By Topic

Dielectrics and Electrical Insulation, IEEE Transactions on

Issue 5 • Date Oct. 2003

Filter Results

Displaying Results 1 - 16 of 16
  • Dynamical modeling of cellular response to short-duration, high-intensity electric fields

    Page(s): 778 - 787
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1807 KB) |  | HTML iconHTML  

    The interaction of ultra-short duration, high-intensity electric fields with biological cells has recently begun to generate significant interest due to the possibility for non-thermal manipulation of cellular functions. It is clear that a full understanding requires a dynamical model for both electroporation and the electrostatic potential evolution. Here, dynamical aspects related to electroporation are reviewed. The simple model used in the literature is somewhat incorrect and unphysical for a variety of reasons. Our model for the pore formation energy, E(r), includes a dependence on pore population, density, a variable surface tension, and is dynamic in nature. It is shown that membranes can survive a strong electric pulse and recover provided the pore distribution has a relatively large spread. If, however, the population consists predominantly of larger radii pores, then irreversibility can result. Physically, such a distribution could arise if pores at adjacent sites coalesce. Results show that a finite time delay exists for pore formation, and can lead to a transient overshoot of the transmembrane potential Vmem beyond 1.0 V. Pore re-sealing is shown to consist of an initial fast process, a 10-4 s delay, followed by a much slower closing at a time constant of about 10-1 s. This establishes a time-window for effective killing by a second pulse. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Electroporation of biological membranes from multicellular to nano scales

    Page(s): 754 - 768
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (660 KB) |  | HTML iconHTML  

    Electroporation, widely used in research and applications, is briefly reviewed. Both cell and artificial planar bilayer membranes exhibit dramatic changes if the transmembrane voltage is raised to ∼0.2 to 1 V by various electric field pulses. Ionic and molecular transport increases by orders of magnitude, with both reversible and irreversible outcomes. Initially the term breakdown was used, but ion pair generation of classic dielectric breakdown was ruled out. Instead, a stochastic pore hypothesis is consistent with features of electroporation in planar lipid membranes. There is a rapid, nonlinear conduction increase through a rapidly evolving pore population, and this causes the fast membrane discharge previously termed "breakdown". Phenomena due to primary aqueous pores and secondary processes such as heating and chemical exchange have been observed in planar bilayers, cell single systems encountered mainly in vitro, multicellular systems relevant to in vivo applications, and possibly subcellular structures such as mitochondria. For membrane systems that approach nanoscales, modified behavior should occur because of conformational constraints, and deterministic processes may become more important. Understanding electroporation is a subset of a general problem: obtaining a quantitative description of how electromagnetic field-altered changes in chemical species within a biological system govern observed effects. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Pulse generators for pulsed electric field exposure of biological cells and tissues

    Page(s): 820 - 825
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4205 KB) |  | HTML iconHTML  

    This paper describes three pulse generators: a spark gap switched coaxial cable, a spark gap switched Blumlein, and a solid state modulator, developed for applying ultrashort electrical pulses to biological materials in culture. Research has shown that ultrashort pulsed electric fields can induce apoptosis in biological cells, and that pulses as short as 10 ns with field amplitude greater than 1 W/m cause membrane phospholipid rearrangement and activation of the effector enzymes of apoptosis. Pulses of very short duration use only tens of mJ per mL per pulse to induce apoptosis and other intracellular effects without causing thermal trauma. The pulse generators discussed here, each of a different topology, deliver ns pulsed electric fields (nsPEF) to cells in liquid suspension, and can be modified to drive electrodes for external, surgical, or endoscopic treatment of tissues in situ. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Effects of submicrosecond, high intensity pulsed electric fields on living cells - intracellular electromanipulation

    Page(s): 788 - 794
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2372 KB) |  | HTML iconHTML  

    Development of technology to produce nanosecond duration pulsed electric fields has allowed examination of the effects of ultrashort duration, high intensity electric fields on living cells. Theoretically, high intensity (MV/m) electric field applications with durations of less than one microsecond, when shortened toward nanoseconds, should increasingly affect intracellular rather than surface membranes of living cells. Experimentally, square-wave, 60 ns duration, high energy (36-53 kV/cm) pulses applied in trains of 1-10 pulses result in progressive increases in the numbers of permeabilized intracellular granules in a human eosinophil cell model-without large surface membrane effects. Electron micrographic examination of cells treated in this way demonstrates alteration of intracellular granule morphology consistent with permeabilization of granule membrane, i.e., intracellular electromanipulation. Continuous microscopic examination of individual living cells exposed to long or short duration pulsed electric field applications shows that permeabilization of surface membrane (median 5 minutes) with anodic preference (electroporation) and prompt cellular swelling follow a single, long duration (100 microsecond) pulse. In contrast, after a single short duration (60 ns) pulse, onset of surface membrane permeability is delayed (median 17 minutes), the increased permeability shows no anodic preference, and cellular swelling is absent suggesting that these effects are due to intracellular electromanipulation rather than direct effects on the surface membrane. Submicrosecond, intense pulsed electric fields applied to living cells achieve preferential effects on intracellular rather than surface membranes, potentially providing new approaches for selective/generalized cell or tissue ablation, growth stimulation and tissue remodeling. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The bilayer lipid membrane (BLM) under electrical fields

    Page(s): 717 - 727
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1333 KB) |  | HTML iconHTML  

    Transmembrane voltage pulses are known to create transient "pores" in the lipid bilayer. This phenomenon, termed electroporation (EP), has been extensively investigated. EP occurs following electric field pulses of up to 106 V/cm with duration between μs and ms to membranes in close contact and is believed to initiate primarily in the lipid bilayer. This paper begins with a brief summary of the origin of lipid bilayer research. One of practical applications of EP is cell transfection for gene expression. Other applications include encapsulation of drugs in controlled-release and insertion of proteins in living cells. It seems likely that the presence of membrane proteins affect the EP of the lipid bilayer by changing its mechanical properties. Transport of ions such as Na+, K+, Cl- through membrane channels discharge the membrane potential, and at times an external pulse of sufficient amplitude and duration tends to cause dielectric breakdown of the lipid bilayer. Molecular transport through primary pores and pores enlarged by secondary processes provides the basis for transporting molecules into and out of cells. Some recent relevant papers on BLM under electric fields are referenced. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Ultrashort pulsed electric fields induce membrane phospholipid translocation and caspase activation: differential sensitivities of Jurkat T lymphoblasts and rat glioma C6 cells

    Page(s): 795 - 809
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3015 KB) |  | HTML iconHTML  

    Megavolt-per-meter electric pulses with durations shorter than charging time constants associated with external cell membrane dielectric properties can generate significant voltages on the membranes of intracellular structures. Nanosecond-duration, high-field (2-4 MV/m) pulses are not immediately lethal to cells and do not produce the conductive openings in the cytoplasmic membrane associated with long-pulse, low-field electroporation, but can induce profound physiological changes, including apoptosis (programmed cell death). We demonstrate rapid, non-destructive, field-dependent translocation of the plasma membrane inner leaflet phospholipid phosphatidylserine in Jurkat T lymphocytes, and we show that cells which exhibit a similar geometry in suspension, rat glioma C6 cells, are highly resistant to these pulses and respond differently even to much higher doses. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Biodielectrics

    Page(s): 715 - 716
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (163 KB)  

    First Page of the Article
    View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A model for bilayer membrane electroporation based on resultant electromechanical stress

    Page(s): 769 - 777
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (831 KB) |  | HTML iconHTML  

    Reconsideration of the effect of an electrical field applied across a phospholipid bilayer membrane shows that, in addition to a compressive stress normal to the membrane plane, transverse traction stresses are generated in the lateral plane of the membrane. In the fields usually employed for electroporation these transverse stresses are likely to be sufficient to reduce the membrane tension considerably, causing electroporation and rupture. This mode of field-induced change in the membrane provides a natural model for the various forms of electroporation. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Charge motion in technical insulators: facts, fancies and simulations

    Page(s): 826 - 841
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1661 KB) |  | HTML iconHTML  

    Technical insulators, whether gas, liquid or solid, are largely characterized by unipolar ionic flow. The carriers are supplied by injection, or by bulk ionization, and the charge transport is space charge perturbed. The author discusses theoretical modeling of steady state, time dependent, and oscillatory conditions. Continuum equations have provided the basis for early models of corona currents. First he shows the validity of the Deutsch assumption in gases, and then extends the calculation to describe the situation far downwind. These equations also account for many effects in solids such as injection transients and open circuit decay. We discuss their application to electrode blocking capacitance, and to discharge currents in shorted samples. We note that even the simplest bipolar flows require many parameters to describe them. Next, we consider the problem of reconstructing distributions from acoustic pulse and similar measurements that necessarily contain instrumental broadening of the signals. It is then necessary to attempt to explain the observed evolution of the charge density by simulations. We discuss some of the problems associated with the algorithms, and with modeling the microscopic details of the carrier motion when the numerical approximation is necessarily mesoscopic. We mention some applications of the theory to approximation is necessarily mesoscopic. We mention some applications of the theory to measurements made with AFM probes, with the SEM mirror method, and with a Faraday cage. We mention the difficulties in accounting for low frequency oscillations in cables. Finally, we outline the materials problems (identity of carriers and traps), the numerical problems (reconstruction, discrimination between the effects of various carrier types and dipoles, and deduction of parameters), and the logical problems (distinction between simulation and accurate modeling) which need our future attention. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Electrical injury: mechanisms, manifestations, and therapy

    Page(s): 810 - 819
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3157 KB) |  | HTML iconHTML  

    Human contact with strong electrical power sources often results in complex injury patterns which have been difficult to explain and even more difficult for survivors to overcome. Fundamentally, there are two basic modes of tissue injury: direct effects of strong electric fields on proteins and cellular structures and indirect effects related to joule heating. Historically, tissue injury due to direct effects of electric forces have received no consideration with respect to understanding electrical injury. Recently, substantial progress has been made in understanding this aspect. The structural characteristics of nerve and skeletal muscle tissue renders them particularly vulnerable to injury by supraphysiological electric fields. How the injury manifests from the combination of thermal and electric effects depends on several variables including the tissue field strength, duration of exposure, frequency, and current path. This review describes the destructive changes to cellular structure resulting from exposure to commercial electrical power sources and the resulting manifestations at the organ system level. Finally, several important new therapeutic approaches to treat and possibly reverse the molecular alterations of electrical shock are discussed. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Time domain dielectric spectroscopy study of biological systems

    Page(s): 728 - 753
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2994 KB) |  | HTML iconHTML  

    The main principles of time domain dielectric spectroscopy, its application to conductive systems and possible methods of electrode polarization corrections in time domain are introduced. A comprehensive theoretical and experimental study of static and dynamic dielectric properties of different biological systems including globular, and membrane proteins, hydrate water, human erythrocytes, and normal and malignant blood cells of different types is presented in the paper. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Current practice in space charge and polarization profile measurements using thermal techniques

    Page(s): 883 - 902
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3429 KB) |  | HTML iconHTML  

    Thermal techniques for probing space charge and electric field distributions in dielectric materials became available approximately 30 years ago. The techniques have reached maturity and they have been employed not only for the primary purpose of electric field or polarization profiling, but also in a wide range of problems posed by materials research. The present survey provides an overview of the historical development, the experimental implementation of the different techniques, the theoretical foundation, methods for the data analysis and a comparison of thermal and acoustic techniques. The thermal wave technique LIMM is used as an example among the thermal techniques, for a discussion of data analysis techniques and for the spatial resolution that can be achieved with thermal wave techniques. A tour d'horizon is provided through recent applications of thermal techniques, in order to demonstrate their capabilities for dielectric material characterisation. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Review of modern diagnostic techniques for assessing insulation condition in aged transformers

    Page(s): 903 - 917
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1232 KB) |  | HTML iconHTML  

    Cellulosic paper and oil insulation in a transformer degrade at higher operating temperatures. Degradation is accelerated in the presence of oxygen and moisture. Power transformers being expensive items need to be carefully monitored throughout their operation. Well established time-based maintenance and conservative replacement planning is not feasible in a current market driven electricity industry. Condition based maintenance and online monitoring are now gaining importance. Currently there are varieties of chemical and electrical diagnostic techniques available for insulation condition monitoring of power transformers. This paper presents a description of commonly used chemical diagnostics techniques along with their interpretation schemes. A number of new chemical techniques are also described in this paper. A number of electrical diagnostic techniques have gained exceptional importance to the utility professionals. Among these techniques polarisation/depolarisation current measurement, return voltage measurement and frequency domain dielectric spectroscopy at low frequencies are the most widely used. This paper describes analyses and interpretation of these techniques for transformer insulation condition assessment. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Selectivity of damped AC (DAC) and VLF voltages in after-laying tests of extruded MV cable systems

    Page(s): 874 - 882
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1859 KB) |  | HTML iconHTML  

    The purpose of HV after-laying tests on cable systems on-site is to check the quality of installation. The test on extruded MV cable systems is usually a voltage test. However, in order to enhance the quality of after installation many researchers have proposed performance of diagnosis tests such as detection, location and identification of partial discharges (PD) and tan δ measurements. Damped AC voltage (DAC) also called oscillating voltage waves (OVW) is used for PD measurement in after-laying tests of new cables and in diagnostic test of old cables. Continuous AC voltage of very low frequency (VLF) is used for withstand voltage tests as well as for diagnostic tests with PD and tan δ measurements. Review on the DAC and VLF tests to detect defects during on-site after-laying tests of extruded MV cable systems is presented. Selectivity of DAC and VLF voltages in after-laying testing depends on different test parameters. PD process depends on type and frequency of the test voltage and hence, the breakdown voltage is different. The withstand voltage of XLPE cable insulation decreases linearly with increasing frequency in log scale. Experimental studies with artificial XLPE cable model indicate that detection of defects with DAC or VLF voltage can be done at a lower voltage than with DC. DAC voltage is sensitive in detecting defects that cause a breakdown due to void discharge, while VLF is sensitive in detecting defects that cause breakdown directly led by inception of electrical trees. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Application of dielectric response measurement on power cable systems

    Page(s): 862 - 873
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1978 KB) |  | HTML iconHTML  

    Water treeing is one of the factors leading to failure of medium voltage XLPE cables in long-term service. Increased moisture content inside oil-paper insulated cable is not desirable. To identify water tree degraded XLPE cables or oil-paper cables with high moisture content, diagnostic tests based on dielectric response (DR) measurement in time and frequency domain are used. Review of individual DR measurement techniques in the time and frequency domains indicates that measurement of one parameter in either domain may not be sufficient to reveal the status of the cable insulation. But a combination of several DR parameters can improve diagnostic results with respect to water trees present in XLPE cables or increased moisture content in oil-paper cables. DR measurement is a very useful tool that reveals average condition of cable systems. However, it is unlikely that DR measurement will detect few, but long water trees. In addition, DR cannot locate the defect or water tree site within the cable system. Combination of DR and partial discharge (PD) measurements can improve diagnostic results with respect to global and local defects. However, it is doubtful whether PD test can identify the presence of water trees inside a cable in a nondestructive manner. Further research is needed for more detailed conclusions regarding the status of a particular insulation and for predicting the remaining life of the insulation system. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Dielectric resonance spectroscopy: a versatile tool in the quest for better piezoelectric polymers

    Page(s): 842 - 861
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2100 KB) |  | HTML iconHTML  

    Piezoelectric polymers are widely used in sensor and actuator applications. Compared to ceramic materials, they have the advantage of mechanical flexibility and an acoustic impedance similar to those of water or air. Their electrical, electromechanical and mechanical properties can be investigated by analyzing piezoelectric resonances in their dielectric spectrum. Apart from its ability to reveal the high-frequency behavior of piezoelectric polymer films, this technique is appealing from a practical point of view because several important parameters can be measured with a single scan that only requires standard dielectric spectroscopy equipment commonly found in many laboratories. This article outlines the theoretical foundations of piezoelectric resonance, examines the experimental aspects, and reviews recent applications in the field of piezoelectric polymers. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

Aims & Scope

IEEE Transactions on Dielectrics and Electrical Insulation contains topics concerned with dielectric phenomena and measurements with development and characterization of gaseous, vacuum, liquid and solid electrical insulating materials and systems.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Reuben Hackam