Clinically unrecognized mitral regurgitation is prevalent in lone atrial fibrillation

AIM:To investigate the prevalence of clinically unrecognized mitral regurgitation(MR) in lone atrial fibrillation(AF).METHODS:We studied the prevalence and severity of MR by transesophageal echocardiography(TEE) in patients with "lone" AF as compared to a matched cohort of patients in normal sinus rhythm(NSR) undergoing TEE for other indications besides recognized valvular heart disease.RESULTS:A total of 157 subjects(57 in the AF group and 100 in the NSR group) with structurally normal cardiac valves were included in the study.In the AF group,moderate MR or more was noted in 66% of thepatients,mild MR in 18%,trace or no MR in 16%.In the control group,moderate MR was noted in 6% of patients,mild MR 31%,trace or no MR in 63 % of patients.Moderate MR or greater was significantly more prevalent in the AF group compared to the NSR group(66% vs 6%,P < 0.0001).CONCLUSION:Clinically unrecognized moderate MR is prevalent in "lone" AF-either as an etiologic factor leading to "lone" AF or developing after onset of AF.

Data-driven Bayesian inference of turbulence model closure coefficients incorporating epistemic uncertainty

We introduce a framework for statistical inference of the closure coefficients using machine learning methods.The objective of this framework is to quantify the epistemic uncertainty associated with the closure model by using experimental data via Bayesian statistics.The framework is tailored towards cases for which a limited amount of experimental data is available.It consists of two components.First,by treating all latent variables(non-observed variables)in the model as stochastic variables,all sources of uncertainty of the probabilistic closure model are quantified by a fully Bayesian approach.The probabilistic model is defined to consist of the closure coefficients as parameters and other parameters incorporating noise.Then,the uncertainty associated with the closure coefficients is extracted from the overall uncertainty by considering the noise being zero.The overall uncertainty is rigorously evaluated by using Markov-Chain Monte Carlo sampling assisted by surrogate models.We apply the framework to the Spalart-Allmars one-equation turbulence model.Two test cases are considered,including an industrially relevant full aircraft model at transonic flow conditions,the Airbus XRF1.Eventually,we demonstrate that epistemic uncertainties in the closure coefficients result into uncertainties in flow quantities of interest which are prominent around,and downstream,of the shock occurring over the XRF1 wing.This data-driven approach could help to enhance the predictive capabilities of CFD in terms of reliable turbulence modeling at extremes of the flight envelope if measured data is available,which is important in the context of robust design and towards virtual aircraft certification.The plentiful amount of information about the uncertainties could also assist when it comes to estimating the influence of the measured data on the inferred model coefficients.Finally,the developed framework is flexible and can be applied to different test cases and to various turbulence models.