DigitUMa

University of Madeira Institutional Repository

Bem-vindo ao Repositório Digital da UNIVERSIDADE DA MADEIRA.

O Repositório da Universidade da Madeira (UMa), conhecido pelo acrónimo DigitUMa, tem como objetivo a disponibilização, em regime de livre acesso e texto integral, de toda a produção científica realizada pelos docentes, investigadores da UMa, discentes dos 2º e 3º ciclos e pelos funcionários.

O Repositório Institucional, DigitUMa, assenta na política de Acesso Aberto à informação e conhecimento científicos.

Email antonio.freitas@staff.uma.pt

Recent Submissions

Soluble extracellular polymeric substances and microplastics: exposure-response and circular reuse for removal

Publication . Rodrigues, Filipa; Mendonça, Ivana; Faria, Marisa; Gomes, Ricardo; Gómez Pinchetti, Juan L.; Ferreira, Artur; Cordeiro, Nereida; cordeiro, nereida

Microplastics (MPs) are pervasive in aquatic systems, threatening ecosystems, human health, and microalgal production. Soluble extracellular polymeric substances (S-EPS) can agglomerate particles and aid removal. This study examines S-EPS from the cyanobacterium Cyanocohniella rudolphia (BEA 0786B) to (i) model and optimise S-EPS production, (ii) assess production in water contaminated with polystyrene MPs (PS-MPs), and (iii) test S EPS as a bioflocculant for PS-MPs removal. Response surface methodology (RSM) defined a cost-lean operating window and predicted an optimum S-EPS titre of 113 mg/L at 7 days using 10 g/L nitrogen, 0.98 g/L phosphorus, and a biomass-to-medium ratio of 1:6.87 (w/v). Cultures were challenged with PS-MPs (50 μg/L and 5 mg/L) under static or aerated conditions, and at both exponential and stationary phases, and showed stimulated S-EPS synthesis with increases of up to 34%, depending on hydrodynamics and growth stage. Purified S-EPS were evaluated as a bioflocculant at 2 g/L PS-MPs to probe robustness and rate-limiting mechanisms and to delineate a conservative operating window. Maximum removal of 82% was achieved in freshwater at pH 3.5 with Fe3+ 0.05% (w/w), 25 ◦C, S-EPS dose 400 mg/L (S-EPS:PS-MPs 1:5, w/w), and 60 min flocculation. Zeta potential trends and microscopy support charge neutralisation/bridging as the dominant mechanism. Compatible with standard coagulation/flocculation units, the approach links cost-lean, cultivation-derived S-EPS (typically dis carded) to their reuse as a low-additive pretreatment for algal-cultivation intake waters (freshwater/low salinity), reducing reliance on synthetic coagulants and added salinity/metal-sludge burdens. Overall, C. rudolphia is a promising S-EPS producer, whose production is enhanced by exposure to PS-MPs, and its S-EPS acts as an efficient, bio-based flocculant for PS-MPs. The results support process designs to safeguard microalgal operations and to mitigate microplastic pollution in water. This work integrates RSM-optimised S-EPS produc tion, environmental-level exposure-response, and a high-load removal benchmark, enabling circular, low additive, drop-in pretreatment compatible with standard coagulation/flocculation units.

2025-12Journal article

Open access

Genetic diversity and conservation of the Madeira Island (Portugal) endemic Geranium maderense Yeo (Geraniaceae)

Publication . Gouveia, M.; Nyberg, B.; Aedo, C.; Bairos, C.; Sequeira, M. Menezes de; Gouveia, Manuela; Sequeira, Miguel

Geranium maderense is a perennial, monocarpic herb, up to 200 cm tall, producing very showy inflorescences, very rare in the wild, although cultivated throughout the world as an ornamental plant. G. maderense is protected under the EC habitats directive (Annex *B-II, IV) and Bern Convention (Annex I) only found, so far, in two cliff associated sites, and classified as a Critically Endangered species (IUCN). Using unmanned aerial vehicle (UAV; drone) technology, two new populations were detected, and a new distribution map is presented. Inter-simple sequence repeat markers were used to detect genetic diversity in natural populations and garden grown plants. Genetic diversity estimates revealed retention of genetic variation and weak genetic structure in G. maderense populations. Cluster and principal component analyses formed coherent groups, indicating that genetic diversity in the studied wild populations of G. maderense is heterogeneously distributed. Our results provide crucial information for the preservation of natural populations of G. maderense, and allow for the revaluation, following IUCN criteria as Endangered (EN).

2025-12Journal article

Open access

Presidential elections and secretary appointment: an event study for us biotechnology and drugs

Publication . Martins, António Miguel; Albuquerque, Bruno; Sardinha, Luís; Moutinho, Nuno; Martins, António; Albuquerque, Bruno; Sardinha, Luis

The aim of this study is to analyse the effect of the 2024 US presidential election and the appointment of the US health secretary to the largest US listed biotechnology and drug firms. Using an event study methodology, we find that President Donald Trump’s election had no sig nificant impact on the industry. On the contrary, the results show statistically significant negative stock price reactions around the US health secretary appointment. The negative industry reaction to the US health secretary appointment is largely explained by his scepticism about vaccination and criticism about the high prices of drug prescriptions and margins in the industry. These re sults highlight the importance of top government position appointments, especially when such appointments eliminate much of the uncertainty regarding future government action in the in dustry and political uncertainty hypothesis. Finally, cross-section analysis reveals that the firms most penalized by the 2024 US presidential election and the appointment of the US health sec retary are those with the highest investments in R&D and capital expenditures. This could mean lower future investments in new vaccines or drugs, seriously harming society.

2025-11Journal article

Open access

2024 U.S. presidential elections: an event study for U.S. and non-U.S. fossil fuel and renewable listed firms

Publication . Martins, António Miguel; Albuquerque, Bruno; Sardinha, Luís; Moutinho, Nuno; Martins, António; Albuquerque, Bruno; Sardinha, Luis

This study examines the short-term market effect of Donald Trump’ victory in the 2024 US presidential election on largest US and non-US listed worldwide fuel fossil and renewable firms. Employing an event study meth odology, we observe a negative and statistically significant stock price reaction for worldwide renewable listed firms. An analysis by economic zones reveals the existence of negative abnormal returns for renewable energy firms in the US, Europe, India and in the rest of the world. In the case of China, abnormal returns are not sta tistically significant. With respect to worldwide fossil fuel listed firms, abnormal returns are generally not sta tistically significant. However, regarding US firms, we observe positive and statistically significant abnormal returns. These abnormal returns are explained by the change of US energy policy (pro-oil and gas policy) and the expected cut in subsidies and lower profitability of investments in green energies. Finally, our study provide insight into which firm-specific characteristics emerge as value drives around US presidential elections. The results show that despite the change in environmental policy in the US, favourable to fossil energy, the stock markets reward firms with high environmental ratings. Overall, our results indicate that 2024 US presidential election, for implying a change in US energy policy, has relevant policy implications for energy listed firms.

2025-09Journal article

Open access

Shifting currents: expert perspectives on the adoption of direct current in power grids

Publication . Ngirwa, Catherine; Reis, Diogo; Morais, Hugo; Pereira, Lucas; Ngirwa, Catherine

Utilization of renewable energy resources for energy generation brought significant attention to Direct Current (DC) technologies, as many of them produce and store electricity in DC. Compared to Alternating Current, the DC technologies, specifically in Medium-Voltage (MV) and Low-Voltage (LV), are in their infancy, leading to less data availability for decision-making. To inform early-phase technologies, experts are consulted through the structured Expert Elicitation (EE) method, though few have explored it in examining technical and non technical aspects of MVDC and LVDC technologies. Hence, in this paper, we present two EE studies on eleven (11) MVDC and LVDC technologies proposed in the Shift2DC research project — applicable for ports, buildings, industry, and data centers. We found that experts perceived the presented DC technologies as feasible and important. Among the most perceived concerns for DC technologies adoption are a lack of trained personnel, public awareness, and uncertainty in regulations to enforce the use of innovations. Experts proposed the need for educational strategies for the general public and a structured curriculum for training technicians in DC. In addition, experts envisioned enabling emerging technologies, such as digital twins and energy management systems, for DC system management.

2025-11Journal article

Open access