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51.
This research is concerned with preservice teacher understanding of six earth and space science concepts that are often taught in elementary school: the reason for seasons, phases of the moon, why the wind blows, the rock cycle, soil formation, and earthquakes. Specifically, this study examines the effect of readings, hands‐on learning stations, and concept mapping in improving conceptual understanding. Undergraduates in two sections of a science methods course (N= 52) completed an open‐ended survey, giving explanations about the above concepts three times: as a pretest and twice as posttests after various instructional interventions. The answers, scored with a three point rubric, indicated that the preservice teachers initially had many misconceptions (alternative conceptions). A two way ANOVA with repeated measures analysis (pretest/posttest) demonstrated that readings and learning stations are both successful in building preservice teacher's understanding and that benefits from the hands‐on learning stations approached statistical significance. Concept mapping had an additive effect in building understanding, as evident on the second posttest. The findings suggest useful strategies for university science instructors to use in clarifying science concepts while modeling activities teachers can use in their own classrooms. 相似文献
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Nermin Biricik Zhaofu Fei Rosario Scopelliti PaulJ. Dyson 《Helvetica chimica acta》2003,86(10):3281-3287
The polydentate phosphinoamines 1,3‐{(Ph2P)2N}2C6H4 and 2,6‐{(Ph2P)2N}2C5H3N have been prepared in a single step from the reaction of the amines 1,3‐(NH2)2C6H4 or 2,6‐(NH2)2C5H3N with Ph2PCl in presence of Et3N (1 : 4 : 4 molar ratio) in CH2Cl2. Reaction of 1,3‐{(Ph2P)2N}2C6H4 or 2,6‐{(Ph2P)2N}2C5H3N with elemental sulfur or selenium in CH2Cl2 affords the corresponding tetrasulfide or tetraselenide, respectively, in good yield. The complexes [1,3‐{Mo(CO)4(Ph2P)2N}2(C6H4)] and [2,6‐{Mo(CO)4(Ph2P)2N}2(C5H3N)] were prepared from the reaction of these phosphinoamines with [Mo(CO)4(nbd)] (nbd=norbornadiene) in toluene, and the structure of the latter complex has been determined by single‐crystal X‐ray diffraction analysis. 相似文献
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Nermin Gundogan 《European Polymer Journal》2003,39(11):2209-2216
Modulus of elasticity of highly charged N-isopropylacrylamide (NIPA) based hydrogels (PNIPA) are measured at various swelling degrees in water. The sodium salt of 2-acrylamido-2-methylpropane sulfonic acid (AMPS) was used as the ionic comonomer of NIPA in the hydrogel preparation. The mole fraction of AMPS in the comonomer feed was varied between 0 and 1, while the crosslinker ratio was fixed at 1/85. The elasticity data show that the equilibrium swollen PNIPA hydrogels are in the non-Gaussian regime. Equations were derived based on the inverse Langevin function for the swelling ratio and the modulus of highly charged PNIPA hydrogels and checked by experiments. Results of calculations show good agreement to the swelling and elasticity data of highly swollen PNIPA gels. 相似文献
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3‐Amino‐2‐cyano‐4,6‐disubstituted‐thieno{2,3‐b}pyridines and 3‐aminopyridine were diazotized and coupled with 2‐phenylindole, 2‐methylindole, and 1‐methyl‐2‐phenylindole, respectively. These dyes were characterized by UV‐Visible, FT‐IR, 1H NMR, and mass spectroscopic techniques. Solvent effects on the visible absorption spectra of the dyes were evaluated. The color of the dyes is discussed with respect to the nature of the heterocyclic ring and substituent present therein. In addition, effects of temperature, concentration, as well as acid and base on the visible absorption maxima of the dyes are reported. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:622–630, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20361 相似文献
56.
Nickel complex of O, O'-dinonyldithiophosphoric acid was prepared and characterised. Solvent extraction of nickel dinonyldithiophosphate [Ni(DNDTP)2] from acidic aqueous solutions into different organic phases was investigated and concentration of nickel was determined spectrophotometrically. A simple and selective spectrophotometric method was developed and applied to sediment samples. 相似文献
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Murat Aydemir Nermin Meric Bahattin Gümgüm Ertan ?ahin 《Journal of organometallic chemistry》2011,696(13):2584-2588
Reaction of Ph2PNHCH2-C4H3S with [Ru(η6-p-cymene)(μ-Cl)Cl]2, [Ru(η6-benzene)(μ-Cl)Cl]2, [Rh(μ-Cl)(cod)]2 and [Ir(η5-C5Me5)(μ-Cl)Cl]2 yields complexes [Ru(Ph2PNHCH2-C4H3S)(η6-p-cymene)Cl2], 1, [Ru(Ph2PNHCH2-C4H3S)(η6-benzene)Cl2], 2, [Rh(Ph2PNHCH2-C4H3S)(cod)Cl], 3 and [Ir(Ph2PNHCH2-C4H3S)(η5-C5Me5)Cl2], 4, respectively. All complexes were isolated from the reaction solution and fully characterized by analytical and spectroscopic methods. The structure of [Ru(Ph2PNHCH2-C4H3S)(η6-benzene)Cl2], 2 was also determined by single crystal X-ray diffraction. 1-4 are suitable precursors forming highly active catalyst in the transfer hydrogenation of a variety of simple ketones. Notably, the catalysts obtained by using the ruthenium complexes [Ru(Ph2PNHCH2-C4H3S)(η6-p-cymene)Cl2], 1 and [Ru(Ph2PNHCH2-C4H3S)(η6-benzene)Cl2], 2 are much more active in the transfer hydrogenation converting the carbonyls to the corresponding alcohols in 98-99% yields (TOF ≤ 200 h−1) in comparison to analogous rhodium and iridium complexes. 相似文献