A locally conservative variational multiscale method for the simulation of porous media flow with multiscale source term

We present a variational multiscale mixed finite element method for the solution of Darcy flow in porous media, in which both the permeability field and the source term display a multiscale character. The formulation is based on a multiscale split of the solution into coarse and subgrid scales. This decomposition is invoked in a variational setting that leads to a rigorous definition of a (global) coarse problem and a set of (local) subgrid problems. One of the key issues for the success of the method is the proper definition of the boundary conditions for the localization of the subgrid problems. We identify a weak compatibility condition that allows for subgrid communication across element interfaces, a feature that turns out to be essential for obtaining high-quality solutions. We also remove the singularities due to concentrated sources from the coarse-scale problem by introducing additional multiscale basis functions, based on a decomposition of fine-scale source terms into coarse and deviatoric components. The method is locally conservative and employs a low-order approximation of pressure and velocity at both scales. We illustrate the performance of the method on several synthetic cases and conclude that the method is able to capture the global and local flow patterns accurately

Prevalência e fotobiologia dos endossimbiontes fotossintéticos de Exaiptasia diaphana em Berghia stephanieae

Nudibranchs are soft bodied, shell-less marine gastropod molluscs. They are widespread over a wide variety of environments. Some of these species are known due to their stenophagous dietary habits and their ability to retain photosynthetic endosymbionts from their preys. One of such nudibranchs is the aelolid Berghia stephanieae, a stenophagous nudibranch that retains both the photosynthetic endosymbionts and the nematocysts of its prey, the glass anemone Exaiptasia diaphana. Berghia stephanieae is known to be one of the best models for ecological studies addressing the mollusc-photosynthetic dinoflagellate endosymbiosis. However, these studies are often made with the use of invasive techniques, that commonly harm the study subject, and may even lead to their sacrifice. The glass anemone, E. diaphana, is seen as a model species to the study of cnidarian-microbiome symbiosis. As this species establishes a symbiosis with photosynthetic dinoflagellates, it has been used to study bleaching, the phenomenon that results from the loss of photosynthetic endosymbionts or pigments from the animal host. The present work addresses the maintenance of the symbiosis between B. stephanieae and its photosynthetic dinoflagellate endosymbionts acquired through the predation of E. diaphana using a non-invasive methodology, the measurement of pulse amplitude modulated chlorophyll fluorescence. While this methodology is commonly employed on plants and algae, it has already been successfully used to study kleptoplasty in sacoglossan sea slugs, as well as the maintenance of photosynthetic efficiency of photosynthetic dinoflagellate endosymbionts in some nudibranchs. Our experimental trials made possible to detect a positive correlation between the abundance of photosynthetic dinoflagellate endosymbionts within B. stephanieae and the minimum fluorescence of dark-adapted animals (F₀). The abundance of photosynthetic dinoflagellate endosymbionts within B. stephanieae and their photosynthetic efficiency were studied in sea slugs reared under different light intensities (high light, 80 µmol m- ² s - ¹; low light, 10 µmol m- ² s - ¹) and access to food. Exposure to different light intensities had no significant impact in the maintenance of B. stephanieae’s photosynthetic dinoflagellate endosymbionts, nor on their photosynthetic efficiency. However, starvation was shown to have a significant impact by decreasing both the abundance of photosynthetic dinoflagellate endosymbionts within B. stephanieae and their photosynthetic efficiency. The effect of different trophic regimes in the abundance of photosynthetic dinoflagellate endosymbionts within B. stephanieae and their photosynthetic efficiency was also tested. It was possible to show that sea slugs fed with bleached anemones (anemones lacking photosynthetic dinoflagellate endosymbionts) were impacted in a similar way to starved sea slugs, as they both exhibited a decrease in the abundance of photosynthetic dinoflagellate endosymbionts and a lower photosynthetic efficiency. This finding shows that the photosynthetic dinoflagellate endosymbionts present within B. stephanieae need to be replenished regularly by these nudibranchs by preying on symbiotic glass anemones (anemones that have photosynthetic dinoflagellate endosymbionts). Overall, the present study is the starting point to future works on which chlorophyll fluorescence parameter F₀ may be used to infer the abundance, maintenance and photosynthetic efficiency of endosymbionts in nudibranchs. This methodology may be a powerful tool to study the consequences of bleaching of marine organisms on their stenophagous predators, as these are widely unknown and need to be further investigated.Os nudibrânquios são moluscos gastrópodes marinhos de corpo mole, sem concha, que ocorrem numa grande variedade de ambientes. Algumas destas espécies são conhecidas pelos seus hábitos alimentares estenófagos e por reterem endossimbiontes fotossintéticos presentes nas presas das quais se alimentam. Uma dessas espécies é o aeolídeo Berghia stephanieae, um nudibrânquio estenófago que retém os dinoflagelados endossimbiontes fotossintéticos e os nematocistos da sua presa, a anémona de vidro Exaiptasia diaphana. Berghia stephanieae é considerada uma espécie modelo para estudos ecológicos referentes à endossimbiose entre moluscos e dinoflagelados fotossintéticos. No entanto, estes estudos são frequentemente realizados com recurso a metodologias invasivas, que invariavelmente causam danos físicos aos organismos em estudo, ou podem mesmo levar ao seu sacrifício. A anémona de vidro, E. diaphana, é considerada uma espécie modelo para o estudo da simbiose entre os cnidários e os seus microbiomas. Devido à sua simbiose com dinoflagelados fotossintéticos, esta espécie tem sido utilizada para estudar o fenómeno de branqueamento, fenómeno resultante da perda de simbiontes ou pigmentos fotossintéticos presentes num animal hospedeiro. O presente trabalho estuda a prevalência da associação entre B. stephanieae e os dinoflagelados endossimbiontes fotossintéticos obtidos troficamente pela ingestão de E. diaphana através da utilização de uma metodologia não invasiva, a medição da fluorescência de pulso modelado da clorofila. Esta metodologia é utilizada de forma rotineira em plantas e algas, tendo, no entanto, já sido utilizada com sucesso para o estudo da cleptoplastia em lesmas marinhas da superordem Sacoglossa. Esta metodologia foi também já utilizada para estudar a manutenção da eficiência fotossintética de dinoflagelados endossimbiontes fotossintéticos presentes nalgumas espécies de nudibrânquios. Através da sua utilização foi possível identificar uma correlação positiva entre a abundância de dinoflagelados endossimbiontes fotossintéticos presentes em B. stephanieae e a fluorescência mínima de animais adaptados ao escuro (F₀). A abundância de dinoflagelados endossimbiontes fotossintéticos presentes em B. stephanieae e a sua eficiência fotossintética foram estudadas em lesmas marinhas com e sem acesso a fonte de alimento e criadas a diferentes intensidades de luz (luz alta, 80 µmol m- ² s - ¹; luz baixa, 10 µmol m- ² s - ¹). A exposição a diferentes intensidades de luz não teve efeitos na manutenção da eficiência fotossintética ou na abundância dos endossimbiontes fotossintéticos presentes em B. stephanieae. No entanto, a exposição à inanição teve um impacto significativo, fazendo decrescer tanto a abundância dos dinoflagelados endossimbiontes fotossintéticos presentes em B. stephanieae, tal como a sua eficiência fotossintética. Foi também testado o efeito de diferentes regimes tróficos na abundância de dinoflagelados endossimbiontes fotossintéticos presentes em B. stephanieae e a sua eficiência fotossintética. Este estudo permitiu evidenciar que indivíduos alimentados com anémonas branqueadas (anémonas sem dinoflagelados endossimbiontes fotossintéticos) apresentavam um impacto semelhante ao verificado em conspecíficos sujeitos a inanição, ou seja, um decréscimo na abundância de endossimbiontes fotossintéticos, assim como da sua eficiência fotossintética. Estes resultados mostram que os dinoflagelados endossimbiontes fotossintéticos presentes em B. stephanieae necessitam de ser repostos regularmente por estes nudibrânquios através da predação de anémonas vidro que apresentem estes endossimbiontes fotossintéticos. Este estudo serve de ponto de partida para trabalhos futuros nos quais o parâmetro de fluorescência da clorofila F₀ poderá ser usado para inferir a abundância, manutenção e eficiência fotossintética de endossimbiontes fotossintéticos em nudibrânquios, assim como a manutenção da sua simbiose. Esta metodologia pode ser uma ferramenta valiosa para o estudo das consequências do branqueamento de organismos marinhos nos seus predadores estenófagos, consequências essas que são pouco conhecidas e, como tal, carecem de investigação.Mestrado em Biologia Marinha Aplicad

Avaliação do potencial mineiro das escombreiras da mina de São Domingos, Faixa Piritosa Ibérica, Portugal

ABSTRACT: The outcropping São Domingos Iberian Pyrite Belt deposit was mined since Roman time and between 1857 and 1966. The mine is formed by a 120 m depth flooded open pit and galleries until 420 m depth. Associated with felsic volcanic rocks and black shales of the Volcano-Sedimentary Complex, the deposit is formed by massive sulphide and stockwork ore (py, ccp, sp, ga, tt, apy) and related supergene enrichment ore (hematite gossan and covellite/chalcocite). Different mine wastes classes were mapped: gossan, felsic volcanic and shales, shales and landfill. Considering the CONASA mining waste characterization (162 shafts and 160 reverse circulation boreholes/LNEG database), new inferred resources are presented, using block modelling software: 2.38 Mt @ 0.77 g/t Au and 8.26 g/t Ag in non-conditioned volumes. Considering all evaluated wastes, including urban areas, an inferred resource of 4.0 Mt @ 0.64 g/t Au and 7.30 g/t Ag is presented, corresponding to a metal content of 82,878 oz t Au and 955,753 oz t Ag.RESUMO: Localizado na Faixa Piritosa Ibérica, o jazigo de São Domingos foi explorado na época Romana e no período entre 1857 e 1966, tendo sido escavada uma corta com 120 m de profundidade e abertas galerias mineiras até 420 m. O minério é formado por sulfuretos maciços e stockwork (py, ccp, sp, ga, tt, apy) e respetivo enriquecimento supergénico (chapéu de ferro hematítico e zona de covelite/calcocite), encontrando-se associado a rochas vulcânicas félsicas e xistos negros do Complexo Vulcano-Sedimentar. Cartografaram-se diferentes classes de escombreiras: chapéu de ferro, rochas vulcânicas e xistos, xistos e aterros. Considerando a sua caracterização efetuada pela empresa CONASA (162 poços e 160 sondagens de circulação inversa/base de dados LNEG), foram inferidos novos recursos usando software de modelação por blocos: 2,38 Mt @ 0,77 g/t Au e 8,26 g/t Ag (volumes não condicionados). Considerando todos os recursos avaliados (incluindo áreas urbanas) inferem-se valores de 4,0 Mt @ 0.64 g/t Au e 7,30 g/t Ag, correspondendo a um conteúdo em metal de 82 878 oz t Au e 955 753 oz t Ag.info:eu-repo/semantics/publishedVersio

Simplified modelling of the performance of concrete tunnels during fire and post-fire damage classification

The performance of concrete tunnel structures during and after fire is not well understood. This is an obstacle to the adoption of risk-based approaches for fire safety design of tunnel structures. Upon the request of the Belgian fire safety consultancy FESG, a simplified assessment of the collapse probability and post-fire damages for a reference tunnel structure has been made. The structural system is modelled through 2D beam finite elements, where spalling rates have been assumed based on available literature data. Structural stability is verified for both the heating and cooling phases of the fire. In those cases where the structure survives up to burnout, the residual deformations and thermal damage to the tunnel structure are assessed

Unveiling airline preferences for pre-tactical route forecast through machine learning. An innovative system for ATFCM pre-tactical planning support

In this work we describe a novel approach for the prediction of the flight plan to be sent by airspace users during the pre-tactical phase of Air Traffic Flow and Capacity Management (ATFCM). The proposed approach uses machine learning algorithms to extract airspace user preferences in terms of route characteristics, allowing the prediction of new routes not observed during the model training phase. We present the results obtained from applying this approach to short and medium range KLM flights for 52 weeks. Results show that the proposed solution is robust, scalable and capable of reducing the number of wrong predictions provided by the current Network Manager operational solution by 24.3% (4.5% increment on accuracy).Manuel Mateos´ PhD is funded by the 1st SESAR ENGAGE KTN Call for PhDs and is developed in collaboration between Nommon and the Technical University of Catalonia. This PhD study has received funding from the SESAR Joint Undertaking under the European Union’s Horizon 2020 research and innovation programme under grant agreement No 783287.Peer ReviewedPostprint (published version

Valorisation of natural extracts from marine source focused on marine by-products: A review

The wide chemical and biological diversity observed in the marine environment makes the ocean an extraordinary source of high added value compounds (HAVC) which can be employed in many applications. Minerals, lipids, amino acids, polysaccharides and proteins from marine sources have unique features and, surprisingly, their highest concentration is often found in parts of marine organisms that are commonly discarded. Fish heads, viscera, skin, tails, offal and blood, as well as seafood shells possess several HAVC suitable for human health applications, yet most end up as residues throughout the raw material processing. This review updates information on this issue and conveys critical analysis of the chief methodologies to carry out extraction, purification and eventual transformation, with a focus on their actual and potential applications.info:eu-repo/semantics/publishedVersio

Organocatalytic vs. Ru-based electrochemical hydrogenation of nitrobenzene in competition with the hydrogen evolution reaction

The electrochemical reduction of organic contaminants allows their removal from water. In this contribution, the electrocatalytic hydrogenation of nitrobenzene is studied using both oxidized carbon fibres and ruthenium nanoparticles supported on unmodified carbon fibres as catalysts. The two systems produce azoxynitrobenzene as the main product, while aniline is only observed in minor quantities. Although PhNO2 hydrogenation is the favoured reaction, the hydrogen evolution reaction (HER) competes in both systems under catalytic conditions. H2 formation occurs in larger amounts when using the Ru nanoparticle based catalyst. While similar reaction outputs were observed for both catalytic systems, DFT calculations revealed some significant differences related to distinct interactions between the catalytic material and the organic substrates or products, which could pave the way for the design of new catalytic materials