Three upcoming papers (as of May 27, 2015) in Physical Review Letters and Physical Review Applied illustrate beautifully how ideas from one branch of science can inform and catalyze advances in another quite different one:

  • When brittle materials fracture, the rough surfaces have “fractal” structures – in other words, if you scale up any small area, it will look like the larger area of which it was a part. The puzzle has always been why the structures don’t seem to vary much from material to material. Fluid scientists have long known that the patterns in turbulent flow scale up in a similar way and, taking the hint, materials scientists have now found a deep connection, where the growth of cracks follows a similar pattern to the movement of a turbulent liquid.
  • Self-assembly of small particles creates many interesting structures in Nature and in the laboratory (see posts 69-71). Now researchers in Spain have used it to create a magic “magnetic carpet” that can be used to transport cells and other delicate biological cargo to specific locations in the body.
  • “Spin waves” are important in magnetoelectronic devices. Similar ideas also arise in the movement of flocks of birds; when one bird changes its orientation, its neighbors tilt their motion in response, and the information spreads like spin waves in a magnetic material. But analysis shows an unexpected connection, where the waves can’t exist in flocks or materials of a certain size, which may explain why bird flocks obey certain size constraints, and break up otherwise.

These descriptions are necessarily brief, and may seem rather bald. But the pictures that they create are thrilling and beautiful beyond belief.


  • Vernede, Laurent Ponson &J.-P. Bouchaud “Turbulent fracture surfaces: A footprint of damage percolation?” Physical Review Letters, in press.
  • Martinez-Pedrero & Pietro Tierno “Magnetic Propulsion of Self-Assembled Colloidal Carpets: Efficient Cargo Transport via a Conveyor Belt Effect” Physical Review Applied, in press.
  • Andrea Cavagna et al “Silent Flocks: Constraints on Signal Propagation Across Biological Groups”, Physical Review Letters, in press.

FIGURE CREDIT: Andrea Cavagna, CNR

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