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Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Takagi, Yasuhiko*; Nakamura, Tomoki*; Hiroi, Takahiro*; Matsuoka, Moe*; et al.
Nature Astronomy (Internet), 5(3), p.246 - 250, 2021/03
Times Cited Count:30 Percentile:96.87(Astronomy & Astrophysics)Here we report observations of Ryugu's subsurface material by the Near-Infrared Spectrometer (NIRS3) on the Hayabusa2 spacecraft. Reflectance spectra of excavated material exhibit a hydroxyl (OH) absorption feature that is slightly stronger and peak-shifted compared with that observed for the surface, indicating that space weathering and/or radiative heating have caused subtle spectral changes in the uppermost surface. However, the strength and shape of the OH feature still suggests that the subsurface material experienced heating above 300 C, similar to the surface. In contrast, thermophysical modeling indicates that radiative heating does not increase the temperature above 200 C at the estimated excavation depth of 1 m, even if the semimajor axis is reduced to 0.344 au. This supports the hypothesis that primary thermal alteration occurred due to radiogenic and/or impact heating on Ryugu's parent body.
Hirakawa, Moe*; Kikuchi, Yuichiro*; Sakai, Takaaki*; Tanaka, Masaaki; Ohshima, Hiroyuki
Proceedings of 26th International Conference on Nuclear Engineering (ICONE-26) (Internet), 8 Pages, 2018/07
Gas entrainment (GE) from cover gas is one of key issue for Sodium-cooled fast reactors to prevent unexpected effects to core reactivity. By using a computational fluid dynamics (CFD) code, analyses have been conducted to estimate the drifting vortexes on water experiments which were generated as wake vortexes behind a plate obstacle in the circulating water channel. In this paper, the results of comparison between experiments and analyses were discussed and the gas core lengths from the surface vortexes were evaluated by using the evaluation tool named StreamViewer developed by Japan Atomic Energy Agency.
Toyoshima, Atsushi; Li, Z.*; Asai, Masato; Sato, Nozomi; Sato, Tetsuya; Kikuchi, Takahiro; Kaneya, Yusuke; Kitatsuji, Yoshihiro; Tsukada, Kazuaki; Nagame, Yuichiro; et al.
Inorganic Chemistry, 52(21), p.12311 - 12313, 2013/11
Times Cited Count:5 Percentile:23.73(Chemistry, Inorganic & Nuclear)The reduction behavior of mendelevium (Md) was studied using a flow electrolytic chromatography apparatus. By applying appropriate potentials on the chromatography column, the more stable Md is reduced to Md. The reduction potential of the Md + e Md couple was determined to be -0.160.05 V vs. a normal hydrogen electrode.
Li, Z.*; Toyoshima, Atsushi; Asai, Masato; Tsukada, Kazuaki; Sato, Tetsuya; Sato, Nozomi; Kikuchi, Takahiro; Nagame, Yuichiro; Schdel, M.; Pershina, V.*; et al.
Radiochimica Acta, 100(3), p.157 - 164, 2012/03
Times Cited Count:12 Percentile:69.15(Chemistry, Inorganic & Nuclear)Kasamatsu, Yoshitaka*; Toyoshima, Atsushi; Asai, Masato; Tsukada, Kazuaki; Li, Z.; Ishii, Yasuo; Tome, Hayato*; Sato, Tetsuya; Kikuchi, Takahiro; Nishinaka, Ichiro; et al.
Chemistry Letters, 38(11), p.1084 - 1085, 2009/10
Times Cited Count:14 Percentile:49.01(Chemistry, Multidisciplinary)We report on the characteristic anion-exchange behavior of the superheavy element dubnium (Db) with atomic number Z = 105 in HF/HNO solution at the fluoride ion concentration [F] = 0.003 M. The result clearly demonstrates that the fluoro complex formation of Db is significantly different from that of the group-5 homologue Ta in the 6th period of the periodic table while the behavior of Db is similar to that of the lighter homologue Nb in the 5th period.
Akiyama, Kazuhiko; Sueki, Keisuke*; Tsukada, Kazuaki; Yaita, Tsuyoshi; Miyake, Yoko*; Haba, Hiromitsu*; Asai, Masato; Kodama, Takeshi*; Kikuchi, Koichi*; Otsuki, Tsutomu*; et al.
Journal of Nuclear and Radiochemical Sciences, 3(1), p.151 - 154, 2002/06
The oxidation state of actinide elements encapsulated in fullerenes is studied. HPLC elution behavior of actinide-fullerenes is classified into two groups; the elution behavior of the first group, encapsulating U, Np, and Am, is similar to that of the light lanthanide-fullerenes, such as La, Ce, Pr, and Nd, while the behavior of the second group, encapsulating Th and Pa, is quite different from that of any lanthanide-fullerenes. The chemical species in the main HPLC elution peak of each group were identified as M@C82 and M@C84 (M = metal atom) from the mass of the U and Th fullerenes, respectively. The oxidation states of the U and Th atoms in the fullerenes were deduced to be 3+ and 4+, respectively, from the UV/vis/NIR absorption and XANES spectroscopy.
Akiyama, Kazuhiko; Zhao, Y.*; Sueki, Keisuke*; Tsukada, Kazuaki; Haba, Hiromitsu; Nagame, Yuichiro; Kodama, Takeshi*; Suzuki, Shinzo*; Otsuki, Tsutomu*; Sakaguchi, Masahiko*; et al.
Journal of the American Chemical Society, 123(1), p.181 - 182, 2001/01
Times Cited Count:64 Percentile:84.95(Chemistry, Multidisciplinary)no abstracts in English
JRR-2 Control Office; Kambara, Toyozo; Shoda, Katsuhiko; Hirata, Yutaka; Shoji, Tsutomu; Kohayakawa, Toru; Morozumi, Minoru; Kambayashi, Yuichiro; Shitomi, Hajimu; Kokanezawa, Takashi; et al.
JAERI 1027, 57 Pages, 1962/09
no abstracts in English
Kambara, Toyozo; Shoda, Katsuhiko; Hirata, Yutaka; Shoji, Tsutomu; Haginoya, Kinichi; Kohayakawa, Toru; Yamaki, Jikei; Yokota, Mitsuo; Horiki, Oichiro; Yuhara, Shunichi; et al.
JAERI 1023, 120 Pages, 1962/09
no abstracts in English
JRR-2 Operations Office; Kambara, Toyozo; Shoda, Katsuhiko; Hirata, Yutaka; Shoji, Tsutomu; Haginoya, Kinichi; Kohayakawa, Toru; Yamaki, Jikei; Yokota, Mitsuo; Horiki, Oichiro; et al.
JAERI 1024, 79 Pages, 1962/08
no abstracts in English
JRR-2 Critical Experiments Group; Kambara, Toyozo; Shoda, Katsuhiko; Hirata, Yutaka; Shoji, Tsutomu; Kohayakawa, Toru; Morozumi, Minoru; Kambayashi, Yuichiro; Shitomi, Hajimu; Kokanezawa, Takashi; et al.
JAERI 1025, 62 Pages, 1962/03
no abstracts in English
Kasamatsu, Yoshitaka; Toyoshima, Atsushi; Tsukada, Kazuaki; Asai, Masato; Ishii, Yasuo; Nishinaka, Ichiro; Sato, Tetsuya; Li, Z.; Kikuchi, Takahiro; Nagame, Yuichiro; et al.
no journal, ,
Radioactive nuclides of Nb and Ta were produced in the Zr/Hf(p,xn)Nb/Ta and Ge/Gd(F,xn)Nb/Ta reactions at the JAEA tandem accelerator. The products were rapidly transported by He/KCl and He/KF gas-jet systems to the chemistry laboratory. It was found that the transport efficiency using the He/KF gas-jet system is comparable with that by the He/KCl gas-jet system which has been generally used. Subsequently, on-line anion-exchange experiments with the products were performed in HF/HNO solutions. A small physical adsorption of Nb on the surfaces of the tools was observed when the KCl aerosols were used, while better reproducibility of the elution of Nb was obtained using the KF aerosols. We interpret that stable fluoro complexes of Nb are rapidly formed by using the KF aerosols and we can suggest that the He/KF gas-jet system should be used in the on-line anion-exchange experiment of the group 5 elements for the study of the fluoride complexation of the elements.
Tsukada, Kazuaki; Kasamatsu, Yoshitaka; Asai, Masato; Toyoshima, Atsushi; Ishii, Yasuo; Li, Z.; Kikuchi, Takahiro; Sato, Tetsuya; Nishinaka, Ichiro; Nagame, Yuichiro; et al.
no journal, ,
Anion-exchange chromatographic behavior of element 105, dubnium (Db), produced in the Cm(F,5n)Db reaction is investigated together with the homologues Nb and Ta in HF/HNO mixed media using a newly developed on-line experimental system. The result indicates that the adsorption sequence on the anion-exchange resin is TaNbDb, and the fluoride complex formation of Db is expected to be weaker than that of homologues.
Tsukada, Kazuaki; Kasamatsu, Yoshitaka*; Asai, Masato; Toyoshima, Atsushi; Ishii, Yasuo; Li, Z.; Kikuchi, Takahiro; Sato, Tetsuya; Nishinaka, Ichiro; Nagame, Yuichiro; et al.
no journal, ,
Anion-exchange chromatographic behavior of element 105, dubnium (Db), produced in the Cm(F,5n) reaction is investigated together with the homologues Nb and Ta in HF/HNO mixed media using a newly developed on-line experimental system. The result indicates that the adsorption sequence on the anion-exchange resin is Ta Nb Db, and the fluoride complex formation of Db is expected to be weaker than that of homologues.
Suzuki, Michiyo; Sakashita, Tetsuya; Hattori, Yuya; Yanase, Sumino*; Kikuchi, Masahiro; Funayama, Tomoo; Yokota, Yuichiro; Tsuji, Toshio*; Kobayashi, Yasuhiko
no journal, ,
We reported an IR-induced reduction of locomotory rate of in the absence of food. In the previous experiments, wild-type animals were irradiated with -rays in the whole body, and measured the motility using "body bends" (the number of bends in the anterior body region at 20-s intervals). However, the IR-induced effects in the central and posterior body region were not evaluated by the body bends. In the present study, to investigate the IR-induced effects in more detail, we propose a novel method to evaluate the motility of the whole body using the video-based analysis.
Li, Z.; Toyoshima, Atsushi; Tsukada, Kazuaki; Asai, Masato; Sato, Tetsuya; Kikuchi, Takahiro; Sato, Nozomi; Nagame, Yuichiro
no journal, ,
Toyoshima, Atsushi; Tsukada, Kazuaki; Asai, Masato; Sato, Tetsuya; Li, Z.; Sato, Nozomi; Kikuchi, Takahiro; Kitatsuji, Yoshihiro; Nagame, Yuichiro; Oe, Kazuhiro*; et al.
no journal, ,
Reduction of element 101, mendelevium (Md), was studied with flow electrolytic chromatography. Mendelevium-255 with a half-life of 27 min was produced in the Cm(B, 4n) reaction at the JAEA tandem accelerator. Reaction products transported by a KCl/He gas-jet method to the chemistry laboratory were collected on a chemistry apparatus. After removing KCl with HDEHP chromatography, elution behavior of Md in 0.1 M HCl was investigated with a flow electrolytic column apparatus at the applied potentials between 0 -0.9 V vs. a Ag/AgCl reference electrode. Elution behavior of Md was the same as that of Bk at 0 V, showing that the stable Md was not reduced to the divalent state. At -0.9 V, elution of Md was quite similar to that of Sr, demonstrating that Md was successfully reduced to Md.
Toyoshima, Atsushi; Tsukada, Kazuaki; Asai, Masato; Kitatsuji, Yoshihiro; Ishii, Yasuo; Sato, Tetsuya; Li, Z.; Sato, Nozomi; Kikuchi, Takahiro; Nishinaka, Ichiro; et al.
no journal, ,
Oxidation of element 102, nobelium (No), using a developed electrolytic chromatography apparatus on an atom-at-a-time scale will be presented. It was found that the most stable ion, No, is oxidized to No in -hydroxyisobutyric acid (-HIB) solution using the apparatus and that the oxidized No complex with -HIB holds the trivalent state in the column above an applied potential of 1.0 V. Electrochemical reduction of element 101, mendevelium (Md) in HCl will be also presented.
Sato, Tetsuya; Tsukada, Kazuaki; Asai, Masato; Toyoshima, Atsushi; Kasamatsu, Yoshitaka*; Li, Z.; Sato, Nozomi; Kikuchi, Takahiro; Nagame, Yuichiro
no journal, ,
To investigate chemical properties of the transactinide element dubnium (Db, Z=105), we have developed an on-line isothermal gas chromatographic apparatus. The on-line experiments with the group-5 elements using the short lived Nb and Ta as the homologues of Db were conducted. We measured the relative chemical yields of volatile compounds of Nb and Ta as a function of the isothermal temperature in chlorinating condition with mixture of air and the SOCl vapor. It was found that the volatility of compounds of Ta is lower than that of Nb.
Sato, Tetsuya; Tsukada, Kazuaki; Asai, Masato; Toyoshima, Atsushi; Kasamatsu, Yoshitaka*; Li, Z.; Sato, Nozomi; Kikuchi, Takahiro; Haba, Hiromitsu*; Goto, Shinichi*; et al.
no journal, ,
To investigate chemical properties of the transactinide elements dubnium (Db, Z = 105) and seaborgium (Sg, Z = 106), we have developed an on-line isothermal gas chromatographic apparatus. The on-line experiments with the group-5 and -6 elements using the short lived 88Nb and 170Ta as the homologues of Db and 173W as the one of Sg were conducted. We measured the relative chemical yields of volatile compounds of 88Nb, 170Ta and 173W as a function of the isothermal temperature. The behavior of W and Nb was the same as that obtained in previous work by M. Gartner et al., and A. Turler et al., respectively. It was found that the volatility of compounds of Ta is lower than that of Nb.