Fabric analysis of Allende matrix using EBSD     

Lauren E. Watt  Phil A. Bland  Dave J. Prior  Sara S. Russell 《Meteoritics & planetary science》2006,41(7):989-1001

Abstract— Fabric analysis of the interstitial matrix material in primitive meteorites offers a novel window on asteroid formation and evolution. Electron backscatter diffraction (EBSD) has allowed fabrics in these fine‐grained materials to be visualized in detail for the first time. Our data reveal that Allende, a CV3 chondrite, possesses a uniform, planar, short‐axis alignment fabric that is pervasive on a broad scale and is probably the result of deformational shortening related to impact or gravitational compaction. Interference between this matrix fabric and the larger, more rigid components, such as dark inclusions (DIs) and calcium‐aluminium‐rich inclusions (CAIs), has lead to the development of locally oriented and intensified matrix fabrics. In addition, DIs possess fabrics that are conformable with the broader matrix fabric. These results suggest that DIs were in situ prior to the deformational shortening event responsible for these fabrics, thus providing an argument against dark inclusions being fragments from another lithified part of the asteroid (Kojima and Tomeoka 1996; Fruland et al. 1978). Moreover, both DIs and Allende matrix are highly porous (?25%) (Corrigan et al. 1997). Mobilizing a highly porous DI during impact‐induced brecciation without imposing a fabric and incorporating it into a highly porous matrix without significantly compacting these materials is improbable. We favor a model that involves Allende DIs, CAIs, and matrix accreting together and experiencing the same deformation events.  相似文献   

A test of arm-induced star formation in spiral galaxies from near-infrared and Hα imaging     

Marc S. Seigar  Phil A. James 《Monthly notices of the Royal Astronomical Society》2002,337(3):1113-1117

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TERRITORIAL SIGNIFICANCE OF TRADITIONAL-POLITICAL ALLEGIANCE OF FRONTIER SETTLEMENTS IN AFRICA: THE EXAMPLE OF THE IFE-IJESA FRONTIER AREA IN SOUTHWESTERN NIGERIA     

Oluwole Aloba  M. Phil.  Ph.D. 《Singapore journal of tropical geography》1990,10(1):1-12

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XMM–Newton observations of UW CrB: detection of X-ray bursts and evidence for accretion disc evolution     

Pasi Hakala  Gavin Ramsay  Panu Muhli  Phil Charles  Diana Hannikainen  Koji Mukai  Osmi Vilhu 《Monthly notices of the Royal Astronomical Society》2005,356(3):1133-1138

UW CrB (MS 1603+2600) is a peculiar short-period X-ray binary that exhibits extraordinary optical behaviour. The shape of the optical light curve of the system changes drastically from night to night, without any changes in overall brightness. Here we report X-ray observations of UW CrB obtained with XMM–Newton . We find evidence for several X-ray bursts, confirming a neutron star primary. This considerably strengthens the case that UW CrB is an accretion disc corona system located at a distance of at least 5–7 kpc (3–5 kpc above the Galactic plane). The X-ray and Optical Monitor (ultraviolet–optical) light curves show remarkable shape variation from one observing run to another, which we suggest are due to large-scale variations in the accretion disc shape resulting from a warp that periodically obscures the optical and soft X-ray emission. This is also supported by the changes in phase-resolved X-ray spectra.  相似文献   

COMMERCIALIZATION OF SMALL-SCALE AGRICULTURE IN ZIMBABWE: SOME EMERGING PATTERNS OF SPATIAL DIFFERENTIATION     

Lovemore M. Zinyama  B.A.  M.Phil.  Dip. Econ. 《Singapore journal of tropical geography》1989,9(2):151-162

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VEGETATION MAPPING IN AFRICA: A CRITIQUE     

Richard Whitlow  B.A.  M.Phil. 《Singapore journal of tropical geography》1985,6(1):64-77

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A Worldwide Study of the H, D and Z Variation On Abnormal Quiet Days (Aqds)     

E. C. Butcher  H. Mccreadie  D. M. Schlapp 《Geophysical Journal International》1993,114(1):175-184

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Abnormal quiet days and the effect of the interplanetary magnetic field on the apparent position of the Sq focus     

E. C. Butcher  G. M. Brown 《Geophysical Journal International》1980,63(3):783-789

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The effect of the IMF on the position of the Sq focus in summer has been discussed by Matsushita who found an apparent poleward motion of the focus on days when the IMF was directed away from the Sun compared to those when the IMF was directed towards the Sun. However, his analysis took no account of the well known phase variability in Sq(H) . It is shown here that if quiet days are separated into 'normal quiet days', NQDs (defined for a station on the poleward side of the focus as days when the minimum in H occurs between 0830 and 1330 LT) and 'abnormal quiet days', AQDs (minimum in H occurring outside the NQD range), then the apparent poleward motion of the focus only occurs on AQDs and even then only when the IMF is directed away from the Sun. This effect is found to occur in both summer and winter and is probably of magnetospheric origin.  相似文献   

THE DROUGHT OF 1970–77 IN UPPER VOLTA     

E. Ofori-Sarpong  M.A.  M.Phil. 《Singapore journal of tropical geography》1983,4(1):53-61

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Testing variograms for positive-definiteness     

Margaret Armstrong  Phil Diamond 《Mathematical Geology》1984,16(4):407-421

A method based on Bochner's theorem is described for demonstrating the positive-definiteness of variogram models and for generating classes of valid variogram functions.Work performed while on leave at the Centre de Géostatistique et de Morphologie Mathématique.  相似文献