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In-plane Anisotropy of the Magnetic and the Electric Properties of the Fe Pnictide Ba(Fe1−xCox)2As2
Yoshiaki Kobayashi,Akihiro Ichikawa,Masayuki Toyoda,Masayuki Itoh,Masatoshi Sato 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.3
The anisotropy of the electronic and the magnetic properties within the FeAs planes of Co(2%)-doped BaFe2As2 has been investigated by using 75As nuclear magnetic resonance (NMR) measurementson the As (As0) sites with all four nearest neighbor sites occupied by Fe. Even in thetetragonal phase at temperatures above 100 K, two sets of NMR spectra with twofold symmetry ofin-plane Knight shifts and electronic nuclear quadrupole frequencies are observed. They originatefrom two domains with their symmetry axes lying at right angles to each other. The anisotropies ofthe electronic and the magnetic properties become pronounced at 140 K, below which an in-planeanisotropy is reported to appear in electrical resistivity under a pressure along one of Fe-Fe directions. 75As NMR measurements have also been carried out for the As (As1) sites surrounded byone Co and three Fe. From the data, we conclude that the spin susceptibility of As1 is ~1/3 thatof As0 and that the antiferromagnetic spin fluctuation of As1 is fairly suppressed as compared withthat of As0. We discuss these behaviors of the FeAs layer in connection with the impurity-inducedlocal orbital order model proposed by theoretical studies.
Phase Separation of Antiferromagnetism and Superconductivity in RbxFe2−ySe2 Observed by Using Rb NMR
Yoshiaki Kobayashi,Shunsuke Saiki,Shouhei Kototani,Masayuki Itoh,Masatoshi Sato 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.3
We have carried out 87Rb NMR measurements on single crystals with and without the superconducting(SC) transition to clarify whether the SC and the antiferromagnetic (AFM) states aremicroscopically coexistent or just phase-separated in the Rb-intercalated iron-selenide RbxFe2−ySe2. The 87Rb NMR spectra observed at temperature below 300 K for these crystals are clearly separableinto two parts with different structures and widths. The broader spectrum can be explainedby the presence of a region with an AFM spin structure proposed by neutron scattering studies. The narrower spectrum in the crystal with the SC transition can be understood from the temperaturedependences of the spectral frequency-position and shape to stem from the SC region withTc = 30.8 K. Thus, we can clearly conclude that the superconductivity and the antiferromagnetismin the present system are phase-separated. Also, the crystal without the SC transition has twophase-separated regions with respective magnetic transitions at 500 and 50 K.
Partial Conductivity of YSZ Doped with 10 mol% $TiO_2$
Kobayashi, Kiyoshi,Kai, Yukiharu,Yamaguchi, Shu,Kawashima, Tsuyoshi,Iguchi, Yoshiaki The Korean Ceramic Society 1998 The Korean journal of ceramics Vol.4 No.2
Using Hebb-Wagner's asymmetric cell, partial conductivities of holes and electrons in yttria stabilized zirconia doped with 10 mol% TiO2 have been estimated by a dc polarization measurement. The current interrruption method and ac impedance measurements have been also made to evaluate the ionic conductivity and to examine the consistency of the partial conductivities. Partial conductivities of electrons(σn) and holes (σp) were found to be pro-peortional to -1/4 and 1/4 power of partial pressure of oxygen gas, respectively, except for σn at reducing conditions. In comparison with 5 mol% doped YSZ, σn was found to increase with the increase of TiO2 concentration, but σp stayed at almost a constant value.
Non-Steady State Gas Permeation Measurements of $TiO_2$-Doped YSZ
Kobayashi, Kiyoshi,Yamaguchi, Shu,Iguchi, Yoshiaki The Korean Ceramic Society 2000 The Korean journal of ceramics Vol.6 No.2
Mobilities of electrons ($\mu_p$) and holes ($\mu_p$) in 2, 5, and 10 mol% $TiO_2$-doped yttria stabilized zirconia (TD-YSZ) have been estimated by a non-steady state gas permeation method using models proposed by Weppner and Maruyama. Values of $\mu_n$ and $\mu_p$ were found to be closed to those in non-doped YSZ reported earlier. The concentration of electrons and holes were calculated from $\mu_n$ and $\mu_p$ values and the partial conductivities of electrons and holes measured by a dc-polarization method. The concentration of electrons at unit oxygen partial pressure increased with increasing $TiO_2$concentration, while the hole concentration was almost independent of $TiO_2$concentration.
CURRENT STATUS OF THE EAVN EXPERIMENTS
HAGIWARA, YOSHIAKI,AN, TAO,JUNG, TAEHYUN,RHO, DUK-GYOO,ZHANG, MING,HAO, LONGFEI,FUJISAWA, KENTA,YONEKURA, YOSHINORI,BAAN, WILLEM,KIM, JONGSOO,KOBAYASHI, HIDEYUKI The Korean Astronomical Society 2015 天文學論叢 Vol.30 No.2
VLBI experiments have been conducted by radio telescopes in the East Asia VLBI Network (EAVN) in which 14 telescopes in China, Japan, and Korea participated. One of the aims of the EAVN is to obtain higher angular resolution that is provided by the 6,000 km baseline between China and Japan and better sensitivity by adding large telescopes. Data were recorded at 1 a Gbps recording rate at all stations and processed on the Korea-Japan Joint VLBI Correlator (KJJVC) at the Korea-Japan Correlation Center (KJCC) after experiments. Fringes were obtained from these experiments conducted at 8 GHz and 22 GHz and post-correlation data analysis of the experiments is undergoing. The outcomes of these experiments open the possibility of conducting EAVN observations with global VLBI networks. In this presentation, the recent status of these experiments and future prospects are presented.
Masatoshi Sato,Yoshiaki Kobayashi,Takayuki Kawamata,Yukio Yasui,Kazunori Suzuki,M. Itoh,Ryoichi Kajimoto,Kazuhiko Ikeuchi,M. Arai,Phillipe Bourges 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.12
To identify the superconducting symmetry of Fe-based superconductors, we studied effects ofnonmagnetic-impurities on Tc, magnetic excitation spectra 00 and NMR 1/T1 − T curve, whichare sensitive to the relative signs between the order parameters on the disconnected Fermi surfacesin reciprocal space, because the symmetry is closely connected with the pairing mechanism:If the signs are opposite (symmetry S±), the mechanism is considered to be a magneticone, but when the signs are the same (symmetry S++), a novel mechanism is plausible becausethe ordinary phonon mechanism cannot realize the Tc value as high as 55 K found in Ln1111(Ln=lanthanide). Results are as follows: (a) The very small rates of Tc-suppression by impurityatoms M of LnFe1−yMyAs0.89−xF0.11+x (M=Ni, Co, Ru) can be explained only by S++. (b) The00-data for Ba(Fe, Co)2As2 (Tc 23 K) and Ca-Fe-Pt-As crystals seem to be well explained byS++ rather than by S±. (c) The nuclear magnetic resonance data can be consistently understoodby S++, too. These results suggest the S++ symmetry and a novel pairing mechanism, which canbe considered to be related to the elastic softening of C66 induced by the orbital fluctuation of thesystem.
Foxf2 represses bone formation via Wnt2b/β-catenin signaling
Tanaka Tomoyuki,Takahashi Akira,Kobayashi Yutaka,Saito Masanori,Xiaolong Sun,Jingquan Chen,Ito Yoshiaki,Kato Tsuyoshi,Ochi Hiroki,Sato Shingo,Yoshii Toshitaka,Okawa Atsushi,Carlsson Peter,Inose Hiroyu 생화학분자생물학회 2022 Experimental and molecular medicine Vol.54 No.-
Differentiation of mesenchymal stem cells (MSCs) into osteoblasts is a critical process for proper skeletal development and acquisition/maintenance of bone mass. However, since this regulatory mechanism has not yet been fully elucidated, the treatment of severe osteoporosis and fractures is a challenge. Here, through a comprehensive analysis of gene expression during the differentiation of MSCs into osteoblasts, we show that the forkhead transcription factor Foxf2 is a crucial regulator of this process. Foxf2 expression transiently increased during MSC osteoblastic differentiation. Overexpression of Foxf2 in MSCs inhibited osteoblastic differentiation, and conversely, knockdown of Foxf2 expression promoted this process. Osteoprogenitor-specific Foxf2 knockout mice developed a high bone mass phenotype due to increased bone formation. RNA-seq analysis and molecular experiments revealed that Foxf2 regulation of bone formation is mediated by Wnt2b. Knockdown of Foxf2 in mouse femurs enhanced bone regeneration in vivo. FOXF2 expression was correlated with hip bone mineral density in postmenopausal women with low bone mass. Finally, inhibition of FOXF2 promoted osteoblastic differentiation of human MSCs. This study uncovers a critical role of Foxf2 in the differentiation of MSCs into osteoblasts and provides insight into the pathogenesis associated with bone-related diseases such as osteoporosis and nonunion after fracture
Saito, Naoaki,Funayama, Akinori,Arai, Yoshiaki,Suda, Daisuke,Takata, Yoshiyuki,Kobayashi, Tadaharu Korean Association of Maxillofacial Plastic and Re 2018 Maxillofacial Plastic Reconstructive Surgery Vol.40 No.-
Background: The free vascularized fibula flap presents many advantages such as sufficient length of the bony segment, good vascularization, better quality of the bone, and a long vascular pedicle, but it is also associated with some disadvantages with regard to prosthetic rehabilitation because of its limited height. Improvement in bone height is necessary for ideal dental implant treatment of reconstructed mandibles. Case presentation: For two squamous cell carcinoma patients, mandibular bone reconstruction was performed secondarily with the peroneal flap after tumor resection. Since the bone height was insufficient at the time of implant treatment, occlusion reconstruction by dental implant was performed after vertical distraction osteogenesis. Conclusions: Vertical distraction osteogenesis is a suitable treatment option for alveolar ridge deficiency resulting from fibula transplantation for mandibular reconstruction following tumor surgery.