Browsing by Author "Almeida, Pedro"
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- Cork oak physiological responses to manipulated water availability in a Mediterranean woodlandPublication . Besson, Cathy Kurz; Lobo-do-Vale, Raquel; Rodtigues, Maria Lucília; Almeida, Pedro; Herd, Alastair; Grant, Olga Mary; David, Teresa Soares; Schmidt, Markus; Otieno, Denis; Keenan, Trevor F.; Gouveia, Célia; Mériaux, Catherine; Chaves, M.Manuela; Pereira, João SantostThis study details the physiological responses of cork oak (Quercus suber L.) to manipulated water inputs.Treatments named as dry, ambient and wet, which received 80, 100 and 120% of the annual precipitation,respectively, were applied to a Mediterranean woodland in southern Portugal. Tree ecophysiology andgrowth were monitored from 2003 to 2005.The impacts of the water manipulation were primarily observed in tree transpiration, especially dur-ing summer drought. Rainfall exclusion reduced the annual stand canopy transpiration by 10% over the2-year study period, while irrigation increased it by 11%. The accumulated tree transpiration matchedprecipitation in spring 2004 and 2005 at the stand level, suggesting that cork oak trees rely on precip-itation water sources during the peak of the growing season. However, during the summer droughts,groundwater was the main water source for trees.Despite the significant differences in soil water content and tree transpiration, no treatment effectscould be detected in leaf water potential and leaf gas exchange, except for a single event after spring irri-gations in the very dry year 2005. These irrigations were intentionally delayed to reduce dry spell durationduring the peak of tree growing season. They resulted in an acute positive physiological response of treesfrom the wet treatment one week after the last irrigation event leading to a 32% raise of stem diame-ter increment the following months. Our results suggest that in a semi-arid environment precipitationchanges in spring (amount and timing) have a stronger impact on cork oak physiology and growth thanan overall change in the total annual precipitation.The extreme drought of 2005 had a negative impact on tree growth. The annual increment of treetrunk diameter in the ambient and dry treatments was reduced, while it increased for trees from the wettreatment. Water shortage also significantly reduced leaf area. The latter dropped by 10.4% in responseto the extreme drought of 2005 in trees from the ambient treatment. The reduction was less pronouncedin trees of the wet treatment (−7.6%), and more pronounced in trees of the dry treatment (−14.7%).Cork oak showed high resiliency to inter-annual precipitation variability. The annual accumulated treetranspiration, the minimum midday leaf water potential and the absolute amount of groundwater used
- Design de informação interactivo: contributos para a definição de uma área projectualPublication . Almeida, Pedro; Cardoso, Miguel
- Detection of Microcalcifications in Digital Breast Tomosynthesis using Faster R-CNN and 3D Volume RenderingPublication . Matela, Nuno; Almeida, Pedro; Clarkson, Matthew; Mota, AnaMicrocalcification clusters (MCs) are one of the most important biomarkers for breast cancer and Digital Breast Tomosynthesis (DBT) has consolidated its role in breast cancer imaging. As there are mixed observations about MCs detection using DBT, it is important to develop tools that improve this task. Furthermore, the visualization mode of MCs is also crucial, as their diagnosis is associated with their 3D morphology. In this work, DBT data from a public database were used to train a faster region-based convolutional neural network (R-CNN) to locate MCs in entire DBT. Additionally, the detected MCs were further analyzed through standard 2D visualization and 3D volume rendering (VR) specifically developed for DBT data. For MCs detection, the sensitivity of our Faster R-CNN was 60% with 4 false positives. These preliminary results are very promising and can be further improved. On the other hand, the 3D VR visualization provided important information, with higher quality and discernment of the detected MCs. The developed pipeline may help radiologists since (1) it indicates specific breast regions with possible lesions that deserve additional attention and (2) as the rendering of the MCs is similar to a segmentation, a detailed complementary analysis of their 3D morphology is possible.
- Detection of Microcalcifications in Digital Breast Tomosynthesis using Faster R-CNN and 3D Volume RenderingPublication . Mota, Ana M.; Clarkson, Matthew J.; Almeida, Pedro; Matela, NunoMicrocalcification clusters (MCs) are one of the most important biomarkers for breast cancer and Digital Breast Tomosynthesis (DBT) has consolidated its role in breast cancer imaging. As there are mixed observations about MCs detection using DBT, it is important to develop tools that improve this task. Furthermore, the visualization mode of MCs is also crucial, as their diagnosis is associated with their 3D morphology. In this work, DBT data from a public database were used to train a faster region-based convolutional neural network (R-CNN) to locate MCs in entire DBT. Additionally, the detected MCs were further analyzed through standard 2D visualization and 3D volume rendering (VR) specifically developed for DBT data. For MCs detection, the sensitivity of our Faster R-CNN was 60% with 4 false positives. These preliminary results are very promising and can be further improved. On the other hand, the 3D VR visualization provided important information, with higher quality and discernme nt of the detected MCs. The developed pipeline may help radiologists since (1) it indicates specific breast regions with possible lesions that deserve additional attention and (2) as the rendering of the MCs is similar to a segmentation, a detailed complementary analysis of their 3D morphology is possible.
- Os efeitos da resolução do contrato de trabalho desportivo por iniciativa do jogador profissional de futebolPublication . Almeida, PedroO presente texto incide sobre alguns dos efeitos que poderão emergir da resolução (com invocação de justa causa) do contrato de trabalho desportivo por iniciativa do praticante desportivo no contexto do futebol profissional em Portugal. Tendo por base de análise a Lei n.º 54/2017, e com atenção ao disposto em sede regulamentar e de contratação coletiva neste âmbito, colocamos o foco na responsabilidade pela cessação contratual e na possibilidade de aplicação de sanções desportivas aos jogadores por uma eventual desvinculação indevida.
- Effects of flow regulation on the movement patterns and habitat use of a potamodromous cyprinid speciesPublication . Alexandre, Carlos; Almeida, Pedro; Neves, T.; Mateus, C. S.; Costa, José Lino; Quintella, BernardoRiver regulation for hydroelectricity production results in rapid changes of flow and habitat features, but its effects in the movement patterns of freshwater fish are not well understood. Radiotelemetry was used to track Iberian barbel during a year cycle in non-regulated and regulated rivers. We applied a kernel density method to estimate and compare home range sizes of the two populations. Seasonal patterns of movement and the intra-annual variation in habitat preferences were also compared. Barbel inhabiting regulated river exhibit larger and more continuous home and core ranges, in opposition to the smaller and patchy areas used by fish inhabiting the non-regulated river. Seasonal movements of both populations were differentiated by the drought period. Barbel from the non-regulated river had to search for suitable refuges, with specific habitat characteristics, in which they remained aggregated during harsh summer conditions. Conversely, barbel from regulated river kept a continuous distribution along the river. This study contributes to the management of regulated rivers by providing insights about which flow components are more altered by hydropeaking operations and which are the most critical annual periods for fish movements. It also suggests several restoration actions, such as the protection of fish summer refuges, the restoration of large-scale temporal streamflow variability and the reduction of daily rates of discharge rise and fall, which should be continuously monitored in order to increase their efficiency and provide new knowledge.
- Evaporation and carbonic anhydrase activity recorded in oxygen isotope signatures of net CO2 fluxes from a Mediterranean soilPublication . Wingate, Lisa; Seibt, Ulli; Maseyk, Kadmiel; Ogée, Jérome; Almeida, Pedro; Yakir, Dan; Pereira, João Santos; Mencuccini, MaurizioThe oxygen stable isotope composition (d18O) of CO2 is a valuable tool for studying the gas exchange between terrestrial ecosystems and the atmosphere. In the soil, it records the isotopic signal of water pools subjected to precipitation and evaporation events. The d18O of the surface soil net CO2 flux is dominated by the physical processes of diffusion of CO2 into and out of the soil and the chemical reactions during CO2–H2O equilibration. Catalytic reactions by the enzyme carbonic anhydrase, reducing CO2 hydration times, have been proposed recently to explain field observations of the d18O signatures of net soil CO2 fluxes. How important these catalytic reactions are for accurately predicting large-scale biosphere fluxes and partitioning net ecosystem fluxes is currently uncertain because of the lack of field data. In this study, we determined the d18O signatures of net soil CO2 fluxes from soil chamber measurements in a Mediterranean forest. Over the 3 days of measurements, the observed d18O signatures of net soil CO2 fluxes became progressively enriched with a well-characterized diurnal cycle. Model simulations indicated that the d18O signatures recorded the interplay of two effects: (1) progressive enrichment of water in the upper soil by evaporation, and (2) catalytic acceleration of the isotopic exchange between CO2 and soil water, amplifying the contributions of ‘atmospheric invasion’ to net signatures. We conclude that there is a need for better understanding of the role of enzymatic reactions, and hence soil biology, in determining the contributions of soil fluxes to oxygen isotope signals in atmospheric CO2.
- Pluralidade e diversidade numa ideia de geraçãoPublication . Almeida, Pedro
- Predictors of Health-Protective and Helping Behaviors during the Covid-19 Pandemic: The Role of Social Support and ResiliencePublication . Fontes, Andrea; Pereira, Cicero Roberto; Menezes, Sofia; Soares, Antonio; Almeida, Pedro; Carvalho, Geórgia; Arriaga, PatríciaThe COVID -19 pandemic dramatically affected people’s lives. In this study, we explored the role of social and personal factors underlying individuals’ adaptive responses during the critical onset period of the outbreak. In particular, we tested two models on the mediating role of health-protective behaviors in the relationship between social support, resilience, and helping behavior. A sample of 1085 participants from Portugal and Brazil took part in an online survey during the first wave of the pandemic. First, through an Exploratory Factor Analysis of the health-protective behaviors to prevent contagion by the coronavirus, we identified two distinct dimensions, one aggregating active protective behaviors and the other as avoidant behaviors. Secondly, we found that resilience and active protective behavior sequentially mediated the relationship between social support and willingness to help. In addition, a multigroup analysis showed that this mediational process was similar in both countries. Given the wide range of social and individual factors that may predict prosocial behaviors, we highlight the role of social support on the intention to help through resilience and active protective behaviors.