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161.
Adrian K. Y. Lam Richard A. J. O'Hair 《Rapid communications in mass spectrometry : RCM》2010,24(12):1779-1790
A combination of electrospray ionisation (ESI), multistage and high‐resolution mass spectrometry experiments is used to examine the gas‐phase fragmentation reactions of the three isomeric phenylalanine derivatives, α‐phenylalanine, β2‐phenylalanine and β3‐phenylalanine. Under collision‐induced dissociation (CID) conditions, each of the protonated phenylalanine isomers fragmented differently, allowing for differentiation. For example, protonated β3‐phenylalanine fragments almost exclusively via the loss of NH3, only β2‐phenylalanine via the loss of H2O, while α‐ and β2‐phenylalanine fragment mainly via the combined losses of H2O + CO. Density functional theory (DFT) calculations were performed to examine the competition between NH3 loss and the combined losses of H2O and CO for each of the protonated phenylalanine isomers. Three potential NH3 loss pathways were studied: (i) an aryl‐assisted neighbouring group; (ii) 1,2 hydride migration; and (iii) neighbouring group participation by the carboxyl group. Finally, we have shown that isomer differentiation is also possible when CID is performed on the protonated methyl ester and methyl amide derivatives of α‐, β2‐ and β3‐phenylalanines. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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Alberto Damiano Daniele Struppa Adrian Vajiac Mihaela Vajiac 《Journal of Geometric Analysis》2009,19(2):288-300
We introduce the notion of antisyzygies, which studies the inverse problem of finding a system of PDEs, given compatibility
conditions. The system obtained possesses the property of removability of compact singularities. We write explicit computations
in the cases of the Cauchy-Fueter system and Maxwell’s system for electromagnetism, and we conclude with a study of systems
of non-maximal rank.
相似文献
166.
Arwut Promraksa Adrian E. Flood Philip A. Schneider 《Journal of Crystal Growth》2009,311(14):3667-3673
The effect of crystallization conditions on the dextran partition coefficient between impure syrup and sugar crystal has been investigated in a batch crystallizer. The crystallizer is operated isothermally at temperatures of 30, 40, and 50 °C, at constant relative supersaturations of 0.05, 0.07, and 0.09, and with mother liquor dextran concentrations of 1000 and 2000 ppm/Brix. The dextran content has been determined by the CSR method. A 1:1 mass ratio of high-fraction dextran (approximately 250,000 Da) and low-fraction dextran (60,000-90,000 Da) is used to represent a wide range of dextran contamination. It is seen that the dextran partition coefficient in sucrose crystallization increases with both increasing supersaturation and increasing crystallization temperature. However it appears that these are secondary effects, with the partition coefficient strongly correlating with crystal growth rate alone, despite the regressed data having large variations in temperature, mother liquor dextran content, and supersaturation. Dextran incorporation into the sugar crystal results from both dextran adsorption onto the crystal surface and mother liquor inclusions. The explanation for the variation in the dextran content in sugar crystal with respect to the growth rate is due to increased adsorption due to the higher surface roughness of crystals grown at high growth rates. Although the dextran concentration in the solution affects the dextran content in the crystal, it does not strongly affect the dextran partition coefficient. 相似文献
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The synthesis of two light-fluorous TEMPO derivatives is reported, along with their application in oxidation reactions. 相似文献
170.
A fast Pareto genetic algorithm approach for solving expensive multiobjective optimization problems 总被引:1,自引:0,他引:1
We present a new multiobjective evolutionary algorithm (MOEA), called fast Pareto genetic algorithm (FastPGA), for the simultaneous
optimization of multiple objectives where each solution evaluation is computationally- and/or financially-expensive. This
is often the case when there are time or resource constraints involved in finding a solution. FastPGA utilizes a new ranking
strategy that utilizes more information about Pareto dominance among solutions and niching relations. New genetic operators
are employed to enhance the proposed algorithm’s performance in terms of convergence behavior and computational effort as
rapid convergence is of utmost concern and highly desired when solving expensive multiobjective optimization problems (MOPs).
Computational results for a number of test problems indicate that FastPGA is a promising approach. FastPGA yields similar
performance to that of the improved nondominated sorting genetic algorithm (NSGA-II), a widely-accepted benchmark in the MOEA
research community. However, FastPGA outperforms NSGA-II when only a small number of solution evaluations are permitted, as
would be the case when solving expensive MOPs. 相似文献