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Journal Articles

Late-Holocene salinity changes in Lake Ogawara, Pacific coast of northeast Japan, related to sea-level fall inferred from sedimentary geochemical signatures

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:0 Percentile:0.03(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.

Journal Articles

Rabi-oscillation spectroscopy of the hyperfine structure of muonium atoms

Nishimura, Shoichiro*; Torii, Hiroyuki*; Fukao, Yoshinori*; Ito, Takashi; Iwasaki, Masahiko*; Kanda, Sotaro*; Kawagoe, Kiyotomo*; Kawall, D.*; Kawamura, Naritoshi*; Kurosawa, Noriyuki*; et al.

Physical Review A, 104(2), p.L020801_1 - L020801_6, 2021/08

 Times Cited Count:12 Percentile:84.06(Optics)

Journal Articles

Characteristics in trace elements compositions of tephras (B-Tm and To-a) for identification tools

Nara, Fumiko*; Yokoyama, Tatsunori; Yamasaki, Shinichi*; Minami, Masayo*; Asahara, Yoshihiro*; Watanabe, Takahiro; Yamada, Kazuyoshi*; Tsuchiya, Noriyoshi*; Yasuda, Yoshinori*

Geochemical Journal, 55(3), p.117 - 133, 2021/00

 Times Cited Count:5 Percentile:58.66(Geochemistry & Geophysics)

The absolute date of the Millennium Eruption (ME) of Changbaishan Volcano is widely recognized as AD 946. The Baegdosan-Tomakomai (B-Tm) tephra dispersed during the ME is a robust-age key bed. In order to identify the tephra, refractive index and major-element compositions of volcanic glass shards are conventionally used. However, trace-element analysis has been rarely carried out, especially for rare-earth elements (REEs) and for tephra layer bulk sediments. Here we present the datasets of major- and trace-element compositions datasets for the glass shards and bulk sediments of the B-Tm and Towada caldera eruptions (To-a) tephra deposits from the Lake Ogawara sediment core, Tohoku region, northern Japan. The depth profiles of the major and trace elements show the significant peaks for the K$$_{2}$$O and some trace elements (Zn, Rb, Zr, Nb, Sn, Y, La, Ce, Nd, Th, and U) at the B-Tm tephra layer in the Lake Ogawara sediment core, but no peaks of these elements at the To-a tephra layer. High concentrations of the trace elements in the B-Tm tephra layer were observed in individual glass shards as well as in the bulk sediment. These concentrations are highlighted by the elemental abundance pattern normalized by the crustal abundance. The elemental pattern in individual glass shards from other Japanese tephras showed significant differences from those of the B-Tm tephra, especially in REEs compositions. The trace-element compositions of the glass shards and bulk sediment show strong advantages for distinguishing the B-Tm tephra from other Japanese tephras.

Journal Articles

Negative muonium ion production with a C12A7 electride film

Otani, Masashi*; Fukao, Yoshinori*; Futatsukawa, Kenta*; Kawamura, Naritoshi*; Matoba, Shiro*; Mibe, Tsutomu*; Miyake, Yasuhiro*; Shimomura, Koichiro*; Yamazaki, Takayuki*; Hasegawa, Kazuo; et al.

Journal of Physics; Conference Series, 1350, p.012067_1 - 012067_6, 2019/12

 Times Cited Count:2 Percentile:73.65

Negative muonium atom ($$mu^+$$e$$^-$$e$$^-$$, Mu$$^-$$) has unique features stimulating potential interesting for several scientific fields. Since its discovery in late 1980's in vacuum, it has been discussed that the production efficiency would be improved using a low-work function material. C12A7 was a well-known insulator as a constituent of alumina cement, but was recently confirmed to exhibit electric conductivity by electron doping. The C12A7 electride has relatively low-work function (2.9 eV). In this paper, the negative muonium production measurement with several materials including a C12A7 electride film will be presented. Measured production rate of the Mu$$^-$$ were 10$$^{-3}$$/s for all the Al, electride, and SUS target. Significant enhancement on electride target was not observed, thus it is presumed that the surface condition should be more carefully treated. There was no material dependence of the Mu$$^-$$ averaged energy: it was 0.2$$pm$$0.1keV.

Journal Articles

New precise measurements of muonium hyperfine structure at J-PARC MUSE

Strasser, P.*; Abe, Mitsushi*; Aoki, Masaharu*; Choi, S.*; Fukao, Yoshinori*; Higashi, Yoshitaka*; Higuchi, Takashi*; Iinuma, Hiromi*; Ikedo, Yutaka*; Ishida, Katsuhiko*; et al.

EPJ Web of Conferences, 198, p.00003_1 - 00003_8, 2019/01

 Times Cited Count:13 Percentile:99.28

Journal Articles

Direct observation of lattice symmetry breaking at the hidden-order transition in URu$$_2$$Si$$_2$$

Tonegawa, Sho*; Kasahara, Shigeru*; Fukuda, Tatsuo; Sugimoto, Kunihisa*; Yasuda, Nobuhiro*; Tsuruhara, Yugo*; Watanabe, Daiki*; Mizukami, Yuta*; Haga, Yoshinori; Matsuda, Tatsuma*; et al.

Nature Communications (Internet), 5, p.4188_1 - 4188_7, 2014/06

 Times Cited Count:52 Percentile:89.17(Multidisciplinary Sciences)

Journal Articles

The Anisotropy of the superfluid density in noncentrosymmetric CePt$$_3$$Si

Bonalde, I.*; Br$"a$mer-Escamilla, W.*; Haga, Yoshinori; Bauer, E.*; Yasuda, Takashi*; Onuki, Yoshichika

Physica C, 460-462(1), p.659 - 660, 2007/09

 Times Cited Count:4 Percentile:22.75(Physics, Applied)

Journal Articles

Coexistence of antiferromagnetism and heavy-fermion superconductivity in CePt$$_{3}$$Si studied by neutron scattering

Kaneko, Koji; Metoki, Naoto; Bernhoeft, N.*; Matsuda, Tatsuma; Haga, Yoshinori; Yasuda, Takashi*; Takeuchi, Tetsuya*; Settai, Rikio*; Onuki, Yoshichika

Journal of the Physical Society of Japan, 75(Suppl.), p.177 - 179, 2006/08

no abstracts in English

Journal Articles

High pressure study on the heavy fermion superconductor CePt$$_3$$Si by AC calorimetry

Tateiwa, Naoyuki; Haga, Yoshinori; Matsuda, Tatsuma; Ikeda, Shugo; Yasuda, Takashi*; Takeuchi, Tetsuya*; Settai, Rikio*; Onuki, Yoshichika

Physica B; Condensed Matter, 378-380, p.381 - 382, 2006/05

 Times Cited Count:1 Percentile:6.65(Physics, Condensed Matter)

We have determined the pressure-temperature phase diagram of heavy-fermion superconductor CePt$$_3$$Si by the ac heat capacity measurement. The N$'e$el temperature $$T_{rm N}$$ = 2.2 K decreases with increasing pressure and becomes zero at the critical pressure $$P_{rm AF}$$ $$simeq$$ 0.6 GPa. On the other hand, the superconducting phase exists in a wider pressure region from ambient pressure to about 1.5 GPa. The phase diagram of CePt$$_3$$Si is thus very unique and has never been reported before for other heavy fermion superconductors.

Journal Articles

$$^{195}$$Pt-NMR study on noncentrosymmetric heavy-fermion superconductor CePt$$_3$$Si

Yogi, Mamoru*; Kitaoka, Yoshio*; Hashimoto, Shin*; Yasuda, Takashi*; Settai, Rikio*; Matsuda, Tatsuma; Haga, Yoshinori; Onuki, Yoshichika; Rogl, P.*; Bauer, E.*

Journal of Physics and Chemistry of Solids, 67(1-3), p.522 - 524, 2006/01

 Times Cited Count:9 Percentile:41.58(Chemistry, Multidisciplinary)

We report on magnetic and novel superconducting properties in heavy-fermion (HF) noncentrosymmetric compound CePt$$_3$$Si via the measurement of $$^{195}$$Pt nuclear spin-lattice relaxation rate 1/$$T$$$$_1$$. This compound reveals the uniform coexistence of antiferromagnetism ($$T_{rm N}$$ =2.2 K) and superconductivity ($$T_{rm c}$$ =0.75 K). CePt$$_3$$Si is the first HF superconductor that reveals a peak in 1/$$T$$$$_1$$ just below $$T_{rm c}$$ and, additionally, does not follow the $$T^3$$ law that was observed for most unconventional HF superconductors. The novel relaxation behavior found below $$T_{rm c}$$ may be relevant with a possible novel SC state being realized in the noncentrosymmetric CePt$$_3$$Si.

Journal Articles

Evidence for novel pairing state in noncentrosymmetric superconductor CePt$$_3$$Si; $$^{29}$$Si-NMR Knight shift study

Yogi, Mamoru*; Mukuda, Hidekazu*; Kitaoka, Yoshio*; Hashimoto, Shin*; Yasuda, Takashi*; Settai, Rikio*; Matsuda, Tatsuma; Haga, Yoshinori; Onuki, Yoshichika; Rogl, P.*; et al.

Journal of the Physical Society of Japan, 75(1), p.013709_1 - 013709_4, 2006/01

 Times Cited Count:64 Percentile:88.19(Physics, Multidisciplinary)

We report the measurements of the $$^{29}$$Si Knight shift $$^{29}$$K$$_s$$ on the noncentrosymmetric heavy-fermion compound CePt$$_3$$Si in which antiferromagnetism (AFM) with $$T_N$$=2.2 K coexists with superconductivity (SC) with $$T_c$$=0.75 K. Its spin part $$^{29}$$K$$_s$$, which is deduced to be K$$_{sc}$$$$>$$0.11 and 0.16 at respective magnetic fields H=2.0061 and 0.8671 T,. does not decrease across the superconducting transition temperature Tc for the field along the c-axis. The temperature dependence of nuclear spin-lattice relaxation of $$^{195}$$Pt below Tc has been accounted for by a Cooper pairing model with a two-component order parameter composed of spin-singlet and spin-triplet pairing components. From this result, it is shown that the Knight-shift data are consistent with the occurrence of the two-component order parameter for CePt$$_3$$Si.

Journal Articles

Novel pressure phase diagram of heavy fermion superconductor CePt$$_{3}$$Si investigated by ac calorimetry

Tateiwa, Naoyuki; Haga, Yoshinori; Matsuda, Tatsuma; Ikeda, Shugo; Yasuda, Takashi*; Takeuchi, Tetsuya*; Settai, Rikio*; Onuki, Yoshichika

Journal of the Physical Society of Japan, 74(7), p.1903 - 1906, 2005/07

 Times Cited Count:70 Percentile:89.06(Physics, Multidisciplinary)

The pressure dependences of the antiferromagnetic and superconducting transition temperatures have been investigated by ac heat capacity measurement under high pressures for the heavy-fermion superconductor CePt$$_3$$Si without inversion symmetry in the tetragonal structure. The N$'e$el temperature $$T_{rm N}$$ = 2.2 K decreases with increasing pressure and becomes zero at the critical pressure $$P_{rm AF}$$ $$simeq$$ 0.6 GPa. On the other hand, the superconducting phase exists in a wider pressure region from ambient pressure to about 1.5 GPa. The pressure phase diagram of CePt$$_3$$Si is thus very unique and has never been reported before for other heavy fermion superconductors.

Oral presentation

Two critical pressure in heavy fermion superconductor CePt$$_3$$Si

Tateiwa, Naoyuki; Haga, Yoshinori; Matsuda, Tatsuma; Ikeda, Shugo; Yasuda, Takashi*; Takeuchi, Tetsuya*; Settai, Rikio*; Onuki, Yoshichika

no journal, , 

Last year, Bauer et al. reported the co-existence of the superconductivity ($$T_{rm sc}$$ = 0.75 K) and antiferromagnetism ($$T_{rm N}$$= 2.2 K) in CePt$$_3$$Si which has no inversion center in the crystal structure. We have investigated the pressure dependence of the antiferromagnetic and superconducting transition temperatures by ac heat capacity measurement. The Neel temperature $$T_{rm N}$$ decreases with increasing pressure and becomes zero at the critical pressure $$P_{AF}$$ $$sim$$ 0.6 GPa. On the other hand, the superconducting phase exists in a wider pressure region from ambient pressure to about 1.5 GPa, which is far above $$P_{AF}$$. The pressure phase diagram of CePt$$_3$$Si is thus very unique and has never been reported before for other heavy fermion superconductors.

Oral presentation

Estimation of the age with the brackish lake environmental changes using continuous sediment core samples from Lake Ogawara

Nara, Fumiko*; Matsunaka, Tetsuya*; Yamasaki, Shinichi*; Tsuchiya, Noriyoshi*; Watanabe, Takahiro; Yamada, Kazuyoshi*; Yasuda, Yoshinori*

no journal, , 

Lake Ogawara, which is the brackish lake in Aomori prefecture, northern Japan, has been formed by the sea level change. Although the lake formation period is roughly estimated at the late Jomon period, the precise formation period is still unclear. The Lake Ogawara formation is directly connected with the sea level change, therefore, determination of the precise formation period of the Lake Ogawara is very important to understand the sea level history during the Jomon period. In this study, we constructed the precise age model based on the radiocarbon (C-14) for the plant residues and total organic carbon (TOC), Cs-137, Pb-210 and tephra identify in the Lake Ogawara sediment core. Two visible tephras (the Baegdosan-Tomakomai: B-Tm and Towada carudera eruption: To-a) were observed in the sediment core. Since the absolute age of the Millennium Eruption (ME) of Changbaishan volcano is widely accepted as AD 946, the B-Tm tephra in the sediment core can be used as the precice chronological key bed layer. Age profile of the trace element (Br), which was derived from the sea water, in the core showed that the Lake Ogawara started to change to the brackish lake at around 2000 cal BP.

Oral presentation

Trace element distributions of Lake Ogawara sediment core: Implication for the past sea level change at the late Holocene

Nara, Fumiko*; Yamasaki, Shinichi*; Watanabe, Takahiro; Tsuchiya, Noriyoshi*; Yamada, Kazuyoshi*; Yasuda, Yoshinori*

no journal, , 

Lake Ogawara is located northernmost Honshu island Japan, Tohoku region alongside Pacific Ocean. In this study, the trace elements (Br and U) in the Lake Ogawara sediment core were analyzed using XRF to reconstruct the past sea level and salinity changes during the late Holocene. The depth profiles of the trace elements (Br and U) showed the gradual decrease from 160 cm depth to the top of the core (corresponding to ca. 2,200 cal BP). These results showed that the sea level was decreased at around 2,200 cal BP.

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