Julia Yeomans OBE FRS

Abstract:

We present a numerical study of the effect of knotting on the ejection of flexible and semiflexible polymers from a spherical, viruslike capsid. The polymer ejection rate is primarily controlled by the knot, which moves to the hole in the capsid and then acts as a ratchet. Polymers with more complex knots eject more slowly and, for large knots, the knot type, and not the flexibility of the polymer, determines the rate of ejection. We discuss the relation of our results to the ejection of DNA from viral capsids and conjecture that this process has the biological advantage of unknotting the DNA before it enters a cell.

Abstract:

Using computational modeling, we investigate the shear response of a droplet that encases a dilute concentration of polymers and nanoparticles. We show that the viscoelastic effects of the encapsulated polymers reduce the shear-induced deformation of the droplet at intermediate capillary numbers, but can induce the breakup of the droplet at high capillary numbers. © 2009 The Royal Society of Chemistry.

Abstract:

We define a model microswimmer with a variable cycle time, thus allowing the possibility of phase locking driven by hydrodynamic interactions between swimmers. We find that, for extensile or contractile swimmers, phase locking does occur, with the relative phase of the two swimmers being, in general, close to 0 or π, depending on their relative position and orientation. We show that, as expected on grounds of symmetry, self T-dual swimmers, which are time-reversal covariant, do not phase-lock. We also discuss the phase behaviour of a line of tethered swimmers, or pumps. These show oscillations in their relative phases reminiscent of the metachronal waves of cilia. © Springer Science+Business Media, LLC 2009.