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Sant'Ambrogio di Torino, Italy

Fiori F.,Marche Polytechnic University | Lussana D.,Nis Center | Riontino G.,Nis Center
Journal of Alloys and Compounds | Year: 2010

A quantitative description of the Mg-rare earth EV31 alloy during the first stages of the precipitation sequence using in situ small-angle X-ray scattering (SAXS) is presented. In situ evolutions of the size, volume fraction and number density of precipitates formed at 150 °C and 200 °C were obtained. A kinetic mechanism suggests that the precursor nanoparticles are nucleated at the beginning of the artificial ageing and, at 200 °C, these particles grow mainly by accretion of the solute from the matrix without further nucleation. The particles grow within two regimes: (i) at the beginning of ageing, the growth is associated with solute diffusion with an apparent activation energies of 0.78 eV (diffusion assisted by vacancies); (ii) further growth is associated with solute diffusion with an apparent activation energies of 1.16 eV (bare solute diffusion). After about 2 h at 200 °C, corresponding to the condition of maximum hardness for this alloy, the present results indicate a volume fraction of about 1.5% occupied by particles with an average Guinier radius of 2 nm. The evolution of the volume fraction at 150 °C, studied for a similar time interval, is weaker than the one found at 200 °C. © 2009 Elsevier B.V. All rights reserved. Source

Vandael D.H.F.,Nis Center | Vandael D.H.F.,AM Technology | Marcantoni A.,Nis Center | Carbone E.,Nis Center
Current Molecular Pharmacology | Year: 2015

Neuronal and neuroendocrine L-type calcium channels (Cav1.2, Cav1.3) open readily at relatively low membrane potentials and allow Ca2+ to enter the cells near resting potentials. In this way, Cav1.2 and Cav1.3 shape the action potential waveform, contribute to gene expression, synaptic plasticity, neuronal differentiation, hormone secretion and pacemaker activity. In the chromaffin cells (CCs) of the adrenal medulla, Cav1.3 is highly expressed and is shown to support most of the pacemaking current that sustains action potential (AP) firings and part of the catecholamine secretion. Cav1.3 forms Ca2+-nanodomains with the fast inactivating BK channels and drives the resting SK currents. These latter set the inter-spike interval duration between consecutive spikes during spontaneous firing and the rate of spike adaptation during sustained depolarizations. Cav1.3 plays also a primary role in the switch from “tonic” to “burst” firing that occurs in mouse CCs when either the availability of voltage-gated Na channels (Nav) is reduced or the β2 subunit featuring the fast inactivating BK channels is deleted. Here, we discuss the functional role of these “neuronlike” firing modes in CCs and how Cav1.3 contributes to them. The open issue is to understand how these novel firing patterns are adapted to regulate the quantity of circulating catecholamines during resting condition or in response to acute and chronic stress. © 2015 Bentham Science Publishers. Source

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