Сорбция радионуклидов 137Cs, 85Sr и 60Co из модельных растворов жидких радиоактивных отходов низкой активности модифицированными горючими сланцами

The results of the study of cesium, strontium, cobalt radionuclides sorption from model solutions simulating liquid radioactive waste on promising sorbents based on thermally modified oil shale are presented. The dependency of texture parameters obtained from the results of nitrogen adsorption-desorption on the treatment method of oil shale and their relationship to sorption parameters such as distribution coefficient and removal efficiency was discussed. Understanding how pore characteristics affect the sorption activity of such complex systems as sorbents is important for the creation of radionuclide sorption materials with improved characteristics. The efficiency of sorption of cesium, strontium and cobalt radionuclides was rather high for sorbent samples: the distribution coefficient was about 103–104 ml/g with a removal efficiency of more than 66 %. The most effective sorbent was obtained from oil shale with a heating rate of 5 deg/min without subsequent steam treatment, which is recommended to be used for low-active radioactive waste treatment.Представлены результаты исследования сорбции радионуклидов цезия, стронция и кобальта перспективными сорбентами на основе термически модифицированных горючих сланцев из растворов, моделирующих жидкие радиоактивные отходы. На основании результатов низкотемпературной адсорбции–десорбции азота установлена зависимость текстурных параметров исследуемых сорбентов от метода обработки горючего сланца, а также описана зависимость эффективности сорбции (по величинам сорбции и коэффициента распределения) радионуклидов от текстурных параметров сорбентов. Понимание того, каким образом характеристики пор оказывают влияние на сорбционную активность таких сложных систем, как сорбенты, важно для создания высокоэффективных сорбционных материалов с усовершенствованными характеристиками. Установлено, что материалы на основе модифицированного горючего сланца сорбируют радионуклиды цезия, стронция, кобальта с высокой эффективностью: коэффициенты распределения каждого радионуклида составляют 103–104 мл/г при степени извлечения более 66 %. Наибольшую эффективность проявляет сорбент, полученный из горючего сланца при нагреве со скоростью 5 град/ мин без последующей обработки паром. Данный сорбент рекомендован к применению для очистки жидких радиоактивных отходов низкой активности от радионуклидов цезия, стронция, кобальта

Study of aging properties of a wire chamber operating with high-pressure hydrogen

Abstract The project for a precision measurement of the mp-capture rate (mCAP experiment) is based on an application of a multi-wire proportional chamber (MWPC) operating in ultra-pure hydrogen at 10 bar pressure. A special test setup was constructed at PNPI to investigate the MWPC performance under the expected experimental conditions. The aging studies of the MWPCs were performed with intense irradiation from an a-source ð 241 AmÞ and a b-source ð 90 SrÞ: After 45 days of continuous irradiation by a-particles no changes in the currents, in the signal shapes, and in the counting rates were observed. It was demonstrated that the MWPCs can operate without degradation at least up to accumulated charges of 0:1 C=cm wire. These irradiation conditions are much more severe than in the real experiment. During the study of the MWPC we have observed an appearance of short duration signals with amplitudes an order of magnitude larger than those of normal signals from the a-particles. The number of such signals (''streamers'') strongly depend on HV. We shall continue these tests in the future with the goal of obtaining more detailed information about aging properties of MWPCs operating with high-pressure hydrogen.

Study of aging properties of a wire chamber operating with high-pressure hydrogen

The project for a precision measurement of the µp-capture rate (µCAP experiment) is based on an application of a multi-wire proportional chamber (MWPC) operating in ultra-pure hydrogen at 10 bar pressure. A special test setup was constructed at PNPI to investigate the MWPC performance under the expected experimental conditions. The aging studies of the MWPCs were performed with intense irradiation from an alpha-source (Am 241 ) and a beta-source (Sr 90 ). After 45 days of continuous irradiation by alpha-particles no changes in the currents, in the signal shapes, and in the counting rates were observed. It was demonstrated that the MWPCs can operate without degradation at least up to accumulated charges of 0.1 C/cm wire. These irradiation conditions are much more severe than in the real experiment. During the study of the MWPC we have observed an appearance of short duration signals with amplitudes an order of magnitude larger than those of normal signals from the alpha-particles. The number of such signals ("streamers") strongly depend on HV. We shall continue these tests in the future with the goal of obtaining more detailed information about aging properties of MWPCs operating with high-pressure hydrogen

Получение мезопористого кремнезема с упорядоченной наноструктурной морфологией из природного кварцевого песка

Silica with ordered nanostructured morphology characteristic of mesoporous molecular sieves with cubic packing of cylindrical pores and a three-dimensional porous structure is obtained from natural quartz sand. It was shown by X-ray diffraction, scanning electron microscopy, and low-temperature nitrogen adsorption-desorption that the obtained silica material is thermally stable, amorphous, consists of submicron grains, has a high specific surface area of 1396 m2/g, a pore volume of 0.780 cm3/g and an average diameter of 2.2 nm with a narrow size distribution of mesopores.Из природного кварцевого песка получен кремнезем с упорядоченной наноструктурной морфологией, характерной для мезопористых молекулярных сит с кубической упаковкой цилиндрических пор и трехмерной пористой структурой. Методами рентгеновской дифракции, сканирующей электронной микроскопии и низкотемпературной адсорбции-десорбции азота показано, что полученный кремнеземный материал термически стабилен, аморфен, состоит из зерен субмикронного размера, обладает высокой удельной поверхностью 1396 м2/г, объемом пор 0,780 см3/г и средним диаметром 2,2 нм с узким распределением мезопор по размеру

Professional English for the students of Electronic Education Institute in specialty of «Informatics and Computer Technologies»

Пособие предназначено для студентов 3 курса ИнЭО, изучающих профессиональный курс английского языка по направлению 09.03.01 «Информатика и вычислительная техника»

Текстурные свойства упорядоченного нанопористого кремнезема, синтезированного на мезогенном темплате

Several synthesis routes have been developed and correlations between the variables of the synthesis procedure and the physicochemical properties of nanoporous silica materials of the MCM-48 type deposited by the template method in the presence of a low-valent iron (II) cation have been investigated. Changes in the structure of silica mesoporous framework, its textural properties and the degree of energy inhomogeneity of the surface were studied depending on the Fe/Si molar ratio, pH values (4 and 9 units), stepwise calcination (673 and 923 K) and extraction of cetylpyridinium template with ethanol from xerogels. Разработано несколько путей синтеза и исследованы корреляции между переменными процедуры синтеза и физико-химическими свойствами нанопористых кремнеземных материалов типа MCM-48, осаждаемых темплатным методом в присутствии низковалентного катиона железа(II). Изучено изменение структуры мезопористого каркаса кремнезема, его текстурных свойств и степени энергетической неоднородности поверхности в зависимости от молярного соотношения Fe :Si, значения рН (4 и 9 единиц), ступенчатого прокаливания (673 и 923 К) и экстракции цетилпиридиниевого темплата этанолом из ксерогелей.

Variational Foundations and Generalized Unified Theory of RVE-Based Multiscale Models

A unified variational theory is proposed for a general class of multiscale models based on the concept of Representative Volume Element. The entire theory lies on three fundamental principles: (1) kinematical admissibility, whereby the macro- and micro-scale kinematics are defined and linked in a physically meaningful way; (2) duality, through which the natures of the force- and stress-like quantities are uniquely identified as the duals (power-conjugates) of the adopted kinematical variables; and (3) the Principle of Multiscale Virtual Power, a generalization of the well-known Hill-Mandel Principle of Macrohomogeneity, from which equilibrium equations and homogenization relations for the force- and stress-like quantities are unequivocally obtained by straightforward variational arguments. The proposed theory provides a clear, logically-structured framework within which existing formulations can be rationally justified and new, more general multiscale models can be rigorously derived in well-defined steps. Its generality allows the treatment of problems involving phenomena as diverse as dynamics, higher order strain effects, material failure with kinematical discontinuities, fluid mechanics and coupled multi-physics. This is illustrated in a number of examples where a range of models is systematically derived by following the same steps. Due to the variational basis of the theory, the format in which derived models are presented is naturally well suited for discretization by finite element-based or related methods of numerical approximation. Numerical examples illustrate the use of resulting models, including a non-conventional failure-oriented model with discontinuous kinematics, in practical computations

Antiviral therapies against Ebola and other emerging viral diseases using existing medicines that block virus entry

Emerging viral diseases pose a threat to the global population as intervention strategies are mainly limited to basic containment due to the lack of efficacious and approved vaccines and antiviral drugs. The former was the only available intervention when the current unprecedented Ebolavirus (EBOV) outbreak in West Africa began. Prior to this, the development of EBOV vaccines and anti-viral therapies required time and resources that were not available. Therefore, focus has turned to re-purposing of existing, licenced medicines that may limit the morbidity and mortality rates of EBOV and could be used immediately. Here we test three such medicines and measure their ability to inhibit pseudotype viruses (PVs) of two EBOV species, Marburg virus (MARV) and avian influenza H5 (FLU-H5). We confirm the ability of chloroquine (CQ) to inhibit viral entry in a pH specific manner. The commonly used proton pump inhibitors, Omeprazole and Esomeprazole were also able to inhibit entry of all PVs tested but at higher drug concentrations than may be achieved in vivo. We propose CQ as a priority candidate to consider for treatment of EBOV

SPO11-Independent DNA Repair Foci and Their Role in Meiotic Silencing

In mammalian meiotic prophase, the initial steps in repair of SPO11-induced DNA double-strand breaks (DSBs) are required to obtain stable homologous chromosome pairing and synapsis. The X and Y chromosomes pair and synapse only in the short pseudo-autosomal regions. The rest of the chromatin of the sex chromosomes remain unsynapsed, contains persistent meiotic DSBs, and the whole so-called XY body undergoes meiotic sex chromosome inactivation (MSCI). A more general mechanism, named meiotic silencing of unsynapsed chromatin (MSUC), is activated when autosomes fail to synapse. In the absence of SPO11, many chromosomal regions remain unsynapsed, but MSUC takes place only on part of the unsynapsed chromatin. We asked if spontaneous DSBs occur in meiocytes that lack a functional SPO11 protein, and if these might be involved in targeting the MSUC response to part of the unsynapsed chromatin. We generated mice carrying a point mutation that disrupts the predicted catalytic site of SPO11 (Spo11YF/YF), and blocks its DSB-inducing activity. Interestingly, we observed foci of proteins involved in the processing of DNA damage, such as RAD51, DMC1, and RPA, both in Spo11YF/YFand Spo11 knockout meiocytes. These foci preferentially localized to the areas that undergo MSUC and form the so-called pseudo XY body. In SPO11-deficient oocytes, the number