Browsing by Author "Silva, Luís"
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- Classification Performance of Multilayer Perceptrons with Different Risk FunctionalsPublication . Silva, Luís; Santos, Jorge; Marques de Sá, JoaquimIn the present paper we assess the performance of information-theoretic inspired risks functionals in multilayer perceptrons with reference to the two most popular ones, Mean Square Error and Cross-Entropy. The information-theoretic inspired risks, recently proposed, are: HS and HR2 are, respectively, the Shannon and quadratic Rényi entropies of the error; ZED is a risk reflecting the error density at zero errors; EXP is a generalized exponential risk, able to mimic a wide variety of risk functionals, including the information-thoeretic ones. The experiments were carried out with multilayer perceptrons on 35 public real-world datasets. All experiments were performed according to the same protocol. The statistical tests applied to the experimental results showed that the ubiquitous mean square error was the less interesting risk functional to be used by multilayer perceptrons. Namely, mean square error never achieved a significantly better classification performance than competing risks. Cross-entropy and EXP were the risks found by several tests to be significantly better than their competitors. Counts of significantly better and worse risks have also shown the usefulness of HS and HR2 for some datasets.
- Sample preparation and chromatographic methods for the determination of protein-bound uremic retention solutes in human biological samples: An overviewPublication . Fernandes, Sara R.; Meireles, Andreia N.; Marques, Sara S.; Silva, Luís; Barreiros, Luisa; Sampaio-Maia, Benedita; Miro, Manuel; Segundo, Marcela A.Protein-bound uremic retention solutes, such as indole-3-acetic acid, indoxyl sulfate, p-cresol and p-cresol sulfate, are associated with the development of several pathologies, namely renal, cardiovascular, and bone toxicities, due to their potential accumulation in the human body, thus requiring analytical methods for monitoring and evaluation. The present review addresses conventional and advanced sample treatment procedures for sample handling and the chromatographic analytical methods developed for quantification of these compounds in different biological fluids, with particular focus on plasma, serum, and urine. The sample preparation and chromatographic methods coupled to different detection systems are critically discussed, focusing on the different steps involved for sample treatment, namely elimination of interfering compounds present in the sample matrix, and the evaluation of their environmental impact through the AGREEprep tool. There is a clear trend for the application of liquid-chromatography coupled to tandem mass spectrometry, which requires protein precipitation, solid-phase extraction and/or dilution prior to analysis of biological samples. Furthermore, from a sustainability point of view, miniaturized methods resorting to microplate devices are highly recommended.