Diagnosis of Alzheimer’s Disease from EEG by Means of Synchrony Measures in Optimized Frequency Bands

Several clinical studies have reported that EEG synchrony is affected by Alzheimer’s disease (AD). In this paper a frequency band analysis of AD EEG signals is presented, with the aim of improving the diagnosis of AD using EEG signals. In this paper, multiple synchrony measures are assessed through statistical tests (Mann–Whitney U test), including correlation, phase synchrony and Granger causality measures. Moreover, linear discriminant analysis (LDA) is conducted with those synchrony measures as features. For the data set at hand, the frequency range (5-6Hz) yields the best accuracy for diagnosing AD, which lies within the classical theta band (4-8Hz). The corresponding classification error is 4.88% for directed transfer function (DTF) Granger causality measure. Interestingly, results show that EEG of AD patients is more synchronous than in healthy subjects within the optimized range 5-6Hz, which is in sharp contrast with the loss of synchrony in AD EEG reported in many earlier studies. This new finding may provide new insights about the neurophysiology of AD. Additional testing on larger AD datasets is required to verify the effectiveness of the proposed approach.

Contribución al diseño de GNSS-SDR, un receptor GNSS de código abierto

[ANGLÈS] This project introduces GNSS-SDR, an open source Global Navigation Satellite System software-defined receiver. The lack of reconfigurability of current commercial-of-the-shelf receivers and the advent of new radionavigation signals and systems make software receivers an appealing approach to design new architectures and signal processing algorithms. With the aim of exploring the full potential of this forthcoming scenario with a plurality of new signal structures and frequency bands available for positioning, this paper describes the software architecture design and provides details about its implementation, targeting a multiband, multisystem GNSS receiver. The result is a testbed for GNSS signal processing that allows any kind of customization, including interchangeability of signal sources, signal processing algorithms, interoperability with other systems, output formats, and the offering of interfaces to all the intermediate signals, parameters and variables. The source code release under the GNU General Public License (GPL) secures practical usability, inspection, and continuous improvement by the research community, allowing the discussion based on tangible code and the analysis of results obtained with real signals. The source code is complemented by a development ecosystem, consisting of a website (http://gnss-sdr.org), as well as a revision control system, instructions for users and developers, and communication tools. The project shows in detail the design of the initial blocks of the Signal Processing Plane of the receiver: signal conditioner, the acquisition block and the receiver channel, the project also extends the functionality of the acquisition and tracking modules of the GNSS-SDR receiver to track the new Galileo E1 signals available. Each section provides a theoretical analysis, implementation details of each block and subsequent testing to confirm the calculations with both synthetically generated signals and with real signals from satellites in space.

Coherency and sharpness measures by using ICA algorithms. An investigation for Alzheimer’s disease discrimination

In this paper, we present a comprehensive study of different Independent Component Analysis (ICA) algorithms for the calculation of coherency and sharpness of electroencephalogram (EEG) signals, in order to investigate the possibility of early detection of Alzheimer’s disease (AD). We found that ICA algorithms can help in the artifact rejection and noise reduction, improving the discriminative property of features in high frequency bands (specially in high alpha and beta ranges). In addition to different ICA algorithms, the optimum number of selected components is investigated, in order to help decision processes for future works.

Robust Detection of Incumbents in Cognitive Radio Networks Using Groups

Cognitive radio is a wireless technology aimed at improvingthe efficiency use of the radio-electric spectrum, thus facilitating a reductionin the load on the free frequency bands. Cognitive radio networkscan scan the spectrum and adapt their parameters to operate in the unoccupiedbands. To avoid interfering with licensed users operating on a givenchannel, the networks need to be highly sensitive, which is achieved byusing cooperative sensing methods. Current cooperative sensing methodsare not robust enough against occasional or continuous attacks. This articleoutlines a Group Fusion method that takes into account the behavior ofusers over the short and long term. On fusing the data, the method is basedon giving more weight to user groups that are more unanimous in their decisions.Simulations have been performed in a dynamic environment withinterferences. Results prove that when attackers are present (both reiterativeor sporadic), the proposed Group Fusion method has superior sensingcapability than other methods.

A Secure and Anonymous Cooperative Sensing Protocol for Cognitive Radio Networks

Spectrum is an essential resource for the provision of mobile services. In order to control and delimit its use, governmental agencies set up regulatory policies. Unfortunately, such policies have led to a deficiency of spectrum as only few frequency bands are left unlicensed, and these are used for the majority of new emerging wireless applications. One promising way to alleviate the spectrum shortage problem is adopting a spectrum sharing paradigm in which frequency bands are used opportunistically. Cognitive radio is the key technology to enable this shift of paradigm.Cognitive radio networks are self-organized systems in which devices cooperate to use those spectrum ranges that are not occupied by licensed users. They carry out spectrum sensing in order to detect vacant channels that can be used for communication. Even though spectrum sensing is an active area of research, an important issue remains unsolved: the secure authentication of sensing reports. Not providing security enables the input of false data in the system thus empowering false results. This paper presents a distributed protocol based on wireless physical layer security, symmetric cryptography and one-way functions that allows determining a final sensing decision from multiple sources in a quick and secure way, as well as it preserves users¿ privacy.

Spectrum Sharing Models in Cognitive Radio

Spectrum scarcity demands thinking new ways tomanage the distribution of radio frequency bands so that its use is more effective. The emerging technology that can enable this paradigm shift is the cognitive radio. Different models fororganizing and managing cognitive radios have emerged, all with specific strategic purposes. In this article we review the allocation spectrum patterns of cognitive radio networks andanalyse which are the common basis of each model.We expose the vulnerabilities and open challenges that still threaten the adoptionand exploitation of cognitive radios for open civil networks.

Polarimetric radar interferometry for improved mine detection and surface clutter rejection

A recently developed technique, polarimetric radar interferometry, is applied to tackle the problem of the detection of buried objects embedded in surface clutter. An experiment with a fully polarimetric radar in an anechoic chamber has been carried out using different frequency bands and baselines. The processed results show the ability of this technique to detect buried plastic mines and to measure their depth. This technique enables the detection of plastic mines even if their backscatter response is much lower than that of the surface clutter.

Diseño e implementación de un receptor multifrecuencia basado en muestreo paso banda aplicado al sistema Galileo

Este trabajo tiene como objetivo diseñar e implementar un receptor multifrecuencia requerido para aplicaciones Galileo centradas a realizar correcciones de errores y estudios de la ionosfera. Estas características obligan a buscar alternativas respecto los receptores superheterodinos convencionales dado que para éstos los retardos de propagación entre las diferentes bandas de interés son inaceptables. Por ello, se presenta un receptor basado en la técnica de muestreo paso banda, que permite trasladar el espectro mediante el conversor ADC a través de un aliasing intencionado, eliminando así los retardos de propagación entre bandas de interés, dado que todas se albergan en un mismo canal. En este trabajo nos hemos centrado únicamente en las etapas críticas del receptor presentado, siendo éstas la etapa de filtrado y conversión digital. La etapa de filtrado requerirá filtros muy selectivos, ya que el ruido existente fuera de banda se solapará a nuestra banda de interés, degradando la SNR del sistema a medida que tenga más potencia. Esta etapa se ha realizado mediante una estructura duplexora conjuntamente con dos filtros de líneas acopladas. La etapa de conversión se ha realizado fabricando el layout de un conversor comercial, del cual se ha validado el correcto funcionamiento para la aplicación requerida.

On the existence of hysteresis in the Kuramoto model with bimodal frequency distributions

We investigate the transition to synchronization in the Kuramoto model with bimodal distributions of the natural frequencies. Previous studies have concluded that the model exhibits a hysteretic phase transition if the bimodal distribution is close to a unimodal one, due to the shallowness the central dip. Here we show that proximity to the unimodal-bimodal border does not necessarily imply hysteresis when the width, but not the depth, of the central dip tends to zero. We draw this conclusion from a detailed study of the Kuramoto model with a suitable family of bimodal distributions.

Disseny, modelat i fabricació d'una antena "trap" per aplicacions WLAN

En aquest treball s’ha dissenyat i fabricat una antena monopol en estructura planar capaç de treballar correctament a les freqüències WLAN de 2,45-2,5 GHz (802.11b/g) i 4,9-5,875 GHz (802.11a/h/j). Per arribar a aquest objectiu primer s’ha presentat el model de línia de transmissió acabada en circuit obert per simular el comportament d’una antena. S’han comparat i verificat els resultats amb el model d’antena de fil. Seguidament, s’ha estudiat el comportament que introdueix el fet de carregar l’antena amb un ressonador LC. Finalment, s’ha passat del model d’antena de fil a una estructura planar. Aquesta geometria ha permès la realització del trap LC de forma distribuïda a través d’un ressonador CLL. El principi de disseny de l’antena està basat en la introducció d’aquest ressonador CLL amb freqüència de ressonància situada entre les dos bandes de treball i que junt amb l’ajust dels diversos paràmetres que defineixen l’antena han permès obtenir més 1 GHz d’ample de banda a la freqüència de 5 GHz.

Design of Novel Frequency Generation Circuit with Application to Ultra-Wideband Distributed Oscillators

Given the urgence of a new paradigm in wireless digital trasmission which should allow for higher bit rate, lower latency and tigher delay constaints, it has been proposed to investigate the fundamental building blocks that at the circuital/device level, will boost the change towards a more efficient network architecture, with high capacity, higher bandwidth and a more satisfactory end user experience. At the core of each transciever, there are inherently analog devices capable of providing the carrier signal, the oscillators. It is strongly believed that many limitations in today's communication protocols, could be relieved by permitting high carrier frequency radio transmission, and having some degree of reconfigurability. This led us to studying distributed oscillator architectures which work in the microwave range and possess wideband tuning capability. As microvave oscillators are essentially nonlinear devices, a full nonlinear analyis, synthesis, and optimization had to be considered for their implementation. Consequently, all the most used nonlinear numerical techniques in commercial EDA software had been reviewed. An application of all the aforementioned techniques has been shown, considering a systems of three coupled oscillator ("triple push" oscillator) in which the stability of the various oscillating modes has been studied. Provided that a certain phase distribution is maintained among the oscillating elements, this topology permits a rise in the output power of the third harmonic; nevertheless due to circuit simmetry, "unwanted" oscillating modes coexist with the intenteded one. Starting with the necessary background on distributed amplification and distributed oscillator theory, the design of a four stage reverse mode distributed voltage controlled oscillator (DVCO) using lumped elments has been presented. All the design steps have been reported and for the first time a method for an optimized design with reduced variations in the output power has been presented. Ongoing work is devoted to model a wideband DVCO and to implement a frequency divider.

Engineering the thermal emission of macroporous silicon

Todos los cuerpos emiten luz espontaneamente al ser calentados. El espectro de radiacion es una funcion de la temperatura y el material. Sin embargo, la mayoria de los materiales irradia, en general, en una banda espectral amplia. Algunas matereiales, por el contrario, son capaces de concentrar la radiacion termica en una banda espectral mucho mas estrecha. Estos materiales se conocen como emisores selectivos y su uso tiene un profundo impacto en la eficiencia de sistemas sistemas tales como iluminacion y conversion de energia termofotovoltaica. De los emisores selectivos se espera que sean capaces de operar a altas temperaturas y que emitan en una banda espectral muy concisa. Uno de los metodos mas prometedores para controlar y disenar el espectro de emision termico es la utilizacion de cristales fotonicos. Los cristales fotonicos son estructuras periodicas artificiales capaces de controlar y confinar la luz de formas sin precedentes. Sin embargo, la produccion de dichas estructuras con grandes superficies y capaces de soportar altas temperaturas sigue siendo una dificil tarea. Este trabajo esta dedicada al estudio de las propiedades de emision termica de estructuras 3D de silicio macroporoso en el rango espectral mid-IR (2-30 m). En particular, este trabajo se enfoca en reducir la elevada emisividad del silicio cristalino. Las muestras estudiadas en este trabajo tienen una periodicidad de 4 m, lo que limitan los resultados obtenidos a la banda del infrarrojo medio, aunque estructuras mucho mas pequenas son tecnologicamente realizables con el metodo de fabricacion utilizado. Hemos demostrado que el silicio macroporoso 3D puede inhibir completamente la emision termica en su superficie. Mas aun, esta banda se puede ajustar en un amplio margen mediante pequenos cambios durante la formacion de los macroporos. Tambien hemos demostrado que tanto el ancho como la frecuencia de la banda de inhibicion se puede doblar mediante la aplicacion de tecnicas de postprocesado adecuadas. Finalmente hemos mostrado que es posible crear bandas de baja emisividad arbitrariamente anchas mediante estructuras macroporosas aperiodicas.

Nuclear relaxation contribution to static and dynamic (infinite frequency approximation) nonlinear optical properties by means of electrical property expansions: Application to HF, CH4, CF4, and SF6

Electrical property derivative expressions are presented for the nuclear relaxation contribution to static and dynamic (infinite frequency approximation) nonlinear optical properties. For CF4 and SF6, as opposed to HF and CH4, a term that is quadratic in the vibrational anharmonicity (and not previously evaluated for any molecule) makes an important contribution to the static second vibrational hyperpolarizability of CF4 and SF6. A comparison between calculated and experimental values for the difference between the (anisotropic) Kerr effect and electric field induced second-harmonic generation shows that, at the Hartree-Fock level, the nuclear relaxation/infinite frequency approximation gives the correct trend (in the series CH4, CF4, SF6) but is of the order of 50% too small

Bands width, credibility and exchange risk: Lessons from the EMS experience

This paper presents an analysis of the credibility of the EMScurrencies that covers the period before and after the increase in thebands of fluctuation. Our credibility indicator is based on the inferredprobabilities derived from the estimation of a Markov-switching model(Hamilton (1989)) applied to the expected rate of depreciation. Theresults show that, for most of the currencies, credibility has improved,at least transitorily, after the increase in the bands. However, for allcurrencies, the credibility measured by the indicator proposed in thispaper has been eroded recently even with the widened bands.

Editorial: Language, frequency and bibliometric indexes

This editorial examines the actions undertaken in number 5 and announces two important changes for the numbers 6 and 7, namely frequency and languages. Furthermore, the use of some bibliometric indicators, such as impact factor and refusal rate, is critically analyzed.