43,571 research outputs found
Stretching of proteins in a uniform flow
Stretching of a protein by a fluid flow is compared to that in a force-clamp
apparatus. The comparison is made within a simple topology-based dynamical
model of a protein in which the effects of the flow are implemented using
Langevin dynamics. We demonstrate that unfolding induced by a uniform flow
shows a richer behavior than that in the force clamp. The dynamics of unfolding
is found to depend strongly on the selection of the amino acid, usually one of
the termini, which is anchored. These features offer potentially wider
diagnostic tools to investigate structure of proteins compared to experiments
based on the atomic force microscopy.Comment: J. Chem. Phys. (in press
A metapopulation model with Markovian landscape dynamics
We study a variant of Hanski's incidence function model that allows habitat
patch characteristics to vary over time following a Markov process. The widely
studied case where patches are classified as either suitable or unsuitable is
included as a special case. For large metapopulations, we determine a recursion
for the probability that a given habitat patch is occupied. This recursion
enables us to clarify the role of landscape dynamics in the survival of a
metapopulation. In particular, we show that landscape dynamics affects the
persistence and equilibrium level of the metapopulation primarily through its
effect on the distribution of a local population's life span.Comment: This manuscript version is made available under the CC-BY-NC-ND 4.0
license http://creativecommons.org/licenses/by-nc-nd/4.0
Low Temperature Susceptibility of the Noncentrosymmetric Superconductor CePt_3Si
We report ac susceptibility measurements of polycrystalline CePt_3Si down to
60 mK and in applied fields up to 9 T. In zero field, a full Meissner state
emerges at temperatures T/Tc < 0.3, where Tc=0.65 K is the onset transition
temperature. Though transport measurements show a relatively high upper
critical field Bc2 ~ 4-5 T, the low temperature susceptibility, \chi', is quite
fragile to applied field, with \chi' diminishing rapidly in fields of a few kG.
Interestingly, the field dependence of \chi' is well described by the power
law, 4\pi\chi'=(B/B_c)^{1/2}, where Bc is the field at which the onset of
resistance is observed in transport measurements.Comment: 5 figure
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