The Structure and Reactivity of Stereochemically Rigid Phosphoranyl Radicals

Abstract

The structure and reactivity of phosphoranyls prepared by the reaction of tert. buthylperoxide with phosphorus (III) compounds, containing 5-membered cycles have been investigated. The ESR spectra of diastereomeric isomers of phosphoranils obtained from 1,2,3 oxazaphospholans displayd the difference in HFS-constants. β-Scission rates of diastereomers was shown to differ in 1.3 time in magnititude. The reactivity of phosphoranyls formed by the interaction of tert. buthyl, methyl, boron centered carbonyl radicals with 2,6,7-tris(trichlorometyl)-1,4-diphospha-3,5,8-trioxabicyclo(2,2,2)octane was also studied. Their unusual reactivity, namely, the ability to be added to multiple C?O bonds of substituted phenoxyls occurs due to their rigid structure.     

Highly dispersive large mode area photonic bandgap fiber

An all-silica photonic bandgap fiber composed of a low-index core surrounded by alternating high- and low-index rings allows us to achieve a large mode area (500 microm(2)) and large chromatic dispersion. Sharp resonances from the even Bragg mode to odd ring modes theoretically lead to 20,000 ps/(nm km) chromatic dispersion when large bends are applied. By nature, sharp resonances are sensitive to inhomogeneities along the fiber length. Under experimental conditions, the resonances are broadened and the dispersion coefficient is decreased to 1000 ps/(nm km). However, to the best of our knowledge, this is the largest dispersion coefficient reported using a large mode area fiber.     

Vacuum polarization in the model of dirac fermions with an anomalous magnetic moment that interact with a background axial-vector condensate and magnetic field

Vacuum polarization is considered in a model that takes the anomalous magnetic moment (AMM) of Dirac fermions in a uniform magnetic field in the presence of an additional axial-vector interaction into account. Corrections to the effective Lagrangian of the model that are quadratic with respect to the AMM and axial-vector interaction in different configurations of the given model parameters are calculated.     

Numerical and experimental investigations of the effect of repeated cyclic thermal loads on the strength of materials of recoverable liquid-propellant rocket engines

Elements of the liquid-propellant rocket engines (LPREs) are subject to the action of intense mechanical and thermal loads, which are temporally related to the start-up, normal regime, and switch-off periods of the working cycle. Recoverable LPREs experience these loads many times. Repeated (cyclic) loads lead to the manifestation of processes typical of fatigue, whereby residual stresses and (plastic) deformations are retained and accumulated in the LPRE materials. Numerical investigations using models of the nonstationary thermal and stressed-strained state and the plastic behavior of materials have been performed in order to determine the limiting numbers of loading cycles for the structural materials employed in various units of LPREs. A special computational-experimental procedure is described, which allows these materials to be studied in a stressed-strained state close to that in real LPREs.     

Laser-diode-pumped phosphosilicate-fiber Raman laser with an output power of 1 W at 1.48 mum

An all-fiber 1.48-mum generator based on a laser-diode-pumped Yb-doped double-clad laser and a cascaded Raman wavelength converter has been developed. Second-order Raman Stokes radiation was generated in a phosphosilicate-fiber resonator formed by two pairs of Bragg gratings. A slope efficiency of the Raman converter of 48% with respect to the power emitted by the double-clad Yb laser has been achieved. We obtained an output power of 1 W at a slope efficiency of 34% with respect to the laser-diode array power, with a total optical-to-optical efficiency of 23%.     

Diffusion stratification in a rotating linearly-stratified fluid

The velocity characteristics of the circulation developing in a homogeneously-rotating linearly-density-stratified fluid are investigated experimentally. It is shown that various wave and vortex regimes of motion in which the fluid velocities can reach 1 cm/s are possible. A steady-state rigid-body rotation regime exists for certain parameters of the system. Moscow, Cambridge (Great Britain). Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 2, pp. 58–67, March–April, 1998. The work was carried out in the Department of Applied Mathematics and Theoretical Physics of Cambridge University (Great Britain) and in the Obukhov Atmospheric Physics Institute of the RAS.     

Kinetic study of the reaction of 2,4,6-tri-tert-butylphenolates with quinolide compounds by the ESR method

Conclusions The kinetic parameters of the reaction of a sterically hinderedphenolate with quinolide compounds are quite dependent on the nature of the substituent in the quinolide compound, the solvating capacity of the medium, and the nature of the metal cation in the phenolate.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2094–2096, September, 1972.