688 research outputs found
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
EPR studies of manganese centers in SrTiO3: Non-Kramers Mn3+ ions and spin-spin coupled Mn4+ dimers
X- and Q-band electron paramagnetic resonance (EPR) study is reported on the
SrTiO3 single crystals doped with 0.5-at.% MnO. EPR spectra originating from
the S = 2 ground state of Mn3+ ions are shown to belong to the three distinct
types of Jahn-Teller centres. The ordering of the oxygen vacancies due to the
reduction treatment of the samples and consequent formation of oxygen vacancy
associated Mn3+ centres are explained in terms of the localized charge
compensation. The EPR spectra of SrTiO3: Mn crystals show the presence of next
nearest neighbor exchange coupled Mn4+ pairs in the directions.Comment: 17 pages, 8 figure
Structure of Turbulence in Katabatic Flows below and above the Wind-Speed Maximum
Measurements of small-scale turbulence made over the complex-terrain
atmospheric boundary layer during the MATERHORN Program are used to describe
the structure of turbulence in katabatic flows. Turbulent and mean
meteorological data were continuously measured at multiple levels at four
towers deployed along the East lower slope (2-4 deg) of Granite Mountain. The
multi-level observations made during a 30-day long MATERHORN-Fall field
campaign in September-October 2012 allowed studying of temporal and spatial
structure of katabatic flows in detail, and herein we report turbulence and
their variations in katabatic winds. Observed vertical profiles show steep
gradients near the surface, but in the layer above the slope jet the vertical
variability is smaller. It is found that the vertical (normal to the slope)
momentum flux and horizontal (along the slope) heat flux in a slope-following
coordinate system change their sign below and above the wind maximum of a
katabatic flow. The vertical momentum flux is directed downward (upward)
whereas the horizontal heat flux is downslope (upslope) below (above) the wind
maximum. Our study therefore suggests that the position of the jet-speed
maximum can be obtained by linear interpolation between positive and negative
values of the momentum flux (or the horizontal heat flux) to derive the height
where flux becomes zero. It is shown that the standard deviations of all wind
speed components (therefore the turbulent kinetic energy) and the dissipation
rate of turbulent kinetic energy have a local minimum, whereas the standard
deviation of air temperature has an absolute maximum at the height of
wind-speed maximum. We report several cases where the vertical and horizontal
heat fluxes are compensated. Turbulence above the wind-speed maximum is
decoupled from the surface, and follows the classical local z-less predictions
for stably stratified boundary layer.Comment: Manuscript submitted to Boundary-Layer Meteorology (05 December 2014
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
Advanced Three Level Approximation for Numerical Treatment of Cosmological Recombination
New public numerical code for fast calculations of the cosmological
recombination of primordial hydrogen-helium plasma is presented. The code is
based on the three-level approximation (TLA) model of recombination and allows
us to take into account some fine physical effects of cosmological
recombination simultaneously with using fudge factors. The code can be found at
http://www.ioffe.ru/astro/QC/CMBR/atlant/atlant.htmlComment: 10 pages, 7 figures, 1 table, to be submitted to MNRA
Combination of aerobic and anaerobic means in physical culture classes
The aim of research is to support the usefulness of using combination of aerobic and anaerobic means in educational-training classes on physical culture. The study involved 186 students of Belgorod National Research University and Belgorod University of Cooperation, Economics and La
Spatial-temporal dynamics of the terahertz field generated by femtosecond filament
We present the study on spatial distribution of the maximum of terahertz field amplitude in time domain when generated by a femtosecond filament. It is shown that as a result of the propagation of the terahertz field forms a spherical wave front, on the edge of which the maximum of amplitude has a temporary delay in contrary to its central part
Effects of CMB temperature uncertainties on cosmological parameter estimation
We estimate the effect of the experimental uncertainty in the measurement of
the temperature of the cosmic microwave background (CMB) on the extraction of
cosmological parameters from future CMB surveys. We find that even for an ideal
experiment limited only by cosmic variance up to l = 2500 for both the
temperature and polarisation measurements, the projected cosmological parameter
errors are remarkably robust against the uncertainty of 1 mK in the FIRAS
instrument's CMB temperature monopole measurement. The maximum degradation in
sensitivity is 20%, for the baryon density estimate, relative to the case in
which the monopole is known infinitely well. While this degradation is
acceptable, we note that reducing the uncertainty in the current temperature
measurement by a factor of five will bring it down to the per cent level. We
also estimate the effect of the uncertainty in the dipole temperature
measurement. Assuming the overall calibration of the data to be dominated by
the dipole error of 0.2% from FIRAS, the sensitivity degradation is
insignificant and does not exceed 10% in any parameter direction.Comment: 12 pages, 2 figures, uses iopart.cls, v2: added discussion of CMB
dipole uncertainty, version accepted by JCA
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
Two-Photon 2s<->1s Transitions during Recombination of Hydrogen in the Universe
Based on the standard cosmological model, we calculate the correction to the
rate of two-photon 2s1s transitions in the hydrogen atom under primordial
hydrogen plasma recombination conditions that arises when the induced
transitions under equilibrium background radiation with a blackbody spectrum
and plasma recombination radiation are taken into account.Comment: 20 pages, 9 figure
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