Paul Fatti

Applying mixture models to derive activity states of large herbivores from movement rates obtained using GPS telemetry

Abstract Context. To interpret spatial utilisation distributions, there is a need to translate animal locations obtained from global positioning system (GPS) telemetry into the activities performed and, hence, benefits derived, from particular places and times of day. Derived activity patterns also reveal how animals cope in changing environmental conditions. Aim. The aim of our research was to develop and test an objective, consistent and biologically faithful method for deriving activity states from movement rates between successive GPS locations. Methods. The method entails fitting mixtures of component statistical distributions to the frequency distribution of hourly step displacements. Breakpoints indicating transitions between predominant movement modes were identified by fitting exponential segments. Breakpoints were incorporated as off-sets for gamma distributions, but not needed for log-normal distributions. This procedure was applied to movement data for three large grazing ungulates. Key results. Models consistently distinguished four movement modes interpreted as representing resting, foraging, mixed movement and travelling activity. Breakpoints and parameter estimates were consistent among seasons and herds of each ungulate species. The exponential-segment model and both mixture models closely represented observed daily activity patterns. However, some adjustment of the derived time budgets was needed to be consistent with observations. Key conclusions. Mixture models provide an objective, reliable and biologically meaningful procedure for assessing seasonal, annual and spatial variation in the activity patterns of large ungulates from GPS data. Implications. The method can potentially be applied to other mobile foragers large enough to carry GPS collars.

Autotransplantation of maxillary canine teeth. A follow-up of 35 cases up to 4 years.

Abstract 35 cases of autotransplantation of nonendodontically treated maxillary canines were followed for up to 4 years and were assessed according to loss of the transplanted tooth, onset of sensibility, mobility, intact lamina dura and presence of tooth resorption. The results of this study compare favourably with other studies and favour the hypothesis that little is to be gained by not endodontically treating autotransplanted teeth immdiately after splint removal. It is also suggested that immobilization by means of a rigid splint, removing the tooth from occlusal forces, may account for the relatively low incidence of resorption in this series.

The effect of complete dentures on head posture

This study investigated possible changes in head posture after insertion of complete dentures in patients who had been edentulous for at least 6 months. The craniovertical angle was measured with a plastic ruler and protractor assembly, which was aligned with dots made on the skin over the zygomatic arch. Readings were made before denture insertion, immediately after insertion, and 15 and 30 minutes later. Two-way ANOVA was used to analyze the results. When the predenture insertion values were included, statistically significant changes (p less than 0.01) in head posture were found. However, when the predenture values were excluded, no statistically significant differences were found. The results support the conclusions that head posture is significantly altered immediately after insertion of dentures in edentulous patients but within the next 30 minutes there is no statistically significant alteration in head posture.