Axisymmetric solitary waves on the surface of a ferrofluid

We report the first observation of axisymmetric solitary waves on the surface of a cylindrical magnetic fluid layer surrounding a current-carrying metallic tube. According to the ratio between the magnetic and capillary forces, both elevation and depression solitary waves are observed with profiles in good agreement with theoretical predictions based on the magnetic analogue of the Korteweg-deVries equation. We also report the first measurements of the velocity and the dispersion relation of axisymmetric linear waves propagating on the cylindrical ferrofluid layer that are found in good agreement with theoretical predictions.Comment: to be published in Phys. Rev. Let

Elongation of confined ferrofluid droplets under applied fields

Ferrofluids are strongly paramagnetic liquids. We study the behavior of ferrofluid droplets confined between two parallel plates with a weak applied field parallel to the plates. The droplets elongate under the applied field to reduce their demagnetizing energy and reach an equilibrium shape where the magnetic forces balance against the surface tension. This elongation varies logarithmically with aspect ratio of droplet thickness to its original radius, in contrast to the behavior of unconfined droplets. Experimental studies of a ferrofluid/water/surfactant emulsion confirm this prediction.Comment: 12 pages, 7 figures. Submitted to Phys. Rev.

Instability of the origami of a ferrofluid drop in a magnetic field

Capillary origami is the wrapping of an usual fluid drop by a planar elastic membrane due to the interplay between capillary and elastic forces. Here, we use a drop of magnetic fluid whose shape is known to strongly depend on an applied magnetic field. We study the quasi-static and dynamical behaviors of such a magnetic capillary origami. We report the observation of an overturning instability that the origami undergoes at a critical magnetic field. This instability is triggered by an interplay between magnetic and gravitational energies in agreement with the theory presented here. Additional effects of elasticity and capillarity on this instability are also discussed.Comment: in press in PRL (2011

SPECIFIC FEATURES OF ELECTROENCEPHALOGRAPHIC PAROXYSMAL ACTIVITY REGISTRATION IN OLD AGE GROUP PATIENTS

The differential diagnosis of epilepsy and other paroxysmal states mimicking this condition is very important in the daily activity of a neurologist (an epileptologist) since diagnostic accuracy directly ensures the efficacy and safety of treatment. According the data available in the literature, both overdiagnosis of epilepsy (20–25 % of all new diagnosed cases) and its underdiagnosis (as high as 10 %) are frequent diagnostic errors. Such errors are most commonly related to the misinterpretation of electrophysiological evidence in both young patients (in whom paroxysmal phenomena are a result of functional immaturity of brain structures) and elderly patients (in whom paroxysmal activity is a consequence of the development of degenerative processes in the neurons).Objective: to show examples of electroencephalographic (EEG) paroxysmal activity in old age group patients suffering from non-epileptic paroxysms.Now EEG investigation is a highly sensitive technique that requires a physician’s knowledge of neuroanatomy and neurophysiology to correct interpretation of the findings. Non-epileptiform paroxysmal events may be detected not only in children who have immature cerebral cortical neurons and median brainstem structures, but also in the elderly in whom their emergence is due to the development of degenerative processes in the neurons. The similarity of these phenomena with typical EEG epileptiform patterns is not coincidental. The basis for their occurrence is the similar mechanism for glutamate excitotoxicity, but, unlike epilepsy, which is triggered by ischemic and hypoxic processes, rather than by the exhausted reserve abilities of nerve cells during overstimulation. Therefore the detection of this pathological EEG paroxysmal activity calls for careful differential diagnosis

Characterization of Alternanthera mosaic virus and its Coat Protein

A new isolate of Alternanthera mosaic virus (AltMV-MU) was purified from Portulaca grandiflora plants. It has been shown that the AltMV-MU coat protein (CP) can be efficiently reassembled in vitro under different conditions into helical RNA-free virus-like particles (VLPs) antigenically related to native virus. The AltMV-MU and VLPs were examined by atomic force and transmission electron microscopies. The encapsidated AltMV-MU RNA is nontranslatable in vitro. However, it can be translationally activated by CP phosphorylation or by binding to the TGB1protein from the virus-coded movement triple gene block

Lutetium oxide analysis by direct arc atomic emission spectrometry

Ортосиликат лютеция является перспективным сцинтилляционным материалом, оптические свойства которого напрямую зависят от его примесного состава. Требования к исходным оксидам, используемым для выращивания кристаллов состава Lu2SiO5:Ce достаточно жесткие: содержание основного вещества Lu2O3 – 99.999 % мас. Критическими являются красящие примеси: Fe, Ni, Cr, Co, Cu, V и Mn, содержание каждого из которых должно быть не более 0.0005 – 0.0010 % мас., Pr, Nd, Sm, Er, Tb, Yb – не более 0.0005 % мас. каждого. Также необходимо контролировать содержние Al, As, Bi, Cd, Ce, Dy Eu, Gd, Ho, La, Mg, Mo, Pb, Sb, Sc, Si, Sn, Tm. Ti, Zn, Y. Для определения примесного состава оксида лютеция одним из перспективных методов анализа является дуговая атомно-эмиссионная спектрометрия. Преимуществами данного метода являются анализ химического состава без перевода пробы в раствор и широкий диапазон определяемых концентраций (10-6 – 10-1 % мас.). Для реализации потенциальных аналитических возможностей метода исследованы следующие условия эксперимента: межэлектродное расстояние, форма и размер графитовых электродов, соотношение оксида лютеция и спектрального буфера (графитовый порошок), тип носителей (соединений, влияющих на испарение аналитов), режимы работы генератора. Для большинства элементов нижняя граница диапазона определяемых концентраций находится в интервале n∙10-6 – n∙10-4 % мас., что значительно ниже, чем в действующих методиках прямого дугового атомно-эмиссионного анализа. Контроль правильности результатов, которые были получены по разработанной методике, осуществлен с использованием метода масс-спектрального анализа с индуктивно связанной плазмой. Благодаря результатам, полученным с помощью современного спектрального оборудования и программных средств, разработана методика анализа оксида лютеция без предварительного растворения пробы, с улучшенными метрологическими показателями и расширенным кругом определяемых примесей по сравнению со стандартизованной методикой.The requirements for the composition of initial oxides for the lutetium orthosilicate crystals are quite stringent: the content of the basic substance Lu2O3 is 99.999 wt%. Critical are coloring impurities: Fe, Ni, Cr, Co, Cu, V, Mn, the content of each should be no more than 0.0005 - 0.0010 wt%, Pr, Nd, Sm, Er, Tb, Yb no more than 0.0005 wt% for each one. It is also necessary to control the content of Al, As, Bi, Cd, Mg, Mo, Pb, Sb, Si, Sn, Ti, Zn, Y, La, Ce, Sc, Eu, Gd, Dy, Ho, Tm. To determine the impurity composition of lutetium oxide, one of the promising methods of analysis is direct arc atomic emission spectroscopy (DC Arc). The advantages of this method are the determination of the chemical composition without sample dissolution, a wide range of concentrations (10-6 - 10-1% wt%), a large number of determined elements. To realize the potential analytical capabilities of the method, the experimental conditions were studied: the interelectrode distance, the shape and size of graphite electrodes, the ratio of Lu2O3 to the spectral buffer, the type of carriers and operating modes of the generator. For most elements, the limits of determination are n ∙ 10-6 - n ∙ 10-4 wt%, that is significantly lower than in the current methods of DC Arc. The trueness of results is controlled by ICP-MS. The complex application of new approaches and modern capabilities of spectral equipment made it possible to develop a method with improved metrological characteristics.Исследование выполнено за счет гранта Российского научного фонда (проект № 20-13-00180). Исследования проводились с использованием оборудования ЦКП ФМИ ИОНХ РАН.The study was supported by the grant from the Russian Science Foundation (project No. 20-13-00180). This research was performed using the equipment of the JRC PMR IGIC RAS

Половые различия в про- и антиоксидантной системах головного мозга в отдаленном постреанимационном периоде (экспериментальное исследование)

Objective: to study gender differences in the pro- and antioxidant systems of the brain in the late postresuscitative period after clinical death. Materials and methods. The brain tissue was studied for the resistance of membrane structures to free radical oxidation and the level of proteins with antioxidant activity in 40 adult albino rats of both sexes in the control and after experienced 12-minute cardiac arrest 4 months of the postresuscitative period. Results. There were gender differences in the level of protective proteins and in the resistance of brain membrane structures in the control and in the late postresuscitative periods. Furthermore, not only quantitative changes in the level of protective proteins, but also their spectrum alteration, were revealed in the postresuscitative period. Conclusion. Further investigations of gender-dependent mechanisms for the occurrence of postresuscitative diseases are needed to develop specific methods for its therapy and prevention. Key words: systemic circulatory arrest; cerebral cortex; free radical oxidation; the body’s protective systems: antioxidant defense enzymes, HSP70, heme oxygenase-1, peroxiredoxin.Цель исследования — изучение половых различий в уровне про- и антиоксидантных систем мозга в отдаленном постреанимационном периоде после клинической смерти. Материал и методы. У 40 взрослых белых крыс обоего пола в контроле и после перенесённой 12-мин остановки сердца через 4 месяца постреанимационного периода в ткани мозга исследовали резистентность мембранных структур к свободнорадикальному окислению и уровень белков с антиокси-дантной активностью. Результаты. Показаны половые различия в уровне защитных белков и резистентности мембранных структур мозга в контроле и на отдаленных сроках после реанимации. Кроме того, в постреанимационный период выявлены не только количественные сдвиги в уровне защитных белков, но и изменение их спектра. Заключение. Необходимы дальнейшие исследования зависимых от пола молекулярных механизмов развития постреанимационной болезни для разработки специфических методов ее терапии и профилактики. Ключевые слова: остановка системного кровообращения, кора головного мозга, свободнорадикальное окисление, защитные системы организма — ферменты антиоксидантной защиты, HSP70, гем-оксигеназа-1, пероксиредоксин

Cathode fall characteristics in a dc atmospheric pressure glow discharge

Copyright 2003 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the authors and the American Institute of Physics. This article appeared in the Journal of Applied Physics and may be found at: http://link.aip.org/link/?JAPIAU/94/5504/1Atmospheric pressure glow discharges are attractive for a wide range of material-processing applications largely due to their operation flexibility afforded by removal of the vacuum system. These relatively new atmospheric plasmas are nonequilibrium plasmas with gas temperature around 100 °C and electron temperature in the 1–10 eV range. Their appearance is characteristically diffuse and uniform, and their temporal features are repetitive and stable. Of the reported numerical studies of atmospheric glow discharges, most are based on the hydrodynamic approximation in which electrons are assumed to be in equilibrium with the local electric field. Spectroscopic and electrical measurements suggest however that the cathode fall region is fundamentally nonequilibrium. To this end we consider a hybrid model that treats the cathode fall region kinetically but retains a hydrodynamic description for the region between the thin cathode fall layer and the anode. Using this hybrid model, a helium discharge system excited at dc is studied numerically for a very wide current density range that spans from Townsend dark discharge, through normal glow discharge, to abnormal glow discharge. Numerical results confirm many distinct characteristics of glow discharges and compare well with that of low-pressure glow discharges. Generic relationships, such as that between the electric field and the current density, are also established and are in good agreement with experimental data. This hybrid model is simple and insightful as a theoretical tool for atmospheric pressure glow discharges

ЧИСЛЕННЫЕ РЕШЕНИЯ ДЛЯ СОБСТВЕННЫХ МОД АБСОЛЮТНОЙ ПАРАМЕТРИЧЕСКОЙ РАСПАДНОЙ НЕУСТОЙЧИВОСТИ НЕОДНОРОДНОЙ ПЛАЗМЫ НА НЕЛИНЕЙНОЙ СТАДИИ

A mathematical model for the nonlinear absolute decay parametric instability of inhomogeneous plasma is developed. Decay of the Langmuir pump wave on the Langmuir and ion-acoustic waves is considered in detail. The numerical solutions describing the eigen modes of the instability are obtained. It is shown that at the nonlinear stage of the instability, a depletion of a pump wave and a broadening of an ion-acoustic wave spectrum are observed. The simulation results are in agreement with the experimental ones.Создана математическая модель, описывающая нелинейную абсолютную параметрическую неустойчивость в неоднородной плазме. Подробно рассмотрен распад ленгмюровской волны накачки на ленгмюровскую и ионно- звуковую волны. Получены численные решения, описывающие собственные моды неустойчивости. Показано, чтов нелинейной стадии неустойчивости наблюдается истощение накачки и уширение спектра ионно-звуковой волны. Результаты численных расчетов согласуются с экспериментальными результатами