4,768 research outputs found
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 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
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
- …