Browsing by Issue Date, starting with "2000-06"
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- Metallothioneins in the clam Ruditapes decussatus: an overviewPublication . Bebianno, Maria João; Serafim, MA; Simes, DinaThe clam Ruditapes decussatus is a suspension-feeding bivalve mollusc widely distributed in European waters and in the Mediterranean. Due to is economic importance it is heavily harvested in many countries, and particularly in Portugal. Its ability to accumulate high metal concentrations along with its economic importance was the main reason for its selection as a bioindicator. Metallothionein (MT) concentrations in the clams R. decussatus followed by gel filtration chromatography, differential pulse polarography and SDS-PAGE, after Cd exposure, revealed that MT is induced in different tissues (whole soft tissues, gills, digestive gland and remaining tissues) but the level of MT induction is tissue dependent. MT from the gills and the digestive gland give a more sensitive response to assess the effects of metal exposure directly from the water or from the food than in the whole soft tissues. MT levels were also measured in the gills, digestive gland and remaining tissues of R. decussatus collected in the Ria Formosa lagoon (Portugal) from areas of different metal load and during the period of sexual differentiation of the clam. Data revealed that there were significant differences of MT concentrations among sites and season but not among sex. Purification of MT from the digestive gland of R. decussatus revealed four MT isoforms. The molecular weight of one of these isoforms, determined by SDS-PAGE, was of the same order of magnitude as that of MT from other bivalve species. Similarly the amino acid sequence of the beta domain of the MT of the digestive gland of the clam also shows some degree of similarity with the similar MT sequence from mussels and oysters. It is, therefore suggested that there is some degree of similarity in the MT structure among these species.
- Real-time implementation of a Doppler signal spectral estimator using sequential and parallel processing techniquesPublication . Madeira, M. M.; Tokhi, M. O.; Ruano, M. GraçaDoppler signal spectral estimation has been used to evaluate blood flow parameters in order to diagnose cardiovascular diseases. The modified covariance (MC) method has proved to provide accurate estimation of the two spectral parameters employed in clinical diagnosis, namely mean frequency and bandwidth. The aim of the work reported in this paper is to determine an efficient real-time implementation of the MC spectral estimator by investigating several architectures and implementation methods. A comparative performance analysis of the implementation of the MC algorithm on several homogeneous and heterogeneous architectures incorporating transputers, digital signal processing (DSP) devices and a vector processor is reported. The performances of these architectures are evaluated and compared in terms of computational time (execution and communication) and gradient measurements. Analysis of the results reveals that both the homogeneous and heterogeneous DSP-based parallel architectures meet the real-time requirements. (C) 2000 Elsevier Science B.V. All rights reserved.
- Reforço sísmico de edifícios – Análise de um caso de estudoPublication . Carreira, A. S.; Gomes, AugustoNeste artigo apresenta-se uma metodologia para o dimensionamento do reforço sísmico de edifícios existentes com estrutura de betão armado. Aplica-se o método a um caso de estudo real, para o qual se efectua uma análise de um conjunto de soluções de reforço, estabelecendo-se comparação entre as diversas respostas obtidas em termos de frequência, esforços e deslocamentos horizontais.