Ye, M.*; Xu, T.*; Li, G.*; Qiao, S.*; 竹田 幸治; 斎藤 祐児; Zhu, S.-Y.*; Nurmamat, M.*; 角田 一樹*; 石田 行章*; et al.
Physical Review B, 99(14), p.144413_1 - 144413_7, 2019/04
We investigate the microscopic origin of ferromagnetism coupled with topological insulators in V-doped (Sb,Bi)Te employing X-ray magnetic circular dichroism and angle-resolved two-photon photoemission spectroscopies, combined with first-principles calculations. We found an magnetic moment at the Te site anti-parallel to that of the V and Sb sites, which plays a key role in the ferromagnetic order. We ascribe it to the hybridization between Te 5 and V 3 majority spin states at the Fermi energy, consistent with the Zener-type - exchange interaction scenario. The substitution of Bi for Sb suppresses the bulk ferromagnetism by introducing extra electron carriers in the majority spin channel of the Te states that compensates the antiparallel magnetic moment on the Te site. Our findings reveal important clues to designing magnetic topological insulators with higher Curie temperature that work under ambient conditions.
Elekes, Z.*; Kripk, *; Sohler, D.*; Sieja, K.*; 緒方 一介*; 吉田 数貴; Doornenbal, P.*; Obertelli, A.*; Authelet, G.*; 馬場 秀忠*; et al.
Physical Review C, 99(1), p.014312_1 - 014312_7, 2019/01
(,)反応によるNiの核構造の探索実験を行った。Lenzi, Nowacki, Poves, Sieja相互作用を用いた殻模型計算では実験結果を説明しうる陽子空孔状態が得られており、理論的な断面積計算は実験値とよい一致を与えた。実験で得られたすべての状態を理論的に一意に決定することはできなかったが、過去の実験結果と同様にNi同位体でのZ = 28の大きなshell gapを示す結果が得られた。
林 眞琴*; Root, J. H.*; Rogge, R. B.*; 徐 平光
Quantum Beam Science (Internet), 2(4), p.21_1 - 21_16, 2018/12
The rolled joint of pressure tube, consisting of three axial symmetric parts, modified SUS403 stainless steel, Zr-2.5Nb pressure tube and Inconel-718, has been examined by neutron diffraction for residual stresses. It was heat treated at 350C for 30, 130 and 635 hours to simulate the thermal aging of the rolled joint over the lifetime of the advanced thermal reactor at 288C for 1, 5 and 30 years. The crystal lattice strains at various locations in the rolled joint before and after the aging treatments were measured by neutron diffraction and the residual stress distribution in the rolled joint was evaluated by using the Kroner elastic model and the generalized Hooke's law. In the crimp region of the rolled joint, it was found that the aging treatment had weak effect on the residual stresses in the Inconel and the SUS403. In the non-aged Zr-2.5Nb, the highest residual stresses were found near its interface with the SUS430. In the Zr-2.5Nb in the crimp region near its interface with the SUS430, the average compressive axial stress was -440 MPa, having no evident change during the long-time aging. In the Zr-2.5Nb outside closest to the crimp region, the tensile axial and hoop stresses were relieved during the 30 hours aging. The hoop stresses in the crimp region evolved from an average tensile stress of 80 MPa to an average compressive stress of 230 MPa after the 635 hours aging, suggesting that the rolled joint had a good long-term sealing ability against the leakage of high temperature water.
Xu, Q. N.*; 谷田 聖; Belle Collaboration*; 他176名*
Physical Review D, 98(7), p.072001_1 - 072001_17, 2018/10
We report the measurement of , with decays to and using 941 fb of data collected with the Belle detector at the KEKB asymmetric-energy collider. The mass and width are measured to be MeV/ and MeV, respectively. First observation of with a significance of including systematic error is obtained, and the mass is measured to be MeV/. The products of the two-photon decay width and branching fraction of decays to are determined to be eV for and eV for . A new decay mode for the to with is observed with a statistical significance of . The mass and width are determined to be MeV/ and MeV. The cross sections for and are measured for the first time.
関根 由莉奈; Kim, S. B.*; Zhang, Y.*; Bandodkar, A. J.*; Xu, S.*; Choi, J.*; 入江 将大*; Ray, T. R.*; Kohli, P.*; 香西 直文; et al.
Lab on a Chip, 18(15), p.2178 - 2186, 2018/08
近年、スウェットに含まれる代謝産物やイオン等を用いたPoint of Careが高く注目されている。本研究では、それらのバイオマーカーを効果的にその場で検出することを目的として、ソフトで薄いウェアラブルマイクロ流路デバイスとスマートフォンを基盤とした蛍光イメージングシステムを提案する。精密に設計されたマイクロ流路は、皮膚から汗を時間シーケンス制御で集めることを可能にした。また、集められた汗から蛍光検出剤によって検出された塩化物,ナトリウム,亜鉛濃度をスマートフォンを基盤とした蛍光イメージングシステムで正確に定量分析することに成功した。このシステムを実際に試験したところ、正確に効率よく作動することを確認した。
Xu, Z. Y.*; Heylen, H.*; 旭 耕一郎*; Boulay, F.*; Daugas, J. M.*; de Groote, R. P.*; Gins, W.*; Kamalou, O.*; Koszors, .*; Lykiardopoupou, M.*; et al.
Physics Letters B, 782, p.619 - 626, 2018/07
徐 平光; Harjo, S.; 小島 真由美*; 鈴木 裕士; 伊藤 崇芳*; Gong, W.; Vogel, S. C.*; 井上 純哉*; 友田 陽*; 相澤 一也; et al.
Journal of Applied Crystallography, 51(3), p.746 - 760, 2018/06
Neutron diffraction texture measurements provide bulk textures with excellent grain statistics even for large grained materials, together with the crystallographic parameters and microstructure information such as phase fractions, coherent crystallite size, root mean square microstrain, macroscopic/intergranular stress/strain. The procedure for high stereographic resolution texture and residual stress evaluation was established at the TAKUMI engineering materials diffractometer. The pole figure evaluation of a limestone standard sample with a trigonal crystal structure suggested that the obtained precision for texture measurement is comparable with the oversea well-established neutron beam lines utilized for texture measurements. A high strength martensite-austenite multilayered steel was employed for further verification of the reliability of simultaneous Rietveld analysis of multiphase textures and macro stress tensors. By using a geometric mean micro-mechanical model, the macro stress tensor analysis with a plane stress assumption showed a RD-TD in-plane compressive stress (about -330 MPa) in martensite layers and a RD-TD in-plane tensile stress (about 320 MPa) in austenite layers. The phase stress partitioning was ascribed to the additive effect of volume expansion during martensite transformation and the linear contraction misfit during water quenching.
Tang, C.*; Song, Q.*; Chang, C.-Z.*; Xu, Y.*; 大沼 悠一; 松尾 衛*; Liu, Y.*; Yuan, W.*; Yao, Y.*; Moodera, J. S.*; et al.
Science Advances (Internet), 4(6), p.eaas8660_1 - eaas8660_6, 2018/06
This work demonstrates markedly modified spin dynamics of magnetic insulator (MI) by the spin momentum-locked Dirac surface states of the adjacent topological insulator (TI). As the Bi concentration is systematically tuned in 5-nm-thick (BiSb)Te TI films, the weight of the surface relative to bulk states peaks at = 0.32 when the chemical potential approaches the Dirac point. At this concentration, the Gilbert damping constant of the precessing magnetization in 10-nm-thick YFeO MI films in the MI/TI heterostructures is enhanced by an order of magnitude, the largest among all concentrations. In addition, the MI acquires additional strong magnetic anisotropy that favors the in-plane orientation with similar Bi concentration dependence. These extraordinary effects of the Dirac surface states distinguish TI from other materials such as heavy metals in modulating spin dynamics of the neighboring magnetic layer.
Dimitriou, P.*; Belgya, T.*; Cho, Y.-S.*; Filipescu, D.*; Firestone, R.*; Goriely, S.*; 岩本 信之; 河野 俊彦*; Kopecky, J.*; Krticka, M.*; et al.
EPJ Web of Conferences (Internet), 178, p.06005_1 - 06005_3, 2018/05
Zhang, Y.-X.*; Wang, Y,-J.*; Colonna, M.*; Danielewicz, P.*; 小野 章*; Tsang, M. B.*; Wolter, H.*; Xu, J.*; Chen, L.-W.*; Cozma, D.*; et al.
Physical Review C, 97(3), p.034625_1 - 034625_20, 2018/03
2017年4月に開催された国際会議Transport2017において、重イオン核反応モデルの国際的な比較が議論された。重イオン加速器の安全評価や宇宙飛行士の被ばく評価等で重要な役割を果たすため、世界中で重イオン核反応の様々な理論モデルが開発されている。本研究はモデル間の共通点と差異を明らかにし、各モデルの問題点を明らかにした。比較において、辺の長さが20fmの直方体に320個の中性子と320個の陽子をランダム配置し、それらが時間発展に伴って起こす散乱の回数や散乱時のエネルギーなどを計算する条件が設定された。また、結果以外にも、理論モデルを構成するアルゴリズムについても比較を行った。発表者は重イオン核反応モデルJQMD(JAERI Quantum Molecular Dynamics)を用いて計算を行い、世界で開発されている15の計算コードによる計算結果と比較した。コードアルゴリズムの比較では、JQMDは必ず陽子から 優先的に衝突確率を計算し、その後に中性子の衝突を計算するため、物理描像の妥当性が指摘された。一方、JQMDは他のモデルとほぼ同じ計算結果を出すことも判明した。衝突回数や運動量の計算値が平均から2倍以上乖離するモデルもある中で、JQMDは本計算条件で安定した性能を発揮することが確認された。
Kim, S. B.*; Zhang, Y.*; Won, S. M.*; Bandodkar, A. J.*; 関根 由莉奈; Xue, Y.*; Koo, J.*; Harshman, S. W.*; Martin, J. A.*; Park, J. M.*; et al.
Small, 14(12), p.1703334_1 - 1703334_11, 2018/03
This paper introduces super absorbent polymer valves and colorimetric sensing reagents as enabling components of soft, skin-mounted microfluidic devices designed to capture, store and chemically analyze sweat released from eccrine glands. The valving technology enables robust means for guiding the flow of sweat from an inlet location into a collection of isolated reservoirs, in a well-defined sequence. Analysis in these reservoirs involves a color responsive indicator of chloride concentration with a formulation tailored to offer stable operation with sensitivity optimized for the relevant physiological range. Evaluations on human subjects with comparisons against ex situ analysis illustrate the practical utility of these advances.
Shand, C. M.*; Podolyk, Zs.*; Grska, M.*; Doornenbal, P.*; Obertelli, A.*; Nowacki, F.*; Otsuka, T.*; Sieja, K.*; Tostevin, J. A.*; Tsunoda, T.*; et al.
Physics Letters B, 773, p.492 - 497, 2017/10
Low-lying states in neutron-rich Zn nuclei were measured for the first time via in-beam -ray spectroscopy at RIKEN. These include the 4 to 2 in Zn and the 2 to 0 and 4 to 2 in Zn. The reduced E() energies and increased E(4)/E(2) ratios at =52,54 compared to Zn attest that the magicity is confined just on the neutron number =50 only. The levels observed in Zn suggest the onset of deformation towards heavier Zn isotopes. The data were compared to state-of-the-art shell model calculations.
友田 陽*; 関戸 信彰*; 徐 平光; 川崎 卓郎; Harjo, S.; 田中 雅彦*; 篠原 武尚; Su, Y.; 谷山 明*
鉄と鋼, 103(10), p.570 - 578, 2017/10
Various methods were employed to measure the austenite volume fraction in a 1.5Mn-1.5Si-0.2C steel. It has been confirmed that the volume fractions determined by transmission electron microscopy, scanning electron microscopy/electron back scatter diffraction, X-ray diffraction and neutron diffraction exhibit a general trend to become larger in this order, although the values obtained by X-ray and neutron diffraction are similar in the present steel because austenite is relatively stable. The austenite volume fractions determined by diffraction methods have been found to be affected by the measuring specimen direction, i.e., texture, even by applying the conventional correcting procedure. To avoid this influence, it is recommended to measure both of volume fraction and texture simultaneously using neutron diffraction. Although synchrotron X-ray shows higher angle resolution, its small incident beam size brings poor statistic reliability. The influence of texture cannot be avoided for transmission Bragg edge measurement, either, which must be overcome to realize 2D or 3D volume fraction mapping.
Jungclaus, A.*; Grawe, H.*; 西村 俊二*; Doornenbal, P.*; Lorusso, G.*; Simpson, G. S.*; Sderstrm, P.-A.*; 炭竃 聡之*; Taprogge, J.*; Xu, Z. Y.*; et al.
Physics Letters B, 772, p.483 - 488, 2017/09
A new high-spin isomer in the neutron-rich nucleus Cd was populated in the projectile fission of a U beam at the Radioactive Isotope Beam Factory at RIKEN. A half-life of T = 6.3(8) ms was measured for the new state which was tentatively assigned a spin/parity of (15). The isomeric state decays via the emission of a 309-keV ray with multipolarity. The experimental results are compared to shell model calculations performed using state-of-the-art realistic effective interactions and to the neighbouring nucleus Cd. The comparison with calculations shows that adjustments of the pairing and multipole parts of the effective interaction derived from the CD-Bonn nucleon-nucleon potential are required in order to describe the properties of nuclei in the region around Sn.
友田 陽*; 佐藤 成男*; Uchida, M.*; 徐 平光; Harjo, S.; Gong, W.; 川崎 卓郎
Materials Science Forum, 905, p.25 - 30, 2017/08
Microstructural change during hot compressive deformation at 700 C followed by isothermal annealing for a Fe-32Ni austnitic alloy was monitored using neutron diffraction. The evolution of deformation texture with 40% compression and its change to recrystallization texture during isothermal annealing were presented by inverse pole figures for the axial and radial directions. The change in dislocation density was tracked using the convolutional muli-profile whole profile fitting method. To obtain the fitting results with good statistics, at least 60 s time-slicing for the event-mode recorded data was needed. The average dislocation density in 60 s after hot compression was determined to be 2.8 10 m that decreased with increasing of annealing time.
東 喜三郎*; Li, Y.; 長谷川 邦夫; Xu, S.*
Proceedings of 2017 ASME Pressure Vessels and Piping Conference (PVP 2017) (CD-ROM), 9 Pages, 2017/07
Materials made of alloy 82/182/600 used in light-water reactors are known to be susceptible to stress corrosion cracking. It is known that the depth of some cracks due to primary water stress corrosion cracking is larger than the half of crack length . The stress intensity factor solution for cracks plays an important role to predict crack propagation and failure. However, Section XI of the ASME Boiler and Pressure Vessel Code does not provide the solutions for cracks with large aspect ratios. In this study, closed-form stress intensity factor influence coefficients for deep surface cracks in plates are discussed. The crack tip stress distribution was represented by a fourth degree polynomial equation. Influence coefficient tables obtained by using finite element analysis in previous studies were used for curve fitting. The closed-form solutions for the coefficient were developed at the surface points, the deepest points, and the maximum points of the cracks with aspect ratios ranged from 1.0 to 8.0.
Flavigny, F.*; Doornenbal, P.*; Obertelli, A.*; Delaroche, J.-P.*; Girod, M.*; Libert, J.*; Rodriguez, T. R.*; Authelet, G.*; Baba, H.*; Calvet, D.*; et al.
Physical Review Letters, 118(24), p.242501_1 - 242501_6, 2017/06
The first -ray spectroscopy of very neutron rich Kr isotopes was carried out at the RIBF at RIKEN Nishina center. Excited states in these isotopes were populated via (p,2p) reactions using radioactive Rb beams accelerated to 220 MeV/nucleon. The new data show a significant increase in deformation beyond N=60, as well as competing configurations (shape-coexistence) at low energy. The data were compared with beyond-mean-field calculations which predict level energies in good agreement with observation, and suggest oblate-prolate shape coexistence.
小島 真由美*; 城 鮎美*; 鈴木 裕士; 井上 純哉*; 菖蒲 敬久; 徐 平光; 秋田 貢一; 南部 将一*; 小関 敏彦*
材料, 66(6), p.420 - 426, 2017/06
The strain distribution in a multilayered steel composite, which consists of martensite and austenite layers, was evaluated by energy dispersive X-ray diffraction to investigate the homogeneity of deformation in the martensite layer under uniaxial loading. A dog-bone shape specimen with a martensite layer with 0.2 mm in a thickness, sandwiching by austenite layers with 0.4 mm in thickness, was utilized in this study. A change in strains as a function of tensile loading was measured at the center of the martensite layer as well as near the interface between the martensite and austenite layers. Furthermore, the residual strain distributions were measured in the martensite layer of the unloaded specimens after different applied strains. As a result, slight inhomogeneous deformation was found at the beginning of the plastic deformation in the martensite layer although no local deformation was recognized even near the interface between austenite and martensite layers. After further deformation, mismatch of plastic deformation between austenite and martensite layers was reduced, and the martensite layer deformed homogeneously. Therefore, an unstable interface phenomenon might not be caused by the intrinsic factors with a mesoscopic scale discussed in this experiment.
徐 平光; 友田 陽*; 新垣 優; Harjo, S.; 末吉 仁*
Materials Characterization, 127, p.104 - 110, 2017/05
The volume fractions of austenite () in TRIP steels were evaluated using time-of-flight neutron diffraction through four methods. They include the analysis method with random texture assumption, the correction method of () peak intensities, the Rietveld refinement method using the summed spectrum without distinguishing the specimen orientations, and the combined Rietveld analysis method for textures and volume fractions. It was found that for a near-random spectrum obtained by the summation of all the measured neutron spectra, the Rietveld refinement provided a satisfactory precision for . Moreover, the precision was further improved through the combined Rietveld analysis method. If the texture measurement is unavailable, it is suggested to measure the neutron spectrum along the transverse direction, and to analyze the using conventional correction method of () peak intensities. It was also confirmed that the increment of evidently improved the combinations of tensile strength and uniform elongation (TSUEl).
Vaquero, V.*; Jungclaus, A.*; Doornenbal, P.*; Wimmer, K.*; Gargano, A.*; Tostevin, J. A.*; Chen, S.*; Ncher, E.*; Sahin, E.*; 志賀 慶明*; et al.
Physical Review Letters, 118(20), p.202502_1 - 202502_5, 2017/05
Excited states in Sn were populated following one-neutron knockout reaction from an unstable Sn beam at the RIBF laboratory in RIKEN. In addition to the already known rays, additional strength was observed for the first time in the excitation-energy range 3.5-5.5 MeV. Since the neutron separation energy of Sn is low, this observation provides direct evidence for the radioactive decay of neutron-unbound states in this nucleus. The ability of decay to compete with neutron emission was attributed to a mismatch between the wave functions of the initial and final states in the neutron emission case. These findings suggest that in the region south-east of Sn, nuclear structure effects play a significant role in the decay of unbound states, which are instead usually ignored in the evaluation of neutron-emission probabilities in astrophysical simulations.