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排序方式: 共有147条查询结果,搜索用时 46 毫秒
1.
The thermodynamic interactions in poly(styrene-block-ferrocenyldimethylsilane) and poly(isoprene-block-ferrocenyldimethylsilane) copolymers were systematically tuned by oxidation of the ferrocene moieties with silver nitrate. Small-angle X-ray scattering experiments show that oxidizing 8% of the ferrocene moieties lowers the order-disorder transition temperature of the copolymers by as much as 40 degrees C. 相似文献
2.
The use of quantitative carbon nuclear magnetic resonance spectroscopy ((13)C NMR) for the determination of resin loadings has been investigated. Magic angle spinning (MAS) NMR spectra have been obtained for solvent-swollen resins on a conventional 7 mm CP/MAS probe using the two pulse phase modulation (TPPM) proton decoupling sequence. Loadings of resin-bound organic compounds were evaluated via addition of tetrakis(trimethylsilyl)silane as reference or using the carbon resonances of the polymeric resin material as an internal standard. Results for several functionalized Wang and trityl resins are consistent with those obtained using well-established analytical methods. The (13)C NMR method has interesting applications in the field of solid-phase organic synthesis (SPOS), since no functional group acting as a support for the attachment of a quantifiable chromophore must be available in the material of interest. 相似文献
3.
Phenols are converted to salicylaldehydes with paraformaldehyde, MgCl2-Et3N in THF, and subsequent treatment with methyl (triphenylphosphoranylidene)acetate gave the corresponding methyl ortho-hydroxycinnamate derivatives. The sequence is conveniently carried out as a one-pot procedure. 相似文献
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5.
Research on Chemical Intermediates - The inhibition effect of two selected polyethylene glycols (PEGs) with different molecular weight and the synergistic effect with rare earth Ce4+ ions on... 相似文献
6.
Shrouk M. Hassan Jehan M. Morsy Hany M. Hassanin Elham S. Othman 《Journal of heterocyclic chemistry》2021,58(1):305-314
A novel series of 6-alkyl-4-bromopyrano[3,2-c]quinoline-2,5-diones ( 2a–c ), 6-alkyl-3,4-dibromopyrano[3,2-c]quinoline-2,5-diones ( 4a–c ), and 6-alkyl-3-amino-bromopyrano[3,2-c]quinoline-2,5-diones ( 6a–c ) were synthesized via appropriate conventional methods and in good yields. The structures of target compounds were approved by elemental analysis, IR, 1H NMR, 13C NMR, and mass spectrometry. The antitumor inhibitory activities of the new compounds were evaluated on several cancer cell lines, A-549 (human lung cancer), HCT-116 (human colon cancer), MCF-7 (breast cancer), and HePG-2 (human liver cancer). Moreover, 50% inhibitory concentrations, IC50, were established. 5-Fluorouracil was used as a positive control in the viability assay. The screening results showed that most of the examined compounds exposed powerful inhibition activity toward various cell lines. Particularly, Compound 4c exhibited higher cytotoxic activity against four tumor cell lines than the reference drug, 5-fluorouracil, with significantly lower IC50 values. Accordingly, most of the synthesized compounds would be a better prospective growth in the anticancer drug discovery. 相似文献
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Novel responsive solids were prepared by randomly cross-linking the polyisoprene chains of a disordered polystyrene-polyisoprene block copolymer. Our experiments show that block copolymer chains, composed of hundreds of repeat units, can undergo reversible order-disorder transitions despite the quenched randomness that arises due to the attachment of one of the blocks to a cross-linked network. The structure, properties, and phase behavior of these materials are determined by a delicate interplay between the density of cross-links and the nature of the ordered state. 相似文献
9.
Hany Nasef Valerio Beni Veli C. Őzalp Ciara K. O’Sullivan 《Analytical and bioanalytical chemistry》2010,396(7):2565-2574
Cystic fibrosis is one of the most common genetically inherited diseases in northern Europe, with the DF508 mutation being
the most common, and among the Caucasian population being responsible for almost 70% of cases. In this work, we report on
the use of thermally modulated electrochemical impedance spectroscopy for the discrimination of the DF508 mutation from the
wild-type sequence. DNA probes (15 and 21 bases long) were immobilised on the surface of gold electrodes and the variation
of the charge-transfer resistance was monitored as a function of hybridisation. Two sets of targets were used in this work:
synthetic 15-mer sequences and two single-stranded synthetic analogues of PCR products 82 (mutant) and 85 (wild type) bases
long. Hybridisation with short targets resulted in very sequence specific charge-transfer-resistance variation with a discrimination
factor at room temperature between fully complementary and mismatched sequences of approximately fivefold. However, in the
case of the single-stranded synthetic PCR product analogues, a lower discrimination factor was recorded (1.5-fold). The effect
of temperature was investigated to improve discrimination and the use of a posthybridisation wash at elevated temperature
resulted in a fivefold improvement in the discrimination factor. Using an electrode array with probes immobilised against
each of the mutant and wild-type sequences, we achieved an unequivocal detection of the DF508 mutation. 相似文献
10.
Hany H. Sherief Magdy A. Ezzat 《International Journal of Solids and Structures》1996,33(30):4449-4459
The one-dimensional problem of distribution of thermal stresses and temperature is considered in a generalized thermoelastic electrically conducting half-space permeated by a primary uniform magnetic field when the bounding plane is suddenly heated to a constant temperature.The Laplace transform technique is used to solve the problem. Inverse transforms are obtained in an approximate manner using asymptotic expansions valid for small values of time.Nurnerical computations for two particular cases are carried out. 相似文献