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991.
Complex Applications of HLM in Studies of Science and Mathematics Achievement: Cross‐Classified Random Effects Models 下载免费PDF全文
Mario Moreno Michael Harwell S. Selcen Guzey Alison Phillips Tamara J. Moore 《School science and mathematics》2016,116(6):338-351
Hierarchical linear models have become a familiar method for accounting for a hierarchical data structure in studies of science and mathematics achievement. This paper illustrates the use of cross‐classified random effects models (CCREMs), which are likely less familiar. The defining characteristic of CCREMs is a hierarchical data structure defined by multiple random factors at higher levels. We illustrate CCREMs using data for approximately 10,000 students from more than 250 high schools who attended one of 27 four‐year postsecondary institutions. The appropriate use of CCREMs helps to ensure unbiased estimates of effects and credible inferences. 相似文献
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993.
B M Chamberlain M Cheng D R Moore T M Ovitt E B Lobkovsky G W Coates 《Journal of the American Chemical Society》2001,123(14):3229-3238
A series of zinc(II) and magnesium(II) alkoxides based upon a beta-diiminate ligand framework has been prepared. [(BDI-1)ZnO(i)Pr](2) [(BDI-1) = 2-((2,6-diisopropylphenyl)amido)-4-((2,6-diisopropylphenyl)imino)-2-pentene] exhibited the highest activity and stereoselectivity of the zinc complexes studied for the polymerization of rac- and meso-lactide to poly(lactic acid) (PLA). [(BDI-1)ZnO(i)()Pr](2) polymerized (S,S)-lactide to isotactic PLA without epimerization of the monomer, rac-lactide to heterotactic PLA (P(r) = 0.94 at 0 degrees C), and meso-lactide to syndiotactic PLA (P(r) = 0.76 at 0 degrees C). The polymerizations are living, as evidenced by the narrow polydispersities of the isolated polymers in addition to the linear nature of number average molecular weight versus conversion plots and monomer-to-catalyst ratios. The substituents on the beta-diiminate ligand exert a significant influence upon the course of the polymerizations, affecting both the degree of stereoselectivity and the rate of polymerization. Kinetic studies with [(BDI-1)ZnO(i)Pr](2) indicate that the polymerizations are first order with respect to monomer (rac-lactide) and 1.56 order in catalyst. Polymerization experiments with [(BDI-1)MgO(i)Pr](2) revealed that this complex is extremely fast for the polymerization of rac-lactide, polymerizing 500 equiv in 96% yield in less than 5 min at 20 degrees C. 相似文献
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Sally J. Oxenford Stephen P. Moore Giorgio Carbone Graeme Barker Peter O’Brien Mark R. Shipton John Gilday Kevin R. Campos 《Tetrahedron: Asymmetry》2010,21(11-12):1563-1568
The use of aziridinium ions in two different projects is described. First, the stereospecificity of the ring opening of aziridinium ions with MeNH2 as a route to chiral diamines has been explored. When the aziridinium ion contained a phenyl or para-methoxyphenyl substituent, stereospecific ring opening occurred. In contrast, switching the para-methoxy group to a para-N,N-dimethylamino group gave a racemic diamine product. Second, starting from N-Boc pyrrolidine, asymmetric lithiation-trapping-ring expansion (via an aziridinium ion) was used to synthesise a piperidine alcohol. In this way, a formal synthesis of (?)-swainsonine was completed. 相似文献
998.
Ohne Zusammenfassung
Ueberseizt von J. Matula (Wien). 相似文献
999.
Th. Moore E. D. Campbell W. H. Andrews H. Grossmann Grossmann und Schück 《Fresenius' Journal of Analytical Chemistry》1909,48(12):778-780
Ohne Zusammenfassung 相似文献
1000.
Arthur V. Knishevitsky Nikolai I. Korotkikh Alan H. Cowley Jennifer A. Moore Tatyana M. Pekhtereva Oles P. Shvaika Gregor Reeske 《Journal of organometallic chemistry》2008,693(8-9):1405-1411
The stable biscarbenes, 1,4- and 1,3-bis[1-(1-adamantyl)-3-phenyl-1,2,4-triazol-5-yliden-4-yl]benzenes (4a,b) have been prepared. Treatment of 4b with copper(I) chloride and copper(I) iodide in acetonitrile or acetonitrile/toluene solution afforded the biscarbene copper(I) complexes 5a and 5b, respectively. The reactions of 4a and 4b with diphenyldiazomethane and sulfur resulted in the novel bisazine (6) and bisthione (7) derivatives, respectively. The X-ray crystal structures of 4a and 5b were determined. 相似文献