Том 108, № 8 (2018)

Normal blood levels of potassium are critical for maintaining normal heart electrical rhythm. Both low blood potassium levels (hypokalemia) and high blood potassium levels (hyperkalemia) can lead to abnormal heart rhythms. The aim of the work presented is to study the effect of potassium concentration on the excitation wave in the cardiac tissue. Results have been obtained both in the experimental model, which is a monolayer of neonatal rat cardiomyocytes, and in the modified Korhonen computer model, designed for ventricular rat neonatal cardiomyocytes. The existence of non-sodium excitation waves under a strong hyperkalemia (more than 10 mM K + in the extracellular environment) in the cardiomyocyte monolayer has been found and has also be confirmed by inactivation of sodium channels with a specific channel blocker.

We study the radiative correction to p_⊥-broadening of a fast quark in a quark–gluon plasma beyond the soft gluon approximation. We find that the radiative processes can suppress considerably p_⊥-broadening. This differs dramatically from previous calculations to logarithmic accuracy in the soft gluon approximation, predicting a considerable enhancement of p_⊥-broadening.

Collisions between carbon and beryllium nuclei at initial kinetic energies of carbon nuclei of 0.6, 0.95, and 2.0 GeV/nucleon have been simulated within the Liège intranuclear cascade model. Invariant proton production cross sections at an angle of 3.5° have been determined. It has been shown that the dependence of experimental invariant proton production cross sections on the cumulative variable can be explained in terms of Fermi processes of motion of nucleons in a nucleus, multiple scattering, and production of delta resonances. Results of simulation have been compared to experimental data and results obtained within the quark cluster model.

The optical orientation of the angular momenta of alkali atoms in the presence of a buffer gas (molecular nitrogen) has been studied experimentally. It has been shown that, even at a low concentration of molecular nitrogen in the cell, the excitation of ¹³³Cs atoms from the lower hyperfine level with F = 3, which belongs to the ground ²S_1/2 state, results in a larger amplitude of the magnetic resonance than the excitation from the hyperfine level with F = 4. This result has been theoretically explained under the assumption that the spin state of the alkali atomic nucleus does not change at collision with a nitrogen molecule, which is accompanied by a nonradiative transition of the alkali atom from the excited ²P_1/2 state to the ground ²S_1/2 state.

The generation of a vortex flow by waves on a water surface, which simulate an energy cascade in a system of gravity waves at frequencies of 3, 4, 5, and 6 Hz, has been studied experimentally. It has been found that pumping is accompanied by the propagation of waves on the surface at different angles to the fundamental mode and by a nonlinear interaction between waves resulting in the generation of new harmonics. It has been shown that large-scale flows are formed by modes of the lowest frequency of 3 Hz intersecting at acute angles. The energy distribution of the vortex motion can be described by a power-law function of the wavenumber and is independent of the energy distribution in a system of surface waves. The energy coming to large-scale vortex flows directly from the wave system is transferred to small scales. A direct rather than inverse energy flux is established in the system of vortices.

The superparamagnetism of an ensemble of ϵ-Fe₂O₃ nanoparticles with a mean size of 3.9 nm dispersed in a xerogel SiO₂ matrix is studied by the Mössbauer spectroscopy method. It is shown that most nanoparticles at room temperature are in the superparamagnetic (unblocked) state. As the temperature decreases, the progressive blocking of the magnetic moments of the particles occurs, which is manifested in the Mössbauer spectra as the transformation of the quadrupole doublet into a Zeeman sextet. The analysis of the relative intensity of the superparamagnetic (quadrupole doublet) and magnetically split (sextets) spectral components in the range of 4–300 K provides the particle size distribution, which is in agreement with the transmission electron microscopy data. The values of the effective magnetic anisotropy constants (K_eff) are determined, and the contribution of surface anisotropy (K_S) is estimated for particles of various sizes. It is shown that the quantity K_eff is inversely proportional to the particle size, which indicates the significant contribution of the surface to the magnetic state of the ϵ-Fe₂O₃ nanoparticles with the size of several nanometers.

X-ray photoelectron spectroscopy and electronic structure calculations in the framework of the coherent potential approach show that impurity Fe³⁺ ions substituting In in iron-doped In₂O₃ indium oxide(III) are in a paramagnetic state in the absence of oxygen vacancies.

Cloning of chimera states, which is a new effect caused by the short-term interaction in a multiplex network, has been described. This effect is observed when two ring networks of linearly coupled two-frequency (bistable) oscillators are combined into the multiplex network. At certain values of the strength and duration of the inter-ring (multiplex) interaction, a copy of a chimera state with accuracy to phases in the incoherent part is formed in the ring with an initially random phase distribution. It has been shown that the effect is structurally stable and is due to the competition of self-sustained oscillations in individual rings.

It has been shown that a local region with an increased concentration of a nonpolymerizable component can be formed in a photopolymerizable composite layer via a diffusion process stimulated by the motion of the area of initiating illumination. Furthermore, it has been demonstrated that this region can be transferred to a given place of the polymerized material. The dependences of the formation path, width, and amplitude of the local inhomogeneity of the nonpolymerizable component on the velocity of the boundary of illumination area along the polymerized layer have been determined by numerical simulation. The results of the experiment have been presented.

Observations of current structures with magnetic shear by the Cluster satellite quartet in the magnetotail and the Wind satellite in the solar wind have been reported. In current structures with magnetic shear, the following structural features have been identified: (i) thickening of a current layer, (ii) plasma density distribution asymmetric with respect to the layer plane, and (iii) formation of an asymmetric current density profile. The kinetic features of the dynamics of ions in current layers with initial shear deformation have been considered. A mechanism has been proposed for the formation of self-consistent current sheets with a nonzero shear magnetic field component.

The indication of affiliation for the first author should be: V. A. Vlasenko^a, ^*