Virtual Legendrian Isotopy

An elementary stabilization of a Legendrian link $L$ in the spherical cotangent bundle $ST^*M$ of a surface $M$ is a surgery that results in attaching a handle to $M$ along two discs away from the image in $M$ of the projection of the link $L$. A virtual Legendrian isotopy is a composition of stabilizations, destabilizations and Legendrian isotopies. In contrast to Legendrian knots, virtual Legendrian knots enjoy the property that there is a bijective correspondence between the virtual Legendrian knots and the equivalence classes of Gauss diagrams. We study virtual Legendrian isotopy classes of Legendrian links and show that every such class contains a unique irreducible representative. In particular we get a solution to the following conjecture of Cahn, Levi and the first author: two Legendrian knots in $ST^*S^2$ that are isotopic as virtual Legendrian knots must be Legendrian isotopic in $ST^*S^2.$Comment: 10 pages, 4 figur

The nature of compensatory and restorative processes in the livers of animals irradiated during hypokinesia

The nature of postirradiation repair in the livers of rats irradiated during hypokinesia is investigated. Hepatocyte population counts, mitotic activity, binuclear cell content, and karyometric studies were done to ascertain the effects of combined hypokinesia and radiation. Hypokinesia is shown to change the nature and rate of post-irradiation changes in the liver, the effect varying with the timing of irradiation relative to the length of hypokinesia. It is concluded that the changes in the compensatory and restorative processes are caused by stress developed in response to isolation and restricted mobility. By changing neuroendocrine system activity, the stress stimulates cell and tissue repair mechanisms at a certain stage essential to the body's reaction of subsequent irradiation

Ultra-hard fluid and scalar field in the Kerr-Newman metric

An analytic solution for the accretion of ultra-hard perfect fluid onto a moving Kerr-Newman black hole is found. This solution is a generalization of the previously known solution by Petrich, Shapiro and Teukolsky for a Kerr black hole. Our solution is not applicable for an extreme black hole due to violation of the test fluid approximation. We also present a stationary solution for a massless scalar field in the metric of a Kerr-Newman naked singularity.Comment: 9 pages, 3 figures, revtex4; v2: presentation improved, figures added, matches published versio

Thick fluid disks around binary black holes

A model of a thick fluid disk around a binary black hole is considered. A binary black hole is described by the Majumdar-Papapetrou solution. The hydrodynamic equations in this metric are written out. Exact analytical solutions are presented. Generalization to the case of a toroidal magnetic field is carried out

Morphological features of river channels and floodplains in the Far East of Russia under various natural conditions

Geographical analysis of river channel processes in rivers located along the meridional transect, running from the Arctic Ocean coast to Tibet and the East China Sea, confirmed that fluvial processes dominate in the formation of morphology and dynamics of river channels and floodplains in all natural zones and under different conditions of channel deformation development. However, even a small disturbance in “climate” conditions by other exogenous geomorphological processes changes the morphology and dynamics of channels and floodplains as well as the dynamics of fluvial processes. The effect of zonal factors depends on the size of a given river and is more pronounced in medium and small rivers than the large ones. Furthermore, the effect of zonal factors on the processes of river channels and floodplains depends on specific environmental conditions of the climate zones: the more extreme the manifestation of certain climatic phenomena, the more pronounced they are in the morphology and dynamics of river channels and floodplains