Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Teranishi, Mika*; Yamaguchi, Hiroko*; Sakamoto, Ayako; Hidema, Jun*
no journal, ,
Sato, Tatsuhiko; Nagamatsu, Aiko*; Takeda, Kazuo*; Niita, Koji*; Puchalska, M.*; Sihver, L.*
no journal, ,
Estimation of doses for astronauts due to space radiation exposure has been an essential issue in the planning of long-term space missions. For that purpose, we developed a simulation tool for estimating radiation environments as well as doses for astronauts stayed in the Kibo module in ISS. The tool consists of the Particle and Heavy Ion Transport Simulation code, PHITS, in combination with the virtual Kibo module developed by JAXA. The accuracy of the simulation was examined on the basis of the experimental data obtained from the Area PADLES and MATROSHKA-Kibo measurements. It was found from the examination that the calculated doses agree with the measured data fairly well. The results of the examination also suggested that the consideration of the east-west asymmetry is important to reproduce the location-dependence of doses inside the Kibo module.
Nagamatsu, Aiko*; Sato, Tatsuhiko; Kitajo, Keiichi*; Shimada, Ken*; Sakane, Sayuri*; Takeda, Kazuo*; Niita, Koji*
no journal, ,
Continuous space-radiation dosimetry is one of the key missions at the International Space Station (ISS) for radiation health management of crew members and for scientific activities. Since the Japanese Experiment Module KIBO was attached to the ISS in 2008, we have been performing continuous space radiation dosimetry using a passive and integrating dosimeters, PADLES (Passive Dosimeter for Life-Science Experiments in Space). To date, several hundreds of PALDES having returned from the ISS showed anisotropy of the radiation environment and changes in the dose rate due to ISS attitudes and differences in shielding conditions. On this occasion, an overview of JAXA's continuous radiation dosimetry activities and the preliminary results will be presented with the discussions, which based on the simulation analysis with Particle and Heavy Ion Transport code System PHITS.
Yamamoto, Hiroyuki; Nojima, Takehiro; Esaka, Fumitaka
no journal, ,
X-ray photoelectron spectroscopy (XPS) is widely used as a non-destructive chemical state analysis method for solid surface. However, depth profiling is often limited due to insufficient analyzing depth. Ion irradiation is often used for depth profiling of XPS, however, chemical state changes are inevitable. Non-destructive analysis is therefore required. In the present study, we examined a method to perform depth profiling with X-ray absorption spectroscopy (XAS) by changing electron energies for detection ranging from 5 to 50 eV using electron spectrometer. Thin Au films (several nm) deposited on Si(100) substrate are used for the specimen. On the basis of the observed results from XAS spectra, significant increase of Si/Au ratio by reducing electron energy. These results indicate non-destructive chemical depth profiling in XAS can be performed by changing electron energies for detection.
Suzuki, Michiyo; Hattori, Yuya; Sakashita, Tetsuya; Funayama, Tomoo; Yokota, Yuichiro; Kobayashi, Yasuhiko
no journal, ,
Sakashita, Tetsuya; Suzuki, Michiyo; Hattori, Yuya; Ikeda, Hiroko; Muto, Yasuko*; Yokota, Yuichiro; Funayama, Tomoo; Hamada, Nobuyuki*; Shirai, Kana*; Kobayashi, Yasuhiko
no journal, ,
We applied the microbeam irradiation of the central nervous tissue in to analyze direct radiation effects at a tissue level. Also, to investigate the mechanism of modulatory effects of irradiation on the salt chemotaxis learnign (SCL), we used two
mutants (
and
) related to the SCL. Well-fed adults of wild-type and mutant
were irradiated with 12,000 carbon ion particles corresponding to 500 Gy at micro-aperture area. Immediately after microbeam irradiation, the SCL performance was examined based on the chemotaxis index (CI). CI during the SCL was decreased in the wild-type and
mutant animals, but microbeam irradiation did not significantly affect CIs of
mutants. The difference of the SCL between
and
mutants will be discussed at the meeting.
Sekine, Yurina; Chi, S.*; Fernandez Baca, J.*; Fukazawa, Tomoko*; Fukazawa, Hiroshi
no journal, ,
Hydrogels are unique polymer materials consisting of large amount of water in their three-dimensional networks. The structure of water is an important factor governing the chemical and physical properties of gel materials. To investigate structure and properties of water in poly-N,N,-dimethylacrylamide (PDMAA) gel, neutron diffraction and differential scanning calorimetry (DSC) curve of the high (90wt%) and low (55wt%) DO content gels were measured. The neutron diffraction patterns show that amorphous, cubic, and hexagonal ices exist in the low D
O content gel at low temperature, whereas only hexagonal ice exists in the high D
O content gel. The DSC result shows that the low D
O content gel contains only intermediate and bound water. In contrast, high D
O content gel contains free, intermediate, and bound water. Therefore the results indicate that amorphous and cubic ices are only formed when the hydrogels do not have the free water.
Ko, B.-S.*; Hasegawa, Shin; Hamada, Takashi; Yoshimura, Kimio; Maekawa, Yasunari
no journal, ,
Hirade, Tetsuya
no journal, ,
Ps has a negative work function in insulating materials and the repulsion between Ps and surrounding molecules can form a bubble in liquids. It is needed to lose energy to have a stable bubble state. The Ps bubble stabilizes within about 10 ps in usual liquids, but not in room temperature ionic liquids (IL). It would take about 1 ns in TMPA-TFSI. The ortho-Ps pick off annihilation probability depends on the size of the Ps bubble and hence the change of the ortho-Ps pick-off annihilation rate caused by the change of the bubble size on the lifetime spectra was expected. The results obtained from the lifetime spectra for TMPA-TFSI indicate that the Ps bubble oscillates in IL before the Ps bubble stabilization. On the other hand, the ortho-Ps pick-off annihilation rate obtained at older positron age region showed smaller annihilation rates than the expected one with the surface tension of IL. Positron annihilation methods will be a very strong tool to investigate the structure of IL.
Sato, Tatsuhiko; Hamada, Nobuyuki*; Kumada, Hiroaki*
no journal, ,
The planning of heavy ion therapy and BNCT requires radiation dose assessment with consideration of RBE for different radiation quality. We developed a model assembly for estimating the surviving fraction of cells irradiated with various types of ionizing radiation, considering Bcl-2 overexpression and nontargeted effects in the same framework. Using the model assembly in combination with PHITS, the RBE-weighted doses were estimated for several irradiation conditions in carbon-ion therapy and BNCT, the boron concentration and the Bcl-2 overexpression status in each cell being taken into account. The simulation suggested that the consideration of radioresistance due to Bcl-2 overexpression results in the significant increase of the RBE-weighted doses in tumor regions. On the other hand, consideration of nontargeted effects gives trivial impact on the RBE-weighted doses in tumor regions, but slightly increases the values in normal tissue regions.
Kumagai, Yuta; Kimura, Atsushi; Taguchi, Mitsumasa
no journal, ,
Zeolite minerals are suitable adsorbents for removal of radioactive cesium in water, because of their high radiation resistances. However, irradiation of zeolites results in decomposition of water adsorbed on the zeolites. Water decomposition produces hydrogen (H) and hydrogen peroxide (H
O
). H
production has a risk of making an explosive gas mixture. H
O
causes corrosion of metals and alloys. Therefore, the radiation effects are required to be assessed and controlled. In this study, H
and H
O
production by irradiation of zeolites in aqueous solution are comparatively studied among different types of zeolites, A-, X-, Y- and mordenite-types. The mixtures of the zeolites and aqueous solution were irradiated by
Co
-rays. The A-type and the X-type zeolites produced more H
than the Y-type and the mordenite-type. In contrast, the H
O
production was inhibited by the addition of zeolites. The A-type and the X-type zeolites showed remarkable inhibition. The A-type and the X-type contains more aluminum in their frameworks than the others do. Therefore, the results suggest that aluminum sites have an important role in the reactions induced by irradiation.
Tanaka, Atsushi
no journal, ,
Hiroki, Akihiro; Yamashita, Shinichi*; Kimura, Atsushi; Nagasawa, Naotsugu; Taguchi, Mitsumasa
no journal, ,
The polymer gel dosimeters consisting of 2-hydroxyethyl methacrylate, nonaethylene glycol dimethacrylate, and tetrakis (hydroxymethyl) phosphoniumu chloride with radiation-crosslinked hydroxypropyl cellulose gel were irradiated with 290 MeV/u C ions at HIMAC. Absorbance of the irradiated dosimeters at 660 nm increased with an increase in the dose up to 10 Gy. The dose response of the dosimeter irradiated with C ions was about 0.007 Abs. Gy, which decreased in about one-tenth of the
-irradiated sample. RGB value of the image obtained by using a flat-bed image scanner also increased with increasing dose. Distribution of the dose estimated from RGB value of the scanned image was almost agreement with that of a general radiochromic film for the radiotherapy.
Homma, Toshimitsu
no journal, ,
Funayama, Tomoo; Yokota, Yuichiro; Sakashita, Tetsuya; Suzuki, Michiyo; Ikeda, Hiroko; Kobayashi, Yasuhiko
no journal, ,
In JAEA-Takasaki, there are two microbeam systems for biological study: collimating heavy-ion microbeam system, and focusing heavy-ion microbeam system. Using the collimating microbeam system, we have carried out the cultured-cell studies of heavy-ion hit effect and analysis of bystander effects. Moreover, we have promoted the microbeam studies of small individuals, such as
, silkworm, and medaka fish. In these studies, we carried out not only researches aimed to explore the effects of heavy-ion radiation, but also the researches of physiological or developmental biology by applying microbeam as the tool of the radio-microsurgery. The focusing microbeam system was developed for overcoming the limitations of the collimating system. Using the system, we developed the experimental system to irradiate cells rapidly and accurately with the scanned microbeam spot of high-energy heavy-ions.
Asaka, Tomomi*; Ito, Kazusa*; Hashimoto, Chika*; Yasuda, Takako*; Nagata, Kento*; Nishimaki, Toshiyuki*; Katsumura, Takafumi*; Ota, Hiroki*; Suzuki, Michiyo; Funayama, Tomoo; et al.
no journal, ,
Radiotherapy has been widely used in cancer target. It is thought that the irradiation to the particular area of the individual could induce the irradiation impact to the nearby and distant tissues of the irradiated area in addition to the irradiated region. However, it is still difficult to analyze influences to the whole body using mice because of its big body size. Medaka, , is small enough to examine the acute somatic effects induced in all tissues at the cellular levels. In this study, we developed a method to conduct local irradiation on adult medaka using low energy carbon-ion beam in TIARA, JAEA-Takasaki. The irradiated fish were measured the heart rate to evaluate the impact to the heart, chemically fixed, serially sectioned and Hematoxylin/eosin stained. The results suggested that there would be the systemic effects by local irradiation in addition to the effects in the irradiated region, which is probably caused by immune system though blood.
Suzuki, Masao*; Funayama, Tomoo; Yokota, Yuichiro; Suzuki, Michiyo; Ikeda, Hiroko; Sakashita, Tetsuya; Kobayashi, Yasuhiko; Murakami, Takeshi*
no journal, ,
We irradiated either 4-cell lines with wild-type P53 or 4-cell lines with mutated-type P53 using the microbeams of JAEA-Takasaki collimated by 20m in diameter. We can easily estimate the number of the directly irradiated cells to be just 0.04% of the total cells on the dish using the highly controlled microbeam irradiation system. The percent survival in the cells with wild-type P53 was around 90%, while almost 100% was observed in the cells with mutated-type P53. The results are consistent with the data using the carbon-ion broad beams with the shielding method at HIMAC. Our overall results showed that bystander cell-killing effect was observed in the cells with wild-type P53, but not in the P53-mutated cells. There is clear evidence that the spot scanning irradiation system of carbon ions enables the enhanced cell killing in cells with wild-type P53 gene via gap-junction mediated bystander effect.
Murata, Kazutoshi*; Noda, Shinei*; Oike, Takahiro*; Takahashi, Akihisa*; Yoshida, Yukari*; Suzuki, Yoshiyuki*; Ono, Tatsuya*; Funayama, Tomoo; Kobayashi, Yasuhiko; Takahashi, Takeo*; et al.
no journal, ,
This study aimed to investigate the effect of carbon ion (C-ion) irradiation on cell motility through the ras homolog gene family member (Rho) signaling pathway in the human lung adenocarcinoma cell line A549. Cell motility was assessed by a wound-healing assay, and the formation of cell protrusions was evaluated by F-actin staining. Cell viability was examined by the WST-1 assay. The expression of myosin light chain 2 (MLC2) and the phosphorylation of MLC2 at Ser19 (P MLC2-S19) were analyzed by Western blot. The data suggest that C-ion irradiation increases cell motility in A549 cells via the Rho signaling pathway and that ROCK inhibition reduces that effect.
Shikazono, Naoya; Akamatsu, Ken
no journal, ,