Review of Robust Cooperative Spectrum Sensing Techniques for Cognitive Radio Networks

Cognitive radio networks sense spectrum occupancy and manage themselves to operate in unused bands without disturbing licensed users. The detection capability of a radio system can be enhanced if the sensing process is performed jointly by a group of nodes so that the effects of wireless fading and shadowing can be minimized. However, taking a collaborative approach poses new security threats to the system as nodes can report false sensing data to reach a wrong decision. This paper makes a review of secure cooperative spectrum sensing in cognitive radio networks. The main objective of these protocols is to provide an accurate resolution about the availability of some spectrum channels, ensuring the contribution from incapable users as well as malicious ones is discarded. Issues, advantages and disadvantages of such protocols are investigated and summarized.     

Novel Sol–Gel Nano‐Glass–Ceramics Comprising Ln3+‐Doped YF3 Nanocrystals: Structure and High Efficient UV Up‐Conversion

Transparent glass‐ceramics containing Ln³⁺‐doped YF₃ nanocrystals are successfully obtained under adequate thermal treatment of precursor sol–gel glasses for the first time, to the best of our knowledge. Precipitation of YF₃ nanocrystals is confirmed by X‐ray diffraction and high‐resolution transmission electron microscopy images. An exhaustive structural analysis is carried out using Eu³⁺ and Sm³⁺ as probe ions of the final local environment in the nano‐structured glass–ceramic. Noticeable changes in luminescence spectra, related to relative intensity and Stark structure of band components, along with remarkably different lifetime values, allow us to discern between ions residing in precipitated YF₃ nanocrystals and those remaining in a glassy environment. A large fraction of optically active ions is efficiently partitioned into nanocrystals of small size, around 11 nm. Moreover, bright and efficient up‐conversion, including very intense high‐energy emissions in the UV range, due to 4‐ and 5‐infrared photon processes, are achieved in Yb³⁺–Tm³⁺ co‐doped samples. Up‐conversion mechanisms are analysed in depth by means of intensity dependence on sensitiser Yb³⁺ concentration and pump power.     

Spatial Analysis of Metal–PLGA Hybrid Microstructures Using 3D SERS Imaging

The incorporation of gold nanoparticles in biodegradable polymeric nanostructures with controlled shape and size is of interest toward different applications in nanomedicine. Properties of the polymer such as drug loading and antibody functionalization can be combined with the plasmonic properties of gold nanoparticles, to yield advanced hybrid materials. This study presents a new way to synthesize multicompartmental microgels, fibers, or cylinders, with embedded anisotropic gold nanoparticles. Gold nanoparticles dispersed in an organic solvent can be embedded within the poly(lactic‐co‐glycolic acid) (PLGA) matrix of polymeric microstructures, when prepared via electrohydrodynamic co‐jetting. Prior functionalization of the plasmonic nanoparticles with Raman active molecules allows for imaging of the nanocomposites by surface‐enhanced Raman scattering (SERS) microscopy, thereby revealing nanoparticle distribution and photostability. These exceptionally stable hybrid materials, when used in combination with 3D SERS microscopy, offer new opportunities for bioimaging, in particular when long‐term monitoring is required.     

驱动压电PVDF换能器的高频高电压放大器

压电换能器用于NDE（非破坏性评估）应用。PVDF（聚偏氟乙烯）换能器有很多优点．包括大带宽和高灵敏度。这些换能器需要高电压和大带宽的放大器。图1中的电路源于往期的一个设计实例（参考文献1）。电路的工作原理基本相同,但本设计可以在高至500kHz频率下驱动一个2．3nF的容性负载。     

Poincaré Sphere Method for Optimizing the Phase Modulation Response of a Twisted Nematic Liquid Crystal Display

We report an experimental procedure for achieving spatial modulation of the phase of an input wave field with an off-the-shelf twisted nematic liquid crystal display. This method involves illumination of an addressed liquid crystal display (LCD) with circularly polarized light and measurement of the Stokes parameters of the outgoing beam as the applied voltage is changed. The analysis of the distribution of the polarization states in the S₁-S₂ plane suggests a simple way to optimize the liquid crystal phase response by means of a properly oriented quarter wave-plate followed by an analyzer. Laboratory results for a commercial display are presented. A phase modulation depth of 240deg is obtained at 514 nm with a residual intensity variation which is lower than 4%     

3D Printed Microstructures Erasable by Darkness

To advance the applications of direct laser writing (DLW), adaptability of the printed structure is critical, prompting a shift toward printing structures that are comprised of different materials, and/or can be partially or fully erased on demand. However, most structures that contain these features are often printed by complex processes or require harsh developing techniques. Herein, a unique photoresist for DLW is introduced that is capable of printing 3D microstructures that can be erased by exposure to darkness. Specifically, microstructures based on light-stabilized dynamic materials are fabricated that remain stable when continously irradiated with green light, but degrade once the light source is switched off. The degradation and light stabilization properties of the printed materials are analyzed in-depth by time-lapse scanning electron microscopy. It is demonstrated that these resists can be used to impart responsive behavior onto the printed structure, and –critically– as a temporary locking mechanism to control the release of moving structural features.     

Relationship of the Halstead-Reitan Neuropsychological Battery to the Luria-Nebraska Neuropsychological Battery.

Compared the major 14 scores of the Halstead-Reitan Neuropsychological Test Battery with the 14 summary scale scores of the Luria-Nebraska battery to investigate whether the batteries could predict one another and their effectiveness in a sample of 48 brain-damaged and 60 normal patients (mean age of all Ss 39 yrs). Discriminant analysis found both batteries equally effective in identifying brain damage, with hit rates of over 85%. A high degree of relationship between the Luria-Nebraska scale scores and the selected 14 scores of the Halstead-Reitan was found. (12 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Estimacion parametrica Bayesiana no parametrica de funciones de supervivencias con observaciones parcialmente censuradas

Resumen Usando técnicas bayesianas paramétricas se introduce el problema de estimación bayesiana no paramétrica de funciones de supervivencia a partir de muestras censuradas parcialmente por la derecha. Se obtienen estimadores considerando procesos neutrales por la derecha, se dan las expresiones particulares de algunos de eilos y se estudian las propiedades asintóticas desde un punto de vista bayesiano. Finalmente se simula una aplicación a un proceso de Dirichlet. Financiado con el Proyecto de Investigación del Consejo Superior de Investigaciones Cientificas I.D. 603/760 (CAICYT).     

Bronchioalveolar adenocarcinoma associated with a chylous ascites. An unusual case

A case of bronchioloalveolar carcinoma with long evolution associated to chylous is reported. The natural clinical history of the adenocarcinoma follows with an unusual dissemination as an atypical manifestation of lymphatic metastasis.     

Effect of glycerol and corn oil on physicochemical properties of polysaccharide films - A comparative study

The aim of this work was to evaluate the influence of glycerol and corn oil on physicochemical properties of polysaccharide-based films. The polysaccharides used were galactomannan from Gleditsia triacanthos and chitosan. Fourier-transform infrared spectroscopy, differential scanning calorimetry and thermogravimetric analysis were performed, together with determinations of moisture content, solubility, water vapor permeability and mechanical properties. Structure-properties relationships were established, relating the two polysaccharides’ structures with the way they interact with water, other film’s constituents (glycerol and oil) and the resulting properties. The presence of glycerol and corn oil originated a more hydrophilic structure and a decreased affinity of the film matrix to water, respectively, in both polysaccharides. However, the two polysaccharides presented different behaviors in terms of glass transition temperature, water vapor permeability and elongation-at-break that have been related with the particularities of their structure: while for the galactomannan the specific sorption sites for water are the O-H groups, for chitosan those are O-H and/or NH₂ groups.The present work provides insight regarding the physicochemical properties of polysaccharide-based films and established relationships with polymers’ structure, showing that the two polysaccharides studied here have adequate properties to be used as packaging materials for specific food applications.