Formation of por-Si/SnOx nanocomposite by high-power ion beams of nanosecond duration

Layers of por-Si/SnO _x nanocomposite formed by high-power ion beam irradiation with nanosecond duration have been studied. The results of structural and elemental analyses of these layers are presented. The high sensitivity of this nanocomposite to low NO₂ concentrations at room temperature has been revealed.     

Comparative measurements of thermal neutron fluxes at ground level at the baksan neutrino observatory and LGNS laboratory

Thermal neutron fluxes were measured using two types of scintillation detectors based on the inorganic scintillator ZnS(Ag): ⁶LiF+ZnS(Ag) and ¹⁰B₂O₃ + KCl+ZnS(Ag). The preliminary results from these measurements are given. The thermal neutron concentration as a function of altitude above sea level was determined. The measurements were performed at three locations: in Moscow, at the Baksan Neutrino Observatory of the Russian Academy of Sciences, and at the Gran Sasso National Laboratory. Variations of neutron count rates associated with lunar cycles were observed at the remote laboratories.     

Spectroscopic ellipsometry study of porous silicon-tin oxide nanocomposite layers

The layer-by-layer distribution of components in a porous silicon-tin oxide nanocomposite produced by the following three methods is studied by spectroscopic ellipsometry: chemical vapor deposition, atomic layer deposition, and magnetron sputtering. It is shown that, in the nanocomposites fabricated by these methods, SnO _x penetrates to a depth more than 400 nm and is nonuniformly distributed over the porous layer thickness. The nanocomposite prepared by magnetron sputtering followed by heat treatment has the maximum penetration depth and the maximum uniformity of layer-by-layer SnO _x distribution.     

Effect of the orientation of substituents on the chemical shifts of 13C. IV—13C NMR spectra of N,N-diisopropylamides and -thioamides

N,N-diisopropylamides and -thioamides show hindered rotation around the N? CH bonds, and the presence of mixtures of conformational isomers can be demonstrated at temperatures below 273 K in solution. ¹H and ¹³C NMR spectra of these conformers are measured and assigned. The ¹³C data serve to study through-space effects on ¹³C chemical shifts, which strongly depend on the conformations of the isopropyl groups. For amides, a through-space shielding of the N-methine carbons is found to exist only for conformers in which the methine hydrogen atom is spatially close to the oxygen atom. Chemical shift differences between amides and thioamides can be rationalized in terms of through-bond and through-space contributions, and serve for a better understanding of the shift differences in N,N-dialkylamides and -thioamides.