Fabrication of hollow silica–alumina composite spheres and their activity for hydrolytic dehydrogenation of ammonia borane

In this study, we investigated the influence of the preparation conditions of hollow silica–alumina composite spheres on their activity for the hydrolytic dehydrogenation of ammonia borane. Hollow silica–alumina composite spheres were prepared by polystyrene template method, and the polystyrene template particles were removed by calcination. The as-prepared hollow spheres were calcined at 523–873 K for 3 h. From the results of elemental analysis, polystyrene templates were completely removed by calcination at 873 K. small particles around the hollow spheres were observed from the images of transmission electron microscopy. To obtain homogeneous hollow spheres, the as-prepared hollow spheres were calcined at 873 K for 0–12 h. From the results of transmission electron microscopy, homogeneous hollow spheres were obtained by calcination for 0 h. The activity of the hollow spheres was the 2.6 times higher that of the hollow spheres calcined for 3 h. From the results of activity tests and ammonia temperature-programming desorption, the activity of the hollow spheres depends on amount of acid sites.     

The behavior of chlorobenzenes in Ise bay, estimated from their concentrations in various environmental media

Field survey of pollutants in various environmental media is indispensable for modeling the behavior of organic compounds discharged into the coastal environment. In this study, the concentrations of chlorobenzenes were measured in Ise Bay where industrial wastewater enters. Some chlorobenzene congeners, 1, 3-dichlorobenzene and 1, 2, 4-trichlorobenzene, were detected in seawater, suspended particulate and bottom sediment samples and their behavior was analyzed.The horizontal distributions showed that these chlorobenzene concentrations in the surface water and sediments were higher in the area near the shore of the industrial area than in the offshore area. The soluble chlorobenzene concentrations in the bottom water were low at all stations. The vertical distribution survey at each sampling site showed that the soluble concentrations were high in the surface water and low in the bottom water, but that those in the suspended particulates and the bottom sediments (dry solid base) had relatively similar concentrations. This indicated that chlorobenzenes in the bottom suspended particulates and in the bottom sediments were not equilibrated with chlorobenzenes in the bottom seawater. This could be explained by the following chlorobenzene behavior: the chlorobenzenes were adsorbed by suspended particulates in the surface water and settled to the bottom swiftly through less polluted seawater in the lower water layer with little desorption. This caused the chlorobenzene concentration gradient in the bottom sediment which reflected the chlorobenzene concentration absorbed by suspended particulates in the surface water.The behavior of chlorobenzenes suggested in this study showed that the use of chemical fate models based on the assumption that the soluble fraction and the fraction adsorbed by suspended particulates are always in equilibrium may yield misleading results.     

A Novel (N + 1/2) Pulse Swallow Programmable Divider for the Prescaler PLL Frequency Synthesizer

In this paper, we propose a new speedup method of frequency switching time of the prescaler PLL frequency synthesizer using (N + \tfrac12)(N + \tfrac{1}{2}) pulse swallow programmable divider. The (N + \tfrac12)(N + \tfrac{1}{2}) pulse swallow programmable divider can set half the division ratio (\tfracD2)(\tfrac{D}{2}) in comparison with the desired division ratio D. In the improved prescaler method, since the total division ratio including (\tfrac12)(\tfrac{1}{2}) fixed prescaler becomes desired division ratio D, the reference frequency which is two times bigger than that of the conventional prescaler method can be used. Therefore, the loop gain, the natural angular frequency and the damping factor are increased, and the frequency switching time can be speeded up. By the experimental results, it is observed that the frequency switching time of the improved prescaler method is two times faster than that of the conventional prescaler method.     

Light-induced denaturation of bacteriorhodopsin solubilized by octyl-{beta}-glucoside

The structural stability of bacteriorhodopsin (bR) solubilizedby octyl-ß-glucoside was studied by measuring the denaturationkinetics under visible light irradiation and in the dark. Thedenaturation of bR solubilized by 50 mM octyl-ß-glucosidewas very slow at room temperature when it was left in the dark.However, its spontaneous denaturation was accelerated when thesolubilized bR was irradiated by visible light. The denaturationkinetics under visible light irradiation and in the dark couldbe well described by a single decay constant. The activationenergy for the denaturation of bR was estimated from the temperaturedependence of decay time constants. The activation energy undervisible light irradiation was 12.5 kcal/mol, which was muchsmaller than the corresponding value in the dark, 26.2 kcal/mol.These results strongly suggest that some of the photointermediatestates are less stable than the ground state of bR. The criticaltemperature and the activation energy for denaturation of bRin the solubilized state were much lower than those in the 2Dcrystalline state. Comparing the denaturation behavior in the2D crystalline state and that in the octyl-ß-glucoside-solubilizedstate, our findings suggest that protein–protein interactioncontributes to the stability of this protein.     

Archiving of food samples from restaurants and caterers--quantitative profiling of outbreaks of foodborne salmonellosis in Japan

The Ministry of Health, Labor and Welfare (former MHW) of Japan issued a Directive in 1997 advising restaurants and caterers to freeze portions of both raw food and cooked dishes for at least 2 weeks. This system has been useful for determining vehicle foods at outbreaks. Enumeration of bacteria in samples of stored food provide data about pathogen concentrations in the implicated food. Data on Salmonella concentrations in vehicle foods associated with salmonellosis outbreaks were collected in Japan between 1989 and 1998. The 39 outbreaks that occurred during this period were categorized by the settings where the outbreaks took place, and epidemiological data from each outbreak were summarized. Characteristics of outbreak groups were analyzed and compared. The effect of new food-storage system on determination of bacterial concentration was evaluated. Freezing and nonfreezing conditions prior to microbial examination were compared in the dose-response relationship. Data from outbreaks in which implicated foods had been kept frozen suggested apparent correlation between the Salmonella dose ingested and the disease rate. Combined with results of epidemiological investigation, quantitative data from the ingested pathogen could provide complete dose-response data sets.     

New Pb-based 1212 Cuprate Superconductors Containing Sulfur, (Pb0.75S0.25)Sr2 (Y1?xCax)Cu2Oz

New Pb-based 1212 layered cuprates containing sulfur have been synthesized in the (Pb_0.75S_0.25) Sr₂ (Y_1−x Ca _x ) Cu₂O _z system. X-ray diffraction analysis shows that the almost single-phase samples are obtained within a region of 0.0≤x≤0.5. The crystal structure of each sample has a tetragonal symmetry with the typical lattice constants a=0.3837 nm and c=1.186 nm. As Ca content x is increasing, the semiconductor-like behavior is suppressed. But after only annealing under ambient O₂ pressure, none of the samples show any trace of superconductivity. On the other hand, when the samples are annealed under high O₂ pressure of about 13.6 MPa, they show resistivity dropping phenomenon in a region of 0.5≤x≤0.7. Among them, the lowest resistivity sample with x=0.6 has an onset temperature of the resistivity dropping at about 22.5 K. Moreover, this sample shows a diamagnetic signal at about 21.5 K. These phenomena are attributed to superconductivity.     

Influence of Oxidation Temperature and Cr Content on the Adhesion and Microstructure of Scale on Low Cr Steels

Descalability of steels during hot rolling processes is essential in order to maintain the surface quality of steel products, because the remaining scale can be impressed into the steel, producing surface defects. Therefore, a quantitative evaluation of scale adhesion at high temperature is needed in order to find suitable heating conditions for hot rolling processes that promote the formation of scale that easily detach. Round bar shape specimens of low Cr steels were oxidized in a fuel combustion environment, and then compressed at high temperature to detach the scale. The area fraction of the remaining scale was evaluated by image analysis. Under a thick outer oxide scale, a thin continuous inner oxide layer, which consisted of Cr and Si oxides, strongly adhered to the substrate, resulting in poor descalability. On the other hand, if this inner scale changed into a discontinuous layer with a porous FeO layer beneath, the descalability improved. It was found that scales with greater descalability formed on steels containing less Cr and for oxidation at higher temperatures.     

Irradiation-induced changes of the atomic distributions around the interfaces of carbides in a nuclear reactor pressure vessel steel

Irradiation-induced changes of the atomic distributions of solute and impurity elements around carbides in a reactor pressure vessel steel of a Belgium nuclear power reactor were investigated by laser-assisted local electrode-type three-dimensional atom probe, before and after in-service irradiation of 12 years. Before irradiation, nano-scale Fe-Mn-Cr-Mo carbides were found to be intragranular. The atomic distributions of Mn, Cr and Mo inside the carbide indicate that their concentrations around the inner carbide-matrix interface were enhanced, while a clear segregation of P at the interface was observed. After irradiation, the Mn concentration in the carbide increased substantially. In addition, the enhancement of Mn, Cr and Mo concentrations around the interface and the segregation of P were markedly intensified.     

Preparation of carbon alloy catalysts for polymer electrolyte fuel cells from nitrogen-containing rigid-rod polymers

‘Carbon Alloy Catalysts’ (CAC), non-precious metal catalysts for the oxygen reduction reaction (ORR), were prepared from various kinds of nitrogen-containing rigid-rod aromatic polymers, polyimides, polyamides and azoles, by carbonization at 900 °C under nitrogen flow. The catalytic activity for ORR was evaluated by the onset potential, which was taken at a current density of −2 μA cm⁻². Carbonized polymers having high nitrogen content showed higher onset potential. In particular, CACs derived from azole (Az5) had an onset potential of 0.8 V, despite being was prepared without any metals.     

Graphitization of inner surface of copper beam duct of KEKB positron ring

In order to evaluate the best technique to reduce electron cloud instability, we measured the electron cloud density in copper ducts coated with titanium nitride and non-evaporable getter used in the KEK B-factory (KEKB) positron ring. In this study, we developed a new system for the graphitization of copper beam ducts. The graphitization of a copper surface by intense electron bombardment resulted in the reduction in the secondary electron yield (SEY) to 1.0 in a laboratory experiment and to 1.1 in a real beam duct. The electron cloud density in the graphitized duct is 30% lower than that in an uncoated copper duct. Thus, it has been confirmed that the graphitization of a beam duct leads to a reduction in the electron cloud density in the duct.