Klein-Gordon oscillator in a topologically nontrivial space-time

In this study, we analyze solutions of the wave equation for scalar particles in a space-time with nontrivial topology. Solutions for the Klein--Gordon oscillator are found considering two configurations of this space-time. In the first one, it is assumed the $S^{1}\times R^{3}$ space where the metric is written in the usual inertial frame of reference. In the second case, we consider a rotating reference frame adapted to the circle S1. We obtained compact expressions for the energy spectrum and for the particles wave functions in both configurations. Additionally, we show that the energy spectrum of the solution associated to the rotating system has an additional term that breaks the symmetry around $E = 0$

Momentum Space Regularizations and the Indeterminacy in the Schwinger Model

We revisited the problem of the presence of finite indeterminacies that appear in the calculations of a Quantum Field Theory. We investigate the occurrence of undetermined mathematical quantities in the evaluation of the Schwinger model in several regularization scenarios. We show that the undetermined character of the divergent part of the vacuum polarization tensor of the model, introduced as an {\it ansatz} in previous works, can be obtained mathematically if one introduces a set of two parameters in the evaluation of these quantities. The formal mathematical properties of this tensor and their violations are discussed. The analysis is carried out in both analytical and sharp cutoff regularization procedures. We also show how the Pauli Villars regularization scheme eliminates the indeterminacy, giving a gauge invariant result in the vector Schwinger model.Comment: 10 pages, no figure

Phase Transition and Monopoles Densities in a Nearest Neighbors Two-Dimensional Spin Ice Model

In this work, we show that, due to the alternating orientation of the spins in the ground state of the artificial square spin ice, the influence of a set of spins at a certain distance of a reference spin decreases faster than the expected result for the long range dipolar interaction, justifying the use of the nearest neighbor two dimensional square spin ice model as an effective model. Using an extension of the model presented in ref. [Scientific Reports 5, 15875 (2015)], considering the influence of the eight nearest neighbors of each spin on the lattice, we analyze the thermodynamics of the model and study the monopoles and string densities dependence as a function of the temperature.Comment: 11 pages, 8 figure

Editorial: Special Issue contributed by the 10th International Chemical and Biological Engineering Conference - CHEMPOR 2008

The 10th International Chemical and Biological Engineering Conference - CHEMPOR 2008, was held in Braga, Portugal, from the 4th to the 6th of September, 2008. The conference was jointly organized by the University of Minho, the “Ordem dos Engenheiros,” and the Institute for Biotechnology and Bioengineeing, with the support of “Sociedade Portuguesa de Qu´ımica” and “Sociedade Portuguesa de Biotecnologia”. The CHEMPOR series traditionally brings together both young and established researchers and end users to discuss recent developments in different areas of Chemical Engineering. The scope of this edition was extended to Biological Engineering research. One of the major core areas of the conference program was life quality, due to the importance that Chemical and Biological Engineering plays in this area. “Integration of Life Sciences & Engineering” and “Sustainable Process-Product Development through Green Chemistry” were two of the leading themes with papers addressing such important issues. This was complemented with additional leading themes including “Advancing the Chemical and Biological Engineering Fundamentals,” “Multi-Scale and/or Multi-Disciplinary Approach to Process-Product Innovation”, “Systematic Methods and Tools for Managing the Complexity”, and “Educating Chemical and Biological Engineers for Coming Challenges.” Papers contributed for this special issue represent a good sample of the important themes that were addressed. This special issue presents a set of fifteen selected research papers, which have undergone the peer-review process of Chemical Product and Process Modeling journal. We wish to thank the authors who have contributed to yield a high scientific standard to this special issue. We also extend our gratefulness to all reviewers, through their dedicated efforts, having assisted us in this task.Uminho -Universidade do Minh

Application of image analysis techniques in biotechnology

Image analysis is commonly used nowadays in a wide range of applications due to the development of faster computers, advanced frame grabbers, and sophisticated software. Although the availability of commercial sophisticated software some efforts have been made at CEB-IBQF in software development using MATLAB programming environment. This programming approach permits to tailor the software to our specific needs. In-house software currently in use and development include: automatic differentiation of flocs and granules through fractal dimension; monitoring methanogenic auto-fluorescence; determination of the reduction in mobility of ciliates exposed to toxics; automatic quantification of filamentous bacteria; automatic counting of viable/non-viable yeasts by epifluorescence microscopy with acridine orange as dying agent. Other developments cover automatic determination of the number of yeast flocs and their size distribution, dynamics of bacterial adhesion, estimation of the tortuosity of porous media, and automatic detection, counting of ink spots in recycled paper simultaneous and monitoring of lactic acid bacteria and yeast during Vinho Verde fermentation using phase contrast microscopy coupled to image analysis