Engineering topics
Publications and source records attributed to Kovalchuk, M V.
A method for measuring double-crystal rocking curves with the aid of an X-ray-acoustic analyzer is proposed and implemented. This method makes it possible to perform precise measurements with a high time resolution and without the mechanical rotation of the crystal. The results of testing the method are presented.
Crystals of phosphopantetheine adenylyltransferase from Mycobacterium tuberculosis, thymidine phosphorylase from Escherichia coli, carboxypeptidase T from Thermoactinomyces vulgaris and its mutant forms, and crystals of complexes of these proteins with functional ligands and inhibitors were grown by the capillary counter-diffusion method in the Japanese Experimental Module Kibo on the International Space Station. The high-resolution X-ray diffraction data sets suitable for the determination of high-resolution three-dimensional structures of these proteins were collected from the grown crystals on the SPring-8 synchrotron radiation facility. The conditions of crystal growth for the proteins and the data-collection statistics are reported. The crystals grown in microgravity diffracted to a higher resolution than crystals of the same proteins grown on Earth.
Layered superconducting ferromagnetic nanosystems Cu(32 nm)/V(40-80 nm)/Fe(0.5-4 nm)/MgO(001) have been investigated by reflectometry and the diffuse scattering of synchrotron radiation. The data obtained make it possible to determine the important characteristics of samples such as the layer thickness and the rms heights and lateral correlation lengths of roughness at the interfaces.
A complex study of the effect ofintroduction of nanoscale InAs inserts of different thicknesses into an In{sub 0.53}Ga{sub 0.47}As quantum well on the electrical properties and structural features of In{sub 0.50}Al{sub 0.50}As/In{sub 0.53}Ga{sub 0.47}As/In{sub 0.50}Al{sub 0.50}As nanoheterostructures with bilateral {delta}-Si doping grown on InP substrates has been performed. The layers of nanoheterostructures with a weak lattice mismatch are found to be equally (cube-on-cube) oriented. The introduction of a nanoscale InAs insert leads to an increase in mobility. At an insert thickness of about 1.8 nm, the effect of increasing mobility is saturated due to structural deterioration. The segregation of the second (apparently, wurtzite) phase is revealed; this process, as well as the formation of other defects in the nanoheterostructure layers, is due to local strains caused by variations of the indium content in the layers.
Monolayers of porphyrin-fullerene dyad TBD6a were formed on the surface of a water subphase and then transported on a solid substrate by the Langmuir-Schaefer method. A simulation was performed for the structure of a single molecule and for a molecular monolayer, according to the area per molecule in the monolayer formed, which was calculated based on an analysis of the {pi}-A isotherm. A unit cell was chosen for the proposed molecular packing (a = 1.54 nm, b = 1.50 nm, c = 1.75 nm, {alpha} = 80.0 Degree-Sign , {beta} = 90.0 Degree-Sign , and {gamma} = 90.0 Degree-Sign ), and the atomic coordinates were calculated. A comparison of the interplanar spacings and diffraction peak intensities in the experimental and calculated (for the unit cell proposed) diffraction patterns indicates that a platelike texture is formed in the monolayer and that the crystal structure of the domains corresponds to the model chosen.
The purely resonant Bragg reflections (13, 13, 0) and (14, 0, 0) in yttrium aluminum garnet Y{sub 3}Al{sub 5}O{sub 12} at energies near the K absorption edge of yttrium have been studied experimentally and theoretically. The anisotropic tensor atomic factor of yttrium corresponding to dipole-dipole resonance transitions depends on three independent parameters changing with energy. The intensities of the reflections (14, 0, 0) and (13, 13, 0) are shown to depend on the parameter difference f{sub 1}(E) - f{sub 2}(E) and the parameter f{sub 3}(E), respectively, which are attributable to distortions of the wave functions of the excited atoms and change greatly with photon energy E. Studying various reflections has allowed one to determine the various components of the tensor atomic factor and to compare them with the results of numerical calculations.
The results reported at the Conference on Application of X-Rays, Synchrotron Radiation, Neutrons, and Electrons in Nano-, Bio-, Information-, and Cognitive Technologies (RSNE-NBIC 2009) are briefly reviewed. This review is based on a cycle of studies [1-6] where a new method for studying the structure of real crystals-diffuse-dynamic multiparameter diffractometry (DDMD)-was proposed and substantiated.
The method for determining the local lattice parameters using quasi-multiple X-ray diffraction (which was proposed and used only for crystals of the cubic system) has been expanded to measure the local crystal lattice parameters for the trigonal, hexagonal, and tetragonal systems. Local variations in the lattice parameters in the tetragonal paratellurite (TeO{sub 2}) and trigonal lanthanum-gallium tantalate (La{sub 3}Ga{sub 5.5}Ta{sub 0.5}O{sub 14}) crystals have been investigated. Reflections necessary for implementing the quasi-multiple X-ray diffraction scheme are found for these crystals. The pairs of reflections that were found were used to complete quasi-multiple X-ray diffraction schemes on a laboratory X-ray source and determine the variation in the lattice parameter a along the surface of these crystals. The relative measurement error was 4 x 10{sup -6} at a spatial resolution of 140 {mu}m. The accuracy of the method and the parameters determining this characteristic were analyzed based on the results. The locality of the method and the limits of the spatial resolution of an X-ray diffraction measurement of lattice parameters are estimated.