Computational modeling of acute myocardial infarction

This is an Accepted Manuscript of an article published by Taylor & Francis Group in Computer Methods in Biomechanics and Biomedical Engineering on October, 2016, available online at: http://www.tandfonline.com/10.1080/10255842.2015.1105965Myocardial infarction, commonly known as heart attack, is caused by reduced blood supply and damages the heart muscle because of a lack of oxygen. Myocardial infarction initiates a cascade of biochemical and mechanical events. In the early stages, cardiomyocytes death, wall thinning, collagen degradation, and ventricular dilation are the immediate consequences of myocardial infarction. In the later stages, collagenous scar formation in the infarcted zone and hypertrophy of the non-infarcted zone are auto-regulatory mechanisms to partly correct for these events. Here we propose a computational model for the short-term adaptation after myocardial infarction using the continuum theory of multiplicative growth. Our model captures the effects of cell death initiating wall thinning, and collagen degradation initiating ventricular dilation. Our simulations agree well with clinical observations in early myocardial infarction. They represent a first step toward simulating the progression of myocardial infarction with the ultimate goal to predict the propensity toward heart failure as a function of infarct intensity, location, and size.Peer ReviewedPostprint (author's final draft

Recent Load Calibrations Experience with the YF-12 Airplane

The use of calibrated strain gages to measure wing loads on the YF-12A airplane is discussed as well as structural configurations relative to the thermal environment and resulting thermal stresses. A thermal calibration of the YF-12A is described to illustrate how contaminating thermal effects can be removed from loads equations. The relationship between ground load calibrations and flight measurements is examined for possible errors, and an analytical approach to accommodate such errors is presented

A study of the effect of radical load distributions on calibrated strain gage load equations

For several decades, calibrated strain gages have been used to measure loads on airplanes. The accuracy of the equations used to relate the strain gage measurements to the applied loads has been based primarily on the results of the load calibration. An approach is presented for studying the effect of widely varying load distributions on strain gage load equations. The computational procedure provides a link between the load calibration and the load to be measured in flight. A matrix approach to equation selection is presented, which is based on equation standard error, load distribution, and influence coefficient plots of the strain gage equations, and is applied to a complex, delta-wing structure

Waveguide photonic limiters based on topologically protected resonant modes

We propose a concept of chiral photonic limiters utilising topologically protected localised midgap defect states in a photonic waveguide. The chiral symmetry alleviates the effects of structural imperfections and guaranties a high level of resonant transmission for low intensity radiation. At high intensity, the light-induced absorption can suppress the localised modes, along with the resonant transmission. In this case the entire photonic structure becomes highly reflective within a broad frequency range, thus increasing dramatically the damage threshold of the limiter. Here we demonstrate experimentally the principle of operation of such photonic structures using a waveguide consisting of coupled dielectric microwave resonators.Comment: 6 pages, 4 figure

Voices Count: Employing A Critical Narrative Research Bricolage For Insights Into Dyscalculia

This qualitative study involved interviewing adult participants who were identified, or who self identified as having dyscalculia (also known as a mathematical learning disorder), with the objective of obtaining depth of perspective on how this phenomenon is interpreted, responded to, and managed by these individuals and those around them. This study utilizes a theoretical and methodological framework known as bricolage (Kincheloe, 2005) which involves the synthesis of narrative, auto-ethnographic, critical, feminist, neuroscientific, and psychometric perspectives, to explicate the constitution and experience of dyscalculia. This study also explores epistemological privilege within the discipline of educational psychology, and draws on the work Billington (1996, 2013) who advocates for greater employment of critical approaches within educational psychology; particularly, drawing on the work of Foucault, to explicate how the privileging of certain modes of inquiry contributes to the marginalization of those under study. Findings suggest that cognitive approaches to understanding dyscalculia are neither in agreement, nor above scrutiny, and that social factors, co-morbid conditions and pedagogical approaches to mathematics instruction play a role in the emergence and remediation of dyscalculia. Ultimately, dyscalculia is explicated as a multidimensional phenomenon that raises important questions about how learning differences are approached and understood in educational research and practice

The use of a simplified structural model as an aid in the strain gage calibration of a complex wing

The use of a relatively simple structural model to characterize the load responses of strain gages located on various spars of a delta wing is examined. Strains measured during a laboratory load calibration of a wing structure are compared with calculations obtained from a simplified structural analysis model. Calculated and measured influence coefficient plots that show the shear, bending, and torsion characteristics of typical strain gage bridges are presented. Typical influence coefficient plots are shown for several load equations to illustrate the derivation of the equations from the component strain gage bridges. A relatively simple structural model was found to be effective in predicting the general nature of strain distributions and influence coefficient plots. The analytical processes are shown to be an aid in obtaining a good load calibration. The analytical processes cannot, however, be used in lieu of an actual load calibration of an aircraft wing

Fostering an Entrepreneurial Mindset in Systems Simulation

Simulation is tool frequently used by companies when designing systems to evaluate alternative system designs. In particular, simulation is employed when the dynamic behavior of a system is not well understood and the decisions that are being made have significant economic or social impacts. However, courses in systems simulation typically focus on the technical and statistical aspects of model building and the comparison of design alternatives focused on operational performance of the system (that is, performance metrics that can be collected within the simulation itself.) This paper investigates how an entrepreneurial mindset can be fostered through activities/methods that encourage students to look beyond the operational aspects of system design to the overall value and impact of design alternatives. The development, implementation, and outcomes of two KEEN modules are presented to demonstrate the integration of an entrepreneurial mindset in a systems simulation course

Preliminary Results of Aerodynamic Heating Studies on the X-15 Airplane

Aerodynamic heating analysis of X-15 aircraft in fligh

Computational Modeling of Hip Replacement Surgery: Total Hip Replacement vs. Hip Resurfacing

The motivation of the present work is the computational simulation of hip replacement surgery by means of a finite element approach based on open system thermodynamics. Its key feature is a non-constant material density, which is allowed to adapt with respect to changes in the mechanical loading environment. From a computational point of view, the density is treated as an internal variable. Its evolution is governed by a first order rate equation, the balance of mass, which is enhanced by an additional mass production term to account for growth. An implicit Euler backward scheme is suggested for its time discretization. The algorithmic determination of the material density based on a local Newton iteration is presented. To ensure quadratic convergence of the global Newton Raphson solution scheme, a consistent linearization of the discrete algorithmic equations is carried out. Finally, two alternative medical techniques in hip arthritis are compared, the conventional total hip replacement strategy and the more recent hip resurfacing technology. The result of the suggested remodeling algorithm is shown to agree remarkably well with clinically observed phenomena