Vol 106, No 9 (2017)

The mechanism of the low voltage defibrillation is based on the drift of the spiral wave induced by a high frequency wave train. In the process, it is first necessary to unpin the wave from the stabilizing obstacle. We study the conditions of unpinning of a rotating wave anchored to the defect by posing the main accent on the boundary conditions of it. The computer simulations performed using the Korhonen model showed that the fluxes through the border of the defect in the cardiac tissue can significantly modify the excitation pattern, and the working frequency gap for the unpinning of reentry waves could be substantially reduced, making overdrive pacing procedure less effective or practically inapplicable.

We consider the effects of electron scattering off a quantum magnetic impurity on the current–voltage characteristics of the helical edge of a two-dimensional topological insulator. We compute the backscattering contribution to the current along the edge for a general form of the exchange interaction matrix and arbitrary value of the magnetic impurity spin. We find that the differential conductance may exhibit a nonmonotonic dependence on the voltage with several extrema.

The theory of the coherent photogalvanic valley Hall effect in two-dimensional systems with the Dirac spectrum of charge carriers is formulated. The study deals with a two-dimensional sample irradiated by two electromagnetic waves, at the fundamental and doubled frequencies. Both frequencies exceed the band gap of the material, whereas the wave with the fundamental frequency having circular polarization and a high intensity is taken into account in a nonperturbative manner. The wave at the doubled frequency is linearly polarized and the electrical conductivity of the two-dimensional system is calculated with respect to it. The effect under study manifests itself as the dc Hall current in the direction orthogonal to the electric field of the weak electromagnetic wave. It is assumed that, in equilibrium, the sample is in the insulating state with the completely occupied valence band and empty conduction band. The strong electromagnetic wave induces a nonequilibrium filling of the bands and the system passes to a strongly nonequilibrium steady state. The behavior of the Hall current in the case of nonequilibrium distribution functions is analyzed both including and disregarding the intraband relaxation and interband recombination.

The molecular structure of neutral n-triacontanol mesophases at the n-hexane–water interface has been studied by diffuse X-ray scattering using synchrotron radiation. According to the experimental data, a transition to the multilayer adsorption of alkanol occurs at a temperature below the transition from a gas phase to a liquid Gibbs monolayer.

A method to evaluate the particle–phonon coupling (PC) corrections to the single-particle energies in semi-magic nuclei, based on a direct solving the Dyson equation with PC corrected mass operator, is used for finding the odd–even mass difference between 18 even Pb isotopes and their odd-proton neighbors. The Fayans energy density functional (EDF) DF3-a is used which gives rather high accuracy of the predictions for these mass differences already on the mean-field level, with the average deviation from the existing experimental data equal to 0.389 MeV. It is only a bit worse than the corresponding value of 0.333 MeV for the Skyrme EDF HFB-17, which belongs to a family of Skyrme EDFs with the highest overall accuracy in describing the nuclear masses. Account for the PC corrections induced by the low-laying phonons 2₁⁺ and 3₁^- significantly diminishes the deviation of the theory from the data till 0.218 MeV.

The fusion in air of four femtosecond laser beams each with the peak power several times higher than the critical self-focusing power has been studied experimentally. It has been shown that a superfilament formed in such a regime ensures the efficient energy input to a medium. It has been shown that the linear density of the input energy increases approximately quadratically with both the energy of a laser pulse and the number of fused beams.

Two cases of the two-dimensional motion of a charged particle in an electromagnetic field have been integrated. In these cases, the Hamiltonian commutes with the angular momentum. Variables are separable in polar coordinates. The vector potential and potential energy have been taken from my recent work regarding two cases of the two-dimensional Schrödinger equation, which belong to quasi-exactly solvable problems. In these cases, semiclassical and exact wavefunctions have been compared in classically forbidden regions.

The distributions of the electric field strength, current density, and trajectories of emitted electrons have been simulated taking into account the topology of a graphene/SiC nanotip emitter. The analysis of the resulting models has shown an increase in the electric field strength and current density on concentric nanobulges at the periphery of the emitter. It has been shown that nanobulges are sources of the intense emission of electrons. The superposition of trajectories of these electrons results in the appearance of several rings on an emission image.