Search Results (321)

Zirconium (Zr) thin films were deposited on silicon (Si) substrates via pulsed laser deposition (PLD) using a 248 nm excimer laser. The effects of substrate temperature on film morphology and crystallinity were systematically investigated. X-ray diffraction (XRD) revealed that the Zr(100) plane exhibited the strongest orientation at 400 °C while Zr (002) was maximum at 500 °C. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses demonstrated an increase in surface roughness with temperature, with the smoothest surface observed at lower temperatures and significant island formation at 500 °C due to the transition to 3D growth. At 500 °C, interdiffusion effects led to the formation of zirconium silicide at the Zr/Si interface. To further interpret the experimental findings, computational modeling was employed to analyze the transition from 2D layer-by-layer growth to 3D island formation at elevated temperatures. Using a multi-parameter kinetics-free model based on free energy minimization, the critical film thickness for this transition was determined to be ~1–2 nm, aligning well with experimental observations. A separate kinetic model of island nucleation and growth predicts that this shift is driven by the kinetics of adatom surface diffusion. Additionally, the kinetic simulations revealed that, at 400 °C, adatom diffusivity optimally balances crystallization and surface energy minimization, yielding the highest film quality. At 500 °C, the rapid increase in diffusivity leads to the proliferation of 3D islands, consistent with the roughness trends observed in SEM and AFM data. These findings underscore the critical role of deposition parameters in tailoring Zr thin films for applications in advanced coatings and electronic devices. Full article

Atrial fibrillation (AF) is the supraventricular tachy-arrhythmia most commonly detected in the general population, with significant sex-related differences in epidemiology, pathophysiology, and treatment outcomes. Emerging evidence highlights the role of sex hormones—particularly estrogen and testosterone—in modulating left atrial electrophysiologic substrate, structural remodeling, inflammation, and thromboembolic risk. Hormonal fluctuations across different lifespan influence AF onset, progression, and therapeutic response, yet current management approaches largely overlook such determinants. This narrative review integrates data from basic, translational, and clinical research to examine hormonal effects on atrial substrate, disease progression, and differential results of treatments, including stroke prevention, pharmacological options, and transcatheter ablation. It also explores the potential of hormone-targeted interventions, antifibrotic therapies, and precision strategies tailored to hormonal status. Addressing these mechanisms could optimize patient-specific management, improve outcomes and guide future clinical practice recommendations. Advancing toward sex-specific, hormone-informed AF care requires further mechanistic studies, hormonal profiling, and sex-stratified clinical trials. Full article

Hastelloy X exhibits outstanding thermal fatigue resistance, making it a promising material for repairing 50CrVA landing gear via directed energy deposition (DED). However, the substantial differences in composition and thermophysical properties between 50CrVA and Hastelloy X pose challenges by affecting interfacial microstructure and surface quality. This study investigates the effect of DED process parameters (laser power p, powder feed rate f, scanning speed v, and overlap rate) on the dilution ratio (η), microscopic morphology, surface flatness (ζ), and porosity of Hastelloy X claddings on a 50CrVA substrate. An optimization methodology integrating thermal–flow coupled simulation models and orthogonal experiments is developed to fabricate high-quality claddings. Furthermore, the corrosion–wear performance of the claddings is evaluated. The results indicate that the η of a single track increases with higher p or lower f, while it first increases and then decreases with the increase in v. Ablation marks tend to occur at excessive p or insufficient f, while low v causes surface ripples. The ζ of a single layer initially improves and subsequently deteriorates with increasing overlap rate. Porosity is significantly influenced by p and f. The optimal p, f, v, and overlap rate are 1600 W, 2.4 g/min, 240 mm/min, and 55%, respectively. The wear resistance of the cladding is nearly identical to that of the substrate, while corrosion resistance is significantly improved. This work provides a theoretical foundation for high-performance repair of 50CrVA landing gear in aircraft. Full article

Silica fiber-reinforced silica aerogel (SFRSA) has low dielectric constant, light weight and high temperature resistance characteristics, making it one of the preferred materials for heat-resistant absorptive layers on the surfaces of high-speed aircraft. However, due to its ultra-high porosity, poor rigidity, and sensitivity to organic solvents, existing machining and chemical etching processes struggle to achieve patterned preparation of metallic layers on aerogel substrates. In order to address this issue, the present study employs femtosecond laser etching of the metal layer on the SFRSA surface. Orthogonal experiments were conducted to analyze the impact of different laser process parameters on the etching quality. With straightness as the primary factor, the optimal process parameters obtained were a laser power set to 2.15 W, a laser etching speed of 200 mm/s, and a laser etching time of 9. This achieved an etching width of 26.16 μm, a heat-affected zone of 39.16 μm, and straightness of 7.9 μm. Finally, Raman spectroscopy was used to study laser-ablated samples; thermogravimetric analysis (TGA) and Pyrolysis-Gas Chromatography–Mass Spectrometry analysis (Py-GC-MS) were employed to investigate the changes in the metal layer at high temperatures. A compositional analysis was conducted, revealing a decrease in carbon content within the etched region following laser ablation. The production of CO₂ gas and surface oxidation indicated that laser etching primarily operates via a photothermal mechanism. Full article

Ventricular arrhythmias (VAs) are common and clinically important complications in patients supported by left ventricular assist devices (LVADs), occurring in up to 50% of cases within the first year after implantation. Despite the hemodynamic support provided by LVADs, VAs are linked to increased morbidity and mortality, primarily through recurrent implantable cardioverter defibrillator (ICD) shocks and right ventricular failure. The underlying mechanisms of VAs in this population are multifactorial, involving structural myocardial remodeling, device-related factors, and pre-existing arrhythmic substrates. Catheter ablation has become a valuable treatment option when antiarrhythmic drug therapy and device reprogramming are inadequate, though procedural timing (pre-, intra-, or post-implantation) and approaches remain under discussion. Epicardial access during LVAD surgery may provide advantages for selected patients, while ablation after implantation poses technical challenges due to altered anatomy and electromagnetic interference. This review offers a comprehensive overview of the epidemiology, pathophysiology, risk stratification, and management of VAs in LVAD recipients, emphasizing technical considerations, procedural safety, and clinical outcomes of catheter ablation. A multidisciplinary approach remains essential in guiding personalized treatment and optimizing outcomes for this complex population. Undergoing studies will provide more insight into optimal management of arrhythmias, particularly regarding the optimal timing of catheter ablation. The impact of new technologies such as non-invasive mapping alongside pre-procedural imaging needs also to be further evaluated. Full article

Atrial fibrillation (AF) is the most common sustained supraventricular arrhythmia, affecting 2–3% of the adult population and contributing significantly to morbidity, mortality, and healthcare burden. Catheter ablation has become a cornerstone in the treatment of symptomatic, drug-refractory AF, with pulmonary vein isolation (PVI) established as the standard approach, especially in paroxysmal AF. Over the past three decades, ablation technologies have evolved considerably—from radiofrequency and cryoballoon to the recent advent of pulsed field ablation—enhancing procedural safety, efficiency, and lesion durability. Despite these technological advancements, long-term outcomes have plateaued, suggesting that success may depend not just solely on the energy source used, but also on a more individualized, mechanism-based approach. The classification of AF based on duration alone fails to capture the complexity of its underlying pathophysiology. Tailored strategies that consider arrhythmic mechanisms, electrophysiological triggers, and patient-specific substrates—especially in persistent AF—are increasingly recognized as essential for durable results. Tools such as high-density mapping, autonomic modulation, and substrate-targeted ablation are expanding therapeutic horizons. Moreover, special populations, such as athletes, present unique arrhythmic profiles influenced by structural and autonomic remodeling, requiring nuanced management. The integration of lifestyle interventions, neuromodulation techniques, and emerging genetic and pharmacological insights further supports a comprehensive, personalized approach. In this paper, we explore whether future success in AF ablation lies more in refining technology or in advancing our understanding of arrhythmic mechanisms to guide patient-specific therapy. Full article

Background/Objectives: For many years, catheter ablation (CA) has been a cornerstone in atrial fibrillation (AF) rhythm control therapy; however, recurrence remains common. Multiple parameters have been proposed to quantify AF arrhythmogenic substrate, yet reliable predictors of long-term outcomes are lacking. To assess the value of non-invasive amplified P-wave duration (PWD), echocardiographic parameters, biomarkers, and electroanatomical mapping (EAM) were used in predicting left atrial (LA) fibrosis and arrhythmia recurrence after CA. Methods: We included 196 patients undergoing first CA for paroxysmal or persistent AF. Amplified 12-lead ECG PWD parameters [Pmax, Pmin and left atrial P-wave (LAP)], echocardiographic parameters, and biomarkers were assessed pre-procedure. We measured low-voltage areas (LVA, 0.2–0.5 mV) on high-density voltage EAM during sinus rhythm as a surrogate of fibrosis. Freedom from arrhythmia was evaluated at 6 and 12 months. Results: Patients with LVA on EAM had prolonged Pmax (148 vs. 135 ms, p < 0.0001), Pmin (111 vs. 101.5 ms, p = 0.0001), LAP (73.5 vs. 55.5 ms, p < 0.0001), larger LA diameter (p = 0.0002), area (p = 0.0365) and volume (p = 0.004), higher E/E’ (p = 0.0007) and E/A ratios (p = 0.037), more mitral regurgitation (p = 0.0315), and higher pro-BNP levels (p = 0.0094). Univariate analysis showed 12-month recurrence rates higher with greater Pmax, Pmin, LAP, LVA presence and extent; however, in multivariate analysis, only P-wave parameters remained independently associated with recurrence. Conclusions: Prolonged PWD parameters strongly reflect LA substrate (Pmax, Pmin) and independently predict post-ablation AF recurrence (Pmax, Pmin, and LAP). LA size, diastolic dysfunction, and mitral regurgitation were associated with LA fibrosis, while pro-BNP was associated with both fibrosis and arrhythmia recurrence. Integrating these simple, non-invasive markers into a multimodal assessment alongside EAM could improve pre-procedural risk stratification and guide individualized ablation strategies. Full article

This study aims to develop an efficient laser cleaning process for removing paint coatings from low-pressure turbine blades while suppressing substrate remelting, focusing on elucidating the underlying paint removal mechanisms on coated aluminum alloy substrates. A pulsed fiber laser (1064 nm, 100 ns) was used to perform single-factor and orthogonal experiments, with laser power (70–100 W), scanning speed (1000–3000 mm/s), and repetition frequency (150–300 kHz) as the main variables. The energy density for each of the 16 orthogonal test samples ranged from 11.9 to 51.0 J/cm². Complete paint removal without substrate damage was achieved within an optimal energy density window of approximately 17–27 J/cm² (e.g., 23.8 J/cm²), whereas higher values above 35 J/cm² (e.g., 35.7 J/cm²) frequently caused localized remelting and pitting. The optimized parameter combination (90 W, 1500 mm/s, 300 kHz) achieved 98% paint removal efficiency in four passes with no observable substrate degradation. Mechanistic analysis indicated that low-to-moderate energy densities promoted interfacial debonding and controlled film ablation, while high energy densities led to substrate melting and reflow. This work clarifies the quantitative correlation between laser parameters, paint removal mechanisms, and remelting suppression, providing a scientific basis for turbine blade maintenance applications. Full article

CZTS (C-I/C-II) ultrathin films in 61 nm and 313 nm thicknesses were grown on microscopic glass and n-Si wafer substrates via laser ablation, respectively. C-II ultrathin film with higher thickness has a more developed crystal structure and consists of larger particles compared to C-I ultrathin film with reduced thickness. C-II ultrathin film absorbs more photons and has a lower band gap. The photovoltaic performance of the produced Ag/CZTS (C-II)/n-Si/Al solar cell is higher compared to the other solar cell-based C-I ultrathin film. The more improved crystal structure of C-II ultrathin film has increased the efficiency of the solar cell. The calculated photovoltaic parameters of the solar cells modeled with the SCAPS-1D simulation program were found to be compatible with the experimental parameters. This situation has proven that the operating performance of solar cells is reliable. Full article

Atrial fibrillation (AF), the most prevalent sustained cardiac arrhythmia, poses a significant burden on global morbidity and healthcare expenditure. Although endocardial catheter ablation and surgical ablation are established therapeutic strategies, each exhibits inherent limitations in achieving comprehensive substrate modification. Hybrid ablation therapy, integrating both endocardial and epicardial approaches, aims to overcome these limitations by enabling the more extensive and transmural targeting of arrhythmogenic foci and the complex atrial substrate. This review synthesizes the electrophysiological basis and mechanistic rationale underpinning hybrid AF ablation, highlighting its potential for an enhanced efficacy compared to isolated techniques. Furthermore, it introduces the emerging paradigm of three-dimensional ablation within this evolving field. Full article

Background/Objectives: Catheter ablation is an established therapy for ventricular tachycardia (VT), though outcomes remain limited in patients with non-ischemic dilated cardiomyopathy (NIDCM) due to complex arrhythmogenic substrates. Late iodine enhancement computed tomography (LIE-CT) offers a promising alternative to cardiac MRI for preprocedural substrate visualization. This study evaluated procedural characteristics and outcomes of LIE-CT-supported VT ablation versus conventional mapping (CM) in NIDCM patients. Methods: NIDCM patients undergoing VT ablation between January 2022 and August 2024 were retrospectively analyzed. LIE-CT data were processed using inHEART software. Patients were matched 1:1 by propensity score based on baseline characteristics, electrical storm, and prior ablations. Results: A total of 46 patients (mean age 59 ± 16.4 years, 74% male) were included (23 LIE-CT, 23 CM). Procedure durations were comparable (231.5 ± 74.2 vs. 220.2 ± 70.2 min, p = 0.5), but mapping time (35.9 ± 15.3 vs. 54 ± 5 min, p < 0.001) and fluoroscopy time (14.7 ± 5.1 vs. 21.3 ± 10.6 min, p = 0.02) were significantly shorter with LIE-CT. Epicardial access was more frequent (52% vs. 26%, p < 0.001), and bipolar ablation for intramural scar was performed in 17% of LIE-CT cases. There were no significant differences in acute kidney injury or 30-day mortality. At a median follow-up of 367 days, VT-free survival was 57% with LIE-CT and 52% with CM (p = 0.8). Conclusions: LIE-CT-supported VT ablation and substrate visualization was safe, without additional risk of acute kidney injury, and enabled more efficient and targeted VT ablation. Prospective studies are warranted to assess its impact on long-term outcomes in NIDCM patients. Full article

Alumina ceramic substrates are ideal materials for next-generation microelectronic systems and devices, widely used in aerospace, 5G communications, and LED lighting. High-quality hole processing is essential for system interconnection and device packaging. Millisecond lasers have emerged as a promising choice for hole processing in alumina ceramic due to their high processing efficiency. However, existing research has rarely explored the mechanisms and processing techniques of millisecond laser oblique hole formation. This study systematically investigates the dynamic evolution of oblique hole processing in alumina ceramic through theoretical simulations, online detection, and process experiments. Through the simulation model, we have established the relationship between material temperature and hole depth. By analyzing the ablation phenomena on the upper and lower surfaces of the ceramic during the transient interaction process between the millisecond laser and the ceramic, the material removal mechanism in this process is elucidated. Additionally, this study examines the millisecond laser oblique hole processing technology by analyzing the influence of various laser parameters on hole formation. It reveals that appropriately increasing the single-pulse energy of millisecond lasers can optimize the material removal rate and hole taper. Ultimately, the formation mechanism of millisecond laser oblique hole processing in alumina ceramics is comprehensively summarized. The results provide theoretical and methodological guidance for high-speed laser drilling of alumina ceramic substrates. Full article

Pulsed laser annealing (PLA) was performed on a 0.3 μm thick hydrogenated amorphous carbon (a-C:H) film deposited on silicon substrate by plasma-enhanced chemical vapor deposition (PECVD). The 532 nm, 32 ns PLA ranged in fluence from 0.2 to 0.94 J cm⁻². There were no visible signs of film delamination over the entire fluence range for a single pulse. As the fluence increased, graphitization of the amorphous film bulk was observed. However, at the near surface of the film, there was a concomitant increase in sp³ content. The sp³ bonding observed is the result of the formation of a thin diamond-like layer on the surface of the carbon film. Along with increasing laser fluence, the film swelled by 75% up to 0.6 J cm⁻². In addition, carbon fiber formation was observed at 0.6 J cm⁻², increasing in size and depth up through 0.94 J cm⁻². The origin of this transformation may be associated with a rapid outgassing of hydrogen from the amorphous carbon during the PLA step. Additionally, there was a dramatic increase in the visible light absorption of these thin films with increasing laser fluence, despite the films being less than a micron thick. These results suggest that PLA of a-C:H film is a useful method for modifying the surface structure for optical or electrochemical applications without film ablation. Full article

Ventricular tachycardia (VT) remains a major cause of morbidity and mortality in patients with structural heart disease. While catheter ablation has become a cornerstone in VT management, recurrence rates remain substantial due to limitations in electroanatomic mapping (EAM), particularly in cases of deep or heterogeneous arrhythmogenic substrates. Cardiac imaging, especially when multimodal and integrated with mapping systems, has emerged as a critical adjunct to enhance procedural efficacy, safety, and individualized strategy. This comprehensive review explores the evolving role of various imaging modalities, including echocardiography, cardiac magnetic resonance (CMR), computed tomography (CT), positron emission tomography (PET), and intracardiac echocardiography (ICE), in the preprocedural and intraprocedural phases of VT ablation. We highlight their respective strengths in substrate identification, anatomical delineation, and real-time guidance. While limitations persist, including costs, availability, artifacts in device carriers, and lack of standardization, future advances are likely to redefine procedural workflows. Full article

Background: Atrial fibrosis is a key contributor to atrial cardiomyopathy and can be assessed invasively using mean left atrial voltage (MLAV) from electroanatomical mapping. However, the invasive nature of this procedure limits its clinical applicability. Machine learning (ML), particularly regression tree-based models, may offer a non-invasive approach for predicting MLAV using clinical and echocardiographic data, improving non-invasive atrial fibrosis characterisation beyond current dichotomous classifications. Methods: We prospectively included and followed 113 patients with paroxysmal or persistent atrial fibrillation (AF) undergoing pulmonary vein isolation (PVI) with ultra-high-density voltage mapping (uHDvM), from whom MLAV was estimated. Standardised two-dimensional transthoracic echocardiography was performed before ablation, and clinical and echocardiographic variables were analysed. A regression tree model was constructed using the Classification and Regression Trees—CART-algorithm to identify key predictors of MLAV. Results: The regression tree model exhibited moderate predictive accuracy (R² = 0.63; 95% CI: 0.55–0.71; root mean squared error = 0.90; 95% CI: 0.82–0.98), with indexed minimum LA volume and passive emptying fraction emerging as the most influential variables. No significant differences in AF recurrence-free survival were found among MLAV tertiles or model-based generated groups (log-rank p = 0.319 and p = 0.126, respectively). Conclusions: We present a novel ML-based regression tree model for non-invasive prediction of MLAV, identifying minimum LA volume and passive emptying fraction as the most significant predictors. This model offers an accessible, non-invasive tool for refining atrial cardiomyopathy characterisation by reflecting the fibrotic substrate as a continuum, a crucial advancement over existing dichotomous approaches to guide tailored therapeutic strategies. Full article