4161 research outputs found
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Tetrahedrite Nanocomposites for High Performance Thermoelectrics
No full textABSTRACT: Thermoelectric (TE) materials offer a promising solution to reduce green gas emissions, decrease energy consumption, and improve energy management due to their ability to directly convert heat into electricity and vice versa. Despite their potential, integrating new TE materials into bulk TE devices remains a challenge. To change this paradigm, the preparation of highly efficient tetrahedrite nanocomposites is proposed. Tetrahedrites were first prepared by solid state reaction, followed by the addition of MoS2 nanoparticles (NPs) and hot-pressing at 848 K with 56 MPa for a duration of 90 min to obtain nanocomposites. The materials were characterized by XRD, SEM-EDS, and Raman spectroscopy to evaluate the composites' matrix and NP distribution. To complement the results, lattice thermal conductivity and the weighted mobility were evaluated. The NPs' addition to the tetrahedrites resulted in an increase of 36% of the maximum figure of merit (zT) comparatively with the base material. This increase is explained by the reduction of the material's lattice thermal conductivity while maintaining its mobility. Such results highlight the potential of nanocomposites to contribute to the development of a new generation of TE devices based on more affordable and efficient materials
Modulating microalgal metabolism and its integration into dark fermentation: Challenges and opportunities with wastewater-grown biomass
No full textABSTRACT: Microalgae represent a promising feedstock for the sustainable production of bioproducts and bioenergy, due to their versatile biochemical composition and environmental adaptability. Given the wide range of bioproducts that can be derived from their biomass, its biochemical composition suggests more favorable conversion routes and can be enhanced through cultivation conditions focused on the synthesis of one (or more) metabolites of interest to the biotechnology market. Accordingly, this review focuses on approaches for modulating microalgal metabolism, such as nutrient depletion and reactor configuration characteristics, among others, as well as on key outcomes obtained through two-stage cultivation, which combine phases of high biomass and metabolite productivity. From a resource recovery perspective, emphasis was placed on approaches that are more readily applicable to wastewater treatment plants. Furthermore, as energy-oriented routes are more suitable for valorizing of biomass grown in wastewater and considering that biohydrogen has been shown to be an emerging product of scientific relevance, this review also analyzes the limitations and strategies for integrating its production via dark fermentation. Pretreatment techniques and co-fermentation approaches were discussed as strategies to overcome the challenges associated with the anaerobic fermentation/digestion of microalgae due to their characteristics and biochemical composition. Finally, biorefinery configurations that integrate these processes were discussed from a scale-up perspective
Pretreatment Tunes scCO2 Extract Composition and Bioactivity in Three Microalgae: Chemometric and Molecular Docking Insights
No full textABSTRACT: This study explores the impact of enzymatic (ENZ), microwave (MW), and ultrasound (US) pretreatments on supercritical CO2 (scCO2) extraction efficiency, chemical composition, and cytotoxic activity of Tetraselmis sp., Tetradesmus obliquus, and Chlorococcum sp. Pretreatments significantly enhanced extraction yields, with ENZ being most effective for Tetraselmis and Chlorococcum, and MW for T. obliquus. UPLC-HRMS profiling revealed species- and pretreatment-specific shifts: ENZ and US improved pigment recovery in Tetraselmis, while MW enriched carotenoids and chlorophyll derivatives. In Chlorococcum, MW boosted pigment diversity, whereas ENZ and US favored fatty acid derivatives in the extracts. Multivariate analysis confirmed significant compositional changes, particularly after ENZ and MW pretreatments. Tetraselmis extracts, especially those pretreated with MW, exhibited the strongest cytotoxic activity and highest selectivity indices against HeLa and MDA-MB-453 cancer cell lines. Correlation analysis identified compounds such as 2,3-dihydroxypropyl stearate, fucoxanthin, and (3 beta)-3-hydroxystigmast-5-en-7-one as strongly linked to cytotoxicity. Molecular docking further showed that abundant compounds in Tetraselmis extracts have high predicted affinities for cancer-related targets (e.g., BCL2, EGFR, PDK1). The results suggest that cytotoxic effects arise from both specific bioactive compounds and their synergistic interactions. These findings show that pretreatments can purposefully tune scCO2 extracts and provide a data-driven basis for designing more sustainable microalgal extraction workflows
Pre-Mesoproterozoic crustal architecture and implications for the Mesoproterozoic evolution of the SW Angolan Shield from structural, geochemical, and isotopic evidence [Resumo]
No full textABSTRACT: Several studies suggest the existence of multiple tectonic domains within the Angolan Shield [1], yet the Archaean to Palaeoproterozoic basement of SW Angola and NW Namibia remains largely unexplored. Similarly, distinct Mesoproterozoic (1534–1065 Ma) igneous suites are documented in the SW Angolan Shield, including the largest known gabbro-anorthosite complex (~42,500 km²), the Kunene Complex (KC), but the geological evolution of the region during the Mesoproterozoic is still debated. Traditionally linked to anorogenic contexts [2], recent studies propose a collisional setting for the KC [3]. A combined isotopic (U-Pb, Sr-Nd), gravimetric, and structural approach allows for a refined crustal framework of the SW Angolan Shield and provides new insights into the emplacement of the KC and the regional evolution of the southern Congo Craton. This integrated dataset delineates several Archaean to Palaeoproterozoic domains surrounding the KC, featured by a specific gravimetric response and geochronological time span: Cassinga Zone (2667–2568 Ma and 1982–1971 Ma), Central Eburnean Zone (2038–1947 Ma; intruded by 1844–1744 Ma magmatism in its southern region, the Lubango Area), Namibe and Epupa Zones (1861–1739 Ma), and the Kalahari Area (~1775 Ma?). These contrasting crustal domains significantly influenced the genesis and emplacement of the KC
Bridging gaps in biorefineries: The unexplored role of social dimension in life cycle assessment research
No full textABSTRACT: This review examines the disregarded role of social dimensions in Life Cycle Assessment (LCA) within biorefinery implementation, addressing the question: "How can the inclusion of social factors in LCA improve sustainability assessments, and what are the implications of the limited Social Life Cycle Assessment (S-LCA) studies in biorefineries?" A systematic literature review was conducted using Web of ScienceTM, focusing on studies that integrate social dimensions in LCA. Bibliometric analysis using the bibliometrix R-package and VOSviewer identified key trends, influential papers, and research gaps. Results revealed a significant gap in incorporating social dimensions into biorefinery LCA, with most studies focusing primarily on environmental and economic impacts. Limited attention is given to social aspects such as community well-being, labor rights, and social equity. Case studies that included social factors demonstrated a more comprehensive sustainability assessment, emphasizing the importance of stakeholder engagement and social acceptability in biorefinery projects. This review highlights the need for standardized social indicators and methodologies to integrate social dimensions effectively. The lack of S-LCA in biorefinery implementation reflects a critical gap in sustainability assessments. Addressing this requires developing a unified S-LCA methodology, fostering interdisciplinary collaboration, and encouraging stakeholder participation to ensure diverse perspectives are considered. Ultimately, incorporating social dimensions is essential for achieving a more balanced and comprehensive evaluation of biorefinery sustainability.N/
El Proyecto UTE-PLANAGEO (Plan Nacional de Geología de Angola). Objetivos, métodos, y resultados
No full textABSTRACT: The National Geology Plan of Angola (PLANAGEO) has been one of the most important Angolan infrastructure projects throughout the past twenty years. The objectives of PLANAGEO were: (a) to enhance Angola's geological and mineral resources knowledge; (b) to foster diversification of the national economy; and, (c) to attract foreign investment and promote the country development. The project integrated regional interdisciplinary geological surveys, including geological/aerogeophysical/geochemical mapping, raw materials and mineral resources prospecting, as well as specific studies in target areas. The project was launched by the Angolan government (Presidential Resolution 52/09), and implemented by the Geological Survey of Angola (IGEO), under the oversight of the Angolan Ministry of Mineral Resources, Oil and Gas (MIREMPET). In 2011, UTE consortium, a joint venture of IGME, the National Laboratory of Energy and Geology of Portugal (LNEG) and the Spanish company Impulso Industrial Alternativo (IIA) bid the call for tenders. In 2013 IGEO awarded UTE a contract to undertake PLANAGEO´s activities in the southwestern region of Angola, covering roughly 480.000 km2. From July of 2014 to the end of 2022, the UTE consortium conducted interdisciplinary studies and investigations that resulted in a comprehensive collection of maps and scientific reports and documents, comprising: Airborne geophysical mag/rad mapping. Geological mapping at 1:250.000 scale (and 1:500.000 and 1:1.000.000 synthesis). Geological mapping at 1:100.000 scale in selected areas. Geochemical mapping at 1:250.000 scale. Raw materials and Mineral resources mapping in target areas, at 1:50.000 scale
NEWS4CSP Project: New Coatings Approaches to Protect Metallic Materials From Heat Transfer Fluids
No full textABSTRACT: The efficiency of Concentrated Solar Power technologies increases with the opera-tion temperature of the power block, which can be achieved using advanced power cycles operating at temperatures ≥650°C. Molten Salt (MS) based HTF have been facing critical chal-lenging issues of severe corrosion and lower specific heat capacity. This paper aims to present the NEWS4CSP project to the CSP scientific community, highlighting the main concepts being pursued and the preliminary results obtained regarding the application of new coatings to in-crease the anticorrosive protection of structural materials in contact with MS. Two different types of powder coatings (nickel and cobalt alloys) were applied to AISI 430 stainless steel using two coating technologies: High Velocity Oxy-Fuel (HVOF) and Laser Cladding (LC). LC proved to be the most suitable technique of these two coating application technologies. The Co-Cr coating alloy showed good anticorrosive behaviour even after 3000 h of testing. The obtained results are very promising, nevertheless, more studies are needed to optimise its application by LC. These include optimizing the thickness and chemical composition, as well as gaining a deeper understanding of the degradation mechanisms and whether this behaviour is maintained over longer periods
Friedrich Welwitsch: prolegómenos da geologia de Angola
No full textABSTRACT: Recent work at the drill core library of LNEG at Alfragide has brought to light a small collection of rocks and fossils gathered by the Austrian physician and botanist Friedrich Welwitsch during his prolific expedition to Angola (Iter Angolense, 1853-1860) on behalf of the Portuguese crown. The samples were seen and mentioned by Paul Choffat, in 1889, but have remained completely forgotten ever since. Revisiting the samples, this article, which extends the evocation of 150 years of Welwitsch's passing, recalls the scientific partnership with the French naturalist Arthur Morelet, who studied mollusk faunas, and reviews the geological notes taken during the years of herborisations. Considering those notes and samples, it can be said that these pioneering elements in the study of the geology of Angola are, in essence, consistent with the recent knowledge and geological mapping of that territory.RESUMO: Trabalhos recentes trouxeram à luz, na Litoteca do LNEG em Alfragide, uma pequena coleção de rochas e fósseis constituída pelo médico e botânico austríaco Friedrich Welwitsch durante a prolífica expedição que, ao serviço da coroa portuguesa, efetuou a Angola: Iter Angolense, 1853-1860. As amostras que a integram foram vistas e referidas em 1889, por Paul Choffat, permanecendo, desde então, totalmente esquecidas. Ancorado na revisitação destas amostras, o presente artigo, que prolonga a evocação dos 150 anos sobre o passamento de Welwitsch, recorda a parceria científica com o naturalista francês Arthur Morelet, estudioso das faunas de moluscos, e passa em revista as notas de carácter geológico, tomadas durante anos de herborizações. Considerando no seu todo anotações e amostras, pode afirmar-se que estes elementos pioneiros do estudo da geologia de Angola compatibilizam, na sua essência, com os conhecimentos recentes e cartografia geológica daquele território
Empowering Citizen Science Through Stakeholder Engagement
No full textABSTRACT: The chapter examines how citizen science projects, particularly in geohazard monitoring, can be strengthened through systematic stakeholder engagement. Using the AGEO project as a case study, with five established Citizen Observatories across Europe, it details how stakeholders were identified, classified, and engaged across political, economic, knowledge and socio-cultural systems. The paper identifies five crucial factors for successful engagement: relevance, accessibility, trust, recognition/incentives, and sustainability. It concludes that citizen science, supported by technological advances and proper stakeholder engagement, can make significant contributions to disaster preparedness and risk reduction, particularly in the context of climate change, by fostering collaboration between experts and communities.Project AGEO – Platform for Atlantic Geohazard Risk Managemen