Residual Conductivity Research Articles

Influences of residual stomatal conductance on the intrinsic water use efficiency of two C3 and two C4 species

Influences of residual stomatal conductance on the intrinsic water use efficiency of two C3 and two C4 species

Ultralow-temperature heat transport of quantum spin liquid candidates: A brief review

Abstract Heat can be carried by any kind of quasiparticles in solids and therefore low-temperature heat transport is powerful in probing the charge-neutral excitations in many quantum materials. In recent years, ultralow-temperature heat transport has been used to detect the exotic excitations in quantum spin liquids. The non-zero residual thermal conductivity κ 0/T is strong evidence of itinerant spinons and the gapless property of disorder state. The thermal Hall effect can also be contributed by the spinons or Majorana fermions in quantum spin liquids. Here we review representative thermal conductivity results of different quantum spin liquid candidates and discuss the role of spinons in both carrying heat and scattering phonons. We further review different experimental phenomena and underlying mechanisms of thermal Hall effect in some quantum spin liquid candidates with three-dimensional pyrochlore structure, two-dimensional honeycomb and triangular lattice. We expect this review to provide a useful guidance for the understanding of the ultralow-temperature heat transport in quantum spin liquids.

Biomass‐based crosslinked composite anion exchange membranes using bacterial cellulose template towards enhanced ionic conductivity and alkaline stability

AbstractA balanced relationship among ionic conductivity, mechanical properties and alkaline stability of anion exchange membranes (AEMs) is essential for their practical application in fuel cells. Herein, a porous substrate (BC@LDH) with hierarchical structure was constructed using natural bacterial cellulose (BC) as a template and then in situ grew inorganic hydroxide ion conductor (layered double hydroxide, LDH). The membrane was fabricated via a filling together with sol–gel crosslinking strategy after impregnating an ionomer containing both quaternary ammonium and hydroxyl groups into the porous substrate and then crosslinked by organosiloxane. Due to the synergistic enhancement effect of BC, LDH and cross‐linking, the obtained membrane exhibited a tensile strength of 47.48 MPa that was 88.3% higher than that of the pure ionomer membrane, and showed an ionic conductivity of 70.7 mS cm−1 (80°C) which benefited from the introduction of ionic conductor LDH. More importantly, its alkaline stability was significantly improved and the residual conductivity ratio was still as high as 81.5% even after hot alkali treatment for 580 h. The direct methanol fuel cell assembled with this membrane exhibited a peak power density of 13.6 mW cm−2 with an open‐circuit voltage of 0.72 V, indicating its potential application in biomass‐based AEMs for fuel cells.Highlights Hierarchical porous substrate comprising LDHs anchored BC fiber was prepared. LDH@BC served as a reinforcing substrate and an ion transport medium. The crosslinked membrane showed significantly improved alkaline stability. The membrane had high ionic conductivity and mechanical strength. Providing a new way to design biomass‐based AEMs with high performance.

Safety and efficacy of perventricular device closure of ventricular septal defects in children

Abstract Objectives To evaluate safety and efficacy of perventricular device closure techniques for the closure of ventricular septal defects (VSD) in children in United Arab Emirates. Methods In the year 2023-24, 13 children underwent per-ventricular device closures of VSD under the guidance of transesophageal echocardiography without cardiopulmonary bypass(CPB). The mean age at operation was 3.76 years (range 3 months-14 years). The ventricular septal defect sizes ranged from 2.7-6 mm. The device sizes ranged from 5-12mm. All patients except two required symmetrical device. Eight defects were peri membranous, 3 were sub-aortic and 2 were muscular. Ventricular septal defect occlusion device (Memoport, Beijing, China) were used through a 3-cm skin incision in the lower third of the sternum. Results All patients underwent VSD device closure successfully. The mean procedural duration was 42 minutes. None of the patients required CPB. The mean ventilation time and ICU stay was 3 hrs. and 24 hrs. respectively. None of the patients required inotropic support or blood transfusions. There were no residual shunt (except small shunt through the device), arrhythmias including heart block post operatively. At follow up, (3 months-7 months) there were no residual shunts, conduction disturbances, device dislodgement or major aortic or tricuspid valve complications. There was no mortality. Conclusions Perventricular device closure of VSD is highly successful, less invasive, safe and effective. It is associated with quick recovery, short length of stay and better cosmetic incision. Moreover, it avoids CPB.

Flow Characteristics and Heat Transfer Enhancement of Electro-Thermo-Convection in Dielectric Liquids With Residual Conductivity

Abstract The flow features and heat transfer enhancement of electro-thermo-convection (ETC) in dielectric liquids with residual conductivity between concentric electrodes are numerically studied based on an injection–conduction model. The strongly coupled flow field, electric field, and positive/negative charge density of the ETC system are solved numerically based on the finite volume framework of OpenFOAM®. The total variation-diminishing algorithm is adopted to handle the complex nonlinearity of the positive/negative charge transport equations. The bifurcation of plentiful flow states that are characterized by variable plumes and vortex pairs in the ETC system is investigated. It is discovered that the residual conductivity postpones the beginning of ETC flow, inhibits the convection intensity, and also diminishes heat transfer of the ETC system. In addition, the transition sequences of ETC flow are also influenced by residual conductivity. A higher residual conductivity suppresses the occurrence of different intermediate steady-states. Three different transition sequences of steady ETC states at different Rayleigh numbers (Ra) are identified. The critical point where the ETC flow bifurcates to S8 is postponed at higher Ra. And the ETC system is more prone to chaos in a system of higher Ra. The periodicity of the ETC system is analyzed and found that Ra has little influence on the periodicity.

Dynamic interactions between groundwater level and discharge by phreatophytes

Many traditional models that predict plant–groundwater use based on groundwater level variations, such as the White method, make various simplifying assumptions. For example, these models often neglect the role of plant hydraulic redistribution, a process that can contribute up to 80% of transpiration. Thus, this work aims to avoid such assumptions and subsequently explore the dynamic interactions between groundwater levels and phreatophytic vegetation, including plant nocturnal transpiration, hydraulic redistribution, and response to atmospheric conditions, in shallow-groundwater ecosystems using Loblolly pine (Pinus taeda) as a model species. The model scenarios are formulated using a stomatal-optimization model coupled to the soil–plant–atmosphere continuum. Flow through soil and groundwater are described using the Richards equation and a linear reservoir approximation, respectively, with groundwater in contact with an external water body of fixed elevation. Results show that nocturnal transpiration, mediated by plant residual conductance, and hydraulic redistribution, are able to reduce groundwater levels at night and alter the groundwater recharge rate. Projected atmospheric conditions of increased carbon dioxide and elevated temperature have opposing effects on groundwater levels, which tend to roughly cancel each other under a projected scenario of 500 ppm carbon dioxide and 1.5 oC warming. Such detailed modeling can be used to provide further insights into coupled interactions between vegetation, climate and groundwater levels in phreatophyte-dominated ecosystems.

The prospects for the use of alternative gel formers for hydraulic fracturing

The article discusses the relevance of using alternative gel-forming agents in the preparation of fracturing fluids for hydraulic fracturing (HF). Besides the obvious tasks, such as increasing the residual conductivity of the fractures created during stimulation, it also addresses the impact of alternative gelforming agents on the treatment process. The author, supported by field data, concludes that under otherwise equal conditions, replacing traditional fracturing fluids with alternative ones significantly reduces frictional pressure losses in the pipes, which is particularly important when treating deep and extensive horizontal wells with limited internal pipe diameters. Moreover, the aforementioned impact of gel-forming agents on frictional pressure losses allows for a reserve of power in the hydraulic fracturing fleet equipment. Consequently, the treatment can be performed with higher flow rates under otherwise equal conditions, without the need for additional high-pressure pumps or the deployment of more expensive, stronger, larger-diameter tubing. Another important conclusion reached by the author is that due to the specific properties of alternative fracturing fluids, their ability to transport and retain proppant is significantly increased. This property of fracturing fluids is especially important when treating low-permeability, fractured formations and during the stimulation of long horizontal wells. On the other hand, the use of alternative gel-forming agents raises the requirements for the controlled breakdown of fracturing fluids, complicating the task of selecting a rational formulation and necessitating additional research.

Theoretical analysis of entropy generation in multilayer insulations: A case study of performance optimization of variable density multilayer insulations for liquid hydrogen storage systems

Liquid hydrogen (LH2) is a promising and economical clean energy for achieving global carbon neutrality. Multi-layer insulation (MLI) with high performance is essential for the safe storage and operation of LH2. To perform a better optimization of MLI, the second law of thermodynamics becomes a complement to the first law of thermodynamics. However, very few studies have carried out the optimization of MLI performance through the second law of thermodynamics. For the sake of achieving more efficient optimization of MLI as well as revealing the fundamental indicators limiting the performance of MLI, this paper analyzes the characteristics of entropy generation produced by the solid heat conduction, thermal radiation, and residual gas conduction distributed in the MLI schemes by a validated layer-by-layer model.For a 40-layer MLI arranged with a constant layer density of 20 layers/cm, the first 15 layers near the cold boundary occupy more than 98% of the total entropy generation, providing an effective range of layers for thermodynamic optimization. Besides, an optimization of variable-density MLI (VDMLI) separated into two segments based on the entropy generation minimization is conducted. The optimal VDMLI has substantially lowered the entropy generation from the solid heat conduction but at the cost of increasing the entropy generation from radiation and residual gas conduction. This study provides a reliable optimization method of MLI, which allows the safe storage of clean energy with a low boiling temperature.

Health monitoring of bonded joints through electrical measurements

The aim of this research work is to explore the possibility of continuously monitoring the presence of damage in bonded joints through electrical measurements. Initially, an analytical model for estimating the crack length based on the electric resistance increase measured across the bond area is presented. The model is successfully validated through finite element analyses and experimental tests on single lap joints made of a conductive adhesive and aluminium or carbon/epoxy adherends. For the last case, the model is extended to account for damage scenarios where a residual conductivity is present across crack faces, due, for instance, to fibre bridging. Eventually, a procedure for predicting the crack length and the stiffness reduction in bonded joint based on electrical measurement is developed.

Tuning poly(isatin biphenyl) anion exchange membranes by copolymerization and branching

The cardo structure and long side chain of poly(isatin biphenyl) are conducive to the motion and aggregation of cations over mainchain type membranes, therefore it is used as the pristine membrane. It is well known that random copolymerization and branching can effectively modify the configuration and properties of polymers. Herein, we use random copolymerization and branching to improve the behaviors of poly(isatin biphenyl) anion exchange membranes (AEMs). High-curvature random copolymers (QPIDBP-n) and high free volume branched polymers (b-QPIBP-x) are synthesized via polycondensation. The random copolymerization results in the formation of a twisted chain structure, while the introduction of branching agent leads to the formation of orderly stacking of chains. Both of these approaches have been demonstrated to boost the microphase-separated morphology of the pristine polymer. A series of QPIDBP-n and b-QPIBP-x are tested and an optimal ratio is explored. QPIDBP-40 and b-QPIBP-5 exhibit high overall performance. Among the as-prepared membranes, b-QPIBP-5 exhibits the highest conductivity (80 °C, 160.7 mS cm−1) with a swelling ratio of 20.7 %. The residual conductivity of b-QPIBP-5 is 93.1 % after the 1200 h alkali stability test. The cell assembled by b-QPIBP-5 achieves a peak power density of 680 mW cm−2. Moreover, the b-QPIBP-5 based cell holds 88.6 % voltage after the in-situ stability test for 50 h.

Graphene oxide nanosheets reinforced quaternized poly(2,6-dimethyl-1,4-phenylene oxide) composite membranes with enhanced hydroxide ions conduction at subzero temperature

The realization of high hydroxide ion conductivity on the premise of enough alkaline stability is basic of the practical application of anion exchange membranes (AEMs). In this research, we propose a facile way to enhance the hydroxide ion conductivity at subzero temperature through constructing multilayered microstructures of AEMs. Graphene oxide (GO) nanosheets and 3,6-diazaspiro[5.5]undecane bromide (DSUBr) are alternately deposited on the surface of a quaternized poly(2,6-dimethyl-1,4-phenylene oxide) (QPPO) membrane with the layer by layer self-assembly process. Multilayered and compact microstructures are retained even if the prepared QPPO/(GO/DSUOH)5 membranes are immersed in 2 M KOH solution for 300 h. The hydroxide ions conduction resistance is reduced, deriving from the well-ordered dispersion of components. For example, the QPPO/2-(GO/DSUOH)5 membrane exhibits the hydroxide ion conductivities of 0.922 mS/cm at −25 °C and 58.5 mS/cm at 80 °C. Furthermore, the prepared AEMs possess the enhanced hydroxide ion conductivity owing to the fine dimension and component stabilities. After the ten-cycle hydroxide ion conductivity stability test, the retention rates of hydroxide ion conductivity are 99.4 % at −25 °C and 105 % at 30 °C. Additionally, the residual hydroxide ion conductivity reaches 61.6 mS/cm at 80 °C in 2 M KOH solution for 624 h. A single fuel cell equipped with the QPPO/2-(GO/DSUOH)5 membrane exhibits the maximum power densities of 80.8 mW/cm2 at 30 °C and 351.6 mW/cm2 at 60 °C.

Perventricular device closure of the ventricular septal defects in children-first experience in the United Arab Emirates

BackgroundVentricular septal defect (VSD) is the most common congenital cardiac malformation, accounting for approximately 30% of congenital heart defects. Conventional surgical repair using cardiopulmonary bypass is invasive and associated with morbidities and prolonged hospital stay. With the advent of interventional approaches and availability of different occluding devices, the technique of perventricular device closure is evolving and being implemented successfully in larger groups of patients. We present herein, our initial experience of perventricular device closure for the ventricular septal defects in children to assess risks and benefits.MethodsFrom March, 2023 to February, 2024, we have performed perventricular closure of ventricular septal defects in 13 children, under guidance of transesophageal echocardiography without cardiopulmonary bypass support. The median age at operation was 2 year (range 1.3–10 years) with the median body weight 11 kg (range 8.7–16.6 kg). Sixty-nine percent were males. The ventricular septal defect sizes ranged from 2.7 to 6 mm (mean 4.7 mm). Seven defects were perimembranous, four sub-aortic and two were muscular. One patient also underwent pulmonary artery de-banding with pulmonary artery balloon angioplasty and other one patent ductus arteriosus ligation, concomitantly. For defect closure, we used ventricular septal defect occlusion device (MemoPart™, Lepu Medical Technology Company, China) through a 3-cm skin incision in the lower- third of the sternum. The device sizes ranged from 5 to 8 mm (mean 6.9+-1.8 mm) and all patients except for two required symmetrical devices.ResultsAll patients underwent device closure successfully. The procedural duration ranged between 32 and 52 min. None of the patients required cardiopulmonary bypass. The mean ventilation time and intensive care unit stay was 3 and 24 h, respectively. None of the patients required inotropic support or blood transfusions. Moreover, no patients developed any arrhythmias including heart block. The average length of hospital stay was 4.4 days. At the latest follow up, there were no residual shunts, conduction disturbances, device dislodgement or major aortic or tricuspid valve complications seen in any patients. There was no mortality.ConclusionsPerventricular device closure of ventricular septal defects is a less invasive, extremely safe and effective method in children. It is associated with very fast recovery, shorter hospitalization time and better cosmetic incision. Moreover, it avoids cardiopulmonary bypass. The modifications and refinements in the design, material and implantation techniques will help in expanding the indications and prevent complications in the long-term.

Three-dimensional fracture space characterization and conductivity evolution analysis of induced un-propped fractures in shale gas reservoirs

Huge numbers of induced unpropped (IU) fractures are generated near propped fractures during hydraulic fracturing in shale gas reservoirs. But it is still unclear how their fracture space and conductivity evolve under in-situ conditions. This paper prepares three types of samples, namely, manually split vertical/parallel to beddings (MSV, MSP) and parallel natural fractures (NFP), to represent the varied IU fractures as well as their surface morphology. Laser scan and reconstruction demonstrate that the initial fracture spaces of MSVs and MSPs are limited as the asperities of newly created surfaces are well-matched, and the NFPs have bigger space due to inhomogeneous geological corrosion. Surface slippage and consequent asperity mismatch increase the fracture width by several times, and the increase is proportional to surface roughness. Under stressful conditions, the slipped MSVs retain the smallest residual space and conductivity due to the newly sharp asperities. Controlled by the bedding structures and clay mineral hydrations, the conductivity of MSPs decreases most after treated with a fracturing fluid. The NFPs remain the highest conductivity, benefitting from their dispersive, gentle, and strong asperities. The results reveal the diverse evolution trends of IU fractures and can provide reliable parameters for fracturing design, post-fracturing evaluation, and productivity forecasting.

Post-ablation atrial arrhythmogenic channels predict atrial fibrillation recurrence - iatrogenic substrate revisited

Abstract Background Fibrosis is a hallmark of atrial fibrillation (AF) arrhythmogenic substrate, and the extent of atrial fibrosis, as determined by late gadolinium enhancement (LGE)-MRI, predicts AF recurrence after ablation. However, ablation fundamentally alters the individual composition of fibrotic tissue, and inhomogeneous ablation lesions may constitute an arrhythmogenic substrate themselves. From ventricular arrhythmias (VA) we know that it is not the extent of scar tissue that determines arrhythmogenicity, but rather the scar-pervading channels of surviving tissue with residual conduction. Purpose To investigate post-ablation arrhythmogenic substrate in terms of atrial scar channels using LGE-MRI. Methods Patients with PVI-only AF ablation were included. All patients received a systematic 12-months follow-up and an LGE-MRI 3 months post-ablation. Scar channels were defined as corridors of borderzone tissue (residual conduction), protected by dense scar. Channels were automatically identified using a software algorithm that has been extensively validated in the ventricle and was now adapted for the atrium. To differentiate healthy tissue, borderzone and dense scar, LGE was quantified based on the signal intensity ratios of each voxel relative to the blood pool. Signal intensity ratio thresholds defining dense scar and borderzone, were then empirically tested to enhance the predictive value of the identified channels. The algorithm was then applied to an independent validation cohort using the empirically determined thresholds. Results 150 patients were included. 10 different combinations of signal intensity ratio thresholds defining borderzone tissue and dense scar were empirically tested regarding the prediction of potentially arrhythmogenic channels in 50 patients (derivation cohort). For each of the threshold combinations, the number of predicted channels was linked to 12-months arrhythmia-free survival using logistic regression. The computed channels best predicted 12-months arrhythmia recurrence, when based on signal intensity ratios of 1.1-1.32 (borderzone) and >1.32 (dense scar). This threshold combination was then validated in an independent cohort of 100 patients. Patients with scar channels had significantly lower arrhythmia-free survival than those without (55% vs. 88%, p=0.016, Fig. 1). The number of detected scar channels was predictive of 12-months arrythmia recurrence (OR 4.9; p=0.012) – independent of other factors like LA diameter, AF type or the extent of native atrial fibrosis (pre-ablation LGE-MRI). Of note, the number of gaps in the PV-encircling lesions was not predictive of AF recurrence. Conclusions LGE-MRI-detected post-ablation scar channels predict recurrent AF after PVI and may be a surrogate of iatrogenic substrate. In light of large-area ablations with PFA and other single-shot devices fueling a trend towards more and more extensive lesions, the concept of iatrogenic arrhythmogenic substrate may have to be reconsidered.

Radiofrequency catheter ablation for redo procedures after pulmonary vein isolation with the cryoballoon technique: 9-year outcome

Abstract Catheter ablation has become the first line of therapy in patients with symptomatic, recurrent, drug-refractory atrial fibrillation. Cryoablation has been shown to be a safe and effective technique for pulmonary vein isolation. However, there is a significant arrhythmia recurrence rate after cryoablation procedures and there are no established strategies for redo procedures in these patients. Therefore, we have summarized our experience with radiofrequency catheter ablation for redo procedures after pulmonary vein isolation with the cryoballoon technique (including an analysis of pulmonary vein conduction recovery patterns after procedures performed with the first or second generation cryoballoon). Methods Two hundred and twenty patients (paroxysmal AF: 140 patients, persistent AF: 80 patients) had to undergo a redo procedure after initially successful circumferential PV isolation with the cryoballoon technique (First generation: 110 patients (group A); second generation: 110 patients (group B)). The redo ablation procedures were performed using a segmental approach or a circumferential ablation strategy (three-dimensional mapping system) depending on the intra-procedural findings. Results During the redo procedure, a mean number of 1.6 re-conducting PVs were detected (using a circular mapping catheter; group A: 2.2 re-conducting PVs, group B: 1.0 re-conducting PVs). There was a slightly higher incidence of chronic PV reconnections related to the left-sided PV ostia than to the right-sided PVs in both groups. Furthermore, sites of chronic PV reconnection were found more frequently in the inferior parts of the PV ostia than in the superior parts. In 97 patients in group A, a segmental approach was sufficient to eliminate the residual PV conduction because there were only a few recovered PV fibers (1-3 reconnected PVs; group A1). In the remaining 13 patients in group A, a circumferential ablation strategy was used because of a complete recovery of the PV-LA conduction of all four pulmonary veins (group A2). In group B, a segmental approach was sufficient in nearly all patients (109/110) because there was only a minor reconnection of 1-2 PVs. All recovered PVs could be isolated sucessfully again. At 108-month follow-up, 69.1 % of all patients were free from an arrhythmia recurrence (152/220 patients; group A: 72/110 patients (65.5 %), group B: 80/110 patients (72.3 %)). There were no major complications in both groups. Conclusions In patients with an initial circumferential PVI using the cryoballoon technique, a repeat ablation procedure can be performed safely and effectively using radiofrequency catheter ablation. In most cases only a few re-conducting PV fibers were found and therefore, a segmental re-ablation approach seems to be sufficient in the majority of patients (especially in patients treated with the second generation cryoballoon).

The hybrid ablation approach to treating long-standing persistent atrial fibrillation: real-world data from a tertiary institution

Abstract Background Pulmonary vein isolation(PVI) is effective treatment for atrial fibrillation(AF) but efficacy of endocardial ablation-alone for long-standing persistent AF is limited(1). Hybrid AF ablation may offer better outcomes but studies were on patients with paroxysmal/persistent-AF(2) and relied on Holter-alone to assess recurrences(3). Our hybrid-AF ablation patients were all long-standing persistent cases and monitored with implantable loop recorders(ILR). Aim Evaluate long-term outcomes of hybrid-AF ablation using ILR data. Methods The hybrid approach at our institution consisted of a first-stage minimally invasive surgical epicardial ablation of the left atrial posterior wall via radiofrequency (RF) ablation. An ILR was implanted at the same setting. A few months later, the second-stage endocardial catheter ablation was performed to ensure PVI and ‘touch-up’ of any residual conduction gaps in the left atrium. All epicardial ablation cases were performed at the cardiothoracic operating-room in our tertiary hospital (‘hub’) whilst the endocardial RF-cases were performed at either the hub or satellite centre(‘spoke’) as part of our institution’s ‘hub-and-spoke’ model. Inclusion criteria for hybrid AF-ablation were long-standing persistent AF, body mass index (BMI) <40 and standard indications for AF ablation as per ESC 2020 AF guidelines(4). Once both aspects of the hybrid approach were completed, patients were followed up in ILR remote monitoring clinics. AF recurrence was defined as AF/atrial tachycardia(AT) lasting >30s. All data were obtained retrospectively via hospital electronic patient records. Results 38 consecutive patients completed both aspects of hybrid ablation between December 2017-August 2023 with mean follow up of 19±13months(mean±SD). Baseline data, procedure characteristics and details of complications are shown in Table 1. ILR data was obtained in 36/38 patients(ILR implantation precluded in one due to previous breast cancer surgery. One had ILR battery depletion contributed by significant delay between the 2 stages of the hybrid ablation). AF/AT recurred in one third of patients during the blanking period(3 months) whilst 45% remained in sinus rhythm at 1-year; at 2yrs, 39% maintained SR and 25% at 3yrs (Figure 1). Post-hybrid ablation, two patients underwent re-do AF/AT ablation. The relatively high recurrence rate compared to other studies may be due to: very long duration of AF prior to hybrid-ablation(7.0±3.6years), significant delay between both stages of the procedure(9±11months) due to the pandemic and competing waiting list pressures, multiple comorbidities (82% had >2 comorbidities, 42% were obese) and the higher arrhythmia pickup rate with ILRs compared with intermittent rhythm monitoring. Conclusion Our study provides real world insight into the challenges of delivering a hybrid AF ablation service but highlights its utility in long-standing persistent AF patients.Table 1Figure 1

How to easily detect residual conduction gaps in redo procedure of pulmonary vein isolation: Post Encircling Mapping (PEM)

Abstract Background Pulmonary vein isolation (PVI) is the cornerstone of the interventional catheter-based treatment of atrial fibrillation. Unfortunately, persistent pulmonary vein isolation is difficult to achieve, and up to 70% of pulmonary vein reconnection rate has been documented (1). Atrial mapping during pacing from CS in combination with LAT (local activation time) mapping may help to identify these residual gaps (2). Methods We collected data from consecutive radiofrequency (RF) redo PVI procedures performed in our center from 01/01/2022 to 01/10/2023. Re-isolation was obtained based on bipolar map and Local Activation Time (LAT) map during pacing from distal coronary sinus (CS) -table 1 for the workflow-. We compared data obtained from analysis of bipolar maps and LAT maps; "discrepancy" between bipolar map and LAT map was defined as a difference which may lead to a different approach to the ablation strategy (figure 1); then, we compared procedural timing (radiofrequency time, fluoroscopy time, and skin-to-skin time) with our historical cohort of RF redo PVI procedures (01/01/2011 – 31/12/2021). Results We performed 34 radiofrequency redo procedure from 01/01/2022 to 01/10/2023. In 13 out of 112 veins treated (11.6%), we observed discrepancy between bipolar map and LAT map. We observed a lower radiofrequency time for patients treated on the basis of LAT map (01-01-2022 – 01-10-2022) when compared with our historical cohort (1023.21 ± 521.51 sec vs 1358.50 +/- 746.53 sec, p= 0.038); no differences were found in terms of skin-to-skin time and fluoroscopy time. Conclusions To perform a LAT map during pacing from distal CS may help to better identify residual gaps in redo AF procedures, allowing a reduction in radiofrequency time, without increasing skin to skin time and fluoroscopy time.Discrepancy between bipolar and LAT map

Atrial voltage analysis following vein of marshall alcohol infusion predicts mitral line block

Abstract Background The vein of Marshall (VOM) is a promising therapeutic target for the atrial fibrillation (AF) treatment, fitting perfectly with the "Coumel triangle" as it contains triggers of focal activities and stable reentries, autonomic parasympathetic and sympathetic connection and it represents substrate for perimitral flutters. Lateral mitral line (ML) represents a fundamental part of the anatomical ablation setup for the treatment of AF but its bidirectional block is very difficult to achieve by endocardial ablations. Ethanol infusion into the VoM (VOM-EI) has demonstrated high effectiveness in facilitating ML block. Newly-formed bipolar lesion after VOM-EI is considered an index of effectiveness of the alcoholization procedure. Voltage analysis assessment after VOM-EI in predicting ML block is poorly investigated. Purpose To compare unipolar and bipolar low-voltage areas (LVAs) along VOM trajectory after VOM-EI, and their role in predicting ML block. Methods We enrolled 59 patients undergoing catheter ablation for persistent AF or mitral isthmus dependent atrial flutter. We performed first a high-density voltage map of the left atrium. After VOM-EI, a LA remap was performed. The area width difference was obtained and defined as ∆LVA (see Figure 1). Normal Bipolar voltage cutoffs were 0.50 mV in case of sinus rhythm or 0.29 mV in case of AF. Unipolar cutoffs were respectively 2.7 mV in sinus rhythm and 1.1 mV in AF. The anatomical lesions set, after VOM-EI, included wide antral PVI, linear lesion for dome and ML isthmus following the newly-formed lesion after the VOM-EI. Systematic lines block validation was performed. ML block was defined after coronary sinus electrograms sequence inversion (septal-to-lateral) during left atrial appendage pacing. In case of residual conduction gaps, RF applications into the coronary sinus-great cardiac vein were done to target residual epicardial gaps. Ablation time to obtain ML block (AblTime) was obtained. Results In our group, 56/59 patients (94.5%) achieved mitral isthmus block. Bipolar and unipolar low voltage areas after VOM-EI were 9.9 ± 6.9 cm2 and 12.2 ± 5.9 cm2 respectively. Bipolar ∆LVAs were significantly lower compared with unipolar ∆LVA (8.2 ± 6.5 cm2 vs 9.4 ± 6.0 cm2; p= 0.03). A strong linear correlation between AblTime and bipolar ∆LVA (R: 0.76) and a significant correlation between AblTime and unipolar ∆LVA (R: 0.6) were found (Figure 2). Patients that required coronary sinus applications to reach ML block (13/59, 22%), presented lower ∆LVAs at logistic regression both at bipolar (p<0.01) and unipolar (p=0.03) analysis. Conclusions Unipolar and bipolar voltage analysis along the mitral isthmus trajectory predicts ML block achievement, with VOM-EI inducing wider unipolar LVAs than bipolar LVAs. Furthermore, wider unipolar and bipolar LVAs post VOM-EI are linked to a shorter AblTime and an increased probability of avoiding the need to target epicardial gaps via the CS musculature.LVA along VOM territory after VOM EI∆LVAs linear correlation with AblTime

Simulated safety analysis of a total loss of feedwater accident in the steam generator of CPR1000 nuclear power plant

As M310 series units, CPR1000 Nuclear Power Plant in China is also the first batch of demonstration nuclear power plants in China to try out SOP(the state-oriented procedure) accident procedures. The establishment of SOP accident regulations is an important work to mitigate the consequences of radioactive accidents in the design of nuclear power plants, and it is also the embodiment of the defense-in-depth requirements in the implementation of nuclear safety regulations. It can handle superimposed accidents, human errors in program implementation and events not considered in the primary cause sequence. In order to study the efficiency of its upgraded SOP procedure and its ability to deal with severe accidents, the typical primary cause event of severe accidents in nuclear power plants–such as the total loss of feedwater accident of steam generators has been adopted for research. The initial state of the simulation is the full power operation of the nuclear power plant, the simulation process is from the loss of all the water supply accidents to the whole accident processing. A total of 30 simulation experiments were carried out. The temperature and pressure of the key parameters obtained are the average values of 30 simulation experiments. The stability and efficiency of the updated SOP are evaluated by the treatment time of the water supply loss accident and the changes of reactor temperature and pressure after the accident. The results show that the upgraded SOP procedure is more stable and efficient. The upgraded SOP procedure, when dealing with other types of accidents, has improved the treatment of residual heat conduction in the core, increased the efficiency of accident treatment, and enhanced the safety of the reactor. At the same time, based on the weaknesses of the upgraded SOP procedure, constructive suggestions on changing the setting value of the steam generator bypass valve have also been put forward accordingly. Furthermore, it can be concluded from many simulated accidents that this change will win about 5% more of the disposal time for nuclear power plants under accidents, which provides references for the subsequent upgrading of M310 series power plant procedures.

Analysis of the effectiveness of the latest 4th-generation cryoballoon catheters in pulmonary vein isolation using high-resolution mapping

BackgroundLong-term data showed that up to 27% of pulmonary veins are reconnected using cryoballoon ablation. This study aimed to evaluate the efficacy of the latest 4th-generation cryoballoon catheters using ultra high-resolution mapping. MethodsIn patients with atrial fibrillation, a standard pulmonary vein isolation (PVI) with the latest 4th-generation cryoballoon catheter (Arctic Front Advance PRO, Medtronic Minneapolis, USA) and the spiral mapping catheter (Achieve Advance, Medtronic, Minneapolis, MN, USA) was performed. Subsequently, high-resolution mapping was achieved using the novel multipolar grid mapping catheter (Advisor HD Grid SE, Abbott Laboratories, USA). Follow-up was obtained after 6 months by means of a 7-day Holter electrocardiogram. ResultsIn our study, acute PVI was successfully achieved in all 31 patients. The latest 4th-generation cryoballoon catheter is safe in the acute phase of PVI. Additional high-resolution mapping (mean points per map 21,001 ± 4911) using the multipolar grid mapping catheter enabled us to identify residual gaps only in the carina pulmonary vein region; therefore, no additional ablation was performed. Three of 31 patients (10%) presented with atrial arrhythmia recurrence always related with pulmonary vein reconnection; using high-resolution mapping had no additional benefit in identifying pulmonary veins in which reconnection will occur. ConclusionThe utility of additional high-density mapping, facilitated by the HD Grid catheter after PVI with the 4th-generation cryoballoon catheter do not substantiate a discernible advantage over conventional mapping methodologies, particularly, the spiral mapping catheter. Residual carinal conduction was observed in a substantial cohort of patients (48%), highlighting a persistent challenge in achieving complete electrical isolation.