Recyclization reactions of heterocycles

2,5-Dimethyl-1,3,4-oxa- and -1,3,4-thiadiazoles are recyclized to 2,5-dimethyl-4-amino-1,2,4-triazole on reaction with hydrazine. Recyclization occurs with greater difficulty and only with oxadiazole in the case of alkylhydrazines. Nitration of 2,5-dimethyl-4-amino-1,2,4-triazole gives its N-nitroamino derivative.See [1] for communication XVIII.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 853–855, June, 1976.     

Optical properties and electronic structure of BiTeCl and BiTeBr compounds

Optical properties of BiTeCl and BiTeBr compounds with a strong Rashba spin–orbit coupling are studied in the 0.08–5.0 eV range using the optical ellipsometry method. Fundamental characteristics of the electronic structure are obtained. Similarly to BiTeI, spectra of the imaginary part of dielectric permittivity constant ε₂(E) in the energy interval between the plasma edge and the threshold of an intense interband absorption (0.7 eV in BiTeCl and 0.6 eV in BiTeBr) display a fine structure of electronic transitions at 0.25 and 0.55 eV in BiTeCl and 0.20 and 0.50 eV in BiTeBr. These features are assigned to electronic transitions between the bulk conduction zones split by the Rashba spin–orbit interaction. The parameters of the electronic structure of BiTeCl and BiTeBr are compared with the BiTeI compound that was studied earlier. In the BiTeCl–BiTeBr–BiTeI row, the absorption edge and main features of the fundamental absorption exhibit a shift to low energies.     

Synthesis and application of polyhedral oligosilsesquioxanes and spherosilicates

Data on methods for the synthesis of reactive polyhedral oligomeric silsesquioxanes and spherosilicates are summarized and their influence on the properties of polymer systems is considered. It has been shown that these compounds hold promise for electronics, optics, aerospace technology, and medicine.     

Synthesis and Crystal Structures of New Potassium Fluorotrifluoroacetatometallates: Kn[M3(µ3-F)(CF3COO)6L3]L' (M = Co,Ni; L = CF3COO–, CF3COOH,H2O; L' = CF3COOH,H2O; n = 1, 2)

Russian Journal of Coordination Chemistry - Four new representatives of potassium fluorotrifluoroacetatometallates are synthesized and crystallographically studied:...     

Formation of a crystallographically oriented colony of products of eutectoid decomposition in the process of plastic deformation of steel by drawing

Methods of transmission electron microscopy and EBSD analysis have been used to study the evolution of the structural state of a eutectoid steel in the process of plastic deformation by drawing. It has been established that the reason for steel embrittlement is in the formation in the former grains of the high-temperature phase of a specific element of the structure, namely, a crystallographically oriented colony of products of eutectoid decomposition, including a conglomerate of morphological colonies with a common orientation along the cleavage plane of one of the constituents of the eutectoid. The process of its formation means multiple changes in the scale of the structure and, therefore, increase in the temperature threshold of the material brittleness.     

Features and mechanisms of growth of cubic silicon carbide films on silicon

The mechanisms and specific features of the growth of silicon carbide layers through vacuum chemical epitaxy in the range of growth temperatures from 1000 to 700°C have been considered. The structure of the heterojunction formed has been studied using the results of the performed investigations of photoluminescence spectra in the near-infrared wavelength range and the data obtained from the mass spectrometric analysis. It has been found that, in the silicon layer adjacent to the 3C-SiC/Si heterojunction, the concentration of point defects significantly increases and the dislocation structure is not pronounced. According to the morphological examinations of the surface of the growing film, by analogy with the theory of thermal oxidation of silicon, the theory of carbidization of surface silicon layers has been constructed. A distinctive feature of the model under consideration is the inclusion of the counter diffusion fluxes of silicon atoms from the substrate to the surface of the structure. The growth rate of films and the activation energy of diffusion processes have been estimated. The performed experiments in combination with the developed growth model have explained the aggregates of voids observed in practice under the silicon carbide layer formed in the silicon matrix and the possibility of forming a developed surface morphology (the island growth of films) even under conditions using only one flow of hydrocarbons in the reactor.     

A refined diffusion model of the interaction of laser radiation with biological tissue

A refined diffusion model of laser radiation propagation in a highly scattering medium that, in contrast to the conventional variant, takes into account the initial single directivity of the photon source is presented. The two variants of the diffusion model are numerically compared. For small thicknesses of the scattering layer, the refined model is shown to be more accurate than the classical model.     

Nonstationary two-flux model of radiation transport for optical tomography of scattering media

A nonstationary two-flux model is formulated for the transport of radiation in an inhomogeneous scattering medium and is applied to the situation where such a medium is irradiated by the narrow beam of a pulsed laser. It is shown that when the time distribution of the transmitted photons is measured it is possible simultaneously to reconstruct the two spatial functions (the coefficients of absorption coefficient and of scattering of the radiation by the medium) by means of an inverse Radon transformation and the solution of a system of nonlinear differential equations on the projection lines. An analytic solution is obtained in quadratures for these differential equations. The results constitute a method of solving problems in optical tomography in an inhomogeneous scattering medium Zh. Tekh. Fiz. 67, 61–65 (May 1997)     

Detection of infrasound from the Vitim bolide on September 24, 2002

An infrasonic signal from an atmospheric bolide explosion was detected on September 24, 2002 near the Vitim river, Irkutsk region (57.9 N, 112.9 E). The signal was detected by three spatially separated microbarographs of the Polar Geophysical Institute (PGI), Kola Science Center, Russian Academy of Sciences, Apatity (67.6 N, 33 E) at a distance of 4000 km from the source. The acoustic gravity signal from a falling meteorite at high latitudes was detected at such a distance for the first time in Russia.