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Vitamin D is critical to children’s skeletal development and health. Despite this, the factors which determine vitamin D concentrations during infancy remain incompletely understood. This article reviews the literature assessing the factors which can affect vitamin D status in infancy, including antenatal and postnatal vitamin D supplementation. Observational data supports that dietary intake of vitamin D, UV exposure, and geographic factors contribute significantly to infants’ vitamin D status, but the relationship is unclear regarding genetic variation, ethnicity, and maternal vitamin D status. Randomised controlled trials have compared higher versus lower doses of infant vitamin D supplementation, but no studies have compared infant vitamin D supplementation to placebo and eliminated external sources of vitamin D to fully quantify its effect on vitamin D status. Knowledge gaps remain regarding the factors associated with optimal vitamin D concentrations in infants—including key factors such as ethnicity and genetic variation—and further studies are needed.

We are studying inspection systems based on the use of fast neutrons for detecting illicit substances such as explosives and drugs in luggage and cargo containers. Fast neutron techniques can determine the quantities of light elements such as carbon, nitrogen, and oxygen in a volume element. Illicit substances containing these elements are characterized by distinctive elemental densities or density ratios. We discuss modeling and tomographic reconstruction studies for fast-neutron transmission spectroscopy .

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