Stability and determinants of sociometric status and friendship choice: A longitudinal perspective.

In a design that combined assessment of short- and long-term stability, 175 boys and 159 girls in the 5th grade were met twice while they were in 5 elementary schools and 3 times after they had entered a single consolidated middle school. At each of these meetings, Ss were asked to nominate 3 same-sex best friends and 3 disliked same-sex peers and to nominate peers for 14 roles in a hypothetical class play. Although there was greater consistency in the Ss' choices of best friends than disliked peers, the stability of acceptance was roughly equal to the stability of rejection. Correction of the test–retest correlations for measurement error indicated that previous studies probably underestimated stability on these measures. Analysis of the association between sociometric measures and social reputation revealed possible causal links between social reputation and subsequent social preference and social impact as assessed by structural equation modeling techniques. No evidence indicated greater consistency of liked and disliked peer choices among girls than among boys, and popularity was only slightly related to consistency in friendship relations. Results indicate that by early adolescence sociometric standing appears to be a relatively stable phenomenon. The need for the assessment of qualitative aspects of friendship relations is stressed. (37 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Smoke measurements in large-and small-scale fire testing — Part II

A new extinction photometer design has been developed that will provide the stability and accuracy necessary for taking smoke measurements in fire testing.     

O(2)-responsive chemical sensors based on hybrid xerogels that contain fluorinated precursors

We report the development and analytical figures of merit associated with several new O(2)-responsive sensor materials. These new sensing materials are formed by sequestering the luminophore tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) ([Ru(dpp)(3)](2+)) within hybrid xerogels that are composed of two of the following methoxysilanes: tetramethoxysilane, n-propyl-trimethoxysilane, 3,3,3-trifluoropropyl-trimethoxysilane, phenethyl-trimethoxysilane, and pentafluorophenylpropyl-trimethoxysilane. Steady-state and time-resolved luminescence measurements are used to investigate these hybrid xerogel-based sensor materials and elucidate the underlying reasons for the observed performance. The results show that many of the [Ru(dpp)(3)](2+)-doped composites form visually uniform, crack-free xerogel films that can be used to construct O(2) sensors that have linear calibration curves and excellent long-term stability. To the best of our knowledge, the [Ru(dpp)(3)](2+)-doped fluorinated hybrid xerogels also exhibit the highest O(2) sensitivity of any reported [Ru(dpp)(3)](2+)-based sensor platform.     

Reactions taking place in the system N,N,N′,N′,N″‐ pentakis(hydroxymethyl)melamine–oxirane in aqueous media

The results of studies on effects of the amount and type of oxirane, amount of catalyst and water, and temperature on the course of reactions taking place in the system N,N,N′,N′,N″‐pentakis(hydroxymethyl)melamine (PHMM)–oxirane carried out in aqueous media are reported. Quantitative determination of the content of functional groups present in the system and of side products formed in reactions of oxirane with water, made it possible to analyze in detail the processes taking place in the system. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 824–836, 2000