Identification of an insertion sequence, IS1203 variant, in a Shiga toxin 2 gene of Escherichia coli O157:H7

An insertion sequence composed of 1310 bp was found in Shiga toxin 2 genes of some isolates of Escherichia coli O157:H7. This insertion sequence showed extremely high homology with IS1203 of E. coli O111:H(-). This IS1203 variant was inserted in the region encoding the amino-terminus of the B subunit with a duplication of 3 bp at the target site, resulting in inactivation of the Shiga toxin 2 gene.     

Abrasive wear resistance of spheroidal vanadium carbide cast irons

The effect of the chemical composition and heat treatment on the microstructure and abrasive wear resistance of V-Mn, V-Ni-Cr, and V-Mo spheroidal vanadium carbide cast irons (18–23 vol %) has been studied. The wear resistance has been determined under conditions of wear by abrasives with various hardnesses, i.e., corundum and quartz and compared to that of high-chromium cast iron with 13% Cr. It has been found that the advisability of using high-vanadium cast irons is governed by the hardness of the abrasive. When a hard abrasive, i.e., corundum was used, V-Mo cast iron with the maximum concentration of spheroidal VC carbides, which were uniformly distributed in the martensitic matrix, had the highest wear resistance. When a soft abrasive, i.e., quartz, was applied, high-chromium cast iron with a hardness of 68 HRC, which contained the largest amount of M₇C₃ carbides, was more wear-resistant. In the course of isothermal exposure at 300–1000°C, V-Ni-Cr and V-Mo cast irons with an austenitic structure had high resistance to phase and structural transformations. However, the properties and microstructure of V-Mo cast irons with a martensitic matrix depended strongly on the temperature of exposure during heat treatment.     

Error estimation of recursive orthogonal polynomial expansion method for large Hamiltonian system

Recursive polynomial expansion method is an efficient scheme to evaluate Green functions for large systems without direct diagonalization of the Hamiltonian. It is based on a polynomial expansion of the Green function, and has many advantages compared with other methods. However, there are little reports on its error estimations. In this paper, the cut-off error of the method is estimated analytically, which results from the truncation of expansion at finite orders. It is found that the error is inversely proportional to the number of expansion order N except for the singular points for the system with point spectrum. For the system with continuous spectrum, the error is inversely proportional to N^3/2 and decreases much faster in terms of the expansion order.     

Effects of 4He impurities on 3He nuclear spin-lattice relaxation in hcp solid 3He

Nuclear spin-lattice relaxation properties of hcp solid ³He with ⁴He impurities have been studied. At temperatures below the exchange plateau region, three kinds of relaxation time were observed. To analyze the data, a phenomenological four-bath model was developed, the four baths being the Zeeman bath, the phonon bath, an X-bath, and a Y-bath. The X-bath consists of the exchange bath and a part of the ⁴He-⁴He elastic interaction bath. The Y-bath is the main part of the elastic interaction bath. We measured the concentration dependence of the energy constants of all the baths, as well as the temperature and concentration dependences of the three kinds of relaxation time. The relaxation behavior corresponding to the process between the X-bath and the Y-bath could not be expressed by a single exponential function of time and the relaxation rate was strongly dependent on the concentration. This process may be related to the internal thermal equilibrium process within the elastic interaction bath. The impurity-dependent relaxation time between the X-bath and the phonon bath had a temperature dependence of T ^–n with n = 7.4±0.3.     

Hybridized synergy effect among TiO2, Pt and graphite silica on photocatalytic hydrogen production from water–methanol solution

The photocatalytic production of hydrogen gas from aqueous methanol solution was performed using powdered mixtures of graphite silica (GS) and platinized TiO₂ (Pt/TiO₂) or those of GS, Pt and TiO₂. The addition of GS to Pt/TiO₂ resulted in the decrease of the amount of H₂ gas, whereas the addition of GS to mixtures of TiO₂ and Pt led to the incremental production of H₂ gas. This effect is attributed to the aggregation of GS, TiO₂ and Pt in suspension. The new additional electron transfer process of TiO₂ → Pt → GS caused the increment of the amount of hydrogen gas.     

Antioxidant activity of Japanese pepper (Zanthoxylum piperitum DC.) fruit

Antioxidants were extracted from Japanese pepper (Zanthoxylum piperitum DC.) fruit and characterized. The antioxidant activity of the methanol extract from Japanese pepper fruit was found to be equal to that of α-tocopherol and stable under heat treatment. The main compounds that gave a significant antioxidant activity from the methanol extract were identified to be hyperoside (quercetin-3-O-galactoside) and quercitrin (quercetin-3-O-rhamnoside) as determined by HPLC, mass spectrometry, UV/Vis spectroscopy, and TLC. Radical-scavenging activities of hyperoside and quercitrin from Japanese pepper fruit were evaluated using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) method. As a result, hyperoside and quercitrin scavenged DPPH radical strongly with IC₅₀ values of 16 and 18 μM, respectively. These observations show the presence of strong antioxidants, namely hyperoside and quercitrin in Japanese pepper fruit.     

Ozonation of trichloroethylene in acetic acid solution with soluble and solid humic acid

The combined flushing and oxidation process using acetic acid and ozone has been used successfully to remove trichloroethylene (TCE) completely from contaminated soil. In this study, the effects of humic acid, a fraction of the organic matter in soil, over the performance of TCE decomposition was evaluated. TCE decomposition by ozone was enhanced by the presence of humic acid at concentrations lower than 8mgCL(-1) and then inhibited at higher concentrations. It is possible that the presence of the soluble humic acid fraction during the ozonation of TCE in acetic acid solutions produces hydroxyl radicals during the TCE ozonation which appears to be the reason for the enhanced TCE decomposition rate. Solid humic acid reduced TCE decomposition rate by acting as an ozone scavenger. Similarly, sorbed TCE reduced the amount of TCE available for decomposition by ozone in solution.     

Polymeric ultraviolet absorber

Polymeric fine powder, prepared by polymerization of glycidylmethacrylate–divinylbenzene, was reacted with 2,4-dihydroxylbenzophenone. The resultant polymer was effective as a polymeric ultraviolet absorber, and no migration was observed in polypropylene.     

Computer aided-molecular design of high performance nano-carbon materials: Na on graphenes

The electronic states of sodium ion (Na⁺) trapped on the model surfaces of amorphous carbon have been investigated by means of hybrid density functional theory (DFT) calculations to elucidate the nature of interaction between Na⁺/Na and the amorphous carbon surfaces. Also, direct molecular orbital-molecular dynamics (MO-MD) calculation [Tachikawa and Shimizu, J. Phys. Chem. B, 110 (2006) 20445] was applied to diffusion processes of the Na⁺ ion on the model surface of amorphous carbon. Seven models of graphene sheets (n = 7, 14, 19, 29, 37, 44 and 52, where n means numbers of rings in each carbon cluster) were considered in the present study. The B3LYP/LANL2MB calculations showed that the sodium ion is located at 2.24-2.26 Å from the graphene surfaces. The direct MO-MD calculations showed that the Na⁺ ion diffuses freely on the surface above 300 K. At higher temperature (1100 K), the Na⁺ ion moved from the center to edge region of the model surface. The nature of the interaction between Na⁺ and the amorphous carbon surfaces was discussed on the basis of theoretical results.     

Characteristics of creeping discharge developed in a narrow gap between insulators and effect of a backside electrode

Discharge characteristics have been investigated for a needle–plane electrode configuration containing insulating barriers with a narrow gap which has been placed between the needle and the plane. The characteristics of creeping discharge developed in the narrow gap of the barrier filled with SF₆ are especially considered. In the case of a configuration with a backside electrode below the needle, the corona generated from the needle easily extended to the gap. On the other hand, for a configuration without a backside electrode, the corona has hardly extended to the gap, and on increasing the applied voltage the corona developed greatly in the gap. This difference in corona extension should affect the flashover characteristics in the present system. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 146(2): 27–36, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10248