Department of Chemistry

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https://hdl.handle.net/10919/23842

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Browsing Department of Chemistry by Department "Biomedical Engineering and Mechanics"

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    Debonding of confined elastomeric layer using cohesive zone model
    Mukherjee, Bikramjit; Dillard, David A.; Moore, Robert Bowen; Batra, Romesh C. (Elsevier, 2016-04-01)
    Wavy or undulatory debonding is often observed when a confined/sandwiched elastomeric layer is pulled off from a stiff adherend. Here we analyze this debonding phenomenon using a cohesive zone model (CZM). Using stability analysis of linear equations governing plane strain quasi-static deformations of an elastomer, we find (i) a non-dimensional number relating the elastomer layer thickness, h, the long term Young's modulus, E∞, of the interlayer material, the peak traction, Tc, in the CZM bilinear tractionseparation (TS) relation, and the fracture energy, Gc, of the interface between the adherend and the elastomer layer, and (ii) the critical value of this number that provides a necessary condition for undulations to occur during debonding. For the elastomer modeled as a linear viscoelastic material with the shear modulus given by a Prony series and a rate-independent bilinear TS relation in the CZM, the stability analysis predicts that a necessary condition for a wavy solution is that Tc2h=GcE∞ exceed 4:15. This is supported by numerically solving governing equations by the finite element method (FEM). Lastly, we use the FEM to study three-dimensional deformations of the peeling (induced by an edge displacement) of a flexible plate from a thin elastomeric layer perfectly bonded to a rigid substrate. These simulations predict progressive debonding with a fingerlike front for sufficiently confined interlayers when the TS parameters satisfy a constraint similar to that found from the stability analysis of the plane strain problem.
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    Friction of Extensible Strips: an Extended Shear Lag Model with Experimental Evaluation
    Mojdehi, Ahmad R.; Holmes, Douglas P.; Williams, Christopher B.; Long, Timothy E.; Dillard, David A. (2016-02-22)
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    The role of the gap junction perinexus in cardiac conduction: Potential as a novel anti-arrhythmic drug target
    Hoagland, Daniel T.; Santos, Webster L.; Poelzing, Steven; Gourdie, Robert G. (Elsevier, 2018-09-19)
    Cardiovascular disease remains the single largest cause of natural death in the United States, with a significant cause of mortality associated with cardiac arrhythmias. Presently, options for treating and preventing myocardial electrical dysfunction, including sudden cardiac death, are limited. Recent studies have indicated that conduction of electrical activation in the heart may have an ephaptic component, wherein intercellular coupling occurs via electrochemical signaling across narrow extracellular clefts between cardiomyocytes. The perinexus is a 100-200 nm-wide stretch of closely apposed membrane directly adjacent to connexin 43 gap junctions. Electron and super-resolution microscopy studies, as well as biochemical analyses, have provided evidence that perinexal nanodomains may be candidate structures for facilitating ephaptic coupling. This work has included characterization of the perinexus as a region of close inter-membrane contact between cardiomyocytes (<30 nm) containing dense clusters of voltage-gated sodium channels. Here, we review what is known about perinexal structure and function and the potential that the perinexus may have novel and pivotal roles in disorders of cardiac conduction. Of particular interest is the prospect that cell adhesion mediated by the cardiac sodium channel b subunit (Scn1b) may be a novel anti-arrhythmic target.