L12有序结构Ni74.5Pd2Al23.5合金超点阵内禀层错的形成机制

用ＴＥＭ研究了Ｌ１２长程有序结构Ｎｉ７４．５Ｐｄ２Ａｌ２３．５合金室温变形后的位错结构．结果表明,加Ｐｄ韧化的Ｎｉ７４．５Ｐｄ２Ａｌ２３．５合金室温变形组织中存在着大量超点阵内禀层错．这些层错是从以反相畴态分解的ａ／２〈０１１〉位错通过进一步的分解和反应转变来的．层错的形成是合金变形过程中位错交互作用的二次产物,并不成为影响Ｎｉ７４．５Ｐｄ２Ａｌ２３．５合金变形和韧性的主要因素．     

Transmission electron microscopy investigation of the Ar+ ion irradiation effect in semiconductor GaAs

Room temperature irradiation effect of GaAs compound semiconductor by 100 keV Ar⁺ ions has been systematically studied by means of transmission electron microscopy. The dose dependenceoof the Ar⁺ ion irradiation and room temperature annealing effects have been investigated. The experimental results show that the structure of GaAs transforms from perfect crystalline through weakly and severely damaged crystalline to amorphous states with the increase of the irradiation dose and the damaged states are changed during room temperature annealing. Yang Xiangxiu: born in 1968, Doctor     

Induction of vanadium accumulation and nuclear sequestration causing cell suicide in human Chang liver cells

Very little is known about the modulation of vanadium accumulation in cells, although this ultratrace element has long been seen as an essential nutrient in lower life forms, but not necessarily in humans where factors modulating cellular uptake of vanadium seem unclear. Using nuclear microscopy, which is capable of the direct evaluation of free and bound (total) elemental concentrations of single cells we show here that an NH₄Cl acidification prepulse causes distinctive accumulation of vanadium (free and bound) in human Chang liver cells, concentrating particularly in the nucleus. Vanadium loaded with acidification but leaked away with realkalinization, suggests proton-dependent loading. Vanadyl(4), the oxidative state of intracellular vanadium ions, is known to be a potent source of hydroxyl free radicals (OH^.). The high oxidative state of nuclei after induction of vanadyl(4) loading was shown by the redox indicator methylene blue, suggesting direct oxidative damage to nuclear DNA. Flow cytometric evaluation of cell cycle phase-specific DNA composition showed degradation of both 2N and 4N DNA phases in G₁, S and G₂/M cell cycle profiles to a solitary 1N DNA peak, in a dose-dependent manner, effective from micromolar vanadyl(4) levels. This trend was reproduced with microccocal nuclease digestion in a time response, supporting the notion of DNA fragmentation effects. Several other approaches confirmed fragmentation occurring in virtually all cells after 4 mM V(4) loading. Ultrastructural profiles showed various stages of autophagic autodigestion and well defined plasma membrane outlines, consistent with programmed cell death but not with necrotic cell death. Direct intranuclear oxidative damage seemed associated with the induction of mass suicide in these human Chang liver cells following vanadium loading and nuclear sequestration.     

制备电镜生物样品的低温取代仪

本文介绍了一种用微型计算机控制的用于生物样品制备的低温取代仪。该仪不仅简单、价廉和自动化程度高,而且通过鼠肾脏的低温制备,从超微结构表明了该方法能够精确地控制取代温度,获得良好的取代效果。     

胡子鲶消化道粘膜表面结构的扫描电镜观察

本文应用扫描电镜对胡子鲶的口唇、颌齿、舌、咽部、食道、胃、肠等部位的粘膜表面结构进行了观察,描述了消化道各部分粘膜表面结构的特征,并对胡子鲶消化道上的味蕾类型和分布、粘膜皱褶的类型进行了分析讨论.     

莫高窟壁画酥碱病害产生机理

通过对莫高窟壁画地仗层和洞窟围岩中盐分的分析对比，揭示了壁画酥碱病害的成因及形成要理，研究认为，在水分运移的同时，围岩及地仗层中的易溶盐发生水分、离子交换和重结晶作用，引起盐分向地仗层迁多和积累，盐分的积累导致地仗土颗粒间距增大，粒间连结力降低，从而使壁画发生粉化，掉块和散休。     

高聚物的STEM象观察

将分析电子显微镜的扫描透射电子象模式(STEM)应用于两种高分子物的研究。以 ABS/PVC高分子合金和角蛋白纤维为试验材料,叙述了样品制备过程和电镜观察的结果。实验证明,STEM具有对试样穿透能力强和电子束损伤小的特点,特别适用于高聚物材料。在高放大倍数下的观察,能获得直接透射象(TEM)难以观察到的某些微结构情景。