Selective photorefractive scattering in LiNbO<Subscript>3</Subscript>:Rh crystals

Photorefractive scattering occurs in rhodium-doped lithium niobate crystals irradiated by coherent light. The photorefractive scattering has both wide-angle and selective components. The results of experimental investigation of selective photorefractive scattering in LiNbO₃:Rh crystals and calculation of the spatial structure of scattering are reported. The selective scattering is regarded as a kind of a frequency-degenerate fourwave vector interaction.     

Crystal and molecular structure of bis(2-isotropyliminomethinylphenyl) telluride

Scientific-Research Institute of Physical and Organic Chemistry, Rostov State University. A. N. Nesmeyanov Institute of Heteroorganic Compounds, Academy of Sciences of the USSR. Translated from Zhurnal Strukturnoi Khimii, Vol. 32, No. 3, pp. 104–106, May–June, 1991.     

NMR and X-ray diffraction studies of the influence of adsorbed molecule nature on phase transitions in a ZSM-5 silicalite

Pulsed NMR and X-ray diffraction analysis are employed to study the influence of adsorbed toluene, p-xylene, acetone, and di(ethylene glycol) (DEG) molecules on phase transitions in a ZSM-5 silicalite. In the region of phase transitions, times T₁ and T₂ of longitudinal and transverse magnetic relaxation of apolar molecules adsorbed in silicalite micropores increase and decrease in a jumpwise manner, respectively, with a rise in the total content of the liquid. Such changes in T₁ and T₂ occur for hexane, decane, toluene, and p-xylene molecules. Qualitatively different concentration dependences of T₁ and T₂ are observed for polar acetone and DEG molecules, because these liquids do not cause a earrangement in the crystal lattice of silicalite; this is confirmed by the X-ray diffraction data.Translated from Kolloidnyi Zhurnal, Vol. 66, No. 6, 2004, pp. 802–806.Original Russian Text Copyright © 2004 by Pimenov, Skirda, Maksimenko, Morozov, Opanasyuk.     

Intermolecular interactions in rifabutin–2-hydroxypropyl-β-cyclodextrin–water solutions,according to solubility data

The formulations of rifabutin (RB) and 2-hydroxypropyl-β-cyclodextrin (HP-β-CD), obtained using different preparation techniques, are studied by means of differential scanning calorimetry and molecular spectroscopy (FTIR, NMR, Raman scattering, and photon correlation light scattering). It is established that molecules of RB do not form inclusion complexes with the molecules of HP-β-CD, and an increase in the solubility of RB determined earlier is caused by the formation of weak intermolecular associates.     

Pion electromagnetic characteristics in the quark model with confinement

Pion electromagnetic characteristics such as electric polarizability and rms radius were calculated. Pions are considered a nonrelativistic system of two pointlike spinor quarks with a linear potential at large distances and a Coulomb one at short ones.     

Effect of the morphology on the mechanisms of the magnetization reversal of multilayered thin Co/Pd films

A comparative study of the magnetization curves of continuous and porous multilayered Pd_10nm/[Co_0.3nm]/Pd_0.55nm]15/Pd_2nm films deposited on an anodized TiO₂ template was performed by magnetometry. Based on the comparison of the dependences of coercive field H_C on angle θ between the easy-magnetization axis and the direction of external magnetic field H with theoretical dependences H_C(θ) for the magnetization reversal by domain walls motion (according to the Kondorski model) and the rotation of magnetic moments (by the Stoner–Wohlfarth model), the differences in the mechanisms of magnetization reversal for two mentioned types of the films were revealed. The correlation between the difference in the morphologies of the continuous and porous films and revealed change in the mechanisms of the magnetization reversal, as well as the changes in values of H_C and calculated constants of the magnetic anisotropy, is discussed.     

Choosing the state of a spatially distributed system in calculating a spectrum of Lyapunov exponents

The problem of choosing the set of parameters that determine the state of a spatially distributed system when calculating a spectrum of Lyapunov exponents is considered. The possibility of reducing the number of necessary quantities due to the features of the employed mathematical model is discussed. The proposed method is successfully applied to a hydrodynamic model of a Piers diode.     

Microwave radiation absorbers based on corrugated composites with carbon fibers

A complex analysis of the dependence of the absorption coefficient of polymer composites with nonmagnetic carbon inclusions on the real and imaginary parts of the complex permittivity, as well as on the material thickness is performed in frequency range 26–37 GHz. The composites containing 0.2 wt % of carbon fibers have been obtained. It has been experimentally found that the corrugation of the composite surface substantially increases the absorbability (from 63 to 92% at a frequency of 30 GHz and a thickness of 4.50 mm) upon a decrease in the sample mass (by 28%). A method has been proposed for calculating the absorptance of corrugated composites in the microwave range.