Competing spin modulations in the magnetically frustrated semimetal EuCuSb

Takahashi, Hidefumi*; Aono, Kai*; Nambu, Yusuke*; Kiyanagi, Ryoji; Nomoto, Takuya*; Sakano, Masato*; Ishizaka, Kyoko*; Arita, Ryotaro*; Ishiwata, Shintaro*

Physical Review B, 102(17), p.174425_1 - 174425_6, 2020/11

https://doi.org/10.1103/PhysRevB.102.174425

The competing magnetic ground states of the itinerant magnet EuCuSb, which has a hexagonal layered structure, were studied via magnetization, resistivity, and neutron-diffraction measurements on single-crystal samples. EuCuSb has a three-dimensional semimetallic band structure as confirmed by band calculation and angle-resolved photoelectron spectroscopy, consistent with the nearly isotropic metallic conductivity in the paramagnetic state. However, below the antiferromagnetic transition temperature of (8.5 K), the resistivity, especially along the hexagonal axis, increases significantly. This implies the emergence of anisotropic magnetic ordering coupled to the conducting electrons. Neutron-diffraction measurements show that the Eu spins, which order ferromagnetically within each layer, are collinearly modulated (up-up-down-down) along the hexagonal axis below , followed by the partial emergence of helical spin modulation below (6 K). Based on the observation of anomalous magnetoresistance with hysteretic behavior, we discuss the competing nature of the ground state inherent in a frustrated Heisenberg-like spin system with a centrosymmetric structure.

Development of real-time rotating waveplate Stokes polarimeter using multi-order retardation for ITER poloidal polarimeter

Imazawa, Ryota; Kawano, Yasunori; Ono, Takehiro; Itami, Kiyoshi

Review of Scientific Instruments, 87(1), p.013503_1 - 013503_7, 2016/01

AA2015-0219.pdf:1.34MB

https://doi.org/10.1063/1.4939444

no abstracts in English

Elucidations of the catalytic cycle of NADH-cytochrome reductase by X-ray crystallography; New insights into regulation of efficient electron transfer

Yamada, Mitsugu*; Tamada, Taro; Takeda, Kazuki*; Matsumoto, Fumiko*; Ono, Hiraku*; Kosugi, Masayuki*; Takaba, Kiyofumi*; Shoyama, Yoshinari*; Kimura, Shigenobu*; Kuroki, Ryota; et al.

Journal of Molecular Biology, 425(22), p.4295 - 4306, 2013/11

https://doi.org/10.1016/j.jmb.2013.06.010

NADH-Cytochrome reductase (b5R), a flavoprotein consisting of NADH and flavin adenine dinucleotide (FAD) binding domains, catalyzes electron transfer from the two-electron carrier NADH to the one-electron carrier cytochrome (Cb5). The crystal structures of both the fully reduced form and the oxidized form of porcine liver b5R were determined. In the reduced b5R structure determined at 1.68 resolution, the relative configuration of the two domains was slightly shifted in comparison with that of the oxidized form. This shift resulted in an increase in the solvent-accessible surface area of FAD and created a new hydrogen-bonding interaction between the N5 atom of the isoalloxazine ring of FAD and the hydroxyl oxygen atom of Thr66, which is considered to be a key residue in the release of a proton from the N5 atom. The isoalloxazine ring of FAD in the reduced form is flat as in the oxidized form and stacked together with the nicotinamide ring of NAD. Determination of the oxidized b5R structure, including the hydrogen atoms, determined at 0.78 resolution revealed the details of a hydrogen-bonding network from the N5 atom of FAD to His49 via Thr66. Both of the reduced and oxidized b5R structures explain how backflow in this catalytic cycle is prevented and the transfer of electrons to one-electron acceptors such as Cb5 is accelerated. Furthermore, crystallographic analysis by the cryo-trapping method suggests that re-oxidation follows a two-step mechanism. These results provide structural insights into the catalytic cycle of b5R.

Thermal and optical analyses of retro-reflector for poloidal polarimeter on ITER

Imazawa, Ryota; Kawano, Yasunori; Ono, Takehiro; Kusama, Yoshinori

Plasma and Fusion Research (Internet), 6(Sp.1), p.2402032_1 - 2402032_5, 2011/08

https://doi.org/10.1585/pfr.6.2402032

This paper describes results from the first integrated analysis on the feasibility of a retro-reflector (RR) installed in the ITER vacuum vessel. We make thermal and structural analyses of passively-cooled RR and terrace retro-reflector array (TERRA) by using heat load conditions on ITER. In the case of RR, the temperature reaches over 600C, and the flatness of deformed mirror surface forming RR is approximately 80 m. Although the maximal displacement of mirror surface is large, 69% of the incident-laser power returns to a diagnostic room, disturbance of phase is and rotation angle of polarization plane is less than 0.06 . On the other hand, the temperature of TERRA is approximately 350C, and the flatness of the deformed mirror surface is less than 10 m. The flatness of the mirror surface of the deformed TERRA is much smaller than laser wavelength (118 m), but the global shape is curved to ruin the coherent phase of laser light. The curvature radius of TERRA is 21 m, and 49% of the incident-laser power returns to the diagnostic room, disturbance of phase is , and rotation angle of polarization plane is less than 0.06. Since the optimized incident angles of flat and curved TERRA are different, a real-time feedback control of the incident angle is necessary for applying TERRA to ITER poloidal polarimeter.

Terrace retro-reflector array for poloidal polarimeter on ITER

Imazawa, Ryota; Kawano, Yasunori; Ono, Takehiro; Kusama, Yoshinori

Review of Scientific Instruments, 82(2), p.023116_1 - 023116_5, 2011/02

https://doi.org/10.1063/1.3541810

Anti-FGF23 neutralizing antibodies show the physiological role and structural features of FGF23

Yamazaki, Yuji*; Tamada, Taro; Kasai, Noriyuki*; Urakawa, Itaru*; Aono, Yukiko*; Hasegewa, Hisashi*; Fujita, Toshiro*; Kuroki, Ryota; Yamashita, Takeyoshi*; Fukumoto, Seiji*; et al.

Journal of Bone and Mineral Research, 23(9), p.1509 - 1518, 2008/09

https://doi.org/10.1359/jbmr.080417

Fibroblast growth factor (FGF)23 is proposed to play a physiological role in the regulation of phosphate and vitamin D metabolism; deranged circulatory levels of FGF23 cause several diseases with abnormal mineral metabolism. We developed two antibodies (FN1 and FC1) that recognize the N- and C-terminal regions of FGF23, respectively. Both FN1 and FC1 inhibited FGF23 activity in a cell-based Klotho-dependent reporter assay. The present study using neutralizing antibodies confirms that FGF23 is a physiological regulator of phosphate and vitamin D metabolism. Then, we addressed the mechanism of action for these neutralizing antibodies. Structural analysis of the FGF23/FN1-Fab complex revealed that FN1 masked putative FGF receptor-binding sites in the N-terminal domain of FGF23, while biochemical analyses showed that FC1 interfered with the association between FGF23 and Klotho by binding to the C-terminal domain of FGF23. Taken together, our results suggest that the N- and C-terminal domains of FGF23 are responsible for association with cognate FGF receptors and Klotho, respectively, and that these interactions are indispensable for FGF23 activity.

Progress in development of ITER poloidal polarimeter

Imazawa, Ryota; Ono, Takehiro; Kawano, Yasunori

no journal, , 

no abstracts in English

Measurement of mass and total kinetic energy distribution for spontaneous fission of Md

Asai, Masato; Ishibashi, Yuichi*; Tsukada, Kazuaki; Sato, Tetsuya; Aoki, Ryota*; Ito, Yuta; Uchibaba, Yuta*; Orlandi, R.; Gong, G.-M.*; Suzaki, Fumi; et al.

no journal, , 

Measurement of mass and total kinetic energy (TKE) distribution for the spontaneous fission (SF) of Md has been performed to clarify the fission mechanism in the neutron-rich fermium region. Md nuclei were produced with the Es target and O beam, and mass-separated with an on-line isotope separator (ISOL). We discuss the mechanism of fission observed in the SF of Md on the basis of the observed mass-TKE distribution.

Progress in ITER diagnostics development in Japan

Kusama, Yoshinori; Kondoh, Takashi; Ishikawa, Masao; Hatae, Takaki; Yatsuka, Eiichi; Hayashi, Toshimitsu; Ono, Takehiro; Kawano, Yasunori; Imazawa, Ryota; Ogawa, Hiroaki; et al.

no journal, , 

no abstracts in English

Development of ITER poloildal polarimeter

Imazawa, Ryota; Ono, Takehiro; Kawano, Yasunori; Itami, Kiyoshi

no journal, , 

no abstracts in English