880 resultados para investment cycles
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We inferred the phylogeny of 33 species of ticks from the subfamilies Rhipicephalinae and Hyalomminae from analyses of nuclear and mitochondrial DNA and morphology. We used nucleotide sequences from 12S rRNA, cytochrome c oxidase I, internal transcribed spacer 2 of the nuclear rRNA, and 18S rRNA. Nucleotide sequences and morphology were analyzed separately and together in a total-evidence analysis. Analyses of the five partitions together (3303 characters) gave the best-resolved and the best-supported hypothesis so far for the phylogeny of ticks in the Rhipicephalinae and Hyalomminae, despite the fact that some partitions did not have data for some taxa. However, most of the hidden conflict (lower support in the total-evidence analyses compared to that in the individual analyses) was found in those partitions that had taxa without data. The partitions with complete taxonomic sampling had more hidden support (higher support in the total-evidence analyses compared to that in the separate-partition analyses) than hidden conflict. Mapping of geographic origins of ticks onto our phylogeny indicates an African origin for the Rhipicephalinae sensu lato (i.e., including Hyalomma spp.), the Rhipicephalus-Boophilus lineage, the Dermacentor-Anocentor lineage, and the Rhipicephalus-Booophilus-Nosomma-Hyalomma-Rhipicentor lineage. The Nosomma-Hyalomma lineage appears to have evolved in Asia. Our total-evidence phylogeny indicates that (i) the genus Rhipicephalus is paraphyletic with respect to the genus Boophilus, (ii) the genus Dermacentor is paraphyletic with respect to the genus Anocentor, and (iii) some subgenera of the genera Hyalomma and Rhipicephalus are paraphyletic with respect to other subgenera in these genera. Study of the Rhipicephalinae and Hyalomminae over the last 7 years has shown that analyses of individual datasets (e.g., one gene or morphology) seldom resolve many phylogenetic relationships, but analyses of more than one dataset can generate well-resolved phylogenies for these ticks. (C) 2001 Academic Press.
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Participatory plant breeding (PPB) has been suggested as an effective alternative to formal plant breeding (FPB) as a breeding strategy for achieving productivity gains under low input conditions. With genetic progress through PPB and FPB being determined by the same genetic variables, the likelihood of success of PPB approaches applied in low input target conditions was analyzed using two case studies from FPB that have resulted in significant productivity gains under low input conditions: (1) breeding tropical maize for low input conditions by CIMMYT, and (2) breeding of spring wheat for the highly variable low input rainfed farming systems in Australia. In both cases, genetic improvement was an outcome of long-term investment in a sustained research effort aimed at understanding the detail of the important environmental constraints to productivity and the plant requirements for improved adaptation to the identified constraints, followed up by the design and continued evaluation of efficient breeding strategies. The breeding strategies used differed between the two case studies but were consistent in their attention to the key determinants of response to selection: (1) ensuring adequate sources of genetic variation and high selection pressures for the important traits at all stages of the breeding program, (2) use of experimental procedures to achieve high levels of heritability in the breeding trials, and (3) testing strategies that achieved a high genetic correlation between performance of germplasm in the breeding trials and under on-farm conditions. The implications of the outcomes from these FPB case studies for realizing the positive motivations for adopting PPB strategies are discussed with particular reference for low input target environment conditions.
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The relationships between reproductive condition, level of reproductive investment and adrenocortical modulation to capture stress in marine turtles form the basis of this study. When subjected to either capture or ecological stressors, nesting marine turtles have demonstrated adrenocortical responses that are both small in magnitude, and slow in responsiveness. These observations were further investigated to determine whether this minimal stress response was a physiological strategy to maximize reproductive investment in adult green Chelonia mydas and hawksbill Eretmochelys imbricata turtles. Female green and hawksbill turtles exhibited a decrease in adrenocortical responsiveness with progressive reproductive condition. Breeding turtles exhibited most suppression of their adrenocortical response to capture compared to both non-breeding and pre-breeding female counterparts. Nesting green turtles maintained a suppressed adrenocortical response to capture throughout the nesting season despite decreased reproductive investment. In contrast, male green and hawksbill turtles were less able to modulate their corticosterone (B) response to acute capture stress. During breeding, male turtles possessed significantly greater adrenocortical responses to capture than females. These results could indicate that the large reproductive investment necessary for female marine turtle reproduction might underlie the marked decrease in adrenocortical responsiveness. This hormonal mechanism could function as one strategy by which female marine turtles maximize their current reproductive event, even though under certain situations this mechanism could entail costs to female survival.
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Complex life cycles are a hallmark of parasitic trematodes. In several trematode taxa, however, the life cycle is truncated: fewer hosts are used than in a typical three-host cycle, with fewer transmission events. Eliminating one host from the life cycle can be achieved in at least three different ways. Some trematodes show even more extreme forms of life cycle abbreviations, using only a mollusc to complete their cycle, with or without sexual reproduction. The occurrence of these phenomena among trematode families are reviewed here and show that life cycle truncation has evolved independently many times in the phylogeny of trematodes. The hypotheses proposed to account for life-cycle truncation, in addition to the factors preventing the adoption of shorter cycles by all trematodes are also discussed. The study of shorter life cycles offers an opportunity to understand the forces shaping the evolution of life cycles in general.
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Let K(r,s,t) denote the complete tripartite graph with partite sets of sizes r, s and t, where r less than or equal to s less than or equal to t. Necessary and sufficient conditions are given for decomposability of K(r, s, t) into 5-cycles whenever r, s and t are all even. This extends work done by Mahmoodian and Mirza-khani (Decomposition of complete tripartite graphs into 5-cycles, in: Combinatorics Advances, Kluwer Academic Publishers, Netherlands, 1995, pp. 235-241) and Cavenagh and Billington. (C) 2002 Elsevier Science B.V. All rights reserved.
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We collected data on plasma levels of testosterone+5a-dihydrotestosterone (T+DHT) and corticosterone (CORT) from adult female green sea turtles (Chelonia mydas) from southern Queensland during distinct stages of their reproductive cycle. Those females capable of breeding in a given year had elevated plasma steroid levels (T+DHT 0.91 +/- 0.08; CORT 1.05 +/- 0.29 ng/ml), associated with follicular development, until courtship began in October. At the beginning of the nesting season in November plasma levels of 2 CORT were related to when the female first nested (r(2) = 0.06; F = 10.45; P = 0.01). However, they were not correlated with the number of clutches a female laid in that season (F = 3.65; P = 0.08). We repeatedly sampled 23 turtles over the nesting season and profiled changes in steroids immediately following oviposition of each clutch. Levels of T+DHT (range 0.41-0.58 ng/ml) and CORT (range 2.13-2.81 ng/ml) were similar through the early stages of the nesting season and inter-nesting period, and declined to near basal levels (T+DHT 0.37 +/- 0.03 and CORT 1.85 +/- ng/ml) following the last clutch for the season. Steroid hormone levels were also low (T+DHT 0.38 +/- 0.16; CORT 0.46 +/- 0.21 ng/ml) in four independent post-breeding (atretic) females; samples for these females were taken at a time when body condition was presumably at the lowest for the season. Subtle changes in the nesting environment, such as variation in nesting habitat or the time of night that nesting occurred, were associated with a small and slow CORT increase. We suggest CORT is increased in nesting females to assist in lipid transfer to prepare the ovarian follicles and/or the reproductive organs for ovulation.
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Analysis of the equity premium puzzle has focused on private-sector capital markets. However, the existence of an anomalous equity premium raises important issues in the evaluation of public-sector investment projects. These issues are explored below. We begin by formalizing the argument that an equity premium may arise from uninsurable systematic risk in labour income, and show that, other things being equal, increases in public ownership of equity will improve welfare, up to the point where the equity premium is eliminated. Finally, we consider policy implications and the optimal extent of public ownership.
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Esta dissertação tem como objetivo investigar as práticas pedagógicas inclusivas instituídas no cotidiano da educação infantil a partir de um olhar para a infância e para a criança com deficiência e transtornos globais do desenvolvimento. Apontamos como objetivos específicos: definir o que está sendo reconhecido como práticas educacionais inclusivas a partir de indicadores estabelecidos para identificá- las no contexto de uma escola de educação infantil; investigar como a escola reflete, dialoga sobre as questões da inclusão das crianças na primeira infância na unidade de educação infantil e como se configuram as propostas de formação dos professores neste espaço, a fim de constituir práticas pedagógicas inclusivas na unidade escolar; escutar as crianças com deficiência e transtornos globais do desenvolvimento e as demais crianças sobre como estão compreendendo o acontecimento das práticas pedagógicas em geral e as práticas pedagógicas inclusivas da unidade de ensino de educação infantil. Para tanto, desenvolvemos um estudo de natureza qualitativa, tendo como base a metodologia do estudo de caso etnográfico numa perspectiva colaborativa, no qual realizamos análise documental, entrevistas semiestruturadas, observações participantes, ciclos de formação com os professores e roda de conversa com as crianças, que foram registrados por meio de fotografias, áudio e videogravações. O estudo foi desenvolvido no contexto de uma escola pública de educação infantil do município de Cachoeiro de Itapemirim – ES. Os participantes foram oito crianças público-alvo da educação especial, com idade entre dois a seis anos de idade, dez professores, três pedagogas, uma diretora, uma coordenadora e duas auxiliares de turma que se envolveram direta ou indiretamente com o estudo. O estudo foi realizado durante quatorze meses, no período de 28 de outubro de 2011 a 10 de dezembro de 2012, em uma Escola Municipal de Educação Básica do município de Cachoeiro do Itapemirim/ES, que atende exclusivamente aos alunos da educação infantil, em duas turmas de creche e três de pré-escola. Os aportes teóricos fundamentam-se na abordagem histórico-cultural e nos estudos de Phelippe Meirieu. Os dados foram organizados em temáticas e “episódios interativos” e analisados por meio da abordagem microgenética e das análises das narrativas. A análise dos resultados evidenciou a importância do investimento na formação dos professores, a constituição de relações de colaboração entre professores regentes e de Educação Especial e a assunção de que toda criança tem capacidade de aprender, pois esses elementos influenciam as práticas pedagógicas constituídas nos espaços-tempos da Educação Infantil mediante o desafio de inclusão escolar de crianças com deficiência e com transtornos globais do desenvolvimento.
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Globalization creates new opportunities for firms to invest abroad and many economies are making active efforts to attract Foreign Direct Investment (FDI) in order to promote economic growth. Decisions to invest abroad depend on a complex set of factors, but the least corrupt countries may attract more foreign direct investment because they provide a more favorable climate for investors. In this paper we investigate the impact of corruption on FDI inflows in 73 countries, over the period 1998-2008. Our results suggest that countries where corruption is lower, the FDI inflows are greater, and so controlling corruption may be an important strategy for increase FDI inflows.
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As stated by the New Institutional Economics theory, transaction costs play a relevant role in economics and, according to the extent of such costs, agents make investment decisions. Actually, transaction costs may represent a disincentive to entrepreneurship. This work aims to verify whether transaction costs are related to investment rate and foreign direct investment rate (FDI) in different business environments. The results suggest that foreign investors do not have precise information about other countries as domestic investors do; as it is observed, only the relation between transaction costs and investment rate is significant. Furthermore, there is evidence that the business environments of BRIC countries are less developed when compared to business environments of other countries in the study