Biomedical subjects

A A Minzoni

Publications and source records attributed to A A Minzoni.

3 recordsLinked to original sources

PubMed2006

Evolution of Benjamin-Ono solitons in the presence of weak Zakharov-Kutznetsov lateral dispersion.

The effect of weak lateral dispersion of Zakharov-Kutznetsov-type on a Benjamin-Ono solitary wave is studied both asymptotically and numerically. The asymptotic solution is based on an approximate variational solution for the solitary wave, which is then modulated in time through the use of conservation equations. The effect of the dispersive radiation shed as the solitary wave evolves is also included in the modulation equations. It is found that the weak lateral dispersion produces a strongly anisotropic, stable solitary wave which decays algebraically in the direction of propagation, as for the Benjamin-Ono solitary wave, and exponentially in the transverse direction. Moreover, it is found that initial conditions with amplitude above a threshold evolve into solitary waves, while those with amplitude below the threshold evolve as lumps for a short time, then merge into radiation. The modulation equations are found to give a quantitatively accurate description of the evolution of an initial condition into an anisotropic solitary wave. The existence of stable solitary waves is in contrast to previous studies of Benjamin-Ono-type equations subject to the stronger Kadomstev-Petviashvili or Benjamin-Ono-type lateral dispersion, for which the solitary waves either decay or collapse. The present study then completes the catalog of possible behaviors under lateral dispersion.

Journal Article↗

PubMed1991

Modulated long-term potentiation in the cat superior cervical ganglion in vivo.

In the sympathetic ganglion a high frequency conditioning train produces a post-train potentiation (PTrP) which decays with a temporal course that can be described by two components: an early faster component known as post-tetanic potentiation (PTP), and a long-lasting one which is known as long-term potentiation (LTP). The magnitude of PTP and LTP is thought to be a function of the subliminal fringe size. Moreover, under full activation of ganglion cells LTP does not appear due to the saturation conditions. LTP emerges only when the subliminal fringe is increased, and to achieve this, a low-level tetanization must be performed. However, another possibility, explored in this paper, is that in addition to the desaturation effect of the low-level conditions of tetanization, a different mechanism, responsible for the LTP appearance, may be introduced by these low-level conditions of tetanization. This possibility implies a variable LTP according to the input conditions; accordingly, the shape of LTP was compared in 4 experimental conditions in which the input to the ganglion cells was different; (1) supramaximal activation of the intact cervical sympathetic trunk (CST), (SPM); (2) submaximal activation of the intact CST, (SBM); (3) supramaximal activation of the partially transected CST, (TRN): and (4) supramaximal activation of the intact CST under partial nicotinic block with hexamethonium. (BLK). Even when PTrP was evoked with the same subliminal fringe obtained under the 3 low-level conditions of tetanization, the degree of potentiation and the proportion of PTP and LTP were different. After either SPM or SBM conditions LTP was negligible, though PTP developed to a certain degree.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1986

A synaptic model for the kindling effect.

In this work we present a model of the kindling effect based on the Hopf bifurcation for a system of ordinary differential equations. The model shows how quantitative changes in the physiological parameters at the microscopic, synaptic scale, produce the afterdischarge which is a macroscopic effect at the neuronal network scale. The presynaptic mechanisms are based on the vesicular hypothesis, or more generally on the quantal theory of synaptic transmission. The postsynaptic processes rely on Granit's law. This model gives a consistent framework which organizes and explains several experimental observations.

Animals↗