Consistent Gravitationally-Coupled Spin-2 Field Theory

Inspired by the translational gauge structure of teleparallel gravity, the theory for a fundamental massless spin-2 field is constructed. Accordingly, instead of being represented by a symmetric second-rank tensor, the fundamental spin-2 field is assumed to be represented by a spacetime (world) vector field assuming values in the Lie algebra of the translation group. The flat-space theory naturally emerges in the Fierz formalism and is found to be equivalent to the usual metric-based theory. However, the gravitationally coupled theory, with gravitation itself described by teleparallel gravity, is shown not to present the consistency problems of the spin-2 theory constructed on the basis of general relativity.Comment: 16 pages, no figures. V2: Presentation changes, including addition of a new sub-section, aiming at clarifying the text; version accepted for publication in Class. Quantum Grav

Validation of High-Fidelity Numerical Simulations of Acoustic Liners Under Grazing Flow

High-fidelity numerical simulations with the lattice-Boltzmann method are carried out to characterize the response of an acoustic liner in the presence and in the absence of grazing flow. The liner’s impedance is numerically computed with different methods, i.e. in-situ, mode matching and Prony-like Kumaresan-Tufts, and the results are compared against experimental data, measured in the Federal University of Santa Catarina (UFSC) liner test rig, and the Goodrich semiempirical model. The no-flow results show a reasonable agreement with the semiempirical model but some differences with respect to the experimental educed results are present. It is found that, even in the absence of grazing flow, when applying the in-situ method, there are large variations of the local impedance depending on the sampling location on the face sheet. In presence of grazing flow, simulations with acoustic plane wave propagating in the same direction and in the direction opposite to the mean flow are carried out. Results show that, with the current grid resolution, the numerical educed impedance still overestimates the experimental one particularly at low frequencies, while better agreement is obtained with the in-situ numerical estimation, for both cases. The effects of the grazing flow on the local impedance measurements show high influence of near-orifice wake development. A drastic reduction of the effective percentage of open area is observed when there is grazing flow, as a result of the formation of vortices in the orifices of the liner

Exclusive Breastfeeding After 40 Years of Age – Where Are We Going?

info:eu-repo/semantics/publishedVersio

Hodge Dual for Soldered Bundles

In order to account for all possible contractions allowed by the presence of the solder form, a generalized Hodge dual is defined for the case of soldered bundles. Although for curvature the generalized dual coincides with the usual one, for torsion it gives a completely new dual definition. Starting from the standard form of a gauge lagrangian for the translation group, the generalized Hodge dual yields precisely the lagrangian of the teleparallel equivalent of general relativity, and consequently also the Einstein-Hilbert lagrangian of general relativity.Comment: 8 pages, no figures. Accepted for publication in Journal of Physics

Severidade da queima das folhas e quantificação de fenóis solúveis totais e lagnina solúveil em cultivares de cenoura.

O objetivo deste trabalho foi avaliar a severidade da doença em cultivares tradicionais de cenoura (Brasília, BRS Planalto, Juliana, BRS Esplanada, Branca Lunar, Amarela Solar e Londrina) em campo, bem com quantificar as concentrações de fenóis solúveis totais e lignina solúvel nas folhas.Resumo 1265

Speed and power predictors of change of direction ability in elite snow athletes

Change of direction ability (COD speed) is an important physical component of snow sports. The aim of this study was to investigate the relationships between regular speed and vertical jumping ability, and COD speed in elite snow athletes. Moreover, the correlations between relative mean propulsive power (assessed in the jump squat exercise) and COD speed were quantified. Sixteen elite snow sport athletes executed squat jumps, countermovement jumps, jump squats, and 25 m sprint tests, in addition to a Zig-zag change of direction speed test. The outcomes revealed that vertical jumping height and mean propulsive power are strongly correlated (r ≈ 0.90) with COD speed. Furthermore, snow athletes capable of sprinting faster in a linear course of 25 m performed better in COD speed tests ( r = 0.91). Our results support the use of loaded and unloaded vertical jumping and regular speed tests to evaluate/monitor predictors of COD speed in elite snow athletes. Finally, these relationships suggest that plyometrics and regular speed training should be considered by coaches as effective strategies to enhance COD ability in this specific group of subjects