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Biblioteca Digital do IPB (53.442 recursos)

A Biblioteca Digital do IPB, tem por objectivo divulgar e permitir o livre acesso à produção científica produzida pela comunidade académica, promovendo a integração, partilha e a visibilidade da informação científica e garantindo a preservação da memória intelectual do Instituto Politécnico de Bragança.

DTQB - Capítulos/Artigos em Livros/Revistas Internacionais

Mostrando recursos 1 - 20 de 29

  1. The effect of a static magnetic field on the flow of iron oxide magnetic nanoparticles through glass capillaries

    Pereira, Nelson; Mujika, M.; Arana, Sergio; Correia, Teresa Montenegro; Silva, A.; Gomes, Helder; Rodrigues, Pedro João; Lima, R.
    lron oxide nanoparticles were developed using Solvolherrnal synthesis and suspended in a physiological fluid consLiluted by erYlhrocytes in a rder to perfarm studies af flow behaviour in glass microchannels. The main purpose af this work was to study lhe influence af different iron oxide nanoparticles and magnetic fields in lhe plasma layer thickness and also the inftuence Df lhe magnelic field in lhe area composed of nanoparticles auracled to the waU af lhe microchannel. The results obtained show lhat nanoparticJes with magnetic characteristics promote the thinning of the plasma layer, in contrast to the behaviour observcd with mmoparticles without magnetic characteristics. It was also observed upon application of magnetic...

  2. Chitosan as an antimicrobial agent for footwear leather components

    Barros, M.C.; Fernandes, I.P.; Pinto, V.; Ferreira, M.J.; Barreiro, M.F.; Amaral, J.S.
    Chitosan is being increasingly used in distinct areas such as pharmaceutical, biomedical, cosmetics, food processing and agriculture. Among the interesting biological activities that have been ascribed to chitosan, the antimicrobial activity is probably the one to generate the higher number of applications. Within this work the role of chitosan in diverse applications has been reviewed with particular emphasis for those exploring its antimicrobial power. Furthermore, the mechanism to explain the antimicrobial activity of this emerging biopolymer is also discussed. The viability of using chitosan to effectively provide a functional coating for leather products was presented through an experimental case study....

  3. CFD simulation of stirred yoghurt processing in plate heat exchangers

    Maia, João M.; Nóbrega, João M.; Fernandes, Carla S.; Dias, Ricardo P.

  4. Granular beds composed of different particle sizes: experimental and CFD approaches

    Dias, Ricardo P.; Fernandes, Carla S.
    The porosity, tortuosity, permeability and heat exchange characteristics from binary packings, containing mixtures of small d and large D spherical particles, are analysed in the present work. Binary packing porosity (ε), tortuosity (τ), permeability and heat exchange performance are dependent on the volume fraction of large particles, xD, present in the mixtures, as well as on the particle size ratio, δ = d/D. In the region of minimum porosity from the binary mixtures (containing spheres with diameter d and D), heat exchange performance and permeability from binary packing are higher than that of the packing containing the small particles d alone (mono-size packing). The δ region where the...

  5. Characterization of Three Portuguese Varietal Olive Oils Based on Fatty Acids, Triacylglycerols, Phytosterols and Vitamin E Profiles: Application of Chemometrics

    Amaral, J.S.; Mafra, I.; Oliveira, M.B.P.P.
    In Portugal, olive oil production is considered an ancient activity, where old olive groves can still be observed. In the last few years monovarietal groves seem to be increasing, though some disadvantages, such as the susceptibility to insects and diseases, can result from the growth of individual olive varieties (Aguilera et al., 2005). In some typical producer countries, the olive cultivation is being improved by renewing old trees, reducing the association with other crops, selecting the olive varieties suited to local agroclimates and planting new single variety orchards (Criado et al., 2008). This is leading to an increase in the prevalence of monovarietal olive oils.

  6. Polycyclic aromatic hydrocarbons (PAH) in olive oils and other vegetable oils: potential for carcinogenesis

    Mafra, I.; Amaral, J.S.; Oliveira, M.B.P.P.

  7. Modeling of association effects in mixtures of carboxylic acids with associating and non-associating components

    Ferreira, Olga; Fornari, Tiziana; Brignole, Esteban A.; Bottini, Susana B.

  8. Infinite dilution activity coefficients of solvents in fatty oil derivatives

    Ferreira, Olga; Foco, Gloria

  9. Continuous biosorption of single and binary metal solutions in a fixed-bed column using algae gelidium and granulated algal waste from agar extraction

    Vilar, Vitor; Botelho, Cidália; Martins, Ramiro; Boaventura, Rui
    This paper describes the biosorption of single (Zn(II) and Cr(III)) and binary (Cd(II)/Zn(II) and Cu(II)/Cr(III)) metal solutions in a packed bed column using algae Gelidium and an algal waste from the agar extraction industry immobilized with polyacrylonitrile. In the sorption process, Zn(II) breaks through the column faster than Cd(II) due to its lower affinity for the biosorbent. An overshoot in the outlet Zn(II) concentration was observed and explained by competitive adsorption between Cd(II) and Zn(II), whereby the higher Cd(II) affinity for the biosorbent displaces bound Zn(II) ions. The same was verified for the binary system Cu(II)/Cr(III), where an overshoot in...

  10. Compositional characteristics and health aspects of Hazelnut (Corylus avellana L.): an overview

    Alasalvar, C.; Shahidi, F.; Amaral, J.S.; Oliveira, M.B.P.P.
    Hazelnut (Corylus avellana L.) belongs to the Betulaceae family and is a popular tree nut worldwide, mainly distributed in the coasts of the Black Sea region of Turkey, southern Europe (Italy, Spain, Portugal, and France), and in some areas of the United States (Oregon and Washington). Hazelnut is also cultivated in some other countries such as New Zealand, China, Azerbaijan, Chile, Iran, and Georgia, among others.

  11. HPLC/DAD analysis of phenolic compounds from lavender and its application to quality control

    Areias, F.; Valentão, P.; Andrade, P.B.; Moreira, M.M.; Amaral, J.S.; Seabra, R.M.
    A reversed phase HPLC procedure is proposed for the determination of eight phenolic compounds (2-O-glucosilcoumaric acid, o-coumaric acid, rosmarinic acid, apigenin-7-O-glucoside, coumarin, herniarin, luteolin, and apigenin) in lavender. The chromatographic separation was achieved using a reversed–phase Spherisorb ODS 2 (5 μm particle size: 25.0 x 0.46 cm) column. From the several extractive solvents assayed, only ethanol was able to extract all the mentioned compounds. Best resolution was obtained using a gradient of water-formic acid (19:1) and acetonitrile. Ten samples were subjected to quantification, all of them showing a common composition pattern.

  12. Solubility in food, pharmaceutical and cosmetic industries

    Pinho, Simão; Macedo, Eugénia A.

  13. New plates for different types of plate heat exchangers

    Fernandes, Carla S.; Dias, Ricardo P.; Maia, João M.
    The first patent for a plate heat exchanger was granted in 1878 to Albretch Dracke, a German inventor. The commercial embodiment of these equipments has become available in 1923. However, the plate heat exchanger development race began in the 1930’s and these gasketed plate and frame heat exchangers were mainly used as pasteurizers (e.g. for milk and beer). Industrial plate heat exchangers were introduced in the 1950’s and initially they were converted dairy models. Brazed plate heat exchangers were developed in the late 1970’s. However, copper brazed units did not start selling until the early 80’s. Nickel brazing came to...

  14. Effects of food thermal processing on vitamin E contents

    Casal, Susana; Amaral, J.S.; Oliveira, M.B.P.P.
    Food processing, carried out both industrially or during home meal preparation, is expected to affect the content, activity and availability of bioactive compounds, namely natural antioxidants such as vitamin E. It is particularly important that the effects of processing are taken into consideration when assessing vitamin stability in foods, since they can be subjected to a number of adverse factors during processing, being heat the most common deleterious factor. In this chapter, some processing methods that may contribute to vitamin E decrease are reviewed, together with those that can contribute to the highest antioxidants retention or even increase availability. Focusing mainly on the literature published in the last...

  15. Teaching electrolyte thermodynamics

    Pinho, Simão; Macedo, Eugénia A.
    Electrolyte solutions can be found in many natural and industrial processes. Some examples are the absorption of acid gases, such as carbon dioxide, for removal from effluent gas streams, avoiding atmospheric pollution; the fractional crystallization processes in which several salts are separated as pure phases from a multicomponent mixture; for the production of fertilizers such as ammonium phosphate, ammonium nitrate, or potassium sulfate; for extractive distillation using salt as the extractive agent; and for precipitation of globular proteins from an aqueous solution by the addition of salts.

  16. Advances in simulated moving bed chromatographic separations

    Gomes, Pedro Sá; Minceva, M.; Pais, L.S.; Rodrigues, A.E.
    The development of some unconventional Simulated Moving Bed (SMB) strategies, such as the introduction of nonsynchronous inlet/outlet shifts (the Varicol process), variable flux or variable composition in the inlet/outlet streams (PowerFeed and Modicon, respectively), and also the use of multiple feed or distributed feed, have increased the potential of this technique for a wide range of binary separations. For multiple component separations, different strategies has been investigated, including a cascade of SMB, more complex SMB units composed by several adsorption zones, and the JO process operating in two different separation steps.

  17. Flow and mass transfer

    Rodrigues, A.E.; Mata, V.G.; Zabka, M.; Pais, L.S.
    In the last decade, a growing interest in large-pore, permeable, or flow-through particles for engineering applications as catalysts supports, adsorbents, HPLC packings, ceramic membranes, supports for mammalian cell culture/biomass growth, and building materials can be observed. In particular in the area of separation engineering, perfusion chromatography appeared as a key technique for separation of proteins.

  18. Modelling and simulation in SMB for chiral purification

    Rodrigues, A.E.; Pais, L.S.
    Simulated moving bed (SMB) is a powerful technique for the preparative-scale chromatography which allows the continuous injection and separation of binary mixtures. The concept has been known since 1961, the technology having been developed by UOP in the areas of petroleum refining and petrochemicals, and known as the “Sorbex” process. Other successful SMB processes in the carbohydrate industry are the production of high-fructose corn syrup (“Sarex” process) and the recovery of sucrose from molasses. Other companies developed alternative processes for the fructose-glucose separation.

  19. Simulated moving bed adsorptive reactor

    Leão, C.P.; Pais, L.S.; Santos, M.; Rodrigues, A.E.
    The Simulated Moving Bed (SMB) technology is a mature one with above 100 applications in chemical industry (UOP Sorbex processes). Now it is finding applications in fine chemistry and pharmaceuticals (chiral separations). In this work, separation is coupled with reaction. The test system is enzymatic inversion of sucrose coupled with glucose/fructose separation using Ca2+ resin as adsorbent. Modeling, simulation and operation of a pilot plant is addressed.

  20. Oxidação catalítica degradativa de poluentes orgânicos em efluentes líquidos

    Faria, Joaquim; Gomes, Helder; Figueiredo, José
    A presença de compostos orgânicos em efluentes líquidos além de potencialmente tóxica, tende a aumentar drasticamente a carência química de oxigénio (CQO) das águas residuais. A oxidação aeróbia em solução (OAS)* tem por objectivo reduzir a CQO de efluentes líquidos por meio de um processo severo de oxidação degradativa total dos poluentes orgânicos presentes. A concepção de catalisadores específicos com vista a reduzir as condições extremas de operação tem conduzido ao desenvolvimento de uma tecnologia absolutamente nova de processos de oxidação aeróbia catalisada em solução (OACS).

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