190 research outputs found
Resonant phenomena in extended chaotic systems subject to external noise: the Lorenz'96 model case
We investigate the effects of a time-correlated noise on an extended chaotic
system. The chosen model is the Lorenz'96, a kind of "toy" model used for
climate studies. Through the analysis of the system's time evolution and its
time and space correlations, we have obtained numerical evidence for two
stochastic resonance-like behavior. Such behavior is seen when both, the usual
and a generalized signal-to-noise ratio function are depicted as a function of
the external noise intensity or the system size. The underlying mechanism seems
to be associated to a "noise-induced chaos reduction". The possible relevance
of these and other findings for an "optimal" climate prediction are discussed.Comment: Submitted to Europhysics Letters (LaTex, 12 pgs, 5 figures
Limit cycle induced by multiplicative noise in a system of coupled Brownian motors
We study a model consisting of nonlinear oscillators with {\em global
periodic} coupling and {\em local multiplicative} and additive noises. The
model was shown to undergo a nonequilibrium phase transition towards a
broken-symmetry phase exhibiting noise-induced "ratchet" behavior. A previous
study \cite{[7]} focused on the relationship between the character of
thehysteresis loop, the number of ``homogeneous'' mean-field solutions and the
shape of the stationary mean-field probability distribution function. Here we
show --as suggested by the absence of stable solutions when the load force is
beyond a critical value-- the existence of a limit cycle induced by
both:multiplicative noise and {\em global periodic} coupling.Comment: Submitted to Phys. Rev. E, RevTex, 18 pgs, 5 figure
The rise and fall of countries in the global value chains
Countries become global leaders by controlling international and domestic transactions connecting geographically dispersed production stages. We model global trade as a multi-layer network and study its power structure by investigating the tendency of eigenvector centrality to concentrate on a small fraction of countries, a phenomenon called localization transition. We show that the market underwent a significant drop in power concentration precisely in 2007 just before the global financial crisis. That year marked an inflection point at which new winners and losers emerged and a remarkable reversal of leading role took place between the two major economies, the US and China. We uncover the hierarchical structure of global trade and the contribution of individual industries to variations in countries’ economic dominance. We also examine the crucial role that domestic trade played in leading China to overtake the US as the world’s dominant trading nation. There is an important lesson that countries can draw on how to turn early signals of upcoming downturns into opportunities for growth. Our study shows that, despite the hardships they inflict, shocks to the economy can also be seen as strategic windows countries can seize to become leading nations and leapfrog other economies in a changing geopolitical landscape
Stochastic resonance between dissipative structures in a bistable noise-sustained dynamics
We study an extended system that without noise shows a monostable dynamics,
but when submitted to an adequate multiplicative noise, an effective bistable
dynamics arise. The stochastic resonance between the attractors of the
\textit{noise-sustained dynamics} is investigated theoretically in terms of a
two-state approximation. The knowledge of the exact nonequilibrium potential
allows us to obtain the output signal-to-noise ratio. Its maximum is predicted
in the symmetric case for which both attractors have the same nonequilibrium
potential value.Comment: RevTex, 13 pages, 6 figures, accepted in Physical Review
Use of anakinra in severe COVID-19: a case report
Coronavirus Disease 19 is a global healthcare emergency with high lethality rate. Relevant inflammatory cytokine storm is associated with severity of disease and IL1 inhibition is a cornerstone treatment for hyperinflammatory diseases. We present here the case of a patient with critical COVID-19 successfully treated with IL-1 receptor antagonist (anakinra)
Duration of quarantine in hospitalized patients with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection: a question needing an answer
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