Children who are viewed as ready for kindergarten and/or first grade typically exhibit high attention, approach, and adaptability coupled with low activity and reactivity. These characteristics tend to be especially valued by teachers and describe a child who is "teachable," or school ready. Since many children enter formal schooling earlier by attending pre-K for 4-year olds, often called 4-year-old kindergarten, there is a need to examine school readiness earlier than kindergarten, which may look very different developmentally.
View Article and Find Full Text PDFThe best evidence for gender differences in child temperament is in the broad areas of effortful control and surgency, and to an extent negative affectivity, domains that encompass temperament dimensions of inhibitory control, activity level, and shyness. We examined the influence of child gender in a methodologically comprehensively assessed twin sample. We used mother, father, and Laboratory Temperament Assessment Battery (Lab-TAB) ratings to assess temperament in 3 year-olds.
View Article and Find Full Text PDFAn apparatus is described which measures the equilibrium distribution of a hydrocarbon between a gas and aqueous phase. Soluble hydrocarbons are extracted from an aqueous salt solution by very small bubbles of hydrogen generated electrolytically from a gold electrode located at the bottom of a cylindrical cell. The partition coefficient is determined from the volume of the aqueous solution and the solute concentration in the head-space after a measured volume of hydrogen has bubbled through the cell.
View Article and Find Full Text PDFJ Res Natl Bur Stand (1977)
January 1982
A theoretical relationship is developed to provide a quantitative definition of hydrophobicity using established theoretical and semi-empirical relationships. A method of predicting partition coefficients of relatively water-insoluble third components between water and an immiscible second component is devised and tested. Comparison with experimental data for four classes of compounds in the water/-octanol system at 25 °C shows excellent agreement, indicating that values for substances for which direct determination is experimentally precluded can be calculated with confidence.
View Article and Find Full Text PDFThe aqueous solubility of 14 organic solutes has been calculated from their octanol/water partition coefficient and from their solute activity coefficient in octanol at infinite dilution. The solute activity coefficients were calculated from the Flory-Huggins and Hildebrand-Scatchard (FH-HS) equations and were found to be in good agreement with the activity coefficients determined from GC specific retention volume measurements. The calculated solubilities were in good agreement with the experimental solubilities.
View Article and Find Full Text PDFGenerator columns packed with a solid support and loaded with a liquid organic phase make it possible to rapidly and conveniently equilibrate water with the organic phase. By coupling the generator column to an extractor column for high pressure liquid chromatographic analysis of the aqueous solution, errors from surface adsorption and loss to the atmosphere are avoided. Using this method, the mean values and confidence limits at a 95 percent confidence level of the aqueous solubility, , and the octanol-water partition coefficient, , of n-propylbenzene at 25 °C were found to be = (4.
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