400 research outputs found
Entanglement of transverse modes in a pendular cavity
We study the phenomena that arise in the transverse structure of
electromagnetic field impinging on a linear Fabry-Perot cavity with an
oscillating end mirror. We find quantum correlations among transverse modes
which can be considered as a signature of their entanglement.Comment: 10 pages, 4 eps figures, ReVTeX file, to appear in J. Opt. B: Quantum
Semiclass. Op
Spatial entanglement of twin quantum images
We show that spatial entanglement of two twin images obtained by parametric
down-conversion is complete, i.e. concerns both amplitude and phase. This is
realised through a homodyne detection of these images which allows for
measurement of the field quadrature components. EPR correlations are shown to
exist between symmetrical pixels of the two images. The best possible
correlation is obtained by adjusting the phase of the local oscillator field
(LO) in the area of maximal amplification. The results for quadrature
components hold unchanged even in absence of any input image i.e. for pure
parametric fluorescence. In this case they are not related to intensity and
phase fluctuations.Comment: 19 pages, 2 figure
Space-time coupling in the up-conversion of broadband down-converted light
We investigate the up-conversion process of broadband light from parametric
down-conversion (PDC), focusing on the spatio-temporal spectral properties of
the sum-frequency generated (SFG) radiation. We demonstrate that the incoherent
component of the SFG spectrum is characterized by a skewed geometry in
space-time, which originates from a compensation between the group-velocity
mismatch and the spatial walk-off of the fundamental and the SFG fields. The
results are illustrated both by a theoretical modeling of the optical system
and by experimental measurements.Comment: 11 pages, 9 figures. arXiv admin note: text overlap with
arXiv:1308.236
Spatio-temporal entanglement of twin photons: an intuitive picture
We draw an intuitive picture of the spatio-temporal properties of the
entangled state of twin photons, where they are described as classical
wave-packets. This picture predicts a precise relation between their temporal
and transverse spatial separations at the crystal output. The space-time
coupling described by classical arguments turns out to determine in a precise
way the spatio-temporal structure of the quantum entanglement, analysed by
means of the biphotonic correlation and of the Schmidt dimensionality of the
entanglement.Comment: 12 pages, 3 figure
Coherence properties of high-gain twin beams generated in pump-depletion regime
Twin-beam coherence properties are analyzed both in the spatial and spectral
domains at high-gain regime including pump depletion. The increase of the size
of intensity auto- and cross-correlation areas at increasing pump power is
replaced by a decrease in the pump depletion regime. This effect is interpreted
as a progressive loss in the mode selection occurring at high-gain
amplification. The experimental determination of the number of spatio-spectral
modes from -function measurements confirms this explanation.Comment: 7 pages, 7 figure
Chaotic imaging in frequency downconversion
We analyze and realize the recovery, by means of spatial intensity
correlations, of the image obtained by a seeded frequency downconversion
process in which the seed field is chaotic and an intensity modulation is
encoded on the pump field. Although the generated field is as chaotic as the
seed field and does not carry any information about the modulation of the pump,
an image of the pump can be extracted by measuring the spatial intensity
correlations between the generated field and one Fourier component of the seed
Measurement of sub-shot-noise spatial correlations without subtraction of background
In this paper we present the first measurement of sub-shot-noise spatial
correlations without any subtraction of background, a result opening the way to
realize sub-shot-noise imaging of weak objectsComment: 4 pages, 4 figure
Strategies to Reverse Endothelial Progenitor Cell Dysfunction in Diabetes
Bone-marrow-derived cells-mediated postnatal vasculogenesis has been reported as the main responsible for the regulation of vascular homeostasis in adults. Since their discovery, endothelial progenitor cells have been depicted as mediators of postnatal vasculogenesis for their peculiar phenotype (partially staminal and partially endothelial), their ability to differentiate in endothelial cell line and to be incorporated into the vessels wall during ischemia/damage. Diabetes mellitus, a condition characterized by cardiovascular disease, nephropathy, and micro- and macroangiopathy, showed a dysfunction of endothelial progenitor cells. Herein, we review the mechanisms involved in diabetes-related dysfunction of endothelial progenitor cells, highlighting how hyperglycemia affects the different steps of endothelial progenitor cells lifetime (i.e., bone marrow mobilization, trafficking into the bloodstream, differentiation in endothelial cells, and homing in damaged tissues/organs). Finally, we review preclinical and clinical strategies that aim to revert diabetes-induced dysfunction of endothelial progenitor cells as a means of finding new strategies to prevent diabetic complications
Translating the Game: Ribosomes as Active Players
Ribosomes have been long considered as executors of the translational program. The fact that ribosomes can control the translation of specific mRNAs or entire cellular programs is often neglected. Ribosomopathies, inherited diseases with mutations in ribosomal factors, show tissue specific defects and cancer predisposition. Studies of ribosomopathies have paved the way to the concept that ribosomes may control translation of specific mRNAs. Studies in Drosophila and mice support the existence of heterogeneous ribosomes that differentially translate mRNAs to coordinate cellular programs. Recent studies have now shown that ribosomal activity is not only a critical regulator of growth but also of metabolism. For instance, glycolysis and mitochondrial function have been found to be affected by ribosomal availability. Also, ATP levels drop in models of ribosomopathies. We discuss findings highlighting the relevance of ribosome heterogeneity in physiological and pathological conditions, as well as the possibility that in rate-limiting situations, ribosomes may favor some translational programs. We discuss the effects of ribosome heterogeneity on cellular metabolism, tumorigenesis and aging. We speculate a scenario in which ribosomes are not only executors of a metabolic program but act as modulators
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