Oxygen content and defect structure of the perovskite La0.5Ba0.5CoO3–δ

Received: 28.06.2018. Accepted: 25.07.2018. Published: 30.07.2018.Perovskite-type complex oxide La0.5Ba0.5CoO3–δ, promising cathode material for solid oxide fuel cells and precursor for synthesis of double perovskite LaBaCo2O6–δ, was prepared as a single-phase material. Its oxygen content was measured by two independent techniques in the temperature range 1000–1100 °C and at oxygen partial pressures corresponding to the stability field of cubic phase. The defect chemistry of this material was studied using the measured δ = f(pO2, T) dependences. The defect structure model based on the localized nature of the electronic defects was proposed and successfully verified

Oxygen content and defect structure of the perovskite La0.5Ba0.5CoO3–δ

Perovskite-type complex oxide La0.5Ba0.5CoO3–δ, promising cathode material for solid oxide fuel cells and precursor for synthesis of double perovskite LaBaCo2O6–δ, was prepared as a single-phase material. Its oxygen content was measured by two independent techniques in the temperature range 1000–1100 °C and at oxygen partial pressures corresponding to the stability field of cubic phase. The defect chemistry of this material was studied using the measured δ=f(pO2,T) dependences. The defect structure model based on the localized nature of the electronic defects was proposed and successfully verified

Очистка бензольной фракции и бензола от непредельных и сернистых соединений новым модифицированным адсорбентом на основе природной глины

Objectives. This study aimed to create a method for purifying benzene fractions using a modified natural clay-based adsorbent, which removes both unsaturated and sulfur compounds from benzene or benzene fractions obtained by pyrolysis of petrochemical raw materials.Methods. Chemical and chromatographic methods were used to conduct flow analyses before and after purification. Testing was conducted under conditions that were similar to industrial conditions. The functional characteristics of the adsorbents (moisture resistance and bulk density) were evaluated by strength tests after wetting with water and by weighing batches of the adsorbents fixed in volume.Results. Three clay-based adsorbent samples were developed, and tested under laboratory conditions. Thereafter, the CS-Sorb-6890 (M) sample—an Ni-modified adsorbent—was tested under experimental industrial conditions. A positive effect was obtained, and a method for purifying benzene fractions (benzene) from sulfur compounds and olefins is proposed.Conclusions. The obtained results revealed that the modified active clay-based adsorbent successfully removed sulfur and unsaturated compounds from the benzene fraction simultaneously. The total sulfur concentration was reduced to 0.00004 wt % after 90% of it was removed. The conversion of the unsaturated compounds reached 100%.Цели. Создание способа очистки бензольной фракции (бензола) с помощью модифицированного адсорбента на основе природной глины, который позволит одновременно удалять непредельные и сернистые соединения из бензола или бензольной фракции, полученных пиролизом нефтехимического сырья.Методы. Анализы потоков до и после очистки выполняли химическими и хроматогра- фическими методами. Тестирование проводили в условиях, приближенных к промышленным. Функциональные характеристики адсорбентов (влагостойкость, насыпная плотность) оценивали с помощью испытаний на прочность после смачивания водой и методом взвешивания фиксированных по объему партий адсорбентов.Результаты. Разработаны три образца адсорбента на основе глины, проведено их тестирование в лабораторных условиях, после чего образец CS-Sorb-6890 (M) – адсорбент с нанесенным Ni – прошел испытания в опытно-промышленных условиях. Получен положительный эффект, предложен способ очистки бензольной фракции (бензола) от сернистых соединений и олефинов.Выводы. Достигнутые результаты свидетельствуют о том, что созданный модифицированный адсорбент на основе активной глины успешно удаляет одновременно сернистые и непредельные соединения из бензольной фракции. Удаление общей серы максимально составило 90%, и ее концентрация минимизирована до 0.00004 мас. %. Конверсия непредельных соединений достигла 100%

Thermodynamics of Formation of Solid Solutions between BaZrO3 and BaPrO3

Received: 30.03.2020. Accepted: 11.05.2020. Published: 30.06.2020.A linear relationship between the standard enthalpy of formation from binary oxides, ΔfH°ox, and the Goldschmidt tolerance factor, t, for some AIIBIVO3 (A = Ca, Sr, Ba; B = Ti, Zr, Hf, Ce, Pr, Tb, U, Pu, Am) perovskite oxides was used for estimation of ΔfH°ox of Pr-substituted barium zirconates BaZr1–xPrxO3. A dependence of the relative change of the standard entropies, S°298, on the relative change of the molar volumes in the reactions of formation of AIIBIVO3 (A = Ca, Sr, Ba; B = Ti, Zr, Hf, Ce) from binary oxides was also found to be linear. Using this dependence, a relatively precise method of estimating S°298 was proposed, and S°298 of BaPrO3 was calculated as (162.8 ± 2.8) J·mol–1·K–1. Knowing S°298 of BaPrO3 and using the literature data for S°298 of BaZrO3, the values of S°298 of BaZr1–xPrxO3 were predicted on the assumption that BaZr1–xPrxO3 is a regular or ideal solution of BaPrO3 in BaZrO3 as evidenced by the very small enthalpy of mixing calculated based on the estimated ΔfH°ox. The values of standard entropy changes, ΔfS°ox, and Gibbs energy changes, ΔfG°ox, for the reactions of formation of BaZr1–xPrxO3 from BaO, ZrO2 and PrO2 were also estimated. Substituting Pr for Zr in BaZr1–xPrxO3 results in ΔfH°ox and ΔfG°ox becoming more positive, indicating the decrease of the relative stability with respect to the corresponding binary oxides. Expanded uncertainties of the estimated values of ΔfH°ox and ΔfG°ox are equal to 14 kJ · mol–1, and those of S°298 and ΔfS°ox — less than 2.8 J · mol–1·K–1 and 3.5 J · mol–1·K–1, respectively, for BaZr1–xPrxO3 (x = 0.0–1.0).This work was supported by the Russian Science Foundation (project No. 18‑73‑00022)

Dynamic Evolution Model of Isothermal Voids and Shocks

We explore self-similar hydrodynamic evolution of central voids embedded in an isothermal gas of spherical symmetry under the self-gravity. More specifically, we study voids expanding at constant radial speeds in an isothermal gas and construct all types of possible void solutions without or with shocks in surrounding envelopes. We examine properties of void boundaries and outer envelopes. Voids without shocks are all bounded by overdense shells and either inflows or outflows in the outer envelope may occur. These solutions, referred to as type $\mathcal{X}$ void solutions, are further divided into subtypes $\mathcal{X}_{\rm I}$ and $\mathcal{X}_{\rm II}$ according to their characteristic behaviours across the sonic critical line (SCL). Void solutions with shocks in envelopes are referred to as type $\mathcal{Z}$ voids and can have both dense and quasi-smooth edges. Asymptotically, outflows, breezes, inflows, accretions and static outer envelopes may all surround such type $\mathcal{Z}$ voids. Both cases of constant and varying temperatures across isothermal shock fronts are analyzed; they are referred to as types $\mathcal{Z}_{\rm I}$ and $\mathcal{Z}_{\rm II}$ void shock solutions. We apply the `phase net matching procedure' to construct various self-similar void solutions. We also present analysis on void generation mechanisms and describe several astrophysical applications. By including self-gravity, gas pressure and shocks, our isothermal self-similar void (ISSV) model is adaptable to various astrophysical systems such as planetary nebulae, hot bubbles and superbubbles in the interstellar medium as well as supernova remnants.Comment: 24 pages, 13 figuers, accepted by ApS

Carbon Supported Polyaniline as Anode Catalyst: Pathway to Platinum-Free Fuel Cells

The effectiveness of carbon supported polyaniline as anode catalyst in a fuel cell (FC) with direct formic acid electrooxidation is experimentally demonstrated. A prototype FC with such a platinum-free composite anode exhibited a maximum room-temperature specific power of about 5 mW/cm2Comment: 11 pages, 3 Postscript figures, atricle tex styl

СИНДРОМ ПРОФЕССИОНАЛЬНОГО «ВЫГОРАНИЯ» У ВРАЧЕЙ АНЕСТЕЗИОЛОГОВ-РЕАНИМАТОЛОГОВ

To study burnout syndrome in anesthesiologists, we conducted a survey study in 48 doctors working in Arkhangelsk region. It was found that 62.5% of them have a high level of burnout, characterized by emotional exhaustion and stress in work, deterioration of health and social adaptation. More than half of the anesthesiologists have a high index of organizational stress and Behavioral type A, use maladaptive coping strategies in dealing with intractable situations arising during work. These results led to preparation of recommendations for prevention and correction of burnout in anesthesiologists. С целью изучения синдрома профессионального «выгорания» у анестезиологов-реаниматологов обследовано 48 врачей Архангельской области. Установлено, что 62,5% из них имеют высокий уровень профессионального «выгорания», характеризующийся эмоциональным истощением и напряжением в работе, ухудшением здоровья и социальной адаптации. Более половины врачей имеют высокий показатель организационного стресса и поведенческий тип А, используют неадаптивные копинг-стратегии в борьбе с возникшими трудноразрешимыми ситуациями. Предложены рекомендации по профилактике и коррекции профессионального «выгорания» у врачей анестезиологов-реаниматологов.

Oscillations of neutrinos and mesons in quantum field theory

This report deals with the quantum field theory of particle oscillations in vacuum. We first review the various controversies regarding quantum-mechanical derivations of the oscillation formula, as well as the different field-theoretical approaches proposed to settle them. We then clear up the contradictions between the existing field-theoretical treatments by a thorough study of the external wave packet model. In particular, we show that the latter includes stationary models as a subcase. In addition, we explicitly compute decoherence terms, which destroy interferences, in order to prove that the coherence length can be increased without bound by more accurate energy measurements. We show that decoherence originates not only in the width and in the separation of wave packets, but also in their spreading through space-time. In this review, we neither assume the relativistic limit nor the stability of oscillating particles, so that the oscillation formula derived with field-theoretical methods can be applied not only to neutrinos but also to neutral K and B mesons. Finally, we discuss oscillations of correlated particles in the same framework.Comment: v2, 124 pages, 10 figures (7 more); updated review of the literature; complete derivation of the oscillation probability at short and large distance; more details on the influence of the spreading of the amplitude on decoherence; submitted to Physics Report