307 research outputs found

    Study of the lateral strength of brickwork panels with openings

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    Species Extinction Risk Might Increase Out Of Reserves: Allowances For Conservation Of Threatened Butterfly Actinote Quadra (lepidoptera: Nymphalidae) Under Global Warming

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    Climate change is an important factor affecting species dispersal and distribution through time and the accelerated global warming has currently concerned decision makers and conservationists. Because protected areas are spatially static, species extinction risk is generally expected to increase under climate change scenarios as a consequence of range shift and decrease. This study aims to understand the current conservation status of Actinote quadra, a neotropical threatened butterfly species, as well as predict how it will be in the future. By coupling ecological niche modeling and climatic simulations, we predicted the species distribution in different future global warming scenarios (2050 and 2070) and estimated the proportion of species range overlapping protected areas through time. Our findings showed a generalized decrease of the potential distribution of A. quadra in the end of 21st century, with the most prominent range loss predicted to occur out of protected areas. Although climate change will potentially drive A. quadra into reserves, the predicted range collapse would be enough to increase its extinction risk from vulnerable, like currently categorized, to the status of critically endangered in accordance to IUCN red list criteria. Taking into account the fragmented and discontinuous landscapes across the Atlantic Forest's hotspot, we propose a conservation strategy for A. quadra based on potential ecological corridors linking climatically suitable areas and discuss the need for amplifying and connecting the current protected areas to maintain this threatened species at longer time under a global warming scenario. (C) 2015 Associacao Brasileira de Ciencia Ecologica e Conservacao. Published by Elsevier Editora Ltda. All rights reserved.132159165FAPEG [2012/1026.700.1086]Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

    Um estudo comparativo analítico e numérico dos efeitos das vinculações nas vibrações livres de placas quadradas finas

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    Dissertação (mestrado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Civil e Ambiental, 2014.As estruturas em estudo se caracterizam por placas finas, são lâminas nas quais uma dimensão, a espessura, é muito menor que as outras e classifica-se em fina respeitando determinadas relações. Estas placas se constituem num tipo estrutural de grande utilização na engenharia e na indústria: pavimento de uma ponte, muros de contenção, caixas d’água, lajes de piso ou cobrimento, cascos de navio, partes componentes de automóveis, estruturas aeroespaciais e reatores nucleares são alguns dos exemplos de seu vasto emprego. Estas estruturas muitas vezes trabalham sobre ação dinâmica: vento, caminhada ou corrida de pessoas, movimentos de veículos e outros movimentos ritmados, são exemplos de solicitações dinâmicas ocasionando o surgimento de esforços que se desenvolvem ao longo do tempo, podendo também causar sérios problemas. Como um estudo completo é de enorme complexidade e também se faz necessário entender a placa e o fenômeno em sua essência, foi estudada a base do cálculo dinâmico para o bom entendimento. Os resultados foram obtidos de maneira analítica e numérica, comparando ambos entre si, evidenciando as frequências naturais da estrutura, os modos de vibração e suas deformadas e a eficácia da análise numérica por meio de tabelas e gráficos que permitem uma visualização adequada do fenômeno. ______________________________________________________________________________ ABSTRACTThe structures studied are characterized by thin plates, a three-dimensional solid in which one dimension, the thickness, is much smaller than the others and the plate ranks as thin respecting certain relationships. These plates constitute a structure of great use in engineering and industry: a bridge deck, retaining walls, water tanks, slabs or floor coverings, ship hulls, automobile parts components, aerospace structures and nuclear reactors are some examples of its vast employment. These structures often work on dynamic action: wind, people walking or running over it, movement of vehicles and other rhythmic movements are examples of dynamic loads resulting in stresses that develop over time and can also cause serious problems. As a full study is highly complex and it is also necessary to understand the plate and the phenomenon in its essence, the basis of the dynamic analysis was studied for the proper understanding. The results were obtained from numerical and analytical solutions, compared to each other, showing the natural frequencies of the structure, the mode shapes and effectiveness of numerical analysis in tables and charts that allow adequate visualization of the phenomenon

    O DESENHO CONSTITUCIONAL HIPERPRESIDENCIALISTA NA AMÉRICA LATINA

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    Neste artigo pretendemos investigar o desenho constitucional oriundo da distribuição de poderes que, surgido com o movimento constitucionalista e adotado pela primeira vez pela constituição dos Estados Unidos, foi fundamentalmente modificado quando da sua recepção na América Latina, de modo que o presidencialismo americano se tornou hiperpresidencialismo latino-americano. Como perspectiva geral, desenhos hiperpresidencialistas indicam que os Presidentes da República possuem prerrogativas institucionais superiores às conferidas originariamente ao Presidente dos Estados Unidos e, mais especificamente, aos correlatos Poderes Legislativo e Judiciário do próprio país onde se encontram. A metodologia utilizado foi a do direito constitucional comparado

    Defensive Strategies of a Noctuid Caterpillar in a Myrmecophytic Plant: are Dyops Larvae Immune to Azteca Ants?

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    Immature stages of insects are generally susceptive to their natural enemies, but many species developed defensive and evasive mechanisms to circumvent predation. Gregarious larvae of the noctuid moth Dyops cf. cuprescens feed on leaves of young Cecropia pachystachya shrubs colonized by Azteca ants. Ants avoid contact with larval clusters, retreating to the nest when larvae are moving near the stems. Provoked encounters revealed that Dyops caterpillars present several specialized behaviors to avoid and overcome ant attacks, such as fleeing to under leaf, jumping off the leaf, curling and wriggling vigorously the anterior portion of the body, spitting droplets of oral fluids, or killing ants by pouncing them. These mechanisms allow the caterpillars to overcome ant attacks and consume leaves of ant-colonized plants. By feeding on a heavily protected plant, larvae can enjoy not only a competitor-free plant, but possibly also the enemy-free space created by the aggressive ants
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