Browsing by Issue Date, starting with "2011-12"
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- Detection and characterization of Wolbachia infections in natural populations of aphids : is the hidden diversity fully unraveled?Publication . Augustinos, Antonis A.; Santos-Garcia, Diego; Dionyssopoulou, Eva; Moreira, Marta; Papapanagiotou, Aristeidis; Scarvelakis, Marios; Doudoumis, Vangelis; Ramos, Silvia; Aguiar, António F.; Borges, Paulo A. V.; Khadem, Manhaz; Latorre, Amparo; Tsiamis, George; Bourtzi, KostasAphids are a serious threat to agriculture, despite being a rather small group of insects. The about 4,000 species worldwide engage in highly interesting and complex relationships with their microbial fauna. One of the key symbionts in arthropods is Wolbachia, an a-Proteobacterium implicated in many important biological processes and believed to be a potential tool for biological control. Aphids were thought not to harbour Wolbachia; however, current data suggest that its presence in aphids has been missed, probably due to the low titre of the infection and/or to the high divergence of the Wolbachia strains of aphids. The goal of the present study is to map the Wolbachia infection status of natural aphids populations, along with the characterization of the detected Wolbachia strains. Out of 425 samples from Spain, Portugal, Greece, Israel and Iran, 37 were found to be infected. Our results, based mainly on 16S rRNA gene sequencing, indicate the presence of two new Wolbachia supergroups prevailing in aphids, along with some strains belonging either to supergroup B or to supergroup A.
- Estatística: Um pouco de HistóriaPublication . Silva, Osvaldo; Sousa, ÁureaA Estatística deriva da palavra latina Status (estado), o que reflecte o facto de a sua origem ter tido como base a recolha e apresentação de dados quantitativos de interesse do Estado. Contudo, o seu conceito actual evoluiu, dizendo-se que a Estatística = Ciência + Tecnologia + Arte. […].
- A relevância do currículo no ensino básico: Contributos de um projecto de investigação-acçãoPublication . Sousa, Francisco; Mira Leal, SusanaO interesse dos autores da presente comunicação em aprofundar o estudo de questões curriculares convergiu com a preocupação de alguns docentes do ensino básico em combater o desinteresse de alguns alunos em relação à escola e ao currículo. Assim emergiu um projecto de investigação-acção colaborativa, designada por "Investigação para um Currículo Relevante" (ICR), que decorre nos Açores. Reflectiremos sobre os resultados do ciclo de investigação-acção desenvolvido ao longo do ano escolar 2009/2010, destacando algumas estratégias desenvolvidas pelos professores investigadores com o objectivo de incrementar o reconhecimento da relevância do currículo por parte dos alunos e melhorar o seu desempenho escolar.
- Mobility and market power in the Portuguese financial systemPublication . Teixeira, JoãoThis paper investigates the level of price and non-price competition in the Portuguese financial system. We study the determinants of market power in banking and discuss the role of switching costs. We show that the degree of customer mobility is low and that price instruments have a higher impact on market share than non-price instruments.
- Outsourcing and vertical integration : a survey of empirical literaturePublication . Teixeira, JoãoThis paper provides a survey of the empirical literature of outsourcing and vertical integration. This literature shows that outsourcing and integration behave in waves, with periods of greater outsourcing activity and others of a greater activity of vertical integration.
- Que lugar para a Teoria e Desenvolvimento Curricular na Formação Pedagógica de Formadores em Portugal?Publication . Sousa, FranciscoNesta comunicação, discutirei o espaço ocupado pela Teoria e Desenvolvimento Curricular no mapeamento epistemológico dos conteúdos programáticos dos cursos de formação pedagógica inicial de formadores. A partir de uma análise ao referencial que orienta os referidos cursos, espero evidenciar orientações teóricas implícitas na política de formação a que o referencial de subordina e discutir algumas implicações práticas dessas orientações para a formação de formadores. Da análise conclui-se que a Teoria e Desenvolvimento Curricular é a área científica que mais alimenta a formação inicial de formadores em Portugal. Conclui-se também que o referencial analisado veicula uma perspectiva predominantemente técnica do currículo.
- The role of cash on the outsourcing decisionPublication . Teixeira, JoãoThis paper investigates the effect of cash on a firm’s choice between vertical integration and outsourcing. We model the production decision in a Principal-Agent framework, and show that what motivates the choice of outsourcing are the firms’ cost differentials in effort and the benefit provided by the supplier’s effort alone. This latter benefit is linked with greater probabilities of reaching high production values in good states of nature. Suppliers use cash as a strategic instrument to collect the surplus from outsourcing, and their wealth constraint or limited liability ensures them more attractive compensation schemes.
- Outsourcing : a survey of theoretical modelsPublication . Teixeira, JoãoThis paper provides a survey of theoretical models of outsourcing and vertical integration. It develops an overview of the models that rely on incomplete contracting and on strategic outsourcing.
- Outsourcing : the role of debt financingPublication . Teixeira, JoãoThis paper investigates the effect of capital structure on a firm’s choice between vertical integration and outsourcing. Suppliers use debt as a strategic instrument to collect the surplus from outsourcing, and their wealth constraint or limited liability ensures them more attractive compensation schemes. Investigating the buyer’s capital structure, we find that outsourcing with risky debt is more likely to occur for high values of the outsourcing surplus.
- Association between Plasma and Milk Urea on the Insemination Day and Pregnancy Rate in Early Lactation Dairy CowsPublication . Chaveiro, António E.; Andrade, M.; Borba, Alfredo Emílio Silveira de; Silva, Joaquim Fernando Moreira daLactatingdairy cows (n=177) feed with grass and corn silage ad libitum kept in pasture, were randomly assigned to evaluate how urea nitrogen in plasma and milk can be related to their pregnancy rate. Blood and milk samples were collected on the artificial insemination (AI) day to evaluate plasma urea nitrogen (PUN) and milk urea nitrogen (MUN) as well as progesterone levels, excluding cows with progesterone higher than 0.5 ng/ml. Cows were considered pregnant if six weeks after artificial insemination, they did not return to estrus.Concentrations of PUN or MUN greater than the average (16 mg/dl) were associated with decreased pregnancy rates (13% and 14%, respectively) (p< 0.05) as compared to the cows with urea levels less than this value on the insemination day. As PUN and MUN increased to greater than 16 mg/dl, the likelihood ratio for pregnancy decreased. There was a high correlation between PUN and MUN concentrations (r²= 0.97, p≤ 0.001). The results of this study indicate that an increase in PUN or MUN can exert director indirect effects in reproduction, impairing the conception of grazing dairy cows.
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