The virial method and the classical ellipsoids     

Norman R. Lebovitz 《Journal of Astrophysics and Astronomy》1996,17(3-4):167-182

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Impact processing of chondritic planetesimals: Siderophile and volatile element fractionation in the Chico L chondrite     

Marc D. Norman  David W. Mittlefehldt 《Meteoritics & planetary science》2002,37(3):329-344

Abstract— A large impact event 500 Ma ago shocked and melted portions of the L‐chondrite parent body. Chico is an impact melt breccia produced by this event. Sawn surfaces of this 105 kg meteorite reveal a dike of fine‐grained, clast‐poor impact melt cutting shocked host chondrite. Coarse (1–2 cm diameter) globules of FeNi metal + sulfide are concentrated along the axis of the dike from metal‐poor regions toward the margins. Refractory lithophile element abundance patterns in the melt rock are parallel to average L chondrites, demonstrating near‐total fusion of the L‐chondrite target by the impact and negligible crystal‐liquid fractionation during emplacement and cooling of the dike. Significant geochemical effects of the impact melting event include fractionation of siderophile and chalcophile elements with increasing metal‐silicate heterogeneity, and mobilization of moderately to highly volatile elements. Siderophile and chalcophile elements ratios such as Ni/Co, Cu/Ga, and Ir/Au vary systematically with decreasing metal content of the melt. Surprisingly small (?10²) effective metal/silicate‐melt distribution coefficients for highly siderophile elements probably reflect inefficient segregation of metal despite the large degrees of melting. Moderately volatile lithophile elements such K and Rb were mobilized and heterogeneously distributed in the L‐chondrite impact breccias whereas highly volatile elements such as Cs and Pb were profoundly depleted in the region of the parent body sampled by Chico. Volatile element variations in Chico and other L chondrites are more consistent with a mechanism related to impact heating rather than condensation from a solar nebula. Impact processing can significantly alter the primary distributions of siderophile and volatile elements in chondritic planetesimals.  相似文献   

Obscured AGB Stars in the LMC     

Jacco Th. Van Loon  Albert A. Zijlstra  Patricia A. Whitelock  M.A.T. Groenewegen  Cecile Loup  Peter Te Lintel Hekkert  Norman R. Trams  L.B.F.M. Waters 《Astrophysics and Space Science》1997,255(1-2):403-404

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A concordance model of the Lyman α forest at z= 1.95     

Tridivesh Jena  Michael L. Norman  David Tytler  David Kirkman  Nao Suzuki  Angela Chapman  Carl Melis  Pascal Paschos  Brian O'Shea  Geoffrey So  Dan Lubin  Wen-Ching Lin  Dieter Reimers  Eckardt Janknecht  Cora Fechner 《Monthly notices of the Royal Astronomical Society》2005,361(1):70-96

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THE AIR PHOTOGRAPH REQUIREMENTS OF GEOLOGISTS     

J. W. Norman 《The Photogrammetric Record》1968,6(32):133-149

The geologist's use of air photographs and the characteristics studied by photogeologists are briefly described. The influence of photographic factors such as scale, season, time of day, film type, processing, overlap and dimensional accuracy are considered from the geologist's viewpoint.  相似文献   

ANALYTICAL AERIAL TRIANGULATION BLOCK ADJUSTMENT; THE DIRECT HEIGHT SOLUTION INCORPORATING TIE-STRIPS     

A. D. N. Smith    M. J. Miles  P. Verrall 《The Photogrammetric Record》1967,5(29):327-350

The historical development of analytical aerial triangulation block adjustment is mentioned by way of introduction. The advantages of separating the plan and height adjustments are given and the observation equations of a typical adjustment section are analysed to show that this convenient practice is justified in normal circumstances. The principles of a direct solution of the normal equations suitable for a moderate-sized computer, are explained and developed in detail for the height adjustment. The advantages of tie-strips in the height adjustment are demonstrated and the difficulties which then arise are discussed. An approximate method which overcomes these difficulties is developed. Details of the computer programmes used are given in Appendix B.  相似文献   

Variations in the Rate of Anaerobic Succinate Accumulation within the Central and Marginal Regions of an Euryoxic Bivalve Mantle     

Ed  Greenfield Miles A.  Crenshaw 《Marine Ecology》1981,2(4):353-362

Abstract. Anaerobic metabolism in the central and marginal portions of the mantle of Mercenaria mercenaria was compared. Anaerobic succinate accumulation was more rapid in the central region. This difference may be due to higher phosphoenolpyruvate carboxykinase activity in the central region. Thus, the central region is more specialized for anaerobic metabolism and the marginal region more for net shell growth. The original rate of succinate accumulation in the mantle is similar in isolated mantles and intact clams, suggesting that mantle succinate production does not require translocation of precursors from other tissues. However, in intact clams, the rate of succinate accumulation in the central region of the mantle slows after four hours. The reduced rate is probably caused by reducing the metabolic rate. Succinate accumulation and shell dissolution are slower in freshly collected clams than in clams that had been stored anaerobically. The difference may be due to induction of PEPCK synthesis during storage. Shell derived calcium did not accumulate in the mantle and, therefore did not alter the intracellular calcium concentration in the mantle.  相似文献   

Extraction and comparison of acoustic backscatter from a calibrated multi- and single-beam sonar     

Melvin  Gary D; Cochrane  Norman A; Li  Yanchao 《ICES Journal of Marine Science》2003,60(3):669-677

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A technique for conducting seismic refraction experiments on the ocean bed using bottom shots     

R. E. Kirk  K. Robertson  R. B. Whitmarsh  P. R. Miles 《Marine Geophysical Researches》1991,13(2):153-160

A technique has been devised for firing arrays of bottom shots on the ocean bed in depths upto 4000 m or more. Ten kilogram explosive charges are dropped from the surface while the shooting ship is navigated acoustically. They are detonated at preset times by an electronic timer which initiates an electrical detonator, detonating cord and cast PETN/TNT explosive. Ranges to ocean bottom seismographs, and the shot instants, can be calculated from the arrival-time differences of the direct and surface-reflected water waves. The accuracy, which is dependent on water-depth and range, was better than 22 m in range and 14 msec in shot instant for our experiments.  相似文献   

Magnetoacoustic-gravity surface waves     

Alan J. Miles  H. R. Allen  B. Roberts 《Solar physics》1992,141(2):205-234

The linearized theory for the parallel propagation of magnetoacoustic-gravity surface waves is developed for an interface of a horizontal magnetic field above a field-free medium. The media either side of the interface are taken to be isothermal. The dispersion relation is obtained for the case of a constant Alfvén speed. In the absence of gravity the interface may support one or two surface modes, determined by the relative temperatures and magnetism of the two media. The effect of gravity on the modes is examined and dispersion diagrams and eigenfunctions are given. In the usual - k _x diagnostic diagram, the domain of evanescence is shown to be divided into two distinct regions determining whether a given mode will have a decaying or growing vertical velocity component. In the absence of a magnetic field the transcendental dispersion relation may be rewritten as a polynomial. This polynomial possesses two acceptable solutions only one of which may exist in any given circumstances (depending on the ratio of the densities). If the gas density within the field exceeds that in the field-free medium, then the f-mode may propagate. The f-mode exists in a restricted band of horizontal wavenumber and only when the field-free medium is warmer than the magnetic atmosphere. An analytical form for the wave speed of the f-mode is obtained for small values of the Alfvén speed. It is shown that the f-mode is related to the fast magnetoacoustic surface wave, merging into that mode at short wavelengths.  相似文献