Cosmology and Astrometry     

Sazhin  M. V.  Zharov  V. E.  Kalinina  T. A.  Sementsov  V. N. 《Astronomy Reports》2018,62(12):1026-1029

Astronomy Reports - It has recently become clear that the potential role of astrometry in cosmological studies has been underestimated. Some areas of cosmology that should be investigated using...  相似文献   

The spectrum of random ICRF source angular velocities     

M. V. Sazhin  O. S. Sazhina  A. O. Marakulin 《Astronomy Reports》2011,55(11):945-953

The spectrum of the random angular velocities of ICRF sources is analyzed. This spectrum is calculated assuming that the apparent angular velocities of the sources are random and uncorrelated, and that the directions of the motions of each source are uniformly distributed over a circle. The amplitudes of the vector spherical harmonics display a white-noise spectrum. Published observational data are considered, and preliminary conclusions are drawn about the nature of the observed dipole and quadrupole harmonics in the spectrum of angular velocities.  相似文献   

Bacterioplankton of the Kara Sea shelf     

N. D. Romanova  A. F. Sazhin 《Oceanology》2015,55(6):858-862

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The role of gametes of the macroalgae <Emphasis Type="Italic">Ascophyllum nodosum</Emphasis> (L.) Le Jolis and <Emphasis Type="Italic">Fucus vesiculosus</Emphasis> L. (Fucales,Phaeophyceae) in summer nanoplankton of the White Sea coastal waters     

O. V. Maximova  A. F. Sazhin 《Oceanology》2010,50(2):198-208

Studies of macrophytes in the coastal zone of the Artic Seas, including the White Sea, have shown the essential role of these algae in the activity of the coastal half-latitude ecosystems. In summer, during the macrophyte reproduction period, a great number of reproduction products are released into the water. For a short time, this considerably affects the ratio of the nanoplankton in the populations that inhibit the vast and shallow coastal areas. At different coastal sites in Chernorechenskaya Inlet, Kadalaksha Bay, during the period of intensive reproduction of Ascophyllum nodosum and Fucus vesiculosus, 42 plankton samples were collected in 2005. During this period the concentration of antherozoids in the water reached 55000 cells/ml (216 mg C/m³). The number of eggs was within the range of 0.05–0.7 cells/ml. The proportion of antherozoids in the total biomass of nanoplankton varied at different coastal sites from 0.37 to 99%, with a mean of 46% for the reproduction period of A. nodosum, and only 7% for the reproduction period of F. vesiculosus. As was shown by counts of F. vesiculosus female gametes in sedimentation traps, 1 m² of the macrophyte bed (assuming 100% coverage) produces 18000–108000 eggs per day (0.33–2 mg C). The calculated flux of the reproductive material from the brown algae beds to the coastal water shows good agreement with the sample counts.  相似文献   

Viruses,bacteria, and heterotrophic nanoflagellates in Laptev Sea plankton     

A. I. Kopylov  A. F. Sazhin  E. A. Zabotkina  A. V. Romanenko  N. D. Romanova  P. R. Makarevich  M. P. Wenger 《Oceanology》2016,56(6):789-798

The paper considers the concentrations and functional characteristics of viruses, bacteria, and heterotrophic nanoflagellates determined for the first time in the Laptev Sea in August-September, 2014. The abundance of bacteria, viruses, and heterotrophic nanoflagellates varied from 110.1 × 10³ to 828.4 × 10³ cells/mL, from 384.2 × 10³ to 2932.8 × 10³ particles/mL, and from 108 to 651 cells/mL, respectively. The daily bacterioplankton production varied from 4.2 × 10³ to 381.7 × 10³ cells/mL, with an average of 117.6 × 10³ cells/mL. Electron transmission microscopy has for the first time shown that the frequency of visibly infected bacterial cells varied from 0.2 to 2.0% (0.8% on average) of N_B. The average virus-induced mortality of bacteria was 6.3% of bacterioplankton production, with variations ranging from 1.4 to 16.9%. Grazing on bacteria by heterotrophic nanoflagellates contributed more to bacteria mortality than virus-induced bacterial lysis. By grazing on bacteria, heterotrophic nanoflagellates consumed large quantities of viruses located on the surface and inside bacterial cells.  相似文献   

Parallax distortion by the weak microlensing effect     

M. V. Sazhin  V. E. Zharov  T. A. Kalinina 《Monthly notices of the Royal Astronomical Society》2001,323(4):952-964

Parallax measurements allow distances to celestial objects to be determined. Together with measurements of their position on the celestial sphere, they give a full three-dimensional picture of the location of the objects relative to the observer. The distortion of the parallax value of a distant source affected by weak microlensing is considered. This means that the weak microlensing leads to distortion of the distance scale. The gravitational deflection causes a retrograde apparent motion of the image, which is revealed as a negative parallax. It is shown that the distortions may significantly change the parallax values when they amount to several microseconds of arc. In particular, at this level many measured values of parallaxes should be negative.  相似文献   

Analytical and numerical analysis of the generalized Shkarofsky function     

N. M. Temme  A. E. Sumner  S. S. Sazhin 《Astrophysics and Space Science》1992,194(2):173-196

The main analytical properties of the generalized Shkarofsky function and a numerical code for its computation are discussed. The results of a numerical analysis are compared with the results of an asymptotic analysis for parameter values relevant to the problem of whistler-mode propagation in the Earth's magnetosphere. This comparison allows us to specify the range of applicability of different approximations to the generalized Shkarofsky function, which have been used for the analysis of relativistic effects on whistler-mode propagation and instability.  相似文献   

A new approximate solution of parallel whistler-mode dispersion equation     

Sergei S. Sazhin 《Astrophysics and Space Science》1990,172(2):235-247

A new approximation of the real part of the nonrelativistic plasma dispersion function ?Z of a real argument ξ₀ is proposed: namely, $$\Re Z_A (\xi _0 ) = \frac{{2\xi _0 }}{{1 - 2\xi _0^2 }}.$$ This approximation gives the exact value for ?Z when d²?Z/dξ ₀ ² = 0 and gives the correct expressions for the first two terms of its expansion for large ξ₀. On the basis of this approximation, a new approximate expression for whistler-mode refractive index is derived for the case of wave propagation parallel to the magnetic field in a hot anisotropic and dense plasma. Under certain conditions this expression is more convenient for practical applications in magnetospheric and/or astrophysical conditions than other approximate expressions. The approximation ?Z _A was also used in deriving the approximate expression for whistler-mode instability or damping (γ), although in this case it seems to have little merit when compared with the previously used expressions for γ.  相似文献   

Adaptation of the ionospheric radio channel parameters to the current conditions using observations of the signals of reference radio stations     

V. A. Golygin  V. I. Sazhin  V. E. Unuchkov 《Geomagnetism and Aeronomy》2007,47(1):67-71

A method of adaptation of the ionospheric channel parameters to the current conditions is proposed. The observational data on the temporal behavior of signals of radio stations with known location and set of working frequencies (the so-called reference stations) are used as information describing the current state of the channel. A facility that makes possible to determine by simple means the moments of radio rises and declines on the reference paths has been created. A technique that relates for these instants working frequencies of the stations with maximum usable frequencies of the paths has been developed. By means of an approximate solution of the inverse problem using the method of characteristics for the calculation of radiowave propagation and the monthly average semiempirical model of the ionosphere, the height profile of electron density in a certain spatial region is refined. The efficiency of the proposed method of adaptation of the ionospheric channel parameters using the data of vertical sounding is assessed and the expediency of practical application of such adaptation is shown.  相似文献   

Two-stage algorithm for reconstructing the images of the gravitational lens QSO 2237+0305     

E. A. Koptelova  E. V. Shimanovskaya  B. P. Artamonov  M. V. Sazhin  A. G. Yagola 《Astronomy Reports》2004,48(10):826-833

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