Cohort studies are often enriched for a primary exposure of interest to improve cost-effectiveness, which presents analytical challenges not commonly discussed in epidemiology. In this paper, we use causal diagrams to represent exposure-enriched cohort studies, illustrate a scenario wherein the risk ratio for the effect of a secondary exposure on an outcome is biased, and propose an analytical ...

China’s market potential is unparalleled, although many foreign business practitioners have commented that operating profitably in China is difficult, and more complex and time consuming than should be necessary. Given these facts, a lot of research on doing business in China gives recognition to the concept of Guanxi, a social and business relationship network, as the key to conducting success...

Mating is one aspect of behaviour that has been much ignored in mosquito biology. Yet, the success of a transgenic release strategy depends on normal, competitive mating between introduced and wild individuals. An overview is presented of current knowledge of mating behaviour in Culicidae, including timing of mating, means of sperm transfer, refractory behaviour and multiple mating. Most lacuna...

BACKGROUND Adolescent tobacco use remains a major public health priority to reduce the prevalence of tobacco use in community. The aim of this study was determining the association of the transitions in smoking stages with prevalence of cigarette smoking in the classes and schools in adolescents of Tabriz City (northwest of Iran). METHODS Fifty-six high schools were randomly selected, and 490...

OBJECTIVE Induced abortion is widely practiced in China. However, the information on induced abortion is limited. A national cross-sectional survey was designed to determine the risk factors of induced abortion among Chinese women with one child. METHODS We sampled 16,881 Chinese women with one living child for the study. A structured questionnaire was used to collect induced abortion and rel...