The Hamilton-Jacobi Approach to Teleparallelism

We intend to analyse the constraint structure of Teleparallelism employing the Hamilton-Jacobi formalism for singular systems. This study is conducted without using an ADM 3+1 decomposition and without fixing time gauge condition. It can be verified that the field equations constitute an integrable system.Comment: 12 pages, no figur

Destruction of long-range antiferromagnetic order by hole doping

We study the renormalization of the staggered magnetization of a two-dimensional antiferromagnet as a function of hole doping, in the framework of the t-J model. It is shown that the motion of holes generates decay of spin waves into ''particle-hole'' pairs, which causes the destruction of the long-range magnetic order at a small hole concentration. This effect is mainly determined by the coherent motion of holes. The value obtained for the critical hole concentration, of a few percent, is consistent with experimental data for the doped copper oxide high-Tc superconductors.Comment: 12 pages, 2 figure

The canonical structure of Podolsky's generalized electrodynamics on the Null-Plane

In this work we will develop the canonical structure of Podolsky's generalized electrodynamics on the null-plane. This theory has second-order derivatives in the Lagrangian function and requires a closer study for the definition of the momenta and canonical Hamiltonian of the system. On the null-plane the field equations also demand a different analysis of the initial-boundary value problem and proper conditions must be chosen on the null-planes. We will show that the constraint structure, based on Dirac formalism, presents a set of second-class constraints, which are exclusive of the analysis on the null-plane, and an expected set of first-class constraints that are generators of a U(1) group of gauge transformations. An inspection on the field equations will lead us to the generalized radiation gauge on the null-plane, and Dirac Brackets will be introduced considering the problem of uniqueness of these brackets under the chosen initial-boundary condition of the theory

Tração animal: uma experiência piloto no Pará.

bitstream/item/58717/1/CPATU-Doc62.pd

SIEXP - descrição das variáveis experimentais para as culturas do trigo, triticale, centeio, cevada e canola.

Editores técnicos: Joseani Mesquita Antunes, Ana Lídia Variani Bonato, Márcia Barrocas Moreira Pimentel

The Teleparallel Lagrangian and Hamilton-Jacobi Formalism

We analyze the Teleparallel Equivalent of General Relativity (TEGR) from the point of view of Hamilton-Jacobi approach for singular systemsComment: 11 pages, no figures, to appear in GR

Vertebrate fauna at the Allosaurus fossil-site of Andrés (Upper Jurassic), Pombal, Portugal

An overview of the faunistic diversity of the Andres fossil-site from the Portuguese Upper Jurassic is presented. This work provides a preliminary approach on the vertebrate fauna known at present. Although this quarry is known since the 1990’s, due to the description on the first robust evidence of a member of the neotetanuran genus Allosaurus outside North America, the results presented here are mainly derived from the analysis of the elements found during the second and third field seasons in 2005. At the moment, among the material collected from Andrés it was identified remains that represent a diverse vertebrate fauna, including fishes, sphenodonts, crocodrylomorphs, pterosaurs, and at least, seven distinct dinosaur forms. The recovery of this diverse and abundant osteological collection from one unique fossil-site is noteworthy for the Upper Jurassic Portuguese record, and only comparable with those from the Guimarota coalmine. Due to these two features plus the good preservation of the fossils, the Andres quarry may be a site of reference for the analysis of vertebrate ecosystems from the Portuguese Upper Jurassic. Dinosaur elements are the most abundant fossils, and among them it is particulary common the presence of remains identified as Allosaurus. These new evidences allow testing the previus phylogenetical hypothesys ascribing the firsts theropod remains from Andrés to A. fragilis, a species described in synchronic levels of the North American Morrison Formation. The similarity between the Allosaurus remains collected in Andres and some specimens from the Morrison Formation seems to point the existence of a genetic flow between some continental vertebrates on both sides of the proto-north Atlantic during the Upper Jurassic. Favourable tectonic conditions for the occurrence of punctual contacts between the two continents is, at present, the best scenario for explain this situation.Se presenta un analisis de la diversidad faunistica del yacimiento de Andrés en el Jurasico Superior de la Cuenca Lusitanica. El presente trabajo pretende establecer un análisis preliminar de la fauna de vertebrados identificada en el yacimiento hasta la fecha. Aunque conocido desde la decada de 1990, debido a la descripcion de la primera evidencia robusta de un neotetanuro del genero Allosaurus fuera de Norteamerica, los resultados presentados derivan principalmente del analisis de elementos encontrados durante la segunda y tercera campanas de excavacion en 2005. Hasta el momento han sido identificados entre el material recogido en Andrés, representantes de diversos taxones de vertebrados que incluyen que incluyen peces, esfenodontos, crocodilomorfos, pterosaurios y, al menos, siete formas distintas de dinosaurios. La presencia de esta diversidad y abundancia de restos osteologicos en el mismo yacimiento representa una situacion unica en el registro del Jurasico Superior portugues, tan solo comparable a la del yacimiento clasico de la mina de carbon de Guimarota. Atendiendo a estas dos caracteristicas y a la buena preservacion de los fosiles, el yacimiento de Andres puede ser considerado como una localidad de referencia para el estudio de los ecosistemas con vertebrados del Jurasico Superior portugues. Los restos de dinosaurios son los fosiles mas abundantes y, entre ellos, son particularmente comunes los asignables a Allosaurus. Estas nuevas evidencias proporcionan a A. fragilis, una especie descrita en niveles sincronicos de la Formacion Morrison en Norteamerica. La similitud entre los restos de Allosaurus recogidos en Andres y algunos de los ejemplares de la Formacion Morrison, sugiere la existencia de un flujo genético entre algunos vertebrados continentales de ambos lados del proto-Atlántico norte durante el Jurásico Superior. La existencia de condiciones tectonicas favorables para la existencia de contactos puntuales entre los dos continentes es actualmente el mejor escenario para explicar esta situacion

Are coffee silverskin extracts safe for topical use? An in vitro and in vivo approach

Recent changes in regulatory requirements and social views on animal testing have incremented the development of reliable alternative tests for predicting skin and ocular irritation potential of products based on new raw materials. In this regard, botanical ingredients used in cosmetic products are among those materials, and should be carefully reviewed concerning the potential presence of irritant constituents. In particular, cosmetic products used on the face, in vicinity of the eyes or that may come in contact with mucous membranes, should avoid botanical ingredients that contain, or are suspected to contain, such ingredients. In this study, we aimed to evaluate the effect of a new cosmetic ingredient, namely, coffee silverskin (CS), with an in vitro skin and ocular irritation assay using reconstructed human epidermis, EpiSkin™, and human corneal epithelial model, SkinEthics™ HCE, and an in vivo assay. Three different extracts of CS were evaluated. The histology of the models after extracts applications was analysed. The in vitro results demonstrated that extracts were not classified as irritant and the histological analyses proved that extracts did not affect both models structure. The content of caffeine, 5-hydroxymethyl furfural and chlorogenic acid was quantified after the epidermal assay. The in vivo test carried out with the most promising extract (hydroalcoholic) showed that, with respect to irritant effects, these extracts can be regarded as safe for topical application