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Classificationofaircleanlinessinanykindofclean roomsandcleanzoneswillbeaccomplishedintermsofconcentrationofairborneparticles .Alightdiscreteair borneparticlecounter (hereafterreferringtoasAPC)isusedtodeterminetheconcentrationofairborneparticlesequaltoandlargerthanthespecifiedsizesatdesignatedsamplinglocation[1,2 ] .Inthepracticalmeasurementofparticleconcentrationincleanrooms,itisfoundthetest ingresultsofparticlenumberinthesameareacountedbydifferentparticlecountersarequitedifferentanduptoanord… 相似文献
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徐志英 《南宁职业技术学院学报》2010,15(1):92-94
提出了一种新的网络层快速切换方法,该方法在链路层同步转发切换方法的基础上通过增加两个网络层切换实体来实现网络层快速切换,实现了IP移动检测的零时延。仿真结果表明,该基于链路层切换技术的网络层快速切换能够减少结点在子网间切换带来的时延,从而满足了实时应用的要求。 相似文献
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追求卓越:美国高中AP课程述评——兼谈近年来美国高中教育质量的提高 总被引:5,自引:0,他引:5
任长松 《课程.教材.教法》2007,(12)
目前,美国每三名高中毕业生中就有一名在高中阶段便已选修了大学水平的AP课程。AP课程自1955-1956学年设立至今已有50多年的历史。美国高中有60%已经开设AP课程。尤其是近年来,AP课程的发展迅猛,选修的学生数量显著增长(许多科目近五年来增长两三倍),成绩合格者所占比例也大幅上升,令联邦政府和全美上下大为振奋。AP课程的开设反映了美国教育重视个性与兴趣、充分发挥学生潜能的鲜明特征,凸显了美国教育"追求卓越"的基本精神和加快优秀人才培养的努力方向。 相似文献
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随着无线局域网络被广泛应用于校园网络场所,其安全问题显得尤为突出。分析了校园无线网络存在的安全问题,结合本校校园无线网络安全建设实际,提出了相应的校园无线网络安全防范措施。 相似文献
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Xiao-yan LI Fu GUO Sheng-yun MA Mu-yuan ZHU Wei-huai PAN Hong-wu BIAN 《Journal of Zhejiang University. Science. B》2019,(4):322-331
目的:本文通过研究microRNA172a(miR172a)对成花途径中关键靶基因APETALA2类(AP2-like)的调控作用及其机理分析,探索通过操纵miRNA表达改变观赏植物花期的基因工程分子育种新策略。创新点:本研究基于植物miR172序列和功能的高度保守性,通过转基因的方法操纵大岩桐miR172的表达,进而影响AP2-like基因的表达,并起到调控花期的作用。方法:本研究借用拟南芥miR172a的已知序列构建组成型过表达载体35S:miR172a和抑制miR172表达的35S:MIM172载体。利用农杆菌介导法成功获得了35S:miR172a过表达株系以及抑制miR172作用的35S:MIM172株系,并利用cDNA末端快速扩增技术(rapid amplification of cDNA ends,RACE)克隆得到了大岩桐AP2-likecDNA全序列,并通过实时荧光定量聚合酶链式反应技术(qPCR)检测转基因株系中AP2-like的表达变化。结论:短日照条件下,35S:miR172a过表达株系花期比野生型提前(47.00±2.16)天;35S:MIM172株系花期延迟(7.00±4.28)天。在35S:miR172a过表达株系中miR172的表达水平明显上升,其靶基因SsAP2-like的表达量明显下降;35S:MIM172株系中miR172的积累水平受到抑制,而SsAP2-like的表达量明显上升,表明miR172介导调控SsAP2的表达对大岩桐成花转变具有促进作用。通过改变miR172的表达调控关键靶基因进而改变花期的方法可以作为调节观赏植物开花时间的有效策略。 相似文献
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Vanessa Witenko Rebeca Mireles-Rios Victor M. Rios 《Journal of Latinos & Education》2017,16(3):176-191
Using affiliation network data collected at a large high school, this study examined differences between who encourages Latina/o and White students to enroll in advanced courses. Previous research has shown a positive association between emotional support and academic achievement, and thus, this study shifts the focus from who informs students to who encourages them. This study revealed that on average, Latina/o and White students have different networks of encouragement. 相似文献
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Mechanism of acute pancreatitis complicated with injury of intestinal mucosa barrier 总被引:4,自引:0,他引:4
Acute pancreatitis (AP) is a common acute abdomen in clinic with a rapid onset and dangerous pathogenetic condition AP can cause an injury of intestinal mucosa barrier, leading to translocation of bacteria or endotoxin through multiple routes, bacterial translocation (BT), gutorigin endotoxaemia, and secondary infection of pancreatic tissue, and then cause systemic inflammatory response syndrome (SIRS) or multiple organ dysfunction syndrome (MODS), which are important factors influencing AP's severity and mortality. Meanwhile, the injury of intestinal mucosa barrier plays a key role in AP's process. Therefore, it is clinically important to study the relationship between the injury of intestinal mucosa barrier and AP. In addition, many factors such as microcirculation disturbance, ischemical reperfusion injury, excessive release of inflammatory mediators and apoptosis may also play important roles in the damage of intestinal mucosa barrier. In this review, we summarize studies on mechanisms of AP. 相似文献
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无线局域网络中的核心设备——无线接入点(Access Point),其性能的好坏将直接影响网络的系统容量与业务处理能力,无线接入点的研究对于无线局域网的应用与发展具有重要意义.为此,IEEE 802.11无线局域网标准工作组制订了IAPP(Inter-Access Point Protocol)协议,支持无线用户在AP间的移动.通过分析IAPP协议和在AP上实现IAPP功能,从理论和实践两个方面对无线局域网移动性进行了深入研究. 相似文献