Chromatin 3D organization
Chromosomes have a complex 3D spatial organization serving vital functional purposes, where distant DNA sites colocalize to form 'compartments'. The principles governing such a self-organization remain, though, elusive. We proposed a Statistical Mechanics model where chromosomes conformations are established by their interactions, in particular, with specific DNA-binding molecular factors. We showed that such interactions produce spontaneously definite conformational classes (with their 'scaling properties') and induce switch-like architectural transformations (via 'phase transitions') associated to, e.g., loci colocalization, chromosomal looping and territories. Our scenario can reconcile within a single framework current FISH and Hi-C experimental results.
Symmetry Breaking at X-Chromosome Inactivation
In female mammal embryo, X-Chromosome Inactivation is the vital process whereby each cell inactivates one, randomly selected X to equalise X products w.r.t. males. Such a chromosome wide stochastic regulation has attracted substantial interests: it is unknown how the X's undergo random, yet opposite fates. We proposed a possible physical explanation: a Symmetry Breaking mechanism, with a related set of new 'particles' involved (see Figure) and a corresponding phase diagram. This scenario is supported by recent experiments.
Statistical Mechanics of Granular Media
Granular media are the second most dealt with material in human activities after water. As they are non-thermal systems (having zero kinetic energy), standard thermodynamics does not apply and a first principles theory for their description is still missing. We considered the idea that they could be described via a generalized Statistical Mechanics approach where time averages are replaced by suitable ensemble averages, at least in the limit of vanishing drive. We have been among the very first to test such a scenario in analytical and computer models and to derive the system phase diagram.
Rheology of Granular Media
The rheology of non-thermal systems such as granular suspensions is currently focus of intense research for both fundamental science and practical applications. We explored the nature of the system flow diagram and its flow regimes and found they are separated by sharp, yet stochastic transitions: (a) disordered grain flow, (b) ordered grain flow and (c) grain jamming. We discovered that disordered flow has an Ostwald-de Waele-type power-law shear-stress constitutive relation, while a nearly solid plug appears in ordered flow.
Last update 20/01/2010