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

https://doi.org/10.1038/s41550-020-01271-2

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.

Analyses on structural transition of peptide amphiphile micelles with small angle neutron scattering and circular dichroism

Sakamoto, Naoki*; Shimada, Tomoko*; Motokawa, Ryuhei; Koizumi, Satoshi*

Hamon, 22(2), p.172 - 177, 2012/05

https://doi.org/10.5611/hamon.22.2_172

Systematic analysis method for radioactive wastes generated from nuclear research facilities

Kameo, Yutaka; Ishimori, Kenichiro; Haraga, Tomoko; Shimada, Asako; Katayama, Atsushi; Nakashima, Mikio*; Takahashi, Kuniaki

Nihon Genshiryoku Gakkai Wabun Rombunshi, 10(3), p.216 - 225, 2011/09

https://doi.org/10.3327/taesj.J10.029

Analytical methods have been developed for simple and rapid determination of radioactive nuclides, which are selected as important nuclides for safety assessment of disposal of wastes generated from research facilities. We advanced the development of a high-efficiency non-destructive measurement technique for -ray emitting nuclides, simple and rapid methods for pretreatment of hard-to dissolve samples and subsequent radiochemical separations, and rapid determination methods for long-lived nuclides. In order to establish a system to analyze the important nuclides in various kinds of samples, actual radioactive wastes such as concentrated liquid waste, activated concrete, and metal pipes, were analyzed by the present method. The results showed that the present method was well suited for a rapid and simple determination of low-level radioactive wastes generated from research facilities.

Analysis of Th, U, Pu, and Am in radioactive metal waste using extraction chromatography

Shimada, Asako; Haraga, Tomoko; Hoshi, Akiko; Kameo, Yutaka; Nakashima, Mikio; Takahashi, Kuniaki

Journal of Radioanalytical and Nuclear Chemistry, 286(3), p.765 - 770, 2010/12

https://doi.org/10.1007/s10967-010-0750-y

Simple and rapid determination methods for low-level radioactive wastes generated from nuclear research facilities (Guidelines for determination of radioactive waste samples)

Kameo, Yutaka; Shimada, Asako; Ishimori, Kenichiro; Haraga, Tomoko; Katayama, Atsushi; Hoshi, Akiko; Nakashima, Mikio

JAEA-Technology 2009-051, 81 Pages, 2009/10

JAEA-Technology-2009-051.pdf:3.6MB

Simple and rapid determination methods were developed for an evaluation of important nuclides, U, and Th in wastes generated from research facilities at Nuclear Science Research Institute and Oarai Research and Development Center. The present methods were assumed to apply to solidified products made from miscellaneous wastes by plasma melting at the Advanced Volume Reduction Facilities. In order to reduce costs of radiochemical analysis and to establish a routine analytical system, counting efficiency of non-destructive -ray measurements was improved, and times for pretreatment of solidified product samples and subsequent radiochemical separations were shortened. In addition to this, rapid and high sensitive detection methods were developed for a determination of long-lived nuclides. The present paper describes guidelines for the determination of radionuclides in the low-level radioactive wastes by using the present simple and rapid methods.

Benchmarking of nuclear fuel cycle simulators in Atomic Energy Society of Japan

Nishihara, Kenji; Takeshita, Kenji*; Shimada, Takashi*; Aizawa, Naoto*; Nakase, Masahiko*; Wada, Satoshi*; Wakasaki, Shingo*; Matsui, Minefumi*; Yasunaga, Yoshiaki*; Okamura, Tomohiro*; et al.

no journal, , 

Nuclear fuel cycle simulators (NFCSs) are widely used but suffer from uncertainties and a lack of benchmarking for large, complex scenarios. To address this, the Atomic Energy Society of Japan established a committee to develop standard reactor libraries and benchmarking scenarios. Multiple Japanese NFCSs will analyze these scenarios, and the results will be published to improve NFCS reliability.

Analysis of radiation induced mutation in organ cells derived from human induced pluripotent stem cells

Shimada, Mikio*; Kanzaki, Norie; Yanagihara, Hiromi*; Miyake, Tomoko*; Matsumoto, Yoshihisa*

no journal, , 

Although mutation frequency depends on organ cell types and differentiation level, it is not fully understood that organ cell types dependent mutation frequency in human cells. In this study, we aimed to establish measurement system of radiation dependent mutation frequency for analyze radiation effect to the human body. For this purpose, we derived four different organ cells such as neural cells, skin keratinocytes, heart muscle cells and blood cells from hiPSCs. Further, using artificial intelligence technology and machine leaning method, we w analyzed differences of mutation frequency during samples.

Transcriptional alteration of DNA damage response genes after ionizing radiation exposure in induced pluripotent stem cells

Shimada, Mikio*; Tsukada, Kaima*; Miyake, Tomoko*; Kanzaki, Norie; Yanagihara, Hiromi*; Matsumoto, Yoshihisa*

no journal, , 

Induced pluripotent stem cells (iPSCs) are generated by transduction of reprogramming transcriptional factors. iPSCs have multipotency to differentiate all organs and expected for the application of regenerative medicine. However, it is reported that cancer risk of iPSCs, because of expression of reprogramming factors increased DNA damage. It is important to analysis DNA damage response of iPSCs to prevent chromosomal abnormality and tumor formation. In this study, we attempted to elucidate the molecular mechanism of maintenance of genome stability in iPSCs. RNA-seq analysis by the next generation sequencer showed increased expression of genome maintenance genes such as DNA repair, cell cycle checkpoint and apoptosis. Interestingly, expression level of these genes was decreased after differentiation to the neural stem cells. Furthermore, colony formation assay showed high sensitivity and apoptosis activity to the IR exposure in iPSCs. These results suggested that instead of DNA repair, increasing of apoptosis activity maintain cell population having accurate genome DNA. These molecular insight have important implication for safety medical application of iPSCs.