Educando para un futuro sostenible: una aportación desde las clases de ciencias de la ESO

Se presenta una propuesta de organización de las clases de ciencias en la ESO que permite estudiar algunos de los problemas que caracterizan la crisis social y ecológica que vivimos, así como las medidas necesarias para solucionarlos. Esta orientación hacia la educación para la sostenibilidad intenta responder a los diferentes llamamientos que desde diferentes ámbitos se han venido haciendo a los educadores, especialmente a la Década de la Educación para un Futuro Sostenible, instaurada por la ONU (2005-2014)

Mixed-Valence Lanthanide-Activated Phosphors: Invariance of the Intervalence Charge Transfer (IVCT) Absorption Onset across the Series

This document is the Accepted Manuscript version of a Published Work that appeared in final form in The Journal of Physical Chemistry C, © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see: https://pubs.acs.org/doi/10.1021/acs.jpcc.9b11084Recently, direct evidence was given for the existence of intervalence charge transfer (IVCT) states of Eu2+/Eu3+ pairs in Eu-doped fluorite hosts and their signature in absorption spectra was characterized [ J. Phys. Chem. Lett. 2019, 10, 1851]. Here we show, by means of multiconfigurational ab initio calculations, that the IVCT absorptions of all 2+/3+ mixed valence lanthanides doped in CaF2 start basically at the same energy. This is rationalized with a simplified model of IVCT absorptions. Emissions above that energy are expected to be partly or totally quenched when 2+/3+ pairs are formed. On the basis of this finding and existing calculations, we report expected IVCT absorptions of mixed valence lanthanides doped in several fluoride, oxide, and sulfide hostsThis work was partially supported by Ministerio de Economía y Competitividad, Spain (Dirección General de Investigación y Gestión del Plan Nacional de I+D+i, MAT2017-83553-P

The influence of copolymer composition on PLGA/nHA scaffolds´ cytotoxicity and in vitro degradation

The influence of copolymer composition on Poly(Lactide-co-Glycolide)/ nanohydroxyapatite (PLGA/nHA) composite scaffolds is studied in the context of bone tissue engineering and regenerative medicine. The composite scaffolds are fabricated by thermally-induced phase separation and the effect of bioactive nanoparticles on their in vitro degradation in phosphate-buffered solution at 37 °C is analyzed over eight weeks. The indirect cytotoxicity evaluation of the samples followed an adaptation of the ISO 10993-5 standard test method. Based on the measurement of their molecular weight, molar mass, pH, water absorption and dimensions, the porous scaffolds of PLGA with a lower lactide/glycolide (LA/GA) molar ratio degraded faster due to their higher hydrophilicity. All of the samples without and with HA are not cytotoxic, demonstrating their potential for tissue engineering applications.SGIker (UPV/EHU, MICINN, GV/EJ, ERDF and ESF) is really appreciated. This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2013 and Grant SFRH/BD/111478/2015 (S.R). The authors acknowledge funding by the Spanish Ministry of Economy and Competitiveness (MINECO) through the project MAT2016-76039-C4-3-R (Agencia Estatal de Investigación(AEI)/FEDER, Unión Europea(UE))info:eu-repo/semantics/publishedVersio

Observation of isotropic-dipolar to isotropic-Heisenberg crossover in Co-and Ni-substituted manganites

High-precision ac susceptibility data have been taken on the La0.7Pb0.3Mn1?y (Co, Ni)yO3 (y = 0, 0.1, 0.2 and 0.3) manganite system over a wide range of amplitudes and frequencies of the ac driving field in a temperature range that embraces the critical region near the ferromagnetic (FM)?paramagnetic (PM) phase transition (occurring at the Curie point TC). Elaborate data analysis was performed that (i) enabled the first observation of a crossover from a three-dimensional (3D; d = 3) isotropic long-range dipolar asymptotic critical behavior to a d = 3 isotropic short-range Heisenberg critical regime as the temperature is raised from TC in the compositions y 6= 0 (no such crossover is observed in the parent compound, y = 0) and (ii) brought out clearly the importance of dipole?dipole interactions between the eg electron spins and/or between eg?t2g electron spins in establishing long-range FM order in the insulating state. The final charge and spin states of Co and Ni ions, substituting for the Mn3+ and/or Mn4+ ions, are arrived at by using a scenario of substitution that is consistent not only with the present results but also with the previously published structural, thermo-gravimetric, bulk magnetization, dc magnetic susceptibility and electrical resistivity data on the same system. The marked similarity seen between the magnetic behavior of the manganite system in question and the quenched random-exchange ferromagnets, within and outside the critical region, suggests that the percolation model forms an adequate description of the FM metal-to-PM insulator transition

Evidence for two disparate spin dynamic regimes within Fe-substituted La0.7 Pb0.3 (Mn1-x Fex) O3 (0≤x≤0.2) colossal magnetoresistive manganites: Neutron spin-echo measurements

10 págs.; 7 figs.; 1 tab. ; PACS number s : 75.25. z, 75.30.Ds, 75.40.Gb, 75.47.GkThe spin dynamics of substituted colossal magnetoresistive (CMR) manganites of general formula La0.7 Pb0.3 (Mn1-x Fex) O3, 0≤x≤0.2 is investigated by means of neutron spin-echo measurements. Substitution of Mn by Fe leads to a strong decrease of the temperature of macroscopic magnetic long-range ordering with a concomitant enhancement of the CMR effect. For x=0.2, a long-range-ordered state is not achieved as a result of the increase in antiferromagnetic interactions brought forward by Fe+3 -Mn couplings. The results display two relaxations having well separated decay constants. A fast process with a relaxation time of about 10 ps within the paramagnetic phase is found for all compositions. It shows a remarkably strong dependence with temperature and sample composition as the apparent activation energy for spin diffusion as well as the preexponential term exemplify. The physical origin of such a fast relaxation is assigned to heavily damped or overdamped spin waves (spin diffusion) on the basis of some signatures of excitations having finite frequencies found for the parent compound La0.7 Pb0.3 Mn O3 at temperatures just below Tc, together with preliminary data on the effect of Fe doping on the stiffness constant. A slower relaxation is present for all compositions. Its temperature dependence follows the behavior of the macroscopic magnetization, and its intensity grows within the ordered ferromagnetic state. Its physical origin is ascribed to collective reorientation of nanoscale ferromagnetic domains on the basis of the wave-vector dependence of its relaxation rate and amplitude. © 2007 The American Physical Society.J.G. and J.M.B. thank the Spanish Ministerio de Educacion y Ciencia for financial support under research Grant No. MAT2005-0686-C04-03. F.J.B. and P.R. acknowledge financial support from the European Commission through NMI3 to carry out preliminary measurements at the FZJ facilities.Peer Reviewe

3D cytocompatible composites of PCL/Magnetite

A study of Magnetite (Fe3O4) as a suitable matrix for the improved adhesion and proliferation of MC3T3-E1 pre-osteoblast cells in bone regeneration is presented. Biodegradable and magnetic polycaprolactone (PCL)/magnetite (Fe3O4) scaffolds, which were fabricated by Thermally Induced Phase Separation, are likewise analyzed. Various techniques are used to investigate in vitro degradation at 37 °C, over 104 weeks, in a phosphate buffered saline (PBS) solution. Magnetic measurements that were performed at physiological temperature (310 K) indicated that degradation neither modified the nature nor the distribution of the magnetite nanoparticles. The coercive field strength of the porous matrices demonstrated ferromagnetic behavior and the probable presence of particle interactions. The added nanoparticles facilitated the absorption of PBS, with no considerable increase in matrix degradation rates, as shown by the Gel Permeation Chromatography (GPC) results for Mw, Mn, and I. There was no collapse of the scaffold structures that maintained their structural integrity. Their suitability for bone regeneration was also supported by the absence of matrix cytotoxicity in assays, even after additions of up to 20% magnetite.This work was supported by the Spanish Ministry of Economy and Competitiveness (MINECO) through the project MAT2016-76039-C4-3-R (AEI/FEDER, UE) and from the Basque Government Industry Department under the ELKARTEK, HAZITEK and PIBA programs. Supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2013, project POCI-01-0145-FEDER-028237 and grant SFRH/BD/111478/2015 (S.R.) is acknowledged.Technical and human support provided by SGIker (UPV/EHU, MICINN, GV/EJ, ERDF and ESF) is gratefully appreciated. The authors acknowledge funding by the Spanish Ministry of Economy and Competitiveness (MINECO) through the project MAT2016-76039-C4-3-R (AEI/FEDER, UE) and from the Basque Government Industry and Education Department under the ELKARTEK and HAZITEK and PIBA (PIBA-2018-06) programs. Supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2013, project POCI-01-0145-FEDER-028237 and grant SFRH/BD/111478/2015 (S.R.) is acknowledged