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81.
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Yew Hoong Leong Sook Fwe Yap Khiok Seng Quek Eng Guan Tay Cherng Luen Tong Yao Teck Ong 《International Journal of Mathematical Education in Science & Technology》2013,44(8):1257-1267
In this article, we share our learning experience as a Lesson Study team. The Research Lesson was on Figural Patterns taught in Year 7. In addition to helping students learn the skills of the topic, we wanted them to develop a problem-solving disposition. The management of these two objectives was a challenge to us. From the lesson observation and the students’ classwork, it turned out better than we expected. 相似文献
84.
Li L Murthy NN Telser J Zakharov LN Yap GP Rheingold AL Karlin KD Rokita SE 《Inorganic chemistry》2006,45(18):7144-7159
A dinuclear copper(II) complex [Cu(II)2(PD'O-)(H2O)2](ClO4)3 (5) with terminal Cu(II)-H(2)O moieties and a Cu...Cu distance of 4.13 A (X-ray structure) has been synthesized and characterized by EPR spectroscopy (ferromagnetic coupling observed) and cyclic voltammetry. Dizinc(II) and mononuclear copper(II) analogues [Zn(II)2(PD'O-)(H2O)2]3+ (7) and [Cu(II)(mPD'OH)(H2O)]2+ (6), respectively, have also been synthesized and structurally characterized. Reacting 5/MPA/O(2) (MPA = 3-mercaptopropionic acid) with DNA leads to a highly specific oxidation of guanine (G) at a junction between single- and double-stranded DNA. Mass spectrometric analysis of the major products indicates a gain of +18 and +34 amu relative to initial DNA strands. The most efficient reaction requires G at the first and second unpaired positions of each strand extending from the junction. Less reaction is observed for analogous targets in which the G cluster is farther from the junction or contains less than four Gs. Consistent with our previous systems, the multinuclear copper center is required for selective reaction; mononuclear complex 6 is not effective. Hydrogen peroxide as a substitute for MPA/O2 also does not lead to activity. Structural analysis of a [Cu(II)2(PD'O-)(G)]3+ complex (8) and dizinc analogue [Zn(II)(2)(PD'O-)(G)](ClO4)3 (9) (G = guanosine) reveals coordination of the G O6 and N7 atoms with the two copper (or zinc) centers and suggests that copper-G coordination likely plays a role in recognition of the DNA target. The Cu2-O2 intermediate responsible for guanine oxidation appears to be different from that responsible for direct-strand scission induced by other multinuclear copper complexes; the likely course of reaction is discussed. 相似文献
85.
Wei Boon Yap Beng Ti Tey Noorjahan Banu Mohamed Alitheen Wen Siang Tan 《Journal of chromatography. A》2010,1217(21):3473-3480
Hepatitis B core antigen (HBcAg) is used as a diagnostic reagent for the detection of hepatitis B virus infection. In this study, immobilized metal affinity-expanded bed adsorption chromatography (IMA-EBAC) was employed to purify N-terminally His-tagged HBcAg from unclarified bacterial homogenate. Streamline Chelating was used as the adsorbent and the batch adsorption experiment showed that the optimal binding pH of His-tagged HBcAg was 8.0 with a binding capacity of 1.8 mg per ml of adsorbent. The optimal elution condition for the elution of His-tagged HBcAg from the adsorbent was at pH 7 in the presence of 500 mM imidazole and 1.5 M NaCl. The IMA-EBAC has successfully recovered 56% of His-tagged HBcAg from the unclarified E. coli homogenate with a purification factor of 3.64. Enzyme-linked immunosorbent assay (ELISA) showed that the antigenicity of the recovered His-tagged HBcAg was not affected throughout the IMA-EBAC purification process and electron microscopy revealed that the protein assembled into virus-like particles (VLP). 相似文献
86.
Takacs JM Schroeder SD Han J Gifford M Jiang XT Saleh T Vayalakkada S Yap AH 《Organic letters》2003,5(20):3595-3598
[reaction: see text] Screening combinations of five catalyst precursors with 13 phosphorus ligands identified cyclization catalysts that favor carbocyclization-trapping with N-hydroxyphthalimide over a competing cycloisomerization mode. 相似文献
87.
Alleviation of thermally induced phase mismatch in CsLiB6O10 crystal by means of temperature-profile compensation 总被引:1,自引:0,他引:1
A new mechanism was found to alleviate the thermally induced phase mismatch of nonlinear optical crystals. By cooling CsLiB>(6)O(10) at an elevated crystal temperature with gas, we improved laser conversion efficiency from green (532 nm) to UV (266 nm) 2.3 times compared with that without cooling. In situ observation of the temperature profile on the output surface revealed that such cooling initiates a negative temperature profile that compensates for the positive profile generated from laser absorption. A 10.6-W UV output with excellent stability was generated. The optimum crystal length was substantially extended. 相似文献
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89.
A family of guanidinate-supported imido metal complexes are novel, effective catalysts for C=N metathesis of alkyl and aryl carbodiimides and evidence suggests that this reaction proceeds via a sequential addition/elimination pathway. 相似文献
90.
Sugiyama H Aharonian G Gambarotta S Yap GP Budzelaar PH 《Journal of the American Chemical Society》2002,124(41):12268-12274
The reaction of [[2,6-(i-Pr)(2)PhN=C(Me)](2)(C(5)H(3)N)]MnCl(2) with alkylating agents formed a dinuclear Mn(I) derivative via ligand reductive coupling. In the case of the trivalent Cr analogue, a similar reaction afforded reduction toward Cr(II) but also alkylation at the pyridine ring para position followed by an unprecedented cycloaddition that generated a tricyclic system. 相似文献