arXiv subjects
Publications and source records attributed to M. Timko.
In the classical approximation, we examine the problem of radiation by channeled positrons in the field of a longitudinal ultrasonic wave when the condition of parametric resonance is satisfied. We show that in the case of planar channeling the intensity of the spectral distribution of the radiation can be several times larger than when the resonance condition is not satisfied.
An analytical expression is received for the effective interaction potential of a fast charged particle with the ionic crystal CsCl near the direction of axis <100> as a function of the temperature of the medium. A possibility of positron channeling in this potential is shown. By numerical analysis it is shown that the effective potential of axial channeling of positrons along the axis <100> of negatively charged ions practically does not depend on temperature of the media.
The influence of the shape anisotropy of magnetic particles on the isotropic-nematic phase transition was studied in ferronematics based on the nematic liquid crystal 4-(trans-4-n-hexylcyclohexyl)-isothiocyanato-benzene (6CHBT). The liquid crystal was doped with spherical or rod-like magnetic particles of different size and volume concentrations. The phase transition from isotropic to nematic phase was observed by polarizing microscope as well as by capacitance measurements. The influence of the concentration and the shape anisotropy of the magnetic particles on the isotropic-nematic phase transition in liquid crystal is demonstrated. The results are in a good agreement with recent theoretical predictions.
Magnetic Fréedericksz transition was studied in ferronematics based on the nematic liquid crystal 4-(trans-4'-n-hexylcyclohexyl)-isothiocyanatobenzene (6CHBT). 6CHBT was doped with rod-like magnetic particles of different size and volume concentration. The volume concentrations of magnetic particles in the prepared ferronematics were $ϕ_1$ = 10$^{-4}$ and $ϕ_2$ = 10$^{-3}$. The structural changes were observed by capacitance measurements that demonstrate a significant influence of the concentration, the shape anisotropy, and/or the size of the magnetic particles on the magnetic response of these ferronematics.