Engineering Fragile Topology in Photonic Crystals: Topological Quantum Chemistry of Light

In recent years, there have been rapid advances in the parallel fields of electronic and photonic topological crystals. Topological photonic crystals in particular show promise for coherent transport of light and quantum information at macroscopic scales. In this work, we apply for the first time the recently developed theory of "Topological quantum chemistry" to the study of band structures in photonic crystals. This method allows us to design and diagnose topological photonic band structures using only group theory and linear algebra. As an example, we focus on a family of crystals formed by elliptical rods in a triangular lattice. We show that the symmetry of Bloch states in the Brillouin zone can determine the position of the localized photonic wave packets describing groups of bands. By modifying the crystal structure and inverting bands, we show how the centers of these wave packets can be moved between different positions in the unit cell. Finally, we show that for shapes of dielectric rods, there exist isolated topological bands which do not admit a well-localized description, representing the first physical instance of "fragile" topology in a truly noninteracting system. Our work demonstrates how photonic crystals are the natural platform for the future experimental investigation of fragile topological bands.Comment: v1. 4 pages + references main text, 5+epsilon page supplementary material v2. Published version, 4pgs + references. Supplemental material available at https://doi.org/10.1103/PhysRevResearch.1.03200

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

Service-learning as an innovative and useful teaching method for tourism studies

This paper explores two emerging issues in tourism education: sustainability and studentcentered service learning. The concept of sustainability referring to strategies for maintaining economic, social/cultural, and environmental viability of a business or location, is relevant in any economic sector. However, sustainability is even more important in the tourism sector because tourism is a primary revenue generator in 83% of the countries of the world. Additionally, implementation of sustainable practices in tourism can be a vehicle for educating many cultures around the world in the concept of sustainability. Nowadays, the concept of sustainability is infrequently addressed in by educational institutions offering degrees in tourism studies. However, to meet the needs society, companies, and future generations of tourism managers and professionals, educators must address this important issue as it applies to tourism development. Student-centered service learning methodologies are needed in European and also American Education Institutions to help the students develop the competecences they need in a changing labor market. Service learning accomplishes two goals: 1) educating students for their profession and 2) preparing them to be engaged, ethical citizens (Flannery and Pragman 2008). The use of service learning in business curriculum has become more common since mid 1990’s and is actively supported by business educators who believe that it not only does furthers the mission of the universities to develop students’ business skills, use critical thinking, and ability to solve problems in authentic situations, but also infuses social responsibility and ethics (Flannery and Progman, 2008). One of the basic constituents of service learning is that it occurs within a community with other students and community partners. Another important feature of service learning is that it can include a variety of teaching methodologies such as class lectures, discussion, assigned readings, independent research, collaborative projects, and reflections (Cook, 2008). Considering the benefits of student-centered service learning and the need to prepare tourism professionals with a clear understanding of the concept of sustainability, the purpose of this presentation is to outline the process of designing and implementing curriculum. Examples of student-centered service learning courses with a focus on sustainability will be provided

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