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Biomedical subjects

K Affeld

Publications and source records attributed to K Affeld.

At least 19 recordsLinked to original sources
PubMed1990

Computer aided time-lapse video analysis of hepatocyte morphology during adhesion to cellulose membranes.

An investigation was performed to demonstrate that time-lapse cinematography and computer aided video analysis of cell morphology is suitable to study and compare the characteristics of hepatocytes during the adhesion process to membranes. We chose to compare ordinary cellulose Cuprophan membranes and membranes coated with collagen or fibronectin. Striking differences between uncoated cellulose and fibronectin or collagen coating were seen in the cell count per square millimeter and adhesion behaviour. On the investigated uncoated Cuprophan the hepatocytes were found to attach but not to spread whilst on collagen coated Cuprophan most of the cells spread spherically, and on fibronectin coated membranes most of the cells flattened spherically or polygonally. Time-lapse video microscopy seems to be a valuable technique for assessing the morphologic behaviour of cells in a detailed and quantitative manner in order to improve the hepatocyte culture technique in bioreactors for hybrid systems.

Animals↗
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↗
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↗
PubMed1976

[Observation in 10 calves with a survival time of more than 100 hours after total heart replacement (author's transl)].

It is reported on 10 calves surviving total artificial heart replacement more than 100 hours. Pneumatically driven double-chambered blood pumps made of silastic were implanted. During the experiments an increase of the right atrial pressure as well as a rise of the perfusion volumes (CO) and of the blood volumes could be found regularly. At autopsy congestion of the organs especially of the liver was a regular finding. The changed hemodynamic is first seen as possible reason for this developments. The influence of anemia and the possible disturbances in the neurohumoral autoregulation of the animals by unphysiologic pressure curves are discussed.

Animals↗
PubMed1976

New methods for the in vitro investigations of the flow patterns in artificial hearts.

With the 3 applied methods one can investigate and obtain most of the interesting aspects of the flow within blood pumps: an integral picture of the flow, the development and position of stagnation flow, the time course of the velocity in points of special interest, the turbulence, and an integral picture of the mean boundary layer flow. The measurements have shown that the flow in the blood pumps is turbulent, the turbulence can be considered harmless, because its intensity is much weaker than that of a valve; there is a correspondence between the hotfilm method and the dye-washout method, and that there is a correspondence between the dye-washout method and the in vivo clot formation. Pumps, which have been designed according to these measurements, have been implanted in a series of calves. The pumps now have a smooth continuous inner surface and usually show no thrombus formation at all (anticoagulants are used) at the postmortem. Some animals do very well, such as the one in Figure 16 during his daily walk of 500 M on the treadmill. The animal is in its 45th day of survival and remains well to date.

Animals↗