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71.
Klingshirn MA Broker GA Holbrey JD Shaughnessy KH Rogers RD 《Chemical communications (Cambridge, England)》2002,(13):1394-1395
The palladium-catalyzed copolymerization of styrene and CO in an ionic liquid solvent, 1-hexylpyridinium bis(trifluoromethanesulfonyl)imide, gave improved yields and increased molecular weights compared to polymerizations run in methanol. 相似文献
72.
Modeling elasticity in crystal growth 总被引:2,自引:0,他引:2
A new model of crystal growth is presented that describes the phenomena on atomic length and diffusive time scales. The former incorporates elastic and plastic deformation in a natural manner, and the latter enables access to time scales much larger than conventional atomic methods. The model is shown to be consistent with the predictions of Read and Shockley for grain boundary energy, and Matthews and Blakeslee for misfit dislocations in epitaxial growth. 相似文献
73.
We describe a simple scheme, which we call the Raman smart pump, to allow for the achievement of flat gain over broad bands with backward-pumped Raman amplification. The proposed method, based on time-division multiplexing, also removes all interaction among the various pump wavelengths and allows for dynamic gain control through simple electronic means. 相似文献
74.
Stueber D Orendt AM Facelli JC Parry RW Grant DM 《Solid state nuclear magnetic resonance》2002,22(1):29-49
The principal values of the 13C chemical shift tensors in potassium carbonate (K2CO3), trithiocarbonate (K2CS3), bicarbonate (KHCO3), methylcarbonate (KO2COCH3), S-methyl-monothiocarbonate (KO2CSCH3), O-methyl-monothiocarbonate (KOSCOCH3), S-methyl-dithiocarbonate (KOSCSCH3), and O-methyl-dithiocarbonate (KS2COCH3), were measured in solid-state nuclear magnetic resonance experiments. Chemical shift tensor calculations on the corresponding isolated anions were used to assign the chemical shift tensor orientations in the molecular frames of all anions. The correlation between experimental and calculated principal values improves significantly when the calculations are performed on isolated anions with proton-optimized X-ray geometries rather than on isolated anions with fully optimized geometries. Further considerable improvement in the correlation is achieved by utilizing the embedded ion method, which was recently developed to include electrostatic crystal potentials in chemical shift tensor calculations on ionic compounds. Similarities and differences in the chemical shift tensor orientations and principal values of the trigonal sp2 carbon atoms in the carbonate and thiocarbonate anions are compared with those known for condensed polyaromatic hydrocarbons. 相似文献
75.
McGeorge G Alderman DW Grant DM 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1999,137(1):138-143
Many solid-state spectra have been shown to have problems related to the poor proton decoupling of carbon nuclei in methylene groups under conditions of slow magic-angle turning. Two-pulse phase-modulation (TPPM) decoupling during the 2D PHORMAT chemical shift separation experiment is shown to be more effective in comparison to that obtainable at much higher spin rates using conventional CW decoupling. TPPM decoupling can also alleviate similar inadequacies when observing the 15N nucleus, particularly with NH2 groups. This is demonstrated in the 15N resonances of fully labeled l-arginine hydrochloride, where a line narrowing of about a factor of two was observed at moderate rotation rates. This significant advantage was also obtained at turning frequencies as low as 500 Hz. 相似文献
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79.
E.W. Duck D. Grant J.R. Horder D.K. Jenkins A.E. Marlow S.R. Wallis A.G. Doughty J.M. Marandon G.A. Skinner 《European Polymer Journal》1974,10(6):481-488
VOCl3-Et3Al2C13(chlorinated activator) catalysts have been employed for the polymerization of ethylene at T between 15 and 85° in n-hexane. Using butylperchlorocrotonate as the activator, the following catalyst efficiencies (g polymerization, hr, atmosphere ethylene in the cap gas) were achieved: 106,1 MFI = 0-00; 105,8, e.g. MFI = 1 0 (with 9 per cent H2 present in the cap gas) and 106–9 MFI = 0?4 (with 44 mmole/1 styrene in the hexane medium). Reactions between the aluminium alkyl and the activator molecules produced other chlorinated species of high average activator effectiveness. The catalyst system could be reactivated by further additions of Et3Al2Cl3. The minimum value of the polymerization propagation rate constant is estimated to be 10122?6x10,461 cm3/mole sec. 相似文献
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