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Journal Articles

Effect of particle size on the colonization of biofilms and the potential of biofilm-covered microplastics as metal carriers

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:3 Percentile:94.91(Environmental Sciences)

Microplastics (MPs) with different particle sizes were co-cultured with a model freshwater fungus, ${it Acremonium strictum}$ 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.

Journal Articles

Simultaneous sequestration of Co$$^{2+}$$ and Mn$$^{2+}$$ by fungal manganese oxide through asbolane formation

Aoshima, 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:1 Percentile:0.04(Geochemistry & Geophysics)

In this study, we conducted sequestration experiments of Co$$^{2+}$$ by ${it Acremonium strictum}$ KR21-2 in a Mn$$^{2+}$$/Co$$^{2+}$$ binary solution at pH7. The sequestration of Co$$^{2+}$$ by newly formed BMOs readily progressed in parallel with the exogenous Mn$$^{2+}$$, with higher efficiency than that in single Co$$^{2+}$$ solutions. This is attributed to a synergetic effect on Co$$^{2+}$$ sequestration through the formation of asbolane in Mn$$^{2+}$$/Co$$^{2+}$$ binary systems.

Journal Articles

Sorption of Pu(IV) on biogenic Mn oxide and complexation of Pu(IV) with organic ligands secreted by fungal cells

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:0.02(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.

Journal Articles

Preferential elimination of Ba$$^{2+}$$ through irreversible biogenic manganese oxide sequestration

Tani, Yukinori*; Kakinuma, Satomi*; Chang, J.*; Tanaka, Kazuya; Miyata, Naoyuki*

Minerals (Internet), 11(1), p.53_1 - 53_14, 2021/01

 Times Cited Count:2 Percentile:58.94(Geochemistry & Geophysics)

In this study, we examined the Ba$$^{2+}$$ sequestration potential of enzymatically active biogenic Mn oxides (BMOs) with and without exogenous Mn$$^{2+}$$. The BMOs readily oxidized exogenous Mn$$^{2+}$$ to produce another BMO phase, and subsequently sequestered Ba$$^{2+}$$ at a pH of 7.0, with irreversible Ba$$^{2+}$$ 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$$^{2+}$$ incorporation into the interlayer.

Journal Articles

Sequestration and oxidation of Cr(III) by fungal Mn oxides with Mn(II) oxidizing activity

Suzuki, Ryohei*; Tani, Yukinori*; Naito, Hirotaka*; Miyata, Naoyuki*; Tanaka, Kazuya

Catalysts, 10(1), p.44_1 - 44_15, 2020/01

 Times Cited Count:5 Percentile:35.42(Chemistry, Physical)

We prepared biogenic Mn oxides (BMOs) using ${it Acremonium strictum}$ strain KR21-2, and subsequently conducted single or repeated treatment experiments in Cr(NO$$_{3}$$)$$_{3}$$ 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).

Journal Articles

Adsorption of Cs onto biogenic birnessite; Effects of layer structure, ionic strength, and competition cations

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

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.

Journal Articles

Hydrological and climate changes in southeast Siberia over the last 33 kyr

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:8 Percentile:46.53(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.

Journal Articles

Fungus-promoted transformation of lanthanides during the biooxidation of divalent manganese

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:17 Percentile:63.69(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.

Journal Articles

Thermal expansion of a Au-Al-Yb intermediate valence quasicrystal

Watanuki, Tetsu; Kashimoto, Shiro*; Ishimasa, Tsutomu*; Machida, Akihiko; Yamamoto, Shin*; Tanaka, Yukinori*; Mizumaki, Masaichiro*; Kawamura, Naomi*; Watanabe, Shinji*

Solid State Communications, 211, p.19 - 22, 2015/06

 Times Cited Count:6 Percentile:30.94(Physics, Condensed Matter)

The thermal expansion of a Au-Al-Yb intermediate-valence quasicrystal has been studied by X-ray diffraction measurements. We have found anomalous thermal expansion behavior, namely zero thermal expansion below 50 K. By comparison with an isostructural Au-Al-Tm quasicrystal, the contribution of the Yb valence variation was extracted, and it was shown that its negative thermal expansion component due to the valence shift toward the divalent state by cooling compensated for the positive thermal expansion of the original lattice.

Journal Articles

Intermediate-valence icosahedral Au-Al-Yb quasicrystal

Watanuki, Tetsu; Kashimoto, Shiro*; Kawana, Daichi*; Yamazaki, Teruo*; Machida, Akihiko; Tanaka, Yukinori*; Sato, Taku*

Physical Review B, 86(9), p.094201_1 - 094201_6, 2012/09

 Times Cited Count:56 Percentile:89.52(Materials Science, Multidisciplinary)

A quasiperiodic, intermediate-valence (IV) system is realized in an icosahedral Au-Al-Yb quasicrystal. X-ray absorption spectroscopy near the Yb $$L$$$$_{3}$$-edge indicates that quasiperiodically arranged Yb ions assume a mean valence of 2.61, between a divalent state (4$$f$$$$^{14}$$, $$J$$ = 0) and a trivalent one (4$$f$$$$^{13}$$, $$J$$ = 7/2). Magnetization measurements demonstrate that the 4$$f$$ holes in this quasicrystal have a localized character. The magnetic susceptibility shows a Curie-Weiss behavior above $$sim$$100 K with an effective magnetic moment of 3.81 $$mu$$$$_{rm B}$$ per Yb. Moreover, a crystalline approximant to this quasicrystal is an IV compound. We propose a heterogeneous IV model for the quasicrystal, whereas the crystalline approximant is most likely a homogeneous IV system. At temperatures below $$sim$$10 K, specific heat and magnetization measurements reveal non-Fermi-liquid behavior in both the quasicrystal and its crystalline approximant without either doping, pressure, or field tuning.

Journal Articles

Specific sorption behavior of actinoids on biogenic Mn oxide

Tanaka, Kazuya*; Tani, Yukinori*; Onuki, Toshihiko

Chemistry Letters, 40(8), p.806 - 807, 2011/08

 Times Cited Count:8 Percentile:32.85(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.

Journal Articles

A Specific Ce oxidation process during sorption of rare earth elements on biogenic Mn oxide produced by Acremonium sp. strain KR21-2

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:76 Percentile:88.46(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.

Oral presentation

Ce oxidation by Mn oxide produced by Acremonium sp. strain KR21-2

Tanaka, Kazuya; Tani, Yukinori*; Onuki, Toshihiko

no journal, , 

no abstracts in English

Oral presentation

Specific oxidation process of Ce(III) by Mn-oxidizing fungus strain KR21-2

Tanaka, Kazuya; Tani, Yukinori*; Onuki, Toshihiko

no journal, , 

no abstracts in English

Oral presentation

Intermediate-valence quasicrystals of Yb based alloys

Watanuki, Tetsu; Kawana, Daichi*; Machida, Akihiko; Tsai, A. P.*; Tanaka, Yukinori*; Kashimoto, Shiro*; Ishimasa, Tsutomu*

no journal, , 

no abstracts in English

Oral presentation

Intermediate-valence quasicrystals of Yb based alloys

Watanuki, Tetsu; Kawana, Daichi*; Machida, Akihiko; Tsai, A. P.*; Kashimoto, Shiro*; Tanaka, Yukinori*; Ishimasa, Tsutomu*

no journal, , 

no abstracts in English

Oral presentation

Intermediate-valence Yb-based quasicrystals

Watanuki, Tetsu; Kawana, Daichi*; Machida, Akihiko; Tsai, A. P.*; Kashimoto, Shiro*; Tanaka, Yukinori*; Ishimasa, Tsutomu*; Yamazaki, Teruo*; Sato, Taku*

no journal, , 

Quasiperiodic intermediate-valence systems were prepared by applying pressure to Yb-based quasicrystals. In these systems, each quasiperiodic lattice point has a charge degree of freedom. Synchrotron radiation X-ray absorption spectroscopy experiments near the Yb L3-edge demonstrate that the Yb valence in a Cd-Yb icosahedral quasicrystal increases continuously upon compression from a divalent state at ambient pressure and reaches 2.33 at 31.7 GPa, where the quasiperiodically arranged Yb ions take a valence fluctuation state. For the case of a Cd-Mg-Yb icosahedral quasicrystal, the Yb valence reaches a value of 2.71 at 57.6 GPa. By following the trend of Yb-based intermediate-valence crystalline compounds, this large valence increase suggests that the 4f electron system in this quasicrystal varies from a valence fluctuation regime to a strong correlated electron regime. Additionally, we have recently found that Au-Al-Yb icosahedral quasicrystal is an IV compound at ambient pressure.

Oral presentation

Intermediate-valence Yb-based quasicrystals, measurements of the valence and physical properties

Watanuki, Tetsu; Kawana, Daichi*; Machida, Akihiko; Kashimoto, Shiro*; Tanaka, Yukinori*; Ishimasa, Tsutomu*; Yamazaki, Teruo*; Sato, Taku*; Tsai, A. P.*

no journal, , 

no abstracts in English

Oral presentation

Intermediate-valence icosahedral Au-Al-Yb quasicrystal

Watanuki, Tetsu; Kashimoto, Shiro*; Yamazaki, Teruo*; Kawana, Daichi*; Machida, Akihiko; Tanaka, Yukinori*; Ishimasa, Tsutomu*; Sato, Taku*

no journal, , 

A quasiperiodic, intermediate-valence (IV) system is realized in an icosahedral Au-Al-Yb quasicrystal. X-ray absorption spectroscopy near the Yb L3-edge indicates that quasiperiodically arranged Yb ions assume a mean valence of 2.61, between a divalent state (4f14, J = 0) and a trivalent one (4f13, J = 7/2). Magnetization measurements demonstrate that the 4f holes in this quasicrystal have a localized character. The magnetic susceptibility shows a Curie-Weiss behavior above 100 K with an effective magnetic moment of 3.81 muB per Yb. Moreover, a crystalline approximant to this quasicrystal is an IV compound. We propose a heterogeneous IV model for the quasicrystal, whereas the crystalline approximant is most likely a homogeneous IV system. At temperatures below 10 K, specific heat and magnetization measurements reveal non-Fermi-liquid behavior in both the quasicrystal and its crystalline approximant without either doping, pressure, or field tuning.

Oral presentation

Pressure dependence of Yb valence in an intermediate-valence Au-Al-Yb-quasicrystals

Watanuki, Tetsu; Machida, Akihiko; Kawana, Daichi*; Tanaka, Yukinori*; Ishimasa, Tsutomu*

no journal, , 

no abstracts in English

31 (Records 1-20 displayed on this page)