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Journal Articles

Thermally altered subsurface material of asteroid (162173) Ryugu

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 $$^{circ}$$C, similar to the surface. In contrast, thermophysical modeling indicates that radiative heating does not increase the temperature above 200 $$^{circ}$$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.

Journal Articles

Local magnetic states of the weakly ferromagnetic iron-based superconductor Sr$$_{2}$$VFeAsO$$_{3-delta}$$ studied by X-ray magnetic circular dichroism

Horio, Masafumi*; Takeda, Yukiharu; Namiki, Hiromasa*; Katagiri, Takao*; Wakabayashi, Yuki*; Sakamoto, Shoya*; Nonaka, Yosuke*; Shibata, Goro*; Ikeda, Keisuke*; Saito, Yuji; et al.

Journal of the Physical Society of Japan, 87(10), p.105001_1 - 105001_2, 2018/10

 Times Cited Count:2 Percentile:21.38(Physics, Multidisciplinary)

Journal Articles

Control of coordination and luminescence properties of lanthanide complexes using octadentate oligopyridine-amine ligands

Wada, Atsushi*; Watanabe, Masayuki; Yamanoi, Yoshinori*; Nankawa, Takuya; Namiki, Kosuke*; Yamasaki, Mikio*; Murata, Masaki*; Nishihara, Hiroshi*

Bulletin of the Chemical Society of Japan, 80(2), p.335 - 345, 2007/02

 Times Cited Count:22 Percentile:57.43(Chemistry, Multidisciplinary)

Lanthanide complexes with linear and cyclic octadentate oligopyridine-amine ligands were synthesized, and their molecular structures were determined by single-crystal X-ray crystallography. All of the complexes had a distorted capped square antiprism (CSAP) geometry, and the coordination environments of lanthanide complexes were more distortedfor the complexes with the linear ligand than those with the cyclic ligand. The Eu$$^{3+}$$ complexes with the linear ligand showed more intense emissions, which were attributed to the $$^{5}$$D$$_{0}$$ $$rightarrow$$ $$^{7}$$F$$_{2}$$ transition, than the complex withthe cyclic ligand in acetonitrile, which can be attributed to the distortion in the coordination environments. These results indicate that the coordination environments of lanthanide complexes, and thus the luminescence properties, can be controlled by tuning the geometrical structures of polydentate ligands.

JAEA Reports

None

Narita, Osamu; Ishida, Junichiro; Katagiri, Hiromi; Hayashi, Naomi; Miyagawa, Naoto; Watanabe, Hitoshi; Kobayashi, Mitsuru; Namiki, Atsushi; Sumiya, Shuichi; ; et al.

PNC TN8420 89-009, 238 Pages, 1989/08

PNC-TN8420-89-009.pdf:4.32MB

None

Oral presentation

Control of metal-metal distance of dinuclear complex by counter anion; Structure and property of lanthanide tris(2-pyridine)carbinol complexes

Watanabe, Masayuki; Nankawa, Takuya; Wada, Atsushi*; Namiki, Kosuke*; Murata, Masaki*; Nishihara, Hiroshi*; Kimura, Takaumi

no journal, , 

A tripodal ligand, tris(2-pyridyl)carbinol affords a novel tetradentate coordination mode in homodinuclear lanthanide complexes, which exhibit remarkably short distances between metal ions. Structures of dinuclear complexes synthesized from triflates exhibited the same structure other than the difference in the bond lengths which was induced by lanthanide contraction across the lanthanide series from Pr to Lu. In these complexes, the distance between two lanthanide ions was remarkably short. In this study the same type of dinuclear complexes were synthesized from nitrates. The nitrate ion can coordinate in both monodentate fand bidentate fashions. Since ionic radii are dependent upon the coordination number, nitrate could affect the metal-metal distance. In fact, dinuclear complexes exhibited longer distance between lanthanide ions than the triflates due to the increase of ionic radii of lanthanide ions. Some features of these dinuclear systems, which are induced from the difference of metal-metal distance, will be discussed in the presentation.

Oral presentation

Radiation protection feature and research at Tokai reprocessing plant

Momose, Takumaro; Endo, Kuniaki; Ito, Yasuhisa; Yamashita, Tomoyuki; Namiki, Atsushi; Sanada, Yukihisa; Akiyama, Kiyomitsu; Takeishi, Minoru; Tago, Itaru; Furuta, Sadaaki

no journal, , 

The first reprocessing pilot plant in Japan (Tokai Reprocessing Plant; TRP) has been operated since 1977 at Nuclear Fuel Cycle Engineering Laboratories, JAEA. General radiation protection in TRP is performed with continuous monitoring and sampling methods. The continuous monitors measuring $$gamma$$-ray, neutron, particulate alpha and beta nuclides in the air are installed in the radiation controlled area as a central monitoring system to prevent from unnecessary exposure. Air and water effluents from the TRP are also monitored by continuous monitors or sampling methods to comply with regulations. In addition to this, environmental monitoring has been carried out to assess influences on public and environment by the plant operation. A feature of radiation protection and its recent relevant researches at TRP will be introduced in this presentation.

Oral presentation

Experience of radiation protection at the Tokai Reprocessing Plant; Dismantlement work of glove box for process solution analysis

Shioya, Satoshi; Hirayama, Tsutomu*; Ebashi, Tsutomu; Namiki, Atsushi; Momose, Takumaro

no journal, , 

no abstracts in English

Oral presentation

Radiation management for the protection of beta-ray dose in Tokai Reprocessing plant, 2; Basic parameter on the management

Shioya, Satoshi; Sakuyama, Mitsuhiro*; Adachi, Yasuyuki*; Sato, Kenichiro*; Sanada, Yukihisa; Namiki, Atsushi; Momose, Takumaro

no journal, , 

no abstracts in English

Oral presentation

Radiation control at Tokai Reprocessing Plant after the accident of Fukushima Daiichi Nuclear Power Plant

Watanabe, Yuki; Nakamura, Keisuke; Akasu, Kohei; Okuyama, Shun; Namiki, Atsushi

no journal, , 

no abstracts in English

Oral presentation

Evaluation of work management system using wearable device in Tokai Reprocessing Plant

Imahashi, Atsushi; Nakamura, Keisuke; Watanabe, Yuki; Namiki, Atsushi; Takahashi, Yoshiharu*; Kinugawa, Nobuyuki*

no journal, , 

no abstracts in English

Oral presentation

Study on dosimetry method of the $$beta$$-ray 3 mm depth dose equivalent and protection measures with respect to the lens of the eye, 3; Adaptability to field works

Takimoto, Misaki; Okuyama, Shun; Yamazaki, Takumi; Ito, Yasuhisa; Takada, Chie; Tsujimura, Norio; Shiba, Kozo; Okada, Kazuhiko; Namiki, Atsushi

no journal, , 

no abstracts in English

11 (Records 1-11 displayed on this page)
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