Mechanistic investigation of nanoparticle motion in pulsed voltage miniaturized electrical field flow fractionation device by in situ fluorescence imaging

In our previous study, we reported a miniaturized electrical field flow fractionation device (micro-EFFF) that used a pulsed voltage (PV) to increase the effective electric field and, hence, improved the separation performance. In this work, we developed two micro-EFFFs with planar or segmented electrode design and investigated the particle movement in the flow channels under a PV. Numerical simulation was used to understand the electric field distribution in the micro-EFFFs. When the calculations for the micro-EFFF with a segmented electrode (segmented micro-EFFF) and the micro-EFFF with planar electrodes (planar micro-EFFF) are compared, a stronger electric field at the top electrode segments is found in the segmented micro-EFFF, with the strongest field at the edges of the electrode segments. Nanoparticle motion in both devices was in situ visualized by using a fluorescence microscope equipped with a CCD-camera. Results reveal that electrophoresis governs the nanoparticle movement in the planar micro-EFFF and dielectrophoresis dominates the movement in the segmented micro-EFFF. Two models are postulated to explain the experimental observations of the nanoparticle movement. The mechanistic understanding of controlling nanoparticle motion in a miniaturized environment will help the design and application of micro-EFFF for the separation of charged biomolecules (proteins and DNAs).     

A nucleic acid biosensor for gene expression analysis in nanograms of mRNA

An ultrasensitive nucleic acid biosensor for direct detection of genes in mRNA extracted from animal tissues is described. It is based on amperometric detection of a target gene by forming an mRNA/redox polymer bilayer on a gold electrode. The mRNA was directly labeled with cisplatin-biotin conjugates through coordinative bonds with purine bases in the mRNA molecules. A subsequent binding of glucose oxidase-avidin conjugates to the labeled mRNA and the introduction of a poly(vinylimidazole-co-acrylamide) partially imidazole-complexed with [Os(bpy)(2)(im)] (bpy = 2,2'-bipyridine, im = imidazole) redox polymer overcoating to the electrode allowed for electrochemical detection of the oxidation current of glucose in solution. Depending on individual genes, detection limits of subfemtograms were achieved. As compared to a sandwich-type assay, the sensitivity was improved by as much as 25-fold through the incorporation of multiple enzyme labels to the mRNA molecules. Less than 2-fold gene expression difference was unambiguously differentiated in as little as 5.0 ng of mRNA. With the greatly improved sensitivity, at least 1000-fold more sensitive than fluorescence-based techniques, the amount of mRNA needed in the assay was cut down from microgram to nanogram levels.     

网管接口时延性能指标的定义与测试方法

提出了网管接口时延性能的衡量指标——网管接口操作时延的定义。对IP网中点到点的数据包传输时延进行了研究,提出了在以太网中基于ICM P的网络传输时延的测试方法,并通过实验对此方法进行了验证。将网络传输时延测试方法应用于网管接口测试的实际环境中,得到一种测试网管接口操作时延的可行方法。     

基于L-系统的植物模拟研究

该文根据L-系统原理,通过改变参数L-系统和随机L-系统的参数,得到同一类植物的不同基因组合,利用计算机模拟生成了丰富多样的植物形态。又根据L-系统符号解释的扩展,模拟了类似棕榈的植物生长平衡过程。     

四连杆曲柄飞剪机剪切力测试与分析

通过对四连杆曲柄飞剪机剪切力的测试与分析,弄清了剪切力与工艺参数之间的定量关系,为合理安排生产,确保飞剪机安全运行,掌握飞剪机的最大生产能力,正确评估飞剪机的工作状态提供了重要依据。在测试中,解决了不少技术难题,如剪刃受力静不定系统的转化、剪刃的技术改造方法、标定时实际剪切状态的模拟、剪切力信号的获取方法、应力测量时的温度补偿与导线的热辐射防护等。     

Ti50Ni43Cu7合金在不同应力作用下的回复特性研究

研究了Ti50Ni43Cu7合金在290 MPa和245 MPa两种应力作用下的回复特性.测试了Ti50Ni43Cu7合金在两种应力作用不同循环次数下的回复应变.结果表明:在290 MPa应力作用下,随着循环次数的增加,残余应变的增加和马氏体的稳定化导致回复应变逐渐减少,回复应变趋于稳定.在245 MPa应力作用下,随着循环次数的增加,应力诱发马氏体相变临界应力值下降,预应变的增加大于残余应变的增加,回复应变逐步增大,随着马氏体的稳定化,回复应变趋于稳定.     

搞好电子设计竞赛 深化实践教学改革

从介绍近年来在指导学生参加全国大学生电子设计竞赛工作中的一些认识和体会,分析学生在竞赛中所暴露的有关实践教学方面的一些问题,并阐述我院在以电子设计为契机,深化实践教学改革的一些做法。     

丝绸、羊毛织物再定形中尺寸变化的可逆性

织物上有两种尺寸变化,它们都与定形有关,这就是不可逆的收缩和可逆的尺寸变化,涤纶等合纤在定形时产生的收缩是不可逆的,而丝绸、羊毛等天然纤维织物在定形与再定形时发生的尺寸变化具有一定的可逆性。     

潍北凹陷孔店组烃源岩评价及油源分析

潍北凹陷孔店组二段既有好、较好、较差烃源岩,也发育有机质富集层烃源岩(又称为优质烃源岩)。有机质富集层烃源岩沉积环境为亚热带型湿热古气候条件下的滨浅湖相淡-微咸水沉积,古生物以被子、裸子植物孢粉组合为主,含有介形类及少量藻类化石,干酪根类型为 , ₂及 ₁型,岩性为碳质泥岩及深灰色泥岩,有机碳含量大于4.5%,氯仿沥青“A”含量大于0.17%。依据原油的物理性质将潍北凹陷原油分为稠油、中密度油和低密度油,根据原油的生物标志物特征又可将本区原油分为低熟油和成熟油。大部分低熟油样品具有高Pr/Ph比值,低伽马蜡烷/C₃₀藿烷比值及高C₂₉甾烷含量的特征。稠油及大部分中密度油属于低熟油,油源对比表明主要来源于孔店组二段有机质富集层烃源岩。部分中密度油及低密度油属于成熟油,其油源与低熟油相同。     

北京地铁复-八线车站施工对环境影响的预测与分析

介绍了对北京地铁复-八线天安门西车站暗挖施工过程中对地层沉降以及管线变形的预测及分析,分析的结果对该地铁站的施工起到了重要的指导作用.施工过程中的监测结果非常好地证实了最初的预测,并据此采取了及时有效的控制措施,这一经验有助于指导北京地区同类工程的地层沉降控制问题.