256 research outputs found
The colored Hanbury Brown--Twiss effect
The Hanbury Brown--Twiss effect is one of the celebrated phenomenologies of
modern physics that accommodates equally well classical (interferences of
waves) and quantum (correlations between indistinguishable particles)
interpretations. The effect was discovered in the late thirties with a basic
observation of Hanbury Brown that radio-pulses from two distinct antennas
generate signals on the oscilloscope that wiggle similarly to the naked eye.
When Hanbury Brown and his mathematician colleague Twiss took the obvious step
to propose bringing the effect in the optical range, they met with considerable
opposition as single-photon interferences were deemed impossible. The Hanbury
Brown--Twiss effect is nowadays universally accepted and, being so fundamental,
embodies many subtleties of our understanding of the wave/particle dual nature
of light. Thanks to a novel experimental technique, we report here a
generalized version of the Hanbury Brown--Twiss effect to include the frequency
of the detected light, or, from the particle point of view, the energy of the
detected photons. In addition to the known tendencies of indistinguishable
photons to arrive together on the detector, we find that photons of different
colors present the opposite characteristic of avoiding each others. We
postulate that fermions can be similarly brought to exhibit positive
(boson-like) correlations by frequency filtering.Comment: 18 pages, includes supplementary material of the derivation
Examination of the Feynman-Hibbs Approach in the Study of Ne-Coronene Clusters at Low Temperatures
Feynman-Hibbs (FH) effective potentials constitute an appealing approach for
investigations of many-body systems at thermal equilibrium since they allow us
to easily include quantum corrections within standard classical simulations. In
this work we apply the FH formulation to the study of Ne-coronene clusters
( 1-4, 14) in the 2-14 K temperature range. Quadratic (FH2) and quartic
(FH4) contributions to the effective potentials are built upon Ne-Ne and
Ne-coronene analytical potentials. In particular, a new corrected expression
for the FH4 effective potential is reported. FH2 and FH4 cluster energies and
structures -obtained from energy optimization through a basin-hoping algorithm
as well as classical Monte Carlo simulations- are reported and compared with
reference path integral Monte Carlo calculations. For temperatures K,
both FH2 and FH4 potentials are able to correct the purely classical
calculations in a consistent way. However, the FH approach fails at lower
temperatures, especially the quartic correction. It is thus crucial to assess
the range of applicability of this formulation and, in particular, to apply the
FH4 potentials with great caution. A simple model of isotropic harmonic
oscillators allows us to propose a means of estimating the cut-off temperature
for the validity of the method, which is found to increase with the number of
atoms adsorbed on the coronene molecule
Transcripción revisada del informe de Pedro de Ayala de 1498 sobre las expediciones inglesas de descubrimiento
The report sent by Pedro de Ayala to the Catholic Monarchs from London in 1498 is one of the main sources on the earliest English expeditions to North America. The history of its deciphering, interpretation and translation is presented and, as none of the transcriptions carried out up to now is found to be entirely satisfactory, a new one is proposed based on a literal deciphering of the document, along with translations into French and English. Furthermore, some particularly difficult parts of the text are discussed in detail that, having been misunderstood in earlier editions of the report, led to probably erroneous conclusions about the biography of John Cabot, the itinerary of his voyage of 1497, and the name of the monk who went with him on his expedition of 1498.El informe enviado por Pedro de Ayala a los Reyes Católicos desde Londres en 1498 es una de las fuentes fundamentales sobre las primeras expediciones inglesas a Norteamérica. En este estudio se presenta la historia de su descifrado, interpretación y traducción y, constatando que ninguna de las transcripciones realizadas hasta ahora es completamente exacta, se propone una nueva basada en un descifrado literal del documento, acompañada de traducciones
al francés y al inglés. Se discuten asimismo en detalle algunas frases particularmente difíciles del texto que, debido a su malinterpretación en ediciones anteriores, condujeron a conclusiones probablemente erróneas sobre la biografía de Juan Caboto, el itinerario de su viaje de 1497 y el nombre del religioso que fue con él en su expedición de 1498
Cooperative coupling of ultracold atoms and surface plasmons
Cooperative coupling between optical emitters and light fields is one of the
outstanding goals in quantum technology. It is both fundamentally interesting
for the extraordinary radiation properties of the participating emitters and
has many potential applications in photonics. While this goal has been achieved
using high-finesse optical cavities, cavity-free approaches that are broadband
and easy to build have attracted much attention recently. Here we demonstrate
cooperative coupling of ultracold atoms with surface plasmons propagating on a
plane gold surface. While the atoms are moving towards the surface they are
excited by an external laser pulse. Excited surface plasmons are detected via
leakage radiation into the substrate of the gold layer. A maximum Purcell
factor of is reached at an optimum distance of
from the surface. The coupling leads to the observation of
a Fano-like resonance in the spectrum.Comment: 9 pages, 4 figure
Teaching biological rhythms in endocrinology: cortisol and wrist temperature. Póster
This work has been developed as part of the Endocrinology and
Metabolism student’s laboratory formation from Biology degree at the
University of Murcia. Endocrinology and Metabolism is an elective oneterm
course that is taught in the fourth year (4.5 ECTS) for "Biosanitary
and Biotechnology" intensification. The course focuses on the study of
global and intermediary human metabolism and hormonal regulation,
both under normal and special situations.
It is our objective to get undergraduate students of
Endocrinology and Metabolism with the importance of hormonal
diurnal fluctuations in endocrine systems through their involvement in
an innovative research program. In addition, with the participation of
PhD student in this program, we try to improve their skills in innovative
teaching.
In humans cortisol circadian rhythm peaks in the morning and
shows the lowest levels during the midnight. This fluctuation of cortisol
plasma level is reflected in saliva, allowing a simple, non invasive and
unstressful sample collection. The influence of different factors,
exercise, schedule and weekend shifts, on the rhythmic pattern of
cortisol has been studied along various years.Campus Mare Nostrum, Universidad Politécnica de Cartagena, Universidad de Murcia, Región de Murci
Five key attributes can increase marine protected areas performance for small-scale fisheries management
Marine protected areas (MPAs) have largely proven to be effective tools for conserving marine ecosystem, while socio-economic benefits generated by MPAs to fisheries are still under debate. Many MPAs embed a no-take zone, aiming to preserve natural populations and ecosystems, within a buffer zone where potentially sustainable activities are allowed. Small-scale fisheries (SSF) within buffer zones can be highly beneficial by promoting local socio-economies. However, guidelines to successfully manage SSFs within MPAs, ensuring both conservation and fisheries goals, and reaching a win-win scenario, are largely unavailable. From the peer-reviewed literature, grey-literature and interviews, we assembled a unique database of ecological, social and economic attributes of SSF in 25 Mediterranean MPAs. Using random forest with Boruta algorithm we identified a set of attributes determining successful SSFs management within MPAs. We show that fish stocks are healthier, fishermen incomes are higher and the social acceptance of management practices is fostered if five attributes are present (i.e. high MPA enforcement, presence of a management plan, fishermen engagement in MPA management, fishermen representative in the MPA board, and promotion of sustainable fishing). These findings are pivotal to Mediterranean coastal communities so they can achieve conservation goals while allowing for profitable exploitation of fisheries resources
Graphene plasmonics: A platform for strong light-matter interaction
Graphene plasmons provide a suitable alternative to noble-metal plasmons
because they exhibit much larger confinement and relatively long propagation
distances, with the advantage of being highly tunable via electrostatic gating.
We report strong light- matter interaction assisted by graphene plasmons, and
in particular, we predict unprecedented high decay rates of quantum emitters in
the proximity of a carbon sheet, large vacuum Rabi splitting and Purcell
factors, and extinction cross sections exceeding the geometrical area in
graphene ribbons and nanometer-sized disks. Our results provide the basis for
the emerging and potentially far-reaching field of graphene plasmonics,
offering an ideal platform for cavity quantum electrodynamics and supporting
the possibility of single-molecule, single-plasmon devices.Comment: 39 pages, 15 figure
Reduction of the ATPase inhibitory factor 1 (IF1) leads to visual impairment in vertebrates
In vertebrates, mitochondria are tightly preserved energy producing organelles, which sustain nervous system development and function. The understanding of proteins that regulate their homoeostasis in complex animals is therefore critical and doing so via means of systemic analysis pivotal to inform pathophysiological conditions associated with mitochondrial deficiency. With the goal to decipher the role of the ATPase inhibitory factor 1 (IF1) in brain development, we employed the zebrafish as elected model reporting that the Atpif1a−/− zebrafish mutant, pinotage (pnttq209), which lacks one of the two IF1 paralogous, exhibits visual impairment alongside increased apoptotic bodies and neuroinflammation in both brain and retina. This associates with increased processing of the dynamin-like GTPase optic atrophy 1 (OPA1), whose ablation is a direct cause of inherited optic atrophy. Defects in vision associated with the processing of OPA1 are specular in Atpif1−/− mice thus confirming a regulatory axis, which interlinks IF1 and OPA1 in the definition of mitochondrial fitness and specialised brain functions. This study unveils a functional relay between IF1 and OPA1 in central nervous system besides representing an example of how the zebrafish model could be harnessed to infer the activity of mitochondrial proteins during development
Subwavelength vacuum lattices and atom–atom interactions in two-dimensional photonic crystals
Quantum simulation with cold atoms in optical lattices is an attractive avenue for explorations of quantum many-body physics. A principal challenge in the field is to increase the energy and length scales in current set-ups, thereby reducing temperature and coherence-time requirements. Here, we present a new paradigm for high-density, two-dimensional optical lattices in photonic crystal waveguides. Specially engineered two-dimensional photonic crystals provide a practical platform to trap atoms and engineer their interactions in ways that surpass the limitations of current technologies and enable investigations of novel quantum many-body matter. Our schemes remove the constraint on the lattice constant set by the free-space optical wavelength in favour of deeply sub-wavelength atomic arrays. We further describe possibilities for atom–atom interactions mediated by photons in two-dimensional photonic crystal waveguides with energy scales several orders of magnitude larger than for exchange interactions in free-space lattices and with the capability to engineer strongly long-range interactions
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