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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:43 Percentile:96.93(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

How different is the core of $$^{25}$$F from $$^{24}$$O$$_{g.s.}$$ ?

Tang, T. L.*; Uesaka, Tomohiro*; Kawase, Shoichiro; Beaumel, D.*; Dozono, Masanori*; Fujii, Toshihiko*; Fukuda, Naoki*; Fukunaga, Taku*; Galindo-Uribarri, A.*; Hwang, S. H.*; et al.

Physical Review Letters, 124(21), p.212502_1 - 212502_6, 2020/05

 Times Cited Count:14 Percentile:74.18(Physics, Multidisciplinary)

The structure of a neutron-rich $$^{25}$$F nucleus is investigated by a quasifree ($$p,2p$$) knockout reaction. The sum of spectroscopic factors of $$pi 0d_{5/2}$$ orbital is found to be 1.0 $$pm$$ 0.3. The result shows that the $$^{24}$$O core of $$^{25}$$F nucleus significantly differs from a free $$^{24}$$O nucleus, and the core consists of $$sim$$35% $$^{24}$$O$$_{rm g.s.}$$, and $$sim$$65% excited $$^{24}$$O. The result shows that the $$^{24}$$O core of $$^{25}$$F nucleus significantly differs from a free $$^{24}$$O nucleus. The result may infer that the addition of the $$0d_{5/2}$$ proton considerably changes the neutron structure in $$^{25}$$F from that in $$^{24}$$O, which could be a possible mechanism responsible for the oxygen dripline anomaly.

Journal Articles

Yeast genes involved in uranium tolerance and uranium accumulation; A Functional screening using the nonessential gene deletion collection

Sakamoto, Fuminori; Nankawa, Takuya; Onuki, Toshihiko; Fujii, Tsutomu*; Iefuji, Haruyuki*

Geomicrobiology Journal, 29(5), p.470 - 476, 2012/05

 Times Cited Count:6 Percentile:17.37(Environmental Sciences)

We screened 4908 non-essential gene deletion mutant yeast strains for uranium sensitivity and low accumulation by growth in agar medium containing uranium. All mutant strains grew successfully on agar media containing 0 or 0.5 mM uranium for one week at 30 centigrade. Thirteen strains with single gene deletions showed reduced growth in the agar medium containing 0.5 mM uranium and were identified as uranium-sensitive mutant strains. The phosphate transporter genes of PHO86, PHO84, PHO2, and PHO87 were among the deleted genes in the uranium-sensitive mutant strains, suggesting that genes concerned with phosphate transport contribute to uranium tolerance. Seventeen single-deletion strains showed lower uranium accumulation than the wild-type after exposure to agar medium containing 0.5 mM uranium, and were identified as mutant strains with low uranium accumulation.

Journal Articles

Response of ${it Saccharomyces cerevisiae}$ to heavy element stress; Lead vs. uranium

Sakamoto, Fuminori; Onuki, Toshihiko; Fujii, Tsutomu*; Iefuji, Haruyuki*

Geomicrobiology Journal, 27(3), p.240 - 244, 2010/05

 Times Cited Count:8 Percentile:24.12(Environmental Sciences)

We have examined the responses of ${it Saccharomyces cerevisiae}$ in media containing Pb$$^{2+}$$ ions and compared it to those in media containing UO$$_{2}$$$$^{2+}$$ ions to elucidate the stress effects of heavy elements. Cultivation of ${it S. cerevisiae}$ in a medium containing 1.0$$times$$10$$^{-4}$$ M Pb showed nearly the same growth as that in the control medium while growth was inhibited in the medium containing 1.0$$times$$10$$^{-3}$$ M Pb. Backscattering electron image analyses of thin sections of cells showed that Pb had accumulated inside the cells. Two-dimensional (2D) gel electrophoresis analysis of the proteins extracted from the ${it S. cerevisiae}$ exposed to Pb$$^{2+}$$ ions showed that several specific protein spots were expressed after cultivation with Pb, that did not appear in the control medium. Our results suggest that Pb$$^{2+}$$ more weakly inhibits the growth of ${it S. cerevisiae}$ than UO$$_{2}$$$$^{2+}$$, and produces different stresses in ${it S. cerevisiae}$ than UO$$_{2}$$$$^{2+}$$.

Journal Articles

Protein expression of ${it Saccharomyces cerevisiae}$ in response to uranium exposure

Sakamoto, Fuminori; Nankawa, Takuya; Kozai, Naofumi; Fujii, Tsutomu*; Iefuji, Haruyuki*; Francis, A. J.; Onuki, Toshihiko

Journal of Nuclear and Radiochemical Sciences, 8(2), p.133 - 136, 2007/10

Protein expression of ${it Saccharomyces cerevisiae}$ grown in the medium containing $$^{238}$$U(VI) and $$^{233}$$U(VI) was examined by two-dimensional gel electrophoresis. ${it S. cerevisiae}$ of BY4743 was grown in medium containing $$^{238}$$U of 0, 2.0, and 5.0 $$times$$ 10$$^{-4}$$ M or $$^{233}$$U of 2.5 $$times$$ 10$$^{-6}$$ (radioactivity was higher by 350 times than 2.0 $$times$$ 10$$^{-4}$$ M $$^{238}$$U) and 5.0 $$times$$ 10$$^{-6}$$ M for 112 h at 30$$^{circ}$$C. The growths of the yeast grown in the above media were in the following order: control $$>$$ 2.5 $$times$$ 10$$^{-6}$$ M $$^{233}$$U $$>$$ 2.0 $$times$$ 10$$^{-4}$$ M $$^{238}$$U $$>$$ 5.0 $$times$$ 10$$^{-6}$$ M $$^{233}$$U $$>$$ 5.0 $$times$$ 10$$^{-4}$$ M $$^{238}$$U. This result indicated that not only radiological but also chemical effect of U reduced the growth of the yeast. The concentrations of U in the medium containing $$^{238}$$U or $$^{233}$$U decreased, suggesting U accumulation by the yeast cells. The 2-D gel electrophoresis analysis showed the appearance of several spots after exposure to $$^{238}$$U or to $$^{233}$$U but not in the control containing no uranium. These results show that the yeast cells exposed to U express several specific proteins.

Journal Articles

Effect of uranium (VI) on the growth of yeast and influence of metabolism of yeast on adsorption of U (VI)

Sakamoto, Fuminori; Onuki, Toshihiko; Kozai, Naofumi; Wakai, Eiichi; Fujii, Tsutomu*; Iefuji, Haruyuki*; Francis, A. J.

Journal of Nuclear and Radiochemical Sciences, 6(1), p.99 - 101, 2005/07

We have carried out the growth experiments of 3 strains of yeast in a medium containing uranium (VI) to elucidate the effect of U (VI) on the growth of microorganisms. Hansenula fabianii J640 grew in the liquid medium containing 0.1 mM U (VI) at lower rate than the control, but Saccharomyces cerevisiae did not grow under this condition. The H. fabianii J640 pre-cultured for 21 h in the liquid medium without U (VI) grew even after the exposure to 1 mM U (VI), but did not grow without pre-cultivation. For the pre-cultured H. fabianii J640, radioactivity of U in the medium was the same as the initial one for 110 h, and then gradually decreased. TEM-EDS analysis of H. fabianii J640 exposed to 1 mM U (VI) for 165 h showed accumulation of U (VI) on the cells. When H. fabianii J640 was not pre-cultured, radioactivity of U in the medium was lower than the initial one. These results indicated that U (VI) inhibits the growth of yeast, and that the adsorption of U (VI) by the cells depends on the metabolism of yeast.

Journal Articles

Accumulation of Cu and its oxidation state in ${it Tremolecia atrata}$ (rusty-rock lichen) mycobiont

Fujii, Hiromitsu*; Hara, Kojiro*; Komine, Masashi*; Ozaki, Takuo; Onuki, Toshihiko; Yamamoto, Yoshikazu*

Journal of Nuclear and Radiochemical Sciences, 6(1), p.115 - 118, 2005/07

We studied the association of a Cu tolerant mycobiont, Tremolecia atrata (rusty-rock lichen) with Cu. T. atrata mycobiont cell aggregates, which grew into a sperical shape, rapidly absorbed Cu into their inner and outer parts. The EDS/SEM study showed that Cu was more highly accumulated in the inner part than the outer part of the aggregates. The XANES study revealed that the Cu absorbed by the T. atrata mycobiont was both monovalent and divalent. These results suggested that the T. atrata mycobiont's high tolerance to Cu is attributable to its ability to store Cu(I) inside the cytoplasm and to adsorb Cu(II) on the cell wall.

Journal Articles

The Nuclear interaction at Oklo 2 billion years ago

Fujii, Yasunori*; Iwamoto, Akira; Fukahori, Tokio; Onuki, Toshihiko; Nakakawa, Masayuki; Hidaka, Hiroshi*; Oura, Yasutsugu*; M$"o$ller, P.*

Nuclear Physics B, 573(1-2), p.377 - 401, 2000/05

 Times Cited Count:191 Percentile:97.63(Physics, Particles & Fields)

no abstracts in English

Journal Articles

Application of neutron radiography to visualization of cryogenic fluid boiling two-phase flows

Takenaka, Nobuyuki*; Asano, Hitoshi*; Fujii, Terushige*; Ushiro, Toshihiko*; Iwatani, Junji*; Murata, Yutaka*; Mochiki, Koichi*; Taguchi, Akira*; Matsubayashi, Masahito; Tsuruno, Akira

Nuclear Instruments and Methods in Physics Research A, 377(1), p.174 - 176, 1996/07

 Times Cited Count:1 Percentile:23.5(Instruments & Instrumentation)

no abstracts in English

JAEA Reports

VHTRC experiment for verification test of H$$infty$$ reactivity estimation method

Fujii, Yoshio; Suzuki, Katsuo; Akino, Fujiyoshi; Yamane, Tsuyoshi; Fujisaki, Shingo; Takeuchi, Motoyoshi; Ono, Toshihiko

JAERI-Data/Code 96-001, 102 Pages, 1996/02

JAERI-Data-Code-96-001.pdf:2.32MB

no abstracts in English

Oral presentation

Study on redox equilibrium of Pu$$^{4+}$$/Pu$$^{3+}$$ in molten NaCl-2CsCl

Nagai, Takayuki; Tayama, Toshimitsu; Myochin, Munetaka; Uehara, Akihiro*; Kakimizu, Toshihiko*; Fujii, Toshiyuki*; Shirai, Osamu*; Yamana, Hajimu*

no journal, , 

no abstracts in English

Oral presentation

Transportation of the laser-driven MeV proton beam for the application; Spatial focusing and spectral enhancement with PMQs

Nishiuchi, Mamiko; Daito, Izuru; Mori, Michiaki; Orimo, Satoshi; Ogura, Koichi; Sagisaka, Akito; Sakaki, Hironao; Hori, Toshihiko; Yogo, Akifumi; Pirozhkov, A. S.; et al.

no journal, , 

From our previous research, we have successfully produce MeV proton beam by 1Hz repetition rate stabely from the interaction between the femto-second TW laser with solid target. Produced proton beam exhibits lower emittance. The number of proton beam is 10$$^{13}$$. However, it shows large divergence angle of 10 degree. The energy spectrum exhibits 100% energy spread. These are problematic for some specific applications. In this study we transported the laser-driven proton beam with permanent quadrapole magnet for the future application. We successfully obtain focused proton beam as well as the monochromatic proton beam. Those spatial distribution at the focus point as well as the spectral information is well reproduced by the montecalro simulation.

Oral presentation

Response of Saccharomyces cerevisiae to heavy element stress; Lead vs. uranium

Sakamoto, Fuminori; Onuki, Toshihiko; Fujii, Tsutomu*; Iefuji, Haruyuki*

no journal, , 

In this study, we cultured Saccharomyces cerevisiae in media containing Pb or U with adjusted concentration and compared influence of Pb and 4U on the growth of S. cerevisiae. S. cerevisiae grew in media containing 1 $$times$$ 10$$^{-5}$$ or 1 $$times$$ 10$$^{-4}$$ M Pb, but did not grow in the medium containing 1 $$times$$ 10$$^{-3}$$ M Pb. S. cerevisiae did not grow in the medium containing 1 $$times$$ 10$$^{-4}$$ and 1 $$times$$ 10$$^{-3}$$ M U. These results indicated that inhibitory effect of U on the growth of S. cerevisiae is greater than that of Pb and that Pb and U obstruct the growth of S. cerevisiae by a different mechanism. S. cerevisiae did not grow in the medium containing 1 $$times$$ 10$$^{-4}$$ M natural U, but grew in the medium containing $$^{233}$$U with alpha radioactivity equivalent to 1 $$times$$ 10$$^{-4}$$ M natural U. These results indicated that the growth of S. cerevisiae is not influenced by chemotoxicity but radiotoxicity of 1 $$times$$ 10$$^{-4}$$ M Pb and U.

Oral presentation

Energetic proton beam generation driven by J-KAREN laser

Mori, Michiaki; Ogura, Koichi; Yogo, Akifumi; Nishiuchi, Mamiko; Kiriyama, Hiromitsu; Pirozhkov, A. S.; Sagisaka, Akito; Orimo, Satoshi; Tampo, Motonobu; Daito, Izuru; et al.

no journal, , 

Experimental studies of laser-driven ion acceleration aimed at ion therapy for cancer treatment are being conducted at the PMRC of JAEA using the J-KAREN Ti:Sapphire laser system at JAEA's APRC. In recent experiments thin foil targets have been irradiated with focused 38 fs laser pulses at the 1.8J laser energy. The energy spectrum of the proton beam is observed to extend to a cut-off value in excess of 7-MeV. Our results expose the prospects and challenges associated with developing a laser-driven ion therapy facility.

Oral presentation

7-MeV class proton beam generation driven by J-KAREN laser

Mori, Michiaki; Ogura, Koichi; Yogo, Akifumi; Nishiuchi, Mamiko; Kiriyama, Hiromitsu; Pirozhkov, A. S.; Sagisaka, Akito; Orimo, Satoshi; Tampo, Motonobu; Daito, Izuru; et al.

no journal, , 

no abstracts in English

15 (Records 1-15 displayed on this page)
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