Electric Pulse Amplitude Research Articles

Fiber-Optically Triggered Four Parallel GaAs Photoconductive Semiconductor Switches

Four parallel GaAs photoconductive semiconductor switches (PCSSs) were triggered simultaneously by four 1064 nm laser beams. The transient characteristics of four linear electrical pulses were investigated. When the energy of four laser beams were 16.4 mJ, 15.6 mJ, 15.3 mJ, and 13.7 mJ, respectively, four stable electrical pulses of about 25 ns width and 10 ns rise time were obtained at the same bias voltage of 8 kV. The maximum switching voltage amplitude was 3.8 kV. With the triggering pulse energy and bias voltage kept constant, the three GaAs PCSSs were triggered at 10 Hz laser pulse. The method of synchronization calculation was given, and the synchronization of four parallel GaAs PCSSs was calculated to be 79 ps. The influence of bias voltage and laser energy on the voltage amplitude of electrical pulse was analyzed. Furthermore, relationship between the synchronization and the jitter time was also discussed.

Repetitive transcranial magnetic stimulator with controllable pulse parameters

The characteristics of transcranial magnetic stimulation (TMS) pulses influence the physiological effect of TMS. However, available TMS devices allow very limited adjustment of the pulse parameters. We describe a novel TMS device that uses a circuit topology incorporating two energy storage capacitors and two insulated-gate bipolar transistor (IGBT) modules to generate near-rectangular electric field pulses with adjustable number, polarity, duration, and amplitude of the pulse phases. This controllable pulse parameter TMS (cTMS) device can induce electric field pulses with phase widths of 10–310 µs and positive/negative phase amplitude ratio of 1–56. Compared to conventional monophasic and biphasic TMS, cTMS reduces energy dissipation up to 82% and 57% and decreases coil heating up to 33% and 41%, respectively. We demonstrate repetitive TMS trains of 3000 pulses at frequencies up to 50 Hz with electric field pulse amplitude and width variability less than the measurement resolution (1.7% and 1%, respectively). Offering flexible pulse parameter adjustment and reduced power consumption and coil heating, cTMS enhances existing TMS paradigms, enables novel research applications and could lead to clinical applications with potentially enhanced potency.

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.

Decoding of retinal ganglion cell spike trains evoked by temporally patterned electrical stimulation

For successful restoration of vision by retinal prostheses, the neural activity of retinal ganglion cells (RGCs) evoked by electrical stimulation should represent the information of spatiotemporal patterns of visual input. We propose a method to evaluate the effectiveness of stimulation pulse trains so that the crucial temporal information of a visual input is accurately represented in the RGC responses as the amplitudes of pulse trains are modulated according to the light intensity. This was enabled by spike train decoding. The effectiveness of the stimulation was evaluated by the accuracy of decoding pulse amplitude from the RGC spike train, i.e., by the similarity between the original and the decoded pulse amplitude time series. When the parameters of stimulation were suitably determined, the RGC responses were reliably modulated by varying the amplitude of electrical pulses. Accordingly, the temporal pattern of pulse amplitudes could be successfully decoded from multiunit RGC spike trains. The range of pulse amplitude and the pulse rate were critical for accurate representation of input information in RGC responses. These results suggest that pulse amplitude modulation is a feasible means to encode temporal visual information by RGC spike trains and thus to implement stimulus encoding strategies for retinal prostheses.

Nonlinear electromechanical response of the ferroelectret ultrasonic transducers

The ultrasonic transmission between two air-coupled polypropylene (PP) ferroelectret (FE) transducers in dependence on the amplitude of the high-voltage exciting pulse revealed a strongly nonlinear electromechanical response of the FE transmitter. This phenomenon is described by a linear increase of the inverse electromechanical transducer constant \(t_{33}^{(1)}\) of the PP FE film with an increase of the exciting electrical pulse amplitude. Enlargement of \(t_{33}^{(1)}\) by a factor of 4 was achieved by application of 3500 V exciting pulses. The electrostriction contribution to \(t_{33}^{(1)}\) can be attributed to the electrostatic force between electrodes and the Maxwell stress effect. The nonlinear electromechanical properties of the PP FE result in a strong increase of its air-coupled ultrasonic (ACUS) figure of merit (FOM) under the high-voltage excitation, which exceeds results of the PP FE technological optimization. The FOM increase can be related to the increase of PP FE coupling factor and/or to the decrease of its acoustic impedance. A significant enhancement of the ACUS system transmission (12 dB) and signal-to-noise ratio (32 dB) was demonstrated by the increase of excitation voltage up to 3500 V. The nonlinear electromechanical properties of the PP FEs seem to be very important for their future applications.

Peak equalization of rational-harmonic-mode-locking fiberized semiconductor laser pulse via optical injection induced gain modulation

Optical injection induced gain modulation of a semiconductor optical amplifier (SOA) is demonstrated to equalize the peak intensity of pulses generating from the rational-harmonic-mode-locking (RHML) SOA based fiberized semiconductor laser. This is achieved by adjusting the temporal shape of the injected optical signal generated from a Mach-Zehnder intensity modulator, in which the DC biased level exceeding Vpi and the electrical pulse amplitude of 1.5Vpi are concurrently employed. Numerical simulation on the injected optical signal profile and the SOA gain during the inverse-optical-pulse injection induced gain modulation process are also demonstrated. After a peculiar inverse-optical-pulse injection, each pulse in the 5th-order RHML pulse-train experiences different gain from temporally varied SOA gain profile, leading the pulse peak to equalize one another with a minimum standard deviation of 2.5% on the peak intensity variation. The optimized 5th-order RHML pulse exhibits a signal-to-noise suppression ratio of 20 dB and a reduced variation on temporal spacing from 11 to 4 ps. The clock amplitude jitter is compress from 35.3% to 7.3%, which is less than the limitation up to 10% for 5th order RHML generation.

Formation and droplet size of EHD drippings induced by superimposing an electric pulse to background voltage

The effect of electric voltages on droplet size was investigated. Results show that both background voltage and amplitude of electric pulse could affect the process of droplet formation and droplet size while the width of pulsed voltage had a slight effect on droplet size. Pulsed voltages introduced a tangential electric stress that led to relatively greater droplet formation while greater background voltage was associated with smaller droplets. Due to different components of the normal and tangential electric stress three dripping modes were created. Based on above observations, a simplified discussion is presented on the relationships between droplet size and above parameters.

Optimization of bulk cell electrofusion in vitro for production of human–mouse heterohybridoma cells

Cell electrofusion is a phenomenon that occurs, when cells are in close contact and exposed to short high-voltage electric pulses. The consequence of exposure to pulses is transient and nonselective permeabilization of cell membranes. Cell electrofusion and permeabilization depend on the values of electric field parameters including amplitude, duration and number of electric pulses and direction of the electric field. In our study, we first investigated the influence of the direction of the electric field on cell fusion in two cell lines. In both cell lines, applications of pulses in two directions perpendicular to each other were the most successful. Cell electrofusion was finally used for production of human–mouse heterohybridoma cells with modified Koehler and Milstein hybridoma technology, which was not done previously. The results, obtained by cell electrofusion, are comparable to usually used polyethylene glycol mediated fusion on the same type of cells.

The temperature effect during pulse application on cell membrane fluidity and permeabilization

Cell membrane permeabilization is caused by the application of high intensity electric pulses of short duration. The extent of cell membrane permeabilization depends on electric pulse parameters, characteristics of the electropermeabilization media and properties of cells exposed to electric pulses. In the present study, the temperature effect during pulse application on cell membrane fluidity and permeabilization was determined in two different cell lines: V-79 and B16F-1.While cell membrane fluidity was determined by electron paramagnetic resonance (EPR) method, the cell membrane electropermeabilization was determined by uptake of bleomycin and clonogenic assay. A train of eight rectangular pulses with the amplitude of 500 V/cm, 700 V/cm and 900 V/cm in the duration of 100 μs and with repetition frequency 1 Hz was applied. Immediately after the pulse application, 50 μl droplet of cell suspension was maintained at room temperature in order to allow cell membrane resealing. The cells were then plated for clonogenic assay. The main finding of this study is that the chilling of cell suspension from physiological temperature (of 37 °C) to 4 °C has significant effect on cell membrane electropermeabilization, leading to lower percent of cell membrane permeabilization. The differences are most pronounced when cells are exposed to electric pulse amplitude of 900 V/cm. At the same time with the decreasing of temperature, the cell membranes become less fluid, with higher order parameters in all three types of domains and higher proportion of domain with highest order parameter. Our results indicate that cell membrane fluidity and domain structure influence the electropermeabilization of cells, however it seems that some other factors may have contributing role.

Optimization of electrode position and electric pulse amplitude in electrochemotherapy

Background. In addition to the chemotherapeutic drug being present within the tumor during electric pulse delivery, successful electrochemotherapy requires the entire tumor volume to be subjected to a sufficiently high electric field, while the electric field in the surrounding healthy tissue is as low as possible to prevent damage. Both can be achieved with appropriate positioning of the electrodes and appropriate amplitude of electric pulses. Methods. We used 3D finite element numerical models and a genetic optimization algorithm to determine the optimum electrode configuration and optimum amplitude of electric pulses for treatment of three subcutaneous tumor models of different shapes and sizes and a realistic brain tumor model acquired from medical images. Results. In all four tumor cases, parallel needle electrode arrays were a better choice than hexagonal needle electrode arrays, since their utilization required less electric current and caused less healthy tissue damage. In addition, regardless of tumor geometry or needle electrode configuration, the optimum depth of electrode insertion was in all cases deeper than the deepest part of the tumor. Conclusions. Our optimization algorithm was able to determine the best electrode configuration in all four presented models and with further improvement it could be a useful tool in clinical electrochemotherapy treatment planning.

MOSFET-Based Pulse Power Supply for Bacterial Transformation

In this paper, a MOSFET-based pulsed power supply capable of supplying square pulses of up to 3000 V and widths from nanoseconds to milliseconds is presented and used for an investigation into electroporation-mediated delivery of a plasmid DNA molecule into the pathogenic bacterium <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Escherichia</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">coli</i> O157:H7. It was concluded that increasing the electric field strength and pulse amplitude resulted in an increase in the number of transformants. However, increasing the number of pulses had the effect of reducing the number of transformants. In all the experiments, the number of cells that were inactivated by the exposure to the pulsed electric field were also measured.

Electroporator with automatic change of electric field direction improves gene electrotransfer in-vitro

BackgroundGene electrotransfer is a non-viral method used to transfer genes into living cells by means of high-voltage electric pulses. An exposure of a cell to an adequate amplitude and duration of electric pulses leads to a temporary increase of cell membrane permeability. This phenomenon, termed electroporation or electropermeabilization, allows various otherwise non-permeant molecules, including DNA, to cross the membrane and enter the cell. The aim of our research was to develop and test a new system and protocol that would improve gene electrotransfer by automatic change of electric field direction between electrical pulses.MethodsFor this aim we used electroporator (EP-GMS 7.1) and developed new electrodes. We used finite-elements method to calculate and evaluate the electric field homogeneity between these new electrodes. Quick practical test was performed on confluent cell culture, to confirm and demonstrate electric field distribution. Then we experimentally evaluated the effectiveness of the new system and protocols on CHO cells. Gene transfection and cell survival were evaluated for different electric field protocols.ResultsThe results of in-vitro gene electrotransfer experiments show that the fraction of transfected cells increases by changing the electric field direction between electrical pulses. The fluorescence intensity of transfected cells and cell survival does not depend on electric field protocol. Moreover, a new effect a shading effect was observed during our research. Namely, shading effect is observed during gene electrotransfer when cells are in clusters, where only cells facing negative electro-potential in clusters become transfected and other ones which are hidden behind these cells do not become transfected.ConclusionOn the basis of our results we can conclude that the new system can be used in in-vitro gene electrotransfer to improve cell transfection by changing electric field direction between electrical pulses, without affecting cell survival.

Charge injection into discrete states of individual electroluminescent Au nanoclusters

Nanoscale break junctions created through electromigration naturally produce arrays of individual gold nanoclusters spanning the electrodes. These spatially resolvable individual nanoclusters electroluminesce in response to pulsed external electric fields, producing a noncontroversial, corroborative readout of nanoscale charge injection. Modulation of the electrical pulse sequence timing, polarity, and amplitude reveals electroluminescence from discrete electronic energy levels and provides a measurement of the relative coupling between an emitting cluster and its individual electrodes.

Micro pulsed radio-frequency electroporation chips

Electroporation (EP) is one of the most important physical methods in biotechnology, which employs electrical pulses to transiently permeabilize cell membranes. In this study, a new micro pulsed radio-frequency electroporation cell (μPREP) chip was fabricated using a lift-off technique and SU-8 photolithography. The biological tests were carried out using three different plant protoplasts (cabbage, spinach and oil rape) on the micro EP chip and a pulsed RF electric field was applied to the microchip. The variations of fluorescent intensity and cell viability as functions of the electric pulse amplitude and duration time during the electroporation process were studied in detail at the single-cell level. Using such chip design and test method, one can easily optimize the efficiency and cell viability. Also, a large amount of statistical data can be quickly obtained. Finally, results of this parametric study were presented in the “phase diagram”, from which the critical electric field for inducing single-cell electroporation under different conditions can be clearly determined.

Broadband characterization of a microwave probe for picosecond electrical pulse measurements

The time-domain characterization of high-frequency devices with coaxial connectors requires the transfer of picosecond electrical pulses between coplanar and coaxial lines. Microwave probes are often used for this purpose. In this paper, the propagation of ultrashort electrical pulses over a microwave probe attached to a coplanar waveguide is experimentally studied by time-domain electro-optic sampling. From the experimental data, the attenuation and dispersion constants of the probe are determined up to 400 GHz. Moreover, the complex reflection and transmission coefficients of the junction between the microwave probe and the coplanar waveguide are extracted. Simple approximations are given for these quantities. These data can be used to predict the amplitude and shape of ultrashort electrical pulses after propagation over the microwave probe for arbitrary input pulses in the considered frequency range.

Role of pulse shape in cell membrane electropermeabilization

The role of the amplitude, number, and duration of unipolar rectangular electric pulses in cell membrane electropermeabilization in vitro has been the subject of several studies. With respect to unipolar rectangular pulses, an improved efficiency has been reported for several modifications of the pulse shape: separate bipolar pulses, continuous bipolar waveforms, and sine-modulated pulses. In this paper, we present the results of a systematic study of the role of pulse shape in permeabilization, cell death, and molecular uptake. We have first compared the efficiency of 1-ms unipolar pulses with rise- and falltimes ranging from 2 to 100 μs, observing no statistically significant difference. We then compared the efficiency of triangular, sine, and rectangular bipolar pulses, and finally the efficiency of sine-modulated unipolar pulses with different percentages of modulation. We show that the results of these experiments can be explained on the basis of the time during which the pulse amplitude exceeds a certain critical value.

Response speed and optical investigation of inGaN/gaN multiple quantum well light‐emitting diodes (LED)

AbstractTransmission experiments for a local area network (LAN) using blue‐light‐emitting diodes (LEDs) with InGaN/GaN multiple quantum well (MQW) and plastic optical fibers (POFs) have been conducted. Audio analog signals have been transmitted up to 1800 kHz, which corresponds to an optical 1.5 dB bandwidth of LED response. The response speed of these diodes has been investigated by varying the operating conditions: dc bias, pulse amplitude, and pulse shape. The LED rise time is reduced from 0.26 μs to 0.19 μs by changing the electrical pulse amplitude from 0.5 V to 1.2 V, whereas the fall time (0.20 μs) does not change. On the other hand, the fall time is reduced from 0.20 μs to 0.14 μs by adding negative pulses after the applied positive pulses. It is shown that the direct‐modulation speed of these diodes is limited by the time constant associated with device capacitance. Electroluminescence and photocurrent spectra of the LEDs were also investigated; blueshifts were observed for both peaks in the spectra. © 2001 Scripta Technica, Electr Eng Jpn, 137(3): 47–51, 2001

Detection of positive and negative ions in a wire ionization counter filled with atmospheric air

The physical processes occurring during the detection of individual ions in a wire counter filled with atmospheric air are studied, and the amplitude distribution of electric pulses is measured. It is shown that a positive ion is detected due to electron emission from the surface of a negatively charged wire, whereas a negative ion is detected due to electron detachment near a positively charged wire. The secondary processes accompanying the neutralization of positive ions at a negatively charged external electrode and negatively charged wire are considered. It is established that, in contrast to standard proportional counters, these secondary processes result in an increase in the number of electric pulses rather than in an increase in the electric pulse amplitude. The wire counter allows the detection of both ions produced inside the detector and ions injected into the detector from the ambient air. Possible applications of air-filled wire detectors are described.

Measuring drop size distribution and kinetic energy of rainfall using a force transducer

The relatively high cost of commercially available raindrop spectrometers and disdrometers has inhibited detailed and intensive research on drop size distribution, kinetic energy and momentum of rainfall which are important for understanding and modelling soil erosion caused by raindrop detachment. In this study, an approach to find the drop size distribution, momentum and kinetic energy of rainfall using a relatively inexpensive device that uses a piezoelectric force transducer for sensing raindrop impact response is introduced. The instrument continuously and automatically records, on a time-scale, the amplitude of electrical pulses produced by the impact of raindrops on the surface of the transducer. The size distribution of the raindrops and their respective kinetic energy are calculated by analysing the number and amplitude of pulses recorded, and from the measured volume of total rainfall using a calibration curve. Simultaneous measurements of the instrument, a rain gauge and a dye-stain method were used to assess the performance of the instrument. Test results from natural and simulated rainfalls are presented. Copyright © 2000 John Wiley & Sons, Ltd.

InGaN/GaN MQW LEDの応答速度と光学的評価

Transmission experiments for a local area network (LAN) using blue-light-emitting diodes (LEDs) with InGaN/GaN multiple quantum well (MQW) and plastic optical fibers (POFs) have been conducted. Audio analog signals have been transmitted up to 1800 kHz, which corresponds to an optical 1.5 dB bandwidth of LED response. The response speed of these diodes has been investigated by varying the operating conditions: dc bias, pulse amplitude, and pulse shape. The LED rise time is reduced from 0.26 μs to 0.19 μs by changing the electrical pulse amplitude from 0.5 V to 1.2 V, whereas the fall time (0.20 μs) does not change. On the other hand, the fall time is reduced from 0.20 μs to 0.14 μs by adding negative pulses after the applied positive pulses. It is shown that the direct-modulation speed of these diodes is limited by the time constant associated with device capacitance. Electroluminescence and photocurrent spectra of the LEDs were also investigated; blueshifts were observed for both peaks in the spectra. © 2001 Scripta Technica, Electr Eng Jpn, 137(3): 47–51, 2001