A 3-form Gauge Potential in 5D in connection with a Possible Dark Sector of 4D-Electrodynamics

We here propose a 5-dimensional {\bf Abelian gauge} model based on the mixing between a $U(1)$ potential and an Abelian 3-form field by means of a topological mass term. An extended covariant derivative is introduced to minimally couple a Dirac field to the $U(1)$ potential, while this same covariant derivative non-minimally couples the 3-form field to the charged fermion. A number of properties are discussed in 5D; in particular, the appearance of a topological fermionic current. A 4-dimensional reduced version of the model is investigated and, { \bf in addition to the $U(1)$ electric- and magnetic-sort of fields,} there emerges an extra set of electric- and magnetic-like fields which contribute a negative pressure and may be identified as a possible fraction of dark energy. The role of the topological fermionic current is also contemplated upon dimensional reduction from 5D to 4D. Other issues we present in 4 space-time dimensions are the emergence {\bf of a pseudo-scalar massive particle,} an extra massive neutral gauge boson,{\bf which we interpret as a kind of paraphoton}, and the calculation of spin- and velocity-dependent interparticle potentials associated to the exchange of the intermediate bosonic fields of the model.Comment: -- 30 pages -- L. P. R. Ospedal appears as a new co-author; modifications by inclusion of the gravitational sector and the attainment of a spin- and velocity-dependent potential as an application have been worked out in this Revised Versio

Ordenha higiênica de leite de cabra.

Passos para ordenha higiênica; Limpeza da sala de ordenha e dos vasilhames.bitstream/item/132809/1/ID-38686.pd

Noncommutative Metafluid Dynamics

In this paper we define a noncommutative (NC) Metafluid Dynamics \cite{Marmanis}. We applied the Dirac's quantization to the Metafluid Dynamics on NC spaces. First class constraints were found which are the same obtained in \cite{BJP}. The gauge covariant quantization of the non-linear equations of fields on noncommutative spaces were studied. We have found the extended Hamiltonian which leads to equations of motion in the gauge covariant form. In addition, we show that a particular transformation \cite{Djemai} on the usual classical phase space (CPS) leads to the same results as of the $\star$-deformation with $\nu=0$. Besides, we will shown that an additional term is introduced into the dissipative force due the NC geometry. This is an interesting feature due to the NC nature induced into model.Comment: 11 page

Hamiltonian symplectic embedding of the massive noncommutative U(1) Theory

We show that the massive noncommutative U(1) theory is embedded in a gauge theory using an alternative systematic way, which is based on the symplectic framework. The embedded Hamiltonian density is obtained after a finite number of steps in the iterative symplectic process, oppositely to the result proposed using the BFFT formalism. This alternative formalism of embedding shows how to get a set of dynamically equivalent embedded Hamiltonian densities.Comment: 16 pages, no figures, revtex4, corrected version, references additione

Channels and parameters acquisition in cooperative OFDM systems

CODIV, FP7/ICT/2007/215477CADWIN, PTDC/EEA – TEL/099241/2008Portuguese Foundation for Science and Technology (FCT

Satisfação com as práticas de gestão de recursos humanos e intenção de turn over num hotel de cinco estrelas: o papel mediador da perceção de suporte organizacional

Employees’ satisfaction with human resources management (HRM) practices has been envisaged as a solid predictor of turnover; nonetheless, how these practices may influence employee’s behavior is still an unclear process. There are suggestions that HRM practices may be distal determinants of turnover, as their effects may be mediated by more proximal variables such as perceived organizational support. This study empirically tested a model of research arising from these theoretical suggestions in a five-star hotel. The data collected from the survey of 152 workers were subjected to structural equation analyses. The results showed that the theoretical model had a strong fit to the data, giving empirical support to the prediction that satisfaction with HRM practices reduces turnover intentions, by increasing perceived organizational support. The importance of these results is discussed and interpreted from the point of view of strategic gains associated to the quality of HRM practices for the management of voluntary turnover.info:eu-repo/semantics/publishedVersio

Involvement of a cinnamyl alcohol dehydrogenase of Quercus suber in the defence response to infection by Phytophthora cinnamomi

A gene encoding a potential NADPH-dependent cinnamyl alcohol dehydrogenase (QsCAD1) (GenBank accession no: AY362455) was identified in Quercus suber (cork oak). Its complete cDNA sequence was obtained by RACE-PCR, starting from total RNA extracted from roots of seedlings of Q. suber, infected with Phytophthora cinnamomi, the causal agent of the decline and sudden death of Q. suber and Quercus ilex subsp. rotundifolia in the Iberian Peninsula. Sequence information to perform the RACE-PCR was acquired from a polymorphic fragment (C9), specifically identified by cDNA-AFLP, in leaves of epicormic shoots of a cork oak tree that suffered sudden death. RT-PCR and hybridization analysis showed that the QsCAD1 gene is up-regulated in root seedlings of Q. suber infected with P. cinnamomi. QsCAD1 has a high structural homology with VR-ERE (Vigna radiata), an enzyme that detoxifies eutypine (produced by Eutypa lata, the causal agent of eutypa dieback of grapevines), to eutypinol, and with QrCAD1 (Q. ilex subsp. rotundifolia), EgCAD1 (Eucalyptus gunnii), MdCAD1 (Malus x domestica). Taken together, these results suggest that these enzymes, and namely QsCAD1 belong to a new group of CAD potentially involved in deactivation of toxins produced by phytopathogens