A review of techniques employed to estimate the number of motor units in a muscle.

Being the smallest functional units under neural control, motor units play an integral role in muscle physiology. However, at the present time, there does not exist any widely accepted technique for quantifying or estimating the number of motor units in a muscle. Specifically, the existing techniques are the increment-counting technique, a technique based on spike-triggered averaging, and a macro-EMG based technique which vary in invasiveness from noninvasive to highly invasive, respectively. We discuss each of these techniques, along with their associated shortcomings, in detail.

A critical review of experimental observations on ear-drum structure and function.

This paper presents a review of the experimental data available concerning ear-drum structure, properties and behaviour, in order to provide a basis for quantitative modelling and to identify areas where further information is required. The review of anatomy and structure indicates a lack of quantitative data about thickness, fibre distribution, three-dimensional curvature, and post-natal development. The mechanical properties of the ear-drum and attached structures are very poorly known, particularly with respect to isotropy, uniformity and damping. A historical review of observations of ear-drum vibration patterns shows general agreement that at low frequencies the displacements of the manubrium are smaller than those of the surrounding drum. Possible reasons are suggested for the apparent incompatibility of Békésy's capacitive-probe measurements with this picture.

Mechanical hazards in clinical equipment.

A wide variety of mechanical hazards are associated with clinical instrumentation containing mechanical components. Therefore, safety considerations for clinical equipment must be extended to include mechanical safety standards, maintenance programs, and operating procedures. Mechanical risk classes have been developed from the study of mechanical-mode failures of medical devices. To facilitate the development of priorities for clinical engineering involvement in mechanical safety programs, most mechanical devices which are commonly used in clinical practice have been assigned an appropriate risk classification. General recommendations for the development of such programs are also presented.

Modeling of the cat eardrum as a thin shell using the finite-element method.

A finite-element model of the cat eardrum is presented which includes the effects of the three-dimensional curved conical shape of the drum. The model is valid at low frequencies (below 1-2 kHz) and within the range of linear vibration amplitudes. The material properties used are based on a review of the literature. The critical material parameters are the stiffness (2 times 10(8) dyn cm(-2)) and thickness (40 micrometer) of the pars tensa. The model exhibits a vibration pattern and amplitude very similar to those observed experimentally using laser holography. A number of parameters are varied in order to study their relative importance in the model.