[The population dynamics of Salmonella typhi and Tetrahymena pyriformis during joint cultivation]. / Dinamika populiatsii Salmonella typhi i Tetrahymena pyriformis pri sovmestnom kul'tivirovanii.

The data on changes in the number, as well as cultural and biological properties of S. typhi and free-living T. pyriformis in the course of their joint cultivation at 2 degrees C and 25 degrees C are presented. As suggested on the basis of the results of this experiment, the interaction of S. typhi with T. pyriformis may facilitate the preservation of the bacteria in the environment and be a stage in their migration along trophic chains.

[The use of non-Euclidean metrics in epidemiological classifications]. / Ispol'zovanie neevklidovykh metrik v épidemiologicheskikh klassifikatsiiakh.

A non-Euclidean metric, stable to pollutions in sample data, for hierarchical cluster analysis in epidemiology is proposed. The simplicity of calculations permits its easy use in practice. On the basis of this metric the towns of Tula Province have been grouped according to morbidity rates in the shigellosis of Flexner and Sonne with the conjugated value of parameters.

[Validity of epidemiological classification: construction of a discriminant criterion]. / Dostovernost' épidemiologicheskikh klassifikatsii: postroenie diskriminantnogo kriteriia.

A new criterion has been proposed to assess the validity of group division differences obtained by preliminary cluster analysis. The method was used to provide evidence for the validity of differences between the groups as to epidemiological classifications. The paper shows it expedient to use the method in the epidemiological analysis.