Photochemical synthesis of silver nanoparticles in polyvinyl alcohol matrices

Photochemical synthesis was used to obtain silver nanoparticles in a polymer matrix. The structural and optical properties of the composite material were studied by electron and IR spectroscopy, X-ray diffraction, and electron microscopy. The chemical reactions in polyvinyl alcohol in the preparation of the nanoparticles were studied.     

Evaluation of the effective speed of sound in phononic crystals by the monodromy matrix method (L)

A scheme for evaluating the effective quasistatic speed of sound c in two- and three-dimensional periodic materials is reported. The approach uses a monodromy-matrix operator to enable direct integration in one of the coordinates and exponentially fast convergence in others. As a result, the solution for c has a more closed form than previous formulas. It significantly improves the efficiency and accuracy of evaluating c for high-contrast composites as demonstrated by a two-dimensional scalar-wave example with extreme behavior.     

Elastic waves in a solid subjected to shear deformation

All-Union Scientific Research Institute of Nondestructive Testing, Kishinev. Odessa Polytechnical Institute. Translated from Prikladnaya Mekhanika, Vol. 26, No. 1, pp. 77–82, January, 1990.     

Electronic structure and absorption spectra of the anionic σ complexes of nitrobenzenes and nitrostyrenes

Institute of High-Molecular Compounds, Academy of Sciences of the USSR. Translated from Zhurnal Strukturnoi Khimii, Vol. 32, No. 4, pp. 36–45, July–August, 1991.     

Measurement of Spatial-Frequency and Amplitude Responses of a CCD-Matrix Image-Registration Device

A unique method for studying spatial-frequency and amplitude responses of an image-registration device on the basis of a CCD matrix is developed. A monochromatic light-intensity distribution arising from Fraunhofer diffraction on two equal slits is used as an input signal. A quantitative approach to a spatial resolution of the CCD matrix for registration of a periodic image is developed. The dependence of the rms contrast degree of the output signal on the spatial frequency of the image recorded is studied experimentally. The optical scheme developed and the method proposed for treatment of a digitized signal allow one to determine the amplitude response of the registration device over the whole surface of the CCD matrix and to determine the admissible level of the average intensity of the radiation registered.     

Synthesis of 2-(2-hydroxyaroylmethylene)hexahydropyrimidines from 2-trichloromethylchromones and trimethylenediamine

The reactions of 2-trichloromethylchromones with trimethylenediamine in ethanol at room temperature afford 2-(2-hydroxyaroylmethylene)hexahydropyrimidines. Under analogous conditions, 2-methylchromone gives a mixture ofN,N′-trimethylenebis[3-amino-1-(2′-hydroxyphenyl)-2-buten-1-one] andN,N′-trimethylenebis(imine) of 2-hydroxyacetophenone. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2140–2143, November, 1999.     

Stress–strain state of the alveolar crest under the primary strut of a subperiosteal implant

The stress–strain state in the alveolar bone crest is analyzed over a wide range of stiffness ratios between the bone and the primary strut of the subperiosteal implant. Recommendations on the rational design of subperiosteal implants are given     

Effect of orientation of the heat-release surface on heat transfer to liquid nitrogen

The heat transfer from the surface of high-temperature superconductors to liquid nitrogen is studied. The effect of the heat flux density and heat-release surface orientation in the gravitational field on heat exchange characteristics is studied. It is shown that the heat transfer coefficient in the region of developed bubble boiling on a double-side cooled tape has a minimum at tilt angles close to 45°. The relations describing the dependence of the heat transfer coefficient on the heat-release surface orientation are derived.     

Phase transitions in solutions of hydroxypropoyl cellulose and cyanoethyl cellulose

LC phase transitions in mixtures of cyanoethyl cellulose and hydroxypropyl cellulose with different solvents have been studied by the cloud point and polarization microscopy methods and polarization photoelectric measurements. It has been found that, as the solvent polarity is decreased and the molecular mass of a polymer is increased, boundary curves delimiting the regions of isotropic and anisotropic solutions shift to the region of lower concentrations.     

On the quasistatic effective elastic moduli for elastic waves in three-dimensional phononic crystals

Effective elastic moduli for 3D solid–solid phononic crystals of arbitrary anisotropy and oblique lattice structure are formulated analytically using the plane-wave expansion (PWE) method and the recently proposed monodromy-matrix (MM) method. The latter approach employs Fourier series in two dimensions with direct numerical integration along the third direction. As a result, the MM method converges much quicker to the exact moduli in comparison with the PWE as the number of Fourier coefficients increases. The MM method yields a more explicit formula than previous results, enabling a closed-form upper bound on the effective Christoffel tensor. The MM approach significantly improves the efficiency and accuracy of evaluating effective wave speeds for high-contrast composites and for configurations of closely spaced inclusions, as demonstrated by three-dimensional examples.