Transition from Knudsen to molecular diffusion in activity of absorbing irregular interfaces

We investigate through molecular dynamics the transition from Knudsen to molecular diffusion transport towards 2d absorbing interfaces with irregular geometry. Our results indicate that the length of the active zone decreases continuously with density from the Knudsen to the molecular diffusion regime. In the limit where molecular diffusion dominates, we find that this length approaches a constant value of the order of the system size, in agreement with theoretical predictions for Laplacian transport in irregular geometries. Finally, we show that all these features can be qualitatively described in terms of a simple random-walk model of the diffusion process.Comment: 4 pages, 4 figure

Teleparallel origin of the Fierz picture for spin-2 particle

A new approach to the description of spin-2 particle in flat and curved spacetime is developed on the basis of the teleparallel gravity theory. We show that such an approach is in fact a true and natural framework for the Fierz representation proposed recently by Novello and Neves. More specifically, we demonstrate how the teleparallel theory fixes uniquely the structure of the Fierz tensor, discover the transparent origin of the gauge symmetry of the spin 2 model, and derive the linearized Einstein operator from the fundamental identity of the teleparallel gravity. In order to cope with the consistency problem on the curved spacetime, similarly to the usual Riemannian approach, one needs to include the non-minimal (torsion dependent) coupling terms.Comment: 5 pages, Revtex4, no figures. Accepted for publication in Phys. Rev.

Elliptic Flow and Dissipation in Heavy-Ion Collisions at E_{lab} = (1--160)A GeV

Elliptic flow in heavy-ion collisions at incident energies $E_{lab}\simeq$ (1--160)A GeV is analyzed within the model of 3-fluid dynamics (3FD). We show that a simple correction factor, taking into account dissipative affects, allows us to adjust the 3FD results to experimental data. This single-parameter fit results in a good reproduction of the elliptic flow as a function of the incident energy, centrality of the collision and rapidity. The experimental scaling of pion eccentricity-scaled elliptic flow versus charged-hadron-multiplicity density per unit transverse area turns out to be also reasonably described. Proceeding from values of the Knudsen number, deduced from this fit, we estimate the upper limit the shear viscosity-to-entropy ratio as $\eta/s \sim 1-2$ at the SPS incident energies. This value is of the order of minimal $\eta/s$ observed in water and liquid nitrogen.Comment: 10 pages, 7 figures, version accepted by Phys. Rev.

Polyphenolic and chromatic characterization of tropical red wines produced in the São Francisco river Valley (Northeast Brazil).

Young varietal and experimental wines from Vitis vinifera - Petit Verdot,Tempranillo and Syrah - cultivated in a tropical semiarid region (Northeast Brazil) were evaluated with regard to their phenolic composition and chromatic characteristics during a storage period of 12-month. The wine was stored in bottles and evaluated using spectrophotometry and high efficiency liquid chromatography to determine color, total polyphenols, anthocyanins, flavanols and flavonols. The Petit Verdot had a less color variation when compared to wines from temperate climates. Although the wines followed the traditional pattem of decreasing polyphenol concentration during storage, the concentrations of these compounds remained higher than those reported in literature, such as for the anthocyanins in Petit Verdot wines and transresveratrolin Syrah, showing possible beneficial health effects even after storag

Neighborhood properties of complex networks

A concept of neighborhood in complex networks is addressed based on the criterion of the minimal number os steps to reach other vertices. This amounts to, starting from a given network $R_1$, generating a family of networks $R_\ell, \ell=2,3,...$ such that, the vertices that are $\ell$ steps apart in the original $R_1$, are only 1 step apart in $R_\ell$. The higher order networks are generated using Boolean operations among the adjacency matrices $M_\ell$ that represent $R_\ell$. The families originated by the well known linear and the Erd\"os-Renyi networks are found to be invariant, in the sense that the spectra of $M_\ell$ are the same, up to finite size effects. A further family originated from small world network is identified

Ocorrência e caracterização de bactérias isoladas de nódulos de amendoinzeiro (Arachis hypogaea L.) em solos paranaenses, Brasil.

RESUMO: O objetivo deste trabalho foi avaliar a ocorrência e caracterizar morfofisiologicamente e geneticamente bactérias isoladas de nódulos de amendoinzeiro (Arachis hypogaea L.), em solos paranaenses, Brasil. Em amostras de 36 municípios representativos do estado Paraná foi observada nodulação do amendoim em 84,4%, independente se em áreas cultivadas, ou em florestas. Nos testes de caracterização morfofisiológica de 44 estirpes autenticadas, 75% das estirpes apresentaram taxa de crescimento rápido em meio de cultura com manitol; 25 acidificaram o meio, cinco alcalinizaram e 14 não resultaram em modificação do pH. A capacidade de produzir sideróforos foi observada em 43% das estirpes e 16% foram capazes de solubilizar fosfato de cálcio em meio de cultura. O sequenciamento do gene 16S rRNA mostrou a formação de três principais grupos, correspondentes a três filos: Alfaproteobacteria, Betaproteobacteria e Firmicutes. O gênero com maior ocorrência foi o Bacillus

Desempenho de clones de Eucalyptus no oeste do Estado do Paraná.

Disponível em:

Gravitation: Global Formulation and Quantum Effects

A nonintegrable phase-factor global approach to gravitation is developed by using the similarity of teleparallel gravity with electromagnetism. The phase shifts of both the COW and the gravitational Aharonov-Bohm effects are obtained. It is then shown, by considering a simple slit experiment, that in the classical limit the global approach yields the same result as the gravitational Lorentz force equation of teleparallel gravity. It represents, therefore, the quantum mechanical version of the classical description provided by the gravitational Lorentz force equation. As teleparallel gravity can be formulated independently of the equivalence principle, it will consequently require no generalization of this principle at the quantum level.Comment: Latex (IOP style), 14 pages, 3 figures. To appear in Classical and Quantum Gravit

Trapped and excited w modes of stars with a phase transition and R>=5M

The trapped $w$-modes of stars with a first order phase transition (a density discontinuity) are computed and the excitation of some of the modes of these stars by a perturbing shell is investigated. Attention is restricted to odd parity (``axial'') $w$-modes. With $R$ the radius of the star, $M$ its mass, $R_{i}$ the radius of the inner core and $M_{i}$ the mass of such core, it is shown that stars with $R/M\geq 5$ can have several trapped $w$-modes, as long as $R_{i}/M_{i}<2.6$. Excitation of the least damped $w$-mode is confirmed for a few models. All of these stars can only exist however, for values of the ratio between the densities of the two phases, greater than $\sim 46$. We also show that stars with a phase transition and a given value of $R/M$ can have far more trapped modes than a homogeneous single density star with the same value of $R/M$, provided both $R/M$ and $R_{i}/M_{i}$ are smaller than 3. If the phase transition is very fast, most of the stars with trapped modes are unstable to radial oscillations. We compute the time of instability, and find it to be comparable to the damping of the $w$-mode excited in most cases where $w$-mode excitation is likely. If on the other hand the phase transition is slow, all the stars are stable to radial oscillations.Comment: To appear in Physical Review