Thermal modification of most representative Portuguese wood species. A preliminary study

The thermal modification has proved to be an effective method to improve the durability of wood elements. Until now, most applications of thermally modified wood have been limited to non-structural applications since the wood’s heat treatment leads to a significant reduction in mechanical performances. However, there is no knowledge about these treatments applied on the wood species more used in Portuguese constructions. In order to evaluate the effect of heat treatment on the wood species of Maritime pine (Pinus pinaster), Eucalyptus (Eucalyptus globulus), Beech (Fagus sylvatica), Acacia (Acacia melanoxylon) and Oak (Quercus faginea), an experimental program consisted of mechanical bending tests and dimensional stability tests (shrinkage, swelling and equilibrium moisture content) was defined. For comparison purposes, all tests were made with test specimens of non-modified and thermally modified wood using four temperature values (200ºC, 240ºC, 260ºC and 300ºC) and three exposed periods (2, 4 and 8 hours). The obtained results show that the behaviour of the studied experimented species was similar to the one of other species already studied in the available literature. It was possible to point out that mechanical properties decrease with the severity of the thermal treatment, while the dimensional stability improved.The support given by Portuguese industry Santos & Santos through the supply of the wood specimens used in the experimental campaign is acknowledged

Low cost high performance concrete using low quality fly ash

High performance concretes (HPC) usually have been produced using silica fume, high quality fly ash and carefully chosen aggregates. These constituents increase drastically the initial cost of HPCs. The objectives of this research work were twofold. On one hand, it intended to study the possibility of producing low cost HPC, with 28 day strengths in the range of 65 MPa, using low quality fly ash and locally available crushed aggregates. On the other hand, to verify the impact of carbon content of fly ash on the strength and durability of HPC. For this purpose it was decided to enhance the ‘as received’ fly ash by eliminating particles coarser than 75m, thus reducing the carbon content by 50%. Compressive strength and diffusion coefficient of concretes replacing 0, 20%, 40%, and 60% of Portland cement by ‘as received’ fly ash, and 20% and 40% replacement by ‘enhanced’ fly ash, were determined. Comparing the results obtained, it was found that HPC with up to 65 MPa can be made by replacing up to 40% of cement by ‘as received’ and ‘enhanced’ fly ash and using the crushed granite aggregates. It was also observed that the carbon content did have little impact on the strength and durability of concrete. Furthermore, it was observed that the durability of concrete, as measured by diffusion coefficient, increased drastically when fly ash replaced partially Portland cement

Cutinase purification on poly(ethylene glycol)–hydroxypropyl starch aqueous two-phase systems

The partition behaviour of cutinase on poly(ethylene glycol) (PEG)–hydroxypropyl starch aqueous two-phase systems was characterized. The effect of molecular mass of PEG, the pH of the system and tie-line length on cutinase partition coefficient and cutinase yield to the top phase was investigated for systems prepared with a purified hydroxypropyl starch (Reppal PES 100) and a crude one (HPS). The effect of the presence of different salts, such as sodium chloride, sodium sulphate and ammonium sulphate, on cutinase partition was also studied. The results lead to the conclusion that aqueous two-phase systems composed of PEG and hydroxypropyl starch are not efficient in the purification of cutinase. In the majority of cases, the partition coefficients were very close to 1, with pH being the factor which affects most cutinase partition. Partition coefficients were significantly improved when salts were added to the systems. For PEG 4000–Reppal PES 100 [at pH 4.0; 0.5 M (NH4)2 SO4], the partition coefficient for cutinase was 3.7, while a value of 12 was obtained for PEG 4000–HPS (at pH 4.0; 1 M NaC1). An isoelectric point (pI ) of 7.8 was confirmed for cutinase by constructing a cross partition graphic from the results obtained in the experiments with different salts. 1998 Elsevier Science B.V. All rights reserved

Betões de elevado desempenho de custo reduzido utilizando materiais correntes

Para a produção de betões de elevado desempenho (BED) é genericamente aceite que são necessários materiais criteriosamente seleccionados, obrigando assim a um acréscimo significativo do custo inicial dos BED quando confrontados com betões correntes. Este trabalho pretende abordar duas características: possibilidade de produzir betões de elevado desempenho que incorporam materiais considerados correntes, nomeadamente cinzas volantes com teor de inqueimados superior ao máximo regulamentar e inertes britados; verificação do efeito do teor de inqueimados na resistência e durabilidade dos BED. Para tal, processou-se ao melhoramento das cinzas volantes através da eliminação das partículas de dimensão superior a 75 m, reduzindo assim cerca de 50% do teor em carbono. Foram realizadas diferentes composições de betão, incorporando cinzas na proporção de 0, 20%, 40% e 60% de substituição de cimento Portland e utilizando 0, 20% e 40% de cinzas com dimensões inferiores a 75 m (cinzas melhoradas). Os valores das resistências à compressão e respectivos coeficientes de difusão foram analisados, satisfazendo assim o propósito deste trabalho. Os resultados obtidos permitem concluir que é possível a produção de BED com cinzas volantes de baixa qualidade e inertes britados. As resistências à compressão determinadas indiciam a possibilidade de produção de BED com percentagens de substituição de cinzas volantes até cerca de 40%, permitindo a obtenção de cerca de 60 a 65 MPa de resistência à compressão aos 56 dias de idade. Foi também possível constatar que a influência do teor de inqueimados das cinzas volantes é reduzida, não sendo significativa na resistência e durabilidade dos BED analisados. A durabilidade dos betões produzidos, aferida pelo valor do seu coeficiente de difusão, aumentou drasticamente com a substituição de cimento Portland por cinzas volantes em percentagens convenientes

Production of enzymatic extracts for aquafeeds by solid-state fermentation with Aspergillus ibericus of winery and olive mill wastes

[Excerpt] Introduction The replacement of fishmeal by plant ingredients in aquafeeds imposed new formulation strategies to overcome some nutritional restrictions associated with these alternative ingredients. Thus, supplementation of plant-based diets with feed additives, as exogenous enzymes and antioxidants compounds, has recently attracted increasing interest to improve feed utilization and to promote animal health. Solid state fermentation (SSF) of agro-industrial wastes has a high potential for the production of these additives, being a practical, economical, and environmentally-friendly process. Olive mill and winery wastes have valuable compounds that may be valorized thought SSF and that may be used as additives for aquafeeds. This study was conducted to optimize the production of non-starch carbohydrases through the SSF of the olive mill and winery wastes and to test its efficacy to improve the release of pentoses during digestion of a plant-based diet in European seabass.[...]Work supported by FCT PhD grant SFRH/BD/131219/2017, SFRH/BDP/114942/2016, IJFCT-POCI 01-0145-FEDER-030377 and MAR-02.01.01-FEAMP-0111info:eu-repo/semantics/publishedVersio

Caracterização de betões de elevado desempenho de custo reduzido

Para a produção de betões de elevado desempenho exigem-se normalmente materiais criteriosamente seleccionados. Neste trabalho procurou realizar-se betões de elevado desempenho que incorporam materiais considerados correntes, nomeadamente cinzas volantes com teor de inqueimados superior ao máximo regulamentar e inertes britados. As cinzas volantes utilizadas apresentam uma perda ao fogo elevada (cerca de 7%), os inertes não sofreram qualquer tipo de tratamento prévio (lavagem, peneiração, etc.) e são todos (incluindo as areias) provenientes da britagem de rochas graníticas. Foi assim possível obter betões com valores da resistência à compressão aos 90 dias de idade na ordem dos 65 MPa. São apresentadas neste trabalho as características de betões incorporando cinzas volantes em percentagem de substituição de cimento de 0, 20%, 40% e 60%. As características mecânicas determinadas consistiram na aferição da resistência à compressão do betão ao longo do tempo e na determinação do módulo de elasticidade. Uma outra característica determinada foi o coeficiente de difusão de cloretos. Os resultados dos ensaios mostram que estamos na presença de betões de elevado desempenho pelo menos até uma percentagem de 40% de substituição de cimento por cinzas volantes. No entanto, uma das desvantagens destes betões é a evolução mais lenta da resistência à compressão ao longo do tempo. No entanto, utilizando a cura a vapor, comum em prefabricação, essa desvantagem é anulada, devido à maior sensibilidade à temperatura que as cinzas volantes apresentam

Considerações gerais sobre organogênese.

bitstream/CNPA/18322/1/DOC150.pd

Micropropagação in vitro de ricinus communis l. utilizando a citocinina 6-bencilaminopurina.

A micropropagação é utilizada principalmente nas plantas de difícil propagação, permitindo a obtençãoo de grande número de plantas sadias e geneticamente uniformes, em curto período de tempo. A citocinina 6-bencilaminopurina (BAP) tem sido muito eficaz para promover multiplicação em diversas esp»cies e parece ser a citocinina, por excelência, para multiplicação de partes aéreas e indução de gemas adventícias. Objetivou-se, com este trabalho induzir, in vitro, o superbrotamento da cultivar de mamona BRS Nordestina , através dos explantes gema apical e eixo embrionrio, afim de determinar o melhor meio nutritivo suplementado com BAP. Sementes foram desinfestadas em solução de hipoclorito de sódio a 2,5% de cloro ativo e lavadas quatro vezes em água bidestilada estéril, permanecendo 24h na última água; posteriormente, foram cultivadas em tubos contendo meio MS e em frascos com sais de MS suplementado com vitaminas do meio B5 utilizando-se BAP nas concentrações -10,00; 0,05; 0,10; 0,30 mg.L ; em todos os meios foram adicionados 0,05 -1 mg.L de GA . Utilizaram-se 10 frascos por tratamento, cada um contendo três 3 explantes em delineamento inteiramente casualizado. O tratamento com 0,30 -1 -1mg.L de BAP e 0,05 mg.L de GA favoreceu o melhor superbrotamento de 3 brotos sadios, com uma m»dia de 6,13 brotos por explante. O BAP induz o superbrotamento nesta cultivar de mamona.bitstream/CNPA/19899/1/BOLETIM84.pd

Behaviour of cementitious matrices subjected to the combined action of chloride ions and carbonation

Carbonation and chloride action are the two leading causes of degradation in reinforced concrete structures. Despite the combined action of these two mechanisms being a reality, there is little research on the effect of this combination in cementitious matrices. Furthermore, the incorporation of fly ash in cementitious matrices has been frequently used in order to make the matrix more resistant to the action of chlorides. On the other hand, it is known that Ca(OH)2 existing in the matrix is consumed by the pozzolanic reactions, which makes easier the carbonation front advance. Therefore, this paper presents a study of the behavior of cementitious matrices, with and without fly ash, subjected to the combined action of chlorides and carbonation. Two different kinds of mortars were produced: reference (only cement CEM I 42.5R) and fly ash mortar (40% replacement of cement). After curing, the specimens were subjected to three different wetting-drying cycles, considering NaCl solutions and CO2 atmospheres. Afterwards, chloride profiles and carbonation front were measured. Results show that carbonation has a direct influence on chloride penetration, decreasing it for cement mortars with 0% fly ash and increasing it for mortars with 40% cement replacement by fly ash. Moreover, the evolution of carbonation is also influenced by chloride presence, which decreases under the combined action.The authors thank the Foundation for Science and Technology (FCT) for supporting this research. The authors also thank the SECIL for making available cement used in this research and the CIMENTEIRA DO LOURO for providing the aggregates used. This work is co-financed by FEDER funds through the Competitively Factors Operational Programme - COMPETE and by national funds through FCT within the scope of the project POCI-01-0145-FEDER007136.info:eu-repo/semantics/publishedVersio