117 research outputs found
A fluctuating environment as a source of periodic modulation
We study the intermittent fluorescence of a single molecule, jumping from the
"light on" to the "light off" state, as a Poisson process modulated by a
fluctuating environment. We show that the quasi-periodic and
quasi-deterministic environmental fluctuations make the distribution of the
times of sojourn in the "light off" state depart from the exponential form, and
that their succession in time mirrors environmental dynamics. As an
illustration, we discuss some recent experimental results, where the
environmental fluctuations depend on enzymatic activity.Comment: 13 pages, 4 figures. Accepted for publication on Chem. Phys. Let
Renewal, Modulation and Superstatistics
We consider two different proposals to generate a time series with the same
non-Poisson distribution of waiting times, to which we refer to as renewal and
modulation. We show that, in spite of the apparent statistical equivalence, the
two time series generate different physical effects. Renewal generates aging
and anomalous scaling, while modulation yields no aging and either ordinary or
anomalous diffusion, according to the prescription used for its generation. We
argue, in fact, that the physical realization of modulation involves critical
events, responsible for scaling. In conclusion, modulation rather than ruling
out the action of critical events, sets the challenge for their identification
Fluorescence intermittency in blinking quantum dots: renewal or slow modulation?
We study time series produced by the blinking quantum dots, by means of an
aging experiment, and we examine the results of this experiment in the light of
two distinct approaches to complexity, renewal and slow modulation. We find
that the renewal approach fits the result of the aging experiment, while the
slow modulation perspective does not. We make also an attempt at establishing
the existence of an intermediate condition.Comment: 27 pages, 8 figures. Accepted for pubblication on Journal of Chemical
Physic
Fractal Complexity in Spontaneous EEG Metastable-State Transitions: New Vistas on Integrated Neural Dynamics
Resting-state EEG signals undergo rapid transition processes (RTPs) that glue otherwise stationary epochs. We study the fractal properties of RTPs in space and time, supporting the hypothesis that the brain works at a critical state. We discuss how the global intermittent dynamics of collective excitations is linked to mentation, namely non-constrained non-task-oriented mental activity
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