Cooling and fragmentation of gas in rotating protogalaxies     

E. O. Vasiliev  E. I. Vorobyov  Yu. A. Shchekinov 《Astronomy Reports》2010,54(10):890-901

The dynamical, thermal, and chemical evolution of gas in protogalaxies with non-zero angular momentum is considered. It is shown that, in protogalaxies with a total mass (dark and baryonic) of M = 10⁷ M⊙ at redshifts z = 12 whose gas has rotational angular momentum (spin parameter λ ≳ 0.005), a disk-like structure forms during the initial collapse of the galaxy, in contrast to non-rotating protogalaxies, whose collapse is spherically symmetric. The existence of initial angular momentumfor gas in protogalaxies increases the cooling time of the gas, delaying the formation of the first stars. Increasing the rotational angular momentum of the gas leads to cooling of the gas to lower temperatures (T < 100 K), at which HD molecules dominate in the cooling, while the total mass of cool gas (T < 1000 K) is decreased. The stability of disk-like structures in the central regions of protogalaxies is analyzed. It is shown that the disk that is formed is gravitationally unstable, and multiple fragmentation at various distances from the center is possible when the initial rotational angular momentum of the protogalaxy is increased. The possible birth of several stars in the first protogalaxies is discussed.  相似文献   

The first <Superscript>40</Superscript>Ar/<Superscript>39</Superscript>Ar age data for trap intrusions of the western part of the Siberian Platform     

Yu. R. Vasiliev  M. P. Mazurov  S. N. Prusskaya  A. V. Travin 《Doklady Earth Sciences》2010,432(2):750-753

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Geology,mineralogy, and genesis of palygorskite clay from Borshchevka deposit in the Kaluga Region and outlook for its technological use     

V. V. Nasedkin  A. L. Vasiliev  N. M. Boeva  P. E. Belousov 《Geology of Ore Deposits》2014,56(3):208-227

In this paper we consider localization and paleogeographic conditions of palygorskite deposition in the Moscow Syneclise, which is regarded as a palygorskite province. The geology and mineralogy of the Borshchevka deposit are also characterized. Mineralogical and chemical analyses of rocks from the Steshevo Horizon (C_1st), which is the most promising for palygorskite and associated smectite, have been carried out. The morphology and crystal structure of palygorskite varieties differing in origin are characterized, as well as possible use of palygorskite from the Borshchevka deposit as a drilling mud, foundry sand, and sorbent.  相似文献   

The nature of the heat source of mafic magmatism during the formation of the Vilyui rift based on the ages of dike swarms and results of numerical modeling     

O.P. Polyansky  A.V. Prokopiev  O.V. Koroleva  M.D. Tomshin  V.V. Reverdatto  A.V. Babichev  V.G. Sverdlova  D.A. Vasiliev 《Russian Geology and Geophysics》2018,59(10):1217-1236

Possible mechanisms of rifting and the thermal regime of the lithosphere beneath the rift zone of the Vilyui sedimentary basin are considered based on the available isotopic ages of dike swarms, rates of sedimentation, and results of numerical modeling. Temporal correlations between the intrusion of mafic magma and a sharp increase in the rate of subsidence and sedimentation in the rift basin prove the contribution of both plate-tectonic and magmatic factors to the formation of the Vilyui rift. The results show a relationship between the rapid extension of the lithosphere and the formation of mafic dike swarms in the Yakutsk-Vilyui Large Igneous Province of the Siberian Platform at the Frasnian-Famennian boundary, with a peak at ~ 374.1 Ma, and at the end of the Late Devonian, with a peak at ~ 363.4 Ma. There were two pulses of dike formation during rapid subsidence of the basin basement in the period 380-360 Ma, with a sedimentation rate of 100-130 m/Myr, at a background rate of 10-20 m/Myr. Analysis of numerical thermomechanical models revealed that the best-fit model is that combining the mechanisms of intraplate extension (passive rifting) and the ascent of a mantle magmatic diapir (active rifting). A conclusion about the nature of the heat source of trap magmatism has been drawn: The plume-driven regime of the lithosphere can better explain the dynamics of extension during rifting than the decompression melting mechanism.  相似文献   

Methane in ground ice and frozen Quaternary deposits of Western Yamal     

A. A. Vasiliev  I. D. Streletskaya  V. P. Melnikov  G. E. Oblogov 《Doklady Earth Sciences》2015,465(2):1289-1292

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Gravitational Hall Effect and Gravitomagnetic Dynamo     

Oprea  Iuliana  Agop  M. 《Studia Geophysica et Geodaetica》1998,42(3):431-435

In the linear approximation of the gravitational field and using the gravitational quantum Hall effect, the gravitational conductivity is defined and the gravitomagnetic analogous of the kinematic dynamo is formulated.  相似文献   

Messinian events in the Black Sea          下载免费PDF全文

Christiaan G. C. van Baak  Eleanora P. Radionova  Larisa A. Golovina  Isabella Raffi  Klaudia F. Kuiper  Iuliana Vasiliev  Wout Krijgsman 《地学学报》2015,27(6):433-441

Past hydrological interactions between the Mediterranean Sea and Black Sea are poorly resolved due to complications in establishing a high‐resolution time frame for the Black Sea. We present a new greigite‐based magnetostratigraphic age model for the Mio‐Pliocene deposits of DSDP Hole 380/380A, drilled in the southwestern Black Sea. This age model is complemented by ⁴⁰Ar/³⁹Ar dating of a volcanic ash layer, allowing a direct correlation of Black Sea deposits to the Messinian salinity crisis (MSC) interval of the Mediterranean Sea. Proxy records divide these DSDP deposits into four intervals: (i) Pre‐MSC marine conditions (6.1–6.0 Ma); (ii) highstand, fresh to brackish water conditions (~6.0–5.6 Ma); (iii) lowstand, fresh‐water environment (5.6–5.4 Ma) and (iv) highstand, fresh‐water conditions (5.4–post 5.0 Ma). Our results indicate the Black Sea was a major fresh‐water source during gypsum precipitation in the Mediterranean Sea. The introduction of Lago Mare fauna during the final stage of the MSC coincides with a sea‐level rise in the Black Sea. Across the Mio‐Pliocene boundary, sea‐level and salinity in the Black Sea did not change significantly.  相似文献   

Flood risk perception along the Lower Danube river,Romania     

Iuliana Armas  Radu Ionescu  Cristina Nenciu Posner 《Natural Hazards》2015,79(3):1913-1931

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Nonequilibrium carbon ionization states and the extragalactic far-UV background with HeII absorption     

Evgenii O. Vasiliev  Shiv K. Sethi  Biman B. Nath 《Astrophysics and Space Science》2011,335(1):211-215

Using nonequilibrium calculations of the ionic states and the recently calculated extragalactic ultraviolet background radiation with absorption by intergalactic HeII we determine the ratios of CIII to CIV expected at z∼2–3, as functions of metallicity, gas density and temperature. We constrain the spectrum of the extragalactic ultraviolet background radiation by fitting the observed abundance ratios carbon ions at these redshifts with those expected from different models of the background radiation. Our analysis of the observed ratios shows that ‘delayed reionization’ models, which assume a large fraction of HeII at z∼3, is not favored by data. Our results suggest that HeII reionization was inhomogeneous, consistent with the predictions from recent simulations.  相似文献   

Cascades of subglacial lakes in Antarctica     

V. M. Kotlyakov  L. N. Vasiliev  A. B. Kachalin  M. Yu. Moskalevsky  A. S. Tyuflin 《Doklady Earth Sciences》2012,443(2):509-512

Progress in understanding cascades of subglacial lakes in Antarctica and in the dynamics of their surface was derived using satellite laser altimetry measurements ICESat. The morphological and dynamical signs indicate subglacial lakes and the positions of their shore lines. Oscillations of surfaces in transition zones are periodic, while the changes in surface elevation above subglacial lakes are random. The pattern of surface displacements above cascades of subglacial lakes in Antarctica and their transition zones as similar. In the sense of technology, this paper initiates the method of mapping subglacial lakes based on satellite laser measurements of elevation.  相似文献