Numerical Investigation of the Performance of Three Hinge Designs of Bileaflet Mechanical Heart Valves

Thromboembolic complications (TECs) of bileaflet mechanical heart valves (BMHVs) are believed to be due to the nonphysiologic mechanical stresses imposed on blood elements by the hinge flows. Relating hinge flow features to design features is, therefore, essential to ultimately design BMHVs with lower TEC rates. This study aims at simulating the pulsatile three-dimensional hinge flows of three BMHVs and estimating the TEC potential associated with each hinge design. Hinge geometries are constructed from micro-computed tomography scans of BMHVs. Simulations are conducted using a Cartesian sharp-interface immersed-boundary methodology combined with a second-order accurate fractional-step method. Leaflet motion and flow boundary conditions are extracted from fluid–structure-interaction simulations of BMHV bulk flow. The numerical results are analyzed using a particle-tracking approach coupled with existing blood damage models. The gap width and, more importantly, the shape of the recess and leaflet are found to impact the flow distribution and TEC potential. Smooth, streamlined surfaces appear to be more favorable than sharp corners or sudden shape transitions. The developed framework will enable pragmatic and cost-efficient preclinical evaluation of BMHV prototypes prior to valve manufacturing. Application to a wide range of hinges with varying design parameters will eventually help in determining the optimal hinge design

All-cause and Cardiovascular mortality among ethnic German immigrants from the Former Soviet Union: a cohort study

BACKGROUND: Migration is a phenomenon of particular Public Health importance. Since 1990, almost 2 million ethnic Germans (Aussiedler) have migrated from the former Soviet Union (FSU) to Germany. This study compares their overall and cardiovascular disease (CVD) mortality to that of Germany's general population. Because of high overall and CVD mortality in the FSU and low socio-economic status of Aussiedler in Germany, we hypothesize that their mortality is higher. METHODS: We conducted a retrospective cohort study for 1990–2002 with data of 34,393 Aussiedler. We assessed vital status at population registries and causes of death at the state statistical office. We calculated standardized mortality ratios (SMRs) for the whole cohort and substrata of covariables such as age, sex and family size. To assess multivariate effects, we used Poisson regression. RESULTS: 1657 cohort members died before December 31, 2002, and 680 deaths (41.03%) were due to CVD. The SMR for the whole cohort was 0.85 (95%-CI 0.81–0.89) for all causes of death and 0.79 (95%-CI 0.73–0.85) for CVD. SMRs were higher than one for younger Aussiedler and lower for older ones. There was no clear effect of duration of stay on SMRs. For 1990–93, SMRs were significantly lower than in subsequent years. In families comprising at least five members upon arrival in Germany, SMRs were significantly lower than in smaller families. CONCLUSION: In contrast to our hypothesis on migrants' health, overall and CVD mortality among Aussiedler is lower than in Germany's general population. Possible explanations are a substantially better health status of Aussiedler in the FSU as compared to the local average, a higher perceived socio-economic status of Aussiedler in Germany, or selection effects. SMR differences between substrata need further exploration, and risk factor data are needed

Exploring the viability of a local social network for creating persistently engaging energy feedback and improved human well-being

Long-term engagement of residents is crucial for demand response management, and thus grid stability in energy systems, but current approaches often fail to maintain or even achieve the necessary changes in consumer behaviour. Thus future customer engagement approaches will have to relate more strongly to customer needs in order to achieve long-term engagement. This study presents an approach based on a central need identified in psychological research, namely the need to belong to a group. A mixed methods approach was used to examine how an energy feedback approach that connects to this need could be designed. First, based on the Theory of Planned Behaviour and Social Identity Theory, a survey was conducted to examine the influence of e.g. norms held by the local social group of neighbours on energy behaviour. In contrast to previous studies on the influence of social groups on sustainable behaviour, no significant influence was found. However, other findings indicated that this was due to the low level of group identity, leading to the assumption that the need for social belonging was not fulfilled in the survey group. Second, focus group discussions were conducted to test this assumption in more detail. Findings from the focus groups confirm the assumption and reveal detailed insights on residential needs for stronger connections between neighbours. We conclude that a local social network could be a suitable solution to the need for local social belonging and, while also providing a context for energy feedback. Thus, implementing a local social network could lead to both persistently engaging energy feedback and also improve human well-being.QC 20190823InteGri