具有三维聚焦之微型流式细胞/颗粒计数仪

本研究提出一种新式的微型细胞颗粒计数器,此微型细胞颗粒计数器结合二维水力聚焦及微文件流结构(micro-weir structure)于微管道中,可进行高精确度及均一性的细胞或颗粒计数,本研究是利用简单的等向性(isotropie)的湿式蚀刻技术来制作微文件流结构于玻璃基材上,而此微型细胞颗粒计数器的主要构成的组件包含二维边鞘流的聚焦结构,其主要功能为将细胞或颗粒聚焦于x-Y平面上,而微文件流结构的目的在于将细胞或颗粒在z方向的筛选,最后利用雷射诱导荧光系统将细胞或颗粒侦测出.在实验与数值分析的结果,显示此微型细胞颗粒计数器确实可进行高精确度及均一性的细胞或颗粒的计数,并且可以提供一个微型化的生物分析系统.     

流式细胞仪样品流速及聚焦流测量方法研究

为提高流式细胞仪的探测分辨率和数据检测的稳定性,需要精确控制样品流速,并分析样品流速和鞘液流速对样品聚焦流的影响,可通过样品聚焦流直径和样品聚焦流在流动室流道中的相对位置来评价样品的聚焦状况。利用蠕动泵运动特点,设计了一种平均流量称重法测量样品流速的方法,并与微流量传感器测量结果作比较;采用最小二乘法线性拟合蠕动泵的控制电压和样品流速之间的函数关系,并采用显微成像法直接测量和分析样品流速和鞘液流速对样品聚焦流直径、偏离流动室流道中心线的距离的影响。实验结果显示,采用平均流量称重法与微流量传感器测得的样品流速的线性相关系数高达0.982 8;蠕动泵的样品流速与其控制电压的线性相关系数高于0.99,说明利用该线性关系可以实现样品流速的精确控制;采用的显微成像法能快速方便地测得样品聚焦流的直径及位置,为流式细胞仪样品流速、鞘液流速的调控以及液流器件组装精度的测试提供了指导方法。     

变孔径环形超声换能器的聚焦性能仿真研究

在河工模型地形测量应用中,为适应提高方位向分辨率和减小盲区的要求,提出一种变孔径环形超声换能器的设计,并分析了该换能器的聚焦性能及其随目标点距离变化的情况。该换能器使用环形结构,能得到方位向的高分辨率,提高地形成像的质量;利用变孔径技术,又保证在对较大起伏地形进行成像时,保持了最佳的显示效果。分析结果表明,设计的超声换能器在提供较高方位向分辨率的同时,有效地减小了近场盲区,满足河工模型地形测量的要求,并为其它成像系统和医学应用提供参考。     

Hydrodynamic focusing of a particle flux

Based on numerical integration of the equations of mechanics of multiphase media, an effect of focusing of a particle flux generated by a source located on the upper wall of a closed vessel has been revealed and investigated.Notation t time - x, y Cartesian coordinates - U₁ (u ₁, v₁),P, ₁ velocity, pressure, and density of the gas - ₂,U ₂ mean density and velocity of the dispersed phase - V _k , r _k velocity and radius vector of a macroparticle - g gravitational acceleration - e(0–1) gravity force vector - dynamic viscosity of the gas - f friction force of particles in the gas - Eu, Re Euler and Reynolds numbers - dimensionless time of the high-rate relaxation of particles Élektrogorsk Research Center, Russia; Institute of Mechanics and Biomechanics, Sofia, Bulgaria; Institute for Problems in Mechanics, Russian Academy of Sciences, Moscow. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 68, No. 3, pp. 355–360, May–June, 1995.     

Analytical electric field and sensitivity analysis for two microfluidic impedance cytometer designs

Microfabricated impedance cytometers have been developed to measure the electrical impedance of single biological particles at high speed. A general approach to analytically solve the electric field distributions for two different designs of cytometers: parallel facing electrodes and coplanar electrodes, using the Schwarz-Christoffel Mapping method is presented. Compared to previous analytical solutions, our derivations are more systematic and solutions are more straightforward. The solutions have been validated by comparison with numerical simulations performed using the finite element method. The influences on the electric field distribution due to the variations in the geometry of the devices have been discussed. A simple method is used to determine the impedance sensitivity of the system and to compare the two electrode designs. For identical geometrical parameters, we conclude that the parallel electrodes design is more sensitive than the coplanar electrodes.     

Thermostatic and dynamic performance of an ultrasonic density probe

The thermally static and dynamic performance of an ultrasonic density probe for liquids is investigated in the density range of 750 to 1300 kg/m³ at temperature ranging from 0 to 40°C. The single transducer probe uses a pulse echo technique to obtain the characteristic acoustic impedance of the liquid and, subsequently, the speed of sound through the liquid to obtain the density of the liquid. Variations in the initial sound amplitude are addressed by the design of a layered two material probe. It is shown that it is possible to obtain an accuracy of 0.4% in the experiments carried out. For changing temperature, the probe exhibits large errors because of problems in estimating the temperatures in certain regions of the probe     

Microfluidic flow cytometer for quantifying photobleaching of fluorescent proteins in cells

Traditional flow cytometers are capable of rapid cellular assays on the basis of fluorescence intensity and light scatter. Microfluidic flow cytometers have largely followed the same path of technological development as their traditional counterparts; however, the significantly smaller transport distance and resulting lower cell speeds in microchannels provides for the opportunity to detect novel spectroscopic signatures based on multiple, nontemporally coincident excitation beams. Here, we characterize the design and operation of a cytometer with a three-beam, probe/bleach/probe geometry, employing HeLa suspension cells expressing fluorescent proteins. The data collection rate exceeds 20 cells/s under a range of beam intensities (5 kW to 179 kW/cm(2)). The measured percent photobleaching (ratio of fluorescence intensities excited by the first and third beams: S(beam3)/S(beam1)) partially resolves a mixture of four red fluorescent proteins in mixed samples. Photokinetic simulations are presented and demonstrate that the percent photobleaching reflects a combination of the reversible and irreversible photobleaching kinetics. By introducing a photobleaching optical signature, which complements traditional fluorescence intensity-based detection, this method adds another dimension to multichannel fluorescence cytometry and provides a means for flow-cytometry-based screening of directed libraries of fluorescent protein photobleaching.     

Microchip flow cytometry using electrokinetic focusing

Flow cytometry of fluorescently labeled and unlabeled latex particles is demonstrated on a microfabricated device. The latex particles were detected and counted using laser light scattering and fluorescence coincidence measurements. Sample confinement was accomplished using electrokinetic focusing at a cross intersection, and detection occurred 50 μm downstream from the intersection. Particles with diameters of 1 and 2 μm were analyzed and distinguished from each other based on their light scattering intensity and fluorescence. A maximum sample throughput of 34 particles/s was achieved. Sample mixtures with varying proportions of fluorescently labeled and unlabeled particles were also analyzed and found to be within experimental error of the expected ratios.     

The effects of focusing and refraction on Gaussian ultrasonic beams

A scalar theory of the propagation of Gaussian ultrasonic beams through lenses and interfaces is presented. For radiation into a fluid, the Fresnel approximation is employed to derive the laws of propagation of Guassian beams (previously employed in the analysis of coherent optical systems). These are then generalized to situations commonly found in nondestructive evaluation by treating the effects of propagation through lenses and through curved interfaces at oblique incidence. A numerical example illustrates the ease with which insight into diffraction phenomena for complex geometries can be gained by this approach. The limitations imposed on the theory by aberrations and the scalar assumption are discussed, and the relationship of the Gaussian theory to the radiation of piston transducers is explored.     

Choosing ultrasonic flow transducers

We consider flowmeters using piezoelectric transducers attached to pipes; these devices are characterized by high error and low sensitivity. Translated from Izmeritel'naya Tekhnika, No. 10, pp. 18–20, October, 1997.     

Measurement of scattering properties of individual particles with a scanning flow cytometer

A hydrofocusing head with an optical cuvette has been developed for the flow cytometer to generate complete scatter patterns of single particles at scattering angles ranging from 10° to 120°. The scatter signal has been measured as a function of the angle (a flying indicatrix) by the use of particle motion within a scanning system of the flow cytometer by the use of a single photomultiplier. Scattering data measured with the flow cytometer have been compared with those calculated from Mie theory for latex particles. A calculation algorithm has been used to estimate the size and the refractive index of spherical particles from the scattering data measured.     

Analysis of an ultrasonic method of measuring the flow rate of materials

A metrological analysis of an ultrasonic method of measuring the flow rate of materials is presented. Translated from Izmeritel'naya Tekhnika, No. 1, pp. 34–36, January, 2000.     

基于相关性延迟分析的SAFT算法

针对超声经典合成孔径聚焦(SAFT)算法需对每点进行延迟聚焦、运算量大等问题,提出基于相关性延迟分析的合成孔径聚焦算法,并建立数学模型,采用Matlab分别对经典SAFT算法和基于相关性延迟分析的SAFT算法进行仿真分析。结果表明:基于相关性延迟分析的SAFT算法具有图像质量优、分辨率高、实时性好等特点。     

基于全聚焦算法的骨折超声成像研究

为研究便捷、安全、无电离辐射的骨折检测方法,提出了超声双层折射修正全聚焦算法.首先从信号处理入手,通过回波信号与标准发射信号进行互相关计算,得出噪声含量极低的回波信号.继而利用Filed-Ⅱ裂纹仿真实验验证全聚焦成像对均匀介质检测的可行性,仿真结果显示裂纹宽度平均相对误差为5.60％;最后对离体牛胫骨进行全矩阵数据采集...     

超声相控阵全聚焦无损检测技术概述

超声相控阵全聚焦成像技术基于接收信号后处理的思想,对检测回波数据进行离线分析成像,是超声检测领域里的一项新技术。因其成像分辨率高、覆盖面广、对小缺陷灵敏度高等优势,在航空航天、高铁、石油管道、核电站等工业领域已有初步应用。文章介绍了全聚焦成像技术的检测原理及优缺点,介绍了其国内外发展历程,总结了研究热点及发展趋势。     

超声相控阵全聚焦成像算法比较分析

先进的成像算法推动了超声相控阵技术的发展,全聚焦方法(Total Focusing Method,TFM)是一种基于全矩阵捕获的虚拟聚焦后处理及缺陷图像重构算法.文章基于一维线阵相控阵纵波探头全矩阵数据模式,利用Matlab软件结合Field Ⅱ自带开源函数包编写了算法程序,比较了TFM和1/2矩阵方法成像效果并对缺陷...     

Analytical calculation of the longitudinal electric field resulting from the tight focusing of an ultrafast transverse-magnetic laser beam

A purely time-domain approach is proposed for the propagation of vectorial ultrafast beams in free space beyond the paraxial and the slowly varying envelope approximations. As an example of application of this method, we describe in detail the vectorial properties of an ultrafast tightly focused transverse-magnetic (TM(01)) beam, where special attention is given to the longitudinal electric field component. We show that for spot sizes at the waist comparable to the wavelength, the beam diverges more rapidly than expected from paraxial theory. A consequence of this phenomenon is a faster decrease of the amplitude of the longitudinal field away from the waist and a faster evolution of the axial Gouy phase shift in the vicinity of the focus. It has been observed that the phase of the beam has an overall variation of 2pi from z=-infinity to infinity, independent of the beam spot size at the waist and pulse duration.     

Multinode acoustic focusing for parallel flow cytometry

Flow cytometry can simultaneously measure and analyze multiple properties of single cells or particles with high sensitivity and precision. Yet, conventional flow cytometers have fundamental limitations with regards to analyzing particles larger than about 70 μm, analyzing at flow rates greater than a few hundred microliters per minute, and providing analysis rates greater than 50,000 per second. To overcome these limits, we have developed multinode acoustic focusing flow cells that can position particles (as small as a red blood cell and as large as 107 μm in diameter) into as many as 37 parallel flow streams. We demonstrate the potential of such flow cells for the development of high throughput, parallel flow cytometers by precision focusing of flow cytometry alignment microspheres, red blood cells, and the analysis of a CD4+ cellular immunophenotyping assay. This approach will have significant impact toward the creation of high throughput flow cytometers for rare cell detection applications (e.g., circulating tumor cells), applications requiring large particle analysis, and high volume flow cytometry.