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SUMMARY:Packing of wires in cavities and growing surfaces - Professor Hans
  Herrmann  ETH Zürich\, Switzerland
DTSTART:20130613T103000Z
DTEND:20130613T113000Z
UID:TALK44828@talks.cam.ac.uk
CONTACT:Catherine Pearson
DESCRIPTION:We investigate the morphologies and maximum packing density of
  thin wires packed into spherical cavities. Using simulations and experime
 nts with nylon lines\, we find that ordered as well as disordered structur
 es emerge\, depending on the amount of internal torsion. We find that the 
 highest packing densities are achieved in a low torsion packing for large 
 systems\, but in a high torsion packing for small systems. An analysis of 
 both situations is given in terms of energetics and comparison is made to 
 analytical models of DNA packing in viral capsids. In two dimensions we al
 so find different morphologies and present the associated morphological ph
 ase diagram based on experiments with metallic wires and confirmed by nume
 rical simulations using discrete elements. During crumpling\, the number o
 f loops increases according to a power-law with different exponents in eac
 h morphology. Furthermore\, we observe a power-law divergence of the struc
 ture's bulk. We also investigate the morphology of thin discs and rings gr
 owing in circumferential direction. Recent analytical results suggest that
  this growth produces symmetric excess cones (e-cones). We study the stabi
 lity of such solutions considering self-contact and bending stress. Contra
 ry to what was assumed in previous analytical solutions\, beyond a critica
 l growth factor\, no symmetric e-cone solution is energetically minimal an
 y more. Instead\, we obtain skewed e-cone solutions having lower energy\, 
 characterized by a skewness angle and repetitive spiral winding with incre
 asing growth. These results are generalized to discs with varying thicknes
 s and rings with holes of different radii. Experiments with cardboard conf
 irm the simulations.
LOCATION:Open Plan Area\, BP Institute\, Madingley Rise CB3 0EZ
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