Low Voltage Pulse Research Articles

Hybrid silicon–organic nanoparticle memory device

We demonstrate a nonvolatile electrically erasable programmable read-only memory device using gold nanoparticles as charge storage elements deposited at room temperature by chemical processing. The nanoparticles are deposited over a thermal silicon dioxide layer that insulates them from the device silicon channel. An organic insulator deposited by the Langmuir–Blodget technique at room temperature separates the aluminum gate electrode from the nanoparticles. The device exhibits significant threshold voltage shifts after application of low-voltage pulses (⩽±6 V) to the gate and has nonvolatile retention time characteristics.

Stress measurement and stress relaxation during magnetron sputter deposition of cubic boron nitride thin films

Dynamic in situ analysis of stress and film thickness provide fast and more physical information on growth and stress evolution in cBN layers than integrating (ex situ) methods. Especially, features of the layered structure of boron nitride films, like the evolution of instantaneous stress and growth rates during deposition can be resolved by in situ methods. This work is concerned with dynamic in-situ stress measurement by means of cantilever bending during magnetron sputter deposition of cBN thin films. Laser deflection in combination with in situ ellipsometry is used to determine the instantaneous stress of the films. The results show in agreement with results that were obtained previously from ion beam assisted deposition (IBAD), that the hBN and cBN layers exhibit different levels of stress under constant deposition conditions. The stress increases from less than −4 GPa to very high values (−10 GPa) after the coalescence of the cBN nuclei. Therefore, it is possible to establish the point of cBN nucleation instantly. A simultaneous medium energy ion bombardment is used for stress relaxation during film deposition. A modified substrate bias voltage, combining negative high and low voltage pulses, is used to enable an ion bombardment of the growing film with energies up to 8 keV. In this way, cBN films with a stress as low as −1.7 GPa could be produced without destroying the sp 3-bonds significantly.

Stability of 180° domain in ferroelectric thin films

Ferroelectric random access memory (FRAM) has attracted much attention in the last two decades due to its ideal properties such as nonvolatility, high speed, and low power consumption. There is a strong incentive to develop high-density FRAMs, in which the switched domains, developed under low voltage or short pulses, are necessarily very small, and are therefore usually unstable and suffer from significant backswitching upon removal of the external voltage. In this investigation, a general form of energy expression for a ferroelectric material containing 180° domains is derived, from which evolution equations of the domain are established. By choosing the change in internal energy as the Liapunov function, a general formulation is developed to determine the stability conditions of the switched domain. This is applied to the case of an ellipsoidal 180° domain and yields a criterion for the stability of switched domains. We note that our approach is generally applicable to many other fields, including phase transformation, nucleation, expansion of dislocation loops in thin films, etc.

Bistable transflective cholesteric light shutters

We have presented a bistable transflective cholesteric light shutter. The shutter contains dual-frequency cholesteric liquid crystals that incorporate a photocurable monomer. The electro-optical properties and optical microscope images of the shutter were examined. Good correlations between the cholesteric textures and optical properties of the shutters were obtained. The shutter was switched into a wide-band homogeneous transmission mode by a low frequency voltage pulse, and into a selective reflection mode using a high-frequency voltage pulse. The concentration of the monomer apparently affected the electro-optical characteristics of the shutter.

Gene electro-transfer improves transduction by modifying the fate of intramuscular DNA.

Intramuscular gene delivery through injection of plasmid DNA has long been considered a promising approach for safe and simple in vivo gene expression for vaccination and gene therapy purposes. Recently, intramuscular gene delivery has been improved by applying low-voltage electric pulses after plasmid injection, a procedure that has been variably called gene electro-transfer, in vivo electroporation or electrical stimulation. Different types of electrical treatments have been used with excellent results both in terms of transgene expression levels and immunization outcome. This approach, therefore, holds promise for safe gene delivery to animals and humans designed for non-viral gene therapy and DNA-based vaccination. The molecular mechanisms underlying this increment in transduction efficiency are, however, still unclear. Plasmid DNA status and kinetics following gene electro-transfer was analyzed by different methods (Southern analysis, Q-PCR and transformation into competent bacteria). A large amount of plasmid DNA is degraded in the first 4 h post-injection, with or without electroporation; later, the amount of intramuscular plasmid DNA is higher in electroporated samples. On electroporation, plasmid is partially protected from degradation, presumably by its early compartmentalization into the nuclei of muscle cells. By investigating the intracellular outcome and persistence of plasmid DNA following simple injection or gene electro-transfer we provide useful information on the mechanisms of plasmid entry and expression and underline some of the steps that could be taken to further improve this methodology.

Mechanisms of in vivo DNA electrotransfer: respective contributions of cell electropermeabilization and DNA electrophoresis.

Efficient cell electrotransfection can be achieved using combinations of high-voltage (HV; 800 V/cm, 100 micros) and low-voltage (LV; 80 V/cm, 100 ms) pulses. We have developed equipment allowing the generation of various HV and LV combinations with precise control of the lag between the HV and LV pulses. We injected luciferase-encoding DNA in skeletal muscle, before or after pulse delivery, and measured luciferase expression after various pulse combinations. In parallel, we determined permeabilization levels using uptake of (51)Cr-labeled EDTA. High voltage alone resulted in a high level of muscle permeabilization for 300 seconds, but very low DNA transfer. Combinations of one HV pulse followed by one or four LV pulses did not prolong the high permeabilization level, but resulted in a large increase in DNA transfer for lags up to 100 seconds in the case of one HV + one LV and up to 3000 seconds in the case of one HV + four LV. DNA expression also reached similar levels when we injected the DNA between the HV and LV pulses. We conclude that the role of the HV pulse is limited to muscle cell permeabilization and that the LV pulses have a direct effect on DNA. In vivo DNA electrotransfer is thus a multistep process that includes DNA distribution, muscle permeabilization, and DNA electrophoresis.

How to test mode switching in pacemakers implanted in patients: the MOST study.

Optimal management of atrial arrhythmias with dual chamber pacemakers requires proper performance of automatic mode switching (AMS). The aim of this study was to develop a reliable technique to test the AMS function by using an external electronic device capable of mimicking the occurrence of supraventricular arrhythmias (Supraventricular Arrhythmia Simulator [SAS]). The SAS delivers low voltage pulse trains (200 mV, 20 ms) through two skin electrodes. Each pulse train lasts 15 seconds and starts synchronously with a pacing pulse of the implanted pacemaker to avoid interference from the operator. The pulse train rate is set at 350, 250, and 160 beats/min to simulate AF, atrial flutter, and atrial tachycardia (AT), respectively. Thirty-five patients implanted with Vitatron pacemakers, whose AMS system has been previously validated, were enrolled. Atrial and ventricular sensing were programmed in unipolar mode at 0.5 mV and in bipolar mode at > 2 mV, respectively. All pulses from the SAS were detected by the atrial channel at an amplitude ranging from 1 to 3 mV. The test proved to be safe and reliable at rest and during exercise. AMS occurred immediately at onset or at offset of atrial arrhythmias, and no adverse interference on pacemaker function was seen from the SAS. In conclusion, the described technique and the SAS are safe and reliable for patient and pacemaker function and can be proposed as a useful method to verify proper performance of AMS function irrespective of the type of implanted devices.

A High-Voltage Pulse Generator with Inductive Energy Storage and Thyratron

A high-voltage pulse generator with an inductive energy storage is described. Its operation is based on the current interruption by a thyratron. It was shown that a TГИ2-500/20 thyratron is capable of reliably interrupting the current with an amplitude of 800–850 A in an inductive energy storage, forming from a low-voltage (0.5–2 kV) power source voltage pulses with an amplitude of up to 90 kV and leading edge duration of 200–250 ns at the load.

Electrochemical Properties of Poly-3-methylthiophene Films: A Cyclic Voltammetry and Chronoamperometry Study

The charge transfer in poly-3-methylthiophene films in 0.05–0.5 M LiClO4 solutions in acetonitrile is studied by cyclic voltammetry and chronoamperometry. An analysis of data on the current relaxation following a film perturbation by a low-voltage pulse reveals two constituents of the current relaxation, both exponentially dependent on time. Dependence of parameters of the empirical equation derived for the current relaxation on experimental variables is studied.

Methane conversion using a high‐frequency pulsed plasma: Discharge features

AbstractThe pulsed plasma of methane was experimentally characterized using single and sequential pulse modes. At a single pulse mode, only pulsed corona and streamer discharges occurred at a low pulse voltage. A pulsed spark discharge developed afrer the pulsed streamer discharge at a high pulse voltage. An image analysis indicated that the weak luminescence could be found in the latter period of the pulsed corona discharge. The pulsed streamer and spark discharges bridged the discharge gap and emitted a relatively strong light. At a sequential pulse mode, the streamer or spark discharge developed easily and evenly at a low pulse voltage, as the pulse frequency increased in comparison with that at the single pulse mode. The high‐frequency pulsed plasma was more practical than other plasmas due to its relatively high energy efficiency at room temperature and atmospheric pressure.

Immunomodulation by Electrically Enhanced Delivery of Plasmid DNA Encoding IL-12 to Murine Skeletal Muscle

Recent reports have shown the successful delivery of plasmid DNA to skeletal muscle by in vivo electroporation. However, most of these reports have used what has been characterized as low-voltage, millisecond pulses. One of the purposes of this study was to examine a wide range of parameters to establish a better understanding of the effects of field strength and pulse length. Two electroporation conditions, one utilizing low-voltage millisecond pulses and the other high-voltage microsecond pulses, were compared for their ability to deliver a molecule that can be measured systemically, IL-12. Not only was this molecule efficiently delivered, but one of the molecules it induces (IFN-γ) was also measured systemically, with expression peaking at greater than 200 pg/ml serum levels on day 7 and still as high as 40 pg/ml on day 21 when using electrical parameters of 100 V/cm, 20-ms pulses. Of the two types of parameters tested, low-voltage, millisecond pulses resulted in higher, prolonged expression of plasmid DNA than high-voltage, microsecond pulses. In summary, this report provides evidence that in vivo electroporation is an efficient method for the delivery of plasmid DNA, and its use in immunotherapy protocols should be furthered examined.

Enhancing B- and T-cell immune response to a hepatitis C virus E2 DNA vaccine by intramuscular electrical gene transfer.

We describe an improved genetic immunization strategy for eliciting a full spectrum of anti-hepatitis C virus (HCV) envelope 2 (E2) glycoprotein responses in mammals through electrical gene transfer (EGT) of plasmid DNA into muscle fibers. Intramuscular injection of a plasmid encoding a cross-reactive hypervariable region 1 (HVR1) peptide mimic fused at the N terminus of the E2 ectodomain, followed by electrical stimulation treatment in the form of high-frequency, low-voltage electric pulses, induced more than 10-fold-higher expression levels in the transfected mouse tissue. As a result of this substantial increment of in vivo antigen production, the humoral response induced in mice, rats, and rabbits ranged from 10- to 30-fold higher than that induced by conventional naked DNA immunization. Consequently, immune sera from EGT-treated mice displayed a broader cross-reactivity against HVR1 variants from natural isolates than sera from injected animals that were not subjected to electrical stimulation. Cellular response against E2 epitopes specific for helper and cytotoxic T cells was significantly improved by EGT. The EGT-mediated enhancement of humoral and cellular immunity is antigen independent, since comparable increases in antibody response against ciliary neurotrophic factor or in specific anti-human immunodeficiency virus type 1 gag CD8(+) T cells were obtained in rats and mice. Thus, the method described potentially provides a safe, low-cost treatment that may be scaled up to humans and may hold the key for future development of prophylactic or therapeutic vaccines against HCV and other infectious diseases.

Termination of reentry by infra- and supra-threshold pulses

Two different experimental methods to terminate a reentrant activity were studied within the framework of nonlinear electronic circuits, which mimic the discrete nature of cardiac tissue at a microscopic scale. It was shown that trains of low voltage (with infra- and supra-threshold stimulating amplitude) and low frequency (period larger than that of reentry) pulses can be used efficiently to terminate a pinned reentry when applied near to the reentry.

Low-jitter generators of high-voltage pulses with a subnanosecond rise time and an increased actuation accuracy

Two low-jitter high-voltage pulse generators with a subnanosecond rise time are described. The generators are connected in the Marx circuit and have the following characteristics: the amplitude of the output pulse developed across a 50-Ω load is 50 and 70 kV, respectively; duration of the pulse edge is no more than 0.3 ns; operating frequency is up to 10 pulses/s. The instability of the delay of the pulse edge relative to the edge of the low-voltage triggering pulse does not exceed 10 and 30 ns for the first and second generator, respectively. The generators are designed for exact synchronization of the facility used in experiments on the subnanosecond pulsed breakdown.

Importance of association between permeabilization and electrophoretic forces for intramuscular DNA electrotransfer

Gene transfer using electrical pulses is a rapidly expanding field. Many studies have been performed in vitro to elucidate the mechanism of DNA electrotransfer. In vivo, the use of efficient procedures for DNA electrotransfer in tissues is recent, and the question of the implied mechanisms is largely open. We have evaluated the effects of various combinations of square wave electric pulses of variable field strength and duration, on cell permeabilization and on DNA transfection in the skeletal muscle in vivo. One high voltage pulse of 800 V/cm, 0.1 ms duration (short high pulse) or a series of four low voltage pulses of 80 V/cm, 83 ms duration (long low pulses) slightly amplified transfection efficacy, while no significant permeabilization was detected using the 51Cr-EDTA uptake test. By contrast, the combination of one short high pulse followed by four long low pulses led to optimal gene transfer efficiency, while inducing muscle fibers permeabilization. These results are consistent with additive effects of electropermeabilization and DNA electrophoresis on electrotransfer efficiency. Finally, the described new combination, as compared to the previously reported use of repeated identical pulses of intermediate voltage, leads to similar gene transfer efficiency, while causing less permeabilization and thus being likely less deleterious. Thus, combination of pulses of various strengths and durations is a new procedure for skeletal muscle gene transfer that may represents a clear improvement in view of further clinical development.

Efficient and regulated erythropoietin production by naked DNA injection and muscle electroporation.

We show that an electric treatment in the form of high-frequency, low-voltage electric pulses can increase more than 100-fold the production and secretion of a recombinant protein from mouse skeletal muscle. Therapeutical erythopoietin (EPO) levels were achieved in mice with a single injection of as little as 1 microgram of plasmid DNA, and the increase in hematocrit after EPO production was stable and long-lasting. Pharmacological regulation through a tetracycline-inducible promoter allowed regulation of serum EPO and hematocrit levels. Tissue damage after stimulation was transient. The method described thus provides a potentially safe and low-cost treatment for serum protein deficiencies.

Improvement of the Switching Parameters of Addressable Bistable Type PDLC Displays with Dual Frequency Driven Liquid Crystal

AbstractImprovement of switching parameters is reported of bistable polymer dispersed liquid crystal (PDLC) with dual frequency driven liquid crystal in an acrylate polymer matrix. Low frequency voltage pulses result in the transparent state while high frequency pulses return to the opaque state; which is a time useful for practical applications, e.g. still pictures. Both states are maintained even when removing the applied voltage. Repeatedly applying of high frequency voltage pulses recover the device to the initial scattering state with high reproducibility. Polymer content and surface treatment of substrates drastically affect the PDLC droplet formation and also bistability as a result.

A New, Low-Power Consumption, One-Dimensional Sonic Anemometer-thermometer.

A low power (0.1W) and light weight (probe weight 270g and circuit weight 80g) one-dimensional sonic anemometer-thermometer was developed. The measuring span of the anemometer is 10cm, sound frequency is 40kHz and alternation frequency of the sound direction is 78Hz. The low power consumption was attained by using ceramic transducers, which can be driven by low voltage pulses (5V peak-to-peak) and by adapting CMOS logic to the circuit.A field test was carried out in a coniferous forest with a commercial sonic anemometer and a fine thermocouple thermometer. Comparison of the output signal and spectra from each sonic anemometer indicated good agreement.The characteristics of the sonic anemometer-thermometer are low power consumption and light weight. These features are useful for measurements from a small tethered balloon or at places where the electrical power is limited.

Recent advances in electrochromics for smart windows applications

Electrochromic smart windows are able to vary their throughput of radiant energy by low-voltage electrical pulses. This function is caused by reversible shuttling of electrons and charge balancing ions between an electrochromic thin film and a transparent counter electrode. The ion transport takes place via a solid electrolyte. Charge transport is evoked by a voltage applied between transparent electrical conductors surrounding the electrochromic film/electrolyte/counter electrode stack. This review summarizes recent progress concerning: (i) calculated optical properties of crystalline WO 3, (ii) electrochromic properties of heavily disordered W oxide and oxyfluoride films produced by reactive magnetron bias sputtering, (iii) novel transparent reactively sputter-deposited Zr–Ce oxide counter electrodes and (iv) a new proton-conducting antimonic-acid-based polymer electrolyte. Special in depth presentations are given on elastic light scattering from W-oxide-based films and of electronic band structure effects affecting opto–chronopotentiometry data in Zr–Ce oxide. The review also contains some new device data for an electrochromic smart window capable of very high optical transmittance.

Targeted gene transfer to corneal endothelium in vivo by electric pulse.

A novel method of in vivo targeted gene transfer to intentionally selected areas of the corneal endothelium was developed. Plasmid DNA with the lacZ gene coding for beta-galactosidase was injected into the anterior chamber of adult Wistar rats, and eight pulses of electricity at intensities ranging from 5 to 40 V/cm were delivered for 50 ms to the cornea with a specially designed electric probe in order to determine the effect of gene transfer on the corneal endothelial cells. Gene expression was visualized by enzymatic color reaction using X-gal in enucleated eyes on days 1, 3, 7, 14 and 21 after gene transfer. The treated eyes were then photographed and the X-gal-positive areas were evaluated by an image analyzer. The ratios of the areas (X-gal-positive area/area of entire corneal endothelium x 100%) were then calculated to determine gene transfection efficiency. The expression of beta-galactosidase was clearly detected in the cytoplasm of the corneal endothelial cells as early as day 1 and lasted until day 21. The most intense gene expression was observed on days 1 and 3 (5.21% on day 1 and 6.45% on day 3). The expression of beta-galactosidase on day 3 was most evident following delivery of 20 V electric pulses (0.09% at 5 V, 0.03% at 10 V, 6.45% at 20 V). beta-Galactosidase expression was limited to the corneal endothelial cells in highly selected areas and no beta-galactosidase expression was detected in any other intra- or axtraocular tissues. In addition, no cell damage was apparent in the cornea and no inflammation was detected in any other intraocular tissues. Thus, low-voltage electric pulses successfully transferred the gene of interest to highly selective areas of the corneal endothelium without inducing any pathological changes. This targeted gene transfer method appears to have great potential for use in gene therapy for ocular diseases.