Jack M. Rogers

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A new computational method was developed for modeling the effects of the geometric complexity, nonuniform muscle fiber orientation, and material inhomogeneity of the ventricular wall on cardiac impulse propagation. The method was used to solve a modification to the FitzHugh-Nagumo system of equations. The geometry, local muscle fiber orientation, and(More)
An automated method to estimate vector fields of propagation velocity from observed epicardial extracellular potentials is introduced. The method relies on fitting polynomial surfaces T(x, y) to the space-time (x, y, t) coordinates of activity. Both speed and direction of propagation are computed from the gradient of the local polynomial surface. The(More)
OBJECTIVE To test the hypothesis that enthesophyte formation and osteophyte growth are positively associated and to look for associations between bone formation at different sites on the skeleton so that a simple measure of bone formation could be derived. METHODS Visual examination of 337 adult skeletons. All common sites of either enthesophyte or(More)
The regional mechanics of the beating heart are directly related to factors such as ventricular pumping performance, coronary blood flow, myocardial energetics and oxygen consumption, vulnerability to ischemia and injury, hypertrophy and remodeling, and arrhythmogenesis. Important characteristics include: the complex three-dimensional geometry and fibrous(More)
Optical mapping of electrical activity from the surface of the heart is a powerful tool for studying complex arrhythmias. However, a limitation of traditional optical mapping is that the mapped region is restricted to the field of view of the sensor, which makes it difficult to track electrical waves as they drift in and out of view. To address this, we(More)
Five hundred and sixty intact skeletons and several thousand disarticulated vertebrae have been examined with special reference to spinal fusion. In period they ranged from a 21st dynasty Egyptian mummy to a mid-19th century skeleton. Osteophytes were found in about half of the specimens, as reported previously. Fifteen skeletons with extensive blocks of(More)
We developed a new method for fabricating plunge needle electrodes for use in cardiac mapping. The needles have 12 electrodes with 1-mm spacing, are 0.5 mm in diameter, and are fabricated from fiberglass reinforced epoxy. They are stiff enough to be easily inserted into beating hearts and durable enough to be reused many times. We found that these new(More)
BACKGROUND The roles of Purkinje fibers (PFs) and focal wave fronts, if any, in the maintenance of ventricular fibrillation (VF) are unknown. If PFs are involved in VF maintenance, it should be possible to map wave fronts propagating from PFs into the working ventricular myocardium during VF. If wave fronts ever arise focally during VF, it should be(More)
OBJECTIVES To examine objectively spatial patterns of osteophytes around the distal end of the femur and to identify distinct subgroups. METHODS A sample of 107 human femora from a large skeletal population were selected for study. These femora included subjects with evidence of late stage osteoarthritis (that is, with eburnation present) and those with(More)