First principles calculations of oxygen adsorption on the UN (001) surface

Fabrication, handling and disposal of nuclear fuel materials require comprehensive knowledge of their surface morphology and reactivity. Due to unavoidable contact with air components (even at low partial pressures), UN samples contain considerable amount of oxygen impurities affecting fuel properties. The basic properties of O atoms adsorbed on the UN(001) surface are simulated here combining the two first principles calculation methods based on the plane wave basis set and that of the localized atomic orbitals.Comment: 9 page

Investigation of helium plasma stream parameters in experiments on surface modification

Processing of different constructional materials with pulsed plasma streams is one of prospective methods of surface modification. The main objection of this study is adjustment of plasma treatment regimes for different materials that allows achieving optimal thickness of modified layer with simultaneously minimal value of surface roughness. With use of optical spectroscopy, detailed information about the basic plasma parameters – electron density, electron and ion temperatures, plasma stream duration and velocity, was obtained. Integrated spectra of plasma radiation were analyzed. The majority of helium and impurity spectral lines were investigated on a subject of Stark broadening. Plasma pressure and energy density values measured with piezodetectors and calorimeters are in good agreement with plasma parameters obtained by optical techniques.Один з перспективних методів модифікації поверхні – це обробка різних конструкційніх матеріалів імпульсними плазмовими потоками. Головна ціль досліджень є оптимізація режимів плазмової обробки різних матеріалів, що одночасно дозволяє досягати оптимальної товщини модифікованого шару та мінімальної величини шорсткості поверхні. Детальна інформація про основні параметри плазми – електронна густина, електронна та іонна температури, тривалість та швидкість плазмового потоку, була отримана за допомогою оптичної діагностики. Проаналізовані інтегральні спектри випромінювання плазми. Більшість гелієвих та домішкових спектральних ліній досліджувались на предмет Штарківського розширення. П`єзодатчиками та калориметрами виміряні величини тиску та густини енергії плазми, які добре погоджуються з параметрами плазми, отриманими за допомогою оптичної діагностики.Одним из перспективных методов модификации поверхности является обработка различных конструкционных материалов импульсными плазменными потоками. Главная цель этой работы – оптимизация режимов плазменной обработки для различных материалов, что одновременно позволяет достигать максимальной толщины модифицированного слоя и минимальной величины шероховатости поверхности. Детальная информация об основных плазменных параметрах – электронная плотность, электронная и ионная температуры, длительность генерации и скорость плазменного потока, была получена с помощью оптической диагностики. Проанализированы интегральные спектры излучения плазмы. Большинство гелиевых и примесных спектральных линий исследовались на предмет Штарковского уширения. Пьезодатчиками и калориметрами измерены соответственно величины давления и плотности энергии плазмы, которые хорошо согласуются с параметрами плазмы, полученными с помощью оптической диагностики

Investigations of pulsed plasma streams generated by “Prosvet” device operated with different gases

The paper presents the investigations of plasma streams generated by pulsed plasma gun “Prosvet” operated with different gases: krypton (m = 84), nitrogen (m = 14) and helium (m = 4). Contour parameters of working gas spectral lines (full intensities and half-widths) are used for determination of spatial distributions of the electron density and temperature. Temporal distributions of the spectral lines intensities (both neutrals and ions of working gas), impurity spectral lines and continuum intensities are analyzed. Plasma stream velocity was estimated by time-of-flight method between two monochromators (MUM) connected with photo-multiplier. Longitudinal distributions of the plasma pressure for different time moments and varied distances from the accelerator output have been used for investigation of the plasma stream dynamics and study the plasma compression in the focus region for different operational regimes of plasma accelerator. Experiments show that operation regime of the accelerator and plasma stream parameters strongly depend on the gas atomic mass

A theoretical framework and research agenda for studying team attributions in sport

The attributions made for group outcomes have attracted a great deal of interest in recent years. In this article we bring together much of the current research on attribution theory in sport and outline a new conceptual framework and research agenda for investigating the attributions of team members. The proposed framework draws on multiple conceptual approaches including models of attribution, group dynamics and stress responses to provide a detailed hypothetical description of athletes' physiological, cognitive and affective responses to group competition. In describing this model we outline important antecedents of team attributions before hypothesising how attributions can impact hormonal and cardiovascular responses of athletes, together with cognitive (goals, choices, expectations), affective (self-esteem, emotions), and behavioural (approach-avoidance actions) responses of groups and group members. We conclude by outlining important methodological considerations and implications for structured context specific attribution-based interventions

Influence exerted by new pyrimidine derivatives on cerebral circulation auto-regulation and vasodilatating function of vessels endothelium in rats' brains under chronic hemic hypoxia

Our research goal was to examine influences exerted by new pyrimidine derivatives coded as BL0 and BL2 on cerebral hemodynamics auto-regulation parameters and vasodilatating function of vessels endothelium as risk factors causing ischemic and hemorrhagic strokes under chronic hemic hypoxia. We performed an experiment on white Wistar rats to prove that endothelial dysfunction which evolves under chronic hemic hypoxia leads to disorders in endothelium-mediated mechanisms for cerebral circulation auto-regulation in rats. We modeled hypoxia in animals via granting them free access to 0.2 % sodium nitrite solution instead of ordinary drinking water. Endothelial dysfunction was confirmed as per disorders in vasodilatation and vasoconstriction reactions at intravenous introduction of acetyl choline (0.1 mg/kg) and methyl ether hydrochloride nitro-L-arginine (10 mg/kg). Cerebral blood flow speed was measured with MM-D-K-Minimax v.2.1. ultrasound Doppler. We assessed cerebral circulation auto-regulation as per compression test results which allowed us to calculate overshoot coefficient and auto-regulation power. Examined pyrimidine derivatives and comparison preparations were introduced orally 60 minutes prior to taking readings. Mexidol doses were calculated on the basis of interspecific recalculation of a maximum daily dose for a man. Nicergoline dose was taken as a most effective one as per literature data. When new pyrimidine derivatives BL0 and BL2 are applied under chronic hemic hypoxia, it causes overshoot coefficient to grow authentically higher than in a negative control group but it doesn't exert any positive influence on collateral reserve parameter, namely auto-regulation power. BL0 and BL2 improve endothelium vasodilatating function at intravenous acetylcholine introduction (0.1 mg/kg) and don't exert any influence on vasoconstricting function at L-NAME intravenous introduction (10 mg/kg). The examined substance BL0 has more apparent pharmacological effects thus exceeding the second substance BL2 and such comparison preparations as Mexidol and Nicergoline in some parameters

Reference systems for assessing viability and accuracy of pH sensors in high temperature subcritical and supercritical aqueous solutions

This paper describes an effort in developing reference systems to be used in high temperature subcritical and supercritical aqueous solutions for assessing the viability and accuracy of high-temperature pH sensors. Each of these reference systems consists of a couple of three-component aqueous solutions in which the concentration of NaCl is greater than the concentration of another solute, such as HCl and NaOH. The viability of the reference systems was tested using the recently published experimental data employing a flow-through electrochemical cell at temperatures from 25°C to 400°C and densities from 0.17 to 1 g cm −3 [S.N. Lvov, X.Y. Zhou, and A.V. Bandura, 1999a, Estimation of Isothermal Potential for HCl/NaCl and NaOH/NaCl Systems in High Temperatures Supercritical Aqueous Solutions, J. Supercrit. Fluids, in preparation; S.N. Lvov, X.Y. Zhou, and D.D. Macdonald, 1999, Flow-Through Electrochemical Cell for Accurate pH Measurements at Temperature up to 400°C, J. Electroanal. Chem., 463, 146–156]. The applicability of the method was tested for dilute (0.01 and 0.001 mol kg −1) HCl aqueous solutions having background NaCl electrolyte in the amount of 0.1 mol kg −1. The most significant property of the reference systems is that the pH difference, and hence, the cell potential, can easily be estimated with sufficient accuracy using only the analytical concentrations of the electrolytes without considering the speciation calculations, given the fact that the association and dissociation constants at supercritical temperatures have not been accurately determined yet