Quasinormal modes of a black hole with a cloud of strings in Einstein-Gauss-Bonnet gravity

The quasinormal modes for a scalar field in the background spacetime corresponding to a black hole, with a cloud of strings, in Einstein-Gauss-Bonnet gravity, and the tensor quasinormal modes corresponding to perturbations in such spacetime, were both calculated using the WKB approximation. In the obtained results we emphasize the role played by the parameter associated with the string cloud, comparing them with the results already obtained for the Boulware-Deser metric. We also study how the Gauss-Bonnet correction to general relativity affects the results for the quasinormal modes, comparing them with the same background in general relativity.Comment: 15 pages, 7 figures; To appear in IJMP

Tuning edge state localization in graphene nanoribbons by in-plane bending

The electronic properties of graphene are influenced by both geometric confinement and strain. We study the electronic structure of in-plane bent graphene nanoribbons, systems where confinement and strain are combined. To understand its electronic properties, we develop a tight-binding model that has a small computational cost and is based on exponentially decaying hopping and overlap parameters. Using this model, we show that the edge states in zigzag graphene nanoribbons are sensitive to bending and develop an effective dispersion that can be described by a one-dimensional atomic chain model. Because the velocity of the electrons at the edge is proportional to the slope of the dispersion, the edge states become gradually delocalized upon increasing the strength of bending.Comment: 11 pages, 8 figure

Identification and Characterization of the Transcriptional Regulator ChrB in the Chromate Resistance Determinant of Ochrobactrum tritici 5bvl1

Ochrobactrum tritici 5bvl1 is able to resist to high concentrations of chromate through the expression of an inducible chromate-resistant determinant, found in a mobile element (TnOtChr), which carries the genes, chrB, chrA, chrC and chrF. The regulation of chr operon present in TnOtChr, which is controlled by a transcriptional regulator, ChrB, was characterized in the current work. Fusions of chr promoter, or chr promoter and chrB gene, upstream of a gfp reporter gene, identified the most probable promoter sequence within the tnpR-chrB intergenic region. This region contains an AT-rich imperfect inverted repeat sequence, which overlaps a part of the 210 sequence. The results of the in vitro DNA-binding assays with purified ChrB (His- or no-tagged) showed that the protein binds directly to the chr promoter region. In order to identify the ChrB functional domain for sensing chromate stress and for DNA-binding, site-directed mutagenesis of ChrB was performed. Among several single amino acid mutants, three mutants (R180; R187 and H229) prevented chromate induction without any modification to the protein’s stability. Interestingly, two ChrB mutants (R18 and R23) were constitutively active, regardless of chromate stress conditions, indicating that the residues most probably belong to the protein-DNA binding site. As such, the ChrB was classified as a transcriptional regulator that recognizes a specific DNA sequence, regulating the expression of a chromate resistance determinant.This work was funded by Fundação para a Ciência e Tecnologia (FCT) under the PTDC/MAR/109057/2008 project. Rita Branco was supported by a grant, SFRH/BPD/48330/2008, from FCT

Seleção de linhagens-elite de arroz de terras altas para a região norte do Estado de Mato Grosso.

Este trabalho foi realizado com o objetivo de avaliar o desempenho das linhagens geradas pelo programa de melhoramento genético da Embrapa nos ensaios de valor de cultivo e uso (VCU), na região norte do estado de Mato Grosso

Thin Films for Medical and Environmental Applications

A material that presents both the appropriate set of bulk properties in conjunction with an optimal surface performance is hardly found. For this reason, there is the need of modifying its surface. This is a standard procedure in many application fields but particularly important in the medical and environmental research. In this chapter, we describe the use of sputtering, as the chosen technology for the deposition of thin films. The use of the modified surfaces in the medical and environmental fields will be highlighted by two case studies in each one. In biomedicine, the surface modification of medical invasive devices for orthopedic and neural applications will be presented. For the environmental aspect, the results of two bioremediation tools, for arsenic and uranium removal, based on the immobilization of bacterial cells will be discussed

Turbidimetric and nephelometric flow analysis$econcepts and applications

A review on flow analysis with turbidimetric and nephelometric detection is presented. A brief discussion of the principles of turbidimetry and nephelometry is given. Particular emphasis is devoted to coupling different flow techniques (flow injection, sequential injection, multicommutation) to these detection techniques. Applications in environmental, pharmaceutical, biological, and food samples are summarized and compared in terms of application range, flow configuration, repeatability, and sampling rate