Arkhangelsk State Technical University

The motion of a system of interacting nonlinear charged oscillators is investigated numerically. Because of nonlinearity, the total collective electric field gives rise to a phasing effect—correlations in the phases of the oscillators. The consequence is superradiation—the enhanced spontaneous short-term emission of the energy stored in the oscillators. It is shown that the oscillations of the oscillators become stochastic because of the dipole-dipole interaction between them and their nearest neighbors. As a result, as the density of the oscillators increases, distant collective correlations are suppressed, superradiation ceases to be generated, and radiation is shielded in the medium. The phenomena considered in the present paper can play an important role in cyclotron emission from a plasma and thus should be taken into account in emission calculations. The process whereby the energy of the transverse electron motion in electron cooling devices decreases is analyzed as an example. This process occurs as a result of the development of cyclotron maser instability and has the nature of superradiation. The onset of correlations between individual electrons moving in their Larmor circles is the initial, linear stage of instability developing in the plasma. Superradiation is the final, nonlinear instability stage.

Ixodes persulcatus Schultze ticks are traditionally associated with transmission of Lyme disease, babesiosis, and tick-borne encephalitis. Here we compared the prevalence of infection with Borrelia burgdorferi, and rickettsial and ehrlichial agents in I. persulcatus ticks collected in different locations of the North Western administrative region of Russia. Altogether, 27.7% of ticks were infected with at least one organism, while the DNA of two or more bacteria was found in 11.8% of ticks tested. The highest average prevalence of Anaplasmataceae (20.8%) was detected in ticks from Arkhangel'sk province, while the prevalence in ticks from Novgorod province and St. Petersburg, respectively, was 7.3% and 12.2%. Only Ehrlichia muris DNA was identified by DNA sequencing. In comparison, the prevalence of B. burdorferi DNA was 16.6%, 5.8%, and 24.5% in the respective locations. The 382-bp amplicon of gltA from Candidatus Rickettsia tarasevichiae was detected in 2.75% and 1.6%, respectively, of ticks from Arkhangel'sk and Novgorod provinces, extending further west and north the area where this rickettsia is known to be present. DNA of the rickettsia-like endosymbiont Montezuma was primarily associated with female ticks, 8-28% of which were infected. Since I. persulcatus is so commonly infected with multiple agents that may cause human diseases, exposure to these ticks poses significant risk to human health in this region.

The nonperturbative theory of the energy losses of fast heavy highly charged structure ions colliding with neutral complex atoms is developed with allowance for simultaneous excitations of the electron shells of an ion and an atom. Formulas for effective stopping that are similar to the Bethe-Bloch formulas have been derived. As an example, the energy losses of partially stripped uranium ions colliding with argon atoms are calculated.

The kinetics of lignosulfonic acid nitrosation in the presence of acetic and nitric acids used for generation of nitrous acid in combination with sodium nitrite was studied as applied to colorimetric determination of lignosulfonic acids.

An approach based on the sudden-perturbation approximation is presented for the treatment of single and multiple electron losses of high and intermediate energy projectiles in their collisions with neutral targets. Using this approach, we calculate electron loss cross sections of hydrogen-like Pb81+ and Au78+ projectiles in the collisions with neutral atoms. Also, multiple electron loss cross sections are calculated for U10+ and U28+ projectiles in their collisions with N2 and Ar targets.

A spectrophotometric method for determination of furfural and pentoses based on their color reaction with sulfuric acid in the presence of mercury(II) was developed.

The velocity of molecular gas slipping over a spherical surface is calculated by exact analytical methods including the accommodation coefficients for the first two moments of the distribution function. An extension of the BGK approach to the Boltzmann kinetic model for the case of rotational degrees of freedom is used as the basic equation.

Let (x,d) be a locally compact geodesically complete CAT(0)-space of topological dimension greater than 1. It is proved that if each geodesic segment in X is uniquely extended to a complete geodesic, then the metric d is determined by the diagonal tube V ⊂ X × X corresponding to an arbitrary positive r. This partly generalizes V. N. Berestovskii's results on A. D. Aleksandrov spaces of negative curvature. Bibliography: 8 titles.

Electron transitions occurring during the interaction of a heavy relativistic atom with a spatially inhomogeneous ultrashort electromagnetic pulse are considered by solving the Dirac equation. The corresponding transition probabilities are expressed in terms of known inelastic atomic form factors, which are widely used in the theory of relativistic collisions between charged particles and atoms. By way of example, the inelastic processes accompanying the interaction of ultrashort pulses with hydrogen-like atoms are considered. The probabilities of ionization and production of a bound-free electron-positron pair on a bare nucleus, which are accompanied by the formation of a hydrogen-like atom in the final state and a positron in the continuum, are calculated. The developed technique makes it possible to take into account exactly not only the spatial inhomogeneity of an ultrashort electromagnetic pulse, but also the magnetic interaction.