A blowdown cryogenic cavitation tunnel and CFD treatment for flow visualization around a foil

Cavitation is one of the major problems in the development of rocket engines. There have been few experimental studies to visualize cryogenic foil cavitation. Therefore a new cryogenic cavitation tunnel of blowdown type was built. The foil shape is "plano-convex". This profile was chosen because of simplicity, but also of being similar to the one for a rocket inducer impeller. Working fluids were water at room temperature, hot water and liquid nitrogen. In case of Angle of Attack (AOA)=8°, periodical cavity departure was observed in the experiments of both water at 90℃ and nitrogen at -190℃ under the same velocity 10 m/sec and the same cavitation number 0.7. The frequencies were observed to be 110 and 90 Hz, respectively, and almost coincided with those of vortex shedding from the foil. Temperature depression due to the thermodynamic effect was confirmed in both experiment and simulation especially in the cryogenic cavitation.     

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.     

Cryogenic cavitating flow in 2D laval nozzle

Cavitation is one of the troublesome problems in rocket turbo pumps, and since most of high-efficiency rocket propellants are cryogenic fluids, so called "thermodynamic effect" becomes more evident than in water. In the present study, numerical and experimental study of liquid nitrogen cavitation in 2D Laval nozzle was carried out, so that the influence of thermodynamic effect was examined. It was revealed that temperature and cavitation have strong inter-relationship with each other in thermo-sensitive cryogenic fluids.     

Inhibitory action of emulsified sulfoquinovosyl acylglycerol on mammalian DNA polymerases

We reported previously that sulfoquinovosyl diacylglycerol and sulfoquinovosyl monoacylglycerol (SQDG/SQMG) are potent inhibitors of mammalian DNA polymerases and DNA topoisomerase II, and can be potent immunosuppressive agents and anticancer chemotherapy agents [Matsumoto, Y., Sahara, H., Fujita T., Shimozawa, K., Takenouchi, M., Torigoe, T., Hanashima, S., Yamazaki, T., Takahashi, S., Sugawara, F., et al., An Immunosuppressive Effect by Synthetic Sulfonolipids Deduced from Sulfonoquinovosyl Diacylglycerols of Sea Urchin, Transplantation 74, 261-267 (2002); Sahara, H., Hanashima, S., Yamazaki, T., Takahashi, S., Sugawara, F., Ohtani, S., Ishikawa, M., Mizushina, Y., Ohta, K., Shimozawa, K., et al., Anti-tumor Effect of Chemically Synthesized Sulfolipids Based on Sea Urchin's Natural Sulfonoquinovosylmonoacylglycerols, Jpn. J. Cancer Res. 93, 85-92 (2002)]. In those experiments, the in vivo effectiveness greatly depended on the degree of water solubility of SQDG/SQMG. In the present work, we studied the emulsification of SQDG/SQMG in terms of their use in in vivo experiments. Lipid emulsions containing SQDG/SQMG (oil-in-water emulsions) in which the particle size was smaller than 100 nm were designed and synthesized, and then the biochemical modes of emulsified SQDG/SQMG were studied in comparison with those of SQDG/SQMG solubilized by DMSO. Emulsified SQDG/SQMG are also selective mammalian DNA polymerase inhibitors and potent antineoplastic agents but do not inhibit the DNA topoisomerase II activity. The growth inhibition effect of emulsified SQMG to NUGC-3 cancer cells was twofold stronger than DMSO-soluble SQMG (69 and 151 microM, respectively). From these results, the properties of lipid emulsions containing SQDG/SQMG and their possible use in in vivo experiments including clinical use are discussed.     

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.