Influence of flow confinement on the drag force on a static cylinder

The influence of confinement on the drag force $F$ on a static cylinder in a viscous flow inside a rectangular slit of aperture $h_0$ has been investigated from experimental measurements and numerical simulations. At low enough Reynolds numbers, $F$ varies linearly with the mean velocity and the viscosity, allowing for the precise determination of drag coefficients $\lambda_{||}$ and $\lambda_{\bot}$ corresponding respectively to a mean flow parallel and perpendicular to the cylinder length $L$. In the parallel configuration, the variation of $\lambda_{||}$ with the normalized diameter $\beta = d/h_0$ of the cylinder is close to that for a 2D flow invariant in the direction of the cylinder axis and does not diverge when $\beta = 1$. The variation of $\lambda_{||}$ with the distance from the midplane of the model reflects the parabolic Poiseuille profile between the plates for $\beta \ll 1$ while it remains almost constant for $\beta \sim 1$. In the perpendicular configuration, the value of $\lambda_{\bot}$ is close to that corresponding to a 2D system only if $\beta \ll 1$ and/or if the clearance between the ends of the cylinder and the side walls is very small: in that latter case, $\lambda_{\bot}$ diverges as $\beta \to 1$ due to the blockage of the flow. In other cases, the side flow between the ends of the cylinder and the side walls plays an important part to reduce $\lambda_{\bot}$: a full 3D description of the flow is needed to account for these effects

Diffusion in pores and its dependence on boundary conditions

We study the influence of the boundary conditions at the solid liquid interface on diffusion in a confined fluid. Using an hydrodynamic approach, we compute numerical estimates for the diffusion of a particle confined between two planes. Partial slip is shown to significantly influence the diffusion coefficient near a wall. Analytical expressions are derived in the low and high confinement limits, and are in good agreement with numerical results. These calculations indicate that diffusion of tagged particles could be used as a sensitive probe of the solid-liquid boundary conditions.Comment: soumis \`a J.Phys. Cond. Matt. special issue on "Diffusion in Liquids, Polymers, Biophysics and Chemical Dynamics

Many-particle hydrodynamic interactions in parallel-wall geometry: Cartesian-representation method

This paper describes the results of our theoretical and numerical studies of hydrodynamic interactions in a suspension of spherical particles confined between two parallel planar walls, under creeping-flow conditions. We propose a novel algorithm for accurate evaluation of the many-particle friction matrix in this system--no such algorithm has been available so far. Our approach involves expanding the fluid velocity field into spherical and Cartesian fundamental sets of Stokes flows. The interaction of the fluid with the particles is described using the spherical basis fields; the flow scattered with the walls is expressed in terms of the Cartesian fundamental solutions. At the core of our method are transformation relations between the spherical and Cartesian basis sets. These transformations allow us to describe the flow field in a system that involves both the walls and particles. We used our accurate numerical results to test the single-wall superposition approximation for the hydrodynamic friction matrix. The approximation yields fair results for quantities dominated by single particle contributions, but it fails to describe collective phenomena, such as a large transverse resistance coefficient for linear arrays of spheres

Association of epicardial adipose tissue with proteomics, coronary flow reserve, cardiac structure and function, and quality of life in heart failure with preserved ejection fraction: insights from the PROMIS-HFpEF study

Aim: Epicardial adipose tissue (EAT) may play a role in the pathophysiology of heart failure with preserved ejection fraction (HFpEF). We investigated associations of EAT with proteomics, coronary flow reserve (CFR), cardiac structure and function, and quality of life (QoL) in the prospective multinational PROMIS-HFpEF cohort.Methods and results: Epicardial adipose tissue was measured by echocardiography in 182 patients and defined as increased if ≥9 mm. Proteins were measured using high-throughput proximity extension assays. Microvascular dysfunction was evaluated with Doppler-based CFR, cardiac structural and functional indices with echocardiography and QoL by Kansas City Cardiomyopathy Questionnaire (KCCQ). Patients with increased EAT (n = 54; 30%) had higher body mass index (32 [28-40] vs. 27 [23-30] kg/m2 ; p Conclusion: Increased EAT was associated with cardiac structural alterations and proteins expressing adiposity, inflammation, lower insulin sensitivity and endothelial dysfunction related to HFpEF pathology, probably driven by general obesity. Potential local mechanical or paracrine effects mediated by EAT remain to be elucidated.</p

A prospective study of nutrition education and oral nutritional supplementation in patients with Alzheimer's disease

<p>Abstract</p> <p>Background</p> <p>Weight loss in patients with Alzheimer's disease (AD) is a common clinical manifestation that may have clinical significance.</p> <p>Objectives</p> <p>To evaluate if there is a difference between nutrition education and oral nutritional supplementation on nutritional status in patients with AD.</p> <p>Methods</p> <p>A randomized, prospective 6-month study which enrolled 90 subjects with probable AD aged 65 years or older divided into 3 groups: Control Group (CG) [n = 27], Education Group (EG) [n = 25], which participated in an education program and Supplementation Group (SG) [n = 26], which received two daily servings of oral nutritional supplementation. Subjects were assessed for anthropometric data (weight, height, BMI, TSF, AC and AMC), biochemical data (total protein, albumin, and total lymphocyte count), CDR (Clinical Dementia Rating), MMSE (Mini-mental state examination), as well as dependence during meals.</p> <p>Results</p> <p>The SG showed a significant improvement in the following anthropometric measurements: weight (H calc = 22.12, p =< 0.001), BMI (H calc = 22.12, p =< 0.001), AC (H calc = 12.99, p =< 0.002), and AMC (H calc = 8.67, p =< 0.013) compared to the CG and EG. BMI of the EG was significantly greater compared to the CG. There were significant changes in total protein (H calc = 6.17, p =< 0.046), and total lymphocyte count in the SG compared to the other groups (H cal = 7.94, p = 0.019).</p> <p>Conclusion</p> <p>Oral nutritional supplementation is more effective compared to nutrition education in improving nutritional status.</p

Prokineticin-1:a novel mediator of the inflammatory response in third-trimester human placenta

Prokineticin-1 (PK1) is a recently described protein with a wide range of functions, including tissue-specific angiogenesis, modulation of inflammatory responses, and regulation of hemopoiesis. The aim of this study was to investigate the localization and expression of PK1 and PK receptor-1 (PKR1), their signaling pathways, and the effect of PK1 on expression of the inflammatory mediators cyclooxygenase (COX)-2 and IL-8 in third-trimester placenta. PK1 and PKR1 were highly expressed in term placenta and immunolocalized to syncytiotrophoblasts, cytotrophoblasts, fetal endothelium, and macrophages. PK1 induced a time-dependent increase in expression of IL-8 and COX-2, which was significantly reduced by inhibitors of Gq, cSrc, epidermal growth factor receptor (EGFR), and MAPK kinase. Treatment of third-trimester placenta with 40 nm PK1 induced a rapid phosphorylation of cSrc, EGFR, and ERK1/2. Phosphorylation of ERK1/2 in response to PK1 was dependent on sequential phosphorylation of cSrc and EGFR. Using double-immunofluorescent immunohistochemistry, PKR1 colocalized with IL-8 and COX-2 in placenta. These data suggest that PK1 may have a novel role as a mediator of the inflammatory response in placenta