Ablation Rate Research Articles

Laser-Induced Decomposition and Mechanical Degradation of Carbon Fiber-Reinforced Polymer Subjected to a High-Energy Laser with Continuous Wave Power up to 120 kW

Carbon fiber-reinforced polymer (CFRP), noted for its outstanding properties including high specific strength and superior fatigue resistance, is increasingly employed in aerospace and other demanding applications. This study investigates the interactions between CFRP composites and high-energy lasers (HEL), with continuous wave laser powers reaching up to 120 kW. A novel automated sample exchange system, operated by a robotic arm, minimizes human exposure while enabling a sequence of targeted laser tests. High-speed imaging captures the rapid expansion of a plume consisting of hot gases and dust particles during the experiment. The research significantly advances empirical models by systematically examining the relationship between laser power, perforation times, and ablation rates. It demonstrates scalable predictions for the effects of high-energy laser radiation. A detailed examination of the damaged samples, both visually and via micro-focused computed X-ray tomography, offers insights into heat distribution and ablation dynamics, highlighting the anisotropic thermal properties of CFRP. Compression after impact (CAI) tests further assess the residual strength of the irradiated samples, enhancing the understanding of CFRP’s structural integrity post-irradiation. Collectively, these tests improve the knowledge of the thermal and mechanical behavior of CFRP under extreme irradiation conditions. The findings not only contribute to predictive modeling of CFRP’s response to laser irradiation but enhance the scalability of these models to higher laser powers, providing robust tools for predicting material behavior in high-performance settings.

Abstract 4118804: Use and Clinical Outcomes Associated with Urgent versus Elective Catheter Ablation of Atrial Fibrillation in the United States

Introduction: Catheter ablation of atrial fibrillation (AF) is an increasingly important evidence-based treatment option for select patients. Although typically performed as an outpatient elective procedure, the use and clinical outcomes of AF ablation pursued urgently among inpatients have not been adequately characterized. Hypothesis: Rate of urgent AF ablation, defined as an AF ablation procedure pursued among inpatients hospitalized for a non-procedural indication, has increased over time, and may be associated with worse outcomes. Aims: To describe the use and outcomes of urgent versus elective AF ablation. Methods: Using the NCDR AFib Ablation Registry, patients who underwent AF ablation from 1/1/2016 to 6/30/2023 were stratified according to whether AF ablation was urgent or elective. Logistic regression models were fitted to determine patient and hospital-level factors associated with use of urgent AF ablation. Cochrane-Armitage tests were used to test for trends over time. Unadjusted and adjusted in-hospital event rates were reported. Results: Among 140,051 patients, 2,714 (1.9%) underwent urgent inpatient AF ablation and 137,337 (98.1%) elective ablation. Compared with the elective cohort, those undergoing urgent ablation had higher rates of co-morbid conditions including: diabetes (30.6% vs. 20.4%, P<0.0001), coronary artery disease (30.8% vs. 22.7%, P<0.0001), and heart failure (47.1% vs 20.8%, P<0.0001). Urgent AF ablation was more often used among patients of Black race (OR 1.68; 95% CI: 1.41 – 2.0) and those with AF at the time of the procedure (OR 1.73; 95% CI: 1.36 – 2.20). Higher hospital procedural volume of AF ablations ([per 100 cases] OR 1.22; 95% CI: 1.20 – 1.25) was also associated with higher odds of urgent AF ablation. The use of urgent AF ablation increased from 0.5% in 2016, to 2.0% in 2023 (P<0.0001). Unadjusted event rates for AF-related complications were significantly higher for the urgent cohort (Figure). The adjusted rate of any procedure-related complication was significantly higher in the urgent cohort (urgent 4.9% vs. elective 2.4%, P<0.0001). Conclusions: The rate of urgent inpatient AF ablation has increased over time. Compared with elective AF ablation, after adjustment for patient risk factors, urgent AF ablation is associated with significantly higher rates of procedural complications. Use of urgent, inpatient AF ablation should be carefully considered within clinical contexts and offered to select patients.

Optimisation of laser surface ablation of alumina/GO coating on AZ31D magnesium alloy using Cuckoo Search Algorithm method

ABSTRACT Graphene oxide (GO) and alumina (Al2O3) work in concert to give magnesium alloys advantageous surface qualities and protection from adverse environments. This paper aims to investigate the effect of laser surface treatment on plasma sprayed alumina-graphene oxide (GO) coating on AZ31D magnesium alloy. Key ablation quality responses; HAZ width, surface roughness and ablation rate were correlated with laser parameters using the Response Surface Methodology and optimised using the metaheuristic Cuckoo Search Algorithm Method. Laser power significantly influenced all ablation characteristics of the composite coating. The addition of 1.5 wt% GO in the alumina coating caused a significant reduction in HAZ width (43.32%), surface roughness (25.11%) and ablation rate (76.58%) when treated with optimal combinations of laser power (8 W), scanning speed (950 mm/s) and frequency (78.2 kHz). The surface quality was characterised by smooth textures, and resolidified splats along with deep pits when ablated with lower and intermediate power whereas surfaces ablated with higher power showed debonded splats with peripheral surface destruction. While a prominent 2D peak at 16 W confirmed the presence of GO layers during high-power laser contacts, the ID/IG ratio below unity across all specimens indicated minimal defect concentrations.

Comparison of the ablative performance of silicone rubber‐based composites by analyzing a large number of samples

AbstractSilicone rubber‐based materials are important thermal protection materials for high‐temperature applications. In this work, a holistic analysis of silicone rubber‐based materials was conducted with an aim to comparatively study the ablative performance of different rubber matrices using the oxyacetylene flame. Six types of silicone rubber‐based composites were prepared in large quantities using a customized device, and the relationship between the ablative properties and influencing factors was elucidated, which was useful in guiding the design and preparation of flexible ablative materials for thermal protection purpose. The expansion and ceramicization of char layer, which was realized by introducing expandable graphite and alumina was found helpful in reducing line ablation rate. The increase in the thickness of char layer and the decrease in surface roughness indicated a successful implementation of the above strategy, which led to a significant decrease in line ablation rate and an increase in thermal insulation performance of the studied system. Moreover, a thermal ablative composite with excellent moldability after ablation process was prepared which showed a promising application as a reusable thermal protection material. This work provided guidelines for developing flexible thermal ablative composites, which can be targeted for practical applications in aerospace and fire protection sectors.

Optical properties of carbon dots generated in liquid by pulsed IR laser at 1064 nm

Biocompatible carbon dots (CDs) have been synthesized by the laser ablation of graphite and vegetable carbon (charcoal) placed in a phosphate-buffered saline (PBS) solution. The carbon nanoparticles are produced by a pulsed IR laser beam, operating at 1064 nm, 100 mJ energy, and 3 ns pulse duration, interacting with the carbon matrix placed in the liquid at a 0.2 Hz repetition rate. The ablation rate, in terms of removed carbon mass per laser shot, was evaluated to be about 75.8 ng/pulse and 758 ng/pulse for graphite and charcoal, respectively. Optical and electronic microscopy, UV-Vis spectroscopy, and luminescence measurements were employed to evince the CDs dispersion through its photoluminescence emission. The UV excitation at a 365 nm wavelength induces CDs luminescence in the visible region, as a result of electron transition, at a wavelength band depending on the laser spot size, i.e., of the laser fluence. CDs luminescence emission obtained from charcoal is independent of the laser fluence, showing a major emission peak around 475 nm and a secondary emission peak at 515 nm. CDs luminescence emission obtained from graphite depends on the laser fluence, showing a minor wavelength band, around 474 nm, at high laser fluences and a major wavelength band, around 670 nm, at low laser fluence. The CDs luminescence of the produced biocompatible solution finds many applications in the bio-medical field, as will be presented and discussed.

Hydrodissection technique for pain relief during peri-microwave ablation in patients with subpleural non-small cell lung cancers.

This study aimed to assess the application value of the hydrodissection technique (HT) for pain relief during peri-microwave ablation (MWA) in patients with subpleural non-small cell lung cancers (NSCLCs). This retrospective study comprised 218 patients with subpleural NSCLCs who underwent computed tomography (CT)-guided percutaneous MWA. The patients were divided into two groups: HT-assisted MWA (HT group) and local pleural anesthesia (LPA)-assisted MWA (LPA group). Differences in the effective rates of pain relief during MWA, visual analog scale (VAS) scores post-MWA, complications, and complete ablative rates were assessed. The HT group comprised 101 patients (62 males and 39 females; mean age, 61.93 ± 10.57 years), while the LPA group comprised 117 patients (66 males and 51 females; mean age, 62.95 ± 11.16 years). The effective rate of pain relief in the HT group (82/101 patients, 81.19%) was significantly higher than that in the LPA group (66/117 patients, 56.41%), (p < 0.0001). The VAS scores at 6, 12, 24, and 48 h post-MWA were not statistically different between the two groups. The incidence of pneumothorax (grade ≥3) was significantly lower in the HT group (11/101 patients, 10.89%) than in the LPA group (27/117, 23.07%), (p = 0.0161). The complete ablative rates at 1, 3, 6, 12, and 24 months post-MWA were comparable of two groups. These results indicate that HT-assisted MWA of patients with subpleural NSCLCs could effectively provide pain relief and decrease the occurrence of pneumothorax, yielding a satisfactory local therapeutic response.

Vapor Channel Oscillations in Laser Lithotripsy.

Laser-based endoscopic procedures present special challenges to deliver energy for ablation or coagulation of target tissues. When optical fiber-target quasi-contact (< 0.5 mm distance) cannot be maintained or is undesirable, the creation of intervening vapor bubbles and channels provide for the necessary transmission of laser energy to the target. This work investigates the characteristics and the dynamics of vapor channels that directly affect ablation efficiency and ablation rate and are known to effect stone movement, all of which impact procedure efficiency and safety. A simplified, experimental model for thulium fiber laser (1940 nm) lithotripsy consists of a water-filled cuvette and a vertically oriented laser fiber (200 μm core diameter) with its tip at 9 mm for "quasi-free" bubble generation and at vapor channel working distances 1-5 mm from and centered on the transparent cuvette bottom simulating a target's surface. Laser power transmission is recorded and synchronized with video frames from a high-speed camera (24,260 frames per second) to capture the induced vapor channels' and bubbles' development. Laser-induced channel transmission from 0% to 100% for 1, 2, and 3 mm fiber-target distances undergoes oscillations with average periods of 0.32, 0.64, and 1.0 ms, respectively, for 500 W laser output power. For fixed fiber-target distances of 0.5, 1, and 2 mm, the variation of these average oscillation frequencies across laser powers from 500 to 1000 W is much smaller, not exceeding 14%. For fiber-target distances in the range of 1-5 mm, the fraction of the 500 W laser's total pulse energy delivered to the target for 1, 2, and 3 ms pulses linearly decreases from 0.78 to less than 0.2. The channel and bubble dynamics begin with a spherical seed bubble expansion centered on the distal fiber tip that evolves into a pear shape whose surface exhibits periodic irregularities attributable to laser beam interruption by water droplets within the developing bubble. The study of laser-induced channel oscillations provides quantitative information relating fiber-target distance to channel oscillation frequency and energy transmission onto a target. These oscillations directly effect ablation efficiency and ablation rates that are important parameters for the optimization of a procedure's safety and duration. Insights that may lead to further reduction in retropulsion are also presented. Lasers Surg. Med. 00:00-00, 2024. © 2024 Wiley Periodicals LLC.

Thermal ablation of soft tissue by a single shock wave sonication of discrete foci within the given volume

New protocols have been developed for shockwave irradiation of soft tissue volumes using trajectories uniformly filled within the given shape by discrete foci, while pulsed millisecond sonication immediately formed a single ablation. The influence of the initial peak power with the same time-average power, the interfocus distance and the geometry of the external contour of the trajectory on the shape, volume and ablation rate was analyzed. The most advantageous is the saturation mode using a trajectory with an interfocus step 1.5 times greater than the transverse size of a single lesion. To obtain volumes of thermal ablation on the order of cubic centimeters, layer-by-layer sonication protocols are proposed, which allow to 2.5 times greater thermal ablation rate compared with protocols used in clinical practice. The advantage of the proposed shockwave protocols is the possibility of obtaining localized and predictable thermal damage without accompanying MRI monitoring.

Preparation and performance of C/Ta4HfC5-SiC composite fabricated by PIP combined with RMI process

Based on self-made Ta4HfC5 precursor, C/Ta4HfC5-SiC composite material were prepared by precursor impregnation and pyrolysis (PIP) combined with reactive melting infiltration (RMI) process. The density and open porosity of C/Ta4HfC5-SiC composite material are 2.71 ± 0.73 g/cm3 and 7.07 ± 1.29 %, respectively. Pores are distributed at multiple levels, including primarily nanopores below 40 nm, micropores between 0.04 - 8.5 μm, and a small number of macropores between 10 - 285 μm. The Ta4HfC5 phase exists in two forms: dispersed particles in the matrix and a "layered interface" on the surface of fibers within the bundle. The average bending strength, elastic modulus and fracture toughness of C/Ta4HfC5-SiC composite are 84.24 ± 8.71 MPa, 16.13 ± 5.42 GPa and 3.62 ± 0.63 MPa∙m1 /2, respectively, showing a clear brittle fracture mode during the test. The line ablation rate and mass ablation rate of 60 s assessed by the oxyacetylene flame were 7.20 ± 0.35 μm/s and 10.84 ± 0.84 mg/s, respectively. The oxidation products such as Ta2O5, HfO2, Ta(Hf)CxOy formed by Ta4HfC5 phase during ablation present as thicker oxide layers, forming the main anti-ablation components.

Study of spectral features and depth distributions of boron layers on tungsten substrates by ps-LIBS in a vacuum environment

Boronization is used in present-devices as wall condition technique due to its effectiveness in reducing oxygen and other impurities in the vessel as well as improving plasma performance. The technique is also currently under consideration as wall conditioning method for the proposed full-tungsten (W) wall of the International Thermonuclear Experimental Reactor (ITER). However, the impact of the deposited Boron (B) layer thickness, and its homogeneity after the boronization process is uncertain as well as knowledge about the layer lifetime and improved conditions. In this study, an approach of the picosecond-laser-induced breakdown spectroscopy (ps-LIBS) is investigated to analyze the depth distribution of B-films on W-substrates by using three optical spectrometers in a vacuum environment. The depth distribution of two types of B-films on W-substrates with the thicknesses of 130 nm and 260 nm were sequentially measured under different laser spot sizes (varying the laser fluence). The B-films on the W-substrates were made by magnetron sputtering to simulate the thin B layers during the boronization. The measured average ablation rate of ps-LIBS shows a notable decrease with increasing laser spot size. Additionally, the spectral lines of B and W exhibit distinct intensity distributions under different spot sizes due to the different excitation thresholds of the B-films and the W-substrates. The interface between B-films and W-substrates, as well as the thickness of the B-films, were determined using the normalized intensity and intensity ratio method, respectively. The results from ps-LIBS measurements regarding the depth are in good agreement with those obtained through the Focused Ion Beam combined with Scanning Electron Microscopy (FIB-SEM) and Energy Dispersive X-ray Spectroscopy (EDS). These initial findings verify the feasibility to characterize the thickness and uniformity of thin B films in the order of 100 nm and below on W-substrates using ps-LIBS.

Study on the anti-ablation behavior of (Ti,W)3AlC2 under oxyacetylene flame above 2500 K

To evaluate the reliability of (Ti,W)3AlC2 in aerospace ablation conditions, the ablation behavior of (Ti,W)3AlC2 ceramic is investigated by using oxyacetylene flame above 2550 K. Results show a four-stage process exists with the formation of TiO2-Al2TiO5-Al2O3. Once the central ablation temperature exceeds 2350 K, the innermost Al2O3 layer melts and collapses, exposing the decomposed TiCx-Al matrix directly to the flame with rapid oxidation and a remarkable increase of the linear ablation rate. The melt finally flows out with the flame from the ablation center and solidifies into a stripe-like TiO2-Al2TiO5 eutectic oxide above the protective oxide layer. The refractory W particles detected in the eutectic TiO2-Al2TiO5 may retard the flowing rate of the fluid by increasing its viscosity, resulting in a better ablation resistance performance in the later period of the ablation process, making the linear ablation rate lower from 10.30 μm/s of Ti3AlC2 to 9.01 μm/s of (Ti,W)3AlC2.

SiC high‐tech ceramics — a comparison of laser processes

AbstractExtensive R&amp;D applied various laser sources — from nanosecond VIS‐wavelength to femtosecond IR and water‐jet guided lasers — to enhance the quality and efficiency of laser structuring, fine cutting, and drilling of silicon carbide. Tests focused on surface roughness, cutting line precision, and high ablation rates. Challenges due to diverse material compositions, like diamond layers, required combined methods to develop viable approaches. To meet economic constraints, mechanical grinding was integrated with recurring laser processing.

Ablation performance of Ta0.8Hf0.2C-SiC coating fabricated via pack cementation for carbon/carbon composites

Ta0.8Hf0.2C solid solution combines the excellent oxidation and ablation resistance of TaC and HfC, making it ideal for ultra-high temperature applications. Herein, a Ta0.8Hf0.2C-SiC coating was fabricated on carbon/carbon (C/C) composites via pack cementation, with the volume fraction of Ta0.8Hf0.2C being only 0.57%. The coating provided over 350seconds of thermal protection at 2.4MW/m2 (2150 ℃) and 170seconds at 6.2MW/m2 (2400 ℃) for C/C composites, demonstrating exceptional ablation resistance with low addition of Ta0.8Hf0.2C. The mass and linear ablation rates were only 0.5110mg/s and 0.0277 μm/s at 2150 ℃, and 0.3947mg/s and 0.6229 μm/s at 2400 ℃, respectively. The solid solution structure of Ta0.8Hf0.2C ensures uniform atomic-scale distribution of Ta and Hf, which facilitaes the in-situ pinning of liquid-phase Ta2O5 by HfO2/Hf6Ta2O17 particles.

Influence of Silicon Carbide Incorporation on Thermal and Ablation Properties of Carbon Fabric-Phenolic Resin Composites

To shield re-entry spacecraft from the extreme heat experienced during hypersonic flight through a planet's or the earth's atmosphere, thermal protection systems (TPS) were developed. This work involved the fabrication of composites using a polyacrylonitrile (PAN) based carbon fabric (Cf)-phenolic resin matrix (PR) modified with different weight percentages (wt.%) of silicon carbide (SiC), namely 0 wt.% (Cf/PR), 1wt.%, 3wt.%, and 5wt.%. The composites were prepared using the hydraulic hot press method. The manufactured composites were analyzed for their thermal conductivity and resistance to ablation using an oxyacetylene torch test. Furthermore, the ablated composites underwent X-ray diffraction (XRD), revealing a SiO2 compound layer on the ablated composite surface. The experimental results demonstrated that the Cf/PR composites modified with 3wt.% of SiC exhibited superior characteristics. The composites consist of 3wt.% Cf/PR-SiC exhibited a thermal conductivity value of 0.57 W/m K. Additionally, these composites showed a noticeable decrease in the mass ablation rate (MAR) at 0.0052 mm/sec and linear ablation rates (LAR) at 0.025061 gm/sec. This study proposed an effective way to improve the thermal and ablation characteristics of TPS materials.

Long-term efficacy and safety of ablation for atrial fibrillation in patients with hypertrophic cardiomyopathy

Abstract Background Hypertrophic cardiomyopathy (HCM) is often accompanied by atrial fibrillation (AF) but data on safety and long-term outcomes after catheter ablation for AF in HCM are scarce. Purpose To investigate safety, long-term efficacy and clinical outcomes following AF ablation in patients with HCM and in matched controls. Methods Patients with HCM (n=76) undergoing a first catheter ablation for AF or atrial flutter between 1999 and 2022 at a University Hospital in Sweden were included (age 64±12 years, 43% female). Diagnosis of HCM was based on the European Society of Cardiology definition (left ventricular wall thickness ≥15 mm or ≥13 mm not solely explained by abnormal loading conditions, and combined with family history, genetic components and/or electrocardiogram abnormalities). Patients with HCM were matched with controls (n=152) based on age, gender, ablation type and intervention-year. Patients were followed for a mean of 5 years and study endpoints included heart failure hospitalization (HFH), stroke and mortality. Cox regression analyses were performed for the association between HCM and the endpoints. Results Among the overall population, 121 (53%) underwent pulmonary vein isolation (PVI), 62 (27%) isthmus ablation and 45 (20%) His-Bundle ablation. Patients with HCM had a shorter mean duration of AF before ablation (48 months vs. 66 months; p=0.047) and more severe symptoms as indicated by a higher EHRA class (EHRA class IV: 30% vs. 10%; p&amp;lt;0.01). Procedural success rate of PVI and isthmus ablation was lower in patients with versus without HCM (88% vs. 97%; p=0.02). Procedure related complications (vascular complications, tamponade) were overall similar in both groups (9% in HCM vs. 5% in controls, p=0.17) except for higher rates of pulmonary oedema in patients with HCM (7% vs 1%, p=0.03). There was a nearly two-fold increase in risk of AF recurrence after PVI or isthmus ablation in patients with HCM compared to controls (OR 1.95; 95% CI 1.06-3.58; p=0.03). During follow-up, patients with HCM had an increased risk of HFH (HR 2.55, 95% CI 1.21-5.36, p=0.01) but not of stroke or mortality (Figure 1). Conclusion AF ablation was overall safe in patients with HCM but less effective. Patients with HCM had an increased risk of the individual endpoint of HFH after AF ablation but not stroke or mortality during long-term follow-up.

Disparities in the access to atrial fibrillation ablation in Denmark

Abstract Background Atrial fibrillation (AF) is a common arrhythmia that can lead to serious complications such as stroke, heart failure, as well as reduced quality of life. Radiofrequency and cryoablation are safe and effective treatments for AF, but they are not offered equally to all patients. Purpose The study aims to identify the demographic groups more or less likely to undergo AF ablation. Methods Using nationwide National Registries, all Danish patients with newly diagnosed AF between the 1st of January 2005, and the 31st of December 2018 were identified. The association between patients, stratified by gender, age, level of education and attachment to the job market, and the likelihood of receiving AF ablation was investigated using multivariable Cox proportional-hazard analysis. Cumulative incidence of AF ablation among these groups was calculated using the Aalen-Johansen estimator, taking death as a competing risk into account. Results A total of 176,248 patients were included in the study. Men were more likely to receive ablation than women (7% vs 3%). When analysing age, patients aged 25-44 and 45-64 were most likely to receive ablation, while only 0.7% of patients aged 80 or above received ablation. The rate of ablation significantly decreased with decreasing level of education. Patients with a Ph.D. or doctorate degree were more likely to receive ablation than patients with only basic school education (22% vs 2%). Finally full-time employed patients were most likely to receive ablation, followed by self-employed, unemployed, on sick leave, undergoing education, and early retired patients. Retired patients were the least likely to receive ablation (3%). Conclusion This study found that women, older patients, patients with lower levels of education, and patients who are not employed or who are retired are less likely to receive AF ablation. These findings suggest that there are significant social and economic disparities in AF ablation treatment in Denmark.Ablation by educationForest plot: Cox analysis

Impact of obesity and early recurrence of atrial fibrillation on very late recurrence following cryoballoon pulmonary vein isolation

Abstract Background Obesity and early recurrence of atrial fibrillation (ERAF) post cryoballoon (CB) pulmonary vein isolation (PVI) both portend a lower 1-year success rate of ablation. Even after an initial successful ablation, about 1/3 of patients develop a very late recurrence (VLR) of AF, defined as the first AF recurrence more than a year after ablation (excluding an initial 90 day blanking period [BP]). The impact of obesity and ERAF on VLR is still unknown. Purpose To evaluate the impact of obesity and ERAF on VLR following CB PVI. Methods We enrolled consecutive patients with symptomatic AF who underwent CB PVI and had an implantable loop recorder for long-term ECG monitoring. We identified patients who had no AF recurrence (outside the BP) in the first-year post ablation. ERAF was defined as any episode of AF recorded in the first 90 days post ablation. Patients were grouped as either obese (BMI ≥ 30 kg/m2) or non-obese (BMI &amp;lt;30 kg/ m2). AF recurrences after 1-year post-ablation were ascertained using the loop recorder. Results From the initial cohort of 210 patients, 109 (52%) patients (64 ± 10 years; 75 [68%] male; 64 [59%] PAF; CHA2DS2-VASc 2.3 ± 1.4, 38 [35%] with obesity and 41 [38%] had ERAF) were AF-free during the first year. During a follow-up of 961 ± 196 days, 51 (47%) patients had VLR. Non-obese patients without ERAF had the best outcome (Figure). In multivariate analysis, obesity and ERAF were the only significant predictors of VLR (Table). As compared to non-obese patients without ERAF, obese patients with ERAF had a 4-fold greater likelihood of VLR. Conclusions About 50% of patients have no AF recurrence in the first year after CB PVI. Non-obese patients have the best outcome regardless of ERAF occurrence. On the other hand, obese patients with ERAF almost always have VLR.

Comparative Efficacy of Cavotricuspid Isthmus Ablation in Sinus Rhythm Versus Typical Atrial Flutter

Background: Cavotricuspid isthmus (CTI)-dependent atrial flutter (AFL) is the most common atrial macro-reentrant tachycardia, characterized by a typical ECG pattern (type I ECG). Often, tachycardia terminates before it can be confirmed by an electrophysiological study (EPS), necessitating CTI ablation in sinus rhythm (SR). This study aims to compare the success rate of CTI ablation in patients with type I ECG during SR versus ongoing CTI-dependent AFL, focusing on arrhythmia recurrence. Methods: We screened patients at Ulm University Heart Center from January 2010 to November 2020 with type I ECG who underwent CTI ablation. Patients were divided into two groups: those whose tachycardia terminated before EPS and underwent ablation in SR, and those with ongoing CTI-dependent AFL during EPS. CTI ablation was deemed complete when a bidirectional conductance block was achieved, confirmed after 30 min. Results: A total of 230 patients were included, all showing typical AFL in ECG recordings. Of these, 67 patients underwent ablation in SR, while 163 were ablated during ongoing AFL. The median follow-up time was 2.7 years. Recurrence of CTI-dependent AFL occurred in 8.3% of patients: 4.5% in the SR ablation group and 9.8% in the ongoing AFL group. Kaplan–Meier estimation showed similar efficacy for both methods regarding arrhythmia recurrence (log-rank p = 0.07). Conclusions: Our decade-long study indicates that CTI ablation during SR is as effective as ablation during ongoing CTI-dependent AFL in achieving long-term freedom from arrhythmia. This research supports the efficacy of both techniques in clinical settings, validating a widely practiced approach.

Microstructure and ablation behavior of C/C–HfC–SiC composites fabricated by reactive melt infiltration with Hf–Si alloy

AbstractC/C–HfC–SiC composites were prepared by reactive melt infiltration using Hf–Si alloy (Hf, more than 95 wt%) with a density of 3.86 g/cm3 and an open porosity of 8.34%. The microstructure, mechanical properties, and ablation behavior at high temperatures were studied in detail. SiC played a crucial role in alleviating the thermal mismatch between HfC and PyC, which formed at the interface between the carbon matrix and the HfC matrix. The flexural strength and modulus of C/C–HfC–SiC composites were 237 MPa and 37.6 GPa, respectively. The C/C–HfC–SiC composites exhibited excellent ablation resistance with a linear ablation rate of 8.9 × 10−3 mm/s and maintained a surface temperature above 2925°C during ablation. During this process, HfO₂ remained in a molten state with high viscosity and served as a thermal barrier, while the volatilization of SiO₂ effectively removed heat, protecting the composites from further ablation.

Thermal stability and anti-ablation performance of plasma spray coated-YSZ on Al2TiO5 modified novel ablative carbon-phenolic composites

Abstract Despite ongoing challenges, ablative thermal protection systems are among the most promising methods for safeguarding spacecraft during re-entry thermal protection systems (TPS). A novel aluminium titanate (Al2TiO5/AT) and a highly efficient thermal barrier of coating (TB/TBCs) made from yttria-stabilized zirconia (YSZ), powder, but deposited using the plasma spray technique on polyacrylonitrile (PAN)-based carbon fiber fabric(C)-reinforced with resorcinol phenol formaldehyde resin (RF) composites (C-RF)) would be a potential candidate for TPS applications. This study investigates the composites with varying wt.% of AT that were developed, namely 0 wt.% (YSZ-C-RF), 1 wt.%, 3 wt.%, and 5 wt.% (YSZ-AT-C-RF) by utilizing a hot press moulding machine. Thermal stability and ablation performance of unmodified C-RF with modified YSZ-C-RF and YSZ-AT-C-RF composites are examined through thermogravimetric analysis (TGA) and oxyacetylene torch test/OAT (4.0 MW/m2 for 60 sec). Also, the phase composition and microstructure of the ablated surface are determined by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The TBC of YSZ has an obvious influence on the residual weight ratios at high temperatures in C-RF and also plays a positive role in increasing thermal stability under nitrogen atmosphere for enhancing ablation resistance concerning YSZ-C-RF. The mass and linear ablation rates (MAR and LAR) of the composites after modifying the surface by YSZ-coated particles are reduced by 82.98% and 15.65%, respectively. Similarly, the introduction of AT particles and TBC of YSZ results in evidence of improving the thermal stability and the ablation resistance in varying wt.% of YSZ-AT-C-RF composites. The primary optimum AT weight loading for enhancing ablation resistance in YSZ-C-RF composites is 1wt.%. The modification of 1wt.% AT particles and YSZ-Coated particles reduce MAR and LAR by 54.79% and 61.94%, respectively. This work offers a meaningful method to remarkably enhance the ablation performance of the modified C-RF and YSZ-AT-C-RF composites.&amp;#xD;