An efficient H2O2-based oxidative bromination of alkenes, alkynes, and aromatics by a divanadium-substituted phosphotungstate

A divanadium-substituted phosphotungstate TBA(4)[γ-HPV(2)W(10)O(40)] (TBA = tetra-n-butylammonium) could act as an effective homogeneous catalyst for the H(2)O(2)-based oxidative bromination.     

Natural radioactive nuclides in cigarettes and dose estimation for smokers

²¹⁰Po and ²¹⁰Pb contained in cigarettes might contribute to an increase in an effective dose. This article reports the effective dose of radionuclides to smokers based on results of a review of various parameters related to dose estimation for smokers. The annual effective dose to smokers was found to be 0.27 mSv year^?1, which was lower than an intervention exemption level (1 mSv year^?1) given in International Commission on Radiological Protection (ICRP Publ. 82).     

Preparation of micron-sized, monodispersed, monomer-adsorbed polymer particles utilizing the dynamic swelling method with loosely cross-linked seed particles

Influence of the water-addition rate (R _w ) (ml/h) on the monodispersity of monomer-adsorbed polymer particles prepared by utilizing the dynamic swelling method (DSM) with 1.9-μm-sized, monodispersed, loosely cross-linked polystyrene/styrene-divinylbenzene copolymer [1/(47.5–2.5), w/w] composite particles was examined theoretically and experimentally. The thermodynamic simulation under a kinetic control state indicates that, at the R _w values below 4, the cross-linked composite particles adsorb all styrenes separated from ethanol/water media. The experimental result at the R _w value of 2.66 supported it. At the R _w values above 5.32 and below 1.33, polydispersed styrene-adsorbed particles were prepared. The former depended on the formation of some pure styrene droplets not containing the composite particle. The latter depended on coalescence among the adsorbed particles by DSM. Received: 5 April 2000 Accepted: 5 October 2000     

Annealing behavior of spin density in UHV evaporated amorphous silicon

The ESR of amorphous silicon films evaporated in UHV has been measured at room temperature. Up to 900°C the annealing behavior of the spin density in the amorphous silicon films is quite different from that of films deposited in conventional HV.     

Development of a compact XRF probe using a ring‐type secondary target

Recently, on‐site analysis is being performed in many fields, and the use of compact instruments is required. In this article, we developed a compact x‐ray fluorescence (XRF) probe using a ring‐type secondary target. Employing the ring‐type target, coaxial optical geometry (irradiation and detection) could be achieved. We applied this probe to standard steel materials and standard solutions. In addition, a solid sample in solution was directly measured. As an application of the XRF probe, the monitoring of a chemical reaction was demonstrated that enabled observation of an increase in metallic ions. Copyright © 2008 John Wiley & Sons, Ltd.     

High-efficiency metal-semiconductor-metal photodetectors on heteroepitaxially grown Ge on Si

We demonstrate extremely efficient germanium-on-silicon metal-semiconductor-metal photodetectors with responsivities (R) as high as 0.85 A/W at 1.55 microm and 2V reverse bias. Ge was directly grown on Si by using a novel heteroepitaxial growth technique, which uses multisteps of growth and hydrogen annealing to reduce surface roughness and threading dislocations that form due to the 4.2% lattice mismatch. Photodiodes on such layers exhibit reverse dark currents of 100 mA/cm2 and external quantum efficiency up to 68%. This technology is promising to realize monolithically integrated optoelectronics.     

Differential cross section and photon-beam asymmetry for the gamma n --> K+ Sigma- reaction at E gamma = 1.5-2.4 GeV

Differential cross sections and photon-beam asymmetries have been measured for the gamma n --> K+ Sigma- and gamma p --> K+Sigma0 reactions separately using liquid deuterium and hydrogen targets with incident linearly polarized photon beams of E gamma = 1.5-2.4 GeV at 0.6 < cos ThetacmK< 1. The cross section ratio of sigma K+ Sigma-/sigma K+ Sigma0, expected to be 2 on the basis of the isospin 1/2 exchange, is found to be close to 1. For the K+ Sigma- reaction, large positive asymmetries are observed, indicating the dominance of K* exchange. The large difference between the asymmetries for the K+ Sigma- and K+ Sigma0 reactions cannot be explained by simple theoretical considerations based on Regge model calculations.     

Effect of surfactant agents and lipids on optical resolution of amino acid by ultrafiltration membranes containing bovine serum albumin

Ultrafiltration experiments for the optical resolution of racemic phenylalanine were performed in a solution system containing bovine serum albumin (BSA) and surfactant agents (Triton X-100, Tween 20, sodium dodecyl sulfate), lipid (phosphaticylcholine) and fatty acid (palmitic acid sodium salt). It was found that -phenylalanine preferentially existed in the permeate at pH 7.0 due to the binding of BSA to -phenylalanine in the feed and that the separation factors (=concentration ratio of -isomer to -isomer in the permeate) increased with a decrease in the BSA solution containing no additives and in the BSA solution containing Triton X-100 or Tween 20. The unusual tendency that the separation factors were less than unity was observed and the separation factors decreased with a decrease in the feed concentration of phenylalanine during the ultrafiltration containing the palmitic acid sodium salt or the phosphatidylcholine. This is caused by the fact that the binding constants of -phenylalanine to BSA are higher than those of -phenylalanine in the BSA solution containing the palmitic acid sodium salt or phosphatidylcholine. Since there were found conformational changes of BSA in the presence of palmitic acid sodium salt based on circular dichroism measurements of BSA solution, the conformational changes of BSA were attributed to the higher affinity of -phenylalanine to BSA than that of -phenylalanine in the BSA solution containing the palmitic acid sodium salt or phosphatidylcholine.