Yatagai F.,RIKEN |
Honma M.,Japan National Institute of Health Sciences |
Takahashi A.,Nara Medical University |
Omori K.,Japan Aerospace Exploration Agency |
And 12 more authors.
Radiation and Environmental Biophysics | Year: 2011
To estimate the space-radiation effects separately from other space-environmental effects such as microgravity, frozen human lymphoblastoid TK6 cells were sent to the "Kibo" module of the International Space Station (ISS), preserved under frozen condition during the mission and finally recovered to Earth (after a total of 134 days flight, 72 mSv). Biological assays were performed on the cells recovered to Earth. We observed a tendency of increase (2.3-fold) in thymidine kinase deficient (TK -) mutations over the ground control. Loss of heterozygosity (LOH) analysis on the mutants also demonstrated a tendency of increase in proportion of the large deletion (beyond the TK locus) events, 6/41 in the in-flight samples and 1/17 in the ground control. Furthermore, in-flight samples exhibited 48% of the ground-control level in TK - mutation frequency upon exposure to a subsequent 2 Gy dose of X-rays, suggesting a tendency of radioadaptation when compared with the ground-control samples. The tendency of radioadaptation was also supported by the post-flight assays on DNA double-strand break repair: a 1.8- and 1.7-fold higher efficiency of in-flight samples compared to ground control via non-homologous end-joining and homologous recombination, respectively. These observations suggest that this system can be used as a biodosimeter, because DNA damage generated by space radiation is considered to be accumulated in the cells preserved frozen during the mission, Furthermore, this system is also suggested to be applicable for evaluating various cellular responses to low-dose space radiation, providing a better understanding of biological space-radiation effects as well as estimation of health influences of future space explores. © 2010 Springer-Verlag.
Hirose M.,Waseda University |
Asakawa M.,Waseda University |
Okada T.,Japan Aerospace Exploration Agency |
Machida S.,Japan Aerospace Exploration Agency |
And 5 more authors.
13th International Conference on Fracture 2013, ICF 2013 | Year: 2013
In this study, crack propagation tests were conducted to clarify property for the fatigue crack propagation of Friction Stir Welded (FSW) 2024-T3 aluminum alloy. FSW panel has residual stress around weld line and the longitude residual stress is higher around it. The peak tensile residual stress is about 180 MPa in this case. To understand fatigue crack growth property on FSW panel, crack opening stress measurement of the base material and FSW joint using an extensometer with the modified tool is also conducted during the crack growth test. The modified tool is jig to mount the extensometer to the specimen with magnets. The test results indicate that the accuracy of crack opening stress measurement is improved. In addition, the crack growth acceleration and decelerate around the FSW line under the low applied stress range (25 MPa) is bigger than that under high applied stress range (50 MPa). This means the effect of residual stress under low stress range is relatively larger than that under high stress range.
Paradis P.-F.,Japan Aerospace Exploration Agency |
Ishikawa T.,Japan Aerospace Exploration Agency |
Watanabe Y.,Advanced Engineering Services |
Okada J.,Japan Aerospace Exploration Agency
Advances in Optical Technologies | Year: 2011
Electrostatic levitation combined with laser heating is becoming a mature technique that has been used for several fundamental and applied studies in fluid and materials sciences (synthesis, property determination, solidification studies, atomic dynamic studies, etc.). This is attributable to the numerous processing conditions (containerless, wide heating temperature range, cooling rates, atmospheric compositions, etc.) that levitation and radiative heating offer, as well as to the variety of diagnostics tools that can be used. In this paper, we describe the facility, highlighting the combined advantages of electrostatic levitation and laser processing. The various capabilities of the facility are discussed and are exemplified with the measurements of the density of selected iron-nickel alloys taken over the liquid phase. Copyright © 2011 Paul-François Paradis et al.
Uno M.,Japan Aerospace Exploration Agency |
Ogawa K.,Advanced Engineering Services |
Takeda Y.,Advanced Engineering Services |
Sone Y.,Japan Aerospace Exploration Agency |
And 3 more authors.
Journal of Power Sources | Year: 2011
A lithium-ion battery was developed using off-the-shelf pouch cells and launched with a small scientific satellite "REIMEI." The cells were potted with polyurethane or epoxy resin to protect the battery from vacuum in space. Preliminary experimental test results of pouch cells potted in a soft aluminum cap suggested that the cells tended to swell in vacuum, although they had been reinforced with the resins. Bread board models (BBMs), in which pouch cells were potted with resins in a hard aluminum case, were fabricated for cycle life performance tests in the laboratory. The test results indicated that the performance of epoxy-potted BBM was superior to that of the polyurethane-potted BBM. The measured cell resistance implied that the electrolyte solution leaked through the polyurethane resin, resulting in premature deterioration. The epoxy resin was used for the flight battery. The end-of-discharge-voltage (EoDV) trend of the flight battery on orbit was compared with the laboratory test results corrected based on a post-launch cycle test using a fresh cell. The corrected EoDV trend in the laboratory was in good agreement with the on-orbit trend for the early cycle period, indicating that the on-orbit battery was not inadvertently affected by conditions in space. © 2011 Elsevier B.V. All rights reserved.