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

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

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Nonlinear diffusion & thermo-electric coupling in a two-variable model of cardiac action potential

This work reports the results of the theoretical investigation of nonlinear dynamics and spiral wave breakup in a generalized two-variable model of cardiac action potential accounting for thermo-electric coupling and diffusion nonlinearities. As customary in excitable media, the common Q10 and Moore factors are used to describe thermo-electric feedback in a 10-degrees range. Motivated by the porous nature of the cardiac tissue, in this study we also propose a nonlinear Fickian flux formulated by Taylor expanding the voltage dependent diffusion coefficient up to quadratic terms. A fine tuning of the diffusive parameters is performed a priori to match the conduction velocity of the equivalent cable model. The resulting combined effects are then studied by numerically simulating different stimulation protocols on a one-dimensional cable. Model features are compared in terms of action potential morphology, restitution curves, frequency spectra and spatio-temporal phase differences. Two-dimensional long-run simulations are finally performed to characterize spiral breakup during sustained fibrillation at different thermal states. Temperature and nonlinear diffusion effects are found to impact the repolarization phase of the action potential wave with non-monotone patterns and to increase the propensity of arrhythmogenesis

Dynamics of charge-displacement channeling in intense laser-plasma interactions

The dynamics of transient electric fields generated by the interaction of high intensity laser pulses with underdense plasmas has been studied experimentally with the proton projection imaging technique. The formation of a charged channel, the propagation of its front edge and the late electric field evolution have been characterised with high temporal and spatial resolution. Particle-in-cell simulations and an electrostatic, ponderomotive model reproduce the experimental features and trace them back to the ponderomotive expulsion of electrons and the subsequent ion acceleration.Comment: 5 figures, accepted for publication in New Journal of Physic

A Case of Bilateral Pigment Dispersion Syndrome Following Many Years of Uninterrupted Treatment With Atropine 1% for Bilateral Congenital Cataracts

PURPOSE: Describe an unusual case of bilateral pigment dispersion syndrome (PDS) following years of uninterrupted treatment with atropine 1% for bilateral congenital cataracts, speculate on potential mechanisms leading to this condition. DESIGN: This is a case report. CASE: A 45-year-old white patient on long-term treatment with atropine 1% ointment since his infancy for bilateral congenital cataracts developed PDS with secondary ocular hypertension. RESULTS: The patient showed all the hallmarks of PDS with secondary ocular hypertension. An anterior segment Swept-Source optical coherence tomography was obtained to review the iris profile. The patient showed good pressure response to topical prostaglandin therapy. CONCLUSIONS: This is the second case report of PDS in a patient with chronic use of topical atropine. The proposed mechanisms for pigment dispersion are discussed and the possibility raised of dispersion being a potential side effect of the drug

THE REALIZATION OF A NEW GEOMAGNETIC OBSERVATORY IN CENTRAL ITALY, REPLACING L'AQUILA GEOMAGNETIC OBSERVATORY

The geomagnetic Observatory of L'Aquila was founded by Istituto Nazionale di Geofisica e Vulcanologia (INGV) in 1958, on the occasion of the International Geophysical Year. It is the main Italian geomagnetic observatory and since 1999 is part of the Intermagnet network. In 2009 L’Aquila was struck by a strong earthquake; the town was seriously damaged, and since then many activities moved to the suburbs; close to the Geomagnetic Observatory new activities were planned. Then the necessity to find in the surroundings a new place, suitable for the installation of a Geomagnetic Observatory, arose. Several tests were made and a possible location was found in Castel Del Monte, 40km from L’Aquila; a preliminary analysis of the electromagnetic background noise and of the spatial magnetic field gradients has shown that the place can meet the requirements for a Geomagnetic Observatory. Meanwhile, in 2010, a new Geomagnetic Observatory was installed in Duronia, 130 km South-East from L’Aquila and since 2012 it is part of the Intermagnet network