Repositório Científico de Acesso Aberto da ULisboa
Repositório Institucional da Universidade de Lisboa
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Identifying Active and Inactive App Usage Using Finite Mixture Models
Publication . Barata,Ana Sofia Dias Alves; Antunes,Marília Cristina de Sousa; Silva,Giovani Loiola da; Faculty of Sciences
The CINDERELLA project aims to improve aesthetic outcomes and patient satisfaction following breast cancer surgery through the CINDERELLA app, an AI-based platform predicting aesthetic results from personal data and pre- and post-operative images. Usage data from the application present a unique opportunity to investigate user behaviour. Due to a bug, app usage time was incorrectly stored. A possibility is to retrieve this information from the login data, which, by its turn, can lead to the record of inflated usage times between sessions. Inflated times may also occur when users leave the app open while engaging in other tasks. Therefore, app usage data can be thought of as a mixture of two types of records: those reflecting active user periods (exact times) and those reflecting inactive periods (inflated tames). Finite mixture models offer a robust framework for addressing classification challenges when the underlying process is not fully observable. This study proposes a two-component finite mixture model to classify session times into exact or inflated categories, exploring parametric specifications including log-normal and Gamma distributions. Covariates capturing socio-demographic factors, clinical characteristics, and user–application interactions were incorporated using mixtures of generalized linear models. Model estimation was conducted using EM (Maximum Likelihood framework) and NUTS (Bayesian framework) algorithms. Data analysis results indicate that the proposed models effectively distinguish exact and inflated usage times, with covariate inclusion improving model fit and classification flexibility. Frequentist and Bayesian approaches yield comparable results for well-specified models. The study highlights the heterogeneity of user behaviour and the importance of accounting for covariates and latent outliers, offering a robust methodology for analysing digital application usage. Future work may include additional mixture components, random effects, and labelled data for enhanced validation and precision.
Temperature-Diet Interactions in Ampullaceana balthica: Life-History Trait Responses at the Edges of a Latitudinal Gradient
Publication . Zimmermann,Clara Dorothea; Carreira,Bruno Martins; Rebelo,Rui Miguel Borges Sampaio e; Faculty of Sciences
Climate warming is reshaping freshwater ecosystems by altering the physiological performance of ectotherms and their ecological interactions. Although temperature plays a central role in governing metabolic processes, its interaction with nutritional status remains poorly understood. Furthermore, the extent to which local adaptation constrains the phenotypic plasticity displayed by ectotherms in response to warming is largely unknown. Here, we investigated how temperature and diet jointly influence the thermal tolerance, growth rate, and reproduction in two geographically distant populations of the freshwater snail Ampullaceana balthica inhabiting widely different climatic regions. Using a fullfactorial design crossing population origin (Portugal, Sweden), temperature (14°C, 20°C), and diet type (animal, plant, mixed), we quantified critical thermal maximum (CTmax) alongside with key lifehistory traits (growth rate, reproduction). Our results revealed pronounced population-specific responses to warming that most probably reflect local adaptation. The Portuguese population showed higher thermal tolerance and maintained performance under elevated temperatures, while the Swedish population performed better under cooler conditions, suggesting divergent thermal performance curves shaped by their native climates. Growth and reproduction were strongly influenced by diet, with responses differing markedly between populations. Portuguese snails performed more efficiently on nitrogen-rich diets, whereas Swedish snails exhibited higher performance on carbon-rich diets. These contrasting results suggest different nutritional strategies, possibly adapted to the trophic landscapes of their home environments, with diet modulating key traits under warming. Overall, this study showed that thermal and nutritional responses in A. balthica are context-dependent, and shaped by the interaction of environmental temperature, resource quality, and population-specific evolutionary history. Highlighting the combined roles of local adaptation and phenotypic plasticity, this study underscores the importance of incorporating intraspecific variation to model ectotherm resilience, population persistence, and alterations in ecosystem functioning under future climate change.
Primary Cilia and the Thioredoxin 1/Thioredoxin Reductase 1 System in the Cellular Response to Hyperglycemia
Publication . Faria,Rodrigo dos Santos Baltazar; Carmona,Bruno Filipe Sousa; Rodrigues,Maria Gabriela Gomes de Figueiredo; Faculty of Sciences
Diabetes Mellitus is a global health challenge where chronic hyperglycemia leads to Diabetic Retinopathy (DR), a primary cause of vision loss and preventable blindness. The retina is particularly susceptible to glucose toxicity due to its high metabolic demand and insulin-independent glucose uptake, which directly exposes retinal cells to reactive oxygen species (ROS). While the Retinal Pigment Epithelium (RPE) is vital for maintaining retinal homeostasis, its neuroprotective capacity is severely impaired under these pathological conditions. This study aimed to characterize the thioredoxin system (Trx-1/TrxR-1) response to hyperglycemia (25 mM D-glucose) in hTERT RPE-1 cells, with a specific focus on the mediatory role of the primary cilium (PC). By employing an optimized protocol to mimic the pathophysiological conditions of DR, alongside fluorescence microscopy and Western blot analysis, we demonstrated that both the levels and subcellular localization of Trx-1 remained unchanged. These findings suggest that, under these experimental conditions, the induction of oxidative stress is likely moderate. A key finding of this work was the observation of a functional uncoupling between Trx-1 and TrxR-1, where the PC selectively modulated TrxR-1 dynamics without affecting Trx-1. Enzymatic assays revealed a paradox: Trx-1 activity remained stable while TrxR-1 activity decreased in ciliated cells, likely due to compensatory mechanisms such as the glutathione system. Overall, together with our previous observations, these findings support the concept that the PC functions as a metabolic signaling hub, communicating cellular metabolic status to the genomic integrity machinery and potentially regulating γH2AX foci through Trx-1/TrxR-1–mediated control of ATM (ataxia telangiectasia mutated) phosphorylation.
What happens to temperate reefs without cleaners?
Publication . Pinto,Patrícia Gabriel da Silva; Paula,José Ricardo Maceiras de; Repolho,Tiago Filipe Baptista da Rosa; Faculty of Sciences
Cleaning interactions play a key role in regulating ectoparasite pressure and structuring reef fish communities. However, experimental evidence for their ecological importance is largely restricted to tropical systems dominated by obligate cleaner species. In contrast, the role of facultative cleaners in temperate reefs remains poorly understood, despite their increasing exploitation in aquaculture and growing interest as ecosystem-relevant species. Here, we experimentally investigated the ecological consequences of facultative cleaner loss by removing the cleaner wrasse Centrolabrus exoletus from temperate rocky reefs in Cascais, Portugal. Sixteen isolated rocky patch reefs were assigned to control and cleaner-removal treatments, and fish assemblages were monitored over time using stationary stereo-video surveys to quantify changes in ectoparasite pressure and reef fish community structure. Ambient ectoparasite pressure was quantified through the abundance of gnathiid isopods collected with passive light traps. Reefs without cleaners exhibited a clear increase in gnathiid abundance through time, whereas parasite abundance declined on control reefs. In parallel, reef fish communities showed gradual, time-dependent divergence between treatments, particularly in species richness, dominance structure, and selected functional groups, while total abundance showed weak treatment effects, and biomass exhibited contrasting temporal trajectories between control and removal reefs. These findings demonstrate that facultative cleaner species can influence temperate reef ecosystems through indirect, time-dependent processes, primarily through parasite regulation. This study highlights the ecological relevance of cleaning interactions beyond tropical reef systems and underscores the importance of considering biotic interactions when assessing reef community dynamics in temperate environments.
Implant size on drug release design
Publication . Pimenta,Dorina Juhász-Tóth; Ferreira,Helena Isabel Fialho Florindo Roque; University of Lisbon
O desenvolvimento de sistemas de libertação controlada de fármacos tem como objetivo melhorar a eficácia terapêutica, a adesão do paciente e otimizar o perfil farmacocinético dos princípios ativos. Entre os materiais utilizados nesses sistemas, o etileno vinil acetato (EVA) destaca-se pela sua alta biocompatibilidade, estabilidade química e capacidade de libertação sustentada do fármaco por longos períodos. Apesar do seu uso já bem estabelecido em sistemas do tipo reservatório e revestimentos, a sua aplicação em sistemas de matriz permanece relativamente pouco explorada. Este estudo investiga o impacto da geometria do implante, especificamente o comprimento e o diâmetro, na libertação do fármaco em sistemas matriz a partir de implantes de EVA. Implantes cilíndricos compostos por EVA com teor de 40 wt. % de vinil acetato, carregados com 20% de risperidona, foram produzidos por extrusão a quente. A caracterização físico-química incluiu a determinação do teor real de fármaco, eficiência de encapsulação, análise calorimétrica, avaliação morfológica por macroscopia e estudos de libertação in vitro. Os estudos de libertação foram realizados sob condições de saturação durante 28 dias e os resultados foram analisados utilizando o modelo de difusão de Higuchi. Os resultados revelaram que o comprimento do implante não teve efeito significativo sobre o perfil de libertação, enquanto o diâmetro teve. Implantes com menores diâmetros libertaram o fármaco mais rapidamente, resultando em maior libertação cumulativa, enquanto implantes com diâmetros maiores proporcionaram uma libertação mais lenta e sustentada. Assim, à medida que o diâmetro aumenta, a libertação do fármaco torna-se progressivamente mais lenta. A análise morfológica corroborou estes resultados, mostrando zonas de depleção que se propagam da superfície do implante em direção ao núcleo. De modo geral, este trabalho reforça o papel do copolímero de EVA como um material matricial robusto e versátil para sistemas de libertação prolongada e destaca a importância da otimização geométrica, em particular do diâmetro, como um parâmetro prático para ajustar a cinética de libertação dos fármacos. Estes resultados podem apoiar futuras pesquisas e o desenvolvimento de implantes de longa duração para diversas aplicações terapêuticas.