The Relation of Reciprocated and Nonreciprocated Friendship Nominations to Peer Social Competence for Chinese Elementary School Children.

The authors examined associations between different forms of children's friendship nomination reciprocity (mutual, unilateral given, unilateral received) and other measures of children's peer social competence (liking, loneliness, overt aggression, perceived popularity) for 501 Chinese third- to sixth-grade students. Using a multigroup path analysis (with gender as group), for both boys and girls, all three forms of friendship nominations were negatively related to self-reported loneliness. Mutual friendship nominations and unilateral received friendship nominations were positively related to peer nominations for liking and to peer nominations of perceived popularity.

Sequential coprecipitation and matrix removal for determination of cadmium impurities from multivitamin supplements by inductively coupled plasma mass spectrometry and method validation by isotope dilution analysis of SRM 3280 multivitamin/multielement tablets.

In this paper, we examined three different sequential coprecipitation schemes based on Mg(OH) and CaF precipitation using triethylamine (TEA) and hydrofluoric acid (HF), respectively, for determination of cadmium (Cd) impurities from multivitamin/mineral (MVM) supplements by isotope dilution (ID) inductively coupled plasma mass spectrometry (ICP-MS). The schemes involved three-step coprecipitation with either TEA alone or in combination with HF and are designated as Scheme 1 (TEA-TEA-TEA), Scheme 2 (TEA-HF-TEA) and Scheme 3 (HF-TEA-TEA) according to the addition sequence of each reagent. Experiments were carried out with MVM solutions spiked with 60 μg L Cd from a multielement standard solution.