Change in Oxygen Content of Y2O3-Nd2O3-Doped Silicon Nitride During Firing

The oxygen content of silicon nitride with 1 mol% Y₂O₃—Nd₂O₃ additive was measured after firing to determine the compositional change during gas-pressure sintering. Oxygen content decreases from 2.5 to 0.94 wt% during firing for 4 h at 1900°C and 10-MPa pressure in N₂. This decrease in oxygen results from the release of SiO gas generated by a thermaldecomposition reaction between Si₃N₄ and SiO₂. The resultant sintered silicon nitride material contains less than 1 wt% oxygen.     

Effects of calcining conditions of kaolinite on pore structures of mesoporous materials prepared by the selective leaching of calcined kaolinite

This paper describes the effects of calcining conditions of kaolinite on pore structures of the porous materials obtained from the selective leaching of calcined kaolinite using KOH solution. Mesoporous -Al₂O₃ was the predominant crystalline phase in the samples calcined in the temperature range between 950°C and 1050°C for 24 h. The mean specific surface area of these samples was approximately 250 m² · g^–1 and the mean total pore volume was approximately 0.8 ml · g^–1. The pore size distribution curves of these samples showed a sharp peak at around 2–3 nm pore radius. This peak was sharper for the sample calcined at 1000°C for 24 h. On the other hand, the pore sizes of the sample calcined at 1100°C for 24 h increased abruptly to 10–20 nm and this change corresponded to the formation of mullite in the sample. The pore sizes of the samples calcined at 1100°C varied with calcining time. The specific surface area and total pore volume decreased, the longer the calcining time of the samples, and this was correlated with an increase in the amount of mullite in the samples.     

Resistance to wear and cavitation erosion of bearing alloys

Sliding wear and vibratory cavitation erosion tests in paraffin oil were carried out on bearing alloys, i.e. tin-based and lead-based white metals, Cu-Pb alloy and leaded bronze. In lubricated wear under mild conditions the surface is worn smooth and a slight difference exists between the wear resistances of the four alloys. In cavitation erosion an eroded surface which is much rougher than the worn surface is formed. Cavitation erosion is affected strongly by the composition and crystal structure of the alloy and thus the erosion resistances of the four alloys differ greatly, the ranking of resistance being lead-based white metal < Cu-Pb alloy < tin-based white metal < leaded bronze. The surface damage, which is caused by the joint action of cavitation erosion and wear, was also investigated by rubbing the eroded surfaces which had been exposed to cavitation erosion for various times. This damage becomes larger with increasing cavitation damage. The resistance to this damage differs much more in the four alloys tested and tends to correlate with the results of the erosion tests rather than those of the wear tests. Therefore, it is clear that the cavitation erosion resistance should be considered in the selection of bearing materials.     

An outbreak of food-borne listeriosis due to cheese in Japan, during 2001

Food-borne outbreaks caused by Listeria monocytogenes have been recognized in US and European countries. Only sporadic cases, of neonatal listeriosis, have been reported in Japan. Since L. monocytogenes has been often isolated from foods in Japan, food-borne outbreaks potentially could have occurred. In February 2001, L. monocytogenes serotype 1/2b was isolated from a washed-type cheese during routine Listeria monitoring of 123 domestic cheeses. Further samples from products and the environments at the plant that produced the contaminated cheese were examined for L. monocytogenes. L. monocytogenes serotype 1/2b was detected in 15 cheese samples, at most probable number that ranged from <30 to 4.6 x 10(9)/100 g, and in environmental samples. Studies with people who had consumed cheese from the plant revealed 86 persons who had been infected with L. monocytogenes. Thirty-eight of those people had developed clinical symptoms of gastroenteritis or the common cold type after the consumption of cheese. Isolates from those patients exhibited the same serotype, pathogenicity for mice and HeLa cells, DNA fingerprinting patterns and PCR amplification patterns. From the epidemiological and genetic evidence, it appeared that the outbreak was caused by cheese. This is the first documented incidence of food-borne listeriosis in Japan.     

Direct and Indirect Exciton Dynamics in Few‐Layered ReS2 Revealed by Photoluminescence and Pump‐Probe Spectroscopy

Atomically thin‐layered ReS₂ with a distorted 1T structure has attracted attention because of its intriguing optical and electronic properties. Here, the direct and indirect exciton dynamics of a three‐layered ReS₂ is investigated by polarization‐resolved transient photoluminescence (PL) and ultrafast pump‐probe spectroscopy. The various time scales of the decay signals of the time‐resolved PL (<10 ps), with monitoring of the populations of electron–hole pairs (exciton), and the transient differential reflectance (≈1 and 100 ps), with monitoring of the populations of electrons and/or holes in the excited states, are observed. These results reveal the characteristic exciton dynamics: rapid relaxation of direct excitons (electron–hole pairs) and slow relaxation of the momentum‐mismatched indirect excitons accompanied by a one‐phonon emission process. These findings provide important information regarding the indirect bandgap nature of few‐layered ReS₂ and its characteristic exciton dynamics, boosting the understanding of the novel electronic and optical properties of atomically thin‐layered ReS₂.     

Effects of V content on hydrogen storage properties of V–Ti–Cr alloys with high desorption pressure

Hydrogen storage is one of the most important issues to realize hydrogen society especially for on-board usage. Recently, high-pressure metal hydride (MH) tank attracts many attentions due to its high volumetric hydrogen storage density and relatively easy heat management. To emphasize its merits, further improvements of properties of MH, such as capacity, hydrogen desorption capability at low temperature and durability, are required. In this paper, V–Ti–Cr alloys of V-rich compositions were investigated with perspective of increasing of hydrogen desorption pressure and durability. In both of 60at%V–Ti–Cr and 80at%V–Ti–Cr alloys, good relationship between hydrogen desorption pressure and Ti content was observed. In comparing with 60at%V–Ti–Cr alloys, 80at%V–Ti–Cr alloys showed good durability. It is quite notable that relationship between limitation line (upper substitution limit of Ti by Cr without degradation of hydrogen capacity) and desorption pressure for V–Ti–Cr ternary system with V-rich composition is clarified. And also, it is revealed that in the case of V–Ti–Cr ternary system, not only Ti/Cr ratio but also V content is important factor to obtain alloys with high hydrogen desorption pressure. 75at%V–5at%Ti–Cr as-cast sample showed good durability, hydrogen desorption capability at low temperature and relatively high effective hydrogen capacity simultaneously.     

Efficient electron transport in 4,4′-bis[N-(1-napthyl)-N-phenyl-amino] biphenyl and the applications in white organic light emitting devices

The electron transport capability of 4,4′-bis[N-(1-napthyl)-N-phenyl-amino] biphenyl (α-NPD) was investigated by fundamental physical measurements named as current–voltage (I–V) electrical property evaluation and displacement current measurement (DCM). In electron-dominated devices, the I–V characteristics of α-NPD were similar as that of (8-hydroxyquinolino) aluminum (Alq₃) owing to their same order of electron mobilities. The interface of Al/LiF and α-NPD was proven to be an Ohmic contact through the evaluation of I–V characteristics at low bias regime (<3 V). And an electron injection barrier, 0.21 eV, at Al/LiF/α-NPD was obtained by extrapolating the temperature dependent I–V curves. The electron transport behavior in α-NPD film was further confirmed by DCM evaluations. Furthermore, an efficient white organic light emission device was successfully fabricated by using α-NPD as hole transport layer and electron transport layer, respectively.     

Cathode properties of metal trifluorides in Li and Na secondary batteries

Fluorine compounds have high discharge voltage due to its highly ionic metal-ligand bonds. In them, perovskite-type metal trifluorides with corner sharing matrix have large bottlenecks of diffusion pathways for intercalants. Iron trifluoride composites (FeF₃-C) prepared by planetary ball milling with carbon showed reversible charge/discharge behavior not only for Li, but also for Na anodes. X-ray diffraction and ⁵⁷Fe Mössbauer spectroscopy were applied to characterize the electrochemical properties of FeF₃ vs. Li and Na anodes. The cathode performances of the other commercially available transition metal trifluorides such as MF₃ (M = Ti, V, Mn, Co) have been also investigated.     

Cloning and characterization of a β-N-acetylglucosaminidase (BmFDL) from silkworm Bombyx mori

In insects, β-N-acetylglucosaminidase (GlcNAcase) participates in critical physiological processes such as fertilization, metamorphosis, and glycoconjugate degradation. Insects produce glycoproteins carrying paucimannosidic-type N-glycans, the terminal GlcNAc residue of which is cleaved by a GlcNAc-linkage specific GlcNAcase, also known as the fused lobes (FDL) protein. To obtain information on the structure of GlcNAcases and insight into their contribution to physiological processes, we cloned Bombyx mori FDL (BmFDL) from silkworm larvae. The full-length cDNA (1.9 kb) encoded a protein of 633 amino acids with 42% amino acid sequence identity to Drosophila melanogaster FDL (DmFDL). Recombinant BmFDL cleaved only β-1,2-linked GlcNAc residues from the α-1,3 branch of biantennary N-glycan. This substrate specificity was similar to that of DmFDL. Microsomal FDL activity was inhibited by anti-BmFDL antibodies. Taken together, our results suggest that BmFDL is a N-glycan-processing GlcNAcase in B. mori.     

Hydrogenation and dehydrogenation processes of palladium thin films measured in situ by spectroscopic ellipsometry

The hydrogenation and dehydrogenation switching processes of Pd thin films were analyzed by measuring in situ in real time the variation in ellipsometric Ψ and Δ during hydrogenation and dehydrogenation using spectroscopic ellipsometry. The hydrogenation proceeded from the film surface and a mixture layer of metal and hydride was formed at the surface. With time elapse, the thickness of the mixture layer increased rapidly. After the whole Pd metal layer transformed to the mixture layer, the concentration of hydride in the mixture layer increased. Finally, the concentration reached 1; the whole Pd in the mixture layer was hydrogenated, and the hydrogenation of Pd was complete. On the other hand, the dehydrogenation proceeded in a way completely opposite to the hydrogenation process; the concentration of hydride in the mixture layer decreased, Pd metal layer was formed at the interface between the film and the substrate, and the whole layer returned to Pd metal. The dehydrogenation proceeds much faster than hydrogenation.