Changes in the Distribution of Broadleaf Tree Species in the Central Part of the Southern Urals since the 1970s

Russian Journal of Ecology - Changes in the distribution of broadleaf tree species—Tilia cordata Mill., Quercus robur L., Acer platanoides L., and Ulmus glabra Huds.—in the central part...     

Radial increment of larch and pine in central Yakutia as dependent on climate change over the past 120 years

The results of studies on the radial increment of larch and pine in central Yakutia are presented. The application of dendroclimatological methods to the study of tree-ring chronologies has made it possible to evaluate tree growth response to the dynamics of climatic factors over the past 120 years. The results of analysis of radial tree increment show that the onset of the growing season has shifted to earlier dates by the end of the 20th century.     

Holarctic Collared Lemmings: Traces of Their Spread as Related to the History of the Arctic Biota

Among recent lemmings (D. torquatus from the Yamal Peninsula and D. groenlandicus from Somerset, Bathurst, Melville, and Devon islands), there are populations with archaic sets of morphotypes characteristic of the end of the Late Pleistocene. In some parts of the species range, lemming morphotypes follow the pattern characteristic of the Holocene stage of their evolution. Lemmings with the best developed tooth system live in the Bering Sea sector of the Arctic (Wrangel Island, Chukotka and Alaska). The correspondence of the boundaries of the groups distinguished by odontological traits to the phylogeographic data on mitochondrial DNA (mtDNA) and chromosomal groups is discussed.     

Soil phytoremediation from the breakdown products of the chemical warfare agent, yperite

A plant-based bioremediation (phytoremediation) strategy has been developed and shown to be effective for the clean-up of soil contaminated by the breakdown products of the chemical warfare agent (CWA), yperite. The method involves exploiting the plant growth hormone, indole-3-acetic acid (IAA), to intensify the phytoremediation. For determination of the yperite breakdown products, gas chromatography is used. Soil and plant samples were analysed with a gas chromatograph fitted with an atomic emission detector. The method of standard-free determination was employed to identify sulphur-containing substances (SCSs). A series of soil tests was conducted, which showed that the level of SCSs decreased 4, 8, and more than 20-fold compared with that found in contaminated soil. This decrease was dependent upon the IAA concentrations used for plant treatment. The treated plants accumulated 2.7 to 2.9-fold larger amounts of the SCSs than did the untreated plants. Owing to its simplicity, environmental safety and inexpensiveness, the method can be recommended for the restoration of soil fertility in areas of storage and destruction of blister CWAs.     

Computation of particles’ ascent from a cavity behind passing shock wave

We study numerically the dynamics of particles of dispersed phase in a turbulent gas flow in planar shock waves (SWs) sliding along a solid surface with a depression of trapezoid shape. The ascent of particles from the cavity walls has been computed in the approximation of a rarefied gas–particle mixture. A considerable influence of the passing SW strength and the initial location of particles on the characteristics of particles’ ascent, the non-monotonicity of the dependence of the particle-ascent height on the initial longitudinal coordinate, and the SW Mach number, and a possibility of the formation of particles’ accumulation and removal zones on the depression bottom are shown.     

About stability of the ignition process of small solid particle

The distributed mathematical model of magnesium particle ignition is developed taking into account the heterogeneous chemical reaction and the domain of particle thermal influence on gas. The problem solvability in the stationary case has allowed one to expand classification of regular modes of heating as well as the modes of extinction and ignition of a particle. The limiting size of a gas layer near a particle is found that determines an ignition mode. It is shown that the ignition delay time grows if we take into account the gas layer near the particle. Stability of some heating modes within the framework of finite and infinitesimal perturbations is studied. An opportunity to control the ignition process by high-frequency thermal action on the unstable particle gas states is shown.     

Problems in predicting <Superscript>137</Superscript>Cs levels in lake waters of eastern Fennoscandia

With regard to data on two-year exposure of Chernobyl-derived ¹³⁷Cs in lakes with average depths ranging from 2 to 15 m, contamination of lake waters has been estimated using a sorption-diffusion model with ¹³⁷Cs distribution and diffusion coefficients of 4000 l/kg and 1.0 × 10⁻⁷ cm², respectively.     

Ignition wave in a two-velocity two-temperature multiphase mixture

The theory of stationary adiabatic and non-adiabatic ignition waves in magnesium aerosuspension is developed on the basis of the mathematical model based on two-velocity two-temperature approach of mechanics of heterogeneous media. Specifically, the conditions such that the particle cloud ignites under the action of an initiating shock wave (SW) are defined. An agreement between the adiabatic one-velocity model and the adiabatic two-velocity model on the ignition delay time for small particles is shown. Influence of particle size on this characteristic is compared for both models. Validation of the two-velocity model is performed on the basis of comparison with the experimental data. The unified formula for calculation of the induction period of the magnesium particle mixture in oxygen which takes into account its dependence on the SW Mach number and particle radius is found.