BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Talks.cam//talks.cam.ac.uk//
X-WR-CALNAME:Talks.cam
BEGIN:VEVENT
SUMMARY:Two questions of shape - Pierre Haas (University of Cambridge)
DTSTART:20190214T130000Z
DTEND:20190214T140000Z
UID:TALK120034@talks.cam.ac.uk
CONTACT:Anne Herrmann
DESCRIPTION:Nonlinear and Nonlocal Elasticity in Coarse-Grained Differenti
 al-Tension Models of Epithelia: \n\nThe shapes of epithelial tissues resul
 t from a complex interplay of contractile forces in the cytoskeleta of the
  cells in the tissue\, and adhesion forces between them. A host of discret
 e\, cell-based models describe these forces by assigning different surface
  tensions to the apical\, basal\, and lateral sides of the cells. These di
 fferential-tension models have been used to describe the deformations of e
 pithelia in different living systems\, but the underlying continuum mechan
 ics at the scale of the epithelium are still unclear. We derive a continuu
 m theory for a simple differential-tension model of a two-dimensional epit
 helial monolayer and study the buckling of this epithelium under imposed c
 ompression. The analysis reveals how the cell-level properties encoded in 
 the differential-tension model lead to nonlinear and nonlocal elastic beha
 viour at the continuum level.\n\nShape-Shifting Polyhedral Droplets:\n\nCo
 oled oil emulsion droplets in aqueous surfactant solution have been observ
 ed to flatten into a remarkable host of polygonal shapes with straight edg
 es and sharp corners\, but different driving mechanisms — (i) a partial 
 phase transition of the bulk oil phase and (ii) buckling of the interfacia
 lly frozen surfactant monolayer — have been proposed. Combining experime
 nt and theory\, we analyse the initial stages of the phase diagram of thes
 e ‘shape-shifting’ droplets\, during which a polyhedral droplet flatte
 ns into a polygonal platelet. Using reflected-light microscopy\, we reveal
  how an icosahedral droplet evolves through an intermediate octahedral sta
 ge to flatten into a hexagonal platelet. This behaviour is reproduced by a
  theoretical model of the phase transition mechanism\, but the buckling me
 chanism can only reproduce the flattening if surface tension decreases by 
 several orders of magnitude during cooling so that the flattening is drive
 n by buoyancy.
LOCATION:MR11\, Centre for Mathematical Sciences\, Wilberforce Road\, Camb
 ridge
END:VEVENT
END:VCALENDAR