Surface Modification of Ferritic Stainless Steel by Active Screen Plasma Nitriding

Plasma nitriding is a surface modification process with a low environmental impact. Active screen plasma nitriding (ASPN) is one of the new plasma nitriding technologies, and can eliminate problems related to conventional direct current plasma nitriding (DCPN). In this study, ferritic stainless steel SUS430 samples were treated by ASPN to increase their wear resistance without decreasing their corrosion resistance. ASPN was performed in a nitrogen-hydrogen atmosphere with 25%N2 + 75%H2 for 18 ks at 623 K, 673 K, 723 K, 773 K, and 823 K under 600 Pa using an SUS304 screen. When the sample was treated at 673 K by ASPN, the pitting corrosion resistance and wear resistance of its surface were improved because of the formation of the Sα phase and a deposited layer containing Ni on the sample surface

Effect of Gas Pressure on Active Screen Plasma Nitriding Response

An austenitic stainless steel AISI 304 was active screen plasma nitrided using a 304 steel screen to investigate the effect of the gas pressure on the nitriding response. The sample was treated for 18 ks at 723 K in 25 % N2 +75 % H2. The gas pressure was changed to 100, 600, and 1200 Pa. The distance between the screen and the sample was also changed to 10, 30, and 50 mm. The nitrided samples were characterized by observing their appearance and surface roughness by optical microscopy, X-ray diffraction, and microhardness testing. After nitriding, polygonal particles with a normal distribution were observed at the center and edges of all the nitrided sample surfaces. The particles on the sample surface became finer with an increase in the gas pressure. The nitrided layer with a greater and homoge-neous thickness was obtained at a low gas pressure of 100 Pa

Effect of Nitriding parameter on Active Screen Plasma Nitriding Response of SACM645 Steel

A nitriding steel SACM645 was active screen plasma nitrided using an austenitic stainless steel screen to investigate the effect of nitriding parameters such as gas pressure and the distance between the screen and the sample on the nitriding response. The sample was treated for 18 ks at 823 K in 25% N2 + 75% H2. The gas pressure was changed to 100, 600, and 1200 Pa. The distance between the screen and the sample was also changed to 10, 30, and 50 mm. The nitrided samples were characterized by observing their surface morphology and cross sectional microstructure by scanning electron microscopy, X ray diffraction, and microhardness testing. After nitriding, polygonal particles with a normal distribution were observed at the center and edges of all nitrided sample surfaces. The particles on the sample surface became finer with an increase in the gas pressure. A nitrided layer with a greater and homogeneous thickness was obtained at a low gas pressure of 100 Pa

DOCK2 is involved in the host genetics and biology of severe COVID-19

「コロナ制圧タスクフォース」COVID-19疾患感受性遺伝子DOCK2の重症化機序を解明 --アジア最大のバイオレポジトリーでCOVID-19の治療標的を発見--. 京都大学プレスリリース. 2022-08-10.Identifying the host genetic factors underlying severe COVID-19 is an emerging challenge. Here we conducted a genome-wide association study (GWAS) involving 2, 393 cases of COVID-19 in a cohort of Japanese individuals collected during the initial waves of the pandemic, with 3, 289 unaffected controls. We identified a variant on chromosome 5 at 5q35 (rs60200309-A), close to the dedicator of cytokinesis 2 gene (DOCK2), which was associated with severe COVID-19 in patients less than 65 years of age. This risk allele was prevalent in East Asian individuals but rare in Europeans, highlighting the value of genome-wide association studies in non-European populations. RNA-sequencing analysis of 473 bulk peripheral blood samples identified decreased expression of DOCK2 associated with the risk allele in these younger patients. DOCK2 expression was suppressed in patients with severe cases of COVID-19. Single-cell RNA-sequencing analysis (n = 61 individuals) identified cell-type-specific downregulation of DOCK2 and a COVID-19-specific decreasing effect of the risk allele on DOCK2 expression in non-classical monocytes. Immunohistochemistry of lung specimens from patients with severe COVID-19 pneumonia showed suppressed DOCK2 expression. Moreover, inhibition of DOCK2 function with CPYPP increased the severity of pneumonia in a Syrian hamster model of SARS-CoV-2 infection, characterized by weight loss, lung oedema, enhanced viral loads, impaired macrophage recruitment and dysregulated type I interferon responses. We conclude that DOCK2 has an important role in the host immune response to SARS-CoV-2 infection and the development of severe COVID-19, and could be further explored as a potential biomarker and/or therapeutic target