Orientation of first-ranked galaxies in rich clusters     

George Rhee  Nico Roos 《Astrophysics and Space Science》1989,157(1-2):201-210

We present new evidence that first ranked galaxies are aligned with their parent cluster and with the direction of the nearest neighbour cluster (scale 15h ^–1 Mpc). The effect is stronger for cD and gE galaxies than for first-ranked galaxies of later type. The relevance of this result for different galaxy formation scenarios is discussed. In hierarchical clustering scenarios like the cold dark matter theory, galactic halos and clusters of galaxies are expected to have moderate asphericity. We present some numerical results of an on-going study of the dissipationless collapse of moderately aspherical systems. Our results indicate that the central part of the collapsed and virialized system does show the large scale elongation imposed by the initial conditions. It is pointed out that this may have important implications also for the properties of disk galaxies in dark halos.  相似文献   

Presidential address     

George Joseph 《Journal of the Indian Society of Remote Sensing》1995,23(4):159-162

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Elastic finite-difference modelling and imaging for earthquake sources     

Liang-Zie Hu  George A. McMechan 《Geophysical Journal International》1988,95(2):303-313

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The circumstellar imager: Direct detection of extra-solar planetary systems     

Christ Ftaclas  Andreas L. Nonnenmacher  Richard J. Terrile  Steven H. Pravdo  George D. Gatewood  Eugene H. Levy 《Astrophysics and Space Science》1994,212(1-2):441-452

The Astrometric Imaging Telescope (AIT) is designed to probe the circumstellar environment by both direct imaging and indirect astrometric measurements. The Circumstellar Imager (CI) is a coronagraphic camera and is the direct imaging component of the AIT. The CI is designed to obtain high-sensitivity images of the circumstellar region. It provides crucial non-inferential information relating to the frequency, origin, and evolution of planetary systems and all forms of circumstellar matter. Such imaging is usually limited by the scattered and diffracted light halos of the star itself, which are greatly suppressed in the CI by mating a novel high-efficiency coronagraph with a phasecompensated optical system. For faint point sources in the circumstellar region, the CI will have a sensitivity in excess of 5 magnitudes fainter than the as-designed Hubble Space Telescope (HST). Laboratory data are shown for the coronagraph, which, in a diffraction-limited environment, is capable of suppressing the stellar diffraction sidelobes by several orders of magnitude without significant sacrifice of field of view. In order to realize the high rejection levels inherent in the coronagraph design, it is necessary to limit scatter in the optical systems, imposing a mid-spatial frequency figure error requirement an order of magnitude smaller than that of the HST. Experimental data directed toward meeting this requirement are also shown.Paper presented at the Conference onPlanetary Systems: Formation, Evolution, and Detection held 7–10 December, 1992 at CalTech, Pasadena, California, U.S.A.  相似文献   

Meteorite finds by EUROMET near Frontier Mountain,North Victoria Land,Antarctica     

George Delisle  Ian Franchi  Antonio Rossi  Rainer Wieler 《Meteoritics & planetary science》1993,28(1):126-129

Abstract— A team from EUROMET (a joint initiative of scientific institutions in Europe interested in meteorites) was sent for the first time to Antarctica in the 1990/91 season to undertake a systematic search for meteorites. The project was organised within the framework of the Italian Antarctic Program (Programma Nationale di Richerche in Antartide, PNRA). The search was carried out in the vicinity of Frontier Mountain (North Victoria Land) and 256 meteorite fragments were discovered, most of which were wind-blown across the blue-ice field to the NE of Frontier Mountain and finally caught in an ice depression about 5 km to the N. The larger meteorites which remained on the ice surface from which they were uncovered may have been transported down to the mountain edge where they have subsequently been destroyed or covered in debris. A search for meteorites at neighbouring Sequence Hills, where similar glaciological conditions as at Frontier Mountain exist, proved unsuccessful. At this location the surface of the blue ice in the valleys with suspected meteorite concentrations was covered by meltwater lakes.  相似文献   

Time as an independent variable for current ripples developing towards linguoid equilibrium morphology     

Jaco H. Baas  Albert P. Oost  Orsolya K. Sztano  Poppe L. de Boer  George Postma 《地学学报》1993,5(1):29-35

Flume experiments show that current ripples on very fine sand surfaces always develop towards a linguoid shape with constant height and wavelength provided that sufficient time is allowed for their formation. Straight and sinuous current ripples only reflect intermediate stages in ripple development and may be regarded as non-equilibrium bedforms. The time period which current ripples require to reach linguoid equilibrium morphology is related to an inverse power of flow velocity. In the transitional stage from current ripples to upper stage plane bed (i.e. washed-out ripple stage) only the equilibrium wavelength remains constant, whereas equilibrium height rapidly decreases to zero. Our observations imply that bed-roughness parameters in sediment transport calculations can be simplified when equilibrium conditions are attained, and that inferences about flow energy from the dimensions of current ripples in very fine sand need to be regarded with caution.  相似文献   

Maximum Water-Table Drawdown at a Fully Penetrating Pumping Well     

Michael J. Gefell  George M. Thomas  Stephen J. Rossello 《Ground water》1994,32(3):411-419

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Developments in earth and planetary sciences,Vol. 4, Magnetospheric plasma physics: Edited by A. Nishida. Reidel,Dordrecht, 1982, xii + 348 pp., index, $49.50     

George Siscoe 《Icarus》1983,56(1):190-192

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A New Magnitude-Frequency Relation for Earthquakes and a Classification of Relation Types     

George Purcaru 《Geophysical Journal International》1975,42(1):61-79

Summary. In this paper some aspects of the deviations of frequency distributions of earthquakes from a linear trend are considered. For recurrence curves with inflexions, the formula
is proposed as a magnitude-frequency relation, with critical magnitude M _cr. Comparison with actual data shows better agreement than other formulae. The slope of the frequency graph is considered in the most general case to be a function of M and some parameters p ₁, p ₂, …. A classification of the types of magnitude-frequency relation is given and all known types of relations N : M and N: K ( K = log E , E = seismic energy) are summarized.  相似文献   

A comparison of solar EUV intensities and K-coronameter measurements     

George L. Withbroe 《Solar physics》1971,18(3):458-473

Characteristics of the emission observed above the solar limb in four EUV lines, Sixii 499, Mgx 625, Neviii 770, and Ovi 1032 are discussed. The mean temperature of the corona derived from the ratios of the intensities of Sixii 499 and Mgx 625 is 1.8 million K. There do not appear to be significant temperature differences in regions with low EUV intensities and those with high EUV intensities, suggesting that the EUV emission from the lithium-like ions depends primarily on the integral of n _e ² along the line of sight.The EUV data are compared with K-coronameter measurements in order to yield new estimates of the abundances of Si, Mg, Ne and O relative to hydrogen. Within the uncertainties of the analysis, these coronal abundances are in agreement with the corresponding photospheric values.  相似文献