Coupling between counterpropagating cladding modes in fiber Bragg gratings

We present an experimental demonstration of energy transfer between counterpropagating cladding modes in a fiber Bragg grating (FBG). A strong FBG written in a standard photosensitive optical fiber is illuminated with a single cladding mode, and the power transferred between the forward propagating cladding mode and different backward propagating cladding modes is measured by using two auxiliary long period gratings. Resonances between cladding modes having 30 pm bandwidth and 8 dB rejection have been observed

Long range absorption in the scattering of 6He on 208Pb and 197Au at 27 MeV

Quasi-elastic scattering of 6He at E_lab=27 MeV from 197Au has been measured in the angular range of 6-72 degrees in the laboratory system employing LEDA and LAMP detection systems. These data, along with previously analysed data of 6He + 208Pb at the same energy, are analyzed using Optical Model calculations. The role of Coulomb dipole polarizability has been investigated. Large imaginary diffuseness parameters are required to fit the data. This result is an evidence for long range absorption mechanisms in 6He induced reactions.Comment: 10 pages, 10 figures, minor corrections. To appear in Nucl. Phys.

Boson expansion methods applied to a two-level model in the study of multiple giant resonances

We apply boson expansion methods to an extended Lipkin-Meshkov-Glick model including anharmonicities in analogy with previous microscopic calculations. We study the effects of different approximations present in these calculations, among which the truncation of the hamiltonian and of the space, in connection with the study of the properties of two-phonon and three-phonon states. By comparing the approximate results on the spectrum with the exact ones we conclude that the approximations made in the microscopic calculations on two-phonon states are well justified. We find also that a good agreement with the exact results for the three-phonon state is obtained by using a bosonic hamiltonian truncated at the fourth order. This result makes us confident that such approximation can be used in realistic calculations, thus allowing a theoretical study of triple excitations of giant resonances.Comment: 12 pages, 2 figures, Latex with epsfig.st

Informe Optoel 2021

[No abstract available

Internal attribution of outcome moderates the cortisol response to a cooperative task in women

Las observaciones etológicas actuales indican que las conductas cooperativas desempeñan un papel adaptativo. En humanos, las situaciones competitivas han sido mayoritariamente investigadas en varones, aunque en escasas ocasiones se ha estudiado la cooperación. Se pretende analizar la respuesta psicológica y del cortisol a una situación cooperativa, en comparación con una competitiva en el laboratorio en mujeres. Se establecieron cuatro grupos en función de la tarea y su resultado: cooperación positiva, cooperación negativa, competición con victoria y competición con derrota. La cooperación produce efectos diferentes en cortisol que la competición, pero no en las variables psicológicas, aunque estos efectos únicamente se producen cuando se considera el resultado y su atribución. Solo las participantes que cooperaron y fueron evaluadas positivamente y las que compitieron y perdieron mostraron descensos signifi cativos de cortisol. La atribución interna se asocia a niveles de cortisol más estables, sugiriendo un efecto modulador de la controlabilidad en la vivencia de la situación. Estos resultados podrían hacerse extensibles a situaciones en las que la negociación, la mediación y las estrategias cooperativas son relevantes para la toma de decisiones y/o resolución de conflictos

Simultaneous gain and phase profile determination on an interferometric BOTDA

24th International Conference on Optical Fibre Sensors, 96343Y, Curitiba, Brazil, September 28, 2015.Up to now, complex (phase and intensity) measurements in Brillouin Optical Time-Domain Analysis (BOTDA) systems required complex phase modulation methods and high-bandwidth (multi-GHz) detection. In this work, we propose a novel technique that is able to retrieve simultaneously both gain/loss and phase characteristics of the Brillouin interaction by just introducing a Sagnac Interferometer (SI) 011 a standard BOTDA sensing scheme. The technique is described analytically and demonstrated experimentally. With this technique, a reliability increase is produced since redundant measurements can be performed.European CommissionMinisterio de Economía y CompetitividadUniversidad de AlcaláComunidad de MadridGeneralitat Valencian

Raman phonons as a probe of disorder, fluctuations and local structure in doped and undoped orthorhombic and rhombohedral manganites

We present a rationalization of the Raman spectra of orthorhombic and rhombohedral, stoichiometric and doped, manganese perovskites. In particular we study RMnO3 (R= La, Pr, Nd, Tb, Ho, Er, Y and Ca) and the different phases of Ca or Sr doped RMnO3 compounds as well as cation deficient RMnO3. The spectra of manganites can be understood as combinations of two kinds of spectra corresponding to two structural configurations of MnO6 octahedra and independently of the average structure obtained by diffraction techniques. The main peaks of compounds with regular MnO6 octahedra, as CaMnO3, highly Ca doped LaMnO3 or the metallic phases of Ca or Sr doped LaMnO3, are bending and tilt MnO6 octahedra modes which correlate to R-O(1) bonds and Mn-O-Mn angles respectively. In low and optimally doped manganites, the intensity and width of the broad bands are related to the amplitude of the dynamic fluctuations produced by polaron hopping in the paramagnetic insulating regime. The activation energy, which is proportional to the polaron binding energy, is the measure of this amplitude. This study permits to detect and confirm the coexistence, in several compounds, of a paramagnetic matrix with lattice polaron together with regions without dynamic or static octahedron distortions, identical to the ferromagnetic metallic phase. We show that Raman spectroscopy is an excellent tool to obtain information on the local structure of the different micro or macro-phases present simultaneously in many manganites.Comment: Submitted to PR

Cuestionario del rol docente en las organizaciones universitarias: diseño y validación en el marco del Espacio Europeo de Educación Superior

El propósito de esta investigación es diseñar y validar un cuestionario para medir las percepciones, actitudes y comportamientos del profesorado universitario res- pecto a su práctica docente y su relación con los estudiantes en el marco del Espacio Europeo de Educación Superior (EEES); considerando ciertos conceptos imprescindi- bles para el desempeño académico incardinados con el objetivo 4 de los Objetivos de Desarrollo Sostenible (ODS). El cuestionario se orienta a cumplir una doble finalidad, por un lado, posibilitar vías para incrementar la calidad de los procesos de enseñanza- aprendizaje mediante el autodiagnóstico de los docentes, y, por otro lado, orientar un camino de mejora continua e innovación metodológica y competencial. En un primer momento, se elaboró un borrador inicial de cuestionario con 11 dimensiones compues- tas por 72 ítems, que, tras realizar un análisis psicométrico limitado, se redujo a única- mente 2 dimensiones con 20 ítems, que corresponde al cuestionario testado mediante una muestra de 360 docentes de universidades de toda España. La aplicación del análisis factorial sobre las respuestas arrojó tres factores con una alta fiabilidad: for- mación integral, formación en valores, innovación pedagógica y TIC. A la vista de los resultados, cabe inferir que este cuestionario posee una validez clara y fiable para ser utilizado en el ámbito universitario, dado que posee factores conectados estrechamente tanto con los principios del EEES como con el objetivo 4 de los ODS

Undamning the Douro river catchment: a stepwise approach for prioritizing dam removal

Dams provide water supply, flood protection, and hydropower generation benefits, but also harm native species by altering the natural flow regime, and degrading the aquatic and riparian habitats. In the present study, which comprised the Douro River basin located in the North of Portugal, the cost-benefit assessment of dams was based upon a balance between the touristic benefits of a dammed Douro, and the ecological benefits of less fragmented Douro sub-catchments. Focused on four sub-catchments (Sabor, Tâmega, Côa and Corgo), a probabilistic stream connectivity model was developed and implemented to recommend priorities for dam removal, where this action could significantly improve the movement of potadromous fish species along the local streams. The proposed model accounts for fish movement across the dam or weir (permeability), which is a novel issue in connectivity models. However, before any final recommendation on the fate of a dam or weir, the connectivity results will be balanced with other important socio-economic interests. While implementing the connectivity model, an inventory of barriers (dams and weirs) was accomplished through an observation of satellite images. Besides identification and location of any obstacles, the inventory comprised the compilation of data on surrounding land use, reservoir water use, characteristics of the riparian gallery, and permeability conditions for fish, among others. All this information was stored in a geospatial dataset that also included geographical information on the sub-catchment drainage network. The linear (drainage network) and point (barriers) source data were processed in a computer program that provided or returned numbers for inter-barrier stream lengths (habitat), and the barrier permeability. These numbers were finally used in the same computer program to calculate a habitat connector index, and a link improvement index, used to prioritize dam removal based upon structural connectivity criteria. The results showed that habitat patch connectivity in the Sabor, Tâmega and Côa sub-catchments is not dramatically affected by the installed obstacles, because most link improvement values were generally low. For the opposite reason, in the Corgo sub-catchment, obstacles may constitute a relatively higher limitation to connectivity, and in this case the removal of eight obstacles could significantly improve this connectivity. Using the probabilistic model of structural connectivity, it was possible to elaborate a preliminary selection of dams/weirs that critically limit stream connectivity, and that will be the focus of field hydraulic characterization to precisely determine fish movement along the associated river stretches. Future work will also include the implementation of a multi-criteria decision support system for dam removal or mitigation of the critical structures, as well to define exclusion areas for additional obstaclesinfo:eu-repo/semantics/publishedVersio