A Bias-Aware EnKF Estimator for Aerodynamic Flows

Ensemble methods can integrate measurement data and CFD-based models to estimate the state of fluid systems in a robust and cost-efficient way. However, discretization errors can render numerical solutions a biased representation of reality. Left unaccounted for, biased forecast and observation models can lead to poor estimator performance. In this work, we propose a low-rank representation for the bias whose dynamics is represented by a colorednoise process. System state and bias parameters are simultaneously corrected on-line with the Ensemble Kalman Filter (EnKF) algorithm. The proposed methodology is demonstrated to achieve a 70% error reduction for the problem of estimating the state of the two-dimensional low-Re flow past a flat plate at high angle of attack using an ensemble of coarse-mesh simulations and pressure measurements at the surface of the body, compared to a bias-blind estimator. Strategies to determine the bias statistics and to deal with nonlinear observation functions in the context of ensemble methods are discussed

Editor's Choice - Assessment of International Outcomes of Intact Abdominal Aortic Aneurysm Repair over 9 Years

Background: Case mix and outcomes of complex surgical procedures vary over time and between regions. This study analyses peri-operative mortality after intact abdominal aortic aneurysm (AAA) repair in 11 countries over 9 years. Methods: Data on primary AAA repair from vascular surgery registries in 11 countries for the years 2005-2009 and 2010-2013 were analysed. Multivariate adjusted logistic regression analyses were carried out to adjust for variations in case mix. Results: A total of 83,253 patients were included. Over the two periods, the proportion of patients >= 80 years old increased (18.5% vs. 23.1%; p <.0001) as did the proportion of endovascular repair (EVAR) (44.3% vs. 60.6; p <.0001). In the latter period, 25.8% of AAAs were less than 5.5 cm. The mean annual volume of open repairs per centre decreased from 12.9 to 10.6 between the two periods (p <.0001), and it increased for EVAR from 10.0 to 17.1 (p <.0001). Overall, peri-operative mortality fell from 3.0% to 2.4% (p <.0001). Mortality for EVAR decreased from 1.5% to 1.1% (p <.0001), but the outcome worsened for open repair from 3.9% to 4.4% (p = .008). The peri-operative risk was greater for octogenarians (overall, 3.6% vs. 2.1%, p <.0001; open, 9.5% vs. 3.6%, p <.0001; EVAR, 1.8% vs. 0.7%, p <.0001), and women (overall, 3.8% vs. 2.2%, p <.0001; open, 6.0% vs. 4.0%, p <.0001; EVAR, 1.9% vs. 0.9%, p <.0001). Peri-operative mortality after repair of AAAs Conclusions: In this large international cohort, total peri-operative mortality continues to fall for the treatment of intact AAAs. The number of EVAR procedures now exceeds open procedures. Mortality after EVAR has decreased, but mortality for open operations has increased. The peri-operative mortality for small AM treatment, particularly open surgical repair, is still considerable and should be weighed against the risk of rupture. (C) 2017 European Society for Vascular Surgery. Published by Elsevier Ltd. All rights reserved.Peer reviewe

Editor's Choice - Carotid Stenosis Treatment : Variation in International Practice Patterns

Objectives: The aim was to determine current practice for the treatment of carotid stenosis among 12 countries participating in the International Consortium of Vascular Registries (ICVR). Methods: Data from the United States Vascular Quality Initiative (VQI) and the Vascunet registry collaboration (including 10 registries in Europe and Australasia) were used. Variation in treatment modality of asymptomatic versus symptomatic patients was analysed between countries and among centres within each country. Results: Among 58,607 procedures, octogenarians represented 18% of all patients, ranging from 8% (Hungary) to 22% (New Zealand and Australia). Women represented 36%, ranging from 29% (Switzerland) to 40% (USA). The proportion of carotid artery stenting (CAS) among asymptomatic patients ranged from 0% (Finland) to 26% (Sweden) and among symptomatic patients from 0% (Denmark) to 19% (USA). Variation among centres within countries for CAS was highest in the United States and Australia (from 0% to 80%). The overall proportion of asymptomatic patients was 48%, but varied from 0% (Denmark) to 73% (Italy). There was also substantial centre level variation within each country in the proportion of asymptomatic patients, most pronounced in Australia (0-72%), Hungary (5-55%), and the United States (0-100%). Countries with fee for service reimbursement had higher rates of treatment in asymptomatic patients than countries with population based reimbursement (OR 5.8, 95% CI 4.4-7.7). Conclusions: Despite evidence about treatment options for carotid artery disease, the proportion of asymptomatic patients, treatment modality, and the proportion of women and octogenarians vary considerably among and within countries. There was a significant association of treating more asymptomatic patients in countries with fee for service reimbursement. The findings reflect the inconsistency of the existing guidelines and a need for cooperation among guideline committees all over the world. (C) 2017 European Society for Vascular Surgery. Published by Elsevier Ltd. All rights reserved.Peer reviewe

Realisation of magnetically and atomically abrupt half-metal/semiconductor interface: Co2FeSi0.5Al0.5/Ge(111)

Halfmetal-semiconductor interfaces are crucial for hybrid spintronic devices. Atomically sharp interfaces with high spin polarisation are required for efficient spin injection. In this work we show that thin film of half-metallic full Heusler alloy Co2FeSi0.5Al0.5 with uniform thickness and B2 ordering can form structurally abrupt interface with Ge(111). Atomic resolution energy dispersive X-ray spectroscopy reveals that there is a small outdiffusion of Ge into specific atomic planes of the Co2FeSi0.5Al0.5 film, limited to a very narrow 1 nm interface region. First-principles calculations show that this selective outdiffusion along the Fe-Si/Al atomic planes does not change the magnetic moment of the film up to the very interface. Polarized neutron reflectivity, x-ray reflectivity and aberration-corrected electron microscopy confirm that this interface is both magnetically and structurally abrupt. Finally, using first-principles calculations we show that this experimentally realised interface structure, terminated by Co-Ge bonds, preserves the high spin polarization at the Co2FeSi0.5Al0.5/Ge interface, hence can be used as a model to study spin injection from half-metals into semiconductors

Effect of the Glycemic Index of Carbohydrates on Acne vulgaris

Acne vulgaris may be improved by dietary factors that increase insulin sensitivity. We hypothesized that a low-glycemic index diet would improve facial acne severity and insulin sensitivity. Fifty-eight adolescent males (mean age ± standard deviation 16.5 ± 1.0 y and body mass index 23.1 ± 3.5 kg/m2) were alternately allocated to high or low glycemic index diets. Severity of inflammatory lesions on the face, insulin sensitivity (homeostasis modeling assessment of insulin resistance), androgens and insulin-like growth factor-1 and its binding proteins were assessed at baseline and at eight weeks, a period corresponding to the school term. Forty-three subjects (n = 23 low glycemic index and n = 20 high glycemic index) completed the study. Diets differed significantly in glycemic index (mean ± standard error of the mean, low glycemic index 51 ± 1 vs. high glycemic index 61 ± 2, p = 0.0002), but not in macronutrient distribution or fiber content. Facial acne improved on both diets (low glycemic index −26 ± 6%, p = 0.0004 and high glycemic index −16 ± 7%, p = 0.01), but differences between diets did not reach significance. Change in insulin sensitivity was not different between diets (low glycemic index 0.2 ± 0.1 and high glycemic index 0.1 ± 0.1, p = 0.60) and did not correlate with change in acne severity (Pearson correlation r = −0.196, p = 0.244). Longer time frames, greater reductions in glycemic load or/and weight loss may be necessary to detect improvements in acne among adolescent boys