Bases de poder del supervisor, conducta cooperadora y compromiso con la organización

Este trabajo analiza, en el contexto español, las bases de poder de los supervisores y la incidencia que las mismas tienen sobre la conducta cooperadora y el compromiso con la organización de sus subordinados. Los datos analizados pertenecen a 335 sujetos con la menos un año de experiencia laboal a tiempo completo. Mediante la contrastación de un modelo estructural, que relaciona las diversas bases de poder del jefe entre sí y con la conducta cooperadora y el grado de compromiso de los subordinados, se tratan de comprobar las relaciones existentes entre las variables mencionadas. Asimismo, se indican los principales resultados alcanzados y las implicaciones más relevantes que se pueden deducir a partir de los mismos de cara a las prácticas de los directivos

A band-pass/stop filter made of SRRs and C-SRRs

Frequency Selective Surfaces (FSS) are usually classified into two big groups depending on wether they are made of unconnected elements or connected elements. Close to their resonance frequency, the first type behaves like a band-stop filter while the second type like a band-pass filter. In this paper we propose a new type of surface made of Split Ring Resonators (SRRs) and, at the same time, Complementary Split Ring Resonators (CSRRs), placed in such a way that the surface is self-complementary. The main result is that this FSS shows band-stop features for one linear polarization state and band-pass features for the orthogonal polarization. Therefore, it is in the middle between the two usual groups of FSS, what could drive us to new designs of band-pass/stop filters which are are easily switchable from band-pass to band-stop, and viceversa, by simply rotating the surface through 90 degrees.Universidad Nacional de Colombia DIB-8003310Ministerio de Ciencia e Innovación CSD2008-0006

Thin perfect absorbers based on metamaterials for optical frequencies

In this work a bidimensional array of particles is approached like a system of dipoles characterized by their electric and magnetic polarizabilities. The interaction between particles has been taken into account by adding contribution of every dipole at the position of the central dipole. This array was modeled later as a surface which supports effective electric and magnetic surface currents. From these currents, the boundary conditions for perfect absorption were established. This model was applied onto an array of coated nanospheres, whose scattering is described by the Mie theory, obtaining values of absorption up to 99%.En este trabajo un arreglo bidimensional de partículas es aproximado como un arreglo de dipolos caracterizados por sus polarizabilidades eléctricas y magnéticas. La interacción entre las partículas es tenida en cuenta sumando las contribuciones al campo de todos los dipolos sobre la posición del dipolo central. Posteriormente se modeló el arreglo como una superficie que soporta corrientes superficiales eléctricas y magnéticas efectivas. Con dichas corrientes se establecieron las condiciones de frontera necesarias para obtener absorción perfecta. Este modelo se aplicó a un arreglo de nanoesferas recubiertas, cuya dispersión es descrita por la teor_á de Mie, obteniéndose valores de absorción hasta del 99%

Spatial angular filtering by FSSs made of chains of interconnected SRRs and CSRRs

Two frequency selective surfaces (FSSs) made of an infinite set of parallel 1-D chains of interconnected split ring resonators (I-SRRs) and interconnected complementary split ring resonators (I-CSRRs) are studied. The main result was that the central frequencies of the stopband and passband can be strongly tuned by controlling the angle of incidence.Colombian Administrative Departament of Science, Technology and Innovation 1101-521-29389Ministerio de Ciencia e Innovación CSD2008-00066, TEC2010-1694

Self-complementary metasurface for designing narrow band pass/stop filters

A self-complementary metasurface is studied in this paper. The metasurface is a 2-D periodical arrangement of unit cells formed by a metallic printed split ring resonator and its complementary counterpart. It is demonstrated that this structure behaves like a very selective band-pass filter for a certain linear polarization while band-stop filtering is achieved for the orthogonal polarization over the same frequency range. This idea opens the door to a new class of frequency selective surfaces made of connected and unconnected elements, whose filtering properties are mechanically tunable from band-pass to band-stop by rotating the surface or the polarization.Colombian Administrative Departament of Science, Technology and Innovation 1101-521-29389Ministerio de Ciencia e Innovación CSD2008-00066, TEC2010-1694

Improving B1 homogeneity in abdominal imaging at 3 T with light and compact metasurface

Radiofrequency field inhomogeneity is a significant issue in imaging large fields of view in high- and ultrahigh-field MRI. Passive shimming with coupled coils or dielectric pads is the most common approach at 3 T. We introduce and test light and compact metasurface, providing the same homogeneity improvement in clinical abdominal imaging at 3 T as a conventional dielectric pad. The metasurface comprising a periodic structure of copper strips and parallel-plate capacitive elements printed on a flexible polyimide substrate supports propagation of slow electromagnetic waves similar to a high-permittivity slab. We compare the metasurface operating inside a transmit body birdcage coil to the state-of-the-art pad by numerical simulations and in vivo study on healthy volunteers. Numerical simulations with different body models show that the local minimum of B1+ causing a dark void in the abdominal domain is removed by the metasurface with comparable resulting homogeneity as for the pad without noticeable SAR change. In vivo results confirm similar homogeneity improvement and demonstrate the stability to body mass index. The light, flexible, and cheap metasurface can replace a relatively heavy and expensive pad based on the aqueous suspension of barium titanate in abdominal imaging at 3 T.Comment: 18 pages, 6 figures, 4 supplementary figure

Triplet-sensitization by lead halide perovskite thin films for near-infrared-to-visible upconversion

Lead halide-based perovskite thin films have attracted great attention due to the explosive increase in perovskite solar cell efficiencies. The same optoelectronic properties that make perovskites ideal absorber materials in solar cells are also beneficial in other light-harvesting applications and make them prime candidates as triplet sensitizers in upconversion via triplet-triplet annihilation in rubrene. In this contribution, we take advantage of long carrier lifetimes and carrier diffusion lengths in perovskite thin films, their high absorption cross sections throughout the visible spectrum, as well as the strong spin-orbit coupling owing to the abundance of heavy atoms to sensitize the upconverter rubrene. Employing bulk perovskite thin films as the absorber layer and spin-mixer in inorganic/organic heterojunction upconversion devices allows us to forego the additional tunneling barrier owing from the passivating ligands required for colloidal sensitizers. Our bilayer device exhibits an upconversion efficiency in excess of 3% under 785 nm illumination

MAPPING COMMUNITY INTEREST HABITATS IN THE COLUMBRETES ARCHIPELAGO, AN EXTRAORDINARY HOT SPOT OF BIODIVERSITY

The Columbretes Archipelago and their submerged surroundings are part of an unusual, Pleistocene volcanic field located in the Western Mediterranean designated as a Site of Community Importance (SCI) of the Natura 2000 Network. In the present study, 4 benthic habitats of community interest (1110, 1170, 1180 and 8330) have been identified by analyzing several sources of information. Generalized additive models (GAMs) have been used to model the potential distribution of reefs (1170) and maërl beds (1110). Our results highlight the diversity and extent of these habitats and allow comparisons to other marine SCIs of Spain. This can be attributed to the variability of the environment of this site. The Columbretes Islands combine a relatively shallow environment with volcanic structures, hydrothermalism with active degassing, current-driven sedimentary lobes and the influence of inland flows. Understanding high biodiversity spots is crucial as they offer natural laboratories to describe how ecosystems respond to the effects of global change. The knowledge obtained will be of paramount importance for the conservation of species and habitats. Furthermore, it will establish a baseline for future monitoring and assist in the development of effective management plans