Thin film electro-osmotic pumps for biomicrofluidic applications

Electro-osmotic flow (EOF) pumps are attractive for fluid manipulation in microfluidic channels. Open channel EOF pumps can produce high pressures and flow rates, and are relatively easy to fabricate on-chip or integrate with other microfluidic or electrical components. An EOF pump design that is conducive to on-chip fabrication consists of multiple small channel arms feeding into a larger flow channel. We have fabricated this type of pump design using a thin film deposition process that avoids wafer bonding. We have evaluated pumps fabricated on both silicon and glass substrates. Consistent flow rate versus electric field were obtained. For the range of 40–400 V, flow rates of 0.19–2.30 μL∕min were measured. Theoretical calculations of pump efficiency were made, as well as calculations of the mechanical power generated by various pump shapes, to investigate design parameters that should improve future pumps.     

Transport of particles and microorganisms in microfluidic channels using rectified ac electro-osmotic flow

A new method is demonstrated to transport particles, cells, and other microorganisms using rectified ac electro-osmotic flows in open microchannels. The rectified flow is obtained by synchronous zeta potential modulation with the driving potential in the microchannel. Experiments were conducted to transport both neutral, charged particles, and microorganisms of various sizes. A maximum speed of 50 μm∕s was obtained for 8 μm polystyrene beads, without any electrolysis, using a symmetrical square waveform driving electric field of 5 V∕mm at 10 Hz and a 360 V gate potential with its polarity synchronized with the driving potential (phase lag=0°).     

Mixing enhancement in microfluidic channel with a constriction under periodic electro-osmotic flow

We present a new approach to enhance mixing in T-type micromixers by introducing a constriction in the microchannel under periodic electro-osmotic flow. Two sinusoidal ac electric fields with 180° phase difference and similar dc bias are applied at the two inlets. The out of phase ac electric field induces oscillation of fluid interface at the junction of the two inlet channels and the constriction. Due to the constriction introduced at the junction, fluids from these two inlets form alternative plugs at the constricted channel. These plugs of fluids radiate downstream from the constriction into the large channel and form alternate thin crescent-shaped layers of fluids. These crescent-shaped layers of fluids increase tremendously the contact surface area between the two streams of fluid and thus enhance significantly the mixing efficiency. Experimental results and mixing mechanism analysis show that amplitude and frequency of the ac electric field and the length of the constriction govern the mixing efficiency.     

行业创新空间关联及三维外部性的研究

 参考国际知识产权组织提供的专利IPC分类与行业技术对照表,分析我国各行业区域创新倾向的空间关联性;扩展传统的两维度外部性研究思路,构建包含三个维度创新外部性的空间计量模型,研究各行业创新在产业间、产业内、地理空间三个维度的溢出与区域创新水平的关系。结果显示我国不同行业三个维度的外部性存在显著差异,进一步对各行业进行归类,为我国各地区制定产业创新发展规划与空间布局调整提供实证依据。     

经阴道超声(二维联合三维)检查对宫腔占位性病变的诊断价值

目的:探讨经阴道超声(二维联合三维)检查对宫腔占位性病变的诊断价值。方法:收集2014年1月~2014年8月在广西中医药大学第一附属医院经阴道超声(二维联合三维)检查、诊断并经手术病理证实的82例宫腔占位病变资料进行回顾性分析。结果:实验组82例,经阴道超声检查结果为:子宫内膜息肉54例,子宫粘膜下肌瘤13例,子宫内膜癌2例,子宫内膜增生过长2例,所有病例都经病理证实,诊断符合率为90.1%。结论:以上四种常见宫腔占位病变经阴道超声检查,其声像图可作为对其诊断和鉴别诊断的重要依据。     

椭圆定义及其应用点滴谈

椭圆是圆锥曲线的一部分,是解析几何的一个重要内容,定义简明而内容充实,同时也蕴含着数形结合定义运用,等价转换等数学思想方法,下面就此作一些浅析.     

Rapid formation of size-controlled three dimensional hetero-cell aggregates using micro-rotation flow for spheroid study

Spheroids that are formed from aggregated cells have enhanced biological function compared to individual cells. In particular, hetero-spheroids composed of different types of cells, such as hepatocytes and endothelial cells, express tissue specific functions at a high level, which is advantageous for more precise drug screening and biological research. In this study, we propose rapid formation of size-controlled three-dimensional hetero-cell aggregates consisting of hepatocytes and endothelial cells using micro-rotation flow. Based on previous data, these aggregates are expected to ultimately become hetero-spheroids. The hepatocytes are coated with collagen gel films less than 200 nm thick, which were experimentally verified to increase adhesion strength between hepatocytes and endothelial cells. Gel-coated hepatocytes and endothelial cells are collected in an array by micro-rotational flow, thereby forming hetero-cell aggregates within 2 min. This array allowed the size of the three-dimensional cell aggregates to be hydrodynamically controlled, with standard deviations of less than 19%, by varying the cell density of the medium without altering the device geometry. Endothelial cells were successfully and uniformly dispersed in the aggregates. The proposed microfluidic device, with its capability of rapidly forming size-controlled hetero-cell aggregates, will offer an efficient experimental platform for future hetero-spheroid study that will contribute to drug screening and regenerative medicine.     

Microfluidic device for trapping and monitoring three dimensional multicell spheroids using electrical impedance spectroscopy

In this paper, we report the design, fabrication, and testing of a lab-on-a-chip based microfluidic device for application of trapping and measuring the dielectric properties of microtumors over time using electrical impedance spectroscopy (EIS). Microelectromechanical system (MEMS) techniques were used to embed opposing electrodes onto the top and bottom surfaces of a microfluidic channel fabricated using Pyrex substrate, chrome gold, SU-8, and polydimethylsiloxane. Differing concentrations of cell culture medium, differing sized polystyrene beads, and MCF-7 microtumor spheroids were used to validate the designs ability to detect background conductivity changes and dielectric particle diameter changes between electrodes. The observed changes in cell medium concentrations demonstrated a linear relation to extracted solution resistance (Rs), while polystyrene beads and multicell spheroids induced changes in magnitude consistent with diameter increase. This design permits optical correlation between electrical measurements and EIS spectra.     

Polydimethyl siloxane wet etching for three dimensional fabrication of microneedle array and high-aspect-ratio micropillars

Among various transdermal drug delivery (TDD) approaches, utilizing the microneedles (MNs) not only can penetrate the skin but also deliver the drug with reduced tissue damage, reduced pain, and no bleeding. However, the MNs with larger height are required to overcome the skin barrier for effective TDD. Unlike 2D patterning, etching polydimethyl siloxane (PDMS) micropillars for fabrication of 3D microstructures is presented. The PDMS micropillars were first constructed by casting PDMS on the computer numerical control-machined cylindrical microwells, which then went through etching process to obtain the MNs for subsequent fabrication of polymer MNs or high aspect ratio micropillars.     

奥运村及奥运场馆太阳能-热泵中央热水系统示范研究进展

1项目简介该项目由中国科学院、北京市西城区科学技术委员会、北京市西城区体育局联合组织并资助。项目承担单位:广州能源研究所。总体目标是:针对2008年北京奥运会奥运村和奥运场馆需要大量生活热水和加热的热能,研究利用清洁无污染的太阳能、并辅助以热泵技术,以游泳场馆为应用实例,研制一套基于太阳能为主要热能来源,以热泵为辅助的全年热水供给系统。该项目将摒弃以往大型太阳能热水系统辅助以具有污染和安全隐患的燃油(气)锅炉或高能耗的电辅助加热系统,以先进的热泵技术解决太阳能在阴雨天气时不能提供足够温度的热水的缺点,由于运用…     

三维创新空间下的银行创新成长模式探讨——以五大股份制商业银行为例

企业的创新空间由技术创新、制度创新和管理创新三个维度构成.在三维创新空间下,处于某一生命周期阶段的银行创新成长模式可分为:基于技术创新的成长模式、基于制度创新的成长模式、基于管理创新的成长模式和混合创新的成长模式四种.在成长过程中,我国五大股份制商业银行由于经营理念、市场定位和战略规划不同,其创新成长模式也有所差异.     

Fast algorithm for image denoising with different boundary conditions

In recent works several authors have considered the L₁ fidelity term, the L₂ fidelity term and the combined L₁ and L₂ fidelity term for denoising models, and they used the fast Fourier transform (FFT) algorithm which can only use periodic boundary conditions (BCs). In this paper, we combine the augmented Lagrangian method (ALM) and the symmetric Red–Black Gauss–Seidel (SRBGS) method to propose three algorithms that are suitable for different BCs. Experimental results show that the proposed algorithms are effective and the model with the combined L₁ and L₂ fidelity term demonstrates more advantages in efficiency and accuracy than other models with the L₁ fidelity term or the L₂ fidelity term.     

Two dimensional quaternion valued singular spectrum analysis with application to image denoising

Compared to the traditional single color plane based image denoising methods, the quaternion valued singular value decomposition (QSVD) exploits the relationship among different color planes. Hence, it has been applied to the color image denoising. On the other hand, compared to the non-overlapping based image denoising methods, the two dimensional real valued singular spectrum analysis (2DSSA) constructs the trajectory matrix with many elements in the matrix being overlapped. Since the 2DSSA exploits the local information within each color plane, it has also been applied to the single color plane based image denoising. However, neither these two image denoising methods can exploit the relationship among the color planes and the local information within each color plane simultaneously. Therefore, this paper proposes a two dimensional quaternion valued singular spectrum analysis (2DQSSA) based method for performing the color image denoising. Our proposed method can enjoy the advantages of both methods. However, the most critical issue for the 2DQSSA is on the selection of these 2DQSSA components. This paper finds that the optimal total number of the 2DQSSA components used for performing the reconstruction is monotonic decreasing with respect to the power of the noise in the image. Therefore, the polynomial fitting approach is proposed to model this relationship. Since the 2DQSSA based denoising method exploits the relationship among the red color plane, the green color plane and the blue color plane, the 2DQSSA based denoising method outperforms the conventional single color plane based denoising methods. Moreover, since the 2DQSSA based denoising method also exploits the local relationship within each color plane, the 2DQSSA based denoising method outperforms the non-overlapping based methods.     

Hybrid modified function projective synchronization of two different dimensional complex nonlinear systems with parameters identification

In this article, a novel synchronization scheme is proposed to achieve hybrid modified function projective synchronization (HMFPS) in two different dimensional complex nonlinear systems with fully unknown parameters. In the complex space, the response system are asymptotically synchronized up to the different order’s drive system by the state transformation with a scaling function matrix, and all of unknown parameters in both drive and response systems are achieved to be identified. Based on the Lyapunov stability theory, an adaptive controller and updated laws of parameters are developed. Respectively on the ways of increased order and reduced order, the corresponding numerical simulations demonstrate the effectiveness and feasibility of the proposed scheme.     

Three dimensional microfluidics with embedded microball lenses for parallel and high throughput multicolor fluorescence detection

We report a 3D microfluidic device with 32 detection channels and 64 sheath flow channels and embedded microball lens array for high throughput multicolor fluorescence detection. A throughput of 358 400 cells/s has been accomplished. This device is realized by utilizing solid immersion micro ball lens arrays for high sensitivity and parallel fluorescence detection. High refractive index micro ball lenses (n = 2.1) are embedded underneath PDMS channels close to cell detection zones in channels. This design permits patterning high N.A. micro ball lenses in a compact fashion for parallel fluorescence detection on a small footprint device. This device also utilizes 3D microfluidic fabrication to address fluid routing issues in two-dimensional parallel sheath focusing and allows simultaneous pumping of 32 sample channels and 64 sheath flow channels with only two inlets.     

Analysis and pinning control for generalized synchronization of delayed coupled neural networks with different dimensional nodes

This paper investigate the generalized synchronization and pinning adaptive generalized synchronization for delayed coupled different dimensional neural networks with hybrid coupling, respectively. First, some sufficient conditions for reaching the generalized synchronization and pinning generalized synchronization of the considered network are acquired by using some inequality techniques and Lyapunov functional method. Second, because the precise parameter values of network cannot be obtained in some situations, we also purse the study on the generalized synchronization analysis and pinning control for the case of coupled different dimensional neural networks with parameter uncertainties. Third, two numerical examples are provided for substantiating the effectiveness of the derived results.     

有固定端的等截面单跨超静定梁的快速解法

利用等截面悬臂梁在三种基本受力状况下的梁端转角和梁端挠度公式,采用直接叠加法和变形协调条件,可快速地求解在支座位移或荷载作用下有固定端的等截面单跨超静定梁.     

Microfluidic devices fitted with “flowver” paper pumps generate steady,tunable gradients for extended observation of chemotactic cell migration

Microfluidics approaches have gained popularity in the field of directed cell migration, enabling control of the extracellular environment and integration with live-cell microscopy; however, technical hurdles remain. Among the challenges are the stability and predictability of the environment, which are especially critical for the observation of fibroblasts and other slow-moving cells. Such experiments require several hours and are typically plagued by the introduction of bubbles and other disturbances that naturally arise in standard microfluidics protocols. Here, we report on the development of a passive pumping strategy, driven by the high capillary pressure and evaporative capacity of paper, and its application to study fibroblast chemotaxis. The paper pumps—flowvers (flow + clover)—are inexpensive, compact, and scalable, and they allow nearly bubble-free operation, with a predictable volumetric flow rate on the order of μl/min, for several hours. To demonstrate the utility of this approach, we combined the flowver pumping strategy with a Y-junction microfluidic device to generate a chemoattractant gradient landscape that is both stable (6+ h) and predictable (by finite-element modeling calculations). Integrated with fluorescence microscopy, we were able to recapitulate previous, live-cell imaging studies of fibroblast chemotaxis to platelet derived growth factor (PDGF), with an order-of-magnitude gain in throughput. The increased throughput of single-cell analysis allowed us to more precisely define PDGF gradient conditions conducive for chemotaxis; we were also able to interpret how the orientation of signaling through the phosphoinositide 3-kinase pathway affects the cells’ sensing of and response to conducive gradients.     

3种作物类期刊入选F5000论文的文献计量学分析

【目的】分析3种作物类期刊146篇入选F5000论文,以明确其文献计量学特征。【方法】 收集入选论文的相关信息及在万方和WoS中被引频次,并进行统计分析。【结果】 146篇入选F5000论文在万方数据库中篇均被引41.3次;以栽培技术类论文数最多,占43.2%,且篇均被引频次较高,仅次于综述类论文。61篇论文（41.8%）在WoS中被引用,篇均被引3.4次;以综述和生物技术类论文为主。入选论文主要来自大学;最多一位作者有13篇论文,存在核心作者;89.0%的论文由国家项目资助。【结论】 入选F5000论文受到国内学者广泛关注,但在WoS中影响力较小;作物类期刊应重视向大学组约稿,特别是高质量的方法类和研究热点论文及知名专家的综述,将有利于提高期刊的总被引频次和影响力。