1,221 research outputs found
Development of a rapid stress corrosion test for aluminum alloys Annual report, 1 Mar. 1966 - 1 Mar. 1967
Accelerated stress corrosion tests for aluminum alloy
Effective free energy for pinned membranes
We consider membranes adhered through specific receptor-ligand bonds. Thermal
undulations of the membrane induce effective interactions between adhesion
sites. We derive an upper bound to the free energy that is independent of
interaction details. To lowest order in a systematic expansion we obtain
two-body interactions which allow to map the free energy onto a lattice gas
with constant density. The induced interactions alone are not strong enough to
lead to a condensation of individual adhesion sites. A measure of the thermal
roughness is shown to depend on the inverse square root of the density of
adhesion sites, which is in good agreement with previous computer simulations.Comment: to appear as a Rapid Communication in Phys. Rev.
Hydrodynamic lift of vesicles under shear flow in microgravity
The dynamics of a vesicle suspension in a shear flow between parallel plates
has been investigated under microgravity conditions, where vesicles are only
submitted to hydrodynamic effects such as lift forces due to the presence of
walls and drag forces. The temporal evolution of the spatial distribution of
the vesicles has been recorded thanks to digital holographic microscopy, during
parabolic flights and under normal gravity conditions. The collected data
demonstrates that vesicles are pushed away from the walls with a lift velocity
proportional to where is the shear rate,
the vesicle radius and its distance from the wall. This scaling as well
as the dependence of the lift velocity upon vesicle aspect ratio are consistent
with theoretical predictions by Olla [J. Phys. II France {\bf 7}, 1533--1540
(1997)].Comment: 6 pages, 8 figure
Spherical Vesicles Distorted by a Grafted Latex Bead: An Exact Solution
We present an exact solution to the problem of the global shape description
of a spherical vesicle distorted by a grafted latex bead. This solution is
derived by treating the nonlinearity in bending elasticity through the
(topological) Bogomol'nyi decomposition technique and elastic compatibility. We
recover the ``hat-model'' approximation in the limit of a small latex bead and
find that the region antipodal to the grafted latex bead flattens. We also
derive the appropriate shape equation using the variational principle and
relevant constraints.Comment: 12 pages, 2 figures, LaTeX2e+REVTeX+AmSLaTe
Observation of an Efimov resonance in an ultracold mixture of atoms and weakly bound dimers
We discuss our recent observation of an atom-dimer Efimov resonance in an
ultracold mixture of Cs atoms and Cs_2 Feshbach molecules [Nature Phys. 5, 227
(2009)]. We review our experimental procedure and present additional data
involving a non-universal g-wave dimer state, to contrast our previous results
on the universal s-wave dimer. We resolve a seeming discrepancy when
quantitatively comparing our experimental findings with theoretical results
from effective field theory.Comment: Conference Proceeding ICPEAC 2009 Kalamazoo, to appear in Journal of
Physics: Conference Serie
Observation of an Efimov resonance in an ultracold mixture of atoms and weakly bound dimers
We discuss our recent observation of an atom-dimer Efimov resonance in an
ultracold mixture of Cs atoms and Cs_2 Feshbach molecules [Nature Phys. 5, 227
(2009)]. We review our experimental procedure and present additional data
involving a non-universal g-wave dimer state, to contrast our previous results
on the universal s-wave dimer. We resolve a seeming discrepancy when
quantitatively comparing our experimental findings with theoretical results
from effective field theory.Comment: Conference Proceeding ICPEAC 2009 Kalamazoo, to appear in Journal of
Physics: Conference Serie
Observation of an Efimov resonance in an ultracold mixture of atoms and weakly bound dimers
We discuss our recent observation of an atom-dimer Efimov resonance in an
ultracold mixture of Cs atoms and Cs_2 Feshbach molecules [Nature Phys. 5, 227
(2009)]. We review our experimental procedure and present additional data
involving a non-universal g-wave dimer state, to contrast our previous results
on the universal s-wave dimer. We resolve a seeming discrepancy when
quantitatively comparing our experimental findings with theoretical results
from effective field theory.Comment: Conference Proceeding ICPEAC 2009 Kalamazoo, to appear in Journal of
Physics: Conference Serie
The lamellar-to-isotropic transition in ternary amphiphilic systems
We study the dependence of the phase behavior of ternary amphiphilic systems
on composition and temperature. Our analysis is based on a curvature elastic
model of the surfactant film with sufficiently large spontaneous curvature and
sufficiently negative saddle-splay modulus that the stable phases are the
lamellar phase and a droplet microemulsion. In addition to the curvature
energy, we consider the contributions to the free energy of the long-ranged van
der Waals interaction and of the undulation modes. We find that for bending
rigidities of order k_B T, the lamellar phase extends further and further into
the water apex of the phase diagram as the phase inversion temperature is
approached, in good agreement with experimental results.Comment: LaTeX2e, 11 pages with references and 2 eps figures included,
submitted to Europhys. Let
Role of disclinations in determining the morphology of deformable fluid interfaces
We study the equilibrium shapes of vesicles, with an in-plane nematic order,
using a Monte-Carlo scheme and show that highly curved shapes, like tubes and
discs, with a striking similarity to the structures engendered by certain
curvature sensing peripheral membrane proteins, can be spontaneously generated
by anisotropic directional curvature with nematic disclinations playing and
important role. We show that the coupling between nematic order and local
curvature could lead to like defects moving towards each other and unlike
defects moving away, in turn leading to tube formation. Thermally induced
defect pair production lead to branched tubular structures. It is also shown
that helical arrangement of the membrane tubes, with nematic field spiraling
around it, is a dominant soft mode of the system.Comment: 6 Figures; Soft Matter, Advance Article 201
The gas of elastic quantum strings in 2+1 dimensions: finite temperatures
The finite temperature physics of the gas of elastic quantum strings as
introduced in J. Zaanen, Phys. Rev. Lett. 84, 753 is investigated. This model
is inspired on the stripes in the high Tc superconductors. We analyze in detail
how the kinetic interactions of the zero temperature quantum problem crossover
into the entropic interactions of the high temperature limit.Comment: 14 pages, 2 figure
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