Strongly nonlinear dynamics of electrolytes in large ac voltages

We study the response of a model micro-electrochemical cell to a large ac voltage of frequency comparable to the inverse cell relaxation time. To bring out the basic physics, we consider the simplest possible model of a symmetric binary electrolyte confined between parallel-plate blocking electrodes, ignoring any transverse instability or fluid flow. We analyze the resulting one-dimensional problem by matched asymptotic expansions in the limit of thin double layers and extend previous work into the strongly nonlinear regime, which is characterized by two novel features - significant salt depletion in the electrolyte near the electrodes and, at very large voltage, the breakdown of the quasi-equilibrium structure of the double layers. The former leads to the prediction of "ac capacitive desalination", since there is a time-averaged transfer of salt from the bulk to the double layers, via oscillating diffusion layers. The latter is associated with transient diffusion limitation, which drives the formation and collapse of space-charge layers, even in the absence of any net Faradaic current through the cell. We also predict that steric effects of finite ion sizes (going beyond dilute solution theory) act to suppress the strongly nonlinear regime in the limit of concentrated electrolytes, ionic liquids and molten salts. Beyond the model problem, our reduced equations for thin double layers, based on uniformly valid matched asymptotic expansions, provide a useful mathematical framework to describe additional nonlinear responses to large ac voltages, such as Faradaic reactions, electro-osmotic instabilities, and induced-charge electrokinetic phenomena.Comment: 30 pages, 17 eps-figures, RevTe

Influence of intermartensitic transitions on transport properties of Ni2.16Mn0.84Ga alloy

Magnetic, transport, and x-ray diffraction measurements of ferromagnetic shape memory alloy Ni$_{2.16}$Mn$_{0.84}$Ga revealed that this alloy undergoes an intermartensitic transition upon cooling, whereas no such a transition is observed upon subsequent heating. The difference in the modulation of the martensite forming upon cooling from the high-temperature austenitic state [5-layered (5M) martensite], and the martensite forming upon the intermartensitic transition [7-layered (7M) martensite] strongly affects the magnetic and transport properties of the alloy and results in a large thermal hysteresis of the resistivity $\rho$ and magnetization $M$. The intermartensitic transition has an especially marked influence on the transport properties, as is evident from a large difference in the resistivity of the 5M and 7M martensite, $(\rho_{\mathrm{5M}} - \rho_{\mathrm{7M}})/\rho _{\mathrm{5M}} \approx 15$, which is larger than the jump of resistivity at the martensitic transition from the cubic austenitic phase to the monoclinic 5M martensitic phase. We assume that this significant difference in $\rho$ between the martensitic phases is accounted for by nesting features of the Fermi surface. It is also suggested that the nesting hypothesis can explain the uncommon behavior of the resistivity at the martensitic transition, observed in stoichiometric and near-stoichiometric Ni-Mn-Ga alloys.Comment: 7 pages, 6 figures, REVTEX

Mechanisms of Manganese-Assisted Nonradiative Recombination in Cd(Mn)Se/Zn(Mn)Se Quantum Dots

Mechanisms of nonradiative recombination of electron-hole complexes in Cd(Mn)Se/Zn(Mn)Se quantum dots accompanied by interconfigurational excitations of Mn$^{2+}$ ions are analyzed within the framework of single electron model of deep {\it 3d}-levels in semiconductors. In addition to the mechanisms caused by Coulomb and exchange interactions, which are related because of the Pauli principle, another mechanism due to {\it sp-d} mixing is considered. It is shown that the Coulomb mechanism reduces to long-range dipole-dipole energy transfer from photoexcited quantum dots to Mn$^{2+}$ ions. The recombination due to the Coulomb mechanism is allowed for any states of Mn$^{2+}$ ions and {\it e-h} complexes. In contrast, short-range exchange and ${\it sp-d}$ recombinations are subject to spin selection rules, which are the result of strong {\it lh-hh} splitting of hole states in quantum dots. Estimates show that efficiency of the {\it sp-d} mechanism can considerably exceed that of the Coulomb mechanism. The phonon-assisted recombination and processes involving upper excited states of Mn$^{2+}$ ions are studied. The increase in PL intensity of an ensemble of quantum dots in a magnetic field perpendicular to the sample growth plane observed earlier is analyzed as a possible manifestation of the spin-dependent recombination.Comment: 14 pages, 2 figure

Formation of memristor structures based on ZnO thin films by scratching probe nanolithography

This work was supported by Grant of the President of the Russian Federation No. MK-2721.2018.8. and by RFBR according to the research project № 18-37-0029

PROSPECTS AND RESULTS OF STUDYING THE COLLECTION OF CHICKPEA FROM VIR AT OMSK STATE AGRARIAN UNIVERSITY

In 2012-1016, 23 chickpea accessions from VIR and 23 accessions from the collection of chickpea somaclones of the Siberian Research Institute of Forages were studied at Omsk State Agrarian University. The research performed in the southern forest-steppe of West Siberia resulted in identifying chickpea accessions with a shorter growing season, high plant productivity, good processability, and high symbiotic activity. The possibility of using cluster analysis for comprehensive assessment of source material for chickpea breeding was demonstrated. The nature of inheritance of agronomic traits in F1 chickpea hybrids was revealed, and recommendations for selection were formulated. A correlation was established between the major characters

Formation of social and occupational youth mobility in project activities

The article introduces an experience of forming social and occupational mobility of students at pedagogical University during the project activityРассматривается опыт формирования социально-профессиональной мобильности студентов педагогического вуза в процессе проектной деятельност

ОСОБЛИВОСТІ ВИКЛАДАННЯ ХІМІЧНИХ ДИСЦИПЛІН ІНОЗЕМНИМ СТУДЕНТАМ В МЕДИЧНОМУ ВИЩОМУ НАВЧАЛЬНОМУ ЗАКЛАДІ

The article discusses the features of the educational process of chemical disciplines learning by foreign students. During the process of teching methods developing, such as teaching material in class; workshops; control of knowledge, it is necessary to take into account the characteristics of school education in countries from which the students come. It has been proved in practice that the development of quality guidelines, reference summaries, charts and tables that summarize the material, help foreign students with significant language problems to learn difficult material on themedical and bioorganic chemistry courses.У статті розглядаються особливості організації навчально процесу з викладання хімічних дисциплін іноземним студентам. Показана необхідність урахування особливостей шкільної освіти у країнах, з яких приїхали студенти, при розробці методів: викладання матеріалу на лекціях; проведення практичних занять; контролю знань. Доведено на практиці, що розробка якісних методичних вказівок, опорних конспектів, схем та таблиць, що узагальнюють матеріал, сприяють кращому засвоєнню складного та об’ємного матеріалу з курсів медичної та біоорганічної хімії іноземними студентами, що мають значні мовні проблеми

ПОРІВНЯЛЬНИЙ АНАЛІЗ КІРЛІАНОГРАФІЧНОГО СВІТІННЯ БІОЛОГІЧНОЇ ТКАНИНИ З БІОХІМІЧНИМИ ПРОЦЕСАМИ

Kirlian diagram samples Conducted. Achilles tendon dead people with various postmorbidnym period (from 5:0 until 22 days) and optoelectronics is part of the standard terms of the x-ray film developer. The results obtained were compared with biochemical indicators of the level of enzymes and content of degradation products of proteins, trace elements, derived from the investigated samples. For kirlianograficeskih studies used an experimental device, RIVERS 1, developed by Ukrainian Scientific Research Institute of mechanical engineering technologies (Dnepropetrovsk). For mathematical processing of results using Matlab program.The growing shortage of ATP causes the breach and termination of ion exchange, increases reactive oxygen generation, lipid peroxidation destroys cell membranes. The process of self digestion (autoliza) tissue tendons, as shown by the results of the experiments, had cyclical changes metabolism enzyme activity (ALT), carbohydrate (LDH), nucleotides, of total protein and micronutrients.Cравнивали кирлианографические изображения образцов и жидкой части ахиллова сухожилия разного по-стморбидного периода (от 5 часов до 22 суток) с показателями биохимических исследований в процессе аутолиза. Кирлианографию проводили на рентгеновской пленке. Использовали экспериментальный прибор «РЕК 1» (г. Днепропетровск). Процесс самопереваривания (аутолиза) тканей сухожилия, как показали результаты экспериментов, имел циклический характер изменения активности ферментов обмена аминокислот (АЛТ), углеводов (ЛДГ), нукле-отидов (мочевая кислота, мочевина), содержания общего белка и микроэлементов. Изменение площади засветки и фрактальности кирлиановских изображений также имело цикличный характер по давности аутолиза, что ображало характер энергетических изменений по содержанию взаимодействующих веществ.Порівняли кірліанографічне зображення зразків та рідини ахілового сухожилка різного постморбідного періоду (від 5 годин до 22 діб) із показниками біохімічних досліджень в процесі аутолізу. Кірліанографію проводили на рентгенівській плівці. Використовували експериментальний прилад «РЕК 1» (м. Дніпропетровськ). Процес саморуйнування тканин сухожилка, як показали результати експериментів, мав циклічний характер змінення активності ферментів обміну амінокислот (АЛТ), вуглеводів (ЛДГ), нуклеотидів (сечова кислота, сечовина), вмісту загального білка та мікроелементів. Зміни площі засвітки та фрактальності кірліанограм крапель біологічної речовини в процесі аутолізу також мали циклічність з часом, що віддзеркалювало характер енергетичних змін за вмістом речовин взаємодії

Acute hematogenous osteomyelitis of long tubular and flat bones in children

The clinical-statistical analysis of treatment and diagnostics effectiveness of long tubular and flat bones osteomyelitis in 119 children older than 6 months has been carried out. Polymorphism of osteomyelitis clinical picture of pelvic bones, anatomical features of their location and structure create difficulties for early diagnostics and rational treatment. The method of choice in complex diagnostics was computed tomography, that allowed to establish topical diagnosis in the early stages in 52.9% of cases of pelvic bones osteomyelitis, degree of bone destruction and its prevalence, to determine the treatment policy. Operative intervention was required for 90.8% of patients in acute phase of hematogenous osteomyelitis.Проведен клинико-статистический анализ результативности диагностики и лечения остеомиелита длинных трубчатых и плоских костей у 119 детей старше 6 месяцев. Полиморфизм клинической картины остеомиелита костей таза, анатомические особенности их расположения и строения создают трудности для ранней диагностики и рационального лечения. Методом выбора в комплексной диагностике явилась компьютерная томография, что позволило в 52,9% случаев остеомиелита костей таза в ранние сроки установить топический диагноз, степень деструкции кости и её распространенность, определить лечебную тактику. В острую фазу гематогенного остеомиелита оперативное вмешательство требовалось 90,8% больных