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It has become widely accepted that the most dangerous cardiac arrhythmias are due to re-entrant waves, i.e., electrical wave(s) that re-circulate repeatedly throughout the tissue at a higher frequency than the waves produced by the heart's natural pacemaker (sinoatrial node). However, the complicated structure of cardiac tissue, as well as the complex ionic(More)
INTRODUCTION Discordant alternans has the potential to produce larger alternans of the ECG T wave than concordant alternans, but its mechanism is unknown. METHODS AND RESULTS We demonstrate by one- and two-dimensional simulation of action potential propagation models that discordant alternans can form spontaneously in spatially homogeneous tissue through(More)
We describe a useful setting for interactive, real-time study of mathematical models of cardiac electrical activity, using implicit and explicit integration schemes implemented in JAVA. These programs are intended as a teaching aid for the study and understanding of general excitable media. Particularly for cardiac cell models and the ionic currents(More)
We consider competition in patch-dynamical and more general diffusion-extinction models. These models identify three time scales in ecology. We begin with a reformulation of Levin's 1978 basic model, using a geometric description of diffusion. As in Levin's model, diffusion drives short-term dynamics, and longer-term dynamics depends upon a(More)
Scatter factor (SF) is an invasogenic and angiogenic cytokine the cellular receptor of which is encoded by a proto-oncogene (c-met). We measured the immunoreactive SF content (nanograms of SF per milligram of protein) in tissue extracts from 166 breast cancers and correlated the values with various known prognostic parameters. Invasive cancers had nearly(More)
BACKGROUND Interleukin 1beta (IL-1beta) is a multifunctional cytokine that up-regulates the inflammatory response. It is not known whether IL-1beta plays a major role in human malignancy. To determine whether IL-1beta might be involved in breast carcinoma progression, the authors measured the IL-1beta content in tissue extracts from >200 invasive breast(More)
Mathematical models of cardiac cells have become important tools for investigating the electrophysiological properties and behavior of the heart. As the number of published models increases, it becomes more difficult to choose a model appropriate for the conditions to be studied, especially when multiple models describing the species and region of the heart(More)
PURPOSE We previously reported increased titers of scatter factor in urine of 20 patients with transitional cell carcinoma of the bladder compared to noncancer and cancer control groups. Scatter factor was also found in bladder tumor extracts but the number of samples examined was too small for detailed analysis. We report a followup study of larger numbers(More)
BACKGROUND Asthma morbidity is seasonal, with the fewest exacerbations occurring in summer and the most exacerbations in early fall. OBJECTIVE To determine if the fall increase in pediatric asthma emergency department (ED) visits is related to the school year start. DESIGN Time-series study of daily asthma ED visits taken from an administrative claims(More)
The size of realistic cardiac tissue models has been limited by their high computational demands. In particular, the Luo-Rudy phase II membrane model, used to simulate a thin sheet of ventricular tissue with arrays of coupled ventricular myocytes, is usually limited to 100 x 100 arrays. We introduce a new numerical method based on domain decomposition and a(More)