Two dimensional LiMgAs; a novel Topological Quantum Catalyst for Hydrogen Evolution Reaction

Quantum materials such as Topological Insulators (TI) have been promising due to diverse applications of their robust surface/edge states in the bulk (3D) and two-dimensional (2D) regime. Such conducting surface states in 3D systems, host "\textit{electron bath}" which are known to facilitate catalysis. However, the analogous effects in 2D scenarios wherein, conducting helical edge states giving rise to Fermionic accumulation has been scarcely addressed. Using density functional theory based \textit{first-principles} calculations, we demonstrate that, the conducting edge states in 2D TI such as LiMgAs can be exploited to facilitate excellent catalytic response towards Hydrogen evolution reactions. The Gibbs free energy in such cases was found to be as low as $-$0.02 eV which is quite superior as compared to other materials reported in literature. The concept presented herein can be extended to other well known 2D TI and used to realise novel topological quantum catalysts for ultra-high performance and efficient catalytic applications.Comment: 5 pages, 4 figure

The impact of pulmonary regurgitation on right ventricular size and function in patients with repaired tetralogy of Fallot and additional haemodynamic abnormalities

Purpose: Right ventricular (RV) outflow tract obstruction (RVOTO) was demonstrated to be protective against RV dilatation in patients with repaired tetralogy of Fallot and chronic pulmonary regurgitation (PR). We hypothesised that the presence of additional haemodynamic abnormalities (more than mild tricuspid regurgitation, residual ventricular septal defect) reduces this protective association. Accordingly, we aimed to assess the impact of PR on RV size and function in this population. Material and methods: Consecutive patients with additional haemodynamic abnormalities after tetralogy of Fallot (TOF) repair, who had undergone cardiovascular magnetic resonance, were included. Results: Out of 90 patients studied, 18 individuals (mean age 32.5 ± 10.7 years, 72.2% males) met the inclusion criteria. There were no differences in RV volumes and ejection fraction between patients with and without RVOTO. Neither PR fraction (PRF) nor PR volume (PRV) correlated with RV end-diastolic volume (r = 0.36; p = 0.15 and r = 0.37; p = 0.14, respectively, for PRF and PRV) or RV end-systolic volume (r = 0.2; p = 0.42 and r = 0.19; p = 0.45, respectively, for PRF and PRV). Similarly, no significant correlations were observed between PRF or PRV and RV ejection fraction (r = –0.04; p = 0.87 and r = –0.03; p = 0.9, respectively). Conclusions: Additional haemodynamic abnormalities are associated with the abolition of the protective effect of RVOTO on RV size. There was no significant relationship between measures of PR and RV volumes in patients after TOF repair with concomitant haemodynamic abnormalities. These abnormalities acted as confounding factors in the assessment of the impact of pulmonary regurgitation on RV size and function

Influence of percutaneous pulmonary valve implantation on exercise capacity: Which group of patients benefits most from the intervention?

Background: The aim of the study was to evaluate the role of cardiopulmonary exercise testing (CPET) parameters in assessing exercise capacity improvement after percutaneous pulmonary valve implantation (PPVI). Additionally, it aimed to determine if there are any baseline characteristics influencing that change. Methods and results: The study comprised 32 patients (mean age 26 ± 9); 53% males; diagnosis: tetralogy of Fallot (n = 18), pulmonary atresia (n = 6), Ross procedure (n = 4), other (transposition of great arteries, pulmonary stenosis, double outlet right ventricle, common arterial trunk type II — n = 4) who underwent successful PPVI due to right ventricular out­flow tract dysfunction (predominant pulmonary regurgitation — n = 17, predominant pulmo­nary stenosis — n = 15). Treadmill CPET was performed before and a year after PPVI along with clinical evaluation, cardiac magnetic resonance and transthoracic echocardiography. Twelve months post successful PPVI (pulmonary valve competence restoration and pulmonary gradient reduction from 58.8 ± 47.1 to 26.6 ± 10.8 mm Hg) there was a significant decrease in the ventilatory equivalent for CO2 at peak exercise (EQCO2) (25.3 ± 3.3 to 24.3 ± 3.0, p = 0.04) and oxygen consumption at peak exercise (pVO2) (20.4 ± 5.0 to 22.6 ± 5.3 mL/kg/min, p = 0.04). Improved EQCO2 correlated with an increase in right and left ventricular ejection fraction (respectively R = –0.57, p = 0.002; R = –0.56, p = 0.002). In this study, no baseline factors that might affect improvement in exercise function were found. Conclusions: Successful PPVI leads to an improvement in exercise capacity and hemodynamic response to exercise. The correlation between the improvement in EQCO2 or peak VO2 and baseline characteristics was too weak to reliably identify the group of patients that will benefit from the procedur