9,326 research outputs found

    Organogênese in vitro de videira.

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    O objetivo do presente trabalho foi avaliar o efeito da N6-benzilaminopurina (BAP) no processo de regeneração via organogênese in vitro,em sete cultivares de videira

    Decoherence of Semiclassical Wigner Functions

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    The Lindblad equation governs general markovian evolution of the density operator in an open quantum system. An expression for the rate of change of the Wigner function as a sum of integrals is one of the forms of the Weyl representation for this equation. The semiclassical description of the Wigner function in terms of chords, each with its classically defined amplitude and phase, is thus inserted in the integrals, which leads to an explicit differential equation for the Wigner function. All the Lindblad operators are assumed to be represented by smooth phase space functions corresponding to classical variables. In the case that these are real, representing hermitian operators, the semiclassical Lindblad equation can be integrated. There results a simple extension of the unitary evolution of the semiclassical Wigner function, which does not affect the phase of each chord contribution, while dampening its amplitude. This decreases exponentially, as governed by the time integral of the square difference of the Lindblad functions along the classical trajectories of both tips of each chord. The decay of the amplitudes is shown to imply diffusion in energy for initial states that are nearly pure. Projecting the Wigner function onto an orthogonal position or momentum basis, the dampening of long chords emerges as the exponential decay of off-diagonal elements of the density matrix.Comment: 23 pg, 2 fi

    Melon prdutivity under different soil coverings and irrigation system in Petrolina - PE

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    The objective of this work was to evaluate the influence of irrigation system and soil cover on yield of yellow melon in Petrolina / PE. The experiment was carried out in the period from April 09, 2016 to June 8, 2016 and was conducted at the Petrolina campus in the IF Sertão - PE rural area, with a randomized complete block design, 2 x 2 x 3 plot scheme, (One and two lines of drippers per row of plants), and the subsubparcels, three soil cover (black mulching cover), two plots of hybrids (Gladial and 10/00), subplots, two irrigation systems, Cover with mulching grey and without soil cover) and six replicates. Mulching efficiency (MPP) was studied in the soil cover and irrigation system located with drippers for the production of yellow hybrid melon 10/00 and Gladial under field conditions. It was verified the statistical influence of the soil cover on melon productivity

    Damage spreading in the mode-coupling equations for glasses

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    We examine the problem of damage spreading in the off-equilibrium mode coupling equations. The study is done for the spherical pp-spin model introduced by Crisanti, Horner and Sommers. For p>2p>2 we show the existence of a temperature transition T0T_0 well above any relevant thermodynamic transition temperature. Above T0T_0 the asymptotic damage decays to zero while below T0T_0 it decays to a finite value independent of the initial damage. This transition is stable in the presence of asymmetry in the interactions. We discuss the physical origin of this peculiar phase transition which occurs as a consequence of the non-linear coupling between the damage and the two-time correlation functions.Comment: 5 pages, 2 figures, Revtex fil

    Effect of the solvent on the conformation of monocrotaline as determined by isotropic and anisotropic NMR parameters.

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    The conformation in solution of monocrotaline, a pyrrolizidine alkaloid presenting an eleven-membered macrocyclic diester ring, has been investigated using a combination of isotropic and anisotropic NMR parameters measured in four solvents of different polarity (D2 O, DMSO-d6 , CDCl3 , and C6 D6 ). Anisotropic NMR parameters were measured in different alignment media, based on their compatibility with the solvent of interest: cromoglycate liquid crystal solution was used for D2 O, while a PMMA polymer gel was chosen for CDCl3 and C6 D6 , and a poly-HEMA gel for DMSO-d6 . Whereas the pyrrolizidine ring shows an E6 exo-puckered conformation in all of the solvents, the macrocyclic eleven-membered ring adopts different populations of syn-parallel and anti-parallel relative orientation of the carbonyl groups according to the polarity of the solvent

    Bose Glass in Large N Commensurate Dirty Boson Model

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    The large N commensurate dirty boson model, in both the weakly and strongly commensurate cases, is considered via a perturbative renormalization group treatment. In the weakly commensurate case, there exists a fixed line under RG flow, with varying amounts of disorder along the line. Including 1/N corrections causes the system to flow to strong disorder, indicating that the model does not have a phase transition perturbatively connected to the Mott Insulator-Superfluid (MI-SF) transition. I discuss the qualitative effects of instantons on the low energy density of excitations. In the strongly commensurate case, a fixed point found previously is considered and results are obtained for higher moments of the correlation functions. To lowest order, correlation functions have a log-normal distribution. Finally, I prove two interesting theorems for large N vector models with disorder, relevant to the problem of replica symmetry breaking and frustration in such systems.Comment: 16 pages, 7 figure
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