Making quantitative biomicrofluidics from microbore tubing and 3D-printed adapters

Microfluidic technology has tremendously facilitated the development of in vitro cell cultures and studies. Conventionally, microfluidic devices are fabricated with extensive facilities by well-trained researchers, which hinder the widespread adoption of the technology for broader applications. Enlightened by the fact that low-cost microbore tubing is a natural microfluidic channel, we developed a series of adaptors in a toolkit that can twine, connect, organize, and configure the tubing to produce functional microfluidic units. Three subsets of the toolkit were thoroughly developed: the tubing and scoring tools, the flow adaptors, and the 3D cell culture suite. To demonstrate the usefulness and versatility of the toolkit, we assembled a microfluidic device and successfully applied it for 3D macrophage cultures, flow-based stimulation, and automated near real-time quantitation with new knowledge generated. Overall, we present a new technology that allows simple, fast, and robust assembly of customizable and scalable microfluidic devices with minimal facilities, which is broadly applicable to research that needs or could be enhanced by microfluidics.     

坐骨神经三维可视化实现功能与技术研究

坐骨神经痛是坐骨神经通路及其分布区的疼痛。针灸治疗坐骨神经痛取穴足太阳膀胱经和足少阳胆经两经为主,以辨症取穴为辅的配穴原则和规律在临床应用更为广泛,效果更为显著。实现坐骨神经痛三维可视化研究需模拟人体模型。采用Poly建模,利用Biped绑定骨骼和人体网格,Physique修改器控制角色在运动中皮肤肌肉的变形,并用NURBS系统和复合对象中的“放样”实现经络模拟。     

ICT and an NGO: Difficulties in attempting to be extremely transparent

This paper analyzes the opportunities offered by information and communication technologies (ICTs) and the related ethical issues, within the transparency practices of nongovernmental organizations (NGOs). Based upon a one-year study of a European NGO, the Italian Association of Blind People, it presents compelling empirical evidence concerning the main ethical, social and economic challenges that NGOs face in the development of more transparent relationships with the public and the related role of ICTs, in particular, the organization’s website. This study shows that, although the attempt to be completely transparent has great ethical value, ICT-enabled information disclosure is limited by privacy and security concerns and by pressure from financial supporters and benefactors and potential NGO competitors who vie for grants and donations. The paper provides some implications and suggestions for managers of NGOs and policy makers.     

Measurement of single leukemia cell's density and mass using optically induced electric field in a microfluidics chip

We present a method capable of rapidly (∼20 s) determining the density and mass of a single leukemic cell using an optically induced electrokinetics (OEK) platform. Our team had reported recently on a technique that combines sedimentation theory, computer vision, and micro particle manipulation techniques on an OEK microfluidic platform to determine the mass and density of micron-scale entities in a fluidic medium; the mass and density of yeast cells were accurately determined in that prior work. In the work reported in this paper, we further refined the technique by performing significantly more experiments to determine a universal correction factor to Stokes'' equation in expressing the drag force on a microparticle as it falls towards an infinite plane. Specifically, a theoretical model for micron-sized spheres settling towards an infinite plane in a microfluidic environment is presented, and which was validated experimentally using five different sizes of micro polystyrene beads. The same sedimentation process was applied to two kinds of leukemic cancer cells with similar sizes in an OEK platform, and their density and mass were determined accordingly. Our tests on mouse lymphocytic leukemia cells (L1210) and human leukemic cells (HL-60) have verified the practical viability of this method. Potentially, this new method provides a new way of measuring the volume, density, and mass of a single cell in an accurate, selective, and repeatable manner.     

Distinctive translational and self-rotational motion of lymphoma cells in an optically induced non-rotational alternating current electric field

In this paper, the translational motion and self-rotational behaviors of the Raji cells, a type of B-cell lymphoma cell, in an optically induced, non-rotational, electric field have been characterized by utilizing a digitally programmable and optically activated microfluidics chip with the assistance of an externally applied AC bias potential. The crossover frequency spectrum of the Raji cells was studied by observing the different linear translation responses of these cells to the positive and negative optically induced dielectrophoresis force generated by a projected light pattern. This digitally projected spot served as the virtual electrode to generate an axisymmetric and non-uniform electric field. Then, the membrane capacitance of the Raji cells could be directly measured. Furthermore, Raji cells under this condition also exhibited a self-rotation behavior. The repeatable and controlled self-rotation speeds of the Raji cells to the externally applied frequency and voltage were systematically investigated and characterized via computer-vision algorithms. The self-rotational speed of the Raji cells reached a maximum value at 60 kHz and demonstrated a quadratic relationship with respect to the applied voltage. Furthermore, optically projected patterns of four orthogonal electrodes were also employed as the virtual electrodes to manipulate the Raji cells. These results demonstrated that Raji cells located at the center of the four electrode pattern could not be self-rotated. Instead any Raji cells that deviated from this center area would also self-rotate. Most importantly, the Raji cells did not exhibit the self-rotational behavior after translating and rotating with respect to the center of any two adjacent electrodes. The spatial distributions of the electric field generated by the optically projected spot and the pattern of four electrodes were also modeled using a finite element numerical simulation. These simulations validated that the electric field distributions were non-uniform and non-rotational. Hence, the non-uniform electric field must play a key role in the self-rotation of the Raji cells. As a whole, this study elucidates an optoelectric-coupled microfluidics-based mechanism for cellular translation and self-rotation that can be used to extract the dielectric properties of the cells without using conventional metal-based microelectrodes. This technique may provide a simpler method for label-free identification of cancerous cells with many associated clinical applications.     

Cell separation and transportation between two miscible fluid streams using ultrasound

This paper presents a two-stream microfluidic system for transporting cells or micro-sized particles from one fluid stream to another by acoustophoresis. The two fluid streams, one being the original suspension and the other being the destination fluid, flow parallel to each other in a microchannel. Using a half-wave acoustic standing wave across the channel width, cells or particles with positive acoustic contrast factors are moved to the destination fluid where the pressure nodal line lies. By controlling the relative flow rate of the two fluid streams, the pressure nodal line can be maintained at a specific offset from the fluid interface within the destination fluid. Using this transportation method, particles or cells of different sizes and mechanical properties can be separated. The cells experiencing a larger acoustic radiation force are separated and transported from the original suspension to the destination fluid stream. The other particles or cells experiencing a smaller acoustic radiation force continue flowing in the original solution. Experiments were conducted to demonstrate the effective separation of polystyrene microbeads of different sizes (3 μm and 10 μm) and waterborne parasites (Giardia lamblia and Cryptosporidium parvum). Diffusion occurs between the two miscible fluids, but it was found to have little effects on the transport and separation process, even when the two fluids have different density and speed of sound.     

Micromixing visualization and quantification in a microscale multi-inlet vortex nanoprecipitation reactor using confocal-based reactive micro laser-induced fluorescence

A technique for visualizing and quantifying reactive mixing for laminar and turbulent flow in a microscale chemical reactor using confocal-based microscopic laser induced fluorescence (confocal μ-LIF) was demonstrated in a microscale multi-inlet vortex nanoprecipitation reactor. Unlike passive scalar μ-LIF, the reactive μ-LIF technique is able to visualize and quantify micromixing effects. The confocal imaging results indicated that the flow in the reactor was laminar and steady for inlet Reynolds numbers of 10, 53, and 93. Mixing and reaction were incomplete at each of these Reynolds numbers. The results also suggested that although mixing by diffusion was enhanced near the midplane of the reactor at Re_j = 53 and 93 due to very thin bands of acidic and basic fluid forming as the fluid spiraled towards the center of the reactor, near the top, and bottom walls of the reactor, the lower velocities due to fluid friction with the walls hindered the formation of these thin bands, and, thus, resulted in large regions of unmixed and unreacted fluid. At Re_j = 240, the flow was turbulent and unsteady. The mixing and reaction processes were still found to be incomplete even at this highest Reynolds number. At the reactor midplane, the flow images at Re_j = 240 showed unmixed base fluid near the center of the reactor, suggesting that just as in the Re_j = 53 and 93 cases, lower velocities near the top and bottom walls of the reactor hinder the mixing and rection of the acidic and basic streams. Ensemble averages of line-scan profiles for the Re_j = 240 were then calculated to provide statistical quantification of the microscale mixing in the reactor. These results further demonstrate that even at this highest Reynolds number investigated, mixing and reaction are incomplete. Visualization and quantification of micromixing using this reactive μ-LIF technique can prove useful in the validation of computational fluid dynamics models of micromixing within microscale chemical reactors.     

谐振磁场中自旋系统的演化和几何相因子

量子不变量理论是研究几何相因子问题的有效方法。利用Ｌｅｗｉｓ－Ｒｉｅｓｅｎｆｅｌｄ不变量理论研究了谐振磁场中的自旋系统,给出了两种不同循环演化周期的精确解,并进而分别计算了此系统两种不同的几何相因子。研究表明,不同循环演化周期的几何相因子与初始态的选择有关。     

The influence of task and gender on search and evaluation behavior using Google

To improve search engine effectiveness, we have observed an increased interest in gathering additional feedback about users’ information needs that goes beyond the queries they type in. Adaptive search engines use explicit and implicit feedback indicators to model users or search tasks. In order to create appropriate models, it is essential to understand how users interact with search engines, including the determining factors of their actions. Using eye tracking, we extend this understanding by analyzing the sequences and patterns with which users evaluate query result returned to them when using Google. We find that the query result abstracts are viewed in the order of their ranking in only about one fifth of the cases, and only an average of about three abstracts per result page are viewed at all. We also compare search behavior variability with respect to different classes of users and different classes of search tasks to reveal whether user models or task models may be greater predictors of behavior. We discover that gender and task significantly influence different kinds of search behaviors discussed here. The results are suggestive of improvements to query-based search interface designs with respect to both their use of space and workflow.     

论学术批评实名制与科研"恶集富"效应

辞旧迎新的春节前后,举国上下一片欢腾.但在申奥成功、加入世贸、足球出线等等喜庆氛围中,隐隐传来阵阵难以遏拒的"叹息":假冒伪劣、"诚信"危机,足球"黑哨",学术腐败…….正是在这样的社会背景下,中国科学院出台了<中国科学院院士科学道德自律准则>.围绕"准则"的出台,权威人士发表访谈;中央电视台的<经济半小时>节目还独家公布了有关"准则"内部会议的录音.一时间,社会舆论纷纷扬扬,公众传媒见仁见智,各种"看法"、"说法"接踵而来.     

Investigation of the heat transfer of a non-Newtonian fluid flow in an axisymmetric channel with porous wall using Parameterized Perturbation Method (PPM)

In the present article Parameterized Perturbation Method (PPM) is used to obtain the solutions of momentum and heat transfer equations of non-Newtonian fluid flow in an axisymmetric channel with porous wall for turbine cooling applications. The validity of the results of PPM solution were verified by comparison with numerical results obtained using a fourth order Runge–Kutta method. These comparisons reveal that Parameterized Perturbation Method is a powerful approach for solving this problem. The analytical investigation is carried out for different governing parameters namely, Reynolds number, injection Reynolds number, Prandtl number and power law index. The results show that skin friction coefficient increases with increase of Reynolds number, especially at high Reynolds numbers. Also it can be found that Nusselt number has direct relationship with Reynolds number, Prandtl number and power law index.     

基于国家开发型项目的政府介入与中小企业创新研究

开发型项目作为政府介入的一种国家科技计划,其资金投入与中小企业创新存在明显的正相关关系,开发型项目投入较高的区域,中小企业的创新能力相应较强,创新区域等级较高。因此正确评价政府介入行为,并使政府介入行为与市场自组织行为有机结合起来,将使创新资源得到高效配置。     

Trajectory tracking of an autonomous vehicle using immersion and invariance control

An Immersion and Invariance [I & I] controller is designed to control the nonlinear lateral vehicle’s motion, using the steering angle as the only input. Similar to most of the lateral vehicle’s dynamics control law, the cornering stiffness parameters are involved in our proposed controller. Because of the tight relation between tire/road properties and the cornering stiffness parameters, they are not available from the outputs of the sensors and therefore, should be estimated for utilizing in the control law. An online data-driven identification is employed for estimating the cornering stiffness parameters. In addition, a robust model-based fault detection and approximation method in the presence of uncertainties via neural networks is presented. The performance of the obtained control law is investigated via simulation tests in different situations and in the presence of the disturbance. Moreover, some validation tests are performed using the CarSim software to show the effectiveness of our algorithm.     

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.     

超微LaMO3（M=Fe,Cr,Mn,Co）的导电性与粒度的关系

用Ｓｏｌ－Ｇｅｌ法合成了ＬａＭＯ＿３（Ｍ＝Ｆｅ，Ｃｒ，Ｍｎ，Ｃｏ）超微粉末．Ｘ射线衍射分析表明，不同焙烧温度下所合成的化合物均为单相．ＳＥＭ分析表明，粒子呈球形，室温电阻率测量表明，电阻率随粒度的变化呈两种类型：ＬａＦｅＯ＿３，ＬａＣｒＯ＿３随粒度的增大，电阻率增加；而ＬａＭｎＯ＿３，ＬａＣｏＯ＿３随粒度的增大，电阻率减小．     

网络学术论坛中的科研合作行为及其反思——以“小木虫”学术论坛为例

阐述了网络论坛的产生及发展历程,以小木虫论坛为例对网络论坛中的科研合作行为进行分析,具体包括论坛中参与者的科研合作诉求、科研合作行为、科研合作效果、科研合作保障机制等内容,并讨论这种网络环境中的科研合作行为对科研活动及科技创新的影响,最后提出学术网络论坛的发展方向.     

ABC法与数学规划相结合对供应商选择问题的研究

本文提出91作业成本法(ABC法)与数学规划相结合的方法来解决供应商评价和选择的决策问题。首先简要回顾了已有的对供应商评价和选择问题的研究，然后构建了供应商选择的步骤模型，并用一个案例进行了说明。     

Generation of pornographic blacklist and its incremental update using an inverse chi-square based method

This study presented an inverse chi-square based web content classification system that works along with an incremental update mechanism for incremental generation of pornographic blacklist. The proposed system, as indicated from the experimental results, can classify bilingual (English and Chinese) web pages at an average precision rate of 97.11%; while maintaining a favorably low false positive rate. Such satisfactory performance was obtained under a cost-effective parameter configuration used in inverse chi-square calculations. The proposed incremental update mechanism operates on the linking structure of pornographic hubs to locate newly added pornographic sites. The resulting blacklist has been empirically verified to be comparatively responsive to the growth dynamics of pornography sites than three public domain blacklists.