Homogeneous nucleation of dislocation loops under stress in perfect crystals

We present an analysis and results on the homogeneous nucleation of a dislocation loop under stress in a perfect crystal. By using a variational boundary integral method in the Peierls-Nabarro framework, we have determined the saddle-point configurations of embryonic dislocation loops and their associated activation energies under stress levels up to the ideal shear strength. The high-energy barriers under the usual levels of applied shear stresses, differing markedly from the ideal shear strength, confirm the widely held view that thermal motion should play no role in such nucleation. The result provides means for more definitive solutions of fundamental problems involving homogeneous nucleation of dislocation loops and has significant implications for models based on the mechanism of nucleation of dislocations from a perfect crystal.     

Application of the stagnant stage concept for monitoring Mn partitioning at the austenite-ferrite interface in the intercritical region for Fe–Mn–C alloys

The length of the stagnant stage during the new ferrite growth starting from a mixture of austenite and ferrite has been investigated for a Fe-0.17Mn-0.023C (wt%) alloy. It was found that the stagnant stage depends on the thermal path followed to create the mixture, and deduce that the tie-lines for austenite to ferrite transformation are quite different from those for ferrite to austenite transformation. The length of the stagnant stage is determined by the very local partitioning effect at the interface, and it can be used as a tool to monitor the Mn partitioning.     

Understanding scale-dependent yield stress of metals at micrometre scales

The mechanical softening behaviour of micrometre-scale metals (free-standing metal foils and wires) with decreasing either the geometrical or the microstructural scale (i.e. the smaller, the weaker) has recently been reported. Here, we present a mechanism-based model to understand the softening behaviour, which is based on competition between the effects of surface grain relaxation and the interior grain strengthening effect. The model describes well the yield stress of Cu foils with different ratios of the thickness to grain size.     

我国护理教育面临的困境及对策研究

梳理了目前国内外护理教育发展的基本情况,从满足我国护理事业发展需求、充分考虑现代护理学的学科特点、明确护理高等教育不同层次的培养目标等方面分析了护理教育发展的主要思路,并提出具体的建议和措施,力图通过加强护理学教育来进一步推动我国护理事业的发展。     

结果预期对青少年攻击性行为的影响：中介效应与调节效应

采用攻击性问卷、关系攻击行为量表、结果预期量表、移情量表和自我控制能力问卷对720名中学生进行调查,考察了结果预期与青少年攻击性行为的关系,以及自我控制在其中的中介作用和移情在其中的调节作用。结果发现:(1)结果预期与青少年的攻击性行为(外部攻击和关系攻击)存在显著负相关;(2)自我控制在结果预期与青少年攻击性行为之间起着完全中介作用;(3)在结果预期对青少年外部攻击行为的预测中,移情发挥了调节作用。在高移情个体中,结果预期并不预测外部攻击行为,而在低移情个体中,结果预期显著地反向预测外部攻击行为;(4)自我控制在结果预期与青少年外部攻击行为之间的中介作用受到移情的调节,高水平的移情能力可以有效地缓解青少年因低自我控制而导致的高攻击性。     

肿瘤临终关怀中的家属辞世教育

晚期癌症患者的家属在临终家居照顾及医院宁养照顾中起到重要的作用,对临终患者家属的关怀照顾是临终关怀的重要组成部分,通过从家属心理特点、影响家属心理的因素、家属辞世教育方法三个方面具体阐述在家属辞世教育的工作步骤,从而更好的指导社会医疗实践,促进临终关怀工作在我国的发展.     

防止耐药菌的院内爆发

临床上多重耐药菌感染的现象正在日渐严重,从而引发了越来越严重的耐药菌院内感染现象.从医务工作者角度来控制这一现象的有效措施包括:规范医护人员的手卫生,控制侵入性操作引起的感染,合理使用抗生素,有效筛查和隔离疑似感染患者等.     

肠梗阻导管研发中的思路与启示

肠梗阻是腹部外科中一种常见的疾患,严重青可危及生命。胃肠减压是肠梗阻治疗的主要措施之一。既往胃管减压效果较差。近年开始应用的肠梗阻导管可对肠道进行有效的减压．效果明显。肠梗阻导管的发明和临床应用充分体现了假说对科学实践的指导意义。     

阿尔茨海默病生物学标志物研究进展

阿尔茨海默病（AD）是常见的中枢神经系统变性疾病,是痴呆最常见的病因,发病率高.病理特征为老年斑及神经元纤维缠结.AD的确诊有赖病理学,临床诊断极其耗时.由于尚无准确的早期诊断方法,常使AD患者错过早期治疗的时机,这成为制约有效防控AD的瓶颈问题.因此寻找高敏感性、特异性、无创性的生物学标志物对AD的早期诊断至关重要.本文仅将目前较为广泛研究的生物学标志物及其研究现状作一概述.分别对脑脊液、血液、尿液及唾液中的AD标志物作逐一介绍.     

关注肿瘤患者避免过度诊疗——解析ASCO大会关于肿瘤诊疗的5项建议

现代肿瘤的诊疗水平已经有了长足的进步,先进的诊断技术使得很多肿瘤得以早期发现并积极治疗,很多晚期患者也不再面临无药可用的境地,但由于临床医生的认识存在偏差,存在过度诊断和过度治疗的问题,进而给患者带来不必要的负担和痛苦。美国临床肿瘤学会（ASC0）年会上发布了一篇名为“ASCO为改善肿瘤治疗质量及医疗花费的5项建议”的文章,特别提出要重视五项临床广泛应用、花费较大,但缺乏高级临床证据的肿瘤治疗或干预措施,也提示我们需要充分评估,综合思考,为合适的患者提供正确的诊治方案,才能给患者带来更大的获益。