Tecnologías y Aprendizaje. Avances en Iberoamérica

El principio de la tecnología de Objetos de Aprendizaje (OA) consiste en producir unidades de aprendizaje, etiquetadas por medio de metadatos para su fácil almacenamiento, búsqueda y recuperación. Para implementar este modelo ha sido necesaria la especificación de estándares que faciliten la reusabilidad y que normen la gestión de estos contenidos en los Repositorios de Objetos de Aprendizaje (ROA). Simultáneamente se han generado múltiples Herramientas de Autor (HA) cuya finalidad es facilitar la producción de material digital. Ante la gran cantidad de HA disponibles en el mercado es necesario identificar aquellas que permiten el soporte de los estándares propios de los OA y que facilitan de esta forma obtener una mayor producción; la cual es necesaria para mantener los ROA existentes. En este trabajo se hace una selección de los criterios técnicos y didácticos necesarios para evaluar las HA que facilitan la producción de OA y que además estén al alcance de los docentes mexicanos, con la finalidad de promover la producción de OA que alimenten a los ROA ya instalados en el país

Cation distribution of cobalt ferrite electrosynthesized nanoparticles. A methodological comparison

The present work seeks to analyse the structural and magnetic properties of cobalt ferrite nanoparticles obtained by electrochemical synthesis by high-resolution transmission electronic microscopy (HRTEM), X-ray absorption spectroscopy (XAS), Mössbauer spectroscopy (MS), neutron diffraction (ND) and SQUID magnetometer. The cationic distribution is analyzed by different techniques. The inversion degree determined by the most accurate measurements was 0.73(1), and the formula for the nanoparticles therefore was (↑Co0.27Fe0.73)[↓Co0.73Fe1.27]O4. The magnetic moment found from DC and Mössbauer spectroscopy measurements was 3.8(3) μB, and the coercivity was 7870 Oe at 100 K.This work is supported by the MINECO/FEDER Project MAT2015- 67557-C2-2-P. The authors are grateful to the Institut Laue Langevin and the Spanish CRG D1B for the neutron beam-time allocated (experiment codes 5-31-2259 and CRG-1940; https://doi.org/10. 5291/ILL-DATA.5-31-2259) and to the SpLine CRG beamline staff at ESRF for assistance during XAS experiments

Novel, simple, and environmentally safe method for wastewater pollutant removal

In this work, a new methodology has been developed for the elimination of cobalt, nickel and a mixture of both metals from synthetic wastewater in a continuous way. This methodology consists of the electrochemical formation of ferrites of these metals through the oxidation of iron sheets and the reduction of water. Two critical process parameters, current densities and initial pollutant concentration, were analysed. An initial batch prototype resulted in efficiencies on the order of 98% under conditions of applied densities of 50 mA/cm2 and concentrations of both metals of until 100 ppm of the ions. The obtained particles have been characterized by ꭕ-ray diffraction to determine the formation of ferrites without the appearance of secondary phases. The formed particle sizes are approximately 30 nm, with hemispherical or flower-like shapes. A flow system prototype was designed for the recirculation of the solution with 100 ppm of both contaminating metals, obtaining approximately 90% recovery with an easy magnetic harvestingThis research was funded by the Spanish Ministry of Science, Innovation, and Universities under projects PGC2018-095642-B-I00 and PGC2018-096016-B-I00. L.G. acknowledges financial support from the Ramón y Cajal program (RYC-2014-15512). E. Mazario. acknowledges financial support from the Madrid Government (Comunidad de Madrid Spain) under the Multiannual Agreement with Universidad Autonoma de Madrid in the line of action encouraging youth research doctors, in the context of the V PRICIT (Regional Programme of Research and Technological Innovation), (SI1-PJI-2019-00366). L. Duque acknowledges for the contract obtained from Ayudas para la contrataciónde ayudantes investigación y técnicos de laboratorio of Comunidad Autónoma de Madrid. The authors would like to acknowledge the use of the Advanced Microscopy Laboratory (INA-Universidad de Zaragoza) for access to their instrumentation and expertis

UWE en Sistema de Recomendación de Objetos de Aprendizaje. Aplicando Ingeniería Web: Un Método en Caso de Estudio

La Ingeniería Web propone nuevos métodos para el diseño de aplicaciones que se ejecutan en esta nueva plataforma que es la World Wide Web. Uno de estos métodos es UWE (UML Web Engineering), el cual aprovecha la notación estándar del UML e incorpora elementos que son propios del desarrollo Web. En este artículo se presenta un caso de estudio para el diseño de un Sistema de Recomendación de Objetos de Aprendizaje, donde el modelado básico se realiza mediante el UWE. Se modela una aplicación Web que permite a los usuarios realizar la composición de los Objetos de Aprendizaje que el mismo sistema le recomienda al usuario previo análisis de las características tanto del mismo como de los Objeto de Aprendizaje almacenados en un repositorio especializado llamado AGORA

Ofloxacin degradation over nanosized Fe3O4 catalyst viathermal activation of persulfate ions

In this work, an Fe3O4 catalyst was synthetized in a single step via electrochemical synthesis. The Fe3O4 catalyst was used to evaluate the degradation of Ofloxacin (OFX) using a heterogeneous advanced oxidation process with sodium persulfate (PS). PS activation was successfully achieved via thermal conventional heating directly and subsequently applied for the degradation of OFX. The degradation kinetics were studied under different conditions, such as catalyst and oxidant concentration and temperature. The results show that a higher reaction temperature, catalyst and initial PS dose strongly influence the degradation efficiency. Thermal activation of persulfate was tested at 20, 40 and 60 °C. At 60 °C, the half-time of OFX was 23 times greater than at 20 °C, confirming the activation of persulfate. Mineralization studies also showed that under optimized conditions (20 mM of persulfate, 1 g/L catalyst and 100 mg/L OFX), a 66% reduction in organic matter was observed, in contrast to that obtained at 40 °C and 20 °C, which was null. The reusability, as tested through the fourth reuse cycle, resulted in a 38% reduced degradation efficiency when comparing the first and last cycle. Furthermore, the electrosynthesized catalyst presented similar degradation efficiencies in both real water and MilliQ, mainly because of the (Formula presented.) generation at high (Formula presented.) concentrations that takes place in (Formula presented.) contaminated waterThis research was funded by the Madrid Government (Comunidad de Madrid-Spain) under the Multiannual Agreement with Universidad Autónoma de Madrid in the line of action encouraging youth research doctors, in the context of the V PRICIT (Regional Programme of Research and Technological Innovation), (SI1-PJI-2019-00366), and by the Spanish Ministry of Science and In-novation under project no. PID2021-123431OB-I0

Electrofenton with reticular vitreous carbon and iron oxide nanoparticles for dye removal: a preliminary study

In this work, an RVC electrode coated with magnetic iron oxide nanoparticles was used for the degradation of methylene blue as a model dye. The electrofenton process was carried out by the reduction of oxygen dissolved in the electrolyte on the modified RVC electrode to produce hydrogen peroxide. The presence of the magnetite/maghemite nanoparticles in the structure produces the formation of OH∙ radicals that oxidize methylene blue. The RVC/coated was prepared by two different methodologies: Methodology A: by immersion of the electrode in a solution saturated with magnetite nanoparticles; and Methodology B: by electrochemical synthesis. Scanning electron microscopy, X-ray diffraction and Mössbauer spectroscopy shows a uniform coating of the electrode. The Mössbauer spectroscopy determines the only presence of maghemite using methodology A and the presence of 60% of magnetite and a 40% of maghemite when methodology B was used. The dipping methodology is the one that has provided the best results in the electrofenton degradation of methylene blue, obtaining a 100% removal after 35 min, applying a current of 100 mA in a 20 mg L−1 solution of methylene blue, and a concentration of 50 mM sodium sulfat

Improved Suzuki–Miyaura reaction conversion efficiency using magnetic nanoparticles and inductive heating

The use of magnetic nanoparticles in C–C coupling reactions enables the facile recovery of the catalyst under environmentally friendly conditions. Herein, the synthesis of Pd/Fe@Fe3O4 nanoparticles by the reduction of Pd2+ and oxidation of Fe on the surface of preformed Fe@Fe3O4 is reported. The nanoparticles were characterized using a variety of analytical techniques (transmission electron microscopy, Mössbauer spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction) to determine their size, structure, and chemical composition. The catalytic efficiency of these nanoparticles in classical Suzuki–Miyaura coupling reactions was investigated. The nanoparticles achieved high catalytic activity with the application of local heating by an alternating magnetic field. An investigation was conducted at identical temperatures to compare global heating with the application of an external magnetic field; magnetic heating demonstrated excellent substrate conversion in lesser time and at a lower temperature. The catalyst could also be recycled and reused three times, with ~ 30% decrease in the substrate conversion, which is most likely due to the agglomeration of the Pd nanoparticles or poisoning of the Pd catalyst. This approach, which takes advantage of the catalytic activity and magnetic susceptibility of magnetic nanoparticles, can be applied to several organic transformations to improve their efficiencyWe are grateful for financial support provided by the Government of Spain through project PGC2018-095642-B-I00. In addition, A. Villacampa and L. Duque acknowledge the Community of Madrid for Predoctoral contracts PEJD-2019-PRE/IND-15356 and PEJ-2019-AI/IND-12506, respectively, co-financed by the European Social Fund through the Youth Employment Operational Program and the Youth Employment Initiative (YEI

Highly efficient Cu2O@CuxFeyO4 nanohybrid catalyst for the degradation of emerging pollutants

Cu2O@CuxFeyO4 nanohybrids (NHs) have been electrosynthesized by a simple and environmentally safe method to be used as catalysts for tetracycline degradation. NHs shown an average diameter of 14(5) nm and exhibit high crystallinity with spherical morphology. XPS results demonstrate a cuprite-enriched surface; meanwhile, the inner layer is composed by a nonstoichiometric copper spinel structure. The degradation has been monitored by UV–Visible spectroscopy, TOC analysis, and HPLC. The electrochemical characterization demonstrates the synergetic effect of Fe3+/Fe2+ and Cu2+/Cu+ coupling to enhance the activation of persulfate. This effect results in a greater degradation efficiency of NHs than other catalysts, namely, CuxOy, Fe3O4, and a mixture of both and Cu2O. It has been found that a previous adsorption stage before degradation does not improve the elimination of the pollutant and its length in time, with a TOC reduction of 72.6 % in 2 h. Conversely, conducting the oxidative process in a direct step resulted in a more rapid and efficient process, 82.3 % of reduction in 1 h. Through this method, the catalyst reutilization resulting in a decrease of 50 % in TOC degradation from the third use, while the TCY concentration degraded remains almost constant. This reduced catalytic activity with use might be a consequence of 1) the absence of the single Cu-oxide layer due to the leaching of mainly Cu ions but also Fe ions during the degradation tests, and, 2) the passivation of the outermost layer, mainly covered by C–O species and OH groups, which hinders access to active catalyst sitesThis research was funded by the Madrid Government (Comunidad de Madrid-Spain) under the Multiannual Agreement with Universidad Autonoma ´ de Madrid in the line of action encouraging youth research doctors, in the context of the V PRICIT (Regional Programme of Research and Technological Innovation) (SI1-PJI-2019-00366) and by the Spanish Ministry of Science and Innovation under project PID2021- 123431OB-I00. FJP acknowledges financial support from Grant PID2021-126169OB-I00 funded by MCIN/AEI/10.13039/5011000110 33 and by “ERDF A way of making Europe”. The authors would like to acknowledge to L. Gutierrez and the Advanced Microscopy Laboratory (INA-Universidad de Zaragoza) for access to their instrumentation and expertis

Wireless magneto-ionics: voltage control of magnetism by bipolar electrochemistry

Modulation of magnetic properties through voltage-driven ion motion and redox processes, i.e., magneto-ionics, is a unique approach to control magnetism with electric field for low-power memory and spintronic applications. So far, magneto-ionics has been achieved through direct electrical connections to the actuated material. Here we evidence that an alternative way to reach such control exists in a wireless manner. Induced polarization in the conducting material immersed in the electrolyte, without direct wire contact, promotes wireless bipolar electrochemistry, an alternative pathway to achieve voltage-driven control of magnetism based on the same electrochemical processes involved in direct-contact magneto-ionics. A significant tunability of magnetization is accomplished for cobalt nitride thin films, including transitions between paramagnetic and ferromagnetic states. Such effects can be either volatile or non-volatile depending on the electrochemical cell configuration. These results represent a fundamental breakthrough that may inspire future device designs for applications in bioelectronics, catalysis, neuromorphic computing, or wireless communications.Comment: 32 pages, 4 figures, Supplementary Information (9 figures