Transport of blood particles: Chaotic advection even in a healthy scenario.

We study the advection of blood particles in the carotid bifurcation, a site that is prone to plaque development. Previously, it has been shown that chaotic advection can take place in blood flows with diseases. Here, we show that even in a healthy scenario, chaotic advection can take place. To understand how the particle dynamics is affected by the emergence and growth of a plaque, we study the carotid bifurcation in three cases: a healthy bifurcation, a bifurcation with a mild stenosis, and the another with a severe stenosis. The result is non-intuitive: there is less chaos for the mild stenosis case even when compared to the healthy, non-stenosed, bifurcation. This happens because the partial obstruction of the mild stenosis generates a symmetry in the flow that does not exist for the healthy condition. For the severe stenosis, there is more irregular motion and more particle trapping as expected.

Directed chaotic transport in the tokamap with mixed phase space.

On the basis of the tokamap, characteristic features of magnetic field lines and zeroth-order guiding-center particle motion in the whole body of a magnetically confined plasma, e.g., a tokamak plasma, are investigated. It is shown that the tokamap exhibits a poloidal transport that can be considered as a Hamiltonian ratchet. In a situation with partially chaotic magnetic field lines the locking of the averaged poloidal velocity occurs to a value that does not depend precisely on the initial conditions. The so-called sum rule predicts the mean velocity in agreement with the observed magnitude. Possible consequences for the onset of poloidal plasma rotation in ergodized plasmas are elucidated.

Chaotic advection in blood flow.

In this paper we argue that the effects of irregular chaotic motion of particles transported by blood can play a major role in the development of serious circulatory diseases. Vessel wall irregularities modify the flow field, changing in a nontrivial way the transport and activation of biochemically active particles. We argue that blood particle transport is often chaotic in realistic physiological conditions. We also argue that this chaotic behavior of the flow has crucial consequences for the dynamics of important processes in the blood, such as the activation of platelets which are involved in the thrombus formation.