湖拟鲤年龄和生长研究

赛里木湖湖拟鲤体长与鳞径关系为:L=0.278R-0.1582,体重与体长的关系为:W=0.01364L~3.2172应用Von·Bertal anffy生长方程拟合其生长规律,其主要生物学参数为:L∞=24.35cm,W∞=386.93g,K=0.2658,t_o-=0.7573年,拐点年龄t_1=3.45年。拐点体重(?)i=118.06g。生长指标比原产地额尔齐斯河显著减小,t=2.98>t_(0.05),P<0.05。     

渤海石油平台用钢A537疲劳裂纹的扩展特征

对渤海石油平台管节点用钢A537在238K,237K和303K三个温度下的疲劳裂纹扩展情况进行了试验研究.试验结果表明.这种钢材在每一个测试温度下的疲劳裂纹扩展均遵循Paris规律.不同温度下的疲劳裂纹扩展曲线随应力强度因子幅值的增加而有汇合趋势,并在某一高扩展速率处相交.试验还表明,温度降低,A537钢的裂纹扩展速率下降,而Paris指数n则大为增加.在裂纹扩展后期,低温下裂纹扩展速率的增长速度远大于室温,因此,低温时的扩展速率反而高于室温时的扩展速率.     

激光沉积高温超导薄膜的研究

本文利用激光剥离超导靶材的技术,在相当低的基片温度下,原位生长出了零电阻温度90K左右、C-轴取向择优生长的Y-Ba-Cu-O超导薄膜;给出了激光剥离材料的新模型;推导了激光剥离材料的功率密度阈值、剥离层厚度和被剥离而喷射出来的粒子所受到的反冲压的数学表达式.     

16MnR钢裂纹体空穴扩张的有限元分析

本文采用弹塑性有限元方法,对16MnR钢的三点弯曲试件进行了应力应变分析,发现空穴扩张比V_G在裂尖前方存在一极大值,且V_G值随COD单调增加,文中指出,对高韧性材料,当裂尖前方V_G～y曲线的极大值达到某一临界值时,可作为主裂纹向前扩展的判据.     

2.25Cr-1Mo钢蠕变裂纹扩展的有限元模拟

编制了有限元程序CCGC-1以模拟计算高温材料蠕变裂纹的扩展。在静态裂纹时,本程序与BERSAFE程序计算的结果相当符合。同时本程序又可模拟裂纹的扩展,使蠕变的数值计算更符合实际情况。例如对国产2.25 Cr-1 Mo钢在565℃下蠕变裂纹扩展问题进行计算得到的C~*对裂纹扩展速率dα/dt的关联结果,与其他同事用实验得到的结果基本一致。     

播娘蒿对小麦早期生长的生化他感作用研究

探讨了麦田杂草播娘蒿对小麦早期生长发育的影响。发现播娘蒿种子淋洗物对小麦种子萌发和幼苗初期生长主要表现抑制效应,但淋洗物中的个别成分又有促进效果。证明了播娘蒿与小麦之间有生化他感作用存在,认为生化他感作用是播娘蒿作为麦田杂草影响小麦生长发育的另一种方式。     

三轴应力场中空穴扩张临界值与材料的微观断裂延性

选用一种球化碳钢的轴对称光滑和不同缺口拉伸试样研究了材料在三轴应力场中的宏、微观断裂延性。基于不同应力三轴性水平下空穴扩张与聚合的特性,给出了一个新的材料微观断裂延性表达式。结合空穴扩张的临界尺寸与断口韧窝几何的三维测量结果,证明了在不同的三轴应力水平下,材料微观断裂延性与实测宏观断裂延性之间均有着良好的一致性。从而揭示了材料断裂延性随应力三轴性水平升高而下降的微观机理。     

非晶态硅薄膜的生长规律及其特性

非晶态半导体研究所涉及的重要问题之一,是探索制备薄膜材料的优化生长条件。文中对利用等离子体技术制备的非晶态硅薄膜的生长参数作了分析,优化了生长条件。并就生长参数对薄膜特性的影响进行了讨论。利用透射电子显微镜TEM观测了薄膜的结构与晶粒度,作了动力学理论分析,其结果与实验相一致。     

Alzheimer's disease: fundamental and therapeutic aspects

Alzheimer's disease is the most common type of progressive and debilitating dementia affecting aged people. In some early — as well as late-onset familial cases, a genetic linkage with chromosomes 14, 21 (early-onset) or 19 (late-onset) has been indicated. Furthermore, a direct or indirect role has been attributed to normal or structurally altered amyloid -protein (concentrated in senile plaques) and/or excessively phosphorylated tau protein (located in neurofibrillary tangles). Degeneration of cholinergic neurons and concomitant impairment of cortical and hippocampal neurotransmission lead to cognitive and memory deficits. Several compounds are being tested in attempts to prevent and/or cure Alzheimer's disease, including tacrine, which has very modest efficacy in a sub-group of patients, and new acetylcholinesterase inhibitors. Pilot experiments have also been launched using nerve growth factor (NGF) to prevent or stabilize the processes of cholinergic pathway degeneration. Alternatively, antioxidants, free radical scavengers and/or non steroidal anti-inflammatory agents may be screened as potential therapies for neurodegenerative diseases induced by multiple endogenous and/or exogenous factors. The recent use of transgenic mice, in parallel with other genetic, biochemical and neurobiological systems, in vivo and/or in vitro (cell cultures), should accelerate the discovery and development of specific drugs for the treatment of Alzheimer's disease.