Current research on thermodynamics of jamming: Simulations and experiments are being performed to investigate the statistical mechanics of jammed particulate matter.

(a) Simulations of grains (100 microns) interacting via Hertz-Mindlin contact forces [1]. A slow shear flow, indicated by the arrows, is applied to the jammed system. We follow the tracer particle trajectories to obtain the diffusivity. An external force $F$ is then applied to the tracers in response to which we measure the particle mobility. These dynamical measurements yield an “effective temperature” obtained from an Einstein relation which is indeed very close to that obtained by a flat average over the ensemble of jammed configurations as proposed by Edwards and coworkers [2].

(b) A novel fluorescence mechanism using confocal microscopy is providing new insight into the microstructure and the mechanics of jammed matter [3]. The suitable model system is an emulsion comprised of oil droplets of approximately 3 microns dispersed in a refractive index matching solution. The system forms a random close packed structure by creaming or centrifugation giving rise to a force network. Based on the bright contact areas, the interdroplet forces can be extracted. The resulting micromechanics is being used to develop statistical theories of jammed materials.

[1] H. A. Makse and J. Kurchan, “Testing the Thermodynamic Approach to Granular Matter with a Numerical Model of a Decisive Experiment”, Nature 415, 614-617 (2002).

[2] Edwards, S. F. The role of entropy in the specification of a powder, in Granular matter: an interdisciplinary approach, (ed Mehta, A.) 121-140 (Springer-Verlag, New York, 1994)

[3] J. Brujic, S. F. Edwards, I. Hopkinson, and H. A. Makse, “Measuring the distribution of interdroplet forces in a compressed emulsion system”, Physica A 327, 201-212 (2003).

PDF version of the Nature Article

News and Views Nature Editorial by B. Behringer


1 2 3 4
February 5th, 2017

Science: Predictions: The Pulse of the People

Volume 355 of Science (February 03, 2017) focuses on the use of scientific methods to predict population-level trends. The work […]

November 27th, 2016

Predicting election trends with Twitter: Hillary Clinton versus Donald Trump.

The recently-concluded United States Presidential election was the end to one of the most divisive and vitriolic campaign seasons in […]

August 6th, 2015

Nature: Optimal Percolation: Destruction perfected

NATURE | NEWS & VIEWS Nature 524, 38–39 (06 August 2015) In complex networks, some nodes are more important than others. […]

October 6th, 2014

Nature Physics: Brain Network of Networks: Why natural networks are more stable than man-made networks

Connecting complex networks is known to exacerbate perturbations and lead to cascading failures, but natural networks of networks like the […]

May 6th, 2014

MIT Tech Review: The Emerging Science of Superspreaders (And How to Tell If You’re One Of Them)

From MIT Technology Review. Nobody has figured out how to spot the most influential spreaders of information in a real-world […]

February 6th, 2014

Scientific Reports: Large cities are less green but help to reduce suicidal rates

Work done in collaboration with Jose S. Andrade from Universidade Federal de Ceara, Brazil. Large cities are more productive than […]

February 6th, 2014

Soft Matter: Fundamental challenges in packing problems: from spherical to non-spherical particles

by Adrian Baule and Hernan Makse. Random packings of objects of a particular shape are ubiquitous in science and engineering. […]

July 6th, 2013

Nature Communications: Mean-field theory of random close packings of axisymmetric particles

by Adrian Baule, Romain Mari, Lin Bo, Louis Portal, Hernan A. Makse. Finding the densest random packing of particles with […]

March 21st, 2013

PLoS ONE: Novel insights into the evolution of protein networks

March 21, 2013. Paper in PLOS ONE. System-wide networks of proteins are indispensable for organisms. Function and evolution of these […]

November 7th, 2012

Hernan Makse is elected a Fellow of the American Physical Society

Dr. Hernan Makse’s APS citation reads: “For his contributions to a broad range of topics in non-equilibrium systems ranging from […]