Evaluation of hyperelastic models for unidirectional short fibre reinforced materials using a representative volume element with refined boundary conditions

The simulation of a short fibre reinforced structure by means of the FEM requires the knowledge of the material behaviour at every Gauss point. In order to obtain such information, a representative volume element (RVE) containing unidirectional short fibres is analysed in the presented work. In order to cover the complete anisotropic effect of the fibres, deformations with different angles to the fibre direction have to be conducted. In contrast to other works, this task is tackled using the application of periodic boundary conditions to the RVE in tensorial form, which enables a simple access to consider varying fibre angles with one and the same RVE. As the RVE’s average response represents the homogenised behaviour at a macroscopic material point, the material models’ parameters can be identified by fitting them to stress-strain curves obtained from simulations with the RVE. The findings of these analyses are used to assess the applicability of several hyperelastic models describing transversal isotropic materials under consideration of large deformations. For example it is shown, that the formulation of mixed invariants with the isochoric right Cauchy-Green tensor is insufficient to reproduce the RVE’s behaviour at purely volumetric deformations. Both the modelling and the calculations are carried out with the commercial FEMsoftware ABAQUS. Insight is given to the implementation of the boundary conditions as well as the underlying constitutive equations

Catheter-based intervention for symptomatic patient with severe mitral regurgitation and very poor left ventricular systolic function - Safe but no room for complacency

Many patients with left ventricular systolic dysfunction have concomitant mitral regurgitation (MR). Their symptoms and prognosis worsen with increasing severity of MR. Percutaneous MitraClip((R)) can be used safely to reduce the severity of MR even in patients with advanced heart failure and is associated with improved symptoms, quality of life and exercise tolerance. However, a few patients with very poor left ventricular systolic function may experience significant haemodynamic disturbance in the peri-procedural period. We present three such patients, highlighting some of the potential problems encountered and discuss their possible pathophysiological mechanisms and safety measures.published_or_final_versio

Effects of Oral Glucose Load on Endothelial Function and on Insulin and Glucose Fluctuations in Healthy Individuals

Background/aims. Postprandial hyperglycemia, an independent risk factor for cardiovascular disease, is accompanied by endothelial dysfunction. We studied the effect of oral glucose load on insulin and glucose fluctuations, and on postprandial endothelial function in healthy individuals in order to better understand and cope with the postprandial state in insulin resistant individuals. Methods. We assessed post-oral glucose load endothelial function (flow mediated dilation), plasma insulin, and blood glucose in 9 healthy subjects. Results. The largest increases in delta FMD values (fasting FMD value subtracted from postprandial FMD value) occurred at 3 hours after both glucose or placebo load, respectively: 4.80 ± 1.41 (P = .009) and 2.34 ± 1.47 (P = .15). Glucose and insulin concentrations achieved maximum peaks at one hour post-glucose load. Conclusion. Oral glucose load does not induce endothelial dysfunction in healthy individuals with mean insulin and glucose values of 5.6 mmol/L and 27.2 mmol/L, respectively, 2 hours after glucose load

Rifampicin reduces plasma concentration of linezolid in patients with infective endocarditis

BACKGROUND\nOBJECTIVES\nPATIENTS AND METHODS\nRESULTS\nCONCLUSIONS\nLinezolid in combination with rifampicin has been used in treatment of infective endocarditis especially for patients infected with staphylococci.\nBecause rifampicin has been reported to reduce the plasma concentration of linezolid, the present study aimed to characterize the population pharmacokinetics of linezolid for the purpose of quantifying an effect of rifampicin cotreatment. In addition, the possibility of compensation by dosage adjustments was evaluated.\nPharmacokinetic measurements were performed in 62 patients treated with linezolid for left-sided infective endocarditis in the Partial Oral Endocarditis Treatment (POET) trial. Fifteen patients were cotreated with rifampicin. A total of 437 linezolid plasma concentrations were obtained. The pharmacokinetic data were adequately described by a one-compartment model with first-order absorption and first-order elimination.\nWe demonstrated a substantial increase of linezolid clearance by 150% (95% CI: 78%-251%), when combined with rifampicin. The final model was evaluated by goodness-of-fit plots showing an acceptable fit, and a visual predictive check validated the model. Model-based dosing simulations showed that rifampicin cotreatment decreased the PTA of linezolid from 94.3% to 34.9% and from 52.7% to 3.5% for MICs of 2 mg/L and 4 mg/L, respectively.\nA substantial interaction between linezolid and rifampicin was detected in patients with infective endocarditis, and the interaction was stronger than previously reported. Model-based simulations showed that increasing the linezolid dose might compensate without increasing the risk of adverse effects to the same degree.Pharmacolog

Association between transcatheter aortic valve replacement and subsequent infective endocarditis and in-hospital death

Importance Limited data exist on clinical characteristics and outcomes of patients who had infective endocarditis after undergoing transcatheter aortic valve replacement (TAVR). Objective To determine the associated factors, clinical characteristics, and outcomes of patients who had infective endocarditis after TAVR. Design, Setting, and Participants The Infectious Endocarditis after TAVR International Registry included patients with definite infective endocarditis after TAVR from 47 centers from Europe, North America, and South America between June 2005 and October 2015. EXPOSURE Transcatheter aortic valve replacement for incidence of infective endocarditis and infective endocarditis for in-hospital mortality. MAIN OUTCOMES AND MEASURES Infective endocarditis and in-hospital mortality after infective endocarditis. Results A total of 250 cases of infective endocarditis occurred in 20 006 patients after TAVR (incidence, 1.1% per person-year; 95% CI, 1.1%-1.4%; median age, 80 years; 64% men). Median time from TAVR to infective endocarditis was 5.3 months (interquartile range [IQR], 1.5-13.4 months). The characteristics associated with higher risk of progressing to infective endocarditis after TAVR was younger age (78.9 years vs 81.8 years; hazard ratio [HR], 0.97 per year; 95% CI, 0.94-0.99), male sex (62.0% vs 49.7%; HR, 1.69; 95% CI, 1.13-2.52), diabetes mellitus (41.7% vs 30.0%; HR, 1.52; 95% CI, 1.02-2.29), and moderate to severe aortic regurgitation (22.4% vs 14.7%; HR, 2.05; 95% CI, 1.28-3.28). Health care?associated infective endocarditis was present in 52.8% (95% CI, 46.6%-59.0%) of patients. Enterococci species and Staphylococcus aureus were the most frequently isolated microorganisms (24.6%; 95% CI, 19.1%-30.1% and 23.3%; 95% CI, 17.9%-28.7%, respectively). The in-hospital mortality rate was 36% (95% CI, 30.0%-41.9%; 90 deaths; 160 survivors), and surgery was performed in 14.8% (95% CI, 10.4%-19.2%) of patients during the infective endocarditis episode. In-hospital mortality was associated with a higher logistic EuroSCORE (23.1% vs 18.6%; odds ratio [OR], 1.03 per 1% increase; 95% CI, 1.00-1.05), heart failure (59.3% vs 23.7%; OR, 3.36; 95% CI, 1.74-6.45), and acute kidney injury (67.4% vs 31.6%; OR, 2.70; 95% CI, 1.42-5.11). The 2-year mortality rate was 66.7% (95% CI, 59.0%-74.2%; 132 deaths; 115 survivors). Conclusions and Relevance Among patients undergoing TAVR, younger age, male sex, history of diabetes mellitus, and moderate to severe residual aortic regurgitation were significantly associated with an increased risk of infective endocarditis. Patients who developed endocarditis had high rates of in-hospital mortality and 2-year mortality

A Bleeding Digital Heart: Identifying Residual Data Generation from Smartphone Applications Interacting with Medical Devices

The integration of medical devices in everyday life prompts the idea that these devices will increasingly have evidential value in civil and criminal proceedings. However, the investigation of these devices presents new challenges for the digital forensics community. Previous research has shown that mobile devices provide investigators with a wealth of information. Hence, mobile devices that are used within medical environments potentially provide an avenue for investigating and analyzing digital evidence from such devices. The research contribution of this paper is twofold. First, it provides an empirical analysis of the viability of using information from smartphone applications developed to complement a medical device, as digital evidence. Second, it includes documentation on the artifacts that are potentially useful in a digital forensics investigation of smartphone applications that interact with medical devices

Optimization of Combined Casing Treatment Structure Applied in a Transonic Axial Compressor Based on Surrogate Model

For modern high load compressors, an excellent stability-enhancing capability by casing treatment (CT) is desirable. However, it is very time consuming to accomplish effective CT design. In this study, a new combined CT structure composed of axial skewed slots and end-wall injection, was proposed to be installed in transonic axial compressors to improve the overall performance. Considering the high computation cost for CFD simulation of the flow field in transonic compressor, a Gaussian Process Regression (GPR) surrogate model combined with Latin hypercube sampling, was utilized to predict compressor performance. For optimization process, a multi-objective evolutionary algorithm (NSGA-Ⅱ) was adopted to obtain the Pareto-optimal front. The main geometric parameters of the slot and the mass-flow rate of injection were selected as design parameters, with the peak efficiency and pressure ratio being two objectives. The results indicated that the surrogate model works well in capturing the key features of the concerning target and accelerating the optimization process. The optimal scheme of the combined CT was found able to increase stall margin (SM) by 19.5% with low efficiency penalty, showing a better performance than the reference combined casing treatment (CCT) scheme. What’s more, the analysis results of entropy generation showed that the superior effect of optimized scheme (OPT) can be attributed to the improvement of exchange flow in slots and the decreased loss in the whole passage