Optical Phonon Spectrum of the Ge2Sb2Te5 Single Crystal

JETP Letters - Raman scattering by optical phonons of the Ge2Sb2Te5 single crystal grown by the Bridgman method is studied for the first time. Another method for obtaining this compound based on...     

The stability of vortex filaments

The article discusses the problem of the nonlinear oscillations of concentrated vortexes, For a vortical annulus and a spiral vortical filament, the article demonstrates the character of the change in the form and the frequency of the oscillations with an increase in the amplitude. In the case of standing waves, the solution is obtained in the form of a series with respect to the amplitude of the perturbations, with an accuracy up to terms of the third order of smallness, inclusive. For running waves, the solution is constructed using a method analogous to the Stewart method. The same problem is solved using direct numerical integration of the starting equations of motion. The values of the critical amplitudes which bring about the breakdown of a vortical annulus are obtained. It is shown that as a result of the nonlinearity of the equations in solution of the problem with the starting data higher harmonics can separate out intensively. For a spiral vortical filament, a study was made of the nonlinear interaction of the perturbations; it is shown, in particular, that a perturbation which is stable according to the linear theory may become unstable as a result of nonlinear interaction with neighboring perturbations along the length of the wave and of perturbations of the frequency.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 3, pp. 42–49, May–June, 1973.The authors thank G. I. Petrov for his direction of the work, as well as V. Ya. Shkadov for his interest in the work.     

Stress Concentration in a Soft Ferromagnetic with an Elliptic Inclusion in a Homogeneous Magnetic Field

The paper addresses a stress–strain problem for an infinite soft ferromagnetic body with an elliptic inclusion. The body is in a homogeneous magnetic field B ₀₁. The basic stress–strain characteristics and induced magnetic field in the body and inclusion are determined and their features in the neighborhood of the inclusion are studied. The magnetoelastic and Maxwell stresses are plotted against the ratio of ellipse axes and the latitude angle. Maximum stresses versus magnetic induction and mechanical and magnetic properties of the material are tabulated     

Alkoxysilyl derivatives of polyhedral oligosilsesquioxanes containing amino and hydroxyl groups and sol-gel hybrid materials on their basis

A mixture of polyhedral oligosilsesquioxanes of the empirical formula [(HOCH₂CH(OH)CH₂)₂N(CH₂)₃SiO_1.5] _n characterized by narrow molecular-mass distributions has been synthesized by the hydrolytic condensation of the product resulting from the interaction of glycidol and 3-aminopropyltriethoxysilane. The said oligosilsesquioxanes have been involved in reaction with 3-isocyanatopropyltriethoxysilane to give rise to urethane-containing alkoxysilyl derivatives of various degrees of substitution. Organo-inorganic hybrids have been prepared on their basis through the sol-gel method. The structure and properties of the products have been studied by matrix laser desorption/ionization mass spectrometry, GPC, X-ray diffraction, DSC, and thermogravimetry. It has been demonstrated that the properties of the polymer materials thus prepared may be controlled by variation of the ratio of hydroxyl and alkoxysilyl groups in oligosilsesquioxane derivatives and by incorporation of low-molecular-mass sol-gel precursors.     

Three-dimensional periodic lattice of ZrO<Subscript>2</Subscript> nanocrystals in transparent silica matrix

The conditions for synthesizing an opal-zirconia-carbon nanocomposite in the form of monolithic (without pores) transparent silica with an ordered distribution of nanocrystals throughout the sample have been determined. Zirconia nanocrystals form a three-dimensional periodic lattice of nanoclusters with sizes ranging from several nanometers to several tens of nanometers. This nanocomposite exhibits properties typical of photonic crystals. The samples have been studied using electron microscopy, X-ray diffraction, photoluminescence, and Raman scattering. The structural state and spatial arrangement of zirconia nanocrystals and carbon clusters in the nanocomposite have been elucidated. Optical transmission and optical reflection photoluminescence spectra of the nanocomposites have been measured.