Electric Pulse Shape Research Articles

Asymmetric pulses delivered by a cochlear implant allow a reduction in evoked firing rate and in spatial activation in the guinea pig auditory cortex

Despite that fact that the cochlear implant (CI) is one of the most successful neuro-prosthetic devices which allows hearing restoration, several aspects still need to be improved. Interactions between stimulating electrodes through current spread occurring within the cochlea drastically limit the number of discriminable frequency channels and thus can ultimately result in poor speech perception. One potential solution relies on the use of new pulse shapes, such as asymmetric pulses, which can potentially reduce the current spread within the cochlea. The present study characterized the impact of changing electrical pulse shapes from the standard biphasic symmetric to the asymmetrical shape by quantifying the evoked firing rate and the spatial activation in the guinea pig primary auditory cortex (A1). At a fixed charge, the firing rate and the spatial activation in A1 decreased by 15 to 25 % when asymmetric pulses were used to activate the auditory nerve fibers, suggesting a potential reduction of the spread of excitation inside the cochlea. A strong “polarity-order” effect was found as the reduction was more pronounced when the first phase of the pulse was cathodic with high amplitude. These results suggest that the use of asymmetrical pulse shapes in clinical settings can potentially reduce the channel interactions in CI users.

Exploration of sensations evoked during electrical stimulation of the median nerve at the wrist level

Objective. Nerve rehabilitation following nerve injury or surgery at the wrist level is a lengthy process during which not only peripheral nerves regrow towards receptors and muscles, but also the brain undergoes plastic changes. As a result, at the time when nerves reach their targets, the brain might have already allocated some of the areas within the somatosensory cortex that originally processed hand signals to some other regions of the body. The aim of this study is to show that it is possible to evoke a variety of somatotopic sensations related to the hand while stimulating proximally to the injury, therefore, providing the brain with the relevant inputs from the hand regions affected by the nerve damage. Approach. This study included electrical stimulation of 28 able-bodied participants where an electrode that acted as a cathode was placed above the Median nerve at the wrist level. The parameters of electrical stimulation, amplitude, frequency, and pulse shape, were modulated within predefined ranges to evaluate their influence on the evoked sensations. Main results. Using this methodology, the participants reported a wide variety of somatotopic sensations from the hand regions distal to the stimulation electrode. Significance. Furthermore, to propose an accelerated stimulation tuning procedure that could be implemented in a clinical protocol and/or standalone device for providing meaningful sensations to the somatosensory cortex during nerve regeneration, we trained machine-learning techniques using the gathered data to predict the location/area, naturalness, and sensation type of the evoked sensations following different stimulation patterns.

Microwave Photonic PS-Pulse and 140 GHz RF Comb Generator

A microwave photonic RF comb generator is presented by combining an fs-pulse laser and a high-speed broadband photodetector module. The subsystem generates pulses with a FWHM of 5.8 ps and a flat RF comb up to 140 GHz. Furthermore, the capability of pulse distribution over fiber is investigated. The dispersion of the single mode fiber is managed by using an optical bandpass filter, because reducing the optical spectral width limits the pulse broadening. With this scheme, the electrical pulse shape remains constant up to 500 m of fiber transmission. For a demonstration with 1500 m of fiber, the optical bandpass filter dispersion management results in a tradeoff between minimum electrical pulse width and fiber length.

Does the shape of the electric pulse matter in electroporation?

Electric pulses are widely used in biology, medicine, industry, and food processing. Numerous studies indicate that electroporation (EP) is a pulse-dependent process, and the electric pulse shape and duration strongly determine permeabilization efficacy. EP protocols are precisely planned in terms of the size and charge of the molecules, which will be delivered to the cell. In reversible and irreversible EP applications, rectangular or sine, polar or bipolar pulses are commonly used. The usage of pulses of the asymmetric shape is still limited to high voltage and low voltage (HV/LV) sequences in the context of gene delivery, while EP-based applications of ultra-short asymmetric pulses are just starting to emerge. This review emphasizes the importance and role of the pulse shape for membrane permeabilization by EP.

Strategies for improved temporal response of glass-based optical switches

We present an optimization of the dynamics of integrated optical switches based on thermal phase shifters. These devices have been fabricated in the volume of glass substrates by femtosecond laser micromachining and are constituted by an integrated Mach–Zehnder interferometer and a superficial heater. Simulations, surface micromachining and innovative layouts allowed us to improve the temporal response of the optical switches down to a few milliseconds. In addition, taking advantage of an electrical pulse shaping approach where an optimized voltage signal is applied to the heater, we proved a switching time as low as 78 µs, about two orders of magnitude shorter with respect to the current state of the art of thermally-actuated optical switches in glass.

Effects of electrical pulse polarity shape on intra cochlear neural responses in humans: Triphasic pulses with anodic and cathodic second phase

Modern cochlear implants employ charge-balanced biphasic and triphasic pulses. However, the effectiveness of electrical pulse shape and polarity is still a matter of debate. For this purpose, a previous study (Bahmer & Baumann, 2013) conducted electrophysiological and psychophysical measurements following triphasic pulse stimulation with constant cathodic second phase and varying anodic first and third phases. Pulse stimulation with constant anodic second phase was not investigated.Therefore, in this study, pulse stimulation with cathodic and anodic second phase was applied for the recording of electrically evoked compound action potentials (ECAPs) as well as for psychophysical thresholds in cochlear implant (CI) recipients. First it was investigated whether the temporal polarity distribution has a different effect on neuronal stimulation when the second phase is cathodic or anodic; second, whether the electrophysiological and psychophysical results show a comparable difference between triphasic stimulation with anodic and cathodic second phases.The results showed that variation of the temporal polarity distribution of the triphasic pulse had a smaller effect on the ECAP response when the second phase was anodic compared to when it was cathodic, whereas for psychophysical detection thresholds this variation had a similar effect for both polarities. While electrophysiological responses and psychophysical detection thresholds showed a high correlation for variations of the triphasic pulse with cathodic second phase, the results for variations of the triphasic pulse with anodic second phase showed only moderate correlation. Furthermore, the difference between triphasic stimulation with cathodic and anodic second phases did not correlate between the electrophysiological and psychophysical results.In summary, after stimulation with different configurations of triphasic pulses used in the present study, the polarity of the second phase has an effect on electrophysiological response at suprathreshold level but not on the psychophysical detection thresholds. Thus, at different stimulation levels a possible substitution of the psychophysical test by an electrophysiological measurement (e.g. neural health measurement of the cochlea) could not be corroborated by the present results.

(Invited) Monolithic Ge Integration on the 3 μm SOI Platform for 40 GHz Photodiodes

Silicon photonics offers the possibility to integrate a large number of photonic components on a small Si chip in a similar fashion as microelectronic circuits have been realized for many decades. This enables low power consumption, small footprint and low-cost mass production. Application areas for Si photonics reach from optical communication and computing to optical sensing and imaging. Monolithic germanium PIN detectors are one of the key components in photonic integrated circuits (PICs) and convert light into electrical signals. Germanium is the preferred material for photodetectors in silicon photonics as it absorbs light in the datacom and telecom wavelength range (1.2-1.7 μm) due to its small bandgap. Germanium is also tolerated in the IC-clean manufacturing lines, unlike many other potential semiconductor materials. Electron and hole mobilities in germanium are high, enabling high-bandwidth detectors. Challenges in Ge integration on silicon-on-insulator (SOI) wafers include unintentional oxidization and etching in many of the standard silicon technology processing steps, fast diffusion of n-type dopants in Ge and relatively large lattice mismatch between Ge and Si.High refractive index contrast between silicon (3.5) and silicon dioxide (1.5) is the key to achieve ultra-dense photonics integration. Most of the silicon photonics research is carried out using submicron-thick SOI waveguides and latest microelectronics fabrication technologies that involve (and require) very small wafer topography. In this paper, we present Ge photodiode integration on a 3 µm SOI platform with 3 µm thick Si waveguides. Those offer ultra-low propagation losses (~0.1 dB/cm), ultra-dense integration (μm-scale bends), small polarization dependency (down-to-zero birefringence) and ability to tolerate relatively high optical powers (>1W). One major limitation on the 3 µm SOI platform has been the lack of as fast modulators and photodetectors as those integrated on sub-µm SOI platforms. In this work, we monolithically integrated a fast horizontal PIN photodiode on the 3 µm SOI platform. The 3 dB cutoff frequency was 40 GHz and the responsivity was 1.0 A/W at -1 V bias and 1.55 µm wavelength. This high bandwidth indicates that the detector is limited by the transit time of the carriers over the i-region, rather than the junction capacitance. The electric field in the i-region at -1 V is sufficient to keep the carrier drift speed close to the maximum carriers velocity in Ge.The design of the 40 GHz PD included analytical calculations and numerical simulations. Physical dimensions of the detector were chosen so that they are compatible with the 3 µm SOI process flow and meet the bandwidth and responsivity targets. Germanium was selectively grown into cavities in the 3 µm SOI layer, leading to very low amount of stress-induced crystal defects. The Ge waveguide detector and the Si waveguides were patterned with a common hard mask to achieve self-alignment between them. The n- and p-contacts were directly made into Ge using Ti/Al metallization. The vertical sidewalls of the Ge detector were implanted in order to create a horizontal PIN structure. Due to high confinement of light into the 3 µm thick SOI and Ge waveguides, the 3 µm thick and 1 µm wide Ge detector could be made as short as 9 µm. This led to small junction capacitances. The electrical output pulse shape was not distorted by the slow diffusion current of electrons and holes because the incoming light does not enter the doped regions. The development of 40 GHz PDs was an important step in improving the feasibility of the 3 µm SOI platform in high-bandwidth applications. Figure 1

Parametric Study of the Reltron Oscillators

In this paper, effect of the input DC electrical parameters, such as, pulse shape, cathode voltage and the postacceleration voltage on the performance of reltron oscillator have been investigated. For this purpose, a typical reltron oscillator has been designed and simulated. The mode of excitation, resonant frequency and electric field patterns in the RF modulation cavity of the reltron structure has been studied through electromagnetic simulation. The RF output performance and effect of DC electric pulse shape is studied through 3D PIC simulation. To get a practical insight of the excitation signal effect on the performance of device operation, various pulse shapes with different rise, hold and fall time have been studied the pulse of hold time 70 ns and rise and fall time of 5 ns gives maximum stable RF power. Device parametric analysis for the different cathode and post-acceleration voltages has also been investigated. With a beam current of 750 A, cathode voltage of 200 kV and post-acceleration voltage of 800 kV, the device provides ~350 MW with ~46% efficiency.

Uniform magnetization dynamics of a submicron ferromagnetic disk driven by the spin–orbit coupled spin torque

A simple model of magnetization dynamics in a ferromagnet/doped semiconductor hybrid structure with Rashba spin–orbit interaction (SOI), driven by an applied pulse of the electric field, is proposed. The electric current excited by the applied field is spin-polarized, due to the SOI and therefore it induces the magnetization rotation in the ferromagnetic layer via s-d exchange coupling. Magnetization dynamics dependence on the electric pulse shape and magnitude is analyzed for realistic values of the parameters. We show that it is similar to the dynamics of a damped nonlinear oscillator with the time-dependent frequency proportional to the square root of the applied electric field. The magnetization switching properties of an elliptic magnetic element are examined as a function of the applied field magnitude and direction.

Zero to 1,600 m/s in 40 microns: Sensitive pulse shaping for materials characterization on Z

Dynamic materials properties experiments on Sandia National Laboratories Z Machine require increasingly precise electrical current pulse shaping. In the experiment described here, a copper flyer plate is accelerated from rest to 1,600 m/s over a 40 micron flight gap in 50 ns. This flyer then impacts a cerium sample, shock melting the cerium, before subsequent quasi-isentropic ramping to mega-bar pressures. Through predictive simulations, postdicted analysis, and a new computational tool for characterizing inherent Z Machine timing accuracy, qualitative estimates of pulse controllability and experimental design robustness are arrived upon.

Experimental Techniques for Retrieving Flow Information from within Inkjet Nozzles

In drop-on-demand (DOD) inkjet printing microdroplets are ejected from the nozzle as a result of the internal acoustics set in motion by a pressure pulse from an expanding bubble or a piezoelement. The acoustic response, both in the frequency domain and in the time domain, and the resulting droplet formation processes are well-modeled and characterized by various experimental techniques. However, the behavior of the liquid meniscus in the nozzle is a critical mediator between these regimes and poorly accessible in experiment. The meniscus shape and motion vary between different print head designs, electrical pulse shapes and wetting conditions. In the last decade several novel approaches have been proposed and implemented to study experimentally the meniscus motion within inkjet nozzles. These experimental methods are reviewed here and compared in terms of accuracy and applicability.

Side-effects of electrotrawling: Exploring the safe operating space for Dover sole (Solea solea L.) and Atlantic cod (Gadus morhua L.)

Electrotrawling is currently the most promising alternative for conventional beam trawls targeting sole and shrimp, meeting both the fisherman’s aspirations and the need for more environmentally friendly fishing techniques. Before electrotrawling can be further developed and implemented on a wider scale, more information is needed about the effects of electrical pulses on marine organisms. Adult Dover sole (Solea solea L.) and Atlantic cod (Gadus morhua L.) were used in the present study as model species for flatfish and roundfish, respectively. These animals were exposed to homogeneously distributed electrical fields with varying values of the following parameters: frequency (5–200Hz), electrical field strength (100–200V/m), pulse polarity, pulse shape, pulse duration (0.25–1ms) and exposure time (1–5s). The goal was to determine the range of pulse parameters which can be regarded as safe and thereby also to evaluate the effect of the pulses already being used in commercial electrotrawls. Fish behaviour during and shortly after exposure, 14-days post exposure mortality rates, as well as gross and histological examination were used to evaluate possible effects. During exposure, both species showed an escape response below a frequency of 20Hz and a cramp reaction above 40Hz. These reactions were immediately followed by post-exposure escape behaviour and at high electrical loads cod showed tonic-clonic epileptiform seizures. No mortality was observed and histological examination did not reveal any abnormalities, except for one cod showing a spinal injury. These data reveal the absence of irreversible lesions in sole as a direct consequence of exposure to electric pulses administered in the laboratory, while in cod, more research is needed to assess cod’s vulnerability for spinal injuries when exposed to the cramp pulses.

Nyquist 4-ary pulse amplitude modulation scheme based on electrical Nyquist pulse shaping and fiber Bragg grating filter

Intensity modulation and direct detection signal are sensitive to power fading and nonlinear intersymbol interference (ISI) induced by modulator chirp, fiber dispersion, and square-law photo-detection. We propose and experimentally demonstrate a Nyquist 4-ary pulse amplitude modulation and direct detection scheme relying on pulse-shaping with an electrical filter and optical equalization with a vestigial-sideband (VSB) filter in the transmitter. The power fading could be eliminated by using the VSB filter. Compared with conventional 4-ary pulse amplitude modulation, the Nyquist signal has a stronger resistance to nonlinear ISI.

Determining the safety range of electrical pulses for two benthic invertebrates: brown shrimp (Crangon crangon L.) and ragworm (Alitta virens S.)

Abstract Pulse trawling is currently the most promising alternative for conventional beam trawls targeting sole and shrimp, meeting both the fisher's aspirations and the need for more environmentally friendly fishing techniques. Before electrotrawling can be further developed and implemented on a wider scale, however, more information is needed about the effects of electrical pulses on marine organisms. The organisms used in the present experiments were brown shrimp (Crangon crangon L.) and king ragworm (Alita virens S.) as model species for crustaceans and polychaetes, respectively. These animals were exposed to a homogeneously distributed electrical field with varying values of the following parameters: frequency (5–200 Hz), electrical field strength (150–200 V m−1), pulse polarity, pulse shape, pulse duration (0.25–1 ms), and exposure time (1–5 s). The goal of this study was to determine the range of safe pulses and thereby also to evaluate the effect of the pulses already being used on commercial electrotrawls. Behaviour during and shortly after exposure, 14-d mortality rates, and gross and histological examination were used to evaluate possible effects. The vast majority of shrimp demonstrated a tail flip response when exposed to electric pulses depending on the frequency, whereas ragworm demonstrated a squirming reaction, independent of the frequency. No significant increase in mortality or injuries was encountered for either species within the range of pulse parameters tested. Examination of the hepatopancreas of shrimp exposed to 200 V m−1 revealed a significantly higher severity of an intranuclear baculoform virus infection. These data reveal a lack of irreversible lesions in ragworm and shrimp as a direct consequence of exposure to electric pulses administered in the laboratory. Despite these promising results, other indirect effects cannot be ruled out and further research hence is warranted.

Effects of electrical pulse polarity shape on intra cochlear neural responses in humans: Triphasic pulses with cathodic second phase

Charge balanced pulses are used in modern cochlear implants to avoid direct current (DC) stimulation that may damage neural tissues. In this context the effect of electrical pulse shape and polarity is still a matter of debate and the most effective pulse shape needs to be determined (Bahmer et al., 2010a; Undurraga et al., 2010; Wieringen et al., 2008; Macherey et al., 2008). Therefore, we conducted electrophysiological measurements, namely electrical compound action potentials (ECAPs) to assess response strength elicited by various pulse shapes and polarities in five cochlear implant recipients (SonataTI100/PulsarCI100 devices, MED-EL Innsbruck). ECAP response strength depending on pulse shape was compared with individual psychophysical thresholds. Results indicated the weakest response amplitude and highest thresholds for symmetric triphasic pulse shapes (with cathodic second phase), and the strongest response amplitude and lowest thresholds for biphasic pulses with anodic first phase. Biphasic pulses with cathodic first phase generated intermediate response amplitude and thresholds.

Spread of excitation varies for different electrical pulse shapes and stimulation modes in cochlear implants

In Cochlear Implants (CI) Bipolar (BP) electrical stimulation has been suggested as a method to reduce the spread of current along the cochlea. However, behavioral measurements in BP mode have shown either similar or worse performance than in Monopolar (MP) mode. This could be explained by a bimodal excitation pattern, with two main excitation peaks at the sites of the stimulating electrodes. We measured the Spread of Excitation (SOE) by means of the Electrically Evoked Compound Action Potential (ECAP), obtained using the forward-masked paradigm. The aim was to measure the bimodality of the excitation and to determine whether it could be reduced by using asymmetric pulses. Three types of maskers shapes were used: Symmetric (SYM), Pseudomonophasic (PS), and Symmetric with a long Inter-Phase Gap (SYM-IPG) pulses. Maskers were presented in BP + 9 (wide), BP + 3 (narrow) and MP (only SYM) mode on fixed electrodes. The SOE obtained with the MP masker showed a main excitation peak close to the masker electrode. Wide SYM maskers produced bimodal excitation patterns showing two peaks close to the electrodes of the masker channel, whereas SYM-IPG maskers showed a single main peak near the electrode for which the masker's second phase (responsible for most of the masking) was anodic. Narrow SYM maskers showed complex and wider excitation patterns than asymmetric stimuli consistent with the overlap of the patterns produced by each channel's electrodes. The masking produced by narrow SYM-IPG and PS stimuli was more pronounced close to the masker electrode for which the effective phase was anodic. These results showed that the anodic polarity is the most effective one in BP mode and that the bimodal patterns produced by SYM maskers could be partially reduced by using asymmetric pulses.

Quantum motion in superposition of Aharonov–Bohm with some additional electromagnetic fields

The structure of additional electromagnetic fields to the Aharonov-Bohm field, for which the Schr\"odinger, Klein-Gordon, and Dirac equations can be solved exactly are described and the corresponding exact solutions are found. It is demonstrated that aside from the known cases (a constant and uniform magnetic field that is parallel to the Aharonov-Bohm solenoid, a static spherically symmetrical electric field, and the field of a magnetic monopole), there are broad classes of additional fields. Among these new additional fields we have physically interesting electric fields acting during a finite time, or localized in a restricted region of space. There are additional time-dependent uniform and isotropic electric fields that allow exact solutions of the Schrodinger equation. In the relativistic case there are additional electric fields propagating along the Aharonov-Bohm solenoid with arbitrary electric pulse shape.

A Comparison between Electrical and Optical Chromatic Dispersion Compensation in Wavelength Divison Multiplexing Network Regarding to Electrical Pulse Shapes

Problem statement: Besides of some impairment that has been inherited form single channel, specialists confronted with new obstacles in WDM implementation which bared them for achieving desired performance. Although Chromatic Dispersion (CD) exists in single channel too, it can worsens new nonlinearities which are occurs just in WDM systems. So CD compensation in WDM is even more vital than single channel one. Approach: A wide range of optical and electrical CD compensation techniques have been represented. In this study we evaluate the efficiency of feed Forward-Decision Feedback Equalizer (FFE-DFE) as one type of electrical compensation methods and Dispersion Compensation Fiber as one type of optical compensator. Also we will look how electrical pulse shapes induced by pulse generator in transmitter, can impact on the performance of the either optical or electrical compensations. Results: After implementation, it was revealed that overall optical compensation with DCF gives us better performance than electrical equalizer and NRZ is more vulnerable than two other pulse shapes. Conclusion: Chromatic compensation was implemented with different pulse shapes and RZ pulse shape with optical compensation showed the best performance.

The Role of Electrical Pulse Shapes in Electrical and Optical Chromatic Dispersion Compensation

Problem statement: The performance of the optical network is highly dependent to Chromatic Dispersion (CD). CD has been a big issue when higher bitrate or longer distance is desired. Many methods have been represented to mitigate or eliminate this phenomenon. A wide range of optical and electrical compensation has been investigated. Approach: In this study we evaluate the efficiency of the electrical pulse shapes including (NRZ,RZ and Triangular form) in electrical compensation with Feed Forward-Decision Feedback Equalizer (FFE-DFE) technique and optical compensation; Dispersion Compensation Fiber. Results: It was compared the mentioned situation with Quality factor versus increasing the distance with different pulse shapes. It was observed that in Electrical compensation there is no considerable with different pulse shapes while in optical compensation NRZ is definitely more susceptible than others. Optical and electrical compensators were compared regarding to jitter and optical compensator showed much better performance. Conclusion: chromatic compensation was implemented with different pulse shapes and RZ pulse shape with optical compensation showed best performance.

Analytical Study of the Injection of a Moving Projectile Into a Railgun

Calculations are performed for an initially moving projectile into a railgun. The injection velocity is provided by a 26-mm-diameter conventional propellant gun. A plasma armature is assumed for the railgun. A capacitor-based pulsed-power supply, located at Barricade C, Aberdeen Proving Ground, MD, is assumed to provide the electrical energy for boosting the velocity to 2.5 km/s. Various scenarios are examined with respect to electrical pulse shape, the effect on stored electrical energy, and its distribution in the railgun. Three types of comparisons are used to illustrate the effect of injection velocity on stored electrical energy: (1) efficiency; (2) peak loads; and (3) energy storage. Examples for each category are discussed, illustrating complementary areas for propellant gun and railgun operation. Results are promising; however, the initial velocity must be considered in detailed simulations in order for any advantages to be realized.