Biblioteca Digital do IPB
Repositório de Publicações do Instituto Politécnico de Bragança
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Mechanical Characterization of Eco-Friendly Composites: Green Epoxy Resin Reinforced with Coir Fibers
Publication . Ribeiro, J.E.; Lopes, Hernani; Rocha, João
The increasing demand for sustainable materials has fostered the development of natural fiber-reinforced composites as eco-friendly alternatives to petroleum-based systems. This work investigates the mechanical performance of GreenPoxy resin reinforced with coir fibers through a comprehensive experimental program. Fiber properties were first characterized by density and tensile tests, while the resin was evaluated under tensile and flexural loading. Composite laminates were then fabricated by hand lay-up using 3% and 6% fiber volume fractions, with both untreated and retted fibers. Mechanical behavior was analyzed using Taguchi design and ANOVA to assess the effects of fiber treatment and content. Untreated fibers displayed slightly higher intrinsic strength, while mercerization enhanced fiber–matrix adhesion, particularly at higher fractions. The composites exhibited promising properties, confirming the potential of coir/GreenPoxy systems for sustainable structural applications.
Proteomic analysis may explain differences in Citrus × limon and Citrus × sinensis susceptibility to Trioza erytreae
Publication . Magalhães, Tomás; Anjos, Liliana; Dandlen, Susana; Power, Deborah Mary; Pereira, José Alberto; Duarte, Amílcar Manuel Marreiros; Marques, Natália Tomás
The psyllid Trioza erytreae is a vector for Huanglongbing, one of the most destructive citrus diseases worldwide. Citrus × limon is the preferred host, although the mechanisms underlying this preference remain poorly understood. This study compared the responses of C. × limon ’Eureka’ and C. × sinensis ‘Valencia’ plants to T. erytreae infestation, specifically to nymph feeding. The number of successfully developed nymphs observed in C. × limon was three times that of ‘Valencia’ plants. The enriched vascular sap proteome of young leaves from infested and control plants was compared using nanoscale liquid chromatography coupled to tandem mass spectrometry. This study identified 48 and 1265 differentially abundant proteins (DAPs) in infested C. × limon and C. × sinensis, respectively. There was a marked host-specific response, with little overlap in proteomic features. Common citrus host responses to infestation were the downregulation of ‘Amino sugar and nucleotide sugar metabolism’ and the upregulation of galactose, vitamin B6, and selenocompound metabolisms. The downregulation of photosynthesis-related proteins and the activation of defence-related pathways in C. × sinensis suggest a robust response, which may explain the low success rate of nymph development on this host. The lower number of DAPs in C. × limon infested with T. erytreae, in comparison to the respective control, may be indicative of a reduced stress response. Further investigation into the identified candidate proteins and pathways is expected to contribute to the elucidation of the interaction between T. erytreae and C. × limon.
Drought, grazing routes and resource use by small-ruminant pastoralists in Montesinho, northeastern Portugal
Publication . Oliveira, Ana Carolina Farias de; Castro, José; Aleixo-Pais, Isa G.; Seripieri, Vitor Henrique Mistro; Castro, Marina
Climate projections for the Mediterranean area indicate a rise in temperature and an increase in drought frequency, which directly impact water availability and consequently, ecosystems. In the protected area of Montesinho in northeast Portugal, sheep and goat pastoralism characterizes the landscape and plays an important socio-economic role. However, like in many regions of the globe, this historical activity is becoming increasingly unsustainable due to shifting climatic conditions. To understand the impact of climate change on water availability in the park and its consequences for small ruminant pastoralism, trends in rainfall and temperature were analyzed using historical climate data from 1951 to 2022, and semi-structured interviews with local shepherds provided insight into their perceptions on this matter. We used TWI and NDVI to map relative moisture and green forage patterns underlying shepherds’ grazing-route decisions. Findings revealed a decrease in precipitation during winter and spring, with a significant increase during autumn months, and local knowledge revealed a focus on drying springs and shifts in seasonal patterns that led to pastoral adaptations like adjusting grazing routes and increasing reliance on alternative water sources. This study concluded that pastoralism in this region faces significant climatic challenges, highlighting the need to implement adaptive strategies to improve the livelihood of these communities and increase their resilience in a fast-changing environment. Large-scale aid and locally addressed actions, such as improving water infrastructures and promoting drought-tolerant vegetation growth, are key to the long-term sustainability of this ancient practice.
Influence of Time and Temperature Variables on the Heat Treatment of an AL-MG SI Alloy
Publication . Ribeiro, J.E.; Lopes, Hernani; Rocha, João
This study investigates the effect of time and temperature on the heat treatment of 6082 Al-Mg-Si alloy. Solubilization, quenching, and artificial aging were performed under parameter combinations defined using the Taguchi method. Mechanical testing supported the development of a multiple linear regression model, which identified aging temperature as the most significant factor influencing ultimate tensile strength and yield strength. High aging temperatures promoted coarse precipitate formation and reduced strength, while lower temperatures minimized this effect and maintained or improved mechanical performance. The results demonstrate the potential of combining statistical design with predictive modeling to optimize heat treatment parameters and enhance alloy performance for industrial applications.
Influência da idade e flexibilidade na velocidade membros inferiores de idosos
Publication . Alves, Mauro; Encarnação, Samuel; Beiroto, Marta; Vieira, Luísa; Pereira, Fátima; Piasseta, Milena; Teixeira, José Eduardo; Forte, Pedro; Monteiro, A.M.
Com o avançar da idade observa-se a redução natural da capacidade funcional. Dentro das capacidades funcionais, a força/velocidade muscular dos membros inferiores (MMII) é fundamental para realizar satisfatoriamente as atividades da vida diária (AVDs). Fatores como a idade e os níveis de flexibilidade podem afetar o desempenho de MMII em idosos. Objetivo: Analisar a influência da idade cronológica e da flexibilidade de MMII na velocidade de membros inferiores de idosos fisicamente ativos. Métodos: Este foi um estudo observacional, transversal e prospetivo, com 41 idosos (34 idosas e 7 idosos), média de de 69 ± 12,7 anos, que foram submetidos aos testes de seat and reach: flexibilidade de MMII, e sit to stand five time (STS 5x): para avaliar a velocidade dos MMII. Os dados foram apresentados em média ± desvio padrão e valores percentuais. Foi realizada uma análise de regressão múlplica hieráquica entre a idade cronológica e a flexibilidade de MMII para a variável de resposta velocidade de MMII. O tamanho do efeito foi calculado por meio do coeficiente de determinação (R2). Foi adotado um nível de significância de p < 0,05. Resultados: Não foi encontrada influência da idade cronológica e do nível de flexibilidade de MMII com a velocidade de MMII dos idosos fisicamente ativos, F = 1,186, gl = 39, p = 0,31, R2 = 0,008. Conclusão: Conclui-se que a idade cronológica e a flexibilidade de MMII não determinaram a velocidade de MMII de idosos fisicamente ativos.