Browsing by Author "Monteiro, Helena"
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- Characterization of an antioxidant surfactant-free topical formulation containing Castanea sativa leaf extractPublication . Almeida, Isabel F.; Maleckova, Jitka; Saffi, Raquel; Monteiro, Helena; Góios, Filipa; Amaral, Maria Helena; Costa, Paulo Cardoso; Garrido, Jorge; Silva, Paulo; Pestana, Nazaré; Bahia, Maria FernandaContext: Inclusion of antioxidants in topical formulations can contribute to minimize oxidative stress in the skin, which has been associated with photoaging, several dermatosis and cancer. Objective: A Castanea sativa leaf extract with established antioxidant activity was incorporated into a semisolid surfactant-free formulation. The objective of this study was to perform a comprehensive characterization of this formulation. Materials and methods: Physical, microbiological and functional stability were evaluated during 6 months storage at 20 °C and 40 °C. Microstructure elucidation (cryo-SEM), in vitro release and in vivo moisturizing effect (Corneometer® CM 825) were also assessed. Results and discussion: Minor changes were observed in the textural and rheological properties of the formulation when stored at 20 °C for 6 months and the antioxidant activity of the plant extract remained constant throughout the storage period. Microbiological quality was confirmed at the end of the study. Under accelerated conditions, higher modifications of the evaluated parameters were observed. Cryo-SEM analysis revealed the presence of oil droplets dispersed into a gelified external phase. The release rate of the antioxidant compounds (610 ± 70 µgh−0.5) followed Higuchi model. A significant in vivo moisturizing effect was demonstrated, that lasted at least 4 h after product’s application. Conclusion: The physical, functional and microbiological stability of the antioxidant formulation was established. Specific storage conditions should be recommended considering the influence of temperature on the stability. A skin hydration effect and good skin tolerance were also found which suggests that this preparation can be useful in the prevention or treatment of oxidative stress-mediated dysfunctions.
- Indoor Air Quality Improvement Using Nature-Based Solutions: Design Proposals to Greener CitiesPublication . Mata, Teresa M.; Oliveira, Gisela M.; Monteiro, Helena; Silva, Gabriela Ventura; Caetano, Nídia; Martins, António A.Low indoor air quality is an increasingly important problem due to the spread of urbanization. Because people spend most of their time inside, poor indoor air quality causes serious human health issues, resulting in significant economic losses. In this work, the current state of affairs is presented and analyzed, focusing on the current problems and the available solutions to improve the quality of indoor air, and the use of nature-based solutions. These involve the cultivation of microalgae in closed photobioreactors. In these systems, photosynthetic organisms can capture CO2 and other pollutants generated in indoor environments, which they use to grow and develop biomass. Several possible layouts for the implementation of microalgae-based indoor air cleaning systems are presented, taking into account the systems that are currently available at a commercial scale. A critical analysis of the microalgae indoor purification systems is presented, highlighting their advantages and disadvantages, and suggesting potential improvements and future lines of research and development in the area
- Life cycle energy of vehicles on lightweighting and alternative powertrain strategies—A reviewPublication . Monteiro, Helena; Alonso, Rita; Gonçalves, Margarida; Iten, Muriel; Caetano, Nídia S.To improve vehicles environmental performance, different strategies have been explored namely to reduce the use stage energy. In order to avoid problem shifting, a life cycle perspective should be used to compare alternative solutions. This paper aims to compare existing studies focused on life cycle energy (LCE) of vehicles to analyze the impacts and benefits regarding two trending improvement strategies: lightweight materials and alternative powertrain selection. A Literature review was performed to systematize quantitatively the LCE results of different studies (e.g. presented among figures, tables, and literature text). The LCE results were compiled and normalized for the same driving distance, 200 000 km, per life cycle stage. Moreover, the study discusses research findings on the application of the two strategies to improve overall vehicles’ LCE. As lightweight materials have generally higher embodied energy, the material selection is highly influenced by end-of-life scenarios. It was observed that carbon/glass fiber composites generally have the highest embodied energy, being a preferable option for vehicles that last longer driving distances. Innovative powertrains sourced by renewable energy sources, electric mixes, can significantly reduce vehicles’ LCE use stage, counteracting the benefit of lightweight design. Thus, the benefit of both strategies should be studied together.