On a certain boundary value problem of N. P. Vekua with a piecewise-smooth shift on a piecewise Lyapunov contour

Odessa. Translated from Sibirskii Matematicheskii Zhurnal, Vol. 33, No. 2, pp. 108–115, March–April, 1992.     

Furylcyclohexenones. Conversion of 6-ethoxycarbonylcyclohexenones into 4,5-dihydroindazoles. Molecular and crystal structure of 4-phenyl-6-(5-methyl-2-furyl)-4,5-dihydroindazol-3-one

4,5-Dihydrodiazoles containing furyl substituents in positions 4 or 6 were obtained by condensation of hydrazine hydrate and 6-ethoxycarbonylcyclohexenones. XSA showed that in the crystalline state, the pyrazolone fragment of the dihydroindazole molecules has a betaine structure. See [1] for Communication 1. Kuban State Technological University, Krasnodar 350072. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1459–1465, November, 1997.     

Interaction of a Supersonic Turbulent Wake with Acoustic Disturbances

The effect of an external acoustic field on disturbances in a supersonic turbulent wake is investigated experimentally.     

Magneto-Optical Effects in Colloidal Solutions of Barium Hexaferrite

Hydrothermal synthesis was used to obtain lamellar magnetic particles of barium hexaferrite, and colloidal solutions were prepared on their basis. Magneto-optical effects in colloid solutions of barium hexaferrite were examined. It was found that the aqueous colloidal solution of coarse planar particles of barium hexaferrite is a magneto-optical medium that is nearly two orders of magnitude more effective than the colloid formed from isometric cobalt ferrite particles. It was shown that measuring the frequency dependence of the magneto-optical effects and approximating the experimental data with the Debye function makes it possible to find the frequency f₀ characteristic of the given colloid and to calculate the characteristic size of particles (or aggregates) creating the optical anisotropy in the colloid under the action of a magnetic field. A dichroism is observed in the aqueous colloid formed by coarse planar barium hexaferrite particles. This phenomenon is due to the change in the light scattering on coarse particles upon their orientation by a magnetic field.     

Structural features and the nature of the hydrogen bond in the enol form of α-diphenylphosphoryl-α-acetylacetonitrile based on X-ray diffraction data

It has been established by X-ray structural analysis that pure -diphenylphosphoryl--acetylacetonitrile exists in the enol form (aZ isomer). In crystals, a strong intramolecular P=O...H...O hydrogen bond is formed; the O...O distance is 2.551 Å. It has been demonstrated that the H atom is characterized by a high lability along the hydrogen bond, which exhibits a covalent component in the H...O region.Deceased.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1520–1524, August, 1995.The X-ray structural study was supported by the American Crystallography Association and the International Science Foundation (Grant No. M1F000).     

Photohemolysis sensitized by the furocoumarin imperatorin and its oxyfunctionalized derivatives

The dark and photosensitized (366 nm) hemolytic effects of imperatorin and its photooxidation products, the hydroperoxides I and II as well as the corresponding alcohol of the hydroperoxide I (imperatorin alcohol), were studied on human erythrocytes. Imperatorin was shown to photosensitize hemolysis, its fluence (D) dependence of the rate of photohemolysis (V) followed the equation V = V0 + aD2 + bD1/2, in which V0 is the dark hemolysis rate and a and b are constants. At fluences below 200 kJ/m2, the main hemolytic contribution derives from the bD1/2 component, which is due to the in situ formation of the imperatorin hydroperoxides, while at fluences higher than 200 kJ/m2, the main contribution corresponds to the aD2 component due to the two-photon damage of cell membranes. Hydroperoxides I and II induce oxyhemoglobin cross-linking, as well as its conversion to methemoglobin and hemichrome. These reactions involve hydroxyl and alkoxy radicals, as the hemolysis and oxyhemoglobin conversion could be inhibited by t-butanol and butylated hydrotoluene. For comparison, the dark hemolytic effect of the imperatorin alcohol was approximately 10-fold less than of the hydroperoxides.     

Adaptation of microthermal probes for the determination of biochemical species

A glucose sensitive enzymatic thermal sensor based on a pair of commercial microthermal probes was fabricated by cross-linking of the corresponding enzymes (glucose oxidase and catalase) with bovine serum albumin onto the chip surfaces. The characteristics of this sensor were optimised by testing it in different conditions. To find the maximal sensitivity, the calibration curves of this sensor were measured in different buffer solutions with and without the addition of H(2)O(2) to the analysed samples at various rates of sample flow stream. Different buffer solutions and hydrogen peroxide concentraions were used to realise the principles of a chemical and biochemical amplification of the biosensor response. It was shown that the level of the biosensor response and its dynamic range increase if hydrogen peroxide is added to the analysed samples and depend on the type of buffer solutions tested and the rate of the sample flow stream.     

Molecular and crystal structure of the clathrochelate complex FeDm3(BF)2⋅C6H6 and parameters of its 57Fe Mossbauer spectra

The molecular and crystal structure of the macrobicyclic complex FeDm₃(BF)₂C₆H₆ was established by X-ray diffraction analysis at 138, 208, and 291 K. The X-ray diffraction data were compared with the ⁵⁷Fe Mossbauer spectral parameters of this complex in the temperature range of 135-290 K. A substantial disagreement between the experimental values of quadrupole splitting and the corresponding values calculated based on the concept of partial quadrupole splitting was attributed to the displacement of the Fe atom from the center of the cavity of the macrobicyclic ligand and to the distortion of the axial symmetry of the electron density distribution about the metal atom.     

Synthesis, molecular and crystal structure, and features of the electronic structure of bis(O’i)-chelated bis(2,2-dimethylbenzo-[2H]-4-oxo-1,3-oxazino-3-methyl)difluorosilane

A method has been developed for the synthesis of a bis(O→Si)-chelated bis(2,2-dimethylbenzo[2H]-4-oxo-1,3-oxazino-3-methyl)difluorosilane from 2,2-dimethyl-3-trimethylsilylbenzo[2H]-1,3-oxazin-4-one and bis(chloromethyl)dichlorosilane via the intermediate formation of the corresponding unstable bis-chelated dichloride, subsequent hydrolysis with NaHCO₃ and, without separation, treatment of the hydrolysis product with boron trifluoride etherate. Analysis of the electron density distribution showed the presence of dative bonding in both O→Si-F fragments. Dedicated to Prof. Edmunds Lukevics on the occasion of his 70th birthday __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1866–1879, December, 2006.     

Effect of carbon nanostructures on the carbonization of polyacrylonitrile

Composite materials based on polyacrylonitrile with carbon nanofillers (technical-grade carbon, thermally expanded graphite, carbon nanotubes) were synthesized. A carbonization of film and fiber composite samples in the temperature range 20–1000°C provided a noticeable increase in the thermal stability of fibers and a rise in the electrical conductivity of the composite material. Dependences of the degree of carbonization on the concentration of nanostructures, type of material, and nature of modifier were determined. Differential-thermal and X-ray diffraction analyses revealed the formation of oriented nucleus structures of turbostratic carbon in the temperature range 450–550°C.