Browsing by Author "Fernandes, A."
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- Anti-Corrosion performance of a new silane coating for corrosion protection of AZ31 Magnesium alloy in Hank’s solutionPublication . Zomorodian, A.; Brusciotti, F.; Fernandes, A.; Carmezim, M. J.; Silva, Maria Teresa Oliveira de Moura e; Fernandes, J. C. S.; Montemor, M. F.Mg alloys can be used as bioresorsable metallic implants. However, the high corrosion rate of magnesium alloys has limited their biomedical applications. Although Mg ions are essential to the human body, an excess may cause undesirable health effects. Therefore, surface treatments are required to enhance the corrosion resistance of magnesium parts, decreasing its rate to biocompatible levels and allowing its safe application as bioresorbable metallic implants. The application of biocompatible silane coatings is envisaged as a suitable strategy for retarding the corrosion process of magnesium alloys. In the current work, a new glycidoxypropyltrimethoxysilane (GPTMS) based coating was tested on AZ31 magnesium substrates subjected to different surface conditioning procedures before coating deposition. The surface conditioning included a short etching with hydrofluoric acid (HF) or a dc polarisation in alkaline electrolyte. The silane coated samples were immersed in Hank's solution and the protective performance of the coating was studied through electrochemical impedance spectroscopy (EIS). The EIS data was treated by new equivalent circuit models and the results revealed that the surface conditioning process plays a key role in the effectiveness of the silane coating. The HF treated samples led to the highest impedance values and delayed the coating degradation, compared to the mechanically polished samples or to those submitted to dc polarisation.
- Bio-oils/FCC co-processing: insights into the adsorption of guaiacol on Y zeolites with distinct acidity and textural propertiesPublication . Silva, João; Ribeiro, M. F.; Graça, I.; Fernandes, A.The guaiacol adsorption capacity of several Y zeolites with different physicochemical properties was tested by performing breakthrough adsorption experiments, in order to investigate the guaiacol adsorption on Fluid Catalytic Cracking catalysts during bio-oils/FCC feedstocks co-processing. X-Ray diffraction, nitrogen sorption measurements and pyridine adsorption followed by Infrared Spectroscopy were used to determine the framework Si/Al ratio, the textural parameters, and finally the nature and amount of acid sites. Klinkenberg model was used to fit the experimental data and to obtain the guaiacol adsorption capacity and ka (overall coefficient of mass transfer) and Ke (adsorption equilibrium constant) parameters, which are directly related to, respectively, kinetic and thermodynamic aspects. Ke values, and so guaiacol adsorption, were observed to increase with the total number of Bronsted and Lewis acid sites on the zeolites, as well as with the amount of Na exchange. Conversely, mesoporosity increases the diffusion rate of guaiacol inside the zeolite structure, leading to higher ka values and decreasing guaiacol retention. Overall, data show that guaiacol adsorption on the FCC catalysts, and so its impact on the activity, might decrease with the catalyst age, owing to the changes on the FCC catalyst properties taking place during operation.
- Desilication of MOR zeolite: Conventional versus microwave assisted heatingPublication . Paixão, V.; Monteiro, R.; Andrade, M.; Fernandes, A.; Rocha, J.; Carvalho, A. P.; Martins, A.MOR zeolites were modified via desilication treatments with NaOH, under conventional and microwave heating. The samples were characterized by powder X-ray diffraction, (27)Al and (29)Si NMR spectroscopy. TEM and N(2) adsorption at -196 degrees C. The acidity of the samples and the space available inside the pores were evaluated through a catalytic model reaction, the isomerization of m-xylene, for which the profiles of the coke thermal decomposition were also analyzed. Powder X-ray diffraction and (29)Si and (27)Al MNR results show that in comparison with conventional heating, microwave irradiation (a less time consuming process) leads to identical amount of Si extraction from the zeolite framework. With this treatment. in addition to the customary mesopores development promoted by conventional heating, a partial conversion of the zeolite microporosity into larger micropores, is observed. The microwave irradiated and conventionally heated samples show different catalytic behavior in the m-xylene isomerization model reaction. It was observed that, by controlling the experimental conditions, it is possible to obtain samples with catalytic properties closer to the parent material, which is also confirmed by the respective coke analysis. (C) 2011 Elsevier B.V. All rights reserved.
- Difusão molecular em ressonância magnética para estudo de lesões mamárias malignasPublication . Jaguegivane, Seena; Janardo, J.; Pereira, M.; Fernandes, A.; Ribeiro, Margarida; Ferreira, AidaObjetivos – Com este estudo pretendeu-se i) avaliar o contributo da aplicação da sequência de difusão na caracterização das lesões mamárias malignas; ii) considerar se a sequência de difusão deve incorporar o protocolo standard em RM mamária e iii) correlacionar os resultados dos valores de coeficiente aparente de difusão (ADC) e os resultados histológicos. Metodologia – A amostra incluiu 18 pacientes do sexo feminino, com idades compreendidas entre 38 e 71 anos, que apresentavam lesões mamárias malignas confirmadas histologicamente. Foi adicionado ao protocolo de RM mamária a sequência de difusão, de modo a calcular os valores de ADC das lesões observadas. Resultados – Verificou-se que a range de valores de ADC para lesões malignas em ROI’s calculados no centro da lesão apresentavam uma média e desvio-padrão de (0,89 ± 0,14x10-3mm2/s). O método da utilização dos valores de ADC na caracterização de lesões mamárias malignas demonstrou uma sensibilidade de 100%. Conclusões – Neste estudo, com uma sensibilidade de 100%, a ponderação em difusão demonstrou ser uma técnica vantajosa na caracterização de lesões mamárias malignas pelo que se sugere a sua introdução no protocolo standard da RM mamária. ABSTRACT - Aims – The aim of this study was i) to evaluate the potential of the DWI sequence in the characterization of malignant breast lesions; ii) to verify if this sequence should incorporate the breast MRI protocol and iii) to correlate the apparent diffusion coefficients (ADC) values and histological results. Methodology – The sample includes 18 female patients between the ages of 38 and 71 years, who presented with malignant breast lesion confirmed by histology. The DWI sequence was added to the MRI standard protocol to calculate the ADC values. Results – In the results obtained we observed that the range of the ADC values calculated in the center of the malignant lesions, showed a mean and standard deviation of 0.89 ± 0.14 x10-3 mm2 / s. This method of using the ADC values for the detection of malignant lesions showed a sensitivity of 100%. Conclusion – The DWI technique proved to be a useful method in the characterization of malignant breast lesions, as it showed a sensitivity of 100%, so we suggest its inclusion in the Breast MR standard protocol.
- Evolução e contributo dos sistemas de distribuição de medicamentos para a segurança do doentePublication . Fernandes, A.; Monteiro, A.; Zorrinho, V.; Coelho, André; Graça, AnabelaA distribuição de medicamentos é uma função da farmácia hospitalar que, com metodologia e circuitos próprios, torna disponível o medicamento correto, na quantidade e qualidade certas, para cumprimento da prescrição médica proposta, para cada doente e todos os doentes do hospital. Assim, um sistema de distribuição de medicamentos é o método que abrange os procedimentos que ocorrem entre a prescrição e a administração de um medicamento. Um sistema de distribuição de medicamentos deve ser racional, eficiente, económico, organizado, seguro e estar de acordo com o esquema terapêutico prescrito. No final da década 50, os sistemas tradicionais de distribuição de medicamentos necessitavam de ser repensados, visando melhorar a segurança na distribuição e administração de medicamentos. Nos anos 60, farmacêuticos hospitalares apresentaram um novo sistema: a dose unitária, capaz de diminuir a incidência de erros de medicação. Estes sistemas podem dividir-se então em coletivos (sistema de distribuição tradicional e sistema de reposição de stocks nivelados) ou individuais (sistema de distribuição personalizada e sistema de distribuição por dose unitária). Os seus objetivos são reduzir os erros de medicação, racionalizar a distribuição, aumentar o controlo sobre os medicamentos, reduzir os custos com os medicamentos e aumentar a segurança para os doentes. Há, portanto, necessidade de cada hospital manter um sistema de distribuição de medicamentos adequado às suas necessidades. Sendo o erro de medicação qualquer discrepância entre a medicação prescrita e a administrada, a verificação da qualidade de qualquer sistema de distribuição tem como um dos indicadores a incidência dos erros de medicação. A ASHP, nas Guidelines on Preventing Medication Errors in Hospitals, refere que, para minimizar o erro, devem ser projetadas formas seguras de requisitar, dispensar e administrar os medicamentos. Objectivo do estudo: descrever e comparar os diferentes sistemas de distribuição de medicamentos, utilizados em meio hospitalar, notando a sua evolução e utilização ao longo dos tempos, bem como salientar o seu contributo para a segurança do doente (segurança da medicação).
- Microwave synthesis of SAPO-11 materials for long chain n-alkanes hydroisomerization: effect of physical parameters and chemical gel compositionPublication . Bertolo, R.; Silva, J.M.; Ribeiro, M.F.; Martins, A.; Fernandes, A.The present work concerns the preparation of SAPO-11 materials using microwave (MW) heating during the crystallization process. Different experimental conditions such as crystallization temperature and time were explored, together with different Si sources. The final materials were fully characterized using chemical analysis, XRD diffraction, pyridine adsorption followed by FTIR, nitrogen sorption and NMR spectroscopy and compared with the respective conventional SAPO-11 materials, synthesized using the same initial chemical composition of the gel but under conventional electric heating. The results showed that SAPO-11 materials can be synthesized in less time (within minutes) and at lower temperature (170 °C) with MW heating than with conventional heating (respectively 24 h and 200 °C). MW heating allows nanosized SAPO-11 materials to be obtained but the nature of the Si source used has a marked influence on the textural properties and, especially, on the acidity of SAPO-11. The catalytic properties of the materials (with 0.5 wt.% Pt) were evaluated in the hydroisomerization of long chain n-alkanes using n-decane as model molecule. Optimized MW samples using colloidal AS-40 Si source showed higher yields in monobranched isomers due to a joint effect of low acidity and suitable textural properties.
- Temperature distribution of a Fast-Field Cycling Nuclear Magnetic Resonance relaxometer's electromagnet with reduced volumePublication . Videira, P.; Sebastião, P.; Roque, A.; Sousa, D. M.; Fernandes, A.; Margato, ElmanoThe temperature distribution of a Fast Field Cycling (FFC) Nuclear Magnetic Resonance (NMR) electromagnet plays an important role in the operation of this type of apparatus. The designed electromagnet presents a reduced volume and is iron and copper based, fulfilling the technical requirements for the magnetic field. With this solution, it is possible to increase the overall performance in comparison with former similar FFC relaxometers. Electromagnet's simulation results evaluating the temperature distribution, heating effects and cooling requirements are presented.
- Towards a sustainable production of biologically active building blocks from dye-rich wastewatersPublication . Fernandes, A.; Bonardo, L.; Royo, B.; Robalo, Maria Paula; Martins, L. O.Looking beyond the traditional economy of “take, make and dispose” we established a multi-step enzymatic system for an eco-friendly biological treatment of dye-rich wastewaters simultaneously producing commercially interesting compounds. The dyeing process is responsible for the release into the environment of about 2.8 × 105 tons of dyes and dyestuff each year. The major component of these wastewaters are azo (-N=N-) dyes, which are recalcitrant and hazardous molecules.