1,105 research outputs found
How does torsional rigidity affect the wrapping transition of a semiflexible chain around a spherical core?
We investigated the effect of torsional rigidity of a semiflexible chain on
the wrapping transition around a spherical core, as a model of nucleosome, the
fundamental unit of chromatin. Through molecular dynamics simulation, we show
that the torsional effect has a crucial effect on the chain wrapping around the
core under the topological constraints. In particular, the torsional stress (i)
induces the wrapping/unwrapping transition, and (ii) leads to a unique complex
structure with an antagonistic wrapping direction which never appears without
the topological constraints. We further examine the effect of the stretching
stress for the nucleosome model, in relation to the unique characteristic
effect of the torsional stress on the manner of wrapping
Ring polymers in melts and solutions: scaling and crossover
We propose a simple mean-field theory for the structure of ring polymer
melts. By combining the notion of topological volume fraction and a classical
van der Waals theory of fluids, we take into account many body effects of
topological origin in dense systems. We predict that although the compact
statistics with the Flory exponent is realized for very long chains,
most practical cases fall into the crossover regime with the apparent exponent
during which the system evolves toward a topological dense-packed
limit.Comment: 4 pages, 3 figure
Length-dependent translocation of polymers through nanochannels
We consider the flow-driven translocation of single polymer chains through
nanochannels. Using analytical calculations based on the de Gennes blob model
and mesoscopic numerical simulations, we estimate the threshold flux for the
translocation of chains of different number of monomers. The translocation of
the chains is controlled by the competition between entropic and hydrodynamic
effects, which set a critical penetration length for the chain before it can
translocate through the channel. We demonstrate that the polymers show two
different translocation regimes depending on how their length under confinement
compares to the critical penetration length. For polymer chains longer than the
threshold, the translocation process is insensitive to the number of monomers
in the chain as predicted in Sakaue {\it et al.}, {\it Euro. Phys. Lett.}, {\bf
72} 83 (2005). However, for chains shorter than the critical length we show
that the translocation process is strongly dependent on the length of the
chain. We discuss the possible relevance of our results to biological
transport.Comment: To appear in Soft Matter. 10 pages 9 Figure
Maxwell stress in fluid mixtures
We examine the structure of Maxwell stress in binary fluid mixtures under an
external electric field and discuss its consequence. In particular, we show
that, in immiscible blends, it is intimately related to the statistics of
domain structure. This leads to a compact formula, which may be useful in the
investigation of electro-rheological effects in such systems. The stress tensor
calculated in a phase separated fluid under a steady electric field is in a
good agreement with recent experiments.Comment: 5 page
Feedback-free optical cavity with self-resonating mechanism
We demonstrated the operation of a high finesse optical cavity without
utilizing an active feedback system to stabilize the resonance. The effective
finesse, which is a finesse including the overall system performance, of the
cavity was measured to be , and the laser power stored in
the cavity was kW, which is approximately 187,000 times greater
than the incident power to the cavity. The stored power was stabilized with a
fluctuation of , and we confirmed continuous cavity operation for more
than two hours. This result has the potential to trigger an innovative
evolution for applications that use optical resonant cavities such as compact
photon sources with laser-Compton scattering or cavity enhanced absorption
spectroscopy.Comment: 5 pages, 7 figure
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