坐标变换在弧齿圆锥齿轮切齿调整计算中的应用

本文论述了在弧齿圆锥齿轮切齿加工时,利用坐标变换的理论,使刀具与毛胚的安装尺寸调整计算这个比较复杂,难深的过程,变得简捷、明僚,充分展示了坐标变换方法在齿轮传动理论研究上的广阔前景.     

聚苯乙烯凝胶平均孔径尺寸的研究

研究了聚苯乙烯凝胶合成及其孔径的控制,并用两种不同的方法计算了各类凝胶的平均孔径。     

量子化学方法研究HZSM-5沸石结构酸性(Ⅳ)

HZSM-5沸石分子筛硅铝骨架结构基本单元为五元环,它通过氧桥联接而得到单元为四元环、六元环。本文采用CNDO/2半经验量子化学的方法,对HZSM-5沸石基本结构单元—四、五、六元环的电荷分布进行计算。依据Mortier等人处理y型沸石分子筛酸性的基本思想,从而得到了HZSM-5沸石分子筛酸性结构参数α_0。Barthomeuf等认为沸石分子筛可作为一个多元酸的电解质溶液,因此其质子酸度应用活度来表示。a_(H~+)=[H~+]f_(H~+),而活度系数f_(H~+)为结构参数乘以一个常数,f_(H~+)=Kα_0,我们取K=32,[H~+]=nH~+αN_(A_1)/Z_(cat),从理论上求出HZSM-5沸石分子筛在不同硅铝比时的活度,其结果和实验值相一致。这为从理论上计算HZSM-5沸石分子筛的酸性提供了一个参考方法。     

GCC box in<Emphasis Type="Italic">Arabidopsis PDF1.2</Emphasis> promoter is an essential and sufficient cis-acting element in response to MeJA treatment

The expression of Arabidopsis PDF1.2 gene isregulated by jasmonic acid (JA) and ethylene (ET). It also has been well documented that GCC box is an element responsive to ET, however, the responsive mechanism of JA in such plant defense gene expression is unclear. In this paper, the authors define the essential cis-acting element in PDF1.2 promoter responsive to methyl jasmonate (MeJA) through fragment deletions and site-directed mutageneses combiningAgrobacterium-mediated transient reporter gene expression in tobacco leaves. Firstly, the MeJA inducible expression o fPDF1.2 was confirmed by using the upstream -1.86 kb fragment of PDFI.2 gene. Secondly, the upstream -300— -243 bp fragment of the promoter was evidenced to respond to MeJA. To further characterize this promoter region, three point mutations were introduced into the -300— -243 bp fragment of the promoter. This result showed that the mutation of GCC box abolished MeJA induction, whereas the mutations of the G box-like and the imperfect palindrome sequence did not significantly decrease MeJA inducible effect, indicating that GCC box in PDFI.2 is essential for MeJA induction. The sufficient responsiveness to MeJA of this GCC box was further investigated by 4xGCC fused upstream to the CaMV 35S minimal promoter. This result suggested that the fused promoter was able to activate reporter gene expression in response to MeJA. Thus these results indicate that the GCC box in PDFI.2 is an essential and sufficient element to confer MeJA induction.     

VEGF links hippocampal activity with neurogenesis, learning and memory

An enriched environment is associated with hippocampal plasticity, including improved cognitive performance and increased neurogenesis. Here, we show that hippocampal expression of vascular endothelial growth factor (VEGF) is increased by both an enriched environment and performance in a spatial maze. Hippocampal gene transfer of VEGF in adult rats resulted in approximately 2 times more neurogenesis associated with improved cognition. In contrast, overexpression of placental growth factor, which signals through Flt1 but not kinase insert domain protein receptors (KDRs), had negative effects on neurogenesis and inhibited learning, although it similarly increased endothelial cell proliferation. Expression of a dominant-negative mutant KDR inhibited basal neurogenesis and impaired learning. Coexpression of mutant KDR antagonized VEGF-enhanced neurogenesis and learning without inhibiting endothelial cell proliferation. Furthermore, inhibition of VEGF expression by RNA interference completely blocked the environmental induction of neurogenesis. These data support a model in which VEGF, acting through KDR, mediates the effect of the environment on neurogenesis and cognition.     

谐波对电能计量影响的分析及对策研究

本文介绍了谐波产生的原因及其对感应式电能表和电子式电能表的影响 ,从感应式电能表和电子式电能表频率响应曲线入手 ,分析了由于谐波的存在而引起的电能计量仪表误差的变化情况 ,并提出了减小电能计量误差的方法和对策     

突发公共事件应急管理中公权力与私权利的协调

在突发公共事件应急管理中,如何协调好国家公权力和公民私权利之间的关系既是解决突发公共事件本身的需要,也是建设和谐社会的内在要求,还是国际人权保护的必然要求。在突发公共事件应急管理中,必须牢固树立法治理念,同时在比例原则、行政公开原则、权责统一原则等一般原则及公权力优先原则、有限行政紧急权原则、有限救济原则、基本人权不得克减原则等特殊原则的指导下,通过建立和完善突发事件分级、公民抵制权、国家赔偿、信息公开等一系列具体的制度,切实协调好公权力与私权利之间的关系。     

周边固定的三角形板的弯曲

应用功的互等定理研究了在一集中载荷作用下三边固定三角形板的弯曲问题，给出了该问题的精确解。     

定量评估试题库的方法

以定量的方法对试题库进行了质量分析，该方法充分反映了试题的客观规律．这为试题库的建设与质量管理提供了科学的依据，从而能够获得稳定、可靠的标准试卷．     

Distributed modeling of the beginning and ending dates and durations of limited temperatures over the rugged terrain of Chongqing

A physically based empirical model was established for the beginning and ending dates (BED) of limited temperatures.Data used were daily mean temperatures from 34 conventional stations in the Chongqing region,measured from 1961 to 2000.Using this model in combination with the distributed modeling results of monthly mean temperatures,we developed a method for creating a distributed simulation of the BED and durations of limited temperatures in the rugged terrain of Chongqing.Spatial distribution maps were generated at a resolution of 100×100 m for the BED and durations of the limited temperatures of 0,10,15 and 20.Simulations suggest that the distributed model is able to successfully reveal the macroscopic trends and local distributions.For the modeled BED,the mean absolute bias error is 0.6-2.4 d.Cross-validation and case-year tests show mean absolute bias errors of 1.3-2.8 d and 0.7-2.5 d,respectively.Comparison shows that the simulation results are consistent with the field investigations.This implies that the simulations are as good as observations,thus providing a viable technique for simulating mountainous heat resources using conventional meteorological data.