FC - Dissertações de Mestrado
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- Biologging an invader: habitat use and activity patterns of the European catfish in the lotic Tagus River (Portugal)Publication . Castro, Beatriz Mendes Fernandes Ribeiro de; Quintela, Bernardo Silva Ruivo, 1976-; Ribeiro, Filipe Manuel Vidas, 1975-The European catfish (Silurus glanis), an invasive species recently introduced to the Iberian Peninsula, presents a significant ecological threat due to its large size, high fecundity, and strong predatory potential. As a voracious apex predator, it can disrupt fish assemblages across the region. While biotelemetry studies have examined its habitat use and activity patterns in nonnative areas, most focused on lentic systems using passive telemetry, leaving its lotic behaviour understudied. Since its first record in Portugal (2014) and subsequent establishment in the Tagus and Douro rivers, understanding its habitat use and activity patterns in these dynamic environments has become crucial for effective management. To address this, 12 adult catfish were tagged with radio telemetry archival tags equipped with temperature, pressure (depth), and 3Daccelerometer sensors to assess habitat use and activity patterns in a lotic stretch of the lower Tagus River. A controlled experiment with two individuals validated acceleration-derived activity thresholds, classifying behaviours as immobile (<0.03 g), mobile (0.03–0.78 g) or burst movement (>0.78 g). The remaining 10 fish were actively tracked for a year. Results showed that catfish occupied deeper habitats in winter (mean depth: 3 m) and moved to shallower areas in spring and summer (mean depth: 1.6 m). Activity persisted year-round but was lower in winter and autumn and higher in warmer seasons. Circadian depth use patterns remained stable, with fish preferring shallower depths during the day and deeper habitats at night. Activity peaked at dusk and was lowest during daylight hours. Individuals exhibited strong site fidelity, consistently occupying small areas near riverbanks. These patterns were strongly correlated with several environmental predictors, possibly linked to prey availability and reproduction cycles. Findings provide valuable insights for targeted management strategies, including optimizing timing and location of fishing efforts to improve mass removal actions aimed at controlling this invasive species.
- Produção de biocombustíveis avançados pelo processo de hidrodesoxigenação utilizando bio óleos e óleos alimentares usadosPublication . Carvalho, Miguel Luís João de; Costa, Paula Alexandra da Conceição; Pinto, FilomenaThe increasing demand for sustainable alternatives to fossil fuels has driven research into the production of advanced biofuels. This study investigates the hydrodeoxygenation process for the valorization of eucalyptus bio-oil and waste cooking oils (WCO), using CoMo catalyst with the aim of optimizing the reaction conditions to maximize the yield of hydrocarbons suitable for use as transport fuels. The experimental work evaluated the influence of temperature, initial H₂ pressure, and feedstock composition on the production of hydrocarbons, utilizing a fractional factorial design approach. To this end, a factorial matrix was constructed that integrates individual coefficients (main effects of temperature, initial H₂ pressure, and feedstock composition), interaction coefficients (combined effects of the factors), and quadratic coefficients. The study proposes five scenarios for constructing this matrix, culminating in the selection of a scenario composed of eight coefficients, which demonstrated the greatest influence on the yield of the solid, gaseous, and organic liquid phases. The investigation into the effect of temperature involved reactions conducted at 300°C and 440°C, with initial hydrogen pressures of 0,09 MPa and 1,1 MPa. The results demonstrated that higher temperatures favored the formation of gaseous products due to increased thermal cracking and decarboxylation reactions, while the yields of the liquid phase decreased. The best yield of n-alkanes was obtained at 440°C using only WCO, reaching 30,5% (v/v), with n-C17 and n-C15 as the predominant hydrocarbons. However, an increase in oxygenated compounds was observed when bio-oil was used, indicating a lower efficiency in oxygen removal. The effect of hydrogen pressure was studied through experiments at 0,09 MPa and 1,1 MPa, while keeping the temperature and residence time constant. The findings confirmed that higher hydrogen pressures increased the efficiency of hydrodeoxygenation, significantly reducing the content of oxygenated compounds in the liquid phase and enhancing the yield of saturated hydrocarbons. The highest yield of n-alkanes was achieved at 440°C with WCO, with concentrations ranging between 12– 12,8% (v/v) in the C5–C10 range (compounds characteristic of petrol) and between 17,7–19,4% (v/v) in the C11–C20 range (compounds characteristic of diesel). The greater availability of H₂ favored decarbonization over decarboxylation, resulting in lower CO₂ formation and a higher production of CO in the gaseous phase. Conversely, lower pressures promoted coke formation due to the increased polymerization of oxygenated compounds. The effect of feedstock composition was examined by analyzing the use of bio-oil, WCO, and 50:50 mixtures under conditions of 400°C and 0,55 MPa, with the aim of investigating the synergy between the two types of feedstocks. However, the presence of bio-oil in the mixture led to increased coke formation, adversely affecting catalyst efficiency and hydrocarbon yield. The application of more severe conditions (440°C and 1,1 MPa) resulted in a significant increase in polycyclic aromatic hydrocarbons, indicating that these conditions favored aromatization reactions over the saturation of hydrocarbons. The results demonstrate that the reaction conditions play a crucial role in defining the composition of the biofuel, with both temperature and hydrogen pressure directly influencing the efficiency of oxygen removal, the distribution of products, and the balance between liquid and gaseous yields. This study highlights that the conversion of WCO is more efficient than that of bio-oil due to its lower oxygen content, while the incorporation of bio-oil increases the production of aromatic and solid by-products, thereby reducing process efficiency. The 50:50 mixture provided a compromise between product yield and hydrocarbon quality.
- Contrasting capture methods and health indicators among juvenile sharks in the nursery area of Boa Vista, Cabo VerdePublication . Fliehmann, Judith Anna Margarete; Santos, Catarina da Conceição Pereira; Rosa, Rui Afonso Bairrão da, 1976-Stress levels in neonate and juvenile sharks can influence the health and survival of the individual, as well as the overall population resilience. This thesis explores interspecific differences in health and stress indicators in juvenile sharks caught in Sal Rei Bay (SRB), a multi-specific shark nursery area in Boa Vista Island, Cabo Verde. Body condition, capture resilience, and a range of biochemical parameters (cholesterol, glucose, phosphate, creatine, alanine aminotransferase, alkaline phosphatase, potassium, total protein) were assessed in four shark species frequenting SRB — milk shark (Rhizoprionodon acutus), blacktip shark (Carcharhinus limbatus), scalloped hammerhead shark (Sphyrna lewini), and Atlantic weasel shark (Paragaleus pectoralis) — caught using artisanal fishing methods traditionally employed in the region (gillnets and angling). Recuperation scores varied among species and generally indicated faster recovery in individuals captured by angling compared to gillnets. Milk sharks, however, tended to recover quicker after gillnet capture. Hammerhead sharks showed the overall slowest recovery. Significant species-specific differences were revealed in nearly all analysed indicators, with a frequent influence of the umbilical scar. A significant influence of gear type was only detected for the two biomarkers alanine aminotransferase and alkaline phosphatase. The present results showcase the influence of species, development, and fishing-method on physiological indicators in juvenile sharks in SRB, discussing how species-specific ecological and behavioural characteristics might have influenced the results obtained. The influence of environmental and other anthropogenic pressures should be considered more thoroughly in future studies. By yielding the first fundamental insights into the interspecific differences in stress levels among juvenile sharks in the SRB nursery area, the present dissertation contributes to the design of future and ongoing monitoring efforts. Further, it enhances the comprehension of local interactions between sharks and the local artisanal fishery, addressing a knowledge gap for formulating effective, locally-tailored conservation strategies.
- Gleaning insectivorous bats eat seasonably in a West African rice farming landscape: implications for ecosystem servicesPublication . Morais, Inês Ribeiro dos Santos Brás de; Rainho, Ana, 1971-Insectivorous bats are key predators of arthropods, yet their ecological roles in African agroecosystems remain underexplored. This study investigates the dietary variation of two slit-faced bats (Nycteris cf. hispida and Nycteris thebaica/gambiensis) inhabiting a rural landscape in Guinea-Bissau, West Africa. Understanding the feeding patterns of these bats is essential for assessing their contribution to natural pest control and biodiversity conservation. Using DNA metabarcoding and next-generation sequencing, we examined spatial and temporal variations in prey consumption to assess dietary overlap, flexibility and potential pest suppression. Specifically, we focused on the following objectives: a) to assess whether the diet composition of N. cf. hispida varies spatially (between roosts) and temporally; b) to characterise how the diet of the two Nycteris species varies throughout the sampling period and to compare these patterns; c) to evaluate whether both predators track seasonal changes in prey, particularly potential agricultural pests. We analysed 166 faecal samples that revealed 488 distinct OTUs. Nycteris cf. hispida exhibited pronounced temporal variation in its diet, likely reflecting changes in arthropod occurrence, while N. thebaica/gambiensis showed less pronounced seasonal shifts. Despite shared roosts, differences in prey composition and foraging strategies suggest partial niche differentiation, with N. cf. hispida favouring ground-dwelling invertebrates and N. thebaica/gambiensis exploiting more aerial arthropods. Both bats consumed potential agricultural pests, including Spodoptera littoralis, Macrotermes bellicosus and Orseolia oryzae. These results highlight the dynamic foraging response of Nycteris bats to changes in prey availability and their potential role in controlling insect pests in West African rice systems. This study contributes to a growing body of evidence supporting insectivorous bats' ecological and economic value and underscores the importance of conserving bat populations in rural landscapes.
- Predicting Football Results: a Bayesian Approach with a ZeroModified Poisson DistributionPublication . Palma, Vítor Hugo Anastácio; Martins, Rui Manuel da Costa, 1979-Football is a global phenomenon, and as such, it was only a matter of time until statistics joined the field. This dissertation explores the application of the Zero-Modified Poisson (ZMP) model within a Bayesian framework for predicting football match outcomes. Traditional Poisson-based approaches often fail to account for irregularities in goal distributions, such as zero inflation or zero deflation, which are common in football scoring patterns. The incorporation of the Zero-Modified Poisson model provides the flexibility to handle varying frequencies of zero outcomes while accommodating unequal means and variances in contrast with the standard Poisson, which assumes equaldispersion. Using match data from the 2022/23 Italian Serie A, a Bayesian hierarchical model is implemented via the NIMBLE r package, where team-specific parameters for attack, defense, and home advantage were estimated using Markov Chain Monte Carlo (MCMC) techniques. After the parameter estimation, two simulation methods were employed to generate probabilistic forecasts: a round-by-round and a full-season one. In order to check the performance of the model the first simulation method was replicated with 3 other Poisson models to check if the handling of zero inflation and deflation really gave an advantage in the predictive power of the ZMP
- Intrinsic and extrinsic motivations behind the exploratory behavior of Octopus vulgaris under environmental enrichment and deprivationPublication . Santos, Catarina Caldeira; Rosa, Rui Afonso Bairrão da, 1976-As global demand for seafood continues to rise, wild finfish stocks are increasingly being depleted. In this context, aquaculture emerges as a pivotal solution, offering a more sustainable alternative to meet consumption demands while alleviating pressure on wild stocks. However, this also raises concerns regarding the welfare and sustainability of farmed aquatic species. Research has shown that animals kept in impoverished environments exhibit more frequent signs of stress, while those under enriched conditions demonstrate enhanced survival, faster growth, improved learning, and increased social interactions. Yet, a higher tendency toward exploration does not necessarily equate to better welfare, as exploratory behavior can be influenced by emotional states and environmental conditions, correlating either with positive cognitive engagement or stress-induced hyperactivity. This dissertation investigates the exploratory behavior of Octopus vulgarisin response to both prey (extrinsic exploration) and novel objects (intrinsic exploration) stimulation under two contrasting rearing/environmental conditions. Using a cross-over experimental design, nine specimens were exposed to a control and a deprived environment (lacking sand, shells, shelters, and rocks) over five days. With daily 20-minute recording sessions, I assessed activity levels, latency to interact with stimuli, interaction duration, and interaction frequency. Results revealed that octopuses in deprived environments exhibited significantly higher activity levels, along with increased interaction frequency. This suggests that environmental deprivation may induce boredom or stress, driving heightened and more rapid engagement with available stimuli. Conversely, those in control environments displayed lower but more selective interactions, potentially reflecting positive emotional states and improved welfare conditions. These findings underscore the profound role of environmental supplementation in improving octopus’ welfare, contributing to the ethical and scientifically informed management of O. vulgaris in controlled settings.
- Desenvolvimento de Metodologias Analíticas Inovadoras para Análise Vestigial de Pesticidas Piretróides em Matrizes AquosasPublication . Miguéis, Renata Martinho Brochado; Nogueira, José Manuel Florêncio, 1965-A utilização excessiva de produtos fitofarmacêuticos na agricultura nas últimas décadas tem resultado na contaminação de recursos hídricos, impactando negativamente diversos ecossistemas. Os piretróides são compostos químicos pertencentes à classe dos inseticidas, amplamente utilizados atualmente para o controle de pragas de insetos. Apesar da baixa toxicidade que esta classe de fitofarmacêuticos apresenta, a utilização em larga escala promove a contaminação pela acumulação progressiva nos solos agrícolas e, consequentemente, a sua infiltração nas águas circundantes. Tendo em conta esta preocupação e em conformidade com as diretivas nacional e europeia, é imprescindível estabelecer metodologias analíticas eficazes e sensíveis para reduzir o consumo de alimentos e água contaminados por pesticidas que excedam os limites permitidos pela legislação vigente, minimizando assim os impactos negativos na saúde pública e ambiental. O presente trabalho consistiu no desenvolvimento, por meio da otimização, validação e aplicação a matrizes reais, de uma abordagem analítica inovadora baseada nos princípios da química verde, alternativa aos métodos convencionais, para a determinação de sete piretróides (Aletrina, Tetrametrina, Bifentrina, Fenpropatrina, Lambda-Cialotrina, Cipermetrina e Fenvalerato). Para esse efeito, recorreu-se a microextração em fibra oca seguida de microdessorção líquida e cromatografia em fase gasosa acoplada a espetrometria de massa (HFμE-μLD/GC-MS(SIM)). Neste sentido, foram estudados diversos parâmetros, tendo obtido as melhores condições experimentais otimizadas (microextração: n-C7, 3 h (1600 rpm), pH 5,5, 5% MeOH; retroextração: n-C7, 2 min sob agitação realizada por vortéx) foram alcançadas recuperações médias compreendidas entre 65,2 e 102,0 % com RSD < 8,8 %. A metodologia revelou, por meio de validação, excelente linearidade (r 2 > 0,9956) nas gamas lineares de concentração entre 0,02 e 10,00 μg L-1 . Foi alcançado limites de deteção e quantificação compreendidos entre 5,0 e 50,0 μg L -1 e 15,0 e 150,0 μg L-1 , respetivamente. Recorrendo ao método de adição padrão, a metodologia otimizada e validada, foi aplicada a matrizes aquosas reais que evidenciaram excelentes linearidades (r 2 > 0,9957), não tendo sido detetado níveis vestigiais dos analitos nas matrizes (< LOD). Além disso, verificou-se a viabilidade da reutilização das fibras, sustentada por estudos de degradação dos compostos alvo e pela aplicação de um protocolo de lavagem otimizado, que garantiu tanto a preservação do desempenho analítico quanto a prevenção de contaminação cruzada entre os ciclos de uso. A metodologia proposta evidenciou ser uma técnica alternativa para a análise vestigial de piretróides em amostras aquosas ambientais. Como principais vantagens destacam-se as pequenas quantidades de amostras utilizada, volumes negligenciáveis de solventes orgânicos, rápida cinética imposta, baixa relação custo-benefício, fácil manipulação e bom desempenho analítico para a monitorização de pesticidas piretróides em matrizes aquosas ambientais.
- Estudo da composição e abundância de microplásticos no registo sedimentar da lagoa da Fajã dos Cubres – AçoresPublication . Arruda, Rodrigo Botelho; Domingos, Isabel Maria Madaleno, 1960-; Raposeiro, Pedro Miguel Valente MendesO presente estudo investiga a composição e abundância de partículas de microplástico no registo sedimentar da Lagoa da Fajã dos Cubres, localizada nos Açores. A investigação justifica-se pela crescente preocupação com a contaminação por microplásticos em ecossistemas costeiros e pela escassez de dados sobre a sua presença em lagoas insulares, particularmente neste arquipélago. Para tal, foram desenvolvidas e adaptadas metodologias de extração e quantificação de partículas de microplástico, combinando oxidação com peróxido de hidrogénio e separação por densidade. As partículas extraídas foram caracterizadas quanto ao tamanho, cor e tipologia, tendo sido analisada a variação temporal da sua concentração. Os resultados evidenciam um aumento da deposição de partículas de microplástico a partir da década de 1980, com um pico de abundância em 1988. As fibras representam a fração dominante (94% das partículas identificadas), sugerindo uma origem maioritariamente associada a atividades humanas, tais como a lavagem de têxteis e a degradação de redes de pesca. As partículas transparentes e azuis foram as mais frequentes, refletindo padrões típicos da contaminação por plásticos em ambientes costeiros. Os dados obtidos destacam o papel das lagoas costeiras como reservatórios eficazes de microplásticos e sublinham a necessidade de monitorização contínua e políticas de mitigação para minimizar os impactos ambientais associados. Este estudo fornece informações essenciais no apoio à gestão ambiental local, permitindo a definição de medidas específicas de monitorização e mitigação para a Lagoa da Fajã dos Cubres, contribuindo assim para a preservação sustentável deste ecossistema costeiro insular.
- Laser-Induced Crystallization of Amorphous Silicon for Poly-Si/SiOx Passivating ContactsPublication . Olho Azul, João Pedro Jones; Lobato, Killian, 1980-; Hahn, GisoLaser-induced crystallization (LIC) was investigated to develop a suitable method to transform 100 nm-thick amorphous silicon (a-Si) into polycrystalline silicon (poly-Si) for poly-Si/SiOx passivating contacts in silicon solar cells. The project explores the influence of laser wavelength, scanning techniques and key laser parameters – such as power P, defocus D, and pulse spots distance L – on passivation quality, conductivity, and crystallinity. A comparison between 532 nm (green) and 355 nm (UV) nanosecond pulsed lasers highlights the impact of the absorption coefficients of a-Si for different wavelengths on crystallization, passivation quality and sample elemental composition due to the laser treatments. Results showed that the 355 nm source was more suited to the project as the 532 nm source treatments frequently resulted in layer ablation and a consequent absence of the oxide layer. The investigation also assesses the role of hydrogenation by silicon nitride (SiNx) deposition followed by a high-temperature, short-duration thermal step (fast firing), testing peak temperatures ranging from 700 to 900◦C. The results showed that firing temperature had a significant impact on passivation, identifying 750◦C as the optimal temperature. Further samples were processed with the 355 nm laser source, followed by a hydrogenation process by firing at 750◦C. The highest achieved implied open-circuit voltage iVoc results were: (0.677 ± 0.015)V, for a non-lasered sample, followed by (0.672 ± 0.012)V for a laser-treated wafer with P = 1.5W, D = 7.0mm and L = 35µm. However, individual measurements in several samples revealed higher iVoc values, with a maximum of 0.695V observed for P = 1.0W, D = 6.0mm, and L = 35µm. Additionally, crystallinity and conductivity of the a-Si layer improved due to laser treatments, in comparison to reference non-lasered wafers.
- Steatosis quantification in Non-Alcoholic Fatty Liver Disease: A statistical approach for comparing different image processing proceduresPublication . Mindouro, Andreia Sofia Pedro; Sousa, Lisete Maria Ribeiro de, 1972-; Paixão, TiagoThe liver plays a crucial role in metabolism and immunity, aiding in nutrient metabolism, detoxification, protein production, digestion, and vitamin storage. The liver is essential for overall well-being. Hepatic steatosis, or fatty liver, is primarily caused by obesity, type 2 diabetes, poor diet, and chronic alcohol consumption. A specific form, Non-alcoholic fatty liver disease (NAFLD), is linked to metabolic issues and high-fat diets. NAFLD is characterized by fat accumulation in liver cells without alcohol involvement, ranging from benign steatosis to more severe conditions like cirrhosis. Diagnosing NAFLD typically involves blood or imaging tests, though liver biopsy remains the most accurate method. However, the standard scoring system for assessing steatosis based on biopsy results is prone to inaccuracies due to variability among observers. Animal models, particularly mice, are commonly used in research to study NAFLD progression and evaluate treatments. New techniques such as machine learning and quantitative data analysis have improved the accuracy of NAFLD diagnosis. In this study, mouse liver samples will be used to compare two automated image analysis plugins, Waikato Environment for Knowledge Analysis (Weka) and Saturation, to determine their accuracy in assessing steatosis. Weka applies machine learning techniques, specifically the Random Forest classifier, to distinguish vacuoles from other cellular components based on morphological features. The study also aims to identify the optimal combinations of magnification, resolution, and the number of images for accurate analysis, and to assess whether there is a pattern in vacuole size related to the steatosis percentage. The appropriate application of statistical methods, such as generalized linear mixed models and bootstrap techniques, enables robust data interpretation and supports scientific communication and evidence-based decision-making. Weka detected more vacuoles than Saturation, especially at low magnification and high resolution. Three to four images were sufficient for reliable estimates, and vacuole size was associated with steatosis severity. Accurate classification of steatosis is vital, as NAFLD is a significant manifestation of metabolic syndrome and poses increased mortality risks, particularly from cardiovascular diseases. Early diagnosis and targeted treatment are key to improving patient outcomes and addressing this global health concern.