609 research outputs found
Uniform polarization scattering with fiber-coil-based polarization controllers
A detailed study of fiber-coil-based polarization controllers (PCs) is performed. First, a method to deterministically calculate the PC configuration in order to transform between any two states of polarization is presented. In a second stage, the case in which the configuration angles are randomly changed is studied. The cases of a single PC and of the system obtained with the concatenation of several PCs are analyzed. For both cases, a general expression for the variance of the Stokes parameters is obtained. Using this expression, it is demonstrated that it is possible to achieve uniform polarization scattering using a concatenation of fiber-coil-based PCs. Finally, it is shown that fiber-coil-based PC's can be used to emulate both, first- and second-order polarization- mode dispersions
Energy of general 4-dimensional stationary axisymmetric spacetime in the teleparallel geometry
The field equation with the cosmological constant term is derived and the
energy of the general 4-dimensional stationary axisymmetric spacetime is
studied in the context of the hamiltonian formulation of the teleparallel
equivalent of general relativity (TEGR). We find that, by means of the integral
form of the constraints equations of the formalism naturally without any
restriction on the metric parameters, the energy for the asymptotically flat/de
Sitter/Anti-de Sitter stationary spacetimes in the Boyer-Lindquist coordinate
can be expressed as . It is surprised to learn that the
energy expression is relevant to the metric components ,
and only. As examples, by using this formula
we calculate the energies of the Kerr-Newman (KN), Kerr-Newman Anti-de Sitter
(KN-AdS), Kaluza-Klein, and Cveti\v{c}-Youm spacetimes.Comment: 12 page
Bio-economic multi‐stock reference points as a tool to overcome the drawbacks of landing obligation
Bioeconomic multistock reference points as a tool for overcoming the drawbacks of the landing obligation
The landing obligation policy was one of the major innovations introduced in the last Common Fisheries Policy reform in Europe. It is foreseen that the policy will affect the use of fishing opportunities and hence the economic performance of the fleets. The problem with fishing opportunities could be solved if single-stock total allowable catches (TACs) could be achieved simultaneously for all the stocks. In this study, we evaluate the economic impact of the landing obligation policy on the Spanish demersal fleet operating in the Iberian Sea region. To generate TAC advice, we used two sets of maximum sustainable yield (MSY) reference points, the single-stock MSY reference points defined by ICES and a set of multistock reference points calculated simultaneously using a bioeconomic optimization model. We found that the impact of the landing obligation is time and fleet dependent and highly influenced by assumptions about fleet dynamics. At fishery level, multistock reference points mitigate the decrease in the net present value generated by the implementation of the landing obligation. However at fleet level, the effect depends on the fleet itself and the period. To ensure the optimum use of fishing opportunities, the landing obligation should be accompanied by a management system that guarantees consistency between single-stock TACs. In this regard, multistock reference points represent an improvement over those currently in use. However, further investigation is necessary to enhance performance both at fleet level and in the long term.Versión del edito
Planar non-volatile memory based on metal nanoparticles
Resistive switching properties of silver nanoparticles hosted in an insulating polymer matrix (poly(N-vinyl-2-pyrrolidone) are reported. Planar devices structures using interdigitated gold electrodes were fabricated. These devices have on/off resistance ratio as high as 103 , retention times reaching to months and good endurance cycles. Temperature-dependent measurements show that the charge transport is weakly thermal activated (73 meV) for both states suggesting that nanoparticles will not aggregate into a metallic filament
Medidas de morbidade produzidas por duas fontes diversas: Ribeirão Preto, SP (Brasil), 1975
Lagochilascariasis leading to severe involvement of ocular globes, ears and meninges
A case report of a 31 year-old woman from Paraíba State (North-Eastern Brazil) that presented severe involvement of ocular globes, ears and meninges. Diagnosis was established after enucleation of her left eye, when adult worms were seen in the midst of a granulomatous inflammatory process. Her response to the initial treatment with levamisole and cambendazole was good, but there was a relapse after the fifth month of treatment even with maintenance doses of both medications. She later received ivermectin and albendazol and responded well.Paciente do sexo feminino, com 31 anos, procedente da Paraíba, apresentava envolvimento severo de ambos os globos oculares, com perda da visão à esquerda, comprometimento da audição e das meninges. Após enucleação do olho esquerdo fragmento de helminto identificado como Lagochilascaris minor foi observado em processo inflamatório granulomatoso. Inicialmente a paciente foi tratada com levamisol e cambendazol, com bom resultado. Verificou-se, todavia, piora do quadro após cinco meses, com eliminação de larvas do ascarídeo em lesão presente na órbita esquerda, embora a medicação fosse mantida com administração periódica. Houve boa resposta terapêutica, com regressão do quadro, após substituição dos anti-helmínticos anteriores pela associação ivermectina e albendazol
Application of the laser radiation in patients of pressure ulcers: clinical and histomorphometric analysis of the derm
Gravitational Energy of Kerr and Kerr Anti-de Sitter Space-times in the Teleparallel Geometry
In the context of the Hamiltonian formulation of the teleparallel equivalent
of general relativity we compute the gravitational energy of Kerr and Kerr
Anti-de Sitter (Kerr-AdS) space-times. The present calculation is carried out
by means of an expression for the energy of the gravitational field that
naturally arises from the integral form of the constraint equations of the
formalism. In each case, the energy is exactly computed for finite and
arbitrary spacelike two-spheres, without any restriction on the metric
parameters. In particular, we evaluate the energy at the outer event horizon of
the black holes.Comment: 11 pages, 1 figure, to appear in JHEP11(2003)00
Comparison of tests for the detection of circulating filarial antigen (Og4C3-ELISA and AD12-ICT) and ultrasound in diagnosis of lymphatic filariasis in individuals with microfilariae
- …