616 research outputs found
Anisotropic Random Networks of Semiflexible Polymers
Motivated by the organization of crosslinked cytoskeletal biopolymers, we
present a semimicroscopic replica field theory for the formation of anisotropic
random networks of semiflexible polymers. The networks are formed by
introducing random permanent crosslinks which fix the orientations of the
corresponding polymer segments to align with one another. Upon increasing the
crosslink density, we obtain a continuous gelation transition from a fluid
phase to a gel where a finite fraction of the system gets localized at random
positions. For sufficiently stiff polymers, this positional localization is
accompanied by a {\em continuous} isotropic-to-nematic (IN) transition occuring
at the same crosslink density. As the polymer stiffness decreases, the IN
transition becomes first order, shifts to a higher crosslink density, and is
preceeded by an orientational glass (statistically isotropic amorphous solid)
where the average polymer orientations freeze in random directions.Comment: 5 pages, 2 figures; final version with expanded discussion to appear
in PR
Graphic variation in the Mongolian text of Muqaddimat al- Adab : what word-medial final allographs imply
A two-pion exchange three-nucleon force based on a realistic -N interaction
The contribution of a -exchange three-body force to the three-nucleon binding energy is calculated in terms of a amplitude. The latter is based on a meson-theoretical model of interaction developed by the J\"ulich group. Similar to a previous study based on simple phenomenological potentials a very small effect of the resulting three-body force is found. Possible origins of the two-orders-of-magnitude descrepancy between the present result and the values obtained for the Tucson-Melbourne three-body force are investigated. Evidence is provided that this discrepancy is most likely due to strikingly different off-shell properties of the amplitudes underlying the two approaches
Powers of an infinite dimensional Brownian motion associated with the product of distributions
Linear response of a grafted semiflexible polymer to a uniform force field
We use the worm-like chain model to analytically calculate the linear
response of a grafted semiflexible polymer to a uniform force field. The result
is a function of the bending stiffness, the temperature, the total contour
length, and the orientation of the field with respect to that of the grafted
end. We also study the linear response of a worm-like chain with a periodic
alternating sequence of positive and negative charges. This can be considered
as a model for a polyampholyte with intrinsic bending siffness and negligible
intramolecular interactions. We show how the finite intrinsic persistence
length affects the linear response to the external field.Comment: 6 pages, 3 figure
Stationary distributions of the Bernoulli type Galton-Watson branching process with immigration
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