E. Ben-Isaac, Z. Y. K. Park, G.Popescu, F. L. H. Brown, N. S. Gov and Y. Shokef, Effective Temperature of Red Blood Cell Membrane Fluctuations, Phys. Rev. Lett, 106, (2011).

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Biologically driven nonequilibrium fluctuations are often characterized by their non-Gaussianity or by an ‘‘effective temperature’’, which is frequency dependent and higher than the ambient temperature. We address these two measures theoretically by examining a randomly kicked particle, with a variable number of kicking motors, and show how these two indicators of nonequilibrium behavior can contradict. Our results are compared with new experiments on shape fluctuations of red-blood cell membranes, and demonstrate how the physical nature of the motors in this system can be revealed using these global measures of nonequilibrium.