Nanosecond Electrical Pulses Research Articles

Simulations of Voltage Transients Across Intracellular Mitochondrial Membranes Due to Nanosecond Electrical Pulses

Simulations to quantify the induction of transmembrane potentials across the mitochondrial membranes have been carried out, taking account of their irregular shape. Our results demonstrate that short (60 ns), high-intensity pulses have the capacity to create membrane potentials, while longer 600-ns pulses are not as effective. Also, the plasma membrane effects are always greater than those at the mitochondria, and that poration at the inner mitochondrial membrane is more difficult than at the outer mitochondrial membrane. In the shorter pulse range, geometric dependence is very pronounced, and so short pulses could be very effective in highly irregular shaped cells, such as neurons. Finally, bioeffects due to the longer 600-ns pulses as seen experimentally, is likely due to other (secondary) effects such as calcium inflow from the porated plasma membrane at the mitochondrial sites.

Influence of powerful nanosecond electrical pulses on an array of double-walled nanotubes

We obtain a system of equations for the surface current density by taking the effect of intershell tunneling in the array of double-walled carbon nanotubes in the presence of a nonstationary electrical pulse into account. We show that if there is no tunneling, then the resonance frequency of surface currents for the symmetric mode increases by a factor of approximately \(\sqrt 2 \) in addition to the twofold increase in their concentration in the direction transverse to the nanotube axis as compared with single-walled nanotubes. We show that bending the carbon nanotube surfaces does not affect the electrical conduction in the millimeter range of generated radiation. We discuss the influence of the nonstationary electrical pulse on the asymmetric mode of longitudinal surface currents.

A microfluidic device with removable packaging for the real time visualisation of intracellular effects of nanosecond electrical pulses on adherent cells

The biological mechanisms induced by the application of nanosecond pulsed electric fields (nsPEFs: high electrical field amplitude during very short duration) on cells remain partly misunderstood. In this context, there is an increasing need for tools that allow the delivering of such pulses with the possibility to monitor their effects in real-time. Thanks to miniaturization and technology capabilities, microtechnologies offer great potential to address this issue. We report here the design and fabrication of a microfluidic device optimized for the delivery of ultra short (10 ns) and intense (up to 280 kV cm(-1)) electrical pulses on adherent cells, and the real time monitoring of their intracellular effects. Ultra short electric field pulses (nsPEFs or nanopulses) affect both the cell membrane and the intracellular organelles of the cells. In particular, intracellular release of calcium from the endoplasmic reticulum was detected in real time using the device, after exposure of adherent cells to these nsPEFs. The high intensity and spatial homogeneity of the electric field could be achieved in the device thanks to the miniaturization and the use of thick (25 μm) electroplated electrodes, disposed on a quartz substrate whose transparency allowed real time monitoring of the nsPEFs effects. The proposed biochip is compatible with cell culture glass slides that can be placed on the chip after separate culture of several days prior to exposure. This device allows the easy exposure of almost any kind of attached cells and the monitoring in real time while exposed to nsPEFs, opening large possibilities for potential use of the developed biochips.

Inhibition of Culex quinquefasciatus (Diptera: Culicidae) viability by nanosecond pulsed electric field radiation

Radiation effects of high-intensity nanosecond pulsed electric fields on the viability of Culex quinquefasciatus (Diptera: Culicidae) were determined. Statistical analyses from results show that the treatment energy density of up to 17.76 J m −3 produced the optimum result in which the number of survived mosquitoes was decreased by 20% ( P < 0.05). Furthermore, the average developmental rate into adult forms of treated fourth-instart lavae was found lower compared to that of the control ( P < 0.05). The present study indicates that electrical pulse characteristics, especially the pulse amplitude, might be responsible for the decrease in mosquito viability. ► The influence of electromagnetic fields on the mosquito viability was examined. ► Post-exposure survivals and the rate of larva-to-adult transformation were determined. ► Fourth-instar larvae were exposed to radiation from nanosecond electrical pulses. ► Electrical pulse amplitude might be responsible for the decrease in viability.

Bioelectric Effects of Intense Ultrashort Pulses

Models for electric field interactions with biological cells predict that pulses with durations shorter than the charging time of the outer membrane can affect intracellular structures. Experimental studies in which human cells were exposed to pulsed electric fields of up to 300 kV/cm amplitude, with durations as short as 10 ns, have confirmed this hypothesis. The observed effects include the breaching of intracellular granule membranes without permanent damage to the cell membrane, abrupt rises in intracellular free calcium levels, enhanced expression of genes, cytochrome c release, and electroporation for gene transfer and drug delivery. At increased electric fields, the application of nanosecond pulses induces apoptosis (programmed cell death) in biological cells, an effect that has been shown to reduce the growth of tumors. Possible applications of the intracellular electroeffects are enhancing gene delivery to the nucleus, controlling cell functions that depend on calcium release (causing cell immobilization), and treating tumors. Such nanosecond electrical pulses have been shown to successfully treat melanoma tumors by using needle arrays as pulse delivery systems. Reducing the pulse duration of intense electric field pulses even further into the subnanosecond range will allow for the use of wideband antennas to deliver the electromagnetic fields into tissue with a spatial resolution in the centimeter range. This review carefully examines the above concepts, provides a theoretical basis, and modeling results based on both continuum approaches and atomistic molecular dynamics methods. Relevant experimental data are also presented, and some of the many potential bioengineering applications discussed.

Nanosecond Electroporation: Another Look

As the medical field moves from treatment of diseases with drugs to treatment with genes, safe and efficient gene delivery systems are needed to make this transition. One such safe, non-viral, and efficient gene delivery system is electroporation (electrogenetherapy). Exciting discoveries using electroporation could make this technique applicable to drug and vaccine delivery in addition to gene delivery. Typically milli and microsecond pulses have been used for electroporation. Recently, the use of nanosecond electrical pulses (10-300 ns) at very high magnitudes (10-300 kV/cm) has been studied for direct DNA transfer to the nucleus in vitro. This article reviews the work done using high-intensity nanosecond pulses, termed as nanosecond electroporation (nsEP), in electroporation gene delivery systems.

The Effect of Intense Subnanosecond Electrical Pulses on Biological Cells

Nanosecond electrical pulses have been successfully used to treat melanoma tumors by using needle arrays as pulse delivery systems. Reducing the pulse duration of intense electric field pulses from nanoseconds into the subnanosecond range will allow us to use wideband antennas to deliver the electromagnetic fields into tissue with a spatial resolution in the centimeter range. To explore the biological effect of intense subnanosecond pulses, we have developed a generator that provides voltage pulses of 160 kV amplitude, 200 ps rise time, and 800 ps pulse width. The pulses are delivered to a cylindrical Teflon chamber with polished flat electrodes at either end. The distance between the electrodes is variable and allows us to generate electric fields of up to 1 MV/cm in cell suspensions. The pulses have been applied to B16 (murine melanoma) cells, and the plasma membrane integrity was studied by means of trypan blue exclusion. For pulse amplitudes of 550 kV/cm, approximately 50% of the cells took up trypan blue right after pulsing, whereas only 20% were taking it up after 1 h. This indicates that the plasma membrane in a majority of the cells affected by the pulses recovers with a time constant of about 1 h. The cells that show trypan blue uptake after this time suffer cell death through apoptosis. Evaluation of the experimental results and molecular dynamics modeling results indicate that with a pulse duration of 800 ps, membrane charging and nanopore formation are the dominant bioelectric effects on B16 cells. This information has been used in a continuum model to estimate the increase in membrane permeability and, consequently, the increase in pore size caused by repetitive pulsing.

Fast reversible thermoelectrical switching in manganite thin films

The authors report on fast reversible switching of epitaxial and polycrystalline La0.83Sr0.17MnO3 films from the ferromagnetic to the paramagnetic state induced by high power nanosecond electrical pulses. It was demonstrated that for the epitaxial films adiabatic and uniform Joule heating is the reason of the switching. For polycrystalline films, electronic processes reduce the film resistance within a subnanosecond. For longer times, adiabatic nonhomogeneous heating plays the main role in the switching dynamics. Possible device applications of this phenomenon are also discussed.

Synchronized and configurable source of electrical pulses for x-ray pump-probe experiments

A method is described for the generation of software tunable patterns of nanosecond electrical pulses. The bipolar, high repetition rate (up to 250 MHz), fast rise time (<30 ps), square pulses are suitable for applications such as the excitation sequence in dynamic pump-probe experiments. Synchronization with the time structure of a synchrotron facility is possible as well as fine control of the relative delay in steps of 10 ps. The pulse generator described here is used to excite magnetic nanostructures with current pulses. Having an excitation system which can match the high repetition rate of a synchrotron allows for utilization of the full x-ray flux and is needed in experiments which require a large photon flux. The fast rise times allow for picosecond time resolution in pump-probe experiments. All pulse pattern parameters are configurable by software.

Time Domain Dielectric Spectroscopy Measurements of HL-60 Cell Suspensions After Microsecond and Nanosecond Electrical Pulses

Pulsed electric fields (PEFs) above a certain voltage threshold cause electroporation for microsecond pulses and intracellular effects for submicrosecond pulses. Models describing these effects often depend on the electrical properties of the cell, which are altered by the PEF. We used time domain dielectric spectroscopy to provide data for these models and to measure effects on cell suspension conductivity. We applied single 50-/spl mu/s and 10-ns pulses to HL-60 cells, with the voltages chosen so the pulses have approximately the same energy. For 1.1-kV/cm, 50-/spl mu/s pulses, the conductivity rose within a minute after the pulse and dropped dramatically approximately 40 min after the pulse. For 78-kV/cm, 10-ns pulses, we observed a brief delay prior to the conductivity rise and noted the same drop in conductivity after approximately 40 min. For both pulse durations, higher voltages frequently led to membrane poration followed by a gradual recovery approximately 30-40 min after the pulse. For 2-kV/cm, 50-/spl mu/s pulses, we observed significantly more scatter in Trypan Blue uptake measurements due to stronger effects on the cell membrane. By using a cell model, we showed that a 50-/spl mu/s pulse caused a much larger rise in membrane conductivity than a 10-ns pulse of the same energy.

Microhollow cathode discharges

By reducing the dimensions of hollow cathodes into the hundred micrometer range, stable, direct current, high (atmospheric) pressure glow discharges in rare gases, rare gas–halide mixtures and in air could be generated. The electron energy distribution in these microdischarges is non-Maxwellian, with a pronounced high-energy tail. The high electron energy together with the high gas density, which favors three-body collisions, is the reason for an efficient excimer generation in these microplasmas. Excimer efficiencies from 1% to 9% have been measured for argon, xenon, argon fluoride, and xenon chloride direct current excimer emitters, with a radiant excimer emittance of up to 2 W/cm2 for xenon. Adding small amounts of oxygen to argon has allowed us to generate vacuum ultraviolet line radiation at 130.5 nm with an efficiency approaching 1%. Pulsing xenon discharges with nanosecond electrical pulses has led to an increase in intensity to 15 W/cm2 and to a simultaneous increase in efficiency to more than 20%. Operating the discharges in an abnormal glow mode has allowed us to generate microdischarge arrays without individual ballast. Applications of these plasma arrays are excimer lamps and plasma reactors.

Depolarization of ferroelectrics by nanosecond electrical pulses

It is shown that the ordinary pulsed action on a ferroelectric cold cathode, which induces electron emission, results in depolarization of the ferroelectric. This phenomenon must be taken into account in the development and use of cold cathodes.

Flux flow during high power nanosecond S-N switching in thin high-T/sub c/ films

The resistance-vs-current and voltage-vs-current dependences of polycrystalline Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O thin film microstrips are studied by nanosecond electrical pulses. It was found that up to a certain current I/sub c1/(I/sub c1/>I/sub c/) thermal processes do not play any role in the origin of the dissipative state. In this case the V-I curve consists of several direct lines which have different slopes to the current axis. The results are discussed in terms of motion of vortices in superconducting film with several types of pinning centers. >

Picosecond superconductor opening switches

Picosecond opening switches using high-T/sub c/ superconductor devices made of TlPbSrCaCuO, TlBaCaCuO, and YBCO films have been successfully demonstrated. The switches were controlled by picosecond laser pulses. A switching risetime of 78 picoseconds and a switching efficiency of 80% have been achieved. The switches were used in an inductive energy storage pulsed power system. Nanosecond electrical pulses with a peak power gain of 22 were obtained. >

Nanosecond inductive energy storage pulsed power system using YBCO superconductor opening switches

An inductive energy storage pulsed power system (IESPPS) using high T/sub c/ superconductor (HTS) opening switches, made of YBCO films, was successfully demonstrated. Nanosecond electrical pulses with a pulse compression ratio of 10 and a power gain of more than 40 were produced.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A pulsed particle beam source for nano- to microsecond luminescence decay studies

A simple device for pulsing accelerated particle beams especially suited for luminescence decay measurements over a large time domain (ns to several μs) is presented: the continuous particle beam is permanently deflected by a transverse magnetic field and periodically realigned by nanosecond electrical field pulses. Particle pulses with a duration of 1 ns and an adjustable repetition rate up to 100 kHz have been obtained. The main advantages of this “external” type pulsing method are (i) the suitability for various kinds of particle beams, (ii) the delivery of a well-time-defined synchronous electrical pulse, and (iii) the independence of the particle energy.

Phonon emission from a metallic film excited by nanosecond electrical pulses

We report the first measurements of heat pulses generated by electrical excitation of a thin metallic film on a nanosecond time scale. Using heater power densities of between 8 and 800 Wmm -2, we found a significant variation of the phonon pulse length reaching the bolometer and also of the ratio of transverse to longitudinal polarisation amplitudes. The phenomena were attributed to diffusive propagation due to highly frequency dependent phonon scattering within a thin damaged layer at the surface of the sapphire substrate.

Rogowski coil for measuring fast, high-level pulsed currents

This paper describes the theory and design of Rogowski-wound coils used to measure nanosecond electrical curent pulses in the megampere range. The coils have risetimes of less than one nanosecond, microsecond decay times and typical sensitivities in the range of 10−3 to 10−4 V A−1. They operate in large radiation fields, under intense electron bombardment and at high rates of current rise.