Numerical simulation and PIV measurement of the flow-field in optical disc drives

A system of numerical flow simulation with an automated mesh generator and parallelized solver was developed and applied to the flow-field inside an optical disc drive. In this simulation system, a uniformly spaced Cartesian grid is used to reduce time and automatically generate a mesh from CAD data for complicated geometries, such as optical disc drives. The simulation results of optical disc drives are validated by particle image velocimetry (PIV) and pressure-distribution measurements. The measured velocity distributions above a rotating disc and around a pick-up unit show quantitative agreement with the simulated distributions. For the pressure distributions on a top case of an optical disc drive, although there is an error of 10% between simulated and measured results, the position of the peaks and distribution of pressure show good agreement. Comparing both sets of measurements, the simulation results in a Cartesian grid system are sufficiently accurate to enable the flow-field to be quantitatively assessed. This numerical flow simulation is applied to investigate the detailed flow-field in a commercial optical disc drive.     

Laser-induced shockwave chromatography: a separation and analysis method for nanometer-sized particles and molecules

A microscopic chromatography has been developed where nanometer-size molecules or particles are separated according to their size by the laser-induced shockwave in a water-filled capillary. As the shockwave passed through the mixture of molecules/particles in solution, they move to the direction of the propagation of the shockwave. The distance from the point of shockwave generation depends on the particle size or molecular weight. This technique has some advantages compared to conventional chromatography, in terms of quick analysis of molecular weight and applicability to sticky and adsorbing polymers. Experimental results obtained for proteins, their aggregates, and inorganic nanoparticles are presented.     

Development of a packaging material using antistatic ionomer part 2: charge distributions of potassium ionomer

Generally, plastics and plastic films are low in moisture absorption and high in electric insulation. They are inherently easy to be charged with static and can cause a variety of static troubles. We developed a functional packaging material to solve these static problems, by using potassium ionomer. We reported good antistatic performance (e.g. short static decay time, and excellent ash test) of potassium ionomer films in a previous paper. However, a mechanism underlying the antistatic property of potassium ionomer has not yet been fully elucidated. In this study, we measured the space charge distributions of potassium ionomer using the pulsed electro‐acoustic method. As a result of the space charge measurements, we found characteristic charge distribution of potassium ionomer film. On the basis of the existence of this characteristic charge distribution, we speculate that the space electric charge distribution of a potassium ionomer film under a direct current electric field shows apparent electric charge movement. Copyright © 2006 John Wiley & Sons, Ltd.     

Characterization of an Exo-Maltotetraose-forming Amylase of Pseudomonas stutzeri and Application in p-Nitrophenyl β-D-Galactosyl-α-Maltooligosaccharides Production

Some kinetic characteristics and hydrolytic action patterns on various β-D -galactosyl-maltooligosaccharides (Gal-Gn), ranging in size from D.P. (degree of polymerization) 5 to 8, of an exo-maltotetraose-forming amylase of Pseudomonas stutzeri (G4-amylase) were examined to produce a few p-nitrophenyl β-D -galactosyl-α-maltooligosaccharides (Gal-GnP, n = 4,5). The relative hydrolytic reaction rates for larger Gal-Gn by the enzyme were larger than those for smaller saccharides tough the values for unmodified linear maltooligosachharides were almost same. Michaelis constants (Km) for hydrolysis of Gal-G4, Gal-G5, Gal-G6 and Gal-G7 by the enzyme were 1.3, 1.9, 1.3 and 1.3mM, and apparent molecular activities (ko) for these saccharides were 5.9, 38, 91 and 126s⁻¹, respectively. The values of ko/Km for them were remarkably smaller than those for unmodified linear maltooligosaccharides. The G4-amylase cleaved 2 points of the α-1,4-glucosidic linkage in β-1,4-Gal-G4 to give β-1,4-Gal-G2 and -Gal-G3 in the molar ratio of 3:1, whereas the enzyme attacked 3 points of the linkage in β-1,4-Gal-G5, -Gal-G6 and -Gal-G7 to form β-1,4-Gal-G2,-Gal-G3 and Gal-G4 in the molar ratios of 2:5:1, 1:3:6 and 1:3:6, in the early stage of the reaction, respectively. On the other hand, the enzyme showed no action on β-1,6-Gal-G4 and formed β-1,6-Gal-G4 solely from β-1,6-Gal-G5, and β-1,6-Gal-G4 and -Gal-G5 were from β-1,6-Gal-G6 and -Gal-G7 in the ratios of 8:1 and 2:1, respectively. The enzyme also catalyzed the transfer action to produce Gal-G3P, Gal-G4P and Gal-G5P, of which the formation ratio was coincided well with the hydrolytic action pattern on each Gal-Gn, from Gal-Gn tested as a donor and p-nitrophenyl α-glucoside (GP) as an acceptor in an aqueous solution containing 40% (v/v) methanol. By using this novel reaction, Gal-G5P is now producing on an industrial scale to apply as a substrate for the assay of human α-amylase.     

Characterization and hydrogen sorption behaviors of FeNiCr-carbon composites derived from Fe,Ni and Cr-containing polyacrylonitrile fibers prepared by electrospinning method

In order to enhance hydrogen storage capacity of carbonaceous materials through metal modification, FeNiCr-carbon composites were prepared by calcination of Fe, Ni and Cr-containing polyacrylonitrile (PAN) fibers fabricated by electrospinning method. Fe (III), Ni (II) and Cr (III) acetylacetonates (M (acac)_n) were selected as metal sources. Increase of specific surface area and formation of micropores were observed on heat decomposition of M (acac)_n particularly through introduction of steam. Maximal hydrogen content, 1.62 mass%, was obtained at 77 K under 0.8 MPa of hydrogen for a FeNiCr-carbon composite, which contained about 15.5 mass% of metals and had specific surface area of 501 m² g^?1. The hydrogen content exceeded the hydrogen physisorption limit, 2.34 mass% per 1000 m² g^?1, which was calculated on the basis of the commensurate–incommensurate transition with an enhancing factor ρ of 1.126. After hydrogenation at 653 K, no hydrogen desorption peaks were observed for FeNiCr powders derived from M (acac)_n, and one peak at 828 K for a carbonaceous sample prepared from unmodified PAN fibers. From the most promising FeNiCr-carbon composite, another peak was recorded at 752 K in addition to the peak at 828 K. The former would be originated from hydrogen on novel sorption sites additionally created on the composite formation.     

Monitoring of acrylamide concentrations in potato chips in Japan between 2006 and 2010

Acrylamide levels in commercially available potato chips in Japan were monitored between August 2006 and June 2010 using the xanthydrol derivative gas chromatography-mass spectrometry (GC-MS) method. Seasonal and annual changes in acrylamide concentrations were determined. Nationwide bimonthly sampling of potato chips was carried out using a four-level design, and seasonal variations were detected in which the minimum acrylamide concentration was observed in August, and the maximum between February and June. Seasonal variations became less apparent after August 2008 as a result of annual effects and/or mitigation measures taken by the potato chip producers. Sampling uncertainties were separated into time-to-time, city-to-city, and lot-to-lot variation, and the largest variation was shown to be lot-to-lot including bag-to-bag.