9,670 research outputs found
Local entropic effects of polymers grafted to soft interfaces
In this paper, we study the equilibrium properties of polymer chains
end-tethered to a fluid membrane. The loss of conformational entropy of the
polymer results in an inhomogeneous pressure field that we calculate for
gaussian chains. We estimate the effects of excluded volume through a relation
between pressure and concentration. Under the polymer pressure, a soft surface
will deform. We calculate the deformation profile for a fluid membrane and show
that close to the grafting point, this profile assumes a cone-like shape,
independently of the boundary conditions. Interactions between different
polymers are also mediated by the membrane deformation. This pair-additive
potential is attractive for chains grafted on the same side of the membrane and
repulsive otherwise.Comment: 10 pages, 9 figure
Hawking radiation for non asymptotically flat dilatonic black holes using gravitational anomaly
The -dimensional scalar field action may be reduced, in the background
geometry of a black hole, to a 2-dimensional effective action. In the near
horizon region, it appears a gravitational anomaly: the energy-momentum tensor
of the scalar field is not conserved anymore. This anomaly is removed by
introducing a term related to the Hawking temperature of the black hole. Even
if the temperature term introduced is not covariant, a gauge transformation may
restore the covariance. We apply this method to compute the temperature of the
black hole of the dilatonic non asymptotically flat black holes. We compare the
results with those obtained through other methods.Comment: Latex file, 22 pages. Some discussions enlarged. New references.
Accepted for publication in the European Physical Journal
Scattering from Solutions of Star Polymers
We calculate the scattering intensity of dilute and semi-dilute solutions of
star polymers. The star conformation is described by a model introduced by
Daoud and Cotton. In this model, a single star is regarded as a spherical
region of a semi-dilute polymer solution with a local, position dependent
screening length. For high enough concentrations, the outer sections of the
arms overlap and build a semi-dilute solution (a sea of blobs) where the inner
parts of the actual stars are embedded. The scattering function is evaluated
following a method introduced by Auvray and de Gennes. In the dilute regime
there are three regions in the scattering function: the Guinier region (low
wave vectors, q R << 1) from where the radius of the star can be extracted; the
intermediate region (1 << q R << f^(2/5)) that carries the signature of the
form factor of a star with f arms: I(q) ~ q^(-10/3); and a high wavevector zone
(q R >> f^(2/5)) where the local swollen structure of the polymers gives rise
to the usual q^(-5/3) decay. In the semi-dilute regime the different stars
interact strongly, and the scattered intensity acquires two new features: a
liquid peak that develops at a reciprocal position corresponding to the
star-star distances; and a new large wavevector contribution of the form
q^(-5/3) originating from the sea of blobs.Comment: REVTeX, 12 pages, 4 eps figure
Neural Relax
We present an algorithm for data preprocessing of an associative memory
inspired to an electrostatic problem that turns out to have intimate relations
with information maximization
Informações sobre a fase de viveiro de algumas espécies florestais na Amazônia brasileira.
bitstream/item/31917/1/CPATU-BP49.pd
Germinação de sementes de jutaí-açu (Hymenaea courbaril L.) e de jutaí-mirim (H. parvifolia Huber) escarificadas com ácido sulfúrico comercial.
bitstream/item/33541/1/CPATU-CirTec19-2.pd
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