Eugeniy B. Shadrin

A method of transcranial electromagnetic stimulation of the mammalian brain is proposed. The method is based on the interference of currents caused by high-frequency orthogonal oscillations of electric fields, which are modulated by low-frequency meander pulses. The effectiveness of the method was confirmed by the results of experiments on stimulating the brain of rats and rabbits.

Dielectric spectroscopy methods revealed the existence of two types of relaxation processes in the semiconductor phase of VO₂:Fe films. The characteristic relaxation times are denoted by τ₁ and τ₂. It is shown that the temperature dependences of τ₁ and τ₂ have hysteresis, the position of the loops of which coincides with the points of the semiconductor-metal phase transition in VO₂:Fe films. τ₁ corresponds to undoped, and τ₂ corresponds to Fe-doped nanocrystallites of the VO₂ film. It is shown that the physical mechanism of the relaxation process is due to the establishment of equilibrium after the action of an electric field on conduction electrons. The numerical values of the parameters of the distribution of relaxers over relaxation times are determined.

The electronic configuration of chemical bonds between ions forming the structure of the AgI superionics existing in three different crystal modifications is discussed: α-, β- and γ-phases.On the basis of the formulated schemes of hybridization of ion orbitals, the structural phase transitions γ->β and β->α occurring with increasing temperature are considered.It is shown that in the high-temperature superionic α-phase of the AgI crystal in an external electric field, along with an increase in electronic conductivity, hopping conductivity occurs due to a weakening of the coordination bonds between the ions of the substance and the jumps of silver ions along the ion-conducting channels

A method of transcranial electromagnetic stimulation of the mammalian brain is proposed. The method is based on the interference of currents caused by high-frequency orthogonal oscillations of electric fields, which are modulated by low-frequency meander pulses. The effectiveness of the method was confirmed by the results of experiments on stimulating the brain of rats and rabbits. Keywords: electromagnetic stimulation, interference, alpha-rhythms, theta-rhythms, serotonin, beta-endorphins, neuron.

A comparative analysis of the physical parameters of strongly correlated oxides VO and V₂O₃ has been carried out. It has been established that the semiconductor--metal phase transition in both VO and V₂O₃ has a complex Mott-Peierls character. Namely, as the temperature increases in both oxides, before the Peierls abrupt structural phase transition, the Mott phase transition, which is extended in temperature, take place. It has been discussed the reason for the fact that, despite the stabilization of the semiconductor phase by high-strength π-dimers or sigma-dimers, the temperatures of phase transitions are low (T_c=126 K (VO) and T_c=140 K (V₂O₃)). Keywords: Magnelis series, phase transformations, electron-electron correlations.

Электропроводящие свойства окислов ряда Магнели: VO и V 2 O 5

Активация нейромедиаторов мозга животных интерференционными транскраниальными токами

The frequency dependences of the dielectric loss tangent tan δ( f ) and the Cole–Cole diagrams of silver sulfide thin films are studied at various temperatures in the range 0–200°C. The experimental data are compared to the calculation of the complex impedance of the electric circuit proposed for Ag₂S-containing samples before and after the temperature semiconductor–superionic phase transition. A microscopic model of the phase transition in Ag₂S is proposed on the base of the analysis of obtained results and literature data.

A complex character of the mechanism of thermal phase transformations from the insulating phase to the metallic phase has been revealed in thin V₂O₃ films. The insulator–metal phase transition in V₂O₃ is shown to consist of two stages: the hysteresis-less temperature-extended electron Mott transition extended in temperature and the stepwise structural Peierls transition with temperature hysteresis. The features of the insulator–metal phase transition revealed for V₂O₃ are discussed. These features are analyzed on the base of their comparison with characteristic features of analogous phase transition in VO₂ films.

The frequency dependences of the dissipation factor tanδ(f) and the Cole–Cole diagrams for germanium- and magnesium-doped vanadium-dioxide films in the range of 0.1–10⁶ Hz are obtained. Measurements at temperatures between 173–373 K are performed. It is found that, at room temperature, an additional maximum in the tanδ(f) dependence and an additional semicircle in the Cole–Cole diagram of the VO₂:Ge films as compared with those of undoped films appear at low frequencies. In the VO₂:Mg films, similar additional features in the dielectric spectra are observed at high frequencies. It is shown that the shape of the Cole–Cole diagrams for all the films is almost temperature independent in the mentioned temperature range, while the frequencies f₀ corresponding to the tanδ(f) maxima increase with temperature. To interpret the dielectric spectroscopy data, a combined equivalent electrical circuit of the film sample is proposed. The mechanisms of the effect of Ge and Mg impurities on the characteristics of the complex Mott–Peierls semiconductor–metal phase transition are established.