Particle captured by a field-modulating vortex through dielectrophoresis force

In microfluidic technology, dielectrophoresis (DEP) is commonly used to manipulate particles. In this work, the fluid-particle interactions in a microfluidic system are investigated numerically by a finite difference method (FDM) for electric field distribution and a lattice Boltzmann method (LBM) for the fluid flow. In this system, efficient particle manipulation may be realized by combining DEP and field-modulating vortex. The influence of the density ($\rho_{\rm p}$), radius ($r$), and initial position of the particle in the $y$ direction ($y_{\rm p0}$), and the slip velocity ($u_{0}$) on the particle manipulation are studied systematically. It is found that compared with the particle without action of DEP force, the particle subjected to a DEP force may be captured by the vortex over a wider range of parameters. In the $y$ direction, as $\rho_{\rm p}$ or $r $ increases, the particle can be captured more easily by the vortex since it is subjected to a stronger DEP force. When $u_{0}$ is low, particle is more likely to be captured due to the vortex-particle interaction. Furthermore, the flow field around the particle is analyzed to explore the underlying mechanism. The results obtained in the present study may provide theoretical support for engineering applications of field-controlled vortices to manipulate particles.     

基于Boxcar滤波器的荧光检测二氧化硫信号的去噪研究

荧光法以物质发射的荧光强度与浓度之间的线性关系进行定量分析。当采用荧光法检测大气中的二氧化硫等有害气体时,由于光电探测器等光电元件在无荧光时,仍会产生暗电流噪声,使得本底噪声信号对测量结果有直接的影响。在分析Boxcar滤波算法的基础上,运用小波滤波、EMD滤波和Boxcar滤波三种算法对淹没在本底噪声中的荧光信号进行有效提取和恢复,较之前两种滤波方法,Boxcar滤波效果更佳,对本底噪声的抑制更强,并验证了取样次数影响着荧光信号的信噪比。     

Effect of Joule heating on the electroosmotic microvortex and dielectrophoretic particle separation controlled by local electric field

Dielectrophoresis (DEP) technology has become important application of microfluidic technology to manipulate particles. By using a local modulating electric field to control the combination of electroosmotic microvortices and DEP, our group proposed a device using a direct current (DC) electric field to achieve continuous particle separation. In this paper, the influence of the Joule heating effect on the continuous separation of particles is analyzed. Results show that the Joule heating effect is caused by the local electric field, and the Joule heating effect caused by adjusting the modulating voltage is more significant than that by driving voltage. Moreover, a non-uniform temperature distribution exists in the channel due to the Joule heating effect, and the temperature is the highest at the midpoint of the modulating electrodes. The channel flux can be enhanced, and the enhancement of both the channel flux and temperature is more obvious for a stronger Joule heating effect. In addition, the ability of the vortices to trap particles is enhanced since a larger DEP force is exerted on the particles with the Joule heating effect; and the ability of the vortex to capture particles is stronger with a stronger Joule heating effect. The separation efficiency can also be increased because perfect separation is achieved at a higher channel flux. Parameter optimization of the separation device, such as the convective heat transfer coefficient of the channel wall, the length of modulating electrode, and the width of the channel, is performed.     

腺嘌呤、脱氧核糖和脱氧腺苷与烷基胺的相互作用研究

用LKB－2277精密微量热仪测定了288．15K，298．15K和308．15K时的DNA组成成分腺嘌呤，脱氧核糖和脱氧腺苷与烷基胺（乙胺、丙胺、丁胺和正庚胺）之间的相互作用焓变，实验结果表明，烷基胺与它们混合时在所测的温度范围内的相互作用焓变表现出明显的规律性，紫外光谱研究也证实腺嘌呤和脱氧腺苷与正庚胺发生相互作用，通过和正庚烷与腺嘌呤，脱氧腺苷相互作用焓变大小的比较，讨论了烷基胺与腺嘌呤，脱氧腺苷相互作用可能发生的靶点。     

脉冲半导体激光器电源电路分析

直接调制的大电流窄脉宽驱动电源是脉冲半导体激光器获得高峰值功率输出的重要保证。建立了脉冲半导体激光器驱动电源的等效电路及其LRC回路模型，对线性常系数二阶齐次微分方程的分析解进行了分析，并与实验结果做了比较。结果显示，当电源主要参数满足R≥2√L/C关系时，可获得较为理想的非振荡放电过程，实测脉冲波形及其特性与计算结果相符合。     

丙烯酸羟丙酯与1-(2-叔丁基过氧异丙基)-3-异丙烯基苯共聚行为研究

丙烯酸羟丙酯与1－（2－叔丁基过氧异丙基）－3－异丙烯基苯（D120）能进行自由基共聚合反应，聚合后过氧基团以侧基的形式被保留在共聚物大分子链上，凝胶色谱分析发现：随原料单体中D120比例增加，共聚物的分子量减小，分子量分布变窄；DSC分析发现共聚物中过氧基团的分解温度随D120结构单元含量的增加而下降，但仍高于D120单体过氧基团的分解温度，苯乙烯与D120的竞聚率为：γD120=0.98,γHPA=0.72。     

甲基丙烯酸甲酯与1-(2-叔丁基过氧异丙基)-3-异丙烯基苯的共聚研究

讨论了甲基丙烯酸甲酯与１－（２－叔丁基过氧异丙基）－３－异丙烯基苯的共聚行为。通过自由基共聚得到了带过氧侧基的聚合物。通过红外光谱，紫外光谱和凝胶色谱对共聚物进行了表征。用碘量法测定了共聚物中活性氧的含量，并由此测定了两者的竞聚率，ｒＤ１２０＝０．６９±０．０８，ｒＭＭＡ＝０．６３±０．０８。