Browsing by Author "Silva, Fernando"
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- As Bibliotecas Escolares na era digital: que desafios?Publication . Quadros-Flores, Paula; Silva, Fernando; Santos, NatividadeVivemos uma era que exige mudanças no modo de comunicar, de relacionar e de estar no mundo. Uma era que nos conecta e disponibiliza um manancial de possibilidades gratuitas que permitem ao utilizador da Internet ser um consumidor e um produtor, integrar redes de aprendizagem e aceder a informações relevantes na vida de qualquer cidadão. As bibliotecas escolares estão atentas a esta realidade, mas como respondem a tal desafio? Este artigo analisa páginas online de bibliotecas escolares na região metropolitana do Porto. Foram adotados parâmetros adaptados de Cremades Garcia e Jiménez García (2013) para compreender o dinamismo das bibliotecas escolares online. Os resultados mostram que a resposta das Bibliotecas Escolares (BE) tem em conta o seu público alvo, pelo que existe uma correlação positiva aparente entre a tipologia de escola (Básica, Secundária e Básica e Secundária) e o modo como estas desenham as suas páginas Web. Porém, ainda se encontram num processo de transformação para responder às exigências atuais, pois são mais espaços repositórios e menos espaços de construção pelos utilizadores, pelo que se levantam questões e se propõem orientações
- A cyclam salt as an antifungal agent: Interference with Candida spp. and Cryptococcus neoformans mechanisms of virulencePublication . Cerqueira, Fátima; Medeiros, Rui; Lopes, Inês; Campos, Carla; Ferraz, Maria Pia; Silva, Fernando; Alves, Luís G.; Pinto, EugéniaThe importance of fungal infections, particularly those caused by yeasts, is increasing among the medical community. Candida albicans and Cryptococcus neoformans are amongst the high-priority fungal species identified by the World Health Organization (WHO) and are considered in the critical group, while Candida krusei is included in the medium-priority group. The cyclam salt H4[H2(4-CF3PhCH2)2Cyclam]Cl4 proved to be active against the growth of these three yeasts, and the aim of this work was to verify its interference with their virulence mechanisms, whether shared or unique. H4[H2(4-CF3PhCH2)2Cyclam]Cl4 significantly inhibited biofilm production and catalase activity, being able to interfere with C. albicans dimorphic transition and C. neoformans melanin production. At the minimal inhibitory concentration (MIC) values, H4[H2(4-CF3PhCH2)2Cyclam]Cl4 had no antioxidant effect, as determined by the DPPH method. When using the RAW264.7 macrophage cell line, H4[H2(4-CF3PhCH2)2Cyclam]Cl4 reduced nitric oxide (NO) detection (the Griess reaction), but this effect was associated with a significant toxic effect on the cells.
- Fractional order dynamics in classical electromagnetic phenomenaPublication . Tenreiro Machado, J. A.; Jesus, Isabel S.; Galhano, Alexandra; Albert, W. Malpica; Silva, Fernando; Tar, József K.The Maxwell equations play a fundamental role in the well established formulation of the electromagnetic theory. These equations lead to the derivation of precise mathematical models useful in many applications in physics and engineering. The Maxwell equations involve only the integer-order calculus and, therefore, it is natural that the resulting classical models adopted in electrical engineering reflect this perspective. Recently, a closer look of some phenomena present in electrical systems, such as motors, transformers and lines, and the motivation towards the development of comprehensive models, seem to point out the requirement for a fractional calculus approach. Bearing these ideas in mind, in this study we shall address the well-known ‘skin effect’ and we reevaluate the results demonstrating its fractional-order dynamics.
- Protein Imprinted Material electrochemical sensor for determination of Annexin A3 in biological samplesPublication . Rebelo, Tânia S.C.R.; Pereira, Carlos M.; Sales, Goreti; Noronha, João P.; Silva, FernandoThe development of fast and reliable methods for protein determination are of great relevance to a diversity of areas from industry to diagnostics. Molecular Imprinted Materials (MIM) has proved to be an interesting methodology for protein analysis however further studies of the effect of the experimental parameters and starting materials in the performance of the MIM are still required. Caffeic acid (CAF) is employed for the first time as a monomer to tailor a synthetic receptor for a protein target. This was done by bulk-electropolymerization, applying a constant potential of +2.0 V, for 30 s, on a carbon screen- printed electrode, immersed in a solution of protein and CAF prepared in phosphate buffer. Annexin A3 (ANXA3) was selected as protein target due to the fact that this is an emerging biomarker in prostate cancer. The assembly of the protein imprinted material (PIM) was followed by Electrochemical Impedance Spectroscopy (EIS) and Raman Spectroscopy. A non-imprinted material (NIM) was prepared in parallel as control. Square wave voltammetry (SWV) was used to monitor the electrochemical signal of the [Fe(CN)6]3 /[Fe (CN)6]4 redox for the quantification of ANXA3. The optimized PIM-based device showed average detection limits (LOD) of 0.095 ng/mL, a linear behavior against log (concentration) between 0.10, and 200 ng/mL and good selectivity. The NIM-based device showed random behavior against protein concentration. Finally, the PIM-sensor was successfully applied to the analysis of ANXA3 in spiked urine samples.
- Protein imprinted materials designed with charged binding sites on screen-printed electrode for microseminoprotein-beta determination in biological samplesPublication . Rebelo, Tânia S.C.R.; Pereira, Carlos M.; Sales, Goreti; Noronha, J.P.; Silva, FernandoIn the past few years a large effort is being made aiming at the development of fast and reliable tests for cancer biomarkers. Protein imprinted sensors can be a fast and reliable strategy to develop tailor made sensors for a large number of relevant molecules. This work aims to produce, optimize and use in biological samples a biosensor for microseminoprotein-beta (MSMB). Caffeic acid (CAF) electropolimerization was performed in the presence of microseminoprotein-beta (MSMB) creating target protein specific cavities on the surface of a screen-printed carbon. Dopamine was introduced as charged monomer labelling the binding site and was allowed to self-organize around the protein. The subsequent electropolimerization was made by applying a constant potential of +2.0 V, for 30 s, on a carbon screen-printed electrode, immersed in a solution of protein and CAF prepared in phosphate buffer. The sensor with charged monomers showed a more sensitive response, with an average slope of−7.59 A/decade, linear concentration range of 0.5–100 ng/mL and a detection limit of 0.12 ng/mL. The corresponding non-imprinted sensor displayed an inconsistent response over the range of the calibration curve. The biosensor was successfully applied to the analysis of MSMB in serum and urine samples.
- Sarcosine oxidase composite screen-printed electrode for sarcosine determination in biological samplesPublication . Rebelo, Tânia S. C. R.; Pereira, Carlos M.; Sales, M. Goreti F.; Noronha, João P.; Costa-Rodrigues, João; Silva, Fernando; Fernandes, M. H.Prostate Cancer (PCa) is the most common form of cancer in men in Europe with a 61.4 % incidence among all cancer cases and a 12.1 % mortality [1] and, therefore, its early detection is fundamental for increasing the survival rate. Currently, diagnosis and management of patients with PCa is only based on the determination of the biomarker Prostate Specific Antigen (PSA). However, the method used for PCa detection has poor sensitivity and specificity, leading to false negative and false positive test results and many patients are sent to unnecessary biopsy procedures [2]. Therefore, there is a need to seek for new biomarkers and more effective screening. In this work, a biosensor device was developed for the quantification of sarcosine via electrochemical detection of H2O2 (at 0.6 V) generated from the catalyzed oxidation of sarcosine. The detection was carried out after the modification of carbon screen printed electrodes (SPEs) by immobilization of sarcosine oxidase (SOX) on the electrode surface. The strategies used herein included the activation of the carbon films by an electrochemical step and the formation of an NHS/EDAC layer to bond the enzyme to the electrode, the use of metallic or semiconductor nanoparticles layer previously or during the enzyme immobilization. In order to improve the sensor stability and selectivity a polymeric layer with extra enzyme content was further added. The proposed methodology for the detection of sarcosine allowed obtaining a limit of detection (LOD) of 1.6x10-5 mM, using a linear concentration range between 1x10-5 and 1x10-4 mM. The biosensor was successfully applied to the analysis of sarcosine in urine samples.
- Sarcosine oxidase composite screen-printed electrode for sarcosine determination in biological samplesPublication . Rebelo, Tânia S. C. R.; Pereira, Carlos M.; Sales, M. Goreti F.; Noronha, João P. C.; Costa-Rodrigues, João; Silva, Fernando; Fernandes, M.H.As the prostate cancer (PCa) progresses, sarcosine levels increase both in tumor cells and urine samples, suggesting that this metabolite measurements can help in the creation of non-invasive diagnostic methods for this disease. In this work, a biosensor device was developed for the quantification of sarcosine via electrochemical detection of H2O2 (at 0.6 V) generated from the catalyzed oxidation of sarcosine. The detection was carried out after the modification of carbon screen printed electrodes (SPEs) by immobilization of sarcosine oxidase (SOX) on the electrode surface. The strategies used herein included the activation of the carbon films by an electrochemical step and the formation of an NHS/EDAC layer to bond the enzyme to the electrode, the use of metallic or semiconductor nanoparticles layer previously or during the enzyme immobilization. In order to improve the sensor stability and selectivity a polymeric layer with extra enzyme content was further added. The proposed methodology for the detection of sarcosine allowed obtaining a limit of detection (LOD) of 16 nM, using a linear concentration range between 10 and 100 nM. The biosensor was successfully applied to the analysis of sarcosine in urine samples.