Athough the Grace curve is often used to select the material components and optimal flow rates in blending operations, its validity for industrial mixing practice remains to be seen. Among other reasons, the flow field in industrial mixers is not homogeneous. This causes the actual shear/ elongation rate imposed upon a (moving) droplet to be time‐dependent. To investigate the importance thereof, analytical models are used which describe the droplet stretching rate as a function of the droplet shape, viscosity ratio and time‐varying capillary number. Both experiments and model predictions show that droplet breakup can be caused by inhomogeneous flow fields, even if the average capillary number is sub‐critical. Moreover, the model predicts how the critical capillary number is influenced by a non‐spherical initial shape. At higher aspect ratios the critical capillary number can be reduced significantly, especially for higher viscosity ratio droplets.

Endothelial cells play an important role in the autoregulation of the vascular diameter for maintaining physiological flow and shear stress. An increase in blood flow causes an increase in shear stress, which is sensed by the endothelial cells, resulting in the release of vasoactive substances. An impaired endothelial mediated vasomotive response seems reflective for several cardiovascular pathologies, such as failure of atherosclerosis and arterio-venous fistulas (AVF).

Carotid endarterectomy is the procedure of choice in patients with a recent symptomatic stenosis of 70–99%. Currently, the selection of candidates eligible for carotid endarterectomy is based on stenosis size only. However, the treatment is only beneficial for patients with unstable plaques, which comprises only 16% of the patient population [1]. Hence, identifying plaque stability at an early stage would permit timely intervention, while substantially reducing overtreatment of stable plaques. The objective of this study is to distinguish between stable and unstable carotid atherosclerotic plaques by determining the plaque geometry, the plaque composition and the mechanical properties of plaque components in three dimensions (3D). Mechanical properties from healthy vessels were assessed earlier by van den Broek et al. [2] using ultrasound (US) imaging. They obtained a dynamic dataset in 2D + t. When blood pressure and vessel wall movement are known, mechanical properties can be extracted from these data using a constitutive model. However, atherosclerotic plaques are mostly asymmetric, and present calcifications will cause unfavorable acoustic shadowing when using US. In this study, the focus is on the assessment of plaque geometry, from in vitro echo-CT data, overcoming the aforementioned problems. In an experimental set-up (Fig. 1) both healthy and endarterectomy specimens were mounted, and exposed to physiological intraluminal pressures. Echo-CT was used to image the arterial segments in 3D+t. Automated geometry assessment of the arterial segments will be demonstrated and validated using microCT (μCT).

What is the in vivo axial strain of a porcine coronary artery?van den Broek, C.N.; van Tuijl, S.; Rutten, M.C.M.; van de Vosse, F.N.

Knowledge of the mechanical properties of arteries is important to understand vascular function during disease and the effect of interventions, such as PTCA treatment. A mechanical model of the vascular tree would facilitate the improvement of (balloon-)catheters and stents. The aim of this research is to propose general parameter values for the fiber-reinforced material model as proposed by Driessen et al. (2005) that can describe the arterial wall behavior of the porcine left anterior descending coronary artery (LAD, fig. 1a) at physiological axial stretch.