On the application of a single‐crystal κ‐diffractometer and a CCD area detector for studies of thin films

A multipurpose six‐axis κ‐diffractometer, together with the brilliance of the ESRF light source and a CCD area detector, has been explored for studying epitaxial relations and crystallinity in thin film systems. The geometrical flexibility of the six‐axis goniometer allows measurement of a large volume in reciprocal space, providing an in‐depth understanding of sample crystal relationships. By a set of examples of LaAlO₃ thin films deposited by the atomic layer deposition technique, the possibilities of the set‐up are presented. A fast panoramic scan provides determination of the crystal orientation matrices, prior to more thorough inspection of single Bragg nodes. Such information, in addition to a broadening analysis of families of single reflections, is shown to correlate well with the crystallinity, crystallite size, strain and epitaxial relationships in the thin films. The proposed set‐up offers fast and easy sample mounting and alignment, along with crucial information on key features of the thin film structures.     

Dynamic properties of zirconium dioxide refractories

The results of static and dynamic tests for three groups of ceramic materials based on zirconium dioxide ZrO₂ and for zirconium dioxide concrete are reported. The static and dynamic tests were performed according to the conventional procedure and Kolsky procedure, respectively. The ceramic samples were obtained using different manufacturing technologies and had different initial densities and porosities. In the experiments, static and dynamic strain curves were obtained and strength characteristics were determined. The dynamic strength properties of ceramics and concrete are shown to depend on the stress growth rate. The dynamic curves of ceramics are compared with those of structural and zirconium dioxide concretes.     

Special and extreme triple shock-wave configurations

Triple shock-wave configurations in steady supersonic flows of an inviscid perfect gas are considered. Triple configurations with special intensities of shock waves and extreme ratios of various flow parameters behind these configurations are determined. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 4, pp. 39–53, July–August, 2006.     

Synthesis of CF<Subscript>3</Subscript>-substituted 1,2,3,4-tetrahydroisoquinolines and 1,2,3,6-tetrahydropyridines

A three-step method for the preparation of CF₃-substituted 1,2,3,4-tetrahydroisoquino-lines and 1,2,3,6-tetrahydropyridines has been suggested. The first step includes alkylation of isoquinoline or 4-methylpyridine at the nitrogen atom with the formation of salts, which are involved into the reaction with Grignard reagent or lithium triethylborohydride to give enamines. The enamines undergo nucleophilic trifluoromethylation upon the action of Me₃SiCF₃ under acidic conditions.     

On the invertibility of differential operators of the second order

We present sufficient conditions for the invertibility of a second-order differential operator with variable coefficients in the space L_p.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 47, No. 3, pp. 411–413, March, 1995.This paper was partially supported by the International Science Foundation, Grant No. ZA000.     

Assessment of Subgrid-Scale Models for Decaying Compressible MHD Turbulence

Large eddy simulation method is formulated for study of compressible magnetohydrodynamic turbulence and assessment of different subgrid-scale models as applied for decaying case is performed. The filtered equations of compressible magnetopause using the mass-weighted filtering operation are obtained. Mass-weighted filtered equations for large-scale turbulent component comprise subgrid-scale terms and five models for closure of the subgrid-scale terms are suggested. In present paper the obtained results of numerical computations for large eddy simulation are compared with the results of direct numerical simulation of three-dimensional compressible magnetohydrodynamic turbulence. Assessment of five subgrid-scale models of large eddy simulation for MHD flows is fulfilled. The comparisons between large eddy simulation and direct numerical simulation are carried out regarding the temporal evolution of the global quantities kinetic and magnetic energy, cross helicity and the spectra of kinetic and magnetic energy.     

Excitons in heteroepitaxial CdSe/CdS structures

X-ray diffractometry and low-temperature exciton spectroscopy are used to study heteroepitaxial CdSe/CdS layers grown at temperatures of 350–485 °C by MOCVD. The high-temperature samples are found to display the exciton and x-ray diffraction spectra characteristic of hexagonal Wurtzite (W) structures, while the low-temperature samples display the features characteristic of the cubic structure of sphalerite (ZB). A number of the samples have x-ray spectra characteristic of structures with stacking faults (SF), which represent a separate crystalline phase in the structures studied here. It is found that the individual crystalline phases are spatially separated. Fiz. Tverd. Tela (St. Petersburg) 40, 887–889 (May 1998)     

Platinum nanoparticles generated in functionality-enhanced reaction media based on polyoctadecylsiloxane with long-chain functional modifiers

Functionality-enhanced nanostructured matrices generated by intercalating polyoctadecylsiloxane (PODS) with octadecene (ODC) or octadecylamine (ODA) are employed as reaction media in which to grow Pt nanoparticles. Small-angle X-ray scattering (SAXS) signatures confirm that the amphiphilic PODS matrix orders into lamellae with a periodicity (d) of 5.24 nm, which corresponds to the siloxy bilayer and a double layer of alkyl tails. The regular packing of the hydrophobic tails becomes distorted upon introduction of ODC or ODA. Incorporation of K[(C2H4)PtCl3].H2O (a Zeise salt) into the PODS/ODC matrix, followed by reduction of the Pt ions by NaBH4 or H2, results in the localization of Pt compounds and nanoparticles along the siloxy bilayers, which remain dimensionally unchanged. Electron density profiles deduced from PODS/ODA, however, provide evidence for considerable structural reorganization upon metalation with H2PtCl6.6H2O. In this case, the siloxy bilayers broaden due to the presence of PtCl62- ions, and the hydrophobic layers become distorted due to the formation of (PtCl62-)(ODAH+)2 complexes. Subsequent reduction by NaBH4 restores the inherent PODS organization, while H2 reduction partially preserves the distorted matrix, indicating that some Pt nanoparticles form in close proximity to the siloxy bilayer. Transmission electron microscopy reveals that relatively monodisperse Pt nanoparticles measuring approximately 1 nm in diameter are located along the siloxy bilayers, whereas anomalous SAXS further indicates that nanoparticles form aggregates of comparable size to d within the PODS double layers.     

Study of the reactione + e −→K + K − in the energy range1350 \leqq \sqrt s \leqq 2400 MeV

Thee ⁺ e ^?→K ⁺ K ^? cross section has been measured from about 750 events in the energy interval \(1350 \leqq \sqrt s \leqq 2400 MeV\) with the DM2 detector at DCI. TheK ^± form factor |F _F ^±| cannot be explained by the ρ, ω, ? and ρ′(1600). An additional resonant amplitude at 1650 MeV has to be added as suggested by a previous experiment.