Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Nara, Fumiko*; Watanabe, Takahiro; Matsunaka, Tetsuya*; Yamasaki, Shinichi*; Tsuchiya, Noriyoshi*; Seto, Koji*; Yamada, Kazuyoshi*; Yasuda, Yoshinori*
Palaeogeography, Palaeoclimatology, Palaeoecology, 592, p.110907_1 - 110907_11, 2022/04
Times Cited Count：2 Percentile：50.18(Geography, Physical)Radiocarbon dating, tephrochronology, and geochemical signatures such as bromine (Br), iodine (I), total sulfur (TS), total organic carbon (TOC), and total nitrogen (TN) in a continuous sediment core (OG12-2) were applied to estimate past salinity change on the Lake Ogawara, Pacific coast of northeast Japan. Since the Lake Ogawara was the inner bay of the Pacific Ocean and became the brackish lake in the late Holocene, clarifying the past salinity change on the lake Ogawara could give us important insight into the past sea level changes of the Pacific Ocean. The core OG12-2 has two tephra layers, the Towada eruption and the Changbaishan eruption (B-Tm: AD 946). The age model for the core OG12-2 was established using the radiocarbon measurements of the plant residues in the core, also was constrained by the B-Tm tephra. Depletions of marine-derived elements (Br, I, and TS), from 88.4 to 64.2 mg/kg, 20.0 to 14.1 mg/kg, and 3.1 to 1.1 mass %, respectively, were observed in the layers with 2200-2000 cal BP. These results indicate paleosalinity changes from saline (inner bay) to brackish conditions within Lake Ogawara caused by sea level fluctuations during the late Holocene.
Fe M
ssbauer spectroscopy of RFe
(R = Y, Gd) hydrides synthesized under ultra-high-pressure hydrogenMitsui, Takaya; Masuda, Ryo*; Seto, Makoto; Hirao, Naohisa*; Matsuoka, Takehiro*; Nakamura, Yumiko*; Sakaki, Koji*; Enoki, Hirotoshi*
Journal of Alloys and Compounds, 580(Suppl.1), p.S264 - S267, 2013/12
Times Cited Count：8 Percentile：42.58(Chemistry, Physical)
ssbauer study using synchrotron radiationMasuda, Ryo; Mitsui, Takaya; Ito, Keiji*; Sakaki, Koji*; Enoki, Hirotoshi*; Nakamura, Yumiko*; Seto, Makoto
Hyperfine Interactions, 204(1-3), p.139 - 142, 2012/03
Times Cited Count：2 Percentile：76.72(Physics, Atomic, Molecular & Chemical)We have been developing a system for in situ Mssbauer studies using synchrotron radiation (SR) to elucidate the mechanism of hydrogenation processes. In the system, samples reacts in an atmosphere chamber and SR-based Mssbauer spectra using variable-frequency nuclear monochromator and energy spectra of inelastic nuclear resonant scattering (NRS) of SR are measured. As a feasibility study, the temperature dependence of the Mssbauer and inelastic NRS spectra of Fe in 
-GdFe
H
under vacuum were measured. In both spectra, clear differences were observed between 373 K and 573 K. These differences can be interpreted by the change of microscopic environment around Fe at the dehydrogenation. Thus, it is confirmed that this system works well enough to perform the in-situ Mssbauer study on the dehydrogenation of -GdFeH.
ssbauer spectroscopy using Doppler-shifted 14.4 keV single line Fe-Mssbauer radiationMitsui, Takaya; Seto, Makoto; Masuda, Ryo; Kiriyama, Koji; Kobayashi, Yasuhiro*
Japanese Journal of Applied Physics, Part 2, 46(28), p.L703 - L705, 2007/07
Times Cited Count：17 Percentile：54.91(Physics, Applied)Synchrotron radiation Mssbauer spectroscopy was performed using a pure nuclear Bragg reflection of a FeBO
singlecrystal at the N
el temperature and a Bragg reflection of an oscillating Si single crystal. The developed optical systemfor nuclear diffraction could produce a Doppler-shifted 14.4 keV single-line Fe-Mssbauer radiation and it enabled us to observe the energy-domain synchrotron radiation Mssbauer spectrum with an absorber at rest.
Kanaya, Toshiji*; Takahashi, Nobuaki; Nishida, Koji*; Seto, Hideki*; Nagao, Michihiro*; Takeda, Takayoshi*
Physica B; Condensed Matter, 385-386(1), p.676 - 681, 2006/11
Times Cited Count：13 Percentile：51.98(Physics, Condensed Matter)We report neutron spin-echo measurements on three types of poly(vinyl alcohol) (PVA) gels. The first is PVA gel in a mixture of dimethyl sulfoxide (DMSO) and water with volume ratio 60/40, the second is PVA gel in an aqueous borax solution and the third is chemically cross-linked PVA gel. The observed normalized intermediate scattering functions I(Q,t)/I(Q,0) were very different among them. The I(Q,t)/I(Q,0) of the first and third gels showed a non-decaying component in addition to a decaying component, but the second one did not have the non-decaying one. This clearly indicates that the fluctuations in the first and third PVA gels consist of static and dynamic fluctuations whereas the second PVA gel does include only the dynamic fluctuations. The dynamic and static fluctuations of the PVA gels were analyzed in terms of a restricted motion in the gel network and the Zimm motion, respectively.
Takahashi, Nobuaki; Kanaya, Toshiji*; Nishida, Koji*; Seto, Hideki*; Nagao, Michihiro*; Takeda, Takayoshi*
no journal, ,
We have extensively studied nano-scale structure and dynamics of three types of poly(vinyl alcohol) (PVA) gels by using small-angle neutron scattering (SANS) and neutron spin-echo (NSE) techniques; two physical gels and one chemical gel. The first one was a PVA gel in a mixture of deuterated dimethyl sulfoxide (DMSO-d6) and D2O with volume fraction of DMSO-d6 being 0.6, in which cross-links were made of crystallites. On the basis of NSE results, SANS intensity was divided into static and dynamic fluctuations to find that the former contribution was dominant in the present wave vector (Q) range. The latter, dynamic fluctuations were analyzed in terms of fluctuations of cross-links in the quasi-equilibrium position. The second gel was PVA in aqueous borax solution. The intermediate scattering functions of the gel as well as the sol were well described by Zimm mode and gel mode in Q regions of above and below a critical wave vector (Qc). The last one was the chemically cross-linked PVA gel. The intermediate scattering function was also described by Zimm mode in a short-time region, suggesting that it behaves like polymer solution. However, in a long-time region, the data points deviated from Zimm-scaled master curve, suggesting that it was restricted by the cross-links made of covalent bonds.
Niimi, Kenichiro; Nakajima, Hideo; Hamada, Kazuya; Takano, Katsutoshi; Okuno, Kiyoshi; Kakui, Hideo*; Yamaoka, Hiroto*; Chida, Yutaka*; Seto, Masaru*; Soejima, Koji*; et al.
no journal, ,
no abstracts in English
ssbauer study on the hydrides of C15 RFe (R=Sm,Gd) compoundsMasuda, Ryo; Mitsui, Takaya; Ito, Keiji*; Sakaki, Koji*; Enoki, Hirotoshi*; Nakamura, Yumiko*; Kobayashi, Yasuhiro*; Kitao, Shinji*; Seto, Makoto
no journal, ,
Noguchi, Koji; Yasuo, Kiyoshi; Seto, Nobuhiko; Iwasaki, Shogo; Inami, Shinichi
no journal, ,
At the Tokai reprocessing plant, release of the low radioactive fluid to the ocean is carried out using sea release facilities. It was confirmed that there was a leak point on the sea release facilities. Therefore, check and investigation were performed and the leak point was identified. The leak part was cut and the part was then collected to investigate the cause of the leak. As a result, it was estimated that the leak occurred after the pipe was mechanically damaged and a successive change occurred on the part. For this leak point, a series of works for the cause investigation was carried out in detail, the repair work was performed, and preventive measures were taken against recurrences. This paper describes the summary of the sea release facilities, the situation of the outbreak of the leak, and the process that confirmed the leak point.
