175 research outputs found

    A molecular theory for two-photon and three-photon fluorescence polarization

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    In the analysis of molecular structure and local order in heterogeneous samples, multiphoton excitation of fluorescence affords chemically specific information and high-resolution imaging. This report presents the results of an investigation that secures a detailed theoretical representation of the fluorescence polarization produced by one-, two-, and three-photon excitations, with orientational averaging procedures being deployed to deliver the fully disordered limits. The equations determining multiphoton fluorescence response prove to be expressible in a relatively simple, generic form, and graphs exhibit the functional form of the multiphoton fluorescence polarization. Amongst other features, the results lead to the identification of a condition under which the fluorescence produced through the concerted absorption of any number of photons becomes completely unpolarized. It is also shown that the angular variation of fluorescence intensities is reliable indicator of orientational disorder

    Continuous Uniform Finite Time Stabilization of Planar Controllable Systems

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    Continuous homogeneous controllers are utilized in a full state feedback setting for the uniform finite time stabilization of a perturbed double integrator in the presence of uniformly decaying piecewise continuous disturbances. Semiglobal strong C1\mathcal{C}^1 Lyapunov functions are identified to establish uniform asymptotic stability of the closed-loop planar system. Uniform finite time stability is then proved by extending the homogeneity principle of discontinuous systems to the continuous case with uniformly decaying piecewise continuous nonhomogeneous disturbances. A finite upper bound on the settling time is also computed. The results extend the existing literature on homogeneity and finite time stability by both presenting uniform finite time stabilization and dealing with a broader class of nonhomogeneous disturbances for planar controllable systems while also proposing a new class of homogeneous continuous controllers

    Aplicação de fungicidas em sementes de soja e seus efeitos na nodulação e fixação biológica de nitrogênio

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    Electronic Spectra of Cyano-5-phenyltetrazoles

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    Absorption and luminescence spectra of ortho-, meta- and para- cyano-5-phenyltetrazole in aqueous solutions at room and low temperature were measured. Investigations wene carried out in super acidic (H; = -8) to basic (pR = 12)media. Three dissociation forms were identified (anion, molecule and cation), and the corresponding acid-base equilibrium constants in the ground state, speetrophotometrically, and in the first excited singlet state from the titration curves and by Forster cycle were determined
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