Low Voltage Research Articles

Vector field heterogeneity as a novel omnipolar mapping metric for functional substrate characterization in scar-related ventricular tachycardias

Abstract Background Identification of functionally critical sites to target for ablation in scar-related VT during substrate mapping remains challenging. Vector Field Heterogeneity (VFH) is a novel omnipolar metric to quantify locally heterogeneous propagation patterns. Objective Assess the diagnostic value of VFH for characterizing abnormal propagation patterns during ventricular substrate mapping and compare between sites of VT isthmus, low voltage bystander areas (LVA) and normal voltage areas (NVA). Methods High-density substrate maps and VT activation maps acquired with a 16-pole grid catheter in patients with scar-related VT were retrospectively reviewed. Based on the VT activation maps with either entrainment and/or VT termination with RF ablation to confirm critical sites, the correlating substrate maps were segmented into sites corresponding to isthmus-site, LVA (omnipolar voltage <1.5mV) and NVA (>1.5mV). To compute the VFH, contact mapping data including all EGMs of each grid-catheter acquisition (16 unipols) was exported and processed offline. From each of the 4×4 electrode array acquisitions, omnipolar-derived vector maps of the directions of electrical propagation for recorded sites were estimated using an orientation-independent cross-clique configuration of 4 adjacent unipols, respectively, resulting in 9 vectors with a spatial resolution of 1.4mm2 each. The angle between each vector and horizontal bipole was assessed and compared between neighbouring vectors using finite differences to derive a VFH value per 2x2 EGM clique as a quantitative metric of local heterogeneity ranging from 0 (perfect planar wave) to 1 (maximal disorganisation - "chaos"). The VFH metric was estimated for each segment of the substrate map and compared against each other. Results Nine patients with scar related VT were included (100% male, age 62±20y, ischemic 66.7%, LVEF 36±16%). On average 3.5 VTs (1-8) were induced per case. Avg. substrate map point count was 3825±3190. Computed median VFH metric at sites corresponding to VT isthmus was 0.58±0.30, LVA bystander 0.47±0.39, NVA sites 0.20±0.34. VFH at isthmus-sites was statistically significant higher (i.e. more disorganised) than at LVA bystander sites (p<0.01). VFH in NVA was significantly lower (i.e. more organised) compared to isthmus and LVA sites (p<0.01, respectively). Median omnipolar voltage at isthmus sites was 0.16±0.27mV compared to LVA bystander 0.22±0.36mV (p=0.0816) and NVA 2.97±3.38mV (p<0.01). Conclusion VFH is a promising novel omnipolar mapping metric for electrical substrate characterisation in scar related VTs. VFH mapping identified a quantifiable and significant increase in electrical heterogeneity at sites corresponding to the critical isthmus compared to LVA bystander and normal voltage sites. VFH may provide new insights in the arrhythmogenicity of scar tissue and support more specific functional mapping strategies to identify targets for ablation without the need to induce VT.

Long-term prognosis in patients undergoing atrial fibrillation ablation

Abstract Aims The aim of the analysis was to assess the risk of atrial fibrillation (AF) recurrence in the long-term observation of contemporary patients undergoing pulmonary vein isolation (PVI), who did not have recurrence during the first year after catheter ablation. Methods Retrospective analysis has been performed. Inclusion criteria: (1) the patients undergoing their first PVI in years 2017–2022, (2) the electroanatomical system, contact force catheters and lesion indexes (Ablation Index or Lesion Size Index) were used, (3) no recurrences were observed during the first 12 months of follow-up, and (4) follow-up longer than 12 months was available. Demographic, clinical and echocardiographic data were collected. Follow-up was based on ambulatory visits with ECG/holter monitoring or implanted device interrogation, when available. Results A total of 247 patients were included. The median follow-up was 22 months (interquartile range, 16–31 months). After 24 months, ablation efficacy was 84%, and after 36 months, it was 72%. In the univariate Cox regression analysis, age, previous electrical cardioversion, glomerular filtration rate (eGFR) and the presence of coronary artery disease were linked to AF-free survival. Interestingly, nonparoxysmal AF, left atrial (LA) dimension, heart failure, hypertension or diabetes were not linked to the risk of long-term recurrences. In multivariate Cox regression analysis, presence of coronary artery disease and previous electrical cardioversion were independently linked to the risk of long-term recurrence. In 127 (51.4%) patients, information about the presence of low voltage areas (LVA) was available, and in 21 (16.5%) patients in this group, the presence of LVA was found. Survival of patients with LVA was strikingly worse than that of those without (Figure 1), log-rank test p <0.0001. Conclusions Patients who had no recurrences within one year after PVI, still have substantial risk of recurrence in the next 2 years. That concerns specially the patients who had LVA in the electroanatomical mapping.

The prevalence and prognostic impact of low voltage zone in patients with cardiomyopathy after catheter ablation for atrial fibrillation

Abstract Background The low voltage zone (LVZ) in left atrium (LA) was observed in 20-30% of patients undergoing catheter ablation of atrial fibrillation (AF). Furthermore, LVZ was associated with not only AF recurrence but also prognosis. However, the prevalence and prognostic impact of LVZ in patients diagnosed with cardiomyopathy remained unclear. Purpose In this study, we focused on the patients with cardiomyopathy after AF ablation and investigated the prevalence and prognostic impact of LVZ after AF ablation. Methods This study is a single-center retrospective observational study. We enrolled 125 patients diagnosed with cardiomyopathy. All patients underwent voltage mapping after pulmonary vein isolation. LVZ was defined as regions where bipolar peak-to-peak voltage was <0.5mV. We set 5 cm² as the cutoff of the presence of LVZ. The etiology of cardiomyopathy was divided into arrhythmia-induced cardiomyopathy (AICM) and non-AICM consisting of idiopathic dilated cardiomyopathy (iDCM), hypertrophic cardiomyopathy (HCM), ischemic cardiomyopathy (ICM), transthyretin amyloidosis wild type (ATTRwt) and others (1 Fabry disease, 1 cardiac sarcoidosis, 1 restrictive cardiomyopathy). AICM was defined as patient whose LVEF was recovered above 50% after maintenance of sinus rhythm. We investigated the proportion of LVZ by etiology, and the association between LVZ and the composite endpoint consisting of all cause death, heart failure hospitalization, ventricular assisting device implantation, ventricular arrhythmia and stroke. Results Out of 125 patients [age 68 (58-73), female 32 (25%), LVEF 34.0 (25-43)], 51 (41%) had LVZ. Sixty-four patients were AICM etiology (LVEF pre to post: 30.7±10.7% to 61.1±6.7% ) and 61 was Non-AICM etiology (LVEF: 40.7 ± 18.1 to 44.7±15.7, P=0.0062). The presence of LVZ was lower in AICM than in non-AICM group (20.3% vs. 62.3%, P<0.0001). The etiology of non-AICM was consisting of 26 iDCM, 18 HCM, 7 ICM, 7 ATRRwt and 3 other etiology. The prevalence of LVZ was lower in AICM than in non-AICM (20.3 vs. 62.3%, P<0.0001). Detail is shown in Figure 1. Next, the incidence of composite endpoint was higher in patients with LVZ than in those without (HR 4.6, 95%CI 2.1-10.0, P=0.0001) (Figure 2A). Among 4 groups stratified by AICM/non-AICM and with/without LVZ, there was significant difference in the incidence of the composite endpoint (Figure 2B, P<0.0001). After adjusted with age, gender, Non-AICM, LVZ, LVZ tended to have association with composite endpoint (2.21, 0.87-5.65, P=0.097) and Non-AICM showed strong association (5.58, 1.55-20.12, P=0.0086). LVZ was associated with HF hospitalization (4.35, 1.21-15.61, P=0.024). Conclusions The prevalence of LVZ was 60% in Non-AICM, while it was 20% in AICM. LVZ tended to be associated with poor prognosis of cardiomyopathy after AF ablation. LVZ was associated with HF hospitalization in patients with cardiomyopathy. LVZ might be the marker for poor prognosis in cardiomyopathy cohort.

Discordance between left atrial volume and scar burden in patients with atrial fibrillation and its impact on atrial fibrillation recurrence after catheter ablation

Abstract Background Large left atrial (LA) volume and a high burden of LA low voltage zone (LVZ) are associated with atrial fibrillation (AF) recurrence after AF catheter ablation. There is a scarcity of information on the association between LA volume and LVZ and its impact on the risk of AF recurrence. Purpose To investigate the relationship between the LA volume and LVZ, as well as how these factors contribute to the recurrence of atrial fibrillation (AF). Methods From Nov 2021 to Oct 2023, drug-refractory AF patients who underwent AF catheter ablation were included. LA volume was assessed using the LA volume index (LAVI) using echocardiography. The LVZ was evaluated by conducting high-density electroanatomical mapping using a multipolar catheter. The cut-off value associated with AF recurrence was 48ml/m2 in LAVI and 4.5% in scar burden. Patients were categorised into four groups according to the LAVI and scar burden: Group 1 (Low LVZ and small LA), group 2 (Low LVZ and large LA), group 3 (High LVZ and small LA), and group 4 (High LVZ and large LA). Results A total of 170 patients were included (mean age 62± 9 years, 82% of men, 68.2% of non-paroxysmal AF and 81 [48%] in group 1; 32 [19%] in group 2, 27 [16%] in group 3, 30 [17%] in group 4, respectively). Among total, mean follow-up duration was 266.5 ± 174.4 days, and 8.8% of patients received additional LA ablation beyond pulmonary vein isolation. Among the four groups, group 2 and 4 were significantly associated with higher risks of AF recurrence compared to group 1 (HR 2.36 [1.04-5.34], p=0.039; 3.56 [1.59-7.95], p=0.002, respectively). The risk of AF recurrence was highest in group 4, followed by group 2 (log-rank P=0.002). Comparing group 2 and 3, AF recurrence occurred predominantly within 6-month after catheter ablation in group 2, while after 1-year in group 3 (log-rank P=0.83). Conclusion About one-third of patients showed discordance between the LAVI and LVZ, which are both independent predictors for AF recurrence. A substantial LA volume seems to contribute to early AF recurrence, whereas a high scar burden appears to affect late AF recurrence.

Unipolar electroanatomical mapping outperforms bipolar voltage in detecting LGE areas in the left atrium

Abstract Introduction In atrial fibrillation (AF) management, understanding left atrial substrate is crucial. While both electroanatomical mapping (EAM) and late gadolinium enhancement MRI (LGE MRI) are reliable methods in assessing atrial substrate and are associated with the ablation outcome, recent findings have highlighted significant discrepancies between bipolar low voltage areas (LVA) in EAM and LGE areas. Objective Explore the relationship between LGE areas and unipolar LVAs by utilizing multipolar high-density (HD) mapping. Methods Nineteen patients scheduled for AF ablation underwent pre-ablation LGE-MRI. Left atrial (LA) segmentation was conducted using a convolutional neural network, which subsequently generated a 3D mesh integrating the LGE data. HD-EAM was performed in sinus rhythm for each patient, capturing at least 4000 points. The EAM map and LGE MRI mesh were co-registered. LVA areas were defined using voltage cut-offs of 0.5 mV for bipolar and 2.5 mV for unipolar measurements. Correspondence between LGE areas and LVAs on the anterior and posterior LA wall was analyzed. Results Both bipolar and unipolar LVA demonstrated high precision in detecting LGE areas (100% and 88% respectively). However, unipolar LVA exhibited a remarkable accuracy of 81% for detecting LGE areas specifically, whereas bipolar LVA displayed a significantly lower accuracy of 28%. These findings were consistent across the different atrial walls. Conclusion Incorporating unipolar voltage data into electroanatomical mapping in the atrium may bridge the observed gap between LGE areas and bipolar LVAs. Our findings highlight the significance of unipolar voltage in evaluating the left atrial substrate, potentially offering a more comprehensive insight into the different layers of atrial walls, and opening the door for new approaches in AF therapy.

Novel approach of slow pathway ablation in common atrioventricular nodal reentrant tachycardia by peak frequency map

Abstract Background It is difficult to visualize slow pathway in atrioventricular nodal reentrant tachycardia (AVNRT) even with recent high-density mapping. This could be because the slow pathway potential is buried by the potential of atrial working cells during sinus rhythm and tachycardia. In other words, it is extremely difficult for conventional 3D mapping systems to annotate slow pathway potential even though the histological run of slow pathway is known .[1], [2] Purpose The purpose of this study is to visualize the atrial myocardial junction of rightward inferior extension by the peak frequency map of Ensite X in common AVNRT and to evaluate whether relative high frequency (HF) sites in low voltage area extending from Koch's triangle to tricuspid annulus (TA) is effective targets of slow pathway ablation and the characteristics of junctional rhythm (JR) after radiofrequency application. Methods This study is single-center prospective cohort study. In 37 consecutive common AVNRT patients, novel approach and conventional approach of slow pathway ablation were performed in 17 and 20 patients, respectively. The conventional approach is anatomical and electrophysiological approach. Peak frequency map was performed during sinus rhythm with HD-grid catheter in novel approach patients. A frequency scanning is performed to locate relative HF sites on the tricuspid annulus. Radiofrequencey application is 30 W, 30-60 sec, and the end point was no inducibility or until one echo under load of isoproterenol. Results The success rate was 100 % with two approaches. The relative HF sites in low voltage area were distributed at the TA side from 4 to 5 o'clock in all novel approach patients, mean peak frequency in success site was 419 ± 87 Hz. The distance to His bundle from success site was farther (24.8 ± 4.9 vs. 12.8 ± 4.4 mm, p<0.001), JR was slower (93 ± 14 vs. 118 ± 10 bpm, p=0.013), time to JR occurrence was shorter (3.0 ± 1.3 vs. 7.6 ± 4.6 sec, p=0.003), and elimination rate of jump up (78 % vs. 40 %, p=0.06) was higher in novel approach. Conclusions The relative HF sites in low voltage area at TA side from 4 to 5 o'clock by peak frequency map could be novel target of slow pathway ablation with high success rate and sufficient safety and efficiency.peak frequency map

Vector Field Heterogeneity (VFH) as a novel quantitative marker of electrical disarray in Arrhythmogenic CardioMyopathy (ACM) with ventricular tachycardia

Abstract Background ACM is a hereditary condition characterized by fibrofatty infiltration and replacement of cardiac myocytes predominantly presenting with ventricular arrhythmias (VA). Cardiac imaging allows for detailed structural phenotyping of scar patterns in ACM. Yet, there is a lack of tools to objectively quantify the electrical substrate alterations that may enable a more precise identification of critical sites that predispose to VA. Purpose To quantify locally disorganized cardiac electrical propagation wavefronts using the Vector Field Heterogeneity (VFH) metric from high-density multi-electrodes in patients with ACM with VT and compare to healthy controls. Methods High density epicardial substrate maps acquired with a 16-pole grid catheter during SR or RV pacing in patients with ACM with VA, who underwent clinically indicated catheter ablation, were retrospectively reviewed. Patients with structurally normal heart and idiopathic VA with epicardial ablation were analysed as a control group. Unipolar contact mapping data was exported & processed offline. From the 4×4 electrode array EGMs, vector maps of the directions of electrical propagation for recorded sites were computed. The VFH was then computed as a quantitative measure of local heterogeneity of propagation, with higher VFH expected to correlate with sites of (micro)structural tissue alterations. VFH was compared between ACM and control patients as well as at sites of normal, border zone & scar based on omnipolar voltage in ACM patients (>1.5mV, 0.5mV–1.5mV, <0.5mV, respectively). Results 10 patients with ACM (70% male, aged 52 ±18 years, ARVC 70%, biventricular 30%, RVEF 40.7±4.7%, LVEF 66±12%) and 2 patients with structurally normal heart (female, 38 & 61 years) were included. Epicardial maps had an average of 9258 ±5412 EGM points. Median VFH was statistically significantly higher in the ACM cohort compared to control for global maps (0.33±0.33 vs 0.13±0.22, p<0.001) and at sites with voltage >1.5mV (i.e. greater disorganization in ACM, p<0.001). In ACM, assessment of VFH according to omnipolar voltage sites (as a surrogate of scar) showed a quantifiable statistically significant increase in electrical disorganized propagation at sites of lower voltage (<0.5mV, median VFH 0.53±0.36) compared to borderzone (0.5-1.5mV, VFH 0.29±0.41) and normal voltage (>1.5mV, VFH 0.15±0.26), p <0.001 respectively. Conclusion Heterogenous electrical propagation as quantified by VFH is significantly increased in patients with ACM at sites of scar, but importantly also in areas of normal voltages when compared to non-ACM controls, possibly indicating microstructural alterations that are missed in traditional assessments of the arrhythmogenic substrate. Identifying and quantifying disorganized conduction patterns by VFH is a promising new mapping approach that could allow improved substrate characterization. Its diagnostic value to guide ablation therapy is currently being validated.VFH Metric ACM and ControlVFH Map Examples

High-Performance Organic Field-Effect Transistors and Inverters with Good Flexibility and Low Operating Voltage.

Organic field-effect transistors (OFETs) with good flexibility and low operating voltage, are of great meaning for the low power stretchable and wearable electronic devices. The operating voltage and flexibility are easily affected by the dielectric layers in the OFETs. Bilayer dielectrics comprising both high- and low-permittivity (k) insulating polymers, have been reported. The flexible bilayer dielectrics can combine the advantages of both insulating polymers, which are high charge carriers from low-k polymers and low operating voltage from high-k polymers. However, the effect of film thicknesses in the bilayer dielectrics on the OFET performance is seldom investigated. Here, bilayer dielectrics comprising high-k polyvinyl alcohol (PVA) and low-k polymethylmethacrylate (PMMA) were fabricated. And PVA/PMMA bilayers with three different PVA film thicknesses are carefully investigated. The 300 nm PVA/100 nm PMMA bilayer dielectric makes the pentacene OFETs show the highest hole mobility of 1.24 cm2V-1s-1 and the corresponding inverters give a high voltage gain of 40 and a noise margin of 2.3 V (77% of 1/2 VDD) at low operating voltage of 6 V. Both the pentacene transistors and the inverters still work properly under bending radium of 5.85 mm, proving the good prospects of the PVA/PMMA bilayer dielectric in practical applications.

Low-Cost High-Voltage Power Supply for Hydraulically Amplified Self-Healing Electrostatic Applications

HASEL (Hydraulically Amplified Self-Healing Electrostatic) actuators have gathered momentum in recent years; they are made of very-low-cost materials, making it easy for anyone to develop their own actuators, and they are “soft” and can achieve tasks that are very difficult to complete with traditional rigid actuators, e.g., grasping soft objects. Unfortunately, HASEL actuators are driven by high-voltage (HV) power supplies, which are expensive to control accurately and difficult to scale up for multichannel applications, e.g., prostheses. This paper presents a low-cost HV power supply designed for HASEL applications that generates 2–10 kV DC at 5% of the cost of the existing HV power supplies used in HASEL actuators. At the core of our design, there is a new control strategy based on controlling the charging and discharging of the actuator from the supply’s low-voltage (LV) side rather than switching the HV side with expensive HV optocouplers. Discharge is achieved via a secondary transformer and multiplier circuit, generating a negative HV output capable of discharging the HASEL effectively and safely up to 10 kV.

A non-isolated converter of switching current stress in DC-DC converter for integrating PV and battery storage system

ABSTRACT High-gain DC-DC converters have seen significant adoption in renewable energy systems like Photovoltaic (PV), Fuel Cells (FC), and other systems. However, their effectiveness is increasingly tied to the availability of renewable resources. As Renewable Energy Sources (RES) typically generate electricity at low voltage levels, integrating high-gain DC-DC converters with RES is crucial for optimal performance. This paper introduces an innovative DC-DC converter design that achieves high gain and is specifically able to integrate smoothly with RES like PV systems and battery storage. The innovation of the proposed converter lies in its integration of conventional boost and buck-boost converters, enabling a high voltage gain while minimizing output voltage ripple and reducing switch current stress. Additionally, its unidirectional power transfer port allows efficient energy flow from solar PV or battery sources to the load, making it highly adaptable for managing fluctuating energy sources, a feature that distinguishes it from current modern converters. Its design simplifies architecture by combining traditional converter types, reducing the number of components, which leads to cost savings, lower weight, and improved reliability. Additionally, the design minimizes output voltage ripple and reduces switching current stress, enhancing the converter’s durability under variable operating conditions. The converter’s performance is evaluated through simulation and experimental studies, demonstrating a 96.3% efficiency and 5.5 times of voltage gain. The converter’s feasibility and effectiveness are validated under dynamic scenarios with varying solar irradiation, making it an ideal solution for clean energy generation systems, including hybrid energy generation setups. The proposed converter topology offers an auspicious solution for high-gain DC-DC conversion in renewable energy systems.

Ensuring Stable Operation of Wind Farms Connected to Distribution Networks

Wind farms with type IV wind turbines from various manufacturers are being massively put into operation. These wind turbines comply with the requirements of the grid codes of the countries where they are designed and/or manufactured, but do not factor in the specific features of the distribution networks of other countries to which they are connected. The study at issue involves a comparative analysis of the requirements of grid codes of different countries for the stable operation of wind turbines under standard disturbances. The low voltage ride through (LVRT) characteristic makes it possible to prevent wind turbine shutdowns in case of short-term voltage dips of a given depth and duration. The calculations of transient processes indicate that wind turbines may not meet the requirements of the grid code of a particular country for their stable operation. As a result, standard disturbances will block the reactive current injection and the wind turbine will be switched off. This is often caused by the relay protection devices with a time delay of 1–2 s, which are used in distribution networks and implement the functions of long-range redundancy. Excessive shutdowns of wind turbines lead to emergency rises in the loads for the generating units of conventional power plants, aggravating the post-accident conditions and disconnecting consumers of electricity. This article presents a method for checking the LVRT characteristic settings for compliance with the technical requirements for wind turbines. To prevent wind turbine outages, one should either change the configuration of the LVRT characteristic, upgrade the relay protection devices in the distribution network adjacent to the wind farm, or implement group or individual technical solutions at the wind farm. The performance of the proposed technical solutions is confirmed by the calculations of transient processes.

Influence of Ti Layers on the Efficiency of Solar Cells and the Reduction of Heat Transfer in Building-Integrated Photovoltaics

This study examined the potential application of metallic coatings to mitigate the adverse effects of ultraviolet (UV) and infrared (IR) light on photovoltaic modules. Titanium coatings were applied on low-iron glass surfaces using magnetron sputtering at powers of 1000, 1250, 1500, 1750, 2000, and 2500 W. The module with uncoated glass served as a reference. The Ti layer thickness varied from 7 nm to 20 nm. Transmittance and reflectance spectra were used to calculate visible light transmittance Lt, UV light transmittance Ltuv, solar transmittance g, and visible light reflectance Lr. The obtained parameters indicated that the thinnest Ti layer (1000 W) coating did not significantly affect light transmittance, but thicker layers did, altering the Lt, g, and Lr factors. However, every sample noticeably changed Ltuv, probably due to the natural formation of a UV-reflective thin TiO2 layer. The differences in fill factor (FF) were minimal, but thicker coatings resulted in lower open-circuit voltages (Uoc) and short-circuit currents (Isc), leading to a reduction in power conversion efficiency (PCE). Notably, a Ti coating deposited at 2500 W reduced the power of the photovoltaic module by 78% compared to the uncoated sample but may protect modules against the unwanted effects of overheating.

A Durable Textile With Advanced Thermal Functions and Electromagnetic Shielding.

In the face of increasingly variable cold climates and diverse individual temperature regulation demands, personal thermal management (PTM) textiles with electromagnetic shielding have obtained significant attention. However, the PTM textiles face several challenges, including single heating mode, insufficient durability, and complex preparation processes. Herein, an all-day PTM textile Cotton@PDA/AgNPs (CPANS) with energy-free PRH, energy-saving solar heating, compensatory electricalheating, electromagnetic interference (EMI) shielding, and outstanding durability is fabricated by sequentially growing polydopamine (PDA) and silver nanoparticles (AgNPs) on the cotton fabric (CF). The CPANS exhibits low mid-infrared emissivity (36.6%) and high absorptivity (70.8%), which guarantees the energy-saving heating capability. Moreover, the conductivity of the CPANS is ≈11109Sm-1, enabling an electrical heating temperature of ≈177°C under a low voltage of 1.1V and superb EMI shielding effectiveness (≈60dB). The remarkable adhesive properties of the PDA ensure that the desired durability of the CPANS remains high even after rigorous physical treatments. This innovation shows enormous potential for wearable integrated garments in the future and offers a new ideal for PTM fabrics in the cold.

Review of Low Voltage Ride-Through Capabilities in Wind Energy Conversion System

The significance of low voltage ride-through (LVRT) capability in wind energy conversion systems (WECSs) is paramount for ensuring grid stability and reliability during voltage dips. This systematic review delves into the advancements, challenges, and methodologies associated with LVRT capabilities in WECSs. By synthesizing recent research findings, this review highlights technological innovations, control strategies, and regulatory requirements that influence LVRT performance. Key insights include the efficacy of various LVRT techniques, the role of grid codes in shaping LVRT standards, and the integration of advanced control algorithms to improve system resilience. The study offers a comprehensive understanding of the current landscape of LVRT in WECSs and pinpoints future research directions to optimize their performance in increasingly complex grid environments. During the LVRT process, the stator of a double-fed induction generator (DFIG) is directly linked to the power grid. When the external power grid experiences a failure, the stator flux produces a significant transient component, resulting in substantial overvoltage and overcurrent on the rotor side of the DFIG. Failure to implement preventative measures may result in damage to the converter, therefore compromising the safety and stability of how the power system functions.

Photoinduced Zn-Air Battery-Assisted Self-Powered Sensor Utilizing Cobalt and Sulfur Co-Doped Carbon Nitride for Portable Detection Device.

Most self-powered electrochemical sensors (SPESs) are limited by low open circuit voltage and power density, leading to a narrow detection range and low sensitivity. Herein, a photoinduced Zn-air battery-assisted SPES (ZAB-SPES) is proposed based on cobalt and sulfur co-doped carbon nitride with the cyano group (Co, S-CN). The cyano functionalization remarkably enhances visible light utilization, and the cyano moiety acts as an electron-withdrawing group to promote electron enrichment. Co and S co-doping can create a p-n homojunction within carbon nitride, enabling the efficient migration and separation of carriers, thereby significantly improving the performance of the oxygen reduction reaction. The synergistic effects endow Co, S-CN photocathode with an open circuit voltage of 1.85V and the maximum power density of 43.5µW cm-2 in the photoinduced ZAB. Employing heavy metal copper ions as the target model, the photoinduced ZAB-SPES exhibited dual-mode and sensitive detection. Furthermore, a portable detection device based on the photoinduced ZAB-SPES is designed and exhibits high linearity in the range of 5 ~ 600nM with a detection limit of 1.7nM. This work offers a portable detection method based on the photoinduced ZAB-SPES in the aquatic environment.

Effects of atrial fibrillation ablation on arrhythmia burden and ventricular function in end-stage heart failure: Lessons from CASTLE-HTx.

The CASTLE-HTx trial showed the benefit of atrial fibrillation (AF) ablation compared to medical therapy in decreasing mortality, need for left ventricular assist device implantation or heart transplantation (HTx) in patients with end-stage heart failure (HF). Herein we describe the effects of catheter ablation on AF burden, arrhythmia recurrences, and ventricular function in end-stage HF. The CASTLE-HTx protocol randomized 194 patients in end-stage HF with AF to catheter ablation and medical therapy or medical therapy alone. AF burden, left ventricular ejection fraction (LVEF), and type of AF were assessed at baseline and at each follow-up visit. Overall, 97 patients received ablation; 66 patients (68%) underwent pulmonary vein isolation (PVI) and 31 patients (32%) were treated with PVI and additional ablation. Electroanatomic mapping showed the extent of left atrial low voltage (cardiomyopathy) >10% in 31 (31.9%) patients. At 12 months post-ablation, persistent AF was present in 31/89 patients (34.8%), which was significantly less frequent compared to baseline (p = 0.0001). Median AF burden reduction was 36.3 (interquartile range 13.6-63.3) percentage points at 12 months and LVEF improved from 29.2 ± 6.2% to 39.1 ± 8.3% (p < 0.001) following ablation. AF burden reduction <50% was significantly associated with LVEF improvement ≥5% at 12 months after ablation (p = 0.017). Atrial fibrillation ablation in end-stage HF leads to a substantial decrease in AF burden, a regression from persistent to paroxysmal AF and notably improved LVEF. Favourable ablation outcomes were observed in patients regardless of the presence or absence of signs indicating left atrial cardiomyopathy.

Configurational Isomerization‐Induced Orientation Switching: Non‐Fused Ring Dipodal Phosphonic Acids as Hole‐Extraction Layers for Efficient Organic Solar Cells

AbstractPhosphonic acid (PA) self‐assembled molecules have recently emerged as efficient hole‐extraction layers (HELs) for organic solar cells (OSCs). However, the structural effects of PAs on their self‐assembly behaviors on indium tin oxide (ITO) and thus photovoltaic performance remain obscure. Herein, we present a novel class of PAs, namely “non‐fused ring dipodal phosphonic acids” (NFR‐DPAs), featuring simple and malleable non‐fused ring backbones and dipodal phosphonic acid anchoring groups. The efficacy of configurational isomerism in modulating the photoelectronic properties and switching molecular orientation of PAs atop electrodes results in distinct substrate surface energy and electronic characteristics. The NFR‐DPA with linear (C2h symmetry) and brominated backbone exhibits favorable face‐on orientation and enhanced work function modification capability compared to its angular (C2v symmetry) and non‐brominated counterparts. This makes it versatile HELs in mitigating interfacial resistance for energy barrier‐free hole collection, and affording optimal active layer morphology, which results in an impressive efficiency of 19.11 % with a low voltage loss of 0.52 V for binary OSC devices and an excellent efficiency of 19.66 % for ternary OSC devices. This study presents a new dimension to design PA‐based HELs for high‐performance OSCs.

Azopyridine Aqueous Electrochemistry Enables Superior Organic AZIBs.

Azo compounds (AZO), such as azobenzene, are classic organic electrode materials featuring a redox potential close to Zn/Zn2+. Recent studies show that azobenzene could work as a cathode in aqueous zinc-ion batteries (AZIBs), providing a voltage output of around 0.7 V. However, the energy storage mechanism of AZO cathodes in AZIBs remains unclear, and their practical usage in AZIBs is hindered by the low voltage. In this study, azopyridine isomers, the hydrophilic analogues of azobenzene, were adopted as cathodes for AZIBs, and the energy storage mechanism was unveiled through aqueous electrochemical studies. Through in situ electrochemical characterizations and theoretical computations, we reveal that both the electron-withdrawing effect of the pyridyl group and the H+-involved -N = N-/-NH-NH- redox reaction uplift the redox potential of the azopyridine cathodes. These findings led to the first AZO-based AZIB, providing a voltage output of 1.4 V. The proposed air-stable AZIBs deliver a high energy/power density and a capacity of around 200 mAh g-1. This work discovers different azopyridine electrochemistry in aqueous and organic electrolytes and enabling AZIBs to outperform its competitors from the AZO family.

Carrier Generation and Recombination in AC-QLEDs with a Synergistic Capacitance Effect of ZnO/PVDF Heterofunction Layers.

The alternating current-driven electroluminescence (AC-EL) of Cd-based quantum dots is garnering increasing attention due to advantages such as high efficiency and an extended operating lifetime. However, the generation and transport mechanisms of charge carriers within devices still need to be more understood. Here, we construct a simple device and investigate its luminance mechanisms within a single cycle using time-resolved spectroscopy. We tested the luminance-voltage and luminance-frequency characteristics of the device as the thickness of the insulating layer varied, finding that they both exhibited a trend of initially increasing and then decreasing as the voltage or frequency increased. We subsequently investigated the transient electroluminescent characteristics of the device, which featured a P(VDF-TrFE-CFE) layer as the insulator. This layer prevents carrier injection from the Al electrode, while the ZnO layer acts as a charge-generating layer to provide additional carriers. We observed that with an increase in AC voltage, the strongest luminance peak is advanced in the cycle compared to when lower voltages were applied. The position of the strongest luminance peak is delayed with an increasing AC frequency. The C-V characteristics demonstrated that the synergistic P(VDF-TrFE-CFE)/ZnO exhibited a displacement current transforming to a conduct current, which activates the forward operation of the QLED and enables it to emit light. The mechanism we present may serve as a benchmark for improving the luminance and longevity of such devices.

Interface Engineering Induced by Low Ru Doping in Ni/Co@NC Derived from Ni-ZIF-67 for Enhanced Electrocatalytic Overall Water Splitting.

Electrochemical water splitting is a promising approach for hydrogen evolution reactions (HER); however, the oxygen evolution reaction (OER) remains a major bottleneck due to its high energy requirements. High-performance electrocatalysts capable of facilitating HER, OER, and overall water splitting (OWS) are highly needed to improve OER kinetics. In this work, we synthesized a trimetallic heterostructure of Ru, Ni, and Co incorporated into N-doped carbon (denoted as Ru/Ni/Co@NC) by first synthesizing Ni/Co@NC from Ni-ZIF-67 polyhedrons via high-temperature carbonization, followed by Ru doping using the galvanic replacement method. Benefiting from increased active surface sites, modulated electronic structure, and enhanced interfacial synergistic effects, Ru/Ni/Co@NC exhibited exceptional electrocatalytic performance for both HER and OER processes. The optimized Ru/Ni/Co@NC catalyst, with a minimal Ru mass ratio of ∼2.07%, demonstrated significantly low overpotential values of 34 mV for HER and 174 mV for OER at a current density of 10 mA/cm2 with corresponding Tafel slope values of 33.42 and 34.39 mV/dec, respectively. Further, the optimized catalyst was loaded onto carbon paper and used as anode and cathode materials for alkaline water splitting. Interestingly, a low cell voltage of just 1.44 V was obtained. The enhanced electrolytic performance was further elaborated by density functional theory (DFT) calculations, which confirmed that Ru doping in Ni/Co introduced additional active sites for H*, enhancing adsorption/desorption abilities for HER (ΔGH* = -0.30 eV), lowering water dissociation barrier (ΔGb = 0.49 eV) and reducing the energy barrier for the rate-determining step of OER (O* → OOH*) to 1.62 eV in an alkaline environment. These findings reflect the significant potential of ZIF-67-based catalysts in energy conversion and storage applications.