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Journal Articles

Robustness of ferromagnetism in van der Waals magnet Fe$$_3$$GeTe$$_2$$ to hydrostatic pressure

Wang, Y.*; Zeng, X.-T.*; Li, B.*; Su, C.*; Hattori, Takanori; Sheng, X.-L.*; Jin, W.*

Chinese Physics B, 34(4), p.046203_1 - 046203_6, 2025/03

 Times Cited Count:0 Percentile:0.00(Physics, Multidisciplinary)

Two-dimensional van der Waals ferromagnet Fe$$_3$$GeTe$$_2$$ (FGT) holds a great potential for applications in spintronic devices, due to its high Curie temperature, easy tunability, and excellent structural stability in air. In this study, we have performed high-pressure neutron powder diffraction (NPD) up to 5 GPa, to investigate the evolution of its structural and magnetic properties with hydrostatic pressure. The NPD data clearly reveal the robustness of the ferromagnetism in FGT, despite of an apparent suppression by hydrostatic pressure. As the pressure increases from 0 to 5 GPa, the Curie temperature is found to decrease monotonically from 225(5) K to 175(5) K, together with a dramatically suppressed ordered moment of Fe, which is well supported by the first-principles calculations. Although no pressure-driven structural phase transition is observed up to 5 GPa, quantitative analysis on the changes of bond lengths and bond angles indicate a significant modification of the exchange interactions, which accounts for the pressure-induced suppression of the ferromagnetism in FGT.

Journal Articles

Imaging Josephson vortices on curved junctions

Fujisawa, Yuita*; Krishnadas, A*; Nakamura, Tomonori*; Hsu, C.-H.*; Smith, B. R. M.*; Pardo-Almanza, M*; Hiyane, Hoshu*; Nagai, Yuki; Machida, Tadashi*; Okada, Yoshinori*

Physical Review B, 110(22), p.224511_1 - 224511_5, 2024/12

 Times Cited Count:0 Percentile:0.00(Materials Science, Multidisciplinary)

Understanding the nature of vortices in type-II superconductors has been vital for deepening the physics of exotic superconductors and applying superconducting materials to future electronic devices. A recent study has shown that the LiTi$$_{2}$$O$$_{4}$$(111) thin film offers a unique experimental platform to unveil the nature of the vortex along the curved Josephson junction. This study successfully visualized individual Josephson vortices along the curved Josephson junctions using in-situ spectroscopic scanning tunneling microscopy on LiTi$$_{2}$$O$$_{4}$$ (111) epitaxial thin films. Notably, the local curvature of the Josephson junction was discovered to control the position of Josephson vortices. Furthermore, the numerical simulation reproduces the critical role of the curvature of the Josephson junction. This study provides guidelines to control Josephson vortices through geometrical ways, such as mechanical controlling of superconducting materials and their devices.

Journal Articles

Fluorous and organic extraction systems; A Comparison from the perspectives of coordination structures, interfaces, and bulk extraction phases

Ueda, Yuki; Micheau, C.; Akutsu, Kazuhiro*; Tokunaga, Kohei; Yamada, Masako*; Yamada, Norifumi*; Bourgeois, D.*; Motokawa, Ryuhei

Langmuir, 40(46), p.24257 - 24271, 2024/11

 Times Cited Count:0 Percentile:0.00(Chemistry, Multidisciplinary)

Microscopic structures in liquid-liquid extraction, such as structuration between extractants or extracted complexes in bulk organic phases and at interfaces, can influence macroscopic phenomena, such as the distribution behavior of solutes, including extraction efficiency, selectivity, and phase separation of the organic phase. In this study, we correlated the macroscopic behavior of the extraction of Zr(IV) ions from nitric acid solutions with microscopic structural information in order to understand at the molecular level the key factors contributing to the higher metal ion extraction performance in the fluorous extraction system comprising fluorous phosphate (TFP) in perfluorohexane as compared to the analogous organic extraction system comprising organic phosphate (THP) in n-hexane. Extended X-ray absorption fine structure, neutron reflectometry, and small-angle neutron scattering revealed the local coordination structure around the Zr(IV) ion, the accumulation of extractant molecules at the interface, and the structuration of extractant molecules in the bulk extraction phase, respectively. In the fluorous extraction system, extractant aggregates with were formed after contact with nitric acid. In contrast, in the organic extraction system, only extractant dimers were formed. We speculate that differences in the local coordination structure around the Zr(IV) ion and the structuration of the extractant molecules in the bulk extraction phase contribute to the high Zr(IV) extraction performance in the fluorous extraction system. In particular, the size of the aggregates hardly changed with increasing Zr(IV) concentration in the fluorous phase, which may be closely related to the absence of phase splitting in the fluorous extraction system.

Journal Articles

Gradient residual stress and fatigue life prediction of induction hardened carbon steel S38C axles; Experiment and simulation

Qin, T. Y.*; Hu, F. F.*; Xu, P. G.; Zhang, H.*; Zhou, L.*; Ao, N.*; Su, Y. H.; Shobu, Takahisa; Wu, S. C.*

International Journal of Fatigue, 185, p.108336_1 - 108336_13, 2024/08

 Times Cited Count:9 Percentile:93.27(Engineering, Mechanical)

Journal Articles

"Invisible" radioactive cesium atoms revealed; Pollucite inclusion in cesium-rich microparticles (CsMPs) from the Fukushima Daiichi Nuclear Power Plant

Miyazaki, Kanako*; Takehara, Masato*; Minomo, Kenta*; Horie, Kenji*; Takehara, Mami*; Yamasaki, Shinya*; Saito, Takumi*; Onuki, Toshihiko*; Takano, Masahide; Shiotsu, Hiroyuki; et al.

Journal of Hazardous Materials, 470(15), p.134104_1 - 134104_11, 2024/05

 Times Cited Count:1 Percentile:31.14(Engineering, Environmental)

Journal Articles

Organization of malonamides from the interface to the organic bulk phase

Micheau, C.; Ueda, Yuki; Motokawa, Ryuhei; Akutsu, Kazuhiro*; Yamada, Norifumi*; Yamada, Masako*; Moussaoui, S. A.*; Makombe, E.*; Meyer, D.*; Berthon, L.*; et al.

Journal of Molecular Liquids, 401, p.124372_1 - 124372_12, 2024/05

 Times Cited Count:2 Percentile:60.60(Chemistry, Physical)

Journal Articles

Petrophysical properties of representative geological rocks encountered in carbon storage and utilization

Hu, Q.*; Wang, Q. M.*; Zhang, T.*; Zhao, C.*; Iltaf, K. H.*; Liu, S. Q.*; Fukatsu, Yuta

Energy Reports (Internet), 9, p.3661 - 3682, 2023/12

 Times Cited Count:11 Percentile:64.37(Energy & Fuels)

Journal Articles

Extraction of $$^{99}$$Mo hot atoms made by a neutron capture method from $$alpha$$-MoO$$_{3}$$ to water

Quach, N. M.*; Ngo, M. C.*; Yang, Y.*; Nguyen, T. B.*; Nguyen, V. T.*; Fujita, Yoshitaka; Do, T. M. D.*; Nakayama, Tadachika*; Suzuki, Tatsuya*; Suematsu, Hisayuki*

Journal of Radioanalytical and Nuclear Chemistry, 332(10), p.4057 - 4064, 2023/10

 Times Cited Count:4 Percentile:71.02(Chemistry, Analytical)

Technetium-99m ($$^{99m}$$Tc) is the most widely used medical radioisotope in the world and is produced from molybdenum-99 ($$^{99}$$Mo). Production of $$^{99}$$Mo via the neutron capture method draws attention as an alternative to fission-derived $$^{99}$$Mo due to non-proliferation issues, but the specific radioactivity of $$^{99}$$Mo is extremely low. In this work, a porous $$alpha$$-MoO$$_{3}$$ wire was prepared as an irradiation target in order to improve the specific activity by extracting $$^{99}$$Mo. Porous $$alpha$$-MoO$$_{3}$$ wire is synthesized from Mo metal wire by a two-step heating procedure. The hot atom effect of $$^{99}$$Mo was confirmed by activity and isotope measurements of the porous $$alpha$$-MoO$$_{3}$$ wire after neutron irradiation and the water used for extraction. In term of the extraction effectiveness, the effectiveness of $$^{99}$$Mo extraction in the porous $$alpha$$-MoO$$_{3}$$ wire was comparable to that of commercial $$alpha$$-MoO$$_{3}$$ powder.

Journal Articles

Interlaboratory comparison of electron paramagnetic resonance tooth enamel dosimetry with investigations of the dose responses of the standard samples

Toyoda, Shin*; Inoue, Kazuhiko*; Yamaguchi, Ichiro*; Hoshi, Masaharu*; Hirota, Seiko*; Oka, Toshitaka; Shimazaki, Tatsuya*; Mizuno, Hideyuki*; Tani, Atsushi*; Yasuda, Hiroshi*; et al.

Radiation Protection Dosimetry, 199(14), p.1557 - 1564, 2023/09

 Times Cited Count:1 Percentile:23.64(Environmental Sciences)

Interlaboratory comparison studies are important for radiation dosimetry in order to demonstrate how the technique is universally available. The set of standard samples are examined in each participating laboratory in the present study. After a set of standard samples together with the samples with unknown doses, which were prepared in the same laboratory as the standard samples, are measured at a participating laboratory, those samples are sent to another participating laboratory for next measurement. There is some small difference observed in the sensitivity (the slope of the dose response line) of the standard samples while the differences in the obtained doses for the samples with unknown doses are rather systematic, implying that the difference is mostly due to the samples but not to measurements.

Journal Articles

$$beta$$-MoO$$_{3}$$ whiskers in $$^{99}$$Mo/$$^{rm 99m}$$Tc radioisotope production and $$^{99}$$Mo/$$^{rm 99m}$$Tc extraction using hot atoms

Ngo, M. C.*; Fujita, Yoshitaka; Suzuki, Tatsuya*; Do, T. M. D.*; Seki, Misaki; Nakayama, Tadachika*; Niihara, Koichi*; Suematsu, Hisayuki*

Inorganic Chemistry, 62(32), p.13140 - 13147, 2023/08

 Times Cited Count:5 Percentile:60.95(Chemistry, Inorganic & Nuclear)

Technetium-99m ($$^{rm 99m}$$Tc) is one of the most important radioisotopes for diagnostic radio-imaging applications. $$^{rm 99m}$$Tc is a daughter product of the $$^{99}$$Mo isotope. There are two methods used to produce $$^{99}$$Mo/$$^{rm 99m}$$Tc: the nuclear fission (n,f) and the neutron capture (n,$$gamma$$) methods. Between them, the (n,f) method is the main route, used for approximately 90% of the world's production. However, the (n,f) method faces numerous problems, including the use of highly enriched uranium, the release of highly radioactive waste, and nonproliferation problems. Therefore, the (n,$$gamma$$) method is being developed as a future replacement for the (n,f) method. In this work, $$beta$$-MoO$$_{3}$$ whiskers prepared by the thermal evaporation method and $$alpha$$-MoO$$_{3}$$ particles were irradiated in a nuclear reactor to produce $$^{99}$$Mo/$$^{rm 99m}$$Tc via neutron capture. The irradiated targets were dispersed into water to extract the $$^{99}$$Mo/$$^{rm 99m}$$Tc. As a result, $$beta$$-MoO$$_{3}$$ whisker yielded higher $$^{99}$$Mo extraction rate than that from $$alpha$$-MoO$$_{3}$$. In addition, by comparing the dissolved $$^{98}$$Mo concentrations in water, we clarified a prominent hot-atom of $$beta$$-MoO$$_{3}$$ whiskers. This research is the first demonstration of $$beta$$-MoO$$_{3}$$ being used as an irradiation target in the neutron capture method. On the basis of the results, $$beta$$-MoO$$_{3}$$ is considered a promising irradiation target for producing $$^{99}$$Mo/$$^{rm 99m}$$Tc by neutron capture and using water for the radioisotope extraction process in the future.

Journal Articles

Occurrence of radioactive cesium-rich micro-particles (CsMPs) in a school building located 2.8 km south-west of the Fukushima Daiichi Nuclear Power Plant

Fueda, Kazuki*; Komiya, Tatsuki*; Minomo, Kenta*; Horie, Kenji*; Takehara, Mami*; Yamasaki, Shinya*; Shiotsu, Hiroyuki; Onuki, Toshihiko*; Grambow, B.*; Law, G. T. W.*; et al.

Chemosphere, 328, p.138566_1 - 138566_12, 2023/07

 Times Cited Count:5 Percentile:50.39(Environmental Sciences)

Journal Articles

Corrosion fatigue crack growth behavior of a structurally gradient steel for high-speed railway axles

Ao, N.*; Zhang, H.*; Xu, H. H.*; Wu, S. C.*; Liu, D.*; Xu, P. G.; Su, Y. H.; Kang, Q. H.*; Kang, G. Z.*

Engineering Fracture Mechanics, 281, p.109166_1 - 109166_14, 2023/03

 Times Cited Count:13 Percentile:82.23(Mechanics)

Journal Articles

Pore connectivity influences mass transport in natural rocks; Pore structure, gas diffusion and batch sorption studies

Yuan, X.*; Hu, Q.*; Lin, X.*; Zhao, C.*; Wang, Q.*; Tachi, Yukio; Fukatsu, Yuta; Hamamoto, Shoichiro*; Siitari-Kauppi, M.*; Li, X.*

Journal of Hydrology, 618, p.129172_1 - 129172_15, 2023/03

 Times Cited Count:6 Percentile:58.63(Engineering, Civil)

Journal Articles

Deuterated malonamide synthesis for fundamental research on solvent extraction systems

Micheau, C.; Ueda, Yuki; Akutsu, Kazuhiro*; Bourgeois, D.*; Motokawa, Ryuhei

Solvent Extraction and Ion Exchange, 41(2), p.221 - 240, 2023/02

 Times Cited Count:4 Percentile:41.44(Chemistry, Multidisciplinary)

Journal Articles

Radiochemical research for the advancement of $$^{99}$$Mo/$$^{rm 99m}$$Tc generator by (n, $$gamma$$) method, 4

Fujita, Yoshitaka; Seki, Misaki; Ngo, M. C.*; Do, T. M. D.*; Hu, X.*; Yang, Y.*; Takeuchi, Tomoaki; Nakano, Hiroko; Fujihara, Yasuyuki*; Yoshinaga, Hisao*; et al.

KURNS Progress Report 2021, P. 118, 2022/07

no abstracts in English

Journal Articles

Volatilization of B$$_{4}$$C control rods in Fukushima Daiichi nuclear reactors during meltdown; B-Li isotopic signatures in cesium-rich microparticles

Fueda, Kazuki*; Takami, Ryu*; Minomo, Kenta*; Morooka, Kazuya*; Horie, Kenji*; Takehara, Mami*; Yamasaki, Shinya*; Saito, Takumi*; Shiotsu, Hiroyuki; Onuki, Toshihiko*; et al.

Journal of Hazardous Materials, 428, p.128214_1 - 128214_10, 2022/04

 Times Cited Count:12 Percentile:66.41(Engineering, Environmental)

Journal Articles

Mechanisms responsible for adsorption of molybdate ions on alumina for the production of medical radioisotopes

Fujita, Yoshitaka; Niizeki, Tomotake*; Fukumitsu, Nobuyoshi*; Ariga, Katsuhiko*; Yamauchi, Yusuke*; Malgras, V.*; Kaneti, Y. V.*; Liu, C.-H.*; Hatano, Kentaro*; Suematsu, Hisayuki*; et al.

Bulletin of the Chemical Society of Japan, 95(1), p.129 - 137, 2022/01

 Times Cited Count:10 Percentile:60.41(Chemistry, Multidisciplinary)

In this work, the mechanisms responsible for the adsorption of molybdate ions on alumina are investigated using in-depth surface analyses carried out on alumina specimens immersed in solutions containing different molybdate ions at different pH values. The obtained results reveal that when alumina is immersed in an acidic solution containing molybdate ions, the hydroxyl groups present on the surface are removed to generate positively charged sites, and molybdate ions (MoO$$_{4}$$$$^{2-}$$ or AlMo$$_{6}$$O$$_{24}$$H$$_{6}$$$$^{3-}$$) are adsorbed by electrostatic interaction. Alumina dissolves slightly in an acidic solution to form AlMo$$_{6}$$O$$_{24}$$H$$_{6}$$$$^{3-}$$, which is more easily desorbed than MoO$$_{4}$$$$^{2-}$$. Furthermore, the enhancement in the Mo adsorption or desorption property may be achieved by enriching the surface of the alumina adsorbent with many -OH groups and optimizing Mo solution to adsorb molybdate ions on alumina as MoO$$_{4}$$$$^{2-}$$ ions. These findings will assist researchers in engineering more efficient and stable alumina-based adsorbents for molybdenum adsorption used in medical radioisotope ($$^{99}$$Mo/$$^{99m}$$Tc) generators.

Journal Articles

Study of the axial $$U(1)$$ anomaly at high temperature with lattice chiral fermions

Aoki, Shinya*; Aoki, Yasumichi*; Cossu, G.*; Fukaya, Hidenori*; Hashimoto, Shoji*; Kaneko, Takashi*; Rohrhofer, C.*; Suzuki, Kei

Physical Review D, 103(7), p.074506_1 - 074506_18, 2021/04

 Times Cited Count:27 Percentile:84.12(Astronomy & Astrophysics)

We investigate the axial $$U(1)$$ anomaly of two-flavor QCD at temperatures 190-330 MeV. In order to preserve precise chiral symmetry on the lattice, we employ the M$"o$bius domain-wall fermion action as well as overlap fermion action implemented with a stochastic reweighting technique. Compared to our previous studies, we reduce the lattice spacing to 0.07 fm, simulate larger multiple volumes to estimate finite size effect, and take more than four quark mass points, including one below physical point to investigate the chiral limit. We measure the topological susceptibility, axial $$U(1)$$ susceptibility, and examine the degeneracy of $$U(1)$$ partners in meson/baryon correlators. All the data above the critical temperature indicate that the axial $$U(1)$$ violation is consistent with zero within statistical errors. The quark mass dependence suggests disappearance of the $$U(1)$$ anomaly at a rate comparable to that of the $$SU(2)_L times SU(2)_R$$ symmetry breaking.

Journal Articles

Symmetries of the light hadron spectrum in high temperature QCD

Rohrhofer, C.*; Aoki, Yasumichi*; Cossu, G.*; Fukaya, Hidenori*; Gattringer, C.*; Glozman, L. Ya.*; Hashimoto, Shoji*; Lang, C. B.*; Suzuki, Kei

Proceedings of Science (Internet), 363, p.227_1 - 227_7, 2020/08

Properties of QCD matter change significantly around the chiral crossover temperature, and the effects on $$U(1)_A$$ and topological susceptibilities, as well as the meson spectrum have been studied with much care. Baryons and the effect of parity doubling in this temperature range have been analyzed previously by various other groups employing different setups. Here we construct suitable operators to investigate chiral and axial $$U(1)_A$$ symmetries in the baryon spectrum. Measurements for different volumes and quark-masses are done with two flavors of chirally symmetric domain-wall fermions at temperatures above the critical one. The possibility of emergent $$SU(4)$$ and $$SU(2)_{CS}$$ symmetries is discussed.

Journal Articles

Axial U(1) symmetry and mesonic correlators at high temperature in $$N_f=2$$ lattice QCD

Suzuki, Kei; Aoki, Shinya*; Aoki, Yasumichi*; Cossu, G.*; Fukaya, Hidenori*; Hashimoto, Shoji*; Rohrhofer, C.*

Proceedings of Science (Internet), 363, p.178_1 - 178_7, 2020/08

We investigate the high-temperature phase of QCD using lattice QCD simulations with $$N_f=2$$ dynamical M$"o$bius domain-wall fermions. On generated configurations, we study the axial $$U(1)$$ symmetry, overlap-Dirac spectra, screening masses from mesonic correlators, and topological susceptibility. We find that some of the observables are quite sensitive to lattice artifacts due to a small violation of the chiral symmetry. For those observables, we reweight the M$"o$bius domain-wall fermion determinant by that of the overlap fermion. We also check the volume dependence of observables. Our data near the chiral limit indicates a strong suppression of the axial $$U(1)$$ anomaly at temperatures $$geq$$ 220 MeV.

76 (Records 1-20 displayed on this page)