The study of protein polymorphism in natural populations has stimulated heated controversy over the effects of various evolutionary forces on the observed patterns of genetic variation. One viewpoint is that a majority of the mutations at a locus are selectively equivalent and that variations in gene frequencies in time and space are primarily a result of nonselective evolutionary forces. The opposing view is that most mutations have sufficient effect on individual fitness that variations in gene frequencies are adaptations resulting from the action of natural selection. I compared gene frequency distributions among various loci to assess the roles of selective and nonselective evolutionary forces in determining patterns of allozyme variation in populations of rodents. I used two versions of the Lewontin-Krakauer test on temporal variation in allozyme frequencies reported for populations of the prairie vole, Microtus ochrogaster. The tests revealed that the changes in gene frequency were homogeneous among loci which suggests that nonselective forces such as genetic drift and migration were the primary cause of gene frequency change within populations. I also compared the spatial gene frequency distributions reported for 17 species of rodents to assess which evolutionary factors account for the genetic differentiation of populations within each species. Most loci showed similar degrees of differentiation, a pattern expected if nonselective forces operated in population differentiation. I found a positive relationship between the amount of differentiation of populations and the magnitude of positive association among rare alleles. This result suggests an active role of genetic drift in population differentiation within rodent species. The analysis of allozyme distributions in populations of rodents indicates that nonselective evolutionary forces play a substantial role in determining patterns of genetic variation. According to Wright's Shifting Balance Theory, the random differentiation of populations may actually accelerate adaptive evolution, which may account for the rapid evolutionary rates found in rodents.

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A model of the electromechanical characteristics, electrostatic characteristics and coil eddy current losses of a reed relay was developed. These characteristics were returned from reed and coil dimensions. The model was intended as an aid to the design of reed relays for Radio Frequency (RF) and high voltage applications. An electromechanical model of a reed switch and coil was developed using a combination of an axisymmetric finite element model and analytical methods. The characteristics returned from this model were operate, release and differential amp turns, contact gap and contact force. Inclusion of results for contact resistance against contact force yielded the contact resistance characteristics. Electrostatic force between reed contacts was calculated and a criteria for contact arcing in a vacuum applied to allow prediction of breakdown voltage in an evacuated reed switch. The above elements were incorporated in a "Reed Switch Design Program" in which operating, contact resistance and breakdown voltage characteristics were calculated from reed and coil dimensions. Results were found to be in agreement with measured values for three reed switch types. Eddy current losses in relay coils were investigated through experimental measurement of losses occurring in coils mounted around a copper conductor carrying a high frequency current. The losses occurring in the coil were found to present an effective resistance to the current in the conductor. The influence of coil dimensions and the magnetic properties of the conductor on losses were observed. An analytical model of eddy current losses was derived from first principals results and were found concordant with those measured. An "RF Reed Relay Design Program" embodying the eddy current loss model and preceding work was created to demonstrate how relay performance (and efficiency) can be enhanced by tuning reed and coil dimensions. An example of its successful application to product development at Crydom Magnetics Ltd is presented. Proposals for future work are included.

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