1,470 research outputs found
Coupled dynamics of sequence selection and compactification in mean-field hetero-polymers
We study a simple solvable model describing the genesis of monomer sequences
for hetero-polymers (such as proteins), as the result of the equilibration of a
slow stochastic genetic selection process which is assumed to be driven by the
competing demands of functionality and reproducibility of the polymer's folded
structure. Since reproducibility is defined in terms of properties of the
folding process, one is led to the analysis of the coupled dynamics of (fast)
polymer folding and (slow) genetic sequence selection. For the present
mean-field model this analysis can be carried out using the finite-dimensional
replica method, leading to exact results for (first- and second-order)
transitions and to rich phase diagrams.Comment: 21 pages, 7 figure
Correlations and fluctuations of a confined electron gas
The grand potential and the response of a phase-coherent confined noninteracting electron gas depend
sensitively on chemical potential or external parameter . We compute
their autocorrelation as a function of , and temperature. The result
is related to the short-time dynamics of the corresponding classical system,
implying in general the absence of a universal regime. Chaotic, diffusive and
integrable motions are investigated, and illustrated numerically. The
autocorrelation of the persistent current of a disordered mesoscopic ring is
also computed.Comment: 12 pages, 1 figure, to appear in Phys. Rev.
Solvable Lattice Gas Models of Random Heteropolymers at Finite Density: II. Dynamics and Transitions to Compact States
In this paper we analyse both the dynamics and the high density physics of
the infinite dimensional lattice gas model for random heteropolymers recently
introduced in \cite{jort}. Restricting ourselves to site-disordered
heteropolymers, we derive exact closed deterministic evolution equations for a
suitable set of dynamic order parameters (in the thermodynamic limit), and use
these to study the dynamics of the system for different choices of the monomer
polarity parameters. We also study the equilibrium properties of the system in
the high density limit, which leads to a phase diagram exhibiting transitions
between swollen states, compact states, and regions with partial
compactification. Our results find excellent verification in numerical
simulations, and have a natural and appealing interpretation in terms of real
heteropolymers.Comment: 12 pages, 8 eps figures, revised version (to be published in EPJ
Tunneling conduction in graphene/(poly)vinyl alcohol composites
Graphene/(Poly)vinyl alcohol (PVA) composite film with thickness
were synthesized by solidification of a PVA solution comprising of dispersed
graphene nanosheets. The close proximity of the graphene sheets enables the
fluctuation induced tunneling of electrons to occur from one sheet to another.
The dielectric data show that the present system can be simulated to a parallel
resistance-capacitor network. The high frequency exponent of the frequency
variation of the ac conductivity indicates that the charge carriers move in a
two-dimensional space. The sample preparation technique will be helpful for
synthesizing flexible conductors.Comment: 10 pages, 8 figure
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