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271 results on '"Muroya, Yusa"'

56. Scavenging of "dry" electrons prior to hydration by azide ions: effect on the formation of H2 in the radiolysis of water by 60Co γ-rays and tritium β-electrons.

Author

Sanguanmith, Sunuchakan, Meesungnoen, Jintana, Muroya, Yusa, and Jay-Gerin, Jean-Paul

Subjects
TRITIUM, LINEAR energy transfer, MONTE Carlo method, RADIOLYSIS, ELECTRONS, CHEMICAL structure
Abstract

Copyright of Canadian Journal of Chemistry is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Published
2021
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66. Chemical repair activity of free radical scavenger edaravone; Reduction reactions with dGMP hydroxyl radical adducts and suppression of base lesions and AP sites on irradiated plasmid DNA

Author

Hata, Kuniki, Urushibara, Ayumi, Yamashita, Shinichi, Lin, M., Muroya, Yusa, Shikazono, Naoya, Yokoya, Akinari, Fu, H., and Katsumura, Yosuke

Abstract

Reactions of edaravone (3-methyl-1-phenyl-2-pyrazolin-5-one) toward deoxyguanosine monophosphate (dGMP) hydroxyl radical adducts were investigated by pulse radiolysis technique. Edaravone was found to reduce the dGMP hydroxyl radical adducts through electron transfer reactions. The rate constants of the reactions were higher than 4 $\times$ 10$^{8}$ dm$^{3}$ mol$^{-1}$ s$^{-1}$ and similar to those of the reactions of ascorbic acid, which is a representative antioxidant. Yields of single-strand breaks, base lesions, and abasic sites produced in pUC18 plasmid DNA by $\gamma$ ray irradiation in the presence of low concentrations of edaravone were also quantified, and the chemical repair activity of edaravone was estimated by a method recently developed by the authors. By comparing suppression efficiencies to the induction of each DNA lesion, it was found that base lesions and abasic sites were suppressed by the chemical repair activity of edaravone, although the suppression of single-strand breaks was not very effective. This phenomenon is attributed to the chemical repair activity of edaravone toward base lesions and abasic sites. However, the chemical repair activity of edaravone for base lesions was lower than that of ascorbic acid.

Published
2015

70. Effect of water density on the absorption maximum of hydrated electrons in sub- and supercritical water up to 400 °C.

Author

Jay-Gerin, Jean-Paul, Mingzhang Lin, Katsumura, Yosuke, Hui He, Muroya, Yusa, and Meesungnoen, Jintana

Subjects
ELECTRONS, ABSORPTION, SPECTRUM analysis, RADIATION chemistry, MICROSCOPICAL technique
Abstract

The optical absorption spectra of the hydrated electron (eaq-) in supercritical (heavy) water (SCW) are measured by electron pulse radiolysis techniques as a function of water density at three temperatures of 380, 390, and 400 °C, and over the density range of ∼0.2–0.65 g/cm3. In agreement with previous work, the position of the eaq- absorption maximum (EAmax) is found to shift slightly to lower energies (spectral “redshift”) with decreasing density. A comparison of the present EAmax-density data with other measurements already reported in the literature in subcritical (350 °C) and supercritical (375 °C) water reveals that at a fixed pressure, EAmax decreases monotonically with increasing temperature in passing through the phase transition at tc. By contrast, at constant density, EAmax exhibits a minimum as the water passes above the critical point into SCW. These behaviors are explained in terms of simple microscopic arguments based on the crucial role played by local density and configurational fluctuations (associated with criticality) in providing pre-existing polymeric clusters, which act as trapping sites for electrons. [ABSTRACT FROM AUTHOR]

Published
2008
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73. Time-dependent radiolytic yields of the solvated electrons in 1,2-ethanediol, 1,2-propanediol, and 1,3-propanediol from picosecond to microsecond

Author

Mingzhang Lin, Mostafavi, Mehran, Muroya, Yusa, Zhenhui Han, Lampre, Isabelle, and Katsumura, Yosuke

Subjects
Water chemistry -- Research, Ethanes -- Chemical properties, Radiolysis -- Usage, Chemicals, plastics and rubber industries
Abstract

The absorption spectra of the solvated electron in 1,2-ethanediol (12ED), 1,2-propanediol (12PD), and 1,3-propanediol (13PD) are determined by nanosecond pulse radiolysis techniques. The radiolytic yield in these viscous solvents is found to be strongly different from that of water solution.

Published
2006

74. Pulse radiolysis of 4,4'-bipyridyl aqueous solutions at elevated temperatures: Spectral changes and reaction kinetics up to 400 degree C

Author

Lin, Mingzhang, Katsumura, Yosuke, He, Hui, Muroya, Yusa, Han, Zhenhui, Miyazaki, Toyoaki, and Kudo, Hisaaki

Subjects
Chemistry, Physical and theoretical -- Research, Pyridine -- Chemical properties, Aqueous solution reactions -- Research, Radiolysis -- Research, Chemicals, plastics and rubber industries
Abstract

The spectral changes as well as the reaction kinetics of the transient species of 4,4'-bipyridyl (4,4'-bpy) are experimentally investigated by pulse radiolysis techniques up to 400 degree Celsius. The results show that the transient species such as OH adduct 4,4'-bpyOH., monoprotonated electron adduct 4,4'-bpyH. and doubly protonated electron adduct 4,4'-bpyH2+. have 15-20 nm blue shifts from room temperature to 400 degree Celsius.

Published
2005

78. Synthesis of Allene Derivatives and their Photophysical Processes

Author

muroya Yusa, Yamashita Takashi, Kato Jun, Katsumura Yousuke, and Mishiguchi Takuto

Subjects
chemistry.chemical_classification, Materials science, Polymers and Plastics, Double bond, Allene, Organic Chemistry, Cumulene, Photochemistry, chemistry.chemical_compound, chemistry, Excited state, Intramolecular force, Radiolysis, Ultrafast laser spectroscopy, Materials Chemistry, Flash photolysis, Physics::Chemical Physics
Abstract

Allenes, one of the compounds with cumulative double bonds, are attracting much interests due to the characteristics of their twisted π-conjugated bonds. Several allenes were synthesized to characterize their electronic features by their ground-state absorption, transient absorption and emission spectra to be found that they increase conjugation length in the excited state due to their conformational change. Photophysical process and active species were determined by laser flash photolysis and electron beam pulse radiolysis to find that intramolecular charge transfer of an allene is induced upon electron beam irradiation.

Published
2005

84. Upgrade of Cartridge-type Exchangeable Na2KSb Cathode RF Gun

Author

Uesaka, Mitsuru, Kanbe, Kohta, Miyoshi, Kunihiro, Muroya, Yusa, and Ueda, Toru

Subjects
03 Linear Colliders, Lepton Accelerators and New Acceleration Techniques, A08 Linear Accelerators, Accelerator Physics
Abstract

We are commissioning the cathode, Na2KSb at the wavelength of 266, 400 nm with thermo-mechanically modified structure and improved vacuum system (2·10⁻⁰⁸ Pa). We could improve RF reflection waveform and obtain the maximum energy of 22 MeV. We estimate the electrical field of 50 MV at the cathode. So far, we have obtained the quantum efficiencies of 1.1, 0.01% and the maximal charges of 4.6, 1 nC for 266, 400 nm. We are observing and checking carefully individual difference of QE of the cathodes for 266, 400 nm, and we have obtained 22 MeV energy. This new RF photocathode RF gun system has been already used for subpicosecond time-resolved radiation chemistry., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan

Published
2010
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