Random walk and quantitative stratigraphical sequences

A sequence of digitized observations on short-normal resistivity determinations seems to show trend from higher to lower values. An appropriate statistical model proves it to have less range than expected on the distribution of its successive increments. On a two-tailed statistical procedure for testing deviations from a random walk, the series tends towards ‘stasis’ rather than trend. The random walk model is shown to be plausible for the problem considered.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73590/1/j.1365-3121.1992.tb00465.x.pd

Modulation of social interactions by immune stimulation in honey bee, Apis mellifera, workers

International audienceBACKGROUND:Immune response pathways have been relatively well-conserved across animal species, with similar systems in both mammals and invertebrates. Interestingly, honey bees have substantially reduced numbers of genes associated with immune function compared with solitary insect species. However, social species such as honey bees provide an excellent environment for pathogen or parasite transmission with controlled environmental conditions in the hive, high population densities, and frequent interactions. This suggests that honey bees may have developed complementary mechanisms, such as behavioral modifications, to deal with disease.RESULTS:Here, we demonstrate that activation of the immune system in honey bees (using bacterial lipopolysaccharides as a non-replicative pathogen) alters the social responses of healthy nestmates toward the treated individuals. Furthermore, treated individuals expressed significant differences in overall cuticular hydrocarbon profiles compared with controls. Finally, coating healthy individuals with extracts containing cuticular hydrocarbons of immunostimulated individuals significantly increased the agonistic responses of nestmates.CONCLUSION:Since cuticular hydrocarbons play a critical role in nestmate recognition and other social interactions in a wide variety of insect species, modulation of such chemical profiles by the activation of the immune system could play a crucial role in the social regulation of pathogen dissemination within the colony

Evolution in morphometric traits in North American Collignoniceratinae (Ammonoidea, Cephalopoda)

Volume: 5Start Page: 45End Page: 5

Microevolution in miocene Brizalina (foraminifera) studied by canonical variate analysis and analysis of landmarks

A stratigraphically oriented series of the Micoene formainiferal species Brizalina mandoroveensis from Ikang, Cameroon, was analyzed both by conventional multivariate morphometric procedures and by the tensor biometric method of Bookstein (1986; Statist. Sci. 1, 181-142), a method which analyzes sets of landmark points rather than specific variables of shape or size. The conventional analysis used five size-measures upon 170 specimens from five stratigraphic levels; the tensor analysis encompassed six landmarks (12 coordinates) upon 50 specimens. Whereas certain features appeared in both analyses, such as the separation between levels one and five, the techniques did not always agree with respect to the interpretation of those findings or about most details in the sequence of mean phenotypes. The canonical variate analysis bases its ordination upon a general size factor (the meaning of which is obscured by the foreshortening of within-group variation which is built into the technique). The tensor analysis locates a similar ordination using mainly features of shape.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28219/1/0000672.pd