ESTG - Artigos em revistas internacionais
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- Induction of xylanolytic activity by Aureobasidium pullulans using xerographic paperPublication . Marques, Susana; Gírio, Francisco M.; Pala, Helena; Gama, Francisco Miguel; Mota, Manuel; Amaral-Collaço, M. T.
- Effect of cellulase adsorption on the surface and interfacial properties of cellulosePublication . Dourado, F.; Pala, Helena; Mota, Manuel; Gama, Francisco MiguelThe surface properties of several purified cellulose (Sigmacell 101, Sigmacell 20, Avicel pH 101, andWhatman CF 11) were characterised, before and after cellulase adsorption. The following techniques were used: thin-layer wicking (except for the cellulose Whatman), thermogravimetry, and differential scanning calorimetry (for all of the above celluloses). The results obtained from the calorimetric assays were consistent with those obtained from thinlayer wicking – Sigmacell 101, a more amorphous cellulose, was the least hydrophobic of the analysed celluloses, and had the highest specific heat of dehydration. The other celluloses showed less affinity for water molecules, as assessed by the two independent techniques. The adsorption of protein did not affect the amount of water adsorbed by Sigmacell 101. However, this water was more strongly adsorbed, since it had a higher specific heat of dehydration. The more crystalline celluloses adsorbed a greater amount of water, which was also more strongly bound after the treatment with cellulases. This effect was more significant for Whatman CF-11. Also, the more crystalline celluloses became slightly hydrophilic, following protein adsorption, as assessed by thin-layer wicking. However, this technique is not reliable when used with cellulase treated celluloses.
- The first twenty years of the strategic management journalPublication . Phelan, Steven E.; Ferreira, Manuel; Salvador, RommelThe Strategic Management Journal (SMJ) has now entered its third decade of publication and consistently ranks among the most influential journals in management. While several authors have examined the impact of SMJ vis-a-vis other management publications, few studies have examined the internal changes in the publication over time, particularly with regard to the diversity and content of the journal. The current study finds that there has been a significant shift in the number of authors, publication lags, reference lists, and page lengths in SMJ over the past 20 years, while the diversity of authorship has stayed relatively constant. There has also been a marked rise in the proportion of empirical papers being published. The implications of these results are discussed.
- Enzymatic modification of paper fibresPublication . Pala, Helena; Mota, Manuel; Gama, Francisco MiguelThe enzymatic mode of action in paper fibre upgrading is still uncertain. In an attempt to clarify how enzymes modify pulp and paper properties, several parameters were analysed in the present work: (i) thermal analysis of the water–solid surface interactions; (ii) fibre cake permeability; (iii) particle size analysis. The results obtained suggest that enzymes modify the interfacial properties of fibres, increasing the water affinity, which in turn change the technical properties of pulp and paper, such as drainability and strength. The modification of paper and pulps following a treatment with cellulosebinding domains further supports this hypothesis.
- Cellulose-binding domains as a tool for paper recyclingPublication . Pala, Helena; Pinto, R.; Mota, Manuel; Duarte, A. P.; Gama, Francisco MiguelTreatement of secondary paper fibres with cellulose-binding domains allows for improvements of pulp durability and of paper mechanical properties. The interfacial system fibre-water-fibre, may be affected by the CBD treatement, influencing the pulp and paper technical properties. Inverse Gas Chromatography provides experimental evidence that support this hypothesis.
- Characterization and application of glycanases secreted by Aspergillus terreus CCMI 498 and Trichoderma viride CCMI 84 for enzymatic deinking of mixed office wastepaperPublication . Marques, Susana; Pala, Helena; Alves, L.; Amaral-Collaço, M. T.; Gama, Francisco Miguel; Gírio, Francisco M.Two enzymatic extracts obtained from xylan-grown Aspergillus terreus CCMI 498 and cellulose-grown Trichoderma viride CCMI 84 were characterised for different glycanase activities. Both strains produce extracellular endoxylanase and endoglucanase enzymes. The enzymes optimal activity was found in the temperature range of 45 /60 8C. Endoglucanase systems show identical activity profiles towards temperature, regardless of the strain and inducing substrate. Conversely, the endoxylanases produced by both strains showed maximal activity at different pH values (from 4.5 to 5.5), being the more acidic xylanase produced by T. viride grown on cellulose. The endoglucanase activities have an optimum pH at 4.5 /5.0. The endoxylanase and endoglucanase activities exhibited high stability at 50 8C and pH 5.0. Mannanase, b-xylosidase, and amylase activities were also found, being the first two activities only present for T. viride extract. These two enzymatic extracts were used for mixed office wastepaper (MOW) deinking. When the enzymatic extract from T. viride was used, a further increase of 24% in ink removal was obtained by comparison with the control. Both enzymes contributed to the improvement of the paper strength properties and the obtained results clearly indicate that the effective use of enzymes for deinking can also contribute to the pulp and paper properties improvement.
- Enzymatic versus chemical deinking of non-impact ink printed paperPublication . Pala, Helena; Mota, Manuel; Gama, Francisco MiguelEnzymatic versus chemical deinking is examined for MOW and photocopy prints. Several enzymatic preparations and two fibre/ink particle separation methods are tested. Deinking was monitored by image analysis and standard pulp and paper characterisation procedures. The effectiveness of the fibre/ink particle separation method depends on the ink particle’s size: for smaller particles a washing step is recommended whereas for larger particles, the use of flotation is necessary. The enzymatic treatment is a competitive alternative for MOWand photocopy paper deinking. However, the process requires the selection of an adequate enzymatic preparation for each paper grade.
- Using SSM to rethink the analysis of energy efficiency initiativesPublication . Neves, Luís Miguel Pires; Martins, António Gomes; Antunes, Carlos Alberto Henggeler; Dias, Luís Miguel CândidoThis paper reflects an attempt to rethink the process of analysis of energy efficiency initiatives using soft systems methodology (SSM) as a problem structuring tool. The aim of the work is to provide public and private initiative promoters or evaluators with a structured support for a more informed decision regarding the implementation of energy efficiency measures. The SSM approach contributed with the identification of all market players and their relations, as well as the insight into the deficiencies of current methodologies. Some future work directions are also proposed.
- Experimental and numerical rolling contact fatigue study on the 32CrMoV13 steelPublication . Coelho, Luís Manuel de Jesus; Dias, A.; Lieurade, H. P.; Maitournam, H.The aim of this work is to study pure rolling contact fatigue in 32CrMoV13 quenching and tempering steel. The study involves both experimental and numerical work. The influence of the roughness and the residual stresses on the mechanisms and zones of cracking were studied. The results show a rapid reduction in roughness during the first minute of test but even so there will be specimen deterioration. The residual stress profile after rolling contact tests have high compression values in the surface and at a depth of approximately 240 μm, which is related with the Hertzian maximal shear stress. The numerical simulation of the Hertzian loading was used both to determine the elastic shakedown of thematerial and to apply a high-cycle multiaxial fatigue criterion. The threedimensional finite element analysis used in the numerical calculation includes elastic-linear kinematic hardening plastic material and allows the introduction of an initial residual stress state. Taking into account the elastoplastic load induced by the Hertz pressure, low-cycle fatigue tests were used to characterize the mechanical properties of the material. In order to validate the numerical simulation, the results of the calculation after elastic shakedown were compared with the values measured by X-ray diffraction after rolling contact tests. The results showed a reasonable agreement between calculated and measured stresses. The Dang Van high-cycle multiaxial fatigue criterion showed a good relationship with the experimental findings.
- Contabilidade ambiental: estudo de caso aplicado à indústria de portas e janelas de madeiraPublication . Eugénio, TeresaEste trabalho pretende ser um contributo para a introdução das matérias ambientais nos sistemas de gestão e contabilidade das empresas. Na base deste estudo está uma empresa que se dedica ao fabrico de portas e janelas em madeira, de média dimensão, com cerca de 100 trabalhadores, situada na zona centro de Portugal. Foram efectuadas várias visitas à fabrica, reuniões com o responsável, recolha de elementos do sector e análise de toda a informação disponível na empresa em termos de dados ambientais e dados financeiros. Esta empresa não era certificada por nenhum programa de gestão ambiental nem tinha ainda qualquer contacto com a construção de informação financeira de carácter ambiental. Pretendemos identificar as fases de um trabalho de recolha de informação prévia e de implementação de um modelo que possa ser aplicado a qualquer empresa do gênero que pretenda dar os primeiros passos com o objectivo de produzir informação financeira completa, onde constem também os valores ambientais e de onde se possa fazer uma análise global, da empresa como um todo, identificando o seu desempenho em termos de custos e proveitos ambientais.