5,595 research outputs found
Invisibility and PT Symmetry: A Simple Geometrical Viewpoint
We give a simplified account of the properties of the transfer matrix for a
complex one-dimensional potential, paying special attention to the particular
instance of unidirectional invisibility. In appropriate variables, invisible
potentials appear as performing null rotations, which lead to the
helicity-gauge symmetry of massless particles. In hyperbolic geometry, this can
be interpreted, via M\"{o}bius transformations, as parallel displacements, a
geometric action that has no Euclidean analogy.Comment: 13 pages. No figure. Accepted for publication in Symmetr
The many facets of the Fabry-Perot
We address the response, both in amplitude and intensity, of a Fabry-Perot
from a variety of viewpoints. These complementary pictures conspire to achieve
a comprehensive and consistent theory of the operation of this system.Comment: 15 pages, 9 figure
Tourism's Impact on Long-Run Mexican Economic Growth
Tourism is one of the most important factors in the productivity of Mexican economy with significant multiplier effects on economic activity. This paper investigates possible causal relationships among tourism expenditure, real exchange rate and economic growth by using quarterly data. Johansen cointegration analysis shows the existence of one cointegrated vector among real GDP, tourism expenditure and real exchange rate where the corresponding elasticities are positive. The tourism-led growth hypothesis is confirmed through cointegration and causality testing. Tourism expenditure and Real Exchange Rate (RER) are weakly exogenous to real GDP. A modified version of the Granger Causality test shows that causality goes unidirectionally from tourism expenditure and RER to real GDP. Impulse response analysis shows that a shock in tourism expenditure produces a short fall and then a positive effect on growth.economic growth Johansen cointegration test Granger causality tourism-led growth hypothesis.
Size-Controlled Water-Soluble Ag Nanoparticles
Ag nanoparticles of two different sizes (1 and 4 nm) were prepared within an apoferritin cavity by using an Ag+-loaded apoferritin as a nanoconfined environment for their construction. The initial amount of Ag' ions injected in the apoferritin cavity dictates the size of the final Ag particles. The protein shell prevents bulk aggregation of the metal particles, which renders them water soluble and extremely stable
El sistema ejecutivo y las lesiones frontales en el niño
Frontal lobe syndrome in adulthood is characterised
by executive function deficits leading to altered behavioural control with
difficulties in social interactions and in maintaining stable jobs and
interpersonal relationships. Generalisation of this concept to children with
early frontal lobe damage is not straightforward. There are complex interactions
between the effects of the lesion itself and the effects in other interconnected
regions, timing of lesion, how long it was since the lesion occurred to the time
of evaluation, and how old the child is at examination. These facts lead to
consider that there might be a number of 'frontal syndromes' in childhood rather
than a unique one. We report 9 cases of children with early frontal lobe lesions
who were followed up for an average of 10 years. CONCLUSION: A variety of
different outcomes suggests that prognosis for these patients might be better
that previously reported
Effects of lactisole on pancreatic islet B-cells electrophysiology
Sucralose mimics the effects of glucose upon several variables of pancreatic islet B-cell metabolism and function, including bioelectrical activity. The present study aimed at investigating whether lactisole, which was recently found to act as an antagonist of the sweet taste receptor TIR3 in pancreatic islet B-cells, also opposes the effects of glucose and/or sucralose upon B-cell electrophysiology. A dual effect of lactisole, both inhibitory and stimulatory, was observed upon the electrical activity of mouse pancreatic islet B-cells. The present findings thus document that agents supposed to act specifically on the TIR3 sweet receptor may either mimic or oppose the effect of glucose upon islet B-cell electrical activity
Brewster quasi bound states in the continuum in all-dielectric metasurfaces from single magnetic-dipole resonance meta-atoms
Bound states in the continuum (BICs) are ubiquitous in many areas of physics,
attracting especial interest for their ability to confine waves with infinite
lifetimes. Metasurfaces provide a suitable platform to realize them in
photonics; such BICs are remarkably robust, being however complex to tune in
frequency-wavevector space.Here we propose a scheme to engineer BICs and
quasi-BICs with single magnetic-dipole resonance meta-atoms. Upon changing the
orientation of the magnetic-dipole resonances, we show that the resulting
quasi-BICs,emerging from the symmetry-protected BIC at normal incidence, become
transparent for plane-wave illumination exactly at the magnetic-dipole angle,
due to a Brewster-like effect. While yielding infinite Q-factors at
normalincidence(canonical BIC), these are termed Brewster quasi-BICs since a
transmission channel is always allowed that slightly widens resonances at
oblique incidences. This is demonstrated experimentally through reflectance
measurements in the microwave regime with high-refractive-index mm-disk
metasurfaces. Such Brewster-inspired configuration is a plausible scenario to
achieve quasi-BICs throughout the electromagnetic spectrum inaccessible through
plane-wave illumination at given angles, which could be extrapolated to other
kind of waves.Comment: 15 pages, 7 figures; typos corrected, Figs. 3 & 5 modified, new Fig.
7 & references adde
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