Scaling law for the viscoelasticity-induced particle migration in stirred vessels

In this study, we investigate the viscoelasticity-induced migration of solid particles immerged in the three-dimensional flow field created by the rotation of a Rushton turbine. At the same time, we propose a scaling law for predicting the characteristic particle migration time as a function of the Weissenberg number. Particle image velocimetry is adopted to reconstruct the three-dimensional velocity and deformation rate fields generated by the rotation of the Rushton turbine in both Newtonian and viscoelastic fluids; concurrently, particle tracking is used to measure the evolution of the particle distribution in the tank. The experimental campaign shows that the deformation rate field is essentially bi-dimensional and confined to the r-θ plane. Accordingly, the particles migrate only in the radial direction driven by the presence of gradients of shear rate on the r-θ plane. Finally, the scaling law is validated against experimental data obtained at different Weissenberg numbers, impeller diameters and fluid compositions. The results show good agreement between the scaling law and the experimental data

A fast algorithm for Direct Numerical Simulation of natural convection flows in arbitrarily-shaped periodic domains

A parallel algorithm is presented for the Direct Numerical Simulation of buoyancy-induced flows in open or partially confined periodic domains, containing immersed cylindrical bodies of arbitrary cross-section. The governing equations are discretized by means of the Finite Volume method on Cartesian grids. A semi-implicit scheme is employed for the diffusive terms, which are treated implicitly on the periodic plane and explicitly along the homogeneous direction, while all convective terms are explicit, via the second-order Adams-Bashfort scheme. The contemporary solution of velocity and pressure fields is achieved by means of a projection method. The numerical resolution of the set of linear equations resulting from discretization is carried out by means of efficient and highly parallel direct solvers. Verification and validation of the numerical procedure is reported in the paper, for the case of flow around an array of heated cylindrical rods arranged in a square lattice. Grid independence is assessed in laminar flow conditions, and DNS results in turbulent conditions are presented for two different grids and compared to available literature data, thus confirming the favorable qualities of the method

Natural convection in asymmetric triangular enclosures heated from below

Triangular enclosures are typical configurations of attic spaces found in residential as well as industrial pitched-roof buildings. Natural convection in triangular rooftops has received considerable attention over the years, mainly on right-angled and isosceles enclosures. In this paper, a finite volume CFD package is employed to study the laminar air flow and temperature distribution in asymmetric rooftop-shaped triangular enclosures when heated isothermally from the base wall, for aspect ratios (AR) 0.2 64 AR 64 1.0, and Rayleigh number (Ra) values 8 7 105 64 Ra 64 5 7 107. The effects of Rayleigh number and pitch angle on the flow structure and temperature distributions within the enclosure are analysed. Results indicate that, at low pitch angle, the heat transfer between the cold inclined and the hot base walls is very high, resulting in a multi-cellular flow structure. As the pitch angle increases, however, the number of cells reduces, and the total heat transfer rate progressively reduces, even if the Rayleigh number, being based on the enclosure height, rapidly increases. Physical reasons for the above effect are inspected

Bifurcations of Natural Convection Flows from an Enclosed Cylindrical Heat Source

A numerical analysis of transitional natural convection from a confined thermal source is presented. The system considered is an air-filled, square-sectioned 2D enclosure containing a horizontal heated cylinder. The resulting flow is investigated with respect to the variation of the Rayleigh number, for three values of the aspect ratio A. The first bifurcation of the low-Ra fixed-point solution is tracked for each A-value. Chaotic flow features are detailed for the case A = 2.5. The supercritical behaviour of the system is investigated using nonlinear analysis tools and phase-space representations, and the effect of the flow on heat transfer is discussed

Comparative assessment of angiotensin receptor blockers in different clinical settings

Cardiovascular and renal disease can be regarded as progressing along a sort of continuum which starts with cardiovascular risk factors (hypertension, diabetes, dyslipidemia, smoking, etc), evolves with progression of atherosclerotic lesions and organ damage, and then becomes clinically manifest with the major clinical syndromes (myocardial infarction, stroke, heart failure, end-stage renal disease). The blood pressure control remains a fundamental mechanism for prevention of cardiovascular disease. The renin–angiotensin system is believed to play an important role along different steps of the cardiovascular disease continuum. Convincing evidence accumulated over the last decade that therapeutic intervention with angiotensin receptor blockers (ARBs) is effective to slow down or block the progression of cardiovascular disease at different steps of the continuum, with measurable clinical benefits. However, despite the shared mechanism of action, each ARB is characterized by specific pharmacological properties that may influence its clinical efficacy. Indeed, important differences among available ARBs emerged from clinical studies. Therefore, generalization of results obtained with a specific ARB to all available ARBs may be misleading. The present review provides a comparative assessment of the different ARBs in their efficacy on major clinical endpoints along the different steps of the cardiovascular disease continuum

Statins in acute coronary syndrome: very early initiation and benefits.

The use of 3-hydroxy-3-methylglutaryl coenzyme A reductase (statins) is associated with a marked reduction in morbidity and mortality in patients at high cardiovascular risk or with established cardiovascular disease. In the last decade, several randomized controlled studies have demonstrated the benefit of statins in patients with acute coronary syndrome (ACS). These studies showed that use of statins in patients with ACS is associated with a significant reduction of the risk of recurrent cardiovascular events. Current American College of Cardiology/American Heart Association (ACC/AHA) guidelines recommend (Level of Evidence 1A) the use of statin therapy before hospital discharge for all patients with ACS regardless of the baseline low-density lipoprotein. Although there is no consensus on the preferable time of administration of statins during ACS, some clinical trials and pooled analyses provided substantial support for the institution of an early initiation to improve strategies that target the pathophysiologic mechanism operating during myocardial infarction. In particular, recent findings suggested that the earlier the treatment is started after the diagnosis of ACS the greater the expected benefit. Experimental studies with statins in ACS have shown several other effects that could extend the clinical benefit beyond the lipid profile modification itself. In particular, statins demonstrated the ability to induce anti-inflammatory effects, modulate endothelium and inhibit the thrombotic signaling cascade. Given these recognized potential benefit, statins should conceivably modulate the pathophysiological processes involved in the very early phase of plaque rupture and coronary thrombosis

Aggressive blood pressure reduction in patients at high vascular risk: is it dangerous?

Summary Introduction The aim of this review was to summarize the current state of evidence regarding the optimal blood pressure goals in patients with high vascular risk. In particular, this review critically addresses the issue of the "J-curve" paradox – a hypothesis indicating that low treatment-induced blood pressure values are characterized by an increase, rather than a decrease, in the incidence of cardiovascular events. Materials and methods We reviewed evidence from studies published in peer-reviewed journals indexed in Medline, EMBASE and CINAHL that compared different BP goals. Results Post-hoc analyses of randomized trials specifically conducted to test the hypothesis of the "J-shaped curve" yielded conflicting results. However, trials directly comparing different blood pressure goals and meta-analyses showed that in-treatment blood pressure values below the usual goal of less than 140/90 mmHg improve outcomes in patients at increased vascular risk. Discussion The fear that an excessive reduction in blood pressure may be dangerous is inconsistent with the available data and probably conditioned by the adverse impact of other risk factors that may be more frequent in patients with low values of achieved blood pressure. The association between blood pressure reduction and cardiovascular risk seems to be linear and not J-shaped

Electrocardiography for diagnosis of left ventricular hypertrophy in hypertensive patients with atrial fibrillation

Abstract Left ventricular (LV) hypertrophy at electrocardiography (ECG) predicts incident atrial fibrillation (AF). However, the diagnostic performance of ECG for diagnosis of LV hypertrophy in patients with AF is still not well characterized. We analyzed 563 hypertensive patients enrolled in the Umbria-Atrial Fibrillation (Umbria-FA) registry, an ongoing prospective observational registry in patients with AF. All patients underwent ECG and standard echocardiography at their entry in the Register. Mean age was 74 years and 43% of patients were women. Prevalence of ECG-LV hypertrophy, defined by Perugia criterion corrected for body mass index, was 23%. Echocardiographic LV mass was the reference standard. Sensitivity, specificity and diagnostic accuracy of ECG-LV hypertrophy were 37.4% (95% confidence interval [CI]: 31.6–43.4), 90.0% (95% CI: 86.0–93.2) and 64.5% (95% CI: 60.4–68.3), respectively. Performance was comparable in patients with AF or sinus rhythm at ECG recording. The area under the receiver-operating characteristic (ROC) curve was 0.622 (95% CI: 0.580–0.664) in the group with AF and 0.662 (95% CI: 0.605–0.720) in that with sinus rhythm (p = 0.266 for comparison). These data suggest that standard ECG is reliable for diagnosis of LV hypertrophy in patients with a history of AF, regardless of the presence of AF or sinus rhythm at the time of ECG recording

Traumatic rupture of the thoracic aorta: Ten years of delayed management

ObjectiveTraumatic rupture of the thoracic aorta is a highly fatal condition in which patient outcome is strongly conditioned by other associated injuries. Delayed aortic treatment has been proposed to improve results.MethodsThe charts of 69 patients with traumatic rupture of the thoracic aorta observed between 1980 and 2003 were reviewed. Patients were grouped according the timing of repair: group I, immediate repair (21 patients); and group II, delayed repair (48 patients). In group II, 45 patients were treated surgically or by endovascular procedure.ResultsIn-hospital mortalities were 4 of 21 patients (19%) in group I and 2 of 48 patients (4.2%) in group II. There were 3 cases of paraplegia in group I and none in group II.ConclusionImprovement of patient outcome with traumatic rupture of the thoracic aorta can be achieved by delaying surgical repair until after management of major associated injuries if there are no signs of impending rupture. Endovascular treatment is feasible and safe and may represent a valid alternative to open surgery in selected cases

Single-Cell NGS-Based Analysis of Copy Number Alterations Reveals New Insights in Circulating Tumor Cells Persistence in Early-Stage Breast Cancer

Simple Summary Circulating tumor cells (CTCs) are crucial for the identification of patients with a higher risk of relapse, including those diagnosed with breast cancer (BC). The aim of this study was to explore their molecular aspects in 11 early-stage BC patients during patient management, focusing on copy number alterations (CNAs) and exploiting a single-CTC next-generation sequencing approach. CTCs showed different degrees of aberration based on access time. Moreover, CTCs, in particular those persisting even months after tumor resection, shared CNAs with matched tumor tissue. Enrichment analyses of CNAs on CTCs highlighted peculiar aberrations, especially associated with interferon (IFN)-associated terms. The study of CTCs CNAs can provide information about the molecular mechanisms involving CTC-related processes and their survival ability in occult niches, supporting the goal of exploiting their application in patients' surveillance and follow-up. Circulating tumor cells (CTCs) are a rare population of cells representing a key player in the metastatic cascade. They are recognized as a validated tool for the identification of patients with a higher risk of relapse, including those diagnosed with breast cancer (BC). However, CTCs are characterized by high levels of heterogeneity that also involve copy number alterations (CNAs), structural variations associated with gene dosage changes. In this study, single CTCs were isolated from the peripheral blood of 11 early-stage BC patients at different time points. A label-free enrichment of CTCs was performed using OncoQuick, and single CTCs were isolated using DEPArray. Libraries were prepared from single CTCs and DNA extracted from matched tumor tissues for a whole-genome low-coverage next-generation sequencing (NGS) analysis using the Ion Torrent S5 System. The analysis of the CNA burden highlighted that CTCs had different degrees of aberration based on the time point and subtype. CTCs were found even six months after surgery and shared CNAs with matched tumor tissue. Tumor-associated CNAs that were recurrent in CTCs were patient-specific, and some alterations involved regions associated with BC and survival (i.e., gains at 1q21-23 and 5p15.33). The enrichment analysis emphasized the involvement of aberrations of terms, associated in particular with interferon (IFN) signaling. Collectively, our findings reveal that these aberrations may contribute to understanding the molecular mechanisms involving CTC-related processes and their survival ability in occult niches, supporting the goal of exploiting their application in patients' surveillance and follow-up