vertical trajectories. Then, an iterative scheme is employed to determine the speed that meets a specified arrival time. Several special case trajectories are also explained. Two flight scenarios are used to illustrate the use of trajectory synthesis algorithms.
C1 UNIV MINNESOTA,DEPT AEROSP ENGN & MECH,MINNEAPOLIS,MN 55455.
RP Slattery, R (reprint author), NASA,AMES RES CTR,AIR TRAFF MANAGEMENT BRANCH,MS 210-9,MOFFETT FIELD,CA 94035, USA.
NR 17
TC 40
Z9 45
U1 1
U2 4
PU AMER INST AERONAUT ASTRONAUT
PI RESTON
PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091
SN 0731-5090
J9 J GUID CONTROL DYNAM
JI J. Guid. Control Dyn.
PD MAR-APR
PY 1997
VL 20
IS 2
BP 232
EP 238
DI 10.2514/2.4056
PG 7
WC Engineering, Aerospace; Instruments & Instrumentation
SC Engineering; Instruments & Instrumentation
GA WL635
UT WOS:A1997WL63500003
ER
PT J
AU Padgett, C
KreutzDelgado, K
Udomkesmalee, S
AF Padgett, C
KreutzDelgado, K
Udomkesmalee, S
TI Evaluation of star identification techniques
SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS
LA English
DT Article
ID MATCHING ALGORITHM; PATTERN
AB Traditionally, star sensors have used fairly large fields of view and bright stars to perform tracking and identification. Recent trends in space missions have brought out the need for smaller field-of-view sensors, capable of performing multiple functions that will reduce spacecraft payload and cost. A number of different strategies are used or have been suggested for identifying star fields for attitude determination in space. We offer a general classification of the existing techniques and select three representative algorithms for more comprehensive evaluation. The identification rates and performance of the three algorithms are presented over a variety of noise conditions using two different sized onboard catalogs. Substantial differences in algorithm performance are identified for various noise levels, which should provide some indication of the suitability of the algorithm for smaller fields of view.
C1 UNIV CALIF SAN DIEGO,LA JOLLA,CA 92093.
CALTECH,JET PROP LAB,DEPT ELECT & COMP ENGN,PASADENA,CA 91109.
RP Padgett, C (reprint author), CALTECH,JET PROP LAB,TECH STAFF,4800 OAK GROVE DR,PASADENA,CA 91109, USA.
NR 21
TC 49
Z9 66
U1 3
U2 9
PU AMER INST AERONAUT ASTRONAUT
PI RESTON
PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091
SN 0731-5090
J9 J GUID CONTROL DYNAM
JI J. Guid. Control Dyn.
PD MAR-APR
PY 1997
VL 20
IS 2
BP 259
EP 267
DI 10.2514/2.4061
PG 9
WC Engineering, Aerospace; Instruments & Instrumentation
SC Engineering; Instruments & Instrumentation
GA WL635
UT WOS:A1997WL63500007
ER
PT J
AU Carpenter, JR
Bishop, RH
AF Carpenter, JR
Bishop, RH
TI Navigation filter estimate fusion for enhanced spacecraft rendezvous
SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS
LA English
DT Article; Proceedings Paper
CT AIAA Guidance, Navigation, and Control Conference
CY AUG 01-03, 1994
CL SCOTTSDALE, AZ
SP AIAA
AB Techniques for optimally mixing the outputs from a pair of Kalman filters are presented, generalizing previous results. These techniques are derived under the assumption that the designs of the filters are fixed and cannot be modified to support fusion requirements. Conditions for using the optimally fused estimates to periodically reinitialize the Kalman filters are described. The results are applied to an optimal spacecraft rendezvous problem, and simulated performance results indicate that use of the optimally fused data leads to significantly improved robustness to initial target vehicle state errors.
C1 UNIV TEXAS,DEPT AEROSP ENGN & ENGN MECH,AUSTIN,TX 78712.
RP Carpenter, JR (reprint author), NASA,JOHNSON SPACE CTR,AEROSCI & FLIGHT MECH DIV,HOUSTON,TX 77058, USA.
NR 22
TC 0
Z9 1
U1 0
U2 0
PU AMER INST AERONAUT ASTRONAUT
PI RESTON
PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091
SN 0731-5090
J9 J GUID CONTROL DYNAM
JI J. Guid. Control Dyn.
PD MAR-APR
PY 1997
VL 20
IS 2
BP 338
EP 345
DI 10.2514/2.4043
PG 8
WC Engineering, Aerospace; Instruments & Instrumentation
SC Engineering; Instruments & Instrumentation
GA WL635
UT WOS:A1997WL63500018
ER
PT J
AU Singh, M
Dickerson, RM
Olmstead, FA
Eldridge, JI
AF Singh, M
Dickerson, RM
Olmstead, FA
Eldridge, JI
TI SiC (SCS-6) fiber reinforced-reaction formed SiC matrix composites:
Microstructure and interfacial properties
SO JOURNAL OF MATERIALS RESEARCH
LA English
DT Article
ID CERAMICS
AB Microstructural and interfacial characterization of unidirectional SiC (SCS-B) fiber reinforced-reaction formed SIC (RFSC) composites has been carried out. Silicon-1.7 at. % molybdenum alloy was used as the melt infiltrant, instead of pure silicon, to reduce the activity of silicon in the melt as well as to reduce the amount of free silicon in the matrix. Electron microprobe analysis was used to evaluate the microstructure and phase distribution in these composites. The matrix is SiC with a bi-modal grain-size distribution and small amounts of MoSi2, silicon, and carbon, Fiber push-outs tests on these composites showed that a desirably low interfacial shear strength was achieved. The average debond shear stress at room temperature varied with specimen thickness from 29 to 64 MPa, with higher values observed for thinner specimens. Initial frictional sliding stresses showed little thickness dependence with values generally close to 30 MPa, Push-out test results showed very little change when the test temperature was increased to 800 degrees C from room temperature, indicating an absence of significant residual stresses in the composite.
C1 CASE WESTERN RESERVE UNIV,DEPT MECH ENGN,CLEVELAND,OH 44106.
NASA,LEWIS RES CTR,CLEVELAND,OH 44135.
RP Singh, M (reprint author), NYMA INC,LEWIS RES CTR GRP,CLEVELAND,OH 44135, USA.
NR 18
TC 6
Z9 6
U1 0
U2 1
PU MATERIALS RESEARCH SOCIETY
PI WARRENDALE
PA 506 KEYSTONE DR, WARRENDALE, PA 15086
SN 0884-2914
J9 J MATER RES
JI J. Mater. Res.
PD MAR
PY 1997
VL 12
IS 3
BP 706
EP 713
DI 10.1557/JMR.1997.0105
PG 8
WC Materials Science, Multidisciplinary
SC Materials Science
GA WM879
UT WOS:A1997WM87900024
ER
PT J
AU Bansal, NP
AF Bansal, NP
TI Chemical vapor deposited SiC (SCS-0) fiber-reinforced strontium
aluminosilicate glass-ceramic composites
SO JOURNAL OF MATERIALS RESEARCH
LA English
DT Article
ID MECHANICAL-PROPERTIES; MATRIX COMPOSITES; CRACKING; FRACTURE
AB Unidirectional SrO . Al2O3 . 2SiO(2) glass-ceramic matrix composites reinforced with uncoated chemical vapor deposited (CVD) SiC (SCS-0) fibers have been fabricated by hot-pressing under appropriate conditions using the glass-ceramic approach. Almost fully dense composites having a fiber volume fraction of 0.24 have been obtained. Monoclinic celsian, SrAl2Si2O8, was the only crystalline phase observed in the matrix by x-ray diffraction. No chemical reaction was observed between the fiber and the matrix after high temperature processing. In three-point flexure, the composite exhibited a first matrix cracking stress of similar to 231 +/- 20 MPa and an ultimate strength of 265 +/- 17 MPa. Examination of fracture surfaces revealed limited short length fiber pull-out. From fiber push-out, the fiber/matrix interfacial debonding and frictional strengths were evaluated to be similar to 17.5 +/- 2.7 MPa and 11.3 +/- 1.6 MPa, respectively. Some fibers were strongly bonded to the matrix and could not be pushed out. The micromechanical models were not useful in predicting values of the first matrix cracking stress as well as the ultimate strength of the composites.
RP Bansal, NP (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA.
NR 24
TC 8
Z9 8
U1 0
U2 0
PU MATERIALS RESEARCH SOCIETY
PI WARRENDALE
PA 506 KEYSTONE DR, WARRENDALE, PA 15086
SN 0884-2914
J9 J MATER RES
JI J. Mater. Res.
PD MAR
PY 1997
VL 12
IS 3
BP 745
EP 753
DI 10.1557/JMR.1997.0109
PG 9
WC Materials Science, Multidisciplinary
SC Materials Science
GA WM879
UT WOS:A1997WM87900028
ER
PT J
AU Lewicki, DG
Ballarini, R
AF Lewicki, DG
Ballarini, R
TI Effect of rim thickness on gear crack propagation path
SO JOURNAL OF MECHANICAL DESIGN
LA English
DT Article
ID STRESS INTENSITY FACTOR; TOOTH
AB Analytical and experimental studies were performed to investigate the effect of rim thickness on gear tooth crack propagation. The goal was to determine whether cracks grew through gear teeth or through gear rims for various rim thicknesses. A finite element based computer program (FRANC, FRacture ANalysis Code) simulated gear tooth crack propagation. The analysis used principles of linear elastic fracture mechanics. Quarter-point, triangular elements were used at the crack tip to represent the stress singularity. The program had an automated crack propagation option in which cracks were grown numerically using an automated re-meshing scheme. Crack tip stress intensity factors were estimated to determine crack propagation direction. Gears with various backup ratios (rim thickness divided by tooth height) were tested to validate crack path predictions. Gear bending fatigue tests were performed in a spur gear fatigue rig. From both predictions and tests, gears with backup ratios of 3.3 and 1.0 produced tooth fractures while a backup ratio of 0.3 produced rim fractures. For a backup ratio of 0.5, the experiments produced rim fractures and the predictions produced both rim and tooth fractures, depending on the initial geometry of the crack.
RP Lewicki, DG (reprint author), USA,RES LAB,NASA,LEWIS RES CTR,VEHICLE PROP DIRECTORATE,CLEVELAND,OH, USA.
NR 25
TC 30
Z9 32
U1 1
U2 3
PU ASME-AMER SOC MECHANICAL ENG
PI NEW YORK
PA 345 E 47TH ST, NEW YORK, NY 10017
SN 1050-0472
J9 J MECH DESIGN
JI J. Mech. Des.
PD MAR
PY 1997
VL 119
IS 1
BP 88
EP 95
DI 10.1115/1.2828793
PG 8
WC Engineering, Mechanical
SC Engineering
GA WT434
UT WOS:A1997WT43400013
ER
PT J
AU McPhail, MJW
Duxbury, G
May, RD
AF McPhail, MJW
Duxbury, G
May, RD
TI The nu(1), 2 nu(2), and 2 nu(3)+nu(4) band system of carbonyl fluoride
SO JOURNAL OF MOLECULAR SPECTROSCOPY
LA English
DT Article
ID DIODE-LASER SPECTROMETER; STRATOSPHERE; SPECTRUM; GASES
AB The infrared spectrum of carbonyl fluoride, COF2, has been measured in the region from 1880 to 1980 cm(-1) using a Bruker Fourier transform spectrometer at 0.003 cm(-1) resolution and diode laser spectroscopy al Doppler-limited resolution. In this region the nu(1) band at 1945 cm(-1) dominates the spectrum and is in Fermi resonance with the 2 nu(2) band at 1914 cm(-1) and in B-type Coriolis resonance with the 2 nu(3) + nu(4) band at 1936 cm(-1). From the nu(1) band, 820 lines wen successfully fitted using an S-type Watson Hamiltonian in the IIIl representation, yielding rotational and fourth order centrifugal distortion constants, a Coriolis parameter of 0.00339(24) cm(-1), and an obs-calc RMS or 0.0006 cm(-1). Only 400 lines from 2 nu(2) could be successfully fitted, with an obs-calc RMS of 0.0005 cm(-1), because of interference from nu(1) over much of the 2 nu(2) R branch. (C) 1997 Academic Press.
C1 CALTECH,JET PROP LAB,PASADENA,CA 91109.
RP McPhail, MJW (reprint author), UNIV STRATHCLYDE,DEPT PHYS & APPL PHYS,JOHN ANDERSEN BLDG,107 ROTTENROW,GLASGOW G4 0NG,LANARK,SCOTLAND.
NR 18
TC 8
Z9 8
U1 0
U2 1
PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS
PI SAN DIEGO
PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495
SN 0022-2852
J9 J MOL SPECTROSC
JI J. Mol. Spectrosc.
PD MAR
PY 1997
VL 182
IS 1
BP 118
EP 123
DI 10.1006/jmsp.1996.7220
PG 6
WC Physics, Atomic, Molecular & Chemical; Spectroscopy
SC Physics; Spectroscopy
GA WN854
UT WOS:A1997WN85400012
ER
PT J
AU Riggins, DW
McClinton, CR
Vitt, PH
AF Riggins, DW
McClinton, CR
Vitt, PH
TI Thrust losses in hypersonic engines .1. Methodology
SO JOURNAL OF PROPULSION AND POWER
LA English
DT Article
AB Expressions for the thrust losses of a scramjet engine are developed in terms of irreversible entropy increases and the degree of incomplete combustion. A method is developed that allows the calculation of the lost engine thrust or thrust potential caused by different loss mechanisms within a given flowfield. This method allows the performance-based assessment of the trade between mixing enhancement and resultant increased flow losses in scramjet combustors. An engine effectiveness parameter for use in optimization of engine components is defined in terms of thrust losses.
C1 NASA,LANGLEY RES CTR,ANAL OFF,HAMPTON,VA 23681.
ANALYT SERV & MAT INC,HAMPTON,VA 23666.
RP Riggins, DW (reprint author), UNIV MISSOURI,DEPT MECH & AEROSP ENGN,ROLLA,MO 65409, USA.
NR 14
TC 27
Z9 27
U1 1
U2 5
PU AMER INST AERONAUT ASTRONAUT
PI RESTON
PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091
SN 0748-4658
J9 J PROPUL POWER
JI J. Propul. Power
PD MAR-APR
PY 1997
VL 13
IS 2
BP 281
EP 287
DI 10.2514/2.5160
PG 7
WC Engineering, Aerospace
SC Engineering
GA WN156
UT WOS:A1997WN15600017
ER
PT J
AU Kusic, GL
Cull, RC
AF Kusic, GL
Cull, RC
TI Power system analysis of multikilowatt space/planet stations
SO JOURNAL OF PROPULSION AND POWER
LA English
DT Article; Proceedings Paper
CT AIAA 31st Intersociety Energy Conversion Engineering Conference
CY AUG 11-16, 1996
CL WASHINGTON, DC
AB This paper describes a method to design modular power systems of multikilowatt size for satellite or planetary applications where the power source is periodic solar radiation. Energy for the eclipse period is from batteries or other storage mechanisms. Weight and efficiency of the electrical system are primary design parameters because the system must be rocket-boosted from Earth. Electrical losses are calculated for the network. Losses and weight of power converters are based on space application equipment, A three-module example operated at a specific load profile demonstrates how the method of the paper can be used for load scheduling and weight/power loss tradeoff.
C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135.
RP Kusic, GL (reprint author), UNIV PITTSBURGH,DEPT ELECT ENGN,PITTSBURGH,PA 15261, USA.
NR 10
TC 0
Z9 0
U1 0
U2 0
PU AMER INST AERONAUT ASTRONAUT
PI RESTON
PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091
SN 0748-4658
J9 J PROPUL POWER
JI J. Propul. Power
PD MAR-APR
PY 1997
VL 13
IS 2
BP 318
EP 323
DI 10.2514/2.5166
PG 6
WC Engineering, Aerospace
SC Engineering
GA WN156
UT WOS:A1997WN15600022
ER
PT J
AU Olynick, D
Tam, T
AF Olynick, D
Tam, T
TI Trajectory-based validation of the shuttle heating environment
SO JOURNAL OF SPACECRAFT AND ROCKETS
LA English
DT Article
AB Chemically reacting, three-dimensional, full Navier-Stokes calculations are generated around the shuttle orbiter and are compared with the STS-2 Right database at eight trajectory locations. Numerical estimates of quantities necessary for thermal protection system design, surface temperature and heating profiles, integrated heat load, bond-line temperatures, and thermal protection system thicknesses are compared with the STS-2 shuttle data. The effects of surface kinetics, turbulence, and grid resolution are investigated. It is concluded that trajectory-based thermal protection system sizing, the use of a Navier-Stokes flow solver combined with a conduction analysis applied over an entry trajectory, is a beneficial tool for future thermal protection system design. This conclusion is based on a reasonable agreement between the flight data and numerical predictions of surface heat transfer and temperature profiles, integrated heat loads and bond-line temperatures at most of the wind-side thermocouples. The effects of turbulent heating on thermal protection system design are illustrated. For future large entry vehicles, it is concluded that the prediction of turbulent transition will be a major driver in the thermal protection system design process. Finally, one potential payoff of using trajectory-based thermal protection system sizing, a reduction in thermal protection system mass, is illustrated.
RP Olynick, D (reprint author), NASA,AMES RES CTR,REACTING FLOW ENVIRONM BRANCH,MS 230 2,MOFFETT FIELD,CA 94035, USA.
NR 28
TC 6
Z9 7
U1 0
U2 0
PU AMER INST AERONAUT ASTRONAUT
PI RESTON
PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091
SN 0022-4650
J9 J SPACECRAFT ROCKETS
JI J. Spacecr. Rockets
PD MAR-APR
PY 1997
VL 34
IS 2
BP 172
EP 181
DI 10.2514/2.3206
PG 10
WC Engineering, Aerospace
SC Engineering
GA WT011
UT WOS:A1997WT01100005
ER
PT J
AU Ryan, RS
Townsend, JS
AF Ryan, RS
Townsend, JS
TI Fundamentals and issues in launch vehicle design
SO JOURNAL OF SPACECRAFT AND ROCKETS
LA English
DT Article; Proceedings Paper
CT AIAA Dynamics Specialist Conference
CY APR 18-19, 1996
CL SALT LAKE CITY, UT
SP AIAA
AB The fundamentals of launch vehicle design are examined using simplified single-stage, two-stage, and Space Shuttle performance equations. The single-stage to-orbit launch vehicle is very sensitive to the performance-critical parameters of mass efficiency, propulsion efficiency, and loss management. Cost and operations coupled in the performance equation further complicates the design process. Launch vehicle design is optimized tr hen the performance and programmatic drivers are balanced. Programmatic drivers include affordability, reusability, operability, abort/safety, and reliability. The issues, disciplines, and potential problems that characterize the building of a future launch system are presented. The history of the Space Shuttle is used as the benchmark exampl. Robustness is the hey to uncoupling the design factors so that optimization can occur, but typically robust designs define low-performance systems. Future space launch vehicles must develop new technologies to reshape the design parameter sensitivities of the robustness and performance functions.
RP Ryan, RS (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,STRUCT & DYNAM LAB,HUNTSVILLE,AL 35812, USA.
NR 8
TC 3
Z9 3
U1 0
U2 1
PU AMER INST AERONAUT ASTRONAUT
PI RESTON
PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091
SN 0022-4650
J9 J SPACECRAFT ROCKETS
JI J. Spacecr. Rockets
PD MAR-APR
PY 1997
VL 34
IS 2
BP 192
EP 198
DI 10.2514/2.3209
PG 7
WC Engineering, Aerospace
SC Engineering
GA WT011
UT WOS:A1997WT01100008
ER
PT J
AU Woodard, SE
Lay, RR
Jarnot, RF
Gell, DA
AF Woodard, SE
Lay, RR
Jarnot, RF
Gell, DA
TI Experimental investigation of spacecraft in-flight disturbances and
dynamic response
SO JOURNAL OF SPACECRAFT AND ROCKETS
LA English
DT Article
AB In September 1991, NASA launched the Upper Atmosphere Research Satellite. In addition to its atmospheric sciences mission, analysis of data from the first 370 days after launch was used to investigate in-flight spacecraft disturbances and responses. The investigation included a three-orbit in-flight experiment to determine how each onboard instrument and subsystem disturbance contributed to the overall spacecraft dynamic response. The investigation quantified the spacecraft dynamic response produced by the solar array and high-gain antenna harmonic drive disturbances. The solar array's harmonic drive output resonated two solar array modes. Friction in the solar array gear drive provided sufficient energy dissipation, which prevented the solar panels from resonating catastrophically; however, the solar array vibration amplitude was excessively large. The resulting vibration had a latitude-specific pattern. Thermal elastic bending of the spacecraft's two flexible appendages as the spacecraft crosses the Earth's terminator and solar array modal contribution to the spacecraft response were also examined.
C1 CALTECH,JET PROP LAB,PASADENA,CA 91109.
UNIV MICHIGAN,DEPT ATMOSPHER OCEAN & SPACE SCI,SPACE PHYS RES LAB,ANN ARBOR,MI 48109.
RP Woodard, SE (reprint author), NASA,LANGLEY RES CTR,STRUCT DYNAM BRANCH,STRUCT DIV,MS 230,HAMPTON,VA 23681, USA.
NR 14
TC 9
Z9 10
U1 0
U2 2
PU AMER INST AERONAUT ASTRONAUT
PI RESTON
PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091
SN 0022-4650
J9 J SPACECRAFT ROCKETS
JI J. Spacecr. Rockets
PD MAR-APR
PY 1997
VL 34
IS 2
BP 199
EP 204
DI 10.2514/2.3210
PG 6
WC Engineering, Aerospace
SC Engineering
GA WT011
UT WOS:A1997WT01100009
ER
PT J
AU Kleb, WL
AF Kleb, WL
TI Simulation of an aerospace vehicle pitch-over maneuver
SO JOURNAL OF SPACECRAFT AND ROCKETS
LA English
DT Article
RP Kleb, WL (reprint author), NASA,LANGLEY RES CTR,AEROTHERMODYNAM BRANCH,AERO & GAS DYNAM DIV,HAMPTON,VA 23681, USA.
NR 20
TC 0
Z9 0
U1 0
U2 0
PU AMER INST AERONAUT ASTRONAUT
PI RESTON
PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091
SN 0022-4650
J9 J SPACECRAFT ROCKETS
JI J. Spacecr. Rockets
PD MAR-APR
PY 1997
VL 34
IS 2
BP 254
EP 256
PG 3
WC Engineering, Aerospace
SC Engineering
GA WT011
UT WOS:A1997WT01100018
ER
PT J
AU Stassinopoulos, EG
Brucker, GJ
Adolphsen, JN
Barth, J
AF Stassinopoulos, EG
Brucker, GJ
Adolphsen, JN
Barth, J
TI Radiation-induced anomalies in satellites (vol 33, pg 877, 1996)
SO JOURNAL OF SPACECRAFT AND ROCKETS
LA English
DT Correction, Addition
C1 RADIAT EFFECTS CONSULTANTS,W LONG BRANCH,NJ 07764.
UNISYS,LANHAM,MD 20706.
RP Stassinopoulos, EG (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20770, USA.
NR 1
TC 0
Z9 0
U1 0
U2 0
PU AMER INST AERONAUT ASTRONAUT
PI RESTON
PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091
SN 0022-4650
J9 J SPACECRAFT ROCKETS
JI J. Spacecr. Rockets
PD MAR-APR
PY 1997
VL 34
IS 2
BP 264
EP 264
PG 1
WC Engineering, Aerospace
SC Engineering
GA WT011
UT WOS:A1997WT01100022
ER
PT J
AU Sui, CH
Lau, KM
Takayabu, YN
Short, DA
AF Sui, CH
Lau, KM
Takayabu, YN
Short, DA
TI Diurnal variations in tropical oceanic cumulus convection during TOGA
COARE
SO JOURNAL OF THE ATMOSPHERIC SCIENCES
LA English
DT Article
ID WESTERN PACIFIC; DEEP CONVECTION; CLOUD CLUSTERS; PRECIPITATION; CYCLE;
CIRCULATION; RAINFALL
AB Diurnal variations in atmospheric convection, dynamic/thermodynamic fields, and heat/moisture budgets over the equatorial Pacific warm pool region are analyzed based on data collected from different observation platforms during the Intensive Observation Period of the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE). Results reveal that the diurnal variations in rainfall/convection over the TOGA COARE region can be classified into three distinct stages: warm morning cumulus, afternoon convective showers, and nocturnal convective systems. Afternoon rainfall comes mostly from convective cells, but the nocturnal rainfall is derived from deeper convective cells and large areas of stratiform clouds. Results further show that afternoon convective showers are more evident in the large-scare undisturbed periods when the diurnal SST cycle is strong, but the nocturnal convective systems and morning cumulus are more enhanced in the disturbed periods when more moisture is available. The primary cause of the nocturnal rainfall maximum is suggested to be associated with more (less) available precipitable water in the night (day) due to the diurnal radiative cooling/heating cycle and the resultant change in tropospheric relative humidity.
C1 NATL INST ENVIRONM STUDIES,TSUKUBA,IBARAKI,JAPAN.
RP Sui, CH (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 913,GREENBELT,MD 20771, USA.
RI Lau, William /E-1510-2012;
OI Lau, William /0000-0002-3587-3691; SUI, CHUNG-HSIUNG/0000-0003-2842-5660
NR 36
TC 168
Z9 173
U1 4
U2 11
PU AMER METEOROLOGICAL SOC
PI BOSTON
PA 45 BEACON ST, BOSTON, MA 02108-3693
SN 0022-4928
J9 J ATMOS SCI
JI J. Atmos. Sci.
PD MAR 1
PY 1997
VL 54
IS 5
BP 639
EP 655
DI 10.1175/1520-0469(1997)054<0639:DVITOC>2.0.CO;2
PG 17
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA WM247
UT WOS:A1997WM24700004
ER
PT J
AU Atlas, R
AF Atlas, R
TI Atmospheric observations and experiments to assess their usefulness in
data assimilation
SO JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN
LA English
DT Article; Proceedings Paper
CT 2nd WMO International Symposium on Assimilation of Observations in
Meteorology and Oceanography
CY MAR 13-17, 1995
CL TOKYO, JAPAN
SP World Meteorol Org
ID NUMERICAL WEATHER PREDICTION; OBSERVING SYSTEM; WIND DATA; IMPACT;
TEMPERATURE
AB Atmospheric observations consist of a mixture of in situ, visual, and remotely sensed observations. These provide an extensive database for research and numerical weather prediction. However, significant data deficiencies still exist, and new observing systems are continually being proposed. Observing system experiments (OSE's) are conducted to assess the usefulness of different types of existing atmospheric observations. Observing system simulation experiments (OSSE's) are conducted to evaluate the potential impact of proposed observing systems, as well as to determine tradeoffs in their design, and to evaluate data assimilation methodology.
This paper contains a review of the development of the global atmospheric observing system, a description of the principal types of data, an overview of OSE and OSSE methodology, and results from recent experiments to evaluate the relative utility of the principal atmospheric observing systems and the potential for new observing systems. These experiments show the critical contributions being made by both conventional and space-based observations, and indicate considerable potential for future satellite observing systems to improve data assimilation.
RP Atlas, R (reprint author), NASA, GODDARD SPACE FLIGHT CTR, DATA ADM OFF, ATMOSPHERES LAB, CODE 910-4, GREENBELT, MD 20771 USA.
RI Atlas, Robert/A-5963-2011
OI Atlas, Robert/0000-0002-0706-3560
NR 48
TC 105
Z9 106
U1 0
U2 10
PU METEOROLOGICAL SOC JAPAN
PI TOKYO
PA C/O JAPAN METEOROLOGICAL AGENCY 1-3-4 OTE-MACHI, CHIYODA-KU, TOKYO,
100-0004, JAPAN
SN 0026-1165
EI 2186-9057
J9 J METEOROL SOC JPN
JI J. Meteorol. Soc. Jpn.
PD MAR
PY 1997
VL 75
IS 1B
BP 111
EP 130
PG 20
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA XG476
UT WOS:A1997XG47600002
ER
PT J
AU Busalacchi, AJ
AF Busalacchi, AJ
TI Oceanic observations
SO JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN
LA English
DT Article; Proceedings Paper
CT 2nd WMO International Symposium on Assimilation of Observations in
Meteorology and Oceanography
CY MAR 13-17, 1995
CL TOKYO, JAPAN
SP World Meteorol Org
ID WIND STRESS; VARIABILITY
AB For many years, merchant ships and the naval fleets of various countries have been the major source of data over and in the open ocean. Oceanographic research experiments and process studies in the field have also contributed to the climatological data bases for the global ocean, but, for the most part, these have been limited in duration and extent. However, over the last 10 years under the auspices of the World Climate Research Program and the International Geosphere Biosphere Program the role of the oceans in global and climate change has taken on increased significance. This has created a need for a considerably improved understanding of the seasonal, interannual, decadal and longer time-scale variability of the physical and biogeochemical attributes of the global ocean. As a result, over the past 10 years several major international field programs have been implemented and have had a tremendous impact on the number of in situ observations obtained for the global ocean. The Tropical Ocean Global Atmosphere (TOGA) program, the World Ocean Circulation Experiment (WOOF), and the Joint Global Ocean Flux Study (JGOFS) were designed with observational, modelling, and process study components aimed at analyzing different aspects of the ocean's role in the coupled climate system. In parallel with the field programs, continuous space-based observations of sea surface temperature, sea surface topography, and sea surface winds spanning nearly a decade or longer have become a reality During this same time period, numerical ocean models and computational power have advanced to the point where the oceanographic observations, both in situ and remotely sensed, can be assimilated into numerical ocean models in order to provide a four-dimensional (x-y-z-t) depiction of the evolving state of the global ocean.
RP Busalacchi, AJ (reprint author), NASA, GODDARD SPACE FLIGHT CTR, LAB HYDROSPHER PROC, GREENBELT, MD 20771 USA.
NR 28
TC 8
Z9 8
U1 1
U2 2
PU METEOROLOGICAL SOC JAPAN
PI TOKYO
PA C/O JAPAN METEOROLOGICAL AGENCY 1-3-4 OTE-MACHI, CHIYODA-KU, TOKYO,
100-0004, JAPAN
SN 0026-1165
EI 2186-9057
J9 J METEOROL SOC JPN
JI J. Meteorol. Soc. Jpn.
PD MAR
PY 1997
VL 75
IS 1B
BP 131
EP 154
PG 24
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA XG476
UT WOS:A1997XG47600003
ER
PT J
AU Cohn, SE
AF Cohn, SE
TI An introduction to estimation theory
SO JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN
LA English
DT Article; Proceedings Paper
CT 2nd WMO International Symposium on Assimilation of Observations in
Meteorology and Oceanography
CY MAR 13-17, 1995
CL TOKYO, JAPAN
SP World Meteorol Org
ID ATMOSPHERIC DATA ASSIMILATION; 4-DIMENSIONAL DATA ASSIMILATION; KALMAN
FILTER; POTENTIAL USEFULNESS; LIOUVILLE EQUATION; ERROR COVARIANCES;
FORECAST SKILL; MODEL-ERROR; PREDICTION; INTERPOLATION
AB Despite the explosive growth of activity in the field of Earth System data assimilation over the past decade or so, there remains a substantial gap between theory and practice. The present article attempts to bridge this gap by exposing some of the central concepts of estimation theory and connecting them with current and future data assimilation approaches. Estimation theory provides a broad and natural mathematical foundation for data assimilation science.
Stochastic-dynamic modeling and stochastic observation modeling are described first. Optimality criteria for linear and nonlinear state estimation problems are then explored, leading to conditional-mean estimation procedures such as the Kalman filter and some of its generalizations, and to conditional-mode estimation procedures such as variational methods. A detailed derivation of the Kalman filter is given to illustrate the role of key probabilistic concepts and assumptions. Extensions of the Kalman filter to nonlinear observation operators and to non-Gaussian errors are then described. In a simple illustrative example, rigorous treatment of representativeness error and model error is highlighted in finite-dimensional estimation procedures for continuum dynamics and observations of the continuum state.
RP Cohn, SE (reprint author), NASA, GODDARD SPACE FLIGHT CTR, DATA ASSIMILAT OFF, CODE 910-3, GREENBELT, MD 20771 USA.
RI Cohn, Stephen/K-1954-2012
OI Cohn, Stephen/0000-0001-8506-9354
NR 80
TC 241
Z9 244
U1 4
U2 22
PU METEOROLOGICAL SOC JAPAN
PI TOKYO
PA C/O JAPAN METEOROLOGICAL AGENCY 1-3-4 OTE-MACHI, CHIYODA-KU, TOKYO,
100-0004, JAPAN
SN 0026-1165
EI 2186-9057
J9 J METEOROL SOC JPN
JI J. Meteorol. Soc. Jpn.
PD MAR
PY 1997
VL 75
IS 1B
BP 257
EP 288
PG 32
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA XG476
UT WOS:A1997XG47600011
ER
PT J
AU Miller, RN
Busalacchi, AJ
Hackert, EC
AF Miller, RN
Busalacchi, AJ
Hackert, EC
TI Applications of data assimilation to analysis of the ocean on large
scales
SO JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN
LA English
DT Article; Proceedings Paper
CT 2nd WMO International Symposium on Assimilation of Observations in
Meteorology and Oceanography
CY MAR 13-17, 1995
CL TOKYO, JAPAN
SP World Meteorol Org
ID TROPICAL PACIFIC-OCEAN; EQUATIONS; MODEL; ARRAY
AB It is commonplace to begin talks on this topic by noting that oceanographic data are too scarce and sparse to provide complete initial and boundary conditions for large-scale ocean models. Even considering the availability of remotely-sensed data such as radar altimetry from the TOPEX and ERS-1 satellites, a glance at a map of available subsurface data should convince most observers that this is still the case. Data are still too sparse for comprehensive treatment of interannual to interdecadal climate change through the use of models, since the new data sets have not been around for very long.
In view of the dearth of data, we must note that the overall picture is changing rapidly. Recently, there have been a number of large scale ocean analysis and prediction efforts, some of which now run on an operational or at least quasi-operational basis, most notably the model based analyses of the tropical oceans. These programs are modeled on numerical weather prediction.
Aside from the success of the global tide models, assimilation of data in the tropics, in support of prediction and analysis of seasonal to interannual climate change, is probably the area of large scale ocean modeling and data assimilation in which the most progress has been made. Climate change is a problem which is particularly suited to advanced data assimilation methods. Linear models are useful, and the linear theory can be exploited. For the most part, the data are sufficiently sparse that implementation of advanced methods is worthwhile.
As an example of a large scale data assimilation experiment with a recent extensive data set, we present results of a tropical ocean experiment in which the Kalman filter nas used to assimilate three years of altimetric data from Geosat into a coarsely resolved linearized long wave shallow water model.
Since nonlinear processes dominate the local dynamic signal outside the tropics, subsurface dynamical quantities cannot be reliably inferred from surface height anomalies. Because of its potential for large scale synoptic coverage of the deep ocean, acoustic travel time data should be a natural complement to satellite altimetry. Satellite data give us vertical integrals associated with thermodynamic and dynamic processes, while acoustic travel times provide horizontal integrals from which dynamics of the deep ocean can be inferred.
Linearized analysis indicates that detailed information can be retrieved by means of data assimilation from integral sources of data such as acoustic travel times. Static analysis of tomographic data without data assimilation cannot provide nearly so much detail. It can be shown that integrated quantities along the edges and diagonals of a simple square array combined with a linearized quasigeostrophic model is an observable system, down to scales much shorter than the dimensions of the array. Nonlinearities complicate the picture, but the linear results, along with a few preliminary numerical experiments give us cause for optimism.
C1 NASA, GODDARD SPACE FLIGHT CTR, LAB HYDROSPHER PROC, GREENBELT, MD 20771 USA.
HUGHES STX CORP, GREENBELT, MD 20771 USA.
RP Miller, RN (reprint author), OREGON STATE UNIV, COLL OCEANOG & ATMOSPHER SCI, CORVALLIS, OR 97331 USA.
RI Hackert, Eric/A-9915-2011
NR 33
TC 1
Z9 1
U1 0
U2 1
PU METEOROLOGICAL SOC JAPAN
PI TOKYO
PA C/O JAPAN METEOROLOGICAL AGENCY 1-3-4 OTE-MACHI, CHIYODA-KU, TOKYO,
100-0004, JAPAN
SN 0026-1165
EI 2186-9057
J9 J METEOROL SOC JPN
JI J. Meteorol. Soc. Jpn.
PD MAR
PY 1997
VL 75
IS 1B
BP 445
EP 462
PG 18
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA XG476
UT WOS:A1997XG47600024
ER
PT J
AU Kalnay, E
Anderson, DLT
Bennett, AF
Busalacchi, AJ
Cohn, SE
Courtier, P
Derber, J
Lorenc, AC
Parrish, D
Purser, J
Sato, N
Schlatter, T
AF Kalnay, E
Anderson, DLT
Bennett, AF
Busalacchi, AJ
Cohn, SE
Courtier, P
Derber, J
Lorenc, AC
Parrish, D
Purser, J
Sato, N
Schlatter, T
TI Data assimilation in the ocean and in the atmosphere: What should be
next?
SO JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN
LA English
DT Editorial Material
C1 UNIV OXFORD, OXFORD, ENGLAND.
OREGON STATE UNIV, CORVALLIS, OR 97331 USA.
NASA, GODDARD SPACE FLIGHT CTR, WASHINGTON, DC USA.
JAPAN METEOROL AGCY, TOKYO, JAPAN.
RP Kalnay, E (reprint author), NATL CTR ENVIRONM PREDICT, WASHINGTON, DC USA.
RI Kalnay, Eugenia/F-4393-2010; Cohn, Stephen/K-1954-2012;
OI Cohn, Stephen/0000-0001-8506-9354; Kalnay, Eugenia/0000-0002-9984-9906
NR 9
TC 9
Z9 9
U1 0
U2 0
PU METEOROLOGICAL SOC JAPAN
PI TOKYO
PA C/O JAPAN METEOROLOGICAL AGENCY 1-3-4 OTE-MACHI, CHIYODA-KU, TOKYO,
100-0004, JAPAN
SN 0026-1165
EI 2186-9057
J9 J METEOROL SOC JPN
JI J. Meteorol. Soc. Jpn.
PD MAR
PY 1997
VL 75
IS 1B
BP 489
EP 496
PG 8
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA XG476
UT WOS:A1997XG47600027
ER
PT J
AU Bullock, SR
Reddy, BR
Venkateswarlu, P
NashStevenson, SK
AF Bullock, SR
Reddy, BR
Venkateswarlu, P
NashStevenson, SK
TI Site-selective energy upconversion in CaF2:Ho3+
SO JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS
LA English
DT Article
ID CRYSTAL-FIELD ANALYSIS; UP-CONVERSION; SRF2; FLUORESCENCE; EXCITATION;
HOLMIUM; GLASSES; LASER; HO-3+; IONS
AB From the absorption spectrum of CaF2:Ho3+, Judd-Ofelt intensity parameters were estimated as Ohm(2) = 0.018 x 10(-20) cm(2), Ohm(4) = 0.57 x 10(-20) cm(2), and Ohm(6) = 0.587 x 10(-20) cm(2). Radiative transition probabilities and radiative lifetimes were also estimated for some of the levels. We observed red-to-green, -blue, and -violet energy upconversion in CaF2:Ho3+ with efficiencies of 0.08%, 0.13% and 1.35 x 10(-3)%, respectively, on resonant excitation of the F-5(5) state. Under site-selective excitation we also found that the blue-upconversion signal intensity was approximately three times larger than that of the green-upconversion signal intensity. On resonantly exciting the I-5(4) State we detected strong green upconversion signals from the S-5(2) State and found that excited-state absorption from I-5(7) was responsible for this process. Upconversion efficiency of the process was determined to be 8.1%. On resonantly exciting the I-5(5) state, we detected strong red emission in CaF2:Ho3+ and strong green emission in LaF3:Ho3+. Such a host-dependent upconversion frequency emission is also explained. (C) 1997 Optical Society of America.
C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812.
RP Bullock, SR (reprint author), ALABAMA A&M UNIV,DEPT PHYS,POB 1268,NORMAL,AL 35762, USA.
NR 19
TC 31
Z9 31
U1 0
U2 3
PU OPTICAL SOC AMER
PI WASHINGTON
PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036
SN 0740-3224
J9 J OPT SOC AM B
JI J. Opt. Soc. Am. B-Opt. Phys.
PD MAR
PY 1997
VL 14
IS 3
BP 553
EP 559
DI 10.1364/JOSAB.14.000553
PG 7
WC Optics
SC Optics
GA WM652
UT WOS:A1997WM65200009
ER
PT J
AU Brindley, WJ
AF Brindley, WJ
TI Thermal barrier coatings of the future
SO JOURNAL OF THERMAL SPRAY TECHNOLOGY
LA English
DT Editorial Material
C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135.
NR 2
TC 16
Z9 17
U1 2
U2 2
PU ASM INTERNATIONAL
PI MATERIALS PARK
PA SUBSCRIPTIONS SPECIALIST CUSTOMER SERVICE, MATERIALS PARK, OH 44073-0002
SN 1059-9630
J9 J THERM SPRAY TECHN
JI J. Therm. Spray Technol.
PD MAR
PY 1997
VL 6
IS 1
BP 3
EP 4
DI 10.1007/BF02646305
PG 2
WC Materials Science, Coatings & Films
SC Materials Science
GA WM436
UT WOS:A1997WM43600001
ER
PT J
AU Miller, RA
AF Miller, RA
TI Thermal barrier coatings for aircraft engines: History and directions
SO JOURNAL OF THERMAL SPRAY TECHNOLOGY
LA English
DT Article
DE historical review; thermal barrier coatings; zirconia
ID TURBINE-BLADES; ALLOYS; MODEL; LIFE
AB Thin thermal barrier coatings (TBCs) for protecting aircraft turbine section airfoils are examined. The discussion focuses on those advances that led first to TBC use for component life extension and more recently as an integral part of airfoil design, Development has been driven by laboratory rig and furnace testing, corroborated by engine testing and engine field experience, The technology has also been supported by performance modeling to demonstrate benefits and life modeling for mission analysis. Factors that have led to the selection of current state-of-the-art plasma-sprayed and physical-vapor-deposited zirconia-yttria/MCrAlX TBCs are emphasized, as are observations fundamentally related to their behavior, Current directions in research into TBCs and recent progress at NASA are also noted.
C1 NASA, LEWIS RES CTR, CLEVELAND, OH 44135 USA.
NR 70
TC 331
Z9 377
U1 20
U2 131
PU SPRINGER
PI NEW YORK
PA 233 SPRING ST, NEW YORK, NY 10013 USA
SN 1059-9630
EI 1544-1016
J9 J THERM SPRAY TECHN
JI J. Therm. Spray Technol.
PD MAR
PY 1997
VL 6
IS 1
BP 35
EP 42
DI 10.1007/BF02646310
PG 8
WC Materials Science, Coatings & Films
SC Materials Science
GA WM436
UT WOS:A1997WM43600004
ER
PT J
AU Brindley, WJ
AF Brindley, WJ
TI Properties of plasma-sprayed bond coats
SO JOURNAL OF THERMAL SPRAY TECHNOLOGY
LA English
DT Article
DE bond coat; failure; strain response; thermal barrier coatings
ID COATINGS; BEHAVIOR
AB Increasing bond coat oxidation resistance has been clearly linked to increasing durability of the ceramic layer of thermal barrier coatings (TBCs), However, recent studies have shown that significant differences in TBC life can be achieved for different bond coats that exhibit little or no difference in oxidation behavior, These data suggest that bond coat properties other than oxidation resistance can also influence TBC life, Determination of which properties affect TBC life and how they do so could be valuable in designing new, more durable TBCs, This paper reviews the results of comparative studies of the properties of three bond coat compositions that have similar oxidation behavior but different TBC lives. An analysis of the properties indicates that the thermal cycle residual stress, calculated from the coefficient of thermal expansion and the stress relaxation behavior of the three alloys, is strongly correlated to the observed differences in TBC life.
C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135.
NR 18
TC 38
Z9 38
U1 3
U2 7
PU ASM INTERNATIONAL
PI MATERIALS PARK
PA SUBSCRIPTIONS SPECIALIST CUSTOMER SERVICE, MATERIALS PARK, OH 44073-0002
SN 1059-9630
J9 J THERM SPRAY TECHN
JI J. Therm. Spray Technol.
PD MAR
PY 1997
VL 6
IS 1
BP 85
EP 90
DI 10.1007/BF02646316
PG 6
WC Materials Science, Coatings & Films
SC Materials Science
GA WM436
UT WOS:A1997WM43600010
ER
PT J
AU Bloomberg, JJ
Peters, BT
Smith, SL
Huebner, WP
Reschke, MF
AF Bloomberg, JJ
Peters, BT
Smith, SL
Huebner, WP
Reschke, MF
TI Locomotor head-trunk coordination strategies following space flight
SO JOURNAL OF VESTIBULAR RESEARCH-EQUILIBRIUM & ORIENTATION
LA English
DT Article; Proceedings Paper
CT 3rd International Symposium on the Head/Neck System
CY JUL 02-06, 1995
CL VAIL, CO
DE head-trunk coordination; locomotion; space flight; human subjects
ID VESTIBULO-OCULAR REFLEX; CIRCULAR LOCOMOTION; POSTURAL CONTROL; TARGET
DISTANCE; RUNNING MONKEY; STABILIZATION; GAZE; EYE; RESPONSES; STABILITY
AB During locomotion, angular head movements act in a compensatory fashion to oppose the vertical trunk translation that occurs during each step in the gait cycle. This coordinated strategy between head and trunk motion serves to aid gaze stabilization and perhaps simplifies the sensory coordinate transformation between the head and trunk, allowing efficient descending motor control during locomotion, Following space flight, astronauts often experience oscillopsia during locomotion in addition to postural and gait instabilities, suggesting a possible breakdown in head-trunk coordination. The goal of the present investigation was to determine if exposure to the microgravity environment of space flight induces alteration in head-trunk coordination during locomotion, Astronaut subjects were asked to walk (6.4 km/h, 20 s trials) on a motorized treadmill while visually fixating on a centrally located earth-fixed target positioned either 2 m (FAR) or 30 cm (NEAR) from the eyes, In addition, some trials were also performed during periodic visual occlusion, Head and trunk kinematics during locomotion were determined with the aid of a video-based motion analyzing system. We report data collected preflight (10 days prior to launch) and postflight (2 to 4 hours after landing), The coherence between pitch head and vertical trunk movements during gaze fixation of both FAR and NEAR targets was significantly reduced following space flight indicating decreased coordination between the head and trunk during postflight locomotion, Astronauts flying on their first mission showed greater alterations in the frequency spectra of pitch head movements as compared to their more experienced counterparts, These modifications in the efficacy of head movement control may account for the reported disruption in gaze performance during locomotion and may contribute to postflight postural and gait dysfunction. (C) 1997 Elsevier Science Inc.
C1 KRUG LIFE SCI,HOUSTON,TX 77058.
RP Bloomberg, JJ (reprint author), NASA,LYNDON B JOHNSON SPACE CTR,LIFE SCI RES LABS,MAIL CODE SD35,HOUSTON,TX 77058, USA.
NR 48
TC 70
Z9 72
U1 0
U2 2
PU PERGAMON-ELSEVIER SCIENCE LTD
PI OXFORD
PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB
SN 0957-4271
J9 J VESTIBUL RES-EQUIL
JI J. Vestib. Res.-Equilib. Orientat.
PD MAR-JUN
PY 1997
VL 7
IS 2-3
BP 161
EP 177
PG 17
WC Neurosciences; Otorhinolaryngology
SC Neurosciences & Neurology; Otorhinolaryngology
GA XB961
UT WOS:A1997XB96100007
PM 9178222
ER
PT J
AU McDonald, PV
Bloomberg, JJ
Layne, CS
AF McDonald, PV
Bloomberg, JJ
Layne, CS
TI A review of adaptive change in musculoskeletal impedance during space
flight and associated implications for postflight head movement control
SO JOURNAL OF VESTIBULAR RESEARCH-EQUILIBRIUM & ORIENTATION
LA English
DT Article; Proceedings Paper
CT 3rd International Symposium on the Head/Neck System
CY JUL 02-06, 1995
CL VAIL, CO
DE human performance; vestibular system; gaze; locomotion
ID VESTIBULOOCULAR REFLEX; HUMAN LOCOMOTION; VIBRATION; TRUNK; GAIT;
STABILIZATION; MANIPULATION; PERFORMANCE; FREQUENCY; WALKING
AB We present a review of converging sources of evidence which suggest that the differences between loading histories experienced in 1-g and weightlessness are sufficient to stimulate adaptation in mechanical impedance of the musculoskeletal system, As a consequence of this adaptive change we argue that we should observe changes in the ability to attenuate force transmission through the musculoskeletal system both during and after space flight. By focusing attention on the relation between human sensorimotor activity and support surfaces, the importance of controlling mechanical energy flow through the musculoskeletal system is demonstrated. The implications of such control are discussed in light of visual-vestibular function in the specific context of head and gaze control during postflight locomotion, Evidence from locomotory biomechanics, visual-vestibular function, ergonomic evaluations of human vibration, and specific investigations of locomotion and head and gaze control after space flight, is considered. (C) 1997 Elsevier Science Inc.
C1 NASA,LYNDON B JOHNSON SPACE CTR,SPACE BIOMED RES INST,HOUSTON,TX 77058.
RP McDonald, PV (reprint author), KRUG LIFE SCI,1290 HERCULES DR,SUITE 120,HOUSTON,TX 77058, USA.
NR 63
TC 6
Z9 6
U1 1
U2 5
PU PERGAMON-ELSEVIER SCIENCE LTD
PI OXFORD
PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB
SN 0957-4271
J9 J VESTIBUL RES-EQUIL
JI J. Vestib. Res.-Equilib. Orientat.
PD MAR-JUN
PY 1997
VL 7
IS 2-3
BP 239
EP 250
PG 12
WC Neurosciences; Otorhinolaryngology
SC Neurosciences & Neurology; Otorhinolaryngology
GA XB961
UT WOS:A1997XB96100011
PM 9178226
ER
PT J
AU Horz, F
Cintala, M
AF Horz, F
Cintala, M
TI The Barringer Award address - Presented 1996 July 25, Berlin, Germany -
Impact experiments related to the evolution of planetary regoliths
SO METEORITICS & PLANETARY SCIENCE
LA English
DT Article
ID AGGLUTINATE MELTING MECHANISMS; ORDINARY CHONDRITES; SHOCK METAMORPHISM;
CRATER EJECTA; TERRESTRIAL IMPACT; SOLAR-SYSTEM; METEORITES; SIZE;
SPECTROSCOPY; VELOCITY
AB Impact-induced comminution of planetary surfaces is pervasive throughout the solar system and occurs on submillimeter to global scales, resulting in comminution products that range from fine-grained surface soils, to massive, polymict ejecta deposits, to collisionally fragmented objects. Within this wide range of comminution products, we define regoliths in a narrow sense as materials that were processed by repetitive impacts to dimensional scales comparable to or smaller than that of component minerals of the progenitor rock(s). In this paper, we summarize a wide variety of impact experiments and other observations that were primarily intended to understand the evolution of regoliths on lunar basalt flows, and we discuss some of their implications for asteroidal surfaces.
Cratering experiments in both rock and noncohesive materials, combined- with photogeologic observations of the lunar surface, demonstrate that craters <500 m in diameter contribute most to the excavation of local bedrock for subsequent processing by micrometeorites. The overall excavation rate and, thus, growth rate of the debris layer decreases with time, because the increasingly thicker fragmental layer will prevent progressively larger projectiles from reaching bedrock. Typical growth rates for a 5 m thick lunar soil layer are initially (similar to>3 Ga ago) a few mm/Ma and slowed to <1 mm/Ma at present. The coarse-grained crater ejecta are efficiently comminuted by collisional fragmentation processes, and the mean residence time of a 1 kg rock is typically approximate to 10 Ma. The actual comminution of either lithic or monomineralic detritus is highly mineral specific, with feldspar and mesostasis comminuting preferentially over pyroxene and olivine, thus resulting in mechanically fractionated fines, especially at grain sizes <20 mu m. Such fractionated fines also participate preferentially in the shock melting of lunar soils, thus giving rise to ''agglutinate'' melts. As a consequence, agglutinate melts are systematically enriched in feldspar components relative to the bulk composition of their respective host soil(s). Compositionally homogeneous, impact derived glass beads in lunar soils seem to result from micrometeorite impacts on rock surfaces, reflecting lithic regolith components and associated mineral mixtures. Cumulatively, experimental and observational evidence from lunar mare soils suggests that regoliths derive substantially from the comminution of local bedrock; the addition of foreign, exotic components is not necessary to explain the modal and chemical compositions of diverse grain size fractions from typical lunar soils.
Regoliths on asteroids are qualitatively different from those of the Moon. The modest impact velocities in the asteroid belt, some 5 km s(-1), are barely sufficient to produce impact melts. Also, substantially more crater mass is being displaced on low-gravity asteroids compared to the Moon; collisional processing of surface boulders should therefore be more prominent in producing comminuted asteroid surfaces. These processes combine into asteroidal surface deposits that have suffered modest levels of shock metamorphism compared to the Moon. Impact melting does not seem to be a significant process under these conditions. However, the role of cometary particles encountering asteroid surfaces at presumably higher velocities has not been addressed in the past. Unfortunately, the asteroidal surface processes that seemingly modify the spectral properties of ordinary chondrites to match telescopically obtained spectra of S-type asteroids remain poorly understood at present, despite the extensive experimental and theoretical insights summarized in this report and our fairly mature understanding of lunar surface processes and regolith evolution.
RP Horz, F (reprint author), NASA,LYNDON B JOHNSON SPACE CTR,PLANETARY SCI BRANCH,HOUSTON,TX 77058, USA.
NR 179
TC 50
Z9 50
U1 1
U2 5
PU METEORITICAL SOC
PI FAYETTEVILLE
PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701
SN 0026-1114
J9 METEORIT PLANET SCI
JI Meteorit. Planet. Sci.
PD MAR
PY 1997
VL 32
IS 2
BP 179
EP 209
PG 31
WC Geochemistry & Geophysics
SC Geochemistry & Geophysics
GA WN693
UT WOS:A1997WN69300008
ER
PT J
AU Chen, LW
Fabian, AC
Gendreau, KC
AF Chen, LW
Fabian, AC
Gendreau, KC
TI ASCA and ROSAT observations of the QSF3 field: The x-ray background in
the 0.1-7 keV band
SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
LA English
DT Article
DE cosmology, observations; diffuse radiation; large-scale structure of
Universe; X-rays, general
ID ORIGIN; DIFFUSE; SPECTRA
AB The X-ray background from 0.1 to 7 keV has been studied using data of high spectral and spatial resolution from the ASCA Solid-state Imaging Spectrometers and ROSAT Position Sensitive Proportional Counter. Analysing both the diffuse background radiation and resolved sources, we have carried out a series of joint spectral fits of the ASCA and ROSAT data. As found previously with ASCA data alone, the spectrum of the X-ray background can be fitted well by a single power law from 1 to 7 keV; to account for the Galactic emission below 1 keV, a model with a power law plus two thermal components fits well to the measurements of ASCA and ROSAT from 0.1 to 7 keV. Overall, the photon index of the power-law model ranges from 1.4 to 1.5, and no obvious excess is found between 1 and 3 keV as predicted from some previous observations. Below 1 keV, the models become more complicated and involve a mixture of extragalactic and Galactic sources. As some of the extragalactic contributions should be from point sources, we have examined the ASCA and ROSAT spectra of resolved sources individually: a stellar source having a well-fitted thermal spectrum and two AGN having a much steeper power-law spectrum (with a photon index of about 3); the accumulated spectrum of other nonstellar sources resolved by ROSAT is also steeper than the average AGN spectrum. Fitting the X-ray background spectrum observed by ASCA and the accumulated point source spectrum by ROSAT together by varying the contribution from steep-spectrum sources, such as quasars, to the background, we find that the steep-spectrum sources contribute less than 30 per cent in the 0.5-2 keV band and drop to below 10 per cent over 2-10 keV. This fraction is provided by sources brighter than a few times 10(-15) erg cm(-2) s(-1) (in the 0.5-2 keV band). Constrained by our spectral fitting results, the major contributor of the X-ray background must be a single population with similar flat spectra.
C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771.
RP Chen, LW (reprint author), UNIV CAMBRIDGE,INST ASTRON,MADINGLEY RD,CAMBRIDGE CB3 0HA,ENGLAND.
NR 31
TC 101
Z9 101
U1 0
U2 0
PU BLACKWELL SCIENCE LTD
PI OXFORD
PA P O BOX 88, OSNEY MEAD, OXFORD, OXON, ENGLAND OX2 0NE
SN 0035-8711
J9 MON NOT R ASTRON SOC
JI Mon. Not. Roy. Astron. Soc.
PD MAR 1
PY 1997
VL 285
IS 3
BP 449
EP 471
PG 23
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WN236
UT WOS:A1997WN23600004
ER
PT J
AU Jones, LR
McHardy, IM
Merrifield, MR
Mason, KO
Smith, PJ
Abraham, RG
BranduardiRaymont, G
Newsam, AM
Dalton, G
RowanRobinson, M
Luppino, G
AF Jones, LR
McHardy, IM
Merrifield, MR
Mason, KO
Smith, PJ
Abraham, RG
BranduardiRaymont, G
Newsam, AM
Dalton, G
RowanRobinson, M
Luppino, G
TI X-ray QSO evolution from a very deep ROSAT survey
SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
LA English
DT Article
DE surveys; galaxies, active; quasars, general; cosmology, observations;
diffuse radiation; X-rays, galaxies
ID ACTIVE GALACTIC NUCLEI; N-LOG-S; COSMOLOGICAL EVOLUTION;
PARAMETER-ESTIMATION; LUMINOSITY FUNCTION; STARBURSTS; ASTRONOMY;
SAMPLES; QUASARS; SPECTRA
AB In the deepest optically identified X-ray survey yet performed, we have identified 32 X-ray-selected QSOs to a flux limit of 2 x 10(-15) erg cm(-2) s(-1) (0.5-2 keV), The survey, performed with the ROSAT Position Sensitive Proportional Counter (PSPC), has 89 per cent spectroscopic completeness. The QSO log(N)-log(S) relation is found to have a break to a flat slope at faint fluxes. The surface density of QSOs at the survey limit is 230 +/- 40 per square degree, the largest so far of any QSO survey, We use this survey to measure the QSO X-ray luminosity function at low luminosities (L(X)<10(44.5) erg s(-1)) and high redshifts (1 100 MeV) was observed. The corresponding isotropic luminosity is 2.9 x 10(49) ergs s(-1). We find that PKS 1622-297 exhibits gamma-ray intraday variability. A flux increase by a factor of at least 3.6 was observed to occur in less than 7.1 hr (with 99% confidence). Assuming an exponential rise, the corresponding doubling time is less than 3.8 hr. A significant flux decrease by a factor of similar to 2 in 9.7 hr was also observed. Without beaming, the rapid flux change and large isotropic luminosity are inconsistent with the Elliot-Shapiro condition (assuming that gas accretion is the immediate source of power for the gamma-rays). This inconsistency suggests that the gamma-ray emission is beamed. A minimum Doppler factor of 8.1 is implied by the observed lack of pair-production opacity (assuming X-rays are emitted cospatially with the gamma-rays). Simultaneous observation by EGRET and OSSE finds a spectrum adequately fitted by a power law with photon index of -1.9. Although the significance is not sufficient to establish this beyond doubt, the high-energy gamma-ray spectrum appears to evolve from hard to soft as a flare progresses.
C1 LANDESSTERNWARTE KONIGSTUHL,D-69117 HEIDELBERG,GERMANY.
UNIV CALIF LOS ANGELES,LOS ANGELES,CA 90024.
NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20701.
HARVARD SMITHSONIAN CTR ASTROPHYS,CAMBRIDGE,MA 02138.
USN,RES LAB,WASHINGTON,DC 20375.
RP Mattox, JR (reprint author), BOSTON UNIV,DEPT ASTRON,725 COMMONWEALTH AVE,BOSTON,MA 02215, USA.
RI Johnson, Neil/G-3309-2014
NR 43
TC 113
Z9 115
U1 1
U2 1
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD FEB 20
PY 1997
VL 476
IS 2
BP 692
EP 697
DI 10.1086/303639
PN 1
PG 6
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WH858
UT WOS:A1997WH85800021
ER
PT J
AU Stecker, FW
deJager, OC
AF Stecker, FW
deJager, OC
TI On the absorption of high-energy gamma rays by intergalactic infrared
radiation
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE gamma rays, theory; infrared, general; quasars, individual (Markarian
421, 3C 279); radiative transfer
ID FIELDS
AB We present a new calculation of the intergalactic gamma-ray pair-production absorption coefficient as a function of both energy and redshift up to the redshift of 3C 279, z = 0.54. In reexamining this problem, we make use of new observational data on the intergalactic infrared radiation field (IIRF), together with recent theoretical models of the galactic, spectral energy distributions of the IIRF from stars and dust reradiation and estimates of the IIRF from galaxy counts and COBE results. We present our results for two fairly well defined IIRF spectral energy distributions, one which is within 1 sigma of our previous estimate of the IIRF at similar to 20 mu m. Then we apply our results to the gamma-ray spectrum of Mrk 421 and obtain good agreement with the observational data, including the recent results of the HEGRA group.
C1 POTCHEFSTROOM UNIV CHRISTIAN HIGHER EDUC, DEPT PHYS, ZA-2520 POTCHEFSTROOM, SOUTH AFRICA.
RP NASA, GODDARD SPACE FLIGHT CTR, HIGH ENERGY ASTROPHYS LAB, GREENBELT, MD 20771 USA.
RI Stecker, Floyd/D-3169-2012
NR 39
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 FEB 20
PY 1997
VL 476
IS 2
BP 712
EP 716
DI 10.1086/303668
PN 1
PG 5
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WH858
UT WOS:A1997WH85800023
ER
PT J
AU Ceccarelli, C
Haas, MR
Hollenbach, DJ
Rudolph, AL
AF Ceccarelli, C
Haas, MR
Hollenbach, DJ
Rudolph, AL
TI O I 63 micron-determined mass-loss rates in young stellar objects
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE infrared, stars; ISM, jets and outflows; stars, circumstellar matter;
stars, mass loss; stars, pre-main-sequence
ID MAGNETOCENTRIFUGALLY DRIVEN FLOWS; HERBIG-HARO OBJECTS; OPHIUCHI DARK
CLOUD; MOLECULAR OUTFLOW; PHOTODISSOCIATION REGIONS; BIPOLAR OUTFLOWS;
STAR FORMATION; BINARY-SYSTEM; PHYSICAL CONDITIONS; IRAS OBSERVATIONS
AB We present observations of the O I 63 mu m emission toward five young, highly collimated outflow sources: IRAS 16293-2422, VLA 1623, L1448-mm, L1448-IRS 3, and NGC 1333-IRAS 4A. We have partially mapped the O I 63 mu m emission associated with the first three outflows, but have made single-beam observations of the latter two. We discuss how the O I 63 mu m emission can be used to measure mass outflow rates and compare these with the determination of outflow rates from CO observations. We find that the O I-derived mass outflow rates are in good agreement with the CO-derived rates in two of the five sources, but are a factor similar to 2-4 times lower than the CO-derived rates in L1448-mm, L1448-IRS 3, and IRAS 16293-2422. This provides additional support to arguments already made by numerous authors that the CO-derived rates may be overestimates. We discuss the correlation between the spatial distribution of the CO and O I emission and argue that the outflow occurs in multiple events that gradually evacuate the path of the wind through the ambient medium.
C1 CNR,IST FIS SPAZIO INTERPLANETARIO,I-00044 FRASCATI,ITALY.
HARVEY MUDD COLL,DEPT PHYS,CLAREMONT,CA 91711.
NASA,AMES RES CTR,MOFFETT FIELD,CA 94035.
NR 96
TC 31
Z9 31
U1 0
U2 0
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD FEB 20
PY 1997
VL 476
IS 2
BP 771
EP 780
DI 10.1086/303643
PN 1
PG 10
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WH858
UT WOS:A1997WH85800028
ER
PT J
AU Corbet, RHD
Charles, PA
Southwell, KA
Smale, AP
AF Corbet, RHD
Charles, PA
Southwell, KA
Smale, AP
TI A low-amplitude X-ray and optical outburst from the periodic transient
A0538-66: Accretion onto a magnetosphere?
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE accretion, accretion disks; stars, individual (A0538-66); stars,
neutron; X-rays, stars
ID GAMMA CASSIOPEIAE; PULSAR; BINARY; STATE; VARIABILITY; PULSATIONS;
EMISSION; SPECTRUM; PSR-1259-63; PHOTOMETRY
AB We present ASCA observations made in 1995 February around the time of a predicted outburst from the 16.65 day period recurrent transient A0538-66, together with simultaneous optical photometry. Optical spectroscopy was also obtained near the time of a predicted outburst approximately 2 months earlier. We find that A0538-66 is active, both in X-rays and optically, although at a much lower level than during the largest super-Eddington outbursts that have been seen in the past. The optical spectra show variable Balmer emission, but not the strong He II 4686 Angstrom emission that accompanies large outbursts. The average X-ray luminosity is similar to 5.5 x 10(36) ergs s(-1), and we find evidence for the presence of an iron line in the X-ray spectrum. This can be interpreted either as a single line at 6.54 +/- 0.04 keV or, alternatively, as a blend of emission at both 6.4 and 6.7 keV. A simple power law, or power law plus high-energy cutoff, does not fit the continuum spectrum well. Instead, a more complicated model is required, and we find that a power law plus blackbody gives a good fit to the continuum, although other models cannot be excluded completely. No evidence for the presence of previously detected 69 ms pulsations is found in our data, although our sensitivity is limited by the low count rate during our observations and the unknown orbital parameters of this system.
We consider X-ray production processes that may account for the observed behavior. In particular, accretion onto the magnetosphere rather than the surface of a neutron star is discussed. Our data do not, however, exclude conclusively the possibility that accretion onto the neutron star is still occurring either because the magnetic field of the neutron star is low or because material is leaking past the magnetic barrier. If the X-ray flux is powered by energy released at the magnetosphere, then the presence of an iron line in the spectrum at greater than 6.4 keV, which is rare for Be star X-ray binaries, may be an indicator that such a process is occurring.
C1 UNIV OXFORD,DEPT ASTROPHYS,OXFORD OX1 3RH,ENGLAND.
NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771.
RP Corbet, RHD (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 662,GREENBELT,MD 20771, USA.
NR 38
TC 21
Z9 21
U1 0
U2 0
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD FEB 20
PY 1997
VL 476
IS 2
BP 833
EP 841
DI 10.1086/303644
PN 1
PG 9
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WH858
UT WOS:A1997WH85800033
ER
PT J
AU Mori, M
Bertsch, DL
Dingus, BL
Esposito, JA
Fichtel, CE
Hunter, SD
Kanbach, G
Kniffen, DA
Lin, YC
Mattox, JR
MayerHasselwander, HA
Michelson, PF
vonMontigny, C
Mukherjee, R
Nolan, PL
Ramanamurthy, PV
Schneid, E
Sreekumar, P
Thompson, DJ
AF Mori, M
Bertsch, DL
Dingus, BL
Esposito, JA
Fichtel, CE
Hunter, SD
Kanbach, G
Kniffen, DA
Lin, YC
Mattox, JR
MayerHasselwander, HA
Michelson, PF
vonMontigny, C
Mukherjee, R
Nolan, PL
Ramanamurthy, PV
Schneid, E
Sreekumar, P
Thompson, DJ
TI Cygnus X-3 and EGRET gamma-ray observations
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE gamma rays, observations; stars, individual (Cygnus X-3)
ID RADIO OUTBURST; MILLISECOND PULSAR; EMISSION; SEARCH; PERIODICITY;
TELESCOPE; STARS
AB The Energetic Gamma Ray Experiment Telescope (EGRET) aboard the Compton Gamma Ray Observatory observed the Cygnus region in 14 different viewing periods during 1991 May to 1994 July. We present here our results on unpulsed and pulsed emissions of gamma rays at E > 50 MeV from Cyg X-3. While we detect a gamma-ray source consistent with the position of Cyg X-3, there was no evidence for the characteristic similar to 4.79 hr periodicity observed in X-rays and infrared.
C1 MIYAGI UNIV EDUC,DEPT PHYS,SENDAI,MIYAGI 980,JAPAN.
MAX PLANCK INST EXTRATERR PHYS,D-85748 GARCHING,GERMANY.
HAMPDEN SYDNEY COLL,DEPT PHYS,HAMPDEN SYDNEY,VA 23943.
STANFORD UNIV,HANSEN EXPT PHYS LAB,STANFORD,CA 94305.
UNIV MARYLAND,DEPT ASTRON,COLLEGE PK,MD 20742.
GRUMMAN CORP,BETHPAGE,NY 11714.
RP Mori, M (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 661,GREENBELT,MD 20771, USA.
RI Nolan, Patrick/A-5582-2009; Hunter, Stanley/D-2942-2012; Thompson,
David/D-2939-2012
OI Thompson, David/0000-0001-5217-9135
NR 55
TC 29
Z9 29
U1 0
U2 0
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD FEB 20
PY 1997
VL 476
IS 2
BP 842
EP 846
DI 10.1086/303667
PN 1
PG 5
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WH858
UT WOS:A1997WH85800034
ER
PT J
AU Baring, MG
Ogilvie, KW
Ellison, DC
Forsyth, RJ
AF Baring, MG
Ogilvie, KW
Ellison, DC
Forsyth, RJ
TI Acceleration of solar wind ions by nearby interplanetary shocks:
Comparison of Monte Carlo simulations with Ulysses observations
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE acceleration of particles; interplanetary medium; scattering; shock
waves; solar wind
ID EARTHS BOW SHOCK; STREAM INTERACTION REGIONS; INTERSTELLAR PICKUP IONS;
FIELD-ALIGNED BEAMS; PARTICLE-ACCELERATION; ALPHA-PARTICLES; OBLIQUE
SHOCKS; HYBRID SIMULATIONS; TERMINATION SHOCK; PARALLEL SHOCKS
AB Various theoretical techniques have been devised to determine distribution functions of particles accelerated by the first-order Fermi mechanism at collisionless astrophysical shocks. The most stringent test of these models as descriptors of the phenomenon of diffusive acceleration is a comparison of the theoretical predictions with observational data on particle populations. Such comparisons have yielded good agreement between observations at the quasi-parallel portion of the Earth's bow shock and three theoretical approaches, namely, Monte Carlo kinetic simulations, hybrid plasma simulations, and numerical solution of the diffusion-convection equation. Testing of the Monte Carlo method is extended in this paper to the realm of oblique interplanetary shocks: here observations of proton and He2+ distributions made by the SWIGS ion mass spectrometer on Ulysses at nearby interplanetary shocks (less than about 3 AU distant from the Sun) are compared with test-particle Monte Carlo simulation predictions of accelerated populations. The plasma parameters used in the simulation are obtained from measurements of solar wind particles and the magnetic field upstream of individual shocks; pickup ions are omitted from the simulations, since they appear, for the most part, at greater heliospheric distances. Good agreement between downstream spectral measurements and the simulation predictions are obtained for two shocks by allowing the parameter lambda/r(g), the ratio of the mean-free scattering length to the ionic gyroradius, to vary in an optimization of the fit to the data; generally lambda/r(g) less than or similar to 5, corresponding to the case of strong scattering. Simultaneous H+ and He2+ data, presented only for the 1991 April 7 shock event, indicate that the acceleration process is roughly independent of the mass or charge of the species. This naturally arises if all particles interact elastically with a massive background, as occurs in collisionless ''scattering'' off a background magnetic field, and is a patent property of the Monte Carlo technique, since it assumes elastic and quasi-isotropic scattering of particles in the local plasma frame.
C1 NASA, GODDARD SPACE FLIGHT CTR, EXTRATERR PHYS LAB, GREENBELT, MD 20771 USA.
N CAROLINA STATE UNIV, DEPT PHYS, RALEIGH, NC 27695 USA.
UNIV LONDON IMPERIAL COLL SCI TECHNOL & MED, BLACKETT LAB, LONDON SW7 2BZ, ENGLAND.
RP Baring, MG (reprint author), NASA, GODDARD SPACE FLIGHT CTR, HIGH ENERGY ASTROPHYS LAB, CODE 661, GREENBELT, MD 20771 USA.
NR 74
TC 54
Z9 54
U1 0
U2 3
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD FEB 20
PY 1997
VL 476
IS 2
BP 889
EP 902
DI 10.1086/303645
PN 1
PG 14
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WH858
UT WOS:A1997WH85800039
ER
PT J
AU Morrissey, PF
Feldman, PD
Clarke, JT
Wolven, BC
Strobel, DF
Durrance, ST
Trauger, JT
AF Morrissey, PF
Feldman, PD
Clarke, JT
Wolven, BC
Strobel, DF
Durrance, ST
Trauger, JT
TI Simultaneous spectroscopy and imaging of the Jovian aurora with the
Hopkins Ultraviolet Telescope and the Hubble Space Telescope
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE planets and satellites, individual (Jupiter); ultraviolet, solar system
ID MOLECULAR-HYDROGEN; BAND SYSTEM; JUPITER; SPECTRUM; ELECTRON;
PRECIPITATION; PERFORMANCE; RESOLUTION; ENCOUNTER; VOYAGER
AB Simultaneous ultraviolet spectra and images of the north polar aurora of Jupiter were obtained on 1995 March 9 with the Hopkins Ultraviolet Telescope (HUT) and the Hubble Space Telescope (HST). This unique data set contains a well-calibrated flux measurement that includes all of the H-2 Lyman and Werner band emission from 900 to 1650 Angstrom, as well as information about the spatial extent of the aurora. For these observations, we oriented the 10 '' x 57 '' slit of the HUT spectrograph parallel to the equator of Jupiter so that it was underfilled by the aurora and minimally contaminated by extraneous reflected solar light from low to mid latitudes. The aurora was imaged simultaneously using the FIST Wide Field and Planetary Camera 2 (WFPC2). Images were taken through a Wood's filter and also through a Wood's filter/CaF2, filter combination. These images have recorded the aurora in the light of atomic and molecular hydrogen with relatively low reflected solar contamination. The molecular hydrogen aurora is found to extend over 4.5 +/- 0.5 x 10(-10) sr, with an average brightness of 106 +/- 12 kR integrated over the band of wavelengths from 900 to 1650 Angstrom, excluding H I lambda 1216. We measure a 13% larger emitting area (5.1 +/- 0.5 x 10(-10) sr) and significantly different morphology for the combined atomic and molecular hydrogen aurora (Ly alpha + H-2), although these differences could be a result of time variability. Color ratios derived from the data indicate a total auroral energy deposition rate of 13 ergs s(-1) cm(-2) by 3-30 keV electrons. We find little evidence for ions as primary auroral particles in the HUT spectra. Our analysis places upper limits on sulfur ion emissions that are an order of magnitude lower than those from the IUE observations, and, therefore, the emissions could be entirely from the Io torus in the background of the planet.
C1 UNIV MICHIGAN,DEPT ATMOSPHER & OCEAN SCI,SPACE PHYS RES LAB,ANN ARBOR,MI 48109.
CALTECH,JET PROP LAB,PASADENA,CA 91109.
RP Morrissey, PF (reprint author), JOHNS HOPKINS UNIV,DEPT PHYS & ASTRON,BALTIMORE,MD 21218, USA.
RI Clarke, John/C-8644-2013
NR 25
TC 19
Z9 19
U1 0
U2 2
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD FEB 20
PY 1997
VL 476
IS 2
BP 918
EP &
DI 10.1086/303648
PN 1
PG 7
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WH858
UT WOS:A1997WH85800041
ER
PT J
AU Bernstein, MP
Sandford, SA
Allamandola, LJ
AF Bernstein, MP
Sandford, SA
Allamandola, LJ
TI The infrared spectra of nitriles and related compounds frozen in Ar and
H2O
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE infrared, general; methods, laboratory; molecular data
ID AROMATIC HYDROCARBON CATIONS; MICRON ABSORPTION; GRAIN MANTLES; ICE
ANALOGS; SOLID ARGON; INTERSTELLAR; SPECTROSCOPY; MATRIX; COMPLEXES;
MOLECULES
AB We present the 2320-2050 cm(-1) (4.31-4.88 mu m) infrared spectra of 16 solid-state nitriles, isonitriles, and related compounds in order to facilitate the assignment of absorption features in a spectral region now becoming accessible to astronomers for the first time through the Infrared Space Observatory (ISO). This frequency range spans the positions of the strong C=N stretching vibration of these compounds and is inaccessible from the ground due to absorption by CO2 in the terrestrial atmosphere. Band positions, profiles, and intrinsic strengths (A values) were measured for compounds frozen in Ar and H2O matrices at 12 K. The molecular species examined included acetonitrile, benzonitrile (phenylcyanide), 9-anthracenecarbonitrile, dimethylcyanamide, isopropylnitrile (isobutyronitrile), methylacrylonitrile, crotononitrile, acrylonitrile (vinyl cyanide), 3-aminocrotononitrile, pyruvonitrile, dicyandiamide, cyanamide, n-butylisocyanide, methylisocyanoacetate, diisopropylcarbodiimide, and hydrogen cyanide. The CEN stretching bands of the majority of nitriles fall in the 2300-2200 cm(-1) (4.35-4.55 mu m) range and have similar positions in both Ar and H2O matrices, although the bands are generally considerably broader in the H2O matrices. In contrast, the isonitriles and a few exceptional nitriles and related species produce bands at lower frequencies spanning the 2200-2080 cm(-1) (4.55-4.81 mu m) range. These features also have similar positions in both Ar and H2O matrices, and the bands are broader in the H2O matrices. Three of the compounds (pyruvonitrile, dicyandiamide, and cyanamide) show unusually large shifts of their C=N stretching frequencies when changing from Ar to H2O matrices. We attribute these shifts to the formation of H2O:nitrile complexes with these compounds. The implications of these results for the identification of the 2165 cm(-1) (4.62 mu m) ''XCN'' interstellar feature and the 4550 cm(-1) (2.2 mu m) feature of various objects in the solar system are discussed.
RP Bernstein, MP (reprint author), NASA,AMES RES CTR,ASTROPHYS BRANCH,MAIL STOP 245-6,MOFFETT FIELD,CA 94035, USA.
NR 38
TC 77
Z9 77
U1 1
U2 19
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD FEB 20
PY 1997
VL 476
IS 2
BP 932
EP 942
DI 10.1086/303651
PN 1
PG 11
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WH858
UT WOS:A1997WH85800043
PM 11541246
ER
PT J
AU Park, S
Finley, JP
Snowden, SL
Dame, TM
AF Park, S
Finley, JP
Snowden, SL
Dame, TM
TI Evidence for an X-ray-emitting galactic bulge: Shadows cast by distant
molecular gas
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE galaxy, structure; ISM, structure; X-rays, galaxies; X-rays, ISM
ID CLOUD; ROSAT; IMAGE; SKY
AB A mosaic of seven ROSAT PSPC pointed observations in the direction of (l, b similar to 10 degrees, 0 degrees) reveals deep X-ray shadows in the 0.5-2.0 keV band cast by dense molecular gas. The comparison between the observed on-cloud and off-cloud X-ray fluxes indicates that similar to 43% of the diffuse X-ray background in this direction in both the 0.75 and 1.5 keV bands originates behind the molecular gas, which is located at 2-4 kpc from the Sun. Given the short mean free path of X-rays in the 0.75 keV band in the Galactic plane (similar to 1 kpc assuming an average space density or 1 cm(-1)), this large percentage of the observed flux that originates beyond the molecular gas most likely indicates a strong enhancement in the distribution of X-ray-emitting gas in the Galactic center region, possibly associated with a Galactic X-ray bulge.
C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771.
HARVARD SMITHSONIAN CTR ASTROPHYS,CAMBRIDGE,MA 02138.
RP Park, S (reprint author), PURDUE UNIV,DEPT PHYS,1396 PHYS BLDG,W LAFAYETTE,IN 47907, USA.
NR 31
TC 17
Z9 17
U1 0
U2 0
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD FEB 20
PY 1997
VL 476
IS 2
BP L77
EP &
DI 10.1086/310501
PN 2
PG 6
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WH861
UT WOS:A1997WH86100006
ER
PT J
AU Siskind, DE
Bacmeister, JT
Summers, ME
Russell, JM
AF Siskind, DE
Bacmeister, JT
Summers, ME
Russell, JM
TI Two-dimensional model calculations of nitric oxide transport in the
middle atmosphere and comparison with Halogen Occultation Experiment
data
SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
LA English
DT Article
ID LOWER THERMOSPHERE; SEASONAL-VARIATION; UPPER-STRATOSPHERE; THERMAL
STRUCTURE; NUMERICAL-MODEL; ENERGY BUDGET; MIXING RATIOS; WATER-VAPOR;
MESOSPHERE; VARIABILITY
AB A two-dimensional chemical transport model has been used to examine the physical processes governing the transport of high levels of thermospheric nitric oxide (NO) downward into the middle atmosphere. Three different facets of this transport are studied. The first facet involves diffusion from the thermosphere to the summertime mesopause region. The second facet involves downward advection by the mean meridional circulation in the wintertime mesosphere and the effects of planetary wave mixing on the latitudinal gradient of NO. The third facet is the residual amount of NO deposited in the springtime upper stratosphere and its senstivity to the magnitude and duration of the unmixed descent which occurred the previous winter. Comparison of the model with observations by the Halogen Occultation Experiment (HALOE) suggest the following: (1) A clear auroral enhancement in summertime NO exists at 89 km. Model calculations suggest this results from both in situ ionization and dissociation of N-2 as well as downward diffusion from the thermosphere above 100 km. (2) Using HALOE CH4 observations as a tracer, enhanced NO in the wintertime mesosphere is seen to be transported to latitudes as far equatorward as 30 degrees-40 degrees. The model is in good agreement with these observations when planetary wave mixing is included. Without this mixing, the. enhanced NO remains confined to high latitudes that are not observed by HALOE in winter. (3) The model overestimates the net NO deposited into the upper stratosphere. This appears to be related to the model springtime warming being delayed relative to the real atmosphere. Inclusion of an additional source of drag in the polar stratosphere in late winter yields better agreement with observations.
C1 NASA, LANGLEY RES CTR, DIV ATMOSPHER SCI, HAMPTON, VA 23665 USA.
RP Siskind, DE (reprint author), USN, RES LAB, EO HULBURT CTR SPACE RES, CODE 7641, 4555 OVERLOOK AVE SW, WASHINGTON, DC 20375 USA.
NR 60
TC 65
Z9 65
U1 0
U2 4
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA
SN 2169-897X
J9 J GEOPHYS RES-ATMOS
JI J. Geophys. Res.-Atmos.
PD FEB 20
PY 1997
VL 102
IS D3
BP 3527
EP 3545
DI 10.1029/96JD02970
PG 19
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA WK266
UT WOS:A1997WK26600002
ER
PT J
AU Kumer, JB
Kawa, SR
Roche, AE
Mergenthaler, JL
Smith, SE
Taylor, FW
Connell, PS
Douglass, AR
AF Kumer, JB
Kawa, SR
Roche, AE
Mergenthaler, JL
Smith, SE
Taylor, FW
Connell, PS
Douglass, AR
TI UARS first global N2O5 data sets: Application to a stratospheric warming
event in January 1992
SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
LA English
DT Article
ID SIMULTANEOUS INSITU MEASUREMENTS; DIODE-LASER SPECTROMETER; NORTHERN
WINTER 1991/92; MESOSPHERIC SOUNDER; REACTIVE NITROGEN; NO2; MODEL;
EVOLUTION; CLAES; O-3
AB For the first time, global measurements of N2O5 are available for study. N2O5 has long been a missing link in large-scale observations of stratospheric nitrogen species, the chemical family that comprises the major global loss cycle for ozone above about 25 km [McElroy et al., 1992]. N2O5 is also an important intermediate in conversion of NOx to HNO3, thus limiting the effect of nitrogen-catalyzed ozone destruction below about 25 km [Fahey et al., 1993]. The new N2O5 observations come from both the Cryogenic Limb Array Etalon Spectrometer (CLAES) and Improved Stratospheric and Mesospheric Sounder (ISAMS) instruments on the Upper Atmosphere Research Satellite (UARS), providing near-global coverage at high spatial and temporal resolution for almost 20 months. Here we focus on data obtained near 40 km during a stratospheric warming in January 1992. The N2O5 fields show globally coherent structures with large variation in response to global transport coupled with highly temperature dependent chemistry. Comparison of the data with chemistry and transport models indicates that our understanding of processes controlling N2O5 amounts and the interaction with other reactive nitrogen Species is largely accurate under most conditions; however, an exceptional disagreement is found in the prolonged polar dark. This example demonstrates the utility of global data to understand the combined effects of chemistry and transport on N2O5 under a wide range of conditions.
C1 LAWRENCE LIVERMORE NATL LAB, LIVERMORE, CA 94550 USA.
NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA.
UNIV OXFORD, DEPT PHYS, OXFORD OX1 2JD, ENGLAND.
RP Kumer, JB (reprint author), LOCKHEED PALO ALTO RES LABS, 3251 HANOVER ST, PALO ALTO, CA 94304 USA.
RI Douglass, Anne/D-4655-2012; Kawa, Stephan/E-9040-2012
NR 50
TC 15
Z9 15
U1 0
U2 0
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA
SN 2169-897X
J9 J GEOPHYS RES-ATMOS
JI J. Geophys. Res.-Atmos.
PD FEB 20
PY 1997
VL 102
IS D3
BP 3575
EP 3582
DI 10.1029/96JD03055
PG 8
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA WK266
UT WOS:A1997WK26600005
ER
PT J
AU Beyerle, G
Luo, BP
Neuber, R
Peter, T
McDermid, IS
AF Beyerle, G
Luo, BP
Neuber, R
Peter, T
McDermid, IS
TI Temperature dependence of ternary solution particle volumes as observed
by lidar in the Arctic stratosphere during winter 1992/1993
SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
LA English
DT Article
ID SULFURIC-ACID; AEROSOL MEASUREMENTS; PHYSICAL STATE; CLOUDS; DROPLETS;
GROWTH; SPITSBERGEN; BACKSCATTER; INVERSION; HNO3
AB Multiwavelength lidar measurements of stratospheric aerosols performed at the Arctic Network for the Detection of Stratospheric Change station on Spitsbergen during winter 1992/1993 are analyzed. Altitude profiles of particle median radius and volume density are derived for measurements with aerosol depolarization smaller than 0.01. Below an altitude corresponding to 450 K potential temperature the Pinatubo aerosol layer dominated the stratospheric aerosol content with volume densities df more than 5 mu m(3) cm(-3), whereas above 450 K, volume densities were close to background values of 0.1 mu m(3) cm(-3). However, at all altitude levels between 350 and 550 K, volume densities consistently increased by a factor of 2-30 when temperatures approached the frost point. The observations are compared to results from thermodynamic model calculations at altitude levels of 400, 440, and 480 K. Good agreement between the observed and theoretically derived temperature dependencies of volume density suggests that nondepolarizing polar stratospheric cloud particles, as well as volcanic aerosols, at low temperatures are composed of a ternary liquid solution of sulfuric and nitric acid. At all altitude levels, model results indicated more than 90% HNO3 gas phase depletion as temperatures approached the frost point. A mean profile of total H2SO4 volume mixing ratio is derived, decreasing from about 4 parts per billion by volume (ppbv) at 350 K to about 0.5 ppbv above 450 K.
C1 UNIV MUNICH, LEHRSTUHL BIOKLIMATOL & IMMISS FORSCH, D-85354 FREISING, GERMANY.
ALFRED WEGENER INST POLAR & MARINE RES, D-14473 POTSDAM, GERMANY.
MAX PLANCK INST CHEM, D-55122 MAINZ, GERMANY.
RP Beyerle, G (reprint author), CALTECH, TABLE MT FACIL, JET PROP LAB, WRIGHTWOOD, CA 92397 USA.
RI Neuber, Roland/B-4923-2014;
OI Neuber, Roland/0000-0001-7382-7832; Beyerle, Georg/0000-0003-1215-2418
NR 32
TC 25
Z9 25
U1 0
U2 1
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA
SN 2169-897X
J9 J GEOPHYS RES-ATMOS
JI J. Geophys. Res.-Atmos.
PD FEB 20
PY 1997
VL 102
IS D3
BP 3603
EP 3609
DI 10.1029/96JD03385
PG 7
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA WK266
UT WOS:A1997WK26600007
ER
PT J
AU Thomason, LW
Kent, GS
Trepte, CR
Poole, LR
AF Thomason, LW
Kent, GS
Trepte, CR
Poole, LR
TI A comparison of the stratospheric aerosol background periods of 1979 and
1989-1991
SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
LA English
DT Article
ID AIRCRAFT SULFUR EMISSIONS; SAM-II; EXTINCTION MEASUREMENTS; CORRELATIVE
MEASUREMENTS; SATELLITE EXPERIMENTS; VOLCANIC AEROSOL; MT-PINATUBO;
SAGE; LIDAR; DUSTSONDES
AB A comparison of global stratospheric aerosol levels measured in 1979 by the Stratospheric Aerosol and Gas Experiment (SAGE) and in 1989-1991 by SAGE II is presented. These periods exhibit the lowest stratospheric aerosol levels in the era of modern measurements and are often referred to as background periods. We find that, depending on latitude, the 1-mu m aerosol optical depth in 1989-1991 was 10 to 30% higher than that observed in 1979. We demonstrate that the latter period (prior to the June 1991 eruption of Mount Pinatubo) was characterized by an ongoing global recovery from the eruptions of El Chichon in 1982 and Nevado del Ruiz in 1985, with a further complication introduced by the February 1990 Kelut eruption. Therefore the differences between 1979 and 1989-1991 cannot be completely attributed to nonvolcanic sources.
C1 SCI & TECHNOL CORP, HAMPTON, VA 23666 USA.
SCI APPLICAT INT CORP, HAMPTON, VA 23666 USA.
RP Thomason, LW (reprint author), NASA, LANGLEY RES CTR, DIV ATMOSPHER SCI, MAIL STOP 475, HAMPTON, VA 23681 USA.
OI Thomason, Larry/0000-0002-1902-0840
NR 29
TC 59
Z9 61
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 FEB 20
PY 1997
VL 102
IS D3
BP 3611
EP 3616
DI 10.1029/96JD02960
PG 6
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA WK266
UT WOS:A1997WK26600008
ER
PT J
AU Borrmann, S
Solomon, S
Dye, JE
Baumgardner, D
Kelly, KK
Chan, KR
AF Borrmann, S
Solomon, S
Dye, JE
Baumgardner, D
Kelly, KK
Chan, KR
TI Heterogeneous reactions on stratospheric background aerosols, volcanic
sulfuric acid droplets, and type I polar stratospheric clouds: Effects
of temperature fluctuations and differences in particle phase
SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
LA English
DT Article
ID SITU MEASUREMENTS; GROWTH; REMOVAL; HNO3
AB Northern hemispheric ER-2 (NASA) data from stratospheric aerosol measurements during background conditions, periods disturbed by the influence of Mount Pinatubo, ana polar stratospheric cloud (PSC) type I events are used to study the heterogeneous reactions of ClONO2 with H2O and of HOCl and ClONO2 with HCl in comparison to the gas phase reaction rate of OH with HCl. To calculate the reaction rates, the measured data of pressure, temperature, water vapor, and aerosol surface are utilized together with recent laboratory results for the heterogeneous reactive uptake coefficients. Because observations are limited, the mixing ratios of the gas phase species entering these rate calculations (i.e., ClONO2, HOCl, HCl, and N2O5) are taken from a two-dimensional model. It is found that in dense volcanic clouds at temperatures below 200 K the resulting heterogeneous reaction rates of chlorine activation can be of similar magnitude as the gas phase reaction rate. The heterogeneous rates in PSCs can exceed the gas phase fates by more than 2 orders of magnitude. For the ClONO2 and HOCl reactions the measured aerosol surfaces during the PSC events are treated both as liquid (e.g., ternary solution) droplets and: as solid NAT to compare the effects of the different phases. The reaction rates on NAT are significantly lower than on liquid droplets. Indeed, this study shows that a transition from liquid ternary solutions to NAT is expected to reduce the rate of chlorine activation based on present chemical understanding and on observed aerosol surface areas, Additionally, the effect of temperature and surface area fluctuations on the heterogeneous reaction rates is discussed.
C1 NOAA, AERON LAB, BOULDER, CO 80303 USA.
NATL CTR ATMOSPHER RES, BOULDER, CO 80307 USA.
NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA.
RP Borrmann, S (reprint author), UNIV MAINZ, INST ATMOSPHER PHYS, BECHERWEG 21, D-55099 MAINZ, GERMANY.
RI Borrmann, Stephan/E-3868-2010
NR 16
TC 32
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 FEB 20
PY 1997
VL 102
IS D3
BP 3639
EP 3648
DI 10.1029/96JD02976
PG 10
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA WK266
UT WOS:A1997WK26600010
ER
PT J
AU Rosenfield, JE
Considine, DB
Meade, PE
Bacmeister, JT
Jackman, CH
Schoeberl, MR
AF Rosenfield, JE
Considine, DB
Meade, PE
Bacmeister, JT
Jackman, CH
Schoeberl, MR
TI Stratospheric effects of Mount Pinatubo aerosol studied with a coupled
two-dimensional model
SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
LA English
DT Article
ID ATMOSPHERIC HEATING RATE; MT-PINATUBO; SULFURIC-ACID; 2-DIMENSIONAL
MODEL; MIDDLE ATMOSPHERE; SIZE DISTRIBUTION; OZONE DEPLETION; TROPICAL
OZONE; NIMBUS-7 SBUV; POLAR VORTEX
AB A new interactive radiative-dynamical-chemical zonally averaged two-dimensional model has been developed at Goddard Space Flight Center. The model includes a linear planetary wave parameterization featuring wave-mean flow interaction and the direct calculation of eddy mixing from planetary wave dissipation. It utilizes family gas phase chemistry approximations and includes heterogeneous chemistry on the surfaces of both stratospheric sulfate aerosols and polar stratospheric clouds. This model has been used to study the effects of the sulfate aerosol cloud formed by the eruption of Mount Pinatubo in June 1991 on stratospheric temperatures, dynamics, and chemistry. Aerosol extinctions and surface area densities were constrained by satellite observations and were used to compute the aerosol effects on radiative heating rates, photolysis rates, and heterogeneous chemistry. The net predicted perturbations to the column ozone amount were low-latitude depletions of 2-3% and northern and southern high-latitude depletions of 10-12%, in good agreement with observations. In the low latitudes a depletion of roughly 1-2% was due to the altered circulation (increased upwelling) resulting from the perturbation of the heating rates, with the heterogeneous chemistry and photolysis rate perturbations contributing roughly 0.5% each. In the high latitudes the computed ozone column depletions were mainly a result of heterogeneous chemistry occurring on the surfaces of the volcanic aerosol. Temperature anomalies predicted were a low-latitude warming peaking at 2.5 K in mid-1992 and high-latitude coolings of 1-2 K which were associated with the high-latitude ozone reductions. The sensitivity of the predicted perturbations to changes in the specification of the planetary wave forcings was examined. The maximum globally averaged column ozone depletions ranged from 2 to 4% for the cases studied.
C1 USN, RES LAB, WASHINGTON, DC 20375 USA.
GEN SCI CORP, LAUREL, MD USA.
APPL RES CORP, LANDOVER, MD 20785 USA.
RP Rosenfield, JE (reprint author), NASA, GODDARD SPACE FLIGHT CTR, CODE 916, GREENBELT, MD 20771 USA.
RI Jackman, Charles/D-4699-2012
NR 64
TC 74
Z9 74
U1 0
U2 1
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA
SN 2169-897X
J9 J GEOPHYS RES-ATMOS
JI J. Geophys. Res.-Atmos.
PD FEB 20
PY 1997
VL 102
IS D3
BP 3649
EP 3670
DI 10.1029/96JD03820
PG 22
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA WK266
UT WOS:A1997WK26600011
ER
PT J
AU Menzies, RT
Tratt, DM
AF Menzies, RT
Tratt, DM
TI Airborne lidar observations of tropospheric aerosols during the Global
Backscatter Experiment (GLOBE) Pacific circumnavigation missions of 1989
and 1990
SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
LA English
DT Article
ID PINATUBO VOLCANIC AEROSOL; ATMOSPHERIC AEROSOL; STRATOSPHERIC AEROSOL;
MAUNA-LOA; CO2-LASER WAVELENGTHS; CO2 WAVELENGTHS; ASIAN DUST; HAWAII;
CALIFORNIA; EVOLUTION
AB Tropospheric and lower stratospheric aerosol backscatter profiles were obtained with an airborne backscatter lidar at 9.25-mu m wavelength during the NASA Global Backscatter Experiment (GLOBE) airborne field campaigns in November 1989 and May/June 1990. The range of latitudes extended from 70 degrees N to 62 degrees S over the Pacific Ocean basin. The data provide evidence that the tropics are an effective sink for aerosol particles in the lidar-active size range, most likely through efficient wet deposition processes. A reduction of planetary boundary layer (PBL) thickness and aerosol mass density was observed within the tropical regions of enhanced cumulus convection. PBL thickness maxima were consistently observed in the southern hemisphere at Subtropical and high latitudes. The downward transport of volcanic aerosol from the February 1990 Kelut eruption into the upper troposphere was observed in the southern hemisphere during the May/June 1990 period. A springtime enhancement of aerosol in the middle troposphere, due to convection and transport of surface material, was observed in both hemispheres, although the seasonal enhancement was much more dramatic in the northern hemisphere due to the influence of the Asian continental source. Above the PBL the observed springtime enhancement was in the form of extensive layers, with the high-altitude layers reaching the midlatitude tropopause near 140 degrees E longitude.
RP Menzies, RT (reprint author), CALTECH, JET PROP LAB, MS 168-214, 4800 OAK GROVE DR, PASADENA, CA 91109 USA.
RI Tratt, David/A-7884-2009
OI Tratt, David/0000-0002-3942-6848
NR 40
TC 10
Z9 10
U1 0
U2 0
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA
SN 2169-897X
J9 J GEOPHYS RES-ATMOS
JI J. Geophys. Res.-Atmos.
PD FEB 20
PY 1997
VL 102
IS D3
BP 3701
EP 3714
DI 10.1029/96JD03405
PG 14
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA WK266
UT WOS:A1997WK26600014
ER
PT J
AU Caudill, TR
Flittner, DE
Herman, BM
Torres, O
McPeters, RD
AF Caudill, TR
Flittner, DE
Herman, BM
Torres, O
McPeters, RD
TI Evaluation of the pseudo-spherical approximation for backscattered
ultraviolet radiances and ozone retrieval
SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
LA English
DT Article
AB The pseudo-spherical approximation for solving the radiative transfer equation has been used for many years in an attempt to account for the sphericity of the atmosphere. However, even with this ''correction'' there has been some uncertainty about the accuracy of the radiances calculated by using this method at large solar zenith angles. With a new model for numerically solving the radiative transfer equation in a spherical atmosphere the accuracy of the pseudo-spherical approximation can now be evaluated. The comparisons between the pseudospherical and spherical models presented in this paper for backscattered ultraviolet (BUV) radiances show virtually no difference for the nadir direction. The off-nadir radiances, however, show large differences (+/-8%) for a solar zenith angle of 85 degrees and depend on the solar zenith angle and azimuth angle as well as the view angle. These differences increase rapidly at larger solar zenith angles to nearly 20% at 88 degrees. This disagreement is primarily caused by the incorrect attenuation of the solar radiation along the observers' line of sight in the pseudo-spherical method. Differences are also exhibited in the multiple-scatter component but are generally much smaller than the solar attenuation term. In general, the resultant error in total ozone estimation can be as large as 6% but is less than 1% for the Nimbus 7 total ozone mapping spectrometer.
C1 UNIV ARIZONA, INST ATMOSPHER PHYS, TUCSON, AZ 85721 USA.
NASA, GODDARD SPACE FLIGHT CTR, ATMOSPHERES LAB, GREENBELT, MD 20771 USA.
HUGHES STX CORP, GREENBELT, MD 20770 USA.
RI McPeters, Richard/G-4955-2013; Torres, Omar/G-4929-2013
OI McPeters, Richard/0000-0002-8926-8462;
NR 17
TC 34
Z9 34
U1 0
U2 2
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA
SN 2169-897X
J9 J GEOPHYS RES-ATMOS
JI J. Geophys. Res.-Atmos.
PD FEB 20
PY 1997
VL 102
IS D3
BP 3881
EP 3890
DI 10.1029/96JD03266
PG 10
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA WK266
UT WOS:A1997WK26600026
ER
PT J
AU Tuck, AF
Brune, WH
Hipskind, RS
AF Tuck, AF
Brune, WH
Hipskind, RS
TI Airborne Southern Hemisphere Ozone Experiment Measurements for Assessing
the Effects of Stratospheric Aircraft (ASHOE/MAESA): A road map
SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
LA English
DT Article
AB ASHOE/MAESA used instruments aboard the ER-2 aircraft to study transport, photochemistry, radiation, and microphysics in the lower stratosphere over a range of seasons and latitudes. During the period from February tp November 1994 the ER-2 aircraft flew the suite of instruments between 60 degrees N and 70 degrees S in the longitude sector 115 degrees W to 160 degrees E. Of the 45 flights, 28 were entirely in the southern hemisphere between March and October, 6 were from Hawaii, 2 crossed the tropics between Hawaii and Fiji, and the remainder were from northern California. Data from these and associated ground-based, balloon-borne, and satellite instruments were combined with a variety of operational and research meteorological models to guide the flight planning and to interpret the results. The scientific rationale for the mission is given and the aircraft payload listed. A synopsis of the flights is supplied.
C1 PENN STATE UNIV, DEPT METEOROL, UNIVERSITY PK, PA 16802 USA.
NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA.
RP Tuck, AF (reprint author), NOAA, AERON LAB, 325 BROADWAY, R-E AL 6, BOULDER, CO 80303 USA.
RI Tuck, Adrian/F-6024-2011
OI Tuck, Adrian/0000-0002-2074-0538
NR 1
TC 21
Z9 21
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 FEB 20
PY 1997
VL 102
IS D3
BP 3901
EP 3904
DI 10.1029/96JD02745
PG 4
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA WK266
UT WOS:A1997WK26600029
ER
PT J
AU Kawa, SR
Newman, PA
Lait, LR
Schoeberl, MR
Stimpfle, RM
Kohn, DW
Webster, CR
May, RD
Baumgardner, D
Dye, JE
Wilson, JC
Chan, KR
Loewenstein, M
AF Kawa, SR
Newman, PA
Lait, LR
Schoeberl, MR
Stimpfle, RM
Kohn, DW
Webster, CR
May, RD
Baumgardner, D
Dye, JE
Wilson, JC
Chan, KR
Loewenstein, M
TI Activation of chlorine in sulfate aerosol as inferred from aircraft
observations
SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
LA English
DT Article
ID POLAR STRATOSPHERIC CLOUD; NITRIC-ACID TRIHYDRATE; TOTAL REACTIVE
NITROGEN; SULFURIC-ACID; SIZE DISTRIBUTIONS; PHYSICAL-CHEMISTRY;
VAPOR-PRESSURES; PARTICLE-SIZE; JANUARY 24; VORTEX
AB The abundance of reactive chlorine in the lower stratosphere is observed to increase sharply with exposure to temperatures below about 195 K, a temperature which is near the nitric acid trihydrate (NAT) equilibrium condensation point. Measurements from the NASA ER-2 aircraft and a model of chemistry along back trajectories are used to examine the mechanism for this apparent temperature threshold in chlorine activation. The flight of July 28, 1994, from the Airborne Southern Hemisphere Ozone Experiment/Measurements for Assessing the Effects of Stratospheric Aircraft (ASHOE/MAESA) campaign in the southern hemisphere is studied because it provides measurements in ail ongoing activation episode. Isentropic back trajectories from the aircraft sampling points indicate that the sampled air was cooling at the rate of 20 to 30 K d(-1) to temperatures below the NAT condensation point and had not been below the NAT condensation point prior to that for at least 10 days. Hence the observed amount of active chlorine should be kinetically limited by the recent parcel temperatures. The measurements show enhanced ClO and decreased HCl at temperatures below 195 K even in the absence of significant polar stratospheric cloud particle surface area. The model of chemistry along back trajectories, constrained by the ER-2 chemical and microphysical measurements, indicates that an initial inorganic chlorine (Cl-y) partitioning of approximately half HCl and half ClONO2 is consistent with the observations. At this initial Cl-y partitioning, the model using heterogeneous reactions on liquid sulfate and ternary solutions with the most recent sticking coefficient evaluations closely reproduces the latitude gradient and temperature threshold of chlorine activation observed in the data. The sudden increase in activation in the model is a result of the steep exponential temperature dependence of the sticking coefficient for HCl + ClONO2 on liquid aqueous solutions.
C1 HUGHES STX CORP, GREENBELT, MD USA.
HARVARD UNIV, DEPT CHEM, CAMBRIDGE, MA 02138 USA.
CALTECH, JET PROP LAB, PASADENA, CA 91125 USA.
NATL CTR ATMOSPHER RES, BOULDER, CO 80307 USA.
UNIV DENVER, DEPT ENGN, DENVER, CO 80208 USA.
NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA.
RP Kawa, SR (reprint author), NASA, GODDARD SPACE FLIGHT CTR, CODE 916, GREENBELT, MD 20771 USA.
RI Newman, Paul/D-6208-2012; Kawa, Stephan/E-9040-2012
OI Newman, Paul/0000-0003-1139-2508;
NR 70
TC 38
Z9 38
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 FEB 20
PY 1997
VL 102
IS D3
BP 3921
EP 3933
DI 10.1029/96JD01992
PG 13
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA WK266
UT WOS:A1997WK26600031
ER
PT J
AU Gao, RS
Fahey, DW
Salawitch, RJ
Lloyd, SA
Anderson, DE
Demajistre, R
McElroy, CT
Woodbridge, EL
Wamsley, RC
Donnelly, SG
DelNegro, LA
Proffitt, MH
Stimpfle, RM
Kohn, DW
Kawa, R
Lait, LR
Loewenstein, M
Podolske, JR
Keim, ER
Dye, JE
Wilson, JC
Chan, KR
AF Gao, RS
Fahey, DW
Salawitch, RJ
Lloyd, SA
Anderson, DE
Demajistre, R
McElroy, CT
Woodbridge, EL
Wamsley, RC
Donnelly, SG
DelNegro, LA
Proffitt, MH
Stimpfle, RM
Kohn, DW
Kawa, R
Lait, LR
Loewenstein, M
Podolske, JR
Keim, ER
Dye, JE
Wilson, JC
Chan, KR
TI Partitioning of the reactive nitrogen reservoir in the lower
stratosphere of the southern hemisphere: Observations and modeling
SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
LA English
DT Article
ID IN-SITU MEASUREMENTS; ANTARCTIC OZONE HOLE; INSITU MEASUREMENTS; ER-2
AIRCRAFT; SULFURIC-ACID; 72-DEGREES-S LATITUDE; SUPERSONIC AIRCRAFT;
VOLCANIC AEROSOLS; CHLORINE RADICALS; SULFATE AEROSOLS
AB Measurements of nitric oxide (NO), nitrogen dioxide (NO2), and total reactive nitrogen (NOy = NO + NO2 + NO3 + HNO3 + ClONO2 + 2N(2)O(5) + ...) were made during austral fall, winter, and spring 1994 as part of the NASA Airborne Southern Hemisphere Ozone Experiment/Measurements for Assessing the Effects of Stratospheric Aircraft mission. Comparisons between measured NO2 values and those calculated using a steady state (SS) approximation are presented for flights at mid and high latitudes. The SS results agree with the measurements to within 8%, suggesting that the kinetic rate coefficients and calculated NO2 photolysis rate used in the SS approximation are reasonably accurate for conditions in the lower stratosphere. However, NO2 values observed in the Concorde exhaust plume were significantly less than SS values. Calculated NO2 photolysis rates showed good agreement with values inferred from solar flux measurements, indicating a strong self-consistency in our understanding of UV radiation transmission in the lower stratosphere. Model comparisons using a full diurnal, photochemical steady state model also show good agreement with the NO and NO2 measurements, suggesting that the reactions affecting the partitioning of the NOy reservoir are well understood in the lower stratosphere.
C1 UNIV COLORADO, COOPERAT INST RES ENVIRONM SCI, BOULDER, CO 80309 USA.
CALTECH, JET PROP LAB, PASADENA, CA 91109 USA.
JOHNS HOPKINS UNIV, APPL PHYS LAB, LAUREL, MD 20723 USA.
ATMOSPHER ENVIRONM SERV, DOWNSVIEW, ON M3H 5T4, CANADA.
UNIV CALIF SAN DIEGO, SCRIPPS INST OCEANOG, LA JOLLA, CA 92093 USA.
UNIV COLORADO, DEPT CHEM & BIOCHEM, BOULDER, CO 80309 USA.
HARVARD UNIV, DEPT CHEM, CAMBRIDGE, MA 02138 USA.
NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA.
NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA.
NATL CTR ATMOSPHER RES, MMM, BOULDER, CO 80307 USA.
UNIV DENVER, DEPT ENGN, DENVER, CO 80208 USA.
RP Gao, RS (reprint author), NOAA, AERON LAB, 325 BROADWAY, R-E-AL6, BOULDER, CO 80303 USA.
RI Salawitch, Ross/B-4605-2009; Kawa, Stephan/E-9040-2012; Gao,
Ru-Shan/H-7455-2013; Fahey, David/G-4499-2013
OI Salawitch, Ross/0000-0001-8597-5832; Fahey, David/0000-0003-1720-0634
NR 60
TC 48
Z9 48
U1 1
U2 5
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA
SN 2169-897X
J9 J GEOPHYS RES-ATMOS
JI J. Geophys. Res.-Atmos.
PD FEB 20
PY 1997
VL 102
IS D3
BP 3935
EP 3949
DI 10.1029/96JD01967
PG 15
WC Meteorology & Atmospheric Sciences
SC Meteorology & Atmospheric Sciences
GA WK266
UT WOS:A1997WK26600032
ER
PT J
AU Huang, J
AF Huang, J
TI A high-gain circularly polarized Ka-band microstrip reflect array
SO MICROWAVE AND OPTICAL TECHNOLOGY LETTERS
LA English
DT Article
DE reflect-array antenna; microstrip; Ka band; circular polarization
ID ANTENNA
AB A half-meter 32-GHz, circularly polarized microstrip reflect-array antenna has been dec;eloped. Excellent efficiency, good bandwidth, and low average side-lobe and cross-polarization levels are achieved. It is believed that this is electrically the largest microstrip reflect array (6924 elements) that has ever been developed. (C) 1997 John Wiley & Sons, Inc.
RP Huang, J (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA.
NR 13
TC 3
Z9 3
U1 0
U2 0
PU JOHN WILEY & SONS INC
PI NEW YORK
PA 605 THIRD AVE, NEW YORK, NY 10158-0012
SN 0895-2477
J9 MICROW OPT TECHN LET
JI Microw. Opt. Technol. Lett.
PD FEB 20
PY 1997
VL 14
IS 3
BP 163
EP 166
DI 10.1002/(SICI)1098-2760(19970220)14:3<163::AID-MOP8>3.0.CO;2-I
PG 4
WC Engineering, Electrical & Electronic; Optics
SC Engineering; Optics
GA WE110
UT WOS:A1997WE11000008
ER
PT J
AU Webb, RS
Rind, DH
Lehman, SJ
Healy, RJ
Sigman, D
AF Webb, RS
Rind, DH
Lehman, SJ
Healy, RJ
Sigman, D
TI Influence of ocean heat transport on the climate of the Last Glacial
Maximum
SO NATURE
LA English
DT Article
ID NORTH-ATLANTIC; SURFACE-TEMPERATURE; ICE-AGE; WATER CIRCULATION;
RECONSTRUCTIONS; MODEL; DEEP; RECORD
AB A series of climate simulations using an atmospheric general circulation model shows that maintaining ocean heat transport at close to present-day values, but with otherwise glacial boundary conditions, leads to an enhanced cooling, particularly in the tropics. This is in agreement with recent geochemical evidence from fossil corals, ground waters, and ice. Near-modern ocean heat transport may have been sustained in all ocean basins during the Last Glacial Maximum in order to balance the formation and export of Glacial North Atlantic Intermediate Water.
C1 NASA,GODDARD INST SPACE STUDIES,NEW YORK,NY 10025.
UNIV COLORADO,DEPT GEOL SCI,BOULDER,CO 80309.
UNIV COLORADO,INSTAAR,BOULDER,CO 80309.
WOODS HOLE OCEANOG INST,WOODS HOLE,MA 02543.
RP Webb, RS (reprint author), NOAA,NATL GEOPHYS DATA CTR,PALEOCLIMATOL PROGRAM,325 BROADWAY,BOULDER,CO 80303, USA.
RI Sigman, Daniel/A-2649-2008; Healy, Richard/J-9214-2015
OI Sigman, Daniel/0000-0002-7923-1973; Healy, Richard/0000-0002-5098-8921
NR 44
TC 121
Z9 126
U1 0
U2 9
PU MACMILLAN MAGAZINES LTD
PI LONDON
PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW
SN 0028-0836
J9 NATURE
JI Nature
PD FEB 20
PY 1997
VL 385
IS 6618
BP 695
EP 699
DI 10.1038/385695a0
PG 5
WC Multidisciplinary Sciences
SC Science & Technology - Other Topics
GA WJ423
UT WOS:A1997WJ42300037
ER
PT J
AU Covault, C
AF Covault, C
TI Shuttle retrieves Hubble; Russians launch to Mir
SO AVIATION WEEK & SPACE TECHNOLOGY
LA English
DT Article
C1 NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058.
RP Covault, C (reprint author), KENNEDY SPACE CTR SPACEPORT,KENNEDY SPACE CTR,FL 32899, USA.
NR 0
TC 0
Z9 0
U1 0
U2 0
PU MCGRAW HILL INC
PI NEW YORK
PA 1221 AVENUE OF THE AMERICAS, NEW YORK, NY 10020
SN 0005-2175
J9 AVIAT WEEK SPACE TEC
JI Aviat. Week Space Technol.
PD FEB 17
PY 1997
VL 146
IS 7
BP 53
EP 55
PG 3
WC Engineering, Aerospace
SC Engineering
GA WH454
UT WOS:A1997WH45400014
ER
PT J
AU Xu, KM
Noor, AK
Tang, YY
AF Xu, KM
Noor, AK
Tang, YY
TI Three-dimensional solutions for free vibrations of initially-stressed
thermoelectroelastic multilayered plates
SO COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING
LA English
DT Article
ID 3-DIMENSIONAL SOLUTIONS; BIDIRECTIONAL COMPOSITES; ACTUATORS
AB Analytic three-dimensional solutions are presented for the free vibration frequencies of initially stressed hybrid multilayered composite plates. The plates consist of a combination of fiber-reinforced cross-ply and piezothermoelastic layers. The initial stresses are generated by either a temperature change and/or an electric field. Sensitivity coefficients are also evaluated and used to study the sensitivity of the vibrational response to variations in the different mechanical, thermal and piezoelectric material properties of the plate. Both the temperature change and the electric field are assumed to be independent of the surface coordinates, but have arbitrary variation through the thickness of the plate. A linear constitutive model is used, and the material properties are assumed to be independent of both the temperature and the electric field. The thermoelectroelastic response of the plate is subjected to time-varying displacements, strains and stresses. A mixed formulation is used with the fundamental unknowns consisting of the three increments of the transverse stress components and the three displacement components. Each of the fundamental unknowns is expressed in terms of a double Fourier series in the Cartesian surface coordinates. A state space approach is used to generate the vibrational response and to evaluate the sensitivity coefficients. Approximate and closed-form expressions are developed relating the vibration frequency for the initially-stressed plate to the corresponding frequency of the unstressed plate. A nonlinear eigen-derivative theory is applied to obtain the sensitivity coefficients of the vibration frequency of the plate. Approximate expressions for the sensitivity coefficients are also derived. Extensive numerical results are presented showing the effects of variation in the plate thickness and the location of the piezothermoelastic layers on the vibration frequencies and their sensitivity coefficients.
C1 UNIV VIRGINIA,NASA,LANGLEY RES CTR,CTR ADV COMPUTAT TECHNOL,HAMPTON,VA 23681.
NR 17
TC 47
Z9 51
U1 1
U2 3
PU ELSEVIER SCIENCE SA LAUSANNE
PI LAUSANNE
PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND
SN 0045-7825
J9 COMPUT METHOD APPL M
JI Comput. Meth. Appl. Mech. Eng.
PD FEB 15
PY 1997
VL 141
IS 1-2
BP 125
EP 139
DI 10.1016/S0045-7825(96)01065-1
PG 15
WC Engineering, Multidisciplinary; Mathematics, Interdisciplinary
Applications; Mechanics
SC Engineering; Mathematics; Mechanics
GA WM953
UT WOS:A1997WM95300007
ER
PT J
AU Shih, TH
AF Shih, TH
TI Some developments in computational modeling of turbulent flows
SO FLUID DYNAMICS RESEARCH
LA English
DT Article; Proceedings Paper
CT International Symposium on Mathematical Modelling of Turbulent Flows
CY DEC 18-20, 1995
CL UNIV OF TOKYO, TOKYO, JAPAN
HO UNIV OF TOKYO
ID LOW-REYNOLDS-NUMBER; RENORMALIZATION-GROUP; PRESSURE STRAIN;
BOUNDARY-LAYERS; CHANNEL FLOW; STRESS; EQUATION; GRADIENT
AB In this paper, some recent developments of two turbulence closure schemes at ICOMP, NASA Lewis will be discussed. One is the Reynolds-stress algebraic equation model and the other is the Reynolds-stress transport equation model. Various model constraints required by the rapid distortion theory, the invariant theory and the realizability principle, etc. will be described in the model development. The models discussed are for high-turbulent Reynolds number flows, so that the near-wall turbulence and the low-Reynolds-number turbulence are not discussed here.
RP Shih, TH (reprint author), NASA,LEWIS RES CTR,ICOMP,CTR MODELING TURBULENCE & TRANSIT,22800 CEDAR POINT RD,BROOKPARK,OH 44142, USA.
NR 61
TC 2
Z9 5
U1 0
U2 0
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0169-5983
J9 FLUID DYN RES
JI Fluid Dyn. Res.
PD FEB 15
PY 1997
VL 20
IS 1-6
BP 67
EP 96
DI 10.1016/S0169-5983(96)00041-X
PG 30
WC Mechanics; Physics, Fluids & Plasmas
SC Mechanics; Physics
GA WH783
UT WOS:A1997WH78300006
ER
PT J
AU Taguchi, S
Slavin, JA
Lepping, RP
AF Taguchi, S
Slavin, JA
Lepping, RP
TI IMP 8 observations of traveling compression regions in the mid-tail near
substorm expansion phase onset
SO GEOPHYSICAL RESEARCH LETTERS
LA English
DT Article
ID MAGNETOTAIL; ISEE-3; CONFIGURATION; PLASMOIDS; AVERAGE
AB The large data set returned by the IMP 8 magnetic field investigation has been examined to understand the characteristics of traveling compression regions (TCRs). Using 15 years of the AL index, we identified 565 isolated substorm events with well-developed expansion phase for which IMP 8 was in the mid-tail lobes and providing magnetic field measurements. From this data set, 17 substorms were found to produce the bipolar B(Z)TCRs frequently observed farther down the tail. However, another 14 cases have field compressions during which the field tilts north-then-south, but the maximum B-Z does not reach a positive value, i.e., the B-Z variation is not bipolar. These ''negative B-Z'' compression regions (NCRs) are examined in some detail and found to occur at larger \Z\ values. The usual bipolar B(Z)TCRs, in contrast, are found at smaller \Z\ values closer to lobe-plasma sheet interface. We interpret an NCR as a TCR which is observed at large \Z\ where the growth phase flaring is too strong for the lobe field draping about the plasmoid to produce a positive B-Z between the leading edge and the center of the compression region. Hence, at IMP 8 distances TCRs are often not accompanied by true bipolar B-Z signatures; rather only a north-then-south tilting of the field relative to flared lobe field is observed.
C1 UNIV ELECTROCOMMUN,DEPT ELECT ENGN,CHOFU,TOKYO 182,JAPAN.
RP Taguchi, S (reprint author), NASA,GODDARD SPACE FLIGHT CTR,EXTRATERR PHYS LAB,CODE 696,GREENBELT,MD 20771, USA.
RI Slavin, James/H-3170-2012
OI Slavin, James/0000-0002-9206-724X
NR 13
TC 13
Z9 13
U1 0
U2 0
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009
SN 0094-8276
J9 GEOPHYS RES LETT
JI Geophys. Res. Lett.
PD FEB 15
PY 1997
VL 24
IS 4
BP 353
EP 356
DI 10.1029/97GL00121
PG 4
WC Geosciences, Multidisciplinary
SC Geology
GA WJ181
UT WOS:A1997WJ18100001
ER
PT J
AU Arduini, C
Laneve, G
Herrero, FA
AF Arduini, C
Laneve, G
Herrero, FA
TI Local time and altitude variation of equatorial thermosphere midnight
density maximum (MDM): San Marco drag balance measurements
SO GEOPHYSICAL RESEARCH LETTERS
LA English
DT Article
ID TIDES
AB We present the first study of the local time and altitude variation of the MDM, the density component of the equatorial midnight pressure bulge, an important feature in the nighttime motions of the ionosphere-thermosphere system in the equatorial region. The neutral density data of the San Marco 3 (SM3) and San Marco 5 (SM5) satellites were averaged to obtain 24 hr density variations from April to December in 1971 and 1988. From these variations, the MDM amplitude as a function of altitude and local time was obtained at altitudes from 220 to 400 km at the geographic equator. We show the first evidence of downward phase propagation of the MDM together with a vertical structure not observed before, which may suggest an ionospheric interaction or perhaps a viscous dissipation effect. In 1971, the MDM propagates rather gradually from about 350 to 220 km in about two hours. in 1988, there appear two regions in which the MDM time shows little change with height with a discontinuous jump in between the two regions. The net effect is stilt a downward displacement bf the MDM with local time. The results show significant seasonal and solar activity effects. During low solar activity periods (1971), the MDM occurs earlier in equinox than in solstice for all altitudes, consistent with the seasonal variation of the midnight temperature maximum (MTM). However, with higher solar activity (1988) and at altitudes below 340 km, the MDM occurs earlier in solstice than in equinox, raising new questions on solar activity effects on the relative phases of the tidal oscillations of the neutral density and the neutral temperature.
C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771.
RP Arduini, C (reprint author), UNIV ROME,PROGETTO SAN MARCO,ROME,ITALY.
OI Laneve, Giovanni/0000-0001-6108-9764
NR 10
TC 19
Z9 19
U1 0
U2 1
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009
SN 0094-8276
J9 GEOPHYS RES LETT
JI Geophys. Res. Lett.
PD FEB 15
PY 1997
VL 24
IS 4
BP 377
EP 380
DI 10.1029/97GL00189
PG 4
WC Geosciences, Multidisciplinary
SC Geology
GA WJ181
UT WOS:A1997WJ18100007
ER
PT J
AU Newman, PA
Rosenfield, JE
AF Newman, PA
Rosenfield, JE
TI Stratospheric thermal damping times
SO GEOPHYSICAL RESEARCH LETTERS
LA English
DT Article
ID PLANETARY-WAVES; POLAR VORTEX; PARAMETERIZATION; TEMPERATURES; WINTER
AB Radiative damping of stratospheric temperature waves has wide implications for stratospheric physical processes. Damping is linearly parameterized as proportional to the local temperature. Thermal damping is calculated using the Goddard radiative transfer model and 17 years observations. Damping times of stratospheric temperatures are calculated for each month at all latitudes. These damping times are consistent with previous stratospheric estimates, but show shorter tropical time scales. Damping times range from an annual global average of 28 days (100 hPa) to 4 days (1 hPa). A considerable annual cycle is seen over much of the stratosphere, which is directly related to the annual cycle of temperatures, with longer damping times associated with colder temperatures.
C1 GEN SCI CORP,LAUREL,MD.
RP Newman, PA (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 916,GREENBELT,MD 20771, USA.
RI Newman, Paul/D-6208-2012
OI Newman, Paul/0000-0003-1139-2508
NR 16
TC 37
Z9 37
U1 1
U2 5
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009
SN 0094-8276
J9 GEOPHYS RES LETT
JI Geophys. Res. Lett.
PD FEB 15
PY 1997
VL 24
IS 4
BP 433
EP 436
DI 10.1029/96GL03720
PG 4
WC Geosciences, Multidisciplinary
SC Geology
GA WJ181
UT WOS:A1997WJ18100021
ER
PT J
AU McConnell, JR
Winterle, JR
Bales, RC
Thompson, AM
Stewart, RW
AF McConnell, JR
Winterle, JR
Bales, RC
Thompson, AM
Stewart, RW
TI Physically based inversion of surface snow concentrations of H2O2 to
atmospheric concentrations at South Pole
SO GEOPHYSICAL RESEARCH LETTERS
LA English
DT Article
AB Inversion of chemical records archived in ice cores to atmospheric concentrations requires a detailed understanding of atmosphere-to-snow-to-ice transfer processes. A unique year-round series of surface snow samples, collected from November, 1994 through January, 1996 at South Pole and analyzed for H2O2, were used to test a physically based model for the atmosphere-to-snow component of the overall transfer function. A comparison of photochemical model estimates of atmospheric H2O2, which are in general agreement with the first measurements of atmospheric H2O2 at South Pole, with the inverted atmospheric record (1) demonstrate that the surface snow acts as an excellent archive of atmospheric H2O2 and (2) suggest that snow temperature is the dominant factor determining atmosphere-to-surface snow transfer at South Pole. The estimated annual cycle in atmospheric H2O2 concentration is approximately symmetric about the summer solstice, with a peak value of similar to 280 pptv and a minimum around the winter solstice of similar to 1 pptv, although some asymmetry results from the springtime stratospheric ozone hole over Antarctica.
C1 NASA,GODDARD SPACE FLIGHT CTR,ATMOSPHERES LAB,GREENBELT,MD 20771.
RP McConnell, JR (reprint author), UNIV ARIZONA,DEPT HYDROL & WATER RESOURCES,TUCSON,AZ, USA.
RI Thompson, Anne /C-3649-2014
OI Thompson, Anne /0000-0002-7829-0920
NR 10
TC 23
Z9 23
U1 1
U2 4
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009
SN 0094-8276
J9 GEOPHYS RES LETT
JI Geophys. Res. Lett.
PD FEB 15
PY 1997
VL 24
IS 4
BP 441
EP 444
DI 10.1029/97GL00183
PG 4
WC Geosciences, Multidisciplinary
SC Geology
GA WJ181
UT WOS:A1997WJ18100023
ER
PT J
AU MacMillan, DS
Ma, C
AF MacMillan, DS
Ma, C
TI Atmospheric gradients and the VLBI terrestrial and celestial reference
frames
SO GEOPHYSICAL RESEARCH LETTERS
LA English
DT Article
ID BASE-LINE INTERFEROMETRY
AB Gradients in the atmospheric refractive index can lead to errors in estimated vertical and horizontal station coordinates. These errors produce systematic errors in the terrestrial and celestial reference frames determined from our very long baseline interferometry (VLBI) measurements. Estimation of gradients for our global VLBI data set changes the terrestrial reference frame length scale by -0.7 ppb and produces station position adjustments that vary approximately monotonically with latitude. Estimating gradients reduces the radio source declinations by an amount that peaks at about 0.5 mas near the equator and decreases toward the poles. VLBI gradient estimates are consistent with gradients derived from a global three-dimensional model of assimilated meteorological data. Both indicate that mean atmospheric delay gradients point toward the equator in both the northern and southern hemispheres. The correlation coefficient between VLBI and meteorological model gradients for VLBI sessions for the VLBI antenna at Westford, Massachusetts was 0.56.
RP MacMillan, DS (reprint author), NASA,GODDARD SPACE FLIGHT CTR,NVI INC,CODE 9201,GREENBELT,MD 20771, USA.
RI Ma, Chopo/D-4751-2012
NR 11
TC 39
Z9 43
U1 1
U2 1
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009
SN 0094-8276
J9 GEOPHYS RES LETT
JI Geophys. Res. Lett.
PD FEB 15
PY 1997
VL 24
IS 4
BP 453
EP 456
DI 10.1029/97GL00143
PG 4
WC Geosciences, Multidisciplinary
SC Geology
GA WJ181
UT WOS:A1997WJ18100026
ER
PT J
AU Brown, LL
Golombek, MP
AF Brown, LL
Golombek, MP
TI Tectonic stability of the San Luis Hills, northern Rio Grande rift,
Colorado: Evidence from paleomagnetic measurements
SO GEOPHYSICAL RESEARCH LETTERS
LA English
DT Article
ID NEW-MEXICO; ROTATIONS
AB The San Luis Basin is the largest of four tilted, fault bounded Neogene basins of the northern Rio Grande rift in New Mexico and Colorado. It formed during the second of two episodes of extension beginning in middle Oligocene and extending to the present. The San Luis Hills are an intrarift horst of Oligocene intermediate and basalt rocks preserved in the middle of the San Luis Basin. Previous paleomagnetic and structural studies in the Espanola Basin to the south indicate counterclockwise rotation of that region during the most recent extension. Paleomagnetic samples from the two exposed formations in the San Luis Hills yield a mean direction of inclination = 55.6 degrees and declination = 347.2 degrees (alpha(95) = 6.8 degrees, N=23) that is coincident with the expected Oligocene direction for North America. These rocks show no indication of rotation or severe tilting during rift extension.
C1 CALTECH,JET PROP LAB,DIV EARTH & SPACE SCI,PASADENA,CA 91109.
RP Brown, LL (reprint author), UNIV MASSACHUSETTS,DEPT GEOSCI,AMHERST,MA 01003, USA.
NR 18
TC 0
Z9 0
U1 0
U2 0
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009
SN 0094-8276
J9 GEOPHYS RES LETT
JI Geophys. Res. Lett.
PD FEB 15
PY 1997
VL 24
IS 4
BP 473
EP 476
DI 10.1029/97GL00127
PG 4
WC Geosciences, Multidisciplinary
SC Geology
GA WJ181
UT WOS:A1997WJ18100031
ER
PT J
AU Gupta, KK
AF Gupta, KK
TI Development and application of an integrated multidisciplinary analysis
capability
SO INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING
LA English
DT Article
DE multidisciplinary analysis; FEM; aeroelasticity; aeroservoelasticity
ID EULER
AB The paper presents details of a numerical formulation and associated general-purpose finite element (FE) software developed for the integrated aeroelastic and aeroservoelastic (ASE) analysis of complex engineering systems, encompassing such disciplines as structures, unsteady aerodynamics, and feedback controls. A linear analysis, involving panel methods for derivation of unsteady aerodynamic forces, is achieved by transforming the equations of motion from the frequency to the Laplace domain and formulating a state-space matrix relationship, the related matrices being further augmented by the analog elements such as actuators and filters as well as digital or analog controllers. For non-linear problems, FE-based structural and computational fluid dynamics (CFD) solutions are adopted for the relevant analyses.
Numerical results pertaining to a number of practical problems, obtained by utilizing the associated computer program, are compared to those derived from relevant flight and wind tunnel tests as well as other analyses, and they are presented here in some detail. Such results, involving damping and frequency responses, relate to the stability characteristics of the aerospace vehicles and testify to the efficacy of the present solution procedure.
RP Gupta, KK (reprint author), NASA,DRYDEN FLIGHT RES CTR,EDWARDS AFB,CA, USA.
NR 20
TC 11
Z9 11
U1 1
U2 3
PU JOHN WILEY & SONS LTD
PI W SUSSEX
PA BAFFINS LANE CHICHESTER, W SUSSEX, ENGLAND PO19 1UD
SN 0029-5981
J9 INT J NUMER METH ENG
JI Int. J. Numer. Methods Eng.
PD FEB 15
PY 1997
VL 40
IS 3
BP 533
EP 550
DI 10.1002/(SICI)1097-0207(19970215)40:3<533::AID-NME78>3.3.CO;2-N
PG 18
WC Engineering, Multidisciplinary; Mathematics, Interdisciplinary
Applications
SC Engineering; Mathematics
GA WC804
UT WOS:A1997WC80400009
ER
PT J
AU Bauschlicher, CW
AF Bauschlicher, CW
TI The effect of an electric field on the vibrational frequency of CN
SO INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY
LA English
DT Article
ID BASIS-SETS; CO; HYDROGEN; ABINITIO; SHIFTS
AB Ab initio calculations are used to compute the change in the vibrational frequency of CN with an applied electric field aligned parallel to the bond axis. The effect of the field on the CN- vibrational frequency is of the same magnitude as for CN, but in the opposite direction. These results are compared to previous results for CO. (C) 1997 John Wiley & Sons, Inc.
RP Bauschlicher, CW (reprint author), NASA,AMES RES CTR,MOFFETT FIELD,CA 94035, USA.
NR 22
TC 6
Z9 6
U1 0
U2 2
PU JOHN WILEY & SONS INC
PI NEW YORK
PA 605 THIRD AVE, NEW YORK, NY 10158-0012
SN 0020-7608
J9 INT J QUANTUM CHEM
JI Int. J. Quantum Chem.
PD FEB 15
PY 1997
VL 61
IS 5
BP 859
EP 863
PG 5
WC Chemistry, Physical; Mathematics, Interdisciplinary Applications;
Physics, Atomic, Molecular & Chemical
SC Chemistry; Mathematics; Physics
GA WD275
UT WOS:A1997WD27500011
ER
PT J
AU Nghiem, SV
Martin, S
Perovich, DK
Kwok, R
Drucker, R
Gow, AJ
AF Nghiem, SV
Martin, S
Perovich, DK
Kwok, R
Drucker, R
Gow, AJ
TI A laboratory study of the effect of frost flowers on C band radar
backscatter from sea ice
SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS
LA English
DT Article
ID SCATTERING; SURFACE; SNOW
AB C band images of Arctic sea ice taken by the ERS 1 synthetic aperture radar show transitory regions of enhanced radar backscatter from young sea ice. Published field observations associate this increase with frost flower growth and the capture of blowing snow by the flowers. To investigate the first part of this phenomenon, we carried out a laboratory experiment on the response of C band radar backscatter to frost flowers growing on the surface of newly formed saline ice. The experiment took place in a 5 m by 7 m by 1.2 m deep saline water pool located in a two-story indoor refrigerated facility at the Cold Regions Research and Engineering Laboratory. Sodium chloride ice was grown in this pool at an air temperature of -28 degrees C, The frost flowers first appeared on the ice surface as dendrites and then changed to needles as the ice sheet grew thicker and the surface temperatures became colder. The frost flowers reached to a height of 10-15 mm, and beneath each cluster of frost flowers a slush layer formed to a thickness of approximately 4 mm. Far-field radar measurements of the backscatter from the ice were made at incident angles from 20 degrees to 40 degrees and at approximately 6-hour intervals throughout the 3-day period of the experiment. A backscatter minimum occurred early in the flower growth at the time coincident with an abrupt doubling in the ice surface salinity. Once the full flower coverage was achieved, we removed first the crystal flowers and then the slush layer from the ice surface. The results for these cases show that the crystals have little impact on the backscatter, while the underlying slush patches yield a backscatter increase of 3-5 dB over that of bare ice. The laboratory results suggest that this relative backscatter. increase of approximately 5 dB can be used as an index to mark the full areal coverage of frost flowers.
C1 UNIV WASHINGTON,SCH OCEANOG,SEATTLE,WA 98195.
USA,COLD REG RES & ENGN LAB,HANOVER,NH 03755.
RP Nghiem, SV (reprint author), CALTECH,JET PROP LAB,CTR SPACE MICROELECT TECHNOL,MAIL STOP 300-235,PASADENA,CA 91109, USA.
RI Kwok, Ron/A-9762-2008
OI Kwok, Ron/0000-0003-4051-5896
NR 13
TC 21
Z9 21
U1 1
U2 2
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009
J9 J GEOPHYS RES-OCEANS
JI J. Geophys. Res.-Oceans
PD FEB 15
PY 1997
VL 102
IS C2
BP 3357
EP 3370
DI 10.1029/96JC03208
PG 14
WC Oceanography
SC Oceanography
GA WH737
UT WOS:A1997WH73700012
ER
PT J
AU Bhatt, RT
Palczer, AR
AF Bhatt, RT
Palczer, AR
TI Effects of thermal cycling on thermal expansion and mechanical
properties of SiC fibre-reinforced reaction-bonded Si3N4 composites
SO JOURNAL OF MATERIALS SCIENCE
LA English
DT Article
ID SILICON-NITRIDE; MATRIX COMPOSITES; OXIDATION; STRENGTH; CARBIDE
AB Thermal expansion curves for SiC fibre-reinforced reaction-bonded Si3N4 matrix composites (SiC/RBSN) and unreinforced RBSN were measured from 25 to 1400 degrees C in nitrogen and in oxygen. The effects of fibre/matrix bonding and cycling on the thermal expansion curves and room-temperature tensile properties of unidirectional composites were determined. The measured thermal expansion curves were compared with those predicted from composite theory. Predicted thermal expansion curves parallel to the fibre direction were between the measured curves for the strongly- and weakly-bonded composites, but those normal to the fibre direction for both bonding cases were similar to that of the unreinforced RBSN. Thermal cycling in nitrogen for both bonding cases resulted in no net dimensional changes at room temperature and no loss in tensile properties from the as-fabricated condition. In contrast, thermal cycling in oxygen for both composites caused volume expansion primarily due to internal oxidation of RBSN. Cyclic oxidation affected the mechanical properties of the weakly-bonded SiC/RBSN composites the most, resulting in loss of strain capability beyond matrix fracture and catastrophic, brittle fracture. Increased bonding between the SiC fibre and RBSN matrix due to oxidation of the carbon-rich fibre surface coating and an altered residual stress pattern in the composite due to internal oxidation of the matrix are the main reasons for the poor mechanical performance of these composites.
RP Bhatt, RT (reprint author), NASA, LEWIS RES CTR, CLEVELAND, OH 44135 USA.
NR 16
TC 6
Z9 6
U1 1
U2 6
PU SPRINGER
PI NEW YORK
PA 233 SPRING ST, NEW YORK, NY 10013 USA
SN 0022-2461
J9 J MATER SCI
JI J. Mater. Sci.
PD FEB 15
PY 1997
VL 32
IS 4
BP 1039
EP 1047
DI 10.1023/A:1018586624315
PG 9
WC Materials Science, Multidisciplinary
SC Materials Science
GA WJ853
UT WOS:A1997WJ85300026
ER
PT J
AU Bansal, NP
Dickerson, RM
AF Bansal, NP
Dickerson, RM
TI Tensile strength and microstructural characterization of HPZ ceramic
fibers
SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES
MICROSTRUCTURE AND PROCESSING
LA English
DT Article
DE ceramic fiber; coatings; microstructure; tensile strength; Weibull
statistics
AB Tensile strengths of as-received HPZ fiber and those surface coated with BN, BN/SiC, and BN/Si3N4 have been determined at room temperature using a two-parameter Weibull distribution. Nominally similar to 0.4 mu m BN and 0.2 mu m SiC or Si3N4 coatings were deposited on the fibers by chemical vapor deposition (CVD) using a continuous reactor. The average tensile strength of uncoated HPZ fiber was 2.0 +/- 0.56 GPa (290 +/- 81 ksi) with a Weibull modulus of 4.1. For the BN coated fibers, the average strength and the Weibull modulus increased to 2.39 +/- 0.44 GPa (346 +/- 64 ksi) and 6.5, respectively. The HPZ/BN/SiC fibers showed an average strength of 2.0 +/- 0.32 GPa (290 +/- 47 ksi) and Weibull modulus of 7.3. Average strength of the fibers having a dual BN/Si3N4 surface coating degraded to 1.15 +/- 0.26 GPa (166 +/- 38 ksi) with a Weibull modulus of 5.3. The chemical composition and thickness of the fiber coatings were determined using scanning Auger analysis. Microstructural analysis of the fibers and the coatings was carried out by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). A microporous silica-rich layer similar to 200 nm thick is present on the as-received HPZ fiber surface. The BN coatings on the fibers are amorphous to partly turbostratic and contaminated with carbon and oxygen. The silicon carbide coating was crystalline whereas the silicon nitride coating was amorphous. The silicon carbide and silicon nitride coatings are non-stoichiometric, non-uniform, and granular. Within a fiber tow, the fibers on the outside had thicker and more granular coatings than those on the inside.
C1 NYMA INC,LEWIS RES CTR GRP,BROOKPARK,OH 44142.
RP Bansal, NP (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA.
NR 6
TC 7
Z9 9
U1 2
U2 7
PU ELSEVIER SCIENCE SA LAUSANNE
PI LAUSANNE
PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND
SN 0921-5093
J9 MAT SCI ENG A-STRUCT
JI Mater. Sci. Eng. A-Struct. Mater. Prop. Microstruct. Process.
PD FEB 15
PY 1997
VL 222
IS 2
BP 149
EP 157
DI 10.1016/S0921-5093(96)10530-X
PG 9
WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary;
Metallurgy & Metallurgical Engineering
SC Science & Technology - Other Topics; Materials Science; Metallurgy &
Metallurgical Engineering
GA WP119
UT WOS:A1997WP11900007
ER
PT J
AU Nicolas, DP
AF Nicolas, DP
TI Video printers vs. instant film: A comparison
SO MICROSCOPY RESEARCH AND TECHNIQUE
LA English
DT Meeting Abstract
C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812.
NR 0
TC 0
Z9 0
U1 0
U2 0
PU WILEY-LISS
PI NEW YORK
PA DIV JOHN WILEY & SONS INC, 605 THIRD AVE, NEW YORK, NY 10158-0012
SN 1059-910X
J9 MICROSC RES TECHNIQ
JI Microsc. Res. Tech.
PD FEB 15
PY 1997
VL 36
IS 4
BP 343
EP 343
PG 1
WC Anatomy & Morphology; Biology; Microscopy
SC Anatomy & Morphology; Life Sciences & Biomedicine - Other Topics;
Microscopy
GA WV933
UT WOS:A1997WV93300022
ER
PT J
AU Coble, K
Dodelson, S
Frieman, JA
AF Coble, K
Dodelson, S
Frieman, JA
TI Dynamical Lambda models of structure formation
SO PHYSICAL REVIEW D
LA English
DT Article
ID PARTICLE-PHYSICS MODELS; PSEUDO-GOLDSTONE BOSONS; LARGE-SCALE STRUCTURE;
COLD DARK-MATTER; COSMOLOGICAL CONSTANT; MASS FLUCTUATIONS; CMB
ANISOTROPIES; POWER SPECTRUM; UNIVERSE; CONSEQUENCES
AB Models of structure formation with a cosmological constant Lambda provide a good fit to the observed power spectrum of galaxy clustering. However, they suffer from several problems. Theoretically, it is difficult to understand why the cosmological constant is so small in Planck units. Observationally, while the power spectra of cold dark matter plus Lambda models have approximately the right shape, the COBE-normalized amplitude for a scale-invariant spectrum is too high, requiring galaxies to be antibiased relative to the mass distribution. Attempts to address the first problem have led to models in which a dynamical field supplies the vacuum energy, which is thereby determined by fundamental physics scales. We explore the implications of such dynamical Lambda models for the formation of large-scale structure. We find that there are dynamical models for which the amplitude of the COPE-normalized spectrum matches the observations. We also calculate the cosmic microwave background anisotropies in these models and show that the angular power spectra are distinguishable from those of standard cosmological constant models.
C1 FERMILAB NATL ACCELERATOR LAB,NASA,FERMILAB ASTROPHYS CTR,BATAVIA,IL 60510.
RP Coble, K (reprint author), UNIV CHICAGO,DEPT ASTRON & ASTROPHYS,CHICAGO,IL 60637, USA.
NR 52
TC 214
Z9 215
U1 0
U2 1
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 0556-2821
J9 PHYS REV D
JI Phys. Rev. D
PD FEB 15
PY 1997
VL 55
IS 4
BP 1851
EP 1859
DI 10.1103/PhysRevD.55.1851
PG 9
WC Astronomy & Astrophysics; Physics, Particles & Fields
SC Astronomy & Astrophysics; Physics
GA WK491
UT WOS:A1997WK49100017
ER
PT J
AU Kogut, A
Hinshaw, G
Banday, AJ
AF Kogut, A
Hinshaw, G
Banday, AJ
TI Limits to global rotation and shear from the COBE DMR four-year sky maps
SO PHYSICAL REVIEW D
LA English
DT Article
AB Small departures from a homogeneous isotropic spacetime create observable features in the large-scale anisotropy of the cosmic microwave background. We cross correlate the maps of the cosmic microwave background anisotropy from the Cosmic Background Explorer Differential Microwave Radiometers four-year data set with template maps from Bianchi type VIIh cosmological models to limit global rotation or shear in the early universe. On the largest scales, spacetime is well described by the Friedmann-Robertson-Walker metric, with departures from isotropy about each spatial point limited to shear sigma/H-0<10(-9) and rotation omega/H-0<6x10(-8) for 0.1 less than or equal to Omega(0) less than or equal to 1.
C1 MAX PLANCK INST ASTROPHYS,D-85740 GARCHING,GERMANY.
RP Kogut, A (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,HUGHES STX CORP,CODE 685,GREENBELT,MD 20771, USA.
RI Kogut, Alan/D-6293-2012
NR 18
TC 44
Z9 45
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 FEB 15
PY 1997
VL 55
IS 4
BP 1901
EP 1905
DI 10.1103/PhysRevD.55.1901
PG 5
WC Astronomy & Astrophysics; Physics, Particles & Fields
SC Astronomy & Astrophysics; Physics
GA WK491
UT WOS:A1997WK49100022
ER
PT J
AU Friend, AD
Stevens, AK
Knox, RG
Cannell, MGR
AF Friend, AD
Stevens, AK
Knox, RG
Cannell, MGR
TI A process-based, terrestrial biosphere model of ecosystem dynamics
(Hybrid v3.0)
SO ECOLOGICAL MODELLING
LA English
DT Review
DE model; ecosystem; competition; trade-offs; forest; types; productivity
ID SOIL ORGANIC-MATTER; STOMATAL CONDUCTANCE; CLIMATE-CHANGE; CANOPY
PHOTOSYNTHESIS; PRIMARY PRODUCTIVITY; FOREST SUCCESSION;
PICEA-SITCHENSIS; CO2 ASSIMILATION; GLOBAL RADIATION; DIRECT COMPONENT
AB A numerical process-based model of terrestrial ecosystem dynamics is described and tested. The model, Hybrid v3.0, treats the daily cycling of carbon, nitrogen, and water within the biosphere and between the biosphere and the atmosphere. It combines a mass-balance approach with the capacity to predict the relative dominance of different species or generalised plant types (such as evergreen needleleaved trees, cold deciduous broadleaved trees, and C3 grasses). The growth of individual trees is simulated on an annual timestep, and the growth of a grass layer is simulated on a daily timestep. The exchange of carbon, nitrogen, and water with the atmosphere and the soil is simulated on a daily timestep (except the flux of tree litter to the soil, which occurs annually). Individual trees and the grass layer compete with each other for light, water, and nitrogen within a 'plot'. Larger and taller plants shade smaller ones; they also take up a greater proportion of the available water and nitrogen. The above-ground space in each plot is divided into 1 m deep layers for the purposes of calculating irradiance interception; horizontal variation in the plot environment is not treated. The soil is represented as a single layer, with a daily hydrological budget. Decomposition of soil organic matter is calculated using an empirical sub-model. The initial size of each tree seedling is stochastic. To predict the mean behaviour of the model for a particular boundary condition it is necessary to simulate a number of plots. Hybrid v3.0 has been written with three major requirements in mind: (i) the carbon, water, and nutrient cycles must be fully coupled in the soil-plant-atmosphere system; (ii) the internal constraints on the model's behaviour, and the driving forces for the model, must be the same as those which operate in nature (e.g., climate, nitrogen deposition, and the atmospheric concentrations of CO2 and O-2); and (iii) the model must be constructed so that it is capable of predicting transient as well as equilibrium responses to climate change. These conditions have largely been met by constructing the model around a set of fundamental hypotheses regarding the general constraints under which plants and soils behave, independently of any particular location or time. The model is thus potentially capable of making reliable predictions of ecosystem behaviour and structure under future, new, atmospheric conditions. The model is tested for a site in eastern North America. A quasi-equilibrium is reached after approximately 250 years with 10 plots. It is found that more plots are not necessary in order to obtain a reliable estimate of mean behaviour. Predictions of productivity, leaf area index, foliage nitrogen, soil carbon, and biomass carbon are all within the range expected for this location.
C1 NASA,GODDARD SPACE FLIGHT CTR,BIOSPHER SCI BRANCH,GREENBELT,MD 20771.
RP Friend, AD (reprint author), INST TERR ECOL,EDINBURGH RES STN,BUSH ESTATE,PENICUIK EH26 0QB,MIDLOTHIAN,SCOTLAND.
RI Knox, Robert/E-9657-2011
NR 114
TC 315
Z9 348
U1 4
U2 73
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0304-3800
J9 ECOL MODEL
JI Ecol. Model.
PD FEB 14
PY 1997
VL 95
IS 2-3
BP 249
EP 287
DI 10.1016/S0304-3800(96)00034-8
PG 39
WC Ecology
SC Environmental Sciences & Ecology
GA WW594
UT WOS:A1997WW59400010
ER
PT J
AU Meador, MAB
HardyGreen, D
Auping, JV
Gaier, JR
Ferrara, LA
Papadopoulos, DS
Smith, JW
Keller, DJ
AF Meador, MAB
HardyGreen, D
Auping, JV
Gaier, JR
Ferrara, LA
Papadopoulos, DS
Smith, JW
Keller, DJ
TI Optimization of electrically conductive films: Poly(3-methylthiophene)
or polypyrrole in Kapton
SO JOURNAL OF APPLIED POLYMER SCIENCE
LA English
DT Article
DE conductive polymers; polythiophene; polypyrrole; statistical design of
experiments
ID CHEMICAL OXIDATIVE POLYMERIZATION; COMPOSITES; POLYTHIOPHENE; SURFACE;
PYRROLE
AB A method to generate conductive films composed of small amounts of conductive polymer absorbed into the surface of polyimide films has been optimized. Both pyrrole (PY) and 3-methylthiophene (3MT) were evaluated as precursors for the conductive phase. Predictive models were empirically derived for each precursor to describe the effects of polymerization variables on the conductivity of the films. The variables studied were found to be highly synergistic. An optimum set of conditions was found for each conductive polymer that produces the highest conductivity. Using p-3MT as the conductive phase, films with conductivity as high as 5.7 Omega(-1) cm(-1) can be produced, an improvement of four orders of magnitude over previously reported results with Kapton as a base polymer. The highest conductivity achieved using p-PY as the conductive phase was 0.041 Omega(-1) cm(-1), still a two order of magnitude improvement over previously reported results. Mean mechanical properties of the 3MT-treated films were not significantly lower than that for untreated Kapton. The conductivities of p-3MT/Kapton films tested over time under ambient temperature in air persist fairly well for 300 days. (C) 1997 John Wiley & Sons, Inc.
C1 REALWORLD QUAL SYST INC,ROCKY RIVER,OH 44116.
RP Meador, MAB (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA.
OI Meador, Mary Ann/0000-0003-2513-7372
NR 27
TC 11
Z9 11
U1 0
U2 0
PU JOHN WILEY & SONS INC
PI NEW YORK
PA 605 THIRD AVE, NEW YORK, NY 10158-0012
SN 0021-8995
J9 J APPL POLYM SCI
JI J. Appl. Polym. Sci.
PD FEB 14
PY 1997
VL 63
IS 7
BP 821
EP 834
DI 10.1002/(SICI)1097-4628(19970214)63:7<821::AID-APP1>3.0.CO;2-S
PG 14
WC Polymer Science
SC Polymer Science
GA WC957
UT WOS:A1997WC95700001
ER
PT J
AU Cane, MA
Clement, AC
Kaplan, A
Kushnir, Y
Pozdnyakov, D
Seager, R
Zebiak, SE
Murtugudde, R
AF Cane, MA
Clement, AC
Kaplan, A
Kushnir, Y
Pozdnyakov, D
Seager, R
Zebiak, SE
Murtugudde, R
TI Twentieth-century sea surface temperature trends
SO SCIENCE
LA English
DT Article
ID OCEAN-ATMOSPHERE INTERACTION; NINO-SOUTHERN OSCILLATION; SULFATE
AEROSOLS; EL-NINO; TROPICAL CLIMATOLOGY; GREENHOUSE GASES; PACIFIC;
MODEL; SIMULATION; CO2
AB An analysis of historical sea surface temperatures provides evidence for global warming since 1900, in line with land-based analyses of global temperature trends, and also shows that over the same period, the eastern equatorial Pacific cooled and the zonal sea surface temperature gradient strengthened. Recent theoretical studies have predicted such a pattern as a response of the coupled ocean-atmosphere system to an exogenous heating of the tropical atmosphere. This pattern, however, is not reproduced by the complex ocean-atmosphere circulation models currently used to simulate the climatic response to increased greenhouse gases. Its presence is likely to lessen the mean 20th-century global temperature change in model simulations.
C1 NASA, GODDARD SPACE FLIGHT CTR, LAB HYDROSPHER PROC, UNIV SPACE RES ASSOC, GREENBELT, MD 20771 USA.
RP Cane, MA (reprint author), LAMONT DOHERTY EARTH OBSERV, PALISADES, NY 10964 USA.
RI Cane, Mark/I-8086-2012; Kushnir, Yochanan/B-4472-2013
NR 39
TC 278
Z9 287
U1 0
U2 28
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 FEB 14
PY 1997
VL 275
IS 5302
BP 957
EP 960
DI 10.1126/science.275.5302.957
PG 4
WC Multidisciplinary Sciences
SC Science & Technology - Other Topics
GA WH388
UT WOS:A1997WH38800039
ER
PT J
AU Cornwell, DM
Thomas, HJ
AF Cornwell, DM
Thomas, HJ
TI High-power (>0.9 W cw) diffraction-limited semiconductor laser based on
a fiber Bragg grating external cavity
SO APPLIED PHYSICS LETTERS
LA English
DT Article
ID AMPLIFIER
AB We have developed a high-power (>0.9 W cw) diffraction-limited semiconductor laser based on a tapered semiconductor optical amplifier using a fiber Bragg grating in an external cavity configuration. Frequency-selective feedback from the fiber grating is injected into the amplifier via direct butt coupling through a single mode fiber, resulting in a spectrally stable and narrow (<0.3 nm) high-power laser for solid-state laser pumping, laser remote sensing, and optical communications. (C) 1997 American Institute of Physics.
C1 MONTANA STATE UNIV,DEPT PHYS,BOZEMAN,MT 59717.
RP Cornwell, DM (reprint author), NASA,GODDARD SPACE FLIGHT CTR,OPT BRANCH,CODE 7175,GREENBELT,MD 20771, USA.
NR 8
TC 7
Z9 7
U1 0
U2 0
PU AMER INST PHYSICS
PI WOODBURY
PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999
SN 0003-6951
J9 APPL PHYS LETT
JI Appl. Phys. Lett.
PD FEB 10
PY 1997
VL 70
IS 6
BP 694
EP 695
DI 10.1063/1.119263
PG 2
WC Physics, Applied
SC Physics
GA WG827
UT WOS:A1997WG82700007
ER
PT J
AU Ohsaka, K
Chung, SK
Rhim, WK
Peker, A
Scruggs, D
Johnson, WL
AF Ohsaka, K
Chung, SK
Rhim, WK
Peker, A
Scruggs, D
Johnson, WL
TI Specific volumes of the Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 alloy in the
liquid, glass, and crystalline states
SO APPLIED PHYSICS LETTERS
LA English
DT Article
ID SUPERCOOLED LIQUID; METALLIC-GLASS; MELTS
AB The specific volumes of the Zr41.2Ti13.8CU12.5Ni10.0Be2.25 alloy as a function of temperature, T, are determined by employing an image digitizing technique and numerical calculation methods applied to the electrostatically levitated spherical alloy. The linear fitting of the volumes of the alloy in the liquid, V-l, glass, V-g, and crystalline V-c, states in the temperature ranges shown in parentheses are V-l(T) = 0.1583 + 8.877 x 10(-6)T(cm(3)/g) (700-1300 K); V-g(T) = 0.1603 + 5.528 x 10(-6)T (400-550 K); V-c(T) = 0.1583 + 6.211 x 10(-6)T(400-850 K). The average volume thermal expansion coefficients within the temperature ranges are determined to be 5.32, 3.39, and 3.83 x 10(-5) (1/K) for the liquid, glass, and crystalline states, respectively. (C) 1997 American Institute of Physics.
C1 AMORPHOUS TECHNOL INT,LAGUNA NIGUEL,CA 92656.
CALTECH,WM KECK LAB ENGN MAT,PASADENA,CA 91125.
RP Ohsaka, K (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA.
NR 16
TC 78
Z9 79
U1 0
U2 17
PU AMER INST PHYSICS
PI WOODBURY
PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999
SN 0003-6951
J9 APPL PHYS LETT
JI Appl. Phys. Lett.
PD FEB 10
PY 1997
VL 70
IS 6
BP 726
EP 728
DI 10.1063/1.118250
PG 3
WC Physics, Applied
SC Physics
GA WG827
UT WOS:A1997WG82700018
ER
PT J
AU Kazanas, D
Perlman, E
AF Kazanas, D
Perlman, E
TI Low-state gamma-ray emission from blazars and the gamma-ray background
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE diffuse radiation; gamma rays, observations
ID LUMINOSITY FUNCTION; RADIATION; GALAXIES; UNIVERSE
AB We examine the contribution of flat spectrum radio sources (FSRSs), or blazars, to the diffuse gamma-ray background (DGRB), prompted by the association of the extragalactic gamma-ray sources detected by the EGRET instrument aboard the Compton Gamma Ray Observatory (CGRO) with this class of objects by using their well-studied log N-log S distribution. The basic assumption of our study are that (1) there exists steady state gamma-ray emission at the EGRET energy band from the entire population of FSRSs with gamma-ray luminosity that is proportional to their radio luminosity, i.e., (vF(v))(100 MeV) = f(vF(v))(5 GHz); (2) the ensemble of blazars produce the DGRB. Under these assumptions, the estimated average value of the proportionality constant is [f] similar or equal to 70, compared to a mean observed value of [f](obs) similar or equal to 750 seen among the EGRET-detected blazars. We explore the implications of this result for AGN models and address the results that should be achieved by the next generation of gamma-ray satellites.
RP Kazanas, D (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 661,GREENBELT,MD 20771, USA.
NR 25
TC 10
Z9 10
U1 0
U2 0
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD FEB 10
PY 1997
VL 476
IS 1
BP 7
EP 11
DI 10.1086/303612
PN 1
PG 5
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WG534
UT WOS:A1997WG53400002
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 ASCA observations of Seyfert 1 galaxies .1. Data analysis, imaging, and
timing
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE galaxies, active; galaxies, nuclei; galaxies, Seyfert; X-rays, galaxies
ID X-RAY VARIABILITY; ACTIVE GALACTIC NUCLEI; EMISSION; NGC4051; SAMPLE;
AGN
AB We present the first in a series of papers describing the X-ray properties of a sample of 18 Seyfert 1 galaxies, using data obtained by ASCA. The imaging data reveal a number of serendipitous hard X-ray sources in some source fields, but none contribute significantly to the hard X-ray flux of the active galactic nuclei. All but one of the Seyferts show evidence for variability on timescales of minutes to hours, with the amplitude anticorrelated with the source luminosity, confirming previous results. In at least eight sources there is evidence that the variability amplitude below 2 keV is greater than that in the hard X-ray band, perhaps indicating variable components other than the power law in the soft band. Ultrarapid variability, implying significant power at frequencies greater than 10(-3) Hz is detected in at least five sources but is difficult to detect in most cases, because of the sampling and signal-to-noise ratio. In Mrk 766 and MCG -6-30-15 there is also an indication that the high-frequency power spectra are variable in shape and/or intensity. There is similar evidence in NGC 4151 but on longer timescales.
RP Nandra, K (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,CODE 660,GREENBELT,MD 20771, USA.
NR 52
TC 325
Z9 326
U1 0
U2 0
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD FEB 10
PY 1997
VL 476
IS 1
BP 70
EP 82
DI 10.1086/303600
PN 1
PG 13
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WG534
UT WOS:A1997WG53400009
ER
PT J
AU Harding, AK
Baring, MG
Gonthier, PL
AF Harding, AK
Baring, MG
Gonthier, PL
TI Photon-splitting cascades in gamma-ray pulsars and the spectrum of PSR
1509-58
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE gamma rays, theory; pulsars, individual (PSR 1509-58); stars, magnetic
fields
ID STRONG MAGNETIC-FIELDS; QUANTUM ELECTRODYNAMICS; PAIR CREATION; POLAR
CAPS; RADIATION; GAPS; EMISSION; GEMINGA; EGRET; REPEATERS
AB Magnetic photon splitting gamma --> gamma gamma, a quantum electrodynamics process that becomes important only in magnetic fields approaching the quantum critical value, B-cr = 4.41 x 10(13) G, is investigated as a mechanism for attenuation of gamma-rays emitted near the surface of strongly magnetized pulsars. Since splitting has no threshold, it can attenuate photons and degrade their energies below the threshold for one-photon pair production, and in high enough fields it may dominate photon attenuation above Fair threshold. We model photon-splitting attenuation and subsequent splitting cascades in gamma-ray pulsars, including the dipole field and curved spacetime geometry of the neutron star magnetosphere. We focus specifically on PSR 1509-58, which has the highest surface magnetic field of all the gamma-ray pulsars (B-0 = 3 x 10(13) G). We find that splitting will not be important for most gamma-ray pulsars, i.e., those with B-0 less than or similar to 0.2B(cr), either in competition with pair production attenuation in pair cascades, or in photon escape cutoffs in the spectrum. Photon splitting will be important for gamma-ray pulsars having B-0 greater than or similar to 0.3B(cr), where the splitting attenuation lengths and escape energies become comparable to or less than those for pair production. We compute Monte Carlo spectral models for PSR 1509-58, assuming that either a full photon-splitting cascade or a combination of splitting and pair production (depending on which splitting modes operate) attenuate a power-law input spectrum. We find that photon splitting, or combined splitting and pair production, can explain the unusually low cutoff energy (between 2 and 30 MeV) of PSR 1509 - 58, and that the model cascade spectra, which display strong polarization, are consistent with the observed spectral points and upper limits for polar cap emission at a range of magnetic colatitudes up to similar to 25 degrees.
C1 HOPE COLL, DEPT PHYS, HOLLAND, MI 49423 USA.
RP Harding, AK (reprint author), NASA, GODDARD SPACE FLIGHT CTR, HIGH ENERGY ASTROPHYS LAB, GREENBELT, MD 20771 USA.
RI Harding, Alice/D-3160-2012
NR 71
TC 97
Z9 98
U1 0
U2 0
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD FEB 10
PY 1997
VL 476
IS 1
BP 246
EP 260
DI 10.1086/303605
PN 1
PG 15
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WG534
UT WOS:A1997WG53400025
ER
PT J
AU Kirkpatrick, JD
Beichman, CA
Skrutskie, MF
AF Kirkpatrick, JD
Beichman, CA
Skrutskie, MF
TI The coolest isolated M dwarf and other 2MASS discoveries
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE infrared, stars; stars, late-type; stars, low-mass, brown dwarfs;
surveys
ID GUIDE STAR CATALOG; BROWN DWARF; SPECTRAL SEQUENCE; LOW-LUMINOSITY;
MAIN-SEQUENCE; EMISSION; PLEIADES; MEMBERS
AB We have obtained follow-up spectroscopy of eight late dwarf candidates discovered in a 105 deg(2) area observed with the 2MASS Prototype Camera during test runs between 1992 and 1994. These objects were chosen because of their red infrared colors (e.g., J - K-s greater than or equal to 1.10) and/or red OIR colors (e.g., R - K-s greater than or equal to 6.00). All eight are late M dwarfs, six of which have spectral types later than van Biesbroeck 8 (type M7 V). Despite the fact that we have only followed up a fraction of the reddest sources discovered, the number of known M dwarfs of type M7 and cooler has been increased by 30%. Extrapolation of these results alone shows that over 2000 dwarfs of similar spectral type and with K-s less than or equal to 14.0 will be imaged by 2MASS over the entire sky. One of these new discoveries is astonishingly cool and has a tentative type of greater than or equal to M10 V. This dwarf, one of the least luminous objects yet discovered, could itself be a high-mass brown dwarf, thus providing another empirical data point in a regime where few such objects are now recognized. Only the substellar suspect GD 165 B and the bona fide brown dwarf GL 229 B, both discovered as companions to known stars, are cooler. Thus, this 2MASS discovery becomes the coolest isolated object so far identified.
C1 UNIV MASSACHUSETTS,DEPT PHYS & ASTRON,FIVE COLL,DEPT ASTRON,AMHERST,MA 01003.
RP Kirkpatrick, JD (reprint author), CALTECH,JET PROP LAB,INFRARED PROC & ANAL CTR,4800 OAK GROVE DR,PASADENA,CA 91125, USA.
NR 31
TC 77
Z9 77
U1 0
U2 0
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD FEB 10
PY 1997
VL 476
IS 1
BP 311
EP &
DI 10.1086/303613
PN 1
PG 10
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WG534
UT WOS:A1997WG53400031
ER
PT J
AU Justtanont, K
Tielens, AGGM
Skinner, CJ
Haas, MR
AF Justtanont, K
Tielens, AGGM
Skinner, CJ
Haas, MR
TI Observations of high rotational CO lines in post-asymptotic giant branch
stars and planetary nebulae
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE infrared, stars; stars, AGB and post-AGB; stars, circumstellar matter;
stars, individual (NGC 7027, GL 618, GL 2688)
ID PHOTODISSOCIATION REGIONS; CIRCUMSTELLAR ENVELOPES; NGC-7027; EMISSION;
RADIATION; IMAGES; WINDS
AB We have observed bright emission in high rotational CO lines (J = 13-12, 17-16, and 22-21) in the post-AGB object GL 2688 and the planetary nebulae, GL 618 and NGC 7027. These stars represent different evolutionary stages, as reflected by their effective temperatures. The observations reveal copious amounts of warm, dense molecular gas (n similar to 10(7) cm(-3); T similar to 10(3) K), implying that the AGB is terminated by a short-lived phase of high mass-loss rate. We investigate heating mechanisms for these objects. For NGC 7027, UV photons from the central star produce a photodissociation region and the gas cools via CO rotational transitions, as well as via fine-structure atomic lines. A shock is thought to heat the gas in GL 2688, which cools mainly via the [O I] 63 mu m line and molecular rotational lines. For GL 618, both mechanisms may coexist.
C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035.
SPACE TELESCOPE SCI INST,BALTIMORE,MD 21218.
NASA,AMES RES CTR,MOFFETT FIELD,CA 94035.
OI /0000-0003-1689-9201
NR 38
TC 11
Z9 11
U1 0
U2 0
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD FEB 10
PY 1997
VL 476
IS 1
BP 319
EP 326
DI 10.1086/303623
PN 1
PG 8
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WG534
UT WOS:A1997WG53400032
ER
PT J
AU Ofman, L
Davila, JM
AF Ofman, L
Davila, JM
TI Solar wind acceleration by solitary waves in coronal holes
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE MHD; solar wind; Sun, corona; Sun, magnetic fields; waves
ID SHEAR ALFVEN WAVES; RESONANT ABSORPTION; MODEL; ATMOSPHERE; PLASMA;
REFLECTION; SOLITONS; LEAKY
AB Coronal holes are well-known sources of the high-speed solar wind; however, the exact acceleration mechanism of the fast wind is still unknown. We solve numerically the time-dependent, nonlinear, resistive 2.5-dimensional MHD equations and find that solitary waves are generated in coronal holes nonlinearly by torsional Alfven waves. The solitary wave phase velocity was found to be slightly above the sound speed in the coronal hole; for example, with the driving Alfven wave amplitude v(d) approximate to 36 km s(-1) and plasma beta = 5%, the solitary wave phase speed is similar to 185 km s(-1). We show with a more simplified analytical model of the coronal hole that sound waves are generated nonlinearly by Alfven waves. We find numerically that these waves steepen nonlinearly into solitary waves. In addition, ohmic heating takes place in the coronal hole inhomogeneities owing to phase-mixing of the torsional Alfven waves. When solitary waves are present, the solar wind speed and density fluctuate considerably on timescales of similar to 20-40 minutes in addition to the Alfvenic fluctuations. The solitary wave-driven wind might be in better qualitative agreement with observations than the thermally driven and WKB Alfven wave solar wind models.
C1 STX CORP,GREENBELT,MD.
RP Ofman, L (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771, USA.
NR 40
TC 60
Z9 61
U1 0
U2 1
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD FEB 10
PY 1997
VL 476
IS 1
BP 357
EP 365
DI 10.1086/303603
PN 1
PG 9
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WG534
UT WOS:A1997WG53400035
ER
PT J
AU Steinacker, J
Meyer, JP
Steinacker, A
Reames, DV
AF Steinacker, J
Meyer, JP
Steinacker, A
Reames, DV
TI The helium valley: Comparison of impulsive solar flare ion abundances
and gyroresonant acceleration with oblique turbulence in a hot multi-ion
plasma
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE acceleration of particles; plasmas; Sun, abundances; Sun, corona; Sun,
flares; Sun, magnetic fields; Sun, particle emission
ID STRUCTURES OBSERVING CAMPAIGN; LOW-BETA PLASMA; ENERGETIC PARTICLES;
ACTIVE-REGION; SELECTIVE ACCELERATION; ELECTRON ACCELERATION; ELEMENTAL
ABUNDANCES; HE-3-RICH EVENTS; CYCLOTRON WAVES; CORONAL PLASMA
AB We present a detailed interpretation of the heavy ion abundance enhancements observed in impulsive flare energetic particles, in terms of the conditions for gyroresonant acceleration by moderately oblique waves in a hot solar coronal plasma.
On the basis of a realistic coronal plasma containing its complete set of minor ions, we analyze first all parallel wave modes in terms of their dispersion relation, damping timescale, and condition for gyroresonant acceleration of thermal ions, as a function of temperature. We identify the ''Helium Valley,'' the region in the frequency-wavenumber plane of strong wave damping by thermal He-4(+2) ions, as crucial for explaining the observed abundances: any ions with charge-to-mass ratio in the neighborhood of 0.5 cannot be accelerated preferentially, relative to He-4(+2).
Then solving the dispersion relation equation for oblique waves in a hot e-p-He plasma, we discuss this general class of waves in terms of polarization and damping timescale. For waves propagating at moderate angles to the magnetic field (theta not approximate to 90 degrees), our calculations indicate that the first harmonic n = 1 gyroresonance is dominant, and that the corresponding He valley narrows down for increasing angle theta. Using this analysis, we calculate the limits of the He valley and investigate the preferential gyroresonant acceleration of heavy ions by moderately oblique waves (theta not approximate to 90 degrees) in a solar coronal plasma. Only for nearly perpendicular waves (theta approximate to 90 degrees), are higher order resonances important and regions of wave damping by interaction with thermal particles vanishingly narrow in frequency.
We estimate the fraction of ions of each element outside the He valley as a function of temperature and compare the resulting enhanced abundances with the observed enhancements, for the case of a spectrum of non-quasi-perpendicular waves, as produced by a cascading of the general turbulence. The results allow us to specify the range of possible temperatures for the source plasma of the accelerated particles to between similar to 2.4 and similar to 4.5 x 10(6) K, i.e., comparable to active region (AR), but not to flaring gas, temperatures. This points to an acceleration of the ions taking place, either in the AR gas surrounding the flare itself or within the flaring loop but before it became heated. Constraints are set on the typical time At over which the ions are accelerated preferentially. We find times between similar to 5 x 10(-4) and similar to 3 x 10(-2) s (for our nominal plasma with density and field of n(e) = 10(10) cm(-3) and B = 100 G); it could be similar to 10 times larger, if the typical conditions in quiescent ARs (n(e) similar to 2 x 10(9) cm(-3) and B similar to 200 G) apply also to the bulk similar to 3 x 10(6) K gas of flaring ARs. We discuss another physical interpretation of At, if wave cascading is effective. Preliminary calculations have shown that the proposed selective acceleration mechanism can be applied in underdense (omega(p)/Omega(e) < 1) as well as in overdense plasmas (our nominal case), provided that quasi-perpendicular waves (generated, e.g., by an electron beam) are not dominant.
C1 CTR ETUDES SACLAY, DAPNIA, DSM, CEA, SERV ASTROPHYS, F-91191 GIF SUR YVETTE, FRANCE.
NASA, GODDARD SPACE FLIGHT CTR, HIGH ENERGY ASTROPHYS LAB, GREENBELT, MD 20771 USA.
RP Steinacker, J (reprint author), MAX PLANCK GESELL, ARBEITSGRP STAUB STERNENTSTEHUNGSGEBIETEN, SCHILLERGASSCHEN 2-3, D-07745 JENA, GERMANY.
NR 80
TC 17
Z9 17
U1 0
U2 0
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD FEB 10
PY 1997
VL 476
IS 1
BP 403
EP 427
DI 10.1086/303589
PN 1
PG 25
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WG534
UT WOS:A1997WG53400039
ER
PT J
AU Lin, YC
Bertsch, DL
Dingus, BL
Esposito, JA
Fichtel, CE
Hartman, RC
Hunter, SD
Kanbach, G
Kniffen, DA
Mattox, JR
MayerHasselwander, HA
Michelson, PF
vonMontigny, C
Mukherjee, R
Nolan, PL
Schneid, EJ
Sreekumar, P
Thompson, DJ
Willis, TD
AF Lin, YC
Bertsch, DL
Dingus, BL
Esposito, JA
Fichtel, CE
Hartman, RC
Hunter, SD
Kanbach, G
Kniffen, DA
Mattox, JR
MayerHasselwander, HA
Michelson, PF
vonMontigny, C
Mukherjee, R
Nolan, PL
Schneid, EJ
Sreekumar, P
Thompson, DJ
Willis, TD
TI Comparison of X-ray- and radio-selected BL Lacertae objects in
high-energy gamma-ray observations
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE BL Lacertae objects, general; gamma rays, observations
AB In the course of the Compton Gamma Ray Observatory mission, the EGRET telescope has detected 14 BL Lacertae objects in high-energy gamma rays through Phase 4. According to the BL Lac sample in Ciliegi, Bassani, & Caroli, two of these 14 sources are X-ray selected (XBL) and 10 are radio-selected (RBL); two are not listed in this sample. An examination of the radio fluxes and the X-ray fluxes for the BL Lac objects detected by EGRET reveals that it seems a strong radio flux must be present if high-energy gamma rays are to be detected in a BL Lac object, while detection is independent of the X-ray flux of the source. This result is in agreement with the picture of the coaligned radio jet and X-ray jet model of the broadband properties of BL Lac objects. For the BL Lac objects listed in Ciliegi et al. that are not detected by EGRET, co-adding of the EGRET data for the undetected RBLs in such a way that the source positions coincide with each other yields a flux excess at a 3.5 sigma level, but similar co-adding of the EGRET data for the undetected XBLs yields no flux excess.
C1 NASA,GODDARD SPACE FLIGHT CTR,UNIV SPACE RES ASSOC,GREENBELT,MD 20771.
MAX PLANCK INST EXTRATERR PHYS,D-85740 GARCHING,GERMANY.
BOSTON UNIV,DEPT ASTRON,BOSTON,MA 02215.
HAMPDEN SYDNEY COLL,HAMPDEN SYDNEY,VA 23943.
NORTHROP GRUMMAN AEROSPACE CORP,BETHPAGE,NY 11714.
RP Lin, YC (reprint author), STANFORD UNIV,EXPT PHYS LAB,STANFORD,CA 94305, USA.
RI Nolan, Patrick/A-5582-2009; Hunter, Stanley/D-2942-2012; Thompson,
David/D-2939-2012
OI Thompson, David/0000-0001-5217-9135
NR 20
TC 15
Z9 15
U1 0
U2 0
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD FEB 10
PY 1997
VL 476
IS 1
BP L11
EP L14
DI 10.1086/310494
PN 2
PG 4
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WG535
UT WOS:A1997WG53500003
ER
PT J
AU Ofman, L
Davila, JM
AF Ofman, L
Davila, JM
TI Do first results from soho UVCS indicate that the solar wind is
accelerated by solitary waves?
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE MHD; solar wind; Sun, corona; Sun, magnetic fields; waves
ID CORONAL HOLES; ALFVEN WAVES; ATMOSPHERE; MODEL
AB The Ultraviolet Coronagraph Spectrometer (UVCS) on board the recently launched US-European Solar and Heliospheric Observatory (SOHO) satellite has found O VI and H I emission lines with a broad component that corresponds to similar to 300 km s(-1) unresolved motions at about 0.7 solar radii above the photosphere. These motions appear to be independent of ion mass. We suggest that the large Doppler broadening of the ion emission lines observed by the UVCS are signatures of solitary waves in the solar wind plasma. According to our recent 2.5-dimensional (i.e., three-dimensional with azimuthal symmetry) MHD simulations, these waves may contribute significantly to the solar wind acceleration and may generate velocity fluctuations with a magnitude that agrees with the above observations.
C1 HUGHES STX CORP,GREENBELT,MD.
RP Ofman, L (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,CODE 680,GREENBELT,MD 20771, USA.
NR 27
TC 29
Z9 30
U1 0
U2 1
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD FEB 10
PY 1997
VL 476
IS 1
BP L51
EP L54
DI 10.1086/310491
PN 2
PG 4
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WG535
UT WOS:A1997WG53500013
ER
PT J
AU Veynante, D
Trouve, A
Bray, KNC
Mantel, T
AF Veynante, D
Trouve, A
Bray, KNC
Mantel, T
TI Gradient and counter-gradient scalar transport in turbulent premixed
flames
SO JOURNAL OF FLUID MECHANICS
LA English
DT Article
ID DIRECT SIMULATIONS; COMBUSTION; EVOLUTION; VELOCITY; EQUATION; FLOWS
AB In premixed turbulent combustion, the modelling of the turbulent flux of the mean reaction progress variable, (c) over tilde, <(rho u(i) '' c '')over bar>, remains somewhat controversial. Classical gradient transport assumptions based on the eddy viscosity concept are often used while both experimental data and theoretical analysis have pointed out the existence of counter-gradient turbulent diffusion. Direct numerical simulation (DNS) is used in this paper to provide basic information on the turbulent flux of (c) over tilde and study the occurrence of counter-gradient transport. The numerical configuration corresponds to two- or three-dimensional premixed flames in isotropic turbulent flow. The simulations correspond to various flame and flow conditions that are representative of flamelet combustion. They reveal that different flames will feature different turbulent transport properties and that these differences can be related to basic dynamical differences in the flame-flow interactions: counter-gradient diffusion occurs when the flow field near the flame is dominated by thermal dilatation due to chemical reaction, whereas gradient diffusion occurs when the flow field near the flame is dominated by the turbulent motions. The DNS-based analysis leads to a simple expression to describe the turbulent flux of (c) over tilde, which in turn leads to a simple criterion to delineate between the gradient and counter-gradient turbulent diffusion regimes. This criterion suggests that the occurrence of one regime or the other is determined primarily by the ratio of turbulence intensity divided by the laminar flame speed, u'/s(L), and by the flame heat release factor, tau = (T-b - T-u)/T-u, where T-u and T-b are respectively the temperature within unburnt and burnt gas. Consistent with the Bray-Moss-Libby theory, counter-gradient (gradient) diffusion is promoted by low (high) values of u'/s(L) and high (low) values of tau. DNS also shows that these results are not restricted to the turbulent transport of (c) over tilde. Similar results are found for the turbulent transport of flame surface density, C. The turbulent fluxes of (c) over tilde and Sigma are strongly correlated in the simulated flames and counter-gradient (gradient) diffusion of (c) over tilde always coincides with counter-gradient (gradient) diffusion of C.
C1 ECOLE CENT PARIS,F-92295 CHATENAYMALABRY,FRANCE.
INST FRANCAIS PETR,F-92506 RUEIL MALMAISON,FRANCE.
UNIV CAMBRIDGE,DEPT ENGN,CAMBRIDGE CB2 1PZ,ENGLAND.
STANFORD UNIV,CTR TURBULENCE RES,NASA AMES,STANFORD,CA 94305.
RP Veynante, D (reprint author), CNRS,LAB EM2C,F-92295 CHATENAYMALABRY,FRANCE.
NR 36
TC 188
Z9 188
U1 5
U2 14
PU CAMBRIDGE UNIV PRESS
PI NEW YORK
PA 40 WEST 20TH STREET, NEW YORK, NY 10011-4211
SN 0022-1120
J9 J FLUID MECH
JI J. Fluid Mech.
PD FEB 10
PY 1997
VL 332
BP 263
EP 293
PG 31
WC Mechanics; Physics, Fluids & Plasmas
SC Mechanics; Physics
GA WL978
UT WOS:A1997WL97800012
ER
PT J
AU Roman, DR
Csatho, B
Jezek, KC
Thomas, RH
Krabill, WB
vonFrese, RRB
Forsberg, R
AF Roman, DR
Csatho, B
Jezek, KC
Thomas, RH
Krabill, WB
vonFrese, RRB
Forsberg, R
TI A comparison of geoid undulations for west central Greenland
SO JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
LA English
DT Article
ID LASER ALTIMETRY; ICE-SHEET; GRAVITY
AB The accuracy of a new local gravity field model, GEOID94A, is examined at a site on the western Greenland ice sheet. The model, developed by the Danish National Survey and Cadastre, incorporates several new gravity data sets including an extensive amount of airborne gravity data. Model-derived geoid undulations were compared to independently determined undulations found by differencing the elevations from Global Positioning System controlled airborne laser altimetry and optical levelling surveys. Differences between the two sets of undulations were less than +/-6 cm RMS. The comparison improved (+/-5 cm RMS) when GEOID94A undulations were adjusted by local gravity observations also acquired at the site. Our comparisons demonstrate that GEOID94A adequately models the long to intermediate wavelengths of the gravity field. We conclude that GEOID94A constitutes a reliable reference model for studies of Greenland's gravity field.
C1 NATL SURVEY & CADASTRE, DIV GEODET, DK-2400 COPENHAGEN NV, DENMARK.
NASA, GODDARD SPACE FLIGHT CTR,WALLOPS FLIGHT FACIL, LAB HYDROSPHER PROC,OBSERVAT SCI BRANCH, WALLOPS ISL, VA 23337 USA.
NASA, WASHINGTON, DC 20546 USA.
OHIO STATE UNIV, DEPT GEOL SCI, COLUMBUS, OH 43210 USA.
RP Roman, DR (reprint author), OHIO STATE UNIV, BYRD POLAR RES CTR, 108 SCOTT HALL 1090 CARMACK RD, COLUMBUS, OH 43210 USA.
NR 18
TC 0
Z9 0
U1 1
U2 2
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA
SN 2169-9313
EI 2169-9356
J9 J GEOPHYS RES-SOL EA
JI J. Geophys. Res.-Solid Earth
PD FEB 10
PY 1997
VL 102
IS B2
BP 2807
EP 2814
DI 10.1029/96JB02697
PG 8
WC Geochemistry & Geophysics
SC Geochemistry & Geophysics
GA WH694
UT WOS:A1997WH69400009
ER
PT J
AU Meador, MAB
Johnston, JC
Cavano, PJ
AF Meador, MAB
Johnston, JC
Cavano, PJ
TI Elucidation of the cross-link structure of nadic-end-capped polyimides
using NMR of C-13-labeled polymers
SO MACROMOLECULES
LA English
DT Article
ID IMIDE DERIVATIVES; N-PHENYLNADIMIDE; PMR-15; POLYMERIZATION;
ISOMERIZATION; MODEL
AB Solid NMR of C-13 isotope-labeled samples of PMR-15 was used to follow the cross-linking reaction of the nadic end cap. Some samples were labeled on one of the carbon atoms of the nadic end cap, and others on the methylene carbon atom of the methylenedianiline portion of the polymer. NMR spectra were run on these samples both before and after cross-linking. In this way, direct evidence of the major products of cross-linking under normal cure conditions is provided. The majority (similar to 85%) of the cross-linking derives from olefin polymerization through the double bond of the end cap. Approximately 15% of the products could come from a pathway involving a retro-Diels-Alder reaction. However, all of the products could be explained by a biradical intermediate without a retro-Diels-Alder reaction. Evidence is also presented that the methylene moiety in the methylenedianiline part of the polymer chain also participates in the cross-linking, albeit to a small extent, by a radical transfer reaction. Different cure conditions (higher temperatures, longer times) could change the relative distribution of the products.
C1 CASE WESTERN RESERVE UNIV,CLEVELAND,OH 44106.
RP Meador, MAB (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA.
OI Meador, Mary Ann/0000-0003-2513-7372
NR 12
TC 32
Z9 35
U1 0
U2 2
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036
SN 0024-9297
J9 MACROMOLECULES
JI Macromolecules
PD FEB 10
PY 1997
VL 30
IS 3
BP 515
EP 519
DI 10.1021/ma9607170
PG 5
WC Polymer Science
SC Polymer Science
GA WH384
UT WOS:A1997WH38400026
ER
PT J
AU Shebalin, JV
AF Shebalin, JV
TI Numerical solution of the coupled Dirac and Maxwell equations
SO PHYSICS LETTERS A
LA English
DT Article
DE Dirac equation; Maxwell equations; classical field theory; spectral
methods
ID TURBULENCE
AB The Dirac and Maxwell equations are treated classically and solved numerically to simulate the nonlinear self-interaction of a fermion. The symmetry which linear analysis predicts between 'electronic' and 'positronic' states appears to be broken dynamically, resulting, on average, in the emergence of matter-antimatter asymmetry.
RP Shebalin, JV (reprint author), NASA,LANGLEY RES CTR,HAMPTON,VA 23681, USA.
NR 9
TC 4
Z9 4
U1 0
U2 1
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0375-9601
J9 PHYS LETT A
JI Phys. Lett. A
PD FEB 10
PY 1997
VL 226
IS 1-2
BP 1
EP 6
DI 10.1016/S0375-9601(96)00906-1
PG 6
WC Physics, Multidisciplinary
SC Physics
GA WF939
UT WOS:A1997WF93900001
ER
PT J
AU Ricca, A
Bauschlicher, CW
AF Ricca, A
Bauschlicher, CW
TI The structure and stability of BnH+ clusters
SO JOURNAL OF CHEMICAL PHYSICS
LA English
DT Article
ID GAUSSIAN-BASIS SETS; WAVE-FUNCTIONS; ELECTRON CORRELATION; BORON;
ENERGY; APPROXIMATION; DISSOCIATION; DIMER
AB The geometries of the BnH+ clusters for n=1-13 have been optimized at the B3LYP level of theory. Excluding B2H+, the ground states of all clusters are low-spin coupled. The structures appear to be related to the bare B-n(+) clusters in two ways: (1) an H atom is added to the B-n(+) cluster or (2) a BH is added to the B-n-1(+) cluster. The B-n(+)-H binding energies are computed at the B3LYP level of theory, and calibrated using the CCSD(T) level of theory. The computed results tend to fall between the experimental best estimates and the experimental lower bounds. The B-n-1(+)-H binding energies show an inverse correspondence with the B-n-1(+)-B values, while the (+)(Bn-1)-B and to parallel each other. (C) 1997 American Institute of Physics.
RP Ricca, A (reprint author), NASA, AMES RES CTR, STC 230-3, MOFFETT FIELD, CA 94035 USA.
NR 30
TC 34
Z9 34
U1 0
U2 4
PU AMER INST PHYSICS
PI MELVILLE
PA CIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1,
MELVILLE, NY 11747-4501 USA
SN 0021-9606
J9 J CHEM PHYS
JI J. Chem. Phys.
PD FEB 8
PY 1997
VL 106
IS 6
BP 2317
EP 2322
DI 10.1063/1.473095
PG 6
WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical
SC Chemistry; Physics
GA WG307
UT WOS:A1997WG30700029
ER
PT J
AU Thummel, HT
Bauschlicher, CW
AF Thummel, HT
Bauschlicher, CW
TI On the reaction of FNO2 with CH3, tert-butyl, and C13H21
SO JOURNAL OF PHYSICAL CHEMISTRY A
LA English
DT Article
ID GAUSSIAN-BASIS SETS; ELECTRON CORRELATION; MOLECULES; ENERGIES; ATOMS;
SURFACE; 1ST-ROW
AB Theoretical studies are reported for the reaction of FNO2 with the radicals CH3, tert-butyl, and C13H21, Which are templates for the radical site of a hydrogenated diamond (111) surface. All structures are fully optimized using density functional theory based on the B3LYP functional. Calibration calculations are performed for CH3 + FNO2 using the coupled cluster approach, the internally contracted multireference configuration interaction method, and second-order perturbation theory based upon the complete-active-space SCF reference wave function. These calibration calculations support the B3LYP approach for the calculation of bond energies but show that the B3LYP barrier is too low. Combining the calibration calculations with the larger clusters yields our best estimate of a barrier of about 10 kcal/mol for the reaction of FNO2 with a radical site on hydrogenated diamond (111).
C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035.
NR 31
TC 22
Z9 22
U1 0
U2 1
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036
SN 1089-5639
J9 J PHYS CHEM A
JI J. Phys. Chem. A
PD FEB 6
PY 1997
VL 101
IS 6
BP 1188
EP 1192
DI 10.1021/jp963201r
PG 5
WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical
SC Chemistry; Physics
GA WL090
UT WOS:A1997WL09000028
ER
PT J
AU Banks, HT
Smith, RC
Brown, DE
Metcalf, VL
Silcox, RJ
AF Banks, HT
Smith, RC
Brown, DE
Metcalf, VL
Silcox, RJ
TI The estimation of material and patch parameters in a PDE-based circular
plate model
SO JOURNAL OF SOUND AND VIBRATION
LA English
DT Article
ID BEAMS
AB The estimation of material and patch parameters for a system involving a circular plate, to which piezoceramic patches are bonded, is considered. A partial differential equation (PDE) model for the thin circular plate is used, with the passive and active contributions from the patches included in the internal and external bending moments. This model contains piecewise constant parameters describing the density, flexural rigidity, Poisson ratio and Kelvin-Voigt damping for the system, as well as patch constants and a coefficient for viscous air damping. Examples demonstrating the estimation of these parameters with experimental acceleration data and a variety of inputs to the experimental plate are presented. By using a physically derived PDE model to describe the system, parameter sets consistent across experiments are obtained, even when phenomena such as damping due to electric circuits affect the system dynamics. (C) 1997 Academic Press Limited.
C1 IOWA STATE UNIV SCI & TECHNOL, DEPT MATH, AMES, IA 50011 USA.
NASA, LANGLEY RES CTR, LOCKHEED ENGN & SCI CO, HAMPTON, VA 23681 USA.
NASA, LANGLEY RES CTR, US ARMY RES LAB, HAMPTON, VA 23681 USA.
NASA, LANGLEY RES CTR, ACOUST DIV, HAMPTON, VA 23681 USA.
NASA, LANGLEY RES CTR, INST COMP APPLICAT SCI & ENGN, HAMPTON, VA 23681 USA.
RP Banks, HT (reprint author), N CAROLINA STATE UNIV, CTR RES SCI COMPUTAT, RALEIGH, NC 27695 USA.
NR 21
TC 11
Z9 11
U1 0
U2 0
PU ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
PI LONDON
PA 24-28 OVAL RD, LONDON NW1 7DX, ENGLAND
SN 0022-460X
J9 J SOUND VIB
JI J. Sound Vibr.
PD FEB 6
PY 1997
VL 199
IS 5
BP 777
EP 799
DI 10.1006/jsvi.1996.0649
PG 23
WC Acoustics; Engineering, Mechanical; Mechanics
SC Acoustics; Engineering; Mechanics
GA WG619
UT WOS:A1997WG61900004
ER
PT J
AU Jen, AKY
Cai, YM
Bedworth, PV
Marder, SR
AF Jen, AKY
Cai, YM
Bedworth, PV
Marder, SR
TI Synthesis and characterization of highly efficient and thermally stable
diphenylamino-substituted thiophene stilbene chromophores for nonlinear
optical applications
SO ADVANCED MATERIALS
LA English
DT Article
ID SUSCEPTIBILITIES; STABILITY; POLYIMIDE; POLYENES
C1 CALTECH,BECKMAN INST,MOL MAT RESOURCE CTR,PASADENA,CA 91125.
ROI TECHNOL,OPT MAT DIV,MONMOUTH JCT,NJ 08852.
CALTECH,JET PROP LAB,PASADENA,CA 91109.
RI Jen, Alex/E-5957-2012
NR 20
TC 124
Z9 127
U1 3
U2 22
PU WILEY-V C H VERLAG GMBH
PI WEINHEIM
PA POSTFACH 10 11 61, D-69451 WEINHEIM, GERMANY
SN 0935-9648
J9 ADV MATER
JI Adv. Mater.
PD FEB
PY 1997
VL 9
IS 2
BP 132
EP 135
DI 10.1002/adma.19970090207
PG 4
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 WH746
UT WOS:A1997WH74600005
ER
PT J
AU Anderson, JL
AF Anderson, JL
TI Back from the future: How we got there from here
SO AEROSPACE AMERICA
LA English
DT Article
RP Anderson, JL (reprint author), NASA,OFF SPACE SCI,WASHINGTON,DC 20546, USA.
NR 0
TC 0
Z9 0
U1 0
U2 0
PU AMER INST AERONAUT ASTRONAUT
PI RESTON
PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091
SN 0740-722X
J9 AEROSPACE AM
JI Aerosp. Am.
PD FEB
PY 1997
VL 35
IS 2
BP 32
EP 36
PG 5
WC Engineering, Aerospace
SC Engineering
GA WG818
UT WOS:A1997WG81800012
ER
PT J
AU Taylor, R
AF Taylor, R
TI National Capital Section's Small Spacecraft Missions Symposium.
SO AEROSPACE AMERICA
LA English
DT Editorial Material
RP Taylor, R (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA.
NR 0
TC 0
Z9 0
U1 0
U2 0
PU AMER INST AERONAUT ASTRONAUT
PI RESTON
PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091
SN 0740-722X
J9 AEROSPACE AM
JI Aerosp. Am.
PD FEB
PY 1997
VL 35
IS 2
BP B5
EP B5
PG 1
WC Engineering, Aerospace
SC Engineering
GA WG818
UT WOS:A1997WG81800014
ER
PT J
AU Fenno, CC
Bayliss, A
Maestrello, L
AF Fenno, CC
Bayliss, A
Maestrello, L
TI Panel-structure response to acoustic forcing by a nearly sonic jet
SO AIAA JOURNAL
LA English
DT Article
ID BOUNDARY-CONDITIONS; NOISE; RADIATION; FLOWS; SOUND; LAYER
AB A model of a high subsonic jet with a nearby array of flexible, aircraft-type panels is studied numerically in two dimensions. The jet Is excited by a limited duration, spatially localized starter pulse in the potential core. The long time evolution of unsteady disturbances in the jet, the responses of the panels, and the ensuing radiation are computed and compared with those of a lower Mach number jet. The results show that, for high subsonic Mach numbers, the spectral response of both the jet (near and far field) and of the panels is concentrated in a relatively narrow frequency band centered at a Strouhal number (based on jet exit velocity) of approximately 0.25 and associated harmonics. This behavior of the jet and the panels is caused by nearly periodic vortex shedding from the nozzle lip. In contrast, for lower Mach numbers vortex shedding is very much weaker and the panels act as narrowband filters emphasizing the natural frequencies of the panels. Radiation from the panels is weakest in upstream directions and exhibits zones of silence due to destructive interference of radiation from the different panels.
C1 NORTHWESTERN UNIV,DEPT ENGN SCI & APPL MATH,EVANSTON,IL 60208.
RP Fenno, CC (reprint author), NATL RES COUNCIL,NASA,LANGLEY RES CTR,FLUID MECH & ACOUST DIV,MAIL STOP 463,HAMPTON,VA 23681, USA.
RI Bayliss, Alvin/B-7337-2009
NR 27
TC 3
Z9 3
U1 1
U2 1
PU AMER INST AERONAUT ASTRONAUT
PI RESTON
PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091
SN 0001-1452
J9 AIAA J
JI AIAA J.
PD FEB
PY 1997
VL 35
IS 2
BP 219
EP 227
DI 10.2514/2.99
PG 9
WC Engineering, Aerospace
SC Engineering
GA WE652
UT WOS:A1997WE65200002
ER
PT J
AU Rumsey, CL
AF Rumsey, CL
TI Computation of acoustic waves through sliding-zone interfaces
SO AIAA JOURNAL
LA English
DT Article; Proceedings Paper
CT AIAA/CEAS 2nd Joint Aeroacoustics Conference
CY MAY 06-08, 1996
CL STATE COLL, PA
SP AIAA, CEAS
AB The effect of a patched sliding-zone interface on the transmission of acoustic waves is examined for two- and three-dimensional model problems. A simple but general interpolation scheme at the patched boundary passes acoustic waves without distortion, provided that a sufficiently small time step is taken. A guideline is provided for the maximum permissible time step or zone speed that gives an acceptable error introduced by the sliding-zone interface.
RP Rumsey, CL (reprint author), NASA,LANGLEY RES CTR,FLUID MECH & ACOUST DIV,MAIL STOP 128,HAMPTON,VA 23681, USA.
NR 21
TC 1
Z9 2
U1 0
U2 0
PU AMER INST AERONAUT ASTRONAUT
PI RESTON
PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091
SN 0001-1452
J9 AIAA J
JI AIAA J.
PD FEB
PY 1997
VL 35
IS 2
BP 263
EP 268
DI 10.2514/2.116
PG 6
WC Engineering, Aerospace
SC Engineering
GA WE652
UT WOS:A1997WE65200007
ER
PT J
AU Back, MR
White, RA
Kwack, EY
Back, LH
AF Back, MR
White, RA
Kwack, EY
Back, LH
TI Hemodynamic consequences of stenosis remodeling during coronary
angioplasty
SO ANGIOLOGY
LA English
DT Article
ID ARTERY FLOW VELOCITY; BLOOD-FLOW; SHEAR-STRESS; STEADY FLOW; RESERVE;
HUMANS; ATHEROSCLEROSIS; PULSATILE; GEOMETRY; MODELS
AB Quantitative hemodynamic assessment during various endovascular interventions including balloon angioplasty is lacking. Translesional pressure drops measured by angioplasty catheters can cause flow blockage and thus lead to inaccurate estimates of preintervention and postintervention flow rates. A new analytical model of the flow rate-pressure drop relation across vascular stenoses is utilized that is nonlinear yet relatively simple in principle, easily applicable in vivo, and compatible with the presence of catheters. The model incorporates in vitro experimental evidence, angiographic data on the dimensions and shapes of coronary arterial stenoses before and after balloon angioplasty, reported translesional pressure gradients, and measurements of coronary flow reserve. Reasonable estimates of mean coronary artery flow rates and translesional pressure drops in the absence of angioplasty catheters are obtained.
Prior to angioplasty significant flow restriction across a 68% diameter stenosis exists during hyperemic flow conditions. Following successful balloon dilation, increased minimal cross-sectional area (residual 40% diameter stenosis) results in an improved flow rate-pressure drop relation. Despite minimal flow restriction during hyperemic conditions following angioplasty remodeling, residual luminal constriction leads to elevated wall shear stress levels within the entry region of the stenosis. The flow analysis described may be of clinical utility in evaluating the hemodynamic significance of the anatomic severity of stenoses in coronary and peripheral arteries before and after endovascular therapeutic interventions.
C1 UNIV CALIF LOS ANGELES,HARBOR MED CTR,DIV VASC SURG,TORRANCE,CA 90509.
CALTECH,JET PROP LAB,PASADENA,CA.
NR 24
TC 17
Z9 17
U1 0
U2 2
PU WESTMINSTER PUBL INC
PI GLEN HEAD
PA 708 GLEN COVE AVE, GLEN HEAD, NY 11545
SN 0003-3197
J9 ANGIOLOGY
JI Angiology
PD FEB
PY 1997
VL 48
IS 2
BP 99
EP 109
DI 10.1177/000331979704800201
PG 11
WC Peripheral Vascular Disease
SC Cardiovascular System & Cardiology
GA WH362
UT WOS:A1997WH36200001
PM 9040263
ER
PT J
AU Farrugia, CJ
Osherovich, VA
Burlaga, LF
AF Farrugia, CJ
Osherovich, VA
Burlaga, LF
TI The non-linear evolution of magnetic flux ropes .3. Effects of
dissipation
SO ANNALES GEOPHYSICAE-ATMOSPHERES HYDROSPHERES AND SPACE SCIENCES
LA English
DT Article
ID NONLINEAR EVOLUTION; CLOUDS
AB We study the evolution (expansion or oscillation) of cylindrically symmetric magnetic flux ropes when the energy dissipation is due to a drag force proportional to the product of the plasma density and the radial speed of expansion. The problem is reduced to a single, second-order, ordinary differential equation for a damped, non-linear oscillator. Motivated by recent work on the interplanetary medium and the solar corona, we consider polytropes whose index, gamma, may be less than unity. Numerical analysis shows that, in contrast to the small-amplitude case, large-amplitude oscillations are quasi-periodic with frequencies substantially higher than those of undamped oscillators. The asymptotic behaviour described by the momentum equation is determined by a balance between the drag force and the gradient of the gas pressure, leading to a velocity of expansion of the flux rope which may be expressed as (1/2 gamma)r/t, where r is the radial coordinate and r is the time. In the absence of a drag force, we found in earlier work that the evolution depends both on the polytropic index and on a dimensionless parameter, kappa. Parameter kappa was found to have a critical value above which oscillations are impossible, and below which they can exist only for energies less than a certain energy threshold. In the presence of a drag force, the concept of a critical kappa remains valid, and when kappa is above critical, the oscillatory mode disappears altogether. Furthermore, critical kappa remains dependent only on gamma and is, in particular, independent of the normalized drag coefficient, v*. Below critical kappa, however, the energy required for the flux rope to escape to infinity depends not only on kappa (as in the conservative force case) but also on v*. This work indicates how under certain conditions a small change in the viscous drag coefficient or the initial energy may alter the evolution drastically. It is thus important to determine v* and kappa from observations.
C1 UNIV MALTA,DEPT MATH SCI & TECH EDUC,MSIDA,MALTA.
NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771.
NR 18
TC 8
Z9 8
U1 0
U2 2
PU SPRINGER VERLAG
PI NEW YORK
PA 175 FIFTH AVE, NEW YORK, NY 10010
SN 0992-7689
J9 ANN GEOPHYS-ATM HYDR
JI Ann. Geophys.-Atmos. Hydrospheres Space Sci.
PD FEB
PY 1997
VL 15
IS 2
BP 152
EP 164
DI 10.1007/s005850050430
PG 13
WC Astronomy & Astrophysics; Geosciences, Multidisciplinary; Meteorology &
Atmospheric Sciences
SC Astronomy & Astrophysics; Geology; Meteorology & Atmospheric Sciences
GA WJ812
UT WOS:A1997WJ81200003
ER
PT J
AU Mauskopf, PD
Bock, JJ
DelCastillo, H
Holzapfel, WL
Lange, AE
AF Mauskopf, PD
Bock, JJ
DelCastillo, H
Holzapfel, WL
Lange, AE
TI Composite infrared bolometers with Si3N4 micromesh absorbers
SO APPLIED OPTICS
LA English
DT Article
DE infrared bolometers; silicon nitride; micromesh
ID SUBMILLIMETER WAVELENGTHS; HIGH-SENSITIVITY; OPTIMIZATION
AB We report the design and performance of 300-mK composite bolometers that use micromesh absorbers and support structures patterned from thin films of low-stress silicon nitride. The small geometrical filling factor of the micromesh absorber provides 20x reduction in heat capacity and cosmic ray cross section relative to a solid absorber with no loss in IR-absorption efficiency. The support structure is mechanically robust and has a thermal conductance, G < 2 x 10(-11) W/K, which is four times smaller than previously achieved at 300 mK. The temperature rise of the bolometer is measured with a neutron transmutation doped germanium thermistor attached to the absorbing mesh. The dispersion in electrical and thermal parameters of a sample of 12 bolometers optimized for the Sunyaev-Zel'dovich Infrared Experiment is +/-7% in R(T), +/-5% in optical efficiency, and +/-4% in G. (C) 1997 Optical Society of America
C1 CALTECH,JET PROP LAB,PASADENA,CA 91109.
RP Mauskopf, PD (reprint author), CALTECH,MAIL STOP 59-33,PASADENA,CA 91125, USA.
RI Holzapfel, William/I-4836-2015
NR 18
TC 111
Z9 111
U1 1
U2 9
PU OPTICAL SOC AMER
PI WASHINGTON
PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036
SN 0003-6935
J9 APPL OPTICS
JI Appl. Optics
PD FEB 1
PY 1997
VL 36
IS 4
BP 765
EP 771
DI 10.1364/AO.36.000765
PG 7
WC Optics
SC Optics
GA WF061
UT WOS:A1997WF06100003
PM 18250736
ER
PT J
AU Krainsky, IL
Asnin, VM
Dayton, JA
AF Krainsky, IL
Asnin, VM
Dayton, JA
TI Secondary electron emission from chemical vapor deposited diamond films
with negative electron affinity
SO APPLIED SURFACE SCIENCE
LA English
DT Article; Proceedings Paper
CT Proceedings of the International Vacuum Electron Sources
Conference(IVESC'96)
CY JUL 01-04, 1996
CL EINDHOVEN, NETHERLANDS
SP Eindhoven Univ Technol, Philips Display Components, Philips Res, Naval Res Lab, Balzers Pfeiffer Gmbh, NASA, Roy Neth Acad Sci, KNAW, Municipality Eindhoven, Semicon Assoc, Neth Vacuum Soc, NEVAC, Fdn Fundam Res Matter, FOM, Elsevier Sci Inc, Spectra-Mat Inc, Vacuum Microelectronics 158
ID EXCITON BREAKUP; SURFACE; PHOTOEMISSION
AB Strong negative electron affinity effects have been observed on the surface of as-grown chemical vapor deposited polycrystalline diamond films using secondary electron emission. The effect appears as a large and narrow peak in the low energy part of the spectrum of the electron energy distribution and can be described in the model of effective negative electron affinity. We also observed, for the first time, a fine structure in the low energy peak of the secondary electrons which reflects the energy structure of the conduction band.
RP Krainsky, IL (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA.
NR 26
TC 16
Z9 18
U1 0
U2 1
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0169-4332
J9 APPL SURF SCI
JI Appl. Surf. Sci.
PD FEB
PY 1997
VL 111
BP 265
EP 269
DI 10.1016/S0169-4332(96)00731-3
PG 5
WC Chemistry, Physical; Materials Science, Coatings & Films; Physics,
Applied; Physics, Condensed Matter
SC Chemistry; Materials Science; Physics
GA WN690
UT WOS:A1997WN69000046
ER
PT J
AU McKinnell, S
Thomson, AJ
Black, EA
Wing, BL
Guthrie, CM
Koerner, JF
Helle, JH
AF McKinnell, S
Thomson, AJ
Black, EA
Wing, BL
Guthrie, CM
Koerner, JF
Helle, JH
TI Atlantic salmon in the North Pacific
SO AQUACULTURE RESEARCH
LA English
DT Article
ID SALAR L; POPULATIONS; SIZE
AB The first catches of Atlantic salmon, Salmo salar L., in British Columbia (BC) waters occurred in 1987. The first reported escape of Atlantic salmon (2000 individuals) occurred in 1988. From 1988 to 1995, 97 799 Atlantic salmon were reported escaped from net pens in BC but the true number was higher as not all escapes are reported. Since 1987 a total of 9096 Atlantic salmon was caught in the coastal marine waters of BC, Washington and Alaska, and 188 were caught in fresh water. Most catches occurred in the Johnstone Strait area, where the abundance of salmon farms is highest. The most distant recovery occurred in 1994 when an Atlantic salmon was caught near the western end of the Alaska Peninsula. There have been no reports of successful reproduction of Atlantic salmon in the wild and no feral juveniles have been found. Atlantic salmon caught in the ocean in BC have substantial amounts of adipose tissue and they are heavier at length than fish caught in Alaska. The proportion of fish with prey items in their stomachs is generally low but higher in Alaska (13.1%) than in BC (5.8%). Most fish caught in fresh water are either maturing or mature.
C1 MINIST AGR FISHERIES & FOOD,VICTORIA,BC,CANADA.
NATL MARINE FISHERIES SERV,ALASKA FISHERIES SCI CTR,AUKE BAY LAB,JUNEAU,AK.
ALASKA DEPT FISH & GAME,KETCHIKAN,AK.
RP McKinnell, S (reprint author), FISHERIES & OCEANS CANADA,PACIFIC BIOL STN,NANAIMO,BC V9R 5K6,CANADA.
NR 32
TC 23
Z9 28
U1 2
U2 17
PU BLACKWELL SCIENCE LTD
PI OXFORD
PA P O BOX 88, OSNEY MEAD, OXFORD, OXON, ENGLAND OX2 0NE
SN 1355-557X
J9 AQUAC RES
JI Aquac. Res.
PD FEB
PY 1997
VL 28
IS 2
BP 145
EP 157
PG 13
WC Fisheries
SC Fisheries
GA WV298
UT WOS:A1997WV29800007
ER
PT J
AU Schneegurt, MA
Sherman, DM
Sherman, LA
AF Schneegurt, MA
Sherman, DM
Sherman, LA
TI Composition of the carbohydrate granules of the cyanobacterium,
Cyanothece sp strain ATCC 51142
SO ARCHIVES OF MICROBIOLOGY
LA English
DT Article
DE nitrogen fixation; glycogen; circadian rhythms; Cyanothece;
Cyanobacteria
ID NITROGEN-FIXATION; UNICELLULAR CYANOBACTERIA; STRUCTURAL-PROPERTIES;
POLYACRYLAMIDE GELS; DODECYL-SULFATE; CELL-WALL; PROTEINS; GLOEOTHECE;
MEMBRANES; PYROPHOSPHORYLASE
AB Cyanothece sp. strain ATCC 51142 is an aerobic, unicellular, diazotrophic cyanobacterium that temporally separates O-2-sensitive N-2 fixation from oxygenic photosynthesis. The energy and reducing power needed for N-2 fixation appears to be generated by an active respiratory apparatus that utilizes the contents of large interthylakoidal carbohydrate granules. We report here on the carbohydrate and protein composition of the granules of Cyanothece sp. strain ATCC 51142. The carbohydrate component is a glucose homopolymer with branches every nine residues and is chemically identical to glycogen. Granule-associated protein fractions showed temporal changes in the number of proteins and their abundance during the metabolic oscillations observed under diazotrophic conditions. There also were temporal changes in the protein pattern of the granule-depleted supernatant fractions from diazotrophic cultures. None of the granule-associated proteins crossreacted with antisera directed against several glycogen-metabolizing enzymes or nitrogenase, although these proteins were tentatively identified in supernatant fractions. It is suggested that the granule-associated proteins are structural proteins required to maintain a complex granule architecture.
C1 PURDUE UNIV,DEPT BIOL SCI,W LAFAYETTE,IN 47907.
PURDUE UNIV,NASA,SPECIALIZED CTR RES & TRAINING,W LAFAYETTE,IN 47907.
PURDUE UNIV,DEPT BOT & PLANT PATHOL,W LAFAYETTE,IN 47907.
NR 41
TC 29
Z9 29
U1 0
U2 6
PU SPRINGER VERLAG
PI NEW YORK
PA 175 FIFTH AVE, NEW YORK, NY 10010
SN 0302-8933
J9 ARCH MICROBIOL
JI Arch. Microbiol.
PD FEB-MAR
PY 1997
VL 167
IS 2-3
BP 89
EP 98
DI 10.1007/s002030050420
PG 10
WC Microbiology
SC Microbiology
GA WM889
UT WOS:A1997WM88900003
PM 9133330
ER
PT J
AU Hutchings, JB
Neff, SG
AF Hutchings, JB
Neff, SG
TI JHK imaging and photometry of low z QSOs and radio galaxy
SO ASTRONOMICAL JOURNAL
LA English
DT Article
ID QUASI-STELLAR OBJECTS; HOST GALAXIES; EVOLUTION; IMAGES; LOUD
AB We describe J,H,K deep imaging of 90 arcmin fields around 4 QSOs and one radio galaxy at redshifts in the range 0.06 to 0.30, and show their images, luminosity profiles, and NIR 2-color diagrams of objects, We find that the QSO hosts are all resolved, and compare them with previous CCD images. The host galaxy colors are consistent with old and young stellar populations at the QSO redshift. The colors of nearby galaxies suggest that all the AGN Live in groups of generally smaller companion galaxies, mostly with evolved populations at the same redshift. The two radio-loud objects live in richer cluster environments than the others. Gissel population models indicate reddening in the galaxies, star-forming regions, and possibly a systematic H-K offset. The QSO luminosity profiles are complex and reveal some of their tidal disturbance and star-formation history. (C) 1997 American Astronomical Society.
C1 NASA,GODDARD SPACE FLIGHT CTR,ASTROPHYS LAB,GREENBELT,MD 20771.
RP Hutchings, JB (reprint author), NATL RES COUNCIL CANADA,DOMINION ASTROPHYS OBSERV,5071 W SAANICH RD,VICTORIA,BC V8X 4M6,CANADA.
NR 15
TC 19
Z9 19
U1 0
U2 0
PU AMER INST PHYSICS
PI WOODBURY
PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999
SN 0004-6256
J9 ASTRON J
JI Astron. J.
PD FEB
PY 1997
VL 113
IS 2
BP 550
EP 561
DI 10.1086/118275
PG 12
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WE934
UT WOS:A1997WE93400008
ER
PT J
AU Holtzman, JA
Mould, JR
Gallagher, JS
Watson, AM
Grillmair, CJ
Ballester, GE
Burrows, CJ
Clarke, JT
Crisp, D
Evans, RW
Griffiths, RE
Hester, JJ
Hoessel, JG
Scowen, PA
Stapelfeldt, KR
Trauger, JT
Westphal, JA
AF Holtzman, JA
Mould, JR
Gallagher, JS
Watson, AM
Grillmair, CJ
Ballester, GE
Burrows, CJ
Clarke, JT
Crisp, D
Evans, RW
Griffiths, RE
Hester, JJ
Hoessel, JG
Scowen, PA
Stapelfeldt, KR
Trauger, JT
Westphal, JA
TI Stellar populations in the Large Magellanic Cloud: Evidence for a
significant number of older stars or a steeper IMF?
SO ASTRONOMICAL JOURNAL
LA English
DT Article
ID MAIN-SEQUENCE LUMINOSITY; RADIATIVE OPACITIES; EVOLUTIONARY SEQUENCES;
MODELS; CLUSTERS; AGE
AB We present deep photometry obtained with the HST in an outer LMC field. A well-defined main sequence is seen down to V > 26. We derive a luminosity function from the data and use it to constrain the IMF and the star formation history. We derive limits on the IMF slope, alpha (with dN/dM proportional to M(alpha)), from stars on the main sequence which are fainter than the oldest turnoff. For most choices of star formation history and metallicity, we derive slopes which are consistent the Salpeter (alpha = -2.35) or local solar neighborhood IMF, although the preferred values are steeper. We can rule out IMF slopes shallower than -1.6 and steeper than -3.1 for the mass range 0.6 less than or similar to M less than or similar to 1.1 M.. Assuming a Salpeter IMF over the entire observed mass range, we derive star formation histories from the entire luminosity function, which covers the mass range 0.6 less than or similar to M less than or similar to 3 M.. We find that the luminosity function is inconsistent with the scenario in which the bulk of the field stars in the LMC are younger than 4 Gyr. Instead, we find that there must be a comparable number of stars older and younger than 4 Gyr. Our best model has a star formation rate which is roughly constant for 10 Gyr then increases by about a factor of three for the past 2 Gyr. Such a model is also roughly consistent with the distribution of stars in the color-magnitude diagram. Similar model parameters are derived if we adopt the Kroupa, Tout, and Gilmore solar neighborhood LMF instead of a Salpeter slope. Alternatively, we can fit the luminosity function with a predominantly young population if we use a steeper single power law IMF slope with alpha similar to -2.75 over the entire range of observed masses. (C) 1997 American Astronomical Society.
C1 AUSTRALIAN NATL UNIV,MT STROMLO & SIDING SPRING OBSERV,WESTON,ACT 2611,AUSTRALIA.
UNIV WISCONSIN,DEPT ASTRON,MADISON,WI 53706.
CALTECH,JET PROP LAB,PASADENA,CA 91109.
UNIV MICHIGAN,DEPT ATMOSPHER OCEAN & SPACE SCI,ANN ARBOR,MI 48109.
ESA,DEPT SPACE SCI,DIV ASTROPHYS,BALTIMORE,MD 21218.
SPACE TELESCOPE SCI INST,BALTIMORE,MD 21218.
CARNEGIE MELLON UNIV,DEPT PHYS,PITTSBURGH,PA 15213.
ARIZONA STATE UNIV,DEPT PHYS & ASTRON,TEMPE,AZ 85287.
CALTECH,DIV GEOL & PLANETARY SCI,PASADENA,CA 91125.
RP Holtzman, JA (reprint author), NEW MEXICO STATE UNIV,DEPT ASTRON,DEPT 4500 BOX 30001,LAS CRUCES,NM 88003, USA.
RI Stapelfeldt, Karl/D-2721-2012; Clarke, John/C-8644-2013
NR 31
TC 86
Z9 86
U1 0
U2 4
PU AMER INST PHYSICS
PI WOODBURY
PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999
SN 0004-6256
J9 ASTRON J
JI Astron. J.
PD FEB
PY 1997
VL 113
IS 2
BP 656
EP 668
DI 10.1086/118284
PG 13
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WE934
UT WOS:A1997WE93400017
ER
PT J
AU Harris, WE
Phelps, RL
Madore, BF
Pevunova, O
Skiff, BA
Crute, C
Wilson, B
Archinal, BA
AF Harris, WE
Phelps, RL
Madore, BF
Pevunova, O
Skiff, BA
Crute, C
Wilson, B
Archinal, BA
TI IC 1257: A new globular cluster in the Galactic halo
SO ASTRONOMICAL JOURNAL
LA English
DT Article
ID GALAXIES; LYNGA-7; STARS; AGES
AB New CCD photometry of the faint, compact star cluster IC 1257 (l = 17 degrees, b = +15 degrees), obtained with the Palomar 5 m telescope,(1) reveals that it is a highly reddened globular cluster well beyond the Galactic center. With an apparent distance modulus (m - M)(V) = 19.2 and a foreground reddening E(B - V) = 0.75, it is 24 kpc from the Sun and similar to 16 kpc beyond the Galactic center. The morphology of its color-magnitude diagram is similar to that of M13, and suggests that it has moderately low metallicity ([Fe/H] similar or equal to -1.7). (C) 1997 American Astronomical Society.
C1 OBSERV CARNEGIE INST WASHINGTON,PASADENA,CA 91101.
CALTECH,JET PROP LAB,NASA,IPAC EXTRAGALACT DATABASE,PASADENA,CA 91125.
CALTECH,CTR INFRARED PROC & ANAL,PASADENA,CA 91125.
LOWELL OBSERV,FLAGSTAFF,AZ 86001.
LOS ANGELES ASTRON SOC & WESTERN OBSERV,LOS ANGELES,CA.
HOUSTON MUSEUM NAT SCI,GEORGE OBSERV,HOUSTON,TX.
HOUSTON ASTRON SOC,HOUSTON,TX.
USN OBSERV,WASHINGTON,DC 20392.
RP Harris, WE (reprint author), MCMASTER UNIV,DEPT PHYS & ASTRON,HAMILTON,ON L8S 4M1,CANADA.
NR 24
TC 11
Z9 11
U1 0
U2 0
PU AMER INST PHYSICS
PI WOODBURY
PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999
SN 0004-6256
J9 ASTRON J
JI Astron. J.
PD FEB
PY 1997
VL 113
IS 2
BP 688
EP 691
DI 10.1086/118287
PG 4
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WE934
UT WOS:A1997WE93400020
ER
PT J
AU Borissova, J
Catelan, M
Spassova, N
Sweigart, AV
AF Borissova, J
Catelan, M
Spassova, N
Sweigart, AV
TI Stellar photometry of the globular cluster NGC 6229 .1. Data reduction
and morphology of the brighter part of the CMD
SO ASTRONOMICAL JOURNAL
LA English
DT Article
ID COLOR-MAGNITUDE DIAGRAM; HORIZONTAL-BRANCH STARS; CCD-PHOTOMETRY;
PHOTOGRAPHIC PHOTOMETRY; EVOLUTIONARY SEQUENCES; HALO CLUSTERS; GALACTIC
HALO; GIANT; METALLICITY; POPULATIONS
AB BV CCD photometry of the central (1.5' X 2.0') part of the mildly concentrated outer-halo globular cluster NGC 6229 is presented. The data reduction in such a crowded field was based on a wavelet transform analysis. Our larger dataset extends the previous results by Carney et al. [AJ, 101, 1699, (1991)] for the outer and less crowded fields of the cluster, and confirms that NGC 6229 has a peculiar color-magnitude diagram for its position in the Galaxy. In particular, NGC 6229's horizontal branch (HB) presents several interesting features, among which stand out: a well populated and very extended blue tail; a rather blue overall morphology, with (B - R)/(B + V + R) = 0.24 +/- 0.02; a bimodal color distribution, resembling those found for NGC 1851 and NGC 2808; and gaps on the blue HB. NGC 6229 is the first bimodal-HB cluster to be identified in the Galactic outer halo. A low value of the R parameter is confirmed, suggestive of a low helium abundance or of the presence of a quite substantial population of extreme HB stars fainter than our photometric limit (similar or equal to 2.5 mag below the RR Lyrae level in V). Twelve new possible variable stars were found in the central part of the cluster. The morphology of the red giant branch (RGB) also seems to be peculiar. In particular, the RGB luminosity function ''bump'' is not a prominent feature and has only been tentatively identified, on the basis of a comparison with a previously reported detection for M3 (NGC 5272). We also find evidence that red HB stars are more centrally concentrated than blue HB stars and the RGB population. Finally, we compare the properties of NGC 6229 with those for other outer-halo globular clusters, and call attention to what appears to be a bimodal HB distribution for the outer-halo cluster population, where objects with very red or very blue HB types are much more frequently found than clusters with intermediate HB types. (C) 1997 The American Astronomical Society.
C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771.
RP Borissova, J (reprint author), BULGARIAN ACAD SCI,DEPT ASTRON,72 TSARIGRADSKO CHAUSSEE,BG-1784 SOFIA,BULGARIA.
NR 82
TC 20
Z9 20
U1 0
U2 0
PU AMER INST PHYSICS
PI WOODBURY
PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999
SN 0004-6256
J9 ASTRON J
JI Astron. J.
PD FEB
PY 1997
VL 113
IS 2
BP 692
EP 705
DI 10.1086/118288
PG 14
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WE934
UT WOS:A1997WE93400021
ER
PT J
AU NoriegaCrespo, A
VanBuren, D
Dgani, R
AF NoriegaCrespo, A
VanBuren, D
Dgani, R
TI Bow shocks around runaway stars .3. The high resolution maps
SO ASTRONOMICAL JOURNAL
LA English
DT Article
ID EVOLUTION; IRAS
AB In a recent survey for bow shock structures around OB runaway stars using the ISSA/IRAS archival data and excess maps at 60 mu m, 58 candidates were found. These objects are surrounded by extended infrared emission at 60 mu m, characteristic of warm dust heated by ultraviolet photons, a signature of wind bow shocks. High resolution IRAS (HiRes) images have been produced for these 58 objects and some of those spatially resolved are presented in this study. The images were used to distinguish between multiple confused IR sources, possible artifacts and unambiguous bow shocks, as the sources of the extended 60 mu m emission. Six new bow shocks have been identified using this method, and three have been rejected. Twenty two of the targets, however, remain spatially unresolved even at the nominal HiRes resolution of similar to 1'. For the larger and better defined bow shocks some internal substructure is discernible. The length of these features suggest that they arise as the result of a subtle dynamical instability. It cannot be ruled out, however, that some of the bow shock morphology could be imprinted by the surrounding medium. (C) 1997 American Astronomical Society.
C1 CALTECH,JET PROP LAB,PASADENA,CA 91125.
RP NoriegaCrespo, A (reprint author), CALTECH,CTR INFRARED PROC & ANAL,PASADENA,CA 91125, USA.
NR 18
TC 46
Z9 46
U1 0
U2 0
PU AMER INST PHYSICS
PI WOODBURY
PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999
SN 0004-6256
J9 ASTRON J
JI Astron. J.
PD FEB
PY 1997
VL 113
IS 2
BP 780
EP 786
DI 10.1086/118298
PG 7
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WE934
UT WOS:A1997WE93400031
ER
PT J
AU Marechal, P
Pagani, L
Langer, WD
Castets, A
AF Marechal, P
Pagani, L
Langer, WD
Castets, A
TI Searching for (OO)-O-16-O-18
SO ASTRONOMY & ASTROPHYSICS
LA English
DT Article
DE ISM:clouds, molecules, abundances; radio lines:ISM
ID DENSE INTERSTELLAR CLOUDS; MOLECULAR CLOUDS; CHEMISTRY; MANTLES; OXYGEN;
GAS
AB After our first tentative detection of the molecular oxygen (OO)-O-16-O-18 isotopomer obtained during the winter '92/93 (Pagani et al. 1993), we attempted to confirm our results by making a deep search in other sources and in other positions in L134N. We have not been able to confirm the original detection in any other place in L134N but we obtain good upper limits towards NGC 2264(IRS2), TMC2, OMC3 and L134N (4', -1') and (5.2', -1) which give an O-2/CO ratio upper limit near 0.1 - the lowest yet obtained toward galactic sources - instead of 0.3-0.4 as predicted by gas phase chemical equilibrium models. As our sample consists of eight cold or lukewarm dark clouds, the low abundance of O-2 With respect to CO seems to be a general characteristic of dark clouds.
C1 CALTECH, JET PROP LAB, PASADENA, CA 91109 USA.
OBSERV GRENOBLE, F-38041 GRENOBLE, FRANCE.
RP Marechal, P (reprint author), OBSERV PARIS, DEMIRM, 61 AV OBSERV, F-75014 PARIS, FRANCE.
NR 20
TC 25
Z9 25
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 FEB
PY 1997
VL 318
IS 1
BP 252
EP 255
PG 4
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WH394
UT WOS:A1997WH39400034
ER
PT J
AU Sekanina, Z
AF Sekanina, Z
TI The problem of split comets revisited
SO ASTRONOMY & ASTROPHYSICS
LA English
DT Letter
DE tidally and nontidally split comets; comet pairs; principal and
secondary nuclei; configurations of fragments; separation velocity;
differential deceleration
AB The results from studies of D/Shoemaker-Levy 9 and other recent split comets and comet pairs lead to the recognition of fundamental differences between breakup products of the tidally and the nontidally split comets and to the conclusive identification of the so-called dissipating comets as secondary nuclei of previously split comets, whose separately arriving principal nuclei had in most cases been missed. The primary attribute of the nontidally split comets is the leading position of the principal nucleus, with all the companion nuclei trailing behind, eventually along the orbit. No such configuration has been observed for the tidally split comets of more than two components. Dominant effects in the relative motions of fragments derived from the tidal disruptions are due to separation velocities, while differential decelerations (due, presumably, to outgassing-driven nongravitational perturbations) prevail for fragments derived from the nontidal breakups. This diversity is interpreted in terms of major differences between the breakup mechanisms for the two categories of objects and between the resulting mass distributions of fragments.
RP Sekanina, Z (reprint author), CALTECH, JET PROP LAB, 4800 OAK GROVE DR, PASADENA, CA 91109 USA.
NR 18
TC 50
Z9 50
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 FEB
PY 1997
VL 318
IS 1
BP L5
EP L8
PG 4
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WH394
UT WOS:A1997WH39400002
ER
PT J
AU Bandy, AJ
Gorski, KM
Bennett, CL
Hinshaw, G
Kogut, A
Lineweaver, C
Smoot, GF
Tenorio, L
AF Bandy, AJ
Gorski, KM
Bennett, CL
Hinshaw, G
Kogut, A
Lineweaver, C
Smoot, GF
Tenorio, L
TI Root mean square anisotropy in the COBE DMR four-year sky maps
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE cosmic microwave background; cosmology, observations
ID MICROWAVE; FLUCTUATIONS; NOISE
AB The sky rms is the simplest model-independent characterization of a cosmological anisotropy signal. We show that the rms temperature fluctuations determined from the COBE Differential Microwave Radiometer (DMR) 4 yr sky maps are frequency independent, consistent with the Planckian spectrum expected for the cosmic microwave background signal and therefore with the hypothesis that they are cosmological in origin. The typical rms amplitude is similar to 35 +/- 2 mu K at 7 degrees and similar to 29 +/- 1 mu K at 10 degrees. An analysis of the rms anisotropy determined from the data in both Galactic and ecliptic coordinates is used to determine the rms quadrupole normalization, Q(rms-PS), for a scale-invariant Harrison-Zeldovich power-law model. Corrections are applied for small biases observed in the likelihood analysis. While there are variations depending on the data selection, all results are consistent with a Q(rms-PS) normalization of similar to 18 +/- 2 mu K. This is also shown to be true for a ''standard'' cold dark matter model of cosmological anisotropy. The difference in the normalization amplitudes derived when the quadrupole is either included or excluded from the analysis is attributable to contamination of the observed sky quadrupole by foreground Galactic emission.
C1 MAX PLANCK INST ASTROPHYS,D-85740 GARCHING,GERMANY.
OBSERV STRASBOURG,STRASBOURG,FRANCE.
UNIV CALIF BERKELEY,LAWRENCE BERKELEY LAB,SPACE SCI LAB,BERKELEY,CA 94720.
UNIV CALIF BERKELEY,CTR PARTICLE ASTROPHYS,BERKELEY,CA 94720.
RP Bandy, AJ (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HUGHES STX CORP,ASTRON & SOLAR PHYS LAB,CODE 685,GREENBELT,MD 20771, USA.
RI Kogut, Alan/D-6293-2012
NR 21
TC 59
Z9 58
U1 0
U2 0
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD FEB 1
PY 1997
VL 475
IS 2
BP 393
EP 398
DI 10.1086/303585
PN 1
PG 6
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WE355
UT WOS:A1997WE35500001
ER
PT J
AU Dwek, E
Arendt, RG
Fixsen, DJ
Sodroski, TJ
Odegard, N
Weiland, JL
Reach, WT
Hauser, MG
Kelsall, T
Moseley, SH
Silverberg, RF
Shafer, RA
Ballester, J
Bazell, D
Isaacman, R
AF Dwek, E
Arendt, RG
Fixsen, DJ
Sodroski, TJ
Odegard, N
Weiland, JL
Reach, WT
Hauser, MG
Kelsall, T
Moseley, SH
Silverberg, RF
Shafer, RA
Ballester, J
Bazell, D
Isaacman, R
TI Detection and characterization of cold interstellar dust and polycyclic
aromatic hydrocarbon emission, from COBE observations
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE dust, extinction; infrared, ISM, lines and bands; ISM, abundances; ISM,
clouds
ID INFRARED-EMISSION; TEMPERATURE-FLUCTUATIONS; SPECTRAL OBSERVATIONS;
EXTINCTION CURVE; MOLECULAR CLOUDS; SMALL GRAINS; IR EMISSION; COAL
MODEL; ULTRAVIOLET; LATITUDE
AB Using data obtained by the DIRBE instrument on the COBE spacecraft, we present the mean 3.5-240 mu m spectrum of high-latitude dust. Combined with a spectrum obtained by the FIRAS instrument, these data represent the most comprehensive wavelength coverage of dust in the diffuse interstellar medium, spanning the 3.5-1000 mu m wavelength regime. At wavelengths shorter than similar to 60 mu m the spectrum shows an excess of emission over that expected from dust heated by the local interstellar radiation field and radiating at an equilibrium temperature. The DIRBE data thus extend the observations of this excess, first detected by the IRAS satellite at 25 and 12 mu m, to shorter wavelengths. The excess emission arises from very small dust particles undergoing temperature fluctuations. However, the 3.5-4.9 mu m intensity ratio cannot be reproduced by very small silicate or graphite grains. The DIRBE data strongly suggest that the 3.5-12 mu m emission is produced by carriers of the ubiquitous 3.3, 6.2, 7.7, 8.6, and 11.3 mu m solid state emission features that have been detected in a wide variety of astrophysical objects. The carriers of these features have been widely identified with polycyclic aromatic hydrocarbons (PAHs).
Our dust model consists of a mixture of PAH molecules and bare astronomical silicate and graphite grains with optical properties given by Draine & Lee. We obtain a very good fit to the DIRBE spectrum, deriving the size distribution, abundances relative to the total hydrogen column density, and relative contribution of each dust component to the observed IR emission. At wavelengths above 140 mu m the model is dominated by emission from T approximate to 17-20 K graphite and 15-18 K silicate grains. The model provides a good fit to the FIRAS spectrum in the 140-500 mu m wavelength regime but leaves an excess Galactic emission component at 500-1000 mu m. The nature of this component is still unresolved.
We find that (C/H) is equal to (7.3 +/- 2.2) x 10(-5) for PAHs and equal to (2.5 +/- 0.8) x 10(-4) for graphite grains, requiring about 20% of the cosmic abundance of carbon to be locked up in PAHs, and about 70% in graphite grains [we adopt (C/H). = 3.6 x 10(-4)]. The model also requires all of the available magnesium, silicon, and iron to be locked up in silicates. The power emitted by PAHs is 1.6 x 10(-31) W per H atom, by graphite grains 3.0 x 10(-31) W per H atom, and by silicates 1.4 x 10(-31) W per H atom, adding up to a total infrared intensity of 6.0 x 10(-31) W per H atom, or similar to 2 L. M.(-1).
The [C II] 158 mu m line emission detected by the FIRAS provides important information on the gas phase abundance of carbon in the diffuse ISM. The 158 mu m line arises predominantly from the cold neutral medium (CNM) and shows that for typical CNM densities and temperatures C+/H = (0.5-1.0) x 10(-4), which is similar to 14%-28% of the cosmic carbon abundance. The remaining carbon abundance in the CNM, which must be locked up in dust, is about equal to that required to provide the observed IR emission, consistent with notion that most (greater than or similar to 75%) of this emission arises from the neutral component of the diffuse ISM.
The model provides st good fit to the general interstellar extinction curve. However, at UV wavelengths it predicts a larger extinction. The excess extinction may be the result of the UV properties adopted for the PAHs. If real, the excess UV extinction may be accounted for by changes in the relative abundances of PAHs and carriers of the 2200 Angstrom, extinction bump.
C1 NASA,GODDARD SPACE FLIGHT CTR,HUGHES STX,GREENBELT,MD 20771.
NASA,GODDARD SPACE FLIGHT CTR,APPL RES CORP,GREENBELT,MD 20771.
UNIV PARIS 11,IST ASTROPHYS SPATIALE,F-91405 ORSAY,FRANCE.
SPACE TELESCOPE SCI INST,BALTIMORE,MD 21218.
EMPORIA STATE UNIV,EMPORIA,KS 66801.
NASA,GODDARD SPACE FLIGHT CTR,GEN SCI CORP,GREENBELT,MD 20771.
RP Dwek, E (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,CODE 685,GREENBELT,MD 20771, USA.
RI Moseley, Harvey/D-5069-2012;
OI Reach, William/0000-0001-8362-4094
NR 71
TC 193
Z9 193
U1 0
U2 5
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD FEB 1
PY 1997
VL 475
IS 2
BP 565
EP 579
DI 10.1086/303568
PN 1
PG 15
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WE355
UT WOS:A1997WE35500019
ER
PT J
AU MoriartySchieven, GH
Andersson, BG
Wannier, PG
AF MoriartySchieven, GH
Andersson, BG
Wannier, PG
TI The L1457 molecular/atomic cloud complex: H I and CO maps
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE ISM, individual (L1457); ISM, molecules; ISM, structure; radio lines,
ISM
ID WARM NEUTRAL HALOS; INTERSTELLAR-MEDIUM; 50 PC; MBM-12; STARS;
POLARIZATION; CALIBRATION; HYDROGEN; SUN
AB L1457 is the closest known molecular cloud (65 pc), and it lies near the edge of the local hot bubble and well out of the Galactic plane (b similar to -34 degrees). We have mapped an 8 degrees x 8 degrees region at 35' resolution and a 3 degrees x 5 degrees region at similar to 2' resolution in H I 21 cm emission. We have also mapped a 2 degrees x 4 degrees region at 2' resolution in (CO)-C-12 J = 1-0. We find that there is an extended component of atomic gas, clearly associated with the molecular complex and comparable to it in total mass. The H I structure at small scales in the vicinity of the molecular clouds is remarkable, consisting largely of long, narrow filaments less than 20' (0.2 pc) in width and 1 degrees-4 degrees in length. A thin (<10') limb-brightened atomic halo is seen to surround the CO at some velocities, but it is ill-defined at other velocities. The halo may be disturbed by external pressure, perhaps from the hot gas in the local bubble.
The molecular clouds are part of a large structure similar to 5 degrees x 3 degrees in extent with a small ''funnel-shaped'' extension to the south. The structure, which we call the L1457 atomic/molecular complex, is dominated by H I in the north and H, in the south extension. Roughly one-half the mass of the complex is molecular. The structure of this complex at both large- and small-scale suggests that the south end has been recently compressed.
C1 JOINT ASTRON CTR,HILO,HI 96720.
CALTECH,JET PROP LAB,PASADENA,CA 91109.
RP MoriartySchieven, GH (reprint author), NATL RES COUNCIL CANADA,DOMINION RADIO ASTROPHYS OBSERV,BOX 248,PENTICTON,BC V2A 6K3,CANADA.
NR 28
TC 22
Z9 22
U1 0
U2 0
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD FEB 1
PY 1997
VL 475
IS 2
BP 642
EP 660
PN 1
PG 19
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WE355
UT WOS:A1997WE35500025
PM 11540053
ER
PT J
AU Hwang, U
Gotthelf, EV
AF Hwang, U
Gotthelf, EV
TI X-ray emission-line imaging and spectroscopy of Tycho's supernova
remnant
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE ISM, individual (Tycho's supernova); supernova remnants; X-rays, ISM
ID NOVA REMNANT; CASSIOPEIA-A; ASCA; ABUNDANCES; SATELLITE; SPECTRUM;
SN-1572; PUPPIS; MODELS
AB We present X-ray images of Tycho's supernova remnant in emission-line features of Mg, Si, S, Ar, Ca, and Fe, plus the continuum, using data obtained by the imaging spectrometers on board the Advanced Satellite for Cosmology and Astrophysics (ASCA). All the images show the shell-like morphology characteristic of previously obtained broadband X-ray images, but they are clearly distinct from each other. We use image reconstruction techniques to achieve a spatial resolution of similar to 0'8. Line intensity ratios are used to make inferences about the remnant's physical state, on average for the entire remnant and with angular position around the rim. The average temperature of the Si and S ejecta in the remnant is (0.8-1.1) x 10(7) K, and the average ionization age is (0.8-1.3) x 10(11) cm(-3) s. For a constant ionization age, the observed relative brightness variations of Si and S line image profiles with azimuthal angle imply differences of roughly a factor of 1.3-1.8 in the temperature. We compare the radial brightness profiles of our images with simple geometrical models and find that a spherical emitting geometry is favored over a torus. A spherical geometry is further supported by the absence of systematic Doppler shifts across the remnant. The radial fit results also suggest that some radial mixing of the ejecta has occurred. However, the azimuthally averaged Fe K image peaks at a markedly lower radius than the other images. The average Fe K/Fe L line intensity ratio and the position of the Fe K energy centroid support a temperature several times higher and an ionization age approximately a factor of 10 lower than for the other elements, and imply that the Fe ejecta must have retained some of its stratification. Although many of the features in the 4-6 keV X-ray continuum correspond to those in the radio, there is no obvious correlation between the relative brightness in these bands.
RP Hwang, U (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA.
NR 52
TC 81
Z9 82
U1 0
U2 1
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD FEB 1
PY 1997
VL 475
IS 2
BP 665
EP &
DI 10.1086/303546
PN 1
PG 21
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WE355
UT WOS:A1997WE35500027
ER
PT J
AU Hartmann, L
Cassen, P
Kenyon, SJ
AF Hartmann, L
Cassen, P
Kenyon, SJ
TI Disk accretion and the stellar birthline
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE accretion, accretion disks; stars, evolution; stars, formation; stars,
pre-main-sequence
ID T-TAURI STARS; AURIGA MOLECULAR CLOUD; SPECTRAL ENERGY-DISTRIBUTIONS;
FU-ORIONIS OBJECTS; EVOLUTION; PROTOSTARS; MODELS; EMISSION
AB We present a simplified analysis of some effects of disk accretion on the early evolution of fully convective, low-mass pre-main-sequence stars. Our analysis builds on the previous seminal work of Stahler, but it differs in that the accretion of material occurs over a small area of the stellar surface, such as through a disk or magnetospheric accretion column, so that most of the stellar photosphere is free to radiate to space. This boundary condition is similar to the limiting case considered by Palla & Stahler for intermediate-mass stars. We argue that for a wide variety of disk mass accretion rates, material will be added to the star with relatively small amounts of thermal energy. Protostellar evolution calculated assuming this ''low-temperature'' limit of accretion generally follows the results of Stahler because of the thermostatic nature of deuterium fusion, which prevents protostars from contracting below a ''birthline'' in the H-R diagram. Our calculated protostellar radii tend to fall below Stahler's at higher masses; the additional energy loss from the stellar photosphere in the case of disk accretion tends to make the protostar contract. The low-temperature disk accretion evolutionary tracks never fall below the deuterium-fusion birthline until the internal deuterium is depleted, but protostellar tracks can lie above the birthline in the H-R diagram if the initial radius of the protostellar core is large enough or if rapid disk accretion (such as might occur during FU Ori outbursts) adds significant amounts of thermal energy to the star. These possibilities cannot be ruled out by either theoretical arguments or observational constraints at present, so that individual protostars might evolve along a multiplicity of birthlines with a modest range of luminosity at a given mass. Our results indicate that there are large uncertainties in assigning ages for the youngest stars from H-R diagram positions, given the uncertainty in birthline positions. Our calculations also suggest that the relatively low disk accretion rates characteristic of T Tauri stars below the birthline cause low-mass stars to contract only slightly faster than normal Hayashi track evolution, so that ages for older pre-main-sequence stars estimated from H-R diagram positions are relatively secure.
C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035.
RP Hartmann, L (reprint author), HARVARD SMITHSONIAN CTR ASTROPHYS,60 GARDEN ST,CAMBRIDGE,MA 02138, USA.
OI Kenyon, Scott/0000-0003-0214-609X
NR 46
TC 114
Z9 114
U1 0
U2 1
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD FEB 1
PY 1997
VL 475
IS 2
BP 770
EP 785
DI 10.1086/303547
PN 1
PG 16
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WE355
UT WOS:A1997WE35500036
ER
PT J
AU Mukai, K
Wood, JH
Naylor, T
Schlegel, EM
Swank, JH
AF Mukai, K
Wood, JH
Naylor, T
Schlegel, EM
Swank, JH
TI The x-ray eclipse of the dwarf nova HT Cassiopeiae: Results from ASCA
and ROSAT HRI observations
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE binaries, eclipsing; novae, cataclysmic variables; stars, individual (HT
cassiopeiae); x-rays, stars
ID CATACLYSMIC VARIABLES; BOUNDARY-LAYER; ACCRETION DISKS; OY CARINAE;
EMISSION; SUPEROUTBURST; SAMPLE; STAR
AB We report on a 1 day ASCA observation and ROSAT HRI observations of the eclipsing dwarf nova HT Gas. The presence of the X-ray eclipse, originally detected in a ROSAT PSPC observation, is confirmed at a much higher significance level. The quality of the ASCA light curve is high enough to allow detailed investigation of the eclipse depth, width, and shape. The eclipse is found to be deep, compatible with being total The eclipse width is comparable to that of the white dwarf, as derived from optical light curves, and in fact may be narrower. The eclipse transition is also found to be short, which puts a limit of 1.15 times the white dwarf radius as the total size of the X-ray emission region. The out-of-eclipse spectrum of HT Cas is found to be consistent with a single temperature (kT similar to 10 keV), absorbed (N-H similar to 3.3 x 10(21) cm(-2)), thermal model.
C1 UNIV SPACE RES ASSOC,WASHINGTON,DC.
UNIV KEELE,DEPT PHYS,KEELE ST5 5BG,STAFFS,ENGLAND.
RP Mukai, K (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771, USA.
RI Swank, Jean/F-2693-2012; Naylor, Tim /A-9465-2015
NR 34
TC 42
Z9 42
U1 0
U2 0
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD FEB 1
PY 1997
VL 475
IS 2
BP 812
EP 822
DI 10.1086/303571
PN 1
PG 11
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WE355
UT WOS:A1997WE35500040
ER
PT J
AU Corbet, RHD
Mihara, T
AF Corbet, RHD
Mihara, T
TI The spin-down rate and X-ray flux of 1E 1048.1-5937
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE stars, individual (1E 1048.1-5937); stars, neutron; X-rays, stars
ID PULSAR 1E1048.1-5937; PERIOD; STARS; ASCA
AB We present the results of observations of the pulsating X-ray source 1E 1048.1-5937 made with the ASCA GIS detectors. The source continues to exhibit spin-down at the faster rate reported from ROSAT observations rather than the slower spin-down rate initially measured. The X-ray spectrum can be satisfactorily fitted with a power-law model, and we cannot discriminate between this and the power law plus blackbody combination used for two Other members of this class. The mean flux is approximately a factor of 3 weaker than measured with EXOSAT, which is consistent with X-ray emission being powered by accretion. While these results reinforce the similarity to 1E 2259+586, the pulsed fraction of 1E 1048.1-5937 is much larger with little energy dependence.
C1 INST PHYS & CHEM RES,WAKO,SAITAMA 35101,JAPAN.
RP Corbet, RHD (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 662,GREENBELT,MD 20771, USA.
RI Mihara, Tatehiro/C-5536-2017
OI Mihara, Tatehiro/0000-0002-6337-7943
NR 22
TC 31
Z9 30
U1 0
U2 0
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD FEB 1
PY 1997
VL 475
IS 2
BP L127
EP L130
DI 10.1086/310480
PN 2
PG 4
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WE356
UT WOS:A1997WE35600014
ER
PT J
AU Ford, E
Kaaret, P
Tavani, M
Barret, D
Bloser, P
Grindlay, J
Harmon, BA
Paciesas, WS
Zhang, SN
AF Ford, E
Kaaret, P
Tavani, M
Barret, D
Bloser, P
Grindlay, J
Harmon, BA
Paciesas, WS
Zhang, SN
TI Evidence from quasi-periodic oscillations for a millisecond pulsar in
the low-mass X-ray binary 4U 0614+091
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE accretion, accretion disks; pulsars, general; stars, individual (4U
0614+091); stars, neutron; X-rays, stars
ID TIMING EXPLORER; GX5-1
AB We have detected quasi-periodic oscillations (QPOs) near 1 kHz from the low-mass X-ray binary 4U 0614+091 in observations with the Rossi X-Ray Timing Explorer. The observations span several months and sample the source over a large range of X-ray luminosity. In every interval, QPOs are present above 400 Hz with fractional rms amplitudes from 3% to 12% over the full Proportional Counter Array energy band, At high count rates, two high-frequency QPOs are detected simultaneously. The difference in their frequency centroids is consistent with a constant value of 323 +/- 4 Hz in all observations. During one interval, a third signal is detected at 328 +/- 2 Hz. This suggests that the system has a stable ''clock'' that is most likely the neutron star with spin period 3.1 ms. Thus, our observations of 4U 0614+091, and those of 4U 1728-34 and KS 1731-260, provide the first evidence for millisecond pulsars within low-mass X-ray binary systems and reveal the ''missing-link'' between millisecond radiopulsars and the late stages of binary evolution in low-mass X-ray binaries. The constant difference in the high-frequency QPOs suggests a beat-frequency interpretation. In this model, the high-frequency QPO is associated with the Keplerian frequency of the inner accretion disk, and the lower frequency QPO is a ''beat'' between the differential rotation frequency of the inner disk and the spinning neutron star. Assuming the high-frequency QPO is a Keplerian orbital frequency for the accretion disk, we find a maximum mass of 1.9 M. and a maximum radius of 17 km for the neutron star.
C1 COLUMBIA UNIV, COLUMBIA ASTROPHYS LAB, NEW YORK, NY 10027 USA.
HARVARD SMITHSONIAN CTR ASTROPHYS, CAMBRIDGE, MA 02138 USA.
NASA, GEORGE C MARSHALL SPACE FLIGHT CTR, HUNTSVILLE, AL 35812 USA.
UNIV ALABAMA, DEPT PHYS, HUNTSVILLE, AL 35899 USA.
NASA, GEORGE C MARSHALL SPACE FLIGHT CTR, UNIV SPACE RES ASSOC, HUNTSVILLE, AL 35812 USA.
RP Ford, E (reprint author), COLUMBIA UNIV, DEPT PHYS, 538 W 120TH ST, NEW YORK, NY 10027 USA.
NR 23
TC 57
Z9 58
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 FEB 1
PY 1997
VL 475
IS 2
BP L123
EP L126
DI 10.1086/310483
PN 2
PG 4
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WE356
UT WOS:A1997WE35600013
ER
PT J
AU Hyung, S
Aller, LH
Feibelman, WA
AF Hyung, S
Aller, LH
Feibelman, WA
TI The spectrum of the planetary nebula NGC 6884
SO ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES
LA English
DT Article
DE infrared, ISM, lines and bands; ISM, abundances; ISM, individual (NGC
6884); ultraviolet, ISM
ID STATISTICAL DISTANCE SCALE; CENTRAL STARS; H-I; ABUNDANCES; CONTINUUM;
EVOLUTION; NGC-6572; SULFUR; MODEL
AB The bright, compact, moderately high-excitation planetary nebula, NGC 6884 (Perek-Kohoutek 82 +07 degrees 1) has a rich spectrum promising good diagnostics and offering a good target for the Hamilton Echelle Spectrograph at Lick Observatory. We combine International Ultraviolet Explorer (IUE), near-UV, visual, and IR data to obtain N(ion)/N(H+) for more than 30 species from H to [Fe VI]. These diagnostics suggest a rather large density range and an electron temperature near 10,000 K. The relative structural simplicity of this planetary nebula makes it worthwhile to attempt a plausible photoionization model and deduce atomic abundances, T*, and other properties implied for the central star. It is believed substantially improved chemical compositions are found.
C1 NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771.
RP Hyung, S (reprint author), UNIV CALIF LOS ANGELES,DEPT PHYS & ASTRON,LOS ANGELES,CA 90095, USA.
NR 39
TC 16
Z9 16
U1 0
U2 0
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637
SN 0067-0049
J9 ASTROPHYS J SUPPL S
JI Astrophys. J. Suppl. Ser.
PD FEB
PY 1997
VL 108
IS 2
BP 503
EP 513
DI 10.1086/312969
PG 11
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WF165
UT WOS:A1997WF16500006
ER
PT J
AU Kumar, VK
Billica, RD
Waligora, JM
AF Kumar, VK
Billica, RD
Waligora, JM
TI Utility of Doppler-detectable microbubbles in the diagnosis and
treatment of decompression sickness
SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE
LA English
DT Article; Proceedings Paper
CT 11th Man in Space Symposium
CY MAR 27-31, 1995
CL TOULOUSE, FRANCE
ID DECISION-MAKING; ALTITUDE
AB Background: Doppler-detectable microbubbles (DMB) are frequently used to evaluate altitude decompression stress. However, the role of DMB in the therapy of decompression sickness (DCS) has not been examined. Hypothesis: The ability of Doppler to detect microbubbles during decompression (Doppler test) may be used in the diagnosis of DCS, and to aid clinical decisions about treatment options for DCS. Methods: We examined the data on DMB and symptoms from NASA Database on DCS (n = 516). The accuracy of Doppler test was obtained from the Receiver Operating Characteristic (ROC) for DMB (grades I through IV), and efficacy was obtained by calculating predictive or posttest probabilities. Threshold analysis was used to obtain the probabilities for testing and/or treatment decisions. Results: The Doppler test was useful for both screening and confirming DCS, when different criteria (grade I for screening; grade IV for confirming) were used for a positive test. Calculation of predictive values and threshold analysis showed that: 1) early recompression was the therapy of choice when post-test probability of disease was >0.25 in individuals with non-specific pain at altitude, and early recompression with 100% oxygen for 2 h at site level was optimal therapy when this probability was >0.33; 2) hyperbaric therapy was optimal when post-test probability was >0.04 in individuals with uncertain symptoms post-flight. Conclusions: The Doppler test was of greater utility in excluding DCS than confirming its presence, and was useful in making therapeutic decisions on DCS when confronted with non-specific symptoms at altitude.
C1 KRUG LIFE SCI,HOUSTON,TX.
NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058.
NR 21
TC 8
Z9 10
U1 0
U2 0
PU AEROSPACE MEDICAL ASSOC
PI ALEXANDRIA
PA 320 S HENRY ST, ALEXANDRIA, VA 22314-3579
SN 0095-6562
J9 AVIAT SPACE ENVIR MD
JI Aviat. Space Environ. Med.
PD FEB
PY 1997
VL 68
IS 2
BP 151
EP 158
PG 8
WC Public, Environmental & Occupational Health; Medicine, General &
Internal; Sport Sciences
SC Public, Environmental & Occupational Health; General & Internal
Medicine; Sport Sciences
GA WG529
UT WOS:A1997WG52900011
PM 9125093
ER
PT J
AU Kaiser, MK
Montegut, MJ
AF Kaiser, MK
Montegut, MJ
TI Of red planets and indigo computers: Mars database visualization as an
example of platform downsizing
SO BEHAVIOR RESEARCH METHODS INSTRUMENTS & COMPUTERS
LA English
DT Article; Proceedings Paper
CT Symposium on High-Performance Computer Applications in the Behavioral
Sciences
CY MAY 10-12, 1996
CL MINNEAPOLIS, MN
SP Univ Minnesota Supercomp Inst, Federat Behav Psychol & Cognit Sci
AB The last decade has witnessed tremendous advancements in the computer hardware and software used to perform scientific visualization. In this paper, we consider how the visualization of a particular data set, the digital terrain model derived from the Viking orbiter imagery, has been realized in four distinct projects over this period. These examples serve to demonstrate how the vast improvements in computational performance both decrease the cost of such visualization efforts and permit an increasing level of interactivity. We then consider how even today's graphical systems require the visualization designer to make intelligent choices and tradeoffs in database rendering. Finally, we discuss how insights gleaned from an understanding of human visual perception can guide these design decisions, and suggest new options for visualization hardware and software.
RP Kaiser, MK (reprint author), NASA,AMES RES CTR,MAIL STOP 262-2,MOFFETT FIELD,CA 94035, USA.
NR 10
TC 5
Z9 5
U1 0
U2 0
PU PSYCHONOMIC SOC INC
PI AUSTIN
PA 1710 FORTVIEW RD, AUSTIN, TX 78704
SN 0743-3808
J9 BEHAV RES METH INS C
JI Behav. Res. Methods Instr. Comput.
PD FEB
PY 1997
VL 29
IS 1
BP 48
EP 53
PG 6
WC Psychology, Mathematical; Psychology, Experimental
SC Psychology
GA WM110
UT WOS:A1997WM11000009
PM 11539867
ER
PT J
AU Mulligan, JB
AF Mulligan, JB
TI Image processing for improved eye-tracking accuracy
SO BEHAVIOR RESEARCH METHODS INSTRUMENTS & COMPUTERS
LA English
DT Article; Proceedings Paper
CT Symposium on High-Performance Computer Applications in the Behavioral
Sciences
CY MAY 10-12, 1996
CL MINNEAPOLIS, MN
SP Univ Minnesota Supercomp Inst, Federat Behav Psychol & Cognit Sci
ID OCULAR TORSION; MOVEMENTS
AB Video cameras provide a simple, noninvasive method for monitoring a subject's eye movements. An important concept is that of the resolution of the system, which is the smallest eye movement that can be reliably detected. While hardware systems are available that estimate direction of gaze in real time from a video image of the pupil, such systems must limit image processing to attain real-time performance and are limited to a resolution of about 10 are minutes. Two ways to improve resolution are discussed. The first is to improve the image processing algorithms that are used to derive an estimate. Offline analysis of the data can improve resolution by at least one order of magnitude for images of the pupil. A second avenue by which to improve resolution is to increase the optical gain of the imaging setup (i.e., the amount of image motion produced by a given eye rotation). Ophthalmoscopic imaging of retinal blood vessels provides increased optical gain and improved immunity to small head movements but requires a highly sensitive camera. The large number of images involved in a typical experiment imposes great demands on the storage, handling, and processing of data. A major bottleneck had been the real-time digitization and storage of large amounts of video imagery, but recent developments in video compression hardware hare made this problem tractable at a reasonable cost. Images of both the retina and the pupil can be analyzed successfully using a basic toolbox of image-processing routines (filtering, correlation, thresholding, etc.), which are, for the most part, well suited to implementation on vectorizing supercomputers.
RP Mulligan, JB (reprint author), NASA,AMES RES CTR,MS 262-2,MOFFETT FIELD,CA 94035, USA.
NR 26
TC 21
Z9 21
U1 0
U2 2
PU PSYCHONOMIC SOC INC
PI AUSTIN
PA 1710 FORTVIEW RD, AUSTIN, TX 78704
SN 0743-3808
J9 BEHAV RES METH INS C
JI Behav. Res. Methods Instr. Comput.
PD FEB
PY 1997
VL 29
IS 1
BP 54
EP 65
PG 12
WC Psychology, Mathematical; Psychology, Experimental
SC Psychology
GA WM110
UT WOS:A1997WM11000010
PM 11539868
ER
PT J
AU Edwards, LK
Link, SW
Null, CH
AF Edwards, LK
Link, SW
Null, CH
TI High-performance computer applications in the behavioral sciences
SO BEHAVIOR RESEARCH METHODS INSTRUMENTS & COMPUTERS
LA English
DT Editorial Material
AB This symposium revisited the 1985 conference on Advanced Computing for Psychology. That meeting examined the application of new supercomputers in the behavioral sciences. The present symposium reviewed high-performance computing as applied to psychological models, human vision, neuralphysiological processes, and statistical analysis. The recent past and the projected future of high-performance computing in the behavioral sciences were evaluated.
C1 FED BEHAV PSYCHOL & COGNIT SCI,WASHINGTON,DC.
NASA,AMES RES CTR,MOFFETT FIELD,CA 94035.
RP Edwards, LK (reprint author), UNIV MINNESOTA,DEPT EDUC PSYCHOL,323 BURTON HALL,178 PILLSBURY DR SE,MINNEAPOLIS,MN 55455, USA.
RI Puziy, Alexander/D-6759-2011; Shevelev, Yuriy/D-7811-2014
OI Puziy, Alexander/0000-0001-7841-3380;
NR 2
TC 0
Z9 0
U1 0
U2 0
PU PSYCHONOMIC SOC INC
PI AUSTIN
PA 1710 FORTVIEW RD, AUSTIN, TX 78704
SN 0743-3808
J9 BEHAV RES METH INS C
JI Behav. Res. Methods Instr. Comput.
PD FEB
PY 1997
VL 29
IS 1
BP 122
EP 125
PG 4
WC Psychology, Mathematical; Psychology, Experimental
SC Psychology
GA WM110
UT WOS:A1997WM11000023
ER
PT J
AU Southward, RE
Thompson, DW
StClair, AK
AF Southward, RE
Thompson, DW
StClair, AK
TI Control of reflectivity and surface conductivity in metallized polyimide
films prepared via in situ silver(I) reduction
SO CHEMISTRY OF MATERIALS
LA English
DT Article
ID CHEMICAL-VAPOR-DEPOSITION; PHOTOEMISSION; PRECURSORS; ADHESION
AB Optically reflective and surface-conductive polyimide films have been prepared by the incorporation of silver(I) acetate and trifluoroacetylacetone into a dimethylacetamide solution of the poly(amic acid) formed from 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride (BTDA) and 4,4'-oxydianiline (4,4'-ODA). Thermal curing of the silver(I)-containing poly(amic acid) leads to imidization with concomitant silver(I) reduction, yielding a reflective and conductive silver surface if the silver(O) concentration is greater than ca. 12% by weight and the film is cured to a final temperature of 340 degrees C. The metallized BTDA/4,4'-ODA films retain the essential mechanical properties of undoped films and have good thermal stability particularly in nitrogen atmospheres. The bulk of the polymer is not electrically conducting. Films were characterized by X-ray, DSC, TGA, XPS, TEM, SEM, and AFM.
C1 COLL WILLIAM & MARY,DEPT CHEM,WILLIAMSBURG,VA 23185.
COLL WILLIAM & MARY,DEPT APPL SCI,WILLIAMSBURG,VA 23185.
NASA,LANGLEY RES CTR,DIV MAT,HAMPTON,VA 23681.
NR 49
TC 44
Z9 46
U1 0
U2 4
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036
SN 0897-4756
J9 CHEM MATER
JI Chem. Mat.
PD FEB
PY 1997
VL 9
IS 2
BP 501
EP 510
DI 10.1021/cm960349e
PG 10
WC Chemistry, Physical; Materials Science, Multidisciplinary
SC Chemistry; Materials Science
GA WJ270
UT WOS:A1997WJ27000018
ER
PT J
AU Adam, N
Awerbuch, B
Slonim, J
Wegner, P
Yesha, Y
AF Adam, N
Awerbuch, B
Slonim, J
Wegner, P
Yesha, Y
TI Globalizing business, education, culture through the Internet
SO COMMUNICATIONS OF THE ACM
LA English
DT Article
C1 JOHNS HOPKINS UNIV,BALTIMORE,MD 21218.
UNIV WATERLOO,DEPT COMP SCI,FAC MATH,WATERLOO,ON N2L 3G1,CANADA.
BROWN UNIV,PROVIDENCE,RI 02912.
UNIV MARYLAND BALTIMORE CTY,BALTIMORE,MD 21228.
NASA,CTR EXCELLENCE SPACE DATA & INFORMAT SCI,WASHINGTON,DC 20546.
RP Adam, N (reprint author), RUTGERS STATE UNIV,CTR INFORMAT MANAGEMENT INTEGRAT & CONNECT,PISCATAWAY,NJ 08855, USA.
NR 4
TC 16
Z9 16
U1 0
U2 3
PU ASSOC COMPUTING MACHINERY
PI NEW YORK
PA 1515 BROADWAY, NEW YORK, NY 10036
SN 0001-0782
J9 COMMUN ACM
JI Commun. ACM
PD FEB
PY 1997
VL 40
IS 2
BP 115
EP 121
DI 10.1145/253671.253748
PG 7
WC Computer Science, Hardware & Architecture; Computer Science, Software
Engineering; Computer Science, Theory & Methods
SC Computer Science
GA WE048
UT WOS:A1997WE04800029
ER
PT J
AU Thomas, RE
Carls, MG
Rice, SD
Shagrun, L
AF Thomas, RE
Carls, MG
Rice, SD
Shagrun, L
TI Mixed function oxygenase induction in pre- and post-spawn herring
(Clupea pallasi) by petroleum hydrocarbons
SO COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY C-PHARMACOLOGY TOXICOLOGY &
ENDOCRINOLOGY
LA English
DT Article
DE aryl hydrocarbon hydroxylase; cytochrome P-450; ethoxyresorufin
O-deethylase; mixed function oxygenase; polycyclic aromatic hydrocarbon;
Pacific herring; pre-spawn
ID SOLE PAROPHRYS-VETULUS; TAUTOGOLABRUS-ADSPERSUS; HYDROXYLASE-ACTIVITY;
FUNCTION OXIDASE; RAINBOW-TROUT; FISH; REPRODUCTION; XENOBIOTICS;
METABOLISM; OIL
AB We compared the uptake of water-accommodated fractions of Alaska North Slope crude oil in pre- and post-spawn herring (Clupea pallasi) and the resulting induction of mixed function oxygenase activity. Both groups of herring accumulated significant quantities of polycyclic aromatic hydrocarbons in muscle tissue. Pre-spawn herring accumulated higher concentrations of hydrocarbons and retained them longer. Induction of mixed function oxygenase activity in pre-spawn fish was one-third to one-half that in post-spawn fish. Inability of pre-spawn herring to induce mixed function oxygenases at as high a level as post-spawn fish may explain higher tissue concentrations and retention of hydrocarbons in the pre-spawn animals. (C) 1997 Elsevier Science Inc.
C1 NATL MARINE FISHERIES SERV,AUKE BAY LAB,JUNEAU,AK 99801.
RP Thomas, RE (reprint author), CALIF STATE UNIV LOS ANGELES,DEPT BIOL SCI,CHICO,CA 95929, USA.
NR 43
TC 11
Z9 12
U1 0
U2 3
PU PERGAMON-ELSEVIER SCIENCE LTD
PI OXFORD
PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB
SN 0742-8413
J9 COMP BIOCHEM PHYS C
JI Comp. Biochem. Physiol. C-Pharmacol. Toxicol. Endocrinol.
PD FEB
PY 1997
VL 116
IS 2
BP 141
EP 147
DI 10.1016/S0742-8413(96)00147-8
PG 7
WC Biochemistry & Molecular Biology; Endocrinology & Metabolism;
Toxicology; Zoology
SC Biochemistry & Molecular Biology; Endocrinology & Metabolism;
Toxicology; Zoology
GA WU072
UT WOS:A1997WU07200005
ER
PT J
AU Karaoglan, L
Noor, AK
Kim, YH
AF Karaoglan, L
Noor, AK
Kim, YH
TI Frictional contact/impact response of textile composite structures
SO COMPOSITE STRUCTURES
LA English
DT Article
ID SENSITIVITY
AB The results of a detailed study of the frictional contact/impact response of axisymmetric textile composite structures are presented. The structures are assumed to consist of an arbitrary number of perfectly bonded layers of woven fabric or braided preforms. The material of each layer is assumed to be hyperelastic and the effect of geometric nonlinearity is included. The equations of motion of the structure are established in the current configuration and a displacement finite element model is used for the spatial discretization. A Coulomb friction model is used and the temporal integration is performed by using an explicit central difference scheme. Both the dynamic response and the sensitivity coefficients are evaluated. The sensitivity coefficients measure the sensitivity of the response to variations in the textile preform architecture and constituent properties, as well as to variations in the effective layer properties. Numerical results are presented for the frictional contact/impact response of a spherical cap made of textile (woven and braided) composite material, impacting a rigid surface. Results are compared with those of a spherical cap made of tape laminate. (C) 1997 Published by Elsevier Science Ltd.
C1 SEOUL NATL UNIV,SEOUL,SOUTH KOREA.
RP Karaoglan, L (reprint author), UNIV VIRGINIA,NASA,LANGLEY RES CTR,CTR ADV COMPUTAT TECHNOL,MAIL STOP 369,HAMPTON,VA 23681, USA.
NR 10
TC 11
Z9 11
U1 2
U2 4
PU ELSEVIER SCI LTD
PI OXFORD
PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB
SN 0263-8223
J9 COMPOS STRUCT
JI Compos. Struct.
PD FEB
PY 1997
VL 37
IS 2
BP 269
EP 280
DI 10.1016/S0263-8223(97)80018-9
PG 12
WC Materials Science, Composites
SC Materials Science
GA XW028
UT WOS:A1997XW02800014
ER
PT J
AU Baroth, E
AF Baroth, E
TI How the Internet changes data acquisition
SO EE-EVALUATION ENGINEERING
LA English
DT Article
RP Baroth, E (reprint author), CALTECH,JET PROP LAB,MEASUREMENT TECHNOL CTR,MEASUREMENT TEST & ENGN SUPPORT SECT,PASADENA,CA 91109, USA.
NR 1
TC 0
Z9 0
U1 0
U2 0
PU NELSON PUBLISHING
PI NOKOMIS
PA 2504 NORTH TAMIAMI TRAIL, NOKOMIS, FL 34275-3482
SN 0149-0370
J9 EE-EVAL ENG
JI EE-Eval. Eng.
PD FEB
PY 1997
VL 36
IS 2
BP S1
EP &
PG 5
WC Engineering, Electrical & Electronic
SC Engineering
GA WG080
UT WOS:A1997WG08000009
ER
PT J
AU McCoy, TJ
Keil, K
Clayton, RN
Mayeda, TK
Bogard, DD
Garrison, DH
Wieler, R
AF McCoy, TJ
Keil, K
Clayton, RN
Mayeda, TK
Bogard, DD
Garrison, DH
Wieler, R
TI A petrologic and isotopic study of lodranites: Evidence for early
formation as partial melt residues from heterogeneous precursors
SO GEOCHIMICA ET COSMOCHIMICA ACTA
LA English
DT Article
ID FE-TI OXIDES; ORDINARY CHONDRITES; ACAPULCO METEORITE; COSMOGENIC
NUCLIDES; IRON-METEORITES; OXYGEN ISOTOPES; EQUILIBRIA; MINERALOGY;
OLIVINE; CLASSIFICATION
AB We have conducted petrologic, chemical, and isotopic studies of lodranites in an attempt to constrain their genesis. Lodran, Gibson, Y-791491, Y-791493, Y-74357, Y-8002, Y-75274, MAC 88177, LEW 88280, EET 84302, FRO 90011, and QUE 93148 are classified as lodranites. Lodranites and acapulcoites are indistinguishable on the basis of oxygen isotopic compositions but are distinct in average grain sizes of their mafic silicates, with lodranites being significantly coarser-grained. Lodranites exhibit a diverse range of petrologic and mineralogic features: they range widely in mafic silicate compositions (Fa(3-13)), plagioclase (0-11.4 vol%), Fe,Ni metal (0.5-20 vol%), and troilite (0.2-5.3 vol%) contents; and shock levels (S1-S4). They appear to have experienced high peak temperatures and rapid cooling in the temperature range recorded by metallographic cooling rates (i.e., 700-350 degrees C). The only dated lodranite, Gibson, cooled to Ar closure temperatures at 4.49 +/- 0.01 Ga.
Lodranites formed from chemically and isotopically heterogeneous precursors in which the mineral and oxygen isotopic compositions were correlated. Heating of their parent body to temperatures between similar to 1050-1200 degrees C resulted in formation of Fe,Ni-FeS and basaltic partial melts. Depletions of troilite and/or plagioclase in most lodranites testify to the removal of some of these partial melts, although melt migration was complex. Lodranites appear to have experienced a complex cooling history of slow cooling at high temperatures, followed by rapid cooling at intermediate temperatures, possibly related to breakup of the parent body. Lodranites were liberated from their parent body during 1-3 impact events, with most having cosmic ray exposure ages of 5.5-7 Ma. The acapulcoites are samples from the same parent body but were heated to lower temperatures and, thus, experienced lower degrees of partial melting. Copyright (C) 1997 Elsevier Science Ltd.
C1 UNIV HAWAII MANOA, SCH OCEAN & EARTH SCI & TECHNOL, HAWAII INST GEOPHYS & PLANETOL, HONOLULU, HI 96822 USA.
NASA, LYNDON B JOHNSON SPACE CTR, HOUSTON, TX 77058 USA.
UNIV CHICAGO, ENRICO FERMI INST, CHICAGO, IL 60637 USA.
ETH ZURICH, CH-8092 ZURICH, SWITZERLAND.
RP McCoy, TJ (reprint author), SMITHSONIAN INST, DEPT MINERAL SCI, MRC 119, WASHINGTON, DC 20560 USA.
RI Wieler, Rainer/A-1355-2010
OI Wieler, Rainer/0000-0001-5666-7494
NR 69
TC 87
Z9 89
U1 0
U2 5
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 FEB
PY 1997
VL 61
IS 3
BP 623
EP 637
DI 10.1016/S0016-7037(96)00359-6
PG 15
WC Geochemistry & Geophysics
SC Geochemistry & Geophysics
GA WK514
UT WOS:A1997WK51400011
ER
PT J
AU McCoy, TJ
Keil, K
Muenow, DW
Wilson, L
AF McCoy, TJ
Keil, K
Muenow, DW
Wilson, L
TI Partial melting and melt migration in the acapulcoite-lodranite parent
body
SO GEOCHIMICA ET COSMOCHIMICA ACTA
LA English
DT Article
ID DIFFERENTIATED ASTEROIDS; EXPLOSIVE VOLCANISM; UREILITE METEORITES;
CHONDRITES; ORIGIN
AB We review petrologic evidence that the acapulcoites and lodranites formed by <1 vol% to probably >20 vol% whole rock partial melting of a chondritic precursor material. At low degrees of partial melting, only Fe,Ni-FeS cotectic melting occurred. Migration distances for partial melts were short, resulting in the formation of acapulcoites with essentially chondritic troilite and plagioclase contents, but achondritic textures. At high degrees of partial melting, both Fe,Ni-FeS and basaltic (plagioclase-pyroxene) partial melts formed, and the melts may have migrated out of the source rock. The partial melt residues, which are more or less depleted in Fe,Ni-FeS and plagioclase, are the lodranites. Melt migration was complex: most acapulcoites, which experienced relatively low degrees of partial melting, lost little if any of the partial melt. One acapulcoite, LEW 86220, represents a unique case in which Fe,Ni-FeS and basaltic partial melts appear to have migrated from a lodranite source region into a cooler acapulcoite region, where they were trapped. In cases of the relatively high degrees of partial melting experienced by lodranites, melts may have been partly, selectively, or totally removed from the rocks, and Fe,Ni-FeS and/or basaltic partial melts may have been removed to different degrees and may, in fact, have been trapped on occasion in greater than chondritic proportions. We model vein and dike formation and melt migration by calculating the excess pressures and vein and dike sizes for varying degrees of partial melting. Our calculations are broadly consistent with observations, indicating that melt migration is inefficient at low degrees of partial melting and extremely efficient at high degrees of partial melting. Although the size of the acapulcoite-lodranite parent body and the volatile contents of the chondritic precursor rocks are poorly constrained, the lack of basaltic rocks in the world's meteorite collections complementary to the lodranites suggests that basaltic partial melts may have been accelerated off the body by explosive volcanism of the type envisioned by Wilson and Keil (1991) and ejected into space. The diversity of rocks from the acapulcoite-lodranite parent body may provide a basis for better understanding the diverse range of spectral subtypes recognized among the S-type asteroids. Copyright (C) 1997 Elsevier Science Ltd.
C1 UNIV HAWAII MANOA,SCH OCEAN & EARTH SCI & TECHNOL,HAWAII INST GEOPHYS & PLANETOL,HONOLULU,HI 96822.
NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058.
UNIV HAWAII MANOA,DEPT CHEM,HONOLULU,HI 96822.
UNIV LANCASTER,INST ENVIRONM & BIOL SCI,DIV ENVIRONM SCI,LANCASTER LA1 4YQ,ENGLAND.
RP McCoy, TJ (reprint author), SMITHSONIAN INST,DEPT MINERAL SCI,MRC 119,WASHINGTON,DC 20560, USA.
NR 40
TC 88
Z9 88
U1 1
U2 7
PU PERGAMON-ELSEVIER SCIENCE LTD
PI OXFORD
PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB
SN 0016-7037
J9 GEOCHIM COSMOCHIM AC
JI Geochim. Cosmochim. Acta
PD FEB
PY 1997
VL 61
IS 3
BP 639
EP 650
DI 10.1016/S0016-7037(96)00365-1
PG 12
WC Geochemistry & Geophysics
SC Geochemistry & Geophysics
GA WK514
UT WOS:A1997WK51400012
ER
PT J
AU Jensen, EJ
Toon, OB
AF Jensen, EJ
Toon, OB
TI The potential impact of soot particles from aircraft exhaust on cirrus
clouds
SO GEOPHYSICAL RESEARCH LETTERS
LA English
DT Article
ID UPPER TROPOSPHERE; NUCLEATION SIMULATIONS; LOWER STRATOSPHERE; WAKE
AB Homogeneous freezing of sulfate aerosols may dominate ice nucleation in cirrus, implying that large supersaturations are required for cirrus cloud initiation at low temperatures. However, insoluble particles from the surface or soot particles injected directly into the upper troposphere by jet aircraft may act as heterogeneous ice nuclei. If the soot particles are sufficiently effective ice nuclei, then they will allow ice nucleation at lower supersaturations than those required for homogeneous freezing, resulting in an increase in the areal coverage of cirrus clouds. Simulations using a detailed ice cloud model indicate that cirrus driven by slow, steady lifting (a few cm-s(-1)) will be transient, precipitating clouds if only pure sulfate haze aerosols are present. However, if effective heterogeneous nuclei are present, then extensive, persistent, diffuse cirrus should form. In addition, heterogeneous ice nucleation on insoluble particles may modify the number of ice crystals nucleated in cirrus, resulting in alterations of the cloud evolution and radiative properties. Heterogeneous freezing on relatively few insoluble particles (N-inv less than or equal to 0.1 cm(-3)) should result in fewer ice crystals nucleating than if homogeneous freezing were to occur. However, if large numbers of insoluble particles are present, the ice crystal number density may be increased.
C1 BAY AREA ENVIRONM RES INST,SAN FRANCISCO,CA.
RP Jensen, EJ (reprint author), NASA,AMES RES CTR,MS 245-4,MOFFETT FIELD,CA 94035, USA.
NR 18
TC 92
Z9 92
U1 1
U2 11
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009
SN 0094-8276
J9 GEOPHYS RES LETT
JI Geophys. Res. Lett.
PD FEB 1
PY 1997
VL 24
IS 3
BP 249
EP 252
DI 10.1029/96GL03235
PG 4
WC Geosciences, Multidisciplinary
SC Geology
GA WG511
UT WOS:A1997WG51100012
ER
PT J
AU Nolt, IG
Ade, PAR
Alboni, F
Carli, B
Carlotti, M
Cortesi, U
Epifani, M
Griffin, MJ
Hamilton, PA
Lee, C
Lepri, G
Mencaraglia, F
Murray, AG
Park, JH
Park, K
Raspollini, P
Ridolfi, M
Vanek, MD
AF Nolt, IG
Ade, PAR
Alboni, F
Carli, B
Carlotti, M
Cortesi, U
Epifani, M
Griffin, MJ
Hamilton, PA
Lee, C
Lepri, G
Mencaraglia, F
Murray, AG
Park, JH
Park, K
Raspollini, P
Ridolfi, M
Vanek, MD
TI Stratospheric HBr concentration profile obtained from far-infrared
emission spectroscopy
SO GEOPHYSICAL RESEARCH LETTERS
LA English
DT Article
ID UPPER LIMIT; SUBMILLIMETER; KINETICS; BROMINE
AB Hydrogen bromide (HBr) is the principal bromine sink species for the ozone loss chemistry induced by bromine-containing gases in the stratosphere. We report a 1994 balloon-based measurement of the daytime stratospheric HBr profile between 20 and 36.5 km altitude. The average concentration result of 1.31 +/- 0.39 parts per trillion in volume (pptv) and an analysis for the concentration versus altitude profile are consistent with previously reported measurements. These results strengthen the evidence for a significantly higher HBr concentration than that predicted by current photochemical models which, on the basis of recent kinetics results, do not include significant HBr production by the reaction branch, BrO + HO2 --> HBr + O-3.
C1 UNIV LONDON QUEEN MARY & WESTFIELD COLL,LONDON E1 4NS,ENGLAND.
CNR,IROE,I-50127 FLORENCE,ITALY.
UNIV OREGON,EUGENE,OR 97403.
UNIV BOLOGNA,DIPARTIMENTO CHIM FIS & INORGAN,I-40136 BOLOGNA,ITALY.
RP Nolt, IG (reprint author), NASA,LANGLEY RES CTR,HAMPTON,VA 23665, USA.
RI Cortesi, Ugo/D-2704-2012
OI Cortesi, Ugo/0000-0002-2827-5239
NR 20
TC 31
Z9 31
U1 0
U2 4
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009
SN 0094-8276
J9 GEOPHYS RES LETT
JI Geophys. Res. Lett.
PD FEB 1
PY 1997
VL 24
IS 3
BP 281
EP 284
DI 10.1029/97GL00034
PG 4
WC Geosciences, Multidisciplinary
SC Geology
GA WG511
UT WOS:A1997WG51100020
ER
PT J
AU Gosling, JT
Bame, SJ
Feldman, WC
McComas, DJ
Riley, P
Goldstein, BE
Neugebauer, M
AF Gosling, JT
Bame, SJ
Feldman, WC
McComas, DJ
Riley, P
Goldstein, BE
Neugebauer, M
TI The northern edge of the band of solar wind variability: Ulysses at -4.5
AU
SO GEOPHYSICAL RESEARCH LETTERS
LA English
DT Article
ID INTERACTION REGIONS; PLASMA
AB Ulysses observations reveal that the northern edge of the low-latitude band of solar wind variability at similar to 4.5 AU was located at N30 degrees in the latter part of 1996 when solar activity was at a minimum. This edge latitude is intermediate between edge latitudes found during previous encounters with the band edge along different portions of Ulysses' polar orbit about the Sun. Corotating interaction regions, CIRs, near the northern edge of the band were tilted in such a manner that the forward and reverse shocks bounding the CIRs were propagating equatorward and poleward, respectively, providing definite confirmation that CIRs have opposed tilts in the opposite solar hemispheres. No shocks or coronal mass ejections, CMEs, were detected during the similar to 1.5 y traverse of the northern, high-latitude northern hemisphere; however, al the northern edge of the band of variability an expanding CME was observed that was driving a shock into the high-speed wind.
C1 CALTECH,JET PROP LAB,PASADENA,CA 91109.
RP Gosling, JT (reprint author), LOS ALAMOS NATL LAB,MS D466,LOS ALAMOS,NM 87545, USA.
NR 12
TC 42
Z9 42
U1 0
U2 0
PU AMER GEOPHYSICAL UNION
PI WASHINGTON
PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009
SN 0094-8276
J9 GEOPHYS RES LETT
JI Geophys. Res. Lett.
PD FEB 1
PY 1997
VL 24
IS 3
BP 309
EP 312
DI 10.1029/97GL00001
PG 4
WC Geosciences, Multidisciplinary
SC Geology
GA WG511
UT WOS:A1997WG51100027
ER
PT J
AU Huntress, WT
AF Huntress, WT
TI Probing the planets
SO GEOTIMES
LA English
DT Editorial Material
RP Huntress, WT (reprint author), NASA,WASHINGTON,DC 20546, USA.
NR 0
TC 0
Z9 0
U1 0
U2 0
PU AMER GEOLOGICAL INST
PI ALEXANDRIA
PA 4220 KING ST, ALEXANDRIA, VA 22302-1507
SN 0016-8556
J9 GEOTIMES
JI Geotimes
PD FEB
PY 1997
VL 42
IS 2
BP 5
EP 5
PG 1
WC Geosciences, Multidisciplinary
SC Geology
GA WF545
UT WOS:A1997WF54500005
ER
PT J
AU Paylor, ED
Gubbels, TL
AF Paylor, ED
Gubbels, TL
TI Satellites and remote sensing
SO GEOTIMES
LA English
DT Article
RP Paylor, ED (reprint author), NASA,OFF MISSION PLANET EARTH,300 E ST SW,WASHINGTON,DC 20546, USA.
NR 0
TC 0
Z9 0
U1 0
U2 0
PU AMER GEOLOGICAL INST
PI ALEXANDRIA
PA 4220 KING ST, ALEXANDRIA, VA 22302-1507
SN 0016-8556
J9 GEOTIMES
JI Geotimes
PD FEB
PY 1997
VL 42
IS 2
BP 45
EP 46
PG 2
WC Geosciences, Multidisciplinary
SC Geology
GA WF545
UT WOS:A1997WF54500052
ER
PT J
AU Gornitz, V
Rosenzweig, C
Hillel, D
AF Gornitz, V
Rosenzweig, C
Hillel, D
TI Effects of anthropogenic intervention in the land hydrologic cycle on
global sea level rise
SO GLOBAL AND PLANETARY CHANGE
LA English
DT Article
DE deforestation; groundwater; human activities; hydrology; irrigation;
reservoirs; sea-level change; water storage
ID TROPICAL DEFORESTATION; CLIMATE CHANGE; PRECIPITATION; FUTURE; MODEL;
GCM
AB Recent studies suggest that anthropogenic modification of land hydrology (e.g. through groundwater mining, dam building, irrigation, deforestation, wetlands drainage, and urbanization) could significantly impact sea-level rise, although the magnitude and sign of this effect have been widely debated. This paper attempts a comprehensive overview of the effects of human activities on land hydrology. Estimates are provided for the volumes of water associated with each of the major anthropogenic processes and the corresponding equivalent in sea level. Groundwater mining and runoff from paved and built-up areas are two major sources of water added to the ocean. In contrast, storage of water behind dams, losses through percolation, and evapotranspiration from irrigated fields withhold water that would otherwise flow to the sea. The net effect of these processes holds back the equivalent of 0.8 +/- 0.4 mm/yr from sea-level rise. This is a magnitude comparable to, but in the opposite direction from the currently observed sea-level rise of 1-2 mm/yr. These estimates are still preliminary, awaiting better documentation. Coupling of improved land hydrology models with GCMs will help in analysis of feedbacks, especially the partitioning of water among runoff, infiltration, and evaporation.
C1 NASA,GODDARD SPACE FLIGHT CTR,INST SPACE STUDIES,NEW YORK,NY 10025.
UNIV MASSACHUSETTS,DEPT PLANT SOIL & ENVIRONM,AMHERST,MA 01003.
RP Gornitz, V (reprint author), COLUMBIA UNIV,CTR CLIMATE SYST RES,NEW YORK,NY 10025, USA.
NR 77
TC 28
Z9 32
U1 0
U2 6
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0921-8181
J9 GLOBAL PLANET CHANGE
JI Glob. Planet. Change
PD FEB
PY 1997
VL 14
IS 3-4
BP 147
EP 161
DI 10.1016/S0921-8181(96)00008-2
PG 15
WC Geography, Physical; Geosciences, Multidisciplinary
SC Physical Geography; Geology
GA WK148
UT WOS:A1997WK14800004
ER
PT J
AU Simonelli, DP
Pollack, JB
McKay, CP
AF Simonelli, DP
Pollack, JB
McKay, CP
TI Radiative heating of interstellar grains falling toward the solar
nebula: 1-D diffusion calculations
SO ICARUS
LA English
DT Article
ID AXISYMMETRICAL DUST CLOUDS; PROTOSTELLAR DISKS; ROTATING PROTOSTARS;
MOLECULAR CLOUDS; YOUNG STARS; EVOLUTION; ACCRETION; DEUTERIUM; MODELS;
ORIGIN
AB As the dense molecular cloud that was the precursor of our Solar System was collapsing to form a protosun and the surrounding solar-nebula accretion disk, infalling interstellar grains were heated much more effectively by radiation from the forming protosun than by radiation from the disk's accretion shock. Accordingly, we have estimated the temperatures experienced by these infalling grains using radiative diffusion calculations whose sole energy source is radiation from the protosun. Although the calculations are 1-dimensional, they make use of 2-D, cylindrically symmetric models of the density structure of a collapsing, rotating cloud. The temperature calculations also utilize recent models for the composition and radiative properties of interstellar grains (Pollack ef al. 1994. Astrophys. J. 421, 615-639), thereby allowing us to estimate which grain species might have survived, intact, to the disk accretion shock and what accretion rates and molecular-cloud rotation rates aid that survival. Not surprisingly, we find that the large uncertainties in the free parameter values allow a wide range of grain-survival results: (1) For physically plausible high accretion rates or low rotation rates (which produce small accretion disks), all of the infalling grain species, even the refractory silicates and iron, will vaporize in the protosun's radiation field before reaching the disk accretion shock. (2) For equally plausible low accretion rates or high rotation rates (which produce large accretion disks), all non-ice species, even volatile organics, will survive intact to the disk accretion shock.
These grain-survival conclusions are subject to several limitations which need to be addressed by future, more sophisticated radiative-transfer models. Nevertheless, our results can serve as useful inputs to models of the processing that interstellar grains undergo at the solar nebula's accretion shock, and thus help address the broader question of interstellar inheritance in the solar nebula and present Solar System. These results may also help constrain the size of the accretion disk; for example, if we require that the calculations produce partial survival of organic grains into the solar nebula, we infer that some material entered the disk intact at distances comparable to or greater than a few AU. Intriguingly, this is comparable to the heliocentric distance that separates the C-rich outer parts of the current Solar System from the C-poor inner regions. (C) 1997 Academic Press.
C1 NASA,AMES RES CTR,DIV SPACE SCI,MOFFETT FIELD,CA 94035.
RP Simonelli, DP (reprint author), CORNELL UNIV,CTR RADIOPHYS & SPACE RES,SPACE SCI BLDG,ITHACA,NY 14853, USA.
FU NCI NIH HHS [NCA2-528, NCA2-381]
NR 25
TC 9
Z9 9
U1 0
U2 0
PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS
PI SAN DIEGO
PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495
SN 0019-1035
J9 ICARUS
JI Icarus
PD FEB
PY 1997
VL 125
IS 2
BP 261
EP 280
DI 10.1006/icar.1996.5570
PG 20
WC Astronomy & Astrophysics
SC Astronomy & Astrophysics
GA WP280
UT WOS:A1997WP28000003
PM 11540163
ER
EF