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61.
A novel dodeca-ligated undecagold cluster having a nonagold core plus two exo-attached gold atoms was synthesized. Unlike the conventional icosahedron-based "core-only" isomer, the [9+2] cluster showed an intense visible absorption band. Theoretical calculation showed the involvement of the exo gold atoms in the generation of the unique electronic structure. 相似文献
62.
Bunchiro Yamada Hiroaki Kamei Takayuki Otsu 《Journal of polymer science. Part A, Polymer chemistry》1980,18(6):1917-1922
Thermal decomposition of α,α′-azobisisobutyronitrile (AIBN) and dimethyl α,α′-azobisisobutyrate (MAIB) in the presence of a large amount of tin tetrachloride was investigated to determine the effect of complex formation on the decomposition rates and yields of the recombination products. The addition of tin tetrachloride significantly increased the decomposition rates; the observed first-order rate constant increased by factors of 4.5 and 17 at molar ratios of [SnCl4]/[AIBN] = 21.65 and [SnCl4]/[MAIB] = 19.53, respectively. It was found that the decomposition of these azo compounds was also accelerated by the addition of a comparable amount of donor solvent such as ethyl acetate or propionitrile to tin tetrachloride and that the enhancement in rate was accounted for by a larger frequency factor in the Arrhenius equation. Furthermore, the addition of tin tetrachloride seemed to suppress the formation of recombination products, tetramethyl succinonitrile and dimethyl tetramethylsuccinate, of the radicals produced by decomposition. 相似文献
63.
Hironobu Ikehata Toshio Mori Yasuhiro Kamei Thierry Douki Jean Cadet Masayuki Yamamoto 《Photochemistry and photobiology》2020,96(1):94-104
The cyclobutane pyrimidine dimer (CPD) is a main mutagenic photolesion in DNA produced by UVR. We previously studied the wavelength-dependent kinetics of mutation induction efficiency using monochromatic UVR sources and transgenic mice developed for mutation assay and established the action spectra of UVR mutagenicity in the mouse epidermis and dermis. Here, we further established the action spectra of CPD and pyrimidine(6-4)pyrimidone photoproduct formation in the same tissues and in naked DNA using the same sources and mouse strain. Quantitative ELISA helped us estimate the photolesion formation efficiencies on a molecule-per-nucleotide basis. Using these action spectra, we confirmed that the UVR mutation mostly depends on CPD formation. Moreover, the mutagenicity of a CPD molecule (CPD mutagenicity) was found to vary by wavelength, peaking at approximately 313 nm in both the epidermis and dermis with similar wavelength-dependent patterns. Thus, the CPD formation efficiency is a main determinant of UVR mutagenicity in mouse skin, whereas a wavelength-dependent variation in the qualitative characteristics of CPD molecules also affects the mutagenic consequences of UVR insults. In addition, the CPD mutagenicity was always higher in the epidermis than in the dermis, suggesting different cellular responses to UVR between the two tissues irrespective of the wavelength. 相似文献
64.
Tanabe K Iida H Haruna K Kamei T Okamoto A Nishimoto S 《Journal of the American Chemical Society》2006,128(3):692-693
Amperometry was employed to characterize the anthraquinone (AQ)-photoinjected hole transport through a 20-mer oligodeoxynucleotide (ODN) duplex, as immobilized on the surface of a gold electrode, and its triplex forms converted by association with several third oligopyrimidine (OPD) short strands. While the cathodic photocurrent was observed upon irradiation at 365 nm of the AQ photosensitizer linked to the end of DNA duplex, a marked lowering of the current density was identified to occur by the triplex formation of a duplex with a given third OPD short strand. The photocurrent through the DNA duplex showed a reversible fall-rise response concomitant with alternating association-dissociation cycle of the OPD short-strand, as regulated by temperature change around the corresponding melting temperature of the DNA triplex. Both the switched photoirradiation and the thermally alternating duplex-triplex conversion could provide tools of regulating the DNA hole transport. 相似文献
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Akira Kitamura Kenso Fujiwara Morihiro Mihara Mark Cowper Gento Kamei 《Journal of Radioanalytical and Nuclear Chemistry》2013,298(1):485-493
The solubility of thorium and americium in pore water squeezed from a cement paste was investigated by a batch method from oversaturation. The cement paste was prepared by mixing ordinary Portland cement with deionised water; in some cases the deionised water contained a polycarboxylic acid–base type superplasticiser. Following solidification, pore water was squeezed from the cement paste and collected for use in the solubility experiments. The aim of these was to investigate whether there was any effect of superplasticiser on the solubility of thorium and americium in the squeezed cement pore waters. The obtained solubility values in the two squeezed pore waters (with and without superplasticiser present) were similar. Thermodynamic calculations were performed with the thermodynamic database developed by Japan Atomic Energy Agency and compared with the experimental data to verify their applicability. These results showed that the superplasticiser used in the present study after mixing with the cement paste did not have a significant effect on solubility of thorium and americium, and the thermodynamic calculations were applicable in the present system. Size distribution of colloidal species of thorium and americium was also investigated. 相似文献
70.
Yoshiyuki Kojima Shinnosuke Kamei Takeshi Toyama Nobuyuki Nishimiya 《Journal of luminescence》2009,129(7):751-754
The emission intensity of phosphors is often subject to concentration quenching after doping of the activator in the host crystal rises above a certain limit. This study describes the preparation of novel phosphors based on tobermorite that do not exhibit concentration quenching. In the preparation of phosphors, Eu3+ ions are exchanged with intercalated Ca2+ ions within the tobermorite by dipping in EuCl3 solution. The emission intensity of the Eu3+ doped tobermorite increased with increasing Eu/Ca atomic ratio and attained a maximum value of 8.6% for a Eu/Ca atomic ratio of 0.22. Heating of the phosphor at 800 °C resulted in a three-fold improvement in emission intensity. 相似文献