高效液相色谱—核磁共振联用技术

本文简要地综述了高效液相色谱与核磁共振联用技术,并列举了该技术在药物、天然产物以及异构体研究中的应用。     

“两个必然”和“两个决不会”的内在统一

对于马克思主义“两个必然”和“两个决不会”的关系存在着“补充论”、“修正论”、“取代论”的不同观点。“两个必然”和“两个决不会”的科学论断都是社会基本矛盾运动规律的体现,二者是内在的高度统一的理论。就资本主义社会发展趋势而言,“两个决不会”具有相对性,是“两个必然”的内在要求,“两个必然”理论中包含着“两个决不会”思想,是“两个决不会”运动的最终结果。     

基于可达性的用户最优动态交通配流模型研究

以多种已有模型为基础，建立了动态配流流量细化原则，并依据这一原则，在避免估算路段走行时间的情况下构造了一个改进的新模型．该模型的解释性强，具有全局收敛性，并考虑了距离不同带来的可达性的影响．在对该模型最优解条件的充要性进行说明的同时，对新模型的择路机理也予以了推证．     

焦炉煤气还原硫酸钠制硫化钠的研究

在固定床反应器内600～700℃的温度范围研究了焦炉煤气还原硫酸钠制硫化钠的反应速率和影响因素，在固定床内随着温度的提高，反应速率增大，并能达到较高的转化率．温度低于680℃，表现为催化反应，Fe2O3是活性较高的催化剂；在700℃以上表现为非催化反应。焦炉煤气中氢气的浓度和硫酸钠的颗粒直径对反应有一定的影响．在反应器内只要控制合适条件，往硫酸钠中加入脂肪酸的钠盐可以避免烧结，并能获得更高的反应速率。     

优化股权结构:规范和完善上市公司治理结构的关键

本文首先提出公司治理的概念 ,并以此作为分析和研究的出发点 ,从现代企业理论和产权理论的角度 ,阐明了股权结构和股权流动安排与上市公司治理内部监控机制、激励机制和外部约束机制之间的关系 ,得出优化股权结构和股权流动安排是规范和完善上市公司治理的关键这一结论     

非拓扑孤子模型的相变特征与袋常数的温度依赖性

本文计算了在有限温度和密度下非拓扑孤子模型的有效势;得到了袋常数对温度和化学势的依赖关系;分析了禁闭解除相变的特征.结果表明:该模型的禁闭解除相变为一级;相变特征的分析表明有退禁闭相与禁闭相的两相共存.     

Potential exposures and risks from beryllium-containing products.

Beryllium is the strongest of the lightweight metals. Used primarily in military applications prior to the end of the Cold War, beryllium is finding new applications in many commercial products, including computers, telecommunication equipment, and consumer and automotive electronics. The use of beryllium in nondefense consumer applications is of concern because beryllium is toxic. Inhalation of beryllium dust or vapor causes a chronic lung disease in some individuals at concentrations as low as 0.01 microg/m3 in air. As beryllium enters wider commerce, it is prudent to ask what risks this might present to the general public and to workers downstream of the beryllium materials industry. We address this question by evaluating the potential for beryllium exposure from the manufacturing, use, recycle, and disposal of beryllium-containing products. Combining a market study with a qualitative exposure analysis, we determine which beryllium applications and life cycle phases have the largest exposure potential. Our analysis suggests that use and maintenance of the most common types of beryllium-containing products do not result in any obvious exposures of concern, and that maintenance activities result in greater exposures than product use. Product disposal has potential to present significant individual risks, but uncertainties concerning current and future routes of product disposal make it difficult to be definitive. Overall, additional exposure and dose-response data are needed to evaluate both the health significance of many exposure scenarios, and the adequacy of existing regulations to protect workers and the public. Although public exposures to beryllium and public awareness and concern regarding beryllium risks are currently low, beryllium risks have psychometric qualities that may lead to rapidly heightened public concern.     

A Two-dimensional Heat Transfer Model for Atmosphere-land System in the Lake-dominated Alaskan Arctic

1 Introduction Shallow tundra lakes are one of the dominating landscape features in the Alaskan Arctic. They typically cover 20% of the total area of the North Slope of Alaska, and up to about 40% in the coastal plain [1,2]. Many lakes are, in their entirety or in part, shallower than the maximum annual ice thickness, consequently, some ice freezes completely to the lake bottom, nevertheless, large areas of water are deeper than the maximum ice thickness and the ice remains afloat througho…     

位相物体像全息图的拍摄

讨论了位相物体激光像面全息摄影的特点，从全息与橱窗装饰艺术结合的设想出发，设计了位相物体像全息图的拍摄实验，取得好的实验教学效果．     

近二十年中国汉民族起源、形成研究综述(二)

汉民族是我国乃至世界上最大的民族 ,而关于汉民族的研究 ,长期以来却被国内学术界所忽视 ,汉民族史常被淹没在通史和断代史研究之中。十一届三中全会后 ,汉民族研究如雨后春笋 ,一直在不断地兴旺勃发。特别是近二十年来 ,汉民族研究取得了蔚为壮观的成绩 ,为世人瞩目。