A simple oxidation–reduction process for the activation of a stainless steel surface to synthesize multi-walled carbon nanotubes and its application to phenol degradation in water

Aligned multi-walled carbon nanotubes (MWCNTs) were synthesized directly on a stainless steel surface by surface activation by intense oxidation in air followed by a moderate reduction in H₂ without any wet process. This method is extremely simple compared with conventional ways that need catalyst loading steps or acid pre-etching steps to synthesize carbon nanotubes on stainless steel surfaces. It was found that the length of MWCNT bundles could reach 80 μm when the oxidation step was properly controlled. It was demonstrated that MWCNTs synthesized on stainless steel meshes could be used as a catalyst support to enhance ozone oxidation in the decomposition of phenol in water.     

Effect of pre-dehydration treatment on the in vitro digestibility of starch in cookie

In order to understand the effect of pre-dehydration on the in vitro digestibility of cookie starch, cookie dough samples were dehydrated by vacuum treatment, and melting temperature (T(m)) of the crystalline amylopectin in the dough, internal temperature and water content of the dough during baking, and non-hydrolysed starch content of the obtained cookies were investigated. The T(m) of crystalline amylopectin increased with decreased water content of the dough, and the result was described as a T(m)-curve. The internal temperature of non-dehydrated dough surpassed the T(m)-curve during baking. Pre-dehydrated dough, on the other hand, always indicated a lower internal temperature than the T(m)-curve. The non-hydrolysed starch content obtained under a given condition increased significantly with a decrease in the initial water content of cookies. This will be because the melting of crystalline amylopectin was prevented, at least partially, during baking.     

Fabrication and fluorescence properties of multilayered core–shell particles composed of quantum dot,gadolinium compound,and silica

A preparation method for multilayered quantum dot/silica/gadolinium compound/silica (QD/Si/Gd/Si) core–shell particles is proposed. Silica (Si)-coated quantum dot (QD/Si) core–shell particles were prepared by a Stöber method at room temperature in water/ethanol solution with TEOS and NaOH in the presence of QD nanoparticles. Succeeding gadolinium compound (Gd)-coating of the QD/Si core–shell particles was performed by a homogeneous precipitation method using Gd(NO₃)₃, urea, and polyvinylpyrrolidone in the presence of the QD/Si particles, which resulted in production of multilayered QD/silica/gadolinium compound (QD/Si/Gd) core–shell particles. For Si-coating of the QD/Si/Gd particles, the Stöber method was performed at room temperature in water/ethanol solution with TEOS and NaOH in the presence of the QD/Si/Gd particles. Consequently, Si-coated QD/Si/Gd, i.e., multilayered QD/Si/Gd/Si, core–shell particles were obtained. The QD/Si/Gd/Si particles revealed strong fluorescence, which was almost comparable to the QD particles with no shells. These particles are expected to be harmless to living bodies, and have dual functions of magnetic resonance imaging and fluorescence.     

Use of fluorine-doped silicon oxide for temperature compensation of radio frequency surface acoustic wave devices

This paper investigates acoustic properties, including the temperature coefficient of elasticity (TCE), of fluorine-doped silicon oxide (SiOF) films and proposes the application of the films to the temperature compensation of RF SAW devices. From Fourier transform infrared spectroscopy (FT-IR), SiOF films were expected to possess good TCE properties. We fabricated a series of SAW devices using the SiOF-overlay/Cu-grating/LiNbO(3)-substrate structure, and evaluated their performance. The experiments showed that the temperature coefficient of frequency (TCF) increases with the fluorine content r, as we expected from the FT-IR measurement. This means that the Si-O-Si atomic structure measurable by the FT-IR governs the TCE behavior of SiO(2)-based films even when the dopant is added. In comparison with pure SiO(2) with the film thickness h of 0.3 wavelengths (λ), TCF was improved by 7.7 ppm/°C without deterioration of the effective electromechanical coupling factor K2 when r = 3.8 atomic % and h = 0.28λ. Fluorine inclusion did not obviously influence the resonators' Q factors when r < 8.8 atomic %.     

Development of supercomputers in Japan: Hardware and software

Japanese supercomputer development activities in the industry is reviewed. Architectures and softwares of Japanese supercomputer systems in the last 20 years are described and discussed. Special emphasis is put on the similarities and differences of the systems.     

Towards Thermoconductive,Electrically Insulating Polymeric Composites with Boron Nitride Nanotubes as Fillers

Ultilizing boron nitride nanotubes (BNNTs) as fillers, composites are fabricated with poly(methyl methacrylate), polystyrene, poly(vinyl butyral), or poly(ethylene vinyl alcohol) as the matrix and their thermal, electrical, and mechanical properties are evaluated. More than 20‐fold thermal conductivity improvement in BNNT‐containing polymers is obtained, and such composites maintain good electrical insulation. The coefficient of thermal expansion (CTE) of the BNNT‐loaded polymers is dramatically reduced because of interactions between the polymer chains and the nanotubes. Moreover, the composites possess good mechanical properties, as revealed by Vickers microhardness tests. This detailed study indicates that BNNTs are very promising nanofillers for polymeric composites, allowing the simultaneous achievement of high thermal conductivity, low CTE, and high electrical resistance, as required for novel and efficient heat‐releasing materials.     

Synthetic Routes and Formation Mechanisms of Spherical Boron Nitride Nanoparticles

A new concept is proposed to explain the formation of spherical boron nitride (BN) nanoparticles synthesized by the chemical vapor deposition (CVD) reaction of trimethoxyborane (B(OMe)₃) with ammonia. The intermediate phases formed during the CVD under different reaction conditions are analyzed by X‐ray diffraction, electron microscopy, thermogravimetry, and spectroscopy techniques. The transition mechanism from an intermediate B(OMe)_3–xH_3–xN (x < 2) phase having single B? N bonds to the BN nanoparticles is elucidated. This particularly emphasizes the CVD temperature effect governing the conversion of the N? H···O? B hydrogen bonds in (OMe)₃B · NH₃ into the N? B bonds in B(OMe)_3–xH_3–xN. The spherical morphology strongly depends on the remnant impurity oxygen formed upon Me₂O group elimination in the intermediate. Two types of spherical BN nanoparticles primarily attractive for immediate commercialization (with C and H impurities at a level less than 1 wt %) are synthesized by the adjustment of experimental parameters: high oxygen‐containing (～6.3 wt %) BN spheres with a diameter of ～90 nm and a specific surface area of 26.8 m² g^?1; and low oxygen‐containing (<1 wt %) BN spheres with a diameter of ～30 nm and a surface area of 52.7 m² g^?1. Finally, the regarded synthetic techniques are fully optimized in the present work.     

Theanine,Antistress Amino Acid in Tea Leaves,Causes Hippocampal Metabolic Changes and Antidepressant Effects in Stress-Loaded Mice

By comprehensively measuring changes in metabolites in the hippocampus of stress-loaded mice, we investigated the reasons for stress vulnerability and the effect of theanine, i.e., an abundant amino acid in tea leaves, on the metabolism. Stress sensitivity was higher in senescence-accelerated mouse prone 10 (SAMP10) mice than in normal ddY mice when these mice were loaded with stress on the basis of territorial consciousness in males. Group housing was used as the low-stress condition reference. Among the statistically altered metabolites, depression-related kynurenine and excitability-related histamine were significantly higher in SAMP10 mice than in ddY mice. In contrast, carnosine, which has antidepressant-like activity, and ornithine, which has antistress effects, were significantly lower in SAMP10 mice than in ddY mice. The ingestion of theanine, an excellent antistress amino acid, modulated the levels of kynurenine, histamine, and carnosine only in the stress-loaded SAMP10 mice and not in the group-housing mice. Depression-like behavior was suppressed in mice that had ingested theanine only under stress loading. Taken together, changes in these metabolites, such as kynurenine, histamine, carnosine, and ornithine, were suggested to be associated with the stress vulnerability and depression-like behavior of stressed SAMP10 mice. It was also shown that theanine action appears in the metabolism of mice only under stress loading.     

Recent progress in advanced optical materials based on gadolinium aluminate garnet (Gd3Al5O12)

This review article summarizes the recent achievements in stabilization of the metastable lattice of gadolinium aluminate garnet (Gd₃Al₅O₁₂, GAG) and the related developments of advanced optical materials, including down-conversion phosphors, up-conversion phosphors, transparent ceramics, and single crystals. Whenever possible, the materials are compared with their better known YAG and LuAG counterparts to demonstrate the merits of the GAG host. It is shown that novel emission features and significantly improved luminescence can be attained for a number of phosphor systems with the more covalent GAG lattice and the efficient energy transfer from Gd³⁺ to the activator. Ce³⁺ doped GAG-based single crystals and transparent ceramics are also shown to simultaneously possess the advantages of high theoretical density, fast scintillation decay, and high light yields, and hold great potential as scintillators for a wide range of applications. The unresolved issues are also pointed out.