Actividad gamma del electroencefalograma. Métodos de análisis con objetivos clínicos

Objetivos: El objetivo general de la presente tesis doctoral ha sido investigar la identificación de la actividad gamma [30-90 Hz] del electroencefalograma (EEG) utilizando un sistema monocanal, para posibles aplicaciones clínicas. Métodos: Se ha obtenido la actividad gamma del EEG de las áreas motoras de la corteza cerebral en 25 sujetos sanos, con movimiento real e imaginario. Se analiza la señal mediante un método no lineal que utiliza transformaciones tiempo-frecuencia con wavelets. Posteriormente se añade un filtro, basado en la función matemática de descomposición en modo empírico (EMD: Empirical Mode Decomposition) y se comparan los resultados. Resultados: Se identifica la actividad de la banda gamma de las áreas motoras cerebrales durante el movimiento voluntario real e imaginario. Se obtiene un método para cuantificar la plasticidad cerebral analizando la actividad gamma motora. Se demuestra que filtrando las señales EEG mediante EMD, se obtienen mejores resultados que con el análisis original de la señal. Conclusiones: En esta tesis se demuestra que es posible obtener la actividad gamma del EEG de una forma simplificada, en relación a la adquisición y a la utilización de métodos relativamente sencillos de análisis de las señales. Los resultados experimentales de la tesis, principalmente las variaciones de la actividad gamma de las áreas motoras cerebrales, se pueden utilizar desde un punto de vista práctico para proponer aplicaciones clínicas. Palabras clave: Electroencefalografía, actividad gamma, áreas motoras, densidad espectral de potencia, aplicaciones clínicas, descomposición en modo empírico, plasticidad cerebral, tareas motoras reales, tareas motoras imaginarias

Formación y empleo juvenil. El caso de los jóvenes españoles en la última década

Durante los últimos años las condiciones en el empleo se han visto afectadas por grandes cambios como son, entre otros, la globalización, la digitalización y el impacto de dos crisis económicas: la llamada Gran Recesión con sus inicios en la crisis inmobiliaria de 2008 y la actual Crisis económica y sanitaria causada por la Covid-19. Así, en relación con el empleo creado recientemente, se parte de un claro deterioro de su calidad, con un incremento desproporcionado de la temporalidad, del trabajo a jornada parcial con carácter no voluntario, con unos salarios a la baja y una reducción de otros derechos laborales. Este deterioro ha dado lugar a la consolidación del término empleo precario o precarización del trabajo para referirse a una buena parte de los empleos creados en las últimas décadas y que han recaído en buena medida en los jóvenes que se han ido incorporando a la actividad laboral que, por otra parte, forman la generación mejor preparada académicamente de la Historia de España. La relación existente entre la formación de los jóvenes y las características de su empleo en los últimos años, pretende ser el objetivo del presente trabajo. Averiguar si la posesión de unas determinadas credenciales educativas reduce significativamente la probabilidad de caer en una cadena de contratos temporales y con jornada parcial, alternados con periodos de paro y salarios en su nivel mínimo; si la posesión de determinados títulos educativos aumenta la probabilidad de obtener un empleo de más calidad y más satisfactorio.Grado en Relaciones Laborales y Recursos Humano

Suppression of cyclic prefix in down-link LTE like systems to increase capacity

The proceeding at : 77th Vehicular Technology Conference (VTC Spring), took place 2013, June 02-05, in Dresden (Germany).In this paper it is presented a proposal to increase the capacity of Down-Link (DL) transmissions in Long Term Evolution (LTE) like systems based on Multiple-Input Multiple-Output (MIMO)-Orthogonal Frequency Division Multiplexing (OFDM). The augment of the data rate is achieved with the total or partial suppression of the Cyclic Prefix (CP), which requires the use of a variable number of samples without conveying any information. The proposal is based on an iterative cancellation of the main impairments that the CP suppression supposes, the Inter Symbol and Inter Carrier Interferences. The interference mitigation procedure demands adequate channel estimations obtained in two different stages. Firstly, this new scheme requires the utilization of a preamble symbol appended to the beginning of the data transmission, which enables an initial Maximum Likelihood channel estimation. Secondly, time-variant channels will be estimated using a Least Squares estimator by the use of scattered pilots within the LTE frame structure. Through simulations it has been demonstrated that, despite the interferences arisen due to the CP suppression, our proposal attains adequate channel estimations which converge to theoretical bounds and the overall system obtains values of Bit Error Rate similar to the ideal situation of not suppressing the CP. It is also presented that considering the typical values of CP in the LTE standard the increment of the capacity employing this strategy can range between 7% and 25%.This work has been partly funded by the Spanish national projects GRE3NSYST (TEC2011-29006-C03-03) and COMONSENS (CSD2008-00010).Publicad

Iterative Joint Estimation Procedure for Channel and Frequency Offset in Multi-Antenna OFDM Systems With an Insufficient Cyclic Prefix

This paper addresses a strategy to improve the joint channel and frequency offset (FO) estimation in multi-antenna systems, widely known as multiple-input-multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM), in the presence of intersymbol interference (ISI) and intercarrier interference (ICI) occasioned by an insufficient cyclic prefix (CP). The enhancement is attained by the use of an iterative joint estimation procedure (IJEP) that successively cancels the interferences located in the preamble of the OFDM frame, which is used for the joint estimation and initially contains the interferences due to a CP shorter than the channel length. The IJEP requires at certain steps a proper iterative interference cancellation algorithm, which makes use of an initial FO compensation and channel estimation obtained due to the use of a symmetric sequence in the preamble. After the iterative cancellation of interferences, the procedure performs an additional joint channel and FO estimation whose mean square error converges to the Cramer-Rao bound (CRB). Later on, this subsequent joint estimation permits the removal of the interferences in the data part of the frame, which are also due to an insufficient CP, in the same iterative fashion but saving iterations compared with the use of other estimation strategies. The appraisal of the procedure has been performed by assessing the convergence of the simulated estimators to the CRB as a function of the number of iterations. Additionally, simulations for the evaluation of the bit error rate (BER) have been carried out to probe how the utilization of the proposed IJEP clearly improves the performance of the system. It is concluded that, with a reduced number of iterations in the preamble, the IJEP converges to the theoretical bounds, thus reducing the disturbances caused by a hard wireless channel or a deliberately insufficient CP.This work was supported in part by the Spanish na-tional projects GRE3N-SYST (TEC2011-29006-C03-03) and COMONSENS (CSD2008-00010).Publicad

Design of a die for the manufacturing of a cooling fan for a generator

Grado en Ingeniería Mecánic

Estimación de canal y desplazamiento de frecuencia en sistemas MIMO-OFDM con prefijo cíclico insuficiente

La presente Tesis aborda el análisis de la estimación de canal y desplazamiento de frecuencia en sistemas MIMO-OFDM (Multiple-Input Multiple-Output Orthogonal Frequency Division Multiplexing) en condiciones de prefijo cíclico insuficiente. La motivación fundamental es estudiar uno de los sistemas más utilizados actualmente, como es MIMO-OFDM, pero con la intención de mejorar una de las características intrínsecas que le proporciona mayores ventajas, como es el uso del prefijo cíclico. Dicho prefijo cíclico permite mantener la ortogonalidad entre subportadoras y evita la aparición de interferencias entre símbolos y entre portadoras, facilitando también la ecualización en entornos multitrayecto, siempre que su longitud sea mayor que la del canal. Sin embargo, produce un decremento de la capacidad del sistema, al no llevar información por ser una réplica de las últimas muestras de cada símbolo OFDM, y disminuye la eficiencia de la estimación de parámetros. La Tesis se centra, por tanto, en analizar un sistema MIMO-OFDM con prefijo cíclico insuficiente, menor a la longitud del canal, que puede ser debido a una supresión intencionada para incrementar la capacidad, a canales largos altamente dispersivos o para eliminar patrones repetitivos de la señal que facilitan la interceptabilidad de la señal OFDM. Por consiguiente, para abordar el objetivo principal de esta Tesis es necesario analizar aquellos inconvenientes que surgen de la existencia de un prefijo cíclico insuficiente. Por un lado, se analiza el impacto sobre las comunicaciones MIMO-OFDM en términos de interferencias en la parte de datos de la estructura de trama así como sobre la estimación de canal y desplazamiento de frecuencia. También se evalúan las secuencias utilizadas como preámbulo para dichas estimaciones tanto desde el punto de vista de sus características y utilización como desde el punto de vista de rango de adquisición del desplazamiento de frecuencia. Se demuestra claramente que los estimadores propuestos convergen a sus límites teóricos y que las secuencias seleccionadas tienen el mayor rango de adquisición posible. Por otro lado, una vez analizado el efecto sobre la parte de datos de la trama, también se analiza el impacto sobre el propio preámbulo que se utiliza para labores de estimación y se presentan los resultados correspondientes a la tasa de error, demostrando que el rendimiento obtenido se equipara al de aquellos sistemas con prefijo cíclico suficiente. Debido a que las estrategias propuestas incrementan la complejidad del sistema, se analiza con detalle el coste computacional de la implementación del esquema de receptor propuesto concluyéndose que el coste que supone es muy inferior comparado con el ahorro que propicia en términos de capacidad y energía. Finalmente, se propone la implementación de algunas de las estrategias definidas anteriormente en un sistema real como es el enlace descendente del estándar LTE (Long Term Evolution). En primer lugar, se propone una estructura de trama y receptor aplicados a una aproximación simplificada del estándar. Posteriormente, se adaptan las estrategias propuestas a una versión más fidedigna de dicho estándar. Los resultados obtenidos en ambos casos ponen de manifiesto las notables mejoras que implica la utilización de los receptores propuestos dando lugar a rendimientos del sistema similares a los obtenidos en el caso de haber utilizado un prefijo cíclico suficiente.This Thesis tackles the analysis of channel and frequency offset estimation in MIMOOFDM (Multiple-Input Multiple-Output Orthogonal Frequency Division Multiplexing) systems in conditions of insufficient cyclic prefix. The main motivation is to study one of the most currently used systems, as is MIMO-OFDM, but with the intention of improving one of its intrinsic characteristics that provides more advantages, as the use of the cyclic prefix is. This cyclic prefix allows to keep the orthogonality between subcarriers and avoid the appearance of inter symbol and inter carrier interferences, making easier the equalization in multi-path environments provided that its length is longer than the channel length. However, it produces a decrease in the system capacity, since it does not bear any information because it is a replica of some last samples in every OFDM symbol, and decrease the efficiency of parameters estimation. Therefore, this Thesis is focused on analyzing a MIMO-OFDM system with insufficient cyclic prefix, shorter than the channel length, which can arise due to an intentional suppression to increase the system capacity, to highly dispersive long channels or to eliminate repetitive patterns in the OFDM signal that ease the signal interception. Consequently, to tackle the main objective of this Thesis it is necessary to analyze those inconveniences arisen from the existence of an insufficient cyclic prefix. On the one hand, the impact in MIMO-OFDM communications is analyzed in terms of interferences in the data part of the frame structure and in terms of channel and frequency offset estimation. In addition, those sequences used as preamble are assessed in relation with these estimations both concerning their characteristics and handling and considering which is the acquisition range of the frequency offset. It is clearly demonstrated that the proposed estimators converge to their theoretical limits and that the selected sequences have the highest possible acquisition range. On the other hand, once the effect over the data part of the frame has been analyzed, it is also evaluated the impact over the own preamble used for estimation tasks and the results corresponding to the error rate are presented, showing that the performance is similar to that one obtained in systems with insufficient cyclic prefix. Due to the fact that the proposed strategies increase the system complexity, the computational cost of the proposed receiver has been analyzed with detail to conclude that the implicit cost is much lower compared with the saving in terms of capacity or energy. Finally, the implementation of some of the previously defined schemes has been proposed for a real system, such as the down link in the LTE (Long Term Evolution) standard. In first place, it is proposed a frame structure and receiver for a simplified version of the standard. Later, these proposed strategies are adapted to a more similar version of the standard. The results in both cases prove the dramatic improvements of the utilization of these two proposed receivers giving rise to system performances comparable to those obtained in the case of having used a insufficient cyclic prefix.Programa Oficial de Doctorado en Multimedia y ComunicacionesPresidente: Ana García Armada.- Secretario: Iván Alejandro Pérez Álvarez.- Vocal: María del Carmen Aguayo Torre

Nuevos métodos de verificación de las predicciones numéricas de precipitación: el método SAL aplicado en la mesoescala

Ponencia presentada en: XXXII Jornadas Científicas de la AME y el XIII Encuentro Hispano Luso de Meteorología celebrado en Alcobendas (Madrid), del 28 al 30 de mayo de 2012

Fundamental High-Speed Limits in Single-Molecule, Single-Cell, and Nanoscale Force Spectroscopies

Force spectroscopy is enhancing our understanding of single-biomolecule, single-cell, and nanoscale mechanics. Force spectroscopy postulates the proportionality between the interaction force and the instantaneous probe deflection. By studying the probe dynamics, we demonstrate that the total force acting on the probe has three different components: the interaction, the hydrodynamic, and the inertial. The amplitudes of those components depend on the ratio between the resonant frequency and the frequency at which the data are measured. A force–distance curve provides a faithful measurement of the interaction force between two molecules when the inertial and hydrodynamic components are negligible. Otherwise, force spectroscopy measurements will underestimate the value of unbinding forces. Neglecting the above force components requires the use of frequency ratios in the 50–500 range. These ratios will limit the use of high-speed methods in force spectroscopy. The theory is supported by numerical simulations.We thank the European Research Council, ERC-AdG-340177 (3DNanoMech), and the Ministerio de Economía y Competitividad (CSD2010-00024) for financial support.Peer reviewe

Superior fruit total soluble solid content of red x pink F1 hybrids over nearly-isogenic parental lines

Comunicación realizada en el congresoPink-coloured tomatoes are reputed as good flavoured and are very popular in local markets. Pink tomatoes show a transparent, colourless fruit cuticle in contrast to the naringenin-chalcone flavonoid-rich, orange-yellow cuticle of normal, red tomatoes due to the y (colourless epidermis) recessive mutation in MYB12 gene located in chromosome 1. In order to investigate the basis of the alleged higher quality of pink vs. red tomatoes and, especially, our previous observations of good flavour in hybrids between red and pink tomato varieties, two red x pink F1 crosses between pairs of tomato near-isogenic lines were obtained, namely ‘Ailsa Craig’ wt/wt x ‘Ailsa Craig’ y/y and ‘Ponderosa Red’ wt/wt x ‘Ponderosa Red’ y/y, being the latter a pink tomato line in which y allele was introgressed from its closely related ‘Ponderosa Pink’ cultivar. The parental lines and the two F1 hybrids were grown to harvest in a greenhouse and total soluble solids (°Brix) and titratable acidity (TA) were measured in red ripe fruits. While no differences for °Brix were observed between the parents of each cross, significantly higher °Brix was measured in the two red x pink F1’s compared to their corresponding parental lines. No clear differences between parental lines and F1 crosses were shown for TA. The experiment was repeated but including also the pink x red, reciprocal F1 crosses. The overdominance for °Brix but not for TA was confirmed in the red x pink hybrids while the pink x red hybrids produced °Brix values similar to those of their parents.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Subsurface imaging of silicon nanowire circuits and iron oxide nanoparticles with sub-10 nm spatial resolution

Non-destructive subsurface characterization of nanoscale structures and devices is of significant interest in nanolithography and nanomanufacturing. In those areas, the accurate location of the buried structures and their nanomechanical properties are relevant for optimization of the nanofabrication process and the functionality of the system. Here we demonstrate the capabilities of bimodal and trimodal force microscopy for imaging silicon nanowire devices buried under an ultrathin polymer film. We resolve the morphology and periodicities of silicon nanowire pairs. We report a spatial resolution in the sub-10 nm range for nanostructures buried under a 70 nm thick polymer film. By using numerical simulations we explain the role of the excited modes in the subsurface imaging process. Independent of the bimodal or trimodal atomic force microscopy approach, the fundamental mode is the most suitable for tracking the topography while the higher modes modulate the interaction of the tip with the buried nanostructures and provide subsurface contrast.This work was funded by the European Union FP7/2007-2013 under Grant Agreement No. 318804 (SNM), the Ministerio de Economía y Competitividad (Spain) under grants MAT2013-44858-R, CSD2010-00024 and the European Research Council ERC-AdG-340177 (3DNanoMech).Peer reviewe