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structure transition under high pressureYamanaka, Takamitsu*; Nakamoto, Yuki*; Sakata, Masafumi*; Shimizu, Katsuya*; Hattori, Takanori
Physics and Chemistry of Minerals, 51(1), p.4_1 - 4_10, 2024/02
Times Cited Count：0 Percentile：0.34(Materials Science, Multidisciplinary)Neutron and synchrotron X-ray diffraction and electric conductivity measurements of FeTiO ilmenite were performed under pressures. Ilmenite structure is retained up to 28 GPa. Structure analysis revealed that FeO
and TiO are compressible and less compressible below 8 GPa, respectively. The resistivity is lowest along the Fe-Ti direction that has shortest interatomic distance among all the metal ion pairs. The resistivity in the direction normal to c-axis monotonically decreases with pressure, whereas that along c-axis shows hallow-shape with pressure. Maximum entropy analysis shows that electron configuration of Fe
(3
) is more strongly changed than Ti
(3
) under compression. The anisotropic electrical conductivity and non-uniform structure change of Fe-Ti interatomic distance can be explained by the possible spin transition from high-spin state to intermediate-spin state of Fe cation.
Fe
O
solid solutions under high-pressure and high-temperature conditionsYamanaka, Takamitsu*; Hirao, Naohisa*; Nakamoto, Yuki*; Mikouchi, Takashi*; Hattori, Takanori; Komatsu, Kazuki*; Mao, H.-K.*
Physics and Chemistry of Minerals, 49(10), p.41_1 - 41_14, 2022/10
Times Cited Count：0 Percentile：0.02(Materials Science, Multidisciplinary)Magnetic and crystal structure of MnFeO solid solutions under high-PT conditions are investigated by neutron diffraction and synchrotron M
ssbauer spectroscopy. The ferrimagnetic-paramagnetic transition and tetragonal-cubic transition of Mn
FeO spinel occur at 100
C and 180C, respectively, suggesting both the transitions are not coupled. The structure transition temperature decreases with pressure. Mssbauer experiments and neutron diffraction revealed that the Fe occupancy in tetrahedral site increases increase with pressure, suggesting MnFeO phase approaches inverse spinel. Magnetic structure refinement clarified paramagnetic and ferrimagnetic structure of MnFeO and MnFeO. These spinels transform into high-pressure orthorhombic phases at 18.4 and 14.0 GPa, respectively, indicating lower transition pressure with increasing Mn content.
FeO spinel and postspinel with elevating pressureYamanaka, Takamitsu*; Rahman, S.*; Nakamoto, Yuki*; Hattori, Takanori; Jang, B. G.*; Kim, D. Y.*; Mao, H.-K.*
Journal of Physics and Chemistry of Solids, 167, p.110721_1 - 110721_10, 2022/08
Times Cited Count：1 Percentile：15.7(Chemistry, Multidisciplinary)High-pressure neutron diffraction proved that MnFeO and MnFeO spinels transform into CaMnO-type structure above 18 GPa and 14 GPa, respectively. The transition pressure of MnFeO solutions decreases with increasing Mn content. Synchrotron X-ray M
ssbauer experiments revealed that Fe and Fe
distribution at the tetrahedral (A) and octahedral (B) sites in the spinel structure changes with pressure. MnFeO and MnFeO spinels are ferrimagnetic and the CaMnO-type phase is paramagnetic. The temperature dependence of resistivity indicates that both spinels are semiconductors wherein electrons hop between cations at the A and B sites. A pressure-induced shortening of B-B distance promoted conduction via greater electron mobility between adjacent B cations. The Fe and Fe occupancies at the B sites in MnFeO are much larger than those in MnFeO. The CaMnO-type phase is metallic. Theoretical calculation confirmed the metallic character and Fe d-orbitals strongly renormalized compared to Mn d-orbitals.
U accumulations in 
naturally growing at the mill tailings pond; Iron plaque formation possibly related to root-endophytic bacteria producing siderophoresNakamoto, Yukihiro*; Doyama, Kohei*; Haruma, Toshikatsu*; Lu, X.*; Tanaka, Kazuya; Kozai, Naofumi; Fukuyama, Kenjin; Fukushima, Shigeru; Ohara, Yoshiyuki; Yamaji, Keiko*
Minerals (Internet), 11(12), p.1337_1 - 1337_17, 2021/12
Times Cited Count：1 Percentile：10.87(Geochemistry & Geophysics)Mine drainage is a vital water problem in the mining industry worldwide because of the heavy metal elements and low pH. Rhizofiltration using wetland plants is an appropriate method to remove heavy metals from the water via accumulation in the rhizosphere. is one of the candidate plants for this method because of metal accumulation, forming iron plaque around the roots. At the study site, which was the mill tailings pond in the Ningyo-toge uranium mine, 
has been naturally growing since 1998. The results showed that accumulated Fe, Mn, and U in the nodal roots without/with iron plaque compared with other plant tissues. Among the 837 bacterial colonies isolated from nodal roots, 88.6% showed siderophore production activities. Considering iron plaque formation around roots, we hypothesized that microbial siderophores might influence iron plaque formation because bacterial siderophores have catechol-like functional groups. The complex of catechol or other phenolics with Fe was precipitated due to the networks between Fe and phenolic derivatives. The experiment using bacterial products of root endophytes, such as 
spp. and 
spp., showed precipitation with Fe ions, and we confirmed that several 
spp. and 
spp. produced unidentified phenolic compounds. In conclusion, root-endophytic bacteria such as spp. and spp., isolated from metal-accumulating roots of , might influence iron plaque formation as the metal accumulation site. Iron plaque formation is related to tolerance in , and spp. and spp. might indirectly contribute to tolerance.
PtFukuda, Takashi*; Yamaguchi, Takashi*; Kakeshita, Tomoyuki*; Harjo, S.; Nakamoto, Tatsushi*
Journal of Applied Physics, 126(2), p.025107_1 - 025107_6, 2019/07
Times Cited Count：1 Percentile：4.41(Physics, Applied)Furusawa, Akinori; Nishimura, Akihiko; Takebe, Toshihiko*; Nakamura, Masaki*; Takenaka, Yusuke*; Saijo, Shingo*; Nakamoto, Hiroyuki*
E-Journal of Advanced Maintenance (Internet), 9(2), p.44 - 51, 2017/08
The aim of this work is to investigate the applicability of ultrasonic guided wave for evaluation of laser beam butt-welding quality. Ten in total test pipes having welding seam is prepared. Two piece of pipe are jointed and continuous laser beam is irradiated on the edges, varying laser irradiation power, welding side and surface profile of the adjacent edges of the pipe. Ultrasonic guided wave testing experiment is performed on the pipes. Torsional mode guided wave is excited by EMAT. The experimental results are analyzed and issues are discussed. The reflection wave bullet from the poor interface of the welding seam is clearly observed, whereas no reflection from fine welded line. From the aspect of laser irradiation power, welding side and surface profile of the adjacent edges, the relation between the interface condition and detection wave bullet are analyzed. It is found that the ultrasonic guided wave technologies have the potential for evaluating laser beam butt-welding seam.
Nakamoto, Tatsushi*; Sugano, Michinaka*; Xu, Q.*; Kawamata, Hiroshi*; Enomoto, Shun*; Higashi, Norio*; Idesaki, Akira; Iio, Masami*; Ikemoto, Yukio*; Iwasaki, Ruri*; et al.
IEEE Transactions on Applied Superconductivity, 25(3), p.4000505_1 - 4000505_5, 2015/06
Times Cited Count：0 Percentile：0(Engineering, Electrical & Electronic)Recently, development of superconducting magnet system with high radiation resistance has been demanded for application in accelerator facilities such as CERN LHC. In order to realize superconducting magnet system with high radiation resistance, it is necessary to develop electrical insulator with high radiation resistance because the electrical insulator is made of organic materials whose radiation resistance is inferior to that of inorganic materials. We developed a glass fiber reinforced plastic with bismaleimide-triazine resin. The developed material showed excellent radiation resistance; the material evolved gases of 5
10 
mol/g and maintained flexural strength of 640MPa (90% of initial value).
Oda, Yasuhisa; Oshima, Katsumi; Nakamoto, Takashi*; Hashimoto, Yasunori*; Yamamoto, Tsuyoshi; Hayashi, Kazuo*; Ikeda, Yukiharu; Ikeda, Ryosuke; Kajiwara, Ken; Takahashi, Koji; et al.
Purazuma, Kaku Yugo Gakkai-Shi, 90(7), p.365 - 373, 2014/07
no abstracts in English
(
3) under high pressureMatsuoka, Takehiro*; Kitayama, Takayasu*; Shimizu, Katsuya*; Nakamoto, Yuki*; Kagayama, Tomoko*; Aoki, Katsutoshi; Oishi, Yasuo*; Takemura, Kenichi*
High Pressure Research, 26(4), p.391 - 394, 2006/12
Times Cited Count：3 Percentile：26.57(Physics, Multidisciplinary)The electrical and structural properties of yttrium hydride YHx was studied by the in-situ measurements of the electrical resistance and X-ray diffraction up to 86 GPa. The electrical resistivity increased with applying pressure up to 10 GPa and showed a maximum which accompanied with the structural transition of metal lattice from hcp to fcc structure. In fcc phase the resistivity decreased significantly, however the value still remained larger by 4 orders of magnitude that that of pure yttrium metal. We could not confirm the insulator to metal transition up to 23 GPa. The resistivity showed another maximum in the large pressure region 40 60 GPa without the structural phase transition of metal lattice.
Np Moessbauer spectra and coordination numbers of Np atoms in neptunyl(V) compoundsSaeki, Masakatsu; Nakada, Masami; Nakamoto, Tadahiro*; Yamashita, Toshiyuki; ; Krot, N. N.*
Journal of Radioanalytical and Nuclear Chemistry, 239(2), p.221 - 225, 1999/00
Times Cited Count：7 Percentile：49.7(Chemistry, Analytical)no abstracts in English
Saeki, Masakatsu; Nakada, Masami; Nakamoto, Tadahiro*; ; Yamashita, Toshiyuki
Journal of Alloys and Compounds, 271-273, p.176 - 179, 1998/00
Times Cited Count：4 Percentile：39.22(Chemistry, Physical)no abstracts in English
Np Moessbauer spectroscopic study on pentavalent neptunium glycolate complexNakamoto, Tadahiro*; Nakada, Masami; ; Saeki, Masakatsu; Yamashita, Toshiyuki
Journal of Radioanalytical and Nuclear Chemistry, 227(1-2), p.137 - 141, 1998/00
Times Cited Count：2 Percentile：38.16(Chemistry, Analytical)no abstracts in English
Saeki, Masakatsu; Nakada, Masami; Yamashita, Toshiyuki; Nakamoto, Tadahiro*; Krot, N. N.*
Radiochimica Acta, 80(2), p.89 - 94, 1998/00
no abstracts in English
Murakami, Hiroyuki*; Kanamori, Masashi; Nakamoto, Athushi*; Seki, Akio
PNC TN841 81-57, 19 Pages, 1981/10
no abstracts in English
; Nakamoto, Athushi*; Kanamori, Masashi; Murakami, Hiroyuki*; Tsukuda, Masahiro*
PNC TN841 79-43, 94 Pages, 1979/06
no abstracts in English
Harjo, S.; Tsuchida, Noriyuki*; Nakamoto, Tatsushi*; Aizawa, Kazuya; Abe, Jun*; Gong, W.
no journal, ,
Furusawa, Akinori; Nishimura, Akihiko; Torimoto, Kazuhiro; Takenaka, Yusuke*; Toyama, Ryoji*; Nakamoto, Hiroyuki*
no journal, ,
The aim of this work presented here is to investigate the applicability of ultrasonic guided wave for evaluation of laser beam butt welding quality. First, laser beam butt welded pipes are prepared. Two pipes are jointed and continuous wave laser beam is irradiated on the line. The test pipes are divided into two groups according to the difference in laser welding quality. One group is fine quality welded, another group is poor. Second, ultrasonic guided wave testing experiment is performed on the pipes. Torsional mode guided wave is excited by Electromagnetic Acoustic Transducers. Finally, the experimental results are analyzed and issues are discussed. The reflection wave bullet from the poor welded line is clearly observed, whereas no reflection from fine welded line. It is found that the ultrasonic guided wave technologies have the potential for laser beam butt welding line evaluation.
Yamaji, Keiko*; Nakamoto, Yukihiro*; Haruma, Toshikatsu*; Doyama, Kohei*; Ohara, Yoshiyuki; Tanaka, Kazuya; Fukuyama, Kenjin; Fukushima, Shigeru
no journal, ,
no abstracts in English
U) and heavy metal (Fe, Mn) accumulation mechanism in phragmites australis influenced by root endophytic bacteriaNakamoto, Yukihiro*; Yamaji, Keiko*; Haruma, Toshikatsu*; Doyama, Kohei*; Ohara, Yoshiyuki; Tanaka, Kazuya; Fukuyama, Kenjin; Fukushima, Shigeru
no journal, ,
no abstracts in English
influenced by root endophytic bacteriaNakamoto, Yukihiro*; Yamaji, Keiko*; Haruma, Toshikatsu; Doyama, Kohei*; Ohara, Yoshiyuki; Fukuyama, Kenjin; Fukushima, Shigeru
no journal, ,
no abstracts in English
