FN Thomson Reuters Web of Science™ VR 1.0 PT J AU KOUVELIOTOU, C AF KOUVELIOTOU, C TI BATSE RESULTS ON OBSERVATIONAL PROPERTIES OF GAMMA-RAY BURSTS SO ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES LA English DT Article DE GAMMA-RAYS, BURSTS AB BATSE has observed over 600 gamma-ray bursts since its activation on 1991 April 21. We present here results on the global properties of the first 542 events. Their angular distribution is consistent with isotropy; their peak intensity distribution shows a depletion at low intensities, consistent with inhomogeneity in Euclidean space. RP KOUVELIOTOU, C (reprint author), UNIV SPACE RES ASSOC, NASA MSFC, HUNTSVILLE, AL 35812 USA. NR 23 TC 17 Z9 18 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0067-0049 EI 1538-4365 J9 ASTROPHYS J SUPPL S JI Astrophys. J. Suppl. Ser. PD JUN PY 1994 VL 92 IS 2 BP 637 EP 642 DI 10.1086/192032 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NM319 UT WOS:A1994NM31900061 ER PT J AU HURLEY, K LI, P SOMMER, M SMETTE, A KOUVELIOTOU, C FISHMAN, G CLINE, T BOER, M NIEL, M LAROS, J KLEBESADEL, R FENIMORE, E AF HURLEY, K LI, P SOMMER, M SMETTE, A KOUVELIOTOU, C FISHMAN, G CLINE, T BOER, M NIEL, M LAROS, J KLEBESADEL, R FENIMORE, E TI THE OPTICAL AND X-RAY CONTENT OF THE 1992 MAY 1 GAMMA-RAY BURST ERROR BOX SO ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT INTEGRAL Workshop on the Multiwavelength Approach to Gamma-Ray Astronomy CY FEB 02-05, 1993 CL LES DIABLERETS, SWITZERLAND SP INT GAMMA RAY ASTROPHYS LAB DE GAMMA-RAYS, BURSTS ID COUNTERPART AB A gamma-ray burst which occurred on 1992 May 1 was observed by three spacecraft in the third interplanetary network, and rapidly localized to a small error box. The coordinates were promptly circulated to a wide astronomical community, and radio, optical, and X-ray counterpart searches were carried out. A weak X-ray source was found in the error box, and two radio sources were discovered outside the error box, but in alignment with the X-ray source. The X-ray source position contains approximately 25 optical objects down to 23d magnitude. We discuss the prospects for identifying the burster counterpart. C1 MAX PLANCK INST EXTRATERR PHYS,W-8046 GARCHING,GERMANY. EUROPEAN SO OBSERV,W-8046 GARCHING,GERMANY. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. CTR ETUD SPATIALE RAYONNEMENTS,F-31029 TOULOUSE,FRANCE. LOS ALAMOS NATL LAB,LOS ALAMOS,NM 87545. RP HURLEY, K (reprint author), UNIV CALIF BERKELEY,SPACE SCI LAB,BERKELEY,CA 94708, USA. OI Boer, Michel/0000-0001-9157-4349 NR 9 TC 10 Z9 10 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 JUN PY 1994 VL 92 IS 2 BP 655 EP 657 DI 10.1086/192035 PG 3 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NM319 UT WOS:A1994NM31900064 ER PT J AU HOLT, SS AF HOLT, SS TI GAMMA-RAY ASTRONOMY - A STATUS-REPORT SO ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT INTEGRAL Workshop on the Multiwavelength Approach to Gamma-Ray Astronomy CY FEB 02-05, 1993 CL LES DIABLERETS, SWITZERLAND SP INT GAMMA RAY ASTROPHYS LAB DE GAMMA-RAYS, GENERAL AB Gamma-rays provide us with powerful insight into the highest energy processes occurring in the cosmos. This review highlights some of the progress in our understanding of gamma-ray astronomy that has been enabled by new data from GRANAT and the Compton Gamma-Ray Observatory, and suggests requirements for future progress. In particular, the unique role of the INTEGRAL mission and concurrent multiwavelength observations is highlighted. RP HOLT, SS (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. NR 22 TC 0 Z9 0 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 JUN PY 1994 VL 92 IS 2 BP 693 EP 697 DI 10.1086/192043 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NM319 UT WOS:A1994NM31900072 ER PT J AU GOLDSMITH, JEM BISSON, SE FERRARE, RA EVANS, KD WHITEMAN, DN MELFI, SH AF GOLDSMITH, JEM BISSON, SE FERRARE, RA EVANS, KD WHITEMAN, DN MELFI, SH TI RAMAN LIDAR PROFILING OF ATMOSPHERIC WATER-VAPOR - SIMULTANEOUS MEASUREMENTS WITH 2 COLLOCATED SYSTEMS SO BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY LA English DT Article ID MOISTURE; AEROSOLS AB Raman lidar is a leading candidate for providing the detailed space- and time-resolved measurements of water vapor needed by a variety of atmospheric studies. Simultaneous measurements of atmospheric water vapor are described using two collocated Raman lidar systems. These lidar systems, developed at the NASA/Goddard Space Flight Center and Sandia National Laboratories, acquired approximately 12 hours of simultaneous water vapor data during three nights in November 1992 while the systems were collocated at the Goddard Space Flight Center. Although these lidar systems differ substantially in their design, measured water vapor profiles agreed within 0.15 g kg-1 between altitudes of 1 and 5 km. Comparisons with coincident radiosondes showed all instruments agreed within 0.2 g kg-1 in this same altitude range. Both lidars also clearly showed the advection of water vapor in the middle troposphere and the pronounced increase in water vapor in the nocturnal boundary layer that occurred during one night. C1 NASA,GODDARD SPACE FLIGHT CTR,HUGHES STX CORP,GREENBELT,MD 20771. RP GOLDSMITH, JEM (reprint author), SANDIA NATL LABS,LIVERMORE,CA 94551, USA. NR 17 TC 24 Z9 24 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 JUN PY 1994 VL 75 IS 6 BP 975 EP 982 DI 10.1175/1520-0477(1994)075<0975:RLPOAW>2.0.CO;2 PG 8 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA NU745 UT WOS:A1994NU74500002 ER PT J AU DESMARAIS, DJ AF DESMARAIS, DJ TI TECTONIC CONTROL OF THE CRUSTAL ORGANIC-CARBON RESERVOIR DURING THE PRECAMBRIAN SO CHEMICAL GEOLOGY LA English DT Article ID PHANEROZOIC TIME; EARTH; GEOCHEMISTRY; EVOLUTION; PALEOSOL; MODEL AB Carbon isotopic trends indicate that the crustal reservoir of reduced, organic carbon increased during the Proterozoic, particularly during periods of widespread continental rifting and orogeny. No long-term trends are apparent in the concentration of organic carbon in shales, cherts and carbonates. The age distribution of 261 sample site localities sampled for well-preserved sedimentary rocks revealed a 500-700-Ma periodicity which coincided with tectonic cycles. It is assumed that the numbers of sites are a proxy for mass of sediments. A substantial increase in the number of sites in the late Archean correlates with the first appearance between 2.9 and 2.5 Ga of extensive continental platforms and their associated sedimentation. It is proposed that the size of the Proterozoic crustal organic carbon reservoir has been modulated by tectonic control of the volume of sediments deposited in environments favorable for the burial and preservation of organic matter. Stepwise increases in this reservoir would have caused the oxidation state of the Proterozoic environment to increase in a stepwise fashion. RP NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. NR 33 TC 47 Z9 47 U1 0 U2 4 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0009-2541 EI 1878-5999 J9 CHEM GEOL JI Chem. Geol. PD JUN 1 PY 1994 VL 114 IS 3-4 BP 303 EP 314 PG 12 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA NP384 UT WOS:A1994NP38400009 PM 11539297 ER PT J AU OLSSON, P AF OLSSON, P TI HIGH-ORDER FINITE-DIFFERENCES METHODS ON NONSMOOTH DOMAINS SO COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING LA English DT Article; Proceedings Paper CT 2nd International Conference on Spectral and High Order Methods (ICOSAHOM 92) CY JUN 22-26, 1992 CL MONTPELLIER, FRANCE AB We demonstrate how to obtain stable high order approximations of parabolic and symmetric hyperbolic systems using finite difference methods. The idea behind the scheme is to use difference operators which satisfy a summation-by-parts rule, which in one space dimension reads (u, Dv)k = u(N)v(N) - u0v0 - (Du, v)h. This principle generalizes to domains with curved and non-smooth boundaries. Well-posed analytic boundary conditions are incorporated into the semi-discrete system by means of projection operators. The resulting system can be shown to be stable. In an appendix, we have included an explicit example of a stable difference operator, which is third order accurate at the boundary, and sixth order accurate in the interior. C1 UPPSALA UNIV,DEPT SCI COMP,S-75104 UPPSALA,SWEDEN. RP OLSSON, P (reprint author), NASA,AMES RES CTR,RIACS,MAIL STOP T041-5,MOFFETT FIELD,CA 94035, USA. NR 8 TC 0 Z9 0 U1 0 U2 0 PU ELSEVIER SCIENCE SA LAUSANNE PI LAUSANNE 1 PA PO BOX 564, 1001 LAUSANNE 1, SWITZERLAND SN 0045-7825 J9 COMPUT METHOD APPL M JI Comput. Meth. Appl. Mech. Eng. PD JUN PY 1994 VL 116 IS 1-4 BP 265 EP 272 DI 10.1016/S0045-7825(94)80032-4 PG 8 WC Engineering, Multidisciplinary; Mathematics, Interdisciplinary Applications; Mechanics SC Engineering; Mathematics; Mechanics GA NY743 UT WOS:A1994NY74300031 ER PT J AU REDDING, DC AF REDDING, DC TI CONTROL CHALLENGES FROM SPACE-BASED AND GROUND-BASED ASTRONOMICAL TELESCOPES SO CONTROL ENGINEERING PRACTICE LA English DT Article DE CONTROL SYSTEM SYNTHESIS; MODELING; SENSORS; ACTUATORS; OPTICAL VARIABLES CONTROL ID ADAPTIVE OPTICS; RETRIEVAL AB Actively controlled optics are revolutionizing the telescope builders' art, by enabling the use of large segmented mirrors, multiple-aperture telescopes, space telescopes, active atmospheric compensation and other innovations. Designing high-performance controllers for these instruments requires an accurate means of calculating optical performance: a particular method is presented. A detailed example illustrates some of the challenges that arise. RP REDDING, DC (reprint author), JET PROP LAB, 4800 OAK GROVE DR, PASADENA, CA 91109 USA. NR 36 TC 0 Z9 0 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0967-0661 J9 CONTROL ENG PRACT JI Control Eng. Practice PD JUN PY 1994 VL 2 IS 3 BP 469 EP 478 DI 10.1016/0967-0661(94)90785-4 PG 10 WC Automation & Control Systems; Engineering, Electrical & Electronic SC Automation & Control Systems; Engineering GA NR739 UT WOS:A1994NR73900012 ER PT J AU NEWSOM, JR ANDERSON, WW AF NEWSOM, JR ANDERSON, WW TI THE NASA-LARC CONTROLS-STRUCTURES INTERACTION (CSI) TECHNOLOGY PROGRAM SO CONTROL ENGINEERING PRACTICE LA English DT Article DE CONTROL SYSTEM DESIGN; STRUCTURAL CONTROL; SPACE VEHICLES; SATELLITE CONTROL; OPTIMIZATION AB The integration of active control systems for controlling the structural dynamics of flexible spacecraft can significantly benefit performance. Recognizing the potential improvement for future spacecraft, NASA has an ongoing Controls-Structures Interaction (CSI) technology program whose objective is to develop and validate the technology needed to integrate active control systems and flexible structures to meet the requirements of future space missions. The purpose of this paper is to describe the ongoing CSI activities at the LaRC. RP NEWSOM, JR (reprint author), NASA,LANGLEY RES CTR,HAMPTON,VA 23681, USA. NR 16 TC 1 Z9 1 U1 1 U2 2 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0967-0661 J9 CONTROL ENG PRACT JI Control Eng. Practice PD JUN PY 1994 VL 2 IS 3 BP 479 EP 490 DI 10.1016/0967-0661(94)90786-2 PG 12 WC Automation & Control Systems; Engineering, Electrical & Electronic SC Automation & Control Systems; Engineering GA NR739 UT WOS:A1994NR73900013 ER PT J AU BRILL, RW DEWAR, H GRAHAM, JB AF BRILL, RW DEWAR, H GRAHAM, JB TI BASIC CONCEPTS RELEVANT TO HEAT-TRANSFER IN FISHES, AND THEIR USE IN MEASURING THE PHYSIOLOGICAL THERMOREGULATORY ABILITIES OF TUNAS SO ENVIRONMENTAL BIOLOGY OF FISHES LA English DT Article DE THERMOREGULATION; TEMPERATURE; SCOMBROIDEI; THUNNINI ID ALBACORE THUNNUS-ALALUNGA; BEHAVIORAL THERMOREGULATION; SKIPJACK TUNA; TEMPERATURE; BRAIN; MUSCLE; WATER AB Aerobic heat production and heat loss via the gills are inexorably linked in all water breathing teleosts except tunas. These processes are decoupled in tunas by the presence of vascular counter-current heat exchangers, and sustained (i.e., steady state) muscle temperatures may exceed water temperature by 10-degrees-C or more in larger individuals. The presence of vascular counter-current heat exchangers is not clearly advantageous in all situations, however. Mathematical models predict that tunas could overheat during strenuous activity unless the efficacy of vascular heat exchangers can be reduced, and that they may be activity limited in warmer waters. Tunas may likewise be forced out of potentially usable habitats as they grow because they have to occupy cooler waters. Vascular counter-current heat exchangers also slow rates of heating and cooling. A reduced rate of muscle temperature decrease is clearly advantageous when diving into colder water to chase prey or avoid predators. A reduced rate of heat gain from the environment would be disadvantageous, however, when fish return to the warmer surface waters. When subjected to changes in ambient temperature, tunas cannot defend a specific body temperature and do not thermoregulate in the mammalian sense. Yet when appropriately analyzed, data taken under steady state and non-steady state conditions indicate that tunas are not strictly prisoners of their own thermoconserving mechanisms. They apparently can modify overall efficiency of their vascular counter-current heat exchangers and thus avoid overheating during bouts of strenuous activity, retard cooling after diving into colder water, and rapidly warm their muscles after voluntarily entering warmer water. The exact physiological mechanisms employed remain to be elucidated. C1 UNIV CALIF SAN DIEGO,SCRIPPS INST OCEANOG,PHYSIOL RES LAB,LA JOLLA,CA 92093. RP BRILL, RW (reprint author), NOAA,NATL MARINE FISHERIES SERV,SW FISHERIES SCI CTR,HONOLULU LAB,HONOLULU,HI 96822, USA. NR 68 TC 52 Z9 58 U1 3 U2 22 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0378-1909 J9 ENVIRON BIOL FISH JI Environ. Biol. Fishes PD JUN PY 1994 VL 40 IS 2 BP 109 EP 124 DI 10.1007/BF00002538 PG 16 WC Ecology; Marine & Freshwater Biology SC Environmental Sciences & Ecology; Marine & Freshwater Biology GA NN692 UT WOS:A1994NN69200001 ER PT J AU LEBOEUF, RL MEHTA, RD AF LEBOEUF, RL MEHTA, RD TI IMPROVED METHODS FOR LINEAR-ESTIMATION OF VELOCITY RECORDS SO EXPERIMENTS IN FLUIDS LA English DT Article ID PLANE MIXING LAYER; STOCHASTIC ESTIMATION AB Traditionally, linear mean-square (MS or stochastic) estimation coefficients are calculated using cross-correlations between each of the data at reference and estimation locations. Since the cross-correlation between data at reference and estimation locations typically decreases rapidly with increasing separation distance, the resulting estimated fluctuations diminish away from the reference locations. Two new schemes have been developed to optimally determine estimation coefficients which yield an improved estimated energy representation. One approach involves a non-linear least-square fit to both the estimation covariance and the cross-correlation between data at reference and estimation locations. By also minimizing the error in the estimation covariance, realistic energy levels can be estimated without significantly altering the correlation between true and estimated velocity signals as given by the traditional MS method. Another scheme, developed for use with a single-point, two-component reference, maximizes the correlation coefficient between the estimate and its measured counterpart. It is shown that for this simple case, the estimated covariance can be set equal to the measured covariance without compromising the correlation coefficient at all. The effectiveness of the proposed techniques is demonstrated by comparing their estimates with those given by the MS method in a plane turbulent mixing layer. In general, the estimation schemes appear to give improved results when references from the edge of the mixing layer are employed. It is also demonstrated how the results of the proposed estimation methods can be used to infer details regarding the mixing layer structure and kinematics. C1 STANFORD UNIV,JIAA,DEPT AERONAUT & ASTRONAUT,STANFORD,CA 94305. RP LEBOEUF, RL (reprint author), NASA,AMES RES CTR,MS 260-1,MOFFETT FIELD,CA 94035, USA. NR 12 TC 1 Z9 1 U1 0 U2 0 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 SN 0723-4864 J9 EXP FLUIDS JI Exp. Fluids PD JUN PY 1994 VL 17 IS 1-2 BP 32 EP 38 DI 10.1007/BF02412801 PG 7 WC Engineering, Mechanical; Mechanics SC Engineering; Mechanics GA NW365 UT WOS:A1994NW36500005 ER PT J AU ZARRAOA, N RIUS, A SARDON, E RYAN, JW AF ZARRAOA, N RIUS, A SARDON, E RYAN, JW TI RELATIVE MOTIONS IN EUROPE STUDIED WITH A GEODETIC VLBI NETWORK SO GEOPHYSICAL JOURNAL INTERNATIONAL LA English DT Article DE GEODESY; TECTONIC MOTIONS; VERY LONG BASE-LINE INTERFEROMETRY (VLBI) AB Since 1988, the European geodetic Very Long Baseline Interferometry (VLBI) community and the NASA Goddard Space Flight Center, have set up the observation of a series of geodetic VLBI experiments with the purpose of studying possible crustal deformations in Western Europe. In this work we present the results of the analysis of the complete data set with the software package OCCAM 3.0. These results show the detection of significant motions at the centimetre per year level in the southern European stations, close to the boundary between the African and Eurasian plates. Meanwhile, they show no significant motions at that level in central Europe or the Iberian Peninsula. The extraordinary quality of the data and the consistency of the analysis have made it possible to obtain significant geodynamical results in a relatively short time-span. C1 STATENS KARTVERK,INST GEODET,N-3500 HONEFOSS,NORWAY. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. CSIC,INTA,ASTROFIS ESPACIAL & FIS FUNDAMENTAL LAB,MADRID 6,SPAIN. RP ZARRAOA, N (reprint author), UCM,CSIC,INST ASTRON & GEODESIA,E-28040 MADRID,SPAIN. RI Antonio, Rius/A-4873-2012 OI Antonio, Rius/0000-0002-5947-2649 NR 14 TC 14 Z9 14 U1 0 U2 0 PU BLACKWELL SCIENCE LTD PI OXFORD PA OSNEY MEAD, OXFORD, OXON, ENGLAND OX2 0EL SN 0956-540X J9 GEOPHYS J INT JI Geophys. J. Int. PD JUN PY 1994 VL 117 IS 3 BP 763 EP 768 DI 10.1111/j.1365-246X.1994.tb02468.x PG 6 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA NQ595 UT WOS:A1994NQ59500014 ER PT J AU DAVID, SJ MURCRAY, FJ GOLDMAN, A RINSLAND, CP MURCRAY, DG AF DAVID, SJ MURCRAY, FJ GOLDMAN, A RINSLAND, CP MURCRAY, DG TI THE EFFECT OF THE MT-PINATUBO AEROSOL ON THE HNO3 COLUMN OVER MAUNA-LOA, HAWAII SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID INFRARED MEASUREMENTS; STRATOSPHERIC N2O; ERUPTION AB A very high resolution infrared solar spectrometer system for the Network for Detection of Stratospheric Change has been routinely operated at the Mauna Loa Observatory in Hawaii since November, 1991. Solar absorption spectra are normally taken one day a week at sunrise. We report the analysis of these spectra for the vertical column amount of nitric acid (H NO,) vapor. The observations began four months after the arrival of volcanic aerosols from Mt. Pinatubo over the site. Although quite variable, total HNO3 columns were initially about 7x10(15) molecules/cm2 and have decreased about 30% in the following two years. C1 NASA,LANGLEY RES CTR,HAMPTON,VA 23665. RP DAVID, SJ (reprint author), UNIV DENVER,DEPT PHYS,DENVER,CO 80208, USA. NR 23 TC 15 Z9 15 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 JUN 1 PY 1994 VL 21 IS 11 BP 1003 EP 1006 DI 10.1029/94GL00876 PG 4 WC Geosciences, Multidisciplinary SC Geology GA NQ215 UT WOS:A1994NQ21500010 ER PT J AU GRUN, E HAMILTON, DP BAGUHL, M RIEMANN, R HORANYI, M POLANSKEY, C AF GRUN, E HAMILTON, DP BAGUHL, M RIEMANN, R HORANYI, M POLANSKEY, C TI DUST STREAMS FROM COMET SHOEMAKER-LEVY-9 SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID GOSSAMER RING; JUPITER; DISCOVERY; EJECTION; GRAINS AB In 1991 and 1992, the dust detector onboard the Ulysses spacecraft detected several dust streams apparently originating from the jovian system. The timing and measured speeds of the final two dust streams are compatible with dust from comet Shoemaker-Levy 9's (SL9) disruption in 1992. Our further investigations of stream characteristics and dust acceleration mechanisms, however, shed some doubt that two of the eleven dust streams are of SL9 origin. In July 1994 when SL9 impacts Jupiter, the Galileo spacecraft will be about 3500 jovian radii away from the planet. Submicronsized dust released into, and accelerated by, the jovian magnetosphere during this event may reach Galileo and impact its dust detector between September and November 1994. We also discuss the possibility of directly sampling dust from SL9 during Galileo's orbital tour. C1 UNIV COLORADO,ATMOSPHER & SPACE PHYS LAB,BOULDER,CO 80309. JET PROP LAB,PASADENA,CA 91109. RP GRUN, E (reprint author), MAX PLANCK INST KERNPHYS,POB 103980,D-69029 HEIDELBERG,GERMANY. NR 9 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 JUN 1 PY 1994 VL 21 IS 11 BP 1035 EP 1038 DI 10.1029/94GL00701 PG 4 WC Geosciences, Multidisciplinary SC Geology GA NQ215 UT WOS:A1994NQ21500018 ER PT J AU FARRELL, WM KAISER, ML DESCH, MD MACDOWALL, RJ AF FARRELL, WM KAISER, ML DESCH, MD MACDOWALL, RJ TI POSSIBLE RADIO-WAVE PRECURSORS ASSOCIATED WITH THE COMET SHOEMAKER-LEVY-9 JUPITER IMPACTS SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SYSTEM; SATURN AB We suggest that prior to its impact with Jupiter, comet Shoemaker-Levy 9 will behave as an electrical generator in the Jovian magnetosphere, converting planetary rotational energy to electrical energy via a dust/plasma interaction. This electrical energy will then be deposited in the dayside auroral region where it may drive various auroral phenomena including cyclotron radio emission. Such emission could be detected by spacecraft like Ulysses and Galileo many hours prior to the actual comet impact with the upper atmosphere. We apply the theory originally developed to explain the spokes in Saturn's rings. This theory allows us to quantify the driving potential associated with the comet and, consequently, to determine the radio power created in the auroral region. We conclude that if enough fine dust is present in the cometary system, comet-induced auroral radio emissions will reach detectable levels. This emission should be observable in the dayside hemisphere about 12-24 hours prior to each fragment impact. RP FARRELL, WM (reprint author), NASA,GODDARD SPACE FLIGHT CTR,EXTRATERR PHYS LAB,CODE 695,GREENBELT,MD 20771, USA. RI MacDowall, Robert/D-2773-2012; Farrell, William/I-4865-2013 NR 7 TC 11 Z9 11 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 JUN 1 PY 1994 VL 21 IS 11 BP 1067 EP 1070 DI 10.1029/94GL01066 PG 4 WC Geosciences, Multidisciplinary SC Geology GA NQ215 UT WOS:A1994NQ21500026 ER PT J AU AHRENS, TJ TAKATA, T OKEEFE, JD ORTON, GS AF AHRENS, TJ TAKATA, T OKEEFE, JD ORTON, GS TI IMPACT OF COMET SHOEMAKER-LEVY-9 ON JUPITER SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SPECTROMETER EXPERIMENT; SOLAR-SYSTEM; GALILEO; BREAKUP AB Three-dimensional numerical simulations of the impact of Comet Shoemaker - Levy 9 on Jupiter and the resulting vapor plume expansion were conducted using the Smoothed Particle Hydrodynamics (SPH) method. An icy body with a diameter of 2 km can penetrate to an altitude of -350 km (0 km = 1 bar) and most of the incident kinetic energy is transferred to the atmosphere between -100 km to -250 km. This energy is converted to potential energy of the resulting gas plume. The unconfined plume expands vertically and has a peak radiative power approximately equal to the total radiation from Jupiter's disc. The plume rises a few tens of atmospheric scale heights in approximately 10(2), seconds. The rising plume reaches the altitude of approximately 3000 km, but no atmospheric gas is accelerated to the escape velocity (approximately 60 km/s). C1 JET PROP LAB,PASADENA,CA 91109. RP AHRENS, TJ (reprint author), CALTECH,LINDHURST LAB EXPTL GEOPHYS,SEISMOL LAB 252-21,PASADENA,CA 91125, USA. NR 26 TC 38 Z9 38 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 JUN 1 PY 1994 VL 21 IS 11 BP 1087 EP 1090 DI 10.1029/94GL01325 PG 4 WC Geosciences, Multidisciplinary SC Geology GA NQ215 UT WOS:A1994NQ21500031 ER PT J AU DEMING, D AF DEMING, D TI PROSPECTS FOR JOVIAN SEISMOLOGICAL OBSERVATIONS FOLLOWING THE IMPACT OF COMET SHOEMAKER-LEVY-9 SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID JUPITER; OSCILLATIONS; SATURN AB The impact of each fragment of comet SL-9 will produce a downward-propagating pressure wave which will travel at the sound speed through the jovian interior. Since the sound speed increases with depth, most of the energy in the pressure pulse will be strongly refracted and return to the surface, as recently computed by Marley (1994). This wave may in principle be observable as it propagates into the stratosphere, using sufficiently sensitive thermal infrared imaging. If so, it will provide a unique opportunity to constrain models of the jovian interior. This paper extends Marley's calculations to include the effect of the limited spatial resolution which will be characteristic of real observations. The wave pattern on the disk will consist of closely spaced regions of alternating temperature increases and decreases. Spatial averaging will significantly reduce the observed amplitude for resolutions attainable using earth-based telescopes, but the waves should remain above the detection limit. RP DEMING, D (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 693,GREENBELT,MD 20771, USA. NR 13 TC 4 Z9 4 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 JUN 1 PY 1994 VL 21 IS 11 BP 1095 EP 1098 DI 10.1029/94GL00889 PG 4 WC Geosciences, Multidisciplinary SC Geology GA NQ215 UT WOS:A1994NQ21500033 ER PT J AU ROSEKIND, MR GANDER, PH MILLER, DL GREGORY, KB SMITH, RM WELDON, KJ CO, EL MCNALLY, KL LEBACQZ, JV AF ROSEKIND, MR GANDER, PH MILLER, DL GREGORY, KB SMITH, RM WELDON, KJ CO, EL MCNALLY, KL LEBACQZ, JV TI FATIGUE IN OPERATIONAL SETTINGS - EXAMPLES FROM THE AVIATION ENVIRONMENT SO HUMAN FACTORS LA English DT Article ID CIRCADIAN-RHYTHMS; SLEEP; PERFORMANCE AB The need for 24-h operations creates nonstandard and altered work schedules that can lead to cumulative sleep loss and circadian disruption. These factors can lead to fatigue and sleepiness and affect performance and productivity on the job. The approach, research, and results of the NASA Ames Fatigue Countermeasures Program are described to illustrate one attempt to address these issues in the aviation environment. The scientific and operational relevance of these factors is discussed, and provocative issues for future research are presented. C1 NASA,AMES RES CTR,SAN JOSE STATE UNIV FDN,MOFFETT FIELD,CA 94035. STERLING SOFTWARE,PALO ALTO,CA. NASA,AMES RES CTR,FLIGHT HUMAN FACTORS BRANCH,MOFFETT FIELD,CA 94035. RP ROSEKIND, MR (reprint author), NASA,AMES RES CTR,FATIGUE COUNTERMEASURES PROGRAM,MAIL STOP 262-4,MOFFETT FIELD,CA 94035, USA. NR 48 TC 48 Z9 48 U1 1 U2 7 PU HUMAN FACTORS SOC PI SANTA MONICA PA BOX 1369, SANTA MONICA, CA 90406 SN 0018-7208 J9 HUM FACTORS JI Hum. Factors PD JUN PY 1994 VL 36 IS 2 BP 327 EP 338 PG 12 WC Behavioral Sciences; Engineering, Industrial; Ergonomics; Psychology, Applied; Psychology SC Behavioral Sciences; Engineering; Psychology GA NZ351 UT WOS:A1994NZ35100012 PM 8070796 ER PT J AU VILAS, F JARVIS, KS GAFFEY, MJ AF VILAS, F JARVIS, KS GAFFEY, MJ TI IRON ALTERATION MINERALS IN THE VISIBLE AND NEAR-INFRARED SPECTRA OF LOW-ALBEDO ASTEROIDS SO ICARUS LA English DT Article ID CCD REFLECTANCE SPECTRA; OUTER-BELT; METEORITES; WATER; EARTH AB Absorption features centered near 0.60-0.65 and 0.80-0.90 mum have been identified in the spectra of five low-albedo main-belt and outer-belt asteroids. These absorption features are attributed respectively to the 6A1 --> 4T1 (G) and 6A1 --> 4T1 (G) charge transfer transitions in minerals such as goethite, hematite, and jarosite that are products of the aqueous alteration of anhydrous silicates. A shoulder near 0.63 mum has also been identified in the absorption feature centered near 0.7 mum attributed to oxidized iron in phyllosilicates found predominantly in C- and G-class asteroid reflectance spectra. The coexistence of iron oxides with phyllosilicates in asteroids believed to have undergone aqueous alteration would be expected based upon analogy with terrestrial aqueous alteration and the observed mineralogy of carbonaceous chondrites. The number of low-albedo asteroids having only iron alteration absorption features compared to the number of low-albedo asteroids having spectral characteristics indicative of phyllosilicates is small. Either the conditions under which these asteroids formed are rare, or the iron alteration minerals could be formed in the interiors of objects where phyllosilicates dominate the surface mineralogy. (C) 1994 Academic Press, Inc. C1 WRIGHT STATE UNIV,DEPT GEOL,DAYTON,OH 45435. RENSSELAER POLYTECH INST,DEPT EARTH & ENVIRONM SCI,TROY,NY 12181. RP VILAS, F (reprint author), NASA,LYNDON B JOHNSON SPACE CTR,SN3,HOUSTON,TX 77058, USA. NR 36 TC 83 Z9 83 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 0019-1035 J9 ICARUS JI Icarus PD JUN PY 1994 VL 109 IS 2 BP 274 EP 283 DI 10.1006/icar.1994.1093 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA PC055 UT WOS:A1994PC05500005 ER PT J AU HIROI, T AF HIROI, T TI RECALCULATION OF THE ISOTROPIC H-FUNCTIONS SO ICARUS LA English DT Article AB The isotropic H functions defined in radiative transfer theory by Chandrasekhar (Radiative Transfer, Dover, New York, 1960) have been numerically recalculated for a larger number of single scattering albedo (w) values. The obtained H functions should be accurate to five decimal places at least. The H function values become highly nonlinear as w approaches 1, where calculations were performed with many more points than in Chandrasekhar (1960). A simple linear interpolation of Chandrasekhar's H function table could result in as much as 8% error in the H function values and 16% in the H-2 values that appear in multiple scattering terms such as in Hapke (J. Geophys. Res. 86, 3039-3054, 1981). On the other hand, Hapke's approximations (J. Geophys. Res. 86, 3039-3054, 1981; Theory of Reflectance and Emittance Spectroscopy, Cambridge Univ. Press, New York, 1993) give H values within 4.1% and 0.8% error, respectively. (C) 1994 Academic Press, Inc. RP HIROI, T (reprint author), NASA,LYNDON B JOHNSON SPACE CTR,SN3,HOUSTON,TX 77058, USA. NR 3 TC 11 Z9 11 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 JUN PY 1994 VL 109 IS 2 BP 313 EP 317 DI 10.1006/icar.1994.1096 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA PC055 UT WOS:A1994PC05500008 ER PT J AU WU, TK SHILLUE, WP AF WU, TK SHILLUE, WP TI DICHROIC DESIGN FOR THE ORBITING VLBI EARTH STATION ANTENNA SO IEE PROCEEDINGS-MICROWAVES ANTENNAS AND PROPAGATION LA English DT Article DE DICHROIC DESIGN; ORBITING VLBI EARTH STATION ANTENNA ID FREQUENCY-SELECTIVE SURFACES; SINGLE AB In the paper the design and performance of a single screen frequency selective surface (FSS) with gridded square loop patch element are described for diplexing the X- and Ku-band signals in an orbiting very long baseline interferometer (OVLBI) earth station reflector antenna system. The FSS grids were designed using an analysis code incorporating the accurate integral equation technique. The effects of the dielectric substrate and superstrate are accurately evaluated by this technique. Excellent agreement is obtained between the predicted and measured results. This validates the FSS design using the gridded square loop element. If the grid is sandwiched between two 0.889 mm thick Teflon slabs, the resonant frequency drift is noticeably reduced as the incident angle steered from normal to 40-degrees. C1 NATL RADIO ASTRON OBSERV,GREEN BANK,WV 24944. RP WU, TK (reprint author), JET PROP LAB,MAIL STOP T1703,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 14 TC 9 Z9 9 U1 0 U2 0 PU IEE-INST ELEC ENG PI HERTFORD PA MICHAEL FARADAY HOUSE SIX HILLS WAY STEVENAGE, HERTFORD, ENGLAND SG1 2AY SN 1350-2417 J9 IEE P-MICROW ANTEN P JI IEE Proc.-Microw. Antennas Propag. PD JUN PY 1994 VL 141 IS 3 BP 181 EP 184 DI 10.1049/ip-map:19941035 PG 4 WC Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA PA301 UT WOS:A1994PA30100007 ER PT J AU DAVARIAN, F AF DAVARIAN, F TI AN UPDATE ON NASA K(A)-BAND PROPAGATION MEASUREMENTS SO IEEE ANTENNAS AND PROPAGATION MAGAZINE LA English DT Article C1 JET PROP LAB,PROPAGAT PROGRAM,PASADENA,CA 91109. RP DAVARIAN, F (reprint author), JET PROP LAB,SPECTRUM ENGN GRP,PASADENA,CA 91109, USA. NR 7 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 1045-9243 J9 IEEE ANTENNAS PROPAG JI IEEE Antennas Propag. Mag. PD JUN PY 1994 VL 36 IS 3 BP 14 EP 18 DI 10.1109/74.294239 PG 5 WC Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA PT612 UT WOS:A1994PT61200004 ER PT J AU REDMILL, K OZGUNER, U MUSGRAVE, J MERRILL, W AF REDMILL, K OZGUNER, U MUSGRAVE, J MERRILL, W TI INTELLIGENT HIERARCHICAL THRUST VECTOR CONTROL FOR A SPACE-SHUTTLE SO IEEE CONTROL SYSTEMS MAGAZINE LA English DT Article C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP REDMILL, K (reprint author), OHIO STATE UNIV,DEPT ELECT ENGN,2015 NEIL AVE,COLUMBUS,OH 43210, USA. RI Ozguner, Umit/A-4523-2008; Redmill, Keith/L-3726-2013 NR 14 TC 1 Z9 1 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0272-1708 J9 IEEE CONTR SYST MAG JI IEEE Control Syst. Mag. PD JUN PY 1994 VL 14 IS 3 BP 13 EP 23 DI 10.1109/37.291461 PG 11 WC Automation & Control Systems SC Automation & Control Systems GA PU936 UT WOS:A1994PU93600006 ER PT J AU YANG, SJ BHATTACHARYA, PK BROCK, T ALTEROVITZ, SA TAUB, SR YOUNG, PG AF YANG, SJ BHATTACHARYA, PK BROCK, T ALTEROVITZ, SA TAUB, SR YOUNG, PG TI LOW-TEMPERATURE MICROWAVE CHARACTERISTICS OF 0.1 MU-M GATE-LENGTH PSEUDOMORPHIC IN0.52AL0.48AS/INXGA1-XAS (X = 0.85 AND 0.95) MODFETS SO IEEE ELECTRON DEVICE LETTERS LA English DT Article ID LOW-NOISE AMPLIFIERS; CRYOGENIC TEMPERATURES AB We have studied the microwave characteristics of 0.1 mum gate-length pseudomorphic In0.522Al0.48As/InxGa1-xAs (x = 0.85 and 0.95) modulation-doped field-effect transistors (MODFET's) at 300 K and lower temperatures down to 77 K. A maximum f(T) of 151 GHz has been measured for a 0.1 x 55 mum2 gate In0.52Al0.48As/In0.85Ga0.15As MODFET at 77 K and this represents an improvement of 33% over the room temperature value. This behavior has been analyzed. C1 NASA,LEWIS RES CTR,DIV SPACE ELECTR,CLEVELAND,OH 44135. UNIV TOLEDO,DEPT ELECT ENGN,TOLEDO,OH 43606. RP YANG, SJ (reprint author), UNIV MICHIGAN,DEPT ELECT ENGN & COMP SCI,SOLID STATE ELECTR LAB,ANN ARBOR,MI 48109, USA. NR 7 TC 4 Z9 4 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 0741-3106 J9 IEEE ELECTR DEVICE L JI IEEE Electron Device Lett. PD JUN PY 1994 VL 15 IS 6 BP 209 EP 211 DI 10.1109/55.286694 PG 3 WC Engineering, Electrical & Electronic SC Engineering GA NR950 UT WOS:A1994NR95000007 ER PT J AU WU, TK AF WU, TK TI MEANDER-LINE POLARIZER FOR ARBITRARY ROTATION OF LINEAR-POLARIZATION SO IEEE MICROWAVE AND GUIDED WAVE LETTERS LA English DT Article AB A versatile meander-line polarizer is described and demonstrated for arbitrary rotation of linear polarization. This polarizer consists of eight-layer meander-line grids with rigid foam spacers between any two layers. It is shown that the field polarization rotation angle through this meander-line polarizer is twice the angle between the incident polarization and the polarizer grating lines. Hence, any polarization rotation can be accomplished by a simple mechanical rotation of this low-mass polarizer instead of rotating or modifying the much heavier antenna and its complex feed components. RP WU, TK (reprint author), JET PROP LAB,PASADENA,CA 91109, USA. NR 0 TC 18 Z9 18 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 JUN PY 1994 VL 4 IS 6 BP 199 EP 201 DI 10.1109/75.294292 PG 3 WC Engineering, Electrical & Electronic SC Engineering GA NW048 UT WOS:A1994NW04800016 ER PT J AU KORMANYOS, BK REBEIZ, GM AF KORMANYOS, BK REBEIZ, GM TI OSCILLATOR DESIGN FOR MAXIMUM ADDED POWER SO IEEE MICROWAVE AND GUIDED WAVE LETTERS LA English DT Article AB We report on a linearized technique for the determination of embedding networks that maximize the added power in a two-port oscillator design. The embedding networks are similar to the optimum networks presented by Kotzebue [1], but they are determined without the assumption of a constant voltage at the input port of the active device. The method presented here will result in a more accurate determination of the embedding networks for maximum power output from a device with a given set of two-port parameters. RP KORMANYOS, BK (reprint author), UNIV MICHIGAN,NASA,CTR SPACE TERAHERTZ TECHNOL,DEPT ELECT ENGN & COMP SCI,ANN ARBOR,MI 48109, USA. NR 0 TC 7 Z9 7 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 1051-8207 J9 IEEE MICROW GUIDED W JI IEEE Microw. Guided Wave Lett. PD JUN PY 1994 VL 4 IS 6 BP 205 EP 207 DI 10.1109/75.294294 PG 3 WC Engineering, Electrical & Electronic SC Engineering GA NW048 UT WOS:A1994NW04800018 ER PT J AU HANSEN, C CROCKETT, T WHITMAN, S AF HANSEN, C CROCKETT, T WHITMAN, S TI PARALLEL RENDERING SO IEEE PARALLEL & DISTRIBUTED TECHNOLOGY LA English DT Editorial Material C1 NASA,LANGLEY RES CTR,INST COMP APPLICAT SCI & ENGN,HAMPTON,VA 23061. DAVID SARNOFF RES CTR,PRINCETON,NJ 08543. RP HANSEN, C (reprint author), LOS ALAMOS NATL LAB,ADV COMP LAB,MS B-287,LOS ALAMOS,NM 87545, USA. NR 0 TC 6 Z9 8 U1 0 U2 0 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1264 SN 1063-6552 J9 IEEE PARALL DISTRIB JI IEEE Parallel Distrib. Technol. PD SUM PY 1994 VL 2 IS 2 BP 7 EP 7 PG 1 WC Computer Science, Theory & Methods; Engineering, Electrical & Electronic SC Computer Science; Engineering GA PT788 UT WOS:A1994PT78800003 ER PT J AU CROCKETT, TW ORLOFF, T AF CROCKETT, TW ORLOFF, T TI PARALLEL POLYGON RENDERING FOR MESSAGE-PASSING ARCHITECTURES SO IEEE PARALLEL & DISTRIBUTED TECHNOLOGY LA English DT Article C1 MINERVA SOFTWARE,MINNEAPOLIS,MN 55415. RP CROCKETT, TW (reprint author), NASA,LANGLEY RES CTR,INST COMP APPLICAT SCI & ENGN,MS 132C,HAMPTON,VA 23681, USA. NR 14 TC 6 Z9 6 U1 0 U2 0 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1264 SN 1063-6552 J9 IEEE PARALL DISTRIB JI IEEE Parallel Distrib. Technol. PD SUM PY 1994 VL 2 IS 2 BP 17 EP 28 DI 10.1109/88.311569 PG 12 WC Computer Science, Theory & Methods; Engineering, Electrical & Electronic SC Computer Science; Engineering GA PT788 UT WOS:A1994PT78800005 ER PT J AU HOPPE, DJ EPP, LW LEE, JF AF HOPPE, DJ EPP, LW LEE, JF TI A HYBRID SYMMETRICAL FEM MOM FORMULATION APPLIED TO SCATTERING BY INHOMOGENEOUS BODIES OF REVOLUTION SO IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION LA English DT Article ID FINITE-ELEMENT METHOD; ELECTROMAGNETIC SCATTERING; OBJECTS; FIELD AB A new symmetric formulation of the Hybrid Finite Element Method (HFEM) is described which combines elements of the Electric Field Integral Equation (EFIE) and the Magnetic Field Integral Equation (MFIE) for the exterior region along with the finite element solution for the interior region. The formulation is applied to scattering by inhomogeneous bodies of revolution. To avoid spurious modes in the interior region a combination of vector and nodal based finite elements are used. Integral equations in the exterior region are used to enforce the Sommerfeld radiation condition by matching both the tangential electric and magnetic fields between interior and exterior regions. Results from this symmetric formulation as well as formulations based solely on the EFIE or MFIE are compared to exact series solutions and integral equation solutions for a number of examples. The behaviors of the symmetric, EFIE, and MFIE solutions are examined at potential resonant frequencies of the interior and exterior regions, demonstrating the advantage of this symmetric formulation. C1 WORCESTER POLYTECH INST,DEPT ELECT ENGN,WORCESTER,MA 01609. RP HOPPE, DJ (reprint author), JET PROP LAB,TECH STAFF,PASADENA,CA 91109, USA. RI Lee, Jin-Fa/A-9436-2008 NR 15 TC 26 Z9 27 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 0018-926X J9 IEEE T ANTENN PROPAG JI IEEE Trans. Antennas Propag. PD JUN PY 1994 VL 42 IS 6 BP 798 EP 805 DI 10.1109/8.301698 PG 8 WC Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA NY452 UT WOS:A1994NY45200004 ER PT J AU EPP, LW STANTON, PH JORGENSEN, RE MITTRA, R AF EPP, LW STANTON, PH JORGENSEN, RE MITTRA, R TI EXPERIMENTAL-VERIFICATION OF AN INTEGRAL-EQUATION SOLUTION FOR A THIN-WALLED DICHROIC PLATE WITH CROSS-SHAPED HOLES SO IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION LA English DT Note ID SCATTERING AB In order to add the capability of an X-band up link onto the NASA/JPL Deep space Network (DSN) 70-m antenna, a new dichroic plate is needed to replace the Pyle-guide shaped dichroic plate currently in use. The replacement dichroic plate must exhibit an additional pass band at the new up-link frequency of 7.165 GHz, while maintaining a pass band at the existing down-link frequency of 8.425 GHz. Because of the wide frequency separation of these two pass bands, conventionally designed air-filled dichroic plates exhibit grating lobe problems. A new method of solving this problem using a dichroic plate with cross-shaped holes is presented and verified experimentally. Two checks of the integral equation solution are described here. One is the comparison to a modal analysis for the limiting cross shape of a square hole. As a final check a prototype dichroic plate with cross-shaped holes was built and measured. C1 UNIV ILLINOIS,DEPT ELECT & COMP ENGN,ELECTROMAGNET COMMUN LAB,URBANA,IL 61801. SANDIA NATL LABS,DIV 2753,ALBUQUERQUE,NM 87185. RP EPP, LW (reprint author), JET PROP LAB,PASADENA,CA 91109, USA. NR 8 TC 6 Z9 6 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-926X J9 IEEE T ANTENN PROPAG JI IEEE Trans. Antennas Propag. PD JUN PY 1994 VL 42 IS 6 BP 878 EP 882 DI 10.1109/8.301716 PG 5 WC Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA NY452 UT WOS:A1994NY45200018 ER PT J AU TROXLER, RE RODRIGUE, GP PETERS, PN AF TROXLER, RE RODRIGUE, GP PETERS, PN TI FIELD RESPONSE OF ULTRA-THIN TYPE-II SUPERCONDUCTING TRANSMISSION-LINES SO IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY LA English DT Article ID PENETRATION DEPTH MEASUREMENTS; MICROSTRIP RESONATOR TECHNIQUE; FILMS AB This work describes the effect of a tangential magnetic field on the superconducting penetration depth, lambda, as modeled by the theory of Ginzburg and Landau. In particular, an increasing magnetic field decreases the magnitude of the order parameter Psi. Consequently,the London equations have been modified to include field dependent values of the penetration depth, lambda(T,H), and complex conductivity, sigma(T,H). The analysis assumes that the superconducting films are free of vortices. For Type II films, this criteria can only be met when the thickness of the conductors is less than 1.8 xi(GL). The G-L theory is used to find closed form solutions that describe the electromagnetic characteristics of a kinetic inductance transmission line including phase velocity; impedance, and energy loss, as functions of power, temperature and magnetic fields. Limitations of power are also discussed. To validate these concepts, experiments verifying the effects of temperature and bias field were implemented using niobium superconductors 500 Angstrom thick separated by 1000 Angstrom of Al2O3. Potential device applications include variable phase-shifters, tunable filters, and extremely sensitive bulometers. C1 NASA, GEORGE C MARSHALL SPACE FLIGHT CTR, SPACE SCI LAB, HUNTSVILLE, AL 35812 USA. GEORGIA INST TECHNOL, SCH ELECT ENGN, ATLANTA, GA 30332 USA. NR 25 TC 2 Z9 2 U1 2 U2 4 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 1051-8223 J9 IEEE T APPL SUPERCON JI IEEE Trans. Appl. Supercond. PD JUN PY 1994 VL 4 IS 2 BP 65 EP 75 DI 10.1109/77.291693 PG 11 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA PU040 UT WOS:A1994PU04000005 ER PT J AU BAYARD, DS AF BAYARD, DS TI EXTENDED HORIZON LIFTINGS FOR STABLE INVERSION OF NONMINIMUM-PHASE SYSTEMS SO IEEE TRANSACTIONS ON AUTOMATIC CONTROL LA English DT Note ID TIME-INVARIANT PLANTS; CONTROLLERS AB The lifting of Lozano [9] is generalized and shown to be one in a large class of liftings which enjoy the same zero annihilation properties (i.e., placement of transmission zeros to the origin). The new class of liftings allows for longer horizons and leads to plant-inverse controllers for nonminimum-phase systems having significantly reduced control gains and peak torque requirements. RP BAYARD, DS (reprint author), JET PROP LAB,PASADENA,CA 91109, USA. NR 14 TC 13 Z9 13 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 0018-9286 J9 IEEE T AUTOMAT CONTR JI IEEE Trans. Autom. Control PD JUN PY 1994 VL 39 IS 6 BP 1333 EP 1338 DI 10.1109/9.293208 PG 6 WC Automation & Control Systems; Engineering, Electrical & Electronic SC Automation & Control Systems; Engineering GA NU018 UT WOS:A1994NU01800034 ER PT J AU PALUMBO, DL AF PALUMBO, DL TI THE DERIVATION AND EXPERIMENTAL-VERIFICATION OF CLOCK SYNCHRONIZATION THEORY SO IEEE TRANSACTIONS ON COMPUTERS LA English DT Article DE CLOCK SYNCHRONIZATION; EXPERIMENTAL VERIFICATION; BYZANTINE FAILURE; FORMAL METHODS; PROOF OF CORRECTNESS AB The objective of this work is to validate mathematically derived clock synchronization theories and their associated algorithms through experiment. Two theories are considered, the Interactive Convergence Clock Synchronization Algorithm and the Mid-Point Algorithm. Special clock circuitry was designed and built so that several operating conditions and failure modes (including malicious failures) could be tested. Both theories are shown to predict conservative upper bounds (i.e., measured values of clock skew were always less than the theory prediction). Insight gained during experimentation led to alternative derivations of the theories. These new theories accurately predict the clock system's behavior. It is found that a 100% penalty is paid to tolerate worst case failures. It is also shown that under optimal conditions (with minimum error and no failures) the clock skew can be as much as 3 clock ticks. Clock skew grows to 6 clock ticks when failures are present. Finally, it is concluded that one cannot rely solely on test procedures or theoretical analysis to predict worst case conditions. RP PALUMBO, DL (reprint author), NASA,LANGLEY RES CTR,HAMPTON,VA 23681, USA. NR 17 TC 1 Z9 1 U1 0 U2 0 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1264 SN 0018-9340 J9 IEEE T COMPUT JI IEEE Trans. Comput. PD JUN PY 1994 VL 43 IS 6 BP 676 EP 686 DI 10.1109/12.286301 PG 11 WC Computer Science, Hardware & Architecture; Engineering, Electrical & Electronic SC Computer Science; Engineering GA NR953 UT WOS:A1994NR95300004 ER PT J AU CUNNINGHAM, TJ GEE, RC FOSSUM, ER BAIER, SM AF CUNNINGHAM, TJ GEE, RC FOSSUM, ER BAIER, SM TI DEEP CRYOGENIC NOISE AND ELECTRICAL CHARACTERIZATION OF THE COMPLEMENTARY HETEROJUNCTION FIELD-EFFECT TRANSISTOR (CHFET) SO IEEE TRANSACTIONS ON ELECTRON DEVICES LA English DT Article AB This paper discusses a characterization at 4 K of the complementary heterojunction field-effect transistor (CHFET), to examine its suitability for deep cryogenic (< 10K) readout electronics applications. The CHFET is a GaAs-based transistor analogous in structure and operation to silicon CMOS. The electrical properties including the gate leakage current, subthreshold transconductance, and input-referred noise voltage were examined. It is shown that both n-channel and p-channel CHFET's are fully functional at 4 K, with no anomalous behavior, such as hysteresis or kinks. Complementary circuit designs are possible, and a simple CHFET-based multiplexed op-amp is presented and characterized at 4 K. The noise and gate leakage current of the CHFET are presently several orders of magnitude too large for readout applications, however. The input-referred noise is on the order of 1 muV/square-root Hz at 100 Hz for a 50 x 50 mum n-channel CHFET. The gate current is strongly dependent on the doping at the gate edge, and is on the order of 10(-14) A for a 10 x 10 mum2 n-channel CHFET with light gate-edge region doping. C1 HONEYWELL SYST & RES CTR,BLOOMINGTON,MN 55420. RP CUNNINGHAM, TJ (reprint author), JET PROP LAB,CTR SPACE MICROELECTR TECHNOL,PASADENA,CA 91109, USA. NR 14 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 0018-9383 J9 IEEE T ELECTRON DEV JI IEEE Trans. Electron Devices PD JUN PY 1994 VL 41 IS 6 BP 888 EP 894 DI 10.1109/16.293298 PG 7 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA NR955 UT WOS:A1994NR95500005 ER PT J AU SOARES, S PADIN, SF AF SOARES, S PADIN, SF TI A WIDE-BAND TRACKING DELAY FOR RADIO ASTRONOMY SO IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES LA English DT Article AB Design details for a 0.5 to 4 GHz tracking delay for the Owens Valley Millimeter Array are presented. The delay uses a binary sequence of segments ranging from 512 ns to 1/128 ns to provide any delay value up to 1 mus with a maximum error of 7 ps. The segments are realized in optical fiber, coaxial cable and microstrip transmission line. C1 CALTECH,OWENS VALLEY RADIO OBSERV,BIG PINE,CA 93513. RP SOARES, S (reprint author), JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 8 TC 1 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 0018-9480 J9 IEEE T MICROW THEORY JI IEEE Trans. Microw. Theory Tech. PD JUN PY 1994 VL 42 IS 6 BP 951 EP 955 DI 10.1109/22.293559 PG 5 WC Engineering, Electrical & Electronic SC Engineering GA NV883 UT WOS:A1994NV88300004 ER PT J AU MARSHALL, P DALE, C LABEL, K AF MARSHALL, P DALE, C LABEL, K TI CHARGED-PARTICLE EFFECTS ON OPTOELECTRONIC DEVICES AND BIT ERROR RATE MEASUREMENTS ON 400 MBPS FIBER BASED DATA LINKS SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 2nd European Conference on Radiations and their Effects on Components and Systems (RADECS 93) CY SEP 13-16, 1993 CL ST MALO, FRANCE AB Proton test results on a fiber optic data link operating at 400 megabits/s (Mbps) are described to elucidate the roles of important variables such as proton angle of entry and the optical signal strength. Interpretation of these data reveals that direct ionization events from protons can result in bit errors, though these effects can be mitigated with increased optical signal strength. We explore the consequences of these results to suggest single event tolerant approaches for satellite applications, and conclude that radiation tolerant links and busses can operate in even the most severe orbital environments with acceptable error rates of < 10(9). C1 SFA INC,LANDOVER,MD 20785. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP MARSHALL, P (reprint author), USN,RES LAB,WASHINGTON,DC 20375, USA. NR 9 TC 6 Z9 6 U1 1 U2 2 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD JUN PY 1994 VL 41 IS 3 BP 528 EP 533 DI 10.1109/23.299794 PN 1 PG 6 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA NU414 UT WOS:A1994NU41400017 ER PT J AU SUN, XH ROVER, DT AF SUN, XH ROVER, DT TI SCALABILITY OF PARALLEL ALGORITHM-MACHINE COMBINATIONS SO IEEE TRANSACTIONS ON PARALLEL AND DISTRIBUTED SYSTEMS LA English DT Article DE SCALABLE HIGH PERFORMANCE COMPUTING; PERFORMANCE METRICS; PERFORMANCE EVALUATION OF PARALLEL ALGORITHMS AND MACHINES; SCALABILITY; SCIENTIFIC COMPUTATION; VISUALIZATION ID PERFORMANCE AB Scalability has become an important consideration in parallel algorithm and machine designs. The word scalable, or scalability, has been widely and often used in the parallel processing community. However, there is no adequate, commonly accepted definition of scalability available. Scalabilities of computer systems and programs are difficult to quantify, evaluate, and compare. In this paper, scalability is formally defined for algorithm-machine combinations. A practical method is proposed to provide a quantitative measurement of the scalability. The relation between the newly proposed scalability and other existing parallel performance metrics is studied. A harmony between speedup and scalability has been observed. Theoretical results show that a large class of algorithm-machine combinations is scalable and the scalability can be predicted through premeasured machine parameters. Two algorithms have been studied on an nCUBE 2 multicomputer and on a MasPar MP-1 computer. These case studies have shown how scalabilities can be measured, computed, and predicted. Performance instrumentation and visualization tools also have been used and developed to understand the scalability related behavior. C1 NASA,LANGLEY RES CTR,1 CASE,HAMPTON,VA 23681. MICHIGAN STATE UNIV,DEPT ELECT ENGN,E LANSING,MI 48824. NR 17 TC 73 Z9 92 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 1045-9219 J9 IEEE T PARALL DISTR JI IEEE Trans. Parallel Distrib. Syst. PD JUN PY 1994 VL 5 IS 6 BP 599 EP 613 DI 10.1109/71.285606 PG 15 WC Computer Science, Theory & Methods; Engineering, Electrical & Electronic SC Computer Science; Engineering GA NM893 UT WOS:A1994NM89300004 ER PT J AU SANGER, TD AF SANGER, TD TI NEURAL-NETWORK LEARNING CONTROL OF ROBOT MANIPULATORS USING GRADUALLY INCREASING TASK-DIFFICULTY SO IEEE TRANSACTIONS ON ROBOTICS AND AUTOMATION LA English DT Article ID MOVEMENTS; POSTURE; JOINT AB Trajectory Extension Learning is an incremental method for training an artificial neural network to approximate the inverse dynamics of a robot manipulator. Training data near a desired trajectory is obtained by slowly varying a parameter of the trajectory from a region of easy solvability of the inverse dynamics toward the desired behavior. The parameter can be average speed, path shape, feedback gain, or any other controllable variable. As learning proceeds, an approximate solution to the local inverse dynamics for each value of the parameter is used to guide learning for the next value of the parameter. Convergence conditions are given for two variations on the algorithm. Examples are shown of application to a real 2-joint direct drive robot arm and a simulated 3-joint redundant arm, both using simulated equilibrium point control. RP JET PROP LAB, PASADENA, CA 91109 USA. NR 60 TC 37 Z9 37 U1 1 U2 6 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA SN 1042-296X J9 IEEE T ROBOTIC AUTOM JI IEEE Trans. Robot. Autom. PD JUN PY 1994 VL 10 IS 3 BP 323 EP 333 DI 10.1109/70.294207 PG 11 WC Automation & Control Systems; Engineering, Electrical & Electronic; Robotics SC Automation & Control Systems; Engineering; Robotics GA NU659 UT WOS:A1994NU65900006 ER PT J AU BAYARD, DS MILMAN, MH SCHUMITZKY, A AF BAYARD, DS MILMAN, MH SCHUMITZKY, A TI DESIGN OF DOSAGE REGIMENS - A MULTIPLE MODEL STOCHASTIC-CONTROL APPROACH SO INTERNATIONAL JOURNAL OF BIO-MEDICAL COMPUTING LA English DT Article; Proceedings Paper CT MEDINFO92 Satellite Conference on Estimation and Control of Patient Variability for Individualized Antibiotic Therapy CY 1992 CL CLAUDE BERNARD UNIV, LYON 1, LYON, FRANCE SP ABBOTT DIAGNOST, ADCAPT, EUG, AMER MED INFORMAT ASOSC, ASSISTANCE TRANSIT MELODY, AUDIPHARM, AU PLAISIR GOURMAND, BAYER PHARMA LABS, BIG BAND JAZZ O FEEL, BRISTOL LABS, CABINET LEPINE, DAKOTA PHARM LABS, EUROMEETING, TFI, HEXATOUR, FEDERAT INT PHARM, HOSPICES CIVILS LYON, HOECHHST LABS, INBIOMED, LEACM, INST PASTEUR LYON, INT MED INFORMAT ASSOC, IPHARMEX, JANSSEN FRANCE LABS, LA TIRELIRE BISTROT PASSERELLE, LILLY LABS, MERCK SHARP & DOHME, CHIBRET LABS, MICRO INFORMAT DIFFUS, MINIST RECH & ENSEIGNEMENTS SUPER, NORGAN LABS, REG RHONE ALPES, ROCHE LABS, ROUSSEL LABS, SANOFI WINTHROP LABS, CHOAY DEPT, SYVA LABS, UNIV CL BERNARD LYON 1, UPJOHN LABS HO CLAUDE BERNARD UNIV, LYON 1 DE PHARMACOKINETICS; DOSAGE REGIMENS; STOCHASTIC CONTROL; STATISTICAL MODELS; DRUG MONITORING; AMINOGLYCOSIDES ID AMINOGLYCOSIDE AB This paper presents a general stochastic control framework for determining drug dosage regimens where the sample times, dosing times, desired goals, etc., occur at different times and in an asynchronous fashion. In the special case of multiple models with linear dynamics and quadratic cost (MMLQ), it is shown that the optimal open-leap stochastic control with linear control/state constraints can be solved exactly and efficiently as a quadratic program. This provides a simple and flexible method for computing open-loop feedback designs of drug dosage regimens. An implementation of the MMLQ adaptive control approach is demonstrated on a Lidocaine infusion process. For this example, the resulting MMLQ regimen is more effective than the MAP Bayesian regimen at reducing interpatient variability and keeping patients in the therapeutic range. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. UNIV SO CALIF,DEPT MATH,LOS ANGELES,CA 90089. RP BAYARD, DS (reprint author), UNIV SO CALIF,SCH MED,APPL PHARMACOKINET LAB,2250 ALCAZAR ST,CSC 134-B,LOS ANGELES,CA 90033, USA. FU NLM NIH HHS [LM-05401] NR 10 TC 24 Z9 24 U1 0 U2 0 PU ELSEVIER SCI IRELAND LTD PI CLARE PA CUSTOMER RELATIONS MANAGER, BAY 15, SHANNON INDUSTRIAL ESTATE CO, CLARE, IRELAND SN 0020-7101 J9 INT J BIOMED COMPUT JI Int. J. Bio-Med. Comput. PD JUN PY 1994 VL 36 IS 1-2 BP 103 EP 115 DI 10.1016/0020-7101(94)90100-7 PG 13 WC Computer Science, Interdisciplinary Applications; Computer Science, Theory & Methods; Engineering, Biomedical; Medical Informatics SC Computer Science; Engineering; Medical Informatics GA NU027 UT WOS:A1994NU02700011 PM 7927848 ER PT J AU HAJJ, GA IBANEZMEIER, R KURSINSKI, ER ROMANS, LJ AF HAJJ, GA IBANEZMEIER, R KURSINSKI, ER ROMANS, LJ TI IMAGING THE IONOSPHERE WITH THE GLOBAL POSITIONING SYSTEM SO INTERNATIONAL JOURNAL OF IMAGING SYSTEMS AND TECHNOLOGY LA English DT Article ID TOMOGRAPHY AB Observing the Global Positioning System with a satellite in low earth orbit in an occulting geometry provides a powerful means of imaging the ionosphere. Tomographic imaging of the ionosphere from space and ground is examined using singular value decomposition analysis. The resolution and covariance matrices are examined, and simulations are performed that indicate that space data are significantly more effective than ground data in resolving both horizontal and vertical structures. It is shown that narrow vertical structures, such as the E layer, can be probed with occultation data. (C) 1994 John Wiley and Sons, Inc. RP HAJJ, GA (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 40 TC 127 Z9 132 U1 0 U2 2 PU JOHN WILEY & SONS INC PI NEW YORK PA 605 THIRD AVE, NEW YORK, NY 10158-0012 SN 0899-9457 J9 INT J IMAG SYST TECH JI Int. J. Imaging Syst. Technol. PD SUM PY 1994 VL 5 IS 2 BP 174 EP & DI 10.1002/ima.1850050214 PG 0 WC Engineering, Electrical & Electronic; Optics; Imaging Science & Photographic Technology SC Engineering; Optics; Imaging Science & Photographic Technology GA QD782 UT WOS:A1994QD78200012 ER PT J AU HORZ, F CINTALA, M BERNHARD, RP SEE, TH AF HORZ, F CINTALA, M BERNHARD, RP SEE, TH TI DIMENSIONALLY SCALED PENETRATION EXPERIMENTS - ALUMINUM TARGETS AND GLASS PROJECTILES 50 MU-M TO 3.2-MM IN DIAMETER SO INTERNATIONAL JOURNAL OF IMPACT ENGINEERING LA English DT Article ID HYPER-VELOCITY IMPACT AB Spherical soda-lime glass projectiles 50, 150, 1000 and 3175 mum in diameter (D(p)) in aluminum targets (series 1100, ''annealed'') of variable thickness T were used to determine how the penetration-hole diameter (D(h)) varied as a function of D(p)/T at a constant impact velocity of 6 km/s. The target thickness ranged from infinite half-space geometries to 0.8 mum thick foils. Virtually identical morphologies characterize the penetration holes, no matter what projectile size, at equivalent D(p)/T conditions. The relative hole diameter (D(h)/D(p)) decreases systematically with increasing D(p)/T from D(h) congruent-to 4D(p) for massive targets, to D(h) = D(p) for very thin foils. A modest dependence on the absolute projectile size is observed; comparatively small cracters, yet relatively large penetration holes are produced by the smallest (50 mum) impactors. Nevertheless, linear dimensional scaling seems suitable for first-order estimates of D(p) from the measurement of D(h) and T on space-exposed surfaces. The projectile fragments and the debris dislodged from the target were intercepted by witness plates that were located behind the target. The dispersion angle of this debris cloud depends on the thickness of the target. In addition, millimeter-sized impactors are collisionally fragmented with greater ease than small impactors. Furthermore, we observe that systematic changes in the specific energy of dislodged projectile and target material occur as a function of D(p)/T. While linear scaling of target and projectile dimensions is a useful framework to explain many observations and associated shock processes, we suggest that consideration of the absolute and relative shock-pulse duration in the projectile (t(p)) and target (t(t)) may ultimately be the more useful approach. It implicitly accounts for all dimensions and, additionally, for specific impact velocities and pertinent material properties, via equations-of-state, for the impacting pair. C1 LOCKHEED ESC,HOUSTON,TX 77058. RP HORZ, F (reprint author), NASA,LYNDON B JOHNSON SPACE CTR,DIV SOLAR SYST EXPLORAT,SN4,HOUSTON,TX 77058, USA. NR 38 TC 24 Z9 24 U1 1 U2 4 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0734-743X J9 INT J IMPACT ENG JI Int. J. Impact Eng. PD JUN PY 1994 VL 15 IS 3 BP 257 EP 280 DI 10.1016/S0734-743X(05)80017-X PG 24 WC Engineering, Mechanical; Mechanics SC Engineering; Mechanics GA NR707 UT WOS:A1994NR70700006 ER PT J AU FEBVRE, P MCGRATH, WR BATELAAN, P BUMBLE, B LEDUC, HG GEORGE, S FEAUTRIER, P AF FEBVRE, P MCGRATH, WR BATELAAN, P BUMBLE, B LEDUC, HG GEORGE, S FEAUTRIER, P TI A LOW-NOISE SIS RECEIVER MEASURED FROM 480 GHZ TO 650 GHZ USING NB JUNCTIONS WITH INTEGRATED RF TUNING CIRCUITS SO INTERNATIONAL JOURNAL OF INFRARED AND MILLIMETER WAVES LA English DT Article DE SUPERCONDUCTORS; SIS JUNCTIONS; SIS MIXERS; SIS RECEIVERS; INTEGRATED TUNING CIRCUITS ID TRANSMISSION-LINE; MICROSTRIP; WAVELENGTHS; DESIGN; STRIP AB A heterodyne receiver using an SIS waveguide mixer with two mechanical tuners has been characterized from 480 GHz to 650 GHz. The mixer uses either a single 0.5 x 0.5 mum2 Nb/AlO(x)/Nb SIS tunnel junction or a series array of two 1 mum2 Nb tunnel junctions. These junctions have a high current density, in the range 8 - 13 kA/cm2. Superconductive RF circuits are employed to tune the junction capacitance. DSB receiver noise temperatures as low as 200 +/- 17 K at 540 GHz, 271 K +/- 22 K at 572 GHz and 362 +/- 33 K at 626 GHz have been obtained with the single SIS junctions. The series arrays gave DSB receiver noise temperatures as low as 328 +/- 26 K at 490 GHz and 336 +/- 25 K at 545 GHz. A comparison of the performances of series arrays and single junctions is presented. In addition, negative differential resistance has been observed in the DC I-V curve near 490, 545 and 570 GHz. Correlations between the frequencies for minimum noise temperature, negative differential resistance, and tuning circuit resonances are found. A detailed model to calculate the properties of the tuning circuits is discussed, and the junction capacitance as well as the London penetration depth of niobium are determined by fitting the model to the measured circuit resonances. C1 OBSERV PARIS,DEMIRM,F-92195 MEUDON,FRANCE. RP FEBVRE, P (reprint author), JET PROP LAB,CTR SPACE MICROELECTR TECHNOL,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 26 TC 12 Z9 12 U1 0 U2 2 PU PLENUM PUBL CORP PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 SN 0195-9271 J9 INT J INFRARED MILLI JI Int. J. Infrared Millimeter Waves PD JUN PY 1994 VL 15 IS 6 BP 943 EP 965 DI 10.1007/BF02096128 PG 23 WC Engineering, Electrical & Electronic; Optics; Physics, Applied SC Engineering; Optics; Physics GA NU009 UT WOS:A1994NU00900002 ER PT J AU BAYR, KJ HALL, DK KOVALICK, WM AF BAYR, KJ HALL, DK KOVALICK, WM TI OBSERVATIONS ON GLACIERS IN THE EASTERN AUSTRIAN ALPS USING SATELLITE DATA SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article AB Ground-based measurements on the Pasterze Glacier and the Kleines Fleisskees, located in the eastern Alps of Austria, have shown that these glaciers have receded significantly. Landsat Thematic Mapper (TM) data of these glaciers were acquired in August of 1984, 1986, 1988 and 1990, and have been studied in detail. The 1984-1990 retreat of the Pasterze Glacier has been measured using digital TM data, but the 1984-1988 retreat of the Kleines Fleisskees has not been observed using the TM data because the magnitude of recession between 1984 and 1988 was small relative to the resolution of the TM data. Significant increases in the area of exposed ice (ice facies) on both the Pasterze Glacier and the Kleines Fleisskees were observed and measured using TM data acquired in early August from 1984 to 1988. The area of the Pasterze Glacier and Kleines Fleisskees basins, as measured using TM data, is 20.8+/-1.02 km2 and 1.56 +/- 0.188 km2, respectively. The percentage of the Pasterze Glacier comprised of bare ice increased from 23 per cent in August of 1984 to 36 per cent in August of 1988. Data from nearby meteorological stations show no significant new snowfall during the months of July and early August in 1984, 1986 or 1988 prior to the Landsat overpasses, to obliterate the delineation of the ice facies. The Kleines Fleisskees was also measured using the same TM scene. 40 per cent of this glacier consisted of the ice facies in 1984, and 59 per cent in 1988. Field measurements show that both the Pasterze Glacier and the Kleines Fleisskees have been losing mass for more than 100 years. C1 NASA,GODDARD SPACE FLIGHT CTR,HYDROL SCI BRANCH,GREENBELT,MD 20771. HUGHES STX CORP,LANHAM,MD 20706. RP BAYR, KJ (reprint author), KEENE STATE COLL,229 MAINE ST,KEENE,NH 03431, USA. RI Hall, Dorothy/D-5562-2012 NR 26 TC 47 Z9 51 U1 3 U2 23 PU TAYLOR & FRANCIS LTD PI LONDON PA ONE GUNDPOWDER SQUARE, LONDON, ENGLAND EC4A 3DE SN 0143-1161 J9 INT J REMOTE SENS JI Int. J. Remote Sens. PD JUN PY 1994 VL 15 IS 9 BP 1733 EP 1742 PG 10 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA NV167 UT WOS:A1994NV16700002 ER PT J AU LIN, Q VESECKY, JF ZEBKER, HA AF LIN, Q VESECKY, JF ZEBKER, HA TI COMPARISON OF ELEVATION DERIVED FROM INSAR DATA WITH DEM OVER LARGE RELIEF TERRAIN SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article AB Surface elevation of terrain can be estimated from interferometric synthetic aperture radar (INSAR) observations from satellites. In this paper, we compare a satellite SAR estimate of surface elevation with a digital elevation map (DEM) compiled by the USGS from survey data. To compare the elevation obtained from SAR with a DEM, a new registration method is developed to register the SAR images with the DEM. To convert the DEM into the same format as the SAR data, a phase difference image is generated from the DEM according to SAR imaging geometry. The mean squared error between the simulated phase difference and the measured phase difference is minimised using a downhill simplex minimization algorithm. Registration parameters such as orientation, range and azimuth offsets are obtained in the minimization process. Elevation data generated from the Seasat SAR over an area west of Yellowstone National Park are compared with a DEM using the proposed registration algorithm. The root mean squared (rms) error between the computed elevation and the DEM is found to be 6.0 per cent of the total terrain variations in the image. Layover effects and other error sources are also explored in the paper. C1 STANFORD UNIV,DEPT ELECT ENGN,STAR LAB,STANFORD,CA 94305. JET PROP LAB,PASADENA,CA 91109. NR 12 TC 37 Z9 39 U1 1 U2 8 PU TAYLOR & FRANCIS LTD PI LONDON PA ONE GUNDPOWDER SQUARE, LONDON, ENGLAND EC4A 3DE SN 0143-1161 J9 INT J REMOTE SENS JI Int. J. Remote Sens. PD JUN PY 1994 VL 15 IS 9 BP 1775 EP 1790 PG 16 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA NV167 UT WOS:A1994NV16700005 ER PT J AU FREEMAN, A AF FREEMAN, A TI AN ALGORITHM FOR ESTIMATING THE NOISE-LEVELS IN POLARIMETRIC SAR IMAGE DATA SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article ID CALIBRATION AB A novel algorithm is used to estimate the noise level in polarimetric SAR image data channels, by using the measured signature of an idealized surface with Bragg Scattering. This estimated noise level can then be used to correct the measured backscatter signatures from polarimetric SAR image data. RP FREEMAN, A (reprint author), JET PROP LAB,PASADENA,CA 91109, USA. NR 7 TC 4 Z9 4 U1 1 U2 1 PU TAYLOR & FRANCIS LTD PI LONDON PA ONE GUNDPOWDER SQUARE, LONDON, ENGLAND EC4A 3DE SN 0143-1161 J9 INT J REMOTE SENS JI Int. J. Remote Sens. PD JUN PY 1994 VL 15 IS 9 BP 1791 EP 1798 PG 8 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA NV167 UT WOS:A1994NV16700006 ER PT J AU FREEMAN, A VILLASENOR, J KLEIN, JD HOOGEBOOM, P GROOT, J AF FREEMAN, A VILLASENOR, J KLEIN, JD HOOGEBOOM, P GROOT, J TI ON THE USE OF MULTIFREQUENCY AND POLARIMETRIC RADAR BACKSCATTER FEATURES FOR CLASSIFICATION OF AGRICULTURAL CROPS SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article ID CALIBRATION AB The significance of several key multi-frequency, polarimetric backscatter parameters extracted from calibrated and noise-corrected NASA/JPL DC-8 SAR data are examined. The data were collected during the 1989 MAESTRO-1 campaign over the Flevoland agricultural test site. Calibration uncertainty estimates are used to specify minimum separations between features. Thirteen different backscatter types were identified from the test site data, including eleven different crops, one forest and one water area. Using the parameters with the highest separation for a given class, a hierarchical algorithm was developed to classify the entire image. All three frequencies and all polarizations were used to construct the rules for the classifier. Results indicate that multi-frequency, polarimetric radar backscatter signatures can be useful in classifying several different ground cover types in agricultural areas. C1 TNO,PHYS & ELECTR LAB,2597 AK THE HAGUE,NETHERLANDS. RP FREEMAN, A (reprint author), JET PROP LAB,PASADENA,CA 91109, USA. NR 13 TC 28 Z9 30 U1 1 U2 4 PU TAYLOR & FRANCIS LTD PI LONDON PA ONE GUNDPOWDER SQUARE, LONDON, ENGLAND EC4A 3DE SN 0143-1161 J9 INT J REMOTE SENS JI Int. J. Remote Sens. PD JUN PY 1994 VL 15 IS 9 BP 1799 EP 1812 PG 14 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA NV167 UT WOS:A1994NV16700007 ER PT J AU SAGAN, C OSTRO, SJ AF SAGAN, C OSTRO, SJ TI LONG-RANGE CONSEQUENCES OF INTERPLANETARY COLLISIONS SO ISSUES IN SCIENCE AND TECHNOLOGY LA English DT Article C1 JET PROP LAB,PASADENA,CA 91109. RP SAGAN, C (reprint author), CORNELL UNIV,PLANETARY STUDIES LAB,ITHACA,NY 14853, USA. NR 8 TC 7 Z9 7 U1 0 U2 0 PU NATL ACAD SCIENCES PI WASHINGTON PA 2101 CONSTITUTION AVE NW, WASHINGTON, DC 20418 SN 0748-5492 J9 ISSUES SCI TECHNOL JI Issues Sci. Technol. PD SUM PY 1994 VL 10 IS 4 BP 67 EP 72 PG 6 WC Engineering, Multidisciplinary; Engineering, Industrial; Multidisciplinary Sciences; Social Issues SC Engineering; Science & Technology - Other Topics; Social Issues GA NX340 UT WOS:A1994NX34000025 ER PT J AU CUNNINGHAM, TJ FOSSUM, ER AF CUNNINGHAM, TJ FOSSUM, ER TI GAAS JFETS INTENDED FOR DEEP CRYOGENIC VLWIR READOUT ELECTRONICS SO JOURNAL DE PHYSIQUE IV LA English DT Article; Proceedings Paper CT 1st European Workshop on Low Temperature Electronics (WOLTE 1) CY JUN 29-JUL 01, 1994 CL GRENOBLE, FRANCE SP INST NATL POLYTECH, GRENOBLE, CNRS, PARIS, DIRECT RECH ETUDES & TECH PARIS, FRANCE TELECOM, CTR NATL ETUDE TELECOMMUN, PARIS, MAIRIE VILLE GRENOBLE, CONSEIL GEN ISERE, GRENOBLE, BUTTERWORTH HEINEMANN, CRYOGEN, OXFORD, SOC ELECTRICIENS & ELECTRONICIENS, GRENOBLE & PARIS AB GaAs junction field-effect transistors (JFETs) are promising for deep cryogenic (<10K) readout electronics applications. This paper presents the structure and fabrication of GaAs JFETs and their performance at 4 K. It is shown that these JFETs operate normally at 4 K, with no anomalous behavior such as kinks or hysteresis. The noise voltage follows a 1/square-root f dependence and is approximately 1 muV/square-root Hz at 1 Hz for a ring JFET that is 1250 mum in circumference and 5 mum long. The gate leakage current reaches 1 pA at a gate voltage of -6 V. RP CUNNINGHAM, TJ (reprint author), JET PROP LAB,MAIL STOP 300-315,PASADENA,CA 91109, USA. NR 4 TC 3 Z9 3 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 1155-4339 J9 J PHYS IV JI J. Phys. IV PD JUN PY 1994 VL 4 IS C6 BP 147 EP 152 DI 10.1051/jp4:1994623 PG 6 WC Physics, Multidisciplinary SC Physics GA NU914 UT WOS:A1994NU91400024 ER PT J AU FEBVRE, P LERIDON, B MAOLI, R GEORGE, S FEAUTRIER, P RUFFIE, G MCGRATH, WR BEAUDIN, G AF FEBVRE, P LERIDON, B MAOLI, R GEORGE, S FEAUTRIER, P RUFFIE, G MCGRATH, WR BEAUDIN, G TI NEW ELEMENTS FOR ANALYSIS OF SERIES ARRAYS OF SUPERCONDUCTING JUNCTIONS FOR SUBMILLIMETER HETERODYNE-DETECTION SO JOURNAL DE PHYSIQUE IV LA English DT Article; Proceedings Paper CT 1st European Workshop on Low Temperature Electronics (WOLTE 1) CY JUN 29-JUL 01, 1994 CL GRENOBLE, FRANCE SP INST NATL POLYTECH, GRENOBLE, CNRS, PARIS, DIRECT RECH ETUDES & TECH PARIS, FRANCE TELECOM, CTR NATL ETUDE TELECOMMUN, PARIS, MAIRIE VILLE GRENOBLE, CONSEIL GEN ISERE, GRENOBLE, BUTTERWORTH HEINEMANN, CRYOGEN, OXFORD, SOC ELECTRICIENS & ELECTRONICIENS, GRENOBLE & PARIS ID SIS; RECEIVER AB Some specific features of series arrays of superconducting junctions used as mixing elements in radioastronomical spectroscopy are analysed. The influence of the area and insulating barrier inhomogeneities between the different junctions is examined with a simple and accurate technique. It uses the variation of the maximum Josephson currents of the individual junctions as a function of an applied external magnetic field. It is also shown with this technique that the possibility for some junctions of the array to trap some random flux can prevent stable and sensitive operation of the mixer. Some experimental performances of mixers working near 380 and 550 GHz with series arrays are given. The difficulty of fully suppressing the Josephson currents of each junction at a time appears to be partly responsible for lower sensitivity and instabilities. Another cause of degraded performance comes from the different embedding impedances of each individual junction at the working frequency. It is due to a spreading of the geometrical parameters either of the junctions or of the individual tuning circuits used to compensate the junction capacitance for the 550 GHz mixer. The best performance of the array is then the result of a compromise where all junctions do not operate with optimum efficiency. C1 OBSERV PARIS,F-92195 MEUDON,FRANCE. JET PROP LAB,PASADENA,CA 91109. RP FEBVRE, P (reprint author), ECOLE NORMALE SUPER,DEMIRM,24 RUE LHOMOND,F-75231 PARIS 05,FRANCE. NR 17 TC 0 Z9 0 U1 0 U2 1 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 1155-4339 J9 J PHYS IV JI J. Phys. IV PD JUN PY 1994 VL 4 IS C6 BP 237 EP 242 DI 10.1051/jp4:1994638 PG 6 WC Physics, Multidisciplinary SC Physics GA NU914 UT WOS:A1994NU91400038 ER PT J AU SARAVANOS, DA AF SARAVANOS, DA TI INTEGRATED DAMPING MECHANICS FOR THICK COMPOSITE LAMINATES AND PLATES SO JOURNAL OF APPLIED MECHANICS-TRANSACTIONS OF THE ASME LA English DT Article ID FIBER; MICROMECHANICS AB A method for predicting the damped dynamic characteristics of thick composite laminates and plates is presented. Unified damping mechanics relate the damping of composite plates to constituent properties, fiber volume ratio, fiber orientation, laminate configuration, plate geometry, temperature, and moisture. Discrete layer damping mechanics for thick laminates, entailing piecewise continuous displacement fields and including the effects of interlaminar shear damping, are described. A semi-analytical method for predicting the modal damping and natural frequencies of thick simply-supported specially composite plates is included. Applications demonstrate the validity, merit, and ranges of applicability of the new theory. The applications further illustrate the significance of interlaminar shear damping, and investigate the effects of lamination, thickness aspect ratio, fiber content, and temperature. RP SARAVANOS, DA (reprint author), NASA,LEWIS RES CTR,OHIO AEROSP INST,21000 BROOKPART,MS 49-8,CLEVELAND,OH 44135, USA. NR 24 TC 30 Z9 32 U1 0 U2 0 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 SN 0021-8936 J9 J APPL MECH-T ASME JI J. Appl. Mech.-Trans. ASME PD JUN PY 1994 VL 61 IS 2 BP 375 EP 385 DI 10.1115/1.2901454 PG 11 WC Mechanics SC Mechanics GA NU630 UT WOS:A1994NU63000021 ER PT J AU MAWST, LJ TU, C ZMUDZINSKI, C BOTEZ, D MARTIN, R MAZED, M AF MAWST, LJ TU, C ZMUDZINSKI, C BOTEZ, D MARTIN, R MAZED, M TI SINGLE-FREQUENCY ANTIGUIDED LASER ARRAY WITH BURIED DISTRIBUTED-FEEDBACK GRATING SO JOURNAL OF APPLIED PHYSICS LA English DT Article ID LIMITED-BEAM OPERATION; QUANTUM-WELL LASERS; HIGH-POWER; MOCVD REGROWTH; DIODE-LASERS; AMPLIFIER; FILTER; CW AB Single-frequency, in-phase mode operation has been obtained from a ten-element antiguided phase-locked array with Talbot-type filters by incorporating a buried distributed feedback grating using a three-step metalorganic chemical vapor deposition process. Stabilized frequency with 25 dB side-mode suppression ratio is achieved to 50 mW pulsed output power. In-phase or a mixture of in-phase and out-of-phase modes are observed in nonresonant (nonoptimized) devices. Means of improving device performance (e.g., use of resonant longitudinally uniform arrays or nearly resonant Talbot-filter arrays without gratings in the filter) are discussed. C1 TRW CO INC,RES CTR D1-1024,REDONDO BEACH,CA 90278. JET PROP LAB,MICRODEVICES LAB,PASADENA,CA 91109. NR 19 TC 2 Z9 2 U1 3 U2 3 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 JUN 1 PY 1994 VL 75 IS 11 BP 7220 EP 7223 DI 10.1063/1.356677 PG 4 WC Physics, Applied SC Physics GA NQ267 UT WOS:A1994NQ26700006 ER PT J AU CHEN, JS KOLAWA, E NICOLET, MA RUIZ, RP AF CHEN, JS KOLAWA, E NICOLET, MA RUIZ, RP TI OHMIC CONTACTS TO N-GAAS WITH A PT/GE/AU CONTACTING LAYER AND A TA-SI-N BARRIER - ELECTRICAL AND METALLURGICAL CHARACTERISTICS SO JOURNAL OF APPLIED PHYSICS LA English DT Article ID V-COMPOUND SEMICONDUCTORS; THIN-FILMS; GE; AU; METALLIZATIONS; SCHOTTKY; SYSTEM; GOLD AB Pt/Ge/Au trilayers of various Pt:Ge compositions, overlaid with a Ta-Si-N barrier layer and an Au metallization layer, are investigated as ohmic contacts to n-type GaAs. After annealing in flowing argon at 450-degrees-C for 15 min, a Contact resistivity of 3.7 x 10(-6) OMEGA CM2 is obtained for the sample of atomic ratio Pt/Ge = 1. The contact resistivity of this sample degrades only slightly to 5.0 X 10(-6) OMEGA cm2 upon aging at 450-degrees-C for 60 h, while the surface stays smooth. Contact resistivities of samples with other Pt/Ge atomic ratios are in the range of 10(-5)-10(-4) OMEGA CM2. TO understand this electrical behavior, the contacts are characterized by backscattering spectrometry, x-ray diffraction, and transmission electron microscopy in conjunction with energy-dispersive analysis of x rays. The reaction products vary with the Pt:Ge compositions due to the difference of the chemical reactivity between Pt, Ge, and GaAs. The formation and distribution of a ternary PtGe:As phase are the determining factors for the contact resistivity. The outstanding thermal stability of the contact is due to the Ta-Si-N barrier layer which closes the GaAs-trilayer system and protects their chemical equilibria from being disrupted by an inflow of Au from the metallization layer. Without the barrier layer, the morphology of the contact degrades badly at 450-degrees-C after 20 h or less. C1 JET PROP LAB,PASADENA,CA 91109. RP CHEN, JS (reprint author), CALTECH,PASADENA,CA 91125, USA. RI Chen, Jen-Sue/A-3298-2015 NR 45 TC 9 Z9 9 U1 0 U2 2 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 JUN 1 PY 1994 VL 75 IS 11 BP 7373 EP 7381 DI 10.1063/1.356651 PG 9 WC Physics, Applied SC Physics GA NQ267 UT WOS:A1994NQ26700030 ER PT J AU BRASUNAS, JC LAKEW, B AF BRASUNAS, JC LAKEW, B TI TRANSITION-EDGE NOISE IN YBA2CU3O7-X THIN-FILMS BEFORE AND AFTER EXPOSURE TO IONIZING-RADIATION SO JOURNAL OF APPLIED PHYSICS LA English DT Note ID BOLOMETER; IRRADIATION AB YBa2Cu3O7-x, thin films have been irradiated with gamma rays to a total dose of 100 krad while the films were held at 77 K. For a 1 X 1 mm2 pattern there was no change either in transition width or in low-frequency noise; thus, high-T(c), bolometers made with such films will be robust with respect to this level of gamma rays. For a 3 X 10 mm2 film, which has a lower noise level, there was a change in the slope of noise versus frequency, suggesting a nonthermal origin for the excess noise. C1 HUGHES STX CORP,LANHAM,MD 20706. RP BRASUNAS, JC (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. RI brasunas, john/I-2798-2013 NR 12 TC 1 Z9 1 U1 0 U2 1 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 0021-8979 J9 J APPL PHYS JI J. Appl. Phys. PD JUN 1 PY 1994 VL 75 IS 11 BP 7565 EP 7566 DI 10.1063/1.356633 PG 2 WC Physics, Applied SC Physics GA NQ267 UT WOS:A1994NQ26700063 ER PT J AU MURTHY, G WATENPAUGH, DE BALLARD, RE HARGENS, AR AF MURTHY, G WATENPAUGH, DE BALLARD, RE HARGENS, AR TI SUPINE EXERCISE DURING LOWER-BODY NEGATIVE-PRESSURE EFFECTIVELY SIMULATES UPRIGHT EXERCISE IN NORMAL GRAVITY SO JOURNAL OF APPLIED PHYSIOLOGY LA English DT Article DE ARTIFICIAL GRAVITY; PLANTARFLEXION; DORSIFLEXION; INTRAMUSCULAR PRESSURE; ORTHOSTATIC TOLERANCE; HEART RATE; SYNCOPE; VASCULAR TRANSMURAL PRESSURE; SPACEFLIGHT; MICROGRAVITY; WEIGHTLESSNESS ID RESPONSES AB Exercise within a lower body negative pressure (LBNP) chamber in supine posture was compared with similar exercise against Earth's gravity (without LBNP) in upright posture in nine healthy male volunteers. We measured footward force with a force plate, pressure in soleus and tibialis anterior muscles of the leg with transducer-tipped catheters, calf volume by strain gauge plethysmography, heart rate, and systolic and diastolic blood pressures during two conditions: 1) exercise in supine posture within an LBNP chamber during 100-mmHg LBNP (exercise-LBNP) and 2) exercise in upright posture against Earth's gravity without LBNP (exercise-1 G). Subjects exercised their ankle joints (dorsi- and plantarflexions) for 5 min during exercise-LBNP and for 5 min during exercise-1 G. Mean footward force produced during exercise-LBNP (743 +/- 37 N) was similar to that produced during exercise-1 G (701 +/- 24 N). Peak contraction pressure in the antigravity soleus muscle during exercise-LBNP (115 +/- 10 mmHg) was also similar to that during exercise-1 G (103 +/- 13 mmHg). Calf volume increased significantly by 3.3 +/- 0.5% during exercise-LBNP compared with baseline values. Calf volume did not increase significantly during exercise-1 G. Heart rate was significantly higher during exercise-LBNP (99 +/- 5 beats/min) than during exercise-1 G (81 +/- 3 beats/min). These results indicate that exercise in supine posture within an LBNP chamber can produce similar musculoskeletal stress in the legs and greater systemic cardiovascular stress than exercise in the upright posture against Earth's gravity. RP MURTHY, G (reprint author), NASA,AMES RES CTR,DIV LIFE SCI 23911,MOFFETT FIELD,CA 94035, USA. NR 25 TC 20 Z9 20 U1 0 U2 0 PU AMER PHYSIOLOGICAL SOC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 SN 8750-7587 J9 J APPL PHYSIOL JI J. Appl. Physiol. PD JUN PY 1994 VL 76 IS 6 BP 2742 EP 2748 PG 7 WC Physiology; Sport Sciences SC Physiology; Sport Sciences GA NR916 UT WOS:A1994NR91600067 PM 7928909 ER PT J AU MENEGHINI, R KUMAGAI, H AF MENEGHINI, R KUMAGAI, H TI CHARACTERISTICS OF THE VERTICAL PROFILES OF DUAL-FREQUENCY, DUAL-POLARIZATION RADAR DATA IN STRATIFORM RAIN SO JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY LA English DT Article AB Airborne dual-wavelength and dual-polarization radar data are analyzed for measurements taken in stratiform rain in the western Pacific during September 1990. The focus of the paper is on the vertical profiles of the linear depolarization ratio, LDR (10 GHz); the reflectivity factor, dBZ (10 GHz); and the dual-frequency ratio, DFR (10, 34.45 GHz). Statistical characterizations of the maxima of these quantities and the relative locations at which they occur suggest that the eccentricity of the melting particles is fairly large and that the shape and size of the particles are correlated. To try to explain these features, two types of simulation are presented. In the first, a set of measured drop size distributions is used in the context of a standard model of the melting layer. Variations in snow density, as well as shape, size, and orientation distributions are used to study the relationship between these parameters and the radar measurements. To reduce the amount of ambiguity in the estimation, a second type of simulation is described in which the size distribution of the snow is estimated. Comparisons between the simulated and measured profiles indicate that radar measurements can be used to derive certain characteristics of the particle size and shape distributions in the melting layer. C1 COMMUN RES LABS,TOKYO,JAPAN. RP MENEGHINI, R (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 975,GREENBELT,MD 20771, USA. NR 0 TC 12 Z9 12 U1 0 U2 1 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0739-0572 J9 J ATMOS OCEAN TECH JI J. Atmos. Ocean. Technol. PD JUN PY 1994 VL 11 IS 3 BP 701 EP 711 DI 10.1175/1520-0426(1994)011<0701:COTVPO>2.0.CO;2 PG 11 WC Engineering, Ocean; Meteorology & Atmospheric Sciences SC Engineering; Meteorology & Atmospheric Sciences GA NM073 UT WOS:A1994NM07300008 ER PT J AU DURDEN, SL IM, E LI, FK RICKETTS, W TANNER, A WILSON, W AF DURDEN, SL IM, E LI, FK RICKETTS, W TANNER, A WILSON, W TI ARMAR - AN AIRBORNE RAIN-MAPPING RADAR SO JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY LA English DT Article AB A new airborne rain-mapping radar (ARMAR) has been developed by NASA and the Jet Propulsion Laboratory for operation on the NASA Ames DC-8 aircraft. The radar operates at 13.8 GHz, the frequency to be used by the radar on the Tropical Rainfall Measuring Mission (TRMM). ARMAR simulates the TRMM radar geometry by looking downward and scanning its antenna in the cross-track direction. This basic compatibility between ARMAR and TRMM allows ARMAR to provide information useful for the TRMM radar design, for rain retrieval algorithm development, and for postlaunch calibration. ARMAR has additional capabilities, including multiple polarization, Doppler velocity measurement, and a radiometer channel for brightness temperature measurement. The system has been tested in both ground-based and airborne configurations. This paper describes the design of the system and shows results of field tests. RP DURDEN, SL (reprint author), JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 0 TC 73 Z9 79 U1 0 U2 0 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0739-0572 J9 J ATMOS OCEAN TECH JI J. Atmos. Ocean. Technol. PD JUN PY 1994 VL 11 IS 3 BP 727 EP 737 DI 10.1175/1520-0426(1994)011<0727:AAARMR>2.0.CO;2 PG 11 WC Engineering, Ocean; Meteorology & Atmospheric Sciences SC Engineering; Meteorology & Atmospheric Sciences GA NM073 UT WOS:A1994NM07300010 ER PT J AU MENZIES, RT TRATT, DM FLAMANT, PH AF MENZIES, RT TRATT, DM FLAMANT, PH TI AIRBORNE CO2 COHERENT LIDAR MEASUREMENTS OF CLOUD BACKSCATTER AND OPACITY OVER THE OCEAN SURFACE SO JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY LA English DT Article AB The use of an airborne CO2 lidar to obtain cloud backscatter and extinction data at a thermal infrared wavelength is described. The extinction in this spectral region is proportional to the cloud liquid water content. The use of coherent detection results in high sensitivity and narrow field of view, the latter property greatly reducing multiple-scattering effects. Backscatter measurements in absolute units are obtained through a hard target calibration methodology. For clouds of low to moderate optical thickness at the lidar wavelength, both geometric thickness and optical thickness can be measured. The sea surface reflectance signal is used to obtain estimates of the cloud optical thickness. The utility of this technique results from studies that indicate that the spatial scale of variability of the sea surface reflectance is generally large compared with that of cloud optical thickness. Selected results are presented from data taken during flights over the Pacific Ocean. C1 ECOLE POLYTECH,METEOROL DYNAM LAB,CNRS,F-91128 PALAISEAU,FRANCE. RP MENZIES, RT (reprint author), JET PROP LAB,PASADENA,CA 91109, USA. RI Tratt, David/A-7884-2009 OI Tratt, David/0000-0002-3942-6848 NR 0 TC 5 Z9 5 U1 0 U2 0 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0739-0572 J9 J ATMOS OCEAN TECH JI J. Atmos. Ocean. Technol. PD JUN PY 1994 VL 11 IS 3 BP 770 EP 778 DI 10.1175/1520-0426(1994)011<0770:ACCLMO>2.0.CO;2 PG 9 WC Engineering, Ocean; Meteorology & Atmospheric Sciences SC Engineering; Meteorology & Atmospheric Sciences GA NM073 UT WOS:A1994NM07300013 ER PT J AU HALPERN, D HOLLINGSWORTH, A WENTZ, F AF HALPERN, D HOLLINGSWORTH, A WENTZ, F TI ECMWF AND SSM/I GLOBAL SURFACE WIND SPEEDS SO JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY LA English DT Article AB Monthly mean 2.5-degrees x 2.5-degrees resolution 10-m-height wind speeds from the Special Sensor Microwave/Imager (SSM/I) instrument and the European Centre for Medium-Range Weather Forecasts (ECMWF) forecast-analysis system are compared between 60-degrees-S and 60-degrees-N during 1988-91. The SSM/I data were uniformly processed while numerous changes were made to the ECMWF forecast-analysis system. The SSM/I measurements, which were compared with moored-buoy wind observations, were used as a reference dataset to evaluate the influence of the changes made to the ECMWF system upon the ECMWF surface wind speed over the ocean. A demonstrable yearly decrease of the difference between SSM/I and ECMWF wind speeds occurred in the 10-degrees-S-10-degrees-N region, including the 5-degrees-S-5-degrees-N zone of the Pacific Ocean, where nearly all of the variations occurred in the 160-degrees-E-160-degrees-W region. The apparent improvement of the ECMWF wind speed occurred at the same time as the yearly decrease of the equatorial Pacific SSM/I wind speed, which was associated with the natural transition from La Nina to El Nino conditions. In the 10-degrees-S-10-degrees-N tropical Atlantic, the ECMWF wind speed had a 4-yr trend, which was not expected nor was it duplicated with the SSM/I data. No yearly trend was found in the difference between SSM/I and ECMWF surface wind speeds in middle latitudes of the Northern and Southern Hemispheres. The magnitude of the differences between SSM/I and ECMWF was 0.4 m s-1 or 100% larger in the Northern than in the Southern Hemisphere extratropics. In two areas (Arabian Sea and North Atlantic Ocean) where ECMWF and SSM/I wind speeds were compared to ship measurements, the ship data had much better agreement with the ECMWF analyses compared to SSM/I data. In the 10-degrees-S-10-degrees-N area the difference between monthly standard deviations of the daily wind speeds dropped significantly from 1988 to 1989 but remained constant at about 30% for the remaining years. C1 EUROPEAN CTR MEDIUM RANGE WEATHER FORECASTS,READING,BERKS,ENGLAND. REMOTE SENSING SYST,SANTA ROSA,CA. RP HALPERN, D (reprint author), JET PROP LAB,DIV EARTH & SPACE SCI,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 0 TC 19 Z9 20 U1 0 U2 0 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0739-0572 J9 J ATMOS OCEAN TECH JI J. Atmos. Ocean. Technol. PD JUN PY 1994 VL 11 IS 3 BP 779 EP 788 DI 10.1175/1520-0426(1994)011<0779:EASGSW>2.0.CO;2 PG 10 WC Engineering, Ocean; Meteorology & Atmospheric Sciences SC Engineering; Meteorology & Atmospheric Sciences GA NM073 UT WOS:A1994NM07300014 ER PT J AU MAZELY, TL FRIEDL, RR SANDER, SP AF MAZELY, TL FRIEDL, RR SANDER, SP TI MEASUREMENT OF THE V-T ENERGY-TRANSFER RATES OF HIGHLY EXCITED (2)A(1) NO2 SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID FLUORESCENCE LIFETIME; STATE DISTRIBUTION; NITROGEN-DIOXIDE; LASER PHOTOLYSIS; NITRIC-ACID; NM; PHOTODISSOCIATION; EXCITATION; HNO3; MECHANISM AB Production of electronic ground state NO2 ((2)A(1)) from 248 nm photolysis of HNO3 was detected by laser induced fluorescence (LIF). A growth in the LIF signal was observed following the photolysis and has been interpreted as the relaxation of NO2 through the higher vibrational levels of the X((2)A(1)) state; an energy region where the probe laser photodissociates the NO2 instead of inducing fluorescence. The rate coefficients for NO2 relaxation through these high vibrational levels were determined by fits of time resolved LIF signal to a stepladder kinetic model. The results of the kinetic analysis suggest that the observed relaxation begins at the B-2(2) threshold near 9500 cm(-1) and extends downward through approximately 5 vibrational levels of the ground electronic surface. The derived quenching rate coefficients (in units of 10(-12) cm(3) molecule(-1) s(-1)) are 0.51+/-0.05, 1.0+/-0.1, 1.4+/-0.2, 2.6+/-0.6, and 8.7+/-1.1 for Ar, He, N-2, O-2, and CO2 collision partners, respectively. The discrepancies between these coefficients and previous literature values are rationalized in terms of a dependence of the vibrational relaxation rate on total internal energy. RP MAZELY, TL (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 35 TC 12 Z9 12 U1 0 U2 2 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 0021-9606 J9 J CHEM PHYS JI J. Chem. Phys. PD JUN 1 PY 1994 VL 100 IS 11 BP 8040 EP 8046 DI 10.1063/1.466797 PG 7 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA NN731 UT WOS:A1994NN73100018 ER PT J AU NELSON, CM MOORE, TA OKUMURA, M MINTON, TK AF NELSON, CM MOORE, TA OKUMURA, M MINTON, TK TI PRIMARY AND SECONDARY DISSOCIATION PATHWAYS IN THE ULTRAVIOLET PHOTOLYSIS OF CL2O SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID MOLECULAR-BEAM; PHOTODISSOCIATION; HOCL; SPECTRUM; CHLORINE; STATE; CLO AB The photodissociation of dichlorine monoxide (Cl2O) at 308, 248, and 193 nm was studied by photofragment translational energy spectroscopy. The primary channel upon excitation at 308 and 248 nm was Cl-O bond fission with production of ClO+Cl. A fraction of the ClO photoproducts also underwent spontaneous secondary dissociation at 248 nm. The center-of-mass translational energy distribution for the ClO+Cl channel at 248 nm appeared to be bimodal with a high energy component that was similar in shape to the 308 nm distribution and a second, low energy component with a maximum close to the threshold for the 2CL+O(P-3) channel. Observation of a bimodal distribution suggests that two pathways with different dissociation dynamics lead to ClO+Cl products. The high product internal energy of the second component raises the possibility that ClO is formed in a previously unobserved spin-excited state a (4) Sigma(-). Following excitation at 193 nm, a concerted dissociation pathway leading to Cl-2+O was observed in addition to primary Cl-O bond breakage. In both processes, most of the diatomic photofragments were formed with sufficient internal energy that they spontaneously dissociated. The time-of-flight distributions of the Cl-2+O products suggest that these fragments are formed in two different channels Cl-2((II)-I-3)+O((3)p) and Cl-2(X (1) Sigma)+O(D-1). C1 CALTECH,ARTHUR AMOS NOYES LAB CHEM PHYS,PASADENA,CA 91125. CALTECH,JET PROP LAB,PASADENA,CA 91109. RI Okumura, Mitchio/I-3326-2013 OI Okumura, Mitchio/0000-0001-6874-1137 NR 40 TC 47 Z9 47 U1 0 U2 2 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 0021-9606 J9 J CHEM PHYS JI J. Chem. Phys. PD JUN 1 PY 1994 VL 100 IS 11 BP 8055 EP 8064 DI 10.1063/1.466799 PG 10 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA NN731 UT WOS:A1994NN73100020 ER PT J AU MILLER, JR RUSSELL, GL CALIRI, G AF MILLER, JR RUSSELL, GL CALIRI, G TI CONTINENTAL-SCALE RIVER FLOW IN CLIMATE MODELS SO JOURNAL OF CLIMATE LA English DT Article ID RUNOFF; VARIABILITY AB The hydrologic cycle is a major part of the global climate system. There is an atmospheric flux of water from the ocean surface to the continents. The cycle is closed by return flow in rivers. In this paper a river routing model is developed to use with grid box climate models for the whole earth. The routing model needs an algorithm for the river mass flow and a river direction file, which has been compiled for 4-degrees X 5-degrees and 2-degrees X 2.5-degrees resolutions. River basins are defined by the direction files. The river flow leaving each grid box depends on river and lake mass, downstream distance, and an effective flow speed that depends on topography. As input the routing model uses monthly land source runoff from a 5-yr simulation of the NASA/GISS atmospheric climate model (Hansen et al.). The land source runoff from the 4-degrees X 5-degrees resolution model is quartered onto a 2-degrees x 2.5-degrees grid. and the effect of grid resolution is examined. Monthly flow at the mouth of the world's major rivers is compared with observations, and a global error function for river flow is used to evaluate the routing model and its sensitivity to physical parameters. Three basinwide parameters are introduced: the river length weighted by source runoff, the turnover rate, and the basinwide speed. Although the values of these parameters depend on the resolution at which the rivers are defined, the values should converge as the grid resolution becomes finer. When the routing scheme described here is coupled with a climate model's source runoff, it provides the basis for closing the hydrologic cycle in coupled atmosphere-ocean models by realistically allowing water to return to the ocean at the correct location and with the proper magnitude and timing. C1 NASA,GODDARD SPACE FLIGHT CTR,INST SPACE STUDIES,GREENBELT,MD 20771. HUGHES STX CORP,NEW YORK,NY. RP MILLER, JR (reprint author), RUTGERS STATE UNIV,COOK COLL,INST MARINE & COASTAL SCI,DEPT MARINE & COASTAL SCI,POB 231,NEW BRUNSWICK,NJ 08903, USA. NR 26 TC 159 Z9 166 U1 2 U2 8 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0894-8755 J9 J CLIMATE JI J. Clim. PD JUN PY 1994 VL 7 IS 6 BP 914 EP 928 DI 10.1175/1520-0442(1994)007<0914:CSRFIC>2.0.CO;2 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA NR974 UT WOS:A1994NR97400004 ER PT J AU CHARLES, JB LATHERS, CM AF CHARLES, JB LATHERS, CM TI SUMMARY OF LOWER-BODY NEGATIVE-PRESSURE EXPERIMENTS DURING SPACE-FLIGHT SO JOURNAL OF CLINICAL PHARMACOLOGY LA English DT Article; Proceedings Paper CT 12th Frontiers of Clinical Pharmacology Symposium, Pharmacology Beyond Earths Boundaries CY MAY 06-08, 1992 CL HOUSTON, TX ID HEAD-UP TILT; RESPONSES; BEDREST AB This paper summarizes the lower body negative pressure experiments performed in space, beginning with the experiments conducted on Skylab, because this program provided the most cardiovascular physiology data for United States space flight. Data obtained during studies of lower body negative pressure for use as a countermeasure after months of Russian space flight are also presented. Lower body negative pressure experiments conducted aboard Space Shuttle flights provide data about the deadaptation response of the cardiovascular system to orthostatic stress occurring during periods of zero gravity, and about protection against postflight orthostatic intolerance. Data obtained using Russian and American lower body negative pressure devices indicate that, when a crew member stands, as opposed to being supported by a seat or saddle as in the American device, there may be a slight detrimental effect in terms of the cardiovascular response to this orthostatic stress. Comparison of heart rate and blood pressure response to entry and landing of the Shuttle indicate that, although lower body negative pressure is a different stress and is applied in a different manner, the maximum heart rates during lower body negative pressure are reached at approximately the same point that the maximum heart rates are reached during entry and landing. Thus, the use of a lower body negative pressure stress in flight is a fairly good predictor of the cardiovascular response to the actual entry and landing of the Shuttle. C1 US FDA,DIV CARDIORENAL PROD,ROCKVILLE,MD. RP CHARLES, JB (reprint author), NASA,LYNDON B JOHNSON SPACE CTR,SPACE BIOMED RES INST,MAIL CODE SD5,HOUSTON,TX 77058, USA. NR 15 TC 16 Z9 20 U1 0 U2 1 PU LIPPINCOTT-RAVEN PUBL PI PHILADELPHIA PA 227 EAST WASHINGTON SQ, PHILADELPHIA, PA 19106 SN 0091-2700 J9 J CLIN PHARMACOL JI J. Clin. Pharmacol. PD JUN PY 1994 VL 34 IS 6 BP 571 EP 583 PG 13 WC Pharmacology & Pharmacy SC Pharmacology & Pharmacy GA NQ189 UT WOS:A1994NQ18900005 PM 8083388 ER PT J AU SICONOLFI, SF CHARLES, JB MOORE, AD BARROWS, LH AF SICONOLFI, SF CHARLES, JB MOORE, AD BARROWS, LH TI COMPARING THE EFFECTS OF 2 IN-FLIGHT AEROBIC EXERCISE PROTOCOLS ON STANDING HEART-RATES AND VO2PEAK BEFORE SO JOURNAL OF CLINICAL PHARMACOLOGY LA English DT Article; Proceedings Paper CT 12th Frontiers of Clinical Pharmacology Symposium, Pharmacology Beyond Earths Boundaries CY MAY 06-08, 1992 CL HOUSTON, TX ID BODY NEGATIVE-PRESSURE; SIMULATED WEIGHTLESSNESS; RESPONSES; FITNESS; TOLERANCE; TILT AB The effects of regular aerobic exercise on orthostatic tolerance have been the subject of a long-standing controversy that will influence the use of exercise during space flight. To examine these effects, astronauts performed continuous (CE) aerobic exercise (n 8), interval (IE) aerobic exercise (n = 4), or no (NE) exercise (n = 5) during flights of 7 to 11 days. Heart rate (HR) responses to an orthostatic challenge (stand test) were measured 10 days before flight and on landing day. VO2peak (graded treadmill exercise) was measured 7 to 21 days before and 2 days after flight. No significant differences across the groups were observed in standing HRs before or after flight. However, the within-group mean HRs significantly increased in the NE (71-89 beats/min) and CE (60-85 beats/min) groups after space flight. The HRs for the IE group did not significantly increase (75-86 beats/min) after space flight. VO2peak decreased (P<.05) in the NE (-9.5%) group, but did not change in the CE(-2.4%) and IE (1%) groups. The relationship (r=0.237) between the was not significant. These preliminary results indicate that: the Delta HR and Delta VO2peak was not significant. These preliminary results indicate that; (1) continuous exercise does not affect the orthostatic HR response after space flight; (2) interval exercise may minimize an increase in the postflight orthostatic HR; and (3) both exercise protocols can maintain VO2peak. C1 KRUG LIFE SCI,HOUSTON,TX. RP SICONOLFI, SF (reprint author), NASA,LYNDON B JOHNSON SPACE CTR,SPACE BIOMED RES INST SD5,HOUSTON,TX 77058, USA. NR 24 TC 6 Z9 6 U1 0 U2 0 PU LIPPINCOTT-RAVEN PUBL PI PHILADELPHIA PA 227 EAST WASHINGTON SQ, PHILADELPHIA, PA 19106 SN 0091-2700 J9 J CLIN PHARMACOL JI J. Clin. Pharmacol. PD JUN PY 1994 VL 34 IS 6 BP 590 EP 595 PG 6 WC Pharmacology & Pharmacy SC Pharmacology & Pharmacy GA NQ189 UT WOS:A1994NQ18900007 PM 8083389 ER PT J AU KUMAR, KV POWELL, MR WALIGORA, JM AF KUMAR, KV POWELL, MR WALIGORA, JM TI EARLY STOPPING OF AEROSPACE MEDICAL TRIALS - APPLICATION OF SEQUENTIAL PRINCIPLES SO JOURNAL OF CLINICAL PHARMACOLOGY LA English DT Article; Proceedings Paper CT 12th Frontiers of Clinical Pharmacology Symposium, Pharmacology Beyond Earths Boundaries CY MAY 06-08, 1992 CL HOUSTON, TX AB A two-period, crossover trial was conducted in the hypobaric chamber on human subjects to compare the influence of inflight exercise (experimental) and restricted activity (control) on altitude decompression sickness (DCS) during simulated extravehicular activities. Out of 39 pairs (total of 78 exposures), 4 cases of Dcs occurred under control and 5 occurred under experimental conditions. Analysis of the crossover results showed that the P values for differences in DCS occurrence was 0.56. Under these circumstances, it was necessary to decide whether additional information would be obtained by accruing more subjects. This problem was examined by using a skew sequential design in which the ''stopping rule'' was based on an alpha of 0.05 (one-sided) and power of 80%. The result of this analysis was in favor of the null hypothesis, and the trial was terminated. The authors recommend the use of similar stopping rules in aerospace trials to optimize sample size without compromising statistical validity. C1 NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058. RP KUMAR, KV (reprint author), KRUG LIFE SCI,1290 HERCULES DR,SUITE 120,HOUSTON,TX 77058, USA. NR 8 TC 3 Z9 3 U1 0 U2 0 PU LIPPINCOTT-RAVEN PUBL PI PHILADELPHIA PA 227 EAST WASHINGTON SQ, PHILADELPHIA, PA 19106 SN 0091-2700 J9 J CLIN PHARMACOL JI J. Clin. Pharmacol. PD JUN PY 1994 VL 34 IS 6 BP 596 EP 598 PG 3 WC Pharmacology & Pharmacy SC Pharmacology & Pharmacy GA NQ189 UT WOS:A1994NQ18900008 PM 8083390 ER PT J AU COWINGS, PS TOSCANO, WB MILLER, NE PICKERING, TG SHAPIRO, D STEVENSON, J MALONEY, S KNAPP, J AF COWINGS, PS TOSCANO, WB MILLER, NE PICKERING, TG SHAPIRO, D STEVENSON, J MALONEY, S KNAPP, J TI AUTOGENIC-FEEDBACK TRAINING - A POTENTIAL TREATMENT FOR ORTHOSTATIC INTOLERANCE IN AEROSPACE CREWS SO JOURNAL OF CLINICAL PHARMACOLOGY LA English DT Article; Proceedings Paper CT 12th Frontiers of Clinical Pharmacology Symposium, Pharmacology Beyond Earths Boundaries CY MAY 06-08, 1992 CL HOUSTON, TX ID BLOOD-PRESSURE; MOTION SICKNESS; HEART-RATE; BIOFEEDBACK; STRESS AB Postflight orthostatic intolerance has been identified as a serious biomedical problem associated with long-duration exposure to microgravity in space. High priority has been given to the development of countermeasures for this disorder that are both effective and practical. A considerable body of clinical research has demonstrated that people can be taught to increase their own blood pressure voluntarily, and that this is an effective treatment for chronic orthostatic intolerance in paralyzed patients. The current pilot study was designed to examine the feasibility of adding training in control of blood pressure to an existing preflight training program designed to facilitate astronaut adaptation to microgravity. Using an operant conditioning procedure, autogenic-feedback training (AFT), three men and two women participated in four to nine training (15-30-minute) sessions. At the end of training, the average increase in systolic and diastolic pressure, as well as mean arterial pressures, that the subjects mode ranged between 20 and 50 mm Hg under both supine and 45 degrees head-up tilt conditions. These findings indicate that AFT may be a useful alternative treatment or supplement to existing approaches for preventing postflight orthostatic intolerance. Furthermore, the use of operant conditioning methods for training cardiovascular responses map contribute to the general understanding of the mechanisms of orthostatic intolerance. C1 UCSF,SCH MED,LANGLEY PORTER INST,SAN FRANCISCO,CA. YALE UNIV,DEPT PSYCHOL,NEW HAVEN,CT 06520. CORNELL UNIV,SCH MED,DEPT CARDIOL,NEW YORK,NY 10021. UNIV CALIF LOS ANGELES,SCH MED,DEPT PSYCHIAT,LOS ANGELES,CA. NASA,AMES RES CTR,DIV AEROSP HUMAN FACTORS RES,MOFFETT FIELD,CA 94035. NASA,BIONETICS CORP,MOFFETT FIELD,CA. RP COWINGS, PS (reprint author), NASA,AMES RES CTR,DIV SPACE LIFE SCI,MAIL STOP 239-A2,MOFFETT FIELD,CA 94035, USA. NR 36 TC 8 Z9 8 U1 1 U2 2 PU LIPPINCOTT-RAVEN PUBL PI PHILADELPHIA PA 227 EAST WASHINGTON SQ, PHILADELPHIA, PA 19106 SN 0091-2700 J9 J CLIN PHARMACOL JI J. Clin. Pharmacol. PD JUN PY 1994 VL 34 IS 6 BP 599 EP 608 PG 10 WC Pharmacology & Pharmacy SC Pharmacology & Pharmacy GA NQ189 UT WOS:A1994NQ18900009 PM 8083391 ER PT J AU RESCHKE, MF BLOOMBERG, JJ HARM, DL PALOSKI, WH AF RESCHKE, MF BLOOMBERG, JJ HARM, DL PALOSKI, WH TI SPACE-FLIGHT AND NEUROVESTIBULAR ADAPTATION SO JOURNAL OF CLINICAL PHARMACOLOGY LA English DT Article; Proceedings Paper CT 12th Frontiers of Clinical Pharmacology Symposium, Pharmacology Beyond Earths Boundaries CY MAY 06-08, 1992 CL HOUSTON, TX ID HEAD STABILIZATION; LOCOMOTOR TASKS; REFLEX; HUMANS; GAZE AB Space flight represents a form of sensory stimulus rearrangement requiring modification of established terrestrial response patterns through central reinterpretation. Evidence of sensory reinterpretation is manifested as postflight modifications of eye/head coordination, locomotor patterns, postural control strategies, and illusory perceptions of self or surround motion in conjunction with head movements. Under normal preflight conditions, the head is stabilized during locomotion, but immediately postflight reduced head stability, coupled with inappropriate eye/head coordination, results in modifications of gait. Postflight postural control exhibits increased dependence on vision which compensates for inappropriate interpretation of otolith and proprioceptive inputs. Eye movements compensatory for perceived self motion, rather than actual head movements have been observed postflight. Overall, the in-flight adaptive modification of head stabilization strategies, changes in head/eye coordination, illusionary motion, and postural control are maladaptive for a return to the terrestrial environment. RP RESCHKE, MF (reprint author), NASA,LYNDON B JOHNSON SPACE CTR,SPACE BIOMED RES INST,DIV MED SCI,NEUROSCI LAB,MAIL CODE SD5,HOUSTON,TX 77058, USA. NR 26 TC 33 Z9 33 U1 1 U2 1 PU LIPPINCOTT-RAVEN PUBL PI PHILADELPHIA PA 227 EAST WASHINGTON SQ, PHILADELPHIA, PA 19106 SN 0091-2700 J9 J CLIN PHARMACOL JI J. Clin. Pharmacol. PD JUN PY 1994 VL 34 IS 6 BP 609 EP 617 PG 9 WC Pharmacology & Pharmacy SC Pharmacology & Pharmacy GA NQ189 UT WOS:A1994NQ18900010 PM 8083392 ER PT J AU HARM, DL PARKER, DE AF HARM, DL PARKER, DE TI PREFLIGHT ADAPTATION TRAINING FOR SPATIAL ORIENTATION AND SPACE MOTION SICKNESS SO JOURNAL OF CLINICAL PHARMACOLOGY LA English DT Article; Proceedings Paper CT 12th Frontiers of Clinical Pharmacology Symposium, Pharmacology Beyond Earths Boundaries CY MAY 06-08, 1992 CL HOUSTON, TX ID PROLONGED WEIGHTLESSNESS AB Two part-task preflight adaptation trainers (PATs) are being developed at the NASA Johnson Space Center to preadapt astronauts to novel sensory stimulus conditions similar to those present in microgravity to facilitate adaptation to microgravity and readaptation to Earth. This activity is a major component of a general effort to develop countermeasures aimed at minimizing sensory and sensorimotor disturbances and Space Motion Sickness (SMS) associated with adaptation to microgravity and readaptation to Earth. Design principles for the development of the two trainers are discussed, along with a detailed description of both devices. In addition, a summary of four ground-based investigations using one of the trainers to determine the extent to which various novel sensory stimulus conditions produce changes in compensatory eye movement responses, postural equilibrium, motion sickness symptoms, and electrogastric responses are presented. Finally, a brief description of the general concept of dual-adapted states that underly the development of the PATs, and ongoing and future operational and basic research activities is presented. RP HARM, DL (reprint author), NASA,LYNDON B JOHNSON SPACE CTR,NEUROSCI LAB,MAIL CODE SD5,HOUSTON,TX 77058, USA. NR 19 TC 20 Z9 22 U1 0 U2 1 PU LIPPINCOTT-RAVEN PUBL PI PHILADELPHIA PA 227 EAST WASHINGTON SQ, PHILADELPHIA, PA 19106 SN 0091-2700 J9 J CLIN PHARMACOL JI J. Clin. Pharmacol. PD JUN PY 1994 VL 34 IS 6 BP 618 EP 627 PG 10 WC Pharmacology & Pharmacy SC Pharmacology & Pharmacy GA NQ189 UT WOS:A1994NQ18900011 PM 8083393 ER PT J AU BAGIAN, JP WARD, DF AF BAGIAN, JP WARD, DF TI A RETROSPECTIVE STUDY OF PROMETHAZINE AND ITS FAILURE TO PRODUCE THE EXPECTED INCIDENCE OF SEDATION DURING SPACE-FLIGHT SO JOURNAL OF CLINICAL PHARMACOLOGY LA English DT Article; Proceedings Paper CT 12th Frontiers of Clinical Pharmacology Symposium, Pharmacology Beyond Earths Boundaries CY MAY 06-08, 1992 CL HOUSTON, TX ID PERFORMANCE AB Since March 1989, intramuscular (IM) promethazine has been successfully used to treat the symptoms of space motion sickness. The incidence of sedation associated with promethazine administration on the ground is large and may result in operational impact. The authors undertook a retrospective study to quantify the incidence of sedation from promethazine use during Space Shuttle flights. Crew medical debriefings from 14 shuttle missions were reviewed for crew members who had been treated with IM promethazine and their corresponding symptoms were identified. Twenty-one crew members received IM promethazine (25-50 mg), and only one experienced any associated sedation with no operational impact. This sedation incidence of less than 5% is in stark contrast to the 60 to 73% incidence of sedation seen in ground-based studies. The incidence of sedation during space flight from IM promethazine is substantially less than that seen on the ground and does not present an operational problem during Space Shuttle flights. Future investigations of environmental stressors and pharmacodynamic changes associated with space flight may explain the huge disparity between the space-flight and groundbased data. RP BAGIAN, JP (reprint author), NASA,LYNDON B JOHNSON SPACE CTR,ASTRONAUT OFF,HOUSTON,TX 77058, USA. NR 10 TC 15 Z9 16 U1 0 U2 1 PU LIPPINCOTT-RAVEN PUBL PI PHILADELPHIA PA 227 EAST WASHINGTON SQ, PHILADELPHIA, PA 19106 SN 0091-2700 J9 J CLIN PHARMACOL JI J. Clin. Pharmacol. PD JUN PY 1994 VL 34 IS 6 BP 649 EP 651 PG 3 WC Pharmacology & Pharmacy SC Pharmacology & Pharmacy GA NQ189 UT WOS:A1994NQ18900015 PM 9766972 ER PT J AU SIMANONOK, KE CHARLES, JB AF SIMANONOK, KE CHARLES, JB TI SPACE SICKNESS AND FLUID SHIFTS - A HYPOTHESIS SO JOURNAL OF CLINICAL PHARMACOLOGY LA English DT Article ID ATRIAL NATRIURETIC PEPTIDE; BLOOD-VOLUME; WATER IMMERSION; WEIGHTLESSNESS; MECHANISMS; RESPONSES; PRESSURE; HUMANS; DOGS AB In a sample of 64 first-time Space Shuttle crew members, 9 preflight variables related to fluid, electrolyte, and cardiovascular status were previously found to be significantly related to space sickness. The nine variables are serum uric acid, red cell count, environmental temperature at the launch site, serum phosphate, urine osmolality, serum thyroxine, sitting systolic blood pressure, calculated blood volume, and serum chloride. Using discriminant analysis, these preflight variables were used to correctly classify the 64 astronauts according to their space sickness incidence (NOTSICK or SICK) with 80% success, using two methods of pseudo-crossvalidation. Symptoms of motion sickness may be induced on Earth, either with a sufficiently high level of vestibular stimulation or with less vestibular stimulation after reducing the threshold for motion sickness induction. Some of the nine predictor variables support a fluid shift hypothesis of space sickness etiology by which central volume expansion in weightlessness may lower the threshold required for novel vestibular stimulation to cause space sickness. According to this hypothesis, some astronauts suffer a greater central volume expansion than do others, causing them to have greater physiologic responses to fluid shifts, which, in turn, proportionally reduces their threshold for induction of space sickness. The hypothesis is supported by preflight and postflight echocardiographic comparisons of heart volumes in 19 shuttle astronauts. The postflight left ventricular diastolic volume index was decreased by 34 +/- 3% in the astronauts with MODERATE or SEVERE space sickness, but only 9 +/- 5% (P < .05) in the NONE or MILD group, indicating that an exaggerated physiologic adaptation to fluid shifts is associated with space sickness. C1 NASA, LYNDON B JOHNSON SPACE CTR, SPACE BIOMED RES INST, HOUSTON, TX 77058 USA. UNIV SPACE RES ASSOC, HOUSTON, TX USA. NR 40 TC 8 Z9 8 U1 0 U2 1 PU WILEY-BLACKWELL PI HOBOKEN PA 111 RIVER ST, HOBOKEN 07030-5774, NJ USA SN 0091-2700 EI 1552-4604 J9 J CLIN PHARMACOL JI J. Clin. Pharmacol. PD JUN PY 1994 VL 34 IS 6 BP 652 EP 663 PG 12 WC Pharmacology & Pharmacy SC Pharmacology & Pharmacy GA NQ189 UT WOS:A1994NQ18900016 PM 8083397 ER PT J AU TIETZE, KJ PUTCHA, L AF TIETZE, KJ PUTCHA, L TI FACTORS AFFECTING DRUG BIOAVAILABILITY IN-SPACE SO JOURNAL OF CLINICAL PHARMACOLOGY LA English DT Article; Proceedings Paper CT 12th Frontiers of Clinical Pharmacology Symposium, Pharmacology Beyond Earths Boundaries CY MAY 06-08, 1992 CL HOUSTON, TX ID LIVER BLOOD-FLOW; TRANSIT-TIME; GASTROINTESTINAL TRANSIT; ACETAMINOPHEN ABSORPTION; PSYCHOLOGICAL STRESS; PHARMACOKINETICS; NIFEDIPINE; POSTURE; REST AB Microgravity-induced changes in the bioavailability of drugs may influence the efficacy or toxicity of drugs. The bioavailability of orally administered drugs may be altered by changes in dissolution rate, intestinal microflora, intraluminal enzymes, epithelial enzymes, rate of passage across the gastrointestinal epithelium, gastric emptying rate, intestinal transit time, hepatic first pass metabolism, and gastrointestinal and hepatic blood pow. Limited data from antiorthostatic bed rest and inflight studies provide preliminary evidence that the bioavailability of orally administered drugs in space may be decreased or subject to more interindividual variation than expected from ground-based studies. C1 NASA,LYNDON B JOHNSON SPACE CTR,BIOMED OPERAT & RES BRANCH,HOUSTON,TX 77058. RP TIETZE, KJ (reprint author), PHILADELPHIA COLL PHARM & SCI,PHARM ADM,DEPT PHARM PRACTICE,600 S 43RD ST,PHILADELPHIA,PA 19104, USA. NR 41 TC 21 Z9 23 U1 0 U2 2 PU LIPPINCOTT-RAVEN PUBL PI PHILADELPHIA PA 227 EAST WASHINGTON SQ, PHILADELPHIA, PA 19106 SN 0091-2700 J9 J CLIN PHARMACOL JI J. Clin. Pharmacol. PD JUN PY 1994 VL 34 IS 6 BP 671 EP 676 PG 6 WC Pharmacology & Pharmacy SC Pharmacology & Pharmacy GA NQ189 UT WOS:A1994NQ18900018 PM 8083399 ER PT J AU SRINIVASAN, RS BOURNE, DWA PUTCHA, L AF SRINIVASAN, RS BOURNE, DWA PUTCHA, L TI APPLICATION OF PHYSIOLOGICALLY-BASED PHARMACOKINETIC MODELS FOR ASSESSING DRUG DISPOSITION IN-SPACE SO JOURNAL OF CLINICAL PHARMACOLOGY LA English DT Article; Proceedings Paper CT 12th Frontiers of Clinical Pharmacology Symposium, Pharmacology Beyond Earths Boundaries CY MAY 06-08, 1992 CL HOUSTON, TX ID WEIGHTLESSNESS; ACETAMINOPHEN; SIMULATION; ASTRONAUTS; MICE AB Exposure to weightlessness induces physiologic changes that may lead to pharmacokinetic and pharmacodynamic alterations of drugs administered to crew members in flight. Preliminary data from flight and ground-based studies indicate that pharmacologically significant changes occur in the kinetics of medications given in weightlessness and in simulated microgravity (head-down bed rest). Conducting flight studies on all available medications to identify the changes in their pharmacokinetic behavior in weightlessness is not feasible. An alternative approach for obtaining such information is to use computer simulations employing physiologically based pharmacokinetic (PBPK) models. Information thus obtained would be helpful in predicting the therapeutic effectiveness of medications in space, and also in developing plans for flight studies. This paper presents a brief review of relevant physiologic factors and pharmacokinetic implications of space flight, and includes a preliminary PBPK model for estimating plasma concentration-time profiles of acetaminophen under different experimental conditions. C1 UNIV OKLAHOMA,OKLAHOMA CITY,OK. NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058. RP SRINIVASAN, RS (reprint author), KRUG LIFE SCI,1290 HERCULES DR,SUITE 120,HOUSTON,TX 77058, USA. NR 29 TC 9 Z9 10 U1 1 U2 3 PU LIPPINCOTT-RAVEN PUBL PI PHILADELPHIA PA 227 EAST WASHINGTON SQ, PHILADELPHIA, PA 19106 SN 0091-2700 J9 J CLIN PHARMACOL JI J. Clin. Pharmacol. PD JUN PY 1994 VL 34 IS 6 BP 692 EP 698 PG 7 WC Pharmacology & Pharmacy SC Pharmacology & Pharmacy GA NQ189 UT WOS:A1994NQ18900021 PM 8083402 ER PT J AU TAYLOR, GR AF TAYLOR, GR TI SPACE STATION FREEDOM LIFE SCIENCES ACTIVITIES SO JOURNAL OF CLINICAL PHARMACOLOGY LA English DT Article; Proceedings Paper CT 12th Frontiers of Clinical Pharmacology Symposium, Pharmacology Beyond Earths Boundaries CY MAY 06-08, 1992 CL HOUSTON, TX AB Life sciences activites being planned for Space Station Freedom (SSF) as of Fall 1992 are discussed. Planning for these activities is ongoing. Therefore, this description should be viewed as indicative of the prevailing ideas at one particular time in the SSF development cycle. The proposed contributions of the Canadian Space Agency (CSN) the European Space Agency (ESA), Japan, and the United States are all discussed in detail. In each case, the life sciences goals, and the way in which each partner proposes to acheive their goals, are reviewed. RP TAYLOR, GR (reprint author), NASA,LYNDON B JOHNSON SPACE CTR,SPACE & LIFE SCI DIRECTORATE,MISSION SCI MANAGEMENT OFF,HOUSTON,TX 77058, USA. NR 12 TC 0 Z9 0 U1 0 U2 0 PU LIPPINCOTT-RAVEN PUBL PI PHILADELPHIA PA 227 EAST WASHINGTON SQ, PHILADELPHIA, PA 19106 SN 0091-2700 J9 J CLIN PHARMACOL JI J. Clin. Pharmacol. PD JUN PY 1994 VL 34 IS 6 BP 703 EP 708 PG 6 WC Pharmacology & Pharmacy SC Pharmacology & Pharmacy GA NQ189 UT WOS:A1994NQ18900023 PM 8083404 ER PT J AU ASTHANA, R AF ASTHANA, R TI A TEST OF NEUMANN CRITERION FOR ADSORPTION ON SOLIDS IN SOME CERAMIC-METAL SYSTEMS SO JOURNAL OF COLLOID AND INTERFACE SCIENCE LA English DT Letter ID CONTACT ANGLES; WETTABILITY; ENERGY RP ASTHANA, R (reprint author), NASA,LEWIS RES CTR,MS 105-1,CLEVELAND,OH 44135, USA. NR 20 TC 4 Z9 4 U1 0 U2 0 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0021-9797 J9 J COLLOID INTERF SCI JI J. Colloid Interface Sci. PD JUN PY 1994 VL 165 IS 1 BP 256 EP 258 DI 10.1006/jcis.1994.1227 PG 3 WC Chemistry, Physical SC Chemistry GA NH649 UT WOS:A1994NH64900029 ER PT J AU STRATTON, DM GANS, J WILLIAMS, E AF STRATTON, DM GANS, J WILLIAMS, E TI COAGULATION ALGORITHMS WITH SIZE BINNING SO JOURNAL OF COMPUTATIONAL PHYSICS LA English DT Article AB The Smoluchowski equation describes the time evolution of an aerosol particle size distribution due to aggregation or coagulation. Any algorithm for computerized solution of this equation requires a scheme for describing the continuum of aerosol particle sizes as a discrete set. One standard from of the Smoluchowski equation accomplishes this by restricting the particle sizes to integer multiples of a basic unit particle size (the monomer size). This can be inefficient when particle concentrations over a large range of particle sizes must be calculated. Two algorithms employing a geometric size binning convention are examined: the first assumes that the aerosol particle concentration as a function of size can be considered constant within each size bin; the second approximates the concentration as a linear function of particle size within each size bin. The output of each algorithm is compared to an analytical solution in a special case of the Smoluchowski equation for which an exact solution is known. The range of parameters more appropriate for each algorithm is examined. (C) 1994 Academic Press, Inc. C1 UNIV CALIF SANTA CRUZ,SANTA CRUZ,CA 95060. SAN FRANCISCO STATE UNIV,SAN FRANCISCO,CA 94143. RP STRATTON, DM (reprint author), NASA,AMES RES CTR,SETI INST,MOFFETT FIELD,CA 94035, USA. NR 4 TC 4 Z9 4 U1 1 U2 2 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0021-9991 J9 J COMPUT PHYS JI J. Comput. Phys. PD JUN PY 1994 VL 112 IS 2 BP 364 EP 369 DI 10.1006/jcph.1994.1106 PG 6 WC Computer Science, Interdisciplinary Applications; Physics, Mathematical SC Computer Science; Physics GA NP005 UT WOS:A1994NP00500014 ER PT J AU WATRING, DA JOHNSON, M AF WATRING, DA JOHNSON, M TI AMPOULE FAILURE SENSOR DEVELOPMENT FOR SEMICONDUCTOR CRYSTAL-GROWTH EXPERIMENTS SO JOURNAL OF CRYSTAL GROWTH LA English DT Article AB Currently there are no devices to detect an ampoule failure in semiconductor crystal growth experiments. If an ampoule fails, it will go undetected until the containing cartridge is breached due to chemical degradation. The experiment will then be terminated resulting in a failed experiment and a loss of data. The objective of this research was to develop a reliable failure sensor that would detect a specific liquid or vapor material before the metallic cartridge is degraded and the processing furnace contaminated. The sensor is a chemical fuse made from a metal with which the semiconductor material reacts more rapidly than it does with the containing cartridge. Upon ampoule failure, the sensor is exposed to the vapor or liquid semiconductor and the chemical reaction causes a resistance change in the sensor material. The sensor shows a step change in resistance on the order of megohms when exposed to mercury zinc telluride (HgZnTe), mercury cadmium telluride (HgCdTe), or gallium arsenide (GaAs). This ampoule failure sensor is being tested for possible use on the second United States Microgravity Mission (USML-2) and is the subject of a NASA patent application [1]. RP WATRING, DA (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812, USA. NR 4 TC 0 Z9 0 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 JUN PY 1994 VL 140 IS 1-2 BP 41 EP 44 DI 10.1016/0022-0248(94)90493-6 PG 4 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA NM991 UT WOS:A1994NM99100006 ER PT J AU GAWRONSKI, W AF GAWRONSKI, W TI PREDICTIVE CONTROLLER AND ESTIMATOR FOR NASA DEEP SPACE NETWORK ANTENNAS SO JOURNAL OF DYNAMIC SYSTEMS MEASUREMENT AND CONTROL-TRANSACTIONS OF THE ASME LA English DT Article AB This paper presents a modified output prediction procedure, and a new controller design based on the predictive control law. Also, a predictive estimator is developed for implementing the controller. The predictive controller was designed and simulated for tracking control of the NASA Deep Space Network 70-m antenna. Simulation results show significant improvement in tracking performance compared to the linear quadratic controller and estimator presently in use. RP GAWRONSKI, W (reprint author), JET PROP LAB,PASADENA,CA 91109, USA. NR 22 TC 7 Z9 7 U1 0 U2 2 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 JUN PY 1994 VL 116 IS 2 BP 241 EP 248 DI 10.1115/1.2899216 PG 8 WC Automation & Control Systems; Instruments & Instrumentation SC Automation & Control Systems; Instruments & Instrumentation GA NT348 UT WOS:A1994NT34800009 ER PT J AU PULKKINEN, TI BAKER, DN TOIVANEN, PK PELLINEN, RJ FRIEDEL, RHW KORTH, A AF PULKKINEN, TI BAKER, DN TOIVANEN, PK PELLINEN, RJ FRIEDEL, RHW KORTH, A TI MAGNETOSPHERIC FIELD AND CURRENT DISTRIBUTIONS DURING THE SUBSTORM RECOVERY PHASE SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID GROWTH-PHASE; MAGNETIC-FIELD; CURRENT SHEET; MODEL; SATELLITE; TAIL AB We have studied 11 substorm recovery phase events in which magnetic field and energetic particle data were available near the midnight sector from the GEOS 2 satellite. Comparison with the Tsyganenko magnetic field model shows that, after the expansion phase, B(Z) is large and decreases gradually toward the model value during the recovery phase, whereas deviations of B(X) and B(Y) relative to the model values are small after the effects of the substorm current wedge have disappeared. We have modeled this sequence by using temporally evolving current systems implemented as additions to the Tsyganenko model. The tail current sheet thickness and the cross-tail current intensity at different radial distances were varied using six free parameters in the model. The parameters were evaluated using a least squares fit for each of the 11 events separately. The results suggest that at the beginning of the recovery phase the current sheet was relatively thick close to the inner edge of the plasma sheet. Model fittings produced two different field configurations. In seven events the cross-tail current was weak, and the field configuration was highly dipolar. In four events the near-Earth current was weak, but stronger currents remained in the midtail region. In these latter events the field configuration at the beginning of the recovery phase included a region where B(Z) was negative. This negative B(Z) and the associated near-Earth neutral line disappeared later as the current system developed toward the quiet time configuration. The magnetic field configuration, current distributions, and particle drift paths during the substorm recovery phase are examined and compared with those prevailing during the substorm growth phase. C1 MAX PLANCK INST AERON,W-3411 KATLENBURG DUHM,GERMANY. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP PULKKINEN, TI (reprint author), FINNISH METEOROL INST,DEPT GEOPHYS,BOX 503,SF-00101 HELSINKI,FINLAND. RI Friedel, Reiner/D-1410-2012; Pulkkinen, Tuija/D-8403-2012 OI Friedel, Reiner/0000-0002-5228-0281; Pulkkinen, Tuija/0000-0002-6317-381X NR 21 TC 30 Z9 30 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD JUN 1 PY 1994 VL 99 IS A6 BP 10955 EP 10966 DI 10.1029/93JA02718 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NP993 UT WOS:A1994NP99300002 ER PT J AU BAKER, DN PULKKINEN, TI HONES, EW BELIAN, RD MCPHERRON, RL ANGELOPOULOS, V AF BAKER, DN PULKKINEN, TI HONES, EW BELIAN, RD MCPHERRON, RL ANGELOPOULOS, V TI SIGNATURES OF THE SUBSTORM RECOVERY PHASE AT HIGH-ALTITUDE SPACECRAFT SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID PLASMA SHEET DYNAMICS; CURRENT DISRUPTION; ISEE 1; EXPANSION; ONSET; MAGNETOTAIL; EVENT; MULTISATELLITE; PROPAGATION; CDAW-9 AB The substorm recovery phase typically commences approixmately 30 min after the substorm expansion phase onset and covers a period of roughly 1 hour. Several signatures have previously been associated with the recovery phase such as plasma sheet expansion in the midtail and magnetic field return toward the quiet time configuration. However, the detailed temporal sequence during the recovery phase is still not very well established. A total of 66 events in February-April 1979 have been investigated where ISEE 2 observed a plasma sheet expansion associated with fast earthward flows. Of these, 50 events were clearly associated with the substorm recovery phase as identified in ground magnetic records. For this data set, energetic electron (>30 keV), and proton (> 145 keV) observations from two geostationary spacecraft were available in 41 cases. Of the 41 cases, 32 of the midtail plasma sheet recoveries were associated with distinctive ion or electron flux increases at geostationary orbit. These flux increases, often in both protons and electrons, were generally observed from the predusk to the postdawn sector. However, very few enhancements were found near local noon. The lack of large energy dispersion in the flux increases and the simultaneous occurrence of both electron and ion enhancements suggests that the particles do not drift from a more distant location (as in substorm expansion phase onsets) but are accelerated or redistributed locally. These events are suggested to be associated with a large-scale reconfiguration of the near-Earth tail as the neutral line retreats to large distances. C1 UNIV CALIF LOS ANGELES,INST GEOPHYS & PLANETARY PHYS,LOS ANGELES,CA 90024. LOS ALAMOS NATL LAB,LOS ALAMOS,NM 87545. FINNISH METEOROL INST,DEPT GEOPHYS,SF-00101 HELSINKI,FINLAND. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RI Pulkkinen, Tuija/D-8403-2012 OI Pulkkinen, Tuija/0000-0002-6317-381X NR 37 TC 18 Z9 18 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD JUN 1 PY 1994 VL 99 IS A6 BP 10967 EP 10979 DI 10.1029/93JA02719 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NP993 UT WOS:A1994NP99300003 ER PT J AU MOSES, JJ SLAVIN, JA AGGSON, TL HEELIS, RA WINNINGHAM, JD AF MOSES, JJ SLAVIN, JA AGGSON, TL HEELIS, RA WINNINGHAM, JD TI MODELING IONOSPHERIC CONVECTION DURING A MAJOR GEOMAGNETIC STORM ON OCTOBER 22-23, 1981 SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID INTERPLANETARY MAGNETIC-FIELD; HIGH-LATITUDE IONOSPHERE; MAGNETOSPHERIC SUBSTORMS; DAYSIDE MAGNETOSPHERE; IMF-BY; POLAR; DEFLATION; FLOW AB Following, the passage of an interplanetary shock at approximately 0500 UT, a major geomagnetic storm developed on October 22-23, 1981. Numerous auroral substorms occurred during this storm leading to an AE index greater than 1000 nT. We have used the expanding/contracting polar cap (ECPC) model (Moses et al., 1989) and data from the Dynamics Explorer 2 spacecraft to study the ionospheric electric fields for 12 consecutive traversals of the polar regions. The ECPC model can determine the voltage drops across the dayside merging and nightside reconnection gaps. We determined the relationship of the AL index (i.e., the intensity of the westward electrojet) to the nightside reconnection potential drop. An excellent linear correlation was found between the nightside reconnection gap voltage drop and the AL index. These results show that the solar wind strongly drives the magnetosphere-ionosphere system throughout the geomagnetic storm. A substantial level of dayside merging seems to occur throughout the event. Nightside reconnection varies from satellite pass to satellite pass and within the substorm recovery phase. We find that tail reconnection is an important feature of the recovery phase of substorms. C1 UNIV TEXAS,CTR SPACE SCI,RICHARDSON,TX 75083. SW RES INST,SAN ANTONIO,TX 78284. RP MOSES, JJ (reprint author), NASA,GODDARD SPACE FLIGHT CTR,EXTRATERR PHYS LAB,GREENBELT,MD 20771, USA. RI Slavin, James/H-3170-2012 OI Slavin, James/0000-0002-9206-724X NR 24 TC 5 Z9 5 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD JUN 1 PY 1994 VL 99 IS A6 BP 11017 EP 11025 DI 10.1029/94JA00401 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NP993 UT WOS:A1994NP99300007 ER PT J AU KAYMAZ, Z SISCOE, GL LUHMANN, JG LEPPING, RP RUSSELL, CT AF KAYMAZ, Z SISCOE, GL LUHMANN, JG LEPPING, RP RUSSELL, CT TI INTERPLANETARY MAGNETIC-FIELD CONTROL OF MAGNETOTAIL MAGNETIC-FIELD GEOMETRY - IMP-8 OBSERVATIONS SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID QUANTITATIVE MODELS; TAIL; IMF; CONFIGURATION; MAGNETOSPHERE; CONVECTION; LOBE; RE AB Four years of IMP 8 magnetic field measurements, 1978-1982, when ISEE 3 took upstream interplanetary magnetic field (IMF) measurements, have been analyzed to produce full cross-section magnetic maps of the magnetotail at about 33R(E) downwind from Earth. This paper describes how the field geometry in the cross-sectional plane responds to different IMF orientations: dominant B(y), dominant +B(z), and dominant -B(z). The dominant B(y) case exhibits marked departures from bilateral symmetry that have the sense of superimposing a fraction of the IMF on the symmetrical tail field. However, the ''superimposed'' perturbation field, measured as a fraction of the IMF, is highly nonuniform: It is maximum in the flanks of the plasma sheet and minimum in the lobes. There is also a rotation of the current sheet which varies with IMF strength and with distance. The two dominant B(z) cases show no systematic departures from bilateral symmetry. However, the shapes and the relative sizes of the dipolar and flaring field regions of their cross sections are markedly different. The difference field, obtained by subtracting the positive B(z) case from the negative B(z) case, shows that the strongest perturbations run the north-south extent of the flanks, instead of residing in the lobes, as might be expected from the dayside reconnection model. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20770. UNIV CALIF LOS ANGELES,INST GEOPHYS & PLANETARY PHYS,LOS ANGELES,CA 90024. UNIV CALIF LOS ANGELES,DEPT EARTH & SPACE SCI,LOS ANGELES,CA 90024. UNIV CALIF LOS ANGELES,DEPT ATMOSPHER SCI,LOS ANGELES,CA 90024. NR 27 TC 55 Z9 59 U1 1 U2 5 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD JUN 1 PY 1994 VL 99 IS A6 BP 11113 EP 11126 DI 10.1029/94JA00300 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NP993 UT WOS:A1994NP99300015 ER PT J AU HESSE, M WINSKE, D AF HESSE, M WINSKE, D TI HYBRID SIMULATIONS OF COLLISIONLESS RECONNECTION IN CURRENT SHEETS SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID GENERAL MAGNETIC RECONNECTION; TEARING MODE; SIMULATIONS; INSTABILITY; PLASMAS; LINE AB Thin current sheets, with thicknesses of the order of a few ion gyroradii, are believed to exist quite commonly at the Earth's magnetopause as well as in the magnetotail current sheet just prior to substorm onset. Analytical theory predicts that sheets of this kind can become the locus of an ion-tearing instability. We use a modified hybrid simulation code that treats the ions fully kinetically and the electrons as a fluid with a model for the full pressure tensor to study the ion tearing mode development in one-dimensional current sheets of various thicknesses, with varying initial electron to ion temperature ratios. Further, we investigate the electron anisotropy dependence of the ion tearing mode growth rate and compare the growth rates found in the numerical simulations to linear growth rates for the pure ion-tearing instability derived from analytic theory. Estimates of the numerical accuracy of the simulations and of possible electron distribution functions resulting in the modeled anisotropies are also presented. C1 LOS ALAMOS NATL LAB,DIV APPL THEORET PHYS,LOS ALAMOS,NM 87545. RP HESSE, M (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ELECTRODYNAM BRANCH,GREENBELT,MD 20771, USA. RI Hesse, Michael/D-2031-2012 NR 44 TC 75 Z9 76 U1 1 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD JUN 1 PY 1994 VL 99 IS A6 BP 11177 EP 11192 DI 10.1029/94JA00676 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NP993 UT WOS:A1994NP99300019 ER PT J AU CORONITI, FV MOSES, SL GREENSTADT, EW TSURUTANI, BT SMITH, EJ AF CORONITI, FV MOSES, SL GREENSTADT, EW TSURUTANI, BT SMITH, EJ TI MAGNETIC AND ELECTRIC-FIELD WAVES IN SLOW SHOCKS OF THE DISTANT GEOMAGNETIC TAIL - ISEE-3 OBSERVATIONS SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID SHEET BOUNDARY-LAYER; ION-CYCLOTRON INSTABILITY; BAND ELECTROSTATIC NOISE; PLASMA-WAVES; MODE SHOCKS; MAGNETOTAIL; TURBULENCE; GENERATION; MAGNETOSHEATH AB During the first pass through the distant geomagnetic tail by ISEE 3 the slow shocks encountered on February 2 and 11, 1983, provide particularly clear examples of the magnetic field and plasma wave properties of the shock transition. The Magnetic ramp contains transverse polarized magnetic field oscillations with frequencies just below the ion cyclotron frequency and amplitudes of 2-4 nT. These waves are plausibly generated by the electromagnetic ion/ion cyclotron instability predicted by Winske and Omidi (1990). The electric field plasma waves within the shock ramp exhibit two spectral peaks. A midfrequency emission occurs near the ion plasma frequency and electron cyclotron frequency but well below the maximum Doppler shift frequency for electrostatic waves. The midfrequency waves extend into the upstream region where the spectral peak occurs at a slightly higher frequency. A new high-frequency emission with frequencies between the maximum Doppler shift frequency and the electron plasma frequency occurs throughout the downstream region. This emission disappears at the start of the magnetic ramp and is replaced upstream by electron plasma oscillations. The high-frequency emissions are clearly polarized parallel to the magnetic field. The polarization of the midfrequency waves is less certain; both parallel and a fairly broad angular distribution about the parallel electric fields are consistent with the measurements. C1 JET PROP LAB,PASADENA,CA 91109. RP CORONITI, FV (reprint author), TRW CO INC,SPACE & ELECTR GRP,REDONDO BEACH,CA 90278, USA. NR 26 TC 11 Z9 11 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD JUN 1 PY 1994 VL 99 IS A6 BP 11251 EP 11263 DI 10.1029/94JA00734 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NP993 UT WOS:A1994NP99300024 ER PT J AU STERN, DP AF STERN, DP TI THE RELATIONSHIP BETWEEN MAGNETOSPHERIC CONVECTION AND IONOSPHERIC HEATING - COMMENT SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Note ID EARTHS MAGNETOTAIL; PLASMA SHEET RP STERN, DP (reprint author), NASA,GODDARD SPACE FLIGHT CTR,EXTRATERRESTRIAL PHYS LAB,CODE 695,GREENBELT,MD 20771, USA. NR 13 TC 1 Z9 1 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD JUN 1 PY 1994 VL 99 IS A6 BP 11341 EP 11342 DI 10.1029/94JA00540 PG 2 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NP993 UT WOS:A1994NP99300032 ER PT J AU KAR, J HARTLE, RE GREBOWSKY, JM KASPRZAK, WT DONAHUE, TM CLOUTIER, PA AF KAR, J HARTLE, RE GREBOWSKY, JM KASPRZAK, WT DONAHUE, TM CLOUTIER, PA TI EVIDENCE OF ELECTRON-IMPACT IONIZATION ON THE NIGHTSIDE OF VENUS FROM PIONEER VENUS ORBITER ION MASS-SPECTROMETER MEASUREMENTS NEAR SOLAR MINIMUM SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID CYCLE CHANGES; IONOSPHERE; PRECIPITATION; MODEL; FLOWS AB Nightside ion composition measurements from the Pioneer Venus Orbiter ion mass spectrometer are compared for solar maximum conditions encountered during the early part of the mission and near solar minimum conditions that prevailed just prior to the end of the mission. A drastic decrease in the O+ ion abundance takes place as the solar activity level approaches solar minimum conditions. This indicates a greatly reduced flux of O+ ion transport across the terminator. At the same time, distinct O2+ layers were observed with peak densities only slightly reduced from solar maximum conditions. The relationship between the solar minimum O+ and O2+ profiles provides die first clear in situ evidence for a nightside ionosphere maintained primarily by electron impact, presumably penetrating solar wind electrons. Observation of excess production of mass 28 ions (over chemical production) provides further evidence of the presence of electron impact ionization. A modest change in He+ densities in the region of the predawn bulge does not have a counterpart in neutral helium. Absent a corresponding change in ionizing electron fluxes, this result indicates that during solar maximum the ionization of nightside helium is primarily due to transport of He+ while electron impact can account for He+ densities as solar minimum is approached. Further, the behavior of hydrogen ions over a solar cycle suggests that impact ionization was significant in producing H+ in 1992, but less than that for He+ ions in that year. C1 UNIV MICHIGAN,DEPT ATMOSPHER OCEAN & SPACE SCI,SPACE PHYS RES LAB,ANN ARBOR,MI 48109. RICE UNIV,DEPT SPACE PHYS & ASTRON,HOUSTON,TX 77251. RP KAR, J (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ATMOSPHERES LAB,GREENBELT,MD 20771, USA. RI Grebowsky, Joseph/I-7185-2013 NR 24 TC 6 Z9 6 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD JUN 1 PY 1994 VL 99 IS A6 BP 11351 EP 11355 DI 10.1029/93JA02850 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NP993 UT WOS:A1994NP99300036 ER PT J AU GARY, JB HEELIS, RA HANSON, WB SLAVIN, JA AF GARY, JB HEELIS, RA HANSON, WB SLAVIN, JA TI FIELD-ALIGNED POYNTING FLUX OBSERVATIONS IN THE HIGH-LATITUDE IONOSPHERE SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID ION-CYCLOTRON WAVES; ELECTRIC-FIELDS; MAGNETIC-FIELD; SATELLITE; CURRENTS; VECTOR AB We have used data from Dynamics Explorer 2 to investigate the rate of conversion of electromagnetic energy into both thermal and bulk flow particle kinetic energy in the high-latitude ionosphere. The flux tube integrated conversion rate E.J can be determined from spacecraft measurements of the electric and magnetic field vectors by deriving the field-aligned Poynting flux, S(parallel-to) = S.B(o), where B(o) is in the direction of the geomagnetic field. Determination of the Poynting flux from satellite observations is critically dependent upon the establishment of accurate values of the fields and is especially sensitive to errors in the baseline (unperturbed) geomagnetic field. We discuss our treatment of the data in some detail, particularly in regard to systematically correcting the measured magnetic field to account for attitude changes and model deficiencies. S(parallel-to) can be used to identify the relative strengths of the magnetosphere and thermospheric winds as energy drivers and we present observations demonstrating the dominance of each of these. Dominance of the magnetospheric driver is indicated by S(parallel-to) directed into the ionosphere. Electromagnetic energy is delivered to and dissipated within the region. Dominance of the neutral wind requires that the conductivity weighted neutral wind speed in the direction of the ion drift be larger than the ion drift, resulting in observations of an upward directed Poynting flux. Electromagnetic energy is generated within the ionospheric region in this case. We also present observations of a case where the neutral atmosphere motion may be reaching a state of sustained bulk flow velocity as evidenced by very small Poynting flux in the presence of large electric fields. C1 NASA,GODDARD SPACE FLIGHT CTR,EXTRATERRESTRIAL PHYS LAB,GREENBELT,MD 20771. RP GARY, JB (reprint author), UNIV TEXAS,CTR SPACE SCI,PHYS PROGRAMS,MS FO22,POB 830688,RICHARDSON,TX 75083, USA. RI Slavin, James/H-3170-2012 OI Slavin, James/0000-0002-9206-724X NR 23 TC 33 Z9 33 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD JUN 1 PY 1994 VL 99 IS A6 BP 11417 EP 11427 DI 10.1029/93JA03167 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NP993 UT WOS:A1994NP99300043 ER PT J AU LAAKSO, H AGGSON, TL PFAFF, RF HANSON, WB AF LAAKSO, H AGGSON, TL PFAFF, RF HANSON, WB TI DOWNDRAFTING PLASMA-FLOW IN EQUATORIAL BUBBLES SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID F-REGION; SPREAD-F; IRREGULARITIES; IONOSPHERE AB The electric field experiment carried aboard the San Marco D equatorial ionospheric satellite regularly measured updrafting in plasma depletion channels or ''equatorial bubbles'' which form on the bottomside of the nightside equatorial F region. We report here observations of downdrafting vertical plasma velocities inside such depletion regions in the nightside equatorial ionosphere. Both updrafting and downdrafting motions can be expected on the basis of a generalized gradient drift/collisional Rayleigh-Taylor instability process in the ionospheric F region. Although the gravitation can only drive upward plasma flow in plasma depletion regions, both background westward zonal electric fields and upward vertical neutral winds can cause an occurrence of downdrafting (i.e., a downward motion of the plasma within the bubble) if those parameters are strong enough. We show that as the background zonal electric field becomes westward (often after approximately 2100 LT) in the equatorial ionosphere, the plasma interior to an existing bubble at altitudes of approximately 400 km and less at the magnetic equator may assume a downdrafting motion, while at higher altitudes in the same bubble channel, the plasma flow remains upward. Such a simultaneous occurrence of the updrafting and downdrafting plasma flow in a single bubble channel may lead to the pinching off of the upper part of the depletion region from the lower altitude regions, causing the decay of a bubble or the formation of a ''dead'' bubble. C1 UNIV TEXAS,CTR SPACE SCI,RICHARDSON,TX 75083. FINNISH METEOROL INST,DEPT GEOPHYS,SF-00101 HELSINKI,FINLAND. RP LAAKSO, H (reprint author), NASA,GODDARD SPACE FLIGHT CTR,EXTRATERRESTRIAL PHYS LAB,CODE 696,GREENBELT,MD 20771, USA. RI Pfaff, Robert/F-5703-2012 OI Pfaff, Robert/0000-0002-4881-9715 NR 18 TC 21 Z9 21 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD JUN 1 PY 1994 VL 99 IS A6 BP 11507 EP 11515 DI 10.1029/93JA03169 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NP993 UT WOS:A1994NP99300051 ER PT J AU GOLDSTEIN, ML ROBERTS, DA FITCH, CA AF GOLDSTEIN, ML ROBERTS, DA FITCH, CA TI PROPERTIES OF THE FLUCTUATING MAGNETIC HELICITY IN THE INERTIAL AND DISSIPATION RANGES OF SOLAR-WIND TURBULENCE SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID AMPLITUDE ALFVEN WAVES; MHD TURBULENCE; MAGNETOHYDRODYNAMIC FLUCTUATIONS; HELIOCENTRIC DISTANCE; INNER HELIOSPHERE; RADIAL EVOLUTION; STREAM STRUCTURE; FIELD; DEPENDENCE; ORIGIN AB We investigated the inertial and dissipation ranges of the reduced magnetic helicity spectrum of solar wind fluctuations and have found that this spectrum appears insensitive to solar cycle variations and changes in solar wind flow parameters. In the inertial range of the spectrum, the reduced helicity is large but random and independent of heliocentric distance between 0.3 and 10 AU. At small scales, in the dissipation range of the spectrum, a correlation appears to exist between the average value of the normalized reduced magnetic helicity and the polarity of magnetic sectors, suggesting that these fluctuations, if outward propagating, are predominantly right-hand polarized. In the inertial range the statistical properties of the normalized magnetic helicity are well approximated by a simple model of the magnetic field in which the total magnetic field vector randomly walks with only small variations in magnitude. The behavior of the inertial range spectrum is very similar to that seen in three- and two-and-a-half-dimensional simulations of the incompressible and compressible equations describing magnetohydrodynamic turbulence, consistent with the paradigm that the solar wind is a turbulent magnetofluid. RP GOLDSTEIN, ML (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 692,GREENBELT,MD 20771, USA. RI Roberts, Dana/D-4625-2012; Goldstein, Melvyn/B-1724-2008 NR 56 TC 153 Z9 154 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 JI J. Geophys. Res-Space Phys. PD JUN 1 PY 1994 VL 99 IS A6 BP 11519 EP 11538 DI 10.1029/94JA00789 PG 20 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NP993 UT WOS:A1994NP99300053 ER PT J AU NAIDU, K BARNES, A AF NAIDU, K BARNES, A TI MOTION OF THE HELIOSPHERIC TERMINATION SHOCK .3. INCIDENT INTERPLANETARY SHOCKS SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID INTERSTELLAR-MEDIUM; SOLAR-WIND AB In this paper the response of the heliospheric termination shock to an incident interplanetary shock is examined. This paper is an extension of a recent study by Barnes (1993), which treated the analogous problem for an incident contact discontinuity. The termination shock is treated as a strong gasdynamic shock. The postinteraction configuration consists of a moving termination shock, a postshock contact discontinuity, and either a shock or rarefaction wave propagating the disturbance signal into the downstream medium. For a decrease in dynamic pressure a rarefaction wave propagates downstream, and the new termination shock propagates inward, while for an enhancement of dynamic pressure the termination shock moves outwards and a weak outer shock propagates into the downstream medium; speeds of motion of the termination shock are typically of the order of approximately 100 km/s. The results are similar to those presented by Barnes (1993) indicating that the results of that paper are robust within the gasdynamic model, in the sense of being independent of the details of the initial disturbance. RP NAIDU, K (reprint author), NASA,AMES RES CTR,THEORET STUDIES BRANCH,MOFFETT FIELD,CA 94035, USA. NR 17 TC 21 Z9 21 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD JUN 1 PY 1994 VL 99 IS A6 BP 11553 EP 11560 DI 10.1029/94JA00581 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NP993 UT WOS:A1994NP99300056 ER PT J AU DRAPER, SL LOCCI, IE AF DRAPER, SL LOCCI, IE TI AL2O3 FIBER STRENGTH DEGRADATION IN METAL AND INTERMETALLIC MATRIX COMPOSITES SO JOURNAL OF MATERIALS RESEARCH LA English DT Article AB The mechanisms for fiber damage in single crystal Al2O3 fiber-reinforced composites were investigated. Both fiber fragmentation and fiber strength degradation were observed in composites with a variety of matrix compositions. Four mechanisms that may be contributing to the fiber strength loss have been proposed and include matrix reaction, reaction with binders, residual stress-induced damage, and pressure from hot pressing. The effect of matrix reaction was separated from the other three effects by sputter-coating the matrices on cleaned fibers and annealing with a temperature profile that simulates processing conditions. These experiments revealed that Y and Cr in FeCrAlY base alloys and Zr in NiAl alloys reacted with the fiber, and grooves and adherent particles were formed on the fiber surface which were responsible for the strength loss. The effects of the matrix reaction appeared to dominate over the other possible mechanisms, although evidence for reaction with binders was also found. Ridges on the fiber surface, which reflected the grain boundaries of the matrix, were also observed. In order for single-crystal Al2O3 to be used as a fiber in MMC's and IMC's, a matrix or protective coating which minimizes matrix reaction during processing will be necessary. Of the matrices investigated, the Thermo-span(TM) alloy was the least damaging to fiber properties. C1 DEPT MAT SCI & ENGN,CLEVELAND,OH 44106. RP DRAPER, SL (reprint author), NASA,LEWIS RES CTR,DIV MAT,21000 BROOKPARK RD,CLEVELAND,OH 44135, USA. NR 26 TC 26 Z9 26 U1 0 U2 0 PU MATERIALS RESEARCH SOCIETY PI PITTSBURGH PA 9800 MC KNIGHT ROAD SUITE 327, PITTSBURGH, PA 15237 SN 0884-2914 J9 J MATER RES JI J. Mater. Res. PD JUN PY 1994 VL 9 IS 6 BP 1397 EP 1411 DI 10.1557/JMR.1994.1397 PG 15 WC Materials Science, Multidisciplinary SC Materials Science GA NN764 UT WOS:A1994NN76400011 ER PT J AU HARDING, DR SUTTER, JK SCHUERMAN, MA CRANE, EA AF HARDING, DR SUTTER, JK SCHUERMAN, MA CRANE, EA TI OXIDATION PROTECTIVE BARRIER COATINGS FOR HIGH-TEMPERATURE POLYMER MATRIX COMPOSITES SO JOURNAL OF MATERIALS RESEARCH LA English DT Article ID CHEMICAL VAPOR-DEPOSITION; SILICON-NITRIDE FILMS; AL2O3 THIN-FILMS; HYDROGEN CONTENT; DIAMOND FILMS; CVD DIAMOND; SIN-H; STRESS AB Three coating techniques (metal-organic chemical vapor deposition, magnetron sputtering, and plasma-enhanced chemical vapor deposition) were employed to deposit different coating materials (alumina, a superalloy, and silicon nitride) on graphite-fiber-reinforced polyimide composites to protect against oxidation at elevated temperatures. Adhesion and integrity of the coatings were evaluated by isothermal aging (371-degrees-C for 500 h) and thermal cycling (25 to 232-degrees-C for 1000 cycles and -18 to 232-degrees-C for 300 cycles). Best results were achieved with a plasma-deposited, amorphous silicon nitride (a-SiN: H) coating, which withstood stresses from 0.18 to -1.6 GPa. The major factors affecting the suitability of a-SiN: H as an oxidation protective coating are the surface finish of the polymer composite and the presence of a sizable hydrogen content in the coating. C1 XAVIER UNIV,CINCINNATI,OH 45207. JOHN CARROLL UNIV,CLEVELAND,OH 44118. RP HARDING, DR (reprint author), NASA LEWIS RES CTR,NYMA,3001 AEROSP TECHNOL BLVD,CLEVELAND,OH 44142, USA. NR 35 TC 12 Z9 12 U1 2 U2 7 PU MATERIALS RESEARCH SOCIETY PI PITTSBURGH PA 9800 MC KNIGHT ROAD SUITE 327, PITTSBURGH, PA 15237 SN 0884-2914 J9 J MATER RES JI J. Mater. Res. PD JUN PY 1994 VL 9 IS 6 BP 1583 EP 1595 DI 10.1557/JMR.1994.1583 PG 13 WC Materials Science, Multidisciplinary SC Materials Science GA NN764 UT WOS:A1994NN76400032 ER PT J AU FRIEDL, RR MAY, RD DUXBURY, G AF FRIEDL, RR MAY, RD DUXBURY, G TI THE NU(6), NU(7), NU(8), AND NU(10) BANDS OF HO2NO2 SO JOURNAL OF MOLECULAR SPECTROSCOPY LA English DT Article ID ACID HOONO2; SPECTRA; INTENSITIES; COMPUTER AB Two new fundamental vibration-rotation bands have been observed for HO2NO2 and assigned. They are nu7 at 648 cm-1 and nu8 at 466 cm-1. On the basis of these assignments the previously observed bands at 722, 801.5, and 919 cm-1 are assigned to nu10, nu7 + nu12, and 2 nu8, respectively. A partial rotational analysis of the atmospherically relevant nu6 band has been carried out, and the effects of tunneling, Coriolis interactions, and hot bands on the rotational structure have been characterized. The band origin derived from this analysis is 802.54(3) CM-1. (C) 1994 Academic Press, Inc. C1 UNIV STRATHCLYDE,DEPT PHYS & APPL PHYS,GLASGOW G4 ONG,SCOTLAND. RP FRIEDL, RR (reprint author), JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 22 TC 9 Z9 9 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 JUN PY 1994 VL 165 IS 2 BP 481 EP 493 DI 10.1006/jmsp.1994.1151 PG 13 WC Physics, Atomic, Molecular & Chemical; Spectroscopy SC Physics; Spectroscopy GA NN999 UT WOS:A1994NN99900018 ER PT J AU SPENCER, MN CHACKERIAN, C GIVER, LP BROWN, LR AF SPENCER, MN CHACKERIAN, C GIVER, LP BROWN, LR TI THE NITRIC-OXIDE FUNDAMENTAL-BAND - FREQUENCY AND SHAPE-PARAMETERS FOR ROVIBRATIONAL LINES SO JOURNAL OF MOLECULAR SPECTROSCOPY LA English DT Article ID OVERTONE BANDS; GAS-MIXTURES; CO LASER; NO AB Solar McMath FTS spectra, recorded with a full instrumental width of about 0.0064 cm-1, were obtained of the fundamental vibration-rotation band (v = 1 <-- 0) of (NO)-N-14-O-16. These spectra have been used to determine N2-induced-broadening and N2-induced-shift coefficients as well as line intensities and positions. Measurements were made from 1780 to 1952 cm-1, up to Absolute value of m almost-equal-to 22.5, for the P and R branches of the 2PI1/2 and 2PI3/2 subbands and a few transitions of the Q branch. The rotationless transition moments of the two sub-bands were found to be within 1/2% of each other. The first-order Herman-Wallis intensity factor, C, measured for the first time, is in excellent agreement with theoretical predictions. The band intensity is 114.9 +/- 3.4 cm-2 atm-1 at 296 K. The v = 1 <-- 0 N2-broadened widths and N2-induced pressure shifts are, respectively, 3% different and a factor of 2 smaller than those measured by Pine et al. [J. Mol. Spectrosc. 114, 132-147 ( 1985 ) ] for the v = 2 <-- 0 band. The broadening coefficients are, where comparisons can be made, a few to about twenty percent smaller and the intensities about four percent larger than results reported by Ballard et al. [J. Mol. Spectrosc. 127, 70-82 (1988)]. Line positions are retrieved and calibrated to an accuracy of +/-5 X 10(-5) cm-1 using the 1-0 band of CO. Comparisons of calculated positions based on the constants of Hinz et al. [J. Mol. Spectrosc. 119, 120-125 ( 1986)] reveal very good agreement for the 2PI3/2 subband and a systematic divergence for the 2PI/2 positions. The effects of hyperfine splittings are also detected for low m transitions. (C) 1994 Academic Press, Inc. C1 JET PROP LAB,PASADENA,CA 91109. RP SPENCER, MN (reprint author), NASA,AMES RES CTR,ATMOSPHER PHYS RES BRANCH,MOFFETT FIELD,CA 94035, USA. NR 38 TC 47 Z9 47 U1 2 U2 14 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 JUN PY 1994 VL 165 IS 2 BP 506 EP 524 DI 10.1006/jmsp.1994.1154 PG 19 WC Physics, Atomic, Molecular & Chemical; Spectroscopy SC Physics; Spectroscopy GA NN999 UT WOS:A1994NN99900021 ER PT J AU CHACKERIAN, C GOORVITCH, D HURE, JM ROUEFF, E AF CHACKERIAN, C GOORVITCH, D HURE, JM ROUEFF, E TI COMMENTS ON THE ROVIBRATIONAL INTENSITIES OF HIGH VJ STATES OF THE CO MOLECULE IN ITS X(1)SIGMA+ GROUND-STATE SO JOURNAL OF MOLECULAR SPECTROSCOPY LA English DT Note ID DIPOLE C1 OBSERV MEUDON,DAEC,F-92195 MEUDON,FRANCE. OBSERV MEUDON,CNRS,URA 173,F-92195 MEUDON,FRANCE. RP CHACKERIAN, C (reprint author), NASA,AMES RES CTR,MOFFETT FIELD,CA 94035, USA. NR 4 TC 7 Z9 7 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 0022-2852 J9 J MOL SPECTROSC JI J. Mol. Spectrosc. PD JUN PY 1994 VL 165 IS 2 BP 583 EP 585 DI 10.1006/jmsp.1994.1159 PG 3 WC Physics, Atomic, Molecular & Chemical; Spectroscopy SC Physics; Spectroscopy GA NN999 UT WOS:A1994NN99900026 ER PT J AU ROTHSCHILD, LJ GIVER, LJ WHITE, MR MANCINELLI, RL AF ROTHSCHILD, LJ GIVER, LJ WHITE, MR MANCINELLI, RL TI METABOLIC-ACTIVITY OF MICROORGANISMS IN EVAPORITES SO JOURNAL OF PHYCOLOGY LA English DT Article DE APHANOTHECE HALOPHYTICA; CARBON FIXATION; CYANOBACTERIA; EVAPORITE; GYPSUM; MARS; NITROGEN FIXATION; PHOTOSYNTHESIS; SALT; SYNECHOCOCCUS ID RIBULOSE-1,5-BISPHOSPHATE CARBOXYLASE OXYGENASE; CYANOBACTERIUM APHANOTHECE-HALOPHYTICA; BLUE-GREEN-ALGA; HALOTOLERANT CYANOBACTERIUM; NITROGEN-FIXATION; MICROBIAL MAT; MARINE; DENITRIFICATION; BACTERIA; DESERTS AB Crystalline salt is generally considered so hostile to most forms of life that it has been used for centuries as a preservative. Here, we present evidence that prokaryotes inhabiting a natural evaporite crust of halite and gypsum are metabolically active while inside the evaporite for at least 10 months. In situ measurements demonstrated that some of these ''endoevaporitic'' microorganisms (probably the cyanobacterium Synechococcus Nageli) fixed carbon and nitrogen. Denitrification was not observed. Our results quantified the stow microbial activity that can occur in salt crystals. Implications of this study include the possibility that microorganisms found in ancient evaporite deposits may have been part of an evaporite community. RP ROTHSCHILD, LJ (reprint author), NASA,AMES RES CTR,MAIL STOP 239-12,MOFFETT FIELD,CA 94035, USA. RI Mancinelli, Rocco/L-8971-2016 NR 61 TC 72 Z9 74 U1 1 U2 12 PU PHYCOLOGICAL SOC AMER INC PI LAWRENCE PA 810 EAST 10TH ST, LAWRENCE, KS 66044 SN 0022-3646 J9 J PHYCOL JI J. Phycol. PD JUN PY 1994 VL 30 IS 3 BP 431 EP 438 DI 10.1111/j.0022-3646.1994.00431.x PG 8 WC Plant Sciences; Marine & Freshwater Biology SC Plant Sciences; Marine & Freshwater Biology GA NU798 UT WOS:A1994NU79800008 PM 11539827 ER PT J AU PETEET, DM DANIELS, R HEUSSER, LE VOGEL, JS SOUTHON, JR NELSON, DE AF PETEET, DM DANIELS, R HEUSSER, LE VOGEL, JS SOUTHON, JR NELSON, DE TI WISCONSINAN LATE-GLACIAL ENVIRONMENTAL-CHANGE IN SOUTHERN NEW-ENGLAND - A REGIONAL SYNTHESIS SO JOURNAL OF QUATERNARY SCIENCE LA English DT Article DE AMS RADIOCARBON DATES; POLLEN DATA; PLANT MACROFOSSILS; REGIONAL DEGLACIATION; TEMPERATURE RECONSTRUCTIONS AB A synthesis of vegetational and climatic history during the Wisconsinan Late-glacial (I 3-9 ka BP) is presented for the southern New England region. The interpretations are based on a number of pollen-stratigraphical investigations supported by plant macrofossil data. Chronology is based partly on AMS dates of plant macrofossils. Reference is made briefly to the controversial nature of the evidence for deglaciation in the region. A curve representing mean July temperature changes in the region during the period 13-9 ka BP is provided. RP PETEET, DM (reprint author), NASA,GODDARD INST SPACE STUDIES,2880 BROADWAY,NEW YORK,NY 10025, USA. NR 0 TC 14 Z9 14 U1 0 U2 1 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX, ENGLAND PO19 1UD SN 0267-8179 J9 J QUATERNARY SCI JI J. Quat. Sci. PD JUN PY 1994 VL 9 IS 2 BP 151 EP 154 DI 10.1002/jqs.3390090209 PG 4 WC Geosciences, Multidisciplinary; Paleontology SC Geology; Paleontology GA NX990 UT WOS:A1994NX99000008 ER PT J AU FATOOHI, RA AF FATOOHI, RA TI ADAPTING A NAVIER-STOKES SOLVER FOR 3 PARALLEL MACHINES SO JOURNAL OF SUPERCOMPUTING LA English DT Article DE CRAY SUPERCOMPUTER; MIMD MACHINE; NAVIER-STOKES EQUATIONS; PARALLEL ALGORITHMS; PERFORMANCE ANALYSIS; SIMD MACHINE AB This paper presents the results of parallelizing a three-dimensional Navier-Stokes solver on a 32K-processor Thinking Machines CM-2, a 128-node Intel iPSC/860, and an 8-processor CRAY Y-MP. The main objective of this work is to study the performance of the flow solver, INS3D-LU code, on two distributed-memory machines, a massively parallel SIMD machine (CM-2) and a moderately parallel MIMD machine (iPSC/860), and compare it with its performance on a shared-memory MIMD machine with a small number of processors (Y-MP). The code is based on a Lower-Upper Symmetric-Gauss-Seidel implicit scheme for the pseudocompressibility formulation of the three-dimensional incompressible Navier-Stokes equations. The code was rewritten in CM-FORTRAN with shift operations and run on the CM-2 using the slicewise model. The code was also rewritten with distributed data and Intel message-passing calls and run on the iPSC/860. The timing results for two grid sizes are presented and analyzed using both 32-bit and 64-bit arithmetic. Also, the impact of communication and load balancing on the performance of the code is outlined. The results show that reasonable performance can be achieved on these parallel machines. However, the CRAY Y-MP outperforms the CM-2 and iPSC/860 for this particular algorithm. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. NR 9 TC 4 Z9 4 U1 0 U2 1 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0920-8542 J9 J SUPERCOMPUT JI J. Supercomput. PD JUN PY 1994 VL 8 IS 2 BP 91 EP 115 DI 10.1007/BF01204657 PG 25 WC Computer Science, Hardware & Architecture; Computer Science, Theory & Methods; Engineering, Electrical & Electronic SC Computer Science; Engineering GA PA391 UT WOS:A1994PA39100001 ER PT J AU EAGLES, DM AF EAGLES, DM TI A CONJECTURED EXPLANATION FOR ROOM-TEMPERATURE SUPERCONDUCTIVITY IN NARROW CHANNELS IN OXIDIZED POLYPROPYLENE SO JOURNAL OF SUPERCONDUCTIVITY LA English DT Article DE ROOM-TEMPERATURE SUPERCONDUCTIVITY; HIGH-CURRENT SUPERCONDUCTIVITY; OXIDIZED POLYPROPYLENE AB Two groups of scientists have observed conductivity at least five orders of magnitude higher than that of copper at room temperature in narrow channels perpendicular to surfaces of films in oxidized polypropylene, For pulsed currents, this conductivity starts at a minimum value of applied current, and is destroyed at a current of about 30-60 times this value. Because of the existence of an upper critical current and of the observation that electronic thermal conductivity is negligible in the channels, it is thought that the channels are superconducting. A study is made of the hypothesis that these results are due to enhanced pairing, as first suggested by Parmenter, when the drift velocity of current carriers becomes close to the velocity of sound or, in work by Hone and by the present author, to an appropriate phase velocity of optical phonons. Such enhancements can be expected to be larger in quasi-one-dimensional systems. C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,CODE ES74,HUNTSVILLE,AL 35812. NR 10 TC 5 Z9 5 U1 0 U2 2 PU PLENUM PUBL CORP PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 SN 0896-1107 J9 J SUPERCOND JI J. Supercond. PD JUN PY 1994 VL 7 IS 3 BP 679 EP 682 DI 10.1007/BF00728485 PG 4 WC Physics, Applied; Physics, Condensed Matter SC Physics GA NM852 UT WOS:A1994NM85200038 ER PT J AU WORCESTER, PF CORNUELLE, BD HILDEBRAND, JA HODGKISS, WS DUDA, TF BOYD, J HOWE, BM MERCER, JA SPINDEL, RC AF WORCESTER, PF CORNUELLE, BD HILDEBRAND, JA HODGKISS, WS DUDA, TF BOYD, J HOWE, BM MERCER, JA SPINDEL, RC TI A COMPARISON OF MEASURED AND PREDICTED BROAD-BAND ACOUSTIC ARRIVAL PATTERNS IN TRAVEL TIME-DEPTH COORDINATES AT 1000-KM RANGE SO JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA LA English DT Article ID PACIFIC-OCEAN; RAY CHAOS; MESOSCALE; TOMOGRAPHY; SOUND; PROPAGATION; SPEED; EQUATIONS; SEAWATER; FRONTS AB Broadband acoustic signals were transmitted from a moored 250-Hz source to a 3-km-long vertical line array of hydrophones 1000 km distant in the eastern North Pacific Ocean during July 1989. The sound-speed field along the great circle path connecting the source and receiver was measured directly by nearly 300 expendable bathythermograph (XBT), conductivity-temperature-depth (CTD), and air-launched expendable bathythermograph (AXBT) casts while the transmissions were in progress. This experiment is unique in combining a vertical receiving array that extends over much of the water column, extensive concurrent environmental measurements, and broadband signals designed to measure acoustic travel times with 1-ms precision. The time-mean travel times of the early raylike arrivals, which are evident as wave fronts sweeping across the receiving array, and the time-mean of the times at which the acoustic reception ends (the final cutoffs) for hydrophones near the sound channel axis, are consistent with ray predictions based on the direct measurements of temperature and salinity, within measurement uncertainty. The comparisons show that subinertial oceanic variability with horizontal wavelengths shorter than 50 km, which is not resolved by the direct measurements, significantly (25 ms peak-to-peak) affects the time-mean ray travel times. The final cutoffs occur significantly later than predicted using ray theory for hydrophones more than 100-200 m off the sound channel axis. Nongeometric effects, such as diffraction at caustics, partially account for this observation. C1 UNIV CALIF SAN DIEGO, SCRIPPS INST OCEANOG, MARINE PHYS LAB, LA JOLLA, CA 92093 USA. WOODS HOLE OCEANOG INST, WOODS HOLE, MA 02543 USA. UNIV WASHINGTON, APPL PHYS LAB, SEATTLE, WA 98105 USA. USN, STENNIS SPACE CTR, RES LAB, BAY ST LOUIS, MS 39529 USA. RP UNIV CALIF SAN DIEGO, SCRIPPS INST OCEANOG, LA JOLLA, CA 92093 USA. RI Duda, Timothy/A-7282-2010; OI Duda, Timothy/0000-0002-5797-5955; Howe, Bruce/0000-0001-5711-5253; Cornuelle, Bruce/0000-0003-2110-3319 NR 42 TC 45 Z9 45 U1 0 U2 2 PU ACOUSTICAL SOC AMER AMER INST PHYSICS PI MELVILLE PA STE 1 NO 1, 2 HUNTINGTON QUADRANGLE, MELVILLE, NY 11747-4502 USA SN 0001-4966 EI 1520-8524 J9 J ACOUST SOC AM JI J. Acoust. Soc. Am. PD JUN PY 1994 VL 95 IS 6 BP 3118 EP 3128 DI 10.1121/1.409977 PG 11 WC Acoustics; Audiology & Speech-Language Pathology SC Acoustics; Audiology & Speech-Language Pathology GA NR920 UT WOS:A1994NR92000010 ER PT J AU ANGOTTI, CM LEVINE, MS AF ANGOTTI, CM LEVINE, MS TI REVIEW OF 5 YEARS OF A COMBINED DIETARY AND PHYSICAL-FITNESS INTERVENTION FOR CONTROL OF SERUM-CHOLESTEROL SO JOURNAL OF THE AMERICAN DIETETIC ASSOCIATION LA English DT Article ID LIPOPROTEIN LEVELS; WOMEN; EXERCISE; DISEASE; WALKING; LIPIDS; HEALTH; MEN AB A chart review covering the first 5 years of clinical experience with a combined dietary and exercise intervention program for the reduction of hypercholesterolemia at the National Aeronautics and Space Administration headquarters demonstrated the programs success in maintaining densitY lipoprotein cholesterol (HDL-C) levels while significantly lowering total serum cholesterol levels. This combined Program also resulted in improved ratios of total serum cholesterol to HDL-C and lowered levels of low-density lipoprotein cholesterol, thus further reducing the risk for cardiovascular disease. The National Aeronautics and Space Administration Cardiovascular Risk Reduction Program was developed after it was determined that although dietary intervention alone improved total cholesterol levels, it often resulted in a more than proportionate decrease in HDL-C and a worsening of the ratio of cholesterol to HDL-C. An approach was needed that would positively affect all factors of the lipid profile. The findings from the program indicate that reduction of cardiovascular risk can be accomplished easily and effectively at the worksite through dietary intervention, personal monitoring, and a reasonable exercise program. RP ANGOTTI, CM (reprint author), NASA,HEADQUARTERS,MAIL CODE UOO,300 E ST SW,WASHINGTON,DC 20546, USA. NR 21 TC 8 Z9 8 U1 0 U2 0 PU AMER DIETETIC ASSN PI CHICAGO PA 216 W JACKSON BLVD #800, CHICAGO, IL 60606-6995 SN 0002-8223 J9 J AM DIET ASSOC JI J. Am. Diet. Assoc. PD JUN PY 1994 VL 94 IS 6 BP 634 EP 638 DI 10.1016/0002-8223(94)90160-0 PG 5 WC Nutrition & Dietetics SC Nutrition & Dietetics GA NQ249 UT WOS:A1994NQ24900011 PM 8195552 ER PT J AU KEPPENNE, CL DETTINGER, MD GHIL, M AF KEPPENNE, CL DETTINGER, MD GHIL, M TI AN APPROACH TO STATISTICAL SPATIAL-TEMPORAL MODELING OF METEOROLOGICAL FIELDS - COMMENT SO JOURNAL OF THE AMERICAN STATISTICAL ASSOCIATION LA English DT Article ID SINGULAR-SPECTRUM ANALYSIS; INTRASEASONAL OSCILLATIONS; GLOBAL ATMOSPHERE; TIME-SERIES; HEMISPHERE; DYNAMICS; CLIMATE C1 UNIV CALIF LOS ANGELES,INST GEOPHYS & PLANETARY PHYS,LOS ANGELES,CA 90024. US GEOL SURVEHY,SAN DIEGO,CA 92123. RP KEPPENNE, CL (reprint author), JET PROP LAB,PASADENA,CA 91109, USA. NR 25 TC 1 Z9 1 U1 1 U2 1 PU AMER STATISTICAL ASSOC PI ALEXANDRIA PA 1429 DUKE ST, ALEXANDRIA, VA 22314 SN 0162-1459 J9 J AM STAT ASSOC JI J. Am. Stat. Assoc. PD JUN PY 1994 VL 89 IS 426 BP 384 EP 387 PG 4 WC Statistics & Probability SC Mathematics GA NN155 UT WOS:A1994NN15500005 ER PT J AU MARCUS, SL GHIL, M DICKEY, JO AF MARCUS, SL GHIL, M DICKEY, JO TI THE EXTRATROPICAL 40-DAY OSCILLATION IN THE UCLA GENERAL-CIRCULATION MODEL .1. ATMOSPHERIC ANGULAR-MOMENTUM SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID INTRASEASONAL OSCILLATIONS; TROPICAL ATMOSPHERE; SEASONAL-VARIATIONS; 50-DAY OSCILLATION; GLOBAL ATMOSPHERE; LENGTH; PACIFIC; FLUCTUATIONS; CONVECTION; PARAMETERIZATION AB Variations in atmospheric angular momentum (AAM) are examined in a three-year simulation of the large-scale atmosphere with perpetual January forcing. The simulation is performed with a version of the UCLA general circulation model that contains no tropical Madden-Julian Oscillation (MJO). In addition, the results of three shorter experiments with no topography are analyzed. The three-year standard topography run contains no significant intraseasonal AAM periodicity in the tropics, consistent with the lack of the MJO, but produces a robust, 42-day AAM oscillation in the Northern Hemisphere (NH) extratropics. The model tropics undergoes a barotropic, zonally symmetric oscillation, driven by an exchange of mass with the NH extratropics. No intraseasonal periodicity is found in the average tropical latent heating field, indicating that the model oscillation is dynamically rather than thermodynamically driven. The no-mountain runs fail to produce an intraseasonal AAM oscillation, consistent with a topographic origin for the NH extratropical oscillation in the standard model. The spatial patterns of the oscillation in the 500-mb height field, and the relationship of the extratropical oscillation to intraseasonal variations in the tropics, will be discussed in Part II of this study. C1 UNIV CALIF LOS ANGELES,DEPT ATMOSPHER SCI,CTR CLIMATE DYNAM,LOS ANGELES,CA 90024. RP MARCUS, SL (reprint author), JET PROP LAB,SPACE GEODET SCI & APPLICAT GRP,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 61 TC 27 Z9 27 U1 0 U2 0 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0022-4928 J9 J ATMOS SCI JI J. Atmos. Sci. PD JUN 1 PY 1994 VL 51 IS 11 BP 1431 EP 1446 DI 10.1175/1520-0469(1994)051<1431:TEDOIT>2.0.CO;2 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA NQ997 UT WOS:A1994NQ99700007 ER PT J AU SMITH, EA WAI, MMK COOPER, HJ RUBES, MT AF SMITH, EA WAI, MMK COOPER, HJ RUBES, MT TI LINKING BOUNDARY-LAYER CIRCULATIONS AND SURFACE PROCESSES DURING FIFE-89 .1. OBSERVATIONAL ANALYSIS SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID MESOBETA-SCALE MODEL; SEVERE-STORM ENVIRONMENT; CENTRAL UNITED-STATES; SOIL-MOISTURE; MESOSCALE CIRCULATIONS; BIOSPHERE MODEL; PRAIRIE GRASSLAND; FIELD EXPERIMENT; ENERGY-BALANCE; FLUXES AB Surface, aircraft, and satellite observations are analyzed for the 21-day 1989 intensive field campaign of the First ISLSCP Field Experiment (FIFE) to determine the effect of precipitation, vegetation, and soil moisture distributions on the thermal properties of the surface including the heat and moisture fluxes, and the corresponding response in the boundary-layer circulation. Mean and variance properties of the surface variables are first documented at various time and space scales. These calculations are designed to set the stage for Part II, a modeling study that will focus on how time-space dependent rainfall distribution influences the intensity of the feedback between a vegetated surface and the atmospheric boundary layer. Further analysis shows strongly demarked vegetation and soil moisture gradients extending across the FIFE experimental site that were developed and maintained by the antecedent and ongoing spatial distribution of rainfall over the region. These gradients are shown to have a pronounced influence on the thermodynamic properties of the surface. Furthermore, perturbation surface wind analysis suggests for both short-term steady-state conditions and long-term averaged conditions that the gradient pattern maintained a diurnally oscillating local direct circulation with perturbation vertical velocities of the same order as developing cumulus clouds. Dynamical and scaling considerations suggest that the embedded perturbation circulation is driven by surface heating/cooling gradients and terrain effects rather than the manifestation of an inertial oscillation. The implication is that at even relatively small scales (<30 km), the differential evolution in vegetation density and soil moisture distribution over a relatively homogenous ecotone can give rise to preferential boundary-layer circulations capable of modifying local-scale horizontal and vertical motions. C1 FLORIDA STATE UNIV,SUPERCOMP COMPUTAT RES INST,TALLAHASSEE,FL 32306. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP SMITH, EA (reprint author), FLORIDA STATE UNIV,DEPT METEOROL,B-161,TALLAHASSEE,FL 32306, USA. NR 69 TC 33 Z9 33 U1 0 U2 1 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0022-4928 J9 J ATMOS SCI JI J. Atmos. Sci. PD JUN 1 PY 1994 VL 51 IS 11 BP 1497 EP 1529 DI 10.1175/1520-0469(1994)051<1497:LBLCAS>2.0.CO;2 PG 33 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA NQ997 UT WOS:A1994NQ99700011 ER PT J AU WANG, SP WANG, Q AF WANG, SP WANG, Q TI ROLES OF DRIZZLE IN A ONE-DIMENSIONAL 3RD-ORDER TURBULENCE CLOSURE-MODEL OF THE NOCTURNAL STRATUS-TOPPED MARINE BOUNDARY-LAYER SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID STRATOCUMULUS; PARAMETERIZATION; MICROPHYSICS; CLOUDINESS; SIMULATION; STABILITY; BUDGETS AB This study focuses on the effects of drizzle in a one-dimensional third-order turbulence closure model of the nocturnal stratus-topped marine boundary layer. When the simulated drizzle rate is relatively small (maximum approximately 0.6 mm day-1), steady-state solutions are obtained. The boundary layer stabilizes essentially because drizzle causes evaporative cooling of the subcloud layer. This stabilization considerably reduces the buoyancy flux and turbulence kinetic energy below the stratus cloud. Thus, drizzle tends to decouple the cloud from the subcloud layer in the model, as suggested by many observational studies. In addition, the evaporation of drizzle in the subcloud layer creates small scattered clouds, which are likely to represent cumulus clouds, below the solid stratus cloud in the model. The sensitivity experiments show that these scattered clouds help maintain a coupled boundary layer. When the drizzle rate is relatively large (maximum approximately 0.9 mm day-1), the response of the model becomes transient with bursts in turbulent fluxes. This phenomenon is related to the formation of the scattered cloud layer below the solid stratus cloud. It appears that the model is inadequate to represent the heat and moisture transport by strong updrafts covering a small fractional area in cumulus convection. C1 PENN STATE UNIV,DEPT METEOROL,UNIV PK,PA 16802. RP WANG, SP (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,INST GLOBAL CHANGE RES & EDUC,HUNTSVILLE,AL 35812, USA. NR 38 TC 26 Z9 27 U1 0 U2 0 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0022-4928 J9 J ATMOS SCI JI J. Atmos. Sci. PD JUN 1 PY 1994 VL 51 IS 11 BP 1559 EP 1576 DI 10.1175/1520-0469(1994)051<1559:RODIAO>2.0.CO;2 PG 18 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA NQ997 UT WOS:A1994NQ99700014 ER PT J AU NAGASUBRAMANIAN, G SURAMPUDI, S HALPERT, G AF NAGASUBRAMANIAN, G SURAMPUDI, S HALPERT, G TI CYCLOALIPHATIC EPOXIDE-BASED PHOTOCURED GELLED ELECTROLYTES FOR SECONDARY LITHIUM BATTERY APPLICATIONS - ELECTROCHEMICAL KINETIC-STUDIES SO JOURNAL OF THE ELECTROCHEMICAL SOCIETY LA English DT Article ID IONIC-CONDUCTIVITY AB Cycloaliphatic epoxide-based thin gelled films prepared by ultraviolet photocuring were characterized electrochemically. Mixtures of ethylene carbonate and various organic liquids in different volume ratios were used as solvents. General composition of the electrolyte was cycloaliphatic epoxide (being sold under the trade name ENVIBAR by Union Carbide) 10 to 28 weight percent (w/o), polyethylene oxide (200,000 Mw) 4 to 10 w/o, LiAsF6, 6 to 22 w/o, and mixed solvents (of different volume ratios) 80 to 40 w/o. Thin gelled films were formed on lithium (Li) electrodes and subjected to electrochemical studies. Typical values of bulk electrolyte specific conductivity and interfacial resistance obtained from ac impedance and dc measurements at room temperatures are 2 x 10(-3) S cm-1 and 3.2 OMEGA cm2, respectively Charge/discharge characteristics of the cells of the Li/electrolyte/TiS2 type were evaluated. Cathode utilization was only 33% of the total capacity. RP NAGASUBRAMANIAN, G (reprint author), JET PROP LAB,PASADENA,CA 91109, USA. NR 21 TC 4 Z9 4 U1 0 U2 1 PU ELECTROCHEMICAL SOC INC PI PENNINGTON PA 10 SOUTH MAIN STREET, PENNINGTON, NJ 08534 SN 0013-4651 J9 J ELECTROCHEM SOC JI J. Electrochem. Soc. PD JUN PY 1994 VL 141 IS 6 BP 1414 EP 1417 DI 10.1149/1.2054939 PG 4 WC Electrochemistry; Materials Science, Coatings & Films SC Electrochemistry; Materials Science GA NQ338 UT WOS:A1994NQ33800007 ER PT J AU BAUDIN, C BELL, B KEDAR, S AF BAUDIN, C BELL, B KEDAR, S TI INCREASING LEVELS OF ASSISTANCE IN REFINEMENT OF KNOWLEDGE-BASED RETRIEVAL-SYSTEMS SO KNOWLEDGE ACQUISITION LA English DT Article C1 NORTHWESTERN UNIV,INST LEARNING SCI,EVANSTON,IL 60201. RP BAUDIN, C (reprint author), NASA,AMES RES CTR,ARTIFICIAL INTELLIGENCE RES BRANCH,MOFFETT FIELD,CA 94035, USA. NR 24 TC 2 Z9 2 U1 0 U2 1 PU ACADEMIC PRESS LTD PI LONDON PA 24-28 OVAL RD, LONDON, ENGLAND NW1 7DX SN 1042-8143 J9 KNOWL ACQUIS JI Knowl. Acquis. PD JUN PY 1994 VL 6 IS 2 BP 179 EP 196 DI 10.1006/knac.1994.1010 PG 18 WC Computer Science, Artificial Intelligence; Information Science & Library Science SC Computer Science; Information Science & Library Science GA NX979 UT WOS:A1994NX97900006 ER PT J AU CHILDERS, DL SKLAR, FH HUTCHINSON, SE AF CHILDERS, DL SKLAR, FH HUTCHINSON, SE TI STATISTICAL TREATMENT AND COMPARATIVE-ANALYSIS OF SCALE-DEPENDENT AQUATIC TRANSECT DATA IN ESTUARINE LANDSCAPES SO LANDSCAPE ECOLOGY LA English DT Article DE ESTUARIES; COASTAL LANDSCAPES; AQUATIC TRANSECT DATA; COMPARATIVE STATISTICS; ANCOVA; FLOATING WINDOW; VARIABLE SCALE ANALYSIS AB Estuarine ecosystem dynamics have evolved around and respond to landscape-level influences that are dynamic in space and time. The estuarine water column is effectively the physical and biologial integrator of these landscape inputs. In this paper, we present a floating window Analysis of Covariance (ANCOVA) technique to statistically compare and contrast aquatic transect data that were taken at different times and under different tidal conditions, yet were geographically parallel and spatially articulate. The floating window ANCOVA compared two transects by testing whether the means of the dependent variable were significantly different while also testing whether the slopes of patterns in the dependent variable were significantly different. By varying the size of the floating window where the ANCOVA was run, we were able to examine how scale affected the magnitude and spatial pattern of that variable. The percentages of total models run, at a given window size, that generated significantly different magnitudes (means) and patterns (slopes) in the dependent variable were referred to as the ''degree of dissimilarity''. Plots of window size versus degree of dissimilarity elucidated temporal and spatial variability in water column parameters at a range of scales. The advantages of this new statistical method in relation to traditional spatial statistics are discussed. We demonstrated the efficacy of the floating window ANCOVA method by comparing chlorophyll and salinity transect data taken at the North Inlet, SC estuary during flooding and ebbing tides in Winter, Spring, and Summer 1991. Chlorophyll concentrations represented the biological characteristics of the estuarine water column and salinity represented the physical processes affecting that water column. We found total dissimilarity in the magnitude of salinity data from one season to the next at all scales, but inter-seasonal similarity in spatial patterns over both short (hourly) and long (monthly) time scales. We also found a large seasonal dissimilarity in the magnitude of chlorophyll levels, as expected. Spatial patterns in phytoplankton biomass (as chlorophyll concentrations) appeared to be largely controlled by the physical processes represented with the salinity data. Often, we observed greater dissimilarity in biological and physical parameters from one tide to the next [on a given day] than from one season to the next. In these cases, the greatest flood-ebb differences were associated with landscape-level influences - from rivers and the coastal ocean - that varied greatly with direction of tidal flow. We are currently using spatially articulate aquatic transect data and the floating window ANCOVA technique to validate spatial simulation models at different scales. By using this variable-scale statistical technique to determine coherence between the actual transect data and model output from simulations run at different scales, we will test hypotheses about the scale-dependent relationships between data resolution and model predictability in landscape analysis. RP CHILDERS, DL (reprint author), NATL MARINE FISHERIES SERV,SE FISHERY SCI CTR,GALVESTON LAB,4700 AVE U,GALVESTON,TX 77551, USA. NR 0 TC 8 Z9 8 U1 0 U2 2 PU S P B ACADEMIC PUBLISHING BV PI LELYSTAD PA PLATINASTRAAT 33, 8211 AR LELYSTAD, NETHERLANDS SN 0921-2973 J9 LANDSCAPE ECOL JI Landsc. Ecol. PD JUN PY 1994 VL 9 IS 2 BP 127 EP 141 PG 15 WC Ecology; Geography, Physical; Geosciences, Multidisciplinary SC Environmental Sciences & Ecology; Physical Geography; Geology GA NU094 UT WOS:A1994NU09400005 ER PT J AU WHARTON, RA MEYER, MA MCKAY, CP MANCINELLI, RL SIMMONS, GM AF WHARTON, RA MEYER, MA MCKAY, CP MANCINELLI, RL SIMMONS, GM TI SEDIMENT OXYGEN PROFILES IN A SUPER-OXYGENATED ANTARCTIC LAKE SO LIMNOLOGY AND OCEANOGRAPHY LA English DT Article ID ALGAL MATS; ICE; SUPERSATURATION; MICROELECTRODE; CONSUMPTION; INSITU; HOARE; OCEAN; RICH AB Perennially ice-covered lakes are found in the McMurdo Dry Valleys of southern Victoria Land, Antarctica. In contrast to temperate lakes that have diurnal photic periods, antarctic (and arctic) lakes have a yearly photic period. An unusual feature of the antarctic lakes is the occurrence of O2 at supersaturated levels in certain portions of the water column. Here we report the first sediment O2 profiles obtained using a microelectrode from a perennially ice-covered antarctic lake. Sediment cores collected in January and October 1987 from Lake Hoare in Taylor Valley show oxygenation down to 15, and in some cases, 25 cm. The oxygenation of sediments several centimeters below the sediment-water interface is atypical for lake sediments and may be characteristic of perennially ice-covered lakes. There is a significant difference between the observed January and October sediment O2 profiles. Several explanations may account for the difference, including seasonality. A time-dependent model is presented which tests the feasibility of a seasonal cycle resulting from the long photoperiod and benthic primary production in sediments overlain by a highly oxygenated water column. C1 NASA,AMES RES CTR,DIV SPACE SCI,MOFFETT FIELD,CA 94035. VIRGINIA POLYTECH INST & STATE UNIV,DEPT BIOL,BLACKSBURG,VA 24061. RP WHARTON, RA (reprint author), DESERT RES INST,CTR BIOL SCI,RENO,NV 89506, USA. RI Mancinelli, Rocco/L-8971-2016 FU NCCDPHP CDC HHS [DPP 84-1630] NR 37 TC 8 Z9 9 U1 1 U2 6 PU AMER SOC LIMNOLOGY OCEANOGRAPH PI LAWRENCE PA 810 EAST 10TH ST, LAWRENCE, KS 66044-8897 SN 0024-3590 J9 LIMNOL OCEANOGR JI Limnol. Oceanogr. PD JUN PY 1994 VL 39 IS 4 BP 839 EP 853 PG 15 WC Limnology; Oceanography SC Marine & Freshwater Biology; Oceanography GA PC982 UT WOS:A1994PC98200007 PM 11539366 ER PT J AU FUSARO, RL AF FUSARO, RL TI STATE OF THE SOCIETY MESSAGE SO LUBRICATION ENGINEERING LA English DT Editorial Material RP FUSARO, RL (reprint author), NASA,LEWIS RES CTR,21000 BROOKPK RD,MS-23-3,CLEVELAND,OH 44135, USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU SOC TRIBOLOGISTS & LUBRICATION ENGINEERS PI PARK RIDGE PA 838 BUSSE HIGHWAY, PARK RIDGE, IL 60068 SN 0024-7154 J9 LUBR ENG JI Lubric. Eng. PD JUN PY 1994 VL 50 IS 6 BP 431 EP 432 PG 2 WC Engineering, Mechanical SC Engineering GA NQ866 UT WOS:A1994NQ86600001 ER PT J AU HELMICK, LS JONES, WR AF HELMICK, LS JONES, WR TI DETERMINATION OF THE THERMAL-STABILITY OF PERFLUOROPOLYALKYL ETHERS BY TENSIMETRY SO LUBRICATION ENGINEERING LA English DT Article DE LUBRICATION FUNDAMENTALS; SYNTHETIC LUBRICANTS ID FLUIDS; DEGRADATION; LUBRICANTS AB The thermal decomposition temperatures of several perfluoropolyalkyl ether fluids were determined with a computerized tensimeter. In general, the decomposition temperatures of the commercial fluids were all similar and significantly higher than those for non-commercial fluids. Correlation of the decomposition temperatures with the molecular structures of the primary components of the commercial fluids revealed that the stability of the fluids was not affected by carbon chain length, branching, or adjacent difluoroformal groups. Instead, stability was limited by the presence of small quantities of thermally unstable material and/or chlorine-containing material arising from the use of chlorine-containing solvents during synthesis. Finally, correlation of decomposition temperatures with molecular weights for two fluids supports a chain cleavage reaction mechanism for one and an unzipping reaction mechanism for the other. C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP HELMICK, LS (reprint author), CEDARVILLE COLL,CEDARVILLE,OH 45314, USA. NR 25 TC 11 Z9 11 U1 0 U2 0 PU SOC TRIBOLOGISTS & LUBRICATION ENGINEERS PI PARK RIDGE PA 838 BUSSE HIGHWAY, PARK RIDGE, IL 60068 SN 0024-7154 J9 LUBR ENG JI Lubric. Eng. PD JUN PY 1994 VL 50 IS 6 BP 449 EP 457 PG 9 WC Engineering, Mechanical SC Engineering GA NQ866 UT WOS:A1994NQ86600004 ER PT J AU DELLACORTE, C STEINETZ, BM AF DELLACORTE, C STEINETZ, BM TI TRIBOLOGICAL COMPARISON AND DESIGN SELECTION OF HIGH-TEMPERATURE CANDIDATE CERAMIC FIBER SEAL MATERIALS SO LUBRICATION ENGINEERING LA English DT Article DE SEALS; HIGH TEMPERATURE; CERAMICS ID WEAR AB This paper describes a research program to evaluate ceramic fiber material candidates for high-temperature seal applications. To select a material and incorporate it in an advanced ceramic fiber seal, a comparison of tribological properties must be made, taking into consideration anticipated use conditions such as seal loads, temperatures, and sliding velocity. To this end, pin-on-disk tests were used to evaluate potential seal materials by sliding a tow or bundle of the candidate ceramic fiber against a superalloy test disk. Tests were conducted in air under a 2.65 N load, at a sliding velocity of 0.025 m/sec and at temperatures from 25-degrees to 900-degrees-C. Friction was measured during the tests, and fiber wear, indicated by the extent of fibers broken in the tow or bundle, was measured at the end of each test. For the conditions studied, oxide-based fibers were generally superior to carbide-based fibers. A dimensional analysis of the wear data shows that the fiber durability is related to a dimensionless durability ratio which represents the ratio of the fiber strength to the fiber stresses imposed by sliding. The analysis lends insight into fiber performance under these test conditions and may be useful in predicting material behavior based upon measured properties such as fiber diameter, tensile strength, and test load. RP DELLACORTE, C (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 15 TC 0 Z9 0 U1 1 U2 3 PU SOC TRIBOLOGISTS & LUBRICATION ENGINEERS PI PARK RIDGE PA 838 BUSSE HIGHWAY, PARK RIDGE, IL 60068 SN 0024-7154 J9 LUBR ENG JI Lubric. Eng. PD JUN PY 1994 VL 50 IS 6 BP 469 EP 477 PG 9 WC Engineering, Mechanical SC Engineering GA NQ866 UT WOS:A1994NQ86600006 ER PT J AU PELLETIER, RE HOLLADAY, KW AF PELLETIER, RE HOLLADAY, KW TI MAPPING SEDIMENT AND WATER PROPERTIES IN A SHALLOW COASTAL ENVIRONMENT WITH AIRBORNE ELECTROMAGNETIC PROFILE DATA - CASE-STUDY - THE CAPE LOOKOUT, NC AREA SO MARINE TECHNOLOGY SOCIETY JOURNAL LA English DT Article ID OCEAN AB Airborne Electromagnetic profile (AEM) data has been demonstrated to provide good airborne measurements of shallow ocean bathymetry but has received limited use in very shallow coastal barrier island and estuarine environments. This paper illustrates the utility of the AEM for developing maps of physical properties useful in characterizing sediment and water in these types of complex coastal environments. The test site is the Cape Lookout area at the southern end of North Carolina's Outer Banks. Inverse methods were applied to a two-layer model to calculate water depth, water conductivity and sediment conductivity values from transect data. These calculated model parameters were then used to develop interpolated spatial maps for these variables. The analysis provided generally good agreement between the map values and ground truth. The water depth model, used to generate a bathymetric map, fit the actual data points very well and much better than the initial sediment and water conductivity models that required additional filtering to produce good spatial maps. The sediment conductivity maps corresponded fairly well with known shallow sediment types and the water conductivity maps demonstrated the expected variation in an estuarine environment such as this. Spatially the maps depict very good general trends for the variables studied as well as identifying some special areas of interest at a more detailed scale. An understanding of the spatial distribution of these sediment and water variables has broad utility in a variety of physical and biological coastal process models. C1 SVERDRUP TECH INC,NEW ORLEANS,LA. UNIV NEW ORLEANS,NEW ORLEANS,LA 70148. RP PELLETIER, RE (reprint author), NASA,COMMERCIAL REMOTE SENSING OFF,BAY ST LOUIS,MS, USA. NR 10 TC 5 Z9 5 U1 0 U2 0 PU MARINE TECHNOLOGY SOC INC PI WASHINGTON PA C/O I CLAYION MATTHEWS, 1828 L ST, NW, 9TH FL, WASHINGTON, DC 20036 SN 0025-3324 J9 MAR TECHNOL SOC J JI Mar. Technol. Soc. J. PD SUM PY 1994 VL 28 IS 2 BP 57 EP 63 PG 7 WC Engineering, Ocean; Oceanography SC Engineering; Oceanography GA PQ197 UT WOS:A1994PQ19700009 ER PT J AU MANNEY, GL FARRARA, JD MECHOSO, CR AF MANNEY, GL FARRARA, JD MECHOSO, CR TI SIMULATIONS OF THE FEBRUARY 1979 STRATOSPHERIC SUDDEN WARMING - MODEL COMPARISONS AND 3-DIMENSIONAL EVOLUTION SO MONTHLY WEATHER REVIEW LA English DT Article ID PLANETARY WAVE BREAKING; POTENTIAL VORTICITY; POLAR VORTEX; MIDDLE; PARAMETERIZATION; RESOLUTION; ATMOSPHERE; WINTER AB The evolution of the stratospheric flow during the major stratospheric sudden warming of February 1979 is studied using two primitive equation models of the stratosphere and mesosphere. The United Kingdom Meteorological Office Stratosphere-Mesosphere Model (SMM) uses log pressure as a vertical coordinate. A spectral, entropy coordinate version of the SMM (entropy coordinate model, or ECM) that has recently been developed is also used. Both models produce similar successful simulations through the peak of the warming, capturing the splitting of the vortex and the development of small-scale structures, such as narrow baroclinic zones. The ECM produces a more realistic recombination and recovery of the polar vortex in the midstratosphere after the warming, due mainly to better conservation properties for Rossby-Ertel potential vorticity in this model. Another advantage of the ECM is the automatic increase in vertical resolution near baroclinic zones. Comparison of SMM simulations with forecasts performed using the University of California, Los Angeles general circulation model confirms the previously noted sensitivity of stratospheric forecasts to tropospheric forecast and emphasizes the importance of adequate vertical resolution in modeling the stratosphere. The ECM simulations provide a schematic description of the three-dimensional evolution of the polar vortex and the motion of air through it. During the warming, the two cyclonic vortices tilt westward and equatorward with height. Strong upward velocities develop in the lower stratosphere on the west (cold) side of a baroclinic zone as it forms over Europe and Asia. Strong downward velocities appear in the upper stratosphere on the east (warm) side, strengthening the temperature gradients. After the peak of the warming, vertical velocities decrease, downward velocities move into the lower stratosphere, and upward velocities move into the upper stratosphere. Transport calculations show that air with high ozone mixing ratios is advected toward the pole from low latitudes during the warming, and air with low ozone mixing ratios is transported to the midstratosphere from both higher and lower altitudes along the baroclinic zone in the polar regions. Trajectories of parcels moving around the vortex oscillate up and down as they move through regions of ascending and descending motions, with an overall increase in pressure in the polar regions. Tracer transport and trajectory calculations show enhanced diabatic descent in the region between cyclone and anticyclone during the warming, consistent with the temperature structure shown. C1 UNIV CALIF LOS ANGELES,LOS ANGELES,CA 90024. RP MANNEY, GL (reprint author), JET PROP LAB,4800 OAK GROVE DR,MAIL STOP 183701,PASADENA,CA 91109, USA. NR 32 TC 28 Z9 29 U1 0 U2 2 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 JUN PY 1994 VL 122 IS 6 BP 1115 EP 1140 DI 10.1175/1520-0493(1994)122<1115:SOTFSS>2.0.CO;2 PG 26 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA NQ156 UT WOS:A1994NQ15600006 ER PT J AU DOWNIE, JD AF DOWNIE, JD TI DESIGN OF TERNARY CORRELATION FILTERS TO REDUCE PROBABILITY OF ERROR SO OPTICAL ENGINEERING LA English DT Article ID PHASE-ONLY FILTERS; AMPLITUDE FILTERS; BINARY PHASE; NOISE RATIO; DISCRIMINATION; ALGORITHM; SIGNAL AB The problem of designing ternary phase and amplitude filters (TPAFs) that reduce the probability of image misclassification for a two-class image set is studied. The Fisher ratio is used as a measure of the correct classification rate. and an attempt is made to maximize this quantity in the filter designs. Given the nonanalytical nature of the design problem, a simulated annealing optimization technique is employed. Computer simulation results are presented for several cases including single in-class and out-of-class image sets and multiple image sets corresponding to the design of synthetic discriminant function filters. Significant improvements are found in expected rates of correct classification in comparison to binary phase-only filters and other TPAF designs. Approaches to accelerate the filter design process are also discussed. RP DOWNIE, JD (reprint author), NASA,AMES RES CTR,INST THEORET PHYS,PHOTON GRP,M-S 269-3,MOFFETT FIELD,CA 94035, USA. NR 14 TC 7 Z9 7 U1 0 U2 0 PU SOC PHOTO-OPT INSTRUM ENG PI BELLINGHAM PA PO BOX 10, BELLINGHAM, WA 98227-0010 SN 0091-3286 J9 OPT ENG JI Opt. Eng. PD JUN PY 1994 VL 33 IS 6 BP 1777 EP 1784 DI 10.1117/12.171600 PG 8 WC Optics SC Optics GA NR248 UT WOS:A1994NR24800007 ER PT J AU JOHNSTON, AR LIU, DTH FOROUHAR, S LUTES, GF MASERJIAN, J FOSSUM, ER AF JOHNSTON, AR LIU, DTH FOROUHAR, S LUTES, GF MASERJIAN, J FOSSUM, ER TI OPTICAL LINKS FOR CRYOGENIC FOCAL-PLANE ARRAY READOUT SO OPTICAL ENGINEERING LA English DT Article DE CRYOGENIC FOCAL PLANE ARRAY; OPTICAL FIBER LINK; MULTIPLE-QUANTUM-WELL WAVE-GUIDE MODULATOR ID MODULATOR; POLYMERS AB An optical link can provide an interface channel for a focal plane array that is immune to electro-magnetic interference (EMI) and can lower the heat load on the dewar. Our approach involves the use of fiber optics and an on-focal-plane optical modulator to provide an interface to the focal plane array (FPA). The FPA drives the modulator with an electrical signal. We evaluated specially fabricated AlGaAs/GaAs multiple-quantum-well (MQW) optical modulators, operating near 840 nm, for analog modulation, and we have used the results to calculate the performance of an optical interface link using experimentally determined device parameters. Link noise and dynamic range for an analog link were estimated from a separate experiment using pigtailed fiber components. The performance of the MQW modulator system is compared to alternative strategies. Significant improvement in performance in comparison to conventional electronic interfaces appears to be possible. RP JET PROP LAB, 4800 OAK GROVE DR, PASADENA, CA 91109 USA. NR 20 TC 3 Z9 3 U1 0 U2 3 PU SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS PI BELLINGHAM PA 1000 20TH ST, PO BOX 10, BELLINGHAM, WA 98225 USA SN 0091-3286 EI 1560-2303 J9 OPT ENG JI Opt. Eng. PD JUN PY 1994 VL 33 IS 6 BP 2013 EP 2019 DI 10.1117/12.169726 PG 7 WC Optics SC Optics GA NR248 UT WOS:A1994NR24800043 ER PT J AU TOWNSEND, LW AF TOWNSEND, LW TI OPTICAL-MODEL ANALYSES OF HEAVY-ION FRAGMENTATION IN HYDROGEN TARGETS SO PHYSICAL REVIEW C LA English DT Article ID ABRASION-ABLATION; MOMENTUM-TRANSFER; NUCLEON EMISSION; CROSS-SECTIONS; PROJECTILES AB Quantum-mechanical optical-model methods for calculating cross sections for the fragmentation of high-energy heavy ions by hydrogen targets are presented. The cross sections are calculated with a knockout-ablation collision formalism which has no arbitrary fitting parameters. Predictions of elemental production cross sections from the fragmentation of 1.2A GeV La-139 nuclei and of isotope production cross sections from the fragmentation of 400A MeV S-32 nuclei are in good agreement with recently reported experimental measurements. RP TOWNSEND, LW (reprint author), NASA,LANGLEY RES CTR,HAMPTON,VA 23681, USA. NR 25 TC 6 Z9 6 U1 0 U2 1 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0556-2813 J9 PHYS REV C JI Phys. Rev. C PD JUN PY 1994 VL 49 IS 6 BP 3158 EP 3161 DI 10.1103/PhysRevC.49.3158 PG 4 WC Physics, Nuclear SC Physics GA NU224 UT WOS:A1994NU22400035 PM 9969594 ER PT J AU CHEN, CX ALBERGO, S CACCIA, Z COSTA, S CRAWFORD, HJ CRONQVIST, M ENGELAGE, J FERRANDO, P FONTE, R GREINER, L GUZIK, TG INSOLIA, A JONES, FC KNOTT, CN LINDSTROM, PJ MITCHELL, JW POTENZA, R ROMANSKI, J RUSSO, GV SOUTOUL, A TESTARD, O TULL, CE TUVE, C WADDINGTON, CJ WEBBER, WR WEFEL, JP ZHANG, X AF CHEN, CX ALBERGO, S CACCIA, Z COSTA, S CRAWFORD, HJ CRONQVIST, M ENGELAGE, J FERRANDO, P FONTE, R GREINER, L GUZIK, TG INSOLIA, A JONES, FC KNOTT, CN LINDSTROM, PJ MITCHELL, JW POTENZA, R ROMANSKI, J RUSSO, GV SOUTOUL, A TESTARD, O TULL, CE TUVE, C WADDINGTON, CJ WEBBER, WR WEFEL, JP ZHANG, X TI INTERACTIONS IN HYDROGEN OF RELATIVISTIC NEON TO NICKEL PROJECTILES - TOTAL CHARGE-CHANGING CROSS-SECTIONS SO PHYSICAL REVIEW C LA English DT Article ID NUCLEAR-REACTIONS; CARBON TARGETS; FRAGMENTATION; ENERGY; HELIUM; FORMULA; RADII; LI-11; MASS AB A liquid hydrogen target was used to study the nuclear fragmentation of beams of relativistic heavy ions, Ne-22 to Ni-58, over an energy range 400 to 900 MeV/nucleon. The experiments were carried out at the Lawrence Berkeley Laboratory Bevalac HISS facility, using the charge-velocity-rigidity method to identify the charged fragments. Here we describe the general concept of the experiment and present total charge-changing cross sections obtained from 17 separate runs. These new measured cross sections display an energy dependence which follows semiempirical model predictions. The mass dependence of the cross sections behaves as predicted by optical models, but within the experimental energy range, the optical model parameters display a clear energy dependence. The isospin of the projectile nuclei also appears to be an important factor in the interaction process. C1 CENS,SERV ASTROPHYS,F-91191 GIF SUR YVETTE,FRANCE. LAWRENCE BERKELEY LAB,BERKELEY,CA 94720. NEW MEXICO STATE UNIV,DEPT ASTRON,LAS CRUCES,NM 88003. UNIV CATANIA,IST NAZL FIS NUCL,I-95129 CATANIA,ITALY. UNIV CALIF BERKELEY,SPACE SCI LAB,BERKELEY,CA 94720. UNIV MINNESOTA,DEPT PHYS & ASTRON,MINNEAPOLIS,MN 55455. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP CHEN, CX (reprint author), LOUISIANA STATE UNIV,DEPT PHYS & ASTRON,BATON ROUGE,LA 70803, USA. RI Insolia, Antonio/M-3447-2015; TUVE', Cristina/P-3933-2015 OI Insolia, Antonio/0000-0002-9040-1566; TUVE', Cristina/0000-0003-0739-3153 NR 45 TC 42 Z9 44 U1 0 U2 2 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0556-2813 J9 PHYS REV C JI Phys. Rev. C PD JUN PY 1994 VL 49 IS 6 BP 3200 EP 3210 DI 10.1103/PhysRevC.49.3200 PG 11 WC Physics, Nuclear SC Physics GA NU224 UT WOS:A1994NU22400040 ER PT J AU ZHOU, Y VAHALA, G THANGAM, S AF ZHOU, Y VAHALA, G THANGAM, S TI DEVELOPMENT OF A TURBULENCE MODEL-BASED ON RECURSION RENORMALIZATION-GROUP THEORY SO PHYSICAL REVIEW E LA English DT Article ID NAVIER-STOKES TURBULENCE; EDDY-VISCOSITY; REYNOLDS-STRESS; ISOTROPIC TURBULENCE; STATISTICAL-ANALYSIS; SIMULATION; CLOSURES; FLOWS AB An anisotropic turbulence model for the local interaction part of the Reynolds stresses is developed using the recursion renormalization group theory (r-RNG)-an interaction contribution that has been omitted in all previous Reynolds stress RNG calculations. The local interactions arise from the nonzero wave number range, 0 < k < k(c), where k(c) is the wave number separating the subgrid from resolvable scales while the nonlocal interactions arise in the k --> 0 limit. From epsilon-RNG, which can only treat nonlocal interactions, it has been shown that the nonlocal contributions to the Reynolds stress give rise to terms that are quadratic in the mean strain rate. Based on comparisons of nonlocal contributions to the eddy viscosity and Prandtl number from r-RNG and epsilon-RNG theories (epsilon is a small parameter), it is assumed that the nonlocal contribution to the Reynolds stress will also be very similar. It is shown here, by r-RNG, that the local interaction effects give rise to significant higher-order dispersive effects. The importance of these new terms for separated flows is investigated by considering turbulent flow past a backward facing step. On incorporating this r-RNG model for the Reynolds stress into the conventional transport models for turbulent kinetic energy and dissipation, it is found that very good predictions for the turbulent separated flow past a backward facing step are obtained. The r-RNG model performance is also compared with that of the standard K-epsilon model (K is the kinetic energy of the turbulence and epsilon is the turbulence dissipation), the epsilon-RNG model, and other two-equation models for this back step problem to demonstrate the importance of the local interactions. C1 COLL WILLIAM & MARY,WILLIAMSBURG,VA 23185. STEVENS INST TECHNOL,HOBOKEN,NJ 07030. RP ZHOU, Y (reprint author), NASA,LANGLEY RES CTR,INST COMP APPLICAT SCI & ENGN,HAMPTON,VA 23681, USA. NR 39 TC 14 Z9 14 U1 0 U2 2 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 1063-651X J9 PHYS REV E JI Phys. Rev. E PD JUN PY 1994 VL 49 IS 6 BP 5195 EP 5206 DI 10.1103/PhysRevE.49.5195 PN A PG 12 WC Physics, Fluids & Plasmas; Physics, Mathematical SC Physics GA NW029 UT WOS:A1994NW02900059 ER PT J AU HAAS, BL HASH, DB BIRD, GA LUMPKIN, FE HASSAN, HA AF HAAS, BL HASH, DB BIRD, GA LUMPKIN, FE HASSAN, HA TI RATES OF THERMAL RELAXATION IN DIRECT SIMULATION MONTE-CARLO METHODS SO PHYSICS OF FLUIDS LA English DT Article ID TRANSLATIONAL ENERGY-TRANSFER; VIBRATION-DISSOCIATION; PARTICLE SIMULATION; MODELS; NONEQUILIBRIUM; MECHANICS AB For internal energy relaxation in rarefied gas mixtures, exact relationships are derived between the selection probability P employed in direct simulation Monte Carlo (DSMC) methods and the macroscopic relaxation rates dictated by collision number Z in Jeans' equation. These expressions apply to the Borgnakke-Larsen model for internal energy exchange mechanics and are not limited to the assumption of constant Z. Although Jeans' equation leads to adiabatic relaxation curves, which coalesce to a single solution when plotted against the cumulative number of collisions, it is shown that the Borgnakke-Larsen selection probabilities depend upon the intermolecular potential, the number of internal degrees of freedom, and the DSMC selection methodology. Furthermore, simulation results show that the common assumption P = 1/Z is invalid, in general, and leads to considerably slower relaxation than stipulated by Z in Jeans' equation. Moreover, inconsistent definitions of collision rates appearing in the literature can lead to considerable errors in DSMC models. Finally, for general gas mixtures, Borgnakke-Larsen DSMC kinetics match Jeans' behavior exactly only when using a selection methodology, which prohibits multiple relaxation events during a single collision. C1 N CAROLINA STATE UNIV,RALEIGH,NC 27695. UNIV SYDNEY,DEPT AERONAUT ENGN,SYDNEY,NSW 2006,AUSTRALIA. N CAROLINA STATE UNIV,DEPT MECH & AEROSP ENGN,RALEIGH,NC 27695. RP HAAS, BL (reprint author), NASA,INST THERMOSCI,MOFFETT FIELD,CA 94035, USA. NR 31 TC 43 Z9 44 U1 0 U2 10 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 1070-6631 J9 PHYS FLUIDS JI Phys. Fluids PD JUN PY 1994 VL 6 IS 6 BP 2191 EP 2201 DI 10.1063/1.868221 PG 11 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA NQ069 UT WOS:A1994NQ06900025 ER PT J AU HOFLUND, GB GILBERT, RE MELENDEZ, O AF HOFLUND, GB GILBERT, RE MELENDEZ, O TI STUDY OF CO CHEMISORPTION ON POLYCRYSTALLINE PT SO REACTION KINETICS AND CATALYSIS LETTERS LA English DT Article ID PLATINUM SURFACE; CARBON-MONOXIDE; ADSORPTION; OXIDATION; OXIDE; PRETREATMENT; TEMPERATURE; NO AB The chemisorption of CO on a sputtered and annealed polycrystalline Pt surface has been examined using ion scattering spectroscopy (ISS) and temperature programmed desorption (TPD). Data obtained from an isotopic TPD experiment indicate that adsorption is molecular with no detectable CO dissociation. ISS data demonstrate that the CO bonds to the Pt through the C with the O pointing away from the surface and that about 80% of the Pt surface is covered at saturation based on the relative sizes of the ISS Pt peak heights obtained from the clean and CO-saturated surfaces. Coverage versus exposure plots have been determined from both the ISS and TPD data, and the agreement is generally good. The sticking coefficient is close to 1 up to 0=0.5 and than falls rapidly with increasing exposure to the saturation exposure of 90 L. The Kisliuk adsorption model, which assumes adsorption at a single type of site, is able to provide a good fit of the ISS uptake data but is not as successful in fitting the TPD uptake data. C1 UNIV NEBRASKA,DEPT CHEM ENGN,LINCOLN,NE 68588. NASA,DMMSLI,KENNEDY SPACE CTR,FL 32899. RP HOFLUND, GB (reprint author), UNIV FLORIDA,DEPT CHEM ENGN,GAINESVILLE,FL 32611, USA. NR 17 TC 4 Z9 4 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0133-1736 J9 REACT KINET CATAL L JI React. Kinet. Catal. Lett. PD JUN PY 1994 VL 52 IS 2 BP 357 EP 365 DI 10.1007/BF02067809 PG 9 WC Chemistry, Physical SC Chemistry GA QA677 UT WOS:A1994QA67700016 ER PT J AU RASH, JL AF RASH, JL TI ARTIFICIAL-INTELLIGENCE AND ADVANCED COMPUTING TECHNOLOGIES FOR SPACE APPLICATIONS SO ROBOTICS AND COMPUTER-INTEGRATED MANUFACTURING LA English DT Editorial Material RP RASH, JL (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0736-5845 J9 ROBOT CIM-INT MANUF JI Robot. Comput.-Integr. Manuf. PD JUN PY 1994 VL 11 IS 2 BP 51 EP 51 DI 10.1016/0736-5845(94)90008-6 PG 1 WC Computer Science, Interdisciplinary Applications; Engineering, Manufacturing; Robotics SC Computer Science; Engineering; Robotics GA RC263 UT WOS:A1994RC26300001 ER PT J AU REYNOLDS, AP ROYSTER, DM AF REYNOLDS, AP ROYSTER, DM TI RETAINED MECHANICAL-PROPERTIES OF A NEW AL-LI-CU-MG-AG ALLOY AS A FUNCTION OF THERMAL EXPOSURE TIME AND TEMPERATURE SO SCRIPTA METALLURGICA ET MATERIALIA LA English DT Article C1 NASA LANGLEY RES CTR,HAMPTON,VA 23681. RP REYNOLDS, AP (reprint author), ANALYT SERV & MAT,HAMPTON,VA 23666, USA. RI Reynolds, Anthony/F-2585-2010 NR 6 TC 9 Z9 9 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0956-716X J9 SCRIPTA METALL MATER JI Scr. Metall. Materialia PD JUN 1 PY 1994 VL 30 IS 11 BP 1485 EP 1490 DI 10.1016/0956-716X(94)90250-X PG 6 WC Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Materials Science; Metallurgy & Metallurgical Engineering GA NC656 UT WOS:A1994NC65600022 ER PT J AU JENKINS, P LANDIS, GA FATEMI, NS SCHEIMAN, D LI, XN BAILEY, SG AF JENKINS, P LANDIS, GA FATEMI, NS SCHEIMAN, D LI, XN BAILEY, SG TI AN INP SOLAR-CELL WITH A LIGHT-TRAPPING FRONT SURFACE SO SOLAR ENERGY MATERIALS AND SOLAR CELLS LA English DT Article AB Low-angle (311) V-grooves can be produced on a (100) InP surface by a maskless anisotropic etch. This can reduce the surface reflectivity of a glass-covered InP solar cell. Light reflected from grooved surface is trapped by total internal reflection at the glass/air interface and directed back to the solar cell. Results from ITO/InP solar cells on low-angle V-grooved substrates are presented, showing a 5.8% increase in short-circuit current, and a nearly equal rise in efficiency. C1 SVERDRUP TECHNOL INC, LEWIS RES CTR GRP, 21000 BROOKPARK RD, CLEVELAND, OH 44135 USA. NREL, GOLDEN, CO 80401 USA. NASA, LEWIS RES CTR, CLEVELAND, OH 44135 USA. NR 16 TC 5 Z9 5 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0927-0248 EI 1879-3398 J9 SOL ENERG MAT SOL C JI Sol. Energy Mater. Sol. Cells PD JUN PY 1994 VL 33 IS 2 BP 125 EP 133 DI 10.1016/0927-0248(94)90201-1 PG 9 WC Energy & Fuels; Materials Science, Multidisciplinary; Physics, Applied SC Energy & Fuels; Materials Science; Physics GA PA165 UT WOS:A1994PA16500002 ER PT J AU KYLE, HL HOYT, DV HICKEY, JR AF KYLE, HL HOYT, DV HICKEY, JR TI A REVIEW OF THE NIMBUS-7 ERB SOLAR DATASET SO SOLAR PHYSICS LA English DT Article; Proceedings Paper CT IAU Colloquium NO 143 on the Sun as a Variable Star: Solar and Stellar Irradiance Variations CY JUN 20-25, 1993 CL BOULDER, CO SP INT ASTRON UNION ID IRRADIANCE AB Fourteen years (November 16, 1978 through January 24, 1993) of Nimbus-7 total solar irradiance measurements have been made. The measured mean annual solar energy just outside of the Earth's atmosphere was about 0.1% (1.4 W/m2) higher in the peak years of 1979 (cycle 21) and 1991 (cycle 22) than in the quiet Sun years of 1985/86. Comparison with shorter, independent solar measurement sets and with empirical models qualitatively confirms the Nimbus-7 results. But these comparisons also raise questions of detail for future studies: in which years did the peaks actually occur and just how accurate are the models and the measurements? C1 RES & DATA SYST CORP,GREENBELT,MD 20770. EPPLEY LAB INC,NEWPORT,RI 02840. RP KYLE, HL (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. NR 6 TC 26 Z9 27 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 JUN PY 1994 VL 152 IS 1 BP 9 EP 12 DI 10.1007/BF01473176 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NY582 UT WOS:A1994NY58200003 ER PT J AU PAP, JM WILLSON, RC FROHLICH, C DONNELLY, RF PUGA, L AF PAP, JM WILLSON, RC FROHLICH, C DONNELLY, RF PUGA, L TI LONG-TERM VARIATIONS IN TOTAL SOLAR IRRADIANCE SO SOLAR PHYSICS LA English DT Article; Proceedings Paper CT IAU Colloquium NO 143 on the Sun as a Variable Star: Solar and Stellar Irradiance Variations CY JUN 20-25, 1993 CL BOULDER, CO SP INT ASTRON UNION ID MODULATION; SUNSPOTS; CYCLE AB For more than a decade total solar irradiance has been monitored simultaneously from space by different satellites. The detection of total solar irradiance variations by satellite-based experiments during the past decade and a half has stimulated modeling efforts to help identify their causes and to provide estimates of irradiance data, using 'proxy' indicators of solar activity, for time intervals when no satellite observations exist. In this paper total solar irradiance observed by the Nimbus-7/ERB, SMM/ACRIM I, and UARS/ACRIM II radiometers is modeled with the Photometric Sunspot Index and the Mg II core-to-wing ratio. Since the formation of the Mg II line is very similar to that of the Ca II K line, the Mg core-to-wing ratio, derived from the irradiance observations of the Nimbus-7 and NOAA9 satellites, is used as a proxy for the bright magnetic elements. It is shown that the observed changes in total solar irradiance are underestimated by the proxy models at the time of maximum and during the beginning of the declining portion of solar cycle 22 similar to behavior just before the maximum of solar cycle 21. This disagreement between total irradiance observations and their model estimates is indicative of the fact that the underlying physical mechanism of the changes observed in the solar radiative output is not well-understood. Furthermore, the uncertainties in the proxy data used for irradiance modeling and the resulting limitation of the models should be taken into account, especially when the irradiance models are used for climatic studies. C1 WORLD RADIAT CTR,PHYS METEOROL OBSERV DAVOS,DAVOS,SWITZERLAND. NOAA,SPACE ENVIRONM LAB,BOULDER,CO 80303. RP PAP, JM (reprint author), JET PROP LAB,PASADENA,CA 91109, USA. NR 31 TC 22 Z9 22 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 JUN PY 1994 VL 152 IS 1 BP 13 EP 21 DI 10.1007/BF01473177 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NY582 UT WOS:A1994NY58200004 ER PT J AU FROHLICH, C PAP, JM HUDSON, HS AF FROHLICH, C PAP, JM HUDSON, HS TI IMPROVEMENT OF THE PHOTOMETRIC SUNSPOT INDEX AND CHANGES OF THE DISK-INTEGRATED SUNSPOT CONTRAST WITH TIME SO SOLAR PHYSICS LA English DT Article; Proceedings Paper CT IAU Colloquium NO 143 on the Sun as a Variable Star: Solar and Stellar Irradiance Variations CY JUN 20-25, 1993 CL BOULDER, CO SP INT ASTRON UNION ID SOLAR IRRADIANCE VARIATIONS AB The photometric sunspot index (PSI) was developed to study the effects of sunspots on solar irradiance. It is calculated from the sunspot data published in the Solar-Geophysical Data catalogue. It has been shown that the former PSI models overestimate the effect of dark sunspots on solar irradiance; furthermore results of direct sunspot photometry indicate that the contrast of spots depends on their area. An improved PSI calculation is presented; it takes into account the area dependence of the contrast and calculates 'true' daily means for each observation using the differential rotation of the spots. Moreover, the observations are screened for outliers which improves the homogeneity of the data set substantially, at least for the period after December 1981 when NOAA started to report data from a few instead of one to two stations. A detailed description of the method is provided. The correlation between the newly calculated PSI and total solar irradiance is studied for different phases of the solar cycles 21 and 22 using bi-variate spectral analysis. The results can be used as a 'calibration' of PSI in terms of gain, the factor by which PSI has to be multiplied to yield the observed irradiance change. This factor changes with time from about 0.6 in 1980 to 1.1 in 1990. This unexpected result cannot be interpreted by a change of the contrast relative to the quiet Sun (as it is normally defined and determined by direct photometry) but rather as a change of the contrast between the spots and their surrounding as seen in total irradiance (integrated over the solar disk). This may partly be explained by a change in the ratio between the areas of the spots and the surrounding faculae. C1 JET PROP LAB,PASADENA,CA 91109. UNIV HAWAII,INST ASTRON,HONOLULU,HI 96822. RP FROHLICH, C (reprint author), WORLD RADIAT CTR,PHYS METEOROL OBSERVAT DAVOS,DAVOS,SWITZERLAND. NR 16 TC 44 Z9 44 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 JUN PY 1994 VL 152 IS 1 BP 111 EP 118 DI 10.1007/BF01473192 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NY582 UT WOS:A1994NY58200019 ER PT J AU GUHATHAKURTA, M FISHER, RR AF GUHATHAKURTA, M FISHER, RR TI LATITUDINAL VARIABILITY OF LARGE-SCALE CORONAL TEMPERATURE AND ITS ASSOCIATION WITH THE DENSITY AND THE GLOBAL MAGNETIC-FIELD SO SOLAR PHYSICS LA English DT Article; Proceedings Paper CT IAU Colloquium NO 143 on the Sun as a Variable Star: Solar and Stellar Irradiance Variations CY JUN 20-25, 1993 CL BOULDER, CO SP INT ASTRON UNION AB In this paper we utilize the latitude distribution of the coronal temperature during the period 1984-1992 that was derived in a paper by Guhathakurta et al, 1993, utilizing ground-based intensity observations of the green (5303 angstrom Fe XIV) and red (6374 angstrom Fe X) coronal forbidden lines from the National Solar Observatory at Sacramento Peak, and establish its association with the global magnetic field and the density distributions in the corona. A determination of plasma temperature, T, was estimated from the intensity ratio Fe X/Fe XIV (where T is inversely proportional to the ratio), since both emission lines come from ionized states of Fe, and the ratio is only weakly dependent on density. We observe that there is a large-scale organization of the inferred coronal temperature distribution that is associated with the large-scale, weak magnetic field structures and bright coronal features; this organization tends to persist through most of the magnetic activity cycle. These high-temperature structures exhibit time-space characteristics which are similar to those of the polar crown filaments. This distribution differs in spatial and temporal characterization from the traditional picture of sunspot and active region evolution over the range of the sunspot cycle, which are manifestations of the small-scale, strong magnetic field regions. RP GUHATHAKURTA, M (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GSFC,GREENBELT,MD 20771, USA. NR 9 TC 9 Z9 9 U1 0 U2 0 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0038-0938 J9 SOL PHYS JI Sol. Phys. PD JUN PY 1994 VL 152 IS 1 BP 181 EP 188 DI 10.1007/BF01473202 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NY582 UT WOS:A1994NY58200029 ER PT J AU TOBISKA, WK AF TOBISKA, WK TI MODELED SOFT-X-RAY SOLAR IRRADIANCES SO SOLAR PHYSICS LA English DT Article; Proceedings Paper CT IAU Colloquium NO 143 on the Sun as a Variable Star: Solar and Stellar Irradiance Variations CY JUN 20-25, 1993 CL BOULDER, CO SP INT ASTRON UNION ID THERMOSPHERIC NITRIC-OXIDE; FLUX; EUV AB Solar soft X-rays have historically been inaccurately modeled in both relative variations and absolute magnitudes by empirical solar extreme ultraviolet (EUV) irradiance models. This is a result of the use of a limited number of rocket data sets which were primarily associated with the calibration of the AE-E satellite EUV data set. In this work, the EUV91 solar EUV irradiance model has been upgraded to improve the accuracy of the 3.0 to 5.0 nm relative irradiance variations. The absolute magnitude estimate of the flux in this wavelength range has also been revised upwards. The upgrade was accomplished by first digitizing the SOLRAD 11 satellite 4.4 to 6.0 nm measured energy flux data set, then extracting and extrapolating a derived 3.0 to 5.0 nm photon flux from these data, and finally by performing a correlation between these derived data and the daily and 81-day mean 10.7 cm radio flux emission using a multiple linear regression technique. A correlation coefficient of greater than 0.9 was obtained between the dependent and independent data sets. The derived and modeled 3.0 to 5.0 nm flux varies by more than an order of magnitude over solar cycle, ranging from a flux below 1 x 10(8) to a flux greater than 1 x 10(9) photons cm-2 S-1. Solar rotational (27-day) variations in the flux magnitude are a factor of 2. The derived and modeled irradiance absolute values are an order of magnitude greater than previous values from rocket data sets related to the calibration of the AE-E satellite. RP TOBISKA, WK (reprint author), JPL,TELOS,MS 264-765,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 12 TC 13 Z9 13 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 JUN PY 1994 VL 152 IS 1 BP 207 EP 215 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NY582 UT WOS:A1994NY58200033 ER PT J AU CHAN, KL MAYR, HG AF CHAN, KL MAYR, HG TI ROTATING CONVECTION AND THE SOLAR DIFFERENTIAL ROTATION SO SOLAR PHYSICS LA English DT Article ID CIRCULATION; DYNAMOS; MODELS AB We discuss the implication of a numerical experiment on rotating convection and its relevance to the construction of a model for the solar differential rotation. C1 NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. RP APPL RES CORP, LANDOVER, MD 20785 USA. OI Chan, Kwing/0000-0002-6428-1812 NR 32 TC 2 Z9 2 U1 0 U2 0 PU SPRINGER PI DORDRECHT PA VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS SN 0038-0938 EI 1573-093X J9 SOL PHYS JI Sol. Phys. PD JUN PY 1994 VL 152 IS 1 BP 283 EP 290 DI 10.1007/BF01473216 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NY582 UT WOS:A1994NY58200043 ER PT J AU PAP, JM FROHLICH, C HUDSON, HS TOBISKA, WK AF PAP, JM FROHLICH, C HUDSON, HS TOBISKA, WK TI THE SUN AS A VARIABLE-STAR - SOLAR AND STELLAR IRRADIANCE VARIATIONS - PREFACE SO SOLAR PHYSICS LA English DT Editorial Material C1 WORLD RADIAT CTR,PHYS METEOROL OBSERV DAVOS,DAVOS,SWITZERLAND. UNIV HAWAII,INST ASTRON,HONOLULU,HI 96822. RP PAP, JM (reprint author), JET PROP LAB,TELOS MS 264-765,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 0 TC 1 Z9 1 U1 0 U2 0 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0038-0938 J9 SOL PHYS JI Sol. Phys. PD JUN PY 1994 VL 152 IS 1 BP R9 EP R12 DI 10.1007/BF01473174 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NY582 UT WOS:A1994NY58200001 ER PT J AU SAUKE, TB BECKER, JF LOEWENSTEIN, M GUTIERREZ, TD BRATTAN, CG AF SAUKE, TB BECKER, JF LOEWENSTEIN, M GUTIERREZ, TD BRATTAN, CG TI AN OVERVIEW OF ISOTOPIC ANALYSIS USING TUNABLE DIODE-LASER SPECTROMETRY SO SPECTROSCOPY LA English DT Article ID SPECTROSCOPY; RATIOS; CO2 AB Lead-salt tunable diode lasers are currently available with operating temperatures above 77 K and with excellent single-mode characteristics, making them useful for spectroscopy in the mid-infrared spectral range. In this article, we describe a stable isotope laser spectrometer and a direct-absorbance infrared spectroscopic technique that can determine isotopic ratios of carbon and oxygen, Initial results of C-13/C-12 measurements indicate an accuracy of better than 0.4%. Higher accuracy is expected from improvements now being implemented. C1 NASA,AMES RES CTR,SOLAR SYST EXPLORAT BRANCH,MOFFETT FIELD,CA 94035. NASA,AMES RES CTR,ATMOSPHER CHEM & DYNAM BRANCH,MOFFETT FIELD,CA 94035. SAN JOSE STATE UNIV,DEPT PHYS,SAN JOSE,CA 95192. NR 16 TC 5 Z9 5 U1 0 U2 0 PU ADVANSTAR COMMUNICATIONS PI DULUTH PA 131 W FIRST ST, DULUTH, MN 55802 SN 0887-6703 J9 SPECTROSCOPY JI Spectroscopy PD JUN PY 1994 VL 9 IS 5 BP 34 EP & PG 0 WC Spectroscopy SC Spectroscopy GA RF248 UT WOS:A1994RF24800008 ER PT J AU SINGH, J VELLAIKAL, M AF SINGH, J VELLAIKAL, M TI MICROSTRUCTURAL EVOLUTION OF DIAMOND GROWTH ON IRON SILICIDE SILICON SUBSTRATES BY HOT-FILAMENT CHEMICAL-VAPOR-DEPOSITION SO SURFACE & COATINGS TECHNOLOGY LA English DT Article ID THIN-FILMS; NUCLEATION; PHASE AB During hot filament chemical vapor deposition (HFCVD), the presence of iron silicide on the surface of silicon substrates was found to enhance diamond nucleation density. Specimens were prepared by laser ablating iron onto the substrate, followed by isothermal annealing at 700-degrees-C. A high resolution transmission electron microscope showed that an amorphous diamond-like carbon (DLC) layer about 8-10 nm thick formed on the iron silicide phase during HFCVD. The DLC layer locally recrystallized which created a nucleation site for the subsequent growth of diamond. DLC will be a precursor layer for diamond growth. C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. N CAROLINA STATE UNIV,DEPT MAT SCI & ENGN,RALEIGH,NC 27695. NR 25 TC 7 Z9 7 U1 2 U2 4 PU ELSEVIER SCIENCE SA LAUSANNE PI LAUSANNE 1 PA PO BOX 564, 1001 LAUSANNE 1, SWITZERLAND SN 0257-8972 J9 SURF COAT TECH JI Surf. Coat. Technol. PD JUN PY 1994 VL 64 IS 3 BP 131 EP 137 DI 10.1016/0257-8972(94)90099-X PG 7 WC Materials Science, Coatings & Films; Physics, Applied SC Materials Science; Physics GA NQ529 UT WOS:A1994NQ52900001 ER PT J AU BACMEISTER, JT NEWMAN, PA GARY, BL CHAN, KR AF BACMEISTER, JT NEWMAN, PA GARY, BL CHAN, KR TI AN ALGORITHM FOR FORECASTING MOUNTAIN WAVE-RELATED TURBULENCE IN THE STRATOSPHERE SO WEATHER AND FORECASTING LA English DT Article AB A global mountain wave parameterization for prediction of wave-related displacements and turbulence is described. The parameterization is used with input from National Meteorological Center analyses of wind and temperature to examine small-scale disturbances encountered by the National Aeronautics and Space Administration high-altitude ER-2 during the Second Airborne Arctic Stratosphere Experiment. The magnitude and location of observed large wave events are well reproduced. A strong correlation is suggested between patches of moderate turbulence encountered by the ER-2 and locations where breaking mountain waves are predicted by the parameterization. These facts suggest that useful forecasts of global mountain wave activity, including wave-related clear-air turbulence, can be made quickly and inexpensively using our mountain wave parameterization with input from current numerical forecast models. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. NASA,JET PROP LAB,PASADENA,CA. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RP BACMEISTER, JT (reprint author), USN,RES LAB,EO HULBURT CTR SPACE RES,CODE 7641,WASHINGTON,DC 20375, USA. RI Newman, Paul/D-6208-2012 OI Newman, Paul/0000-0003-1139-2508 NR 0 TC 48 Z9 48 U1 0 U2 3 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0882-8156 J9 WEATHER FORECAST JI Weather Forecast. PD JUN PY 1994 VL 9 IS 2 BP 241 EP 253 DI 10.1175/1520-0434(1994)009<0241:AAFFMW>2.0.CO;2 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA QL524 UT WOS:A1994QL52400007 ER PT J AU DEYOUNG, RJ WEN, ST AF DEYOUNG, RJ WEN, ST TI LASER ELEMENTAL MASS ANALYSIS AT LARGE DISTANCES SO APPLIED PHYSICS LETTERS LA English DT Article ID ION TRAP AB A Nd:YAG laser is used to produce a plasma on targets of Al, Cu, Ge, Ag, and a lunar simulant. Ion energies for 1 X 10(9) W/cm2 were found to be between 550 and 900 eV Some of these ions travel down a 11.1-m evacuated tube to an ion trap 1-m time-of-flight spectrometer producing a mass spectrum of a lunar simulant, demonstrating the ability to analyze targets at significant remote distances. C1 HAMPTON UNIV,HAMPTON,VA 23668. RP DEYOUNG, RJ (reprint author), NASA,LANGLEY RES CTR,HAMPTON,VA 23681, USA. NR 6 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 MAY 30 PY 1994 VL 64 IS 22 BP 2943 EP 2945 DI 10.1063/1.111418 PG 3 WC Physics, Applied SC Physics GA NN752 UT WOS:A1994NN75200011 ER PT J AU GUNAPALA, SD PARK, JS LIN, TL LIU, JK BANDARA, KMSV AF GUNAPALA, SD PARK, JS LIN, TL LIU, JK BANDARA, KMSV TI VERY LONG-WAVELENGTH GAAS ALXGA1-XAS INFRARED HOT-ELECTRON TRANSISTOR SO APPLIED PHYSICS LETTERS LA English DT Article ID PHOTODETECTORS AB We have demonstrated a bound-to-continuum state GaAs/AlxGa1-xAs infrared hot electron transistor which has a peak response at lambda(p)=16.3 mum. This device utilizes a bound-to-continuum quantum well infrared photodetector as a photosensitive emitter and a wide AlxGa1-xAs barrier between the base and the collector as an energy discriminating filter. An excellent photocurrent transfer ratio of alpha(p)=0.12 and very low dark current transfer ratio of alpha(d)=7.2X10(-5) is achieved at a temperature of T=60 K. C1 UNIV PERADENIYA,DEPT PHYS,PERADENIYA,SRI LANKA. RP GUNAPALA, SD (reprint author), JET PROP LAB,CTR SPACE MICROELECTR TECHNOL,PASADENA,CA 91109, USA. NR 9 TC 1 Z9 1 U1 1 U2 1 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 0003-6951 J9 APPL PHYS LETT JI Appl. Phys. Lett. PD MAY 30 PY 1994 VL 64 IS 22 BP 3003 EP 3005 DI 10.1063/1.111385 PG 3 WC Physics, Applied SC Physics GA NN752 UT WOS:A1994NN75200031 ER PT J AU MAVRIPLIS, DJ MARTINELLI, L AF MAVRIPLIS, DJ MARTINELLI, L TI MULTIGRID SOLUTION OF COMPRESSIBLE TURBULENT-FLOW ON UNSTRUCTURED MESHES USING A 2-EQUATION MODEL SO INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS LA English DT Article DE UNSTRUCTURED MULTIGRID TURBULENCE MESHES ID NAVIER-STOKES EQUATIONS; LOW REYNOLDS-NUMBER; TRIANGULAR MESHES; CHANNEL FLOW; WALL AB The steady state solution of the system of equations consisting of the full Navier-Stokes equations and two turbulence equations has been obtained using a multigrid strategy on unstructured meshes. The flow equations and turbulence equations are solved in a loosely coupled manner. The flow equations are advanced in time using a multistage Runge-Kutta time-stepping scheme with a stability-bound local time step, while the turbulence equations are advanced in a point-implicit scheme with a time step which guarantees stability and positivity. Low-Reynolds-number modifications to the original two-equation model are incorporated in a manner which results in well-behaved equations for arbitrarily small wall distances. A variety of aerodynamic flows are solved, initializing all quantitities with uniform freestream values. Rapid and uniform convergence rates for the flow and turbulence equations are observed. C1 PRINCETON UNIV,PRINCETON,NJ 08544. RP MAVRIPLIS, DJ (reprint author), NASA,LANGLEY RES CTR,INST COMP APPLICAT SCI & ENGN,HAMPTON,VA 23665, USA. NR 24 TC 16 Z9 18 U1 0 U2 2 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX, ENGLAND PO19 1UD SN 0271-2091 J9 INT J NUMER METH FL JI Int. J. Numer. Methods Fluids PD MAY 30 PY 1994 VL 18 IS 10 BP 887 EP 914 DI 10.1002/fld.1650181002 PG 28 WC Computer Science, Interdisciplinary Applications; Mathematics, Interdisciplinary Applications; Mechanics; Physics, Fluids & Plasmas SC Computer Science; Mathematics; Mechanics; Physics GA NM346 UT WOS:A1994NM34600001 ER PT J AU FISHMAN, GJ BHAT, PN MALLOZZI, R HORACK, JM KOSHUT, T KOUVELIOTOU, C PENDLETON, GN MEEGAN, CA WILSON, RB PACIESAS, WS GOODMAN, SJ CHRISTIAN, HJ AF FISHMAN, GJ BHAT, PN MALLOZZI, R HORACK, JM KOSHUT, T KOUVELIOTOU, C PENDLETON, GN MEEGAN, CA WILSON, RB PACIESAS, WS GOODMAN, SJ CHRISTIAN, HJ TI DISCOVERY OF INTENSE GAMMA-RAY FLASHES OF ATMOSPHERIC ORIGIN SO SCIENCE LA English DT Article ID THUNDERSTORMS AB Detectors aboard the Compton Gamma Ray Observatory have observed an unexplained terrestrial phenomenon: brief, intense flashes of gamma rays. These flashes must originate in the atmosphere at altitudes above at least 30 kilometers in order to escape atmospheric absorption and reach the orbiting detectors. At least a dozen such events have been detected over the past 2 years. The photon spectra from the events are very hard (peaking in the high-energy portion of the spectrum) and are consistent with bremsstrahlung emission from energetic (million-electron volt) electrons. The most likely origin of these high-energy electrons, although speculative at this time, is a rare type of high-altitude electrical discharge above thunderstorm regions. C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,UNIV SPACE RES ASSOC,HUNTSVILLE,AL 35812. UNIV ALABAMA,DEPT PHYS,HUNTSVILLE,AL 35899. RP FISHMAN, GJ (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,SPACE SCI LAB,HUNTSVILLE,AL 35812, USA. RI Horack, John/J-6670-2016 NR 23 TC 384 Z9 385 U1 0 U2 10 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 SN 0036-8075 J9 SCIENCE JI Science PD MAY 27 PY 1994 VL 264 IS 5163 BP 1313 EP 1316 DI 10.1126/science.264.5163.1313 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA NN767 UT WOS:A1994NN76700041 PM 17780850 ER PT J AU DEJAGER, OC STECKER, FW SALAMON, MH AF DEJAGER, OC STECKER, FW SALAMON, MH TI ESTIMATE OF THE INTERGALACTIC INFRARED RADIATION-FIELD FROM GAMMA-RAY OBSERVATIONS OF THE GALAXY MRK421 SO NATURE LA English DT Article ID MARKARIAN-421 AB THE magnitude of the intergalactic infrared radiation field (IIRF) is of fundamental importance to investigations of the evolution of galaxies. Bursts of star formation, which seem to be critically important to galaxy evolution, are characterized by large infrared luminosities(1), yet ie have little knowledge of the frequency and intensity of starbursts in the early Universe. Unfortunately, direct observational determinations of the IIRF are plagued by the difficulty of separating the extragalactic emission from Galactic foreground radiation and the zodiacal light in the Solar System, and have so far produced only upper limits that are far above theoretical expectations(2). We have previously proposed(3) a way to use ground-based observations of high-energy gamma-rays to probe the IIRF, and here we apply our method to the spectrum(4,5) of the BL Lac object Mrk421. The intensity we derive for the IIRF is consistent with the conversion of at least 30% of the energy from stellar nucleosynthesis to infrared radiation, both from emission by cool stars and as a result of absorption and re-emission by interstellar dust grains. C1 NASA, GODDARD SPACE FLIGHT CTR, HIGH ENERGY ASTROPHYS LAB, GREENBELT, MD 20771 USA. UNIV UTAH, INST HIGH ENERGY ASTROPHYS, SALT LAKE CITY, UT 84112 USA. UNIV UTAH, DEPT PHYS, SALT LAKE CITY, UT 84112 USA. RP DEJAGER, OC (reprint author), POTCHEFSTROOM UNIV CHRISTIAN HIGHER EDUC, DEPT PHYS, SPACE RES UNIT, POTCHEFSTROOM 2520, SOUTH AFRICA. RI Stecker, Floyd/D-3169-2012 NR 24 TC 55 Z9 55 U1 0 U2 1 PU NATURE PUBLISHING GROUP PI LONDON PA MACMILLAN BUILDING, 4 CRINAN ST, LONDON N1 9XW, ENGLAND SN 0028-0836 J9 NATURE JI Nature PD MAY 26 PY 1994 VL 369 IS 6478 BP 294 EP 296 DI 10.1038/369294a0 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA NN109 UT WOS:A1994NN10900040 ER PT J AU HIROI, T PIETERS, CM AF HIROI, T PIETERS, CM TI ESTIMATION OF GRAIN SIZES AND MIXING RATIOS OF FINE POWDER MIXTURES OF COMMON GEOLOGIC MINERALS SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID REFLECTANCE SPECTRA; QUANTITATIVE-ANALYSIS; SPECTROSCOPY; ABUNDANCES AB Two different approaches for modeling reflectance spectra of intimate mixtures, Hapke's model and the isograin model, are used to estimate grain sizes and mixing ratios of powder mixtures of three geologic minerals: olivine, orthopyroxene, and plagioclase. In Hapke's model, scattering and extinction efficiencies are mixed separately, and both models employ semiempirical refractive index spectra for component minerals. Mixing ratios of mixtures of grain size 45-75 mum are well estimated by both models assuming a common grain size of 60 mum and optimizing the constants for the single-particle scattering. For each model, effective grain size ratios for mineral constituents in mixtures of grain size <25 mum, are derived successfully that allows mineral abundances to be accurately predicted within -4 wt%. On the other hand, neither model can accurately predict mineral reflectance spectra for its smaller grain sizes (<25 and 25-45 mum) using an absorption coefficient spectrum derived from a larger grain size (45-75 mum). The errors in both models are significantly reduced if surface roughness effects of the smaller grain-size fractions are modeled. C1 BROWN UNIV,DEPT GEOL SCI,PROVIDENCE,RI 02912. RP HIROI, T (reprint author), NASA,LYNDON B JOHNSON SPACE CTR,DIV SOLAR SYST EXPLORAT,SN3,HOUSTON,TX 77058, USA. NR 11 TC 57 Z9 57 U1 1 U2 5 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 MAY 25 PY 1994 VL 99 IS E5 BP 10867 EP 10879 DI 10.1029/94JE00841 PG 13 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA NQ252 UT WOS:A1994NQ25200002 ER PT J AU GIBSON, MA KNUDSEN, CW BRUENEMAN, DJ ALLEN, CC KANAMORI, H MCKAY, DS AF GIBSON, MA KNUDSEN, CW BRUENEMAN, DJ ALLEN, CC KANAMORI, H MCKAY, DS TI REDUCTION OF LUNAR BASALT 70035 - OXYGEN YIELD AND REACTION-PRODUCT ANALYSIS SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID IRON AB Oxygen production from a lunar rock has been experimentally demonstrated for the first time. A 10 g sample of high-Ti basalt 70035 was reduced with hydrogen in seven experiments at temperatures of 900-1050-degrees-C and pressures of 14.7-150 psia. In all experiments, water evolution began almost immediately and was essentially complete in tens of minutes. Oxygen yields ranged from 2.93 to 4.61% of the starting sample weight, and showed weak dependence on temperature and pressure. Analysis of the solid samples demonstrated total reduction of Fe2+ in ilmenite and small degrees of reduction in olivine and pyroxene. TiO2 Was also partially reduced to one or more suboxides. Data from these experiments provide a basis for predicting the yield of oxygen from lunar basalt as well as new constraints on natural reduction in the lunar regolith. C1 LOCKHEED ENGN & SCI CO,HOUSTON,TX. SHIMIZU CORP,SPACE PROJECT OFF,TOKYO,JAPAN. NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058. RP GIBSON, MA (reprint author), CARBOTEK DEV LABS,16223 PK ROW,SUITE 100,HOUSTON,TX 77084, USA. NR 46 TC 12 Z9 13 U1 1 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD MAY 25 PY 1994 VL 99 IS E5 BP 10887 EP 10897 DI 10.1029/94JE00787 PG 11 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA NQ252 UT WOS:A1994NQ25200004 ER PT J AU HUNING, JR AF HUNING, JR TI OZONE CAMPAIGN WILL FORGE AHEAD SO AVIATION WEEK & SPACE TECHNOLOGY LA English DT Letter RP HUNING, JR (reprint author), NASA,AIRBORNE SCI OFF,MISS PLANET EARTH,WASHINGTON,DC 20546, USA. NR 1 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 MAY 23 PY 1994 VL 140 IS 21 BP 6 EP 6 PG 1 WC Engineering, Aerospace SC Engineering GA NN323 UT WOS:A1994NN32300003 ER PT J AU DOWNEY, JP AF DOWNEY, JP TI STATIC AND DYNAMIC SCALING PROPERTIES OF SINGLE, SELF-AVOIDING POLYMER-CHAINS IN 2 DIMENSIONS VIA THE BOND FLUCTUATION METHOD OF MONTE-CARLO SIMULATION SO MACROMOLECULES LA English DT Article ID LATTICE MODELS; COORDINATION-NUMBER; 0 POINT AB Monte Carlo simulations utilizing the bond fluctuation method for a square lattice were performed to simulate the dynamics of two-dimensional polymer chains. Relaxation times of the modes were determined as were average intrachain distances. Scaling exponents were found relating the relaxation times with mode number and the total number of chain segments. Scaling exponents relating intrachain distance with mode number and the total number of chain segments were also found. Scaling behavior indicated that internal fragments of the chains were more expanded than would be the case of a self-similar chain but that the higher order modes relaxed more quickly relative to the lower order modes than would be the case for a Rouse chain. Small but noticeable cross-correlations between the modes were observed. RP DOWNEY, JP (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,ES74,HUNTSVILLE,AL 35812, USA. NR 18 TC 5 Z9 5 U1 0 U2 1 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0024-9297 J9 MACROMOLECULES JI Macromolecules PD MAY 23 PY 1994 VL 27 IS 11 BP 2929 EP 2932 DI 10.1021/ma00089a006 PG 4 WC Polymer Science SC Polymer Science GA NP311 UT WOS:A1994NP31100006 ER PT J AU TONG, WM WILLIAMS, RS YANASE, A SEGAWA, Y ANDERSON, MS AF TONG, WM WILLIAMS, RS YANASE, A SEGAWA, Y ANDERSON, MS TI ATOMIC-FORCE MICROSCOPE STUDY OF GROWTH-KINETICS - SCALING IN THE HETEROEPITAXY OF CUCL ON CAF2(111) SO PHYSICAL REVIEW LETTERS LA English DT Article ID LUMINESCENCE; CONTINUUM AB We used the molecular beam epitaxial growth of CuCl on CaF2(111) to determine if scaling theory provides insight into the kinetic mechanisms of heteroepitaxy. We measured quantitative surface topographs of several films representing the island nucleation, growth, and coalescence regimes of film growth with an atomic force microscope, and found that the static scaling exponent of all the surfaces was alpha = 0.84 +/- 0.05. This alpha value is closer to theoretical predictions in which surface diffusion is the dominant smoothening mechanism than to those involving evaporation and recondensation. C1 RIKEN,PHOTODYNAM RES CTR,AOBA KU,SENDAI 98932,JAPAN. JET PROP LAB,SPACE MAT SCI & TECHNOL SECT,PASADENA,CA 91109. RP TONG, WM (reprint author), UNIV CALIF LOS ANGELES,CTR SOLID STATE SCI,DEPT CHEM & BIOCHEM,LOS ANGELES,CA 90024, USA. RI Tong, William/D-2564-2010; Williams, R. Stanley/A-8281-2009 OI Williams, R. Stanley/0000-0003-0213-4259 NR 21 TC 73 Z9 74 U1 0 U2 3 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0031-9007 J9 PHYS REV LETT JI Phys. Rev. Lett. PD MAY 23 PY 1994 VL 72 IS 21 BP 3374 EP 3377 DI 10.1103/PhysRevLett.72.3374 PG 4 WC Physics, Multidisciplinary SC Physics GA NM835 UT WOS:A1994NM83500022 ER PT J AU AFZAL, RS AF AFZAL, RS TI MARS OBSERVER LASER ALTIMETER - LASER TRANSMITTER SO APPLIED OPTICS LA English DT Article DE DIODE PUMPED; SOLID-STATE LASER; SPACE QUALIFIED AB The Mars Observer Laser Altimeter utilizes a space-qualified diode-laser-pumped Q-switched Nd:YAG laser transmitter. A simple numerical model of the laser energetics is presented, which predicts the pulse energy and pulse width. Comparisons with the measured data available are made. The temperature dependence of the laser transmitter is also predicted. This dependence prediction is particularly important in determining the operational temperature range of the transmitter. Knowing the operational temperature range is especially important for a passive, thermally controlled laser operating in space. RP AFZAL, RS (reprint author), NASA, GODDARD SPACE FLIGHT CTR, CODE 924, GREENBELT, MD 20771 USA. NR 11 TC 73 Z9 81 U1 1 U2 4 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 0003-6935 J9 APPL OPTICS JI Appl. Optics PD MAY 20 PY 1994 VL 33 IS 15 BP 3184 EP 3188 PG 5 WC Optics SC Optics GA NM308 UT WOS:A1994NM30800005 PM 20885685 ER PT J AU PILDIS, RA BREGMAN, JN SCHOMBERT, JM AF PILDIS, RA BREGMAN, JN SCHOMBERT, JM TI EXTRAPLANAR EMISSION-LINE GAS IN EDGE-ON GALAXIES SO ASTROPHYSICAL JOURNAL LA English DT Article DE GALAXIES, ISM; GALAXIES, STRUCTURE ID WARM IONIZED-GAS; NGC-891; NGC-4565; DISK AB Seven edge-on galaxies were imaged in Halpha in order to determine if extraplanar emission-line gas (as seen in NGC 891) is a common feature of spiral galaxies. Four of the seven are found to have one or two prominent filamentary extraplanar structures apiece, with typical filament Halpha luminosities of 10(37)-10(38) ergs s-1 and scales of 1-2 kpc. Unlike NGC 891, none of the galaxies has an extensive emission-line halo, to within the sensitivity of the observations, approximately 24 mag per square arcsec in Halpha (equivalent to an emission measure of 19 pc cm-6)-more than 7 times fainter than the diffuse emission of NGC 891. C1 CALTECH,JET PROP LAB,CTR INFRARED PROC & ANAL,PASADENA,CA 91125. RP PILDIS, RA (reprint author), UNIV MICHIGAN,DEPT ASTRON,ANN ARBOR,MI 48109, USA. NR 16 TC 39 Z9 39 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 20 PY 1994 VL 427 IS 1 BP 160 EP & DI 10.1086/174129 PN 1 PG 0 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NM046 UT WOS:A1994NM04600011 ER PT J AU JONES, DL WEHRLE, AE AF JONES, DL WEHRLE, AE TI MORPHOLOGICAL-CHANGES IN THE NGC-6251 JET SO ASTROPHYSICAL JOURNAL LA English DT Article DE GALAXIES, INDIVIDUAL (NGC-6251); GALAXIES, JETS ID GALAXY; M87; SEARCH; MOTION; VLBI AB The giant radio galaxy NGC 6251 is a particularly good object for observational tests of relativistic jet models. Due to its high declination and approximately 0.5 Jy radio nucleus, high-quality VLBI images of the central regions of the source can be made with northern hemisphere arrays. In addition, the large-scale radio morphology strongly suggests that the radio axis lies close to the plane of the sky, so Doppler boosting should be less extreme than in the core-dominated superluminal sources. Earlier 18 cm VLBI observations of NGC 6251 revealed an unexpectedly large jet/counterjet brightness ratio and small transverse motion of a feature in the parsec-scale jet. These early results are difficult to reconcile with the simplest symmetric relativistic jet models. In this paper we present a third-epoch 18 cm VLBI image of the parsec-scale radio jet in NGC 6251, and compare jet morphology over a 5 year time span. The jet shows a minor brightness peak at nearly the same distance from the core as the ''25 mas knot'' seen in the first- and second-epoch VLBI images. This feature is much less pronounced in the third epoch, and a relatively bright, new knot has appeared approximately 12 mas from the core. If this new component had a constant brightness during the 5 years separating the first and third observing epochs, then it must have moved away from the core with an apparent speed of at least 1.2c (compared with an upper limit of 0.23c for motion of the 25 mas knot). However, we cannot yet rule out a local brightening of the inner jet in favor of a new moving component. We determine a lower limit for the jet/counterjet brightness ratio of 100:1 within 6 mas of the core. We also present a new VLA image of the kpc-scale jet with 3'' resolution, made from data obtained during the VLBI observations. The rate of decrease in jet surface brightness from parsec to kiloparsec scales is similar to jets in known superluminal radio sources. C1 JET PROP LAB,CTR INFRARED PROC & ANAL CTR,PASADENA,CA 91125. RP JONES, DL (reprint author), JET PROP LAB,MAIL CODE 238-332,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 19 TC 18 Z9 18 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 20 PY 1994 VL 427 IS 1 BP 221 EP 226 DI 10.1086/174134 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NM046 UT WOS:A1994NM04600016 ER PT J AU BHATIA, AK KASTNER, SO KEENAN, FP CONLON, ES WIDING, KG AF BHATIA, AK KASTNER, SO KEENAN, FP CONLON, ES WIDING, KG TI THE FE-XIV SPECTRUM - PREDICTED LINE-INTENSITIES AND SOLAR IDENTIFICATIONS SO ASTROPHYSICAL JOURNAL LA English DT Article DE ATOMIC DATA; LINE, IDENTIFICATION; SUN, CORONA; SUN, GENERAL; SUN, UV RADIATION ID TRANSITION-PROBABILITIES; ISOELECTRONIC SEQUENCE; XUV OBSERVATIONS; CROSS-SECTIONS; CORONAL LINES; COMPACT FLARE; EUV SPECTRUM; NI-XVI; IONS; WAVELENGTHS AB Level populations and line intensities have been calculated in a 40-level model of Fe XIV which includes the configurations 3p3 and 3s3p3d. The results have been compared against intensities of weaker, unidentified, or tentatively classified lines in published solar line lists including a recent GSFC/SERTS high-resolution list, and in presently measured archival NRL/S082A active region spectra. Seven new lines are identified as Fe XIV transitions; five other observed, unidentified lines are considered to be Fe XIV transitions on the basis of wave-length coincidence, but require further observations to obtain photometric intensities for verification; one line at 216.93 angstrom is shown to be due to some other ion than Fe XIV. In addition, a unique forbidden infrared (congruent-to 1.25 mum) line originating in the high metastable level 3s3p3d(F-4(9/2)) is found to have an unusual intensity dependence on electron density. C1 MATH SCI CONSULTANTS INC,GREENBELT,MD 20770. QUEENS UNIV BELFAST,DEPT PURE & APPL PHYS,BELFAST BT7 1NN,ANTRIM,NORTH IRELAND. USN,RES LAB,EO HULBURT CTR SPACE RES,WASHINGTON,DC 20375. RP BHATIA, AK (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ASTRON BRANCH,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771, USA. NR 44 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 MAY 20 PY 1994 VL 427 IS 1 BP 497 EP 510 DI 10.1086/174160 PN 1 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NM046 UT WOS:A1994NM04600042 ER PT J AU BARTHELMY, SD BARTLETT, LM GEHRELS, N LEVENTHAL, M TEEGARDEN, BJ TUELLER, J BELYAEV, S LEBEDEV, V KLAPDORKLEINGROTHAUS, HV AF BARTHELMY, SD BARTLETT, LM GEHRELS, N LEVENTHAL, M TEEGARDEN, BJ TUELLER, J BELYAEV, S LEBEDEV, V KLAPDORKLEINGROTHAUS, HV TI GRIS BACKGROUND REDUCTION RESULTS USING ISOTOPICALLY ENRICHED GE SO ASTROPHYSICAL JOURNAL LA English DT Article DE GAMMA-RAYS, OBSERVATIONS; INSTRUMENTATION, DETECTORS ID GAMMA-RAY SPECTROMETERS AB The Gamma Ray Imaging Spectrometer (GRIS) was flown twice from Alice Springs, Australia, in the spring of 1992 for a total of 32 hr at float altitude. One of the seven Ge detectors was isotopically enriched (>97% Ge-70). This was the first time an enriched-Ge detector was used for astrophysical observations. Because of its thick anticoincidence shield, the GRIS instrument background is dominated by internal beta-decay in the energy range of 200-1000 keV. Half of the contribution in this beta-decay ''hump'' is due to neutron-activated Ge-74. In this energy range, GRIS observed a factor of 2 reduction in the background in the enriched detector, as predicted. In future instruments (e.g., INTEGRAL), with thicker anticoincidence shields and smaller apertures, the background reduction will be even larger. Three strong instrumental background lines (54, 67, and 139 keV) are also eliminated. The elimination of the first two is particularly important for cylotron line observations. C1 MAX PLANCK INST NUCL PHYS,W-6900 HEIDELBERG 1,GERMANY. UNIV MASSACHUSETTS,AMHERST,MA 01003. UNIV SPACE RES ASSOC,WASHINGTON,DC. IV KURCHATOV INST,MOSCOW,RUSSIA. RP BARTHELMY, SD (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. RI Gehrels, Neil/D-2971-2012; Tueller, Jack/D-5334-2012; Barthelmy, Scott/D-2943-2012 NR 4 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 MAY 20 PY 1994 VL 427 IS 1 BP 519 EP 521 DI 10.1086/174162 PN 1 PG 3 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NM046 UT WOS:A1994NM04600044 ER PT J AU PETUCHOWSKI, SJ BENNETT, CL HAAS, MR ERICKSON, EF LORD, SD RUBIN, RH COLGAN, SWJ HOLLENBACH, DJ AF PETUCHOWSKI, SJ BENNETT, CL HAAS, MR ERICKSON, EF LORD, SD RUBIN, RH COLGAN, SWJ HOLLENBACH, DJ TI THE [N-II] 205-MICRON LINE IN M82 - THE WARM IONIZED MEDIUM SO ASTROPHYSICAL JOURNAL LA English DT Article DE GALAXIES, INDIVIDUAL (M82); ISM, GENERAL ID PHOTODISSOCIATION REGIONS; CONTINUUM OBSERVATIONS; INTERSTELLAR-MEDIUM; INFRARED-EMISSION; GAS; NUCLEUS; GALAXY; MODEL; RADIO AB Detection of the 205 mum fine structure line of N II in the nearby starburst galaxy M82 is reported. The intensity within a 54'' (FWHM) beam is (7.1 +/- 1.2) X 10(-19) W cm-2. The ratio of the intensity of the recently detected 122 mum line to that of the 205 mum line is =4.2(-1.2)+1.6, significantly larger than the corresponding Galactic value of 1.6 +/- 0.3, reflecting higher electron densities within the central 850 pc of M82 in comparison to the COBE Galactic average. The 205 mum line profile is consistent with other far-infrared fine-structure line profiles observed in M82. The observations are interpreted in the context of a two-component model of the ionized medium in M82. We find that a component of density as low as approximately 50 cm(-3) can comprise up to 70% of the total mass of warm ionized gas within the beam. The balance of the ionized mass is comprised of a component of density greater than or similar to 100 cm-3. A model is explored in which the denser ionized medium constitutes the boundaries of neutral surfaces which border the expanding hot plasma from the nuclear region. C1 NASA, AMES RES CTR, DIV SPACE SCI, MOFFETT FIELD, CA 94035 USA. RP PETUCHOWSKI, SJ (reprint author), NASA, GODDARD SPACE FLIGHT CTR, ASTRON & SOLAR PHYS LAB, MC 685, GREENBELT, MD 20771 USA. RI Colgan, Sean/M-4742-2014 NR 32 TC 20 Z9 20 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 MAY 20 PY 1994 VL 427 IS 1 BP L17 EP L20 DI 10.1086/187354 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NM047 UT WOS:A1994NM04700005 ER PT J AU Nielsen, JE Rood, RB Douglass, AR Cerniglia, MC Allen, DJ Rosenfield, JE AF Nielsen, J. Eric Rood, Richard B. Douglass, Anne R. Cerniglia, Mark C. Allen, Dale J. Rosenfield, Joan E. TI Tracer evolution in winds generated by a global spectral mechanistic model SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article AB The lower boundary of a spectral mechanistic model is prescribed with 100 hPa geopotentials, and its performance during a November 1989 through March 1990 integration is compared with National Meteorological Center observations. Although the stratopause temperatures quickly become biased near the pole in both hemispheres, the model develops a residual mean circulation which shows significant descent over the winter pole and ascent in the tropics and over the summer pole at pressures less than 10 hPa. The daily correspondence of observed to modeled features in the upper stratosphere and mesosphere degrades after one month. However, the long-term variability qualitatively follows the observations. The results of off-line transport experiments are also described. A passive tracer is instantaneously injected into the flow over the poles and evolves in a manner which is consistent with the residual mean circulation. It demonstrates a significant cross-equatorial flux in the mesosphere near solstice, and air which originates in the southern hemisphere polar mesosphere can be found descending deep into the northern polar stratosphere at the end of the integration. Nitrous oxide is also transported, and its ability to act as a dynamical tracer is evaluated by comparison to the evolution of the passive tracer. C1 [Nielsen, J. Eric; Cerniglia, Mark C.; Allen, Dale J.] NASA, Goddard Space Flight Ctr, Appl Res Corp, Greenbelt, MD 20771 USA. [Rosenfield, Joan E.] NASA, Goddard Space Flight Ctr, Univ Space Res Associates, Greenbelt, MD 20771 USA. RP Nielsen, JE (reprint author), NASA, Goddard Space Flight Ctr, Appl Res Corp, Code 916, Greenbelt, MD 20771 USA. RI Allen, Dale/F-7168-2010; Douglass, Anne/D-4655-2012; Rood, Richard/C-5611-2008 OI Allen, Dale/0000-0003-3305-9669; Rood, Richard/0000-0002-2310-4262 FU EOS project FX The authors thank the reviewers for their valuable comments. Funds for computations were provided by the EOS project. This is contribution number 73 from the Stratospheric General Circulation with Chemistry Project. NR 43 TC 9 Z9 9 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 MAY 20 PY 1994 VL 99 IS D3 BP 5399 EP 5420 DI 10.1029/93JD03578 PG 22 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA V04QH UT WOS:000207072400010 ER PT J AU Baum, BA Arduini, RF Wielicki, BA Minnis, P Tsay, SC AF Baum, Bryan A. Arduini, Robert F. Wielicki, Bruce A. Minnis, Patrick Tsay, Si-Chee TI Multilevel cloud retrieval using multispectral HIRS and AVHRR data: Nighttime oceanic analysis SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article AB A multispectral, multiresolution (MSMR) method is developed for analyzing scenes of overlapping cloud layers. The MSMR method is applied to data from the NOAA 11 advanced very high resolution radiometer (AVHRR) and the high-resolution infrared radiometer sounder (HIRS-2). The data are from a nighttime oceanic scene in which a semitransparent cirrus veil overlays a large-scale stratus cloud. Low-cloud and clear-sky radiances are determined using a spatial coherence technique. Middle to upper level cloud pressures and radiances are estimated from HIRS-2 15-mu m CO2 band radiometric data. The MSMR method improves the interpretation of a nighttime, oceanic scene containing thin cirrus over a large-scale stratiform cloud. If, for example, the same scene is analyzed using only the AVHRR 10.8-mu m channel, the accompanying retrieved cloud heights are found to be between the cirrus and stratus cloud heights and are incorrectly identified as midlevel altostratus clouds. Theoretical radiative transfer model results for both water droplet spheres and randomly oriented hexagonal ice crystals are compared to observed AVHRR brightness temperature differences (BTD) between the 3.7- and 10.8-mu m channels (BTD34) and between the 10.8- and 12-mu m channels (BTD45) to distinguish among the effects of cloud optical depth, particle size, and phase for both single-layer clouds and overlapping two-layer clouds. Theoretical BTD calculations are used to estimate the range of effective particle sizes for each cloud layer. The data for the cirrus in the case study region near Bermuda are consistent with theoretical results for relatively small randomly oriented hexagonal ice crystals. The observed BTD34 and BTD45 values are lower for the cirrus above a lower-level cloud than for single-level cirrus with no underlying cloud. In certain cases the BTD analysis provides a way to distinguish between clouds composed of supercooled water droplets rather than ice particles. Analysis of nighttime data permits determination of stratus infrared optical depths smaller than 4. C1 [Baum, Bryan A.; Wielicki, Bruce A.; Minnis, Patrick] NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. [Tsay, Si-Chee] NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. [Arduini, Robert F.] Lockheed Engn & Sci Co, Hampton, VA 23666 USA. RP Baum, BA (reprint author), NASA, Langley Res Ctr, Div Atmospher Sci, Mail Code 420, Hampton, VA 23681 USA. RI Baum, Bryan/B-7670-2011; Tsay, Si-Chee/J-1147-2014; Minnis, Patrick/G-1902-2010 OI Baum, Bryan/0000-0002-7193-2767; Minnis, Patrick/0000-0002-4733-6148 NR 50 TC 64 Z9 65 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 MAY 20 PY 1994 VL 99 IS D3 BP 5499 EP 5514 DI 10.1029/93JD02856 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA V04QH UT WOS:000207072400017 ER PT J AU KENT, GS MCCORMICK, MP WANG, PH AF KENT, GS MCCORMICK, MP WANG, PH TI VALIDATION OF STRATOSPHERIC AEROSOL AND GAS EXPERIMENT-I AND EXPERIMENT-II SATELLITE AEROSOL OPTICAL DEPTH MEASUREMENTS USING SURFACE RADIOMETER DATA SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SAM-II; CORRELATIVE MEASUREMENTS; EXTINCTION MEASUREMENTS; TROPOSPHERIC AEROSOL; SAGE; LIDAR; MODEL; BACKSCATTER; DUSTSONDES; AIRBORNE AB The stratospheric aerosol measurement II, stratospheric aerosol and gas experiment (SAGE) I, and SAGE II series of solar occultation satellite instruments were designed for the study of stratospheric aerosols and gases and have been extensively validated in the stratosphere. They are also capable, under cloud-free conditions, of measuring the extinction due to aerosols in the troposphere. Such tropospheric extinction measurements have yet to be validated by appropriate lidar and in situ techniques. In this paper published atmospheric aerosol optical depth measurements, made from high-altitude observatories during volcanically quiet periods, have been compared with optical depths calculated from local SAGE I and SAGE II extinction profiles. Surface measurements from three such observatories have been used, one located in Hawaii and two within the continental United States. Data have been intercompared on a seasonal basis at wave-lengths between 0.5 and 1.0 mum and found to agree within the range of measurement errors and expected atmospheric variation. The mean rms difference between the optical depths for corresponding satellite and surface measured data sets is 29%, and the mean ratio of the optical depths is 1.09. C1 NASA, LANGLEY RES CTR, DIV ATMOSPHER SCI, HAMPTON, VA 23665 USA. RP KENT, GS (reprint author), SCI & TECHNOL CORP, 101 RES DR, HAMPTON, VA 23666 USA. NR 26 TC 10 Z9 11 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 MAY 20 PY 1994 VL 99 IS D5 BP 10333 EP 10339 DI 10.1029/94JD00167 PG 7 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA NN517 UT WOS:A1994NN51700003 ER PT J AU KAUFMAN, YJ GITELSON, A KARNIELI, A GANOR, E FRASER, RS NAKAJIMA, T MATTOO, S HOLBEN, BN AF KAUFMAN, YJ GITELSON, A KARNIELI, A GANOR, E FRASER, RS NAKAJIMA, T MATTOO, S HOLBEN, BN TI SIZE DISTRIBUTION AND SCATTERING PHASE FUNCTION OF AEROSOL-PARTICLES RETRIEVED FROM SKY BRIGHTNESS MEASUREMENTS SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID TROPOSPHERIC AEROSOLS; NONSPHERICAL PARTICLES; SATELLITE MEASUREMENTS; AIRBORNE MEASUREMENTS; RADIATIVE PROPERTIES; OPTICAL-PROPERTIES; DESERT AEROSOLS; SOLAR-RADIATION; AIR-POLLUTION; MT-PINATUBO AB Ground-based measurements of the solar transmission and sky radiance in a horizontal plane through the Sun are taken in several geographical regions and aerosol types: dust in a desert transition zone in Israel, sulfate particles in Eastern and Western Europe, tropical aerosol in Brazil, and mixed continental/maritime aerosol in California. Stratospheric aerosol was introduced after the eruption of Mount Pinatubo in June 1991. Therefore measurements taken before the eruption are used to analyze the properties of tropospheric aerosol; measurements from 1992 are also used to detect the particle size and concentration of stratospheric aerosol. The measurements are used to retrieve the size distribution and the scattering phase function at large scattering angles of the undisturbed aerosol particles. The retrieved properties represent an average on the entire atmospheric column. A comparison between the retrieved phase function for a scattering angle of 120-degrees, with phase function predicted from the retrieved size distribution, is used to test the assumption of particle homogeneity and sphericity in radiative transfer models (Mie theory). The effect was found to be small (20% +/- 15%). For the stratospheric aerosol (sulfates), as expected, the phase function was very well predicted using the Mie theory. A model with a power law size distribution, based on the spectral dependence of the optical thickness, alpha, cannot estimate accurately the phase function (up to 50% error for lambda = 0.87 mum). Before the Pinatubo eruption the ratio between the volumes of sulfate and coarse particles was very well correlated with alpha. The Pinatubo stratospheric aerosol destroyed this correlation. The aerosol optical properties are compared with analysis of the size, shape, and composition of the individual particles by electron microscopy of in situ samples. The measured volume size distributions before the injection of stratospheric aerosol consistently show two modes, sulfate particles with r(m) < 0.2 mum and coarse particles with r(m) > 0.7 mum. The ''window'' in the tropospheric aerosol in this radius range was used to observe a stable stratospheric aerosol in 1992, with r(m) approximately 0.5 mum. A combination of such optical thickness and sky measurements can be used to assess the direct forcing and the climatic impact of aerosol. Systematic inversion for the key aerosol types (sulfates, smoke, dust, and maritime aerosol) of the size distribution and phase function can give the relationship between the aerosol physical and optical properties that can be used to compute the radiative forcing. This forcing can be validated in dedicated field experiments. C1 MINIST ENVIRONM, INST ENVIRONM RES, TEL AVIV, ISRAEL. TEL AVIV UNIV, SACKLER SCH MED, TEL AVIV, ISRAEL. UNIV TOKYO, CTR CLIMATE SYST RES, TOKYO 113, JAPAN. NASA, GODDARD SPACE FLIGHT CTR, ARC, GREENBELT, MD 20771 USA. NASA, GODDARD SPACE FLIGHT CTR, TERR PHYS LAB, GREENBELT, MD 20771 USA. BEN GURION UNIV NEGEV, INST DESERT RES, SEDE BOQER, ISRAEL. RP KAUFMAN, YJ (reprint author), NASA, GODDARD SPACE FLIGHT CTR, ATMOSPHERES LAB, CODE 913, GREENBELT, MD 20771 USA. RI Gitelson, Anatoly/G-3452-2012; Nakajima, Teruyuki/H-2370-2013 OI Nakajima, Teruyuki/0000-0002-9042-504X NR 45 TC 159 Z9 169 U1 2 U2 20 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 MAY 20 PY 1994 VL 99 IS D5 BP 10341 EP 10356 DI 10.1029/94JD00229 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA NN517 UT WOS:A1994NN51700004 ER PT J AU JENSEN, EJ TOON, OB WESTPHAL, DL KINNE, S HEYSMFIELD, AJ AF JENSEN, EJ TOON, OB WESTPHAL, DL KINNE, S HEYSMFIELD, AJ TI MICROPHYSICAL MODELING OF CIRRUS .1. COMPARISON WITH 1986 FIRE IFO MEASUREMENTS SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID HOMOGENEOUS NUCLEATION RATE; ATMOSPHERIC BOUNDARY-LAYER; GENERAL-CIRCULATION MODEL; OCTOBER 1986; RADIATIVE-TRANSFER; ICE CRYSTALS; SOLUTION DROPLETS; CLOUD DROPLETS; WATER-CONTENT; TEMPERATURE AB We have used a one-dimensional model of cirrus formation to study the development of cirrus clouds during the 1986 First ISCCP (International Satellite Cloud Climatology Project) Regional Experiment (FIRE) intensive field observations (IFO). The cirrus model includes microphysical, dynamical, and radiative processes. Sulfate aerosols, solution drops, ice crystals, and water vapor are all treated as interactive elements in the model. Ice crystal size distributions are fully resolved based on calculations of homogeneous freezing nucleation, growth by water vapor deposition, evaporation, coagulation, and vertical transport. We have focused on the cirrus observed on November 1, 1986. Vertical wind speed for the one-dimensional simulation is taken from a mesoscale model simulation for the appropriate time period. The mesoscale model simulation suggested that strong upward motions over Wyoming and subsequent horizontal transport of upper level moisture were responsible for the cirrus observed over Wisconsin on this date. We assumed that our one-dimensional model could be used to represent a vertical column moving from Wyoming to Wisconsin over a period of several hours. Ice crystal nucleation occurs in our model in the 8 to 10-km region as a result of the strong updrafts (and cooling) early in the simulation. Growth, coagulation, and sedimentation of these ice crystals result in a broad cloud region (5-10 km thick) with an optical depth of 1-2 after a few hours, in agreement with the FIRE measurements. Comparison with aircraft microphysical measurements made over Wisconsin indicates that the simulation generated reasonable ice water content, but the predicted ice number densities are too low, especially for radii less than about 50 mum. Sensitivity tests suggest, that better agreement between simulated and observed microphysical properties is achieved if the nucleation rate is higher or stronger vertical mixing (perhaps associated with multidimensional motions) is present. C1 NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. SAN JOSE STATE UNIV, SAN JOSE, CA 95192 USA. NATL CTR ATMOSPHER RES, BOULDER, CO 80307 USA. RP JENSEN, EJ (reprint author), UNIV CALIF SAN DIEGO, SCRIPPS INST OCEANOG, LA JOLLA, CA 92093 USA. NR 52 TC 113 Z9 113 U1 0 U2 7 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAY 20 PY 1994 VL 99 IS D5 BP 10421 EP 10442 DI 10.1029/93JD02334 PG 22 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA NN517 UT WOS:A1994NN51700011 ER PT J AU JENSEN, EJ TOON, OB WESTPHAL, DL KINNE, S HEYMSFIELD, AJ AF JENSEN, EJ TOON, OB WESTPHAL, DL KINNE, S HEYMSFIELD, AJ TI MICROPHYSICAL MODELING OF CIRRUS .2. SENSITIVITY STUDIES SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID ICE CLOUDS; VOLCANIC AEROSOLS; WATER-CONTENT; TEMPERATURE; CLOUDINESS; PHASE AB The one-dimensional cirrus model described in part 1 of this issue has been used to study the sensitivity of simulated cirrus microphysical and radiative properties to poorly known model parameters, poorly understood physical processes, and environmental conditions. Model parameters and physical processes investigated include nucleation rate, mode of nucleation (e.g., homogeneous freezing of aerosols and liquid droplets or heterogeneous deposition), ice crystal shape, and coagulation. These studies suggest that the leading sources of uncertainty in the model are the phase change (liquid-solid) energy barrier and the ice-water surface energy which dominate the homogeneous freezing nucleation rate and the coagulation sticking efficiency at low temperatures which controls the production of large ice crystals (radii greater than 100 mum). Environmental conditions considered in sensitivity tests were CN size distribution, vertical wind speed, and cloud height. We found that (unlike stratus clouds) variations in the total number of condensation nuclei (CN) have little effect on cirrus microphysical and radiative properties, since nucleation occurs only on the largest CN at the tail of the size distribution. The total number of ice crystals which nucleate has little or no relationship to the number of CN present and depends primarily on the temperature and the cooling rate. Stronger updrafts (more rapid cooling) generate higher ice number densities, ice water content, cloud optical depth, and net radiative forcing. Increasing the height of the clouds in the model leads to an increase in ice number density, a decrease in effective radius, and a decrease in ice water content. The most prominent effect of increasing cloud height was a rapid increase in the net cloud radiative forcing which can be attributed to the change in cloud temperature as well as change in cloud ice crystal size distributions. It has long been recognized that changes in cloud height or cloud area have the greatest potential for causing feedbacks on climate change. Our results suggest that variations in vertical velocity or cloud microphysical changes associated with cloud height changes may also be important. C1 NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. SAN JOSE STATE UNIV, SAN JOSE, CA 95192 USA. NATL CTR ATMOSPHER RES, BOULDER, CO 80307 USA. RP JENSEN, EJ (reprint author), UNIV CALIF SAN DIEGO, SCRIPPS INST OCEANOG, LA JOLLA, CA 92093 USA. RI Heymsfield, Andrew/E-7340-2011 NR 26 TC 36 Z9 36 U1 0 U2 9 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 MAY 20 PY 1994 VL 99 IS D5 BP 10443 EP 10454 DI 10.1029/94JD00226 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA NN517 UT WOS:A1994NN51700012 ER PT J AU DRISCOLL, KT BLAKESLEE, RJ KOSHAK, WJ AF DRISCOLL, KT BLAKESLEE, RJ KOSHAK, WJ TI TIME-AVERAGED CURRENT ANALYSIS OF A THUNDERSTORM USING GROUND-BASED MEASUREMENTS SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID ELECTRIC-FIELDS; MODEL AB The amount of upward current provided to the ionosphere by a thunderstorm that appeared over the Kennedy Space Center (KSC) on July 11, 1978, is reexamined using an analytic equation that describes a bipolar thunderstorm's current contribution to the global circuit in terms of its generator current, lightning currents, the altitudes of its charge centers, and the conductivity profile of the atmosphere. Ground-based measurements, which were obtained from a network of electric field mills positioned at various distances from the thunderstorm, were used to characterize the electrical activity inside the thundercloud. The location of the lightning discharges, the type of lightning, and the amount of charge neutralized during this thunderstorm were computed through a least squares inversion of the measured changes in the electric fields following each lightning discharge. These measurements provided the information necessary to implement the analytic equation, and consequently, a time-averaged estimate of this thunderstorm's current contribution to the global circuit was calculated. From these results the amount of conduction current supplied to the ionosphere by this small thunderstorm was computed to be less than 25% of the time-averaged generator current that flowed between the two vertically displaced charge centers. C1 AUBURN UNIV, DEPT ELECT ENGN, AUBURN, AL 36830 USA. RP DRISCOLL, KT (reprint author), NASA, GEORGE C MARSHALL SPACE FLIGHT CTR, MAIL CODE E543, HUNTSVILLE, AL 35812 USA. NR 26 TC 13 Z9 13 U1 1 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 MAY 20 PY 1994 VL 99 IS D5 BP 10653 EP 10661 DI 10.1029/94JD00098 PG 9 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA NN517 UT WOS:A1994NN51700030 ER PT J AU PRICE, C RIND, D AF PRICE, C RIND, D TI POSSIBLE IMPLICATIONS OF GLOBAL CLIMATE-CHANGE ON GLOBAL LIGHTNING DISTRIBUTIONS AND FREQUENCIES SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID THUNDERSTORMS; THUNDERCLOUDS; CONVECTION; WATER AB The Goddard Institute for Space Studies (GISS) general circulation model (GCM) is used to study the possible implications of past and future climate change on global lightning frequencies. Two climate change experiments were conducted: one for a 2 X CO2 climate (representing a 4.2-degrees-C global warming) and one for a 2% decrease in the solar constant (representing a 5.9-degrees-C global cooling). The results suggest a 30% increase in global lightning activity for the warmer climate and a 24% decrease in global lightning activity for the colder climate. This implies an approximate 5-6% change in global lightning frequencies for every 1-degrees-C global warming/cooling. Both intracloud and cloud-to-ground frequencies are modeled, with cloud-to-ground lightning frequencies showing larger sensitivity to climate change than intracloud frequencies. The magnitude of the modeled lightning changes depends on season, location, and even time of day. C1 COLUMBIA UNIV, NASA, GODDARD INST SPACE STUDIES, NEW YORK, NY 10025 USA. NR 35 TC 110 Z9 119 U1 1 U2 20 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAY 20 PY 1994 VL 99 IS D5 BP 10823 EP 10831 DI 10.1029/94JD00019 PG 9 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA NN517 UT WOS:A1994NN51700055 ER PT J AU EAGLES, DM AF EAGLES, DM TI POSSIBLE HIGH-CURRENT SUPERCONDUCTIVITY AT ROOM-TEMPERATURE IN OXIDIZED POLYPROPYLENE AND OTHER QUASI-ONE-DIMENSIONAL SYSTEMS SO PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS LA English DT Article ID OXIDIZED POLYPROPYLENE; FILMS; CONDUCTIVITY; MECHANISM; LAYERS AB Application is made to quasi one-dimensional systems of the idea of Parmenter, that, in narrow cylindrical regions with thickness smaller than the magnetic-field penetration depth, pairing may be enhanced at very high drift velocities. Enhancements for drift velocities equal to the velocity of sound or to an appropriate phase velocity of optical phonons, of excitonic excitations or of plasmons may be considered. Such enhancements can be larger in quasi one-dimensional systems. Calculations made here, based on Eliashberg theory, indicate that the enhancement of interactions is not great enough to produce high-current superconductivity which has an energy gap in the laboratory frame which is comparable to or greater than that at zero current if the Fermi energy E(F) is large compared with the relevant phonon, plasmon or exciton energy, HBARomega, but simpler calculations indicate that, if E(F) << HBARomega, high-current superconductivity with strong pairing may occur. A theory for E(F) is similar to HBARomega would be useful. The applicability of these ideas to explain reports of room-temperature superconductivity in narrow channels perpendicular to surfaces of films of oxidised polypropylene is discussed. C1 NASA, GEORGE C MARSHALL SPACE FLIGHT CTR, HUNTSVILLE, AL 35812 USA. MAGNET POWER INC, STONY BROOK, NY 11790 USA. RP EAGLES, DM (reprint author), CNRS, CTR RECH PHYS HAUTES TEMP, F-45071 ORLEANS 2, FRANCE. NR 40 TC 12 Z9 12 U1 1 U2 3 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0921-4534 EI 1873-2143 J9 PHYSICA C JI Physica C PD MAY 20 PY 1994 VL 225 IS 3-4 BP 222 EP 234 DI 10.1016/0921-4534(94)90718-8 PG 13 WC Physics, Applied SC Physics GA NP354 UT WOS:A1994NP35400004 ER PT J AU BELTON, MJS GREELEY, R GREENBERG, R MCEWEN, A KLAASEN, KP HEAD, JW PIETERS, C NEUKUM, G CHAPMAN, CR GEISSLER, P HEFFERNAN, C BRENEMAN, H ANGER, C CARR, MH DAVIES, ME FANALE, FP GIERASCH, PJ INGERSOLL, AP JOHNSON, TV PILCHER, CB THOMPSON, WR VEVERKA, J SAGAN, C AF BELTON, MJS GREELEY, R GREENBERG, R MCEWEN, A KLAASEN, KP HEAD, JW PIETERS, C NEUKUM, G CHAPMAN, CR GEISSLER, P HEFFERNAN, C BRENEMAN, H ANGER, C CARR, MH DAVIES, ME FANALE, FP GIERASCH, PJ INGERSOLL, AP JOHNSON, TV PILCHER, CB THOMPSON, WR VEVERKA, J SAGAN, C TI GALILEO MULTISPECTRAL IMAGING OF THE NORTH POLAR AND EASTERN LIMB REGIONS OF THE MOON SO SCIENCE LA English DT Article ID LUNAR IMPACT BASINS; MARE VOLCANISM; WESTERN LIMB; DEPOSITS; CRATERS; STRATIGRAPHY; ERUPTION; ORIGIN; FLYBY; EARTH AB Multispectral images obtained during the Galileo probe's second encounter with the moon reveal the compositional nature of the north polar regions and the northeastern limb. Mare deposits in these regions are found to be primarily low to medium titanium lavas and, as on the western limb, show only slight spectral heterogeneity. The northern light plains are found to have the spectral characteristics of highlands materials, show little evidence for the presence of cryptomaria, and were most likely emplaced by impact processes regardless of their age. C1 ARIZONA STATE UNIV,DEPT GEOL,TEMPE,AZ 85287. UNIV ARIZONA,LUNAR & PLANETARY LAB,TUCSON,AZ 85721. US GEOL SURVEY,FLAGSTAFF,AZ 86001. CALTECH,JET PROP LAB,PASADENA,CA 91109. BROWN UNIV,DEPT GEOL,PROVIDENCE,RI 02912. DEUTSCH FORSCHUNGSANSTALT LUFT & RAUMFAHRT,W-8031 OBERPFAFFENHOFEN,GERMANY. PLANETARY SCI INST,TUCSON,AZ 85719. INST SPACE & TERR SCI,CONCORD L4K 3C8,ON,CANADA. US GEOL SURVEY,MENLO PK,CA 94025. RAND CORP,SANTA MONICA,CA 90406. UNIV HAWAII MANOA,INST GEOPHYS,HONOLULU,HI 96822. CORNELL UNIV,DEPT ASTRON,ITHACA,NY 14853. CALTECH,PASADENA,CA 91125. NASA HEADQUARTERS,WASHINGTON,DC 20546. RP BELTON, MJS (reprint author), NATL OPT ASTRON OBSERV,TUCSON,AZ 85719, USA. NR 40 TC 35 Z9 36 U1 2 U2 7 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 SN 0036-8075 J9 SCIENCE JI Science PD MAY 20 PY 1994 VL 264 IS 5162 BP 1112 EP 1115 DI 10.1126/science.264.5162.1112 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA NM146 UT WOS:A1994NM14600022 PM 17744892 ER PT J AU LOWMAN, PD AF LOWMAN, PD TI THE GEOLOGY OF MULTIRING IMPACT BASINS - THE MOON AND OTHER PLANETS. - SPUDIS,PD SO SCIENCE LA English DT Book Review RP LOWMAN, PD (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GEODYNAM BRANCH,GREENBELT,MD 20771, USA. NR 1 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 MAY 20 PY 1994 VL 264 IS 5162 BP 1180 EP 1181 DI 10.1126/science.264.5162.1180 PG 2 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA NM146 UT WOS:A1994NM14600042 PM 17744900 ER PT J AU HARMON, JK SLADE, MA VELEZ, RA CRESPO, A DRYER, MJ JOHNSON, JM AF HARMON, JK SLADE, MA VELEZ, RA CRESPO, A DRYER, MJ JOHNSON, JM TI RADAR MAPPING OF MERCURYS POLAR ANOMALIES SO NATURE LA English DT Article ID MARS; STABILITY; IMAGES; ICE AB GROUND-based radar observations of Mercury have revealed unusually strong, highly depolarized echoes from the north(1,2) and south(2) poles. These anomalous echoes have been cited as evidence of polar ice deposits(1-5). Thermal studies(3-5) suggest that the permanently shaded floors of large polar craters are cold enough to preserve water ice in a stable state over aeons, in spite of Mercury's proximity to the Sun. Here we present high-resolution radar maps of Mercury's polar regions, derived from delay-Doppler measurements. We have resolved the north and south polar anomalies into numerous crater-sized features, and we have been able to identify the source craters for many of these features after making small corrections to the pole positions on the Mariner-10 images. The coincidence with crater locations, together with other properties of the radar features, are consistent with the polar-ice hypothesis. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. RP HARMON, JK (reprint author), NATL ASTRON & IONOSPHERE CTR,ARECIBO,PR 00613, USA. NR 10 TC 99 Z9 99 U1 0 U2 4 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW SN 0028-0836 J9 NATURE JI Nature PD MAY 19 PY 1994 VL 369 IS 6477 BP 213 EP 215 DI 10.1038/369213a0 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA NM067 UT WOS:A1994NM06700049 ER PT J AU DEYOUNG, RJ AF DEYOUNG, RJ TI VISIBLE SPECTRUM OPTICAL-ABSORPTION IN TE2 VAPOR SO APPLIED PHYSICS LETTERS LA English DT Article AB The absorption spectrum of Te2 vapor has been measured throughout the visible spectrum. The absorption cross section (A state) was determined to be 2.18 X 10(-18) cm2. At wavelengths above 500 nm, absorption takes place from vibrational levels above the ground level, allowing more efficient absorption of visible (solar) spectrum light. From an absorption point of view, Te2 appears to be a good candidate for a direct solar-pumped laser. RP DEYOUNG, RJ (reprint author), NASA,LANGLEY RES CTR,DIV SPACE SYST,HAMPTON,VA 23681, USA. NR 5 TC 3 Z9 3 U1 1 U2 2 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 MAY 16 PY 1994 VL 64 IS 20 BP 2631 EP 2633 DI 10.1063/1.111500 PG 3 WC Physics, Applied SC Physics GA NL618 UT WOS:A1994NL61800005 ER PT J AU STAN, MA PATTON, MO WARNER, JD YANG, JW PIROUZ, P AF STAN, MA PATTON, MO WARNER, JD YANG, JW PIROUZ, P TI GROWTH OF 2H-SIC ON 6H-SIC BY PULSED-LASER ABLATION SO APPLIED PHYSICS LETTERS LA English DT Article AB A 2H-SiC thin film has been grown on a 6H-SiC substrate by laser ablation using an excimer laser. The deposition of 2H-SiC film occurred in a high vacuum system (almost-equal-to 10(-6) Torr) with the substrate temperature near 1200-degrees-C. Plan-view and cross-sectional transmission electron microscopy (TEM) were used to measure the lattice parameters and to identify the polytype. Cross-sectional TEM images clearly show the symmetry of the film as c-axis oriented 2H-SiC containing columnar grains with an average diameter of 20 nm and a length of 100 nm. C1 KENT STATE UNIV,DEPT PHYS,KENT,OH 44242. CASE WESTERN RESERVE UNIV,DEPT MAT SCI & ENGN,CLEVELAND,OH 44106. RP STAN, MA (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 13 TC 27 Z9 27 U1 1 U2 2 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 MAY 16 PY 1994 VL 64 IS 20 BP 2667 EP 2669 DI 10.1063/1.111486 PG 3 WC Physics, Applied SC Physics GA NL618 UT WOS:A1994NL61800017 ER PT J AU MAZZOLA, MS SADDOW, SE NEUDECK, PG LAKDAWALA, VK WE, S AF MAZZOLA, MS SADDOW, SE NEUDECK, PG LAKDAWALA, VK WE, S TI OBSERVATION OF THE D-CENTER IN 6H-SIC P-N DIODES GROWN BY CHEMICAL-VAPOR-DEPOSITION SO APPLIED PHYSICS LETTERS LA English DT Article ID SPECTROSCOPY AB The D-center in 6H-SiC is a boron-related deep hole trap observed previously in LPE-grown 6H-SiC diodes. We report deep level transient spectroscopy (DLTS) measurements in which the D-center signature is observed in high-purity n- and p-type epitaxial layers formed by chemical vapor deposition (CVD). An activation energy of 0.58 eV and a capture cross section between 1X10(-14) cm2 and 3X10(-14) cm2 was determined for this level. Even though the D-center in these diodes is thought to arise from unintended trace contamination, we observed within the same diode a factor of twenty greater density of this level in the n -type layer than in the p-type layer, which is explained by a recently proposed site competition model for impurity doping during 6H-SiC CVD growth. C1 AMSRL WT NF,ARMY RES LAB,ADELPHI,MD 20783. NASA,LEWIS RES CTR,CLEVELAND,OH 44135. OLD DOMINION UNIV,DEPT ELECT & COMP ENGN,NORFOLK,VA 23529. RP MAZZOLA, MS (reprint author), MISSISSIPPI STATE UNIV,DEPT ELECT & COMP ENGN,MISSISSIPPI STATE,MS 39762, USA. NR 8 TC 35 Z9 35 U1 0 U2 3 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 0003-6951 J9 APPL PHYS LETT JI Appl. Phys. Lett. PD MAY 16 PY 1994 VL 64 IS 20 BP 2730 EP 2732 DI 10.1063/1.111457 PG 3 WC Physics, Applied SC Physics GA NL618 UT WOS:A1994NL61800038 ER PT J AU AIKIN, AC AF AIKIN, AC TI ENERGETIC PARTICLE-INDUCED ENHANCEMENTS OF STRATOSPHERIC NITRIC-ACID SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID RELATIVISTIC ELECTRONS; CHEMISTRY; ROCKET AB Inclusion of complete ion chemistry in the calculation of minor species production during energetic particle deposition events leads to significant enhancement in the calculated nitric acid concentration during precipitation. An ionization rate of 1.2 x 10(3) cm-3 s-1 imposed for 1 day increases HNO3 from 3 x 10(5) to 6 x 10(7) cm-3 at 50 km. With an ionization rate of 600 cm-3 s-1, the maximum HNO3 is 3 x 10(7) cm-3. Calculations which neglect negative ions predict that nitric acid will fall during precipitation events. The decay time for converting HNO3 into odd nitrogen and hydrogen is more than 1 day for equinoctial periods at 70-degrees latitude. Examination of nitric acid data should yield important information on the magnitude and frequency of charged particle events. RP AIKIN, AC (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ATMOSPHERE LAB,CODE 916,GREENBELT,MD 20771, USA. NR 19 TC 12 Z9 12 U1 1 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 MAY 15 PY 1994 VL 21 IS 10 BP 859 EP 862 DI 10.1029/94GL00914 PG 4 WC Geosciences, Multidisciplinary SC Geology GA NM103 UT WOS:A1994NM10300004 ER PT J AU SISKIND, DE MINSCHWANER, K ECKMAN, RS AF SISKIND, DE MINSCHWANER, K ECKMAN, RS TI PHOTODISSOCIATION OF O-2 AND H2O IN THE MIDDLE ATMOSPHERE - COMPARISON OF NUMERICAL-METHODS AND IMPACT ON MODEL O-3 AND OH SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SCHUMANN-RUNGE BANDS; CROSS-SECTIONS; NITRIC-OXIDE; STRATOSPHERE; ABSORPTION; OXYGEN; MESOSPHERE; RESOLUTION; NM AB We have compared three photochemical diurnal models of O3 and OH in the upper stratosphere and mesosphere which use different techniques for calculating the absorption of solar ultraviolet radiation by the O2 Schumann-Runge bands. One model uses a detailed line-by-line representation of the O2 cross section from 1750-2050 angstrom, while the two others use lower resolution, parameterized cross sections. Using the parameterized cross sections, the calculated O3 profiles for both day and night agree with those obtained from the line-by-line model to within 6%. This appears to eliminate inaccuracies in the parameterized O2 cross section as a major cause of previously reported model O3 deficits. A portion of the residual differences from the line-byline model are attributed to inaccuracies in the calculated H2O photolysis rate. A parameterized H2O cross section is offered which improves the accuracy of this calculation. C1 NATL CTR ATMOSPHER RES,ADV STUDY PROGRAM,BOULDER,CO 80307. NASA,LANGLEY RES CTR,HAMPTON,VA 23681. RP SISKIND, DE (reprint author), USN,RES LAB,EO HULBURT CTR SPACE RES,CODE 7641,WASHINGTON,DC 20375, USA. NR 14 TC 10 Z9 10 U1 2 U2 6 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 MAY 15 PY 1994 VL 21 IS 10 BP 863 EP 866 DI 10.1029/94GL00457 PG 4 WC Geosciences, Multidisciplinary SC Geology GA NM103 UT WOS:A1994NM10300005 ER PT J AU THAKOOR, S AF THAKOOR, S TI ENHANCED FATIGUE AND RETENTION IN FERROELECTRIC THIN-FILM MEMORY CAPACITORS BY POST-TOP-ELECTRODE ANNEAL TREATMENT SO JOURNAL OF APPLIED PHYSICS LA English DT Article AB Remanent polarization in thin ferroelectric films of lead zirconate titanate (PZT) is of considerable interest for rad-hard, nonvolatile memory applications. The fatigue and retention characteristics of PZT films, however, are influenced markedly by the processing and patterning techniques for the capacitor. A post-top-electrode anneal treatment of thin-film ferroelectric capacitor device structures, with the top electrode defined by conventional lift-off patterning, that clearly shows a significant enhancement in the retention and fatigue characteristics of ferroelectric memories is described. In addition to the remanent polarization characteristics of Ti-Pt/PZT/Pt sandwich structure, studied using conventional electronic probe techniques, an optical probe is employed to probe the probable influence of Schottky junction(s) and/or stress at the electrode/PZT interfaces in the device. The significant improvement in the fatigue/retention performance of the devices by the post-top-electrode anneal treatment is attributed primarily to the formation of stable interfaces, as shown by the voltage cycling studies. The effects of operational history on retention performance provide further insight into the role of time-dependent depolarization/polarization components in the functioning of the memory. RP THAKOOR, S (reprint author), JET PROP LAB,CTR SPACE MICROELECTR TECHNOL,PASADENA,CA 91109, USA. NR 23 TC 18 Z9 19 U1 0 U2 0 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 0021-8979 J9 J APPL PHYS JI J. Appl. Phys. PD MAY 15 PY 1994 VL 75 IS 10 BP 5409 EP 5414 DI 10.1063/1.355696 PN 1 PG 6 WC Physics, Applied SC Physics GA NN732 UT WOS:A1994NN73200087 ER PT J AU JAIN, RK WEINBERG, I FLOOD, DJ AF JAIN, RK WEINBERG, I FLOOD, DJ TI DIFFUSION LENGTH VARIATION AND PROTON DAMAGE COEFFICIENTS FOR INP INXGA1-XAS GAAS SOLAR-CELLS, (VOL 74, PG 2948, 1993) SO JOURNAL OF APPLIED PHYSICS LA English DT Correction, Addition RP JAIN, RK (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 1 TC 0 Z9 0 U1 0 U2 0 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 0021-8979 J9 J APPL PHYS JI J. Appl. Phys. PD MAY 15 PY 1994 VL 75 IS 10 BP 5464 EP 5464 DI 10.1063/1.357036 PN 1 PG 1 WC Physics, Applied SC Physics GA NN732 UT WOS:A1994NN73200102 ER PT J AU LEE, TJ RENDELL, AP DYALL, KG JAYATILAKA, D AF LEE, TJ RENDELL, AP DYALL, KG JAYATILAKA, D TI OPEN-SHELL RESTRICTED HARTREE-FOCK PERTURBATION-THEORY - SOME CONSIDERATIONS AND COMPARISONS SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID POLYATOMIC TRANSIENT MOLECULES; GENERALIZED MOLLER-PLESSET; ELECTRONIC-ENERGY LEVELS; FULL CL TREATMENT; SELF-CONSISTENT; DIFFERENT FORMS; SPIN ORBITALS; NITRIC-ACID; BASIS SETS; CONVERGENCE AB A comparative study is presented of the various recently developed open-shell perturbation theories that are based on a restricted Hartree-Fock reference wave function. Included in this study are issues concerning spin contamination, implementational considerations, and numerical comparisons at the second-order of perturbation theory for equilibrium geometries, vibrational frequencies, and singlet-triplet energy differences. Based on all of these considerations, it is concluded that the z-averaged perturbation theory (ZAPT) method is to be preferred over the other recently devised spin-orbital perturbation theories, while the spin-free OPT2 method possesses some advantages and disadvantages relative to the ZAPT method. In particular, it is shown that OPT2 energies are not invariant to rotations among singly-occupied degenerate molecular orbitals. C1 SERC, DARESBURY LAB, WARRINGTON WA4 4AD, CHESHIRE, ENGLAND. ELORET INST, PALO ALTO, CA 94303 USA. UNIV WESTERN AUSTRALIA, DEPT CHEM, NEDLANDS, WA 6009, AUSTRALIA. RP LEE, TJ (reprint author), NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. RI Rendell, Alistair/A-4883-2008; Jayatilaka, Dylan/B-3498-2012; Lee, Timothy/K-2838-2012 OI Rendell, Alistair/0000-0002-9445-0146; Jayatilaka, Dylan/0000-0002-3349-5834; NR 52 TC 79 Z9 79 U1 1 U2 12 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 MAY 15 PY 1994 VL 100 IS 10 BP 7400 EP 7409 DI 10.1063/1.466883 PG 10 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA NL685 UT WOS:A1994NL68500038 ER PT J AU GRENFELL, TC COMISO, JC LANGE, MA EICKEN, H WENSNAHAN, MR AF GRENFELL, TC COMISO, JC LANGE, MA EICKEN, H WENSNAHAN, MR TI PASSIVE MICROWAVE OBSERVATIONS OF THE WEDDELL SEA DURING AUSTRAL WINTER AND EARLY SPRING SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID MARGINAL ICE-ZONE; INSITU OBSERVATIONS; EARLY SUMMER; SIGNATURES; BRINE; MODEL; GHZ AB The results of multispectral passive microwave observations (6.7 to 90-GHz) are presented from the cruises of the FS Polarstern in the Weddell Sea from July to December 1986. This paper includes primarily the analysis of radiometric observations taken at ice station sites. Averaged emissivity spectra for first-year (FY) ice were relatively constant throughout the experiment and were not statistically different from FY ice signatures in the Arctic. Detailed ice characterization was carried out at each site to compare the microwave signatures of the ice with the physical properties. Absorption optical depths of FY ice were found to be sufficiently high that only the structure in the upper portions of the ice contributed significantly to interstation emissivity variations. The emissivities at 90-GHz, e(90), had the greatest variance. Both e(90) at vertical polarization and GR(e)(90,18.7) (defined as [e(V)(90)-e(V)(18.7)]/e)V)[(90)+e(V)(18.7)]) depended on the scattering optical depth which is a function of the snow grain diameter and layer thickness. The variance showed a latitude dependence and is probably due to an increase in the strength of snow metamorphism nearer the northern edge of the ice pack. The contribution of variations of near-surface brine volume to the emissivity was not significant over the range of values encountered at the station sites. Emissivity spectra are presented for a range of thin ice types. Unsupervised principal component analysis produced three significant eigenvectors and showed a separation among four different surface types: open water, thin ice, FY ice, and FY ice with a thick snow cover. A comparison with SMMR satellite data showed that averaged ice concentrations derived from the ship's ice watch log were consistent with the satellite concentrations. The surface based emissivities for FY ice were also compared with emissivities calculated from scanning multichannel microwave radiometer (SMMR) satellite radiances. Best agreement was found at 6.7 and 10-GHz, while at 18 and 37-GHz, SMMR emissivities were slightly lower than surface based results. For the three lower frequencies agreement was found within a confidence limit of 95% and for 37-GHz within about 90%. C1 NASA, GODDARD SPACE FLIGHT CTR, HYDROSPHER SCI LAB, GREENBELT, MD 20771 USA. UNIV LAPLAND, CTR ARCTIC, ROVANIEMI, FINLAND. ALFRED WEGEMER INST POLAR & MEERESFORSCH, BREMERHAVEN, GERMANY. RP GRENFELL, TC (reprint author), UNIV WASHINGTON, DEPT ATMOSPHER SCI, AK-40, SEATTLE, WA 98195 USA. NR 34 TC 17 Z9 18 U1 1 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD MAY 15 PY 1994 VL 99 IS C5 BP 9995 EP 10010 DI 10.1029/93JC03237 PG 16 WC Oceanography SC Oceanography GA NL930 UT WOS:A1994NL93000019 ER PT J AU LIU, AK PENG, CY SCHUMACHER, JD AF LIU, AK PENG, CY SCHUMACHER, JD TI WAVE-CURRENT INTERACTION STUDY IN THE GULF OF ALASKA FOR DETECTION OF EDDIES BY SYNTHETIC-APERTURE RADAR SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID REFRACTION; AGULHAS; SEA AB High resolution ERS-1 Synthetic Aperture Radar (SAR) images are used to detect a mesoscale eddy. Such features limit dispersal of pollock larvae and therefore likely influence recruitment of fish in the Gulf of Alaska. During high sea states and high winds, the direct surface signature of the eddy was not clearly visible, but the wave refraction in the eddy area was observed. The rays of the wave field are traced-out directly from the SAR image. The ray pattern gives information on the refraction pattern and on the relative variation of the wave energy along a ray through wave-current interaction. These observations are simulated by a ray-tracing model which incorporates a surface current field associated with the eddy. The numerical results of the model show that the waves are refracted and diverge in the eddy field with energy density decreasing. The model-data comparison for each ray shows the model predictions are in good agreement with the SAR data. C1 SCI SYST & APPLICAT INC,LANHAM,MD 20706. NOAA,PACIFIC MARINE ENVIRONM LAB,SEATTLE,WA 98115. RP LIU, AK (reprint author), NASA,GODDARD SPACE FLIGHT CTR,OCEANS & ICE BRANCH,GREENBELT,MD 20771, USA. NR 31 TC 27 Z9 29 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD MAY 15 PY 1994 VL 99 IS C5 BP 10075 EP 10085 DI 10.1029/94JC00422 PG 11 WC Oceanography SC Oceanography GA NL930 UT WOS:A1994NL93000024 ER PT J AU WEISSMAN, DE DAVIDSON, KL BROWN, RA FRIEHE, CA LI, F AF WEISSMAN, DE DAVIDSON, KL BROWN, RA FRIEHE, CA LI, F TI THE RELATIONSHIP BETWEEN THE MICROWAVE RADAR CROSS-SECTION AND BOTH WIND-SPEED AND STRESS - MODEL FUNCTION STUDIES USING FRONTAL AIR-SEA INTERACTION EXPERIMENT DATA SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID INTERACTION EXPERIMENT FASINEX; DRAG COEFFICIENT; OCEAN SURFACE; WATER-SURFACE; HEAT-FLUX; DEPENDENCE; WAVE; STATE; SCATTEROMETER; SPECTRA AB The Frontal Air-Sea Interaction Experiment (FASINEX) provided a unique data set with coincident airborne scatterometer measurements of the ocean surface radar cross section (RCS) (at Ku band) and near-surface wind and wind stress. These data have been analyzed to study new model functions which relate wind speed and surface friction velocity (square root of the kinematic wind stress) to the radar cross section and to better understand the processes in the boundary layer that have a strong influence on the radar backscatter. Studies of data from FASINEX indicate that the RCS has a different relation to the friction velocity than to the wind speed. The difference between the RCS models using these two variables depends on the polarization and the incidence angle. The radar data have been acquired from the Jet Propulsion Laboratory airborne scatterometer. These data span 10 different flight days. Stress measurements were inferred from shipboard instruments and from aircraft flying at low altitudes, closely following the scatterometer. Wide ranges of radar incidence angles and environmental conditions needed to fully develop algorithms are available from this experiment. C1 USN,POSTGRAD SCH,DEPT METEOROL,MONTEREY,CA 93940. UNIV CALIF IRVINE,DEPT MECH ENGN,IRVINE,CA 92717. NASA,JET PROP LAB,PASADENA,CA 91109. UNIV WASHINGTON,DEPT ATMOSPHER SCI,SEATTLE,WA 98195. RP WEISSMAN, DE (reprint author), HOFSTRA UNIV,DEPT ENGN,HEMPSTEAD,NY 11550, USA. NR 46 TC 26 Z9 27 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-OCEANS JI J. Geophys. Res.-Oceans PD MAY 15 PY 1994 VL 99 IS C5 BP 10087 EP 10108 DI 10.1029/93JC03371 PG 22 WC Oceanography SC Oceanography GA NL930 UT WOS:A1994NL93000025 ER PT J AU MANNING, JP OEY, LY PACKER, D VITALIANO, J FINNERAN, TW YOU, KW FROMM, S AF MANNING, JP OEY, LY PACKER, D VITALIANO, J FINNERAN, TW YOU, KW FROMM, S TI OBSERVATIONS OF BOTTOM CURRENTS AND ESTIMATES OF RESUSPENDED SEDIMENT TRANSPORT AT THE NEW-YORK-BIGHT 12-MILE DUMPSITE SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID COMBINED WAVE; SHELF AB To document storm events that may induce a redistribution of sediment in the vicinity of the New York Bight 12-mile sewage sludge dumpsite, current meter moorings were deployed in water depths from 20 m (near the mouth of New York Harbor) to 53 m (within the Hudson Shelf Valley) from July 1986 through June 1989. Ten usable instrument records ranging from one month to one year in duration were obtained; eight of them near-bottom records. Seasonal and geographic variability of wind-induced flow were examined. The wind is most efficient in driving the subtidal currents in the 2-10 day frequency band during winter when the water column is well mixed and when the eastward component of the wind often induces and sustains an up-valley (northward) bottom flow. Maximum efficiency occurs for wind from 300-degrees (WNW) and at sites located within the Hudson Shelf Valley. A continental shelf bottom boundary layer model (Glenn and Grant, 1987) was used to estimate resuspended sediment transport. Model inputs include bottom currents (observed), orbital wave velocities (estimated), and sediment grain size (from the literature). Model output indicates that sediment resuspension at the current meter sites occurs approximately 5% of the time, primarily during winter months. The difference in along-valley flux between two moorings provides a rough estimate (6-month time series) of deposition and erosion. The net deposition (+.02 mm) was no greater than the deposition and erosion resulting from individual storms. A three-dimensional circulation model (You et al., 1991) is applied to increase the spatial resolution of the near-bottom current field (4 km grid) for a storm event in May of 1987. Given these velocities that vary in space and time, the redistribution of sediment was modeled for different surface wave conditions. Areas of deposition aligned with the Hudson Shelf Valley due to less wave-induced resuspension in deeper waters. Given all the uncertainties in the input variables (grain size, surface waves) and the simplistic assumptions made in modeling the deposition and erosion, it is still uncertain how much sludge is permanently removed from the area, but episodic redistribution of surficial sediment evidently occurs throughout the Inner New York Bight. C1 PRINCETON UNIV,ATMOSPHER & OCEAN SCI PROGRAM,PRINCETON,NJ 08542. STEVENS INST TECHNOL,DEPT CIVIL ENVIRONM & OCEAN ENGN,HOBOKEN,NJ 07030. NOAA,NATL MARINE FISHERIES SERV,JAMES J HOWARD LAB,HIGHLANDS,NJ 07732. RP MANNING, JP (reprint author), NOAA,NATL MARINE FISHERIES SERV,WOODS HOLE,MA 02543, USA. NR 25 TC 11 Z9 11 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD MAY 15 PY 1994 VL 99 IS C5 BP 10221 EP 10239 DI 10.1029/93JC03273 PG 19 WC Oceanography SC Oceanography GA NL930 UT WOS:A1994NL93000034 ER PT J AU SINGH, J AF SINGH, J TI NUCLEATION AND GROWTH-MECHANISM OF DIAMOND DURING HOT-FILAMENT CHEMICAL-VAPOR-DEPOSITION SO JOURNAL OF MATERIALS SCIENCE LA English DT Article ID THIN-FILMS; METHANE; ACETYLENE AB High-resolution transmission electron microscopy (HRTEM) was employed to study the nucleation and subsequent growth mechanism of crystalline diamond grown on copper TEM grids by the hot-filament chemical vapour deposition process. The HRTEM revealed direct evidence for the formation of a diamond-like amorphous carbon layer 8-14 nm thick, in which small diamond microcrystallites about 2-5 nm across were embedded. These diamond microcrystallites were formed as a result of direct transformation of the diamond-like carbon into diamond. Large diamond crystallites were observed to grow from these microcrystallites. The diamond surface was found to be non-uniform. It is envisaged that the diamond microcrystallites present in the amorphous, diamond-like carbon layer provide nucleation sites on which the large diamond crystallites grew. A mechanism of diamond growth has been proposed, based on the experimental findings, and is consistent with available theoretical models and numerous experimental observations reported in the literature. C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. NR 21 TC 53 Z9 54 U1 0 U2 4 PU CHAPMAN HALL LTD PI LONDON PA 2-6 BOUNDARY ROW, LONDON, ENGLAND SE1 8HN SN 0022-2461 J9 J MATER SCI JI J. Mater. Sci. PD MAY 15 PY 1994 VL 29 IS 10 BP 2761 EP 2766 DI 10.1007/BF00356830 PG 6 WC Materials Science, Multidisciplinary SC Materials Science GA NP101 UT WOS:A1994NP10100028 ER PT J AU CHAO, WC LIN, SJ AF CHAO, WC LIN, SJ TI TROPICAL INTRASEASONAL OSCILLATION, SUPER CLOUD CLUSTERS, AND CUMULUS CONVECTION SCHEMES SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID 40-50 DAY OSCILLATION; EQUATORIAL BETA-PLANE; WESTERN PACIFIC; SIMPLE-MODEL; WAVE-CISK; ATMOSPHERE; DYNAMICS; WIND; SELECTION; ORIGIN AB A new framework for interpreting the origin of the tropical intraseasonal oscillation (TISO), which avoids the speed and scale selection problems in the previous theories, is proposed in this study. In this interpretation TISO is viewed as an oscillation driven by an eastward moving convective region. This convective region consists of one or more super cloud clusters originating in the Indian Ocean and terminating in mid-Pacific, and is then followed by another convective region arising in the Indian Ocean in a period of 40-50 days. Additionally, a formal analogy is pointed out between super cloud clusters and the middle-latitude baroclinic wave packets. This study includes a simulation of TISO in a 2D model to support our interpretation. Experiments were conducted with four different convection schemes. The authors advocate that the successful simulation of TISO depends on the successful simulation of super cloud clusters. which in turn depends on the successful simulation of the life cycle of cloud clusters, which further in turn depends on the choice of cumulus convection scheme. What makes a cumulus convection scheme successful in simulating TISO is discussed. C1 GEN SCI CORP,LAUREL,MD. RP CHAO, WC (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ATMOSPHERES LAB,CODE 913,GREENBELT,MD 20771, USA. NR 44 TC 41 Z9 44 U1 0 U2 3 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 MAY 15 PY 1994 VL 51 IS 10 BP 1282 EP 1297 DI 10.1175/1520-0469(1994)051<1282:TIOSCC>2.0.CO;2 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA NL467 UT WOS:A1994NL46700005 ER PT J AU BRAZIER, KTS BERTSCH, DL FICHTEL, CE FIERRO, JM HARTMAN, RC HUNTER, SD KANBACH, G KNIFFEN, DA LIN, YC MATTOX, JR MAYERHASSELWANDER, HA MICHELSON, PF VONMONTIGNY, C NEL, HI NOLAN, PL SCHNEID, E SREEKUMAR, P THOMPSON, DJ AF BRAZIER, KTS BERTSCH, DL FICHTEL, CE FIERRO, JM HARTMAN, RC HUNTER, SD KANBACH, G KNIFFEN, DA LIN, YC MATTOX, JR MAYERHASSELWANDER, HA MICHELSON, PF VONMONTIGNY, C NEL, HI NOLAN, PL SCHNEID, E SREEKUMAR, P THOMPSON, DJ TI UPPER LIMITS ON THE HIGH-ENERGY GAMMA-RAY FLUXES FROM PSR-1951+32 AND 1509-58 SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE PULSARS, INDIVIDUAL, PSR-1509; 58; PULSARS, INDIVIDUAL, PSR 1951 + 32; GAMMA-RAYS, OBSERVATIONS ID SUPERNOVA REMNANT CTB-80; X-RAY; GALACTIC PLANE; PULSAR; TELESCOPE; EMISSION; DISTANCES; CTB80; SHELL AB The high-energy gamma-ray telescope EGRET observed the positions of two young pulsars, PSR 1951 + 32 and 1509 - 58, during its all-sky survey. Despite their youth and relative proximity to the Earth, neither pulsar is detected as a point source or in periodicity analysis. Flux limits of a few x 10(-7) photon cm-2 s-1 are obtained for emission above 100 MeV, and approximately 10(-6) photon cm-2 s-1 for 30-100 MeV. For the conventional assumption of beaming into 1 sr, the flux limits suggest that less than 3.2 per cent of the radiation from PSR 1509-58, and less than 1.8 per cent from PSR 1951 + 32, is in the form of beamed high-energy gamma-rays. The PSR 1509 - 58 limits lie approximately one order of magnitude below the extrapolated hard X-ray spectrum and suggest that the spectrum steepens in the MeV region. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. STANFORD UNIV,HANSEN EXPTL PHYS LAB,STANFORD,CA 94305. POTCHEFSTROOM UNIV CHRISTIAN HIGHER EDUC,DEPT PHYS,POTCHEFSTROOM 2520,SOUTH AFRICA. GRUMMAN AEROSP CORP,BETHPAGE,NY 11714. HAMPDEN SYDNEY COLL,HAMPDEN SYDNEY,VA 23943. POTCHEFSTROOM UNIV CHRISTIAN HIGHER EDUC,GRO SCI SUPPORT CTR,POTCHEFSTROOM 2520,SOUTH AFRICA. NASA,GODDARD SPACE FLIGHT CTR,UNIV RES ASSOC,GREENBELT,MD 20771. RP BRAZIER, KTS (reprint author), MAX PLANCK INST EXTRATERR PHYS,GIESSENBACHSTR,D-85740 GARCHING,GERMANY. RI Nolan, Patrick/A-5582-2009; Hunter, Stanley/D-2942-2012; Thompson, David/D-2939-2012 OI Thompson, David/0000-0001-5217-9135 NR 32 TC 14 Z9 14 U1 0 U2 0 PU BLACKWELL SCIENCE LTD PI OXFORD PA OSNEY MEAD, OXFORD, OXON, ENGLAND OX2 0EL SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD MAY 15 PY 1994 VL 268 IS 2 BP 517 EP 520 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NM561 UT WOS:A1994NM56100024 ER PT J AU CHENG, BL SCHRAMM, DN TRURAN, JW AF CHENG, BL SCHRAMM, DN TRURAN, JW TI CONSTRAINTS ON THE STRENGTH OF A PRIMORDIAL MAGNETIC-FIELD FROM BIG-BANG NUCLEOSYNTHESIS SO PHYSICAL REVIEW D LA English DT Article AB The effects of magnetic fields on big bang nucleosynthesis (BBN) are calculated, and the impact on the abundances of the light elements are investigated numerically. An upper limit on the strength of primordial magnetic fields compatible with observations of light element abundances is thus obtained. In the framework of standard BBN theory, the maximum strength of the primordial magnetic fields, on scales greater than 10(4) cm but smaller than the event horizon at the BBN epoch (approximately 1 min, approximately 2 x 10(12) cm), is less-than-or-equal-to 10(11) G. This limit is shown to allow magnetic fields at the time of recombination no stronger than approximately 0.1 G on scales greater-than-or-equal-to 10(11) cm. Our results also strongly indicate that, at the BBN epoch, and for field strengths B less-than-or-equal-to 10(13) G, the effects of magnetic fields on the primordial abundances of light elements are dominated by effects from reaction rates in the presence of primeval magnetic fields rather than by magnetic density effects on the expansion rate. C1 NASA,FERMILAB ASTROPHYS CTR,FERMI NATL ACCELERATOR LAB,BATAVIA,IL 60510. UNIV ILLINOIS,DEPT ASTRON,URBANA,IL 61801. UNIV CHICAGO,DEPT ASTRON & ASTROPHYS,CHICAGO,IL 60637. NR 31 TC 64 Z9 64 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 MAY 15 PY 1994 VL 49 IS 10 BP 5006 EP 5018 DI 10.1103/PhysRevD.49.5006 PG 13 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA NN990 UT WOS:A1994NN99000004 ER PT J AU KOLB, EW TKACHEV, II AF KOLB, EW TKACHEV, II TI NONLINEAR AXION DYNAMICS AND THE FORMATION OF COSMOLOGICAL PSEUDOSOLITONS SO PHYSICAL REVIEW D LA English DT Article ID STRONG-CP PROBLEM; INVISIBLE AXION; BOSE STARS; PARTICLES; CONSTRAINTS; INFLATION; CONSERVATION; MINICLUSTERS; INSTANTONS; UNIVERSE AB The (3 + 1)-dimensional evolution of an inhomogeneous axion field configuration around the QCD epoch is studied numerically, including important nonlinear effects due to the attractive self-interaction. It is found that axion perturbations on scales corresponding to causally disconnected regions at T approximately 1 GeV can lead to very dense pseudosoliton configurations we call axitons. These configurations evolve to axion miniclusters with a present density rho(a) greater than or similar to 10(-8) g cm-3. This is high enough for the collisional 2a --> 2a process to lead to Bose-Einstein relaxation in the gravitationally bound clumps of axions, forming Bose stars. C1 UNIV CHICAGO,ENRICO FERMI INST,DEPT ASTRON & ASTROPHYS,CHICAGO,IL 60637. RUSSIAN ACAD SCI,INST NUCL RES,MOSCOW 117312,RUSSIA. RP KOLB, EW (reprint author), NASA,FERMILAB ASTROPHYS CTR,FERMI NATL ACCELERATOR LAB,BATAVIA,IL 60510, USA. NR 51 TC 76 Z9 76 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 MAY 15 PY 1994 VL 49 IS 10 BP 5040 EP 5051 DI 10.1103/PhysRevD.49.5040 PG 12 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA NN990 UT WOS:A1994NN99000008 ER PT J AU WANG, Y AF WANG, Y TI MASS AND RADIUS OF COSMIC BALLOONS SO PHYSICAL REVIEW D LA English DT Article ID BALLS AB Cosmic balloons are spherical domain walls with relativistic particles trapped inside. We derive the exact mass and radius relations for a static cosmic balloon using Gauss-Codazzi equations. The cosmic balloon mass as a function of its radius, M(R), is found to have a functional form similar to that of fermion soliton stars, with a fixed point at 2GM(R)IR congruent-to 0.486, which corresponds to the limit of infinite central density. We derive a simple analytical approximation for the mass density of a spherically symmetric relativistic gas star. When applied to the computation of the mass and radius of a cosmic balloon, the analytical approximation yields fairly good agreement with the exact numerical solutions. RP WANG, Y (reprint author), NASA,FERMILAB ASTROPHYS CTR,FERMI NATL ACCELERATOR LAB,BATAVIA,IL 60510, USA. RI Wang, Yun/B-5724-2011 OI Wang, Yun/0000-0002-4749-2984 NR 10 TC 3 Z9 3 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 MAY 15 PY 1994 VL 49 IS 10 BP 5063 EP 5067 DI 10.1103/PhysRevD.49.5063 PG 5 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA NN990 UT WOS:A1994NN99000010 ER PT J AU DODELSON, S GYUK, G TURNER, MS AF DODELSON, S GYUK, G TURNER, MS TI PRIMORDIAL NUCLEOSYNTHESIS WITH A DECAYING TAU-NEUTRINO SO PHYSICAL REVIEW D LA English DT Article ID MASSIVE NEUTRINOS; COSMOLOGICAL CONSTRAINTS; EXPERIMENTAL LIMITS; LIGHT-ELEMENTS; EARLY UNIVERSE; BIG-BANG; PARTICLES; LIFETIMES; SN-1987A; SEARCH AB A comprehensive study of the effect of an unstable tau neutrino on primordial nucleosynthesis is presented. The standard code for nucleosynthesis is modified to allow for a massive decaying tau neutrino whose daughter products include neutrinos, photons, e +/- pairs, and/or noninteracting (sterile) daughter products. tau-neutrino decays influence primordial nucleosynthesis in three distinct ways. (i) the energy density of the decaying tau neutrino and its daughter products affect the expansion rate tending to increase He-4, D, and He-3 production; (ii) electromagnetic (EM) decay products heat the EM plasma and dilute the baryon-to-photon ratio tending to decrease He-4 production and increase D and He-3 production; and (iii) electron neutrinos and antineutrinos produced by tau-neutrino decays increase the weak rates that govern the neutrino-to-proton ratio, leading to decreased He-4 production for short lifetimes (less-than-or-similar-to 30 sec) and masses less than about 10 MeV and increased He-4 production for long lifetimes or large masses. The precise effect of a decaying tau neutrino on the yields of primordial nucleosynthesis and the mass-lifetime limits that follow depend crucially upon decay mode. We identify four generic decay modes that serve to bracket the wider range of possibilities: tau neutrino decays to (1) sterile daughter products (e.g., nu(tau) --> nu(mu) + phi; phi is a very weakly interacting scalar particle); (2) sterile daughter product(s)+daughter products(s) that interacts electromagnetically (e.g., nu(tau) --> nu(mu) + gamma); (3) electron neutrino+sterile daughter product(s) (e.g., nu(tau) --> nu(e) + phi); and (4) electron neutrino + daughter product(s) that interact electromagnetically (nu(tau) --> nu(e) + e+/-). Mass-lifetime limits are derived for the four generic decay modes assuming that the abundance of the massive tau neutrino is determined by its electroweak annihilations. In general, nucleosynthesis excludes a tau neutrino of mass 0.4 MeV-30 MeV for lifetimes greater than about 300 sec. These nucleosynthesis bounds are timely since the current laboratory upper bounds to the tau-neutrino mass are around 30 MeV, and together the two bounds very nearly exclude a long-lived tau neutrino more massive than about 0.4 MeV. Further, our nucleosynthesis bounds together with other astrophysical and laboratory bounds exclude a tau neutrino of mass 0.4 MeV -30 MeV of any lifetime that decays with EM daughter product(s). We use our results to constrain the mass times relic abundance of a hypothetical, unstable species with similar decay modes. Finally, we note that tau neutrino of mass 1 MeV to 10 MeV and lifetime 0.1 sec-10 sec whose decay products include an electron neutrino can reduce the He-4 yield to less than that for two massless neutrino species. This fact could be relevant if the primordial mass fraction of He-4 is found to be less than about 0.23 and can also lead to a modification of the nucleosynthesis bound to the number of light (<< 1 MeV) neutrino (and other) particle species. C1 UNIV CHICAGO,DEPT PHYS,CHICAGO,IL 60637. UNIV CHICAGO,ENRICO FERMI INST,DEPT ASTRON & ASTROPHYS,CHICAGO,IL 60637. RP DODELSON, S (reprint author), NASA,FERMILAB ASTROPHYS CTR,FERMI NATL ACCELERATOR LAB,BATAVIA,IL 60510, USA. NR 50 TC 55 Z9 55 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 MAY 15 PY 1994 VL 49 IS 10 BP 5068 EP 5079 DI 10.1103/PhysRevD.49.5068 PG 12 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA NN990 UT WOS:A1994NN99000011 ER PT J AU MCEWAN, MJ MCCONNELL, CL FREEMAN, CG ANICICH, VG AF MCEWAN, MJ MCCONNELL, CL FREEMAN, CG ANICICH, VG TI REACTIONS OF ISOMERIC C3H3+ IONS - A COMBINED LOW-PRESSURE HIGH-PRESSURE STUDY SO JOURNAL OF PHYSICAL CHEMISTRY LA English DT Article ID MOLECULE REACTIONS; ASSOCIATION REACTIONS; CH3+/CH3CN SYSTEM; SOOT FORMATION; DIACETYLENE; ACETYLENE; CATIONS; HYDROCARBONS; CHEMISTRY; MODEL AB We report the results of a low-pressure (ICR) and high-pressure (SIFT) investigation of the ion-molecule reactions of C3H3+. Two isomeric forms of C3H3+ are present: HCCCH2+ and c-C3H3+. Rate coefficients and product ratios are reported for each technique for a variety of neutral reactants including H-2, NH3, C2H2, CH3OH, and CH3CN. Most reactions occur via a long-lived association complex. Large differences in reactivity and differences in product distributions between the two techniques are rationalized in terms of the association complex lifetime. C1 CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. RP MCEWAN, MJ (reprint author), UNIV CANTERBURY, DEPT CHEM, CHRISTCHURCH 1, NEW ZEALAND. NR 39 TC 25 Z9 25 U1 0 U2 5 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0022-3654 J9 J PHYS CHEM-US JI J. Phys. Chem. PD MAY 12 PY 1994 VL 98 IS 19 BP 5068 EP 5073 DI 10.1021/j100070a021 PG 6 WC Chemistry, Physical SC Chemistry GA NL776 UT WOS:A1994NL77600021 ER PT J AU COLIN, P SCHRAMM, DN PEIMBERT, M AF COLIN, P SCHRAMM, DN PEIMBERT, M TI COUNTS OF GALAXIES IN A MERGER MODEL SO ASTROPHYSICAL JOURNAL LA English DT Article DE COSMOLOGY, THEORY; GALAXIES, EVOLUTION; GALAXIES, INTERACTIONS; GALAXIES, LUMINOSITY FUNCTION, MASS FUNCTION; GALAXIES, PHOTOMETRY ID HIGH-REDSHIFT GALAXIES; GIANT BRANCH EVOLUTION; MASS-LOSS RATES; H-R DIAGRAMS; POPULATION SYNTHESIS; LUMINOSITY FUNCTIONS; STELLAR POPULATION; FAINT GALAXIES; DISK GALAXIES; NUMBER COUNT AB A model for the photometric evolution of galaxies has been developed and has been applied to the problem of galaxy counts. The integrated colors of galaxies are calculated using the most recently computed evolutionary tracks from Maeder and collaborators complemented with evolutionary tracks derived by other authors. The asymptotic giant branch lifetime is left as a free parameter. A series of cosmological models using different values of the cosmological constant, LAMBDA0, and the density parameter, OMEGA0, have been computed. The universality hypothesis of the luminosity function of galaxies has been abandoned. The influence of galaxy merging on the counts has been considered in a simple manner by assuming that the number of strongly interacting galaxies in a comoving volume increases with redshift as a power law given by (1 + z)3.8. Taking a Schechter parametrization for the luminosity function of the different types of galaxies, we are able to reproduce the observations reasonably well. We have also considered models with a Gaussian distribution for the luminosity function of the brighter galaxies that provide a poorer fit to the observations. It is shown that galaxy count data are not yet able to make unambiguous cosmological statements since evolutionary assumptions are critical. In particular, an OMEGA0 = 1, LAMBDA0 = 0 cosmology is shown to be consistent with the data. C1 UNIV CHICAGO,CHICAGO,IL 60637. FERMILAB NATL ACCELERATOR LAB,NASA,CTR ASTROPHYS,BATAVIA,IL 60510. RP COLIN, P (reprint author), NATL AUTONOMOUS UNIV MEXICO,INST ASTRON,MEXICO CITY 04510,DF,MEXICO. NR 67 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 MAY 10 PY 1994 VL 426 IS 2 BP 459 EP 472 DI 10.1086/174082 PN 1 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NK032 UT WOS:A1994NK03200001 ER PT J AU SCHAEFER, BE AF SCHAEFER, BE TI THE PEAK BRIGHTNESS OF SN-1937C IN IC-4182 AND THE HUBBLE CONSTANT SO ASTROPHYSICAL JOURNAL LA English DT Article DE COSMOLOGY, OBSERVATIONS; DISTANCE SCALE; GALAXIES, INDIVIDUAL (IC-4182); SUPERNOVAE, INDIVIDUAL (1937C) ID LIGHT CURVES; IA SUPERNOVAE; GLOBAL VALUE; GALAXIES; CALIBRATION; DISTANCES; MAGNITUDE; SCALE; H0 AB The light curve of the Type Ia supernova SN 1937C (in IC 4182) is important because Sandage et al. have measured a distance to the host galaxy by means of Cepheid variables and thus have derived the Hubble constant. However, the peak brightness of SN 1937C has only been derived with the relatively poor original comparison star brightnesses and without regard to a large body of data in the literature. In this paper, I will correct these and other procedural difficulties. I find that the late time photographic light curve appears to have a broken exponential decay with equivalent half-lives of 46 and 58 days with the break near 300 days after maximum. I also find that the peak B-magnitude was 8.71 +/- 0.14 on JD 2428770.0 +/- 1.0 at which time the B - V was -0.03 +/- 0.13. With these improved peak brightnesses, the distance modulus of Sandage et al., and peak absolute magnitudes in the center of the range of modem estimates, I derive the Hubble constant to be 50 km s-1 Mpc-1. RP SCHAEFER, BE (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 661,GREENBELT,MD 20771, USA. NR 69 TC 38 Z9 38 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 10 PY 1994 VL 426 IS 2 BP 493 EP 501 DI 10.1086/174085 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NK032 UT WOS:A1994NK03200004 ER PT J AU CORNETT, RH OCONNELL, RW GREASON, MR OFFENBERG, JD ANGIONE, RJ BOHLIN, RC CHENG, KP ROBERTS, MS SMITH, AM SMITH, EP TALBERT, FD STECHER, TP AF CORNETT, RH OCONNELL, RW GREASON, MR OFFENBERG, JD ANGIONE, RJ BOHLIN, RC CHENG, KP ROBERTS, MS SMITH, AM SMITH, EP TALBERT, FD STECHER, TP TI UIT - ULTRAVIOLET SURFACE PHOTOMETRY OF THE SPIRAL GALAXY-M74 (NGC-628) SO ASTROPHYSICAL JOURNAL LA English DT Article DE GALAXIES, INDIVIDUAL (NGC-628); GALAXIES, PHOTOMETRY; GALAXIES, SPIRAL; ULTRAVIOLET, GALAXIES ID H-II REGIONS; IMAGING TELESCOPE; STAR FORMATION; GALAXIES; EXTINCTION; POPULATIONS; IMAGES; DUST AB Ultraviolet photometry, obtained from Ultraviolet Imaging Telescope (UIT) images at 1520 angstrom [far-UV; magnitudes m(152)] and 2490 angstrom [near-UV; magnitudes m(249)], of the spiral galaxy M74 (NGC 628) is compared with Halpha, R, V, and B surface photometry and with models. M74's surface brightness profiles have a central peak with an exponential falloff; the exponential scale lengths of the profiles increase with decreasing wavelength for-the broad-band images. The slope of the continuum-subtracted Halpha profile is intermediate between those of far-UV and near-UV profiles, consistent with the related origins of Halpha and UV emission in extreme Population I material. M74's color profiles all become bluer with increasing radius. The [m(152) - m(249)] color as measured by UIT averages near 0.0 (the color of an A0 star) over the central 20'' radius and decreases from approximately -0.2 to approximately -0.4 from 20'' to 200''. The spiral arms are the dominant component of the surface photometry colors; interarm regions are slightly redder. In the UV, M74's nuclear region resembles its disk/spiral arm material in colors and morphology, unlike galaxies such as M81. No UV '' bulge '' is apparent. The m(152) - m(249) colors and models of M74's central region clearly demonstrate that there is no significant population of O or B stars present in the central 10''. M74's UV morphology and [m(152) - m(249)] color profiles are similar to those of M33, although M74 is approximately 0.5 mag redder. M81 has a smooth UV bulge which is much redder than the nuclear regions of M74 and M33. M74 is approximately 0.4 mag bluer than M81 in its outer disk, although M81 has bright UV sources only in spiral arms more than 5 kpc from its center. We investigate possible explanations for the color profiles of the galaxies and the differences among the galaxies: abundances; reddening due to internal dust; IMF variations, and the history of formation of the dominant generations of stars. Abundance and IMF variations do not produce large enough m(152) - m(249) or UV - V color differences. Comparing model UV/optical colors with those of M74 shows that M74's disk has undergone significant star formation over the past 500 Myr, and that either the star-formation history or the extinction varies systematically across M74's disk. Realistic reddening models show that the effects of dust alone are not sufficient to produce the variations within M74. However, evolutionary models produced by combining data from stellar atmosphere models and observed spectra generate UV - V colors which are compatible with the observations, provided relatively recent star formation is present in the stellar population. Comparison of M74, M33, and M81 (UV - V) colors shows that M74 colors range from the bluest of M33's colors to the bluest of M81's. All material with these colors in all three galaxies has the morphological appearance of spiral arm/disk material. The failure of reddening models to cover the range of colors, and the known abundance range in such material, leads to the conclusion that star-formation history varies significantly as a function of radius in these galaxies, and that such variation is required to explain the range of colors observed in M74, M33, and M81. C1 UNIV VIRGINIA,DEPT ASTRON,CHARLOTTESVILLE,VA 22903. SAN DIEGO STATE UNIV,DEPT ASTRON,SAN DIEGO,CA 92182. SPACE TELESCOPE SCI INST,BALTIMORE,MD 21218. NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771. NATL RADIO ASTRON OBSERV,CHARLOTTESVILLE,VA 22903. RP CORNETT, RH (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HUGHES STX CORP,CODE 681,GREENBELT,MD 20771, USA. NR 39 TC 37 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 MAY 10 PY 1994 VL 426 IS 2 BP 553 EP 562 DI 10.1086/174092 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NK032 UT WOS:A1994NK03200011 ER PT J AU CHEN, W GEHRELS, N LEVENTHAL, M AF CHEN, W GEHRELS, N LEVENTHAL, M TI ON THE OPTICAL COUNTERPARTS, LONG-TERM VARIABILITIES, RADIO JETS, AND ACCRETION SOURCES IN 1E-1740.7-2942 AND GRS-1758-258 SO ASTROPHYSICAL JOURNAL LA English DT Article DE BLACK HOLE PHYSICS; GALAXY, CENTER; GAMMA RAYS, OBSERVATIONS; ISM, JETS AND OUTFLOWS ID X-RAY SOURCES; GALACTIC-CENTER REGION; SOURCE 1E1740.7-2942; SPHERICAL ACCRETION; MOLECULAR CLOUDS; STAR FORMATION; BLACK-HOLE; PLASMA; MODEL AB In this paper we discuss a variety of issues concerning the exciting and mysterious Galactic center gamma-ray sources 1E 1740.7-2942 and GRS 1758-258. We discuss the problem associated with the highly uncertain X-ray absorption column toward 1E 1740.7-2942 and use the recent ROSAT results to narrow its range to 0.5-1 X 10(3) cm-2. Then the current upper limits from deep optical and near-IR searches of stellar objects at these source locations are plotted on an H-R diagram, from which we find the mass of a potential companion star of the (supposed) black hole in GRS 1758-258 to be less than 4 M. and in 1E 1740.7-2942 to be less than 9 M. The observed well-collimated radio jets in 1E 1740.7 - 2942 require the existence of a stable accretion disk (presumably from binary accretion). The apparent association of 1E 1740.7-2942 with a high-density molecular cloud, on the other hand, points to possible accretion directly from the interstellar medium (ISM). We present an analysis of the energetics and kinematics of the radio jets in 1E 1740.7 - 2942. We find that the jets of 1E 1740.7-2942 are most probably made of normal proton-electron plasma (<20%) and electron-positron pairs. The observed good alignment of the radio core with its lobes implies that the source is moving in the ISM slowly (< 10 km s-1). We present the long-term X-ray light curves of the two sources which include both the Granat/SIGMA's 3 yr monitoring data and all the data from previous imaging balloon and satellite observations over the last decade. The large amplitude, nonperiodic hard X-ray variabilities of these two sources appear to be similar, which suggest a common origin. The possible physical mechanisms responsible for producing both the long-term X-ray variations and the radio jets are postulated. Since the optical/near-IR and radio observations have excluded these systems as high-mass X-ray binaries like Cyg X-1 which accrete from strong stellar winds of massive companions, we consider Roche lobe-overflowing, low-mass X-ray binaries and Bondi-Hoyle accretion directly from a high-density surrounding medium. We propose a plausible scenario in which both sources are binary systems with a black hole primary and a low-mass companion and they are accreting mainly from the ISM at a rate self-regulated by the interaction between the accretion flow and the emerging hard X-ray flux. C1 UNIV MARYLAND,DEPT ASTRON,COLLEGE PK,MD 20742. RP CHEN, W (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 661,GREENBELT,MD 20771, USA. RI Gehrels, Neil/D-2971-2012 NR 70 TC 35 Z9 35 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 MAY 10 PY 1994 VL 426 IS 2 BP 586 EP 598 DI 10.1086/174095 PN 1 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NK032 UT WOS:A1994NK03200014 ER PT J AU MASTICHIADIS, A OZERNOY, LM AF MASTICHIADIS, A OZERNOY, LM TI X-RAY AND GAMMA-RAY EMISSION OF SAGITTARIUS-A-ASTERISK AS A WIND-ACCRETING BLACK-HOLE SO ASTROPHYSICAL JOURNAL LA English DT Article DE X-RAYS, GENERAL; GALAXY, CENTER; GAMMA-RAYS, THEORY ID ACTIVE GALACTIC NUCLEI; RADIATION; QUASARS AB If, as many believe, Sgr A* is a massive black hole at the Galactic center, one should expect it to be a source of X-ray and gamma-ray activity, behaving basically as a scaled-down active galactic nucleus. An unavoidable source of accretion is the wind from IRS 16, a nearby group of hot, massive stars. Since the density and velocity of the accreting matter are known from observations, the accretion rate is basically a function of the putative black hole mass, M(h), only; this value represents a reliable lower limit to a real rate, given the other possible sources of accreting matter. Based on this and on the theories about shock acceleration in active galactic nuclei, we have estimated the expected production of relativistic particles and their hard radiation. These values turn out to be a function of M(h) as well. Comparing our results with available X-ray and gamma-ray observations which show Sgr A* to have a relatively low activity level, we conclude tentatively that the putative black hole in the Galactic center cannot have a mass greater than approximately 6 x 10(3) M.. This conclusion is consistent with the upper limits to the black hole mass found by different methods earlier, although much more work is needed to make calculations of shock acceleration around black holes more reliable. C1 NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY PHYS LAB,GREENBELT,MD 20771. NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771. GEORGE MASON UNIV,INST COMP SCI & INFORMAT,FAIRFAX,VA 22030. NR 30 TC 26 Z9 26 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 10 PY 1994 VL 426 IS 2 BP 599 EP 603 DI 10.1086/174096 PN 1 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NK032 UT WOS:A1994NK03200015 ER PT J AU BHAT, PN FISHMAN, GJ MEEGAN, CA WILSON, RB KOUVELIOTOU, C PACIESAS, WS PENDLETON, GN SCHAEFER, BE AF BHAT, PN FISHMAN, GJ MEEGAN, CA WILSON, RB KOUVELIOTOU, C PACIESAS, WS PENDLETON, GN SCHAEFER, BE TI SPECTRAL EVOLUTION OF A SUBCLASS OF GAMMA-RAY BURSTS OBSERVED BY BATSE SO ASTROPHYSICAL JOURNAL LA English DT Article DE GAMMA-RAYS, BURSTS AB Among the gamma-ray bursts observed by the Burst and Transient Source Experiment (BATSE) on board the Compton Gamma Ray Observatory we define a subclass of bursts based on similar morphology: a sharp rise followed by a longer decay time. About 7% of all the gamma-ray bursts observed by BATSE fall into this subclass. We study the spectral evolution of these bursts by fitting models to time-segmented burst spectra and find no clear distinction between the spectral evolutionary properties of this subclass and those of other bursts. Further, we study the high time resolution spectral evolution of this subclass of GRBs using their spectral hardness ratios. A majority of the bursts show hardness ratio leading the counting rate and also display a continuous hard to soft evolution. The time lag between the counting rate and the hardness ratio is found to be directly correlated with the rise time of the counting rate profile. We also find, for the first time, evidence for spectral variation in a timescale of 64 ms. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP BHAT, PN (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,SPACE SCI LAB ES66,HUNTSVILLE,AL 35812, USA. NR 30 TC 44 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 MAY 10 PY 1994 VL 426 IS 2 BP 604 EP 611 DI 10.1086/174097 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NK032 UT WOS:A1994NK03200016 ER PT J AU SWEIGART, AV AF SWEIGART, AV TI THE DETERMINATION OF THE CORE MASS AT THE HELIUM FLASH IN GLOBULAR-CLUSTER STARS SO ASTROPHYSICAL JOURNAL LA English DT Article DE GLOBULAR CLUSTERS, GENERAL; STARS, EVOLUTION; STARS, GIANTS; STARS, HORIZONTAL-BRANCH; STARS, INTERIORS ID GIANT BRANCH STARS; OOSTERHOFF PERIOD GROUPS; EVOLUTIONARY SEQUENCES; HORIZONTAL BRANCHES; STELLAR EVOLUTION; AGE; METALLICITY; SYSTEM; CARBON; SEMICONVECTION AB Evolutionary sequences for the red giant branch (RGB) phase of a representative globular cluster star have been computed in order to investigate the reliability of the current canonical values of the core mass M(c) at the helium flash. These computations were motivated by recent suggestions that the canonical values of M(c) may be systematically too small due to the numerical algorithms for shifting the hydrogen shell and advancing the chemical composition during the RGB phase. Our results show that these algorithms do not, in fact, introduce a significant error in the values of M(c). Moreover, we demonstrate that a procedure for advancing the chemical composition which is implicit only in the hydrogen abundance will systematically underestimate the amount of hydrogen fuel consumption between RGB models and therefore should not be used in RGB computations. Overall we estimate the uncertainty in the core masses of Sweigart & Gross (1978) due to numerical effects to be almost-equal-to 0.003 M.. From a consideration of the available canonical models we conclude that a change in the canonical values of M(c) by a few 10(-2) M. would require either a substantial change in the canonical input physics or some noncanonical effect such as rotation. Finally our models show that the use of short time steps can significantly increase the extent of the inner tail of the hydrogen shell. This effect may enhance the likelihood of hydrogen mixing following a helium shell flash in an asymptotic giant branch star. RP SWEIGART, AV (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,CODE 681,GREENBELT,MD 20771, USA. NR 43 TC 16 Z9 16 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 MAY 10 PY 1994 VL 426 IS 2 BP 612 EP 620 DI 10.1086/174098 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NK032 UT WOS:A1994NK03200017 ER PT J AU FEIBELMAN, WA HYUNG, S ALLER, LH AF FEIBELMAN, WA HYUNG, S ALLER, LH TI SPECTRUM OF IC-2149 AND ITS CENTRAL STAR SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM, ABUNDANCES; PLANETARY NEBULAE, (IC-2149); STARS, EARLY-TYPE; ULTRAVIOLET, ISM ID PLANETARY-NEBULAE; TERM ANALYSIS; STELLAR AB Although the asymmetric optical image of IC 2149 does not fall into any standard morphologies (Balick et al. 1993), the overall shape and its radio frequency image show a bilateral symmetry. The central star of spectral class O7.5 is a remarkable object with a rich spectrum showing many Fe ions. We discuss this spectrum in detail. The nebula has been studied utilizing our theoretical photoionization models. Detailed analyses of spectral data are done in both the UV region (lambda < 3000 angstrom; IUE) and the optical region (3500 angstrom approximately 10500 angstrom; the Hamilton Echelle at Lick Observatory). The plasma diagnostics suggest an electron temperature of 9000 approximately 10,000 K and an electron density near 5600 cm-3. Our model calculations were carried out with due regard to the above plasma diagnostics. The observations can be interpreted by a model of IC 2149 which consists of two components (an equatorial ring and a polar cone), but the total emission is dominated by the relatively denser equatorial shell. Carbon, nitrogen, and oxygen appear to be depleted by a factor of about 3; ratios of other elements are also lower than in the Sun. C1 UNIV CALIF LOS ANGELES,DEPT ASTRON,LOS ANGELES,CA 90024. RP FEIBELMAN, WA (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,CODE 6841,GREENBELT,MD 20771, USA. NR 36 TC 20 Z9 20 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 10 PY 1994 VL 426 IS 2 BP 653 EP 663 DI 10.1086/174102 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NK032 UT WOS:A1994NK03200021 ER PT J AU LONG, KS WADE, RA BLAIR, WP DAVIDSEN, AF HUBENY, I AF LONG, KS WADE, RA BLAIR, WP DAVIDSEN, AF HUBENY, I TI OBSERVATIONS OF THE BRIGHT NOVALIKE VARIABLE IX-VELORUM WITH THE HOPKINS ULTRAVIOLET TELESCOPE SO ASTROPHYSICAL JOURNAL LA English DT Article DE BINARIES, CLOSE; NOVAE, CATACLYSMIC VARIABLES; STARS, INDIVIDUAL (IX-VELORUM); ULTRAVIOLET, STARS ID RESOLUTION IUE SPECTRA; X-RAY-EMISSION; CATACLYSMIC VARIABLES; ACCRETION DISKS; DWARF NOVAE; CPD -48-DEGREES-1577; WHITE-DWARF; STARS; CPD-48-DEGREES-1577; DISTRIBUTIONS AB The Hopkins Ultraviolet Telescope, an experiment flown on the Space Shuttle as part of the Astro-1 mission, was used to obtain a spectrum of the novalike variable IX Vel (= CPD -48-degrees 1577) in the wavelength range 830-1860 angstrom. The observation revealed a rich absorption-line and continuum spectrum that peaks near 1050 angstrom at a flux of 1.6 x 10(-11) ergs cm-2 s-1 angstrom-1. In the sub-Lyman-alpha region, some of the more prominent absorption lines are S VI lambdalambda933, 945, C III lambda977, Lyman-beta, O VI lambdalambda1032, 1038, P V lambdalambda1118, 1128, and C III lambda1176. No emission was detected below the Lyman limit. The overall continuum shape of IX Vel in the FUV can be approximated using models of an optically thick accretion disk in which the integrated spectrum has been constructed by summing model stellar atmospheres or proper disk model spectra. However, if the distance to IX Vel is approximately 95 pc, standard disk models without reddening cannot simultaneously reproduce the color and flux in the UV. While interstellar reddening can reconcile this difference, the amount of reddening appears inconsistent with the absence of a 2200 angstrom bump in the spectrum and the very low H I column density measured along the line of sight. Improved fits to the data can be obtained by modifying the accretion disk structure within three white dwarf radii. None of the models reproduces the profiles of the Li- and Na-like ions, which are observed as strong but relatively narrow absorption lines, and which are almost surely due to a wind above the disk. C1 PENN STATE UNIV,DEPT ASTRON & ASTROPHYS,UNIV PK,PA 16802. JOHNS HOPKINS UNIV,DEPT PHYS & ASTRON,BALTIMORE,MD 21218. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP LONG, KS (reprint author), SPACE TELESCOPE SCI INST,3700 SAN MARTIN DR,BALTIMORE,MD 21218, USA. NR 49 TC 47 Z9 47 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 10 PY 1994 VL 426 IS 2 BP 704 EP 715 DI 10.1086/174107 PN 1 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NK032 UT WOS:A1994NK03200026 ER PT J AU CLIVER, EW CROSBY, NB DENNIS, BR AF CLIVER, EW CROSBY, NB DENNIS, BR TI ARE SOLAR GAMMA-RAY LINE FLARES DIFFERENT FROM OTHER LARGE FLARES SO ASTROPHYSICAL JOURNAL LA English DT Article DE SUN, FLARES; SUN, X-RAYS, GAMMA-RAYS ID CORONAL MASS EJECTIONS; X-RAY; MAXIMUM-MISSION; ENERGETIC PARTICLES; EMISSION; ACCELERATION; SPECTROMETER; ELECTRONS; EVENTS; BURSTS AB We reevaluate evidence indicating that gamma-ray-line (GRL) flares are fundamentally different from other large flares without detectable GRL emission and find no compelling support for this proposition. For large flares observed by the Solar Maximum Mission (SMM) from 1980 to 1982, we obtain a reasonably good correlation between 4-8 MeV GRL fluences and > 50 keV hard X-ray fluences and find no evidence for a distinct population of large hard X-ray flares that lack commensurate GRL emission. Our results are consistent with the acceleration of the bulk of the approximately 100 keV electrons and approximately 10 MeV protons (i.e., the populations of these species that interact in the solar atmosphere to produce hard X-ray and GRL emission) by a common process in large flares of both long and short durations. C1 COPENHAGEN UNIV OBSERV,DK-1350 COPENHAGEN K,DENMARK. NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771. RP CLIVER, EW (reprint author), PHILLIPS LAB,GEOPHYS DIRECTORATE GPSG,BEDFORD,MA 01731, USA. RI Dennis, Brian/C-9511-2012 NR 34 TC 18 Z9 18 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 10 PY 1994 VL 426 IS 2 BP 767 EP 773 DI 10.1086/174113 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NK032 UT WOS:A1994NK03200032 ER PT J AU ANSONG, O ANTOINE, MD NWOKOGU, GC HERGENROTHER, PM AF ANSONG, O ANTOINE, MD NWOKOGU, GC HERGENROTHER, PM TI SYNTHESIS OF DIFUNCTIONAL TRIARYLETHANES WITH PENDENT ETHYNYL GROUPS - MONOMERS FOR CROSS-LINKABLE CONDENSATION POLYMERS SO JOURNAL OF ORGANIC CHEMISTRY LA English DT Article ID PHENYLETHYNYL GROUPS; POLY(PHENYLQUINOXALINES); KETONES; ESTERS AB Synthetic schemes have been developed and optimized for the preparation of groups of 4,4'-diamino- and 4,4'-dihydroxytriarylethanes with an ethynyl group pendent on the third aryl group. Palladium(0)-catalyzed reaction of an aryl halide moiety with an acetylene is used for the attachment of the ethynyl group. The third aryl group is either a phenyl or a phenoxyphenyl group, while the other end of the ethynyl group is either unprotected or bears an n-butyl or phenyl group. The variations in the structure of the third aryl group and the cap on its acetylene group are chosen to probe their influence on the mechanical properties of the resulting crosslinked thermoplastics. C1 HAMPTON UNIV,DEPT CHEM,HAMPTON,VA 23668. NASA,LANGLEY RES CTR,HAMPTON,VA 23665. NR 25 TC 6 Z9 6 U1 1 U2 7 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0022-3263 J9 J ORG CHEM JI J. Org. Chem. PD MAY 6 PY 1994 VL 59 IS 9 BP 2506 EP 2510 DI 10.1021/jo00088a035 PG 5 WC Chemistry, Organic SC Chemistry GA NL362 UT WOS:A1994NL36200035 ER PT J AU RAY, RD STEINBERG, DJ CHAO, BF CARTWRIGHT, DE AF RAY, RD STEINBERG, DJ CHAO, BF CARTWRIGHT, DE TI DIURNAL AND SEMIDIURNAL VARIATIONS IN THE EARTHS ROTATION RATE INDUCED BY OCEANIC TIDES SO SCIENCE LA English DT Article ID PERIODIC CHANGES AB Recent space-geodetic observations have revealed daily and subdaily variations in the Earth's rotation rate. Although spectral analysis suggests that the variations are primarily of tidal origin, comparisons to previous theoretical predictions based on various ocean models have been less than satisfactory. This disagreement is partly caused by deficiencies in physical modeling. Rotation predictions based on a reliable tidal-height model, with corresponding tidal currents inferred from a modified form of Laplace's momentum equations, yield predictions of tidal variations in Universal Time that agree with very long baseline interferometer observations to 2 microseconds. This agreement resolves a major discrepancy between theory and observation and establishes the dominant role of oceanic tides for inducing variation in the Earth's rotation at these frequencies. RP RAY, RD (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GEODYNAM BRANCH,CODE 926,GREENBELT,MD 20771, USA. RI Ray, Richard/D-1034-2012; Chao, Benjamin Fong/N-6156-2013 NR 21 TC 58 Z9 61 U1 0 U2 3 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 SN 0036-8075 J9 SCIENCE JI Science PD MAY 6 PY 1994 VL 264 IS 5160 BP 830 EP 832 DI 10.1126/science.264.5160.830 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA NJ949 UT WOS:A1994NJ94900029 PM 17794725 ER PT J AU DIBROZOLO, FR BUNCH, TE FLEMING, RH MACKLIN, J AF DIBROZOLO, FR BUNCH, TE FLEMING, RH MACKLIN, J TI FULLERENES IN AN IMPACT CRATER ON THE LDEF SPACECRAFT SO NATURE LA English DT Article ID ENVIRONMENT; C-60 AB THE fullerenes C-60 (ref. 1) and C-70 have been found to occur naturally on Earth(2,3), and have also been invoked to explain features in the absorption spectra of interstellar clouds(1,4). But no definitive spectroscopic evidence exists for fullerenes in space and attempts to find fullerenes in carbonaceous chondrites have been unsuccessful(5,6), Here we report the observation of fullerenes associated with carbonaceous impact residue in a crater on the Long Duration Exposure Facility (LDEF) spacecraft. Laser ionization mass spectrometry and Raman spectroscopy indicate the presence of fullerenes in the crater and in adjacent ejecta. Man-made fullerenes survive experimental hypervelocity (similar to 6.1 km s(-1)) impacts into aluminium targets, suggesting that space fullerenes contained in a carbonaceous micrometeorite could have survived the LDEF impact at velocities towards the lower end of the natural particle encounter range (<13 km s(-1)). We also demonstrate that the fullerenes were unlikely to have formed as instrumental artefacts, nor are they present as contaminants. Although we cannot specify the origin of the fullerenes with certainty, the most plausible source is the chondritic impactor. If, alternatively, the impact produced the fullerenes in situ on LDEF, then this suggests a viable mechanism for fullerene production in space. C1 NASA, AMES RES CTR, PLANETARY BIOL BRANCH, MOFFETT FIELD, CA 94035 USA. UNIV WASHINGTON, DEPT CHEM, SEATTLE, WA 98195 USA. RP DIBROZOLO, FR (reprint author), CHARLES EVANS & ASSOCIATES, REDWOOD CITY, CA 94063 USA. NR 17 TC 36 Z9 36 U1 0 U2 2 PU NATURE PUBLISHING GROUP PI LONDON PA MACMILLAN BUILDING, 4 CRINAN ST, LONDON N1 9XW, ENGLAND SN 0028-0836 EI 1476-4687 J9 NATURE JI Nature PD MAY 5 PY 1994 VL 369 IS 6475 BP 37 EP 40 DI 10.1038/369037a0 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA NJ860 UT WOS:A1994NJ86000044 PM 11541208 ER PT J AU KAUFMAN, YJ TANRE, D AF KAUFMAN, YJ TANRE, D TI EFFECT OF VARIATIONS IN SUPERSATURATION ON THE FORMATION OF CLOUD CONDENSATION NUCLEI SO NATURE LA English DT Article ID AEROSOL; CHEMISTRY; CLIMATE; OCEAN AB SULPHATE aerosols can act as nuclei for cloud formation, thereby cooling the climate by increasing the Earth's albedo(1-5): however the magnitude of this effect is very uncertain(3,6). Recently, Langner et al.(7) calculated that at most 6% of the anthropogenic sulphur emission forms new particles, while 44% adds mass to existing sulphate particles activated in clouds. It was therefore suggested(7,8) that previous studies(1,2,9) had overestimated the effect of sulphate aerosols on climate. Although it has been proposed that sub-CCN-size particles can grow to CCN-size in clouds(7,10), this was thought to require the large supersaturations present in cumuliform clouds, rather than the smaller values characteristic of marine stratiform clouds, which are most important for radiative forcing. Here we show that natural variability of even low average supersaturations allows particles as small as 0.015 mu m to grow to become CCN. This process can quadruple the CCN concentration and significantly increase the corresponding aerosol effect on climate. C1 UNIV LILLE 1,OPT ATMOSPHER LAB,F-59655 VILLENEUVE DASCQ,FRANCE. RP KAUFMAN, YJ (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 913,GREENBELT,MD 20771, USA. NR 26 TC 45 Z9 45 U1 4 U2 8 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW SN 0028-0836 J9 NATURE JI Nature PD MAY 5 PY 1994 VL 369 IS 6475 BP 45 EP 48 DI 10.1038/369045a0 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA NJ860 UT WOS:A1994NJ86000047 ER PT J AU PARK, JS LIN, TL JONES, EW DELCASTILLO, HM GUNAPALA, SD AF PARK, JS LIN, TL JONES, EW DELCASTILLO, HM GUNAPALA, SD TI LONG-WAVELENGTH STACKED SIGE/SI HETEROJUNCTION INTERNAL PHOTOEMISSION INFRARED DETECTORS USING MULTIPLE SIGE/SI LAYERS SO APPLIED PHYSICS LETTERS LA English DT Article ID MOLECULAR-BEAM EPITAXY; QUANTUM-WELLS AB Utilizing low temperature silicon molecular beam epitaxy growth, long-wavelength stacked SiGe/Si heterojunction internal photoemission (HIP) infrared detectors with multiple SiGe/Si layers have been fabricated and demonstrated. Using an elemental boron source, high doping concentration (almost-equal-to 4 X 10(20) cm-3) has been achieved and high crystalline quality multiple SiO.7Ge0.3/Si layers have been obtained. The detector structure consists of several periods of degenerately boron doped (almost-equal-to 4 X 10(20) cm-3) thin (less-than-or-equal-to 50 angstrom) SiO.7Ge0.3 layers and undoped thick (almost-equal-to 300 angstrom) Si layers. The multiple p + -Si 0.7Ge0.3/undoped-Si layers show strong infrared absorption in the long-wavelength regime mainly through free-carrier absorption. The stacked SiO.7Ge0.3/Si HIP detectors with p = 4 X 10(20) cm-3 exhibit strong photoresponse at wavelengths ranging 2-20 mum with quantum efficiencies of about 4% and 1.5% at 10 and 15 mum wavelengths, respectively. The detectors show near ideal thermionic-emission limited dark current characteristics. RP PARK, JS (reprint author), JET PROP LAB,CTR SPACE MICROELECTR TECHNOL,PASADENA,CA 91109, USA. NR 8 TC 23 Z9 24 U1 0 U2 2 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 MAY 2 PY 1994 VL 64 IS 18 BP 2370 EP 2372 DI 10.1063/1.111617 PG 3 WC Physics, Applied SC Physics GA NK026 UT WOS:A1994NK02600015 ER PT J AU WILT, DM FATEMI, NS HOFFMAN, RW JENKINS, PP BRINKER, DJ SCHEIMAN, D LOWE, R FAUER, M JAIN, RK AF WILT, DM FATEMI, NS HOFFMAN, RW JENKINS, PP BRINKER, DJ SCHEIMAN, D LOWE, R FAUER, M JAIN, RK TI HIGH-EFFICIENCY INDIUM GALLIUM-ARSENIDE PHOTOVOLTAIC DEVICES FOR THERMOPHOTOVOLTAIC POWER-SYSTEMS SO APPLIED PHYSICS LETTERS LA English DT Article ID ENERGY-CONVERSION; CELLS AB The development of indium gallium arsenide (E(g)=0.75 eV) photovoltaic devices for thermophotovoltaic power generation is described. A device designed for broadband response had an air mass zero efficiency of 11.2 % and an internal quantum yield of over 90% in the range of 800 to 1500 nm. Devices designed for narrow-band response have also been developed. Both structures are based on a n/p junction which also makes them applicable for integration into indium phosphide based, monolithic, tandem solar cells for solar photovoltaic applications. C1 SVERDRUP TECHNOL,BROOKPART,OH 44121. ANALEX CORP,BROOKPARK,OH 44121. CLEVELAND STATE UNIV,CLEVELAND,OH 44115. RP WILT, DM (reprint author), NASA,LEWIS RES CTR,PHOTOVOLTA BRANCH,CLEVELAND,OH 44135, USA. NR 7 TC 20 Z9 20 U1 0 U2 2 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 MAY 2 PY 1994 VL 64 IS 18 BP 2415 EP 2417 DI 10.1063/1.111585 PG 3 WC Physics, Applied SC Physics GA NK026 UT WOS:A1994NK02600030 ER PT J AU LAVERY, D AF LAVERY, D TI PERSPECTIVES ON FUTURE SPACE ROBOTICS SO AEROSPACE AMERICA LA English DT Article RP LAVERY, D (reprint author), NASA,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 MAY PY 1994 VL 32 IS 5 BP 32 EP 37 PG 6 WC Engineering, Aerospace SC Engineering GA NK789 UT WOS:A1994NK78900010 ER PT J AU BEKEY, I POWELL, R AUSTIN, R AF BEKEY, I POWELL, R AUSTIN, R TI NASA STUDIES ACCESS TO SPACE SO AEROSPACE AMERICA LA English DT Article RP BEKEY, I (reprint author), NASA,WASHINGTON,DC 20546, USA. NR 0 TC 10 Z9 10 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0740-722X J9 AEROSPACE AM JI Aerosp. Am. PD MAY PY 1994 VL 32 IS 5 BP 38 EP 43 PG 6 WC Engineering, Aerospace SC Engineering GA NK789 UT WOS:A1994NK78900011 ER PT J AU MANKBADI, RR HAYER, ME POVINELLI, LA AF MANKBADI, RR HAYER, ME POVINELLI, LA TI STRUCTURE OF SUPERSONIC JET FLOW AND ITS RADIATED SOUND SO AIAA JOURNAL LA English DT Article ID COHERENT STRUCTURES; INSTABILITY WAVES; SUBSONIC JET; SHEAR FLOWS; NOISE; FIELD; TURBULENCE; ACOUSTICS AB The present paper explores the use of large-eddy simulations as a tool for predicting noise from first principles. A high-order numerical scheme is used to perform large-eddy simulations of a supersonic jet now with emphasis on capturing the time-dependent flow structure representing the sound source. The wavelike nature of this structure under random inflow disturbances is demonstrated. This wavelike structure is then enhanced by taking the inflow disturbances to be purely harmonic. Application of Lighthill's theory to calculate the far-field noise, with the sound source obtained from the calculated time-dependent near field, is demonstrated. Alternative approaches to coupling the near-field sound source to the far-field sound are discussed. C1 NASA,LEWIS RES CTR,INST COMPUTAT MECH PROPULS,CLEVELAND,OH 44135. NASA,LEWIS RES CTR,DIV INTERNAL FLUID MECH,CLEVELAND,OH 44135. RP MANKBADI, RR (reprint author), NASA,LEWIS RES CTR,COMPUTAT AEROACOUST,CLEVELAND,OH 44135, USA. NR 50 TC 48 Z9 49 U1 0 U2 5 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0001-1452 J9 AIAA J JI AIAA J. PD MAY PY 1994 VL 32 IS 5 BP 897 EP 906 DI 10.2514/3.12072 PG 10 WC Engineering, Aerospace SC Engineering GA NJ389 UT WOS:A1994NJ38900001 ER PT J AU EKLUND, DR FLETCHER, DG HARTFIELD, RJ MCDANIEL, JC NORTHAM, GB DANCEY, CL WANG, JA AF EKLUND, DR FLETCHER, DG HARTFIELD, RJ MCDANIEL, JC NORTHAM, GB DANCEY, CL WANG, JA TI COMPUTATIONAL EXPERIMENTAL INVESTIGATION OF STAGED INJECTION INTO A MACH-2 FLOW SO AIAA JOURNAL LA English DT Article ID INDUCED IODINE FLUORESCENCE; SUPERSONIC COMBUSTOR AB The staged normal injection of two jets of air into a Mach 2 freestream behind a rearward-facing step has been investigated using laser-induced iodine fluorescence and laser doppler anemometry techniques. A detailed data set has been compiled that includes profiles of pressure, temperature, two components of velocity, and mole fraction of the injectant at 44 locations, plus planar surveys of pressure, temperature, velocity, and mole fraction. A companion numerical study was performed using the SPARK Navier-Stokes code. Good overall agreement was observed for this complex, highly three-dimensional flowfield. Discrepancies were observed in the computed and measured total temperatures, turbulent mixing, and shock strengths. The effect of grid resolution was investigated by calculating solutions on grids of 60,000 points, 200,000 points, and 450,000 points. Differences in the solutions on the two finer grids were small. The effect of turbulence modeling was investigated by calculating solutions with three different algebraic models for the jet turbulence. Overall, the turbulence models were found to have the greatest effect on the numerical solutions, followed by the grid resolution and the injectant Mach number. C1 UNIV VIRGINIA,DEPT MECH & AEROSP ENGN,CHARLOTTESVILLE,VA 22903. NASA,LANGLEY RES CTR,EXPTL METHODS BRANCH,HAMPTON,VA 23681. VIRGINIA POLYTECH INST & STATE UNIV,DEPT MECH ENGN,BLACKSBURG,VA 24061. RP EKLUND, DR (reprint author), NATL RES COUNCIL,HAMPTON,VA 23681, USA. NR 21 TC 9 Z9 9 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 MAY PY 1994 VL 32 IS 5 BP 907 EP 916 DI 10.2514/3.12073 PG 10 WC Engineering, Aerospace SC Engineering GA NJ389 UT WOS:A1994NJ38900002 ER PT J AU KAO, KH LIOU, MS CHOW, CY AF KAO, KH LIOU, MS CHOW, CY TI GRID ADAPTATION USING CHIMERA COMPOSITE OVERLAPPING MESHES SO AIAA JOURNAL LA English DT Article ID GENERATION AB The objective of this paper is to perform grid adaptation using composite overlapping meshes in regions of large gradient to accurately capture the salient features during computation. The chimera grid scheme, a multiple overset mesh technique, is used in combination with a Navier-Stokes solver. The numerical solution is first converged to a steady state based on an initial coarse mesh. Solution-adaptive enhancement is then performed by using a secondary fine grid system which oversets on top of the base grid in the high-gradient region, but without requiring the mesh boundaries to join in any special way. Communications through boundary interfaces between those separated grids are carried out using trilinear interpolation. Applications to the Euler equations for shock reflections and to a shock wave/boundary layer interaction problem are tested. With the present method, the salient features are well-resolved. C1 UNIV COLORADO,DEPT AEROSP ENGN SCI,BOULDER,CO 80309. RP KAO, KH (reprint author), NASA,LEWIS RES CTR,INST COMPUTAT MECH PROPULS,CLEVELAND,OH 44135, USA. NR 21 TC 17 Z9 19 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 MAY PY 1994 VL 32 IS 5 BP 942 EP 949 DI 10.2514/3.12078 PG 8 WC Engineering, Aerospace SC Engineering GA NJ389 UT WOS:A1994NJ38900007 ER PT J AU YOON, SK KWAK, DC AF YOON, SK KWAK, DC TI MULTIGRID CONVERGENCE OF AN IMPLICIT SYMMETRICAL RELAXATION SCHEME SO AIAA JOURNAL LA English DT Article ID EULER EQUATIONS; ALGORITHM; FLOWS AB The multigrid method has been applied to an existing three-dimensional compressible Euler solver to accelerate the convergence of the implicit symmetric relaxation scheme. This lower-upper symmetric Gauss-Seidel implicit scheme is shown to be an effective multigrid driver in three dimensions. A grid refinement study is performed including the effects of large cell aspect ratio meshes. Performance figures of the present multigrid code on Cray computers including the new C90 are presented. A reduction of three orders of magnitude in the residual for a three-dimensional transonic inviscid flow using 920 k grid points is obtained in less than 4 min on a Cray C90. RP NASA, AMES RES CTR, COMPUTAT ALGORITHMS & APPLICAT BRANCH, MOFFETT FIELD, CA 94035 USA. NR 23 TC 8 Z9 8 U1 0 U2 0 PU AMER INST AERONAUTICS ASTRONAUTICS PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091-4344 USA SN 0001-1452 EI 1533-385X J9 AIAA J JI AIAA J. PD MAY PY 1994 VL 32 IS 5 BP 950 EP 955 DI 10.2514/3.12079 PG 6 WC Engineering, Aerospace SC Engineering GA NJ389 UT WOS:A1994NJ38900008 ER PT J AU DUFFY, SF PALKO, JL AF DUFFY, SF PALKO, JL TI ANALYSIS OF WHISKER-TOUGHENED CERAMIC COMPONENTS USING AN INTERACTIVE RELIABILITY MODEL SO AIAA JOURNAL LA English DT Article ID FRACTURE; STRENGTH; COMPOSITES AB Realizing wider use of ceramic matrix composites requires the development of advanced structural analysis technologies. This article focuses on the use of interactive reliability models to predict component probability of failure. The deterministic Willam-Warnke failure criterion is the theoretical basis for the reliability model presented herein. The model has been incorporated into a test-bed software program. This computer program is coupled to a general-purpose finite element program. A simple structural problem is presented to illustrate the reliability model and the computer algorithm. C1 NASA,LEWIS RES CTR,DIV STRUCT,STRUCT INTEGR BRANCH,CLEVELAND,OH 44135. RP DUFFY, SF (reprint author), CLEVELAND STATE UNIV,DEPT CIVIL ENGN,CLEVELAND,OH 44115, USA. NR 28 TC 0 Z9 0 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0001-1452 J9 AIAA J JI AIAA J. PD MAY PY 1994 VL 32 IS 5 BP 1043 EP 1048 DI 10.2514/3.12092 PG 6 WC Engineering, Aerospace SC Engineering GA NJ389 UT WOS:A1994NJ38900021 ER PT J AU LIM, TW KASHANGAKI, TAL AF LIM, TW KASHANGAKI, TAL TI STRUCTURAL DAMAGE DETECTION OF SPACE TRUSS STRUCTURES USING BEST ACHIEVABLE EIGENVECTORS SO AIAA JOURNAL LA English DT Article ID FINITE-ELEMENT MODELS; EIGENSTRUCTURE ASSIGNMENT; STIFFNESS; IDENTIFICATION; ADJUSTMENT AB A method is presented by which measured modes and frequencies from a modal test can be used to determine the location and magnitude of damage in a space truss structure. The damage is located by computing the Euclidean distances between the measured mode shapes and the best achievable eigenvectors. The best achievable eigenvectors are the projection of the measured mode shapes onto the subspace defined by the refined analytical model of the structure and the measured frequencies. Loss of both stiffness and mass properties can be located and quantified. To examine the performance of the method when experimentally measured modes are employed, various damage detection studies using a laboratory eight-bay truss structure were conducted. The method performs well even though the measurement errors inevitably make the damage location more difficult. C1 NASA,LANGLEY RES CTR,SPACECRAFT DYNAM BRANCH,HAMPTON,VA 23665. RP LIM, TW (reprint author), UNIV KANSAS,DEPT AEROSP ENGN,LAWRENCE,KS 66047, USA. NR 17 TC 93 Z9 105 U1 1 U2 7 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 MAY PY 1994 VL 32 IS 5 BP 1049 EP 1057 DI 10.2514/3.12093 PG 9 WC Engineering, Aerospace SC Engineering GA NJ389 UT WOS:A1994NJ38900022 ER PT J AU OBAYASHI, S WADA, Y AF OBAYASHI, S WADA, Y TI PRACTICAL FORMULATION OF A POSITIVELY CONSERVATIVE SCHEME SO AIAA JOURNAL LA English DT Note ID GODUNOV-TYPE METHODS C1 NASA,LEWIS RES CTR,INST COMPUTAT MECH PROPULS,CLEVELAND,OH 44135. RP OBAYASHI, S (reprint author), NASA,AMES RES CTR,MCAT INST,MOFFETT FIELD,CA 94035, USA. NR 6 TC 13 Z9 14 U1 0 U2 2 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0001-1452 J9 AIAA J JI AIAA J. PD MAY PY 1994 VL 32 IS 5 BP 1093 EP 1095 DI 10.2514/3.12104 PG 3 WC Engineering, Aerospace SC Engineering GA NJ389 UT WOS:A1994NJ38900033 ER PT J AU KAMBHAMPATI, S KEDAR, S AF KAMBHAMPATI, S KEDAR, S TI A UNIFIED FRAMEWORK FOR EXPLANATION-BASED GENERALIZATION OF PARTIALLY ORDERED AND PARTIALLY INSTANTIATED PLANS SO ARTIFICIAL INTELLIGENCE LA English DT Article AB Most previous work in explanation-based generalization (EBG) of plans dealt with totally ordered plans. These methods cannot be directly applied to generalizing partially ordered partially instantiated plans, a class of plans that have received significant attention in planning. In this paper we present a natural way of extending the explanation-based generalization methods to partially ordered partially instantiated (POPI) plans. Our development is based on modal truth criteria for POPI plans [3]. We develop explanation structures from these truth criteria, and use them as a common basis to derive a variety of generalization algorithms. Specifically we present algorithms for precondition generalization, order generalization, and possible correctness generalization of POPI plans. The systematic derivation of the generalization algorithms from the modal truth criterion obviates the need for carrying out a separate formal proof of correctness of the EBG algorithms. Our development also systematically explicates the tradeoffs among the spectrum of possible generalizations for POPI plans, and provides an empirical demonstration of the relative utility of EBG in partial ordering, as opposed to total ordering, planning frameworks. C1 NASA,AMES RES CTR,AI RES BRANCH,STERLING FED SYST,MOFFETT FIELD,CA 94035. RP KAMBHAMPATI, S (reprint author), ARIZONA STATE UNIV,DEPT COMP SCI & ENGN,TEMPE,AZ 85287, USA. NR 39 TC 12 Z9 12 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0004-3702 J9 ARTIF INTELL JI Artif. Intell. PD MAY PY 1994 VL 67 IS 1 BP 29 EP 70 DI 10.1016/0004-3702(94)90011-6 PG 42 WC Computer Science, Artificial Intelligence SC Computer Science GA NM844 UT WOS:A1994NM84400002 ER PT J AU SILBERMANN, NA SMITH, HA BOLTE, M HAZEN, ML AF SILBERMANN, NA SMITH, HA BOLTE, M HAZEN, ML TI RR-LYRAE STARS AND COLOR MAGNITUDE DIAGRAM OF THE GLOBULAR-CLUSTER NGC-6388 SO ASTRONOMICAL JOURNAL LA English DT Article ID OOSTERHOFF PERIOD GROUPS; HORIZONTAL-BRANCH; METAL ABUNDANCES; PHOTOMETRY; GALAXY; AGE; SYSTEM; METALLICITY AB We present new V, B - V and V, V - R color-magnitude diagrams for the bulge globular cluster NGC 6388. These diagrams indicate that NGC 6388 is a metal-rich globular cluster with color-magnitude morphology similar to that of 47 Tucanae. We have conducted a search for new variable stars close to NGC 6388, finding three new RR Lyrae stars. The membership of these and previously discovered RR Lyrae stars near NGC 6388 is discussed. There is reason for believing that some of these variables are nonmembers. Others, however, may belong to the cluster and may be similar to the RR Lyrae star V9 in 47 Tuc. C1 UNIV CALIF SANTA CRUZ,NASA,STSCI,UCO,SANTA CRUZ,CA 95064. UNIV CALIF SANTA CRUZ,LICK OBSERV,SANTA CRUZ,CA 95064. HARVARD SMITHSONIAN CTR ASTROPHYS,CAMBRIDGE,MA 02138. RP SILBERMANN, NA (reprint author), MICHIGAN STATE UNIV,DEPT PHYS & ASTRON,E LANSING,MI 48824, USA. NR 33 TC 15 Z9 15 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 MAY PY 1994 VL 107 IS 5 BP 1764 EP 1772 DI 10.1086/116984 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NJ373 UT WOS:A1994NJ37300014 ER PT J AU SHAHIDSALESS, B YEOMANS, DK AF SHAHIDSALESS, B YEOMANS, DK TI RELATIVISTIC EFFECTS ON THE MOTION OF ASTEROIDS AND COMETS SO ASTRONOMICAL JOURNAL LA English DT Article ID FRAMES; SATELLITE; SYSTEM AB We study the effects arising from relativistic perturbations on the motion of asteroids and comets and show that for a number of such objects, inclusion of relativistic contributions in the equations of motion gives rise to significant improvements in the orbital solutions. Furthermore we argue that ignoring relativistic corrections to the equations of motion, while using masses derived from relativistic ephemerides yields incorrect solutions corresponding to an inconsistent, non-Newtonian, nonrelativistic model. C1 JET PROP LAB,PASADENA,CA 91109. NR 20 TC 10 Z9 10 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 MAY PY 1994 VL 107 IS 5 BP 1885 EP 1889 DI 10.1086/116999 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NJ373 UT WOS:A1994NJ37300029 ER PT J AU GREINER, J HASINGER, G MOLENDI, S EBISAWA, K AF GREINER, J HASINGER, G MOLENDI, S EBISAWA, K TI NEAR-SIMULTANEOUS ROSAT AND GINGA OBSERVATIONS OF THE 1991 X-RAY TRANSIENT IN MUSCA SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE X-RAYS, STARS; BLACK HOLES; BINARIES, CLOSE; ACCRETION DISKS ID THICK ACCRETION DISKS; BLACK-HOLE CANDIDATES; NOVA-MUSCAE; SOURCE A0620-00; DISCOVERY; INSTABILITY; SPECTRA; GRANAT; MODEL; STATE AB During its All-Sky-Survey ROSAT has observed the Musca 1991 X-ray transient on January 24/25, two weeks after outburst, for about 170s. The intensity was found to be nearly 6 Crab in the ROSAT band. A combined fit of ROSAT and Ginga data from 1991 January 25 with a multitemperature disk black-body model plus a power law component results in a maximal temperature of the disk of about kT = 0.96 keV at an absorbing column of N(H) = 2.2 x 10(21) cm-2. With the knowledge of the mass function f(M) = 3.1 M. from optical observations we derive a minimum distance to the black hole binary of at least 4-5 kpc. Including the accretion disk inclination angle of i = 26-degrees +/- 25-degrees determined from the shape of the positron annihilation line, and the quiescent optical brightness together with the most probable spectral type of the companion we derive a black hole mass of M = (6 +/- 1.5) M. and a distance of about (11 +/- 3) kpc. Additional ROSAT observations in August 1991 and March 1992 suggest that the exponential intensity decay until 240 days after the outburst is followed by a steeper decline between days 240 and 410. C1 INST SPACE & ASTRONAUT SCI, SAGAMIHARA, KANAGAWA 229, JAPAN. NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. RP GREINER, J (reprint author), MAX PLANCK INST EXTRATERR PHYS, D-85740 GARCHING, GERMANY. NR 44 TC 23 Z9 23 U1 0 U2 3 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD MAY PY 1994 VL 285 IS 2 BP 509 EP 523 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NM403 UT WOS:A1994NM40300022 ER PT J AU PONZ, JD THOMPSON, RW MUNOZ, JR AF PONZ, JD THOMPSON, RW MUNOZ, JR TI THE FITS IMAGE EXTENSION SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article DE ASTRONOMICAL DATA BASES; MISCELLANEOUS TECHNIQUES; IMAGE PROCESSING AB The Flexible Image Transport System (FITS) image extension provides a convenient means of storing two or more related but not necessarily identical multidimensional arrays in a single file. It conforms to the guidelines and rules for generalized FITS extensions and is structured in a manner identical to that of a primary header and data unit; thereby making it simple to interpret and compatible with existing FITS readers. The structure of the image extension and its potential uses are discussed. C1 GSFC, CSC, CODE 6849, GREENBELT, MD 20771 USA. ESTEC, SSD, ESA, 2200 AG NOORDWIJK, NETHERLANDS. RP ECNOD VILLAFRANCA, ESA, POB 50727, E-28080 MADRID, SPAIN. NR 6 TC 13 Z9 15 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 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD MAY PY 1994 VL 105 IS 1 BP 53 EP 55 PG 3 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NN278 UT WOS:A1994NN27800007 ER PT J AU SREEKUMAR, P BERTSCH, DL DINGUS, BL ESPOSITO, JA FICHTEL, CE HARTMAN, RC HUNTER, SD KANBACH, G KNIFFEN, DA LIN, YC MATTOX, JR MAYERHASSELWANDER, HA MICHELSON, PF VONMONTIGNY, C NOLAN, PL SCHNEID, EJ THOMPSON, DJ AF SREEKUMAR, P BERTSCH, DL DINGUS, BL ESPOSITO, JA FICHTEL, CE HARTMAN, RC HUNTER, SD KANBACH, G KNIFFEN, DA LIN, YC MATTOX, JR MAYERHASSELWANDER, HA MICHELSON, PF VONMONTIGNY, C NOLAN, PL SCHNEID, EJ THOMPSON, DJ TI A STUDY OF M31, M87, NGC 253, AND M82 IN HIGH-ENERGY GAMMA-RAYS SO ASTROPHYSICAL JOURNAL LA English DT Article DE COSMIC RAYS; GALAXIES, GENERAL; GAMMA RAYS; OBSERVATIONS ID LARGE MAGELLANIC CLOUD; CONTINUUM OBSERVATIONS; GALAXY M82; RADIO HALO; NGC-253; CO AB The data from the Energetic Gamma Ray Experiment Telescope (EGRET) all-sky survey are examined for emission from the nearby galaxies M31, M87, NGC 253, and M82 in the high-energy (E > 30 MeV) gamma-ray range. No significant emission is observed from any of these galaxies. The derived upper limits for all four galaxies are consistent with that expected from cosmic-ray interactions. For M87, the combination of the high-energy gamma-ray and radio data point to a lower limit of 7 muG for the magnetic field in the disk and 4 muG for the magnetic field in the halo, consistent with equipartition arguments. A study of NGC 253 and M82 show that EGRET observations do not sufficiently constrain the mean cosmic-ray energy density to provide more details on the cosmic-ray distribution in starburst galaxies. C1 MAX PLANCK INST EXTRATERR PHYS,W-8046 GARCHING,GERMANY. HAMPDEN SYDNEY COLL,HAMPDEN SYDNEY,VA 23943. STANFORD UNIV,HANSEN EXPTL PHYS LAB,STANFORD,CA 94305. COMP SCI CORP,COMPTON OBSERV SCI SUPPORT CTR,ASTRON PROGRAMS,GREENBELT,MD. GRUMMAN AEROSP CORP,BETHPAGE,NY 11714. RP SREEKUMAR, P (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 662,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; Dingus, Brenda/0000-0001-8451-7450 NR 35 TC 28 Z9 28 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 MAY 1 PY 1994 VL 426 IS 1 BP 105 EP 108 DI 10.1086/174044 PN 1 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NG668 UT WOS:A1994NG66800011 ER PT J AU DOPITA, MA VASSILIADIS, E MEATHERINGHAM, SJ FORD, HC BOHLIN, R WOOD, PR STECHER, TP MARAN, SP HARRINGTON, JP AF DOPITA, MA VASSILIADIS, E MEATHERINGHAM, SJ FORD, HC BOHLIN, R WOOD, PR STECHER, TP MARAN, SP HARRINGTON, JP TI HUBBLE-SPACE-TELESCOPE OBSERVATIONS OF PLANETARY-NEBULAE IN THE MAGELLANIC CLOUDS .2. SMP 85, A YOUNG PLANETARY SO ASTROPHYSICAL JOURNAL LA English DT Article DE MAGELLANIC CLOUDS; PLANETARY NEBULAE, INDIVIDUAL (SMP 85) ID INTERNAL DYNAMICS; ANGULAR DIAMETERS; KINEMATICS; FLUXES; STARS AB We have obtained Hubble Space Telescope Planetary Camera images in the [O III] lambda5007 angstrom emission line, and FOS UV spectrophotometry of, the low-excitation planetary nebula SMP 85 in the Large Magellanic Cloud. By combining these results with existing optical spectrophotometry, absolute flux measurements, and dynamical and density information, we have been able to construct a fully self-consistent nebular model. This proves that SMP 85 is a dense, young, carbon-rich ob ect which started to be ionized about 500-1000 years ago, and which contains a substantial inner reservoir of atomic or molecular Fas, probably in the form of many small cloudlets. These cloudlets have been ejected at a velocity not exceeding 6 km s-1, a result which, together with the morphology is an important clue to mass loss during late AGB evolution. We have directly detected the central star through its UV continuum emission, and from both Zanstra techniques and nebular modeling derive a stellar temperature of 46000 +/- 2000 K, a stellar luminosity of 7300 +/- 700 L., and a core mass of 0.63-0.67 M.. The nebular analysis also demonstrates that there is severe depletion of the nebular gases onto dust grains, most likely of the calcium magnesium silicate variety; a surprising result in view of the carbon-rich nature of the ionized nebula. C1 SPACE TELESCOPE SCI INST,BALTIMORE,MD 21218. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. UNIV MARYLAND,DEPT ASTRON,COLL PK,MD 20742. RP DOPITA, MA (reprint author), AUSTRALIAN NATL UNIV,INST ADV STUDIES,MT STROMLO & SIDING SPRINGS OBSERV,WESTON,ACT 2611,AUSTRALIA. RI Dopita, Michael/P-5413-2014 OI Dopita, Michael/0000-0003-0922-4986 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 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 1 PY 1994 VL 426 IS 1 BP 150 EP 158 DI 10.1086/174050 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NG668 UT WOS:A1994NG66800017 ER PT J AU HORNE, K MARSH, TR CHENG, FH HUBENY, I LANZ, T AF HORNE, K MARSH, TR CHENG, FH HUBENY, I LANZ, T TI HST ECLIPSE MAPPING OF DWARF NOVA OY CARINAE IN QUIESCENCE - AN FE II CURTAIN WITH MACH-SIMILAR-OR-EQUAL-TO-6 VELOCITY DISPERSION VEILS THE WHITE-DWARF SO ASTROPHYSICAL JOURNAL LA English DT Article DE ACCRETION, ACCRETION DISKS; BINARIES, ECLIPSING; NOVAE, CATACLYSMIC VARIABLES; STARS, INDIVIDUAL (OY CARINAE); WHITE DWARFS ID MODEL STELLAR ATMOSPHERES; ACCRETION DISK AB HST observations of the eclipsing dwarf nova OY Car in its quiescent state are used to isolate the ultraviolet spectrum (1150-2500 angstrom at 9.2 angstrom FWHM resolution) of the white dwarf, the accretion disk, and the bright spot. The white dwarf dominates the ultraviolet flux, with the disk and bright spot contributions increasing longward of 2000 angstrom. The white dwarf spectrum has a Stark-broadened photospheric La absorption, but is veiled by a forest of blended Fe II features that we attribute to absorption by intervening disk material. A fit gives T(W) congruent-to 16.5 x 10(3) K for the white dwarf with a solar-abundance, log g = 8 model atmosphere, and T congruent-to 10(4) K, n(e) congruent-to 10(13) cm-3, N(H) congruent-to 10(22) cm-2, and velocity dispersion DELTAV congruent-to 60 km s-1 for the veil of homogeneous solar-abundance LTE gas. The veil parameters probably measure characteristic physical conditions in the quiescent accretion disk or its chromosphere. The large velocity dispersion is essential for a good fit; it lowers chi2/778 from 22 to 4. Keplerian shear can produce the velocity dispersion if the veiling gas is located at R congruent-to 5R(W) with DELTAR/R approximately 0.3, but this model leaves an unobscured view to the upper hemisphere of the white dwarf, incompatible with absorptions that are up to 80% deep. The veiling gas may be in the upper atmosphere of the disk near its outer rim, but we then require supersonic (Mach congruent-to 6) but sub-Keplerian (DELTAV/V(Kep) congruent-to 0.07) velocity disturbances in this region to produce both the observed radial velocity dispersion and vertical motions sufficient to elevate the gas to z/R = cos i = 0.12. Such motions might be driven by the gas stream, since it may take several Kepler periods to reestablish the disk's vertical hydrostatic equilibrium. The temperature and column density of the gas we see as Fe II absorption in the ultraviolet are similar to what is required to produce the strong Balmer jump and line emissions seen in optical spectra of OY Car and similar quiescent dwarf novae. The outer accretion disk is detected at mid-eclipse with a spectrum that rises from 0.05 to 0.3 mJy between 2000 and 2500 A, consistent with combinations of cool blackbodies, blended Fe II emission lines, and Balmer continuum emission. The total disk flux density is 0.5 mJy at 2500 angstrom, and this shallow disk eclipse implies a roughly flat surface brightness distribution. The bright spot, somewhat bluer than the disk, has a flux density rising from 0.05 to 0.15 mJy between 1600 and 2500 angstrom. The C IV emission line has a broad shallow eclipse, but the radial velocity variations observed during the eclipse do not clearly distinguish between a disk or wind origin. The only possible indications of boundary layer emission are fast UV flares that appear to arise from near the central object-not from the bright spot. C1 UNIV UTRECHT,INST STERREKUNDIG,3508 TA UTRECHT,NETHERLANDS. UNIV OXFORD,DEPT ASTROPHYS,OXFORD OX1 3RH,ENGLAND. UNIV SCI & TECHNOL CHINA,CTR ASTROPHYS,HEFEI,PEOPLES R CHINA. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP HORNE, K (reprint author), SPACE TELESCOPE SCI INST,3700 SAN MARTIN DRIVE,BALTIMORE,MD 21218, USA. NR 23 TC 91 Z9 91 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 MAY 1 PY 1994 VL 426 IS 1 BP 294 EP 307 DI 10.1086/174064 PN 1 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NG668 UT WOS:A1994NG66800031 ER PT J AU BIRD, MK VOLLAND, H PATZOLD, M EDENHOFER, P ASMAR, SW BRENKLE, JP AF BIRD, MK VOLLAND, H PATZOLD, M EDENHOFER, P ASMAR, SW BRENKLE, JP TI THE CORONAL ELECTRON-DENSITY DISTRIBUTION DETERMINED FROM DUAL-FREQUENCY RANGING MEASUREMENTS DURING THE 1991 SOLAR CONJUNCTION OF THE ULYSSES SPACECRAFT SO ASTROPHYSICAL JOURNAL LA English DT Article DE INTERPLANETARY MEDIUM; SOLAR WIND; SUN, CORONA; SUN, RADIO RADIATION AB Dual-frequency ranging and Doppler measurements were conducted in support of the Ulysses Solar Corona Experiment at and around the spacecraft's first solar conjunction in 1991 August. The differential group delay time between range codes on the two downlink carrier signals at the wavelengths 13.1 and 3.6 cm, a direct measure of the total electron content between spacecraft and ground station, was used to derive the electron density distribution in the solar corona. Linear power-law representations of the coronal electron density were derived for the range of solar distances from 4 R. to 40 R. on both sides of the Sun. The corona was found to be very nearly symmetric; the radial falloff exponent being 2.54 +/- 0.05 for occultation ingress (east solar limb) and 2.42 +/- 0.05 for egress (west limb), respectively. The departure of these exponents from the inverse square relation implies that significant solar wind acceleration is occurring within the radial range of the observations. The electron density level was found to be considerably lower than that observed during the 1988 December solar occultation of Voyager 2. Although the smoothed sunspot number R(Z) (a standard indicator of solar activity) was almost the same in 1988 December and 1991 August, the mean electron density at 20 R. was found to be 1.7 +/- 0.1 x 10(3) cm-3 during the Ulysses conjunction, a decline by almost a factor of 4 from the value obtained during the Voyager conjunction. C1 JET PROP LAB,PASADENA,CA 91109. UNIV COLOGNE,INST GEOPHYS & METEOROL,D-50923 COLOGNE,GERMANY. RUHR UNIV BOCHUM,INST HOCHFREQUENZTECH,D-44780 BOCHUM,GERMANY. RP BIRD, MK (reprint author), UNIV BONN,INST RADIOASTRON,HUGEL 71,D-53121 BONN,GERMANY. NR 19 TC 61 Z9 63 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 MAY 1 PY 1994 VL 426 IS 1 BP 373 EP 381 DI 10.1086/174073 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NG668 UT WOS:A1994NG66800040 ER PT J AU DEMING, D PLYMATE, C AF DEMING, D PLYMATE, C TI ON THE APPARENT VELOCITY OF INTEGRATED SUNLIGHT .2. 1983-1992 AND COMPARISONS WITH MAGNETOGRAMS SO ASTROPHYSICAL JOURNAL LA English DT Article DE SOLAR SYSTEM, GENERAL; SUN, GENERAL; SUN, INFRARED; TECHNIQUES, INTERFEROMETRIC ID SOLAR AB We report additional results in our program to monitor the wavelength stability of lines in the 2.3 mum spectrum of integrated sunlight. We use the McMath Fourier transform spectrometer (FTS) of the National Solar Observatory to monitor 16 AV = 2 lines of (CO)-C-12-O-16, as well as five atomic lines. Wavenumber calibration is achieved using a low-pressure N2O absorption cell and checked against terrestrial atmospheric lines. Imperfect optical integration of the solar disk remains the principal source of error, but this error has been reduced by improved FTS/telescope collimation and observing procedures. The present results include data from an additional 13 quarterly observing runs since 1985. We continue to find that the apparent velocity of integrated sunlight is variable, in the sense of having a greater redshift at solar maximum. This is supported by the temporal dependence of the integrated light velocity, and by the presence of a correlation between velocity and the disk-averaged magnetic flux derived from Kitt Peak magnetograms. The indicated peak-to-peak apparent velocity amplitude over a solar cycle is approximately the same as the velocity amplitude of the Sun's motion about the solar system barycenter. This represents about half the amplitude which we inferred in Paper I (Deming et al. 1987), but the present result has a much greater statistical significance. Our results have implications for those investigations which search for the Doppler signatures of planetary-mass companions to solar-type stars. We contrast our results to the recent finding by McMillan et al. 1993 that solar absorption lines in the violet spectral region are wavelength-stable over the solar cycle. C1 NATL SOLAR OBSERV,TUCSON,AZ 85726. RP DEMING, D (reprint author), NASA,GODDARD SPACE FLIGHT CTR,PLANETARY SYST BRANCH,CODE 693,GREENBELT,MD 20771, USA. NR 11 TC 26 Z9 26 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 1 PY 1994 VL 426 IS 1 BP 382 EP 386 DI 10.1086/174074 PN 1 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NG668 UT WOS:A1994NG66800041 ER PT J AU ASCHWANDEN, MJ BASTIAN, TS AF ASCHWANDEN, MJ BASTIAN, TS TI VLA STEREOSCOPY OF SOLAR ACTIVE REGIONS .1. METHOD AND TESTS SO ASTROPHYSICAL JOURNAL LA English DT Article DE METHODS, NUMERICAL; SUN, ACTIVITY; SUN, RADIO RADIATION; TECHNIQUES, IMAGE PROCESSING ID EMISSION; FLARES; SUN AB We develop a new technique for extracting three-dimensional information from multiday solar VLA observations. While standard stereoscopic methods provide a three-dimensional view of an object by combining simultaneous observations from two different aspect angles, we relax the condition of simultaneity and exploit solar rotation to vary the aspect angle. The solar radio images are decomposed into Gaussian source components, which are then cross-correlated in maps from preceding and following days. This provides measurements of the three-dimensional position of correlated source centroids. In this first paper, we describe the stereoscopic method and perform tests with simulated and real radio maps (from the VLA at 20 cm), in order to study the accuracy of altitude measurements, and the limitations introduced by (i) source confusion, (ii) source motion, and (iii) the assumed differential rotation rate. The tests demonstrate that (i) the information content of a VLA map relevant for stereoscopic correlation can be conveniently represented in terms of a small number of Gaussian components; (ii) the fitting of the three-dimensional source position is stable within a numerical accuracy of less-than-or-similar-to 0.02 map pixels; (iii) the relative accuracy of the altitude determination is uniform over the solar disk, and (iv) source confusion does not affect the accuracy of stereoscopic position measurements for sources with a signal-to-noise ratio of greater-than-or-similar-to 36. C1 NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771. NATL RADIO ASTRON OBSERV,SOCORRO,NM 87801. RP ASCHWANDEN, MJ (reprint author), UNIV MARYLAND,DEPT ASTRON,COLL PK,MD 20742, USA. NR 18 TC 35 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 MAY 1 PY 1994 VL 426 IS 1 BP 425 EP 433 DI 10.1086/174078 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NG668 UT WOS:A1994NG66800045 ER PT J AU ASCHWANDEN, MJ BASTIAN, TS AF ASCHWANDEN, MJ BASTIAN, TS TI VLA STEREOSCOPY OF SOLAR ACTIVE REGIONS .2. ALTITUDE, RELATIVE MOTION, AND CENTER-TO-LIMB DARKENING OF 20 CENTIMETER EMISSION SO ASTROPHYSICAL JOURNAL LA English DT Article DE METHODS, NUMERICAL; SUN, ACTIVITY; SUN, RADIO RADIATION; TECHNIQUES, IMAGE PROCESSING ID LARGE ARRAY OBSERVATIONS; STRUCTURES OBSERVING CAMPAIGN; MULTIPLE WAVELENGTH OBSERVATIONS; HIGH SPATIAL-RESOLUTION; X-RAY TELESCOPE; CORONAL LOOPS; MICROWAVE OBSERVATIONS; DIFFERENTIAL ROTATION; SUN; SUNSPOT AB A newly developed method of stereoscopic correlation is applied to solar radio maps at a wavelength of 20 cm. On the basis of stereoscopic correlations..between radio maps obtained on 6 different days we establish the presence of 66 radio source components associated with 22 active regions. We find the following statistical results for active region source structures at 20 cm: 1. The observed lifetime is consistent with an exponential distribution having an e-folding time scale of > 18 days. 2. The average altitude of 20 cm sources is 25 +/- 15 Mm; 90% of the sources are found in heights < 40 Mm. 3. The average diameter of discrete source structures is 48 +/- 15 Mm, implying a vertical/horizontal aspect ratio of q(A) almost-equal-to 0.5. 4. No significant source motion has been found with respect to the standard differential rotation rate of OMEGA = 13.45-degrees - 3-degrees sin 2 B. 5. We find a statistical limb darkening, which can be described by the relation T(B)(alpha)/T(B)(0) = 0.4 +/- 0.6 cos2 alpha for sources with T(B) > 0.5 MK. 6. The degree of source polarization is 15% +/- 10% and is independent of source location. 7. Bright sources (greater-than-or-equal-to 0.5 MK), or equivalently, long-lived sources (greater-than-or-similar-to 5 days) show a systematic variation of their altitude as function of the center-limb distance. We investigated a number of homogeneous and inhomogeneous active region models and found that inhomogeneous (both temperature and density) models are required to reproduce all observational constraints. C1 NATL RADIO ASTRON OBSERV,SOCORRO,NM 87801. NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771. RP ASCHWANDEN, MJ (reprint author), UNIV MARYLAND,DEPT ASTRON,COLL PK,MD 20742, USA. NR 56 TC 33 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 MAY 1 PY 1994 VL 426 IS 1 BP 434 EP 448 DI 10.1086/174079 PN 1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NG668 UT WOS:A1994NG66800046 ER PT J AU HORACK, JM EMSLIE, AG MEEGAN, CA AF HORACK, JM EMSLIE, AG MEEGAN, CA TI CONSTRAINTS ON THE LUMINOSITY FUNCTION OF GAMMA-RAY BURSTS DETECTED BY BATSE SO ASTROPHYSICAL JOURNAL LA English DT Article DE GAMMA-RAYS, BURSTS AB We have utilized the integral moment analysis technique of Horack & Emslie to extract information on the allowable form of the luminosity function for gamma-ray bursts observed by BATSE. Using the general properties of moments, we are able to derive constraints on-the range of luminosity from which the gamma-ray bursts must be sampled. These constraints are independent of the form of the radial distribution of the gamma-ray bursts, and depend only on the assumptions that space is Euclidean and that the luminosity function phi(L) is distance independent. For power-law luminosity functions of the form phi(L) = A(o)L(-alpha), we find that the range of luminosity from which 80% of the gamma-ray bursts must be sampled cannot exceed -6.5, with a 3 sigma upper limit of 12-15, regardless of the value of alpha. RP HORACK, JM (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,ES-66,HUNTSVILLE,AL 35812, USA. RI Horack, John/J-6670-2016 NR 13 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 MAY 1 PY 1994 VL 426 IS 1 BP L5 EP L9 DI 10.1086/187326 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NG669 UT WOS:A1994NG66900002 ER PT J AU STOTHERS, RB CHIN, CW AF STOTHERS, RB CHIN, CW TI LUMINOUS BLUE VARIABLES AT QUIESCENCE - THE ZONE OF AVOIDANCE IN THE HERTZSPRUNG-RUSSELL DIAGRAM SO ASTROPHYSICAL JOURNAL LA English DT Article DE STARS, EVOLUTION; STARS, OSCILLATIONS; STARS, VARIABLES, OTHER ID WOLF-RAYET STARS; LARGE MAGELLANIC CLOUD; MASS-LOSS; HR CARINAE; P-CYGNI; DISTANCE; WRA-751; NEBULA; VARIABILITY; EVOLUTION AB Two phases of dynamical instability are theoretically predicted to exist during the evolution of supergiants of normal metallicity that are initially more massive than approximately 60 M.. One phase occurs briefly in the yellow or red region of the Hertzsprung-Russell diagram for stars in the early stages of core helium burning, and the other phase occurs for a longer time in the blue or blue-white region for stars exhausting their core helium. Probably only the second phase exists in the case of supergiants with initial masses between approximately 60 M.. and approximately 30 M. or with low metallicities. The cause of instability is the partial ionization of hydrogen and helium in a quasi-isolated outer region of the stellar envelope, above the layer where the iron opacity attains a large local maximum. Predicted luminosities, effective temperatures, ejected nebular masses, remnant masses, eruption recurrence times, and lifetimes, though very approximate, are generally consistent with available observational data for the important class of unstable supergiants known as luminous blue variables. RP STOTHERS, RB (reprint author), NASA,GODDARD SPACE FLIGHT CTR,INST SPACE STUDIES,2880 BROADWAY,NEW YORK,NY 10025, USA. NR 39 TC 27 Z9 27 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 1 PY 1994 VL 426 IS 1 BP L43 EP L46 DI 10.1086/187335 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NG669 UT WOS:A1994NG66900011 ER PT J AU FISHMAN, GJ MEEGAN, CA WILSON, RB BROCK, MN HORACK, JM KOUVELIOTOU, C HOWARD, S PACIESAS, WS BRIGGS, MS PENDLETON, GN KOSHUT, TM MALLOZZI, RS STOLLBERG, M LESTRADE, JP AF FISHMAN, GJ MEEGAN, CA WILSON, RB BROCK, MN HORACK, JM KOUVELIOTOU, C HOWARD, S PACIESAS, WS BRIGGS, MS PENDLETON, GN KOSHUT, TM MALLOZZI, RS STOLLBERG, M LESTRADE, JP TI THE 1ST BATSE GAMMA-RAY BURST CATALOG SO ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES LA English DT Article DE CATALOGS; GAMMA-RAYS, BURSTS ID GALACTIC HALO; V/VMAX TEST; PULSARS; ORIGIN AB The Burst and Transient Source Experiment on the Compton Gamma-Ray Observatory detected 260 cosmic gamma-ray bursts during the period 1991 April 19 to 1992 March 5. This paper presents the occurrence times, locations, peak count rates, peak fluxes, fluences, durations, and plots of time histories for these bursts. The angular distribution is consistent with isotropy. The intensity distribution shows a deficit in the number of weak bursts, which is not consistent with a homogeneous distribution of burst sources in Euclidean space. The duration distribution shows evidence for a separate class of bursts with durations less than about 2 seconds. C1 UNIV SPACE RES ASSOC,COLUMBIA,MD 21044. UNIV ALABAMA,DEPT PHYS,HUNTSVILLE,AL 35899. MISSISSIPPI STATE UNIV,DEPT PHYS,MISSISSIPPI STATE,MS 39762. RP FISHMAN, GJ (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812, USA. RI Horack, John/J-6670-2016 NR 37 TC 278 Z9 284 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0067-0049 J9 ASTROPHYS J SUPPL S JI Astrophys. J. Suppl. Ser. PD MAY PY 1994 VL 92 IS 1 BP 229 EP 283 DI 10.1086/191968 PG 55 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NF993 UT WOS:A1994NF99300012 ER PT J AU SCHAEFER, BE TEEGARDEN, BJ FANTASIA, SF PALMER, D CLINE, TL MATTESON, JL BAND, DL FORD, LA FISHMAN, GJ MEEGAN, CA WILSON, RB PACIESAS, WS PENDLETON, GN BRIGGS, MS LESTRADE, JP AF SCHAEFER, BE TEEGARDEN, BJ FANTASIA, SF PALMER, D CLINE, TL MATTESON, JL BAND, DL FORD, LA FISHMAN, GJ MEEGAN, CA WILSON, RB PACIESAS, WS PENDLETON, GN BRIGGS, MS LESTRADE, JP TI BATSE SPECTROSCOPY CATALOG OF BRIGHT GAMMA-RAY BURSTS SO ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES LA English DT Article DE CATALOGS; GAMMA-RAYS, BURSTS ID KONUS EXPERIMENT; SPECTRAL BREAKS; PHYSICS; PHOTON AB This paper presents comprehensive results on the spectra of 30 bright gamma my bursts (GRBs) as observed by the Spectroscopy Detectors (SDs) of the Burst And Transient Source Experiment (BATSE). The data selection was strict in including only spectra that are of high reliability for continuum shape studies. This BATSE Spectroscopy Catalog presents fluences, model fits (for five spectral models for three energy ranges), and photon spectra in a standard manner for each burst. Complete information is provided to describe the data selection and analysis procedures. The catalog results are also presented in electronic format (from the Compton Observatory Science Support Center) and CD-ROM format (AAS CD-ROM series, Vol. 2). These electronic formats also present the count spectra and detector response matrices so as to allow for independent study and fitting by researchers outside the BATSE Team. This BATSE Spectroscopy Catalog complements the catalog from BATSE Large Area Detector (LAD) data by Fishman et al. (1994). C1 UNIV CALIF SAN DIEGO,LA JOLLA,CA 92093. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. UNIV ALABAMA,DEPT PHYS,HUNTSVILLE,AL 35899. MISSISSIPPI STATE UNIV,MISSISSIPPI STATE,MS 39762. RP SCHAEFER, BE (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 661,GREENBELT,MD 20771, USA. NR 38 TC 53 Z9 55 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 MAY PY 1994 VL 92 IS 1 BP 285 EP 310 DI 10.1086/191969 PG 26 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NF993 UT WOS:A1994NF99300013 ER PT J AU GOORVITCH, D CHACKERIAN, C AF GOORVITCH, D CHACKERIAN, C TI ROVIBRATIONAL INTENSITIES OF THE MINOR ISOTOPES OF THE CO X-(1)SIGMA+ STATE FOR V-LESS-THAN-OR-EQUAL-TO-20 AND J-LESS-THAN-OR-EQUAL-TO-150 SO ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES LA English DT Article DE MOLECULAR DATA; MOLECULAR PROCESSES ID DUNHAM COEFFICIENTS AB Electric dipole transition matrix elements for rovibrational transitions in the X 1SIGMA+ state of the CO minor isotopes (CO)-C-14-O-16 and (CO)-C-13-O-17 are calculated for the first time for all the DELTAupsilon = +1, +2, and +3 transitions for which upsilon less-than-or-equal-to 20 and J less-than-or-equal-to 150. Improved electric dipole transition matrix elements are also calculated for the minor isotopes (CO)-C-12-O-17, (CO)-C-12-O-18, and (CO)-C-13-O-18. We have fitted polynomials to these matrix elements as a function of the parameter m which is defined in terms of the lower state angular momentum quantum number J; the convenient to use polynomial representations are given in tabular form. These results for the minor species of CO complement those previously reported by us for (CO)-C-12-O-16 and (CO)-C-13-O-16. C1 NASA,AMES RES CTR,DIV EARTH SYST SCI,MOFFETT FIELD,CA 94035. RP GOORVITCH, D (reprint author), NASA,AMES RES CTR,DIV SPACE SCI,MAIL STOP N245-6,MOFFETT FIELD,CA 94035, USA. NR 12 TC 25 Z9 25 U1 0 U2 2 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 MAY PY 1994 VL 92 IS 1 BP 311 EP 321 DI 10.1086/191970 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NF993 UT WOS:A1994NF99300014 ER PT J AU BHATIA, AK AF BHATIA, AK TI ELECTRON-IMPACT EXCITATION OF FLUORINE-LIKE IONS SO ATOMIC DATA AND NUCLEAR DATA TABLES LA English DT Article ID GROUND-STATE; COLLISION STRENGTHS; FE-XVIII; TOKAMAK PLASMAS; ATOMIC DATA; TRANSITIONS; ANGSTROMS; SPECTRUM; LINES; RATES AB Calculations of collision strengths for fluorine-like ions, using close-coupling and distorted-wave approximations, have been carried out by various authors. Effective collision strengths at a number of electron temperatures have been calculated from the available data and these results are presented in this paper. Recommended results are indicated and suggestions for future work are given. (C) 1994 Academic Press, Inc. RP BHATIA, AK (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771, USA. NR 39 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 0092-640X J9 ATOM DATA NUCL DATA JI Atom. Data Nucl. Data Tables PD MAY-JUL PY 1994 VL 57 IS 1-2 BP 253 EP 272 DI 10.1006/adnd.1994.1017 PG 20 WC Physics, Atomic, Molecular & Chemical; Physics, Nuclear SC Physics GA NX988 UT WOS:A1994NX98800010 ER PT J AU LUDWIG, DA CONVERTINO, VA AF LUDWIG, DA CONVERTINO, VA TI PREDICTING ORTHOSTATIC INTOLERANCE - PHYSICS OR PHYSIOLOGY SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Article ID BAROREFLEX RESPONSES; VAGAL BAROREFLEX; AEROBIC FITNESS; BLOOD-PRESSURE; BOOTSTRAP; VOLUME; REFLEX AB To adequately assess the viability of any particular causal theory of orthostatic intolerance, physical and physiological parameters thought to be associated with orthostasis must be evaluated simultaneously within the same individual. Time, cost, and complexity of instrumentation generally limit studies of orthostatic intolerance to a single independent effect for any given sample of subjects. We, therefore, measured 6 key physical and physiological variables associated with various theories of orthostatic intolerance in 14 males to test the hypothesis that physical factors rather than physiological reflex mechanisms were dominant in contributing to orthostatic tolerance. Measurements included height, plasma volume (expressed as percent of total weight), variation in R-R interval, leg compliance, and carotid-cardiac (high pressure), and cardiopulmonary (low pressure) baroreflex sensitivity. Subjects' orthostatic intolerance was quantified by time to syncope during progressive supine lower body decompression. Correlations, regression coefficients, and indices of replicability were calculated using 500 to 1000 bootstrap resamplings of the original 14 observations. Although all six measurements correlated with time to syncope when evaluated individually, only height (negative), percent plasma volume weight (positive), and, to a lesser extent, carotid-cardiac baroreflex sensitivity yielded consistent (reproducible) results when all measures were tested simultaneously. These results suggest that while orthostatic intolerance may be dependent upon a variety of physiological reflexes, physical factors such as height and plasma volume tend to dominate the prediction of time to syncope during lower body negative pressure (LBNP). Physiological reflexes, which act to maintain adequate profusion to the brain during normal terrestrial posture in humans, may be overwhelmed by the additional orthostatic challenge imposed by progressive lower body decompression. C1 NASA,BIOMED OPERAT & RES OFF,KENNEDY SPACE CTR,FL 32899. RP LUDWIG, DA (reprint author), UNIV N CAROLINA,DEPT MATH & STAT,383 BRYAN BLDG,GREENSBORO,NC 27412, USA. NR 36 TC 64 Z9 65 U1 1 U2 4 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 MAY PY 1994 VL 65 IS 5 BP 404 EP 411 PG 8 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA NH517 UT WOS:A1994NH51700003 PM 8024522 ER PT J AU WATENPAUGH, DE BALLARD, RE STOUT, MS MURTHY, G WHALEN, RT HARGENS, AR AF WATENPAUGH, DE BALLARD, RE STOUT, MS MURTHY, G WHALEN, RT HARGENS, AR TI DYNAMIC LEG EXERCISE IMPROVES TOLERANCE TO LOWER-BODY NEGATIVE-PRESSURE SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Article ID BAROREFLEX; EXPOSURES; PUMP AB Lower body negative pressure (LBNP) of 100 mm Hg generates a footward force approximating one body weight for most subjects, yet LBNP may also produce syncope by pooling blood in the lower body. We hypothesized that dynamic leg exercise would improve LBNP tolerance by reducing lower body fluid accumulation. Seven healthy merle subjects underwent four supine LBNP tolerance tests: 1) the control condition: conventional, resting LBNP with a saddle (SADL); 2) resting LBNP against a footplate instead of a saddle (FP); 3) cyclic, non-load-bearing ankle plantar- and dorsiflexion movements during LBNP with a saddle (SADLEX); and 4) LBNP with cyclic ankle plantar- and dorsiflexion exercise against the footplate (FPEX). Tolerance tests consisted of reducing chamber pressure in 10 mm Hg decrements every 3 min to -100 mm Hg or presyncope. Tolerance was assessed by integrating the area under the LBNP x time step function. Exercise doubled LBNP tolerance relative to resting LBNP (SADL: 771 +/- 162 mm Hg x min; FP: 819 +/- 212; SADLEX: 1461 +/- 175; FPEX: 1656 +/- 160; p < 0.05). During FPEX, footward force oscillations averaged 215 +/- 14 N (21.9 +/- 1.4 kg), and mean peak force of 872 +/- 26 N (88.9 +/- 2.7 kg; n = 5) was produced by plantarflexing against 100 mm Hg LBNP. calf volume increased slightly less when exercise accompanied LBNP (SADLEX and FPEX), while heart rate increased more. Therefore, exercise improved tolerance in part by skeletal muscle pumping of venous blood from the legs. However, because this pumping effect was relatively small, movement-induced sympathetic nervous system activation probably also improved LBNP tolerance by increasing heart rate and peripheral vasoconstriction to maintain blood pressure. RP WATENPAUGH, DE (reprint author), NASA,AMES RES CTR,DIV LIFE SCI 239 11,MOFFETT FIELD,CA 94035, USA. NR 24 TC 12 Z9 12 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 MAY PY 1994 VL 65 IS 5 BP 412 EP 418 PG 7 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA NH517 UT WOS:A1994NH51700004 PM 8024523 ER PT J AU REES, JM ROTTMAN, JW AF REES, JM ROTTMAN, JW TI ANALYSIS OF SOLITARY DISTURBANCES OVER AN ANTARCTIC ICE SHELF SO BOUNDARY-LAYER METEOROLOGY LA English DT Article ID WAVES; FLUIDS AB Large amplitude, propagating, solitary disturbances have been observed in the atmospheric boundary layer over a gently sloping Antarctic Ice Shelf The waves are usually trapped within the lowest 40 m and are observed only when the surface layer is strongly stably stratified and prevailing wind speeds are low. It is shown that the waves are trapped due to the combined effects of velocity curvature and stratification. The observed wavelengths can be bounded using simple heuristic arguments based on the Scorer parameter. Properties of the waves are compared with results from the weakly nonlinear numerical model of Rottman and Einaudi (1993). C1 UNIV SPACE RES ASSOC,NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP REES, JM (reprint author), UNIV SHEFFIELD,SCH MATH & STAT,APPL MATH SECT,SHEFFIELD S10 2UN,ENGLAND. NR 24 TC 17 Z9 17 U1 1 U2 1 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0006-8314 J9 BOUND-LAY METEOROL JI Bound.-Layer Meteor. PD MAY PY 1994 VL 69 IS 3 BP 285 EP 310 DI 10.1007/BF00708859 PG 26 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA NX503 UT WOS:A1994NX50300003 ER PT J AU WILKES, R MEGARGLE, R AF WILKES, R MEGARGLE, R TI INTEGRATION OF INSTRUMENTS AND A LABORATORY INFORMATION MANAGEMENT-SYSTEM AT THE INFORMATION LEVEL - AN INDUCTIVELY-COUPLED PLASMA SPECTROMETER SO CHEMOMETRICS AND INTELLIGENT LABORATORY SYSTEMS LA English DT Article AB A software upgrade to an analytical instrument computer and a laboratory information management system (LIMS) is described. The instrument is a modified Jarrell-Ash model 750 inductively coupled plasma (ICP) spectrometer that is connected through a custom designed interface to a DEC PDP-11/23 computer. The LIMS is a customized system based on the MUMPS operating system running on a DEC PDP-11/24 computer. Both computers are located in the Chemical Analysis Branch of the Materials Division of NASA Lewis Research Center in Cleveland, OH. The improved software in both computers allows them to share information about sample batches submitted to the laboratory for analysis and the analytical results obtained for those batches. This has decreased the amount of manual transcription required of the analyst, reducing errors and freeing up time for more analyses to be performed. The local storage of batch information on the ICP computer also lessens the impact of LIMS down time. C1 CLEVELAND STATE UNIV,DEPT CHEM,CLEVELAND,OH 44115. RP WILKES, R (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 4 TC 0 Z9 0 U1 1 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0169-7439 J9 CHEMOMETR INTELL LAB JI Chemometrics Intell. Lab. Syst. PD MAY PY 1994 VL 26 IS 1 BP 47 EP 54 DI 10.1016/0169-7439(94)90018-3 PG 8 WC Automation & Control Systems; Chemistry, Analytical; Computer Science, Artificial Intelligence; Instruments & Instrumentation; Mathematics, Interdisciplinary Applications; Statistics & Probability SC Automation & Control Systems; Chemistry; Computer Science; Instruments & Instrumentation; Mathematics GA NT451 UT WOS:A1994NT45100006 ER PT J AU ZAK, M ZAK, AP AF ZAK, M ZAK, AP TI UNPREDICTABLE DYNAMICS AND COLLECTIVE BRAIN SO COMPUTERS & MATHEMATICS WITH APPLICATIONS LA English DT Article; Proceedings Paper CT 5th International Workshop of the Bellman Continuum CY JAN 11-12, 1993 CL WAIKOLOA, HI SP UNIV HAWAII MANOA, DEPT INFORMAT & COMP SCI, UNIV HAWAII HILO, DEPT COMP SCI & ENGN ID STABILIZATION PRINCIPLE; TURBULENCE; CHAOS AB Revision of the mathematical formalism of Newtonian dynamics suggests that its determinism and reversibility result from additional mathematical restrictions which are not consistent with the physical nature of motions. The removal of these restrictions, and a new model for Newtonian dynamics, as well as its applications to modelling neural intelligence are discussed. RP ZAK, M (reprint author), JET PROP LAB,PASADENA,CA 91109, USA. NR 25 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 0898-1221 J9 COMPUT MATH APPL JI Comput. Math. Appl. PD MAY PY 1994 VL 27 IS 9-10 BP 185 EP 197 DI 10.1016/0898-1221(94)90137-6 PG 13 WC Mathematics, Applied SC Mathematics GA NK052 UT WOS:A1994NK05200023 ER PT J AU ROACH, P KASHANI, A AF ROACH, P KASHANI, A TI 1993 SPACE CRYOGENICS WORKSHOP SO CRYOGENICS LA English DT Editorial Material RP ROACH, P (reprint author), NASA,AMES RES CTR,MOFFETT FIELD,CA 94035, USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU BUTTERWORTH-HEINEMANN LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB SN 0011-2275 J9 CRYOGENICS JI Cryogenics PD MAY PY 1994 VL 34 IS 5 BP 339 EP 339 DI 10.1016/0011-2275(94)90116-3 PG 1 WC Thermodynamics; Physics, Applied SC Thermodynamics; Physics GA NH914 UT WOS:A1994NH91400001 ER PT J AU LIPA, JA SWANSON, DR NISSEN, JA CHUI, TCP AF LIPA, JA SWANSON, DR NISSEN, JA CHUI, TCP TI LAMBDA-POINT EXPERIMENT IN MICROGRAVITY SO CRYOGENICS LA English DT Article; Proceedings Paper CT 1993 Space Cryogenics Workshop CY JUL 20-21, 1993 CL SAN JOSE, CA SP NASA, AMER RES CTR CRYOGEN GRP DE SPACE CRYOGENICS; LAMBDA-POINT; THERMOMETRY ID RESOLUTION AB In October 1992 a low temperature experiment was flown on the Space Shuttle in low earth orbit, using the JPL low temperature reserarch facility. The objective of the mission was to measure the heat capacity and thermal relaxation of helium very close to the lambda point with the smearing effect of gravity removed. We describe the experiment with emphasis on the high resolution thermometry and the thermal control system. We also report preliminary results from the measurements made during the flight and compare them with related measurements performed on the ground. The sample was a sphere 3.5 cm in diameter contained within a copper calorimeter of very high thermal conductivity. The calorimeter was attached to a pair of paramagnetic salt thermometers with noise levels in the 10(-10) K range. During the mission we found that the resolution of the thermometers was degraded somewhat, due to the impact of charged particles. This effect limited the useful resolution of the measurements to almost-equal-to 2 nK from the lambda point. C1 JET PROP LAB,PASADENA,CA 91109. RP LIPA, JA (reprint author), STANFORD UNIV,DEPT PHYS,STANFORD,CA 94305, USA. NR 11 TC 15 Z9 15 U1 1 U2 3 PU BUTTERWORTH-HEINEMANN LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB SN 0011-2275 J9 CRYOGENICS JI Cryogenics PD MAY PY 1994 VL 34 IS 5 BP 341 EP 347 DI 10.1016/0011-2275(94)90118-X PG 7 WC Thermodynamics; Physics, Applied SC Thermodynamics; Physics GA NH914 UT WOS:A1994NH91400002 ER PT J AU DIPIRRO, M SHIRRON, P TUTTLE, J AF DIPIRRO, M SHIRRON, P TUTTLE, J TI ON-ORBIT SUPERFLUID TRANSFER - PRELIMINARY-RESULTS FROM THE SHOOT FLIGHT DEMONSTRATION SO CRYOGENICS LA English DT Article; Proceedings Paper CT 1993 Space Cryogenics Workshop CY JUL 20-21, 1993 CL SAN JOSE, CA SP NASA, AMER RES CTR CRYOGEN GRP DE SPACE CRYOGENICS; SUPERFLUID HELIUM TRANSFER; SHOOT AB Preliminary results from the Superfluid On-Orbit Transfer (SHOOT) Flight Demonstration which flew on Space Shuttle STS-57 in June 1993 are presented. SHOOT demonstrated the technology required to transfer superfluid helium between Dewars in low gravity. In addition a number of components developed for SHOOT were flight proven and are now available for use on other payloads. Included in this paper are a description of the transfer process, the transfer rates and losses, observations of the differences between ground transfers and those done on-orbit, and the performance of a number of components. Among these components are liquid acquisition devices, phase separators, liquid/vapour discriminators, thermomechanical pumps, three types of valves, venturi flow meters and a heat pulse mass gauging system. C1 HUGHES STX INC,LANHAM,MD 20706. RP DIPIRRO, M (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 713,GREENBELT,MD 20771, USA. NR 15 TC 9 Z9 9 U1 0 U2 0 PU BUTTERWORTH-HEINEMANN LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB SN 0011-2275 J9 CRYOGENICS JI Cryogenics PD MAY PY 1994 VL 34 IS 5 BP 349 EP 356 DI 10.1016/0011-2275(94)90119-8 PG 8 WC Thermodynamics; Physics, Applied SC Thermodynamics; Physics GA NH914 UT WOS:A1994NH91400003 ER PT J AU WEINTZ, KF BASCI, MI UBER, JM AF WEINTZ, KF BASCI, MI UBER, JM TI SHOOT DEWAR SUPPORT STRAP DESIGN AND PERFORMANCE SO CRYOGENICS LA English DT Article; Proceedings Paper CT 1993 Space Cryogenics Workshop CY JUL 20-21, 1993 CL SAN JOSE, CA SP NASA, AMER RES CTR CRYOGEN GRP DE SPACE CRYOGENICS; SHOOT; SUPPORT STRAPS AB The Superfluid Helium On-Orbit Transfer (SHOOT) experiment consists of two Dewars and associated avionics to facilitate transfer tests in orbit. In each Dewar the cryogen tank is suspended from the vacuum shell by six fibreglass composite support strap assemblies. These strap assemblies perform a dual role of providing structural support and minimizing heat transfer into the cryogen. The design of the straps addresses the inertial and thermal loads, including those induced by cryogenic cool-down. The strap design requires that a preload tension be maintained throughout the mission. The prediction of the required strap preload and the application of actual preload are presented. Methods for tracking the preload as well as actual preload histories are also discussed. To reduce the heat load the vapour cooled shields (VCSs) are thermally and structurally anchored to the straps through aluminium VCS blocks. The original block design was qualified and flown on the Cosmic Background Explorer (COBE). The COBE type epoxy bond design failed during SHOOT verification testing at Goddard Space Flight Center (GSFC). A new friction clamp design was qualified and installed in the SHOOT Dewars. The structural design, thermal characteristics and verification testing of this new design are summarized. SHOOT flew on the space shuttle Endeavour in June 1993 and performed successfully. C1 SWALES & ASSOCIATES INC,BELTSVILLE,MD 20705. RP WEINTZ, KF (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 7131,GREENBELT,MD 20771, USA. NR 6 TC 3 Z9 3 U1 2 U2 4 PU BUTTERWORTH-HEINEMANN LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB SN 0011-2275 J9 CRYOGENICS JI Cryogenics PD MAY PY 1994 VL 34 IS 5 BP 357 EP 360 DI 10.1016/0011-2275(94)90120-1 PG 4 WC Thermodynamics; Physics, Applied SC Thermodynamics; Physics GA NH914 UT WOS:A1994NH91400004 ER PT J AU SHIRRON, PJ DIPIRRO, MJ TUTTLE, J AF SHIRRON, PJ DIPIRRO, MJ TUTTLE, J TI FLIGHT PERFORMANCE OF THE SHOOT LIQUID ACQUISITION DEVICES SO CRYOGENICS LA English DT Article; Proceedings Paper CT 1993 Space Cryogenics Workshop CY JUL 20-21, 1993 CL SAN JOSE, CA SP NASA, AMER RES CTR CRYOGEN GRP DE SPACE CRYOGENICS; SHOOT; LIQUID ACQUISITION DEVICES ID HELIUM AB The Superfluid Helium On-Orbit Transfer (SHOOT) Flight Demonstration, launched on STS-57 in June 1993, demonstrated the technology required for the management and transfer of superfluid helium in low gravity, and was the first orbital experiment using liquid acquisition systems with cryogens. Its primary experimental objective was to test the performance of two different liquid acquisition devices (LADs) which use surface tension forces to gather the liquid and feed it to the superfluid pumps. One system consists of c-channels whose open sides are covered by fine mesh screens which face the tank walls. The other consists of a series of Mylar(TM) Vanes which extend radially from the centre of the tank. Several superfluid transfers were performed during relatively quiescent periods and during two transfers adverse orbiter accelerations of 0.034 and 0.069 m s-2 (3.5 x 10(-3) and 7.0 x 10(-3) g) were generated to move liquid away from the pumps to test the ability of each LAD to work against relatively large hydrostatic heads. Discrete liquid/vapour discriminators placed strategically within the tanks were used to detect failure of the LADs to supply liquid to the pumps. One goal was to test whether, if such a failure occurs, the transfer process can spontaneously recover without operator intervention. Overall performance of both LADs during transfers with and without adverse accelerations is presented. C1 HUGHES STX INC,LANHAM,MD 20706. RP SHIRRON, PJ (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 713,GREENBELT,MD 20771, USA. NR 8 TC 5 Z9 5 U1 0 U2 0 PU BUTTERWORTH-HEINEMANN LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB SN 0011-2275 J9 CRYOGENICS JI Cryogenics PD MAY PY 1994 VL 34 IS 5 BP 361 EP 368 DI 10.1016/0011-2275(94)90121-X PG 8 WC Thermodynamics; Physics, Applied SC Thermodynamics; Physics GA NH914 UT WOS:A1994NH91400005 ER PT J AU TUTTLE, J DIPIRRO, MJ SHIRRON, PJ AF TUTTLE, J DIPIRRO, MJ SHIRRON, PJ TI THERMAL STRATIFICATION OF LIQUID-HELIUM IN THE SHOOT DEWARS SO CRYOGENICS LA English DT Article; Proceedings Paper CT 1993 Space Cryogenics Workshop CY JUL 20-21, 1993 CL SAN JOSE, CA SP NASA, AMER RES CTR CRYOGEN GRP DE SPACE CRYOGENICS; SHOOT; THERMAL STRATIFICATION AB The Superfluid Helium On-Orbit Transfer (SHOOT) project was a shuttle payload designed to demonstrate the technology needed to transfer superfluid helium between two Dewars in space. It was launched with normal liquid helium which was pumped to superfluid temperatures on-orbit. During the 93h prelaunch ground hold, the liquid was thermally stratified, with temperatures of almost-equal-to 4.3 K at the top and rising slowly from 2.2K at the bottom of each Dewar over time. This stratification was helpful, as it allowed for more efficient removal of the parasitic heat inputs. There were also temperature gradients in the Dewars during the on-orbit pumpdown, with a much higher degree of beneficial stratification in the port Dewar than in the starboard. We describe the liquid temperature profiles during ground hold and on-orbit pumpdown, discussing the effects of this stratification and comparing the performances of the two Dewars. We also discuss the results of a computer model of the isothermal pumpdown of a SHOOT Dewar on-orbit. C1 HUGHES STX INC,LANHAM,MD 20706. RP TUTTLE, J (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 713,GREENBELT,MD 20771, USA. NR 6 TC 2 Z9 2 U1 0 U2 0 PU BUTTERWORTH-HEINEMANN LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB SN 0011-2275 J9 CRYOGENICS JI Cryogenics PD MAY PY 1994 VL 34 IS 5 BP 369 EP 374 DI 10.1016/0011-2275(94)90122-8 PG 6 WC Thermodynamics; Physics, Applied SC Thermodynamics; Physics GA NH914 UT WOS:A1994NH91400006 ER PT J AU VOLZ, S CONATY, C WEINTZ, K AF VOLZ, S CONATY, C WEINTZ, K TI VERIFICATION TESTING OF THE SUPERFLUID-HELIUM ON-ORBIT TRANSFER (SHOOT) EXPERIMENT SO CRYOGENICS LA English DT Article; Proceedings Paper CT 1993 Space Cryogenics Workshop CY JUL 20-21, 1993 CL SAN JOSE, CA SP NASA, AMER RES CTR CRYOGEN GRP DE SPACE CRYOGENICS; SHOOT; VERIFICATION TESTING AB The Superfluid Helium On-Orbit Transfer (SHOOT) project is a secondary shuttle cross-bay payload which flew on the STS-57/Endeavour mission. It was designed to develop and demonstrate the technologies required to resupply liquid helium containers in space, and to develop new technologies that may be used in other future space cryogenic systems. The SHOOT payload consists of two superfluid helium Dewars with helium management cryostats connected by a transfer line, and six avionics boxes for valve and heater control, temperature, pressure and fluid position monitoring and data processing and telemetry. The cryostats contain numerous specialized helium management components; including high and low flow phase separators, liquid/vapour discriminators, flowmeters, liquid level detectors, cryogenic mechanical valves and cryogenic relief valves and burst discs, and two varieties of fluid acquisition systems. To prepare the SHOOT payload for launch a series of functional, structural, thermal and reliability tests were conducted at every level of hardware assembly, from materials tests to system level thermal, structural and functional performance tests. We present here the verification tests and analyses developed and completed at each level of assembly. We discuss the trade-offs considered for, and the success (or failure) of, models and analyses to predict performance results. Finally, we present some lessons learned of potential interest to future cryogenic missions, whether on the Space Shuttle or on expendable launch vehicles. RP VOLZ, S (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 7134,GREENBELT,MD 20771, USA. NR 15 TC 2 Z9 2 U1 0 U2 0 PU BUTTERWORTH-HEINEMANN LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB SN 0011-2275 J9 CRYOGENICS JI Cryogenics PD MAY PY 1994 VL 34 IS 5 BP 375 EP 382 DI 10.1016/0011-2275(94)90123-6 PG 8 WC Thermodynamics; Physics, Applied SC Thermodynamics; Physics GA NH914 UT WOS:A1994NH91400007 ER PT J AU NAES, LG NAST, TC BELL, GA PICKETT, DA STOUFFER, C CYGNAROWICZ, C AF NAES, LG NAST, TC BELL, GA PICKETT, DA STOUFFER, C CYGNAROWICZ, C TI ORBITAL OPERATION OF CRYOGENIC LIMB ARRAY ETALON SPECTROMETER (CLAES) CRYOSTAT SO CRYOGENICS LA English DT Article; Proceedings Paper CT 1993 Space Cryogenics Workshop CY JUL 20-21, 1993 CL SAN JOSE, CA SP NASA, AMER RES CTR CRYOGEN GRP DE SPACE CRYOGENICS; CLAES; CRYOSTAT AB The Cryogenic Limb Array Etalon Spectrometer (CLAES) is one of nine instruments aboard the Upper Atmospheric Research Satellite (UARS). UARS was developed by the NASA Goddard Space Flight Center for the purpose of understanding the physics of the upper atmosphere. In support of this mission, the CLAES instrument was designed to provide the detailed spectroscopic measurements of trace species and atmospheric constituents that are critical to our understanding into the photochemistry of the upper atmosphere. UARS was launched into low earth orbit on 12 September 1991 on STS-48. Three days later, the UARS was deployed from the cargo bay and after several days of (satellite) outgassing, the CLAES aperture door was opened. The instrument remained operational for over 19.8 months before the open-cycle cryogenic cooler was depleted. The CLAES instrument drew upon the synergistic talents of the Lockheed Palo Alto Research Laboratory in that the principle investigator, as well as the sensor, electronics and cryostat design, development and testing team were all members of the research laboratory. The significant scientific contributions derived from the CLAES instrument and the sensor design have been well documented. This paper discusses the design, test and orbital performance of the dual stage solid neon/CO2 cryostat used to cool the C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP NAES, LG (reprint author), LOCKHEED MISSILES & SPACE CO,DIV RES & DEV,THERMAL SCI LABS,CRYOGEN LAB,PALO ALTO,CA 94304, USA. NR 4 TC 1 Z9 1 U1 0 U2 0 PU BUTTERWORTH-HEINEMANN LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB SN 0011-2275 J9 CRYOGENICS JI Cryogenics PD MAY PY 1994 VL 34 IS 5 BP 393 EP 398 DI 10.1016/0011-2275(94)90126-0 PG 6 WC Thermodynamics; Physics, Applied SC Thermodynamics; Physics GA NH914 UT WOS:A1994NH91400010 ER PT J AU SHAPIRO, JC VILLERE, GL AF SHAPIRO, JC VILLERE, GL TI DESCRIPTION OF SHOOT COMMAND AND MONITORING-SYSTEM SO CRYOGENICS LA English DT Article; Proceedings Paper CT 1993 Space Cryogenics Workshop CY JUL 20-21, 1993 CL SAN JOSE, CA SP NASA, AMER RES CTR CRYOGEN GRP DE SPACE CRYOGENICS; SHOOT; COMMAND AND MONITORING SYSTEM AB This paper describes the command and monitoring software developed for the Superfluid Helium On-Orbit Transfer (SHOOT) experiment, which was a payload flown aboard the Space Shuttle Endeavour during the STS-57 mission. The SHOOT command and monitoring system (CMS) was used for all phases of the experiment from early hardware testing, system integration and pad servicing, through to flight operations and post-flight data analysis. The design, architecture and features of the CMS are discussed, with an emphasis on the operations unique to a space-borne experiment. In addition, certain aspects which relate directly to cryogenics and superfluid helium are RP SHAPIRO, JC (reprint author), NASA,AMES RES CTR,ARTIFICIAL INTELLIGENCE RES BRANCH,MAIL STOP 269-2,MOFFETT FIELD,CA 94035, USA. NR 3 TC 0 Z9 0 U1 0 U2 0 PU BUTTERWORTH-HEINEMANN LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB SN 0011-2275 J9 CRYOGENICS JI Cryogenics PD MAY PY 1994 VL 34 IS 5 BP 407 EP 413 DI 10.1016/0011-2275(94)90128-7 PG 7 WC Thermodynamics; Physics, Applied SC Thermodynamics; Physics GA NH914 UT WOS:A1994NH91400012 ER PT J AU MCMURRAY, RE AF MCMURRAY, RE TI INFRARED DETECTOR REQUIREMENTS WHICH DRIVE CRYOGENIC DEVELOPMENT SO CRYOGENICS LA English DT Article; Proceedings Paper CT 1993 Space Cryogenics Workshop CY JUL 20-21, 1993 CL SAN JOSE, CA SP NASA, AMER RES CTR CRYOGEN GRP DE SPACE CRYOGENICS; INFRARED DETECTORS; AVAILABLE DESIGNS AB In recent years infrared detector technology has progressed from simple discrete detectors, which still represent the state-of-the-art at some infrared wavelengths, to large multiplexed two-dimensional arrays of detector pixels. This evolution has increased the heat load at the focal plane for the detector coolers. Also, there is an increasing move towards more electronics on the focal plane itself, and the cryogenic burden can be substantial. In this paper a number of different detector technologies aimed at various wavelength regimes will be discussed. Each of the devices has its own optimum operating temperature, and the heat load at that temperature is determined both by the readout electronics and the infrared loading on the focal plane. In general, for lower noise readout operation using conventional FET first stage readouts, increasing the current (and therefore power) on the FET decreases the noise in the channel. For the lowest background observations this power is dominant. At higher infrared backgrounds FET noise is less important, but the optical power on the focal plane can become significant. Power and temperature requirements for a broad spectrum of detector types are surveyed and compared. RP MCMURRAY, RE (reprint author), NASA,AMES RES CTR,M-S 244-10,MOFFETT FIELD,CA 94035, USA. NR 5 TC 3 Z9 3 U1 0 U2 1 PU BUTTERWORTH-HEINEMANN LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB SN 0011-2275 J9 CRYOGENICS JI Cryogenics PD MAY PY 1994 VL 34 IS 5 BP 425 EP 429 DI 10.1016/0011-2275(94)90131-7 PG 5 WC Thermodynamics; Physics, Applied SC Thermodynamics; Physics GA NH914 UT WOS:A1994NH91400015 ER PT J AU ROSS, RG JOHNSON, DL MON, GR SMEDLEY, G AF ROSS, RG JOHNSON, DL MON, GR SMEDLEY, G TI CRYOCOOLER RESONANCE CHARACTERIZATION SO CRYOGENICS LA English DT Article; Proceedings Paper CT 1993 Space Cryogenics Workshop CY JUL 20-21, 1993 CL SAN JOSE, CA SP NASA, AMER RES CTR CRYOGEN GRP DE CRYOCOOLERS; RESONANCE CHARACTERIZATION; SPACE CRYOGENICS AB An important issue in the design and scaling-up of Stirling cryocoolers is achieving good drive motor efficiency and launch survivability. The important common thread linking these two topics is the dynamic resonant response of the compressor and displacer moving masses. The fundamental equations governing cryocooler mechanical efficiency and launch vibration response are presented and explored in terms of their implications for cooler design. The resonant frequency, damping and drive motor force parameters associated with the cooler are shown to be key to efficient operation. Means of measuring these parameters are presented and shown to have broad applicability to additional parameters such as drive stiction and vibration transmitted to the instrument. The resonant parameters of the BAe 55 K AIRS proof-of-concept cooler are used as an example to demonstrate the good correlation between the analytical fundamentals and the measured characteristics of a state-of-the-art cryocooler design. RP ROSS, RG (reprint author), JET PROP LAB,MAIL STOP 233-105,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 13 TC 6 Z9 8 U1 1 U2 2 PU BUTTERWORTH-HEINEMANN LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB SN 0011-2275 J9 CRYOGENICS JI Cryogenics PD MAY PY 1994 VL 34 IS 5 BP 435 EP 442 DI 10.1016/0011-2275(94)90133-3 PG 8 WC Thermodynamics; Physics, Applied SC Thermodynamics; Physics GA NH914 UT WOS:A1994NH91400017 ER PT J AU HOPKINS, RA NIECZKOSKI, SJ BREON, SR AF HOPKINS, RA NIECZKOSKI, SJ BREON, SR TI UPDATE ON THE DESIGN AND PERFORMANCE OF THE CRYOGENIC SUBSYSTEM FOR THE AXAF X-RAY SPECTROMETER SO CRYOGENICS LA English DT Article; Proceedings Paper CT 1993 Space Cryogenics Workshop CY JUL 20-21, 1993 CL SAN JOSE, CA SP NASA, AMER RES CTR CRYOGEN GRP DE SUPERFLUID HELIUM DEWAR; STIRLING CYCLE COOLER; SPACE CRYOGENICS AB The cryogenic subsystem (CSS) for the AXAF X-ray spectrometer (XRS) uses state-of-the-art superfluid helium Dewar technology along with Stirling cycle coolers to achieve a five year orbital lifetime with minimum system mass and size. The Dewar provides a 1.5K temperature environment for operation of the cryogenic instrument assembly, which includes an adiabatic demagnetization refrigerator for cooling the detectors to 0.1 K. As a result of the AXAF programme being split into two separate missions, the XRS is the sole instrument comprising the AXAF spectrometer (AXAF-S). Launch is planned in December 1999. Substantial configuration changes have been made to the CSS to meet the new AXAF-S requirements. Changes are primarily the result of the new spacecraft configuration, increased instrument duty cycle and increased mission lifetime requirement. The programme status, the newly baselined CSS design and its predicted performance are discussed. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP HOPKINS, RA (reprint author), BALL ELECTROOPT CRYOGEN DIV,MAIL CODE RA-5,POB 1062,BOULDER,CO 80306, USA. NR 5 TC 1 Z9 1 U1 0 U2 0 PU BUTTERWORTH-HEINEMANN LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB SN 0011-2275 J9 CRYOGENICS JI Cryogenics PD MAY PY 1994 VL 34 IS 5 BP 443 EP 450 DI 10.1016/0011-2275(94)90134-1 PG 8 WC Thermodynamics; Physics, Applied SC Thermodynamics; Physics GA NH914 UT WOS:A1994NH91400018 ER PT J AU WARING, RH PETERSON, DL AF WARING, RH PETERSON, DL TI OREGON TRANSECT ECOSYSTEM RESEARCH (OTTER) PROJECT SO ECOLOGICAL APPLICATIONS LA English DT Editorial Material DE ECOSYSTEM MODELING; GROUND-BASED MEASUREMENTS; OREGON TRANSECT; OTTER PROJECT; REMOTELY SENSED DATA; SATELLITE IMAGERY C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RP WARING, RH (reprint author), OREGON STATE UNIV,CORVALLIS,OR 97331, USA. RI Waring, Richared/C-4796-2014 OI Waring, Richared/0000-0003-2533-3664 NR 0 TC 3 Z9 3 U1 0 U2 1 PU ECOLOGICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE, NW, STE 400, WASHINGTON, DC 20036 SN 1051-0761 J9 ECOL APPL JI Ecol. Appl. PD MAY PY 1994 VL 4 IS 2 BP 210 EP 210 DI 10.2307/1941927 PG 1 WC Ecology; Environmental Sciences SC Environmental Sciences & Ecology GA NH001 UT WOS:A1994NH00100004 ER PT J AU PETERSON, DL WARING, RH AF PETERSON, DL WARING, RH TI OVERVIEW OF THE OREGON TRANSECT ECOSYSTEM RESEARCH-PROJECT SO ECOLOGICAL APPLICATIONS LA English DT Article DE CONIFEROUS FORESTS; COOPERATIVE RESEARCH; DATA BASE; ECOLOGICAL FLUXES; ECOSYSTEM SIMULATION; OREGON TRANSECT; OTTER PROJECT; REMOTE SENSING ID TEMPERATE CONIFEROUS FORESTS; LEAF-AREA INDEX; REGIONAL APPLICATIONS; PACIFIC NORTHWEST; GENERAL-MODEL; AVHRR DATA; REFLECTANCE; CANOPY; EVAPOTRANSPIRATION; PHOTOSYNTHESIS AB The Oregon Transect Ecosystem Research (OTTER) project is a study of ecosystem functions in coniferous forests using the methods of computer modeling, experimental and theoretical remote sensing, and ecological field and laboratory techniques. The study is focused on predicting the major fluxes of carbon, nitrogen, and water, and the factors that dynamically regulate them. The OTTER project was conceived to test two major questions: (1) Can a generalized ecosystem simulation model, designed to use mainly parameters available from remote sensing, predict the functioning of forests across an environmentally variable region? and (2) To what extent can the variables required by this model be derived from remotely sensed data? The scientific objectives and scope of the project demanded that a coordinated effort be made to link ground measurements with remote sensing and modeling requirements. OTTER was selected as a focus for a National Aeronautics and Space Administration (NASA)-sponsored Multi-sensor Aircraft Campaign (MAC; combining NASA aircraft and sensors with those of others) on the basis of experience gained in past ecosystem studies and remote-sensing projects, and the importance of the OTTER objectives to NASA's long-range science goals and plans. Having several independent approaches available, both on the ground and from various remote-sensing platforms, proved valuable in estimating and validating many of the critical variables. This experience and cross comparison should help simplify future studies of a similar nature. Edited data sets from the OTTER project arc now available to the scientific community on optical disks or via on-line data banks at NASA (Washington, D.C., USA) and Oregon State University (Corvallis, Oregon, USA). C1 OREGON STATE UNIV,DEPT FOREST SCI,CORVALLIS,OR 97331. RP PETERSON, DL (reprint author), NASA,AMES RES CTR,ECOSYST SCI & TECHNOL BRANCH,MOFFETT FIELD,CA 94035, USA. RI Waring, Richared/C-4796-2014 OI Waring, Richared/0000-0003-2533-3664 NR 54 TC 44 Z9 44 U1 0 U2 1 PU ECOLOGICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE, NW, STE 400, WASHINGTON, DC 20036 SN 1051-0761 J9 ECOL APPL JI Ecol. Appl. PD MAY PY 1994 VL 4 IS 2 BP 211 EP 225 DI 10.2307/1941928 PG 15 WC Ecology; Environmental Sciences SC Environmental Sciences & Ecology GA NH001 UT WOS:A1994NH00100005 ER PT J AU MATSON, P JOHNSON, L BILLOW, C MILLER, J PU, RL AF MATSON, P JOHNSON, L BILLOW, C MILLER, J PU, RL TI SEASONAL PATTERNS AND REMOTE SPECTRAL ESTIMATION OF CANOPY CHEMISTRY ACROSS THE OREGON TRANSECT SO ECOLOGICAL APPLICATIONS LA English DT Article DE AIRBORNE SENSORS; AVIRIS; CASI; CLIMATIC GRADIENT; CONIFERS; FOLIAR NITROGEN; FOREST CANOPY CHEMISTRY; MULTIVARIATE ANALYSIS; OREGON TRANSECT; OTTER PROJECT; PRODUCTIVITY; RED EDGE; REMOTE SENSING; SEASONAL PATTERNS ID INFRARED REFLECTANCE SPECTROSCOPY; RED-EDGE; FOREST ECOSYSTEMS; LEAF REFLECTANCE; NITROGEN; PINE; VEGETATION; NUTRIENT; PLANTS; FERTILIZATION AB We examined seasonal changes in canopy chemical concentrations and content in conifer forests growing along a climate gradient in western Oregon, as part of the Oregon Transect Ecosystem Research (OTTER) study. The chemical variables were related to seasonal patterns of growth and production. Statistical comparisons of chemical variables with data collected from two different airborne remote-sensing platforms were also carried out. Total nitrogen (N) concentrations in foliage varied significantly both seasonally and among sites; when expressed as content in the forest canopy, nitrogen varied to a much greater extent and was significantly related to aboveground net primary production (r = 0.99). Chlorophyll and free amino acid concentrations varied more strongly than did total N and may have reflected changes in physiological demands for N. Large variations in starch concentrations were measured from pre- to post-budbreak in all conifer sites. Examination of remote-sensing data from two different airborne instruments suggests the potential for remote measurement of some canopy chemicals. Multivariate analysis of high-resolution spectral data in the near infrared region indicated significant correlations between spectral signals and N concentration and canopy N content; the correlation with canopy N content was stronger and was probably associated in part with water absorption features of the forest canopy. The spectral bands that were significantly correlated with lignin concentration and content were similar to bands selected in the other laboratory and airborne studies; starch concentrations were not significantly related to spectral reflectance data. Strong relationships between the spectral position of specific reflectance features in the visible region and chlorophyll were also found. C1 NASA,AMES RES CTR,ECOSYST SCI & TECHNOL BRANCH,MOFFETT FIELD,CA 94035. NASA,AMES RES CTR,JOHNSON CONTROLS WORLD SERV,MOFFETT FIELD,CA 94035. YORK UNIV,EARTH OBSERV LAB,DOWNSVIEW M3J 1K1,ON,CANADA. NR 75 TC 109 Z9 116 U1 1 U2 20 PU ECOLOGICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE, NW, STE 400, WASHINGTON, DC 20036 SN 1051-0761 J9 ECOL APPL JI Ecol. Appl. PD MAY PY 1994 VL 4 IS 2 BP 280 EP 298 DI 10.2307/1941934 PG 19 WC Ecology; Environmental Sciences SC Environmental Sciences & Ecology GA NH001 UT WOS:A1994NH00100011 ER PT J AU NELSON, R GREGOIRE, TG AF NELSON, R GREGOIRE, TG TI 2-STAGE FOREST SAMPLING - A COMPARISON OF 3 PROCEDURES TO ESTIMATE AGGREGATE VOLUME SO FOREST SCIENCE LA English DT Article DE VARIABLE-RADIUS-PLOT SAMPLING; PPS SAMPLING ID POISSON AB Three two-stage forest sampling procedures are examined in order (1) to quantify the variance penalty (if any) associated with second-stage sample restrictions; and (2) to quantify the variance gains (if any) associated with the incorporation of tree height data at the second stage. The three two-stage procedures share a common first stage, i.e., horizontal point sampling (HPS), which selects trees with probability proportional to tree basal area. The second stage selection approaches vary, as follows: 1. Trees are selected with replacement with probability proportional to tree height from a single list composed of all trees sampled across all first-stage sample points. 2. Trees are selected with replacement with probability proportional to tree height from separate fists compiled on each first-stage sample point. 3. Trees are selected randomly, with replacement, on each first-stage point. The results indicate that little or no reduction in variance accrues from incorporating height data into the two-stage sample design for the three mapped stands considered. HPS/simple random sampling yielded variances ranging from 7.1% larger to 9.2% smaller than the smallest HPS/list sampling variance, while maintaining an advantage in an even-aged stand. It is hypothesized that the HPS/list sampling procedures may prove more useful in mature, all-aged stands where height may account for a significant portion of volume or biomass variation. No loss of precision is noted when second-stage sampling is restricted by point on these three forest tracts. An investigation into the effects of first- and second-stage sample sizes provide a convincing argument to select only one tree per first-stage sample point when sampling is restricted by point. Considering both precision of estimation and field efficiency, these results suggest that the HPS/simple random sampling procedure is the most useful of the three tested. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP NELSON, R (reprint author), VIRGINIA POLYTECH INST & STATE UNIV,COLL FORESTRY & WILDLIFE RESOURCES,BLACKSBURG,VA 24061, USA. RI Nelson, Ross/H-8266-2014 NR 15 TC 5 Z9 5 U1 0 U2 1 PU SOC AMER FORESTERS PI BETHESDA PA 5400 GROSVENOR LANE, BETHESDA, MD 20814 SN 0015-749X J9 FOREST SCI JI For. Sci. PD MAY PY 1994 VL 40 IS 2 BP 247 EP 266 PG 20 WC Forestry SC Forestry GA NK041 UT WOS:A1994NK04100003 ER PT J AU BLUTH, GJS KUMP, LR AF BLUTH, GJS KUMP, LR TI LITHOLOGIC AND CLIMATOLOGIC CONTROLS OF RIVER CHEMISTRY SO GEOCHIMICA ET COSMOCHIMICA ACTA LA English DT Article; Proceedings Paper CT Symposium in Honor of Heinrich D Holland CY MAY 08-09, 1992 CL RESTON, VA ID ATMOSPHERIC CARBON-DIOXIDE; DISSOLVED-LOAD; GEOCHEMISTRY; AMAZON; TIME; ENVIRONMENT; ROCKS AB The chemistries of rivers draining a variety of lithologic and climatic regions have been surveyed for the purpose of quantifying the fluxes of bicarbonate and silica from rivers with respect to bedrock lithology and runoff. In all, 101 different rivers, each draining a primary lithology, were examined across the United States, Puerto Rico, and Iceland. To minimize seasonal effects, only rivers with at least two years of data were used. Basaltic catchments were examined in the greatest detail. In a survey of Hawaiian Island watersheds, the average river chemistries could be related to the distribution of soil associations within each catchment. An analysis of cation activity relationships among rivers draining basaltic catchments shows that the river compositions define slopes which are consistent with an equilibrium (ion exchange) control on cation ratios. Among different lithologies, unique weathering rate relationships were developed with yields at typical present-day runoff rates (1-100 cm/y) increasing in the order sandstones, granites, basalts, shales, and carbonates. The bicarbonate and silica fluxes for each of these lithologies have been quantified for use in global studies of chemical denudation. Our study confirms that the dissolved yield of a given drainage basin is determined by a balance between physical and chemical weathering; thus, a warm, wet climate, or the presence of abundant vegetation cannot guarantee high rates of chemical denudation unless accompanied by high rates of physical removal. C1 PENN STATE UNIV,DEPT GEOSCI,UNIV PK,PA 16802. RP BLUTH, GJS (reprint author), NASA,GODDARD SPACE FLIGHT CTR,UNIV SPACE RES ASSOC & GEODYNAM BRANCH,CODE 921,GREENBELT,MD 20771, USA. RI Kump, Lee/H-8287-2012 NR 68 TC 264 Z9 275 U1 5 U2 68 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 MAY PY 1994 VL 58 IS 10 BP 2341 EP 2359 DI 10.1016/0016-7037(94)90015-9 PG 19 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA NQ012 UT WOS:A1994NQ01200015 ER PT J AU MOLNAR, P GIPSON, JM AF MOLNAR, P GIPSON, JM TI VERY LONG-BASE-LINE INTERFEROMETRY AND ACTIVE ROTATIONS OF CRUSTAL BLOCKS IN THE WESTERN TRANSVERSE RANGES, CALIFORNIA SO GEOLOGICAL SOCIETY OF AMERICA BULLETIN LA English DT Article ID SAN-ANDREAS FAULT; OAK-RIDGE FAULT; SOUTHERN-CALIFORNIA; VENTURA BASIN; LINE INTERFEROMETRY; MOJAVE-DESERT; STRIKE-SLIP; TECTONIC ROTATIONS; SEISMIC RISK; DEFORMATION AB Changes in baseline vectors between very long baseline interferometry (VLBI) receiving stations in the Western Transverse Ranges imply that east-west blocks of crust in this region rotate clockwise about vertical axes with respect to the Pacific and North American plates. Minimum apparent rotations, given by the ratios between components of velocity perpendicular to baseline vectors and the lengths of the baselines, imply minimum current rotation rates of a few degrees per million years. The relevant VLBI receivers lie on different crustal blocks that are separated by major active faults. Both geologic and other geodetic observations imply north-south convergence between such blocks at several millimeters per year. Corrections to perpendicular components of velocity for such relative movements between blocks yield likely clockwise rotation rates of 6-degrees/m.y. +/- 2-degrees m.y., which are indistinguishable from the average rate inferred from paleomagnetic declinations of rocks in the Western Transverse Ranges with ages less than 15 m.y. Thus, rotation seems to have occurred continuously and apparently with only small variations in rate during a period when the tectonics of southern California changed dramatically. This apparent independence of the rotation rate on the changing surface kinematics is consistent (1) with such rotation being a manifestation of continuous deformation at depth in the lower crust and upper mantle, (2) with weak faults separating upper-crustal blocks, and (3) with the important resistance to continental deformation lying in the upper mantle and/or lower crust. C1 UNIV JOSEPH FOURIER,GEOPHYS INTERNE & TECTONOPHYS LAB,F-38041 GRENOBLE,FRANCE. NVI INC,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20770. MIT,DEPT EARTH ATMOSPHER & PLANETARY SCI,CAMBRIDGE,MA 02139. RP MOLNAR, P (reprint author), UNIV CALIF SANTA CRUZ,INST CRUSTAL STUDIES,SANTA CRUZ,CA 95064, USA. NR 60 TC 31 Z9 31 U1 0 U2 0 PU GEOLOGICAL SOC AMERICA PI BOULDER PA PO BOX 9140 3300 PENROSE PLACE, BOULDER, CO 80301 SN 0016-7606 J9 GEOL SOC AM BULL JI Geol. Soc. Am. Bull. PD MAY PY 1994 VL 106 IS 5 BP 594 EP 606 DI 10.1130/0016-7606(1994)106<0594:VLBIAA>2.3.CO;2 PG 13 WC Geosciences, Multidisciplinary SC Geology GA NJ870 UT WOS:A1994NJ87000003 ER PT J AU FREEDMAN, AP IBANEZMEIER, R HERRING, TA LICHTEN, SM DICKEY, JO AF FREEDMAN, AP IBANEZMEIER, R HERRING, TA LICHTEN, SM DICKEY, JO TI SUBDAILY EARTH ROTATION DURING THE EPOCH-92 CAMPAIGN SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID MOMENTUM AB Global Positioning System (GPS) data were used to estimate Earth rotation variations over an 11-day period during the Epoch '92 campaign in the summer of 1992. Earth orientation was measured simultaneously by several very long baseline interferometry (VLBI) networks. GPS and VLBI estimates of UT1 with 3-hour time resolution were then compared and analyzed. The high frequency behavior of both data sets is similar, although drifts between the two series of approximately 0.1 ms over 2-5 days are evident. The geodetic results were also compared with models for UT1 fluctuations at tidal periods and with estimates of atmospheric angular momentum made at 6-hour intervals. Most of the geodetic signal in the diurnal and semidiurnal frequency bands can be attributed to tidal processes, whereas UT1 variations over a few days are mostly atmospheric in origin. C1 MIT,DEPT EARTH ATMOSPHER & PLANETARY SCI,CAMBRIDGE,MA 02139. RP FREEDMAN, AP (reprint author), JET PROP LAB,MAIL STOP 238-332,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 15 TC 10 Z9 11 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 MAY 1 PY 1994 VL 21 IS 9 BP 769 EP 772 DI 10.1029/94GL00420 PG 4 WC Geosciences, Multidisciplinary SC Geology GA NK051 UT WOS:A1994NK05100007 ER PT J AU MCKENZIE, RL ROSEN, JM KJOME, NT MCGEE, TJ GROSS, MR SINGH, UN FERRARE, RF KIMVILAKANI, P UCHINO, O NAGAI, T AF MCKENZIE, RL ROSEN, JM KJOME, NT MCGEE, TJ GROSS, MR SINGH, UN FERRARE, RF KIMVILAKANI, P UCHINO, O NAGAI, T TI MULTIWAVELENGTH PROFILES OF AEROSOL BACKSCATTER OVER LAUDER, NEW-ZEALAND, 24 NOVEMBER 1992 SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SULFURIC-ACID; RAMAN LIDAR AB Simultaneous profiles of aerosol backscatter ratio were measured over Lauder, New Zealand (45-degrees-S, 170-degrees-E) on the night of November 24, 1992. Instrumentation comprised two complementary lidar systems and a backscattersonde, to give measurements at wavelengths 351, 490, 532 and 940 nm. The data from the lidars and the backscattersonde were self-consistent, enabling the wavelength dependence of aerosol backscatter to be determined as a function of altitude. This wavelength-dependence is a useful parameter in radiative transfer calculations. In the stratosphere, the average wavelength exponent between 351 and 940 nm was -1.23 +/- 0.1, which was in good agreement with values derived from measured physical properties of aerosols. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. HUGHES STX CORP,LANHAM,MD 20706. IDEA,BELTSVILLE,MD 20705. METEOROL RES INST,TSUKUBA,JAPAN. UNIV WYOMING,DEPT PHYS & ASTRON,LARAMIE,WY 82071. RP MCKENZIE, RL (reprint author), NATL INST WATER & ATMOSPHER RES,LAUDER,NEW ZEALAND. RI McGee, Thomas/G-4951-2013 NR 15 TC 12 Z9 12 U1 2 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD MAY 1 PY 1994 VL 21 IS 9 BP 789 EP 792 DI 10.1029/94GL00186 PG 4 WC Geosciences, Multidisciplinary SC Geology GA NK051 UT WOS:A1994NK05100012 ER PT J AU REISINGER, AR JONES, NB MATTHEWS, WA RINSLAND, CP AF REISINGER, AR JONES, NB MATTHEWS, WA RINSLAND, CP TI SOUTHERN-HEMISPHERE GROUND-BASED MEASUREMENTS OF CARBONYL FLUORIDE (COF2) AND HYDROGEN-FLUORIDE (HF) - PARTITIONING BETWEEN FLUORIDE RESERVOIR SPECIES SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID STRATOSPHERE; SPECTRA AB We report infrared ground based total column measurements of the stratospheric fluorine reservoir gases COF2 and HF above Lauder, New Zealand (45-degrees-S, 167.8-degrees-E) obtained between April 1993 and January 1994. The average retrieved COF2 and HF total columns are 2.81(+/-0.56)x10(14) and 9.91(+/-1.09)x10(14) molecules/cm2, respectively. The daily average COF2 and HF columns are correlated; this correlation is likely the result of dynamics. The average HF/COF2 column ratio on days with measurements of both HF and COF2 is 3.63 (+/-0.55). Comparison of this ratio with model calculations implies that the quantum yield for COF2 photolysis is near unity. Our measured COF2 columns are higher than all previously reported values, but inconsistencies among the earlier measurements and uncertainty in the latitudinal gradient of the COF2 column preclude an accurate determination of the long-term COF2 trend. C1 NIWA,50061 OMAKAU,NEW ZEALAND. NASA,LANGLEY RES CTR,HAMPTON,VA 23681. RP REISINGER, AR (reprint author), UNIV BREMEN,INST REMOTE SENSING,POB 330 440,D-28534 BREMEN,GERMANY. RI Jones, Nicholas/G-5575-2011; Reisinger, Andy/E-1201-2016 OI Jones, Nicholas/0000-0002-0111-2368; Reisinger, Andy/0000-0002-6631-7188 NR 15 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 MAY 1 PY 1994 VL 21 IS 9 BP 797 EP 800 DI 10.1029/94GL00693 PG 4 WC Geosciences, Multidisciplinary SC Geology GA NK051 UT WOS:A1994NK05100014 ER PT J AU HSU, KJ DEMORE, WB AF HSU, KJ DEMORE, WB TI RATE CONSTANTS FOR THE REACTIONS OF OH WITH CH3CL, CH2CL2, CHCL3, AND CH3BR SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SUBSTITUTED METHANES; METHYL CHLOROFORM; LIFETIMES AB Rate constants for the reactions of OH with CH3Cl, CH2Cl2, CHCl3, and CH3Br have been measured by a relative rate technique m which the reaction rate of each compound was compared to that of HFC-152a (CH3CHF2) and (for CH2Cl2) HFC-161 (CH3CH2F). Using absolute rate constants for HFC-152a and HFC-161, which we have determined relative to those for CH4, CH3CCl3, and C2H6, temperature dependent rate constants of both compounds were derived. The derived rate constant for CH3Br is in good agreement with recent absolute measurements . However, for the chloromethanes all the rate constants are lower at atmospheric temperatures than previously reported, especially for CH2Cl2 where the present rate constant is about a factor of 1.6 below the JPL 92-20 value. The new rate constant appears to resolve a discrepancy between the observed atmospheric concentrations and those calculated from the previous rate constant and estimated release rates. RP HSU, KJ (reprint author), JET PROP LAB,PASADENA,CA 91109, USA. NR 23 TC 23 Z9 23 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 MAY 1 PY 1994 VL 21 IS 9 BP 805 EP 808 DI 10.1029/94GL00601 PG 4 WC Geosciences, Multidisciplinary SC Geology GA NK051 UT WOS:A1994NK05100016 ER PT J AU MANNEY, GL ZUREK, RW ONEILL, A SWINBANK, R KUMER, JB MERGENTHALER, JL ROCHE, AE AF MANNEY, GL ZUREK, RW ONEILL, A SWINBANK, R KUMER, JB MERGENTHALER, JL ROCHE, AE TI STRATOSPHERIC WARMINGS DURING FEBRUARY AND MARCH 1993 SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB Two stratospheric warmings during February and March 1993 are described using UKMO analyses, calculated PV and diabatic heating, and N2O observed by the CLAES instrument on the UARS. The first warming affected temperatures over a larger region, while the second produced a larger region of reversed zonal winds. Tilted baroclinic zones formed in the temperature field, and the polar vortex tilted westward with height. Narrow tongues of high PV and low N2O were drawn off the polar vortex, and irreversibly mixed. Tongues of material were drawn from low latitudes into the region between the polar vortex and the anticyclone; diabatic descent was also strongest in this region. Increased N2O over a broad region near the edge of the polar vortex indicates the importance of horizontal transport. N2O decreased in the vortex, consistent with enhanced diabatic descent during the warmings. C1 UNIV READING,CTR GLOBAL ATMOSPHER MODELLING,READING RG6 2AU,ENGLAND. METEOROL OFF,BRACKNELL RG12 2SZ,BERKS,ENGLAND. LOCKHEED PALO ALTO RES LABS,PALO ALTO,CA 94304. RP MANNEY, GL (reprint author), JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 9 TC 31 Z9 32 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 MAY 1 PY 1994 VL 21 IS 9 BP 813 EP 816 DI 10.1029/94GL00093 PG 4 WC Geosciences, Multidisciplinary SC Geology GA NK051 UT WOS:A1994NK05100018 ER PT J AU FARRIS, MH RUSSELL, CT FITZENREITER, RJ OGILVIE, KW AF FARRIS, MH RUSSELL, CT FITZENREITER, RJ OGILVIE, KW TI THE SUBCRITICAL, QUASI-PARALLEL, SWITCH-ON SHOCK SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID ISEE-2 OBSERVATIONS; BOW SHOCKS; THICKNESS AB The conditions that lead to subcritical, quasi-parallel bow shocks are very rare. Even more rarely, a subcritical, quasi-parallel shock can also be termed a switch-on shock, where the tangential component of the magnetic field, which is very small upstream, is said to ''switch on'' downstream. The Rankine-Hugoniot conservation relations predict that the jump in the tangential component of the magnetic field across the shock is very large for these upstream conditions. In this study, we find that the measured jumps in the plasma conditions are in accord with predictions made by the Rankine-Hugoniot conservation relations. The structure of the switch-on shock, not predicted by the Rankine-Hugoniot equations, is very similar to that of the subcritical, quasi-perpendicular shock, with the exception that the precursor wave in front of the shock ramp damps more slowly. C1 UNIV CALIF LOS ANGELES,INST GEOPHYS & PLANETARY PHYS,LOS ANGELES,CA 90024. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. OI Russell, Christopher/0000-0003-1639-8298 NR 14 TC 8 Z9 8 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 MAY 1 PY 1994 VL 21 IS 9 BP 837 EP 840 DI 10.1029/94GL00697 PG 4 WC Geosciences, Multidisciplinary SC Geology GA NK051 UT WOS:A1994NK05100024 ER PT J AU NUNES, JA AF NUNES, JA TI DIVINE,T.NEIL - (1939-1994) - IN-MEMORIAM SO ICARUS LA English DT Item About an Individual RP NUNES, JA (reprint author), JET PROP LAB,PASADENA,CA 91109, USA. NR 0 TC 1 Z9 1 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 MAY PY 1994 VL 109 IS 1 BP 2 EP 2 DI 10.1006/icar.1994.1073 PG 1 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA PA751 UT WOS:A1994PA75100002 ER PT J AU TAKATA, T OKEEFE, JD AHRENS, TJ ORTON, GS AF TAKATA, T OKEEFE, JD AHRENS, TJ ORTON, GS TI COMET SHOEMAKER-LEVY-9 - IMPACT ON JUPITER AND PLUME EVOLUTION SO ICARUS LA English DT Article ID VOYAGER AB The impact of fragments of Comet Shoemaker-Levy 9 on Jupiter and the resulting vapor plume expansion are investigated by conducting three-dimensional numerical simulations using the smoothed particle hydrodynamics (SPH) method. An icy body, representing the cometary fragments, with a velocity of 60 km/sec and a diameter of 2 km can penetrate to 350 km below the 1-bar pressure level in the atmosphere. Most of the initial kinetic energy of the fragment is transferred to the atmosphere between 50 km and 300 km below the 1-bar pressure level. The shock-heated atmospheric gas in the wake is totally dissociated and partially ionized. Scaling our SPH results to other sizes indicates that fragments larger than approximately 100 m in diameter can penetrate to below the visible cloud decks. The energy deposited in the atmosphere is explosively released in the upward expansion of the resulting plume. The plume preferentially expands upward rather than horizontally due to the density gradient of the ambient atmosphere. It rises greater-than-or-equal-to 10(2) km in approximately 10(2) sec. Eventually the total atmospheric mass ejected to above 1 bar is greater-than-or-equal-to 40 times the initial mass of the impactor. The plume temperature at a radius approximately 10(3) km is >10(3) K for 10(3) sec for a 2-km fragment. We predict that impact-induced plumes will be observable with the remote sensing instruments of the Galileo spacecraft. As the impact site rotates into the view of Earth some 20 min after the impact, the plume expansion will be observable using the Hubble Space Telescope and from visible and infrared instruments on groundbased telescopes. The rising plume reaches approximately 3000 km altitude in approximately 10 min and will be visible from Earth. (C) 1994 Academic Press, Inc. C1 JET PROP LAB,PASADENA,CA 91109. RP TAKATA, T (reprint author), CALTECH,DIV GEOL & PLANETARY SCI,PASADENA,CA 91125, USA. NR 43 TC 43 Z9 43 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 MAY PY 1994 VL 109 IS 1 BP 3 EP 19 DI 10.1006/icar.1994.1074 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA PA751 UT WOS:A1994PA75100003 ER PT J AU BAINES, KH HAMMEL, HB AF BAINES, KH HAMMEL, HB TI CLOUDS, HAZES, AND THE STRATOSPHERIC METHANE ABUNDANCE IN NEPTUNE SO ICARUS LA English DT Article ID VOYAGER MEASUREMENTS; UPPER-ATMOSPHERE; ROTATION PERIOD; URANUS; CONSTRAINTS; SPECTROPHOTOMETRY; PROFILES; ALBEDO; TITAN AB Analysis of high-spatial-resolution (approximately 0.8 arcsec) methane band and continuum imagery of Neptune's relatively homogeneous Equatorial Region yields significant constraints on (1) the stratospheric gaseous methane mixing ratio (f(CH4,s)), (2) the column abundances and optical properties of stratospheric and tropospheric hydrocarbon hazes, and (3) the wavelength-dependent single-scattering albedo of the 3-bar opaque cloud. From the center-to-limb behavior of the 7270-angstrom and 8900-angstrom CH4 bands, the stratospheric methane mixing ratio is limited to f(CH4,s) < 1.7 x 10(-3), with a nominal value of f(CH4,s) = 3.5 x 10(-4), one to two orders of magnitude less than pre-Voyager estimates, but in agreement with a number of recent ultraviolet and thermal infrared measurements, and largely in agreement with the tropopause mixing ratio implied by Voyager temperature measurements. Upper limits to the stratospheric haze mass column abundance and 6190-angstrom and 8900-angstrom haze opacities are 0.61 mug CM-2 and 0.075 and 0.042, respectively, with nominal values of 0.20 mug cm-2 and 0.025 and 0.014 for the 0.2-mum radius particles preferred by the recent Voyager PPS analysis of Pryor et al. (1992, Icarus 99, 302-316). The tropospheric CH4 haze opacities are comparable to that found in the stratosphere, i.e., upper limits of 0.104 and 0.065 at 6190 angstrom and 8900 angstrom, respectively, with nominal values of 0.085 and 0.058. This indicates a column abundance less than 11.0 mug cm-2, corresponding to the methane gas content within a well-mixed 3% methane tropospheric layer only 0. 1 cm think near the 1.5-bar CH4 condensation level. Constraints on the single-scattering albedos of these hazes include (1) for the stratospheric component, 6190-angstrom and 8900-angstrom imaginary indices of refraction less than 0.047 and 0.099, respectively, with 0.000 (conservative scattering) being the nominal value at both wavelengths, and (2) CH4 haze single-scattering albedos greater than 0.85 and 0.50 at these two wavelengths, with conservative scattering again begin the preferred value. However, conservative scattering is ruled out for the opaque cloud near 3 bars marking the bottom of the visible atmosphere. Specifically, we find cloud single-scattering albedos of 0.915 +/- 0.006 at 6340 angstrom, 0.775 +/- 0.012 at 7490 angstrom, and 0.803 +/- 0.010 at 8260 angstrom. Global models utilizing a complete global spectrum confirm the red-absorbing character of the 3-bar cloud. The global-mean model has approximately 7.7 times greater stratospheric aerosol content then the Equatorial Region. An analysis of stratospheric haze precipitation rates indicates a steady-state haze production rate of 0. 185-1.5 x 10(-14) g cm-2 sec-1, in agreement with recent theoretical photochemical estimates. Finally, reanalysis of the Voyager PPS 7500-angstrom phase angle data utilizing the f(CH4,s) value derived here confirms the Pryor et al. result of a tropospheric CH4 haze opacity of a few tenths in the 22-30-degrees-S latitude region, several times that of the Equatorial Region or of the globe. The factor-of-10 reduction in f(CH4,s), below that assumed by Pryor et al. implies decreased gas absorption and consequently a decrease in the forward-scattering component of tropospheric aerosols. (C) 1994 Academic Press, Inc. C1 MIT,DEPT EARTH ATMOSPHER & PLANETARY SCI,CAMBRIDGE,MA 02139. RP BAINES, KH (reprint author), JET PROP LAB,MS 169-237,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 36 TC 53 Z9 53 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 MAY PY 1994 VL 109 IS 1 BP 20 EP 39 DI 10.1006/icar.1994.1075 PG 20 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA PA751 UT WOS:A1994PA75100004 PM 11539136 ER PT J AU FRIEDSON, AJ AF FRIEDSON, AJ TI GRAVITY-WAVES IN TITAN ATMOSPHERE SO ICARUS LA English DT Article ID RADIO OCCULTATION; CONVECTION; TURBULENCE; BREAKDOWN; VOYAGER-1 AB Scintillations (high frequency variations) observed in the radio signal during the occultation of Voyager 1 by Titan (Hinson and Tyler, 1983, Icarus 54, 337-352) provide information concerning neutral atmospheric density fluctuations on scales of hundreds of meters to a few kilometers. Those seen at altitudes higher than 25 km above the surface were interpreted by Hinson and Tyler as being caused by linear, freely propagating (energy-conserving) gravity waves, but this interpretation was found to be inconsistent with the scintillation data below the 25-km altitude level. Here an attempt is made to interpret the entire scintillation profile between the surface and the 90-km altitude level in terms of gravity waves generated at the surface. Numerical calculations of the density fluctuations caused by two-dimensional, nonhydrostatic, finite-amplitude gravity waves propagating vertically through Titan's atmosphere are performed to produce synthetic scintillation profiles for comparison with the observations. The numerical model accurately treats the effects of wave transience, nonlinearity, and breakdown due to convective instability in the overturned part of the wave. The results indicate that wave phase speeds could not have exceeded 2 m sec-1 and must have been oriented in the meridional (north-south) direction if there were strong zonal winds on Titan. The high-altitude scintillation data were accurately recovered with a freely propagating wave solution, confirming the analytic model of Hinson and Tyler. The amplitude, phase speed, and horizontal and vertical wavelengths of the freely propagating waves are consistent with their having been generated in the convective boundary layer at Titan's surface. It is found that the low-altitude scintillation data can be fit by a model where a component of the gravity waves becomes convectively unstable and breaks near the 15 km level. A definitive value for the amplitude of the breaking wave cannot be obtained without better knowledge of its horizontal wavelength and phase speed. If the breaking wave had the same horizontal wavelength, approximately 4 km, as the freely propagating waves, then its vertical perturbation velocity near the surface would have been approximately 1.4 cm sec-1, and its phase speed would have been approximately 20 cm sec-1. This component could also have been generated by convection near the surface. Alternatively, it is estimated that the breaking wave could have been forced by topographic relief of 60-300 meters. The large-scale structure of the observed scintillation profile in the entire altitude range between 5 and 85 km can be simulated by a model where the freely propagating and breaking waves are forced at the surface simultaneously. Further analysis of the Voyager 1 Titan low-altitude scintillation data, using inversion theory appropriate for strong scattering, could potentially remove some of the ambiguities remaining in this analysis and allow a better determination of the strength and source of the waves. (c) 1994 Academic Press, Inc. RP FRIEDSON, AJ (reprint author), JET PROP LAB,MS 169-237,PASADENA,CA 91109, USA. NR 19 TC 21 Z9 21 U1 2 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 MAY PY 1994 VL 109 IS 1 BP 40 EP 57 DI 10.1006/icar.1994.1076 PG 18 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA PA751 UT WOS:A1994PA75100005 ER PT J AU KRASNOPOLSKY, VA POLLACK, JB AF KRASNOPOLSKY, VA POLLACK, JB TI H2O-H2SO4 SYSTEM IN VENUS CLOUDS AND OCS, CO, AND H2SO4 PROFILES IN VENUS TROPOSPHERE SO ICARUS LA English DT Article ID SULFURIC-ACID SYSTEM; CHEMICAL-COMPOSITION; DARK SIDE; WATER; ATMOSPHERE; VAPOR; SPECTROSCOPY; REFLECTIVITY; ABUNDANCE; HYDROGEN AB A coupled problem of diffusion and condensation is solved for the H2SO4-H2O system in Venus' cloud layer. The position of the lower cloud boundary and profiles of the H2O and H2SO4 vapor mixing ratios and of the H2O/H2SO4 ratio of sulfuric acid aerosol and its flux are calculated as functions of the column photochemical production rate of sulfuric acid, PHI(H2SO4). Variations of the lower cloud boundary are considered. Our basic model, which is constrained to yield f(H2O) (30 km) = 30 ppm (Pollack et al. 1993), predicts the position of the lower cloud boundary at 48.4 km coinciding with the mean Pioneer Venus value, the peak H2SO4 mixing ratio of 5.4 ppm, and the H2SO4 production rate PHI(H2SO4) = 2.2 x 10(12) CM-2 sec-1. The sulfur to sulfuric acid mass flux ratio in the clouds is 1:27 in this model, and the mass loading ratio may be larger than this value if sulfur particles are smaller than those of sulfuric acid. The model suggests that the extinction coefficient of sulfuric acid particles with radius 3.7 mum (mode 3) is equal to 0. 3 km-1 in the middle cloud layer. The downward flux of CO is equal to 1.7 x 10(12) CM-2 sec-1 in this model. Our second model, which is constrained to yield f(H2SO4) = 1 0 ppm at the lower cloud boundary, close to the value measured by the Magellan radiooccultations, predicts the position of this boundary to be at 46.5 km, which agrees with the Magellan data; f(H2O)(30 km) = 90 ppm, close to the data of Moroz et al. (1983) at this altitude; PHI(H2SO4) = 6.4 x 10(12) CM-2 Sec-1; and PHI(co) = 4.2 x 10(12) CM-2 sec-1. The S/H2SO4 flux mass ratio is 1:18, and the extinction coefficient of the mode 3 sulfuric acid particles is equal to 0.9 km-1 in the middle cloud layer. A strong gradient of the H2SO4 vapor mixing ratio near the bottom of the cloud layer drives a large upward flux of H2SO4, which condenses and forms the excessive downward flux of liquid sulfuric acid, which is larger by a factor of 4-7 than the flux in the middle cloud layer. This is the mechanism of formation of the lower cloud layer. Variations of the lower cloud layer are discussed. Our modeling of the OCS and CO profiles in the lower atmosphere measured by Pollack et al. (1993) provides a reasonable explanation of these data and shows that the rate coefficient of the reaction SO3 + CO --> CO2 + SO2 is equal to 10(-11) exp(-(13,100 +/- 1000)/T) cm/s. The main channel of the reaction between SO3 and OCS is CO2 + (SO)2, and its rate coefficient is equal to 10(-11) exp(-(8900 +/- 500)/T) cm3/s. In the conditions of Venus' lower atmosphere, (SO)2 is removed by the reaction (SO)2. + OCS --> CO + S2 + SO2. The model predicts an OCS mixing ratio of 28 ppm near the surface. (C) 1994 Academic Press, Inc. C1 NASA,AMES RES CTR,THEORET STUDIES BRANCH,MOFFETT FIELD,CA 94035. RP KRASNOPOLSKY, VA (reprint author), NASA,GODDARD SPACE FLIGHT CTR,EXTRATERR PHYS LAB,CODE 693,GREENBELT,MD 20771, USA. RI Krasnopolsky, Vladimir/L-5085-2013 NR 71 TC 76 Z9 76 U1 0 U2 7 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 MAY PY 1994 VL 109 IS 1 BP 58 EP 78 DI 10.1006/icar.1994.1077 PG 21 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA PA751 UT WOS:A1994PA75100006 PM 11539137 ER PT J AU JAMES, PB CLANCY, RT LEE, SW MARTIN, LJ SINGER, RB SMITH, E KAHN, RA ZUREK, RW AF JAMES, PB CLANCY, RT LEE, SW MARTIN, LJ SINGER, RB SMITH, E KAHN, RA ZUREK, RW TI MONITORING MARS WITH THE HUBBLE-SPACE-TELESCOPE - 1990-1991 OBSERVATIONS SO ICARUS LA English DT Article ID SOUTH POLAR-CAP; WIND STREAKS; SEASONAL RECESSION; MARTIAN ATMOSPHERE; SYRTIS MAJOR; WATER-VAPOR; VIKING; CLOUDS; DUST; MARINER-9 AB Images of Mars obtained using the Planetary Camera on the Hubble Space Telescope during 1990 and 1991 are described and analyzed. Multispectral images of Mars record the martian season between L(S) = 348-degrees and 60-degrees corresponding to late winter and spring in the northern hemisphere. The wavelengths of these observations varied between 230 nm in the ultraviolet and 890 nm in the near infrared. We use these images to discuss atmospheric and polar phenomena, to constrain the aerosols and ozone in the martian atmosphere, and to compare surface albedo features within this data set as well as with previous observations. Two methods are used to constrain the opacity of the martian atmosphere: comparisons of ultraviolet images with atmospheric scattering models and examination of contrast changes of surface features observed at visible wavelengths. Our observations are consistent with a Mars which was quite different from the planet when it was viewed by Viking; we estimate an upper limit of 0. 1 for equatorial dust opacity near vernal equinox, compared to values of 0.4 to 0.5 measured in Chryse by Viking Lander 1. Later, at L(S) = 60-degrees, an upper limit of 0.2 was found for dust in the southern hemisphere. Except for suggestions of local dust activity near the north polar cap in late spring, there was no visual evidence of dust storms on the planet. The Hartley band of ozone is within the F230W filter bandpass, and the 230W/336W ratio is therefore sensitive to ozone. High latitude ozone is observed at a concentration similar to that observed by Mariner 9; a seasonal dependence in ozone concentration was observed with concentration decreasing at northern arctic latitudes and increasing at southern mid-latitudes as L(S) increases from 350-degrees to 60-degrees. Despite the difference in dust loading, the behavior of condensate clouds and the recession of the north polar cap are consistent with those observed during Viking years. Late winter images of the north polar region reveal an active north polar hood with a maximum (UV) opacity of about 0.25 near 50-degrees latitude; the hood seems to have an annular form, with the central, polar regions having smaller opacity. Clouds observed in the northern hemisphere to the south of the hood boundary are suggestive of fronts similar to those observed during the Mariner 9 mission. A diurnal variation in the hood clouds which is (anti) correlated with the amount of water vapor in the atmosphere is noted. Spring images show significant clouds in the Tharsis, Elysium, and Arabia regions; the most optically thick components of these clouds are those near Elysium, Alba Patera, and Tithonius in the afternoon, although these regions also are bright on the morning limb. The cloud associated with Elysium had the largest optical depth for a cloud in the UV, 0.4. Most of the HST monitoring sequences were targeted on the Syrtis Major region, an area which was intensively studied during the Viking Mission. During Viking there were major changes in the region which were attributed to the two major 1977 global dust storms on Mars. Our series of images was projected onto map grids and photometrically corrected in order to study changes in the Syrtis albedo features. To first order, Syrtis does not change over the time period of these observations, as would have been expected if they followed major global dust storms during the preceding season. Images were deconvolved using the Richardson-Lucy iterative algorithm to remove the defocussing effects of the spherical aberration of the HST primary. Even when Mars subtended less than 5 arcsec, in May 1991, the images were scientifically useful and comparable to photographic images obtained at opposition. Although the data are subject to the solar pointing constraint for HST, the relatively slow movement of the allowed observation window, which is more than one half martian year, with respect to the martian seasons will permit us to address the question of major variations in the martian atmosphere. (C) 1994 Academic Press, Inc. C1 UNIV COLORADO,LASP,BOULDER,CO 80309. LOWELL OBSERV,FLAGSTAFF,AZ 86001. UNIV ARIZONA,LPL,TUCSON,AZ 85721. SPACE TELESCOPE SCI INST,BALTIMORE,MD 21218. JET PROP LAB,PASADENA,CA 91109. RP JAMES, PB (reprint author), UNIV TOLEDO,DEPT PHYS & ASTRON,TOLEDO,OH 43606, USA. RI Kahn, Ralph/D-5371-2012 OI Kahn, Ralph/0000-0002-5234-6359 NR 61 TC 60 Z9 61 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 0019-1035 J9 ICARUS JI Icarus PD MAY PY 1994 VL 109 IS 1 BP 79 EP 101 DI 10.1006/icar.1994.1078 PG 23 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA PA751 UT WOS:A1994PA75100007 ER PT J AU HABERLE, RM TYLER, D MCKAY, CP DAVIS, WL AF HABERLE, RM TYLER, D MCKAY, CP DAVIS, WL TI A MODEL FOR THE EVOLUTION OF CO2 ON MARS SO ICARUS LA English DT Article ID CLIMATIC-CHANGE; MARTIAN ATMOSPHERE; CHAOTIC OBLIQUITY; ORIGIN; WATER; VALLEYS; HISTORY; IMPACT; MORPHOLOGY; LUMINOSITY AB We have constructed a model that predicts the evolution of CO2 on Mars from the end of the heavy bombardment period to the present. The model draws on published estimates of the main processes believed to affect the fate of CO2 during this period: chemical weathering, regolith uptake, polar cap formation, and atmospheric escape. Except for escape, the rate at which these processes act is controlled by surface temperatures which we calculate using a modified version of the Gierasch and Toon energy balance model (1973, J. Atmos. Sci. 30, 1502-1508). The modifications account for the change in solar luminosity with time, the greenhouse effect, and a polar and equatorial energy budget. Using published estimates for the main parameters, we find no evolutionary scenario in which CO2 is capable of producing a warm (global mean temperatures >250 K) and wet (surface pressures > 30 mbar) early climate, and then evolves to present conditions with approximately 7 mbar in the atmosphere, <300 mbar in the regolith, and <5 mbar in the caps. Such scenarios would only exist if the early sun were brighter than standard solar models suggest, if greenhouse gases other than CO2 were present in the early atmosphere, or if the polar albedo were significantly lower than 0.75. However, these scenarios generally require the storage of large amounts Of CO2 (>1 bar) in the carbonate reservoir. If the warm and wet early Mars constraint is relaxed, then we find best overall agreement with present day reservoirs for initial CO2 inventories of 0.5-1.0 bar. We also find that the polar caps can have a profound effect on how the system evolves. If the initial amount Of CO2 is less than some critical value, then there is not enough heating of the poles to prevent permanent caps from forming. Once formed, these caps control how the system evolves, because they set the surface pressure and, hence, the thermal environment. If the initial amount of CO2 is greater than this critical value, then caps do not form initially, but can form later on, when weathering and escape lower the surface pressure to a point at which polar heating is no longer sufficient to prevent cap formation and the collapse of the climate system. Our modeling suggests this critical initial amount Of CO2 is between 1 and 2 bar, but its true value will depend on all factors affecting the polar heat budget. (C) 1994 Academic Press, Inc. C1 SAN JOSE STATE UNIV,DEPT METEOROL,SAN JOSE,CA 95192. RP HABERLE, RM (reprint author), NASA,AMES RES CTR,DIV SPACE SCI,245-3,MOFFETT FIELD,CA 94035, USA. NR 68 TC 57 Z9 57 U1 0 U2 4 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0019-1035 J9 ICARUS JI Icarus PD MAY PY 1994 VL 109 IS 1 BP 102 EP 120 DI 10.1006/icar.1994.1079 PG 19 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA PA751 UT WOS:A1994PA75100008 PM 11539135 ER PT J AU SPRAGUE, AL KOZLOWSKI, RWH WITTEBORN, FC CRUIKSHANK, DP WOODEN, DH AF SPRAGUE, AL KOZLOWSKI, RWH WITTEBORN, FC CRUIKSHANK, DP WOODEN, DH TI MERCURY - EVIDENCE FOR ANORTHOSITE AND BASALT FROM MIDINFRARED (7.3-13.5-MU-M) SPECTROSCOPY SO ICARUS LA English DT Article ID SPECTRAL IRRADIANCE CALIBRATION; REFLECTANCE SPECTRA; REGIONS; IRON; SOIL; MOON AB Spectroscopic observations (7.3-13.5 mum) of three locations on the surface of Mercury are reported. The observed spectral radiance emanated from equatorial and low latitude regions between 12 and 32-degrees mercurian longitude on 8 December 1990, from the longitudinal region 22-44-degrees on 10 December 1990, and from the longitudinal region 110-130-degrees on 12 July 1992; all locations are primarily intercrater plains. Spectra indicate compositional differences among these three locations. The emissivity maximum, or Christiansen emission peak, occurs at 8.1 mum in the 8 December 1990 spectra, but at shorter wavelengths in the data of 10 December 1990 and 12 July 1992. Emission peaks near 8 mum indicate rocks of intermediate or mafic composition. Spectra from 22 to 44-degrees longitude resemble spectra of terrestrial basalt and diorite with SiO2 content between 49 and 55%. The Christiansen feature in spectra from near 110-130-degrees longitude strongly suggests the presence of plagioclase, in particular labradorite, while the overall spectrum resembles anorthosite. The spectra from all three locations on Mercury show distinct and recognizable features, the principal Christiansen emission peak being the most prominent, but they also contain features that we have not yet identified. The general indication from the spectra is that Mercury's surface consists of minerals more depleted in oxidized iron than those on the Moon. We also explore the theoretical and observational complexities of ground-based mid-infrared spectroscopy of airless bodies in general and Mercury in particular. A spectroscopic study of quartzite in both reflectance and emittance illustrates the practical, spectral validity of Kirchhoff's Law. (C) 1994 Academic Press, Inc. C1 SUSQUEHANNA UNIV,SELINSGROVE,PA 17870. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RP SPRAGUE, AL (reprint author), UNIV ARIZONA,LUNAR & PLANETARY LAB,TUCSON,AZ 85721, USA. NR 36 TC 76 Z9 76 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 MAY PY 1994 VL 109 IS 1 BP 156 EP 167 DI 10.1006/icar.1994.1083 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA PA751 UT WOS:A1994PA75100012 ER PT J AU DEBRABANDER, GN BOYD, JT BEHEIM, G AF DEBRABANDER, GN BOYD, JT BEHEIM, G TI INTEGRATED OPTICAL RING-RESONATOR WITH MICROMECHANICAL DIAPHRAGM FOR PRESSURE SENSING SO IEEE PHOTONICS TECHNOLOGY LETTERS LA English DT Article ID SENSOR AB An optical pressure sensor has been fabricated which uses an integrated-optical ring resonator to measure the strain induced in a micromachined silicon diaphragm. A silicon substrate is etched from the side opposite the silicon oxynitride optical waveguides to produce a rectangular diaphragm whose long edge lies underneath a straight section in the ring. Pressure-induced changes in the resonant frequency of the ring are measured using a frequency swept laser diode. A linear response to pressure is observed for the TM mode with a sensitivity of 0.0094 rad/kPa. This pressure sensor is rugged, is amenable to batch fabrication, and it provides a link-insensitive readout. C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP DEBRABANDER, GN (reprint author), DEPT ELECT & COMP ENGN,CINEMNATI,OH 45221, USA. NR 13 TC 39 Z9 39 U1 1 U2 7 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 1041-1135 J9 IEEE PHOTONIC TECH L JI IEEE Photonics Technol. Lett. PD MAY PY 1994 VL 6 IS 5 BP 671 EP 673 DI 10.1109/68.285575 PG 3 WC Engineering, Electrical & Electronic; Optics; Physics, Applied SC Engineering; Optics; Physics GA NL837 UT WOS:A1994NL83700027 ER PT J AU MORRIS, KA JUANG, JN AF MORRIS, KA JUANG, JN TI DISSIPATIVE CONTROLLER DESIGNS FOR 2ND-ORDER DYNAMIC-SYSTEMS SO IEEE TRANSACTIONS ON AUTOMATIC CONTROL LA English DT Note AB The passivity theorem may be used to design robust controllers for structures with positive transfer functions. This paper extends this result to more general configurations using dissipative system theory. A stability theorem for robust control of structures with displacement sensors is given and applied to several common classes of controllers. C1 NASA,LANGLEY RES CTR,HAMPTON,VA 23665. RP MORRIS, KA (reprint author), UNIV WATERLOO,DEPT APPL MATH,WATERLOO N2L 3G1,ONTARIO,CANADA. NR 16 TC 13 Z9 13 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 0018-9286 J9 IEEE T AUTOMAT CONTR JI IEEE Trans. Autom. Control PD MAY PY 1994 VL 39 IS 5 BP 1056 EP 1063 DI 10.1109/9.284893 PG 8 WC Automation & Control Systems; Engineering, Electrical & Electronic SC Automation & Control Systems; Engineering GA NM783 UT WOS:A1994NM78300026 ER PT J AU VILNROTTER, VA AF VILNROTTER, VA TI CHANNEL ASSIGNMENTS FOR IMPROVED GAIN IN BASEBAND ARRAY FEED COMPENSATION SYSTEMS SO IEEE TRANSACTIONS ON COMMUNICATIONS LA English DT Article AB The performance of a real-time digital combining system for use with array feeds has been considered in previous articles. The purpose of the combining operation is to recover signal-to-noise ratio (SNR) losses due to antenna deformations and atmospheric effects. Previously, arbitrary signal powers and noise variances were assumed, but no attempt was made to match the receiver channels to the available signal powers. Here it is shown that for any signal power and noise variance distribution, a ''best'' channel assignment exists that maximizes the combined SNR in the limit of vanishingly small combining losses. This limit can be approached in practice by observing sufficiently many samples. Specific signal power and noise variance distributions are considered, and it is shown that even relatively ''noisy'' channels can be used effectively to recover SNR losses resluting from signals diverted out of a ''high-quality'' channel by antenna deformations. RP VILNROTTER, VA (reprint author), JET PROP LAB,PASADENA,CA 91109, USA. NR 5 TC 3 Z9 3 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 0090-6778 J9 IEEE T COMMUN JI IEEE Trans. Commun. PD MAY PY 1994 VL 42 IS 5 BP 2127 EP 2133 DI 10.1109/26.285148 PG 7 WC Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA NM488 UT WOS:A1994NM48800008 ER PT J AU NEUDECK, PG LARKIN, DJ STARR, JE POWELL, JA SALUPO, CS MATUS, LG AF NEUDECK, PG LARKIN, DJ STARR, JE POWELL, JA SALUPO, CS MATUS, LG TI ELECTRICAL-PROPERTIES OF EPITAXIAL 3C-SIC AND 6H-SIC P-N-JUNCTION DIODES PRODUCED SIDE-BY-SIDE ON 6H-SIC SUBSTRATES SO IEEE TRANSACTIONS ON ELECTRON DEVICES LA English DT Article ID SIC THIN-FILMS; CHEMICAL VAPOR-DEPOSITION; FIELD-EFFECT TRANSISTORS; BETA-SILICON-CARBIDE; GROWTH; ELECTRONICS; MICROWAVE; DEVICES; ALPHA AB 3C-SiC (beta-SiC) and 6H-SiC p-n junction diodes have been fabricated in regions of both 3C-SiC and 6H-SiC epitaxial layers which were grown side-by-side on low-tilt-angle 6H-SiC substrates via a chemical vapor deposition (CVD) process. Several runs of diodes exhibiting state-of-the-art electrical characteristics were produced, and performance characteristics were measured and compared as a function of doping, temperature, and polytype. The first 3C-SiC diodes which rectify to reverse voltages in excess of 300 V were characterized, representing a six-fold blocking voltage improvement over experimental 3C-SiC diodes produced by previous techniques. When placed under sufficient forward bias, the 3C-SiC diodes emit significantly bright green-yellow light while the 6H-SiC diodes emit in the blue-violet. The 6H-SiC p-n junction diodes represent the first reported high-quality 6H-SiC devices to be grown by CVD on very low-tilt-angle (< 0.5-degrees off the (0001) silicon face) 6H substrates. The reverse leakage current of a 200 mum diameter circular device at 1100 V reverse bias was less than 20 nA at room temperature, and excellent rectification characteristics were demonstrated at the peak characterization temperature of 400-degrees-C. C1 OHIO AEROSP INST,BROOKPARK,OH 44142. CALSPAN CORP,FAIRVIEW PK,OH 44126. NASA,LEWIS RES CTR,ENGINE SENSOR TECHN BRANCH,CLEVELAND,OH 44135. RP NEUDECK, PG (reprint author), NASA,LEWIS RES CTR,HIGH TEMP INTEGRATED ELECTR & SENSORS GRP,CLEVELAND,OH 44135, USA. NR 73 TC 36 Z9 36 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 0018-9383 J9 IEEE T ELECTRON DEV JI IEEE Trans. Electron Devices PD MAY PY 1994 VL 41 IS 5 BP 826 EP 835 DI 10.1109/16.285038 PG 10 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA NN185 UT WOS:A1994NN18500031 ER PT J AU ROSENFELD, D ALTEROVITZ, SA AF ROSENFELD, D ALTEROVITZ, SA TI CARRIER TRANSIT-TIME THROUGH A BASE WITH DOPANT DEPENDENT MOBILITY SO IEEE TRANSACTIONS ON ELECTRON DEVICES LA English DT Note ID BIPOLAR-TRANSISTOR AB The transit time through a base with exponential grading of dopant density is modeled and calculated. The dependence of the mobility on dopant concentration (and hence the spatial dependence) is taken into account and an analytical solution is derived. C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP ROSENFELD, D (reprint author), TECHNION ISRAEL INST TECHNOL,FAC ELECT ENGN,IL-32000 HAIFA,ISRAEL. NR 6 TC 8 Z9 8 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-9383 J9 IEEE T ELECTRON DEV JI IEEE Trans. Electron Devices PD MAY PY 1994 VL 41 IS 5 BP 848 EP 849 DI 10.1109/16.285042 PG 2 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA NN185 UT WOS:A1994NN18500034 ER PT J AU RODRIGUEZ, E MARTIN, JM AF RODRIGUEZ, E MARTIN, JM TI CORRELATION-PROPERTIES OF OCEAN ALTIMETER RETURNS SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article ID SURFACE AB The correlation properties of altimeter returns are useful in the optimal design of altimeter systems. They are also necessary for implementing maximum likelihood estimation algorithms for altimeter waveform parameter estimation. In this paper, we derive a simple expression for the bin-to-bin and pulse-to-pulse correlation of altimeter waveforms. This expression is a triple convolution of the specular point probability density function, a product of altimeter point target responses, and a generalized surface impulse response. This result is analogous to the usual expression for the mean altimeter waveform. We compare tbese theoretical predictions against real data, using measurements from the Skylab and Geosat altimeters. Finally, we present a simple application of the results to altimeter system design. RP RODRIGUEZ, E (reprint author), JET PROP LAB,RADAR SCI & ENGN SECT,OCEAN APPLICAT SENSING & INFORMAT SYST GRP,PASADENA,CA 91109, USA. NR 10 TC 13 Z9 13 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 MAY PY 1994 VL 32 IS 3 BP 553 EP 561 DI 10.1109/36.297974 PG 9 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA NY447 UT WOS:A1994NY44700009 ER PT J AU FREEMAN, A ZINK, M AF FREEMAN, A ZINK, M TI AN APPLICATION OF THE MONOPULSE PRINCIPLE TO DETERMINING ELEVATION ANGLES IN SAR IMAGES SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article ID CALIBRATION AB In mapping nonflat regions of the Earth using air-borne synthetic aperture radar, (SAR), terrain height variations cause two problems in radiometric calibration: the first being that the local incidence angle for any pixel may vary from that given by the flat (or curved) Earth assumption, the second, being that the wrong elevation angle may be used in correcting for the radiometric variation of the antenna pattern. In tracking radars, simultaneous amplitude or phase measurements made by the same radar antenna, but modulated differently, are compared to determine the angular position of targets. This is known as the monopulse principle. In this paper, we show how polarimetric SAR da a can be used in a novel application of the monopulse principle to determine the elevation angle and thus, the height at the different parts of the image. Our approach begins with the observation that, provided like- and cross-polarized backscatter are uncorrelated, then the algorithm described in [1] for calculating antenna crosstalk yields a measurable quantity whose amplitude (and phase) depends only on elevation angle (or off-boresight angle). Thus, if we determine the crosstalk for a given point in the image, we can relate that measurement the elevation angle appropriate to that point. Knowledge of the slant range to the point then allows determination of the height of the platform above it. This operation, repeated at many locations throughout the image, allows us to build up a topographic map of the height of the aircraft above each location. The approach described in this paper gives sufficient resolution in elevation to allow the antenna pattern radiometric correction to be done properly, since it allows the determination of elevation angles at rid of points in the image. Knowledge of the slant range to each point and the height of the aircraft then allows us to build up a grid of height estimates for the imaged area. Unfortunately, the spatial resolution of the grid was not sufficient to turn the height maps into usable maps of local incidence angle. In the paper we also describe how our approach may be improve upon, using an active, phased array antenna. C1 DLR,INST HOCHFREQUENZTECH,W-8031 OBERPFAFFENHOFEN,GERMANY. RP FREEMAN, A (reprint author), JET PROP LAB,PASADENA,CA 91109, USA. NR 14 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 MAY PY 1994 VL 32 IS 3 BP 616 EP 625 DI 10.1109/36.297979 PG 10 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA NY447 UT WOS:A1994NY44700015 ER PT J AU KAUFMAN, YJ REMER, LA AF KAUFMAN, YJ REMER, LA TI DETECTION OF FORESTS USING MID-IR REFLECTANCE - AN APPLICATION FOR AEROSOL STUDIES SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article ID VEGETATION INDEX; AVHRR DATA; ATMOSPHERIC CORRECTION; NOAA-AVHRR; SATELLITE; SCATTERING; EMISSIVITY; ALGORITHM; BRAZIL; CLOUD AB The detection of dark, dense vegetation is an important step in the remote sensing of aerosol loading. Current methods that employ the red (0.64 mum) and the near-IR (0.84 mum) regions are unsatisfactory in that the presence of aerosols in the scene distorts the apparent reflectance in the visible and near-IR ranges of the spectrum. The mid-IR spectral region is also sensitive to vegetation due to the absorption of liquid water in the foliage, but s not sensitive to the presence of most aerosols (except for dust). Therefore, mid-IR channels on the AVHRR and ECS MODIS (e.g., the 3.75 mum or the 3.95 mum channels) have a unique potential for the remote sensing of dark, dense vegetation, particularly in the presence of biomass burning smoke or industrial/urban haze. The reflective part of the 3.75 mum channel (rho3.75) is applied to images of the AVHRR over the eastern United States. This channel was found to be correlated to reflectance at 0.64 mum (rho0.64), less sensitive to haze than the visible channel and superior to both the 0.64 mum reflectance and the normalized difference vegetation index (NDVI) to determine forest pixels in an image. However, its application to monitor the seasonal evolution of vegetation is presently questionable. For the purpose of the remote sensing of aerosol over dark, dense vegetation, it is proposed that the dark, dense vegetation be determined from rho3.75 < 0.025. These findings may have further implications for other specific applications of the remote sensing of vegetation in hazy atmospheres. C1 SCI SYST & APPLICAT INC,LANHAM,MD 20706. RP KAUFMAN, YJ (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ATMOSPHERES LAB,GREENBELT,MD 20771, USA. NR 36 TC 159 Z9 172 U1 3 U2 12 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 MAY PY 1994 VL 32 IS 3 BP 672 EP 683 DI 10.1109/36.297984 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 NY447 UT WOS:A1994NY44700020 ER PT J AU OTOSHI, TY AF OTOSHI, TY TI MAXIMUM AND MINIMUM RETURN LOSSES FROM A PASSIVE 2-PORT NETWORK TERMINATED WITH A MISMATCHED LOAD SO IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES LA English DT Article AB An analytical expression is derived for determining load-reflection coefficient phase-angle values that will lead to maximum and minimum return losses from a terminated two-port network. The expression is derived in terms of two-port network S-parameters and a load whose reflection-coefficient magnitude is a constant but can be any value greater than zero and less than or equal to unity. The equation is useful for cases where it is desirable to know how to position a load (1) to obtain maximum return loss for network-matching purposes or (2) to obtain minimum return loss for some types of reflector antenna applications. Two examples are given: One shows that for some types of reflector antennas with a mesh-type surface that is backed by another reflecting surface, a resonance phenomenon can occur and cause unexpectedly large dissipative losses (>30 dB) to occur. The other example shows that when a particular type of reflector antenna with a dielectric layer becomes wet from rain or condensation, large (>10 dB) signal losses can occur. For both examples, equations presented in this article were used to calculate the exact load-reflection coefficient phase values that led to worst-case return loss values. In practical situations, once the phenomenon is understood and predictable, steps can be taken to avoid these resonance regions. RP OTOSHI, TY (reprint author), JET PROP LAB,COMMUN ELEMENTS RES SECT,PASADENA,CA 91109, USA. NR 10 TC 4 Z9 4 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 MAY PY 1994 VL 42 IS 5 BP 787 EP 792 DI 10.1109/22.293526 PG 6 WC Engineering, Electrical & Electronic SC Engineering GA NU262 UT WOS:A1994NU26200005 ER PT J AU YOUNG, JL AF YOUNG, JL TI TEM COUPLING BETWEEN ORTHOGONAL CROSSING WIRES - A CLOSED-FORM APPROXIMATION SO IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES LA English DT Article ID TRANSMISSION-LINES; EXCITATION; MODEL; CABLE; LONG AB The equations describing the coupling mechanism between two crossing, orthogonal thin wires over a perfectly conducting ground plane are derived from first principles. Cast in the form of two cross-coupled Fredholm integral equations of the second kind, the equations are manipulated in such a way as to show the nature of the coupling between the TEM modes, the evanescent modes and the radiation terms. 'rhe assumption is made that the coupling between the evanescent and radiation terms to the TEM mode is weak after the first wave bounce. By neglecting such effects, we derive a closed-form approximation for the equivalent lumped junction capacitances. The resulting expressions are surprisingly simple and are amenable to desktop calculation. The final formulas are numerically compared with previously published data. RP YOUNG, JL (reprint author), UNIV IDAHO,DEPT ELECT ENGN,NASA,SPACE ENGN RES CTR,MOSCOW,ID 83843, USA. RI Young, Jeffrey/B-1591-2017 OI Young, Jeffrey/0000-0001-6647-4303 NR 15 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 0018-9480 J9 IEEE T MICROW THEORY JI IEEE Trans. Microw. Theory Tech. PD MAY PY 1994 VL 42 IS 5 BP 884 EP 890 DI 10.1109/22.293540 PG 7 WC Engineering, Electrical & Electronic SC Engineering GA NU262 UT WOS:A1994NU26200019 ER PT J AU BUDKA, TP TRIPPE, MW WEINREB, S REBEIZ, GM AF BUDKA, TP TRIPPE, MW WEINREB, S REBEIZ, GM TI A 75 GHZ TO 115 GHZ QUASI-OPTICAL AMPLIFIER SO IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES LA English DT Note AB A wideband quasi-optical amplifier employing two pyramidal back-to-back horns has been developed. Using a four-stage W-band low noise amplifier (LNA) designed and fabricated by Martin Marietta Laboratories, the quasi-optical amplifier gives a system gain greater than 11 dB from 86 GHz to 113 GHz without any low frequency oscillations. A peak system gain of 15.5 dB is measured at 102 GHz, and the measured noise figure of the system is 7.4 dB at 94 GHz. The quasi-optical amplifier design maintains the same polarization of the received and transmitted signal, provides better than -40 dB isolation, and can be fabricated monolithically at millimeter-wave frequencies. C1 MARTIN MARIETTA CORP,BALTIMORE,MD 21227. RP BUDKA, TP (reprint author), UNIV MICHIGAN,NASA,CTR SPACE TERAHERTZ TECHNOL,ANN ARBOR,MI 48109, USA. RI Weinreb, Steven/K-8747-2012 NR 7 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 0018-9480 J9 IEEE T MICROW THEORY JI IEEE Trans. Microw. Theory Tech. PD MAY PY 1994 VL 42 IS 5 BP 899 EP 901 DI 10.1109/22.293546 PG 3 WC Engineering, Electrical & Electronic SC Engineering GA NU262 UT WOS:A1994NU26200021 ER PT J AU LEE, S KIL, RM AF LEE, S KIL, RM TI INVERSE MAPPING OF CONTINUOUS-FUNCTIONS USING LOCAL AND GLOBAL INFORMATION SO IEEE TRANSACTIONS ON NEURAL NETWORKS LA English DT Article ID NETWORKS AB This paper presents a method for solving inverse mapping of a continuous function learned by a multilayer feedforward mapping network. The method is based on the iterative update of input vector toward a solution, while escaping from local minima. The input vector update is determined by the pseudo-inverse of the gradient of Lyapunov function, and, should an optimal solution be searched for, the projection of the gradient of a performance index on the null space of the gradient of Lyapunov function. The update rule is allowed to detect an input vector approaching local minima through a phenomenon called ''update explosion.'' At or near local minima, the input vector is guided by an escape trajectory generated based on ''global information,'' where global information is referred to here as predefined or known information on forward mapping. Or, the input vector is relocated to a new position based on the probability density function (PDF) constructed over the input vector space by Parzen estimate. The constructed PDF reflects the history of local minima detected during the search process, and represents the probability that a particular input vector can lead to a solution based on the update rule. The proposed method has a substantial advantage in computational complexity as well as convergence property over the conventional methods based on Jacobian pseudo-inverse or Jacobian transpose. Simulation results demonstrate the effectiveness of the proposed method in solving inverse mapping for various forward mappings. C1 UNIV SO CALIF, DEPT ELECT ENGN SYST & COMP SCI, LOS ANGELES, CA 90089 USA. UNIV SO CALIF, DEPT ELECT ENGN SYST, LOS ANGELES, CA 90089 USA. RP JET PROP LAB, PASADENA, CA 91109 USA. NR 20 TC 12 Z9 12 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA SN 1045-9227 EI 1941-0093 J9 IEEE T NEURAL NETWOR JI IEEE Trans. Neural Netw. PD MAY PY 1994 VL 5 IS 3 BP 409 EP 423 DI 10.1109/72.286912 PG 15 WC Computer Science, Artificial Intelligence; Computer Science, Hardware & Architecture; Computer Science, Theory & Methods; Engineering, Electrical & Electronic SC Computer Science; Engineering GA NR360 UT WOS:A1994NR36000008 PM 18267808 ER PT J AU BUNTINE, WL WEIGEND, AS AF BUNTINE, WL WEIGEND, AS TI COMPUTING 2ND DERIVATIVES IN FEEDFORWARD NETWORKS - A REVIEW SO IEEE TRANSACTIONS ON NEURAL NETWORKS LA English DT Note AB The calculation of second derivatives is required by recent training and analysis techniques of connectionist networks, such as the elimination of superfluous weights, and the estimation of confidence intervals both for weights and network outputs. We here review and develop exact and approximate algorithms for calculating second derivatives. For networks with \w\ weights, simply writing the full matrix of second derivatives requires O(\w\2) operations. For networks of radial basis units or sigmoid units, exact calculation of the necessary intermediate terms requires of the order of 2h + 2 backward/forward-propagation passes where h is the number of hidden units in the network. We also review and compare three approximations (ignoring some components of the second derivative, numerical differentiation, and scoring). Our algorithms apply to arbitrary activation functions, networks, and error functions (for instance, with connections that skip layers, or radial basis functions, or cross-entropy error and Softmax units, etc.). C1 UNIV COLORADO,DEPT COMP SCI,BOULDER,CO 80309. UNIV COLORADO,INST COGNIT SCI,BOULDER,CO 80309. RP BUNTINE, WL (reprint author), NASA,AMES RES CTR,RIACS,MOFFETT FIELD,CA 94035, USA. OI Buntine, Wray/0000-0001-9292-1015 NR 27 TC 36 Z9 36 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 1045-9227 J9 IEEE T NEURAL NETWOR JI IEEE Trans. Neural Netw. PD MAY PY 1994 VL 5 IS 3 BP 480 EP 488 DI 10.1109/72.286919 PG 9 WC Computer Science, Artificial Intelligence; Computer Science, Hardware & Architecture; Computer Science, Theory & Methods; Engineering, Electrical & Electronic SC Computer Science; Engineering GA NR360 UT WOS:A1994NR36000014 PM 18267814 ER PT J AU KOOI, JW CHAN, M BUMBLE, B LEDUC, HG SCHAFFER, PL PHILLIPS, TG AF KOOI, JW CHAN, M BUMBLE, B LEDUC, HG SCHAFFER, PL PHILLIPS, TG TI 180-425 GHZ LOW-NOISE SIS WAVE-GUIDE RECEIVERS EMPLOYING TUNED NB/AIOX/NB TUNNEL-JUNCTIONS SO INTERNATIONAL JOURNAL OF INFRARED AND MILLIMETER WAVES LA English DT Article ID MODEL MEASUREMENTS; MIXER; GAIN AB We report recent results on a 20% reduced height 270-425 GHz SIS waveguide receiver employing a 0.49 mum2 Nb/AlO(x)/Nb tunnel junction. A 50% operating bandwidth is achieved by using a RF compensated junction mounted in a two-tuner reduced height waveguide mixer block. The junction uses an ''end-loaded'' tuning stub with two quarter-wave transformer sections. We demonstrate that the receiver can be tuned to give 0-2 dB of conversion gain and 50-80% quantum efficiency over parts of it's operating range. The measured instantaneous bandwidth of the receiver is almost-equal-to 25 GHz which ensures virtually perfect double sideband mixer response. Best noise temperatures are typically obtained with a mixer conversion loss of 0.5 to 1.5 dB giving uncorrected receiver and mixer noise temperatures of 50K and 42K respectively at 300 and 400 GHz. The measured double sideband receiver noise temperature is less than 100K from 270 GHz to 425 GHz with a best value of 48K at 376 GHz, within a factor of five of the quantum limit. The 270-425 GHz receiver has a full 1 GHz IF passband and has been successfully installed at the Caltech Submillimeter Observatory in Hawaii. Preliminary tests of a similar junction design in a full height 230 GHz mixer block indicate large conversion gain and receiver noise temperatures below 50K DSB from 200-300 GHz. Best operation is again achieved with the mixer tuned for 0.5-1.5 dB conversion loss which at 258 GHz resulted in a receiver and mixer noise temperature of 34K and 27K respectively. C1 JET PROP LAB,CTR SPACE MICROELECTR TECHNOL,PASADENA,CA 91109. RP KOOI, JW (reprint author), CALTECH,SUBMILLIMETER OBSERV,DIV PHYS MATH & ASTRON,PASADENA,CA 91125, USA. NR 36 TC 13 Z9 13 U1 0 U2 0 PU PLENUM PUBL CORP PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 SN 0195-9271 J9 INT J INFRARED MILLI JI Int. J. Infrared Millimeter Waves PD MAY PY 1994 VL 15 IS 5 BP 783 EP 805 DI 10.1007/BF02096576 PG 23 WC Engineering, Electrical & Electronic; Optics; Physics, Applied SC Engineering; Optics; Physics GA NL092 UT WOS:A1994NL09200002 ER PT J AU IVANCIC, WD CHU, P SHYY, DJ AF IVANCIC, WD CHU, P SHYY, DJ TI TECHNICAL ISSUES REGARDING SATELLITE PACKET-SWITCHING SO INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS LA English DT Article DE FAST PACKET SWITCH; BISDN; MESHED VSAT; ON-BOARD PROCESSING AB Many concepts for advanced communication satellite networks have recently been proposed. Critical technical issues relating to satellite packet switching for meshed very small aperture terminal networks and broadband networks are addressed. Hardware considerations, networking and testing issues are discussed. RP IVANCIC, WD (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 0 TC 2 Z9 2 U1 0 U2 0 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX, ENGLAND PO19 1UD SN 0737-2884 J9 INT J SATELL COMMUN JI Int. J. Satell. Commun. PD MAY-JUN PY 1994 VL 12 IS 3 BP 257 EP 267 DI 10.1002/sat.4600120309 PG 11 WC Engineering, Aerospace; Telecommunications SC Engineering; Telecommunications GA PA185 UT WOS:A1994PA18500007 ER PT J AU ABOUDI, J PINDERA, MJ ARNOLD, SM AF ABOUDI, J PINDERA, MJ ARNOLD, SM TI ELASTIC RESPONSE OF METAL-MATRIX COMPOSITES WITH TAILORED MICROSTRUCTURES TO THERMAL-GRADIENTS SO INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES LA English DT Article AB A new micromechanical theory is presented for the response of heterogeneous metal matrix composites subjected to thermal gradients. In contrast to existing micromechanical theories that utilize classical homogenization schemes in the course of calculating microscopic and macroscopic field quantities, in the present approach the actual microstructural details are explicitly coupled with the macrostructure of the composite. Examples are offered that illustrate limitations of the classical homogenization approach in predicting the response of thin-walled metal matrix composites with large-diameter fibers to thermal gradients. These examples include composites with a finite number of fibers in the thickness direction that may be uniformly or nonuniformly spaced, thus admitting so-called functionally gradient composites. The results illustrate that the classical approach of decoupling micromechanical and macromechanical analyses in the presence of a finite number of large-diameter fibers, finite dimensions of the composite, and temperature gradient may lead to serious errors in the calculation of both macroscopic and microscopic field quantities. The usefulness of the new outlined approach in generating favorable stress distributions in the presence of thermal gradients by appropriately tailoring the internal microstructural details of the composite is also demonstrated. C1 UNIV VIRGINIA,DEPT CIVIL ENGN & APPL MECH,CHARLOTTESVILLE,VA 22903. NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP ABOUDI, J (reprint author), TEL AVIV UNIV,FAC ENGN,IL-69978 TEL AVIV,ISRAEL. NR 10 TC 42 Z9 42 U1 0 U2 2 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0020-7683 J9 INT J SOLIDS STRUCT JI Int. J. Solids Struct. PD MAY PY 1994 VL 31 IS 10 BP 1393 EP 1428 DI 10.1016/0020-7683(94)90184-8 PG 36 WC Mechanics SC Mechanics GA NK122 UT WOS:A1994NK12200004 ER PT J AU WHITTENBERGER, JD AF WHITTENBERGER, JD TI THE INTERNATIONAL-SYMPOSIUM ON STRUCTURAL INTERMETALLICS SO JOM-JOURNAL OF THE MINERALS METALS & MATERIALS SOCIETY LA English DT Editorial Material RP WHITTENBERGER, JD (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 0 TC 0 Z9 0 U1 0 U2 0 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 MAY PY 1994 VL 46 IS 5 BP 46 EP 47 PG 2 WC Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering; Mineralogy; Mining & Mineral Processing SC Materials Science; Metallurgy & Metallurgical Engineering; Mineralogy; Mining & Mineral Processing GA NJ968 UT WOS:A1994NJ96800011 ER PT J AU STORMS, BL JANG, CS AF STORMS, BL JANG, CS TI LIFT ENHANCEMENT OF AN AIRFOIL USING A GURNEY FLAP AND VORTEX GENERATORS SO JOURNAL OF AIRCRAFT LA English DT Article; Proceedings Paper CT AIAA 31st Aerospace Sciences Meeting CY JAN 11-14, 1993 CL RENO, NV SP AMER INST AERONAUT & ASTRONAUT AB Experimental measurements of surface pressure distributions and wake profiles were obtained for an NACA 4412 airfoil to determine the lift, drag, and pitching-moment coefficients for various configurations. The addition of a Gurney flap increased the maximum lift coefficient from 1.49 up to 1.96, and decreased the drag near the maximum lift condition. There was, however, a drag increment at low-to-moderate lift coefficients. Additional nose-down pitching moment was also generated by increasing the Gurney nap height. Good correlation was observed between the experiment and Navier-Stokes computations of the airfoil with a Gurney flap. Two deployable configurations were also tested with the hinge line forward of the trailing edge by one and 1.5 flap heights, respectively. These configurations provided performance comparable to that of the Gurney flap. The application of vortex generators to the baseline airfoil delayed boundary-layer separation and yielded an increase in the maximum lift coefficient of 0.34. In addition, there was a significant drag penalty associated with the vortex generators, which suggests that they should be placed where they will be concealed during cruise. The two devices were also shown to work well in concert. RP STORMS, BL (reprint author), NASA,AMES RES CTR,FIXED WING AERODYNAM BRANCH,MS 247-2,MOFFETT FIELD,CA 94035, USA. NR 0 TC 70 Z9 84 U1 1 U2 8 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 MAY-JUN PY 1994 VL 31 IS 3 BP 542 EP 547 DI 10.2514/3.46528 PG 6 WC Engineering, Aerospace SC Engineering GA NR637 UT WOS:A1994NR63700011 ER PT J AU RIVERS, RA JACKSON, EB RAGSDALE, WA AF RIVERS, RA JACKSON, EB RAGSDALE, WA TI PRELIMINARY PILOTED SIMULATION STUDIES OF THE HL-20 LIFTING BODY SO JOURNAL OF AIRCRAFT LA English DT Article AB NASA Langley Research Center is developing a lifting body vehicle, designated the HL-20, as one option or the proposed Personnel Launch System for NASA's future manned access to space requirements. Data derived from wind-tunnel and computational fluid dynamics analyses or the conceptual design led to the derivation of a flight simulator model to investigate the potential flight characteristics of the HL-20. A simulation investigation was initiated to determine if satisfactory unpowered horizontal landings could be accomplished. Control law design and trajectory development were directed toward this end. The study uncovered several deficiencies subsequently corrected through design changes, and it validated the predicted subsonic aerodynamic properties. Expanding the investigation to the Mach 4 to Mach 1 regime revealed flight characteristics necessitating the development of innovative control techniques. This article will present the significant results uncovered to date by flight simulator evaluations of a lifting body class of vehicle, and will demonstrate the effectiveness of flight simulation as an integrated part of the conceptual design phase. RP RIVERS, RA (reprint author), NASA,LANGLEY RES CTR,AIRCRAFT OPERAT BRANCH,HAMPTON,VA 23681, 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 0021-8669 J9 J AIRCRAFT JI J. Aircr. PD MAY-JUN PY 1994 VL 31 IS 3 BP 556 EP 563 DI 10.2514/3.46530 PG 8 WC Engineering, Aerospace SC Engineering GA NR637 UT WOS:A1994NR63700013 ER PT J AU DRESS, DA BOYDEN, RP CRUZ, CI AF DRESS, DA BOYDEN, RP CRUZ, CI TI MEASURED AND THEORETICAL SUPERSONIC DYNAMIC STABILITY CHARACTERISTICS OF A NATIONAL AEROSPACE PLANE CONFIGURATION SO JOURNAL OF AIRCRAFT LA English DT Article AB Wind-tunnel tests of a National Acro Space Plane configuration were conducted in the NASA Langley Unitary Plan Wind Tunnel (UPWT). The model used is a Langley designed blended body configuration. Dynamic stability characteristics were measured on this configuration at Mach numbers of 2.0, 2.5, 3.5, and 4.5. In addition to tests of the baseline configuration, component breakdown tests were conducted. The test results show that the baseline configuration generally has stable damping about all three axes, with only isolated exceptions. In addition, there was generally good agreement between the in-phase dynamic parameters and the corresponding static data which were measured during another series of tests in UPWT. Also included are comparisons of the experimental damping parameters with results from the engineering predictive code aerodynamic preliminary analysis system. These comparisons show good agreement at low angles of attack; however, the comparisons are generally not as good at the higher angles of attack. RP DRESS, DA (reprint author), NASA,LANGLEY RES CTR,DIV APPL AERODYNAM,SUPERSON HYPERSON AERODYNAM BRANCH,M-S 413,HAMPTON,VA 23681, USA. NR 0 TC 1 Z9 1 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0021-8669 J9 J AIRCRAFT JI J. Aircr. PD MAY-JUN PY 1994 VL 31 IS 3 BP 597 EP 602 DI 10.2514/3.46536 PG 6 WC Engineering, Aerospace SC Engineering GA NR637 UT WOS:A1994NR63700019 ER PT J AU HOLLAND, SD PERKINS, JN AF HOLLAND, SD PERKINS, JN TI INVISCID PARAMETRIC ANALYSIS OF 3-DIMENSIONAL INLET PERFORMANCE SO JOURNAL OF AIRCRAFT LA English DT Article AB The advantages and design requirements of propulsion/airframe integration for the high Mach number flight of air-breathing vehicles have led to extensive study of the three-dimensional sidewall-compression scramjet inlet in recent years. Inlets of this genre afford a relatively simple, generic geometry while producing a highly complex, three-dimensional flowfield dominated by shock/shock and shock/boundary-layer interactions. While the importance of the viscous effects in high-speed inlet interactions is recognized, the present work addresses in a parametric fashion the inviscid effects of leading-edge sweep (between 0-70 deg) and inflow Mach number (between 2-12) on the inlet performance. Two-dimensional oblique shock theory is appropriately modified to account for the three-dimensional effects of leading-edge sweep and is applied throughout the inlet configuration to obtain inviscid shock impingement locations, mass capture, inlet compression, total pressure recovery, and kinetic energy efficiency. Comparison of these results with CFD indicates that the parametric trends are identified by this computationally quick and inexpensive method for preliminary design applications. RP HOLLAND, SD (reprint author), NASA,LANGLEY RES CTR,EXPTL HYPERS BRANCH,DIV SPACE SYST,M-S 408,HAMPTON,VA 23681, USA. NR 0 TC 0 Z9 2 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 MAY-JUN PY 1994 VL 31 IS 3 BP 610 EP 615 DI 10.2514/3.46538 PG 6 WC Engineering, Aerospace SC Engineering GA NR637 UT WOS:A1994NR63700021 ER PT J AU MIDDLETON, DB PERSON, LH SRIVATSAN, R AF MIDDLETON, DB PERSON, LH SRIVATSAN, R TI TAKEOFF PERFORMANCE MONITORING-SYSTEM DISPLAY OPTIONS SO JOURNAL OF AIRCRAFT LA English DT Article AB This article summarizes the development of head-up and head-down cockpit displays for an airplane takeoff performance monitoring system (TOPMS). Basic TOPMS displays provide pilots with real-time graphic information concerning their airplane's current and projected runway performance. The displays also indicate the status of associated airplane systems (e.g., flaps, engines) and optionally, they provide ''GO/NO-GO'' advice and a continually updated prediction of where the airplane can be braked to a stop. The displays have been developed and evaluated on the NASA Transport System Research Vehicle (TSRV) B-737 simulator by more than 40 government, airline, and industry pilots who rated the displays favorably and judged them easy to monitor. The TOPMS has also been flight tested successfully on the TSRV B-737. Based on these evaluations and on discussions with the commercial aircraft community, the displays have evolved to a baseline final configuration containing basic performance and system-status data to which GO/NO-GO advisory and predicted stop point information can be added as options. RP MIDDLETON, DB (reprint author), NASA,LANGLEY RES CTR,DIV GUIDANCE & CONTROL,HAMPTON,VA 23681, USA. NR 0 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 MAY-JUN PY 1994 VL 31 IS 3 BP 666 EP 671 DI 10.2514/3.46546 PG 6 WC Engineering, Aerospace SC Engineering GA NR637 UT WOS:A1994NR63700029 ER PT J AU NALLASAMY, M AF NALLASAMY, M TI UNSTEADY BLADE PRESSURES ON A PROPFAN - PREDICTED AND MEASURED COMPRESSIBILITY EFFECTS SO JOURNAL OF AIRCRAFT LA English DT Article AB The effect of compressibility on unsteady blade pressures is studied by solving the three-dimensional Euler equations. The operation of the eight-bladed SR7L propfan at 4.75-deg angle of attack was considered. Euler solutions were obtained for three Mach numbers, 0.6, 0.7, and 0.8, and the predicted blade pressure waveforms were compared with flight data. The predictions show that the change in pressure waveforms are minimal when the Mach number is increased from 0.6 to 0.7, as observed in the flight experiments. Increasing the Mach number from 0.7 to 0.8 produces significant changes in predicted pressure levels. The predicted amplitudes, however, differ from measurements at some transducer locations. Also, the predicted appearance of a shock in the highly loaded portion of the blade revolution is not indicated by the measurements. At all three Mach numbers the measured (installed propfan) pressure waveforms at the majority of transducer locations show a relative phase lag compared to the computed (propfan alone) waveforms. This appears to be due to installation effects. Measured waveforms in the blade tip region show nonlinear variations which are not captured by the present numerical procedure. RP NALLASAMY, M (reprint author), NASA,LEWIS RES CTR GRP,DEPT AEROMECH,CLEVELAND,OH 44135, USA. NR 0 TC 1 Z9 1 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0021-8669 J9 J AIRCRAFT JI J. Aircr. PD MAY-JUN PY 1994 VL 31 IS 3 BP 730 EP 736 DI 10.2514/3.46554 PG 7 WC Engineering, Aerospace SC Engineering GA NR637 UT WOS:A1994NR63700037 ER PT J AU RODGERS, EB BAIK, JJ PIERCE, HF AF RODGERS, EB BAIK, JJ PIERCE, HF TI THE ENVIRONMENTAL INFLUENCE ON TROPICAL CYCLONE PRECIPITATION SO JOURNAL OF APPLIED METEOROLOGY LA English DT Article ID SEASON TYPHOON DEVELOPMENT; UPPER TROPOSPHERIC TROUGH; ANGULAR-MOMENTUM; NUMERICAL-SIMULATION; DIURNAL-VARIATION; OUTFLOW LAYER; MODEL; INTENSITY; ATLANTIC; INTENSIFICATION AB The intensity, spatial, and temporal changes in precipitation were examined in three North Atlantic hurricanes during 1989 (Dean, Gabrielle, and Hugo) using precipitation estimates made from Special Sensor Microwave/Imager (SSM/I) measurements. In addition, analyses from a barotropic hurricane forecast model and the European Centre for Medium-Range Weather Forecast model were used to examine the relationship between the evolution of the precipitation in these tropical cyclones and external forcing. The external forcing parameters examined were 1) mean climatological sea surface temperatures, 2) vertical wind shear, 3) environmental tropospheric water vapor flux, and 4) upper-tropospheric eddy relative angular momentum flux convergence. The analyses revealed that 1) the SSM/I precipitation estimates were able to delineate and monitor convective ring cycles similar to those observed with land-based and aircraft radar and in situ measurements; 2) tropical cyclone intensification was observed to occur when these convective rings propagated into the inner core of these systems (within 111 km of the center) and when the precipitation rates increased; 3) tropical cyclone weakening was observed to occur when these inner-core convective rings dissipated; 4) the inward propagation of the outer convective rings coincided with the dissipation of the inner convective rings when they came within 55 km of each other; 5) in regions with the combined warm sea surface temperatures (above 26-degrees-C) and low vertical wind shear (less than 5 m s-1), convective rings outside the region of strong lower-tropospheric inertial stability could be initiated by strong surges of tropospheric moisture, while convective rings inside the region of strong lower-tropospheric inertial stability could be enhanced by upper-tropospheric eddy relative angular momentum flux convergence. C1 NASA,GODDARD SPACE FLIGHT CTR,UNIV SPACE RES ASSOC,ATMOSPHERES LAB,GREENBELT,MD 20771. SSAI,LANHAM,MD. RP RODGERS, EB (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ATMOSPHERES LAB,MESOSCALE DYNAM & PRECIPITAT BRANCH,CODE 912,GREENBELT,MD 20771, USA. NR 58 TC 30 Z9 34 U1 1 U2 3 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 MAY PY 1994 VL 33 IS 5 BP 573 EP 593 DI 10.1175/1520-0450(1994)033<0573:TEIOTC>2.0.CO;2 PG 21 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA NJ724 UT WOS:A1994NJ72400001 ER PT J AU BENJAMIN, I WILSON, M POHORILLE, A AF BENJAMIN, I WILSON, M POHORILLE, A TI SCATTERING OF NE FROM THE LIQUID-VAPOR INTERFACE OF GLYCEROL - A MOLECULAR-DYNAMICS STUDY SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID INTERMOLECULAR POTENTIAL FUNCTIONS; X-RAY; WATER; SURFACE; SIMULATION; ORIENTATION; MODEL; ION AB A model potential for the scattering of Ne off liquid glycerol is developed. The model is based on a nine-site description of glycerol which takes into account torsional flexibility and hydrogen bonding. This model is used to carry out molecular dynamics calculations of the scattering as a function of collision energy. The results for the sticking probability and energy transfer are in good agreement with experiments. The model predicts a wide angular distribution of the scattered atoms with a mild decrease in the energy transfer as a function of exit angle for a fixed incident angle. The model also provides insight into the importance of the corrugated nature of the surface and the types of liquid modes that play a major role in the energy transfer process. C1 UNIV CALIF SAN FRANCISCO, DEPT PHARMACEUT CHEM, SAN FRANCISCO, CA 94143 USA. NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. RP BENJAMIN, I (reprint author), UNIV CALIF SANTA CRUZ, DEPT CHEM, SANTA CRUZ, CA 95064 USA. NR 49 TC 45 Z9 45 U1 1 U2 10 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 MAY 1 PY 1994 VL 100 IS 9 BP 6500 EP 6507 DI 10.1063/1.467059 PG 8 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA NH846 UT WOS:A1994NH84600041 ER PT J AU JIANG, XJ FUNG, I AF JIANG, XJ FUNG, I TI OCEAN RESPONSE TO SURFACE HEAT ANOMALIES SO JOURNAL OF CLIMATE LA English DT Article ID TRANSIENT CLIMATE RESPONSE; ATMOSPHERIC CARBON-DIOXIDE; WORLD OCEAN; ANNUAL CYCLE; MODEL; CO2; BALANCE; STORAGE; WATER AB An ocean general circulation model (OGCM) is used to study the response of ocean heat and mass transport to positive and negative heat flux anomalies at the ocean surface. As expected, tropical and low-latitude mixed layers respond rapidly (e-folding time about 50-70 years) to external forcing, while the response of the high-latitude mixed layer, especially the Southern Ocean and northern North Atlantic, is very slow (e-folding time greater than 300 yr). The overall response is faster for negative than positive heat flux anomaly at the surface. The meridional heat transport changes by 15% in the first 50 yr in the southern high latitudes. Surprisingly, for the next 400-500 yr the change is very small. The analysis shows that the meridional mass transport intensifies in response to a negative surface heat flux anomaly but weakens in response to a positive heat flux anomaly. For example, at model year 100 the NADW is reduced from about 18 Sv to about 10 Sv for the positive heat flux experiment but increased to about 26 Sv for the negative heat flux experiment. C1 COLUMBIA UNIV,DEPT APPL PHYS,NEW YORK,NY 10027. RP JIANG, XJ (reprint author), NASA,GODDARD INST SPACE STUDIES,2880 BROADWAY,NEW YORK,NY 10025, USA. NR 30 TC 3 Z9 3 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 MAY PY 1994 VL 7 IS 5 BP 783 EP 791 DI 10.1175/1520-0442(1994)007<0783:ORTSHA>2.0.CO;2 PG 9 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA NL465 UT WOS:A1994NL46500012 ER PT J AU LATHERS, CM CHARLES, JB PUTCHA, L AF LATHERS, CM CHARLES, JB PUTCHA, L TI THE 12TH-FRONTIERS-SYMPOSIUM - PHARMACOLOGY BEYOND EARTHS BOUNDARIES SO JOURNAL OF CLINICAL PHARMACOLOGY LA English DT Editorial Material C1 NASA,LYNDON B JOHNSON SPACE CTR,CARDIOPULM GRP,HOUSTON,TX 77058. RP LATHERS, CM (reprint author), US FDA,DIV CARDIORENAL,ROCKVILLE,MD 20857, USA. 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 0091-2700 J9 J CLIN PHARMACOL JI J. Clin. Pharmacol. PD MAY PY 1994 VL 34 IS 5 BP 361 EP 362 PG 2 WC Pharmacology & Pharmacy SC Pharmacology & Pharmacy GA NL960 UT WOS:A1994NL96000001 ER PT J AU FREY, MAB LATHERS, C DAVIS, J FORTNEY, S CHARLES, JB AF FREY, MAB LATHERS, C DAVIS, J FORTNEY, S CHARLES, JB TI CARDIOVASCULAR-RESPONSES TO STANDING - EFFECT OF HYDRATION SO JOURNAL OF CLINICAL PHARMACOLOGY LA English DT Article; Proceedings Paper CT 12th Frontiers Symposium: Pharmacology Beyond Earths Boundaries CY MAY 06, 1992 CL NASA, JOHNSON SPACE CTR, HOUSTON, TX HO NASA, JOHNSON SPACE CTR ID HYPERHYDRATION; BLOOD AB Many astronauts experience intolerance to orthostatic stress after space flight, despite the ingestion of salt tablets and water equivalent to 0.9% saline just before their return to Earth. Previous research indicates that the ingestion of 1.07% saline solution increased plasma volume more than did 0.9% saline. Therefore, the authors hypothesized that the 1.07% saline would be more effective in reducing orthostatic stress during standing. In this study, six men (22-47 years) performed a 5-minute ''stand test'' (5 minutes supine followed by 5 minutes standing) under four hydration conditions: 1) hypohydrated (HYPO, 20 mg intravenous [IV] Lasix), 2) euhydrated (EU), 3) rehydrated with 1 L 0.9% saline 2 hours after Lasix, or 4) rehydrated with 1 L 1.07% saline. Stand tests were done 4 to 5 hours after rehydration. Plasma volume was reduced 10% after Lasix, and was restored by both rehydration solutions. When subjects stood, their diastolic pressure, mean pressure, heart rate (HR), and peripheral resistance increased (P <.05), and their stroke volume (SV), cardiac output (CO), and thoracic fluid (TF, by impedance cardiography) decreased (P <.05). Systolic arterial pressure (SBP) increased when subjects stood after saline, but decreased if subjects were HYPO or EU (P <.05 for 1.07% versus HYPO and EU). Heart rate (HR), another indicator of orthostatic stress, did not differ among hydration states. During the last minute of the stand test, TF was greater if subjects had fluid countermeasures. Stroke volume, CO, and TF were significantly less during minute 5 of standing than during minute 3. Whether they would continue to fall in a longer stand test is not known. The results for SBP indicate that 1.07% saline may have advantages over 0.9% saline as a countermeasure to postspace-flight or postbedrest orthostatic intolerance. C1 UNIV SPACE RES ASSOC,HOUSTON,TX. ALMA COLL,ALMA,MI. NASA,LYNDON B JOHNSON SPACE CTR,CARDIOVASC LAB,HOUSTON,TX 77058. NR 16 TC 14 Z9 14 U1 0 U2 1 PU LIPPINCOTT-RAVEN PUBL PI PHILADELPHIA PA 227 EAST WASHINGTON SQ, PHILADELPHIA, PA 19106 SN 0091-2700 J9 J CLIN PHARMACOL JI J. Clin. Pharmacol. PD MAY PY 1994 VL 34 IS 5 BP 387 EP 393 PG 7 WC Pharmacology & Pharmacy SC Pharmacology & Pharmacy GA NL960 UT WOS:A1994NL96000004 PM 8089250 ER PT J AU LATHERS, CM CHARLES, JB AF LATHERS, CM CHARLES, JB TI ORTHOSTATIC HYPOTENSION IN PATIENTS, BED REST SUBJECTS, AND ASTRONAUTS SO JOURNAL OF CLINICAL PHARMACOLOGY LA English DT Article; Proceedings Paper CT 12th Frontiers Symposium: Pharmacology Beyond Earths Boundaries CY MAY 06, 1992 CL NASA, JOHNSON SPACE CTR, HOUSTON, TX HO NASA, JOHNSON SPACE CTR ID SHY-DRAGER SYNDROME; MIDODRINE; AGENT; INTOLERANCE; MANAGEMENT; SPACE AB Orthostatic hypotension after even short space flights has affected a significant number of astronauts. Given the need for astronauts to function at a high level of efficiency during and after their return from space, the application of pharmacologic and other treatments is strongly indicated. This report addresses the clinical problem of orthostatic hypotension and its treatments to ascertain whether pharmacologic or physiologic treatment may be useful in the prevention of orthostatic hypotension associated with space flight. Treatment of orthostatic hypotension in patients now includes increasing intravascular volume with high sodium intake and mineralocorticoids, or increasing vascular resistance through the use of drugs to stimulate alpha or block beta vascular receptors. Earlier treatment used oral sympathomimetic ephedrine hydrochloride alone or with ''head-up'' bed rest.(1) Then long-acting adrenocortical steroid desoxycorticosterone preparations with high-salt diets were used to expand volume. Fludrocortisone was shown to prevent the orthostatic drop in blood pressure.(2) The combination of the sympathomimetic amine hydroxyamphetamine and a monoamine oxidase inhibitor tranylcypromine(3) has been used, as has indomethacin alone.(4) Davies et al.(5) used mineralocorticoids at low doses concomitantly with alpha-agonists to increase vasocontrictor action. Schirger et al(6) used tranylcypromine and methylphenidate with or without a Jobst elastic leotard garment or the alpha-adrenergic agonist midodrine (which stimulates both arterial and venous systems without direct central nervous system or cardiac effects). Vernikos et al(7) established that the combination of fludrocortisone, dextroamphetamine, and atropine exhibited a beneficial effect on orthostatic hypotension induced by 7-day 6 degrees head-down bed rest (a model used to simulate the weightlessness of space Fight), Thus, there are numerous drugs that, in combination with mechanical techniques, including lower body negative pressure to elevate transmural pressure, could be studied to treat orthostatic hypotension after space flight. C1 NASA,LYNDON B JOHNSON SPACE CTR,INST BIOMED RES,HOUSTON,TX 77058. RP LATHERS, CM (reprint author), US FDA,DIV CARDIORENAL PROD,HFD 110,5600 FISHERS LANE,ROCKVILLE,MD 20857, USA. NR 37 TC 16 Z9 16 U1 0 U2 0 PU LIPPINCOTT-RAVEN PUBL PI PHILADELPHIA PA 227 EAST WASHINGTON SQ, PHILADELPHIA, PA 19106 SN 0091-2700 J9 J CLIN PHARMACOL JI J. Clin. Pharmacol. PD MAY PY 1994 VL 34 IS 5 BP 403 EP 417 PG 15 WC Pharmacology & Pharmacy SC Pharmacology & Pharmacy GA NL960 UT WOS:A1994NL96000006 PM 7522239 ER PT J AU WHITSON, PA CINTRON, NM PIETRZYK, RA SCOTTO, P LOEPPKY, JA AF WHITSON, PA CINTRON, NM PIETRZYK, RA SCOTTO, P LOEPPKY, JA TI ACUTE EFFECTS OF HEAD-DOWN TILT AND HYPOXIA ON MODULATORS OF FLUID HOMEOSTASIS SO JOURNAL OF CLINICAL PHARMACOLOGY LA English DT Article; Proceedings Paper CT 12th Frontiers Symposium: Pharmacology Beyond Earths Boundaries CY MAY 06, 1992 CL NASA, JOHNSON SPACE CTR, HOUSTON, TX HO NASA, JOHNSON SPACE CTR ID ATRIAL NATRIURETIC FACTOR; WATER IMMERSION; BLOOD-PRESSURE; ALDOSTERONE; RESPONSES; PEPTIDE; RENIN; RADIOIMMUNOASSAY; ELECTROLYTE; MECHANISMS AB In an effort to understand the interaction between acute postural fluid shifts and hypoxia on hormonal regulation of fluid homeostasis, the authors measured the responses to head-down tilt with and without acute exposure to normobaric hypoxia. Plasma atrial natriuretic peptide (ANP), cyclic guanosine monophosphate (cGMP), cyclic adenosine monophosphate (cAMP), plasma aldosterone (ALD), and plasma renin activity (PRA) were measured in six healthy male volunteers who were exposed to a head-down tilt protocol during normoxia and hypoxia. The tilt protocol consisted of a 17 degrees head-up phase (30 minutes), a 28 degrees head-down phase (1 hour), and a 17 degrees head-up recovery period (2 hours, with the last hour normoxic in both experiments). Altitude equivalent to 14,828 ft was simulated by having the subjects breathe an inspired gas mixture with 13.9% oxygen. The results indicate that the postural fluid redistribution associated with a 60-minute head-down tilt induces the release of ANP and cGMP during both hypoxia and normoxia. Hypoxia increased cGMP, cAMP, ALD, and PRA throughout the protocol and significantly potentiated the increase in cGMP during head-down tilt. Hypoxia had no overall effect on the release of ANP, but appeared to attenuate the increase with head-down tilt. This study describes the acute effects of hypoxia on the endocrine response during fluid redistribution and suggests that the magnitude, but not the direction, of these changes with posture is affected by hypoxia. C1 LOVELACE FDN MED EDUC & RES,ALBUQUERQUE,NM 87108. NASA,LYNDON B JOHNSON SPACE CTR,KRUG LIFE SCI INC,BIOMED OPERAT & RES BRANCH,HOUSTON,TX 77058. UNIV NAPLES,DEPT HUMAN PHYSIOL,NAPLES,ITALY. NR 33 TC 4 Z9 4 U1 0 U2 0 PU LIPPINCOTT-RAVEN PUBL PI PHILADELPHIA PA 227 EAST WASHINGTON SQ, PHILADELPHIA, PA 19106 SN 0091-2700 J9 J CLIN PHARMACOL JI J. Clin. Pharmacol. PD MAY PY 1994 VL 34 IS 5 BP 427 EP 433 PG 7 WC Pharmacology & Pharmacy SC Pharmacology & Pharmacy GA NL960 UT WOS:A1994NL96000009 PM 8089253 ER PT J AU FORTNEY, SM TURNER, C STEINMANN, L DRISCOLL, T ALFREY, C AF FORTNEY, SM TURNER, C STEINMANN, L DRISCOLL, T ALFREY, C TI BLOOD-VOLUME RESPONSES OF MEN AND WOMEN TO BED REST SO JOURNAL OF CLINICAL PHARMACOLOGY LA English DT Article; Proceedings Paper CT 12th Frontiers Symposium: Pharmacology Beyond Earths Boundaries CY MAY 06, 1992 CL NASA, JOHNSON SPACE CTR, HOUSTON, TX HO NASA, JOHNSON SPACE CTR ID EXERCISE; PLASMA; SPACE AB This paper reviews a series of studies that indicate that estrogens play an important role in blood volume regulation. The first study illustrates that the plasma volume (PV) of ambulatory women fluctuates during the menstrual cycle, increasing during periods of elevated estrogens. In the second study, it was shown that exogenous and endogenous elevations in blood estrogens attenuate the decrease in PV during bed rest. In the third study, the hypothesis was tested that women, who naturally have a higher blood estrogen content compared with men, will have a smaller loss of PV during bed rest. Ten men and ten women underwent a 13-day, 6 degrees head-down bed rest. Plasma volume and red cell mass (RCM) were measured before and after bed rest using I-125 and Cr-51 labeling, respectively. Before bed rest, the men and women had similar blood volume (BV) and PV (mL/kg body weight), but the women had a smaller (P <.01) RCM (22.2 +/- 0.9 versus 26.2 +/- 0.8 mL/kg, mean +/- SE). During bed rest, the decrease in RCM (mL/kg) was similar in men and women. However, the decrease in BV was greater in men (8.0 +/- 0.8 mL/kg versus 5.8 +/- 0.8 mL/kg), because of a greater reduction in PV (6.3 +/- 0.6 mL/kg versus 4.1 +/- 0.6 mL/kg). Because the decline in BV has been proposed to contribute to the cardiovascular deconditioning after bed rest, it is possible that women may experience less cardiac and circulatory strain on reambulation. C1 PFIZER INC,PHARMACEUT,GROTON,CT 06340. BAYLOR COLL MED,HOUSTON,TX 77030. KRUG LIFE SCI INC,HOUSTON,TX. RP FORTNEY, SM (reprint author), NASA,LYNDON B JOHNSON SPACE CTR,MAIL CODE SD-5,HOUSTON,TX 77058, USA. NR 29 TC 41 Z9 41 U1 0 U2 0 PU LIPPINCOTT-RAVEN PUBL PI PHILADELPHIA PA 227 EAST WASHINGTON SQ, PHILADELPHIA, PA 19106 SN 0091-2700 J9 J CLIN PHARMACOL JI J. Clin. Pharmacol. PD MAY PY 1994 VL 34 IS 5 BP 434 EP 439 PG 6 WC Pharmacology & Pharmacy SC Pharmacology & Pharmacy GA NL960 UT WOS:A1994NL96000010 PM 8089254 ER PT J AU SIMANONOK, KE SRINIVASAN, RS MYRICK, EE BLOMKALNS, AL CHARLES, JB AF SIMANONOK, KE SRINIVASAN, RS MYRICK, EE BLOMKALNS, AL CHARLES, JB TI A COMPREHENSIVE GUYTON MODEL ANALYSIS OF PHYSIOLOGICAL-RESPONSES TO PREADAPTING THE BLOOD-VOLUME AS A COUNTERMEASURE TO FLUID SHIFTS SO JOURNAL OF CLINICAL PHARMACOLOGY LA English DT Article; Proceedings Paper CT 12th Frontiers Symposium: Pharmacology Beyond Earths Boundaries CY MAY 06, 1992 CL NASA, JOHNSON SPACE CTR, HOUSTON, TX HO NASA, JOHNSON SPACE CTR ID WEIGHTLESSNESS; MECHANISMS; IMMERSION; FLIGHT AB The Guyton model of fluid, electrolyte, and circulatory regulation is an extensive mathematical model capable of simulating a variety of experimental conditions. It has been modified for use at NASA to simulate head-down tilt, a frequently used analog of weightlessness. Weightlessness causes a headward shift of body fluids that is believed to expand central blood volume, triggering a series of physiologic responses resulting in large losses of body fluids. We used the modified Guyton model to test the hypothesis that preadaptation of the blood volume before weightless exposure could counteract the central volume expansion caused by fluid shifts, and thereby attenuate the circulatory and renal responses that result in body fluid losses. Simulation results show that circulatory preadaptation, by a procedure resembling blood donation immediately before head-down bedrest, is effective in damping the physiologic responses to fluid shifts and reducing body fluid losses. After 10 hours of head-down tilt, preadaptation also produces higher blood volume, extracellular volume, and total body water for 20 to 30 days of bedrest, compared with non-preadapted control. These results indicate that circulatory preadaptation before current Space Shuttle missions may be beneficial for the maintenance of reentry and postflight orthostatic tolerance in astronauts. This paper presents a comprehensive examination of the simulation results pertaining to changes in relevant physiologic variables produced by blood volume reduction before a prolonged head-down tilt. The objectives were to study and develop the countermeasure theoretically, to aid in planning experimental studies of the countermeasure, and to identify potentially disadvantageous physiologic responses that may be caused by the countermeasure. C1 KRUG LIFE SCI INC,HOUSTON,TX 77058. UNIV SPACE RES ASSOC,HOUSTON,TX. RICE UNIV,HOUSTON,TX 77251. NASA,LYNDON B JOHNSON SPACE CTR,SPACE BIOMED RES INST,HOUSTON,TX 77058. NR 25 TC 7 Z9 7 U1 1 U2 2 PU LIPPINCOTT-RAVEN PUBL PI PHILADELPHIA PA 227 EAST WASHINGTON SQ, PHILADELPHIA, PA 19106 SN 0091-2700 J9 J CLIN PHARMACOL JI J. Clin. Pharmacol. PD MAY PY 1994 VL 34 IS 5 BP 440 EP 453 PG 14 WC Pharmacology & Pharmacy SC Pharmacology & Pharmacy GA NL960 UT WOS:A1994NL96000011 PM 8089255 ER PT J AU SCHRAEDER, PL LATHERS, CM CHARLES, JB AF SCHRAEDER, PL LATHERS, CM CHARLES, JB TI THE SPECTRUM OF SYNCOPE SO JOURNAL OF CLINICAL PHARMACOLOGY LA English DT Article; Proceedings Paper CT 12th Frontiers Symposium: Pharmacology Beyond Earths Boundaries CY MAY 06, 1992 CL NASA, JOHNSON SPACE CTR, HOUSTON, TX HO NASA, JOHNSON SPACE CTR ID DEATH AB Syncope is a loss of consciousness and postural tone. Although arising suddenly from prolonged recumbency or returning from weightlessness to Earth's gravity con result in syncope from orthostatic or vasovagal effects, there are many other possible causes. These causes can be divided into several groups. Causes listed in the cardiovascular category, especially cardiac causes, are more likely to occur in the elderly; noncardiac causes are more common in the younger population. The cases described herein illustrate the often unexpected mechanisms of syncope in otherwise healthy individuals. Two of the cases emphasize the usefulness of prolonged combined EEG/EKG monitoring. The categories of loss of consciousness experienced by air crew members are reviewed. The most important screening tool in identifying the mechanism(s) of syncope is a detailed history emphasizing a search for underlying disease, the specific associated circumstances, and pre- and post-event symptoms. The type of diagnostic studies, i.e., cardiac or neurologic, undertaken should be based on the historical data. Seizures must be considered as a possible mechanism of otherwise unexplained loss of consciousness in nonelderly persons, including air crew members. C1 US FDA,DIV CARDIORENAL,ROCKVILLE,MD 20857. UNIV MED & DENT NEW JERSEY,ROBERT WOOD JOHNSON MED SCH,CAMDEN,NJ 08103. NASA,LYNDON B JOHNSON SPACE CTR,SPACE BIOMED RES INST,HOUSTON,TX 77058. NR 21 TC 6 Z9 8 U1 0 U2 0 PU LIPPINCOTT-RAVEN PUBL PI PHILADELPHIA PA 227 EAST WASHINGTON SQ, PHILADELPHIA, PA 19106 SN 0091-2700 J9 J CLIN PHARMACOL JI J. Clin. Pharmacol. PD MAY PY 1994 VL 34 IS 5 BP 454 EP 459 PG 6 WC Pharmacology & Pharmacy SC Pharmacology & Pharmacy GA NL960 UT WOS:A1994NL96000012 PM 8089256 ER PT J AU MUKAI, CN LATHERS, CM CHARLES, JB BENNET, BS AF MUKAI, CN LATHERS, CM CHARLES, JB BENNET, BS TI CARDIOVASCULAR-RESPONSES TO REPETITIVE EXPOSURE TO HYPERGRAVITY AND HYPOGRAVITY STATES PRODUCED BY PARABOLIC FLIGHT SO JOURNAL OF CLINICAL PHARMACOLOGY LA English DT Article; Proceedings Paper CT 12th Frontiers Symposium: Pharmacology Beyond Earths Boundaries CY MAY 06, 1992 CL NASA, JOHNSON SPACE CTR, HOUSTON, TX HO NASA, JOHNSON SPACE CTR ID ACUTE HEMODYNAMIC-RESPONSES; WEIGHTLESSNESS AB Physiologic changes to repetitive hyper- and hypogravity stresses occurring during eight to ten parabolas on NASA's KC-135 aircraft were studied. Hemodynamic responses in 11 subjects in 4 different postures (supine, standing, sitting, and semisupine Space Shuttle launch position) were determined using noninvasive impedance cardiography. Five seconds of heart rate, cardiac index, thoracic fluid index, stroke index, ejection velocity index, and ventricular ejection time data were averaged during four different gravity (g) states: 1.3g (before parabola onset); 1.9g (parabola entry); Og (parabola peak); and 1.7g (parabola exit) for each subject. The standing position was associated with the largest changes in the cardiovascular response to hypo- and hypergravity. The thoracic fluid index did not indicate a headward redistribution during transition from a simulated launch position to weightlessness. Analysis of the eight to ten parabolas revealed that, in general, values obtained at 1.8g differed from 1.6g, Og differed from 1.6 and 1.3g, and 1.6g differed from 1.3g. The factors of gravity, thoracic fluid index, and cardiac index exhibited significant differences that were most likely to occur between parabola 1 versus parabolas 6, 7, and 8, and parabola 2 versus parabolas 4 through 8. Only the parameter of thoracic fluid index exhibited significance for parabolas 3 versus parabolas 6 and 7. C1 US FDA,DIV CARDIORENAL,ROCKVILLE,MD. KRUG LIFE SCI INC,HOUSTON,TX. RP MUKAI, CN (reprint author), NASA,LYNDON B JOHNSON SPACE CTR,SPACE BIOMED RES INST,MAIL CODE KN-NASDA,2101 NASA RD 1,HOUSTON,TX 77058, USA. NR 8 TC 15 Z9 15 U1 1 U2 3 PU LIPPINCOTT-RAVEN PUBL PI PHILADELPHIA PA 227 EAST WASHINGTON SQ, PHILADELPHIA, PA 19106 SN 0091-2700 J9 J CLIN PHARMACOL JI J. Clin. Pharmacol. PD MAY PY 1994 VL 34 IS 5 BP 472 EP 479 PG 8 WC Pharmacology & Pharmacy SC Pharmacology & Pharmacy GA NL960 UT WOS:A1994NL96000015 PM 8089258 ER PT J AU KRUTZ, RW SAWIN, CF STEGMANN, BJ BURTON, RR AF KRUTZ, RW SAWIN, CF STEGMANN, BJ BURTON, RR TI PREINFLATION BEFORE ACCELERATION ON TOLERANCE TO SIMULATED SPACE-SHUTTLE REENTRY G-PROFILES IN DEHYDRATED SUBJECTS SO JOURNAL OF CLINICAL PHARMACOLOGY LA English DT Article; Proceedings Paper CT 12th Frontiers Symposium: Pharmacology Beyond Earths Boundaries CY MAY 06, 1992 CL NASA, JOHNSON SPACE CTR, HOUSTON, TX HO NASA, JOHNSON SPACE CTR AB This study was conducted to determine if preinflation of a standard five-bladder anti-g suit 10 minutes before exposure to a centrifuge simulation of a Space Shuttle reentry would provide significantly better protection against orthostasis than the standard symptomatic inflation regimen. This study differed significantly from prior studies: The rate of g onset was slower, peak g was lower, duration of exposure was longer, and the subjects were dehydrated to mimic conditions observed in astronauts immediately postflight. Preinflation demonstrated physiological advantages as determined by arterial blood pressure and heart rate changes in seven healthy male, experienced centrifuge subjects. C1 NASA,LYNDON B JOHNSON SPACE CTR,SPACE BIOMED RES INST,HOUSTON,TX 77058. KRUG LIFE SCI INC,SAN ANTONIO,TX. ARMSTRONG LAB,SAN ANTONIO,TX. NR 4 TC 5 Z9 5 U1 0 U2 0 PU LIPPINCOTT-RAVEN PUBL PI PHILADELPHIA PA 227 EAST WASHINGTON SQ, PHILADELPHIA, PA 19106 SN 0091-2700 J9 J CLIN PHARMACOL JI J. Clin. Pharmacol. PD MAY PY 1994 VL 34 IS 5 BP 480 EP 483 PG 4 WC Pharmacology & Pharmacy SC Pharmacology & Pharmacy GA NL960 UT WOS:A1994NL96000016 PM 8089259 ER PT J AU LATHERS, CM CHARLES, JB AF LATHERS, CM CHARLES, JB TI COMPARISON OF CARDIOVASCULAR FUNCTION DURING THE EARLY HOURS OF BED REST AND SPACE-FLIGHT SO JOURNAL OF CLINICAL PHARMACOLOGY LA English DT Article; Proceedings Paper CT 12th Frontiers Symposium: Pharmacology Beyond Earths Boundaries CY MAY 06, 1992 CL NASA, JOHNSON SPACE CTR, HOUSTON, TX HO NASA, JOHNSON SPACE CTR ID HEAD-DOWN TILT; ZERO GRAVITY; ORTHOSTATIC INTOLERANCE; UP TILT; BEDREST; ADAPTATION; RESPONSES AB This paper reviews the cardiovascular responses of six healthy male subjects to 6 hours in a 5 degrees head-down bed rest model of weightlessness, and compares these responses to those obtained when subjects were positioned in head-up tilts of 10 degrees, 20 degrees, and 42 degrees, simulating 1/6, 1/3, and 2/3 G, respectively. Thoracic fluid index, cardiac output, stroke volume, and peak flow were measured using impedance cardiography. Cardiac dimensions and volumes were determined from two-dimensional guided M-mode echocardiograms in the left lateral decubitus position at 0, 2, 4, and 6 hours. Cardiovascular responses to a stand test were compared before and after bed rest. The impedance values were related to tilt angle for the first 2 hours of tilt; however, after 3 hours, at all four angles, values began to converge, indicating that cardiovascular homeostatic mechanisms seek a common adapted state, regardless of effective gravity level (tilt angle) up to 2/3 G. Echocardiography revealed that left ventricular end-diastolic and end-systolic volume, stroke volume, ejection fraction, heart rate, and cardiac output had returned to control values by hour 6 for all tilt angles. The lack of a significant immediate change in left ventricular end-diastolic volume, despite decrements in stroke volume (P <.05) and heart rate (not significant), indicates that multiple factors may play a role in the adaptation to simulated hypogravity. The echocardiography data indicated that no angle of tilt, whether head-down or head-up for 4 to 6 hours, mimicked exactly the changes in cardiovascular function recorded after 4 to 6 hours of space flight. Changes in left ventricular end-diastolic volume during space flight and tilt may be similar, but follow a different time course. Nevertheless, head-down tilt at 5 degrees for a hours mimics some (stroke volume, systolic and diastolic blood pressure, mean arterial blood pressure, and total resistance), but not all, of the changes occurring in an equivalent time of space flight. The magnitude of the change in the mean heart rate response to standing was greater after six hours of tilt at -5 degrees or 10 degrees. Thus, results from the stand test after 6 hours of bed rest at -5 degrees and 10 degrees, but not at 20 degrees or 42 degrees, are similar to those obtained after space flight. C1 NASA,LYNDON B JOHNSON SPACE CTR,SPACE BIOMED RES INST,HOUSTON,TX 77058. RP LATHERS, CM (reprint author), US FDA,DIV CARDIORENAL PROD,5600 FISHERS LANE,HFD 110,ROCKVILLE,MD 20857, USA. NR 22 TC 5 Z9 5 U1 0 U2 0 PU LIPPINCOTT-RAVEN PUBL PI PHILADELPHIA PA 227 EAST WASHINGTON SQ, PHILADELPHIA, PA 19106 SN 0091-2700 J9 J CLIN PHARMACOL JI J. Clin. Pharmacol. PD MAY PY 1994 VL 34 IS 5 BP 489 EP 499 PG 11 WC Pharmacology & Pharmacy SC Pharmacology & Pharmacy GA NL960 UT WOS:A1994NL96000018 PM 8089261 ER PT J AU LEACH, CS LANE, HW KRAUHS, JM AF LEACH, CS LANE, HW KRAUHS, JM TI SHORT-TERM SPACE-FLIGHT ON NITROGENOUS COMPOUNDS, LIPOPROTEINS, AND SERUM-PROTEINS SO JOURNAL OF CLINICAL PHARMACOLOGY LA English DT Article; Proceedings Paper CT 12th Frontiers Symposium: Pharmacology Beyond Earths Boundaries CY MAY 06, 1992 CL NASA, JOHNSON SPACE CTR, HOUSTON, TX HO NASA, JOHNSON SPACE CTR ID ALKALINE-PHOSPHATASE ACTIVITY; ENZYME-ACTIVITY; METABOLISM AB Biochemical variables in blood were measured in venous blood samples from 38 to 72 Space Shuttle astronauts before and immediately after flights of 2 to 11 days. Mean pre- and postflight values were compared using the paired t-test or the Wilcoxon signed-rank test. The largest change in serum enzymes was a 21% increase (P =.0014) in gamma-glutamyl-transpeptidase, which may have been related to stress. The median value of apolipoprotein (apo) A-I decreased from 152 to 127 mg/dL (P <.0001), but the change in apo B (77 to 73 mg/dL) was not statistically significant, and the mean apo A-I/apo B ratio remained well above 1.5. A decrease in dietary fat and cholesterol intake during shuttle missions may have been a cause of the change in apo A-I. Twelve of the 16 nonenzyme serum proteins measured were significantly elevated (P <.05), possibly because of hemoconcentration and increased protein catabolism. The 56% increase in haptoglobin may be related to release of suppressed erythropoiesis at landing. C1 KRUG LIFE SCI INC,HOUSTON,TX. RP LEACH, CS (reprint author), NASA,LYNDON B JOHNSON SPACE CTR,BIOMED OPERAT & RES BRANCH,MAIL CODE SA,HOUSTON,TX 77058, USA. NR 56 TC 6 Z9 8 U1 0 U2 0 PU LIPPINCOTT-RAVEN PUBL PI PHILADELPHIA PA 227 EAST WASHINGTON SQ, PHILADELPHIA, PA 19106 SN 0091-2700 J9 J CLIN PHARMACOL JI J. Clin. Pharmacol. PD MAY PY 1994 VL 34 IS 5 BP 500 EP 509 PG 10 WC Pharmacology & Pharmacy SC Pharmacology & Pharmacy GA NL960 UT WOS:A1994NL96000019 PM 7916353 ER PT J AU BILLICA, R AF BILLICA, R TI MEDICAL-MANAGEMENT OF US ASTRONAUTS SO JOURNAL OF CLINICAL PHARMACOLOGY LA English DT Article; Proceedings Paper CT 12th Frontiers Symposium: Pharmacology Beyond Earths Boundaries CY MAY 06, 1992 CL NASA, JOHNSON SPACE CTR, HOUSTON, TX HO NASA, JOHNSON SPACE CTR AB The medical management of U.S. astronauts involves a comprehensive health care program and a variety of NASA and support organizations. The scope of this program includes aspects of medical monitoring and certification, health maintenance and countermeasures programs, medical intervention, psychosocial support, and environmental health monitoring. Each of these areas have activities in all mission phases preflight, inflight, and postflight. The wide range of potential health hazards from space flight mandates an aggressive health care program to maintain crew health and performance, and to prevent unwanted mission and long-term health consequences. RP BILLICA, R (reprint author), NASA,LYNDON B JOHNSON SPACE CTR,MED OPERAT BRANCH,MAIL CODE SD-5,HOUSTON,TX 77058, USA. NR 9 TC 0 Z9 0 U1 0 U2 0 PU LIPPINCOTT-RAVEN PUBL PI PHILADELPHIA PA 227 EAST WASHINGTON SQ, PHILADELPHIA, PA 19106 SN 0091-2700 J9 J CLIN PHARMACOL JI J. Clin. Pharmacol. PD MAY PY 1994 VL 34 IS 5 BP 510 EP 512 PG 3 WC Pharmacology & Pharmacy SC Pharmacology & Pharmacy GA NL960 UT WOS:A1994NL96000020 PM 8089262 ER PT J AU FORSYTHE, E PUSEY, ML AF FORSYTHE, E PUSEY, ML TI THE EFFECTS OF TEMPERATURE AND NACL CONCENTRATION ON TETRAGONAL LYSOZYME FACE GROWTH-RATES SO JOURNAL OF CRYSTAL GROWTH LA English DT Article ID CRYSTAL-GROWTH; MICROSCOPY; KINETICS AB Measurements were made of the (110) and (101) face growth rates of the tetragonal form of hen egg white lysozyme at 0.1M sodium acetate buffer, pH 4.0, from 4 to 22-degrees-C and with 3.0%, 5.0%, and 7.0% NaCl used as the precipitating salt. The data were collected at supersaturation ratios ranging from approximately 4 to approximately 63. Both decreasing temperature and increasing salt concentrations shifted plots of the growth rate versus C/C(sat) to the right, i.e. higher supersaturations were required for comparable growth rates. The observed trends in the growth data are counter to those expected from the solubility data. If tetragonal lysozyme crystal growth is by addition of ordered aggregates from the solution, then the observed growth data could be explained as a result of the effects of lowered temperature and increased salt concentration on the kinetics and equilibrium processes governing protein-protein interactions in solution. The data indicate that temperature would be a more tractable means of controlling the growth rate for tetragonal lysozyme crystals contrary to the usual practice in, e.g., vapor diffusion protein crystal growth, where both the precipitant and protein concentrations are simultaneously increased. However, the available range for control is dependent upon the protein concentration, with the greatest growth rate control being at the lower concentration. C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,BIOPHYS ES 76,HUNTSVILLE,AL 35812. UNIV SPACE RES ASSOC,HUNTSVILLE,AL 35806. NR 22 TC 55 Z9 55 U1 0 U2 7 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-0248 J9 J CRYST GROWTH JI J. Cryst. Growth PD MAY PY 1994 VL 139 IS 1-2 BP 89 EP 94 DI 10.1016/0022-0248(94)90032-9 PG 6 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA NG313 UT WOS:A1994NG31300012 ER PT J AU SINGH, NB STEWART, AM HAMACHER, RD MAZELSKY, R DUVAL, WMB SANTORO, GJ DEWITT, R LEHOCZKY, SL AF SINGH, NB STEWART, AM HAMACHER, RD MAZELSKY, R DUVAL, WMB SANTORO, GJ DEWITT, R LEHOCZKY, SL TI CONVECTO-DIFFUSIVE GROWTH OF LEAD BROMIDE CRYSTALS - A TEST OF THEORIES SO JOURNAL OF CRYSTAL GROWTH LA English DT Article AB A comparative study of thermosolutal convection was carried out by growing lead bromide single crystals in a transparent Bridgman furnace. We doped the high purity lead bromide by silver bromide and studied the microsegregation of silver in the matrix of the crystal. Theories based on two extremes: complete diffusive or convective transport did not agree with the experimental data. X-ray rocking curves and contour scans showed that increasing solutal convection deteriorated the crystal quality. C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP SINGH, NB (reprint author), WESTINGHOUSE ELECT CORP,CTR SCI & TECHNOL,1310 BEULAH RD,PITTSBURGH,PA 15235, USA. NR 8 TC 11 Z9 11 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 MAY PY 1994 VL 139 IS 1-2 BP 158 EP 164 DI 10.1016/0022-0248(94)90040-X PG 7 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA NG313 UT WOS:A1994NG31300020 ER PT J AU FEYNMAN, J HUNDHAUSEN, AJ AF FEYNMAN, J HUNDHAUSEN, AJ TI CORONAL MASS EJECTIONS AND MAJOR SOLAR-FLARES - THE GREAT ACTIVE-CENTER OF MARCH 1989 SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID TRANSIENTS; EVOLUTION; RECONNECTION; ARCADE; BURSTS; LAUNCH AB The solar flare and coronal mass ejection (CME) events associated with the large and complex March 1989 active region are discussed. This active region gave us a chance to study the relation of CME with truly major solar flares. The work concentrates on questions of the relation of CMEs and flares to one another and to other types of activity on the Sun. As expected, some major (X-3B class) flares had associated CMEs. However, an unexpected finding is that others did not. In fact, there is strong evidence that the X4-4B flare of March 9th had no CME. This lack of a CME for such an outstanding flare event has important implications to theories of CME causation. Apparently, not all major flares cause CMEs or are caused by CMEs. The relations between CMEs and other types of solar activity are also discussed. No filament disappearances are reported for major CMEs studied here. Comparing these results with other studies, CMEs occur in association with flares and with erupting prominences, but neither are required for a CME. The relation between solar structures showing flaring without filament eruptions and structures showing filament eruptions without flares becomes important. The evolutionary relation between an active flaring sunspot region and extensive filaments without sunspots is reviewed, and the concept of an ''evolving magnetic structure'' (EMS) is introduced. It is suggested that all CMEs arise in EMSs and that CMEs provide a major path through which azimuthal magnetic fields escape from the Sun during the solar cycle. C1 NATL CTR ATMOSPHER RES, HIGH ALTITUDE OBSERV, BOULDER, CO 80203 USA. RP JET PROP LAB, 4800 OAK GROVE DR, MAIL STOP 169 506, PASADENA, CA 91109 USA. NR 40 TC 58 Z9 60 U1 1 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9380 EI 2169-9402 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD MAY 1 PY 1994 VL 99 IS A5 BP 8451 EP 8464 DI 10.1029/94JA00202 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NK217 UT WOS:A1994NK21700001 ER PT J AU LOCKWOOD, M SMITH, MF AF LOCKWOOD, M SMITH, MF TI LOW AND MIDDLE ALTITUDE CUSP PARTICLE SIGNATURES FOR GENERAL MAGNETOPAUSE RECONNECTION RATE VARIATIONS .1. THEORY SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID FLUX-TRANSFER EVENTS; INTERPLANETARY MAGNETIC-FIELD; LATITUDE BOUNDARY-LAYER; LARGE CONVECTIVE VELOCITIES; ACCELERATED FLOW EVENTS; NORTH-SOUTH COMPONENT; POLAR CUSP; DAYSIDE MAGNETOPAUSE; PLASMA INJECTION; MAGNETOSHEATH PLASMA AB We present predictions of the signatures of magnetosheath particle precipitation (in the regions classified as open low-latitude boundary layer, cusp, mantle and polar cap) for periods when the interplanetary magnetic field has a southward component. These are made using the ''pulsating cusp'' model of the effects of time-varying magnetic reconnection at the dayside magnetopause. Predictions are made for both low-altitude satellites in the topside ionosphere and for midaltitude spacecraft in the magnetosphere. Low-altitude cusp signatures, which show a continuous ion dispersion signature, reveal ''quasi-steady reconnection'' (one limit of the pulsating cusp model), which persists for a period of at least 10 min. We estimate that ''quasi-steady'' in this context corresponds to fluctuations in the reconnection rate of a factor of 2 or less. The other limit of the pulsating cusp model explains the instantaneous jumps in the precipitating ion spectrum that have been observed at low altitudes. Such jumps are produced by isolated pulses of reconnection: that is, they are separated by intervals when the reconnection rate is zero. These also generate convecting patches on the magnetopause in which the field lines thread the boundary via a rotational discontinuity separated by more extensive regions of tangential discontinuity. Predictions of the corresponding ion precipitation signatures seen by midaltitude spacecraft are presented. We resolve the apparent contradiction between estimates of the width of the injection region from midaltitude data and the concept of continuous entry of solar wind plasma along open field lines. In addition, we reevaluate the use of pitch angle-energy dispersion to estimate the injection distance. C1 NASA,GODDARD SPACE FLIGHT CTR,EXTRATERR PHYS LAB,GREENBELT,MD 20771. UNIV LONDON IMPERIAL COLL SCI TECHNOL & MED,LONDON SW7 2AZ,ENGLAND. RP LOCKWOOD, M (reprint author), RUTHERFORD APPLETON LAB,DIDCOT OX11 0QX,OXON,ENGLAND. RI Lockwood, Mike/G-1030-2011 OI Lockwood, Mike/0000-0002-7397-2172 NR 111 TC 134 Z9 134 U1 2 U2 6 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD MAY 1 PY 1994 VL 99 IS A5 BP 8531 EP 8553 DI 10.1029/93JA03399 PG 23 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NK217 UT WOS:A1994NK21700007 ER PT J AU HESSE, M BIRN, J AF HESSE, M BIRN, J TI MHD MODELING OF MAGNETOTAIL INSTABILITY FOR LOCALIZED RESISTIVITY SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID FIELD-ALIGNED CURRENTS; SUBSTORM CURRENT WEDGE; EXTENDED MAGNETOTAIL; CURRENT DIVERSION; BOUNDARY-LAYERS; RECONNECTION; SIMULATIONS; GENERATION; ORBIT; SHEET AB We present results of a three-dimensional MHD simulation of magnetotail evolution initiated by a sudden occurrence or increase of spatially localized resistivity as the major expected consequence of some localized microinstability. Because of the absense of a quantitative model, possible variations of resistivity levels with current density, or the reduction thereof, are not incorporated in the present investigation. The emphasis of the study is on an investigation of the changes to the overall evolution brought about by this localization, in particular, on the disruption and diversion of the cross-tail current and the nonlinear evolution of the magnetotail instability. The immediate consequences of the occurrence of the localized resistance and the resulting electric field are a reduction and diversion of the electric current around the region of high resistivity, associated with an increase of B(z) (''dipolarization'') at the earthward edge and a decrease of B(z) at the tailward edge of this region. These effects, however, are localized and do not involve a reduction of the total cross-tail current and hence do not lead to the global development of a ''substorm current wedge,'' which includes not only the reduction of the cross-tail current but also the buildup of a global field-aligned current system of ''region 1'' type (toward the Earth on the dawnside and away on the duskside of the tail). Such signatures develop at a later time, as consequences of a three-dimensional tearing instability, which is triggered by the occurrence of the resistivity. These features are found in combination with plasmoid formation and ejection, quite similar to results of earlier simulations with uniform resistivity. Differences are found in the timescale of the evolution, which tends to be shorter for localized resistivity, and in the propagation of the dipolarization effects in the equatorial plane. Whereas for uniform resistivity the temporal increase in B(z) tends to propagate tailward, apparently due to a pileup effect in the near-Earth region, an earthward propagation is found for the localized resistivity. This propagation results from an earthward convection of the gradient in B(z), which is set up by the reconnection process further tailward. C1 LOS ALAMOS NATL LAB,SPACE PLASMA PHYS GRP,LOS ALAMOS,NM 87545. RP HESSE, M (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ELECTRODYNAM BRANCH,GREENBELT,MD 20771, USA. RI Hesse, Michael/D-2031-2012 NR 30 TC 29 Z9 29 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD MAY 1 PY 1994 VL 99 IS A5 BP 8565 EP 8576 DI 10.1029/94JA00441 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NK217 UT WOS:A1994NK21700009 ER PT J AU FUNG, SF VINAS, AF AF FUNG, SF VINAS, AF TI EXCITATION OF HIGH-FREQUENCY ELECTROMAGNETIC-WAVES BY ENERGETIC ELECTRONS WITH A LOSS CONE DISTRIBUTION IN A FIELD-ALIGNED POTENTIAL DROP SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID AURORAL KILOMETRIC RADIATION; WEAKLY RELATIVISTIC ELECTRONS; CYCLOTRON MASER; GENERATION; PLASMA; AMPLIFICATION; INSTABILITY; EMISSION; GROWTH AB The electron cyclotron maser instability (CMI) driven by momentum space anisotropy, partial derivative f/partial derivative p perpendicular-to > 0, has been invoked to explain many aspects, such as the modes of propagation, harmonic emissions, and the source characteristics of the auroral kilometric radiation (AKR). Recent satellite observations of AKR sources indicate that the source regions are often imbedded within the auroral acceleration region characterized by the presence of a field-aligned potential drop. In this paper we investigate the excitation of the fundamental extraordinary mode radiation due to the accelerated electrons. The momentum space distribution of these energetic electrons is modeled by a realistic upward loss cone as modified by the presence of a parallel potential drop below the observation point. On the basis of linear growth rate calculations we present the emission characteristics, such as the frequency spectrum and the emission angular distribution as functions of the plasma parameters. We will discuss the implication of our results on the generation of the AKR from the edges of the auroral density cavities. C1 NASA,GODDARD SPACE FLIGHT CTR,EXTRATERR PHYS LAB,GREENBELT,MD 20771. RP FUNG, SF (reprint author), NASA,GODDARD SPACE FLIGHT CTR,SPACE PHYS DATA FACIL,GREENBELT,MD 20771, USA. RI Fung, Shing/F-5647-2012 NR 31 TC 12 Z9 12 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD MAY 1 PY 1994 VL 99 IS A5 BP 8671 EP 8686 DI 10.1029/94JA00251 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NK217 UT WOS:A1994NK21700018 ER PT J AU KAYMAZ, Z SISCOE, GL TSYGANENKO, NA LEPPING, RP AF KAYMAZ, Z SISCOE, GL TSYGANENKO, NA LEPPING, RP TI MAGNETOTAIL VIEWS AT 33R(E)-IMP 8 MAGNETOMETER OBSERVATIONS SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID MAGNETOSPHERIC MAGNETIC-FIELD; GEOMAGNETIC NEUTRAL SHEET; TAIL CURRENT SHEET; PLASMA SHEET; POSITION; SHAPE; CONFIGURATION AB This paper presents magnetic field vector (B) maps, electric current vector (curl B) maps, magnetic force (JxB) contour maps, and total field contour maps covering the full tail cross section in the yz plane. The maps are based on 16 years of 5-min averages of IMP 8 magnetic field data. During this time, IMP 8 traversed the tail between -25R(E) and -40R(E) in the x direction. Its average x distance was -33R(E). For this average distance we show separate maps for low and high dipole tilts, corresponding to equinox and northern hemisphere summer seasons. The low-tilt (equinox) maps show symmetrical field and current patterns; the high-tilt (solstice) maps show the cross-tail current sheet arcing above the equatorial diagonal in the center and dipping below it on the flanks. The shape of warped current sheet fits Fairfield's (1980) displaced ellipse model fairly well. The distance at which the current sheet is hinged to the magnetic equator is found to be 9.88R(E) and is independent of Kp. The z profile of current density shows a central peak, 3R(E) full width at half maximum, and smaller, flanking shoulders. A Harris sheet profile with a 7R(E) thickness fits the B(x) profile. Though these are magnetic field data, the JxB maps clearly outline the plasma sheet. This approach also gives a 7R(E) thickness. Many of the average field and current features inferred and demonstrated in earlier studies are confirmed here; some of them are seen for the first time in full cross-section view. Among new features revealed are a large current vortex in the winter hemisphere lobe, a dawn-dusk asymmetry in the JxB force in the plasma sheet (it is stronger on the duskside), and a separation of the cross-tail current sheet into core and wing parts. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20770. UNIV CALIF LOS ANGELES,DEPT ATMOSPHER SCI,LOS ANGELES,CA 90024. RI Tsyganenko, Nikolai/J-7377-2012 OI Tsyganenko, Nikolai/0000-0002-5938-1579 NR 27 TC 30 Z9 31 U1 0 U2 7 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD MAY 1 PY 1994 VL 99 IS A5 BP 8705 EP 8730 DI 10.1029/93JA03564 PG 26 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NK217 UT WOS:A1994NK21700020 ER PT J AU COLE, KD HOEGY, WR AF COLE, KD HOEGY, WR TI ELECTRIC CURRENTS IN THE SUBSOLAR REGION OF THE VENUS LOWER IONOSPHERE SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID MAGNETOHYDRODYNAMIC MODEL; PLANETARY IONOSPHERES; MAGNETIC-FIELDS AB The ion and electron momentum equations, along with Ampere's law, are solved for the ion and electron drift velocities and the electric field in the subsolar Venus ionosphere, assuming a partially ionized gas and a single ion species having the ion mean mass. AU collision terms among the ions, electrons and neutral particles are retained in the equations. A general expression for the evolution of the magnetic field is derived and compared with earlier expressions (Luhmann et al., 1984; Cloutier, 1984; Cravens et al., 1984). Subsolar region data in the altitude range 150-300 kin from the Pioneer Venus Orbiter are used to calculate altitude profiles of the components of the current due to the electric field, gradients of pressure, and gravity. Altitude profiles of the ion and electron velocities as well as the electric field, electrodynamic heating, and the energy density are determined. Only orbits having a complete set of measured plasma temperatures and densities, neutral densities, and magnetic field were considered for analysis; the results are shown only for orbit 202. The vertical velocity at altitudes above 220 km is upgoing for orbit 202. This result is consistent with observations of molecular ions at high altitudes and of plasma flow to the nightside, both of which require upward velocity of ions from the dayside ionosphere. Above about 230 km the momentum equations are extremely sensitive to the altitude profiles of density, temperature, and magnetic field. C1 LA TROBE UNIV,DEPT PHYS,BUNDOORA,VIC 3083,AUSTRALIA. RP COLE, KD (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ATMOSPHERES LAB,GREENBELT,MD 20771, USA. NR 18 TC 1 Z9 1 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 JI J. Geophys. Res-Space Phys. PD MAY 1 PY 1994 VL 99 IS A5 BP 8791 EP 8800 DI 10.1029/94JA00203 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NK217 UT WOS:A1994NK21700026 ER PT J AU HYSELL, DL KELLEY, MC SWARTZ, WE PFAFF, RF SWENSON, CM AF HYSELL, DL KELLEY, MC SWARTZ, WE PFAFF, RF SWENSON, CM TI STEEPENED STRUCTURES IN EQUATORIAL SPREAD-F .1. NEW OBSERVATIONS SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID INSITU MEASUREMENTS; RADAR OBSERVATIONS; IRREGULARITIES; WAVELENGTH; BUBBLES; INSTABILITY; IONOSPHERE; TURBULENCE; PROBE AB Sounding rocket data from the 1990 CRRES/EQUIS equatorial spread F campaign on Kwajalein Atoll are presented. Two Terrier Malamute sounding rockets were launched into active spread F conditions on July 30 and August 2, respectively, and achieved apogee slightly below 500 km, just above the F peak. Plasma frequency probes aboard both rockets showed that the unstable nighttime F region is characterized by propagating steepened structures. Power density spectra for the structures typically exhibit two regions that obey k-n scaling, where n is approximately equal to 2 at wavelengths greater than 80-100 m and approximately equal to 5 at shorter wavelengths. These spectral indices are quite variable, and the long-wavelength spectral index in particular seems to decrease with increasing amplitude of density fluctuations. The rocket payloads also measured vector electric fields in the plane perpendicular to B over wavelengths ranging from over 60 km to less than 6 m. Both vector components of the perpendicular electric field are proportional to deltan/n at wavelengths longer than 300 m but assume a Boltzmann relationship (with ]deltaE\2 is similar to k2\deltan/n\2) at smaller scales. The perturbed zonal electric field, deltaE(x), dominates the vertical field, deltaE(z), at long wavelengths, but the situation is reversed at smaller scales. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. UTAH STATE UNIV,SCH ELECT ENGN,LOGAN,UT 84322. RP HYSELL, DL (reprint author), CORNELL UNIV,SCH ELECT ENGN,ENGN & THEORY CTR BLDG,ITHACA,NY 14853, USA. RI Pfaff, Robert/F-5703-2012 OI Pfaff, Robert/0000-0002-4881-9715 NR 25 TC 33 Z9 33 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD MAY 1 PY 1994 VL 99 IS A5 BP 8827 EP 8840 DI 10.1029/93JA02961 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NK217 UT WOS:A1994NK21700028 ER PT J AU GANGULI, G KESKINEN, MJ ROMERO, H HEELIS, R MOORE, T POLLOCK, C AF GANGULI, G KESKINEN, MJ ROMERO, H HEELIS, R MOORE, T POLLOCK, C TI COUPLING OF MICROPROCESSES AND MACROPROCESSES DUE TO VELOCITY SHEAR - AN APPLICATION TO THE LOW-ALTITUDE IONOSPHERE SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID ION-CYCLOTRON INSTABILITY; LOWER HYBRID ACCELERATION; AURORAL-F-REGION; ELECTRIC-FIELD; MAGNETIC-FIELD; SATELLITE-OBSERVATIONS; EQUATORIAL ELECTROJET; ELECTROSTATIC SHOCKS; POLAR MAGNETOSPHERE; PLASMA AB Recent observations indicate that low-altitude (below 1500 km) ion energization and thermal ion upwelling are colocated in the convective flow reversal region. In this region the convective velocity V perpendicular-to is generally small but spatial gradients in V perpendicular-to can be large. As a result, Joule heating is small. The observed high level of ion heating (few electron volts or more) cannot be explained by classical Joule heating alone but requires additional heating sources such as plasma waves. At these lower altitudes, sources of free energy are not obvious and hence the nature of ion energization remains ill understood. The high degree of correlation of ion heating with shear in the convective velocity (Tsunoda et al., 1989) is suggestive of an important role of velocity shear in this phenomenon. We provide more recent evidence for this correlation and show that even a small amount of velocity shear in the transverse flow is sufficient to excite a large-scale Kelvin-Helmholtz mode, which can nonlinearly steepen and give rise to highly stressed regions of strongly sheared flows. Furthermore, these stressed regions of strongly sheared flows may seed plasma waves in the range of ion cyclotron to lower hybrid frequencies, which are potential sources for ion heating. This novel two-step mechanism for ion energization is applied to typical observations of low-altitude thermal ion upwelling events. C1 UNIV TEXAS,RICHARDSON,TX 75083. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. RP GANGULI, G (reprint author), USN,RES LAB,DIV PLASMA PHYS,BEAM PHYS BRANCH,WASHINGTON,DC 20375, USA. RI Moore, Thomas/D-4675-2012 OI Moore, Thomas/0000-0002-3150-1137 NR 73 TC 124 Z9 125 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 JI J. Geophys. Res-Space Phys. PD MAY 1 PY 1994 VL 99 IS A5 BP 8873 EP 8889 DI 10.1029/93JA03181 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NK217 UT WOS:A1994NK21700032 ER PT J AU JUANG, JN PHAN, M AF JUANG, JN PHAN, M TI LINEAR-SYSTEM IDENTIFICATION VIA BACKWARD-TIME OBSERVER MODELS SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article ID PARAMETER-IDENTIFICATION; SERIES MODELS; REDUCTION AB This paper presents an algorithm to identify a state-space model of a linear system using a backward-time approach. The procedure consists of three basic steps. First, the Markov parameters of a backward-time observer are computed from experimental input-output data. Second, the backward-time observer Markov parameters are decomposed to obtain the backward-time system Markov parameters (backward-time pulse response samples) from which a backward-time state-space model is realized using the eigensystem realization algorithm. Third, the obtained backward-time state-space model is converted to the usual forward-time representation. Stochastic properties of this approach will be discussed. Experimental results are given to illustrate when and to what extent this concept works. C1 LOCKHEED ENGN & SCI CO,HAMPTON,VA 23666. RP JUANG, JN (reprint author), NASA,LANGLEY RES CTR,SPACECRAFT DYNAM BRANCH,HAMPTON,VA 23681, USA. NR 15 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 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD MAY-JUN PY 1994 VL 17 IS 3 BP 505 EP 512 DI 10.2514/3.21227 PG 8 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA NM866 UT WOS:A1994NM86600012 ER PT J AU GILMOZZI, R PITTS, RE AF GILMOZZI, R PITTS, RE TI SOLAR MOTION-BASED METHOD OF ATTITUDE RECOVERY - APPLICATION TO INTERNATIONAL ULTRAVIOLET EXPLORER SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article ID IUE AB The International Ultraviolet Explorer is a geosynchronous orbiting telescope launched by NASA January 26, 1978, and operated jointly by NASA and the European Space Agency. The spacecraft was built with six gyroscopes to provide an inertial reference system for spacecraft attitude and control and with prime and redundant mechanical panoramic attitude sensors for coarse attitude determination. Following the failure of the fourth gyroscope in 1985, a new attitude control system was uplinked to the spacecraft using a fine sun sensor and the two remaining gyros for three-axis stabilization. By 1985 both panoramic attitude sensors had failed, and an alternate method developed for coarse attitude determination was not applicable to the newly installed control system. We present here a new method of attitude recovery that uses the relative motion of the sun with respect to the inertial reference provided by the remaining two gyros and that has been employed since 1985. This general technique should be of use to other spacecraft where weight is critical or there is a desire to avoid mechanical devices. C1 ESA,IUE OBSERV,INST SPACE TELESCOPE SCI,BALTIMORE,MD 21218. NASA,IUE OBSERV,COMP SCI CORP,LANHAM,MD 20706. RP GILMOZZI, R (reprint author), ESA,INST SPACE TELESCOPE SCI,DIV SCI PROGRAM,SCI OBSERV BRANCH,3700 SAN MARTIN DR,BALTIMORE,MD 21218, USA. NR 13 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 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD MAY-JUN PY 1994 VL 17 IS 3 BP 614 EP 618 DI 10.2514/3.21241 PG 5 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA NM866 UT WOS:A1994NM86600026 ER PT J AU CONTE, JP DURRANI, AJ SHELTON, RO AF CONTE, JP DURRANI, AJ SHELTON, RO TI SEISMIC RESPONSE MODELING OF MULTISTORY BUILDINGS USING NEURAL NETWORKS SO JOURNAL OF INTELLIGENT MATERIAL SYSTEMS AND STRUCTURES LA English DT Article ID IDENTIFICATION AB A neural network based approach to model the seismic response of multi-story frame buildings is presented. The seismic response of frames is emulated using multi-layer feedforward neural networks with a backpropagation learning algorithm. Actual earthquake accelerograms and corresponding structural response obtained from analytical models of buildings are used in training the neural networks. The application of the neural network model is demonstrated by studying one to six story high building frames subjected to seismic base excitation. Furthermore, the learning ability of the network is examined for the case of multiple inputs where lateral forces at floor levels are included simultaneously with the base excitation. The effects of the network parameters on learning and accuracy of predictions are discussed. Based on this study, it is found that appropriately configured neural network models can successfully learn and simulate the linear elastic dynamic behavior of multi-story buildings. C1 NASA,LYNDON B JOHNSON SPACE CTR,SOFTWARE TECHNOL BRANCH,HOUSTON,TX 77058. RP CONTE, JP (reprint author), RICE UNIV,DEPT CIVIL ENGN,HOUSTON,TX 77251, USA. NR 16 TC 3 Z9 3 U1 1 U2 1 PU TECHNOMIC PUBL CO INC PI LANCASTER PA 851 NEW HOLLAND AVE, BOX 3535, LANCASTER, PA 17604 SN 1045-389X J9 J INTEL MAT SYST STR JI J. Intell. Mater. Syst. Struct. PD MAY PY 1994 VL 5 IS 3 BP 392 EP 402 DI 10.1177/1045389X9400500312 PG 11 WC Materials Science, Multidisciplinary SC Materials Science GA NQ322 UT WOS:A1994NQ32200012 ER PT J AU WOLFENDEN, A RAJ, SV KONDLAPUDI, SKR AF WOLFENDEN, A RAJ, SV KONDLAPUDI, SKR TI STRAIN-AGING AND BREAKAWAY STRAIN AMPLITUDE OF DAMPING IN NIAL AND NIALZR SO JOURNAL OF MATERIALS RESEARCH LA English DT Article ID SINGLE-CRYSTALS; TEMPERATURE; ZIRCONIUM; FRACTURE; BEHAVIOR; BRITTLE; DEFECTS; METALS AB Extruded NiAl and NiAlZr alloys often show discontinuous yielding on strain aging in compression at room temperature. Two sets of experiments were conducted to understand the reasons for this yield-point behavior. First, strain-aging experiments were carried out on NiAl alloys containing 0 to 0.1 at. % Zr. The specimens were all deformed in compression at room temperature at a nominal initial strain rate of 1.1 X 10(-4) s-1, and the effect of annealing at 700 and 1200 K on the stress-strain curves and the yield strength was studied after an initial prestrain. While annealing at 700 and 1200 K consistently reduced the yield strength of both NiAl and NiAlZr, the effects were quite different. In the case of NiAl, annealing at 1200 K did not result in discontinuous yielding, whereas it generally resulted in a sharp yield point for the Zr containing alloys. Second, the PUCOT (piezoelectric ultrasonic composite oscillator technique) was used to measure the dynamic Young modulus, breakaway strain amplitude, and damping for the alloys. Only small differences were observed in the values of Young's modulus, but the breakaway strain was at least a factor of 2 to 3 lower for NiAl than for NiAlZr. The experimentally determined values of damping were used in the Granato-Lucke model to estimate the binding energy for NiAl. While the binding energy values were found to be in agreement with the calculated values of dislocation kink nucleation and migration energies in this material, to within an order of magnitude, other effects, such as dislocation pinning by quenched-in vacancies, cannot be ruled out. The observations made in this study suggest that the yield-point behavior in NiAl may be due to several factors, such as difficulties in double kink nucleation, and single kink migration, as well as dislocation-vacancy interactions; whereas, the yield-point behavior in the Zr-alloyed material is due at least in part to dislocation-solute interaction. C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP WOLFENDEN, A (reprint author), TEXAS A&M UNIV,DEPT MECH ENGN,ADV MAT LAB,COLLEGE STN,TX 77843, USA. NR 42 TC 3 Z9 3 U1 0 U2 2 PU MATERIALS RESEARCH SOCIETY PI PITTSBURGH PA 9800 MC KNIGHT ROAD SUITE 327, PITTSBURGH, PA 15237 SN 0884-2914 J9 J MATER RES JI J. Mater. Res. PD MAY PY 1994 VL 9 IS 5 BP 1166 EP 1173 DI 10.1557/JMR.1994.1166 PG 8 WC Materials Science, Multidisciplinary SC Materials Science GA NH285 UT WOS:A1994NH28500015 ER PT J AU ABRAMS, MC DAVIS, SP RAO, MLP ENGLEMAN, R AF ABRAMS, MC DAVIS, SP RAO, MLP ENGLEMAN, R TI HIGH-RESOLUTION FOURIER-TRANSFORM SPECTROSCOPY OF THE VIBRATION-ROTATION SPECTRUM OF THE OD RADICAL SO JOURNAL OF MOLECULAR SPECTROSCOPY LA English DT Article ID MOLECULAR-CONSTANTS; OH; PARAMETERS; STATES AB The infrared spectrum of the deuterated hydroxyl radical OD has been measured with a Fourier transform spectrometer between 1850 and 9000 cm-1. The source, a deuterium atom ozone diffusion flame, was designed to study the chemiluminescent excitation of the vibration-rotation energy levels of the OD radical. Twenty-one bands were observed, 6 bands in the DELTAupsilon = 1 sequence, 9 bands in the DELTAupsilon = 2 sequence, and 6 bands in the DELTAupsilon = 3 sequence. A global nonlinear least-squares fit, utilizing the unique perturber approximation, of 2112 lines to 76 molecular parameters yielded a standard deviation of 0.007 cm-1 including 35 parameters for the previously unobserved upsilon = 6-10 vibrational states. (C) 1994 Academic Press, Inc. C1 UNIV CALIF BERKELEY,DEPT PHYS,BERKELEY,CA 94720. ANDHRA UNIV,DEPT PHYS,WALTAIR 520003,INDIA. UNIV NEW MEXICO,DEPT CHEM,ALBUQUERQUE,NM 87131. RP ABRAMS, MC (reprint author), JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 20 TC 16 Z9 16 U1 0 U2 6 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 MAY PY 1994 VL 165 IS 1 BP 57 EP 74 DI 10.1006/jmsp.1994.1110 PG 18 WC Physics, Atomic, Molecular & Chemical; Spectroscopy SC Physics; Spectroscopy GA NH311 UT WOS:A1994NH31100004 ER PT J AU WEBER, M BLASS, WE HALSEY, GW HILLMAN, JJ AF WEBER, M BLASS, WE HALSEY, GW HILLMAN, JJ TI I-RESONANCE PERTURBATION OF IR INTENSITIES IN (C2H2)-C-12 NEAR 13.7-MU-M SO JOURNAL OF MOLECULAR SPECTROSCOPY LA English DT Article ID INTEGRATED INFRARED INTENSITIES; HERMAN-WALLIS FACTORS; MOLECULAR-CONSTANTS; LOW-TEMPERATURES; LINE STRENGTHS; ACETYLENE; C2H2; SPECTRUM; REGION; BANDS AB Using TDL and FT spectrometric data at 0.0005 and 0.0025 cm-1 spectral resolution, respectively, individual line intensities of the nu5 fundamental and the seven strongest hot bands, nu4+ nu5 <-- nu4 and 2nu5 <-- nu5, of (C2H2)-C-12 in the 13.7-mum region have been measured. Except for the 2nu5(2f) <-- nu5(1f) hot band, strong intensity perturbation due to l-type doubling and resonances have been quantitatively determined for all hot bands. The zeroth-order vibrational dipole moment derivative for the nu5 bending mode is identical within 10% for all bands observed. Since an extra factor of 1/2 appears in the square vibrational transition moment for the combination band, its intenSity is reduced by half and is comparable in magnitude to the 2nu5 <-- nu5 hot bands. For the nu5 fundamental a square dipole moment derivative of GAMMA(upsilon)2 = 0.09069(24)D2 has been determined. (C) 1994 Academic Press, Inc. C1 UNIV TENNESSEE,DEPT PHYS,KNOXVILLE,TN 37996. RP WEBER, M (reprint author), NASA,GODDARD SPACE FLIGHT CTR,EXTRATERR PHYS LAB,CODE 690,GREENBELT,MD 20771, USA. RI Blass, William/A-2792-2008; Weber, Mark/F-1409-2011 OI Weber, Mark/0000-0001-8217-5450 NR 53 TC 18 Z9 18 U1 1 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 MAY PY 1994 VL 165 IS 1 BP 107 EP 123 DI 10.1006/jmsp.1994.1114 PG 17 WC Physics, Atomic, Molecular & Chemical; Spectroscopy SC Physics; Spectroscopy GA NH311 UT WOS:A1994NH31100008 ER PT J AU CHIMENTO, TC DOSHAY, DG ROSS, MD AF CHIMENTO, TC DOSHAY, DG ROSS, MD TI COMPARTMENTAL MODELING OF RAT MACULAR PRIMARY AFFERENTS FROM 3-DIMENSIONAL RECONSTRUCTIONS OF TRANSMISSION ELECTRON-MICROGRAPHS OF SERIAL SECTIONS SO JOURNAL OF NEUROPHYSIOLOGY LA English DT Article ID COMPUTER GENERATED IMAGERY; GABA-LIKE IMMUNOREACTIVITY; POST-SYNAPTIC POTENTIALS; LONG-TERM POTENTIATION; DENDRITIC SPINES; HAIR-CELLS; INNERVATION PATTERNS; VESTIBULAR ENDORGANS; HIPPOCAMPAL SLICES; PYRAMIDAL CELLS AB 1. We cut serial sections through the medial part of the rat vestibular macula for transmission electron microscopic (TEM) examination, computer-assisted three-dimensional (3-D) reconstruction, and compartmental modeling. The ultrastructural research showed that many primary vestibular neurons have an unmyelinated segment, often branched, that extends between the heminode [putative site of the spike initiation zone (SIZ)] and the expanded terminal(s) (calyx, calyces). These segments, termed the neuron branches, and the calyces frequently have spinelike processes of various dimensions that morphologically are afferent, efferent, or reciprocal to other macular neural elements. The purpose of this research was to determine whether morphometric data obtained ultrastructurally were essential to compartmental models [i.e., they influenced action potential(AP) generation,latency, or amplitude] or whether afferent parts could be collapsed into more simple units without markedly affecting results. We used the compartmental modeling program NEURON for this research.old decreased AP peak latency by less than or equal to 54%. RP CHIMENTO, TC (reprint author), NASA,AMES RES CTR,CTR LIFE SCI BIOCOMPUTAT,MOFFETT FIELD,CA 94035, USA. FU NIMH NIH HHS [MH-47305-01] NR 60 TC 12 Z9 13 U1 0 U2 0 PU AMER PHYSIOLOGICAL SOC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 SN 0022-3077 J9 J NEUROPHYSIOL JI J. Neurophysiol. PD MAY PY 1994 VL 71 IS 5 BP 1883 EP 1896 PG 14 WC Neurosciences; Physiology SC Neurosciences & Neurology; Physiology GA NL773 UT WOS:A1994NL77300023 PM 7914916 ER PT J AU BARRAGY, E CAREY, GF VANDEGEIJN, R AF BARRAGY, E CAREY, GF VANDEGEIJN, R TI PERFORMANCE AND SCALABILITY OF FINITE-ELEMENT ANALYSIS FOR DISTRIBUTED PARALLEL COMPUTATION SO JOURNAL OF PARALLEL AND DISTRIBUTED COMPUTING LA English DT Article ID P-VERSION AB A two-dimensional (h, p) finite element scheme for distributed parallel computation is developed. The approach is based on an element-by-element domain decomposition and is implemented on the nCUBE2 system. Example problems are used to demonstrate performance of the algorithm for a range of (h, p) and to validate a run-time model. The run-time model is then used to examine the scaling properties of conjugate gradients and the (h, p) FEM over a range of p. (C) 1994 Academic Press, Inc. C1 UNIV TEXAS,AUSTIN,TX 78712. JET PROP LAB,PASADENA,CA 91109. NR 15 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 0743-7315 J9 J PARALLEL DISTR COM JI J. Parallel Distrib. Comput. PD MAY PY 1994 VL 21 IS 2 BP 202 EP 212 DI 10.1006/jpdc.1994.1052 PG 11 WC Computer Science, Theory & Methods SC Computer Science GA NM284 UT WOS:A1994NM28400003 ER PT J AU CHUANG, KC VANNUCCI, RD ANSARI, I CERNY, LL SCHEIMAN, DA AF CHUANG, KC VANNUCCI, RD ANSARI, I CERNY, LL SCHEIMAN, DA TI HIGH-FLOW ADDITION CURING POLYIMIDES SO JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY LA English DT Article DE ADDITION POLYIMIDES; BIPHENYLDIAMINE; BENZIDINE ID RIGID-ROD POLYIMIDE; AROMATIC POLYAMIDES AB A new series of high flow PMR-type addition curing polyimides was developed, which employed the substitution of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (BTDB) for p-phenylenediamine (p-PDA) in a PMR-II formulation. These thermoset polyimides, designated as 12F resins, were prepared from BTDB and the dimethyl ester of 4,4'-(hexafluoroisopropylidene)-diphthalic acid (HFDE) with either nadic ester (NE) or p-aminostyrene (PAS) as the endcaps for addition curing. The 12F prepolymers displayed lower melting temperatures in DSC analysis, and higher melt flow in rheological studies than the corresponding PMR-II polyimides. Long-term isothermal aging studies showed that BTDB-based 12F resins exhibited comparable thermo-oxidative stability to p-PDA based PMR-II polyimides. The noncoplanar 2- and 2'-disubstituted biphenyldiamine (BTDB) not only lowered the melt viscosities of 12F prepolymers, but also retained reasonable thermal stability of the cured resins. The 12F polyimide resin with p-aminostyrene endcaps showed the best promise for long-term, high-temperature application at 343-degrees-C (650-degrees-F). (C) 1994 John Wiley & Sons, Inc. C1 JOHNS HOPKINS UNIV,BALTIMORE,MD 21218. SYRACUSE UNIV,UTICA COLL,UTICA,NY 13502. SVERDRUP TECHNOL INC,LEWIS RES CTR GRP,BROOKPARK,OH 44142. RP CHUANG, KC (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 18 TC 15 Z9 17 U1 0 U2 3 PU JOHN WILEY & SONS INC PI NEW YORK PA 605 THIRD AVE, NEW YORK, NY 10158-0012 SN 0887-624X J9 J POLYM SCI POL CHEM JI J. Polym. Sci. Pol. Chem. PD MAY PY 1994 VL 32 IS 7 BP 1341 EP 1350 DI 10.1002/pola.1994.080320715 PG 10 WC Polymer Science SC Polymer Science GA NJ528 UT WOS:A1994NJ52800015 ER PT J AU PIERRE, C SMITH, TE MURTHY, DV AF PIERRE, C SMITH, TE MURTHY, DV TI LOCALIZATION OF AEROELASTIC MODES IN MISTUNED HIGH-ENERGY TURBINES SO JOURNAL OF PROPULSION AND POWER LA English DT Article ID BLADE ASSEMBLIES; FLUTTER; CASCADES; ROTORS AB The effects of blade mistuning on the aeroelastic vibration characteristics of high-energy turbines are investigated, using the first stage of the oxidizer turbopump in the Space Shuttle main rocket engine as an example. A modal aeroelastic analysis procedure is used in concert with a linearized unsteady aerodynamic theory that accounts for the effects of blade thickness, camber, and steady loading. High sensitivity of the dynamic characteristics of mistuned rotors is demonstrated. In particular, the aeroelastic free vibration modes become localized to a few blades, possibly leading to rogue blade failure, and the locus of the aeroelastic eigenvalues loses its regular structure when small mistuning (of the order usually present in actual rotors) is introduced. Perturbation analyses that yield physical insights into these phenomena are presented. A powerful but easily calculated stochastic sensitivity measure that allows the global prediction of mistuning effects is developed. C1 SVERDRUP TECHNOL INC,NASA,LEWIS RES CTR GRP,BROOKPARK,OH 44135. UNIV TOLEDO,NASA,LEWIS RES CTR,STRUCT DYNAM BRANCH,TOLEDO,OH 43606. RP PIERRE, C (reprint author), UNIV MICHIGAN,DEPT MECH ENGN & APPL MECH,ANN ARBOR,MI 48109, USA. NR 17 TC 8 Z9 8 U1 0 U2 2 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0748-4658 J9 J PROPUL POWER JI J. Propul. Power PD MAY-JUN PY 1994 VL 10 IS 3 BP 318 EP 328 DI 10.2514/3.23759 PG 11 WC Engineering, Aerospace SC Engineering GA NM077 UT WOS:A1994NM07700004 ER PT J AU MEHMED, O KURKOV, AP AF MEHMED, O KURKOV, AP TI EXPERIMENTAL INVESTIGATION OF COUNTER-ROTATING PROPFAN FLUTTER AT CRUISE CONDITIONS SO JOURNAL OF PROPULSION AND POWER LA English DT Article AB This article presents wind-tunnel experimental flutter results. at transonic relative flows, for a 0.62-m-diam composite propfan model. A blade row that fluttered was tested alone, and with a stable aft counter-rotating blade row. The major objectives of the experiment were to study the effect of the second blade row on the row in flutter, and to investigate the flutter. Results show that the second row had a small stabilizing effect. Two distinct flutter modes were found within the operating regime of the rotor; both apparently single-degree-of-freedom instabilities, associated respectively with the first and second natural blade modes. For both flutter modes, flutter boundary, frequency, nodal diameter. and blade displacement data are given. The blade displacement data, obtained with an optical method, gives an indication of the flutter mode shape at a span near the blade tip. RP MEHMED, O (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 15 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 MAY-JUN PY 1994 VL 10 IS 3 BP 343 EP 347 DI 10.2514/3.23762 PG 5 WC Engineering, Aerospace SC Engineering GA NM077 UT WOS:A1994NM07700007 ER PT J AU LEWICKI, DG HANDSCHUH, RF HENRY, ZS LITVIN, FL AF LEWICKI, DG HANDSCHUH, RF HENRY, ZS LITVIN, FL TI LOW-NOISE, HIGH-STRENGTH, SPIRAL-BEVEL GEARS FOR HELICOPTER TRANSMISSIONS SO JOURNAL OF PROPULSION AND POWER LA English DT Article AB Advanced-design spiral-bevel gears were tested in an OH-58D helicopter transmission using the NASA 500-hp Helicopter Transmission Test Stand. Three different gear designs tested included 1) the current design of the OH-58D transmission; 2) a higher-strength design the same as the current but with a full fillet radius to reduce gear tooth bending stress (and thus, weight); and 3) a lower-noise design the same as the high-strength but with modified tooth geometry to reduce transmission error and noise. Noise, vibration, and tooth strain tests were performed and significant gear stress and noise reductions were achieved. C1 BELL HELICOPTER TEXTRON INC,DR SYST DES GRP,FT WORTH,TX 76101. UNIV ILLINOIS,DEPT MECH ENGN,CHICAGO,IL 60680. RP LEWICKI, DG (reprint author), NASA,LEWIS RES CTR,USA RES LAB,VEHICLE PROPULS DIRECTORATE,CLEVELAND,OH 44135, USA. NR 14 TC 11 Z9 11 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0748-4658 J9 J PROPUL POWER JI J. Propul. Power PD MAY-JUN PY 1994 VL 10 IS 3 BP 356 EP 361 DI 10.2514/3.23764 PG 6 WC Engineering, Aerospace SC Engineering GA NM077 UT WOS:A1994NM07700009 ER PT J AU MA, Q TIPPING, RH AF MA, Q TIPPING, RH TI THE DETAILED BALANCE REQUIREMENT AND GENERAL EMPIRICAL FORMALISMS FOR CONTINUUM ABSORPTION SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article ID LINE-SHAPE THEORY; WATER CONTINUUM; STATISTICAL-THEORY; ROTATIONAL BANDS; SPECTRAL REGION; VAPOR AB Two general empirical formalisms are presented for the spectral density which take into account the deviations from the Lorentz line shape in the wing regions of resonance lines. These formalisms satisfy the detailed balance requirement. Empirical line shape functions, which are essential to provide the continuum absorption at different temperatures in various frequency regions for atmospheric transmission codes, can be obtained by fitting to experimental data. C1 INST SPACE STUDIES,GODDARD SPACE FLIGHT CTR,NEW YORK,NY 10025. UNIV ALABAMA,DEPT PHYS,TUSCALOOSA,AL 35487. RP MA, Q (reprint author), COLUMBIA UNIV,DEPT APPL PHYS,NEW YORK,NY 10025, USA. NR 24 TC 9 Z9 9 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0022-4073 J9 J QUANT SPECTROSC RA JI J. Quant. Spectrosc. Radiat. Transf. PD MAY PY 1994 VL 51 IS 5 BP 751 EP 757 DI 10.1016/0022-4073(94)90129-5 PG 7 WC Optics; Spectroscopy SC Optics; Spectroscopy GA NQ273 UT WOS:A1994NQ27300008 ER PT J AU MISHCHENKO, MI TRAVIS, LD AF MISHCHENKO, MI TRAVIS, LD TI LIGHT-SCATTERING BY POLYDISPERSE ROTATIONALLY SYMMETRICAL NONSPHERICAL PARTICLES - LINEAR-POLARIZATION SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article ID SIZE SHAPE DISTRIBUTIONS; SPHEROIDAL PARTICLES; OPTICAL-PROPERTIES; PLANETARY-ATMOSPHERES; RADIATIVE-TRANSFER; SINGLE-SCATTERING; AEROSOLS; GRAINS; BACKSCATTERING; WAVELENGTH AB Since most solid particles in the Earth and planetary atmospheres have irregular shapes, quantifying the effects of particle nonsphericity on the results of remote sensing of the atmosphere is an important problem. In this paper, we perform a general theoretical survey of linear polarization of light scattered by polydisperse, randomly oriented, rotationally symmetric particles of size comparable to the wavelength of radiation. Our paper deals with polydispersions of nonspherical particles because (1) averaging light-scattering characteristics over sizes provides more realistic modeling of natural particle ensembles and (2) comparisons of scattering properties of particles of a single size are usually meaningless because of the complicated interference structure and high-frequency ripple of monodisperse scattering patterns. In our computations, we use the T-matrix approach, as extended recently to randomly oriented particles by Mishchenko V. Opt. Soc. Amer. A 8, 871 (1991)]. Following Hansen and Travis [Space Sic. Rev. 16, 527 (1974)], we assume that the scattering properties of polydisperse particles depend primarily on only the effective size parameter and effective variance of the size distribution, the particular shape of the distribution being of minor importance. Therefore, to describe the dispersion of particle sizes in the ensemble, we employ a convenient power law distribution of particle equivalent-sphere size parameters. Size-averaged light-scattering characteristics are calculated by numerically integrating monodisperse quantities using a Gaussian quadrature formula. The results of extensive numerical calculations for particles of different shape and refractive index are presented in the form of color contour diagrams of linear polarization as a function of scattering angle and effective equivalent-sphere size parameter. The influence of particle size distribution, shape, and refractive index on the polarization patterns is examined in detail and implications for polarimetric remote sensing of nonspherical aerosols are discussed. The diagrams displayed include calculations for over 150,000 different monodisperse particles in random orientation with equivalent-sphere size parameters up to 30 and may be used to interpret results of laboratory measurements and remote observations of light scattering by small particles. C1 HUGHES STX CORP,NEW YORK,NY 10025. RP MISHCHENKO, MI (reprint author), NASA,GODDARD INST SPACE STUDIES,2880 BROADWAY,NEW YORK,NY 10025, USA. RI Mishchenko, Michael/D-4426-2012 NR 66 TC 64 Z9 64 U1 0 U2 3 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0022-4073 J9 J QUANT SPECTROSC RA JI J. Quant. Spectrosc. Radiat. Transf. PD MAY PY 1994 VL 51 IS 5 BP 759 EP 778 DI 10.1016/0022-4073(94)90130-9 PG 20 WC Optics; Spectroscopy SC Optics; Spectroscopy GA NQ273 UT WOS:A1994NQ27300009 ER PT J AU KERSLAKE, TW IBRAHIM, MB AF KERSLAKE, TW IBRAHIM, MB TI 2-DIMENSIONAL MODEL OF A SPACE STATION FREEDOM THERMAL-ENERGY STORAGE CANISTER SO JOURNAL OF SOLAR ENERGY ENGINEERING-TRANSACTIONS OF THE ASME LA English DT Article AB The Solar Dynamic Power Module being developed for Space Station Freedom uses a eutectic mixture of LiF-CaF2 phase-change salt contained in toroidal canisters for thermal energy storage. This paper presents results from heat transfer analyses of the phase-change salt containment canister. A two-dimensional, axisymmetric finite difference computer program which models the canister walls, salt, void, and heat engine working fluid coolant was developed. Analyses included effects of conduction in canister walls and solid salt, conduction and free con vection in liquid salt, conduction and radiation across salt vapor-filled void regions, and forced convection in the heat engine working fluid. Void shape and location were prescribed based on engineering judgment. The salt phase-change process was modeled using the enthalpy method. Discussion of results focuses on the role of free convection in the liquid salt on canister heat transfer performance. This role is shown to be important for interpreting the relationship between ground-based canister performance (in 1-g) and expected on-orbit performance (in micro-g). Attention is also focused on the influence of void heat transfer on canister wall temperature distributions. The large thermal resistance of void regions is shown to accentaute canister hot spots and temperature gradients. C1 CLEVELAND STATE UNIV,DEPT MECH ENGN,CLEVELAND,OH 44115. RP KERSLAKE, TW (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 7 TC 4 Z9 5 U1 0 U2 1 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 SN 0199-6231 J9 J SOL ENERG-T ASME JI J. Sol. Energy Eng. Trans.-ASME PD MAY PY 1994 VL 116 IS 2 BP 114 EP 121 DI 10.1115/1.2930498 PG 8 WC Energy & Fuels; Engineering, Mechanical SC Energy & Fuels; Engineering GA NM847 UT WOS:A1994NM84700008 ER PT J AU HAMILTON, HH GREENE, FA AF HAMILTON, HH GREENE, FA TI APPROXIMATE METHOD FOR CALCULATING HEATING RATES ON 3-DIMENSIONAL VEHICLES SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB An approximate method for calculating heating rates on three-dimensional vehicles at angle of attack is presented. The method is based on the axisymmetric analog for three-dimensional boundary layers and uses a generalized body-fitted coordinate system. Edge conditions for the boundary-layer solution are obtained from an inviscid flowfield solution, and because of the coordinate system used, the method is applicable to any blunt body geometry for which a inviscid flowfield solution can be obtained. The method is validated by comparing with experimental heating data and with thin-layer Navier-Stokes calculations on the Shuttle Orbiter at both wind-tunnel and flight conditions and with thin-layer Navier-Stokes calculations on the HL-20 at wind-tunnel conditions. C1 N CAROLINA STATE UNIV,RALEIGH,NC 27695. RP HAMILTON, HH (reprint author), NASA,LANGLEY RES CTR,HAMPTON,VA 23681, USA. NR 16 TC 17 Z9 21 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 MAY-JUN PY 1994 VL 31 IS 3 BP 345 EP 354 DI 10.2514/3.26446 PG 10 WC Engineering, Aerospace SC Engineering GA NU611 UT WOS:A1994NU61100001 ER PT J AU WEILMUENSTER, KJ GNOFFO, PA GREENE, FA AF WEILMUENSTER, KJ GNOFFO, PA GREENE, FA TI NAVIER-STOKES SIMULATIONS OF ORBITER AERODYNAMIC CHARACTERISTICS INCLUDING PITCH TRIM AND BODYFLAP SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article ID SCHEMES AB An analysis of the longitudinal aerodynamics of the Shuttle Orbiter in the hypersonic flight regime is made through the use of computational fluid dynamics. Particular attention is given to establishing the cause of the ''pitching moment anomaly,'' which occurred on the Orbiter's first flight, and to computing the aerodynamics of a complete Orbiter configuration at night conditions. Data from ground-based facilities as well as Orbiter flight data are used to validate the computed results. Analysis shows that the pitching moment anomaly is a real-gas chemistry effect that was not simulated in ground-based. facilities, which used air as a test gas. Computed flight aerodynamics for the Orbiter are within 5 % of the measured flight values and trim bodyflap deflections are predicted to within 10%. RP WEILMUENSTER, KJ (reprint author), NASA,LANGLEY RES CTR,HAMPTON,VA 23681, USA. NR 21 TC 10 Z9 11 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 MAY-JUN PY 1994 VL 31 IS 3 BP 355 EP 366 DI 10.2514/3.26447 PG 12 WC Engineering, Aerospace SC Engineering GA NU611 UT WOS:A1994NU61100002 ER PT J AU GNOFFO, PA WEILMUENSTER, KJ AF GNOFFO, PA WEILMUENSTER, KJ TI MULTIBLOCK ANALYSIS FOR SHUTTLE ORBITER REENTRY HEATING FROM MACH 24 TO MACH 12 SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB A multiblock, laminar heating analysis for the Shuttle Orbiter at three trajectory points ranging from Mach 24.3 to Mach 12.86 on re-entry is described. The analysis is performed using the Langley Aerothermodynamic Upwind Relaxation Algorithm with a seven species chemical nonequilibrium model. A finite-catalytic-wall model appropriate for shuttle tiles at a radiative equilibrium wall temperature is applied. Computed heating levels are generally in good agreement with the flight data, although a few rather large discrepancies remain unexplained. The multiblock relaxation strategy partitions the flowfield into manageable blocks requiring a fraction of the computational resources (time and memory) required by a full domain approach. In fact, the computational cost for a solution at even a single trajectory point would be prohibitively expensive at the given resolution without the multiblock approach. Converged blocks are reassembled to enable a fully coupled converged solution over the entire vehicle, starting from a nearly converged initial condition. C1 LOCKHEED ENGN & SCI CO,HAMPTON,VA 23665. RP GNOFFO, PA (reprint author), NASA,LANGLEY RES CTR,HAMPTON,VA 23681, USA. NR 24 TC 22 Z9 22 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 MAY-JUN PY 1994 VL 31 IS 3 BP 367 EP 377 DI 10.2514/3.26448 PG 11 WC Engineering, Aerospace SC Engineering GA NU611 UT WOS:A1994NU61100003 ER PT J AU STANLEY, DO ENGELUND, WC LEPSCH, R AF STANLEY, DO ENGELUND, WC LEPSCH, R TI PROPULSION REQUIREMENTS FOR REUSABLE SINGLE-STAGE-TO-ORBIT ROCKET VEHICLES SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article ID LAUNCH AB The conceptual design of a single-stage-to-orbit (SSTO) vehicle using a wide variety of evolutionary technologies has recently been completed as a part of NASA's Advanced Manned Launch System (AMLS) study. The employment of new propulsion system technologies is critical to the design of a reasonably sized, operationally efficient SSTO vehicle. This paper presents the propulsion system requirements identified for this near-term AMLS SSTO vehicle. Sensitivities of the vehicle to changes in specific impulse and sea-level thrust-to-weight ratio are examined. The results of a variety of vehicle/propulsion system trades performed on the near-term AMLS SSTO vehicle are also presented. RP STANLEY, DO (reprint author), NASA,LANGLEY RES CTR,DIV SPACE SYST,HAMPTON,VA 23681, USA. NR 27 TC 2 Z9 2 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD MAY-JUN PY 1994 VL 31 IS 3 BP 414 EP 420 DI 10.2514/3.26454 PG 7 WC Engineering, Aerospace SC Engineering GA NU611 UT WOS:A1994NU61100009 ER PT J AU HENINE, WD TAUBER, ME AF HENINE, WD TAUBER, ME TI TRAJECTORY-BASED HEATING ANALYSIS FOR THE EUROPEAN-SPACE-AGENCY ROSETTA EARTH RETURN VEHICLE SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB A coupled, trajectory-based flowfield and material thermal-response analysis is presented for the European Space Agency proposed Rosetta comet nucleus sample return vehicle. The probe returns to Earth along a hyperbolic trajectory with an entry velocity of 16.5 km/s and requires an ablative heal shield on the forebody. Combined radiative and convective ablating flowfield analyses were performed for the significant heating portion of the shallow ballistic entry trajectory. Both quasisteady ablation and fully transient analyses were performed for a heal shield composed of carbon-phenolic ablative material. Quasisteady analysis was performed using the two-dimensional axisymmetric codes RASLE and BLIMPK. Transient computational results were obtained from the one-dimensional ablation/conduction code CMA. Results are presented for heating, temperature, and ablation rate distributions over the probe forebody for various trajectory points. Comparison of transient and quasisteady results indicates that, for the heating pulse encountered by this probe, the quasisteady approach is conservative from the standpoint of predicted surface recession. RP HENINE, WD (reprint author), NASA,AMES RES CTR,THERMAL PROTECT MAT BRANCH,MOFFETT FIELD,CA 94035, USA. NR 11 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 MAY-JUN PY 1994 VL 31 IS 3 BP 421 EP 428 PG 8 WC Engineering, Aerospace SC Engineering GA NU611 UT WOS:A1994NU61100010 ER PT J AU PALASZEWSKI, B AF PALASZEWSKI, B TI LUNAR MISSIONS USING ADVANCED CHEMICAL PROPULSION - SYSTEM-DESIGN ISSUES SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB To provide the transportation of lunar base elements to the Moon, large high-energy propulsion systems will be required. Advanced propulsion systems for lunar missions can provide significant launch mass reductions and payload increases. These mass reductions and added payload masses can be translated into significant launch cost savings for the lunar base missions. In this paper, the masses in low Earth orbit (LEO) were compared for several propulsion systems: nitrogen tetroxide/monomethyl hydrazine (NTO/MMH), oxygen/methane (O2/CH4), oxygen/hydrogen (O2/H-2), and metallized O2/H-2/Al propellants. Also, the payload mass increases enabled with O2/H-2 and O2/H-2/Al systems were addressed. In addition, many system design issues involving the engine thrust levels, engine commonality between the transfer vehicle and the excursion vehicle, and the number of launches to place the lunar mission vehicles into LEO will be discussed. Analyses of small lunar missions launched from a single STS-C night are also presented. RP PALASZEWSKI, B (reprint author), NASA,LEWIS RES CTR,DIV SPACE PROPULS TECHNOL,LAUNCH VEHICLE PROPULS BRANCH,CLEVELAND,OH 44135, USA. NR 22 TC 8 Z9 8 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD MAY-JUN PY 1994 VL 31 IS 3 BP 458 EP 465 DI 10.2514/3.26461 PG 8 WC Engineering, Aerospace SC Engineering GA NU611 UT WOS:A1994NU61100016 ER PT J AU PAI, SS CHAMIS, CC AF PAI, SS CHAMIS, CC TI PROBABILISTIC PROGRESSIVE BUCKLING OF TRUSSES SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB A three-bay, space, cantilever truss is probabilistically evaluated to describe progressive buckling and truss collapse in view of the numerous uncertainties associated with the structural, material, and load variables that describe the truss. Initially, the truss is deterministically analyzed for member forces, and members in which the axial force exceeds the Euler buckling load are identified. These members are then discretized with several intermediate nodes, and a probabilistic buckling analysis is performed on the truss to obtain its probabilistic buckling loads and the respective mode shapes. Furthermore, sensitivities associated with the uncertainties in the primitive variables are investigated, margin of safety values for the truss are determined, and truss end node displacements are noted. These steps are repeated by sequentially removing buckled members until onset of truss collapse is reached. Results show that this procedure yields an optimum truss configuration for a given loading and for a specified reliability. RP PAI, SS (reprint author), NASA,LEWIS RES CTR,DIV STRUCT,STRUCT MECH BRANCH,CLEVELAND,OH 44135, USA. NR 9 TC 2 Z9 2 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD MAY-JUN PY 1994 VL 31 IS 3 BP 466 EP 474 DI 10.2514/3.26462 PG 9 WC Engineering, Aerospace SC Engineering GA NU611 UT WOS:A1994NU61100017 ER PT J AU KOONTZ, S KING, G DUNNET, A KIRKENDAHL, T LINTON, R VAUGHN, J AF KOONTZ, S KING, G DUNNET, A KIRKENDAHL, T LINTON, R VAUGHN, J TI INTELSAT SOLAR-ARRAY COUPON ATOMIC OXYGEN FLIGHT EXPERIMENT SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article ID SPACE STATION AB A Hughes communications satellite (INTELSAT series) belonging to the INTELSAT Organization was marooned in low-Earth orbit (LEO) on March 14, 1990, following failure of the Titan launch vehicle third stage to separate properly. The satellite, INTELSAT VI, was designed for service in geosynchronous orbit and contains several materials that are potentially susceptible to attack by atomic oxygen. Analysis showed that direct exposure of the silver interconnects in the satellite photovoltaic array to atomic oxygen in LEO was the key materials issue. Available data on atomic oxygen degradation of silver are limited and show high variance, so solar array configurations of the INTELSAT VI type and individual interconnects were tested in ground-based facilities and during STS-41 (Space Shuttle Discovery, October 1990) as part of the ISAC flight experiment. Several materials for which little or no flight data exist were also tested for atomic oxygen reactivity. Dry lubricants, elastomers, and polymeric and inorganic materials were exposed to an oxygen atom fluence of 1.1 x 10(20) atoms cm2. Many of the samples were selected to support Space Station Freedom design and decision making. This paper provides an overview of the ISAC flight experiment and a brief summary of results. In addition to new data on materials not before flown, ISAC provided data supporting the decision to rescue INTELSAT VI, which was successfully undertaken in May 1992. C1 INT TELECOMMUN SATELLITE ORG,WASHINGTON,DC 20006. COMMUN SATELLITE CORP,MICROELECTR LAB,CLARKSBURG,MD. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. RP KOONTZ, S (reprint author), NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058, USA. NR 15 TC 13 Z9 13 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 MAY-JUN PY 1994 VL 31 IS 3 BP 475 EP 481 DI 10.2514/3.26463 PG 7 WC Engineering, Aerospace SC Engineering GA NU611 UT WOS:A1994NU61100018 ER PT J AU MITCHELTREE, RA AF MITCHELTREE, RA TI AEROTHERMODYNAMIC METHODS FOR A MARS ENVIRONMENTAL SURVEY MARS ENTRY SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB Computational fluid dynamics models for the thermodynamics and transport properties used in an equilibrium version of the Langley aerothermodynamics upwind relaxation algorithm (LAURA) for Mars atmospheric entries are described. In addition, the physical models used in a nonequilibrium version of LAURA for Mars-entry flows are described. Uncertainties exist in defining constants used in the transport properties for the equilibrium model and in many of the physical models for the nonequilibrium version. Solutions from the two codes using the best available constants are examined at the Mars-entry conditions characteristic of the Mars environmental survey mission. While the flowfields are near thermal equilibrium, chemical nonequilibrium effects are present in the entry cases examined. Convective heating at the stagnation point for these flows (assuming fully catalytic wall boundary conditions) is approximately 100 W/cm2. Radiative heating is negligible. RP MITCHELTREE, RA (reprint author), NASA,LANGLEY RES CTR,DIV SPACE SYST,AEROTHERMODYNAM BRANCH,MS 366,HAMPTON,VA 23681, USA. NR 23 TC 7 Z9 7 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 MAY-JUN PY 1994 VL 31 IS 3 BP 516 EP 523 DI 10.2514/3.26469 PG 8 WC Engineering, Aerospace SC Engineering GA NU611 UT WOS:A1994NU61100024 ER PT J AU HILLARD, GB AF HILLARD, GB TI PLASMA CHAMBER TESTING OF ADVANCED PHOTOVOLTAIC SOLAR-ARRAY COUPONS SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Note RP HILLARD, GB (reprint author), NASA,LEWIS RES CTR,SPACE ENVIRONM EFFECTS BRANCH,CLEVELAND,OH 44135, USA. NR 5 TC 0 Z9 0 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD MAY-JUN PY 1994 VL 31 IS 3 BP 530 EP 532 DI 10.2514/3.26473 PG 3 WC Engineering, Aerospace SC Engineering GA NU611 UT WOS:A1994NU61100028 ER PT J AU WORONOWICZ, MS RAULT, DFG AF WORONOWICZ, MS RAULT, DFG TI CERCIGNANI-LAMPIS-LORD GAS-SURFACE INTERACTION-MODEL - COMPARISONS BETWEEN THEORY AND SIMULATION SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Note C1 NASA,LANGLEY RES CTR,DIV SPACE SYST,AEROTHERMODYNAM BRANCH,HAMPTON,VA 23681. RP WORONOWICZ, MS (reprint author), VIGYAN INC,HAMPTON,VA 23666, USA. NR 10 TC 12 Z9 12 U1 2 U2 4 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD MAY-JUN PY 1994 VL 31 IS 3 BP 532 EP 534 DI 10.2514/3.26474 PG 3 WC Engineering, Aerospace SC Engineering GA NU611 UT WOS:A1994NU61100029 ER PT J AU MARSHALL, JA LUTHCKE, SB AF MARSHALL, JA LUTHCKE, SB TI MODELING RADIATION FORCES ACTING ON TOPEX POSEIDON FOR PRECISION ORBIT DETERMINATION (VOL 31, PG 99, 1994) SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Correction, Addition C1 HUGHES STX,LANHAM,MD 20706. RP MARSHALL, JA (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. RI Luthcke, Scott/D-6283-2012 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 MAY-JUN PY 1994 VL 31 IS 3 BP 535 EP 536 DI 10.2514/3.55671 PG 2 WC Engineering, Aerospace SC Engineering GA NU611 UT WOS:A1994NU61100030 ER PT J AU WHEELER, RM MACKOWIAK, CL SAGER, JC YORIO, NC KNOTT, WM BERRY, WL AF WHEELER, RM MACKOWIAK, CL SAGER, JC YORIO, NC KNOTT, WM BERRY, WL TI GROWTH AND GAS-EXCHANGE BY LETTUCE STANDS IN A CLOSED, CONTROLLED ENVIRONMENT SO JOURNAL OF THE AMERICAN SOCIETY FOR HORTICULTURAL SCIENCE LA English DT Article DE LACTUCA-SATIVA; CELSS; CONTROLLED ECOLOGICAL LIFE SUPPORT SYSTEM; EVAPOTRANSPIRATION; PHOTOSYNTHESIS; RESPIRATION ID HIGH-PRESSURE SODIUM; GRAND-RAPIDS LETTUCE; PLANT-GROWTH; LAMPS AB Two studies were conducted in which 'Waldmann's Green' lettuce (Lactuca sativa L.) was grown hydroponically from seed to harvest in a large (20-m2), atmospherically closed growth chamber for the National Aeronautics and Space Administration's controlled ecological life support system (CELSS) program. The first study used metal-halide (MH) lamps [280 mumol.M-2-S-1 photosynthetic photon flux (PPF)], whereas the second used high-pressure sodium (HPS) lamps (293 mumol.m-2.s-1). Both studies used a 16-hour photoperiod, a constant air temperature (22 to 23C), and 1000 mumol.mol-1 CO2 during the light period. In each study, canopy photosynthesis and evapotranspiration (ET) rates were highly correlated to canopy cover, with absolute rates peaking at harvest (28 days after planting) at 17 mumol CO2/M2 per sec and 4 liters.m-2.day-1, respectively. When normalized for actual canopy cover, photosynthesis and ET rates per unit canopy area decreased with age (between 15 and 28 days after planting). Canopy cover increased earlier during the study with HPS lamps, and final shoot yields averaged 183 g fresh mass (FM)/plant and 8.8 g dry mass (DM)/plant. Shoot yields in the first study with MH lamps averaged 129 g FM/plant and 6.8 g DM/plant. Analysis of leaf tissue showed that ash levels from both studies averaged 22% and K levels ranged from 15% to 17% of tissue DM. Results suggest that lettuce should be easily adaptable to a CELSS with moderate lighting and that plant spacing or transplant schemes are needed to maximize canopy light interception and sustain efficient CO2 removal and water production. C1 UNIV CALIF LOS ANGELES,BIOMED & ENVIRONM SCI LAB,LOS ANGELES,CA 90024. RP WHEELER, RM (reprint author), NATL AERONAUT & SPACE ADM BIOMED OPERAT & RES OFF,KENNEDY SPACE CTR,FL 32899, USA. NR 24 TC 34 Z9 34 U1 2 U2 7 PU AMER SOC HORTICULTURAL SCIENCE PI ALEXANDRIA PA 701 NORTH SAINT ASAPH STREET, ALEXANDRIA, VA 22314-1998 SN 0003-1062 J9 J AM SOC HORTIC SCI JI J. Am. Soc. Hortic. Sci. PD MAY PY 1994 VL 119 IS 3 BP 610 EP 615 PG 6 WC Horticulture SC Agriculture GA NN490 UT WOS:A1994NN49000041 PM 11538197 ER PT J AU LAU, KM SHEU, PJ KANG, IS AF LAU, KM SHEU, PJ KANG, IS TI MULTISCALE LOW-FREQUENCY CIRCULATION MODES IN THE GLOBAL ATMOSPHERE SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID OUTGOING LONGWAVE RADIATION; 40-50 DAY OSCILLATION; NORTHERN-HEMISPHERE WINTER; INTRASEASONAL TIME SCALES; TROPICAL CONVECTION; TELECONNECTIONS; PATTERNS; ANOMALIES; DYNAMICS; FLUCTUATIONS AB In this paper, fundamental multiscale circulation modes in the global atmosphere are identified with the objective of providing better understanding of atmospheric low-frequency variabilities over a wide range of spatial and temporal scales. With the use of a combination of rotated principal component technique, singular spectrum analysis, and phase space portraits, three categories of basic multiscale modes in the atmosphere are found. The first is the interannual mode (IAM), which is dominated by time scales longer than a year and can be attributed to heating and circulation anomalies associated with the coupled tropical ocean-atmosphere, in particular the El Nino-Southern Oscillation. The second is a set of tropical intraseasonal modes consisting of three separate multiscale patterns (ISO-1,-2,-3) related to tropical heating that can be identified with the different phases of the Madden-Julian Oscillation (MJO), including its teleconnection to the extratropics. The ISO spatial and temporal patterns suggest that the extratropical wave train in the North Pacific and North America is related to heating over the Maritime Continent and that the evolution of the MJO around the equator may require forcing from the extratropics spawning convection over the Indian Ocean. The third category represents extratropical intraseasonal oscillations arising from internal dynamics of the basic-state circulation. In the Northern Hemisphere, there are two distinct circulation modes with multiple frequencies in this category: the Pacific/North America (PNA) and the North Atlantic/Eurasia (NAE). In the Southern Hemisphere, two phase-locked modes (PSA-1 and PSA-2) are found depicting an eastward propagating wave train from eastern Australia, via the Pacific South America to the South Atlantic. The extratropical modes exhibit temporal characteristics such as phase locking and harmonic oscillations possibly associated with quadratically nonlinear dynamical systems. Additionally, the observed monthly and seasonal anomalies arise from a complex interplay of the various multiscale low-frequency modes. The relative dominance of the different modes varies widely from month to month and from year to year. On the monthly time scale, while one or two mechanisms may dominate in one year, no single mechanism seems to dominate for all years. There are indications that when the IAM, that is, ENSO heating patterns are strong, the extratropical modes may be suppressed and vice versa. For the seasonal mean, the interannual mode tends to dominate and the contribution from the PNA remains quite significant. C1 APPL RES CORP,LANDOVER,MD. SEOUL NATL UNIV,DEPT ATMOSPHER SCI,SEOUL 151,SOUTH KOREA. RP LAU, KM (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ATMOSPHERES LAB,CODE 913,GREENBELT,MD 20771, USA. RI Lau, William /E-1510-2012; 안, 민섭/D-9972-2015 OI Lau, William /0000-0002-3587-3691; NR 42 TC 53 Z9 55 U1 0 U2 8 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 MAY 1 PY 1994 VL 51 IS 9 BP 1169 EP 1193 DI 10.1175/1520-0469(1994)051<1169:MLFCMI>2.0.CO;2 PG 25 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA NJ978 UT WOS:A1994NJ97800003 ER PT J AU KANG, IS LAU, KM AF KANG, IS LAU, KM TI PRINCIPAL MODES OF ATMOSPHERIC CIRCULATION ANOMALIES ASSOCIATED WITH GLOBAL ANGULAR-MOMENTUM FLUCTUATIONS SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID SOUTHERN OSCILLATION; EL-NINO; LENGTH; SCALES; EARTH AB This paper provides a description of the variability of global atmospheric angular momentum (GAM) and its relationship with principal modes of three-dimensional atmospheric circulation anomalies. The data used are 5-day mean global wind fields from the European Centre for Medium-Range Weather Forecasts initialized dataset for 1980-1989. Significant seasonal variation of GAM is observed with maxima in April and November and a minimum during late July. The amplitude of the annual cycle is largest in the upper troposphere and decreases toward the surface. Although the lower tropospheric contribution to the total angular momentum is relatively small, its annual cycle is out of phase with those of the upper atmosphere and GAM. Also identified is a distinct semiannual component, with double peaks appearing in April and November. This signal is most noticeable in the upper troposphere above the 300-mb level. The principal modes of zonal-mean angular momentum and meridional circulation anomalies and their coupled modes are obtained by using empirical orthogonal function analysis and singular value decomposition. It is shown that the leading modes of the angular momentum and meridional circulation are coupled with each other and are responsible for much of the variability in GAM. The coupled modes represent fluctuations of upper-level subtropical zonal flow, which are linked to the modulation of Hadley circulation intensity in both hemispheres. It is found that GAM is highly correlated with the first eigenvector of upper-level stream function anomalies, which consists of a superrotational flow in the tropics and subtropics, except over the central Pacific where a ''blocked'' flow with two subtropical anticyclonic circulation cells straddling the equator is found. Much of the blocked flow is due to the establishment of dipole anomalies in the velocity potential with centers over the central Pacific and the Maritime Continent on the interannual time scale. On the intraseasonal time scale, GAM fluctuation is dominated by superrotational flow in the tropics, with the blocked flow present to a much lesser extent. The associated velocity potential anomaly has a weak dipole structure with centers over the Indian Ocean and the eastern Pacific. The implications of the above results on the total angular momentum balance of the earth-atmosphere system are also discussed. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP KANG, IS (reprint author), SEOUL NATL UNIV,DEPT ATMOSPHER SCI,SEOUL 151,SOUTH KOREA. RI Lau, William /E-1510-2012; 안, 민섭/D-9972-2015 OI Lau, William /0000-0002-3587-3691; NR 27 TC 31 Z9 32 U1 0 U2 0 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0022-4928 J9 J ATMOS SCI JI J. Atmos. Sci. PD MAY 1 PY 1994 VL 51 IS 9 BP 1194 EP 1205 DI 10.1175/1520-0469(1994)051<1194:PMOACA>2.0.CO;2 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA NJ978 UT WOS:A1994NJ97800004 ER PT J AU JAWORSKE, DA DEGROH, KK PODOJIL, GM MCCOLLUM, TA ANZIC, J AF JAWORSKE, DA DEGROH, KK PODOJIL, GM MCCOLLUM, TA ANZIC, J TI LEVELING COATINGS FOR REDUCING ATOMIC OXYGEN DEFECT DENSITY IN GRAPHITE FIBER-EPOXY COMPOSITES SO JOURNAL OF THE IES LA English DT Article DE ATOMIC OXYGEN; UNDERCUTTING; LEVELING COATINGS; PROTECTIVE COATINGS; COMPOSITES AB Pinholes or other defect sites in a protective oxide coating provide pathways for atomic oxygen in low-Earth orbit to reach underlying material. One concept for enhancing the lifefime of materials in low-Earth orbit is to apply a leveling coating to the material prior to applying any reflective and protective coatings. Using a surface-tension-leveling coating concept, a low-viscosity epoxy was applied to the surface of several composite coupons. A protective layer of 1000 angstrom of SiO2 was deposited on top of the leveling coating, and the coupons were exposed to an atomic oxygen environment in a plasma asher. Pinhole populations per unit area were estimated by counting the number of undercut sites observed by scanning electron microscopy. Defect density values of 180,000 defects/cm2 were reduced to about 1000 defects/cm2 as a result of the applied leveling coating. These improvements occur at a mass penalty of about 2.5 mg/cm2. RP JAWORSKE, DA (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 0 TC 2 Z9 2 U1 0 U2 2 PU INST ENVIRONMENTAL SCI PI MT PROSPECT PA 940 E NORTHWEST HIGHWAY, MT PROSPECT, IL 60056 SN 1052-2883 J9 J IES JI J. IES PD MAY-JUN PY 1994 VL 37 IS 3 BP 26 EP 31 PG 6 WC Engineering, Environmental; Environmental Sciences; Instruments & Instrumentation SC Engineering; Environmental Sciences & Ecology; Instruments & Instrumentation GA NV791 UT WOS:A1994NV79100003 ER PT J AU DOWNIE, JD WALKUP, JF AF DOWNIE, JD WALKUP, JF TI OPTIMAL CORRELATION FILTERS FOR IMAGES WITH SIGNAL-DEPENDENT NOISE SO JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION LA English DT Article ID SPECKLE AB We address the design of optimal correlation filters for pattern detection and recognition in the presence of signal-dependent image noise sources. The particular examples considered are film-grain noise and speckle. Two basic approaches are investigated: (1) deriving the optimal matched filters for the signal-dependent noise models and comparing their performances with those derived for traditional signal-independent noise models and (2) first nonlinearly transforming the signal-dependent noise to signal-independent noise followed by the use of a classical filter matched to the transformed signal. We present both theoretical and computer simulation results that demonstrate the generally superior performance of the second approach in terms of the correlation peak signal-to-noise ratio. C1 TEXAS TECH UNIV,DEPT ELECT ENGN,LUBBOCK,TX 79409. RP DOWNIE, JD (reprint author), NASA,AMES RES CTR,MS 269-3,MOFFETT FIELD,CA 94035, USA. NR 23 TC 21 Z9 21 U1 0 U2 0 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 SN 0740-3232 J9 J OPT SOC AM A JI J. Opt. Soc. Am. A-Opt. Image Sci. Vis. PD MAY PY 1994 VL 11 IS 5 BP 1599 EP 1609 DI 10.1364/JOSAA.11.001599 PG 11 WC Optics SC Optics GA NK239 UT WOS:A1994NK23900006 ER PT J AU ANDRIENKO, YA DUBOVIKOV, MS AF ANDRIENKO, YA DUBOVIKOV, MS TI OPTICAL TOMOGRAPHY OF TENSOR-FIELDS - THE GENERAL-CASE SO JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION LA English DT Article ID KERR EFFECT TOMOGRAPHY; INTEGRATED PHOTOELASTICITY AB A general solution of the tomographic problem for weakly refracting inhomogeneous birefringent media is presented. The solution requires an unusual tomographic experiment in which the considered medium is probed with three series of standard tomographic sets of light rays, when the light is polarized. Data for the tomographic reconstruction are produced by recording the interferometric data and measuring birefringent parameters in the standard way. C1 NASA,GODDARD INST SPACE STUDIES,NEW YORK,NY 10025. RP ANDRIENKO, YA (reprint author), MOSCOW MV LOMONOSOV STATE UNIV,DEPT PHYS,LENINSKII GORY 117234,MOSCOW,RUSSIA. NR 9 TC 13 Z9 13 U1 0 U2 0 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 SN 0740-3232 J9 J OPT SOC AM A JI J. Opt. Soc. Am. A-Opt. Image Sci. Vis. PD MAY PY 1994 VL 11 IS 5 BP 1628 EP 1631 DI 10.1364/JOSAA.11.001628 PG 4 WC Optics SC Optics GA NK239 UT WOS:A1994NK23900009 ER PT J AU REDDY, BR NASHSTEVENSON, S VENKATESWARLU, P AF REDDY, BR NASHSTEVENSON, S VENKATESWARLU, P TI NEAR-INFRARED-TO-BLUE ENERGY UP-CONVERSION IN LAF3-HO3+ SO JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS LA English DT Article ID UP-CONVERSION; FLUORESCENCE; GLASSES; LASER; HO3+; LAF3 AB When the 5F5 levels of Ho3+ in LaF3 were resonantly excited with a red dye laser beam of 640 nm, blue and green emissions were detected from the 5G5, the 5F3, and the 5S2 (5F4) levels at 416, 485, and 546 nm, respectively. We found that excited ions in the 5F5 state undergo nonradiative relaxation to the 516 state and are then upconverted to the 5G5 state by the absorption of a second photon, as well as by energy-transfer interaction. The upconversion efficiency into the 5F3 state was estimated as approximately 1.1 x 10(-4). We also observed energy-upconverted emissions from the 5F3 and the 5S2 levels when the material was excited with an 800-nm near-infrared laser. The absorption of a second laser photon from the 5I6 state was found to be responsible for the upconverted green emission. C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. RP REDDY, BR (reprint author), ALABAMA A&M UNIV,DEPT PHYS,POB 1268,NORMAL,AL 35762, USA. NR 16 TC 35 Z9 35 U1 1 U2 4 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 MAY PY 1994 VL 11 IS 5 BP 923 EP 927 DI 10.1364/JOSAB.11.000923 PG 5 WC Optics SC Optics GA NL959 UT WOS:A1994NL95900033 ER PT J AU OUTLAW, RA DAVIDSON, MR AF OUTLAW, RA DAVIDSON, MR TI SMALL ULTRAHIGH-VACUUM COMPATIBLE HYPERTHERMAL OXYGEN-ATOM GENERATOR SO JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A-VACUUM SURFACES AND FILMS LA English DT Article ID ELECTRON-STIMULATED DESORPTION; ADSORPTION; AG AB The development of a compact, ultrahigh vacuum (UHV) compatible instrument for generating a flux of pure hyperthermal oxygen atoms for NASA applications has been achieved. The instrument combines the mechanisMS of O2 dissociation and transport through a hot Ag membrane to provide a continuous source of O atoms to a vacuum interface where they are subsequently emitted into the vacuum space by electron-stimulated desorption (ESD). A flux of neutral O atoms 4.5 x 10(13) cm-2 s-1 (3P) with a mean ion kinetic energy of approximately 5 eV and a full width at half maximum of 4 eV was detected at a quadrupole mass spectrometer located 10 cm away. The geometry of the instrument is such that it is mounted on a 7-cm flange and can be tailored in length and orientation to fit most UHV systems. The data presented here are for ESD-controlled conditions where increases in the flux are strictly linear with electron bombardment current. Calculation shows that transport-controlled conditions can be achieved at temperatures as low as 350-degrees-C with membrane thicknesses on the order of 10 mum. C1 DACO TECHNOL INC,FLORAHOME,FL 32140. RP OUTLAW, RA (reprint author), NASA,LANGLEY RES CTR,HAMPTON,VA 23665, USA. RI Davidson, Mark/C-1135-2009 NR 15 TC 12 Z9 12 U1 0 U2 1 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 0734-2101 J9 J VAC SCI TECHNOL A JI J. Vac. Sci. Technol. A-Vac. Surf. Films PD MAY-JUN PY 1994 VL 12 IS 3 BP 854 EP 860 DI 10.1116/1.579266 PG 7 WC Materials Science, Coatings & Films; Physics, Applied SC Materials Science; Physics GA NL925 UT WOS:A1994NL92500038 ER PT J AU SHARMA, PK HICKEY, GS AF SHARMA, PK HICKEY, GS TI THERMAL OUTGASSING BEHAVIOR AND PHOTOEMISSION-STUDIES OF HAYNES ALLOY-214 SO JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A-VACUUM SURFACES AND FILMS LA English DT Article AB Processing of many materials at high temperatures requires a high purity environment. The outgassing from hot surfaces of the processing chamber or the heating elements is a potential problem. The total amount of outgassing as well as the time- and temperature- dependent outgassing rates are important. The outgassing from Haynes Alloy 214 has been studied experimentally under a vacuum in the temperature range from room temperature to 600-degrees-C. In addition to the outgassing rates, the composition of the outgassed species was determined through mass spectrometric analysis. Alloy surface composition was determined by x-ray photoelectron spectroscopy. Changes in surface composition before and after heating can be accounted for by the outgassed species. RP SHARMA, PK (reprint author), JET PROP LAB,PASADENA,CA 91109, USA. NR 6 TC 1 Z9 1 U1 1 U2 1 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 0734-2101 J9 J VAC SCI TECHNOL A JI J. Vac. Sci. Technol. A-Vac. Surf. Films PD MAY-JUN PY 1994 VL 12 IS 3 BP 867 EP 872 DI 10.1116/1.579268 PG 6 WC Materials Science, Coatings & Films; Physics, Applied SC Materials Science; Physics GA NL925 UT WOS:A1994NL92500040 ER PT J AU ARRIGO, KR SULLIVAN, CW AF ARRIGO, KR SULLIVAN, CW TI A HIGH RESOLUTION BIO-OPTICAL MODEL OF MICROALGAL GROWTH: TESTS USING SEA-ICE ALGAL COMMUNITY TIME-SERIES DATA SO LIMNOLOGY AND OCEANOGRAPHY LA English DT Article ID PHOTOSYNTHESIS-IRRADIANCE RELATIONSHIPS; STEADY-STATE DESCRIPTION; MCMURDO-SOUND; MICROBIAL COMMUNITIES; PHYTOPLANKTON GROWTH; MARINE-PHYTOPLANKTON; LIGHT-ABSORPTION; SPECTRAL MODEL; BARENTS SEA; ANTARCTICA AB A high resolution, two-dimensional (z, t) time-dependent model of microalgal growth has been developed in which simulated physiological responses are determined by ambient temperature, spectral irradiance, nutrient concentration, and salinity. The model is based on the concept of a maximum temperature-dependent growth rate that is subsequently reduced by limitations imposed from insufficient light or nutrients, as well as sub- or supraoptimal salinity. Limitation terms for these variables are derived from studies of nutrient-, light-, and salinity-dependent algal growth (or photosynthetic) rates that have been normalized to maximum observed rates with respect to each variable. Particular emphasis was placed on developing the formulation for light limitation, which includes the effects of diel changes in spectral irradiance, seasonal changes in photoperiod, and related adjustments in biochemical C: Chl a ratios. This level of detail was needed because the importance of light limitation has been demonstrated on diurnal, seasonal, and annual time scales in polar regions. The model was tested by comparing simulation results to a sea-ice microalgal bloom in McMurdo Sound, Antarctica, in 1982. Environmental information from 1982 and biological coefficients derived from sea-ice communities were used as model input. Model results showed excellent agreement with microalgal bloom dynamics observed in 1982 under a variety of environmental conditions. Predicted Chl a standing crops were consistently within 15% of observations for the congelation ice and platelet ice, regardless of snow thickness (snow-free, 5-cm, and 10-cm snow-cover scenarios were tested), and predicted vertical distributions of Chl a exhibited the same depth-dependent pattern as observations. C1 UNIV SO CALIF, HANCOCK INST MARINE STUDIES, GRAD PROGRAM OCEAN SCI, LOS ANGELES, CA 90089 USA. RP ARRIGO, KR (reprint author), NASA, GODDARD SPACE FLIGHT CTR, OCEANS & ICE BRANCH, CODE 971, GREENBELT, MD 20771 USA. NR 61 TC 44 Z9 47 U1 0 U2 14 PU AMER SOC LIMNOLOGY OCEANOGRAPHY PI WACO PA 5400 BOSQUE BLVD, STE 680, WACO, TX 76710-4446 USA SN 0024-3590 J9 LIMNOL OCEANOGR JI Limnol. Oceanogr. PD MAY PY 1994 VL 39 IS 3 BP 609 EP 631 PG 23 WC Limnology; Oceanography SC Marine & Freshwater Biology; Oceanography GA NT264 UT WOS:A1994NT26400012 ER PT J AU SPIRKOVSKA, L REID, MB AF SPIRKOVSKA, L REID, MB TI HIGHER-ORDER NEURAL NETWORKS APPLIED TO 2D AND 3D OBJECT RECOGNITION SO MACHINE LEARNING LA English DT Article DE DISTORTION INVARIANT; PATTERN RECOGNITION; NEURAL NETWORKS; HIGHER-ORDER; 3-DIMENSIONAL; 2-DIMENSIONAL ID DISCRIMINANT FUNCTION FILTERS; INVARIANCE AB A higher-order neural network (HONN) can be designed to be invariant to geometric transformations such as scale, translation, and in-plane rotation. Invariances are built directly into the architecture of a HONN and do not need to be learned. Thus, for 2D object recognition, the network needs to be trained on just one view of each object class, not numerous scaled, translated, and rotated views. Because the 2D object recognition task is a component of the 3D object recognition task, built-in 2D invariance also decreases the size of the training set required for 3D object recognition. We present results for 2D object recognition both in simulation and within a robotic vision experiment and for 3D object recognition in simulation. We also compare our method to other approaches and show that HONNs have distinct advantages for position, scale, and rotation-invariant object recognition. The major drawback of HONNs is that the size of the input field is limited due to the memory required for the large number of interconnections in a fully connected network. We present partial connectivity strategies and a coarse-coding technique for overcoming this limitation and increasing the input field to that required by practical object recognition problems. RP SPIRKOVSKA, L (reprint author), NASA,MAIL STOP 269-3,MOFFETT FIELD,CA 94035, USA. NR 20 TC 8 Z9 8 U1 0 U2 0 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0885-6125 J9 MACH LEARN JI Mach. Learn. PD MAY PY 1994 VL 15 IS 2 BP 169 EP 199 DI 10.1007/BF00993276 PG 31 WC Computer Science, Artificial Intelligence SC Computer Science GA NU001 UT WOS:A1994NU00100004 ER PT J AU CIOS, KJ BAAKLINI, GY VARY, A SZTANDERA, LM AF CIOS, KJ BAAKLINI, GY VARY, A SZTANDERA, LM TI USING FUZZY-SETS IN THE PREDICTION OF FLEXURAL STRENGTH AND DENSITY OF SILICON-NITRIDE CERAMICS SO MATERIALS EVALUATION LA English DT Article DE CERAMICS; FUZZY SETS THEORY; NEURAL NETWORKS; NONDESTRUCTIVE EVALUATION ID STRUCTURAL CERAMICS AB In this work we use fuzzy sets theory to evaluate and predict flexural strength and density of NASA 6Y silicon nitride ceramic. Processing variables of milling time, sintering time, and sintering nitrogen pressure are used as an input to the fuzzy system. Flexural strength and density are the output parameters of the system. Data from 273 silicon nitride modulus of rupture bars tested at room temperature and 135 bars tested at 1,370-degrees-C (2,500-degrees-F) are used in this study, Generalized mean operator and Hamming distance are used to construct the fuzzy predictive model. The maximum test error for density does not exceed 3.3 percent, and for flexural strength 7.1 percent. These results demonstrate that fuzzy sets theory can be incorporated into the process of designing materials such as ceramics, especially for assessing more complex relationships between the processing variables and parameters like strength, which are governed by randomness of manufacturing processes. C1 UNIV TOLEDO,TOLEDO,OH 43606. RP CIOS, KJ (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 10 TC 2 Z9 2 U1 0 U2 0 PU AMER SOC NON-DESTRUCTIVE TEST PI COLUMBUS PA 1711 ARLINGATE LANE PO BOX 28518, COLUMBUS, OH 43228-0518 SN 0025-5327 J9 MATER EVAL JI Mater. Eval. PD MAY PY 1994 VL 52 IS 5 BP 600 EP 606 PG 7 WC Materials Science, Characterization & Testing SC Materials Science GA NM118 UT WOS:A1994NM11800008 ER PT J AU WENTWORTH, SJ MCKAY, DS LINDSTROM, DJ BASU, A MARTINEZ, RR BOGARD, DD GARRISON, DH AF WENTWORTH, SJ MCKAY, DS LINDSTROM, DJ BASU, A MARTINEZ, RR BOGARD, DD GARRISON, DH TI APOLLO 12 ROPY GLASSES REVISITED SO METEORITICS LA English DT Article AB We analyzed ropy glasses from Apollo 12 soils 12032 and 12033 by a variety of techniques including SEM/EDX, electron microprobe analysis, INAA, and Ar-39-Ar-40 age dating. The ropy glasses have KREEP-like compositions different from those of local Apollo 12 mare soils; it is likely that the ropy glasses are of exotic origin. Mixing calculations indicate that the ropy glasses formed from a liquid enriched in KREEP and that the ropy glass liquid also contained a significant amount of mare material. The presence of solar Ar and a trace of regolith-derived glass within the ropy glasses are evidence that the ropy glasses contain a small regolith component. Anorthosite and crystalline breecia (KREEP) clasts occur in some ropy glasses. We also found within these glasses clasts of felsite (fine-grained granitic fragments) very similar in texture and composition to the larger Apollo 12 felsites, which have a Ar-39-Ar-40 degassing age of 800 +/- 15 Ma (Bogard et al., 1992). Measurements of Ar-39-Ar-40 in 12032 ropy glass indicate that it was degassed at the same time as the large felsite although the ropy glass was not completely degassed. The ropy glasses and felsites, therefore, probably came from the same source. Most early investigators suggested that the Apollo 12 ropy glasses were part of the ejecta deposited at the Apollo 12 site from the copernicus impact. Our new data reinforce this model. If these copy glasses are froin Copernicus, they provide new clues to the nature of the target material at the Copernicus site, a part of the Moon that has not been sampled directly. C1 INDIANA UNIV,DEPT GEOL SCI,BLOOMINGTON,IN 47405. NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058. RP WENTWORTH, SJ (reprint author), LOCKHEED ENGN & SCI CO,2400 NASA RD 1,HOUSTON,TX 77058, USA. NR 22 TC 16 Z9 18 U1 0 U2 0 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 SN 0026-1114 J9 METEORITICS JI Meteoritics PD MAY PY 1994 VL 29 IS 3 BP 323 EP 333 PG 11 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA NR224 UT WOS:A1994NR22400006 ER PT J AU HIROI, T PIETERS, CM TAKEDA, H AF HIROI, T PIETERS, CM TAKEDA, H TI GRAIN-SIZE OF THE SURFACE REGOLITH OF ASTEROID 4 VESTA ESTIMATED FROM ITS REFLECTANCE SPECTRUM IN COMPARISON WITH HED METEORITES SO METEORITICS LA English DT Article AB The grain-size distribution of the regolith of asteroid 4 Vesta has been estimated by comparing its reflectance spectra (0.3-2.6 mum) with those of HED meteorites. The finest grain-size separate (<25 mum) of a particular howardite has a reflectance spectrum most similar to Vesta's. In order to better simulate Vesta's surface mineralogy, reflectance spectra of those finest HED meteorite powders were linearly combined, and Vesta's spectrum was scaled for the best fit between them. Both the albedo and the shape of reflectance spectrum of Vesta were well reproduced by regional mixtures of the finest (<25 mum) powders of HED meteorites. The result suggests the heterogeneity of Vesta's surface and provides an estimate of the visible reflectance of Vesta that is close to its IRAS albedo. Thus, this suggests that fine grains can be generated and retained by relatively small bodies (Vesta is approximately 500 km in diameter). C1 BROWN UNIV,DEPT GEOL SCI,PROVIDENCE,RI 02912. UNIV TOKYO,FAC SCI,INST MINERAL,BUNKYO KU,TOKYO 113,JAPAN. RP HIROI, T (reprint author), NASA,LYNDON B JOHNSON SPACE CTR,SN3,HOUSTON,TX 77058, USA. NR 14 TC 62 Z9 62 U1 0 U2 2 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 SN 0026-1114 J9 METEORITICS JI Meteoritics PD MAY PY 1994 VL 29 IS 3 BP 394 EP 396 PG 3 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA NR224 UT WOS:A1994NR22400013 ER PT J AU JONES, JH AF JONES, JH TI FRACTIONAL CRYSTALLIZATION OF IRON-METEORITES - CONSTANT VERSUS CHANGING PARTITION-COEFFICIENTS SO METEORITICS LA English DT Article AB Analyses of magmatic iron meteorites, plotted on LogC(i) vs. LogC(Ni) diagrams, often form linear arrays. Traditionally, this linearity has been ascribed to fractional crystallization under the assumption of constant partition coefficients (i.e., Rayleigh fractionation). Paradoxically, however, partition coefficients in the Fe-Ni-S-P system are decidedly not constant. This contribution provides a rationale for understanding how trends on LogC(i) vs. LogC(Ni) diagrams can be linear, even when partition coefficients are changing rapidly. RP JONES, JH (reprint author), NASA,LYNDON B JOHNSON SPACE CTR,SN4,HOUSTON,TX 77058, USA. NR 5 TC 10 Z9 10 U1 0 U2 0 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 SN 0026-1114 J9 METEORITICS JI Meteoritics PD MAY PY 1994 VL 29 IS 3 BP 423 EP 426 PG 4 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA NR224 UT WOS:A1994NR22400018 ER PT J AU PICKERING, KE THOMPSON, AM MCNAMARA, DP SCHOEBERL, MR AF PICKERING, KE THOMPSON, AM MCNAMARA, DP SCHOEBERL, MR TI AN INTERCOMPARISON OF ISENTROPIC TRAJECTORIES OVER THE SOUTH-ATLANTIC SO MONTHLY WEATHER REVIEW LA English DT Article ID NATIONAL-METEOROLOGICAL-CENTER; RANGE-WEATHER-FORECASTS; TROPOSPHERIC OZONE; GLOBAL ANALYSES; SATELLITE; SYSTEM; WINDS AB The authors have compared isentropic trajectories computed from meteorological fields from different analysis centers. The analysis was performed for the South Atlantic, where a springtime maximum in tropospheric ozone has sparked considerable interest in the transport meteorology. Using the model of Schoeberl et al., isentropic forward trajectories were computed from an array of points over southern Africa and backward trajectories from an array of points over the South Atlantic. The model was run for an 8-day period in October 1989 with input taken from the twice-daily global gridded data fields from the National Meteorological Center (NMC) and from the European Centre for Medium-Range Weather Forecasts (ECMWF). There were large differences between the trajectories based on the two fields in terms of travel distance, horizontal separation, and vertical separation. Best comparisons for individual trajectories were found in the low-latitude easterlies, and the poorest comparisons were found in the westerlies and in the vicinity of the center of the South Atlantic subtropical anticyclone. Significant differences in wind speeds between the two analyses also led to large trajectory differences. Trajectories were also computed using once-daily NMC fields. The effect of this degradation of the data was small. Trajectories computed from balanced winds computed from the NMC geopotential height and temperature fields showed the largest differences when compared with the ECMWF trajectories. The balanced wind fields should not be used in trajectory construction in the tropical lower troposphere. It is difficult to make a definitive recommendation concerning which set of fields should be used in future transport analyses in this region due to the very large trajectory differences found in this analysis and the lack of any independent verification data. Any extensive analysis of transport in this region should be done only in conjunction with considerable additional data collection. C1 NASA,GODDARD SPACE FLIGHT CTR,ATMOSPHERES LAB,GREENBELT,MD 20771. APPL RES CORP,LANDOVER,MD. RP PICKERING, KE (reprint author), UNIV SPACE RES ASSOC,NASA,GODDARD SPACE FLIGHT CTR,ATMOSPHERES LAB,MAIL CODE 916,GREENBELT,MD 20771, USA. RI Pickering, Kenneth/E-6274-2012; Thompson, Anne /C-3649-2014 OI Thompson, Anne /0000-0002-7829-0920 NR 28 TC 39 Z9 39 U1 0 U2 3 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 MAY PY 1994 VL 122 IS 5 BP 864 EP 879 DI 10.1175/1520-0493(1994)122<0864:AIOITO>2.0.CO;2 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA NJ570 UT WOS:A1994NJ57000007 ER PT J AU LI, Y NAVON, IM YANG, WY ZOU, XL BATES, JR MOORTHI, S HIGGINS, RW AF LI, Y NAVON, IM YANG, WY ZOU, XL BATES, JR MOORTHI, S HIGGINS, RW TI 4-DIMENSIONAL VARIATIONAL DATA ASSIMILATION EXPERIMENTS WITH A MULTILEVEL SEMI-LAGRANGIAN SEMIIMPLICIT GENERAL-CIRCULATION MODEL SO MONTHLY WEATHER REVIEW LA English DT Article ID SHALLOW-WATER EQUATIONS; SHAPE-PRESERVING INTERPOLATION; METEOROLOGICAL OBSERVATIONS; SPECTRAL MODELS; INTEGRATION; ADJOINT; SCHEME; TRANSPORT; OPTIMIZATION; ALGORITHMS AB Four-dimensional variational data assimilation (VDA) experiments have been carried out using the adiabatic version of the NASA/Goddard Laboratory for Atmospheres semi-Lagrangian semi-implicit (SLSI) multilevel general circulation model. The limited-memory quasi-Newton minimization technique was used to find the minimum of the cost function. With model-generated observations, different first-guess initial conditions were used to carry out the experiments. The experiments included randomly perturbed initial conditions, as well as different weight matrices in the cost function. The results show that 4D VDA works well with various initial conditions as control variables. Scaling the gradient of the cost function proves to be an effective method of improving the convergence rate of the VDA minimization process. The impacts of the length of the assimilation interval and the time density of the observations on the convergence rate of the minimization have also been investigated. An improved assimilation was obtained when observations were available in selected segments of the assimilation window. Moreover, our 4D VDA experiments with the SLSI model confirm the results obtained by Navon et al. and Li et al. concerning the impact of the length of the assimilation window. The choice of an adequate time distribution of observations along with an appropriate length of assimilation interval is an important issue that will be further investigated. C1 FLORIDA STATE UNIV, SUPERCOMP COMPUTAT RES INST, 415 SCI LIB, TALLAHASSEE, FL 32306 USA. NASA, GODDARD SPACE FLIGHT CTR, ATMOSPHERES LAB, GREENBELT, MD 20771 USA. FLORIDA STATE UNIV, DEPT MATH, TALLAHASSEE, FL 32306 USA. RI Navon, Ionel/A-5173-2008 OI Navon, Ionel/0000-0001-7830-7094 NR 44 TC 19 Z9 20 U1 0 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 MAY PY 1994 VL 122 IS 5 BP 966 EP 983 DI 10.1175/1520-0493(1994)122<0966:FDVDAE>2.0.CO;2 PG 18 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA NJ570 UT WOS:A1994NJ57000012 ER PT J AU SCHRAMM, DN SHI, X AF SCHRAMM, DN SHI, X TI SOLAR NEUTRINOS - SOLAR PHYSICS AND NEUTRINO PHYSICS SO NUCLEAR PHYSICS B LA English DT Article ID KAMIOKANDE-II DETECTOR; CROSS-SECTION; CAPTURE RATE; OSCILLATIONS; MATTER; SUN; MODEL; FLUX; HELIOSEISMOLOGY; UNCERTAINTIES AB It is shown that the current solar neutrino situation, with results from the Homestake experiment, the Kamiokande experiment, GALLEX and SAGE is unfortunately still ambiguous. The differences between observations and the standard solar theory may still be due to either astrophysical inputs or new neutrino physics. The need for new neutrino physics, MSW or vacuum neutrino mixing is sensitive to the results of the Homestake experiment. If the Homestake experiment is correct, then new neutrino physics is required. A problem with the uncalibrated Homestake experiment would allow an astrophysical solution, which merely consists of a slightly cooler sun than the standard solar model of Bahcall et al. The use of future experiments, SNO, Super Kamiokande and Borexino to resolve this ambiguity are explicitly discussed. The measurement of deeper helioseismology modes by GONG will also further constrain solar model solutions. C1 UNIV CHICAGO, CHICAGO, IL 60637 USA. FERMILAB NATL ACCELERATOR LAB, NASA, FERMILAB ASTROPHYS CTR, BATAVIA, IL 60510 USA. NR 56 TC 4 Z9 4 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0550-3213 EI 1873-1562 J9 NUCL PHYS B JI Nucl. Phys. B PD MAY PY 1994 SU 35 BP 321 EP 333 DI 10.1016/0920-5632(94)90271-2 PG 13 WC Physics, Particles & Fields SC Physics GA NT280 UT WOS:A1994NT28000060 ER PT J AU PERRY, JW MANSOUR, K MARDER, SR PERRY, KJ ALVAREZ, D CHOONG, I AF PERRY, JW MANSOUR, K MARDER, SR PERRY, KJ ALVAREZ, D CHOONG, I TI ENHANCED REVERSE SATURABLE ABSORPTION AND OPTICAL LIMITING IN HEAVY-ATOM-SUBSTITUTED PHTHALOCYANINES SO OPTICS LETTERS LA English DT Article ID TRIPLET-STATE AB The reverse saturable absorption and the optical-limiting response of metal phthalocyanines can be enhanced by use of the heavy-atom effect. Phthalocyanines containing heavy-metal atoms, such as In, Sn, and Pb, show a nearly factor-of-2 enhancement in the ratio of effective excited-state to ground-state absorption cross sections compared with those containing lighter atoms, such as Al and Si. In an f/8 optical geometry, homogeneous solutions of heavy-metal phthalocyanines, at 30% linear transmission, limit 8-ns 532-nm laser pulses to less-than-or-equal-to 3 muJ (the energy for 50% probability of eye damage) for incident energies as high as 800 muJ. C1 CALTECH,BECKMAN INST,PASADENA,CA 91125. RP PERRY, JW (reprint author), JET PROP LAB,PASADENA,CA 91109, USA. RI Perry, Joseph/B-7191-2011 OI Perry, Joseph/0000-0003-1101-7337 NR 14 TC 320 Z9 332 U1 3 U2 27 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 SN 0146-9592 J9 OPT LETT JI Opt. Lett. PD MAY 1 PY 1994 VL 19 IS 9 BP 625 EP 627 DI 10.1364/OL.19.000625 PG 3 WC Optics SC Optics GA NG981 UT WOS:A1994NG98100009 PM 19844393 ER PT J AU BACON, WF EGETH, HE AF BACON, WF EGETH, HE TI OVERRIDING STIMULUS-DRIVEN ATTENTIONAL CAPTURE SO PERCEPTION & PSYCHOPHYSICS LA English DT Article ID ABRUPT VISUAL ONSETS; PERCEPTUAL SELECTIVITY; CONTROL SETTINGS; SEARCH; PARALLEL; DISCRIMINATION; SIMILARITY; CONTINGENT; FEATURES; COLOR AB Theeuwes (1992) found a distracting effect of irrelevant-dimension singletons in a task involving search for a known target. He argued from this that selectivity is determined solely by stimulus salience; the parallel stage of visual processing cannot provide top-down guidance to the attentive stage sufficient to permit completely selective use of task-relevant information. We argue that in the task used by Theeuwes, subjects may have adopted the strategy of searching for an odd form even though the specific target form was known. In Experiment 1, we replicated Theeuwes's findings. Search for a circle target among diamond nontargets was disrupted by the presence of a diamond nontarget that was uniquely colored. In two subsequent experiments, we discouraged the singleton detection strategy, forcing subjects to search for the target feature. There was no distracting effect of a color singleton in these experiments, even with displays physically identical to those of Experiment 1, demonstrating that top-down selectivity is indeed possible during visual search. We conclude that goal-directed selection of a specific known featural identity may override stimulus-driven capture by salient featural singletons. C1 JOHNS HOPKINS UNIV HOSP,DEPT PSYCHOL,BALTIMORE,MD 21218. RP BACON, WF (reprint author), NASA,AMES RES CTR,MAIL STOP 262-2,MOFFETT FIELD,CA 94035, USA. NR 35 TC 544 Z9 557 U1 6 U2 37 PU PSYCHONOMIC SOC INC PI AUSTIN PA 1710 FORTVIEW RD, AUSTIN, TX 78704 SN 0031-5117 J9 PERCEPT PSYCHOPHYS JI Percept. Psychophys. PD MAY PY 1994 VL 55 IS 5 BP 485 EP 496 DI 10.3758/BF03205306 PG 12 WC Psychology; Psychology, Experimental SC Psychology GA NP844 UT WOS:A1994NP84400001 PM 8008550 ER PT J AU LUND, TS ROGERS, MM AF LUND, TS ROGERS, MM TI AN IMPROVED MEASURE OF STRAIN STATE PROBABILITY IN TURBULENT FLOWS SO PHYSICS OF FLUIDS LA English DT Article ID HOMOGENEOUS TURBULENCE; NUMERICAL TURBULENCE; SCALAR; ALIGNMENT; VORTICITY; DYNAMICS; FIELDS AB Probability density functions (PDFs) of the strain-rate tensor eigenvalues are examined. It is found that the accepted normalization used to bound the intermediate eigenvalue between +/-1 leads to a PDF that must vanish at the end points for a non-singular distribution of strain states. This purely kinematic constraint has led previous investigators to conclude incorrectly that locally axisymmetric deformations do not exist in turbulent flows. An alternative normalization is presented that does not bias the probability distribution near the axisymmetric limits. This alternative normalization is shown to lead to the expected flat PDF in a Gaussian velocity field and to a PDF that indicates the presence of axisymmetric strain states in a turbulent field. Extension of the new measure to compressible flow is discussed. Several earlier results concerning the likelihood of various strain states and the correlation of these with elevated kinetic energy dissipation rate are reinterpreted in terms of the new normalization. Most importantly, it is found that regions of axisymmetric expansion play a much more dominant role in the turbulent dissipation process than was previously believed. RP STANFORD UNIV, NASA, AMES RES CTR, CTR TURBULENCE RES, STANFORD, CA 94305 USA. NR 23 TC 55 Z9 55 U1 0 U2 4 PU AMER INST PHYSICS PI MELVILLE PA 1305 WALT WHITMAN RD, STE 300, MELVILLE, NY 11747-4501 USA SN 1070-6631 EI 1089-7666 J9 PHYS FLUIDS JI Phys. Fluids PD MAY PY 1994 VL 6 IS 5 BP 1838 EP 1847 DI 10.1063/1.868440 PG 10 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA NH624 UT WOS:A1994NH62400020 ER PT J AU MARTEN, A DEBERGH, C OWEN, T GAUTIER, D MAILLARD, JP DROSSART, P LUTZ, BL ORTON, GS AF MARTEN, A DEBERGH, C OWEN, T GAUTIER, D MAILLARD, JP DROSSART, P LUTZ, BL ORTON, GS TI 4 MICRON HIGH-RESOLUTION SPECTRA OF JUPITER IN THE NORTH EQUATORIAL BELT - H-3+ EMISSIONS AND THE C-12 C-13 RATIO SO PLANETARY AND SPACE SCIENCE LA English DT Article ID MU-M; FUNDAMENTAL-BAND; UPPER-ATMOSPHERE; C-12-C-13 RATIO; AURORAE; H-3(+); IONOSPHERE; SATURN AB Spectra of the North Equatorial Belt of Jupiter were obtained in March 1992 at an unapodized resolution of 0.1 cm-1 between 2450 and 2600 cm-1 with the Fourier Transform Spectrometer at the 3.6 m Canada-France-Hawaii Telescope on Mauna Kea. Several emissions from the nu2 band of H-3(+) were detected. The excitation temperature derived from the relative intensities of these emissions averaged over a wide range of longitudes is 800 +/- 100 K, and the H-3(+) column density is 1.56(-0.5)+1.0 x 10(11) cm-2. In addition, several strong absorption features due to 13CH4 were observed. A comparison between 12CH4 and 13CH4 absorptions allowed us to obtain a new measurement of the C-12/C-13 ratio. We found that this ratio, estimated for the first time in this spectral range, is 89 (+/-25), in agreement with the terrestrial value. C1 UNIV HAWAII, INST ASTRON, HONOLULU, HI 96822 USA. CNRS, INST ASTROPHYS, F-75005 PARIS, FRANCE. NO ARIZONA UNIV, FLAGSTAFF, AZ 86011 USA. JET PROP LAB, PASADENA, CA 91109 USA. RP MARTEN, A (reprint author), OBSERV PARIS, DESPA, 5 PL JULES JANSSEN, F-92195 MEUDON, FRANCE. NR 47 TC 30 Z9 30 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD MAY PY 1994 VL 42 IS 5 BP 391 EP 399 DI 10.1016/0032-0633(94)90128-7 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA PF109 UT WOS:A1994PF10900004 ER PT J AU IMBRIALE, WA THORBURN, M AF IMBRIALE, WA THORBURN, M TI SPECIAL ISSUE ON RADIO TELESCOPES SO PROCEEDINGS OF THE IEEE LA English DT Editorial Material RP IMBRIALE, WA (reprint author), JET PROP LAB,GROUND ANTENNAS & FACIL ENGN SECT,PASADENA,CA 91109, USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-9219 J9 P IEEE JI Proc. IEEE PD MAY PY 1994 VL 82 IS 5 BP 633 EP 635 DI 10.1109/5.284730 PG 3 WC Engineering, Electrical & Electronic SC Engineering GA NL639 UT WOS:A1994NL63900001 ER PT J AU RAFFERTY, W SLOBIN, SD STELZRIED, CT SUE, MK AF RAFFERTY, W SLOBIN, SD STELZRIED, CT SUE, MK TI GROUND ANTENNAS IN NASA DEEP SPACE TELECOMMUNICATIONS SO PROCEEDINGS OF THE IEEE LA English DT Article ID WAVE-GUIDE ANTENNA; MICROWAVE AB Ground antennas are the major visible components of NASA's Deep Space Network (DSN). The role, key characteristics, and performance of these antennas in deep-space telecommunications are described. The system analyses and tradeoffs to optimize the overall ground-to-spacecraft link and to define future missions are elaborated from an antenna perspective. Overall performance of receiving systems is compared using the widely accepted G/T figure-of-merit, i.e., net antenna gain divided by the operating system noise temperature. Performance of past, present, and future antennas and receiving systems is discussed, including the planned development of a worldwide network of 34-m-diameter beam-waveguide antennas. The need for multifrequency operation, presently at S- and X-bands, and in the future at Ka-band, is discussed. The resulting requirements placed on antenna technology are highlighted. Beam-waveguide antenna performance to further improve performance and operational advantages is discussed. RP RAFFERTY, W (reprint author), JET PROP LAB,PASADENA,CA 91109, USA. NR 24 TC 3 Z9 3 U1 1 U2 2 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-9219 J9 P IEEE JI Proc. IEEE PD MAY PY 1994 VL 82 IS 5 BP 636 EP 645 DI 10.1109/5.284731 PG 10 WC Engineering, Electrical & Electronic SC Engineering GA NL639 UT WOS:A1994NL63900002 ER PT J AU STELZRIED, CT KLEIN, MJ AF STELZRIED, CT KLEIN, MJ TI PRECISION DSN RADIOMETER SYSTEMS - IMPACT ON MICROWAVE CALIBRATIONS SO PROCEEDINGS OF THE IEEE LA English DT Article AB The NASA Deep Space Network (DSN) has a long history of providing large parabolic dish antennas with precision surfaces, low-loss feeds, and ultra-low noise amplifiers for deep-space telecommunications. To realize the benefits of high sensitivity, it is important that receiving systems are accurately calibrated and monitored to maintain peak performance. A method is described to measure system performance and to calibrate the receiving system using procedures, software, and commercial instruments that are easy to implement and efficient to use. The utility of the measurement procedures and the precision of the receiver calibration technique were demonstrated by performing tests at K(a)-band (32 and 33.68 GHz) frequencies at Goldstone on a 34-m beam-waveguide antenna. Observations of multiple calibration radio sources are used to measure the dependence of antenna gain and system noise temperature on source elevation and derive the performance parameters. Receiving system nonlinearities are frequently overlooked as an error source in the calibration of microwave radiometers. The experimental results described in this paper illustrate some of the ways that receiving system nonlinearity can negatively impact system performance. A simple radiometer calibration technique and analysis provide quantitative information that enables the system engineer to adjust and linearize the receiving system. When that is not practical, the experimenter or the operator can apply correction coefficients to the measured values of system noise temperature and thereby compensate for the receiving system nonlinearity. The high-performance antennas and the sensitive receiving systems of the DSN are valuable resources for scientific research in addition to the primary telecommunication tasks that support space missions. The antenna gain and system noise temperature measurements and the radiometer calibration method described in this paper are also useful to perform precision research experiments. RP STELZRIED, CT (reprint author), JET PROP LAB,OFF ASTRON STUDIES EXTRASOLAR PLANETARY SYST,PASADENA,CA 91109, USA. NR 26 TC 7 Z9 7 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 0018-9219 J9 P IEEE JI Proc. IEEE PD MAY PY 1994 VL 82 IS 5 BP 776 EP 787 DI 10.1109/5.284745 PG 12 WC Engineering, Electrical & Electronic SC Engineering GA NL639 UT WOS:A1994NL63900016 ER PT J AU OTOSHI, TY FRANCO, MM LUTES, GF AF OTOSHI, TY FRANCO, MM LUTES, GF TI THE FRACTIONAL FREQUENCY STABILITY OF A 34-M-DIAMETER BEAM-WAVE-GUIDE ANTENNA SO PROCEEDINGS OF THE IEEE LA English DT Article AB Recent advances in fiber-optic technology have made it possible to develop a new technique to isolate and measure the frequency stability of a large beam-waveguide (BWG) antenna. Through the use of the technique described in this paper, at both 46.5-degrees and 37-degrees elevation angles, under good weather conditions, the degradation of the fractional frequency stability of signals passing through the antenna path was measured to be between 13 and 2.2 x 10(-15) for sampling intervals of 1024 s. These stability values apply to the portion of the antenna that includes the main reflector, subreflector, tripod legs, and six BWG mirrors. These test results are believed to be the first successful fractional frequency stability measurements made on the microwave optics portion of a large antenna to a level of 1 or 2 parts in 10(15). RP OTOSHI, TY (reprint author), JET PROP LAB,PASADENA,CA 91109, USA. NR 18 TC 4 Z9 4 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 0018-9219 J9 P IEEE JI Proc. IEEE PD MAY PY 1994 VL 82 IS 5 BP 788 EP 795 DI 10.1109/5.284746 PG 8 WC Engineering, Electrical & Electronic SC Engineering GA NL639 UT WOS:A1994NL63900017 ER PT J AU SHELL, JS CLAUSS, RC PETTY, SM GLASS, GW FIORE, MS KOVATCH, JJ LOREMAN, JR NEFF, DE QUINN, RB TROWBRIDGE, DL AF SHELL, JS CLAUSS, RC PETTY, SM GLASS, GW FIORE, MS KOVATCH, JJ LOREMAN, JR NEFF, DE QUINN, RB TROWBRIDGE, DL TI RUBY MASERS FOR MAXIMUM G/T(OP) SO PROCEEDINGS OF THE IEEE LA English DT Article AB The Deep-Space Network (DSN) includes world-wide networks of 26-, 34- and 70-m antennas in Australia, Spain, and the USA. Ruby masers are used on the 34- and 70-m antennas to minimize the system operating noise temperature and thereby maximize the DSN receiving system figure of merit, antenna gain divided by system operating noise temperature. These systems are used for deep-space telecommunications, solar system radar, and radio astronomy. Cavity, traveling-wave, and reflected-wave maser designs and performance characteristics from 960 MHz to 34 GHz are summarized. Effective noise temperatures of ruby masers are addressed with emphasis on a 33.68-GHz maser where quantum noise is a major source of noise. RP SHELL, JS (reprint author), JET PROP LAB,RADIO FREQUENCY & MICROWAVE SUBSYST SECT,MICROWAVE ELECTR GRP,PASADENA,CA 91109, USA. NR 25 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 0018-9219 J9 P IEEE JI Proc. IEEE PD MAY PY 1994 VL 82 IS 5 BP 796 EP 810 DI 10.1109/5.284747 PG 15 WC Engineering, Electrical & Electronic SC Engineering GA NL639 UT WOS:A1994NL63900018 ER PT J AU JURCEVIC, JS HONEYCUTT, RK SCHLEGEL, EM WEBBINK, RF AF JURCEVIC, JS HONEYCUTT, RK SCHLEGEL, EM WEBBINK, RF TI SPECTROSCOPY AND PHOTOMETRY OF THE DWARF NOVA BZ URSAE MAJORIS AND THE CV LINEWIDTH K, MASS-RATIO RELATION SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC LA English DT Article ID X-RAY BINARIES; CATACLYSMIC VARIABLES; RADIAL-VELOCITY; ECLIPSE; MODEL; CYGNI AB Time-resolved spectroscopy of the dwarf nova BZ Ursae Majoris reveals periodic velocity variations in the hydrogen emission lines with P = 97.9 +/- 0.1 min and K = 73 +/- 6 km s-1. CCD photometry over a 16-month interval shows three outbursts of about 4 mag with a mean separation of 181 days. The mean FWHM for the Hbeta emission is large, prompting a recalibration of the FWHM/K vs. mass ratio relation, giving a mass ratio (M(RD)/M(WD)) of 0.20 for BZ UMa. The short period, long outburst interval, and small mass ratio support the suggestion of BZ UMa being in the SU Ursae Majoris subclass of dwarf novae. C1 INDIANA UNIV,DEPT ASTRON,BLOOMINGTON,IN 47401. NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771. UNIV ILLINOIS,DEPT ASTRON,URBANA,IL 61801. NR 48 TC 23 Z9 24 U1 0 U2 0 PU ASTRONOMICAL SOC PACIFIC PI SAN FRANCISCO PA 390 ASHTON AVE, SAN FRANCISCO, CA 94112 SN 0004-6280 J9 PUBL ASTRON SOC PAC JI Publ. Astron. Soc. Pac. PD MAY PY 1994 VL 106 IS 699 BP 481 EP 485 DI 10.1086/133403 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NQ416 UT WOS:A1994NQ41600007 ER PT J AU CHOUDHARI, M HALL, P STREETT, C AF CHOUDHARI, M HALL, P STREETT, C TI ON SPATIAL EVOLUTION OF LONG-WAVELENGTH GORTLER VORTICES GOVERNED BY A VISCOUS-INVISCID INTERACTION .1. THE LINEAR CASE SO QUARTERLY JOURNAL OF MECHANICS AND APPLIED MATHEMATICS LA English DT Article ID GROWING BOUNDARY-LAYERS; NONLINEAR DEVELOPMENT; RECEPTIVITY AB The generation of long-wavelength Gortler vortices is studied in the linear regime by numerically solving the time-dependent governing equations. It is found that time-dependent surface deformations, which assume a fixed non-zero shape at large times, generate steady Gortler vortices that amplify in the downstream direction. Thus, the Gortler instability in this regime is shown to be convective in nature, contrary to the earlier findings of Ruban and Savenkov. The disturbance pattern created by steady and streamwise-elongated surface obstacles on a concave surface is also examined in detail and contrasted with the flow pattern on a flat surface, due to roughness elements with an aspect ratio of order unity. Some difficulties in applying the Briggs-Bers criterion to unstable physical systems of this type are pointed out. C1 UNIV MANCHESTER,MANCHESTER M13 9PL,LANCS,ENGLAND. NASA,LANGLEY RES CTR,ICASE,HAMPTON,VA 23681. RP CHOUDHARI, M (reprint author), HIGH TECHNOL CORP,HAMPTON,VA 23666, USA. RI Choudhari, Meelan/F-6080-2017 OI Choudhari, Meelan/0000-0001-9120-7362 NR 23 TC 12 Z9 12 U1 0 U2 2 PU OXFORD UNIV PRESS UNITED KINGDOM PI OXFORD PA WALTON ST JOURNALS DEPT, OXFORD, ENGLAND OX2 6DP SN 0033-5614 J9 Q J MECH APPL MATH JI Q. J. Mech. Appl. Math. PD MAY PY 1994 VL 47 BP 207 EP 229 DI 10.1093/qjmam/47.2.207 PN 2 PG 23 WC Mathematics, Applied; Mechanics SC Mathematics; Mechanics GA NQ894 UT WOS:A1994NQ89400002 ER PT J AU OTTO, SR BASSOM, AP AF OTTO, SR BASSOM, AP TI THE EFFECT OF CROSS-FLOW ON TAYLOR VORTICES SO QUARTERLY JOURNAL OF MECHANICS AND APPLIED MATHEMATICS LA English DT Article ID 3-DIMENSIONAL BOUNDARY-LAYERS; GORTLER VORTICES; NONLINEAR DEVELOPMENT; VORTEX MOTIONS; FLOWS; INSTABILITIES; STABILITY AB A number of practically relevant problems. involving the impulsive motion or the rapid rotation of bodies immersed in fluid are susceptible to vortex-like instability modes. Depending upon the configuration of any particular problem the stability properties of any high-wavenumber vortices can take on one of two distinct forms. One of these is akin to the structure of Gortler vortices in boundary-layer flows whilst the other is similar to the situation for classical Taylor vortices. Both the Gortler and Taylor problems have been extensively studied when crossflow effects are excluded from the underlying base flows. Recently, studies have been made concerning the influence of crossflow on Gortler modes and here we use a linearized stability analysis to examine crossflow properties for the Taylor mode. This work allows us to identify the most unstable vortex as the crossflow component increases and we show how, as in the Gortler case, only a very small crossflow component is required in order to completely stabilize the flow. Our investigation forms the basis for an extension to the nonlinear problem and is of potential applicability to a range of pertinent flows. C1 NASA,LANGLEY RES CTR,ICASE,HAMPTON,VA 23681. UNIV EXETER,DEPT MATH,EXETER EX4 4QE,DEVON,ENGLAND. RI Bassom, Andrew/F-6691-2014 NR 18 TC 3 Z9 3 U1 0 U2 0 PU OXFORD UNIV PRESS UNITED KINGDOM PI OXFORD PA WALTON ST JOURNALS DEPT, OXFORD, ENGLAND OX2 6DP SN 0033-5614 J9 Q J MECH APPL MATH JI Q. J. Mech. Appl. Math. PD MAY PY 1994 VL 47 BP 323 EP 339 DI 10.1093/qjmam/47.2.323 PN 2 PG 17 WC Mathematics, Applied; Mechanics SC Mathematics; Mechanics GA NQ894 UT WOS:A1994NQ89400009 ER PT J AU BADHWAR, GD CUCINOTTA, FA ONEILL, PM AF BADHWAR, GD CUCINOTTA, FA ONEILL, PM TI AN ANALYSIS OF INTERPLANETARY SPACE RADIATION EXPOSURE FOR VARIOUS SOLAR-CYCLES SO RADIATION RESEARCH LA English DT Article ID MODEL AB The radiation dose received by crew members in interplanetary space is influenced by the stage of the solar cycle. Using the recently developed models of the galactic cosmic radiation (GCR) environment and the energy-dependent radiation transport code, we have calculated the dose at 0 and 5 cm water depth; using a computerized anatomical man (CAM) model, we have calculated the skin, eye and blood-forming organ (BFO) doses as a function of aluminum shielding for various solar minima and maxima between 1954 and 1989. These results show that the equivalent dose is within about 15% of the mean for the various solar minima (maxima). The maximum variation between solar minimum and maximum equivalent dose is about a factor of three. We have extended these calculations for the 1976-1977 solar minimum to five practical shielding geometries: Apollo Command Module, the least and most heavily shielded locations in the U.S. space shuttle mid-deck, center of the proposed Space Station Freedom cluster and sleeping compartment of the Skylab. These calculations, using the quality factor of ICRP 60, show that the average CAM BFO equivalent dose is 0.46 Sv/year. Based on an approach that takes fragmentation into account, we estimate a calculation uncertainty of 15% if the uncertainty in the quality factor is neglected. C1 NASA,LANGLEY RES CTR,HAMPTON,VA 23665. RP BADHWAR, GD (reprint author), NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058, USA. NR 24 TC 42 Z9 42 U1 0 U2 3 PU RADIATION RESEARCH SOC PI OAK BROOK PA 2021 SPRING RD, STE 600, OAK BROOK, IL 60521 SN 0033-7587 J9 RADIAT RES JI Radiat. Res. PD MAY PY 1994 VL 138 IS 2 BP 201 EP 208 DI 10.2307/3578590 PG 8 WC Biology; Biophysics; Radiology, Nuclear Medicine & Medical Imaging SC Life Sciences & Biomedicine - Other Topics; Biophysics; Radiology, Nuclear Medicine & Medical Imaging GA NH841 UT WOS:A1994NH84100007 PM 8183990 ER PT J AU WHEELER, RJ LECROY, SR WHITLOCK, CH PURGOLD, GC SWANSON, JS AF WHEELER, RJ LECROY, SR WHITLOCK, CH PURGOLD, GC SWANSON, JS TI SURFACE CHARACTERISTICS FOR THE ALKALI FLATS AND DUNES REGIONS AT WHITE-SANDS-MISSILE-RANGE, NEW-MEXICO SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID CALIBRATION AB Two regions at White Sands Missile Range with different surface reflectance characteristics were studied from November 1988 through December 1991. Continuous 6-min measurements of surface albedo on the alkali flats were used to produce a clear-sky surface climatology for the period. Based on the flats measurements, estimates for a dunes albedo were made using calibrated satellite data. In addition to the surface albedo history, sample bidirectional reflectance characteristics in terms of anisotropic factors for the alkali flats region are also presented. Results show that the flats region is non-Lambertian characterized by large anisotropic factors at high solar and viewing zenith angles. The flat's albedo is highly influenced by surface moisture conditions. Reflectance proper-ties of the dunes are complicated by dune shadows, surface irregularities, seasonal vegetative coverage, and soil moisture. C1 NASA,LANGLEY RES CTR,DIV ATMOSPHER SCI,HAMPTON,VA 23665. USA,RES LAB,WHITE SANDS MISSILE RANGE,NM 88002. RP WHEELER, RJ (reprint author), LOCKHEED ENGN & SCI CO,144 RES DR,HAMPTON,VA 23666, USA. NR 9 TC 14 Z9 15 U1 0 U2 1 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 MAY PY 1994 VL 48 IS 2 BP 181 EP 190 DI 10.1016/0034-4257(94)90140-6 PG 10 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA NN409 UT WOS:A1994NN40900007 ER PT J AU BARET, F VANDERBILT, VC STEVEN, MD JACQUEMOUD, S AF BARET, F VANDERBILT, VC STEVEN, MD JACQUEMOUD, S TI USE OF SPECTRAL ANALOGY TO EVALUATE CANOPY REFLECTANCE SENSITIVITY TO LEAF OPTICAL-PROPERTIES SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID SCATTERING; MODEL AB The spectral variation Of canopy reflectance is mostly governed by the optical properties of the elements such as the leaves. Since leaf intrinsic scattering properties show very little spectral variation, leaf optical properties are related to their absorption properties. Spectral analogies are thus observed between two wavelengths for which the optical properties (absorption, reflectance, or transmittance) of the elements are similar. The red edge for green plants shows the full range of variation of leaf optical properties. The relationship between canopy reflectance and leaf reflectance measured concurrently at the red edge over sugar beet canopies was thus used to simulate canopy reflectance over the whole spectral domain from leaf reflectance spectra measured over the whole spectral domain. The results show that the spectral analogies found allows accurate reconstruction of canopy reflectance spectra. Explicit assumptions about the very low spectral variation of leaf intrinsic scattering properties are thus indirectly justified. The sensitivity of canopy reflectance (rho(c)) to leaf optical properties is then investigated from concurrent spectral variations Of canopy (partial derivative rho(c)/partial derivative lambda) and leaf reflectance (partial derivative rho1/partial derivative lambda): partial derivative rho(c)/partial derivative rho1 = (partial derivative rho(c)/partial derivative lambda) (partial derivative rho(l)/partial derivative lambda)-1. This expression is strictly valid only when the optical properties of the soil background or of the other vegetation elements such as bark are either spectrally flat or do not contribute significantly to canopy reflectance. Simulations using the SAIL and PROSPECT models demonstrate that the sensitivity of canopy reflectance to leaf reflectance is significant for large vegetation cover fractions in spectral domains where absorption is low. In these conditions, multiple scattering enhances the leaf absorption features by a factor that can be greater than 2.0. To override the limitations of the SAIL model for the description of the canopy architecture, we tested the previous simulation results on experimental data. Concurrent canopy and leaf reflectance spectra were measured for a range of sugar beet canopies. The results show good agreement with the theoretical findings. Conclusions are drawn about the applicability of these findings, with particular attention to the potential detectability of leaf biochemical composition from canopy reflectance sensed from space. C1 JRC,IRSA AT,ISPRA,ITALY. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. UNIV NOTTINGHAM,NOTTINGHAM NG7 2RD,ENGLAND. RP BARET, F (reprint author), INRA,BP 91,F-84143 MONTFAVET,FRANCE. RI Jacquemoud, Stephane/F-8842-2010; Baret, Fred/C-4135-2011 OI Baret, Fred/0000-0002-7655-8997 NR 11 TC 42 Z9 44 U1 0 U2 10 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 SN 0034-4257 J9 REMOTE SENS ENVIRON JI Remote Sens. Environ. PD MAY PY 1994 VL 48 IS 2 BP 253 EP 260 DI 10.1016/0034-4257(94)90146-5 PG 8 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA NN409 UT WOS:A1994NN40900013 ER PT J AU GENZEL, R HOLLENBACH, D TOWNES, CH AF GENZEL, R HOLLENBACH, D TOWNES, CH TI THE NUCLEUS OF OUR GALAXY SO REPORTS ON PROGRESS IN PHYSICS LA English DT Review ID GALACTIC-CENTER REGION; SAGITTARIUS-A COMPLEX; COMPACT RADIO-SOURCE; MASSIVE BLACK-HOLE; RECOMBINATION LINE OBSERVATIONS; FAR-INFRARED OBSERVATIONS; DEGENERATE NEUTRON CORES; CENTER MOLECULAR CLOUDS; NE-II OBSERVATIONS; OH IR STARS AB The subject of this review is the central 100 parsecs of our Galaxy, with a strong focus on the central few parsecs. Observations of the electromagnetic spectrum over 13 orders of magnitude in wavelength show a broad range of phenomena involving a number of physical processes. We discuss the stellar and interstellar components, the importance of magnetic and gravitational forces, the evidence for stellar formation and a central massive black hole, and the origin and nature of ionization, outflows and interstellar gas dynamics. The density of stars is approximately proportional to R-2 from Galactocentric radii of a few tenths to more than one hundred parsecs, the central density perhaps being more than 10(7) times as large as in the solar vicinity. On all scales one finds massive stars that must have formed within the last 10(7) years. On scales greater-than-or-equal-to 10 pc there are a number of compact x-ray sources, including a spectacular black hole candidate exhibiting time variable, hard x-ray/gamma-ray emission and a twin radio jet. In the central regions stellar collisions are probably frequent and may affect the stellar populations. The Galactic nucleus contains a remarkable concentration of dense and excited interstellar matter. The average density of gas and dust and the average thermal pressures are 10(2)-10(5) times those found in the solar neighbourhood. A component of very hot (10(7)-10(8) K) gas may be the result of a few hundred supernova explosions that occurred in the central 10(2) pc during the last 10(4)-10(5) years. The coronal gas escapes the disk as a Galactic wind. The region between 3 and 30 pc shows evidence for poloidal magnetic fields out of the plane of the disk of the Galaxy, of strength 0.1 to a few mGauss. A circum-nuclear disk or torus of dense molecular gas orbits the centre between 1.5 and 5 pc and probably is fed with gas from massive molecular clouds at R greater-than-or-equal-to 10 pc. The central parsec has a relatively low average gas density, but contains a number of predominantly atomic and ionized streamers. The luminosity of the central few parsecs appears to be dominated by a cluster of hot stars, whose ultraviolet radiation and winds excite, photoionize and perturb the gas streamers. These massive stars may be the products of a small burst of star formation that occurred a few million years ago when there may have been a much greater nuclear concentration of interstellar gas than is presently observed. Alternatively, or additionally, massive stars in the central core may form as the result of mergers of low mass stars if the central stellar density in fact significantly exceeds 10(7) M. pc-3. C1 NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. UNIV CALIF BERKELEY, DEPT PHYS, BERKELEY, CA 94720 USA. RP GENZEL, R (reprint author), MAX PLANCK INST EXTRATERR PHYS, GARCHING, GERMANY. NR 316 TC 174 Z9 175 U1 2 U2 9 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0034-4885 EI 1361-6633 J9 REP PROG PHYS JI Rep. Prog. Phys. PD MAY PY 1994 VL 57 IS 5 BP 417 EP 479 DI 10.1088/0034-4885/57/5/001 PG 63 WC Physics, Multidisciplinary SC Physics GA NP495 UT WOS:A1994NP49500001 ER PT J AU GYEKENYESI, A HEMANN, J BINIENDA, W AF GYEKENYESI, A HEMANN, J BINIENDA, W TI CRACK DEVELOPMENT IN CARBON POLYIMIDE CROSS-PLY LAMINATES UNDER UNIAXIAL TENSION SO SAMPE JOURNAL LA English DT Article ID EPOXY AB This study addresses matrix dominated failures in carbon fiber/polymer matrix composite laminates in a cross-ply layup. The events of interest were intralaminar fracture in the form of transverse cracks in the 90-degrees plies and longitudinal splitting in the 0-degrees plies, and interlaminar fracture in the form of 0/90 delamination. These mechanisms were observed using various non-destructive evaluation (NDE) techniques employed during static tensile tests. X-ray, acoustic emission, and edge view microscopy were the principal methods utilized in a real time environment. A comparison of the NDE results with an analytical model based on the classical linear fracture mechanics concept of strain energy release rate as a criterion for crack growth was performed. The virtual crack-closure theory was incorporated with a finite element model to generate strain energy release rate curves for the analytical case. Celion carbon fiber/polyimide matrix (G30-500/PMR-15) was the material tested with cross-ply lay-ups of (0(2)/90(6))s and (0(4)/90(4))s. The test specimens contained thermally induced cracks caused by the high temperature processing. The investigation of the damaged laminates gave insight into their capability of sustaining further loads, and the sequence of damage events was obtained. The analytical model was updated to compensate for the initial damage and to study further accumulation by taking into account the crack interactions. By correlating the experimental and analytical data, the critical energy release rates were found for the observable events of interest. C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. UNIV AKRON,DEPT CIVIL ENGN,AKRON,OH 44325. RP GYEKENYESI, A (reprint author), CLEVELAND STATE UNIV,CLEVELAND,OH 44115, USA. NR 13 TC 7 Z9 7 U1 2 U2 4 PU SAMPE PUBLISHERS PI COVINA PA 1161 PARKVIEW DRIVE, COVINA, CA 91722 SN 0091-1062 J9 SAMPE J JI Sampe J. PD MAY-JUN PY 1994 VL 30 IS 3 BP 17 EP 28 PG 12 WC Engineering, Multidisciplinary; Materials Science, Multidisciplinary SC Engineering; Materials Science GA PG892 UT WOS:A1994PG89200004 ER PT J AU ROCKSTAD, HK KENNY, TW REYNOLDS, JK KAISER, WJ GABRIELSON, TB AF ROCKSTAD, HK KENNY, TW REYNOLDS, JK KAISER, WJ GABRIELSON, TB TI A MINIATURE HIGH-SENSITIVITY BROAD-BAND ACCELEROMETER BASED ON ELECTRON-TUNNELING TRANSDUCERS SO SENSORS AND ACTUATORS A-PHYSICAL LA English DT Article; Proceedings Paper CT 7th International Conference on Solid-State Sensors and Actuators (Transducers 93) CY JUN 07-10, 1993 CL YOKOHAMA, JAPAN ID DETECTOR; SENSORS; NOISE AB New high sensitivity microsensors have been developed using high-resolution position sensors based on electron tunneling. The design of miniature accelerometers having resolutions approaching 10(-9) g/square-root Hz is discussed. A new dual-element electron tunneling structure, which overcomes bandwidth limitations of single-element structures, allows design of high sensitivity accelerometers operating in a band from a few Hz to several kHz. A miniature accelerometer based on this structure can thus have application as a sensitive acoustic sensor. Thermal vibration of the proof mass is an extremely important constraint in miniature accelerometers, and can be the dominant limitation on the sensitivity. Thermal noise is analyzed for the suspended masses of the dual-element structure, and compared with electronic noise in the tunneling circuit. With a proof mass of 100 mg noise analysis predicts limiting resolutions better than 10(-8) g/square-root Hz between 10 and 100 Hz, and 10(-7) g/square-root Hz at 1 kHz. Prototype accelerometers have been fabricated by silicon micromachining and tested. A noise resolution of 10(-7) g/square-root Hz between 4 and 70 Hz and 6 x 10(-7) g/square-root Hz at 400 Hz is observed in a damped device. The low-frequency responsivity of this device is 100000 V/g, decreasing to 1300 V/g at 600 Hz. C1 USN,CTR AIR WARFARE,WARMINSTER,PA 18974. RP ROCKSTAD, HK (reprint author), JET PROP LAB,CTR SPACE MICROELECTR TECHNOL,PASADENA,CA 91109, USA. NR 22 TC 26 Z9 30 U1 3 U2 12 PU ELSEVIER SCIENCE SA LAUSANNE PI LAUSANNE 1 PA PO BOX 564, 1001 LAUSANNE 1, SWITZERLAND SN 0924-4247 J9 SENSOR ACTUAT A-PHYS JI Sens. Actuator A-Phys. PD MAY PY 1994 VL 43 IS 1-3 BP 107 EP 114 DI 10.1016/0924-4247(93)00676-U PG 8 WC Engineering, Electrical & Electronic; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA NT267 UT WOS:A1994NT26700018 ER PT J AU ERN, A GIOVANGIGLI, V KEYES, DE SMOOKE, MD AF ERN, A GIOVANGIGLI, V KEYES, DE SMOOKE, MD TI TOWARDS POLYALGORITHMIC LINEAR-SYSTEM SOLVERS FOR NONLINEAR ELLIPTIC PROBLEMS SO SIAM JOURNAL ON SCIENTIFIC COMPUTING LA English DT Article; Proceedings Paper CT 1992 Copper Mountain Conference on Iterative Methods in Numerical Linear Algebra CY APR 09-14, 1992 CL COPPER MT RESORT, COPPER MT, CO SP US DOE HO COPPER MT RESORT DE NONLINEAR ELLIPTIC BOUNDARY VALUE PROBLEMS; POLYALGORITHMS; PRECONDITIONED ITERATIVE METHODS; COMPUTATIONAL COMBINATION ID FOURIER-ANALYSIS; PRECONDITIONERS; PERFORMANCE AB The authors investigate the performance of several preconditioned conjugate gradient-like algorithms and a standard stationary iterative method (block-line successive overrelaxation (SOR)) on linear systems of equations that arise from a nonlinear elliptic flame sheet problem simulation. The nonlinearity forces a pseudotransient continuation process that makes the problem parabolic and thus compacts the spectrum of the Jacobian matrix so that simple relaxation methods are viable in the initial stages of the solution process. However, because of the transition from parabolic to elliptic character as the timestep is increased in pursuit of the steady-state solution, the performance of the candidate linear solvers spreads as the domain of convergence of Newton's method is approached. In numerical experiments over the course of a full nonlinear solution trajectory, short recurrence or optimal Krylov algorithms combined with a Gauss-Seidel (GS) preconditioning yield better execution times with respect to the standard block-line SOR techniques, but SOR performs competitively at a smaller storage cost until the final stages. Block-incomplete factorization preconditioned methods, on the other hand, require nearly a factor of two more storage than SOR and are uniformly less effective during the pseudotransient stages. The advantage of GS preconditioning is partly attributable to die exploitation of a dominant convection direction in the examples; nevertheless, a multidomain version of GS with streamwise coupling lagged at rows between adjacent subdomains incurs only a modest penalty. C1 ECOLE NATL PONTS & CHAUSEES,F-75007 PARIS,FRANCE. NASA,LARC,INST COMP APPLICAT SCI & ENGN,HAMPTON,VA 23681. ECOLE POLYTECH,CTR MATH APPL,F-91128 PALAISEAU,FRANCE. ECOLE POLYTECH,CNRS,F-91128 PALAISEAU,FRANCE. RP ERN, A (reprint author), YALE UNIV,DEPT MECH ENGN,NEW HAVEN,CT 06520, USA. NR 26 TC 42 Z9 42 U1 1 U2 4 PU SIAM PUBLICATIONS PI PHILADELPHIA PA 3600 UNIV CITY SCIENCE CENTER, PHILADELPHIA, PA 19104-2688 SN 1064-8275 J9 SIAM J SCI COMPUT JI SIAM J. Sci. Comput. PD MAY PY 1994 VL 15 IS 3 BP 681 EP 703 DI 10.1137/0915044 PG 23 WC Mathematics, Applied SC Mathematics GA NH805 UT WOS:A1994NH80500013 ER PT J AU CHELTON, DB EDDY, WF DEVEAUX, R FELDMAN, R GLAZMAN, RE GRIFFA, A KELLY, KA MACDONALD, GJ ROSENBLATT, M ROZOVSKII, B TUCKER, JR AF CHELTON, DB EDDY, WF DEVEAUX, R FELDMAN, R GLAZMAN, RE GRIFFA, A KELLY, KA MACDONALD, GJ ROSENBLATT, M ROZOVSKII, B TUCKER, JR TI REPORT ON STATISTICS AND PHYSICAL OCEANOGRAPHY SO STATISTICAL SCIENCE LA English DT Article ID ADVECTIVE SURFACE VELOCITIES; OCEAN CIRCULATION MODEL; RANDOM SEA; GENERAL-CIRCULATION; DATA ASSIMILATION; NORTH-ATLANTIC; SATELLITE; ZONE; TEMPERATURE; DISPERSION AB This report, prepared in response to a request from the Office of Naval Research, describes research opportunities in statistics and applied probability arising in physical oceanographic applications. It is expository, with the intended audience being statisticians and quantitatively literate people with a background in statistical applications to science, and federal agency representatives interested in encouraging such cross-disciplinary research. C1 CARNEGIE MELLON UNIV,PITTSBURGH,PA 15213. PRINCETON UNIV,PRINCETON,NJ 08544. UNIV CALIF SANTA BARBARA,SANTA BARBARA,CA 93106. JET PROP LAB,PASADENA,CA 91109. UNIV MIAMI,CORAL GABLES,FL 33124. WOODS HOLE OCEANOG INST,WOODS HOLE,MA 02543. UNIV CALIF SAN DIEGO,LA JOLLA,CA 92093. UNIV SO CALIF,LOS ANGELES,CA 90089. RP CHELTON, DB (reprint author), OREGON STATE UNIV,CORVALLIS,OR 97331, USA. NR 164 TC 10 Z9 10 U1 0 U2 1 PU INST MATHEMATICAL STATISTICS PI HAYWARD PA IMS BUSINESS OFFICE-SUITE 6 3401 INVESTMENT BLVD, HAYWARD, CA 94545 SN 0883-4237 J9 STAT SCI JI Stat. Sci. PD MAY PY 1994 VL 9 IS 2 BP 167 EP 201 PG 35 WC Statistics & Probability SC Mathematics GA NX022 UT WOS:A1994NX02200002 ER PT J AU RAMESHAM, R ROSE, MF ASKEW, RF BEKKER, TL DAYTON, JA KRAINSKY, IL MEARINI, G FILE, D GILMOUR, AS AYRES, V AF RAMESHAM, R ROSE, MF ASKEW, RF BEKKER, TL DAYTON, JA KRAINSKY, IL MEARINI, G FILE, D GILMOUR, AS AYRES, V TI EFFECT OF HYDROGEN ON THE PROPERTIES OF POLYCRYSTALLINE DIAMOND THIN-FILMS SO SURFACE & COATINGS TECHNOLOGY LA English DT Article ID SECONDARY-ELECTRON EMISSION; RESISTIVITY; CARBON; GROWTH AB Microwave plasma-assisted chemical vapor deposition has been used to grow undoped and doped diamond on molybdenum and silicon substrates. Current-voltage (I-V), characteristics, secondary electron emission and depth profiles for various elements by secondary ion mass spectrometry of diamond films have been measured before and after annealing in nitrogen gas at 425-degrees-C. We have analyzed the films for morphology and chemical nature by scanning electron microscopy and Raman spectroscopy respectively. Hydrogen present in the as-deposited diamond films resulted in a decrease in the electrical resistivity and an increase in secondary electron yield. Furthermore, we have observed an increase in resistivity and decrease in yield on annealing. Comparison of these results is presented in this paper. C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. USN,CTR SURFACE WARFARE,PORT HUENEME,CA. USN,CTR SURFACE WARFARE,CRANE,IN. SUNY BUFFALO,BUFFALO,NY 14260. USN,CTR SURFACE WARFARE,DAHLGREN,VA 22448. RP RAMESHAM, R (reprint author), AUBURN UNIV,INST SPACE POWER,231 LEACH CTR,AUBURN,AL 36849, USA. NR 17 TC 9 Z9 9 U1 0 U2 0 PU ELSEVIER SCIENCE SA LAUSANNE PI LAUSANNE 1 PA PO BOX 564, 1001 LAUSANNE 1, SWITZERLAND SN 0257-8972 J9 SURF COAT TECH JI Surf. Coat. Technol. PD MAY PY 1994 VL 64 IS 2 BP 81 EP 86 PG 6 WC Materials Science, Coatings & Films; Physics, Applied SC Materials Science; Physics GA NN237 UT WOS:A1994NN23700004 ER PT J AU CAI, Z MUTHARASAN, R KO, FK STEINETZ, BM AF CAI, Z MUTHARASAN, R KO, FK STEINETZ, BM TI PARAMETRIC STUDY OF LEAKAGE FLOW IN BRAIDED FIBER SEALS SO TEXTILE RESEARCH JOURNAL LA English DT Article ID COMPOSITES AB In applications of braided fiber engine seals, the preload and engine pressures are the two main parameters determining seal leakage, and experiments evaluating seal leakage flow are designed using these pressures. To simplify seal performance evaluation, an empirical expression for the relationship of seal leakage resistance against preload and engine pressures is proposed. The basis for this approach is that seal leakage resistance depends on both preload and engine pressures. The physics of these pressure effects is studied both theoretically and experimentally. The main effect of preload pressure is to change seal porosity and thus leakage flow resistance. At the low porosity range of seal fiber architecture, seal porosity change due to imposed engine pressure is negligible; the effect of engine pressure is related to the flowing fluids, which also contribute to overall seal leakage resistance. Experimental data show that the proposed empirical model can be used to predict seal leakage within a range of engine and preload pressures of practical interest. Its simple form is advantageous in estimating seal performance under various pressures. C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP CAI, Z (reprint author), DREXEL UNIV,PHILADELPHIA,PA 19104, USA. RI Mutharasan, Raj/H-2676-2013 OI Mutharasan, Raj/0000-0002-3734-5438 NR 13 TC 0 Z9 0 U1 0 U2 0 PU TEXTILE RESEARCH INST PI PRINCETON PA PO BOX 625, PRINCETON, NJ 08540 SN 0040-5175 J9 TEXT RES J JI Text. Res. J. PD MAY PY 1994 VL 64 IS 5 BP 280 EP 290 DI 10.1177/004051759406400505 PG 11 WC Materials Science, Textiles SC Materials Science GA NN331 UT WOS:A1994NN33100005 ER PT J AU BRANNAS, E LUNDQVIST, H PRENTICE, E SCHMITZ, M BRANNAS, K WIKLUND, BS AF BRANNAS, E LUNDQVIST, H PRENTICE, E SCHMITZ, M BRANNAS, K WIKLUND, BS TI USE OF THE PASSIVE INTEGRATED TRANSPONDER (PIT) IN A FISH IDENTIFICATION AND MONITORING-SYSTEM FOR FISH BEHAVIORAL-STUDIES SO TRANSACTIONS OF THE AMERICAN FISHERIES SOCIETY LA English DT Article ID SALVELINUS-ALPINUS AB Use of the passive integrated transponder (PIT) as a fish identification and monitoring system for behavioral study of Arctic char Salvelinus alpinus was evaluated. The system was developed in order to track individual differences, mainly in rheotactic behavior. In a preliminary experimental setup, Arctic char (N = 20, 9-140 g each) were PIT-tagged and their movements were recorded at regular intervals in a circular stream channel. Two PIT tag loop detectors, placed on a narrow part of the channel, automatically recorded identity and swimming direction of tagged fish. We demonstrate some of the applications in behavioral research, such as individual, general, and diel locomotor activity patterns, rheotactic behavior, and sociograms showing activity relationships among individuals within a group. C1 NATL MARINE FISHERIES SERV,MANCHESTER,WA 98353. UMEA UNIV,DEPT ECON,S-90187 UMEA,SWEDEN. RP BRANNAS, E (reprint author), SWEDISH UNIV AGR SCI,DEPT AQUACULTURE,S-90183 UMEA,SWEDEN. NR 10 TC 46 Z9 46 U1 2 U2 16 PU AMER FISHERIES SOC PI BETHESDA PA 5410 GROSVENOR LANE SUITE 110, BETHESDA, MD 20814-2199 SN 0002-8487 J9 T AM FISH SOC JI Trans. Am. Fish. Soc. PD MAY PY 1994 VL 123 IS 3 BP 395 EP 401 DI 10.1577/1548-8659(1994)123<0395:UOTPIT>2.3.CO;2 PG 7 WC Fisheries SC Fisheries GA NT404 UT WOS:A1994NT40400013 ER PT J AU QI, J HUETE, AR CABOT, F CHEHBOUNI, A AF QI, J HUETE, AR CABOT, F CHEHBOUNI, A TI BIDIRECTIONAL PROPERTIES AND UTILIZATIONS OF HIGH-RESOLUTION SPECTRA FROM A SEMIARID WATERSHED SO WATER RESOURCES RESEARCH LA English DT Article ID REFLECTANCE FACTOR DISTRIBUTIONS; SURFACE REFLECTANCE; COVER TYPES; ANGLE; AZIMUTH; CANOPY; SYSTEM AB A ground- and air-based high spectral resolution data set was collected during the summer Monsoon '90 experiment at the Walnut Gulch experimental watershed in southeastern Arizona for the purpose of (1) characterizing solar and view angle interactions on dry and wet season canopy spectra, and (2) exploring the use of multidirectional measurements to infer vegetation properties for semiarid watershed studies. Bidirectional reflectance factors were measured up to 40-degrees off nadir with a spectroradiometer over a semidesert grassland site. High-spectral resolution aircraft data were collected over grass and desert shrub sites in order to investigate scaling effects. In this study, solar and view angle effects and interactions on canopy spectra varied with spectral wavelength as well as between dry and wet seasons. The solar zenith angle modified the view angle behavior of the bidirectional reflectance factors. In general, view angle influences and spectral signature contrasts were greatest at the larger solar zenith angles and similarly, Sun angle influences were more apparent at the larger view zenith angle. The scale dependency of the data was relatively minor. The bidirectional measurements were sufficiently characterized by a physically based bidirectional reflectance distribution function (BRDF) model. The parameters retrieved from the inversion of the BRDF model corresponded with observed vegetation variations. C1 LAB ETUDES & RECH TELEDETECT SPATIALE,F-31055 TOULOUSE,FRANCE. JET PROP LAB,HYDROL SOILS & ECOL GRP,PASADENA,CA 91109. UNIV ARIZONA,DEPT SOIL & WATER SCI,TUCSON,AZ 85721. RP QI, J (reprint author), USDA ARS,SW WATERSHED RES CTR,2000 E ALLEN RD,TUCSON,AZ 85719, USA. RI Huete, Alfredo/C-1294-2008 OI Huete, Alfredo/0000-0003-2809-2376 NR 23 TC 14 Z9 15 U1 0 U2 2 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 MAY PY 1994 VL 30 IS 5 BP 1271 EP 1279 DI 10.1029/93WR03058 PG 9 WC Environmental Sciences; Limnology; Water Resources SC Environmental Sciences & Ecology; Marine & Freshwater Biology; Water Resources GA NJ817 UT WOS:A1994NJ81700006 ER PT J AU MENENTI, M RITCHIE, JC AF MENENTI, M RITCHIE, JC TI ESTIMATION OF EFFECTIVE AERODYNAMIC ROUGHNESS OF WALNUT GULCH WATERSHED WITH LASER ALTIMETER MEASUREMENTS SO WATER RESOURCES RESEARCH LA English DT Article ID COMPLEX TERRAIN; BOUNDARY-LAYER; CANOPY; FLOW; PARAMETERIZATION; TOPOGRAPHY; SURFACES; COTTON; DRAG AB A new method to estimate the effective aerodynamic roughness of a complex landscape is presented. High-resolution elevation profiles measured with an airbome laser altimeter have been used to compute geometrical parameters of three landscape elements of the Walnut Gulch experimental watershed, Arizona. Mean crop height, its standard deviation, and the frequency distribution (as a function of penetration depth) of plant elements hit by the laser beam have been calculated for short segments (1 m) measured over intervening grass between shrubs. Longer segments have been applied to obtain the mean height and spacing of taller shrubs and trees. Finally, laser profiles covering the entire watershed gave the mean amplitude and wavelength of hillocks and ridges. The aerodynamic roughness length of the intervening grass is estimated using the ratio of standard deviation to vegetation height, corrected for instrument noise, times mean height. An effective roughness length which parameterizes the total stress due to grass and taller shrubs and trees is calculated first. Finally, a watershed-scale effective roughness length is calculated combining the amplitude and wavelength of hillocks and ridges with the roughness length obtained in the previous step. C1 USDA ARS,BELTSVILLE AGR RES CTR,HYDROL LAB,BARC E,BELTSVILLE,MD 20705. NASA,GODDARD SPACE FLIGHT CTR,HYDROSPHER PROC LAB,GREENBELT,MD 20771. RP MENENTI, M (reprint author), DLO,WINAND STARING CTR INTEGRATED LAND SOIL & WATER RES,AGR RES DEPT,MARIJKEWEG 11-22,POB 125,6700 AC WAGENINGEN,NETHERLANDS. OI Menenti, Massimo/0000-0001-9176-4556 NR 35 TC 74 Z9 75 U1 0 U2 5 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 MAY PY 1994 VL 30 IS 5 BP 1329 EP 1337 DI 10.1029/93WR03055 PG 9 WC Environmental Sciences; Limnology; Water Resources SC Environmental Sciences & Ecology; Marine & Freshwater Biology; Water Resources GA NJ817 UT WOS:A1994NJ81700012 ER PT J AU MORTON, CW HOFMEISTER, WH BAYUZICK, RJ ROBINSON, MB AF MORTON, CW HOFMEISTER, WH BAYUZICK, RJ ROBINSON, MB TI A STATISTICAL APPROACH TO UNDERSTANDING NUCLEATION PHENOMENA SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING LA English DT Article; Proceedings Paper CT NATO Advanced Research Workshop on Undercooled Metallic Melts: Properties, Solidification and Metastable Phases CY JUN 06-12, 1993 CL IL CIOCCO CENTRO INT SPA, IL CIOCCO, ITALY SP NATO, SCI AFFAIRS DIV, EUROPEAN SPACE AGCY, NASA, GERMAN AEROSP RES ESTAB, GERMAN SPACE AGCY, CNR, DORNIER GMBH HO IL CIOCCO CENTRO INT SPA ID DROP AB A series of undercooling experiments using pure metal samples of niobium and zirconium were performed using the Marshall Space Flight Center 105 meter drop tube, and for zirconium using both electromagnetic and electrostatic levitation in the laboratory. The results from a large number of experiments allowed nucleation frequencies to be measured, following the suggestion of Skripov. Using the nucleation frequencies, the nucleation probability distributions and the cumulative distributions, the critical free energy of nucleation and the magnitude of the pre-exponential in the classical nucleation equation were determined. The results for the pre-exponential and critical free energy for zirconium ranged from 10(8) to 10(13) and 15 kT to 24 kT respectively. Higher purity zirconium stock was observed to cause significant shifts in the undercoolings to higher values. For niobium the values were 10(31) and 73 kT for the pre-exponential and the critical free energy, respectively. C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. RP MORTON, CW (reprint author), VANDERBILT UNIV,NASHVILLE,TN 37235, USA. NR 14 TC 19 Z9 19 U1 1 U2 9 PU ELSEVIER SCIENCE SA LAUSANNE PI LAUSANNE 1 PA PO BOX 564, 1001 LAUSANNE 1, SWITZERLAND SN 0921-5093 J9 MAT SCI ENG A-STRUCT JI Mater. Sci. Eng. A-Struct. Mater. Prop. Microstruct. Process. PD APR 30 PY 1994 VL 178 IS 1-2 BP 209 EP 215 DI 10.1016/0921-5093(94)90545-2 PG 7 WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Science & Technology - Other Topics; Materials Science; Metallurgy & Metallurgical Engineering GA NH615 UT WOS:A1994NH61500038 ER PT J AU KEMP, PA AF KEMP, PA TI ASYNCHRONOUS CIRCUIT LATCHES SAFELY SO EDN LA English DT Note RP KEMP, PA (reprint author), NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058, USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU CAHNERS-DENVER PUBLISHING CO PI HIGHLANDS RANCH PA 8773 S RIDGELINE BLVD, HIGHLANDS RANCH, CO 80126-2329 SN 0012-7515 J9 EDN JI EDN PD APR 28 PY 1994 VL 39 IS 9 BP 70 EP 70 PG 1 WC Engineering, Electrical & Electronic SC Engineering GA NH584 UT WOS:A1994NH58400011 ER PT J AU WANG, S TRAJMAR, S ZETNER, PW AF WANG, S TRAJMAR, S ZETNER, PW TI CROSS-SECTIONS FOR ELECTRON-SCATTERING BY GROUND-STATE BA - ELASTIC-SCATTERING AND EXCITATION OF THE ... 6S6P(1)P1 LEVEL SO JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS LA English DT Article ID COHERENCE PARAMETERS; BARIUM; IMPACT AB Differential cross sections for elastic and inelastic (6s6p P-1(1)) electron scattering from ground state Ba atom have been measured at 5 eV, 10 eV, 15 eV and 20 eV impact energies in the angular range from 0-degrees to 130-degrees. Extrapolation to larger angles has been performed using theoretical calculations as a guide, and integral and momentum transfer cross sections were derived. Theoretical calculations based on two-channel close coupling and relativistic and non-relativistic distorted wave methods have been compared with the present results. Good agreement between experiment and various theoretical results is found at small scattering angles but significant deviations exist at larger scattering angles. C1 UNIV MANITOBA,DEPT PHYS,WINNIPEG R3T 2N2,MANITOBA,CANADA. RP WANG, S (reprint author), JET PROP LAB,PASADENA,CA 91109, USA. NR 23 TC 26 Z9 26 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA TECHNO HOUSE, REDCLIFFE WAY, BRISTOL, ENGLAND BS1 6NX SN 0953-4075 J9 J PHYS B-AT MOL OPT JI J. Phys. B-At. Mol. Opt. Phys. PD APR 28 PY 1994 VL 27 IS 8 BP 1613 EP 1621 DI 10.1088/0953-4075/27/8/020 PG 9 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA NK149 UT WOS:A1994NK14900020 ER PT J AU ROTHSCHILD, LJ AF ROTHSCHILD, LJ TI CO2 AND DIATOM MATS SO NATURE LA English DT Letter ID CARBON FIXATION; MODEL RP ROTHSCHILD, LJ (reprint author), NASA,AMES RES CTR,ECOSYST SCI & TECHNOL BRANCH,MAIL STOP 239-12,MOFFETT FIELD,CA 94035, USA. NR 12 TC 2 Z9 2 U1 0 U2 1 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW SN 0028-0836 J9 NATURE JI Nature PD APR 28 PY 1994 VL 368 IS 6474 BP 817 EP 817 DI 10.1038/368817a0 PG 1 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA NH717 UT WOS:A1994NH71700052 PM 11539832 ER PT J AU RAVI, KV KOCH, CA OLSON, DS CHOONG, P VANDERSANDE, JW ZOLTAN, LD AF RAVI, KV KOCH, CA OLSON, DS CHOONG, P VANDERSANDE, JW ZOLTAN, LD TI ELECTRICAL-CONDUCTIVITY OF COMBUSTION-FLAME SYNTHESIZED DIAMOND SO APPLIED PHYSICS LETTERS LA English DT Article ID FILMS AB The electrical conductivity, from room temperature to 1000-degrees-C, of combustion flame synthesized diamond films and free-standing diamond slabs are demonstrated to be up to two orders of magnitude lower than that of type IIa natural diamond crystals. The low conductivity, indicative of high purity, has been achieved at diamond growths rates of 5-10 mum/h, considerably higher than that achievable with other diamond synthesis techniques. These high growth rates have been achieved over areas of 5 cm x 5 cm and both thin (10 mum) films on silicon substrates and thick (approximately 80 mum), free-standing diamond slabs exhibit similar electrical behavior. The high purity of this diamond is attributed to the presence of oxidizing species in the flame ambient which are more effective than hydrogen in removing any nondiamond forms of carbon and other impurities from the growing diamond film. C1 LOCKHEED MISSILES & SPACE CO INC,SUNNYVALE,CA 94088. JET PROP LAB,PASADENA,CA 91109. RP RAVI, KV (reprint author), LOCKHEED MISSILES & SPACE CO INC,DIV RES & DEV,3251 HANOVER ST,PALO ALTO,CA, USA. NR 6 TC 7 Z9 7 U1 1 U2 3 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 0003-6951 J9 APPL PHYS LETT JI Appl. Phys. Lett. PD APR 25 PY 1994 VL 64 IS 17 BP 2229 EP 2231 DI 10.1063/1.111685 PG 3 WC Physics, Applied SC Physics GA NH390 UT WOS:A1994NH39000014 ER PT J AU GUNAPALA, SD BANDARA, KMSV LEVINE, BF SARUSI, G SIVCO, DL CHO, AY AF GUNAPALA, SD BANDARA, KMSV LEVINE, BF SARUSI, G SIVCO, DL CHO, AY TI VERY LONG-WAVELENGTH INXGA1-XAS/GAAS QUANTUM-WELL INFRARED PHOTODETECTORS SO APPLIED PHYSICS LETTERS LA English DT Article AB We demonstrate a long wavelength (lambda(c) = 20 mum) quantum well infrared photodetector using nonlattice matched InxGa1-xAs/GaAs materials system. High optical gains (low capture probabilities) were achieved by using GaAs as a barrier material in this system. A detectivity of D* = 9.7 X 10(10) cm square-root Hz/W at T = 10 K has been achieved. C1 AT&T BELL LABS,MURRAY HILL,NJ 07974. RP GUNAPALA, SD (reprint author), JET PROP LAB,CTR SPACE MICROELECTR TECHNOL,PASADENA,CA 91109, USA. NR 11 TC 39 Z9 39 U1 1 U2 5 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 0003-6951 J9 APPL PHYS LETT JI Appl. Phys. Lett. PD APR 25 PY 1994 VL 64 IS 17 BP 2288 EP 2290 DI 10.1063/1.111646 PG 3 WC Physics, Applied SC Physics GA NH390 UT WOS:A1994NH39000034 ER PT J AU PANDA, J ZAMAN, KBMQ AF PANDA, J ZAMAN, KBMQ TI EXPERIMENTAL INVESTIGATION OF THE FLOW-FIELD OF AN OSCILLATING AIRFOIL AND ESTIMATION OF LIFT FROM WAKE SURVEYS SO JOURNAL OF FLUID MECHANICS LA English DT Article ID TRANSLATING AIRFOIL; VORTEX FORMATION AB The flow field of an airfoil oscillated periodically over a reduced frequency range, 0 less-than-or-equal-to k less-than-or-equal-to 1.6, is studied experimentally at chord Reynolds numbers of R(c) = 22000 and 44000. For most of the data, the NACA0012 airfoil is pitched sinusoidally about one quarter chord between angles of attack alpha of 5-degrees and 25-degrees. The cyclic variation of the near wake flow field is documented through flow visualization and phase-averaged vorticity measurements. In addition to the familiar dynamic stall vortex (DSV), an intense vortex of opposite sign is observed to originate from the trailing edge just when the DSV is shed. The two together take the shape of the cross-section of a large 'mushroom' while being convected away from the airfoil. The phase delay in the shedding of the DSV with increasing k, as observed by previous researchers, is documented for the full range of k. It is observed that the sum of the absolute values of all vorticity convected into the wake over a cycle is nearly constant and is independent of the reduced frequency and amplitude of oscillation but dependent on the mean alpha. The time varying component of the lift is estimated in a novel way from the shed vorticity flux. The analytical foundation of the method and the various approximations are discussed. The estimated lift hysteresis loops are found to be in reasonable agreement with available data from the literature as well as with limited force balance measurements. Comparison of the lift hysteresis loops with the corresponding vorticity fields clearly shows that the major features of the lift variation are directly linked to the evolution of the large-scale vortical structures and the phase delay phenomenon. RP PANDA, J (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 35 TC 52 Z9 52 U1 1 U2 4 PU CAMBRIDGE UNIV PRESS PI NEW YORK PA 40 WEST 20TH STREET, NEW YORK, NY 10011-4211 SN 0022-1120 J9 J FLUID MECH JI J. Fluid Mech. PD APR 25 PY 1994 VL 265 BP 65 EP 95 DI 10.1017/S0022112094000765 PG 31 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA NK463 UT WOS:A1994NK46300003 ER PT J AU BAER, G SCHUBERT, G BINDSCHADLER, DL STOFAN, ER AF BAER, G SCHUBERT, G BINDSCHADLER, DL STOFAN, ER TI SPATIAL AND TEMPORAL RELATIONS BETWEEN CORONAE AND EXTENSIONAL BELTS, NORTHERN LADA-TERRA, VENUS SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID MAGELLAN OBSERVATIONS; SURFACE MODIFICATION; INITIAL ANALYSIS; EISTLA REGIO; HOT-SPOT; EMPLACEMENT; VOLCANISM; TECTONICS; GEOLOGY; ORIGIN AB Preliminary studies of the distribution of coronae and volcanic rises on Venus show that many of these features tend to cluster along zones of rifting and extension. The plains north of Lada Terra are crossed by two such extensional belts. Each belt is composed of grabens, ridges, faults, volcanic flows, coronae, and coronalike features. The longer and more prominent belt is the NW trending Alpha-Lada extensional belt, which is over 6000 km long and 50-200 km wide, and includes the coronae Eve, Tamfana, Carpo, Selu, Derceto, Otygen, and an unnamed corona south of Otygen. The second belt is the NNE trending Derceto-Quetzalpetlatl extensional belt, which is about 2000 lan long and in places over 300 km wide, and includes the coronae Sarpanitum, Eithinoha, and Quetzalpetlatl. The two belts intersect at the 1600 x 600 km wide Derceto volcanic plateau. It is apparent that deformation along the two belts overlapped in time, though deformation along the Alpha-Lada extensional belt probably continued after the deformation along the Derceto-Quetzalpetlatl extensional belt terminated. In certain areas, volcanism originated in grabens within the extensional belts, whereas in other areas, such as in Eve, Selu, Derceto, and Quetzalpetlatl, volcanism originated in the coronae and flowed into the lower parts of the extensional belts. Regional extension has affected the evolution of all the coronae at some stage of their development. Regional deformation occurred before the initiation of Derceto and Eithinoha and after the initiation of Carpo, Tamfana, Otygen, and Sarpanitum. It is thus unlikely that coronae formation along the belts is solely a consequence of the regional extension, and it is also unlikely that regional extension has been caused solely by the coronae. No corona along the belts was formed subsequent to the cessation of the regional extension. We therefore suggest that the regional extension and the coronae are interrelated. Some of the coronae may have determined the location of the surface expression of the regional extension, whereas the locations of other coronae may have been influenced by the concentration of regional extensional stresses. C1 UNIV CALIF LOS ANGELES,INST GEOPHYS & PLANETARY SCI,DEPT EARTH & SPACE SCI,LOS ANGELES,CA 90024. JET PROP LAB,PASADENA,CA 91109. RP BAER, G (reprint author), GEOL SURVEY ISRAEL,30 MALKHE ISRAEL ST,IL-95501 JERUSALEM,ISRAEL. NR 30 TC 30 Z9 30 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD APR 25 PY 1994 VL 99 IS E4 BP 8355 EP 8369 DI 10.1029/93JE03092 PG 15 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA NJ072 UT WOS:A1994NJ07200001 ER PT J AU CLARKE, JT AJELLO, J LUHMANN, J SCHNEIDER, N KANIK, I AF CLARKE, JT AJELLO, J LUHMANN, J SCHNEIDER, N KANIK, I TI HUBBLE-SPACE-TELESCOPE UV SPECTRAL OBSERVATIONS OF IO PASSING INTO ECLIPSE SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID ULTRAVIOLET-SPECTRUM; GALILEAN SATELLITES; ELECTRON-IMPACT; SO2 ATMOSPHERE; PLASMA TORUS; SURFACE; IONOSPHERE; ABUNDANCE; JUPITER; FROSTS AB Time-resolved spectra of Io have been obtained with the Faint Object Spectrograph on the Hubble Space Telescope in January 1992 at times centered on the passage of Io into Jupiter's shadow. Two different eclipse observations covered 1100-1600 angstrom and 2250-3.300 angstrom. In the far-UV range, emission lines of atomic sulfur and oxygen from Io's atmosphere (similar to those previously detected with IUE) have been observed from lo in sunlight, and the spatial extent of the emitting region has been resolved for the first time: this is 0.5-1 Io radii (R(Io)) above the surface. The emission lines are typically 1 kR in brightness while lo is in sunlight, and decrease to a few hundred Rayleighs within 20 min or less of Io's passing into shadow. If the emissions are produced in Io's ionosphere, the decrease in shadow appears consistent with the collisional slowing and recombination of photoelectrons in 100-1000 s, with recombination an important quenching process if the dominant ion is molecular (i.e., SO2+). By contrast, the impact of corotating torus electrons is expected to continue when lo is in shadow. If impact by torus plasma dominates the emission, the decrease in shadow may be due to surface SO2 condensation, with the residual emission in shadow due either to plasma impact of gas above the hot volcanic calderas or electron impact on S and O. In the near-UV range, we have not detected any airglow emissions from lo's atmosphere in shadow, with the main limitation being a high level of scattered light from Jupiter. We derive a 3sigma upper limit to the 2560 angstrom So emission feature of 1 kR, which is close to what is expected from electron impact on SO2 based on the observed brightness of the FUV S and O lines in shadow. A high signal-to-noise spectrum of Io's albedo in sunlight reveals a spectral shape similar to laboratory spectra of SO2 frost reflectivity, and the relative albedo spectrum changed as lo passed into eclipse and part of the disk was in shadow. No specific SO2 gas absorption features appear in the albedo spectrum, although there could be substantial gas absorption near 2800 angstrom if the individual lines are narrow and saturated. Finally, we present preliminary models for the near-UV spectrum of Io as functions of SO2 frost areal coverage and SO2 gas density. C1 JET PROP LAB,PASADENA,CA 91109. UNIV CALIF LOS ANGELES,DEPT SOCIAL STUDIES,LOS ANGELES,CA 90024. UNIV COLORADO,DEPT ASTROPHYS PLANETARY & ATMOSPHER SCI,BOULDER,CO 80309. RP CLARKE, JT (reprint author), UNIV MICHIGAN,DEPT ATMOSPHER OCEAN & SPACE SCI,2455 HAYWARD ST,ANN ARBOR,MI 48109, USA. RI Clarke, John/C-8644-2013; OI SCHNEIDER, NICHOLAS/0000-0001-6720-5519 NR 44 TC 56 Z9 56 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 APR 25 PY 1994 VL 99 IS E4 BP 8387 EP 8402 DI 10.1029/93JE02547 PG 16 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA NJ072 UT WOS:A1994NJ07200003 ER PT J AU SATOH, T KAWABATA, K AF SATOH, T KAWABATA, K TI A CHANGE OF UPPER CLOUD STRUCTURE IN JUPITER SOUTH EQUATORIAL BELT DURING THE 1989-1990 EVENT SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID METHANE BAND PHOTOMETRY; JOVIAN ATMOSPHERE; RED SPOT; REFLECTIVITY; ZONE AB We have analyzed two data sets of Jupiter's limb darkening taken before (March 1990) and after (March 1991) a South Equatorial Belt (SEB) disturbance. The vertical aerosol structure has been determined for the SEB, the Equatorial Zone (EZ), and the North Equatorial Belt (NEB). We find that all regions can be well represented with a two-cloud layer model, with slightly higher NH3-cloud top altitude in the EZ than in the two belts. The cloud single-scattering albedos omega(cl) (determined within +/- 0.003) show little difference in the EZ (from 0.9956 to 0.9952) and the NEB (from 0.9925 to 0.9926) during a 1-year period, while a relatively larger decrease is found in the SEB from 0.9975 to 0.9957, indicating the recovery of the belt through the disturbance. The NH3-cloud top altitude in the SEB shows the most prominent change, lower in 1990 and higher in 1991. We suggest that the brightening and the darkening of the SEB may originate not only from the changes of omega(cl) but also from changes of the ammonia condensation level in the atmosphere, probably due to a decrease of the tropospheric temperature and/or an increase of the ammonia vapor. C1 SCI UNIV TOKYO,COLL SCI,DEPT PHYS,SHINJUKU KU,TOKYO 162,JAPAN. RP SATOH, T (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HUGHES STX CORP,CODE 695,GREENBELT,MD 20771, USA. NR 20 TC 9 Z9 9 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 APR 25 PY 1994 VL 99 IS E4 BP 8425 EP 8440 DI 10.1029/94JE00215 PG 16 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA NJ072 UT WOS:A1994NJ07200006 ER PT J AU NEWMAN, PA AF NEWMAN, PA TI ANTARCTIC TOTAL OZONE IN 1958 SO SCIENCE LA English DT Article ID VORTEX; CLOUD; SO2 AB The Antarctic ozone hole results from catalytic destruction of ozone by chlorine radicals. The hole develops in August, reaches its full depth in early October, and is gone by early December of each year. Extremely low total ozone measurements were made at the Antarctic Dumont d'Urville station in 1958. These measurements were derived from spectrographic prates of the blue sky, the moon, and two stars. These Dumont plate data are inconsistent with 1958 Dobson spectrophotometer ozone measurements, inconsistent with present-day Antarctic observations, and inconsistent with meteorological and theoretical information. There is no credible evidence for an ozone hole in 1958. RP NASA, GODDARD SPACE FLIGHT CTR, ATMOSPHER CHEM & DYNAM BRANCH, CODE 916, GREENBELT, MD 20771 USA. RI Newman, Paul/D-6208-2012 OI Newman, Paul/0000-0003-1139-2508 NR 44 TC 4 Z9 4 U1 0 U2 2 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 EI 1095-9203 J9 SCIENCE JI Science PD APR 22 PY 1994 VL 264 IS 5158 BP 543 EP 546 DI 10.1126/science.264.5158.543 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA NH010 UT WOS:A1994NH01000028 PM 17732736 ER PT J AU HUDGINS, DM SANDFORD, SA ALLAMANDOLA, LJ AF HUDGINS, DM SANDFORD, SA ALLAMANDOLA, LJ TI INFRARED-SPECTROSCOPY OF POLYCYCLIC AROMATIC HYDROCARBON CATIONS .1. MATRIX-ISOLATED NAPHTHALENE AND PERDEUTERATED NAPHTHALENE SO JOURNAL OF PHYSICAL CHEMISTRY LA English DT Article ID CONDENSED AROMATICS; SPECTRAL PROPERTIES; EMISSION FEATURES; ICE ANALOGS; MOLECULES; BANDS; CO AB Ionized polycyclic aromatic hydrocarbons (PAHs) are thought to constitute an important component of the interstellar medium. Despite this fact, the infrared spectroscopic properties of ionized PAHs are almost unknown. The results we present here derive from our ongoing spectroscopic study of matrix isolated PAH ions and include the spectra of the naphthalene cation, C10H8+, and its fully deuterated analog, C10D8+, between 4000 and 200 cm(-1). Ions ace generated by in situ Lyman-alpha photoionization of the neutral precursor. Bands of the C10H8+ ion are observed at 1525.7, 1518.8, 1400.9, 1218.0, 1216.9, 1214.9, 1023.2, and 758.7 cm(-1). Positions and relative intensities of these bands agree well with those in the available literature. The 758.7-cm(-1) band has not previously been reported. C10D8+ ion bands appear at 1466.2, 1463.8, 1379.4, 1373.8, 1077.3, 1075.4, and 1063.1 cm(-1). Compared to the analogous modes in the neutral molecule, the intensities of the cation's CC modes are enhanced by an order of magnitude, while CH modes are depressed by this same factor. Integrated absorption intensities are calculated for the strongest bands of C10H8 and for the observed bands of C10H8+. Absolute intensities derived for the naphthalene cation differ from earlier experimental results by a factor of similar to 50, and from theoretical predictions by a factor of similar to 300. Reasons for these discrepancies and from the astronomical implications of PAH cation spectra are discussed. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. NR 33 TC 165 Z9 165 U1 3 U2 19 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0022-3654 J9 J PHYS CHEM-US JI J. Phys. Chem. PD APR 21 PY 1994 VL 98 IS 16 BP 4243 EP 4253 DI 10.1021/j100067a008 PG 11 WC Chemistry, Physical SC Chemistry GA NH490 UT WOS:A1994NH49000008 PM 12269375 ER PT J AU NESBITT, FL MONKS, PS SCANLON, M STIEF, LJ AF NESBITT, FL MONKS, PS SCANLON, M STIEF, LJ TI ABSOLUTE RATE CONSTANTS FOR THE REACTIONS OF F(P-2) WITH C2H2 AND C2H4 AT T=298 K SO JOURNAL OF PHYSICAL CHEMISTRY LA English DT Article ID HYDROGEN-ATOM ABSTRACTION; RADICAL REACTIONS; FLUORINE-ATOMS; TEMPERATURE; DEPENDENCE; VINYL; THERMOCHEMISTRY; HYDROCARBONS; CHLORINE; KINETICS AB Absolute rate constants for the reactions of C2H2 and C2H4 with F(P-2) atoms have been measured using the discharge-flow kinetic technique coupled to mass spectrometric detection at T = 298 K and 1 Torr nominal pressure. The results obtained were k(F+C2H2) = (6.2 +/- 1.3) x 10(-12) cm(3) molecule(-1) s(-1), which at low pressures is associated with the abstraction channel forming C2H + HF, and k(F+C2H4) = (2.7 +/- 0.5) X 10(-10) cm(3) molecule(-1) s(-1), which is a measure of the total rate. Product studies were also conducted. This study represents the first direct measurements of the rate constants for both F + C2H2 and F + C2H4 reactions. A comparison between the absolute rate constants and previous relative rate measurements is made. Further comparisons are made with the rates and products of the reactions of the other halogen atoms with C2H2 and C2H4 and the reactions of the pseudohalogen CN with the same molecules. The suitability of these reactions as precursors for vinyl and ethynyl for discharge-flow studies is briefly discussed. C1 COPPIN STATE COLL,DEPT NAT SCI,BALTIMORE,MD. RP NESBITT, FL (reprint author), NASA,GODDARD SPACE FLIGHT CTR,EXTRATERR PHYS LAB,GREENBELT,MD 20771, USA. RI Monks, Paul/H-6468-2016 OI Monks, Paul/0000-0001-9984-4390 NR 35 TC 13 Z9 13 U1 0 U2 2 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0022-3654 J9 J PHYS CHEM-US JI J. Phys. Chem. PD APR 21 PY 1994 VL 98 IS 16 BP 4307 EP 4311 DI 10.1021/j100067a016 PG 5 WC Chemistry, Physical SC Chemistry GA NH490 UT WOS:A1994NH49000016 ER PT J AU BERLAND, BS HAYNES, DR FOSTER, KL TOLBERT, MA GEORGE, SM TOON, OB AF BERLAND, BS HAYNES, DR FOSTER, KL TOLBERT, MA GEORGE, SM TOON, OB TI REFRACTIVE-INDEXES OF AMORPHOUS AND CRYSTALLINE HNO3/H2O FILMS REPRESENTATIVE OF POLAR STRATOSPHERIC CLOUDS SO JOURNAL OF PHYSICAL CHEMISTRY LA English DT Article ID NITRIC-ACID TRIHYDRATE; INDUCED THERMAL-DESORPTION; HETEROGENEOUS REACTIONS; ANTARCTIC STRATOSPHERE; HYDROGEN-CHLORIDE; OZONE HOLE; OPTICAL-CONSTANTS; SURFACE-DIFFUSION; ICE; NITRATE AB Optical interference techniques were used to measure the real index of refraction of nitric acid/ice films representative of type I and type II polar stratospheric clouds (PSCs). Possible candidates for type I PSCs include amorphous HNO3/H2O mixtures as well as crystalline nitric acid trihydrate (NAT), dihydrate (NAD), and monohydrate (NAM). Amorphous and crystalline model PSC films were grown in vacuum by vapor deposition on single-crystal Al2O3 substrates at low temperatures. The real indices of refraction at lambda = 632 nm were measured for these films using the time-dependent optical interference during film deposition. The stoichiometries of the HNO3/H2O films were determined using laser-induced thermal desorption (LITD) techniques. For the amorphous films at 130 K, the refractive indices increased with increasing nitric acid content. The values ranged from n = 1.31 +/- 0.01 for pure ice to n = 1.47 +/- 0.01 for nearly pure nitric acid. A Lorentz-Lorenz analysis was in good agreement with the measured refractive indices of the amorphous HNO3/H2O films as a function of HNO3 mole fraction. Growth of HNO3/H2O films at 175 K resulted in the formation of either crystalline NAM or NAD. The crystalline indices were substantially higher than their amorphous analogs. The crystalline refractive indices at 175 K were n 1.52 +/- 0.01 for NAD and n 1.54 +/- 0.01 for NAM. Attempts to measure the refractive index of crystalline NAT were unsuccessful because NAT films would not nucleate under allowable temperature and pressure conditions. C1 UNIV COLORADO,DEPT CHEM & BIOCHEM,BOULDER,CO 80309. UNIV COLORADO,COOPERAT INST RES ENVIRONM SCI,BOULDER,CO 80309. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RI George, Steven/O-2163-2013 OI George, Steven/0000-0003-0253-9184 NR 60 TC 43 Z9 43 U1 2 U2 6 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0022-3654 J9 J PHYS CHEM-US JI J. Phys. Chem. PD APR 21 PY 1994 VL 98 IS 16 BP 4358 EP 4364 DI 10.1021/j100067a024 PG 7 WC Chemistry, Physical SC Chemistry GA NH490 UT WOS:A1994NH49000024 ER PT J AU WEISSMAN, P AF WEISSMAN, P TI SOLAR-SYSTEM FORMATION - CELESTIAL BODY-BUILDING SO NATURE LA English DT Editorial Material ID HALLEY RP WEISSMAN, P (reprint author), CALTECH,JET PROP LAB,DIV EARTH & SPACE SCI,PASADENA,CA 91109, USA. NR 10 TC 2 Z9 2 U1 0 U2 1 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW SN 0028-0836 J9 NATURE JI Nature PD APR 21 PY 1994 VL 368 IS 6473 BP 687 EP 688 DI 10.1038/368687a0 PG 2 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA NG553 UT WOS:A1994NG55300026 ER PT J AU ZHANG, SN FISHMAN, GJ HARMON, BA PACIESAS, WS AF ZHANG, SN FISHMAN, GJ HARMON, BA PACIESAS, WS TI EARTH OCCULTATION OR CODED MASK - REPLY SO NATURE LA English DT Letter RP ZHANG, SN (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812, USA. NR 3 TC 0 Z9 0 U1 0 U2 0 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW SN 0028-0836 J9 NATURE JI Nature PD APR 21 PY 1994 VL 368 IS 6473 BP 698 EP 698 DI 10.1038/368698b0 PG 1 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA NG553 UT WOS:A1994NG55300043 ER PT J AU FRIEMAN, JA GAZTANAGA, E AF FRIEMAN, JA GAZTANAGA, E TI THE 3-POINT FUNCTION AS A PROBE OF MODELS FOR LARGE-SCALE STRUCTURE SO ASTROPHYSICAL JOURNAL LA English DT Article DE COSMOLOGY, THEORY; GALAXIES, CLUSTERING; LARGE-SCALE STRUCTURE OF THE UNIVERSE; METHODS, NUMERICAL ID COLD DARK MATTER; BIASED GALAXY FORMATION; SHANE-WIRTANEN CATALOG; CORRELATION HIERARCHY; DENSITY-FLUCTUATIONS; REDSHIFT SURVEY; IRAS GALAXIES; POWER-LAW; UNIVERSE; SPECTRUM AB We analyze the consequences of models of structure formation for higher order (n-point) galaxy correlation functions in the mildly nonlinear regime. Several variations of the standard Omega=1 cold dark matter model with scale-invariant primordial perturbations have recently been introduced to obtain more power on large scales, R(p) similar to 20 h(-1) Mpc, e.g., low matter-density (nonzero cosmological constant) models, ''tilted'' primordial spectra, and scenarios with a mixture of cold and hot dark matter. They also include models with an effective scale-dependent bias, such as the cooperative galaxy formation scenario of Bower et al. We show that higher-order (n-point) galaxy correlation functions can provide a useful test of such models and can discriminate between models with true large-scale power in the density field and those where the galaxy power arises from scale-dependent bias: a bias with rapid scale dependence leads to a dramatic decrease of the hierarchical amplitudes Q(J) at large scales, r greater than or similar to R(p). Current observational constraints on the three-point amplitudes Q(3) and S-3 can place limits on the bias parameter(s) and appear to disfavor, but not yet rule out, the hypothesis that scale-dependent bias is responsible for the extra power observed on large scales. C1 UNIV OXFORD,DEPT ASTROPHYS,OXFORD OX1 3RH,ENGLAND. RP FRIEMAN, JA (reprint author), FERMILAB NATL ACCELERATOR LAB,NASA,FERMILAB ASTROPHYS CTR,BATAVIA,IL 60510, USA. OI Gaztanaga, Enrique/0000-0001-9632-0815 NR 69 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 APR 20 PY 1994 VL 425 IS 2 BP 392 EP 402 DI 10.1086/173995 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA PM579 UT WOS:A1994PM57900005 ER PT J AU REICHERT, GA RODRIGUEZPASCUAL, PM ALLOIN, D CLAVEL, J CRENSHAW, DM KRISS, GA KROLIK, JH MALKAN, MA NETZER, H PETERSON, BM WAMSTEKER, W ALTAMORE, A ALTIERI, B ANDERSON, KS BLACKWELL, JH BOISSON, C BROSCH, N CARONE, TE DIETRICH, M ENGLAND, MN EVANS, IN FILIPPENKO, AV GASKELL, CM GOAD, M GONDHALEKAR, PM HORNE, K KAZANAS, D KOLLATSCHNY, W KORATKAR, AP KORISTA, KT MACALPINE, GM MAOZ, D MAZEH, T MCCOLLUM, B MILLER, HR DEOLIVEIRA, CM OBRIEN, PT PASTORIZA, MG PELAT, D PEREZ, E PEROLA, GC POGGE, RW PTAK, RL RECONDOGONZALEZ, MC RODRIGUEZESPINOSA, J ROSENBLATT, EI SADUN, AC SANTOSLLEO, M SHIELDS, JC SHRADER, CR SHULL, JM SIMKIN, SM SITKO, ML SNIJDERS, MAJ SPARKE, LS STIRPE, GM STONER, R STORCHIBERGMANN, T SUN, WH WANG, T WELSH, WF WHITE, RJ WINGE, C ZHENG, W AF REICHERT, GA RODRIGUEZPASCUAL, PM ALLOIN, D CLAVEL, J CRENSHAW, DM KRISS, GA KROLIK, JH MALKAN, MA NETZER, H PETERSON, BM WAMSTEKER, W ALTAMORE, A ALTIERI, B ANDERSON, KS BLACKWELL, JH BOISSON, C BROSCH, N CARONE, TE DIETRICH, M ENGLAND, MN EVANS, IN FILIPPENKO, AV GASKELL, CM GOAD, M GONDHALEKAR, PM HORNE, K KAZANAS, D KOLLATSCHNY, W KORATKAR, AP KORISTA, KT MACALPINE, GM MAOZ, D MAZEH, T MCCOLLUM, B MILLER, HR DEOLIVEIRA, CM OBRIEN, PT PASTORIZA, MG PELAT, D PEREZ, E PEROLA, GC POGGE, RW PTAK, RL RECONDOGONZALEZ, MC RODRIGUEZESPINOSA, J ROSENBLATT, EI SADUN, AC SANTOSLLEO, M SHIELDS, JC SHRADER, CR SHULL, JM SIMKIN, SM SITKO, ML SNIJDERS, MAJ SPARKE, LS STIRPE, GM STONER, R STORCHIBERGMANN, T SUN, WH WANG, T WELSH, WF WHITE, RJ WINGE, C ZHENG, W TI STEPS TOWARD DETERMINATION OF THE SIZE AND STRUCTURE OF THE BROAD-LINE REGION IN ACTIVE GALACTIC NUCLEI .5. VARIABILITY OF THE ULTRAVIOLET CONTINUUM AND EMISSION-LINES OF NGC-3783 SO ASTROPHYSICAL JOURNAL LA English DT Article DE GALAXIES, ACTIVE; GALAXIES, INDIVIDUAL (NGC 3783); GALAXIES, NUCLEI; GALAXIES, SEYFERT; ULTRAVIOLET, GALAXIES ID SEYFERT-GALAXY NGC-5548; OPTICAL WAVELENGTHS; EXPLORER IUE; SWP CAMERA; FE-II; NGC-3783; QUASARS; SPECTROSCOPY; ACCURACY; GEOMETRY AB We report on the result of intensive ultraviolet spectral monitoring of the Seyfert 1 galaxy NGC 3783. The nucleus of NGC 3783 was observed with the International Ultraviolet Explorer satellite on a regular basis for a total of 7 months, once every 4 days for the first 172 days and once every other day for the final 50 days. Significant variability was observed in both continuum and emission-line fluxes. The light curves for the continuum fluxes exhibited two well-defined local minima or ''dips,'' the first lasting less than or similar to 20 days and the second less than or similar to 4 days, with additional episodes of relatively rapid flickering of approximately the same amplitude. As in the case of NGC 5548 (the only other Seyfert galaxy that has been the subject of such an intensive, sustained monitoring effort), the largest continuum variations were seen at the shortest wavelengths, so that the continuum became ''harder'' when brighter. The variations in the continuum occurred simultaneously at all wavelengths (Delta t <2 days). Generally, the amplitude of variability of the emission lines was lower than (or comparable to) that of the continuum. Apart from Mg II (which varied little) and N V (which is relatively weak and badly blended with Ly alpha), the light curves of the emission lines are very similar to the continuum light curves, in each case with a small systematic delay or ''lag'' As for NGC 5548, the highest ionization lines seem to respond with shorter lags than the lower ionization lines. The lags found for NGC 3783 are considerably shorter than those obtained for NGC 5548, with values of(formally) similar to 0 days for He II + O III], and similar to 4 days for Ly alpha and C IV. The data further suggest lags of similar to 4 days for Si IV + O IV] and 8-30 days for Si III] + C III]. Mg II lagged the 1460 Angstrom continuum by similar to 9 days, although this result depends on the method of measuring the line flux and may in fact be due to variability of the underlying Fe II lines. Correlation analysis further shows that the power density spectrum contains substantial unresolved power over timescales of less than or similar to 2 days, and that the character of the continuum variability may change with time. C1 ESA IUE OBSERV,E-28080 MADRID,SPAIN. UNIV PARIS 07,OBSERV PARIS,CNRS,URA 173,F-92195 MEUDON,FRANCE. EUROPEAN SPACE TECHNOL CTR,EUROPEAN SPACE AGCY,DIV ASTROPHYS,ISO OBSERV,2200 AG NOORDWIJK,NETHERLANDS. NASA,GODDARD SPACE FLIGHT CTR,COMP SCI CORP,ASTRON PROGRAM,GREENBELT,MD 20771. JOHNS HOPKINS UNIV,DEPT PHYS & ASTRON,BALTIMORE,MD 21218. UNIV CALIF LOS ANGELES,DEPT ASTRON,LOS ANGELES,CA 90024. TEL AVIV UNIV,SCH PHYS & ASTRON,IL-69978 TEL AVIV,ISRAEL. TEL AVIV UNIV,WISE OBSERV,IL-69978 TEL AVIV,ISRAEL. OHIO STATE UNIV,DEPT ASTRON,COLUMBUS,OH 43210. UNIV ROMA LA SAPIENZA,IST ASTRON,I-00161 ROME,ITALY. EUROPEAN SO OBSERV,SANTIAGO 19001,CHILE. NEW MEXICO STATE UNIV,DEPT ASTRON,LAS CRUCES,NM 88003. UNIV CALIF BERKELEY,SPACE SCI LAB,BERKELEY,CA 94720. UNIV STERNWARTE,W-3400 GOTTINGEN,GERMANY. SPACE TELESCOPE SCI INST,BALTIMORE,MD 21218. UNIV CALIF BERKELEY,DEPT ASTRON,BERKELEY,CA 94720. UNIV NEBRASKA,DEPT PHYS & ASTRON,LINCOLN,NE 68588. RUTHERFORD APPLETON LAB,ASTROPHYS GRP,DIDCOT OX11 0QX,OXON,ENGLAND. NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771. UNIV MICHIGAN,DEPT ASTRON,ANN ARBOR,MI 48109. INST ADV STUDY,PRINCETON,NJ 08540. NASA,WASHINGTON,DC 20546. GEORGIA STATE UNIV,DEPT PHYS & ASTRON,ATLANTA,GA 30303. UNIV BRITISH COLUMBIA,DEPT ASTRON,VANCOUVER V6T 1W5,BC,CANADA. UNIV FED RIO GRANDE SUL,INST FIS,DEPT ASTRON,BR-91500 PORTO ALEGRE,RS,BRAZIL. INST ASTROFIS CANARIAS,E-38200 LA LAGUNA,SPAIN. BOWLING GREEN STATE UNIV,DEPT PHYS & ASTRON,BOWLING GREEN,OH 43403. UNIV CALIF SAN DIEGO,CTR ASTROPHYS & SPACE SCI,LA JOLLA,CA 92093. AGNES SCOTT COLL,DEPT PHYS & ASTRON,DECATUR,GA 30030. AGNES SCOTT COLL,BRADLEY OBSERV,DECATUR,GA 30030. UNIV COLORADO,JOINT INST LAB ASTROPHYS,BOULDER,CO 80309. UNIV COLORADO,NATL INST STAND & TECHNOL,BOULDER,CO 80309. MICHIGAN STATE UNIV,DEPT PHYS & ASTRON,E LANSING,MI 48824. UNIV CINCINNATI,DEPT PHYS,CINCINNATI,OH 45221. UNIV TUBINGEN,INST ASTRON,W-7400 TUBINGEN,GERMANY. UNIV WISCONSIN,DEPT ASTRON,MADISON,WI 53706. OSSERV ASTRON BOLOGNA,I-40126 BOLOGNA,ITALY. NATL CENT UNIV,ASTRON INST,CHUNGLI 32054,TAIWAN. UNIV SCI & TECHNOL CHINA,HEFEI 230026,PEOPLES R CHINA. RP REICHERT, GA (reprint author), NASA,GODDARD SPACE FLIGHT CTR,UNIV SPACE RES ASSOC,CODE 668,GREENBELT,MD 20771, USA. RI Brosch, Noah/C-7889-2009; Mendes de Oliveira, Claudia/F-2391-2012; 王, 挺贵/B-8293-2013; Recondo, Carmen/B-1215-2012; Stirpe, Giovanna/O-9393-2015; OI Mendes de Oliveira, Claudia/0000-0002-7736-4297; Recondo, Carmen/0000-0001-9813-6798; Stirpe, Giovanna/0000-0002-3702-8731; Gaskell, C/0000-0003-4888-2009; Perez, Enrique/0000-0001-9737-4559 NR 67 TC 117 Z9 117 U1 3 U2 6 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 20 PY 1994 VL 425 IS 2 BP 582 EP 608 DI 10.1086/174007 PN 1 PG 27 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA PM579 UT WOS:A1994PM57900017 ER PT J AU GONTHIER, PL HARDING, AK AF GONTHIER, PL HARDING, AK TI GENERAL-RELATIVISTIC CORRECTIONS IN THE GAMMA-RAY EMISSION FROM PULSARS SO ASTROPHYSICAL JOURNAL LA English DT Article DE GAMMA RAYS, THEORY; PULSARS, GENERAL; RADIATION MECHANISMS, MISCELLANEOUS; RELATIVITY; STARS, NEUTRON ID NEUTRON STARS; MAGNETIC-FIELDS; PAIR PRODUCTION; POLAR CAPS; HOT SPOTS; SPECTRA; MODEL; GAPS AB We examine the importance of general relativistic corrections to the production of gamma rays near the surface of a neutron star. Due to the change in the magnetic dipole held in curved spacetime, the polar cap angle decreases by 30% compared to flat spacetime. However, the curved photon trajectories compensate for the decrease in the polar cap angle, and, as a result, the pulse profile of the photons emitted parallel to the field is expected to be very similar in curved spacetime and in flat spacetime. We find that the curved spacetime metric significantly increases the magnitude of the magnetic field and, therefore, the attenuation coefficients of curvature radiation gamma rays for pair production in a magnetic field can be increased by factors as large as 100. As a result the survival distance of 1 GeV photons for pair production is decreased by a factor of 2 for B similar to 10(12) G. C1 NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771. RP GONTHIER, PL (reprint author), HOPE COLL,DEPT PHYS,HOLLAND,MI 49423, USA. RI Harding, Alice/D-3160-2012 NR 24 TC 28 Z9 28 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 20 PY 1994 VL 425 IS 2 BP 767 EP 775 DI 10.1086/174020 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA PM579 UT WOS:A1994PM57900030 ER PT J AU HONEYCUTT, RK CANNIZZO, JK ROBERTSON, JW AF HONEYCUTT, RK CANNIZZO, JK ROBERTSON, JW TI THE HIGH-STATE LOW-STATE TRANSITION IN V794 AQUILAE SO ASTROPHYSICAL JOURNAL LA English DT Article DE ACCRETION, ACCRETION DISKS; NOVAE, CATACLYSMIC VARIABLES; STARS, INDIVIDUAL (V794 AQUILAE) ID ACCRETION DISKS; DWARF NOVA; CATACLYSMIC VARIABLES; TT-ARIETIS; MV-LYRAE; MODEL; PHOTOMETRY; EVOLUTION; SYSTEMS AB We present a V-magnitude light curve of the cataclysmic binary V794 Aquilae covering an 800 day time span. The system shows variations of up to 3 mag. In particular, there are two dips of similar to 1 mag which last for about 50 days, and are followed by a rapid recovery to the original brightness, and a third dip of similar to 3 mag lasting about 100 days. These fluctuations are thought to be caused by the response of the accretion disk in the system to the cessation of mass transfer from the mass-losing secondary star. We present computations using a time-dependent accretion disk code to delineate a range of allowed behavior for the accretion disk. To model the observed light curve, we require that the model parameters alpha(cold), and alpha(hot), which characterize the degree of coupling of the viscous dissipation to the orbital shear in the low and high states of the accretion disk, be smaller than they have been inferred to be in the dwarf novae, and that the ratio alpha(hot)/alpha(cold) also be smaller. The fact that alpha seems to vary with the rate of mass transfer may provide support for the model of Vishniac and Diamond, in which the impact of the mass transfer stream onto the outer edge of the accretion disk excites internal waves which transport angular momentum outward and provide the viscous dissipation. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP HONEYCUTT, RK (reprint author), INDIANA UNIV,DEPT ASTRON,SWAIN HALL W,BLOOMINGTON,IN 47405, USA. NR 31 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 APR 20 PY 1994 VL 425 IS 2 BP 835 EP 842 DI 10.1086/174028 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA PM579 UT WOS:A1994PM57900038 ER PT J AU PROFFITT, CR AF PROFFITT, CR TI EFFECTS OF HEAVY-ELEMENT SETTLING ON SOLAR-NEUTRINO FLUXES AND INTERIOR STRUCTURE SO ASTROPHYSICAL JOURNAL LA English DT Article DE DIFFUSION; ELEMENTARY PARTICLES; SUN, ABUNDANCES; SUN, INTERIOR; SUN, OSCILLATIONS ID CONVECTION ZONE; DIFFUSION; MODELS; OSCILLATIONS; HELIOSEISMOLOGY; HELIUM; PHYSICS; MATTER; DEPTH; SUN AB We consider the effects of gravitational settling of both He and heavier elements on the predicted solar neutrino fluxes and interior sound speed and density profiles. We find that while the structural changes that result from the inclusion of both He and heavy-element settling are only slightly larger than the changes resulting from the inclusion of He settling alone, the additional increases in expected neutrino fluxes are of comparable size. Our preferred model with both He and heavy-element settling has neutrino count rates of 9.0 SNU for Cl-37 detectors and 137 SNU for Ga-71 detectors, as compared to 7.1 and 127 SNU for a comparable model without any diffusive separation, or 8.0 and 132 SNU for a model that includes He settling alone. We suggest that the correction factors by which the predicted neutrino fluxes of solar models calculated without including the effects of diffusion should be multiplied are 1.25 +/- 0.08 for Cl detectors, 1.07 +/- 0.02 for Ga detectors, and 1.28 +/- 0.09 for the B-8 flux (1 sigma errors). Comparison of internal sound speed and density profiles strongly suggests that the additional changes in calculated p-mode oscillation frequencies due to the inclusion of heavy-element settling will be small compared to the changes that result from He settling alone, especially for the higher degree modes. All models with diffusive separation give much better agreement with the observed depth of the convection zone than do nondiffusive models. The model that includes both He and heavy-element settling requires an initial He mass fraction Y = 0.280 and has a surface He abundance of Y = 0.251 at the solar age. C1 NASA,GODDARD SPACE FLIGHT CTR,IUE OBSERV,GREENBELT,MD 20771. RP PROFFITT, CR (reprint author), NASA,GODDARD SPACE FLIGHT CTR,COMP SCI CORP,SCI PROGRAMS,CODE 684 9,GREENBELT,MD 20771, USA. NR 42 TC 90 Z9 90 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 20 PY 1994 VL 425 IS 2 BP 849 EP 855 DI 10.1086/174030 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA PM579 UT WOS:A1994PM57900040 ER PT J AU LAROSA, TN MOORE, RL SHORE, SN AF LAROSA, TN MOORE, RL SHORE, SN TI A NEW PATH FOR THE ELECTRON BULK ENERGIZATION IN SOLAR-FLARES - FERMI ACCELERATION BY MAGNETOHYDRODYNAMIC TURBULENCE IN RECONNECTION OUTFLOWS SO ASTROPHYSICAL JOURNAL LA English DT Article DE ACCELERATION OF PARTICLES; MHD; SUN, FLARES; TURBULENCE ID LOW-BETA PLASMA; X-RAY-BURSTS; PHASE AB We recently proposed that a magnetohydrodynamic (MHD) turbulent cascade produces the bulk energization of electrons to similar to 25 keV in the impulsive phase of solar flares (LaRosa and Moore 1993). In that scenario, (1) the cascading MHD turbulence is fed by shear-unstable Alfvenic outflows from sites of strongly driven reconnection in the low corona, and (2) the electrons are energized by absorbing the energy that flows down through the cascade. We did not specify the physical mechanism by which the cascading energy is ultimately transferred to the electrons. Here we propose that Fermi acceleration is this mechanism, the process by which the electrons are energized and by which the cascading MHD turbulence is dissipated. We point out that in the expected cascade MHD fluctuations of scale 1 km can Fermi-accelerate electrons from 0.1 keV to similar to 25 keV on the subsecond timescales observed in impulsive flares, provided there is sufficient trapping and scattering of electrons in the MHD turbulence. We show that these same fluctuations provide the required trapping; they confine the electrons within the turbulent region until the turbulence is dissipated. This results in the energization of all of the electrons in each large-scale (5 x 10(7) cm) turbulent eddy to 25 keV. The Fermi process also requires efficient scattering so that the pitch-angle distribution of the accelerating electrons remains isotropic. We propose that the electrons undergo resonant scattering by high-frequency plasma R-waves that, as suggested by others (Hamilton and Petrosian 1992), are generated by the reconnection. Ions are not scattered by R-waves. Provided that there is negligible generation of ion-scattering plasma turbulence (e.g., L-waves) by the reconnection or the MHD turbulence, the ions will not Fermi-accelerate and the cascading energy is transferred only to the electrons. We conclude that, given this situation, electron Fermi acceleration can plausibly account for the electron bulk energization in impulsive solar flares. C1 INDIANA UNIV,DEPT PHYS & ASTRON,S BEND,IN 46615. RP LAROSA, TN (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,SPACE SCI LAB,HUNTSVILLE,AL 35812, USA. NR 30 TC 42 Z9 42 U1 1 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 20 PY 1994 VL 425 IS 2 BP 856 EP 860 DI 10.1086/174031 PN 1 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA PM579 UT WOS:A1994PM57900041 ER PT J AU COOK, JW KEENAN, FP BHATTA, AK AF COOK, JW KEENAN, FP BHATTA, AK TI THE ALLOWED LINES OF O-IV NEAR 1340-ANGSTROM IN HIGH ELECTRON-DENSITY SOLAR-FLARES SO ASTROPHYSICAL JOURNAL LA English DT Article DE ATOMIC PROCESSES; SUN, FLARES; SUN, UV RADIATION ID RESOLUTION; EMISSION; SUN AB Intersystem lines of O IV near 1400 Angstrom have long been used as electron density diagnostics for solar plasmas at temperatures of around 160,000 K. In addition, however, several allowed lines of O IV near 1340 a should become visible in conditions of high plasma electron number density (>10(12) cm(-3)), such as during a solar flare. We present observations of the 1340 Angstrom and 1400 Angstrom regions of the solar spectrum for two solar flares, obtained by the SO82B spectrograph on board Skylab. We examine three candidate lines for allowed O IV in the flare spectra which occur at the correct wavelengths, but show that two of these are actually blends dominated by resonantly excited molecular lines of H-2. The third candidate line, at 1343.51 Angstrom, we identify as the O IV allowed line. We present the density and temperature sensitivity of the ratio of allowed and intersystem O IV lines R = I(1343.51 Angstrom)/I(1407.39 Angstrom). The 1343.51 Angstrom line is clearly present in the first solar flare spectrum, and the ratio value implies an electron density of log N-e = 12.6. The second flare has a much weaker 1343.51 Angstrom profile, but again the ratio value implies a high electron density. Both these electron density values are in good agreement with estimates for each flare from independent diagnostic ratios. The simple presence alone of a clearly observed O IV 1343.51 Angstrom emission line implies an electron density greater than 10(12) cm(-3). C1 QUEENS UNIV BELFAST,DEPT PURE & APPL PHYS,BELFAST BT7 1NN,ANTRIM,NORTH IRELAND. NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771. RP COOK, JW (reprint author), USN,RES LAB,CODE 7663,WASHINGTON,DC 20375, USA. NR 22 TC 4 Z9 4 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 20 PY 1994 VL 425 IS 2 BP 861 EP 864 DI 10.1086/174032 PN 1 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA PM579 UT WOS:A1994PM57900042 ER PT J AU ARENDT, RG BERRIMAN, GB BOGGESS, N DWEK, E HAUSER, MG KELSALL, T MOSELEY, SH MURDOCK, TL ODEGARD, N SILVERBERG, RF SODROSKI, TJ WEILAND, JL AF ARENDT, RG BERRIMAN, GB BOGGESS, N DWEK, E HAUSER, MG KELSALL, T MOSELEY, SH MURDOCK, TL ODEGARD, N SILVERBERG, RF SODROSKI, TJ WEILAND, JL TI COBE DIFFUSE INFRARED BACKGROUND EXPERIMENT OBSERVATIONS OF GALACTIC REDDENING AND STELLAR POPULATIONS SO ASTROPHYSICAL JOURNAL LA English DT Article DE DUST, EXTINCTION; GALAXY, STELLAR CONTENT; INFRARED, STARS ID VISUAL REFLECTION NEBULAE; ABSOLUTE CALIBRATION; MILKY-WAY; MICRON; PHOTOMETRY; EXTINCTION; TELESCOPE; EMISSION; BAR AB This Letter describes the results of an initial study of Galactic extinction and the colors of Galactic stellar populations in the near-IR using the Diffuse Infrared Background Experiment (DIRBE) aboard the Cosmic Background Explorer (COBE) spacecraft. The near-IR reddening observed by DIRBE is consistent with the extinction law tabulated by Rieke and Lebofsky (1985). The distribution of dust and stars in most of the first and fourth quadrants of the Galactic plane (0 degrees < l < 90 degrees, and 270 degrees < l < 360 degrees, respectively) can be modeled as a stellar background source seen through up to similar to 4 mag of extinction at 1.25 mu m. The unreddened near-IR colors of the Galactic disk are similar to those of late-K and M giants. The Galactic bulge exhibits slightly bluer colors in the 2.2-3.5 mu m range, as noted by Terndrup et al. (1991). Star-forming regions exhibit colors that indicate the presence of a similar to 900 K continuum produced by hat dust or PAHs contributing at wavelengths as short as 3.5 mu m. C1 NASA,GODDARD SPACE FLIGHT CTR,GEN SCI CORP,GREENBELT,MD 20771. GEN RES CORP,DEPT TECHNOL,DANVERS,MA 01923. RP ARENDT, RG (reprint author), NASA,GODDARD SPACE FLIGHT CTR,APPL RES CORP,CODE 6583,GREENBELT,MD 20771, USA. RI Moseley, Harvey/D-5069-2012 NR 23 TC 36 Z9 36 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 20 PY 1994 VL 425 IS 2 BP L85 EP & DI 10.1086/187316 PN 2 PG 0 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA PM580 UT WOS:A1994PM58000007 ER PT J AU HOLBERG, JB HUBENY, I BARSTOW, MA LANZ, T SION, EM TWEEDY, RW AF HOLBERG, JB HUBENY, I BARSTOW, MA LANZ, T SION, EM TWEEDY, RW TI THE DISCOVERY OF NI-V IN THE PHOTOSPHERES OF THE HOT DA WHITE-DWARFS RE-2214-492 AND G191-B2B SO ASTROPHYSICAL JOURNAL LA English DT Article DE STARS, ABUNDANCES; STARS, INDIVIDUAL, RE2214-492, G191-B2B; ULTRAVIOLET, STARS; WHITE DWARFS ID MODEL STELLAR ATMOSPHERES; EMISSION; EXOSAT AB We have co-added six recently obtained IUE echelle spectra of the hot DA white dwarf RE 2214-492 and 10 existing archive spectra of the well-known hot DA, G191-B2B. We find that both stars contain numerous weak features due to Ni v. Nickel is thus the second iron-group element to be found in the spectra of the very hottest DA white dwarfs. In addition to Ni v, we also observe Al III in both stars and present evidence for the possible presence of Ni Iv and Fe Iv in RE 2214-492. The presence of Ni and Al, together with previously reported elements, will contribute significantly to both the EUV opacity and to the apparent complexity of the UV spectra of these stars. Using NLTE model atmospheres we estimate the Ni abundances in RE 2214-492 and G191-B2B to be log [Ni/H] = -5.5 +/- 0.3 and -6.0 +/- 0.3, respectively. C1 NASA, GODDARD SPACE FLIGHT CTR, UNIV SPACE RES ASSOC, GREENBELT, MD 20771 USA. UNIV LEICESTER, X RAY ASTRON GRP, LEICESTER LE1 7RH, LEICS, ENGLAND. NASA, GODDARD SPACE FLIGHT CTR, ASTRON & SOLAR PHYS LAB, GREENBELT, MD 20771 USA. VILLANOVA UNIV, DEPT ASTRON & ASTROPHYS, VILLANOVA, PA 19085 USA. UNIV ARIZONA, STEWARD OBSERV, TUCSON, AZ 85721 USA. RP UNIV ARIZONA, LUNAR & PLANETARY LAB, GOULD SIMPSON BLDG, TUCSON, AZ 85721 USA. NR 23 TC 53 Z9 53 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD APR 20 PY 1994 VL 425 IS 2 BP L105 EP L108 DI 10.1086/187321 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA PM580 UT WOS:A1994PM58000012 ER PT J AU WEILAND, JL ARENDT, RG BERRIMAN, GB DWEK, E FREUDENREICH, HT HAUSER, MG KELSALL, T LISSE, CM MITRA, M MOSELEY, SH ODEGARD, NP SILVERBERG, RF SODROSKI, TJ SPIESMAN, WJ STEMWEDEL, SW AF WEILAND, JL ARENDT, RG BERRIMAN, GB DWEK, E FREUDENREICH, HT HAUSER, MG KELSALL, T LISSE, CM MITRA, M MOSELEY, SH ODEGARD, NP SILVERBERG, RF SODROSKI, TJ SPIESMAN, WJ STEMWEDEL, SW TI COBE DIFFUSE INFRARED BACKGROUND EXPERIMENT OBSERVATIONS OF THE GALACTIC BULGE SO ASTROPHYSICAL JOURNAL LA English DT Article DE GALAXY, STRUCTURE; INFRARED, GALAXIES ID INTERSTELLAR EXTINCTION; MILKY-WAY; GALAXY; GAS; MODEL; BAR AB Low angular resolution maps of the Galactic bulge at 1.25, 2.2, 3.5, and 4.9 mu m obtained by the Diffuse Infrared Background Experiment (DIRBE) onboard NASA's Cosmic Background Explorer (COBE) are presented. After correction for extinction and subtraction of an empirical model for the Galactic disk, the surface brightness distribution of the bulge resembles a flattened ellipse with a minor-to-major axis ratio of approximate to 0.6. The bulge minor axis scale height is found to be 2.degrees 1 +/- 0.degrees 2 for all four near-infrared wavelengths. Asymmetries in the longitudinal distribution of bulge brightness contours are qualitatively consistent with those expected for a triaxial bar with its near end in the first Galactic quadrant (0 degrees < l < 90 degrees). There is no evidence for an out-of-plane tilt of such a bar. C1 NASA,GODDARD SPACE FLIGHT CTR,APPL RES CORP,GREENBELT,MD 20771. NASA,GODDARD SPACE FLIGHT CTR,HUGHES STX,GREENBELT,MD 20771. RP WEILAND, JL (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GEN SCI CORP,CODE 6853,GREENBELT,MD 20771, USA. RI Moseley, Harvey/D-5069-2012; Dwek, Eli/C-3995-2012; Lisse, Carey/B-7772-2016 OI Lisse, Carey/0000-0002-9548-1526 NR 31 TC 137 Z9 138 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 20 PY 1994 VL 425 IS 2 BP L81 EP & DI 10.1086/187315 PN 2 PG 0 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA PM580 UT WOS:A1994PM58000006 ER PT J AU DAVIS, A MARSHAK, A WISCOMBE, W CAHALAN, R AF DAVIS, A MARSHAK, A WISCOMBE, W CAHALAN, R TI MULTIFRACTAL CHARACTERIZATIONS OF NONSTATIONARITY AND INTERMITTENCY IN GEOPHYSICAL FIELDS - OBSERVED, RETRIEVED, OR SIMULATED SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID FULLY-DEVELOPED TURBULENCE; GENERALIZED DIMENSIONS; STRANGE ATTRACTORS; RAIN; FRACTALS AB Geophysical data rarely show any smoothness at any scale, and this often makes comparison with theoretical model output difficult. However, highly fluctuating signals and fractal structures are typical of open dissipative systems with nonlinear dynamics, the focus of most geophysical research. High levels of variability are excited over a large range of scales by the combined actions of external forcing and internal instability. At very small scales we expect geophysical fields to be smooth, but these are rarely resolved with available instrumentation or simulation tools; nondifferentiable and even discontinuous models are therefore in order. We need methods of statistically analyzing geophysical data, whether measured in situ, remotely sensed or even generated by a computer model, that are adapted to these characteristics. An important preliminary task is to define statistically stationary features in generally nonstationary signals. We first discuss a simple criterion for stationarity in finite data streams that exhibit power law energy spectra and then, guided by developments in turbulence studies, we advocate the use of two ways of analyzing the scale dependence of statistical information: singular measures and qth order structure functions. In nonstationary situations, the approach based on singular measures seeks power law behavior in integrals over all possible scales of a nonnegative stationary field derived from the data, leading to a characterization of the intermittency in this (gradient-related) field. In contrast, the approach based on structure functions uses the signal itself, seeking power laws for the statistical moments of absolute increments over arbitrarily large scales, leading to a characterization of the prevailing nonstationarity in both quantitative and qualitative terms. We explain graphically, step by step, both multifractal statistics which are largely complementary to each other. The geometrical manifestations of nonstationarity and intermittency, ''roughness'' and ''sparseness'', respectively, are illustrated and the associated analytical (differentiability and continuity) properties are discussed. As an example, the two techniques are applied to a series of recent measurements of liquid water distributions inside marine stratocumulus decks; these are found to be multifractal over scales ranging from almost-equal-to 60 m to almost-equal-to 60 km. Finally, we define the ''mean multifractal plane'' and show it to be a simple yet comprehensive tool with many applications including data intercomparison, (dynamical or stochastic) model and retrieval validations. C1 UNIV SPACE RES ASSOC, NASA, GSFC, GREENBELT, MD USA. SCI SYST & APPLICAT INC, LANHAM, MD USA. RP DAVIS, A (reprint author), NASA, GODDARD SPACE FLIGHT CTR, CLIMATE & RADIAT BRANCH, GREENBELT, MD 20771 USA. RI Cahalan, Robert/E-3462-2012; Wiscombe, Warren/D-4665-2012; Marshak, Alexander/D-5671-2012 OI Cahalan, Robert/0000-0001-9724-1270; Wiscombe, Warren/0000-0001-6844-9849; NR 45 TC 262 Z9 270 U1 2 U2 16 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD APR 20 PY 1994 VL 99 IS D4 BP 8055 EP 8072 DI 10.1029/94JD00219 PG 18 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA NH263 UT WOS:A1994NH26300001 ER PT J AU GRANT, WB BROWELL, EV FISHMAN, J BRACKETT, VG VEIGA, RE NGANGA, D MINGA, A CROS, B BUTLER, CF FENN, MA LONG, CS STOWE, LL AF GRANT, WB BROWELL, EV FISHMAN, J BRACKETT, VG VEIGA, RE NGANGA, D MINGA, A CROS, B BUTLER, CF FENN, MA LONG, CS STOWE, LL TI AEROSOL-ASSOCIATED CHANGES IN TROPICAL STRATOSPHERIC OZONE FOLLOWING THE ERUPTION OF MOUNT-PINATUBO SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID AIRBORNE LIDAR OBSERVATIONS; GAS EXPERIMENT-II; EL-CHICHON; HETEROGENEOUS CHEMISTRY; SULFATE AEROSOLS; MT-PINATUBO; SAGE-I; SATELLITE; DEPLETION; PROFILES AB The large amount of sulfuric acid aerosol formed in the stratosphere by conversion of sulfur dioxide emitted by the eruption of Mount Pinatubo (15.14-degrees-N, 120.35-degrees-E) in the Philippines around June 15, 1991, has had a pronounced effect on lower stratospheric ozone in the tropics. Measurements of stratospheric ozone in the tropics using electrochemical concentration cell (ECC) sondes before and after the eruption and the airborne UV differential absorption lidar (DIAL) system after the eruption are compared with Stratospheric Aerosol and Gas Experiment II (SAGE II) measurements from several years before the eruption and ECC sonde measurements from the year prior to the eruption to determine the resulting changes. Ozone decreases of up to 33% compared with SAGE II climatological values were found to be directly correlated with altitude regions of enhanced aerosol loading in the 16- to 28-km range. A maximum partial-column decrease of 29 +/- 9 Dobson units (DU) was found over the 16- to 28-km range in September 1991 along with small increases (to 5.9 +/- 2 DU) from 28 to 31.5 km. A large decrease of ozone was also found at 4-degrees to 8-degrees-S from May to August 1992, with a maximum decrease of 33 +/- 7 DU found above Brazzaville in July. Aerosol data from the visible channel of the advanced very high resolution radiometer (AVHRR) and the visible wavelength of the UV DIAL system were used to examine the relationship between aerosol (surface area) densities and ozone changes. The tropical stratospheric ozone changes we observed in 1991 and 1992 are likely be explained by a combination of dynamical (vertical transport) perturbations, radiative perturbations on ozone photochemistry, and heterogeneous chemistry. C1 SCI APPLICAT INT CORP, HAMPTON, VA USA. UNIV MAIEN NGOUABI, BRAZZAVILLE, CONGO. NOAA, NWS, NMC, CTR CLIMATE ANAL, WASHINGTON, DC 20230 USA. NOAA, NESDIS, ORA, SATELLITE RES LAB, WASHINGTON, DC 20230 USA. RP GRANT, WB (reprint author), NASA, LANGLEY RES CTR, DIV ATMOSPHER SCI, HAMPTON, VA 23665 USA. RI Grant, William/B-8311-2009 OI Grant, William/0000-0002-1439-3285 NR 79 TC 79 Z9 80 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 APR 20 PY 1994 VL 99 IS D4 BP 8197 EP 8211 DI 10.1029/93JD03314 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA NH263 UT WOS:A1994NH26300012 ER PT J AU RINSLAND, CP GUNSON, MR ABRAMS, MC LOWES, LL ZANDER, R MAHIEU, E GOLDMAN, A KO, MKW RODRIGUEZ, JM SZE, ND AF RINSLAND, CP GUNSON, MR ABRAMS, MC LOWES, LL ZANDER, R MAHIEU, E GOLDMAN, A KO, MKW RODRIGUEZ, JM SZE, ND TI HETEROGENEOUS CONVERSION OF N2O5 TO HNO3 IN THE POST-MOUNT-PINATUBO ERUPTION STRATOSPHERE SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID MOLECULE SPECTROSCOPY EXPERIMENT; NITRIC-ACID; MIDDLE ATMOSPHERE; EL-CHICHON; AEROSOLS; MODEL; SPACELAB-3; CHEMISTRY; VARIABILITY; PARAMETERS AB Simultaneous stratospheric volume mixing ratio (VMR) profiles of dinitrogen pentoxide (N2O5) and nitric acid (HNO3) at sunrise between 25-degrees-N and 15-degrees-S latitude and profiles of HNO3 at sunset between 42-degrees-S and 53-degrees-S latitude have been derived from 0.01 cm-1 resolution infrared solar occultation spectra recorded 9 1/2 months after the massive eruption of the Mount Pinatubo volcano in the Philippine Islands. The measurements were obtained by the atmospheric trace molecule spectroscopy (ATMOS) Fourier transform spectrometer during the ATLAS 1 shuttle mission (March 24 to April 2, 1992). The measured HNO3 VMRs are higher at all altitudes and latitudes than corresponding values measured by the limb infrared monitor of the stratosphere (LIMS) instrument during the same season in 1979, when the aerosol loading was near background levels. The largest relative increase in the HNO3 VMR occurred near the equator at 30-km altitude, where the ATMOS/ATLAS 1 values are about a factor of 2 higher than the LIMS measurements. Two-dimensional model calculations show that the increase in HNO3 and the ATMOS/ATLAS 1 measurement of a steep decrease in the N2O5 VMR below 30 km can be explained by the enhanced conversion of N2O5 to HNO3 on the surfaces of the Mount Pinatubo sulfate aerosols. Our profile results demonstrate the global impact of the N2O5 + H2O --> 2HNO3 heterogeneous reaction in altering the partitioning of stratospheric odd nitrogen after a major volcanic eruption. C1 JET PROP LAB, PASADENA, CA 91109 USA. UNIV LIEGE, INST ASTROPHYS, LIEGE, BELGIUM. UNIV DENVER, DEPT PHYS, DENVER, CO 80210 USA. ATMOSPHER & ENVIRONM RES INC, CAMBRIDGE, MA USA. RP RINSLAND, CP (reprint author), NASA, LANGLEY RES CTR, DIV ATMOSPHER SCI, HAMPTON, VA 23665 USA. RI Rodriguez, Jose/G-3751-2013; Ko, Malcolm/D-5898-2015 OI Rodriguez, Jose/0000-0002-1902-4649; NR 40 TC 42 Z9 44 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD APR 20 PY 1994 VL 99 IS D4 BP 8213 EP 8219 DI 10.1029/93JD03469 PG 7 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA NH263 UT WOS:A1994NH26300013 ER PT J AU PRASAD, SS LEE, TJ AF PRASAD, SS LEE, TJ TI ATMOSPHERIC CHEMISTRY OF THE REACTION CLO+O2[--]CLO.O2 - WHERE IT STANDS, WHAT NEEDS TO BE DONE, AND WHY SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID TEMPERATURE-DEPENDENCE; CLO; STRATOSPHERE; CONSTANT; KINETICS; DIMER; BRO; HO2 AB Possible existence and chemistry of ClO . O2 was originally proposed to explain the Norrish-Neville effect that O2 suppresses chlorine photosensitized loss of ozone. It was also thought that ClO . O2 might have some atmospheric chemistry significance. Recently, doubts have been cast on this proposal, because certain laboratory data seem to imply that the equilibrium constant of the title reaction is so small that ClO . O2 may be too unstable to matter. However, those data create only a superficial illusion to that effect, because on a closer analysis they do not disprove a moderately stable and chemically significant ClO . O2. Furthermore, our state-of-the-science accurate computational chemistry calculations also suggest that ClO . O2 may be a weakly bound C1OOO radical with a reactive 2A ground electronic state. There is therefore a need to design and perform definitive experimental tests of the existence and chemistry of the ClO . O2 species, which we discuss and which have the potential to mediate the chlorine-catalyzed stratospheric ozone depletion. C1 NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. RP PRASAD, SS (reprint author), CREATIVE RES ENTERPRISES, PLEASANTON, CA USA. RI Lee, Timothy/K-2838-2012 NR 29 TC 21 Z9 21 U1 1 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD APR 20 PY 1994 VL 99 IS D4 BP 8225 EP 8230 DI 10.1029/93JD01809 PG 6 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA NH263 UT WOS:A1994NH26300015 ER PT J AU MASSMAN, WJ PEDERSON, J DELANY, A GRANTZ, D DENHARTOG, G NEUMANN, HH ONCLEY, SP PEARSON, R SHAW, RH AF MASSMAN, WJ PEDERSON, J DELANY, A GRANTZ, D DENHARTOG, G NEUMANN, HH ONCLEY, SP PEARSON, R SHAW, RH TI AN EVALUATION OF THE REGIONAL ACID DEPOSITION MODEL SURFACE MODULE FOR OZONE UPTAKE AT 3 SITES IN THE SAN-JOAQUIN VALLEY OF CALIFORNIA SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID FLUX-GRADIENT RELATIONSHIPS; STOMATAL CONDUCTANCE; DRY DEPOSITION; PLANT; HEAT; TEMPERATURE; MOMENTUM; LAYER; NO2 AB Plants and soils act as major sinks for the destruction of tropospheric ozone, especially during daylight hours when plant stomata open and are thought to provide the dominant pathway for the uptake of ozone. The present study, part of the California Ozone Deposition Experiment, compares predictions of the regional acid deposition model ozone surface conductance module with surface conductance data derived from eddy covariance measurements of ozone flux taken at a grape, a cotton, and a grassland site in the San Joaquin Valley of California during the summer of 1991. Results indicate that the model (which was developed to provide long-term large-area estimates for the eastern United States) significantly overpredicts the surface conductance at all times of the day tor at least two important types of plant cover of the San Joaquin Valley and that it incorrectly partitions the ozone flux between transpiring and nontranspiring components of the surface at the third site. Consequently, the model either overpredicts or inaccurately represents the observed deposition velocities. Other results indicate that the presence of dew does not reduce the rate of ozone deposition, contradicting to model assumptions, and that model assumptions involving the dependency of stomata upon environmental temperature are unnecessary. The effects of measurement errors and biases, arising from the presence of the roughness sublayer and possible photochemical reactions, are also discussed. A simpler model for ozone surface deposition (at least for the San Joaquin Valley) is proposed and evaluated. C1 CALIF AIR RESOURCES BOARD, SACRAMENTO, CA USA. NATL CTR ATMOSPHER RES, BOULDER, CO 80307 USA. UNIV CALIF, KEARNEY AGR CTR, PARLIER, CA USA. ATMOSPHER ENVIRONM SERV, DOWNSVIEW, ON, CANADA. NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. UNIV CALIF DAVIS, DEPT LAND AIR & WATER RESOURCES, DAVIS, CA 95616 USA. RP MASSMAN, WJ (reprint author), US FOREST SERV, FT COLLINS, CO USA. NR 41 TC 52 Z9 55 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 APR 20 PY 1994 VL 99 IS D4 BP 8281 EP 8294 DI 10.1029/93JD03267 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA NH263 UT WOS:A1994NH26300020 ER PT J AU KOBISTEK, RJ BOZZOLO, G FERRANTE, J SCHLOSSER, H AF KOBISTEK, RJ BOZZOLO, G FERRANTE, J SCHLOSSER, H TI MULTILAYER RELAXATION AND SURFACE-STRUCTURE OF ORDERED ALLOYS SO SURFACE SCIENCE LA English DT Article; Proceedings Paper CT 13th European Conference on Surface Science (ECOSS-13) CY AUG 30-SEP 04, 1993 CL UNIV WARWICK, ARTS CTR, WARWICK, ENGLAND SP BRIT VACUUM COUNCIL, EUROPEAN PHYS SOC, INT UNION VACUUM SCI TECH & APPL, INST PHYS, THIN FILMS & SURFACES GRP HO UNIV WARWICK, ARTS CTR ID LOW-ENERGY-ELECTRON; EQUIVALENT-CRYSTAL THEORY; BINARY-ALLOYS; DIFFRACTION; SEGREGATION; PARAMETERS; DEFECTS; SPECTRA; NICKEL; RULE AB Using BFS, a new semiempirical method for alloys, we study the surface structure of fcc ordered binary alloys in the L1(2) structure (Ni3Al and Cu3Au). We show that the surface energy is lowest for the mixed-composition truncation of the low-index faces of such systems. Also, we present results for the interlayer relaxations for planes close to the surface, revealing different relaxations for atoms of different species producing a rippled surface layer. C1 ANALEX CORP, 3001 AEROSP PKY, BROOKPARK, OH 44142 USA. VICTOREEN INC, SOLON, OH 44139 USA. NASA, LEWIS RES CTR, CLEVELAND, OH 44135 USA. CLEVELAND STATE UNIV, DEPT PHYS, CLEVELAND, OH 44115 USA. NR 31 TC 32 Z9 32 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0039-6028 J9 SURF SCI JI Surf. Sci. PD APR 20 PY 1994 VL 307 BP 390 EP 395 DI 10.1016/0039-6028(94)90424-3 PN A PG 6 WC Chemistry, Physical; Physics, Condensed Matter SC Chemistry; Physics GA NH824 UT WOS:A1994NH82400065 ER PT J AU RODRIGUEZ, AM BOZZOLO, G FERRANTE, J AF RODRIGUEZ, AM BOZZOLO, G FERRANTE, J TI STRUCTURE AND ENERGETICS OF HIGH-INDEX FE, AL, CU AND NI SURFACES USING EQUIVALENT CRYSTAL THEORY SO SURFACE SCIENCE LA English DT Article; Proceedings Paper CT 13th European Conference on Surface Science (ECOSS-13) CY AUG 30-SEP 04, 1993 CL UNIV WARWICK, ARTS CTR, WARWICK, ENGLAND SP BRIT VACUUM COUNCIL, EUROPEAN PHYS SOC, INT UNION VACUUM SCI TECH & APPL, INST PHYS, THIN FILMS & SURFACES GRP HO UNIV WARWICK, ARTS CTR ID LOW-ENERGY-ELECTRON; MULTILAYER RELAXATION; 311 SURFACE; METAL; DIFFRACTION; DEFECTS; SPECTRA; NICKEL AB Equivalent crystal theory (ECT) is applied to the study of multilayer relaxations and surface energies of high-index faces of Fc, Al, Ni and Cu. Changes in interplanar spacing as well as registry of planes close to the surface and the ensuing changes of surface energies are discussed in reference to available experimental data and other theoretical calculations. Since ECT is a semiempirical method, we investigate the dependence of the results on the variation of the input used. C1 NATL UNIV LA PLATA, DEPT FIS, CC 67, RA-1900 LA PLATA, ARGENTINA. ANALEX CORP, BROOKPARK, OH 44142 USA. NASA, LEWIS RES CTR, CLEVELAND, OH 44135 USA. NR 32 TC 4 Z9 4 U1 0 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0039-6028 J9 SURF SCI JI Surf. Sci. PD APR 20 PY 1994 VL 307 BP 625 EP 631 DI 10.1016/0039-6028(94)91467-2 PN B PG 7 WC Chemistry, Physical; Physics, Condensed Matter SC Chemistry; Physics GA NH823 UT WOS:A1994NH82300003 ER PT J AU STEIN, CA STEIN, S AF STEIN, CA STEIN, S TI COMPARISON OF PLATE AND ASTHENOSPHERIC FLOW MODELS FOR THE THERMAL EVOLUTION OF OCEANIC LITHOSPHERE SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID HEAT-FLOW; AGE; DEPTH; MANTLE AB Although seafloor depth and heat flow for young oceanic lithosphere can be described by modeling the lithosphere as the boundary layer of a cooling halfspace, a long standing question has been why data at older ages deviate from those expected for a halfspace. Two classes of models have been proposed for these deviations. In one, heat added from below ''flattens'' depth and heat flow. In the other, asthenospheric flow beneath the lithosphere perturbs the depths. We compare recent versions of the model classes: the GDH1 thin-lithosphere plate model [Stein and Stein, 1992] and an asthenospheric flow model [Phipps Morgan and Smith, 19921. The plate model fits heat flow data better than the flow model for all cases considered, and topographic data in all but one case. The flow model significantly overpredicts depths for the North Atlantic, because the assumed asthenospheric flow in the plate motion direction would yield deepening for old ages rather than the observed flattening. Overall, the GDH1 global average model does better than this flow model, whose parameters were fit to specific plates. Moreover, plate models fit to specific plates do better than the flow model. Plate models thus appear more useful than this flow model, suggesting that deviations from a cooling halfspace are largely thermal in origin. RP STEIN, CA (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GEODYNAM BRANCH,CODE 921,GREENBELT,MD 20771, USA. NR 20 TC 15 Z9 17 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 APR 15 PY 1994 VL 21 IS 8 BP 709 EP 712 DI 10.1029/94GL00632 PG 4 WC Geosciences, Multidisciplinary SC Geology GA NG993 UT WOS:A1994NG99300018 ER PT J AU STAHLE, CK WOUTERS, J KELLEY, RL MOSELEY, SH SZYMKOWIAK, AE AF STAHLE, CK WOUTERS, J KELLEY, RL MOSELEY, SH SZYMKOWIAK, AE TI CHARGE COLLECTION AND THERMALIZATION IN A COMPOSITE CALORIMETRIC AND IONIZATION X-RAY-DETECTOR SO JOURNAL OF APPLIED PHYSICS LA English DT Article ID LIQUID-HELIUM TEMPERATURES; SILICON AB A combination calorimetric and ionization x-ray detector has been made by attaching a silicon p-i-n diode to a monolithic silicon microcalorimeter. We were able to measure a charge signal in the absence of applied bias on the diode at a temperature as low as 0.1 K, demonstrating that the junction potential is sufficient to drift the ionized charges to the contacts. A fraction of the electron-hole pairs created became trapped, as was manifested by excess broadening in the measured thermal signal. The fraction of charge trapped was determined from the variation of the thermal signal magnitude with reverse bias. The ability to collect charge without applying a bias is an encouraging result in the development of high resolution combination thermal and ionization detectors. At higher biases high resolution is precluded, but the enhancement of the thermal signal due to the work done on the ionized charges can lead to a low detection threshold. With an applied bias of -25 V, we achieved a detection threshold of 8 eV, based upon energy scaling of the 1sigma value of the baseline noise distribution. C1 KATHOLIEKE UNIV LEUVEN,INST KERN STRALINGSFYS,B-3001 LOUVAIN,BELGIUM. RP STAHLE, CK (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. RI Moseley, Harvey/D-5069-2012; Kelley, Richard/K-4474-2012; Wouters, Jan/D-1800-2015 OI Wouters, Jan/0000-0002-0093-698X NR 14 TC 3 Z9 3 U1 0 U2 1 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 0021-8979 J9 J APPL PHYS JI J. Appl. Phys. PD APR 15 PY 1994 VL 75 IS 8 BP 3723 EP 3731 DI 10.1063/1.356044 PG 9 WC Physics, Applied SC Physics GA NG577 UT WOS:A1994NG57700002 ER PT J AU MA, Q TIPPING, RH AF MA, Q TIPPING, RH TI AN IMPROVED QUASI-STATIC LINE-SHAPE THEORY - THE EFFECTS OF MOLECULAR-MOTION ON THE LINE WINGS SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID INFRARED-ABSORPTION SPECTRA; STATISTICAL-THEORY; ROTATIONAL BANDS; WATER CONTINUUM; CO2 AB A theory is presented for the modification of the line-shape functions and absorption coefficient due to the breakdown of the quasistatic approximation. This breakdown arises from the effects of molecular motion and increases the absorption in the near wings. Numerical calculations for the high-frequency wing of the nu3 band of CO2 broadened by Ar are reported and it is shown that these effects are significant near the bandhead. The importance of such corrections in other spectral regions and for other systems is discussed briefly. C1 NASA,GODDARD SPACE FLIGHT CTR,INST SPACE STUDIES,GREENBELT,MD 20771. UNIV ALABAMA,DEPT PHYS & ASTRON,TUSCALOOSA,AL 35487. RP MA, Q (reprint author), COLUMBIA UNIV,DEPT APPL PHYS,NEW YORK,NY 10025, USA. NR 23 TC 5 Z9 5 U1 1 U2 1 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 0021-9606 J9 J CHEM PHYS JI J. Chem. Phys. PD APR 15 PY 1994 VL 100 IS 8 BP 5567 EP 5579 DI 10.1063/1.467124 PG 13 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA NF081 UT WOS:A1994NF08100019 ER PT J AU ANICICH, VG SEN, AD MCEWAN, MJ SMITH, SC AF ANICICH, VG SEN, AD MCEWAN, MJ SMITH, SC TI A COMPARISON OF AN EXPERIMENTAL UNIMOLECULAR LIFETIME DISTRIBUTION WITH RICE-RAMSPERGER-KASSEL-MARCUS THEORY SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID ASSOCIATION RATE COEFFICIENTS; ION-MOLECULE REACTIONS; LOW-PRESSURE; RADIATIVE ASSOCIATION; CH3+/CH3CN SYSTEM; CAPTURE; MODEL; CH3+ AB The ion-molecule association system (CH3+/CH3CN) has been reexamined by the ion cyclotron double resonance technique. An experimental distribution of lifetimes has been measured for the collision complex (CH3CNCH3+)* formed in the association reaction between CH3+ and CH3CN. The experimental mean lifetime of the association complex formed within the ICR cell was 140 mus. A theoretical examination of the distribution of complex lifetimes using an RRKM model was also undertaken. The matrix of lifetimes for the various values of the total energy of the system (E) and the total angular momentum of the system (J) was obtained. This information was used to visualize the canonical ensemble of collision complexes in the ICR experiment in terms of their lifetimes. Once the distribution of lifetimes predicted by the model was modified to conform to experimental constraints, it was found to give a good approximation of the lifetime distribution determined experimentally. As a result of the new measurements of the complex lifetimes, we report absolute values of the collisional stabilization efficiencies. We also report rate coefficients for unimolecular dissociation and radiative relaxation. C1 UNIV CANTERBURY,DEPT CHEM,CHRISTCHURCH 1,NEW ZEALAND. UNIV QUEENSLAND,DEPT CHEM,BRISBANE,QLD 4072,AUSTRALIA. RP ANICICH, VG (reprint author), JET PROP LAB,MS 183-601,4800 OAK GROVE DR,PASADENA,CA 91109, USA. RI Smith, Sean/H-5003-2015 OI Smith, Sean/0000-0002-5679-8205 NR 28 TC 11 Z9 11 U1 0 U2 2 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 0021-9606 J9 J CHEM PHYS JI J. Chem. Phys. PD APR 15 PY 1994 VL 100 IS 8 BP 5696 EP 5705 DI 10.1063/1.467135 PG 10 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA NF081 UT WOS:A1994NF08100032 ER PT J AU TAWA, GJ MIELKE, SL TRUHLAR, DG SCHWENKE, DW AF TAWA, GJ MIELKE, SL TRUHLAR, DG SCHWENKE, DW TI ALGEBRAIC VARIATIONAL AND PROPAGATION FORMALISMS FOR QUANTAL DYNAMICS CALCULATIONS OF ELECTRONIC-TO-VIBRATIONAL, ROTATIONAL ENERGY-TRANSFER AND APPLICATION TO THE QUENCHING OF THE 3P STATE OF SODIUM BY HYDROGEN MOLECULES SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID INTEGRAL CROSS-SECTIONS; MECHANICAL REACTION PROBABILITIES; CHARGE-TRANSFER PROCESSES; BASIS-SET CALCULATIONS; S-MATRIX VERSION; SCATTERING CALCULATIONS; INELASTIC-COLLISIONS; ADIABATIC REPRESENTATIONS; DIABATIC REPRESENTATION; HYPERSPHERICAL METHOD AB Two approaches, the outgoing wave variational principle (OWVP) and R-matrix propagation (RMProp), are presented for quantum dynamics calculations of inelastic scattering in systems involving two coupled potential energy surfaces (PES). The two formalisms are applied to Na(3p P-2) collisions with H-2 at a total energy of 2.426 eV with zero and unit total angular momentum. This provides a challenging test case because the accessible region of the excited-state potential energy surface intersects the ground-state surface conically and involves H-H internuclear distances that are far larger than their equilibrium values in the ground state. We present the details of the formalisms for treating coupled surfaces, and we present converged results for the quenching probability and final vibrational-rotational quantum state distributions of the quenching agent. Convergence of the transition probabilities is established by convergence checks within each formalism, by obtaining the same results with laboratory-frame and body-frame basis functions in the OWVP formalism, and by obtaining the same results with the OWVP as with RMProp. C1 NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. UNIV MINNESOTA, USA, HIGH PERFORMANCE COMP RES CTR, MINNEAPOLIS, MN 55455 USA. RP TAWA, GJ (reprint author), UNIV MINNESOTA, INST SUPERCOMP, DEPT CHEM, CHEM PHYS PROGRAM, MINNEAPOLIS, MN 55455 USA. 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 182 TC 57 Z9 57 U1 2 U2 3 PU AMER INST PHYSICS PI MELVILLE PA CIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USA SN 0021-9606 J9 J CHEM PHYS JI J. Chem. Phys. PD APR 15 PY 1994 VL 100 IS 8 BP 5751 EP 5777 DI 10.1063/1.467140 PG 27 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA NF081 UT WOS:A1994NF08100037 ER PT J AU HALPERN, D FELDMAN, GC AF HALPERN, D FELDMAN, GC TI ANNUAL AND INTERANNUAL VARIATIONS OF PHYTOPLANKTON PIGMENT CONCENTRATION AND UPWELLING ALONG THE PACIFIC EQUATOR SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID EASTERN TROPICAL PACIFIC; PRIMARY PRODUCTIVITY; UPPER OCEAN; EL-NINO; 110-DEGREES-W; WATERS; COLOR AB The following variables along the Pacific equator from 145-degrees-E to 95-degrees-W were employed: surface layer phytoplankton pigment concentrations derived from Nimbus 7 coastal zone color scanner (CZCS) measurements of ocean color radiances; vertical velocities simulated at the 90-m bottom of the euphotic layer from a wind-driven ocean general circulation model; and nitrate concentrations estimated from model-simulated temperature. The upward flux of nitrate into the euphotic layer was calculated from the simulated vertical motion and nitrate concentration. The CZCS-derived phytoplankton pigment concentration was uniform from 175-degrees to 95-degrees-W. Longitudinal profiles of upwelling, phytoplankton biomass, and 90-m nitrate flux were of different shapes. The small annual cycles of the phytoplankton pigment concentration and nitrate flux were in phase: increased phytoplankton biomass was associated with increased upward nitrate flux, but the phase was not consistent with the annual cycles of the easterly wind or of the upwelling intensity. Variation of phytoplankton pigment concentration was greater during El Nino than during the annual cycle. The substantially reduced phytoplankton pigment concentration observed during El Nino was associated with smaller upward nitrate flux. Phytoplankton biomass during non-El Nino conditions was not related to nitrate flux into the euphotic layer. C1 NASA,GODDARD SPACE FLIGHT CTR,DIV SPACE DATA & COMP,GREENBELT,MD 20771. RP HALPERN, D (reprint author), JET PROP LAB,DIV EARTH & SPACE SCI,PASADENA,CA 91109, USA. NR 49 TC 23 Z9 23 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD APR 15 PY 1994 VL 99 IS C4 BP 7347 EP 7354 DI 10.1029/93JC02145 PG 8 WC Oceanography SC Oceanography GA NG710 UT WOS:A1994NG71000006 ER PT J AU BIGGS, DC MULLERKARGER, FE AF BIGGS, DC MULLERKARGER, FE TI SHIP AND SATELLITE-OBSERVATIONS OF CHLOROPHYLL STOCKS IN INTERACTING CYCLONE-ANTICYCLONE EDDY PAIRS IN THE WESTERN GULF-OF-MEXICO SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID WARM-CORE RING; LAGRANGIAN OBSERVATIONS; GEOSAT ALTIMETRY; CIRCULATION; EVOLUTION; EDDIES; SLOPE; SHELF; CZCS AB When anticyclonic eddies shed by the Loop Current of the Gulf of Mexico reach the western margin of the gulf, they influence the surface circulation over the continental slope and rise. Of particular interest is the generation of cyclone (cold-core)-anticyclone (warm-core) pairs when aging Loop Current eddies interact with the continental margin. In this paper we describe the physical and biological characteristics of these cyclone-anticyclone pairs. Our objective was to determine how eddy pairs affect the distribution of phytoplankton in the region and how satellite ocean color measurements are applicable to tracing of the eddies. We present shipboard data collected between 1980 and 1982 on the hydrography, chlorophyll stocks, and nutrient concentrations of eddy pairs in the western Gulf of Mexico and compare these data with coastal zone color scanner (CZCS) images collected during the time frame of the cruises. Surface pigment concentrations followed a seasonal cycle, with low concentrations (0.05-0.1 mg m-3)found within cyclones and anticyclones from April through early November and higher concentrations (>0.1 mg m-3) found in the winter. CZCS pigment concentrations were locally high in the flow confluence of cyclone-anticyclone pairs. The CZCS imagery shows that some cyclone-anticyclone geometries transport high-chlorophyll shelf water seaward at least 100-200 km off-shelf. C1 NASA HEADQUARTERS,WASHINGTON,DC 20546. UNIV S FLORIDA,DEPT MARINE SCI,ST PETERSBURG,FL 33701. RP BIGGS, DC (reprint author), TEXAS A&M UNIV,DEPT OCEANOG,COLLEGE STN,TX 77843, USA. NR 45 TC 46 Z9 50 U1 1 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD APR 15 PY 1994 VL 99 IS C4 BP 7371 EP 7384 DI 10.1029/93JC02153 PG 14 WC Oceanography SC Oceanography GA NG710 UT WOS:A1994NG71000008 ER PT J AU GLOVER, DM WROBLEWSKI, JS MCCLAIN, CR AF GLOVER, DM WROBLEWSKI, JS MCCLAIN, CR TI DYNAMICS OF THE TRANSITION ZONE IN COASTAL ZONE COLOR SCANNER SENSED OCEAN COLOR IN THE NORTH PACIFIC DURING OCEANOGRAPHIC SPRING SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID ATLANTIC; MODEL; CZCS AB A transition zone in phytoplankton concentration running across the North Pacific basin at 30-degrees to 40-degrees north latitude corresponds to a basin-wide front in surface chlorophyll observed in a composite of coastal zone color scanner (CZCS) images for May, June, and July 1979-1986. This transition zone with low chlorophyll to the south and higher chlorophyll to the north can be simulated by a simple model of the concentration of phytoplankton, zooplankton, and dissolved nutrient (nitrate) in the surface mixed layer of the ocean applied to the North Pacific basin for the climatological conditions during oceanographic springtime (May, June, and July). The model is initialized with a 1-degrees x 1-degrees gridded estimate of wintertime (February, March, and April) mixed layer nitrate concentrations calculated from an extensive nutrient database and a similarly gridded mixed layer,depth data set. Comparison of model predictions with CZCS data provides a means of evaluating the dynamics of the transition zone. We conclude that in the North Pacific, away from major boundary currents and coastal upwelling zones, wintertime vertical mixing determines the total nutrient available to the plankton ecosystem in the spring. The transition zone seen in basin-scale CZCS images is a reflection of the geographic variation in the wintertime mixed layer depth and the nitracline, leading to a latitudinal gradient in phytoplankton chlorophyll. C1 NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. MEM UNIV NEWFOUNDLAND, CTR OCEAN SCI, ST JOHNS A1B 3X7, NEWFOUNDLAND, CANADA. RP WOODS HOLE OCEANOG INST, WOODS HOLE, MA 02543 USA. NR 34 TC 31 Z9 31 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9275 EI 2169-9291 J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD APR 15 PY 1994 VL 99 IS C4 BP 7501 EP 7511 DI 10.1029/93JC02144 PG 11 WC Oceanography SC Oceanography GA NG710 UT WOS:A1994NG71000018 ER PT J AU PRIBBLE, JR WALSH, JJ DIETERLE, DA MULLERKARGER, FE AF PRIBBLE, JR WALSH, JJ DIETERLE, DA MULLERKARGER, FE TI A NUMERICAL-ANALYSIS OF SHIPBOARD AND COASTAL ZONE COLOR SCANNER TIME-SERIES OF NEW PRODUCTION WITHIN GULF-STREAM CYCLONIC EDDIES IN THE SOUTH-ATLANTIC BIGHT SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID STATES CONTINENTAL-SHELF; PHYSICAL-BIOLOGICAL MODEL; PARTICLE TRACING EXPERIMENTS; PHYTOPLANKTON GROWTH; PLANKTON DYNAMICS; ENVIRONMENTAL-FACTORS; FRONTAL EDDY; NUTRIENT; TEMPERATURE; RATES AB Eddy-induced upwelling occurs along the western edge of the Gulf Stream between Cape Canaveral, Florida, and Cape Hatteras, North Carolina, in the South Atlantic Bight (SAB). Coastal zone color scanner images of 1-km resolution spanning the period April 13-21, 1979, were processed to examine these eddy features in relation to concurrent shipboard and current/temperature measurements at moored arrays. A quasi-one-dimensional (z), time-dependent biological model, using only nitrate as a nutrient source, has been combined with a three-dimensional physical model in an attempt to replicate the observed phytoplankton field at the northward edge of an eddy. The model is applicable only to the SAB south of the Charleston Bump, at approximately 31.5-degrees-N, since no feature analogous to the bump exists in the model bathymetry. The modeled chlorophyll, nitrate, and primary production fields of the euphotic zone are very similar to those obtained from the satellite and shipboard data at the leading edges of the observed eddies south of the Charleston Bump. The horizontal and vertical simulated fluxes of nitrate and chlorophyll show that only approximately 10% of the upwelled nitrate is utilized by the phytoplankton of the modeled grid box on the northern edge of the cyclone, while approximately 75% is lost horizontally, with the remainder still in the euphotic zone after the 10-day period of the model. Loss of chlorophyll due-to sinking is very small in this strong upwelling region of the cyclone. The model is relatively insensitive to variations in the sinking parameterization and the external nitrate and chlorophyll fields but is very sensitive to a reduction of the maximum potential growth rate to half that measured. Given the success of this model in simulating the new production of the selected upwelling region, other upwelling regions for which measurements or successful models of physical and biological quantities and rates exist could be modeled similarly. C1 NASA HEADQUARTERS,WASHINGTON,DC 20546. RP PRIBBLE, JR (reprint author), UNIV S FLORIDA,DEPT MARINE SCI,140 7TH AVE S,ST PETERSBURG,FL 33701, USA. NR 66 TC 7 Z9 7 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD APR 15 PY 1994 VL 99 IS C4 BP 7513 EP 7538 DI 10.1029/93JC02907 PG 26 WC Oceanography SC Oceanography GA NG710 UT WOS:A1994NG71000019 ER PT J AU KWOK, R CUNNINGHAM, GF AF KWOK, R CUNNINGHAM, GF TI BACKSCATTER CHARACTERISTICS OF THE WINTER ICE COVER IN THE BEAUFORT SEA SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID SYNTHETIC APERTURE RADAR; MICROWAVE SIGNATURES; MARGINAL ICE; PARAMETERS; SUMMER; IDENTIFICATION; SCATTEROMETER; MELT AB The microwave backscatter statistics of the sea ice cover in the winter Beaufort Sea are characterized using C band synthetic aperture radar (SAR) data collected by the European Earth Resources Satellite 1. Sea ice backscatter signatures were sampled from SAR image data collected during the winter of 1991-1992 and winter of 1992-1993. The spatial and temporal variabilities of the backscatter signatures of different ice types are discussed. The results show considerable seasonal stability of the backscatter signature of multiyear ice as well as of first-year ice. Small amplitude regional variations of the multiyear ice backscatter can be observed. Consistent contrast between multiyear ice and first-year ice is maintained throughout the season. The highest radiometric variability is observed in sea ice in leads. On the basis of these observations the backscatter from the principal ice types (multiyear and first-year) are consistent with scatterometer observations and can be easily identified under winter conditions. Correlations of the regional variations of multiyear ice signatures to physical processes are suggested. RP JET PROP LAB, 4800 OAK GROVE DR, PASADENA, CA 91109 USA. RI Kwok, Ron/A-9762-2008 OI Kwok, Ron/0000-0003-4051-5896 NR 29 TC 43 Z9 45 U1 0 U2 5 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9275 EI 2169-9291 J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD APR 15 PY 1994 VL 99 IS C4 BP 7787 EP 7802 DI 10.1029/94JC00169 PG 16 WC Oceanography SC Oceanography GA NG710 UT WOS:A1994NG71000035 ER PT J AU GOLDSTEIN, RM LI, F SMITH, J PINKEL, R BARNETT, TP AF GOLDSTEIN, RM LI, F SMITH, J PINKEL, R BARNETT, TP TI REMOTE-SENSING OF OCEAN WAVES - THE SURFACE-WAVE PROCESS PROGRAM EXPERIMENT SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID SYNTHETIC APERTURE RADAR; CURRENTS AB An airborne synthetic aperture radar (SAR) has been used as an interferometer to obtain direct, calibrated measurements of the ocean wind wave directional spectrum. Flights over the same area from three different directions produced reasonably consistent results. The SAR-derived wave data agree well with simultaneous observations by a conventional wave measuring system and with a novel in situ acoustic Doppler system. C1 UNIV CALIF SAN DIEGO,SCRIPPS INST OCEANOG,LA JOLLA,CA 92093. RP GOLDSTEIN, RM (reprint author), JET PROP LAB,MS 300-227,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 21 TC 11 Z9 12 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD APR 15 PY 1994 VL 99 IS C4 BP 7945 EP 7950 DI 10.1029/93JC03332 PG 6 WC Oceanography SC Oceanography GA NG710 UT WOS:A1994NG71000046 ER PT J AU ATLAS, D AF ATLAS, D TI FOOTPRINTS OF STORMS ON THE SEA - A VIEW FROM SPACEBORNE SYNTHETIC-APERTURE RADAR SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID WATER-WAVES; RAIN; DEPENDENCE; SCATTERING; MICROBURST AB Synthetic aperture radar (SAR) on board Seasat observed images of stormlike echoes on the sea in 1978. The core of these images is usually an echo-free hole which is attributed to the damping of the short (30-cm) radar detectable gravity waves by the intense rain in the storm core. Although ''the beating down of waves by rain'' is consistent with observations by seafarers and with the first scientific explanation of the phenomenon by Reynolds (1875), neither theory nor experiment has provided definitive support. One experiment appears to provide the key; it shows that the kinetic energy of the rain produces sufficient turbulence in a thin fresh water layer to damp 30-cm waves in 10-20 s, thus producing the echo-free hole. A sequence of positive feedbacks then serves to damp the longer waves. The angular dependence of the sea surface echo cross sections seen by Seasat SAR outside the echo-free hole indicates winds diverging from the downdraft induced by the intense rain core. The wind-generated waves and associated echoes extend out to a sharply defined gust front. The sea surface footprint thus mimics the features of a storm microburst. The variations in surface radar cross section due to a combination of rain and wind effects impacts spaceborne measurements of surface winds by scatterometry and rainfall measurements by radar. Portions of this synthesis remain speculative but serve as hypotheses for further research. RP ATLAS, D (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ATMOSPHERES LAB,CODE 910 2,GREENBELT,MD 20771, USA. NR 45 TC 70 Z9 70 U1 4 U2 11 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD APR 15 PY 1994 VL 99 IS C4 BP 7961 EP 7969 DI 10.1029/94JC00250 PG 9 WC Oceanography SC Oceanography GA NG710 UT WOS:A1994NG71000048 ER PT J AU ROBINSON, RD CARPENTER, KG SLEE, OB NELSON, GJ STEWART, RT AF ROBINSON, RD CARPENTER, KG SLEE, OB NELSON, GJ STEWART, RT TI ULTRAVIOLET AND RADIO OBSERVATIONS OF THE YOUNG, RAPIDLY ROTATING K0 DWARF STAR HD-197890 SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE STARS, ACTIVITY; STARS, INDIVIDUAL, HD-197890; STARS, LATE-TYPE; STARS, ROTATION; RADIO CONTINUUM, STARS; ULTRAVIOLET, STARS ID MAIN-SEQUENCE STARS; MG-II EMISSION; MAGNETIC ACTIVITY; DEPENDENCE AB We present the results of UV observations taken with the International Ultraviolet Explorer (IUE) satellite and microwave observations obtained with the Australia Telescope during an observing campaign of the rapidly rotating K0 dwarf star HD 197890, nicknamed 'Speedy Mic'. This star was recently recognized as a powerful, transient EUV source by the ROSAT WFC, and subsequent investigation showed it to be a ZAMS or possibly a PMS dwarf which may be a member of the Local Association. Our observations show it to have strong, variable UV emission lines near the 'saturation' levels. The radio observations show a level of 'quiescent' emission consistent with other rapidly rotating stars, but there is no evidence for the large flux variations that normally characterize the time history of such objects. C1 CSIRO, AUSTRALIA TELESCOPE NATL FACIL, EPPING, NSW 2121, AUSTRALIA. NASA, GODDARD SPACE FLIGHT CTR, ASTRON & SOLAR PHYS LAB, GREENBELT, MD 20771 USA. RP ROBINSON, RD (reprint author), NASA, GODDARD SPACE FLIGHT CTR, COMP SCI CORP, ASTRON PROGRAMS, CODE 681, GREENBELT, MD 20771 USA. RI Carpenter, Kenneth/D-4740-2012 NR 24 TC 11 Z9 11 U1 0 U2 0 PU WILEY-BLACKWELL PI MALDEN PA COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD APR 15 PY 1994 VL 267 IS 4 BP 918 EP 926 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NF906 UT WOS:A1994NF90600011 ER PT J AU NANDRA, K GEORGE, IM AF NANDRA, K GEORGE, IM TI X-RAY REPROCESSING BY COLD CLOUDS IN ACTIVE GALACTIC NUCLEI SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE RADIATIVE TRANSFER; LINE, FORMATION; GALAXIES, ACTIVE; GALAXIES, NUCLEI; GALAXIES, SEYFERT; X-RAYS, GALAXIES ID SEYFERT-1 GALAXIES; IRON LINE; ACCRETION DISKS; MATTER; REFLECTION; SPECTRA; FLUORESCENCE; VARIABILITY; MCG-6-30-15; ABSORPTION AB Ginga observations have shown that significant spectral features are present in the X-ray spectra of most Seyfert galaxies. These features are usually interpreted in terms of a model in which the primary X-ray continuum is 'reflected' and reprocessed in an accretion disc. Here we consider an alternative geometry, whereby the reprocessing occurs in a distribution of clouds or 'blobs' surrounding the central illuminating source. A Monte Carlo technique is employed to calculate the predicted X-ray spectrum when a single spherical cloud of material is illuminated by a power-law continuum. Using a simplifying approximation, we then derive spectra for a spherical distribution of such clouds. As in the case of disc-reflection models, a significant iron emission line and Compton reflection hump are produced, as long as the optical depth of the individual clouds is large. The spectra show no significant soft X-ray cut-off for covering fractions less than unity. The mean equivalent width of the iron line observed in the Ginga Seyfert sample is obtained in our model for cloud covering fractions of 65-80 per cent. We compare these results to those obtained from accretion-disc models, and suggest means by which the two classes of model may be distinguished. C1 NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771. RP NANDRA, K (reprint author), UNIV CAMBRIDGE,INST ASTRON,MADINGLEY RD,CAMBRIDGE CB3 0HA,ENGLAND. NR 27 TC 51 Z9 51 U1 0 U2 0 PU BLACKWELL SCIENCE LTD PI OXFORD PA OSNEY MEAD, OXFORD, OXON, ENGLAND OX2 0EL SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD APR 15 PY 1994 VL 267 IS 4 BP 974 EP 980 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NF906 UT WOS:A1994NF90600015 ER PT J AU LIU, DTH JOHNSTON, AR AF LIU, DTH JOHNSTON, AR TI THEORY OF RADIATION-INDUCED ABSORPTION IN OPTICAL FIBERS SO OPTICS LETTERS LA English DT Article ID GLASSES; DEFECTS AB A new and simple mathematical model for describing radiation-induced absorption in optical fibers is presented. This model treats the radiation-induced defect generation and the decay process as a series of superposable infinitesimal growth and decay events. Unlike the existing power-law growth equation, the new equation is nonempirical, dose-rate dependent, and describes both the growth and the decay of the induced defect. In the case of constant dose rate the general equation reduces to a simple analytical form that agrees reasonably well with the experiment. RP LIU, DTH (reprint author), JET PROP LAB,PASADENA,CA 91109, USA. NR 12 TC 12 Z9 13 U1 0 U2 0 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 SN 0146-9592 J9 OPT LETT JI Opt. Lett. PD APR 15 PY 1994 VL 19 IS 8 BP 548 EP 550 DI 10.1364/OL.19.000548 PG 3 WC Optics SC Optics GA NF316 UT WOS:A1994NF31600012 PM 19844368 ER PT J AU SELKER, MD AFZAL, RS DALLAS, JL YU, AW AF SELKER, MD AFZAL, RS DALLAS, JL YU, AW TI EFFICIENT, DIODE-LASER-PUMPED, DIODE-LASER-SEEDED, HIGH-PEAK-POWER ND-YLF REGENERATIVE AMPLIFIER SO OPTICS LETTERS LA English DT Article AB Optical amplification of 11 orders of magnitude in a microlens-collimated, diode-laser-pumped regenerative amplifier has been demonstrated. The amplifier was seeded with 20-ps pulses from an FM mode-locked oscillator and with 0.9-ns pulses from a modulated diode laser. Seed pulses from both sources were amplified to energies exceeding 2.6 mJ. With the thermoelectric coolers and the Pockels cell electronics neglected, the diode-seeded system exhibited an electrical-to-optical efficiency of 2.2%. C1 HUGHES STX CORP,LANHAM,MD 20706. RP SELKER, MD (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. NR 10 TC 19 Z9 19 U1 0 U2 3 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 SN 0146-9592 J9 OPT LETT JI Opt. Lett. PD APR 15 PY 1994 VL 19 IS 8 BP 551 EP 553 DI 10.1364/OL.19.000551 PG 3 WC Optics SC Optics GA NF316 UT WOS:A1994NF31600013 PM 19844369 ER PT J AU LUO, XC AF LUO, XC TI STATISTICAL TESTS FOR THE GAUSSIAN NATURE OF PRIMORDIAL FLUCTUATIONS THROUGH CBR EXPERIMENTS SO PHYSICAL REVIEW D LA English DT Article ID DIFFERENTIAL MICROWAVE RADIOMETER; INFLATIONARY UNIVERSE SCENARIO; BACKGROUND-RADIATION; DENSITY PERTURBATIONS; DOMAIN-WALLS; ANISOTROPY; COSMOLOGY; SYMMETRY; TOPOLOGY; STRINGS AB Information about the physical processes that generate the primordial fluctuations in the early Universe can be gained by testing the Gaussian nature of the fluctuations through cosmic microwave background radiation (CBR) temperature anisotropy experiments. One of the crucial aspects of density perturbations that are produced by the standard inflation scenario is that they are Gaussian, whereas seeds produced by topological defects left over from an early cosmic phase transition tend to be non-Gaussian. To carry out this test, sophisticated statistical tools are required. In this paper, we will discuss several such statistical tools, including multivariant skewness and kurtosis, Euler-Poincare characteristics, the three-point temperature correlation function, and Hotelling's T2 statistic defined through bispectral estimates of a one-dimensional data set. The effect of noise present in the current data is discussed in detail and the COBE 53 GHz data set is analyzed. Our analysis shows that, on the large angular scale to which COBE is sensitive, the statistics are probably Gaussian. On the small angular scales, the importance of Hotelling's T2 statistic is stressed, and the minimum sample size required to test Gaussianity is estimated. Although the current data set available from various experiments at half-degree scales is still too small, improvement of the data set by roughly a factor of 2 will be enough to test the Gaussianity statistically. On the arc min scale, we analyze the recent RING data through bispectral analysis, and the result indicates possible deviation from Gaussianity. Effects of point sources are also discussed. It is pointed out that the Gaussianity problem can be resolved in the near future by ground-based or balloon-borne experiments. C1 UNIV CHICAGO,ENRICO FERMI INST,DEPT PHYS,CHICAGO,IL 60637. UNIV CHICAGO,ENRICO FERMI INST,DEPT ASTRON & ASTROPHYS,CHICAGO,IL 60637. FERMILAB NATL ACCELERATOR LAB,NASA,FERMILAB ASTROPHYS CTR,BATAVIA,IL 60510. NR 90 TC 27 Z9 27 U1 0 U2 0 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0556-2821 J9 PHYS REV D JI Phys. Rev. D PD APR 15 PY 1994 VL 49 IS 8 BP 3810 EP 3829 DI 10.1103/PhysRevD.49.3810 PG 20 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA NJ177 UT WOS:A1994NJ17700002 ER PT J AU HU, Y TURNER, MS WEINBERG, EJ AF HU, Y TURNER, MS WEINBERG, EJ TI DYNAMICAL SOLUTIONS TO THE HORIZON AND FLATNESS PROBLEMS SO PHYSICAL REVIEW D LA English DT Article ID COSMOLOGICAL MODELS; EARLY UNIVERSE; INFLATION; SINGULARITY AB We discuss in some detail the requirements on an early-Universe model that solves the horizon and flatness problems during the epoch of classical cosmology (t greater-than-or-equal-to t(i) >> 10(-43) sec). We show that a dynamical resolution of the horizon problem requires superluminal expansion (or very close to it) and that a truly satisfactory resolution of the flatness problem requires entropy production. This implies that a proposed class of adiabatic models in which the Planck mass varies by many orders of magnitude cannot fully resolve the flatness problem. Furthermore, we show that, subject to minimal assumptions, such models cannot solve the horizon problem either. Because superluminal expansion and entropy production are the two generic features of inflationary models, our results suggest that inflation, or something very similar, may be the only dynamical solution to the horizon and flatness problems. C1 UNIV CHICAGO,ENRICO FERMI INST,DEPT PHYS,CHICAGO,IL 60637. UNIV CHICAGO,ENRICO FERMI INST,DEPT ASTRON & ASTROPHYS,CHICAGO,IL 60637. FERMILAB NATL ACCELERATOR LAB,NASA,FERMILAB ASTROPHYS CTR,BATAVIA,IL 60510. RP HU, Y (reprint author), COLUMBIA UNIV,DEPT PHYS,NEW YORK,NY 10027, USA. NR 20 TC 33 Z9 33 U1 0 U2 0 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0556-2821 J9 PHYS REV D JI Phys. Rev. D PD APR 15 PY 1994 VL 49 IS 8 BP 3830 EP 3836 DI 10.1103/PhysRevD.49.3830 PG 7 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA NJ177 UT WOS:A1994NJ17700003 ER PT J AU JUNGNICKEL, DU WALLISER, D AF JUNGNICKEL, DU WALLISER, D TI INHOMOGENEOUS FIELD CONFIGURATIONS AND THE ELECTROWEAK PHASE-TRANSITION SO PHYSICAL REVIEW D LA English DT Article ID HOT GAUGE-THEORIES; FINITE TEMPERATURE; CURVED SPACETIME; SYMMETRY BEHAVIOR; FALSE VACUUM; AMPLITUDES; PROPAGATOR; EXPANSION; PARTICLES; MODEL AB We investigate the effects of inhomogeneous scalar field configurations on the electroweak phase transition. For this purpose we calculate the leading perturbative correction to the wave function correction term Z(phi, T), i.e., the kinetic term in the effective action, for the electroweak standard model at finite temperature and the top quark self-mass. Our finding for the fermionic contribution to Z(phi, T) is infrared finite and disagrees with other recent results. In general, neither the order of the phase transition nor the temperature at which it occurs change, once Z(phi, T) is included. But a nonvanishing, positive (negative) Z(phi, T) enhances (decreases) the critical droplet surface tension and the strength of the phase transition. We find that in the range of parameter space which allows for a first-order phase transition the wave function correction term is negative, indicating a weaker phase transition, and especially for small field values so large that perturbation theory becomes unreliable. C1 FERMILAB NATL ACCELERATOR LAB,NASA,FERMILAB ASTROPHYS CTR,BATAVIA,IL 60510. RP JUNGNICKEL, DU (reprint author), FERMILAB NATL ACCELERATOR LAB,POB 500,BATAVIA,IL 60510, USA. NR 69 TC 2 Z9 2 U1 0 U2 0 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0556-2821 J9 PHYS REV D JI Phys. Rev. D PD APR 15 PY 1994 VL 49 IS 8 BP 3869 EP 3880 DI 10.1103/PhysRevD.49.3869 PG 12 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA NJ177 UT WOS:A1994NJ17700008 ER PT J AU JAFFE, AH AF JAFFE, AH TI QUASI-LINEAR EVOLUTION OF COMPENSATED COSMOLOGICAL PERTURBATIONS - THE NONLINEAR-SIGMA-MODEL SO PHYSICAL REVIEW D LA English DT Article ID LARGE-SCALE STRUCTURE AB We consider the evolution of perturbations to a flat FRW universe that arise from a ''stiff source,'' such as a self-ordering cosmic field that forms in a global symmetry-breaking phase transition and evolves via the Kibble mechanism. Although the linear response of the normal matter to the source depends on the details of the source dynamics, we show that the higher-order nonlinear perturbative equations reduce to a form identical to those of source-free Newtonian gravity in the small wavelength limit. Consequently, the resulting n-point correlation functions and their spectral counterparts will have a hierarchical contribution arising from this gravitational evolution (as in the source-free case) in addition to that possibly coming from non-Gaussian initial conditions. We apply this formalism to the O(N) nonlinear sigma model at large N and find that observable differences from the case of initially Gaussian perturbations and Newtonian gravity in the bispectrum and higher-order correlations are not expected on scales smaller than about 100h-1 Mpc. C1 FERMILAB NATL ACCELERATOR LAB, NASA, FERMILAB ASTROPHYS CTR, BATAVIA, IL 60510 USA. DEPT ASTRON & ASTROPHYS, CHICAGO, IL 60637 USA. RP JAFFE, AH (reprint author), ENRICO FERMI INST, 5640 S ELLIS AVE, CHICAGO, IL 60637 USA. RI Jaffe, Andrew/D-3526-2009 NR 38 TC 27 Z9 27 U1 0 U2 0 PU AMER PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 1550-7998 J9 PHYS REV D JI Phys. Rev. D PD APR 15 PY 1994 VL 49 IS 8 BP 3893 EP 3909 DI 10.1103/PhysRevD.49.3893 PG 17 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA NJ177 UT WOS:A1994NJ17700011 ER PT J AU SIMONS, RN AF SIMONS, RN TI NOVEL COPLANAR STRIPLINE TO SLOTLINE TRANSITION ON HIGH-RESISTIVITY SILICON SO ELECTRONICS LETTERS LA English DT Article DE COPLANAR WAVE-GUIDE; SLOT ANTENNAS; WAVE-GUIDE COMPONENTS; SILICON ID WAVE AB A novel coplanar stripline (CPS) to slotline transition has been fabricated and characterised on a high resistivity silicon wafer. The CPS and the slotline are on opposite sides of the wafer and are coupled electromagnetically. The coupling takes place at the location were the CPS is terminated in a short circuit. The arc of the short circuit crosses the slotline at right angles. The measured average insertion loss and return loss per transition are better than 1.5 and 10 dB, respectively, with a bandwidth greater than 30% at 9.5 GHz. RP SIMONS, RN (reprint author), NASA,LEWIS RES CTR,MAIL STOP 54-5,21000 BROOKPARK RD,CLEVELAND,OH 44135, USA. NR 7 TC 4 Z9 4 U1 0 U2 0 PU IEE-INST ELEC ENG PI HERTFORD PA MICHAEL FARADAY HOUSE SIX HILLS WAY STEVENAGE, HERTFORD, ENGLAND SG1 2AY SN 0013-5194 J9 ELECTRON LETT JI Electron. Lett. PD APR 14 PY 1994 VL 30 IS 8 BP 654 EP 655 DI 10.1049/el:19940431 PG 2 WC Engineering, Electrical & Electronic SC Engineering GA NL309 UT WOS:A1994NL30900029 ER PT J AU KUO, SC ZHANG, ZY KLEMM, RB LIEBMAN, JF STIEF, LJ NESBITT, FL AF KUO, SC ZHANG, ZY KLEMM, RB LIEBMAN, JF STIEF, LJ NESBITT, FL TI PHOTOIONIZATION OF HYDROXYMETHYL (CD2OH AND CD2OD) AND METHOXY (CD3O) RADICALS - PHOTOION EFFICIENCY SPECTRA, IONIZATION ENERGIES, AND THERMOCHEMISTRY SO JOURNAL OF PHYSICAL CHEMISTRY LA English DT Article ID BOND-DISSOCIATION ENERGIES; GAS-PHASE; RATE CONSTANTS; PHOTOELECTRON-SPECTROSCOPY; TOTAL PRESSURE; CH3O; KINETICS; CH2OH; IONS; TEMPERATURE AB Photoion efficiency (PIE) spectra were obtained for CD2OH, CD2OD, and CD3O radicals using the discharge flow-photoionization mass spectrometry technique. The radicals were generated in a flow tube via reaction of F atoms with the appropriate methanol isotopomers (CD3OH --> CD2OH, CD3OD --> CD2OD, and CD3OH --> CD3O), which were in large excess. Deuterated methoxy radicals, CD3O, were also generated via the reaction of CD3 with NO2. Photoionization of the radicals was achieved using high intensity, dispersed synchrotron radiation, and ionization energies (IE) of these radicals were derived from the thresholds of the PIE spectra: IE(CD2OH) = 7.54 +/- 0.02 eV, IE(CD2OD) = 7.53 +/- 0.02 eV, and IE(CD3O) = 10.74 +/- 0.02 eV. The PIE spectra for CD2OH and CD3O are compared to those of a previous photoionization study, and differences are discussed. Integration of previously published photoelectron spectroscopy data for CD2OH yields a curve quite similar to our PIE spectrum. Empirical estimates of IE(CH2OH) and IE(CH3O) are given to corroborate our assignments. Attempts to detect CH3O+ from direct ionization of CH3O, which was generated by two methods (CH3OD + F and CH3 + NO2), were unsuccessful. However, HCO+, presumably formed along with H-2 from CH3O dissociative ionization, was detected at a threshold 8.73 eV. This appearance energy corresponds to a barrier of 17.6 kJ mol(-1) for the process CH3O* --> HCO+ + H-2. Heats of formation for neutral and ion species : were determined using literature values for the proton affinity of CH2O and integrated heat capacities and the IE's measured in this laboratory, and an energy level diagram was developed for T = 298 K. For hydroxymethyl and methoxy radicals the following values were obtained: Delta(f)H degrees(298)(CH2OH) = -20.4 kJ mol(-1) (which agrees well with the recent results of Traeger and Holmes, J. Phys. Chem. 1993, 97, 3453); Delta(f)H degrees(298)(CH3O) = 12.2 kJ mol(-1). Bond dissociation energies were also computed: D degrees(0)(H-CH2OH) = 393.1 kJ mol(-1) and D degrees(0)(CH3OH) = 426.6 kJ mol(-1). The measured ionization energies and the derived thermodynamic quantities are compared with previously reported results. C1 BROOKHAVEN NATL LAB,UPTON,NY 11973. UNIV MARYLAND,DEPT CHEM & BIOCHEM,CATONSVILLE,MD 21228. NASA,GODDARD SPACE FLIGHT CTR,EXTRATERR PHYS LAB,GREENBELT,MD 20771. NR 67 TC 40 Z9 41 U1 0 U2 3 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0022-3654 J9 J PHYS CHEM-US JI J. Phys. Chem. PD APR 14 PY 1994 VL 98 IS 15 BP 4026 EP 4033 DI 10.1021/j100066a021 PG 8 WC Chemistry, Physical SC Chemistry GA NG219 UT WOS:A1994NG21900021 ER PT J AU BHATIA, AK DRACHMAN, RJ AF BHATIA, AK DRACHMAN, RJ TI POLARIZABILITY OF HELIUM AND THE NEGATIVE HYDROGEN-ION SO JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS LA English DT Article ID RYDBERG STATES AB We have carried out precision calculations of the dipole and quadrupole polarizabilities of helium and the negative hydrogen ion and their non-adiabatic extensions. These quantities are obtained from second-order perturbation sums involving energy denominators raised to the power k = 1, 2 or 3. The summation over intermediate states is carried out using Hylleraas two-particle wavefunctions of the appropriate symmetry and angular momentum. The measured mass of the nucleus is retained. The convergence is excellent for the helium case and somewhat poorer for H-. RP BHATIA, AK (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771, USA. NR 9 TC 37 Z9 37 U1 0 U2 4 PU IOP PUBLISHING LTD PI BRISTOL PA TECHNO HOUSE, REDCLIFFE WAY, BRISTOL, ENGLAND BS1 6NX SN 0953-4075 J9 J PHYS B-AT MOL OPT JI J. Phys. B-At. Mol. Opt. Phys. PD APR 14 PY 1994 VL 27 IS 7 BP 1299 EP 1305 DI 10.1088/0953-4075/27/7/005 PG 7 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA NH053 UT WOS:A1994NH05300005 ER PT J AU BARTEL, N BIETENHOLZ, MF RUPEN, MP CONWAY, JE BEASLEY, AJ SRAMEK, RA ROMNEY, JD TITUS, MA GRAHAM, DA ALTUNIN, VI JONES, DL RIUS, A VENTURI, T UMANA, G FRANCIS, RL MCCALL, ML RICHER, MG STEVENSON, CC WEILER, KW VANDYK, SD PANAGIA, N CANNON, WH POPELAR, J DAVIS, RJ AF BARTEL, N BIETENHOLZ, MF RUPEN, MP CONWAY, JE BEASLEY, AJ SRAMEK, RA ROMNEY, JD TITUS, MA GRAHAM, DA ALTUNIN, VI JONES, DL RIUS, A VENTURI, T UMANA, G FRANCIS, RL MCCALL, ML RICHER, MG STEVENSON, CC WEILER, KW VANDYK, SD PANAGIA, N CANNON, WH POPELAR, J DAVIS, RJ TI THE SHAPE, EXPANSION RATE AND DISTANCE OF SUPERNOVA-1993J FROM VLBI MEASUREMENTS SO NATURE LA English DT Article ID RADIO SUPERNOVAE; YOUNG SUPERNOVA; INTERFEROMETRY; MODEL; M82 AB SUPERNOVA 1993J is one of the closest supernovae discovered this century, allowing observations with very high linear resolution. Radio emission from the supernova became visible within days of the first optical peak, and has remained strong, making this an ideal source for very-long-baseline interferometry (VLBI) investigations1-7. Here we report the results of a series of VLBI observations, made from one to three months after the supernova explosion. We find that the supernova is circularly symmetric, which is somewhat surprising in view of suggestions that the progenitor was a member of a binary system8,9, and the asymmetry implied by optical observations10. The supernova shows no sign of deceleration, and the expansion velocities that we estimate from the VLBI measurements are consistent with the maximum optical line velocities11, suggesting that the radio emission indeed arises from the shock front, where the ejecta are hitting the gas that surrounded the progenitor star. We combine the angular expansion rate determined by the VLBI data with the optically derived expansion speed to estimate a distance to M81 of 4.0 +/- 0.6 Mpc, consistent with the value obtained from measurements of Cepheid variables in M81, 3.63 +/- 0.34 Mpc (ref. 12). C1 NATL RADIO ASTRON OBSERV,SOCORRO,NM 87801. HAYSTACK OBSERV,WESTFORD,MA 01886. MAX PLANCK INST RADIOASTRON,D-53010 BONN,GERMANY. JET PROP LAB,PASADENA,CA 91109. FAC CIENCIAS MATEMAT MADRID,INST ASTRON & GEODESIA,E-28040 MADRID,SPAIN. CNR,INST RADIOASTRON,I-40126 BOLOGNA,ITALY. CNR,INST RADIOASTRON,NOTO,ITALY. USN,RES LAB,WASHINGTON,DC 20375. UNIV CALIF BERKELEY,DEPT ASTRON,BERKELEY,CA 94720. SPACE TELESCOPE SCI INST,BALTIMORE,MD 21218. INST SPACE & TERR SCI,N YORK M3J 3K1,ON,CANADA. NAT RESOURCES CANADA,OTTAWA K1A OY3,ON,CANADA. NUFFIELD RADIO ASTRON OBSERV LABS,MACCLESFIELD SK11 9DL,CHESHIRE,ENGLAND. RP BARTEL, N (reprint author), YORK UNIV,DEPT PHYS & ASTRON,N YORK M3J 1P3,ON,CANADA. RI Antonio, Rius/A-4873-2012; OI Antonio, Rius/0000-0002-5947-2649; Venturi, Tiziana/0000-0002-8476-6307 NR 32 TC 52 Z9 52 U1 0 U2 3 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW SN 0028-0836 J9 NATURE JI Nature PD APR 14 PY 1994 VL 368 IS 6472 BP 610 EP 613 DI 10.1038/368610a0 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA NF392 UT WOS:A1994NF39200052 ER PT J AU STAEHLE, RL AF STAEHLE, RL TI KUDOS FOR CLEMENTINE SO AVIATION WEEK & SPACE TECHNOLOGY LA English DT Letter RP STAEHLE, RL (reprint author), JET PROP LAB,PLUTO FAST FLYBY PREPROJECT,PASADENA,CA 91109, USA. NR 1 TC 0 Z9 0 U1 0 U2 0 PU MCGRAW HILL INC PI NEW YORK PA 1221 AVENUE OF THE AMERICAS, NEW YORK, NY 10020 SN 0005-2175 J9 AVIAT WEEK SPACE TEC JI Aviat. Week Space Technol. PD APR 11 PY 1994 VL 140 IS 15 BP 6 EP 6 PG 1 WC Engineering, Aerospace SC Engineering GA NF995 UT WOS:A1994NF99500001 ER PT J AU BAZHENOV, S LI, JX HILTNER, A BAER, E AF BAZHENOV, S LI, JX HILTNER, A BAER, E TI DUCTILITY OF FILLED POLYMERS SO JOURNAL OF APPLIED POLYMER SCIENCE LA English DT Article ID MECHANICAL-PROPERTIES; POLYPROPYLENE; COMPOSITES; STRESS AB The ductility of a calcium carbonate-filled amorphous copolyester PETG in a uniaxial tensile test was examined as a function of the filler volume fraction. A ductile-to-quasi-brittle transition occurred as the volume fraction of filler increased. This transition was from propagation of a stable neck through the entire gauge length of the specimen to fracture in the neck without propagation. The draw stress (lower yield stress) did not depend on the filler content and was equal to the draw stress of the unfilled polymer. It was therefore possible to use a simple model to predict the dependence of the fracture strain on the filler volume fraction. It was proposed that when the fracture strain decreases to the draw strain of the polymer the fracture mechanism changes and the fracture strain drops sharply. The critical filler content at which the fracture mode changes is determined primarily by the degree of strain-hardening of the polymer. (C) 1994 John Wiley & Sons, Inc. C1 NASA,CCDS MAT SPACE STRUCT,CLEVELAND,OH 44106. CASE WESTERN RESERVE UNIV,CTR APPL POLYMER RES,CLEVELAND,OH 44106. RI Bazhenov, Sergey/A-7364-2013 NR 20 TC 51 Z9 55 U1 1 U2 5 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 APR 11 PY 1994 VL 52 IS 2 BP 243 EP 254 DI 10.1002/app.1994.070520211 PG 12 WC Polymer Science SC Polymer Science GA NA317 UT WOS:A1994NA31700011 ER PT J AU FRY, JN GAZTANAGA, E AF FRY, JN GAZTANAGA, E TI REDSHIFT DISTORTIONS OF GALAXY CORRELATION-FUNCTIONS SO ASTROPHYSICAL JOURNAL LA English DT Article DE GALAXIES, CLUSTERING; GALAXIES, DISTANCES AND REDSHIFTS; LARGE-SCALE STRUCTURE OF UNIVERSE; METHODS, NUMERICAL ID POINT CORRELATION-FUNCTIONS; LARGE-SCALE STRUCTURE; IRAS GALAXIES; STATISTICAL-ANALYSIS; FLUCTUATIONS; EVOLUTION; CATALOGS; SKEWNESS; 2-POINT; OBJECTS AB To examine how peculiar velocities can affect the two-, three-, and four-point redshift correlation functions, we evaluate volume-average correlations for configurations that emphasize and minimize redshift distortions for four different volume-limited samples from each of the CfA, SSRS, and IRAS redshift catalogs. We present the results as the correlation length r0 and power index gamma of the two-point correlations, xiBAR0 = (r0/r)gamma, and as the hierarchical amplitudes of the three- and four-point functions, S3 = xiBAR3/xiBAR2(2) and S4 = xiBAR4/xiBAR2(3). We find a characteristic distortion for xiBAR2; the slope gamma is flatter and the correlation length is larger in redshift space than in real space; that is, redshift distortions ''move'' correlations from small to large scales. At the largest scales (up to 12 Mpc), the extra power in the redshift distribution is compatible with OMEGA4/7/b almost-equal-to 1. We estimate OMEGA4/7/b to be 0.53 +/- 0.15, 1.10 +/- 0.16, and 0.84 +/- 0.45 for the CfA, SSRS, and IRAS catalogs. Higher order correlations xiBAR3 and xiBAR4 suffer similar redshift distortions but in such a way that, within the accuracy of our analysis, the normalized amplitudes S3 and S4 are insensitive to this effect. The hierarchical amplitudes S3 and S4 are constant as a function of scale between 1 and 12 Mpc and have similar values in all samples and catalogs, S3 almost-equal-to 2 and S4 almost-equal-to 6, despite the fact that xiBAR2, xiBAR3, and xiBAR4 differ from one sample to another by large factors (up to a factor of 4 in xiBAR2, 8 for xiBAR3, and 12 for xiBAR4). The agreement between the independent estimations of S3 and S4 is remarkable given the different criteria in the selection of galaxies and also the difference in the resulting range of densities, luminosities, and locations between samples. C1 UNIV FLORIDA,DEPT PHYS,GAINESVILLE,FL 32611. UNIV OXFORD,DEPT PHYS,OXFORD OX1 3RH,ENGLAND. RP FRY, JN (reprint author), FERMILAB NATL ACCELERATOR LAB,NASA,FERMILAB ASTROPHYS CTR,BATAVIA,IL 60510, USA. OI Gaztanaga, Enrique/0000-0001-9632-0815 NR 27 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 APR 10 PY 1994 VL 425 IS 1 BP 1 EP 13 DI 10.1086/173956 PN 1 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NE028 UT WOS:A1994NE02800001 ER PT J AU HILL, JK ISENSEE, JE CORNETT, RH BOHLIN, RC OCONNELL, RW ROBERTS, MS SMITH, AM STECHER, TP AF HILL, JK ISENSEE, JE CORNETT, RH BOHLIN, RC OCONNELL, RW ROBERTS, MS SMITH, AM STECHER, TP TI INITIAL MASS FUNCTIONS FROM ULTRAVIOLET STELLAR PHOTOMETRY - A COMPARISON OF LUCKE AND HODGE OB ASSOCIATIONS NEAR 30-DORADUS WITH THE NEARBY FIELD SO ASTROPHYSICAL JOURNAL LA English DT Article DE MAGELLANIC CLOUDS; OPEN CLUSTERS AND ASSOCIATIONS, INDIVIDUAL (30-DORADUS); STARS, LUMINOSITY FUNCTION, MASS FUNCTION; ULTRAVIOLET, STARS ID LARGE MAGELLANIC CLOUD; IMAGING TELESCOPE; STARS AB UV stellar photometry is presented for 1563 stars within a 40' circular field in the LMC, excluding the 10' x 10' field centered on R136 investigated earlier by Hill et al. (1993). Magnitudes are computed from images obtained by the Ultraviolet Imaging Telescope in bands centered at 1615 angstrom and 2558 angstrom. Stellar masses and extinctions are estimated for the stars in associations using the evolutionary models of Schaerer et al. (1993), assuming the age is 4 Myr and that the local LMC extinction follows the Fitzpatrick (1985) 30 Dor extinction curve. The estimated slope of the initial mass function (IMF) for massive stars (> 15 M.) within the Lucke and Hodge (LH) associations is GAMMA = - 1.08 +/- 0.2. Initial masses and extinctions for stars not within LH associations are estimated assuming that the stellar age is either 4 Myr or half the stellar lifetime, whichever is larger. The estimated slope of the IMF for massive stars not within LH associations is GAMMA = - 1.74 +/- 0.3 (assuming continuous star formation), compared with GAMMA = - 1.35, and GAMMA = - 1.7 +/- 0.5, obtained for the Galaxy by Salpeter (1955) and Scalo (1986), respectively, and GAMMA = - 1.6 obtained for massive stars in the Galaxy by Garmany, Conti, & Chiosi (1982). The shallower slope of the association IMF suggests that not only is the star formation rate higher in associations, but that the local conditions favor the formation of higher mass stars there. We make no corrections for binaries or incompleteness. C1 NATL RADIO ASTRON OBSERV,CHARLOTTESVILLE,VA 22903. NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771. SPACE TELESCOPE SCI INST,BALTIMORE,MD 21218. UNIV VIRGINIA,CHARLOTTESVILLE,VA 22903. RP HILL, JK (reprint author), HUGHES STX,4400 FORBES BLVD,LANHAM,MD 20706, USA. NR 23 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 APR 10 PY 1994 VL 425 IS 1 BP 122 EP & DI 10.1086/173968 PN 1 PG 0 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NE028 UT WOS:A1994NE02800013 ER PT J AU HANNER, MS LYNCH, DK RUSSELL, RW AF HANNER, MS LYNCH, DK RUSSELL, RW TI THE 8-13 MICRON SPECTRA OF COMETS AND THE COMPOSITION OF SILICATE GRAINS SO ASTROPHYSICAL JOURNAL LA English DT Article DE COMETS, GENERAL; DUST, EXTINCTION; INFRARED, SOLAR SYSTEM ID INTERPLANETARY DUST PARTICLES; AMORPHOUS SILICATES; SPECTROPHOTOMETRY; AIRBORNE; P/HALLEY; OLIVINE; HALLEY; IDENTIFICATION; SPECTROSCOPY; CONSTRAINTS AB We have analyzed the existing spectra of seven comets which show an emission feature at 7.8-13 mum. Most have been converted to a common calibration, taking into account the SiO feature in late-type standard stars. The spectra are compared with spectra of the Trapezium, interplanetary dust particles (IDPs), laboratory mineral samples, and small particle emission models. The emission spectra show a variety of shapes; there is no unique ''cometary silicate.'' A peak at 11.20-11.25 mum, indicative of small crystalline olivine particles, is seen in only three comets of this sample, P/Halley, Bradfield 1987 XXIX, and Levy 1990 XX. The widths of the emission features range from 2.6 to 4.1 mum (FWHM). To explain the differing widths and the broad 9.8 mum maximum, glassy silicate particles, including both pyroxene and olivine compositions, are the most plausible candidates. Calculations of emission models confirm that small grains of glassy silicate well mixed with carbonaceous material are plausible cometary constituents No single class of chondritic aggregate IDPs exhibits spectra closely matching the comet spectra. A mixture of IDP spectra, particularly the glass-rich aggregates, approximately matches the spectra of comets P/Halley, Levy, and Bradfield 1987 XXIX. Yet, if comets are simply a mix of IDP types, it is puzzling that the classes of IDPs are so distinct. None of the comet spectra match the spectrum of the Trapezium. Thus, the mineralogy of the cometary silicates is not the same as that of the interstellar medium. The presence of a component of crystalline silicates in comets may be evidence of mixing between high- and low-temperature regions in the solar nebula. C1 AEROSP CORP,LOS ANGELES,CA 90009. RP HANNER, MS (reprint author), JET PROP LAB,MAIL STOP 183-601,PASADENA,CA 91109, USA. NR 55 TC 214 Z9 215 U1 0 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 10 PY 1994 VL 425 IS 1 BP 274 EP 285 DI 10.1086/173984 PN 1 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NE028 UT WOS:A1994NE02800029 ER PT J AU CANUTO, VM MINOTTI, FO SCHILLING, O AF CANUTO, VM MINOTTI, FO SCHILLING, O TI DIFFERENTIAL ROTATION AND TURBULENT CONVECTION - A NEW REYNOLDS STRESS MODEL AND COMPARISON WITH SOLAR DATA SO ASTROPHYSICAL JOURNAL LA English DT Article DE CONVECTION; HYDRODYNAMICS; SUN, INTERIOR; SUN, ROTATION; TURBULENCE ID ANGULAR-MOMENTUM TRANSPORT; COMPRESSIBLE CONVECTION; NUMERICAL SIMULATIONS; DEEP ATMOSPHERE; SPHERICAL-SHELL; DYNAMOS; EQUATIONS; MOTIONS; FLOWS; FIELD AB In most hydrodynamic cases, the existence of a turbulent flow superimposed on a mean flow is caused by a shear instability in the latter. Boussinesq suggested the first model for the turbulent Reynolds stresses u(i)u(j)BAR in the form u(i)u(j)BAR = - 2v(t)S(ij) which physically implies that the mean shear S(ij) is the cause (or source) of turbulence represented by the stress u(i)u(j)BAR. In the case of solar differential rotation, exactly the reverse physical process occurs: turbulence (which must pre-exist) generates a mean flow which manifests itself in the form of differential rotation. Thus, the Boussinesq model is wholly inadequate because in the solar case, cause and effect are reversed. One should envisage the sequence of cause and effect relationships as follows: Buoyancy --> Turbulence --> Mean Flow (Differential Rotation) where the source of turbulence has been identified with buoyancy which is present in stars for reasons unrelated to the fact that it may ultimately generate a differential rotation. An alternative way of interpreting the sequence above is by saying that small scales (buoyancy) have more energy than large scales (mean flow, differential rotation), quite contrary to most situations usually encountered in turbulence studies. Thus, the relation between buoyancy, Reynolds stresses and differential rotation must be viewed in a fundamentally different physical light from most standard hydrodynamic flows in which either the mean flow is the cause of turbulence (most laboratory and engineering cases) or both mean flow and buoyancy conspire to generate turbulence (the boundary layer of the Earth's atmosphere). Since the Boussinesq model is inadequate, one needs an alternative model for the Reynolds stresses. We present a new dynamical model for the Reynolds stresses, convective fluxes, turbulent kinetic energy, and temperature fluctuations. The complete model requires the solution of 11 differential equations. We then introduce a set of simplifying assumptions which reduce the full dynamical model to a set of algebraic Reynolds stress models. We explicity solve one of these models that entails only one differential equation. The main results are 1. Shear alone, namely the Boussinesq formula, u(i)u(j)BAR = -2v(t)S(ij), cannot give the expected result since it describes a flow in which turbulence is generated by shear, while in the solar case shear is generated by turbulence. 2. Shear and buoyancy alone do not yield acceptable results. 3. Agreement with the data requires the nonlinear interaction between vorticity and buoyancy. 4. The predicted u(theta)u(phi)BAR agrees very closely with observational data (Gilman & Howard 1984; Virtanen 1989). 5. The model predicts the magnitude and latitudinal behavior of the three components of the turbulent kinetic energy, two of which (u(theta)2BAR and u(theta)2BAR) could be compared to existing data. 6. The maximum production of shear by buoyancy is predicted to occur at a latitude of approximately 40-degrees. 7. The model predicts that 2.5% of the buoyant production rate is required to generate and maintain solar differential rotation. 8. The model predicts four independent anisotropic (turbulent) viscosities v(vv), v(hh), v(vh), and v(hv) which depend on latitude, as well as three independent anisotropic (turbulent) conductivities, chi(rr), chi(phir), and chi(thetar) which also depend on latitude (the present numerical results are restricted to radial temperature gradients). 9. The degree of anisotropy in the turbulent viscosities, measured by the parameter s, is found to depend on latitude and its value is in accordance with the empirical value of approximately 1.3. 10. The buoyancy timescale tau(b) = [(g/H(p)(del - del(ad)]-1/2 predicted by the model is in agreement with the results of stellar structure models. 11. The so-called LAMBDA-effect is naturally (and unavoidably) predicted by the model as a result of the presence of vorticity: while shear depends only on the derivatives of OMEGA, vorticity also depends on OMEGA itself. The overall agreement with the data is obtained with a model that is neither phenomenological nor one that requires a full numerical simulation, since it is algebraic in nature. The new model can play an important role in understanding the complex physics underlying the interplay between solar differential rotation and convection, as many physical processes can naturally be incorporated into the model. RP NASA, 2880 BROADWAY, NEW YORK, NY 10025 USA. OI Schilling, Oleg/0000-0002-0623-2940 NR 66 TC 50 Z9 50 U1 0 U2 2 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD APR 10 PY 1994 VL 425 IS 1 BP 303 EP 325 DI 10.1086/173986 PN 1 PG 23 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NE028 UT WOS:A1994NE02800031 ER PT J AU BROSIUS, JW DAVILA, JM THOMAS, RJ THOMPSON, WT AF BROSIUS, JW DAVILA, JM THOMAS, RJ THOMPSON, WT TI SOLAR CORONAL TEMPERATURE DIAGNOSTICS USING EMISSION-LINES FROM MULTIPLE STAGES OF IONIZATION OF IRON SO ASTROPHYSICAL JOURNAL LA English DT Article DE ATOMIC PROCESSES; SUN, CORONA; SUN, UV RADIATION ID STRUCTURES OBSERVING CAMPAIGN; SPECTROGRAPH; RATES; PLAGE AB We obtained spatially resolved extreme-ultraviolet (EUV) spectra of AR 6615 on 1991 May 7 with NASA/Goddard Space Flight Center's Solar EUV Rocket Telescope and Spectrograph (SERTS). Included are emission lines from four different stages of ionization of iron: Fe+15 lambda335 angstrom, Fe+14 lambda327 angstrom, Fe+13 lambda334 angstrom, and Fe+12 lambda348 angstrom. Using intensity ratios from among these lines, we have calculated the active region coronal temperature along the SERTS slit. Temperatures derived from line ratios which incorporate adjacent stages of ionization are most sensitive to measurement uncertainties and yield the largest scatter. Temperatures derived from line ratios which incorporate nonadjacent stages of ionization are less sensitive to measurement uncertainities and yield little scatter. The active region temperature derived from these latter ratios has an average value of 2.54 x 10(6) K, with a standard deviation approximately 0.12 x 10(6) K, and shows no significant variation with position along the slit. C1 HUGHES STX,LANHAM,MD 20706. APPL RES CORP,LANDOVER,MD 20785. RP BROSIUS, JW (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,CODE 682,GREENBELT,MD 20771, USA. RI Thompson, William/D-7376-2012 NR 28 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 APR 10 PY 1994 VL 425 IS 1 BP 343 EP 347 DI 10.1086/173989 PN 1 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NE028 UT WOS:A1994NE02800034 ER PT J AU CHENG, KP BRUHWEILER, FC KONDO, Y AF CHENG, KP BRUHWEILER, FC KONDO, Y TI A SEARCH FOR ULTRAVIOLET CIRCUMSTELLAR GAS-ABSORPTION FEATURES IN ALPHA-PISCIS-AUSTRINUS (FOMALHAUT), A POSSIBLE BETA-PICTORIS-LIKE SYSTEM SO ASTROPHYSICAL JOURNAL LA English DT Article DE CIRCUMSTELLAR MATTER; ULTRAVIOLET, GENERAL; ULTRAVIOLET, STARS ID PROTO-PLANETARY SYSTEM; MAIN-SEQUENCE; NEARBY STARS; SAO STARS; EXCESSES; MATTER; DISK AB Archival high-dispersion International Ultraviolet Explorer (IUE) spectra have been used to search for circumstellar gas absorption features in alpha PsA (A3 V), a nearby (6.7 pc) proto-planetary system candidate. Recent sub-millimeter mapping observations around the region of alpha PsA indicate a spatially resolved dust disk like the one seen around beta Pic. To determine how closely this putative disk resembles that of beta Pic, we have searched for signatures of circumstellar gaseous absorption in all the available IUE high-dispersion data of alpha PsA. Examination of co-added IUE spectra shows weak circumstellar absorptions from excited levels in the resonance multiplet of Fe II near 2600 angstrom. We also conclude that the sharp C I feature near 1657 angstrom, previously identified as interstellar absorption toward alpha PsA, likely has a circumstellar origin. However, because the weakness of these absorption features, we will consider the presence of circumstellar gas as tentative and should be verified by using the Goddard High-Resolution Spectrograph aboard the Hubble Space Telescope. No corresponding circumstellar absorption is detected in higher ionization Fe III and Al III. Since the collisionally ionized nonphotospheric Al III resonance absorption seen in beta Pic is likely formed close to the stellar surface, its absence in the UV spectra of alpha PsA could imply that, in contrast with beta Pic, there is no active gaseous disk infall onto the central star. In the alpha PsA gaseous disk, if we assume a solar abundance for iron and all the iron is in the form of Fe II, plus a disk temperature of 5000 K, the Fe II UV1 absorption at 2611.8743 angstrom infers a total hydrogen column density along the line of sight through the circumstellar disk of N(H) almost-equal-to 3.8 x 10(17) cm-1. C1 CATHOLIC UNIV AMER,DEPT PHYS,ASTROPHYS PROGRAM,WASHINGTON,DC 20064. RP CHENG, KP (reprint author), NASA,GSFC,CODE 684,GREENBELT,MD 20771, USA. NR 25 TC 2 Z9 2 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 10 PY 1994 VL 425 IS 1 BP L33 EP L36 DI 10.1086/187304 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NE032 UT WOS:A1994NE03200009 ER PT J AU HARMON, BA WILSON, CA PACIESAS, WS PENDLETON, GN BRIGGS, MS RUBIN, BC FINGER, MH FISHMAN, GJ BROCK, MN WILSON, RB MEEGAN, CA AF HARMON, BA WILSON, CA PACIESAS, WS PENDLETON, GN BRIGGS, MS RUBIN, BC FINGER, MH FISHMAN, GJ BROCK, MN WILSON, RB MEEGAN, CA TI OBSERVATION OF GX-339-4 HARD STATE OUTBURSTS IN 1991 AND 1992 SO ASTROPHYSICAL JOURNAL LA English DT Article DE BINARIES, GENERAL; BLACK HOLE PHYSICS; STARS, INDIVIDUAL (GX-339-4) ID BLACK-HOLE CANDIDATE; X-RAY VARIABILITY; GX 339-4; CYGNUS X-1; GX339-4; SPECTRUM; GRANAT AB Two hard state (X-ray low state) outbursts in the GX 339-4 system in 1991 June-October and 1992 September-1993 January were detected and monitored by the Burst and Transient Source Experiment (BATSE) on the Compton Gamma Ray Observatory (CGRO). The outbursts were remarkably similar in both temporal and spectral aspects. The spectrum in the 20-300 keV band evolves from a hard, Comptonized shape to a steeper (alpha almost-equal-to -3) power law during each outburst. RP HARMON, BA (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812, USA. NR 28 TC 24 Z9 24 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 10 PY 1994 VL 425 IS 1 BP L17 EP L20 DI 10.1086/187300 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NE032 UT WOS:A1994NE03200005 ER PT J AU WUNDROW, DW HULTGREN, LS GOLDSTEIN, ME AF WUNDROW, DW HULTGREN, LS GOLDSTEIN, ME TI INTERACTION OF OBLIQUE INSTABILITY WAVES WITH A NONLINEAR PLANE-WAVE SO JOURNAL OF FLUID MECHANICS LA English DT Article ID FREE SHEAR-LAYER; BOUNDARY-LAYERS; ROLL-UP; EVOLUTION; FLOWS AB This paper is concerned with the downstream evolution of a resonant triad of initially non-interacting linear instability waves in a boundary layer with a weak adverse pressure gradient. The triad consists of a two-dimensional fundamental mode and a pair of equal-amplitude oblique modes that form a subharmonic standing wave in the spanwise direction. The growth rates are small and there is a well-defined common critical layer for these waves. As in Goldstein & Lee (1992), the wave interaction takes place entirely within this critical layer and is initially of the parametric-resonance type. This enhances the spatial growth rate of the subharmonic but does not affect that of the fundamental. However, in contrast to Goldstein & Lee (1992), the initial subharmonic amplitude is assumed to be small enough so that the fundamental can become nonlinear within its own critical layer before it is affected by the subharmonic. The subharmonic evolution is then dominated by the parametric-resonance effects and occurs on a much shorter streamwise scale than that of the fundamental. The subharmonic amplitude continues to increase during this parametric-resonance stage - even as the growth rate of the fundamental approaches zero - and the subharmonic eventually becomes large enough to influence the fundamental which causes both waves to evolve on the same shorter streamwise scale. C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP WUNDROW, DW (reprint author), SVERDRUP TECHNOL INC,LEWIS RES CTR GRP,CLEVELAND,OH 44135, USA. NR 21 TC 17 Z9 18 U1 0 U2 0 PU CAMBRIDGE UNIV PRESS PI NEW YORK PA 40 WEST 20TH STREET, NEW YORK, NY 10011-4211 SN 0022-1120 J9 J FLUID MECH JI J. Fluid Mech. PD APR 10 PY 1994 VL 264 BP 343 EP 372 DI 10.1017/S0022112094000698 PG 30 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA NJ113 UT WOS:A1994NJ11300014 ER PT J AU VOORHIES, CV NISHIHAMA, M AF VOORHIES, CV NISHIHAMA, M TI SIMULTANEOUS SOLUTION FOR CORE MAGNETIC-FIELD AND FLUID-FLOW BENEATH AN ELECTRICALLY CONDUCTING MANTLE SO JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH LA English DT Article ID GEOMAGNETIC-FIELD; STEADY FLOWS; BOUNDARY; SURFACE; MOTIONS; MODELS AB The effects of laterally homogeneous mantle electrical conductivity have been included in steady, frozen-flux core surface flow estimation along with refinements in method and weighting. The refined method allows simultaneous solution for both the initial radial geomagnetic field component at the core-mantle boundary and the subadjacent fluid motion; it also features Gauss' method for solving the nonlinear inverse problem associated with steady motional induction. The trade-off between spatial complexity of the derived flows and misfit to the weighted Definitive Geomagnetic Reference Field models is studied for various mantle conductivity profiles. For simple flow and a fixed initial geomagnetic condition a fairly high deep-mantle conductivity performs better than either insulating or weakly conducting profiles; however, a thin, very high conductivity layer at the base of the mantle performs almost as well. Simultaneous solution for both initial geomagnetic field and fluid flow reduces the misfit per degree of freedom even more than does changing the mantle conductivity profile. Moreover, when both core field and flow are estimated, the performance of the solutions and the derived flows become insensitive to the conductivity profile. C1 HUGHES STX CORP, GREENBELT, MD USA. RP VOORHIES, CV (reprint author), NASA, GODDARD SPACE FLIGHT CTR, GEODYNAM BRANCH, CODE 921, GREENBELT, MD 20771 USA. RI Voorhies, Coerte/D-4672-2012 NR 52 TC 7 Z9 7 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9313 EI 2169-9356 J9 J GEOPHYS RES-SOL EA JI J. Geophys. Res.-Solid Earth PD APR 10 PY 1994 VL 99 IS B4 BP 6685 EP 6693 DI 10.1029/94JB00109 PG 9 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA NF970 UT WOS:A1994NF97000001 ER PT J AU FREEDMAN, AP STEPPE, JA DICKEY, JO EUBANKS, TM SUNG, LY AF FREEDMAN, AP STEPPE, JA DICKEY, JO EUBANKS, TM SUNG, LY TI THE SHORT-TERM PREDICTION OF UNIVERSAL TIME AND LENGTH OF DAY USING ATMOSPHERIC ANGULAR-MOMENTUM SO JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH LA English DT Article ID EARTH ROTATION; FLUCTUATIONS; FORECASTS; BUDGET; SCALES AB The ability to predict short-term variations in the Earth's rotation has gained importance in recent years owing to more precise spacecraft tracking requirements. Universal time (UT1), that component of the Earth's orientation corresponding to the rotation angle, can be measured by a number of high-precision space geodetic techniques. A Kalman filter developed at the Jet Propulsion Laboratory (JPL) optimally combines these different data sets and generates a smoothed time series and a set of predictions for UT1, as well as for additional Earth orientation components. These UT1 predictions utilize an empirically derived random walk stochastic model for the length of the day (LOD) and require frequent and up-to-date measurements of either UT1 or LOD to keep errors from quickly accumulating. Recent studies have shown that LOD variations are correlated with changes in the Earth's axial atmospheric angular momentum (AAM) over timescales of several years down to as little as 8 days. AAM estimates and forecasts out to 10 days are routinely available from meteorological analysis centers; these data can supplement geodetic measurements to improve the short-term prediction of LOD and have therefore been incorporated as independent data types in the JPL Kalman filter. We find that AAM and, to a lesser extent, AAM forecast data are extremely helpful in generating accurate near-real-time estimates of UT1 and LOD and in improving short-term predictions of these quantities out to about 10 days. RP FREEDMAN, AP (reprint author), JET PROP LAB, 4800 OAK GROVE DR, PASADENA, CA 91109 USA. OI Eubanks, Thomas Marshall/0000-0001-9543-0414 NR 39 TC 29 Z9 31 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9313 EI 2169-9356 J9 J GEOPHYS RES-SOL EA JI J. Geophys. Res.-Solid Earth PD APR 10 PY 1994 VL 99 IS B4 BP 6981 EP 6996 DI 10.1029/93JB02976 PG 16 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA NF970 UT WOS:A1994NF97000017 ER PT J AU CRISP, J CASHMAN, KV BONINI, JA HOUGEN, SB PIERI, DC AF CRISP, J CASHMAN, KV BONINI, JA HOUGEN, SB PIERI, DC TI CRYSTALLIZATION HISTORY OF THE 1984 MAUNA-LOA LAVA FLOW SO JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH LA English DT Article ID MOUNT-ST-HELENS; CHEMICAL MASS-TRANSFER; SIZE DISTRIBUTION CSD; KILAUEA VOLCANO; MAGMATIC PROCESSES; IGNEOUS ROCKS; POLYMER MELTS; RHEOLOGY; VISCOSITY; SUSPENSIONS AB During a 3-week eruption in 1984, Mauna Loa produced vent lavas that increased in crystallinity from <1 to 30%, and 27-km-long flows that increased in crystallinity as they moved downstream. We examined the crystallization history of these lavas using crystal size distribution (CSD) analysis to study the rates of crystallization, viscosity increase, and latent heating. Typical average growth and nucleation rates were 5 x 10(-9) cm s-1 and 5 cm-3 s-1 for microphenocrysts (20- to 500-mum size crystals nucleated in the rift zone) and 5 x 10(-8) cm s-1 and 5 x 10(4) cm-3 s-1 for microlites (1- to 20-mum size crystals nucleated in the channel). These crystallization rates are high compared with those found in other CSD studies of igneous rocks, probably due to highly nonequilibrium conditions brought on by rapid degassing in the rift zone and cooling in the lava channel. Growth and nucleation rates decreased with time at the vent and with distance downstream. The maximum downstream total crystallinity measured is 39% (25% microlites, 14% microphenocrysts) in a quenched sample 14 km from the vent. Growth and nucleation rates cannot be calculated for postemplacement samples, but they place upper limits of 53-58% on the amount of crystallization in the channel 9-20 km from the vent. Crystallization could have been mostly responsible for the 10(5)-fold downstream increase in apparent viscosity, although degassing and increasing incorporation of solid lava fragments also contributed. Another effect of crystallization on the lava flow was the sizeable latent heating (0.01 J g-1 s-1 over the first half of the flow length, if the crystallinity of downstream quench samples is representative of the hot fluid core), which may have been counteracted by entrainment of cooler material. Measurements of crystallization are shown to be crucial in the study of lava flow emplacement dynamics. C1 UNIV ARIZONA, DEPT GEOSCI, TUCSON, AZ 85721 USA. UNIV OREGON, DEPT GEOL SCI, EUGENE, OR 97403 USA. YALE UNIV, NEW HAVEN, CT 06511 USA. RP CRISP, J (reprint author), JET PROP LAB, MAIL STOP 183-501, 4800 OAK GROVE DR, PASADENA, CA 91109 USA. RI Crisp, Joy/H-8287-2016 OI Crisp, Joy/0000-0002-3202-4416 NR 91 TC 78 Z9 79 U1 0 U2 11 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9313 EI 2169-9356 J9 J GEOPHYS RES-SOL EA JI J. Geophys. Res.-Solid Earth PD APR 10 PY 1994 VL 99 IS B4 BP 7177 EP 7198 DI 10.1029/93JB02973 PG 22 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA NF970 UT WOS:A1994NF97000028 ER PT J AU LEE, TJ AF LEE, TJ TI A COMPARATIVE COUPLED-CLUSTER STUDY OF THE XOCL AND XCLO (X=H, F, CL) ISOMERS - AN INVESTIGATION OF HYPERVALENT CHLORINE COMPOUNDS SO JOURNAL OF PHYSICAL CHEMISTRY LA English DT Article ID SPECTRA; MOLECULES; CL2O2 AB Singles and doubles coupled-cluster theory (CCSD) and the CCSD method that includes a perturbational estimate of the effects of connected triple excitations, CCSD(T), are used to investigate the structure, vibrational frequencies, dipole moments, and relative stabilities of the XOCl and XClO (X = H, F, and Cl) isomers. It is shown that there is a large degree of ionic character involved in the bonding of the simple hypervalent chlorine compounds and that as the electronegativity of the X moiety increases, so does the stability of the XClO species relative to the XOCl isomer. Accurate relative energies are obtained at the CCSD(T) level of theory utilizing large atomic natural orbital basis sets, and these show that HClO and ClClO are less stable than the respective HOCl and ClOCl isomers, but that FClO is actually more stable than the FOCl isomer, indicating that F-Cl hypervalent bonding is more pronounced than Cl-Cl hypervalent bonding. RP LEE, TJ (reprint author), NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. RI Lee, Timothy/K-2838-2012 NR 33 TC 46 Z9 46 U1 0 U2 1 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0022-3654 J9 J PHYS CHEM-US JI J. Phys. Chem. PD APR 7 PY 1994 VL 98 IS 14 BP 3697 EP 3700 DI 10.1021/j100065a026 PG 4 WC Chemistry, Physical SC Chemistry GA NF765 UT WOS:A1994NF76500026 ER PT J AU SAGAN, C OSTRO, SJ AF SAGAN, C OSTRO, SJ TI DANGERS OF ASTEROID DEFLECTION SO NATURE LA English DT Letter C1 JET PROP LAB, PASADENA, CA 91109 USA. RP SAGAN, C (reprint author), CORNELL UNIV, PLANETARY STUDIES LAB, ITHACA, NY 14853 USA. NR 5 TC 9 Z9 9 U1 3 U2 5 PU NATURE PUBLISHING GROUP PI LONDON PA MACMILLAN BUILDING, 4 CRINAN ST, LONDON N1 9XW, ENGLAND SN 0028-0836 J9 NATURE JI Nature PD APR 7 PY 1994 VL 368 IS 6471 BP 501 EP 501 DI 10.1038/368501a0 PG 1 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA NE335 UT WOS:A1994NE33500034 ER PT J AU CHEN, CT MARDER, SR CHENG, LT AF CHEN, CT MARDER, SR CHENG, LT TI SYNTHESES AND LINEAR AND NONLINEAR-OPTICAL PROPERTIES OF UNSYMMETRICAL SQUARAINES WITH EXTENDED CONJUGATION SO JOURNAL OF THE AMERICAN CHEMICAL SOCIETY LA English DT Note ID STILBENE DERIVATIVES; HYPERPOLARIZABILITIES; CHEMISTRY; DYES C1 CALTECH,CTR MOLEC MAT RESOURCE,PASADENA,CA 91125. CALTECH,JET PROP LAB,PASADENA,CA 91109. DUPONT CO INC,CENT RES & DEV,WILMINGTON,DE 19880. RI Chen, Chin-Ti/E-5341-2015 NR 17 TC 94 Z9 98 U1 1 U2 9 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0002-7863 J9 J AM CHEM SOC JI J. Am. Chem. Soc. PD APR 6 PY 1994 VL 116 IS 7 BP 3117 EP 3118 DI 10.1021/ja00086a049 PG 2 WC Chemistry, Multidisciplinary SC Chemistry GA NG378 UT WOS:A1994NG37800049 ER PT J AU GEDNEY, RT AF GEDNEY, RT TI NEW TECHNOLOGIES GET INTO THE ACTS SO AEROSPACE AMERICA LA English DT Article RP GEDNEY, RT (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, 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 APR PY 1994 VL 32 IS 4 BP 39 EP 43 PG 5 WC Engineering, Aerospace SC Engineering GA ND798 UT WOS:A1994ND79800011 ER PT J AU REDA, DC MURATURE, JJ HEINECK, JT AF REDA, DC MURATURE, JJ HEINECK, JT TI TIME AND FLOW-DIRECTION RESPONSES OF SHEAR-STRESS-SENSITIVE LIQUID-CRYSTAL COATINGS SO AIAA JOURNAL LA English DT Article ID VISUALIZATION AB Time and flow-direction responses of shear-stress-sensitive liquid crystal coatings were explored experimentally. For the time-response experiments, coatings were exposed to transient, compressible flows created during the startup and off-design operation of an injector-driven supersonic wind tunnel. Flow transients were visualized with a focusing schlieren system and recorded with a 1000 frame/s color video camera. Liquid crystal responses to these changing-shear environments were then recorded with the same video system, documenting flow-visualization response times equal to, or faster than, the time interval between sequential frames (i.e., 1 ms). For the flow-direction experiments, a planar test surface was exposed to equal-magnitude and known-direction surface shear stresses generated by both normal and tangential subsonic jet-impingement flows. Under shear, the sense of the angular displacement of the liquid crystal dispersed (reflected) spectrum was found to be a function of the instantaneous direction of the applied shear. This technique thus renders dynamic flow reversals or flow divergences visible over entire test surfaces at image recording rates up to 1 kHz. Extensions of the technique to visualize relatively small changes in surface shear stress direction appear feasible. C1 NASA,AMES RES CTR,INST MCAT,MOFFETT FIELD,CA 94035. NASA,AMES RES CTR,IMAGING TECHNOL BRANCH,MOFFETT FIELD,CA 94035. RP REDA, DC (reprint author), NASA,AMES RES CTR,FLUID MECH LAB BRANCH,MS-260-1,MOFFETT FIELD,CA 94035, USA. NR 22 TC 25 Z9 27 U1 0 U2 2 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0001-1452 J9 AIAA J JI AIAA J. PD APR PY 1994 VL 32 IS 4 BP 693 EP 700 DI 10.2514/3.12047 PG 8 WC Engineering, Aerospace SC Engineering GA NE724 UT WOS:A1994NE72400003 ER PT J AU LEE, Y SETTLES, GS HORSTMAN, CC AF LEE, Y SETTLES, GS HORSTMAN, CC TI HEAT-TRANSFER MEASUREMENTS AND COMPUTATIONS OF SWEPT-SHOCK-WAVE BOUNDARY-LAYER INTERACTIONS SO AIAA JOURNAL LA English DT Article ID SHARP-FIN; FLOWFIELD; MODEL; GAUGE AB An experimental and computational research program providing new knowledge of the heat transfer in swept-shock-wave/boundary-layer interactions is described. An equilibrium turbulent boundary layer on a flat plate is subjected to impingement by a swept planar shock wave generated by a sharp fin. Five different interactions with fin angles ranging from 10 to 20 deg at freestream Mach numbers of 3 and 4 produce a variety of interaction strengths ranging from weak to very strong. A foil heater generates a uniform heat flux over the flat plate surface, and miniature thin-film-resistance sensors are used to measure the local surface temperature. The heat convection equation is then solved for the heat transfer distribution within an interaction, yielding an uncertainty of about +/- 10%. These data are compared with numerical Navier-Stokes solutions that employ a k-epsilon turbulence model. A simple peak heat transfer correlation for fin interactions is suggested. C1 NASA,AMES RES CTR,GAS DYNAM LAB,MOFFETT FIELD,CA 94035. NASA,AMES RES CTR,EXPTL FLUID DYNAM BRANCH,MOFFETT FIELD,CA 94035. RP LEE, Y (reprint author), PENN STATE UNIV,DEPT MECH ENGN,UNIVERSITY PK,PA 16802, USA. NR 40 TC 7 Z9 8 U1 0 U2 2 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0001-1452 J9 AIAA J JI AIAA J. PD APR PY 1994 VL 32 IS 4 BP 726 EP 734 DI 10.2514/3.12045 PG 9 WC Engineering, Aerospace SC Engineering GA NE724 UT WOS:A1994NE72400007 ER PT J AU HUANG, PG BRADSHAW, P COAKLEY, TJ AF HUANG, PG BRADSHAW, P COAKLEY, TJ TI TURBULENCE MODELS FOR COMPRESSIBLE BOUNDARY-LAYERS SO AIAA JOURNAL LA English DT Article ID DILATATION-DISSIPATION AB It is shown that to satisfy the generally accepted compressible law of the wall derived from the Van Driest transformation, turbulence modeling coefficients must actually be functions of density gradients. The transformed velocity profiles obtained by using standard turbulence model constants have too small a value of the effective von Karman constant kappa in the log-law region (inner layer). Thus, if the model is otherwise accurate, the wake component is overpredicted and the predicted skin friction is lower than the expected value. The magnitude of the errors that result from neglecting this dependence on density depends on the variable used to specify the length scale. It will be shown that the k-omega model is less dependent on density gradient than the k-epsilon model, although it is not completely free from errors associated with density terms. We propose models designed to reduce the density-gradient effect to an insignificant level. To agree with experimental values for kappa in compressible boundary layers, the apparent eddy viscosity must be increased. This compressibility effect-which is an artifact of conventional turbulence modeling rather than something real-is exactly opposite to that in mixing layers. There the growth rate, and by implication the eddy viscosity, decreases with increasing Mach number: since the growth rate of low-speed mixing layers is not much affected by mean density differences across the layers, the Mach-number effect is a real compressibility effect. However, it first appears at turbulence Mach numbers above those found in nonhypersonic boundary layers. As a consequence, recent compressibility modifications proposed for the mixing layer are liable to increase the errors in predictions of flat-plate compressible boundary layer flows. C1 ELORET INST,PALO ALTO,CA 94303. STANFORD UNIV,DEPT MECH ENGN,STANFORD,CA 94305. RP HUANG, PG (reprint author), NASA,AMES RES CTR,MODELING & EXPL VALIDAT BRANCH,MS 229-1,MOFFETT FIELD,CA 94035, USA. NR 22 TC 38 Z9 41 U1 0 U2 2 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0001-1452 J9 AIAA J JI AIAA J. PD APR PY 1994 VL 32 IS 4 BP 735 EP 740 DI 10.2514/3.12046 PG 6 WC Engineering, Aerospace SC Engineering GA NE724 UT WOS:A1994NE72400008 ER PT J AU BROOKS, VL KEIL, LC AF BROOKS, VL KEIL, LC TI HEMORRHAGE DECREASES ARTERIAL-PRESSURE SOONER IN PREGNANT COMPARED WITH NONPREGNANT DOGS - ROLE OF BAROREFLEX SO AMERICAN JOURNAL OF PHYSIOLOGY LA English DT Article DE ANGIOTENSIN II; RENIN; ADRENOCORTICOTROPIC HORMONE; CORTISOL; BLOOD PRESSURE; SYMPATHETIC NERVOUS SYSTEM; HEART RATE ID RENIN-ANGIOTENSIN SYSTEM; RENAL NERVE ACTIVITY; CONSCIOUS DOGS; PLASMA VASOPRESSIN; DENERVATED DOGS; BLOOD-PRESSURE; RESPONSES; HYPOTENSION; BLOCKADE; RATS AB This study was performed to test the hypothesis that smaller reflex increases in vasopressin, cortisol, adrenocorticotropic hormone (ACTH), and angiotensin II (ANG II) concentrations are produced by hemorrhage in pregnant compared with nonpregnant conscious dogs. Equivalent hemorrhages (1% of the initial blood volume per minute) produced larger decreases in arterial pressure [P < 0.01; 107 +/- 6 to 73 +/- 10 mmHg (pregnant); 109 +/- 6 to 90 +/- 5 mmHg (nonpregnant)] but produced similar increases in plasma vasopressin concentration in the pregnant animals. As a result, the slope of the arterial pressure-to-vasopressin relationship was reduced (P < 0.05). During pregnancy, smaller increases in plasma cortisol concentration and heart rate were also produced for a given decrease in arterial pressure, but the relationship between pressure and ACTH was not significantly affected. In contrast, higher levels of plasma renin activity and plasma ANG II concentration were achieved in the pregnant dogs. In general, the relationships between plasma hormone levels and either left or right atrial pressure were not significantly altered. These results indicate that reflex increases in heart rate, vasopressin, and cortisol concentration are attenuated in pregnant dogs and that this attenuation may contribute to the inability of pregnant animals to achieve normal cardiovascular homeostasis during hemorrhage. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RP BROOKS, VL (reprint author), OREGON HLTH SCI UNIV,DEPT PHYSIOL,L-334,3181 SW SAM JACKSON PK RD,PORTLAND,OR 97201, USA. NR 58 TC 27 Z9 28 U1 0 U2 1 PU AMER PHYSIOLOGICAL SOC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 SN 0002-9513 J9 AM J PHYSIOL JI Am. J. Physiol. PD APR PY 1994 VL 266 IS 4 BP H1610 EP H1619 PN 2 PG 10 WC Physiology SC Physiology GA NJ996 UT WOS:A1994NJ99600044 ER PT J AU ENGELKE, KA SHEA, JD DOERR, DF CONVERTINO, VA AF ENGELKE, KA SHEA, JD DOERR, DF CONVERTINO, VA TI AUTONOMIC FUNCTIONS AND ORTHOSTATIC RESPONSES 24 H AFTER ACUTE INTENSE EXERCISE IN PARAPLEGIC SUBJECTS SO AMERICAN JOURNAL OF PHYSIOLOGY LA English DT Article DE BAROREFLEX; BLOOD PRESSURE; CARDIOVASCULAR REFLEX; HEAD-UP TILT; ORTHOSTATIC HYPOTENSION; PARAPLEGIA ID VAGAL BAROREFLEX; VALSALVA MANEUVER; BLOOD-PRESSURE; PLASMA-VOLUME; BED REST; REFLEX; HYPOTENSION; SENSITIVITY; TOLERANCE; HUMANS AB We tested the hypothesis that a bout of graded exercise designed to elicit maximal effort would increase the sensitivity of autonomically mediated baroreflexes and enhance blood pressure (BP) stability in subjects prone to postural hypotension. Therefore, we measured heart rate (HR), BP, forearm vascular resistance (FVR), and vasoactive hormone responses before and during 15 min of 70 degrees head-up tilt (HUT) in 10 paraplegic subjects (21-65 yr) on two occasions: 1) 24 h after maximal arm-crank exercise (postexercise) and 2) without exercise (control). During HUT, HR increased 30 beats/min in both postexercise and control, but the reduction in systolic BP (SBP) during control (-12.0 +/- 4.6 mmHg) was larger (P = 0.017) than that during HUT after exercise (-0.3 +/- 4.3 mmHg). The postexercise increase in FVR from supine to HUT of 17.0 +/- 2.4 to 24.8 +/- 3.2 peripheral resistance units (PRU) was greater (P = 0.042) than the increase observed during control (18.3 +/- 3.7 to 19.5 +/- 3.1 PRU). The gain of the carotid-cardiac baroreflex was also increased (P = 0.049) after exercise. Responses in norepinephrine, vasopressin, and plasma renin-angiotensin induced by HUT were similar for control and postexercise, and there was no difference in either leg compliance or plasma volume between the two conditions. Additionally, HR and SBP responses to phases II and IV of the Valsalva maneuver, indexes of integrated baroreflex sensitivity, were increased (P < 0.05) after maximal exercise compared with control. Thus acute intense exercise eliminated orthostatic hypotension in paraplegics, was associated with increased FVR and baroreflex sensitivity, and was independent of blood volume changes. C1 AL AOCIY,AEROSP CARDIOVASC RES LAB,BROOKS AFB,TX 78235. UNIV FLORIDA,DEPT PHYSIOL,GAINESVILLE,FL 32610. HUMAN HOSP LUCERNE,LUCERNE SPINAL CTR,ORLANDO,FL 32801. NASA,BIOMED OPERAT & RES OFF,KENNEDY SPACE CTR,FL 32899. NR 32 TC 31 Z9 31 U1 0 U2 1 PU AMER PHYSIOLOGICAL SOC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 SN 0002-9513 J9 AM J PHYSIOL JI Am. J. Physiol. PD APR PY 1994 VL 266 IS 4 BP R1189 EP R1196 PN 2 PG 8 WC Physiology SC Physiology GA NJ996 UT WOS:A1994NJ99600067 ER PT J AU NOOR, AK BURTON, WS PETERS, JM AF NOOR, AK BURTON, WS PETERS, JM TI HIERARCHICAL ADAPTIVE MODELING OF STRUCTURAL SANDWICHES AND MULTILAYERED COMPOSITE PANELS SO APPLIED NUMERICAL MATHEMATICS LA English DT Article; Proceedings Paper CT 3rd ARO Workshop on Adaptive Methods for Partial Differential Equations CY MAY 18-20, 1992 CL RENSSELAER POLYTECH INST, TROY, NY SP USA RES OFF HO RENSSELAER POLYTECH INST DE HIERARCHICAL MODELING; ADAPTIVITY; PREDICTOR CORRECTOR PROCEDURES; FINITE ELEMENTS; PLATES AND SHELLS; THERMAL BUCKLING; FREE VIBRATIONS; SANDWICH STRUCTURES; COMPOSITES ID SUPERCONVERGENT PATCH RECOVERY; PREDICTOR-CORRECTOR PROCEDURES; TRANSITION FINITE-ELEMENTS; SHEAR CORRECTION FACTORS; S-VERSION; PLATES; SHELLS; STRESS; LOAD AB Some recent advances in the hierarchical modeling strategies are reviewed with special emphasis on applications to multilayered composite panels. Discussion focuses on the key elements of hierarchical adaptive modeling; multimodel predictor-corrector modeling procedures; potential for solving large complex problems; and the needed development to realize this potential. Numerical studies are presented for free vibrations of thermally-stressed multilayered composite panels and structural sandwiches with composite face sheets demonstrating the effectiveness of the multimodel predictor-corrector modeling approaches. RP NOOR, AK (reprint author), UNIV VIRGINIA,NASA,LANGLEY RES CTR,CTR COMPUTAT STRUCT TECHNOL,HAMPTON,VA 23681, USA. NR 44 TC 6 Z9 6 U1 0 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-9274 J9 APPL NUMER MATH JI Appl. Numer. Math. PD APR PY 1994 VL 14 IS 1-3 BP 69 EP 90 DI 10.1016/0168-9274(94)90019-1 PG 22 WC Mathematics, Applied SC Mathematics GA NH534 UT WOS:A1994NH53400005 ER PT J AU BISWAS, R DEVINE, KD FLAHERTY, JE AF BISWAS, R DEVINE, KD FLAHERTY, JE TI PARALLEL, ADAPTIVE FINITE-ELEMENT METHODS FOR CONSERVATION-LAWS SO APPLIED NUMERICAL MATHEMATICS LA English DT Article; Proceedings Paper CT 3rd ARO Workshop on Adaptive Methods for Partial Differential Equations CY MAY 18-20, 1992 CL RENSSELAER POLYTECH INST, TROY, NY SP USA RES OFF HO RENSSELAER POLYTECH INST ID COMPUTATIONAL FLUID-DYNAMICS; ADVECTIVE-DIFFUSIVE SYSTEMS; PARABOLIC-SYSTEMS; FORMULATION; SCHEMES; EQUATIONS; OPERATOR AB We construct parallel finite element methods for the solution of hyperbolic conservation laws in one and two dimensions. Spatial discretization is performed by a discontinuous Galerkin finite element method using a basis of piecewise Legendre polynomials. Temporal discretization utilizes a Runge-Kutta method. Dissipative fluxes and projection limiting prevent oscillations near solution discontinuities. A posteriori estimates of spatial errors are obtained by a p-refinement technique using superconvergence at Radau points. The resulting method is of high order and may be parallelized efficiently on MIMD computers. We compare results using different limiting schemes and demonstrate parallel efficiency through computations on an NCUBE/2 hypercube. We also present results using adaptive h- and p-refinement to reduce the computational cost of the method. C1 RENSSELAER POLYTECH INST,DEPT COMP SCI,TROY,NY 12180. NASA,AMES RES CTR,RIACS,MOFFETT FIELD,CA 94035. NR 27 TC 222 Z9 233 U1 1 U2 7 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-9274 J9 APPL NUMER MATH JI Appl. Numer. Math. PD APR PY 1994 VL 14 IS 1-3 BP 255 EP 283 DI 10.1016/0168-9274(94)90029-9 PG 29 WC Mathematics, Applied SC Mathematics GA NH534 UT WOS:A1994NH53400015 ER PT J AU RAMAKRISHNAN, R AF RAMAKRISHNAN, R TI STRUCTURED AND UNSTRUCTURED GRID ADAPTATION SCHEMES FOR NUMERICAL MODELING OF FIELD PROBLEMS SO APPLIED NUMERICAL MATHEMATICS LA English DT Article; Proceedings Paper CT 3rd ARO Workshop on Adaptive Methods for Partial Differential Equations CY MAY 18-20, 1992 CL RENSSELAER POLYTECH INST, TROY, NY SP USA RES OFF HO RENSSELAER POLYTECH INST AB The use of grid adaptation procedures for compressible flows and heat transfer is presented in this paper. Grid adaptation schemes are presented for structured and unstructured grids in the context of finite-difference and finite-element methods. For compressible flow problems with regular domains, the use of finite-difference methods has proven to be quite effective. For such analyses, a dynamic grid adaptation scheme is employed with a MacCormack predictor-corrector scheme to describe compressible flow features. The adaptation procedure uses a grid relocation stencil that is valid at both the interior and boundary points of the finite-difference grid. Linear combinations of spatial derivatives of specific flow variables, calculated with finite-element interpolation functions, are used as adaptation measures. The impact of the grid relocation procedure is demonstrated by simulating the effects of shock impingement on a three-dimensional unsymmetric axial corner. When the domain to be modeled is quite complex, unstructured finite-element or finite-volume formulations are preferred. An unstructured mesh adaptation scheme with refinement and coarsening based on refinement indicators is used to describe inviscid and viscous flow features. This adaptation scheme uses quadrilateral and triangular elements to add grid density to regions of high gradients and remove elements where these gradients are low. Modifications of the mesh adaptation procedure enables its utilization in the analyses of heat transfer problems commonly associated with hypervelocity flows. The strategies used for mesh adaptation, computing refinement indicators, and time marching are described. The effectiveness of this procedure is reflected in good solution accuracy, reduction in the number of elements used, and computational efficiency. RP RAMAKRISHNAN, R (reprint author), NASA,LANGLEY RES CTR,ANALYT SERV & MAT INC,MS 159,HAMPTON,VA 23665, USA. NR 16 TC 5 Z9 5 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-9274 J9 APPL NUMER MATH JI Appl. Numer. Math. PD APR PY 1994 VL 14 IS 1-3 BP 285 EP 310 DI 10.1016/0168-9274(94)90030-2 PG 26 WC Mathematics, Applied SC Mathematics GA NH534 UT WOS:A1994NH53400016 ER PT J AU MAZZARELLA, JM VOIT, GM SOIFER, BT MATTHEWS, K GRAHAM, JR ARMUS, L SHUPE, D AF MAZZARELLA, JM VOIT, GM SOIFER, BT MATTHEWS, K GRAHAM, JR ARMUS, L SHUPE, D TI NEAR-INFRARED CONTINUUM AND 3.3-MU-M POLYCYCLIC AROMATIC HYDROCARBON IMAGING OF THE STARBURST RING IN THE TYPE-1 SEYFERT-GALAXY NGC-7469 SO ASTRONOMICAL JOURNAL LA English DT Article ID ACTIVE GALACTIC NUCLEI; STAR FORMATION; MOLECULAR GAS; EMISSION; NGC-1068; DUST; BAR; SPECTROPHOTOMETRY; EXTINCTION; MORPHOLOGY AB High resolution near-infrared images of the type 1 Seyfert galaxy NGC 7469 have been obtained to probe its dusty nuclear environment. Direct J, H, and K images are relatively featureless, but residual images created by subtracting a smooth model based on best-fitting elliptical isophotes reveal a tight inner spiral whose high surface-brightness portions correspond to a previously detected 3'' (1 kpc) diameter ring of radio continuum emission. The inner infrared spiral arms extended almost-equal-to 4'' NW and SE from the nucleus, and the NW arm joins up with large-scale spiral structure visible in the R band. The residual images also show a bar-like structure aligned with the brightest infrared/radio hotspots at PA almost-equal-to 50-degrees. Three infrared hotspots are detected which align remarkably well with 6 cm radio continuum sources. The near-infrared ring and the hotspots are visible in the residual images, and in a high-resolution direct K-band image restored to an effective resolution of 0.65'' FWHM using the Richardson-Lucy algorithm. The infrared hotspots have luminosities of nuL(nu)(2.2 mum) almost-equal-to 10(8) L. (M(K) almost-equal-to -16 mag), suggesting they are either giant H II regions or individual supernovae. The two brightest regions may be associated with enhanced star formation triggered by orbit crowding of gas where spiral arms emerge from an inner bar. Narrowband (DELTAlambda/lambda approximately 1.5%) imaging in the 3.28 mum dust emission feature and surrounding continuum confirms the 3'' diameter 3.28 mum emission region detected previously using multiaperture photometry. The extended polycyclic aromatic hydrocarbon (PAH) emission is slightly elongated and aligned with published [O III] line emission and 12.5 mum continuum emission, apparently tracing the starburst. The presence of almost-equal-to 25% of the total 3.28 mum PAH emission within R<1'' demonstrates that a starburst within the central few hundred parsecs must supply a significant fraction of the infrared continuum from the nucleus, and there is apparently sufficient shielding material between the starburst and the AGN to preserve the PAHs along our line of sight to the nucleus. C1 JOHNS HOPKINS UNIV,DEPT PHYS & ASTRON,BALTIMORE,MD 21218. CALTECH,PALOMAR OBSERV,PASADENA,CA 91125. UNIV CALIF BERKELEY,DEPT ASTRON,BERKELEY,CA 94720. RP MAZZARELLA, JM (reprint author), CALTECH,JET PROP LAB,CTR INFRARED PROC & ANAL,MS 100-22,PASADENA,CA 91125, USA. NR 44 TC 32 Z9 32 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 APR PY 1994 VL 107 IS 4 BP 1274 EP 1282 DI 10.1086/116939 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NC565 UT WOS:A1994NC56500006 ER PT J AU DEMARTINO, D BUCKLEY, DAH MOUCHET, M MUKAI, K AF DEMARTINO, D BUCKLEY, DAH MOUCHET, M MUKAI, K TI ON THE MODULATED LIGHT IN THE INTERMEDIATE POLAR FO-AQUARII H-2215-086 SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE STARS, CATACLYSMIC VARIABLES; STARS, INDIVIDUAL FO-AQR (H-2215-086); X-RAYS, BINARIES ID X-RAY OBSERVATIONS; DQ HERCULIS STARS; ACCRETION DISKS; CATACLYSMIC VARIABLES; SPECTROSCOPIC OBSERVATIONS; OPTICAL OBSERVATIONS; AQR H2215-086; SIMULATIONS; PHOTOMETRY; ORIGIN AB The modulated light in the Intermediate Polar FO Aqr at the three periods P(spin) = 20.9min, P(orb) = 4.85hr and P(beat) = 22.5min is studied in different spectral ranges to derive information on their nature. In this system the accretion geometry, with or without an accretion disc, is still a matter of debate (Hellier 1991; Norton et al. 1992). The different orbital behaviour of phase coherence between the spin and beat pulses in the X-rays (Norton et al. 1992) and in the optical/IR regions cannot be easily accounted for by only a discless dominated geometry where the accretion flow is switching from one pole to the other each half of the beat period. We therefore propose an accretion scenario where a non-axisymmetric disc is present. In such a non-standard accretion disc an azimuthal structure provides not only the source of variable mass transfer to the white dwarf, but also a reprocessing site which is mainly viewing the X-ray emission from the lower pole. Our spectral analysis shows that reprocessing is also occurring at the surface of the secondary star. The spin pulsation in the optical and IR continua can be explained by the so-called ''accretion curtain'' model (Rosen et al. 1988) though an additional reprocessing component at the spin period cannot be excluded. In contrast to the X-rays, the beat optical/IR modulation is not intrinsic. Reprocessing at the surface of the secondary star and at the thickened part of the disc can also account for the orbital modulation in the UV, optical and IR regions. C1 UNIV CAPE TOWN, DEPT ASTRON, RONDEBOSCH 7700, SOUTH AFRICA. OBSERV PARIS, DAEC, SECT MEUDON, F-92195 MEUDON, FRANCE. S AFRICAN ASTRON OBSERV, CAPE TOWN 7935, SOUTH AFRICA. UNIV DENIS DIDEROT, F-75005 PARIS, FRANCE. NASA, GODDARD SPACE FLIGHT CTR, GSFC, HIGH ENERGY ASTROPHYS LAB, GREENBELT, MD 20771 USA. RP DEMARTINO, D (reprint author), ESA, IUE OBSERV, POB 50727, E-28080 MADRID, SPAIN. NR 42 TC 17 Z9 17 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD APR PY 1994 VL 284 IS 1 BP 125 EP 137 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ND829 UT WOS:A1994ND82900021 ER PT J AU JENNISKENS, P AF JENNISKENS, P TI VERY BROAD-BAND STRUCTURE AND THE LINEAR RISE IN THE EXTINCTION CURVE SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE DUST, EXTINCTION; ULTRAVIOLET, INTERSTELLAR ID INTERSTELLAR EXTINCTION; ULTRAVIOLET EXTINCTION; EMISSION; NEBULA; POLARIZATION; SHAPES; GRAINS AB Measurements of the very broadband structure in the visual part of the extinction curve are compared to IUE extinction curve parameters in the scheme of Fitzpatrick and Massa. The correlation of VBS depth with FUV rise found by Reimann & Friedemann (1991) is shown to be a correlation with linear rise and not with far UV non-linear rise. The correlation with linear rise suggests that the VBS is due to an onset of extinction at about 1.8 mum-1, rather than what has previously been suggested: due to luminescence or the presence of two extinction components longward and shortward of the VBS. The optical properties inferred for the linear rise carrier are consistent with some amorphous solid with a large optical gap. Small carbonaceous grains may be the carrier of the linear rise in extinction, because the erosion of core-mantle particles is expected to produce many of such small grains and offers a natural mechanism for the existence of the inferred two populations of big (a approximately 0.13 mum) and small (a approximately 0.005 mum) grains. C1 STERREWACHT LEIDEN, 2300 RA LEIDEN, NETHERLANDS. RP JENNISKENS, P (reprint author), NASA, AMES RES CTR, MAIL STOP 239-4, MOFFETT FIELD, CA 94035 USA. NR 43 TC 7 Z9 7 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD APR PY 1994 VL 284 IS 1 BP 227 EP 232 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ND829 UT WOS:A1994ND82900031 ER PT J AU WALTER, HG MA, C AF WALTER, HG MA, C TI CORRECTION TO THE LUNI-SOLAR PRECESSION FROM VERY LONG-BASE-LINE INTERFEROMETRY SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE METHODS, ANALYTICAL; CATALOGS; REFERENCE SYSTEMS ID FORCED NUTATIONS; EARTH; CONSTANTS AB The redetermination of the luni-solar precession is performed by using VLBI catalogues of extragalactic radio sources containing positions at observation epochs which cover 9 years. The positions of the sources have been determined by the VLBI network of the Crustal Dynamics Project of NASA from measurements covering consecutive half year and one year intervals between 1981 and 1989. In the course of their reduction the IAU recommended precession terms were applied. On the assumption of an imperfection of the luni-solar precession it is expected that the positions of each source obtained at different epochs but uniformly reduced to the reference system J2000.0 exhibit an apparent proper motion. - We attributed this motion tentatively to precession and solved for a correction of the luni-solar precession by making a least squares fit to the position differences between homonymous sources in the set of catalogues. The 18.6 yr terms of nutation entered the process as parameters the values of which were set by choice from the reservoir of recent determinations. Twenty-five sources contributed to the analysis with the effect that the annual and semi-annual catalogues contain 16 sources on the average. The analysis confirmed the slightly overestimated IAU value of the luni-solar precession yielding a mean correction of -3.59 +/- 1.14 mas yr-1 from the annual and -3.84 +/- 1.16 mas yr-1 from the semi-annual catalogues. We discuss these secular terms and their dependence on the adopted nutation terms. C1 NASA, GODDARD SPACE FLIGHT CTR, GEODYNAM BRANCH, GREENBELT, MD 20771 USA. RP WALTER, HG (reprint author), ASTRON RECH INST, MONCHHOFSTR 12-14, D-69120 HEIDELBERG, GERMANY. RI Ma, Chopo/D-4751-2012 NR 18 TC 12 Z9 12 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD APR PY 1994 VL 284 IS 3 BP 1000 EP 1006 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NJ385 UT WOS:A1994NJ38500027 ER PT J AU RAMANAMURTHY, PV AF RAMANAMURTHY, PV TI MULTIWAVELENGTH INTRA-PEAK PHASE SEPARATIONS IN PULSED EMISSIONS FROM THE CRAB AND THE VELA PULSARS SO ASTRONOMY & ASTROPHYSICS LA English DT Letter DE PULSARS, (CRAB AND VELA); PULSED EMISSION; LIGHT CURVES AB The Crab and the Vela pulsars were observed to emit pulsed radiation in the radio, optical, X-ray and gamma ray windows of the electromagnetic spectrum. In all cases the emission appears in two peaks, except in the case of radio emission from the Vela pulsar which is single peaked. With accurate peak position determinations made possible by recent observations, it is interesting to see if the intra-peak separations at various wavelengths across the electromagnetic spectrum bear any relation to each other. We report here an emerging trend of a monotonic decrease of the intra-peak separation with energy. The rate of decrease is faster in the case of the Vela pulsar than in that of the Crab pulsar. Even the case of single peaked radio emission by the Vela pulsar can be viewed as being consistent with this trend. These trends provide both an opportunity and a challenge to realistic modellings of pulsed emissions by these objects. RP RAMANAMURTHY, PV (reprint author), NASA, GODDARD SPACE FLIGHT CTR, CODE 662, GREENBELT, MD 20771 USA. NR 21 TC 8 Z9 8 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD APR PY 1994 VL 284 IS 1 BP L13 EP L15 PG 3 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ND829 UT WOS:A1994ND82900005 ER PT J AU THE, PS DEWINTER, D PEREZ, MR AF THE, PS DEWINTER, D PEREZ, MR TI A NEW CATALOG OF MEMBERS AND CANDIDATE MEMBERS OF THE HERBIG AE/BE (HAEBE) STELLAR GROUP SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article DE CATALOGS; STARS, BE; STARS, FORMATION; STARS, PRE-MAIN-SEQUENCE; INFRARED, STARS ID INTERMEDIATE-MASS STARS; ORION POPULATION STARS; MAIN-SEQUENCE STARS; EMISSION-LINE STARS; T-TAURI STARS; BE-TYPE STARS; AE-TYPE; POLARIZATION CHARACTERISTICS; INFRARED-EMISSION; MAGELLANIC CLOUDS AB A new up-to-date catalogue of Herbig Ae/Be (HAEBE) stars and related objects is certainly needed, for both well-seasoned researchers and, in particular, for new investigators starting to study the many interesting astrophysical properties of these very young objects. We present a brief discussion of the current observational characteristics that distinguish this class from their main sequence counterparts. The HAEBE and related stars are listed in five tables, containing 287 objects. Table 1 contains all Ae and Be stars which historically are recognized as true HAEBE stars or potential candidate members. Table 2 gives the stars of spectral type Fe, and emission line stars with very uncertain or unknown spectral type. In Table 3 are given all known Extreme Emission Line Objects (EELOs), of which most have not been identified to belong to any specific group. Table 4a and b list other Bep or B[e] stars with strong IR-excess and unknown spectral type. Table 5 contains the non-emission line possible young objects. Furthermore, Table 6 contains 35 stars rejected from former published lists of HAEBE stars. In these tables we are including coordinates, spectral types, visual magnitudes, ranges in photometric variability and references of several key publications related to each object. Relevant remarks, such as the presence of a nebula in the vicinity of an object, are also given. C1 NASA, GODDARD SPACE FLIGHT CTR, GSFC, IUE OBSERV, CSC, GREENBELT, MD 20771 USA. RP THE, PS (reprint author), UNIV AMSTERDAM, ASTRON INST ANTON PANNEKOEK, KRUISLAAN 403, 1098 SJ AMSTERDAM, NETHERLANDS. NR 80 TC 366 Z9 368 U1 0 U2 6 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 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD APR PY 1994 VL 104 IS 2 BP 315 EP 339 PG 25 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NF249 UT WOS:A1994NF24900005 ER PT J AU BERSANELLI, M BENSADOUN, M DEAMICI, G LEVIN, S LIMON, M SMOOT, GF VINJE, W AF BERSANELLI, M BENSADOUN, M DEAMICI, G LEVIN, S LIMON, M SMOOT, GF VINJE, W TI ABSOLUTE MEASUREMENT OF THE COSMIC MICROWAVE BACKGROUND AT 2 GHZ SO ASTROPHYSICAL JOURNAL LA English DT Article DE COSMIC MICROWAVE BACKGROUND; RADIO CONTINUUM, GENERAL ID 12 CENTIMETER WAVELENGTH; RADIATION TEMPERATURE; PRECISE MEASUREMENT; 1.32 MILLIMETERS; 7.5 GHZ; SPECTRUM; UNIVERSE; CN; FREQUENCY; DISTORTIONS AB We measured the intensity of the cosmic microwave background (CMB), radiation at a frequency of 2.0 GHz (15 cm wavelength) with a ground-based total-power radio-frequency (RF) gain radiometer calibrated at the antenna aperture with a quasi-free space cold load. The observations were performed from a remote, high-altitude site near the Amundsen-Scott South Pole Station to minimize systematic effects. The measured thermodynamic temperature of the CMB is T(CMB) = 2.55 +/- 0.14 K (68% confidence level), the limiting factors in the accuracy being the subtraction of the atmospheric and Galactic contributions. The atmospheric emission was evaluated both by direct measurements and by extrapolation from our higher frequency data. The Galactic emission was determined by scaling low-frequency maps and was checked with differential drift scans. Our result is approximately 1 sigma lower than the recent accurate value of T(CMB) obtained by COBE-FIRAS above 60 GHz. The temperature of the sky (i.e., CMB plus Galaxy and extragalactic sources) at the south celestial pole with approximately 22-degrees resolution is T(A,Sky) = 2.83 +/- 0.10 K, and its accuracy is limited by the subtraction of atmospheric emission. C1 JET PROP LAB, PASADENA, CA 91109 USA. UNIV CALIF BERKELEY, SPACE SCI LAB, BERKELEY, CA 94720 USA. LAWRENCE BERKELEY LAB, BERKELEY, CA 94720 USA. RP BERSANELLI, M (reprint author), CNR, IST FIS COSM, VIA BASSINI 15, I-20133 MILAN, ITALY. NR 45 TC 33 Z9 33 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD APR 1 PY 1994 VL 424 IS 2 BP 517 EP 529 DI 10.1086/173910 PN 1 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NC793 UT WOS:A1994NC79300001 ER PT J AU NORRIS, JP NEMIROFF, RJ SCARGLE, JD KOUVELIOTOU, C FISHMAN, GJ MEEGAN, CA PACIESAS, WS BONNELL, JT AF NORRIS, JP NEMIROFF, RJ SCARGLE, JD KOUVELIOTOU, C FISHMAN, GJ MEEGAN, CA PACIESAS, WS BONNELL, JT TI DETECTION OF SIGNATURE CONSISTENT WITH COSMOLOGICAL TIME DILATION IN GAMMA-RAY BURSTS SO ASTROPHYSICAL JOURNAL LA English DT Article DE COSMOLOGY, THEORY; GAMMA-RAYS, BURSTS AB If gamma-ray bursters are at cosmological distances-as suggested by their isotropic distribution on the sky and by their number-intensity relation-then the burst profiles will be stretched in time, by an amount proportional to the redshift, 1 + Z. We have tested data from the Compton Gamma Ray Observatory's Burst and Transient Source Experiment (BATSE) for such time dilation. Out of 590 bursts observed by BATSE, 131 bursts were analyzed; bursts with durations shorter than 1.5 s were excluded. We used three tests to compare the timescales of bright and dim bursts, the latter, on average, being more distant than the former. Our measures of timescale are constructed to avoid selection effects arising from intensity differences by rescaling all bursts to fiducial levels of peak intensity and noise bias. (1) We found that the total rescaled count above background for the dim burst ensemble is approximately twice that for the brightest bursts-translating into longer durations for the dim bursts. (2) Wavelet-transform decompositions of the burst profiles confirmed at this dilation operates over a broad range of timescales. (3) Structure on the shortest timescales was examined using a procedure which aligns the highest peaks of profiles from which the noise has been optimally removed using a wavelet threshold technique. In all three tests, the dim bursts are stretched by a factor of approximately 2 relative to the bright ones, over seven octaves of timescale. We calibrated the measurements by dilating synthetic bursts that approximate the temporal characteristics of bright BATSE bursts. Results are consistent with bursts at BATSE's peak-flux completeness limit being at cosmological distances corresponding to Z approximately 1, and thus with independent cosmological interpretations of the BATSE number-intensity relation. Alternative explanations of our results, arising from the nature of physical processes in bursts, are still possible. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. UNIV SPACE RES ASSOC,COLUMBIA,MD. COMP SCI CORP,SILVER SPRING,MD 20910. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. UNIV ALABAMA,HUNTSVILLE,AL 35899. RP NORRIS, JP (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. NR 17 TC 141 Z9 143 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 1 PY 1994 VL 424 IS 2 BP 540 EP 545 DI 10.1086/173912 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NC793 UT WOS:A1994NC79300003 ER PT J AU CHOKSHI, A LONSDALE, CJ MAZZEI, P DEZOTTI, G AF CHOKSHI, A LONSDALE, CJ MAZZEI, P DEZOTTI, G TI SIMULATIONS OF DEEP GALAXY FIELDS .1. MONTE-CARLO SIMULATIONS OF OPTICAL AND NEAR-INFRARED COUNTS SO ASTROPHYSICAL JOURNAL LA English DT Article DE GALAXIES, CLUSTERING; GALAXIES, EVOLUTION; GALAXIES, FUNDAMENTAL PARAMETERS; GALAXIES, PHOTOMETRY; INFRARED, GALAXIES ID HIGH-REDSHIFT GALAXIES; LUMINOSITY FUNCTION; ELLIPTICAL GALAXIES; SPIRAL GALAXIES; FAINT GALAXIES; NUMBER COUNTS; EVOLUTION; SAMPLE; MODEL; EMISSION AB Monte Carlo simulations of three-dimensional galaxy distributions are performed, following the 1988 prescription of Chokshi & Wright, to study the photometric properties of evolving galaxy populations in the optical and near-infrared bands to high redshifts. Galaxies are spatially distributed according to the spatial two-point correlation function in a range of cluster to field environments and in volume elements appropriate to the cosmological model under consideration. Details of individual galaxy properties, including luminosities, morphologies, disk-to-bulge ratios, and size distributions are simulated to match local observed galaxy properties. Galaxies have evolving gas fraction, metallicity, and spectral energy distributions that include both stellar emission and internal dust absorption and reemission. The simulations result in noiseless two-dimensional galaxy distributions on the sky that can be compared to the observed deep images in the blue and near-infrared bands. In this paper, the first of a series, we present our baseline model in which galaxy numbers are conserved, and in which no explicit ''starburst'' population is included. We use the model in an attempt to simultaneously fit published blue and near-infrared photometric and spectroscopic observations of deep fields. We find that our baseline models, with a formation redshift, z(f), of 1000, and H-0 = 50, are able to reproduce the observed blue counts to b(j) = 22, independent of the value of OMEGA0, and also to provide a satisfactory fit to the observed blue-band redshift distributions, but for no value of OMEGA0 do we achieve an acceptable fit to the fainter blue counts. In the K band, we fit the number counts to the limit of the present-day surveys only for an OMEGA0 = 0 cosmology. We investigate the effect on the model fits of varying the cosmological parameters H-0, the formation redshift z(f), and the local luminosity function. Changing H-0 does not improve the fits to the observations. However, reducing the epoch of galaxy formation used in our simulations has a substantial effect. In particular, a model with z(f) congruent-to 5 in a low OMEGA0 universe improves the fit to the faintest photometric blue data without any need to invoke a new population of galaxies, substantial merging, or a significant starburst galaxy population. For an OMEGA0 = 1 universe, however, reducing z(f) is less successful at fitting the blue-band counts and has little effect at all at K. Varying the parameters of the local luminosity function can also have a significant effect. In particular the steep low end slope of the local luminosity function of Franceschini et al. allows an acceptable fit to the b(j) less-than-or-equal-to 25 counts for OMEGA0 = 1, but is incompatible with OMEGA0 = 0. C1 JET PROP LAB,PASADENA,CA 91109. OSSERV ASTRON PADOVA,I-35122 PADUA,ITALY. RP CHOKSHI, A (reprint author), CALTECH,CTR INFRARED PROC & ANAL,770 S WILSON DR,PASADENA,CA 91125, USA. OI Mazzei, Paola/0000-0002-8004-1034 NR 70 TC 4 Z9 4 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 1 PY 1994 VL 424 IS 2 BP 578 EP & DI 10.1086/173916 PN 1 PG 0 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NC793 UT WOS:A1994NC79300007 ER PT J AU FEDERMAN, SR STROM, CJ LAMBERT, DL CARDELLI, JA SMITH, VV JOSEPH, CL AF FEDERMAN, SR STROM, CJ LAMBERT, DL CARDELLI, JA SMITH, VV JOSEPH, CL TI CHEMICAL-TRANSITIONS FOR INTERSTELLAR C2 AND CN IN-CLOUD ENVELOPES SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM, CLOUDS; ISM, MOLECULES; MOLECULAR PROCESSES ID INTER-STELLAR CLOUDS; LATITUDE MOLECULAR CLOUD; ABSORPTION-LINE OBSERVATIONS; FAR-ULTRAVIOLET EXTINCTION; SCORPIUS OB1 ASSOCIATION; WARM NEUTRAL HALOS; RHO-OPHIUCHI CLOUD; TAURUS DARK CLOUD; ZETA-OPHIUCHI; DIFFUSE CLOUDS AB Observations were made of absorption from CH, C2, and CN toward moderately reddened stars in Sco OB2, Cep OB3, and Taurus/Auriga. For these directions, most of the reddening is associated with a single cloud complex, for example, the rho Ophiuchus molecular cloud, and as a result, the observations probe moderately dense material. When combined with available data for nearby directions, the survey provides the basis for a comprehensive analysis of the chemistry for these species. The chemical transitions affecting C2 and CN in cloud envelopes were analyzed. The depth into a cloud at which a transition takes place was characterized by tau(uv), the grain optical depth at 1000 angstrom. One transition at tau(uv) approximately 2, which arises from the conversion of C+ into CO, affects the chemistries for both molecules because of the key role this ion plays. A second one involving production terms in the CN chemistry occurs at tau(uv) of approximately 3; production via ion-molecule reactions with NH dominates at lower optical depths, while that via neutral-neutral reactions which C2 and CH is more important at larger values for tau(uv). The transition from photo-dissociation to chemical destruction takes place at tau(uv) approximately 4.5 for C2 and CN. The observational data for stars in Sco OB2, Cep OB3, and Taurus/Auriga were studied with chemical rate equations containing the most important production and destruction mechanisms. Because the sample of stars in Sco OB2 includes sight lines with A(v) ranging from 1-4 mag, sight lines dominated by photochemistry could be analyzed separately from those controlled by gas-phase destruction. The analysis yielded values for two poorly known rate constants for reactions involved in the production of CN; the reactions are C2 + N --> CN + C and C+ + NH --> all products. The other directions were analyzed with the inferred values. The predicted column densities for C2 and CN agree with the observed values to better than 50%, and in most instances 20%. When combining the estimates for density and temperature derived from chemical modeling and molecular excitation for a specific cloud, such as the rho Ophiuchus molecular cloud, the portion of the cloud envelope probed by C2 and CN absorption was found to be in pressure equilibrium. C1 UNIV WISCONSIN,DEPT ASTRON,MADISON,WI 53706. PRINCETON UNIV,DEPT ASTROPHYS SCI,PRINCETON,NJ 08544. JET PROP LAB,PASADENA,CA 91109. UNIV TEXAS,MCDONALD OBSERV,AUSTIN,TX 78712. UNIV TEXAS,DEPT ASTRON,AUSTIN,TX 78712. RP FEDERMAN, SR (reprint author), UNIV TOLEDO,DEPT PHYS & ASTRON,TOLEDO,OH 43606, USA. NR 136 TC 116 Z9 116 U1 0 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 1 PY 1994 VL 424 IS 2 BP 772 EP 792 DI 10.1086/173930 PN 1 PG 21 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NC793 UT WOS:A1994NC79300021 ER PT J AU JARRETT, TH DICKMAN, RL HERBST, W AF JARRETT, TH DICKMAN, RL HERBST, W TI AN OPTICAL STUDY OF THE FAINT END OF THE STELLAR LUMINOSITY FUNCTION SO ASTROPHYSICAL JOURNAL LA English DT Article DE STARS, LOW-MASS, BROWN DWARFS; STARS, LUMINOSITY FUNCTION, MASS FUNCTION ID OPHIUCHI DARK CLOUD; LOW-MASS STARS; M-DWARFS; VRI PHOTOMETRY; SYSTEMS; COUSINS; COMPLEX; EXTINCTIONS; MODELS; COUNTS AB We implement a new method by which to study the faint end of the field star luminosity function. The method relies on deep, multicolor photometry of fields projected against highly obscured, nearby molecular clouds. The clouds act as nearly opaque screens and delimit a well-defined survey volume which is in principle free of the problem of distinguishing nearby, intrinsically faint dwarf stars from more distant red giants. This study is based upon deep photographic and CCD photometry at optical (V, R, I) bandpasses toward the most highly obscured portions of the Taurus and Ophiuchus molecular clouds. The total volume delimited by the clouds is approximately 200 pc3. Within this region our survey is complete for all stars brighter than M(V) = 16-17 mag; at R and I, the survey is complete down to the lowest mass stars capable of sustaining core hydrogen burning, Color-color criteria are used to distinguish between background, highly reddened stars and stars located in front of the clouds, and the method of photometric parallax is used to deduce the absolute magnitudes and spectral types of those stars found to lie in front of the clouds. To help further resolve foreground/background ambiguities, we have made proper motion measurements of the candidate foreground stars using the photographic and CCD data, and the Palomar Sky Survey. We estimate the faint end of the field star luminosity function for the composite Taurus and Ophiuchus foreground sample and find that it resembles the local luminosity function down to M(V) approximately 16. At still fainter magnitudes we find more stars than do photometric parallax studies of the polar regions. This difference widens dramatically if even the simplest correction for incompleteness is applied to our data. We therefore tentatively conclude that the luminosity function rises beyond M(V) approximately 16; even if we discard our attempts to correct for incompleteness in the faintest magnitude bins, the luminosity function at least remains flat for the lowest mass stars. Our provisional finding that the luminosity function rises again beyond its well-known peak at M(V) approximately 12-13, implies that the IMF probably rises beyond the turnover point associated with this peak. Even if our most conservative estimate for the faint end of the luminosity function is used-in which no corrections are made for incompleteness-the IMF must at least remain flat down to the edge of the hydrogen-burning main sequence. C1 JET PROP LAB,CTR INFRARED PROC & ANAL,PASADENA,CA 91109. WESLEYAN UNIV,VAN VLECK OBSERV,MIDDLETOWN,CT 06457. NATL SCI FDN,DIV ASTRON SCI,WASHINGTON,DC 20550. RP JARRETT, TH (reprint author), UNIV MASSACHUSETTS,DEPT PHYS & ASTRON,AMHERST,MA 01003, USA. NR 64 TC 30 Z9 30 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 1 PY 1994 VL 424 IS 2 BP 852 EP 869 DI 10.1086/173936 PN 1 PG 18 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NC793 UT WOS:A1994NC79300027 ER PT J AU JUNG, YD AF JUNG, YD TI ONE-PHOTON ANNIHILATION OF THERMAL POSITRONS WITH BOUND ATOMIC ELECTRONS SO ASTROPHYSICAL JOURNAL LA English DT Article DE ATOMIC PROCESS; GAMMA RAYS, BURSTS AB Direct one-photon annihilation rate of positrons with a bound atomic electron is evaluated in the nonrelativistic limit. The K- and L-shell contributions are estimated including the screening and effective Coulomb repulsion effects. The annihilation rate of thermal positrons is calculated for various temperatures. The total number of one-photon annihilation events in the interstellar medium is discussed. These results provide the directional and structural information for cosmic gamma-ray sources. C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,SPACE SCI LAB,HUNTSVILLE,AL 35812. NR 11 TC 14 Z9 14 U1 1 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 1 PY 1994 VL 424 IS 2 BP 988 EP 990 DI 10.1086/173949 PN 1 PG 3 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NC793 UT WOS:A1994NC79300040 ER PT J AU FONTENLA, J SCHMIEDER, B SIMNETT, GM TANDBERGHANSSEN, E AF FONTENLA, J SCHMIEDER, B SIMNETT, GM TANDBERGHANSSEN, E TI TIME EVOLUTION OF A MINIFLARE AS SEEN IN H-ALPHA, UV LINES, AND X-RAYS SO ASTROPHYSICAL JOURNAL LA English DT Article DE SUN, CHROMOSPHERE; SUN, FLARES; SUN, UV RADIATION; SUN, X-RAYS, GAMMA-RAYS ID SOLAR TRANSITION REGION; ENERGY-BALANCE; FLARING LOOPS; GRADUAL PHASE; MODELS; FLARES; SPECTROMETER; EVAPORATION; DIFFUSION; DYNAMICS AB A miniflare that occurred in active region Hale 16896 on 1980 June 15 was observed in Halpha, UV lines, and soft X-rays. These data allow us to analyze the flare emission and derive the energetics and dynamics of the chromospheric plasma involved. Our results indicate that the energy released by the miniflare was about 10(28) ergs, about four orders of magnitude smaller than that of a large flare. However, hard X-rays (5.5-8.0 keV) were observed which indicated a plasma with temperature as high as 27 x 10(6) K. The Halpha wings, C IV, and X-rays all showed a short-lived and compact (3'' x 3'') brightening in a location near the leading sunspot. At this location, small-scale changes in the magnetic field were observed from about 2 hr before to about 6 hr after the miniflare. Only very small velocities seem to have been associated with most of the event in Halpha. The data are consistent with short and dense loops at temperatures above 10(7) K which lost a large fraction of their energy via downward conduction through transition regions at the footpoints. Several secondary events appear to have been triggered by the miniflare along an arch filament which itself was not greatly affected. A number of much less energetic (10(25)-10(26) erg) events preceded and followed the mini-flare. One of these occurred 11 minutes after the mini-flare and displayed a highly Doppler-shifted signature from the foot-point of a C IV arch. This arch delineates the connection that existed between the location of the mini-flare and the location of secondary events triggered by the flare. C1 OBSERV PARIS,DASOP,SECT MEUDON,F-9215 MEUDON,FRANCE. UNIV BIRMINGHAM,DEPT PHYS & SPACE RES,BIRMINGHAM B15 2TT,W MIDLANDS,ENGLAND. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. RP FONTENLA, J (reprint author), UNIV ALABAMA,HUNTSVILLE,AL 35899, USA. NR 26 TC 3 Z9 3 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 1 PY 1994 VL 424 IS 2 BP 1022 EP & DI 10.1086/173953 PN 1 PG 0 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NC793 UT WOS:A1994NC79300044 ER PT J AU NG, CK REAMES, DV AF NG, CK REAMES, DV TI FOCUSED INTERPLANETARY TRANSPORT OF SIMILAR-TO-1 MEV SOLAR ENERGETIC PROTONS THROUGH SELF-GENERATED ALFVEN WAVES SO ASTROPHYSICAL JOURNAL LA English DT Article DE ACCELERATION OF PARTICLES; INTERPLANETARY MEDIUM; SUN, FLARES; SUN, PARTICLE EMISSIONS ID RANDOM MAGNETIC-FIELDS; COSMIC-RAY TRANSPORT; PITCH-ANGLE SCATTERING; INNER HELIOSPHERE; ION-ACCELERATION; RADIAL EVOLUTION; TRAVELING SHOCKS; COLD MEDIA; PROPAGATION; PARTICLES AB We present a model of the focused transport of approximately 1 MeV solar energetic protons through interplanetary Alfven waves that the protons themselves amplify or damp. It is based on the quasi-linear theory but with a phenomenological pitch angle diffusion coefficient in the ''resonance gap.'' For initial Alfven wave distributions that give mean free paths greater than approximately 0.5 AU for approximately 1 MeV protons in the inner heliosphere, the model predicts greater than roughly an order of magnitude amplification (damping) in the outward (inward) propagating resonant Alfven waves at less than or similar to 0.3 AU heliocentric distance. As the strength of proton source is increased, the peak differential proton intensity at approximately 1 MeV at 1 AU increases to a maximum of approximately 250 particles (cm2 s sr MeV)-1 and then decreases slowly. It may be attenuated by a factor of 5 or more relative to the case without wave evolution, provided that the proton source is sufficiently intense that the resulting peak differential intensity of approximately 1 MeV protons at 1 AU exceeds approximately 200 particles (cm2 s sr MeV)-1. Therefore, in large solar proton events, (1) one may have to take into account self-amplified waves in studying solar particle propagation, (2) the number of accelerated protons escaping from a flare or interplanetary shock may have been underestimated in past studies by a significant factor, and (3) accelerated protons escaping from a traveling interplanetary shock at r less than or similar to 0.3 AU should amplify the ambient hydromagnetic waves significantly to make the shock an efficient accelerator, even if initially the mean free path is greater than or similar to 1 AU. C1 NASA, GODDARD SPACE FLIGHT CTR, HIGH ENERGY ASTROPHYS LAB, GREENBELT, MD 20771 USA. RP RMIT, DEPT MATH, MELBOURNE, VIC 3001, AUSTRALIA. NR 74 TC 76 Z9 76 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD APR 1 PY 1994 VL 424 IS 2 BP 1032 EP 1048 DI 10.1086/173954 PN 1 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NC793 UT WOS:A1994NC79300045 ER PT J AU GOPALSWAMY, N KUNDU, MR STCYR, OC AF GOPALSWAMY, N KUNDU, MR STCYR, OC TI NONTHERMAL RADIO-EMISSION ASSOCIATED WITH A CORONAL DISCONNECTION EVENT SO ASTROPHYSICAL JOURNAL LA English DT Article DE SOLAR-TERRESTRIAL RELATIONS; SUN, ACTIVITY; SUN, CORONA; SUN, FLARES; SUN, RADIO RADIATION AB We have found possible radio signatures of a coronal disconnection event observed by the Solar Maximum Mission Coronagraph/Polarimeter. The radio emission seems to be produced by charged particles accelerated during the same reconnection process which is responsible for the disconnection event. We discuss the implications of the radio emission characteristics to the reconnection process. C1 NASA,GODDARD SPACE FLIGHT CTR,ALLIEDSIGNAL TECHN SERV CORP,GREENBELT,MD 20771. RP GOPALSWAMY, N (reprint author), UNIV MARYLAND,DEPT ASTRON,COLL PK,MD 20742, USA. RI Gopalswamy, Nat/D-3659-2012 NR 13 TC 4 Z9 4 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 1 PY 1994 VL 424 IS 2 BP L135 EP L138 DI 10.1086/187293 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NC795 UT WOS:A1994NC79500018 ER PT J AU PERLMAN, ES STOCKE, JT SHAFFER, DB CARILLI, CL MA, CP AF PERLMAN, ES STOCKE, JT SHAFFER, DB CARILLI, CL MA, CP TI HIGH DYNAMIC-RANGE RADIO OBSERVATIONS OF PKS-1413+135 - A BL LACERTAE OBJECT WITH A PARSEC-SCALE COUNTERJET SO ASTROPHYSICAL JOURNAL LA English DT Article DE BL LACERTAE OBJECTS, GENERAL; BL LACERTAE OBJECTS, INDIVIDUAL (PKS 1413+135); GRAVITATIONAL LENSING ID RILEY-I GALAXIES; PARENT POPULATION; CONSTRAINTS; PKS-1413+135; MORPHOLOGY AB We report the results of three high dynamic range, high-resolution radio observations with the VLA, US VLBI Network, and partially completed VLBA on the peculiar BL Lacertae objects PKS 1413 + 135. The VLA observations (resolution - 1.5'') reveal that PKS 1413 + 135 has no kiloparsec-scale extended structure to a dynamic range limit of 10,000:1. However, its milliarcsecond-scale structure appears to be a triple (i.e., a core, jet plus '' counterjet '') at both 3.6 and 18 cm, a unique structure among BL Lac objects but similar to a recently discovered class of VLBI ''mini-triples.'' The presence of a counterjet at fluxes comparable to the main jet is incompatible with the standard relativistically beamed jet model for BL Lac objects and with the high value of core dominance exhibited by this source at arcsec resolution. This suggests a nonstandard interpretation in which the radio source lies far in the background of the spiral galaxy it is projected upon so that its VLBI structure may be affected by gravitational lensing. At 18 cm, the core is much weaker than at 3.6 cm suggesting free-free absorption by the high-column-density gas found along this sightline by previous IR/optical, X-ray and redshifted H I 21 cm observations. We discuss the roles that free-free absorption and gravitational lensing may have for PKS 1413 + 135 and other GHz-peaked spectrum radio sources. C1 RADIOMETR INC,HENDERSON,NV 89014. STERREWACHT LEIDEN,2300 RA LEIDEN,NETHERLANDS. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP PERLMAN, ES (reprint author), UNIV COLORADO,CTR ASTROPHYS & SPACE ASTRON,CAMPUS BOX 389,BOULDER,CO 80309, USA. NR 28 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 APR 1 PY 1994 VL 424 IS 2 BP L69 EP L72 DI 10.1086/187277 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NC795 UT WOS:A1994NC79500002 ER PT J AU SCHLEGEL, EM AF SCHLEGEL, EM TI THE VERY LUMINOUS SUPERNOVA REMNANT IN NGC-6946 SO ASTROPHYSICAL JOURNAL LA English DT Article DE GALAXIES, INDIVIDUAL (NGC 6946); SUPERNOVA REMNANTS ID X-RAY-EMISSION; CIRCUMSTELLAR MEDIUM; SPIRAL GALAXIES; YOUNG REMNANTS; II SUPERNOVAE; NOVA REMNANT; LIGHT-CURVE; NGC 6946; EVOLUTION; BEHAVIOR AB In this paper, I discuss an extremely luminous X-ray source found on the northern arm of the nearly face-on spiral galaxy NGC 694-6. The source was originally discovered in an Einstein observation, but the poor spatial resolution prevented an accurate identification. Here, ROSAT data provide a position to approximately 5''-10''. The spectrum is rather soft, and moderately absorbed. The source appears to be local to NGC 6946 and a supernova remnant, based upon the positional coincidence with an optical counterpart. The luminosity, assuming a distance to NGC 6946 of 5.1 Mpc, is 2.8 x 10(39) ergs s-1, among the highest known X-ray luminosities of a remnant. The optical counterpart is at least 100 years old. RP SCHLEGEL, EM (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 668,GREENBELT,MD 20771, USA. NR 34 TC 33 Z9 33 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 1 PY 1994 VL 424 IS 2 BP L99 EP L102 DI 10.1086/187284 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NC795 UT WOS:A1994NC79500009 ER PT J AU HILL, RJ MADORE, BF FREEDMAN, WL AF HILL, RJ MADORE, BF FREEDMAN, WL TI THE INITIAL MASS FUNCTION FOR MASSIVE STARS IN THE MAGELLANIC CLOUDS .1. UBV PHOTOMETRY AND COLOR-MAGNITUDE DIAGRAMS FOR 14 OB ASSOCIATIONS SO ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES LA English DT Article DE HERTZSPRUNG-RUSSELL (H-R) DIAGRAM; MAGELLANIC CLOUDS; OPEN CLUSTERS AND ASSOCIATIONS, GENERAL; STARS, EARLY-TYPE; STARS, LUMINOSITY FUNCTION, MASS FUNCTION AB UBV CCD photometry has been obtained for 14 OB associations in the Magellanic Clouds using the University of Toronto's 0.6 m telescope and the Carnegie Institution of Washington's 1.0 m reflector, both on Las Campanas, Chile. The data are presented and used to construct color-magnitude diagrams for the purposes of investigating the massive-star content of the associations. C1 UNIV TORONTO,DEPT ASTRON,TORONTO M5S 1A1,ONTARIO,CANADA. JET PROP LAB,CTR INFRARED PROC & ANAL,NASA,IPAC EXTRAGALACT DATABASE,PASADENA,CA 91109. CARNEGIE INST WASHINGTON,THE OBSERV,PASADENA,CA 91101. NR 16 TC 11 Z9 11 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 APR PY 1994 VL 91 IS 2 BP 583 EP 612 DI 10.1086/191949 PG 30 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NB221 UT WOS:A1994NB22100004 ER PT J AU BENNETT, JO MORROW, CA AF BENNETT, JO MORROW, CA TI NASA INITIATIVE TO DEVELOP EDUCATION THROUGH ASTRONOMY (IDEA) SO ASTROPHYSICS AND SPACE SCIENCE LA English DT Article; Proceedings Paper CT 2nd United-Nations/European-Space-Agency Workshop for Developing Countries: Basic Space Science CY NOV 09-13, 1992 CL BOGOTA, COLUMBIA SP UN, EUROPEAN SPACE AGCY AB We describe a progressive program in science education called the Initiative to Develop Education through Astronomy (IDEA). IDEA represents a commitment by the Astrophysics Division of NASA Headquarters to pre-collegiate and public learning. The program enlists the full participation of research astronomers in taking advantage of the natural appeal of astronomy and the unique features of space astrophysics missions to generate valuable learning experiences and scientifically accurate and educationally effective products for students, teachers and citizens. One of the premier projects is called Flight Opportunities for Science Teacher EnRichment (FOSTER) - a program to fly teachers aboard the Kuiper Airborne Observatory during actual research missions. IDEA is managed by a visiting scientist with extensive educational background (each of the authors have served in this role), and the program is unique within NASA science divisions for having a full time scientist devoted to education. IDEA recognizes that the rapidly shifting social and political landscape has caused a fundamental change in how science is expected to contribute to society. It is in the enlightened self-interest of all research scientists to respond to the challenge of connecting forefront research to basic educational needs. IDEA is exploring the avenues needed to facilitate these connections, including supplementing research grants for educational purposes. C1 NASA HEADQUARTERS,DIV ASTROPHYS,WASHINGTON,DC. RP BENNETT, JO (reprint author), UNIV COLORADO,CTR ASTROPHYS & SPACE ASTRON,BOULDER,CO 80309, USA. NR 23 TC 0 Z9 0 U1 1 U2 3 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0004-640X J9 ASTROPHYS SPACE SCI JI Astrophys. Space Sci. PD APR PY 1994 VL 214 IS 1-2 BP 237 EP 252 DI 10.1007/BF00982339 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NV329 UT WOS:A1994NV32900020 ER PT J AU JACOBSON, MZ TURCO, RP JENSEN, EJ TOON, OB AF JACOBSON, MZ TURCO, RP JENSEN, EJ TOON, OB TI MODELING COAGULATION AMONG PARTICLES OF DIFFERENT COMPOSITION AND SIZE SO ATMOSPHERIC ENVIRONMENT LA English DT Article DE AEROSOL MICROPHYSICS; MULTICOMPONENT AEROSOLS; ATMOSPHERIC MODELING; SEMIIMPLICIT SOLUTIONS ID ATMOSPHERIC AEROSOLS; BROWNIAN COAGULATION; SIMULATION; DYNAMICS; EVOLUTION; ANALOGS AB We present a technique for simulating coagulation among any number of aerosol types, each with a different composition. The semi-implicit solution mechanism solves the coagulation equations over size ranges divided into any number of discrete bins. The scheme conserves particle volume, requires no iterations, and is numerically stable, regardless of the time-step. We compared the accuracy of the solution to both analytical and time-series numerical solutions. Practical use of the scheme demonstrates that it is computationally fast in a multiple grid-cell model. C1 NASA,AMES RES CTR,DIV SPACE SCI,MOFFETT FIELD,CA 94035. RP JACOBSON, MZ (reprint author), UNIV CALIF LOS ANGELES,DEPT ATMOSPHER SCI,405 HILGARD AVE,LOS ANGELES,CA 90024, USA. NR 31 TC 131 Z9 134 U1 1 U2 15 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 1352-2310 J9 ATMOS ENVIRON JI Atmos. Environ. PD APR PY 1994 VL 28 IS 7 BP 1327 EP 1338 DI 10.1016/1352-2310(94)90280-1 PG 12 WC Environmental Sciences; Meteorology & Atmospheric Sciences SC Environmental Sciences & Ecology; Meteorology & Atmospheric Sciences GA NR217 UT WOS:A1994NR21700011 ER PT J AU RAYMER, JH THOMAS, KW PELLIZZARI, ED WHITAKER, DA COOPER, SD LIMERO, T JAMES, JT AF RAYMER, JH THOMAS, KW PELLIZZARI, ED WHITAKER, DA COOPER, SD LIMERO, T JAMES, JT TI A BREATH SAMPLING DEVICE FOR MEASURING HUMAN EXPOSURE TO VOLATILE ORGANIC-COMPOUNDS IN MICROGRAVITY SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Note ID ALVEOLAR BREATH AB A compact device for the collection of alveolar air (breath) from humans aboard spacecraft was developed. the system uses silicone one-way valves that operate independent of gravity, and provide minimal backpressure. Small charcoal filters clean ambient air used for inhalation. The device provided good recoveries of organic compounds at the 20 ng/L level, with generally low carryover of these compounds to a blank sample following a sample at exposure to 100 ng/L. When water accumulated in the system, this carryover increased for highly water soluble compounds. The new device wets used in parallel with a larger, previously developed alveolar air sampler that requires gravity for proper operation; comparable results were obtained with the two units. The device measures 47 x 34 x 11.4 cm and weighs approximately 3.2 kg. Sufficient space is available within the ease to accommodate a number of sample collection options. C1 KRUG INT,DIV TECHNOL LIFE SCI,HOUSTON,TX. NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058. RP RAYMER, JH (reprint author), RES TRIANGLE INST,3040 CORNWALLS RD,RES TRIANGLE PK,NC 27709, USA. NR 10 TC 4 Z9 4 U1 0 U2 0 PU AEROSPACE MEDICAL ASSOC PI ALEXANDRIA PA 320 S HENRY ST, ALEXANDRIA, VA 22314-3579 SN 0095-6562 J9 AVIAT SPACE ENVIR MD JI Aviat. Space Environ. Med. PD APR PY 1994 VL 65 IS 4 BP 353 EP 360 PG 8 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA NE707 UT WOS:A1994NE70700014 PM 8002920 ER PT J AU OHRING, G AOKI, T HALPERN, D HENDERSON-SELLERS, A CHARLOCK, T JOSEPH, J LABITZKE, K RASCHKE, E SMITH, W AF OHRING, G AOKI, T HALPERN, D HENDERSON-SELLERS, A CHARLOCK, T JOSEPH, J LABITZKE, K RASCHKE, E SMITH, W TI JOINT IAMAS-IAHS SYMPOSIUM-J1 ON GLOBAL MONITORING AND ADVANCED OBSERVING TECHNIQUES IN THE ATMOSPHERE AND HYDROSPHERE SO BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY LA English DT Editorial Material AB Seventy papers were presented at the two-and-a-half-day Symposium on Global Monitoring and Advanced Observing Techniques in the Atmosphere and Hydrosphere. The symposium was jointly organized by the International Association of Meteorology and Atmospheric Sciences (IAMAS) and the International Association of Hydrological Sciences (IAHS) and took place in Yokohama, Japan, 13-15 July 1993, as part of the IAMAS/IAHS Joint Assembly. Global observing systems are receiving increased attention in connection with such problems as monitoring global climate change. The symposium included papers on observational requirements; measurement methodologies; descriptions of available datasets; results of analysis of observational data; plans for future observing systems, including the Global Climate Observing System (GCOS) and the Global Ocean Observing System (GOOS); and the programs and plans of the space agencies. C1 METEOROL RES INST, RES LAB 4, TOKYO 166, JAPAN. MACQUARIE UNIV, CTR CLIMAT IMPACTS, N RYDE, NSW 2113, AUSTRALIA. UNIV WISCONSIN, COOPERAT INST METEOROL SATELLITE STUDIES, MADISON, WI 53706 USA. FREE UNIV BERLIN, INST METEOROL, W-1000 BERLIN 33, GERMANY. TEL AVIV UNIV, DEPT GEOPHYS & PLANETARY SCI, IL-69978 TEL AVIV, ISRAEL. JET PROP LAB, PASADENA, CA 91109 USA. NASA, LANGLEY RES CTR, HAMPTON, VA 23665 USA. GKSS FORSCHUNGSZENTRUM GEESTHACHT GMBH, INST PHYS, GEESTHACT TESPERHADE, GERMANY. RP OHRING, G (reprint author), NOAA, NESDIS, SATELLITE RES LAB, WASHINGTON, DC 20233 USA. RI Ohring, George/F-5616-2010; Henderson-Sellers, Ann/H-5323-2011 NR 0 TC 0 Z9 0 U1 0 U2 1 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0003-0007 J9 B AM METEOROL SOC JI Bull. Amer. Meteorol. Soc. PD APR PY 1994 VL 75 IS 4 BP 595 EP 599 PG 5 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA NG920 UT WOS:A1994NG92000006 ER PT J AU GRANT, LB DONNELLAN, A AF GRANT, LB DONNELLAN, A TI 1855 AND 1991 SURVEYS OF THE SAN-ANDREAS FAULT - IMPLICATIONS FOR FAULT MECHANICS SO BULLETIN OF THE SEISMOLOGICAL SOCIETY OF AMERICA LA English DT Article ID CALIFORNIA; EARTHQUAKES; SLIP AB Two monuments from an 1855 cadastral survey that span the San Andreas fault in the Carrizo Plain have been right-laterally displaced 11.0 +/- 2.5 m by the 1857 Fort Tejon earthquake and associated seismicity and afterslip. This measurement confirms that at least 9.5 +/- 0.5 m of slip occurred along the main fault trace, as suggested by measurements of offset channels near Wallace Creek. The slip varied by 2 to 3 m along a 2.6-km section of the main fault trace. Using radiocarbon dates of the penultimate large earthquake and measurements of slip from the 1857 earthquake, we calculate an apparent slip rate for the last complete earthquake cycle that is at least 25% lower than the late-Holocene slip rate on the main fault trace. Comparison of short-term broad-aperture strain accumulation rates with the narrow-aperture late-Holocene slip rate indicates that the fault behaves nearly elastically over a time scale of several earthquake cycles. Therefore, slip in future earthquakes should compensate the slip-rate deficit from the 1857 earthquake. C1 CALTECH, SEISMOL LAB, PASADENA, CA 91125 USA. NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. RI Ludwig, Lisa Grant/G-6442-2012 OI Ludwig, Lisa Grant/0000-0001-6538-8067 NR 18 TC 18 Z9 19 U1 0 U2 0 PU SEISMOLOGICAL SOC AMER PI ALBANY PA 400 EVELYN AVE, SUITE 201, ALBANY, CA 94706-1375 USA SN 0037-1106 EI 1943-3573 J9 B SEISMOL SOC AM JI Bull. Seismol. Soc. Amer. PD APR PY 1994 VL 84 IS 2 BP 241 EP 246 PG 6 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA NH746 UT WOS:A1994NH74600001 ER PT J AU RICE, SD THOMAS, RE MOLES, A AF RICE, SD THOMAS, RE MOLES, A TI PHYSIOLOGICAL AND GROWTH DIFFERENCES IN 3 STOCKS OF UNDERYEARLING SOCKEYE-SALMON (ONCORHYNCHUS-NERKA) ON EARLY ENTRY INTO SEAWATER SO CANADIAN JOURNAL OF FISHERIES AND AQUATIC SCIENCES LA English DT Article AB We compared the impact of exposure to seawater on three sockeye salmon (Oncorhynchus nerka) stocks: one that normally migrates to sea as underyearlings (sea-type) and two with the more common life history strategies of 1 (river-type) or 2 (lake-type) yr of freshwater residence prior to seaward migration. Innate differences in survival, ability to regulate tissue chlorides, and oxygen consumption when first introduced into salt water were more evident in April and May when fish were less than 50 mm in length. In fish longer than 50 mm, the only significant differences among the stocks were in saltwater growth. Between June and August, sea-type fish showed faster growth than river-type fish which in turn grew faster than lake-type fish. When introduced into salt water in October, virtually no growth occurred in any stock, regardless of fish size. River-type and lake-type sockeye, which normally overwinter 1 and 2 yr, respectively, in freshwater, can be reared in seawater if underyearlings are raised to a length of 50 mm before release into salt water, similar to the normal life history of sea-type underyearlings. Early life history appears to be influenced more by habitat than by genetics. C1 CALIF STATE UNIV CHICO,DEPT BIOL SCI,CHICO,CA 95929. NOAA,NATL MARINE FISHERIES SERV,AUKE BAY LAB,JUNEAU,AK 99801. NR 26 TC 8 Z9 9 U1 1 U2 1 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 APR PY 1994 VL 51 IS 4 BP 974 EP 980 DI 10.1139/f94-097 PG 7 WC Fisheries; Marine & Freshwater Biology SC Fisheries; Marine & Freshwater Biology GA NR098 UT WOS:A1994NR09800023 ER PT J AU SKILES, JW HANSON, JD AF SKILES, JW HANSON, JD TI RESPONSES OF ARID AND SEMIARID WATERSHEDS TO INCREASING CARBON-DIOXIDE AND CLIMATE-CHANGE AS SHOWN BY SIMULATION STUDIES SO CLIMATIC CHANGE LA English DT Article ID ATMOSPHERIC CO2; SPUR MODEL; STREAMFLOW; RANGELAND; HYDROLOGY; SCENARIOS; RUNOFF; CROP AB The atmospheric concentration of carbon dioxide is expected to double in the next century causing increased temperatures and decreasing precipitation in some regions of the U.S. The increase in CO2 will also directly affect stomatal conductance of plants. At the first-order watershed scale, changes in evaporative demand, transpiration, and runoff will also occur. Previous modeling studies of the effect of increased CO2 on the water budgets of watersheds have been single-factor exercises where a single parameter representing stomatal conductance was reduced and the results noted. After showing validation results of the hydrology module, we used a comprehensive ecosystem model to examine the consequences of changes in precipitation, temperature, and CO2-induced plant-function characteristics on small-basin runoff. As a result of the complex interactions and of the compensatory mechanisms simulated by the model, we conclude that for arid and semiarid watersheds of the western United States, there will be little change or an actual decrease in surface runoff because of increased CO2 and climate change. This is due to the decrease in precipitation imposed on the model simulations. Implementing stomatal closure in the model did not increase runoff from the watersheds when temperatures were increased and precipitation decreased. C1 USDA ARS,FT COLLINS,CO 80522. RP SKILES, JW (reprint author), NASA,AMES RES CTR,JOHNSON CONTROLS WORLD SERV,MAIL STOP 242-4,MOFFETT FIELD,CA 94035, USA. NR 49 TC 14 Z9 15 U1 0 U2 2 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0165-0009 J9 CLIMATIC CHANGE JI Clim. Change PD APR PY 1994 VL 26 IS 4 BP 377 EP 397 DI 10.1007/BF01094403 PG 21 WC Environmental Sciences; Meteorology & Atmospheric Sciences SC Environmental Sciences & Ecology; Meteorology & Atmospheric Sciences GA NQ960 UT WOS:A1994NQ96000003 ER PT J AU JACOBSON, AS BERKIN, AL ORTON, MN AF JACOBSON, AS BERKIN, AL ORTON, MN TI LINKWINDS - INTERACTIVE SCIENTIFIC-DATA ANALYSIS AND VISUALIZATION SO COMMUNICATIONS OF THE ACM LA English DT Article RP JET PROP LAB, DIV EARTH & SPACE SCI, M-S 183-501, 4800 OAK GROVE DR, PASADENA, CA 91109 USA. NR 16 TC 16 Z9 16 U1 0 U2 1 PU ASSOC COMPUTING MACHINERY PI NEW YORK PA 2 PENN PLAZA, STE 701, NEW YORK, NY 10121-0701 USA SN 0001-0782 EI 1557-7317 J9 COMMUN ACM JI Commun. ACM PD APR PY 1994 VL 37 IS 4 BP 43 EP 52 PG 10 WC Computer Science, Hardware & Architecture; Computer Science, Software Engineering; Computer Science, Theory & Methods SC Computer Science GA ND962 UT WOS:A1994ND96200010 ER PT J AU STEELE, RD BACKES, PG AF STEELE, RD BACKES, PG TI ADA AND REAL-TIME ROBOTICS - LESSONS LEARNED SO COMPUTER LA English DT Article RP STEELE, RD (reprint author), JET PROP LAB,ROBOT SYST & ADV COMP TECHNOL SECT,MAIL STOP 198-219,PASADENA,CA 91109, USA. NR 4 TC 0 Z9 0 U1 0 U2 0 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1264 SN 0018-9162 J9 COMPUTER JI Computer PD APR PY 1994 VL 27 IS 4 BP 49 EP 54 DI 10.1109/2.275001 PG 6 WC Computer Science, Hardware & Architecture; Computer Science, Software Engineering SC Computer Science GA NG025 UT WOS:A1994NG02500012 ER PT J AU JIANG, BN LIN, TL POVINELLI, LA AF JIANG, BN LIN, TL POVINELLI, LA TI LARGE-SCALE COMPUTATION OF INCOMPRESSIBLE VISCOUS-FLOW BY LEAST-SQUARES FINITE-ELEMENT METHOD SO COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING LA English DT Article ID NAVIER-STOKES EQUATIONS; DRIVEN CAVITY FLOW; NUMERICAL-SIMULATION; 3-DIMENSIONAL FLOW; FLUID-DYNAMICS; SEMIIMPLICIT; FORMULATION; SCHEMES; SYSTEMS AB The least-square finite element method (LSFEM) based on the velocity-pressure-vorticity formulation is applied to large-scale/three-dimensional steady incompressible Navier-Stokes problems. This method can accommodate equal-order interpolations, and results in a symmetric, positive definite algebraic system which can be solved effectively by simple iterative methods. The first-order velocity-Bernoulli pressure-vorticity formulation for incompressible viscous flows is also tested. The first-order velocity-pressure-stress formulation is not elliptic in the ordinary sense. so we do not recommend its use for Newtonian flows. For three-dimensional flows, a compatibility equation, i.e., zero divergence of vorticity vector, is included to make the first-order system elliptic. As a by-product of proving the ellipticity of first-order systems, a rigorous mathematical technique has been developed to justify the number of permissible boundary conditions for the Navier-Stokes equations. The simple substitution or Newton's method is employed to linearize the partial differential equations, the LSFEM is used to obtain discretized equations, and the system of algebraic equations is solved using the Jacobi preconditioned conjugate gradient method which avoids formation of either element or global matrices (matrix-free) to achieve high efficiency. To show the validity of this method for large-scale computation, we give numerical results for the 2D driven cavity problem at Re = 10000 with 408 x 400 bilinear elements. The flow in a 3D cavity is calculated at Re = 100, 400, and 1000 with 50 x 52 x 50 trilinear elements. The Taylor-Gortler-like vortices are observed for Re = 1000. C1 LIVERMORE SOFTWARE TECHNOL CORP, LIVERMORE, CA 94550 USA. NASA, LEWIS RES CTR, DIV INTERNAL FLUID MECH, CLEVELAND, OH 44135 USA. RP NASA, LEWIS RES CTR, ICOMP, CLEVELAND, OH 44135 USA. NR 50 TC 92 Z9 94 U1 0 U2 7 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0045-7825 EI 1879-2138 J9 COMPUT METHOD APPL M JI Comput. Meth. Appl. Mech. Eng. PD APR PY 1994 VL 114 IS 3-4 BP 213 EP 231 DI 10.1016/0045-7825(94)90172-4 PG 19 WC Engineering, Multidisciplinary; Mathematics, Interdisciplinary Applications; Mechanics SC Engineering; Mathematics; Mechanics GA NK377 UT WOS:A1994NK37700002 ER PT J AU GAFFNEY, RL WHITE, JA GIRIMAJI, SS DRUMMOND, JP AF GAFFNEY, RL WHITE, JA GIRIMAJI, SS DRUMMOND, JP TI MODELING TEMPERATURE AND SPECIES FLUCTUATIONS IN TURBULENT, REACTING FLOW SO COMPUTING SYSTEMS IN ENGINEERING LA English DT Article ID DIFFUSION FLAMES AB Assumed Gaussian and beta probability density functions (PDFs) for temperature are used with series expansions of the reaction-rate coefficients to compute the mean reaction-rate coefficients in a turbulent, reacting flow. The series-expansion/assumed PDF approach does not require any numerical integration, which substantially reduces computational cost with little loss of accuracy. An assumed multivariate beta PDF for species is investigated for use in modeling the interaction of species fluctuations and chemical combustion. The multivariate beta PDF is initially evaluated through a parametric study. Results of the parametric study indicate that species fluctuations can increase or decrease the magnitude of the species production term, depending on the type of reaction. The models are then tested on a two-dimensional high-speed turbulent reacting hydrogen-air mixing layer. For the conditions tested the numerical simulations indicate that the net effect of species fluctuations is to reduce the mean species production rate. C1 NASA,LANGLEY RES CTR,HAMPTON,VA 23665. RP GAFFNEY, RL (reprint author), ANALYT SERV & MAT INC,HAMPTON,VA 23666, USA. NR 22 TC 16 Z9 16 U1 1 U2 4 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0956-0521 J9 COMPUT SYST ENG JI Comput. Syst. Eng. PD APR PY 1994 VL 5 IS 2 BP 117 EP 133 DI 10.1016/0956-0521(94)90044-2 PG 17 WC Computer Science, Interdisciplinary Applications; Engineering, Multidisciplinary SC Computer Science; Engineering GA PD385 UT WOS:A1994PD38500002 ER PT J AU DAVILA, CG AF DAVILA, CG TI SOLID-TO-SHELL TRANSITION-ELEMENTS FOR THE COMPUTATION OF INTERLAMINAR STRESSES SO COMPUTING SYSTEMS IN ENGINEERING LA English DT Article ID FINITE-ELEMENTS AB This paper presents an accurate and practical technique for coupling shell element models to three-dimensional continuum finite element models. The compatibility between these two types of formulations is enforced by degenerating a continuum element through kinematic constraints compatible with shell deformations. Two formulations of two-dimensional/three-dimensional transition elements are presented. The first and simplest formulation is based on the Mindlin-Reissner plate assumptions, and is found to perform well in a variety of problems involving the analysis of geometrically linear/non-linear laminated structures. The second formulation is based on a higher-order shell theory that allows stretching in the through-the-thickness direction. This additional freedom virtually eliminates the interlaminar normal stress boundary layer that can form in lower-order transition elements. Finally, the coupling of two-dimensional to three-dimensional subdomains is enriched with the use of an interface element, which can be used in conjunction with either transition formulation, The interface element improves the efficiency of the solid-to-shell transition modeling scheme by allowing the independent selection of optimal mesh sizes in the shell and the three-dimensional regions of the model. RP DAVILA, CG (reprint author), NASA,LANGLEY RES CTR,COMPUTAT MECH BRANCH,HAMPTON,VA 23681, USA. RI Davila, Carlos/D-8559-2011 NR 20 TC 22 Z9 22 U1 0 U2 2 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0956-0521 J9 COMPUT SYST ENG JI Comput. Syst. Eng. PD APR PY 1994 VL 5 IS 2 BP 193 EP 202 DI 10.1016/0956-0521(94)90050-7 PG 10 WC Computer Science, Interdisciplinary Applications; Engineering, Multidisciplinary SC Computer Science; Engineering GA PD385 UT WOS:A1994PD38500008 ER PT J AU BARNARD, ST SIMON, HD AF BARNARD, ST SIMON, HD TI FAST MULTILEVEL IMPLEMENTATION OF RECURSIVE SPECTRAL BISECTION FOR PARTITIONING UNSTRUCTURED PROBLEMS SO CONCURRENCY-PRACTICE AND EXPERIENCE LA English DT Article ID MATRICES; EIGENVECTORS; ALGORITHM; GRAPHS; GRIDS AB If problems involving unstructured meshes are to be solved efficiently on distributed-memory parallel computers, the meshes must be partitioned and distributed across processors in a way that balances the computational load and minimizes communication. The recursive spectral bisection method (RSB) has been shown to be very effective for such partitioning problems compared to alternative methods, but RSB in its simplest form is expensive. Here a multilevel version of RSB is introduced that attains about an order-of-magnitude improvement in run time on typical examples. C1 NASA,AMES RES CTR,CRAY RES INC,MOFFETT FIELD,CA 94035. NR 41 TC 156 Z9 158 U1 0 U2 7 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX, ENGLAND PO19 1UD SN 1040-3108 J9 CONCURRENCY-PRACT EX JI Concurrency-Pract. Exp. PD APR PY 1994 VL 6 IS 2 BP 101 EP 117 DI 10.1002/cpe.4330060203 PG 17 WC Computer Science, Software Engineering; Computer Science, Theory & Methods SC Computer Science GA ND720 UT WOS:A1994ND72000002 ER PT J AU THY, P LOFGREN, GE AF THY, P LOFGREN, GE TI EXPERIMENTAL CONSTRAINTS ON THE LOW-PRESSURE EVOLUTION OF TRANSITIONAL AND MILDLY ALKALIC BASALTS - THE EFFECT OF FE-TI OXIDE MINERALS AND THE ORIGIN OF BASALTIC ANDESITES SO CONTRIBUTIONS TO MINERALOGY AND PETROLOGY LA English DT Article ID LOW-CA PYROXENE; EXPERIMENTAL PETROLOGY; PHASE-EQUILIBRIUM; FRACTURE-ZONE; FRACTIONATION; LIQUIDS; MAGMA; LAVAS; CRYSTALLIZATION; OLIVINE AB One-atmosphere, melting experiments, controlled at the fayalitc-magnetite-quartz oxygen buffer, on mildly alkalic and transitional basalts from Iceland show that these begin to crystallize Fe-Ti oxide minerals (magnetite and/or ilmenite) at 1105+/-5-degrees-C, apparently independently of bulk composition and the order of silicate and oxide mineral crystallization. Most samples crystallize plagioclase and olivine as the first two crystalline phases, augite as the third phase, and an Fc-Ti oxide mineral as the fourth phase. The main effects of Fe-Ti oxide crystallization are a marked decrease in FeO and TiO2 in the liquid, and a notable increase in SiO2 and Al2O3, and the minor oxides K2O and P2O5, With decreasing temperature. The most silicic glasses are compositionally mugearitic and shoshonitic basaltic andesites. Because the smallest amount of glass that could be analyzed with the microprobe represents 20-55 percent liquid remaining, it can be expected that more silicic liquids will occur at lower temperatures. On normative, pseudoternary projections, the general effect of Fe-Ti oxide crystallization for mildly alkalic and transitional basalts is a marked increase in normative quartz. This is caused by a strong systematic convergence, with the appearance of Fe-Ti oxides, of the bulk solid precipitates toward the liquid compositions, as projected on the triangle plagioclase-diopside-olivine. For alkalic basalts, the bulk solid precipitate shows an increase in normative diopside with falling temperature and Fe-Ti oxide crystallization. This causes the liquids to move toward decreasing normative diopside and relatively little variation in nepheline. The experimental observations imply that mildly alkalic and transitional magmas, without stabilizing a Fe-Ti oxide mineral, will not evolve toward early silica saturation. C1 UNIV CALIF DAVIS,DEPT GEOL,DAVIS,CA 95616. RP THY, P (reprint author), NASA,LYNDON B JOHNSON SPACE CTR,SN2,HOUSTON,TX 77058, USA. NR 43 TC 50 Z9 50 U1 1 U2 10 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 SN 0010-7999 J9 CONTRIB MINERAL PETR JI Contrib. Mineral. Petrol. PD APR PY 1994 VL 116 IS 3 BP 340 EP 351 DI 10.1007/BF00306502 PG 12 WC Geochemistry & Geophysics; Mineralogy SC Geochemistry & Geophysics; Mineralogy GA NH869 UT WOS:A1994NH86900008 ER PT J AU GICQUEL, A HASSOUNI, K FARHAT, S BRETON, Y SCOTT, CD LEFEBVRE, M PEALAT, M AF GICQUEL, A HASSOUNI, K FARHAT, S BRETON, Y SCOTT, CD LEFEBVRE, M PEALAT, M TI SPECTROSCOPIC ANALYSIS AND CHEMICAL-KINETICS MODELING OF A DIAMOND DEPOSITION PLASMA REACTOR SO DIAMOND AND RELATED MATERIALS LA English DT Article; Proceedings Paper CT 4th European Conference on Diamond, Diamond-like and Related Materials (Diamond Films 93) CY SEP 20-24, 1993 CL ALBUFEIRA, PORTUGAL SP AEA TECHNOL, SURF TECHNOL, HARWELL LAB, ASTEX, COMMISS EUROPEAN COMMUNITIES, DG TEER COATING SERV LTD, DIAMOND & RELATED MAT, DRUKKER INT BV, GENASYSTEMS INC, KOBE STEEL USA INC, ELECTR MAT CTR, NORTON DIAMOND FILM, RENISHHAW TRANSDUCER SYST LTD, US DEPT DEF ID OPTICAL-EMISSION SPECTROSCOPY; VAPOR-DEPOSITION; HYDROGEN; DISCHARGES; OXYGEN; GROWTH; FILMS; CARS AB The quality and the growth rate of diamond films produced in a microwave bell jar plasma reactor are strong functions of the plasma characteristics at the plasma-surface interface (temperatures, species concentrations). These local parameters are shown to be functions of the plasma operating conditions (dissociation in volume) and of the boundary conditions at the surface. Spectroscopic measurements of some plasma parameters based on coherent anti-Stokes Raman and optical emission spectroscopy are presented, the deposition results are correlated with these measurements. A zero-dimensional chemical kinetics model is developed for studying the influences of the gas temperature and the electron temperature on the production of atomic hydrogen. C1 NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058. OFF NATL ETUD & RECH AEROSP,F-92322 CHATILLON,FRANCE. RP GICQUEL, A (reprint author), UNIV PARIS 13,CNRS,INGN MAT HAUTES PRESS LAB,AVE JEAN BAPTISTE CLEMENT,F-93430 VILLETANEUSE,FRANCE. NR 21 TC 92 Z9 93 U1 1 U2 19 PU ELSEVIER SCIENCE SA LAUSANNE PI LAUSANNE 1 PA PO BOX 564, 1001 LAUSANNE 1, SWITZERLAND SN 0925-9635 J9 DIAM RELAT MATER JI Diam. Relat. Mat. PD APR PY 1994 VL 3 IS 4-6 BP 581 EP 586 DI 10.1016/0925-9635(94)90229-1 PG 6 WC Materials Science, Multidisciplinary SC Materials Science GA NN160 UT WOS:A1994NN16000056 ER PT J AU NEWMAN, JC AF NEWMAN, JC TI A REVIEW OF MODELING SMALL-CRACK BEHAVIOR AND FATIGUE-LIFE PREDICTIONS FOR ALUMINUM-ALLOYS SO FATIGUE & FRACTURE OF ENGINEERING MATERIALS & STRUCTURES LA English DT Article AB The small-crack effect, where small fatigue cracks grow faster and at lower stress-intensity factors than large cracks, has been found to be significant for many materials and loading conditions. In this paper, plasticity effects and crack-closure modelling of small fatigue cracks are reviewed. A crack-closure model with a cyclic-plastic-zone-corrected effective stress-intensity factor range (related to the cyclic J -integral) and microstructural data on crack-initiation sites were used to calculate small-crack growth rates and fatigue lives for unnotched and notched specimens made of two aluminum alloys. The crack-closure transient from the plastic wake was shown to be the dominant cause of the small-crack effect and plasticity effects on the cyclic-plastic-zone-corrected stress-intensity factor range were negligible except at extremely high stress levels. Small-crack growth rates and fatigue lives under both constant-amplitude and spectrum loading from tests and analyses agreed well. RP NASA, LANGLEY RES CTR, MECH MAT BRANCH, HAMPTON, VA 23665 USA. NR 30 TC 42 Z9 43 U1 1 U2 5 PU WILEY-BLACKWELL PI HOBOKEN PA 111 RIVER ST, HOBOKEN 07030-5774, NJ USA SN 8756-758X EI 1460-2695 J9 FATIGUE FRACT ENG M JI Fatigue Fract. Eng. Mater. Struct. PD APR PY 1994 VL 17 IS 4 BP 429 EP 439 DI 10.1111/j.1460-2695.1994.tb00242.x PG 11 WC Engineering, Mechanical; Materials Science, Multidisciplinary SC Engineering; Materials Science GA NP156 UT WOS:A1994NP15600004 ER PT J AU MANNHEIM, PD KAZANAS, D AF MANNHEIM, PD KAZANAS, D TI NEWTONIAN LIMIT OF CONFORMAL GRAVITY AND THE LACK OF NECESSITY OF THE 2ND-ORDER POISSON EQUATION SO GENERAL RELATIVITY AND GRAVITATION LA English DT Article ID GALACTIC ROTATION CURVES; WEYL GRAVITY; SPIRAL GALAXIES; MOTION AB We study the interior structure of a locally conformal invariant fourth order theory of gravity in the presence of a static, spherically symmetric gravitational source. We find, quite remarkably, that the associated dynamics is determined exactly and without any approximation at all by a simple fourth order Poisson equation which thus describes both the strong and weak field limits of the theory in this static case. We present the solutions to this fourth order equation and find that we are able to recover all of the standard Newton-Euler gravitational phenomenology in the weak gravity limit, to thus establish the observational viability of the weak field limit of the fourth order theory. Additionally, we make a critical analysis of the second order Poisson equation, and find that the currently available experimental evidence for its validity is not as clearcut and definitive as is commonly believed, with there not apparently being any conclusive observational support for it at all either on the very largest distance scales far outside of fundamental sources, or on the very smallest ones within their interiors. Our study enables us to deduce that even though the familiar second order Poisson gravitational equation may be sufficient to yield Newton's Law of Gravity it is not in fact necessary. C1 NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771. RP MANNHEIM, PD (reprint author), UNIV CONNECTICUT,DEPT PHYS,STORRS,CT 06269, USA. NR 17 TC 59 Z9 59 U1 0 U2 1 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 1994 VL 26 IS 4 BP 337 EP 361 DI 10.1007/BF02105226 PG 25 WC Astronomy & Astrophysics; Physics, Multidisciplinary; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA NE516 UT WOS:A1994NE51600001 ER PT J AU YUNCK, TP BERTIGER, WI WU, SC BARSEVER, YE CHRISTENSEN, EJ HAINES, BJ LICHTEN, SM MUELLERSCHOEN, RJ VIGUE, Y WILLIS, P AF YUNCK, TP BERTIGER, WI WU, SC BARSEVER, YE CHRISTENSEN, EJ HAINES, BJ LICHTEN, SM MUELLERSCHOEN, RJ VIGUE, Y WILLIS, P TI 1ST ASSESSMENT OF GPS-BASED REDUCED DYNAMIC ORBIT DETERMINATION ON TOPEX POSEIDON SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID EARTH AB The reduced dynamic GPS tracking technique has been applied for the first time as part of the GPS experiment on TOPEX/Poseidon. This technique employs local geometric position corrections to reduce orbit errors caused by the mis-modeling of satellite forces. Results for a 29-day interval in early 1993 are evaluated through postfit residuals and formal errors, comparison with GPS and laser/DORIS dynamic solutions, comparisons on 6-hr overlaps of adjacent 30-hr data arcs, altimetry closure and crossover analysis. Reduced dynamic orbits yield slightly better crossover agreement than other techniques and appear to be accurate in altitude to about 3 cm RMS. C1 INST GEOG NATL,F-94160 ST MANDE,FRANCE. RP YUNCK, TP (reprint author), JET PROP LAB,M-S 238-638,4800 OAK GROVE DR,PASADENA,CA 91109, USA. RI Willis, Pascal/A-8046-2008 OI Willis, Pascal/0000-0002-3257-0679 NR 12 TC 70 Z9 88 U1 2 U2 7 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 1994 VL 21 IS 7 BP 541 EP 544 DI 10.1029/94GL00010 PG 4 WC Geosciences, Multidisciplinary SC Geology GA NE512 UT WOS:A1994NE51200009 ER PT J AU CHIPPERFIELD, MP GRAY, LJ KINNERSLEY, JS ZAWODNY, J AF CHIPPERFIELD, MP GRAY, LJ KINNERSLEY, JS ZAWODNY, J TI A 2-DIMENSIONAL MODEL STUDY OF THE QBO SIGNAL IN SAGE-II NO2 AND O3 SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID QUASI-BIENNIAL OSCILLATION; INTERANNUAL VARIABILITY; MIDDLE ATMOSPHERE; TRACE GASES; OZONE; WINDS AB Calculations of the QBO signal in SAGE II O3 and NO2 data between 1984 and 1991 are presented and have been investigated by using a two-dimensional model. The isentropic 2D model is a fully interactive radiative-dynamical-chemical model in which the eddy fluxes of chemical species are calculated in a consistent manner. The QBO in the model has been forced by relaxing the equatorial zonal wind toward the observations at Singapore allowing the comparison of the model with observations from specific years. The model reproduces the observed vertical structure of the equatorial ozone anomaly with the well-known transition from dynamical to photochemical control at around 28km. The model also reproduces the observed vertical structure of the SAGE II observed NO2 anomaly. The model studies have shown that it is the QBO modulation of NO2 which is the main cause of QBO signal in O3 above 30km. The model also reproduces the observed latitudinal structure of the QBO signals in O3 and NO2. Due to the differing horizontal distribution of O3 and NO(y) the ozone signal shows a distinct phase change in the subtropics whereas the NO2 anomaly gives a broader signal. C1 RUTHERFORD APPLETON LAB,DIDCOT OX11 0QX,OXON,ENGLAND. UNIV EDINBURGH,DEPT METEOROL,EDINBURGH EH8 9YL,MIDLOTHIAN,SCOTLAND. NASA,LANGLEY RES CTR,HAMPTON,VA 23665. RP CHIPPERFIELD, MP (reprint author), UNIV CAMBRIDGE,DEPT CHEM,LENSFIELD RD,CAMBRIDGE CB2 1EW,ENGLAND. RI Gray, Lesley/D-3610-2009; Chipperfield, Martyn/H-6359-2013 OI Chipperfield, Martyn/0000-0002-6803-4149 NR 7 TC 60 Z9 63 U1 1 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD APR 1 PY 1994 VL 21 IS 7 BP 589 EP 592 DI 10.1029/94GL00211 PG 4 WC Geosciences, Multidisciplinary SC Geology GA NE512 UT WOS:A1994NE51200021 ER PT J AU TSURUTANI, BT ARBALLO, JK MOK, J SMITH, EJ MASON, GM TAN, LC AF TSURUTANI, BT ARBALLO, JK MOK, J SMITH, EJ MASON, GM TAN, LC TI ELECTROMAGNETIC-WAVES WITH FREQUENCIES NEAR THE LOCAL PROTON GYROFREQUENCY - ISEE-3 1 AU OBSERVATIONS SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID INTERPLANETARY AB Low Frequency (LF) electromagnetic waves with periods near the local proton gyrofrequency have been detected in interplanetary space by the magnetometer onboard ISEE-3. Transverse peak-to-peak amplitudes as large as DELTAB/\B\ approximately 0.4 have been noted with compressional components (DELTA\B\/\B\) typically less-than-or-equal-to 0.1. Generally, the waves have even smaller amplitudes, or are not detectable within the solar wind turbulence. The waves are elliptically/linearly polarized and are often, but not always, found to propagate nearly along B(o). Both right- and left-hand polarizations in the spacecraft-frame have been detected. The waves are observed during all orientations of the interplanetary magnetic field, with the Parker spiral orientation being the most common case. Because the waves are detected at and near the local proton cyclotron frequency, the generation mechanism must almost certainly be solar wind pickup of freshly created hydrogen ions. Possible sources for the hydrogen are the Earth's atmosphere, coronal mass ejections from the Sun, comets and interstellar neutral atoms. At this time it is not obvious which potential source is the correct one. Statistical tests employing over one year of ISEE-3 data will be done in the near future to eliminate/confirm some of these possibilities. C1 DEPT PHYS & ASTRON,COLLEGE PK,MD. RP TSURUTANI, BT (reprint author), JET PROP LAB,PASADENA,CA 91109, USA. NR 16 TC 18 Z9 18 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD APR 1 PY 1994 VL 21 IS 7 BP 633 EP 636 DI 10.1029/94GL00566 PG 4 WC Geosciences, Multidisciplinary SC Geology GA NE512 UT WOS:A1994NE51200032 ER PT J AU STANDISH, EM AF STANDISH, EM TI IMPROVED EPHEMERIDES OF PLUTO SO ICARUS LA English DT Article; Proceedings Paper CT Conf on Pluto and Charon CY JUL, 1993 CL FLAGSTAFF, AZ ID JPLS DE-200; POSITIONS; PLANETS AB The history of the pluto ephemerides created at the Jet Propulsion Laboratory is given. The uncertainties of present and possible future ephemerides are illustrated, and it is shown how rapidly the error grows for any present-day ephemeris of Pluto which is extrapolated into the future-tens of thousands of kilometers after only a decade. Continuing the observations into the future not only will reduce the extrapolation time but will provide a substantial improvement to the ephemeris itself. (C) 1994 Academic Press, Inc. RP STANDISH, EM (reprint author), JET PROP LAB,301-150,PASADENA,CA 91109, USA. NR 26 TC 7 Z9 7 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 1994 VL 108 IS 2 BP 180 EP 185 DI 10.1006/icar.1994.1052 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NY462 UT WOS:A1994NY46200003 ER PT J AU YOUNG, EF BINZEL, RP AF YOUNG, EF BINZEL, RP TI A NEW DETERMINATION OF RADII AND LIMB PARAMETERS FOR PLUTO AND CHARON FROM MUTUAL EVENT LIGHTCURVES SO ICARUS LA English DT Article; Proceedings Paper CT Conf on Pluto and Charon CY JUL, 1993 CL FLAGSTAFF, AZ ID ATMOSPHERE; OCCULTATION AB Over the past several years Pluto-Charon mutual events have yielded progressively more accurate estimates of Charon's orbital elements and the radii of Pluto and Charon (e.g., Buie, Tholen, and Horne, 1992, Icarus 97, 211-227). Analysis of the 1988 stellar occultation by Pluto indicates a radius for Pluto that is about 4%, or 50 km, larger than the mutual event radius of 1151 km. One possible explanation for the discrepancy is that the mutual event modeling treats Pluto and Charon as uniformly bright disks. If they are limb-darkened, the mutual event fits could underestimate their radii. In this paper we use an independent mutual event data set (Young and Binzel, 1992, Icarus 102, 134-149) to fit for Pluto and Charon's radii in a manner independent of either object's limb profile or albedo distribution. Our least-squares solution indicates that Pluto's radius is 1164 +/- 22.9 km and Charon's radius is 621 +/- 20.6 km. (C) 1994 Academic Press, Inc. C1 MIT,DEPT EARTH ATMOSPHER & PLANETARY SCI,CAMBRIDGE,MA 02139. RP YOUNG, EF (reprint author), NASA,AMES RES CTR,MS 245-6,MOFFETT FIELD,CA 94035, USA. NR 19 TC 35 Z9 35 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 1994 VL 108 IS 2 BP 219 EP 224 DI 10.1006/icar.1994.1056 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NY462 UT WOS:A1994NY46200007 ER PT J AU STERN, SA PARKER, JW DUNCAN, MJ SNOWDALL, JC LEVISON, HF AF STERN, SA PARKER, JW DUNCAN, MJ SNOWDALL, JC LEVISON, HF TI DYNAMICAL AND OBSERVATIONAL CONSTRAINTS ON SATELLITES IN THE INNER PLUTO CHARON SYSTEM SO ICARUS LA English DT Article; Proceedings Paper CT Conf on Pluto and Charon CY JUL, 1993 CL FLAGSTAFF, AZ AB It is not known if Pluto has other satellites besides its massive partner Charon. In the past, searches for additional satellites in the Pluto-Charon system have extended from the solar-tidal stability boundary (almost-equal-to 90 arcsec from Pluto) inward to about 1 arcsec from Pluto. Here we further explore the inner (i.e., <10 arcsec) region of the Pluto-Charon system to determine where additional satellites might lie. In particular, we report on (i) dynamical simulations to delineate the region where unstable orbits lie around Charon, (ii) dynamical simulations which use the low orbital eccentricity of Charon to constrain the mass of any third body near Pluto, and (iii) analysis of HST archival images to search for satellites in the inner Pluto-Charon system. Although no objects were found, significant new constraints on bodies orbiting in the inner Pluto-Charon system were obtained. (C) 1994 Academic Press, Inc. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. QUEENS UNIV,KINGSTON K7L 3N6,ONTARIO,CANADA. TRINITY UNIV,SAN ANTONIO,TX 78284. RP STERN, SA (reprint author), SW RES INST,SAN ANTONIO,TX 78238, USA. RI Levison, Harold/C-6061-2013 OI Levison, Harold/0000-0001-5847-8099 NR 15 TC 18 Z9 18 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 1994 VL 108 IS 2 BP 234 EP 242 DI 10.1006/icar.1994.1058 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA NY462 UT WOS:A1994NY46200009 ER EF