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51.
Gregory B. Kharas Benjamin L. Hill Nga Y. Du Andrea S. Lorenz Nelly Fliman Amy M. Reznick 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(2):94-98
Electrophilic trisubstituted ethylenes, fluoro ring-substituted ethyl 2-cyano-1-oxo-3-phenyl-2-propenylcarbamates, RC6H3CH = C(CN)CONHCO2C2H5(where R is 4-F-3-CH3, 2-CF3, 4-CF3, 2,4-diF, 2,5-diF, 2,6-diF, 3,4-diF, and 3,5-diF), were prepared and copolymerized with styrene. The monomers were synthesized by the piperidine catalyzed Knoevenagel condensation of ring-substituted benzaldehydes and N-cyanoacetylurethane, and characterized by CHN analysis, IR, 1H- and 13C-NMR. All the ethylenes were copolymerized with styrene (M1) in solution with radical initiation (ABCN) at 70°C. The compositions of the copolymers were calculated from nitrogen analysis and the structures were analyzed by IR, 1H- and 13C-NMR. The order of relative reactivity (1/r 1) for the monomers 4-CF3 (5.4) > 2,6-diF (2.0) > 2,4-diF (1.7) > 2,5-diF (1.0) > 2-CF3 (0.8) > 3,4-diF (0.5) > 3,5-diF (0.4) > 4-F-3-CH3 (0.3). High T g of the copolymers in comparison with that of polystyrene indicates decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene structural unit. Decomposition of the copolymers in nitrogen occurred in two steps, first in 270–420°C with residue (5–13% wt), which then decomposed in the 420–650°C range. 相似文献
52.
TN Vo PL Nguyen LT Tuong LM Pratt PN Vo KP Nguyen NS Nguyen 《Chemical & pharmaceutical bulletin》2012,60(9):1125-1133
Two new lignans, pseuderesinol (1), pseuderanoside (2) and a new triterpene, pseuderanic acid (3) were isolated from the dried root of Pseuderanthemum carruthersii (SEEM.) GUILL. var. atropurpureum (BULL.) FOSB. (Acanthaceae), together with ten known compounds, including five lignans, (+)-eudesmin (4), (+)-magnolin (5), (+)-syringaresinol (6), (+)-episyringaresinol (7), (+)-1-hydroxysyringaresinol (8) and five triterpenes, squalene (9), oleanolic acid (10), lupeol (11), betulin (12), betulinic acid (13). Their chemical structures were elucidated by 1D- and 2D-NMR, computational quantum chemistry, as well as high resolution-electrospray ionization (HR-ESI)-MS spectroscopic analysis. The acetylcholinesterase inhibition and cytotoxic activities against HeLa and MCF-7 cancer cell lines were evaluated on some purified compounds at the concentration of 100?μg/mL. Pseuderesinol (1) and magnolin (5) exhibited moderate cytotoxic activities against the MCF-7 cancer cell line. 相似文献
53.
B. Hippolyte 《The European Physical Journal C - Particles and Fields》2007,49(1):121-124
Strange quark and hadron production will be studied at the large hadron collider (LHC) energies in order to explore the properties
of both pp and heavy-ion collisions. The ALICE experiment will be specifically efficient in the strange sector with the identification
of baryons and mesons over a wide range of transverse momentum. Dedicated measurements are proposed for investigating chemical
equilibration and bulk properties. Strange particles can also help to probe kinematical regions where hard processes and pQCD
dominate. We try to anticipate here several ALICE analyses to be performed as the first Pb–Pb and pp data will be available.
PACS 25.75.-q; 25.75.Dw 相似文献
54.
55.
Wabo HK Tane P Connolly JD Okunji CC Schuster BM Iwu MM 《Natural product research》2005,19(6):591-595
A novel pyranoquinoline alkaloid 3,4-dihydro-3-hydroxy-5-methoxy-2,2,10-trimethylpyrano [2,3-b]quinoline named tabouensinium chloride (1), was isolated from the stem bark of Araliopsis tabouensis along with twelve known quinoline alkaloids. In addition, the known flindisol, lupeol and beta-sitosterol glucoside were also identified. Their structures were deduced from spectral data. 相似文献
56.
57.
Light scattering, sedimentation velocity and intrinsic viscosity measurements were made, at 35° in cyclohexane, for various well fractionated atactic polystyrenes. It was found that these solution properties can vary from a sample to another, revealing structural differences among the samples. The variations in the sedimentation velocity law can entirely be ascribed to the corresponding variations in the chain dimensions. In this respect, the results are in accordance with the Kirkwood-Riseman's theory. On the contrary, this theory in its present state cannot explain the variations in the intrinsic viscosity law in relation with the chain dimensions variations. These results put back in question the possibility, even in a theta solvent, of using intrinsic viscosity measurements, as suggested by Flory, for calculation of chain dimensions. 相似文献
58.
The intrinsic viscosities of styrene-isoprene two- and three-block copolymers have been studied in a number of solvents as a function of molecular weight, composition and temperature. The behaviour of the three-block copolymers is similar in all points to that of the two-block. No conformational transition was observed between 10 and 60°. The intrinsic viscosities measured at 35° are close to the weighted average of the corresponding homopolymers of equal molecular weight. The Stockmayer-Fixman interaction parameters B are also close to the weighted average of the corresponding homopolymers. These results seem to indicate a structure with a limited number of heterocontacts. 相似文献
59.
Nga Sze Ieong Author Vitae Author Vitae 《Journal of organometallic chemistry》2008,693(5):802-807
Although extensive previous studies have shown that strained [1]ferrocenophanes predominantly undergo ring-opening chemistry at the bridging atom E-cyclopentadienyl (E-Cp) bond, recent reports have highlighted that reactivity at the Fe-Cp bond can also occur, especially on photoactivation. We provide an overview of recent results from our group and those of other researchers. In addition, the development of photocontrolled living polymerizations of sila[1]ferrocenophanes using Fe-Cp bond cleavage chemistry is described. 相似文献
60.
Nguyen Quynh Nga 《Differential Equations》2017,53(10):1378-1380
Some results due to Fang and Peterson on generalized variational inequalities in the space ? n are extended to infinite-dimensional spaces. Theorems on the existence of solutions of such inequalities under generalized coercivity conditions are obtained. 相似文献