Synthesis and Structure of Antimony Complex Compounds [(4-N,N-Me2C6H4)3MeSb]I and [(4-N,N-Me2C6H4)3MeSb]2[Hg2I6]·2DMSO

Russian Journal of General Chemistry - It was first found that the alkylation of tris(4-N,N-dimethylaminophenyl)stibine with methyliodide leads to the formation of...     

Compression and heating of spherical fusion targets by indirect (x-ray) drive on the Iskra-5 facility

Experiments have been carried out using the Iskra-5 facility in order to study the behavior of x-ray targets in response to a highly symmetric x-ray field. Results are presented of experiments using targets in the form of a spherical copper hohlraum coated with gold on the inside, with six laser entrance holes and a glass microtarget filled with DT gas located at the center. In some experiments the central capsule was coated with a plastic ablator layer of varying thickness. An analysis of the experimental results showed that on the whole, they are satisfactorily described by spherically symmetric gasdynamic calculations. Zh. éksp. Teor. Fiz. 114, 155–170 (July 1998)     

Cu–CeO<Subscript>2</Subscript> nanocomposites: mechanochemical synthesis,physico-chemical properties,CO-PROX activity

Catalytic systems designated for preferential oxidation of CO in the presence of H₂ are prepared by ball milling of Cu and CeO₂, a simple and cheap one-step process to synthesize such catalysts. It is found that after 60 min of milling, a mixture of 8 wt.% Cu–CeO₂ powders exhibits CO conversion of 96% and CO selectivity of about 65% at 438 K. Two active oxygen states, which are not observed in case of pure CeO2, were detected in the nanocomposite lattice and attributed to the presence of Cu in surface sites as well as in subsurface bulk sites. Correspondingly, oxidation of CO to CO₂ was found to occur in a two-stage process with T _max ≈ 395/460 K, and oxidation of H₂ to H₂O likewise in a two-stage process with T _max ≈ 465/490 K. The milled powder consists of CeO₂ crystallites sized 8–10 nm agglomerated to somewhat larger aggregates, with Cu dispersed on the surface of the CeO₂ crystallites, and to a lesser extent present as Cu₂O.

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Quenching electron runaway in positive high-voltage-impulse discharges in air by laser filaments

Strong hard (ε>100 keV) x rays being observed from impulse atmospheric discharges with maximal voltages from U=0.5 to 0.9 MV just before the breakdown were completely stopped with the use of femtosecond-laser-filament plasma. Runaway electrons generating such x rays and being estimated to achieve their maximal energy, ε~U, near the positive electrode disappear if a laser filament plasma is ignited perpendicularly to the runaway near the positive electrode. A preheating mechanism for formation of the electron runaway in air is proposed.     

Improving the accuracy of multiple integral evaluation by applying Romberg’s method

Romberg’s method, which is used to improve the accuracy of one-dimensional integral evaluation, is extended to multiple integrals if they are evaluated using the product of composite quadrature formulas. Under certain conditions, the coefficients of the Romberg formula are independent of the integral’s multiplicity, which makes it possible to use a simple evaluation algorithm developed for one-dimensional integrals. As examples, integrals of multiplicity two to six are evaluated by Romberg’s method and the results are compared with other methods.     

Effect of external static magnetic field on the emittance and total charge of electron beams generated by laser-Wakefield acceleration

Significant enhancement of emittance and an increase of the total charge of femtosecond electron beams produced by a 12 TW, 40 fs laser pulse, tightly focused in a He gas jet, are observed after applying a static magnetic field, B> or =0.2 T, directed along the axis of laser pulse propagation. The effect appears when plasma produced by a laser prepulse becomes magnetized in the vicinity of the focus point: the electron Larmor frequency exceeds the collisional frequency, while periphery of the plasma remains unmagnetized. The entailed change in the shape of the plasma suppresses the diffraction of the main laser pulse that results in a much higher charge of electrons self-injected during the longitudinal wave breaking of the laser wake as well as the excellent stability of the beams.     

Nonlinear Langevin Equation for a System of Coulomb Particles

The nonlinear Langevin equation for a system of Coulomb particles with random processes, which are functionals of the velocity distribution function of such particles, has been derived and analyzed. It is shown by direct numerical solutions that this equation correctly describes the collisional relaxation of such a system even in the case of anomalous deviation of the initial velocity distribution of particles from the equilibrium distribution. The equation can be conveniently used in the Monte Carlo methods and in “particle-in-cell” methods.     

One-step transformation of the marine alkaloid fascaplysin into homofascaplysins B and B-1. The first syntheses of 3-bromohomofascaplysin B and 3–bromohomofascaplysin B-1

A method for one-step conversion of the marine alkaloid fascaplysin into homofascaplysins B and B-1 was elaborated. It was also used for the first syntheses of the marine alkaloids 3–bromohomofascaplysin B and 3-bromohomofascaplysin B-1. The best results were demonstrated under the action of microwave irradiation in presents of dihydroquinone as a reducing agent.     

Development of a laser-driven plasma cathode for medical applications

In this article, the present status of radiation therapy in Japan and updated medical accelerators are reviewed. In addition, the potential of laser plasma acceleration as a future medical accelerator is discussed. The updated results of laser plasma cathode experiment by the University of Tokyo are described.