University of Coimbra

About: University of Coimbra is a education organization based out in Coimbra, Portugal. It is known for research contribution in the topics: Population & Mitochondrion. The organization has 14318 authors who have published 43067 publications receiving 994733 citations. The organization is also known as: UC & Universidade dos Estudos Gerais.

The application of electrochemical impedance techniques to aluminium corrosion in acidic chloride solution

Abstract: Electrochemical impedance techniques are applied to the study of aluminium corrosion in hydrochloric acid solution in the passive region. Impedance spectra are obtained in stationary solution and in solution moving due to electrode rotation. The form of the spectra shows the importance of multistep dissolution, ionic migration through the oxide layer, relaxation effects and the influence of chloride ion.

The database of the PREDICTS (Projecting Responses of Ecological Diversity In Changing Terrestrial Systems) project

Abstract: The PREDICTS project—Projecting Responses of Ecological Diversity In Changing Terrestrial Systems (www.predicts.org.uk)—has collated from published studies a large, reasonably representative database of comparable samples of biodiversity from multiple sites that differ in the nature or intensity of human impacts relating to land use. We have used this evidence base to develop global and regional statistical models of how local biodiversity responds to these measures. We describe and make freely available this 2016 release of the database, containing more than 3.2 million records sampled at over 26,000 locations and representing over 47,000 species. We outline how the database can help in answering a range of questions in ecology and conservation biology. To our knowledge, this is the largest and most geographically and taxonomically representative database of spatial comparisons of biodiversity that has been collated to date; it will be useful to researchers and international efforts wishing to model and understand the global status of biodiversity.

Phosphorus speciation and availability in intertidal sediments of a temperate estuary: relation to eutrophication and annual P-fluxes

Abstract: For a better understanding of the phosphorus dynamics and bioavailability in temperate climates, sequential chemical extraction techniques were used to study sediment P-pools distribution and relative importance in a eutrophicated estuary. Results indicate a shift in importance from the iron-bound P fraction to the CaCO3-bound P fraction with increasing salinity, which suggests a decrease in bioavailable P from the most inner part of the estuary seaward, as the CaCO3 associated P is believed to be less available for organisms. Salt marsh plants also influence sediment P speciation, through higher organic P fractions (mainly humic acid associated P) when compared to non-vegetated sediments. The ratio of iron-bound P to iron-oxyhydroxides may be used as an indicator of P availability, since it reflects the number of available P sorption sites in the metal oxides. This ratio was lowest in the intermediate zone of the estuary (13.7) when compared to the outer site (29.6) and the upper site (26.1), suggesting saturation of sorption sites. Co-incident with this, the intermediate site is characterized by the occurrence of macroalgal blooms during summer. In the present case, superficial sediments in the Mondego estuary do not show a clear seasonal trend, either in total amounts of exchangeable P or P speciation. Pools of exchangeable P in the surface sediment were ∼30 times higher than the annual net-export of P (14 ton year−1) from the estuary. The annual P release from the sediment appears diminutive in comparison with the pool-size. Management measures to reduce nutrient input into coastal water systems should therefore consider that phosphorus availability may persist as a result of sediment supply, even after reducing the external point sources.