Does food insecurity at home affect non-cognitive performance at school? A longitudinal analysis of elementary student classroom behavior

This paper estimates models of the transitional effects of food insecurity experiences on children's non-cognitive performance in school classrooms using a panel of 4710 elementary students enrolled in 1st, 3rd, and 5th grade (1999-2003). In addition to an extensive set of child and household-level characteristics, we use information on U.S. counties to control for potential confounding effects of the local economic and noneconomic environment on children's household transitions between states of food insecurity and food security. The time horizon of our analysis affords insight into factors underlying children's formation of non-cognitive skills and the efficiency of classroom-based educational production in elementary school. Overall, we find significant negative developmental effects for children with food insecurity at home; and that children experiencing an early transition from food insecurity in 1st grade to food security in 3rd grade have even larger impairments that persist through 5th grade.     

幽门螺杆菌CagA蛋白与CTB融合基因的克隆及其植物表达载体的构建

目的　构建能在水稻胚乳中特异表达的幽门螺杆菌细胞毒素相关蛋白(CagA)和霍乱毒素B亚单位(CTB)的植物表达载体.方法　采用高保真PCR技术分别从质粒pGEM CTB和幽门螺杆菌基因组DNA中扩增出CTB和cagA基因,然后用PCR方法直接融合CTB基因和cagA基因.又用PCR法改造了水稻Wx启动子,在其3′端融合加入Ω序列和Kozak序列.通过一系列亚克隆最终将两个融合基因和NOS终止子插入根癌农杆菌双元载体pCAMBI A1300的表达框架内.结果　PCR验证和测序分析证明,CTB和cagA融合基因以正确的方向插入到载体pCAMBI A1300中,并位于水稻Wx启动子后.结论　成功构建CTB和cagA融合基因的植物表达载体,为幽门螺杆菌口服疫苗的研究奠定基础.     

Basic fibroblast growth factor alleviates brain injury following global ischemia reperfusion in rabbits

The aim of this study was to explore the protective effect of basic fibroblast growth factor (bFGF) on brain injury following global ischemia reperfusion and its mechanisms. Brain injury following global ischemia was induced by four vessels occlusion and systemic hypotension. Twenty-four rabbits were randomized into three groups: group A, only dissection of vessels; group B, intravenous infusion of normal saline after reperfusion for 6 h; group C, 30 μg/kg bFGF injected intravenously at the onset of reperfusion, then infused with 10 μg/(kg·h) for 6 h. Serum neuron specific enolase (NSE), S-100B, tumor necrosis factor-α(TNF-α), interleukin-1 (IL-1), interleukin-8 (IL-8) were measured before ischemia, 30 min after ischemia, 0.5, 1, 3, 6 h after reperfusion. Brain water content was determined and cerebral histopathological damages were compared. NSE and S-100B were increased 1 h after reperfusion and reached their peaks 6 h after reperfusion, but were much higher in group B than those in group C 3, 6 h after reperfusion. In groups B and C, TNF-a was increased after ischemia and IL-1 and IL-8 were increased significantly 0.5 h after reperfusion, then reached their peaks 6 h, 3 h, 6 h after reperfusion respectively. TNF-a and IL-8 at the time points of 1 h and 3 h and IL-1 at 3 h and 6 h in group C were correspondingly lower than those in group B. These indices in group A were nearly unchanged. There were less severe cerebral histopathological damages in group C compared with group B, but no difference in brain water content. It could be concluded that bFGF alleviates brain injury following global ischemia and reperfusion by down-regulating expression of inflammatory factors and inhibiting their activities.     

Bézier曲线的升阶及程序实现

基于Bézier曲线的升阶算法,探讨了程序开发的关键技术,并在Visual C++6.0环境下开发Bézier曲线的升阶程序,曲线升阶在界面中可动态实现.     

网络经济下的电子商务成本分析

电子商务是21世纪新的经济增长点,代表着未来经济的发展方向,而目前电子商务的亏损使得人们对电子商务的成本进行分析和探讨。电子商务使交易形式由实体市场转为虚拟市场,这就可能导致交易成本的变化。B2B模式分析了电子商务的成本构成及电子商务下的企业交易成本的变化,探讨了B2B电子商务模式对交易成本的影响。     

CuO/γ-Al2O3上H2催化还原氮氧化物的初步研究

采用γ—Al2O3和CuO／Y—Al2O3作为H2催化还原氮氧化物的催化剂，考察了反应温度、活性组分添加、原料配比以及原料气空速等对NO转化率的影响。结果表明：γ—Al2O3本身对于NO还原有一定的催化活性；Cu的添加可以使γ—Al2O3催化剂的NO还原活性明显提高；在考察的温度范围内，CuO／Y-AlO3催化剂活性随反应温度的升高明显增加，最高可达100％。随着反应原料气H2／NO(mol)的降低，NO转化率下降。     

光荣的荆棘路--对安徒生自传童话的重新解读

安徒生的童话,在普通而极普遍的现象中赋予了思考的深度,因而常读常新.2005年是安徒生诞辰200周年,为了纪念这位家喻户晓的童话大师,文章选取了他的几篇带有自传色彩的童话作品,并结合作家本人的经历进行重新解读,力图对其人其作有更加准确、全面的认识.     

美国磁石学校领导力教育研究——以科布斯领导力磁石小学为例

磁石学校是美国公立学校的一种特殊形式,它的特色在于提供新颖、个性化的课程。其中,领导力教育是磁石学校特色课程的一种。科布斯小学是全关第一所以领导力培养为主题的磁石小学,自1999年选择这一主题以来,它从一所入学率低、发展停滞的学校发展为2008年全美最优秀的六所磁石学校之一。本文介绍了科布斯小学领导力教育的理念、实施内容和方法、支持资源,并分析了科布斯小学领导力教育取得成功的原因。     

基于出版社业务系统的设计和实现

对管理信息系统的C/S、B/S和三层(多层)结构模式做了比较分析,而且分析了目前国内外出版社管理信息化建设的现状,给出了基于出版社的采用三层结构的C/S模式的业务系统的设计和实现方案.     

基于B/S体系结构管理信息系统的分析研究

传统的管理信息系统采用的是C/S体系结构,它是20世纪后期最为流行的软件体系结构。随着Inter-net的兴起和网络技术的成熟,更多管理信息系统的体系结构开始向B/S结构转变。B/S结构的系统利用不断成熟和普及的浏览器技术,实现了原来需要复杂的专用软件才能实现的强大功能,极大地降低了运行成本。