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Biomedical subjects

K Affeld

Publications and source records attributed to K Affeld.

At least 55 records · Page 3Linked to original sources
PubMed1987

Design of a new pulse duplicator system for prosthetic heart valves.

This paper discusses results of a computer simulation for designing a new pulse duplicator system for mechanical heart valves. The design objective of the system is to obtain a compact, efficient pulse duplicator system capable of accurately measuring the volume flow rate across a valve. The volume flow rate is determined as the derivative of the volume displacement of an actuator piston which directly drives the fluid. The system does not need any circulatory loop, since the piston is controlled on-line to follow command signals representing an aortic impedance. The results of the computer simulation show: the designed PI-controllers of the actuator can precisely control valve motion to follow given command signals, the eigenvalues of the controllers have to be carefully chosen to prevent unstable behaviors of a valve in diastole, and the dimensions of the actuator is optimized by minimizing a cost function of the total efficiency of the system.

Biomechanical Phenomena↗
PubMed1984

Design criteria for percutaneous devices.

A theoretical model of a percutaneous device is described. The model is split into several components, each with its own function. Special structures such as horns, hair, feathers, fingernails, hoofs , teeth, and antlers are taken as examples where nature has solved the problems of "percutaneous devices." These structures have been regarded in relation to dimensional and structural differences of epidermis, dermis, and subcutis. Theoretical guidelines are described for the design of a prosthetic percutaneous device.

Animals↗
PubMed1983

The use of computer graphics to find an optimal fit for a human total artificial heart.

The analysis of the thorax and the vessel system adjacent to the heart of different individuals seems to indicate that a fitting of an artificial heart before the operation should be done. A tailoring of the arterial and atrial connectors seems necessary. Computer graphics using CT-scans as a basis render all the required information and a comprehensible view of the vessel system. Future developments should improve the practicability of the system and make use of modern 3-dimensional viewing techniques already there for application.

Computers↗
PubMed1980

[Chronobiological aspects of artificial total heart replacement in long-term animal experiments--a systemanalytic study (author's transl)].

Biological rhythms (circadian rhythms) have been observed in the hemodynamics of experimental animals (calves). After artificial total heart replacement these rhythms are typically altered compared to control animals. These observations induce a growing consideration of chronobiological aspects in a systemanalysis for the conception of an automatic external control of the artificial heart, which has to be divided in:--parameter-progression (tendencies), --parameter-variation (discrete, oscillations), --parameter-coupling (phase shifts).

Animals↗
PubMed1977

Alloplastic spermatocele: insemination from epididymal reservoir.

Insemination with the sperm of an epididymal reservoir three days after implantation of the prosthesis led to a successful pregnancy with subsequent delivery of five healthy sucklings. Alloplastic spermatocele can function longer than four months as proved by a successful pregnancy.

Animals↗
PubMed1976

[Controlling of artificial blood pumps after total heart replacement - an example of disregulation (author's transl)].

This is a report on the special regulation problem of the left blood pump after replacement of the natural heart by incorporated extracorporally driven blood pumps in an animal experiment. The consequence of the peripheral self-regulation on the transporting capacity of the bloodpumps considering the driving pressure and the systemic pressure losses has been investigated. Two possible controlling principles and the respective fields of application are discussed on the example of a lung oedema.

Animals↗