Static skin effect in organic metals

We have studied theoretically galvanomagnetic phenomena in layered conductors of organic origin with multi-sheet Fermi surface being of the form of a weakly corrugated cylinder and weakly corrugated planes. It is shown that in a strong magnetic field H unrestricted growth of the resistivity of such conductors with increasing H is accompanied by forcing current lines out to the specimen surface. The main dissipation mechanism of electron flows is charge carriers scattering by sample boundary even in bulk conductors whose thickness is larger than conduction electrons free path length l. In the case of the specular reflection at the surface the resistivity grows linearly with the magnetic field increasing

Вариационный вариант модели теплового пробоя слоя твердого диэлектрика при постоянном напряжении

An idealy structured  solid dielectric material formally has zero electrical conductivity (later on "conductivity") and does carry an electric current. However real materials, used as solid dielectrics, have relatively low, but still finite conductivity, which, generally, increases with increasing temperature. Conductivity of solid dielectrics versus temperature corresponds to the exponential function, which by sight corresponds to the formula for Boltzmann distribution of microparticles in energy levels.In case there is a constant difference of potentials on the dielectric layer surfaces an electric current flows through this layer, causing Joule heat, which, under steady-state conditions, should be removed to the external environment. Inadequate heat removal rate leads to increasing temperature of dielectric, its increasing conductivity and electric current density, thereby increasing the volumetric capacity of the energy release  in the dielectric, i.e. a positive feedback effect occurs to cause a quick growth of temperature culminating in the heat destruction of dielectric material (melting, carbonization). This process is called heat breakdown of the dielectric, apart from the electric breakdown.Investigation of conditions for emerging dielectric heat breakdown is associated with the analysis of rather complicated nonlinear mathematical model that permits an analytical solution in a closed form only for a flat or cylindrical dielectric layer through simplifying a dependence of dielectric conductivity on the temperature. In this paper, the model is assigned to a variational form that contains a functional. An analysis of stationary points of this functional allows us to find a combination of parameters that determine the ultimate state of the dielectric layer before the heat breakdown, in particular so-called breakdown voltage.Материал твердого диэлектрика с идеальной структурой формально имеет нулевую электропроводность (далее будем использовать термин "проводимость") и не пропускает электрический ток. Но применяемые в качестве твердых диэлектриков реальные материалы обладают сравнительно малой, но все же конечной проводимостью, которая обычно увеличивается с ростом температуры. Зависимость проводимости твердых диэлектриков от температуры соответствует экспоненциальной функции, по виду совпадающей с формулой для распределения Больцмана микрочастиц по уровням энергии.В случае постоянной разности потенциалов на поверхностях слоя диэлектрика через этот слой проходит электрический ток, вызывая выделение джоулевой теплоты, которая при установившемся режиме работы должна быть отведена во внешнюю среду. Недостаточная интенсивность теплоотвода приводит к росту температуры диэлектрика, увеличению его проводимости и плотности электрического тока, что увеличивает объемную мощность энерговыделения в диэлектрике, т.е. возникает положительная обратная связь, в силу которой происходит быстрый рост температуры, завершающийся тепловым разрушением материала диэлектрика (расплавлением, науглероживанием). Такой процесс носит название теплового пробоя диэлектрика в отличие от пробоя электрического.Исследование условий возникновения теплового пробоя диэлектрика связано с анализом достаточно сложной нелинейной математической модели, допускающей аналитическое решение в замкнутой форме лишь для плоского или цилиндрического слоя диэлектрика путем упрощения зависимости проводимости диэлектрика от температуры. В данной работе этой модели поставлена в соответствие вариационная форма, содержащая функционал, анализ стационарных точек которого позволяет установить сочетание параметров, определяющих предельное состояние слоя диэлектрика перед тепловым пробоем, в частности так называемое пробивное напряжение

Concentration of the combined drag with antimicrobic and antiinflammatory action in rabbits eye anterior chamber at local introduction

Aim was to research objective consisted in an assessment of penetration of an antibacterial preparation of ciprofloxacin and a corticosteroid preparation of dexamethasone as a part of Kombinil-Duo’s combined medicinal form in moisture of the forward camera of an eye in experiment, and also in detection of the minimum overwhelmingconcentration (MOC) of ciprofloxacin in VPKG for the most frequent causative agents of eye infections.Material and methods. In experiment on seven adult individuals of rabbits of breed the Chinchilla (fourteen eyes) eye drops Kombinil — Duo, containing in quality of the main substance ciprofloxacin (3 mg / ml) and dexamethasone(1 mg / ml) are tested. Determination of concentration of the main substances of studied preparations in moisture of the eye camera carried out a method of a highly effective liquid chromatography (VEZhH) in combination with mass and spectrometer detecting (MS) on the liquid Shimadzu LC-20AB chromatograph with the mass and selectivedetector Shimadzu LCMS-2010EV (ESI).Results and conclusion. The maximum concentration of ciprofloxacin in moisture of the forward camera of rabbits eye made 0,25 mkg / ml, and minimum — 0,06 mkg / ml, average concentration — 0,13±0,06 mkg / ml. The anti-inflammatory component presented by dexamethasone in a studied eye form, is defined in the range from 0,14 to 0,63 mkg / ml. Average concentration of dexamethasone equaled 0,24±0,12 mkg / ml. The obtained data testify that average concentration of ciprofloxacin in VPKG exceeds average MPK90 for strains the grampolozhitelnykhof bacteria which are potential activators of postoperative infectious complications: metitsillinchuvstvitelny golden стафилококки (MPK90‑0,06 mkg / ml) and ftorkhinolonchuvstvitelny koagulazonegativny стафилококки (mkg / ml MPK90–0,05). The revealed concentration are sufficient for minimization of risk of development of postoperativeinfectious complications. In a pilot study it is shown that at an instillation in a conjunctival bag of rabbits of a complex preparation of Kombinil-Duo in moisture of the forward camera of an eye concentration of antibacterial means (ciprofloxacin) sufficient for suppression of the main activators causing postoperative complications with ensuring antiinflammatory action (at the expense of dexamethasone) is created. The obtained data can be used in clinical practice for correction of schemes on treatment and prevention of inflammatory diseases of eyes

Mesoporous Layered Double Hydroxides: Synthesis for High Effective Uranium Ions Sorption from Seawater and Salt Solutions on Nanocomposite Functional Materials

A series of sorption materials based on layered double hydroxides (Co-Fe LDH, Ni-Fe LDH, and Zn-Ti LDH) were obtained by a facile and environmentally friendly method of coprecipitation. A low particle size of no more than 10 µm was achieved. The use of transition metals makes it possible to obtain compounds that are mechanically and chemically stable in aggressive environments. XRD analysis revealed that the compounds have a highly organized crystalline structure. Using SEM, it was determined that Co-Fe LDH and Ni-Fe LDH had a loose, highly dispersed surface structure, while Zn-Ti LDH had a monolithic surface structure. U(VI) adsorption on the obtained materials in solutions containing Na2CO3, Na2SO4, KNO3, NaCl, K3PO4, and NaHCO3, was studied in batch mode. The degree of purification in the presence of these salts reached 99.9%, while the distribution coefficient Kd reached 105 mL/g. Sorption capacity qmax and equilibrium adsorption constants Kf and KL for U(VI) adsorption in batch mode (for 24 h) from distilled and seawater were determined using the Freundlich and Langmuir equations. The highest sorption capacity of 101.6 mg/g in seawater and 114.1 mg/g in distilled water was registered for Co-Fe-LDH. The presence of competing ions in seawater can reduce sorption efficiency by up to 40%. The provided research allowed us to conclude that the obtained materials, Co-Fe LDH, Ni-Fe LDH, and Zn-Ti LDH are promising for the sorption removal of U(VI) from aqueous media of medium salinity