62 research outputs found

    Field-effect in electrochemical reactivity of alkylarylselenides

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    The anchimeric assistance of some substituents bearing the carbonyl group alters the nature of the potential-determining reaction of the cation radicals of alkylarylselenides,-instead of a charge-controlled fragmentation of the first order characteristic for these kinds of particles, the orbital-controlled second order disproportionation of dimerization take place. © 1995

    The anodic acetoxylation of alkylarylselenides

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    Electrooxidation of alkylarylselenides in methanol in the presence of sodium acetate leads to the acetoxylation of the methylene group of selenides. © 1993

    Retention of a six-membered ring in the reaction of 2-dialkylaminobenzo[e]- 1,3,2-dioxaphosphinin-4-ones with Pentafluorobenzaldehyde: O,N-exchange at phosphorus

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    The title reaction leads to the formation of diastereoisomeric 2-[(dialkylamino)(pentafluorophenyl)methyl]benzo[e]-1,3,2-dioxaphosphinine-2, 4-diones in a ratio of 70: 30. The configuration of chiral centres for the preferable diastereoisomer was determined by single crystal X-ray diffraction analysis. © 2013 Mendeleev Communications. All rights reserved

    Dynamics of viscous amphiphilic films supported by elastic solid substrates

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    The dynamics of amphiphilic films deposited on a solid surface is analyzed for the case when shear oscillations of the solid surface are excited. The two cases of surface- and bulk shear waves are studied with film exposed to gas or to a liquid. By solving the corresponding dispersion equation and the wave equation while maintaining the energy balance we are able to connect the surface density and the shear viscocity of a fluid amphiphilic overlayer with experimentally accessible damping coefficients, phase velocity, dissipation factor and resonant frequency shifts of shear waves.Comment: 19 pages, latex, 3 figures in eps-forma

    Study of semi-polar gallium nitride grown on m-sapphire by chloride vapor-phase epitaxy

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    In this study, we analyzed the result of the influence of the non-polar plane of a sapphire substrate on the structural, morphological, and optical properties and Raman scattering of the grown epitaxial GaN film. It was found that selected technological conditions for the performed chloride-hydride epitaxy let us obtain the samples of structurally qualitative semi-polar wurtzite gallium nitride with (11¯22) orientation on m-sapphire. Using a set of structural and spectral methods of analysis the structural, morphological, and optical properties of the films were studied and the value of residual bi-axial stresses was determined. A complex of the obtained results means a high structural and optical quality of the epitaxial gallium nitride film. Optimization of the applied technological technique in the future can be a promising approach for the growth of the qualitative GaN structures on m-sapphire substrates

    Bound oxygen influence on the phase composition and electrical properties of semi-insulating silicon films

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    The purpose of this work is to establish of the bound oxygen effect on the phase composition of the Semi-Insulating Polycrystalline Oxygen-doped Silicon (SIPOS) films by means of three independent methods: X-ray diffraction (XRD), Ultrasoft X-ray Emission Spectroscopy (USXES) and Raman spectroscopy, also on their electrophysical properties, depending on the relative oxygen content in the gas mixture flow (γ=N2O/SiH4) of the plasma reactor during the chemical vapor deposition of submicron SIPOS layers on monocrystalline silicon wafers. The increase in the oxygen content in SIPOS layers from γ=0 to maximum at γ=0.15 leads to the reduction of Si nanocrystals size from ~75 nm to 2–5 nm, submerged in amorphous matrix. Oxygen is contained in the bound form of silicon-oxygen clusters SiOSi3 type in the amorphous silicon matrix without SiO2 formation. These nonlinear qualitative and quantitative changes in the atomic structure of the SIPOS layers under the influence of bound oxygen increase not only the resistivity of the films by two orders of magnitude but also the activation energy of conductivity in comparison with silicon at the temperatures above room temperature. © 2020 Elsevier LtdRussian Foundation for Basic Research, RFBR: 19-42-363013MD-42.2019.2Ministry of Science and Higher Education of the Russian FederationThe reported study was funded by RFBR and Government of Voronezh region according to the research project № 19-42-363013.The part of work was carried out with the support of the Ministry of Science and Higher Education of Russia Federation under the grand No. FZGU-2020-0036 .In part of diagnostics of the structures the work of P.V. Seredin was supported by the RF President's Grants Council (Grant MD-42.2019.2)

    Endocrinologic, neurologic, and visual morbidity after treatment for craniopharyngioma

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    Craniopharyngiomas are locally aggressive tumors which typically are focused in the sellar and suprasellar region near a number of critical neural and vascular structures mediating endocrinologic, behavioral, and visual functions. The present study aims to summarize and compare the published literature regarding morbidity resulting from treatment of craniopharyngioma. We performed a comprehensive search of the published English language literature to identify studies publishing outcome data of patients undergoing surgery for craniopharyngioma. Comparisons of the rates of endocrine, vascular, neurological, and visual complications were performed using Pearson’s chi-squared test, and covariates of interest were fitted into a multivariate logistic regression model. In our data set, 540 patients underwent surgical resection of their tumor. 138 patients received biopsy alone followed by some form of radiotherapy. Mean overall follow-up for all patients in these studies was 54 ± 1.8 months. The overall rate of new endocrinopathy for all patients undergoing surgical resection of their mass was 37% (95% CI = 33–41). Patients receiving GTR had over 2.5 times the rate of developing at least one endocrinopathy compared to patients receiving STR alone or STR + XRT (52 vs. 19 vs. 20%, χ2P < 0.00001). On multivariate analysis, GTR conferred a significant increase in the risk of endocrinopathy compared to STR + XRT (OR = 3.45, 95% CI = 2.05–5.81, P < 0.00001), after controlling for study size and the presence of significant hypothalamic involvement. There was a statistical trend towards worse visual outcomes in patients receiving XRT after STR compared to GTR or STR alone (GTR = 3.5% vs. STR 2.1% vs. STR + XRT 6.4%, P = 0.11). Given the difficulty in obtaining class 1 data regarding the treatment of this tumor, this study can serve as an estimate of expected outcomes for these patients, and guide decision making until these data are available

    Field-effect in electrochemical reactivity of alkylarylselenides

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    The anchimeric assistance of some substituents bearing the carbonyl group alters the nature of the potential-determining reaction of the cation radicals of alkylarylselenides,-instead of a charge-controlled fragmentation of the first order characteristic for these kinds of particles, the orbital-controlled second order disproportionation of dimerization take place. © 1995

    Field-effect in electrochemical reactivity of alkylarylselenides

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    The anchimeric assistance of some substituents bearing the carbonyl group alters the nature of the potential-determining reaction of the cation radicals of alkylarylselenides,-instead of a charge-controlled fragmentation of the first order characteristic for these kinds of particles, the orbital-controlled second order disproportionation of dimerization take place. © 1995
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