The analysis of the spin wave excitations in two-dimensional isotropic Heisenberg ferromagnet is performed with a single skyrmion in the ground state. We employ the ideas of semiclassical quantization method, duly modified for the use of the lattice model and Maleyev-Dyson boson representation of spin operators. The resulting Schrödinger equation for magnons describes the dispersion and wave functions of spin-wave excitations with strictly non-negative spectrum. In contrast to usual ferromagnet, we demonstrate the existence of three zero modes, corresponding to conformal symmetries spontaneously violated by the skyrmion configuration.1. Topological defects play an important role in condensed matter physics. The first and the most famous example is vortex lines, defining critical properties of type II superconductors in the external magnetic field [1]. In two dimensions, the role of defects is even more noticeable. So an interaction of vortices in the O(2) model leads to emergence of a quasi-long-range order and a Berezinskii-Kosterlitz-Thouless (BKT) transition [2]. In O(2) symmetric systems with the additional twofold degeneracy of the ground state, such as Josephson junction arrays in the magnetic field or XY helimagnets, vortex excitations with fractional charges lead to a phase transition on domain walls, and as a consequence to separation of a BKT and Ising (chiral) transitions [3,4]. The appearance of so-called Z 2 -vortices corresponds to exceptional thermal properties of twodimensional frustrated magnets with isotropic spins (see [5] and Refs. therein). The superlattice structure observed in magnets [6,7,8,9, 10] and multiferroics [11] with the Dzyaloshinskii-Moria (DM) spin-orbit interaction in the magnetic field is believed to be related to vortex-like excitations, called skyrmions. The similar skyrmion structures appear in the quantum Hall systems [12,13,14,15].In this paper we discuss topological defects in twodimensional quantum ferromagnets. It is known that the usual O(N ) model, describing ferromagnets, has different types of topological defects. The case N = 1 corresponds to the Ising model, where line-like defects are domain walls. The case N = 2 has been mentioned above in a context of point-like vortices and a BKT transition. At N = 3, defects of another type are present. They can be obtained as static classical solution of the O(3) sigma model [16], describing lowtemperature properties of ferromagnets,Taking into account the isotropic condition at spatial infinity ϕ(∞) = ϕ 0 , the field ϕ becomes a map ϕ : R 2 ∪ {∞} S 2 → S 2 , which is characterized by an integer number Q, the topological degree of the map ϕ.The families of solutions consist of configurations related to each other by global field-rotations and coordinate transformations. The latter symmetry includes rescalings (dilatations), that is specific to the two-dimensional sigma model, which is conformal invariant. As a consequence, a size of defects is not defined by the energy minimum conditions, in accordance with the Derrick the...

The article demonstrates a rational scheme of the supercharging system in a helicopter diesel engine with a power of 100 kW, regardless of the flight altitude, and proposes a method for assessing the power losses for a diesel engine depending on the flight altitude using a mathematical model. There are three variants of an engine supercharger scheme with a single-stage turbocharger, a two-stage one with parallel or sequential compressor drive and a turbo-blower. As a result of the computational analysis according to the original method, it was shown that from the point of view of the least energy consumption two-stage scheme with a compressor and a sequential drive is the most rational. To reduce energy losses in the drive with two-stage supercharging, a concept for controlling the pressure system was proposed, which includes changing the rotational speed of the compressor drive and adjusting the throttles. Simulation of the engines running during the climb / descent of the helicopter showed that the proposed pressure scheme and control concept is effective. In order to improve the quality of regulation, the possibility to use an electric drive with the first stage compressor is being considered.

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This review paper presents the results of the recent studies designed to elucidate the etiopathogenetic role ofhuman papilloma virus infection in the development of respiratory papillomatosis in the children. Special attention is given to the possible pathways and mechanisms of the mother-to-child transmission of papilloma virus, its frequency and risk factors during pregnancy and in the postnatal period. The results of investigations into the frequency of papilloma virus infection in the children are presented along withrisk factors contributing to its persistence and the development ofjuvenile respiratory papillomatosis. The possible approaches to the management of this condition are proposed.

Objective : to define the features of the course of pregnancy, delivery, postpartum period and state of newborns in female patients with genital HPV infection, depending on its form and viral load; to assess the factors of the course of gestation and delivery in the vertical transmission of neonatal persistence of HPV infection. Material and methods. The study involved 132 pregnant women with genital HPV infection, their babies immediately after birth (n = 107) and at the age of 6 months (n = 106). The comparison group included pregnant patients, women in delivery and postpartum period who were under supervision and who gave childbirth in Gomel region over 2011-2012 (30087 pregnancies, 33477 births). Results. Pregnancy in women with HPV infection is frequently complicated by the threat of miscarriage (p = 0.0016). The clinical manifestations of HPV infection showed no effect on the gestation. Patients with high HPV load (5 lg GE per 100,000 cells) had birth canal injuries (p = 0.029) 3 times more often. Pregnancy complicated by gestosis and anemia, as well as vaginal childbirth were risk factors for perinatal transmission of HPV. The course of pregnancy and delivery were not determining factors in the persistence of HPV in the baby`s upper airways. Conclusion. We have defined the features of the course of pregnancy and delivery in women with genital HPV infection (the threat of miscarriage, birth canal injury with high viral load of HPV), the factors of perinatal transmission (gestosis and anemia during pregnancy, vaginal delivery).

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The article provides the substantiation of the rational scheme of the boost system of the aircraft diesel engine KhADI-100A to ensure its altitude from the point of view of the lowest losses of the effective engine power. A method is proposed for assessing the power loss of an aircraft diesel engine depending on the flight altitude. Three variants of the supercharging system are considered: with one free turbocharger; parallel drive compressor and free turbocharger; sequential drive compressor and free turbocharger. As a result of the computational study, it was shown that in the case of using one free turbocharger at an altitude of h > 1500 m, the normal operating process of a diesel engine cannot be realized, since in this case, the excess air ratio falls below the critical value for a diesel engine α <1.4. Even if a constant excess air ratio is maintained, the effective engine power, with one free turbocharger, decreases by about 6 ... 11 kW per 1000 m with an increase in flight altitude. In schemes with a driving compressor, the quality of the fuel-air mixture will not change with altitude, and the power losses for their drive are insignificant in comparison - within 1 ... 2 kW per 1000 m of lifting height and can be compensated by increasing the cycle fuel supply without losing the quality of the working process. As a result of the computational study, it was concluded that the most rational from the point of view of the least power consumption is the scheme with a sequential drive compressor and a free turbocharger, the power consumption for the compressor drive at an altitude of 5000 m is 1.4 kW less than in the scheme with a parallel drive compressor and is the maximum value of 8.5 kW. The use of an electrically driven compressor is proposed since in this case the unit gains control flexibility to select the optimal operating mode and the possibility of using alternative energy sources for the drive electric generator (solar batteries, accumulators, thermoelectric generators, etc.).

The use of two-stage fuel injection into the diesel cylinder is an effective means of reducing the noise of its operation and reducing emissions of nitrogen oxides with exhaust gases. In this work, a computational-experimental study is based on a method in which part of the experimental indicator is replaced by the results of its numerical synthesis, performed using mathematical modeling of processes in the engine cylinder. The research was carried out on an experimental single-cylinder engine Ch8.8/8.2, equipped with a high-pressure fuel supply system. The mathematical model of working processes in the cylinder of the experimental engine is developed and identified. When studying the effect of two-stage combustion on the indicator process of the engine, the parameters that determine the law of fuel combustion, i.e. the angles of the beginning of the injection of the main and pilot portions of fuel changed. It is shown that the value of the indicator efficiency of the cycle is almost independent of the introduction and advancement at the angle of rotation of the crankshaft of the moment of pre-combustion at a constant ignition moment of the main portion of the fuel. However, reducing the starting angle of the pilot fuel injection leads to an increase in the maximum pressure of the cycle pz and the maximum rate of pressure rise, as a consequence of increasing engine noise. It is proved that it is possible to start the ignition of the main portion of the fuel without a significant decrease in the average indicator pressure and with a decrease in the values of pz and dr/dφmax when creating pre-combustion of fuel by 20 degrees turning the crankshaft to the main. The rational angle of advance of the injection of the pilot portion of fuel is 10 ... 12 deg. turning the crankshaft to inject the main portion. The obtained results show that the proposed measures - the introduction of pre-combustion 10… 25% of the cycle feed - can reduce the noise level of the engine while maintaining the level of the average indicator pressure and reduce the maximum cycle pressure.