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Kitamura, Yoshimasa; Oka, Toshitaka; Seito, Hajime*; Yokozuka, Eri*; Nagasawa, Naotsugu*; Kumagai, Yuta; Watanabe, Masayuki
no journal, ,
We attempt to fabricate a new disposable solid-state dosimeter capable of detecting the range from mGy to Gy as well as tooth enamel by applying ESR dosimetry technique. In this study, we evaluate the applicability of hydroxyapatite, which is the main component of teeth, to the new dosimeter. The intensity of carbonate radicals was proportional to absorbed dose and the dose-response curve showed a good linear relationship in the range 0-200 Gy, and the detection limit was estimated to be 
100 mGy, slightly higher than that for human teeth.
' center to seismic fault slips with various frictional power densitiesTanaka, Kiriha; Ohashi, Kiyokazu*; Muto, Jun*; Oka, Toshitaka
no journal, ,
ESR fault dating assumes that trapped charges in quartz in a fault material have been released by the last seismic fault slip (ESR signal zeroing). However, the physical condition and the underlying mechanism of the signal zeroing remain unclear. We have performed HVF experiments using ceramic host blocks with frictional power densities (FPDs) of 
, resulting in the incomplete signal zeroing for a trapped charge at the E' center. Moreover, HVF experiments with higher FPD were unsuccessful due to failures of the host blocks during the experiments. This study performed HVF experiments using tough titanium alloy host blocks for simulated quartz gouges with a slip rate of 
, a displacement of 
, and normal stresses of 
. During the experiment, temperature near a sliding surface was measured with thermocouples. ESR measurements to detect the trapped charge were conducted for gouges before and after the experiments. HVF experiments showed that the ESR intensity for the trapped charge increased with an increase in FPD of 
, followed by a decrease with a further increase of 
. The maximum temperature increased from approximately 
to 
with an increase in FPD of , followed by an increase up to 
with a further increase of . Based on previous results, it is likely that the number of the trapped charge increased due to grain fracturing, and then decreased due to larger frictional heating with increasing FPD. This study was unable to demonstrate the signal zeroing. However, the change in the number of a trapped charge by the last seismic fault slip can be quantified using FPD, suggesting that the age of the fault slip can be estimated with an assumption of incomplete signal zeroing.
Oka, Toshitaka; Suzuki, Masatoshi*; Takahashi, Atsushi*; Sato, Taku*; Mitsuyasu, Yusuke*; Kino, Yasushi*; Okutsu, Kenichi*; Sekine, Tsutomu*; Yamashita, Takuma*; Shimizu, Yoshinaka*; et al.
no journal, ,
We examined ESR measurement to estimate the dose of wild Japanese macaque captured at the contaminated area of Fukushima Prefecture. The estimated doses were ranged from several mGy to ~270 mGy, which are comparable to the estimated dose reported in our previous work, suggesting that the maximum dose of wild Japanese macaques captured in this area is estimated to be about 300 mGy. The dose estimation using a novel deconvolution program developed by ourselves will be also discussed.
Yamashita, Takuma*; Mitsuyasu, Yusuke*; Ono, Kenta*; Iwami, Satone*; Hayashi, Teppei*; Kino, Yasushi*; Sekine, Tsutomu*; Oka, Toshitaka; Takahashi, Atsushi*; Shimizu, Yoshinaka*; et al.
no journal, ,
no abstracts in English
Hayashi, Teppei*; Yamashita, Takuma*; Mitsuyasu, Yusuke*; Ono, Kenta*; Iwami, Satone*; Kino, Yasushi*; Sekine, Tsutomu*; Oka, Toshitaka; Takahashi, Atsushi*; Shimizu, Yoshinaka*; et al.
no journal, ,
no abstracts in English
Ishiniwa, Hiroko*; Davis, M.*; Johnson, T.*; Oka, Toshitaka
no journal, ,
no abstracts in English
Della, S. M.*; Trompier, F.*; Aboelezz, E.*; Ciesielski, B.*; D'Oca, M. C.*; Hayes, R.*; Juniewicz, M.*; Maltar-Strmecki, N.*; Marciniak, M.*; Marrale, M.*; et al.
no journal, ,
no abstracts in English
Seito, Hajime*; Yokozuka, Eri*; Oka, Toshitaka; Yamasaki, Shota*; Kitatsuji, Yoshihiro; Nagasawa, Naotsugu*
no journal, ,
no abstracts in English