3,170 research outputs found
151 SMALL HEAT-SHOCK PROTEINS, NOVEL IDENTIFIED MEDIATORS OF MATRIX GENE EXPRESSION, ARE DIFFERENTIALLY EXPRESSED IN OA CHONDROCYTES
Microstructure mapping: a new method for imaging deformation-induced microstructural features of ice on the grain scale
Casimir torque between corrugated metallic plates
We consider two parallel corrugated plates and show that a Casimir torque
arises when the corrugation directions are not aligned. We follow the
scattering approach and calculate the Casimir energy up to second order in the
corrugation amplitudes, taking into account nonspecular reflections,
polarization mixing and the finite conductivity of the metals. We compare our
results with the proximity force approximation, which overestimates the torque
by a factor 2 when taking the conditions that optimize the effect. We argue
that the Casimir torque could be measured for separation distances as large as
1 Comment: 7 pages, 3 figures, contribution to QFEXT07 proceeding
Transverse-mode coupling in a Kerr medium
We analyze nonlinear transverse mode coupling in a Kerr medium placed in an
optical cavity and its influence on bistability and different kinds of quantum
noise reduction. Even for an input beam that is perfectly matched to a cavity
mode, the nonlinear coupling produces an excess noise in the fluctuations of
the output beam. Intensity squeezing seems to be particularly robust with
respect to mode coupling, while quadrature squeezing is more sensitive.
However, it is possible to find a mode the quadrature squeezing of which is not
affected by the coupling.Comment: 11 pages, 6 figures, LaTe
Casimir energy and geometry : beyond the Proximity Force Approximation
We review the relation between Casimir effect and geometry, emphasizing
deviations from the commonly used Proximity Force Approximation (PFA). We use
to this aim the scattering formalism which is nowadays the best tool available
for accurate and reliable theory-experiment comparisons. We first recall the
main lines of this formalism when the mirrors can be considered to obey
specular reflection. We then discuss the more general case where non planar
mirrors give rise to non-specular reflection with wavevectors and field
polarisations mixed. The general formalism has already been fruitfully used for
evaluating the effect of roughness on the Casimir force as well as the lateral
Casimir force or Casimir torque appearing between corrugated surfaces. In this
short review, we focus our attention on the case of the lateral force which
should make possible in the future an experimental demonstration of the
nontrivial (i.e. beyond PFA) interplay of geometry and Casimir effect.Comment: corrected typos, added references, QFEXT'07 special issue in J. Phys.
Lateral Casimir-Polder force with corrugated surfaces
We derive the lateral Casimir-Polder force on a ground state atom on top of a
corrugated surface, up to first order in the corrugation amplitude. Our
calculation is based on the scattering approach, which takes into account
nonspecular reflections and polarization mixing for electromagnetic quantum
fluctuations impinging on real materials. We compare our first order exact
result with two commonly used approximation methods. We show that the proximity
force approximation (large corrugation wavelengths) overestimates the lateral
force, while the pairwise summation approach underestimates it due to the
non-additivity of dispersion forces. We argue that a frequency shift
measurement for the dipolar lateral oscillations of cold atoms could provide a
striking demonstration of nontrivial geometrical effects on the quantum vacuum.Comment: 12 pages, 6 figures, contribution to QFEXT07 proceeding
A spectroscopy approach to measure the gravitational mass of antihydrogen
We study a method to induce resonant transitions between antihydrogen
() quantum states above a material surface in the gravitational field
of the Earth. The method consists of applying a gradient of magnetic field,
which is temporally oscillating with the frequency equal to a frequency of
transition between gravitational states of antihydrogen. A corresponding
resonant change in the spatial density of antihydrogen atoms could be measured
as a function of the frequency of applied field. We estimate an accuracy of
measuring antihydrogen gravitational states spacing and show how a value of the
gravitational mass of the atom could be deduced from such a
measurement. We also demonstrate that a method of induced transitions could be
combined with a free-fall-time measurement in order to further improve the
precision
Thermal and dissipative effects in Casimir physics
We report on current efforts to detect the thermal and dissipative
contributions to the Casimir force. For the thermal component, two experiments
are in progress at Dartmouth and at the Institute Laue Langevin in Grenoble.
The first experiment will seek to detect the Casimir force at the largest
explorable distance using a cylinder-plane geometry which offers various
advantages with respect to both sphere-plane and parallel-plane geometries. In
the second experiment, the Casimir force in the parallel-plane configuration is
measured with a dedicated torsional balance, up to 10 micrometers. Parallelism
of large surfaces, critical in this configuration, is maintained through the
use of inclinometer technology already implemented at Grenoble for the study of
gravitationally bound states of ultracold neutrons, For the dissipative
component of the Casimir force, we discuss detection techniques based upon the
use of hyperfine spectroscopy of ultracold atoms and Rydberg atoms. Although
quite challenging, this triad of experimental efforts, if successful, will give
us a better knowledge of the interplay between quantum and thermal fluctuations
of the electromagnetic field and of the nature of dissipation induced by the
motion of objects in a quantum vacuum.Comment: Contribution to QFEXT'06, appeared in special issue of Journal of
Physics
Quantum Radiation of a Uniformly Accelerated Refractive Body
We study quantum radiation generated by an accelerated motion of a small body
with a refractive index n which differes slightly from 1. To simplify
calculations we consider a model with a scalar massless field. We use the
perturbation expansion in a small parameter n-1 to obtain a correction to the
vacuum Hadamard function for a uniformly accelerated motion of the body. We
obtain the vacuum expectation for the energy density flux in the wave zone and
discuss its properties.Comment: 16 pages, 1 figur
Repulsive Casimir Force: Sufficient Conditions
In this paper the Casimir energy of two parallel plates made by materials of
different penetration depth and no medium in between is derived. We study the
Casimir force density and derive analytical constraints on the two penetration
depths which are sufficient conditions to ensure repulsion. Compared to other
methods our approach needs no specific model for dielectric or magnetic
material properties and constitutes a complementary analysis.Comment: 11 pages. 3 figures. Misprints corrected in Eq. (4
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