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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：44 Percentile：96.93(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.
Kajimoto, Ryoichi; Nakamura, Mitsutaka; Inamura, Yasuhiro; Kamazawa, Kazuya*; Ikeuchi, Kazuhiko*; Iida, Kazuki*; Ishikado, Motoyuki*; Murai, Naoki; Kira, Hiroshi*; Nakatani, Takeshi; et al.
Journal of Physics; Conference Series, 1021(1), p.012030_1 - 012030_6, 2018/06
Times Cited Count：3 Percentile：88.67(Nuclear Science & Technology)Tamura, Hajimu*; Shibata, Kenji*; Takahashi, Naoya; Niwa, Masakazu
JAEA-Testing 2017-001, 52 Pages, 2017/03
JAEA-Testing-2017-001.pdf:2.36MB
It is essential to understand the activity of faults in and around a target area to assess the long-term geosphere stability for geological isolation. Potassium-Argon (K-Ar) dating of fault gouge has been conducted in Tono Geoscience Center as one of the dating technique for faulting. This report includes methods for sample preparation, analyses, and age calculation on the K-Ar dating. This can contribute to an evaluation of calculated K-Ar ages.
processing of clustered DNA damageShikazono, Naoya; Akamatsu, Ken; Takahashi, Momoko*; Noguchi, Miho; Urushibara, Ayumi; O'Neill, P.*; Yokoya, Akinari
Mutation Research; Fundamental and Molecular Mechanisms of Mutagenesis, 749(1-2), p.9 - 15, 2013/09
Times Cited Count：12 Percentile：36.83(Biotechnology & Applied Microbiology)We examined the biological consequences of bi-stranded clustered damage sites, consisting of a combination of DNA lesions using a bacterial plasmid-based assay. The transformation efficiencies were significantly lower for the bi-stranded clustered GAP/AP lesions than for either a single GAP or a single AP site. When the two lesions were separated by 10-20 bp, the transformation efficiencies were comparable with those of the single lesions. This recovery of transformation efficiency for separated lesions requires DNA polymerase I (Pol I) activity. Analogously, the mutation frequency was enhanced in a bi-stranded cluster containing a GAP and an 8-oxoG, and Pol I was found to play an important role in minimising mutations induced as a result of clustered lesions. These results indicate that the biological consequences of clustered DNA damage strongly depend on Pol I activity.
MaximTakahashi, Misa*; Kohama, S.*; Kondo, Komei*; Hakata, Makoto*; Hase, Yoshihiro; Shikazono, Naoya; Tanaka, Atsushi; Morikawa, Hiromichi*
Plant Biotechnology, 22(1), p.63 - 67, 2005/03
no abstracts in English
Takahashi, Hideki*; Furuta, Naoya*
JNC TJ1420 2005-004, 90 Pages, 1994/08
Takahashi, Momoko; Shikazono, Naoya
no journal, ,
Yokokita, Takuya*; Komori, Yukiko*; Kikutani, Yuki*; Kino, Aiko*; Shiohara, Naoya*; Kasamatsu, Yoshitaka*; Yoshimura, Takashi*; Takahashi, Naruto*; Oe, Kazuhiro; Shinohara, Atsushi*
no journal, ,
We are planning to study a redox behavior of element 106, seaborgium (Sg) based on the comparison of the behaviors with those of molybdenum (Mo) and tungsten (W). In this work, we studied solvent extraction behaviors of Mo(VI), Mo(V), W(VI), and W(V) with Aliquat 336 from hydrochloric acid (HCl). Mo(V) is extracted with higher distribution ratios than those of Mo(VI) in 4 to 11 M HCl. Distribution ratios of Mo(V) obtained by reducing Mo(VI) electrochemically are in good agreement with those of [MoCl
].
Takahashi, Momoko; Shikazono, Naoya
no journal, ,
no abstracts in English
Takahashi, Momoko; Shikazono, Naoya
no journal, ,
no abstracts in English
Takahashi, Momoko; Shikazono, Naoya
no journal, ,
DNA is damaged by various factors and unrepaired DNA damage would cause alterations of the genome, and thus various biological effects. To avoid these effects, there are diverse mechanisms to repair DNA damage in cells. Clustered DNA damage, defined as two or more lesions in one to two helical turns of DNA, is induced by ionizing radiation. Clustered DNA damage is considered to be refractory to repair and therefore highly lethal and mutagenic. However, the mechanism on how clustered DNA damage causes mutagenesis or lethality is still largely unknown. We constructed lesion-containing plasmids using a novel approach in order to analyze repair of clustered DNA damage. The method introduced by Karata was modified to construct the plasmid. We found that the constructed plasmid DNA had a defined lesion. As DNA lesions could be placed at any position on either strand, the method allows us to construct cluster DNA damage in a plasmid, and would be highly useful in analyzing processing of clustered DNA damage. We will discuss about the analysis of repair of clustered DNA damage in 
, as an example.
Takahashi, Momoko*; Shikazono, Naoya
no journal, ,
Asami, Keishiro*; Hirano, Naoto*; Takahashi, Naoya; Watanabe, Takahiro
no journal, ,
Ferromanganese (Fe-Mn) crusts covering hard-rocks on seafloor and Fe-Mn nodules enwrapping rock fragment unclear on sediments are known as chemical sedimentary rocks mainly composed of Fe and Mn (ohydro)oxides in submarine environment. Origins of those are classified into three types based on chemical composition which are hydrogenetic origin from ambient seawater, diagenetic origin from sedimentary pore water in early diagenesis, and hydrothermal origin. It is rare to show diagenetic signal in case of hydrogenetic Fe-Mn crusts because they do not occur on sediments, but hard-rocks. However, diagenetic signal was reported about high Ni, Cu and Li contents layers in hydrogenetic Fe-Mn crusts due to elemental addition by dissolution of organic matter and biogenic silica in seawater (Hein et al. 2012). Here, we report the diagenetic signal into hydrogenetic Fe-Mn crusts on peperite from petit-spot volcanoes which are monogenetic volcanoes erupted on bending oceanic plate. Their occurrence likely shows the origin from debris of Fe-Mn nodules (generally implicated in diagenetic origin) before eruption of petit-spot volcanoes.
