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Repositório Científico da UAlg
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Environmental changes at the seafloor of the Faro drift (Gulf of Cadiz) during the transition from the Early to the Middle Pleistocene
Publication . Silveira Molina, Giulia; Schmiedl, Gerhard; Jiménez-Espejo, Francisco; Kuhnert, Henning; Anica Claro Rodrigues, Teresa Isabel; Voelker, Antje
This study explores the ecology of the benthic foraminifera fauna and reconstructs bottom water oxygenation, organic matter fluxes, and Mediterranean Outflow Water (MOW) dynamics in the Gulf of Cadiz during the Early to Middle Pleistocene Transition (EMPT) interval of Marine Isotope Stage (MIS) 28 to MIS 19 (1014–761 ka) using high-resolution multiproxy data from IODP Site U1387. Along with benthic foraminifera assemblages, we integrate stable isotopes (δ 18O and δ 13C), organic carbon, alkenone concentrations, and geochemical and sedimentological proxies (Zr/Al ratio, grain size) to identify environmental drivers across glacial– interglacial cycles and millennial-scale events. Furthermore, the absolute abundance of Planulina ariminensis is applied as a proxy for bottom current strength. Principal component analysis confirms assemblage responses to variations in organic matter quality and oxygenation. Periods of intensified MOW during stadial climate stages correspond to enhanced bottom water ventilation, reflected in higher abundances of epifaunal and porcelaneous taxa, higher diversity, and increased dissolved oxygen, with the exception of the late MIS 22. Intervals of reduced ventilation (e.g. interglacial MIS 27, MIS 25e, MIS 21g, MIS 19c) coincide with higher total alkenone concentrations, potentially contributing to low oxygen conditions and increased proportions of infaunal taxa. Our results reveal that bottom water dynamics at Site U1387 were controlled by local oceanographic processes (e.g. coastal upwelling, river discharge, water column stratification) rather than by global ice volume changes only. These findings highlight the importance of understanding regional oceanographic variations during the EMPT and emphasize the value of combining food supply, oxygenation, and bottom current proxies to interpret benthic foraminifera ecological changes.
Aprendizado por transferência para correção automática de redação
Publication . Silveira, Igor Cataneo; Ribeiro, Eugénio; Mamede, Nuno; Baptista, Jorge
A tarefa de Correção Automática de Redação tem despertado crescente interesse na área de processamento de texto em português. Entre os conjuntos de dados disponíveis, destaca-se um corpus de redações narrativas produzidas por alunos do 5º ao 9º ano do ensino fundamental no Brasil. Essas redações são avaliadas segundo quatro competências: registro formal, coerência temática, estrutura retórica narrativa e coesão textual. Este trabalho explora a criação de um sistema baseado em conhecimentos derivados de outro dataset (desenvolvido com base em textos produzidos para o ENEM) e de outras tarefas (cálculo de complexidade textual e análise de legibilidade). O sistema desenvolvido combina modelos neurais, características (features) curadas calculadas por programas de análise textual e seleção de features em um modelo de Aprendizado em Dois Estágios. Com isso, foi possível elevar a performance em relação ao estado da-arte, nomeadamente, em 9% para a primeira competência, 5,5% para a terceira e 8,9% para a quarta.
Comparative analysis of additive and multiplicative BoD models in healthcare performance evaluation
Publication . Vara, Guilherme; Gomes, Marta Castilho; Caldas, Paulo; Varela, Miguel; Ferreira, Diogo Cunha
Composite indicators play a pivotal role across various fields, serving as powerful tools to condense information into a single, comprehensible metric. They function as a link between complex data and practical conclusions, which makes them valuable assets in diverse fields, assisting decision-makers. Since objectivity is vital for policy- and decision making, many researchers base their studies on the Benefit of-the-Doubt (BoD) methodology, which originated from the widely recognised Data Envelopment Analysis. This study provides a detailed comparison between the linear and multiplicative BoD approaches, incorporating both optimistic and pessimistic viewpoints to assess the performance of the Portuguese public hospitals. The linear approach is an additive linear programming model that constructs a piecewise linear and convex efficient frontier with the benchmarks. In contrast, the multiplicative approach constructs logarithmic curves instead of linear segments to define the efficient frontier allowing for greater flexibility by accommodating nonconvex and nonlinear shapes that better reflect the data distribution. As a result, the multiplicative approach achieves a tighter fit to the data, ultimately yielding higher overall scores. The results show that multiplicative scores in the pessimistic approach are lower than linear scores. Conversely, in the optimistic multiplicative approach, while expected to yield superior scores, certain entities lag due to non-compensatory elements. The implementation of the multiplicative BoD is remarkably simple, requiring only minimal changes when compared to the linear BoD. This raises questions about its low adoption and utilization compared to linear methods, despite its apparent advantages.
Autistic vs. control differences in MRI scan quality across ABIDE-II sites
Publication . Pinheiro, João; Afonso, Beatriz; Seiça, Emanuel Cortesão de; Gonçalves, Rita; Ribeiro, Luís; Reis, Joana
Background: Head motion and variability in scan quality remain major methodological challenges in autism neuroimaging. Large multi-site datasets such as ABIDE-II provide a unique opportunity to systematically quantify diagnostic differences in MRI data quality and assess the influence of site-level heterogeneity. Methods: Functional MRI Quality Assessment Protocol (QAP) metrics were combined with phenotypic data from ABIDE-II. Participants were classified as autistic (ASD) or typically developing (TD). Key quality metrics—including mean framewise displacement (mFD), proportion of volumes exceeding 0.20 mm (FD > 0.20), signal-to-noise ratio (SNR), and entropy focus criterion (EFC)—were analyzed alongside age, sex, IQ, and site. Group differences were evaluated using non parametric tests and linear mixed-effects models with site as a random factor. Additional analyses examined site-level heterogeneity and the impact of quality-control (QC) thresh olds on sample composition. Results: The final sample included 1277 participants (579 ASD; 698 TD) across 14 sites. ASD participants exhibited significantly greater head motion (median mFD = 0.101 vs. 0.081 mm; p < 1 × 10−10) and modest reductions in signal quality (lower SNR, higher EFC). Elevated motion in ASD was observed in 12 of 14 sites, although effect sizes varied substantially. Mixed-effects models confirmed that diagnosis remained a significant predictor of motion after adjusting for covariates. In contrast, signal-quality differences were small and largely explained by site effects. Simulated QC procedures disproportionately excluded ASD participants, with exclusion rates up to 31% compared to 18% in TD. Conclusions: ASD participants show consistently higher head motion, while signal-quality differences are minimal and largely site-driven. Standard QC procedures disproportionately exclude ASD individuals, highlighting the need for improved motion handling and more balanced quality-control strategies in multi-site studies.
Evidências do português médio no corpus de textos antigos
Publication . Bico, Maria Inês; Cardeira, Esperança; Baptista, Jorge; Batista, Fernando
A partir de um conjunto de dados semi-automaticamente anotados do Corpus de Textos Antigos (CTA), este artigo propõe-se a analisar os resultados obtidos sobre a síncope de -d- intervocálico no morfema da 2.ª pessoa plural, e a consequente resolução do hiato, e as terminações de Particípio Passado -udo/-ido nos verbos com origem etimológica nas 2.ª e 3.ª conjugações latinas. A novidade deste artigo está no recurso a métodos de Processamento de Linguagem Natural (PLN) para a otimização da obtenção e extração sistemática dos dados relevantes para análise, contribuindo para um estudo que engloba um maior conjunto de textos. É apresentada a metodologia adotada para a anotação dos dados, e consequente extração dos dados relevantes à análise, afirmando-se a importância do recurso a métodos e ferramentas de PLN para o estudo linguístico e para a descrição dos estados anteriores da língua portuguesa.