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Biomedical subjects

J Ross

Publications and source records attributed to J Ross.

At least 847 records · Page 47Linked to original sources
PubMed1970

Stress distribution in the canine left ventricle during diastole and systole.

A model is proposed for stress analysis of the left ventricular wall (LV wall) based on the realistic assumption that the myocardium is essentially composed of fiber elements which carry only axial tension and vary in orientation through the wall. Stress analysis based on such a model requires an extensive study of muscle fiber orientation and curvature through the myocardium. Accordingly, the principal curvatures were studied at a local site near the equator in ten dog hearts rapidly fixed in situ at end diastole and end systole; the fiber orientation for these hearts had already been established in a previous study. The principal radii of curvature were (a) measured by fitting templates to the endocardial and epicardial wall surfaces in the circumferential and longitudinal directions and (b) computed from measured lengths of semiaxes of ellipsoids of revolution representing the LV wall ("ellipsoid" data). The wall was regarded as a tethered set of nested shells, each having a unique fiber orientation. Results indicate the following. (a) Fiber curvature, k, is maximum at midwall at end systole; this peak shifts towards endocardium at end diastole. (b) The pressure or radial stress through the wall decreases more rapidly near the endocardium than near the epicardium at end diastole and at end systole when a constant tension is assumed for each fiber through the wall. (c) At end diastole the curve for the circumferential stress vs. wall thickness is convex with a maximum at midwall. In the longitudinal direction the stress distribution curve is concave with a minimum at midwall. Similar distributions are obtained at end systole when a constant tension is assumed for each fiber through the wall. (d) The curvature and stress distributions obtained by direct measurements at a selected local site agree well with those computed from "ellipsoid" data.

Animals↗
PubMed1970

Solar abundance of gallium.

The spectral region around the lambda4172 A resonance line of gallium has been synthesized at disk positions mu = 1.0, 0.5, and 0.3. The center-limb variation can be reproduced by Elste's semiempirical model if a macroturbulent smearing of the emergent spectrum due to mass motions with mean velocity decreasing with altitude are introduced. The abundance of Ga derived from disk position mu = 1 is found to be log [N(Ga)/N(H)] + 12 = 2.80.

Journal Article↗
PubMed1970

Effect of respiration on venous return and stroke volume in cardiac tamponade.

Measurements have been made of pressure and blood velocity in venae cavae and aorta in a patient with severe cardiac tamponade in whom there was pulsus paradoxus. The characteristic pressure changes of pulsus paradoxus were associated with variations in peak blood velocity in the ascending aorta and stroke output. Maximum filling of the right side of the heart occurred during inspiration, and was associated in time with minimum left ventricular stroke volume. These findings point to competition for space by the ventricles in the distended pericardial sac as being the major factor in the production of pulsus paradoxus.

Adult↗