A dynamical model of the inner Galaxy     

Ralf Häfner  N. Wyn Evans  Walter Dehnen  James Binney 《Monthly notices of the Royal Astronomical Society》2000,314(3):433-452

  相似文献   

Elementary ideas behind plasma physics     

Walter J. Heikkila 《Astrophysics and Space Science》1988,144(1-2):85-97

  相似文献   

Aufbau und Tektonik des Festlandes von Australien     

Walter Geisler 《International Journal of Earth Sciences》1930,21(2):109-123

Ohne Zusammenfassung  相似文献   

Plate tectonics at Lamont: the first year-1966     

Walter Pitman  E. Bonatti  F. C. Wezel 《地学学报》1995,7(6):598-602

During the period from the mid 1950s to the 1960s it seemed as if the community of earth scientists was slowly being dragged toward accepting continental drift. But resistance was often steadfast. Each new ideal or set of data produced a trickle of new converts, but also generated heated debate. The concept of sea-floor spreading and the corollary hypothesis that the process of spreading would generate a set of symmetrical magnetic anomalies was particularly disputatious. The discovery of the Eltanin 19 magnetic anomaly profile ended the dispute and the trickle became a flood.  相似文献   

Phase-space mixing and the merging of cusps     

Walter Dehnen 《Monthly notices of the Royal Astronomical Society》2005,360(3):892-900

Collisionless stellar systems are driven towards equilibrium by mixing of phase-space elements. I show that the excess-mass function     [where     is the coarse-grained distribution function] always decreases on mixing . D ( f ) gives the excess mass from values of     . This novel form of the mixing theorem extends the maximum phase-space density argument to all values of f . The excess-mass function can be computed from N -body simulations and is additive: the excess mass of a combination of non-overlapping systems is the sum of their individual D ( f ). I propose a novel interpretation for the coarse-grained distribution function, which avoids conceptual problems with the mixing theorem.
As an example application, I show that for self-gravitating cusps (  ρ∝ r ^−γ  as   r → 0  ) the excess mass   D ∝ f ^{−2(3−γ)/(6−γ)}  as   f →∞  , i.e. steeper cusps are less mixed than shallower ones, independent of the shape of surfaces of constant density or details of the distribution function (e.g. anisotropy). This property, together with the additivity of D ( f ) and the mixing theorem, implies that a merger remnant cannot have a cusp steeper than the steepest of its progenitors. Furthermore, I argue that the cusp of the remnant should not be shallower either, implying that the steepest cusp always survives.  相似文献   

BOCAIUVA—A SILICATE-INCLUSION BEARING IRON METEORITE RELATED TO THE EAGLE-STATION PALLASITES     

Daniel J. Malvin  John T. Wasson  Robert N. Clayton  Toshiko K. Mayeda  Walter Silva da Curvello 《Meteoritics & planetary science》1985,20(2):259-273

Bocaiuva is a unique meteorite consisting of major metal having a high Ge/Ga ratio and minor (～ 50 mg/g) silicates. The silicates are generally chondritic and consist of major olivine (Fa.7.7) and orthopyroxene (Fs7.6) and minor plagioclase (Ab49, An49) and clinopyroxene (Fs4.5, Wo42). The low alkali content of the silicates is the only property inconsistent with a chondritic composition. Based on metal composition Bocaiuva seems distantly related to certain iron meteorites having similar Ge contents and similar Ge/Ga ratios, but detailed comparison with six such irons shows none to be closely related to Bocaiuva. Perhaps most closely related is Cold Bay, a member of the Eagle-Station trio of pallasites, but its composition is too different to suggest formation on the same parent body. Oxygen-isotope data show that Bocaiuva silicates are closely related to those in the Eagle-Station pallasites and to the CO and CV chondrites. The composition and texture of the Bocaiuva metal-silicate assembly indicate mixing in an impact event. We suggest that the Eagle-Station pallasites were also formed by impact heating rather than by a long-lived internal heat source.  相似文献   

Microcosms for Aquifer Research: Application to Colonization of Various Sized Particles by Ground-Water Microorganisms   总被引：1，自引：0，他引：1  

Walter K. Dodds  Clay A. Randel  Christopher C. Edler 《Ground water》1996,34(4):756-759

  相似文献   

Variation of the geomagnetic field in Costa Rica during the total solar eclipse of July 11, 1991     

Jorge Brenes  German Leandro  Walter Fernández 《Earth, Moon, and Planets》1993,63(2):105-117

Ground measurements of the geomagnetic field, during the total solar eclipse of July 11, 1991, were carried out at three sites in Costa Rica located within the eclipse's path of totality. Near totality, there was a significant change in the total intensity,F. Its normal decrease in the afternoon hours was interrupted during a period of about 45 min, in whichF varied very little. This was due mainly to a small variation in horizontal intensity,H, during such a period. The departure ofF from normal lasted about 100 min; its maximum departure was near 10 nT and occurred about 38 min after totality, The declination,D, also experienced a small change (about 2.3 min) during the total period of the eclipse. The vertical intensity,Z, and the inclination,I, did not show significant changes.  相似文献   

Halo evolution in the presence of a disc bar     

Paul J. McMillan  Walter Dehnen 《Monthly notices of the Royal Astronomical Society》2005,363(4):1205-1210

  相似文献   

Determination of pteridines and flavins in seawater by reverse-phase,high-performance liquid chromatography with fluorometric detection     

Walter C. Dunlap  Michael Susic 《Marine Chemistry》1985,17(3):185-198

Methods are described for routine analyses of individual pteridines and flavins from marine waters at picomolar concentrations. Samples were concentrated by adsorption on bonded-phase, C₁₈ silica and Florisil Sep-Pak extraction columns connected in series. Sample extracts derived from Sep-Pak eluates were analysed by reverse-phase liquid chromatography with fluorometric detection. These methods proved sensitive for the quantitative identification of pterin, xanthopterin, isoxanthopterin, 6-biopterin, pterin-6-carboxylic acid, 6-hydroxymethylpterin, riboflavin, riboflavin-5′-phosphate, lumiflavin and lumichrome in reef waters at Davies Reef, Great Barrier Reef, Australia.Preliminary experiments were conducted to test the application of these methods to the measurement of pterin and flavin excretion from several reef-dwelling, benthic organisms. Results from these experiments suggest that the benthic community contributes these compounds to the coral reef environment.  相似文献