Vibrational spectra of AlN/GaN superlattices: Theory and experiment

Computer simulation of the dynamics of layered AlN/GaN superlattices is performed to elucidate the microscopic nature of the vibrational states corresponding to the strongest bands in the Raman spectra. Experimental Raman spectra are shown to consist of two groups of lines, one of which exhibits a two-mode behavior and the other shows a one-mode behavior as the relative layer thicknesses are varied. The results of computer simulation and calculations within the dielectric-continuum approximation suggest that the behavior of the observed vibrational modes is dictated by the degree of their localization and that the interlayer coupling is due to long-range dipole-dipole interactions. It is shown that the delocalized modes, which exhibit one-mode behavior, can be used as a sensitive probe of the structure and composition of superlattices.     

Evolution of extinction spectra of monolayer plasmon-resonant colloidal crystals in the process of their synthesis by the moving meniscus method

Regularities of the evolution of the extinction spectra of periodic colloidal structure composed of silver nanoparticles formed from bulk hydrosol on the surface of dielectric substrate are studied using the moving meniscus method. Spectra were calculated by the coupled dipole method. The effect of individual parameters of disperse system on the pattern of extinction contour in the band of plasmon absorption of a synthesized two-dimensional crystalline structure is analyzed.     

Isotopic catalysis and isotopic analysis

Isotopes with magnetic nuclei accelerate the biochemical reactions of adenosine triphosphate synthesis by a factor of two to three. An isotope effect in which isotopes are preserved in the reaction system is known as isotopic catalysis. It has been revealed in enzymatic reactions catalyzed by magnesium, zinc, and calcium ions. Isotopic catalysis is sensitive to paramagnetic impurities, which inhibit it. It is shown that the presence of paramagnetic iron ions eliminates isotope effect and suppresses the isotopic catalysis of adenosine triphosphate synthesis.     

Wave ionosphere perturbations with small periods under magnetic storm conditions

The characteristics of total electron content (TEC) variations obtained using the data of middle-latitude stations for receiving GPS satellite signals were studied. An analysis showed that perturbations of diurnal TEC variations during a geomagnetic storm were determined by strengthening of harmonics with periods of 4–5 and 6–8 h. Perturbations in diurnal TEC variations were retained for several days after a geomagnetic storm. An analysis of the frequency and amplitude characteristics of perturbed variations showed that differences between variations at different latitudes could be explained by the propagation of Poincaré planetary waves in an atmospheric wave channel. The atmospheric channel was formed because of increased heating of pole regions during geomagnetic storms. A comparative analysis of observations made at different stations was used to estimate the width of the atmospheric channel and Poincaré wave frequencies and wave vector components.     

Study of the Influence of the Mutual Orientation of Antennas on the Characteristics of a Meteor Radio Channel

We describe equipment and a method for performing an experiment on a short meteor radio line of length 85 km. The feature of the experiment is monitoring of meteor-matter deposition to the atmosphere using a radar located at one point of the radio line with the simultaneous determination of the main radio-line characteristics.