Interelectrode Spacing Research Articles

Experimental investigation on the performance of a two-stage electrostatic precipitation at corona discharge

In this paper, our attention has been focused on the effect of the presence of dust particles on the characteristics of the corona discharge in an ESP electrostatic precipitator in wires to plate configuration. Different parameters are taken into account, in particular the influence of the polarity, of the source of continuous electric excitation, the number of active electrodes and the dimensions of the particles of the dust. The dust used is recovered in the chimney of a cement plant is sieved to have different particle sizes 80,250 and 500μm. Dust particles pass through the inter-electrode space. By corona effect, there will be an ionization of the gas around the wire, and creation of ions and electrons. The latter bombard the dust that is charged with electricity and are then attracted to the surface of the plates under the effect of the electric field. Dust is deposited on the plate electrodes. A model in the laboratory was used for the measurement of the discharge current and to plot the I-V characteristic as a function of the number of active electrodes in absence and in the presence of different dimensions of the particles of the dust particles.

Ionic wind produced by volume corona discharges and surface dielectric barrier discharges: What role do streamers play?

The present study compares the ionic wind produced by volume DC and AC corona discharges, and by surface dielectric barrier discharges (DBD). On the one hand, in the case of a volume corona discharge ignited between a high-voltage needle and a grounded plate, our measurements highlight that the ionic wind velocity increases in the presence of positive breakdown streamers. On the other hand, in the case of a surface AC DBD, the ionic wind velocity decreases when streamers occur. Why such a difference? The answer is not easy and the debate remains open. However, one answer would be that the streamers occurring in a volume needle-to-plate discharge leave an abundance of positive ions in the inter-electrode space and that these ions drift because of the electric field, just after the streamer propagation. On the other hand, in the case of a surface DBD, the streamers can leave positive ions in their wake but their heads especially deposit positive ions at the location where they stop propagating, i.e. a few millimetres from the electrode (up to about 10–15 mm). Then this positive space charge deposited at a few millimetres from the active electrode edge on the dielectric surface acts as a screen against the electric field due to the applied high voltage, thus preventing the drift of the ions remaining on the surface of the dielectric, close to the electrode edge. Having said that, the reality is that this explanation is certainly very simplistic compared with the very complex phenomena taking place in these two discharges, particularly at the times when the streamers form and propagate.

Local Orientation Transitions to a Lying Helix State in Negative Dielectric Anisotropy Cholesteric Liquid Crystal

Orientation transitions in a cholesteric liquid crystal (CLC) layer with negative dielectric anisotropy, under the influence of a non-uniform spatially periodic electric field created using a planar system of interdigitated electrodes, were studied experimentally and numerically. In the interelectrode space, transitions are observed from a planar Grandjean texture, with the helix axis perpendicular to the layer plane, to states with a lying helix, when the helix axis is parallel to the layer plane and perpendicular to the electrode stripes. It was found that the relaxation time of the induced state in the Grandjean zones, corresponding to two or more half-turns of the helix, significantly exceeded the relaxation time for the first Grandjean zone with one half-turn. An analysis of experimentally observed and numerically simulated textures shows that slow relaxation to the initial state in the second Grandjean zone, as well as in higher-order zones, is associated with the formation of local topologically equivalent states. In these states, the helix has a reduced integer number of helix half-turns throughout the layer thickness or unwound into the planar alignment state.

Research of electrode materials for the creation of multifunctional current sources with increased capacity as a components of the energy sector of an efficient urban environment

As part of creating a comfortable and safe environment, constructing energy-efficient residential and industrial buildings and structures that meet modern requirements and standards, the development of the production of environmentally friendly renewable and new individual energy sources is becoming especially relevant. In this regard, there is a need to increase the energy capacity of electrochemical cells. Research has been carried out on the metallized conductive materials creation based on rolled carbon non-woven material “Busofit” with the sequential application of metal coatings of titanium and silver using ion-plasma sputtering and electric pulse dispersion methods. It has been shown that surface layer metallization of the electrode material with titanium can improve the electrochemical cell characteristics. Additional silver film deposition leads to further cell performance improvement. It has been confirmed that the multilayer structure interfacial resistance between the carbon and the current collector has a significant effect on the conductivity of the electrochemical cell and the stability of its operation. The contact area increase of the electrode with the electrolyte leads to an increase in the rate processes occurring on the electrode surface and in the near-electrode space, which opens up prospects for increasing the energy intensity of the electrochemical system. A significant capacity increase of a water-based capacitor structure is achieved by the formation of a nanostructured dielectric layer of potassium titanate in the interelectrode space. It has been confirmed that the cell voltage cycling helps to stabilize the processes occurring in the surface layer of the electrode material at the interface and determining the range of mechanisms for transmitting electrical energy, which makes it possible to achieve higher energy intensity of the samples. Improvement of technological solutions in the field of ion-plasma technologies and the use of new perspective nanostructured materials creates the prerequisites for the creation of advanced automation and energy supply systems with a higher resource, which expands the possibilities of their use in various construction projects.

The influence of cathodic materials and optimization of the removal of the chromium (VI) from tannery wastewater by electrocoagulation

The present work focuses on the optimization of the removal percentage of Chromium (VI) from a real tannery effluent by electrocoagulation process (EC). The influence of high efficiency cathodic materials (titanium and nickel) was also investigated in this work. The tannery effluent is from the town of Maroua in the Far North Region in Cameroon. The effectiveness of the main operational parameters such as current intensity, initial Cr (VI) concentration, initial pH as well as solution conductivity was examined. All experiments were carried out in an electrocoagulation cell with an effective volume of 400 mL using two electrode combinations as anode/cathode (Al/Ti and Al/Ni). It was found that the Al/Ti combination exhibits higher removal efficiency than Al/Ni under the same operational conditions. Cr (VI) removal efficiencies of 90.93 % and 84.30 % were respectively observed for the Al/Ti and Al/Ni electrodes with an optimal initial pH (pH=6). The maximum current intensity, the maximum initial Cr (VI) concentration as well as the NaCl concentration were 0.4 A, 10 mg/L Cr(VI) and 1.5 g/L respectively. Response surface methodology by the mean of central composite design was performed. The influence of current intensity (100–300 mA), electrolysis time (10–30 min) and interelectrode spacing (1–3 cm), the probability and the mathematical model were highly discussed. According to the experimental design results, the removal of Cr (VI) in the real tannery effluent was up to 99.58 %. For the aforementioned efficiency it requires the optimum values of 211.891 mA, 36.8179 min and 1.609 cm for current intensity, time and the interelectrode spacing, respectively. EC has shown to be easy to operate, to be economic by using cheaper electrodes and efficient for the treatment of real tannery effluent.

Challenges in using Electrocoagulation Process in Removal of Nickel Metal in Wastewater: a Literature Review

In recent years, the surge in nickel production, driven by the growing demand for electric vehicle batteries, has raised concerns regarding environmental consequences. The nickel mining and processing industries contribute to increased nickel levels in wastewater, presenting a serious threat to aquatic ecosystems and human health. This article emphasizes the urgency of developing effective technologies for treating nickel-contaminated wastewater. Electrocoagulation emerges as a promising method, providing high efficiency, minimal sludge production, and cost-effectiveness. The article critically and systematically reviews the potential of the electrocoagulation process in nickel removal from wastewater. In the review, we identify and analyze nearly 32 studies published from 2013 to 2023. We discuss contaminant removal mechanisms and analyze trends in the use of operational parameters. This article identifies the most commonly applied conditions: aluminum electrodes, inter-electrode spacing ≥ 1 cm, current density ≤ 10 mA/cm², initial pH 6 ≤ pH < 11, electrolysis time < 60 min, batch operation, and initial nickel concentration > 50 mg/L. This comprehensive review serves as a foundational resource for advancing electrocoagulation technology in the removal of heavy metals from nickel wastewater.

Discharge and mass transfer characteristics of atmospheric pressure gas-solid two-phase gliding arc

In this work, a gas-solid two-phase gliding arc discharge (GS-GAD) reactor was built. Gliding arc was formed in the gap between the blade electrodes, and solid powder was deposited on the sieve plate positioned beneath the blade electrodes. A range of experimental parameters, including the inter-electrode spacing, gas flow rate, applied voltage, and the type of the powder, were systematically varied to elucidate the influence of solid powder matter on the dynamics of gliding arc discharge (GAD). The discharge images were captured by ICCD and digital camera to investigate the mass transfer characteristics of GS-GAD, and the electrical parameters, such as the effective values of voltage, current, and discharge power were record to reveal the discharge characteristics of GS-GAD. The results demonstrate that powder undergoes spontaneous movement towards the upper region of the gliding arc due to the influence of electric field force. Increasing the discharge voltage, decreasing relative dielectric constant of the powder and reducing the electrode-to-sieve-plate distance all contribute to a greater involvement of powder in the GAD process, subsequently resulting in an enhanced powder concentration within the GAD region. Additionally, powder located beneath the gliding arc experiences downward resistance caused by the opposing gas flow and arc. Excessive gas flow rate notably hampers the powder concentration within the discharge region, and the velocity of powder motion in the upper part of the GAD region is reduced. Under the condition of electrode-to-sieve-plate distance of 30 mm, gas flow rate of 1.5 L/min, and peak-to-peak voltage of 31 kV, the best combination of arc gliding and powder spark discharge phenomena can be achieved with the addition of Al2O3 powder.

Advancing water disinfection strategies: assessing disinfection efficiency with a Bayesian Regularized artificial neural network model

ABSTRACT It is important to find the estimation methodology with the highest accuracy in order to determine the parameters of water disinfection and to provide the most ideal disinfection. In this study, the usability of artificial neural networks in predicting response disinfection efficiency in electrochemical water disinfection processes was investigated. An artificial neural network model was developed using a total of 17 data sets and Response Disinfection Efficiency values were estimated from the model. Current density, treatment time and interelectrode spacing values are defined as input parameters in the network model, which has a multilayer perceptron architecture with 10 neurons in its hidden layer. The coefficient of determination value for the developed model was 0.98682 and the average deviation rate was −0.1%. The study findings showed that neural networks are an ideal tool that can be used to predict response disinfection efficiency in electrochemical water disinfection processes.

Feasibility and sludge analysis of electrocoagulation process for Direct Violet-35 dye remediation

The present study investigates Direct Violet-35 (DV-35) remediation using electrocoagulation process. DV-35 which is an industrial azo dye, after release significantly affects the visual appearance of water bodies and hinders the process of photosynthesis affecting plant growth. Perturbing the food chain, it promotes toxicity, mutagenicity, and carcinogenicity. Therefore, dye remediation is essential before discharge into water streams. To determine the effectiveness of the electrocoagulation process for DV-35 dye remediation, and understand the influence of parameters like current density, inter-electrode spacing, concentration of electrolyte, pH, agitation speed, and initial dye concentration, a detailed study was carried out. Maximum removal efficiency (>98 %) was achieved in 16 min at 263.15 A/m2 current density and pH 7.2 for DV-35 concentration of 50 to 500 mg/L. Further, optimized parameters were applied to real textile effluent achieving 99.8 % efficiency. EC mechanism was corroborated by Sips isotherm matching adequately with experimental results. The findings also demonstrated a heterogeneous surface of the produced EC flocs. Pseudo-second-order was obtained with a low operating cost of 0.0018 US $/m3. The DV-35 removal and functional groups were confirmed by UV/VIS and Fourier transforms infrared spectroscopy analysis. The sludge was examined by X-ray Diffraction and Scanning Electron Microscope revealing Crystalline aluminum oxides i.e. bayerite (Al(OH)3) and diaspore (AlO(OH)). The conclusion of the results revealed EC to be an effective and economical technique for DV-35 remediation from textile wastewater.

Optical Monitoring of Water Side Permeation in Thin Film Encapsulation.

The stability of long-term microfabricated implants is hindered by the presence of multiple water diffusion paths within artificially patterned thin-film encapsulations. Side permeation, defined as infiltration of molecules through the lateral surface of the thin structure, becomes increasingly critical with the trend of developing high-density and miniaturized neural electrodes. However, current permeability measurement methods do not account for side permeation accurately nor quantitatively. Here, a novel optical, magnesium (Mg)-based method is proposed to quantify the side water transmission rate (SWTR) through thin film encapsulation and validate the approach using micrometric polyimide (PI) and polyimide-silicon carbide (PI-SiC) multilayers. Through computed digital grayscale images collected with corroding Mg film microcells coated with the thin encapsulation, side and surface WTRs are quantified. A 4.5-fold ratio between side and surface permeation is observed, highlighting the crucial role of the PI-PI interface in lateral diffusion. Universal guidelines for the design of flexible, hermetic neural interfaces are proposed. Increasing encapsulation's width (interelectrode spacing), creating stronger interfacial interactions, and integrating high-barrier interlayers such as SiC significantly enhance the lateral hermeticity.

Lead performance of stylet-driven leads in left bundle branch area pacing: Results from a large single-center cohort and insights from in vitro bench testing

BackgroundLeft bundle branch area pacing (LBBAP) requires deep septal lead deployment for left-sided conduction stimulation. Advancing leads toward deep septal positions might add mechanical stress on these leads. Concerns about lead performance and reliability remain an unanswered question. ObjectiveThe purpose of this study was to analyze lead performance and integrity of stylet-driven pacing leads (SDLs) for LBBAP. MethodsThis study assessed lead fracture rates of SDL in a large single-center cohort of adult LBBAP patients. Fluoroscopic analysis of lead bending angulations at the septal insertion point and in vitro bench testing of lead preconditioning were performed to simulate clinical use conditions. Lead performance was compared between LBBAP and conventional right ventricular apical pacing (RVp) sites. ResultsThe study included 325 LBBAP patients (66% male; age 71±15 years). During median follow-up of 18 months, 2 patients (0.6%) experienced conductor fracture between tip housing and ring electrode, whereas no such fractures occurred with RVp patients (n = 149; P = .22). X-ray analysis revealed that high lead bending angulations occurred in 1.3% of the patients. Accelerated bench testing of excessive preconditioned leads showcased a higher probability of early conductor fracture compared to standard preconditioned leads. ConclusionThe incidence of early conductor failure in LBBAP seems higher than with conventional RVp sites. The most vulnerable lead part seems to be the interelectrode space between the tip housing and ring electrode. Excessive angulation and preconditioning might contribute to early fatigue fracture.

Estimation of Geotechnical Parameters for Coal Exploration from Quasi-3D Electrical Resistivity Measurements

Geotechnical parameters are crucial for mine planning and operation at different stages of development. However, estimating these parameters requires a large number of boreholes and subsequent detailed analysis of the samples, making it a cumbersome exercise. Moreover, even after conducting these studies, it is not possible to cover the entire operational area. To address this issue, this study presents an indirect method of estimating geotechnical parameters through mathematical relations using resistivity data. The present study incorporated 2D and 3D subsurface imaging techniques for exploring coal reserves and analyzing geotechnical parameters that define subsurface soil properties. Electrical resistivity tomography (ERT) was utilized for data acquisition, employing a Dipole–dipole array with a multielectrode ABEM Terrameter LS instrument. Six parallel profiles were conducted, each 400 m in length, with an inter-electrode spacing of 10 m and a spacing of 50 m between profiles. These profiles were combined into a 3D dataset referred to as quasi-3D ERT. The inversion process for both 2D and 3D data was performed using the Res2dinv and Res3dinv programs, respectively. This study overcame the challenges of 2D resistivity sections by evaluating horizontal depth slices in the x-z plane from layers 1 to 10, reaching a depth of 81.2 m. The geotechnical parameters, including cohesion, friction angle, moisture content, and plastic index, were derived from the resistivity data. The ERT method proved to be cost-effective and efficient in determining soil properties over a large area compared with traditional laboratory analysis of borehole samples. Additionally, the variation of geotechnical parameters with resistivity values exhibited unique characteristics. The results from both the 2D and quasi-3D ERT were well correlated with the borehole data. Such studies are valuable for resource exploration and mine planning purposes.

Combination of Electro- and Radiochemical Processes for Hydrogen and Oxygen Obtaining

It is shown that increase in the hydrogen production process efficiency can be ensured by integrating radiochemical and electrochemical processes. In this case, the obtained effect depends not only on the direct radiolysis of water, but also on the involvement of the ionizing radiation energy in the electrolysis process for the excitation of water molecules that undergo electrolysis, which leads to a decrease in the consumption of electricity for the decomposition of its gaseous components. An analysis of the main factors influencing the reduction of electricity consumption during electrolysis is presented, and the affinity of the spectra of radical ions involved in the radiation and electrochemical processes of water decomposition is shown. As a result of radiation exposure, the most energy-intensive stage of water decomposition, associated with the breaking of intermolecular bonds and the formation of active particles involved in the electrochemical process, begins. It was established that the formation of hydrogen increases due to the addition of its direct output during radiolysis and indirect production during electrolysis, initiated by the activation effects caused by ionizing radiation. It is shown that in order to increase the direct radiolytic yield of hydrogen, elements containing nanosized zirconium dioxide powder should be placed in the interelectrode space of the electrolyzer. It has also been proven that the irradiation of zirconium dioxide placed in water leads to a 4-fold increase in the yield of hydrogen compared to the option of irradiating pure water. To increase the energy potential utilization coefficient of nuclear fuel at NPPs, it is expedient to use the energy of fuel elements located in spent nuclear fuel storage pools for the application of the proposed technology. This will ensure the utilization of the ionizing radiation energy, which in existing technologies is irretrievably lost, because it is discharged in the form of low-temperature thermal emissions into the environment, which leads to thermal pollution of the atmosphere.

Picosecond ultraviolet laser patterned in-plane asymmetric micro-supercapacitors with high-precision capacity matching

Extensive exploratory research on in-plane asymmetric micro-supercapacitors (AMSCs) involves developing various fabrication techniques for in-plane electrodes to streamline the manufacturing process and expanding the operating voltage window (OVW) to increase energy density. Herein, we prepare MXene (Ti3C2Tx) and laser-induced graphene (LIG) electrodes using picosecond ultraviolet laser etching and laser direct writing, respectively, to construct in-plane MXene//LIG AMSCs. The high precision of laser technology guarantees the preparation of in-plane asymmetric electrodes with an interelectrode spacing of 100 μm. Additionally, we adjust the electrode width ratio of the positive and negative electrodes to attain high-precision capacity matching. This capacity matching method not only broadens OVW to 1.2 V, but also increases the energy density up to 1.9 times. The picosecond laser patterning construction approach and the capacity matching method in this work provide new perspectives for in-plane asymmetric supercapacitors.

Effect of electrode configuration on minichannel heat sink with EHD vortex generators

A numerical study has been performed to understand the effects of electrode spacing on thermo-hydraulic performance in a minichannel assisted with electrohydrodynamics (EHD) based active vortex generation. A minichannel design with alternate high voltage and grounded electrodes flushed to the walls of the channel is considered. Multiple cases with different combinations of electrode length and spacing (pitch) at Reynolds number varying from 200 to 1000 are investigated. The numerical framework consisting of the two-way coupled governing equations for flow, thermal, charge, and electric potential fields is developed in the open-source finite-volume framework of OpenFOAM®. Applying an electric field induces the Onsager–Wien effect, producing flow vortices from electrode pairs. The EHD vortices disrupt the inherent laminar flow structure in the minichannel. The flow morphology is characterized by alternate vortex and shear dominant zones near the top and bottom walls. The EHD vortex dominant zones near the channel wall disrupt the laminar boundary layers. Thus, fluid mixing and heat transfer in the minichannel are enhanced. Electrode size and spacing influence the electric field distribution in the flow domain. As a result, electrode length and the inter-electrode spacing notably influenced the flow structure and the resulting heat transfer in the minichannel. The electrode spacing or the pitch decides the number of electrode pairs in the minichannel. An increase in pitch leads to fewer electrode pairs; thus, the electric field intensity is weak. Hence, EHD vortices in configurations with wider electrode spacing are weaker in strength. Longer electrodes produced stronger electric fields due to increased charge accumulation. Therefore, EHD vortices generated by longer electrodes are prominent and influential. The influence of EHD vortices on flow disruption and heat transfer is significant at lower Reynolds numbers. Cases with smaller electrodes perform well at higher Reynolds numbers, whereas usage of bigger electrodes exhibits higher performance at lower Reynolds numbers. Within the parameter space of this study, a minimum of 38.1% and a maximum of 60.6% enhancement in heat transfer is observed. A maximum performance factor of 1.46 is obtained in the present study using an electric current of 30μA with an electric power consumption of 30.1mW, which are notably low. Thus, the results of the present study exhibit that EHD vortex generation using the Onsager–Wien effect is a viable and economical option for thermo-hydraulic performance enhancement in a minichannel. Insights provided in the present study will be helpful to engineers and researchers in designing minichannel heat sinks with EHD-based performance improvement.

Selective Patterned Growth of ZnO Nanoneedle Arrays

Abstract Nanostructured coatings are widely used to improve the sensitivity of various types of sensors by increasing the active surface area compared to smooth films. However, for certain applications (in some cases), it may be necessary to achieve selectivity in the coating process to ensure that nanostructures only form in specific areas leaving interelectrode spaces free of nanostructures. This article discusses several methods for creating intricate ZnO nanostructured patterns, including area selective application of Zn acetate seeds followed by hydrothermal growth, selective thermal decomposition of zinc acetate via laser irradiation followed by hydrothermal growth, and the electrochemical deposition method. These methods enable ZnO nanostructures to grow onto designated surface areas with customised, patterned shapes, and they are rapid, cost-effective, and environmentally benign. The article examines the process of producing a nanostructured coating with a complex shape and discusses several factors that can impact the quality of the final product. These include the influence of the thermocapillary flows and the “coffee stain” effect on the deposition of a seed layer of zinc oxide from an ethanol solution of zinc acetate. Additionally, the study found that using a protective screen during the growth of nanostructures can reduce the occurrence of unintended parasitic structures in areas lacking a seed layer. Overall, the article presents various techniques and strategies to improve the quality of nanostructured coatings. We have proven that the use of laser radiation to create a seed layer does not impact the final morphology of the resulting nanostructures. However, when combined with computer-controlled technology, this approach allows for the creation of intricate patterns made up of micrometre-sized lines which cannot be achieved by using other methods. The article also demonstrates an electrochemical technique for obtaining zinc oxide nano-structures that can selectively coat metal electrodes without requiring a seed layer.

Comparison of additional ablation of spatio-temporal dispersion electrograms and low voltage area beyond pulmonary vein isolation in patients with persistent atrial fibrillation

Abstract Backgrounds Although strategies beyond extensive pulmonary vein isolation (EPVI) including low voltage zone (LVZ) ablation in patients with persistent atrial fibrillation (AF) have not yet been established, recent research showed that ablation targeting spatio-temporal dispersion electrograms (STDE) could achieve high AF-free survival. We hypothesized that EPVI plus STDE approach could reduce AF recurrence after catheter ablation of persistent AF. Purpose The purpose of this study is to assess the AF recurrence after the ablation in different two strategies. Methods We prospectively enrolled consecutive patients with persistent AF undergoing their first catheter ablation at our institution during July 2018 to March 2021. The ablation strategy was divided into 2 groups: 1) EPVI plus LVZ and 2) EPVI plus STDE ablation. STDE was defined as clusters of fractionated electrograms that displayed interelectrode time and space dispersion at a minimum of three adjacent bipolar electrodes such that activation spread over all the cycle length of AF. The definition of LVZ was bipolar amplitude of <0.5mV. Posterior wall isolation was performed if STDE or LVZ were broadly present in posterior wall. The primary endpoint was defined as AF recurrence after the ablation. The blanking period of 3 months was applied. Results Out of 138 patients (66±11 years, 108 men), 64 patients underwent EPVI plus LVZ and 74 EPVI plus STDE ablation. There was no difference in median AF duration (8 [interquartile range (IQR) 4-13] months vs. 12 [IQR 5-22] months; p=0.129) and left atrial volume (151 [IQR 115-168] ml vs. 151 [IQR 127-175] ml; p=0.239) between the two groups. The prevalence of concomitant hypertension (47% vs. 67%; p=0.024) and diabetes mellitus (24% vs. 42%; p=0.027) was lower in the STDE group than in the LVZ group. Posterior wall isolation was performed more frequently in the STDE group than in the LVZ group (38% vs. 19%; p=0.015). At 1 year follow-up, the STDE group achieved higher AF-free rate than the LVZ group (84% [95% confidence interval (CI), 73-91%] vs. 64% [95% CI 52-76%]; P=0.017). Multivariate Cox regression analysis demonstrated that not only AF duration (hazard ratio [HR] 1.03, 95% CI 1.01–1.04; p<0.001), and left atrial volume (HR 1.10, 95% CI 1.02–1.19; p=0.011) but also STDE ablation (HR 0.33, 95% CI 0.14-0.77%, p=0.010) were independently associated with AF recurrence. Conclusions Ablation guided by STDE in addition to EPVI may be a useful treatment strategy for persistent AF.

Abstract 16302: Beyond the Veins: A Critical Right Atrial Termination Site in High Burden Paroxysmal Atrial Fibrillation Identified Using Spatiotemporal Dispersion After Failure of High Quality Pulmonary Vein Isolation

Case Presentation: A 55 year-old female with two-year history of persistent atrial fibrillation (AF) presented for elective catheter ablation. Her smart watch recorded frequent prolonged episodes of AF, and event monitoring confirmed 71% AF burden. Metoprolol improved her symptoms only slightly. At the beginning of the procedure, patient’s rhythm was on sinus (NSR). During the completion of pulmonary vein isolation (PVI), the patient developed typical flutter, which degenerated into AF during ablation. Biatrial dispersion mapping in the right atrium (RA) revealed a single highly dispersed area in the posterior RA. Ablation at this site immediately terminated AF to NSR. The patient was non-inducible and remains free of AF. Discussion: Maintenance of NSR in AF is associated with improved clinical outcomes and quality of life. Catheter ablation has the highest efficacy for minimizing AF burden. PVI has a success rate of 67-89% in treating patients with paroxysmal AF and PVI alone is typically employed. A dispersion area is characterized by local clusters of electrograms which may or may not be fractionated, and display interelectrode time and space dispersion such that activation is spread over the entire AF cycle length. Identification and ablation of dispersion regions in persistent AF has demonstrated a high acute termination rate and improved outcomes in early follow-up, but is difficult to reproduce (Seitz et al. 2017). Here, we present a case of a patient with high burden paroxysmal AF who underwent PVI but remained in AF. Using visual dispersion mapping, we were able to identify a critical RA dispersion area, which rendered patient non-inducible (Figure 1).

Effect of geometric parameters of electrodes on skin heating for the design of non-ablative radiofrequency device.

Non-ablative radiofrequency (RF) has been widely used in clinical and at-home cosmetics devices. RF electrode geometry can influence the heat distribution in the tissue. This study analyzes the influence of geometric parameters of the electrode on the heat distribution in the layered tissue. The finite element simulation of the electrothermal coupling field was performed to obtain the three-dimensional (3D) temperature distribution of the four-layer tissue. The electrode geometric parameters including the inter-electrode spacing (5-12mm), width (1-3mm), length (3-10mm), shapes (bar, dot and circle), and the coupling gel's electrical conductivity (0.2-1.5 S/m) were simulated. The maximum temperature at 2mm depth (T-2mm ) and the temperature difference (Tdiff ) between the maximum skin surface temperature and T-2mm were obtained to evaluate the effectiveness and safety. The effect of geometric parameters on the effectiveness and safety was mixed. The maximum T-2mm occurred with the 5mm inter-electrode spacing, 3mm width, 10mm length, the circle-shaped electrode, and the 1.5 S/m coupling gel's electrical conductivity. The ratio of inter-electrode spacing to width at around four can achieve rapid temperature rise and skin surface temperature protection. The electrode shape influenced the area of temperature rise in the tissue's cross-section. The coupling gel's electrical conductivity should be close to that of the skin to avoid energy accumulation on the skin surface. The electrode's geometric parameters affect the effectiveness and safety of the RF product. This study has provided the simulation procedure for the electrode design.

Modelling the impact of inter-electrode spacing on nitrate removal using Response Surface Methodology (RSM)

Nitrate contamination in water poses a significant concern for environmental engineers, as it has substantial and direct impacts on water quality, the economy, and public health. Consequently, managing nitrate levels in water sources ranks among the top priorities for water authorities. Currently, various treatment methods, including biological treatments and adsorption, are employed to eliminate nitrate from water or wastewater. A substantial body of literature exists focused on the application of electrocoagulation (EC) for nitrate removal from solutions. This method is favoured for its environmentally friendly attributes and ability to swiftly and cost-effectively remove pollutants. In this study, the EC method was employed to eliminate nitrate from water under varying inter-electrode spacing (I-ES) conditions ranging from 4 to 10 mm and different treatment durations (TD) spanning 5 to 55 minutes. The effects of I-ES and TD on nitrate removal were optimised using Response Surface Methodology (RSM). The study's results demonstrated that the most effective nitrate removal, reaching 91.3%, occurred at an I-ES of 4 mm and a TD of 50 minutes. The agreement between the experimentally observed and predicted removal rates was notably high, with an R<sup>2</sup> value of 0.973.