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

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

A package of momentum and heat transfer coefficientsfor the stable atmospheric surface layer

The polar atmospheric surface layer is often stably stratified, which strongly influences turbulent transport processes between the atmosphere and sea ice/ocean. Transport is usually parametrized applying Monin Obukhov Similarity Theory (MOST) which delivers transfer coefficients as a function of stability parameters (see below). In a series of papers (Gryanik and Lüpkes, 2018; Gryanik et al., 2020,2021; Gryanik and Lüpkes, 2022) it has been shown that differences between existing parametrizations are large, especially for strong stability. One reason is that they are based on different data sets, for which the origin of differences is still unclear. In this situation Gryanik et al. (2021) as well as Gryanik and Lüpkes (2022) proposed a numerically efficient method, which can be used for most of the existing data sets and their specific stability dependences. A package of parametrization resulted that is suitable for its application in weather prediction and climate models. Especially, calculation of fluxes over sea ice were improved. Combined with latest parametrizations of surface roughness it has a large impact on large scale fields as shown recently by Schneider et al. (2021) who applied some members of the package

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

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

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

Time-Dependent Corrections to the Ly-alpha Escape Probability During Cosmological Hydrogen Recombination

We consider the effects connected with the detailed radiative transfer during the epoch of cosmological recombination on the ionization history of our Universe. We focus on the escape of photons from the hydrogen Lyman-alpha resonance at redshifts 600<~ z <~ 2000, one of two key mechanisms defining the rate of cosmological recombination. We approach this problem within the standard formulation, and corrections due to two-photon interactions are deferred to another paper. As a main result we show here that within a non-stationary approach to the escape problem, the resulting correction in the free electron fraction, N_e, is about ~1.6-1.8% in the redshift range 800<~z<~1200. Therefore the discussed process results in one of the largest modifications to the ionization history close to the maximum of Thomson-visibility function at z~1100 considered so far. We prove our results both numerically and analytically, deriving the escape probability, and considering both Lyman-alpha line emission and line absorption in a way different from the Sobolev approximation. In particular, we give a detailed derivation of the Sobolev escape probability during hydrogen recombination, and explain the underlying assumptions. We then discuss the escape of photons for the case of coherent scattering in the lab frame, solving this problem analytically in the quasi-stationary approximation and also in the time-dependent case. We show here that during hydrogen recombination the Sobolev approximation for the escape probability is not valid at the level of DP/P~5-10%. This is because during recombination the ionization degree changes significantly over a characteristic time Dz/z~10%, so that at percent level accuracy the photon distribution is not evolving (abridged)Comment: 18 pages, 12 figures, accepted versio