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1.
The apparent molal volumes and compressibilities of NaCl, KCl, and CsCl in mixtures of 18-Crown-6 and water have been calculated from density and speed-of-sound measurements at 25°C. The partial molal volumes and compressibilities of the salts when all cations have formed complexes with 18-Crown-6 molecules have been evaluated. The sign and magnitude of the volume and compressibility changes of complex formation strongly suggest that the charge of the cation becomes very effectively screened by the crown ether. 相似文献
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A. Ríos A. Lynggaard-Jensen H. S. Jacobsen R. Whiteman H. Wacheux B. Karlberg A. B. Lindholm T. Stenstrøm H. Berridge A. Boenke 《Accreditation and quality assurance》1999,4(12):B512-B517
ETACS is the official acronym for the European project "European Testing and Assessment of Comparability of On-line Sensors/Analysers". This project has three main objectives to achieve the comparability of performance data for sensors and analysers in the environmental field. First, to develop a test protocol for validation and comparison of the performance of on-line sensors/analysers. The test protocol is intended to be generic, that is independent of the specific sensors/analysers and the specific parameters to be monitored. Second, the practical testing of this test protocol to assess its applicability and to develop the techniques used. Finally, to achieve widespread acceptance of the test protocol by producer/suppliers, users and relevant authorities to assist its early adoption as an agreed European standard. Laboratory tests for producing the test protocol have been carried out and completed to check the applicability of such a protocol. 相似文献
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The electroreduction of chlorpheniramine maleate has been investigated by a.c. and d.c. polarography, coulometry and cyclic voltammetry. Polarograms recorded from 0.2 M sulphuric acid exhibit a single well-defined 2-electron wave. The current is diffusion-controlled and proportional to the concentration in the entire range 0.3–400 μg ml?1. A simple and rapid method for the determination of chlorpheniramine maleate in tablets is described. 相似文献
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A constraintg(x)0 is said to be a reverse convex constraint if the functiong is continuous and strictly quasi-convex. The feasible regions for linear programs with an additional reverse convex constraint are generally non-convex and disconnected. It is shown that the convex hull of the feasible region is a convex polytope and, as a result, there is an optimal solution on an edge of the polytope defined by only the linear constraints. The only possible edges which can contain such an optimal solution are characterized in relation to the best feasible vertex of the polytope defined by only the linear constraints. This characterization then provides a finite algorithm for finding a globally optimal solution.Research supported by NSF Grant ENG76-12250 and ONR Contract N00014-78-C-0428. 相似文献
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Analyzing a gliadin extract by matrix assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF-MS) combined with an artificial neural network (ANN) is a suitable method for identification of wheat varieties. However, the ANN can not distinguish between all different wheat varieties. Two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) was applied to three pairs of wheat varieties, which can not be classified correctly by ANN. By 2-D PAGE the varieties in the three pairs can be discriminated and these six wheat varieties can be separated from each other, which could not be separated by MALDI-TOF-MS and NN. 相似文献
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Addition of ketene acetals to sulfinimines derived from homochiral N-tert-butanesulfinamide using various Lewis acids furnishes derivatives of aspartic acid in diastereomeric ratios up to 97:3. Following an easy removal of the N-tert-butanesulfinyl chiral auxiliary, optical active beta-amino esters are obtained. 相似文献