"Living fluids: blood flow and microswimmers"
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In this talk  I will focus on passive and active motion in blood suspension and
other suspensions. I will first discuss how to model blood flow from microscopic
considerations (i.e. by taking blood element explicitly into account, e.g. red
blood cells). I will show some dynamics of individual red blood cells, and then
present collective dynamics and some intringuing rheological behaviors in
microcirculation. I will then discuss some issues related to the so-called
ameboid swimming.  Microorganisms, such as bacteria, algae, or spermatozoa, are
able to propel themselves forward thanks to flagella or cilia activity. By
contrast, other organisms employ pronounced changes of the membrane shape to
achieve propulsion, a prototypical example being the Eutreptiella gymnastica.
Cells of the immune system as well as dictyostelium amoebas, traditionally
believed to crawl on a substratum, can also swim in a similar way. A model will
be presented and  it will be shown that fast propulsion can be achieved with
adequate shape adaptations.  The autopropulsion distance over one cycle is a
universal linear function of a simple geometrical dimensionless quantity
A/V^(2/3) (V and A are the cell volume and its membrane area). This study
captures the peculiar motion of Eutreptiella gymnastica with simple force
distribution.