Microstructure and Solute Segregation around the Melt-Pool Boundary of Orientation-Controlled 316L Austenitic Stainless Steel Produced by Laser Powder Bed Fusion

For this article, we studied the microstructure and solute segregation seen around the melt pool boundary of orientation-controlled 316L austenitic stainless steel produced by laser powder bed fusion, using transmission electron microscopy and energy-dispersive x-ray spectroscopy. We found that the solidification cellular microstructures could be visualized with the aid of solute segregation (Cr and Mo) during solidification. Mn–Si–O inclusions (10–15 nm in diameter) were distributed along the lamellar boundaries, as well as in the dislocation cell walls. It is believed that the grain growth of the inclusions can be effectively suppressed by rapid quenching during the laser powder-bed fusion process. A thin region without cellular microstructures was observed at the melt-pool boundary. The cellular spacing widened near the bottom of the melt-pool boundary, owing to the decrease in the cooling rate. Atomic-structure analysis at the lamellar boundary by high-resolution transmission electron microscopy revealed a local interfacial structure, which is complementary to the results of electron back-scatter diffraction.Sato K., Takagi S., Ichikawa S., et al. Microstructure and Solute Segregation around the Melt-Pool Boundary of Orientation-Controlled 316L Austenitic Stainless Steel Produced by Laser Powder Bed Fusion. Materials 16, 218 (2023); https://doi.org/10.3390/ma16010218

Excellent strength–ductility balance of Sc-Zr-modified Al–Mg alloy by tuning bimodal microstructure via hatch spacing in laser powder bed fusion

The bimodal microstructure, which comprises ultrafine grains (UFGs) forming along the melt pool boundary and relatively coarse grains inside the melt pool, is a characteristic of the Sc-Zr-modified Al–Mg-based alloy (Scalmalloy) microstructure manufactured using laser powder bed fusion (LPBF). Focusing on this microstructural feature, we investigated the improvement in the mechanical properties of LPBF-fabricated Scalmalloy by tailoring the volume fraction of UFGs. Our approach was to decrease the laser hatch spacing (d) from 0.1 to 0.04 mm, while the volume fraction of UFGs increased from 34.6 ± 0.6 % (d = 0.1 mm) to 59.5 ± 0.5 % (d = 0.06 mm). The tensile yield stress increased from 296 ± 9 (d = 0.1 mm) to 380 ± 6 MPa (d = 0.06 mm), while maintaining a large elongation (14.8 % ± 1.2 %). The yield stress and elongation were superior to those of the cast counterparts by 2.9 and 4.0 times, respectively. In the sample with d = 0.04 mm, pores formed owing to excessive thermal energy input. Additionally, we investigated multiple strengthening mechanisms of the as-fabricated alloy. This is the first study to improve the mechanical properties of LPBF-fabricated Scalmalloy by optimizing the track-to-track interval and tuning the UFG fraction.Ekubaru Y., Gokcekaya O., Ishimoto T., et al. Excellent strength–ductility balance of Sc-Zr-modified Al–Mg alloy by tuning bimodal microstructure via hatch spacing in laser powder bed fusion. Materials and Design, 221, 110976. https://doi.org/10.1016/j.matdes.2022.110976

Periodontal Tissue as a Biomaterial for Hard-Tissue Regeneration following bmp-2 Gene Transfer

The application of periodontal tissue in regenerative medicine has gained increasing interest since it has a high potential to induce hard-tissue regeneration, and is easy to handle and graft to other areas of the oral cavity or tissues. Additionally, bone morphogenetic protein-2 (BMP-2) has a high potential to induce the differentiation of mesenchymal stem cells into osteogenic cells. We previously developed a system for a gene transfer to the periodontal tissues in animal models. In this study, we aimed to reveal the potential and efficiency of periodontal tissue as a biomaterial for hard-tissue regeneration following a bmp-2 gene transfer. A non-viral expression vector carrying bmp-2 was injected into the palate of the periodontal tissues of Wistar rats, followed by electroporation. The periodontal tissues were analyzed through bone morphometric analyses, including mineral apposition rate (MAR) determination and collagen micro-arrangement, which is a bone quality parameter, before and after a gene transfer. The MAR was significantly higher 3–6 d after the gene transfer than that before the gene transfer. Collagen orientation was normally maintained even after the bmp-2 gene transfer, suggesting that the bmp-2 gene transfer has no adverse effects on bone quality. Our results suggest that periodontal tissue electroporated with bmp-2 could be a novel biomaterial candidate for hard-tissue regeneration therapy.Kawai M.Y., Ozasa R., Ishimoto T., et al. Periodontal Tissue as a Biomaterial for Hard-Tissue Regeneration following bmp-2 Gene Transfer. Materials, 15, 3, 993. https://doi.org/10.3390/ma15030993

Proposal of clustering technique in P2P network

近年、ファイル共有やコミュニケーションツールなどにおいて、 P2Pネットワークアプリケーションが注目を集めている　P2Pネットワークでは効率的な検索や負荷分散などのため、クラスタリングと呼ばれるピアをグループ化する手法が使用されている。しかし、既存のクラスタリングは各ピアのクラスタ用パラメータが頻繁に変化した場合を想定しておらず、ユーザ同士の会話の内容によってグループ化を行うサービスなどには適さない。そこで本報告では、あえて明確なグループ化を行わないことによって柔軟なクラスタリングを行う手法を提案する.また、本手法の適応例としてオンラインゲームの多人数参加型テトリスを実装した。 In recent years, lots of file sharing applications and communication tools based on the P2P network system have been used. On the P2P network, grouping mechanism called clustering is used to increase efficiency of information search or load balancing. However, existing clustering mechanisms does not react to frequent move of peer. Therefore, these axe not suitable for network applications such as communication tools based on groups of peer which are organized according to content of communication. In this report, we proposed clustering mechanism which does not provide strict grouping but flexible grouping, by which a peer is allowed to belong to several groups. Furthermore, we implemented trial application, massively multiplayer online Tetris, as example of network application with proposal clustering mechanism

<原著>日本における肝内結石症の現状

肝内結石症はその病態の複雑さのために治療が困難なことが多く, 確立した治療法がまだ定まっていないのが現状である. 今回, 肝内結石症の発生状況とその病態について1989年から1992年に経験した肝内結石症について全国アンケート調査を行い, その変遷と特徴について他国と比較検討した. 対象としたのは200床以上の病院および大学病院の内科・外科の計2, 749施設で, アンケート回答の施設数は1, 437施設と回収率は52. 3%であった. そのうち, 1989 - 1992年の4年間に肝内結石症を経験した施設は745あり, 1887例の肝内結石症例の個人調査表を送付いただいた. 1989 - 1992年における肝内結石症の頻度は, 総胆石症例 105, 062例のうち肝内結石症は2, 353例(2. 24%) であった. しかし手術施行症例に限定すると, 胆石症としての手術73, 480例のうち, 肝内結石症は1, 280例(1. 8%)に留まった. 地域別の検討では, 肝内結石症の胆石症に占める頻度が最も高いのは九州・沖縄地方で3. 6%, 次いで東北地方の3. 4% と続き, 北海道地方は最も少なかった. 肝内結石症1, 871例のうち, 胆道手術の既往を有する症例は42. 1% にあたる788例もあり, 肝内結石症の治療後にまた肝内結石を再発した症例も788例中182例, 23. 1% と極めて多く, 治療の困難性が示された. 肝内結石症の確定診断に有用であった検査を検索すると, US と CT の肝内結石症における診断能は70% を越え, 両診断法を併せると95% 以上の肝内結石症では存在診断が可能となり, 逆に, 術中にはじめて肝内結石の存在が判明した症例は1, 887例のうち64例とわずか3. 4%に過ぎない. 肝内結石症の病型分類の変遷を IE 型で示すと, 1975 - 1979年には肝内胆管に限局する I 型はわずか20. 6% に過ぎなかったのが, 今回の全国調査では45. 5% に激増し, 逆に, 一般に総胆管結石が積み上げられたとされる IE 型はIE型はほぼ半減した. 肝内結石の種類について従来は, 肝内結石といえばビリルビンカルシウム石であるとされていたが, 今回の全国調査では, 結石の種類について記載のあった1, 375例中, ビリルビンカルレシウム石は74. 8%で, コレステロール胆石も13. 1% にあたる180例に認められていた. しかも純コレステロール石の肝内結石が31例で17. 2% もあり, そのほか混合石51. 1%, 混成石 13. 3% であった

<原著>日本における体外衝撃波結石破砕装置 (ESWL) を用いた胆石治療の現状 : 全国アンケート調査より

To assess the current status of extracorporeal shock wave lithotripsy (ESWL) for the treatment of gall-stones in Japan, we conducted a nationwide survey by sending a questionnaire to 251 institutions using this therapy. Replies were obtained from 50 institutions. The use ofESWL was investigated over the period from its introduction up to October 1992. ESWL was performed on 2, 760 of 10, 058 patients with gallstones (27. 4%). The stones were completely pulverized in 1, 021 of these 2, 760 patients (37. 0%). Complete disappearance was limited to single gallstones less than 20 mm in maximum diameter. A comparison in the number of ESWL sessions revealed no significant difference between the patients with and without a good response. Choledocholithiasis was resolved completely in 44. 0% of 157 patients who underwent ESWL for this condition and intrahepatic stones were cured in 18. 7% of 32 patients. Therefore, ESWL may be a useful form of conservative therapy for biliary calculi.体外衝撃波結石破砕装置(ESWL)を用いた胆石治療の実態を把握するために, ESWL の設置された全国251施設を対象としたアンケート調査を行い, 50施設から回答を得た. 調査期聞は各施設の ESWL 導入時から1992年10月までで, 各施設の10, 058例の胆嚢結石に対し, ESWL 治療は27. 4% に行われた. その治療効果は ESWL 施行2, 760例中, 完全消失が1, 021例37. 0% もあり, 完全消失例を得るための必要条件は, 個数は1個で, 最大径は20 mm 以下であることが判明した. 肝内・総胆管結石に対する ESWL 治療では, 総胆管結石は157例中44. 0% が消失, 肝内結石32例に対しても18. 7% が完全消失し, 今後の保存的治療法の一つとして期待される

Microstructure and Solute Segregation around the Melt-Pool Boundary of Orientation-Controlled 316L Austenitic Stainless Steel Produced by Laser Powder Bed Fusion

For this article, we studied the microstructure and solute segregation seen around the melt pool boundary of orientation-controlled 316L austenitic stainless steel produced by laser powder bed fusion, using transmission electron microscopy and energy-dispersive x-ray spectroscopy. We found that the solidification cellular microstructures could be visualized with the aid of solute segregation (Cr and Mo) during solidification. Mn&ndash;Si&ndash;O inclusions (10&ndash;15 nm in diameter) were distributed along the lamellar boundaries, as well as in the dislocation cell walls. It is believed that the grain growth of the inclusions can be effectively suppressed by rapid quenching during the laser powder-bed fusion process. A thin region without cellular microstructures was observed at the melt-pool boundary. The cellular spacing widened near the bottom of the melt-pool boundary, owing to the decrease in the cooling rate. Atomic-structure analysis at the lamellar boundary by high-resolution transmission electron microscopy revealed a local interfacial structure, which is complementary to the results of electron back-scatter diffraction

Microstructure and Solute Segregation around the Melt-Pool Boundary of Orientation-Controlled 316L Austenitic Stainless Steel Produced by Laser Powder Bed Fusion

Sato K., Takagi S., Ichikawa S., et al. Microstructure and Solute Segregation around the Melt-Pool Boundary of Orientation-Controlled 316L Austenitic Stainless Steel Produced by Laser Powder Bed Fusion. Materials 16, 218 (2023); https://doi.org/10.3390/ma16010218.For this article, we studied the microstructure and solute segregation seen around the melt pool boundary of orientation-controlled 316L austenitic stainless steel produced by laser powder bed fusion, using transmission electron microscopy and energy-dispersive x-ray spectroscopy. We found that the solidification cellular microstructures could be visualized with the aid of solute segregation (Cr and Mo) during solidification. Mn–Si–O inclusions (10–15 nm in diameter) were distributed along the lamellar boundaries, as well as in the dislocation cell walls. It is believed that the grain growth of the inclusions can be effectively suppressed by rapid quenching during the laser powder-bed fusion process. A thin region without cellular microstructures was observed at the melt-pool boundary. The cellular spacing widened near the bottom of the melt-pool boundary, owing to the decrease in the cooling rate. Atomic-structure analysis at the lamellar boundary by high-resolution transmission electron microscopy revealed a local interfacial structure, which is complementary to the results of electron back-scatter diffraction

Development of a Practical Synthesis of a Peripherally Selective Noradrenaline Reuptake Inhibitor Possessing a Chiral 6,7-<i>trans</i>-Disubstituted-1,4-oxazepane as a Scaffold

A practical synthesis of a peripherally selective noradrenaline reuptake inhibitor that has a chiral 6,7-<i>trans</i>-disubstituted-1,4-oxazepane as a new class of scaffold is described. The amino alcohol possessing the desired stereochemistry was obtained with excellent dr and ee, starting from a commercially available aldehyde via a Morita–Baylis–Hillman reaction, Michael addition, isolation as maleic acid salt, reduction, and diastereomeric salt formation with (+)-10-camphorsulfonic acid. The desired single stereoisomer obtained at an early stage of the synthesis was used for seven-membered ring formation in fully telescoped processes, providing the chiral 6,7-<i>trans</i>-disubstituted-1,4-oxazepane efficiently. In addition to controls of dr and ee of the chiral 1,4-oxazepane, and control of <i>N</i>,<i>O</i>-selectivity in S_N2 reaction of the intermediate mesylate with a pyridone derivative, finding appropriate intermediates that were amenable to isolation and upgrade of purity enabled a practical chiral HPLC separation-free, column chromatograph-free synthesis of the drug candidate with excellent chemical and optical purities in a higher overall yield