The inhabitants of the spring ice,under-ice water,and sediments of the white sea in the estuarine zone of the Severnaya Dvina River     

A. F. Sazhin  F. V. Sapozhnikov  T. N. Rat’kova  N. D. Romanova  V. P. Shevchenko  A. S. Filippov 《Oceanology》2011,51(2):295-305

The data on the supra-ice snow, ice, under-ice water, and benthic algal flora obtained in 2007–2008 by sampling in the estuary of the Severnaya Dvina River are analyzed. The river ice and under-ice water in the estuarine zone and in the channel part of the Severnaya Dvina differed greatly in the algal flora’s composition. The fresh water species never exceeded 8.6%, while the ice algae composed 90–96% of the total ice inhabitants’ biomass. In the under-ice water, this value did not exceed 58–64%. The bacteria in the ice composed not more than 2.5–10% of the total biomass, while, in the under-ice water, 36–49%. The shares of ciliates (0.04%) and nematodes (0.005–1.6%) in the total biomass were negligible. In the estuarine zone, the ice was inhabited mainly by nematodes (78% of the total biomass), while, in the river, their share decreased to 9%. The contribution of bacteria was 15% in Dvina Bay and increased to 61% in the river. The importance of algae in the snow was minor: 7% of the total biomass in the marine zone and 30% in the river region. High species diversity of the algal flora in the sandy and sandy-silty littoral grounds was revealed. The values of the total biomass of the bottom algal flora (0.38 g C/m²) were only two to three times lower than the values revealed in similar habitats in the summer. The epipelithic forms (0.15 g C/m²) dominated, being represented by 46 species of algae (49%). The shares of epipsammonic (0.12 g C/m²) and planktonic (0.11 g C/m²) species were almost equal to each other: 25 and 22 species, respectively (27 and 24%).  相似文献   

CSL-1: chance projection effect or serendipitous discovery of a gravitational lens induced by a cosmic string?     

M. Sazhin  G. Longo  M. Capaccioli  J. M. Alcalá  R. Silvotti  G. Covone  O. Khovanskaya  M. Pavlov  M. Pannella  M. Radovich  V. Testa 《Monthly notices of the Royal Astronomical Society》2003,343(2):353-359

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Electrostatic waves at frequencies close to the harmonics of electron gyrofrequency     

S. S. Sazhin 《Astrophysics and Space Science》1987,138(1):99-103

An analytical solution of the dispersion equation for electrostatic waves propagating in a plasma consisting of cold electrons and the electrons with the loss cone distribution function is obtained for wave frequencies close to the harmonics of electron gyrofrequency. Electrostatic emissions at these frequencies were observed in the magnetospheres of the Earth, Jupiter, and Saturn.  相似文献   

Parameters of the early Universe and primordial black holes     

S. O. Alexeyev  M. V. Sazhin  O. S. Khovanskaya 《Astronomy Letters》2002,28(3):139-142

We consider the possibility of low-mass primordial black holes being formed in terms of the inflationary theory of the early Universe. We found a condition on the reheating temperature under which the relic remnants of primordial black holes had been formed by now. These relic remnants may account for a part of the dark matter in our Universe.  相似文献   

Virio- and bacterioplankton in the estuary zone of the Ob River and adjacent regions of the Kara Sea shelf     

A.?I.?KopylovEmail author  A.?F.?Sazhin  E.?A.?Zabotkina  A.?V.?Romanenko  N.?D.?Romanova 《Oceanology》2017,57(1):105-113

The distribution of structural and functional characteristics of virioplankton in the north of the Ob River estuary and the adjacent Kara Sea shelf (between latitudes 71°44′44″ N and 73°45′24″ N) was studied with consideration of the spatial variations in the number (N _B) and productivity (P _B) of bacteria and water properties (temperature, salinity, density) by analyzing samples taken in September 2013. The number of plankton viruses (N _V), the occurrence of visible infected bacteria cells, virus-induced mortality of bacteria, and virioplankton production in the studied region varied within (214?2917) × 10³ particles/mL, 0.3?5.6% of NB, 2.2?64.4% of P _B, and (6?17248) × 10³ particles/(mL day), respectively. These parameters were the highest in water layers with a temperature of +7.3–7.5°C, salinity of 3.75?5.41 psu, and conventional density (στ) of 2.846?4.144. The number of bacterioplankton was (614?822) × 10³ cells/mL, and the N _V/N _B ratio was 1.1?4.5. A large amount of virus particles were attached to bacterial cells and suspended matter. The data testify to the considerable role of viruses in controlling the number and production of heterotrophic bacterioplankton in the interaction zone of river and sea waters.  相似文献   

Almost-parallel electromagnetic wave propagation at frequencies near the electron plasma frequency     

S. S. Sazhin 《Astrophysics and Space Science》1988,145(2):377-380

An approximate dispersion equation for almost-parallel electromagnetic wave propagation in a weakly relativistic plasma at frequencies near the electron plasma frequency is derived and investigated both analytically and numerically. It is pointed out that the cold plasma approximation cannot be applied to the analysis of these waves in any realistic (e.g., magnetospheric or astrophysical) plasma.  相似文献   

Gravitational action of binaries on pulsar timing in globular clusters     

M. V. Sazhin  M. V. Saphonova 《Astrophysics and Space Science》1993,208(1):93-97

The influence of gravitational waves (GW) from binaries in globular clusters on the timing of pulsars situated in this cluster is considered. The probability of observation this effect is estimated. We show that the probability is high enough in clusters Ter 5, M 15, 47 Tuc, NGC 6440. The total list of clusters with pulsars versus probability of event is presented. Total probability of this event reaches 0.97 at least in one cluster.  相似文献   

The Distortion of Microlensing by the Mass Distribution of our Galaxy     

A.F. Zakharov  M.V. Sazhin 《Astrophysics and Space Science》1997,252(1-2):373-374

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A physical model of quasi-electrostatic whistler-mode propagation     

S. S. Sazhin 《Astrophysics and Space Science》1989,161(1):171-174

The process of quasi-electrostatic whistler-mode propagation is interpreted in terms of the periodic energy exchange between wave field and perturbed electron currents.  相似文献   

A relativistic theory of plasma cut-offs     

Sergei S. Sazhin 《Astrophysics and Space Science》1993,203(2):317-327

It is pointed out that at frequencies near the plasma cut-off frequencies, the corrections to wave refractive indices in a cold plasmaN ₀due to the contribution of ions and relativistic effects can be of the same order of magnitude or greater thanN ₀. Expressions for wave refractive indicesN taking into account these corrections are derived in a limiting case |N| I. It is shown that the increase in cut-off frequencies due to effects of ions is negligibly small unless the electron plasma frequency is well below the electron gyrofrequency. The decrease of the cut-off frequencies due to relativistic effects is significant ( 1%) only in a rather hot plasma (T _e 1 keV), which may be observed in a plasma sheet region of the Earth's magnetosphere and in astrophysical conditions. These effects appear to be particularly important in a strongly anisotropic plasma (the electron perpendicular temperature is noticeably greater than the parallel one).  相似文献