Localized surface plasmon resonance interaction with Er3+-doped tellurite glass

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Kinetics, electrochemistry and resonance raman spectra of the (2-mercaptopyridine) (edta)ruthenium(III) complex

The chemistry of the pentadentate edta complexes of ruthenium(III) and (II) with 2-mercaptopyridine (HSpy) has been investigated based on spectroscopic, kinetic and electrochemical techniques. The reaction of [Ru(III)(edta)H2O]- with HSpy proceeds with a specific rate of 1.05 × 104 M-1 S -1 (25°C, I = 0.10 M, acetate buffer), forming a red complex (λmax = 550 nm) which undergoes a relaxation process as a function of pH, with an apparent pKa = 4.35 and kobs = 0.31 S -1. The second reaction depends on the concentration of HSpy and leads to a stable green product (λmax = 630 mn). A pronounced enhancement has been observed in the Raman spectra of the complexes, particularly in the region of the metal-ligand vibrations. The electronic and resonance Raman spectra are consistent with the coordination of HSpy via the sulfur atom in the red complex, and with a chelate binding in the green species. © 1987.

Influence of the resonance in a gravity-gradient stabilized satellite

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Resonance and chaos: I. First-order interior resonances

Analytical models for studying the dynamical behaviour of objects near interior, mean motion resonances are reviewed in the context of the planar, circular, restricted threebody problem. The predicted widths of the resonances are compared with the results of numerical integrations using Poincaré surfaces of section with a mass ratio of 10-3 (similar to the Jupiter-Sun case). It is shown that for very low eccentricities the phase space between the 2:1 and 3:2 resonances is predominantly regular, contrary to simple theoretical predictions based on overlapping resonance. A numerical study of the 'evolution' of the stable equilibrium point of the 3:2 resonance as a function of the Jacobi constant shows how apocentric libration at the 2:1 resonance arises; there is evidence of a similar mechanism being responsible for the centre of the 4:3 resonance evolving towards 3:2 apocentric libration. This effect is due to perturbations from other resonances and demonstrates that resonances cannot be considered in isolation. On theoretical grounds the maximum libration width of first-order resonances should increase as the orbit of the perturbing secondary is approached. However, in reality the width decreases due to the chaotic effect of nearby resonances.

Resonance and chaos: II. Exterior resonances and asymmetric libration

The motion of a test particle in the vicinity of exterior resonances is examined in the context of the planar, circular, restricted three-body problem. The existence of asymmetric periodic orbits associated with the 1 : n resonances (where n = 2, 3, 4, 5) is confirmed; there is also evidence of asymmetric resonances associated with larger values of n. A detailed examination of the evolution of the family of orbits associated with the 1:2 resonance shows the sequence that leads to asymmetric libration. On the basis of numerical studies of the phase space it is concluded that the existence of asymmetric libration means that the region exterior to the perturbing mass is more chaotic than the interior region. The apparent absence of 'particles' in 1 : n resonances in the solar system may reflect this inherent bias.

Metal-insulator transitions in pressed pellets of BF4 - doped poly(3-methylthiophene)

From Electron Spin Resonance (ESR) data in pressed pellets of BF4 - doped Poly(3-methylthiophene) (P3MT) we obtained simultaneously the paramagnetic susceptibility and. the microwave conductivity. We observed a transition from a high-temperature insulator state to a room-temperature metallic state. Around 240K. evidence of a Peierls transition is observed, but if the sample is slowly cooled, this transition is partially suppressed. DC conductivity data taken with the sample quenched to 79 K show a non-linear I-V response for very small electric fields, suggesting depinning of Charge-Density Wave (CDW). The data for heating and cooling the system above room temperature, indicate the formation of bipolarons.

Positron-helium scattering: Resonance and differential cross sections

We study positron-helium scattering using close coupling approximation (CCA) employing different combinations of the following basis functions: He(1s1s), He(1s2s), He(1s2p), Ps(1s). and Ps(2s), where Ps stands for the positronium atom. We observe a prominent S wave resonance of width 2 eV at about 30 eV, in excitation and rearrangement cross sections to He(1s2s), He(1s2p), Ps(1s) and Ps(2s) states. We also report results of differential cross sections for the excitation of helium and positronium formation.

Polarized structure functions of the nucleon in the resonance region

We present predictions for the spin structure functions of the proton in the framework of a unitary isobar model for one-pion photo- and electroproduction. Our results are compared with recent experimental data from SLAC. The first moments of the calculated structure functions fullfil the Gerasimov-Drell-Hearn and Burkhardt-Cottingham sum rules within an error of typically 5-10%.

Array of Bose-Einstein condensates under time-periodic Feshbach-resonance management

The investigation of the dynamics of a discrete soliton in an array of Bose-Einstein condensates under the action of a periodically time-modulated atomic scattering length [Feshbach-resonance management (FRM)] was discussed. The slow and rapid modulations, in comparison with the tunneling frequency were considered. An averaged equation, which was a generalized discrete nonlinear Schrödinger equation, including higher-order effective nonlinearities and intersite nonlinear interactions was derived in the case of the rapid modulation. It was demonstrated that the modulations of sufficient strength results in splitting of the soliton by direct simulations.

New contributions to the determination of resonance frequencies of rectangular microstrip antennas by neural networks

This paper uses artificial neural networks (ANN) to compute the resonance frequencies of rectangular microstrip antennas (MSA), used in mobile communications. Perceptron Multi-layers (PML) networks were used, with the Quasi-Newton method proposed by Broyden, Fletcher, Goldfarb and Shanno (BFGS). Due to the nature of the problem, two hundred and fifty networks were trained, and the resonance frequency for each test antenna was calculated by statistical methods. The estimate resonance frequencies for six test antennas were compared with others results obtained by deterministic and ANN based empirical models from the literature, and presented a better agreement with the experimental values.

Search for a resonance decaying into WZ boson Pairs in pp̄ collisions

We present the first search for an electrically charged resonance W′ decaying to a WZ boson pair using 4.1fb-1 of integrated luminosity collected with the D0 detector at the Fermilab Tevatron pp̄ collider. The WZ pairs are reconstructed through their decays into three charged leptons (≤=e, μ). A total of 9 data events is observed in good agreement with the background prediction. We set 95% C.L. limits on the W′WZ coupling and on the W′ production cross section multiplied by the branching fractions. We also exclude W′ masses between 188 and 520 GeV within a simple extension of the standard model and set the most restrictive limits to date on low-scale technicolor models. © 2010 The American Physical Society.

State Dependent Riccati Equation (SDRE) control method applied in cancellation of a parametric resonance in a magnetically levitated body

Here, a simplified dynamical model of a magnetically levitated body is considered. The origin of an inertial Cartesian reference frame is set at the pivot point of the pendulum on the levitated body in its static equilibrium state (ie, the gap between the magnet on the base and the magnet on the body, in this state). The governing equations of motion has been derived and the characteristic feature of the strategy is the exploitation of the nonlinear effect of the inertial force associated, with the motion of a pendulum-type vibration absorber driven, by an appropriate control torque [4]. In the present paper, we analyzed the nonlinear dynamics of problem, discussed the energy transfer between the main system and the pendulum in time, and developed State Dependent Riccati Equation (SDRE) control design to reducing the unstable oscillatory movement of the magnetically levitated body to a stable fixed point. The simulations results showed the effectiveness of the (SDRE) control design. Copyright © 2011 by ASME.