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Journal Articles

Radiocaesium accumulation capacity of epiphytic lichens and adjacent barks collected at the perimeter boundary site of the Fukushima Dai-ichi Nuclear Power Station

Dohi, Terumi; Omura, Yoshihito*; Yoshimura, Kazuya; Sasaki, Takayuki*; Fujiwara, Kenso; Kanaizuka, Seiichi*; Nakama, Shigeo; Iijima, Kazuki

PLOS ONE (Internet), 16(5), p.e0251828_1 - e0251828_16, 2021/05

 Times Cited Count:1 Percentile:0(Multidisciplinary Sciences)

Journal Articles

Genesis and development processes of fractures in granite; Petrographic indicators of hydrothermal alteration

Yuguchi, Takashi*; Izumino, Yuya*; Sasao, Eiji

PLOS ONE (Internet), 16(5), p.e0251198_1 - e0251198_17, 2021/05

 Times Cited Count:0 Percentile:0(Multidisciplinary Sciences)

This study analyzes the relationships among alteration indicators, areal microvoid fractions in chloritized biotite, and macroscopic fracture frequencies in the Toki granite, central Japan, to establish the genesis and development processes of fractures in granite. Petrographic alteration indicators using biotite chloritization as innovative methods are proposed to evaluate the extent of hydrothermal alteration and fracture frequency within granites. Samples with high macroscopic fracture frequencies correspond to a high number of areal microvoid fractions and large alteration indicators. The alteration indicators contribute to the characterization of present and future distributions of macroscopic fracture frequencies.

Journal Articles

Simulation code for estimating external gamma-ray doses from a radioactive plume and contaminated ground using a local-scale atmospheric dispersion model

Satoh, Daiki; Nakayama, Hiromasa; Furuta, Takuya; Yoshihiro, Tamotsu*; Sakamoto, Kensaku

PLOS ONE (Internet), 16(1), p.e0245932_1 - e0245932_26, 2021/01

 Times Cited Count:1 Percentile:81.22(Multidisciplinary Sciences)

In this study, we developed a simulation code named SIBYL, which estimates external gamma-ray doses at ground level from radionuclides distributed nonuniformly in atmosphere and on ground. SIBYL can combine with the local-scale atmospheric dispersion model LOHDIM-LES, and calculate the dose distributions according to the map of the activity concentrations simulated by LOHDIM-LES. To apply the SIBYL code to emergency responses of nuclear accidents, the time-consuming three-dimensional radiation transport simulations were performed in advance using the general-purpose Monte Carlo code PHITS, and then the results were compiled to the database for the SIBYL's dose calculations. Moreover, SIBYL can consider the dose attenuation by obstacles and the changes of terrain elevations. To examine the accuracy of SIBYL, typical five cases including $$^{85}$$Kr emission from a ventilation shaft and $$^{137}$$Cs dispersion inside urban area were investigated. The results of SIBYL agreed within 10% with those of PHITS at the most of target locations. Furthermore, the calculation speed was approximately 100 times faster than that of PHITS.

Journal Articles

Consistent modelling of material weight loss and gas release due to pyrolysis and conducting benchmark tests of the model; A Case for glovebox panel materials such as polymethyl methacrylate

Ono, Takuya; Tashiro, Shinsuke; Amano, Yuki; Yoshida, Naoki; Yoshida, Ryoichiro; Abe, Hitoshi

PLOS ONE (Internet), 16(1), p.e0245303_1 - e0245303_16, 2021/01

 Times Cited Count:0 Percentile:0.01(Multidisciplinary Sciences)

It is necessary to consider how a glove box's confinement function will be lost when evaluating the amount of radioactive material leaking from a nuclear facility during a fire. In this study, we build a model that consistently explains the weight loss of glove box materials because of heat input from a flame and accompanying generation of the pyrolysis gas. The weight loss suggests thinning of the glove box housing, and the generation of pyrolysis gas suggests the possibility of fire spreading. The target was polymethyl methacrylate (PMMA), used as the glove box panel. Thermal gravimetric tests on PMMA determined the parameters to be substituted in the Arrhenius equation for predicting the weight loss in pyrolysis. The pyrolysis process of PMMA was divided into 3 stages with activation energies of 62 kJ/mol, 250 kJ/mol, and 265 kJ/mol. Furthermore, quantifying the gas composition revealed that the composition of the pyrolysis gas released from PMMA can be approximated as 100 percent methyl methacrylate. This result suggests that the released amount of methyl methacrylate can be estimated by the Arrhenius equation. To investigate the validity of such estimation, a sealed vessel test was performed. In this test, we observed increase of the number of gas molecules during the pyrolysis as internal pressure change of the vessel. The number of gas molecules was similar to that estimated from the Arrhenius equation, and indicated the validity of our method. Moreover, we also performed the same tests on bisphenol-A-polycarbonate (PC) for comparison. In case of PC, the number of gas molecules obtained in the vessel test was higher than the estimated value.

Journal Articles

A Biologically based mathematical model for spontaneous and ionizing radiation cataractogenesis

Sakashita, Tetsuya*; Sato, Tatsuhiko; Hamada, Nobuyuki*

PLOS ONE (Internet), 14(8), p.e0221579_1 - e0221579_20, 2019/08

 Times Cited Count:3 Percentile:41.12(Multidisciplinary Sciences)

Cataracts have long been known, but a biologically based mathematical model is still unavailable for cataratogenesis. We here report for the first time an in silico model for cataractogenesis. First, a simplified cell proliferation model was developed for human lens growth based on stem and progenitor cell proliferation as well as epithelial-fiber cell differentiation. Then, a model for spontaneous cataractogenesis was developed to reproduce the human data on a relationship between age and cataract incidence. Finally, a model for radiation cataractogenesis was developed that can reproduce the human data on a relationship between dose and cataract onset at various ages, which was further applied to estimate cataract incidence following chronic lifetime exposure.

Journal Articles

Root-endophytic Chaetomium cupreum chemically enhances aluminium tolerance in $$Miscanthus sinensis$$ via increasing the aluminium detoxicants, chlorogenic acid and oosporein

Haruma, Toshikatsu*; Yamaji, Keiko*; Ogawa, kazuyoshi*; Masuya, Hayato*; Sekine, Yurina; Kozai, Naofumi

PLOS ONE (Internet), 14(2), p.e0212644_1 - e0212644_16, 2019/02

 Times Cited Count:13 Percentile:87.95(Multidisciplinary Sciences)

Miscanthus sinensis Andersson is a pioneer plant species that grows naturally at mining sites. $$Miscanthus sinensis$$ can detoxify aluminium (Al) by producing phytosiderophores. Root-endophytic Chaetomium cupreum, which produces microbial siderophores, enhances Al tolerance in M. sinensis. We identified the siderophore produced by C. cupreum as oosporein. It was revealed that oosporein could detoxify Al. Inoculation test of C. cupreum onto M. sinensis in acidic mine soil showed that C. cupreum promoted seedling growth, and enhanced Al tolerance.

Journal Articles

Electron-tracking Compton camera imaging of technetium-95m

Hatsukawa, Yuichi*; Hayakawa, Takehito*; Tsukada, Kazuaki; Hashimoto, Kazuyuki*; Sato, Tetsuya; Asai, Masato; Toyoshima, Atsushi; Tanimori, Toru*; Sonoda, Shinya*; Kabuki, Shigeto*; et al.

PLOS ONE (Internet), 13(12), p.e0208909_1 - e0208909_12, 2018/12


 Times Cited Count:0 Percentile:0.01(Multidisciplinary Sciences)

Imaging of $$^{95m}$$Tc radioisotope was conducted using an electron tracking-Compton camera (ETCC). $$^{95m}$$Tc emits 204, 582, and 835 keV $$gamma$$ rays, and was produced in the $$^{95}$$Mo(p,n)$$^{95m}$$Tc reaction with a $$^{95}$$Mo-enriched target. The recycling of the $$^{95}$$Mo-enriched molybdenum trioxide was investigated, and the recycled yield of $$^{95}$$Mo was achieved to be 70% - 90%. The images were obtained with each of the three $$gamma$$ rays. Results showed that the spatial resolution increases with increasing $$gamma$$-ray energy, and suggested that the ETCC with high-energy $$gamma$$-ray emitters such as $$^{95m}$$Tc is useful for the medical imaging of deep tissue and organs in the human body.

Journal Articles

Analysis of scintillation light intensity by microscopic radiation transport calculation and F$"{o}$rster quenching model

Ogawa, Tatsuhiko; Yamaki, Tetsuya*; Sato, Tatsuhiko

PLOS ONE (Internet), 13(8), p.e0202011_1 - e0202011_19, 2018/08

 Times Cited Count:3 Percentile:33.17(Multidisciplinary Sciences)

Scintillators are generally used to detect various kinds of particles such as electrons, gammas, protons and heavy ions. Scintillators emit photons according to the energy deposited to the crystal. It is also known that light yield is suppressed for particles depositing energy densely owing to quenching. Moreover, it is suggested that quenching is attributed to transfer of energy from excited fluorescent molecules to damaged molecules (F$"{o}$rster mechanism). In this study, energy deposition in a scintillator crystal by radiation was calculated using radiation transport codes to finally obtain excitation and damage of fluorescent molecules. Based on the calculation, spatial configuration of exited and damaged molecules. Then the probability that F$"{o}$rster mechanism takes place in excited molecules were estimated to obtain the number of fluorescent molecules that emit photons. As a result, light yield is proportionally increased with increase in the incident energy in case of electron incidence. On the other hand, light yield is increased non-linearly in case of proton incidence. This trend is in a good agreement with the experimental results.

Journal Articles

Analytical model for estimating the zenith angle dependence of terrestrial cosmic ray fluxes

Sato, Tatsuhiko

PLOS ONE (Internet), 11(8), p.e0160390_1 - e0160390_22, 2016/08

 Times Cited Count:37 Percentile:86.27(Multidisciplinary Sciences)

A new model called PARMA4.0 was developed to facilitate instantaneous estimation of not only omnidirectional but also angular differential fluxes of cosmic rays anywhere in Earth's atmosphere at nearly any given time. It consists of its previous version, PARMA3.0, for calculating the omnidirectional fluxes and several mathematical functions proposed in this study for expressing their zenith-angle dependences. The numerical values of the parameters used in these functions were fitted to reproduce the results of the extensive air shower simulation performed by Particle and Heavy Ion Transport code System (PHITS). The accuracy of PARMA4.0 was closely verified using multiple sets of experimental data obtained under various global conditions. This extension enlarges the model's applicability to more areas of research, including design of cosmic-ray detectors, muon radiography, soil moisture monitoring, and cosmic-ray shielding calculation.

Journal Articles

Dynamical behavior of human $$alpha$$-synuclein studied by quasielastic neutron scattering

Fujiwara, Satoru; Araki, Katsuya*; Matsuo, Tatsuhito; Yagi, Hisashi*; Yamada, Takeshi*; Shibata, Kaoru; Mochizuki, Hideki*

PLOS ONE (Internet), 11(4), p.e0151447_1 - e0151447_17, 2016/04

 Times Cited Count:18 Percentile:67.4(Multidisciplinary Sciences)

Journal Articles

Analytical model for estimating terrestrial cosmic ray fluxes nearly anytime and anywhere in the world; Extension of PARMA/EXPACS

Sato, Tatsuhiko

PLOS ONE (Internet), 10(12), p.e0144679_1 - e0144679_33, 2015/12

 Times Cited Count:58 Percentile:91.2(Multidisciplinary Sciences)

By extending our previously established model, here we propose a new model called "PHITS-based Analytical Radiation Model in the Atmosphere (PARMA) version 3.0", which can instantaneously estimate terrestrial cosmic ray fluxes of neutrons, protons, ions with charge up to 28 (Ni), muons, electrons, positrons, and photons nearly anytime and anywhere in the Earth's atmosphere. The models to be used for estimating radiation doses due to cosmic ray exposure, cosmic ray induced ionization rates, and count rates of neutron monitors were validated by investigating their capability to reproduce those quantities measured under various conditions. PARMA3.0 is available freely and is easy to use, as implemented in an open-access software program EXcel-based Program for Calculating Atmospheric Cosmic ray Spectrum (EXPACS). Because of these features, the new version of PARMA/EXPACS can be an important tool in various research fields such as geosciences, cosmic ray physics, and radiation research.

Journal Articles

Two arginine residues suppress the flexibility of nucleosomal DNA in the canonical nucleosome core

Kono, Hidetoshi; Shirayama, Kazuyoshi*; Arimura, Yasuhiro*; Tachiwana, Hiroaki*; Kurumizaka, Hitoshi*

PLOS ONE (Internet), 10(3), p.e0120635_1 - e0120635_15, 2015/03

 Times Cited Count:21 Percentile:63.66(Multidisciplinary Sciences)

Journal Articles

Condition number estimation of preconditioned matrices

Kushida, Noriyuki

PLOS ONE (Internet), 10(3), p.e0122331_1 - e0122331_16, 2015/03

 Times Cited Count:4 Percentile:41.9(Multidisciplinary Sciences)

The present paper introduces a condition number estimation method for preconditioned matrices. The newly developed method provides reasonable results, while the conventional method which is based on the Lanczos connection gives meaningless results. The Lanczos connection based method provides the condition numbers of coefficient matrices of systems of linear equations with information obtained through the preconditioned conjugate gradient method. Estimating the condition number of preconditioned matrices is sometimes important when describing the effectiveness of new preconditionerers or selecting adequate preconditioners. Operating a preconditioner on a coefficient matrix is the simplest method of estimation. However, this is not possible for large-scale computing, especially if computation is performed on distributed memory parallel computers. This is because, the preconditioned matrices become dense, even if the original matrices are sparse. Although the Lanczos connection method can be used to calculate the condition number of preconditioned matrices, it is not considered to be applicable to large-scale problems because of its weakness with respect to numerical errors. Therefore, we have developed a robust and parallelizable method based on Hager's method. The feasibility studies are curried out for the diagonal scaling preconditioner and the SSOR preconditioner with a diagonal matrix, a tri-daigonal matrix and Pei's matrix. As a result, the Lanczos connection method contains around 10% error in the results even with a simple problem. On the other hand, the new method contains negligible errors. In addition, the newly developed method returns reasonable solutions when the Lanczos connection method fails with Pei's matrix, and matrices generated with the finite element method.

Journal Articles

Biogeochemical signals from deep microbial life in terrestrial crust

Suzuki, Yohei*; Konno, Yuta*; Fukuda, Akari*; Komatsu, Daisuke*; Hirota, Akinari*; Watanabe, Katsuaki*; Togo, Yoko*; Morikawa, Noritoshi*; Hagiwara, Hiroki; Aosai, Daisuke*; et al.

PLOS ONE (Internet), 9(12), p.e113063_1 - e113063_20, 2014/12

 Times Cited Count:9 Percentile:36.08(Multidisciplinary Sciences)

We present multi-isotopic evidence of microbially mediated sulfate reduction in a granitic aquifer, a representative of the terrestrial crust habitat. Deep groundwater of meteoric origin was collected from underground boreholes drilled into the Cretaceous Toki granite, central Japan. A large sulfur isotopic fractionation of 20-60 permil diagnostic to microbial sulfate reduction is associated with the investigated groundwater containing sulfate below 0.2 mM. In contrast, a small carbon isotopic fractionation ($$<$$ 30 permil) is not indicative of methanogenesis. Our results demonstrate that the deep biosphere in the terrestrial crust is metabolically active and playing a crucial role in the formation of reducing groundwater even under low energy fluxes.

Journal Articles

Model assembly for estimating cell surviving fraction for both targeted and nontargeted effects based on microdosimetric probability densities

Sato, Tatsuhiko; Hamada, Nobuyuki*

PLOS ONE (Internet), 9(11), p.e114056_1 - e114056_20, 2014/11

 Times Cited Count:9 Percentile:43.31(Multidisciplinary Sciences)

We here propose a new model assembly for estimating the surviving fraction of cells irradiated with various types of ionizing radiation, considering both targeted and nontargeted effects in the same framework. The probability densities of specific energies in cell nucleus and domain calculated by PHITS were employed as the physical index for characterizing the radiation fields. In the model assembly, our previously established double stochastic microdosimetric kinetic (DSMK) model was used to express the targeted effect, whereas a newly developed model was used to express the nontargeted effect. The radioresistance caused by overexpression of anti-apoptotic protein Bcl-2 known to frequently occur in human cancer was also considered by introducing the concept of the adaptive response in the DSMK model. The accuracy of the model assembly was examined by comparing the computationally and experimentally determined surviving fraction of Bcl-2 and Neo cells irradiated with microbeam or broadbeam of energetic heavy ions, as well as the WI-38 normal human fibroblasts irradiated with X-ray microbeam. The model assembly reproduced very well the experimentally determined surviving fraction over a wide range of dose and linear energy transfer (LET) values. Our newly established model assembly will be worth being incorporated into treatment planning systems for heavy-ion therapy, brachytherapy, and boron neutron capture therapy, given critical roles of the frequent Bcl-2 overexpression and the nontargeted effect in estimating therapeutic outcomes and harmful effects of such advanced therapeutic modalities.

Journal Articles

Free-energy landscape of reverse tRNA translocation through the ribosome analyzed by electron microscopy density maps and molecular dynamics simulations

Ishida, Hisashi; Matsumoto, Atsushi

PLOS ONE (Internet), 9(7), p.e101951_1 - e101951_17, 2014/07

 Times Cited Count:14 Percentile:47.37(Multidisciplinary Sciences)

Journal Articles

Microdosimetric analysis confirms similar biological effectiveness of external exposure to $$gamma$$-rays and internal exposure to $$^{137}$$Cs, $$^{134}$$Cs, and $$^{131}$$I

Sato, Tatsuhiko; Manabe, Kentaro; Hamada, Nobuyuki*

PLOS ONE (Internet), 9(6), p.e99831_1 - e99831_10, 2014/06

 Times Cited Count:7 Percentile:35.98(Multidisciplinary Sciences)

The RBEs of the internal exposure to $$^{137}$$Cs, $$^{134}$$Cs and $$^{131}I$$ were evaluated on the basis of the microdosimetric analysis.

Journal Articles

From laboratory to field; ${it OsNRAMP5}$-knockdown rice is a promising candidate for Cd phytoremediation in paddy fields

Takahashi, Ryuichi*; Ishimaru, Yasuhiro*; Shimo, H.*; Bashir, K.*; Senoura, Takeshi*; Sugimoto, Kazuhiko*; Ono, Kazuko*; Suzui, Nobuo; Kawachi, Naoki; Ishii, Satomi; et al.

PLOS ONE (Internet), 9(6), p.e98816_1 - e98816_7, 2014/06

 Times Cited Count:34 Percentile:82.91(Multidisciplinary Sciences)

Journal Articles

Visualization of $$gamma$$H2AX foci caused by heavy ion particle traversal; Distribution between core track versus non-track damage

Nakajima, Nakako*; Brunton, H.*; Watanabe, Ritsuko; Shrikhande, A.*; Hirayama, Ryoichi*; Matsufuji, Naruhiro*; Fujimori, Akira*; Murakami, Takeshi*; Okayasu, Ryuichi*; Jeggo, P.*; et al.

PLOS ONE (Internet), 8(8), p.e70107_1 - e70107_14, 2013/08

 Times Cited Count:48 Percentile:89.39(Multidisciplinary Sciences)

Heavy particle irradiation can produce complex DNA double strand breaks (DSBs) within the particle trajectory. Additionally, secondary electrons, termed delta-electrons, can create low linear energy transfer (LET) damage distant from the track. Using imaging with deconvolution, we show that at 8 hours after exposure to Fe ions, $$gamma$$H2AX foci forming at DSBs within the particle track are large and encompass multiple smaller and closely localised foci, which we designate as clustered $$gamma$$H2AX foci. We also identified simple $$gamma$$H2AX foci distant from the track. They are rapidly repaired. Clustered $$gamma$$H2AX foci induced by heavy particle radiation cause prolonged checkpoint arrest compared to simple $$gamma$$H2AX foci. However, mitotic entry was observed when $$sim$$10 clustered foci remain. Thus, cells can progress into mitosis with multiple clusters of DSBs following the traversal of a heavy particle.

Journal Articles

A Framework for analysis of abortive colony size distributions using a model of branching processes in irradiated normal human fibroblasts

Sakashita, Tetsuya; Hamada, Nobuyuki*; Kawaguchi, Isao*; Ouchi, Noriyuki; Hara, Takamitsu*; Kobayashi, Yasuhiko; Saito, Kimiaki

PLOS ONE (Internet), 8(7), p.e70291_1 - e70291_10, 2013/07

 Times Cited Count:7 Percentile:39.02(Multidisciplinary Sciences)

Clonogenicity gives important information about the cellular reproductive potential following ionizing irradiation. We firstly plotted the experimentally determined colony size distribution of abortive colonies in irradiated normal human fibroblasts, and found the linear relationship on the log-log plot. By applying the simple model of branching processes to the linear relationship, we found the persistent reproductive cell death (RCD) over several generations following irradiation. To verify the estimated probability of RCD, abortive colony size distribution ($$leq$$15 cells/colony) and the surviving fraction were simulated by the Monte Carlo computational approach. Radiation-induced RCD (i.e. excess probability) lasted over 16 generations and mainly consisted of two components in the early and late phases. We found that short-term RCD is critical to the abortive colony size distribution, and long-lasting RDC is important for the dose response of the surviving fraction.

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