長鎖非コードRNA Lionheartは圧負荷による心機能低下を緩和する

京都大学新制・課程博士博士(医学)甲第23060号医博第4687号新制||医||1048(附属図書館)京都大学大学院医学研究科医学専攻(主査)教授 齊藤 博英, 教授 湊谷 謙司, 教授 萩原 正敏学位規則第4条第1項該当Doctor of Medical ScienceKyoto UniversityDFA

Direct observation of local chemical ordering in a few nanometer range in CoCrNi medium-entropy alloy by atom probe tomography and its impact on mechanical properties

ミディアムエントロピー合金の局所規則構造の原子レベル観察に成功 --新しい高強度合金の設計・開発に期待--. 京都大学プレスリリース. 2021-08-30.Local chemical ordering in CoCrNi medium-entropy alloy (MEA) was directly observed by the use of atom probe tomography. It was found that the densities of Cr, Co, and Ni were almost the same along the [111] direction, while those along the [001] direction were modulated to take a slightly enhanced and depleted value alternately within approximately 10 atomic layers corresponding to about 2 nm. The degree of modulation of Co and Ni was stronger than that of Cr. It was suggested that Cr-rich {001} atomic layers and (Ni + Co)-rich {001} layers tended to align mutually in the face-centered-cubic CoCrNi solid solution alloy. The mechanical properties of the MEA was found not to be affected by the presence of the local chemical ordering

<原著>海面位での大気ミュー粒子測定 : 最尤法を使った解析結果

正確な大気ミューオン・フラックス測定は,大気ニュートリノ物理や反陽子検出実験等に必要とされる。重要な科学の基礎となる結果に利用されるために,異なった計測方法で測定される必要がある。近年様々な実験グループからの大気ミューオン測定結果が報告されている。(Rastin, CAPRICE, BESS等。)これらの実験グループの使用するミューオン・スペクトロメーターは2つに大別される。1つは超伝導マグネットを使用したものでもう1つは鉄芯マグネットを使用したものである。超伝導マグネットを使用した検出器は大気上空での観測用に作られているため長時間の観測ができない。一方,鉄芯マグネットを使用した検出器はマグネット中の電磁散乱の影響を受ける。岡山グループは,鉄芯マグネットを使用した検出器で測定している。この解析にはマグネット中の電磁散乱の影響を除去する解析法,即ち最尤法を用いている。最尤法の適応とそれを適応した測定結果を公表する。Exact measurements of atmospheric muon fluxes are needed for atmospheric neutrino physics, experiments detecting the anti-proton and so on. The different measurements methods are utilized for the fundamental important science. Results of the atmospheric muon measurement are reported by various groups in recent years. (Rastin, CAPRICE, BESS, etc.) The spectrometers used by these groups are divided by two types, one is constructed with superconducting magnets and another is with solid iron core magnets. The detector with superconducting magnets is not possible to measure for long observation time since it is made to observe in the upper sky. On the other hand, the results using a solid iron core magnet detector are influenced by large coulomb scattering in the magnet. The Okayama group has been measuring the atmospheric muons with a solid iron core magnet detector. I analyze using the maximum likelihood methods which reject the large coulomb scattering effect in the magnet. I report the adoption of the maximum likelihood methods in the atmospheric muon analyses and the results

コンピュータ・クラスタ「並列統合システム」の開発

昨今，プリント基板の上に，必要なものに絞ったCPUと周辺部品，入出力インタフェースとコネクタを付けただけのコンピュータ，いわゆるシングルボードコンピュータが注目されている。今回，Banana PiとRaspberry Pi合わせて24台組み合わせてコンピュータ・クラスタ「並列統合システム」を製作し，実際にモンテカルロ・シミュレーションを走らせた。この並列統合システムの具体的製作方法と計算能力について述べる。In recent years, attention has been paid to a so-called single board computer built on a single circuit board, with microprocessor(s), memory, input/output (I/O) and other features required of a functional computer. This time, I combined 23 Banana Pi and a Raspberry Pi together to create a computer cluster “the parallel integrated system” and actually run Monte Carlo simulations. The specific production method and computational capacity of this parallel integrated system will be described

Global understanding of deformation behavior in CoCrFeMnNi high entropy alloy under high-strain torsion deformation at a wide range of elevated temperatures

A number of recent studies have investigated deformation behavior of CoCrFeMnNi (Cantor) alloy at elevated temperatures by using plastic deformation to relatively small strains such as tensile testing. Therefore, little has been known about the deformation behavior of this typical FCC high-entropy alloy (HEA) in case that the material is subjected to ultra-high strains at various temperatures. In the present study, the equi-atomic CoCrFeMnNi HEA was successfully deformed over a wide range of strains (von Mises equivalent strains (ε) of 1∼5.5) by torsion at various temperatures ranging from 25 °C to 1100 °C. Deformation twinning was extensively activated at moderate to high strains (ε ≥ 1) and even found in the deformation at elevated temperatures as high as 600 °C where deformation twinning is not normally expected in Cantor alloy. The HEA showed outstanding deformability and the highest strains to fracture reached 4.0∼5.5 at low temperatures below 400 °C. The excellent deformability was attributed to the extensive twin activities including the formation of twin bundles and thin nanotwins as well as microbands formation. However, localized shear deformation that was promoted by the high straining at low temperatures could negatively affect the deformability. The heavy deformation led to a significant reduction of the grain sizes down to 50 nm∼150 nm. A sudden shortage of ductility occurred at intermediate temperatures, where small strains to fracture (1.2∼1.3) were realized at 600 °C∼700 °C. The embrittlement was accompanied by the formation of micro-voids at grain boundaries and intergranular fracture. The susceptibility to the embrittlement was caused by the precipitation of Cr-rich σ-phases at grain boundaries. Dynamic recrystallization (DRX) of the FCC matrix led to an accelerated softening at high temperatures above 600 °C. Nucleation and growth of DRX grains in Cantor alloy were not fundamentally different from those in conventional FCC alloys. This study gives an insight into the microstructure evolution and mechanical response in Cantor alloy under shear deformation over a wide range of strains and temperatures

Destruction of mesoscopic chemically modulated domains in single phase high entropy alloy via plastic deformation

Chemically modulated mesoscopic domains in a fcc single phase CrMnFeCoNi equi-atomic high entropy alloy (HEA) are detected by small angle diffraction performed at a synchrotron radiation facility, whereas the mesoscopic domains cannot be detected by conventional X-ray diffraction and 2D mappings of energy dispersive X-ray spectroscopy by scanning electron microscopy and scanning transmission electron microscopy. The mesoscopic domains are deformed and shrieked, and finally destructed by plastic deformation, which is supported by the comprehensive observations/measurements, such as electrical resistivity, Vickers hardness, electron backscattering diffraction, and hard X-ray photoemission spectroscopy. The destruction of the mesoscopic domains causes the decrease in electrical resistivity via plastic deformation, so called K-effect, which is completely opposite to the normal trend of metals. We confirmed that the presence and the size of local chemical ordering or short-range order domains in the single phased HEA, and furthermore, Cr and Mn are related to form the domains