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Biomedical subjects

U Faust

Publications and source records attributed to U Faust.

At least 19 recordsLinked to original sources
PubMed1996

Fast EIT data acquisition system with active electrodes and its application to cardiac imaging.

A wide-band high-speed data acquisition system for electrical impedance tomography (EIT) is described. 32 active electrodes are used in the system, half of them as receive electrodes and the other half as drive electrodes. A buffer is mounted on the back of each receive electrode and a current source on each drive electrode. A multielectrode system with active electrodes was built to make it convenient to attach all the electrodes on the human thorax. The system is suitable for both dynamic imaging and multifrequency electrical impedance tomography (MFEIT). Its operating frequency can be chosen between 24 kHz and 400 kHz. Current is injected sequentially into 16 adjacent current electrode pairs and the 16 voltages between adjacent receive electrodes are measured for each current injection. ECG is collected to determine the relationship between the reconstructed images and cardiac activity. The collection of one frame of data is completed within 25 ms. The system has been successfully used for imaging the variation of conductivity distribution of the human thorax. The beat-by-beat cardiac-related change of conductivity distribution has been imaged by our system. The quasi-periodic variation of the impedance distribution can be seen from the image sequence with breath-holding.

Electric Impedance↗
PubMed1992

[Mechanical characteristics of biological soft tissue].

In a detailed study mechanical properties of tendons, muscles, nerves, blood-vessels and skin of just slaughtered pigs have been investigated in nearly stationary stress tests. Tensile tests have produced tensile strength, ultimate stress and their appropriate strains, Young's modulus and the work up to fatigue of samples. In hysteresis tests the deformation work has been determined as a function of numbers of stress cycles. The hysteresis decrease with the number of stress cycles and approaches asymptotically to cero. By preconditioning of tendons, nerves and blood-vessels to steady state significant differences of strain at tensile strength and of Young's modulus have been established. Moreover for nerves the tests have revealed significant deviations of tensile strength. Bruise tests have been carried out with muscle tissue. For the described setup the limit force can be specified, at which pathological changes appear. Subsequently conducted histological investigations have demonstrated this. In dynamical bruise tests there appeared no pathological changes in muscle tissue in spite of higher transmitted energy.

Animals↗
PubMed1992

[Online control of evaluation algorithms of the image applied to identification of deglutition function].

Comprehensive software and hardware have been developed for the processing of biosignals. Such automatic signal processing, however not only has advantages, but also drawbacks. The question as to the reliability of the evaluation algorithm arises when the signal is modified, in the presence of interindividual differences, and in particular when noise is superimposed. This is of great interest for long-term recording when the original signal can no longer be inspected visually. The aim of our work was to display the signals on the screen of a monitor simultaneously with lines marking the points (start, end, extreme value, etc.) processed by the specific signal processing algorithm. The program package permits the on-line recording and monitoring of signals, the parallel processing and marking of detected events on the monitor, as well as storage of the parameters extracted. It is a very effective tool for developing, improving and monitoring of algorithms and their efficiency for signal processing.

Algorithms↗
PubMed1990

Post-transcriptional modification of serum creatine kinase in infected intensive care patients.

Low creatine kinase (CK) activities in serum are associated with high fatality rates in intensive care patients. The underlying mechanisms for this phenomenon were investigated. No correlation was found with other biochemical markers of inflammation (CRP, alpha-1 acid glycoprotein, alpha-2 macroglobulin). In the patients' serum a factor is described which is capable of increasing the activation energy of normal CK-MM, indicating molecular changes in CK-structure. This factor is likely to be an enzyme which is present in liver tissue and in fibroblasts. Similar results were obtained after in vitro treatment of normal serum samples with arylsulfatase. Furthermore, bacterial strains isolated in the serum of intensive care patients were found to alter human CK structure. In the investigated patient group, changes in CK activation energy are influenced by serum factors other than carboxypeptidase N activity.

Adolescent↗
PubMed1990

[Pulse oximetry].

Explore the source record for details and available documents.

Calibration↗
PubMed1989

Activation energy and lectin affinity chromatography of gamma-glutamyltransferase as a marker for enzyme heterogeneity.

Lectin affinity chromatography of gamma-glutamyl transferase (GGT,EC 2.3.2.2) is able to detect differences in the carbohydrate moiety of the enzyme. Binding of tissue GGT towards lectins is significantly different from serum GGT, showing increased galactosylation in tissue forms. Kidney GGT is less glycosylated than GGT from other tissues (liver, pancreas, prostate, vesiculae seminales). Increases in sialic acid content of GGT are associated with an increase in the activation energy of the catalyzed reaction. Differences in galactose, fucose and N-acetylhexosamine content induce much smaller effects on activation energy. In liver diseases, serum GGT is characterized by an altered affinity against lectins recognizing galactose, fucose and N-acetyglucosamine and by increased activation energy. In patients with liver disease, use of fixed temperature conversion factors can lead to erroneous calculations of serum GGT enzyme activity (errors up to 13.3%).

Adult↗