Comment concerning. “Données expérimentales sur la diffusion deséléments majeurs entre verres ou liquides de compositions basaltique,rhyolitique et phonolitique,entre 900°C et 1300°C,àpression ordinaire” by C. Alibert and J.P. Carron     

Roy Kenneth Lowry 《Earth and Planetary Science Letters》1981,52(1):221

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The effect of Kelvin-Helmholtz instability on rising flux tubes in the convection zone     

Sydney Z. D'Silva  Arnab Rai Choudhuri 《Solar physics》1991,136(2):201-219

If the solar dynamo operates at the bottom of the convection zone, then the magnetic flux created there has to rise to the surface. When the convection zone is regarded as passive, the rising flux is deflected by the Coriolis force to emerge at rather high latitudes, poleward of typical sunspot zones (Choudhuri and Gilman, 1987; Choudhuri, 1989). Choudhuri and D'Silva (1990) included the effects of convective turbulence on the rising flux through (a) giant cell drag and (b) momentum exchange by small-scale turbulence. The momentum exchange mechanism could enable flux tubes of radii not more than a few hundred km to emerge radially at low latitudes, but the giant cell drag mechanism required unrealistically small flux tube radii (a few meters for a reasonable giant cell upflow) to counteract the Coriolis force. We now include the additional effect of Kelvin-Helmholtz instability in a symmetrical flux ring caused by the azimuthal flow induced during its rise. The azimuthal flow crosses the threshold for the instability only if there is a giant cell upflow to drag the flux tubes appreciably. In the absence of such a drag, as in the case of a passive convection zone or in the case of momentum exchange by small-scale turbulence, the azimuthal velocity never becomes large enough to cause the instability, leaving the results of the previous calculations unaltered. The giant cell drag, aided by Kelvin-Helmholtz instability, however, becomes now a viable mechanism for curbing the Coriolis force - 10⁴ G flux tubes with radii of a few hundred km being dragged radially by upflows of 70 m s^-1.  相似文献   

Book reviews     

Fouad N. Ibrahim  G. Kunkel  David H. Miller  A. Wallner  R. O. Whyte  W. U. Ehrmann  Matthias Kuhle  Robert Giepel  Pieter Lukkes  B. K. Roy  W. R. Stanley  Paul Mosely 《GeoJournal》1986,12(4):464-469

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A note on the self-consistency of the EIH equations of motion     

Rajat Roy  N. C. Rana 《Journal of Astrophysics and Astronomy》1990,11(3):291-295

The self-consistency of the Einstein Infeld and Hoffman (EIH) equations of motion is critically examined in the limiting case of a threebody problem where two bodies are very close to each other and a third quite far removed from them  相似文献   

Vereinfachte Berechnung der Radioaktivität und ihrer Streuung im Wasser für ein festgelegtes Arbeitsschema     

M. M. Bezzegh-Galántai  H. L. Le Roy 《Aquatic Sciences - Research Across Boundaries》1961,23(2):494-514

Ohne Zusammenfassung Herrn Prof. Dr. O. Faag zu seinem 60. Geburtstag in Verebrung gewidmet  相似文献   

Interstellar graphite in meteorites: Isotopic compositions and structural properties of single graphite grains from Murchison     

Ernst Zinner  Sachiko Amari  Brigitte Wopenka  Roy S. Lewis 《Meteoritics & planetary science》1995,30(2):209-226

Abstract— One hundred forty-three carbon grains, ranging in size from 2 to 8 μm, from two chemical and physical separates from the Murchison CM2 chondrite, were analyzed by ion microprobe mass spectrometry for their C- and N-isotopic compositions. Both separates are enriched in the exotic noble gas component Ne-E(L). Ninety grains were also analyzed for their H and O contents and 118, for Si. Thirteen grains were analyzed by micro-sampling laser Raman spectroscopy. Round grains have large C-isotopic anomalies with ¹²C/¹³C ratios ranging from 7 to 4500 (terrestrial ratio = 89). Nitrogen in these grains is also anomalous but shows much smaller deviations from the terrestrial composition, ¹⁴N/¹⁵N ratios ranging from 193 to 680 (terrestrial ratio = 272). Spherulitic aggregates and non-round compact grains have normal C-isotopic ratios but ¹⁵N excesses (up to 35%). Raman spectra of the analyzed grains indicate varying degrees of crystalline disorder of graphite with estimated in-plane crystallite dimensions varying from 18 Å (highly disordered, similar to terrestrial kerogen) to ～750 Å (well-crystallized graphite). Element contents of H, O, and Si are correlated with one another, and H and O are probably present in the form of organic molecules. On the basis of morphology, the round grains fall into two groups: grains with smooth, shell-like surfaces (“onions”) and grains that appear to be dense aggregates of small scales (“cauliflowers”). “Onions” tend to have lower trace element contents, isotopically light C (¹²C/¹³C > 89) and a high degree of crystalline order, whereas “cauliflowers” have a larger spread in trace element contents and C-isotopic ratios (they range from isotopically light to heavy) but tend to have a low degree of crystalline order. However, these differences exist only on average, and no clear distinction can be made for individual grains. A few limited conclusions can be drawn about the astrophysical origin of the carbon grains of this study. The ¹⁵N excesses in spherulitic aggregates and non-round grains can be explained as the result of ion-molecule reactions in molecular clouds. The round grains, on the other hand, must have formed in stellar atmospheres (circumstellar grains). Grains with isotopically light C must have formed in stellar environments characterized by He-burning, either in the atmosphere of Wolf-Rayet stars during the WC phase or in the He-burning, ¹²C-rich zone of a massive star, ejected by a supernova explosion. Isotopically heavy C is produced by H-burning in the CNO cycle. Possible sources for grains with heavy C are carbon stars (AGB stars during the thermally pulsing phase) or novae, but the detailed distribution of ¹²C/¹³C ratios agree neither with the distribution observed in carbon stars nor with theoretical predictions for these two types of stellar sources.  相似文献   

Ground-Water Contamination and Well Construction in Southeast Nebraska     

Mary E. Exner  Roy F. Spalding 《Ground water》1985,23(1):26-34

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Some cylindrically-symmetric cosmological models in general relativity representing viscous fluid and perfect fluid with heat conduction     

S. R. Roy  S. K. Banerjee 《Astrophysics and Space Science》1988,150(2):213-222

The paper considers inhomogeneous space-times admitting a two-parameter group of motions and satisfying Einstein's field equations for viscous fluid and perfect fluid with heat conduction. Some homogenous solutions representing viscous fluid have also been obtained for which the free-gravitational field is of the magnetic type. Various physical and kinematical properties have been discussed.  相似文献   

Evidence for Holocene climate variability from the sediments of a Scottish remote mountain lake     

Richard W. Battarbee  Nigel G. Cameron  Paul Golding  Stephen J. Brooks  Roy Switsur  Doug Harkness  Peter Appleby  Frank Oldfield  Roy Thompson  Don T. Monteith  Andrew McGovern 《第四纪科学杂志》2001,16(4):339-346

High resolution sampling of sediment cores covering approximately the last 4000 yr from Lochan Uaine, a small corrie loch in the Scottish Cairngorm Mountains, show quasi‐periodic cycles in organic matter (measured as percentage loss on ignition). Analysis of these cycles show correspondences between loss on ignition, δ¹³C values and chironomid head capsule abundance. We interpret the changes as reflecting changes in lake productivity and hypothesise that they are driven by climate variability. However, it is not yet clear whether the periods of relatively high organic matter production and preservation are associated with colder or with warmer conditions. Nevertheless the results indicate the value of using sediments from remote, undisturbed mountain lakes as recorders of Holocene climate variability. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

Significant high number commensurabilities in the main lunar problem II: The occurrence of Saros-like near periodicities     

B. A. Steves  G. B. Valsecchi  E. Perozzi  A. E. Roy 《Celestial Mechanics and Dynamical Astronomy》1993,57(1-2):341-358

The effect of changes in the Moon's semimajor axis and the Earth's orbital eccentricity on the occurrence of Saros-like cycles is examined. The Earth-Moon-Sun dynamical system exhibits such cycles for only 25 to 30% of the time interval between –5×10⁷ to +5×10⁷ years. Not only has the present Saros the smallest period during this time, but it also has one of the longest durations and the period closest to an integral number of anomalistic years, thus making it one of the most efficient Saros-like cycles for reversing solar perturbations in the main lunar problem. During the lifetime of a Saros-like cycle, variations of the Earth's orbital eccentricity cause frequent disappearances and reappearances of the cycle.  相似文献