4161 research outputs found
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Zircon U-Pb and Lu-Hf Constraints on the Paleo- to Mesoproterozoic Evolution of the Southwest Angolan Shield (Congo Craton) [Resumo]
No full textABSTRACT: The crustal evolution of the Angolan Shield (AS) remains poorly constrained. To address this, we analysed U-Pb and Lu-Hf isotopes in detrital and igneous zircons to determine the age and provenance of extensive sedimentary strata in southwest Angola, and use them as a proxy for the Paleoproterozoic to Mesoproterozoic evolution of the southwest AS. Mesoproterozoic maximum depositional ages between 1334 ± 8 Ma and 1184 ± 23 Ma for the Iona, Cahama, and Ompupa siliciclastic rocks refute previous correlations with the Paleoproterozoic Chela Group. Detrital zircon U-Pb and Lu-Hf isotopes closely match those of magmatic rocks from the southwest AS, indicating that Mesoproterozoic siliciclastic rocks were primarily derived from the AS
Fractionation of macroalgae carbohydrates using hydrothermal and dilute inorganic salt pretreatments to produce oligosaccharides and furans
No full textABSTRACT: Furans are among the most important compounds derived from biomass, providing conversion pathways for sustainable alternatives to petroleum-based fuels and materials. Furfural, 5-hydroxymethylfurfural (5-HMF), and 5-methylfurfural (5-MF) are furans that can be obtained by carbohydrate dehydration under acidic conditions at elevated temperature and pressure. One of the mechanisms to produce these compounds from lignocellulosic materials relies on prior fractionation of biomass carbohydrates and further dehydration catalysis. However, this is a costly and technically challenging method and it would be advantageous to develop a one-pot conversion mechanism that facilitates simultaneous biomass fractionation and conversion to furans. Ulva lactuca is an alga that has the advantage of being lignin-free and rich in glucose, rhamnose, and xylose, which are ideal for producing 5-HMF, 5-MF, and furfural, respectively. The high diversity of sugar constituents is also relevant for the production of added-value oligosaccharides. Catalysis with inorganic salts has been reported as a successful tool for biomass upgrading to furans when combined with hydrothermal pretreatments, and could provide a cheap and environmentally friendly one-step methodology for furan production. This study therefore aimed to investigate the effect of hydrothermal and dilute acid pretreatments, as well as treatment with inorganic salt solutions (ferric chloride, ferric nitrate, and aluminium nitrate) on U. lactuca biomass to produce oligosaccharides, monosaccharides, and furans (furfural, 5-HMF, and 5-MF). These methods resulted in a maximum sugar solubilization of 65% in non-salt-assisted hydrothermal pretreatments and 84% in salt-assisted hydrothermal pretreatments, with inorganic salt catalysis also resulting in 100% xylose, 36% glucose, and 46% rhamnose conversion to the respective furans
Relatório Final do Projeto LAMINOTECA 1.0: Desenvolvido no período compreendido entre 7 Setembro de 2024 a 21 de outubro de 2025
No full textProjeto LAMINOTECA 1.0 do LNEG (2023.10357.S4P23)RESUMO: O arquivo histórico do Laboratório Nacional de Energia e Geologia (LNEG) engloba um espólio científico resultante de quase 180 anos de atividade geológica e mineira, o que constitui um banco de dados excecional e um verdadeiro repositório geológico nacional. No âmbito das áreas de missão do LNEG, consta a preservação, tratamento e disponibilização deste património único. Este espólio é considerado património científico nacional, com significado histórico e fundamental à investigação estratégica do país e de enorme valor económico. Todavia, é pois, necessário que as coleções existentes se encontrem devidamente organizadas e preparadas para serem disponibilizadas online através da plataforma geoPortal da Energia e Geologia (GEG), infraestrutura online do LNEG. E, para a concretizar este objetivo, será necessário criar e desenvolver um centro de dados digital sobre coleções especificas, que facilite e promova a consulta da informação existente. O projeto LAMINOTECA 1.0 visa estabelecer um novo modelo de organização e valorização do espólio histórico do LNEG, parte integrante do repositório geológico nacional. Paralelamente, promove o reforço funcional do GEG, enquanto plataforma digital central institucional e de acesso público, para disponibilização estruturada e georreferenciada das coleções temáticas, com destaque para as geológicas e mineiras. Esta iniciativa facilitará a pesquisa e consulta especializada, contribuindo para o avanço científico, educativo e económico. Espera-se que este projeto apoie, no futuro, atividades de I&D aplicadas às áreas estratégicas do LNEG, nomeadamente o Plano Nacional de Cartografia e o Plano Nacional de Prospeção no âmbito do Ato das Matérias Primas Críticas, reconhecendo o valor económico e territorial do conhecimento geológico e fomentando a especialização inteligente em petrografia, paleontologia e mineralizações
The Role of Demand and Vres Flexibility in Carbon-Neutral Power Systems: Insights from Portugal and Spain in Prospective 2050 Scenarios
No full textABSTRACT: The goal of a carbon-neutral society by 2050 is speeding up the integration of variable renewable energy sources (vRES) in European power systems. For the expected levels of vRES, the adaptation of the demand will be crucial to manage the stochastic behaviour of these technologies. This work evaluates the impact of four prospective 2050 energy mix scenarios in the Iberian electricity market. All scenarios consider near 100% vRES shares. Scenarios that incentivize demand flexibility (S2 and S4) result in the lowest wholesale prices and costs for society. Peak load reduction using demand response occurred in the two scenarios (S1 and S3) with low demand flexibility and high share of renewable generation. S3 is the most unstable leading to the higher wholesale prices. The results highlight that an equilibrium between demand flexibility and investments in the generation side is essential for reducing costs and ensuring stability
Reducing nutrient requirement using nitrogen-fixing bacteria for microalgae cultivation
No full textABSTRACT: In environments, microalgae have been observed to coexist with bacteria. Different nitrogen-fixing bacteria (NFB) were isolated from Armenian soils and their growth was evaluated in co-cultivation with the microalga Tetradesmus obliquus and cyanobacteria Synechocystis sp. PCC 6803. The most effective mutualistic consortium was T. obliquus-NFB5 (Sphingobacterium sp. L13G8). This resulted an increase in both populations, chlorophyll fluorescence, biomass protein, carbohydrate content, an effect on lipid metabolism, without the need for external nitrogen. The findings demonstrated the significance of employing NFB for microalga growth, as they facilitate the essential nitrogen provision in N-free Bristol medium. Moreover, in mutualistic consortia, microalgae facilitate the exudation of dissolved organic carbon and O2 to bacteria, which, in turn, become available for bacteria, thereby reducing the necessity for energy-consuming aeration processes in co-cultivation. In return, the bacteria provide the microalgae with CO2, B vitamins and demineralize N2, P, S, thereby further supporting the growth of microalgae
Natural Stone Image Classification Using Online Databases and Convolutional Neural Networks
No full textABSTRACT: In this paper, we discuss the relevance of two distinct types of online natural stone databases (technical-institutional repositories and logistics-commercial e-platforms) for extracting (training and testing) input images and creating an automatic visual inspection system for natural stone classification. Using convolutional neural networks (CNNs) and images from a selected online data repository, a Deep Learning (DL) system was developed to estimate the class of the natural stone in a given image. The DL models were developed through transfer learning from existing image classifiers, as pre-trained classifiers were retrained on our dataset. Our best model achieved an Accuracy of 70.3% and an F-score of 0.67 for 70 classes
Use of mining wastes for high-tech thermoelectric applications : The case of START project in Iberian Pyrite Belt [Resumo]
No full textABSTRACT: Europe aims to become the first climate neutral continent by 2050, which means rapidly implementing a green transition to which the European Union (EU) is strongly committed through the European Green Deal. This green transition leverages unprecedented pressure on the intensive use of mineral resources. In this context the START project “Sustainable Energy Harvesting Systems Based on Innovative Mine Waste Recycling” emerged with the objective to use mining waste as a source of raw materials for the development of advanced energy conversion devices. Thermoelectric materials (TE) are functional materials that can directly convert thermal energy into electricity
Satellite-Based Offshore Wind Data Close to the Coast: Comparison With Onshore Meteorological Mast Records and Microscale CFD Simulations [Resumo]
No full textABSTRACT: Satellite observation of environmental phenomena is becoming increasingly accurate, complementing pre-existing measurement techniques. In this work, the offshore wind field recorded by Sentinel-1 on February 6th, 2021, close to the Southwestern Iceland coast is compared with the anemometric measurements provided by a relatively dense network of weather stations in the Reykjanes peninsula and microscale CFD simulations that use the Hvassahraun weather station data to approximate wind velocity and direction in offshore locations. The three methodologies show a good agreement in the 10-minute velocity magnitudes for the set of considered offshore locations, while the 10- minute mean wind direction shows certain scattering, although with a consistent prevalence of Eastern wind directions, in agreement with the anemometric data. The results show obvious complementarities among the three approaches, suggesting further studies to improve accuracy, especially for capturing local effects impacting wind magnitude and directionality.COST Action CA20109 Modenerlands, supported by COST (European Cooperation in Science and Technology
Geophysical Studies with a View to Optimising the Location of a Geothermal Abstraction in S. P. do Sul, Beira Alta, Portugal
No full textRESUMO: As alterações climáticas têm gerado impactos significativos nos territórios termais, tanto de forma direta, por diminuição, desde logo, da recarga dos sistemas aquíferos, e indiretamente através da intensificação da procura de recursos hídricos subterrâneos e da transformação dos usos do solo, fatores que, em conjunto, podem comprometer a qualidade e a disponibilidade dos recursos hidrominerais e geotérmicos. Uma das medidas para mitigar tais problemas passa por construir captações profundas, menos suscetíveis às influências antrópicas e capazes de garantir águas minerais naturais e/ou recursos geotérmicos com maior estabilidade em termos de qualidade, quantidade e temperatura. Neste contexto, o presente trabalho, discute as principais dificuldades associadas à implementação bem-sucedida deste tipo de obras e apresenta, os resultados preliminares de estudos geofísicos, obtidos no âmbito do projeto ThermEcoWat orientados para a identificação
das localizações mais adequadas à implementação de novas captações profundas. Pretende-se, assim, contribuir para o reforço da resiliência dos territórios termais face às pressões associadas às alterações climáticas.ABSTRACT: Climate change exerts increasing pressure on thermal territories, primarily through reduced aquifer recharge and, indirectly, via intensified groundwater demand and land-use changes. These processes jointly threaten the quality, availability, and long-term sustainability of hydro-mineral and geothermal resources. Developing deep drillings emerges as a key mitigation strategy, as they are less vulnerable to anthropogenic impacts and ensure natural mineral waters and/or geothermal resources with greater stability in quality, quantity, and temperature. In this context, the present study discusses the main challenges associated with the successful implementation of such infrastructures and presents preliminary results of geophysical investigations carried out within the scope of the ThermEcoWat project. The ultimate goal is to identify the most suitable locations for new deep drillings, thereby contributing to strengthening the resilience of thermal territories to the pressures associated with climate change