Study of the effect of properties of material on vacuum breakdown initiated by laser radiation

In this work, the effect of various properties of materials on vacuum breakdown initiated by laser radiation is considered. Estimating calculations are performed which show that the material of the target electrode distinctly affects the minimum energy of laser radiation needed for igniting a vacuum spark. The experimental studies carried out confirm the estimating calculations, and a number of materials are revealed which can be arranged in order of increase in the energy needed for the formation of breakdown in vacuum by the impact of a laser pulse.     

Structure of the control parameter space for a nonautonomous piecewise linear oscillator

The variation of the structure of the control parameter space for a nonautonomous nonlinear oscillator is demonstrated with a harmonically excited nonautonomous oscillatory circuit with a piecewise linear capacitance.     

Inversion of the density gradient and the diffusion “gate” in isothermal mixing of gases

The stable quasistationary mixing of ternary gas mixtures in a system of two chambers connected by a capillary is described by a theoretical model which predicts the density distribution of the mixture along the length of the diffusion channel. It is demonstrated that inversion of the density gradient can occur due to a nonlinear concentration distribution of the heavy component in a diffusion “gate” effect. The results obtained using this model are compared with the experimental data. Zh. Tekh. Fiz. 68, 14–17 (May 1998)     

Electronic tongue for quality assessment of ethanol, vodka and eau-de-vie

Rapid quality assessment of alcoholic beverages, including brand identification and detection of products of unacceptable quality or counterfeits is an important practical task. In the present work the multisensor electronic tongue system (ET), based on array of potentiometric chemical sensors was applied to recognition and classification of spirits such as vodka and ethanol used for vodka production and also for eau-de-vie in cognac production. The ET system was capable of detecting presence of contaminant substances in vodka in concentrations exceeding allowed levels as well as of distinguishing vodka complying and not complying with state quality standards. Ten brands of vodka produced at the same distillery using water and ethanol of different purity and various taste additives were discriminated using the instrument. The ET could distinguish synthetic and alimentary grain ethanol as well as alimentary ethanol of different grades (i.e. different degree of purification). A feasibility study was run on several eau-de-vie samples, which included fresh and aged eau-de-vie as well as samples produced using different distillation technology and samples kept in contact with different kinds of oak. The electronic tongue showed a promise as an analytical instrument for rapid quality assessment of spirits.     

Preparation of rare metallic actinides (248Cm,249Bk,249Cf) and investigation of their crystal structure

²⁴⁸Cm and²⁴⁹Bk metals were prepared by thermal reduction of their oxides with thorium and metallic²⁴⁹Cf with metallic lanthanum. These rare actinide samples of 1.0 mg in mass were thin layers on a flat substrate and were investigated by X-ray technique. Dhcp lattice parameters of -Cm, -Bk and -Cf as main phases in X-ray diagrams are presented. The effect of impurities on the -Cm lattice parameters is shown. Fcc lattices for the high temperature form of Cm metal (-Cm) with a=0.4933 nm, and of Cm and Bk monoxides (a=0.502–0.504 nm and a=0.5002 nm, respectively) have been observed. Thermal expansion coefficients for -Cm and -Bk at 80–300 K were calculated. Identification problems of fcc lattices and oxidation features of metals prepared are discussed.     

Fluctuation theorem and thermodynamic entropy

The validity of the identification of a dissipation function appearing in the recently proved fluctuation theorem to the thermodynamic entropy production has been studied for a classical nonlinear Schlögl reaction. This example has indicated that such identification is unjustified. Owing to this result, the applied importance of the mentioned theorem for studying complex nonequilibrium systems is doubtful.     

Synthesis of Cu(II)-containing TiO2-SiO2 binary xerogels by hydrolysis of a mixture of tetrabutoxytitanium, tetraethoxysilane, and copper(II) chloride in a water-ammonia atmosphere

A Cu(II)-containing binary xerogel TiO₂-SiO₂ was synthesized by joint hydrolysis of tetrabutoxytitanium, teraethoxysilane and copper(II) chloride dissolved in their mixture. The synthesis was performed in a vapor of 10% aqueous ammonia under static conditions. EPR spectroscopy was used to examine the state of Cu(II) in the xerogel matrix. Data on specific features of the behavior of saccharose within xerogel pores under heating were obtained. The catalytic activity of the xerogel was tested by the kinetic method on model reactions of hydrogen peroxide decomposition and oxidative dehydrogenation of trimethylhydroquinone.     

Pressure dependence of the mixing rate for the free convection of a binary gas mixture in a two-flask apparatus

A theoretical model of steady-state mixing is considered for a binary gas mixture under conditions of free gravitational convection in a vertical channel with impenetrable walls that connects two flasks. It is shown that the mixing rate in the supercritical regime has a peak and then deceases monotonically with increasing pressure. The experimental results are shown to be in good agreement with theoretical data.     

XeO luminescence in a self-sustained slab radio-frequency discharge

We report the observation of bright luminescence and registration of luminescence spectrum of a XeO molecule in the green spectral region upon excitation of a Xe:O₂ gas mixture in a self-sustained slab radio-frequency discharge.