THE TUNGUSKA EVENT AND THE METEORS WITH TERMINAL FLARES     

B.Yu. Levin  V.A. Bronshten 《Meteoritics & planetary science》1986,21(2):199-215

The comparison of the Tunguska body explosion with the effect of terminal flares of meteors and fireballs leads us to the conclusion that these events are of a similar nature but differ only by their scale. We consider that the dynamics of progressive breaking and evaporation of meteoric bodies during their entry into the terrestrial atmosphere could explain the terminal burst. An extremely porous body model for the Tunguska meteorite was analysed and rejected as unsatisfactory. The realistic values of the initial velocity (～30 km/sec) and of the inclination angle for the Tunguska's trajectory (5–15°) give orbital elements not in contradiction with the cometary origin of the Tunguska body.  相似文献   

The shear strength of clay-filled bedding planes in limestones - back-analysis of a slope failure in a phosphate mine, Israel     

Y. H. Hatzor  M. Levin 《Geotechnical and Geological Engineering》1997,15(4):263-282

The failure of a slope in a phosphate mine by shear-sliding along a clay-filled bedding plane in limestone, and by separation across a tension crack at the back, is back-analysed. The failure cannot be explained using laboratory measured values of the shear strength parameters. In order to simulate field conditions better two physical models of the bedding plane were prepared for testing under triaxial compression. Cylindrical cores with an inclined saw-cut discontinuity were filled with remoulded montmorillonite. It is shown that failure in the models initiates along the contacts between the clay infilling and the limestone boundaries, and not through the clay itself, as would be intuitively expected. Furthermore, it is argued that in the analysis of rock slope stability in general, and particularly in the case of clay-filled discontinuities, the influence of paleo-overburden stress on frictional resistance must be resolved before the appropriate constitutive law can be established for analysis.  相似文献   

Induction of zona radiata and vitellogenin genes in estradiol and nonylphenol exposed male sheepshead minnows (Cyprinodon variegatus)   总被引：1，自引：0，他引：1  

Knoebl I  Hemmer MJ  Denslow ND 《Marine environmental research》2004,58(2-5):547-551

Several genes normally induced by estradiol (E(2)) in female fish, those for vitellogenins (VTGs) and zona radiata proteins (ZRPs), are also inducible in males exposed to estrogenic chemicals. Male sheepshead minnows (SHM) were exposed to both E(2) and para-nonylphenol (NP), at several doses and times to determine a dose-response. Quantitative real time PCR was used to measure mRNA for VTG1, VTG2, ZRP2 and ZRP3. Both E(2) and NP elicited a dose-response increase in all of the mRNAs tested. Exposure to both chemicals resulted in VTG2 expression at about a 10-fold lower level than VTG1, and ZRP2 expression at a lower level than ZRP3.  相似文献   

The remineralization of organic carbon on the North Carolina continental slope     

Neal E. Blair  Gayle R. Plaia  Susan E. Boehme  David J. DeMaster  Lisa A. Levin 《Deep Sea Research Part II: Topical Studies in Oceanography》1994,41(4-6)

The sources and fates of metabolizable organic carbon were examined at three sites on the North Carolina slope positioned offshore of Cape Fear, Cape Lookout and Cape Hatteras. The¹³C/¹²C compositions (δ¹³C) of the solid phase organic matter, and the dissolved inorganic carbon (ΣCO₂) produced during its oxidation, suggested that the labile fraction was predominantly marine in origin. The ΣCO₂ concentration gradient across the sediment-water interface, and by inference the ΣCO₂ flux and production rate, increased northward from Cape Fear to Cape Hatteras. Methane distributions and ΣCO₂ δ¹³C values suggest that the rate of anaerobic diagenesis increased northward as well. The differences in sedimentary biogeochemistry are most likely driven by an along-slope gradient of reactive organic carbon flux to the seabed. This trend in reactive organic carbon flux correlates well with macrofaunal densities previously observed at the three sites. Proximity to the shelf and the transport of particulate material by surface boundary currents may control the deposition of metabolizable material on the Carolina slope.Evidence for methanogenesis was found only on the Cape Hatteras slope. The methane, which was produced at a depth of approximately 1 m in the seabed, was consumed nearly quantitatively in the biologically mixed layer as it diffused upward. Irrigation of the sediments by infauna may have provided the necessary oxidant for the consumption of the methane.  相似文献   

On the possibility of the determination of water's optic characteristics versus relative transparency     

I. M. Levin 《Physical Oceanography》1990,1(3):237-241

Translated by V. Puchkin.  相似文献   

Statistical relations of the run-up height of Tsunami waves to the distance and energy of the source     

P. O. Zav’yalov  B. V. Levin  O. N. Likhacheva 《Oceanology》2006,46(1):10-16

A statistical analysis of the relation between the run-up height of historical tsunami events and the distance and magnitude of the source was performed on the basis of the known Historical Tsunami Data Base [5]. The sample from the database used for the analysis comprises 5638 run-ups caused by 628 seismic events. This analysis, together with the dimensionality theory, shows that the statistical average of the run-up height is inversely proportional to the distance from the source to a power close to 1/2 (that is characteristic of the cylindrically symmetrical case) and directly proportional to the 3/8 power of the earthquake energy.  相似文献   

Eurasian catastrophic floods: The Tsasuchei Jokulhlaup in southern Transbaikalia     

E. V. Sklyarov  O. A. Sklyarova  Yu. V. Men&#;shagin  A. V. Levin 《Doklady Earth Sciences》2007,415(6):919-921

  相似文献   

The ocean-atmosphere response to wind-induced thermocline changes in the tropical South Western Indian Ocean     

Iris Manola  F. M. Selten  W. P. M. de Ruijter  W. Hazeleger 《Climate Dynamics》2015,45(3-4):989-1007

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Modeling of the temperature regime of mud volcano gryphons     

Ershov  V. V.  Domanskii  A. V.  Levin  B. V. 《Doklady Earth Sciences》2010,435(1):1529-1534

This paper is devoted to modeling of the dynamics of the temperature regime of mud volcano gryphons. The model is elaborated on the basis of a nonstationary equation of thermal conductivity with a convective component and describes well the observed regularities of thermal regime of South Sakhalin mud volcano gryphons. It is shown that anomalous changes in the temperature of the water-mud mixture after the Gornozavodsk and Nevelsk earthquakes in 2006–2007 are caused by variations in motion velocity of the mixture in the supply pipes of gryphons. It also has been shown that influx of deep geofluids cannot be considered as the main reason for thermal anomalies.  相似文献   

Accounting for indirect effects and non-commensurate values in ecosystem based fishery management (EBFM)     

Kate Richerson  Phillip S. Levin  Marc Mangel 《Marine Policy》2010,34(1):114-119

Ecosystem-based fishery management (EBFM) requires taking account of indirect effects (such as habitat destruction, incidental mortality, and competition between the fishery and marine mammals or birds) and dealing with non-commensurate values (such as yield from the fishery and production of offspring by the birds or mammals competing for the same resource). The perspective of EBFM requires that the rate of fishing mortality is less than the value that provides maximum sustainable yield (MSY), but the question is how far below this level should the fishery operate? For this problem in multiobjective programming, simple method of solution was developed and illustrated with the fishery for sandeels (Ammodytes spp.) in the Shetland Islands. The yield from the fishery at a given fishing mortality F is scaled by MSY (so that this quantity increases as fishing mortality increases from 0 to that giving MSY) and the breeding success of predators (black-legged kittiwakes Rissa tridactyla and Arctic terns Sterna paradisaea) at a given fishing mortality is scaled by that in the absence of fishing. The result is two non-dimensional quantities that can be combined into a single value function, which can then be explored or optimized. It is shown that a reduction of only about 20 percent in yield can nearly double the breeding performance of the more sensitive predator. Extensions of the method are discussed; these include the use of maximum economic yield (MEY) and state dependent life history, as implemented by stochastic dynamic programming.  相似文献