Charge density study under high pressure

The experimental and analytical method of the high-pressure powder experiment at BL10XU, SPring-8, is described. There is no doubt that BL10XU must be one of the most appropriate beam lines for high pressure X-ray diffraction experiment taking advantage of third generation synchrotron source. As an example of the advanced charge density study under high pressure, the structural change of Cs₂Au₂Br₆ by applying pressure is studied by Rietveld/MEM analysis. It reveals that the structural change of Cs₂Au₂Br₆ by applying pressure occurs basically at electron level, such as valence state change and chemical bonding, which may be called the electronic phase transition.     

Preparation and Properties of Anti-Reflection/Anti-Static Thin Films for Cathode Ray Tubes Prepared by Sol-Gel Method Using Photoirradiation

A new technique for preparing anti-reflection/anti-static thin films for CRTs at low temperature has been developed. Double-layered films of SiO₂/SnO₂ were formed on a CRT panel surface by the sol-gel method using photoirradiation. The new method makes it possible to reduce heat treatment temperature (°C) by almost 50% and treatment time to approximately 33% of the conventional levels.     

Selective chemical vapor deposition synthesis of double-wall carbon nanotubes on mesoporous silica

Double-wall carbon nanotubes (DWNTs) have been selectively synthesized over Fe/Co loaded mesoporous silica by catalytic chemical vapor deposition of alcohol. Several silica materials with desired pore diameter and morphology have been investigated for the DWNT growth. The diameter distribution and selectivity of the DWNT are found to depend on the reaction temperature, pore size, and thermal stability of the support material. A high-yield synthesis of DWNTs has been achieved at 900 degrees C over high-temperature stable mesoporous silica. The outer diameter of DWNTs is found to be in the range of 1.5-5.4 nm with a "d" spacing of 0.38 +/- 0.02 nm between inner and outer layers, which is much larger than those of multiwall carbon nanotubes.     

Dehydrogenation of ethylbenzene with CO2 over Cr-MCM-41 catalyst

M-MCM-41 catalysts (M: V, Cr, Fe, and Ga) prepared by direct hydrothermal synthesis (DHT) have been tested for dehydrogenation of ethylbenzene with CO₂. The synthesized materials were characterized by X-ray diffraction (XRD), N₂ adsorption (77 K), and diffuse reflectance UV–vis spectroscopic measurements. Cr-MCM-41 showed the highest activity among M-MCM-41 catalysts tested, resulting in the production of styrene with the conversion of 65% and the selectivity above 90%. The rate of styrene formation increased with increasing Cr loading up to 1.7 wt.%. It is suggested that Cr(VI)O₄ in tetrahedral coordination is formed as an active monochromate species and reduced to Cr(III)O₆ in octahedral coordination as a less active polychromate species during the reaction. Deactivated catalyst was regenerated by a treatment with gaseous oxygen or CO₂, during which redistribution as well as reoxidation of polymeric Cr(III)O₆ octahedra to monomeric Cr(VI)O₄ tetrahedra was observed. The rate of CO formation increased together with that of styrene formation, while the rate of H₂ formation decreased, with increasing partial pressure of CO₂. It was confirmed that reverse water-gas shift reaction took place over Cr-MCM-41 by a separate experiment. The rate of CO formation during the dehydrogenation of ethylbenzene with CO₂ over Cr-MCM-41 was well accounted for by assuming parallel occurrence of two reactions, i.e., direct oxidative dehydrogenation of ethylbenzene with CO₂ and simple dehydrogenation of ethylbenzene thermodynamically assisted by reverse water-gas shift reaction.     

DNA topology on an increase in positive writhing number of DNA: conformation changes in the time course of cis-diamminedichloroplatinum(II)-DNA adducts

We show that the topological significance of the gel mobility of cis-diamminedichloroplatinum(II) (DDP)-closed circular DNA (ccDNA) adducts decreases with reaction time, until a point at which it joins relaxed DNA, and that the mobility of the adducts increases again. There is no relationship between the relative length of the adducts and the gel mobility. Although the significance of the decrease of gel mobility is due to the unwinding of cis-DDP-DNA (or trans-DDP-DNA) adducts, the conformational significance of the subsequent increase in mobility is unclear. To elucidate the conformational significance for unwinding of the adducts, we measured the writhing number (Wk) of the adducts using electron microscopy and analyzed the topological states of cis-DDP (or trans-DDP) adducts based on the White rule, Lk=Wk+Tk. Where, Lk and Tk represent the linking and twisting number in the ring, respectively. From the data, we found that the Wk of cis-DDP-ccDNA adducts in comparison with trans-DDP-ccDNA adducts increases from a negative to a positive number with time. This suggests that cis-DDP plays a role in the change of the topological state of ccDNA. In the abstraction of platinum from the adducts with CN- ion, the differences in both topological states may explain why Pt in trans-DDP is abstracted more easily than in cis-DDP. To explain the abstraction of Pt ion, we also discuss the findings based on the thermodynamic cycle in a intermolecular crosslink model Pt(NH3)2(guanine)2(2+)-->Pt(CN)4(2-) using the Pt parametrized PM3 method.     

Synthesis of 2-, 4- and 5-(2-alkylcarbamoyl-1-methylvinyl)-7-alkyloxybenzo[b]furans and their leukotriene B4 receptor antagonistic activity

Variable benzo[b]furan derivatives having (E)- and (Z)-2-alkylcarbamoyl-1-methylvinyl groups at the 2-, 4- and 5-positions and a carboxylpropoxy or (1-phenyl)ethoxy group at the 7-position were prepared to find novel and selective leukotriene B4(LTB4) receptor antagonists. (E)-2-(2-diethylcarbamoyl-1-methylvinyl)-7-(1-phenylethoxy)benzo[b]furan (4v) showed selective inhibition to the human BLT2 receptor (hBLT2). On the other hand, (E)-2-acetyl-4-(2-diethylcarbamoyl-1-methylvinyl)-7-(1-phenylethoxy)benzo[b]furan (7v) inhibited both human BLT(1) receptor (hBLT1) and hBLT2. The (E)-2-(2-diethylcarbamoyl-1-methylvinyl) group lay on approximately the same plane as the benzo[b]furan ring, whereas the (E)-4-(2-diethylcarbamoyl-1-methylvinyl) group had the torsion angle (45.7 degree) from the benzo[b]furan ring plane. However, the (Z)-(2-alkylcarbamoyl-1-methylvinyl)benzo[b]furans were inactive. The inhibitory activity depended on the conformation of the 2-diethylcarbamoyl-1-methylvinyl group.