共查询到20条相似文献，搜索用时 15 毫秒
1.
Constantin Piron 《Journal of The Franklin Institute》1974,297(4):299-306
The Very Large Array (VLA) radio telescope which is presently under construction in central New Mexico is considered the highest priority new astronomical facility in the U.S.A. during the next decade. The instrument will consist of 27 separate parabolic antennas each of which will be movable along the arms of a Y-configuration. The technique of earth-rotation aperture synthesis will allow an aperture of 25 miles dia. to be synthesized. When the VLA is completed in 1981 it will be better than any other radio telescope, by one or two orders of magnitude, in terms of resolution, sensitivity and speed. 相似文献
2.
Wei Zhou Lili Niu Feiyan Cai Fei Li Chen Wang Xiaowei Huang Jingjing Wang Junru Wu Long Meng Hairong Zheng 《Biomicrofluidics》2016,10(3)
A microfluidic device based on a pair of slant-finger interdigital transducers (SFITs) is developed to achieve a selective and flexible manipulation of microbubbles (MBs) by surface acoustic waves (SAWs). The resonance frequency of SAWs generated by the SFITs depends on the location of its parallel pathway; the particles at different locations of the SAWs'' pathway can be controlled selectively by choosing the frequency of the excitation signal applied on the SFITs. By adjusting the input signal continuously, MBs can be transported along the acoustic aperture precisely. The displacement of MBs has a linear relationship with the frequency shift. The resolution of transportation is 15.19 ± 2.65 μm when the shift of input signal frequency is at a step of 10 kHz. In addition, the MBs can be controlled in a two-dimensional plane by combining variations of the frequency and the relative phase of the excitation signal applied on the SFITs simultaneously. This technology may open up the possibility of selectively and flexibly manipulating MBs using a simple one-dimensional device. 相似文献
3.
Epshteyn AA Maher S Taylor AJ Holton AB Borenstein JT Cuiffi JD 《Biomicrofluidics》2011,5(4):46501-465016
The design and fabrication of a membrane-integrated microfluidic cell culture device (five layers,≤500 μm total thickness) developed for high resolution microscopy is reported here. The multi-layer device was constructed to enable membrane separated cell culture for tissue mimetic in vitro model applications and pharmacodynamic evaluation studies. The microdevice was developed via a unique combination of low profile fluidic interconnect design, substrate transfer methodology, and wet silane bonding. To demonstrate the unique high resolution imaging capability of this device, we used oil immersion microscopy to image stained nuclei and mitochondria in primary hepatocytes adhered to the incorporated membrane 相似文献
4.
Bacterial culture is a basic technique in both fundamental and applied microbiology. The excessive reagent consumption and laborious maintenance of bulk bioreactors for microbial culture have prompted the development of miniaturized on-chip bioreactors. With the minimal choice of two compartments (N = 2) and discrete time, periodic dilution steps, we realize a microfluidic bioreactor that mimics macroscopic serial dilution transfer culture. This device supports automated, long-term microbial cultures with a nanoliter-scale working volume and real-time monitoring of microbial populations at single-cell resolution. Because of the high surface-to-volume ratio, the device also operates as an effective biofilm-flow reactor to support cogrowth of planktonic and biofilm populations. We expect that such devices will open opportunities in many fields of microbiology. 相似文献
5.
S.S. Mehta C. Ton M. Rysz Z. Kan E.A. Doucette J.W. Curtis 《Journal of The Franklin Institute》2019,356(10):5001-5026
A large class of visual servo controllers relies on an a priori obtained reference image, captured at the desired position and orientation (i.e., pose) of a camera, to yield control signals to regulate the camera from its current pose to a desired pose. In many applications, accessibility and economics of the operation may prohibit acquisition of such a reference image. This paper introduces a new visual servo control paradigm that enables control of the camera in the absence of reference image using a set of terminal constraints. Specifically, the desired pose is encoded using the angle of obliquity of the optical axis with respect to the object plane and its direction of arrival at the plane. A constrained convex optimization problem is formulated over a conic section defined by the terminal constraints to yield an error system for the control problem. Subsequently, this work introduces continuous terminal sliding mode visual servo controllers to regulate the camera to the desired pose. Lyapunov-based stability analysis guarantees that the origin is a finite-time-stable equilibrium of the system. Numerical simulation results are provided to verify the performance of the proposed visual servo controller. 相似文献
6.
Guillaume Mottet Karla Perez-Toralla Ezgi Tulukcuoglu Francois-Clement Bidard Jean-Yves Pierga Irena Draskovic Arturo Londono-Vallejo Stephanie Descroix Laurent Malaquin Jean Louis Viovy 《Biomicrofluidics》2014,8(2)
We present a low cost microfluidic chip integrating 3D micro-chambers for the capture and the
analysis of cells. This device has a simple design and a small footprint. It allows the
implementation of standard biological protocols in a chip format with low volume consumption. The
manufacturing process relies on hot-embossing of cyclo olefin copolymer, allowing the development of
a low cost and robust device. A 3D design of microchannels was used to induce high flow velocity
contrasts in the device and provide a selective immobilization. In narrow distribution channels, the
liquid velocity induces a shear stress that overcomes adhesion forces and prevents cell
immobilization or clogging. In large 3D chambers, the liquid velocity drops down below the threshold
for cell attachment. The devices can be operated in a large range of input pressures and can even be
handled manually using simple syringe or micropipette. Even at high flow injection rates, the 3D
structures protect the captured cell from shear stress. To validate the performances of our device,
we implemented immuno-fluorescence labeling and Fluorescence in Situ Hybridization
(FISH) analysis on cancer cell lines and on a patient pleural effusion sample. FISH is a Food and
Drug Administration approved cancer diagnostic technique that provides quantitative information
about gene and chromosome aberration at the single cell level. It is usually considered as a long
and fastidious test in medical diagnosis. This process can be easily implanted in our platform, and
high resolution fluorescence imaging can be performed with reduced time and computer intensiveness.
These results demonstrate the potential of this chip as a low cost, robust, and versatile tool
adapted to complex and demanding protocols for medical diagnosis. 相似文献
7.
高分辨率全帧CCD相机电路系统的设计 总被引：4，自引：0，他引：4
基于Dalsa公司的面阵CCD评价板EKxxxx设计了一套高分辨率全帧CCD相机电路系统。系统采用专用集成芯片SAA8103和TDA9991构成时序发生器和驱动器，采用TDA9965进行前端信号处理。采用单片机对系统进行控制并应用Camera Link接口简化了体系结构。针对CCD多路输出时各通道存在不均匀性，提出采用两点校正法进行校正。该系统能以较高的帧频获取超高分辨率的图像，适用于航空拍摄、数字后背等场合。 相似文献
8.
合成孔径声呐是一种高分辨率水下成像技术。该技术是基于小孔径基阵及其运动形成等效的大孔径,通过合成的大孔径波束形成过程,实现高分辨率成像。文章介绍了合成孔径声呐原理、特点、科学技术问题以及发展过程,分析了国内外合成孔径声呐研究的最新进展情况,并展望了合成孔径声呐的发展趋势。 相似文献
9.
G. A. Ferrier A. N. Hladio D. J. Thomson G. E. Bridges M. Hedayatipoor S. Olson M. R. Freeman 《Biomicrofluidics》2008,2(4)
The mechanical behavior of cells offers insight into many aspects of their properties. We propose an approach to the mechanical analysis of cells that uses a combination of electromanipulation for stimulus and capacitance for sensing. To demonstrate this approach, polystyrene spheres and yeast cells flowing in a 25 μm×100 μm microfluidic channel were detected by a perpendicular pair of gold thin film electrodes in the channel, spaced 25 μm apart. The presence of cells was detected by capacitance changes between the gold electrodes. The capacitance sensor was a resonant coaxial radio frequency cavity (2.3 GHz) coupled to the electrodes. The presence of yeast cells (Saccharomyces cerevisiae) and polystyrene spheres resulted in capacitance changes of approximately 10 and 100 attoFarad (aF), respectively, with an achieved capacitance resolution of less than 2 aF in a 30 Hz bandwidth. The resolution is better than previously reported in the literature, and the capacitance changes are in agreement with values estimated by finite element simulations. Yeast cells were trapped using dielectrophoretic forces by applying a 3 V signal at 1 MHz between the electrodes. After trapping, the cells were displaced using amplitude and frequency modulated voltages to produce modulated dielectrophoretic forces. Repetitive displacement and relaxation of these cells was observed using both capacitance and video microscopy. 相似文献
10.
RFID即无线射频识别装置,它是一种非接触式的自动识别技术,通过射频信号自动识别目标对象并获取相关数据,识别工作可以在无人工干预的情况下自助完成。这种技术可工作于各种恶劣环境,既可识别高速运动物体又可同时识别多个标签,设备的操作快捷方便,且适合于各类人群使用。目前这项技术已被应用于图书馆中,也就是自助图书馆系统,为读者提供了完全自主的借还平台,在倡导个性化读者服务的今天使图书馆服务发生了崭新的变化。 相似文献
11.
This paper describes a light-addressable electrolytic system used to perform an electrodeposition of calcium alginate hydrogels using a digital micromirror device (DMD). In this system, a patterned light illumination is projected onto a photoconductive substrate serving as a photo-anode to electrolytically produce protons, which can lead to a decreased pH gradient. The low pH generated at the anode can locally release calcium ions from insoluble calcium carbonate (CaCO3) to cause gelation of calcium alginate through sol-gel transition. By controlling the illumination pattern on the DMD, a light-addressable electrodeposition of calcium alginate hydrogels with different shapes and sizes, as well as multiplexed micropatterning was performed. The effects of the concentration of the alginate and CaCO3 solutions on the dimensional resolution of alginate hydrogel formation were experimentally examined. A 3 × 3 array of cell-encapsulated alginate hydrogels was also successfully demonstrated through light-addressable electrodeposition. Our proposed method provides a programmable method for the spatiotemporally controllable assembly of cell populations into cellular microarrays and could have a wide range of biological applications in cell-based biosensing, toxicology, and drug discovery. 相似文献
12.
13.
Buchegger W Haller A van den Driesche S Kraft M Lendl B Vellekoop M 《Biomicrofluidics》2012,6(1):12803-128039
In this study, the pre-steady state development of enzymatic bioreactions using a microfluidic mixer is presented. To follow such reactions fast mixing of reagents (enzyme and substrate) is crucial. By using a highly efficient passive micromixer based on multilaminar flow, mixing times in the low millisecond range are reached. Four lamination layers in a shallow channel reduce the diffusion lengths to a few micrometers only, enabling very fast mixing. This was proven by confocal fluorescence measurements in the channel’s cross sectional area. Adjusting the overall flow rate in the 200 μm wide and 900 μm long mixing and observation channel makes it possible to investigate enzyme reactions over several seconds. Further, the device enables changing the enzyme/substrate ratio from 1:1 up to 3:1, while still providing high mixing efficiency, as shown for the enzymatic hydrolysis using β-galactosidase. This way, the early kinetics of the enzyme reaction at multiple enzyme/substrate concentrations can be collected in a very short time (minutes). The fast and easy handling of the mixing device makes it a very powerful and convenient instrument for millisecond temporal analysis of bioreactions. 相似文献
14.
针对实际应用中具有复杂背景的高分辨率数码图像下车辆牌照定位问题，提出了一种综合利用了车牌纹理特征、几何特征以及色彩特征的快速车牌定位方法。该方法按顺序分为图像预处理、牌照区域粗定位、牌照精确定位三个步骤对牌照由粗到细准确定位出车辆牌照位置所在。实验结果表明．对于场景大，背景复杂的车辆图像，该方法运行速度快，定位准确率高，具较强抗干扰能力。 相似文献
15.
We have designed, built, and evaluated a microfluidic device that uses deterministic lateral displacement for size-based separation. The device achieves almost 100% purity and recovery in continuously sorting two, four, and six micrometer microspheres. We have applied this highly efficient device to the purification of fungal (Aspergillus) spores that are spherical (∼4 μm diameter) with a narrow size distribution. Such separation directly from culture using unfiltered A. niger suspensions is difficult due to a high level of debris. The device produces a two to three increase in the ratio of spores to debris as measured by light scatter in a flow cytometer. The procedure is feasible at densities up to 4.4×106 spores∕ml. This is one of the first studies to apply microfluidic techniques to spore separations and has demonstrated that a passive separation system could significantly reduce the amount of debris in a suspension of fungal spores with virtually no loss of spore material. 相似文献
16.
The ability to separate and analyze chemical species with high resolution, sensitivity, and throughput is central to the development of microfluidics systems. Deterministic lateral displacement (DLD) is a continuous separation method based on the transport of species through an array of obstacles. In the case of force-driven DLD (f-DLD), size-based separation can be modelled effectively using a simple particle-obstacle collision model. We use a macroscopic model to study f-DLD and demonstrate, via a simple scaling, that the method is indeed predominantly a size-based phenomenon at low Reynolds numbers. More importantly, we demonstrate that inertia effects provide the additional capability to separate same size particles but of different densities and could enhance separation at high throughput conditions. We also show that a direct conversion of macroscopic results to microfluidic settings is possible with a simple scaling based on the size of the obstacles that results in a universal curve. 相似文献
17.
Junchao Wang Kaicong Liang Naiyin Zhang Hailong Yao Tsung-Yi Ho Lingling Sun 《Biomicrofluidics》2021,15(2)
With the development of 3D printing techniques, the application of it in microfluidic/Lab-on-a-Chip (LoC) fabrication is becoming more and more attractive. However, to achieve a satisfying printing quality of the target devices, researchers usually require quite an amount of work in calibration trials even for high-end 3D printers. To increase the calibration efficiency of the average priced printers and promote the application of 3D printing technology in the microfluidic community, this work has presented a computer vision (CV)-based method for rapid and precise 3D printing calibration with examples on cylindrical hole/post diameters of 0.2–2.4 mm and rectangular hole/post widths of 0.2–1.0 mm by a stereolithography-based 3D printer. Our method is fully automated, which contains five steps and only needs a camera at hand to provide photos for convolutional neural network recognition. The experimental results showed that our CV-based method could provide calibrated dimensions with just one print of the specific calibration ruler to meet user desire. The higher resolution of the photo provides a higher precision in calibration. Subsequently, only one more print for the target device is needed after the calibration process. Overall, this work has provided a quick and precise calibration tool for researchers to apply 3D printing in the fabrication of their microfluidic/LoC devices with average price printers. Besides, with our open source calibration software and calibration ruler design file, researchers can modify the specific setting based on customized needs and conduct calibration on any type of 3D printer. 相似文献
18.
Emilie Weibull Shunsuke Matsui Manabu Sakai Helene Andersson Svahn Toshiro Ohashi 《Biomicrofluidics》2013,7(6)
Understanding biomolecular gradients and their role in biological processes is essential for fully comprehending the underlying mechanisms of cells in living tissue. Conventional in vitro gradient-generating methods are unpredictable and difficult to characterize, owing to temporal and spatial fluctuations. The field of microfluidics enables complex user-defined gradients to be generated based on a detailed understanding of fluidic behavior at the μm-scale. By using microfluidic gradients created by flow, it is possible to develop rapid and dynamic stepwise concentration gradients. However, cells exposed to stepwise gradients can be perturbed by signals from neighboring cells exposed to another concentration. Hence, there is a need for a device that generates a stepwise gradient at discrete and isolated locations. Here, we present a microfluidic device for generating a stepwise concentration gradient, which utilizes a microwell slide''s pre-defined compartmentalized structure to physically separate different reagent concentrations. The gradient was generated due to flow resistance in the microchannel configuration of the device, which was designed using hydraulic analogy and theoretically verified by computational fluidic dynamics simulations. The device had two reagent channels and two dilutant channels, leading to eight chambers, each containing 4 microwells. A dose-dependency assay was performed using bovine aortic endothelial cells treated with saponin. High reproducibility between experiments was confirmed by evaluating the number of living cells in a live-dead assay. Our device generates a fully mixed fluid profile using a simple microchannel configuration and could be used in various gradient studies, e.g., screening for cytostatics or antibiotics. 相似文献
19.
Homsy A van der Wal PD Doll W Schaller R Korsatko S Ratzer M Ellmerer M Pieber TR Nicol A de Rooij NF 《Biomicrofluidics》2012,6(1):12804-128049
Clinical point of care testing often needs plasma instead of whole blood. As centrifugation is labor intensive and not always accessible, filtration is a more appropriate separation technique. The complexity of whole blood is such that there is still no commercially available filtration system capable of separating small sample volumes (10-100 μl) at the point of care. The microfluidics research in blood filtration is very active but to date nobody has validated a low cost device that simultaneously filtrates small samples of whole blood and reproducibly recovers clinically relevant biomarkers, and all this in a limited amount of time with undiluted raw samples. In this paper, we show first that plasma filtration from undiluted whole blood is feasible and reproducible in a low-cost microfluidic device. This novel microfluidic blood filtration element (BFE) extracts 12 μl of plasma from 100 μl of whole blood in less than 10 min. Then, we demonstrate that our device is valid for clinical studies by measuring the adsorption of interleukins through our system. This adsorption is reproducible for interleukins IL6, IL8, and IL10 but not for TNFα. Hence, our BFE is valid for clinical diagnostics with simple calibration prior to performing any measurement. 相似文献
20.
Francesca Sapuppo Andreu Llobera Florinda Schembri Marcos Intaglietta Victor J. Cadarso Maide Bucolo 《Biomicrofluidics》2010,4(2)
We describe design and miniaturization of a polymeric optical interface for flow monitoring in biomicrofluidics applications based on polydimethylsiloxane technology, providing optical transparency and compatibility with biological tissues. Design and ray tracing simulation are presented as well as device realization and optical analysis of flow dynamics in microscopic blood vessels. Optics characterization of this polymeric microinterface in dynamic experimental conditions provides a proof of concept for the application of the device to two-phase flow monitoring in both in vitro experiments and in vivo microcirculation investigations. This technology supports the study of in vitro and in vivo microfluidic systems. It yields simultaneous optical measurements, allowing for continuous monitoring of flow. This development, integrating a well-known and widely used optical flow monitoring systems, provides a disposable interface between live mammalian tissues and microfluidic devices making them accessible to detection∕processing technology, in support or replacing standard intravital microscopy. 相似文献