Multi-GPU adaptation of a simulator of heart electric activity

[EN] The simulation of the electrical activity of the heart is calculated by solving a large system of ordinary differential equations; this takes an enormous amount of computation time. In recent years graphics processing unit (GPU) are being introduced in the field of high performance computing. These powerful computing devices have attracted research groups requiring simulate the electrical activity of the heart. The research group signing this paper has developed a simulator of cardiac electrical activity that runs on a single GPU. This article describes the adaptation and modification of the simulator to run on multiple GPU. The results confirm that the technique significantly reduces the execution time compared to those obtained with a single GPU, and allows the solution of larger problems.[ES] La simulación de la actividad eléctrica del corazón se calcula mediante la resolución de un gran sistema de ecuaciones diferenciales ordinarias, que necesita una enorme cantidad de tiempo de computación. Sin embargo, en los últimos años se están introduciendo, en el ámbito de la computación de alto rendimiento, las unidades de procesamiento gráfico (GPU). Estos potentes dispositivos han atraído a grupos de investigación que requieren simular la actividad eléctrica del corazón. El grupo de investigación que firma este artículo ha desarrollado un simulador de actividad eléctrica cardíaca que se ejecuta en una sola GPU. En este artículo se describe la adaptación y modificaciones de dicho simulador para su ejecución en múltiples GPU. Los resultados confirman que la técnica empleada permite reducir sensiblemente los tiempos de ejecución respecto a los que se obtienen con una sola GPU, además de permitir afrontar problemas mucho más grandes.Este trabajo ha sido financiado por la Universitat Politècnica de València a través de su Programa de Apoyo a la Investigación y Desarrollo (PAID-06-11) y (PAID-05-12), por la Generalitat Valenciana a través de los proyectos PROMETEO/2009/013 y Ayudas para la realización de proyectos de I+D para grupos de investigación emergentes GV/2012/039, y por el Ministerio Español de Economía y Competitividad y el fondo europeo de Desarrollo Regional (FEDER) de la Comunidad Europea través del proyecto TEC2012-38142-C04.García Mollá, VM.; Vidal Maciá, AM.; Liberos Mascarell, A.; Climent, AM. (2013). Adaptación para multiples GPU de un simulador de actividad eléctrica en el corazón. Revista Cubana de Ciencias Informáticas. 7(4):100-111. http://hdl.handle.net/10251/39802S1001117

Efficient time splitting schemes for the monodomain equation in cardiac electrophysiology

Approximating the fast dynamics of depolarization waves in the human heart described by the monodomain model is numerically challenging. Splitting methods for the PDE-ODE coupling enable the computation with very fine space and time discretizations. Here, we compare different splitting approaches regarding convergence, accuracy, and efficiency. Simulations were performed for a benchmark problem with the Beeler–Reuter cell model on a truncated ellipsoid approximating the left ventricle including a localized stimulation. For this configuration, we provide a reference solution for the transmembrane potential. We found a semi-implicit approach with state variable interpolation to be the most efficient scheme. The results are transferred to a more physiological setup using a bi-ventricular domain with a complex external stimulation pattern to evaluate the accuracy of the activation time for different resolutions in space and time

The body politic: splitting gender medically in eighteenth-century Philadelphia

Before the rise of clinical medicine, Western medicine was undergoing several prerequisite shifts in epistemology and methodology - moving from an eighteenth-century practice of spaces and classes, wherein the symptom is synonymous with the disease, toward a nineteenth-century science of signs and cases, in which symptoms are symbols, or products, of a deeper disease (Foucault 1973). During the former age of classes, about mid-century, a particular shift in the medical perception of sex differences appears in the literature, without any great advances or revisions in human anatomical knowledge or treatment methods. This thesis looks at hospitalization of in-patients at Pennsylvania Hospital spanning 50 years during which this shift in medical body concept took hold in European medicine, and was transmitted to American medical students educated in England and Edinburgh. A correlated change in medical practice is expected after major changes in either medical knowledge or in medical body concept occur. Generally, no significant difference is found in the records of the kind of treatment administered or length of hospitalization of in-patients during the time period analyzed. However, women did experience longer hospitalization for most diagnostic categories. A correlation exists between men hospitalized for increasingly longer periods while a much higher proportion (by 45 percent) of pay patients to poor patients were being admitted after 1783. More research on pay and poor patient demographics is needed before a conclusion on this point may be drawn. This thesis suggests that the lived patient experience may not reflect the image presented by contemporary medical literature. The patient records do appear to indicate that a contrastive view of anatomical sex differences was influencing lengths of hospitalization between men and women. This difference is most visible among lunacy cases, in which the author shows patient autonomy is reduced while the physician\u27s power is inversely increased, and thus the medical body concept more strongly affects the course of treatment. Future research at Pennsylvania Hospital may need to extend into the nineteenth century when hospital records begin to include more complete and detailed information about individual cases. Similar studies at other contemporary hospitals in America and Western Europe may also shed light on the links between patient experience and medical practice advocated in literature

Poet Robert Bly : shaman of the dark side

While Robert Bly suggests that the poet's role is rooted in the shaman's, critics have not yet looked at his poetry in light of the shaman's role. Often seen as divided between the private poems and the public, political poems, Bly's work displays not division, but rather the holism of the twofold shamanic vision where mystical journey into dark realms is publically performed in order to heal the tribe. In his shamanic vision of the dark side, Bly displays a kinship with D. H. Lawrence. In Lawrence's BIRDS, BEASTS AND FLOWERS poems and in many of Bly's poems, deep and detailed images of animals and plants portray attunement with nature and the dark side. Embodying the apparent differences of Bly's poetry, SLEEPERS JOINING HANDS uses the rhetoric of the shaman's performance to persuade the American tribe that the dark energy and horror of the Vietnam War was an effect of an underlying spiritual imbalance, an over-emphasis on the rational