269 research outputs found
Magnetic susceptibility of insulators from first principles
We present an {\it ab initio} approach for the computation of the magnetic
susceptibility of insulators. The approach is applied to compute
in diamond and in solid neon using density functional theory in the local
density approximation, obtaining good agreement with experimental data. In
solid neon, we predict an observable dependence of upon pressure.Comment: Revtex, to appear in Physical Review Lette
Astrocytes and Inflammatory Processes in Alzheimer’s Disease
A significant increase in inflammation has been shown to be a crucial factor in the progression of the Alzheimer’s disease (AD). Moreover, inflammatory signals are already present in mild cognitive impairment (MCI) patients before they develop AD. The amyloid hypothesis argues that in AD, there is an increase in oxidative stress caused by the accumulation of β-amyloid (Aβ) and that its elimination should be a priority. Also, hyperphosphorylation of the protein TAU occurs, which is characteristic of this disease. In AD oxidative stress processes occur and also inflammation. The basal chronic inflammation produces a cascade of cellular, such as astrocytes and microglial cells, and molecular processes in AD patients. We here have tried to explore the action of the inflammatory process and its implication in the neurodegenerative process of the AD. We can see that the role of Aβ is only one component that gives rise to inflammation, probably mediated by activation of microglia and astrocytes with the goal of getting rid of these brain waste products. In fact, it is related to a greater degree with the progression of the disease and worsening of the symptoms with the increase of phosphorylated TAU in different parts of the brain
Morphology evolution of thermally annealed polycrystalline thin films
Investigation of the morphology evolution of annealed polycrystalline Au(111) films by atomic force microscopy and x-ray diffraction leads to a continuous model that correlates such an evolution to local interactions between grains triggering different mechanisms of stress accommodation (grain zipping and shear strain) and relaxation (gap filling and grain rotation). The model takes into consideration findings concerning the in-plane reorientation of the grains during the coalescence to provide a comprehensive picture of the grain-size dependence of the interactions (underlying the origin of the growth stress in polycrystalline systems); and in particular it sheds light on the postcoalescence compressive stress as a consequence of the kinetic limitations for the reorientation of larger surface structuresThis paper was supported by the projects F1-54173 (bilateral program CSIC-Conacyt) 200960I182 (CSIC), and CCG10-UAM/MAT-5537 (DGUI-Comunidad de Madrid and Universidad Aut´onoma deMadrid). A.G.G. acknowledges the financial support of the MICINN Spanish Ministry under the project ESP2006-14282-C02-0
The XIV International Geological Congress of 1926 in Spain
El XIV Congreso Geológico Internacional de 1926 ha sido el único organizado en España. Se exponen las características principales del mismo, a nivel temático y organizativo. Se analizan cuantitativamente el número de asistentes, las lenguas utilizadas, los países representados, las publicaciones, los autores y su productividad. Se muestra así el significado del congreso en la historia de los mismos, el predominio de geólogos franceses y alemanes, el predominio del trabajo individual y el limitado significado real del congreso en la producción científica de su época. Se analiza también el significado en la Historia de la Geología, ligado a la ciencia “normal” en sentido khuniano, pero no a los grandes temas de debate del momento, así como su significativo papel sociológico. También se analiza su importante papel en la Historia de la Geología en España.The XIV International Geological Congress has been the only one organised in Spain. Its main characteristics, at a thematic and organizative level, are showed. The number of attendants, languages, represented countries, papers, authors and scientific productivity are analysed in a quantitative way. The analysis shows the meaning of the Congress in the history of them, the predominance of frenchs and germans and the individual work, the true mening of the Congress in the scientific production, very limited. The meaning in the history of geology is also analysed, linked to the “standard” science in a khunian sense, but not to the main topics in discusion. Also, the significant sociological role is analysed. Also, the role in the Spain´s history of geology, more important, is analysed.Depto. de Geodinámica, Estratigrafía y PaleontologíaFac. de Ciencias GeológicasTRUEpu
Cobalt Metal-Organic Framework based on two dinuclear secondary building units for electrocatalytic oxygen evolution
The synthesis of a new microporous metal-organic framework (MOF) based on two secondary building units, with dinuclear cobalt centers, has been developed. The employment of a well-defined cobalt cluster results in an unusual topology of the Co2-MOF, where one of the cobalt centers has three open coordination positions, which has no precedent in MOF materials based on cobalt. Adsorption isotherms have revealed that Co2-MOF is in the range of best CO2 adsorbents among the carbon materials, with very high CO2/CH4 selectivity. On the other hand, dispersion of Co2-MOF in an alcoholic solution of Nafion gives rise to a composite (Co2-MOF@Nafion) with great resistance to hydrolysis in aqueous media and good adherence to graphite electrodes. In fact, it exhibits high electrocatalytic activity and robustness for the oxygen evolution reaction (OER), with a turnover frequency number value superior to those reported for similar electrocatalysts. Overall, this work has provided the basis for the rational design of new cobalt OER catalysts and related materials employing well-defined metal clusters as directing agents of the MOF structure
Wired metal-organic chalcogenides
Rey Garcia, F.; Jorda Moret, JL. (2017). Bottom-up synthesis: Wired metal-organic chalcogenides. Nature Materials. 16(3):287-288. doi:10.1038/nmat4850S287288163Moliner, M., Rey, F. & Corma, A. Angew. Chem. Int. Ed. 52, 13880–13889 (2013).Zeolites and Catalysis: Synthesis, Reactions and Applications Vol. 2 (eds Cejka, J., Corma, A. & Zones, S. I.) 389–861 (Wiley, 2010).Furukawa, H., Cordova, K. E., O'Keeffe, M. & Yaghi, O. M. Science 341, 1230444 (2013).Yan, H. et al. Nat. Mater. 16, 349–355 (2017).Bedard, R. L., Vail, L. D., Wilson, S. T., Oak, S. & Flanigen, E. M. US patent 4,880,761 (1989).Bowes, C. L. et al. Chem. Mater. 8, 2147–2152 (1996).MacLachlan, M. J. et al. J. Am. Chem. Soc. 121, 12005–12017 (1999).Zheng, N., Bu, X., Wang, B. & Feng, P. Science 298, 2366–2369 (2002).Dance, I. G., Garbutt, R. G. & Scudder, M. L. Inorg. Chem. 29, 1571–1575 (1990).Dance, I. G., Garbutt, R. G., Craig, D. C. & Scudder, M. L. Inorg. Chem. 26, 4057–4064 (1987)
Meltable, Glass-Forming, Iron Zeolitic Imidazolate Frameworks
We describe the first meltable iron-based zeolitic imidazolate framework (ZIF), denoted MUV-24. This material, elusive from direct synthesis, is obtained from the thermal treatment of [Fe3(im)6(Him)2], which yields Fe(im)2 upon loss of the neutral imidazole molecules. Different crystalline phase transformations are observed upon further heating, until the material melts at 482 °C. Vitrification upon cooling of the liquid phase gives rise to the first Fe-metal-organic framework glass. X-ray total scattering experiments show that the tetrahedral environment of the crystalline solids is maintained in the glass, whereas nanoindentation measurements reveal an increase in Young's modulus, in agreement with stiffening upon vitrification
Concept note for ICCAT ecoregion workshop identification of regions in the ICCAT convention area for supporting the implementation of ecosystem based fisheries management
The overall aim of the workshop is to advance in the identification of candidate ecologically
meaningful regions that can serve as a basis to produce a more integrated ecosystem-based
advice, and thereby support the implementation and operationalization of ecosystem-based
fisheries management (EBFM) in the International Commission for the Conservation of Atlantic
Tunas (ICCAT) convention area. The candidate regions should have boundaries that make
ecological sense, and are practical in informing fisheries management. The workshop will gather
CPC national scientists and external experts from different scientific disciplines (e.g.
biogeography, oceanography, ecology, fisheries and fisheries management in the ICCAT area)
to develop a “proof of concept” for broad-scale regionalization of the ICCAT convention area.L'objectif général de l'atelier est de progresser dans l'identification de possibles régions
écologiquement significatives qui peuvent servir de base pour produire un avis écosystémique
plus intégré, et ainsi soutenir la mise en œuvre et la mise en marche de la gestion des pêcheries
basée sur les écosystèmes (EBFM) dans la zone de la Convention de la Commission
internationale pour la conservation des thonidés de l'Atlantique (ICCAT). Les régions candidates
doivent avoir des limites qui ont un sens écologique, et qui sont pratiques pour renseigner la
gestion des pêcheries. L'atelier réunira des scientifiques nationaux des CPC et des experts
externes de différentes disciplines scientifiques (par exemple, la biogéographie, l'océanographie,
l'écologie, la pêche et la gestion des pêcheries dans la zone de l'ICCAT) afin de développer une
preuve conceptuelle pour une régionalisation à grande échelle de la zone de la Convention
ICCATEl objetivo global del taller es avanzar en la identificación de posibles regiones ecológicamente
significativas que puedan servir como base para formular un asesoramiento basado en el
ecosistema más integrado, apoyando la implementación y puesta en marcha de la ordenación
pesquera basada en el ecosistema (EBFM) en la zona del Convenio de la Comisión Internacional
para la Conservación del Atún Atlántico (ICCAT). Las regiones candidatas deberían tener límites
que tengan sentido ecológico y que sean prácticas para aportar información a la ordenación
pesquera. El taller reunirá a científicos nacionales de las CPC y a expertos externos de diversas
disciplinas (por ejemplo, biogeografía, oceanografía, ecología, pesca y ordenación pesquera en
la zona de ICCAT) para desarrollar una demostración conceptual para una regionalización a
gran escala de la zona del Convenio de ICCAT.Versión del edito
Crowding of Polymer Coils and Demixing in Nanoparticle-Polymer Mixtures
The Asakura-Oosawa-Vrij (AOV) model of colloid-polymer mixtures idealizes
nonadsorbing polymers as effective spheres that are fixed in size and
impenetrable to hard particles. Real polymer coils, however, are intrinsically
polydisperse in size (radius of gyration) and may be penetrated by smaller
particles. Crowding by nanoparticles can affect the size distribution of
polymer coils, thereby modifying effective depletion interactions and
thermodynamic stability. To analyse the influence of crowding on polymer
conformations and demixing phase behaviour, we adapt the AOV model to mixtures
of nanoparticles and ideal, penetrable polymer coils that can vary in size. We
perform Gibbs ensemble Monte Carlo simulations, including trial
nanoparticle-polymer overlaps and variations in radius of gyration. Results are
compared with predictions of free-volume theory. Simulation and theory
consistently predict that ideal polymers are compressed by nanoparticles and
that compressibility and penetrability stabilise nanoparticle-polymer mixtures.Comment: 18 pages, 4 figure
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