Experiments on the leak path factor of ruthenium volatilized from high-level liquid waste tanks in a reprocessing plant in case of the boiling and drying accident

In case of the boiling and drying accident of a high-level liquid waste (HLLW) tank, a large amount of ruthenium (Ru) will be volatilized. In order to suppress the release of radioactive materials to the environment, the vapor may be led to the neighboring cells in which it will contact with the cell walls to be partially condensed. To understand the behavior of Ru in this situation, we have prepared an experimental apparatus. It consists of a small tank in which 60 mL simulated HLLW is heated to dryness, a 9.6 L stainless steel box which mimics the neighboring cell accepting the vapor from the small tank, and a condenser where the vapor coming out from the box is cooled to collect the condensate. The results show that more than 99% of the volatilized Ru is removed from the vapor in the box if its temperature is below about 120 °C.     

Thiourea assisted one-pot easy synthesis of CdS/rGO composite by the wet chemical method: Structural,optical, and photocatalytic properties

We report on the synthesis of CdS/reduced graphene oxide (rGO) composite by a wet chemical method. Thiourea was used both as a sulfur source and as a reducing agent to convert graphene oxide to rGO. The structural and morphological confirmation for the reduction of graphene oxide and the formation of the CdS/rGO composite was demonstrated by X-ray diffractometry, Raman spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy analyses. Photoluminescence spectra of the composite exhibited a more efficient luminescence quenching in comparison with pure CdS nanoparticles. The composite demonstrated 99% photodegradation of methyl orange under UV irradiation, which is much superior than the photodegradation of methyl orange under similar conditions exhibited by CdS nanoparticles (72%).     

Rheology and pressure filtration of aqueous SiC suspensions of nanometer-sized bimodal particles

The consolidation behavior of mixed SiC particles (30 and 800 nm diameters) at pH 7 was examined using a developed pressure filtration apparatus at a constant crosshead speed of a piston. The addition of 30 nm SiC to 800 nm SiC changed the rheological properties of colloidal suspension from Newtonian to pseudoplastic flow through Bingham flow with increasing amount of 30 nm SiC. A phase transition from a well dispersed suspension to a flocculated suspension occurred when the applied pressure exceeded a critical pressure (ΔP_tc). The ΔP_tc value decreased with increasing amount of 30 nm SiC. The packing density of bimodal SiC particles was analyzed based on the partial molar volume of each powder. The larger particles were more densely packed than the smaller particles in the mixed powder compact.     

High-temperature creep and resultant anisotropy in ultrasonic velocity in isotropic graphite

Plastic deformation of isotropic graphite in the vicinity of 2500 °C was studied using an Instron-type testing machine. The load-deflection curve was found to show a proportional limit at high temperature. Creep curves of graphite were also measured and were simulated by an empirical equation based on parabolic creep. Following the creep tests, ultrasonic velocity in the elongated graphite was measured. The velocity showed 5%–20% decrease after the creep. Below 2500 °C, the rate of velocity decrease along the elongation axis was always larger than that across the elongation axis. Above 2500 °C, this behaviour was reversed with the rate of velocity decrease across the elongation axis being the larger. The rate of decrease appeared to depend firstly on temperature and secondly on stress.     

Growth mechanism of AlGaAs on terraced substrates by low pressure MOVPE

AlGaAs layers were grown on recessed GaAs substrates by MOVPE at 5 and 100 Torr. The two mechanisms, the gas phase diffusion through the stagnant layer and the surface migration of the growing species, are responsible for the surface step height after the growth. Since the mean free path in the gas phase at 5 Torr (≈20μm) is longer than the recess height (≈1μm), only the surface migration determines the growth at 5 Torr, while both mechanisms contribute to the growth at 100 Torr. The surface diffusion equation is solved to find out the relation between the growth conditions and the surface step height after the growth. It was found that the surface migration length on the (111)A surface is much longer than that on the (100) plane. The optical waveguide is fabricated by growing a double-heterostructure on the recessed substrate, and light confinement in the channel is verified. On leave from Matsushita Kotobuki Electronics Ltd. Fukutake, Saijo 793, Japan     

Stereospecific analysis of fish oil triacyl-sn-glycerols

Stereospecific analysis of fish oil triacyl-sn-glycerols was carried out by novel high-performance liquid chromatography on a chiral stationary phase. The positional distributions of fatty acids were determined without accumulation of errors in a particular position and preferential hydrolysis for a particular fatty acid. High-resolution gas-liquid chromatography on an open tubular column detailed the distribution of unsaturated fatty acid isomers having olefinic bonds in different positions. The distribution of fatty acids was not independent of other fatty acids. The distribution of long-chain highly unsaturated fatty acids 22:6(n-3), 22:5(n-3) and 20:5(n-3) was governed by total amounts of 20:1 and 22:1 in triacyl-sn-glycerols. Long-chain monounsaturated acids 20:1 and 22:1 were influenced by the position of the olefinic bond in 20:1 occurring in triacyl-sn-glycerols. Shorter-chain C14-C18 fatty acids seemed to be influenced by total fatty acid composition. These results introduce a concept of mutual interaction between fatty acids to the investigation of positional distribution of fatty acids.     

Magnetic and Transport Properties of Bilayered Perovskite Sr3Ir2O7

We report magnetic and transport properties of polycrystalline samples of bilayered perovskite Sr₃Ir₂O₇, which is synthesized by using high pressure technique. Magnetic susceptibility shows weak ferromagnetism below 290K with small size of remanent moment (10^–3B/Ir). Resistivity shows insulating behavior below 290K. We discuss the magnetism and conductivity in Sr₃Ir₂O₇ comparing with those of Sr₃Ru₂O₇, which has a quite similar crystal structure to Sr₃Ir₂O₇, from the view point of rotation angle of MO₆ (M=Ir, Ru) octahedra.     

Ergodicity of spike trains: when does trial averaging make sense?

Neuronal information processing is often studied on the basis of spiking patterns. The relevant statistics such as firing rates calculated with the peri-stimulus time histogram are obtained by averaging spiking patterns over many experimental runs. However, animals should respond to one experimental stimulation in real situations, and what is available to the brain is not the trial statistics but the population statistics. Consequently, physiological ergodicity, namely, the consistency between trial averaging and population averaging, is implicitly assumed in the data analyses, although it does not trivially hold true. In this letter, we investigate how characteristics of noisy neural network models, such as single neuron properties, external stimuli, and synaptic inputs, affect the statistics of firing patterns. In particular, we show that how high membrane potential sensitivity to input fluctuations, inability of neurons to remember past inputs, external stimuli with large variability and temporally separated peaks, and relatively few contributions of synaptic inputs result in spike trains that are reproducible over many trials. The reproducibility of spike trains and synchronous firing are contrasted and related to the ergodicity issue. Several numerical calculations with neural network examples are carried out to support the theoretical results.