Preparation of magnetic poly(vinyl alcohol) (PVA) materials by in situ synthesis of magnetite in a PVA matrix

An easy method for manufacturing homogeneous inorganic–organic materials, especially composite fibers, was obtained by the in situ synthesis of inorganic particles within polymer matrices. In this article, nanosized magnetite particles were synthesized in situ within poly(vinyl alcohol) (PVA) solutions by precipitating Fe²⁺ ions or a mixture of Fe²⁺ and Fe³⁺ ions with NaOH solution. As a result, magnetite particles with an average diameter of 20 nm were obtained homogeneously within the solutions because of the tridimensional structure and chelating capacities of PVA. Transparent films were obtained by a casting method, and six kinds of magnetic PVA fibers were also prepared by a wet‐spinning method from the solutions containing magnetite nanoparticles. The mechanical properties and the saturation magnetization of the fibers were measured. These fibers, which contain iron ions with a maximum content of 17.63 wt %, can be successfully fabricated by the in situ synthesis and they exhibit excellent magnetization properties (i.e., the largest saturation magnetization is 13.38 emu/g). © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1239–1247, 2003     

Preparation of Unique TiO2 Nano-particle Photocatalysts by a Multi-gelation Method for Control of the Physicochemical Parameters and Reactivity

A novel multi-gelation method to prepare TiO₂ nano-particle photocatalysts showed good performance in controlling the important parameters determining the photocatalytic reactivity, i.e., the particle size, surface area, crystallinity, pore-volume, pore-diameter as well as the anatase and rutile phase composition of the catalysts. In particular, this method at higher pH swing times could prevent the phase transition from anatase to rutile, leading to higher photocatalytic activity. By adopting variations in the pH swing, the TiO₂ nano-particle photocatalysts showed significantly higher photocatalytic reactivity for the complete oxidation of 2-propanol diluted with water into CO₂ and H₂O. It can be considered a viable alternative method for the preparation of high performance TiO₂ nano-particle photocatalysts for widespread commercial applications.     

Molecular characterization of the PEX5 gene encoding peroxisomal targeting signal 1 receptor from the methylotrophic yeast Pichia methanolica

In this study, we describe the molecular characterization of the PEX5 gene encoding the peroxisomal targeting signal 1 (PTS1) receptor from the methylotrophic yeast Pichia methanolica. The P. methanolica PEX5 (PmPEX5) gene contains a open reading frame corresponding to a gene product of 646 amino acid residues, and its deduced amino acid sequence shows a high similarity to those of Pex5ps from other methylotrophic yeasts. Like other Pex5ps, the PmPex5p possesses seven repeats of the TPR motif in the C-terminal region and three WXXXF/Y motifs. A strain with the disrupted PEX5 gene (pex5Delta) lost its ability to grow on peroxisome-inducible carbon sources, methanol and oleate, but grew normally on glucose and glycerol. Disruption of PmPEX5 caused a drastic decrease in peroxisomal enzyme activities and mislocalization of GFP-PTS1 and some peroxisomal methanol-metabolizing enzymes in the cytosol. Expression of the PmPEX5 gene was regulated by carbon sources, and it was strongly expressed by peroxisome-inducible carbon sources, especially methanol. Taken together, these findings show that PmPex5p has an essential physiological role in peroxisomal metabolism of P. methanolica, including methanol metabolism, and in peroxisomal localization and activation of methanol-metabolizing enzymes, e.g. AOD isozymes, DHAS and CTA.     

Development of split gliding arc for surface treatment of conductive material

A gliding arc is one of the atmospheric-pressure plasmas and available for surface treatment. However, when this gliding arc is used to irradiate conductive materials, arc spots appear on the surface and seriously damage it. In the present study, in order to prevent such arc spot damage on a conductive substrate, a split gliding arc was designed with a multi-hole plate placed at the exit window. This split gliding arc was irradiated onto several metals, and its ability to treat the hydrophilic property was verified.     

A thin‐film silicon solar cell and module

We have developed a new light‐trapping scheme for a thin‐film Si stacked module (Si HYBRID PULS module), where a (a‐Si:H/transparent interlayer/microcrystalline Si) thin‐film was integrated into a large‐area solar cell module. An initial aperture efficiency of 13·1% has been achieved for a 910 × 455 mm Si HYBRID PLUS module, which was independently confirmed by AIST. This is the first report of the independently confirmed efficiency of a large‐area thin‐film Si module with an interlayer. The 19% increase of short‐circuit current of this module was obtained by the introduction of a transparent interlayer that caused internal light‐trapping. A mini‐module was shown to exhibit a stabilized efficiency of 12%. Outdoor performance of a Si HYBRID (a‐Si:H / micro‐crystalline Si stacked) solar cell module has been investigated for over 4 years with two different kinds of module (top and bottom cell limited, respectively). The HYBRID modules limited by the top cell have exhibited a more efficient performance than the modules limited by the bottom cell, in natural sunlight at noon. Copyright © 2005 John Wiley & Sons, Ltd.     

Wear behavior of Al-Al3Ti composite manufactured by a centrifugal method

The purpose of the present study was to develop a wear-resistant, light Al-Al₃Ti composite material. An Al-Al₃Ti composite specimen was machined from a thick-walled tube of Al-Al₃Ti functionally graded material (FGM) manufactured by the centrifugal method from a commercial ingot of Al-5 mass pct Ti master alloy. The alloy was heated to a temperature where solid Al₃Ti particles resided in a liquid Al matrix, and then the centrifugal method was carried out. Al₃Ti particles in a commercial alloy ingot exist as platelets, and this shape was maintained through the casting. Three kinds of wear specimens were prepared, taking into account the morphology of the Al₃Ti particles in the thick-walled FGM tube; the Al₃Ti particles were arranged with their platelet planes nearly normal to the radial direction as a result of the applied centrifugal force. The wear resistance of the Al-Al₃Ti composite was significantly higher than that of pure Al. Wear-resistance anisotropy and dissolution of the Al₃Ti into the Al matrix at the near-surface region, around 100 μm in depth, were also observed. The mechanism of the supersaturated-layer formation and the origin of the anisotropic wear resistance are discussed.     

Novel method to evaluate the net wear volume of bag-filter by fly ash

In order to study the wear of bag-filter by ash dust, sintered magnetite (Fe(3)O(4)) compact was used for counter material for sliding wear test. The precise amount of magnetite particles embedded into bag-filter was determined by a vibration sample magnetometer (VSM) measurement. It is found that net amount of wear of the bag-filter could be precisely determined by the magnetic measurement. It is also found that the net amount of sliding wear of the bag-filter increases with increasing the wear distance, sliding speed and applied load. To discuss the validity of proposed method, shot peening test with deoxidized iron particles was also carried out for bag-filter sample. The data obtained by the shot peening test is consistent with that obtained by the sliding wear test. The proposed method is, thus, very useful to evaluate the net amount of wear of bag-filter by the fly ash.     

Tribological Characteristics of Si3N4 Ceramic in High-Temperature and High-Pressure Water

The effects of sliding speed and dissolved oxygen on the tribological behavior of Si₃N₄ sliding on itself in water were investigated at room temperature and at 120°C saturated vapor pressure. The friction coefficients and specific wear rates at 120°C were much larger than those at room temperature and had a minimum at about 0.4 m/s, whereats -the specific wear rate of the disk increased with increasing the sliding speed. The wear rate at lower sliding speeds in water at 120°C is considered to be primarily controlled by the increase of the contact stress on the asperities which are formed by the dissolution of grain boundaries of the Si₃N₄ ceramic and the subsequent dissolution of the silica layer of the reaction product However, the wear rate at higher sliding speeds is governed by the direct oxidation and microfracture of the Si₃N₄ substrate. The tribochemical reaction to produce NH₃ mainly occurred at all sliding conditions in water at room temperature and 120°C, and the reaction to produce H₂ gas appeared slightly only at the sliding speeds above 0.4 m/s at 120°C. The tribological behavior was independent of dissolved oxygen concentration for all sliding conditions in water at room temperature and 120°C.     

Diffracted X-ray Tracking Method for Measuring Intramolecular Dynamics of Membrane Proteins

Membrane proteins change their conformations in response to chemical and physical stimuli and transmit extracellular signals inside cells. Several approaches have been developed for solving the structures of proteins. However, few techniques can monitor real-time protein dynamics. The diffracted X-ray tracking method (DXT) is an X-ray-based single-molecule technique that monitors the internal motion of biomolecules in an aqueous solution. DXT analyzes trajectories of Laue spots generated from the attached gold nanocrystals with a two-dimensional axis by tilting (θ) and twisting (χ). Furthermore, high-intensity X-rays from synchrotron radiation facilities enable measurements with microsecond-timescale and picometer-spatial-scale intramolecular information. The technique has been applied to various membrane proteins due to its superior spatiotemporal resolution. In this review, we introduce basic principles of DXT, reviewing its recent and extended applications to membrane proteins and living cells, respectively.