Pressure-induced phase transition of Bi2Te3 into the bcc structure

The pressure-induced phase transition of bismuth telluride, Bi2Te3, has been studied by synchrotron x-ray diffraction measurements at room temperature using a diamond-anvil cell (DAC) with loading pressures up to 29.8 GPa. We found a high-pressure body-centered cubic (bcc) phase in Bi2Te3 at 25.2 GPa, which is denoted as phase IV, and this phase apperars above 14.5 GPa. Upon releasing the pressure from 29.8 GPa, the diffraction pattern changes with pressure hysteresis. The original rhombohedral phase is recovered at 2.43 GPa. The bcc structure can explain the phase IV peaks. We assumed that the structural model of phase IV is analogous to a substitutional binary alloy; the Bi and Te atoms are distributed in the bcc-lattice sites with space group Im-3m. The results of Rietveld analysis based on this model agree well with both the experimental data and calculated results. Therefore, the structure of phase IV in Bi2Te3 can be explained by a solid solution with a bcc lattice in the Bi-Te (60 atomic% tellurium) binary system.Comment: 12 pages, 5 figure

Management of academic staff activity: modeling and prediction of rating system indicators

This paper deals with the problem of constructing a system of rating indicators for stimulating the work of the academic staff in higher educational institution. Many areas of teacher activity (for example, educational, scientific, international, etc.) laid the basis of selection the groups of indicators in the system. Social challenge in improving the quality of educational services determines the relevance of research in the field of modeling and prediction of indicators which characterize the work of high school teacher. To predict the dynamics of the structure of the rating indicators in the system, the authors introduced the concept of drift and variability of each group. Using informational hypercube for the structure of input data allowed authors to take into account the individual characteristics of each parameter included in a mathematical model to describe the rating indicators. To make the prediction of the structure and values of rating system indicators the authors introduced the concept of drift. Drift of indicators takes into account the introduction of new indicators, the removal of existing indicators, and movement of indicators between the groups. In the article, authors introduced a novel quantitative indicator of group variability. The value of this indicator determines the prediction strategy of the teacher work in higher school in the future period. To predict the total amount of stimulating, the complex technique offered and it includes four modules: modeling values within the existing range in the previous period; modeling new index value based on the assumptions introduced using a random number generator; exclusion a range of values of deleted indicators; modeling new values based on the study of the modern trend of indicators. The presence of flexible information structure in the form of a hypercube and complex mathematical model allowed authors to carry out numerical simulation for predicting the values of individual and group indicators. During the experiment, the structural stability of values is detected, and it does not lead to a drastic changing of the quantitative ratio between the groups of indicators

Synthesis and Research of Alumina Ceramics Properties

Received: 27.10.2020. Revised: 18.12.2020. Accepted: 18.12.2020. Available online: 21.12.2020.This article belongs to the PCEE-2020 Special Issue.The article describes in detail alumina powder synthesis by different methods at varying parameters. The technique of obtaining ceramics and the research of the optical properties for determining the materials with the maximum luminescence efficiency is presented. The concentration of the luminescence intrinsic centers and various defects differ for ceramics synthesized by different methods. It is determined that ceramics based on the powder synthesized by a sol-gel method has the maximum thermoluminescence intensity in the Fcenter peak, whereas for the peak of 360 °C it is obtained with the powder prepared by precipitation of aluminum nitrate with a PEG-20000 stabilizer.This work was financially supported by the Russian Science Foundation, project No. 18-72-10082

Phase Diagram of Pressure-induced Superconductivity and its Relation to Hall Coefficient in Bi2Te3 Single Crystal

Pressure-induced superconductivity and its relation to corresponding Hall coefficient (RH) have been reported for Bi2Te3, one of known topological insulators. A full phase diagram is presented which shows a complex dependence of the superconducting transition temperature as a function of pressure over an extensive range. High-pressure RH measurements reveal a close relation of these complex behaviors, particularly, a dramatic change of dRH/dP before structural phase transition and a pressure-induced crossover on RH in the high pressure phase were observed.Comment: 14 pages and 3 figure

SOL-GEL SYNTHESIS OF Li7-xLa3Zr2-xTaxO12 (x=0.1-0.7) SOLID ELECTROLYTES

Твердые электролиты Li7-xLa3Zr2-xTaxO12 (x=0.1-0.7) были синтезированы с помощью золь-гель метода. Полученные соединения имеют кубическую структуру Ia-3d. В исследуемой системе наибольшей электропроводностью при 25 °C обладает твердый электролит Li6.4La3Zr1.6Ta0.4O12, 1.2·10-4 См/см.Li7-xLa3Zr2-xTaxO12 (x=0.1-0.7) solid electrolytes have been synthesized by solgel method. The obtaining compounds have a cubic structure Ia-3d. The Li6.4La3Zr1.6Ta0.4O12 solid electrolyte has the highest total conductivity, 1.2·10-4 S/cm at 25 °C

ELECTRICAL CONDUCTIVITY OF Li6.75-3xAlxLa3Zr1.75Nb0.25O12 (x=0–0.25) SOLID ELECTROLYTES

В представленной работе с помощью золь-гель метода синтеза получены твердые электролиты Li6.75-3xAlxLa3Zr1.75Nb0.25O12 (x=0–0.25). Изучены их фазовый состав и электропроводность. Согласно данным РФА, полученные твердые электролиты с x>0.10 содержали примесь в виде La2Zr2O7. Показано, что состав Li6.6Al0.05La3Zr1.75Nb0.25O12 имеет наибольшую электропроводность при 25 °C, которая составляет 6.3·10-4 См/см.Li6.75-3xAlxLa3Zr1.75Nb0.25O12 (x=0–0.25) solid electrolytes have been obtained by sol-gel method. Their phase composition and conductivity have been studied. According to XRD analysis the obtained solid electrolytes with x>0.10 have impurity in the form of La2Zr2O7. The Li6.6Al0.05La3Zr1.75Nb0.25O12 solid electrolyte has the highest total conductivity, 6.3·10-4 S/cm at 25 °C.Исследование выполнено при финансовой поддержке гранта Президента РФ № МК-1382.2019.3

Muon `Depth -- Intensity' Relation Measured by LVD Underground Experiment and Cosmic-Ray Muon Spectrum at Sea Level

We present the analysis of the muon events with all muon multiplicities collected during 21804 hours of operation of the first LVD tower. The measured angular distribution of muon intensity has been converted to the `depth -- vertical intensity' relation in the depth range from 3 to 12 km w.e.. The analysis of this relation allowed to derive the power index, $\gamma$, of the primary all-nucleon spectrum: $\gamma=2.78 \pm 0.05$. The `depth -- vertical intensity' relation has been converted to standard rock and the comparison with the data of other experiments has been done. We present also the derived vertical muon spectrum at sea level.Comment: 7 pages, 3 figures, to be published on Phys. Rev.

Effect of the Nature of Deposited Metal on the Morphology of Electrolytic Deposits

Установлено, что природа ионов металла, разряжающихся на катоде, оказывает значительное влияние на морфологию осадка. Осадки никеля обладают характерной структурой пены: на них присутствуют крупные поры (каналы эвакуации водорода), вокруг которых кристаллизуется металл в форме дендритов. Осадки сплава Ni–Co по своей морфологии близки к рыхлым порошкообразным металлам.It was found that the nature of metal ions discharged at the cathode has a significant effect on the deposit morphology. Pure nickel deposits have a typical foam structure with large pores composed of dendrites. The Ni-Co alloy deposits are characterized by morphology close to loose powder metals

Сравнение реологических и вязкоупругих свойств медицинских изделий гиалуроновой кислоты для внутрисуставного введения

Osteoarthritis (OA) is the most common joint disease that affects more than 80% of people over 55 years and in its final stages leads to disability. One of the safe non-surgical methods of OA treatment is intra-articular injections of hyaluronic acid (HA).Objective: to compare the viscoelastic rheological properties of HA medical products with different concentrations of sodium hyaluronate (SH) available in the Russian Federation.Material and methods. The study was carried out using a modular rheometer MCR 302 (Anton Paar, Austria). All measurements were carried out at a temperature of 25.0±0.1 °C using the measuring system "cone-plane" (angle – 2 ˚ , cone diameter – 40 mm, gap height – 0.169 mm). The determination of the elastic moduli (G’) and viscosity (G”) was carried out depending on the frequency in the linear region of the shear stress, and the dynamic viscosity was determined at a shear rate of 1 sec-1.Results. The evaluation of the rheological properties of the studied samples revealed a positive relationship with the concentration of SH and no relationship with the molecular weight of SH. The highest viscoelastic properties were possessed by medical products in the 1% SH group: Armaviscon and Ripart; in the group with SH concentration of 1.5–1.6%, all the studied samples, except for Hyalubrix, showed similar higher results compared to the previous group; in the group with SH concentration of 2–3%, Armaviscon Platinum had the highest results and Flexotron Ultra and Armaviscon Forte – somewhat lower results.Conclusion. The study of the rheological viscoelastic properties of HA medical products is the most accessible method, on the basis of which it is possible to predict the clinical effect.Остеоартрит (ОА) – наиболее распространенное заболевание суставов, которое поражает более 80% лиц старше 55 лет и на последних стадиях приводит к инвалидности. Одним из безопасных неоперативных методов лечения ОА является использование внутрисуставных инъекции медицинских изделий гиалуроновои кислоты (ГлК).Цель исследования – сравнение вязкоупругих реологических свойств медицинских изделий ГлК с различной концентрацией гиалуроната натрия (ГН), доступных для использования в Российской Федерации.Материал и методы. Исследование проводилось с помощью модульного реометра MCR 302 (Anton Paar, Австрия). Все измерения выполнялись при температуре 25,0±0,1 °С с использованием измерительной системы «конус-плоскость» (угол – 2°, диаметр конуса – 40 мм, высота зазора – 0,169 мм). Определение модулей упругости (G’) и вязкости (G”) осуществляли в зависимости от частоты в линейной области напряжения сдвига, а динамической вязкости – при скорости сдвига 1 с-1.Результаты и обсуждение. Оценка реологических свойств исследуемых образцов выявила положительную связь с концентрацией ГН и отсутствие связи с молекулярной массой ГН. Самыми высокими вязкоупругими свойствами обладали медицинские изделия в группе с концентрацией ГН 1%: Армавискон и Рипарт; в группе с концентрацией ГН 1,5–1,6% все исследуемые образцы, кроме Хиалубрикса, показали схожие, более высокие по сравнению с предыдущей группой, результаты; в группе с концентрацией ГН 2–3% наиболее высокие показатели имел Армавискон Платинум и несколько меньшие – Флексотрон Ультра и Армавискон Форте.Заключение. Изучение реологических вязкоупругих свойств медицинских изделий ГлК является наиболее доступным методом, на основании которого можно прогнозировать клинический эффект

Влияние адаптогена аскорбата лития на микробиоту рубца овец-ярок

Health and productivity of ruminants directly depend on the state of rumen and digestion in intestinal tract. Normal microflora protects the body from pathogenic microbes, stimulates the immune system, participates in metabolic reactions and plays an important role in energy metabolism. Disturbance of species composition of microflora in rumen under effect of various factors leads to a state of dysbiosis, disorders of products digestibility, changes in enzymatic processes and other disorders. Biologically active substances of an adaptogenic nature can show immunomodulatory and antimicrobial activity. Adaptogen lithium ascorbate has stress-protective, neurotrophic, neuroprotective, antioxidant, immunomodulatory properties. In this paper, using molecular genetic methods, the effect of lithium ascorbate on composition of rumen microbiota of sheep was studied for the first time.  Composition of microbiota was determined by NGS sequencing method. In total, 37 phylums, 76 classes, 98 orders, 225 families and 894 species of microorganisms were identified. It has been determined that introduction of lithium ascorbate at a dose of 10 mg/kg of body weight into the main diet of sheep contributed to increase in proportion of cellulolytic bacteria from 73.6±1.6% to 75.4±0.9% and over 40% decrease in total number of infusoria in rumen content. Cellulolytic activity of rumen fluid in sheep of the experimental group increased by 38% compared to the animals of the control group. The number of pathogenic bacteria decreased from 2.7% in sheep of the control group to 1.6% in animals of the experimental group, while the content of beneficial bacilli increased from 0.3% to 0.5%, respectively. Content of undesirable and conditionally pathogenic microflora decreased in the sheep of experimental group. The obtained data confirm positive effect of adaptogen lithium ascorbate, introduced into diet at a dosage of 10 mg/kg of body weight, on qualitative and quantitative composition of microbiota in sheep rumen. Therefore, lithium ascorbate, a broad-spectrum adaptogen, can be recommended as a feed additive to the main diet of sheep to improve rumen digestion and increase productivity.Здоровье и продуктивность жвачных животных напрямую зависят от рубцового и кишечного пищеварения. Нормальная микрофлора защищает организм от патогенных микробов, стимулирует иммунную систему, участвует в метаболических реакциях и играет важную роль в энергетическом обмене. Нарушение видового состава микрофлоры рубца под влиянием различных факторов приводит к изменению усвояемости продуктов пищеварения, изменениям ферментативных процессов и развитию прочих патологических процессов. Биологически активные вещества адаптогенной природы могут проявлять иммуномодулирующую и антимикробную активность. Адаптоген аскорбат лития обладает стресс-протекторными, нейротрофическими, нейропротекторными, антиоксидантными, иммуномодулирующими свойствами и в качестве кормовой добавки влияет на микробиоту рубца. В настоящем исследовании при использовании NGS-секвенирования впервые изучено влияние адаптогена аскорбата лития на бактериальное сообщество рубца овец-ярок романовской породы. На фоне длительного содержания овец на основном рационе в условиях вивария ВНИИФБиП нормофлора рубца не подвергалась негативным изменениям. Введение органической соли лития в состав основного рациона в дозировке 10 мг/кг живой массы способствовало усилению процессов ферментации в рубце, достоверному росту целлюлозолитической активности, снижению суммарной доли патогенных и доли некоторых условно-патогенных микроорганизмов в рубцовом содержимом. Полученные данные свидетельствуют о благотворном влиянии введения аскорбата лития в качестве добавки к основному рациону на состав микробиоты рубца овец