9,734 research outputs found
Phenomenological Renormalization Group Methods
Some renormalization group approaches have been proposed during the last few
years which are close in spirit to the Nightingale phenomenological procedure.
In essence, by exploiting the finite size scaling hypothesis, the approximate
critical behavior of the model on infinite lattice is obtained through the
exact computation of some thermal quantities of the model on finite clusters.
In this work some of these methods are reviewed, namely the mean field
renormalization group, the effective field renormalization group and the finite
size scaling renormalization group procedures. Although special emphasis is
given to the mean field renormalization group (since it has been, up to now,
much more applied an extended to study a wide variety of different systems) a
discussion of their potentialities and interrelations to other methods is also
addressed.Comment: Review Articl
Energy barrier distributions for magnetic nanoparticles with competing cubic and uniaxial anisotropies
AbstractWe report in this study the effect of the competition between cubic and uniaxial anisotropies on the magnetic properties of magnetic nanoparticles. We have employed Monte Carlo simulations in our calculations and we have seen that the observed behavior is very different for the cases where easy uniaxial axes are completely random oriented or parallel to an external magnetic field. We have also calculated the effective energy barrier distribution probed during the isothermal magnetic relaxation and a two peak structure is observed only for a random orientation of uniaxial axes
Emergence of chaos in interacting communities
We introduce a simple dynamical model of two interacting communities whose
elements are subject to stochastic discrete-time updates governed by only
bilinear interactions. When the intra- and inter-couplings are cooperative, the
two communities reach asymptotically an equilibrium state. However, when the
intra- or inter-couplings are anti-cooperative, the system may remain in
perpetual oscillations and, when the coupling values belong to certain
intervals, two possible scenarios arise, characterized either by erratic
aperiodic trajectories and high sensitiveness to small changes of the
couplings, or by chaotic trajectories and bifurcation cascades. Quite
interestingly, we find out that even a moderate consensus in one single
community can remove the chaos. Connections of the model with interacting stock
markets are discussed.Comment: 6 pages, 4 figure
Thermal vortex dynamics in thin circular ferromagnetic nanodisks
The dynamics of gyrotropic vortex motion in a thin circular nanodisk of soft
ferromagnetic material is considered. The demagnetization field is calculated
using two-dimensional Green's functions for the thin film problem and fast
Fourier transforms. At zero temperature, the dynamics of the
Landau-Lifshitz-Gilbert equation is simulated using fourth order Runge-Kutta
integration. Pure vortex initial conditions at a desired position are obtained
with a Lagrange multipliers constraint. These methods give accurate estimates
of the vortex restoring force constant and gyrotropic frequency, showing
that the vortex core motion is described by the Thiele equation to very high
precision. At finite temperature, the second order Heun algorithm is applied to
the Langevin dynamical equation with thermal noise and damping. A spontaneous
gyrotropic motion takes place without the application of an external magnetic
field, driven only by thermal fluctuations. The statistics of the vortex radial
position and rotational velocity are described with Boltzmann distributions
determined by and by a vortex gyrotropic mass ,
respectively, where is the vortex gyrovector.Comment: 18 pages, 17 figure
Suppression of Fusarium moniforme by Streptomyces spp. isolates in relation to dose- response relationship
Suplemento. Edição do IX International Congress of Plant Pathology, 2008, Torino. Abstracts on invited and offered papers
Seed treatment with Streptomyces spp. strains inhibit Colletotrichum Sublineolum in sorghum seed.
Controle de Fusarium moniliforme em sementes de milho por actinomicetos.
bitstream/CNPMS/16146/1/Com_65.pd
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