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171.
Yun Li Binghe Gu H. Dennis Tolley Milton L. Lee 《Journal of chromatography. A》2009,1216(29):5525-5532
Two novel polymeric monoliths for anion-exchange capillary liquid chromatography of proteins were prepared in a single step by a simple photoinitiated copolymerization of 2-(diethylamino)ethyl methacrylate and polyethylene glycol diacrylate (PEGDA), or copolymerization of 2-(acryloyloxy)ethyl trimethylammonium chloride and PEGDA, in the presence of selected porogens. The resulting monoliths contained functionalities of diethylaminoethyl (DEAE) as a weak anion-exchanger and quaternary amine as a strong anion-exchanger, respectively. An alternative weak anion-exchange monolith with DEAE functionalities was also synthesized by chemical modification after photoinitiated copolymerization of glycidyl methacrylate (GMA) and PEGDA. Important physical and chromatographic properties of the synthesized monoliths were characterized. The dynamic binding capacities of the three monoliths (24 mg/mL, 56 mg/mL and 32 mg/mL of column volume, respectively) were comparable or superior to values that have been reported for various other monoliths. Chromatographic performance was also similar to that provided by a modified poly(GMA-ethylene glycol dimethacrylate) monolith. Separation of standard proteins was achieved under gradient elution conditions using these monolithic columns. Peak capacities of 34, 58 and 36 proteins were obtained with analysis times of 20–30 min. This work represents a successful attempt to prepare functionalized monoliths via direct copolymerization of monomers with desired functionalities. Compared to earlier publications, additional surface modifications were avoided and the PEGDA crosslinker helped to improve the biocompatibility of the monolithic backbone. 相似文献
172.
Christoph R. Müller Daniel J. Holland James R. Third Andrew J. Sederman John S. Dennis Lynn F. Gladden 《Particuology》2011,9(4):330-341
This short review describes the capabilities of magnetic resonance (MR) to image opaque single- and two-phase granular systems, such as rotating cylinders and gas-fluidized beds operated in different fluidization regimes. The unique capability of MR to not only image the solids’ distribution (voidage) but also the velocity of the particulate phase is clearly shown. It is demonstrated that MR can provide measurements over different length and time scales. With the MR equipment used for the studies summarized here, temporal and spatial scales range from sub-millisecond to hours and from a few hundred micrometres to a few centimetres, respectively. Besides providing crucial data required for an improved understanding of the underlying physics of granular flows, multi-scale MR measurements were also used to validate numerical simulations of granular systems. It is shown that predictions of time-averaged properties, such as voidage and velocity of the particulate phase, made using the Discrete Element Model agree very well with MR measurements. 相似文献
173.
The critical dose at which an implanted amorphous layer in silicon is formed cannot be explained by a previous energy independent model. An energy dependent correction to this model can explain our ESR data as well as other data. The correction is most important for light ions. 相似文献
174.
Dennis Stanton 《The Ramanujan Journal》2009,19(1):107-113
Two q-analogues of Euler’s theorem on integer partitions with odd or distinct parts are given. A q-lecture hall theorem is given.
Supported by NSF grant DMS-0503660. 相似文献
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176.
Jan-Falk Kannengießer Max Briesenick Dr. Dennis Meier Dr. Volker Huch Dr. Bernd Morgenstern Prof. Dr. Guido Kickelbick 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(66):16461-16476
Organosilanols typically show a high condensation tendency and only exist as stable isolable molecules under very specific steric and electronic conditions at the silicon atom. In the present work, various novel representatives of this class of compounds were synthesized by hydrolysis of alkoxy- or chlorosilanes. Phenyl, 1-naphthyl, and 9-phenanthrenyl substituents at the silicon atom were applied to systematically study the influence of the aromatic substituents on the structure and reactivity of the compounds. Chemical shifts in 29Si NMR spectroscopy in solution, correlated well with the expected electronic situation induced by the substitution pattern on the Si atom. 1H NMR studies allowed the detection of strong intermolecular hydrogen bonds. Single-crystal X-ray structures of the alkoxides and the chlorosilanes are dominated by π-π interactions of the aromatic systems, which are substituted by strong hydrogen bonding interactions representing various structural motifs in the respective silanol structures. 相似文献
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A series of halogen-substituted cyclic enediynes were prepared with use of carbenoid coupling strategy. DFT analysis, initially used to identify synthesis candidates, was also employed to rationalize the propensity for cycloaromatization of the compounds. In all cases studied the halogen atom had a strongly retardative effect on the thermal Bergman cycloaromatization reaction. The isolation of the first C-9 monochloroenediyne is noteworthy, and may find application in prodrug design. 相似文献
180.