76 research outputs found
Biopolymer Elasticity
In recent years molecular elasticity has emerged as an active area of
research: there are experiments that probe mechanical properties of single
biomolecules such as DNA and Actin, with a view to understanding the role of
elasticity of these polymers in biological processes such as transcription and
protein-induced DNA bending. Single molecule elasticity has thus emerged as an
area where there is a rich cross-fertilization of ideas between biologists,
chemists and theoretical physicists. In this article we present a perspective
on this field of research
Onset of Shear Waves In A Bacterial Bath: A Novel Effect
Recent experiments on particle diffusion in bacterial baths indicate the
formation of correlated structures in the form of bacterial swirls. Here we
predict that such a structural ordering would give rise to the new effect of
propagating shear waves in a bacterial bath at length scales of the order of a
swirl, which corresponds to time scales of the order of the lifetime of a
swirl. Our prediction can be tested against future experiments in bacterial
baths.Comment: To appear in Fluctuation and Noise Letter
Jamming dynamics in grain mixtures : An extended hydrodynamic approach
We study jamming in granular mixtures from the novel point of view of
extended hydrodynamics. Using a hard sphere binary mixture model we predict
that a few large grains are expected to get caged more effectively in a matrix
of small grains compared to a few small grains in a matrix of larger ones. A
similar effect has been experimentally seen in the context of colloidal
mixtures.Comment: To appear in ``Fluctuation and Noise Letters'
The Writhe Distribution Of Stretched Polymers
Motivated by experiments in which single DNA molecules are stretched and
twisted we consider a perturbative approach around very high forces, where we
determine the writhe distribution in a simple, analytically tractable model.
Our results are in agreement with recent simulations and experiments.Comment: updated addres
Inequivalence of Statistical Ensembles in Single Molecule Measurements
We study the role of fluctuations in single molecule experimental
measurements of force-extension curves. We use the Worm Like Chain (WLC) model
to bring out the connection between the Helmholtz ensemble characterized by the
Free Energy and the Gibbs ensemble characterized by the Free Energy . We
consider the rigid rod limit of the WLC model as an instructive special case to
bring out the issue of ensemble inequivalence. We point out the need for taking
into account the free energy of transition when one goes from one ensemble to
another. We also comment on the ``phase transition'' noticed in an isometric
setup for semiflexible polymers and propose a realization of its thermodynamic
limit. We present general arguments which rule out non-monotonic
force-extension curves in some ensembles and note that these do not apply to
the isometric ensemble.Comment: to appear in Physical Review
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