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Murase, Kiyoka*; Kataoka, Ryuho*; Nishiyama, Takanori*; Nishimura, Koji*; Hashimoto, Taishi*; Tanaka, Yoshimasa*; Kadokura, Akira*; Tomikawa, Yoshihiro*; Tsutsumi, Masaki*; Ogawa, Yasunobu*; et al.
Journal of Space Weather and Space Climate (Internet), 12, p.18_1 - 18_16, 2022/06
Times Cited Count:0 Percentile:24.42(Astronomy & Astrophysics)We identified two energetic electron precipitation (EEP) events during the growth phase of moderate substorms and estimated the mesospheric ionization rate for an EEP event for which the most comprehensive dataset from ground-based and space-born instruments was available. The mesospheric ionization signature reached below 70 km altitude and continued for ~15 min until the substorm onset, as observed by the PANSY radar and imaging riometer at Syowa Station in the Antarctic region. We also used energetic electron flux observed by the Arase and POES 15 satellites as the input for the air-shower simulation code PHITS to quantitatively estimate the mesospheric ionization rate. Combining the cutting-edge observations and simulations, we shed new light on the space weather impact of the EEP events during geomagnetically quiet times, which is important to understand the possible link between the space environment and climate.
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.
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.
Yoshii, Kenji; Ikeda, Naoshi*; Michiuchi, Takamasa*; Yokota, Yusuke*; Okajima, Yuka; Yoneda, Yasuhiro; Matsuo, Yoji*; Horibe, Yoichi*; Mori, Shigeo*
Journal of Solid State Chemistry, 182(7), p.1611 - 1618, 2009/06
Times Cited Count:15 Percentile:51.51(Chemistry, Inorganic & Nuclear)We have investigated the magnetic and dielectric properties of YbFeMnO (0x1), which is an Fe-site-substituted system of new multiferroic oxides RFeO (R=Y, Ho-Lu). X-ray diffraction measurements show that a solid solution is formed between YbFeO (x=0) and YbFeMnO (x=1) for 0x1. The valence of the Mn ion is determined to be 2+, consistently with the suppression of low-temperature magnetization by the Mn substitution. The magnetic transition temperature and the dielectric constant decrease monotonically with increasing x. This result plausibly confirms that the magnetic and dielectric properties in oxides isostructural with RFeO are governed by the electron transfer between Fe-site ions, unlike ordinary ferroelectrics and dielectrics, in which the ionic displacement plays a key role. The possibility for application is briefly discussed.
Michiuchi, Takamasa*; Yokota, Yusuke*; Komatsu, Takuma*; Hayakawa, Hironori*; Kuroda, Tomoko*; Maeda, Daisuke*; Matsuo, Yoji*; Mori, Shigeo*; Yoshii, Kenji; Hanasaki, Noriaki*; et al.
Ferroelectrics, 378(1), p.175 - 180, 2009/00
Times Cited Count:18 Percentile:59.71(Materials Science, Multidisciplinary)We have synthesized the samples of LuFeO, which shows the ferroelectricity due to charge ordering of Fe ions, under several different reducing conditions using a CO-CO flow. The reducing condition was changed by changing a flow ratio of CO and CO. It was found that the flow ratio of CO/CO of about 5 provided the sample with the highest magnetic transition temperature of 240-250 K. This sample showed the dielectric constant of 10000 at room temperature. The imaginary part of the dielectric response offered the activation energy of 0.4-0.5 eV, which is slightly larger than that reported previously (about 0.3 eV). We will perform further investigation of the physical properties of this sample to clarify full details and their origin of LuFeO.
Yoshii, Kenji; Yoneda, Yasuhiro; Maeda, Daisuke*; Yokota, Yusuke*; Michiuchi, Takamasa*; Komatsu, Takuma*; Ikeda, Naoshi*; Matsuo, Yoji*; Mori, Shigeo*
Japanese Journal of Applied Physics, 47(9), p.7599 - 7602, 2008/09
Times Cited Count:8 Percentile:33.35(Physics, Applied)We have investigated the physical properties of HoFeO and RR'FeO (R, R': rare earths). Dielectric measurements showed their dielectric constants of 1000 at around room temperature, which is characteristic of the RFeO series (R: rare earths). However, the magnetic transition temperatures and the coherency in dielectric response were found to be different from those of RFeO reported so far. Interestingly, these materials suggested higher ferroelectric temperatures than those reported so far, suggesting a possibility of application of these materials.
Kawashima, Yusuke*; Hase, Yoshihiro; Yokota, Yuichiro
JAEA-Review 2007-060, JAEA Takasaki Annual Report 2006, P. 76, 2008/03
no abstracts in English
Kawashima, Yusuke*; Matsumoto, Tetsuo*; Hase, Yoshihiro; Yokota, Yuichiro
JAEA-Review 2006-042, JAEA Takasaki Annual Report 2005, P. 91, 2007/02
no abstracts in English
Kawashima, Yusuke*; Matsumoto, Tetsuo*; Hase, Yoshihiro; Yokota, Yuichiro
no journal, ,
no abstracts in English
Kawashima, Yusuke*; Hase, Yoshihiro; Yokota, Yuichiro
no journal, ,
no abstracts in English
Yasuda, Takako*; Oda, Shoji*; Hibi, Yusuke*; Urushihara, Yusuke*; Mitani, Hiroshi*; Funayama, Tomoo; Yokota, Yuichiro; Muto, Yasuko; Ikeda, Hiroko; Kobayashi, Yasuhiko
no journal, ,
Using heavy-ion microbeam system of JAEA-Takasaki, we irradiated brain of the embryos of the Medaka with carbon ion microbeam. After irradiation, inductions of apoptosis were observed using whole-mount staining of acridine orange. In targeted position of the brain, we observed the induction of radiation induced apoptosis, indicating that the system can irradiate specific region of the brain of the Medaka embryo.
Oda, Shoji*; Yasuda, Takako*; Hibi, Yusuke*; Asaka, Tomomi*; Ikeda, Hiroko; Muto, Yasuko*; Yokota, Yuichiro; Sakashita, Tetsuya; Suzuki, Michiyo; Funayama, Tomoo; et al.
no journal, ,
We have developed a new irradiation protocol for tissue specific irradiation to living embryo and adult medaka, . In the study, a testis of p53 knockout fish were irradiated with multi-shots of microbeam. Less numbers of testis-ova were induced in the in p53- lacking testis 1 week after the irradiation compared to whole body irradiated testis. Specific irradiation of microbeam onto the right (or left) lobe of the optic tectum in medaka embryos of 2 days post fertilization ectopically induced apoptotic cells in the body trunk and the tail in addition to the irradiated position. The systemic effects as endocrine system, autonomic nervous system and immunity reactions occur in adult medaka and these results suggested that the systemic effects might be functional even in developing embryos.
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.