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Based on the numerical simulation and qualitative analysis, the effect of the group velocity dispersion on the formation of light structures during self-focusing and filamentation of femtosecond titanium-sapphire laser pulses in air was studied. It was found that dispersion occurs when the dispersion length is not the smallest process scale. Based on the results of numerical solutions of the nonlinear Schrödinger equation in a Kerr-plasma dissipative dispersion medium using the method of diffraction-beam tubes, the main regularities of filamentation of femtosecond laser pulses in air at various pulse durations, initial beam radii, and peak emission powers were determined. It was shown that the relative (normalized to Rayleigh length) coordinate of the beginning of filamentation increases with increasing the dispersion distortion of the pulse. The length of the filamentation channel is reduced. For shorter laser pulses (tens of femtoseconds) the filamentation failure is observed, when the laser beam radius is increased. For this class of pulses, an increase in the size of the energy replenishing diffraction-beam tube occurs, and the angular divergence of the post-filamentation light channels also increases.

Critical evaluation of the available experimental data on the frequencies of the rotational and vibrational-rotational transitions of the OH molecule in the ground electronic state Х²Π is performed using the Ritz combination principle. The transition frequencies weighted in accordance with the experimental errors have been processed by the RITZ program code. The analysis of the dimensionless weighted deviations made it possible to exclude "bad frequencies" from consideration and to carry out processing with a standard deviation of 1.8. As a result of critical evaluation, a set of 1056 empirical RITZ energy levels is obtained with an appropriate uncertainty for each level. The empirical Ritz energy levels are compared with the calculated levels given in the HITRAN spectroscopic database.

The broadening and shift coefficients of H₂O absorption lines are compared for Ar, He, H₂, and N₂ buffer gases. The broadening and shift coefficients were derived from the analysis of the absorption spectra recorded with a Fourier spectrometer in the spectral range 8650-9020 cm^-1 with a spectral resolution of 0.01 cm^-1. Using two models of line profiles (Voigt and speed-dependent Voigt profiles) the parameters of the H₂O absorption lines were calculated. It is shown that the speed-dependent Voigt profile provides better agreement with experimental data.

In 2013 and 2014 from May to July the bird individual nesting home ranges were regularly mapped along the permanent census route (3.15 km) in the dark-coniferous taiga on the southern slope of the Baikal lake bed. Based on the mapping results, for each bird species the nesting densities and average sizes of the bird individual nesting home range are estimated. Raster maps of spatial allocation (MSA) at the scale of the raster grid of 50 ´ 50 m are obtained for each species. The degree of spatial conservatism (DSC) for each local population is inferred from the pairwise comparisons of the specific MSAs obtained at the same area (31.5 hectares) in different years with the use of the Gamma rank correlation method. Dependence of the population habitat area on DSC was demonstrated earlier [Cherenkov, 2017]. The more habitat area is found, the less dependent the individual spatial allocation within a population is observed in the different years. Based on the specific habitat areas, average sizes of the individual nesting home range and nesting densities estimated, the maximum possible nesting density and habitat saturation are calculated for each species. The population status is inferred from the degree of habitat saturation. The significant DSC estimates ( p < 0.05) are obtained for nine species, their habitat areas and saturation are found. It is shown that habitat saturation in non-migratory birds is twice higher that in migratory ones 54-58 % versus 26 %, ( F = 9.1; p < 0.01). In the two species, the Orange-flanked Bush-robin Tarsiger cyanurus Pallas, 1773 and Taiga Flycatcher Ficedula ( parva ) albicilla Pallas, 1811, the habitat saturation is less than 20 % that indicates the presumably troubled status of their populations.

Investigations of the mechanisms of spatial - behavioral interaction of members of such diverse and significant guilds as red wood ants and small mammals have been started only recently, and many questions remain obscure. In laboratory experiments we investigated inter-relations between red wood ants Formica aquilonia Yarr and the common vole Microtus arvalis Pallas, the bank vole Myodes glareolus Schreber, and the pygmy wood mouse Sylvaemus uralensis Pallas. We first described the defensive behavior of rodents and revealed a stereotype of the hunting behavior of the common vole towards dangerous insects. In all three rodent species, defensive behavior increased with an increase in the number of ants used in the tests, which corresponded to simulated natural situations with gradations of the dynamic density of insects. We speculate about the relationship between the defensive and hunting behavior of rodents towards red wood ants.

In the experiment to study impact of trophic conditions, the activity of zooplankton and fish on phytoplankton structure was shown, at the beginning of the experiment the species and size structure of algae was determined by the N: P ratio. Independently of “top-down” control, this determined the dominance of diatoms, dinoflagellates and chrysophytes algae in mesotrophic conditions, while in eutrophic - cyanobacteria. Further in all variants of the experiment the differences in the ratio N: P were leveled, the phytoplankton was dominated by large filamentous green algae. Fish weakened the press of zooplankton for phytoplankton and contributed to the increase in biomass available for zooplankton diatoms, this is most clearly manifested in eutrophic conditions.

The structure and diversity of zooplankton of the mouth part of the largest river in the European North - Pechora is studied. The river delta, an adjacent piece of the Pechora course, estuary firth (the Korovinsky bay) and lakes on its northern coast - in Timan Tundra belong to the region under study. In the delta of the Pechora River the planktonic fauna was rich and unique on structure, in which rotifers (105 species) and cladocerans (55 species) prevailed. Thermophilic invertebrates are presented in zooplankton, but cold-loving are revealed. Among copepods brackish taxa and also a possible recent invader to the region ( Eurytemora sp.) are found. The analysis alpha- and beta-diversities of planktonic communities of the studied region has showed that in the delta water bodies and lakes in general indexes are the highest. That are caused, in our opinion, variety of environmental conditions and also features of gradients of the dominating environmental factors: temperature, etc.

Harmful potential of bulk bottom sediments (BS) of the Yenisei River was estimated with Allium test. Sediment samples were collected in ten sites at about 100-km stretch of the middle reaches of the Yenisei affected by urban activity of the city of Krasnoyarsk and industrial plants. The samples of sediments differed considerably in concentration of potentially toxic substances (heavy metals, artificial radionuclides and organic pollutants), nutrients and physical properties. Average length of root of onion was considered as indicator of general toxicity, mitotic index - as indicator of cytotoxicity, and percent of ana-telophase cells in the root apices carrying abnormal chromosomes - as indicator of genotoxicity. Both stimulation and inhibition of indicator endpoints was revealed on sediment samples of the Yenisei relatively to control (artificial sediments). Increased genotoxicity was recorded on the sediments sample, contaminated with mixture of organic and chemical toxins. Significant positive correlation of percent of abnormal cells and concentration of copper and petrochemicals in sediment samples was revealed. Extremely strong reactions of onion endpoints to the quality of BS were not revealed, probably due to relatively low level of contamination of the sediment samples. This is in agreement with the results of chemical analyses. Based on the results of the testing we can conclude that the endpoints of the Allium test a re sensitive enough to the quality of BS of the Yenisei River and can be used for their biotesting.

During the period of study it was discovered that the general distribution pattern of species, their structure and the amount of phytoplankton were different from those recorded earlier. The most changes have undergone in the central part of the northern coast of the Neva Bay. During the eutrophication of phytoplankton in summer (late July-early August) in the Neva Bay and in the eastern part of the Gulf of Finland different groups of algae may play a prevalent role. In the Neva Bay Chlorophyta predominated in the samples. In the resort zone of the Gulf of Finland, the main share of biomass in 2011-2015 was represented by cyanobacteria.

The accumulation processes of chemical elements as well as distribution between abiotic (water, bottom sediments) and biotic (seston, zooplankton, fish) components of the Lake Bolshoy Vud’yavr ecosystem polluted by apatite-nepheline mining sewage for a long period, are analyzed. The values of the biological accumulation of the elements and their enrichment of water and bottom sediments are determined. The biogenic and terrigenous contribution of the chemical elements to the composition of bottom sediments has been estimated.