Ionization-overheating instability threshold in the electrodeless microwave discharge plasma

Experiments with a pulsed freely localized electrodeless microwave discharge in air under a pressure corresponding to the ascending branch of the pressure dependence of the breakdown field are described. The discharge is initiated in a focused quasi-optical electromagnetic beam. The minimal threshold values of the electromagnetic field (for which a brighter plasma channel extended along the field is formed in the initially spatially homogeneous diffuse discharge plasma) are determined by varying air pressure for several fixed values of this field in the focal region of the beam. In accordance with the prevailing theory, this phenomenon is interpreted as the result of evolution of ionization-overheating instability in the microwave discharge plasma.     

Synthesis of chitosan-stabilized Au nanoparticles with controllable sizes

Au nanoparticles stabilized by chitosan have been prepared under the combined action of ultraviolet radiation and thermal exposure of its solutions doped with HAuCl₄. With the use of absorption spectrophotometry and small-angle X-ray scattering, it has been shown that the use of chitosan of different molecular masses allows one to control both the sizes of Au particles and their aggregative stability in nanodispersions.     

Cubane derivatives 7. Synthesis and molecular structure of 4-bromo-1-hydroxymethylcubane

The present study concerned with reduction of methyl 4-bromocubanecarboxylate (1) with lithium aluminum hydride and aluminum hydride in THF. An efficient procedure was developed for the synthesis of 4-bromo-1-hydroxymethylcubane (2) based on reduction of compound 1 with aluminum hydride under mild conditions. The structure of 2 was established by X-ray diffraction. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1461–1464, June, 2005.     

Fourier synthesization of optical pulses and “polar” light

It is shown that the direct Fourier synthesization of light beams allows one to create polarity-asymmetric waves, which are able, in the process of nonlinear interaction with a medium, to break its inversion symmetry. As a result, these “polar” waves may show the effect of optical rectification in nonlinear centrosymmetric media by generating light-induced dc electric polarization. At the same time, waves of this type, due to their unusual symmetry properties, can be used for detecting the direction and sign of a dc electric field applied to the medium. The prospects of application of polar waves to data recording and processing are discussed.     

Parameters of transverse-longitudinal discharge in supersonic airflow

Plasma of transverse-longitudinal direct-current discharge in a supersonic aerodynamic channel with a reverse step is studied experimentally. For deposited powers of 2–3 kW, the gas temperature in the discharge achieves 2000 ± 500 K. The results obtained testify to the applicability of discharge plasma for the ignition of supersonic air-fuel flows.     

Refined equations of the theory of thin plates for dynamic problems

Institute of Problems of Mechanics, Russian Academy of Sciences, Moscow. Translated from Prikladnaya Mekhanika, Vol. 30, No. 6, pp. 80–87, June, 1994.