Population dynamics of aquatic snails in Pampulha reservoir

An attempt was made to determine more accurately the density of molluskan populations in the Pampulha reservoir, using the quadrate method, intending to detect the fluctuation of the populations density, the habitat conditions and the possible competitive interactions among Biomphalaria tenagophila, Melanoides tuberculata, Pomacea haustrum and Biomphalaria glabrata, through the analysis of populational parameters. Among the most significative facts observed in the reservoir it has to be mentioned: the almost disappearance of B. glabrata; the invasion, colonization, fixation and fast growing of M. tuberculata population until reaching about 11,000 individuals/[square metre]; the density fluctuations of B. tenagophila, P. haustrum and M. tuberculata alives and deads; differences on the habitat preference of these three molluskan species at the edge (at the limit earth-water, at 0.70m and 1.40m from the shore line); monthly mortality rates and reproduction seasons of the species

Empresas multinacionais e desempenho comercial do Brasil: uma revisão da literatura Multinational enterprises and trade performance in Brazil: a review of the literature

Fazemos uma releitura dos estudos empíricos sobre empresas multinacionais (EMNs) e comércio exterior no Brasil a partir dos modelos teóricos e empíricos de comércio internacional com firmas multinacionais. Percebe-se que aqueles estudos não examinam como características econômicas do país (Brasil) condicionaram a emergência e tipo das EMNs e, assim, seus respectivos impactos sobre comércio exterior. Conseguem isolar, nas análises de impacto comercial, evidências dos serviços tecnológicos das estrangeiras, relativamente às domésticas do mesmo setor, mas não examinam se essas firmas se concentraram ou não em atividades com vantagens comparativas no país, o que seria crucial para determinar seu impacto comercial comparativo.<br>We revisit the empirical research about multinational firms (MNFs) and foreign trade in Brazil from the perspective of the theoretical models of international trade with MNFs, and their empirical tests. We observed that the cited studies did not examine how the economic characteristics of Brazil conditioned the emergence and types, as well as the corresponding impacts of the MNFs on foreign trade. The models analyzing trade impacts succeed to single out the MNF's technology service, as compared to same-sector domestic firms, but do not examine whether or not these firms concentrated in activities with comparative advantages, crucial to determine the comparative trade contribution from these firms