Dynamics of Primordial Hydrogen Recombination with Allowance for a Recoil for Scattering in the Ly-alpha Line

It is shown that taking into account a recoil for radiation scattering in the Ly-alpha line can lead to a noticable acceleration of primordial hydrogen recombination. Thus for LambdaCDM model a decrease of ionization degree exceeds 1% for redshifts z in a range 800 - 1050 achieving approximately 1.3% at z=900. Corresponding corrections to the cosmic microwave background power spectra can achieve 1.1% for TT spectra and 1.7% for EE ones. Radiative transfer in these calculations was treated in a quasistationary approximation. Numerical solutions are also obtained in diffusion approximation for a nonstationary problem of Ly-alpha line radiative transfer under partial frequency redistribution with a recoil. An evolution of a local line profile is traced to as well as an evolution of a relative number of uncompensated transitions from 2p state down to 1s one. It is shown that taking into account nonstationarity of Ly-alpha line radiative transfer can lead to an additional acceleration of primordial hydrogen recombination.Comment: 9 pages, 5 figures; accepted for publication in Astronomy Letter

The importance of secondary school students' physical activity in modern environment

The research was aimed at evaluating physical activity of students, who live in the city and rural areas, identifying the relationship between physical activity and school performance, as well as studying the dependence of the number of diseases on the volume of locomotion. To this end, in the Belgorod Oblast, 1,488 schoolchildren of 5-11 grades were surveyed from 2014 to 201

Optical Absorption and Raman Spectroscopy Study of the Fluorinated Double-Wall Carbon Nanotubes

Double-wall carbon nanotube (DWNT) samples have been fluorinated at room temperature with varied concentration of a fluorinating agent BrF3. Content of the products estimated from X-ray photoelectron data was equal to CF0.20 and CF0.29 in the case of deficit and excess of BrF3. Raman spectroscopy showed considerable decrease of carbon nanotube amount in the fluorinated samples. Analysis of optical absorption spectra measured for pristine and fluorinated DWNT samples revealed a selectivity of carbon nanotube fluorination. Nanotubes with large chiral angle are more inert to the fluorinating agent used

Study on influence of two-phase filtration transformation on formation of zones of undeveloped oil reserves

In order to study the process of fluid filtration during flooding of an oil field, article uses Rapoport – Lis model of non-piston oil displacement by water. During plane-radial filtration in a homogeneous formation, radii of disturbance zones are determined with and without taking into account the end effect. Influence of changes in value of capillary pressure gradient on distribution of water saturation coefficient in the non-piston displacement zone for high and low permeability reservoirs is revealed. Application of an element model for a five-point injection and production well placement system showed that, using traditional flooding technology, flat-radial fluid filtration is transformed into rectilinear-parallel. At solving equation of water saturation, Barenblatt method of integral relations was used, which allows determining the transformation time. By solving the saturation equation for rectilinear-parallel filtration, change in the value of water saturation coefficient at bottomhole of production well for an unlimited and closed deposit is determined. It is shown that an increase in water cut coefficient of a production well is possible only for a closed formation. To determine coefficient of water saturation in a closed deposit, a differential equation with variable coefficients is obtained, an iterative solution method is proposed. In the element of the five-point system, oil-saturated zones not covered by development were identified. For channels of low filtration resistance, conditions for their location in horizontal and vertical planes are established. It is shown that, at maintaining formation pressure, there is an isobar line in formation, corresponding to initial formation pressure, location of which determines direction of fluid crossflow rates. Intensity of crossflows affects application efficiency of hydrodynamic, physical and chemical, thermal and other methods of enhanced oil recovery

Atmospheric Gravity Perturbations Measured by Ground-Based Interferometer with Suspended Mirrors

A possibility of geophysical measurements using the large scale laser interferometrical gravitational wave antenna is discussed. An interferometer with suspended mirrors can be used as a gradiometer measuring variations of an angle between gravity force vectors acting on the spatially separated suspensions. We analyze restrictions imposed by the atmospheric noises on feasibility of such measurements. Two models of the atmosphere are invoked: a quiet atmosphere with a hydrostatic coupling of pressure and density and a dynamic model of moving region of the density anomaly (cyclone). Both models lead to similar conclusions up to numerical factors. Besides the hydrostatic approximation, we use a model of turbulent atmosphere with the pressure fluctuation spectrum f^{-7/3} to explore the Newtonian noise in a higher frequency domain (up to 10 Hz) predicting the gravitational noise background for modern gravitational wave detectors. Our estimates show that this could pose a serious problem for realization of such projects. Finally, angular fluctuations of spatially separated pendula are investigated via computer simulation for some realistic atmospheric data giving the level estimate 10^{-11} rad/sqrt(Hz) at frequency 10^{-4} Hz. This looks promising for the possibility of the measurement of weak gravity effects such as Earth inner core oscillations.Comment: 13 pages, 4 pigures, LaTeX. To be published in Classical and Quantum Gravit

Combustion of lean fuel mixtures with subcritical streamer microwave discharge

A sub-critical microwave discharge is used to achieve a stable ignition and combustion of lean air-fuel mixtures in a long tube. The microwave discharge is burnt at the presence of initiator with the quasi-optical microwave beam. The resonance way of initiation of a microwave discharge is more effective compared to traditional plasma-assisted ways of ignition and stabilization of combustion. The experimental observations show that ignition and combustion of a lean air and propane mixture in a long tube is achieved at low ignition limit with fuel/air ratio lower than 0.55. The results obtained are useful for design of new and improvement of the existing plasma-assisted technologies in aviation industry

Elastic Spin Relaxation Processes in Semiconductor Quantum Dots

Electron spin decoherence caused by elastic spin-phonon processes is investigated comprehensively in a zero-dimensional environment. Specifically, a theoretical treatment is developed for the processes associated with the fluctuations in the phonon potential as well as in the electron procession frequency through the spin-orbit and hyperfine interactions in the semiconductor quantum dots. The analysis identifies the conditions (magnetic field, temperature, etc.) in which the elastic spin-phonon processes can dominate over the inelastic counterparts with the electron spin-flip transitions. Particularly, the calculation results illustrate the potential significance of an elastic decoherence mechanism originating from the intervalley transitions in semiconductor quantum dots with multiple equivalent energy minima (e.g., the X valleys in SiGe). The role of lattice anharmonicity and phonon decay in spin relaxation is also examined along with that of the local effective field fluctuations caused by the stochastic electronic transitions between the orbital states. Numerical estimations are provided for typical GaAs and Si-based quantum dots.Comment: 57 pages, 14 figure

Ignition of premixed air/fuel mixtures by microwave steamer discharge

A variety of methods exists for fast and efficient combustion of air-fuel mixtures. In this study, a microwave subcritical streamer discharge is used to ignite propane-air mixtures at atmospheric pressure. The streamer is initiated at the inner surface of a dielectric tube with the help of a passive half-wave vibrator. By creating a network of ignition lines, the streamer discharge forms the network of burning channels with large total surface area. This leads to the apparent speed of combustion propagation along the cylinder in excess of 100 m/s, which is more than 200 times the laminar flame propagation speed. The axial propagation of the combustion front in a cylindrical tube filled with the air/propane mixture is investigated by high speed video recording in visible light. A simple model is presented to explain observed results