Competing mechanisms of stress-assisted diffusivity and stretch-activated currents in cardiac electromechanics

We numerically investigate the role of mechanical stress in modifying the conductivity properties of the cardiac tissue and its impact in computational models for cardiac electromechanics. We follow a theoretical framework recently proposed in [Cherubini, Filippi, Gizzi, Ruiz-Baier, JTB 2017], in the context of general reaction-diffusion-mechanics systems using multiphysics continuum mechanics and finite elasticity. In the present study, the adapted models are compared against preliminary experimental data of pig right ventricle fluorescence optical mapping. These data contribute to the characterization of the observed inhomogeneity and anisotropy properties that result from mechanical deformation. Our novel approach simultaneously incorporates two mechanisms for mechano-electric feedback (MEF): stretch-activated currents (SAC) and stress-assisted diffusion (SAD); and we also identify their influence into the nonlinear spatiotemporal dynamics. It is found that i) only specific combinations of the two MEF effects allow proper conduction velocity measurement; ii) expected heterogeneities and anisotropies are obtained via the novel stress-assisted diffusion mechanisms; iii) spiral wave meandering and drifting is highly mediated by the applied mechanical loading. We provide an analysis of the intrinsic structure of the nonlinear coupling using computational tests, conducted using a finite element method. In particular, we compare static and dynamic deformation regimes in the onset of cardiac arrhythmias and address other potential biomedical applications

Damage scenario of the earthquake on 23 July 1930 in Melfi: the contribution of technical documentation

As regards the 1930 Irpinia earthquake a detailed research both on the institutional response to the seismic event in Vulture area and reconstruction of the damage scenario for the town of Melfi has been performed. This study was carried out by an analysis of coeval dossiers drawn up by the Special Office of Civil Engineers, which was set up after the earthquake. The research brought to light the typologies and the modalities of the institutional actions taken during the post-seismic period. In general, these territorial interventions had a notable effect on urban systems, especially those involving both the partial shifting of urban areas and the construction of earthquake-proof buildings. The research also identified the damage pattern in Melfi by a deeper study on about 2400 archive files. A preliminary analysis of the damage pattern indicates probable seismic amplification phenomena due to the lithological and geomorphological features of the site. Moreover, the analysis of time-dependent activities of reconstruction has shown that almost all the buildings of the town (90%) were repaired or reconstructed within five years after the seismic disaster

Erratum to: 23 November 1980 Irpinia–Basilicata earthquake (Southern Italy): towards a full knowledge of the seismic effects

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Real-time monitoring via second-harmonic interferometry of a flow gas cell for laser wakefield acceleration

The use of a gas cell as a target for laser weakfield acceleration (LWFA) offers the possibility to obtain stable and manageable laser-plasma interaction process, a mandatory condition for practical applications of this emerging technique, especially in multi-stage accelerators. In order to obtain full control of the gas particle number density in the interaction region, thus allowing for a long term stable and manageable LWFA, real-time monitoring is necessary. In fact, the ideal gas law cannot be used to estimate the particle density inside the flow cell based on the preset backing pressure and the room temperature because the gas flow depends on several factors like tubing, regulators and valves in the gas supply system, as well as vacuum chamber volume and vacuum pump speed/throughput. Here, second-harmonic interferometry is applied to measure the particle number density inside a flow gas cell designed for LWFA. The results demonstrate that real-time monitoring is achieved, and that using low backing pressure gas (< 1 bar) and different cell orifice diameters (< 2 mm) it is possible to finely tune the number density up to the range well suited for LWFA