Goldstone mode of Skyrmion Crystal

We discuss the Goldstone mode of skyrmion crystal in a model of two-dimenssional ferromagnet with Dzyaloshinskii-Moriya interaction in magnetic field. We use stereographic projection approach to construct skyrmion crystal and consider skyrmion's displacement field. The small overlap of the individual skyrmion images restricts the potential energy to the interaction of nearest neighboring displacements. The closed form of the Goldstone mode dispersion is found and its dependence on the magnetic field is studied. We use semiclassical quantization to define the Green's function and show that the propagation of displacements through the crystal changes its tensorial form from isotropic to anisotropic one at large distances.Comment: 6 pages, 4 figure

Generation of powerful terahertz emission in a beam-driven strong plasma turbulence

Generation of terahertz electromagnetic radiation due to coalescence of upper-hybrid waves in the long-wavelength region of strong plasma turbulence driven by a high-current relativistic electron beam in a magnetized plasma is investigated. The width of frequency spectrum as well as angular characteristics of this radiation for various values of plasma density and turbulence energy are calculated using the simple theoretical model adequately describing beam-plasma experiments at mirror traps. It is shown that the power density of electromagnetic emission at the second harmonic of plasma frequency in the terahertz range for these laboratory experiments can reach the level of 1 ${MW/cm}^3$ with 1% conversion efficiency of beam energy losses to electromagnetic emission

Magnon topological transition in skyrmion crystal

We study the magnon spectrum in skyrmion crystal formed in thin ferromagnetic films with Dzyalosinskii-Moria interaction in presence of magnetic field. Focusing on two low-lying observable magnon modes and employing stereographic projection method, we develop a theory demonstrating a topological transition in the spectrum. Upon the increase of magnetic field, the gap between two magnon bands closes, with the ensuing change in the topological character of both bands. This phenomenon of gap closing, if confirmed in magnetic resonance experiments, may deserve further investigation by thermal Hall conductivity experiments.Comment: 6 pages, 4 figure

Second harmonic electromagnetic emission of a turbulent magnetized plasma driven by a powerful electron beam

The power of second harmonic electromagnetic emission is calculated for the case when strong plasma turbulence is excited by a powerful electron beam in a magnetized plasma. It is shown that the simple analytical model of strong plasma turbulence with the assumption of a constant pump power is able to explain experimentally observed bursts of electromagnetic radiation as a consequence of separate collapse events. It is also found that the electromagnetic emission power calculated for three-wave interaction processes occurring in the long-wavelength part of turbulent spectrum is in order-of-magnitude agreement with experimental results

Adiabatic nonlinear waves with trapped particles: II. Wave dispersion

A general nonlinear dispersion relation is derived in a nondifferential form for an adiabatic sinusoidal Langmuir wave in collisionless plasma, allowing for an arbitrary distribution of trapped electrons. The linear dielectric function is generalized, and the nonlinear kinetic frequency shift $\omega_{\rm NL}$ is found analytically as a function of the wave amplitude $a$. Smooth distributions yield $\omega_{\rm NL} \propto \sqrt{a}$, as usual. However, beam-like distributions of trapped electrons result in different power laws, or even a logarithmic nonlinearity, which are derived as asymptotic limits of the same dispersion relation. Such beams are formed whenever the phase velocity changes, because the trapped distribution is in autoresonance and thus evolves differently from the passing distribution. Hence, even adiabatic $\omega_{\rm NL}(a)$ is generally nonlocal.Comment: submitted together with Papers I and II

Dynamics of the anaerobic threshold of ski racers throughout the annual training cycle

To study the dynamics of cardiorespiratory parameters in the anaerobic threshold zone of ski racers throughout the annual training cycle. Materials and methods: 300 examinations of 49 professional ski racers of I category and candidate masters of sports (aged from 15 to 32 years, mean age - 19,7±1,3 (M±m)) were carried out in the breath-by-breath mode on an Oxycon Pro ergospirometric system (Erich Jaeger). Maximal oxygen consumption (MOC: absolute and per kilogram of body weight) was detected during pass-fail test. Heart rate (HR), oxygen consumption (VO2), oxygen pulse and maximal load were registered in the anaerobic threshold zone. Difference between the actual and theoretically calculated HR, VO2 percentage (relate to maximal oxygen consumption) was calculated. Results: pulse increase in the anaerobic threshold zone by 20% prolonged aerobic activity of ski racers and increased maximal aerobic load by 20%. Conclusions: the most favorable values of cardiorespiratory parameters were registered during the preparation period, and the least - during the competition period. This fact requires correction of the training process and rehabilitation

Possibilities of per-oral transpapillary cholangioscopy in oncological practice

Relevance. Diagnosis of malignant diseases causing bile duct strictures is a big challenge. At admission, patients with suspected biliary tract stricture, initially undergo endoscopic retrograde cholangiopancreatography (ERCP) as a diagnostic and treatment method. The morphological diagnosis of bile duct stricture based on ERCP with brush biopsy or intraductal forceps biopsy is limited by their low sensitivity. Consequently, a significant proportion of strictures remains undiagnosed, which led to the development of methods based on cholangioscopy. Aim. To determine the role of per-oral transpapillary cholangioscopy (TCS) in a specialized cancer clinic. Materials and methods. SpyGlass direct visualization system for per-oral intraductal examination from Boston Scientific was clinically tasted in Blokhin National Medical Research Center of Oncology of the Ministry of Health of Russia. Using this electronic system, TCS was performed in 4 patients with various malignant diseases. Results. In all cases, TCS was successful. In all patients, the diagnosis was confirmed with a forceps intraductal biopsy using Spybite forceps. Conclusion. Single-use electronic direct visualization system for per-oral intraductal examination and interventions like SpyGlass can be recommended for use in specialized cancer centers

FEATURES OF PRODUCT CERTIFICATION IN THE FIELD OF INDUSTRIAL SAFETY IN GERMANY

The article presents an overview of the features of the certification system of products С in Germany, the differences between the markings on the industrial safety sign «Geprufte Sicherheit» and the «CE» sign are considered.В статье представлен обзор особенностей системы сертификации продукции С в Германии, рассмотрены отличия маркировок на знак промышленной безопасности «Geprüfte Sicherheit» и знак «CE»