Repositório Institucional da Universidade de Aveiro
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Citizen-side handling of life event services
No full textCHAPAS is a model for the provision of life event e-government services where no direct communication between service providers exists. The citizen, assisted by a personal tool (Chappie), is responsible to gather all the information required by the service he wants to apply to, possibly from services of other providers. In this paper we discuss how life event e-government services are provided in CHAPAS, from the point of view of the interactions of Chappie with services. The immediate advantage of this approach is that services do not need to directly interact with each other to provide complex life event services, thereby citizens having full control of the flow of their personal information
Enforcing flexibility in real-time wireless communications: A bandjacking enabled protocol
No full textWireless communications are being applied in heterogeneous domains ranging from healthcare to industrial manufacturing. However, as wireless channels are highly unreliable, the support of applications having tight hard real-time and fault-tolerance requirements has been provided by dedicated wired communications. Recently, a technique named bandjacking has been evaluated as a feasible solution to mitigate the unreliability associated with wireless channels in contention-based communications environments. This paper builds on this technique to propose an FTT inspired protocol aiming to provide deterministic, reliable and flexible wireless communications
O Cabri-Géomètre e a construção de uma nova cultura matemática: os problemas da investigação
No full textResumo não disponível
ZnO nanostructures grown on vertically aligned carbon nanotubes by laser-assisted flow deposition
No full textNanoscale junctions between conductive and semiconductor materials, by promoting a large interfacial area, are crucial to maximizing
structural and electronic interactions, which are essential for energy conversion and storage technologies. Hierarchically structured
hybrids of ZnO with carbon nanotubes (CNTs) are an example of this co-operative behavior. ZnO is characterized by a wide band gap
and large exciton binding energy and CNTs ensure very high electrical conductivity. In the present work, a 3-D construction based on an
array of 1-D vertically aligned (VA) CNTs constitute the conductive substrate for the growth of ZnO semiconductor nanoparticles using
a laser-assisted flow deposition method. The functional interaction at the nanoscale between both materials is demonstrated by the
enhancement of the high resolved near band edge recombination which accounts for an almost three orders of magnitude increase when
compared with the green spectral band. A rectifying behavior was found for the ZnO/VACNT system
Assessment of a Enhanced ResultSet Component for accessing relational databases
No full textCall Level Interfaces (CLI) provide services aimed at easing the integration of database components and components from client applications. CLI support native SQL statements keeping this way expressiveness and performance of SQL. Thus, they cannot be discarded as a valid option whenever SQL expressiveness and SQL performance are
considered key requirements. Despite the aforementioned performance advantage, CLI do not comprise other important performance features, as concurrency over the in-memory data. In this paper we present and assess a component that is a concurrent version of the ResultSet interface from the JDBC
API. Several threads may interact simultaneously in the same instance of the ResultSet in a concurrent fashion and can be
simultaneously connected to the underlying database. The main contributions of this paper are twofold: i) the design of an Enhanced ResultSet Component to provide a concurrent access to relational databases; ii) the evaluation of its performance. The Enhaced ResultSet performance will be
assessed in a real scenario. The outcome shows that the gain in performance may increase until 80%
Fish consumption and risk of contamination by mercury - Considerations on the definition of edible parts based on the case study of European sea bass
No full textIn the present study, the risk to humans by consuming European sea bass (Dicentrarchus labrax), captured at three sites along a Hg contamination gradient, was evaluated by comparing muscle and kidney total Hg (T-Hg) levels with the European regulations for marketed fish. Moreover, T-Hg and organic Hg (O-Hg) levels in muscle were compared with the Provisional Tolerable Weekly Intake (PTWI) and the Reference Dose (RfD). Although T-Hg levels in muscle were below the European value allowable for marketed fish, kidney’s levels were higher than the set value, stressing the importance of redefining the concept of edible tissue and which tissues should be considered. Mercury weekly ingestion in the contaminated areas was higher than the PTWI, and O-Hg daily ingestion rates were higher than the RfD in all sampling sites. Thus, populations consuming sea bass from the contaminated sites may be at risk, with particular relevance for children and pregnant women
Distribution and accumulation of metals (Cu, Cd, Zn and Pb) in sediments of a lagoon on the northwestern coast of Portugal
No full textProductivity and nutrient cycling in salt marshes: Contribution to ecosystem health
No full textThis study aimed to assess the contribution of different salt marsh halophytes (Spartina maritima, Scirpus maritimus, Halimione portulacoides, Sarcocornia fruticosa, and Sarcocornia perennis) to nutrient cycling and sequestration in warm-temperate salt marshes. Carbon, nitrogen and phosphorus concentration in plant organs and rhizosediment, as well as plant biomass were monitored every two months during one year. Results show that the C retained in the rhizosediment does not seem to be species or site specific. However, some halophytes seem to have a higher contribution to retain C from external sources, namely S. perennis and S. maritima. Regarding N, halophytes colonizing the upper and middle marsh areas had the highest NBPP (net belowground primary production) as well as the retention of N in the rhizosediment. Yet, excluding S. maritimus, all halophytes seem to contribute to the retention of N from external sources. The P retained in the rhizosediment does not seem to be species or site specific. Still, only S. maritima colonizing the lower marsh areas, which also had comparatively lower NBPP, seem to have a higher contribution to retain P from external sources. Additionally, it seems that there is no relation between plants sequestration capacity for nutrients and plant photosynthetic pathway. This work shows that nutrient cycling and accumulation processes by salt marsh halophytes contribute to reduce eutrophication (N and P retention) and also to reduce atmospheric CO2 (C retention), highlighting salt marsh ecosystems services and the crucial role of halophytes in maintaining ecosystem functions and health
Bacterial community composition over a dry winter in meso- and eutrophic Portuguese water bodies
No full textIn order to investigate the bacterial diversity in a number of rivers, reservoirs and lakes in northern and central Portugal during the winter of 2004/5 (atypically dry), we applied molecular methodologies, namely denaturing gradient gel electrophoresis with primers targeting fractions of the bacterial 16S rRNA gene. Environmental parameters such as pH, conductivity, inorganic nutrients, total suspended solids and chlorophyll a were determined in order to characterize the trophic status of the studied water bodies. We found water bodies with oligotrophic to hypereutrophic characteristics. Organisms belonging to the Bacteroidetes and Alphaproteobacteria were found at the highest pH environment. Bacteroidetes were also related to high nutrient concentrations. Verrucomicrobia were associated with the most oligotrophic reservoir and low pH values. Actinobacteria were present in all samples from lakes and reservoirs, indicating its preference for lentic water bodies. Cyanobacteria dominance was related to high pH and conductivity levels. In general the conductivity values recorded in winter 2005 were the highest over recent years and chlorophyll a also reached very high levels. The data emphasize an enhanced risk of eutrophication for the studied water bodies, especially in the subsequent months when the temperature rises
Frequency characterization of memristive devices
No full textThis paper proposes a new methodology suitable for frequency characterization of memristive devices (MDs) and systems. MDs are usually described by their associated hysteresis loops. Their distinctive memory properties stem from this unusual characteristic. Understanding the frequency behavior of these devices is of paramount importance for a multitude of different applications. This paper presents a morphological method, based on loop area and the length for the analysis of the frequency dependence of MDs. An example, considering thin film TiO2 MDs reveals that the peak frequency (frequency where the loop has maximum area) of the device depends strongly on device dimensions and physical properties