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Journal Articles

First-principles simulation of an ejected electron produced by monochromatic deposition energy to water at the femtosecond order

Kai, Takeshi; Toigawa, Tomohiro; Matsuya, Yusuke; Hirata, Yuho; Tezuka, Tomoya*; Tsuchida, Hidetsugu*; Yokoya, Akinari*

RSC Advances (Internet), 13(46), p.32371 - 32380, 2023/11

Although scientific knowledge of photolysis and radiolysis of water is widely used in the life sciences and other fields, the formation mechanism of the spatial distribution of hydrated electrons (spur) resulting from energy deposition to water is still not well understood. The chemical reaction times of hydrated electrons, OH radicals, and H$$_{3}$$O$$^{+}$$ in the spur strongly depend on the spur radius. In our previous study, we elucidated the mechanism at a specific given energy (12.4 eV) by first-principles calculations. In the present study, we performed first-principles calculations of the spur radius at the deposition energies of 11-19 eV. The calculated spur radius is 3-10 nm, which is consistent with the experimental prediction (~4 nm) for the energy range of 8-12.4 eV, and the spur radius gradually increases with increasing energy. The spur radius is a new scientific knowledge and is expected to be widely used for estimating radiation DNA damage.

Journal Articles

Initial yield of hydrated electron production from water radiolysis based on first-principles calculation

Kai, Takeshi; Toigawa, Tomohiro; Matsuya, Yusuke*; Hirata, Yuho; Tezuka, Tomoya*; Tsuchida, Hidetsugu*; Yokoya, Akinari*

RSC Advances (Internet), 13(11), p.7076 - 7086, 2023/03

 Times Cited Count:1 Percentile:84.66(Chemistry, Multidisciplinary)

Scientific insights of water radiolysis are widely used in the life sciences and so on, however, the formation mechanism of radicals, a product of water radiolysis, is still not well understood. We are challenging to develop a simulation code to solve this formation mechanism from the viewpoint of radiation physics. Our first-principles calculations have revealed that the behavior of secondary electrons in water is governed not only by collisional effects but also by polarization effects. Furthermore, from the predicted ratio of ionization to electronic excitation, based on the spatial distribution of secondary electrons, we successfully reproduce the initial yield of hydrated electrons predicted in terms of radiation chemistry. The code provides us a reasonable spatiotemporal connection from radiation physics to radiation chemistry. Our findings are expected to provide newly scientific insights for understanding the earliest stages of water radiolysis.

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

The Surface composition of asteroid 162173 Ryugu from Hayabusa2 near-infrared spectroscopy

Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Arai, Takehiko*; Nakauchi, Yusuke*; Nakamura, Tomoki*; Matsuoka, Moe*; et al.

Science, 364(6437), p.272 - 275, 2019/04

 Times Cited Count:233 Percentile:99.74(Multidisciplinary Sciences)

The near-Earth asteroid 162173 Ryugu, the target of Hayabusa2 sample return mission, is believed to be a primitive carbonaceous object. The Near Infrared Spectrometer (NIRS3) on Hayabusa2 acquired reflectance spectra of Ryugu's surface to provide direct measurements of the surface composition and geological context for the returned samples. A weak, narrow absorption feature centered at 2.72 micron was detected across the entire observed surface, indicating that hydroxyl (OH)-bearing minerals are ubiquitous there. The intensity of the OH feature and low albedo are similar to thermally- and/or shock-metamorphosed carbonaceous chondrite meteorites. There are few variations in the OH-band position, consistent with Ryugu being a compositionally homogeneous rubble-pile object generated from impact fragments of an undifferentiated aqueously altered parent body.

JAEA Reports

Document collection of the 27th Technical Special Committee on Fugen Decommissioning

Kutsuna, Hideki; Kadowaki, Haruhiko; Sakakibara, Yasuhide; Hirata, Tomohiro

JAEA-Review 2013-027, 40 Pages, 2013/09

JAEA-Review-2013-027.pdf:7.42MB

Fugen Decommissioning Engineering Center is establishing "Technical special committee on Fugen decommissioning" which consists of the members well-informed, aiming to make good use of Fugen as a place for technological development, as the central point in the energy research and development base making project of Fukui prefecture. This report compiles presentation materials "The Current Situation of Fugen Decommissioning", "Upgrading of a Removal Technique for a Heavy Water Withdraw and a Tritium Removal" and "Research of Ageing Management of Nuclear Power Plant for Safe Long Term Operating in Fukui", "The Work for Solution and Promotion on Technical Challenge (Public Offering Type)" which is related with the efforts of Fugen in the Fukui energy research and development centralization plan, presented in the 27th Technical special committee on Fugen decommissioning which was held on March 14, 2013.

Oral presentation

Enhancement of IR-light emission from $$beta$$-FeSi$$_{2}$$ nanocrystals by Cu doping

Hirata, Tomoaki*; Kagawa, Seiya*; Nagatsuyu, Tomohiro*; Shibahara, Kohei*; Iwamoto, Ryotaro*; Kawakubo, Yuki*; Noguchi, Masaya*; Mizuki, Tatsuya*; Narumi, Kazumasa; Sakai, Seiji; et al.

no journal, , 

no abstracts in English

Oral presentation

RBS study of behavior of Cu diffusion in $$beta$$-FeSi$$_{2}$$

Noguchi, Masaya*; Mizuki, Tatsuya*; Kawakubo, Yuki*; Hirata, Tomoaki*; Kagawa, Seiya*; Nagatsuyu, Tomohiro*; Iwamoto, Ryotaro*; Shibahara, Kohei*; Narumi, Kazumasa; Maeda, Yoshihito

no journal, , 

no abstracts in English

Oral presentation

Spectral characteristics of asteroid (162173) Ryugu with Hayabusa2 NIRS3

Takir, D.*; Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Arai, Takehiko*; Nakauchi, Yusuke*; Nakamura, Tomoki*; et al.

no journal, , 

JAXA spacecraft and sample return mission Hayabusa2 has arrived at the near-Earth asteroid 162173 Ryugu, which is classified a primitive carbonaceous object. Here we report recent results of near-infrared spectrometer (NIRS3) on the Hayabusa2 spacecraft. The observations provide direct measurements of the surface composition of Ryugu and context for the returned samples. NIRS3 has detected a weak and narrow absorption feature centered at 2.72 micrometer across entire observed surface. This absorption feature is attributed to the presence of OH-bearing minerals. The NIRS3 observations also revealed that Ryugu is the darkest object to be observed up-close by a visiting spacecraft. The intensity of the OH feature and low albedo are consistent with thermally-and/or shock-metamorphosed, and/or carbon-rich space-weathered primitive and hydrated carbonaceous chondrites.

Oral presentation

Computer simulation of the earliest processes of radiation biological effects of; Direct and indirect effects of DNA damage

Kai, Takeshi; Toigawa, Tomohiro; Matsuya, Yusuke; Hirata, Yuho; Tezuka, Tomoya*; Tsuchida, Hidetsugu*; Ito, Yuma*; Yokoya, Akinari*

no journal, , 

Irradiation of living systems forms complex DNA damage that induces biological effects in very rare cases. This complex DNA damage is called cluster damage and is very difficult to detect experimentally. In this study, we have developed physical and chemical codes for analyzing DNA damage, and are working to elucidate the formation mechanism of cluster damage. In this study, we analyzed the results of calculations in a simple system in which energy is deposited to DNA and secondary electrons are emitted, and showed that the formation mechanism of cluster damage strongly depends on the deposition energy to DNA. This scientific insight is expected to contribute to the elucidation of the repair mechanism of DNA damage and lead to the elucidation of radiation biological effects.

Patent

管体掴持機構

佐野 一哉; 中村 保之; 岩井 紘基; 平田 智宏

松田 進*; 今井 富雄*

JP, 2014-035293  Patent licensing information  Patent publication (In Japanese)

【課題】単純な機構で、二重管体構造を一度で引き上げることが可能となり、管体撤去工程などを簡略化することができる管体掴持機構を提供する。 【解決手段】本発明は、管体(P1、P2)を掴持する管体掴持機構10であって、第1の円周上に配された支点を中心として回動する複数の外管掴持爪130と、前記第1の円周の内周にある第2の円周上に配された支点を中心として回動する複数の内管掴持爪230と、前記外管掴持爪130と外側プロフィール部410で当接すると共に、前記内管掴持爪230と内側プロフィール部420で当接する環状カム部材400と、前記環状カム部材400を昇降する環状カム部材駆動用シリンダ450と、からなることを特徴とする。

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