Spatial modulation of X-rays in the presence of external acoustic field

The two-crystal X-ray diffraction from (111?1) reflecting atomic planes of quartz single crystal with AT-cut was experimentally considered in the Laue geometry, when both the crystals are simultaneously in the field of bulk acoustic waves. It is shown that as a result of spatial modulation of reflected beam an odd number of parallel X-ray beams is obtained.     

Alkaline Cleavage of 2,3-Dibromo-2-butene-1,4-diammonium Salts

Decomposition of N,N,N,N′,N′,N′-hexamethyl-2,3-dibromo-2-butene-1,4-diammonium diiodide in alcoholic alkali gives ammonium salts containing a 4,4-dialkoxy-2-butynyl group rather than the corresponding 1,4-elimination products.     

Study of X-ray diffraction from a surface acoustic wave in the grazing geometry with allowance for the curvature of the unperturbed crystal surface

Fresnel X-ray diffraction from a concave crystal surface in the presence of a surface acoustic wave (SAW) has been considered for grazing angles of incidence in noncoplanar symmetric Laue geometry. It is shown that the main peak and diffraction satellites are focused at different distances from a crystal. The effect of deviation from the Bragg angle, the spectral line width, and the SAW amplitude on the X-ray diffraction pattern has been analyzed. It is established that the contrast of an X-ray diffraction pattern of an SAW in Bragg-Laue grazing geometry is related to the character of irregularities of the crystal surface, and the pattern details depend on the measurement mode. The sensitivity of the method is about a nanometer. The focal image of the SAW serves as a scale landmark for determining the crystal surface characteristics.     

Effect of dimethyl sulfoxide on electrochemical and antiradical properties of ascorbic acid

Solvent effect of dimethyl sulfoxide (DMSO) on the oxidation-reduction properties of ascorbic acid (AA) was studied by the electroanalytical method of differential pulse voltammetry (DPV) in a three-electrode cell at 37 °C. Dimethylsulfoxide was found to considerably decrease the oxidation ability of AA due to the formation of molecular complexes between AA and DMSO through the intermolecular hydrogen bonds and shift the anodic peak potential toward the positive values, with its intensity being decreased. Kinetic spectrophotometric measurements in the UV-vis regions of the reaction of the stable free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH^·) with AA confirmed the stabilizing effect of the Lewis base DMSO on the reactivity of the neutral form of AA and its intermediates with respect to DPPH^·. The mechanism of oxidation of AA with the radical DPPH· in the presence of DMSO was considered.     

Radiation from 20 MeV electrons in piezoelectric single crystals in the presence of external acoustic fields

The radiation from electrons interacting with piezoelectric single crystals and the influence of acoustic fields on the frequency-temporal parameters of characteristic energy yields have been investigated experimentally. The experiments were carried out on the extracted 20 MeV electron beam of the linear accelerator LEA-50 of the Alikhanian National Scientific Laboratory. The energy distributions of specific yields of the electron radiation in quartz single crystal were obtained. The amplification of intensity and the shift of energy yields under the influence of hypersonic vibrations were observed.     

Experimental study of different modes of block sliding along interface. Part 3. Numerical modeling

This paper completes a series of studies on the patterns of block sliding along interface. It has been shown that in order to model the whole range of crustal block movements, the empirical rate and state friction law must be supplemented with a term that accounts for the appearance of additional shear resistance associated with the dynamic viscosity of the contact between blocks. With this term, the experimentally observed slow slip events can be modeled with good accuracy. A generalization of results of the entire series of studies published in several issues of the journal suggests that both the dynamic and quasi-static modes of sliding along faults are components of a single deformation process. The parameter that governs the formation and evolution of a fault sliding mode is the ratio between the effective values of the fault zone stiffness and rock mass stiffness. Their variation determines the occurrence of a particular sliding mode.     

Pyroelectric effect in polarized PVC

The pyroelectric effect has been detected in polarized PVC, and the temperature dependence of the pyroelectric constant p has been measured. The latter proved to be constant and equal to 0.1 cgse/deg·cm² at –130 to +30° C. The data show that p is proportional to the piezoelectric modulus d, with the proportionality factor k=3 · 10⁶ at room temperature. As the temperature falls, k decreases.Mekhanika Polimerov, Vol. 4, No. 2, pp. 377–378, 1968     

Two-particle correlations in 1D-lattice systems with δ-interactions

The problem of two interacting particles in finite closed and open chains is solved by the Lifshitz method. The “density-density” correlation function, the dependence of the “surface” energy on the two-particle interaction energy and number of links in the chain, and the two-particle distribution on the chain are found and the nature of the ground state is clarified. Fiz. Tverd. Tela (St. Petersburg) 40, 366–370 (February 1998)