Measurements of the particle size distribution at the outlets of six coal-fired utility boilers showed a peak at a particle diameter near 0.1 micrometer. This submicrometer mode appears to be a general feature of coal combustion that results from a volatilization-condensation process in the boiler. At the boilers tested, the submicrometer mode contained 0.2 to 2.2 percent of the total fly ash mass. The importance of this mode is greater than its small quantity suggests because particles in the submicrometer size range are often much more difficult to collect with conventional particulate control devices than larger particles. Thus, the submicrometer mode may significantly influence the design and selection of future power plant emission controls. The particle mass in the submicrometer mode was correlated with the nitric oxide concentration in the flue gas. This correlation suggests that control of nitric oxide by modification of the combustion conditions may reduce the generation and emission of submicrometer particles.

No abstract

No abstract

This study considered the quality and stability of infant and toddler nonparental child care from 6 to 36 months in relation to language, social, and academic skills measured proximally at 36 months and distally at kindergarten. Quality was measured separately as caregiver-child verbal interactions and caregiver sensitivity, and stability was measured as having fewer sequential childcare caregivers. This longitudinal examination involved a subsample (N = 1,055) from the Family Life Project, a representative sample of families living in rural counties in the United States. Structural equation modeling revealed that children who experienced more positive caregiver-child verbal interactions had higher 36-month language skills, which indirectly led to higher kindergarten academic and social skills. Children who experienced more caregiver stability had higher kindergarten social skills.

No abstract