Dynamics of a CW single-mode Nd:YAG laser with a Cs2 narrow-band saturable absorber

We present the results of experiments with a CW single-mode Nd:YAG laser, tunable in the vicinity of 1064 nm, with an intracavity narrow-band Cs ₂ vapor saturable absorber. It is shown that the laser dynamics is determined by both the pump level and detuning of the laser frequency from the absorption-line center.     

Direct (without degassing) determination of sulfur-containing compounds in unstable gas condensate by gas chromatography

A procedure has been developed for direct determination of sulfur-containing components in the concentration range 0.0002?C0.7 wt % in samples of unstable gas condensate under a pressure of 8 MPa using a gas chromatograph equipped with a flame photometric detector. The determination of the overall composition of samples (including hydrocarbons and inorganic gases) takes no more than 1 h, i.e., is 5 times more rapid than the standard procedure with preliminary sample degassing. In addition, direct (without degassing) determination results is lower errors (the repeatability for the main components is 0.01?C0.06; n = 10).     

Peculiarities of the phase composition and structure of the high-entropy FeWMoCrVSiMnC multicomponent steel

We report on the results of analysis of the phase composition, structure, and hardness of high-entropy FeWMoCrVSiMnC multicomponent steel subjected to synthesis and subsequent thermal treatment. Analysis is carried out using the methods of analytic transmission and scanning structural and orientational electron microscopy, optical metallography, X-ray energy-dispersive spectroscopy, X-ray phase and structural analyses, and Rockwell measurements of hardness. It is found that steel has a high hardness (62 HRC) and is in ultra-fine-disperse composite martensite-multicarbide state. All carbides are distributed uniformly over the steel volume and have nano- and submicrometer scales depending on the carbide type.

     

Annual Meeting of the Division of Biochemistry,Biophysics, and Chemistry of Physiologically Active Compounds of the Russian Academy of Sciences

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Annual Meeting of the Division of Biochemistry, Biophysics, and Chemistry of Physiologically Active Compounds of the Russian Academy of Sciences     

Piecewise parabolic method on a local stencil for ideal magnetohydrodynamics

A numerical scheme based on the piecewise parabolic method on a local stencil (PPML) is proposed for solving the ideal magnetohydrodynamic (MHD) equations. The method makes use of the conservation of Riemann invariants along the characteristics of the MHD equations. As a result, a local stencil can be used to construct a numerical solution. This approach improves the dissipative properties of the numerical scheme and is convenient in the case of adaptive grids. The basic stages in the design of the scheme are illustrated in the two-dimensional case. The conservation of the solenoidal property of the magnetic field is discussed. The scheme is tested using several typical MHD problems.     

Effect of annealing on the structural and microwave magnetic properties of singlelayer and multilayer films of various compositions

The effect of annealing on the structure and microwave magnetic properties of composite single-layer and multilayer films is investigated. It is found that as the threshold annealing temperature is attained, the width of the FMR line increases abruptly, depending on the concentration ratio of metallic alloy and dielectric. It is shown that the FMR line broadening is also associated with the occurrence of and increase in high-frequency modes of absorption. The surfaces of annealed and unannealed films are investigated at various concentrations of metallic alloys and dielectrics using an atomic force microscope. The strong change in the magnetic characteristics after film annealing is associated with a change in surface roughness and inhomogeneity, and in the size distribution of nano- and submicron formations and their spacing.     

Mathematical modeling of self-oscillations in ethane oxidation over nickel

The methodology of constructing a phenomenological model for complex heterogeneous catalytic reactions is described in detail. The proposed approach is applicable to development of mathematical models describing the onset of self-oscillations in hydrocarbon oxidation on the transition metal surface. The approach is based on construction of a microkinetic scheme taking into account the formation of main reaction products and intermediates, on estimation of the heat of reaction, activation energy, and preexponential factor for elementary steps and includes development and a subsequent analysis of the corresponding mathematical model. Catalytic reactions are considered in the ideal adsorption layer approximation without taking into account the relationship between coverages and spatial coordinates. Accordingly, the mathematical model is an independent system of ordinary differential equations. This methodology is used to develop a point (lumped) model for ethane oxidation over nickel, which is based on a 36-step microkinetic scheme taking into account the oxidation and reduction of nickel and the formation of total (CO₂ and H₂O) or partial (CO and H₂) ethane oxidation products, as well as the dehydrogenation of ethane into ethylene. The proposed model predicts the onset of self-oscillations in this reaction at atmospheric pressure in the temperature range from 850 to 1400 K. The kinetic oscillations are caused by the cyclic oxidation and reduction of nickel. The self-oscillations of the reaction rate are accompanied by oscillations of the catalyst temperature. The results of modeling are compared with experimental data.     

Fluorinated γ-carbolines as agents for delaying cognitive and motor dysfunctions in a transgenic model of neurodegenerative disorders

Russian Chemical Bulletin - γ-Carboline derivatives were synthesized by the addition of fluorinated vinylpyridines to 2,6-dimethyl-2,3,4,5-tetrahydro-γ-carboline. The effect of repeated...     

Piecewise parabolic method on local stencil for gasdynamic simulations

A numerical method based on piecewise parabolic difference approximations is proposed for solving hyperbolic systems of equations. The design of its numerical scheme is based on the conservation of Riemann invariants along the characteristic curves of a system of equations, which makes it possible to discard the four-point interpolation procedure used in the standard piecewise parabolic method (PPM) and to use the data from the previous time level in the reconstruction of the solution inside difference cells. As a result, discontinuous solutions can be accurately represented without adding excessive dissipation. A local stencil is also convenient for computations on adaptive meshes. The new method is compared with PPM by solving test problems for the linear advection equation and the inviscid Burgers equation. The efficiency of the methods is compared in terms of errors in various norms. A technique for solving the gas dynamics equations is described and tested for several one-and two-dimensional problems.     

Gravity waves accompanying supernova explosions

Gravitational radiation arising during the formation of a protoneutron star is studied. Here it is mainly large-scale nonuniformities that develop inside the star. The entropy and density profiles of such nonuniformities resemble the “mushroom cloud” of a nuclear explosion. A bubble of hot neutron matter floats to the surface of the star, like the “mushroom cloud” of an explosion in the earth’s atmosphere. Depending on the symmetry of the problem, from two to six bubbles can float upward at the same time. The characteristic masses of such bubbles are 0.01M _⊗ and the radial velocities reach ∼0.1c. The energy radiated in the form of gravitational waves in one cycle of bubbles floating to the surface is ∼10⁻² M _⊗ c ²−10⁻¹⁰ M _⊗ c ². Such cycles occur repeatedly as the neutron star cools. This phase can last up to seconds. The total energy radiated in the form of gravitational radiation can reach 10⁻¹ M _⊗ c ². Pis’ma Zh. éksp. Teor. Fiz. 64, No. 12, 817–822 (25 December 1996)