Quantitative Magnetic Separation of Particles and Cells Using Gradient Magnetic Ratcheting

Extraction of rare target cells from biosamples is enabling for life science research. Traditional rare cell separation techniques, such as magnetic activated cell sorting, are robust but perform coarse, qualitative separations based on surface antigen expression. A quantitative magnetic separation technology is reported using high‐force magnetic ratcheting over arrays of magnetically soft micropillars with gradient spacing, and the system is used to separate and concentrate magnetic beads based on iron oxide content (IOC) and cells based on surface expression. The system consists of a microchip of permalloy micropillar arrays with increasing lateral pitch and a mechatronic device to generate a cycling magnetic field. Particles with higher IOC separate and equilibrate along the miropillar array at larger pitches. A semi‐analytical model is developed that predicts behavior for particles and cells. Using the system, LNCaP cells are separated based on the bound quantity of 1 μm anti‐epithelial cell adhesion molecule (EpCAM) particles as a metric for expression. The ratcheting cytometry system is able to resolve a ±13 bound particle differential, successfully distinguishing LNCaP from PC3 populations based on EpCAM expression, correlating with flow cytometry analysis. As a proof‐of‐concept, EpCAM‐labeled cells from patient blood are isolated with 74% purity, demonstrating potential toward a quantitative magnetic separation instrument.     

Droplet Oscillations in High Gradient Static Magnetic Field

In high intensity and high gradient magnetic fields the volumetric force on diamagnetic material, such as water, leads to conditions very similar to microgravity in a terrestrial laboratory. In principle, this opens the possibility to determine material properties of liquid samples without wall contact, even for electrically non-conducting materials. In contrast, AC field levitation is used for conductors, but then terrestrial conditions lead to turbulent flow driven by Lorentz forces. DC field damping of the flow is feasible and indeed practiced to allow property measurements. However, the AC/DC field combination acts preferentially on certain oscillation modes and leads to a shift in the droplet oscillation spectrum.What is the cause? A nonlinear spectral numerical model is presented, to address these problems.     

The Development of 5.5 T High Gradient Superconducting Magnetic Separator

A new High Gradient Superconducting Magnetic Separator (HGMS) system was developed to process kaolin. This paper describes the development of a 5.5 T central field, 300 mm room temperature bore, HGMS system. A zero boil-off helium cryostat, a double canisters system, and a PLC (Process Logic Controller) fully automatic control system based on SCADA (Supervisory Control And Data Acquisition) system have been designed for the HGMS. Every part works very well. Some experiments on processing kaolin clay used HGMS have been carried out. This paper will show the detailed development of every part.     

Effect of the Magnetic Dipole–Dipole Interaction on the Capture Efficiency in Open Gradient Magnetic Separation

In magnetic separation, the magnetic dipole-dipole (DD) interaction between particles has an important effect on the capture efficiency. By producing transient particle agglomerations, this interaction can considerably speed up the separation process. To take into account adequately this effect in ferromagnetic particle random dispersion, we have developed a modeling approach. The approach is based on the coupling of the magnetic force equation and a local homogenizing model for the material magnetic permeability. To verify the efficiency of the proposed approach on one hand and to estimate the effect of the DD interaction on the particle capture on the other hand, we consider a problem of open gradient magnetic separation (OGMS). We also conducted a limited experimental verification of the transient agglomeration for fine ferromagnetic particles.     

Continuous Flow Low Gradient Magnetophoresis of Magnetic Nanoparticles: Separation Kinetic Modelling and Simulation

Journal of Superconductivity and Novel Magnetism - In recent years, magnetophoresis of magnetic nanoparticles (MNPs) has been emerged as one of the most appealing separation technologies in water...     

Atmospheric correction of SeaWiFS imagery for turbid coastal and inland waters

The standard SeaWiFS atmospheric correction algorithm, designed for open ocean water, has been extended for use over turbid coastal and inland waters. Failure of the standard algorithm over turbid waters can be attributed to invalid assumptions of zero water-leaving radiance for the near-infrared bands at 765 and 865 nm. In the present study these assumptions are replaced by the assumptions of spatial homogeneity of the 765:865-nm ratios for aerosol reflectance and for water-leaving reflectance. These two ratios are imposed as calibration parameters after inspection of the Rayleigh-corrected reflectance scatterplot. The performance of the new algorithm is demonstrated for imagery of Belgian coastal waters and yields physically realistic water-leaving radiance spectra. A preliminary comparison with in situ radiance spectra for the Dutch Lake Markermeer shows significant improvement over the standard atmospheric correction algorithm. An analysis is made of the sensitivity of results to the choice of calibration parameters, and perspectives for application of the method to other sensors are briefly discussed.     

Setting up reliability goals for systems

The quality of life of people of any country depends to a very large extent on the quality and reliability of products and services like transport, communications, power, broadcasting, telecasting, etc. Psychological and physical discomforts are felt by people only when things fail thereby reducing or removing the service. Everybody feels that ‘immortal’ services should be available, but services are created by man and are mortal like him. However, there is a need to have a reliability goal whereby one can guarantee the continuity of a service for a certain lengtht of time/distance with a known risk of failure. Reliability of services is dependent on the reliability of systems comprising them and the management. In this paper the author has tried to focus attention on the need to have reliability goals as distinct from availability goals. The paper gives the basis for setting up reliability goals for a system as well as its subsystems. The allocation of reliability goals for the subsystems is based on the operating experience with similar systems or on the basis of the knowledge of the system or both. Two typical cases of a nuclear power station and a particle accelerator are considered and reliability goals for both system and subsystems are arrived at. The author concludes by stating that reliability goals in respect of simple items produced in large quantities and used anywhere in the world are a necessity. This is so because cost of maintenance is bound to be large with such items.     

Atmospheric correction of SeaWiFS imagery for turbid coastal and inland waters: comment

Ruddick et al. [Appl. Opt. 39, 897 (2000)] extended the standard SeaWiFS atmospheric-correction algorithm for use over turbid coastal and inland waters. However, Ruddick's method is based on the assumption of a spatially homogeneous constant ratio for the water-leaving reflectances normalized by the sun-sea atmospheric transmittance at 765 and 865 nm. Such first-order b(b)/a model-based assumption can result in an inaccuracy for highly turbid water. Using the first- and second-order b(b)/(a + b(b)) models as well as the second-order b(b)/a model (which, more realistically, do not assume spatial homogeneity ratio), we suggest using the modified assumption, R(8)(-1) = alpha0 R(7)(-1) + (l1Q)(-1) (1 - alpha0), instead of Ruddick's assumption, in SeaWiFS atmospheric-correction algorithms for highly turbid waters.     

多色分色模型中中性灰的调控

利用颜色分区理论将多色色空间进行分区,在各分区内设计色块确定 K 与 CMY 的等效关系,结合灰成分替代率,确定了多色分色模型中中性灰调控的方法。 实验证明,分色时不考虑灰平衡会影响最终颜色复制的效果,分色模型中灰平衡方法的确定是非常必要的。     

网上录取计算机网络系统的建立

根据网上录取的要求和流程,从系统的网络平台设计,服务器平台设计以及软件开发平台设计几方面阐述了建立网上招生信息系统模式的可能。     

高保真多色分色模型中间色的设置

高保真印刷技术通过在CMYK的基础上增加其他原色的方法,达到扩大色域的目的,增加的原色与CMYK之间存在替代关系,替代关系可以简化复杂的高保真多色分色模型,并提高其精度。以CMYKRBG七色高保真模型中R为例,设计了渐变测控条,打印输出并测量了各级网点密度,采用多项式回归算法,拟合出了间色平衡曲线,建立了R与MY的替代方程,通过设置间色替代率,获取了R与MY之间的颜色替代量,最后设置了4组不同的间色替代率,通过色差确定了合适的间色替代率的取值范围。实验结果表明:确定的间色替代率在0.2左右,可以提高分色模型的精度。     

Filter Capacity Predictions for the Capture of Magnetic Microparticles by High-Gradient Magnetic Separation

We present experimental and theoretical methods to predict maximum and working filter capacities for the capture of superparamagnetic microparticles through high-gradient magnetic separation (HGMS). For this, we employed various combinations of nine different HGMS filter matrices and two types of superparamagnetic microparticles. By calculating the separated particle mass per filter mesh area, we clearly demonstrated the influences of wire diameter and wire mesh spacing on the particle build-up density. Here, we introduce a simple experimental method for estimating average build-up densities in HGMS. Together with known physical parameters of the filter matrix and the background field, such average build-up densities allow good predictions of the operational working filter capacities.      

Separation of Silver Nanocrystals for Surface-enhanced Raman Scattering Using Density Gradient Centrifugation

One-dimensional silver nanocrystals(AgNCs) have been prepared by a polyol process using sodium hydroxide and nitric acid at a constant silver source concentration.Results indicate that the aciditybasicity plays an important role in silver-nanocrystal formation.Different morphologies of AgNCs were synthesized by changing the NaOH or HNO_3 amount.We demonstrate that nearly monodisperse silver nanocrystals can be separated from polydisperse samples using density gradient centrifugation separation(DGCS).We also demonstrate that the separated AgNCs can be used as substrates for surfaceenhanced Raman scattering(SERS) spectroscopy.The separation approach provides a method of improving the nanocrystal quality produced by large-scale synthetic methods.     

计量标准建标报告在计量工作中的应用

建标报告包含了丰富、有价值的专业技术信息,如何将其应用于日常计量工作是计量工作者应探讨的问题.本文介绍了一些经验体会,供读者参考.     

叶片建模的CAD系统及应用

本文阐述了用于UG二次开发的UG／open API程序设计模块，UG／open MenuScfipt、UG／open Ulstyler和User Tools辅助设计模块的特点，并介绍了利用它们各自的特点进行叶片建模系统开发的过程，以及建模系统的构成、应用等。     

瞬态波形记录仪器计量标准的建立

叙述了瞬态记录仪器计量标准建立中的几个问题 ,包括校准系统的构成、校准项目、校准方法、校准设备的选择 ,以及影响有关指标校准不确定度的几个因素     

建立计量技术体系 促进计量事业发展--国家质检总局局长李长江、副局长王秦平视察计量院

新年伊始,国家质检总局局长李长江、副局长王秦平于2002年1月11日到中国计量科学研究院视察工作,传达国务院领导关于加强计量工作的指示,并向全院职工及离(退)休老同志致以新年问候.随总局领导来院的还有总局人劳司司长安国、计划财务司司长齐京安、科技司司长刘平均、计量司司长宣湘、办公厅副主任刘德平等,院领导及处级以上干部参加了会议.     

Setting up the production process of diatomite-based ceramic foams

The design of the production process of diatomite-based ceramic foams, starting from different percentages of metakaolin, diatomite, and sodium silicate solution as reactive ingredients and vegetable surfactant and silicon powder as blowing agents, has been set up. The foams were obtained using the double effect of different foaming approaches: mechanical stirring and chemical foaming. Six systems were prepared fixing the amount of diatomite (100%) and adding in the starting mixture of different percentages (0.05, 0.1, 0.25, 0.5, 0.75, and 1?wt%) of silicon metal. Once the optimal percentage of silicon metal (0.05%) is chosen thanks to XRD analysis, other three systems were prepared only changing the amount of diatomite (50, 70, and 100?wt%) in starting formulation. The foam obtained with 100% of diatomite results to be the optimized final formulation, as it shows a hierarchical porosity with a high homogeneity of the matrix at the same time. The results highlighted that the best performances in terms of lightness, high porosity as well as homogenous microstructure were obtained using, with respect to the total amount, 6?wt% of mechanical stirred vegetable surfactant together with 0.05?wt% of Si as physical and chemical blowing agents, respectively.     

搭建国际交流平台展示世界先进品牌

堪称目前国内规模最大展览面积达五5万平方米的"第11届中国上海国际印刷包装造纸工业展览会"将于2003年7月17日至20日在上海新国际博览中心隆重举行.