Quantum Effects in the Spacetime of a Magnetic Flux Cosmic String

In this work we compute the vacuum expectation values of the energy-momentum tensor and the average value of a massive, charged scalar field in the presence of a magnetic flux cosmic string for both zero- and finite-temperature cases.Comment: To appear in the Int. Journal of Modern Phys. A (special issue). Proceedings of the Second International Londrina Winter School on Mathematical Methods in Physics, Londrina, Brazil, August 200

Contributions from Dilatonic Strings to the Flat Behaviour of the Rotational Curves in Galaxies

We analyse the flat behaviour of the rotational curves in some galaxies in the framework of a dilatonic, current-carrying string. We determine the expression of the tangential velocity of test objects following a stable circular equatorial orbit in this spacetime.Comment: This version to be published in the Int. Journal of Modern Phys.

Massive scalar field near a cosmic string

The $\zeta$ function of a massive scalar field near a cosmic string is computed and then employed to find the vacuum fluctuation of the field. The vacuum expectation value of the energy-momentum tensor is also computed using a point-splitting approach. The obtained results could be useful also for the case of self-interacting scalar fields and for the finite-temperature Rindler space theory.Comment: 15 pages, standard LaTeX, no figures. Reference [14] correcte

Carbon nanotube: a low-loss spin-current waveguide

We demonstrate with a quantum-mechanical approach that carbon nanotubes are excellent spin-current waveguides and are able to carry information stored in a precessing magnetic moment for long distances with very little dispersion and with tunable degrees of attenuation. Pulsed magnetic excitations are predicted to travel with the nanotube Fermi velocity and are able to induce similar excitations in remote locations. Such an efficient way of transporting magnetic information suggests that nanotubes are promising candidates for memory devices with fast magnetization switchings

Group theory analysis of electrons and phonons in N-layer graphene systems

In this work we study the symmetry properties of electrons and phonons in graphene systems as function of the number of layers. We derive the selection rules for the electron-radiation and for the electron-phonon interactions at all points in the Brillouin zone. By considering these selection rules, we address the double resonance Raman scattering process. The monolayer and bilayer graphene in the presence of an applied electric field are also discussed.Comment: 8 pages, 6 figure

The effect of pre-maturation culture using phosphodiesterase type 3 inhibitor and insulin, transferrin and selenium on nuclear and cytoplasmic maturation of bovine oocytes.

This study aims to evaluate if a pre-maturation culture (PMC) using cilostamide as a meiotic inhibitor in combination with insulin, transferrin and selenium (ITS) for 8 or 24 h increases in vitro embryo production. To evaluate the effects of PMC on embryo development, cleavage rate, blastocyst rate, embryo size and total cell number were determined. When cilostamide (20 M) was used in PMC for 8 or 24 h, 98% of oocytes were maintained in germinal vesicles. Although the majority of oocytes resumed meiosis after meiotic arrest, the cleavage and blastocyst rates were lower than the control (P 0.05) to the control. The deleterious effect of 20 M cilostamide treatment for 24 h on a PMC was confirmed by lower cumulus cell viability, determined by trypan blue staining, in that group compared with the other groups. A lower concentration (10 M) and shorter exposure time (8 h) minimized that effect but did not improve embryo production. More studies should be performed to determine th

Caracterização física e química de bananas orgânicas.

A banana apresenta importância social e econômica na dieta da população. A demanda por alimentos orgânicos vem crescendo ano a ano, tanto no Brasil como em outros países. Esse trabalho objetivou avaliar os atributos físicos e químicos de bananas orgânicas de diferentes cultivares. Os genótipos foram analisados quanto aos seguintes atributos físicos e físico-químicos: número de frutos por penca, diâmetro e comprimento do fruto, espessura da casca, massa do fruto com e sem casca, teor de sólidos solúveis totais, pH, acidez total titulável. Com exceção da cultivar Caipira, os genótipos apresentaram valores semelhantes ao dos cultivados em sistema convencional, para os atributos pH, acidez total, sólidos solúveis totais, embora com menor produção.pdf 248

Cosmic String Wakes in Scalar-Tensor Gravities

The formation and evolution of cosmic string wakes in the framework of a scalar-tensor gravity are investigated in this work. We consider a simple model in which cold dark matter flows past an ordinary string and we treat this motion in the Zel'dovich approximation. We make a comaprison between our results and previous results obtained in the context of General Relativity. We propose a mechanism in which the contribution of the scalar field to the evolution of the wakes may lead to a cosmological observation.Comment: Replaced version to be published in the Classical and Quantum Gravit