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  • ASTROPHYSICS  (826)
  • Organic Chemistry  (765)
  • AERODYNAMICS  (546)
  • FLUID MECHANICS AND HEAT TRANSFER  (498)
  • 42.75
  • 1985-1989  (2,635)
  • 1950-1954
  • 1988  (2,635)
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Keywords
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  • 1985-1989  (2,635)
  • 1950-1954
Year
  • 1
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    Carbon and nitrogen lines in the spectra of Wolf-Rayet stars (1988)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The one-representative-point radiative transfer theory of Castor and van Blerkom (1970) is used to predict the relative energies in emission lines of the ions of carbon and nitrogen in Wolf-Rayet atmospheres for a wide range of parameters. The predicted ratios are compared with observed relative energies of lines in the visible and ultraviolet spectral ranges of six Wolf-Rayet stars. It is found that the lower levels of C II, C III, N III, and N IV are strongly overpopulated relative to their populations in LTE. The differences between WC and WN spectra appear to be due chiefly to a difference in electron temperature in the line-emitting regions. The typical volume of stars studied is estimated to be in the range of 10 to the 41st to 10 to the 44th cu cm. Possible ways in which the line-emitting regions may be arranged around the star are discussed, noting that the high-temperature line-emitting plasma may lie in a thin annular disk approximately 10 to the 15th cm from the star.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal Supplement Series (ISSN 0067-0049); 67; 187-223
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  • 2
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    Bow shocks and bubbles are seen around hot stars by IRAS (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Examination of the IRAS all-sky imagery reveals extended, arcuate, and ringlike features associated with hot luminous stars. They fall into a number of classes: stellar wind bow shocks, stellar wind bubbles, dust shells, dust heated by isolated B stars, bright rims, and dust in H II regions. Here, some objects are discussed in which the star exercises structural control over the spatial distribution of dust: bow shocks, bubbles, and radiation pressure-driven shells. A list of the 15 most prominent objects is presented, a few prototypes are shown, and their characteristics are explained in terms of thermal emission processes and gasdynamics.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 329; L93-L96
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  • 3
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    Bimodal abundances in the energetic particles of solar and interplanetary origin (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: This letter reports the first results from an examination of the daily-averaged abundances of the elements from H through Fe as well as electrons and isotopes of He in energetic particles observed in interplanetary space by the ISEE 3 spacecraft over an 8.5 yr period. The abundances of heavy elements such as Fe/O show, for the first time, clear evidence of the presence of two distinct populations of particles. Earlier observations could be interpreted as extreme variations within a single population. The population with enhanced Fe/O shows correlated enhancements in He-3/He-4, p/e, and He/H. This population is consistent with material that has been processed to high temperatures in the impulsively heated regions of solar flares. The second population, with more normal abundances, is probably accelerated from ambient material by coronal and interplanetary shocks.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 330; L71-L75
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  • 4
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    Theoretical infrared spectra of SN 1987A (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A simple model for the ejecta of SN 1987A is used to show that the expected fluxes in infared fine structure lines from nickel, cobalt, iron, argon, sulfur, silicon, and neon are likely to be detectable for several years following the supernova explosion. Energy sources due to radioactive decay and a central pulsar are considered separately. Most of the mass of heavy elements resides in the inner, pure metal shells of the ejecta, so that the infrared lines will probe the temperature, ejecta masses, and dynamics of this region and not the overlying, hydrogen-rich envelope.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 329; L25-L28
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  • 5
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    Laboratory studies of the infrared spectral propertries of CO in astrophysical ices (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The spectral properties of CO in various ices are presented. Included are peak positions, FWHMs, band profiles, and integrated absorbances of the CO fundamental at 2137/cm in different ices under various conditions. The results reveal that good quality moderate-resolution spectra of the interstellar CO feature can be used to unravel the composition, temperature, and thermal history of interstellar and cometary ices containing CO.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 329; 498-510
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  • 6
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    A direct interaction approximation treatment of turbulence in a compressible fluid. I - Formalism (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The direct interaction approximation is used to treat turbulence in a compressible medium with constant mean gradients. The set of coupled nonlinear integrodifferential equations is derived that is satisfied by the transverse and longitudinal energy spectral functions, Q(T) and Q(L) and by the transverse and longitudinal response functions, G(T) and G(L). Finally, expressions for the average of the product of pairs of physically relevant fluctuating quantities (velocity, temperature, density) are derived in terms of Q(T) and Q(L).
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Physics of Fluids (ISSN 0031-9171); 31; 1034-105
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  • 7
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    A catalog of interplanetary type III storms (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A catalog describing the characteristics of all the interplanetary type III storms observed at kilometric wavelengths by the radio astronomy experiment on the ISEE-3 spacecraft between September 1978 and October 1982 is presented. Three-dimensional trajectories have been determined for about one-third of these storms using radio techniques. Solar coordinate and solar wind parameters derived from the trajectories are also tabulated. A statistical summary of the data is included.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics Supplement Series (ISSN 0365-0138); 73; 2, Ma
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  • 8
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    Generalized energy and potential enstrophy conserving finite difference schemes for the shallow water equations (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The conditions under which finite difference schemes for the shallow water equations can conserve both total energy and potential enstrophy are considered. A method of deriving such schemes using operator formalism is developed. Several such schemes are derived for the A-, B- and C-grids. The derived schemes include second-order schemes and pseudo-fourth-order schemes. The simplest B-grid pseudo-fourth-order schemes are presented.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Monthly Weather Review (ISSN 0027-0644); 116; 650-662
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  • 9
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    Radio properties of the highly polarized, quiescent quasar OI 287 (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The highly polarized, quiescent quasar OI 287 has been observed with high resolution at 2 cm and 6 cm in an effort to determine the origin of some of the object's peculiar properties. The results seem to rule out the classification of OI 287 as a blazar. Extrapolation of the radio core spectrum to midinfrared wavelengths fails to predict the infrared flux by at least an order of magnitude. This supports the conclusion that the infrared emission and the radio emission do not originate in the same synchrotron-emitting component. The high optical polarization could be related to possible broad absorption lines in the unobserved UV regime, or it could be caused by reflection into the line of sight by scattering agents distributed in a thin disk.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 328; 569-577
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  • 10
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    X-ray and gamma-ray emissions expected from supernova 1987A (1988)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The X-ray and gamma-ray spectra expected from SN 1987A have been calculated. Results for the TWOBF7 model are inconsistent with Ginga observation, but the X-ray flux and its spectral shape strongly depend on the chemical composition and expansion velocity of the ejecta. The distributions of density and chemical compositions for SN 1987A are described. For the TWOBF7 model, the X-ray flux between 10 and 20 keV reaches a peak of 6.7 photons/s/sq m about 1 yr after the explosion. For the 15B5 model, the peak flux is larger by a factor of five. The implications of the Ginga satellite's detection of an excess X-ray flux from the direction of the supernova for the models of SN 1987A are considered. How observations of gamma-ray lines can determine the optical thickness of the expanding shell is discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 328; 699-703
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  • 11
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    R Aquarii - The large-scale optical nebula and the Mira variable position (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The R Aquarii symbiotic star system is surrounded by a large-scale optical nebula. Observations of the nebular forbidden O III structure are presented and its morphological significance are discussed in context with previously observed small-scale radio-continuum features, which may be related. It is suggested that a precessing accretion disk may explain the global features of both the large-scale optical emission and the small-scale radio emission. Moreover, an accurate position has been determined of the system's Mira, which suggests that a recent theoretical model, yielding an egg-shaped central H II region for symbiotic systems with certain physical parameters, may apply to R Aquarii. The optical position of the 387 d period Mira variable is consistent with previous findings in the radio, that SiO maser emission is far removed from the Mira photosphere.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal (ISSN 0004-6256); 95; 1478-148
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  • 12
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    Axions from 1987A (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The process of axion emission from SN 1987A by nucleon-nucleon axion bremsstrahlung is investigated based on neutrino observations. The results indicate that the axion luminosity must be less than about 10 to the 53rd erg/s if: (1) axions couple very weakly (with an axion mass of less than about 0.75 x 10 to the -3rd); or (2) axions couple strongly enough to be trapped and radiated from an axion sphere with T sub a of less than about 8 MeV (with an axion mass of greater than about 2.2 eV). Axion trapping is found to occur for axion masses of greater than about 0.016 eV.
    Keywords: ASTROPHYSICS
    Type: Physical Review Letters (ISSN 0031-9007); 60; 1797-180
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  • 13
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    Turbulent diffusivity (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A method for determining the turbulent diffusivity tensor is proposed which has application to problems such as the mixing in the interior of the sun for the solar neutrino problem, the chemical evolution of the galaxy, and grain sedimentation on the primitive solar nebula. A model for determining the turbulent energy spectral function, the eddy decorrelation rate, and the growth rate of the underlying instability is discussed. Good agreement is obtained between the present values for the coefficient of turbulent diffusivity and those obtained from both numerical simulation studies and laboratory data on shear turbulence.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 193; 1-2,
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  • 14
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    Self-similar dynamics of polytropic gaseous spheres (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The fundamental equations governing the self-similar dynamics of 'polytropic' gaseous spheres are derived, and the asymptotic solutions are given. The solutions divide into cases with and without 'critical points' in closed analogy with the solar wind solutions of Holzer and Axford (1970). Properties for solutions with critical points are discussed, and their behavior around the critical point is derived explicitly for n = 1. Numerical examples of self-similar solutions for n = 1 and n = 2 - gamma are presented, and the properties of the solutions are discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 326; 527-538
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  • 15
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    The microwave spectrum of asteroid Ceres (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: This paper presents new measurements of the microwave flux of Ceres obtained at wavelengths between 3.3 mm and 20 cm using the 12 m Kitt Peak antenna and the Very Large Array. These new measurements are combined with previous measurements to confirm a substantial decrease in flux density at centimeter wavelengths compared to millimeter wavelength. Using a statistical technique adapted from terrestrial microwave remote sensing, this spectrum has been compared with that of various candidate materials and models for the subsurface structure of Ceres. It is concluded that Ceres is largely covered with a 3-cm-thick layer whose dielectric properties resemble dry terrestrial clay. This layer may have formed by micrometeorite impact on hydrothermally altered basic or ultrabasic rock or on carbonaceous chondrite material.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal (ISSN 0004-6256); 95; 1263-126
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  • 16
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    Images of star-forming regions. II - The circumstellar environment of L1551 IRS 5 (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The circumstellar environment of L 1551 IRS 5 is investigated based on high-resolution 8000 A (i) and 9000 A (z) broadband CCD images. A small conical reflection nebula extending from a bright semistellar knot located near the cusp of the nebula is noted. It is suggested that the point-like structure at lambda of less than about 3.7 microns may represent a bright knot of dust-scattered light located on the inner surface of a flattened circumstellar disk surrounding the radio source. Evidence is found of sharp changes in the position angle of the jet emanating from IRS 5, possibly resulting from precession of the jet nozzle provided by a dense inner disk which has dynamically decoupled from the much larger flattened molecular structure.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal (ISSN 0004-6256); 95; 1173-118
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  • 17
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    The ultraviolet spectra of M31 globular clusters (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Ultraviolet spectra of 11 of the brightest globular clusters in M31 show that some exhibit residual flux below 3000 A, greater than that expected from the bright, evolved stars in the cluster. There seems to be no apparent correlation of the strength of this ultraviolet flux with parameters such as metallicity, U-B color, visual magnitude, X-ray emission, or location within the parent galaxy. However, comparison of the ultraviolet colors of the M31 globular clusters with those in the Galaxy and in the Large Magellanic Cloud suggests that the M31 clusters may contain a high percentage of blue horizontal-branch stars or that some clusters could be as young as about 2 x 10 to the 9th yr.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal (ISSN 0004-6256); 95; 1071-108
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  • 18
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    Evidence for a radio flare in the nucleus of Virgo A (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: An increase in radio emission has been observed in the nucleus of the galaxy Virgo A by use of VLBI measurements. These 2.29 GHz observations show that the correlated flux density of the milliarcsec structure increased by 30 percent during a four month period in 1977, and eventually returned to the preflare level of about 0.6 Jy. Previous evidence had indicated that the nuclear radio emission was stable, a surprising result for an active galactic nucleus.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal (ISSN 0004-6256); 95; 1037-103
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  • 19
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    Alignments of brightest cluster galaxies with large-scale structures (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Using an independent sample of brightest galaxies in rich clusters in the southern galactic hemisphere, the Argyres et al. (1986) result that galaxy counts on scales to at least 15/h Mpc are systematically higher in the direction of the major axes of brightest cluster galaxies is confirmed.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal (ISSN 0004-6256); 95; 996-998
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  • 20
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    Statistics of galaxy orientations - Morphology and large-scale structure (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Using the Uppsala General Catalog of bright galaxies and the northern and southern maps of the Lick counts of galaxies, statistical evidence of a morphology-orientation effect is found. Major axes of elliptical galaxies are preferentially oriented along the large-scale features of the Lick maps. However, the orientations of the major axes of spiral and lenticular galaxies show no clear signs of significant nonrandom behavior at a level of less than about one-fifth of the effect seen for ellipticals. The angular scale of the detected alignment effect for Uppsala ellipticals extends to at least theta of about 2 deg, which at a redshift of z of about 0.02 corresponds to a linear scale of about 2/h Mpc.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal (ISSN 0004-6256); 95; 975-984
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  • 21
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    Renormalization-group theory for the eddy viscosity in subgrid modeling (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Renormalization-group theory is applied to incompressible three-dimensional Navier-Stokes turbulence so as to eliminate unresolvable small scales. The renormalized Navier-Stokes equation now includes a triple nonlinearity with the eddy viscosity exhibiting a mild cusp behavior, in qualitative agreement with the test-field model results of Kraichnan. For the cusp behavior to arise, not only is the triple nonlinearity necessary but the effects of pressure must be incorporated in the triple term. The renormalized eddy viscosity will not exhibit a cusp behavior if it is assumed that a spectral gap exists between the large and small scales.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Physical Review A - General Physics, 3rd Series (ISSN 0556-2791); 37; 2590-259
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  • 22
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    Indirect IUE observation of O VI from photoexcited fluorescence lines of Fe II, present in the spectrum of RR Telescopii (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A new, highly excited level of Fe II at 13.7 eV has been established by means of six lines in the laboratory spectrum below 2000 A. Confirming transitions appear in the infrared region. Four of the ultraviolet lines coincide with previously unidentified lines in the IUE spectrum of RR Tel reported by Penston et al. in 1983. One of the remaining UV lines coincides with the resonance line of O VI at 1032 A, outside the range of the IUE. This suggests that the new FE II level is selectively photoexcited by O VI in RR Tel, resulting in the strong fluorescence lines observed. This case of a Bowen mechanism provides an indirect observation of O VI, important for diagnostics of, e.g., symbiotic stars.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 327; L85-L88
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  • 23
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    On nonsteady accretion in stellar wind-fed X-ray sources (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The paper reports on the results of hydrodynamical simulations of nonaxisymmetric gas flow past a finite-sized gravitating object. The asymmetry in the flow is assumed to be due to a transverse density gradient. The solutions are found to be highly time-dependent and exhibit phases in which a disk forms. The direction of circulation of the disk alternates between the direct and counter sense on time scales of approximately 1 hr. While the disk is present, the specific angular momentum is high, and the mass accretion rate, low. The angular momentum capture oscillates about a mean which secularly increases. Such temporal behavior may be relevant to those X-ray pulsing systems (e.g., Vela X-1) which exhibit fluctuations in the X-ray luminosity and pulse period on time scales much shorter than the orbital period of the binary system.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 327; L73-L76
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  • 24
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    Moment constraints on physical models for quasi-periodic oscillations from Galactic X-ray sources (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Shot-noise models provide a useful mathematical representation for some physical models for the quasi-periodic oscillations (QPOs) recently observed from several bright Galactic bulge and burst X-ray sources. Expressions are calculated for the first three moments for several versions of QPO shot-noise models that have appeared in the literature. It is shown that measurement of the third moment, together with measurement of the mean intensity and the power spectrum, can provide model-dependent constraints on important parameters of QPO shot-noise models, including the fraction of the X-ray intensity in shots and the shot rate. Under certain condtitions, a complete solution for all the shot-model parameters is possible.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 327; 742-749
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  • 25
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    Primordial lithium - New reaction rates, new abundances, new constraints (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Newly measured nuclear reaction rates for H-3(alpha, gamma)Li-7 (higher than previous values) and Li-7(p, alpha)He-4 (lower than previous values) are shown to increase the Li-7 yield from big band nucleosynthesis for lower baryon-to-photon ratio (less than about 4 x 10 to the 10th). Recent revisions in the He-3(alpha, gamma)Be-7 and the D(p, gamma)He-3 rates enhance the high (greater than 4 x 10 to the 10th) Li-7(Be) production. New, independent determinations of Li abundances in extreme population II stars are in excellent agreement with the work of Spites and give continued confidence in the use of Li-7 in big bang baryon density determinations.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 327; 750-754
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  • 26
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    Ultraviolet spectroscopy of the 'jetlike' condensations of NGC 4151 (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The spectrometers aboard the IUE are used to obtain UV spectroscopy of the jetlike condensations seen extending 18 arcsec from the nucleus of the nearby Seyfert 1 galaxy NGC 4151. New data reduction techniques are used to detect, delineate, and measure weak nebular emission in IUE spectra. Spatially resolved extended emission is seen in both semiforbidden C III 1909 A and C IV 1549 A. The deduced integrated fluxes in the jet are 10 to the 14th and 4 x 10 to the 14th ergs/sq cm/s for C III and C IV, respectively. The observed fluxes are compared with predictions based upon a central source photoionization model. The implied high C IV/C III flux ratio is shown to be inconsistent with this model and suggests an additional source of ionization for the jet.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 327; 664-670
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  • 27
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    Cosmic strings and the microwave sky. I - Anisotropy from moving strings (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A method is developed for calculating the component of the microwave anisotropy around cosmic string loops due to their rapidly changing gravitational fields. The method is only valid for impact parameters from the string much smaller than the horizon size at the time the photon passes the string. The method makes it possible to calculate the temperature pattern around arbitrary string configurations numerically in terms of one-dimensional integrals. This method is applied to temperature jump across a string, confirming and extending previous work. It is also applied to cusps and kinks on strings, and to determining the temperature pattern far from a strong loop. The temperature pattern around a few loop configurations is explicitly calculated. Comparisons with the work of Brandenberger et al. (1986) indicates that they have overestimated the MBR anisotropy from gravitational radiation emitted from loops.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 327; 584-614
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  • 28
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    The centring dynamics of a thin liquid shell in capillary oscillations (1988)
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    Publication Date: 2011-08-19
    Description: The physical mechanism governing the centring of a hollow liquid shell in capillary oscillations, which has been observed in experiments, is investigated theoretically. First, the shell is assumed to be inviscid and to have a thickness that is much less than its spherical radius. A system of one-dimensional nonlinear equations of motion is derived using a thin-sheet model. From a numerical study the nonlinear effects of the wave are found to cause the core to oscillate slowly relative to the shell while the centre of mass of the whole system remains stationary. The effects of small viscosity are then considered in an approximation. Finally the strength of the centring mechanism is compared with that of the decentring effect due to buoyancy. The findings are consistent with the limited experimental information available.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Fluid Mechanics (ISSN 0022-1120); 188; 411-435
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  • 29
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    Developing fluid flow in a curved duct of square cross-section and its fully developed dual solutions (1988)
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    Publication Date: 2011-08-19
    Description: Developing fluid flow in a curved duct of square cross-section is studied numerically by a factored ADI finite-difference method on a staggered grid. A central-difference scheme with primitive variables is used inside the computational domain to reduce numerical diffusion. Two Reynolds numbers, 574 and 790, based upon a bulk velocity and hydraulic diameter are chosen for curvature ratios of 1/6.45 and 1/2.3, respectively. It is found that the secondary flow is far more complicated than expected, with the appearance of at least two pairs of vortices. Main-flow separation is also observed for the higher curvature ratio. Furthermore, it is observed that the flow develops into two quite different states downstream, depending upon the inlet conditions. Solutions of the fully developed Navier-Stokes equations is shown to be not unique beyond a certain critical Reynolds number. Developing flow seems to evolve into the fully developed state along a particular branch into which the fully developed solution bifurcates.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Fluid Mechanics (ISSN 0022-1120); 188; 337-361
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    Multiphase flow in porous media (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A development history and current status evaluation are presented for the theory of permeability and percolation. The microscale phenomena treated in this field have proven difficult to analyze due both to their tortuous geometry and the influence of capilarity. Capilary effects may be not only important but predominant, and are differentiated into those at the fluid-fluid interface, and those involving the existence of a contact line between the solid substrate and this interface. Percolation theory has been borrowed from physics and adapted to the two-phase engineering context.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
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  • 31
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    The detection of high-velocity outflows from M8E-IR (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A high-resolution (0.059/cm) M band (4.6 micron) spectrum of the embedded young stellar object M8E-IR is presented and discussed. The spectrum shows strong absorption to large blueshifts in the rotational lines of the fundamental vibrational band, v = 1-0, of CO. The absorption is interpreted as being due to gas near to, and flowing from, the central object. The outflowing gas is warm (95-330 K) and consists of discrete velocity components with the very high velocities of 90, 130, 150, and 160 km/s. On the basis of a simple model, it is estimated that the observed outflows are less than 100 yr old.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 327; L17-L21
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  • 32
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    The effects of mixing of the ejecta on the gamma-ray lines from SN 1987A (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Mixing of matter in the ejecta is suggested by hydrodynamical calculations for SN 1987A. The X-ray flux calculated including mixing reproduces well the observed X-ray light curve and spectra. The effects of mixing on the gamma-ray lines have been estimated. The line fluxes at times less than 1.5 yr after the explosion strongly depend on mixing, and are greatly increased for values of the mixed mass larger than 4 solar masses. The peak advances to an earlier time and its flux is also greatly enhanced. If 5 solar masses are adopted for the mixed mass, as suggested from the X-ray calculations, the 847 keV line will reach its peak around 1.1 yr after the explosion with flux of 0.00086 photons/sq cm per s. If the mixed mass is less than 4 solar masses, the mixing effect becomes less prominent. The gamma-ray lines expected from SN 1987A should be observable. The way in which gamma-ray line observations can be used to diagnose properties of the ejecta is discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 327; L9-L12
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    A bound on X-ray emission from the intrasupercluster medium (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The Bahcall-Soneira (1984) complete sample of superclusters was searched for X-ray emission in the HEAO 1 A-2 data base. No statistically significant emission from diffuse intrasupercluster gas was detected; a 3-sigma upper limit to the mean individual flux is 10 to the -11th ergs/sq cm per s. Implications of this bound to measurements of the Zeldovich-Sunyaev (1969) effect toward clusters within a supercluster and to the supercluster contribution to the cosmic X-ray background are discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 327; L1-L3
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  • 34
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    The effects of mixing of the ejecta on the hard X-ray emissions from SN 1987A (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The X-ray and gamma-ray emissions expected from SN 1987A have been calculated, taking into account mixing of material in the ejecta. Nuclear gamma rays emitted by Co-56 are scattered down to the hard X-ray band by multiple Compton scatterings. Nomoto's 11E1Y6 model for the ejecta of SN 1987A is used. X-ray light curves in the 10-30 keV band and spectra above 20 keV calculated with an inner mixed region of 5 + or - 1 solar mass are consistent with the observations performed with the Ginga satellite and the Kvant/Roentgen mission. On the basis of this comparison, further evolutions of the hard X-ray, gamma-ray, and optical/infrared emissions are discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 327; L5-L8
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  • 35
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    Light echoes - Novae (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The sudden brilliance of a nova eruption will be reflected on surrounding dust grains to create a phantom nebula. Previous searches for these light echoes have used relatively short exposures with photograhic detectors. This paper reports on a search around eight recent novae with long exposures using a CCD camera. Despite an increase of sensitivity by over an order of magnitude, no light echoes were detected. It is found that the average grain density must be less than about 10 to the -9th per cu cm for distances from 0.1 pc to 1000 pc from the novae. The light echo around Nova Persei 1901 was caused by reflection off clouds with grain densities of several times 10 to the -9th per cu cm which are at distances between 0.1 pc and 10 pc. Echoes from dust in a circumstellar shell or ejected during a previous eruption will be effectively unobservable.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 327; 347-349
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  • 36
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    The extended atmosphere of Lambda Pavonis at the time of the emergence of H-emissions from minimum intensity (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A study of the Be star Lambda Pavonis, particularly of the changes in the Balmer discontinuity in the interval 1949-1982, is presented. Nearly simultaneous observations carried out with the ESO 1.5 m reflector at La Silla and with the IUE satellite correspond to an epoch when the H emission is starting to increase intensity immediately after having reached its minimum strength. These observations suggest the presence of four distinct regions of line formation, with the material moving outward in the transition region.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 327; 335-341
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  • 37
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    The effect of a hot, spherical scattering cloud on quasi-periodic oscillation behavior (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A Monte Carlo technique is used to investigate the effects of a hot electron scattering cloud surrounding a time-dependent X-ray source. Results are presented for the time-averaged emergent energy spectra and the mean residence time in the cloud as a function of energy. Moreover, after Fourier transforming the scattering Green's function, it is shown how the cloud affects both the observed power spectrum of a time-dependent source and the cross spectrum (Fourier transform of a cross correlation between energy bands). It is found that the power spectra intrinsic to the source are related to those observed by a relatively simple frequency-dependent multiplicative factor (a transmission function). The cloud can severely attenuate high frequencies in the power spectra, depending on optical depth, and, at lower frequencies, the transmission function has roughly a Lorentzian shape. It is also found that if the intrinsic energy spectrum is constant in time, the phase of the cross spectrum is determined entirely by scattering. Finally, the implications of the results for studies of the X-ray quasi-periodic oscillators are discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 327; 284-293
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  • 38
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    Force and pressure study of thick cambered/twisted 58 deg delta wings (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft (ISSN 0021-8669); 25; 69-75
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  • 39
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    Progress in analysis and prediction of dynamic stall (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft (ISSN 0021-8669); 25; 6-17
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  • 40
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    Condensation heat transfer in a microgravity environment (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Thermophysics and Heat Transfer (ISSN 0887-8722); 2; 82-84
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  • 41
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    Flow-induced morphological instabilities - The rotating disc (1988)
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    Publication Date: 2011-08-19
    Description: The morphological stability of a rotating and solidifying disk is investigated under the assumption that delta, the thickness of the viscous boundary layer, is much larger than delta(c), the thickness of the solute boundary layer. It is found that axisymmetric disturbances with wavelengths comparable to delta respond to nonparallel flow effects and have stability characteristics quite different from disturbances in a parallel flow. These long waves are unstable because of the nonparallel flow and would decay without it. This analysis thus identifies a new mechanism of morphological change induced by flow.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Crystal Growth (ISSN 0022-0248); 87; 4, Ma; 385-396
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  • 42
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    A unidimensional model of comet ionosphere structure (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The one-dimensional continuity and momentum equations for the plasma formed in the expanding coma of a comet near the sun are studied. An analytic expression for the magnetic field configuration in the presence of outflow, photoionization, dissociative recombination, plasma fluid pressure, and friction between the ions and neutrals is obtained. It is suggested that for a Halley-type comet there will be a region sunward of the nucleus from which the magnetic field is excluded, consistent with Giotto observations. Calculations have been performed for Halley and Giacobini-Zinner type comets, and in the field-free regions it is shown that the dominant terms in the momentum equation balancing the magnetic pressure gradient are the ion neutral friction and the net mass loading momentum gain.
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 93; 1759-176
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  • 43
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    The universe at infrared wavelengths (1988)
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    Publication Date: 2011-08-19
    Description: This article discusses the status of infrared astronomy after the mission of the Infrared Astronomical Satellite (IRAS). Important scientific results from IRAS include: the origin of the interplanetary dust cloud, the formation of solar type stars, the energetics of the interstellar medium, the discovery of ultra-luminous infrared galaxies and their possible relation to the origin of quasars, and the large scale structure of the universe.
    Keywords: ASTROPHYSICS
    Type: (ISSN 0007-084X); 41; 23-34
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    The promise of astrophysical observation conducted from space (1988)
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    Publication Date: 2011-08-19
    Description: The roles of instrumentation and the Space Station in addressing the most important questions in astrophysics are considered. The growth in the power of astronomical instruments over the past several decades is reviewed. Progress that can be made in the coming decades in understanding the origin of the universe, in learning more about quasars, black holes, and the fundamental laws of physics, and in possibly detecting other planetary systems and extraterrestrial life is considered.
    Keywords: ASTROPHYSICS
    Type: (ISSN 0007-084X); 41; 17-22
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  • 45
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    Outgassing asymmetry of periodic comet Encke. I - Apparitions 1924-1984 (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A concept of a collimated flow of ejecta from a discrete source (vent) on the surface of a rotating cometary nucleus is applied to P/Encke, based on positional observations of its sunward fanlike coma at 13 apparitions between 1924 and 1984. The major results include a finding that the observations are consistent with an invariable position of the rotation pole during the 60 yr (yielding an obliquity of 70 deg), although this is not to be interpreted as an indication that the nucleus is not precessing. Two vents are identified on the nucleus surface: one on the northern hemisphere at a latitude of +55 deg, of an estimated sublimitation area of 0.4 sq km, which is active along the inbound leg of the comet's orbit until a few days preperihelion and again beginning several weeks postperihelion; the other on the southern hemisphere at -75 deg, of an estimated area of 0.6 sq km, whose activity prevails in the intervening time. There appears to be a significant difference between the two regions in terms of dust content in their emissions.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal (ISSN 0004-6256); 95; 911-924
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  • 46
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    On the receptivity of free shear layers to two-dimensional external excitation (1988)
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    Publication Date: 2011-08-19
    Description: In this paper, the receptivity of a typical free shear layer to pulse-type and periodic excitation is studied. This is done by solving the initial-value problem completely and studing its long-time behavior. This leads to a wave packet for the pulse. By the superposition of many wave packets, a spatial instability mode when the flow is convectively unstable is generated. This establishes a general and simple relationship between the receptivities for pulse-type and sinusoidal excitations. It is found that a shear layer is very receptive to high-frequency disturbances that are generated near the centerline of the layer.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Fluid Mechanics (ISSN 0022-1120); 187; 155-177
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  • 47
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    Direct simulation of a turbulent boundary layer up to R sub theta = 1410 (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The turbulent boundary layer on a flat plate, with zero pressure gradient, is simulated numerically at four stations between R sub theta = 225 and R sub theta = 1410. The three-dimensional time-dependent Navier-Stokes equations are solved using a spectral method with up to about 10 to the 7th grid points. Periodic spanwise and streamwise conditions are applied, and a multiple-scale procedure is applied to approximate the slow streamwise growth of the boundary layer. The flow is studied, primarily, from a statistical point of view. The solutions are compared with experimental results. The scaling of the mean and turbulent quantities with Reynolds number is compared with accepted laws, and the significant deviations are documented. The turbulence at the highest Reynolds number is studied in detail. The spectra are compared with various theoretical models. Reynolds-stress budget data are provided for turbulence-model testing.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Fluid Mechanics (ISSN 0022-1120); 187; 61-98
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  • 48
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    Detection of the 2(20) to 2(21) transition of HDO in Orion A - Evidence for dense clumped gas in the hot core (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Results of the first detection of the 10.3 GHz 2(20) to 2(21) transition of HDO in Orion A are presented. Two components of OMC-1 have been identified, a hot core and a spike component associated with the compact molecular ridge cloud. The hot core is modeled as having an effective radiation temperature of 350 K and an HDO column density of 8 x 10 to the 16th/sq cm. The spike component is best fitted by a column density in HDO of about 6 x 10 to the 15th/sq cm. The present data are consistent with clumping and with cloud collision models of maser excitation.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 326; 376-383
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    X-ray spectral models of Galactic bulge sources - The emission-line factor (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Current difficulties in finding unique and physically meaningful models for the X-ray spectra of Galactic bulge sources are exacerbated by the presence of strong, variable emission and absorption features that are not resolved by the instruments observing them. Nine Einstein solid state spectrometer (SSS) observations of five Galactic bulge sources are presented for which relatively high resolution objective grating spectrometer (OGS) data have been published. It is found that in every case the goodness of fit of simple models to SSS data is greatly improved by adding line features identified in the OGS that cannot be resolved by the SSS but nevertheless strongly influence the spectra observed by SSS.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 326; 186-193
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    Cosmic string induced peculiar velocities (1988)
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    Publication Date: 2011-08-19
    Description: This paper considers the scenario of a flat universe with a network of heavy cosmic strings as the primordial fluctuation spectrum. The joint probability of finding streaming velocities of at least 600 km/s on large scales and local peculiar velocities of less than 800 km/s is calculated. It is shown how the effects of loops breaking up and being born with a spectrum of sizes can be estimated. It is found that to obtain large-scale streaming velocities of at least 600 km/s, it is necessary that either a large value for beta G mu exist or the effect of loop fissioning and production details be considerable.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 326; 70-76
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    Oxygen chemistry of shocked interstellar clouds. III - Sulfur and oxygen species in dense clouds (1988)
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    Publication Date: 2011-08-19
    Description: The chemical evolution of oxygen and sulfur species in shocked dense clouds is studied. Reaction rate constants for several important neutral reactions are examined, and revised values are suggested. The one-fluid magnetohydrodynamic shock structure and postshock chemical evolution are calculated for shocks of velocity v(s) = 10 km/s through clouds of initial number density n(0) = 100,000/cu cm and of molecule/atom ratios H2/H = 10, 1000, and 100,000 with most sulfur contained initially in molecules SO2 and SO. Abundances of SO2, SO, CS, and OCS remain near their preshock values, except in clouds containing substantial amounts of atomic hydrogen, where significant destruction of sulfur-oxygen species occurs. Abundances of shock-enhanced molecules HS and H2O are sensitive to the molecule/atom ratio. Nonthermal oxygen-hydrogen chemistry has a minor effect on oxygen-sulfur molecules in the case H2/H = 10.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 325; 411-416
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    String-driven inflation (1988)
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    Publication Date: 2011-08-19
    Description: It is argued that, in fundamental string theories, as one traces the universe back in time a point is reached when the expansion rate is so fast that the rate of string creation due to quantum effects balances the dilution of the string density due to the expansion. One is therefore led into a phase of constant string density and an exponentially expanding universe. Fundamental strings therefore seem to lead naturally to inflation.
    Keywords: ASTROPHYSICS
    Type: Physical Review Letters (ISSN 0031-9007); 60; 549-552
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    A direct interaction approximation treatment of high Rayleigh number convective turbulence and comparison with experiment (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A method is proposed for treating steady-state, thermally driven convection using the full direct interaction approximation to treat the nonlinear energy transfer and a prescribed instability function to model the eenrgy input. The instability function used is the growth rate of the mechanism generating the turbulence. This methodology can be easily generalized and applied to other driving mechanisms. The 1/3 power law form of the N vs. R relation for water is duplicated here and the coefficient is computed, using a two-point closure, to be less than about 0.08.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Physics of Fluids (ISSN 0031-9171); 31; 256-262
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    Elemental abundance analyses with coadded Dominion Astrophysical Observatory spectrograms. III - The superficially normal standard stars Theta Leonis, Tau Herculis and Omicron Pegasi (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: ASTROPHYSICS
    Type: Royal Astronomical Society, Monthly Notices (ISSN 0035-8711); 230; 671-694
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  • 55
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    Luminosity excesses in low-mass young stellar objects - A statistical study (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: This paper presents a statistical study in which the observed total luminosity is compared quantitatively with an estimate of the stellar luminosity for a sample of 59 low-mass young stellar objects (YSOs) in the Taurus-Auriga complex. In 13 of the analyzed YSOs, luminosity excesses greater than 0.20 are observed together with greater than 0.6 IR excesses, which typically contribute the bulk of the observed excess luminosity and are characterized by spectral energy distributions which are flat or rise toward long wavelengths. The analysis suggests that YSOs showing the largest luminosity excesses typically power optical jets and/or molecular outflows or have strong winds, as evidenced by the presence of O I emission, indicating a possible correlation between accretion and mass-outflow properties.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal (ISSN 0004-6256); 95; 534-542
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  • 56
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    The IRAS Bright Galaxy Sample. III - 1-10 micron observations and coadded IRAS data for galaxies with L(IR) equal to or greater than 10 to the 11th solar luminosities (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: This paper presents the results of 1-10-micron observations and coadded IRAS data on 61 galaxies from the Bright Galaxy Sample, with IR luminosities, L(IR), equal to or greater than 10 to the 11th solar luminosities. It was found that an increase in the total L(IR) above 10 to the 11th solar luminosity is correlated with increased emission from hot dust with characteristic temperatures about 800 K. This hot dust contributes a substantial fraction of the 2.2- and 3.7-micron emission, resulting in a greatly increased dispersion in R(3.7/1.6) and R(2.2/1.6) for these high-luminosity galaxies, relative to lower-luminosity galaxies. This excess hot-dust emission appears to 'turn on' at luminosities of about 10 to the 11th solar luminosity. The spatial distribution of the 10-micron emission indicated a substantial extended component for most of the galaxies in this sample, implying that star-formation processes contribute significantly to the luminosities.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal (ISSN 0004-6256); 95; 356-373
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    The stellar composition of X-ray surveys from the Einstein Observatory (1988)
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    Publication Date: 2011-08-19
    Description: A new class of X-ray-luminous 'yellow' stellar objects which contributes significantly to the stellar log N-log S distribution, but which cannot be reconciled with normal G and K main-sequence stars. This identification results from a new analysis of the stellar content of three samples of X-ray-selected X-ray sources observed with the Einstein Observatory, namely the 'Medium Sensitivity Survey', the 'High Sensitivity Survey', and the 'Hyades Region Survey'. In this paper, both X-ray and optical properties of the stellar samples in these surveys are reported. The actual stellar content of the surveys is compared with predictions based on current knowledge of stellar X-ray luminosity functions and the stellar composition and spatial distribution in the Galaxy. It is shown that a plausible identification for the excess population of 'yellow' stars is with the active, RS CVn-like binaries.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 324; 1010-101
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    Survey of low-frequency electromagnetic waves stimulated by two coexisting newborn ion species (1988)
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    Publication Date: 2011-08-19
    Description: Parallel electromagnetic instabilities generated by coexisting newborn hydrogen and oxygen ions are studied for different orientations of the interplanetary magnetic field with respect to the solar wind velocity. The wave growth dependence on the densities and temperatures of the newborn species is investigated. The results indicate that in most domains of the Brillouin plane each ion beam can excite resonant instabilities without undue influence from the other newborn ion species. Although comparable resonant instabilities are more efficiently generated by the lighter newborn ions in ion-rich environments, the growth stimulated by the heavier species can withstand large beam density decreases.
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 93; 48-58
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    Abundance effects on the Cepheid distance scale (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A new investigation of the dependence of the period-luminosity (PL) and period-luminosity-color (PLC) relations on the helium and metal abundances in classical Cepheids is presented. Composition dependences are assigned to all quantitites under study, so that the results represent a true theoretical prediction. It is found that the PLC relation in B,V magnitudes is at least five times more sensitive to chemical composition than is the PL relation. If the PL relation is adopted and the helium abundance is held fixed, a Cepheid with Z = 0.005 should be fainter than one with Z = 0.02 by about 0.04 mag. Since the slope of the predicted PL relation is independent of chemical composition, the PL relation can be considered to be effectively universal. Additional supporting observational evidence is described, and theoretical results are also presented for the bolometric PL relation, whose slope and dependence on metal abundance should be roughly applicable to infrared observations of Cepheids.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 329; 712-719
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    Nucleus of Comet IRAS-Araki-Alcock (1983 VII) (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Optical, radar, infrared, UV, and microwave-continuum observations of Comet IRAS-Araki-Alcok were obtained in May 1983, the week of the comet's close approach to earth. The comet has a nucleus dimension and a rotation period which are similar to those of Comet Halley, but a different morphological signature (a persisting sunward fan-shaped coma). Time variations are noted in the projected nucleus cross section. Results suggest significant limb-darkening effects in the relevant domains of radio waves, and that the comet's interior must be extremely cold. It is found that the thermal-infrared fluxes from the inner coma of the comet are dominated by the nucleus.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal (ISSN 0004-6256); 95; 1876-189
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    Long-term temporal variability of Cygnus X-2 (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Observations of the low-mass binary X-ray source Cyg X-2 taken over a five-year period using instruments on OSO 8, HEAO 1, and Einstein are presented. Irregular changes in intensity of up to 60 percent on time scales ranging from minutes to days are seen. The source appears to have long-term low-luminosity states during which dips lasting about three days occur. When these long dips occur, they always appear at the same phase in the optically determined 9.8-day orbital period. There are three distinct types of short-term dips distinguished by differing correlations between spectral hardness and intensity.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 329; 276-289
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    Aerodynamic properties of fractal grains - Implications for the primordial solar nebula (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Gas-grain and grain-grain interactions have a significant role in the evolution of the primordial solar nebula. There is also compelling evidence for larger grains in dense interstellar clouds than in the diffuse interstellar medium. In the usual treatments of grain collisions, where it is assumed that collisions produce compact bodies with a constant density, the gas drag decreases rapidly with size. The first step toward a quantitative analysis of the aerodynamic behavior of fractal aggregates is reported here, and it is shown that for fractals drag decreases very slowly.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 329; L39-L41
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    Velocity spectra in the irrotational flow outside a turbulent shear layer (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The relationship between the spectra of the three normal stresses near a turbulent shear layer is derived from the constraint of irrotationality. The relationship implies that the common practice of determining time scales of the turbulence from spectra in the near field is not valid. This implication is reinforced by a discussion of the scaling of irrotational spectra that follows from the formulation of Phillips (1975).
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Physics of Fluids (ISSN 0031-9171); 31; 1807
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    Ejection mechanisms in the sublayer of a turbulent channel (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The structure of the vorticity field in the viscous wall layer of a turbulent channel is studied by examining the results of a fully resolved direct numerical simulation. It is shown that this region is dominated by intense three-dimensional shear layers in which the dominant vorticity component is spanwise. The advection and reproduction processes of these structures are examined and shown to be consistent with the classical generation mechanism for two-dimensional Tollmien-Schlichting waves. This process is fundamentally different from the usually accepted mechanism involving hairpin vortices.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Physics of Fluids (ISSN 0031-9171); 31; 1311-131
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    The interaction of supernova 1987A with dense circumstellar gas (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The light travel time effects on the evolution of line fluxes, line profiles, and spatial structure of the emission from supernova 1987A are described. Current high spectral resolution observations suggest a lower limit to the age of the shell of 5000 yr and suggest a relatively low shell velocity. The narrow lines are predicted to shift to the red at a rate depending on the shell age. Observations of X-rays below 10 keV by the Ginga satellite are difficult to interpret in terms of circumstellar interaction because of the time variability.
    Keywords: ASTROPHYSICS
    Type: Nature (ISSN 0028-0836); 332; 514-516
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    The influence of supernovae and passing stars on comets in the Oort cloud (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: It is demonstrated here that the passage of luminous stars through the Oort Cloud over the age of the solar system will subject all comets to heating episodes up to at least 16 K, and a sizeable fraction to 30 K. Stochastic supernovae have even more striking effects during monthlong events; conservative estimates of the supernovae are in the Galactic disk suggest that most comets have been heated to 45 K, and a fraction to about 60 K. These results imply that comets are not fully pristine relics of solar system formation.
    Keywords: ASTROPHYSICS
    Type: Nature (ISSN 0028-0836); 332; 407-411
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    Probes of large-scale structure in the universe (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A general formalism is developed which shows that the gravitational instability theory for the origin of the large-scale structure of the universe is now capable of critically confronting observational results on cosmic background radiation angular anisotropies, large-scale bulk motions, and large-scale clumpiness in the galaxy counts. The results indicate that presently advocated cosmological models will have considerable difficulty in simultaneously explaining the observational results.
    Keywords: ASTROPHYSICS
    Type: Nature (ISSN 0028-0836); 332; 328-330
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  • 68
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    Intensity profiles of dust near extended sources on Comet Halley (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The dust particle intensity decreases proportional to 1/R from the Comet Halley, as expected for free outflow. Flattening of the profile is evident within several tens of km from the nucleus. It is shown here that these phenomena can be explained by a model that considers the extended size and nonunifomity of the active region on the surface of the cometary nucleus. A critical scale length, defined by the opening angle of a jetlike feature and the size of the source, can be introduced to describe the flattening. The model is consistent with the observations and provides the basis for studying other mechanisms such as particle fragmentation.
    Keywords: ASTROPHYSICS
    Type: Nature (ISSN 0028-0836); 332; 51
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  • 69
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    Nickel, argon and cobalt in the infrared spectrum of SN1987A - The core becomes visible (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Infrared spectra of supernova 1987A taken in April and November 1987 are presented, showing two distinctly different stages in the evolution of the expanding gas shell. The optical and infrared spectrum in April originated from the hydrogen envelope and show weak hydrogen lines rising above a 5,000-K photospheric continuum. The November spectrum was dominated by strong emission lines from heavy elements as well as many lines from highly excited levels of hydrogen, with peak flux levels in the lines at or slightly above the level of the continuum in April. It is concluded that the inner regions of the supernova were just becoming visible in early 1988. It is expected that these regions contain heavy elements produced by advanced nuclear burning stages in the progenitor star and in the shock wave that ejected all material external to the iron core.
    Keywords: ASTROPHYSICS
    Type: Nature (ISSN 0028-0836); 331; 505
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    Neutral stellar winds that drive bipolar outflows in low-mass protostars (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The Arecibo radio telescope at the 21-cm line of atomic hydrogen has been used to detect a neutral atomic wind in the bipolar flow source HH 7-11. An atomic mass of about 0.015 solar associated with the rapidly flowing gas is deduced. The stellar mass-loss rate is roughly 3 x 10 to the -6th solar mass/yr if the crossing time of the decelerating wind is 5000 yr. The excess emission in the H I line core gives a total duration of the outflow of about 70,000 yr. A detailed analysis of the H I line shape yields a reasonable deceleration rate for the atomic wind if the stellar wind continuously entrains ambient molecular gas as it propagates from the protostar. A stellar wind with the described characteristics and a terminal velocity of 170 km/s would be more than sufficient to drive the known extended CO bipolar outflow in HH 7-11.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 328; 763-776
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    The difference in hydrogen abundance between two classes of type I X-ray bursts (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The hypothesis that the bright type I X-ray bursts differ from faint bursts in that a hydrogen-rich envelope is ejected in the former type and not in the latter is theoretically discussed and experimentally investigated. Color-temperature versus luminosity diagrams of X-ray bursts from MXB 1636-536 and MXB 1608-522 are constructed based on observations from the Tenma satellite and are used to study the hydrogen richness of the surface of the neutron stars resulting from the outbursts. Systematic differences between the bright and faint class diagrams are found which confirm the hypothesis.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 328; 251-255
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    The bipolar outflow from the rotating carbon star, V Hydrae (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A high-resolution optical spectrum of the mass-losing red giant carbon star, V Hya, has been obtained, and the (C-12)O (J = 1-0) millimeter emission in the circumstellar envelope around this star has been mapped. It is found that the CO emission is extended, clearly anisotropic and can be interpreted as the superposition of an isotropic emission with that of a bipolar flow. The optical spectrum of the photosphere suggests that this star is rotating with v sin i between 10 and 20 km/s. These data are interpreted, together, to suggest that the bipolar nature of the outflow results from the flattening of the star induced by its rapid rotation.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 328; L25-L28
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    Mass loss from rapidly rotating magnetic protostars (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: It is proposed that bipolar outflows from young stellar objects originate from a protostar rotating at breakup at its equator because it is being spun up by an adjoining accretion disk. Mass outflow at an appreciable fraction of the infall rate from a surrounding molecular cloud core onto the star and disk can be driven centrifugally if the protostar has a sufficiently strong magnetic field. The expansion of the flow toward the rotational poles may provide a collimation mechanism for focusing an ordinary stellar wind into optical jets.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 328; L19-L23
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    Dual-frequency and dual-polarization VLBI observations of the stellar system Algol (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Results of multiepoch VLBI observations of the stellar system Algol are presented, including dual-polarization and dual-frequency measurements at 2.3 and 8.4 GHz. The brightness temperature of the radio source is generally between 3 x 10 to the 8th K and 5 x 10 to the 9th K and is consistent with gyrosynchrotron emission from energetic electrons with mean energy less than 1 MeV in an active coronal region. Two exceptional events were observed: a high-brightness, broad-band outburst occurring simultaneously at 2.3 and 8.4 GHz, and a short-duration, highly polarized and high-brightness temperature outburst at 1.66 GHz. A simple physical model which includes all three types of emission is suggested.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 328; 232-242
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    Classical bump Cepheids - Reconciliation of theory with observations (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: New models of classical bump Cepheids lying along the Cepheid ridge line in the H-R diagram are computed to obtain a more accurate set of predicted surface velocity curves. Acceptable Cepheid models are found to be 0.5 mag brighter at a fixed stellar mass than standard evolutionary models. All the previously obtained manifestations of the Cepheid mass discrepancy, except for the anomalous double-mode Cepheid masses, are resolved, at least in a statistical sense, by accepting the implied luminosity increase. The need for the luminosity increase is independently inferred from standard evolutionary models of intermediate-mass and high-mass giant and supergiant stars from their location in the observational H-R diagram.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 328; 196-206
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    A finite element computation of turbulent boundary layer flows with an algebraic stress turbulence model (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: An algebraic stress turbulence model and a computational procedure for turbulent boundary layer flows which is based on the semidiscrete Galerkin FEM are discussed. In the algebraic stress turbulence model, the eddy viscosity expression is obtained from the Reynolds stress turbulence model, and the turbulent kinetic energy dissipation rate equation is improved by including a production range time scale. Good agreement with experimental data is found for the examples of a fully developed channel flow, a fully developed pipe flow, a flat plate boundary layer flow, a plane jet exhausting into a moving stream, a circular jet exhausting into a moving stream, and a wall jet flow.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Computer Methods in Applied Mechanics and Engineering (ISSN 0045-7825); 66; 45-63
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    H2 and H I emission line imaging of the ring nebula (NGC 6720) (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Infrared emission-line images of the v = 1-0 S(1) transition of molecular hydrogen and Br-gamma recombination line of atomic hydrogen which cover the entire extent of NGC 6720, the Ring nebula. The maps presented here are the highest angular resolution images of these transitions yet produced for this object and have very low relative positional uncertainty. As a result, the spatial stratification of the ionized and shocked molecular zones within the nebula is clearly resolved. These data, and data from the Infrared Astronomical Satellite, are used to determine the H2, H I, and dust mass within the nebula. Energy sources for the dust heating, formation and destruction of the H2, and overall evolution of the nebula are also discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 325; 604-609
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    Cosmic string wakes and large-scale structure (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The formation of structure from infinite cosmic string wakes is modeled for a universe dominated by cold dark matter (CDM). Cross-sectional slices through the wake distribution tend to outline empty regions with diameters which are not inconsistent with the range of sizes of the voids in the CfA slice of the universe. The topology of the wake distribution is found to be spongy rather than cell-like. Correlations between CDM wakes do not extend much beyond a horizon length, so it is unlikely that CDM wakes are responsible for the correlations between clusters of galaxies. An estimate of the fraction of matter to accrete onto CDM wakes indicates that wakes could be more important in galaxy formation than previously anticipated.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 325; 521-530
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    Interplanetary magnetic field draping about fast coronal mass ejecta in the outer heliosphere (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The possibility that the IMF becomes draped around coronal mass ejections (CMEs) propagating rapidly through the quiescent solar wind into the outer heliosphere is investigated theoretically. The results are presented in diagrams and graphs and discussed in detail. It is found that large sunward-directed structures analogous to the Venus and cometary magnetotails should form when the CME velocity exceeds the solar-wind velocity by more than the local Alfven speed; such structures could hang up swept-up IMF flux for as long as several days. Pioneer 11 magnetic-field measurements at 6.9-9.4 AU from three 20-d periods in 1978 are examined and shown to contain some features consistent with CME draping.
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 93; 2519-252
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    Two-component LDV investigation of three-dimensional shock/turbulent boundary-layer interactions (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: AIAA Journal (ISSN 0001-1452); 26; 52-56
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    Mass loss from S stars (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The mass-loss process in S stars is studied using 65 S stars from the listing of Wing and Yorka (1977). The role of pulsations in the mass-loss process is examined. It is detected that stars with larger mass-loss rates have a greater amplitude of pulsations. The dust-to-gas ratio for the S stars is estimated as 0.002 and the average mass-loss rate is about 6 x 10 to the -8th solar masses/yr. Some of the properties of the S stars, such as scale height, surface density, and lifetime, are measured. It is determined that scale height is 200 pc; the total duration of the S star phase is greater than or equal to 30,000 yr; and the stars inject 3 x 10 to the -6th solar masses/sq kpc yr into the interstellar medium.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal Supplement Series (ISSN 0067-0049); 66; 33-41
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    Symmetries in tetrad theories (1988)
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    Publication Date: 2011-08-19
    Description: The isometry conditions for gravitational fields are given directly at the tetrad level, rather than in terms of the metric. As an illustration, an analysis of the curvature collineations and Killing fields for a twisting type-N vacuum gravitational field is made.
    Keywords: ASTROPHYSICS
    Type: Classical and Quantum Gravity (ISSN 0264-9381); 5; 135-145
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    Lyman-alpha clouds as a relic of primordial density fluctuations (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Primordial density fluctuations are studied using a CDM model and primordial clouds some of which are expanding, driven by pressure gradients created when the medium is photionized, and some of which are massive enough to continue collapsing in spite of the pressure. Normalization of CDM models to the clustering properties on large scales are used to predict the parameters of collapsing clouds of subgalactic mass at early epochs. It is shown that the abundance and dimensions of these clouds are comparable to those of the Lyman-alpha systems. The evolutionary history of the clouds is computed, utilizing a spherically symmetric hydrodynamics code with the dark matter treated as a collisionless fluid, and the H I column density distribution is evaluated as a function of N(H I) and redshift. The observed cloud parameters come out naturally in the CDM model and suggest that Lyman-alpha clouds are the missing link between primordial density fluctuations and the formation of galaxies.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 324; 627-638
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    Detection of H I, OH, CO, and optical imaging of the distant galaxy IRAS 12112 + 0305 (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The detection of H I absorption and OH and CO emission from the galaxy IRAS 12112 + 0305, which is receding from the sun at about 7 percent of the speed of light is reported. This galaxy, which appears to be an ongoing merger, radiates about 2 x 10 to the 12th solar luminosities in the infrared. The H I, OH, and CO spectra are indicative of large turbulent motions. From the millimeter wave CO observations, a total mass of molecular gas of 4 x 10 to the 10th solar masses is inferred. The OH emission in the 1667 MHz line is the most luminous extragalactic OH maser reported so far, with an isotropic luminosity of 1800 solar luminosities.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 324; L59-62
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  • 85
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    Temperature effects on the pickup process of water group and hydrogen ions - Extensions of 'A theory for low-frequency waves observed at Comet Giacobini-Zinner' by M. L. Goldstein and H. K. Wong (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Cometary heavy ions can resonantly excite hydromagnetic wave activity with spacecraft frequency spectra strongly deviating from the ion cyclotron frequency. The influence of the newborn particle temperature on this effect is assessed, its relevance to the interpretation of the observations is discussed, and an alternative, more efficient mechanism to generate spacecraft frequencies of the order of the proton cyclotron frequency is suggested.
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 93; 243-246
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    Evidence for a scaling solution in cosmic-string evolution (1988)
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    Publication Date: 2011-08-19
    Description: Numerical simulations are used to study the most fundamental issue of cosmic-string evolution: the existence of a scaling solution. Strong evidence is found that a scaling solution does indeed exist. This justifies the main assumption on which the cosmic-string theories of galaxy formation is based. The main conclusion coincides with that of Albrecht and Turok (1985) but the results are not consistent with theirs. In fact, the results indicate that the details of string evolution are very different from the standard dogma.
    Keywords: ASTROPHYSICS
    Type: Physical Review Letters (ISSN 0031-9007); 60; 257-260
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    Free-streamline analysis of deformation and dislodging by wind force of drops on a surface (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Free-streamline theory is used to analyze the deformation and dislodging by wind pressure of drops of liquid adhered by surface tension to a solid surface. The critical Weber number for droplets to be dislodged is determined as a function of advancing and receding contact angle. Graphical results for drop shape are in good agreement with observation.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Physics of Fluids (ISSN 0031-9171); 31; 43-48
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    Infrared observations of SN 1987A - Probing the ejecta and its surrounding medium (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: IR observations of the ejecta from SN 1987A are reviewed. The structure lines of heavy elements in the ejectra are discussed, including the discovery of the presence of CO and SiO molecules in the supernova spectrum. Observations of the ambient medium are noted and the mass and distribution of dust in the circumstellar shell are examined. Also, consideration is given to the possible presence of IR arcs around SN 1987A.
    Keywords: ASTROPHYSICS
    Type: Astronomical Society of Australia, Proceedings (ISSN 0066-9997); 7; 4, 19
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    Resurrecting hot dark matter - Large-scale structure from cosmic strings and massive neutrinos (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: These are the results of a numerical simulation of the formation of large-scale structure from cosmic-string loops in a universe dominated by massive neutrinos (hot dark matter). This model has several desirable features. The final matter distribution contains isolated density peaks embedded in a smooth background, producing a natural bias in the distribution of luminous matter. Because baryons can accrete onto the cosmic strings before the neutrinos, the galaxies will have baryon cores and dark neutrino halos. Galaxy formation in this model begins much earlier than in random-phase models. On large scales the distribution of clustered matter visually resembles the CfA survey, with large voids and filaments.
    Keywords: ASTROPHYSICS
    Type: Astronomical Society of the Pacific, Publications (ISSN 0004-6280); 100; 1364-136
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  • 90
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    Unsteady transonic flow simulation on a full-span-wing-body configuration (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: AIAA Journal (ISSN 0001-1452); 26; 1450-145
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  • 91
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    Considerations on the moving contact-line singularity, with application to frictional drag on a slender drop (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: It has previously been shown that the no-slip boundary conditions leads to a singularity at a moving contact line and that this presumes some form of slip. Present considerations on the energetics of slip due to shear stress lead to a yield stress boundary condition. A model for the distortion of the liquid state near solid boundaries gives a physical basis for this boundary condition. The yield stress condition is illustrated by an analysis of a slender drop rolling down an incline. That analysis provides a formula for the frictional drag resisting the drop movement. With the present boundary condition, the length of the slip region becomes a property of the fluid flow.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Fluid Mechanics (ISSN 0022-1120); 197; 157-169
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  • 92
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    Turbulent viscosity (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A model for fully developed turbulence is proposed whose predictions compare favorably with those of the direct interaction approximation (DIA) model and whose main equations are easy to handle. Four different expressions for the turbulent viscosity are derived which contain no free parameters. Two of the expressions are given in terms of properties of the turbulent fluid itself; the other two are given in terms of the instability that generated the turbulence and of the properties of the mean flow. The numerical coefficients entering these relations are evaluated and found to be in good agreement with previous theoretical estimates based on Kraichnan's DIA, the renormalization group method, and turbulence modeling. In the case of shear in the mean flow, the Shakura-Sunyaev alpha parameter is shown to be less than 0.01. The four expressions can be generalized to include the effect of rotation and/or magnetic fields.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 200; 1-2,
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  • 93
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    Radio observations in the fields of COS-B gamma ray sources. IV - First quadrant sources (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The field of five COS-B gamma-ray sources in the first galactic quadrant have been mapped using the Effelsberg radio telescope at several frequencies. Candidate objects as potential radio counterparts of gamma-ray sources are discussed in the light of current observations; however, mostly being due to the crowded nature of the radio fields, no clear identification has been possible.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 200; 1-2,; 195-206
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  • 94
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    Near-infrared imaging of Lynds 1551 IRS 5 (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: High-spatial-resolution 1.6-micron (H) and 2.2-micron (K) images of the well-known young stellar object (YSO) L1551 IRS 5 reveal an extended, conically-shaped reflection nebula. The comparison of the images at the two wavelengths shows a shift in the position of the flux maximum, demonstrating that the H band maximum is not identical with the illuminating star. Morphological differences between the H band and K band images as well as a color map indicate that extinction effects in the reflection nebula are important. The results support a model that posits that, at H and K, the star in IRS 5 is surrounded by an optically thick disk and illuminates the inner wall of the nozzle created by the anisotropic mass outflow from the embedded young star.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 335; 814-819
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  • 95
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    Monte Carlo modeling of the net effects of coma scattering and thermal reradiation on the energy input to cometary nucleus (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A Monte Carlo simulation method is presented that can, to an accuracy of a few percent, calculate the effects of a dusty coma on the total energy input to the cometary nucleus. This method treats nonconservative nonisotropic scattering, as well as the reflection from the nucleus surface. Results are presented as a function of the optical thickness of the dust column in the sun-comet axis. The total energy input to the nucleus appears to be only weakly dependent on the opacity of the coma, the radial distribution of the dust, or the details of the extinction processes.
    Keywords: ASTROPHYSICS
    Type: Icarus (ISSN 0019-1035); 76; 253-269
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  • 96
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    Photochemical and thermal evolution of interstellar/precometary ice analogs (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The photochemical and thermal evolution of H2O-, CH3OH-, NH3-, and CO-containing ices whose relative proportions in mixture are consistent with those of interstellar ice are presently studied experimentally. The UV photolysis of these ice analogs invariably generates H2CO, CO2, CO, CH4, and HCO, largely through the photofragmentation of CH3OH. CO and CH4 leave the samples as warmup proceeds to 100 K; most of the parent ice molecules are found to have sublimed upon the reaching of 200 K, with only a mixture of more refractory substances remaining. A residue of CH2 groups remains even after warmup to 300 K.
    Keywords: ASTROPHYSICS
    Type: Icarus (ISSN 0019-1035); 76; 225-252
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  • 97
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    The condensation and vaporization behavior of H2O:CO ices and implications for interstellar grains and cometary activity (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: IR spectroscopy has been used to ascertain several parameters associated with CO, H2O, and H2O:CO ices' physical behavior. Since CO is noted to be capable of condensing into H2O-rich ices at temperatures that are twice as high as those required for condensation in pure CO, CO is able to condense onto H2O-rich ice grains at temperatures of up to 50 K. CO's presence in H2O ice modestly enhances the effective volatility of the H2O. Attention is given to the implications of these results for cometary models generally and the question of cometary formation specifically.
    Keywords: ASTROPHYSICS
    Type: Icarus (ISSN 0019-1035); 76; 201-224
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  • 98
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    Unsteady transonic aerodynamics and aeroelastic calculations at low-supersonic freestreams (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A computational procedure is presented to simulate transonic unsteady flows and corresponding aeroelasticity of wings at low-supersonic freestreams. The flow is modeled by using the transonic small-perturbation theory. The structural equations of motions are modeled using modal equations of motion directly coupled with aerodynamics. Supersonic freestreams are simulated by properly accounting for the boundary conditions based on pressure waves along the flow characteristics in streamwise planes. The flow equations are solved using the time-accurate, alternating-direction implicit finite-difference scheme. The coupled aeroelastic equations of motion are solved by an integration procedure based on the time-accurate, linear-acceleration method. The flow modeling is verified by comparing calculations with experiments for both steady and unsteady flows at supersonic freestreams. The unsteady computations are made for oscillating wings. Comparisons of computed results with experiments show good agreement. Aeroelastic responses are computed for a rectangular wing at Mach numbers ranging from subtransonic to upper-transonic (supersonic) freestreams. The extension of the transonic dip into the upper transonic regime is illustrated.
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft (ISSN 0021-8669); 25; 955-961
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  • 99
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    Further comparisons of interactive boundary-layer and thin-layer Navier-Stokes procedures (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft (ISSN 0021-8669); 25; 897-903
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  • 100
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    Transonic Navier-Stokes solutions for a fighter-like configuration (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft (ISSN 0021-8669); 25; 875-881
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