The radiative recombination rates of free carriers and lifetimes of free excitons have been calculated in the wide band gap semiconductors GaN, InN, and AlN of the hexagonal wurtzite structure, and in their solid solutions Ga x Al 1Ϫx N, In x Al 1Ϫx N and Ga x In 1Ϫx N on the base of existing data on the energy band structure and optical absorption in these materials. We determined the interband matrix elements for the direct optical transitions between the conduction and valence bands, using the experimental photon energy dependence of absorption coefficient near the band edge. In our calculations we assumed that the material parameters of the solid solutions ͑the interband matrix element, carrier effective masses, and so on͒ could be obtained by a linear interpolation between their values in the alloy components. The temperature dependence of the energy gap was taken in the form proposed by Varshni ͓Physica 34, 149 ͑1967͔͒. The calculations of the radiative recombination rates were performed in a wide range of temperature and alloy compositions.

The radiative recombination rates have been calculated for the first time in the wide band gap wurtzite semiconductors GaN, InN and AlN and their solid solutions Ga x Al 1-x N and In x Al 1-x N on the base of existing data on the energy band structure and optical absorption in these materials. We calculated the interband matrix elements for the direct optical transitions between the conductivity band and the valence one using the experimental photon energy dependence of the absorption coefficient near the band edge. In our calculations we assumed that the material parameters of the solid solutions (the interband matrix element, carrier effective masses and so on) could be obtained by a linear interpolation between their values in the alloy components. The temperature dependence of the energy gap was taken in the form proposed by Varshni. The calculations of the radiative recombination rates were performed in the wide range of temperature and alloy compositions.

A model resulting in charge ordering (CO) similar to that observed in cuprate superconductors is under study. It includes strong long-range electron-phonon interaction (EPI) and high density of correlated carriers. Coexistence of large bipolarons and delocalized carriers is a feature of such system. We develop generalized variation method to calculate the bipolaron size (CO period) in the ground normal state of such system at various doping. The approach allows the revealing of a possible physical reason of strongly different doping behavior of the CO wave vector in different cuprates. Obtained doping dependences of the CO period and temperature of the CO decay demonstrate quantitative agreement with those observed in cuprates. Predicted in the suggested approach ratio of the CO wave vector to the wave vector of the high-energy anomaly (HEA) in ARPES spectrum is in consent with that in cuprates. Calculated resonant x-rays scattering on the CO emerging in the model is in good agreement with experiments on cuprates including the asymmetry of the CO peaks' cross-section. A gap arises in the spectrum of delocalized carriers near antinodal direction due to their scattering on the periodic potential created by autolocalized carriers, analogously to photon crystal effect.

Recently, there has been an increasing number of empirical evidence supporting the hypothesis that spread of avalanches of microposts on social networks, such as Twitter, is associated with some sociopolitical events. Typical examples of such events are political elections and protest movements. Inspired by this phenomenon, we built a phenomenological model that describes Twitter’s self-organization in a critical state. An external manifestation of this condition is the spread of avalanches of microposts on the network. The model is based on a fractional three-parameter self-organization scheme with stochastic sources. It is shown that the adiabatic mode of self-organization in a critical state is determined by the intensive coordinated action of a relatively small number of network users. To identify the critical states of the network and to verify the model, we have proposed a spectrum of three scaling indicators of the observed time series of microposts.

We examine the procedure of thermodynamical derivation of the Ginsburg-Landau equation for current, which is given unclear and contradictory interpretations in existing textbooks. We clarify all steps of this procedure and find as a consequence a limitation on the validity range of the thermodynamic Ginsburg-Landau theory, which does not seem to be explicitely stated up to now: we conclude that the thermodynamic theory is applicable only to a superconducting specimen that is not a part of an external current-carrying loop.

The development of pathogen resistance and the relatively high cost of chemical fungicides dictate the necessity to develop alternative disease control strategies. These strategies include biological methods of plant protection. However, the effectiveness of biological plant protection depends on the biological agent's activity, which strongly depends on external physical factors. The applicant of biological remedies for seed inlay is one of the environmentally safe ways to combat seed and soil infection. However, nowadays, the impact of mechanical means during seed inoculation on the survival of microorganisms remains poorly studied. A laboratory installation has been created that makes it possible to imitate the working process of applying microorganisms to plant seeds during inlay, changing the pressure in the distribution system, the types of sprayers and the temperature of the working composition of the biological product with its further study in order to determine the number of living microorganisms remaining in it after processing. According to the results of the experimental data, graphical dependences were constructed showing the impact of pressure in the sprayer system, the temperature of the biological product and the type of spraying device on the viability of microorganisms. For microorganisms of RECB-50B (based on Bacillus sp.), RECB-14B (based on Pseudomonas putida), RECB-74F (Trichoderma viride) strains, the optimal parameters of the above factors were established during mechanical application of a biological product to the treated seeds: temperature of the working compound is 20 to 25 ºС, the pressure in the biopreparation delivery system is 0.4 MPa, the optimal type of spray nozzle is experimental, adapted for working with biopreparations.

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