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山中 謙太*; 黒田 あす美*; 伊藤 美優*; 森 真奈美*; Bian, H.*; 菖蒲 敬久; 佐藤 茂男*; 千葉 明彦*
Additive Manufacturing, 37, p.101678_1 - 101678_12, 2021/01
被引用回数：24 パーセンタイル：86.94(Engineering, Manufacturing)Ti-6Al-4V alloy is widely used in aerospace and biomedical industries, and its preparation using additive manufacturing techniques has recently attracted considerable attention. Herein, the dislocation structures developed during electron beam and laser beam powder-bed fusion (EB-PBF and LB-PBF, respectively) of the Ti-6Al-4V alloy were quantitatively examined via XRD line profile analysis. Accordingly, a higher dislocation density and finer crystallite size were observed at the top cross-section from the XRD line profile analysis, suggesting that the extent of phase decomposition depended on the duration of the exposure to the elevated temperature. Nonetheless, the saturated dislocation density was as high as 10
m
, where dislocation strengthening affected the overall strength of the EB-PBF specimen. Diffraction peaks of sufficient intensity that enabled the analysis of the dislocation structures in both the 
(')-matrix and the nanosized beta-phase precipitates at the (')-laths were obtained under high-energy synchrotron radiation; this revealed that the beta-phase had a much higher dislocation density than the surrounding (')-matrix. The enhanced dislocation accumulation in the nanosized 
-phase precipitates probably reflects the elemental partitioning that occurred during post-solidification cooling. The valuable insights provided in this study are expected to promote further development of alloy preparation using additive manufacturing processes.
-to-
martensitic transformation of biomedical Co-Cr-Mo alloys by introducing parent phase lattice defects森 真奈美*; 山中 謙太*; 佐藤 茂男*; 椿 真貴*; 佐藤 こずえ*; 熊谷 正芳*; 今福 宗行*; 菖蒲 敬久; 千葉 明彦*
Journal of the Mechanical Behavior of Biomedical Materials, 90, p.523 - 529, 2019/02
被引用回数：19 パーセンタイル：69.91(Engineering, Biomedical)In this study, we examined the effect of pre-existing dislocation structures in a face-centered cubic gamma-phase on strain-induced martensitic transformation (SIMT) to produce a hexagonal close-packed epsilon-phase in a hot-rolled biomedical Co-Cr-Mo alloy. The as-rolled microstructure was characterized by numerous dislocations as well as stacking faults and deformation twins. SIMT occurred just after macroscopic yielding in tensile deformation. Using synchrotron X-ray diffraction line-profile analysis, we successfully captured the nucleation of epsilon-martensite during tensile deformation in terms of structural evolution in the surrounding gamma-matrix: many dislocations that were introduced into the gamma-matrix during the hot-rolling process were consumed to produce epsilon-martensite, together with strong interactions between dislocations in the gamma-matrix. As a result, the SIMT behavior during tensile deformation was accelerated through the consumption of these lattice defects, and the nucleation sites for the SIMT epsilon-phase transformed into intergranular regions upon hot rolling. Consequently, the hot-rolled Co-Cr-Mo alloy simultaneously exhibited an enhanced strain hardening and a high yield strength. The results of this study suggest the possibility of a novel approach for controlling the to SIMT behavior, and ultimately, the performance of the alloy in service by manipulating the initial dislocation structures.
山下 紘正*; 岡 潔; 山中 紀明*; 関 健史; Kim, K.*; 桑名 健太*; 正宗 賢*; 長縄 明大*; 土肥 健純*; 千葉 敏雄*
日本レーザー医学会誌, 33(2), p.122 - 130, 2012/08
原子力機構では配管内の保守・保全を目的として、配管内作業ツールの検討を行っている。本ツールに搭載する複合型光ファイバスコープは、観察とレーザー導光の光軸が同一である。これにより、対象となる狭い配管内での溶接・切断作業においても、目標位置での的確な作業を容易に行うことができる。一方、国立成育医療センターでは、胎児外科手術のうち、双胎間輸血症候群の治療に興味を持ち、レーザー治療の研究を進めている。本件は、原子力機構がこれまでに開発した複合型光ファイバ技術をもとに、胎盤上の血管を観察しながら、同時に、吻合している血管をレーザー光で焼灼して血流を断ち切るためのツール開発を担当し、国立成育医療センターをはじめとした、東京大学,東京電機大学などが別手段で治療方法を検討し、総合的に双胎間輸血症候群に対する治療方法を研究した成果についてまとめたものである。
櫻井 映子*; 谷内 一彦*; 石井 慶造*; 小山 亮平*; 酒巻 学*; 山中 健太郎*; 山崎 浩道*; 松山 成男*; 神谷 富裕; 佐藤 隆博; et al.
no journal, ,
脳の機能性疾患には疾患と微量金属元素の関係が示唆されており、ストレス,てんかん発作,覚せい剤など規制薬物の使用による脳の異常興奮に対して、ヒスタミン神経系が抑制的に働くことを行動薬理学的手法を用いて解析する一方、マイクロPIXE分析法を用いることによって、認知機能に関しては特にヒスタミンH1受容体の機能が深く関与していることが明らかになってきた。また、海馬の新生神経は臭素イオンをよく取り込むことが知られており、マウスの脳の元素分布を大気マイクロPIXE分析法で測定することを試みた。その結果、脳内に存在するヒスタミン受容体の種類により臭素集積量が異なり、実験行動薬理学実験との相関が見られることがわかった。
櫻井 映子*; 石井 慶造*; 山中 健太郎*; 大倉 曉*; 藤木 広太*; 山崎 浩道*; 松山 成男*; 神谷 富裕; 佐藤 隆博; 荒川 和夫*; et al.
no journal, ,
覚醒剤の使用により惹起される覚醒剤精神病では、異常行動の誘起とともに、認知機能の低下が起こることに着目し、覚醒剤を連続投与したマウスを作成して、海馬の歯状回の神経新生と脳内微量元素分布の変化を大気マイクロPIXE法で分析したところ、微量元素の分布が正常マウスとは異なる知見が得られた。
uptake rate in forests in Western Honshu寺本 宗正*; Liang, N.*; Sun, L.*; 近藤 俊明*; 小嵐 淳; 安藤 麻里子; 高木 正博*; 山中 典和*; 平野 高司*; 高木 健太郎*; et al.
no journal, ,
Forest soil is an important sink of atmospheric methane (CH) in natural terrestrial ecosystems. However, there is still large uncertainty for the spatial variation of CH4 uptake rate in forest soils. In this study, we conducted field measurements for soil CH flux and environmental parameters in five forests in Western Honshu. There were significant negative relationships between soil moisture and soil CH uptake rate in the beech forest site and the red pine forest site, indicating that heterogeneity of soil moisture was one of the dominant factors for spatial variation of soil CH absorption in the sites. On the other hand, there was no significant relationship between soil moisture and soil CH uptake rate in the other three forests, suggesting that the dominant factors for the spatial variation of soil CH absorption might be different depending on the ecosystem.
