Multiscale understanding of tricalcium silicate hydration reactions

Tricalcium silicate, the main constituent of Portland cement, hydrates to produce crystalline calcium hydroxide and calcium-silicate-hydrates (C-S-H) nanocrystalline gel. This hydration reaction is poorly understood at the nanoscale. The understanding of atomic arrangement in nanocrystalline phases is intrinsically complicated and this challenge is exacerbated by the presence of additional crystalline phase(s). Here, we use calorimetry and synchrotron X-ray powder diffraction to quantitatively follow tricalcium silicate hydration process: i) its dissolution, ii) portlandite crystallization and iii) C-S-H gel precipitation. Chiefly, synchrotron pair distribution function (PDF) allows to identify a defective clinotobermorite, Ca11Si9O28(OH)2.8.5H2O, as the nanocrystalline component of C-S-H. Furthermore, PDF analysis also indicates that C-S-H gel contains monolayer calcium hydroxide which is stretched as recently predicted by first principles calculations. These outcomes, plus additional laboratory characterization, yielded a multiscale picture for C-S-H nanocomposite gel which explains the observed densities and Ca/Si atomic ratios at the nano- and meso- scales.This work has been supported by Spanish MINECO through BIA2014-57658-C2-2-R, which is co-funded by FEDER, BIA2014-57658-C2-1-R and I3 (IEDI-2016-0079) grants. We also thank CELLS-ALBA (Barcelona, Spain) for providing synchrotron beam time at BL04-MSPD beamline

Anatomías inefables

Ante estas obras de Victoria Diehl es fácil pensar en conocidos modelos anatómicos en cera o en la iconografía de Venus y Evas de las que un vistazo rápido a cualquier libro de historia del arte nos mostraría múltiples variantes. Algo de todo ello hay aquí. Pero también hay algo que hace que los espectadores se detengan a pensar. Algo más allá de lo reconocible que hace que las lenguas del pasado se muevan a un ritmo actual. Hermes, al trasladar sus mensajes los interpreta, los adapta al interlocutor y al medio; los transforma, los traduce, los recrea. Y logra ponernos en movimiento. [...

White dwarf evolutionary sequences for low-metallicity progenitors: The impact of third dredge-up

We present new white dwarf evolutionary sequences for low-metallicity progenitors. White dwarf sequences have been derived from full evolutionary calculations that take into account the entire history of progenitor stars, including the thermally-pulsing and the post-asymptotic giant branch phases. We show that for progenitor metallicities in the range 0.00003--0.001, and in the absence of carbon enrichment due to the occurrence of a third dredge-up episode, the resulting H envelope of the low-mass white dwarfs is thick enough to make stable H burning the most important energy source even at low luminosities. This has a significant impact on white dwarf cooling times. This result is independent of the adopted mass-loss rate during the thermally-pulsing and post-AGB phases, and the planetary nebulae stage. We conclude that in the absence of third dredge-up episodes, a significant part of the evolution of low-mass white dwarfs resulting from low-metallicity progenitors is dominated by stable H burning. Our study opens the possibility of using the observed white dwarf luminosity function of low-metallicity globular clusters to constrain the efficiency of third dredge up episodes during the thermally-pulsing AGB phase of low-metallicity progenitors.Comment: To be published in Astronomy and Astrophysics. 12 pages, 11 figure

El Service-Learning o Aprendizaje-Servicio como método de enseñanza: experiencia de la Pace University (Nueva York) en la creación de Green Maps o Mapas Verdes en el marco del desarrollo sostenible del turismo

El trabajo se centra en el Service-Learning o Aprendizaje-Servicio como método de enseñanza innovador. Como ejemplo de su aplicación presentamos los proyectos internacionales puestos en marcha en los estudios de Turismo de la Pace University (Nueva York) para la creación de green maps o mapas verdes de comunidades locales en el marco del Desarrollo Sostenible del Turismo.This paper focuses on Service-Learning as an innovative teaching method. As an example of its application, we present the international projects initiated by Pace University Tourism students for the creation of Green Maps of local communities in order to contribute towards Sustainable Tourism Development

Life-cycle assessment of the thermal and catalytic pyrolysis over sepiolite of face masks

Since the start of the global COVID-19 pandemic, extensive quantities of face masks have been used and discarded. Most of these masks end up in landfills, causing a high environmental impact and no benefits. However, there are alternative ways to deal with this waste in a more sustainable way. For example, valorisation of face masks through pyrolysis has received special attention because it offers efficient application to produce a liquid oil that can be used as a diesel substitute and a solid char that can be used as an activated carbon substitute after activation. In this context, this study applies the Life-Cycle Assessment methodology to quantify and analyse the environmental impacts of different treatment scenarios based on the pyrolysis of surgical masks and FFP2 masks. It also compares their environmental performance with the conventional practice of landfilling. The scenarios studied include both thermal and catalytic pyrolysis by using sepiolite, a low-cost material abundant in Spain. Data on the pyrolysis process were obtained from laboratory experiments. It was found that the use of the produced oil as a diesel substitute very significantly reduces the environmental impact in all pyrolysis scenarios. Consequently, the pyrolysis of face masks can reduce the environmental impact caused by the treatment of this waste material. Furthermore, the thermal pyrolysis performs environmentally better than the catalytic pyrolysis. In all scenarios, freshwater ecotoxicity and marine ecotoxicity are the environmental impact categories that cause the highest environmental impact overall

Introduction to the teaching of Spanish to immigrants: didactic and intercultural dimensions

Título, resumen y palabras clave también en inglésResumen basado en el de la publicaciónEl trabajo forma parte de un proyecto I+D del Plan Nacional, titulado La formación de los docentes de español para inmigrantes en diferentes contextos educativos (Referencia: EDU2013-43868-P) en el que se han planteado las necesidades de formación especializada de profesores de español como segunda lengua (EL2) a inmigrantes. El punto de partida ha sido la revisión de algunos conceptos básicos relacionados con la enseñanza del español al colectivo inmigrante desde el prisma de la diversidad. El objetivo principal es la orientación para futuros profesores de español; por lo que, se parte de unas nociones de base descriptiva en las que se cuestionan las dimensiones didácticas e interculturales del tipo de enseñanza. Para ello, se hace una reflexión sobre los conceptos básicos que atañen a la enseñanza del español a inmigrantes en contextos escolares y de adultos alfabetizados (tipos de enseñanza de español como segunda lengua, EL2) y se han apuntado algunas medidas de apoyo lingüístico. Finalmente, se hace una reflexión sobre la diversidad cultural y los factores interculturales que inciden sobre el colectivo educativo con objeto de profundizar en los elementos más notables para la iniciación de los futuros docentes en el campo profesional.ES

“Zombie attack” a new way to teach Chemistry

The Higher Education requires new models which allow training people able to adapt and survive in changing environments. It is based on the use of technologies and the adaptation of knowledge to people. It is about an education according to circumstances, which is adapted to context and virtual behaviour of people. One of the main difficulties that lecturers find in the classroom is how to maintain students' attention and interest in their subject, especially when students also think that the subject is not important for their training. In order to motivate these students, innovation in educational techniques and methodologies, such as experiential learning, are progressively being imposed to and/or coordinated with the traditional ones. Escape Room is a very modern concept in education, based on the development of mental skills for the solution of enigmas and problems. It is a tool to develop the cooperative, cognitive, deductive and logical reasoning skills of the students. In this work, an educational gamification experience based on the escape room concept is presented. The students have 1 hour and 30 minutes to carry out this activity. They will have to solve four puzzles and enigmas that will give them the key to open a treasure chest and finally let them escape from the classroom. Logic, ingenuity and teamwork will allow participants to develop not only chemical competence, but also other basic skills. The story that is told throughout the escape room is a zombie attack: the city has been infected (with a virus) and only the occupants of the room where the activity takes place have not been infected. In addition, they can all protect themselves if they are able to open the chest where the antidote is located. The aim of this activity is to enhance the knowledge acquired throughout the semester as well as the development of skills.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec