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71.
Parents’ Attitudes Toward Mathematics and the Influence on Their Students’ Attitudes toward Mathematics: A Quantitative Study 下载免费PDF全文
Margaret J. Mohr‐Schroeder Christa Jackson Maureen Cavalcanti Cindy Jong D. Craig Schroeder Lydia G. Speler 《School science and mathematics》2017,117(5):214-222
The purpose of this study was to investigate parents’ attitudes toward mathematics, their students' attitude toward mathematics, and the influence of the parents’ attitude on the students' attitude toward mathematics. Data analyses revealed statistically significant positive correlations between parents’ and students’ attitudes toward mathematics. Additionally, parents’ mathematics attitude significantly predicted students’ attitudes toward mathematics (n=146). By understanding the influence of parents’ attitudes on students’ attitudes toward mathematics, school efforts can be geared toward fostering favorable attitudes toward mathematics among parents. 相似文献
72.
The synthesis of synthetically useful alpha-CF2-glycosides by radical addition of ethyl bromodifluoroacetate onto 2-benzyloxyglycals is described. The methodology provides an access to alpha-O-glycoside mimics and, potentially, to valuable alpha-O-glycoconjugate analogues. 相似文献
73.
Selected ion flow tube mass spectrometry (SIFT-MS) has been employed to study the ion-molecule reactions of 17 alkyl esters reacting with the common SIFT-MS reagent ions, H3O+, H3O+.nH2O (n = 1, 2, 3), NO+, and O2+. The majority of reactions were observed to proceed at or near collision rate, with the exception of H3O+.3H2O, which was found to be slow for 8 of 17 alkyl esters. Unexpected product ions in the form of the parent carboxylic acid cation were observed to arise from the H3O+ and NO+ reactions of some alkyl esters. The observed reactions have been probed by the ab initio CBS-4M and G2(MP2,SVP) methods. The postulated reaction pathway involves a 1,5 H atom migration from a beta-carbon onto the carbonyl oxygen. 相似文献
74.
Kissane M Murphy M O'Brien E Chopra J Murphy L Collins SG Lawrence SE Maguire AR 《Organic & biomolecular chemistry》2011,9(7):2452-2472
Synthetically versatile conjugate addition of a range of carbon, nitrogen, oxygen, sulfur and selenium nucleophiles to the highly functionalised 2-thio-3-chloroacrylamides is described. The stereochemical and synthetic features of this transformation are discussed in detail. In most instances, the nucleophile replaces the chloro substituent with retention of stereochemistry. With the oxygen nucleophiles, a second addition can occur leading to acetals, while with the nitrogen nucleophiles, E-Z isomerism occurs in the resulting enamine derivatives. The ratio of the E/Z isomers can be rationalised on the basis of the substituent and the level of oxidation. 相似文献
75.
76.
A general approach to controlling the surface composition of poly(ethylene oxide)-based block copolymers for antifouling coatings 总被引:1,自引:0,他引:1
Dimitriou MD Zhou Z Yoo HS Killops KL Finlay JA Cone G Sundaram HS Lynd NA Barteau KP Campos LM Fischer DA Callow ME Callow JA Ober CK Hawker CJ Kramer EJ 《Langmuir : the ACS journal of surfaces and colloids》2011,27(22):13762-13772
To control the surface properties of a polystyrene-block-poly(ethylene oxide) diblock copolymer, perfluorinated chemical moieties were specifically incorporated into the block copolymer backbone. A polystyrene-block-poly[(ethylene oxide)-stat-(allyl glycidyl ether)] [PS-b-P(EO-stat-AGE)] statistical diblock terpolymer was synthesized with varying incorporations of allyl glycidyl ether (AGE) in the poly(ethylene oxide) block from 0 to 17 mol %. The pendant alkenes of the AGE repeat units were subsequently functionalized by thiol-ene chemistry with 1H,1H,2H,2H-perfluorooctanethiol, yielding fluorocarbon-functionalized AGE (fAGE) repeat units. (1)H NMR spectroscopy and size-exclusion chromatography indicated well-defined structures with complete functionalization of the pendant alkenes. The surfaces of the polymer films were characterized after spray coating by X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure spectroscopy (NEXAFS), showing that the P(EO-stat-fAGE) block starts to compete with polystyrene to populate the surface after only 1 mol % incorporation of fAGE. Increasing the incorporation of fAGE led to an increased amount of perfluorocarbons on the surface and a decrease in the concentration of PS. At a fAGE incorporation of 8 mol %, PS was not detected at the surface, as measured by NEXAFS spectroscopy. Water contact angles measured by the captive-air-bubble technique showed the underwater surfaces to be dynamic, with advancing and receding contact angles varying by >20°. Protein adsorption studies demonstrated that the fluorinated surfaces effectively prevent nonspecific binding of proteins relative to an unmodified PS-b-PEO diblock copolymer. In biological systems, settlement of spores of the green macroalga Ulva was significantly lower for the fAGE-incorporated polymers compared to the unmodified diblock and a polydimethylsiloxane elastomer standard. Furthermore, the attachment strength of sporelings (young plants) of Ulva was also reduced for the fAGE-containing polymers, affirming their potential as fouling-release coatings. 相似文献
77.
Gill BD Indyk HE Kumar MC Sievwright NK Manley-Harris M Dowell D 《Journal of AOAC International》2012,95(3):599-602
A method for the routine determination of 5'-mononucleotides (uridine 5'-monophosphate, inosine 5'-monophosphate, adenosine 5'-monophosphate, guanosine 5'-monophosphate, and cytidine 5'-monophosphate) in infant formula and adult nutritionals is described. After sample dissolution and addition of internal standard, potential interferences were removed by anion-exchange SPE followed by HPLC-UV analysis. Single-laboratory validation performance parameters include recovery (92-101%) and repeatability (1.0-2.3% RSD). The method was approved for Official First Action status by an AOAC expert review panel. 相似文献
78.
Wawrzyn GT Quin MB Choudhary S López-Gallego F Schmidt-Dannert C 《Chemistry & biology》2012,19(6):772-783
The secondary metabolome of Basidiomycota represents a largely uncharacterized source of pharmaceutically relevant natural products. Terpenoids are the primary class of bioactive compounds isolated from mushrooms. The Jack O'Lantern mushroom Omphalotus olearius was identified 50 years ago as a prolific producer of anticancer illudin sesquiterpenoids; however, to date there have been exceptionally few studies into the biosynthesis of these important compounds. Here, we report the draft genome sequence of O. olearius, which reveals a diverse network of sesquiterpene synthases and two metabolic gene clusters associated with illudin biosynthesis. Characterization of the sesquiterpene synthases enabled a comprehensive survey of all currently available Basidiomycota genomes, thereby creating a predictive resource for terpenoid natural product biosynthesis in these organisms. Our results will facilitate discovery and biosynthetic production of unique pharmaceutically relevant bioactive compounds from Basidiomycota. 相似文献
79.
80.
The reactions of py‐hz ligands ( L1–L5 ) with Pb(CF3SO3)2?H2O resulted in some rare examples of discrete single‐stranded helical PbII complexes. L1 and L2 formed non‐helical mononuclear complexes [Pb L1 (CF3SO3)2]?CHCl3 and Pb L2 (CF3SO3)2][Pb L2 CF3SO3]CF3SO3?CH3CN, which reflected the high coordination number and effective saturation of PbII by the ligands. The reaction of L3 with PbII resulted in a dinuclear meso‐helicate [Pb2 L3 (CF3SO3)2Br]CF3SO3?CH3CN with a stereochemically‐active lone pair on PbII. L4 directed single‐stranded helicates with PbII, including [Pb2 L4 (CF3SO3)3]CF3SO3?CH3CN and [Pb2 L4 CF3SO3(CH3OH)2](CF3SO3)3?2 CH3OH?2 H2O. The acryloyl‐modified py‐hz ligand L5 formed helical and non‐helical complexes with PbII, including a trinuclear PbII complex [Pb3 L5 (CF3SO3)5]CF3SO3?3CH3CN?Et2O. The high denticity of the long‐stranded py‐hz ligands L4 and L5 was essential to the formation of single‐stranded helicates with PbII. 相似文献