Salt Fluxes in a Complex River Mouth System of Portugal

Measurements of velocity and salinity near the mouth and head of the Espinheiro channel (Ria de Aveiro lagoon, Portugal) are used to study the local variation of physical water properties and to assess the balance, under steady conditions, between the seaward salt transport induced by river discharge and the landward dispersion induced by various mixing mechanisms. This assessment is made using data sampled during complete tidal cycles. Under the assumption that the estuarine tidal channel is laterally homogeneous and during moderate tidal periods (except for one survey), currents and salinity data were decomposed into various spatial and temporal means and their deviations. Near the channel's mouth, the main contributions to the salt transport are the terms due to freshwater discharge and the tidal correlation. Near the channel's head, this last term is less important than the density driven circulation, which is enhanced by the increase in freshwater discharge. The remaining terms, which are dependent on the deviations from the mean depth have a smaller role in the results of salt transport. The computed salt transport per unit width of a section perpendicular to the mean flow is in close agreement to the sum of the advective and dispersive terms (within or very close to 12%). An imbalance of the salt budget across the sections is observed for all the surveys. Considerations are made on how this approach can inform the management of hazardous contamination and how to use these results to best time the release of environmental flows during dry months

Expansão para oeste do peixe-gato-europeu Silurus glanis no rio Douro (Portugal)

The current study reports the first occurrence and the spread of the European catfish Silurus glanis (Family: Siluridae) in the Portuguese section of the Douro River, suggesting a potential expansion of its distribution in Portugal either via westward dispersal across international rivers and/or human-assisted introductions into new reservoirs and drainages. The European catfish has unique features (e.g., opportunistic predator, hunting, and aggregation behaviour) that make it highly suitable for establishing self-sustaining populations in new areas and likely contribute to its invasion success. The species may severely affect native prey communities and modify food web structure and ecosystem functioning. Efficient and sustainable management actions are needed to prevent further introductions in the future.O presente estudo relata a primeira ocorrência do peixe-gato-europeu Silurus glanis (Família: Siluridae) no troço português do rio Douro, sugerindo uma potencial expansão da sua distribuição em Portugal através da dispersão natural da espécie para oeste através deste rio internacional e/ou através de introduções realizadas pelo homem em novas albufeiras. As características particulares do peixe-gato europeu (por exemplo, predador oportunista e comportamento de caça em grupo) aumentam quer o sucesso da sua dispersão quer o estabelecimento de populações auto-sustentáveis em novas massas de água. Esta espécie pode afetar severamente as comunidades de presas nativas e pode modificar a estrutura da teia alimentar, assim como mudar o funcionamento dos ecossistemas. Desta forma são necessárias ações de gestão eficazes para evitar novas introduções desta espécie.FCTinfo:eu-repo/semantics/publishedVersio

The interaction of La3+ complexes of DOTA/DTPA-glycoconjugates with the RCA120 lectin : a saturation transfer difference (STD) NMR spectroscopic study

The study of ligand-receptor interactions using high resolution NMR techniques, namely the Saturation Transfer Difference (STD), is presented for the recognition process between La(III) complexes of DOTA mono(amide) and DTPA bis(amide) glycoconjugates and the galactose specific lectin Ricinus Communis agglutinin (RCA120). This new class of Gd(III)-based potential targeted MRI contrast agents (CAs), bearing one or two terminal sugar (galactosyl or lactosyl) moieties, has been designed for in vivo binding to ASGPR (the asialoglycoprotein receptor), which is specifically expressed at the surface of liver hepatocytes, with the aim of leading to a new possible diagnosis of liver pathologies. The in vitro affinity constants of the divalent La(III)- glycoconjugate complexes to RCA120, used as a simple, water soluble receptor model, were higher than those of the monovalent analogues. The combination of the experimental data obtained from the STD NMR experiments with molecular modelling protocols (Autodock 4.1) allowed us to predict the binding mode of mono and divalent forms of these CAs to the galactose 1 binding sites of RCA120. The atomic details of the molecular interactions allowed corroborating and supporting the interaction of both the sugar moieties and the linkers with the surface of the protein and thus, their contribution to the observed interaction stabilities.Fundação para a Ciência e a Tecnologia (FCT

Synthesis and characterization of moisture cured prepolymer polyurethane films

Polyurethane prepolymers are a group of materials representing a reactive intermediate betweenmonomeric isocyanates and polyurethane polymers. They are the polycondensation reaction product of adiisocyanate (hard segments) and a material with hydroxyl functionality such as a polyol -glycol of high molecular weight (flexible segments). Most polyols used in polyurethane synthesis arebased on polyether, polyester or polycarbonate structures. About isocyanate, its structure determines itsreactivity and is known that aliphatic isocyanates are less reactive than aromatic ones.The properties of these prepolymers and the final products (adhesives, sealants and coatings) can be tunedby selecting suitable polyol and isocyanate components, as well as their molar ratio. When wateremulsifiable polymers are intended, anionic monomer dimethylolpropionic acid (DMPA) is incorporatedin the chain as internal emulsifier.The aim of this work was to synthesize and characterize moisture cured polyurethane prepolymers forhigh gloss coating applications. Desired resin must be emulsifiable in water (for easy cleaning of thereactor and auxiliary equipment) and the respective coating must be transparent, colorless and tack free.The following parameters were studied: chemical nature and molecular weight of polyol (polyether andpolycarbonate, from 400 to 2000 molecular weight), initial molar ratio of isocyanate to hydroxyl groups(NCO/OH ratio from 1.5 to 2.5) and presence or absence of DMPA. The isocyanate used was alwaysisophorone diisocyanate.The coatings obtained were caharacterized in terms of thermal stability, Buchholz hardness, scratchresistance, tack, gloss and yellowness index. The results were analysed and related to the expectedpolymer structures for the different cases. The best performance was obtained for polycarbonate polyolwith higher NCO/OH ratio and containing DMPA

Creation of a vehicular delay-tolerant network prototype

Vehicular Delay-Tolerant Network (VDTN) is a new disruptive network architecture where vehicles act as the communication infrastructure. VDTN follows a layered architecture based on control and data planes separation, and positioning the bundle layer under the network layer. VDTN furnishes low-cost asynchronous communications coping with intermittent and sparse connectivity, variable delays and even no end-to-end connection. This paper presents a VDTN prototype (testbed) proposal, which implements and validates the VDTN layered architecture considering the proposed out-of-band signaling. The main goals of the prototype are emulation, demonstration, performance evaluation, and diagnose of protocol stacks and services, proving the applicability of VDTNs over a wide range of environments.Part of this work has been supported by the Instituto de Telecomunicações, Next Generation Networks and Applications Group (NetGNA), Covilhã Delegation, Portugal in the framework of the VDTN@Lab Project, and by the Euro-NF Network of Excellence from the Seventh Framework Programme of EU

Renormalisation scheme for vector fields on T2 with a diophantine frequency

We construct a rigorous renormalisation scheme for analytic vector fields on the 2-torus of Poincare type. We show that iterating this procedure there is convergence to a limit set with a ``Gauss map'' dynamics on it, related to the continued fraction expansion of the slope of the frequencies. This is valid for diophantine frequency vectors.Comment: final versio

Fluorescence studies of new potential antitumoral di(hetero)arylethers derivatives of a thieno[3,2-b]pyridine encapsulated in nanoliposomes

Contribution (Poster)This work was funded by FCT-Portugal through CFUM, CQ/UM, Project PTDC/QUI/81238/2006 cofinanced by FCT and program FEDER/COMPETE (FCOMP-01-0124-FEDER-007467)

Chaos in the square billiard with a modified reflection law

The purpose of this paper is to study the dynamics of a square billiard with a non-standard reflection law such that the angle of reflection of the particle is a linear contraction of the angle of incidence. We present numerical and analytical arguments that the nonwandering set of this billiard decomposes into three invariant sets, a parabolic attractor, a chaotic attractor and a set consisting of several horseshoes. This scenario implies the positivity of the topological entropy of the billiard, a property that is in sharp contrast with the integrability of the square billiard with the standard reflection law.Comment: 17 figure