Browsing by Issue Date, starting with "2012-03"
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- Does microphytobenthos resuspension influence phytoplankton in shallow systems? A comparison through a Fourier series analysisPublication . Brito, Ana; Fernandes, Teresa; Newton, Alice; Facca, Chiara; Tett, PaulShallow coastal lagoons, especially the ones with clear waters and lighted substrata, are likely to have large microphytobenthos (MPB) communities. MPB is an important component of these systems, representing up to 99% of the chlorophyll concentration when compared to phytoplankton. It is therefore expected that MPB resuspension play a key role in the dynamics of phytoplankton due to the tide and wind action. Water samples were collected twice per month inside and outside Ria Formosa lagoon (Portugal), for nutrients and chlorophyll a (chl a). Sediment samples were also collected for MPB chl a. Chl a was also analysed in water and sediment samples from Venice lagoon (Italy), at least once per month. A truncated Fourier series was fitted to the data to investigate the seasonal and high-frequency components of the time-series. In the Ria Formosa, the best significant fit for MPB was obtained considering the sum of 26 wave-pairs (sin and cosine), which explained 31% of the variability. The seasonal cycle (1e3 waves) explained approximately 5% of the total variability. Within-day variability which includes spatial heterogeneity explained 61% of the variability. The best fit for phytoplankton inside Ria Formosa was obtained considering the sum of 23 wave-pairs. Outside the lagoon the best fit was obtained using only the sum of 16 wave-pairs. For both cases, the sum of waves explained more than 64% of the variability and the seasonal cycle explained more than 31% of the variability. It is expected that primary producers in the water column have a strong seasonal factor due to the direct effect of the solar cycle, which is the case of other clear waters. In the Venice lagoon, which is microtidal, the best fit for MPB was obtained using 10 wave-pairs. However, the best fit for phytoplankton was obtained with only 3 wave-pairs, indicating the importance of the seasonal cycle. Significant relationships were found between phytoplankton inside and outside the Ria Formosa, as well as between microphytobenthos and phytoplankton in the lagoons of Venice and Ria Formosa. These results suggest the influence of MPB resuspension in the phytoplankton community of shallow coastal lagoons and the importance of phytoplankton exportation to the coastal zone.
- Phenolic composition and antioxidant capacity of six Artemisia speciesPublication . Carvalho, Isabel Saraiva de; Cavaco, Teresa; Brodelius, AnaThe aim of this work was to establish the antioxidant capacities and the polyphenolic profile of six different Artemisia species that could potentially be used in the human diet. A high-performance liquid chromatographic method coupled with photodiode-array detector was used to identify and quantify individual phenolic compounds of the Artemisia leaves. A total of 18 polyphenolic compounds were identified and quantified in Artemisia leaves, including hydroxybenzoic acids (4), hydroxycinnamic acids (5), flavonols (3), and catechins (2). It was observed that total phenolic content of A. annua and A. stelleriana leaves were significantly lower than the other four species. Ferulic and caffeic conjugates acids were the most dominant hydroxycinnamic acid and gallic acid and catechin were the most dominant hydroxycinnamic acid and catechins respectively. According to DPPH assays, the antioxidant capacity of A. arborescens spp., A. ludoviciana spp., A. oleandica spp. and A. princepts spp., were found to be higher (reflecting a 2-fold difference) than that of the other two species. Compared with those of major commercial leafy vegetables, leaves of Artemisia contain a higher content of flavonoids and phenolic acids, which provide significant health benefits and may be used as natural colorants.
- Cognitions and types of communication of mathematics teachers: Illustration of an analytical model in a divided episodePublication . Miguel Ribeiro, C.; Carrillo, Jose; Monteiro, RuteIn this article we focus our attention on the classroom and, more specifically, on the actions of the teacher during the teaching process, since we consider that said actions are conditioned or strengthened by their cognitions (beliefs, mathematical knowledge for teaching and objectives). For this reason, we explain and discuss an analytic model in relation to the practice of the teacher, which focuses on their actions, cognitions and type of mathematical communication that promotes (as an exteriorization of cognitions), as well as in their relations. In order to illustrate the modeling process, we use a situation (episode) in which a teacher presents the concept (concept of millesimal) during two different moments. First of all, we tackle what we understand in relation to each of the components of the model and, secondly, we present the modeling process and the relationships between components. Finally, we discuss some of the implications of this type of analysis in the training of teachers.
- Solving a contextual problem with the spreadsheet as an environment for algebraic thinking developmentPublication . Nobre, Sandra; Amado, Nélia; Carreira, SusanaIn this article we report and discuss a contextual problem solving task that was proposed to a class of 8th grade (13–14-year-old) students. These students had been developing a reasonable experience in the use of the spreadsheet to model relations within contextual problems and chose to use this tool to solve the mentioned problem, engaging in the process of translating relations between variables and combining them in chained models, while working with fractions, multiples and expressions. We intend to highlight the role of the spreadsheet in students’ processes of variable identification and translation of the problem conditions, their numerical approaches to algebraic models and their experimental forms of finding solutions to equations.
- Gla-rich protein, a new player in tissue calcification?Publication . Cancela, Leonor; Conceição, N.; Laizé, VincentA novel g-carboxyglutamate (Gla)-containing protein, named Gla-rich protein (GRP) after its high content in Gla residues or upper zone of growth plate and cartilage matrix associated protein after its preferential expression by cartilage chondrocyte, was recently identified in sturgeon, mice, and humans through independent studies. GRP is the most densely g-carboxylated protein identified to date and its structure has been remarkably conserved throughout vertebrate evolution but is apparently absent from bird genomes. Several transcript and genomic variants affecting key protein features or regulatory elements were described and 2 paralogs were identified in the teleost fish genome. In the skeleton, most relevant levels of GRP gene expression were observed in cartilaginous tissues and associated with chondrocytes, suggesting a role in chondrogenesis. But GRP expression was also detected in bone cells, indicative of a more widespread role for the protein throughout skeletal formation. Although the molecular function of GRP is yet unknown, the high content of Gla residues and its accumulation at sites of pathological calcification in different human pathologies affecting skin or the vascular system and in breast cancer tumors suggest that GRP may function as a modulator of calcium availability. Because of its association with fibrillar collagens, GRP could also be involved in the organization and/or stabilization of cartilage matrix. Although transgenic mice did not reveal obvious phenotypic alterations in skeletal development or structure, zebrafish morphants lack craniofacial cartilage and exhibit limited calcification, suggesting a role for GRP during skeletal development, but additional functional data are required to understand its function.
- Comprehensive factorization and I-central extensionsPublication . Bourn, Dominique; Rodelo, DianaWe show that, for a regular reflection functor I between efficiently regular categories, the reflection of an extension to an I-central extension is reduced to the comprehensive factorization of an explicit internal functor. We then analyse the Mal'tsev context where similar results are obtained under weaker conditions on I. (C) 2011 Elsevier B.V. All rights reserved.
- Ecological traits influencing range expansion across large oceanic dispersal barriers: insights from tropical Atlantic reef fishesPublication . Luiz, Osmar J.; Madin, Joshua S.; Ross Robertson, D.; Rocha, Luiz A.; Wirtz, Peter; Floeter, Sergio R.How do biogeographically different provinces arise in response to oceanic barriers to dispersal? Here, we analyse how traits related to the pelagic dispersal and adult biology of 985 tropical reef fish species correlate with their establishing populations on both sides of two Atlantic marine barriers: the Mid-Atlantic Barrier (MAB) and the Amazon-Orinoco Plume (AOP). Generalized linear mixed-effects models indicate that predictors for successful barrier crossing are the ability to raft with flotsam for the deep-water MAB, non-reef habitat usage for the freshwater and sediment-rich AOP, and large adult-size and large latitudinal-range for both barriers. Variation in larval-development mode, often thought to be broadly related to larval-dispersal potential, is not a significant predictor in either case. Many more species of greater taxonomic diversity cross the AOP than the MAB. Rafters readily cross both barriers but represent a much smaller proportion of AOP crossers than MAB crossers. Successful establishment after crossing both barriers may be facilitated by broad environmental tolerance associated with large body size and wide latitudinal-range. These results highlight the need to look beyond larval-dispersal potential and assess adult-biology traits when assessing determinants of successful movements across marine barriers.
- Urbano Tavares Rodrigues, "A Estação Dourada”Publication . Carvalho, Ana Alexandra Mendonça Seabra da Silva Andrade deNa antologia intitulada A Estação Dourada, Urbano Tavares Rodrigues reúne vinte e uma narrativas breves, escritas ao longo de uma década, e que, no seu conjunto, constituem uma perspectiva multifacetada e polifónica da realidade contemporânea. Tal diversidade conflui, no entanto, para o leque temático predilecto do escritor, sendo que os vários temas surgem amiúde interligados em cada texto. O título da colectânea é tomado ao da narrativa inaugural e pode ler-se como uma celebração da estação estival, tanto no sentido meteorológico como simbolizando a maturidade dos trinta/quarenta anos, com os seus aspectos positivos, mas também com os seus reveses.
- Contribuition of earth observation to understanding the upwelling conditions of the SW Coast of PortugalPublication . Icely, John; Moore, Gerald; Goela, Priscila; Cristina, Sónia; Newton, AliceValidation of MERIS (Medium Resolution Imaging Spectrometer) satellite products in the coastal upwelling system off the SW coast of Portugal has occurred since 2008 over a series of sampling campaigns at Stations 2, 10 and 18 km offshore. Data from between the 4th October and the 17th November 2008 demonstrate an upwelling event where temperature declines markedly from 20oC to 16.5oC between the 26th October and the 8th November. Other data confirming these events are profiles for conductivity, temperature and depth, as well as nutrient and chlorophyll concentrations. Nitrate peaks with chlorophyll on the 8th November, but phosphate is at low concentrations and declines before those of the nitrate over this period. The more spatially extensive sea surface temperature combined with wind velocity and direction, as well as MERIS Algal 1, supports the more site-specific observations at the validation stations. Nutrient changes due to physical forcing from upwelling occur earlier than changes in chlorophyll concentration.
- Effects of environmental conditions and fishing operations on the performance of a bottom trawlPublication . Queirolo, Dante; Hurtado, Carlos F.; Gaete, Erick; Soriguer, Milagrosa C.; Erzini, Karim; Gutierrez-Estrada, Juan CarlosTrawl performance was studied based on net spread and variability in the contact of the footrope with the seabed and their relationship with vessel operations, catch weight, and environmental conditions. Artificial neural networks (ANNs) and generalized additive models (GAMs) were used to model the response of each variable. For the variables net spread and variability in footrope contact (VFC), the ANN models were more accurate than the GAMs, with greater generalization capacity in the validation phase. In the best ANN model for net spread, all variables were significant. The relationship between tow direction and wind direction (tactic) was most important in the sensitivity analysis. Net spread increased with increasing towing speed and windspeed, and decreased with increasing wave height. In the ANN model for VFC, there were differences among vessels, and both scope ratio and catch size were not significant. VFC increased with increasing depth and decreased with increasing towing speed and windspeed. The results demonstrate that both operational variables and environmental conditions affect trawl performance, and suggest that survey protocols designed based on this information might help to improve the precision of biomass estimates.