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811.
Verstraeten M Pursch M Eckerle P Luong J Desmet G 《Journal of chromatography. A》2011,1218(16):2252-2263
We report upon the experimental investigation of the heat transfer in low thermal mass LC (LTMLC) systems, used under temperature gradient conditions. The influence of the temperature ramp, the capillary dimensions, the material selection and the chromatographic conditions on the radial temperature gradients formed when applying a temperature ramp were investigated by a numerical model and verified with experimental temperature measurements. It was found that the radial temperature gradients scale linearly with the heating rate, quadratically with the radius of the capillary and inversely to the thermal diffusivity. Because of the thermal radial gradients in the liquid zone inside the capillary lead to radial viscosity and velocity gradients, they form an additional source of dispersion for the solutes. For a temperature ramp of 1 K/s and a strong temperature dependence of the retention of small molecules, the model predicts that narrow-bore columns (i.d. 2.1 mm) can be used. For a temperature ramp of 10 K/s, the maximal inner diameter is of the order of 1 mm before a substantial increase in dispersion occurs. 相似文献
812.
Luengviriya C Storb U Lindner G Müller SC Bär M Hauser MJ 《Physical review letters》2008,100(14):148302
Two kinds of scroll wave instabilities were studied experimentally in the excitable Belousov-Zhabotinsky reaction: three-dimensional meandering and negative line tension of the scroll wave filament. The filament displays a flat zigzag shape in the initial stages of the experiment. As the chemical medium ages, the filament assumes a wiggly shape while its length increases substantially. Numerical simulations underpin the experimental findings and their interpretation. 相似文献
813.
We have calculated product rotational state distributions for the D + H2 reaction trapped in the center of icosahedral argon cluster at various cluster temperatures. All the degrees of freedom are treated classically in the present calculations. The rotational state distributions exhibit considerable dependence on the cluster environment and its temperature as compared with those obtained in the gas phase reaction. 相似文献
814.
G. Lube & L. Tobiska 《计算数学(英文版)》1990,8(2):147-158
A nonconforming finite element method of streamline diffusion type for solving the stationary and incompressible Navier-Stokes equation is considered. Velocity field and pressure field are approximated by piecewise linear and piecewise constant functions, respectively. The existence of solutions of the discrete problem and the strong convergence of a subsequence of discrete solutions are established. Error estimates are presented for the uniqueness case. 相似文献
815.
816.
HansR. Kricheldorf Nico Probst Dennis Langanke Gert Schwarz 《Macromolecular rapid communications》2001,22(10):750-755
It was found that diphenyl carbonate reacts with Bu2SnO above 140°C yielding CO2 and Bu2Sn(OPh)2. This insertion reaction was also successfully applied to a polycarbonate prepared from polytetrahydrofuran diol‐1000 and Bu2SnO containing macrocyclic polyTHF dioxides. Bu2SnO reacted analogously with poly(bisphenol A) carbonates yielding tin‐containing rapidly crystallizing cyclic oligocarbonates. Their treatment with 1,2‐ethanedithiol gave linear oligocarbonates having two OH end groups. Bu2Sn‐containing macrocyclic oligocarbonates reacted in‐situ with several carboxylic acid chlorides, forming telechelic oligocarbonates with functional ester end groups. Bu2Sn‐containing macrocycles also reacted in‐situ with terephthaloyl chlorides yielding a poly(ester carbonate). 相似文献
817.
The main purpose of the development of an Rh(I) Carbonyl Phosphine force field was to predict the molecular structure of Rh(I) complexes as well as to compute possible intermediates or transition states during the oxidative addition of CH3I to these complexes. © 2000 John Wiley & Sons, Inc. J Comput Chem 21: 692–703, 2000 相似文献
818.
Gert Steurs Nico Moons Luc Van Meervelt Boudewijn Meesschaert Wim Michel De Borggraeve 《Molecules (Basel, Switzerland)》2021,26(22)
Steviol glycosides were subjected to bacteria present in a soil sample collected from a Stevia plantation in Paraguay. During the incubation experiments, next to the aglycon steviol, steviol degradation products were also formed. X-ray analysis and NMR methods in combination with chemical synthesis and GIAO NMR calculations were used to fully characterize the structure of these compounds as a tricyclic ketone and the corresponding reduced form. They were nicknamed monicanone and monicanol. The latter has the (S)-configuration at the alcohol site. 相似文献
819.
820.
Gert‐Jan M. Gruter Alasdair Graham Ben McKay Franois Gilardoni 《Macromolecular rapid communications》2003,24(1):73-80
Currently laboratory automation is a rapidly growing field of interest in chemical process research and development. The idea of using automated and parallel methods for the optimization of chemical processes was initiated by the extensive implementation of combinatorial techniques in medicinal chemistry. The techniques applied involve all methods and concepts aimed at dramatically increasing the output of research by extensive use of automation, parallelization and miniaturization, fast analysis, advanced data handling and by efficient automated planning, scheduling and tracking. In this paper, the “Combi” or high‐throughput experimentation approach consists of the integration of parallel experimentation with four key modeling and simulation methodologies, modeling, multivariate statistics, statistical design of experimentation and empirical model generation.