Browsing by Issue Date, starting with "2005-08"
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- Genetic isolation between three closely related taxa: fucus vesiculosus, F. spiralis, and F. ceranoides (Phaophyceae)Publication . Billard, E.; Daguin, C.; Pearson, G. A.; Serrão, Ester; Engel, C. R.; Valero, MyriamAll traditional markers, both phenotypic and phylogenetic, have failed to discriminate between the taxa composing the Fucus vesiculosus L., F. spiralis L., and F. ceranoides L. species complex, particularly in Brittany (France), so we used five microsatellite markers to compare the allelic frequencies of populations of the three taxa in this region. The aim of this study was to assess whether the different populations were grouped according to their geographical location, their habitat (open coast versus estuary), or their a priori taxonomic assignment. Species-specific alleles were identified at one locus, demonstrating the utility of microsatellite markers for recognizing the three taxa in Brittany. Moreover, our results clearly support the separation of F. vesiculosus, F. spiralis, and F. ceranoides into distinct species, independently of geography. We also identified genetic differentiation between estuarine and coastal populations of F. vesiculosus.
- Long-term seismicity of the Reykjanes Ridge (North Atlantic) recorded by a regional hydrophone arrayPublication . Goslin, J.; Lourenço, Nuno; Dziak, R. P.; Bohnenstiehl, D. R.; Haxel, J.; Luis, JoaquimThe seismicity of the northern Mid-Atlantic Ridge was recorded by two hydrophone networks moored in the sound fixing and ranging (SOFAR) channel, on the flanks of the Mid-Atlantic Ridge, north and south of the Azores. During its period of operation (05/2002-09/2003), the northern 'SIRENA' network, deployed between latitudes 40 degrees 20'N and 50 degrees 30'N, recorded acoustic signals generated by 809 earthquakes on the hotspot-influenced Reykjanes Ridge. This activity was distributed between five spatio-temporal event clusters, each initiated by a moderate-to-large magnitude (4.0-5.6 M) earthquake. The rate of earthquake occurrence within the initial portion of the largest sequence (which began on 2002 October 6) is described adequately by a modified Omori law aftershock model. Although this is consistent with triggering by tectonic processes, none of the Reykjanes Ridge sequences are dominated by a single large-magnitude earthquake, and they appear to be of relatively short duration (0.35-4.5 d) when compared to previously described mid-ocean ridge aftershock sequences. The occurrence of several near-equal magnitude events distributed throughout each sequence is inconsistent with the simple relaxation of main shock-induced stresses and may reflect the involvement of magmatic or fluid processes along this deep (>2000 m) section of the Reykjanes Ridge.
- Impact of spherical diffusion on labile trace metal speciation by electrochemical stripping techniquesPublication . Pinheiro, J. P.; Domingos, R. F.The impact of the spherical diffusion contribution in labile trace metal speciation by stripping techniques was studied. It was shown that the relative error in the calculation of the stability constants caused by assuming linear diffusion varies with the efficiency of stirring, the diffusion coefficient of the complex and the value of the stability constant itself. A model system (lead/carboxyl modified latex nanospheres) was studied to quantify the effect of these parameters in the error. The results showed that under the usual experimental conditions the relative error in the calculation of the stability constant is never smaller than 10% when using a Metrohm 663VA stand. A new equation, considering spherical diffusion, was applied to the model system under study and successfully calculated the correct stability constants. Therefore, it is clear that in trace metal speciation determinations using stripping techniques at spherical electrodes the linear approximation should not be used.
- Identification of a new pebp2 alpha A2 isoform from zebrafish runx2 capable of inducing osteocalcin gene expression in vitroPublication . Pinto, Jorge; Conceição, Natércia; S B Viegas, Carla; Leite, Ricardo; Hurst, L. D.; Kelsh, R. N.; Leonor Cancela, M.Introduction: RUNX2 (also known as CBFA1/Osf2/AML3/PEBP2 alpha A) is a transcription factor essential for bone formation in mammals, as well as for osteoblast and chondrocyte differentiation, through regulation of expression of several bone- and cartilage-related genes. Since its discovery, Runx2 has been the subject of intense studies, mainly focused in unveiling regulatory targets of this transcription factor in high vertebrates. However, no single study has been published addressing the role of Runx2 in bone metabolism of low vertebrates. While analyzing the zebrafish (Danio rerio) runx2 gene, we identified the presence of two orthologs of RUNX2, which we named runx2a and runx2b and cloned a pebp2 alpha A-like transcript of the runx2b gene, which we named pebp2 alpha A2. Materials and Methods: Zebrafish runx2b gene and cDNA were isolated by RT-PCR and sequence data mining. The 3D structure of runx2b runt domain was modeled using mouse Runx1 runt as template. The regulatory effect of pebp2 alpha A2 on osteocalcin expression was analyzed by transient co-transfection experiments using a luciferase reporter gene. Phylogenetic analysis of available Runx sequences was performed with TREE-PUZZLE 5.2. and MrBayes. Results and Conclusions: We showed that the runx2b gene structure is highly conserved between mammals and fish. Zebrafish runx2b has two promoter regions separated by a large intron. Sequence analysis suggested that the runx2b gene encodes three distinct isoforms, by a combination of alternative splicing and differential promoter activation, as described for the human gene. We have cloned a pebp2 alpha A-like transcript of the runx2b gene, which we named pebp2 alpha A2, and showed its high degree of sequence similarity with the mammalian pebp2 alpha A. The cloned zebrafish osteocalcin promoter was found to contain three putative runx2-binding elements, and one of them, located at -221 from the ATG, was capable of mediating pebp2 alpha A2 transactivation. In addition, cross-species transactivation was also confirmed because the mouse Cbfa1 was able to induce the zebrafish osteocalcin promoter, whereas the zebrafish pebp2 alpha A2 activated the murine osteocalcin promoter. These results are consistent with the high degree of evolutionary conservation of these proteins. The 3D structure of the runx2b runt domain was modeled based on the runt domain of mouse Runx1. Results show a high degree of similarity in the 3D configuration of the DNA binding regions from both domains, with significant differences only observed in non-DNA binding regions or in DNA-binding regions known to accommodate considerable structure flexibility. Phylogenetic analysis was used to clarify the relationship between the isoforms of each of the two zebrafish Runx2 orthologs and other Runx proteins. Both zebrafish runx2 genes clustered with other Runx2 sequences. The duplication event seemed, however, to be so old that, whereas Runx2b clearly clusters with the other fish sequences, it is unclear whether Runx2a clusters with Runx2 from higher vertebrates or from other fish.
- Effects of clam harvesting on sexual reproduction of the seagrass Zostera noltiiPublication . Alexandre, Ana; Santos, Rui; Serrão, EsterThe sexual reproduction of Zostera noltii in the Ria Formosa lagoon (southern Portugal) was assessed by quantifying the variation in both flowering effort and evolution of maturation stages during the fertile season. The effects of clam harvesting on the sexual reproduction of Z. noltii were investigated using both descriptive and experimental approaches. Meadows disturbed by clam harvesting were compared with undisturbed meadows in 2 sectors of the lagoon. In both sectors, disturbed meadows showed significantly lower vegetative shoot density and significantly higher reproductive effort. The reproductive effort in the western disturbed meadows was 2-fold higher than in undisturbed meadows, whereas in eastern disturbed meadows it was 4-fold higher. In disturbed meadows, early maturation stages were found until the end of the flowering season and higher seed production was observed. Both the negative effect of clam harvesting on Z. noltii density and the positive effect on its reproductive effort were confirmed by manipulative field experiments. Plots that were experimentally harvested during the fertile season showed significantly lower vegetative shoot density and higher reproductive effort than unharvested plots. Results suggest that Z. noltii responds to clam harvesting disturbance by both increasing its reproductive effort and extending its fertile season.
- Problemática da avaliação do potencial de inovação das economias periféricas no contexto da economia do conhecimento. Uma aplicação às empresas portuguesasPublication . Fernandes, Silvia Brito; Noronha, Teresa deAs empresas Portuguesas são na sua maioria pequenas ou médias, não têm departamento de I&D e carecem de recursos humanos qualificados para desenvolvê-la internamente. Os objectivos de negócio estão frequentemente ligados às necessidades dos seus gestores que geralmente consideram a inovação muito cara e arriscada. O nível de confiança entre actores económicos é muito inferior ao da maioria dos países da OCDE, o que explica muitas das condicionantes institucionais, culturais e financeiras que limitam a capacidade empreendedora. Isto ajuda a compreender os baixos níveis de transferência tecnológica e de patentes registadas. Alguns estudos mostram que os esforços em I&D nem sempre estão directamente relacionados com a performance económica,especialmente nas regiões menos desenvolvidas.
- A cognição humana e a abordagem SODA na estruturação de problemas complexos e no apoio à tomada de decisãoPublication . Ferreira, F. A. F.Nos últimos anos, temos assistido a uma crescente tendência em ver as organizações como um fenómeno processual, fortemente dependente das acções e decisões de pessoas, e cuja robustez é fortalecida por uma vertente de pensamento que encara as pessoas, os grupos, as redes sociais, a cognição e os processos de apoio à tomada de decisão como alicerces do fenómeno organizacional. Na verdade, esta tendência tem vindo a revelar-se congruente com a crescente importância de um novo paradigma que pressupõe que até os aspectos mais tangíveis de uma organização comportam construções dos membros que a constituem. Assim,ao ser congruente com o avanço de uma epistemologia social construtivista, esta tendência interpreta a organização como um conjunto de disposições individuais modeladas pelas acções dos restantes membros. É precisamente com base neste novo entendimento que o presente artigo evidencia a emergência de uma estreita relação entre a perspectiva cognitiva e a clara necessidade de desenvolver estratégias metodológicas mais sensíveis e adequadas à natureza dos aspectos organizacionais, vistos como “construções sociais” ou como estruturas e processos que articulam a cognição com as acções dos indivíduos. Nesse sentido, uma resposta a esta necessidade foi encontrada com o recurso à metodologia SODA, proposta por Colin Eden, que tem por corolário o facto dos indivíduos revelarem aquilo que é útil aos seus objectivos e simplificarem a realidade em função dos seus limites cognitivos.
- Modalidades de gestão no abastecimento público de águaPublication . Custódio, Patrícia Isabel PedroO abastecimento público de água pertence a um conjunto de serviços essenciais à vida em sociedade e cuja competência e responsabilidade cabe às autarquias locais. Além dos serviços municipais criados para gerir os sistemas municipais, o Código Administrativo veio possibilitar aos municípios a criação de serviços municipalizados,posteriormente abriu-se a possibilidade dos municípios constituírem empresas públicas e as inovações legislativas mais recentes permitiram aos municípios a abertura de concurso público para concessionar os serviços relativos ao abastecimento domiciliário de água dentro dos espaços municipais. A evolução das modalidades de gestão dos sistemas municipais ficou assim caracterizada pela atribuição de uma maior autonomia organizativa e financeira.
- Theoretical approaches and empirical results on the economic effects of public investmentPublication . Andraz, Jorge Miguel; Pereira, AlfredoThis paper presents an extensive discussion of the literature on the economic impact of public investment on infrastructures both for the US and internationally. The paper expands the focus of previous surveys by concentrating on empirical econometric studies about the effects of public investment as well as on the evolution of the methodological issues motivated by criticisms. From the empirical results reported in the literature, there is a general evidence that suggests that nonmilitary public investment contributes significantly to output growth and production costs reduction, not only as a direct input to production function, but also by its influence on private factors of production. This evidence raises the importance of the endogeneity of private inputs and also public investment, as well as the direction of causality. The studies performed at sectoral and regional levels show very often unbalanced effects from public investment. Moreover, as the geographic focus narrows,the estimated elasticities with respect to public capital become smaller, which suggests the existence of spillover effects.
- Modelling the interaction between the tourism accomodation industry and the environmentPublication . Pintassilgo, Pedro; Silva, João AlbinoNeste artigo apresenta-se um modelo sobre a indústria de alojamento turístico, a qual mantém uma relação dialéctica, de impacte e dependência, com a qualidade ambiental – um recurso comum compósito. Mostra-se que o livre acesso conduz, geralmente, à sobre-exploração económica e ambiental, isto é à “tragédia do recurso comum”. Esta situação afecta, igualmente, a indústria turística no seu todo, pois o alojamento e a qualidade ambiental desempenham papéis centrais nesta actividade económica. O resultado deste cenário é um turismo de massas,caracterizado por turistas com reduzida disponibilidade a pagar. Os resultados do modelo indicam que,exceptuando situações em que as externalidades positivas são muito ignificativas, ou em que o livre acesso enfrenta restrições activas, nomeadamente no que se refere a espaços com as características apropriadas para a actividade, a entrada de empresas deverá ser limitada, tendo por base não só o critério de eficiência económica mas, também, o de sustentabilidade.