IOP Publishing Acta Medica Okayama 1742-6588 3027 1 2025 LES analysis to investigate a random-phase forcing scheme for steadying anisotropic turbulence fields 012009 EN Koki Minami Graduate School of Environmental, Life, Natural Science and Technology, Okayama University Hiroki Suzuki Graduate School of Environmental, Life, Natural Science and Technology, Okayama University Toshinori Kouchi Graduate School of Environmental, Life, Natural Science and Technology, Okayama University Kento Tanaka Graduate School of Environmental, Life, Natural Science and Technology, Okayama University The aim of this study is to investigate the effect of phase randomization on forcing mechanisms that stabilize localized turbulence. A trigonometric forcing based on vector potential is combined with uniform random numbers to create a spatially homogeneous forcing field. The analysis is performed using large-eddy simulation (LES) with the Smagorinsky model as the subgrid scale model. The results demonstrate that steady flows are generated regardless of the presence of phase randomization, successfully forming isotropic turbulence. In contrast, for anisotropic turbulent fields, the addition of phase randomization reduces the degree of anisotropy, indicating a smoothing effect on the anisotropy of the flow. No potential conflict of interest relevant to this article was reported.

IOP Publishing Acta Medica Okayama 1742-6588 3027 1 2025 Fundamental examination of coherent structure model prediction using vortex cores in a two-dimensional Taylor’s analytical solution 012008 EN Xuanyou Gong Graduate School of Environmental, Life, Natural Science and Technology, Okayama University Hiroki Suzuki Graduate School of Environmental, Life, Natural Science and Technology, Okayama University Toshinori Kouchi Graduate School of Environmental, Life, Natural Science and Technology, Okayama University Kento Tanaka Graduate School of Environmental, Life, Natural Science and Technology, Okayama University This study focuses on the possibility that flow around vortex tubes in turbulence may resemble laminar flow, and aims to describe the characteristics of turbulent fields using analytical solutions to the governing equations. In the two-dimensional analytical Taylor solution, the velocity and pressure fields are expressed by trigonometric functions, and a structure in which counter-rotating vortices are arranged in a grid pattern is demonstrated. This solution is used to verify the accuracy of numerical analyses and is expected to contribute to a simple yet unambiguous description of turbulent fields based on vortex structures. Predictions of sub-grid scale components and validation of a coherent structure model using invariants of the velocity gradient tensor are also performed. No potential conflict of interest relevant to this article was reported.

IOP Publishing Acta Medica Okayama 1882-0778 18 10 2025 Multichannel topological elastic waveguide in a multilayer Kagome phononic crystal 107001 EN Yusuke Hata Department of Electrical and Electronic Engineering, Okayama University Kenji Tsuruta Department of Electrical and Electronic Engineering, Okayama University By examining the geometric characteristics of various boundaries formed within the Kagome phononic lattice and vertically stacking the lattices, we designed an elastic waveguide that enables selective propagation of topologically protected edge modes across layers in a bilayer system. This layer-selective transmission is manifested as polarized boundary modes that appear in phononic dispersions of the systems incorporating the bridge, zigzag, and armchair boundaries. We numerically demonstrated that efficient elastic layer converters and splitters can be designed, thereby paving the way for the practical development of three-dimensional elastic-wave devices. No potential conflict of interest relevant to this article was reported.

IOP Publishing Acta Medica Okayama 2053-1583 12 4 2025 Covalent cross-linked graphene oxide aerogels for moisture adsorption 045010 EN Zhijian Cao School of Materials Science and Engineering, University of New South Wales Xiaojun Ren School of Materials Science and Engineering, University of New South Wales Tongxi Lin School of Materials Science and Engineering, University of New South Wales Yuta Nishina Research Institute for Interdisciplinary Science, Okayama University Masamichi Yoshimura Graduate School of Engineering, Toyota Technological Institute Rakesh Joshi School of Materials Science and Engineering, University of New South Wales Covalent cross-linking is an effective approach to enhance the hydrophilicity and water adsorption properties of graphene oxide (GO). We studied moisture absorption in GO cross-linked with poly(ethylene glycol) diamines. At relative humidity (RH) of 85%, the PEG-cross-linked GO exhibited a significantly enhanced water uptake capacity of 0.59 g of water per gram of GO (gg−1), compared to 0.37 for unmodified GO. This is attributed to the presence of alkoxy groups via cross-linking, resulting in the enhanced interaction between GO and water molecules. These findings highlight the potential of PEG-based covalent functionalisation for efficient moisture capture in GO-based materials. No potential conflict of interest relevant to this article was reported.

IOP Publishing Acta Medica Okayama 2399-6528 8 6 2024 Inert structural transition in 4H and 6H SiC at high pressure and temperature: a Raman spectroscopy study 065001 EN Shuhou Maitani Department of Physics, School of Science and Technology, Meiji University Ryosuke Sinmyo Department of Physics, School of Science and Technology, Meiji University Takayuki Ishii Institute for Planetary Materials, Okayama University Kenji Yoza Bruker Japan We conducted Raman spectroscopy measurements of 4H-SiC and 6H-SiC up to 69 GPa and 1023 K to assess the stability and bonding of SiC at high pressure and temperature. Both optic and acoustic modes were observed at wide pressure and temperature ranges. The temperature shifts of the Raman frequencies were fitted by the equation with the Bose–Einstein distribution function, and we found that the shifts were almost insensitive to the pressure. The mode Grüneisen coefficients weakly depend on the pressure and temperature, suggesting the sluggish transition of the crystal structure, unlike the previous experiments showing the transition or decomposition of SiC at high pressure and temperature conditions. Inert transitions are confirmed by Raman measurements and annealing experiments using multiple high-pressure apparatuses. The crystallinity may be a hidden critical parameter in the experiments to determine the stable polytypes of SiC under high pressure and temperature. No potential conflict of interest relevant to this article was reported.

IOP Publishing Acta Medica Okayama 1882-0778 18 9 2025 Fundamentals and advances in transverse thermoelectrics 090101 EN Hiroto Adachi Research Institute for Interdisciplinary Science, Okayama University Fuyuki Ando Research Center for Magnetic and Spintronic Materials, National Institute for Materials Science Takamasa Hirai Research Center for Magnetic and Spintronic Materials, National Institute for Materials Science Rajkumar Modak Research Center for Magnetic and Spintronic Materials, National Institute for Materials Science Matthew A. Grayson Department of Electrical and Computer Engineering, Northwestern University Ken-ichi Uchida Research Center for Magnetic and Spintronic Materials, National Institute for Materials Science Transverse thermoelectric effects interconvert charge and heat currents in orthogonal directions due to the breaking of either time-reversal symmetry or structural symmetry, enabling simple and versatile thermal energy harvesting and solid-state cooling/heating within single materials. In comparison to the complex module structures required for the conventional Seebeck and Peltier effects, the transverse thermoelectric effects provide the complete device structures, potentially resolving the fundamental issue of multi-module degradation of thermoelectric conversion performance. This review article provides an overview of all currently known transverse thermoelectric conversion phenomena and principles, as well as their characteristics, and reclassifies them in a unified manner. The performance of the transverse thermoelectric generator, refrigerator, and active cooler is formulated, showing that thermal boundary conditions play an essential role in discussion on their behaviors. Examples of recent application research and material development in transverse thermoelectrics are also introduced, followed by a discussion of future prospects. No potential conflict of interest relevant to this article was reported.

IOP Publishing Acta Medica Okayama 1742-6588 2892 2024 Crystal Grain Rotation during Tensile Test of Polycrystalline Pure Titanium Thin Sheet Based on Surface Height and Crystal Orientation 012002 EN Naoya Tada Okayama University Hiroaki Ohashi Okayama University Takeshi Uemori Okayama University Junji Sakamoto Okayama University Thin sheets and wires of polycrystalline pure titanium are important materials for various devices used in electrical, mechanical, dental, and medical fields. Since pure titanium shows strong anisotropy in elastic and plastic deformation, and the individual grains comprising a polycrystalline body have different orientations and geometries, inhomogeneous deformation always occurs on the microscopic scale. This inhomogeneity is more significant in thin films than in bulk materials. It is therefore important to investigate the inhomogeneous deformation of pure titanium thin sheets to ensure the reliability of various titanium devices. In this study, thin-sheet specimens made of polycrystalline pure titanium were subjected to tensile testing. Inhomogeneous deformation was evaluated on the basis of two kinds of crystal grain rotations based on surface height and crystal orientation. The results under elastic and plastic tensile conditions were compared. No potential conflict of interest relevant to this article was reported.

IOP Publishing Acta Medica Okayama 1367-2630 27 4 2025 Characterization of the thorium-229 defect structure in CaF2 crystals 043024 EN S. Takatori Research Institute for Interdisciplinary Science (RIIS), Okayama University M. Pimon Faculty of Physics, TU Wien S. Pollitt Faculty of Physics, TU Wien M. Bartokos Faculty of Physics, TU Wien K. Beeks Faculty of Physics, TU Wien A. Grueneis Faculty of Physics, TU Wien T. Hiraki Research Institute for Interdisciplinary Science (RIIS), Okayama University T. Honma Japan Synchrotron Radiation Research Institute N. Hosseini Faculty of Physics, TU Wien A. Leitner Faculty of Physics, TU Wien T. Masuda Research Institute for Interdisciplinary Science (RIIS), Okayama University I Morawetz Faculty of Physics, TU Wien K. Nitta Japan Synchrotron Radiation Research Institute K. Okai Research Institute for Interdisciplinary Science (RIIS), Okayama University T. Riebner Faculty of Physics, TU Wien F. Schaden Faculty of Physics, TU Wien T. Schumm Faculty of Physics, TU Wien O. Sekizawa Japan Synchrotron Radiation Research Institute T. Sikorsky Faculty of Physics, TU Wien Y. Takahashi Department of Earth and Planetary Science, The University of Tokyo Col, L. Toscani De Col Faculty of Physics, TU Wien R. Yamamoto Research Institute for Interdisciplinary Science (RIIS), Okayama University T. Yomogida Department of Earth and Planetary Science, The University of Tokyo A. Yoshimi Research Institute for Interdisciplinary Science (RIIS), Okayama University K. Yoshimura Research Institute for Interdisciplinary Science (RIIS), Okayama University Recent advancements in laser excitation of the low-energy thorium-229 (229Th) nuclear isomeric state in calcium fluoride (CaF2) single crystals render this system a promising candidate for a solid-state nuclear clock. Nonetheless, the precise experimental determination of the microscopic ion configuration surrounding the doped 229Th and its electronic charge state remains a critical challenge. Such characterization is essential for precisely controlling the clock transition and evaluating the performance of this solid-state nuclear clock system. In this study, we use x-ray absorption fine structure spectroscopy of 229Th:CaF2 to investigate the charge state and coordination environment of doped 229Th. The results indicate that 229Th displays a 4+ oxidation state at the substitutional site of a Ca2+ ion, with charge compensated provided by two F− ions positioned at interstitial sites adjacent to 229Th. No potential conflict of interest relevant to this article was reported.

IOP Publishing Acta Medica Okayama 1475-7516 2024 12 2024 Multi-dimensional optimisation of the scanning strategy for the LiteBIRD space mission EN Y. Takase Okayama University, Department of Physics L. Vacher International School for Advanced Studies (SISSA) H. Ishino Okayama University, Department of Physics G. Patanchon ILANCE, CNRS, University of Tokyo International Research Laboratory L. Montier IRAP, Université de Toulouse, CNRS, CNES, UPS S.L. Stever Okayama University, Department of Physics K. Ishizaka Okayama University, Department of Physics Y. Nagano Okayama University, Department of Physics W. Wang Université Paris Cité, CNRS, Astroparticule et Cosmologie J. Aumont IRAP, Université de Toulouse, CNRS, CNES, UPS K. Aizawa The University of Tokyo, Department of Physics A. Anand Dipartimento di Fisica, Università di Roma Tor Vergata C. Baccigalupi International School for Advanced Studies (SISSA) M. Ballardini Dipartimento di Fisica e Scienze della Terra, Università di Ferrara A.J. Banday IRAP, Université de Toulouse, CNRS, CNES, UPS R.B. Barreiro Instituto de Fisica de Cantabria (IFCA, CSIC-UC) N. Bartolo Dipartimento di Fisica e Astronomia "G. Galilei", Università degli Studi di Padova S. Basak School of Physics, Indian Institute of Science Education and Research Thiruvananthapuram M. Bersanelli Dipartimento di Fisica, Università degli Studi di Milano M. Bortolami Dipartimento di Fisica e Scienze della Terra, Università di Ferrara T. Brinckmann Dipartimento di Fisica e Scienze della Terra, Università di Ferrara E. Calabrese School of Physics and Astronomy, Cardiff University P. Campeti INFN Sezione di Ferrara E. Carinos IRAP, Université de Toulouse, CNRS, CNES, UPS A. Carones International School for Advanced Studies (SISSA) F.J. Casas Instituto de Fisica de Cantabria (IFCA, CSIC-UC) K. Cheung Jodrell Bank Centre for Astrophysics, Department of Physics and Astronomy, School of Natural Sciences, The University of Manchester L. Clermont Centre Spatial de Liège, Université de Liège F. Columbro Dipartimento di Fisica, Università La Sapienza A. Coppolecchia Dipartimento di Fisica, Università La Sapienza F. Cuttaia INAF, OAS Bologna G. D'Alessandro Dipartimento di Fisica, Università La Sapienza P. de Bernardis Dipartimento di Fisica, Università La Sapienza T. de Haan Institute of Particle and Nuclear Studies (IPNS), High Energy Accelerator Research Organization (KEK) E. de la Hoz CNRS-UCB International Research Laboratory, Centre Pierre Binétruy, UMI2007 S. Della Torre INFN Sezione Milano Bicocca P. Diego-Palazuelos Max Planck Institute for Astrophysics H.K. Eriksen Institute of Theoretical Astrophysics, University of Oslo J. Errard Université Paris Cité, CNRS, Astroparticule et Cosmologie F. Finelli INAF, OAS Bologna U. Fuskeland Institute of Theoretical Astrophysics, University of Oslo G. Galloni Dipartimento di Fisica e Scienze della Terra, Università di Ferrara M. Galloway Institute of Theoretical Astrophysics, University of Oslo M. Gervasi University of Milano Bicocca, Physics Department T. Ghigna International Center for Quantum-field Measurement Systems for Studies of the Universe and Particles (QUP), High Energy Accelerator Research Organization (KEK) S. Giardiello School of Physics and Astronomy, Cardiff University C. Gimeno-Amo Instituto de Fisica de Cantabria (IFCA, CSIC-UC) E. Gjerløw Institute of Theoretical Astrophysics, University of Oslo R. González González Instituto de Astrofísica de Canarias A. Gruppuso INAF, OAS Bologna M. Hazumi International Center for Quantum-field Measurement Systems for Studies of the Universe and Particles (QUP), High Energy Accelerator Research Organization (KEK) S. Henrot-Versillé Université Paris-Saclay, CNRS/IN2P3, IJCLab L.T. Hergt Department of Physics and Astronomy, University of British Columbia K. Ikuma Okayama University, Department of Physics K. Kohri Institute of Particle and Nuclear Studies (IPNS), High Energy Accelerator Research Organization (KEK) L. Lamagna Dipartimento di Fisica, Università La Sapienza M. Lattanzi INFN Sezione di Ferrara C. Leloup Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU, WPI), UTIAS, The University of Tokyo M. Lembo Dipartimento di Fisica e Scienze della Terra, Università di Ferrara F. Levrier Laboratoire de Physique de l'École Normale Supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université de Paris A.I. Lonappan University of California, San Diego, Department of Physics M. López-Caniego Aurora Technology for the European Space Agency G. Luzzi Space Science Data Center, Italian Space Agency B. Maffei Université Paris-Saclay, CNRS, Institut d'Astrophysique Spatiale E. Martínez-González Instituto de Fisica de Cantabria (IFCA, CSIC-UC) S. Masi Dipartimento di Fisica, Università La Sapienza S. Matarrese Dipartimento di Fisica e Astronomia "G. Galilei", Università degli Studi di Padova F.T. Matsuda Japan Aerospace Exploration Agency (JAXA), Institute of Space and Astronautical Science (ISAS) T. Matsumura Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU, WPI), UTIAS, The University of Tokyo S. Micheli Dipartimento di Fisica, Università La Sapienza M. Migliaccio Dipartimento di Fisica, Università di Roma Tor Vergata M. Monelli Max Planck Institute for Astrophysics G. Morgante INAF, OAS Bologna B. Mot IRAP, Université de Toulouse, CNRS, CNES, UPS R. Nagata Japan Aerospace Exploration Agency (JAXA), Institute of Space and Astronautical Science (ISAS) T. Namikawa Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU, WPI), UTIAS, The University of Tokyo A. Novelli Dipartimento di Fisica, Università La Sapienza K. Odagiri Japan Aerospace Exploration Agency (JAXA), Institute of Space and Astronautical Science (ISAS) S. Oguri Japan Aerospace Exploration Agency (JAXA), Institute of Space and Astronautical Science (ISAS) R. Omae Okayama University, Department of Physics L. Pagano Dipartimento di Fisica e Scienze della Terra, Università di Ferrara D. Paoletti INAF, OAS Bologna F. Piacentini Dipartimento di Fisica, Università La Sapienza M. Pinchera INFN Sezione di Pisa G. Polenta Space Science Data Center, Italian Space Agency L. Porcelli Istituto Nazionale di Fisica Nucleare-aboratori Nazionali di Frascati (INFN-LNF) N. Raffuzzi Dipartimento di Fisica e Scienze della Terra, Università di Ferrara M. Remazeilles Instituto de Fisica de Cantabria (IFCA, CSIC-UC) A. Ritacco Dipartimento di Fisica, Università di Roma Tor Vergata M. Ruiz-Granda Instituto de Fisica de Cantabria (IFCA, CSIC-UC) Y. Sakurai Suwa University of Science D. Scott Department of Physics and Astronomy, University of British Columbia Y. Sekimoto Japan Aerospace Exploration Agency (JAXA), Institute of Space and Astronautical Science (ISAS) M. Shiraishi Suwa University of Science G. Signorelli Dipartimento di Fisica, Università di Pisa R.M. Sullivan Department of Physics and Astronomy, University of British Columbia H. Takakura Japan Aerospace Exploration Agency (JAXA), Institute of Space and Astronautical Science (ISAS) L. Terenzi INAF, OAS Bologna M. Tomasi Dipartimento di Fisica, Università degli Studi di Milano M. Tristram Université Paris-Saclay, CNRS/IN2P3, IJCLab B. van Tent Université Paris-Saclay, CNRS/IN2P3, IJCLab P. Vielva Instituto de Fisica de Cantabria (IFCA, CSIC-UC) I.K. Wehus Institute of Theoretical Astrophysics, University of Oslo B. Westbrook University of California, Berkeley, Department of Physics, Berkeley G. Weymann-Despres Université Paris-Saclay, CNRS/IN2P3, IJCLab E.J. Wollack NASA Goddard Space Flight Center M. Zannoni University of Milano Bicocca, Physics Department Y. Zhou International Center for Quantum-field Measurement Systems for Studies of the Universe and Particles (QUP), High Energy Accelerator Research Organization (KEK) Large angular scale surveys in the absence of atmosphere are essential for measuring the primordial B-mode power spectrum of the Cosmic Microwave Background (CMB). Since this proposed measurement is about three to four orders of magnitude fainter than the temperature anisotropies of the CMB, in-flight calibration of the instruments and active suppression of systematic effects are crucial. We investigate the effect of changing the parameters of the scanning strategy on the in-flight calibration effectiveness, the suppression of the systematic effects themselves, and the ability to distinguish systematic effects by null-tests. Next-generation missions such as LiteBIRD, modulated by a Half-Wave Plate (HWP), will be able to observe polarisation using a single detector, eliminating the need to combine several detectors to measure polarisation, as done in many previous experiments and hence avoiding the consequent systematic effects. While the HWP is expected to suppress many systematic effects, some of them will remain. We use an analytical approach to comprehensively address the mitigation of these systematic effects and identify the characteristics of scanning strategies that are the most effective for implementing a variety of calibration strategies in the multi-dimensional space of common spacecraft scan parameters. We verify that LiteBIRD's standard configuration yields good performance on the metrics we studied. We also present Falcons.jl, a fast spacecraft scanning simulator that we developed to investigate this scanning parameter space. No potential conflict of interest relevant to this article was reported.

IOP Publishing Acta Medica Okayama 1882-0778 16 9 2023 Active control of localized mode and transmission in topological phononic waveguides by non-Hermitian modulation 094001 EN Md. Shuzon Ali Department of Electrical and Electronic Engineering, Okayama University Yusuke Hata Department of Electrical and Electronic Engineering, Okayama University Kenji Tsuruta Department of Electrical and Electronic Engineering, Okayama University We demonstrate the switching behavioral differences between lossy and nearly lossless edge-mode propagation by non-Hermitian modulation based on the phononic band design of a C3v symmetric, two-dimensional phononic crystal with a unit cell composed of three air-filled circular holes in polydimethylsiloxane. We numerically show that strong loss effects lead to the extinction of the localized modes. This mechanism is analogous to the bound-to-unbound transition in non-Hermitian quantum systems. This result suggests that large variations in non-Hermitian modulation can be used for the active control of edge-mode propagation along topological interfaces. No potential conflict of interest relevant to this article was reported.

IOP Publishing Acta Medica Okayama 0021-4922 62 SJ 2023 Reconfigurable waveguide based on valley topological phononic crystals with local symmetry inversion via continuous translation SJ1002 EN Md. Shuzon Ali Department of Electrical and Electronic Engineering, Okayama University Motoki Kataoka Department of Electrical and Electronic Engineering, Okayama University Masaaki Misawa Department of Electrical and Electronic Engineering, Okayama University Kenji Tsuruta Department of Electrical and Electronic Engineering, Okayama University We proposed a reconfigurable valley topological acoustic waveguide constructed using a 2D phononic crystal (PnC) with C3v symmetric arrangement of three rods in the unit cell. An interface between two types of PnCs with differently oriented unit cells exhibits high robustness of the valley transport of acoustic waves via the topologically protected state. Structural reconfiguration was introduced by the continuous translation of rod arrays in the PnCs. The topological phase transition in this translational change was quantitatively identified by the change in the Berry curvature. The translation of the rods leaves a dimer array at the interface, creating a localized/defective mode along the waveguide. Despite the presence of the localized mode, the acoustic wave can propagate along the reconfigurable waveguide the same as the original waveguide. The continuous translation of a rod array can be used to turn on and off the bandgap. This can be a new approach to design a robust acoustic device with a high reconfigurability. No potential conflict of interest relevant to this article was reported.

IOP Publishing Acta Medica Okayama 0021-4922 63 3 2024 Evaluation of transducer for cryogenic actuators by equivalent circuit model 03SP03 EN Kazuki Kubo Graduate School of Environment, Life, Natural, Science and Technology, Okayama University Kairi Yagi Graduate School of Environment, Life, Natural, Science and Technology, Okayama University Takefumi Kanda Graduate School of Environment, Life, Natural, Science and Technology, Okayama University Koa Yasuda Graduate School of Environment, Life, Natural, Science and Technology, Okayama University Daisuke Yamaguchi Graduate School of Environment, Life, Natural, Science and Technology, Okayama University Shuichi Wakimoto Graduate School of Environment, Life, Natural, Science and Technology, Okayama University Cryogenic environments are increasingly used in scientific and industrial fields. Recently, cryogenic environments are also used for storage and supply of liquid hydrogen, which is considered essential for the realization of a decarbonized society. Actuators to drive a valve that controls such a low-temperature fluid are required. In this study, a piezoelectric transducer that can be driven in the cryogenic environment has been fabricated and evaluated. Although the performance of piezoelectric elements degrades at cryogenic temperatures in general, the application of a preload can suppress the degradation of performance. Equivalent circuits were used for evaluation, and force factors and figures of merit were compared. As a result, the force factor was as high as that at RT even at cryogenic temperatures, and a high figure of merit was obtained. The result indicates that the transducer can be used for the driving of micro actuator at cryogenic temperature. No potential conflict of interest relevant to this article was reported.

IOP Publishing Acta Medica Okayama 0021-4922 62 12 2023 Photoelectron holographic evidence for the incorporation site of Se and suppressed atomic displacement of the conducting layer of La(O,F)BiSSe 125001 EN YaJun Li Engineering Research Center of Integrated Circuit Packaging and Testing, Ministry of Education, Tianshui Normal University ZeXu Sun Nara Institute of Science and Technology (NAIST) Noriyuki Kataoka Graduate School of Natural Science and Technology, Okayama University Taro Setoguchi Graduate School of Natural Science and Technology, Okayama University Yusuke Hashimoto Nara Institute of Science and Technology (NAIST) Soichiro Takeuchi Nara Institute of Science and Technology (NAIST) Shunjo Koga Nara Institute of Science and Technology (NAIST) Kazuhisa Hoshi Department of Physics, Tokyo Metropolitan University Yoshikazu Mizuguchi Department of Physics, Tokyo Metropolitan University Tomohiro Matsushita Nara Institute of Science and Technology (NAIST) Takanori Wakita Graduate School of Natural Science and Technology, Okayama University Yuji Muraoka Graduate School of Natural Science and Technology, Okayama University Takayoshi Yokoya Graduate School of Natural Science and Technology, Okayama University La(O,F)BiS2-xSex is a layered material that is considered to be a candidate exotic superconductor as well as a promising thermoelectrical material. We performed soft X-ray photoelectron holography to study the Se incorporation site and the local atomic arrangement of the conducting layer. A comparison of the experimental holograms with the simulated holograms indicates that Se atoms preferentially occupy the S sites in the conducting Bi–S plane of La(O,F)BiS2. A comparison between the state-of-the-art holographic reconstructions of La(O,F)BiSSe and La(O,F)BiS2 suggests that Se substitution suppresses the displacement of S atoms in La(O,F)BiS2. These results provide photoelectron holographic evidence for the Se incorporation site and the Se-induced suppression of in-plane disorder. No potential conflict of interest relevant to this article was reported.

IOP Publishing Acta Medica Okayama 0953-2048 35 5 2022 Experiment and numerical simulation of the combined effect of winding, cool-down, and screening current induced stresses in REBCO coils 054001 EN Hiroshi Ueda Graduate School of Natural Science and Technology, Okayama University Hideaki Maeda Japan Science and Technology Agency Yu Suetomi RIKEN Center for Biosystems Dynamics Research Yoshinori Yanagisawa RIKEN Center for Biosystems Dynamics Research This paper overviews the combined effects of winding, cool-down, and screening current-induced stresses in REBCO coils. First, a simulation method to model the circumferential stress modification effect due to the screening-current is overviewed. The simulation includes coil winding, cooling down, and coil charge up to the operating current. Second, we will compare the numerical simulation results with the experimental results. The numerical simulations for a dry coil and an epoxy impregnated coil agree well with the experimental results. Third, the enhanced circumferential stress did not degrade the performance of a dry winding REBCO coil, but the improved increased compressive stress buckled the coil structure. Finally, it is demonstrated that epoxy impregnation has beneficial effects in reducing the stress modification effect. However, the circumferential stress is enormously enhanced at the coil ends, sometimes resulting in degradation of the coil performance. No potential conflict of interest relevant to this article was reported.

IOP Publishing Acta Medica Okayama 0021-4922 62 SJ 2023 Acoustic metasurfaces and topological phononics for acoustic/elastic device design SJ0803 EN Kenji Tsuruta Department of Electrical and Electronic Engineering, Okayama University This paper reviews recent progress in acoustic metasurfaces and the novel concept of "topological acoustic/phononics" for designing compact yet efficient acoustic devices. After a brief review of this research area and its impact on ultrasonic technologies, some of the efforts to develop highly efficient sound absorption devices using acoustic metasurfaces are introduced. A resonance-based mechanism to achieve efficient absorption in metasurface structures thinner than the wavelength of the incident sound is briefly discussed, and its extensions to a broad spectrum are highlighted. Next, a valley topological phononic system is introduced, and its applications to the design of phononic waveguides are exemplified. The band structure design for extracting topologically protected edge modes is shown together with a numerical and experimental demonstration of the robustness of phononic waveguides constructed in both acoustic and elastic regimes. No potential conflict of interest relevant to this article was reported.

IOP Publishing Acta Medica Okayama 1741-2560 18 4 2021 Modelling the visual response to an OUReP retinal prosthesis with photoelectric dye coupled to polyethylene film 045006 EN Koichiro Yamashita Graduate School of Natural Science and Technology, Okayama University Prathima Sundaram Department of Electrical and Computer Engineering, University of Toronto Tetsuya Uchida Graduate School of Natural Science and Technology, Okayama University Toshihiko Matsuo Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Willy Wong Department of Electrical and Computer Engineering, University of Toronto Objective. Retinal prostheses have been developed to restore vision in blind patients suffering from diseases like retinitis pigmentosa. Approach. A new type of retinal prosthesis called the Okayama University-type retinal prosthesis (OUReP) was developed by chemically coupling photoelectric dyes to a polyethylene film surface. The prosthesis works by passively generating an electric potential when stimulated by light. However, the neurophysiological mechanism of how OUReP stimulates the degenerated retina is unknown. Main results. Here, we explore how the OUReP affects retinal tissues using a finite element model to solve for the potential inside the tissue and an active Hodgkin-Huxley model based on rat vision to predict the corresponding retinal bipolar response. Significance. We show that the OUReP is likely capable of eliciting responses in retinal bipolar cells necessary to generate vision under most ambient conditions. No potential conflict of interest relevant to this article was reported.

IOP Publishing Acta Medica Okayama 1748-6041 16 4 2021 Development of highly durable retinal prosthesis using photoelectric dyes coupled to polyethylene film and quantitative in vitro evaluation of its durability 045001 EN Koichiro Yamashita Graduate School of Natural Science and Technology, Okayama University Tenu Tanaka Graduate School of Natural Science and Technology, Okayama University Toshihiko Matsuo Graduate School of Interdisciplinary Science and Engineering in Health Systems Tetsuya Uchida Graduate School of Natural Science and Technology, Okayama University Retinal prostheses have been developed to restore vision in blind patients suffering from such diseases as retinitis pigmentosa. In our previous studies, we developed a retinal prosthesis called dye-coupled film by chemical coupling of photoelectric dyes, which absorb light and then generate electrical potential, with a polyethylene film surface. The dye-coupled film is nontoxic, and we recovered the vision of a monkey with macular degeneration. The amount of dye on the dye-coupled film, however, decreased to one-third after five months in the monkey’s eye. The photoelectric dye consists of a cation with photoresponsivity and a bromide ion (Br−). Therefore, an anion-exchange reaction could be applied to the dye-coupled film to improve its durability. In this study, the anion-exchange reaction was conducted using bis(trifluoromethanesulfonyl)imide ion (TFSI−), which has lower nucleophilicity than Br−. First, the long-term durability was examined without using animal subjects and in a short period. Subsequently, an elemental analysis was performed to confirm the exchange between Br− and TFSI−, and chemical properties, such as photoresponsivity and durability, before and after the anion exchange, were evaluated. It was quantitatively confirmed that the long-term durability of dye-coupled films can be evaluated in an in vitro environment and in a short period of one-thirtieth by utilizing a saline solution at 60°C, compared with an in vivo environment. In addition, the durability of the dye-coupled film with TFSI− was improved to 270%–320% compared with that of the dye-coupled film with Br−. No potential conflict of interest relevant to this article was reported.

IOP Publishing Acta Medica Okayama 0021-4922 60 SD 2021 Low-frequency sound absorbing metasurface using multilayer split resonators SDDA01 EN Shota Takasugi Department of Electrical and Electronic Engineering, Okayama University Keita Watanabe Department of Electrical and Electronic Engineering, Okayama University Masaaki Misawa Department of Electrical and Electronic Engineering, Okayama University Kenji Tsuruta Department of Electrical and Electronic Engineering, Okayama University Among the acoustic metasurfaces that can control the propagation of sound waves with the structure far thinner than the wavelength at the operating frequency, the split tube structure has shown its effectiveness in the lower frequency band. Here we focus on multiply layered split tubes to broaden the absorption spectrum. By numerical analysis, we show up-to six-layer structure possessing wideband (1–1000 Hz) sound absorption. The absorbing peaks in the frequency band below 1000 Hz are shown to be multiplexed not only by simple superposition of vibrational modes of each layer, but also by hybridization of the modes indicating collective motion of tubes. No potential conflict of interest relevant to this article was reported.

IOP Publishing Acta Medica Okayama 1367-2630 21 2019 Superconductivity in a new layered triangular-lattice system Li2IrSi2 093056 EN K Horigane Research Institute for Interdisciplinary Science, Okayama University, K Takeuchi Graduate School of natural science and technology, Okayama University D Hyakumura Department of Physics and Mathematics, Aoyama Gakuin University R Horie Research Institute for Interdisciplinary Science, Okayama University T Sato Institute for Materials Research, Tohoku University T Muranaka Department of Engineering Science, University of Electro-Communications K Kawashima Department of Physics and Mathematics, Aoyama Gakuin University H Ishii National Synchrotron Radiation Research Center Y Kubozono Research Institute for Interdisciplinary Science, Okayama University S Orimo Institute for Materials Research, Tohoku University M Isobe National Institute for Materials Science (NIMS) J Akimitsu Research Institute for Interdisciplinary Science, Okayama University We report on the crystal structure and superconducting properties of a novel iridium-silicide, namely Li2IrSi2. It has a Ag2NiO2-type structure (space group R-3m) with the lattice parameters a = 4.028 30(6) Å and c = 13.161 80(15) Å. The crystal structure comprises IrSi2 and double Li layers stacked alternately along the c-axis. The IrSi2 layer includes a two-dimensional Ir equilateral-triangular lattice. Electrical resistivity and static magnetic measurements revealed that Li2IrSi2 is a type-II superconductor with critical temperature (Tc) of 3.3 K. We estimated the following superconducting parameters: lower critical field Hc1(0) ~ 42 Oe, upper critical field Hc2(0) ~ 1.7 kOe, penetration depth λ0 ~ 265 nm, coherence length ξ0 ~ 44 nm, and Ginzburg–Landau parameter κGL ~ 6.02. The specific-heat data suggested that superconductivity in Li2IrSi2 could be attributed to weak-coupling Cooper pairs. No potential conflict of interest relevant to this article was reported.

IOP Publishing Acta Medica Okayama 0953-8984 33 3 2020 Soft x-ray irradiation induced metallization of layered TiNCl 035501 EN Noriyuki Kataoka Graduate School of Natural Science and Technology, Okayama University Masashi Tanaka Graduate School of Engineering, Kyushu Institute of Technology Wataru Hosoda Graduate School of Natural Science and Technology, Okayama University Takumi Taniguchi Graduate School of Natural Science and Technology, Okayama University Shin-ichi Fujimori Materials Sciences Research Center, Japan Atomic Energy Agency Takanori Wakita Graduate School of Natural Science and Technology, Okayama University Yuji Muraoka Graduate School of Natural Science and Technology, Okayama University Takayoshi Yokoya Graduate School of Natural Science and Technology, Okayama University We have performed soft x-ray spectroscopy in order to study the photoirradiation time dependence of the valence band structure and chemical states of layered transition metal nitride chloride TiNCl. Under the soft x-ray irradiation, the intensities of the states near the Fermi level (EF) and the Ti3+ component increased, while the Cl 2p intensity decreased. Ti 2p–3d resonance photoemission spectroscopy confirmed a distinctive Fermi edge with Ti 3d character. These results indicate the photo-induced metallization originates from deintercalation due to Cl desorption, and thus provide a new carrier doping method that controls the conducting properties of TiNCl. No potential conflict of interest relevant to this article was reported.

IOP Publishing Acta Medica Okayama 1755-1307 465 2020 Animal Biotechnology Roles in Livestock Production 012001 EN Hiroaki Funahashi Department of Animal Science, Graduate School of Environmental and Life Science, Okayama University Currently, meat and milk productions are significantly increasing especially in Asia. The supply of these products is vital to people's health and well-being, whereas the efficiency of beef production appears to be still lower than other meat productions. Improvements in the quality and functionality of their livestock products, as well as their production efficiency, are required for further production. Animal biotechnologies have contributed to genetic improvement, genetic diversity maintenance of domestic animals, etc. Basic animal biotechnologies, such as artificial insemination and embryo transfer, have been well established and applied as powerful tools for genetic improvement of livestock. In the applications of artificial insemination techniques, the use of sexed semen has been now widely spread, and also efforts are also made in the development of the technology using a small amount of sperm. For embryo transfer, several types of vitrification technologies have been applied to improve pregnancy rates and contributed to the international/domestic supply of livestock embryos. Conventional animal biotechnologies, such as in vitro fertilization and intracellular sperm injection, have been applied to not only livestock production and also human-assisted reproductive medicine. For in-vitro production of embryos in domestic animals, currently, oocytes have been collected from medium or large follicles (3-6 mm or larger in diameter) of ovaries. Although the oocytes derived from small follicles (less than 3 mm in diameter) exist more on the surface of ovaries, the developmental competence of the oocytes has been known to be significantly lower than those from medium follicles. If we could improve the competence of oocytes derived from small follicles significantly, we may be able to increase the number of female gamete resources for in vitro embryo production. Also, the development of techniques for producing transgenic and cloned animals has greatly contributed to the creation of pharmaceuticals and organs for xenotransplantation. Recently, furthermore, genome editing technologies, such as combined use of CRISPR/Cas9 and PiggyBac, have been developed and have made it possible to correct specific parts of the genome and introduce mutations by homologous recombination. In this review, I would like to discuss the application and progress of the above biotechnologies, including our recent research results. No potential conflict of interest relevant to this article was reported.

IOP Publishing Acta Medica Okayama 2632-3338 1 3 2020 On the Occurrence of Clathrate Hydrates in Extreme Conditions: Dissociation Pressures and Occupancies at Cryogenic Temperatures with Application to Planetary Systems 80 EN Hideki Tanaka Research Institute for Interdisciplinary Science, Okayama University Takuma Yagasaki Research Institute for Interdisciplinary Science, Okayama University Masakazu Matsumoto Research Institute for Interdisciplinary Science, Okayama University We investigate the thermodynamic stability of clathrate hydrates at cryogenic temperatures from the 0 K limit to 200 K in a wide range of pressures, covering the thermodynamic conditions of interstellar space and the surface of the hydrosphere in satellites. Our evaluation of the phase behaviors is performed by setting up quantum partition functions with variable pressures on the basis of a rigorous statistical mechanics theory that requires only the intermolecular interactions as input. Noble gases, hydrocarbons, nitrogen, and oxygen are chosen as the guest species, which are key components of the volatiles in such satellites. We explore the hydrate/water two-phase boundary of those clathrate hydrates in water-rich conditions and the hydrate/guest two-phase boundary in guest-rich conditions, either of which occurs on the surface or subsurface of icy satellites. The obtained phase diagrams indicate that clathrate hydrates can be in equilibrium with either water or the guest species over a wide range far distant from the three-phase coexistence condition and that the stable pressure zone of each clathrate hydrate expands significantly on intense cooling. The implication of our findings for the stable form of water in Titan is that water on the surface exists only as clathrate hydrate with the atmosphere down to a shallow region of the crust, but clathrate hydrate in the remaining part of the crust can coexist with water ice. This is in sharp contrast to the surfaces of Europa and Ganymede, where the thin oxygen air coexists exclusively with pure ice. No potential conflict of interest relevant to this article was reported.

IOP Publishing Acta Medica Okayama 1755-1307 240 3 2019 Numerical study of air-entraining and submerged vortices in a pump sump 032001 EN Shinichiro Yanase Department of Mechanical and Systems Engineering, Okayama University Ryo Yamasaki Technical Division, Tsurumi Manufacturing Co. Toshinori Kouchi Department of Mechanical and Systems Engineering, Okayama University Shunsuke Hosoda Department of Mechanical and Systems Engineering, Okayama University Yasunori Nagata Department of Mechanical and Systems Engineering, Okayama University Higuchi Shunji Technical Division, Tsurumi Manufacturing Co. Toshihiko Kawabe Technical Division, Tsurumi Manufacturing Co. Toshihiro Takami Department of Mechanical and Systems Engineering, Okayama University of Science Numerical detection of harmful vortices in pump sumps, such as an air-entraining vortex (AEV) and a submerged vortex (SMV), is crucially important to develop the drain pump machinery. We performed numerical simulations of the benchmark experiments of the pump sump conducted by Matsui et al. (2006 and 2016) using the OpenFOAM and compared the simulation results with the experimental data considering the effects of turbulence model, grid density and detection method of the vortices. We studied the threshold of the gas-liquid volume fraction of the VOF method and the second invariant of velocity gradient tensor to identify AEV and SMV. The methods proposed in the present paper were found to be very effective for the detection of the vortices, and the simulation results by RANS with the SST k-omega model successfully reproduced the experimental data. LES with the Smagorinsky model, however, was sensitive to the grid system and difficult to reproduce the experimental data even for the finest grid system having 3.7 million cells in the present study. No potential conflict of interest relevant to this article was reported.

IOP Publishing Acta Medica Okayama 2515-7639 2 3 2019 Solid-state nuclear magnetic resonance study of setting mechanism of beta-tricalcium phosphate-inositol phosphate composite cements EN Toshiisa Konishi Graduate School of Natural Science and Technology, Okayama University Kohei Yamashita Graduate School of Natural Science and Technology, Okayama University Kohei Nagata Organization for the Strategic Coordination of Research and Intellectual Property, Meiji University Poon Nian Lim Department of Mechanical Engineering, National University of Singapore Eng San Thian Department of Mechanical Engineering, National University of Singapore Mamoru Aizawa Department of Applied Chemistry, School of Science and Technology, Meiji University Solid-state nuclear magnetic resonance (NMR) spectroscopy is a technique, which can be used to provide insight into the chemical structure of non-crystalline and crystalline materials. Hence, the present study aimed to elucidate the setting mechanism of CPC, which was fabricated using beta -tricalcium phosphate (beta -TCP)-inositol phosphate (IP6) composite powder using NMR In addition, the effect of IP6 on the local chemical structure of the beta -TCP-IP6 composite powder and its hardened cement would also be investigated. The H-1 -> P-31 heteronuclear correlation NMR spectrum revealed that an amorphous hydrated layer, along with small amount of hydroxyapatite (HA) was formed on the surface of beta -TCP during the ball-milling process. Results demonstrated that the IP6 in the hydrated layer on the surface of beta -TCP inhibited the formation of HA. Moreover, the setting reaction of the cement was mainly triggered by the dissolution of the amorphous hydrated layer on beta -TCP surface, and subsequent precipitation, followed by the inter-entanglement between the HA crystals on the beta -TCP. No potential conflict of interest relevant to this article was reported.

IOP Publishing Acta Medica Okayama 2053-1591 7 5 2020 Synthesis of solvent-free conductive and flexible cellulose-carbon nanohorn sheets and their application as a water vapor sensor 056402 EN Karthik Paneer Selvam Graduate School of Natural Science and Technology, Okayama University Tomohiro Nakagawa Graduate School of Natural Science and Technology, Okayama University Tatsuki Marui Graduate School of Natural Science and Technology, Okayama University Hirotaka Inoue Graduate School of Natural Science and Technology, Okayama University Takeshi Nishikawa Graduate School of Natural Science and Technology, Okayama University Yasuhiko Hayashi Graduate School of Natural Science and Technology, Okayama University Carbon nanohorns (CNHs) are mixed with cellulose to make freestanding thin-film conductive sheets. CNHs, at different ratios (5, 10, 25, 50 wt%), form composites with cellulose (hydroxyethylcellulose). Freestanding cellulose-carbon nanohorn (CCN) sheets were fabricated using a 100 mu m-thick metal bar coater. Surfactants or any other chemical treatments to tailor the surface properties of CNHs were avoided to obtain composite sheets from pristine CNHs and cellulose. Utilizing the hygroscopic property of hydroxyethylcellulose and the electrical conductivity of CNHs paved a path to perform this experiment. The synthesis technique is simple, and the fabrication and drying of the sheets were effortless. As the loading concentration of CNH increased, the resistance, flexibility, and strength of the CCN composite sheets decreased. The maximum loading concentration possible to obtain a freestanding CCN sheet is 50 wt%. The resistance of the maximum loading concentration of CNH was 53 k omega. The response of the CCN sheets to water vapor was 4 s and recover time was 13 s, and it is feasible to obtain a response for different concentrations of water vapor. High-resolution transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, resistance measurement, tensile strength measurement, and thermogravimetric analysis were used to investigate the mechanical, morphological, electrical, and chemical properties of the CCN sheets. No potential conflict of interest relevant to this article was reported.

IOP Publishing Acta Medica Okayama 2053-1591 7 3 2020 Inhomogeneous superconductivity in thin crystals of FeSe1-xTex (x=1.0, 0.95, and 0.9) 036001 EN Ritsuko Eguchi Research Institute for Interdisciplinary Science, Okayama University Megumi Senda Graduate School of Natural Science and Technology, Okayama University Eri Uesugi Graduate School of Natural Science and Technology, Okayama University Hidenori Goto Research Institute for Interdisciplinary Science, Okayama University Akihiko Fujiwara Department of Nanotechnology for Sustainable Energy, Kwansei Gakuin University Yasuhiko Imai Japan Synchrotron Radiation Research Institute (JASRI) Shigeru Kimura Japan Synchrotron Radiation Research Institute (JASRI) Takashi Noji Department of Applied Physics, Tohoku University Yoji Koike Department of Applied Physics, Tohoku University Yoshihiro Kubozono Research Institute for Interdisciplinary Science, Okayama University We investigated the temperature dependence of resistivity in thin crystals of FeSe1-xTex (x = 1.0, 0.95, and 0.9), though bulk crystals with 1.0 x 0.9 are known to be non-superconducting. With decreasing thickness of the crystals, the resistivity of x = 0.95 and 0.9 decreases and reaches zero at a low temperature, which indicates a clear superconducting transition. The anomaly of resistivity related to the structural and magnetic transitions completely disappears in 55- to 155-nm-thick crystals of x = 0.9, resulting in metallic behavior in the normal state. Microbeam x-ray diffraction measurements were performed on bulk single crystals and thin crystals of FeSe1-xTex. A significant difference of the lattice constant, c, was observed in FeSe1-xTex, which varied with differing Te content (x), and even in crystals with the same x, which was mainly caused by inhomogeneity of the Se/Te distribution. It has been found that the characteristic temperatures causing the structural and magnetic transition (T-t), the superconducting transition (T-c), and the zero resistivity (T-c(zero)) are closely related to the value of c in thin crystals of FeSe1-xTex. No potential conflict of interest relevant to this article was reported.

IOP Publishing Acta Medica Okayama 0964-1726 20 10 2011 Design of a variable-stiffness robotic hand using pneumatic soft rubber actuators EN Jun-ya Nagase Shuichi Wakimoto Toshiyuki Satoh Norihiko Saga Koichi Suzumori In recent years, Japanese society has been ageing, engendering a labor shortage of young workers. Robots are therefore expected to be useful in performing tasks such as day-to-day support for elderly people. In particular, robots that are intended for use in the field of medical care and welfare are expected to be safe when operating in a human environment because they often come into contact with people. Furthermore, robots must perform various tasks such as regrasping, grasping of soft objects, and tasks using frictional force. Given these demands and circumstances, a tendon-driven robot hand with a stiffness changing finger has been developed. The finger surface stiffness can be altered by adjusting the input pressure depending on the task. Additionally, the coefficient of static friction can be altered by changing the surface stiffness merely by adjusting the input air pressure. This report describes the basic structure, driving mechanism, and basic properties of the proposed robot hand. No potential conflict of interest relevant to this article was reported.