430 research outputs found

    Diversidade genética em populações naturais de infalível.

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    Suplemento. Edição dos Trabalhos do 49 Congresso Brasileiro de Olericultura, Águas de Lindóia, ago. 2009

    Ocorrência de fungos micorrízicos em catuaba (Anemopaegma arvense (Vell.) Stell. ex de Souza - Bignoniaceae), uma planta medicinal do Cerrado em risco de extinção.

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    Este trabalho foi realizado com o objetivo de verificar a ocorrência de fungos micorrízicos, identificar suas espécies, e avaliar a colonização em raízes de plantas de diferentes populações e variedades de Anemopaegma arvense, uma planta medicinal do Cerrado em risco de extinção. As avaliações da colonização micorrízica e identificação de espécies de fungos micorrízicos arbusculares (FMAs) foram realizadas no Laboratório de Microbiologia do Solo da Universidade Federal de Lavras (UFLA). Foram utilizadas raízes de 10 plantas coletadas em diferentes locais juntamente com as amostras de solo próximo ao sistema radicular de populações naturais das variedades: glabra, puberula e petiolata. Os esporos foram extraídos do solo por meio da metodologia de peneiramento úmido e, para a avaliação e observação da colonização radicular, as raízes coradas foram observadas em microscópio estereoscópico (ampliação 10 a 40x). Em todas as amostras analisadas foi possível identificar espécies de FMAs, exceto para a variedade puberula, coletada no município de Mogi Guaçu-SP. O número de esporos variou de maneira significativa entre as amostras e os locais amostrados, não havendo distribuição regular. Acaulospora scrubiculata, A. spinosa, A. longula, Escustelospora heterogama, Paraglomus occultum, Gigaspora margarita, Gigaspora sp., dentre outros, encontram-se entre as espécies identificadas. Quanto à avaliação da colonização micorrízica nas raízes, observou-se que todas as variedades foram colonizadas no sitema radicular, verificada por meio da presença de hifas. No entanto, a colonização não foi constatada em todas as amostras avaliadas e também não foi observada a formação de arbúsculos e/ou vesículas.Suplemento 1

    Micorrizas arbusculares em populações naturais de catuaba (Anemopaegma arvense (Vell.) Stell. ex de Souza).

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    O objetivo deste trabalho foi verificar a ocorrência, identificar espécies de fungosmicorrízicos (MAs) e avaliar a colonização em raízes de plantas de diferentes populações evariedades deAnemopaegma arvense(Vell.) Stell. ex de Souza

    Enraizamento in vitro de catuaba (Anemopaegma arvense ) (Vell.) Stell. ex de Souza.

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    Este trabalho teve como objetivo avaliar os efeitos de diferentes concentrações e tipos de poliaminas e diferentes concentrações de dithiothreitol (DTT) no enraizamento in vitro de A. Arvense

    Comparative analysis between condom use clusters and risk behaviours among portuguese university students

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    The research on condom use has been focused on high-risk individuals, paying less attention to those who have moderate risk or safe sexual conducts. In order to design accurate interventions, potential differences among the condom use behavior groups must be considered. The goal was to assess possible differences in individuals presenting different types of risk behavior. 140 heterosexual university students answered a self-reported questionnaire about their sexual history, condom use habits, sexual self-esteem, sexual satisfaction, sexual control, attitudes towards condoms, self-efficacy to condom use, and emotions and feelings during sexual intercourse. A cluster analysis was conducted using the results about condom use and risk behaviors. Three groups with different risk levels emerged, presenting differences over sexual self-efficacy, attitudes towards condoms, socio-demographic variables, and sexual history. The results suggest the condom use inconsistency is highly associated with other risk behaviors but the contrary does not necessarily happens. Condom use consistent users also presented risk behaviors as smoking and drinking. The group differences suggest the risks were more affected by the combination of lack of skills with a negative attitude toward condoms than by contextual or personal variables. These differences sustain the need of an intervention adjusted to the individual's risk levels, since they differ on skills and beliefs that may hinder or promote the adoption of health behaviors.Foundation for Science and Technology/Fundacao para a Ciencia e Tecnologia (Portugal)info:eu-repo/semantics/publishedVersio

    Electron cotunneling through doubly occupied quantum dots: effect of spin configuration

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    A microscopic theory is presented for electron cotunneling through doubly occupied quantum dots in the Coulomb blockade regime. Beyond the semiclassic framework of phenomenological models, a fully quantum mechanical solution for cotunneling of electrons through a one-dimensional quantum dot is obtained using a quantum transmitting boundary method without any fitting parameters. It is revealed that the cotunneling conductance exhibits strong dependence on the spin configuration of the electrons confined inside the dot. Especially for the triplet configuration, the conductance shows an obvious deviation from the well-known quadratic dependence on the applied bias voltage. Furthermore, it is found that the cotunneling conductance reveals more sensitive dependence on the barrier width than the height

    Mesoscopic effects in tunneling between parallel quantum wires

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    We consider a phase-coherent system of two parallel quantum wires that are coupled via a tunneling barrier of finite length. The usual perturbative treatment of tunneling fails in this case, even in the diffusive limit, once the length L of the coupling region exceeds a characteristic length scale L_t set by tunneling. Exact solution of the scattering problem posed by the extended tunneling barrier allows us to compute tunneling conductances as a function of applied voltage and magnetic field. We take into account charging effects in the quantum wires due to applied voltages and find that these are important for 1D-to-1D tunneling transport.Comment: 8 pages, 7 figures, improved Figs., added Refs. and appendix, to appear in Phys. Rev.

    Oxidation resistance of graphene-coated Cu and Cu/Ni alloy

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    The ability to protect refined metals from reactive environments is vital to many industrial and academic applications. Current solutions, however, typically introduce several negative effects, including increased thickness and changes in the metal physical properties. In this paper, we demonstrate for the first time the ability of graphene films grown by chemical vapor deposition to protect the surface of the metallic growth substrates of Cu and Cu/Ni alloy from air oxidation. SEM, Raman spectroscopy, and XPS studies show that the metal surface is well protected from oxidation even after heating at 200 \degree C in air for up to 4 hours. Our work further shows that graphene provides effective resistance against hydrogen peroxide. This protection method offers significant advantages and can be used on any metal that catalyzes graphene growth

    Phonons and related properties of extended systems from density-functional perturbation theory

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    This article reviews the current status of lattice-dynamical calculations in crystals, using density-functional perturbation theory, with emphasis on the plane-wave pseudo-potential method. Several specialized topics are treated, including the implementation for metals, the calculation of the response to macroscopic electric fields and their relevance to long wave-length vibrations in polar materials, the response to strain deformations, and higher-order responses. The success of this methodology is demonstrated with a number of applications existing in the literature.Comment: 52 pages, 14 figures, submitted to Review of Modern Physic
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