Transport properties of polyphenylquinoxalines

The correlation between chemical structure and gas transport properties is considered for a new class of membrane materials based on structurally similar polyphenylquinoxalines that are characterized by different numbers of flexible-O-ether bonds in the repeating unit and different chain rigidities. Permeability, diffusion, and solubility coefficients have been estimated for the gases H₂, He, O₂, N₂, CO, CO₂, and CH₄; separation factors for various gas pairs have been determined. For the materials with a similar level of cohesive energy density, which characterizes interchain interactions, permeability decreases with a decrease in chain rigidity, whereas selectivity of gas separation increases.     

Focusing of shock waves in a highly viscous fluid

The method of combined asymptotic expansions is used to solve the problem of the focusing of a shock wave (in a weakly compressible medium of high viscosity. Asymptotic forms of the solution are constructed in a number of spatial zones. The focusing zone is described by its asymptotic form obtained by combining it with the solution corresponding to viscous geometrical acoustics. The reflection of a shock wave formed as a result of velocity jump near one of the foci of the ellipsoid of revolution is discussed as an example. Analytical relationships descrbing the focusing zone around the second focus are obtained. It is shown that at the focus itself the wave profile has an antisymmetric form, and the compression wave is followed by a rarefaction wave of the same form.     

Achievements in the field of proton-conductive portion electrolyte membranes

The 2000–2006 achievements in the field of synthesis, property examination, and application of proton-exchange membranes are reviewed on the basis of more than 120 papers.     

The small momentum transfer k L o C→K S 0 C regeneration at high energies

Results of the first elastic K _S ^o regeneration experiment on carbon, using magnetic spark chamber spectrometer, are presented in the beam momentum interval 10p50 GeV/c. The d ifferentia cross section d/dt is reconstructed in the range 0·0025–t0·02 (GeV/c)² and its slopeB is found to be momentum independent with an average valueB=(65±11) (GeV/c)^–2. The results are in agreement with the calculations using the coherent production model.     

Cooperative plasticity due to the motion of disorientation and phase separation boundaries

Conclusions As has already been noted above, the theory of planar defects organically includes the mechanics of twinning, grain boundaries, Somigliani dislocations, translational dislocations, disclination, and dispiration. The fundamental propositions of the theory and methods of giving the tensor T are listed in Table 4. The mathematical formalism remains the same throughout, and it is applicable to both discrete objects (it is then necessary to conserve the -function apparatus), and to a continuous (then appropriate smoothing is needed, which usually reduces to replacement of the multiplication procedure by the normal n or by the direction , to operations of finding the gradient, divergence, and curl of regular expressions, and discarding the -functional), In particular, the problem of thermoelasticity is formulated successfully by such a method in the terminology of the present theory.In a broad sence of the word, the development of the theory should be perceived as an extension of the concept of imperfection to defects of sufficiently arbitrary origin. A completely developed formalism was worked out earlier for just linear defects; in the symbols used here, for the case b=b₀ + X (r – r₀) for constant b₀,, and r₀, and without taking account of processes on the boundary S if the linear defect contained such a feature. Let us emphasize that to describe three-dimensional defects occurring because of homogeneous distortion = (V)., it is sufficient to use the apparatus of just the theory of planar defects since the fundamental phenomena are associated with precisely the presence of boundaries and in a formal plane, with the spatial derivatives of , they are always expressed in terms of the functional (S), while in the case of finite surface gradients in terms of (L). The time derivatives of the distortion T, i.e., is written down in the developed representations in terms of the form with all the resulting consequences.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 83–102, June, 1981.     

“Electron ping-pong” on a one-dimensional lattice: Multiple reflections of the wave packet and capture of the wave function by an acceptor

Considering the problem of multiple reflections of a wave function from the ends of a lattice, we observe an interesting phenomenon: the wave function amplitude is concentrated on the impurity center after reflections. The solution obtained by expanding the total wave function a(t) on the impurity center in the partial amplitudes a_k(t), whose contributions become essential only after the kth reflection from the lattice end, seems to agree very well with the results of numerical modeling. We solve the problem of the capture of the wave function by an acceptor. The obtained results can be used to explain experimental data on charge transfer in artificial oligonucleotides and polypeptides. We find expressions for the electron capture probability in some limit cases, which can be considered estimates of the quantum output of the charge transport.     

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.     

Laser-Synchrotron Facility of the National Research Centre “Kurchatov Institute”

Crystallography Reports - The laser-synchrotron facility (LSF) of the National Research Centre “Kurchatov Institute” (NRC KI) is a unique research complex that combines unprecedented...     

Interaction between a composite compression wave and a vortex in a thermodynamically nonideal medium

A numerical analysis is presented of two-dimensional interaction between a transverse vortex and a composite compression wave that can exist in a thermodynamically nonideal medium. It is shown that the interaction of a composite wave involving a “neutrally stable” shock with a vortex generates weakly damped outgoing acoustic waves; i.e., the shock is a source of sound. This phenomenon increases the post-shock acoustic noise level in an initially turbulent flow.     

Regularization methods in radio interferometry

The problem of image retrieval in radio interferometry is a classical example of an ill-posed problem. In this paper, we consider a new approach to the radio-interferometric imaging based on regularization, which is computationally more flexible. A new type of a weighting function suitable for managing the interferometer antenna pattern is obtained. The regularization procedure was implemented in the VLBI-image processing software developed at the Astrospace Center of the Lebedev Physical Institute (ASC LPI). It is shown that the joint use of the developed regularization methods with traditional deconvolution algorithms such as CLEAN and self-calibration improve the quality of images of cosmic radio-emission sources. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 50, No. 6, pp. 453–460, June 2007.