940 research outputs found
LDEF fiber-composite materials characterization
Degradation of a number of fiber/polymer composites located on the leading and trailing surfaces of LDEF where the atomic oxygen (AO) fluences ranged from 10(exp 22) to 10(exp 4) atoms/cm(sup 2), respectively, was observed and compared. While matrices of the composites on the leading edge generally exhibited considerable degradation and erosion-induced fragmentation, this 'asking' process was confined to the near surface regions because these degraded structures acted as a 'protective blanket' for deeper-lying regions. This finding leads to the conclusion that simple surface coatings can significantly retard AO and other combinations of degrading phenomena in low-Earth orbit. Micrometeoroid and debris particle impacts were not a prominent feature on the fiber composites studied and apparently do not contribute in a significant way to their degradation or alteration in low-Earth orbit
On the Geometry of Surface Stress
We present a fully general derivation of the Laplace--Young formula and
discuss the interplay between the intrinsic surface geometry and the extrinsic
one ensuing from the immersion of the surface in the ordinary euclidean
three-dimensional space. We prove that the (reversible) work done in a general
surface deformation can be expressed in terms of the surface stress tensor and
the variation of the intrinsic surface metric
“No calibration” type sensor in routine amperometric bio-sensing: An example of a disposable hydrogen peroxide biosensor
Momentum diffusion for coupled atom-cavity oscillators
It is shown that the momentum diffusion of free-space laser cooling has a
natural correspondence in optical cavities when the internal state of the atom
is treated as a harmonic oscillator. We derive a general expression for the
momentum diffusion which is valid for most configurations of interest: The atom
or the cavity or both can be probed by lasers, with or without the presence of
traps inducing local atomic frequency shifts. It is shown that, albeit the
(possibly strong) coupling between atom and cavity, it is sufficient for
deriving the momentum diffusion to consider that the atom couples to a mean
cavity field, which gives a first contribution, and that the cavity mode
couples to a mean atomic dipole, giving a second contribution. Both
contributions have an intuitive form and present a clear symmetry. The total
diffusion is the sum of these two contributions plus the diffusion originating
from the fluctuations of the forces due to the coupling to the vacuum modes
other than the cavity mode (the so called spontaneous emission term). Examples
are given that help to evaluate the heating rates induced by an optical cavity
for experiments operating at low atomic saturation. We also point out
intriguing situations where the atom is heated although it cannot scatter
light.Comment: More information adde
Vacuum-stimulated cooling of single atoms in three dimensions
Taming quantum dynamical processes is the key to novel applications of
quantum physics, e.g. in quantum information science. The control of
light-matter interactions at the single-atom and single-photon level can be
achieved in cavity quantum electrodynamics, in particular in the regime of
strong coupling where atom and cavity form a single entity. In the optical
domain, this requires permanent trapping and cooling of an atom in a
micro-cavity. We have now realized three-dimensional cavity cooling and
trapping for an orthogonal arrangement of cooling laser, trap laser and cavity
vacuum. This leads to average single-atom trapping times exceeding 15 seconds,
unprecedented for a strongly coupled atom under permanent observation.Comment: 4 pages, 4 figure
Processo agroindustrial: obtenção de um produto seco de caju por desidratação osmótica e secagem.
A cajucultura desempenha papel de destaque na economia nordestina, em razão de o fruto se destacar como produto de exportação, além do potencial de agregação de valor por meio do aproveitamento do pedúnculo
On the suppression of the diffusion and the quantum nature of a cavity mode. Optical bistability; forces and friction in driven cavities
A new analytical method is presented here, offering a physical view of driven
cavities where the external field cannot be neglected. We introduce a new
dimensionless complex parameter, intrinsically linked to the cooperativity
parameter of optical bistability, and analogous to the scaled Rabbi frequency
for driven systems where the field is classical. Classes of steady states are
iteratively constructed and expressions for the diffusion and friction
coefficients at lowest order also derived. They have in most cases the same
mathematical form as their free-space analog. The method offers a semiclassical
explanation for two recent experiments of one atom trapping in a high Q cavity
where the excited state is significantly saturated. Our results refute both
claims of atom trapping by a quantized cavity mode, single or not. Finally, it
is argued that the parameter newly constructed, as well as the groundwork of
this method, are at least companions of the cooperativity parameter and its
mother theory. In particular, we lay the stress on the apparently more
fundamental role of our structure parameter.Comment: 24 pages, 7 figures. Submitted to J. Phys. B: At. Mol. Opt. Phy
Evidence of Low-Temperature Superparamagnetism in Mn_{4}$ Nanoparticle Ensembles
Please refer to the abstract within the main body of the paper
Effect of concentration on the physical properties of cashew juice.
Thermal conductivity, thermal diffusivity, density and viscosity of cashew juice were measured at 30 oC for soluble solids content ranging from 5.5 to 25 oBrix. Thermal conductivity and diffusivity were determined using a linear hest source probe. Both properties were found to decrease with the increase of soluble solids content, while density and viscosity increased. Empirical models were fitted to the experimental data for each property and the accuracy of those models was checked
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