4,463 research outputs found
Field sources in a Lorentz symmetry breaking scenario with a single background vector
This paper is devoted to investigating the interactions between stationary
sources of the electromagnetic field, in a model which exhibits explicit
Lorentz-symmetry breaking due to the presence of a single background vector. We
focus on physical phenomena that emerge from this kind of breaking and which
have no counterpart in Maxwell Electrodynamics
Treatment of bimodality in proficiency test of pH in bioethanol matrix
The pH value in bioethanol is a quality control parameter related to its
acidity and to the corrosiveness of vehicle engines when it is used as fuel. In
order to verify the comparability and reliability of the measurement of pH in
bioethanol matrix among some experienced chemical laboratories, reference
material (RM) of bioethanol developed by Inmetro - the Brazilian National
Metrology Institute - was used in a proficiency testing (PT) scheme. There was
a difference of more than one unit in the value of the pH measured due to the
type of internal filling electrolytic solutions (potassium chloride, KCl or
lithium chloride, LiCl) from the commercial pH combination electrodes used by
the participant laboratories. Therefore, bimodal distribution has occurred from
the data of this PT scheme. This work aims to present the possibilities that a
PT scheme provider can use to overcome the bimodality problem. Data from the PT
of pH in bioethanol were treated by two different statistical approaches:
kernel density model and the mixture of distributions. Application of these
statistical treatments improved the initial diagnoses of PT provider, by
solving bimodality problem and contributing for a better performance evaluation
in measuring pH of bioethanol.Comment: 20 pages, 6 figures, Accepted for publication in Accreditation and
Quality Assurance (ACQUAL
Generation of higher derivatives operators and electromagnetic wave propagation in a Lorentz-violation scenario
We study the perturbative generation of higher-derivative operators as
corrections to the photon effective action, which are originated from a Lorentz
violation background. Such corrections are obtained, at one-loop order, through
the proper-time method, using the zeta function regularization. We focus over
the lowest order corrections and investigate their influence in the propagation
of electromagnetic waves through the vacuum, in the presence of a strong,
constant magnetic field. This is a setting of experimental relevance, since it
bases active efforts to measure non linear electromagnetic effects. After
surprising cancellations of Lorentz violating corrections to the Maxwell's
equation, we show that no effects of the kind of Lorentz violation we consider
can be detected in such a context.Comment: v2: 13 pages, no figures, section IV considerably rewritten, main
results unchanged and are now obtained in a simpler way. To appear in PL
New point-like sources and a conducting surface in Maxwell-Chern-Simons electrodynamics
We investigate some aspects of the Maxwell-Chern-Simons electrodynamics
focusing on physical effects produced by the presence of stationary sources and
a perfectly conducting plate (mirror). Specifically, in addition to point
charges, we propose two new types of point-like sources called topological
source and Dirac point, and we also consider physical effects in various
configurations that involve them. We show that the Dirac point is the source of
the vortex field configurations. The propagator of the gauge field due to the
presence of a conducting plate and the interaction forces between the plate and
point-like sources are computed. It is shown that the image method is valid for
the point-like charges as well as for Dirac points. For the topological source
we show that the image method is not valid and the symmetry of spatial
refection on the mirror is broken. In all setups considered, it is shown that
the topological source leads to the emergence of torques.Comment: 17 Latex pages, 7 figure
Avaliação de feijoeiro com altos teores de minerais com e sem deficiência hídrica.
Com o objetivo de identficar genótipos de feijoeiro comum mais tolerantes à deficiência hídrica, foi conduzido este trabalho na Estação Experimental da Seagro, em Porangatu, GO
Solubility of Thiamine in Pure and Mixed Solvents in Function of Temperature
The present paper details the solid-liquid equilibrium (SLE) of thiamine in pure dimethylsulfoxide (DMSO) and aqueous solvent mixtures of varying DMSO concentrations. The solubilities were measured in the temperature range of 298.15 K to 323.15 K at 5.0 K intervals, under atmospheric pressure, by employing gravimetric analysis. The experimental results indicate that the vitamin’s solubility increases with increasing temperature and the water mass present in the initial solvent mixture. The adjustments using rational models were satisfactory, achieving adequate correlations and predicting the values of the solubility measurements in the laboratory with acceptable accuracy
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