1,827 research outputs found

    Contribución a la corología de las macroalgas marinas bentónicas del litoral malagueño. I.

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    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).

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    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

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    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

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    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

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    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

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    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

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    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

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    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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