Anion-induced conformational transition of poly(l-arginine) and its two homologues

The interaction of various anions with poly(l-arginine) and its two homologues, poly(l-homoarginine) and poly(l-α-amino-γ-guanidinobutyric acid), has been studied in the neutral pH region. These polypeptides were found to change their conformations from coil to helix due to I^?, ClO^?₄ and SCN^?, and among them poly(l-homoarginine) and poly(l-arginine) were found to change conformation at smaller concentrations of the anions than poly(l-lysine). The helix of poly(l-homoarginine) was induced in the lyotropic series of the counteranions. Using the van't Hoff enthalpies for the transition of the polypeptides and the transition enthalpies obtained from calorimetry, the various thermodynamic parameters of the transitions were calculated by use of a theory based on the non-specific and the specific binding interactions of the anions with the charged sites on the polypeptides. The binding constants of ClO^?₄ and SCN^? with poly(l-homoarginine) and poly(l-arginine) were found to be four times as large as those with poly(l-lysine). The free energy changes of the transitions from coil to helix of poly(l-homoarginine) and poly(l-arginine) were found to be more negative than that of poly(l-lysine). From these results, the guanidinium ion can be concluded to form easily the ion pair with the anions on the polymer surface, thus allowing poly(l-homoarginine) and poly(l-arginine) to change their conformations at smaller concentrations of the anions than poly(l-lysine).     

Silicon carbide coating on molybdenum by chemical vapor deposition and its stability under thermal cycle conditions

Silicon carbide film (as thick as 25 μm) was chemically vapor deposited on molybdenum in the temperature range of 1050–1300°C by reaction of hydrogen and ethyltrichlorosilane as an application of a low-Z material to fusion reactor protective plates. The films were characterized by using scanning electron microscopy, X-ray diffraction, electron microprobe analysis, and infrared absorption spectroscopy. The deposits consisted of α and β-SiC and a small amount of SiO₂. Underlayer coatings were also attempted to improve the thermal cycling behavior. The coating with a boron underlayer was successfully cycled 2100 times between 800 and 1000°C, and then 560 times between 600 and 1200°C in air under thermal cycling conditions with a heating rate of 20°C/min. Problems in applying SiC-coated molybdenum to the first wall protective plates in a fusion reactor are discussed.     

Secondary ion emission from beryllium surfaces by Ar and /or (Ar+D2) mixed ion bombardments

With respect to the impurity emission and erosion of a Be first wall, a secondary ion mass spectrometric investigation was carried out along with surface characterization with X-ray photoelectron spectroscopy. It was found that Be is emitted as distinct types of chemical forms from the surface owing to sputtering with Ar⁺ and an (Ar⁺+ D⁺₂) mixture: (i) Be and Be-cluster, (ii) oxide and hydroxide, and (iii) hydride and/or deuteride.     

Study on absorption/desorption characteristics of a metal hydride tank for boil-off gas from liquid hydrogen

We have been performing research on the Totalized Hydrogen Energy Utilization System (THEUS) which has applications to commercial buildings and a planned added function of supplying energy to stations for hydrogen and electric vehicles. In that case we will utilize liquid hydrogen transported from a hydrogen station and all Boil-Off Gas (BOG) will be recovered in THEUS’s metal hydride tanks. It is known that BOG is chiefly composed of para-hydrogen, which has different thermo-physical properties from normal hydrogen. It has been reported that some metal hydride alloys work as a catalyst to accelerate the para-ortho conversion and the conversion proceeds relatively fast in the case of La–Ni₅. The conversion is considered to be an endothermic reaction. A misch metal (Mm)-Ni₅ metal hydride alloy, which contained La and Ni, was used in our THEUS metal hydride tank. To examine the effect of the para-ortho conversion on the THEUS operation, we investigated the absorption/desorption characteristics of the metal hydride tank with BOG. We confirmed that the effect of the heat of conversion was very small and BOG could be treated as normal hydrogen for practical application.     

Influence of separated vortex on aerodynamic noise of an airfoil blade

In order to clarify the mechanism by which aerodynamic noise is generated from separated flow around an airfoil blade, the relation between the attack angle and the aerodynamic noise of the blade was analyzed using a wind tunnel experiment and a CFD code. In the case of rear surface separation, the separated vortex which has a large-scale structure in the direction of the blade chord is transformed into a structure that concentrates at the trailing edge with an increase in the attack angle. The aerodynamic noise level then becomes small according to the vortex scale in the blade chord. When the flow is separated at the leading edge, a separated vortex of low pressure is formed at the vicinity of the trailing edge. The pressure fluctuations on the blade surface at the vicinity of the trailing edge become large due to the vortex in the wake. It is considered that the aerodynamic noise level increases when the flow is separated at the leading edge because the separated vortex is causing the fluctuations due to wake vortex shedding.     

Selective enumeration of viable Enterobacteriaceae and Pseudomonas spp. in milk within 7 h by multicolor fluorescence in situ hybridization following microcolony formation

Rapid and simultaneous enumeration of viable Enterobacteriaceae and viable Pseudomonas spp. in milk was achieved by using multicolor fluorescence in situ hybridization (FISH) with oligonucleotide probes based on 16S ribosomal RNA (rRNA) sequences in combination with a microcolony growth method (multicolor microcolony-FISH; MMC-FISH). The procedure of MMC-FISH method is rather simple; that is milk clearing, filtration of cells, incubation, hybridization and enumeration. Enumeration of targeted bacteria in logarithmic growth phase, stationary phase, or in a starved state in milk by MMC-FISH required 5-7 h, while it took 1-3 days to test for Escherichia coli and Pseudomonas putida by the conventional culture method. The numbers of E. coli and P. putida in each phase or in a starved state in milk determined by MMC-FISH were almost the same or greater than the number of colony forming units determined by the plate counting method. The MMC-FISH allows rapid examination of contamination in milk by viable Enterobacteriaceae and Pseudomonas spp. with growth potential.     

Proton conduction in Nafion composite membranes filled with mesoporous silica

Studies of proton-conductive polymer membranes are vital for the future development of high-performance polymer electrolyte membrane fuel cells (PEM-FC). In particular, a method for inhibiting the volatility of water in the polymer matrix at high temperatures is a crucial issue, directly related to the operation of PEM-FC system. In this study, we focus on polymer composite membranes, which consist of commercial Nafion and mesoporous silica (MPSi) as novel inorganic additives, and investigate an improvement in the total proton conductivities and the good electrochemical stability at high temperatures. MPSi, which can be synthesized with pore sizes from 1 to 10 nm, has a wide range of potential applications because of its extraordinary properties, such as extremely large surface area, flawless surface condition and well-regulated porous structure. We found that the Nafion composites filled with MPSi have approximately 1.5 times higher proton conductivities (more than 0.1 S cm⁻¹ at 80 °C and 95%RH) than pure Nafion and can display good temperature performance relative to pure Nafion and the particle SiO₂ composite. Moreover, the conductivity of Nafion/sulfonated MPSi was the highest (0.094 S cm⁻¹) at 40 °C and 95%RH. These are probably due to the large surface area of MPSi, which can increase the water adsorption in Nafion matrix.