Active Area Research Articles

Transfer learning for anatomical structure segmentation in otorhinolaryngology microsurgery.

Reducing the annotation burden is an active and meaningful area of artificial intelligence (AI) research. Multiple datasets for the segmentation of two landmarks were constructed based on 41257 labelled images and 6 different microsurgical scenarios. These datasets were trained using the multi-stage transfer learning (TL) methodology. The multi-stage TL enhanced segmentation performance over baseline (mIOU 0.6892 vs. 0.8869). Besides, Convolutional Neural Networks (CNNs) achieved a robust performance (mIOU 0.8917 vs. 0.8603) even when the training dataset size was reduced from 90% (30078 images) to 10% (3342 images). When directly applying the weight from one certain surgical scenario to recognise the same target in images of other scenarios without training, CNNs still obtained an optimal mIOU of 0.6190±0.0789. Model performance can be improved with TL in datasets with reduced size and increased complexity. It is feasible for data-based domain adaptation among different microsurgical fields.

Developing TiCo2O4 spinel based on rGO nanosheet to enhance electrochemical performance of OER activity

The reduction of fossil fuel reserves and the deterioration of environmental conditions have led to a worldwide concern with producing significant amounts of energy in a sustainable manner. The production of electrocatalysts for the oxygen evolution reaction (OER) is imperative for widespread commercialization of water electrolyzers. The electrocatalysts must exhibit improved electrocatalytic behavior while being cost-effective. This work presents simple hydrothermal route for producing a TiCo2O4 nanostructure with a spherical morphology, which is supported on reduced graphene oxide sheets (rGO). The nanocomposite has been subjected to an investigation of its morphological, structural and electrochemical characteristics. This material exhibits promise for electrochemical water splitting due to its significant electroactive surface area, distinctive morphology and metal ions (M+) synergetic effect on its electrocatalytic performance. The nanostructure of TiCo2O4/rGO-has been observed to exhibit robust electrocatalytic activity, underscoring the significance of the present study. Additionally, presented are the enduring stability of the OER, along with the reduced overpotential (269 mV@10 mA cm−2), decreased Tafel slope (37.56 mV dec-1) with greater electrochemical active surface area. Our finding suggests that the TiCo2O4/rGO nanohybrid exhibited high electrocatalytic efficiency and can be utilized in diverse electrochemical applications.

Hydrogen generation by hydrolysis of alkaline NaBH4 solution doped with amorphous catalyst Co–Y2O3–B/CNTs

This investigation enhances the catalytic efficiency of Co–B/CNTs for hydrogen production via sodium borohydride hydrolysis by doping with 5%Y2O3. Such doping significantly boosts hydrogen evolution rates, with Co–Y2O3–B/CNTs achieving a production rate of 1083.43 ml g−1·min−1—surpassing Co–B/CNTs by 1.5 times and tripling that of Co–B catalysts. SEM and XRD analyses show Y2O3 doping reduces particle aggregation and maintains the catalyst's amorphous state, thereby increasing the active surface area. Furthermore, XPS analysis demonstrates that introducing yttrium into Co–B/CNTs catalysts improves their surface elemental composition and valence states. This improvement boosts catalyst performance and stability by enhancing electron transfer and particle size optimization. Optimal hydrolysis is achieved at an NaOH concentration of 2.5 mol/L, with higher concentrations diminishing hydrogen production due to increased viscosity from by-product formation. Additionally, Co–Y2O3–B/CNTs catalysts exhibit commendable durability, maintaining more than two-thirds of their initial activity after five reuse cycles, outperforming comparable catalysts to a moderate extent. These findings underscore the beneficial role of Y2O3 in the Co–B/CNTs framework, promoting Y2O3-doped catalysts for their enhanced efficiency, sustainability, and hydrogen production capabilities.

Core-shell Co-NC@NC nanomaterial for efficient oxygen reduction reaction

Transition metal and nitrogen doped carbons (M-N-C) catalysts present significant potential as substitutes for platinum-carbon (Pt/C) in catalyzing oxygen reduction reaction (ORR). Hence, we employ an epitaxial growth strategy to prepare Zn/Co-ZIF@ZIF-8 crystals with core-shell structure. Subsequent pyrolysis and acid etching produce highly porous cobalt-doped nitrogen materials for ORR investigation. The resulting Co-NC@NC catalyst demonstrates a graded porous structure alongside remarkable conductivity, possessing a specific surface area measuring 623 m2 g−1. It showcases heightened ORR activity with a half-wave potential (E1/2) of 0.886 V, superior kinetic performance (illustrated by an extremely low Tafel slope measuring 45.98 mV/dec), and strengthened stability (with mere 25 mV day after 40,000 cycles) when contrast with Pt/C catalysts in 0.1 M KOH. Additionally, it exhibits notable activity and stability in acidic environments. These remarkable attributes are attributable to the graded structure, which facilitates rapid mass transfer, a high electrochemically active area that exposes highly dispersed active sites, and a conductive carbon skeleton network that promotes electron transfer.

Self‐Assembled Molecules Fostering Ordered Spatial Heterogeneity for Efficient Ruddlesden‐Popper Perovskite Solar Cells

Abstract2D Ruddlesden‐Popper perovskites (RPP) with formamidinium‐cesium (FAC) alloyed cations possess powerful thermal‐moisture stability. However, their photovoltaic performance is hindered by the elusive spatial heterogeneity at multiscale lengths, highly associated with their coupled charge selective contacts. Herein, it reports on how the rational formation of self‐assembly molecules (SAMs) govern the orderliness of the spatial heterogeneity and crystal growth model in FACs‐RPP films, which is proposed to dictate the charge‐carrier dynamics. Unlike the disordered RPP film driven by the amorphous polymeric contacts, the laterally ordered crystallized SAM contacts facilitate a spatially ordered 2D/3D heterogeneity of FACs‐RPP film in long range, where distinct minor 2D phases are tightly coupled in short range. Such ordered heterogeneity can improve the energy transfer efficiency, facilitating the charge‐carrier dynamics in a well‐aligned 2D/3D landscape is discovered. Finally, the champion solar cells using selective SAM‐based FACs‐RPP films (n = 5) yield an efficiency of 18.85% (certified 18.19%) and excellent damp‐heat/operational stability, ranking in the top league of reported 2D RPP solar cells. More importantly, this SAM‐based principle can be adapted to diverse 2D structures, active areas, and substrate types. This work provides design directions for leveraging bottom‐selective contacts to tune spatial heterogeneity in state‐of‐the‐art 2D RPP optoelectronics.

Unraveling Electronic and Vibrational Coherences Following a Charge Transfer Process in a Photosystem II Reaction Center

A reaction center is a unique biological system that performs the initial charge separation within a Photosystem II (PSII) multiunit enzyme, which eventually drives the catalytic water-splitting in plants and algae. The possible role of quantum coherences coinciding with the energy and charge transfer processes in PSII reaction center is one of the active areas of research. Here, we study these quantum coherences by using a numerically exact method on an excitonic dimer model, including linear vibronic coupling and employing optimal parameters from experimental two-dimensional coherent spectroscopic measurements. This enables us to precisely capture the excitonic interaction between pigments and the dissipation of the energy from electronic and charge-transfer (CT) states to the protein environment. We employ the time nonlocal (TNL) quantum master equation to calculate the population dynamics, which yields numerically reliable results. The calculated results show that, due to the strong dissipation, the lifetime of electronic coherence is too short to have direct participation in the charge transfer processes. However, there are long-lived vibrational coherences present in the system at frequencies close to the excitionic energy gap. These are strongly coupled with the electronic coherences, which makes the detection of the electronic coherences with conventional techniques very challenging. Additionally, we unravel the strong excitonic interaction of radical pair (PD1 and PD2) in the reaction center, which results in a long-lived electronic coherence of >100 fs, even at room temperature. Our work provide important physical insight to the charge separation process in PSII reaction center, which may be helpful for better understanding of photophysical processes in other natural and artificial light-harvesting systems.

Electrochemical Detection of Glyphosate in Surface Water Samples Based on Modified Screen-Printed Electrodes

This study addresses the necessity to monitor the presence of glyphosate (Gly) in waters, highlighting the need for on-site detection of Gly by using electrochemical sensors in environmental and agricultural monitoring programs. Two approaches were employed: (1) modification with graphene decorated with gold nanoparticles (AuNPs-Gr) and dispersed in either dimethylformamide (DMF) or a solution containing Nafion and isopropanol (NAF), and (2) molecularly imprinted polymers (MIPs) based on polypyrrole (PPy) deposited on gold SPEs (AuSPE). Electrochemical characterization revealed that sensors made of AuNPs-Gr/SPCE exhibited enhanced conductivity, larger active area, and improved charge transfer kinetics compared to unmodified SPEs and SPEs modified with graphene alone. However, the indirect detection mechanism of Gly via complex formation with metallic cations in AuNPs-Gr-based sensors introduces complexities and compromises sensitivity and selectivity. In contrast, MIPPy/AuSPE sensors demonstrated superior performance, offering enhanced reliability and sensitivity for Gly analysis. The MIPPy/AuSPE sensor allowed the detection of Gly concentrations as low as 5 ng/L, with excellent selectivity and reproducibility. Moreover, testing in real surface water samples from the Olt River in Romania showed recovery rates ranging from 90% to 99%, highlighting the effectiveness of the detection method. Future perspectives include expanding the investigation to monitor Gly decomposition in aquatic environments over time, providing insights into the decomposition’s long-term effects on water quality and ecosystem health, and modifying regulatory measures and agricultural practices for mitigating its impact. This research contributes to the development of robust and reliable electrochemical sensors for on-site monitoring of Glyphosate in environmental and agricultural settings.

Highly Selective Ratiometric Sensors for Pb2+ Based on Luminescent Zn(II)-Coordination Polymers with Thiophenedicarboxylate. Crystal Structures and Spectroscopic Studies.

The development of luminescent coordination polymers for the selective sensing of Pb2+ in water constitutes an active area of research that impacts analytical, environmental, and inorganic chemistry. Herein, two novel water-stable 2D Zn-coordination polymers {[Zn2(H2O)2(tdc)2(bpy)]·(H2O)}n 1 and [Zn(tdc)(tmb)]n 2 (tdc = thiophenedicarboxylate; bpy = 4,4'-bipyridine and tmb = 4,4'-trimethylenebipyridine) were synthesized, structurally determined by single crystal X-ray diffraction, and studied in-depth as luminescent sensors for a series of cations (Ca2+, Mg2+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+ Cd2+, Hg2+ and Pb2+) in 20% aqueous ethanol. These Zn-polymers possess photostability in 20% aqueous ethanol with a strong emission at 410 upon excitation at 330nm and quantum yields of around Φ = 0.09. Under these conditions, Pb+2 can be efficiently sensed with polymer 2 through a fluorescent ratiometric response with selectivity over common interfering metal ions such as Cu2+, Cd2+ and Hg2+ in the micromolar concentration range (detection limit = 1.78 ± 10μM). Such selectivity/affinity of Pb2+ over Hg2+ for luminescent chemosensors is still rare. On the basis of spectroscopic tools (1H NMR, far ATR-IR, PXRD), the X-ray crystal structure of 2, and Scanning Electron Microscopy with Energy-Dispersive X-ray Spectroscopic analysis, the ratiometric fluorescent response is proposed via an efficient metal-ion exchange driven through interactions between thiophenedicarboxylate rings and Pb2+ ions. The use of flexible luminescent Zn-coordination polymers as sensors for selective and direct detection of Pb2+ in aqueous media has been unexplored until now.

Earthquake Risk Assessment in Seismically Active Areas of Qinghai Province Based on Geographic Big Data

Earthquakes can cause serious damage to buildings, roads and other infrastructure. The large amount of dust and particulate matter generated when these structures collapse and are damaged can quickly enter the air, leading to a decline in air quality. At the same time, earthquakes may cause secondary disasters such as fires and landslides, which will also produce large amounts of soot and particulate matter, which will have a negative impact on air quality. Therefore, earthquake disaster risk assessment studies are carried out to identify potentially hazardous areas and facilities in advance in order to reduce the air pollution problems that may be caused by earthquakes. Existing research on earthquake disaster risk assessment mainly evaluates earthquake risk from the perspective of geology or seismology, but there are few studies based on multidisciplinary assessment that integrates geology, seismology, engineering and social sciences into socioeconomic factors. To this end, based on remote sensing and GIS technology, this paper takes Qinghai Province, a seismically active area, as the research area, and integrates land use data, natural environment data, social environment data and seismic parameter zoning data to construct a comprehensive assessment model for earthquake disaster vulnerability and risk. The results showed that there were 5 very high-risk areas, 7 high-risk areas, 10 medium-risk areas, 11 low-risk areas and 12 very low-risk areas in Qinghai Province. The high-risk areas are mainly distributed in the central and western parts of Qinghai Province, where the earthquake breeding environment is sufficient, the scale of active faults is huge and the adaptability of the carrier is low. The results of an earthquake disaster risk assessment can provide a reference for the government to formulate environmental protection policies. According to the assessment results, the government can formulate targeted measures to strengthen air pollution control and improve air quality.

Unlocking the potential of hematite photoanodes in acidic electrolytes: Boosting performance with ultra‐small IrOx nanoparticles for efficient water splitting

AbstractPhotoelectrochemical (PEC) water splitting offers a promising route for harnessing solar energy to produce clean hydrogen fuel sustainably. A major hurdle has been boosting the performance of photoanode materials within acidic electrolytes—a critical aspect for advancing PEC technology. In response to this challenge, we report a method to augment the efficacy of hematite photoanodes under acidic conditions by anchoring IrOx nanoparticles, replete with hydroxyl groups, onto their surface. A remarkable and steady photocurrent density of 1.71 mA cm−2 at 1.23 V versus RHE was achieved, marking a significant leap in PEC efficiency of hematite in acidic media. The introduction of the IrOx layer notably expanded the electrochemically active surface area for more active sites, fostering improved charge separation and transfer. It also served as an effective hole capture layer, drawing photogenerated holes from hematite to facilitate swift migration to the active sites for the water oxidation process. This advancement has the potential to fully harness the capabilities of hematite photoanodes in acidic environments, thereby smoothing the path toward more effective and sustainable hydrogen production through PEC water splitting.

Enhancing Flow Batteries: Topology Optimization of Electrode Porosity and Shape Optimization of Cell Design

This research focuses on the improvement of porosity distribution within the electrode of an all‐vanadium redox flow battery (VRFB) and on optimizing novel cell designs. A half‐cell model, coupled with topology and shape optimization framework, is introduced. The multiobjective functional in both cases aims to minimize pressure drop while maximizing reaction rate within the cell. Topology optimization results reveal dependencies on initial value, porosity constraint, and flow rate. The distribution with lower porosity is preferred downstream of the inlet manifold. This design enhances active surface area, thus facilitating more effective conversion of incoming educts and improving mass transport of products. Compared to homogeneous electrodes, two‐part design demonstrates superior performance at specific porosity values. For combined porosities of 0.7 and 0.95, optimized distribution results in 81 % reduction in pressure drop, while conversion rate decreases by 7%. As regards various cell designs, optimization suggests a need to reconsider the vertical format of a rectangular cell. Horizontal cells are favored for nearly all porosities and flow rates. Trapezoidal and radial designs characterized by reduced downstream cross sections lead to higher pressure drops and are not preferred. This work provides further valuable insight into optimizing VRFB electrodes and challenges conventional cell design assumptions.

Performance Analysis of BER and SNR Performance in High-QAM Modulations Using Advancements in MIMO Systems

Wireless communications is one of the most active areas of technology development of our time. This development is being driven primarily by the transformation of what has been largely a medium for supporting voice telephony into a medium for supporting other services, such as the transmission of video, images, text, and data. Today, the widely deployed network type is based on a centralized approach that requires a network point of access, commonly called the Access Point (AP), to serves as a gateway between the mobile device and the Internet. The obtained results demonstrate that spatial diversity along with the power of STBC significantly improves the error performance in frequency selective wireless fading channels. The BER level is depend on the modulation type, SNR value and channel behavior. Modulation schemes that we have used in this paper are 4-QAM, 8-QAM, 16-QAM and 64-QAM which further improved using forward error correction codes (FEC). A comparison is made between the diversity gains of MIMO systems in terms of BER for high QAM modulation scheme. This work presents, a simulation toll MATLAB R2023a used for model implemented using Nakagami channel to study the performance analysis of Bit Error rate (BER) V/S Signal to Noise ratio (SNR). Keywords: AWGN, BER, Fading Channel, MIMO System, Nakagami, OFDM, QAM Modulation, SNR, STBC etc.

Omnipolar mapping and vector mapping in premature ventricular contractions ablation: a comparison with bipolar mapping

Abstract Background Omnipolar Mapping, with HD Grid high-density mapping catheter, overcomes the dependency of EGM characteristics to wavefront orientation, reconstructing the highest peak-to-peak voltage attainable within the electric field and the real wavefront direction, displayed in the form of a local activation vector [1][2]. Methods Consecutive patients who underwent radiofrequency ablation of PVCs from October 2021 to August 2023 at the Hospital Clinic of Barcelona were included in the study. EAM was performed with EnsiteX mapping system, Advisor HDgrid was used as mapping catheter. An activation map was performed if enough PVC burden. The area of interest was determined by earliest activation time combined with the morphology of unipolar electrogram during activation mapping. RF was delivered at the area of interest with target temperature of 45°C and maximum power of 50W. Both bipolar and omnipolar maps were analysed retrospectively. The reviewer was blinded to the ablation set for this analysis. A window of interest was created uniformally for all maps by defining a caliper within 15 ms before the onset of PVC. Activation vectors were displayed on the map and visually analysed. Three specific patterns were identified: Starburst, Homogeneous and Chaotic. Area of the earliest activation was measured. Earliest site of bipolar and omnipolar maps and specific location of star burst pattern were tagged. The site of the effective RF ablation was identified and the distance between points was determined. Results 18 patients were included. Overall, 11(61%) were males; age: 57,9±15,2 ys, 6(33%) patients haven't structural heart disease, 4(22%) presented PVC-induced cardiomyopathy. Mean left ventricular ejection fraction was 46±10. Mean PVC burden was 27±10%. In 9(50%) patients, PVCs were ablated from RVOT, 4(22%) in LVOT, 1(5%) in the left superior fascicle, 1(5%) in the antero-lateral papillary muscle, 2(10%) in the perihissian area and 1(5%) in the aortomitral continuity. Compared with bipolar, omnipolar mapping showed a smaller area of earliest activation(2,13±1,9mm2 vs 3,34±2,1 mm2,p<0,001), a shorter distance of the earliest point to starburst region(4,2±4,1mm vs 7,8±4,2mm,p<0,001) and shorter distance to the effective ablation site(6,1±3,9 mm vs 8,33±4,2mm, p<0,07). No significative difference was found between the effective RF ablation site and the starburst area compared to the distance between the effective RF ablation site and the omnipolar earliest deflection (6,11±3,9mm vs 6,5±4,3mm, p=0,6). No statistical significative difference was found between the timing of the earliest deflection in both settings (33,2±12,5 ms vs 31,5±12 ms, p=0,2) Conclusions Omnipolar mapping allows a better identification of the area of interest in PVC’s ablation compared to bipolar mapping. Vector mapping is a valuable asset to identify the earliest activation point to guide PVCs catheter ablation.Retrospective EAM analysisArea/distance measurements

Identification of reentry vulnerable targets during substrate mapping for ablation in scar related VT: the "visual" reentry vulnerability index

Abstract Introduction Conduction abnormalities including zones of deceleration (DZ) & late activation are functionally important targets for ablation in scar-related ventricular tachycardias (VT). Repolarisation heterogeneities are equally important but are not routinely assessed. Visualisation of a combination of both conduction & repolarisation metrics whilst in sinus in the form of a re-entry vulnerability index (RVI) may enable more precise identification of critical ablation targets. Rationale: To test accuracy of a novel functional substrate mapping strategy combining conduction & repolarisation metrics to "visually" estimate reentry vulnerability sites (RVIv) during scar related VT ablation without the need for offline processing required for "computational" RVI. Methods VT cases using a multipolar grid-catheter for contact mapping were reviewed. DZ &areas of late activation were tagged on omnipolar LAT substrate maps. The corresponding unipolar repolarisation maps depicting local repolarisation time (LRT) based on the Wyatt method (WOI over T-Wave annotating to +dV/dt, UEGM-Filter 0.05-100Hz) were then displayed side-by-side with the LAT map. Timing reference was set to onset of surface QRS. Colour scale of LRT maps was set to start at or ahead of the timing of latest LAT. "Visual RVI" zones were identified if the tagged zone of late activation was overlapping and/or directly adjacent to an area of "early" repolarisation (defined as before or within 100ms of latest LAT point) based on colour. In visually identified RVI areas, temporal (timing difference in ms) & spatial relationship (distance in mm) of EGMs with earliest RT (RTe) to EGM with latest AT (ATL) separated by max. 20mm were measured & RVI calculated (RTe subtracted by ATL). Number of RVIv zones per map, RVI metrics & distance from closest RVI to VT Exit site (defined per activation±entrainment or pace mapping) were assessed. The lower/negative the numeric RVI, the higher the vulnerability for reentry. Results 20 patients with scar-related reentry VT were included (90% male, 63.8±11.6 years, LVEF 36±16%, 60% ischemic/40% non-ischemic). LAT & LRT map point counts were 4835±2625 and 3596±2805. In 17 (85%) patients at least 1 RVIv zone was identified, with on avg. 3.3±1.7 RVIv zones/patient. Manual RVIs were calculated to 10.4±78.9ms ( "most vulnerable" RVI was -227ms) with on avg. 9.5±5.3mm distance between RTe & ATL. All maps with no RVIv zone on the mapped surface were of non-ischemic etiology. The shortest distance of RVIs to functionally critical sites during VT was 8.9±7.4mm (range 0-33mm). Conclusion Visual reentry vulnerability estimation based on a combination of established conduction and novel repolarisation maps is feasible & may help to identify functionally critical zones during substrate mapping. Future efforts should include dedicated automated repolarisation mapping tools to facilitate integration of repolarisation dynamics in functional VT substrate mapping workflows.Figure 1Example Visual RVI Mapping

Peak frequency mapping usefulness and utilization for typical AVNRT ablation

Abstract Background Accurate identification of slow pathway for the AVNRT ablation is important to achieve successful result and avoid complications mainly AV nodal block. There were some developments to produce precise image to locate this such as identify low voltage bridge (LVB) using electro-anatomical mapping and visualization of direct slow pathway capture (DCSP). The peak frequency (PF) associated with bipolar EGMs is a novel parameter which may serve to distinguish near filed (NF) from far field (FF) electrocardiogram (EGM) components. This technique can be used to differentiate sub-components derived from high density mapping. Previous study suggested this mapping appears to assist in substrate differentiation, pathway localization, and contact assessment. However, this approach has been never evaluated clinically in AVNRT ablation Objective This study conducted to evaluate the usefulness and utilization of the peak frequency mapping to identify the slow pathway location. Method The study conducted in November to December 2023 where twenty consecutive patients with common AVNRT were included in the study. Regular bipolar voltage and activation maps were generated with a regular 4 mm tip catheter. Following this, peak frequency maps (PF) were computed online prior ablation and displayed on the activation map with shadowed areas where PF was <200 Hz (figure, left panel). Focal radiofrequency application (RFa) was directed to the areas of late activation (figure, left panel) and low frequency (figure, right panel) (LA-LF). Successful ablation reached if junctional rhythm was recorded during RFa and AVNRT was no longer inducible afterwards. Results Twenty patients (48 ±15 years, 75% female) were enrolled in the study. A late activation low frequency area of 0.92±0.48 cm2 was found in 18 of them. This study revealed that there was a difference between PF in the slow pathway area compared to the adjacent area where the mean PF at the slow pathway area was 175.5 ± 37.1 Hz (analysis per patient) and 170.1 ± 48.10 Hz (analysis per recording site) which was lower and differed significantly than the PF recorded at the adjacent atrial area (279.71 ± 28.11 Hz per patient, 279.91 ± 69.47 Hz per recording site) (P<0.0001). Following the mapping, RFa were successfully applied at these late activation low-frequency (LA-LF) area induced junctional rhythm in 17 patients. AVNRT was no longer inducible after the ablation in all 17 patients. Additional RFa were often given to reinforce the result (11 ± 9 RFa, 4.03 ± 3.35 min RFa time). Conclusion The peak frequency mapping could be performed to map the slow nodal pathway which is often located in an area of late activation and low frequency.

SLAM-guided catheter ablation of AVNRT: single-center experience

Abstract Aims Three-dimensional mapping systems have been utilized to reduce fluoroscopy and minimize complications in patients with AVNRT. Recently, voltage-gradient mapping has been introduced to visualize low-voltage bridges. However, there are some limitations of voltage assessment due to catheter contract. Therefore, new Slow pathway Late Activation Mapping (SLAM) has been recently used to reveal slow conduction zone in AVNRT patients. Method and materials Seven adult patients with diagnosis of typical AVNRT were included. Electro anatomical mapping systems was used in all patients. Voltage and late activation mapping were performed with high-definition multipolar catheter. His cloud was also tagged in all patients. Voltage of 0.20-0.50 mV was used to delineate voltage-bridges. Latest activation in the SP area along with voltage-guided bridges were targeted with either radiofrequency ablation (RFA) or focal cryoablation (Figure 1 and 2). Results Limited fluoroscopy was used in 4 patients. Acute success was achieved in all patients. Patients had no structural heart disease. Detailed clinical and procedural data was depicted in Table. Cryoablation was used in 2 patients due to very small Koch triangle. Each cryolesion applied for 240 secs and overall, 3-4 lesions were delivered. Ablation at late activation areas successfully eliminated slow pathway. In most of cases, one ablation lesion was adequate to see junctional beats and elimination of dual AV nodal physiology. Conclusion SLAM is effective in guiding catheter ablation of AVNRT, with a complete acute success rate and no recurrences at short-term follow-up.

Activation map of koch triangle: a novel approach to AVNRT ablation using CARTO 3 v7

Abstract Background Ablation of slow pathway (SP) is the standard approach for atrioventricular nodal reentry tachycardia (AVNRT) treatment (1). Low-voltage bridge is an optimal target during mapping using low x-ray exposure (2,3). Purpose We want to assess a new tool to identify SP by activation mapping of Koch’s triangle using CARTO PRIME V7 Methods Triangle of Koch 3D-activation map were obtained from intracardiac contact mapping during low x-ray CARTO 3 procedures (Figure 1). In 60 patients (39 % males, mean age 60.3 ± 14.7 years) undergoing ablation for AVNRT, an automatic activation map using a DECANAV mapping catheter and CARTO Confidense, Coherent, and FAM DX software modules were obtained. Results We indentified SP in all patients as the latest atrioventricular node activation area; RF catheter ablation (RFCA) elicited junctional beats. The mean dose-area product (DAP) was 16.5 ± 2.7 cGy/cm2, the mean fluoroscopy time exposure was 2.9 ± 2 min, the mean ablation index was 428.6 ± 96.6, and the mean contact force was 8 ± 2.8 g. There were no adverse event during the procedure and no AVNRT recurrences during a mean follow-up of 14.3 ± 8.3 months. Conclusions Ablation of the SP by automatic mapping using Confidense, Coherent, and FAM DX software modules is a new approach to AVNRT ablation. The CARTO3 V7 system defines a 3D map of the latest AV node activation area during sinus rhythm allowing a highly effective RFCA under low fluoroscopy time exposure without recurrences or AV blocks.Figure 1

Investigation of Proton Exchange Membrane Fuel Cell Performance by Exploring the Synergistic Effects of Reaction Parameters via Power Curve and Impedance Spectroscopy Analysis

In this paper, a comprehensive analysis of the parameters that affect polymer electrolyte membrane fuel-cell performance is presented. Experiments were conducted on a single fuel cell membrane with an active area of 5 cm2. To study the fuel cell operation, parametric studies of temperature, pressure and relative humidity values were conducted under cyclic voltammetry for impedance analysis. The impact of the behavior of all three parameters on the fuel-cell performance were recorded and analyzed. As the temperature increased from 50 °C to 74 °C, the Pt catalyst surface areas demonstrated lower activation losses as the membrane conductivity increased. It is confirmed that an increase in temperature accompanied higher humidity levels to provide sufficient cell hydration that resulted in a higher performance output. The impedance measurements indicate that low humidity levels resulted in higher cell resistance and mass transport losses. As the back pressure increased, the membrane resistance decreased, which also reduced mass transport losses. The results indicate that the important factors affecting the fuel cell performance are mass transport limitation and membrane resistance. Based on the results of this study, the optimum performance can be achieved by operating at higher pressures and temperatures with humidified reactant gases.

Understanding Performance Limitation of Liquid Alkaline Water Electrolyzers

Abstract Liquid alkaline water electrolyzers (LAWEs), being the most commercially mature electrolysis technology, play a pivotal role in large-scale hydrogen production. However, LAWEs suffer from low operational efficiency, primarily due to un-optimized electrode structure and chemical compositions. Thus, we investigated how various electrode configurations could impact LAWE performance. Our results show that Ni felt electrodes outperform the conventional Ni foam thanks to improved electrochemical active surface area (ECSA) and preferred electrode surface structure that minimizes the micro-gaps in between the electrode and separator. By comparing the stainless steel (SS) felt electrodes with Ni felt electrodes, SS not only shows better oxygen evolution reaction activity but also improved hydrogen evolution reaction activity, which is less studied in the literature. We also show that a bilayer structure with small pore radius facing the separator could further improve LAWE performance by further optimizing interfacial contact between electrode and separator. These findings enable LAWEs to sustain 2 A cm-2 at 2.2 V and operate steadily at 1 A cm-2 for nearly 600 h with negligible performance decay. Our studies establish criteria for selecting electrodes to achieve high-performance LAWE and, in turn, expedite the adoption of LAWEs in hydrogen production and the transition towards low-carbon economies.

Partial photoelectrocatalytic oxidation of 3‐methylpiridine in green conditions by nanotube/nanowire Ti/TiO2 plates prepared in aqueous, glycerol, or ethylene glycol medium

Nanotube/nanowire structured TiO2 samples on Ti plates were prepared by anodic oxidation in aqueous, glycerol or ethylene glycol medium under different experimental conditions and characterized by XRD, SEM‐EDX, electrochemical methods (photocurrent profiles and electrochemical impedance spectroscopy). The nanostructured TiO2 was built on relatively large Ti plates, and consequently, in some preparation conditions, different morphologic properties were observed in the underside and upside zones of the electrodes, especially in ethylene glycol medium. The electrodes were tested for selective photoelectrocatalytic oxidation of 3‐methylpyridine to 3‐pyridinemethanol, 3‐pyridinemethanal and vitamin B3 in water under UVA irradiation. The best performance was found with the electrode prepared in ethylene glycol/water/NH4F (98/2/0.3 w/w) medium at 36 V potential for 3 h, while the worst was that prepared in aqueous medium which showed the shortest nanostructure length. Unlike photoelectrocatalysis and photocatalysis, no carbonyl products were obtained in electrocatalytic and photolytic experiments. The selectivity values of the products were similar for the various electrodes, while the morphology of the nanotubes/nanowires and their quantity which affects the total active surface area were essential for the substrate conversion. The results also show that the photocurrent intensity, XRD peak intensity, and electrical conductivity are correlated with photoelectrocatalytic activity of the Ti/TiO2 electrodes.