Measurement of isotopic uranium in water for compliance monitoring by liquid scintillation counting with alpha/beta discrimination

A simple and inexpensive method is described for analysis of uranium (U) activity and mass in water by liquid scintillation counting using $\alpha$/$\beta$ discrimination. This method appears to offer a solution to the need for an inexpensive protocol for monitoring U activity and mass simultaneously and an alternative to the potential inaccuracy involved when depending on the mass-to-activity conversion factor or activity screen.^ U is extracted virtually quantitatively into 20 ml extractive scintillator from a 1-$\ell$ aliquot of water acidified to less than pH 2. After phase separation, the sample is counted for a 20-minute screening count with a minimum detection level of 0.27 pCi $\ell\sp{-1}$. $\alpha$-particle emissions from the extracted U are counted with close to 100% efficiency with a Beckman LS6000 LL liquid scintillation counter equipped with pulse-shape discrimination electronics. Samples with activities higher than 10 pCi $\ell\sp-1$ are recounted for 500-1000 minutes for isotopic analysis. Isotopic analysis uses events that are automatically stored in spectral files and transferred to a computer during assay. The data can be transferred to a commercially available spreadsheet and retrieved for examination or data manipulation. Values for three readily observable spectral features can be rapidly identified by data examination and substituted into a simple formula to obtain $\sp{234}$U/$\sp{238}$U ratio for most samples. U mass is calculated by substituting the isotopic ratio value into a simple equation.^ The utility of this method for the proposed compliance monitoring of U in public drinking water supplies was field tested with a survey of drinking water from Texas supplies that had previously been known to contain elevated levels of gross $\alpha$ activity. U concentrations in 32 samples from 27 drinking water supplies ranged from 0.26 to 65.5 pCi $\ell\sp{-1}$, with seven samples exceeding the proposed Maximum Contaminant Level of 20 $\mu$g $\ell\sp{-1}$. Four exceeded the proposed activity screening level of 30 pCi $\ell\sp{-1}$. Isotopic ratios ranged from 0.87 to 41.8, while one sample contained $\sp{234}$U activity of 34.6 pCi $\ell\sp{-1}$ in the complete absence of its parent, $\sp{238}$U. U mass in the samples with elevated activity ranged from 0.0 to 103 $\mu$g $\ell\sp{-1}$. A limited test of screening surface and groundwaters for contamination by U from waste sites and natural processes was also successful. ^

Is maternal separation anxiety associated with school readiness?

Background. Increasing rates of maternal employment highlight the need for non-maternal child care for infants at an earlier age. Several studies have shown that employment induced maternal depression or psychological distress is associated with the child's socio-emotional and cognitive development. However, separation anxiety, a common phenomenon observed among employed mothers during early years, has seldom been studied. Therefore, the purpose of this study was to evaluate the role of maternal separation anxiety in the child's cognitive development.^ Methods. Data were obtained from Phase I (birth to 36 months) of the National Institute of Child Health and Human Development, Study of Early Child Care and Youth Development (NICHD SECCYD). Bivariate and multivariate analyses were performed to determine the association between separation anxiety groups and child outcomes. Multivariate analysis was also used to examine the mediating and/or moderating effect of sensitivity and moderating effect of difficult temperament.^ Results. Separation anxiety showed a negative association with the Bracken, attachment security, maternal sensitivity and psychological state. Children whose mothers never reported high levels of separation anxiety showed higher levels of school readiness and attachment security compared to those whose mothers experienced high levels of separation anxiety at least once. There was a significant interaction between separation anxiety and maternal sensitivity for the Bracken and attachment security indicating the moderating effect of sensitivity. Maternal sensitivity was also found to partially mediate the association between high levels of separation anxiety and school readiness or attachment security. However, the interaction between difficult temperament and separation anxiety was not significant for any of the child outcomes. ^ Conclusions. High levels of separation anxiety have a negative impact on school readiness, attachment security, maternal sensitivity and psychological state. In addition, mothers who experience high levels of separation anxiety but are sensitive during the mother-child interaction have children with high school readiness and attachment security compared to those who are less sensitive.^ Keywords. Maternal separation anxiety, School readiness. ^