Browsing by Issue Date, starting with "2009-07"
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- Identification, release and olfactory detection of bile salts in the intestinal fluid of the Senegalese sole (Solea senegalensis)Publication . Velez, Zélia; Hubbard, Peter; Welham, K.; Hardege, Jörg D.; Barata, E. N.; Canario, Adelino V. M.Olfactory sensitivity to bile salts is wide-spread in teleosts; however, which bile salts are released in suYcient quantities to be detected is unclear. The current study identiWed bile salts in the intestinal and bile Xuids of Solea senegalensis by mass spectrometry–liquid chromatography and assessed their olfactory potency by the electro-olfactogram.
- Which demographic traits determine population growth in the invasive brown seaweed Sargassum muticum?Publication . Engelen, Aschwin; Santos, Rui1. Life-history traits commonly associated with plant invasiveness are vegetative reproduction or r-selected traits such as short generation times and high rates of reproduction and individual growth. 2. We used matrix modelling to assess which demographic traits are important for the population growth of an invasive seaweed lacking vegetative reproduction and whether demographic and life-history strategies shift with increased dominance of the invader. The vital rates of one of the most successful invading seaweeds, Sargassum muticum, were investigated monthly for 2 years in intertidal pools dominated by the native brown seaweed Cystoseira humilis and by S. muticum, respectively. In order to speculate about the demographic mechanisms that determine invasiveness of S. muticum, and as the study sites were recently colonized, we assumed that C. humilis and S. muticum pools are proxies for early and late phases of invasion, respectively. 3. Both deterministic and stochastic matrix models showed positive rates of population growth, and rates were significantly higher in the pools dominated by S. muticum than in the ones dominated by C. humilis, indicating demographic changes with invader dominance. The variability of population growth rates and of reproductive and elasticity values of S. muticum was higher in the pools dominated by C. humilis, suggesting invader-driven stabilization of environmental conditions. Generation times of the species increased with invader dominance, supporting invader-stabilized environmental conditions. 4. Elasticity analyses revealed that the most important demographic trait for population growth rate at both levels of invader dominance was the persistence of the non-fertile adult fronds rather than reproduction or growth. No major shifts in the life-history strategy of S. muticum between levels of invader dominance were detected. 5. Synthesis. This study suggests that the invasiveness of S. muticum, a perennial invader without vegetative reproduction, relies on K- rather than r-selected traits and without drastic changes in life-history strategy between phases of invasion.
- Screening of sustainable groundwater sources for integration into a regional drought-prone water supply systemPublication . Stigter, T. Y.; Monteiro, José Paulo; Nunes, L.; Vieira, João; Cunha, Maria da Conceição; Ribeiro, Luís; Nascimento, João; Lucas, HelenaThis paper reports on the qualitative and quantitative screening of groundwater sources for integration into the public water supply system of the Algarve, Portugal. The results are employed in a decision support system currently under development for an integrated water resources management scheme in the region. Such a scheme is crucial for several reasons, including the extreme seasonal and annual variations in rainfall, the effect of climate change on more frequent and long-lasting droughts, the continuously increasing water demand and the high risk of a single-source water supply policy. The latter was revealed during the severe drought of 2004 and 2005, when surface reservoirs were depleted and the regional water demand could not be met, despite the drilling of emergency wells. For screening and selection, quantitative criteria are based on aquifer properties and well yields, whereas qualitative criteria are defined by water quality indices. These reflect the well’s degree of violation of drinking water standards for different sets of variables, including toxicity parameters, nitrate and chloride, iron and manganese and microbiological parameters. Results indicate the current availability of at least 1100 l s−1 of high quality groundwater (55% of the regional demand), requiring only disinfection (900 l s−1) or basic treatment, prior to human consumption. These groundwater withdrawals are sustainable when compared to mean annual recharge, considering that at least 40% is preserved for ecological demands. A more accurate and comprehensive analysis of sustainability is performed with the help of steady-state and transient groundwater flow simulations, which account for aquifer geometry, boundary conditions, recharge and discharge rates, pumping activity and season. (tibor.stigter@ist.utl.pt) ality. They permit an advanced analysis of present and future scenarios and show that increasing water demands and decreasing rainfall will make the water supply system extremely vulnerable, with a high risk of groundwater salinization and ecosystem degradation.
- A scalable and open source linear positioning system controllerPublication . Medeiros, M. C.; Fernandes, A. J. A.; Teixeira, C. A.; Ruano, M. GraçaThis paper is on the implementation of a dual axis positioning system controller. The system was designed to be used for space-dependent ultrasound signal acquisition problems, such as pressure field mapping. The work developed can be grouped in two main subjects: hardware and software. Each axis includes one stepper motor connected to a driver circuit, which is then connected to a processing unit. The graphical user interface is simple and clear for the user. The system resolution was computed as 127 mu m with an accuracy of 2.44 mu m. Although the target application is ultrasound signal acquisition, the controller can be applied to other devices that has up to four stepper motors. The application was developed as an open source software, thus it can be used or changed to fit different purposes.
- Representações redundantes para procura evolutivaPublication . Correia, Marisol B.Existe actualmente um grande interesse na influência da redundância e da neutralidade no comportamento dos algoritmos evolutivos. Alguns autores consideram que a procura evolutiva pode ser influenciada de forma positiva pela utilização de representações redundantes, enquanto outros afirmam que a adição de redundância aleatória parece ser inútil na optimização. Em virtude desta falta de consenso e tendo em conta a existência de redundância e de neutralidade no código genético, são propostas nesta dissertação duas novas famílias de representações binárias redundantes. A família de representações neutrais baseia-se na formulação matemática dos códigos de controlo de erros, utilizados em comunicações digitais, enquanto a família de representações não neutrais baseia-se em transformações lineares e permite definir a vizinhança fenotípica pretendida de uma forma simples e directa. É apresentado um estudo experimental destinado a avaliar a influência da redundância e da neutralidade no desempenho de um algoritmo evolutivo simples, especificamente, de uma estratégia evolutiva (1+1)-ES, modelada através de cadeias de Markov e aplicada a paisagens de aptidão NK. Os resultados permitem concluir que a vizinhança fenotípica induzida pela representação redundante domina o comportamento do algoritmo evolutivo, afectando de forma mais profunda a procura do que a neutralidade, e que as melhores representações não apresentam valores extremos de nenhum dos indicadores de qualidade das representações habitualmente considerados na literatura.