黄土高原旱作土壤养分含量与供给

通过对黄土高原地区旱作土壤与灌溉土壤综合考察、矿化培养实验与土壤、雨水分析，表明旱作土壤养分平均含量均低于灌溉土壤，其中有机质、全氮、碱解氮、有效磷的平均含量均属低水平，速效钾含量较高。旱作土壤可为作物利用的养分主要来源于土壤矿化、大气沉降和肥料投入。     

用电导滴定法测定甲酚磺酸

本文采用电导滴定法对宫炎清药物合成的中间体水溶液——含硫酸的甲酚磺酸水溶液进行了分析测定,结果表明,电导滴定曲线能明确地分别标示出磺酸基与硫酸总含量的滴定终点和酚羟基含量的滴定终点.根据酚羟基含量准确得到宫炎清药物合成中间体——甲酚磺酸的含量为491mg/mL.     

地方大学土木工程教学改革的探讨

分析了地方大学的办学特点,提出了地方大学土木工程教育课程体系和教学内容的改革方案,建立与“大类招生,分流培养,模块化教学”相适应的教学机制,阐述了地方大学土木工程教学改革的原则,思路和方法。     

积极推广应用新技术 提高工程科技含量

以建设太原理工大学北区高层建筑为例,详细介绍了在施工过程中各项新技术的推广应用情况。     

资本市场中的头羊-从羊模型

针对目前中国证券市场中普遍存在着个人投资者对机构投资者的羊群行为这一特殊现象 ,建立了一个头羊 -从羊模型 .通过一定的参数假设和计算 ,定量地指出这种羊群行为增加了资产价格的波动 ,并且在大多数情况下头羊的收益大于从羊的收益 .但是随着头羊数量的增加和头羊收到的信息中的噪声增加 ,头羊 -从羊的收益之差减少 .最后从模型结论引申出稳定市场、改善市场结构、增加信息效率的建议.     

基于分形接触的湿度对静摩擦因数影响分析

采用分形接触模型推导并计算了由水膜的弯月面效应引起的附加静摩擦力,得到了由水膜的弯月面效应引起的附加静摩擦力的表达式,表明随着分形维数D的增大和分形粗糙度G的减小,计算的附加静摩擦系数增大,同时随着相对湿度的增加,水膜厚度增加,附加的静摩擦系数增加.     

高炉铁水含硅量预测的计算机在线实现

本文给出了铁水含硅量预测模型的三种在线辨识的方法，讨论了数据库的建立和多种预测模型的计算机在线实现。     

异羟肟酸比色法测定电解混合液中葡萄糖酸的含量

本文报导用异羟肟酸比色法,分析葡萄糖电解氧化制备葡萄糖酸盐过程的电解混合液中葡萄糖酸根含量的研究结果,文中对实验条件及影响因素进行了探讨。实验证明,本方法具有分析方法简单、分析数据稳定、重现性好、可靠、方便等特点。     

Isolation of human epidermal stem cells by adherence and the reconstruction of skin equivalents

The isolation of human epidermal stem cells is critical for their clinical applications. In the present study, we isolated three populations of epidermal keratinocytes according to their ability to adhere to collagen type IV: i.e., rapidly adhering (RA), slowly adhering (SA), and non-adhering (NA) cells. The aim of this study was to characterize RA cells and to investigate the possibility of using these cells for epidermis reconstruction. To identify RA cells, flow cytometric analysis was performed using anti-₆ integrin and anti-CD71 antibodies. RA cells express high levels of ₆ integrin and low levels of CD71, which are considered as markers of an epidermal stem cell nature. Furthermore, electron microscopy showed that RA cells are small and have a high nuclear to cytoplasmic ratio, whereas SA and NA cells have well-developed cellular organelles and abundant tonofilaments. Western blot analysis showed that RA cells are slow cycling and express p63, a putative epidermal stem cell marker, whereas SA and NA cells express c-Myc, which is known to regulate stem cell fate. To compare epidermal regenerative abilities, skin equivalents (SEs) were made using RA, SA, and NA cells. The epidermis constructed from RA cells was well formed compared to those formed from SA or NA cells. In addition, only SEs with RA cells expressed ₆ integrin and ₁ integrin at the basal layer. These results indicate that RA cells represent epidermal stem cells and are predominately comprised of stem cells. Therefore, the isolation of RA cells using a simple technique offers a potential route to their clinical application, because they are easily isolated and provide a high yield of epidermal stem cells.Received 2 July 2004; received after revision 20 August 2004; accepted 10 September 2004     

Caffeine as a psychomotor stimulant: mechanism of action

The popularity of caffeine as a psychoactive drug is due to its stimulant properties, which depend on its ability to reduce adenosine transmission in the brain. Adenosine A₁ and A_2A receptors are expressed in the basal ganglia, a group of structures involved in various aspects of motor control. Caffeine acts as an antagonist to both types of receptors. Increasing evidence indicates that the psychomotor stimulant effect of caffeine is generated by affecting a particular group of projection neurons located in the striatum, the main receiving area of the basal ganglia. These cells express high levels of adenosine A_2A receptors, which are involved in various intracellular processes, including the expression of immediate early genes and regulation of the dopamine- and cyclic AMP-regulated 32-kDa phosphoprotein DARPP-32. The present review focuses on the effects of caffeine on striatal signal transduction and on their involvement in caffeine-mediated motor stimulation.Received 8 July 2003; received after revision 7 September 2003; accepted 6 October 2003