Characterisation of magnesium oxide and its interface with α-Mg in Mg–Al-based alloys

Magnesium oxide (MgO) films and particles have been collected by pressurised filtration of a Mg-8.6wt%Al-0.67wt%Zn (AZ91D) alloy melt. The morphology of the oxides and their interfaces with the α-Mg phase were investigated by high-resolution transmission electron microscopy. It was found that the oxide films consisted of large numbers of sub-micrometre-sized MgO particles, and that melt shearing can effectively break up the oxide films and disperse the oxide particles. For the first time, orientation relationships (ORs) of OR I: [1?1?1]_MgO～2° from (0?0?0?1)_α-Mg and (0?1?1)_MgO?//[2?1?1?0)_α-Mg; and OR II: (1?1?1)_MgO//(1?1?0?1)_α-Mg and [0?1?1]_MgO//[1?2?1?1]_α-Mg, were observed between the MgO particles and the α-Mg matrix. The calculated Bramfitt planar disregistries were 5.5% and 2.5% for the two ORs, respectively, indicating good lattice matching between MgO and α-Mg at the interface. With the evidence of grain refinement effect observed in the sheared AZ91D magnesium alloy, the possibility of MgO particles to act as potent nucleants for heterogeneous nucleation of α-Mg grains is discussed in terms of the crystallographic criterion.     

TEM observation of oxide scale formed on a Ti–Al–Zr alloy oxidized at 360°C in alkaline steam

Ti–Al–Zr alloy has been oxidized at 360°C in alkaline steam at a pressure of 10.3?±?0.7?MPa. Cross-sectional transmission electron microscopy (TEM) observations indicated that the oxide scale of Ti–Al–Zr alloy was composed of outer and inner subscales, in which the outer layer consists of anatase-TiO₂ and the inner layer a mixture of TiO and Ti₂O. The thickness of the Ti₂O, TiO and anatase-TiO₂ were approximately 50, 100 and 400?nm, respectively. These results were confirmed by X-ray energy dispersive spectrometry (EDS) measurements. The enhanced corrosion of titanium alloys in LiOH solution is attributed to a high hexagonal Ti₂O to tetragonal TiO₂ phase transformation rate induced by the substitution of Li⁺ for Ti⁴⁺ in the oxide layer.     

Linear instability signals the initiation of motion of a twin plane under load

This letter presents a study of the atomic mechanism of the initiation of motion of a static twin plane under applied mechanical load in a model shape-memory material. By tracking the deformation under load and using linear stability analysis, we find that the eigenvalues of the Hessian matrix provide an indicator of the initiation of motion of the twin plane. The initiation of motion is signaled by a linear instability and a drop in the lowest eigenvalue to zero as well as a sharp drop in higher eigenvalues. Additionally, by comparing with direct molecular dynamics, we see that the eigenmode associated with the zero eigenvalue is found to accurately predict the initial mode of motion. We also find that the initial motion occurs through the formation of a stacking fault just ahead of the existing twin plane and the broadening of the stacking fault drives further transformation.     

Wear behaviour of a gradient surface produced by a punching process in a Cu-30 Ni alloy

The grain size variation in a gradient surface produced by a punching and recovery process on a Cu-30Ni alloy has been observed by atomic force microscopy. The friction characteristics of the gradient surface in a 3.5 wt% NaCl solution were investigated using a micro-indenter probe, a pin-on-disc type tribometer, a strain sensor and an optical microscope. The results showed that the hardness and grain size can be well represented by the Hall–Petch relationship when the gain size is more than 30?nm. The wear rate, friction coefficient and adhesive force all increase depth below the surface. These variations are attributed to a gradual increasing grain size with depth. The morphologies of the worn track were also studied to understand further the corrosive wear behaviour of gradient surfaces.     

Children dating childhood memories

How accurate are children when dating very long-term memories? Chinese and European Canadian 8-, 11-, and 14-year-olds (N=344) recalled and dated memories from before they went to school in a memory fluency task. Parents provided verification of children's memories and age estimates. Across all age and culture groups, a telescoping effect (i.e., events were dated as taking place more recently than they actually did) was found for earlier memories (before 48 months) and a reverse telescoping effect for later memories (after 48 months). Older children showed a greater tendency to telescope earlier memories and a weaker tendency to reverse telescope later memories than did younger children. Euro-Canadian children showed larger reverse telescoping than Chinese children. These are the first systematic findings concerning the accuracy of children's dating of very long-term memories. They shed new light on the phenomenon of telescoping and have implications for research on childhood amnesia.     

生物制剂治疗克罗恩病进展

克罗恩病是一种以累及消化道为主的复发性炎性疾病.生物制剂的使用为克罗恩病的治疗提供了新的方向.大量临床研究已证实生物治疗主要是抗TNF α单抗对诱导及维持克罗恩病临床缓解、预防并发症的发生有效.目前临床指南多建议对克罗恩病采取递增方案治疗,对重度患者可及早采取更为有效的包括生物治疗在内的治疗方式,但递减治疗方案在临床中的应用尤其是针对初次诊断者也越来越受到重视.目前早期及长期应用生物治疗的安全性及其是否能改变克罗恩病的自然病程证据尚不充分.应针对患者的不同情况,根据风险/效益研究来确定更合适的治疗方案.     

孔子与泰德·本顿的生态观之比较

20世纪后半期,人类面临的最突出的问题就是全球性的生态危机和环境问题。摆脱人类生存的困境,走向具有生态持续性的文明社会是中国现代化实践面临的严峻挑战。本文试将孔子和泰德·本顿的生态观加以比较,求同存异,发掘其中蕴含的积极因素。两者在对自然的解读上,强调自然的客观实在性,重视自然的内在价值和对自然规律的遵循;在人与自然的关系上,阐发人与自然的息息相关性和密不可分性,强调二者相互作用。相互影响;在对自然资源的利用上,强调合理地支配和有限地利用自然,承认自然的极限。这些思想为我国生态文明建设提供了有益的借鉴。     

情绪取向理论建构及实证

该研究尝试用一种新的视角一取向研究视角,对以往情绪理论进行整合研究,建构一种与社会情境结合更紧密,更具概括性的情绪取向理论.情绪取向理论的假设建构模型包括四个维度:理性取向、感性取向、积极取向和消极取向.根据理论模型编制情绪取向量表,以779名被试为研究对象,运用探索性因素分析和验证性因素分析方法对该理论模型进行实证研究.结果证明了该理论建构的存在,理论建构中各维度的因素负荷和拟合指数良好,情绪取向量表具有良好的信度和建构效度.     

认知诊断分类中心的确定

期望反应模式是认知诊断分类的类中心,确定了诊断范围中属性及其层级关系后,类中心的数目由测验Q矩阵决定.类中心应该是完备的,即理论上有多少个知识状态就应该有多少个类中心,这涉及评分方式、Q矩阵设计、Q矩阵评价与修改、认知诊断测验如何实施等问题的讨论.重点给出多级评分认知诊断测验不同属性层级对应的完备Q矩阵设计的例子和罗列了Wang等人（2013）的Q矩阵修改的方法.