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Ambulatory health care in developing countries is often provided by medical or paramedical personnel commonly called village health workers. Medical problems within their realm of competence include diarrhea, infestation with worms, diseases affecting the eyes and the skin, and several kinds of infectious diseases. Also, assessment of malnutrition is among the tasks village health workers have to perform. A knowledge-based system is designed and implemented to provide decision support for those tasks. Expanded decision networks are used to represent the diagnostic processes for diarrhea and infestation with worms. The diagnostic procedures for diseases affecting the skin and the eyes are covered with a rule-based approach using two certainty factors. Treatment schemes and procedural knowledge about drug prescription are represented in a frame structure. The hybrid knowledge engineering tool VIE-KET is used to construct a modular consultation system that provides entry points for diagnosis, therapy, and dr...

The component PIII of the electroretinogram representing the optic generator potential was recorded after stimulation with short stimuli with different light intensity. It is shown that the impulse response function of a linear second order model with intensity-dependent coefficients can be well fit to the recordings. Two of its parameters, after logarithmic transformations, are linearly dependent on the luminance while the third parameter varies only within a small interval. It is therefore possible to describe the relation between PIII and luminance in a linearized second order model. Furthermore, both the type of the function relating the gain of the model to the luminance and its exponent are nearly identical with the psychophysic function relating luminance to subjective brightness. Further physiological implications are also considered.

The temperature dependence of the negative component P III of the rabbit's electroretinogram has been studied in former experiments. A mathematical model of this component is expressed by the transfer function of a second order system. By means of electronic computations of the parameters a good fit to the experimental curves has been attained. The influence of different temperature (10–30° C) is reflected in the model by changes of 2 constants only. The 10 values of these changes are rather high (>2). Possibilities and limitations of the model are discussed.

A computer program is presented which transforms simultaneous recordings of multiple electrodes into graphical approximate representations of isopotential lines.

The electroretinogram of isolated retinae of human eyes which had to be enucleated owing to an absolute glaucoma was split into two components: a negative one identified as P III and an oscillating one. By means of electronic computations two corresponding mathematical functions were fit successively to the experimental curve and then added for comparison. Though this synthetisized curve differs markedly from the empirical one in the later part, it shows a close fit in the initial state. Limitations of the mathematical simulation model are discussed.