Fabrication of universal serial bus flash disk type microfluidic chip electrophoresis and application for protein analysis under ultra low voltage

A simple and effective universal serial bus (USB) flash disk type microfluidic chip electrophoresis (MCE) was developed by using poly(dimethylsiloxane) based soft lithography and dry film based printed circuit board etching techniques in this paper. The MCE had a microchannel diameter of 375 μm and an effective length of 25 mm. Equipped with a conventional online electrochemical detector, the device enabled effectively separation of bovine serum albumin, lysozyme, and cytochrome c in 80 s under the ultra low voltage from a computer USB interface. Compared with traditional capillary electrophoresis, the USB flash disk type MCE is not only portable and inexpensive but also fast with high separation efficiency.     

Study on surface properties of PDMS microfluidic chips treated with albumin

Electrokinetic properties and morphology of PDMS microfluidic chips intended for bioassays are studied. The chips are fabricated by a casting method followed by polymerization bonding. Microchannels are coated with 1% solution of bovine serum albumin (BSA) in Tris buffer. Albumin passively adsorbs on the PDMS surface. Electrokinetic characteristics (electro-osmotic velocity, electro-osmotic mobility, and zeta potential) of the coated PDMS channels are experimentally determined as functions of the electric field strength and the characteristic electrolyte concentration. Atomic force microscopy (AFM) analysis of the surface reveals a “peak and ridge” structure of the protein layer and an imperfect substrate coating. On the basis of the AFM observation, several topologies of the BSA-PDMS surface are proposed. A nonslip mathematical model of the electro-osmotic flow is then numerically analyzed. It is found that the electrokinetic characteristics computed for a channel with the homogeneous distribution of a fixed electric charge do not fit the experimental data. Heterogeneous distribution of the fixed electric charge and the surface roughness is thus taken into account. When a flat PDMS surface with electric charge heterogeneities is considered, the numerical results are in very good agreement with our experimental data. An optimization analysis finally allowed the determination of the surface concentration of the electric charge and the degree of the PDMS surface coating. The obtained findings can be important for correct prediction and possibly for robust control of behavior of electrically driven PDMS microfluidic chips. The proposed method of the electro-osmotic flow analysis at surfaces with a heterogeneous distribution of the surface electric charge can also be exploited in the interpretation of experimental studies dealing with protein-solid phase interactions or substrate coatings.     

Comparative studies on the analysis of glycoproteins and lipopolysaccharides by the gel-based microchip and SDS-PAGE

In order to determine time efficiency between the gel-based microchip (LabChip) and traditional sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), glycoproteins and lipopolysaccharides were analyzed in this study. After 90 min of gel electrophoresis, glycoproteins (bovine serum albumin, lysozyme, ovalbumin, and apo-transferrin) and fluorescent lipopolysaccharides (LPS-O and LPS-S) under reducing conditions could be analyzed by SDS-PAGE, and it would take (including imaging and analyzing) more than 3 h. The same sample could also be assayed on a Bioanalyzer in combination with the LabChip, and it would only need 30 min from start to finish. The assay software automatically calculated the size and concentration of each separated peak and displayed the results in real time, thus eliminating time-consuming procedures such as imaging and analyzing. Compared to the traditional reducing SDS-PAGE, LabChip has a faster turnaround time.     

灯泡线列车掉头解决方案技术分析

当前轨道交通工程中的信号系统设计越来越多的应用了基于无线的列车控制(CBTC)系统[1],CBTC系统面临着一个共同的问题,即在灯泡线上列车掉头时,轨旁无线接入点(AP)与列车无线通信设备之间通信网络的双网切换问题,在确保行车安全的前提下,为了使列车连续有效的与地面通信,必须合理的处理这个问题。     

Ｈｅｉｓｅｎｂｅｒｇ群上一类ｐ-次Ｌａｐｌａｃｅ方程解的存在性

利用变分原理研究Heisenberg群上p-次Laplace方程-△H,pu=λg(ξ)| u |γ-2u,当λ∈R,1＜p＜Q=2n-2,2≤γ＜Qp/Q-p,γ≠p时,方程至少存在一个非平凡解,并且采用Moser迭代技巧进行解的L∞估计.     

谈健美操对学生形体的可塑作用

学校健美操扩展了传统的学校体育教学模式,改善和活跃了体育课堂的气氛;并能充分满足学生的心理生理需要。     

CMC聚合物对重金属离子的吸附性能

通过正交试验得出制备羧甲基纤维素(CMC)聚合物的最佳工艺条件:丙烯酸(AA)/羧甲基纤维素=10,引发剂(硫酸铵)和交联剂(N,N'-亚甲基双丙烯酰胺)用量分别为单体的0.0014倍和0.0015倍.吸胀平衡后,将CMC聚合物在400~450℃下完全灰化16h,消解并用火焰原子吸收法测定聚合物对Zn2+、Cu2+、Pb2+、Cd2+、Cr2+、Ni2+和Mn2+的吸附性能.结果表明,CMC聚合物对重金属离子具有一定的吸附能力,其吸附量随着溶液pH值和重金属离子质量浓度的增加而增大,当pH为9时达到最大;并且CMC聚合物对Pb2+和Cu2+的吸附量要大于其他金属离子.     

Development of flow through dielectrophoresis microfluidic chips for biofuel production: Sorting and detection of microalgae with different lipid contents

In this study, a continuous flow dielectrophoresis (DEP) microfluidic chip was fabricated and utilized to sort out the microalgae (C. vulgaris) with different lipid contents. The proposed separation scheme is to allow that the microalgae with different lipid contents experience different negative or no DEP force at the separation electrode pair under the pressure-driven flow. The microalgae that experience stronger negative DEP will be directed to the side channel while those experience less negative or no DEP force will pass through the separation electrode pair to remain in the main channel. It was found that the higher the lipid content inside the microalgae, the higher the crossover frequency. Separation of the microalgae with 13% and 21% lipid contents, and 24% and 30%–35% lipid contents was achieved at the operating frequency 7 MHz, and 10 MHz, respectively. Moreover, separation can be further verified by measurement of the fluorescence intensity of the neutral lipid inside the sorted algal cells.     

物联网开发网络的识别与刻画研究

开发网络是物联网新产品实现商业化的关键.小世界特征有利于物联网开发网络的形成和发展.中间中心性低表明物联网开发网络缺乏强有力的协调者.应用企业或集成企业对物联网应用的市场需求,是物联网形成和发展的根本动力.物联网开发网络的形成需要经过要素集聚、极核形成、规则创新三个阶段.     

基于序列二次规划法对汽车保险杠系统关于行人小腿保护的优化设计研究

通过有限元分析方法来研究保险杠系统的各设计因素对行人腿部伤害值的影响。所使用的模型中,包括了汽车前部的有限元模型和行人小腿部模型。根据分析结果数据,建立胫骨加速度、膝盖弯曲角度和剪切位移三个目标函数,然后利用SQP算法进行对保险杠系统优化分析,以提高保险杠系统的行人保护性能．     

基于城市职能视角下广西低碳城市发展的模式选择

文章以城市职能分类为视角,运用纳尔逊城市职能统计分析方法确定广西各城市的主导职能和显著职能,将广西14个地级城市分为综合性中心城市、制造与建筑业城市、旅游城市、港口交通城市、服务性城市、资源型城市和无主导职能城市7类,并提出基于不同城市职能的各类城市适合自身发展的低碳模式。     

Properties of value function and existence of viscosity solution of HJB equation for stochastic boundary control problems

In the present paper, we study stochastic boundary control problems where the system dynamics is a controlled stochastic parabolic equation with Neumann boundary control and boundary noise. Under some assumptions, the continuity and differentiability of the value function are proved. We also define a new type of Hamilton–Jacobi–Bellman (HJB) equation and prove that the value function is a viscosity solution of this HJB equation.     

Study of flow behaviors on single-cell manipulation and shear stress reduction in microfluidic chips using computational fluid dynamics simulations

Various single-cell retention structures (SCRSs) were reported for analysis of single cells within microfluidic devices. Undesirable flow behaviors within micro-environments not only influence single-cell manipulation and retention significantly but also lead to cell damage, biochemical heterogeneity among different individual cells (e.g., different cell signaling pathways induced by shear stress). However, the fundamentals in flow behaviors for single-cell manipulation and shear stress reduction, especially comparison of these behaviors in different microstructures, were not fully investigated in previous reports. Herein, flow distribution and induced shear stress in two different single-cell retention structures (SCRS I and SCRS II) were investigated in detail to study their effects on single-cell trapping using computational fluid dynamics (CFD) methods. The results were successfully verified by experimental results. Comparison between these two SCRS shows that the wasp-waisted configuration of SCRS II has a better performance in trapping and manipulating long cylinder-shaped cardiac myocytes and provides a safer “harbor” for fragile cells to prevent cell damage due to the shear stress induced from strong flows. The simulation results have not only explained flow phenomena observed in experiments but also predict new flow phenomena, providing guidelines for new chip design and optimization, and a better understanding of the cell micro-environment and fundamentals of microfluidic flows in single-cell manipulation and analysis.     

The solutions for rate equations of lasers with initial and boundary conditions based on diffusion equation

The rate equations describing a solid-state laser are derived from diffusion equation. To settle the equations, a LD pumped Q-switched laser is considered. With the initial and boundary conditions, the photon intensity φ(r,t)and population inversion n(r,t)are obtained. The calculated values fit the experimental results well.     

藏药多血康对家兔血瘀症模型全血黏度及红细胞流变性的影响

藏医认为人体是由三大基因（龙、赤巴、培根）,七大物质（即液、血、肉、脂、骨、髓、精）和三种排泄物（大便、小便、汗）组合起来的一个有机体。它们是构成人体正常生命活动的物质基础,它们之间相互依存,相互转化,共同处于生命这一统一体中,并且保持着一定的动态平衡,这种平衡在生理上相互联系,在病理上相互影响,某一方面的失调都可影响到其它方面。