Coupling Surface-Enhanced Resonance Raman Scattering and Electronic Tongue as Characterization Tools to Investigate Biological Membrane Mimetic Systems

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

Synthesis and Characterization of Ruteno-Cuprates by Solid State Reactions

A new class of hybrid ruteno-cuprates - such as Ru-1212 and Ru-1222 - was discovered in 1995 by Bauerfeind and collaborators. These materials present superconducting and magnetic states at low temperatures, an atypical duality in other superconductors. The superconductivity is more easily observed in Ru-1222, while Ru-1212 is a more problematic case, due to the strong effects of the preparation details in its superconducting properties, becoming the material superconductor or not. Ru-1212 presents a critical temperature that can vary between 0 and 46 K, depending on the preparation conditions, and a temperature of magnetic transition of around 132 K. The samples were prepared through solid state reactions, by using a mixture of high purity powders, followed by calcination and sinterization in the nitrogen and oxygen atmospheres. This paper shows the preparation process of Ru-1212 samples, followed by their structural and magnetic characterization.

A new oxovanadium(IV)-cucurbit[6]uril complex: Properties and potential for confined heterogeneous catalytic oxidation reactions

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Changing inter-molecular spin-orbital coupling for generating magnetic field effects in phosphorescent organic semiconductors

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

A theoretical study on the gas phase reactions of the anions NbO3-, NbO5-, and NbO2(0H)(2)(-) with H2O and O-2

The potential energy surfaces at the singlet (s) and the triplet (t) electronic states associated with the gas-phase ion/molecule reactions of NbO3-, NbO5-, and NbO2(OH)(2)(-) with H2O and O-2 have been investigated by means of DFT calculations at the B3LYP level. An analysis of the results points out that the most favorable reactive channel comprises s-NbO3- reacting with H2O to give an ion-molecule complex s-NbO3(H2O)without a barrier. From this minima, an intramolecular hydrogen transfer takes place between the incoming water molecule and an oxygen atom of the NbO3- fragment to render the most stable minimum, s-NbO2(OH)(2)(-). This oxyhydroxide system reacts with O-2 along a barrierless process to obtain the triplet t-NbO4(OH)(2)(-)-A intermediate, and the crossing point, CP1, between s and t electronic states has been characterized. The next step is the hydrogen-transfer process between the oxygen atom of a hydroxyl group and the one adjacent oxygen atom to render a minimum with the two OH groups near each other, t-NbO4(OH)(2)(-)-B. From this point, the last hydrogen migration takes place, to obtain the product complex, t-NbO5(H2O)(-), that can be connected with the singlet separated products, s-NbO5- and H2O. Therefore, a second crossing point, CP2, has been localized. The nature of the chemical bonding of the key minima (NbO3-, NbO2(OH)(2)(-), NbO4(OH)(2)(-)-B, and NbO5-) in both electronic states of the reaction and an interaction with O-2 has been studied by topological analysis of Becke-Edgecombe electron-localization function (ELF) and atoms-in-molecules (AIM) methodology. The niobium-oxygen interactions are characterized as unshared-electron (ionic) interactions and some oxygen-oxygen interactions as protocovalent bonds.

Neurophysiological patterns of ulnar nerve neuropathy in leprosy reactions

Background: Leprosy neuropathy, despite being primarily demyelinating, frequently leads to axonal loss. Neurophysiological examination of the nerves during Type 1 (T1R) and Type 2 reactions (T2R) may give some insight into the pathophysiological mechanisms.Methods: Neurophysiological examinations were performed in 28 ulnar nerves during a clinical trial of steroid treatment effectiveness, 19 patients with T1R and nine with T2R. The nerves were monitored during a period of 6 months; there were eight assessments per nerve, for a total of 224 assessments. Nine neurophysiological parameters were assessed at three sites of the ulnar nerve. The compound motor action potential amplitudes elicited at wrist, elbow and above, as well as the conduction velocity and temporal dispersion across the elbow, were chosen to focus on the changes occurring in the parameters at the elbow tunnel.Results and Conclusion: Neurophysiological changes indicating axonal and demyelinating processes during both T1R and T2R were detected across the elbow. Changes in demyelination, i.e. a Conduction Block, as a primary event present during T2R, occurring as an acute phenomenon, were observed regularly; in T1R Temporal Dispersion, a subacute phenomenon, was seen. During treatment remyelination occurred after both types of reactions.

Static potential in QED(3) with nonminimal coupling

Here we study the effect of the nonminimal coupling j(mu)epsilon(munualpha)partial derivative(nu)A(alpha) on the static potential in multiflavor QED(3). Both cases of four and two components fermions are studied separately at leading order in the 1/N expansion. Although a nonlocal Chern-Simons term appears, in the four components case the photon is still massless leading to a confining logarithmic potential similar to the classical one. In the two components case, as expected, the parity breaking fermion mass term generates a traditional Chern-Simons term which makes the photon massive and we have a screening potential which vanishes at large intercharge distance. The extra nonminimal couplings have no important influence on the static potential at large intercharge distances. However, interesting effects show up at finite distances. In particular, for strong enough nonminimal coupling we may have a new massive pole in the photon propagator, while in the opposite limit there may be no poles at all in the irreducible case. We also found that, in general, the nonminimal couplings lead to a finite range repulsive force between charges of opposite signs.

Confinement of spin-0 and spin-1/2 particles in a mixed vector-scalar coupling with unequal shapes for the potentials

The Klein - Gordon and the Dirac equations with vector and scalar potentials are investigated under a more general condition, V-v = V-s + constant. These isospectral problems are solved in the case of squared trigonometric potential functions and bound states for either particles or antiparticles are found. The eigenvalues and eigenfunctions are discussed in some detail. It is revealed that a spin-0 particle is better localized than a spin-1/2 particle when they have the same mass and are subjected to the same potentials.

Tensor coupling and pseudospin symmetry in nuclei

In this work we study the contribution of the isoscalar tensor coupling to the realization of pseudospin symmetry in nuclei. Using realistic values for the tensor coupling strength, we show that this coupling reduces noticeably the pseudospin splittings, especially for single-particle levels near the Fermi surface. By using an energy. decomposition of the pseudospin energy splittings, we show that the changes in these splittings come mainly through the changes induced in the lower radial wave function for the low-lying pseudospin partners and through changes in the expectation value of the pseudospin-orbit coupling term for surface partners. This allows us to confirm the conclusion already reached in previous studies, namely that the pseudospin symmetry in nuclei is of a dynamical nature.

Confining solutions of massive spin-0 bosons by a linear nonminimal vector coupling in the Duffin-Kemmer-Petiau theory

The Duffin-Kemmer-Petiau (DKP) equation, in the scalar sector of the theory and with a linear nominimal vector potential, is mapped into the nonrelativistic harmonic oscillator problem. The behavior of the solutions for this sort of vector DKP oscillator is discussed in detail.

On the nonminimal vector coupling in the Duffin-Kemmer-Petiau theory and the confinement of massive bosons by a linear potential

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Bound states of bosons and fermions in a mixed vector-scalar coupling with unequal shapes for the potentials

The Klein - Gordon and the Dirac equations with vector and scalar potentials are investigated under a more general condition, V(v) + V(s) = constant. These intrinsically relativistic and isospectral problems are solved in the case of squared hyperbolic potential functions and bound states for either particles or antiparticles are found. The eigenvalues and eigenfuntions are discussed in some detail and the effective Compton wavelength is revealed to be an important physical quantity. It is revealed that a boson is better localized than a fermion when they have the same mass and are subjected to the same potentials.

Effects Due to a Scalar Coupling on the Particle-Antiparticle Production in the Duffin-Kemmer-Petiau Theory

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)