4,288 research outputs found
Antibiotic consumption in Portugal: 2010 and 2011
The use of antibiotics has contributed to
a marked decrease in morbidity caused by communicable and infec-
tious diseases over the past few years.
The aim of our study is to evaluate the use of antibiotics in clinic
in 2010 and 2011, considering two different methodologies: the
defined daily dose per 1000 inhabitants per day (DHD) and the
number of packages per 1000 inhabitants per day (PHD)
A new approach on the stability analysis in ELKO cosmology
In this work it has been developed a new approach to study the stability of a
system composed by an ELKO field interacting with dark matter, which could give
some contribution in order to alleviate the cosmic coincidence problem. It is
assumed that the potential which characterizes the ELKO field is not specified,
but it is related to a constant parameter . The strength of the
interaction between matter and ELKO field is characterized by a constant
parameter and it is also assumed that both ELKO field as matter energy
density are related to their pressures by equations of state parameters
and , respectively. The system of equations is analysed
by a dynamical system approach. It has been found the conditions of stability
between the parameters and in order to have stable fixed
points for the system for different values of the equation of state parameters
and , and the results are presented in form of tables.
The possibility of decay of ELKO field into dark matter or vice versa can be
read directly from the tables, since the parameters and
satisfy some inequalities. It allows us to constrain the potential assuming
that we have a stable system for different interactions terms between the ELKO
field and dark matter. The cosmic coincidence problem can be alleviated for
some specific relations between the parameters of the model.Comment: 16 pages, some new comments in the Introduction and at the begining
of Section I
Critical behavior of an Ising model with aperiodic interactions
We write exact renormalization-group recursion relations for a ferromagnetic
Ising model on the diamond hierarchical lattice with an aperiodic distribution
of exchange interactions according to a class of generalized two-letter
Fibonacci sequences. For small geometric fluctuations, the critical behavior is
unchanged with respect to the uniform case. For large fluctuations, the uniform
fixed point in the parameter space becomes fully unstable. We analyze some
limiting cases, and propose a heuristic criterion to check the relevance of the
fluctuations.Comment: latex file, 5 figures, accepted by Braz. Jour. Phy
Steady flow of power-law fluids in a 1:3 planar sudden expansion
The laminar flow of inelastic non-Newtonian fluids, obeying the power-law model, through a planar sudden expansion with a 1:3 expansion ratio was investigated numerically using a finite volume method. A broad range of power-law indices in the range 0.2 n 4 was considered. Shear-thinning, Newtonian and shear-thickening fluids are analyzed, with particular emphasis on the flow patterns and bifurcation phenomenon occurring at high Reynolds number laminar flows. The effect of the generalized Reynolds numbers (based on power-law index, n, and the in flow channel height, h) on the main vortex characteristics and Couette correction are examined in detail in the range varying from 0.01 Regen 600. Values for the critical generalized Reynolds number for the onset of steady flow asymmetry and the appearance of a third main vortex are also included. We found that the shear-thinning behavior increases the critical Regen, while shear-thickening has the opposite effect. Comparison with available literature and with predictions using a commercial software (FluentR 6.3.26) are also presented and discussed. It was found that both results are in good agreement, but that our code is able to achieve converged solution for a broader range of flow conditions, providing new benchmark quality data
Critical exponents for the long-range Ising chain using a transfer matrix approach
The critical behavior of the Ising chain with long-range ferromagnetic
interactions decaying with distance , , is investigated
using a numerically efficient transfer matrix (TM) method. Finite size
approximations to the infinite chain are considered, in which both the number
of spins and the number of interaction constants can be independently
increased. Systems with interactions between spins up to 18 sites apart and up
to 2500 spins in the chain are considered. We obtain data for the critical
exponents associated with the correlation length based on the Finite
Range Scaling (FRS) hypothesis. FRS expressions require the evaluation of
derivatives of the thermodynamical properties, which are obtained with the help
of analytical recurrence expressions obtained within the TM framework. The Van
den Broeck extrapolation procedure is applied in order to estimate the
convergence of the exponents. The TM procedure reduces the dimension of the
matrices and circumvents several numerical matrix operations.Comment: 10 pages, 2 figures, Conference NEXT Sigma Ph
Some remarks on the attractor behaviour in ELKO cosmology
Recent results on the dynamical stability of a system involving the
interaction of the ELKO spinor field with standard matter in the universe have
been reanalysed, and the conclusion is that such system does not exhibit
isolated stable points that could alleviate the cosmic coincidence problem.
When a constant parameter related to the potential of the ELKO field
is introduced in the system however, stable fixed points are found for some
specific types of interaction between the ELKO field and matter. Although the
parameter is related to an unknown potential, in order to satisfy the
stability conditions and also that the fixed points are real, the range of the
constant parameter can be constrained for the present time and the
coincidence problem can be alleviated for some specific interactions. Such
restriction on the ELKO potential opens possibility to apply the ELKO field as
a candidate to dark energy in the universe, and so explain the present phase of
acceleration of the universe through the decay of the ELKO field into matter.Comment: 17 pages, section III with minor changes and section IV rewritten
with a new analysi
A micromechanical model for kink-band formation: Part I - Experimental study and numerical modelling
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