Giacomo Raffaelli

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Large conductance calcium- and voltage-activated potassium channels (BK channels) activate in response to calcium influx during action potentials and contribute to the spike repolarization and fast afterhyperpolarization. BK channels targeted to active zones in presynaptic nerve terminals have been shown to limit calcium entry and transmitter release by(More)
We study time series concerning rare events. The occurrence of a rare event is depicted as a jump of constant intensity always occurring in the same direction, thereby generating an asymmetric diffusion process. We consider the case where the waiting time distribution is an inverse power law with index μ. We focus our attention on μ < 3, and we evaluate the(More)
Paired recordings between CA3 interconnected pyramidal neurons were used to study the properties of short-term depression occurring in these synapses under different frequencies of presynaptic firing (n = 22). In stationary conditions (0.05-0.067 Hz) pairs of presynaptic action potentials (50 ms apart) evoked EPSCs whose amplitude fluctuated from trial to(More)
We describe two types of memory and illustrate each using artificial and actual heartbeat data sets. The first type of memory, yielding anomalous diffusion, implies the inverse power-law nature of the waiting time distribution and the second the correlation among distinct times, and consequently also the occurrence of many pseudoevents, namely, not(More)
We analyze RR heartbeat sequences with a dynamic model that satisfactorily reproduces both the long- and the short-time statistical properties of heart beating. These properties are expressed quantitatively by means of two significant parameters, the scaling delta concerning the asymptotic effects of long-range correlation, and the quantity 1-pi(More)
The statistical properties of pairwise majority voting over S alternatives are analyzed in an infinite random population. We first compute the probability that the majority is transitive (i.e., that if it prefers A to B to C , then it prefers A to C) and then study the case of an interacting population. This is described by a constrained multicomponent(More)
P. Allegrini, P. Grigolini, P. Hamilton, L. Palatella, G. Raffaelli 1 Istituto di Linguistica Computazionale del Consiglio Nazionale delle Ricerche, Area della Ricerca di Pisa-S. Cataldo, Via Moruzzi 1, 56124, Ghezzano-Pisa, Italy Center for Nonlinear Science, University of North Texas, P.O. Box 311427, Denton, Texas, 76203-1427 Dipartimento di Fisica(More)
We analize heartbeat time-series corresponding to several groups of individuals (healthy, heart transplanted, with congestive heart failure (CHF), after myocardial infarction (MI), hypertensive), looking for shortand long-time statistical behaviors. In particular we study the persistency patterns of interbeat times and interbeat-time variations. Long-range(More)
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