East European Journal of Physics

7

Authors: A. V. Glushchenko, M. Y. Kovalevsky

The paper studies the dynamic description of non-equilibrium processes in single-sublattice and multisublattice magnets with the spin s=1. In case of magnets with the spin s=1 and SU(3) symmetry of the exchange interaction, there are eight magnetic integrals of motion: the spin and the quadrupole matrix. If there are multiple sublattices, the number of additional magnetic quantities characterizing the state increases to sixteen. The presence of the Casimir invariants makes it possible to reduce the number of independent degrees of freedom. Exchange energy models are presented in terms of Casimir invariants corresponding to SO(3) or SU(3) symmetry groups for all four types of magnetic degrees of freedom. For the homogeneous part of the exchange energy, we have found conditions for the existence of local minima, which correspond to equilibrium values of the magnet. Along with the known waves (quadrupole and Goldstone – for the spin nematic), spectra of collective excitations that take into account ferro-quadrupole excitation, quadro-nematic, quadro- antiferromagnetic, and antiferro-nematic waves excitation, are also obtained. In the case of many-sublattice magnetic systems, we have shown that the selected form of the homogeneous energy model allows us to find possible magnetic orderings and to investigate them for stability.

8

Authors: D. S. Bondar, I. P. Levchuk, V. I. Maslov, I. N. Onishchenko

Earlier, the authors found a mechanism for the sequence of short relativistic electron bunches, which leads to resonant excitation of the wakefield, even if the repetition frequency of bunches differs from the plasma frequency. In this case, the synchronization of frequencies is restored due to defocusing of the bunches which get into the bad phases with respect to the plasma wave. However, in this case, the bunches are lost, which as a result of this do not participate in the excitation of the wakefield. In this paper, numerical simulation was used to study the dynamics of electron bunches and the excitation of the wakefield in a magnetized plasma by a long sequence of short bunches of relativistic electrons. When a magnetic field is used, the defocussed bunches return to the region of interaction with the field after a certain time. In this case, the electrons of the bunches, returning to the necessary phases of the field, participate in the excitation of the wakefield. Also, the use of a magnetic field leads to an increase of the frequency of the excited wave relative to the repetition frequency of bunches. The latter increases the time for maintaining the resonance and, consequently, leads to an increase of the amplitude of the excited wakefield.

8

Authors: O. Ivashtenko

The greenhouse is a tool for the accumulation of solar energy and its conversion into heat. The article investigates the heating of the greenhouse caused by the difference in the transmissivity of glass in different wavelength ranges. Firstly, some facts from the history of the phenomenon investigation are presented. The principle of greenhouse operation is considered. Then we explain the greenhouse effect theoretically using a simplified model, and carry out an experiment. In our experiment, the heating of a 1 m² surface greenhouse model has been observed. The temperature changes have been registered, and the ultimate temperature has been measured. Further, a model of an ideal greenhouse is proposed in order to reduce heat losses. The main principles and generalizations of the greenhouse effect are discussed. The role of the glass transmission spectrum, which is one of the most important factors determining the maximum temperature is investigated. Maximum temperatures for different spectra are compared. We calculate theoretically the maximum temperature, which can be achieved in an ideal greenhouse under ideal conditions. Then we consider other factors limiting temperature growth. Finally, the ways of application of the greenhouse effect in the development of solar collectors are indicated.

10

Authors: U. Tarabara, K. Vus, S. Girnyk, N. Kamneva, O. Lavryk, M. Mikhailyuta, V. Trusova, G. Gorbenko

The influence of the lysozyme and serum albumin in their native and amyloid forms on the electrokinetic behavior of the negatively charged uni- and multilamellar liposomes from the zwitterionic lipid phosphatidylcholine and anionic lipid cardiolipin has been investigated using the microelectrophoresis technique. The zeta - potential, the surface electrostatic potential and surface charge density of the lipid vesicles have been determined upon varying the lipid-to-protein molar ratio. The complex dependencies of the electrophoretic mobility on the protein concentration and reversal of the surface charge observed for the multilamellar vesicles have been explained by the multilayer protein adsorption on the liposomal surface. It has been found that the native and fibrillar proteins differ in their ability to modify the charge state of the model membranes.

13

Authors: V. B. Ivanskyi, O. N. Letuchyy, А. N. Orobinskyi, H. V. Siroko

The energy and pulse height spectrum of PuBe and 238PuBe neutron sources are measured without taking into account scattered radiation, taking into account this radiation (without the shadow cone) and own scattered radiation from these sources (with a shadow cone) using a NEMUS spectrometer on Bonner spheres with 3He -counter. An analytical solution of the likelihood function equation is given, taking into account the fact that the counting rate of pulses obeys the chi-square distribution used to estimate the variances, the discrete Poisson distribution, and the normal distribution, using the Bayes theorem and the Lagrange multiplier method. The values of the main characteristics of neutron radiation are measured: neutron flux density, ambient dose rate equivalent, individual dose rate equivalent and average neutron radiation energy. Extensive uncertainties were obtained in the measurement of these characteristics with a confidence level of 0.95. Calculation of energy spectrum, basic characteristics of neutron radiation and extended uncertainties is performed by the MAXED (maximum entropy and deconvolution) method using the UMG_3.3 software.