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Tuesday, August 31, 2010

calculating the time required for the pinching

This article reminds me of the one on how a synapse works.


Nature Physics
Published online: 1 August 2010 | doi:10.1038/nphys1737

Universality and self-similarity in pinch-off of rods by bulk diffusion
Larry K. Aagesen1, Anthony E. Johnson1, Julie L. Fife1,2, Peter W. Voorhees1,3, Michael J. Miksis3, Stefan O. Poulsen4, Erik M. Lauridsen4, Federica Marone2 & Marco Stampanoni2,5


Abstract: As rodlike domains pinch off owing to Rayleigh instabilities, a finite-time singularity occurs as the interfacial curvature at the point of pinch-off becomes infinite. The dynamics controlling the interface become independent of initial conditions and, in some cases, the interface attains a universal shape1. Such behaviour occurs in the pinching of liquid jets and bridges2, 3, 4, 5, 6, 7, 8, 9 and when pinching occurs by surface diffusion10, 11, 12. Here we examine an unexplored class of topological singularities where interface motion is controlled by the diffusion of mass through a bulk phase. We show theoretically that the dynamics are determined by a universal solution to the interface shape (which depends only on whether the high-diffusivity phase is the rod or the matrix) and materials parameters. We find good agreement between theory and experimental observations of pinching liquid rods in an Al–Cu alloy. The universal solution applies to any physical system in which interfacial motion is controlled by bulk diffusion, from the break-up of rodlike reinforcing phases in eutectic composites13, 14, 15, 16 to topological singularities that occur during coarsening of interconnected bicontinuous structures17, 18, 19, 20, thus enabling the rate of topological change to be determined in a broad variety of multiphase systems.

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