571 research outputs found
Arrested States of Solids
Solids produced as a result of a fast quench across a freezing or a
structural transition get stuck in long-lived metastable configurations of
distinct morphology, sensitively dependent on the processing history. {\it
Martensites} are particularly well studied examples of nonequilibrium
solid-solid transformations. Since there are some excellent reviews on the
subject, we shall, in this brief article, mainly present a summary of our work
on the nonequilibrium statistical mechanics of Martensites.Comment: 4 figs (3 embedded eps and 1 'slide.gif' separate), review written
for Current Scienc
Bilayer registry in a multicomponent asymmetric membrane : dependence on lipid composition and chain length
A question of considerable interest to cell membrane biology is whether phase
segregated domains across an asymmetric bilayer are strongly correlated with
each other and whether phase segregation in one leaflet can induce segregation
in the other. We answer both these questions in the affirmative, using an
atomistic molecular dynamics simulation to study the equilibrium statistical
properties of a 3-component {\em asymmetric} lipid bilayer comprising an
unsaturated POPC (palmitoyl-oleoyl-phosphatidyl-choline), a saturated SM
(sphingomyelin) and cholesterol with different composition ratios. Our
simulations are done by fixing the composition of the upper leaflet to be at
the coexistence of the liquid ordered () - liquid disordered ()
phases, while the composition of the lower leaflet is varied from the phase
coexistence regime to the mixed phase, across a first-order phase
boundary. In the regime of phase coexistence in each leaflet, we find strong
transbilayer correlations of the domains across the two leaflets,
resulting in {\it bilayer registry}. This transbilayer correlation depends
sensitively upon the chain length of the participating lipids and possibly
other features of lipid chemistry, such as degree of saturation. We find that
the domains in the upper leaflet can {\em induce} phase segregation in
the lower leaflet, when the latter is nominally in the mixed () phase.Comment: 6 figure
- …