410 research outputs found

    "Litoteca": a new project for networking among Portuguese geoparks

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    Networking is one of the four essentials of UNESCO Global Geoparks (UGGp), together with geological heritage of international value, management and visibility; it is focused not only in cooperation with the local people living in the UGGp, but also in cooperating with other UGGp’s, learning from each other and, as a network, increasing the recognition and value of this UNESCO label. This networking purpose, applicable and disseminated both nationally and internationally, is the basis for this abstract, that presents an initiative among the Portuguese Geoparks: the production, exchange and use of a “LITOTECA” (meaning deposit/archive of rock samples) to support educational, scientific and disseminatiorrpromotion of Geoscience initiatives. The “LITOTECA” encompasses a representative rock samples collection of the geodiversity from each Portuguese Geopark territory and its geological history, prepared by each Portuguese Geopark staff and shared with the other territoiy, on an “one for all” basis. Easy to use, made portable and adequately prepared and labeled with a short ID, the geological samples are suitable to be used by the Geopark staff, but also their stakeholders on several activities and for different purposes, from educational activities, to general public sessions, and exhibitions. The Azores UGGp “Litoteca” includes 12 samples that illustrate the lithological geodiversity of the Azores Islands, including ankaramite, surtseyan tuff, ignimbrite, trachyte, basalt, scoria, pumice, volcanic sand, syenite and fossiliferous limestone samples. The rock collection of Naturtejo UGGp shows a good representation of the rock cycle, including 27 sedimentary (diamictites to epigenic limestones), metamorphic (pelitic hornfels to gnaisses) and igneous (S-type granites to dolerites) samples. The Arouca UGGp ‘Litoteca" includes rocE sampIes o( congIomerate, car6onaceous shale, quartzite, slate, metaconglomerate, metagraywacke, black quartzite, quartzodiorite, as well as several granite samples, incIuding the iconic Nodular Granite of Castanheira (“Pedra Parideira/Rocks Delivering Stones”). The Terras de Cavaleiros UGGp coIIection is constituted 6y 12 sampIes representative of oceanic and continental lithosphere sequences and include dunite, serpentinite, gabbro, amphibolite, mafic granulite, and gneiss sampIes, among otfiers. The Aspiring Geopark EstreIa aIso contributed to tKs nctworking initiative with a rocE collection that includes about 30 samples of various granitic rocks, migmatite, dolerite, quartz, schists, shales, slates, hornfels, greywacke, phyllite, as well as glacigenic sediments (till)

    Laughlin states change under large geometry deformations and imaginary time Hamiltonian dynamics

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    We study the change of the Laughlin states under large deformations of the geometry of the sphere and the plane, associated with Mabuchi geodesics on the space of metrics with Hamiltonian S1S^1-symmetry. For geodesics associated with the square of the symmetry generator, as the geodesic time goes to infinity, the geometry of the sphere becomes that of a thin cigar collapsing to a line and the Laughlin states become concentrated on a discrete set of S1S^1--orbits, corresponding to Bohr-Sommerfeld orbits of geometric quantization. The lifting of the Mabuchi geodesics to the bundle of quantum states, to which the Laughlin states belong, is achieved via generalized coherent state transforms, which correspond to the KZ parallel transport of Chern-Simons theory

    Event-based quickflow simulation with OpenLISEM in a burned Mediterranean forest catchment

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    Recently burnt areas typically reveal strong to extreme hydrological responses, as a consequence of loss of protective soil cover and heating-induced changes in topsoil properties. Soil water repellency (SWR) has frequently been referred to as one of the explanatory variables for fireenhanced surface runoff generation but this has been poorly demonstrated, especially at the catchment scale. This study employs a process-based modelling approach to better understand the relevance of SWR in the hydrological response of a small, entirely burnt catchment in central Portugal, in particular by comparing hydrological events under contrasting initial conditions of dry vs wet soils. The OpenLISEM model was applied to a selection of 16 major rainfall runoff events that occurred during the first 2 post-fire years. The automatic calibration procedure resulted in good model performance, but it worsened for validation events. Furthermore, uncertainty analysis revealed an elevated sensitivity of OpenLISEM to event-specific conditions, especially for predicting the events’ total and peak flows. Also, predicted spatial patterns in runoff poorly agreed with the runoff observed in microplots. Model performance improved when events were separated by dry and wet initial moisture conditions, particularly for wet conditions, suggesting the role of variables other than initial soil moisture.info:eu-repo/semantics/publishedVersio

    Direct Experimental Observation of in situ Dehydrogenation of an Amine-Borane System Using Gas Electron Diffraction

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    In situ dehydrogenation of azetidine-BH3, which is a candidate for hydrogen storage, was observed with the parent and dehydrogenated analogue subjected to rigorous structural and thermochemical investigations. The structural analyses utilized gas electron diffraction supported by high-level quantum calculations, while the pathway for the unimolecular hydrogen release reaction in the absence and presence of BH3 as a bifunctional catalyst was predicted at the CBS-QB3 level. The catalyzed dehydrogenation pathway has a barrier lower than the predicted B-N bond dissociation energy, hence favoring the dehydrogenation process over the dissociation of the complex. The predicted enthalpy of dehydrogenation at the CCSD(T)/CBS level indicates that mild reaction conditions would be required for hydrogen release and that the compound is closer to thermoneutral than linear amine boranes. The entropy and free energy change for the dehydrogenation process show that the reaction is exergonic, energetically feasible, and will proceed spontaneously toward hydrogen release, all of which are important factors for hydrogen storage
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