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A number of studies have been made on the sleep characteristics of children born preterm in an attempt to develop methods to address the sleep problems commonly observed among such children. However, the reported sleep characteristics from these studies vary depending on the observation methods used, i.e., actigraphy, polysomnography and questionnaire. In the current study, to obtain reliable data on the sleep characteristics of preterm-born children, we investigated the difference in sleep properties between 97 preterm and 97 term toddlers of approximately 1.5 years of age using actigraphy. Actigraphy units were attached to the toddlers’ waists with an adjustable elastic belt for 7 consecutive days, and a child sleep diary was completed by their parents. In the study, we found that preterm toddlers had more nocturnal awakenings and more daytime activity, suggesting that preterm-born children may have a different process of sleep development in their early development.

A measurement uncertainty estimation in the determination of ethyl aminobenzoate by diazotization titration and HPLC with UV detection (HPLC-UV) was carried out. Fishbone diagrams for determining the ethyl aminobenzoate purity by diazotization titration and HPLC-UV were prepared for the identification of factors that affect measurement uncertainties. In the case of diazotization titration, combined standard uncertainties for titers of a sodium nitrite solution used in the standardization and determination were larger than that for other factors. In the case of the HPLC, combined standard uncertainties for the chromatographic peak areas of ethyl aminobenzoate in standard and sample solutions were larger than that for other factors. A determination of the ethyl aminobenzoate purity in the bulk powder was also carried out using diazotization titration and HPLC-UV. The results concerning the ethyl aminobenzoate purity by diazotization titration and HPLC-UV were 100.5% (RSD = 0.26%, n = 6) and 100.6% (RSD = 0.36%, n = 6), respectively, indicating that both analytical results were essentially identical. The estimated combined standard uncertainties were within the 95% confidence interval of SD, which were obtained by the above-mentioned repetitive measurements.