AC Josephson properties of phase slip lines in wide tin films

Current steps in the current-voltage characteristics of wide superconducting Sn films exposed to a microwave irradiation were observed in the resistive state with phase slip lines. The behaviour of the magnitude of the steps on the applied irradiation power was found to be similar to that for the current steps in narrow superconducting channels with phase slip centers and, to some extent, for the Shapiro steps in Josephson junctions. This provides evidence for the Josephson properties of the phase slip lines in wide superconducting films and supports the assumption about similarity between the processes of phase slip in wide and narrow films.Comment: 7 pages, 2 figures, to be published in Supercond. Sci. Techno

Vortex manipulation in a superconducting matrix with view on applications

We show how a single flux quantum can be effectively manipulated in a superconducting film with a matrix of blind holes. Such a sample can serve as a basic memory element, where the position of the vortex in a [k x l] matrix of pinning sites defines the desired combination of n bits of information (2^n=k*l). Vortex placement is achieved by strategically applied current and the resulting position is read-out via generated voltage between metallic contacts on the sample. Such a device can also act as a controllable source of a nanoengineered local magnetic field for e.g. spintronics applications

Fiske Steps and Abrikosov Vortices in Josephson Tunnel Junctions

We present a theoretical and experimental study of the Fiske resonances in the current-voltage characteristics of "small" Josephson junctions with randomly distributed misaligned Abrikosov vortices. We obtained that in the presence of Abrikosov vortices the resonant interaction of electromagnetic waves, excited inside a junction, with the ac Josephson current manifests itself by Fiske steps in a current-voltage characteristics even in the absence of external magnetic field. We found that the voltage positions of the Fiske steps are determined by a junction size, but the Fiske step magnitudes depend both on the density of trapped Abrikosov vortices and on their misalignment parameter. We measured the magnetic field dependence of both the amplitude of the first Fiske step and the Josephson critical current of low-dissipative small $Nb$ based Josephson tunnel junctions with artificially introduced Abrikosov vortices. A strong decay of the Josephson critical current and a weak non-monotonic decrease of the first Fiske step amplitude on the Abrikosov vortex density were observed. The experimentally observed dependencies are well described by the developed theory.Comment: 21 pages, 7 figures, submitted to Physical Review

Observation of superluminal geometrical resonances in Bi2Sr2CaCu2O8+x intrinsic Josephson junctions

We study Fiske steps in small Bi2Sr2CaCu2O8+x mesa structures, containing only few stacked intrinsic Josephson junctions. Careful alignment of magnetic field prevents penetration of Abrikosov vortices and facilitates observation of a large variety of high quality geometrical resonances, including superluminal with velocities larger than the slowest velocity of electromagnetic waves. A small number of junctions limits the number of resonant modes and allows accurate identification of modes and velocities. It is shown that superluminal geometrical resonances can be excited by subluminal fluxon motion and that flux-flow itself becomes superluminal at high magnetic fields. We argue that observation of high-quality superluminal geometrical resonances is crucial for realization of the coherent flux-flow oscillator in the THz frequency range

Current-voltage characteristic of narrow superconducting wires: bifurcation phenomena

The current-voltage characteristics of long and narrow superconducting channels are investigated using the time-dependent Ginzburg-Landau equations for complex order parameter. We found out that the steps in the current voltage characteristic can be associated with bifurcations of either steady or oscillatory solution. We revealed typical instabilities which induced the singularities in current-voltage characteristics, and analytically estimated period of oscillations and average voltage in the vicinity of the critical currents. Our results show that these bifurcations can substantially complicate dynamics of the order parameter and eventually lead to appearance of such phenomena as multistability and chaos. The discussed bifurcation phenomena sheds a light on some recent experimental findings

Features of exogenous development of Trichuris globulosa (Nematoda, Trichuridae)

Parasitic nematodes of the genus Trichuris Röderer, 1761 are hematophagous helminths, capable of parasitizing many different hosts including humans. The domestic and wild ruminants are hosts of several Trichuris species, with Trichuris globulosa (Linstow, 1901) one of the most prevalent parasites found in cattle. The exogenous stages of the helminth’s life cycle develop in the outer environment, and their activity and survival depend on the abiotic factors. Thus the aim of the work was to determine the influence of temperature on the rate and success of development of infectious eggs of T. globulosa in laboratory culture considering their morphological and metric changes. The results of experimental studies showed that the embryogenesis of T. globulosa eggs, cultured in laboratory conditions and obtained from gonads of female nematodes, occurs in six stages regardless of the temperature regime. At the same time, the rate of transition from one stage to another, the term for the formation of infectious eggs and their viability directly depends on the temperature of the external environment. At the optimal temperature for the development of T. globulosa eggs, 25 °C, 76.3% of eggs reached the mobile larva stage. A decrease in temperature to 20 °C and an increase to 30° C led to an increase in the egg mortality of up to 26% and 32%, respectively, and the viability of eggs decreased. Under such temperature conditions, 74% and 68% of eggs of Trichuris reached the mobile larva stage. With an increase in the culture temperature, the time of embryogenesis decreased and amounted to 56 days at 20 °C, 48 days at 25 °C, and 32 days at 30 °C. Depending on the temperature regime, the zygote stage lasted from the release of eggs from the gonads of female nematodes to 12 days, the stage of blastomere formation from 4 to 12 days, the stage of the bean-shaped embryo from 8 to 24 days, the stage of the tadpole embryo from 16 to 36 days, the stage of larval formation lasted from 16 to 48 days, the stage of mobile larva from days 20 to 56. The formation of the infectious T. globulosa egg from a non-infectious one is shown in an experiment to include the metric changes confirmed by metric indicators. Mature eggs with a mobile larva are shorter and wider, with shorter and narrower plugs and a thinner shell than eggs at the zygote stage. The obtained research results on the influence of temperature on the exogenous development of Trichuris globulosa will make it possible to predict the epizootic situation of trichurosis in animal husbandry, as well as take timely measures to arrest the embryonic stages of nematode development in the external environment

Анализ состояния вопроса утилизации низкопотенциальных энергетических ресурсов на объектах малой энергетики

Studying the issues of recovery of low-potential energy at smallscale energy facilities allowed to show the promising character of the organic Rankine cycle (ORC) technology as a technology for recovery or conversion of low-potential energy.The most promising developments in the field of the use and recovery of waste heat are described regarding application of ORC, which is widely used in geothermal sources, hot water boilers, gas turbine plants. Due to the constantly growing diversity of working fluids, ORC can be used within a wide temperature range from 100°C to over 350°C. Also, developments are underway in the design of ORC generators to increase reliability of its individual system units, such as turbines and expanders. Based on the above factors, it can be concluded that with a deeper study of the problems of adopting ORC technologies, they can become a very promising direction in development of heat power engineering.It has been determined that the main factor hindering the widespread adoption of the ORC technology is associated with high cost of heat exchange equipment due to increased heat exchange surfaces. It is shown that design of mini power plants and energy centres based on the use of low-potential energy requires improvement of mathematical modelling methods to reliably determine operating modes and characteristics of each of the units. Methods for modelling evaporation and condensation systems, including turbines and expanders using organic low-boiling working fluids, should be considered among the methods that are highly sought after. The methods for selecting a working fluid for ORC devices also have a significant impact on characteristics of the installation determining the range of cycle operating temperatures and pressures. The solution of the above problems can lead to a reduction in the cost of heat exchange equipment, and, consequently, to a decrease in costs for design of ORC generators. В статье рассмотрены вопросы утилизации низкопотенциальных энергетических ресурсов на объектах малой энергетики. Показана перспектива использования технологии органического цикла Ренкина (ОЦР) в качестве технологии утилизации или преобразования низкопотенциальной энергии.Приведены разработки в области реализации и утилизации бросового тепла. Наиболее перспективные из них представлены в применении ОЦР, который широко используется на геотермальных источниках, в водогрейных котельных, газотурбинных установках. За счёт постоянного растущего сортамента рабочих тел ОЦР может применяться в широком температурном диапазоне, начиная от 100°С и заканчивая свыше 350°С. Также ведутся разработки в области проектирования ОЦР-генераторов с целью повышения надёжности отдельных узлов системы, таких как турбины и детандеры. Исходя из вышеперечисленных факторов, можно сделать вывод, что при более глубоком исследовании проблем внедрения ОЦР-технологий они могут стать весьма перспективным направлением в развитии теплоэнергетики.Определено, что основным фактором, препятствующим широкому внедрению ОЦР-технологии, является высокая стоимость теплообменного оборудования из-за повышенных теплообменных поверхностей. Показано, что проектирование миниэлектростанций и энергокомплексов на основе использования низкопотенциальной энергии требует совершенствования методов математического моделирования для достоверного определения режимов работы и характеристик каждого из агрегатов. К востребованным следует отнести методы моделирования испарительных и конденсационных систем, в том числе турбин и детандеров, работающих на органических низкокипящих рабочих телах. Методики выбора рабочего тела для ОЦР-устройств также оказывают существенное влияние на характеристики установки, которые определяют диапазон эксплуатационных температур и давлений цикла. Решение вышеуказанных задач способно привести к удешевлению теплообменного оборудования, а, следовательно, снижению издержек на проектирование ОЦР-генераторов.

Chronic valproic acid intoxication in epileptology: diagnosis and treatment

Valproic acid (VA) is used in epileptology for the basic and additional control of simple and complex focal seizures, absences, generalized tonicclonic seizures, and myoclonus. Information has been recently stored on cases of chronic overdosage of VA due to its blood accumulation. These conditions are described in the use of both high and average therapeutic doses of VA preparations in patients with a genetically determined delay in metabolism. The paper presents current methods for clinical and laboratory diagnosis and correction of chronic intoxication when valproic acid preparations are administered during the prehospital, hospital and rehabilitation phases of treatment. The authors note that a personalized approach is of importance for dose adjustment and prediction of unwanted adverse drug reactions associated with the use of VA preparations

Laser Scanning Microscopy of HTS Films and Devices

The work describes the capabilities of Laser Scanning Microscopy (LSM) as a spatially resolved method of testing high_Tc materials and devices. The earlier results obtained by the authors are briefly reviewed. Some novel applications of the LSM are illustrated, including imaging the HTS responses in rf mode, probing the superconducting properties of HTS single crystals, development of twobeam laser scanning microscopy. The existence of the phase slip lines mechanism of resistivity in HTS materials is proven by LSM imaging.Comment: 17 pages, 21 figures, Submitted to Fizika Nizkikh Temperatur (Low Temperature Physics