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In a 1992 Technometrics paper, Lambert (1992, 34, 1-14) described zero-inflated Poisson (ZIP) regression, a class of models for count data with excess zeros. In a ZIP model, a count response variable is assumed to be distributed as a mixture of a Poisson(lambda) distribution and a distribution with point mass of one at zero, with mixing probability p. Both(More)
Loblolly pine (Pinus taeda L.) is the most important plantation species in the southeastern United States and specific gravity (SG) is its most important wood quality trait. Analysis of annual ring SG of breast height (1.37 m) increment cores from 3957 trees representing 147 plantations across the species natural range showed that ring SG increases with(More)
BACKGROUND Whereas excess adiposity is presumed to be advantageous for the skeleton, studies investigating relations between bone strength and fat during youth have been equivocal. OBJECTIVES Relations of percentage body fat (BF) and bone strength indexes were assessed in late adolescent females, taking into consideration surrogates of muscle force [ie,(More)
In this article, we describe estimation and prediction methods for nonlinear modeling of forest growth variables that are subject to nested sources of variability. The multilevel nonlinear mixed-effects models that we consider are useful for a variety of forestry applications, but we concentrate on the problem of estimating, and making projections from,(More)
BACKGROUND Evidence suggests that adults and adolescents throughout the United States are at risk of poor vitamin D status. However, vitamin D concentrations in young American children have not been assessed. OBJECTIVE The relations between serum 25-hydroxyvitamin D [25(OH)D] and bone were examined in prepubertal girls. DESIGN In the present(More)
Exposure to secondhand smoke (SHS) in outdoor settings is a growing public health concern due to recent indoor smoking bans. The objective of this study was to measure salivary cotinine, a metabolite of nicotine, in subjects aged 21-30 exposed to SHS outside bars and restaurants in Athens, Georgia. Nonsmokers participated during 6-hr periods in outdoor(More)
Nonlinear mixed effects models have become important tools for growth and yield modeling in forestry. To date, applications have concentrated on modeling single growth variables such as tree height or bole volume. Here, we propose multivariate multilevel nonlinear mixed effects models for describing several plot-level timber quantity characteristics(More)
Despite adolescent black females experiencing the highest rates of obesity, the effect of excess fat mass on bone structure and strength in this population is unknown. Our findings in postadolescent black females suggest that excess weight in the form of fat mass may adversely influence cortical bone structure and strength. Although adolescent obesity has(More)
UNLABELLED Gymnasts' bone mineral characteristics are generally not known before starting their sport. Prepubertal females who enrolled in beginning artistic gymnastics (n = 65) had lower bone mineral than controls (n = 78). However, 2 years of gymnastics participation versus no participation led to a significantly greater accrual of forearm bone area and(More)
Nearly half of the world's population is exposed to household air pollution (HAP) due to long hours spent in close proximity to unvented cooking fires. We aimed to use PM2.5 and CO measurements to characterize exposure to cookstove generated woodsmoke in real time among control (n=10) and intervention (n=9) households in San Marcos, Cajamarca Region, Peru.(More)