250 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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    Die Solvathülle und ihr Einfluß auf die Fluoreszenz

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    This review paper gives information about the nature of the microenvironment of luminescent molecules in non-polar/polar solvent mixtures. The following problems are discussed: 1. the influence of the environment on the absorption and fluorescence spectra of solute molecules, 2. determination of the effective dielectric constant of the solvent shell and the average degree of filling up the solvent shell with polar molecules, 3. the statistical model of Mazurenko, 4. determination of the average coordination number and the average interaction energy of the solute with the solvent molecules in the ground and excited state, 5. determination of the volume of the solvent shell from the depolarization of photoluminescence in liquid solutions, 6. the influence of the environment of solute on the energy transfer efficiency by gamma-ray excitation

    Efeito da inclusão de fitase e farelo de trigo na dieta de frangos de corte sobre a composição química da tíbia.

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    Para avaliar o efeito da inclusão de fitase e farelo de trigo sobre o teor de cálcio, fósforo, matéria mineral e a relação Ca:P na tíbia de frangos de corte, foram alojadas 384 aves, distribuídas em quatro tratamentos em um arranjo fatorial 2x2 em delineamento de blocos casualizados com oito repetições e 12 aves por unidade experimental. Os tratamentos foram: T1 ? controle negativo (milho e farelo soja) sem fitase; T2 ? controle positivo com 500 FTU/kg de fitase; T3 ? 20% farelo de trigo, sem fitase; T4 ? 20% farelo de trigo, com 500 FTU/kg de fitase. A composição da dieta, independente da presença ou ausência de fitase teve efeito significativo, reduzindo a concentração de fósforo e matéria mineral da tíbia. Para o efeito entre as dietas (com fitase), foi observada diferença significativa para o cálcio, fósforo e matéria mineral, onde a dieta milho e farelo de soja proporcionou maior concentração destas variáveis analisadas em relação a dieta contendo farelo de trigo. To evaluate the effect of inclusion of phytase and wheat bran on calcium, phosphorus, ash and Ca: P ratio in the tibia of broilers, 384 birds were housed, assigned to four treatments in a 2x2 factorial arrangement in randomized block design with eight replicates of 12 birds each. The treatments were: T1 - negative control (corn and soybean meal) without phytase; T2 - positive control with 500 FTU / kg of phytase; T3 - 20% wheat bran, no phytase; T4 - 20% of wheat bran with 500 FTU / kg of phytase. It was found that the diet, independently from the phytase inclusion had a significant effect, reducing the concentration of phosphorus and mineral matter of the tibia. Comparing diets, both with phytase, a significant difference for calcium, phosphorus and mineral matter in the tibia were observed. Diet based on corn and soybean meal provided greater concentration of these parameters
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