Intramolecular Hypervalent X←X Interaction in Mono- and Bicyclic Heteroelement Compounds Containing Se and Te Atoms

Chalcogen-containing heterapentalene and quasimonocyclic compounds having SeÄSeÄSe and TeÄTeÄTe triads or SeÄSe and TeÄTe diads were studied by the ab initio [MP2(full)/6-31G**, MP2(fc)/6-31+G**, and MP2(fc)/LANL2DZ] and DFT methods (B3LYP/6-31G^**, B3LYP/6-31+G^**, and B3LYP/LANL2DZ). Heterapentalene compounds were found to be stable as planar bicyclic structures having a C _2v symmetry. The stability of quasimonocycic -chalcogenovinyl aldehydes increases with increase in the electron-acceptor power of the substituent at the X atom.     

Nuclear composition of 1-to 20-PeV primary cosmic rays according to lateral features of the electron-photon component of all extensive air showers and of extensive air showers accompanying high-energy gamma rays and hadrons in x-ray emulsion chambers at the Tien Shan level

Data from the Tien Shan array Adron on the dependence of the lateral distributions of the electron-photon component (age parameter S) in extensive air showers of cosmic rays on the number of electrons, N _e , which is a quantity that characterizes the primary-nucleus energy E₀, are subjected to a comparative analysis. The distributions in question are given both for all showers and for showers accompanying high-energy gamma rays and hadrons in x-ray emulsion chambers. According to calculations, events associated with the latter are generated predominantly by primary protons, and this makes it possible to assess their role at various values of E₀. The distributions with respect to S suggest a significant fraction of light nuclei, predominantly protons, in the region after the knee in the spectrum for N _e >10⁶, at least up to N _e =5.6×10⁶ (E₀ ～ 10 PeV).     

Synthesis and antiviral activity of nonannulated tetrazolylpyrimidines

Chemistry of Heterocyclic Compounds - Nonannulated tetrazolylpyrimidines in the structure of which the heterocyclic fragments are separated by hydrazinocarbonylmethyl, methylpyrazolyl groups or a...     

The general class of the vacuum spherically symmetric equations of the general relativity theory

The system of the spherical-symmetric vacuum equations of the General Relativity Theory is considered. The general solution to a problem representing two classes of line elements with arbitrary functions g ₀₀ and g ₂₂ is obtained. The properties of the found solutions are analyzed.     

Characteristics of composite films based on methyl cellulose and poly(N-vinylformamide) prepared from solutions in water and dimethyl sulfoxide

The stress-strain characteristics of composite films based on methyl cellulose and poly(vinylformamide) prepared from solutions of polymer blends in water and dimethyl sulfoxide are studied. The temperature of relaxation transitions in the mixed films and the concentration interval where the polymers are compatible are defined via the thermomechanical method and dynamic mechanical analysis. The effect of the nature of a solvent on the mechanism of crystallization of methyl cellulose, the stress—strain characteristics of the composite films, and the compatibility between the polymers is investigated.     

Investigation of primary cosmic rays at energies above 10<Superscript>14</Superscript> eV

A search for sources of primary cosmic rays at energies of 10¹⁴–10¹⁵ eV was performed using the special independent KLARA+Khronotron unit at the Tien Shan Mountain Cosmic Ray Station in a joint experiment of the Lebedev Physics Institute (LPI) and the Central Research Institute for Physics (KFKI). A full data bank of standard events, consisting of 30 million extensive air showers (EASes), was analyzed. Analysis results are presented as maps of the directions of EAS arrival in equatorial coordinates in which the standard deviation of the number of events exceeds a certain value. These could be directions from which neutral primary cosmic particles (e.g., gamma ray photons) arrive from sources of primary cosmic rays. A match is found between separate directions with results, obtained on other stations, and the location of pulsars.