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Journal Articles

Initiatives to address the lifetime improvement of HBC stripper foil for 3GeV synchrotron of J-PARC

Yoshimoto, Masahiro; Nakanoya, Takamitsu; Yamazaki, Yoshio; Saha, P. K.; Kinsho, Michikazu; Yamamoto, Shunya*; Okazaki, Hiroyuki*; Taguchi, Tomitsugu*; Yamada, Naoto*; Yamagata, Ryohei*

Proceedings of 18th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.850 - 854, 2021/10

no abstracts in English

Journal Articles

Analysis of J-HBC stripper foil for the J-PARC RCS

Yoshimoto, Masahiro; Nakanoya, Takamitsu; Yamazaki, Yoshio; Saha, P. K.; Kinsho, Michikazu; Yamamoto, Shunya*; Okazaki, Hiroyuki*; Taguchi, Tomitsugu*; Yamada, Naoto*; Yamagata, Ryohei*

JPS Conference Proceedings (Internet), 33, p.011019_1 - 011019_7, 2021/03

The multi-turn charge-exchange H$$^{-}$$ beam injection scheme with stripper foils is one of the key techniques to achieve a MW-class high power proton beam. The J-PARC RCS adopts Hybrid type Boron-doped Carbon (HBC) stripper foil, which was developed in KEK to improve the lifetime. Indeed, the RCS user operation confirmed that HBC foil has the great advantage of a longer lifetime against high beam irradiation. To examine characteristics of the HBC foils, various beam studies were performed, such as the stripping efficiency measurement and long-term observation with an H$$^{-}$$ beam in the J-PARC RCS, foil analysis using RBS, EDR and PIXE methods, and SEM and TEM observation after the ion beam irradiation in Takasaki Ion Accelerators for Advanced Radiation Application (TIARA) on National Institutes for Quantum and Radiological Science and Technology (QST). Recently, the deposition apparatus for the HBC foils from the KEK Tsukuba-site was relocated to the JAEA Tokai-site, and we started fabrication of new HBC foil in 2017. (The new one fabricated in JAEA we call J-HBC foil.) And, we continue investigations in TIARA with the J-HBC foils. Furthermore, in-depth researches by changing the process parameters of the foil deposition are carried on. Recent results suggest that the amount of the boron doped in the foil is more important parameter than the ratio of the discharge amount of carbon from cathode and anode electrodes. In this presentation, we will report the details of recent analysis of the J-HBC foil.

Journal Articles

Preliminary test of the EA-AGE3 system for $$^{14}$$C measurement of CaCO$$_{3}$$ samples and coral-based estimation of marine reservoir correction in the Ogasawara Islands, Northwestern Subtropical Pacific

Kokubu, Yoko; Mitsuguchi, Takehiro*; Watanabe, Takahiro; Yamada, Tsutomu*; Asami, Ryuji*; Iryu, Yasufumi*

Radiocarbon, 61(5), p.1593 - 1601, 2019/10

 Times Cited Count:0 Percentile:0.01(Geochemistry & Geophysics)

We performed $$^{14}$$C measurements of two fossil and one modern corals using a combined system of an elemental analyzer and an automated graphitization equipment AGE3 (EA-AGE3 system) and JAEA-AMS-TONO. The $$^{14}$$C concentrations (pMC values) of mid-Holocene Okinawa corals obtained by our EA-AGE3 system appear to be slightly higher than those obtained by the conventional graphitization method using phosphoric acid. The pMC increase in our EA-AGE3 system may result in significant underestimation of $$^{14}$$C age especially for older samples (e.g., 10,000 BP); however, the pMC increase is negligible in $$^{14}$$C measurements of modern or recent samples. We applied the EA-AGE3 method to the pre- and post-bomb annual-band samples from the modern Ogasawara coral for $$^{14}$$C measurements. On the basis of the pre-bomb coral $$^{14}$$C data, we estimated marine reservoir correction ($$Delta$$R) around Ogasawara Islands and its stability between $$sim$$1900 and 1950 AD.

Journal Articles

Structure of a highly acidic $$beta$$-lactamase from the moderate halophile ${it Chromohalobacter}$ sp.560 and the discovery of a Cs$$^{+}$$-selective binding site

Arai, Shigeki; Yonezawa, Yasushi*; Okazaki, Nobuo*; Matsumoto, Fumiko*; Shibazaki, Chie; Shimizu, Rumi; Yamada, Mitsugu*; Adachi, Motoyasu; Tamada, Taro; Kawamoto, Masahide*; et al.

Acta Crystallographica Section D, 71(3), p.541 - 554, 2015/03

 Times Cited Count:6 Percentile:49.63(Biochemical Research Methods)

The crystal structure of halophilic $$beta$$-lactamase from ${it Chromohalobacter}$ sp.560 (HaBLA) was determined using X-ray crystallography. Moreover, the locations of bound Sr$$^{2+}$$ and Cs$$^{+}$$ ions were identified by anomalous X-ray diffraction. The location of one Cs$$^{+}$$ specific binding site was identified on HaBLA even in the presence of 9-fold molar excess of Na$$^{+}$$ (90 mM Na$$^{+}$$ /10 mM Cs$$^{+}$$). This Cs$$^{+}$$ binding site is formed by two main-chain O atoms and an aromatic ring of a side chain of Trp. An aromatic ring of Trp interacts with Cs$$^{+}$$ by the cation-$$pi$$ interaction. The observation of a selective and high-affinity Cs$$^{+}$$ binding site provides important information that is useful for designing artificial Cs$$^{+}$$ binding sites useful in bioremediation of radioactive isotopes.

Journal Articles

Elucidations of the catalytic cycle of NADH-cytochrome $$b$$$$_{5}$$ reductase by X-ray crystallography; New insights into regulation of efficient electron transfer

Yamada, Mitsugu*; Tamada, Taro; Takeda, Kazuki*; Matsumoto, Fumiko*; Ono, Hiraku*; Kosugi, Masayuki*; Takaba, Kiyofumi*; Shoyama, Yoshinari*; Kimura, Shigenobu*; Kuroki, Ryota; et al.

Journal of Molecular Biology, 425(22), p.4295 - 4306, 2013/11

 Times Cited Count:18 Percentile:49.48(Biochemistry & Molecular Biology)

NADH-Cytochrome $$b$$$$_{5}$$ reductase (b5R), a flavoprotein consisting of NADH and flavin adenine dinucleotide (FAD) binding domains, catalyzes electron transfer from the two-electron carrier NADH to the one-electron carrier cytochrome $$b$$$$_{5}$$ (Cb5). The crystal structures of both the fully reduced form and the oxidized form of porcine liver b5R were determined. In the reduced b5R structure determined at 1.68${AA}$ resolution, the relative configuration of the two domains was slightly shifted in comparison with that of the oxidized form. This shift resulted in an increase in the solvent-accessible surface area of FAD and created a new hydrogen-bonding interaction between the N5 atom of the isoalloxazine ring of FAD and the hydroxyl oxygen atom of Thr66, which is considered to be a key residue in the release of a proton from the N5 atom. The isoalloxazine ring of FAD in the reduced form is flat as in the oxidized form and stacked together with the nicotinamide ring of NAD$$^{+}$$. Determination of the oxidized b5R structure, including the hydrogen atoms, determined at 0.78${AA}$ resolution revealed the details of a hydrogen-bonding network from the N5 atom of FAD to His49 via Thr66. Both of the reduced and oxidized b5R structures explain how backflow in this catalytic cycle is prevented and the transfer of electrons to one-electron acceptors such as Cb5 is accelerated. Furthermore, crystallographic analysis by the cryo-trapping method suggests that re-oxidation follows a two-step mechanism. These results provide structural insights into the catalytic cycle of b5R.

Journal Articles

The Role of ${it Deinococcus radiodurans}$ RecFOR proteins in homologous recombination

Sato, Katsuya; Kikuchi, Masahiro; Ishaque, A. M.*; Oba, Hirofumi*; Yamada, Mitsugu; Tejima, Kohei; Onodera, Takefumi; Narumi, Issei

DNA Repair, 11(4), p.410 - 418, 2012/04

 Times Cited Count:21 Percentile:59.29(Genetics & Heredity)

In an effort to gain insights into the role of ${it D. radiodurans}$ RecFOR proteins in homologous recombination, we generated ${it recF}$, ${it recO}$ and ${it recR}$ disruptant strains and characterized the disruption effects. Disruption of ${it recR}$ resulted in severe reduction of the transformation efficiency. On the other hand, the ${it recF}$ disruptant strain was the most sensitive phenotype to $$gamma$$ rays, UV irradiation and mitomycin C among the three disruptants. In the ${it recF}$ disruptant strain, the intracellular level of the LexA1 protein did not decrease following $$gamma$$ irradiation. These results demonstrate that the RecF protein plays a crucial role in the homologous recombination repair process by facilitating RecA activation. Thus, the RecF and RecR proteins are involved in the RecA activation and the stability of incoming DNA, respectively, during RecA-mediated homologous recombination processes that initiated the ESDSA pathway in ${it D. radiodurans}$.

Journal Articles

Purification, crystallization and preliminary X-ray diffraction analysis of DNA damage response A protein from ${it Deinococcus radiodurans}$

Yamada, Mitsugu; Sato, Katsuya; Narumi, Issei

Acta Crystallographica Section F, 66(12), p.1614 - 1616, 2010/12

 Times Cited Count:1 Percentile:16.94(Biochemical Research Methods)

DNA damage response A protein (DdrA) from ${it Deinococcus radiodurans}$ has been suggested to be involved in DNA repair processes through binding to 3' ends of single-stranded DNA, thereby protecting the ends from nuclease digestion. In this study, a recombinant C-terminal truncated form of ${it D. radiodurans}$ DdrA (DdrA157), comprising of the first 157 residues of DdrA, was expressed in ${it E. coli}$, purified and crystallized. Single crystals of DdrA157 were obtained by a hanging drop method at 293 K. The crystal belonged to the monoclinic space group ${it P}$2$$_{1}$$, with unit-cell parameters ${it a}$ = 46.31, ${it b}$ = 180.26, ${it c}$ = 114.17 ${AA}$, ${it $beta$}$ = 90.02$$^{circ}$$. The crystal was expected to contain fourteen molecules in the asymmetric unit. Diffraction data were collected to 2.35 ${AA}$ resolution at beamline BL-5 of the Photon Factory and initial phase determinations were attempted by a molecular-replacement method using the human Rad52 structure.

Journal Articles

Formation of isotopically enriched silicon film from fluorosilane produced by isotopically selective infrared multiphoton dissociation

Oba, Hironori; Suzuki, Hiroshi*; Esaka, Fumitaka; Taguchi, Tomitsugu; Yamada, Yoichi; Yamamoto, Hiroyuki; Sasase, Masato*; Yokoyama, Atsushi

Journal of the Vacuum Society of Japan, 52(6), p.292 - 295, 2009/07

no abstracts in English

Journal Articles

Mechanical properties of SiC/SiC composite with magnesium-silicon oxide interphase

Igawa, Naoki; Taguchi, Tomitsugu; Yamada, Reiji; Ishii, Yoshinobu; Jitsukawa, Shiro

Journal of Nuclear Materials, 367-370(1), p.725 - 729, 2007/08

 Times Cited Count:10 Percentile:60.15(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Local crystal structures of Ge$$_{2}$$Sb$$_{2}$$Te$$_{5}$$ revealed by the atomic pair distribution function analysis

Shamoto, Shinichi; Kodama, Katsuaki; Iikubo, Satoshi; Taguchi, Tomitsugu; Yamada, Noboru*; Proffen, T.*

Japanese Journal of Applied Physics, Part 1, 45(11), p.8789 - 8794, 2006/11

 Times Cited Count:14 Percentile:48.45(Physics, Applied)

Two types of optical recording crystalline material Ge$$_{2}$$Sb$$_{2}$$Te$$_{5}$$ have been studied by neutron and X-ray powder diffraction measurements. One is the crystalline cubic-phase Ge$$_{2}$$Sb$$_{2}$$Te$$_{5}$$. The other is nanocrystalline-phase Ge$$_{2}$$Sb$$_{2}$$Te$$_{5}$$. For the nanocrystalline phase, the local crystal structure and the particle size distribution were obtained simultaneously by PDF analysis using a spherical-particle form factor. The lattice parameter is longer than that of the crystalline phase, suggesting an antimony-richer composition than the matrix. This compositional deviation would form the nanoparticle, resulting in nucleation-dominated crystal growth.

Journal Articles

Effect of thick SiC interphase layers on microstructure, mechanical and thermal properties of reaction-bonded SiC/SiC composites

Taguchi, Tomitsugu; Igawa, Naoki; Yamada, Reiji; Jitsukawa, Shiro

Journal of Physics and Chemistry of Solids, 66(2-4), p.576 - 580, 2005/02

 Times Cited Count:47 Percentile:83.35(Chemistry, Multidisciplinary)

SiC/SiC composites are expected to be one of the candidate materials for fusion reactors because of the low radioactivity after neutron irradiation and excellent mechanical properties at high temperature. Reaction-Bonding (RB) process was employed since this process has a possibility of producing a much denser matrix compared with other processes. SiC fibers, however, adhere strongly to the matrix because of high reactiveness of molten Si with the SiC fiber during RB process. In this study, we investigated the effects of SiC layer as an interphase on fracture behavior in the SiC/SiC. The specimen without an interphase layer showed catastrophic failure behavior while the specimen with SiC interphase layer exhibited non-catastrophic failure behavior by 3-point bending testing. The microstructure observation indicated that SiC fibers did not adhere to the matrix in the specimen with SiC interpahse layer. After 3-point bending testing, the pull-out phenomenon occurred in the SiC/SiC with SiC interphase layer while did not occur in the composite without interphase layer.

Journal Articles

Preparation and characterization of magnesium-silicon based oxide coating on high-crystalline SiC fiber as an interphase in SiC/SiC composite

Igawa, Naoki; Taguchi, Tomitsugu; Yamada, Reiji; Ishii, Yoshinobu; Jitsukawa, Shiro

Ceramic Engineering and Science Proceedings, Vol.26, No.2, p.27 - 34, 2005/00

no abstracts in English

Journal Articles

Structures of optical recording materials Ge$$_2$$Sb$$_{2+x}$$Te$$_5$$ studied by pulsed neutron diffraction

Shamoto, Shinichi; Taguchi, Tomitsugu; Matsunaga, Toshiyuki*; Yamada, Noboru*; Ishii, Kenji; Inami, Toshiya

Materials Research Society Symposium Proceedings, Vol.840, p.125 - 130, 2005/00

Metastable cubic Ge$$_2$$Sb$$_{2+x}$$Te$$_5$$ samples, which are widely used as optical recording materials, have been studied by both of pulsed neutron and X-ray powder diffraction measurements. The crystalline cubic phases are found to coexist with two types of amorphous phases, depending on their antimony contents. One has the same first sharp diffraction peak (FSDP) as the amorphous antimony at the higher Q position. Another has a new FSDP at a lower Q position. The origin of the peak shift is discussed in terms of their constituents.

Journal Articles

Thermal diffusivity/conductivity of Tyranno SA fiber- and Hi-Nicalon type S fiber-reinforced 3-D SiC/SiC composites

Yamada, Reiji; Igawa, Naoki; Taguchi, Tomitsugu

Journal of Nuclear Materials, 329-333(Part1), p.497 - 501, 2004/08

 Times Cited Count:27 Percentile:84.02(Materials Science, Multidisciplinary)

SiC fiber reinforced SiC composites (SiC/SiC) have a potential for a structural material for a blanket wall of advanced fusion reactors. To reduce thermal stresses in the wall under heavy thermal loads SiC/SiC composites are expected to have high thermal conductivity as possible. Advanced SiC fibers recently developed, such as Tyranno SA and Hi-Nicalon Type S have been employed for weaving 3D textures as well as those 2D unwoven fabrics. The CVI and PIP/CVI fabrication methods were used. The thermal conductivity at RT was 40-50 W/mK and 35-40 W/mK for Tyranno CVI and PIP/CVI composites, respectively, whereas about 25 and about 17 W/mK at 1000 $$^{circ}$$C. 2D unwoven CVI composites had less than 12 W/mK for RT-1000 $$^{circ}$$C. For Hi-Nicalon Type S, 3D CVI composites had about 35 and about 20 for RT and 1000 $$^{circ}$$C, respectively. The reason of these high thermal conductivities was ascribed to higher density as well as better SiC crystallinity. The fiber configuration effects on the thermal conductivity of SiC/SiC composites were dominant in the low temperature region.

Journal Articles

Preparation of silicon-based oxide layer on high-crystalline SiC fiber as an interphase in SiC/SiC composites

Igawa, Naoki; Taguchi, Tomitsugu; Yamada, Reiji; Ishii, Yoshinobu; Jitsukawa, Shiro

Journal of Nuclear Materials, 329-333(Part1), p.554 - 557, 2004/08

 Times Cited Count:4 Percentile:30.31(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Highly thermal conductive sintered SiC fiber-reinforced 3D SiC/SiC composites; Experiments and finite-element analysis of the thermal diffusivity/conductivity

Yamada, Reiji; Igawa, Naoki; Taguchi, Tomitsugu; Jitsukawa, Shiro

Journal of Nuclear Materials, 307-311(Part2), p.1215 - 1220, 2002/12

 Times Cited Count:22 Percentile:79.54(Materials Science, Multidisciplinary)

SiC fiber-reinforced SiC composites (SiC/SiC) are considered an advanced structural material for blanket modules of a fusion reactor, which requires high thermal conductivity in order to keep thermal stresses in the material lower than the allowable design stress. The sintered SiC fiber recently developed has obtained high thermal conductivity, so it is highly expected that sintered SiC fiber-reinforced SiC/SiC composites would also show high thermal conductivity. In this study several types of 3D SiC/SiC composites were fabricated by either CVI or PIP method. The results of the thermal conductivity measurements show that the maximum thermal conductivity at room temperature was about 60 W/mK for CVI composites or 25W/mK for PIP ones. These values are considerably higher than those of non-sintered SiC fiber reinforced SiC/SiC composites, which indicates a possibility that the developed materials would be promising. The FEM thremal analysis shows the good agreement between the caluculated and experimental results.

Journal Articles

A Finite-element analysis of the thermal diffudivity/conductivity of SiC/SiC composites

Yamada, Reiji; Igawa, Naoki; Taguchi, Tomitsugu

Advanced SiC/SiC Ceramic Composites: Developments and Applications in Energy Systems; Ceramic Transactions Vol. 144, p.289 - 299, 2002/00

A Finite-element method(FEM) was applied for a computer simulation of a laser flash method for measuring thermal diffusivity of SiC/SiC composites. To understand the effect of individual fiber and matrix thermal conductivities as well as fiber volume on the overall composite's thermal diffusivity, the cases of high and low values for the fiber and matrix thermal conductivities were calculated as a function of fiber volume fraction at specimen temperatures of 200 and 900$$^{circ}C$$. The results of calculations showed that if low thermal conductive SiC fibers were used, the increase of fiber volume worsened the composite thermal diffusivity with highly conductive matrix, whereas when using highly conductive SiC fiber, the effect of increasing fiber volume was positive for increasing the composite diffusivity with low matrix thermal conductivity. The specimen temperatures altered the values of the composite thermal diffusivity but the qualitative tendencies above mentioned were maintained.

Journal Articles

Mechanical and thermal properties of dense SiC/SiC composite fabricated by reaction-bonding process

Taguchi, Tomitsugu; Igawa, Naoki; Yamada, Reiji; Futakawa, Masatoshi; Jitsukawa, Shiro

Ceramic Engineering and Science Proceedings (25th Annual Conference on Composites, Advanced Ceramics, Materials, and Structures: A), 22(3), p.533 - 538, 2001/03

no abstracts in English

Journal Articles

Mechanical and thermal properties of 2-D and 3-D SiC/SiC Composites

Yamada, Reiji; Taguchi, Tomitsugu; Igawa, Naoki

Journal of Nuclear Materials, 283-287(Part.2), p.574 - 578, 2000/12

 Times Cited Count:61 Percentile:95.84(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Mg-Si-Al-O coatings on Hi-Nicalon SiC fiber by Alkoxide method

Igawa, Naoki; Taguchi, Tomitsugu; Yamada, Reiji; Jitsukawa, Shiro

Ceramic Engineering and Science Proceedings (24th Annual Conference on Composites, Advanced Ceramics, Materials, and Structures: B), 21(4), p.237 - 242, 2000/09

no abstracts in English

44 (Records 1-20 displayed on this page)