The emerging landscape of health research based on biobanks linked to electronic health records: Existing resources, statistical challenges, and potential opportunities

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154448/1/sim8445_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154448/2/sim8445.pd

Kelvin-Helmholtz instability in the presence of variable viscosity for mudflow resuspension in estuaries

The temporal stability of a parallel shear flow of miscible fluid layers of dif- ferent density and viscosity is investigated through a linear stability analysis and direct numerical simulations. The geometry and rheology of this Newto- nian fluid mixing can be viewed as a simplified model of the behavior of mud- flow at the bottom of estuaries for suspension studies. In this study, focus is on the stability and transition to turbulence of an initially laminar configuration. A parametric analysis is performed by varying the values of three control pa- rameters, namely the viscosity ratio, the Richardson and Reynolds numbers, in the case of initially identical thickness of the velocity, density and viscosity profiles. The range of parameters has been chosen so as to mimic a wide variety of real configurations. This study shows that the Kelvin-Helmholtz instability is controlled by the local Reynolds and Richardson numbers of the inflection point. In addition, at moderate Reynolds number, viscosity strat- ification has a strong influence on the onset of instability, the latter being enhanced at high viscosity ratio, while at high Reynolds number, the influ- ence is less pronounced. In all cases, we show that the thickness of the mixing layer (and thus resuspension) is increased by high viscosity stratification, in particular during the non-linear development of the instability and especially pairing processes. This study suggests that mud viscosity has to be taken into account for resuspension parameterizations because of its impact on the inflec- tion point Reynolds number and the viscosity ratio, which are key parameters for shear instabilities

Distribution dependent SDEs driven by additive fractional Brownian motion

AbstractWe study distribution dependent stochastic differential equations with irregular, possibly distributional drift, driven by an additive fractional Brownian motion of Hurst parameter $$H\in (0,1)$$ H ∈ ( 0 , 1 ) . We establish strong well-posedness under a variety of assumptions on the drift; these include the choice $$\begin{aligned} B(\cdot ,\mu )=(f*\mu )(\cdot ) + g(\cdot ), \quad f,\,g\in B^\alpha _{\infty ,\infty },\quad \alpha &gt;1-\frac{1}{2H}, \end{aligned}$$ B ( · , μ ) = ( f ∗ μ ) ( · ) + g ( · ) , f , g ∈ B ∞ , ∞ α , α &gt; 1 - 1 2 H , thus extending the results by Catellier and Gubinelli (Stochast Process Appl 126(8):2323–2366, 2016) to the distribution dependent case. The proofs rely on some novel stability estimates for singular SDEs driven by fractional Brownian motion and the use of Wasserstein distances. </jats:p

Hypertension, urbanization, social and spatial disparities : a cross-sectional population-based survey in a West African urban environment (Ouagadougou, Burkina Faso)

Data show that hypertension has become a public health problem in developing countries. Many studies have reported social disparities among the affected populations, but few of them pointed out spatial disparities within towns. We aimed to show that hypertension could be a good indicator of the medical change that occurs unequally in towns. A cross-sectional survey was done in April and October 2004 in Ouagadougou, Burkina Faso, among 2087 adults over 35 years old in different kinds of urban areas. Social and demographic data were collected and blood pressure was measured. Prevalence of hypertension was 40.2%. Age, body mass index, level of equipment, absence of community integration, absence of occupation, duration of residence over 20 years, protein-rich diet and absence of physical activity were identified as risk factors, but there were social and spatial disparities according to location of housing (parcelled-out or non-parcelled-out areas) and to integration within the town. The high rate of hypertension found in Ouagadougou and the heterogeneity of the risk within the population highlights that social and spatial risk factors have to be taken into account for the prevention of the non-transmissible diseases in countries in full process of urbanization and medical change