Joule Heating and Current-Induced Instabilities in Magnetic Nanocontacts

We consider the electrical current through a magnetic point contact in the limit of a strong inelastic scattering of electrons. In this limit local Joule heating of the contact region plays a decisive role in determining the transport properties of the point contact. We show that if an applied constant bias voltage exceeds a critical value, the stationary state of the system is unstable, and that periodic, non-harmonic oscillations in time of both the electrical current through the contact and the local temperature in the contact region develop spontaneously. Our estimations show that the necessary experimental conditions for observing such oscillations with characteristic frequencies in the range $10^8 \div 10^9$ Hz can easily be met. We also show a possibility to manipulate upon the magnetization direction of a magnetic grain coupled through a point contact to a bulk ferromagnetic by exciting the above-mentioned thermal-electric oscillations.Comment: 9 pages, 6 figures, submitted to Physical Review

Regulation of superoxide dismutase activity in soybean plants by inoculating seeds with rhizobia containing nanoparticles of metal carboxylates under conditions of different water supply

Soybean is one of the most profitable advanced crops in agricultural production in Ukraine and the world as a whole. Therefore, studies of means of regulation and increase in the adaptive capacity of soybeans in symbiosis with nodule bacteria under the action of unfavourable environmental factors are relevant and should be aimed at the use of complex bacterial compositions involving modern nanotechnological approaches. Nanocarboxylates of ferrum, molybdenum and germanium metals were used as components of rhizobia inoculation suspension for soybean seed treatment to study the effectiveness of their complex effect on the regulation of the activity of the key antioxidant enzyme superoxide dismutase in plants under drought. Various symbiotic systems were used, which included soybean plants and inoculation suspensions based on the active, virulent Tn5-mutant Bradyrhizobium japonicum B1-20 by adding nanoparticles of ferrum, germanium and molybdenum carboxylates to the culture medium in a ratio of 1: 1000. Citric acid was the chelator. A model drought lasting 14 days was created during the period of active fixation of atmospheric molecular nitrogen by root nodules of soybeans in the budding and flowering stages, by means of controlled watering of plants to 30% of the total moisture content. In the stage of bean formation, watering of plants was resumed to the optimal level – 60% of the total moisture content. The control was soybean plants, the seeds of which were inoculated with a suspension of rhizobia without the addition of chelated metals. The following research methods were used in the work – microbiological, physiological and biochemical. According to the results, it was found that when nanoparticles of carboxylates of ferrum, molybdenum and germanium were added to the inoculation suspension of rhizobia, there was an increase in superoxide dismutase activity in root nodules and a decrease in soybean leaves under optimal water supply conditions of plants. This indicates the initial changes in the activity of the antioxidant enzyme in these symbiotic systems, induced by the influence of chelated metals in combination with the rhizobia of the active Tn5-mutant B. japonicum B1-20. Prolonged drought induced an increase in the overall level of superoxide dismutase activity in soybean nodules and leaves, compared to plants grown under optimal watering conditions. The symbiotic system formed by soybeans and B. japonicum with molybdenum carboxylate nanoparticles was the most sensitive to long-term drought exposure, compared to two other soybean-rhizobial symbioses using ferrum and germanium nanocarboxylates. This was manifested in the unstable reaction of the enzyme to the action of drought – suppression or intensification of the level of its activity in the root nodules and leaves of soybeans inoculated with rhizobia containing molybdenum carboxylate nanoparticles. In symbiotic systems with the participation of germanium and ferrum nanocarboxylates, slight changes were revealed in superoxide dismutase activity in root nodules and leaves of plants during drought and restoration of enzyme activity to the level of plants with optimal watering after water stress. It is concluded that the addition to the culture medium of rhizobia Tn5-mutant B1-20 of nanocarboxylates of germanium or ferrum is an effective means of regulating the activity of the antioxidant enzyme superoxide dismutase in soybean root nodules and leaves, which can contribute to an increase in the protective properties and adaptation of plants to the action of dehydration

Central image of Vertisols: evolution of concepts of their morphology and genesis

This paper discuss the changes in understanding of the central image of Vertisols and leading processes of their formation. The early concept described Vertisols as black or dark clayey soils with homogenous undifferentiated profile resulted basically of pedoturbation. The further studies discovered vertical differentiation of Vertisol attributes. The application of trench method discovered spatial heterogeneity of Vertisols with alternation of bowl and diapiric structures. Such spatial complex subsurface pattern seems to be rather common and can be found even in the absence of gilgai microrelief. A new central image of a mature Vertisol is a combination of two structural types, one being homogenous and monotonous, generally corresponding to the initial central image, and the other - heterogeneous profile with fragmented horizons. A leading process forming the new central image of Vertisols was defined as lateral shearing or plastic deformations, i.e., plastic movements and gradual upward pushing of moist material (analogy of defluction process). Pedoturbation or more exactly the vertical falling of surface material into the cracks results in the vertical mixing rather than in deformations. Micromorphological features typical of Vertisols and associated with shrink-swell phenomena, cracking, mixing and lateral shearing that are reflected in the central image of Vertisols are summarized in the paper and illustrated by microphotographs

Модели ГЭБ in vitro: преимущества и недостатки, текущее положение и перспективы развития

There is growing research focusing on endothelial cells as separate units of the blood-brain barrier (BBB), and on the complex relationships between different types of cells within a neurovascular unit. To conduct this type of studies, researches use vastly different in vitro BBB models. The main objective of such models is to study the BBB permeability for different molecules, and to advance the current level of understanding the mechanisms of disease and to develop methods of targeted therapy for the central nervous system. The analysis of the existing Abstract in vitro BBB models and their advantages/disadvantages was conducted using the clinical trial data obtained in Russian/foreign countries. In this review, the authors highlight the most relevant assessment parameters and propose a unified classification of in vitro BBB models. According to the performed analysis, there is a tendency to move from 2D BBB models based on semipermeable inserts to 3D BBB spheroid and microfluidic organ-on-chip models. Moreover, the use of human induced pluripotent stem cells instead of animal primary cells will make it possible to reliably scale the results obtained in vitro to conditions in vivo.Все больше исследователей фокусируют внимание не на эндотелиальных клетках как отдельных единицах гематоэнцефалического барьера (ГЭБ), но на сложных взаимоотношениях различных типов клеток внутри нейроваскулярной единицы, для чего широко используют различные модели ГЭБ in vitro. Основной точкой приложения таких моделей являются исследования проницаемости ГЭБ для различных молекул, патологических и лекарственных, в рамках изучения заболеваний и создания способов таргетной доставки терапевтических веществ в центральную нервную систему. В данной статье на основании российской и зарубежной научной литературы проведен анализ существующих моделей ГЭБ in vitro, их преимуществ и недостатков; освещены ключевые параметры, согласно которым оценивают релевантность модели ГЭБ in vitro; предложена унифицированная классификация таких моделей. По результатам анализа можно заключить, что наблюдается тенденция к переходу от 2D-моделей на полупроницаемых вставках к 3D-моделям на основе клеточных сфероидов и микрофлюидных чипов. Кроме того, использование индуцированных плюрипотентных стволовых клеток человека вместо первичных клеток, выделенных от животных, позволит с большей достоверностью масштабировать результаты, полученные in vitro, на условия in vivo

Current-induced magnetic superstructures in exchange-spring devices

We investigate the potential to use a magneto-thermo-electric instability that may be induced in a mesoscopic magnetic multi-layer (F/f/F) to create and control magnetic superstructures. In the studied multilayer two strongly ferromagnetic layers (F) are coupled through a weakly ferromagnetic spacer (f) by an "exchange spring" with a temperature dependent "spring constant" that can be varied by Joule heating caused by an electrical dc current. We show that in the current-in-plane (CIP) configuration a distribution of the magnetization, which is homogeneous in the direction of the current flow, is unstable in the presence of an external magnetic field if the length L of the sample in this direction exceeds some critical value Lc ~ 10 \mu m. This spatial instability results in the spontaneous formation of a moving domain of magnetization directions, the length of which can be controlled by the bias voltage in the limit L >> Lc. Furthermore, we show that in such a situation the current-voltage characteristics has a plateau with hysteresis loops at its ends and demonstrate that if biased in the plateau region the studied device functions as an exponentially precise current stabilizer.Comment: 8 pages, 6 figure

Экспрессия P-гликопротеина на лимфоцитах периферической крови при тяжелых формах бронхиальной астмы и его роль в определении чувствительности к терапии глюкокортикостероидами

P-glycoprotein (Pgp) is a membrane transporter of hydrophobic molecules providing efflux of xenobiotics from the cytosole outside the cell. In epithelial cells, Pgp is thought to be responsible for resistance to steroids. Severe bronchial asthma (SBA) is a heterogenous disease characterized by resistance to and dependence on steroids. The goal of this study was to assess expression of Pgp on peripheral blood lymphocytes in severe bronchial asthma and to evaluate the role of Pgp in developing the resistance to glucocorticoid therapy (GC). Assessment of Pgp expression revealed difference in response to GC treatment. All the patients were susceptible to GC, however, the time of therapeutic effect appearance and the number of Pgp-immunopositive cells differed significantly. Thus, more prolonged application of GC for reducing clinical manifestations was required in patients with aspirin induced or fatal bronchial asthma. The number of Pgp-immunopositive lymphocytes per one patients was significantly higher in patients with fatal bronchial asthma and in patients with steroid dependent bronchial asthma (6.8 ± 0.1 and 7.2 ± 0.2, respectively) comparing with patients with non stable bronchial asthma being therapeutically resistant (3.2±0.2 and 3.5±0.1, respectively). Thus, our findings suggest possible pathogenic role of Pgp in development of resistance to GC therapy in patients with bronchial asthma. Detection of Pgp expression on peripheral blood lymphocytes would allow optimizing the volume and duration of intensive anti inflammatory therapy and predicting the doses of basic drugs.P-гликопротеин (Pgp) — мембранный транспортер гидрофобных молекул, обеспечивающий выброс ксенобиотиков из цитоплазмы во внеклеточное пространство. В клетках эпителиальной природы Pgp отвечает за стероидорезистентность. Тяжелая БА (ТБА) — гетерогенное заболевание, характеризующееся формированием стероидозависимости или стероидорезистентности. Цель исследования изучить экспрессию Pgp на лимфоцитах периферической крови при тяжелых формах бронхиальной астмы (БА) и его роль в развитии резистентности к глюкокортикостероидной (ГКС) терапии. Изучение экспрессии Pgp выявило различие в ответе на лечение ГКС. Все пациенты были чувствительны к ГКС, но время наступления терапевтического эффекта и количество клеток Pgp+ в исследуемых группах достоверно отличались. Так, у пациентов с аспириновой и фатальной БА (ФБА) потребовалось более продолжительное назначение ГКС для купирования обострения. Количество Pgp+ лимфоцитов на одного больного также достоверно оказалось выше и составило 6,8 ± 0,1 в группе ФБА и 7,2 ± 0,2 у пациентов со стероидозависимой БА, в сравнении с больными с терапевтически резистентной (ТРБА) и нестабильной (НБА) — 3,2 ± 0,2 и 3,5 ± 0,1 соответственно. Таким образом, проведенное нами исследование подтверждает возможную патогенетическую роль Pgp в развитии резистентности пациентов БА к терапии ГКС. Определение уровня экспрессии Pgp+ на лимфоцитах периферической крови поможет оптимизировать объем и продолжительность интенсивной противовоспалительной терапии и прогнозировать дозы базисных препаратов

Soils of the polar archaeological site “Settlement Labytnangi 1 (Komy village)”: morphological analysis and chemical composition

Soils of archaeological sites are highly interesting objects for multidisciplinary research in various fields of soil science, ecology, archaeology, anthropology and other sciences. Currently, the soils of archaeological sites in the Arctic regions have not been studied sufficiently, although many ancient monuments beyond the polar circle have been found. This work is devoted to the study of morphological and chemical properties of soils of the archaeological site “Settlement Labytnangi 1”, which is located beyond the northern polar circle, near the cities of Labytnangi and Salekhard (Yamal-Nenets Autonomous Okrug). Development of these territories (according to archaeological research) began in the Eneolithic (Late IV – III millennia BC) and continues to the present day. Soil types on the territory of the monument are represented by soil-like bodies (urbikvazizems), podzols, turbozems, urbo-agrozems and peat soils with inclusions of archaeological and anthropogenic artifacts dating back to the XX century. Most of the studied soils were previously subjected to the processes of cryoturbation, although at present the lower boundary of the active layer of permafrost lies at a depth of 120–130 cm, according to the conducted electrophysical sounding. Significant changes occurred in the acid-base properties of the studied soils. In addition, anthropogenic activity entailed the introduction of biophilic elements and organic matter into the soil profile, in particular phosphorus, which is concentrated in the urbanized soil horizons (phosphorus concentrations above 2 800 mg/kg were recorded). The concentrations of heavy metals in the soils are at/below the conventional background (vicinity of Salekhard and Labytnangi). However, some excess concentrations of copper (up to 87.5 mg/kg), zinc (up to 303.3 mg/kg), lead (up to 76.1 mg/kg), and cadmium (up to 2.1 mg/kg) in the urbanized soil horizons have been detected. According to the results of the work, we can conclude that the soils of the archaeological site were formed under the strong influence of modern and past anthropogenic activity, which determined their morphological structure and chemical characteristics at present

Интегративный подход как вектор персонализации образовательных практик в медицинском вузе

Introduction. The article discusses the formation of a model of a high quality educational process in a medical university in order to prepare a highly qualified specialist and a versatile educated person. Purpose setting. The objective of the study was to analyze the process of formation of clinical thinking, intellectual and communicative competencies in the process of preparing future specialists for professional activities in a medical university, based on the use of an integrative approach, assessment of the type of thinking and learning; constitutional features of the student and teacher; semantic differential method. Methodology and methods of the study. The methodology of the material presented in the article is based on the introduction of a systematic (holistic) approach to study the individual constitutional (mental and physical) characteristics of teachers and medical students in connection with training and further professional activities. Results. The article analyzes current trends and problematic issues of the educational process in pedagogy and andragogy, due to technological progress, the development of digital technologies, distance types and forms of education, the formation of the so-called «digital generation» of students, requiring the development and implementation of innovative methodological approaches and methods in the educational process training of specialists in medical universities. The necessity of forming not only intellectual and communicative competencies in the process of mastering a profession, but also conceptual and logical schemes of clinical thinking using the method of semantic differential is demonstrated. The role of the constitutional features of the teacher and student in the training of future specialists is shown. The relationship between the professional and personal qualities of a high school teacher and students is illustrated.Conclusion. The use of an integrative approach greatly contributes to improving the quality of the educational process in the professional training of a future medical specialist.Введение. Обсуждается формирование модели качественного образовательного процесса в медицинском вузе с целью подготовки высококвалифицированного специалиста и разносторонне образованной личности. Постановка задачи. Задача исследования – проанализировать процесс формирования клинического мышления, интеллектуальных и коммуникативных компетенций в процессе подготовки будущих специалистов к профессиональной деятельности в медицинском вузе на основе применения интегративного подхода, оценки типа мышления и обучения, конституциональных особенностей обучающегося и преподавателя, метода семантического дифференциала. Методика и методология исследования. Методология материала, представленного в статье, базируется на внедрении системного (целостного) подхода для изучения индивидуальных конституциональных (психических и физических) особенностей педагогов и студентов-медиков в связи с обучением и дальнейшей профессиональной деятельностью. Результаты. В статье проанализированы современные тенденции и проблемные вопросы образовательного процесса в педагогике и андрагогике, обусловленные технологическим прогрессом, развитием цифровых технологий, дистанционных видов и форм обучения, формированием так называемого «цифрового поколения» студентов, требующие разработки и внедрения инновационных методологических подходов и методов в образовательный процесс подготовки специалистов в медицинских вузах. Продемонстрирована необходимость формирования не только интеллектуальных и коммуникативных компетенций в процессе овладения профессией, но и понятийно-логических схем клинического мышления с использованием метода семантического дифференциала. Показана роль конституциональных особенностей преподавателя и студента в подготовке будущих специалистов. Проиллюстрирована зависимость между профессиональными и личными качествами преподавателя высшей школы и обучающихся. Выводы. Применение интегративного подхода в значительной степени способствует повышению качества образовательного процесса при профессиональной подготовке будущего специалиста медицинского профиля