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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 - Comunicações em Conferências Internacionais

Mostrando recursos 1 - 20 de 205

  1. An overview of teacher training in Portugal

    Ferreira, Olga; Silva, Adília; Barreiro, M.F.
    This paper presents an overview of teacher´s training in Portugal concerning initial teacher training (ITE), specialized training and in-service teacher training, as considered by the Portuguese legislation. A special emphasis was given to training in information and communication technologies (ICT) and to teaching of experimental sciences for primary school. Moreover, chemistry teacher’s training was contextualized in this scenario. Presently ITE corresponds to level 7 of the European Qualifications Framework (master degree). It is a career-long professional development, where research-based and in context practice are important features. Nevertheless the implicit valorisation of the teaching career arising from Bologna process implementation, a...

  2. Student's motivation to study chemistry: some insights into the portuguese case

    Ferreira, Olga; Barreiro, M.F.; Silva, Adília
    Chemistry is universally assumed as one of most difficult and demanding science subjects. It is recognized as involving difficult concepts, specialized terminology and mathematics. Moreover, some chemistry curricula are considered quite apart from students` interest, every day-like contexts and techonological issues. Context-based chemical education has ten emerged as a valuable strategy worldwide being presently also followed in the Portuguese educational system.

  3. Development of glycerol-based carbon materials for environmental catalytic applications in advanced oxidation processes

    Gomes, Helder; Ribeiro, Rui; Silva, Adrián; Pinho, Teresa; Figueiredo, José; Faria, Joaquim
    A glycerol-based carbon material was initially produced by partial carbonization of glycerol with sulphuric acid followed by calcination under inert atmosphere. This material, characterized by high thermal stability, low ash content, non-porous structure and basic character, was further activated in air atmosphere at different temperatures (from 150 to 350 oC), resulting in materials with less basic character, due to the incorporation of oxygenated surface groups, and to a notorious evolution of the porosity. These metal-free carbon materials are highly active catalysts for environmental applications, more specifically for the catalytic wet peroxide oxidation process, when the surface chemistry and textural properties...

  4. Optimization of mobile phase composition for preparative separation of profens enantiomers by chiral liquid chromatography

    Ribeiro, António E.; Graça, Nuno S.; Pais, L.S.; Rodrigues, A.E.
    Advancing the chemical engineering fundamentals

  5. A influência de um campo magnético estático no escoamento sanguíneo com nanopartículas magnéticas

    Pereira, Nuno; Mujika, Maite; Arana, Sergio; Correia, Teresa Montenegro; Silva, Adrián; Gomes, Helder; Rodrigues, Pedro; Lima, R.
    De forma a realizar estudos de escoamentos em microcanais e avaliar a influência das nanopartículas, sob a ação de um campo magnético estático, na espessura da camada de plasma, foram produzidas nanoparticulas de óxido de ferro por síntese solvotérmica, sendo posteriormente colocadas em suspensão num fluido fisiológico constituído por eritrócitos. Verificou-se que as nanopartículas com características magnéticas proporcionam a diminuição da espessura da camada de plasma, um comportamento contrário ao observado com nanopartículas sem características magnéticas.

  6. Polymer laboratory: teaching polymer chemistry

    Ferreira, Olga; Plasencia, Paula; Afonso, Maria João A.P.S.; Silva, A.; Barreiro, M.F.
    This work aims to present the results achieved within the science communication project CV/PVI/1386-Laboratório de Polímeros (Polymer Laboratory), financed by Ciência Viva - Agência Nacional para a Cultura Científica e Tecnológica (2006-2008). Several demonstration/experimental kits were developed concerning three main thematics: (1) Polymer concepts; (2) Polymer synthesis and (3) Polymer properties. Additionally, a fourth module entitled “Technological aspects” was also put into practice by taking advantage from the LSRE-IPB installed capacity in the area of Polymer Chemistry. The various modules were designed to reach a wide target public, including students from primary and secondary schools to undergraduate levels, and general...

  7. Effect of real particles packing with large size ratio on porosity and tortuosity of filter bed

    Mota, Manuel; Teixeira, José A.; Dias, Ricardo P.; Yelshin, Alexander
    he complexity of processes involved in the formation of granular beds results in limited information about permeability κ , which directly rela tes with packing porosity ε and tortuosity T . For a mixed bed of particles significantly different in size, the influence of packing affects permeability. For a better understanding of the underlying relationship between κ , ε , and T in mixed beds of particles significantly different in size, simplified porous media model of binary mixture of spheres were used. Boundary analysis of the binary packing showed that the approach based on the fractional porosity of large and...

  8. Application of binary packing for starch separation by hydrodynamic chromatography

    Mota, Manuel; Teixeira, José A.; Dias, Ricardo P.; Yelshin, Alexander
    Columns packed with commercial glass beads of 5 and 19 microns average diameter and binary mixtures with finest fraction of 5 micron (30 % volume fraction of the mixture) were used to analyse starch by hydrodynamic chromatography (HDC). Experiments were carried out at 3 and 15 ºC. The observed resolution increased with the application of binary packing as compared with single-size packing. The best results were obtained at starch’s amylopectin and amylose separation with a glass beads mixture (5 + 19 micron) at 3ºC. In what concerns amylopectin and amylose separation, a lower pressure drop were obtained for the mixed...

  9. Accumulation and release of Pb(II) in aqueous solution by aquatic mosses (Fontinalis antipyretica)

    Martins, Ramiro; Freitas, Olga; Vilar, Vitor; Boaventura, Rui
    The uptake and release of Pb(II) by Fontinalis antipyretica was studied in laboratory, by exposing the plants to different lead concentrations for 144 h and 335 h contamination and decontamination periods, respectively. A first order kinetic model was fitted to the experimental data to determine the uptake and release constants, k1 and k2, and other relevant parameters. The metal accumulation capacity, at equilibrium, follows the order: Pb(II) > Zn(II) > Cd(II) > Cr(VI). A Bioconcentration Factor (BCF) and a Biological Elimination Factor (BEF) were also determined; for 0.9–2.2 mg Pb l–1, BCF decreases from about 30748 to 21296.

  10. Modeling and simulation of fixed-bed and simulated moving bed chromatographic processes using Pdecol and Bacol software packages

    Graça, Nuno S.; Pais, L.S.

  11. Cr(III) uptake by marine algal biomass: equilibrium and kinetics

    Vilar, Vitor; Freitas, Olga; Costa, Pedro; Botelho, Cidália; Martins, Ramiro; Boaventura, Rui
    In this work, biosorption of trivalent chromium by the marine brown algae Sargassum muticum was 37 studied in a batch system. The effect of the solution pH on Cr(III) uptake by Sargassum was 38 investigated. Kinetics and equilibrium experiments were conducted at different pH values (3.0, 4.0 and 39 5.0). Equilibrium data are well described by the Langmuir and Langmuir-Freundlich isotherms and 40 kinetics follows the pseudo-second-order model, at different pH values. The two mass transfer models 41 give comparable results, but they did not provide a perfect representation of the sorption data. The 42 homogeneous diffusivity, Dh, was found to be around 1.6´10-8 cm2 s-1...

  12. Transgenes monitoring in an industrial soybean oil processing by conventional and real-time polymerase chain reaction

    Costa, J.; Mafra, I.; Amaral, J.S.; Oliveira, M.B.P.P.
    In recent years a great effort has been devoted to the development of new methods for the qualitative and quantitative detection of transgenic sequences in food. Most of the developed analytical methods for GMO detection are DNA-based, since protein-based assays are not suitable for processed food. For that purpose, polimerase chain reaction (PCR) and real-time quantitative PCR have been successfully applied. Since the approval of Roundup Ready (RR) soybean in Europe, the production of soybean oil using GM seeds has been increasing. Although several reports show the possibility of DNA detection in crude vegetable oils, due to the chemical treatments...

  13. Desempenho hidráulico de canais sinusoidais durante o fluxo laminar de fluidos não-Newtonianos

    Fernandes, Carla S.; Dias, Ricardo P.; Pinheiro, Jorge Vagaroso de Barros
    Neste trabalho estudou-se numericamente o escoamento isotérmico laminar completamente desenvolvido de fluidos Newtonianos e não-Newtonianos em canais de permutadores de calor de placas do tipo chevron com ângulo de corrugação igual a zero (canais do tipo sinusoidal). Este estudo foi efectuado recorrendo ao software de dinâmica de fluidos computacional, baseado no método de elementos finitos, POLYFLOW®. Para cada uma das geometrias estudadas (com valores de razão de aspecto de canal entre 0 e 1), estudaram-se os factores de fricção de Fanning, f, tendo sido determinadas, para cada um dos canais, curvas de fricção únicas (f Reg = K) para os...

  14. The use of model samples to estimate the level of fraudulent addition of pork meat in poultry meat by real-time PCR

    Soares, Sónia; Amaral, J.S.; Mafra, I.; Oliveira, M.B.P.P.
    The undeclared presence of meat species in grounded and comminuted meat products is a concern because it represents an economic fraud, but also for public health, ethical and religious reasons. Meat species identification allows detecting adulterations such as the fraudulent substitution of cheaper meats for more expensive ones. In this work, model samples were prepared at the laboratory containing poultry meat added with known amounts of pork meat. DNA was extracted from the model samples and a real-time polymerase chain reaction (PCR) technique using the SYBR Green I fluorescent dye coupled to melting curve analysis was proposed to obtain a...

  15. Species identification in heat processed meat products

    Soares, Sónia; Amaral, J.S.; Mafra, I.; Oliveira, M.B.P.P.
    In this work, species-specific PCR techniques were developed and optimized to identify pork, poultry and cow species in Frankfurt sausages. For pork and poultry, which are the most frequently used meats in Frankfurters, reference binary samples (pork in poultry and poultry in pork) were prepared in the laboratory. In both cases, the established conditions allowed the detection of levels as low as 0.1% of added pork/poultry meat. Real-time PCR assays based on the measurement of fluorescence increments using SYBR Green I dye were used for quantitative purposes. Several samples were acquired in the retail market and tested for their label...

  16. Polymerase chain reaction for the detection of allergens: the case of soybean in processed meat products

    Amaral, J.S.; Soares, Sónia; Mafra, I.; Oliveira, M.B.P.P.
    In this work, a polymerase chain reaction (PCR) technique was used for soybean detection in processed meat products. The methodology was optimized using reference binary samples with different known percentages of pork meat and soybean protein, prepared in the laboratory. To evaluate the effect of thermal treatment, binary mixtures were submitted to thermal treatment at 121ºC for 5 min. The species-specific PCR targeting the lectin gene allowed the detection limit of 0.01 ng of soybean DNA in raw materials. The PCR method was successfully applied on 18 commercial Frankfurt sausages.

  17. Detection of seven genetically modified maize events in foog products on the portuguese market

    Mafra, I.; Amaral, J.S.; Oliveira, M.B.P.P.
    Maize, the second most important genetic modified (GM) crop, has the highest number of authorized GM events for food and feed in EU. Since the GMO entered the food chain, the EU has dedicated special attention to consumer information by requiring a compulsory labelling for food products containing more than 0.9% of GM material. The need to monitor and verify the presence of low levels of biotechnology-derived material in complex food products demands sensitive and highly specific analytical methods. Most methods for GMO detection and quantification are based on polymerase chain reaction (PCR), since protein-based assays are not suitable for...

  18. Influência da torra de avelãs sua composição em vitamina E

    Amaral, J.S.; Casal, Susana; Seabra, R.M.; Oliveira, M.B.P.P.
    Neste trabalho avaliou-se o efeito da torra da avelã (Corylus avellana L.) na sua composição em tocoferóis e tocotrienóis. Para tal, procedeu-se à quantificação dos diferentes vitâmeros em avelãs submetidas a diversas torras, compreendendo diferentes temperaturas (125, 145, 165 e 185 e 200 ºC) e tempos de exposição (5, 15 e 30 min). As amostras foram analizadas utilizando-se uma metodologia de HPLC/DAD/FL previamente validada. Apesar de se verificar uma tendência de perdas crescentes com os aumentos de temperatura e tempo de torra, o decréscimo máximo do teor total comparativamente à amostra crua foi de 9,2%, tendo-se observado comportamentos distintos por...

  19. Determinação do perfil de triacilgliceróis das nozes

    Amaral, J.S.; Cunha, S.C.; Neves, N.; Oliveira, M.B.P.P.; Seabra, R.M.
    Neste trabalho determinou-se o perfil em triacilgliceróis de nove cultivares de nozes (Arco, Franquette, Hartley, Lara, Marbot, Mayette, Mellanaise, Parisienne e Rego) utilizando uma técnica de HPLC/ELSD para a separação e quantificação dos compostos. A separação cromatográfica decorreu numa coluna Kromasil 100 C18 (5 μm; 250 x 4,6 mm) e uma mistura de acetona/acetonitrilo (70:30, v/v) foi utilizada como fase móvel, eluindo com um fluxo de 1ml/min num programa isocrático. O detector ELSD foi programado com os seguintes parâmetros: temperatura de evaporação 40 ºC, pressão do ar 3,5 bar e sensibilidade do fotomultiplicador 6. Foram identificados e quantificados 9 triacilgliceróis: LLnLn, LLLn, LLL, OLLn, OLL, PLL, OOL and PLO...

  20. A segmentation approach for the identification of hazelnut cultivars

    Rodrigues, Pedro; Amaral, J.S.; Santos, Alberto; Igrejas, Getúlio
    The development of a methodology for cultivar discrimination and selection during on-line quality selection could be a relevant tool for certain industries that use hazelnuts as ingredients in processed food products. The aim of this work was to obtain a computer vision system that enables an automatic recognition of six hazelnuts cultivars from 3 different origins (US, Italy and Spain). To achieve this objective, an algorithm for tuning the segmentation between the hazelnut shell and crown was developed. Important morphological features that allow the correct identification of the cultivar present in an image were obtained from the segmentation process. Finally,...

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