744 research outputs found
Self collimation of ultrasound in a 3D sonic crystal
We present the experimental demonstration of self-collimation (subdiffractive
propagation) of an ultrasonic beam inside a three-dimensional sonic crystal.
The crystal is formed by two crossed steel cylinders structures in a
woodpile-like geometry disposed in water. Measurements of the 3D field
distribution show that a narrow beam which diffractively spreads in the absence
of the sonic crystal is strongly collimated in propagation inside the crystal,
demonstrating the 3D self-collimation effect.Comment: 3 figures, submitted to Applied Physics Letter
Spontaneous symmetry breaking as a resource for noncritically squeezed light
In the last years we have proposed the use of the mechanism of spontaneous
symmetry breaking with the purpose of generating perfect quadrature squeezing.
Here we review previous work dealing with spatial (translational and
rotational) symmetries, both on optical parametric oscillators and four-wave
mixing cavities, as well as present new results. We then extend the phenomenon
to the polarization state of the signal field, hence introducing spontaneous
polarization symmetry breaking. Finally we propose a Jaynes-Cummings model in
which the phenomenon can be investigated at the single-photon-pair level in a
non-dissipative case, with the purpose of understanding it from a most
fundamental point of view.Comment: Review for the proceedings of SPIE Photonics Europe. 11 pages, 5
figures
Modelo de elementos finitos de la columna lumbar
En este trabajo se describe un modelo de Elementos Finitos de la columna lumbar
humana. El objetivo buscado es la utilización del mismo como herramienta de investigación
aplicada a la cirugía ortopédica de columna lumbar. Para conseguir este objetivo se ha
elaborado un modelo no lineal y paramétrico de la columna lumbar completa, el cual puede
modificarse con facilidad tanto en su geometría como en sus características mecánicas de
modo que puedan reflejarse tanto distintas alteraciones segmentarias como diversas técnicas
de fijación. También se expone la contrastación del modelo, realizada a partir de resultados
experimentales recogidos de la literatura sobre el tema.Peer Reviewe
High-speed noise-free optical quantum memory
Quantum networks promise to revolutionise computing, simulation, and
communication. Light is the ideal information carrier for quantum networks, as
its properties are not degraded by noise in ambient conditions, and it can
support large bandwidths enabling fast operations and a large information
capacity. Quantum memories, devices that store, manipulate, and release on
demand quantum light, have been identified as critical components of photonic
quantum networks, because they facilitate scalability. However, any noise
introduced by the memory can render the device classical by destroying the
quantum character of the light. Here we introduce an intrinsically noise-free
memory protocol based on two-photon off-resonant cascaded absorption (ORCA). We
consequently demonstrate for the first time successful storage of GHz-bandwidth
heralded single photons in a warm atomic vapour with no added noise; confirmed
by the unaltered photon statistics upon recall. Our ORCA memory platform meets
the stringent noise-requirements for quantum memories whilst offering technical
simplicity and high-speed operation, and therefore is immediately applicable to
low-latency quantum networks
Theory of quantum fluctuations of optical dissipative structures and its application to the squeezing properties of bright cavity solitons
We present a method for the study of quantum fluctuations of dissipative
structures forming in nonlinear optical cavities, which we illustrate in the
case of a degenerate, type I optical parametric oscillator. The method consists
in (i) taking into account explicitly, through a collective variable
description, the drift of the dissipative structure caused by the quantum
noise, and (ii) expanding the remaining -internal- fluctuations in the
biorthonormal basis associated to the linear operator governing the evolution
of fluctuations in the linearized Langevin equations. We obtain general
expressions for the squeezing and intensity fluctuations spectra. Then we
theoretically study the squeezing properties of a special dissipative
structure, namely, the bright cavity soliton. After reviewing our previous
result that in the linear approximation there is a perfectly squeezed mode
irrespectively of the values of the system parameters, we consider squeezing at
the bifurcation points, and the squeezing detection with a plane--wave local
oscillator field, taking also into account the effect of the detector size on
the level of detectable squeezing.Comment: 10 figure
Inflammatory and oxidative stress markers associated with decreased cervical length in pregnancy
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134275/1/aji12545_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/134275/2/aji12545.pd
Comparison of melting frost layers after 2 frozen methods in pork cuts (longissimus dorsi)
AbstractThe frost formation and fusion of ice crystal on complex materials have a great importance, since they modify quality meat characteristics. Furthermore, changes take place in fiber morphology by formation of ice crystal during freezing. The aim of this work was to measure the frost formation and melting. Morphological frost difference was found, and the fusion times were different too. All the results can be useful to complement and understand the complex thermal processes with phase change at low temperatures. This study implicates thermal and mass concepts; they explain the frost formation and the melting process as an opposing phenomenon
Quantum squeezing of optical dissipative structures
We show that any optical dissipative structure supported by degenerate
optical parametric oscillators contains a special transverse mode that is free
from quantum fluctuations when measured in a balanced homodyne detection
experiment. The phenomenon is not critical as it is independent of the system
parameters and, in particular, of the existence of bifurcations. This result is
a consequence of the spatial symmetry breaking introduced by the dissipative
structure. Effects that could degrade the squeezing level are considered.Comment: 4 pages and a half, 1 fugure. Version to appear in Europhysics
Letter
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