Evidence for deceleration in the radio jets of GRS 1915+105?     

J. C. A. Miller-Jones  M. P. Rupen  R. P. Fender  A. Rushton  G. G. Pooley  R. E. Spencer 《Monthly notices of the Royal Astronomical Society》2007,375(3):1087-1098

There is currently a clear discrepancy in the proper motions measured on different angular scales in the approaching radio jets of the black hole X-ray binary GRS 1915+105. Lower velocities were measured with the Very Large Array (VLA) prior to 1996 than were subsequently found from higher resolution observations made with the Very Long Baseline Array and the Multi-Element Radio Linked Interferometer Network. We initiated an observing campaign to use all three arrays to attempt to track the motion of the jet knots from the 2006 February outburst of the source, giving us unprecedented simultaneous coverage of all angular scales, from milliarcsecond scales out to arcsecond scales. The derived proper motion, which was dominated by the VLA measurements, was found to be 17.0 mas d⁻¹, demonstrating that there has been no significant permanent change in the properties of the jets since 1994. We find no conclusive evidence for deceleration of the jet knots, unless this occurs within 70 mas of the core. We discuss possible causes for the varying proper motions recorded in the literature.  相似文献   

Estimating the water content of hydrated minerals using reflectance spectroscopy: II. Effects of particle size     

Ralph E. Milliken  John F. Mustard 《Icarus》2007,189(2):574-588

Visible-near infrared reflectance spectra for five particle size fractions of a Hawaiian palagonite (HWMK101) and a nontronite (ferruginous smectite, Clay Minerals Society source clay SWa-1) were measured under ambient, purged, and heated conditions to characterize the effects of surface and volume scattering on the relationship between absolute H₂O content and the strength of the 3 μm absorption feature. Both materials were ground and dry sieved to particle sizes of <25, 25-45, 45-75, 75-125, and 125-250 μm. Particles of the bulk palagonite have an approximate bimodal distribution consisting of small, amorphous particles <5 μm in diameter mixed with crystalline and glass particles <1 mm in diameter, whereas the nontronite particles are polycrystalline aggregates. We find that band parameters value relating the strength of the 3 μm hydration feature to water content increase with particle size for a given water content, regardless of whether reflectance or single scattering albedo spectra are used. Spectra generally increase in reflectance as particle size decreases, a result of the relative increase in volume to surface scattering. Spectra of large particles are commonly saturated in the 3 μm region due to an increase in optical path length, making an accurate estimate of water content indeterminate until the samples dehydrate to the volume-scattering regime. We find that the presence of fines in several of the size fractions of palagonite cause their spectra to be representative of the finest fraction rather than the mean particle size. The nontronite spectra appear to be representative of an effective particle size within the range of the sieved size fractions. Many planetary surfaces are expected to have a large number of small particles which can dominate their spectral signature. Our results for particles <45 μm provide a reasonable model for estimating the H₂O content of hydrated asteroids and regions of Mars.  相似文献   

Trace element profiles from the Geosecs-II test station in the Sargasso Sea     

P.G. BrewerD.W. Spencer 《Earth and Planetary Science Letters》1972

During the GEOSECS-II test cruise a profile of 25 large volume water samples were collected, filtered and stored in the acidified condition. Two laboratories have together determined Fe, Cu, Zn, Co, Sb, Cs and U in these samples. Both laboratories determined Zn and the correlation is good; Zn, Fe and Cu show a maximum in the North Atlantic Deep Water, Cs and U are essentially conservative and Sb show variability within the uncertainty of the technique. Sc is more abundant in deep water than surface water in both the Atlantic and Pacific Oceans.  相似文献   

Body Wave Amplitude Calculations—II     

Ralph A. Wiggins 《Geophysical Journal International》1976,46(1):1-10

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Advanced techniques for clay mineral analysis: J.J. Fripiat (Editor). Elsevier,Amsterdam, 1982, vi + 234 pp., US $42.50/Dfl.100.00 (hardcover)     

Ralph E. Grim 《Sedimentary Geology》1983,34(4):341-342

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Hydrogeology of an Alkaline Fly Ash Landfill in Eastern Iowa   总被引：1，自引：0，他引：1  

Linda Le Seur Spencer  Lon D. Drake 《Ground water》1987,25(5):519-526

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Granites and yet more granites forty years on   总被引：17，自引：0，他引：17  

Wallace Spencer Pitcher 《International Journal of Earth Sciences》1987,76(1):51-79

The theme of this synoptic review is the relationship between cause, process, source and the geological context during the genesis of the granitic rocks. A close environmental relationship occurs because granites can arise as the end-stage of several generative processes, involving different source rocks, each appropriate to a particular tectonic situation. Expressed in geological terms the differences can be used to erect a genetic classification, to set in perspective the intervention of basic magma, to reveal the importance of the volcanoplutonic interface, to evaluate the significance of the texture, to predict the type of mineralisation, to understand the mode of emplacement and to determine the contribution of the various source rocks.

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Zusammenfassung Das Thema dieser synoptischen übersicht behandelt das Verhältnis zwischen Ursache, Prozess, Herkunft und dem geologischen Rahmen während der Genese granitischer Gesteine.Es besteht hier eine enge Beziehung, weil Granite das Endstadium sehr unterschiedlicher Entstehungsprozesse sein können, die verschiedene Ausgangsgesteine einbeziehen und von denen jeder einer speziellen tektonischen Situation entspricht.Geologisch ausgedrückt kann man die Unterschiede dazu verwenden, eine genetische Klassifikation zu erstellen, um damit den Einflu\ basischen Magmas im richtigen Verhältnis zu sehen, die Bedeutung des vulkanisch-plutonischen Grenzbereiches aufzuzeigen, die Wichtigkeit der Textur herauszustreichen und den Typ der Mineralisation vorherzusagen. Auf diese Weise lä\t sich das Verständnis für den Modus der Platznahme erzielen und der Einflu\ verschiedener Ausgangsgesteine abschätzen.

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Résumé Cette revue synoptique a pour thème les relations entre la cause, le processus, la source et le contexte géologique au cours de la genèse des roches granitiques. Il existe entre ces facteurs des relations étroites, car les granites peuvent représenter le stade final de plusieurs processus de genèse, impliquant des roches de départ diverses, et appropriés chacun à une situation tectonique particulière.Exprimées en termes géologiques, les différences peuvent Être utilisées en vue d'établir une classification génétique, de mettre en évidence l'intervention du magma basique, d'exprimer l'importance de l'interface volcano-plutonique, d'estimer la signification de la texture de mise en place et de déterminer la contribution des diverses roches de départ.

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On the solution of transient free-surface flow problems in porous media by the finite element method     

Ralph Ta-Shun Cheng  Chih-Yen Li 《Journal of Hydrology》1973,20(1):49-63

A numerical procedure is presented to deal with solution of transient free-surface flows in porous media. The governing boundary-value problem for the piezometric potential is solved by the finite element method. The initial-value problem which describes the transient motion of the free-surface is solved by the method of quasi-linearization. The numerical scheme has been applied to isotropic and anisotropic earth dam problem and also to a ditch drainage problem. Excellent agreements have been reached when compared with known solutions. This computational procedure is shown to be stable and suitable for this class of problems with the aid of a digital computer.  相似文献   

Minor and trace elements in some meteoritic minerals     

Ralph O. Allen  Brian Mason 《Geochimica et cosmochimica acta》1973,37(6):1435-1456

The mineral phases including olivine, orthopyroxene, clinopyroxene, troilite, nickel-iron, plagioclase, chromite and the phosphates were separated from several meteorites. These were a hypersthene chondrite (Modoc), a bronzite chondrite (Guareña), an enstatite chondrite (Khairpur), and two eucrites (Haraiya and Moore County); diopside was separated from the Nakhla achondrite. The purified minerals were analyzed for trace and minor elements by spark source mass spectrometry and instrumental neutron activation analysis. On the meteorites examined our results show that Co, Ni, Cu, Ge, As, Ru, Rh, Pd, Sn, Sb, W, Re, Os, Ir, Pt and Au are entirely or almost entirely siderophile; Na, Rb, Sr, Y, Ba and the rare earth elements lithophile; Se chalcophile. The transition elements So, Ti, V, Cr and Mn are lithophile in most stony meteorites, but show chalcophile affinities in the enstatite chondrites (and enstatite achondrites), as do Zn, Zr and Nb. In the ordinary chondrites Ga shows both lithophile and siderophile affinities, but becomes entirely siderophile in the enstatite chondrites. Molybdenum and tellurium show strong siderophile and weaker chalcophile affinity. The lithophile elements are distributed among the minerals according to the crystallochemical factors, the most effective controlling factor being ionic size.  相似文献   

Metamorphic petrology — mineralogical,field, and tectonic aspects | Francis J. Turner, 1981. 2nd ed. International Series in the Earth and Planetary Sciences. McGraw-Hill Book Co. GmbH,Hamburg, xv + 524 pp., DM 80.90 (hardcover)     

Ralph Kretz 《Earth》1982,18(1):98-99

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