Residual-strain-induced nanocoils of metallic nanowires

Metallic nanocoils are attractive nanowire (NW) structures, which are expected to have an application as small inductors, but have not been reported before. This study proposes a coating technique for permanently bending a straight, metallic NW into a helix. A physical vapor deposition is applied to oblique NWs standing on a substrate. The deposition produces a biased thickness of the coating on NWs, resulting in a mismatch in internal strains, namely thermal strain and intrinsic strain, between a NW and the coating. These residual strains are driving forces for the bending process of NWs. In particular, the intrinsic strain of the overlayer contributes the bending deformation. In addition, elastic anisotropy of NWs couples bending with a twist, contributing to the formation of helixes. We have demonstrated nanocoils, comprised of Cr-coated Cu NWs, with a coil diameter of about 300 to 500 nm.     

Glycosylceramides obtain from the starfish Asterias amurensis Lütken

Complex lipids in the starfish Asterias amurensis were characterized and the influence of sphingoid bases on human colon carcinoma Caco-2 cells was also investigated. Lipid content of gonad and viscera were 3.3% and 6.8%, respectively, in wet basis. The main lipid class in gonad was ceramide monohexoside (CMH) while triglyceride (TG) was predominant in the viscera. The most abundant fatty acid in the polar lipid was eicosapentaenoic acid (EPA, C20:5n-3), with the gonad and viscera samples having the highest proportion of 41.5% and 32.7%, respectively, of total fatty acids. Starfish internal organ contained enormous amount (0.7% in wet base) of glycosylceramide. Sphingoid bases of the glycosylceramide were mainly consisted of d22:2, d22:1 and d18:3. This sphingoid base exerted an apoptotic activity on Caco-2 cells. Thus, starfish could be used as a potential source of precious and useful complex lipids.     

X-ray absorption of gold nanoparticles with thin silica shell

Silica-coated gold (Au) nanoparticles were prepared and their morphological and X-ray absorption properties were investigated. These core-shell type nanoparticles are very stable in aqueous media and may be suitable for an X-ray contrast agent in biological systems. Transmission electron micrographs confirmed well-separated and relatively homogeneous morphology of the nanoparticles in highly concentrated colloids. Peak position for Au plasmon resonance was red-shifted with increasing shell thickness. X-ray absorption by the colloids of silica-coated Au nanoparticles was stronger than that by those of silica-coated Agl nanoparticles, a recently investigated X-ray contrast agent, at similar experimental conditions.     

SELECTIVE UPTAKE OF CESIUM BY AMMONIUM TUNGSTOPHOSPHATE (AWP) - CALCIUM ALGINATE COMPOSITES

ABSTRACT

The fine crystals of ammonium tungstophosphate (AWP) exchanger were immobilized in the biopolymer consisting of calcium alginate (CaALG) gels. The uptake rate of Cs⁺ for the AWP-CaALG composite was fairly fast and the uptake percentage of Cs^? was above 90 % within 30 min even in the presence of 5 M HNO₃ In a wide HNO₃concentration region of 0.1 - 5 M, the distribution coefficient of Cs^? for the composite was about 10⁴ cm³/g, while those for other nuclides, Na⁺, Sr²⁺, Co²⁺, Eu³⁺ and Am³⁺, were less than 10 cm³/g. The uptake of Cs⁺ followed a Langmuir-type adsorption equation, and the maximum uptake capacity of Cs⁺ increased with the content of AWP immobilized in the composite. The trace amounts of ¹³⁷Cs in the presence of 5 M NaNO₃-l M HNO₃ were selectively adsorbed on the composite column. The AWP-CaALG composite proved to be effective for the selective removal of radioactive cesium from waste solutions containing HNO₃ and NaNO₃     

Anionic polymerization of vinylsilanes

Summary The anionic polymerization of dimethylphenylvinylsilane with sec-butyllithium/N,N,N,N-tetramethylethylenediamine (TMEDA) was investigated. The polymerization proceeded up to 100% yield and afforded the polymer having isomerized-structure units. The polymerization was accompanied by chain transfer reaction to the monomer and the polymerization rate in the presence of TMEDA was much lower than in the absence of TMEDA.     

Enzymatic production of l-alanine from malic acid with malic enzyme and alanine dehydrogenase with coenzyme regeneration

An enzyme reaction system with coenzyme regeneration was investigated for L-alanine production. Alanine dehyrogenase L-alanine: NAD⁺ oxidoreductase (EC 1.4.1.1)] from Corynebacterium flaccumfaciens AHU-1622 was used as the catalyst for reductive amination of pyruvate to L-alanine. NAD- and NADP-linked malic enzyme [L-malate: NAD(P)⁺ oxidoreductase (EC 1.1.1.39)] from Pseudomonas diminuta IFO-13182 was used for the regeneration of NADH. Optimum conditions for L-alanine production were determined, including L-malic acid concentration, MgCl₂ concentration and pH. Under suitable conditions, the conversion of L-malic acid to L-alanine reached 95% after 72 h of incubation at 30°C, yielding 106 mol/m³ of L-alanine. The L-alanine produced was purified in crystal form; its purity was 99.4%, based on HPLC analysis.     

Highly active methanol decomposition catalyst derived from Pd‐hydrotalcite dispersed on mesoporous silica

Pd‐hydrotalcite (abbreviated as Pd(HT)) was dispersed on HMS (hexagonal mesoporous silica) by synthesizing Pd(HT) in an HMS suspension, and the resultant product (Pd(HT)/HMS) was used as a catalyst precursor for methanol decomposition to synthesis gas. The IR spectra of Pd(HT)/HMS showed all the bands of Pd(HT) and HMS with little shift, which indicated that Pd(HT) was synthesized in the Pd(HT)/HMS. Pd(HT)/HMS did not show the XRD pattern of Pd(HT) when the mass ratio of Pd(HT) to HMS was from 2/1 to 1/2. This indicated that Pd(HT) was formed in very small particles in the Pd(HT)/HMS after dispersion. Two endothermic peaks of Pd(HT) in the DTA curve shifted to lower temperatures in the Pd(HT)/HMS because the small Pd(HT) particles formed in the Pd(HT)/HMS were easily collapsed by heat treatment. Pd(HT)/HMS was thermally decomposed and reduced to form a supported Pd catalyst (abbreviated Pd(Mg(Al)O)/HMS) for methanol decomposition. Pd(Mg(Al)O)/HMS at 3.6 wt% showed a 52.5% conversion which was much higher than those over 3.6 wt% Pd(Mg(Al)O) (34.7%) and 3.6 wt% Pd/HMS (13.7%) for methanol decomposition at 523 K. The conversions of methanol over Pd(Mg(Al)O) and Pd/HMS increased with the increase in Pd loadings from 3.6 to 15 wt% and decreased when the Pd loadings were over 15 wt%. In contrast, the conversion over Pd(Mg(Al)O)/HMS increased with the increase in Pd loading even when the Pd loading was up to 30%. 30 wt% Pd(Mg(Al)O)/HMS showed a 91.7% conversion which was about twice that over 15 wt% Pd(Mg(Al)O) (47.1%) at 523 K. The Pd(Mg(Al)O)/HMS catalyst showed a larger BET surface area and Pd metal surface area than those of Pd(Mg(Al)O). By characterization using XPS analyses, the metal–support interaction between small Pd and small Mg(Al)O became stronger in the Pd(Mg(Al)O)/HMS catalyst. Large surface area, high Pd dispersion and strong metal–support interaction caused the high catalytic activity for methanol decomposition to synthesis gas over the Pd(Mg(Al)O)/HMS catalyst. This revised version was published online in July 2006 with corrections to the Cover Date.     

Measurement of in vivo local shear modulus using MR elastography multiple-phase patchwork offsets

Magnetic resonance elastography (MRE) is a method that can visualize the propagating and standing shear waves in an object being measured. The quantitative value of a shear modulus can be calculated by estimating the local shear wavelength. Low-frequency mechanical motion must be used for soft, tissue-like objects because a propagating shear wave rapidly attenuates at a higher frequency. Moreover, a propagating shear wave is distorted by reflections from the boundaries of objects. However, the distortions are minimal around the wave front of the propagating shear wave. Therefore, we can avoid the effect of reflection on a region of interest (ROI) by adjusting the duration of mechanical vibrations. Thus, the ROI is often shorter than the propagating shear wavelength. In the MRE sequence, a motion-sensitizing gradient (MSG) is synchronized with mechanical cyclic motion. MRE images with multiple initial phase offsets can be generated with increasing delays between the MSG and mechanical vibrations. This paper proposes a method for measuring the local shear wavelength using MRE multiple initial phase patchwork offsets that can be used when the size of the object being measured is shorter than the local wavelength. To confirm the reliability of the proposed method, computer simulations, a simulated tissue study and in vitro and in vivo studies were performed.     

HITTM cells—high‐efficiency crystalline Si cells with novel structure

Our unique, high‐efficiency c‐Si solar cell, named the HIT cell, has shown considerable potential to improve junction properties and surface passivation since it was first developed. The improved properties in efficiency and temperature dependence compared to conventional p – n diffused c‐Si solar cells are featured in HIT power 21^TM solar cell modules and other applications which are now on the market. In the area of research, further improvement in the junction properties of the a‐Si/c‐Si heterojunction has been examined, and the highest efficiency to date of 20.1% has recently been achieved for a cell size of 101 cm². The high open circuit voltage exceeding 700 mV, due to the excellent surface passivation of the HIT structure, is responsible for this efficiency. In this paper, recent progress in HIT cells by Sanyo will be introduced. Copyright © 2000 John Wiley & Sons, Ltd.