Apoptosis induction effects of steep pulsed electric fields (SPEF) on human liver cancer cell SMMC-7721 in vitro

To research the apoptosis effects of steep pulsed electric fields (SPEF) on human liver cancer cell SMMC-7721 in vitro, this paper studied Phosphatidylserine (PS) externalization detection utilizing flow cytometry, real-time change of mitochondrial transmembrane potential (Δ Ψ_m) using confocal laser scanning microscope (CLSM) and DNA fragmentation assay by agarose gel electrophoresis. The experiment results by flow cytometry showed that ?sSPEF (SPEF with electric field intensity of 200V/cm and duration of 1.3μs) effectively (P<0.05) induced PS externalization but nsSPEF (SPEF with electric field intensity of 600V/cm and duration of 100ns) did not (P>0.05). On the contrary, nsSPEF induced Δ Ψ_m decrease and DNA fragmentation more notably than μsSPEF. These results indicate that SPEF can distinctly induce apoptosis and the effects are electric field intensity/pulse duration-dependent. Theoretically calculation showed that temperature increase of cell solutions for treated groups exposed to SPEF was less than 1.3K without regard to heat dissipation. Multi-shelled dielectric cell model and frequency spectrum analysis showed that μsSPEF contained abundant low frequency components which mainly acted on plasma membrane, whereas nsSPEF contained plentiful high frequency components which permeated plasma membrane and mainly affected on intracellular organelle.     

Upgrading power system protection

Georgia-Pacific's Broadway Street Paper Mill in Green Bay,Wisconsin, is resolving an arc-flash hazard (AFH) problem by installing microprocessor (μP) bus-differential relays on medium-voltage switchgear and selectively replacing electromechanical (EM) overcurrent relays with μP relays. In addition to providing critical bus-differential protection, the μP relays will provide analog and digital communications for operator monitoring and control via the power-plant distributed control system (DCS) and will be ultimately used as the backbone to replace an aging hardwired load-shedding system.     

Double pulse approach of electropulsation: a fluorescence analysis of the nucleus perturbation at the single cell level

Plasmid Gene transfer and expression can be obtained by the application of electric pulses to a mixture of cells and plasmids (electrogenetherapy, EGT). Electropulsation is rather well characterized at the plasma membrane level. But, the transfer to and across the nuclear envelope remains a problem. Biological approaches showed that EGT was more effective during mitosis. Recently the group of Schoenbach showed that nanosecond ultra high field pulses may affect cytoplasmic organelles including the nucleus. The need for high field was linked on one hand on the time scale and on the other on the size of the target. Therefore we made an approach of the alteration of the nucleus induced by a microsecond high electric pulse (μs HV, up to 9 kV/cm, 5 μs). This perturbation was operated alone or a few seconds after EGT pulses (10x, 0.7 kV/cm, 5 ms) needed to introduce the plasmid in the cytoplasm. Structural alterations of the nucleus organization were investigated. This was obtained by a digitized fluorescence approach at the single cell level, using Hoechst dye as a probe with a high affinity to nucleic acids. The first train of pulses (EGT) induced a huge and rapid (<2min) swelling of cells and of their nucleus associated with a decrease of the mean fluorescence of the nucleus. Mean fluorescence level and volume changes were maintained along the next 10 minutes. The application of a μs HV pulse affects the cell volume and transiently the nucleus volume without any effects on the mean fluorescence level in the nucleus.     

Photoconductive switch design for microwave applications

A procedure for choosing the dimensions of a photoconductive semiconductor switch (PCSS) for operation at microwave switching frequencies, and particularly at 10.0 GHZ, is described. The critical dimension is the switch length (electrode separation), which must be small enough to force photoinduced charge removal during switch turn-off via sweep out rather than recombination. The switch depth in the direction of turn-on optical pulse absorption must be several optical absorption depths long to ensure absorption of all the incident light, which optimizes optical to electrical signal gain. The switch width is determined in conjunction with the peak intensity of the optical pulse because the switch width-optical intensity product, which represents optical power, determines the turn-on time, the on-state switch resistance and the turn-off delay time. Simulations show that a switch with a 0.5 μm length, 5.0 μm depth, and 20 μm width, illuminated with 1.0 W peak power optical pulses at 10 GHz, will have a 4.8 ps turn-on time, a 0.23 Ω on-state resistance, and a 46 ps turn-off time.     

Microprocessor-based protective relays

This article describes the benefits of microprocessor (μP) relay performance and its capabilities beyond previous protective relaying technologies. This article also discusses a multiple quality-measurement approach to observing, measuring, and then calculating μP relay reliability and unavailability. This is an important consideration for industrial and commercial facilities that are being required to repair or replace old electromechanical or solid-state (analog and digital) protective relaying equipment because of equipment malfunctions, misoperations, accidental tripping, or obsolescent parts. Although lP relays have been commercially available for more than 20 years and researched for the past 40 years, industrial and commercial plant engineers tend to be more reluctant to embrace the μP technology. Electric power utilities in North America have aggressively selected to replace older protection equipment by upgrading and replacing the equipment with new μP relays whenever and wherever possible.     

Effect of Discharge Electrode Parameters on the Flow Velocity Profile of the Wire?rod Type Electrohydrodynamic Gas Pump Exit

Experimental investigation has been conducted to study the effects of corona wire diameter, pipe length, and corona polarity on outlet flow velocity distribution profile of a wire-rod type electrohydrodynamic (EHD) gas pump. Upon applying negative or positive dc high voltage between a wire electrode (outer diameter (o.d.) 60 μm, 200 μm, or 300 μm) and a rod electrode (o.d. 3 mm) in atmospheric air, corona discharge occurs and EHD gas flow is generated in the direction from the wire electrode to the rod electrode through a cylindrical pipe (inner diameter (i.d.) 20 mm). For both polarities, the discharge current and average flow velocity increase monotonically on increasing the applied voltage before the onset of spark discharge. Using wire electrodes with a smaller diameter, stable corona discharge between corona onset and spark onset is generated in a wider voltage range, and the discharge current becomes larger, resulting in a higher flow velocity. The maximum average flow velocity of 2.0 m/s, corresponding to a flow rate of 38 l/min, was achieved with a wire of diameter 60 μm by applying a voltage of ?16 kV.     

Research on applications of TVS and thyristor in a pulsed power supply system used for EMG

A compact pulsed power supply (PPS) system is important for the electromagnetic gun (EMG) system, which should supply high energy and large current. The paper presents the setup of compact PPS system based on high energy density capacitors. The PPS system includes ten 50 kJ modules, which can be triggered in sequence. Each module is composed of a capacitor (1000 μF/10 kV), a pulse shaping inductor (20 μH), a crowbar diodes with a crowbar resistor(30mΩ), as well as a main switch which can be a triggered vacuum switch?TVS? or thyristors. The peak value of the output current of each module is 70 kA. Characteristics of the TVS and thyristors are comparatively studied to determine their influence on the output current and energy. The requirements for the diode-stacks of the crowbar are fast-recovery, high voltage withstanding. A proper protection measure is used in order to protect the crowbar diodes from the damage of over-voltage when switch is fired. In the end, the overall discharge currents of the PPS triggered in sequence are presented.     

Thermal Aging Micro-scale Analysis of Power Transformer Pressboard

In order to analyze the thermal aging mechanism of the insulation paper inside the power transformer, a series of accelerated thermal aging tests were performed on pressboard. Subsequently, the Atomic Force Microscope (AFM) together with Scanning Electron Microscope (SEM) and X-ray Diffraction (X-RD) were utilized to observe the micro surface of the thermal-aged pressboard. The experiments and analysis indicate that either the links among the D-glucopyranose units or the hexagonal mesh structures of the D-glucopyranose units were broken under thermal stress; the number of D-glucopyranose units after 6 weeks of aging was 0.8-1 per nm², only about one third of un-aged value. The wall of a cellulose cell was deteriorated and thinned by thermal stress. At the same time, the cracks expanded gradually on the surface of the cellulose, which shortened the average width of cellulose fiber from about 40 μ of un-aged sample to about 25 μ after 6 weeks of aging. Meanwhile, the relative crystallinity and the size of the crystallite in the pressboard decreased nonlinearly with the thermal aging time.     

直流锅炉给水低氧量处理的试验研究

分别在1 000 MW和600 MW超临界机组直流锅炉给水系统进行了加氧处理工艺试验,考察给水低氧量（氧质量浓度﹤30 μg/L）处理控制给水系统腐蚀的可行性。在给水系统钝化膜形成阶段和钝化膜形成后分别进行了给水低氧量处理试验,结果表明在钝化膜形成阶段应保持较高的给水加氧量;在钝化膜形成后,保持给水氧的质量浓度10~20 μg/L能够维持钝化膜长期稳定,使给水系统得到保护;为防止疏水系统管路腐蚀,给水采取低氧量处理时应将给水pH值控制在9.3以上,不宜再低。     

PD pulse burst behavior of a transformer type synthetic organic ester fluid

The partial discharge (PD) pulse burst characteristics of a transformer type synthetic organic ester fluid were compared with those of an equivalent transformer type mineral oil. Wide and narrow bandwidth measurements were carried out to determine simultaneously the apparent charge transfers associated with the overall PD pulse burst as well as that of the individual discrete pulses within the PD pulse burst. The PD pulse burst behavior was found to be similar in both insulating liquids. The discharge cavity formation times ranged from 0.5 to 1.5 μs, while the charge transfers associated with the PD pulse bursts in the liquids were found to extend from approximately 5 to 30 pC.     

Characteristics of partial discharges caused by trees in contact with covered conductor lines

Characteristics of partial discharges (PD) caused by trees in contact with covered conductor (CC) lines have been studied. A tree in contact with a CC distorts the electric field around the conductor and causes partial discharges. According to tests conducted in a high voltage laboratory the rise time of the PD current pulses caused by the trees is relatively long, in the order of 60 ns...0.8 μs. The fault impedance and PD magnitude caused by a tree in contact with a CC and the propagation attenuation of PD pulses was studied in different seasonal conditions in September, November and March on a full scale 110 kV CC trial line. In case of an intact CC the fault impedance is several MΩ. After breakdown of the conductor covering the fault impedance collapses in summer to tens and in winter to hundreds of kΩ. The average PD magnitude measured in March was approximately one fifth of that in September. On a 9.3 km line portion the observed propagation attenuation of the PD signal was 0.37...3.7 dB. The variation in the attenuation is attributed to the variation in the rise times of the PD pulses and the modal composition of the PD signal. The results indicate that PD measurements can be used to detect trees fallen on CC lines.     

Effects of nanosecond pulsed electric fields on the human prostate cancer cell line LNCaP

The effects of nanosecond pulsed electric fields (nsPEF) on the human prostate cancer cell line LNCaP was investigated for changes in protein and DNA concentrations as well as for the 11βHydroxysteroid Dehydrogenase type 2 (11βHSD2) enzyme activity. Electric fields with intensities of 32.5 kV/ cm and pulse widths of 60 ns were applied to cancer cells in trains of 1, 5, and 10 pulses. Protein concentrations were determined through a Bio-Rad DC protein assay, while Hoechst 33258 was used to quantify DNA concentrations. The analyses showed that protein concentrations decreased by 18.77% and 19.04% for 1 and 10 pulses, respectively, while DNA concentrations decreased by 5.29%, 8.95%, and 18.36% for 1, 5, and 10 pulses, respectively, as compared to control groups. The 11βHSD2 enzyme activity in LNCaP cells also decreased following exposure, thus supporting our initial hypothesis that ultrashort pulses affect intracellular structures; thus, a decrease in the enzyme activity could result in enhancing the anti-proliferative actions of glucocorticoids.     

红沿河核电站凝结水精处理系统的启动与运行

凝结水精处理系统（ATE）及其良好运行状态对核电站安全运行至关重要。以红沿河核电站3、4号机组ATE系统为例,对比机组首次启动和正常启动2种工况下ATE出水水质和制水量;介绍混床树脂完全分离的方法,给出树脂再生的重要控制点;对调试期间所遇问题进行分析,给出防范措施。经调试,红沿河核电站3、4号机组ATE运行良好,出水氢电导率、Na⁺质量浓度和SiO₂质量浓度分别为0.08 μS/cm、0.10 μg/L和1.91 μg/L,阳床和混床制水量分别为1.2×10⁵ t和4.4×10⁵ t ;树脂分离和再生的效果良好,阴树脂在阳树脂层内的体积分数小于0.08%,阳树脂在阴树脂层内的体积分数小于0.07%;ATE运行期间,蒸汽发生器排污水中Na⁺、Cl^-和SO₄^2-的浓度符合水化学规范。     

Effects of Saline Water and Temperature on Surface Properties of HTV Silicone Rubber

rubber (SIR) after immersion in saline solutions as a function of time (0 to 3000 h) at different temperatures is reported. The hydrophobicity is determined by measuring the static contact ? between the tangent to the droplet of distilled water and the horizontal surface of the HTV SIR. The conductivity of the saline solution was varied from 0.005 to 100 mS/cm and the temperature from 0 to 98 °C. The contact angle which gives a measure of the hydrophobicity of the surface decreased sharply during immersion. The contact angle decreased from the original value of 100±4.6° to low value of 15° after 3000 h of immersion at 98 °C in a solution of 0.005 mS/cm. The lower the conductivity, the larger was the decrease in the contact angle. The changes in the weight of the HTV SIR due to the uptake of water and the average surface roughness (ASR) are determined during the immersion. The increase/decrease in the weight and surface roughness of the HTV SIR are correlated with the contact angle and hence with the loss of hydrophobicity. The surface free energies Υ_sd, Υsh and Υs, the interfacial energy of HTV SIR and water Υsl, and the energy of adhesion W_siof water on HTV SIR are determined as a function of time during the immersion and related to the loss of hydrophobicity.     

360°风作用下线条风荷载分配系数特性

线条风荷载的准确计算是输电杆塔设计的关键一步,角度风荷载分配系数的选取是否合理将直接影响到设计指标的合理性。对常规线条风荷载（0.5Φ₁=0.5Φ₂=0）的计算原理进行梳理和分析,得到了0~90°范围内的角度风荷载分配系数。同时,通过对风向角θ和线路转角Φ的剖析,推导了线路前后侧360°风吹时的线条角度风荷载分配系数计算公式,并给出了前后侧挡距不同分配比例（0.5Φ₁=0.5Φ₂,0.5L₁∶0.5L₂=5∶5、4∶6、3∶7）时的线条角度风荷载分配系数,分析了分配系数的特点,并进行了对比研究。研究结果揭示了线条角度风荷载分配系数的特点,可作为输电杆塔抗风设计的一种参考。     

Correlation between tan δ diagnostic measurements and breakdown performance at VLF for MV XLPE cables

The main contribution of this paper is to investigate the correlation between Tan ? diagnostic measurements at 0.1 Hz (Very Low Frequency-VLF) and VLF breakdown performance for Medium Voltage (MV) cable samples through a laboratory test program. The cable samples used are a set of 15 kV, Cross-linked Polyethylene (XLPE), unjacketed cables removed from the field, the same service area, and having experienced similar operating conditions for almost four decades. The test program includes Tan δmeasurements at different voltage levels and a subsequent VLF extended step-withstand test. The VLF step test allows the evaluation of risk of failure during VLF Tan δtesting and assessment of the ultimate performance of the cables. The Tan ? diagnostic measurements are represented by the Tan δvalue and Tip-up, which are considered the classical metrics. However, the paper also suggests the use of a new additional diagnostic feature that takes into account the scatter in the Tan δmeasurements for a particular test voltage level.     

某600 MW超临界机组振动故障分析与处理

某电厂引进型600 MW超临界机组3号瓦轴振突然变大,幅值在80 μm至240 μm之间波动,2号瓦瓦温升高到106 ℃,严重威胁到机组的安全运行。通过变油压、变负荷、变真空试验,采用正向推理方法,准确分析了振动故障原因并给出了处理措施,对大型机组类似振动故障分析具有借鉴价值。     

自然雷电下氧化锌避雷器残压特征分析

对自然闪电条件下氧化锌避雷器的残压波形特征进行了分析。通过线路过电压和快电场的变化,对记录的12次自然闪电引起的避雷器残压波形进行了分析。分析结果表明,自然闪电条件下的避雷器残压持续时间约330 μs,明显长于实验室用8/20 μs波形电流冲击得到的几十微秒残压持续时间,波形宽度过长可能会造成压敏电阻体的熔化穿孔。其次,避雷器上残压波形与闪电放电过程紧密相关,具有较多的不规则性。此外,避雷器对前端埋地50 m的线路过电压有一定的抑制作用,对闪电首次回击引起的过电压抑制作用较弱,对继后回击引起的过电压抑制作用较强。     

电厂水汽中痕量铁自动快速测定法的研究与应用

水汽系统铁含量快速测定对及时了解热力系统腐蚀状况非常重要,但痕量铁常规测试方法繁琐或不便现场操作。流动注射（FIA）-TPTZ分光光度法测定水汽中痕量总铁的方法（简称FIA-TPTZ分光光度痕量铁测试法）快速简便,为使该法检出下限降低,对影响该法灵敏度的各主要因素,如试剂泵速、载流泵速、显色盘管长度、缓冲液pH值、水样pH值等进行深化研究。改进后的FIA-TPTZ分光光度痕量铁测试法,在0.5~100 μg/L质量浓度范围内,标准曲线线性回归系数大于0.999,相对标准偏差小于1.0%,检出下限由22.7 μg/L降低至0.5 μg/L,分析速度为60样/h,与现行国标法相比相对误差小于10%,适用于电厂水汽样品中痕量铁的自动快速检测,且易于实现在线监测。     

Generalized solid-state marx modulator topology

A generalized circuit topology for bipolar or unipolar high voltage repetitive pulse power applications is proposed. This circuit merges the negative and positive solid state Marx modulator concepts, which take advantage of the intensive use of semiconductor devices to increase the performance of the original dissipative Marx modulators. The flexibility of the proposed modular circuit enables the operation with negative and/or positive pulses, selectable duty cycles, frequencies and relaxation times between the positive and negative pulse. Additionally, the switching topology enables the discharge of the parasitic capacitances after each pulse, allowing the use of capacitive loads, and the clamping of inductive loads, recovering the reset energy back to the main capacitors. Analysis of efficiency and power loss will be addressed, as well as experimental details for different conditions based on laboratory prototype, with 1200 volt Insulated Gate Bipolar Transistors (IGBT), diodes, and 4.5 μF capacitors.