La participación voluntaria en situaciones de emergencia

El desastre ecológico sufrido en las costas gallegas tras el hundimiento del Prestige generó un cambio de actitud, hacia la participación activa, en la defensa del medio ambiente. Sin embargo, las acciones llevadas a cabo para paliar los efectos del fuel pusieron de manifiesto deficiencias en la organización de estas intervenciones. En buena medida, pudieron deberse al desconocimiento de los mecanismos de actuación y de la labor que habrían de desempeñar las personas voluntarias. Este hecho motivó la realización del presente estudio, en el que se pretendía valorar la participación voluntaria ante emergencias desde la perspectiva ciudadanaThe ecological disaster, which occurred at the Galician coast after the collapse of the Prestige, generated a change of attitude towards the active participation in the defense of the environment. Nevertheless, the actions implemented to overcome the effects of the oil spill showed deficiencies in the organization of this type of tasks. This could mainly be due to the ignorance of the mechanisms of action and of the work to be developed by the volunteers. This fact motivated the accomplishment of the current study with the aim of analyzing the participation of volunteers in emergency situations from the citizens' point of vie

From urea to melamine cyanurate: Study of a class of thermal condensation routes for the preparation of graphitic carbon nitride

Producción CientíficaThis work presents a survey of the intermediates in the well-known thermal synthesis of graphitic carbon nitride from urea. The analysis of the crystalline phases depicts a successive transformation of the precursor into different substances previously used as starting reactants, whereby melamine cyanurate arises as the ultimate precursor of a class of thermal condensation routes to obtain graphitic carbon nitride. The study of the optical properties of the synthesized materials evidences the simultaneous production of an amorphous phase with a significant presence of melon oligomers. These results are also supported by the further characterization of the materials performed using THz-TDS, FT-IR, HRTEM, and XPS techniques, and by theoretical studies conducted using semi-empirical quantum chemistry methods.Junta de Castilla y León (grant VA296P18)Ministerio de Ciencia, Innovación y Universidades (grant PID2020-320 119418GB-I00

A Physical optics simulator for multireflector THz imaging systems

This article presents a physical optics-based simulator for the analysis of terahertz (THz) imaging systems. The simulation starts by calculating the electromagnetic interactions inside the multireflector system and the incident field that the focusing system creates on the target under inspection. In a second step, the electric field that the modeled target scatters back to the system receiver, is also calculated. This allows to predict the imaging behavior of the system for different targets before manufacturing. The simulator results are validated by using measurements from an existing 300-GHz standoff imaging system. This contribution aims to help in the development of better imaging systems for security applications in the near future.Atlantic Research Center for Information and Communication TechnologiesMinisterio de Economía y Competitividad | Ref. TEC2015-65353-RMinisterio de Economía y Competitividad | Ref. TEC2015-73908-JINAgencia Estatal de Investigación | Ref. TEC2017-87061-C3-1-RXunta de Galicia | Ref. GRC2015/01

Comparison of the activities of C2N and BCNO towards Congo red degradation

An n-type organic carbon nitride semiconductor, C2N, was synthesized by the pyrolysis of uric acid, and its properties were investigated by scanning electron and transmission electron microscopies, X-ray powder diffraction, and vibrational, UV-visible and X-ray photoelectron spectroscopies. This novel material, composed of crystalline flakes, featured a broad absorption centered at 700¿nm, possibly due to charge transfer, and a 2.49¿eV band gap. Its catalytic performance was assessed for the treatment of effluents with the diazo dye Congo red, comparing it with that of boron carbon nitrogen oxide, BCNO. Both wide band gap semiconductors exhibited decolorizing activity in the dark, although the mechanisms were different and were not photocatalytic: BCNO was more effective towards the adsorption-coordination due to the presence of B-O, while C2N was effective towards the adsorption and the advancement of the oxidation reaction. Their kinetic constants (0.19 and 0.02 min-1 for BCNO and C2N, respectively) were comparable to those of intermetallic compounds studied for azo dyes degradation in dark conditions. In view of the high color removal efficiency (97% after 20¿min) and good reusability of BCNO, this study suggests a potential application of this catalyst for wastewater treatment, alone or in combination with C2N

Nitrogen-carbon graphite-like semiconductor synthesized from uric acid

A new carbon-nitrogen organic semiconductor has been synthesized by pyrolysis of uric acid. This layered carbon-nitrogen material contains imidazole-, pyridine (naphthyridine)- and graphitic-like nitrogen, as evinced by infrared and X-ray photoelectron spectroscopies. Quantum chemistry calculations support that it would consist of a 2D polymeric material held together by hydrogen bonds. Layers are stacked with an interplanar distance between 3.30 and 3.36 Å, as in graphite and coke. Terahertz spectroscopy shows a behavior similar to that of amorphous carbons, such as coke, with non-interacting layers. This material features substantial differences from polymeric carbon nitride, with some characteristics closer to those of nitrogen-doped graphene, in spite of its higher nitrogen content. The direct optical band gap, dependent on the polycondensation temperature, ranges from 2.10 to 2.32 eV. Although in general the degree of crystallinity is low, in the material synthesized at 600 °C some spots with a certain degree of crystallinity can be found

La participación voluntaria en situaciones de emergencia

El desastre ecológico sufrido en las costas gallegas tras el hundimiento del Prestige generó un cambio de actitud, hacia la participación activa, en la defensa del medio ambiente. Sin embargo, las acciones llevadas a cabo para paliar los efectos del fuel pusieron de manifiesto deficiencias en la organización de estas intervenciones. En buena medida, pudieron deberse al desconocimiento de los mecanismos de actuación y de la labor que habrían de desempeñar las personas voluntarias. Este hecho motivó la realización del presente estudio, en el que se pretendía valorar la participación voluntaria ante emergencias desde la perspectiva ciudadanaThe ecological disaster, which occurred at the Galician coast after the collapse of the Prestige, generated a change of attitude towards the active participation in the defense of the environment. Nevertheless, the actions implemented to overcome the effects of the oil spill showed deficiencies in the organization of this type of tasks. This could mainly be due to the ignorance of the mechanisms of action and of the work to be developed by the volunteers. This fact motivated the accomplishment of the current study with the aim of analyzing the participation of volunteers in emergency situations from the citizens' point of vie

Solar light-driven reduction of crystal violet by a composite of g-C3N4, beta-Ag2Se, gama-Fe2O3 and graphite

In this work, a new g-C3N4-based Z-scheme with ¿-Fe2O3 and ß-Ag2Se both n-type semiconductors, and graphite to favor electron exchange is presented. The composite material was studied by XRD, FTIR, UV-Vis, TEM, XPS, TGA, DSC and TOF-SIMS, and the ability of this photocatalytic system to act as a photo-reductant was assessed using crystal violet (CV+) dye. Solar light driven photo-reduction of CV+ in the presence of tri-sodium citrate evidenced a synergistic enhancement of the activity of the composite toward reduction, with ~20 times higher conversion rates per unit of surface area than those of g-C3N4. Photo-oxidation experiments under Xe lamp irradiation in the presence of H2O2 also showed that the AgFeCN composite featured a higher activity (~8×) than g-C3N4. This Z-scheme may deserve further study as a photo-reductant to obtain hydrogen or hydrogenated compounds. Moreover, the use of CV+ may represent a facile procedure that can aid in the selection of new photocatalysts to be used in hydrogen production

Single and dual reflectarray configurations for multibeam satellite antennas in Ka-band

This contribution proposes the use of single and dual reflectarray configurations to provide multi-spot coverage in Ka-band from a geostationary satellite, using a smaller number of apertures and feeds than conventional reflector systems. First, a 1.8-m parabolic reflectarray antenna has been designed to produce multiple spot beams through the generation of two beams per feed in orthogonal circular polarization (CP) at Tx and Rx frequencies. Moreover, a dual RA configuration has been designed to produce two spot beams in orthogonal CP from a single feed in dual linear polarization (LP). The simulated results are compared for the two designed antennas, showing the feasibility of both configurations and their potential to be used for multiple beam applications in Ka-band

An approach for valid covariance estimation via the Fourier series

The use of kriging for construction of prediction or risk maps requires estimating the dependence structure of the random process, which can be addressed through the approximation of the covariance function. The nonparametric estimators used for the latter aim are not necessarily valid to solve the kriging system, since the positive-definiteness condition of the covariance estimator typically fails. The usage of a parametric covariance instead may be attractive at first because of its simplicity, although it may be affected by misspecification. An alternative is suggested in this paper to obtain a valid covariance from a nonparametric estimator through the Fourier series tool, which involves two issues: estimation of the Fourier coefficients and selection of the truncation point to determine the number of terms in the Fourier expansion. Numerical studies for simulated data have been conducted to illustrate the performance of this approach. In addition, an application to a real environmental data set is included, related to the presence of nitrate in groundwater in Beja district (Portugal), so that pollution maps of the region are generated by solving the kriging equations with the use of the Fourier series estimates of the covariance.Universidade do Minho. Centro de Investigação de Matemática (CMAT)Fundação para a Ciência e a Tecnologia (FCT