Craniofacial Form in Class III Cases

Lateral skull cephalograms from 50 patients who subsequently had surgical correction of their Class III malocclusion were analysed using a complete linkage cluster analysis based on skull shape. Five subgroups Were identified and are described. All subjects had a degree of mandibular prognathism while only 14 per cent had maxillary retrognathism. An increased lower face height was found in 58 per cent.

Factors Influencing the Distribution of Phytoplankton in 97 Headwater Lakes in Insular Newfoundland

Phytoplankton samples collected from 97 headwater lakes throughout insular Newfoundland were analyzed and used as a basis for a statistical evaluation of the environmental factors influencing species distributions. A selected subset of 77 taxa were clustered using a complete-linkage cluster analysis. The final 12 clusters represent the associations of species found occurring together in insular Newfoundland. Physical, chemical, and morphometric data collected with the phytoplankton served to characterize the environment. Factor analysis simplified the original variables, many of which were highly correlated and uninterpretable, into seven derived environmental factors: dystrophy, hardness, salinity, lake size, season, watershed influence, and orthophosphate enrichment. The resulting orthogonally rotated (VARIMAX) scores comprising these seven factors were correlated with species abundances. Spearman correlations showed several relationships between species distributions and the seven derived environmental factors. Although the analysis identified a subset of naturally acidic, dystrophic lakes, it failed to reveal any evidence of anthropogenic acidification in the lakes studied. For the most part, the members from each of the cluster groups demonstrated similar relationships with the derived environmental factors. The evidence suggests that the cluster groups may represent species associations; groups of species that co-occur because of their common requirements for specific environmental conditions. Phytoplankton autecological findings resulting from this study of insular Newfoundland lakes correspond well with conclusions derived independently from a comparable study of 95 headwater lakes in Labrador.

Étude des relations entre les communautés piscicoles et les différents habitats d'une rivière nordique: notion d'habitat optimal

A complete linkage cluster analysis using the physical characteristics of the sampling sites has revealed the existence of five groups corresponding to five habitat types nonequally distributed in a northern Quebec river. According to the results of discriminant analysis using the relative abundance of the fish species present, these habitats support populations which differ by the relative abundance of species and not by the presence or absence of some particular species. A habitat is first characterized by a species living preferentially in this habitat, then by the other species inhabiting the area in an opportunistic way, and finally by some satellite species which do not seem to have any marked requirements. A habitat is considered as optimal for a species first if this species inhabits this area preferentially to others and secondly if this use is more advantageous for growth or condition factor. This seems to be confirmed for two of the most abundant species, northern pike (Esox lucius) and lake whitefish (Coregonus clupeaformis), both of which have a higher condition factor and a better growth in the part of the river where their optimal habitat is more frequently found.

Cluster and Principal Components Analyses of the Group Embedded-Figures Test

The structure of the Group Embedded-figures Test was examined. Data from 173 females and 93 males were subjected to Johnson's complete-linkage cluster analysis and principal components analysis. The results showed the importance of simple form type especially Form E, the cube, and of item position. Recommendations for the future study of the structure of embedded-figures tests were presented.