Bootstrap resampling as a tool for uncertainty analysis in 2-D magnetotelluric inversion modelling

Uncertainty estimation is a vital part of geophysical numerical modelling. There exist a variety of methods aimed at uncertainty estimation, which are often complicated and difficult to implement. We present an inversion technique that produces multiple solutions, based on bootstrap resampling, to create a qualitative uncertainty measure for 2-D magnetotelluric inversion models. The approach is easy to implement, can be used with almost any inversion code, and does not require access to the inversion software's source code. It is capable of detecting the effect of data uncertainties on the model result rather than just analysing the effect of model variations on the model response. To obtain uncertainty estimates for an inversion model, the original data set is resampled repeatedly and alternate data set realizations are created and inverted. This ensemble of solutions is then statistically analysed to determine the variability between the different solutions. The process yields interpretable uncertainty maps for the inversion model and we demonstrate its effectiveness to qualitatively quantify uncertainty in synthetic model tests and a case study.Sebastian Schnaidt, Graham Heinso

Oxidative stress and endothelial dysfunction are associated with reduced cognition in type 2 diabetes

Objective: Type 2 diabetes is associated with cognitive dysfunction, but the mechanisms are unknown. We assessed the relationships of biomarkers of oxidation, endothelial function and inflammation with cognition in participants of the CAROLINA® trial (CARdiovascular Outcome Trial of LINAgliptin Versus Glimepiride in Type 2 Diabetes). Methods: Baseline circulating biomarkers of oxidation (8-iso-prostaglandin F2α), endothelial function (asymmetric dimethylarginine, endothelin-1) and inflammation (C-reactive protein, interleukin-6, tumour necrosis factor-α), based on linear regression, were related to cognition on five domains, as measured with an automated battery. Results: In 37 patients (mean age 66.7 ± 8.7 years, median HbA1c 6.9%/52 mmol/mol), 8-iso-prostaglandin F2α was associated with reduced mental flexibility and attention (standardised regression coefficients −0.47, −0.34), whereas asymmetric dimethylarginine was associated with reduced psychomotor speed and attention (standardised regression coefficients −0.39, −0.34). No significant associations were observed between biomarkers of inflammation and cognition. Conclusion: Elevated biomarkers of oxidation and endothelial function are associated and may play a role in reduced psychomotor speed, mental flexibility and attention in type 2 diabetes