161 research outputs found
Construction of exact solutions by spatial traslations in inhomogeneous Nonlinear Schrodinger equations. Applications to Bose-Einstein condensation
In this paper we study a general nonlinear Schr\"odinger equation with a time
dependent harmonic potential. Despite the lack of traslational invariance we
find a symmetry trasformation which, up from any solution, produces infinitely
many others which are centered on classical trajectories. The results presented
here imply that, not only the center of mass of the wave-packet satisfies the
Ehrenfest theorem and is decoupled from the dynamics of the wave-packet, but
also the shape of the solution is independent of the behaviour of the center of
the wave. Our findings have implications on the dynamics of Bose-Einstein
condensates in magnetic trapsComment: Submitted to Phys. Re
Split vortices in optically coupled Bose-Einstein condensates
We study a rotating two-component Bose-Einstein condensate in which an
optically induced Josephson coupling allows for population transfer between the
two species. In a regime where separation of species is favored, the ground
state of the rotating system displays domain walls with velocity fields normal
to them. Such a configuration looks like a vortex split into two halves, with
atoms circulating around the vortex and changing their internal state in a
continuous way.Comment: 4 EPS pictures, 4 pages; Some errata have been corrected and thep
resentation has been slightly revise
Anomalous rotational properties of Bose-Einstein condensates in asymmetric traps
We study the rotational properties of a Bose-Einstein condensate confined in
a rotating harmonic trap for different trap anisotropies. Using simple
arguments, we derive expressions for the velocity field of the quantum fluid
for condensates with or without vortices. While the condensed gas describes
open spiraling trajectories, on the frame of reference of the rotating trap the
motion of the fluid is against the trap rotation. We also find explicit
formulae for the angular momentum and a linear and Thomas-Fermi solutions for
the state without vortices. In these two limits we also find an analytic
relation between the shape of the cloud and the rotation speed. The predictions
are supported by numerical simulations of the mean field Gross-Pitaevskii
model.Comment: 4 RevTeX pages, 2 EPS figures; typos fixed, reference adde
First recorded case of leucism in the velvet belly lantern shark Etmopterus spinax (Squaliformes: Etmopteridae)
Poster presentado en el SIBIC 2022 IX Iberian Congress of IchthyologyThe capture of a female specimen of the velvet belly lantern shark Etmopterus spinax with abnormal skin coloration is reported. The specimen was captured off northern Spain (Bay of Biscay, North-Eastern Atlantic) in 2021 by bottom trawling. The lack of dermal melanophores combined with a normal retinal pigmentation, lead us to considérate the specimen as leucistic. This is the first case of leucism in E. spinax and the second record of colour aberration in the family Etmopteridae
El fomento de la agricultura ecológica por el programa agroambiental español (2078/92/CEE): perspectivas y realidades
Scattering of dipole-mode vector solitons: Theory and experiment
We study, both theoretically and experimentally, the scattering properties of
optical dipole-mode vector solitons - radially asymmetric composite
self-trapped optical beams. First, we analyze the soliton collisions in an
isotropic two-component model with a saturable nonlinearity and demonstrate
that in many cases the scattering dynamics of the dipole-mode solitons allows
us to classify them as ``molecules of light'' - extremely robust spatially
localized objects which survive a wide range of interactions and display many
properties of composite states with a rotational degree of freedom. Next, we
study the composite solitons in an anisotropic nonlinear model that describes
photorefractive nonlinearities, and also present a number of experimental
verifications of our analysis.Comment: 8 pages + 4 pages of figure
VariaciĂłn temporal de las concentraciones de PCBs en tejido de mejillĂłn de dos zonas de la BahĂa de Santander (España)
Se presenta la variaciĂłn temporal de bifenilos policlorados (PCBs) en mejillĂłn silvestre Mytilus galloprovincialis de dos
zonas de la BahĂa de Santander (norte de España) de 1991 a 2003, asĂ como la posible influencia en sus concentraciones de los
diferentes aportes externos a que están sometidas ambas zonas. Las concentraciones de SCB7 (suma de los CBs Nos. IUPAC:
28, 52, 101, 118, 138, 153 y 180) de la zona de Pantalán, oscilan entre los 21 μg kg–1 en peso húmedo (ph) y los 38 μg kg–1 ph
Mientras que en la zona de Pedreña, con menor influencia antropogĂ©nica, varĂan entre un mĂnimo de 8 ÎĽg kg–1 ph y un máximo
de 15 μg kg–1 ph Para conocer la evolución temporal, se usa el coeficiente de correlación Tau-b de Kendall y se comprueba la
existencia de una tendencia decreciente significativa en los niveles de PCBs en ambas zonas.An analysis was made of the temporal variation of polychlorinated biphenyls (PCBs) in wild mussel, Mytilus
galloprovincialis, from two areas of Santander Bay (northern Spain) during 1991–2003, as well as of the posible influence of
different external contributions on their concentrations. The concentrations of the sum of seven PCBs (IUPAC numbers 28, 52,
101, 118, 138, 153 and 180) from the Pantalán area ranged from 21 to 38 μg kg–1 wet weight, whereas those from the Pedreña
area, subject to less anthropogenic influence, ranged from 8 to 15 μg kg–1 wet weight. To determine the temporal evolution, the
Kendall Tau-b correlation coefficient was used and a decreasing trend in PCB levels was verified for both areas.Publicado
Globally-Linked Vortex Clusters in Trapped Wave Fields
We put forward the existence of a rich variety of fully stationary vortex
structures, termed H-clusters, made of an increasing number of vortices nested
in paraxial wave fields confined by trapping potentials. However, we show that
the constituent vortices are globally linked, rather than products of
independent vortices. Also, they always feature a monopolar global wave front
and exist in nonlinear systems, such as Bose-Einstein condensates. Clusters
with multipolar global wave fronts are non-stationary or at best flipping.Comment: 4 pages, 5 PostScript figure
Prevalence of electrocardiographic findings associated to sudden cardiac death: spontaneous type 1 and type 2 Brugada patterns and QT disorders in spanish population older than forty years
Abstrac
Electromyography: a simple and accessible tool to assess physical performance and health during hypoxia training. A systematic review
Hypoxia causes reduced partial pressure of oxygen in arterial blood and induces
adaptations in skeletal muscle that may affect individuals’ physical performance and muscular
health. These muscular changes are detectable and quantifiable by electromyography (EMG),
an instrument that assesses electrical activity during active contraction at rest. EMG is a relatively
simple and accessible technique for all patients, one that can show the degree of the sensory and
motor functions because it provides information about the status of the peripheral nerves and muscles.
The main goal of this review is to evaluate the scientific evidence of EMG as an instrument for
monitoring different responses of skeletal muscles subjected to external stimuli such as hypoxia and
physical activity. A structured search was conducted following the Preferred Reporting Items for
Systematic Review and Meta-Analyses (PRISMA) guidelines in Medline/PubMed, Scielo, Google
Scholar, Web of Science, and Cochrane Library Plus. The search included articles published in the last
25 years until May 2020 and was restricted to English- and Spanish-language publications. As such,
investigators identified nine articles that met the search criteria. The results determined that EMG
was able to detect muscle fatigue from changes in the frequency spectrum. When a muscle was
fatigued, high frequency components decreased and low frequency components increased. In other
studies, EMG determined muscle activation increased during exercise by recruiting motor units and
by increasing the intensity of muscle contractions. Finally, it was also possible to calculate the mean
quadriceps quadratic activity used to obtain an image of muscle activation. In conclusion, EMG offers
a suitable tool for monitoring the different skeletal muscle responses and has sufficient sensitivity to
detect hypoxia-induced muscle changes produced by hypoxic stimuli. Moreover, EMG enhances an
extension of physical examination and tests motor-system integrity
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