ABSTRACT:The seeded emulsion polymerization of styrene with emulsified monomer feeding was performed by polyethyl acrylate (PEA) latex as seed emulsion. It was shown that the grafting reactions occurred between two components on the composite latex particles. The loci of seeded polymerization were studied by the kinetics of grafting reaction. The highest grafting efficiency in the initial period of seeded emulsion polymerization supported the fact that the surfaces of PEA particles are the sites of polymerization of styrene. The grafting efficiency decreased with increasing monomerto-polymer ratio and initiator concentration.

Assessment literacy (AL) is central to the quality of education because competencies in assessing student learning lead to informed decisions. While the AL of university English teachers in China is particularly crucial as they teach the largest group of adult English language learners in the world, it has regrettably remained largely unexplored. The present study subjected an adapted version of the Teacher Assessment Literacy Questionnaire to rigorous psychometric property analyses, and used it to investigate the AL level of Chinese university English teachers (N=891) and the effects of their demographic characteristics on AL performance. Findings reveal a basic level of AL in certain dimensions with limited influence from demographic characteristics. Discussions are centered around validation of the AL instrument, causes for limited AL competence, and key factors that have impacted AL. This study concludes with a reflection of constructing contextually-grounded AL measures and implications for principles, policy and practice of teacher assessment education.

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Objectives: To compare the long-term in vitro effectiveness of a newer desensitizing agent containing bioactive glass and two other commercial products employed for dentin hypersensitivity.Methods: Fifty occlusal dentin disks from extracted sound human third molars were treated with 0.5M ethylenediaminetetraacetic acid for 2 min then randomly divided into five groups (n=10). Specimens were brushed for 2 min twice daily with Actimins Paste (Group1), Lesening Super Desensitizing Toothpaste (Group2), Colgate Sensitive Pro-Relief Desensitising Polishing Paste (Group3) and distilled water (Group4) at 9:00 am and at 5:00 pm. Specimens in Group5 had no brushings. All specimens were immersed sequentially for 5 min into coffee (pH=5.4) at 10:00 am and undiluted cola (pH=2.5) at 6:00 pm. Dentin permeability was measured weekly over one month using electrochemical impedance spectroscopy (EIS). Data were analyzed using two-way repeated measures ANOVA and post hoc LSD tests. Dentin microstructures were observed at one month by atomic force microscopy and scanning electron microscopy. Results:The three desensitizing agents significantly reduced dentin permeability over one month. Post hoc LSD tests of the EIS values indicated that brushing with Actimins showed no significant difference from Colgate Sensitive (P=0.32), and that both agents had significantly less permeability than Lesening (P<0.05). Conclusions:The three desensitizing agents were effective in occluding dentinal tubules and reducing permeability to varying extents over one month, with Actimins and Colgate Sensitive being the most effective. Actimins might be initially, a faster-working desensitizing agent.Clinical significance: Actimins, a newer desensitizing agent containing bioactive glass, has the potential to relieve dentin hypersensitivity in the presence of long-term daily acidic beverage ingestion.