Charged dust and shock phenomena in the Solar System

International audienceThe results on shock phenomena in dusty plasmas of the Solar System are reviewed. The problems of dust ion acoustic bow shock in interaction of the solar wind with dusty cometary coma and formation of transient atmospheres of atmosphereless cosmic bodies such as Moon, Mercury, asteroids and comets are considered. The latter assumes the evolution of meteoroid impact plumes and production of charged dust grains due to the condensation of both the plume substance and the vapor thrown from the crater and the surrounding regolith layer. Physical phenomena occurring during large meteoroid impacts can be modeled with the aid of active rocket experiments, which involve the release of some gaseous substance in near-Earth space. New vistas in investigation of shock processes in natural dusty plasmas are determined

The effect of fission-energy Xe ion irradiation on the structural integrity and dissolution of the CeO2_2 matrix

© 2016 The Authors.This work considers the effect of fission fragment damage on the structural integrity and dissolution of the CeO₂ matrix in water, as a simulant for the UO₂ matrix of spent nuclear fuel. For this purpose, thin films of CeO₂ on Si substrates were produced and irradiated by 92 MeV 129Xe23+ ions to a fluence of 4.8 × 1015 ions/cm2 to simulate fission damage that occurs within nuclear fuels along with bulk CeO₂ samples. The irradiated and unirradiated samples were characterised and a static batch dissolution experiment was conducted to study the effect of the induced irradiation damage on dissolution of the CeO₂ matrix. Complex restructuring took place in the irradiated films and the irradiated samples showed an increase in the amount of dissolved cerium, as compared to the corresponding unirradiated samples. Secondary phases were also observed on the surface of the irradiated CeO₂ films after the dissolution experiment.The irradiation experiment was performed at the Grand Accélérateur National d’Ions Lourds (GANIL) Caen, France, and supported by the French Network EMIR. The support in planning and execution of the experiment by the CIMAP-CIRIL and the GANIL staff, especially, I. Monnet, C. Grygiel, T. Madi and F. Durantel is much appreciated. Thanks are given to I. Buisman and M. Walker from the Department of Earth Sciences, University of Cambridge for help in conducting electron probe microanalysis and polishing the samples, respectively. A.J. Popel acknowledges funding from the UK EPSRC (grant EP/I036400/1 and EP/L018616/1) and Radioactive Waste Management Ltd (formerly the Radioactive Waste Management Directorate of the UK Nuclear Decommissioning Authority, contract NPO004411A-EPS02)

Ion-Acoustic Solitons in Bi-Ion Dusty Plasma

The propagation of ion-acoustic solitons in a warm dusty plasma containing two ion species is investigated theoretically. Using an approach based on the Korteveg-de-Vries equation, it is shown that the critical value of the negative ion density that separates the domains of existence of compressi- on and rarefaction solitons depends continuously on the dust density. A modified Korteveg-de Vries equation for the critical density is derived in the higher order of the expansion in the small parameter. It is found that the nonlinear coefficient of this equation is positive for any values of the dust density and the masses of positive and negative ions. For the case where the negative ion density is close to its critical value, a soliton solution is found that takes into account both the quadratic and cubic nonlinearities. The propagation of a solitary wave of arbitrary amplitude is investigated by the quasi-potential method. It is shown that the range of the dust densities around the critical value within which solitary waves with positive and negative potentials can exist simultaneously is relatively wide.Comment: 17 pages, 5 figure

Energy resolution and efficiency of phonon-mediated Kinetic Inductance Detectors for light detection

The development of sensitive cryogenic light detectors is of primary interest for bolometric experiments searching for rare events like dark matter interactions or neutrino-less double beta decay. Thanks to their good energy resolution and the natural multiplexed read-out, Kinetic Inductance Detectors (KIDs) are particularly suitable for this purpose. To efficiently couple KIDs-based light detectors to the large crystals used by the most advanced bolometric detectors, active surfaces of several cm$^2$ are needed. For this reason, we are developing phonon-mediated detectors. In this paper we present the results obtained with a prototype consisting of four 40 nm thick aluminum resonators patterned on a 2$\times$2 cm$^2$ silicon chip, and calibrated with optical pulses and X-rays. The detector features a noise resolution $\sigma_E=154\pm7$ eV and an (18$\pm$2)$\%$ efficiency.Comment: 5 pages, 5 figure

Structural trace of adaptation in motive nuclei of spinal cord of rats in hypokinesia and after physical loading in the recovery period

The purpose of this paper is to study the morphological changes of neurocytes in spinal cord of rats in hypokinesia and subsequent physical loading. Studies were performed on 55 laboratory rats of Wistar line. Materials of the research were the anterior horns of the gray matter of L5-S2 spinal segments. Preparations stained by Nissl and Viktorov were examined histologically. Hypokinesia was modeled following on the author’s technique. It was established that during prolonged hypokinesia in neurocytes of spinal cord of rats morphological changes in cell size and shape of the motor nuclei of all segments under study have been recorded. The number of hypochromic, hyperchromic destructively unchanged and hyperchromic destructively altered neurocytes increase; shadow cells appears, as well as cases of satellitosis and neuronophagia. Decrease in of albumen synthetical neurocyte function has been recorded. Physical loading of the average aerobic capacity leads to normalization of structural and functional state of neurocytes and enhances the reparative processes, as evidenced by a number of positive changes in morphometric parameters: increase in the number of normochromic neurocytes and decreasing the number of hyper- and hypochromic neurocytes with destructive signs, absence of pyknotic forms. Morphological parameters of neurocytes and their nuclei after physical loading of average aerobic capacity do not differ from those in the control group of intact animals. In neurocytes of this group of rats RNA concentration increases by 12.6% compared to animals after prolonged hypokinesia. Neurocytes of spinal cord of rats after prolonged hypokinesia develop significant morphological changes which are characterized by emergence of a significant number of hyperchromic neurocytes with signs of destructive changes and shadow cells, as well as and hypochromic neurocytes with signs of destructive changes, reduction in size and change of shape of perikaryons of neurocytes and their nuclei. Morphological changes of neurocytes after prolonged hypokinesia are accompanied by violations of biosynthetic processes, as evidenced by RNA decrease in the cytoplasm of efferent neurocytes of spinal cord of rats. Physical loading of average aerobic capacity leads to normalization of structural and functional state of neurocytes and promotes the reparative processes suported by positive changes in morphometric parameters

Effect of Heat Treatment of a Melt on the Structure and Properties of the Corresponding Crystalline Ingots or Castings

Abstract: The modern concepts of the structure of liquid metals and alloys are considered. Several types of microinhomogeneity and microheterogeneity are shown to exist in liquid metal solutions. Their structural state changes as a result of variations in composition, history, temperature, and pressure or the influence of various external actions. Upon subsequent cooling at an appropriate rate, these changes can persist up to liquidus and affect the structure and properties of the solidified alloy. The main attention is paid to the influence of the heating temperature of a liquid metal. For aluminum-based alloys, the possibility of developing the optimum heat-treatment conditions for melting using the results of studying the structure and properties of melts has been shown. This optimized heat treatment of melts is shown to be an effective method to improve the quality of alloys. © 2020, Pleiades Publishing, Ltd

Optimizing Technological Parameters of the Reduction Processes in Treating Steels in a Ladle Furnace

This work reports the possible development of reduction processes when treating the molten metal and slag using a ladle furnace under conditions of intensive stirring with an inert gas. The industrial data have been received, confirming the possibility of decreasing the concentration of ferrous and manganese oxides in the slag and stabilizing the contents of manganese and silicon in the metal