Contribution of incoherent effects to the orientation dependence of bremsstrahlung from rapid electrons in crystal

The bremsstrahlung cross section for relativistic electrons in a crystal is split into the sum of coherent and incoherent parts (the last is due to a thermal motion of atoms in the crystal). Although the spectrum of incoherent radiation in crystal is similar to one in amorphous medium, the incoherent radiation intensity could demonstrate substantial dependence on the crystal orientation due to the electrons' flux redistribution in the crystal. In the present paper we apply our method of the incoherent bremsstrahlung simulation developed earlier to interpretation of some recent experimental results obtained at the Mainz Microtron MAMI.Comment: VIII International Symposium "Radiation from Relativistic Electrons in Periodic Structures" (RREPS-09) Zvenigorod, Russia, September 7-11, 200

On spectral method in the axial channeling theory

The quantization of the transverse motion energy in the continuous potentials of atomic strings and planes can take place under passage of fast charged particles through crystals. The energy levels for electron moving in axial channeling regime in a system of parallel atomic strings (for instance, [110] strings of a silicon crystal) are found in this work for the electron energy of order of several tens of MeV, when a total number of energy levels becomes large (up to several hundreds). High resolution of the spectral method used for energy level search has been demonstrated. Hence this method could be useful for investigation of quantum chaos problem.Comment: 11 pages, 4 figures, presented on the conference "Channeling-2012", 23-28 September 2012 Alghero, Sardegna, Italy; accepted for publication in Nuclear Instruments and Methods

Transition radiation on semi-infinite plate and Smith-Purcell effect

The Smith-Purcell radiation is usually measured when an electron passes over the grating of metallic stripes. However, for high frequencies (exceeding the plasma frequency of the grating material) none material could be treated as a conductor, but ought to be considered as a dielectric with plasma-like permittivity. So for describing Smith-Purcell radiation in the range of high frequencies new theoretical approaches are needed. In the present paper we apply the simple variant of eikonal approximation developed earlier to the case of radiation on the set of parallel semi-infinite dielectric plates. The formulae obtained describe the radiation generated by the particles both passing through the plates (traditionally referred as "transition radiation") and moving in vacuum over the grating formed by the edges of the plates (traditionally referred as "diffraction radiation", and, taking into account the periodicity of the plates arrangement, as Smith-Purcell radiation).Comment: Submitted to Journal of Physics: Conference Serie

Generalized solutions to linearized equations of Thermo-elastic solid and viscous thermo-fluid

Within the framework of continuum mechanics, the full description Of joint motion of elastic bodies and compressible viscous fluids with taking into account thermal effects is given by the system consisting of the mass, momentum, and energy balance equations, the first and the second laws of thermodynamics, and an additional set of thermo-mechanical state laws. The present paper is devoted to the investigation of this system. Assuming that variations of the physical characteristics of the thermo-mechanical system of the fluid and the solid are small about some rest state, we derive the linearized non-stationary dynamical model, prove its well-posedness, establish additional refined global integral bounds for solutions, and further deduce the linearized incompressible models and models incorporating absolutely rigid skeleton, as asymptotic limits.Comment: submitted to EJD

Nguetseng's Two-scale Convergence Method For Filtration and Seismic Acoustic Problems in Elastic Porous Media

A linear system of differential equations describing a joint motion of elastic porous body and fluid occupying porous space is considered. Although the problem is linear, it is very hard to tackle due to the fact that its main differential equations involve non-smooth oscillatory coefficients, both big and small, under the differentiation operators. The rigorous justification, under various conditions imposed on physical parameters, is fulfilled for homogenization procedures as the dimensionless size of the pores tends to zero, while the porous body is geometrically periodic. As the results, we derive Biot's equations of poroelasticity, equations of viscoelasticity, or decoupled system consisting of non-isotropic Lam\'{e}'s equations and Darcy's system of filtration, depending on ratios between physical parameters. The proofs are based on Nguetseng's two-scale convergence method of homogenization in periodic structures

Angular distribution of radiation by relativistic electrons in a thin crystal

The results of theoretical investigation of angular distributions of radiation from a relativistic electron passing through a thin crystal at a small angle to the crystal axis are presented. The electron trajectories in crystal were simulated using the binary collision model which takes into account both coherent and incoherent effects at scattering. The angular distribution of radiation was calculated as a sum of radiation from each electron. It is shown that there are nontrivial angular distributions of the emitted photons, which is connected to the superposition of the coherent scattering of electrons by atomic rows (doughnut scattering effect) and the suppression of the radiation due to the multiple scattering effect (similar to the Landau-Pomeranchuk-Migdal effect in an amorphous matter). The orientation dependence of angular distribution of radiation is also analyzed

On fractional powers of the Bessel operator on a semiaxis

In this paper we study fractional powers of the Bessel differential operator defined on a semiaxis. Some important properties of such fractional powers of the Bessel differential operator are proved. They include connections with Legendre functions for kernel representations, fractional integral operators of Liouville and Saigo, Mellin transform and index laws. Possible applications are indicated to differential equations with fractional powers of the Bessel differential operator.Comment: English version (pp. 1--8) and Russian version (pp. 9--18

О распознавании форменных объектов крови на основе медицинских изображений

Рассматривается задача постановки возможного диагноза по гематологическому анализу цифрового изображения эритроцитов. Описываются шаги по предварительной обработке изображения для уменьшения шумов и точности сегментации объектов клеток на классы. Для каждого этапа приведены примеры работы фильтро

Иммунная регуляция системы фибринолиза у больных пневмониями

Изучение урокиназной активности мочи у больных пневмонией, а также способность иммунной системы фиксировать и доставлять урокиназу в места наибольшей потребности в ней у больных пневмоние

Оценочная составляющая концепта INTEREST

Рассматриваются некоторые особенности структурной организации одного из концептов внутреннего мира человека - концепта INTEREST, а также анализируются способы языковой репрезентации оценочных признаков данного концептаyesБелгородский государственный университе