Higher Current Intensity Research Articles

Electro-sorption/-desorption with bio-sourced granular activated carbon electrode for phenols recovery and combination with advanced electro-oxidation for residual olive mill wastewater treatment

To face the releasing of hazardous solid and liquid wastes into the environment from the olive oil production industry, it is newly proposed a circular economy approach by implementing electro-sorption of value-added phenolic compounds (PCs) followed by electro-desorption using a bio-sourced granular activated carbon (GAC) electrode made of olive pomace waste. The remaining organic compounds present in the real olive mill wastewater (OMWW) were treated by advanced electrooxidation.The PCs electro-sorption study highlighted efficiency around 72 % in synthetic matrix against 68 % in real effluents, whose electro-sorption capacities could be partly attributed to the high electroactive surface area (7.8 × 103 cm2), high exchange current intensity (I0) value (5.5 × 10−3 A), and low charge transfer resistance (RCT) value (4 Ω) compared to the literature. The study further emphasized the fact that the electro-sorption selectivity was not only dependent on pKa of PCs with respect to solution pH, but also on the size of adsorbed molecules relative to the pore size distribution of GAC. The maximal percentage of PCs recovered from GAC after electro-desorption experiments was 34.5 %, while the global chemical oxygen demand (COD) removal efficiency was 92 % of the pre-filtered real effluent at the cost of scaling during advanced electrooxidation of residual OMWW.

Induction Heating Optimization for Efficient Self-Healing in Asphalt Concrete.

In this study, the practical application of self-healing asphalt mixtures incorporating steel wool fibers and induction heating was investigated, expanding upon previous research that primarily assessed the self-healing properties rather than optimizing the heating process. Specifically, the aim was to enhance the induction heating methodology for a semi-dense asphalt concrete mixture (AC 16 Surf 35/50 S). In this research, the induction heating parameters were refined to improve the self-healing capabilities, focusing on the following three key aspects: (i) energy consumption, (ii) heating rate, and (iii) heating homogeneity. The findings reveal that the current intensity, the percentage of ferromagnetic additives, and coil shape are critical for achieving optimal heating conditions. Higher current intensity and additive percentage correlate with improved heating speed and reduced energy consumption. Additionally, variations in coil shape significantly influence the heating uniformity. Although asphalt mixtures with steel slag coarse aggregates exhibit slightly higher specific heat, this aggregate type is preferable for sustainability, as it allows for the recycling of industrial waste. The optimized mixtures can rapidly reach high temperatures, facilitating effective crack repair. This innovation offers a durable, environmentally friendly, and cost-effective solution for road maintenance, thereby enhancing the longevity and performance of asphalt pavements.

Development of a hybrid material based on Zn-Mg spinel ferrites covered with polypyrrole: structural, morphological, and electrical characteristics

In this study, we synthesized a range of spinel ferrite ZnxMg1-xFe2O4 (x = 0, 0.3) forms using the sol-gel method. Additionally, polypyrrole nanosphere supported by magnesium and zinc ferrites (ZnxMg1-xFe2O4@PPy) were synthesized through in-situ polymerisation. The surfaces of ZnxMg1-xFe2O4 (x = 0, 0.3) and ZnxMg1-xFe2O4@PPy were subjected to spectroscopic analysis. The data obtained from X-ray diffraction (XRD) confirmed the formation of Zn-Mg spinel ferrite. The electrochemical analysis results demonstrated that the Zn0.3Mg0.7Fe2O4@PPy nanocomposites exhibited enhanced redox activity and a higher current intensity. This study highlights the development of hybrid Zn0.3Mg0.7Fe2O4@PPy type nanospheres with substantial and effective electrochemical properties, which could be a suitable option for industrial applications.

Two-Dimensional Nanorod-Shaped Co(II) Coordination Polymer on Three-Dimensional Metallic Foam: A Hybrid Platform for Electrochemical Oxidation of Glucose.

This study unveils a novel electrochemical biosensor for monitoring glucose in biological fluids by employing nanorods of a cobalt-bispyridyl/dicarboxylate framework grown in a layer-by-layer manner on a highly porous nickel substrate. The hybrid microporous system has a bicatalytic effect on glucose oxidation due to the synergistic catalytic impact of the nickel and cobalt ions with varying oxidation states as electroactive sites. In addition, the controlled growth of inorganic-organic frameworks changes the mechanism of electron transfer from a diffusion-controlled process to an adsorption-controlled process, thus yielding a low onset oxidation potential (∼0.21 V/Ag-AgCl) and a high current intensity (∼1 mA) for the oxidation of glucose in alkaline media. A fast response time (∼2 s) and a reasonably high sensitivity (0.14 μA μM-1) within a broad linear range (40-360 μM) have determined the suitability and superiority of the hybrid electrode for glucose monitoring compared to many metal-organic-based biosensors. The facile fabrication process of the Co(II) coordination polymer/Ni substrate with a large surface area that benefits from the synergetic catalytic activity of nickel-cobalt hybrids may pave the way for the development of novel hybrid electrodes for biosensors and direct glucose fuel cells.

Intrinsic and extrinsic relaxation mechanisms for controlling spin current intensity in Fe 100−x Co x /Ta bilayers

Controlling the damping parameter in metallic ferromagnetic thin films is a key step for spintronic applications in which spin currents are generated by spin pumping. The coexistence of two states with low and high damping constant values would allow to obtain states of high and low spin current intensity, respectively. We have fabricated Fe 100−x Co x /Ta (with nominal x = 0, 15, 20, 25, 30 and 35) bilayers in which the Fe 100−x Co x layers grow epitaxially and the Ta layer is polycrystalline. We have found the coexistence of Gilbert damping and two magnon scattering mechanisms linked to a sign change in the magnetocrystalline anisotropy constant that allows the manipulation of low and high intensity states of the measured inverse spin Hall effect voltage. Bilayers with lower Co concentrations ( x⩽ 25%) present different relaxation mechanisms (isotropic Gilbert damping and two magnon scattering) and an extra ferromagnetic resonance linewidth broadening produced due to mosaicity. Bilayers with Co concentration x> 25% present a dominating Gilbert damping for all directions in the film plane. However, in this concentration range the damping constant is anisotropic and when the magnetic field is applied along the hard magnetization direction α increases ∼420% with respect to the value obtained for the easy magnetization direction. Coexistence of isotropic Gilbert damping and two magnon scattering generated spin currents 2.5 times larger when the field is applied along the hard magnetization axis compared to the value observed in the easy magnetization axis. Thesefindings make the Fe 100−x Co x /Ta system an excellent candidate for spintronic device applications.

Electrochemical insights into layered assemblies of silver nanoparticles, poly‐L‐lysine, and bovine serum albumin

AbstractThis study presents a comprehensive exploration of the electrochemical behavior of layer‐by‐layer assemblies comprising silver nanoparticles (AgNPs), poly‐l‐lysine (PLL), and bovine serum albumin (BSA) on gold surfaces. AgNPs were synthesized using the reduction of silver ions with the synergy of ascorbic acid and citrate in the presence of sodium chloride. The obtained silver nanoparticles were characterized using transmission electron microscopy, dynamic light scattering and UV‐Vis spectroscopy. A typical preparation produced AgNPs with a plasmon peak at 402 nm, a diameter of 27.5 nm and zeta potential of −37 mV. Employing a drop‐coating approach, we successfully achieved stable multilayers of AgNPs, PLL, and BSA. Cyclic voltammetry revealed well‐defined, bell‐shaped oxidation and reduction peaks of AgNPs within the multilayers, demonstrating complete conversion to AgCl and back to Ag. Notably, the stripping of AgNPs on a monolayer of PLL prepared at pH 4.00 resulted in the highest current intensity, contrasting with lower intensities observed for PLL monolayers prepared at pH 7.01 and pH 9.01. Despite the absence of a splitting reduction peak in the presence of biopolymer materials, a noteworthy observation emerged: the peak splitting exclusively occurred when PLL/AgNP layers, terminated with PLL, were exposed to BSA in the solution.

Prototype of a 2.45 GHz cylindrical ceramic dielectric antenna surface wave plasma source for flood gun

In modern ion implanters, plasma flood gun (PFG) is used to neutralize wafer charge during doping process, preventing the breakdown damage of floating wafers caused by the space charge accumulation. Surface wave (SW) plasma source is a potential choice for PFG, because of its no metal pollution, simple structure, high current intensity and low cost for ion implanters. At Peking University (PKU), a 2.45 GHz surface wave PFG (SW-PFG) with a cylindrical dielectric antenna was designed and tested recently. It aims to obtain plasma at the gas pressure of several 10−3 Pa and below which is strictly required by the ion implanter. A two-dimensional discharge model was established to optimize the cylindrical dielectric antenna structure. Through optimization of operation parameters, the electron current intensity of 88 mA was obtained with RF power 500 W and gas pressure 5.0 × 10−3 Pa in the experiments, which meets the requirement of ion implanters. Further, through optimization of operation parameters, the electron current intensity could reach 140 mA. In addition, by setting the graphite liner to isolate the metal cavity wall and plasma, the improvement in the long-term operation stability has been confirmed, which laid a solid foundation for the industrial application of the SW-PFG.

Genomic and epigenomic changes by low force electrically induced exercise of human paralyzed muscle

Musculoskeletal deterioration following complete paralysis, such as after a spinal cord injury, results in osteoporotic bone and atrophic, glycolytic, and insulin-resistant skeletal muscle. Decreased bone integrity can be overloaded with very little force; therefore, high force contractions should be avoided in people with long-term spinal cord injury. Together, these changes compromise systemic metabolism for people with SCI and contribute to the development of secondary non-communicable diseases. Electrically induced exercise training offers a unique strategy to ensure full muscle recruitment without high force levels by using high current intensity and a low stimulation frequency (<5Hz) to prevent force summation of stimulus pulses. While acute epigenomic and genomic changes have been found with this low force exercise method; how long-term training affects skeletal muscle and systemic biomarkers of health remains unknown. Purpose: We seek to determine the long-term genomic and epigenomic response of low-force electrically induced exercise in paralyzed skeletal muscle. Methods: 10 males with a complete SCI completed at least 6-months of unilateral electrically induced exercise training using low-force (3Hz) stimulation. Participants completed at least 5 exercise training sessions per week for at least 6-months. A muscle fatigue assessment and fasting venous blood draw were performed before and after training. Percutaneous muscle biopsies were obtained from a trained and untrained vastus lateralis. Gene expression was measured using the Affymetrix HTA 2.0 array and epigenomic expression was measured using Illumina’s MethylEPIC array. Parametric tests were used to compare pre and post training. All participants provided written consent approved by the University of Iowa Institutional Review Board in compliance with the Declaration of Helsinki. Results: Participants maintained a high compliance by completing 119±19% of the training sessions for 7.2±1.2 months. There was a 115±34% change improvement of the fatigue index after training (p=0.002). Serum concentrations of insulin, hsCRP, and myostatin were decreased by 43±8% (p=0.155), 26±8%(p=0.047), 35±9%(p=0.098) after exercise training, respectively. Serum BDNF increased by 68±14%(p=0.093) after exercise training. There was a strong correlation between the primary principal component and the trained limb (R2=0.20, p=0.046). There were 693 and 671 genes to be significantly up or down regulated after exercise training (FDR < 0.05). Of the genes most responsive to exercise training, MYH6, MYH7, and MYL3 were increased in expression and decreased in median methylation. MSTN and ACTN3 were decreased in genomic expression with an increase in median methylation after exercise training. Conclusions: Low-force electrically induced exercise training improved fatigability, a muscle oxidative phenotype transition, and improved serum biomarkers associated with metabolism and inflammation. Together, these data highlight the impact low-force electrically induced exercise can have on paralyzed muscle and is suggestive that this rehabilitation strategy may provide benefits for people living with paralysis. Research Support: This study was funded by the Eunice Kennedy Shriver National Institute of Child Health and Human Development: R01HD084645, R01HD082109. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Gliding strategy analysis and optimisation of underwater gliders balancing energy consumption, motion accuracy and voyage velocity

ABSTRACT This paper presents a novel gliding strategy for underwater gliders, which can better balance the glider energy consumption, motion accuracy and voyage velocity. This strategy is designed according to the performance analysis results of the glider under the conventional gliding strategy. In the shallow water areas with the higher current intensity, the glider adjusts the net buoyancy to a larger value, which can ensure the higher voyage velocity and motion accuracy. In the deep water areas with the smaller current intensity, the glider adjusts the net buoyancy to a smaller value, which can ensure the higher energy utilisation rate. In the different water areas, the movable mass block translation amount will also be adjusted. To improve the performance analysis efficiency, the radial basis function (RBF) neural network is employed to establish surrogate models of the glider dynamic model. Then, we carry out the glider control parameter optimisation using the surrogate models and non-dominated sorting genetic algorithm II. The comparison research between the conventional gliding strategy and the novel gliding strategy shows that the novel gliding strategy can make the glider have the higher motion accuracy under the specific energy utilisation rate. Besides, the novel gliding strategy will not affect the optimal solution of the glider voyage velocity and energy utilisation rate, and it improves the glider motion accuracy by mainly reducing the voyage velocity. The advantage of the novel strategy is mainly to improve the glider motion accuracy, which may provide certain guidance for the actual application of underwater gliders.

Boosted hydrogen evolution kinetics of heteroatom-doped carbons with isolated Zn as an accelerant

Carbon-based single-atom catalysts, a promising candidate in electrocatalysis, offer insights into electron-donating effects of metal center on adjacent atoms. Herein, we present a practical strategy to rationally design a model catalyst with a single zinc (Zn) atom coordinated with nitrogen and sulfur atoms in a multilevel carbon matrix. The Zn site exhibits an atomic interface configuration of ZnN4S1, where Zn's electron injection effect enables thermal-neutral hydrogen adsorption on neighboring atoms, pushing the activity boundaries of carbon electrocatalysts toward electrochemical hydrogen evolution to an unprecedented level. Experimental and theoretical analyses confirm the low-barrier Volmer-Tafel mechanism of proton reduction, while the multishell hollow structures facilitate the hydrogen evolution even at high current intensities. This work provides insights for understanding the actual active species during hydrogen evolution reaction and paves the way for designing high-performance electrocatalysts.

Low-frequency noise in InSnZnO thin film transistors with high-quality SiO2 gate oxide stacks

Low-frequency noise (LFN) in InSnZnO (ITZO) thin-film-transistors (TFT) with high-quality SiO2 gate oxide (GO) stacks is studied. This stack is fabricated by the plasma enhanced chemical vapor deposition (PECVD) and comprises two single layers. One layer is deposited by a SiH4 source (SiH4–SiO2), and the other uses a tetraethyl-orthosilicate precursor (TEOS-SiO2). The drain current noise power spectral densities follow the typical 1/f rule, and the main origin of LFN changes with the variation of drain current intensities. At low drain current intensities, LFN is affected by grain boundaries in the channel. As the drain current intensities increase, LFN originates from the carrier number fluctuations in devices with single TEOS-SiO2 GOs and from the carrier number with correlated mobility fluctuations in devices with SiO2 stacks GOs. At extremely high drain current intensities, the contact noise acts as a significant source of LFN in devices with SiO2 GO stacks. According to the carrier number with correlated mobility fluctuation (ΔN−Δμ) model, the devices with optimal stacks GOs exhibit a relatively low trap density near the ITZO/SiO2 interface. Additionally, these devices have a lower border trap density in GOs compared to those with single compositions. It demonstrates that high-quality SiO2 stacks reduce traps near the SiO2/ITZO interface, leading to enhanced devices performance. This work provides a precise and efficient method to evaluate the quality of GOs in metal oxide TFTs.

Uniformity optimization of ion beam sputtering coating equipment based on strong current ion source

The widespread application of ion beam sputtering coating, especially in optical devices, requires the improvement of beam current intensity and uniformity of large-area uniform coatings. The advent of high current Penning sources offers a potential solution. This study introduces an automated optimization simulation method based on a three-electrode extraction system to investigate its influence on ion beam quality and uniformity. Focusing on high current intensity and uniformity, our simulation explores the effects of plasma electrode, inhibition electrode, and extraction electrode angles and distances on ion beam performance. Evaluation metrics include average beam intensity density, average energy of a single particle, and reciprocal variance of each macro particle position, which are achieved through normalization functions, allowing comprehensive comparison of simulation results. To assess coating efficiency, we estimate sputtering yield and depth. The study identifies patterns among electrodes and emphasizes the influence of different ion ratios on beam extraction. The results indicate that optimizing the angle of the plasma electrode and the distance of the suppressed electrode yields a highly uniform ion beam for low charge ions. However, for highly charged ions, similar optimization will reduce the current strength, so compensation needs to be achieved through electrode shape optimization. This research provides a model for systematically optimizing the three-electrode extraction system, guiding researchers in achieving optimal solutions based on ion source characteristics and application requirements. Additionally, we introduce a method of estimating the sputtering depth of mixed ion beams. This study provides valuable insights for advancing ion beam sputtering coating technology and reference for making the decision on design and application of ion source.

Mo2C-Based Ceramic Electrode with High Stability and Catalytic Activity for Hydrogen Evolution Reaction at High Current Density.

Developing robust electrodes with high catalytic performance is a key step for expanding practical HER (hydrogen evolution reaction) applications. This paper reports on novel porous Mo2C-based ceramics with oriented finger-like holes directly used as self-supported HER electrodes. Due to the suitable MoO3 sintering additive, high-strength (55 ± 6MPa) ceramic substrates and a highly active catalytic layer are produced in one step. The in situ reaction between MoO3 and Mo2C enabled the introduction of O in the Mo2C crystal lattice and the formation of Mo2C(O)/MoO2 heterostructures. The optimal Mo2C-based electrode displayed an overpotential of 333 and 212mV at 70°C under a high current intensity of 1500 mAcm-2 in 0.5m H2SO4 and 1.0m KOH, respectively, which are markedly better than the performance of Pt wire electrode; furthermore, its price is three orders of magnitude lower than Pt. The chronopotentiometric curves recorded in the 50 - 1500 mAcm-2 range, confirmed its excellent long-term stability in acidic and alkaline media for more than 260h. Density functional theory (DFT) calculations showed that the Mo2C(O)/MoO2 heterostructures has an optimum electronic structure with appropriate *H adsorption-free energy in an acidic medium and minimum water dissociation energy barrier in an alkaline medium.

Enhancing conductivity on p-type (Bi,Sb)2Te3 surface by introducing slip trace

Structural modification can effectively tune and optimize the thermoelectric properties of Bi2Te3-based alloys. Herein, we present an innovative and controllable approach to enhance the conductivity of the Bi2Te3-based alloy by introducing slip traces. The effect of slip traces on the conductivity of the Bi2Te3-based alloy was comprehensively investigated using advanced techniques such as Electron Backscatter Diffraction (EBSD) and conductive Atomic Force Microscopy (c-AFM). The results revealed that slip traces were readily formed in (Bi,Sb)2Te3 grains when a load was applied perpendicular to the prismatic plane. The Point Discharge Effect (PDE) was found to promote carriers moving towards the slip traces, leading to the accumulation of positively charged holes. As a result of this process, a higher current intensity was detected at the slip traces. This innovative strategy offers a convenient and effective way to fabricate high-conductivity thermoelectric materials and thus will inspire new technological possibilities for high-performance thermoelectric devices.

Combined influence of airflows and a parallel magnetic field on the discharge characteristics of AC dielectric barrier discharge

The combined influence of airflows and a parallel magnetic field on an AC-driven dielectric barrier discharge plasma is experimentally investigated through image analyses, electrical measurements, and optical diagnoses. After applying a parallel magnetic field, more discharge filaments are generated during one discharge cycle. Besides, the electrical and optical diagnoses show that the magnetic field can increase the plasma parameters, such as the electron temperature and electron density. When airflows and a parallel magnetic field are applied in combination, the discharge uniformity presented in the long-exposure images is significantly enhanced by the airflows and slightly improved by the magnetic field. With increasing airflow velocity, the distribution of discharge filaments goes through four phases, namely, spot-like distribution, line-like distribution, cotton-like distribution, and stripe-like distribution, among which the stripe-like distribution exhibits the highest discharge uniformity. High-speed video analyses reveal that the improved discharge uniformity can be attributed to the changed breakdown positions and the increased number of filaments. Although airflow can significantly improve the macroscopic uniformity of the discharge, it leads to a decrease in the maximum current pulse amplitude, electron temperature, electron density, and gas temperature. Applying a magnetic field in flowing air can not only improve the discharge uniformity but also ensure that the discharge has high maximum current pulse amplitude intensity, electron temperature, and electron density. Based on the analyses of the electron trajectory and the estimation of the force condition of the micro-discharge remnants, the modulated charged particles, reduced electric field, and pre-ionization degree are responsible for the changed discharge uniformity and plasma parameters in the parallel magnetic field and flowing air.

Risk of occurrence of electromagnetic interference from the application of transcutaneous electrical nerve stimulation on the sensing function of implantable defibrillators.

Transcutaneous electrical nerve stimulation (TENS) is an established method for pain relief. But electrical TENS currents are also a source of electromagnetic interference (EMI). Thus, TENS is considered to be contraindicated in implantable cardioverter-defibrillator (ICD) patients. However, data might be outdated due to considerable advances in ICD and cardiac resynchronization therapy (CRT) filtering and noise protection algorithm technologies. The aim of this pilot safety study was to re-evaluate the safety of TENS in patients with modern ICDs. One hundred and seven patients equipped with 55 different models of ICD/CRT with defibrillators from 4 manufacturers underwent a standardized test protocol including TENS at the cervical spine and the thorax, at 2 stimulation modes-high-frequency TENS (80 Hz) and burst-mode TENS (2 Hz). Potential interference monitoring included continuous documentation of ECG Lead II, intracardiac electrograms and the marker channel. Electromagnetic interference was detected in 17 of 107 patients (15.9%). Most frequent were: interpretations as a premature ventricular beats (VS/S) in 15 patients (14%), noise reversion in 5 (4.6%) which resulted in temporary asynchronous pacing in 3 (2.8%), interpretation as ventricular tachycardia/ventricular fibrillation in 2 (1.9%), and premature atrial beat in 2 (1.9%) patients. Electromagnetic interference occurrence was influenced by position (chest, P < 0.01), higher current intensity (P < 0.01), and manufacturer (P = 0.012). Overall, only intermittent and minor EMI were detected. Prior to the use of TENS in patients with ICDs, they should undergo testing under the supervision of a cardiac device specialist.

Miniaturised test-setup for Spark Plasma Sintering – experimental and numerical investigations

ABSTRACT Spark Plasma Sintering (SPS) is an innovative sintering technique, whereby many of the beneficial effects of this process on sintering are still elusive. To allow for the detailed investigations of the SPS process, a custom experimental set-up and a corresponding finite element (FE) model was developed. The miniaturised setup allows for very high current intensities, custom pulse patterns, a wide pressure range and dilatometric measurements. The FE model was employed to calculate the temperature field in the set-up and the sintering specimen itself. A very good correlation of the temperature, current and voltage over the entire process was observed. Our investigations show that the contact conductivities have a significant impact on the process temperature. Also, the imperfect contacts at the interfaces between the graphite foil and the real specimen may lead to a significant variance of the currents necessary to obtain the desired sintering temperature.

Magnetic stimulation of the sciatic nerve using an implantable high-inductance coil with low-intensity current

Objective. Magnetic stimulation using implantable devices may offer a promising alternative to other stimulation methods such as transcranial magnetic stimulation (TMS) or electric stimulation using implantable devices. This alternative may increase the selectivity of stimulation compared to TMS, and eliminate the need to expose tissue to metals in the body, as is required in electric stimulation using implantable devices. However, previous studies of magnetic stimulation of the sciatic nerve used large coils, with a diameter of several tens of mm, and a current intensity in the order of kA. Approach. Since such large coils and high current intensity are not suitable for implantable devices, we investigated the feasibility of using a smaller implantable coil and lower current to elicit neuronal responses. A coil with a diameter of 3 mm and an inductance of 1 mH was used as the implantable stimulator. Main results. Before in vivo experiments, we used 3D computational models to estimate the minimum stimulus intensity required to elicit neuronal responses, resulting in a threshold current above 3.5 A. In in vivo experiments, we observed successful nerve stimulation via compound muscle action potentials elicited in hind-limb muscles when the applied current was above 3.8 A, a significantly reduced current than that used in conventional magnetic stimulation. Significance. We report the feasibility of magnetic stimulation using an implantable millimeter-sized coil and low current of a few amperes to elicit neural responses in peripheral nerves. The proposed method is expected to be an alternative to TMS, with the merit of improved selectivity in stimulation, and to electrical stimulation based on implantable devices, with the merit of avoiding the exposure of conducting metals to neural tissues.

Stimulation-induced respiratory enhancement in corticothalamic regions.

We aimed to identify corticothalamic areas and electrical stimulation paradigms that optimally enhance breathing. Twenty-nine patients with medically intractable epilepsy were prospectively recruited in an epilepsy monitoring unit while undergoing stereoelectroencephalographic evaluation. Direct electrical stimulation in cortical and thalamic regions was carried out using low (<1 Hz) and high (≥10 Hz) frequencies, and low (<5 mA) and high (≥5 mA) current intensities, with pulse width of .1 ms. Electrocardiography, arterial oxygen saturation (SpO2 ), end-tidal carbon dioxide (ETCO2 ), oronasal airflow, and abdominal and thoracic plethysmography were monitored continuously during stimulations. Airflow signal was used to estimate breathing rate, tidal volume, and minute ventilation (MV) changes during stimulation, compared to baseline. Electrical stimulation increased MV in the amygdala, anterior cingulate, anterior insula, temporal pole, and thalamus, with an average increase in MV of 20.8% ± 28.9% (range = 0.2%-165.6%) in 19 patients. MV changes were associated with SpO2 and ETCO2 changes (p < .001). Effects on respiration were parameter and site dependent. Within amygdala, low-frequency stimulation of the medial region produced 78.49% greater MV change (p < .001) compared to high-frequency stimulation. Longer stimulation produced greater MV changes (an increase of 4.47% in MV for every additional 10 s, p = .04). Stimulation of amygdala, anterior cingulate gyrus, anterior insula, temporal pole, and thalamus, using certain stimulation paradigms, enhances respiration. Among tested paradigms, low-frequency, low-intensity, long-duration stimulation of the medial amygdala is the most effective breathing enhancement stimulation strategy. Such approaches may pave the way for the future development of neuromodulatory techniques that aid rescue from seizure-related apnea, potentially as a targeted sudden unexpected death in epilepsy prevention method.

Towards optimizing single pulse electrical stimulation: High current intensity, short pulse width stimulation most effectively elicits evoked potentials

BackgroundWhile single pulse electrical stimulation (SPES) is increasingly used to study effective connectivity, the effects of varying stimulation parameters on the resulting cortico-cortical evoked potentials (CCEPs) have not been systematically explored. ObjectiveWe sought to understand the interacting effects of stimulation pulse width, current intensity, and charge on CCEPs through an extensive testing of this parameter space and analysis of several response metrics. MethodsWe conducted SPES in 11 patients undergoing intracranial EEG monitoring using five combinations of current intensity (1.5, 2.0, 3.0, 5.0, and 7.5 mA) and pulse width at each of three charges (0.750, 1.125, and 1.500 μC/phase) to study how CCEP amplitude, distribution, latency, morphology, and stimulus artifact amplitude vary with each parameter. ResultsStimulations with a greater charge or a greater current intensity and shorter pulse width at a given charge generally resulted in greater CCEP amplitudes and spatial distributions, shorter latencies, and increased waveform correlation. These effects interacted such that stimulations with the lowest charge and highest current intensities resulted in greater response amplitudes and spatial distributions than stimulations with the highest charge and lowest current intensities. Stimulus artifact amplitude increased with charge, but this could be mitigated by using shorter pulse widths. ConclusionsOur results indicate that individual combinations of current intensity and pulse width, in addition to charge, are important determinants of CCEP magnitude, morphology, and spatial extent. Together, these findings suggest that high current intensity, short pulse width stimulations are optimal SPES settings for eliciting strong and consistent responses while minimizing charge.