Preparation,morphology, and physical properties of transparent PSt hybrid materials containing silicone macromonomer

The aim of this study was to prepare transparent polystyrene (PSt) hybrid materials containing silicone macromonomer. Silicone urethane methacrylate (SiUMA) was synthesized by the reaction between the hydroxyl end groups of a silicone macromonomer and the isocyanate group of 2‐methacryloyloxyethyl isocyanate (MOI), and copolymers with different weight proportions were prepared by copolymerization of styrene (St), SiUMA and ethyleneglycol dimethacrylate (EGDMA). Though the prepared P(St‐co‐SiUMA) copolymers which had not introduced EGDMA were opaque, the prepared P(St‐co‐SiUMA‐co‐EGDMA) copolymers were transparent, similarly to pure PSt. DSC and ¹H‐NMR measurements were carried out to investigate the factors in this transparency in detail. From these measurement results, it was confirmed that the reactivity of the copolymerization had a significant influence on the transparency of the product. In addition, the contact angle of P(St‐co‐SiUMA‐co‐EGDMA) with 10 wt % SiUMA was greater than 90°, which was a 10° improvement compared to pure PSt. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of water vapor on tritium permeation behavior in the blanket system

It is found that most hydrogen supplied to the purge gas changed to water vapor due to the water formation reaction in the early stage of the blanket operation and that physical or chemical adsorbed water is released in the high concentration into the blanket purge gas when the blanket temperature becomes higher than several hundreds of degrees K if the pre-treatment is not applied to the solid breeder materials. Effect of coexistence of water vapor in the purge gas on permeation behavior of hydrogen through F82H ferritic steel in the breeding part and palladium–silver (Pd–Ag) in the recovery part is discussed because use of them is generally considered for recovery of bred tritium from the solid blanket. Almost no decrease in permeation rate of F82H is observed in this study when water vapor exists in the blanket purge gas. The permeability of hydrogen isotopes through the Pd–Ag pipe gradually decreases when water vapor exists in the blanket purge gas. Properties required in estimation of the hydrogen permeated to the purge gas are experimentally obtained in this study.     

Basic study of high‐frequency carrier‐type magnetic field sensor using shape anisotropy

We tried to control the magnetic anisotropy of a high‐frequency carrier‐type magnetic field sensor by the shape of the magnetic film instead of induced anisotropy. We confirmed that the impedance of the sensor could be changed by applying a magnetic field. In addition, we tried to control the magnetic anisotropy with magnetostatic energy. We show that the properties of the sensor can be controlled by designing the shape of the magnetic film. © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Deciphering Structural Alterations Associated with Activity Reductions of Genetic Polymorphisms in Cytochrome P450 2A6 Using Molecular Dynamics Simulations

Cytochrome P450 (CYP) 2A6 is a monooxygenase involved in the metabolism of various endogenous and exogenous chemicals, such as nicotine and therapeutic drugs. The genetic polymorphisms in CYP2A6 are a cause of individual variation in smoking behavior and drug toxicities. The enzymatic activities of the allelic variants of CYP2A6 were analyzed in previous studies. However, the three-dimensional structures of the mutants were not investigated, and the mechanisms underlying activity reduction remain unknown. In this study, to investigate the structural changes involved in the reduction in enzymatic activities, we performed molecular dynamics simulations for ten allelic mutants of CYP2A6. For the calculated wild type structure, no significant structural changes were observed in comparison with the experimental structure. On the other hand, the mutations affected the interaction with heme, substrates, and the redox partner. In CYP2A6.44, a structural change in the substrate access channel was also observed. Those structural effects could explain the alteration of enzymatic activity caused by the mutations. The results of simulations provide useful information regarding the relationship between genotype and phenotype.     

Virtual Alanine Scan of the Main Protease Active Site in Severe Acute Respiratory Syndrome Coronavirus 2

Recently, inhibitors of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) main protease (Mpro) have been proposed as potential therapeutic agents for COVID-19. Studying effects of amino acid mutations in the conformation of drug targets is necessary for anticipating drug resistance. In this study, with the structure of the SARS-CoV-2 Mpro complexed with a non-covalent inhibitor, we performed molecular dynamics (MD) simulations to determine the conformation of the complex when single amino acid residue in the active site is mutated. As a model of amino acid mutation, we constructed mutant proteins with one residue in the active site mutated to alanine. This method is called virtual alanine scan. The results of the MD simulations showed that the conformation and configuration of the ligand was changed for mutants H163A and E166A, although the structure of the whole protein and of the catalytic dyad did not change significantly, suggesting that mutations in His163 and Glu166 may be linked to drug resistance.     

Effect of crystallinity on electrochemical insertion/extraction of Li in transition metal oxides - Part II: TiO2, V2O5 and MoO3

Electrochemical insertion/extraction sf Li on cathode materials of anatase type TiO2, quasi-layered structure V2O5 and layered structure MoO3 was measured on samples of which structures were well characterized and showed a wide range of crystallinity. On the basis of experimental results on structure, morphology and charge-discharge characteristics, the effect of crystallinity of the cathode materials on electrochemical Li insertion/extraction performance was discussed. These three transition metal oxides were classified as one group on the basis of whether the crystallinity of these oxides affects to the performance or not, LiMn2O4 and LiCo0.5Ni0.5O2 belongs to the former group and TiO2, V2O5 and MoO3 to the latter.     

Band alignment tuning in twin-plane superlattices of semiconductor nanowires

The band alignments of twin-plane superlattices in semiconductor nanowires are systematically investigated on the basis of density functional calculations. Our calculations demonstrate that for nanowires with small diameters the quantum-confinement effect is prominent within wurtzite structure regions and the energy gap in wurtzite-structured nanowires is remarkably larger than that including zinc-blende structure. This results in the straddling band alignment, in which both electrons and holes are confined in zinc-blende structure region. The analysis using a simple tight-binding methods also clarifies that the straddling band alignments can be realized when the diameters of nanowires are less than 4-8 nm, leading to full control of band alignments by varying the nanowire diameter. Our results provide the ability of band-alignment tuning and open new possibilities for band engineering.     

Density Functional Theory of Freezing of Superfluid Helium 4

We discuss freezing of superfluid helium 4 in the frame of density functional theory. We first review the previous attempts made with different inputs for the liquid properties. We then present a new calculation based on a more recent input. Our resugt confirms the finding by Likos et al. [C. N. Likos, S. Moroni, and G. Senatore, Phys. Rev. B, 55, 8867 (1997)] that the solid is always too stable. However, a slight rescaling leads to freezing parameters and an equation of state for the solid consistent with the experiments. We discuss the physical origin of this rescaling.     

Structural analyses by TEM of iridium deposited on TiO2 powder and rutile single crystal

It was found by transmission electron microscopy (TEM) that deposition precipitation of Ir onto TiO2 powder (Degussa P-25) produced Ir particles preferentially on the rutile phase. Iridium oxide particles supported on rutile TiO2 single crystal by deposition precipitation were also observed by TEM and scanning electron microscopy, and were found to exist as thin films of a few atoms. A structural change caused by hydrogen reduction was observed using high-resolution TEM and this was confirmed to be the iridium oxide film being reduced to metallic iridium particles.     

Analytical TEM observation of Au and Ir deposited on rutile TiO2

As a model catalyst, gold and iridium were co-deposited on a single crystal of rutile TiO2 using the deposition precipitation method in order to clarify the synergetic effect of the combination of Au with Ir on the catalytic performance of the oxidative decomposition of odour and dioxins. Analyses by means of high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy and electron energy-loss spectroscopy revealed that pillars of IrO2 grew on the TiO2 substrate to each of which one Au nanoparticle was attached. This mushroom-like structure appeared to be formed by self-organization of Au, Ir and oxygen. Epitaxial contact was observed between the Au nanoparticle/IrO2 pillar and IrO2 pillar/TiO2 substrate interfaces. The growth process of the structure was investigated by transmission electron microscope observations of the Au-Ir complex before and after heating in air.