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Takagi, Hirotaka*; Takagi, Rina*; Minami, Susumu*; Nomoto, Takuya*; Oishi, Kazuki*; Suzuki, Michito*; Yanagi, Yuki*; Hirayama, Motoaki*; Khanh, N.*; Karube, Kosuke*; et al.
Nature Physics, 19(7), p.961 - 968, 2023/07
Times Cited Count：8 Percentile：96.03(Physics, Multidisciplinary)Takagi, Rina*; Matsuyama, Naofumi*; Ukleev, V.*; Yu, L.*; White, J. S.*; Francoual, S.*; Mardegan, J. R. L.*; Hayami, Satoru*; Saito, Hiraku*; Kaneko, Koji; et al.
Nature Communications (Internet), 13, p.1472_1 - 1472_7, 2022/03
Times Cited Count：55 Percentile：99.61(Multidisciplinary Sciences)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：43 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.
Sekine, Yurina; Takagi, Hajime*; Sudo, Sayoko*; Kajiwara, Yutaro*; Fukazawa, Hiroshi; Fukazawa, Tomoko*
Polymer, 55(24), p.6320 - 6324, 2014/11
Times Cited Count：26 Percentile：67.65(Polymer Science)To investigate the effects of structure of polymer side chains on structure of water in hydrogels, Raman spectra of polyacrylamide (PAA) and poly-
,-dimethylacrylamide (PDMAA) hydrogels were measured. PAA and PDMAA have similar chemical structures, except for the side chain structure. The result shows that the frequency of the OH stretching mode for the PAA hydrogel decreases as the water content decreases, while that for the PDMAA hydrogel increases. We conclude that most of the bound water molecules in the PAA hydrogel form four strong hydrogen bonds with the hydrophilic groups in the side chain of PAA, whereas those in the PDMAA hydrogel form weak hydrogen bonds with surrounding water molecules. The water structure is an important factor governing the physical and chemical properties of gel materials.
Sato, Rina; Yoshimura, Kazuya; Sanada, Yukihisa; Sato, Tetsuro*; Takagi, Marie*
no journal, ,
no abstracts in English
Sato, Rina; Yoshimura, Kazuya; Sanada, Yukihisa; Sato, Tetsuro*; Takagi, Marie*
no journal, ,
no abstracts in English
Sato, Rina; Yoshimura, Kazuya; Sanada, Yukihisa; Sato, Tetsuro*; Mori, Tsubasa*; Takagi, Marie*
no journal, ,
In order to accurately estimate air dose rates of indoors with a high percentage of stay, indoor dose reduction factor was evaluated based on indoor and outdoor air dose rate measurements, taking into account air dose rates due to natural radionuclides. The measurements were conducted on wooden and concrete buildings in 2021 in municipalities with specified reconstruction and revitalization base. Indoor air dose rates were estimated from outdoor air dose rates using representative values of the evaluated indoor dose reduction factors. As a result, indoor air dose rates were estimated more accurately when the effect of natural radionuclides was taken into account, because the error indicators were smaller than those in the case without the effect of natural radionuclides.
