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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:49 Percentile:96.63(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

Role of advection in atmospheric ammonia; A Case study at a Japanese lake basin influenced by agricultural ammonia sources

Kubota, Tomohiro; Kuroda, Hisao*; Watanabe, Mirai*; Takahashi, Akiko*; Nakazato, Ryoji*; Tarui, Mika*; Matsumoto, Shunichi*; Nakagawa, Keita*; Numata, Yasuko*; Ouchi, Takao*; et al.

Atmospheric Environment, 243, p.117856_1 - 117856_9, 2020/12

 Times Cited Count:3 Percentile:12.78(Environmental Sciences)

The dry and wet depositions of atmospheric ammonia (NH$$_{3}$$) is one of the important pathways of nitrogen loads to aquatic ecosystems. Crop and livestock agriculture, one of the largest emitters of NH$$_{3}$$ in Asian countries, are known to cause high spatial and seasonal variation of NH$$_{3}$$ and influence the surrounding lake basin areas via its dry and wet deposition. However, the spatial characteristics of the NH$$_{3}$$ concentration in basin scale are not completely understood for regulation in NH$$_{3}$$ emission. Here we aim to clarify dominant factors of spatial and seasonal variations of the NH$$_{3}$$ concentration in a eutrophic lake basin surrounded by agricultural areas in Japan. Passive sampling over various land use categories in the basin was conducted at 36 sites in total from October 2018 to January 2020. Interestingly, the observed NH$$_{3}$$ concentration near the livestock houses were higher in winter than summer, which was inconsistent with knowledge of seasonal changes of current NH$$_{3}$$ emission inventory based on temperature-driven volatilization process. Comparing monthly NH$$_{3}$$ concentrations with various meteorological factors, we suggested the importance of seasonal advection of NH$$_{3}$$ from high emission sources to which has been rarely paid attention by the previous past studies. As for this, should be considered for lake ecosystem management since deposition of NH$$_{3}$$ is known to be closely related to the ecological processes such as phytoplankton blooming.

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:282 Percentile:99.70(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.

Journal Articles

Non-aqueous selective synthesis of orthosilicic acid and its oligomers

Igarashi, Masayasu*; Matsumoto, Tomohiro*; Yagihashi, Fujio*; Yamashita, Hiroshi*; Ohara, Takashi; Hanashima, Takayasu*; Nakao, Akiko*; Moyoshi, Taketo*; Sato, Kazuhiko*; Shimada, Shigeru*

Nature Communications (Internet), 8, p.140_1 - 140_8, 2017/07

 Times Cited Count:29 Percentile:64.26(Multidisciplinary Sciences)

Journal Articles

Spin-orbit coupling induced semi-metallic state in the 1/3 hole-doped hyper-kagome Na$$_3$$Ir$$_3$$O$$_8$$

Takayama, Tomohiro*; Yaresko, A.*; Matsumoto, Akiyo*; Nuss, J.*; Ishii, Kenji; Yoshida, Masahiro*; Mizuki, Junichiro; Takagi, Hidenori*

Scientific Reports (Internet), 4, p.6818_1 - 6818_6, 2014/10

 Times Cited Count:33 Percentile:81.46(Multidisciplinary Sciences)

Journal Articles

IFMIF; Overview of the validation activities

Knaster, J.*; Arbeiter, F.*; Cara, P.*; Favuzza, P.*; Furukawa, Tomohiro; Groeschel, F.*; Heidinger, R.*; Ibarra, A.*; Matsumoto, Hiroshi*; Mosnier, A.*; et al.

Nuclear Fusion, 53(11), p.116001_1 - 116001_18, 2013/11

AA2013-0294.pdf:2.55MB

 Times Cited Count:65 Percentile:93.95(Physics, Fluids & Plasmas)

The IFMIF/EVEDA project under the Broader Approach Agreement between Japan and EU aims at allowing a rapid construction phase of IFMIF in due time. The three main facilities, (1) the Accelerator Facility, (2) the Target Facility and (3) the Test Facility, are the subject of validation activities that include the construction of either full scale prototypes or smartly devised scaled down facilities that will allow a straightforward extrapolation to IFMIF needs. The installation of a Linac of 1.125 MW (125 mA and 9 MeV) of deuterons started in March 2013 in Rokkasho. The world largest liquid Li test loop is running in Oarai with an ambitious experimental programme for the years ahead. A full scale high flux test module that will house $$sim$$ 1000 small specimens developed jointly in Europe and Japan has been constructed in Germany together with its He gas loop. A full scale medium flux test module to carry out on-line creep measurement has been constructed in Switzerland.

Journal Articles

Recent progress in the energy recovery linac project in Japan

Sakanaka, Shogo*; Akemoto, Mitsuo*; Aoto, Tomohiro*; Arakawa, Dai*; Asaoka, Seiji*; Enomoto, Atsushi*; Fukuda, Shigeki*; Furukawa, Kazuro*; Furuya, Takaaki*; Haga, Kaiichi*; et al.

Proceedings of 1st International Particle Accelerator Conference (IPAC '10) (Internet), p.2338 - 2340, 2010/05

Future synchrotron light source using a 5-GeV energy recovery linac (ERL) is under proposal by our Japanese collaboration team, and we are conducting R&D efforts for that. We are developing high-brightness DC photocathode guns, two types of cryomodules for both injector and main superconducting (SC) linacs, and 1.3 GHz high CW-power RF sources. We are also constructing the Compact ERL (cERL) for demonstrating the recirculation of low-emittance, high-current beams using above-mentioned critical technologies.

Journal Articles

Incident angle dependence of MCD at the Dy $$M$$$$_{5}$$-edge of perpendicular magnetic Dy$$_{x}$$Co$$_{100-x}$$ films

Agui, Akane; Mizumaki, Masaichiro*; Asahi, Toru*; Sayama, Junichi*; Matsumoto, Koji*; Morikawa, Tsuyoshi*; Matsushita, Tomohiro*; Osaka, Tetsuya*; Miura, Yoshimasa*

Journal of Alloys and Compounds, 408-412, p.741 - 745, 2006/02

 Times Cited Count:7 Percentile:45.75(Chemistry, Physical)

no abstracts in English

Journal Articles

MCD measurement at the Tb $$M$$$$_{4,5}$$-edges of Tb$$_{17}$$Fe$$_{x}$$Co$$_{(83-x)}$$ perpendicular magnetization films

Agui, Akane; Mizumaki, Masaichiro*; Asahi, Toru*; Sayama, Junichi*; Matsumoto, Koji*; Morikawa, Tsuyoshi*; Nakatani, Takeshi; Matsushita, Tomohiro*; Osaka, Tetsuya*; Miura, Yoshimasa*

Transactions of the Magnetics Society of Japan, 4(4-2), p.326 - 329, 2004/11

The electronic and spin state of the perpendicular magnetization film Tb$$_{17}$$Fe$$_{x}$$Co$$_{(83-x)}$$ was investigated by means of magnetic circular dichroism spectroscopy for each element. The samples are Tb$$_{17}$$Fe$$_{x}$$Co$$_{(83-x)}$$ while the ratio of a rare-earth metal Tb to transition metals Fe and Co is constant, the composition ratio of Fe and Co is changed. Changing the ratio, we estimated the expected orbital moments $$<$$$$L$$$$_{z}$$$$>$$ of Tb 4f electrons. The macroscopic magnetic property is studied from the microscopic point of view.

Oral presentation

Evaluation of fatigue damage around the weld zones of railway carbody structures using high-energy synchrotron radiation

Shobu, Takahisa; Matsumoto, Keisuke*; Yamamoto, Masataka*; Yagi, Tsuyoshi*; Okino, Tomohiro*

no journal, , 

no abstracts in English

Oral presentation

Magnetic Excitations and their temperature dependence in Sr$$_2$$IrO$$_4$$ and Sr$$_3$$Ir$$_2$$O$$_7$$

Ishii, Kenji; Jarrige, I.*; Yoshida, Masahiro*; Mizuki, Junichiro; Matsumoto, Akiyo*; Kato, Akihiko*; Takayama, Tomohiro*; Takagi, Hidenori*

no journal, , 

no abstracts in English

Oral presentation

Role of advection in atmospheric ammonia; A Case study at a Japanese lake basin influenced by agricultural ammonia sources

Katata, Genki*; Kubota, Tomohiro; Kuroda, Hisao*; Watanabe, Mirai*; Takahashi, Akiko*; Nakazato, Ryoji*; Tarui, Mika*; Matsumoto, Shunichi*; Nakagawa, Keita*; Numata, Yasuko*; et al.

no journal, , 

no abstracts in English

Oral presentation

IFMIF/EVEDA; Progress of validation and design activities under the Broader Approach framework

Sugimoto, Masayoshi; Knaster, J.*; Arbeiter, F.*; Cara, P.*; Favuzza, P.*; Furukawa, Tomohiro; Gioacchino, M.*; Groeschel, F.*; Heidinger, R.*; Ibarra, A.*; et al.

no journal, , 

Under the framework of the Broader Approach agreement between Japan and EURATOM the concept of the International Fusion Materials Irradiation Facility (IFMIF) to provide the intense neutron irradiation test facility for developing the fusion reactor materials has been evolved since 2007, through the activities to prepare the engineering design documents for IFMIF with the associated R&D of prototypical components, named as IFMIF Engineering Validation and Engineering Design Activities (EVEDA) project. Recently the Intermediate IFMIF Engineering Design Report for IFMIF (IIEDR) was delivered in July 2013, which is supported by the major outcomes of the validation activities of the prototypical components: Linear IFMIF Prototype Accelerator, EVEDA Lithium Test Loop, High Flux Test Module capsule, etc. In this article, the progresses of the IIEDR and validation tests and also the outcomes to be achieved till mid 2017, the completion time of IFMIF/EVEDA, will be comprehensively overviewed.

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

Magnetic excitations in iridium oxides and their temperature dependence studied by resonant inelastic X-ray scattering

Ishii, Kenji; Jarrige, I.*; Yoshida, Masahiro*; Mizuki, Junichiro; Matsumoto, Akiyo*; Kato, Akihiko*; Takayama, Tomohiro*; Takagi, Hidenori*

no journal, , 

no abstracts in English

15 (Records 1-15 displayed on this page)
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