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排序方式: 共有448条查询结果,搜索用时 15 毫秒
271.
Dieter Stöffler Gerda Horneck Sieglinde Ott Ulrich Hornemann Charles S. Cockell Ralf Moeller Cornelia Meyer Jean-Pierre de Vera Jörg Fritz Natalia A. Artemieva 《Icarus》2007,186(2):585-588
Bacterial spores (Bacillus subtilis), cyanobacteria (Chroococcidiopsis sp.), and lichen (Xanthoria elegans) embedded in martian analogue rock (gabbro) were exposed to shock pressures between 5 and 50 GPa which is the range of pressures observed in martian meteorites. The survival of Bacillus subtilis and Xanthoria elegans up to 45 GPa and of Chroococcidiopsis sp. up to 10 GPa supports the possibility of transfer of life inside meteoroids between Mars and Earth and it implies the potential for the transfer of life from any Mars-like planet to other habitable planets in the same stellar system. 相似文献
272.
We have carried out 1.25 pc resolution MHD simulations of the ISM, on a Cartesian grid of 0 ≤ (x, y) ≤ 1 kpc size in the galactic plane and ?10 ≤ z ≤ 10 kpc into the halo, thus being able to fully trace the time-dependent evolution of the galactic fountain. The simulations show that large scale gas streams emerge, driven by SN explosions, which are responsible for the formation and destruction of shocked compressed layers. The shocked gas can have densities as high as 800 cm?3 and lifetimes up to 15 Myr. The cold gas is distributed into filaments which tend to show a preferred orientation due to the anisotropy of the flow induced by the galactic magnetic field. Ram pressure dominates the flow in the unstable branch 102 < T ≤ 103.9 K, whereas for T ≤ 100 K (stable branch) magnetic pressure takes over. Near supernovae thermal and ram pressures determine the dynamics of the flow. Up to 80% of the mass in the disk is concentrated in the thermally unstable regime 102 < T ≤ 103.9 K with ~30% of the disk mass enclosed in the T ≤ 103 K gas. The hot gas in contrast is controlled by the thermal pressure, since magnetic field lines are swept towards the dense compressed walls. 相似文献
273.
Madeleine Sélo Jean Benkhelil Jean Mascle Dieter Storzer Neville Exon 《Comptes Rendus Geoscience》2002,334(1):59-66
We present and discuss a few fission track data, and microstructural observations, from rock samples dredged along the western and southwestern continental margin of Tasmania. The results allow assessing the thermal and tectonic regimes that were active prior to and during the margin creation. The different ages, as provided by fission tracks, and deformational styles, as evidenced from microstructures, are then tentatively correlated with the two main rifting episodes, in Late Jurassic–Cretaceous times and Eocene–Oligocene respectively, deduced from kinematical reconstructions, that have led to the present- day southern margin of Tasmania. To cite this article: M. Sélo et al., C. R. Geoscience 334 (2002) 59–66 相似文献
274.
275.
Dieter Breitschwerdt 《Astrophysics and Space Science》2004,289(3-4):489-498
The dynamical evolution of hot optically thin plasmas in the ISMcrucially depends on the heating and cooling processes. It isessential to realize that all physical processes that contributeoperate on different time scales. In particular detailedbalancing is often violated since the statistically inverseprocess of e.g. collisional ionization is recombination of an ionwith two electrons, which as a three-body collision is usuallydominated by radiative recombination, causing a departure fromcollisional ionization equilibrium. On top of these differences inatomic time scales, hot plasmas are often in a dynamical state,thereby introducing another time scale, which canbe the shortest one.The non-equilibrium effects will be illustrated and discussed inthe case of galactic outflows. It will be shown, that spectralanalyses of X-ray data of edge-on galaxies show a clear signaturein the form of ‘multi-temperature’ halos, which can mostnaturally be explained by the ‘freezing-in’ of highly ionizedspecies in the outflow, which contribute to the overall spectrumby delayed recombination. This naturally leads to anon-equilibrium cooling function, which modifies the dynamics,which in turn changes the plasma densities and thermal energybudget, thus feeding back on the ionization structure. Thereforeself-consistent modelling is needed. 相似文献
276.
Peter Perret Dieter Imboden K. Wuhrmann 《Aquatic Sciences - Research Across Boundaries》1976,38(1):63-64
Ohne Zusammenfassung 相似文献
277.
Katerina BARTOSOVA Susanne GIER J. Wright HORTON Jr. Christian KOEBERL Dieter MADER Henning DYPVIK 《Meteoritics & planetary science》2010,45(6):1021-1052
The ICDP–USGS Eyreville drill cores in the Chesapeake Bay impact structure reached a total depth of 1766 m and comprise (from the bottom upwards) basement‐derived schists and granites/pegmatites, impact breccias, mostly poorly lithified gravelly sand and crystalline blocks, a granitic slab, sedimentary breccias, and postimpact sediments. The gravelly sand and crystalline block section forms an approximately 26 m thick interval that includes an amphibolite block and boulders of cataclastic gneiss and suevite. Three gravelly sands (basal, middle, and upper) are distinguished within this interval. The gravelly sands are poorly sorted, clast supported, and generally massive, but crude size‐sorting and subtle, discontinuous layers occur locally. Quartz and K‐feldspar are the main sand‐size minerals and smectite and kaolinite are the principal clay minerals. Other mineral grains occur only in accessory amounts and lithic clasts are sparse (only a few vol%). The gravelly sands are silica rich (~80 wt% SiO2). Trends with depth include a slight decrease in SiO2 and slight increase in Fe2O3. The basal gravelly sand (below the cataclasite boulder) has a lower SiO2 content, less K‐feldspar, and more mica than the higher sands, and it contains more lithic clasts and melt particles that are probably reworked from the underlying suevite. The middle gravelly sand (below the amphibolite block) is finer‐grained, contains more abundant clay minerals, and displays more variable chemical compositions than upper gravelly sand (above the block). Our mineralogical and geochemical results suggest that the gravelly sands are avalanche deposits derived probably from the nonmarine Potomac Formation in the lower part of the target sediment layer, in contrast to polymict diamictons higher in the core that have been interpreted as ocean‐resurge debris flows, which is in agreement with previous interpretations. The mineralogy and geochemistry of the gravelly sands are typical for a passive continental margin source. There is no discernible mixing with marine sediments (no glauconite or Paleogene marine microfossils noted) during the impact remobilization and redeposition. The unshocked amphibolite block and cataclasite boulder might have originated from the outer parts of the transient crater. 相似文献
278.
Dr. Dieter Ortlam 《International Journal of Earth Sciences》1974,63(3):850-884
In the central European Permo-Triassic, eight Violet Horizons (VH 0, VH 1, VH 2, VH 3, VH 4, VH 5, VH 6, and VH A) are recognized as fossil autochthonous soil complexes. The criteria for soil formation and the significance of the Violet Horizons for paleoclimate, paleogeography, and stratigraphy are presented. New proposals are made for the drawing of the Saxonian to Thuringian, Lower to Middle Bunter, and Middle to Upper Bunter boundaries in areas of central Europe. Comparison of the vertebrate fauna of Violet Horizon 5 with the strata of the “Grenzbitumen-Zone” (boundary Bituminous Zone) in the Tessin region (southern Switzerland) indicates a probable correlation of the Upper Bunter with the Anisian and the lower parts of the Muschelkalk with the Ladinian of the Tethys classification. 相似文献
279.
Myo Min Khin Khin LinDepartment of Geology University of Mandalay Mandalay MyanmarFeng Qinglai Faculty of Earth Sciences China University of Geosciences Wuhan Chongpan ChonglakmaniSchool of Geotechnology Suranaree University of Technology Na 《中国地质大学学报(英文版)》2001,12(3)
INTRODUCTIONDuringthepasttwodecades ,amajorityofgeoscientistshaveregardedmainlandSoutheastAsiaascomposedofGond wana derivedterraneswhichcrossed“Paleotethys”tocollidewiththeformerPaleoeurasiancontinentinLateTriassic/Juras sic (Metcalfe ,1999;ScoteseandGolonk… 相似文献
280.
Correlation of Tectono-Stratigraphic Units in Northern Thailand with Those of Western Yunnan (China)
Chongpan Chonglakmani School of Geotechnology Suranaree University of Technology Nakhon Ratchasima ThailandFeng Qinglai Faculty of Earth Sciences China University of Geosciences Wuhan Dieter Meischner Goettingen Center of Geosciences 《中国地质大学学报(英文版)》2001,12(3)
Thecorrelationoftectono stratigraphicunitsofNorthernThailandwiththoseofWesternYunnan (China)isstilllittleunderstood ,partlybecauseofthe paucityofgeologicaldatafromtheUnionofMyanmarandtheLaos,andpartlyduetotheconflictinggeodynamicconceptsadoptedbyvariousa… 相似文献