We study the rapid X-ray time variability in all public data available from the Rossi X-ray Timing Explorer's Proportional Counter Array on the atoll source 4U 1820–30 in the low-luminosity island state. A total of ∼ 46 ks of data were used. We compare the frequencies of the variability components of 4U 1820–30 with those in other atolls sources. These frequencies were previously found to follo...

Parasites are incredibly diverse. An important factor in the evolution of this diversity is the fact that many parasite species are restricted to 1, or just a few, host species. In addition, some parasites exhibit geographic specificity that is nested within their specificity to a particular species of host. The environmental factors that restrict parasites to particular regions within the host...

The determinants of human sensitivity to concurrent variable-interval variable-interval schedules of reinforcement have been difficult to identify, in part because of procedural differences separating published experiments. This experiment investigated vigilance to stimuli correlated with concurrent schedules. Across phases, 3 college students were provided with either no schedule-correlated st...

Concept mapping has become a popular learning tool. However, the processes underlying the task are poorly understood. In the present study, we examined the effect of creating a concept map on the processing of item-specific information. In 2 experiments, subjects learned categorized or ad hoc word lists by making pleasantness ratings, sorting words into categories, or creating a concept map. Me...

The January 2011 issue includes 6 papers that are copublished by Chronic Diseases in Canada (CDIC) and Preventing Chronic Disease (PCD). In this example of copublishing, each journal is the primary publisher of 3 of the papers and secondary publisher of the other 3. Copublication is uncommon among scientific journals; however, it does offer an opportunity for journals to reach a broader readers...

OBJECTIVE To examine the independent and combined associations of the components of physical fitness with academic performance among youths. STUDY DESIGN This cross-sectional study included a total of 2038 youths (989 girls) aged 6-18 years. Cardiorespiratory capacity was measured using the 20-m shuttle run test. Motor ability was assessed with the 4×10-m shuttle run test of speed of movement...

The present study attempted to determine the direction and etiology of the robust relationship between childhood externalizing (EXT) symptoms and parent-child conflict using a genetically informative longitudinal model and data from the ongoing Minnesota Twin Family Study. Participants consisted of 1,506 same-sex twins assessed at ages 11 and 14, and their parents. The relationship between EXT ...