| 1 | Effects of SiC Nanoparticle Content on the Microstructure and Tensile Mechanical Properties of Ultrafine Grained AA6063-SiC_(np) Nanocomposites Fabricated by Powder Metallurgy显示文摘Ultrafine grained AA6063-SiC_(np) nanocomposites with 1, 5 and 10 vol.% SiC_(np) have been fabricated by a novel powder metallurgy process. This process combines high energy ball milling of a mixture of 6063 alloy granules made from machining chips and Si C nanoparticles and thermomechanical powder consolidation by spark plasma sintering and hot extrusion. The microstructure and tensile mechanical properties of the samples were investigated in detail. Increasing the Si C nanoparticle content from 1 to 10 vol.%,the yield strength and ultimate tensile strength increased from 296 and 343 MPa to 545 and 603 MPa respectively, and the elongation to fracture decreased from 10.0%, to 2.3%. As expected, a higher Si C nanoparticle content generates a stronger inhibiting effect to grain growth during the thermomechanical powder consolidation process. Analysis of the contributions of various strengthening mechanisms shows that a higher Si C nanoparticle content leads to a higher contribution from nanoparticle strengthening, but grain boundary strengthening still makes the largest contribution to the strength of the nanocomposite.When the Si C nanoparticle content increased to 10 vol.%, the failure of the nanocomposite was initiated at weakly-bonded interparticle boundaries(IPBs), indicating that with a high flow stress during tensile deformation, the failure of the material is more sensitive to the presence of weakly-bonded IPBs. | X.Yao Z.Zhang Y.F.Zheng C.Kong M.Z.Quadir J.M.Liang Y.H.Chen P.Munroe D.L.Zhang | 2017 | Journal of Materials Science & Technology2017，33，9： | 4 |
| 3 | Ethical challenges in mass drug administration for reducing childhood mortality:a qualitative study显示文摘Background:Mass drug administration(MDA)of medications to entire at-risk communities or populations has shown promise in the control and elimination of global infectious diseases.MDA of the broad-spectrum antibiotic azithromycin has demonstrated the potential to reduce childhood mortality in children at risk of premature death in some global settings.However,MDA of antibiotics raises complex ethical challenges,including weighing near-term benefts against longer-term risks—particularly the development of antimicrobial resistance that could diminish antibiotic efectiveness for current or future generations.The aim of this study was to understand how key actors involved in MDA perceive the ethical challenges of MDA.Methods:We conducted 35 semi-structured interviews from December 2020–February 2022 with investigators,funders,bioethicists,research ethics committee members,industry representatives,and others from both highincome countries(HICs)and low-and middle-income countries(LMICs).Interview participants were identifed via one of seven MDA studies purposively chosen to represent diversity in terms of use of the antibiotic azithromycin;use of a primary mortality endpoint;and whether the study occurred in a high child mortality country.Data were analyzed using constructivist grounded theory methodology.Results:The most frequently discussed ethical challenges related to meaningful community engagement,how to weigh risks and benefts,and the need to target MDA We developed a concept map of how participants considered ethical issues in MDA for child mortality;it emphasizes MDA’s place alongside other public health interventions,empowerment,and equity.Concerns over an ethical double standard in weighing risks and benefts emerged as a unifying theme,albeit one that participants interpreted in radically diferent ways.Some thought MDA for reducing child mortality was ethically obligatory;others suggested it was impermissible.Conclusions:Ethical challenges raised by MDA of antibiotics for childhood mortality-which span socio-cultural issues,the environment,and efects on future generations-require consideration beyond traditional clinical trial review.The appropriate role of MDA also requires attention to concerns over ethical double standards and power dynamics in global health that afect how we view antibiotic use in HICs versus LMICs.Our fndings suggest the need to develop additional,comprehensive guidance on managing ethical challenges in MDA. | Ahmed Alasmar Alex C.Kong Anthony D.So Matthew DeCamp | 2022 | Infectious Diseases of Poverty2022，11，5： | 0 |
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