Low Voltage Region Research Articles

Sodium Ion Diffusion Behavior in Multiple Open/Closed Pore Ratios of Novel β-Cyclodextrin-Derived Hard Carbon Anode Materials.

Plateau-dominated hard carbon with a high rate of performance is challenging to obtain, and the in-depth mechanism of pore structure on the diffusion of sodium ions remains unclear. In this study, a facile liquid-phase molecular reconstruction strategy is proposed to regulate the orientation of the β-cyclodextrin molecules and prepare spherical hard carbon with continuous and ordered pore channels. Through detailed characterization, this approach is confirmed to optimize the accumulation of Na+ in the dispersion region, thus improving the plateau kinetics and enhancing the utilization of closed pores. The as-obtained β-cyclodextrin-derived spherical hard carbon has a much greater specific surface area (129 m2 g-1) than the pristine sample (2.91 m2 g-1) but a similar initial Coulombic efficiency. Additionally, the plateau region still exists when the current density is at 30 C (7.5 A g-1), contributing to a high capacity of 179 mAh g-1. This study provides a meaningful promotion to kinetics of hard carbon at the low-voltage region.

Conductive Hydrogel Systems Enabling Rapid and Controllable Release of Guests at Low-Voltage Region.

Smart delivery materials that respond to electric fields attract interest across various fields, whereas systems enabling rapid, controllable, and safe delivery capabilities remain essential. Based on the hypothesis of utilizing electric field to manipulate inter-component noncovalent bonds in delivery materials, a hydrogel system is hereby reported that is capable of achieving rapid guest release at low-voltage region. This system harnesses the synergistic regulation of electric field-induced host-guest electrostatic repulsion, alongside the dynamic modulation of H-bond interactions within the conductive hydrogel. Consequently, a voltage of 1.5V influences the multi-component non-covalent crosslinking, inducing reversible pore size enlargement, and achieving an accelerated yet controlled release of 39-48% within 120min at 1.5V, with a low-threshold release voltage of 0.5V. This conductive hydrogel system enables the rapid and controlled release of various guest molecules, including drugs, fluorescent probes, and luminophores, underscoring the universality of the strategy. Furthermore, an electrical control device constructed from such hydrogel blocks is demonstrated, which is capable of performing "time-specific" information encoding and access. The mechanism relies on physical processes, avoiding traditional redox reactions, thereby inspiring the development of safe and efficient electrically responsive materials and devices with diverse functionalities, leveraging the synergistic effect of multi-component non-covalent interactions.

Electrochemical Properties and Microstructural Analysis of Li2feso Cathode Material for All-Solid-State Battery

All-solid-state battery configurations using a solid electrolyte provide the promise of next-generation high-performance batteries. One of the main problems with all-solid-state lithium-ion batteries is their low cathode capacity, which requires the use of conductive carbon additives. The oxy-sulfide Li2FeSO with a cubic anti-perovskite structure has been investigated as a new cathode material due to its high theoretical capacity (455 mAhg-1). We constructed an all-solid-state battery with a Li2FeSO electrode that demonstrated a relatively high discharge capacity of approximately 270 mAh g-1 at a high electrode loading ratio (90 wt%) [1]. Hence, we demonstrated that Li2FeSO is suitable for all-solid-state batteries. However, the reason for its superior performance remains unclear. Therefore, in this study, Li2FeSO was synthesized via mechanical milling, and the charge compensation mechanism during the battery reaction was analyzed via its cross-sectional microstructure.Li2O (FujiFilm Wako > 95%), S (Aldrich > 99.98%), and Fe (FujiFilm Wako > 99.9%) were mixed in a 1:1:1 molar ratio for the synthesis of Li2FeSO using an agate mortar. Planetary ball-milling was performed at 650 rpm for 72 h, and the precursor powder was pressed via uniaxial pressing and sintered in a tube furnace under an Ar flow at 650 °C for 2 h. The crystal structure was then characterized using X-ray diffraction (XRD), and the electrochemical properties were measured using direct current polarization and impedance spectroscopy. The cross-sectional microstructure of the cathode composite was observed using field-emission scanning electron microscopy. The intrinsic mechanical properties of the samples were examined using the indentation method [2]. The battery performance was characterized by charge–discharge measurements, and hard X-ray photoelectron spectroscopy (HAXPES) was used to analyze valence changes.The XRD pattern was attributed to the cubic anti-perovskite structure with a Pm3̅m space group. The Li2FeSO all-solid-state battery showed an approximate 270 mAh g-1 reversible discharge capacity (Fig. 1). According to scanning electron microscopy imagery, a dense body was observed, even at a high Li2FeSO active material loading ratio (90 wt%). From an indentation test, the elastic modulus, Mayer hardness, and yield point were found to be 24.9, 0.46, and 0.82 GPa, respectively, which are similar to those of sulfide solid electrolyte all-solid-state batteries. The excellent low modulus and high formability due to the presence of sulfur contribute to superior battery performance. Finally, HAXPES measurements were conducted to analyze the charge compensation mechanism. Fe oxidation in the low-voltage region and S oxidation in the high-voltage region occurred during charging. In contrast, S reduction in the high-voltage region and Fe reduction in the low-voltage region occurred during discharge. Acknowledgments：This work was supported by JSPS KAKENHI (Grant Number JP 21K14716), Tokai Foundation for Industrial Technology, and Hibi Science Foundation. The HAXPES experiments were conducted at BL6N1 at the Aichi Synchrotron Radiation Center, Aichi Science & Technology Foundation, Aichi, Japan (Proposal No. 202205052 and No. 202302108).

High temperature induced abundant closed nanopores for hard carbon as high-performance sodium-ion batteries anodes

Hard carbon (HC) stands out as the preeminent anode material for sodium-ion batteries (SIBs) which are deployed in expansive energy storage infrastructures. Herein, the large enough graphene nanosheets interlayer and abundant nanopores with a diameter of ∼2.1 nm induced by adjusting the pyrolysis temperature in the thermosetting phenolic resin-derived hard carbon matrix to augment the performance of the sodium ion storage. The presence of sufficiently large carbon interlayers has been proven to provide active sites for reversible adsorption, enabling effective storage of sodium ions in the high-voltage slope region, while also promoting rapid Na+ transport. Meanwhile, forming abundant closed nanopores with larger sizes helps sodium ion storage in the low-voltage plateau region. In the optimized samples, the formation of sufficient long graphene nanosheets with a perfect crystal lattice, which further shrinks to form enclosed nanopores, effectively reduces defective sites and specific surface area. Additionally, the appropriate content of C-O and C=O functional groups contributes to an exceptional initial Coulombic efficiency (ICE) of up to 93%. Simultaneously, the optimized sample HC-1500 contributes to a remarkable plateau capacity of 294 mAh g-1 during the charging process (high reversible capacity of 403 mAh g-1 at 0.1 C). Moreover, based on the microstructure evolution and Na storage behavior of hard carbon, an “adsorption (27%) – filling (73%)” sodium storage mechanism that the sodium storage as a quasi-metallic sodium state is demonstrated. Consequently, this study will offer valuable insights for the development of hard carbon anodes tailored for high-energy practical SIBs, while also advancing the understanding of sodium storage mechanisms.

TCAD analysis of conditions for DIBL parameter misestimation in cryogenic MOSFETs

The study aimed to theoretically investigate the transfer characteristics of MOSFETs at cryogenic temperatures to elucidate the experimental conditions affecting the accurate estimation of the drain-induced barrier lowering (DIBL) parameter. Our Technology Computer Aided Design (TCAD) simulation revealed that MOSFETs featuring an underlap between the gate and source/drain edges experience a significant shift in threshold voltage (V t) in the low drain voltage (V d) region, which causes the misestimation of the DIBL parameter. This V t change is due to a notable increase in carrier concentration within the underlap region. To mitigate misestimation in such underlap devices, confirming the dependence of the DIBL parameter on the linear region of V d serves as an effective method to ensure accurate estimation.

Initiating cationic-anionic chemistry with stepwise surface-to-inner conversion in copper selenide superstructures for high-energy rechargeable magnesium batteries

Copper selenides are viewed as the most capable cathode materials for rechargeable magnesium batteries, yet suffer from unsatisfactory energy density due to their low operating voltage plateau (∼0.9 V vs. Mg/Mg2+) and insufficient reversible capacity. Herein, a stepwise conversion from surface cationic-anionic redox to inside electrochemical displacement reaction is realized in copper selenide (Cu2-xSe) superstructure cathodes. A highly reversible high-voltage platform at ∼1.6 V is discovered during discharge process. Ex-situ spectroscopy and microscopy results demonstrate that the high-voltage plateau is contributed by surface Cu2+ charge-carrier transformation and anionic Se2– redox reaction while sufficient inner Cu-Mg replacement conversion at low-voltage region. Following the favorable mechanism, the Cu2-xSe superstructure cathodes can present high specific capacity of 385.4 mAh g–1 at 0.1 A g–1 and outstanding energy density of 426.3 Wh kg–1. Moreover, the Cu2-xSe superstructure cathodes also maintain a reversible capacity of 223.6 mAh g–1 over 700 cycles with 0.0147 % capacity degradation per cycle at 1.0 A g–1 and long-term charge-discharge lifetime for 3000 cycles at 5.0 A g–1. This research reports a new Mg2+ storage mechanism for copper selenide cathodes and provides novel route to develop high-energy-density rechargeable magnesium batteries.

Quantitative and qualitative assessment of left atrial cardiomyopathy as well as prediction of atrial fibrillation recurrences upon PVI using machine learning

Abstract Introduction Atrial fibrillation (AF) is one of the most common heart pathologies in daily clinical practice and confers significant mortality and morbidity. However, AF ablation often proves ineffective - even after successful pulmonary vein isolation (PVI). The prediction of PVI failure for the long-term treatment of AF as well as the improved assessment of the underlying substrate appears pivotal. We hypothesize, that ML can be applied to better characterize the substrate and recurrence in AF patients upon PVI. Methods & Results We retrospectively evaluated data from 205 patients that underwent AF ablation between 2019 and 2023, including high-density 3D electroanatomic maps (sinus rhythm), LA rotational angiography, invasive LA hemodynamic measurements (after transseptal passage), echocardiography, 12-lead ECG and laboratory testing. A neuronal net was trained on selected features extracted from those datasets using supervised learning and employed to predict measures of atrial cardiomyopathy and AF recurrence. Patients were 66±1 years old and received first or second pulmonary vein isolation (PVI) for paroxysmal atrial fibrillation with 18% documented recurrences upon a mean follow-up of 23±1months. First, we extensively refined or developed tools for automated P-wave analysis from 12-lead ECGs as well as local LA voltage and volume quantification. Next, LA hemodynamics and volumes were assessed: Mean LA volume as derived from rotational angiography significantly correlated with LA volume index as obtained using echocardiography. Interestingly, LA size showed no correlation with NT-proBNP, LA low voltage or LA hemodynamics. In addition, global (25±2% of total LA area) and local (i.e. anterior, posterior, roof) LA voltage was determined and shown to be an independent predictor of AF recurrence. In our first unselected subset of 136 patients with 2nd PVI for atrial fibrillation, our ML models predicted LA fibrosis (i.e. low voltage regions; Utah stage) from 12-lead ECGs with an accuracy of 90%. Accuracy was 87% for the prediction of AF recurrences from LA pressure and low-voltage regions. In addition, the algorithm predicted AF recurrences from 12-lead SR ECGs obtained before PVI with an accuracy of 91%. Conclusion Artificial neural networks allow to quantitatively and qualitatively predict measures of atrial cardiomyopathy and atrial fibrillation recurrence probability upon complete PVI with high accuracy.Figures

The evaluation of the efficacy of automated peak frequency annotation algorithm for the identification of critical isthmus of ventricular tachycardia and deceleration zones

Abstract Background Substrate modification techniques have widely been adopted due to hemodynamic instability and non-inducibility of clinical ventricular tachycardia (VT). Accurate annotation of local near field EGMs is paramount to better evaluate the ventricular substrate. Furthermore, annotation of late potentials (LP) necessitates substantial manual input and isochronal late activation mapping (ILAM) involves constant sensitivity adjustments, potentially affecting the accuracy of local ventricular signal representation. Objective This study aims to assess the utility of novel automated peak frequency (PF), which aims to determine near field local activity in low voltage regions in the prediction of the CI of scar related reentrant VTs. Furthermore, the effectiveness of automated PF annotation of near field EGMs to identify deceleration zone (DZ) during ILAM was also evaluated. Methods A total of 18 patients with scar-related VT were analyzed. In all patients, VT isthmuses were identified based on activation maps and acute termination achieved during radiofrequency ablation. Automated PF annotation using Ensite X system (Abbott) was retrospectively performed in all cases specifically in areas of low voltage with fractioned signals. The accuracy of applying the PF value and automated ILAM map for detecting VT isthmus was also assessed. Results Among the study group, 12 (66.7%) had ischemic cardiomyopathy, while 6 (33.3%) had nonischemic cardiomyopathy [3 (16.7%) with arrhythmogenic right ventricular cardiomyopathy, 2 (11.1%) with idiopathic dilated cardiomyopathy, and 1 (5.6%) with hypertrophic cardiomyopathy]. All identified isthmuses were located in areas exhibiting bipolar voltage below 0.5 mV and a PF of 250 Hz with fractionated EGMs Automated NF DZ annotation predicted the VT isthmus in 16/18 (88.9%) of the cases similar to the conventional ILAM with manual adjustment (88.9%). Conclusion Using high-density electroanatomical mapping with near field algorithm, a PF cutoff of 250 Hz accurately identified the low voltage regions to predict the CI of VT. In addition, automated annotation of EGMs during ILAM similarly identified the DZs compared with conventional last deflection algorithm with manual adjustments, which were colocalized with CI of VTs.

Peak frequency mapping characteristics in patients with scar-related atypical atrial reentrant tachycardias; findings from a novel automated annotation algorithm to detect near field signals

Abstract Background Atypical atrial tachycardias are commonly encountered rhythm disorders especially in patients with atrial low-voltage areas mainly due to previous catheter ablations or surgery. The peak frequency (PF) analysis of bipolar EGMs is a novel automated annotation tool which is mainly based on differentiation of near field signals from far field signals. Purpose In this study, we aimed to evaluate the association between PF analysis of voltage maps in low-voltage zones with the critical isthmus and termination sites of ATs. Methods In this retrospective analysis, we included a total of 36 patients (7 with right AT, 25 left AT, 4 biatrial). Omnipolar maps of RA and LA were created during AT using Ensite X Mapping system and HD-Grid catheter. Normal voltage is defined as ≥ 0.5 mV, borderline 0.1-0.5 mV and scar <0.1 mV. Only patients with acute termination of tachycardia with RF ablation were included. The sites within the 10 mm radius from the tachycardia termination site with RF were analysed in terms of voltage characteristics and PF analysis. Results The mean age of the study population was 53±15. Among 36 patients a total of 46 activation maps were created and 44 reentrant ATs were mapped. (24 (54.6%) ATs were macroreentry, 17 (38.6%) ATs were localized reentry and 3 ATs (6.8%) were dual-loop reentry). The low-voltage (LV) zones comprised 31.5±20.6% and 24.5±12.6% of total LA and RA, respectively. All AT termination sites using radiofrequency energy were located within the LV zones having high frequency activity using 250 Hz as the cut-off. The sensitivity of LV-NF zones to predict termination sites of re-entry was 97.2%. Conclusion The PF analysis of atrial substrate in the vicinity of the termination site of re-entrant ATs demonstrated high frequency signals within the low voltage zones. Therefore, addition of PF analysis with emphasis over voltage mapping may refine critical sites of reentry in LV regions.

Effects of different types of fibrotic remodelling in areas of low voltage on atrial fibrillation dynamics: an in-silico study

Abstract Background Personalized computational models include the effects of personalised anatomy and atrial fibrillation (AF) remodelling in a framework that can be used to investigate patient-specific AF mechanisms and test treatment response, but modelling fibrosis remains an unresolved matter. The interpretation of regions exhibiting low voltage in electroanatomic mapping data at different pacing rates also remain unclear. However, these occurrences are correlated with fibrotic remodelling. We aimed to use patient-specific simulations to investigate the effects of fibrosis type on AF properties by modelling conduction velocity slowing, changes in ionic channels, and replacement fibrosis, incorporated in regions of low voltage identified through omnipolar mapping at different pacing rates. Methods Local activation times (LATs) voltage and geometry data were obtained from patients undergoing ablation for persistent AF. LATs were collected in sinus rhythm with coronary sinus pacing at pacing interval (PIs) of 250ms and 600ms. For a total of 10 cases, personalised anatomical models were constructed for electrophysiology simulations, and analysed using an automated pipeline in python. For conductivity models, areas with peak omnipolar voltage (OV) below 0.5mV were assigned low conduction velocity. To incorporate ionic changes, the ionic properties were altered in fibrotic regions (peak OV < 0.5mV). In the simulations where replacement fibrosis was included through a probabilistic percolation method, percolation was modelled by using random number generator to probabilistically remove elements of low voltage. Pulmonary vein isolation was simulated in each model after 5s of AF, and wavefront propagation patterns were analysed to quantify the number of rotational areas or areas of wavefront break-up in 7 anatomical segments. Results The models with conductivity fibrotic remodelling demonstrated rotational drivers in more than two LA anatomical segments for both CS250ms pacing rate and CS600ms pacing rate across all 10 cases. The anterior wall exhibited the largest degree of rotational activity in 7 out of 10 cases for CS250ms pacing rate and in 9 out of 10 cases for CS600ms pacing rate (Figure A). The combination of percolation and conductivity remodelling also exhibited rotational activity on the anterior wall in 9 out of 10 cases at CS250ms pacing rate, and 7 out of 10 cases for CS600ms pacing rate. For the simulations where replacement fibrosis was included (percolation), both the roof and anterior wall exhibited the largest degree of rotational activity in 5 out of 10 cases at CS250ms pacing rate; while at CS600ms pacing rate, the posterior walled exhibited the majority of rotational activity in 7 cases (Figure B). All fibrosis models containing ionic changes terminated in more than half of the 10 cases for both pacing rates (CS250ms and 600). Conclusion The impact of low voltage on fibrotic remodelling causes complex effects on AF dynamics.

Rhythm matters: sinus and pace rhythm map significantly differ in endo/epicardial 3D electroanatomic mapping

Abstract Introduction Left ventricular substrate assessment utilizing ultra-high density multipolar catheters is frequently used to guide ablation procedures in patients with scar related ventricular tachycardia. However, 3D electroanatomic mapping is often performed during either sinus or paced rhythm. The effect of the modality (sinus vs. paced) used during mapping on substrate assessment remains elusive. Methods and Results We compared biventricular endo- and epicardial 3D high-density voltage and activation maps in sinus- and right ventricular-paced rhythm in domestic pigs. Data was acquired using a 20-polar mapping catheter with a cardiac tissue proximity filter based on catheter location and impedance measurements. Ventricular pacing (120 bmp) was performed with a permanent pacemaker electrode in right ventricular septal position, and high-density maps were acquired from the endo- and epicardium in sinus and paced rhythm (criterion for low voltage: <0.5 mV). Electroanatomical voltage and activation high-density (>6500 points per heart) mapping were performed with sufficient coverage in the right and left ventricles and the epicardium. The size of the low voltage area varied significantly between sinus and right ventricular-paced rhythm, particularly in epicardial mapping. In SR, the total low voltage was 7.2 ± 5.8%, while 11.1 ± 0.03% in paced rhythm. SR and paced maps revealed e.g. low voltage areas in the basal to apical anterior wall corresponding to the LAD regions, however, this was especially pronounced in sinus maps (e.g. pig 1: 64.2 cm²) compared to the paced rhythm map (e.g. pig 1: 32.8 cm²). Conclusion The extent of low voltage regions differed significantly in RV/LV, endo- and epicardially. Sinus maps showed the most accurate electrical representation of local voltage and corresponded correctly to local anatomical landmarks like e.g. the LAD with its surrounding epicardial fat tissue.3D biventricular epicardial voltage map

Regulating the “core-shell” microstructure of hard carbon through sodium hydroxide activation for achieving high-capacity SIBs anode

Pore structure engineering has been acknowledged as suitable approach to creating active sites and enhancing ion transport capabilities of hard carbon anodes. However, conventional porous carbon materials exhibit high BET and surface defects. Additionally, the sodium storage mechanism predominantly occurs in the slope region. This contradicts practical application requirements because the capacity of the plateau region is crucial for determining the actual capacity of batteries. In our work, we prepared a novel “core-shell” carbon framework (CNA1200). Introducing closed pores and carboxyl groups into coal-based carbon materials to enhance its sodium storage performance. The closed pore structure dominates in the “core” structure, which is attributed to the timely removal of sodium hydroxide (NaOH) to prevent further formation of active carbon structure. The presence of closed pores is beneficial for increasing sodium ion storage in the low-voltage plateau region. And the “shell” structure originates from coal tar pitch, it not only uniformly connects hard carbon particles together to improve cycling stability, but is also rich in carboxyl groups to enhance the reversible sodium storage performance in slope region. CNA1200 has excellent electrochemical performance, it exhibits a specific capacity of 335.2 mAh g−1 at a current density of 20 mA g−1 with ICE = 51.53 %. In addition, CNA1200 has outstanding cycling stability with a capacity retention of 91.8 % even when cycling over 200 times. When CNA1200 is used as anode paired with Na3V2(PO4)3 cathode, it demonstrates a capacity of 109.54 mAh g−1 at 0.1 C and capacity retention of 94.64 % at 0.5 C. This work provides valuable methods for regulating the structure of sodium-ion battery (SIBs) anode and enhances the potential for commercialization.

Insight into the effect of structural differences among pitch fractions on sodium storage performance of pitch-derived hard carbons

Pitch is an excellent precursor of hard carbons (HCs) with low-cost and high carbon content, enabling its commercial-scale application in sodium-ion batteries. Pre-oxidation is the key to obtaining pitch-derived HCs with disordered microstructures. However, pitch is a mixture of fractions with different molecular weights and structures. With the introduction of oxygen, the cross-linked structure established by each fraction could be different, the effect of which on the microstructure and sodium storage performance of HCs remains unclear. Here, we separate pitch into three fractions and further pre-oxidize and carbonize to produce HCs, in order to systematically investigate the effects of structural differences among pitch fractions on the cross-linking mechanism and microstructure of as-obtained HCs. It is found that tetrahydrofuran-insoluble (THFI) enables the enrichment of polar oxygen functional groups, thus enhancing its oxidative activity to obtain more oxygen for the construction of abundant three-dimensional cross-linked structure. It is conducive to preventing the rearrangement of carbon layers and promoting the development of micropores during high-temperature carbonization process, which facilitates the storage of sodium ions in the low-voltage plateau region. The resulting hard carbon (THFI-1400) has significantly improved overall sodium storage performances. This work provides a new strategy to prepare low-cost and high-performance HCs.

Functional substrate mapping of atrium in patients with atrial scar: A novel method to predict critical isthmus of atrial tachycardia.

Atrial tachycardia (AT) is a common rhythm disorder, especially in patients with atrial structural abnormalities. Although voltage mapping can provide a general picture of structural alterations which are mainly secondary to prior ablations, surgery or pressure/volume overload, data is scarce regarding the functional characteristics of low voltage regions in the atrium to predict critical isthmus of ATs. Recently, functional substrate mapping (FSM) emerged as a potential tool to evaluate the functionality of structurally altered regions in the atrium to predict critical sites of reentry. Current evidence suggested a clear association between deceleration zones of isochronal late activation mapping (ILAM) during sinus/paced rhythm and critical isthmus of reentry in patients with left AT. Therefore, these areas seem to be potential ablation targets even not detected during AT. Furthermore, abnormal conduction detected by ILAM may also have a role to identify the potential substrate and predict atrial fibrillation outcome after pulmonary vein isolation. Despite these promising findings, the utility of such an approach needs to be evaluated in large-scale comparative studies. In this review, we aimed to share our experience and review the current literature regarding the use of FSM during sinus/paced rhythm in the prediction of re-entrant ATs and discuss future implications and potential use in patients with atrial low-voltage areas.

Peak frequency mapping of atypical atrial flutter.

Peak frequency (PF) mapping is a novel method that may identify critical portions of myocardial substrate supporting reentry. The aim of this study was to describe and evaluate PFmapping combined with omnipolar voltage mapping in the identification of critical isthmuses of left atrial (LA) atypical flutters. LA omnipolar voltage and PF maps were generated in flutter using the Advisor HD-Grid catheter (Abbott) and EnSite Precision Mapping System (Abbott) in 12 patients. Normal voltage was defined as ≥0.5 mV, low-voltage as 0.1-0.5 mV, and scar as <0.1 mV. PF distributions were compared with ANOVA and post hoc Tukey analyses. The 1 cm radius from arrhythmia termination was compared to global myocardium with unpaired t-testing. The mean age was 65.8 ± 9.7 years and 50% of patients were female. Overall, 34 312 points were analyzed. Atypical flutters most frequently involved the mitral isthmus (58%) or anterior wall (25%). Mean PF varied significantly by myocardial voltage: normal (335.5 ± 115.0 Hz), low (274.6 ± 144.0 Hz), and scar (71.6 ± 140.5 Hz) (p < .0001 for all pairwise comparisons). All termination sites resided in low-voltage regions containing intermediate or high PF. Overall, mean voltage in the 1 cm radius from termination was significantly lower than the remaining myocardium (0.58vs. 0.95 mV, p < .0001) and PF was significantly higher (326.4vs. 245.1 Hz, p < .0001). Low-voltage, high-PF areas may be critical targets during catheter ablation of atypical atrial flutter.

Coexistence of analog and digital memristive behaviors in MoO3 based devices for artificial synaptic and logic display applications

In-memory logic operations and neuromorphic computing inspired by the brain based on memristors are promising computing modes that can improve computational efficiency and avoid additional power consumption. However, implementing these two functions within the memristor same cell is often limited by the flexible conversion between digital and analog memristive behaviors. In this work, a memristive device with Ag/MoO3/Ti structure was developed using hydrothermal methods, which presents the evolution from capacitance-coupled memristive effect to self-rectifying non-zero crossing analog memristive behavior and then to digital memristive effect by adjusting the amplitude of applied voltage. Under low voltage region (Vamplitude ≤ 1.2 V), the non-zero crossing analog memristive effect with self-rectifying behavior is mainly attributed to the potential barrier at the interface and built-in electric field, while the digital memristive effect under high voltage region (Vamplitude ≥ 1.5 V) is mainly attributed to the formation and fracture of Ag conductive filaments (CFs). Moreover, the mechanism for the non-zero-crossing characteristic of device was proven by parallel connection of memristors and capacitors. Finally, the artificial synaptic and logic display functions were implemented using the as-prepared memristive unit. Therefore, this work provided guidance for understanding the non-zero-crossing memristive effect and the development of high-density multifunctional devices.

Superior device characteristics of needle-contact Ge Schottky barrier diodes for low-power applications

We measured and compared the I–V characteristics of needle- and junction-contact Ge Schottky barrier diodes (SBDs). The threshold voltage (V th) of I–V characteristics in needle-contact SBDs was revealed to be lower than that of junction-contact SBDs, which resulted in higher current in the low-voltage region. This indicates that needle-contact SBDs are more suitable for low-power applications. The lower V th in needle-contact SBDs indicates the lower Schottky barrier height. We proposed a band diagram of needle-contact SBDs, where the lower Schottky barrier height is assumed considering the effect of surface potential. We confirmed the validity of the model by fitting analysis.

A high-entropy carbon-coated Na3V1.9(Mg, Cr, Al, Mo, Nb)0.1(PO4)2F3 cathode for superior performance sodium-ion batteries

A NASICON-type high-entropy carbon-coated Na3V1.9(Mg, Cr, Al, Mo, Nb)0.1(PO4)2F3 (NVPF-HE@C) material was synthesized through the sol-gel route. The incorporation of high entropy elements (Mg, Cr, Al, Mg, Nb) improved the stability of Na2 sites in NVPF without altering its crystal structure, which suppressed the intermediate reactions of Na3V2(PO4)2F3 phase at low potential of 3.4V. This improvement further lifted the specific capacity, capacity retention and Na+ diffusion coefficient of NVPF-HE@C cathode. The fluctuation of Na+ diffusion coefficient at low voltage region decreased 10−14-10−10cm2s−1 to 10−12-10−10cm2s−1. NVPF-HE@C cathode displays the initial specific capacities of 128 mAhg−1 at 1C and 82 mAhg−1 at 5C, while maintaining a low capacity decay of 17% over 800 cycles. The introduction of high-entropy doping provides an effective approach as promoting the electrochemistry properties of NVPF cathode, with potential applicability to other electrode materials in energy storage applications.

Evidence of second-order transition and critical scaling for the dynamical ordering transition in current-driven vortices

Dynamical ordering from a disordered plastic flow to an anisotropically ordered smectic flow induced by a dc force has been studied in various many-particle systems, including vortices in type-II superconductors. However, it remains unclear whether the dynamical ordering is a true phase transition because of lack of suitable experimental methods. Here, we study the response of vortex flow to the transverse force using a cross-shaped amorphous Mox\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_{x}$$\\end{document}Ge1-x\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_{1-x}$$\\end{document} film. From transverse current-voltage (force-velocity) characteristics under various longitudinal currents, we find a change of the transverse response in low voltage (velocity) regions from a nonlinear to linear behavior at a well-defined longitudinal current that marks the dynamical ordering transition. We also find the scaling collapse of the transverse current-voltage curves to a universal scaling function, providing evidence of the second-order transition for the dynamical ordering transition.

New insights into the closed pores formed of hard carbon for sodium-ion batteries

With the advantages of simple preparation, cost-effectiveness, abundant raw materials, and environmentally friendly properties, hard carbon (HC) is the only commercially available anode material for sodium-ion batteries. However, the unstable capacity of HC is attributed to the complex physicochemical characteristics of the precursors, the intricate and difficult-to-control microstructure, and the debated mechanisms of sodium storage. Although recent reports have revealed a strong correlation between closed pores and the capacity of HC in the low-voltage plateau region, there are few systematic overviews of this relationship. This review examines the microstructural properties and precursor selectivity of HC materials and outlines the strategies for the research and development of closed pores, including design theory and characterization. Finally, it summarizes the technical bottlenecks faced by the closed pore research and looks forward to the future development directions.