Double-core evolution and the formation of neutron-star binaries with compact companions

We present the results of a systematic exploration of an alternative evolutionary scenario to form double neutron-star binaries, first proposed by Brown (1995), which does not involve a neutron star passing through a common envelope. In this scenario, the initial binary components have very similar masses, and both components have left the main sequence before they evolve into contact; preferably the primary has already developed a CO core. We have performed population synthesis simulations to study the formation of double neutron star binaries via this channel and to predict the orbital properties and system velocities of such systems. We obtain a merger rate for DNSs in this channel in the range of 0.1 - 12/Myr. These rates are still subject to substantial uncertainties such as the modelling of the contact phase.Comment: MNRAS, accepte

Steel fibre reinforced self-compacting concrete for lightweight and durable pedestrian bridges : creep behaviour

In recent years, pedestrian bridges built from composites materials have notably increased. This growth is related to the durability problems of traditional materials, as well as the need for fastest construction times. In this context, fiber reinforced concrete (FRC) becomes an important material in this type of structures, since the ductility, high post-cracking tensile strength, high compressive stiffness and strength of FRC can be combined with the benefits derived from the use of FRP profiles to obtain high performance structural systems. In addition, FRC exhibits a durable behaviour since, in general, does not have corrosion problems. In this paper a 12 m length single span pedestrian bridge composed by a Steel Fiber Reinforced Self-Compacting Concrete (SFRSCC) deck and two Glass Fiber Reinforced Polymer (GFRP) pultruded I shape profiles was designed. The SFRSCC deck has a constant thickness of 40 mm and 2000 mm wide and a content of hooked ends steel fibers in its mixture, which ensures the necessary strength and ductility for the acting loads. The high post-cracking tensile strength of the SFRSCC allowed the use of pre-stressed solutions in the bridge structural system, which caused an upward deflection and, consequently, tensile stresses in the SFRSCC deck. Two prototypes of this structural system were built and monitored in order to assess their long-term deformational behavior when subjected to a loading configuration correspondent to the load combination for the deflection serviceability limit states. The main results are presented and discussed

Development of a pedestrian bridge with GFRP profiles and fibre reinforced self-compacting concrete deck

In recent years, the number of pedestrian bridges built from composites materials has notably increased. The combination of fiber reinforced polymers (FRP) profiles with fiber reinforced concrete (FRC) elements is being adopted in this type of structures, since the ductility, high post-cracking tensile strength, compressive stiffness and strength of FRC can be combined with the benefits derived from the use of FRP’s profiles to obtain high performance structural systems. In the context of the present work a 12 m long single span pedestrian bridge with two composite Iprofiles was designed. In terms of deflection requirements imposed by serviceability limit states, the influence of the height and thickness of GFRP (Glass Fiber Reinforced Polymer) profiles, as well as the addition of a thin layer of prestressed carbon fiber sheet in the bottom flange of the GFRP profile was evaluated. Using software based on the finite element method, the structural behavior of the developed structural systems was analyzed. Furthermore, two prototypes of this structural system were built and monitored in order to assess their long-term deformational behavior when subjected to a loading configuration correspondent to the load combination for the deflection serviceability limit states. The main results obtained are presented and discussed.This work is part of the research project QREN number 3456, PONTALUMIS- Development of a prototype of a pedestrian bridge in GFRP-ECC concept, involving the Company ALTO - Perfis Pultrudidos, Lda., the ISISE/University of Minho and the ICIST/Technical University of Lisbon. The first and fourth authors wish to acknowledge the research grants under this project. The authors also wish to acknowledge the Civitest Company for the conception and development of the steel fiber reinforced self-compacting concrete used in this work, and to Secil, S&P Clever Reinforcement Iberica Lda. and Hilti Portugal - Productos e Servicos Lda. for the supplied materials and technical support

Influence of fatigue and aggressive exposure on GFRP girder to SFRSCC deck all-adhesive connection

To assess the influence of fatigue loading and environmental conditions on the bond behavior between glass fiber reinforced polymer (GFRP) systems and steel fiber reinforced self-compacting concrete (SFRSCC) that are adhesively bonded, an experimental program composed of push-out tests was carried out. The following three scenarios were selected for the environmental conditions: natural conditions; wet-dry cycles; and temperature cycles. Half of the specimens were submitted to monotonic loading up to failure, and the other half were submitted to a fatigue load configuration of 1-million cycles and then subjected to a monotonic loading up to failure. The results have shown that for the investigated environmental conditions the GFRP-SFRSCC push-out specimens never failed up to 1 million cycles. However, temperature cycles caused a considerable reduction on the stiffness and load carrying capacity in the specimens submitted to fatigue loading, while wet-dry cycles did not modify significantly the maximum shear stress transfer in the investigated connection. This paper describes in detail the experimental program, presenting and discussing the relevant results.AD

Influence of fatigue loading and environmental conditions on the bond behavior between GFRP systems and SFRSCC substrate

To assess the influence of fatigue loading and environmental conditions on the bond behavior between glass fiber reinforced polymer (GFRP) systems and steel fiber reinforced self-compacting concrete (SFRSCC) that are adhesively bonded, an experimental program composed of push-out tests was carried out. The following three scenarios were selected for the environmental conditions: natural conditions; wet-dry cycles; and temperature cycles. Half of the specimens were submitted to monotonic loading up to failure, and the other half were submitted to a fatigue load configuration of 1 -million cycles and then subjected to a monotonic loading up to failure. The results have shown that for the investigated environmental conditions the GFRP-SFRSCC push-out specimens never failed up to 1 million cycles. However, temperature cycles caused a considerable reduction on the stiffness and load carrying capacity in the specimens submitted to fatigue loading, while wet-dry cycles did not modify significantly the maximum shear stress transfer in the investigated connection. This paper describes in detail the experimental program, presenting and discussing the relevant results

Seleção de bucha vegetal por agricultores familiares.

Este trabalho consistiu em dois ensaios de seleção participativa de bucha vegetal. O primeiro ensaio foi implantado na comunidade Cacimba do Baltazar, Petrolina, PE sendo avaliadas quatro variedades locais (VLs) em canteiros de diversidade com seis plantas por VL. O outro ensaio foi conduzido no Campo Experimental de Bebedouro da Embrapa Semiárido com seis VLs em blocos ao acaso com três repetições e seis plantas por parcela. As avaliações foram realizadas por agricultores familiares das comunidades Cacimba do Baltazar, Tanque Novo, Casa Nova, BA e Lagoa do Mari, Sento Sé, BA, usando as ferramentas participativas seleção com espetos de madeira, tempestade de ideias e matriz de classificação. As características definidas pelos agricultores das três comunidades para a seleção foram praticamente as mesmas, ou seja, tamanho do fruto, textura da fibra, produtividade e adequação para artesanato. Os agricultores familiares da Cacimba do Baltazar selecionaram a VL2, seguida pela VL3, VL4 e VL5. No entanto a VL4 recebeu mais votos para tamanho do fruto. Os agricultores familiares da Lagoa do Mari e Tanque Novo selecionaram a VL6, seguida pela VL4, VL7, VL8, VL3 e VL5. As VLs selecionadas serão usadas em programas de melhoramento participativo conforme interesse dos agricultores familiare

Quantum Theory contents insertion in High School curricula

A inovação científica e tecnológica do século XX foi esmagadora. Contudo, a nossa experiência docente permite-nos afirmar que as aprendizagens na escola secundária estão longe de acompanhar a evolução que se verifica na sociedade atual. No entanto, já estão a ser incluídos alguns conteúdos de Física Moderna nos currículos oficiais de vários países, parecendo evidenciar uma preocupação em atualizar a preparação dos jovens para o mundo que os rodeia. Neste artigo relatamos um estudo que fizemos acerca dos currículos de Física de alguns países, sobretudo no que diz respeito à Teoria Quântica, a grande invenção do século XX, tentando identificar os conteúdos selecionados e a maneira como estes se integram nas orientações curriculares gerais.In the XXth century, scientific and technological innovation has been overwhelming. Our teaching profession lead us to believe that studies in High Schools do not follow the evolution of ideas that characterizes our modern society. However, some contents of Modern Physics are already included in the official curricula of several countries, which seem to be worried about the improvement of today’s youth training. In this paper we report a study made about Physics’ curricula in several countries, emphasizing Quantum Theory issues, the biggest invention of the XXth century, trying to identify the selected subjects selected and the way they fit into general curricula orientations

Genome of Diaporthe sp. provides insights into the potential inter-phylum transfer of a fungal sesquiterpenoid biosynthetic pathway.

Made available in DSpace on 2017-08-22T09:28:35Z (GMT). No. of bitstreams: 1 Genome.pdf: 1649894 bytes, checksum: 15ed2d80128563978cbd38ead7301c5c (MD5) Previous issue date: 2017-02-0

Técnicas de cultivo in vitro no sisal.

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Guardiões da Comunidade Tanque Novo (Casa Nova-BA).

Esse trabalho teve como objetivo identificar os guardiões de variedades locais da Comunidade Tanque Novo, em Casa Nova?BA. A metodologia consistiu na aplicação de ferramentas participativas e questionários com agricultores familiares. Foi registrada a existência de 21 guardiões de 78 variedades locais, conservadas há pelo menos 10 anos, de abóbora (1), capim (10), feijão (10), leucena (2), mandioca (29), melancia (13), milho (5) e palma forrageira (8). Constatou-se que 79,5% das sementes tiveram como origem os parentes, amigos ou vizinhos e que as principais utilizações são para alimentação da família e de animais