Detection of trasformer intermittent winding faults by the on-load exciting current Park`s vector approach

This paper presents the application of the on-load exciting current Park's Vector Approach for diagnosing permanent and intermittent turn-to-turn winding faults in operating power transformers. First, an experimental investigation of the behaviour of the transformer under the occurrence of both permanent and intermittent winding faults is presented. Finally, experimental test results demonstrate the effectiveness of the proposed diagnostic technique, which is based on the on-line monitoring of the on-load exciting current Park's Vector patterns.

Analysis of annuli in otoliths, age distribution and growth rates of the Namibian hake (Merluccius capensis)

Dissertação mest., Gestão da Água e da Costa, Universidade do Algarve, 2007

Radiographers perceptions of magnetic resonance imaging: a study of the causes that lead to the exams repetition

Purpose: To know how often occur the repetitions of MRI exams and sequences in radiology departments. Methods and Materials: A self applied-questionnaire was used as instrument and assigned to 57 radiographers who performed MRI exams to determine which were the causes that lead to the repetition. The questionnaires were interpreted and statistically analyzed through descriptive statistics and Spearman’s rho correlations. Results: At a 95% confidence interval, the major results suggest that the patient’s movement during de MRI exams is the main cause to repeat this exams (mean of 3.88 on a 5 points likert scale). However, there are causes related to the radiographer’s and the results showed that the introduction of wrong imaging parameters by the performer are a major cause too (N=26). Spearman rho correlations between radiographer’s time of experience and frequency of MRI exams repetitions were poor and not significant (r=0.141; p=0.297). The correlations between radiographer’s tiredness and frequency of MRI exams repetitions were negative, weak and not significant (r= -0.151; p=0.263). Conclusion: The patients’ movement may disrupt the examination or degrade the images with artifacts. The level of experience doesn’t influence the repetitions of MRI exams, it seems that seniors radiographers don’t have improvements in performance as it should be expected. It’s recommendable to do training courses regularly to improve the performance and systematically evaluate. Several features will need to be identified which would decrease the MRI exams repetitions.

Sistemas nanoparticulados e a vetorização de fármacos no tratamento do cancro

O cancro é hoje em dia um dos principais fatores de morbilidade e mortalidade. No ano de 2010, o National Institute of Health estimou os custos associados ao cancro em cerca de 263,8 biliões de dólares. Desta forma, a investigação nesta área continua a procurar formas de otimizar os tratamentos, aliviando o sofrimento dos doentes e reduzindo os custos associados à doença. O tratamento do cancro tem evoluído no sentido de atingir uma maior seletividade para as células tumorais. As limitações associadas à quimioterapia com apenas um fármaco conduziram ao aparecimento de novas estratégias, nas quais se combinam diferentes terapêuticas, com diferentes mecanismos de ação, levando a um efeito sinergístico. Esta estratégia permite a administração de uma menor dose de cada fármaco, diminuindo assim os efeitos adversos. No entanto, existem limitações clínicas para estas terapêuticas convencionais relacionadas com as propriedades dos transportadores das membranas celulares, a baixa biodisponibilidade e a distribuição dos fármacos junto das células tumorais. A pesquisa de novas estratégias tornou-se uma necessidade para a obtenção de uma distribuição mais efetiva e especifica dos fármacos nas células tumorais. Assim, os nanossistemas foram extensamente estudados para aumentar a eficácia dos tratamentos. A nanotecnologia, através da encapsulação dos fármacos, permitiu melhorar os parâmetros farmacocinéticos dos fármacos, tendo ainda a vantagem de se poder fazer uma vetorização para as células tumorais, tendo por base o reconhecimento de recetores.