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  • 1
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    In:  CASI
    Publikationsdatum: 2006-02-14
    Beschreibung: The specific objectives of this experiment are to establish the population and size distribution of meteoroids in the mass range from 10 to the minus 10 power to 10 to the minus 4 power G, to establish the current population of man-made debris in the same mass range, and to obtain data on the physical properties (composition and density) of meteoroids.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Long Duration Exposure Facility (LDEF); p 136-137
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  • 2
    Publikationsdatum: 2006-02-14
    Beschreibung: The objective of this experiment is to study interplanetary dust, variously referred to as cosmic dust, cometary dust, zodiacial dust, or meteoric dust particles. Specific objectives are to obtain information regarding particle mass and velocity, and to undertake correlative analyses with other experiments, both on LDEF or near the time of the LDEF flight.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Long Duration Exposure Facility (LDEF); p 134-135
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  • 3
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    In:  CASI
    Publikationsdatum: 2006-02-14
    Beschreibung: The primary objective of this experiment is to investigate the feasibility of future missions of multilayer thin-film detectors acting as energy sorter to collect micrometeoroids, if not in their original shape, at least as fragments suitable for chemical analysis. It is expected that this kind of particle collector will help in solving one of the most puzzling topics in cosmic-dust studies: the mineralogical and chemical composition of the particles. This is a matter of great interest in the study of the origin and evolution of the solar system.
    Schlagwort(e): ASTROPHYSICS
    Materialart: NASA. Langley Research Center Long Duration Exposure Facility (LDEF); p 124-126
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  • 4
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    In:  CASI
    Publikationsdatum: 2006-02-14
    Beschreibung: Anchorage dependent cell cultures in fluidized beds are tested. Feasibility calculations indicate the allowed parameters and estimate the shear stresses therein. In addition, the diffusion equation with first order reaction is solved for the spherical shell (double bubble) reactor with various constraints.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Houston Univ. The 1981 NASA ASEE Summer Fac. Fellowship Program, Vol. 2; 19 p
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  • 5
    Publikationsdatum: 2006-02-14
    Beschreibung: Technical improvements of a long life heat rejection system, suitable for long duration high power missions, that can be constructed and deployed in orbit is discussed. A mathematical model is formulated and a computer program developed which describes the transient priming characteristics of a dual passage heat pipe. An experimental test package is described for flight in the KC-135 Zero-g Aircraft, to be used to verify the modeling predictions.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Houston Univ. The 1981 NASA ASEE Summer Fac. Fellowship Program, Vol. 2; 50 p
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  • 6
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    In:  CASI
    Publikationsdatum: 2006-02-14
    Beschreibung: Spacelab experiment to investigate two-phase flow patterns under gravity uses a water-air mixture experiment. Air and water are circulated through the system. The quality or the mixture or air-water is controlled. Photographs of the test section are made and at the same time pressure drop across the test section is measured. The data establishes a flow regime map under reduced gravity conditions with corresponding pressure drop correlations. The test section is also equipped with an electrical resistance heater in order to allow a flow boiling experiment to be carried out using Freon II. High-speed photographs of the test section are used to determine flow patterns. The temperature gradient and pressure drop along the duct can be measured. Thus, quality change can be measured, and heat transfer calculated.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: NASA. Marshall Space Flight Center Spacecraft Dyn. as Related to Lab. Expt. in Space; p 43-57
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  • 7
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    In:  CASI
    Publikationsdatum: 2006-02-14
    Beschreibung: The equations of motion governing an incompressible fluid contained in an orbiting laboratory were examined to isolate various fictitious forces and their relative influence on the fluid. The forces are divided into those arising from the orbital motions and those arising from small local motions of the spacecraft about its center of mass. The latter dominate the nonrotating experiments. Both are important for rotating experiments. A brief discussion of the onset of time-dependence and violent instability in earth-based rotating and processing systems is given.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: NASA. Marshall Space Flight Center Spacecraft Dyn. as Related to Lab. Expt. in Space; p 96-102
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  • 8
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    In:  CASI
    Publikationsdatum: 2006-02-14
    Beschreibung: Natural convection is not always harmful and, therefore, to be avoided. In some situations it may be desirable to have fluid flows in space processes, e.g., to stir the fluid phase for mixing and cooling or to help maintain concentration gradients. In may event, it is important to know the extent and nature of convection in space and the factors on which it depends, in order either to minimize the effects to convection, or to utilize the convection to advantage. The information needed to assess both conventional and unstable convection includes: (1) the magnitude and direction of accelerations; (2) geometric configuration; (3) imposed boundary conditions; and (4) material properties.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: NASA. Marshall Space Flight Center Spacecraft Dyn. as Related to Lab. Expt. in Space; p 69-95
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  • 9
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    In:  CASI
    Publikationsdatum: 2006-02-14
    Beschreibung: Systematic scaling or dimensional analysis reveals that certain scales of geophysical fluid flows (such as stellar, ocean, and planetary atmosphere circulations) can be accurately modeled in the laboratory using a procedure which differs from conventional engineering modeling. Rather than building a model to obtain numbers for a specific design problem, the relative effects of the significant forces are systematically varied in an attempt to deepen understanding of the effects of these forces. Topics covered include: (1) modeling a large-scale planetary atmospheric flow in a rotating cylindrical annulus; (2) achieving a radial dielectric body force; (3) spherical geophysical fluid dynamics experiments for Spacelab flights; (4) measuring flow and temperature; and (5) the possible effect of rotational or precessional disturbances on the flow in the rotating spherical containers.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Spacecraft Dyn. as Related to Lab. Expt. in Space; p 25-31
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  • 10
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    In:  CASI
    Publikationsdatum: 2006-02-14
    Beschreibung: The importance of understanding and modeling the unsteady flow phenomena in turbomachinery is discussed. Historical events in the application and development of gas turbines for aircraft propulsion are traced. Technology advancements over the years are highlighted with focus on the compression system components. Trends in compressor research within the National Advisory Committee for Aeronautics (NACA)/National Aeronautics and Space Administration (NASA) are noted. The impact of technology advancements on the increased occurrences of unsteady flow related problems in advanced engine development programs is discussed. The impact of the new and more demanding requirements being imposed on the propulsion system to meet advanced aircraft mission needs are also noted. Brief discussions on the present day understanding and modeling capability of the unsteady flow phenomena are presented to include discussions on rotating stall, surge, flutter, forced response and noise generation.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Von Karman Inst. for Fluid Dynamics Unsteady Flow in Turbomachines, Vol. 1; p 1-20
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  • 11
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    In:  CASI
    Publikationsdatum: 2006-02-14
    Beschreibung: The objective is to verify the capability of a cascade variable conductance heat pipe (CVCHP) system to provide precise temperature control of long life spacecraft without the need for a feedback heater or other power sources for temperature adjustment under conditions of widely varying power input and ambient environment. Solar energy is the heat source and space the heat sink for thermally loading two series connected variable conductance heat pipes. Electronics and power supply equipment requirements are minimal. A 7.5 V lithium battery supplies the power for thermistor type temperature sensors for monitoring system performance, and a 28 V lithium battery supplies power for valve actuation.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: NASA. Langley Research Center Long Duration Exposure Facility (LDEF); p 66-69
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  • 12
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    In:  CASI
    Publikationsdatum: 2006-02-14
    Beschreibung: The objectives of this experiment are to collect and isotopically analyze interstellar gas atoms around the orbit of the Earth for the purpose of obtaining new data relevant to understanding nucleosynthesis, and to study the dynamics of the interstellar wind inside the heliosphere and the isotopic composition of the interstellar medium outside the heliosphere. The experiment hardware will act as a set of simple cameras with high-purity copper-beryllium collecting foils serving as the film. The experiment housing will mount and thermally control the foils, establish the viewing angles and viewing direction, provide baffling to reject ambient neutral particles, provide a voltage grid to reject ionospheric charged particles, sequence collecting foils, control exposure times, and protect the foils from contamination during the deployment and retrieval of the LDEF. After being returned to Earth, the entrapped atoms can be analyzed by mass spectroscopy to determine the relative abundance of the different isotopes of helium and neon. An attempt will also be made to detect argon.
    Schlagwort(e): ASTROPHYSICS
    Materialart: NASA. Langley Research Center Long Duration Exposure Facility (LDEF); p 98-100
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  • 13
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    In:  CASI
    Publikationsdatum: 2006-02-14
    Beschreibung: The objective of this experiment is to evaluate the zero-g performance of a number of transverse flat plate heat pipe modules. Performance will include the transport capability of the pipes, the temperature drop, and the ability to maintain temperature over varying duty cycles and environments. Additionally, performance degradation, if any, will be monitored over the length of the Long Duration Exposure Facility (LDEF) mission. This information is necessary if heat pipes are to be considered for system designs where they offer benefits not available with other thermal control techniques.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: NASA. Langley Research Center Long Duration Exposure Facility (LDEF); p 74-77
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  • 14
    Publikationsdatum: 2006-02-14
    Beschreibung: The principal objectives of the experiment are to determine zero-g start-up performance for conventional and diode low temperature heat pipes, to evaluate heat pipe performance in zero-g for an extended period of time, to determine zero-g transport capability of each heat pipe, and to determine diode operation, including forward conductance, turndown ratio, and transient behavior. Two heat pipes, a fixed conductance transporter heat pipe and a thermal diode heat pipe, are coupled with a radiant cooler system. Both pipes are charged with ethane. Also integrated with the radiator is a phase change material (PCM) canister which provides temperature stability during transport tests. N-heptane, which has a melting/freezing point of 182 K, is used as the PCM. The high heat capacity (28 W-hr of latent heat) provided by the canister permits high power heat pipe testing at constant temperature.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: NASA. Langley Research Center Long Duration Exposure Facility (LDEF); p 70-73
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  • 15
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    In:  CASI
    Publikationsdatum: 2006-02-14
    Beschreibung: After the external tank separates from the Orbiter about 2000 pounds of residual liquid oxygen remain in the main propulsion system lines. The pressurization of liquid oxygen from a subcritical to a supercritical state by the use of the heaters of the PRSA tanks while in a low-g environment is investigated. The performance of the heaters while bringing the state of the substance from the subcritical state to the supercritical one is studied, with particular emphasis on the time the pressurization process takes, and the temperature of the heater as the process proceeds.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Houston Univ. The 1981 NASA ASEE Summer Fac. Fellowship Program, Vol. 2; 38 p
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  • 16
    Publikationsdatum: 2011-08-19
    Beschreibung: Numerical experiments are used to study thermally driven flows which occur during vertical Bridgman crystal growth of a single component fluid. The solid-liquid interface was specified as parabolic and flow patterns were calculated for various insulation thicknesses, Grashof, Prandtl, and Biot numbers. When the melt is on top and the gravity vector is axially downward it is shown that flow persists as long as a radial temperature gradient is present. If the interface is convex, as viewed from the liquid, a single cell is observed. A concave interface exhibits multiple counterrotating cells. The insulation thickness and Grashof, Prandtl, and Biot numbers influence the flow in a quantitative manner.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Crystal Growth (ISSN 0022-0248); 68; 747-756
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  • 17
    Publikationsdatum: 2011-08-19
    Beschreibung: The stability of the parallel flow between a vertical crystal-melt interface and a vertical wall held at a temperature above the melting point of the crystal is analyzed for Prandtl numbers, P, ranging from 0.01 to 100. Three modes of instability occur: (1) a buoyant mode, (2) a shear mode, and (3) a coupled crystal-melt mode. The buoyant and shear modes are similar to those that occur for flow between two vertical rigid walls held at different temperatures. For Prandtl numbers greater than approximately two, the coupled crystal-melt mode occurs at a lower Grashof number than the other two modes. Specific results are given for succinonitrile (P = 22.8) and lead (P = 0.0225). These calculations and similar calculations for a cylindrical geometry were motivated by and are in general agreement with recent experiments on succinonitrile.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Crystal Growth (ISSN 0022-0248); 66; 514-524
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  • 18
    Publikationsdatum: 2011-08-19
    Beschreibung: The solid-liquid interface position and the temperature gradients in both the solid and liquid at the interface have been studied in a modified Bridgman-Stockbarger crystal growth furnace. These crystal growth factors have been studied as a function of ampoule translation rate, materials properties, and the size and temperature of a small auxiliary heater placed at the edge of the furnace hot zone. It has been found that the interface position with respect to a furnace reference point is essentially constant during a run for a low thermal conductivity material whereas the interface position changes continuously during a run with high thermal conductivity material. However, the ampoule translation rate and auxiliary heater conditions produce interface position changes in both high and low thermal conductivity materials.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Crystal Growth (ISSN 0022-0248); 69; 509-514
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  • 19
    Publikationsdatum: 2011-08-18
    Beschreibung: High spatial resolution images of the T Tauri star HL Tau were obtained at 1.6 microns and 2.2 microns. The original images as well as maximum entropy image reconstructions reveal a circumstellar envelope structure, similar at both wavelenghts, and extended along P.A. = 112 deg; the 10 percent width of the structure is 1.9 sec (300 AU at 160 pc). The extended structure is interpreted as light scattered toward earth by dust in a disk surrounding this young stellar object. Polarization measurements made at 2.2 microns support this hypothesis. The total solid particle mass is, at minimum, 5 x 10 to the -7th solar mass.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 283; L57-L61
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  • 20
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    In:  Other Sources
    Publikationsdatum: 2011-08-18
    Beschreibung: The motion of two and four rectilinear vortices inside a cylindrical pipe is studied under the restriction that the total circulation be zero. In the two-vortex case, it is shown that the motion is always periodic and an expression for the period is derived. In the four-vortex case, the motion is determined not to be periodic in general. However, a class of solutions where the motion is periodic is found. Several sample calculations of the vortex motion are included.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Physics of Fluids (ISSN 0031-9171); 27; 1583-158
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  • 21
    Publikationsdatum: 2011-08-18
    Beschreibung: Systematics of the light curves of classical Cepheids with the longest known periods have been investigated with the help of full-amplitude models of pulsating stellar envelopes. For periods exceeding about 60 days, flat-topped light curves of the S Vul type are found to replace the smooth, asymmetric light curves characteristic of the slightly faster Cepheids. Predicted light and velocity amplitudes (although not the predicted radius amplitudes) agree well with observations. Variables with fluctuating light minima are observed to lie well off the mean period-luminosity relation, as are a few other (more stable?) variables with similarly long periods. The explanation for the long periods is probably low effective temperature rather than a low stellar mass. Because of the abnormal slowness of the classical Cepheids with periods longer than about 100 days, it is recommended that these variables not be used to calibrate the mean period-luminosity relation. Analogies between the slow classical Cepheids and the slow Population II Cepheids are drawn.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 281; 811-814
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  • 22
    Publikationsdatum: 2011-08-18
    Beschreibung: The mechanism responsible for the massive rapidly expanding Galactic feature known as the 3-kpc arm (Rougoor and Oort, 1960) is investigated theoretically in the framework of a density-wave model of the Galaxy. The arm is attributed to outgoing waves excited at the outer Lindblad resonance (OLR) of a small rotating oval distortion near the Galactic center. Linear and nonlinear models are developed, and it is shown that a density crest at 3.5 kpc with expansion velocity 53 km/s can be generated by a distortion turning at 118 km/s kpc with a 10-percent perturbation of the main gravitational field at the OLR (located at 3 kpc). The wave character of the nonlinear solution is found to be the same as that of the linear solution and to give good agreement with the observations in terms of expansion velocity, size, shape, and mass; only the observed asymmetry of the arm is not reproduced.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 281; 600-613
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  • 23
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    In:  Other Sources
    Publikationsdatum: 2011-08-18
    Beschreibung: A complete redshift survey of nearby rich galactic clusters is analyzed in terms of a spatial correlation function, the growth of supercluster, the presence of superclusters around the Bootes void and the discovery of a 300 Mpc void. Abell's (1958) statistical sampling of rich clusters is used for the study. Attention is given to the dependence of the correlation function on the richness of the system, with finding that chances are greater of finding rich neighbors closer together than poor neighbors. Samples of redshifts of 4 or less correlate well with clusters of redshift 5 or more. The size of intergalactic voids is proportional to the surrounding galactic excesses. Finally, the superclusters exist on scales of about 100 Mpc/h, which is larger than expected.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Advances in Space Research (ISSN 0273-1177); 3; 10-12
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  • 24
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    In:  Other Sources
    Publikationsdatum: 2011-08-18
    Beschreibung: Some turbulent solutions of the unaveraged Navier-Stokes equations (equations of fluid motion) are reviewed. Those equations are solved numerically in order to study the nonlinear physics of incompressible turbulent flow. Initial three-dimensional cosine velocity fluctuations and periodic boundary conditions are used in most of the work considered. The three components of the mean-square velocity fluctuations are initially equal for the conditions chosen. The resulting solutions show characteristics of turbulence such as the linear and nonlinear excitation of small-scale fluctuations. For the stronger fluctuations, the initially nonrandom flow develops into an apparently random turbulence. Thus randomness or turbulence can arise as a consequence of the structure of the Navier-Stokes equations. The cases considered include turbulence which is statistically homogeneous or inhomogeneous and isotropic or anisotropic. A mean shear is present in some cases. A statistically steady-state turbulence is obtained by using a spatially periodic body force. Various turbulence processes, including the transfer of energy between eddy sizes and between directional components, and the production, dissipation, and spatial diffusion of turbulence, are considered. It is concluded that the physical processes occurring in turbulence can be profitably studied numerically.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Reviews of Modern Physics (ISSN 0034-6861); 56; 223-254
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  • 25
    Publikationsdatum: 2011-08-18
    Beschreibung: An extensive survey of ultraviolet O type spectra, by means of high-resolution data from the International Ultraviolet Explorer archives, shows a strong correlation between both the photospheric and stellar wind features, and the optical spectral types. In particular, the stellar wind effect in the Si IV resonance doublet displays a strong luminosity dependence which has not been completely described before: there is no effect anywhere on the main sequence, but it develops gradually through the intermediate luminosity classes into a full P Cygni profile in the supergiants. This behavior is in sharp contrast to that of the C IV and N V, which have strong P Cygni profiles throughout most of the O type domain, including the main sequence. The Si IV effect simultaneously provides a sensitive classification criterion and poses an outstanding problem for detailed astrophysical interpretation. In addition, a new emission feature at 1574 A, possibly due to N III or to N IV forbidden line, is reported.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 280; L27-L30
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  • 26
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    Publikationsdatum: 2011-08-18
    Beschreibung: The observations of relatively narrow absorption components of the UV resonance lines in the spectra of early-type stars are reviewed, and some new observational data are presented for Rho Leo (B1 Ib). It is shown that the discrete components which are seen in the UV resonance lines of early-type stars are a result of ejection from local spots above the photospheres of hot stars. It is suggested that localized ejection is caused by magnetic flux lines associated with a bipolar magnetic region on the surface of the star.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 280; 712-728
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  • 27
    Publikationsdatum: 2011-08-18
    Beschreibung: Phenomenological fits to the hard X-ray spectrum of AM Hercules have failed to explain the high equivalent width (0.8 + or - 0.1 keV) of Fe K-alpha emission. The scattering and fluorescent line production in a cold or partially ionized accretion column of hard X-rays emitted at the base are investigated using the Monte Carlo method. It is shown that the Fe emission equivalent width observed in the spectrum of AM Her can be explained without resorting to an overabundance of Fe in the accreting material. For sufficient optical depth across the accretion column, equivalent widths of K-alpha emission even larger than the observed values can be obtained. The accretion rate and gravitational power can be deduced from the optical depth across the column, if the column size is known, and, together with the observed hard X-ray and polarized light luminosities, imply a lower limit for the luminosity in the UV to soft X-ray range, for which the observations give model-dependent values.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 280; 734-743
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  • 28
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    Publikationsdatum: 2011-08-18
    Beschreibung: The present investigation has the objective to provide a summary of the existing evidence on the disappearance of comets and to draw conclusions regarding the physical processes involved in the disappearance. Information concerning the classification of evidence and the causes of apparent disappearance of comets is presented in a table. Attention is given to the dissipating comets, the headless sungrazing comet 1887 I, and the physical behavior of the dissipating comets and the related phenomena. It is found that all comets confined to the planetary region of the solar system decay on astronomically short time scales. However, only some of them appear to perish catastrophically. Some of the observed phenomena could be successfully interpreted. But little insight has been obtained into the character of the processes which the dissipating comets experience.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Icarus (ISSN 0019-1035); 58; 81-100
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  • 29
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    Publikationsdatum: 2011-08-18
    Beschreibung: The X-ray properties of the binary black hole candidates include distinctive bimodal spectral behavior where the X-ray spectra switch between being very soft (alpha greater than 3) and hard (alpha about 0.7). It is pointed out that this spectral transition occurs at about 1 percent L(edd) (for accretion onto a 10 solar masses black hole), and that this corresponds to the luminosity where an optically thick electron-positron pair plasma will form. Active galactic nuclei (AGN) are often considered to be accreting black holes. An X-ray spectral similarity between the above binary sources and both the Seyfert I and BL Lac classes of AGN is demonstrated. As many of these objects radiate most of their luminosity as X-rays, such a similarity may be expected if the underlying mechanisms are similar.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astronomy and Astrophysics (ISSN 0004-6361); 133; 2, Ap
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  • 30
    Publikationsdatum: 2011-08-18
    Beschreibung: An experiment was conducted to measure the heat transfer from a heated cylinder in crossflow in an array of circular cylinders. All cylinders had a length-to-diameter ratio of 3.0. Both in-line and staggered array patterns were studied. The cylinders were spaced 2.67 diameters apart center-to-center in both the axial and transverse directions to the flow. The row containing the heated cylinder remained in a fixed position in the channel and the relative location of this row within the array was changed by adding up to five upstream rows. The working fluid was nitrogen gas at pressures from 100 to 600 kPa. The Reynolds number range based on cylinder diameter and average unobstructed channel velocity was from 5,000 to 125,000. Turbulence intensity profiles were measured for each case at a point one half space upstream of the row containing the heated cylinder. The basis of comparison for all the heat transfer data was the single row with the heated cylinder. For the in-line cases the addition of a single row of cylinders upstream of the row containing the heated cylinder increased the heat transfer by an average of 50 percent above the base case. Adding up to five more rows caused no increase or decrease in heat transfer. Adding rows in the staggered array cases resulted in average increases in heat transfer of 21, 64, 58, 46, and 46 percent for one to five upstream rows, respectively. Previously announced in STAR as N82-19493
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: ASME, Transactions, Journal of Heat Transfer (ISSN 0022-1481); 106; 42-48
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  • 31
    Publikationsdatum: 2011-08-18
    Beschreibung: Preliminary results of an investigation of magnetic fluctuations seen upstream of two interplanetary shocks are presented. The spectral analysis includes calculation of the normalized reduced magnetic helicity spectrum, the normalized reduced cross-helicity spectrum, and the Alfven ratio as discussed by Matthaeus and Goldstein (1982). Minimum variance methods are used to compute wave polarization as a function of frequency. The Taylor 'frozen in flow' hypothesis is assumed to convert frequencies to wave vectors. Some of the basic properties of the waves, including the probable mode of propagation in association with both quasi-parallel forward and reverse shocks, are described. A comparison with previous results on the generation of waves at interplanetary and planetary shocks is presented.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Journal of Geophysical Research (ISSN 0148-0227); 89; 3762-377
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  • 32
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    Publikationsdatum: 2011-08-18
    Beschreibung: The Crab pulsar (PSR 0531+21) is the only pulsar which has been observed throughout almost the entire electromagnetic spectrum from 0.5 keV to over 2000 GeV. In general, the emission from the Crab nebula and its pulsar has been remarkably constant in time (except for the pulsations). However, several recent observations, especially of gamma-ray line emission, indicate possible time variations. The present investigation is concerned with the data obtained with the HEAO C-1 experiment. The data have been studied with the hope of finding information regarding a number of questions, taking into account the existence of line emission from the pulsar, the variation of the shape of the light curve with time, and the spectral variations as a function of pulsar phase. The spectrum of the total phase-averaged pulsed emission is found to be consistent with a single power-law spectrum from 50 keV to 10 MeV.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 278; 784-790
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  • 33
    Publikationsdatum: 2011-08-18
    Beschreibung: The HEAO 2 Einstein Observatory was used to confirm the identification of 4U 0352 + 30 with X Per. The HEAO 2 data were analyzed in order to determine an additional point in the pulse period history of the X-ray source and to search for short binary periods. In addition, a majority of the historical X-ray observations was reanalyzed and more refined values for the pulse period as a function of time were obtained. The period history possess significant scatter, but no evidence for a measurable long-term spin-up trend is found, and hence a lower limit to the spin-up time scale is set. This lower limit is consistent with the presence of a neutron star, but it does not rule out a degenerate dwarf. The period history was also searched for evidence of binary motion, and upper limits to a(x) sin i were obtained.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 278; 711-715
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  • 34
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    Publikationsdatum: 2011-08-18
    Beschreibung: The results of continued IUE monitoring of the symbiotic variable SY Muscae, following an earlier report of a radical enhancement in UV emission from the star, are reported. Over the course of one year, the prominent emission lines of N V, O V, C IV, and He II appear to be gradually decreasing in absolute intensity. This appears to coincide with a steady decline in electron density in the emission line forming region. The data are consistent with a sudden ejection event in which material expelled from the surface of a hot subdwarf has exposed the underlying UV continuum of the star. A number of strong emission lines that are photoexcited by the intense radiation field of the secondary also exhibit broad pedestal emission that suggests turbulent velocities of about 150-300 km/s in an expanding shell or possibly in an accretion disk.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Royal Astronomical Society, Monthly Notices (ISSN 0035-8711); 207; 575-583
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  • 35
    Publikationsdatum: 2011-08-18
    Beschreibung: Abell 30 has been identified as a planetary nebula in which the nucleus has experienced a final helium shell flash after ejection of the original, outer envelope. Around the central star of the nebula, four knots of material are observed. In view of the importance of the chemical composition of the ejected material for studies of advanced stages of stellar evolution, clarification of the physical conditions in the knots is vital. Data obtained of Abell 30 with the aid of the International Ultraviolet Explorer (IUE) satellite are discussed along with aspects of extinction, the He II flux, ionic abundances, the C II lambda 4267 line, questions regarding the existence of a carbon-rich core in the knot, the heating of the nebular gas, the central star, and heating by suprathermal particles from the stellar wind. The UV spectrum of the inner nebulosity of Abell 30 indicates that an extraordinary amount of energy is being deposited in the gas.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 277; 716-724
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  • 36
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    Publikationsdatum: 2011-08-18
    Beschreibung: 10-micron spectra of many extreme carbon stars reveal a prominent emission feature near 11 microns. This is compared with laboratory spectra of SiC grains. Two distinct types of features are found, perhaps indicative of different mechanisms of grain formation in different stars. Estimates are made of probable column densities and total masses of SiC in the circumstellar shells.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Royal Astronomical Society, Monthly Notices (ISSN 0035-8711); 206; 137-147
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  • 37
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    Publikationsdatum: 2011-08-19
    Beschreibung: The magnetic field measurements from Voyager and the magnetohydrodynamic (MHD) processes in the outer heliosphere are reviewed. A bibliography of the experimental and theoretical work concerning magnetic fields and plasmas observed in the outer heliosphere is given. Emphasis in this review is on basic concepts and dynamical processes involving the magnetic field. The theory that serves to explain and unify the interplanetary magnetic field and plasma observations is magnetohydrodynamics. Basic physical processes and observations that relate directly to solutions of the MHD equations are emphasized, but obtaining solutions of this complex system of equations involves various assumptions and approximations. The spatial and temporal complexity of the outer heliosphere and some approaches for dealing with this complexity are discussed.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Space Science Reviews (ISSN 0038-6308); 39; 255-316
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  • 38
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    Publikationsdatum: 2011-08-19
    Beschreibung: A theory of the origin and evolution of the Solar System which considered electromagnetic forces and plasma effects is revised in light of information supplied by space research. In situ measurements in the magnetospheres and solar wind can be extrapolated outwards in space, to interstellar clouds, and backwards in time, to the formation of the solar system. The first extrapolation leads to a revision of cloud properties essential for the early phases in the formation of stars and solar nebulae. The latter extrapolation facilitates analysis of the cosmogonic processes by extrapolation of magnetospheric phenomena. Pioneer-Voyager observations of the Saturnian rings indicate that essential parts of their structure are fossils from cosmogonic times. By using detailed information from these space missions, it is possible to reconstruct events 4 to 5 billion years ago with an accuracy of a few percent.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Space Science Reviews (ISSN 0038-6308); 39; 65-90
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  • 39
    Publikationsdatum: 2011-08-19
    Beschreibung: Measurements of the ARII (6.99 microns), ArIII (8.99 microns), NeI (12.81 microns), SIII (18.71 microns), and SIV (10.51 microns) lines are presented for five compact HII regions along with continuum spectroscopy. From these data and radio data, lower limits to the elemental abundances of Ar, S, and Ne were deduced. The complex G25.4-0.2 is only 5.5 kpc from the galactic center, and is considerably overabundant in all these elements. Complex G45.5+0.06 is at seven kpc from the galactic center, and appears to be approximately consistent with solar abundance. The complex S159 in the Perseus Arm, at 12 kpc from the galactic center, has solar abundance, while M8 in the solar neighborhood may be somewhat overabundant in Ar and Ne. Complex DR 22, at 10 kpc from the galactic center in the Cygnus Arm, is overabundant in Ar. A summary of results from a series of papers on abundances is given.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 285; 174-180
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  • 40
    Publikationsdatum: 2011-08-19
    Beschreibung: The HEAO A-1 Sky Survey Experiment included X-ray data used to define light curves for the flare star EV Lac and for X-ray flares observed in the binary system HD 8357. The data were taken during flare events and were detailed enough to calculate the flare rates and flaring luminosities. The peak luminosities during flares were several times the luminosities in normal X-ray flares emitted by the objects. Peak luminosities reached 30-50 times the normal variations and were associated with an order of magnitude increase in energy output. EV Lac was sufficiently active to be recommended for inclusion in future X-ray monitoring programs.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 284; 270-277
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  • 41
    Publikationsdatum: 2011-08-19
    Beschreibung: The results of regularized Monte Carlo calculations of the optical polarization Stokes parameters expected as a result of scattering from gas streams or accretion wakes in close binary systems whose properties resemble those of X-ray binaries are presented. The physical processes occurring in the system are represented by a model which follows a selected sample of individual photon paths from each emitting element on the surface of the primary to the photon's detection at earth. The result represents the variations in the intensity from each individual emitting element caused by the effects of limb darkening, gravity darkening, and variation in the projected area of the emitting element as seen from the scattering element.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astronomy and Astrophysics (ISSN 0004-6361); 138; 1, Se
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  • 42
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    Publikationsdatum: 2011-08-19
    Beschreibung: The existing data base on certain characteristics of the periodic Comet Kopff, a candidate for a NASA rendezvous mission in the 1990s, is summarized. The comet was discovered in 1906. The data are used to calculate limits to the nuclear mass (0.7-1.5 x 10 to the 16th g), equatorial radius (1.26-1.64 km), and a geometric albedo of 0.08. An equatorial rotation velocity of 8.1-10.7 hr is projected. The estimates are highly dependent on the present photometric data, which in turn depend on the insolation rate, which if different than assumed could mean that all parameters would be revised upward significantly.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astronomical Journal (ISSN 0004-6256); 89; 1573-158
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  • 43
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    Publikationsdatum: 2011-08-19
    Beschreibung: For galactic N and late R type irregularly variable carbon stars, a comparison is made of airborne infrared spectrophotometry to spectral flux distributions derived from model atmospheres. Although the agreement is good in several respects, the H(-) emission peak at 1.6 microns, so prominent in the models, is significantly weakened in the stellar spectrophotometry. It seems unlikely that molecular bands in the stars can completely obliterate this peak. A plausible explanation is that hydrogen is deficient in these stars, most probably from an episode of mass loss. The resultant cold shells surrounding these stars should be amenable to observation by IRAS, or other far-infrared observatories.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 284; L39-L42
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  • 44
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    Publikationsdatum: 2011-08-19
    Beschreibung: A sample consisting primarily of radio bright quasars was observed in X-rays with the Einstein Observatory for times ranging from 1500 to 5000 seconds. Detected sources had luminosities ranging from 0.2 to 41.0 x 10 to the 45th power ergs/sec in the 0.5 to 4.5 keV band. Three of the fourteen objects which were reobserved showed flux increases greater than a factor of two on a time scale greater than six months. No variability was detected during the individual observations. The optical and X-ray luminosities are correlated, which suggests a common origin. However, the relationship (L sub x is approximately L sub op to the (.89 + or - .15) found for historic radio variables may be significantly different than that reported for other radio bright sources. Some of the observed X-ray fluxes were substantially below the predicted self-Compton flux, assuming incoherent synchrotron emission and using VLBI results to constrain the size of the emission region, which suggests relativistic expansion in these sources. Normal CIV emission in two of the sources with an overpredicted Compton component suggests that although they, like BL Lac objects, have highly relativistic material apparently moving at small angle to the line of sight, they have a smaller fraction of the continuum component in the beam.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 284; 491-496
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  • 45
    Publikationsdatum: 2011-08-19
    Beschreibung: High resolution spectra of the interstellar NaI D2 absorption line have been obtained for seven B-type stars aligned with an extensive filamentary nebula. Very fine filaments have now been found on a high contrast print of a deep H-alpha and forbidden N II plate, making identification as a fossilized remnant probable but uncertain. The inferred age is about 20,000 yr, the distance less than 200 pc, the diameter less than 17.5 pec, but the initial energy is only about 2 x 10 to the 47th erg.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Royal Astronomical Society, Monthly Notices (ISSN 0035-8711); 210; 693-699
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  • 46
    Publikationsdatum: 2011-08-18
    Beschreibung: The effects of mass injection and pressure gradients on the drag of surfaces were studied theoretically with the aid of boundary-layer and Navier-Stokes codes. The present investigation is concerned with the effects of spatially varying the injection in the case of flat-plate drag. Effects of suction and injection on wavy wall surfaces are also explored. Calculations were performed for 1.2 m long surfaces, one flat and the other sinusoidal with a wavelength of 30.5 cm. Attention is given to the study of the effect of various spatial blowing variations on flat-plate skin friction reduction, local skin friction coefficient calculated by finite difference boundary-layer code and Navier-Stokes code, and the effect of phase-shifting sinusoidal mass transfer on the drag of a sinusoidal surface.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: AIAA Journal (ISSN 0001-1452); 22; 143-145
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  • 47
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    Publikationsdatum: 2011-08-18
    Beschreibung: The destruction of interstellar grains by nonthermal sputtering, thermal sputtering, and grain-grain collisions is discussed. It is concluded that large grains are easily destroyed by shocks in the interstellar medium, but that small grains are much more persistent. Since the MRN model has many more small grains than large ones, this means that the total number of grains is not significantly reduced even when half or more of the grain material is returned to the gas phase. Thus, the small grains are always available as condensation cores for mantle formation or redepletion of refractory grain materials.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Royal Observatory Lab. and Observational Infrared Spectra of Interstellar Dust; p 26-32
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  • 48
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    Publikationsdatum: 2011-08-18
    Beschreibung: The numerical aspects of simulation unsteady flows which arise in turbomachinery are addressed. In particular the simulation of rotating stall and surge is discussed.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Von Karman Inst. for Fluid Dynamics Unsteady Flow in Turbomachines, Vol. 2; 75 p
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  • 49
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    Publikationsdatum: 2011-08-19
    Beschreibung: The comet thermal model of Weissman and Kieffer is used to calculate gas production rates and other parameters for the 1986 perihelion passages of Halley's Comet. Gas production estimates are very close to revised pre-perihelion estimates by Newburn based on 1910 observations of Halley; the increase in observed gas production post-perihelion may be explained by a variety of factors. The energy contribution from multiply scattered sunlight and thermal emission by coma dust increases the total energy reaching the Halley nucleus at perihelion by a factor of 2.4. The high obliquity of the Halley nucleus found by Sekanina and Larson may help to explain the asymmetry in Halley's gas production rates around perihelion.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Advances in Space Research (ISSN 0273-1177); 4; 9, 19; 221-224
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  • 50
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    Publikationsdatum: 2011-08-19
    Beschreibung: It is pointed out that solid material present in the coma and tail of a comet is revealed by the scattering of sunlight and thermal emission of absorbed solar radiation. The large beam size and low background of the cold Infrared Astronomy Satellite (IRAS) telescope make it extremely well suited to the measurement of faint diffuse thermal emission from solid grains associated with comets. The IRAS project was conducted jointly by the Netherlands, the United Kingdom, and the U.S. Its basic objective involved a survey of the sky in four wavelength regions centered on 12, 25, 60, and 100 microns. The present paper is mainly concerned with IRAS observations of the coma-nucleus regions as defined by the maximum in the intensity distribution. Attention is given to circumstances of comet observations, dust production rates, and a discussion of the results.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Advances in Space Research (ISSN 0273-1177); 4; 9, 19
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  • 51
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    Publikationsdatum: 2011-08-19
    Beschreibung: Measurements of the thermal emission from the cometary dust coma can be used to derive the rate of dust production from the nucleus as well as the size distribution of absorbing grains. More than ten short-period comets have now been observed in the infrared over a wide range in heliocentric distance. Dust production rates are derived for these comets based on theoretical models of the thermal emission from small absorbing grains and calculations of dust grain velocities. The mean size and albedo of the dust grains is similar in these comets, with the exception of Comet Crommelin, which seems to have had larger, darker grains.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Advances in Space Research (ISSN 0273-1177); 4; 9, 19; 189-196
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  • 52
    Publikationsdatum: 2011-08-19
    Beschreibung: The semiempirical photometric theory of gas and dust production in comets (Newburn, 1979, 1981, and 1982) is recalibrated on the basis of the 17-comet compilation of spectrophotometric data of Newburn and Spinrad (1984). The results are presented in graphs and tables, and it is shown that no corrections are required for the constant R and the function delta, but that the mixing ratios (obtained as functions of heliocentric distance) can be improved, with implications for the visual-photometric comet model. Recently calculated light curves for comet Halley are compared, and the use of the nearly identical curves of Bortle and Morris (1984) and Marcus (1983) is recommended.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Advances in Space Research (ISSN 0273-1177); 4; 9, 19; 185-188
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  • 53
    Publikationsdatum: 2011-08-19
    Beschreibung: A numerical algorithm that is second-order accurate in time has been developed for the conjugated problem of a separated, compressible flow field and a conductive solid body. The full two-dimensional time-dependent Navier-Stokes equations are coupled with the time-dependent energy equation for the solid body and are solved simultaneously. using implicit algorithms. The energy equation for the solid body may include arbitrarily distributed heat sources. The algorithm has been exmined for the case of two-dimensional supersonic compression-corner interaction, with a heat source embedded in the wall in the vicinity of the separation bubble and the attached boundary layer. The effect of the heat source on the flow field is studied for steady and transient cases.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Numerical Heat Transfer (ISSN 0149-5720); 7; 395-411
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  • 54
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    Publikationsdatum: 2011-08-19
    Beschreibung: A power-law relationship between the average erosion rate and cumulative erosion is presented. Data analyses from Venturi, magnetostriction, and liquid-impingement devices conform to this unified relation. A normalization technique is also suggested for prediction purposes.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: International Journal of Mechanical Sciences (ISSN 0020-7403); 26; 5, 19
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  • 55
    Publikationsdatum: 2011-08-19
    Beschreibung: Expected enhancement of the N III emission-line spectrum by the Bowen He II to O III to N III resonant photoexcitation process is computed using a six-configuration model. Preliminary comparisons with available solar and nebular observations indicate that the process may play only a small role, although photoexcitation quenching of the N III and O III far-infrared fine-structure lines is noted as a possibly important mechanism. Some features are discussed in connection with the nebular emission at 1750 A, which is suggested as an indicator of excitation class for planetary nebulae.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 287; 945-951
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  • 56
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    Publikationsdatum: 2011-08-19
    Beschreibung: Ariel 5 and SAS 3 X-ray pulse timing data for the 700 s X-ray pulsar 4U 1223 - 62 (GX 301 - 2) are reexamined in order to deduce the orbital elements of this system. The Ariel 5/SAS 3 arrival times are first reanalyzed to obtain the best solution for an orbital period close to 41.5 days and to estimate the uncertainties in it caused by unknown variations in the underlying pulse period. Spectral measurements by OSO 8 and HEAO 1 at a variety of orbital phases are presented and the origin of an unabsorbed, unpulsed soft component is discussed. OSO 8 observations of occasions when the amplitude and shape of the pulse profile changed dramatically are discussed. The global X-ray properties of the system are explained in terms of a simple stellar wind accretion model, and the interaction of the inflowing material with the neutron star magnetosphere is considered.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 287; 856-867
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  • 57
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    Publikationsdatum: 2011-08-19
    Beschreibung: The present investigation is concerned with a comparison of the spectra of four O stars (10 Lac, S Mon, HD 46223, and Zeta Pup) which have similar effective temperatures, taking into account an attempt to find the reason for differences regarding the spectral type of the stars. The photospheres of the stars are examined, taking into account the effective temperatures, radii, speed of rotation, and masses. Information is presented about the equivalent widths and profiles of strong lines in the visible and ultraviolet spectra of each star. It is found that the four stars have similar photospheres but different mantles. The stars are assigned different spectral types because the empirically selected lines used for determining spectral type in class O are sensitive primarily to conditions in the mantle of the star and not to conditions in the photosphere. Questions concerning the reasons for the differences regarding the mantles are also explored.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 287; 874-891
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  • 58
    Publikationsdatum: 2011-08-19
    Beschreibung: High signal-to-noise ratio spectra in the range of 5-8 microns of four sources embedded in molecular clouds are examined using low-temperature laboratory measurements of the 5-8-micron spectra of simple molecules and their mixtures. The absorption, apparent in all four sources, is characterized by highly distinct features ranging from two relatively narrow bands at 6.0 and 6.8 microns in W33A to a broad, shallow, and partially structured feature extending from 5.2 to 7.8 microns in Mon R2-IRS2, BN, and NGC2264. The first feature (W33A) is explained by the OH bending mode in H2O and the CH deformation modes in saturated hydrocarbons; while the second feature (Mon R2-IRS2-type) is explained by the presence of a mixture of saturated and unsaturated hydrocarbons possibly containing strongly electronegative groups.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 287; 697-706
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  • 59
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    Publikationsdatum: 2011-08-19
    Beschreibung: Absorption of high-energy gamma-rays from Cyg X-3 in its own photon field by the reaction gamma + gamma yields e(+) + e(-) is considered. It is found that gamma rays with an energy around 10 to the 12th eV are attenuated, and the observed flux has to be corrected. Gamma rays with energy greater than 10 to the 15th eV which are observed are not affected by the photon field.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 287; 338-340
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  • 60
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    In:  Other Sources
    Publikationsdatum: 2011-08-19
    Beschreibung: The coil planet centrifuge designed by Ito employs flow of a single liquid phase, through a rotating coiled tube in a centrifugal force field, to provide a separation of particles based on sedimentation rates. Mathematical solutions are derived for the linear differential equations governing particle behavior in the coil planet centrifuge device. These solutions are then applied as the basis of a model for optimizing particle separations.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Chromatography (ISSN 0021-9673); 295; 1-11
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  • 61
    Publikationsdatum: 2011-08-19
    Beschreibung: The results of Monte Carlo simulations of steady state shocks generated by a collision operator that isotropizes the particles by means of elastic scattering in some locally defined frame of reference are presented. The simulations include both the back reaction of accelerated particles on the inflowing plasma and the free escape of high-energy particles from finite shocks. Energetic particles are found to be naturally extracted out of the background plasma by the shock process with an efficiency in good quantitative agreement with an earlier analytic approximation (Eichler, 1983 and 1984) and observations (Gosling et al., 1981) of the entire particle spectrum at a quasi-parallel interplanetary shock. The analytic approximation, which allows a self-consistent determination of the effective adiabatic index of the shocked gas, is used to calculate the overall acceleration efficiency and particle spectrum for cases where ultrarelativistic energies are obtained. It is found that shocks of the strength necessary to produce galactic cosmic rays put approximately 15 percent of the shock energy into relativistic particles.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 286; 691-701
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  • 62
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    Publikationsdatum: 2011-08-19
    Beschreibung: A generalized model which accounts for the effects of initially uniform and slow rotation is defined for the spherical collapse of a singular isothermal sphere such as protosolar and binary nebulae. An initial unstable equilibrium state is described for a sound speed of 0.35 km/sec and a rotation rate of 10 to the -14th/sec for the molecular cloud surrounding the accreting core. The total angular momentum and mass of the inner cloud is set equal to solar system values. The evolution of the collapse is traced by applying a perturbation analysis to the similarity solution for a nonrotating condition, and matched asymptotic expansions solve the hydrodynamic equations. The model is concluded a valid tool for studying star and nebular disk formation.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 286; 529-551
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  • 63
    Publikationsdatum: 2011-08-19
    Beschreibung: For the past 25 years, there has existed in the Thermosciences Laboratory of the Mechanical Engineering Department of Stanford University a research program, primarily experimental, concerned with heat transfer through turbulent boundary layers. In the early phases of the program, the topics considered were the simple zero-pressure-gradient turbulent boundary layer with constant and with varying surface temperature, and the accelerated boundary layer. Later equilibrium boundary layers were considered along with factors affecting the boundary layer, taking into account transpired flows, flows with axial pressure gradients, transpiration, acceleration, deceleration, roughness, full-coverage film cooling, surface curvature, free convection, and mixed convection. A description is provided of the apparatus and techniques used, giving attention to the smooth plate rig, the rough plate rig, the full-coverage film cooling rig, the curvature rig, the concave wall rig, the mixed convection tunnel, and aspects of data reduction and uncertainty analysis.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
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  • 64
    Publikationsdatum: 2011-08-19
    Beschreibung: The balloon-borne UV Stellar Spectrometer's high resolution, near-UV spectra of the supergiant Alpha Cyg are subjected to analysis in order to determine the average microturbulent line-of-sight velocity component. A value of 15.0 + or - 0.5 km/sec is obtained, which is close to the 13.7 km/sec local sound velocity, and is consistent with the view that shock waves are the dominant structure in the outer photosphere of Deneb, so that shock wave dissipation determines the thermal structure of the photosphere.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astronomy and Astrophysics (ISSN 0004-6361); 141; 2, De
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  • 65
    Publikationsdatum: 2011-08-19
    Beschreibung: Ultraviolet observations of atomic carbon in cometary comae show that carbon-bearing compounds must comprise a significant fraction (approximately equal to or greater than 10 percent) of the volatiles. One likely source is CO. This compound is an important constituent of at least some cometary nuclei, even though it may not be the ultimate source of atomic carbon in all comets. Feldman (1983) has suggested that the relative abundance of CO may be one of the few fundamental characteristics which distinguish one comet from another. The present investigation is, therefore, concerned with the vibrational and rotational excitation of the CO molecule in cometary comae. Two previously neglected factors are taken into account in the study. The fractional populations of CO as solutions to time-dependent differential equations are derived, and a nonisothermal and cold kinetic temperature profile for the inner coma is considered.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 285; 858-869
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  • 66
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    Publikationsdatum: 2011-08-19
    Beschreibung: Four early-type supergiants - HD 79186 (B5 Ia), HD 96919 (B9 Ia), HD 105056 (ON9.7 Iae), and HD 148379 (B2 Iae) - have been observed with the low-resolution spectrographs of IUE in the large aperture on 14 days. The behavior of the ultraviolet fluxes with time is studied. The light from all four stars seems to vary. Typically the dispersion about the mean magnitude at any wavelength corresponds to + or - 0.085, + or - 0.080, + or - 0.101, and + or - 0.106 mag, respectively. These amplitudes exceed the typical uncertainty in an IUE measurement of flux by about a factor of 3; they are somewhat larger than the variations known in the visible wavelength range. There are insufficient data to investigate periodicity in the observed light changes. The effective temperatures and angular diameters of the stars have been estimated using the present ultraviolet photometry, published UBV and uvby photometry, and the model-atmosphere fluxes reported by Kurucz in 1979. The program stars have dimensions typical for their spectral types. A brief discussion is given of possible causes of the variability of hot supergiants.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 285; 668-673
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  • 67
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    Publikationsdatum: 2011-08-19
    Beschreibung: A modified form of the Lepping-Argentiero single spacecraft, shock normal determination procedure is presented. The modified method incorporates a simple predictor-corrector algorithm which allows a faster convergence rate and the use of average values of the parameters for the starting vector.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Journal of Geophysical Research (ISSN 0148-0227); 89; 11004-11
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  • 68
    Publikationsdatum: 2011-08-19
    Beschreibung: The large-scale radial and temporal variations of the interplanetary magnetic field strength B observed by Voyagers 1 and 2 are discussed. Two components of the magnetic field strength were considered: (1) an average component, B sub zero, based on solar rotation averages, and (2) a fluctuation component, delta B, expressed by 10- or 24-hour averages of B normalized by the best-fit average field for the corresponding time and distance. Observations of the sector structure, interfaces, and shocks are presented to further describe magnetic field strength.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Journal of Geophysical Research (ISSN 0148-0227); 89; 10659-10
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  • 69
    Publikationsdatum: 2011-08-19
    Beschreibung: The current investigation has the objective to provide data which will make it possible to obtain a better estimate regarding the roughness drag for surface waviness. The data employed for this investigation were acquired in connection with a wavy wall study which was conducted as part of an overall program to reduce the skin friction of turbulent boundary layers in external flows. The results of the present investigation show that the low-speed roughness drag of small-amplitude sinusoidal wave trains having wavelengths of the order of the boundary-layer thickness is not only a function of h/lambda (h = total wave height, lambda = wavelength), but, in addition, is also a function of the roughness Reynolds number.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Aircraft (ISSN 0021-8669); 21; 978
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  • 70
    Publikationsdatum: 2011-08-19
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: AIAA Journal (ISSN 0001-1452); 22; 1810-181
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  • 71
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    Publikationsdatum: 2011-08-19
    Beschreibung: Cyclotron emission in the inner regions of an accretion disk around a matter accreting black hole can be appreciable. In the case of the X-ray source Cyg X-1, cyclotron emission may provide the soft photons needed for 'Comptonization' to produce high energy X-rays. The inverse correlation between the fluxes of high energy and low energy X-rays during the 'high' and 'low' states of Cyg X-1, may be understood as a result of the variation of the rate of accretion and the Compton scattering of the cyclotron photons. In the case of the X-ray source GX 339-4, the observed optical flux during the high states does not seem to be due to cyclotron emission, but probably due to reprocessing of high energy X-rays by the outer regions of the disk.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astronomy and Astrophysics (ISSN 0004-6361); 139; 2, Oc
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  • 72
    Publikationsdatum: 2011-08-19
    Beschreibung: Observational results are presented from a new large-scale survey of the first quadrant of the galactic plane at wavelengths of 150, 250, and 300 microns, with a 10 x 10 arcmin beam. The emission detected in the survey arises from compact sources, most of which are identified with known peaks of 5 GHz or CO emission, or both, and from an underlying diffuse background with a typical angular width of about 0.9 deg (FWHM) which accounts for most of the emission. A total of 80 prominent discrete sources are identified and characterized, of which about half have not previously been reported at far-infrared wavelengths. The total infrared luminosity within the solar circle is about 1 to 2 x 10 to the 10th solar luminosity, and is probably emitted by dust that resides in molecular clouds.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 285; 74-88
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  • 73
    Publikationsdatum: 2011-08-19
    Beschreibung: The profile of the forbidden line of C III (1909) is the same in two pseudo-trailed, low-resolution SWP spectra of the nucleus of the Seyfert galaxy NGC 4151 obtained with the IUE in November 1980 and December 1982, respectively. In the 1980 spectrum, the C III forbidden line profile is also very nearly the same as that of the resonance line C IV (1550). In the 1982 spectrum, the continuum is 5 times higher and C IV is both much broader and much brighter. In the difference spectrum, which is interpreted to be the spectrum of a time-variable component, C IV (1550) is the only strong emission feature. The profile of this line closely resembles that of a spherical shell surrounding a less dense gas uniformly expanding from a central opaque object. From values of the profile parameters and from the observed time variability of the object, it is inferred that the shell has a radius of about 10 to the 15th cm, a mass of 0.25 solar mass, an expansion velocity of 13,000 km/s, and an electron density of 10 to the 11th per cu cm. From the line profile and the continuum, it is inferred that the opaque central source has approximate radius of 10 to the 14th cm and temperature 23,000 K.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 285; 69-73
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  • 74
    Publikationsdatum: 2011-08-19
    Beschreibung: A comparison of COS-B gamma-ray observations of the large complex of interstellar clouds in Orion and Monoceros with the Columbia CO and Berkeley H I surveys of this region reveals a good correlation between gamma-ray emission and total gas distribution. The observed gamma-ray emission is explainable in terms of interactions of cosmic rays that are uniformly distributed in this region with the interstellar gas. The correlation is used as the basis of a calibration of the ratio between H2 column density and the integrated CO line intensity; the value of (2.6 + or - 1.2) X 10 to the 20th mol/sq cm K km s thereby obtained is consistent with the value derived from a similar analysis for the inner galaxy.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astronomy and Astrophysics (ISSN 0004-6361); 139; 1, Oc
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  • 75
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    Publikationsdatum: 2011-08-18
    Beschreibung: The broad spectrum of turbulent motions observed in the interstellar medium may be produced by the shearing action of differential galactic rotation. A steady state eddy distribution is maintained as energy cascades down the eddy hierarchy to smaller-scale motions. The characteristic decay time for interstellar turbulence is found to be 50-billion yr. Objections frequently raised against the presence of long-lived turbulent motions in the interstellar medium are therefore invalid, since these arguments usually presuppose that there is no source of fresh turbulent energy.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 246
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  • 76
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    Publikationsdatum: 2011-08-18
    Beschreibung: The problem of forced fluid vibrations in a partially filled spinning spherical tank is solved numerically by using the finite element method. The governing equations include Coriolis acceleration and spatially homogeneous vorticity. An exponential instability is detected in the present simulation for fill ratios below 0.5 and centrifugal acceleration to thrust ratios less than 1.7. This fictitious instability appears in the model as a result of the homogeneous vortex assumption since the free slosh equations are neutrally stable in the Liapunov sense.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Sound and Vibration; 76; May 8
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  • 77
    Publikationsdatum: 2011-08-18
    Beschreibung: Previously reported enhanced soft X-ray emission from the North-Galactic Polar region supports the theory of a hot interstellar component. This paper reports the first detection of line emission from the hot interstellar component in the North-Galactic-Polar region. Measurements were made with solid state Si(Li) detectors aboard a spin-stabilized rocket launched from the White Sands Missile Range on March 22, 1980. Two features are clearly present in the low energy portion of the spectrum derived from the data. They correspond to emission lines from C V (300 eV) and C VI (360 eV), and from O VII (560 eV) and O VIII (650 eV). The detection of emission lines coming from these highly stripped ions is direct evidence for the thermal origin of the emission and confirms the presence of a hot (1-million K) component in the interstellar medium.
    Schlagwort(e): ASTROPHYSICS
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  • 78
    Publikationsdatum: 2011-08-18
    Beschreibung: Consideration is given to particle production and high-energy radiation within apparently superluminal radio components of extragalactic radio sources forming within the apparent region of nuclear activity of a quasar or active galaxy. The physical conditions in compact components observed as radio emitters are derived for the quasars 3C 273 and 3C 345 and extrapolated to those of initial components of sizes on the order of 10 to the 15th cm on the basis of two-dimensional relativistic jet and relativistic three-dimensional models of component expansion. Probabilities that a given particle avoids an inelastic collision in the relativistic plasma are calculated for both cases which show that collisions which produce particles and radiation may be very important during the formation of a compact radio component. The consequences of electron-positron production, bremsstrahlung and proton-proton inelastic collisions ultimately giving rise to neutrinos and gamma rays for the development and energetics of the radio component are then examined, and upper limits to the amount of energy which can be channeled into radio components from an active region without giving rise to a high-energy X-ray source are derived.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 245
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  • 79
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    Publikationsdatum: 2011-08-18
    Beschreibung: It is demonstrated that the X-ray flux from 2A 0311-227 is modulated at the 81 minute orbital period of its optical counterpart. An absorption dip with N sub H approximately equal to 5 x 10 to the 22nd H atoms per sq cm is observed at magnetic phase 0.42 that is interpreted as the accretion column of a magnetic white dwarf passing in front of the X-ray source. The spectrum is thermal with a temperature of 18 keV and a 300 eV equivalent-width iron line at 6.6 keV.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 244
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  • 80
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    Publikationsdatum: 2011-08-18
    Beschreibung: Solar flare models are briefly reviewed with emphasis on the physical mechanisms invoked to explain the flare. The physics of each mechanism and their interrelations are discussed in detail. Mechanisms are classified by their drivers (the source of energy on which they feed). The application of these mechanisms to coronal heating is evaluated.
    Schlagwort(e): ASTROPHYSICS
    Materialart: NASA. Goddard Space Flight Center The Sun as a Star; p 413-470
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  • 81
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    Publikationsdatum: 2011-08-18
    Beschreibung: The dynamics of the expanding corona are discussed emphasizing the physical processes which accelerate the plasma as it flows away from the Sun. The solar wind plays a dominant role in the energy balance of the part of the corona in which it originates. The wind acceleration processes, in large part, with the mechanisms that transport energy to the corona in the first place.
    Schlagwort(e): ASTROPHYSICS
    Materialart: NASA. Goddard Space Flight Center The Sun as a Star; p 373-384
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  • 82
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    Publikationsdatum: 2011-08-18
    Beschreibung: A theory to describe the observed photospheric 5 minute oscillations, chromospheric 3 minute oscillations, and possible motions of the interior with periods ranging from 40 to 160 minutes is discussed. It is similar to the theory of nonradial stellar oscillations developed to describe the low angluar order modes (one or two wavelengths around a circumference); however, the solar oscillations have thousands of wavelengths around a circumference. The properties of waves in stars, their restoring forces, periods and wavelengths, and their propagation and motions are discussed.
    Schlagwort(e): ASTROPHYSICS
    Materialart: NASA. Goddard Space Flight Center The Sun as a Star; p 263-287
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  • 83
    Publikationsdatum: 2011-08-18
    Beschreibung: This paper presents the results of a study of circumstellar gas and dust in a larger sample of stars than that of Hagen (1978). The gas-to-dust ratio varies considerably from star to star. The observations were obtained at Cerro Tololo Interamerican Observatory and Kitt Peak National Observatory. CS gas was observed with 2.5 and 5.1 A/mm echelle spectra obtained with the 4-meter telescopes. CS dust was observed through infrared photometry done with the CTIO 60 and KPNO 50 telescopes.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Smithsonian Astrophysics Observatory 2nd Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun, Vol. 1; p 231-238
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  • 84
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    Publikationsdatum: 2011-08-18
    Beschreibung: Global dynamo theory is applied to the problem of why some stars have field reversing dynamos, and others do not. It is argued that convectively driven dynamos are the most likely source of magnetic fields in stars that have convection zones.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Smithsonian Astrophysics Observatory 2nd Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun, Vol. 1; p 165-179
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  • 85
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    Publikationsdatum: 2011-08-18
    Beschreibung: Large amplitude shock waves are observed to be present in the atmospheres of the Mira variables: spectral line doubling with Delta v 30 km/s is present in infrared spectra. Even the visible spectra contain some evidence for such shocks. These shocks are sufficiently large to clearly dominate the energy balance of the atmosphere. Mira variables also show symptoms of substantial mass loss rates: they are strong maser and infrared continuum sources and have strong circumstellar absorption features. The pulsation induced shocks which are seen to be present are obvious suspects for causing or enhancing the mass loss from these stars. The Miras thus present an ideal case for the study of dynamical effects on atmospheric structure, since both the dynamics and the results are clearly observable. The results are given of calculations of the thermalization and cooling of the shock heated material passing through shock fronts whose properties were selected to be consistent with both the isothermal models and the spectroscopic observations.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Smithsonian Astrophysics Observatory 2nd Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun, Vol. 1; p 147-151
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  • 86
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    Publikationsdatum: 2011-08-18
    Beschreibung: There is now an increasing amount of both observational evidence and theoretical arguments that regions of partially ionized hydrogen extending several stellar radii are an important feature of red giant and supergiant stars. This evidence is discussed and the implications of the existence of extended chromospheres in terms of the nature of the outer atmospheres of, and mass loss from, cool stars are examined.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Smithsonian Astrophysics Observatory 2nd Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun, Vol. 1; p 137-145
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  • 87
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    Publikationsdatum: 2011-08-18
    Beschreibung: Observations at ultraviolet and X-ray wavelengths indicate that the classical picture of a static stellar atmosphere containing a radiative equilibrium temperature distribution is inapplicable to the majority of late type stars. Mass loss and the presence of atmospheric regions characterized by gas temperatures in excess of the stellar effective temperature appear to be almost ubiquitous throughout the HR diagram. Evidence pertaining to the thermal and dynamical structure of the outer envelopes of cool stars is summarized. These results are compared with the predictions of several theoretical models which were proposed to account for mass loss from latetype stars. Models in which the outflow is thermally radiatively, or wave driven are considered for identification of the physical processes responsible for the observed wind properties. The observed variation of both the wind, thermal and dynamical structure as one proceeds from the supergiant branch toward the main sequence in the cool portion of the HR diagram give consideration to potential mechanisms for heating and cooling the flow from low gravity stars.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Smithsonian Astrophysics Observatory 2nd Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun, Vol. 1; p 83-97
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  • 88
    Publikationsdatum: 2011-08-18
    Beschreibung: The atmospheric structure of the dwarf M-stars which is especially important to the general field of stellar chromospheres and coronae was investigated. The M-dwarf stars constitute a class of objects for which the discrepancy between the predictions of the acoustic wave chromospheric/coronal heating hypothesis and the observations is most vivid. It is assumed that they represent a class of stars where alternative atmospheric heating mechanisms, presumably magnetically related, are most clearly manifested. Ascertainment of the validity of a hypothesis to account for the origin of the chromospheric and transition region line emission in M-dwarf stars is proposed.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Smithsonian Astrophysics Observatory 2nd Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun, Vol. 1; p 73-79
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  • 89
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    Publikationsdatum: 2011-08-18
    Beschreibung: The heating of stellar chromospheres and coronae by the dissipation of acoustic waves is an important heating mechanism. It is only in the lower solar chromosphere that short period acoustic wave heating seems undisputed. The arguments leading to the rejection of the so called acoustic heating theory are derived from comparisons of calculated acoustic energy fluxes with observational or theoretical requirements.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Smithsonian Astrophysics Observatory 2nd Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun, Vol. 1; p 67-72
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  • 90
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    Publikationsdatum: 2011-08-18
    Beschreibung: An analysis is presented of the hydrodynamic aspects of the growth of protostellar disks from the accretion of a rotating gas cloud. Streamline equations for the flow onto the disk are derived, including the special case where the disk is very thin. For the radial structure of the disk, detailed equations of conservation of mass, momentum, angular momentum, and energy are given. Exact solutions are found for the case of no internal viscosity. For the more general case where there is viscous stress, hypotheses are formulated with the objective of discovering the main qualitative characteristics of a turbulent system and to estimate the magnitude of the turbulent stress. Solutions are also found for boundary conditions, and the large and small viscosity limits. The relation of energy balance to disk thermal structure is detailed. Finally, trends in the collapse of the dust cloud are discussed in the light of the solutions given.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Icarus; 48; Dec. 198
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  • 91
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    Publikationsdatum: 2011-08-18
    Beschreibung: UV observations using the IUE are employed to discuss the strength and changes of Zeta Aur between a second contact and mid-eclipse in 1979, the relative visibility of the supergiant's chromosphere as compared with the circumstellar (CS) nebular scattering of the B star photons, and the origin of the high speed CS components observed at all orbital phases. Agreement has been found for a spectoscopic radius of 200 solar radii and a 400 pc distance, and eclipse emission lines were recorded from 1238.9-2802.7 microns. An asymmetry in the Fe III lines at 46 plus or minus 15 km/sec was seen during eclipse and is taken to indicate downflowing material. The high speed wind flowing from the K supergiant is thought to expand homogeneously until encountering the B type main sequence star, where an accretion bow shock forms, and the smaller star's passage near the K star at periastron may cause local surface heating and subsequent high speed flows.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 251
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  • 92
    Publikationsdatum: 2011-08-18
    Beschreibung: Two-dimensional maps of the Crab Nebula have been synthesized in 22-64 keV range through the modulation collimator experiment. The effective angular resolution is about 15-arcmin. The result indicates that the Crab morphology is strictly controlled by the pulsar.
    Schlagwort(e): ASTROPHYSICS
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  • 93
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    Publikationsdatum: 2011-08-18
    Beschreibung: A calculation is made of the flux of secondary antiprotons expected for the leaky box model and for the closed galaxy model of Peters and Westergaard (1977). The antiproton/proton ratio observed at several GeV is a factor of 4 higher than the prediction for the leaky box model but is consistent with that predicted for the closed galaxy model. It is found that new low-energy data are not consistent with either model. Attention is given to the possibility of a primary antiproton component.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 251
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 94
    Publikationsdatum: 2011-08-18
    Beschreibung: The 4.8 hour X-ray light curve of Cygnus X-3 is quantitatively described by several proposed models under the assumption that the binary orbit of Cyg X-3 is elliptic. The cocoon model implies an apparent size for the X-ray star's companion, which is larger than that of its critical lobe, and it is suggested that the emission of a dense stellar wind by the companion could lead to such a situation. It is shown that a helium star, with or without a hydrogen-rich envelope, seems to be the most likely Cyg X-3 companion, and that some of the observed variations in the 4.8 hour period can be accounted for by the apparent period variations due to apsidal motion.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 251
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 95
    Publikationsdatum: 2011-08-18
    Beschreibung: Predicted brightness temperatures, computed by means of radiative transfer techniques adapted from the modeling of terrestrial ice and snow fields, are given for cometary nucleus models consisting of homogeneous layers of water ice and refractory grain mixtures presented as functions of wavelength. The computed millimeter-wave spectra are sensitive to the values of such physically significant nucleus parameters as (1) crust thickness, (2) subsurface temperature gradient, and (3) sublimating surface boundary temperature. Although antenna beam dilution is a major obstacle for ground-based molecular spectral line radio observations of comets, a millimeter-wave radiometer in the vicinity of the comet would be immune to this effect and able to make observations of several candidate parent molecules in the gas phase.
    Schlagwort(e): ASTROPHYSICS
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 96
    Publikationsdatum: 2011-08-18
    Beschreibung: Measurements in the 0.1-2.5 micron range are presented for the reflectance spectra of the frosts of several volatiles pertinent to the study of comet nuclei. The frost spectra have distinctive features permitting their identification by spectroscopic reflectance remote sensing, notably in the far UV. It is found that: (1) H2O has a minimum at 0.16 microns and a maximum at 0.13 microns; (2) CO2 has minima near 0.21, 0.18 and 0.125 microns, with maxima at 0.19, 0.135 and 0.120 microns; (3) NH3 is bright at wavelengths longer than 0.21 microns, where reflectance drops to a value of only a few per cent at shorter wavelengths; (4) SO2 has a sharp drop at 0.32 microns, with a minimum at 0.18 microns and a maximum at 0.13 microns. The features in the frost spectra largely correspond to absorption line bands in the gas phase.
    Schlagwort(e): ASTROPHYSICS
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 97
    facet.materialart.
    Unbekannt
    In:  Other Sources
    Publikationsdatum: 2011-08-18
    Beschreibung: A numerical hydrodynamics code has been used to calculate the collapse of rotating, adiabatic clouds. The three-dimensional nature of the calculation allows the clouds to fragment in the dynamic collapse phase. Clouds with adiabatic exponent of 7/5 and initial cos(2 phi) density variations fragment into binary systems if the initial ratio of thermal to gravitational energy is small (about 0.05). Clouds with higher thermal energy, however, damp the density variation and form near-equilibrium ellipsoids, with ratios of rotational to gravitational energy less than the critical value for dynamic growth of nonaxisymmetry in Maclaurin spheroids. Even with an adiabatic pressure law, dynamic fragmentation of a collapsing cloud is possible, implying for star formation theory that the low thermal energy fragments produced in isothermal collapse calculations may undergo a subsequent dynamic fragmentation in the nonisothermal regime.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 250
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 98
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    Unbekannt
    In:  Other Sources
    Publikationsdatum: 2011-08-18
    Beschreibung: Heat transfer characteristics are analyzed for a cooled two-dimensional porous medium having a curved boundary. A general analytical procedure is given in combination with a numerical conformal mapping method used to transform the porous region into an upper half plane. To illustrate the method, results are evaluated for a cosine shaped boundary subjected to uniform external heating. The results show the effects of coolant starvation in the thick regions of the medium, and the extent that internal heat conduction causes the heated surface to have a more uniform temperature.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 99
    Publikationsdatum: 2011-08-18
    Beschreibung: Observations of SS433 made on June 12, 1979, from West Germany, Massachusetts, and West Virginia are discussed. It is noted that SS433 did not show fringes on any baseline although all the calibration sources were seen at their expected strengths. The measured total flux density of SS433 was found to be approximately 0.5 Jy, consistent with previous observations. The source was observed by on-offs at each telescope, which indicates that they were all pointed properly during the observations. The absence of fringes is not attributed to poor observing conditions or instrumental difficulties. It is concluded that if all the 10.65 GHz radiation emanates from a single component, then that component is at least 0.005 arcsec (approximately 10 to the 14th cm) in size. The measurements made on more sensitive intercontinental baselines indicate that there is no component of SS433 smaller than 0.001 arcsec emitting 10.65 GHz radiation above a level of 50 mJy.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astronomy and Astrophysics; 98; 1, Ma; May 1981
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 100
    facet.materialart.
    Unbekannt
    In:  Other Sources
    Publikationsdatum: 2011-08-18
    Beschreibung: The behavior of luminosity-distance with redshift is analyzed within the framework of homogeneous zero-pressure relativistic cosmology. de Sitter's model is shown to have the most redshift sensitive luminosity-distance function of all cosmologies which have q sub 0 not less than -1. Quasar data which suggest a cut-off in absolute luminosity are reanalyzed and the cut-off disappears if either de Sitter's model or the assumption L(L-alpha) = 3 L(H-beta) is used.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Royal Astronomical Society; vol. 195
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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