https://www.selleckchem.com/products/h-151.html BACKGROUND This meta-analysis aimed to evaluate the efficacy and safety of non-vitamin K antagonist oral anticoagulants (NOACs) versus vitamin K antagonists (VKAs) in secondary stroke prevention in atrial fibrillation (AF) patients. METHODS PubMed and Embase electronic databases were systematically searched from January 2009 to July 2019 for relevant randomized clinical trials and observational studies. A random-effects model was applied in the pooled analysis. RESULTS A total of 14 studies (4 randomized clinical trials and 10 observational studies) were included. Based on the randomized clinical trials, compared with VKA use, the use of NOACs was associated with decreased risk of stroke and systemic embolism, major bleeding, and intracranial bleeding. Based on the observational studies, compared with VKAs, the subgroup analysis showed that dabigatran and rivaroxaban were associated with a reduced risk of stroke or systemic embolism, whereas dabigatran and apixaban were associated with a decreased risk of major bleeding. CONCLUSION Based on current data, the use of NOACs is at least non-inferior to the use of VKAs in AF patients for secondary stroke prevention irrespective of NOAC type.Nowadays, boron nitride has attracted a great deal of attention due to its physical (chemical) properties, facile synthesis, and experimental characterization, indicating great potential for industrial application. Based on this, we develop here a theoretical study on boron nitride nanoflakes built-up from hexagonal boron nitride nanosheets exhibiting hexagonal, rectangular, and triangular shapes. In order to investigate geometry effects such as those due to the presence of armchair and zigzag edges and distinct shapes, we analyzed their properties from both classical and quantum viewpoints. Using classical molecular dynamics calculations, we show that the nanosheets preserve their structural stability at high temperatures, while DFT cal