Millisecond Pulses Research Articles

Efficient Gene Transfection by Electroporation—In Vitro and In Silico Study of Pulse Parameters

Gene electrotransfer (GET) is a widely used method for nucleic acids’ delivery into cells. We explored, evaluated, and demonstrated the potential use of different pulse durations for introducing plasmid DNA (pDNA) into cells in vitro and compared the efficiency and dynamics of transgene expression after GET. We performed experiments on cell suspensions of 1306 fibroblasts and C2C12 myoblasts with four ranges of pulse durations (nanosecond, high frequency bipolar (HF-BP), and micro- and millisecond). Six different concentrations of pDNA encoding green fluorescent protein were used. We show that GET can be achieved with nanosecond pulses with a low pulse repetition rate (10 Hz). The GET’s efficiency depends on the pDNA concentration and cell line. Time dynamics of transgene expression are comparable between millisecond, microsecond, HF-BP, and nanosecond pulses but depend greatly on cell line. Lastly, based on the data obtained in the experiments of pDNA concentration effect on GET the model of the probability of pDNA and cell membrane contact during GET was developed. The model shows that pDNA migration is dominated by diffusion for nanosecond and HF-BP pulses and by electrophoresis for micro- and millisecond pulses. Modeling results can provide valuable guidance for further experiments and interpretations of the results obtained by various pulse protocols.

Effects of temperature on the ohmic internal resistance and energy loss of Lithium-ion batteries under millisecond pulse discharge

Battery energy storage technology has a promising future in the field of compact high-power pulse drivers due to its high energy storage density. In this paper, three types of high-performance lithium batteries, such as lithium titanate (LTO) battery, lithium iron phosphate (LFP) battery, and Ni,Co,Al (NCR) ternary lithium-ion battery, have been studied in different ambient temperatures by using DC internal resistance measurement method. The result shows that the ohmic internal resistance of lithium batteries increases when the temperature drops. When the temperature is above -30 °C, the ohmic internal resistances of the three types of battery are nearly identical. At -50 °C, the ohmic internal resistances of LFP battery and LTO battery are about 83 mΩ and 151 mΩ, respectively, and the ohmic internal resistance of NCR li-ion battery increases by one order of magnitude. The energy loss from LTO battery and LFP battery during pulse discharge is similar. In the temperature range of -30 °C to 50 °C, the energy loss of NCR li-ion battery pulse discharge is the largest. At -50 °C, the energy loss of NCR li-ion battery is the least.

Focused ultrasound excites action potentials in mammalian peripheral neurons in part through the mechanically gated ion channel PIEZO2

Neurons of the peripheral nervous system (PNS) are tasked with diverse roles, from encoding touch, pain, and itch to interoceptive control of inflammation and organ physiology. Thus, technologies that allow precise control of peripheral nerve activity have the potential to regulate a wide range of biological processes. Noninvasive modulation of neuronal activity is an important translational application of focused ultrasound (FUS). Recent studies have identified effective strategies to modulate brain circuits; however, reliable parameters to control the activity of the PNS are lacking. To develop robust noninvasive technologies for peripheral nerve modulation, we employed targeted FUS stimulation and electrophysiology in mouse ex vivo skin-saphenous nerve preparations to record the activity of individual mechanosensory neurons. Parameter space exploration showed that stimulating neuronal receptive fields with high-intensity, millisecond FUS pulses reliably and repeatedly evoked one-to-one action potentials in all peripheral neurons recorded. Interestingly, when neurons were classified based on neurophysiological properties, we identified a discrete range of FUS parameters capable of exciting all neuronal classes, including myelinated A fibers and unmyelinated C fibers. Peripheral neurons were excited by FUS stimulation targeted to either cutaneous receptive fields or peripheral nerves, a key finding that increases the therapeutic range of FUS-based peripheral neuromodulation. FUS elicited action potentials with millisecond latencies compared with electrical stimulation, suggesting ion channel–mediated mechanisms. Indeed, FUS thresholds were elevated in neurons lacking the mechanically gated channel PIEZO2. Together, these results demonstrate that transcutaneous FUS drives peripheral nerve activity by engaging intrinsic mechanotransduction mechanisms in neurons [B. U. Hoffman, PhD thesis, (2019)].

Two pathways are required for ultrasound-evoked behavioral changes in Caenorhabditis elegans.

Ultrasound has been shown to affect the function of both neurons and non-neuronal cells, but, the underlying molecular machinery has been poorly understood. Here, we show that at least two mechanosensitive proteins act together to generate C. elegans behavioral responses to ultrasound stimuli. We first show that these animals generate reversals in response to a single 10 msec pulse from a 2.25 MHz ultrasound transducer. Next, we show that the pore-forming subunit of the mechanosensitive channel TRP-4, and a DEG/ENaC/ASIC ion channel MEC-4, are both required for this ultrasound-evoked reversal response. Further, the trp-4;mec-4 double mutant shows a stronger behavioral deficit compared to either single mutant. Finally, overexpressing TRP-4 in specific chemosensory neurons can rescue the ultrasound-triggered behavioral deficit in the mec-4 null mutant, suggesting that both TRP-4 and MEC-4 act together in affecting behavior. Together, we demonstrate that multiple mechanosensitive proteins likely cooperate to transform ultrasound stimuli into behavioral changes.

Assessment of the thermal effect of femtosecond and millisecond laser pulses in microsurgery of mammalian embryos

We compare the thermal effect exerted by femtosecond and millisecond pulses during microsurgical procedures on embryos. The linear and nonlinear absorption of laser pulses in an aqueous medium, as well as heat transfer from the focusing region of the laser beam to adjacent regions, are considered.

Impact Of An Automated Titration Algorithm On Battery Longevity In An Implantable Neurostimulation System For Treatment Of Chronic Heart Failure

Background Autonomic Regulation Therapy (ART) using chronic vagus nerve stimulation (VNS) is a promising new therapy for patients with heart failure (HF) who remain symptomatic despite standard care. In the ANTHEM-HF Pilot Study, a therapeutic VNS intensity was successfully achieved in patients with HFrEF using manually-programmed VNS up-titration. In the ANTHEM-HF Pilot Study (NCT01823887), the mean stimulation parameters were 2.4 ± 0.6 mA amplitude, 5 Hz frequency, 250 µs pulse width, and 23% duty cycle. A TitrationAssist algorithm has been developed for automatically intensifying VNS in small increments to a programmable target and capable of adjustments using a hand-held programmer or magnet. While this algorithm has the potential of dramatically reducing the number and duration of clinic visits for VNS titration, the impact of implementing TitrationAssist on device longevity has not been determined. Methods Current draw was measured from 32 VITARIA pulse generators (LivaNova USA, Houston, USA) with TitrationAssist activated. Testing was performed with a 3000 Ω load at programmed stimulation settings of 250 µsec pulse width, pulse frequency of 5 or 10 Hz, output current of 2.0 or 3.0 mA, and duty cycle of 23% (nominal), 33%, and 50%. The measured data was used in a standard longevity estimate process to determine the minimum longevity reached by at least 95% of devices with 95% confidence. The design requirement for battery longevity was >5 years at 10 Hz / 2.5 mA / 23%. Results Current draw was successfully measured from all 32 pulse generators and used to calculate device longevity. Device longevity, expressed in years, is shown in the table, and exceeds the system longevity requirement. At the expected stimulation parameters of 2.0-3.0 mA amplitude, 5 Hz frequency, 250 µs pulse width, 23% duty cycle, device longevity is expected to be in the range of 7-9 years. Device longevity was not significantly affected by the activation of the TitrationAssist algorithm. Conclusions At the expected stimulation parameters, VITARIA pulse generator battery longevity was determined to be 7-9 years. This exceeds the design requirement and suggests that ART can be titrated using TitrationAssist and chronically delivered without frequent generator replacement. Autonomic Regulation Therapy (ART) using chronic vagus nerve stimulation (VNS) is a promising new therapy for patients with heart failure (HF) who remain symptomatic despite standard care. In the ANTHEM-HF Pilot Study, a therapeutic VNS intensity was successfully achieved in patients with HFrEF using manually-programmed VNS up-titration. In the ANTHEM-HF Pilot Study (NCT01823887), the mean stimulation parameters were 2.4 ± 0.6 mA amplitude, 5 Hz frequency, 250 µs pulse width, and 23% duty cycle. A TitrationAssist algorithm has been developed for automatically intensifying VNS in small increments to a programmable target and capable of adjustments using a hand-held programmer or magnet. While this algorithm has the potential of dramatically reducing the number and duration of clinic visits for VNS titration, the impact of implementing TitrationAssist on device longevity has not been determined. Current draw was measured from 32 VITARIA pulse generators (LivaNova USA, Houston, USA) with TitrationAssist activated. Testing was performed with a 3000 Ω load at programmed stimulation settings of 250 µsec pulse width, pulse frequency of 5 or 10 Hz, output current of 2.0 or 3.0 mA, and duty cycle of 23% (nominal), 33%, and 50%. The measured data was used in a standard longevity estimate process to determine the minimum longevity reached by at least 95% of devices with 95% confidence. The design requirement for battery longevity was >5 years at 10 Hz / 2.5 mA / 23%. Current draw was successfully measured from all 32 pulse generators and used to calculate device longevity. Device longevity, expressed in years, is shown in the table, and exceeds the system longevity requirement. At the expected stimulation parameters of 2.0-3.0 mA amplitude, 5 Hz frequency, 250 µs pulse width, 23% duty cycle, device longevity is expected to be in the range of 7-9 years. Device longevity was not significantly affected by the activation of the TitrationAssist algorithm. At the expected stimulation parameters, VITARIA pulse generator battery longevity was determined to be 7-9 years. This exceeds the design requirement and suggests that ART can be titrated using TitrationAssist and chronically delivered without frequent generator replacement.

Laser-Induced Vacancies-Relief Ordered Structures on Titanium Surface

Generation of coupled vacancy-relief ordered structures on titanium surface induced by laser millisecond pulses irradiation was studied. To explain the geometric features of the structures the model of vacancy-deformation instability was proposed. Numerical calculation performed in accordance with the theoretical model provided good quantitative agreement with experimental results.

Energy functions of fast radio bursts derived from the first CHIME/FRB catalogue

ABSTRACT Fast radio bursts (FRBs) are mysterious millisecond pulses in radio, most of which originate from distant galaxies. Revealing the origin of FRBs is becoming central in astronomy. The redshift evolution of the FRB energy function, i.e. the number density of FRB sources as a function of energy, provides important implications for the FRB progenitors. Here, we show the energy functions of FRBs selected from the recently released Canadian Hydrogen Intensity Mapping Experiment (CHIME) catalogue using the Vmax method. The Vmax method allows us to measure the redshift evolution of the energy functions as it is without any prior assumption on the evolution. We use a homogeneous sample of 164 non-repeating FRB sources, which are about one order of magnitude larger than previously investigated samples. The energy functions of non-repeating FRBs show Schechter function-like shapes at z ≲ 1. The energy functions and volumetric rates of non-repeating FRBs decrease towards higher redshifts similar to the cosmic stellar-mass density evolution: there is no significant difference between the non-repeating FRB rate and cosmic stellar-mass density evolution with a 1 per cent significance threshold, whereas the cosmic star-formation rate scenario is rejected with a more than 99 per cent confidence level. Our results indicate that the event rate of non-repeating FRBs is likely controlled by old populations rather than young populations that are traced by the cosmic star-formation rate density. This suggests old populations, such as old neutron stars and black holes, as more likely progenitors of non-repeating FRBs.

Efficacy of the Treatment of Plantar Warts Using 1064 nm Laser and Cooling

Cutaneous plantar warts may be treated using several optional methods, with the use of laser surgery having increased in the last few years. This work examined the efficacy of laser treatment combined with simple cooling to reduce pain. The cure rate was approximately 84%. There were no significant differences in the efficacy of treatment for different viral genotypes. The laser parameters were 500 msec pulses, 30 W of power, and a fluence of 212 J/cm2 delivered in up to four sessions. Successful treatment was achieved after an average of 3.6 sessions.

Electrically Evoked Compound Action Potentials in Spinal Cord Stimulation: Implications for Preclinical Research Models

ObjectivesThe study aimed to assess the feasibility of recording electrically evoked compound action potentials (ECAPs) from the rat spinal cord. To achieve this, we characterized electrophysiological responses of dorsal column (DC) axons from electrical stimulation and quantified the relationship between ECAP and motor thresholds (ECAPTs and MTs). Material and MethodsNaïve, anesthetized, and freely behaving rats were implanted with a custom-made epidural spinal cord stimulation (SCS) lead. Epidural stimulation and recordings were performed on the same lead using specifically designed equipment. ResultsThe ECAPs recorded from the rat spinal cord demonstrated the expected triphasic morphology. Using 20 μsec pulse duration and 2 Hz frequency rate, the current required in anesthetized rats to generate ECAPs was 0.13 ± 0.02 mA, while the average current required to observe MT was 1.49 ± 0.14 mA. In unanesthetized rats, the average current required to generate ECAPs was 0.09 ± 0.02 mA, while the average current required to observe MT was 0.27 ± 0.04 mA. Thus, there was a significant difference between the ECAPT and MT in both anesthetized and unanesthetized rats (MT was 13.39 ± 2.40 and 2.84 ± 0.33 times higher than ECAPT, respectively). Signal analysis revealed average conduction velocities (CVs) suggesting that predominantly large, myelinated fibers were activated. In addition, a morphometric evaluation of spinal cord slices indicated that the custom-made lead may preferentially activate DC axons. ConclusionsThis is the first evidence demonstrating the feasibility of recording ECAPs from the rat spinal cord, which may be more useful in determining parameters of SCS in preclinical SCS models than MTs. Thus, this approach may allow for the development of a novel model of SCS in rats with chronic pain that will translate better between animals and humans.

Comparison and Improvement of Millisecond Pulsed Laser and Nanosecond Pulsed Laser for Cleaning to Remove Paint Coating from Aluminum Alloy Surface

Comparison and Improvement of Millisecond Pulsed Laser and Nanosecond Pulsed Laser for Cleaning to Remove Paint Coating from Aluminum Alloy Surface

Acidic pH reduces agonist efficacy and responses to synaptic-like glycine applications in zebrafish α1 and rat α1β recombinant glycine receptors.

Many pentameric ligand‐gated ion channels are modulated by extracellular pH. Glycine receptors (GlyRs) share this property, but it is not well understood how they are affected by pH changes. Whole cell experiments on HEK293 cells expressing zebrafish homomeric α1 GlyR confirmed previous reports that acidic pH (6.4) reduces GlyR sensitivity to glycine, whereas alkaline pH (8.4) has small or negligible effects. In addition to that, at pH 6.4 we observed a reduction in the maximum responses to the partial agonists β‐alanine and taurine relative to the full agonist glycine. In cell‐attached single‐channel recording, low pH reduced agonist efficacy, as the maximum open probability decreased from 0.97, 0.91 and 0.66 to 0.93, 0.57 and 0.34 for glycine, β‐alanine and taurine, respectively, reflecting a threefold decrease in efficacy equilibrium constants for all three agonists. We also tested the effect of pH 6.4 in conditions that replicate those at the native synapse, recording outside‐out currents elicited by fast application of millisecond pulses of agonists on α1 and α1β GlyR, at a range of intracellular chloride concentrations. Acidic pH reduced the area under the curve of the currents, by reducing peak amplitude, slowing activation and speeding deactivation. Our results show that acidification of the extracellular pH by one unit, as may occur in pathological conditions such as ischaemia, impairs GlyR gating and is likely to reduce the effectiveness of glycinergic synaptic inhibition. Key points Extracellular pH in the central nervous system (CNS) is known to shift towards acidic values during pathophysiological conditions such as ischaemia and seizures.Acidic extracellular pH is known to affect GABAergic inhibitory synapses, but its effect on signals mediated by glycine receptors (GlyR) is not well characterised.Moderate acidic conditions (pH 6.4) reduce the maximum single channel open probability of recombinant homomeric GlyRs produced by the neurotransmitter glycine or other agonists, such as β‐alanine and taurine.When glycine was applied with a piezoelectric stepper to outside out patches, to simulate its fast rise and short duration at the synapse, responses became shorter and smaller at pH 6.4. The effect was also observed with physiologically low intracellular chloride and in mammalian heteromeric GlyRs.This suggests that acidic pH is likely to reduce the strength of inhibitory signalling at glycinergic synapses.

Effectiveness of millisecond pulse discharge on hypersonic oblique shock wave

The characteristics of millisecond pulse discharge in quiescent air and its effects on a Mach 6 hypersonic oblique shock over a ramp have been experimentally investigated with high-speed schlieren imaging and surface pressure measurement. The discharge between three pairs of electrodes was aligned in the direction of the airflow with pulse widths extending to a few milliseconds. The evolutionary characteristics of the energy deposition induced by the discharge pulses in quiescent air reveals that the discharge generating a significant thermal disturbance and lasting long enough may have greater control authority on hypersonic shock manipulation. In hypersonic flow, the plasma layer generated by the discharge propagates downstream and accumulates at a high penetration depth. Dilution of the ramp-induced ramp shock wave is observed under the disturbance of the plasma layer at a frequency of 100 Hz. Under repetitive pulse discharge, shock wave attenuation was demonstrated by pressure decreasing along the compression surface at the region where the plasma layer covers. The law of transient pressure distribution is acquired with the aid of the p–θ polar curve in shock wave analysis. The modification of pressure distribution indicates that the aerodynamic force of a compression surface can be controlled by deploying the control strategy.

Finite element simulation of temperature field in laser cleaning of TA15 titanium alloy oxide film

<p indent=0mm>Laser cleaning is a noncontact cleaning method that uses a short-pulse high power density laser to irradiate an object. The pollutants are removed by the complex physical and chemical interactions between the laser and the object to be cleaned. The mechanism of laser cleaning is very complex, including photodegradation, photodetachment, and photovibration, which are closely related to the temperature distribution in the laser-cleaning process. In this study, the finite element simulation model of laser cleaning of TA15 titanium alloy oxide film is established by using Comsol Multiphysics commercial simulation software. The influence of spot shape, laser energy, loading mode, and pulse width on the titanium alloy oxide film temperature field is analyzed. The results showed that the substrate was severely damaged by a millisecond pulse laser. The shorter the pulse width, the smaller the surface thermal diffusion. The square flat-top spot was more evenly heated than the Gaussian spot, and the rectangular pulse was less damaged than the Gaussian spot. The laser-cleaning effect of titanium alloy oxide film was the best when the square flat-top laser was loaded in a rectangular pulse.

Aluminum particles generated during millisecond electric pulse application enhance adenovirus-mediated gene transfer in L929 cells

Gene electrotransfer is an attractive method of non-viral gene delivery. However, the mechanism of DNA penetration across the plasma membrane is widely discussed. To explore this process for even larger structures, like viruses, we applied various combinations of short/long and high/low-amplitude electric pulses to L929 cells, mixed with a human adenovirus vector expressing GFP. We observed a transgene expression increase, both in the number of GFP-converted cells and GFP levels, when we added a low-voltage/millisecond-pulse treatment to the adenovirus/cell mixture. This increase, reflecting enhanced virus penetration, was proportional to the applied electric field amplitude and pulse number, but was not associated with membrane permeabilization, nor to direct cell modifications. We demonstrated that this effect is mainly due to adenovirus particle interactions with aggregated aluminum particles released from energized electrodes. Indeed, after centrifugation of the pulsed viral suspension and later on addition to cells, the activity was found mainly associated with the aluminum aggregates concentrated in the lower fraction and was proportional to generated quantities. Overall, this work focused on the use of electrotransfer to facilitate the adenovirus entry into cell, demonstrating that modifications of the penetrating agent can be more important than modifications of the target cell for transfer efficacy.

Power Supply System for Vacuum-Arc Ion Source With Millisecond Pulse Length

This article deals with a vacuum-arc ion source, which generates high-intensity beams of metal ions. The power supply system largely determines the ion source parameters such as accelerating voltage, average current, and pulse current densities of the ion beam. This article proposes the power supply system for the vacuum-arc ion source intended for the generation of pulses with the length up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2000~\mu \text{s}$ </tex-math></inline-formula> at an accelerating voltage up to 50 kV. At the frequency of 50 Hz, the average ion current can reach 50 mA due to long pulses. This article considers the main design solutions for the generation of long pulses. A comparison is given to the novel power supply system based on insulated-gate bipolar transistors (IGBTs) and the earlier thyristor power supply.

Laser ablation of graphite with near infrared microsecond pulses

Laser processing of polycrystalline porous graphite through micro- to millisecond pulses with 1 µm wavelength is investigated. The study aims at finding the best compromise between the efficiency of the process (ablation rate) and the quality (reduced heat-affected zone) for drilling and cutting applications. Our experimental approach is based on experiments involving a monomode kW ytterbium fibre laser (1080 nm) coupled with a laser scanning system. This system is used for parametric studies on pulse duration, power, repetition rate and scanning speed on samples that are analysed with scanning electron microscopy. To improve the understanding of the underlying physical phenomena and processes involved, a finite element numerical model is developed, taking into account energy deposition through optical ray tracing, heat transfer, sublimation of the material and crater formation. Based on these experimental and numerical tools, we identify some optimum parameters to fabricate high aspect ratio shapes in graphite samples of 1.5 mm thickness with excellent edge quality and minimal heat-affected zone. Laser processing under vacuum atmosphere is also studied and exhibit no difference in behaviour compared to ambient atmosphere.

A Study of the Characteristics of Plasma Generated by Infrared Pulse Laser-Induced Fused Silica

When high energy infrared laser pulses are incident on fused silica, the surface of the fused silica is damaged and a laser-induced plasma is produced. Based on the theory of fluid mechanics and gas dynamics, a two-dimensional axisymmetric gas dynamic model was established to simulate the plasma generation process of fused silica induced by a millisecond pulse laser. The results show that the temperature of the central region irradiated by the laser is the highest, and the plasma is first produced in this region. When the laser energy density is 1.0 × 104 J/cm2 and the pulse width is 0.2 ms, the maximum expansion velocity of the laser-induced plasma is 17.7 m/s. Under the same experimental conditions, the results of the simulation and experiment are in good agreement. With an increase in pulse width, the plasma expansion rate gradually decreases.

Assessment of electromechanically stimulated bone marrow stem cells seeded acellular cardiac patch in a rat myocardial infarct model

In this study, we evaluated cardiomyogenic differentiation of electromechanically stimulated rat bone marrow-derived stem cells (rt-BMSCs) on an acellular bovine pericardium (aBP) and we looked at the functioning of this engineered patch in a rat myocardial infarct (MI) model. aBP was prepared using a detergent-based decellularization procedure followed by rt-BMSCs seeding, and electrical, mechanical, or electromechanical stimulations (3 millisecond pulses of 5 V cm−1 at 1 Hz, 5% stretching) to enhance cardiomyogenic differentiation. Furthermore, the electromechanically stimulated patch was applied to the MI region over 3 weeks. After this period, the retrieved patch and infarct region were evaluated for the presence of calcification, inflammatory reaction (CD68), patch to host tissue cell migration, and structural sarcomere protein expressions. In conjunction with any sign of calcification, a higher number of BrdU-labelled cells, and a low level of CD68 positive cells were observed in the infarct region under electromechanically stimulated conditions compared with static conditions. More importantly, MHC, SAC, Troponin T, and N-cad positive cells were observed in both infarct region, and retrieved engineered patch after 3 weeks. In a clear alignment with other results, our developed acellular patch promoted the expression of cardiomyogenic differentiation factors under electromechanical stimulation. Our engineered patch showed a successful integration with the host tissue followed by the cell migration to the infarct region.

Study on the Internal Mechanism of APD Photocurrent Characteristics Caused by the ms Pulsed Infrared Laser Irradiation

In this paper, the sampling current characteristics of the external circuit and the internal mechanism of the current generation in APD irradiated by a millisecond pulse laser were studied. The photocurrent of APD irradiated by a millisecond pulse laser with different energy densities was obtained by the sampling resistance of the external circuit. The photocurrent can be divided into a photocurrent stage, conduction stage and recovery stage in the time domain. This is mainly due to the carrier flow in APD, which leads to the lowering of the barrier between the PN junction. The research results of this paper can be extended to the response of the detector to the high-power infrared pulse laser and provide a certain experimental basis for the design of a millisecond pulse infrared laser detection circuit.