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Separation of 23 dansylated amino acids by micellar electrokinetic chromatography at low temperature
Summary The baseline separation of 23 dansylated amino acids (including 3 didansylated species) is reported. Lowering of the analysis
temperature and fine control of the surfactant concentration were essential in obtaining this result. Calibration graphs with
good linearity were obtained. 相似文献
4.
Mary E. Neubert DAVID G. ABDALLAH Jr Sandra S. Keast Julie M. Kim Soonnam Lee Ryan M. Stayshich Margaret E. Walsh Rolfe G. Petschek Shin-Tson Wu 《Liquid crystals》2003,30(6):711-731
New diphenyldiacetylenes of the type with A, B = H and/or F; m = 0, 1; n = 1-4; and X = C n H 2n + 1 , F, CF 3 or CN were synthesized and their mesomorphic properties determined by hot stage polarizing microscopy and DSC. When m = 0, all of these compounds showed only a nematic phase except when X = CF 3 when both nematic and smectic A phases were seen. Both clearing and melting temperatures were higher than those reported for substitution with the corresponding alkyl chains but the much larger increase in clearing temperatures produced considerably wider nematic phases. Eutectic mixtures of a few of these olefins yielded nematic materials also having much wider temperature ranges and higher clearing temperatures than the eutectic mixtures of the alkyl compounds, while retaining their high birefringence and low viscosities. Such materials are of interest for beam-steering devices.
Four of the diacetylenes with m = 1 ( A, B = H) were also prepared ( X = C 6 H 13 , F, n = 2, 3). When X was C 6 H 13 ( n = 2), the nematic range was smaller in the 2- than in the 1-olefin but wider than in the alkyl series. When X = F, either no nematic phase or a monotropic one was observed, whereas the 1-olefins gave a much wider nematic phase. Both transition temperatures were lower than those for the corresponding 1-olefin and alkyl analogues. The compound with X = C 6 H 13 and n = 2 had a melting temperature below room temperature. 相似文献
Four of the diacetylenes with m = 1 ( A, B = H) were also prepared ( X = C 6 H 13 , F, n = 2, 3). When X was C 6 H 13 ( n = 2), the nematic range was smaller in the 2- than in the 1-olefin but wider than in the alkyl series. When X = F, either no nematic phase or a monotropic one was observed, whereas the 1-olefins gave a much wider nematic phase. Both transition temperatures were lower than those for the corresponding 1-olefin and alkyl analogues. The compound with X = C 6 H 13 and n = 2 had a melting temperature below room temperature. 相似文献
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Zero-schemes on smooth complex projective varieties, forcing all elements of ample and free linear systems to be reducible, are studied. Relationships among the minimal length of such zero-schemes, the positivity of the line bundle associated with the linear system, and the dimension of the variety are established. Bad linear spaces are also investigated. 相似文献
6.
L. G. Marcassa V. A. Nascimento L. L. Caliri A. Caires D. V. Magalhães V. S. Bagnato 《Laser Physics》2006,16(12):1722-1725
In this paper, we report observation of an enhancement of the ground state molecule Rb2 formation in a Rb magneto-optical trap due to a photoassociation laser. Such an enhancement effect is due to flux enhancement of atomic pairs at short internuclear distances. Our experimental observations consist in the measurement of the molecular formation rate constant due to a probe laser as a function of the trap laser intensity. The results are compared with a simple semi-classical model, showing good agreement. We conclude that the production of cold Rb2 may be enhanced using appropriate laser parameters; this may be useful for future experiments involving production and trapping of ultracold ground state molecules. 相似文献
7.
K. Jaques W. Buda L. Dumortier J. Van der Eycken Arnold Venema Pat Sandra 《Journal of separation science》1994,17(2):72-73
Capillary GC on permethyl α-, β-, and γ-cyclodextrins has been applied to separate and quantify the enantiomers of some 2,3-iso-propylidene-1,2,3-cyclohexanetriol derivatives. Quantitative CGC data are compared to those obtained with chiral shift 1H NMR. 相似文献
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Giancarlo Marconi Sandra Monti Francesco Manoli Stefano Ottani 《Journal of inclusion phenomena and macrocyclic chemistry》2007,57(1-4):279-282
The Induced Circular Dichroism of the complex formed by inclusion of Licochalcone-A (a powerful antimalarian of natural origin)
and β-cyclodextrin was measured and calculated. The association constant was determined by titration experiments of ICD and
fluorescence. The lowest energy conformations of the complex were obtained through docking procedures and their Circular Dichroism
was evaluated within the Tinoco framework. The geometry of the complex was found to be consistent with the main experimental
features. 相似文献