Creeping flow of a Herschel-Bulkley fluid with pressure-dependent material moduli

We model the axisymmetric unidirectional flow of a Herschel–Bulkley fluid with rheological parameters that depend linearly on pressure. Adopting an appropriate scaling, we formulate the mathematical problem in cylindrical geometry exploiting an integral formulation for the momentum equation in the unyielded part. We prove that, under suitable assumptions on the data of the problem, explicit solutions can be determined. In particular, we determine the position of the yield surface together with the pressure and velocity profiles. With the aid of some plots, we finally discuss the dependence of the solution on the physical parameters of the problem.</jats:p

Electrophysiology, molecular modelling, and functional analysis of the effects of dietary quercetin and flavonoid analogues on Kir6.1 channels in rat stomach fundus smooth muscle

Flavonoids, ubiquitously distributed in the plant world, are regularly ingested with diets rich in fruit, vegetables, wine, and tea. During digestion, they are partially absorbed in the stomach. The present work aimed to assess the in vitro effects of quercetin and ten structurally related flavonoids on the rat gastric fundus smooth muscle, focussing on ATP-dependent K+ (K(ir)6.1) channels, which play a central role in the regulation of resting membrane potential, membrane excitability and, consequently, of gastric motility. Whole-cell currents through K(ir)6.1 channels (I-Kir6.1) were recorded with the patch-clamp technique and the mechanical activity of gastric fundus smooth muscle strips was studied under isometric conditions. Galangin approximate to tamarixetin &gt; quercetin &gt; kaempferol &gt; isorhamnetin approximate to luteolin approximate to fisetin &gt; (+/-)-taxifolin inhibited pinacidil-evoked, glibenclamide-sensitive I-Kir6.1 in a concentration-dependent manner. Morin, rutin, and myricetin were ineffective. The steric hindrance of the molecule and the number and position of hydroxyl groups on the B ring played an important role in the activity of the molecule. Molecular docking simulations revealed a possible binding site for flavonoids in the C-terminal domain of the K(ir)6.1 channel subunit SUR2B, in a flexible loop formed by residues 251 to 254 of chains C and D. Galangin and tamarixetin, but not rutin relaxed both high K+- and carbachol-induced contraction of fundus strips in a concentration-dependent manner. Furthermore, both flavonoids shifted to the right the concentration-relaxation curves to either pinacidil or L-cysteine constructed in strips pre-contracted by high K+, rutin being ineffective. In conclusion, I-Kir6.1 inhibition exerted by dietary flavonoids might counterbalance their myorelaxant activity, affect gastric accommodation or, at least, some stages of digestion

Modeling peristaltic flow in vessels equipped with valves: implications for vasomotion in bat wing venules

We study the flow of a Newtonian fluid through a vessel provided with valves ensuring a unidirectional motion and whose walls are animated by periodic peristaltic waves. The ultimate target is to describe the phenomenon of vasomotion, consisting in periodic oscillations of blood vessels walls which is particularly important for the blood flow in veins. Here we formulate a mathematical model based on approximations of the flow equations due to the smallness of the radius-to-length ratio. In particular we examine venules equipped with just two valves, showing that the model reproduces the periodic pressure pulses that have been experimentally detected in venules of the bat wing. The flow generated by the synchronous vessel oscillations is recovered in the limit of large peristaltic wavelength.Fil: Farina, A.. Università degli Studi di Firenze; ItaliaFil: Fusi, L.. Università degli Studi di Firenze; ItaliaFil: Fasano, A.. Università degli Studi di Firenze; ItaliaFil: Ceretani, Andrea Noemí. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Austral; ArgentinaFil: Rosso, F.. Università degli Studi di Firenze; Itali

Can Mediterranean Diet Counteract Metabolic Syndrome Diffusion?

n/

Effects of Mediterranean diet and weight loss on blood-lipid profile in overweight adults with hypercholesterolemia

Blood cholesterol has been positively associated with increased cardiovascular risk as a modifiable risk factors together with the lifestyle and diet. Furthermore, an improvement of the blood-lipid profile seems to be able to produce a decrease in cardiovascular events. Cholesterol plasma levels are related to the body mass index (BMI) and are affected by diet. The aim of this study was to evaluate the effectiveness of a Mediterranean diet (MD) weight-loss programme to improve blood cholesterol profiles in overweight adults subjected to real-world outpatient diet. Forty-nine hypercholesteraemic, overweight adults of both sexes were subjected to a dietary weight-loss intervention. Patients were prescribed a slightly hypocaloric MD for 16 weeks, followed by an 8-week follow-up period with a normocaloric diet. Data showed significant weight loss and cholesterol blood profile improvement both under the hypocaloric diet and during the follow-up period. In particular, the decrease in both Total and LDL-cholesterol was greater than their critical differences indicating the clinical relevance of blood lipid improvement induced by MD

An in vitro comparative study of the antioxidant activity and SIRT1 modulation of natural compounds

Oxidative stress arises from an imbalance between the production of free radicals and antioxidant defences. Several studies have suggested that dietary antioxidants (such as polyphenols and berberine) may counteract oxidative stress through the involvement of the Sirtuin 1/Adenosine Monophosphate-Activated Protein Kinase (SIRT1/AMPK) pathway. The aim of this study was to evaluate the direct and specific antioxidant activity of some natural compounds, as well as their ability to modulate the expression of SIRT1 and the activation of AMPK. Quercetin, tyrosol, ferulic acid, catechin, berberine and curcumin were evaluated for their specific and direct antioxidant activity with TOSC assay. Their ability to modulate SIRT1 and AMPK was assessed by immunoblotting assay, while their cytotoxicity by CellTiter-Blue Cell Viability Assay. No statistically significant decrease (p &gt; 0.05) in the number of viable cells was found upon challenging with the natural compounds. Quercetin exhibited the highest antioxidant activity against peroxyl radical and peroxinitrate derivates, while curcumin showed the best anti-hydroxyl activity with respect to the other compounds and, most importantly, respect to the reference antioxidants. Finally, all the tested compounds significantly increased the SIRT1 expression and the activation of AMPK. Our results clearly disclose the specific antioxidant activity of these natural compounds and their ability to increase SIRT1 expression and AMPK activation

On the use of probabilistic worst-case execution time estimation for parallel applications in high performance systems

Some high performance computing (HPC) applications exhibit increasing real-time requirements, which call for effective means to predict their high execution times distribution. This is a new challenge for HPC applications but a well-known problem for real-time embedded applications where solutions already exist, although they target low-performance systems running single-threaded applications. In this paper, we show how some performance validation and measurement-based practices for real-time execution time prediction can be leveraged in the context of HPC applications on high-performance platforms, thus enabling reliable means to obtain real-time guarantees for those applications. In particular, the proposed methodology uses coordinately techniques that randomly explore potential timing behavior of the application together with Extreme Value Theory (EVT) to predict rare (and high) execution times to, eventually, derive probabilistic Worst-Case Execution Time (pWCET) curves. We demonstrate the effectiveness of this approach for an acoustic wave inversion application used for geophysical explorationThis research was funded by the Horizon 2020 Framework Programme, grant number 801137, project RECIPEPeer ReviewedPostprint (published version