1,827 research outputs found
Contribución a la corología de las macroalgas marinas bentónicas del litoral malagueño. I.
Continuando con un proyecto sobre la corología de las macroalgas marinas bentónicas del litoral malagueño (Conde, 1981; Conde, 1984; Conde & Soto, 1986) reseñamos en esta nota la presencia en la zona de 5 nuevas especies, y se confirman otras 5, citadas anteriormente en la literatura o de arribazón. La ordenación de las especies se ha realizado según la propuesta de Gallardo ét al. (1985)
Aspectos ultraestructurales de algunas coralináceas (Rhodophyta) del Mediterráneo andaluz (S. de España).
En el presente artículo se estudian e interpretan al microscopio electrónico de barrido (M.E.B.) algunos caracteres cualitativos de siete especies de algas coralináceas del litoral andaluz, pertenecientes a los géneros Corallina,Jania y Amphiroa.Using the scanning electron microscopy some qualitatives characteristics of seven seaweeds species of the mediterranean coasts of Andalucía (S. of Spain), of the genus Corallina, Junio y Amphiroa have been studied
Polariton Lasing in a Multilevel Quantum Dot Strongly Coupled To a Single Photon Mode
We present an approximate analytic expression for the photoluminescence
spectral function of a model polariton system, which describes a quantum dot,
with a finite number of fermionic levels, strongly interacting with the lowest
photon mode of a pillar microcavity. Energy eigenvalues and wavefunctions of
the electron-hole-photon system are obtained by numerically diagonalizing the
Hamiltonian. Pumping and photon losses through the cavity mirrors are described
with a master equation, which is solved in order to determine the stationary
density matrix. The photon first-order correlation function, from which the
spectral function is found, is computed with the help of the Quantum Regression
Theorem. The spectral function qualitatively describes the polariton lasing
regime in the model, corresponding to pumping rates two orders of magnitude
lower than those needed for ordinary (photon) lasing. The second-order
coherence functions for the photon and the electron-hole subsystems are
computed as functions of the pumping rate.Comment: version accepted in Phys. Rev.
A local characterisation for static charged black holes
We obtain a purely local characterisation that singles out the
Majumdar-Papapetrou class, the near-horizon Bertotti-Robinson geometry and the
Reissner-Nordstr\"om exterior solution, together with its plane and hyperbolic
counterparts, among the static electrovacuum spacetimes. These five classes are
found to form the whole set of static Einstein-Maxwell fields without sources
and conformally flat space of orbits, this is, the conformastat electrovacuum
spacetimes. The main part of the proof consists in showing that a functional
relationship between the gravitational and electromagnetic potentials must
always exist. The classification procedure provides also an improved
characterisation of Majumdar-Papapetrou, by only requiring a conformally flat
space of orbits with a vanishing Ricci scalar of the usual conveniently
rescaled 3-metric. A simple global consideration allows us to state that the
asymptotically flat subset of the Majumdar-Papapetrou class and the
Reissner-Nordstr\"om exterior solution are the only asymptotically flat
conformastat electrovacuum spacetimes.Comment: LaTeX; 31 pages. Uses iopart style file
Osteocondroma lumbar sintomático
Se presenta un caso de osteocondroma solitario espinal localizado en la zona
para-articular de la lámina izquierda de L4 y que producía una lumbociática secundaria a la
estenosis del receso lateral. El osteocondroma espinal sintomático es una lesión neoplásica benigna
poco frecuente y cuyo tratamiento de elección es la extirpación quirúrgica.A case of solitary spinal osteochondroma growing from the left L4 lamina, close
to the facet joint, is presented. The tumor produced a stenosis of the left lateral recess and
the patient suffered from low-back and sciatic pain. Symptomatic spinal osteochondroma is
a rare beningn tumor, surgical removal being the most useful treatment
Tratamiento quirúrgico en las cifosis congénitas: Revisión de 14 pacientes
Los autores efectúan una revisión de 14 pacientes con cifosis congénita,
intervenidos entre los años 1979-1989, con un seguimiento medio de 7 años. La edad
media preoperatoria fue de 11 años (todos ellos mayores de 5 años), con una cifosis media
de 7 9 . En 6 casos se realizó una artrodesis posterior y en 8 una anterior combinada
con una fusión posterior. Inicialmente obtuvieron una corrección media de la curva de
18° con la artrodesis posterior y 20° con la artrodesis combinada. La pérdida postoperatoria
final fue de 10° y 8° respectivamente. En un caso, se produjo una pseudoartrosis
por fusión corta. Como complicaciones postoperatorias en 5 pacientes, una radiculopatía,
una infección superficial y cuatro protusiones de material que requirieron su extracción.
Los autores analizan los factores que han podido influir en los resultados obtenidos,
comparándolos posteriormente con los conseguidos por otros centros hospitalarios importantes.Fourteen patients with congenital kyphosis treated surgically between 1979-
1989 were reviewed. All had a follow-up of 2 years or more, with an average follow-up of 7 years.
The average age at surgery was 11 and the average kyphosis was 79°. Six cases had
posterior fusion only and eigth had combined anterior and posterior fusion. The results showed
an average correction of the curve at surgery of 18° with posterior arthrodesis and 20°
with combined arthrodesis. There was thus an average loss of 10° and 8° respectively from
the time of surgery in both types of treatment. Pseudoarthrosis by short fusion ocurred in
one case. Other complications after surgery were 1 radiculopathy, one wound infection and
four rod protusion (six patients). The factors that have influence in this results were analysed.
A comparison from the results of treatment at other medical centers was also carried
out
High-dimensional decoy-state quantum key distribution over 0.3 km of multicore telecommunication optical fibers
Multiplexing is a strategy to augment the transmission capacity of a
communication system. It consists of combining multiple signals over the same
data channel and it has been very successful in classical communications.
However, the use of enhanced channels has only reached limited practicality in
quantum communications (QC) as it requires the complex manipulation of quantum
systems of higher dimensions. Considerable effort is being made towards QC
using high-dimensional quantum systems encoded into the transverse momentum of
single photons but, so far, no approach has been proven to be fully compatible
with the existing telecommunication infrastructure. Here, we overcome such a
technological challenge and demonstrate a stable and secure high-dimensional
decoy-state quantum key distribution session over a 0.3 km long multicore
optical fiber. The high-dimensional quantum states are defined in terms of the
multiple core modes available for the photon transmission over the fiber, and
the decoy-state analysis demonstrates that our technique enables a positive
secret key generation rate up to 25 km of fiber propagation. Finally, we show
how our results build up towards a high-dimensional quantum network composed of
free-space and fiber based linksComment: Please see the complementary work arXiv:1610.01812 (2016
Firm performance in regulated markets: the case of spanish defence industry
This paper studies the effects of legal reforms associated with defence and public procurement on firm performance. With this aim, a theoretical framework for the reaction of defence firms to regulatory changes is developed. Its predictions have been empirically assessed using the last reforms implemented in Spain. Our results suggest that these new regulations have allowed the main defence contractors to outperform the other defence contractors in terms of productivity, having no effect on profitability. These findings are in line with theoretical priors. Therefore, it can be claimed that governmental interventions have had an effect on firm performance. We also provide evidence that, while the procurement procedures and the contract law put into place in 2011 have principally affected the productivity of large firms, the centralization process established in 2014 has exerted a higher influence on SMEs
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Seasonal cycle of precipitation variability in South America on intraseasonal timescales
The seasonal cycle of the intraseasonal (IS) variability of precipitation in South America is described through the analysis of bandpass filtered outgoing longwave radiation (OLR) anomalies. The analysis is discriminated between short (10--30 days) and long (30--90 days) intraseasonal timescales. The seasonal cycle of the 30--90-day IS variability can be well described by the activity of first leading pattern (EOF1) computed separately for the wet season (October--April) and the dry season (May--September). In agreement with previous works, the EOF1 spatial distribution during the wet season is that of a dipole with centers of actions in the South Atlantic Convergence Zone (SACZ) and southeastern South America (SESA), while during the dry season, only the last center is discernible. In both seasons, the pattern is highly influenced by the activity of the Madden--Julian Oscillation (MJO). Moreover, EOF1 is related with a tropical zonal-wavenumber-1 structure superposed with coherent wave trains extended along the South Pacific during the wet season, while during the dry season the wavenumber-1 structure is not observed. The 10--30-day IS variability of OLR in South America can be well represented by the activity of the EOF1 computed through considering all seasons together, a dipole but with the stronger center located over SESA. While the convection activity at the tropical band does not seem to influence its activity, there are evidences that the atmospheric variability at subtropical-extratropical regions might have a role. Subpolar wavetrains are observed in the Pacific throughout the year and less intense during DJF, while a path of wave energy dispersion along a subtropical wavetrain also characterizes the other seasons. Further work is needed to identify the sources of the 10--30-day-IS variability in South America
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