排序方式: 共有120条查询结果,搜索用时 15 毫秒
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Radim Knob Jan Petr Juraj Ševčík Vítězslav Maier 《Journal of separation science》2013,36(20):3426-3431
A method for the determination of tartaric acid enantiomers using CE with contactless conductivity detection has been developed. Cu(II) as a central metal ion together with l ‐hydroxyproline were used as a chiral selector, the BGE was composed of 7 mM CuCl2, 14 mM trans‐4‐hydroxy‐l ‐proline, and 100 mM ε‐aminocaproic acid; the pH was adjusted to 5 by hydrochloric acid. Separation with a resolution of 1.9 was achieved in 9 min in a polyacrylamide‐coated capillary to suppress the EOF. Various counterions of the BGE were studied, and migration order reversal was achieved when switching from ε‐aminocaproic acid to l ‐histidine. With detection limits of about 20 μM, the method was applied to the analysis of wine and grape samples; only l ‐tartaric acid was found. 相似文献
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Eliška Procházková Michal Šála Radim Nencka Martin Dračínský 《Magnetic resonance in chemistry : MRC》2012,50(3):181-186
We measured the 1H, 13 C and 15 N chemical shifts for a series of purine derivatives bearing a norbornane substituent in position 9 and various substituents in position 6. The experimental data were complemented with density functional theory (DFT) calculations. The comparison of the calculated and experimental chemical shifts provided us with information about the tautomer and conformational equilibria of the studied compounds. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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Václav Žižkovský Radim Kučera Jiří Klimeš Petra Holásková Jiří Dohnal 《Chromatographia》2009,70(1-2):185-189
Degradation products and related compounds occurring in drugs as impurities have often very similar properties as the parent substance. Therefore new analytical separation methods which show appropriate selectivity are required. Apart from improvements on silica-based reversed phases the attention has also been focused on other materials such as modified inorganic supports. In this study a polystyrene-coated zirconia was examined as an alternative in analysis of parent drug (doxazosin) and its impurities. Doxazosin and its five pharmacopoeial impurities were separated within 16 min. The suitability of the developed method was verified and confirmed by means of linearity, precision, inter-day precision, robustness and determination of LOD as well as LOQ. The results proved the potential of zirconia-based stationary phases to be useful alternatives in the field of drug analysis. 相似文献
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Radim Belohlavek George J. Klir Harold W. Lewis III Eileen C. Way 《International Journal of Approximate Reasoning》2009,51(1):23-34
The psychology of concepts has been undergoing significant changes since the early 1970s, when the classical view of concepts was seriously challenged by convincing experimental evidence that conceptual categories never have sharp boundaries. Some researchers recognized already in the early 1970s that fuzzy set theory and fuzzy logic were potentially suitable for modeling of concepts and obtained encouraging results. This positive attitude abruptly changed in the early 1980s, and since that time fuzzy set theory and fuzzy logic have been portrayed as problematic and unsuitable for representing and dealing with concepts. Our aim in this paper is to identify some of the most notorious claims regarding fuzzy set theory and fuzzy logic that have propagated through the literature on psychology of concepts and to show that they are, by and large, false. We trace the origin and propagation of these claims within the literature in this area. It is shown in detail that these claims are consistently erroneous and that they are based on various misunderstandings, misconceptions, and oversights. The ultimate purpose of this paper is to document these various erroneous claims. 相似文献
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We investigate the optimal trade-off between information gained about an unknown coherent state and the state disturbance caused by the measurement process. We propose several optical schemes that can enable this task, and we implement one of them, a scheme that relies on only linear optics and homodyne detection. Experimentally we reach near optimal performance, limited only by detection inefficiencies. In addition, we show that such a scheme can be used to enhance the transmission fidelity of a class of noisy channels. 相似文献
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An algebra with fuzzy equality is a set with operations on it that is equipped with similarity , i.e. a fuzzy equivalence relation, such that each operation f is compatible with . Described verbally, compatibility says that each f yields similar results if applied to pairwise similar arguments. On the one hand, algebras with fuzzy equalities are structures for the equational fragment of fuzzy logic. On the other hand, they are the formal counterpart to the intuitive idea of having functions that are not allowed to map similar objects to dissimilar ones. In this paper, we present a generalization of the well-known Birkhoffs variety theorem: a class of algebras with fuzzy equality is the class of all models of a fuzzy set of identities iff it is closed under suitably defined morphisms, substructures, and direct products.
and Institute for Fuzzy Modeling, University of Ostrava, 30. dubna 22, 701 03 Ostrava, Czech Republic
Mathematics Subject Classification (2000):03B52, 08B05 相似文献
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We report an aptamer biosensing array for thrombin detection by measuring the electrochemical impedance upon aptamer‐protein formation at the surface of CD‐trodes (GCDTs) in the presence of the redox couple [Fe(CN)6]3?/4?. GCDTs are fabricated from recordable compact discs that contain a fine gold layer. The biosensor is constructed by self‐assembling of a thiol‐modified thrombin binding aptamer (TBA) onto a GCDT surface. The sensor reveals good ligand specificity, recognition in a wide range of thrombin concentrations from 20 nM to 1 µM with a limit of detection of 5 nM. 相似文献
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A Ramakrishnan S Neubert B Mei J Strunk L Wang M Bledowski M Muhler R Beranek 《Chemical communications (Cambridge, England)》2012,48(68):8556-8558
Benzene can be activated by visible light (λ > 455 nm) in the presence of TiO(2), which leads to formation of carbonaceous polymeric deposits on the titania surface. These photosynthesized surface-modified materials exhibit enhanced photoactivity in degradation of phenolic compounds, particularly under visible light irradiation. 相似文献
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