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Biomedical subjects

J W Wagner

Publications and source records attributed to J W Wagner.

6 recordsLinked to original sources
PubMed1992

The Social Security Administration's 10-percent sample file of OASDI beneficiaries.

This is another in a series of technical articles describing Social Security Administration sample files and statistical systems. The focus of this article is the 10-percent sample file that provides program and demographic information on Social Security beneficiaries under the Old-Age, Survivors, and Disability Insurance program. The article explains the contents and availability of the 10-percent sample and presents several statistical tabulations as examples of the wide variety of data that can be developed from the file.

Female↗
PubMed1989

A preliminary durability study of two types of low-profile pericardial bioprosthetic valves through the use of accelerated fatigue testing and flow characterization.

Bioprosthetic heart valves are being used more often because of certain advantages they have over artificial valves. The bioprostheses are less thrombogenic, cause a lower incidence of hemolysis, and usually fail in a slow progressive manner. A combination of flow characterization and accelerated testing was used to assess the durability of two types of pericardial valves, the Ionescu-Shiley Low Profile Mitral and the Carpentier-Edwards Low Profile Aortic valve. The flow characterization work was done in an aortic chamber designed for in vivo simulation. The function of the valve was monitored between different stages of the accelerated testing using laser Doppler anemometry. Accelerated testing was performed at 1300 cardiac cycles per minute, and physiologic conditions both in closing pressures and the ambient temperature were maintained. Results indicated a change in flow characteristics owing to cyclic loading of the leaflet tissue. The flow orifice increased over time leading to a decrease in peak velocity. Future developments in Doppler ultrasound may facilitate non-invasive assessment of these peak velocity variations. Calcification of the tissue was not considered, since this was an in vitro study.

Aortic Valve↗
PubMed1985

Metabolism of coronary vasculature in euthyroid, hyperthyroid and recovering hyperthyroid rats: a histochemical study.

Coronary arteries and arterioles from normal rats, from rats made hyperthyroid by administration of desiccated thyroid for 10 weeks, and from hyperthyroid rats which were then fed normal control diets for 10 weeks, were examined histochemically to determine the activity of key metabolic pathways. The primary aims of this study were to determine if the alterations in particular enzyme and substrate activities that occur in thyrotoxic rat myocardium, arteries and arterioles were reversible and would return to normal levels following cessation of the hyperthyroid state. Our results suggest that hyperthyroid rats, even after 10 weeks on the normal diet, still show some compromise in arteriolar aerobic metabolism in favor of anaerobic pathways, while coronary arteries still demonstrate little glucose-6-phosphate dehydrogenase activity. Myocardial metabolic activity approximates that of normal control animals by the end of the 10th week on the normal diet.

Animals↗
PubMedDate not supplied

Holographic velocimetry: an alternative approach for flow characterization of prosthetic heart valves.

In vitro techniques for evaluating circulation through prosthetic heart valves can yield important information concerning valve performance prior to implantation. Laser Doppler velocimetry is the most widely accepted noninvasive flow measurement technique, however, its use is somewhat limited for flow mapping applications. Holographic velocimetry is an alternative noninvasive in vitro approach for flow diagnostics. The advantage of this technique is the ability to do instantaneous full volume measurements for complete three-dimensional flow mapping at any instant in a flow cycle. Holographic velocimetry was used for the evaluation of circulation through a ball and cage valve. Results indicate that just beyond the apex of the cage very low velocity exists in the mean flow direction, while the other two components of velocity are rather large. Studies done further downstream from the valve begin to show the flow characteristics returning to the state of fully developed turbulent flow, as was previously seen upstream from the valve housing.

Evaluation Studies as Topic↗