Radion stabilization from the vacuum on flat extra dimensions

Volume stabilization in models with flat extra dimension could follow from vacuum energy residing in the bulk when translational invariance is spontaneously broken. We study a simple toy model that exemplifies this mechanism which considers a massive scalar field with non trivial boundary conditions at the end points of the compact space, and includes contributions from brane and bulk cosmological constants. We perform our analysis in the conformal frame where the radion field, associated with volume variations, is defined, and present a general strategy for building stabilization potentials out of those ingredients. We also provide working examples for the interval and the $T^n/Z_2$ orbifold configuration.Comment: Comments and clarifications added throughout the text. Typos corrected and references added. Final version, 27 pages, five figures include

Bianchi Type I Cosmology in N=2, D=5 Supergravity

The dynamics and evolution of Bianchi type I space-times is considered in the framework of the four-dimensional truncation of a reduced theory obtained from the N=2,D=5 supergravity. The general solution of the gravitational field equations can be represented in an exact parametric form. All solutions have a singular behavior at the initial/final moment, except when the space-time geometry reduces to the isotropic flat case. Generically the obtained cosmological models describe an anisotropic, expanding or collapsing, singular Universe with a non-inflationary evolution for all times.Comment: revised version to appear in PR

Factors Promoting Inclusion and Success for Underrepresented High School Students in STEM

The focus of this study was to ascertain the best prac-tices and policies for school leaders in recruiting, sup-porting, and retaining underrepresented students in Sci-ence, Technology, Engineering and Mathematic (STEM) courses while encouraging STEM related career fields. This report synthesizes empirical research at two com-prehensive high schools in Northern California funded through a CSU Doctoral Research Fellowship. The policy implications from this study are central to promoting access and inclusion in STEM education and future career pathways. Schools need to market and advertise their STEM programs and begin recruiting within their school, particularly at the middle school level. It was clear from this research that the initial “curiosity” that is promoted by the STEM curriculum needs to be fostered so that stu-dents continue to be interested in STEM once they get to high school

First Order Actions: a New View

We analyse systems described by first order actions using the Hamilton-Jacobi (HJ) formalism for singular systems. In this study we verify that generalized brackets appear in a natural way in HJ approach, showing us the existence of a symplectic structure in the phase spaces of this formalism

Teste preliminar, in vitro, de microrganismos endofíticos para o controle de Cylindrocladium candelabrum e Botrytis cinerea.

Resumo

Flux-dynamics associated with the Second Magnetisation Peak in iron-pnictide Ba_{1-x}K_xFe_2As_2

We report on isofield magnetic relaxation data on a single crystal of $Ba_{1-x}K_xFe_2As_2$ with superconducting transition temperature $T_c$= 32.7 K which exhibit the so called fish-tail effect. A surface map of the superconducting transition temperature shows that the superconducting properties are close to homogeneous across the sample. Magnetic relaxation data, M(t), was used to obtain the activation energy U(M) in order to study different vortex dynamics regimes. Results of this analysis along with time dependent measurements as a function of field and temperature extended to the reversible region of some M(H) curves demonstrate that the irreversibility as well the second magnetization peak position, $H_p(T)$, are time dependent and controlled by plastic motion of the vortex state. In the region delimited by a characteristic field Hon (well below $H_p$), and $H_p$, the vortex dynamics is controlled by collective pinning. For fields below Hon the activation energy, $U_0$, increases with field as expected for collective pinning, but the pinning mechanism is likely to be in the single vortex limit.Comment: 8 pages, 8 figures, one tabl

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

Martírio: When the Kaiowa and Guarani Made Contact

Martírio: quando os Kaiowa e Guarani fizeram contatoMartírio: When the Kaiowa and Guarani Made Contac

Avaliação In Vitro de um Cimento de Ionômero de Vidro Restaurador para Colagem de Bráquetes Ortodônticos

Os materiais ionoméricos apresentam vantagens sobre os compósitos resinosos para a colagem dos bráquetes ortodônticos, tais como resistência de união dentro da faixa clinicamente ideal (6,5 a 10 MPa), facilidade de remoção e menor risco de lesão ao esmalte. O material ionomérico consagrado na literatura como padrão-ouro para colagem de bráquetes (Fuji ORTHO LC) é de difícil aquisição e custo elevado para ser utilizado rotineiramente. Desse modo, o objetivo deste estudo foi verificar in vitro o comportamento de um cimento de ionômero de vidro híbrido (CIV), indicado como material restaurador (Vitro Fil LC), ao ser empregado como material adesivo para a colagem de bráquetes ortodônticos. A amostra constou de 72 dentes pré-molares humanos extraídos, divididos em quatro grupos e submetidos aos mesmos procedimentos de colagem, com exceção do material adesivo. O CIV Vitro Fil LC foi manipulado de duas maneiras diferentes (grupo CIV1 e grupo CIV2) e comparado com o CIV Fuji ORTHO LC (grupo FO) e com o compósito resinoso Transbond XT (grupo XT). Foram avaliados: a resistência de união ao cisalhamento, o índice de remanescente adesivo (IRA) e a presença de fratura de esmalte após a descolagem. Houve diferença estatisticamente significativa entre as médias da resistência de união nos quatro grupos: XT (15,9 + 4,3 MPa), FO (13,0 + 2,6 MPa), CIV1 (10,1 + 1,9 MPa) e CIV2 (5,1 + 2,7 MPa). O IRA e a presença de fraturas foram estatisticamente semelhantes entre os três grupos XT, FO e CIV1. O comportamento do Grupo CIV2 em todas as avaliações sugere que a manipulação empregada neste grupo ocasiona falhas de adesão na interface esmalte/adesivo, o que inviabiliza sua utilização clínica. O grupo CIV1 mostrou resistência de união dentro da faixa clinicamente ideal e comportamento após a descolagem compatível com os materiais padrão-ouro em colagem de bráquetes, o que sugere boa possibilidade de aplicação clínica