Repositório Institucional da Universidade de Aveiro
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Recovery trends of Scrobicularia plana populations after restoration measures, affected by extreme climate events
No full textThe Mondego estuary (Portugal) went through different ecological scenarios over the last decades. An eutrophication process led to a decline in the ecosystem quality. The ensuing restoration plan resulted into a gradual ecological recovery, which was impaired by the occurrence of successive extreme climate events that affected dynamics and productivity of key species. In this study we assess the response of the bivalve Scrobicularia plana to the impacts of these events in a recovery scenario, by comparing populations in two different intertidal habitats: a seagrass bed and a sandflat area. As a general tendency, S. plana, which was negatively affected by eutrophication, responded positively to restoration. However, the occurrence of extreme climate events seemed to affect recruitment success, biomass and production, impairing the recovery process. In the seagrass bed, S. plana maintained a stable and structured population, while in the sandflat area recovery clearly reverted into a decline, mainly concerning biomass and production values. This sequence of multiple stressors might have reduced S. plana resilience to further impacts and therefore, understanding the behavior of biological populations following restoration initiatives requires acknowledgement that some changes may not be easily reversible
Evaluation of the anthropogenic input of caffeine in surface waters of the north and center of portugal by ELISA
No full textThis study comprises the development of an enzyme-linked immunosorbent assay (ELISA) for the quantification of caffeine in complex aqueous matrices without any sample clean-up procedure. Salinity and dissolved organic matter were selected as potential interfering agents. The addition of a sample buffer containing bovine serum albumin (BSA) prior to the sample was found to decrease the influence of those interfering agents. The working range of the developed method was 0.1-100??gL-1. Quantification of caffeine was possible in 43 out of 51 real aqueous samples, at values between <LOD and 15??gL-1. Results correlate well with those obtained by LC-MS/MS. To the best of our knowledge this is the first study dealing with the quantification of caffeine in Portugal's surface waters
Heterotrophic activities of neustonic and planktonic bacterial communities in an estuarine environment (Ria de Aveiro)
No full textThe uppermost millimeter of the water column, the surface microlayer (SML), hosts bacterial communities (bacterioneuston) with potential metabolic adaptations to this unique physical and chemical environment. Hydrolysis and monomer incorporation by bacterioneuston and bacterioplankton communities in the estuarine system, Ria de Aveiro, was investigated and compared during a 2-year survey. The study was conducted at two contrasting sites, typifying the marine and brackish water characteristics of the estuary and with different sources, amounts and composition of organic matter. In the marine zone, bacterioneuston showed higher rates of hydrolysis and lower rates of monomer incorporation than bacterioplankton, whereas in the brackish water zone, neustonic and planktonic microbial communities showed similar activity rates. This pattern may result from the different degree of surface organic and inorganic matter enrichments, which reflect site-specific characteristics, such as hydrodynamics and sources of organic matter composition. In general, the estuarine SML environment favors polymer hydrolysis, but inhibits monomer utilization, in comparison with the subsurface layers. However, the differences between the two communities tend to decrease as autotrophic and heterotrophic activities increase in the brackish-water area
Co-resistance to different classes of antibiotics among ESBL-producers from aquatic systems
No full textIn this study we investigated the co-occurrence of resistance to non-beta-lactams among cefotaxime-resistant extended-spectrum beta-lactamase (ESBL) producers (ESBL+) versus non-ESBL producers (ESBL-), from aquatic environments. Higher prevalence of resistance to tetracycline, fluoroquinolones and aminoglycosides were observed in ESBL+. Among ESBL+ resistant to tetracycline (n=18), tet(A) was detected in 88.9% and tet(B) in 16.7%. Among fluoroquinolone-resistant-ESBL+ (n=15), aacA4-cr and qnrVC4 were identified in 26.6% and 40% strains, respectively. The qnrVC4 gene was detected for the first time in Pseudomonas sp. and Escherichia coli. Class 1 integrase genes were detected in 56.41% of ESBL+ and in 27.67% ESBL-. Gene cassette arrays identified conferred resistance to aminoglycosides (aadA-type genes and aacA4), trimethoprim (dfrA17), chloramphenicol (catB8), fluoroquinolones (qnrVC4) and beta-lactams (blaOXA-10). Conjugation experiments were performed with CTX-M-producers. Transconjugants showed multiresistance to 3 or more classes of antibiotics, and conjugative plasmids were assigned to IncF, IncK and IncI1 replicons. Results obtained showed that co-selection of resistance to aminoglycosides, quinolones and tetracyclines is prevalent among ESBL-producers and that these features are successfully mobilized by IncF, IncK and IncI1 conjugative plasmids. This study reinforces the importance of natural aquatic systems as reservoir of mobile genetic platforms carrying multiple resistance determinants. Moreover, to the best of our knowledge, this constitutes the first observation of IncK::CTX-M-3 in Aeromonas hydrophila and the first report of IncK plasmids in Portugal
Hidrogeologia do quaternário da região norte da ria de Aveiro: aplicação de isótopos ambientais
No full textMestrado em GeoquímicaEsta tese foi dividida em 5 Capítulos e um anexo, cujos conteúdos e
organização passamos a descrever sucintamente, no sentido de darmos uma
ideia global da estrutura do trabalho.
O Capítulo I aborda o tema Geologia de superfície e de subsuperfície.
Apresentam-se as grandes unidades morfoestruturais, distinguem-se as
diversas unidades existentes, apresenta-se um esquema geral da Geologia da
área em estudo e, finalmente, faz-se a reconstrução da história geológica e
paleogeográfica, tentando-se identificar e recriar os ambientes e condições que
estiveram na base de toda a evolução mais recente desta região.
O Capítulo II é dedicado à caracterizagão climática da região. Aqui
determinam-se os excedentes e défices hídricos com a finalidade de chegarmos
a um valor médio anual dos excedentes. O valor médio anual dos destes
permitir-nos-; calcular a parcela correspondente à infiltração que, mais à
frente, terá importância decisiva para o cálculo da recarga dos aquíferos.
No Capítulo III, dedicado à hidrogeologia, são definidos sistemas e
subsistemas aquíferos existentes e as suas características geométricas e
hidráulicas. Aborda-se, ainda, o aspecto da qualidade das águas provenientes
dos diferentes aquíferos, suas utilizações e estimativas das quantidades
extraídas anualmente para os diversos fins.
O Capítulo IV refere-se aos temas hidroquímica e isotopia. No primeiro
definem-se as principais fácies existentes e tendências de evolução das
mesmas através da comparação de análises recentes, com outras anteriores. A
caracterização isotópica permitiu-nos definir idades para as águas das diversas
captações amostradas, tendo sido possível confirmar o sistema de
funcionamento hidráulico proposto anteriormente. Foi ainda possível, através
dos resultados proporcionados pela isotopia, confirmar valores de recarga do
aquífero por nós propostos. Quanto aos mecanismos de salinização das águas
do aquífero da base do Quaternário, também aqui os isótopos deram bons
resultados. Os gradientes hidráulicos criados por explorações excessivas, dão
origem à drenância dos lodos constituintes do tecto do aquífero (lodos que têm
água intersticial bastante salobra) provocando, deste modo, a salinização das
captações.
Finalmente o Capítulo V, o das conclusões, faz uma súmula dos capítulos
precedentes relacionando factos e tirando daí as ilações pertinentes
The role of universities in the development of plurilingual repertoires: the voices of non-traditional adult students
Get PDFThe purpose of this paper is to present a study on the non-traditional adult students’ (NTAS) perceptions concerning the role of
university in the development of their plurilingual repertoires. Data were collected through biographical interviews with NTAS
with fewer and more plurilingual experiences. The results show that NTAS with more plurilingual experiences are more aware of
their plurilingual repertoire and acknowledge higher education as an opportunity to further develop it. It also appears that if
university promotes a favourable environment for the development of plurilingual repertoires, there may be a change in NTAS’
perception regarding lifelong language learning
Cohesive zone beam modelling of mixed-mode I-II delamination
No full textTwo cohesive zone beam models were developed for mixed-mode I-II delamination. The models were assessed by application to the moment-loaded double cantilever beam specimen, for which exact solutions are available. The main difficulties were caused by the very different distributions of the normal and shear tractions in the vicinity of the crack tip. This generated considerable local mode-mix variations along the cohesive zone. The separation controlled damage formulation was more sensitive to those difficulties, which could even compromise the accuracy of results. Instead, the energy controlled damage formulation proved to be robust and thus best suited for cohesive zone beam modelling of delamination
A perceção dos estudantes sobre o uso de tecnologias da comunicação no ensino superior público português
No full textNo âmbito deste artigo apresentam-se resultados
parciais de uma investigação que teve como principal finalidade
conhecer a perceção os estudantes do Ensino Superior Público
Português (ESPP) no uso das Tecnologias da Comunicação no
Suporte à Aprendizagem (TCSA). Para a prossecução dos
objetivos traçados, desenvolveu-se um estudo descritivo e
exploratório de âmbito nacional e optou-se pela disponibilização
de um questionário online para a recolha de dados. Neste artigo
evidenciam-se os resultados que dizem respeito à perceção dos
estudantes sobre: (i) disponibilização de TCSA pelas instituições
de ESPP; (ii) o tipo de unidades curriculares que usam TCSA;
(iii) as principais finalidades de uso das TCSA; (iv) o uso que os
docentes fazem das TCSA; e (v) as atividades promovidas com
recurso às TCSA. Os resultados alcançados permitem concluir
que o acesso às TCSA nas instituições de ESPP é gratuito, sendo
usadas em grande parte das unidades curriculares. Em termos de
finalidades de uso, a tendência das repostas sugere que a maioria
dos estudantes usa as TCSA para a consultar e recolher
informações e/ou conteúdos relacionados com a aprendizagem. A
pertinência e o principal contributo do estudo realizado são o de
permitir a identificação e a caracterização da situação atual do ESPP quanto ao uso de TCSA por parte dos seus estudantes.Within this article we present some results of an
investigation that aimed to identify and characterize the students’
use of Communication Technologies to Support Learning (CTSL)
in Portuguese Public Higher Education (PPHE). In order to
achieve the goals set, a nationwide descriptive study was
developed and an online questionnaire was elaborated and
provided for data collection. This article presents the results
obtained concerning the students’ perception about: (i) the
provision of CTSL by PPHE; (ii) the type of classes that use
CTSL; (iii) the main purposes of using CTSL; (iv) the teachers’
use of CTSL; and (v) the activities promoted through the use
CTSL. The main results obtained allow us to conclude that the
access to CTSL in the PPHE is free, and the CTSL are used in
most classes. In terms of use purposes, the results suggest that
most students use CTSL to access and gather information and /
or content related to their learning activities. The relevance and
main contribution of this study is to enable the identification and
characterization of the current situation regarding the student´s
use of CTSL in PPHE
Walls of the saltpans of the Aveiro Lagoon, Portugal: current status and proposed new solutions using geosynthetics
No full textAs a natural heritage of the region, the Aveiro Lagoon, in Portugal, allowed, over time, for people to live on its
periphery and develop many different activities (agriculture, fishing, trades, industry and tourism), which
resulted in social and human development of the region. One important activity at the time, that is now almost
abandoned, was the salt production in the lagoon. As a consequence, today there is little to no maintenance of the
walls of the saltpans, which leads to a progressive deterioration of those walls, with severe consequences for the
hydrodynamic and environmental behavior of the lagoon. The main objective of the present work is to address
the study of the construction or the rehabilitation of these walls, in order to re-establish some equilibrium in the
lagoon. Thus, the current paper aimed at the characterization of the walls of the saltpans of the Aveiro Lagoon.
On one hand, the traditional solution is briefly described and its hydraulic behavior is characterized by flume
tests. On the other hand, two different new solutions, using geosynthetics, were designed and are briefly
described. Such solutions are: 1) reinforcement of local fine soils using geosynthetics; 2) staked geobags filled
with sand and a clayed centre (recreating the traditional solution). The stability of these solutions was analyzed
and discussed and new research needs are pointed out