High School Economic Composition and College Persistence

Using a longitudinal sample of Texas high school seniors of 2002 who enrolled in college within the calendar year of high school graduation, we examine variation in college persistence according to the economic composition of their high schools, which serves as a proxy for unmeasured high school attributes that are conductive to postsecondary success. Students who graduated from affluent high schools have the highest persistence rates and those who attended poor high schools have the lowest rates. Multivariate analyses indicate that the advantages in persistence and on-time graduation from 4-year colleges enjoyed by graduates of affluent high schools cannot be fully explained by high school college orientation and academic rigor, family background, pre-college academic preparedness or the institutional characteristics. High school college orientation, family background and pre-college academic preparation largely explain why graduates from affluent high schools who first enroll in 2-year colleges have higher transfer rates to 4-year institutions; however, these factors and college characteristics do not explain the lower transfer rates for students from poor high schools. The conclusion discusses the implications of the empirical findings in light of several recent studies that call attention to the policy importance of high schools as a lever to improve persistence and completion rates via better institutional matches.     

行走于教育公正之途——美、英、中三国教育增值评价的研究与实践

20世纪60-70年代,美、英等发达国家先后遭遇大众对教育质量及教育评价方式的质疑,催生了教育增值评价理念的兴起,并逐步拉开了增值评价实践之幕。我国开展增值评价研究一定程度是受到西方国家(尤其是美英)影响的结果,目前还处于理念的推进和实验阶段。了解和研究国内外教育增值评价研究和实践互相促进的过程和成果,对于我们客观估计我国教育增值评价的发展前景不无裨益。     

基于集团化办学的高技能人才培养体系架构

集团化办学是职业教育规模化、连锁化、品牌化发展的必然趋势,也是国家职业教育体制改革的重要探索。集团化办学对高技能人才培养质量提升具有重要的现实意义,有助于进一步深化职业教育改革,拓宽高技能人才培养渠道,实现优质资源共享,提升服务社会经济发展能力。文章提出应遵循因地制宜、以人为本、互惠共赢的原则,紧紧围绕国家战略布局和区域经济发展需要,从创新体制机制,打造基于集团化办学的高技能人才培养新模式;聚合优质资源,挖掘基于集团化办学的高技能人才培养新优势;多元融合发展,搭建基于集团化办学的高技能人才培养新平台;强化保障体系,优化基于集团化办学的高技能人才培养环境四个方面协同推进,架构基于集团化办学的高技能人才培养体系。     

Purification and studies on characteristics of cholinesterases from Daphnia magna

Due to their significant value in both economy and ecology, Daphnia had long been employed to investigate in vivo response of cholinesterase (ChE) in anticholinesterase exposures, whereas the type constitution and property of the enzyme remained unclear. A type of ChE was purified from Daphnia magna using a three-step procedure, i.e., Triton X-100 extraction, ammonium sulfate precipitation, and diethylaminoethyl (DEAE)-Sepharose?-Fast-Flow chromatography. According to sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), molecular mass of the purified ChE was estimated to be 84 kDa. Based on substrate studies, the purified enzyme preferred butyrylthiocholine iodide (BTCh) [with maximum velocity (V _max)/Michaelis constant (K _m)=8.428 L/(min·mg protein)] to acetylthiocholine iodide (ATCh) [with V _max/K _m=5.346 L/(min·mg protein)] as its substrate. Activity of the purified enzyme was suppressed by high concentrations of either ATCh or BTCh. Inhibitor studies showed that the purified enzyme was more sensitive towards inhibition by tetraisopropylpyrophosphoramide (iso-OMPA) than by 1,5-bis(4-allyldimethylammoniumphenyl) pentan-3-one dibromide (BW284C51). Result of the study suggested that the purified ChE was more like a type of pseudocholinesterase, and it also suggested that Daphnia magna contained multiple types of ChE in their bodies.     

北京山区土壤有机碳分布及其影响因素研究

基于野外调查与室内分析相结合的方法,以北京山区650典型土壤类型剖面的1650样品数据,研究土壤有机碳分布及与影响因素间的关系.结果表明,研究区有机碳平均含量为(12.61±9.58)g/kg,属中下水平,变异系数为76.02,中等变异.土壤表层有机碳含量与海拔、植被覆盖度显著正相关,与温度显著负相关,即海拔所造成的水热条件和植被覆盖度的差异是影响其分布的主导环境因子.土壤有机碳含量在剖面中的垂直分布规律为:表层到亚表层下降速率显著,达44.48％,亚表层以下下降速率趋缓,均小于20％,土体构型与之关系密切,均质型土壤有机碳变化速率平缓,有强烈对比的土体构型变化较剧烈;而不同植被类型下,土壤表层到亚表层的有机碳含量下降速率依次为:针叶林(10.15％)＜草甸类(18.75％)＜落叶阔叶林(19.12％)＜中生林草(31.65％)＜中旱生林灌(64.09％),地表上有无枯枝落叶层及其厚薄对此产生了重要影响.在人类活动主要区域内,耕作土壤有机碳平均含量与变异性均小于自然土壤,其中园地的有机碳含量最低,荒草地的变异程度最强,是否受到人类活动的干扰与不合理利用,以及地表植被类型差异与其有着重要关系.     

2004年欧洲足球锦标赛远射状况分析

运用文献资料法、观察法、数理统计法等研究方法,以2004年欧洲足球锦标赛的31场比赛为研究对象,对所有比赛中运用远射的情况进行统计.通过对远射的数量、效果、时机、脚法和区域进行分析,结果发现:远射在比赛中运用有一定的规律性,是射门中一项关键技术,也是破门得分的良好手段之一.中路3区是远射得分的最佳区域,尤其是罚球弧附近.远射的脚法一般以脚背正面或脚背内侧为主.远射的时机决定射门效果.     

谈健身运动参与动机的转变

健身运动分为直接动机和间接动机两种.直接动机是直观性的,不能持久,而间接动机是练习者真正认识到体育的重要以及自身的需要,从而选择与健身终生相伴.就如何变直接动机为间接动机提出了几种行之有效的方法.     

新世纪体操分类的逻辑学探索

以体操的内容为出发点,从逻辑学的角度,对我国现行体操的分类情况进行分析,找出其中存在的缺陷和不足,并在此基础上提出科学的体操分类方法.     

“数字图书馆——新世纪信息技术的机遇与挑战”国际研讨会综述

2002年7月8－12日，在北京召开了由中华人民共和国文化部举办的“数字图书馆－－新世纪信息技术的机遇与挑战”国际研讨会，本文概括了会议中探讨的数字图书馆研究与实践的主要内容。     

Windows2000终端服务的安装及应用

终端服务(Terminal Service)是在Windows 2000 Server产品系列中提供的一种技术，用以在一个远端的Windows 2000 Server上执行应用程序或进行相应的管理工作。本文介绍了终端服务的安装及具体应用。