Scientific, societal and pedagogical approaches to tackle the impact of climate change on marine pollution.

Marine pollution impacts coastal nations around the world, and more so: (a) in confined maritime areas with significant marine traffic, (b) where exploitation of natural and mineral resources is taking place, or (c) in regions witnessing pressure from tourism, local population growth, and industry. In this work, Digital Elevation Models, hydrographic, and climatic data are used together with computer simulations to understand the control of climate change on marine pollution. The results show that different climate change signals can potentially alter the flow and concentration of pollution in the European Seas, when compared to the present day.

Viscoplastic Couette Flow in the Presence of Wall Slip with Non-Zero Slip Yield Stress.

The steady-state Couette flow of a yield-stress material obeying the Bingham-plastic constitutive equation is analyzed assuming that slip occurs when the wall shear stress exceeds a threshold value, the slip (or sliding) yield stress. The case of Navier slip (zero slip yield stress) is studied first in order to facilitate the analysis and the discussion of the results. The different flow regimes that arise depending on the relative values of the yield stress and the slip yield stress are identified and the various critical angular velocities defining those regimes are determined.

Hemodynamics in stenotic vessels of small diameter under steady state conditions: Effect of viscoelasticity and migration of red blood cells.

Background: In microcirculation, the non-Newtonian behavior of blood and the complexity of the microvessel network are responsible for the high flow resistance and the large reduction of the blood pressure. Red blood cell aggregation along with inward radial migration are two significant mechanisms determining the former. Yet, their impact on hemodynamics in non-straight vessels is not well understood.

The effect of head rotation on the geometry and hemodynamics of healthy vertebral arteries.

The geometric and hemodynamic characteristics of the left and right vertebral arteries (LVA, RVA) of six healthy volunteers were investigated for the supine (S) and the prone position (P) a common sleeping posture with head rotation. MRI images were used to reconstruct the subject specific three-dimensional solid models of the LVA and RVA from the level of the carotid bifurcation to the vertebrobasilar junction (VJ). Geometric parameters such as cross sectional area ratio, curvature, tortuosity and branch angle were estimated.

Impact of head rotation on the individualized common carotid flow and carotid bifurcation hemodynamics.

This paper aims at evaluating the changes that head rotation poses on morphological and flow characteristics of the carotid bifurcation (CB) and on the distribution of parameters that are regarded as important in atherosclerosis development, such as relative particle residence time (RRT), normalized oscillatory shear index (nOSI), and helicity (HL). Using a subject-specific approach, six healthy volunteers were MR-scanned in two head postures: supine neutral and prone with rightward head rotation. Cross-sectional flow velocity distribution was obtained using phase-contrast MRI at the common carotid artery (CCA).

Effect of head posture on the healthy human carotid bifurcation hemodynamics.

Head and neck postures may cause morphology changes to the geometry of the carotid bifurcation (CB) that alter the low and oscillating wall shear stress (WSS) regions previously reported as important in the development of atherosclerosis. Here the right and left CB were imaged by MRI in two healthy subjects in the neutral head posture with the subject in the supine position and in two other head postures with the subject in the prone position: (1) rightward rotation up to 80°, and (2) leftward rotation up to 80°. Image-based computational models were constructed to investigate the effect of posture on arterial geometry and local hemodynamics.

Effect of posture change on the geometric features of the healthy carotid bifurcation.

Segmented cross-sectional MRI images were used to construct 3-D virtual models of the carotid bifurcation in ten healthy volunteers. Geometric features, such as bifurcation angle, internal carotid artery (ICA) angle, planarity angle, asymmetry angle, tortuosity, curvature, bifurcation area ratio, ICA/common carotid artery (CCA), external carotid artery (ECA)/CCA, and ECA/ICA diameter ratios, were calculated for both carotids in two head postures: 1) the supine neutral position; and 2) the prone sleeping position with head rotation to the right ( ∼ 80°). The results obtained have shown that head rotation causes 1) significant variations in bifurcation angle [32% mean increase for the right carotid (RC) and 21% mean decrease for the left carotid (LC)] and internal carotid artery angle (97% mean increase for the RC, 43% mean decrease for the LC); 2) a slight increase in planarity and asymmetry angles for both RC and LC; 3) minor and variable curvature changes for the CCA and for the branches; 4) slight tortuosity changes for the braches but not for the CCA; and 5) unsubstantial alterations in area and diameter ratios (percentage changes %).