O desafio da previsão do comportamento fora-do-plano de edifícios existentes de alvenaria

O comportamento sísmico de estruturas existentes em alvenaria é muito condicionado pelo seu comportamento fora-do-plano, originando os chamados mecanismos locais, existindo diversas metodologias que tentam prever o comportamento deste tipo de estruturas e/ou modos de colapso. Este trabalho pretende resumir os principais resultados obtidos num evento subordinado ao tema “Methods and challenges on the out-of-plane assessment of existing masonry buildings”, inserido na 9th IMC (2014) em Guimarães, com o objectivo de prever o comportamento de duas estruturas em alvenaria utilizando métodos de análise correntemente utilizados na análise sísmica de estruturas existentes. Relativamente às estruturas estudadas, uma destas era materializada em alvenaria tradicional de pedra de dois panos, sendo a outra construída em alvenaria de tijolo. Estas estruturas foram ensaiadas à escala real na mesa sísmica do LNEC. No final do presente artigo apresentam-se os principais resultados obtidos com as simulações realizadas e sua comparação com o comportamento real das estruturas.The seismic behaviour of existing masonry buildings is governed by the out-of-plane behaviour in the form of the so-called local mechanisms. Despite recent advances within the area, there are several different methodologies to predict the behaviour of these local mechanisms. The article herein submitted aims to present the main results obtained on a workshop entitled “Methods and challenges on the out-of-plane assessment of existing masonry buildings”, within the 9th IMC (2014) held at Guimarães, with the objective of predict the behaviour of masonry structures making use of any available method for the seismic analysis. Regarding the studied structures, one was built on traditional doubleleaf stone masonry while the other was built on brick masonry, and they were tested at LNEC shaking table. The main conclusions are presented at the end of the article, namely the obtained results with the prediction and the observed experimental behavior

Are braneworlds born isotropic?

It has recently been suggested that an isotropic singularity may be a generic feature of brane cosmologies, even in the inhomogeneous case. Using the covariant and gauge-invariant approach we present a detailed analysis of linear perturbations of the isotropic model ${\cal F}_b$ which is a past attractor in the phase space of homogeneous Bianchi models on the brane. We find that for matter with an equation of state parameter $\gamma > 1$, the dimensionless variables representing generic anisotropic and inhomogeneous perturbations decay as $t\to 0$, showing that the model ${\cal F}_b$ is asymptotically stable in the past. We conclude that brane universes are born with isotropy naturally built-in, contrary to standard cosmology. The observed large-scale homogeneity and isotropy of the universe can therefore be explained as a consequence of the initial conditions if the brane-world paradigm represents a description of the very early universe.Comment: Changed to match published versio

Searching for Anomalous Higgs Couplings in Peripheral Heavy Ion Collisions at the LHC

We investigate the sensitivity of the heavy ion mode of the LHC to anomalous Higgs boson couplings to photons, H-photon-photon, through the analysis of the processes photon photon to b anti-b and photon photon to photon photon in peripheral heavy ion collisions. We suggest cuts to improve the signal over background ratio and determine the capability of LHC to impose bounds on anomalous couplings by searching for a Higgs boson signal in these modes.Comment: 10 pages, RevTeX, 4 figures included using epsfig, revised versio

Quantum corrected geodesics

We compute the graviton-induced corrections to the trajectory of a classical test particle. We show that the motion of the test particle is governed by an effective action given by the expectation value (with respect to the graviton state) of the classical action. We analyze the quantum corrected equations of motion for the test particle in two particular backgrounds: a Robertson Walker spacetime and a 2+1 dimensional spacetime with rotational symmetry. In both cases we show that the quantum corrected trajectory is not a geodesic of the background metric.Comment: LaTeX file, 15 pages, no figure

Back reaction in the formation of a straight cosmic string

A simple model for the formation of a straight cosmic string, wiggly or unperturbed is considered. The gravitational field of such string is computed in the linear approximation. The vacuum expectation value of the stress tensor of a massless scalar quantum field coupled to the string gravitational field is computed to the one loop order. Finally, the back-reaction effect on the gravitational field of the string is obtained by solving perturbatively the semiclassical Einstein's equations.Comment: 29 pages, LaTeX, no figures. A postcript version can be obtained from anonymous ftp at ftp://ftp.ifae.es/preprint.f

Development of SNPs markers (single nucleotide polymorphisms) presents in regulatory regions and genotyping of mapping population Hevea brasiliensis

The rubber tree (Hevea spp.), primary plant used for natural rubber production, have a long breeding cycle. However, the advent of molecular genetic markers favored early assessment methods, allowing the characterization of genotypes, genetic diversity analysis, QTL analysis and identifying genes of interest. In this context, this work aimed at the development and genotyping of new SNP markers presents in regulatory regions in two populations of genetic mapping of rubber tree. The raw data for each pool of samples (GT1 and RRIM701 genotypes) were separately trimmed and de novo assembled in a unique file using the CLC Genomics Workbench software (Version 6.0.1, CLC Bio, Denmark). Next, BWA aligned short reads back to assembled contigs, and Freebayes was used to perform variant calling and SNP detection. Using the varFilter command of vcfutils script, SNPs were filtered only for positions with a minimal mapping quality and coverage of 30 and 10 respectively. Unique and shared SNPs among the two cultivars were extracted with the VCFtools software. The selected SNPs annotation was made in two databases of cis regions: PLACE and ALGEEN-PROMO. Identification of SNP allelic forms was performed using KASPAR chemistry, either with PCR final point analysis on rtPCR equipment (LC480) for testing the polymorphism of the parents, or with Fluidigm technology for progeny genotyping. We obtained an average of 76% success rate in genotyping. The results will be used for saturation of molecular genetic map of H. brasiliensis, the location of these cis regions mutated on the map. (Résumé d'auteur

T and S dualities and The cosmological evolution of the dilaton and the scale factors

Cosmologically stabilizing radion along with the dilaton is one of the major concerns of low energy string theory. One can hope that T and S dualities can provide a plausible answer. In this work we study the impact of S and T duality invariances on dilaton gravity. We have shown various instances where physically interesting models arise as a result of imposing the mentioned invariances. In particular S duality has a very privileged effect in that the dilaton equations partially decouple from the evolution of the scale factors. This makes it easy to understand the general rules for the stabilization of the dilaton. We also show that certain T duality invariant actions become S duality invariance compatible. That is they mimic S duality when extra dimensions stabilize.Comment: Corrected a misleading interpretation of the S duality transformation and a wrong comment on d=10. I thank A.Kaya for pointing this out to me in time. So the new version is dealing with d=10 only. Added references and corrected some typos. Minor re-editing. Omitted a section for elaboration in a further study. Corrected further typo

Simple Dynamics on the Brane

We apply methods of dynamical systems to study the behaviour of the Randall-Sundrum models. We determine evolutionary paths for all possible initial conditions in a 2-dimensional phase space and we investigate the set of accelerated models. The simplicity of our formulation in comparison to some earlier studies is expressed in the following: our dynamical system is a 2-dimensional Hamiltonian system, and what is more advantageous, it is free from the degeneracy of critical points so that the system is structurally stable. The phase plane analysis of Randall-Sundrum models with isotropic Friedmann geometry clearly shows that qualitatively we deal with the same types of evolution as in general relativity, although quantitatively there are important differences.Comment: an improved version, 34 pages, 9 eps figure

Particle creation, classicality and related issues in quantum field theory: I. Formalism and toy models

The quantum theory of a harmonic oscillator with a time dependent frequency arises in several important physical problems, especially in the study of quantum field theory in an external background. While the mathematics of this system is straightforward, several conceptual issues arise in such a study. We present a general formalism to address some of the conceptual issues like the emergence of classicality, definition of particle content, back reaction etc. In particular, we parametrize the wave function in terms of a complex number (which we call excitation parameter) and express all physically relevant quantities in terms it. Many of the notions -- like those of particle number density, effective Lagrangian etc., which are usually defined using asymptotic in-out states -- are generalized as time-dependent concepts and we show that these generalized definitions lead to useful and reasonable results. Having developed the general formalism we apply it to several examples. Exact analytic expressions are found for a particular toy model and approximate analytic solutions are obtained in the extreme cases of adiabatic and highly non-adiabatic evolution. We then work out the exact results numerically for a variety of models and compare them with the analytic results and approximations. The formalism is useful in addressing the question of emergence of classicality of the quantum state, its relation to particle production and to clarify several conceptual issues related to this. In Paper II (arXiv:0708.1237), which is a sequel to this, the formalism will be applied to analyze the corresponding issues in the context of quantum field theory in background cosmological models and electric fields.Comment: RevTeX 4; 32 pages; 28 figures; first of a series of two papers, the second being arXiv:0708.1237 [gr-qc]; high resolution figures available from the authors on reques

Particle creation, classicality and related issues in quantum field theory: II. Examples from field theory

We adopt the general formalism, which was developed in Paper I (arXiv:0708.1233) to analyze the evolution of a quantized time-dependent oscillator, to address several questions in the context of quantum field theory in time dependent external backgrounds. In particular, we study the question of emergence of classicality in terms of the phase space evolution and its relation to particle production, and clarify some conceptual issues. We consider a quantized scalar field evolving in a constant electric field and in FRW spacetimes which illustrate the two extreme cases of late time adiabatic and highly non-adiabatic evolution. Using the time-dependent generalizations of various quantities like particle number density, effective Lagrangian etc. introduced in Paper I, we contrast the evolution in these two limits bringing out key differences between the Schwinger effect and evolution in the de Sitter background. Further, our examples suggest that the notion of classicality is multifaceted and any one single criterion may not have universal applicability. For example, the peaking of the phase space Wigner distribution on the classical trajectory \emph{alone} does not imply transition to classical behavior. An analysis of the behavior of the \emph{classicality parameter}, which was introduced in Paper I, leads to the conclusion that strong particle production is necessary for the quantum state to become highly correlated in phase space at late times.Comment: RevTeX 4; 27 pages; 18 figures; second of a series of two papers, the first being arXiv:0708.1233 [gr-qc]; high resolution figures available from the authors on reques