Ciências e Tecnologia / Sciences and Technology
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Percorrer Ciências e Tecnologia / Sciences and Technology por Domínios Científicos e Tecnológicos (FOS) "Ciências Naturais::Ciências Químicas"
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- Balanceamento de equações químicasPublication . Fernandes, TiagoPorque é que a matéria se conserva nas reações químicas do dia-a-dia? Como o balanceamento ajuda a prever quantidades em situações reais? Que consequências práticas podem surgir de uma equação mal balanceada? Em todas as transformações químicas, incluindo as que ocorrem no quotidiano (combustão de combustíveis, digestão de alimentos ou a corrosão de metais, entre outras), a matéria não é criada nem destruída, apenas reorganizada. Esta é uma ideia fundamental explica porque é que os átomos presentes nos reagentes devem aparecer, em igual número, nos produtos de uma reação química. O balanceamento de equações químicas traduz este princípio em termos quantitativos, e permite prever com rigor as quantidades de reagentes necessários e a quantidade de produtos formados. Esta previsão é essencial nos mais diversos contextos práticos, tais como na indústria química, no laboratório, na medicina, na engenharia ou até atividades domésticas aparentemente simples. Quando uma equação não está corretamente balanceada, as consequências podem ser significativas, traduzindo-se no desperdício de materiais, em cálculos errados, no aumento de custos e em certos casos no aumento de riscos para a segurança. Compreender e aplicar corretamente o acerto de equações químicas é uma competência importante na formação científica.
- Estruturas Metalo-Orgânicas (MOFs) e Polímeros de Coordenação (PCs) no Instituto Superior Técnico: síntese e aplicações atuaisPublication . Kirillov, Alexander M.; Fernandes, Tiago; Pinto, Rosana V.; Bordonhos, Marta; Mohtar, Abeer; Pinto, Moisés L.Este artigo destaca mais de uma década de investigação no Instituto Superior Técnico (IST, ULisboa), conduzida pelos grupos de Moisés L. Pinto (CERENA) e Alexander Kirillov (CQE), com foco no design personalizado de estruturas metalo-orgânicas (MOFs) e polímeros de coordenação (PCs). Os materiais desenvolvidos revelam um enorme potencial na separação de gases, purificação do ar e em aplicações biomédicas, incluindo a libertação controlada de gases terapêuticos e propriedades antimicrobianas. Estes exemplos ilustram como o controlo preciso da estrutura destes materiais permite criar soluções para desafios atuais, abrindo caminho a tecnologias que podem transformar a indústria, o ambiente e a saúde.
- The interplay of bottle storage and wood ageing technology: volatile and sensory profiles of wine spirits aged with chestnut woodPublication . Caldeira, Ilda; Anjos, Ofélia; Vitória, Cláudia; Oliveira Alves, Sheila; Fernandes, Tiago; Canas, Sara; Catarino, SofiaWine spirits are typically aged in wooden barrels. Recently, alternative ageing technologies, such as those using wood fragments in wine spirits stored in stainless steel tanks, have been investigated. However, a significant lack of information regarding the potential evolution of these beverages after bottling still remains. This study assessed the 12-month evolution of aroma in bottled wine spirits aged with chestnut wood using different technologies, including fragment application with several micro-oxygenation strategies and barrels (traditional). Chemical analysis using GC-FID and GC–MS methods, along with sensory analysis, was conducted on all sampled aged wine spirits. Significant changes in volatile compounds were detected over time, including volatile phenols, acids, and esters. Multivariate data analysis distinguished traditional and alternative aged samples, with slight sample discrimination based on bottle storage. Regarding the sensory results, a significant effect of the time in bottle in several sensory attributes was found, while the ageing technologies mainly affected the gustatory attributes. The tasters were also asked to rate the overall quality of the samples, which seems to be favoured by the time in the bottle. This initial assessment of the impact of 1 year of glass bottle storage on the volatile and sensory composition of aged wine spirits highlights that this stage must be considered as an additional technological factor in their production process. However, the differences induced by the wood ageing technologies applied remained evident after 1 year of glass bottle storage.
- Optimization of extraction of bioactive compounds from piper corcovadensis C.DC leaves using a generalized linear modelPublication . Fontoura, Bruno Henrique; Ramos, Luciano de Souza; Dallacorte, Lucas Vinícius; Rodrigues, Michelle Fernanda Faita; Marchese, José Abramo; Fernandes, Tiago; Cunha, Mário Antônio Alves da; Lima, Vanderlei Aparecido de; Carpes, Solange TeresinhaThis concerns P. corcovadensis, an endemic plant of Brazil commonly used by the population due to its therapeutic properties. Optimizing chemical extraction conditions is critical for increasing the availability of bioactive compounds from plants. These compounds have antioxidant potential derived from a plant’s specialized metabolism and can exhibit a variety of biological actions. Therefore, statistical tools such as the Random Forest and Lazy KStar machine learning algorithms were used to determine the optimal condition for the extraction of phenolic compounds from P. corcovadensis leaves, with model evaluated by coefficient of determination (R2), mean square root of calibration error (RMSEC), and residual predictive deviation (RPD). The optimal extraction condition was obtained using a mixture of 80/20% (ethanol/water) at 70 °C for 120 min. For those extracts, there were 11.64 ± 0.04 mg GAE g-1 and antioxidant activity of 21.27 ± 0.53 mmol Trolox g-1, 33.15 ± 11.66 mmol Trolox g-1, and 13.47 ± 1.37 mmol Fe2+ by DPPH, ABTS and FRAP tests. With this study, we have shown that mathematical modelling can also be helpful in experimental sciences and can be used to develop predictive models. It was possible to develop predictive models for total phenolic compounds determination using the Random Forest and Lazy KStar machine learning algorithms. The Random Forest algorithm performed very well for DPPH modelling, giving us the confidence to use it to prediction antioxidant activity.
- Storage time in bottle: influence on physicochemical and phytochemical characteristics of wine spirits aged using traditional and alternative technologiesPublication . Alves, Sheila C. Oliveira; Fernandes, Tiago; Lourenço, Sílvia; Soares, Joana Granja; Silva, Andreia B.; Bronze, Maria Rosário; Catarino, Sofia; Canas, SaraFew studies have investigated the influence on physicochemical and phytochemical compositions during storage in the bottle of wine spirits (WSs) aged using alternative ageing technology (AAT) compared to traditional ageing technology (TAT). The aim of this study was to evaluate the effect of the bottle storage over one and four years on the evolution of chromatic characteristics (CIELab method) and physicochemical characteristics (alcoholic strength, acidity, and total dry extract), total phenolic index (TPI), low molecular weight compound contents (HPLC-DAD technique), in vitro antioxidant activities (DPPH, FRAP, and ABTS assays), and phenolic characterisation (HPLC-DAD-ESI-MS/MS technique) of WSs aged with chestnut wood using TAT (barrels, B) and AAT (micro-oxygenation levels (MOX): O15, O30, and O60; and control (N)). The results showed that after four years of storage in the bottle, the O60 modality resulted in smaller changes in physicochemical characteristics, higher preservation of phenolic content, and greater evolution of chromatic characteristics, ensuring its overall quality compared to other modalities. Antioxidant activity decreased similarly in both technologies, such as phenolic acid content, in particular, gallic acid content. According to the findings of this study, alternative ageing technology might be the best alternative for wine spirit quality and ageing process sustainability.