Search PubMed⌕ Search

Biomedical subjects

W Ebeling

Publications and source records attributed to W Ebeling.

8 recordsLinked to original sources
PubMed1992

M.V. Volkenstein, evolutionary thinking and the structure of fitness landscapes.

High dimensional fitness landscapes are robustly dominated by saddle points, not isolated peaks. We present an argument to this effect that is reminiscent of May's complexity stability analysis and trace out the significance for the dynamics of speciation, the connection between the neutral and punctuated aspects of evolution and evolution on moving landscapes. The paper is written in honor of M.V. Volkenstein (October 23rd, 1912-February 18th, 1992), who devoted his last papers to uniting dynamics with evolutionary thinking.

Biological Evolution↗
PubMed1990

Effects of noise and inhomogeneous attractors in biochemical systems.

Biochemical systems capable of sustained oscillations and deterministic chaos were investigated, and effects of short-correlated noise on oscillations and chaos are reviewed. It is emphasized that fluctuations can be amplified drastically under certain circumstances and, therefore, they can be easily confused with truly chaotic behaviour. Biochemical systems exhibit typically inhomogeneous attractors. Inhomogeneity can be quantified by introducing local densities. The implication of inhomogeneity for time-series analysis is demonstrated by an example of experimental data from a chemical system.

Mathematics↗
PubMed1989

Dynamic pattern processing with adaptive excitable media.

We use an excitable medium for dynamic pattern processing. For this purpose the autowave structures arising from the light-sensitive Belouzov-Zhabotinsky reaction could serve as attractors. The dynamics is simulated as a non-linear network with local interaction in terms of cellular automata. With the help of a set of threshold electrodes the actual state is projected into a space of bytes. At the end of the adaptation procedure for the parameters we achieved the ability of this system for pattern recognition. Dynamic and statis pattern processing are compared with respect to information capacity and adaptation time.

Computer Simulation↗
PubMed1987

Gene analysis and the clinical chemist.

Knowledge of gene analysis methods and concepts will be important to the clinical chemist in the near future. Currently most gene analyses must be performed by indirect techniques, using polynucleotide probes hybridizing close to or on the disease gene but not on the position of the mostly unknown gene mutation (restriction fragment length polymorphism analysis). The sensitivity and specificity of such assays are affected by biological and methodologic factors, and are being continually improved. Preventive medicine is a promising area for gene analysis which will possibly fit well into the domain of clinical chemistry. The application of nucleotide hybridization analysis in tissue matching for organ transplantation, and in the detection and differential diagnosis of malignancies is in its early stages. A very promising, and rapidly emerging, technology is the direct detection and differentiation by gene probing of bacteria and viruses in medical microbiology. Guidelines for the ethical problems of gene analysis already exist within the field of medical ethics.

Chemistry, Clinical↗
PubMed1986

A stochastic description of evolutionary processes in underoccupied systems.

A stochastic description for underoccupied systems (large networks with small overall particle number) is given and represented by graphs. Evolutionary processes on this network are considered, especially the mutation process between components (hopping from one component to another) and the selection process.

Biological Evolution↗
PubMed1986

Modeling of selection processes with age-dependent birth and death rates.

Two simple models for the competition and selection in age-dependent populations are developed and analyzed mathematically. Following Eigen, competition is introduced by the condition of constant overall-number of the population. In the first model this condition is satisfied by regulation of a dilution flux and in the second case by regulation of a food density. The calculation of maximal fitness is given explicitly for both situations. It is shown that fitness depends in a complicated way on the age-dependence of the birth and death rates. Therefore species have to develop special aging strategies in order to survive in a population under selection pressure. In general, early reproduction is of advantage and increases fitness.

Age Factors↗
PubMed1975

[A glucose dehydrogenase for the determination of glucose concentrations in body fluids (author's transl)].

The isolation of glucose dehydrogenase from Bacillus megaterium M 1286 is outlined. Data on the specificity of the enzyme towards carbohydrates are given. A specific method for glucose determination using this enzyme was developed. Methods and results of four variants of this glucose determination are presented: End point determination in the UV range, determination with formazan as reaction product, kinetic determination in the UV range, and continuous flow analysis in the UV range (AutoAnalyzer method).

Alcohol Oxidoreductases↗