†Kenyaichthyidae fam. nov and †Kenyaichthys gen. nov - First Record of a Fossil Aplocheiloid Killifish (Teleostei, Cyprinodontiformes)

The extant Cyprinodontiformes (killifishes) with their two suborders Cyprinodontoidei and Aplocheiloidei represent a diverse and well-studied group of fishes. However, their fossil record is comparatively sparse and has so far yielded members of the Cyprinodontoidei only. Here we report on cyprinodontiform fossils from the upper Miocene Lukeino Formation in the Tugen Hills of the Central Rift Valley of Kenya, which represent the first fossil record of an aplocheiloid killifish. A total of 169 specimens - mostly extraordinarily well preserved and a sample of ten extant cyprinodontiform species were studied on the basis of morphometrics, meristics and osteology. A phylogenetic analysis using PAUP was also conducted for the fossils. Both the osteological data and the phylogenetic analysis provide strong evidence for the assignment of the fossils to the Aplocheiloidei, and justify the definition of the new family dagger Kenyaichthyidae, the new genus dagger Kenyaichthys and the new species dagger K. kipkechi sp. nov. The phylogenetic analysis unexpectedly places dagger Kenyaichthys gen. nov. in a sister relationship to the Rivulidae (a purely Neotropical group),a probable explanation might be lack of available synapomorphies for the Rivulidae, Nothobranchiidae and Aplocheilidae. The specimens of dagger K. kipkechi sp. nov. show several polymorphic characters and large overlap in meristic traits, which justifies their interpretation as a species flock in statu nascendi. Patterns of variation in neural and haemal spine dimensions in the caudal vertebrae of dagger Kenyaichthys gen. nov. and the extant species studied indicate that some previously suggested synapomorphies of the Cyprinodontoidei and Aplocheiloidei need to be revised

Detailed study of Tröger's base separation by SMB process

This investigation of the separation of Tröger's base by the SMB process demonstrates: (1) the major importance of a proper modeling of the separation in order to determine the optimal operating conditions; (2) the need of an accurate modeling of the adsorption isotherms of the feed components. The adsorption of Tröger's base onto the stationary phase ChiralPak AD was successfully described by multilayer adsorption isotherm models. Due to the complexity of these models, the region of suitable operating parameters cannot be determined algebraically by the equilibrium theory. As an alternative, the equilibrium-dispersive model, and a reliable numerical algorithm were used to scan a wide operating region, and to define this separation area. To verify the results of these calculations, the separation area was also experimentally detected by performing measurements of product purity and production rate for selected operating points. The combination of a UV detector and a polarimeter allows the accurate monitoring of the internal concentration profiles of both enantiomers. These profiles were compared to the profiles calculated using the multilayer adsorption isotherm models. In addition, the influence of the heterogeneity of the column set on the performance of the SMB process, is studied. Even under strongly nonlinear conditions, excellent agreements between calculated and experimental profiles were obtained. Copyright © 2004 American Institute of Chemical Engineers (AIChE) [accessed 2013 November 27th

Measurement and modeling of the equilibrium behavior of the Tröger's base enantiomers on an amylose-based chiral stationary phase

The binary isotherms of the two enantiomers of Tröger’s base were measured on a system made of pure 2-propanol as the mobile phase and of Chiralpak AD, a chiral stationary phase (CSP) based on amylose tri-(3,5-dimethylphenyl carbamate). The experimental data were acquired using both frontal analysis and the perturbation method. The results obtained are most unusual. The adsorption of the more-retained (-)-enantiomer is not competitive: the amount adsorbed onto the CSP at equilibrium with a constant concentration of the (-)-enantiomer is independent of the concentration of the (+)-enantiomer. On the other hand, the adsorption of the less-retained enantiomer is cooperative: the amount of this (+)-enantiomer adsorbed by the CSP at equilibrium with a constant concentration of this enantiomer increases with increasing concentration of the (-)-enantiomer. Such a phenomenon has hardly ever been reported. A model equation is proposed that account well for all these isotherm data

Experimentelle und theoretische Untersuchungen der Gradientenchromatographie eines Proteins

Preparative liquid column chromatography is a powerful method for the isolation of proteins from complex mixtures. The use of solvent gradients has proved invaluable in the optimisation of the chromatographic separation process. In contrast to isocratic chromatography, the eluting strength of the solvent is increased during the separation. To this end, an increasing proportion of a solvent of high eluting strength is added to solvent of low eluting strength. This publication is intended to contribute to the general understanding of and to a quantitative description of preparative gradient chromatography of dissolved proteins. The analysis is based on the experimental determination of various chromatograms of the model protein lysozyme on a cation exchanger

Determination and Modeling of equilibrium adsorption isotherms

Workshop on nonlinear and preparative chromatograph