Age segregation of adolescents in and out of school

In a naturalistic study of age segregation during adolescence, 403 adolescents making up 153 separate groups were observed in three high schools and seven out-of-school settings. Age segregation was extensive, especially in school, among older adolescents in same-sex groups of friends. More mixed-age association was observed out of school among younger adolescents who were in mixed-sex groups containing relatives. Adolescents were most often observed with friends who were other adolescents, next with adults, and least frequently observed with children. Parents, particularly fathers, were rarely present. It was suggested that age segregation during adolescence is the result of a lack of contact with relatives.Received his Ph.D. from Michigan State University in 1974. Major research interest is parent-adolescent relations.Major research interests are adolescence and clinical psychology.     

Methods for ensuring the highest DNA concentration and yield in future and retrospective trace DNA extracts

In forensic laboratories, increased extraction efficiency of trace evidence is paramount because analytical success is intrinsically dependent on the quantity of DNA recovered. Moreover, highly concentrated nucleic acids are vital for effective downstream analysis and high quality results. This study investigated the efficiency of extraction with the Qiagen® QIAamp® DNA Investigator kit, and explored improvements to the methodology that would maximise the recovery of low concentration forensic samples. Controlled amounts of starting cellular material were used to mimic trace (or low level) DNA deposits prior to DNA extraction with the Investigator kit. Addition of the provided carrier RNA along with conducting two successive elutions of 50 µL improved the net recovery of DNA to 95%. Concentration with centrifugal filters post-extraction were able to concentrate DNA but a large net loss was observed. For the concentration of historic, retrospectively extracted DNA, centrifugal methods are able to concentrate DNA extracts previously too dilute for analysis. These concentrated volumes, however are small, allowing for minimal downstream analysis attempts before the sample is exhausted.