Fate and exposure models in relation to risk assessment

The recognition of potential long-term effects of substances, has led to the development of regulations and legislation which emphasis the need for assessing the risks posed by both new and existing substances for man and the environment. The evaluation of fate and exposure models is put into perspective in relation to the developments over the last five years in the framework of the EU regulations and national legislation within the European Community. The validation of environmental exposure models (multi-media models) is described in the context of quality assurance of models available to a user group, which is different from the quality assurance aspects for a developers group.     

Maternal investment and sex ratio adjustment in American bison calves

Summary Cow-calf behavior was observed in American bison (Bison bison) to determine if mothers invested differentially in sons and daughters. Cows nursed sons significantly longer than they did daughters in their first three months of life. The increased nursing time for sons was not compensated for by increased grazing time by their mothers. Grazing and activity patterns did not differ significantly between sons and daughters. Cows that had sons bred later in the breeding season than nulliparous cows, barren cows, or cows with daughters. Nine yearling sons compared to only two yearling daughters continued to suckle from their mothers for up to 15 months of age. Cows that had sons the previous year were more apt to be barren in the current year than cows that had daughters in the previous year.     

Das Problem der Krebsverbreitung und Krebsbekämpfung

The Science of Nature -