纳秒脉冲细胞内电处理机理及其研究进展

介绍了细胞内电处理效应的研究现状及其进展 ;重点描述了KarlHSchoenbach提出的脉冲电场与细胞相耦合的球形模型 ;探讨了细胞内电处理机理 ,即当脉冲作用于悬浮生物细胞时 ,随脉冲宽度变小 ,电场对细胞核及核膜影响增强 ,当脉宽大于细胞膜充电时间常数时 ,脉冲电场主要作用在细胞外膜上产生电穿孔 ;当脉宽小于细胞膜充电时间常数时 ,脉冲电场对细胞内进行电处理。     

ns脉冲诱导细胞内电处理机理的研究进展

脉宽为ns级、场强≥10 kV/cm的脉冲电场能够对细胞内部结构产生影响而不会导致细胞外膜穿孔,即细胞内电处理效应。尽管细胞内电处理效应的机理目前还不是很清楚,但国内外学者一致认为细胞内电处理的根本原因是ns脉冲电场在细胞内膜上诱导出的跨膜电位超过了穿孔临界值,从而导致内膜穿孔。基于以上研究详细介绍了目前关于细胞内外膜跨膜电位的计算模型、方法及仿真计算结果,探讨了细胞内电处理的机理。宽脉冲电场难以透过外膜进入细胞内部,主要作用在外膜上,导致外膜发生电穿孔。随着脉冲宽度变小,电场对内膜作用增强。当脉宽减小到ns级时,脉冲电场感应出的内膜跨膜电位比外膜大,电场主要作用于膜内细胞器,诱导内膜穿孔,细胞结构和功能改变,即进行细胞内电处理。     

脉冲电场上升沿对细胞跨膜电位的影响分析

分析了电场生物效应实验和实用中脉冲电场上升沿的形成并基于经典球形单细胞模型推导出计及上升沿的脉冲电场所诱导的细胞跨膜电位的计算解析式。研究发现:脉冲电场上升沿与细胞跨膜电位峰值、波形密切相关,减少脉冲电场发生电路的电感来增大脉冲电场所诱导跨膜电位的峰值可提高电穿孔的效率。     

实际指数脉冲电场对细胞跨膜电位的影响

为了进一步增大细胞跨膜电位峰值,提高脉冲电场电穿孔效率,基于相关文献中球形单细胞多层介电模型的细胞跨膜电位计算方法,分析了实际RC指数衰减脉冲上升沿时间对细胞跨膜电位的影响。通过Matlab软件对细胞跨膜电位的传递函数频率响应进行了仿真分析,结果表明:不同频段的电场对细胞跨膜电位的影响不同。建立了一种改进的RC指数衰减脉冲模型,并进行了仿真计算,结果表明:脉冲电场上升沿时间对细胞跨膜电位有很大影响:上升沿时间越小,频率响应就越高,减小上升沿时间可以提高细胞跨膜电位峰值。仿真结论对改进脉冲电场发生电路的结构和参数设计,以增大细胞跨膜电位峰值并提高电穿孔效率提供了理论依据。     

基于有限元分析的球形单细胞及不规则真实细胞电穿孔动态过程仿真

为深入研究脉冲电场对细胞的作用机制,并进一步推广其在临床上的应用,基于有限元仿真软件建立了考虑胞内细胞器的单细胞五层介电模型,从2维和3维的角度研究分析了脉冲电场诱导细胞发生电穿孔的动态过程。同时,鉴于理论球形细胞与真实细胞结构的差异,建立不规则细胞介电模型,讨论分析脉冲电场作用于理论球形细胞与真实细胞电穿孔效应的差异。仿真结果表明:在1.5 k V/cm、10μs脉冲电场作用下,细胞膜上跨膜电位升高达到穿孔跨膜电位阈值(1 V)后发生穿孔,孔密度急增(达到1016数量级),电导率随着时间快速增加,从而进一步改变跨膜电位的分布,穿孔区域由正对电极的点逐渐往四周扩展,最终穿孔区域达到整个表面积的71.4%。而不规则细胞下的跨膜电位、电导率等分布较复杂,不再具有对称分布性,对于畸形度较大的细胞则必须考虑其形状的影响。仿真结果合理解释了脉冲作用下单细胞电穿孔的作用机制,为进一步分析复杂细胞系统提供理论依据,同时推进了脉冲电场的临床应用。     

脉冲电场食品处理技术

介绍了脉冲电场食品非热处理技术的概念与方法 ,结合国外目前的研究状况 ,给出脉冲电场系统及其参数 ,分析了食品的电特性及细胞电击穿的机理。结合验证实验提出了该技术的可行性和广阔的发展前景     

反向电场细颗粒脱除机理及实验研究

基于反向电场除尘原理,构建了反向电场电袋复合除尘实验装置,并实验测试了其对中位径1.49 μm气溶胶颗粒的捕集性能。该实验装置由预荷电器和带反向电场的袋式除尘器组成。反向电场电袋复合技术的除尘增效机理是,在反向电场对预荷电粒子的静电斥力减缓了预荷电粒子向滤袋的运动速度,且增加了滤料附近场强。实验结果表明:过滤风速越高,反向电场电袋复合除尘器相对于常规电袋复合除尘器的增效作用越明显;当过滤风速由 1.0 m/min增加到2.5 m/min,反向电场电袋复合的除尘效率相对于常规电袋复合的增效幅度由3.9%提升到11.8%,其压力损失比常规电袋复合除尘器的增加约5.0%;反向电场静电复合除尘技术能实现细颗粒物的高效控制,并能为反向电场工业应用提供技术支撑。     

脉冲电场与生物医药技术的交叉及其对肿瘤治疗模式的改变

生命现象与电密切相关。脉冲电场的生物效应促进了生命科学与电气工程技术的交叉融合,使得高功率脉冲技术在生物医药领域形成了快速发展的边缘交叉学科,在医学、农业、给药系统、细胞生物工程上应用广泛。为此,就非热电场灭菌、脉冲电场活化血小板、电化学药物治疗、电转染治疗心肌缺血、脉冲电场消融肿瘤等研究,结合电工和生物新原理、新理论、新技术、新材料,介绍、分析了脉冲电场技术在生物医药应用中的最新进展。主要结论包括:μs脉冲电场对电化学治疗、不可逆电穿孔有重要作用;ns脉冲电场不联合化疗药物而单独使用就可以达到肿瘤消融的目的;脉冲电场消融对外科手术禁区或射频消融不能达到的位置有特殊帮助;改进肿瘤适形电极设计才能进一步提高肿瘤消融效果;目前电脉冲消融肿瘤还需要多中心大规模前瞻性临床试验来验证其长期疗效。提出脉冲电场生物医药领域应用具有广阔的发展前景。     

放电电场对SO2气相传质过程的影响

研究了SO2在放电电场中的气相传质过程。通过模拟试验，研究了外加电压、放电区长度、放电空间大小等与放电电场相关的参数对SO2电迁移和脱硫效率的影响。试验结果表明：放电电场对SO2传质过程具有促进作用，这种促进作用和系统脱硫效率随电压升高、放电区长度和单位能耗增加、放电空间减小而增加。放电电场之后的辅助匀强电场有助于改善SO2的电迁移效果。系统脱硫效率可达95%以上，由放电电场促进SO2传质而引起的脱硫效率增量接近50%。     

电场对带电颗粒在电连接器表面沉积过程的影响

基于尘土颗粒周围电场与其在电接触表面沉积的密切联系导致电接触可靠性下降甚至接触故障,分析了电连接器自身及外加电场对尘土颗粒运动产生影响的过程和机理,提出了衡量电连接器对颗粒吸引能力的判据和计算方法.仿真实验表明,该吸引能力与电连接器两端电压和距离有关,颗粒运动趋势与其进入电场时间有关,而与其所带电荷极性无关.     

Use of dielectrophoretic collection spectra for characterizingdifferences between normal and cancerous cells

An automated analysis system for the rapid measurement of dielectrophoretic collection spectra of mammalian cells is described. Cells are injected onto an electrode configuration having regions with different electric field gradients, and cell movement to or from these regions is determined by computerized image analysis as a function of the applied electric field frequency. Data are presented to show that cultured murine erythroleukemia cells undergo a significant alteration in their dielectrophoretic collection spectrum following treatment with hexamethylene bisacetamide or dimethylsulfoxide, agents that induce terminal differentiation in these otherwise malignant cells. These changes appear to arise from characteristic alterations in membrane capacitance and conductance as the cells differentiate     

基于克尔电光效应的新型CCD光电测试系统

根据克尔电光效应原理 ,用稳定性好、动态范围大、灵敏度更高的CCD 30 0 0光电接收装置建立的新测量系统动态测量了克尔常数较小的液体介质如变压器油中的电场分布 ,并得出在一定电压范围内 ,克尔试验盒中两电极间的光强分布和电场分布之间的对应关系 ,还通过分析光强的空间分布和变化规律得出电场的空间分布和变化规律 ,为液体介质中的电场及空间电荷分布测量提供了一条新途径     

Optimization of electroporation waveforms for cell sterilization

Pores occur naturally in cell membranes. Application of an electric field generates a force which tends to open the pore, a mechanism known as electroporation. The force generated depends on the electric field in the pore and the difference in dielectric constant between the fluid in the pore and the membrane. In this paper, we use transient finite-element analysis to investigate the field as a function of time in a system which consists of an electrolyte, an ellipsoidal bacterial cell membrane, and cytoplasm within the cell membrane. For this shape of cell, the field in the cell membrane is caused largely by the relaxation of the field in the cytoplasm. In addition, we compute the force on the pore wall, both in an analytic approximation and numerically as a function of time during a variety of applied voltage waveforms, using transient finite-element analysis. The numerical data are in good agreement with the analytic approximation and provide a basis for judging the efficacy of waveforms for sterilization based on a "figure of merit" which is suggested in the paper.     

Transient Electric Field Analysis in Consideration of the Electric Field Dependence of Resistivity in the Converter Transformer

In this paper, values of the electric field in the pressboard and oil during the polarity reversal test of the converter transformer were calculated with transient analysis. First, we confirmed the accuracy of the nonlinear analysis in the model test. Next, we carried out nonlinear transient electric field analysis for polarity reversal test of the converter transformer. In the results, when the applied time of dc voltage before the polarity reversal is 360 min, the values of the electric field of oil area are the same as when it is 90 min. Although, the electric field in the pressboard becomes higher in response to the applied time dc voltage, it does not cause a problem on the insulation. Because withstand voltage of pressboard is very high. In the results, the correlation between the applied time of dc voltage before the polarity reversal and the withstand voltage of transformer is considered low. This result can be applied to the design of the converter transformer.     

Transform relationship between Kerr-effect optical phase shift andnonuniform electric field distributions

Electric field distributions measured using the Kerr effect cause a phase shift between light components polarized parallel and perpendicular to the electric field, proportional to the magnitude squared of the electric field components in the plane perpendicular to light propagation integrated over the light path length. One wishes to recover the electric field distribution from measurements of light phase shifts. For axisymmetric geometries where the electric field depends only on the radial coordinate and whose direction is constant along the light path, as is the case along a planar electrode, the total phase shift for light propagating at a constant distance from the center of symmetry and the electric field distribution are related by an Abel transform pair, a special case of Radon transforms typically used in image reconstructions with medical tomography and holography. The more general Radon transform relates the optical phase shift to non-axisymmetric electric field distributions but is restricted to cases where the applied electric field is perpendicular to the plane of light propagation. If the applied electric field direction changes along the light path, it becomes necessary to account for the change in direction of the light components parallel and perpendicular to the applied electric field and the light polarization equations are generalized     

Dielectrophoretic manipulation of particles

We have demonstrated that, in general, the dielectrophoretic (DEP) force experienced by a particle has two components. The first depends upon inhomogeneities in the applied electrical field strength and upon the in-phase part of the resultant dipole moment induced in the particle and can be identified with the conventional dielectrophoretic (cDEP) force. The second relates to nonuniformities in the phase distribution of the applied field and to the out-of-phase part of the induced dipole moment. A nonuniform phase distribution corresponds to a field that travels through space. This second force component gives rise to traveling-wave dielectrophoresis (twDEP). In this paper, we describe several electrode configurations designed to produce electric fields capable of inducing cDEP and twDEP forces for the purpose of manipulating particles. Using DS19 Friend murine erythroleukemia cells as test particles having well-characterized dielectric properties, we investigated the electrokinetic behaviors for these electrodes as a function of frequency and electrode excitation mode. Several characteristic cell electrokinetic behaviors were identified, including trapping, linear motion, levitation, and circulation of the cells, depending on the excitation characteristics of the electrodes and the cell dielectric properties. We describe these findings and rationalize them in terms of the field distributions produced by the electrodes, the particle dielectric properties, and generalized dielectrophoresis theory. The biotechnological applications of dielectrophoretic manipulation are then discussed     

Electrohydrodynamically Enhanced Capillary Evaporator

A two-phase capillary evaporator has been enhanced using electrohydrodynamic (EHD) forces. The evaporator was experimentally investigated under DC applied electric field operating modes as well as without an applied electric field. The results without the applied EHD forces show that the induced flow increases with increasing applied heat loads until a dry out condition is reached. The applied DC voltage electric field provides flow enhancements as high as 200%. A slight polarity effect was observed.     

HVDC输电线路离子流场数值计算方法研究

为了解高压直流输电线路的电磁环境影响及电晕损耗,讨论了高压直流线路周围离子流场计算的数值方法。描述高压直流离子流场控制方程的三阶非线性偏微分方程分解为两个等效的泊松方程后可用有限元迭代方法求解即在每次求解后根据两场的计算结果更新空间电荷密度,反复迭代求解直至计算结果收敛。该算法舍弃了Kaptzov和Deutsch假设,并提出了一种有效的电荷密度更新公式,同时考虑两场电位差别、电场与边界条件的差别,使迭代较快收敛。通过与实验模型的测试结果对比,验证了算法的有效性。