342 research outputs found

    Origin of stabilization of macrotwin boundaries in martensites

    Full text link
    The origin of stabilization of complex microstructures along macrotwin boundaries in martensites is explained by comparing two models based on Ginzburg-Landau theory. The first model incorporates a geometrically nonlinear strain tensor to ensure that the Landau energy is invariant under rigid body rotations, while the second model uses a linearized strain tensor under the assumption that deformations and rotations are small. We show that the approximation in the second model does not always hold for martensites and that the experimental observations along macrotwin boundaries can only be reproduced by the geometrically nonlinear (exact) theory

    Homogeneous nucleation of dislocations as a pattern formation phenomenon

    Full text link
    Dislocation nucleation in homogeneous crystals initially unfolds as a linear symmetry-breaking elastic instability. In the absence of explicit nucleation centers, such instability develops simultaneously all over the crystal and due to the dominance of long range elastic interactions it advances into the nonlinear stage as a collective phenomenon through pattern formation. In this paper we use a novel mesoscopic tensorial model (MTM) of crystal plasticity to study the delicate role of crystallographic symmetry in the development of the dislocation nucleation patterns in defect free crystals loaded in a hard device. The model is formulated in 2D and we systematically compare lattices with square and triangular symmetry. To avoid the prevalence of the conventional plastic mechanisms, we consider the loading paths represented by pure shears applied on the boundary of the otherwise unloaded body. These loading protocols can be qualified as exploiting the 'softest' and the 'hardest' directions and we show that the associated dislocation patterns are strikingly different

    Lactating dairy cows fed diets with different levels of cupuaçu (Theobroma Grandiflorum) meal.

    Get PDF
    Este trabalho teve como objetivo avaliar a inclusão de farinha de cupuaçu (CM) em substituição ao milho moído em dietas para vacas leiteiras em lactação, considerando o consumo voluntário, produção e composição do leite

    Consumo Voluntário, Produção e Composição do Leite de Vacas Leiteiras Suplementadas com Concentrado a Base de Farelo de Cupuaçu.

    Get PDF
    Com o objetivo de avaliar o nível de inclusão do farelo de cupuaçu (Theobroma Grandiflorum) na dieta de vacas leiteiras sobre o consumo total e a produção e composição do leite, foi realizado um ensaio em quadrado latino com vacas mestiças Gir x Holandês com peso vivo (PV) médio de 524 kg, as quais foram alimentadas com dietas à base de silagem de milho e mistura concentrada com 16% de proteína bruta (PB) contendo farelo de soja e farelo de cupuaçu (FC) em substituição ao milho moído em quatro níveis: 0%, 10%, 20% e 40%

    Children and older adults exhibit distinct sub-optimal cost-benefit functions when preparing to move their eyes and hands

    Get PDF
    "© 2015 Gonzalez et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited"Numerous activities require an individual to respond quickly to the correct stimulus. The provision of advance information allows response priming but heightened responses can cause errors (responding too early or reacting to the wrong stimulus). Thus, a balance is required between the online cognitive mechanisms (inhibitory and anticipatory) used to prepare and execute a motor response at the appropriate time. We investigated the use of advance information in 71 participants across four different age groups: (i) children, (ii) young adults, (iii) middle-aged adults, and (iv) older adults. We implemented 'cued' and 'non-cued' conditions to assess age-related changes in saccadic and touch responses to targets in three movement conditions: (a) Eyes only; (b) Hands only; (c) Eyes and Hand. Children made less saccade errors compared to young adults, but they also exhibited longer response times in cued versus non-cued conditions. In contrast, older adults showed faster responses in cued conditions but exhibited more errors. The results indicate that young adults (18 -25 years) achieve an optimal balance between anticipation and execution. In contrast, children show benefits (few errors) and costs (slow responses) of good inhibition when preparing a motor response based on advance information; whilst older adults show the benefits and costs associated with a prospective response strategy (i.e., good anticipation)

    Digestibilidade aparente e consumo de dietas contendo torta de cupuaçu em vacas leiteiras.

    Get PDF
    Esse estudo teve por objetivo avaliar a digestibilidade aparente e o consumo da matéria seca (IMS) e da matéria orgânica (IMO) de dietas com diferentes níveis de inclusão de torta de cupuaçu utilizando vacas lactantes Holandês x Gir. Foi conduzido um ensaio em Quadrado Latino com quatro vacas com média de peso vivo (PV) de 536±42 kg e 102±7.7 dias em lactação. Os tratamentos foram dietas à base de silagem de milho e concentrado com quatro níveis de inclusão de torta de cupuaçu (0, 10, 20 e 40%). A excreção fecal foi estimada com o marcador LIPE®. Não foram observadas diferenças estatísticas entre os tratamentos para todas as variáveis analisadas e as médias de IMS, de IMO, dos coeficientes de digestibilidade da matéria seca (MS) e da matéria orgânica (MO) foram: 7.89 e 6.36kg dia-1 ; 53.13 e 43.25%, respectivamente. A inclusão de até 40% de torta de cupuaçu na dieta de vacas mestiças em lactação não altera a ingestão e a digestibilidade aparente da MS e da MO

    A review of Monte Carlo simulations of polymers with PERM

    Full text link
    In this review, we describe applications of the pruned-enriched Rosenbluth method (PERM), a sequential Monte Carlo algorithm with resampling, to various problems in polymer physics. PERM produces samples according to any given prescribed weight distribution, by growing configurations step by step with controlled bias, and correcting "bad" configurations by "population control". The latter is implemented, in contrast to other population based algorithms like e.g. genetic algorithms, by depth-first recursion which avoids storing all members of the population at the same time in computer memory. The problems we discuss all concern single polymers (with one exception), but under various conditions: Homopolymers in good solvents and at the Θ\Theta point, semi-stiff polymers, polymers in confining geometries, stretched polymers undergoing a forced globule-linear transition, star polymers, bottle brushes, lattice animals as a model for randomly branched polymers, DNA melting, and finally -- as the only system at low temperatures, lattice heteropolymers as simple models for protein folding. PERM is for some of these problems the method of choice, but it can also fail. We discuss how to recognize when a result is reliable, and we discuss also some types of bias that can be crucial in guiding the growth into the right directions.Comment: 29 pages, 26 figures, to be published in J. Stat. Phys. (2011

    Diverse tick-borne microorganisms identified in free-living ungulates in Slovakia

    Get PDF
    Background: Free-living ungulates are hosts of ixodid ticks and reservoirs of tick-borne microorganisms in central Europe and many regions around the world. Tissue samples and engorged ticks were obtained from roe deer, red deer, fallow deer, mouflon, and wild boar hunted in deciduous forests of south-western Slovakia. DNA isolated from these samples was screened for the presence of tick-borne microorganisms by PCR-based methods. Results: Ticks were found to infest all examined ungulate species. The principal infesting tick was Ixodes ricinus, identified on 90.4% of wildlife, and included all developmental stages. Larvae and nymphs of Haemaphysalis concinna were feeding on 9.6% of wildlife. Two specimens of Dermacentor reticulatus were also identified. Ungulates were positive for A. phagocytophilum and Theileria spp. Anaplasma phagocytophilum was found to infect 96.1% of cervids, 88.9% of mouflon, and 28.2% of wild boar, whereas Theileria spp. was detected only in cervids (94.6%). Importantly, a high rate of cervids (89%) showed mixed infections with both these microorganisms. In addition to A. phagocytophilum and Theileria spp., Rickettsia helvetica, R. monacensis, unidentified Rickettsia sp., Coxiella burnetii, "Candidatus Neoehrlichia mikurensis", Borrelia burgdorferi (s.l.) and Babesia venatorum were identified in engorged I. ricinus. Furthermore, A. phagocytophilum, Babesia spp. and Theileria spp. were detected in engorged H. concinna. Analysis of 16S rRNA and groEL gene sequences revealed the presence of five and two A. phagocytophilum variants, respectively, among which sequences identified in wild boar showed identity to the sequence of the causative agent of human granulocytic anaplasmosis (HGA). Phylogenetic analysis of Theileria 18S rRNA gene sequences amplified from cervids and engorged I. ricinus ticks segregated jointly with sequences of T. capreoli isolates into a moderately supported monophyletic clade. Conclusions: The findings indicate that free-living ungulates are reservoirs for A. phagocytophilum and Theileria spp. and engorged ixodid ticks attached to ungulates are good sentinels for the presence of agents of public and veterinary concern. Further analyses of the A. phagocytophilum genetic variants and Theileria species and their associations with vector ticks and free-living ungulates are required.Fil: Kazimírová, Mária. Slovak Academy of Sciences. Institute of Zoology; EslovaquiaFil: Hamšíková, Zuzana. Slovak Academy of Sciences. Institute of Zoology; EslovaquiaFil: Spitalská, Eva. Slovak Academy of Sciences. Institute of Virology. Biomedical Research Center,; EslovaquiaFil: Minichová, Lenka. Slovak Academy of Sciences. Institute of Virology. Biomedical Research Center,; EslovaquiaFil: Mahríková, Lenka. Slovak Academy of Sciences. Institute of Zoology; EslovaquiaFil: Caban, Radoslav. Široká ; EslovaquiaFil: Sprong, Hein. National Institute for Public Health and Environment.Laboratory for Zoonoses and Environmental Microbiology; Países BajosFil: Fonville, Manoj. National Institute for Public Health and Environment.Laboratory for Zoonoses and Environmental Microbiology; Países BajosFil: Schnittger, Leonhard. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Patobiología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Kocianová, Elena. Slovak Academy of Sciences. Institute of Virology. Biomedical Research Center,; Eslovaqui

    Cotton in the new millennium: advances, economics, perceptions and problems

    Get PDF
    Cotton is the most significant natural fibre and has been a preferred choice of the textile industry and consumers since the industrial revolution began. The share of man-made fibres, both regenerated and synthetic fibres, has grown considerably in recent times but cotton production has also been on the rise and accounts for about half of the fibres used for apparel and textile goods. To cotton’s advantage, the premium attached to the presence of cotton fibre and the general positive consumer perception is well established, however, compared to commodity man-made fibres and high performance fibres, cotton has limitations in terms of its mechanical properties but can help to overcome moisture management issues that arise with performance apparel during active wear. This issue of Textile Progress aims to: i. Report on advances in cotton cultivation and processing as well as improvements to conventional cotton cultivation and ginning. The processing of cotton in the textile industry from fibre to finished fabric, cotton and its blends, and their applications in technical textiles are also covered. ii. Explore the economic impact of cotton in different parts of the world including an overview of global cotton trade. iii. Examine the environmental perception of cotton fibre and efforts in organic and genetically-modified (GM) cotton production. The topic of naturally-coloured cotton, post-consumer waste is covered and the environmental impacts of cotton cultivation and processing are discussed. Hazardous effects of cultivation, such as the extensive use of pesticides, insecticides and irrigation with fresh water, and consequences of the use of GM cotton and cotton fibres in general on the climate are summarised and the effects of cotton processing on workers are addressed. The potential hazards during cotton cultivation, processing and use are also included. iv. Examine how the properties of cotton textiles can be enhanced, for example, by improving wrinkle recovery and reducing the flammability of cotton fibre
    corecore