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排序方式: 共有65条查询结果,搜索用时 125 毫秒
1.
Dr. James P. Dombrowski Dr. Micah S. Ziegler Dr. Neelay M. Phadke Erum Mansoor Dr. Daniel S. Levine Dr. Ryan J. Witzke Prof. Dr. Martin Head-Gordon Prof. Dr. Alexis T. Bell Prof. Dr. T. Don Tilley 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(1):307-315
Anionic molecular models for nonhydrolyzed and partially hydrolyzed aluminum and gallium framework sites on silica, M[OSi(OtBu)3]4− and HOM[OSi(OtBu)3]3− (where M=Al or Ga), were synthesized from anionic chlorides Li{M[OSi(OtBu)3]3Cl} in salt metathesis reactions. Sequestration of lithium cations with [12]crown-4 afforded charge-separated ion pairs composed of monomeric anions M[OSi(OtBu)3]4− with outer-sphere [([12]crown-4)2Li]+ cations, and hydroxides {HOM[OSi(OtBu)3]3} with pendant [([12]crown-4)Li]+ cations. These molecular models were characterized by single-crystal X-ray diffraction, vibrational spectroscopy, mass spectrometry and NMR spectroscopy. Upon treatment of monomeric [([12]crown-4)Li]{HOM[OSi(OtBu)3]3} complexes with benzyl alcohol, benzyloxide complexes were formed, modeling a possible pathway for the formation of active sites for Meerwin–Ponndorf–Verley (MPV) transfer hydrogenations with Al/Ga-doped silica catalysts. 相似文献
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In this paper, a constrained optimization problem is formulated to tune the limit cycle minimizing controllers meeting additional loop-shaping performances such as phase margin and gain crossover frequency. A graphical approach is proposed so as to determine the superior controller in terms of better limit-cycle suppression. The framework is illustrated with a suitable case of elementary servo plant which has separable static backlash nonlinearity in its model. For this plant, integer-order controllers and their fractional counterparts (PI and \( PI ^\alpha , [ PI ]^\alpha \) ; PID and \( PI ^\alpha D^\beta \) ) are designed and compared. Interestingly, it is found that the fractional controllers produce better limit-cycle responses than their integer counterparts while both meeting the rest of the specifications. Correspondingly, the better sustained oscillations in the plant output response are obtained with fractional controllers. Such a ‘fractional superiority’ is further verified with the closed-loop nonlinear simulation. 相似文献
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Fiber-reinforced aerogels are a class of reinforced aerogels characterized by very low thermal conductivity, hydrophobicity and most importantly load bearing capability. In this work, an experimental study describing the damage in these fiber-reinforced aerogels through various uniaxial compression tests is presented. While understanding the damage evolution at the micro-scale, we come across three probable sources contributing towards the damage evolution. They are: (a) matrix cracks, (b) debonding of particles due to fiber sliding, and (c) breakage of fibers. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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G. Bossi B. Dubini P. Mariani M. G. Ponzi Bossi F. Rustichelli R. S. Phadke 《Il Nuovo Cimento D》1990,12(9):1293-1308
Summary We report a thermodynamical and structural investigation on the effect of a dicarboxylic acid, the azelaic acid, on a synthetic
phosophatidylcholine in excess water condition. The results indicate that the drug interacts with the lipid headgroup region,
near to the hydrocarbon chains: in particular, at higher concentrations investigated, an interdigitated ?gel phase?, with
rigid chains, stiff and perpendicular to the lamellar planes, is induced. The experimental electron density profiles, obtained
for samples containing low and high quantity of azelaic acid, support the proposed interaction. Moreover, step electron density
models, used to confirm the selected sign combination of the observed structure factors, show the best agreement with the
experimental data when the chain terminal methyl groups are frozen in fixed position.
Work presented at the second USSR-Italy Bilateral Meeting on Liquid Crystals held in Moscow, September 15–21, 1988. 相似文献
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A microscale cyclical electrical field flow fractionation (CyElFFF) channel is characterized with regard to the effect of various operating parameters and comparison made to recent theoretical developments. Challenges associated with various operating conditions are reported along with some of the optimized operating parameters. The effect of retention wall choice, an offset voltage, relaxation steps, and flow rates, along with the basic operating parameters of voltage, frequency, and electrophoretic mobility are reported. Retention of polystyrene nanoparticle standards is accomplished and the first separations using this technique in a microscale system are also demonstrated. Relaxation steps and offset voltages are found to be effective in eliminating early peaks and in improving plate heights. Plate heights were also found to decrease with increasing flow rates, which is the opposite of the behavior seen in most existing chromatographic systems. The experimental results are compared to the analytical and empirical models of CyElFFF and found to be compatible. Suggestions are made for improving the separation and analysis methods used with CyElFFF. 相似文献
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Manisha U. Phadke Vivek K. Jadhav Rajendra K. Jadhav Suraj S. Dave Dattatray S. Patil 《Chromatographia》2008,68(11-12):1003-1007
A simple, fast and precise reversed phase liquid chromatographic method was developed for the simultaneous determination of artesunate (AS) and amodiaquine (AD) in combined pharmaceutical dosage form. Chromatographic separation of the two drugs was performed on a BDS Hypersil C18, 100 mm × 4.6 mm, 3 μm particle size column as stationary phase with a mobile phase comprising of phosphate buffer (pH 3.0 with orthophosphoric acid) and acetonitrile in the proportion of 50:40 (v/v), at a flow rate of 0.8 mL min?1 and UV detection at wavelength 210 nm for AS and 300 nm for AD using photo diode array detection. The proposed method was validated for specificity, accuracy, linearity, range, precision and was successfully applied to the simultaneous determination of AS and AD in the combined fixed dosage form without any excipient’s interference. 相似文献
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