Explore the vast range of titles available.

Microwave (MW) drying of wood has gained popularity in the field of wood modification. The rise in temperature during MW drying leads to increased steam pressure, enhancing wood permeability but potentially decreasing mechanical properties. Understanding temperature and moisture behaviors during MW drying is crucial for its industrial application in wood drying. Therefore, this study aimed to characterize the temperature and moisture behaviors during MW drying of small Portuguese maritime pine (Pinus pinaster Aiton.) wood samples to support a wider use of this technology. The effects on water uptake and the compressive strength parallel to the grain were also investigated. The results indicated three distinct phases in the MW drying rates, with an average of 0.085% of water removed per second. Moreover, the temperature underwent three distinct stages: an initial rapid increase, a period of constant temperature, and a slight decrease until drying was complete. At the beginning of MW drying, the temperatures were below 100 °C, with average temperatures ranging from 126 to 145 °C. Specimens with lower initial moisture content had higher temperatures, and a positive correlation was found between initial moisture content and drying time. In contrast, negative correlations were found between the initial moisture content and average temperature, as well as average temperature and MW drying time. Additionally, the operating condition parameters used in MW drying of pine samples enhanced water impregnability by 65%, generating a slight reduction of 11% in compressive strength. It was also noticed that the initial moisture content did not impact MW-dried samples’ water uptake or compressive strength. Finally, although small clear wood samples of maritime pine were utilized, the temperature and moisture patterns observed closely matched real-scale specimens. Thus, the findings corroborate a wide utilization of MW technology for wood drying, mainly demonstrating positive possibilities for structural-sized wood specimens.

The most widespread wood species in the Portuguese forest and the most widely utilized are maritime pine (Pinus pinaster) and eucalyptus (Eucalyptus globulus Labill). In the case of eucalyptus, except for the pulping sector, it might have limited usage due to drying issues and low permeability. Microwave (MW) treatment is a technology that has been used to improve wood species’ permeability. Therefore, the present paper aimed to evaluate the MW treatment of both Portuguese wood species and to investigate the effects of different MW treatments on wood’s density, water uptake capability, modulus of rupture (MOR), and modulus of elasticity (MOE). Using small clear wood specimens, two MW powers were used, 700 and 1200 W, and the samples were submitted to successive MW cycles of 2 min till they reached the required dryness. The results showed that each wood species had a different behavior during the MW drying in terms of drying rate, supply, and consumption of energy. In general, with the increase in MW power, the densities of both species decreased and the water uptake increased, as a possible indicator that a certain level of microstructural damage might have occurred. Regarding the mechanical properties of MW-treated maritime pine and eucalyptus wood specimens, under the harshest conditions (MW power of 1200 W), MOR and MOE were reduced compared with the wood sample without MW treatment.

The impregnability of Portuguese maritime pine (Pinus pinaster Ait.) subjected to microwave (MW) drying was tested, and the hydrophobicity, anti-swelling efficiency (ASE), and water repellence efficiency (WRE) were evaluated. Small wood heartwood samples of Portuguese maritime pine and two distinct MW treatment settings were employed. The levels of ASE and WRE of the wood elements were evaluated throughout four cycles of drying in an oven and soaking in water. Because of MW applied energy, the wood pine samples were satisfactorily impregnated with the preservative product. Regarding the absolutely dry densities of the samples, very subtle reductions were measured, and they were statistically equivalent to the average density of the non-MW-treated group. Slight improvements were identified in the WRE values of wood samples dried in the microwave. In terms of ASE, both MW-treated groups had a statistically significant increase. The MW treatment decreased the volumetric swelling of the maritime pine wood specimens. Hence, this study raises new insights and previously unexplored paths that can contribute to the expansion and greater application of MW technology in maritime pine and other species.

The most widespread wood species in the Portuguese forest and the most widely utilized are maritime pine (Pinus pinaster) and eucalyptus (Eucalyptus globulus Labill). In the case of eucalyptus, except for the pulping sector, it might have limited usage due to drying issues and low permeability. Microwave (MW) treatment is a technology that has been used to improve wood species’ permeability. Therefore, the present paper aimed to evaluate the MW treatment of both Portuguese wood species and to investigate the effects of different MW treatments on wood’s density, water uptake capability, modulus of rupture (MOR), and modulus of elasticity (MOE). Using small clear wood specimens, two MW powers were used, 700 and 1200 W, and the samples were submitted to successive MW cycles of 2 min till they reached the required dryness. The results showed that each wood species had a different behavior during the MW drying in terms of drying rate, supply, and consumption of energy. In general, with the increase in MW power, the densities of both species decreased and the water uptake increased, as a possible indicator that a certain level of microstructural damage might have occurred. Regarding the mechanical properties of MW-treated maritime pine and eucalyptus wood specimens, under the harshest conditions (MW power of 1200 W), MOR and MOE were reduced compared with the wood sample without MW treatment.

Com origem há cerca de 2.500 milhões de anos, as microalgas podem ser encontradas em quase todo o tipo de ambientes apresentando, deste modo, uma extensa biodiversidade que possibilita a exploração de diferentes metabolitos por elas produzidos.Atualmente, a exploração destes microrganismos abrange uma vasta área, que vai desde a alimentação humana e animal até à farmacêutica. O seu interesse comercial é evidente, produzindo-se cerca de 11 000 toneladas todos os anos.Apesar dos avanços alcançados, persiste a necessidade de otimizar o processo como um todo, para melhorar a sua viabilidade económica. Neste contexto, a otimização da extração de produtos de elevado valor acrescentado, como a astaxantina, é uma das vias a seguir.Este produto é produzido principalmente pela microalga Haematococcus pluvialis; atualmente, são produzidas cerca de 300 toneladas por ano e o seu valor pode atingir os 6300€/kg. O presente trabalho visava trabalhar com a H. pluvialis e otimizar as suas condições de crescimento e de extração de astaxantina. Durante os meses de novembro e dezembro de 2019 realizaram-se alguns ensaios com esta microalga, que permitiram identificar alguns fatores limitantes do crescimento, nomeadamente fosforo e luz. Com o aparecimento da pandemia não foi possível manter a H. pluvialis em condições favoráveis, tendo ocorrido contaminações por outros microrganismos que tornou inviável continuar com esta microalga adquirida na Escócia. Face a isto, o trabalho orientou-se para a Chlorella vulgaris na qual se aplicou a mesma estratégia: identificação das limitações ao crescimento; aumento do crescimento suprindo as carências de fosforo e implementando um método que permite fornecer a intensidade luminosa necessária, mesmo com elevadas concentrações de biomassa; aplicação de condições de stress ( luz, carência de nutrientes e H2O2) e avaliação do impacto na biomassa e nos correspondentes teores de carotenoides e lípidos.Deste modo, foi realizado uma otimização que envolveu alterações no meio de cultura e, posteriormente, foi analisado e caracterizado o efeito da intensidade luminosa ao longo do tempo de cultura, sendo este um dos fatores limitantes na cultura.O método proposto permitiu aumentar em 22% a quantidade de lípidos e em 51% a quantidade de carotenos produzidos pelas células, tendo em conta o acréscimo de biomassa obtido pelos métodos de cultura otimizados, quando comparados a um controlo.Os resultados desta investigação permitem o desenvolvimento de métodos mais eficazes na produção de biomassa, bem como a utilização de um método para a produção de compostos de interesse, apresentando-se o peróxido de hidrogénio como um indutor de stress