Dielectric and electrostictive properties of ferroelectric relaxors

On the basis of ferroelectric relaxors electrostrictive ceramics has been obtained. Searching for electrostrictive ceramic transducers with optimal electromechanical parameters include the following: 1) investigation of different types of complex oxides with the perovskite structure (OPS): ferroelectric, antiferroelectric, non-polar; 2) investigation of OPS with different degree of the cation order; 3) measurements of the electrostrictive coefficient (Q), Curie-Weiss constant (C), coefficient of linear thermal expansion (A), polarization (P) and permittivity (e); 4) X-ray structure analysis. The following rules have been stated out during the experimental investigations: 1) values of the electrostrictive coefficients (Qijki) depend not only on the chemical constitution of OPS but, first of all, on the degree of cation order (i.e. the coefficients increase with an increase in the degree of cation order: non-ordered state — simple state — ordered state; 2) products of the hydrostatic electrostrictive coefficient (Qh', and the Curie-Weiss (C) constant of all ferroelectric and antiferroelect.ric OPS are nearly equal; 3) value of the hydrostatic electrostrictive coefficient (Qh) is nearly proportional to the linear thermal expansion coefficient square (A1 2). Taking into account the above mentioned rules the detailed and systematic investigations of OPS with non-ordered cations and high value of the Curie-Weiss constant (C) and permittivity (e) were carried out. In such OPS high value of induced polarization leads to considerable electrostrictive deformation described by the Mijkt tensor (Mijhi ~ Qijkier)- One can mention PbNb2/3Mg!/3O3 and solid solution prepared on the basis of PbNb2/3Mgi/3O3 as an example. Devices fabricated on the basis of electrostrictive ceramics provide a relative displacement of about IO-3 what is few times more than the one provided by devices on the basis of piezoelectric ceramics

Optically Isotropic and Monoclinic Ferroelectric Phases in PZT Single Crystals near Morphotropic Phase Boundary

We report the finding of unusual scale-dependent symmetry below the ferroelectric Curie temperature in the perovskite Pb(Zr1-xTix)O3 single crystals of morphotropic phase boundary compositions. The crystals of tetragonal symmetry (from x-ray diffraction experiments) on sub-micrometer scale exhibit a macroscopic (optically determined) cubic symmetry. This peculiar optical isotropy is explained by the anomalously small size of tetragonal ferroelectric domains. Upon further cooling the crystals transform to the phase consisting of micrometer-sized domains of monoclinic Cm symmetry.Comment: 7 pages, 3 figure

The influence of Pb vacancies on the properties of PZT-type ceramics transducers

This article is dedicated to prof. J. Ranachowski The result of investigations of the influence of lead vacancies on the crystalline structure of PZT-type ceramic piezoelectric materials is presented. The solid solution of PbTiO3 - PbZrO3 - sigma n=13 Pb(B'1-alpha B''alpha)O3, characterized by the perovskite-type structure (ABO3), is the basis of those materials. The lead vacancies (VPb) was originated by a thermal treatment. Investigations of the influence of the lead deficiency on the crystalline structure of PZT-type ceramics have been performed for solid solutions characterized by compositions corresponding to the tetragonal or rhombohedral boundary of the morphotropic region (PCR-1, PCR-8: Piezoelectric Ceramics of Rostov) and to tetragonal phase region compositions (ceramics of Pb1-x(Zr0.39Ti0.59W0.01Cd0.01) O3). It has been found that the deficiency in lead causes a reconstruction of the perovskite phase crystalline structure or a change of the elementary cell parameters of that phase. The solid solutions on the basis of Pb(Zr,Ti)O3 resolve themselves into PbTiO3, ZrO2 and PbO when the lead deficiency caused by thermal treatment increases

Pressure effect on the in-plane magnetic penetration depth in YBa_2Cu_4O_8

We report a study of the pressure effect (PE) on the in-plane magnetic field penetration depth lambda_{ab} in YBa_2Cu_4O_8 by means of Meissner fraction measurements. A pronounced PE on lambda_{ab}^{-2}(0) was observed with a maximum relative shift of \Delta\lambda^{-2}_{ab}/\lambda^{-2}_{ab}= 44(3)% at a pressure of 10.2 kbar. It arises from the pressure dependence of the effective in-plane charge carrier mass and pressure induced charge carrier transfer from the CuO chains to the superconducting CuO_2 planes. The present results imply that the charge carriers in YBa_2Cu_4O_8 are coupled to the lattice.Comment: 4pages 3 figure

Образовательные трансформации и социальный субъект: некоторые аспекты позитивной динамики

Introduction. Consideration of the prospects for positive transformations in modern Russian education, even at the level of problem formulation, remains relevant from the point of view of assessing possible further constructive transformations. It is important to analyze the possibilities of using traditional and innovative foreign and domestic experience in the face of new challenges.Problem statement. The article actualizes the problem of the correlation between the use of foreign cultural educational samples and domestic unique experience, taking into account the specifics of regional Siberian universities. A special place is occupied by the problems of practical application of the competence-oriented educational model, the use of IT technologies in the educational process, new trends in education, such as digital pedagogy, reverse learning, a variety of interactive and distance forms that constructively affect the subjectivity of the teaching community and students.Methodology of the study. The paper uses traditional methods of humanitarian research, in particular, systemic and structural-functional approaches, comparative and retrospective analysis, elements of sociological research (questionnaires, interviews, content analysis, etc.), as well as some methods of post-non-classical (synergetic) methodological approach. The published data of a sociological survey of teachers of humanities of four Novosibirsk and Altai universities and three educational institutions of additional education, as well as the results of interviewing teachers of higher education in the Siberian region, were used as an empirical basis for the study.Results. The article clarifies forecasts of further changes in the structure and trends in education, current problems of improving the competence-oriented educational model, taking into account foreign experience, based on the latest expert sources and official speeches of Russian educational methodologists and strategists. It is shown that in the form that it exists now, this model is opportunistic, overly formalized, methodologically vulnerable and therefore toxic to the modern qualitative educational process. In this sense, the necessary understanding has been reached at the level of the “regulator”, which is considering ways to reformat some of the Bologna Principles, for example, changing the structure of bachelor’s and master’s degrees. Attention is again focused on the problem of wages and other forms of material incentives for ordinary teachers of provincial universities, which, against the background of an increase in the academic load, as a rule, does not reach the average for the economy in the regions. At the level of the problem statement, the emerging difficulties of grant support for research work in educational organizations are considered.Conclusions. The article actualizes the problem of the correlation between the use of international and domestic unique experience, taking into account the specifics of regional Siberian universities. It is shown that in this direction, educational subjects have reached an understanding of the need for differentiated use of foreign cultural achievements and the active introduction of their own innovations, especially in the field of IT technologies and digital pedagogy. At the level of the problem statement, there is a tendency to tighten and formalize publication and other criteria for obtaining grants even by leading scientists and professors of higher education, not to mention dubious transformations in the system of the former RFH, RFBR and RSF. Obtaining grants is becoming a problem for provincial universities, and the corruption component and elements of scientific protectionism are also not excluded.Введение. Рассмотрение перспектив позитивных преобразований в современном российском образовании даже на уровне постановки проблемы остается актуальным с точки зрения оценки возможных дальнейших конструктивных трансформаций. Важно проанализировать потенциал использования традиционного и инновационного зарубежного и отечественного опыта в условиях новых вызовов.Постановка задачи. В статье актуализируется проблема соотношения использования инокультурных образовательных образцов и отечественного уникального опыта с учетом специфики региональных сибирских вузов. Особое место занимают проблемы практического применения компетентностно-ориентированной образовательной модели, вопросы использования IT-технологий в образовательном процессе, новые тенденции в образовании, такие как цифровая педагогика, «перевернутое обучение», разнообразные интерактивные и дистанционные формы, конструктивно влияющие на субъектность преподавательского сообщества и студенчества.Методика и методология исследования. В работе использованы традиционные методы гуманитарного исследования, в частности системный и структурно-функциональный подходы, сравнительный и ретроспективный анализ, элементы социологического исследования (анкетирование, интервью, контент-анализ и др.), а также некоторые методы постнеклассического (синергетического) методологического подхода. В качестве эмпирической базы исследования использованы опубликованные данные социологического опроса преподавателей гуманитарных дисциплин четырех новосибирских и алтайских вузов и трех учебных заведений дополнительного образования, а также результаты интервьюирования преподавателей высшей школы в Сибирском регионе.Результаты исследования. В статье на основании последних экспертных источников и официальных выступлений отечественных методологов и стратегов образования уточняются прогнозы дальнейших изменений структуры и тенденций в образовании, актуальные проблемы совершенствования компетентностно-ориентированной образовательной модели с учетом зарубежного опыта. Показано, что в таком виде, каком она существует сейчас, эта модель конъюнктурна, излишне формализована, методологически уязвима и поэтому токсична для современного качественного образовательного процесса. В этом смысле достигнуто необходимое понимание на уровне регулятора, который демонстрирует пути переформатирования некоторых болонских принципов, например, изменения структуры бакалавриата и магистратуры. Вновь акцентировано внимание на проблеме заработной платы и других форм материального поощрения рядовых преподавателей провинциальных вузов, которая на фоне роста учебной нагрузки, как правило, не достигает средней по экономике в регионах. На уровне постановки проблемы рассмотрены возникающие трудности грантовой поддержки научно-исследовательской работы в образовательных организациях.Выводы. В статье актуализирована проблема соотношения использования международного и отечественного уникального опыта с учетом специфики региональных сибирских вузов. Показано, что в этом направлении образовательными субъектами достигнуто понимание необходимости дифференцированного использования инокультурных достижений и активного внедрения собственных инноваций, особенно в сфере IT-технологий и «цифровой педагогики». На уровне постановки проблемы констатируется тенденция ужесточения и формализации публикационных и иных критериев получения грантов даже ведущими учеными и профессорами высшей школы, не говоря уже о сомнительных преобразованиях в системе бывших РГНФ, РФФИ и РНФ. Получение грантов становится проблемой для провинциальных вузов, не исключаются также коррупционная составляющая и элементы научного протекционизма

X-ray emission during the muonic cascade in hydrogen

We report our investigations of X rays emitted during the muonic cascade in hydrogen employing charge coupled devices as X-ray detectors. The density dependence of the relative X-ray yields for the muonic hydrogen lines (K_alpha, K_beta, K_gamma) has been measured at densities between 0.00115 and 0.97 of liquid hydrogen density. In this density region collisional processes dominate the cascade down to low energy levels. A comparison with recent calculations is given in order to demonstrate the influence of Coulomb deexcitation.Comment: 5 pages, Tex, 4 figures, submitted to Physical Review Letter

The role of out-of-class work of doctor-interns in improving qualitive academic progress on clinical immunology and allergology under the primary specialization “Internal diseases”.

The use of independent out-of-class work of interns on the specialty "Internal diseases" in the section of clinical immunology and allergology promoted the improvement of the qualitative success of interns

ЭФФЕКТ РАЗЛИЧНЫХ ФЕРМЕНТОВ-АНТИОКСИДАНТОВ НА РЕГЕНЕРАТИВНЫЕ ПРОЦЕССЫ В ЭПИТЕЛИИ ТРАХЕИ ПОСЛЕ ХИМИЧЕСКОГО ОЖОГА

The aim of the study was to investigate a role of different antioxidant enzymes for tracheal epithelium regeneration after chemical burn.Methods. The study was conducted in a rat model of chemical burn of the upper airways caused by inhaled hydrochloric acid.Results. According to results of histological examination, to the 2nd day after the exposure approximately 70 % of the epithelial surface remained injured, mostly due to death of the ciliated cells. The degree of the damage was unchanged to the 4th day after the exposure. Visible regeneration of the tracheal epithelium began to the 7th day. The death of the tracheal epithelial cells was generally due to necrosis though cell apoptosis also occurred. The expression of all antioxidant enzymes was greatly decreased during the 1st day after the exposure followed by its growth to maximum to the 7th day and normal level to the 15th day after the burn. Exposition of superoxide dismutase to the trachea resulted in a significant epithelium destruction. On contrary, peroxiredoxin 6 and a chimeric protein containing peroxiredoxin / superoxide dismutase significantly protected the tracheal epithelium.Conclusion. Peroxiredoxins and their derivates could be used as highly efficient therapeutic agents with potent antioxidant action in patients with burn injury of the upper airways.Проведено исследование на модели химического ожога парами соляной кислоты верхних дыхательных путей (ВДП) крысы. В результате гистологического анализа показано, что после 1-го дня после ожога » 70 % поверхности эпителия остается поврежденной. При этом в основном гибнут реснитчатые клетки, степень повреждения остается приблизительно такой же на 3-и сутки после ожога. Видимая регенерация эпителия трахеи наблюдается на 7-е сутки после ожога. Гибель клеток эпителия трахеи происходит в основном по некротическому пути, хотя наблюдается также апоптоз клеток. В 1-й день после ожога наблюдается резкое снижение экспрессии всех ферментов-антиоксидантов, максимум экспрессии достигается на 7-й день и приходит в норму на 15-й день после ожога. Аппликация суперок-сиддисмутазы (СОД) в обожженную трахею вызывала значительное разрушение эпителия трахеи. В противоположность этому при аппликации в трахею пероксиредоксина (Prx) 6 и химерного белка с Prx-СОД практически полностью сохранялся эпителий трахеи. Таким образом, Prx и его модификации – перспективные эффективные лекарственные средства мощного антиоксидантного действия для лечения ожогов ВДП

Ab Initio Study of the Structural Phase Transition in Cubic Pb_3GeTe_4

In the substitutionally disordered narrow-gap semiconductor Pb_{1-x}Ge_xTe, a finite-temperature cubic-rhombohedral transition appears above a critical concentration $x \approx 0.005$. As a first step towards a first-principles investigation of this transition in the disordered system, a (hypothetical) ordered cubic Pb_3GeTe_4 supercell is studied. First principles density-functional calculations of total energies and linear response functions are performed using the conjugate-gradients method with ab initio pseudopotentials and a plane-wave basis set. Unstable modes in Pb_3GeTe_4 are found, dominated by off-centering of the Ge ions coupled with displacements of their neighboring Te ions. A model Hamiltonian for this system is constructed using the lattice Wannier function formalism. The parameters for this Hamiltonian are determined from first principles. The equilibrium thermodynamics of the model system is studied via Metropolis Monte Carlo simulations. The calculated transition temperature, T_c, is approximately 620K for the cubic Pb_3GeTe_4 model, compared to the experimental value of T_c \approx 350K for disordered Pb_{0.75}Ge_{0.25}Te. Generalization of this analysis to the disordered Pb_{1-x}Ge_xTe system is discussed.Comment: 38 pages, LaTeX, 11 PostScript figure