Browsing by Issue Date, starting with "2021-10"
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- Combined hydrothermal pre-treatment and enzymatic hydrolysis of corn fibre: production of ferulic acid extracts and assessment of their antioxidant and antiproliferative propertiesPublication . Valério, Rita; Serra, Ana Teresa; Baixinho, João; Cardeira, Martim; Fernández, Naiara; Bronze, MR; Duarte, Luís C.; Tavares, Maria L.; Crespo, João; Brazinha, CarlaABSTRACT: Ferulic acid may be used as a nutraceutical ingredient or as a substrate to produce bio-vanillin. There is an increasing market demand for ferulic acid obtained from natural sources such as low-cost agro-industrial by-products, due to its potential applications as nutraceutical ingredient and as a substrate to produce biovanillin. This work aims to study ferulic acid recovery from corn fibre (one of the most abundant natural sources of ferulic acid), involving an integrated process of hydrothermal pre-treatment followed by enzymatic hydrolysis. The objective is primarily to produce natural extracts with a maximum ferulic acid recovery yield, but it is also to assess their antioxidant and antiproliferative properties and their cytotoxicity. Different commercial enzyme preparations were tested for release of ferulic acid from corn fibre. The best results were obtained for Ultraflo (R) XL in a concentration of 2 % (W-enzyme preparation/W- dry corn fibre) at a pH of 5 and at 55 degrees C, presenting a recovery yield of esterified ferulic acid of 7.83 +/- 1.35 % (w(recovered ferulic acid)/w(total esterified ferulic acid)), which corresponds to 0.13 +/- 0.02 % (w(ferulic acid)/w (thy corn fibre)). When using a hydrothermal pretreatment at a temperature of 140 degrees C for 40 min, prior to the use of the same enzymatic hydrolysis procedure, the recovery yield of esterified ferulic acid increased to 28.94 +/- 2.40 % (W- recovered ferulic acid/ w(total esterified ferulic acid)), which corresponds to 4.9 +/- 0.3 % (w(ferulic acid)/w(dry corn fibre)). The use of this pre-treatment leads not only to the highest yield of ferulic acid, but also to the lowest concentration of furfural and hydroxymethylfurfural, without the formation of formic and levulinic acid (not detected). All pre-treatments tested led to an improved quality of the extract in terms of bioactivity.
- Dynamic corrosion testing of metals in solar salt for concentrated solar powerPublication . Sutter, Florian; Oskay, Ceyhun; Galetz, Mathias Christian; Cunha Diamantino, Teresa; Pedrosa, Fátima; Figueira, Isabel; Glumm, Stefan; Bonk, Alexander; Aguero, Alina; Rodríguez, Sergio; Reche-Navarro, Tomas Jesus; Caron, SimonABSTRACT: Potassium nitrate and sodium nitrate in mixing proportion of KNO3-NaNO3 40-60 wt% (also called solar salt) has been successfully used for over a decade as heat storage medium for concentrated solar power parabolic-trough collector plants at temperatures up to 400 degrees C. At temperatures of 560 degrees C, reached in state-of-the-art solar tower systems, corrosion of metallic components in contact with solar salt can become an issue and has caused leaks and plant shut-downs in recently built tower projects. While the corrosion rates of several materials have been determined for different temperatures in static molten salt immersion experiments, there is a lack of corrosion data for dynamic in-service conditions. In this work, a dynamic corrosion test has been conducted on 19 different material types including protective coatings, mimicking flow-rate, temperature gradient and draining of inservice operation of a receiver in a concentrated solar power tower. The measured corrosion rates are presented and compared to static corrosion tests reported in literature.
- Gibbs-Thomson effect as driving force for liquid film migration: Converting metallic into ceramic fibers through intrinsic oxidationPublication . Dias, Marta; Rosinski, M.; Rodrigues, P. C. R.; Correia, J.B.; Carvalho, Patricia AlmeidaABSTRACT: Liquid film migration is of great practical importance in materials engineering. The phenomenon has been shown to depend on thermal gradients and coherency strain, but no single driving mechanism seems capable of justifying the whole array of experimental observations. On the other hand, the inevitable capillarity effects are often disregarded due to the unknown 3-dimensional geometry of the system. Here, we present evidence of liquid film migration governed primarily by capillarity through a microstructural setup of cylindrical interfaces that allows clear interpretation and modeling. The experiments rely on the strong oxygen-gettering ability of tantalum fibers dispersed in a tungsten matrix and on field-enhanced diffusivity provided by pulse plasma compaction. Tantalum scavenges the residual oxygen present in the W powder and, as a result, oxide films grow around the fibers. These oxide tubes, in liquid state during sintering, migrate toward the fiber axis and eventually become oxide rods surrounded by metallic Ta. The process is driven by the Gibbs-Thomson effect that generates the required composition gradient across the liquid film. An analytical description of the film evolution is implemented by combining the incoming O flux with capillarity-driven migration. Possible contributions from other mechanisms are examined and the relevance of the Gibbs-Thomson effect to the general phenomenon of liquid film migration is established.
- Mineral prospectivity mapping for critical raw materials at the European scale with the CBA method [Resumo]Publication . Bertrand, Guillaume; Sadeghi, Martiya; De Oliveira, Daniel Pipa Soares; Tourlière, B.; Arvanitidis, Nikolaos; Gautneb, Håvard; Gloaguen, Eric; Törmänen, Tuomo; Reginiussen, Helge; Decree, Sophie; Pereira, Aurete; Quental, LídiaABSTRACT: This contribution presents pan-European prospectivity maps for lithium, cobalt, natural graphite, niobium, tantalum, phosphates and rare earth elements that were produced by the GeoERA FRAME project. These maps are based on the cell-based association (CBA) method, which was specifically developed for mineral prospectivity mapping at regional to continental scales. The purpose of this method is to address issues such as uncertainties in the location of cartographic objects and the need to consider geological contexts. Several options to calculate favourability scores were statistically tested and compared to improve the accuracy of the method and produce the final maps.
- Nouveau concept de technologie de revêtement anticorrosion inspirée des systèmes microbiens: Projet MICOATEC [Comunicação oral]Publication . Marques, Maria João; Jaume, Julien; Diderot, Anthony; Délia, Marie-Line; Basseguy, RegineRÉSUMÉ: Parmi les stratégies actuellement utilisées pour protéger les matériaux métalliques de la corrosion, et ainsi accroître leur durabilité, les traitements de conversion et les revêtements peuvent être considérés comme les alternatives les plus efficaces et les plus rentables. Ces techniques doivent cependant respecter une réglementation de plus en plus contraignante telle que REACH. Par ailleurs, dans le domaine des interactions micro-organismes/ matériaux conducteurs, il a été mis en évidence que non seulement les micro-organismes peuvent dans certains cas accélérer la corrosion (biocorrosion ou MIC) et dans d’autres l’inhiber protégeant alors le matériau sous-jacent (MIC Inhibition). Dans ce contexte, le projet ANR MICOATEC repose sur le constat que les interactions entre un alliage d’aluminium (AA 5083) et des microorganismes du milieu marin conduisent à la formation d’une couche protectrice contre la corrosion (Figure 1). MICOATEC ambitionne de développer, via une stratégie biomimétique, un nouveau type de procédé pour produire des revêtements anticorrosion.
- Cr(III) dynamic removal in a fixed-bed column by using a co-gasification charPublication . Dias, Diogo; Bernardo, Maria; Pinto, Filomena; Fonseca, Isabel Maria; Lapa, NunoABSTRACT: A char (GC) obtained from the co-gasification of rice husk and polyethylene was used in a fixed-bed column with continuous flow for Cr(III) removal assays from synthetic and industrial wastewaters. For comparison purposes, a commercial activated carbon (CAC) was also used. The best experimental conditions in the continuous removal assays were the following ones: Cr(III) inflow concentration = 5 mg L-1, feed flow rate = 3 mL min(-1), mass of adsorbent in the column = 0.8 g, and inflow temperature = 50 degrees C. Under these conditions, the highest uptake capacities were 1.60 and 2.14 mg g(-1) in the synthetic solution, and 3.25 and 7.83 mg g(-1) in the industrial wastewater, for GC and CAC, respectively. These results are different from those obtained under batch conditions in which GC performed better than CAC. Cr(III) removal by both adsorbents occurred due to precipitation, but CAC presented a slightly higher amount of Cr(III) removed due to its highest porosity. The regeneration of GC and CAC was also studied, but both adsorbents showed no capacity to be used in more than one cycle. This study highlighted the importance of studying Cr(III) removal under continuous conditions, as the removal mechanisms may be completely different from the batch assays, affecting the adsorbents' performance.
- Los peligros geológicos en Iberoamérica. El papel de los servicios de geología y minería iberoamericanos (ASGMI)Publication . Mateos Ruiz, Rosa Maria; Arcedo y Cabrilla, Francisco; Vílchez Mata, Manuel; Dutra dos Santos, Thiago; Ribeiro, Rafael; Mansini, Maria; Dias, Ruben Pereira; Machado, Susana; Carranco, Fausto; León, Johanna; Ruiz Peña, Gloria; López, Cristian; ARCILA RIVERA, Maria Mónica; Tejedo, Alejandra; Alfaro, Alejandro; Sánchez, Josiela; Claros, HéctorRESUMEN Iberoamérica es uno de los territorios del Mundo más expuestos a las catástrofes derivadas de procesos geológicos activos. De los peligros geológicos que acechan el territorio, las inundaciones y avenidas dejan los mayores daños, seguidas de terremotos, movimientos de ladera y erupciones volcánicas. El Grupo de Amenazas Geológicas de la Asociación de Servicios Geológicos y Minería Iberoamericanos (ASGMI) ha compartido un cuestionario entre sus países miembros (10), con la finalidad de recopilar los eventos más dañinos en la última década, conocer sus efectos e impactos socio-económicos, así como analizar las fortalezas y debilidades de los servicios geológicos para generar conocimientos útiles en la toma de decisiones para las diferentes etapas de la gestión del riesgo y el ordenamiento territorial. Todos los países reportan casos dramáticos durante la última década, con miles de fallecidos (> 11.000), graves afecciones a la población y cuantiosos daños económicos valorados en US$50 billones. No obstante, se manifiesta una falta de datos oficiales sobre los daños socio-económicos que generan los peligros geológicos en cada país. La mayoría de los servicios geológicos tiene planes de cartografía temática sobre los diferentes peligros geológicos, aunque se detecta una necesidad de cartografías detalladas de peligrosidad y vulnerabilidad, que se puedan incluir en la planificación urbanística y territorial. La mitad de los servicios geológicos encuestados no tiene competencias oficiales en materia de vigilancia, control y seguimiento de los diferentes peligros geológicos, hecho que determina una debilidad reflejada en el número de expertos en plantilla y en una limitación de su actividad. En general, los servicios geológicos iberoamericanos deben incrementar sus esfuerzos para desarrollar programas de transferencia del conocimiento, mediante estrategias de comunicación educativa e información pública, así como favorecer y facilitar el acceso de sus datos sobre este tipo de fenómenos recurrentes, conocimiento que redunde finalmente en la reducción del riesgo.
- Accelerated aging tests to selective solar absorber coatings for low temperature applicationsPublication . Cunha Diamantino, Teresa; Gonçalves, Rita; Páscoa, Soraia; Alves, Isabel Nascimento; Carvalho, Maria JoãoABSTRACT: The need of a higher role of solar energy within the energy mix in the coming decades obliges the collectors to increase their performance and reliability. It is demanded that the solar absorbers, as the key component of solar thermal collectors, should be low cost with high efficiency for extended lifetimes under different kinds of environments. Commercially, there are presently two main types of solutions as selective solar absorbers coatings for low temperature applications: coatings obtained by physical vapour deposition (PVD) and by paint coatings (PC). These coatings present different physical and chemical characteristics. Therefore, it is important to know how these commercial coatings degrade over time in different environments. Results obtained with two different PVD coatings and three PC, under different accelerated aging tests, are presented. The aging tests performed included different environmental stress corrosion conditions: temperature, humidity, chlorides, sulfur dioxide and nitrogen oxides. The chlorides and the gases SO2 and NO2 affect distinctly the different selective coatings. Cyclic variation of corrosion promoting gases (sulfur dioxide and nitrogen dioxide), higher humidity, salt spraying and drying seem to be an aging test that reflects the different environments where the solar thermal collectors are exposed. In addition to the contaminants, drying/wetting cycles also play an important role in degradation mechanisms of absorber coatings. So, the international standard ISO 22975-3 needs to be revised to include cyclic conditions with these contaminants.
- Assessment of wind and solar PV local complementarity for the hybridization of the wind power plants installed in PortugalPublication . Couto, António; Estanqueiro, AnaABSTRACT: To decarbonize electrical power systems, it is essential to incorporate a high share of variable renewable energy sources while minimizing their costs. An important step towards this goal includes exploring the potential for the so-called hybrid renewable power plants through the combination of (existing) wind and solar power parks. Although that is not the usual approach in their design, hybrid power plants should take advantage of existing synergies, as generation complementarity among the renewable generation technologies, and benefit from using existing infrastructures and the same grid connection point. This investigation assesses the potential of existing Portuguese wind parks for hybridization with solar power photovoltaic generation. Correlation and energy metrics for assessing the complementarity at hourly and daily periods are applied to quantify existing synergies. Results show a high potential for hybrid power plants: levels of complementarity between wind and solar resources are globally high thus allowing to increase the share of variable renewable energy sources with minimal energy curtailment, when compared with scenarios of overplanting additional wind power capacity. The highest and most consistent levels of complementarity are found in the interior regions of central and northern Portugal. The research shows that Portugal has privileged weather conditions that allow the concept of hybrid power plants to be largely explored and extended on a large and efficient scale. This outcome, which may be replicated for other countries, is an important contribution to increasing the penetration of renewable energy in electrical power systems while minimizing the overall costs of renewable energy.
- Thermally modified wood exposed to different weathering conditions: a reviewPublication . Godinho, Delfina; Araújo, Solange; Quilhó, Teresa; Cunha Diamantino, Teresa; Gominho, JorgeABSTRACT: Outdoor wood applications are exposed to several different biotic and abiotic factors, and for that reason, they require protection to increase their service life. Several technologies of wood protection are already commercialized. One of these technologies is thermal modification, which refers to the structural, mechanical, and chemical transformations occurring in the lignocellulosic material when gradually heated up to specific temperature ranges. In the past few years, several researchers have undertaken weathering resistance evaluations on different wood species. Some cases have considered natural exposure in different countries with different climatic conditions, while others focused on artificial exposure under UV and xenon radiation tests. Most works evaluated the weathering effects on the chemical, mechanical and physical, and anatomical shifts compared to the original characteristics of the material. This review has established a considerable lack of studies in the bibliography focusing on abiotic factors, such as the industrial and maritime environment, or even isolated climatic factors such as salt spray (simulating maritime environments) or pollutant gases (simulating industrial environments). This lack of information can be an opportunity for future work. It could help to understand if thermally modified wood is or is not sensitive to pollutant gases or salinity, or to a combination of both. By knowing the degradation mechanisms caused by these factors, it will be possible to study other forms of protection.