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Shimomura, Koichiro*; Koda, Akihiro*; Pant, A. D.*; Sunagawa, Hikaru*; Fujimori, Hiroshi*; Umegaki, Izumi*; Nakamura, Jumpei*; Fujihara, Masayoshi; Tampo, Motonobu*; Kawamura, Naritoshi*; et al.
Interactions (Internet), 245(1), p.31_1 - 31_6, 2024/12
shetta lakes in the Soya Coast region and their paleoenvironmental significance with glacial isostatic adjustment in East AntarcticaInoue, Genki*; Honda, Eisuke*; Ito, Keisuke*; Kang, I.*; Seto, Koji*; Tani, Yukinori*; Watanabe, Takahiro; Kashima, Kaoru*; Otani, Shuji*; Yamanaka, Toshiro*; et al.
Quaternary Science Reviews, 338, p.108822_1 - 108822_18, 2024/08
Times Cited Count：0 Percentile：0.00(Geography, Physical)We studied Holocene paleolimnological changes inferred from biomarkers and microscopic observation of microalgae and cyanobacteria in sediment cores from Rundvshetta lakes (Maruwanminami-ike and Maruwan o-ike) in the Soya Coast of East Antarctica, along with sedimentary facies and radiocarbon dating. Coastal marine environment: Maruwanminami-ike (147-72.5 cm, 5,010-2,590 cal BP) and Maruwan-oike (226-47.2 cm, 5,700-3,190 cal BP) were characterized by low biological production with the predominance of diatoms. Transition period of stratified brackish lake environment: Maruwanminami-ike (72.5-65.6 cm, 2,590-2,500 cal BP) and Maruwan-oike (47.2-28.8 cm, 3,190-2,890 cal BP) were characterized by stratified conditions with marine water overlain by freshwater, and a chemocline developed together with an anoxic layer in the bottom of photic zone.
Shimomura, Koichiro*; Koda, Akihiro*; Pant, A. D.*; Natori, Hiroaki*; Fujimori, Hiroshi*; Umegaki, Izumi*; Nakamura, Jumpei*; Tampo, Motonobu*; Kawamura, Naritoshi*; Teshima, Natsuki*; et al.
Journal of Physics; Conference Series, 2462, p.012033_1 - 012033_5, 2023/03
Times Cited Count：0 Percentile：0.00(Physics, Applied)Wu, C.*; Tanaka, Kazuya; Tani, Yukinori*; Bi, X.*; Liu, J.*; Yu, Q.*
Science of the Total Environment, 821, p.153265_1 - 153265_9, 2022/05
Times Cited Count：47 Percentile：96.89(Environmental Sciences)Microplastics (MPs) with different particle sizes were co-cultured with a model freshwater fungus, 
strain KR21-2, to form biofilms on their surface. We also determined the changes in surface physicochemical properties of the biofilm-covered MPs (BMPs) and the heavy metal adsorption capacity of the original MPs and BMPs. The results revealed that the biofilms improve the adsorption of heavy metals on MPs, and the particle size of MPs plays a crucial role in biofilm colonization and adsorption of heavy metals by BMPs.
and Mn by fungal manganese oxide through asbolane formationAoshima, Miku*; Tani, Yukinori*; Fujita, Rina*; Tanaka, Kazuya; Miyata, Naoyuki*; Umezawa, Kazuhiro*
Minerals (Internet), 12(3), p.358_1 - 358_16, 2022/03
Times Cited Count：8 Percentile：70.60(Geochemistry & Geophysics)In this study, we conducted sequestration experiments of Co by KR21-2 in a Mn/Co binary solution at pH7. The sequestration of Co by newly formed BMOs readily progressed in parallel with the exogenous Mn, with higher efficiency than that in single Co solutions. This is attributed to a synergetic effect on Co sequestration through the formation of asbolane in Mn/Co binary systems.
Tanaka, Kazuya; Tani, Yukinori*; Kozai, Naofumi; Onuki, Toshihiko
Journal of Radioanalytical and Nuclear Chemistry, 331(2), p.1109 - 1114, 2022/02
Times Cited Count：0 Percentile：0.00(Chemistry, Analytical)We investigated the sorption of Pu(IV) on biogenic Mn oxide produced by Mn(II)-oxidizing fungus. The sorption of Pu(IV) on biogenic Mn oxide was similar to that of U(VI) and different from that of Th(IV), possibly due to oxidation of Pu(IV) to Pu(VI). When Pu(IV) was sorbed on hyphae only, it was desorbed into the solution phase over time. Pu(IV) could be solubilized by complexation with organic ligands secreted by fungal cells. In particular, Pu(IV) desorption was observed under circumneutral pH conditions.
Okutsu, Kenichi*; Yamashita, Takuma*; Kino, Yasushi*; Nakashima, Ryota*; Miyashita, Konan*; Yasuda, Kazuhiro*; Okada, Shinji*; Sato, Motoyasu*; Oka, Toshitaka; Kawamura, Naritoshi*; et al.
Fusion Engineering and Design, 170, p.112712_1 - 112712_4, 2021/09
Times Cited Count：3 Percentile：32.32(Nuclear Science & Technology)A muonic molecule which consists of two hydrogen isotope nuclei (deuteron (d) or tritium (t)) and a muon decays immediately via nuclear fusion and the muon will be released as a recycling muon, and start to find another hydrogen isotope nucleus. The reaction cycle continues until the muon ends up its lifetime of 2.2 
s. Since the muon does not participate in the nuclear reaction, the reaction is so called a muon catalyzed fusion (CF). The recycling muon has a particular kinetic energy (KE) of the muon molecular orbital when the nuclear reaction occurs. Since the KE is based on the unified atom limit where distance between two nuclei is zero. A precise few-body calculation estimating KE distribution (KED) is also in progress, which could be compared with the experimental results. In the present work, we observed recycling muons after CF reaction.
Yamashita, Takuma*; Okutsu, Kenichi*; Kino, Yasushi*; Nakashima, Ryota*; Miyashita, Konan*; Yasuda, Kazuhiro*; Okada, Shinji*; Sato, Motoyasu*; Oka, Toshitaka; Kawamura, Naritoshi*; et al.
Fusion Engineering and Design, 169, p.112580_1 - 112580_5, 2021/08
Times Cited Count：3 Percentile：32.32(Nuclear Science & Technology)A muon () having 207 times larger mass of electron and the same charge as the electron has been known to catalyze a nuclear fusion between deuteron (d) and triton (t). These two nuclei are bound by and form a muonic hydrogen molecular ion, dt. Due to the short inter-nuclear distance of dt, the nuclear fusion, d +t
+ n + 17.6 MeV, occurs inside the molecule. This reaction is called muon catalyzed fusion (CF). Recently, the interest on CF is renewed from the viewpoint of applications, such as a source of high-resolution muon beam and mono-energetic neutron beam. In this work, we report a time evolution calculation of CF in a two-layered hydrogen isotope target.
through irreversible biogenic manganese oxide sequestrationTani, Yukinori*; Kakinuma, Satomi*; Chang, J.*; Tanaka, Kazuya; Miyata, Naoyuki*
Minerals (Internet), 11(1), p.53_1 - 53_14, 2021/01
Times Cited Count：4 Percentile：30.45(Geochemistry & Geophysics)In this study, we examined the Ba sequestration potential of enzymatically active biogenic Mn oxides (BMOs) with and without exogenous Mn. The BMOs readily oxidized exogenous Mn to produce another BMO phase, and subsequently sequestered Ba at a pH of 7.0, with irreversible Ba sequestration as the dominant pathway. Extended X-ray absorption fine structure spectroscopy and X-ray diffraction analyses demonstrated alteration from turbostratic to tightly stacked birnessite through possible Ba incorporation into the interlayer.
Suzuki, Ryohei*; Tani, Yukinori*; Naito, Hirotaka*; Miyata, Naoyuki*; Tanaka, Kazuya
Catalysts, 10(1), p.44_1 - 44_15, 2020/01
Times Cited Count：12 Percentile：34.85(Chemistry, Physical)We prepared biogenic Mn oxides (BMOs) using strain KR21-2, and subsequently conducted single or repeated treatment experiments in Cr(NO
) at pH6.0. Under aerobic conditions, newly formed BMOs exhibited a rapid production of Cr(VI) without a significant release of Mn(II), demonstrating that newly formed BMO mediates a catalytic oxidation of Cr(III) with a self-regeneration step of reduced Mn. In anaerobic solution, newly formed BMOs showed a cessation of Cr(III) oxidation in the early stage of the reaction, and subsequently had a much smaller Cr(VI) production with significant release of reduced Mn(II).
Katsuta, Nagayoshi*; Takano, Masao*; Sano, Naomi; Tani, Yukinori*; Ochiai, Shinya*; Naito, Sayuri*; Murakami, Takuma*; Niwa, Masakazu; Kawakami, Shinichi*
Sedimentology, 66(6), p.2490 - 2510, 2019/10
Times Cited Count：8 Percentile：52.01(Geology)Micro-X-ray fluorescence (XRF) scanning spectroscopy of marine and lake sedimentary sequences can provide detailed paleoenvironmental records available through element intensities proxy data. However, problems for effects of interstitial pore water on the micro-XRF intensities have been pointed out so far because of direct measurement on the split wet sediment surfaces. In this study, new methods for the XRF corrections were developed by being considered with the micro-X-ray scanning spectroscopy.
Yu, Q.*; Tanaka, Kazuya; Kozai, Naofumi; Sakamoto, Fuminori; Tani, Yukinori*; Onuki, Toshihiko
ACS Earth and Space Chemistry (Internet), 2(8), p.797 - 810, 2018/08
Times Cited Count：15 Percentile：54.84(Chemistry, Multidisciplinary)Most of Mn oxides are biogenic and known to adsorb cesium (Cs) on the surface. This study investigated structural transformation of biogenic birnessite by accommodating commonly occurring natural heavy metals (Zn, Ni) during the formation of Mn oxides and the influence of those metals on the adsorption behavior of Cs on Mn oxides. It was found that the presence of heavy metals during bio-oxidation of Mn(II), followed by exposure to a low pH aqueous solution, increased the number of available layer vacancies, which consequently increased the adsorption capacity of Cs in the final product birnessite.
Katsuta, Nagayoshi*; Ikeda, Hisashi*; Shibata, Kenji*; Kokubu, Yoko; Murakami, Takuma*; Tani, Yukinori*; Takano, Masao*; Nakamura, Toshio*; Tanaka, Atsushi*; Naito, Sayuri*; et al.
Global and Planetary Change, 164, p.11 - 26, 2018/05
Times Cited Count：11 Percentile：41.44(Geography, Physical)Paleoenvironmental and paleoclimate changes in Siberia were reconstructed by continuous, high-resolution records of chemical compositions from a sediment core retrieved from the Buguldeika Saddle, Lake Baikal, dating back to the last 33 cal. ka BP. The Holocene climate followed by a shift at ca. 6.5 cal. ka BP toward warm and dry, suggesting that the climate system transition from the glacial to interglacial state occurred. In the last glacial period, the deposition of carbonate mud from the Primorsky Range was associated with Heinrich events (H3 and H1) and the Selenga River inflow was caused by meltwater of mountain glaciers in the Khamar-Daban Range. The anoxic bottom-water during Allerod-Younger Dryas was probably a result of weakened ventilation associated with reduced Selenga River inflow and microbial decomposition of organic matters from the Primorsky Range. The rapid decline in precipitation during the early Holocene may have been a response to the 8.2 ka cooling event.
Yu, Q.; Onuki, Toshihiko; Tanaka, Kazuya; Kozai, Naofumi; Yamasaki, Shinya*; Sakamoto, Fuminori; Tani, Yukinori*
Geochimica et Cosmochimica Acta, 174, p.1 - 12, 2016/02
Times Cited Count：19 Percentile：56.38(Geochemistry & Geophysics)Although microorganisms possess high sorption capability for lanthanides (Lns), their biological response affecting Lns migration is unclear. We investigated the effects of microbial activity on transformation of Lns by contact of Lns with Aeremonium strictum under metabolically active condition with Mn(II). A biomolecule that specifically complex to Ce(IV) was found to be released from the fungal cell, facilitating the desorption of Ce(IV) from Mn oxide. This biomolecule was not associated with any other trivalent Lns or Fe, which differed from those non-nuclide-specific organic substances released from resting cells, as reported previously.
Tanaka, Kazuya*; Tani, Yukinori*; Onuki, Toshihiko
Chemistry Letters, 40(8), p.806 - 807, 2011/08
Times Cited Count：8 Percentile：32.12(Chemistry, Multidisciplinary)We made sorption experiments of actinides on Mn oxide in dilute NaCl solution. Sorption affinity of actinides on synthetic Mn oxide was Th(IV) 
U(VI) Np(V). The specific sorption behavior of actinides on biogenic Mn oxide was observed. Thorium sorbed on biogenic Mn oxide was desorbed into solution with increasing time. Neptunium was not sorbed on biogenic Mn oxide. The specific sorption behavior is possibly due to organic ligands released from microorganisms and surface property of biogenic Mn oxide.
Tanaka, Kazuya; Tani, Yukinori*; Takahashi, Yoshio*; Tanimizu, Masaharu*; Suzuki, Yoshinori*; Kozai, Naofumi; Onuki, Toshihiko
Geochimica et Cosmochimica Acta, 74(19), p.5463 - 5477, 2010/10
Times Cited Count：99 Percentile：89.83(Geochemistry & Geophysics)We carried out sorption experiments of Ce by biogenic Mn oxide produced by a Mn(II)-oxidizing fungus strain KR21-2. The results of the sorption experiments indicated that Ce(III) was oxidized to Ce(IV) by biogenic Mn oxide in solution with pH 3.8 - 7. Furthermore, oxidized Ce(IV) by biogenic Mn oxide was complexed with organic ligands released from fungal cells under circumneutral conditions.
Tani, Yukinori*; Miyata, Naoyuki*; Ohashi, Maiko*; Onuki, Toshihiko; Seyama, Haruhiko*; Iwahori, Keisuke*; Soma, Mitsuyuki*
Environmental Science & Technology, 38(24), p.6618 - 6624, 2004/12
Times Cited Count：98 Percentile：86.42(Engineering, Environmental)no abstracts in English
Tanaka, Kazuya; Tani, Yukinori*; Onuki, Toshihiko
no journal, ,
no abstracts in English
Nakashima, Ryota*; Okutsu, Kenichi*; Kino, Yasushi*; Miyashita, Konan*; Yasuda, Kazuhiro*; Yamashita, Takuma*; Okada, Shinji*; Sato, Motoyasu*; Oka, Toshitaka; Kawamura, Naritoshi*; et al.
no journal, ,
The recycling muon emitted after the muon catalized fusion (CF) has a kinetic energy between a few keV to 10 keV. To observed the kinetic energy distribution of the recycling muon, we have to guide and inject muons to Ti foil, and measure the muonic X-ray. In this work, we utilized SIMION code to calculate the electric field and the trajectory of muons from deuteron target to Ti foil.
Miyashita, Konan*; Okutsu, Kenichi*; Kino, Yasushi*; Nakashima, Ryota*; Yasuda, Kazuhiro*; Yamashita, Takuma*; Okada, Shinji*; Sato, Motoyasu*; Oka, Toshitaka; Kawamura, Naritoshi*; et al.
no journal, ,
To observe a kinetic energy distribution of a recycling muon emitted after CF reaction, it is necessary to guide the recycling muons to a detector. In this work, we simulated the muon transportation using PHITS code and designed an experimental system.
