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1.
A. I. Meyers A. H. Reine J. C. Sircar K. B. Rao S. Singh H. Weidmann M. Fitzpatrick 《Journal of heterocyclic chemistry》1968,5(2):151-159
The cyclization of enamines derived from β-aminoesters and β-aminonitriles into bi- and tricyclic enaminoketones ( 6,9,13 and 24 ) has been investigated. The enamines derived from aminonitriles cyclize smoothly with magnesium perchlorate in benzene or toluene, whereas the enamines derived from aminoesters cyclize spontaneously during their formation. The scope and limitation of this process is discussed. 相似文献
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The features of different nebulizer systems (cross-flow-, Meinhard- and GMK-system) in the ICP atomic emission spectrometric
analyses of solutions with different contents of different salts were evaluated. As basis for the comparison of the nebulizer
systems the recovery rates and noise power spectra were used. Both showed that the GMK-system could be used for the widest
diversity of salts (sodium chloride, ammonium sulfate and sodium tetraborate) and concentration range (0–10% (m/v)) followed
by the cross-flow-system and the Meinhard-system in ICP-OES using a 1 kW argon ICP. Of all nebulizer systems the nebulizer
according to Meinhard has the lowest performance for the salts investigated. The noise power spectra of all nebulizer systems
are dominated by interference noise from the sample introduction system. This noise increases with the salt concentration
of the solution and the GMK-system shows the lowest increase, followed by the cross-flow- and Meinhard-system.
Received: 11 October 1999 / Revised: 5 January 2000 / Accepted: 14 January 2000 相似文献
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Latvian Institute of Organic Synthesis, Riga. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1701–1702, December, 1995. Original article submitted September 28. 1995. 相似文献
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Ek M Borgstr?m MT Karlsson LS Hetherington CJ Wallenberg LR 《Microscopy and microanalysis》2011,17(5):752-758
The twin interface structure in twinning superlattice InP nanowires with zincblende structure has been investigated using electron exit wavefunction restoration from focal series images recorded on an aberration-corrected transmission electron microscope. By comparing the exit wavefunction phase with simulations from model structures, it was possible to determine the twin structure to be the ortho type with preserved In-P bonding order across the interface. The bending of the thin nanowires away from the intended 110 axis could be estimated locally from the calculated diffraction pattern, and this parameter was successfully taken into account in the simulations. 相似文献
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Polyelectrolytes are widely used in capillary electrophoresis as coating agents of silica capillaries to prevent adsorption phenomena and improve the repeatability of peptide and protein analysis. A systematic study of the coating experimental conditions has been carried out to optimize coating stability and performance. The main experimental parameters studied were the type and concentration of polyelectrolytes used in several monolayer and multilayer coatings, the ionic strength of coating and stabilizing solutions, and the procedures used for coating and capillary storage. Electroosmotic flow magnitude, direction and repeatability were used to monitor coating stability. Coating ability to limit adsorption was investigated by monitoring variations of migration times, time-corrected peak areas and separation efficiency of test peptides. Capillary-to-capillary and batch-to-batch reproducibility was also studied. In addition, the separation performance of polyelectrolyte coatings were compared to those obtained with bare silica capillaries. 相似文献
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Engström HA Johansson R Koch-Schmidt P Gregorius K Ohlson S Bergström M 《Biomedical chromatography : BMC》2008,22(3):272-277
Continuous monitoring of drug levels and endogenous molecules in biological fluids is a developing research area with many applications. One example is the need to improve life for millions of diabetes mellitus patients by continuously monitoring the glucose level. In order to have a dynamic response, the recognition molecule in a continuous sensor should preferentially have a fast dissociation rate and a dissociation constant in the millimolar range. We have evaluated the monoclonal antibody (mAb) 3F1E8-A2 for its potential to be used in a future glucose sensor application. The mAb was generated from hybridomas by immunizing mice with 10 kDa dextran (an alpha1,6-glucose polymer) with the aim of obtaining mAbs that can recognize the glucose monomer. The mAb was immobilized to macroporous silica and the interaction with dextran-derived oligosaccharides was evaluated with weak affinity chromatography (WAC). To measure the low affinities between the mAb 3F1E8-A2 and different monosaccharides, a competitive weak affinity chromatography approach was employed. It was found that the mAb had a higher specificity for glucose compared with other monosaccharides and the dissociation constant (K(d)) towards glucose was determined as 18.8 +/- 2.6 mm. 相似文献
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Utilizing the fact that solid-harmonic combinations of Cartesian and Hermite Gaussian atomic orbitals are identical, a new scheme for the evaluation of molecular integrals over solid-harmonic atomic orbitals is presented, where the integration is carried out over Hermite rather than Cartesian atomic orbitals. Since Hermite Gaussians are defined as derivatives of spherical Gaussians, the corresponding molecular integrals become the derivatives of integrals over spherical Gaussians, whose transformation to the solid-harmonic basis is performed in the same manner as for integrals over Cartesian Gaussians, using the same expansion coefficients. The presented solid-harmonic Hermite scheme simplifies the evaluation of derivative molecular integrals, since differentiation by nuclear coordinates merely increments the Hermite quantum numbers, thereby providing a unified scheme for undifferentiated and differentiated four-center molecular integrals. For two- and three-center two-electron integrals, the solid-harmonic Hermite scheme is particularly efficient, significantly reducing the cost relative to the Cartesian scheme. 相似文献
10.
Reine Nehmé Catherine Perrin Vincent Guerlavais Jean‐Alain Fehrentz Hervé Cottet Jean Martinez Huguette Fabre 《Electrophoresis》2009,30(21):3772-3779
The diastereoisomeric separation of peptidomimetics of hexarelin, a strong growth hormone secretagogue, in CE has been studied. Highly sulfated‐γ‐CD was found to be an appropriate selector for the separation of the stereoisomers. However, non‐repeatable analyses were obtained on bare fused silica capillary due to the progressive adsorption of the analytes on the capillary wall. Two types of polyelectrolyte coating agents were tested to prevent this phenomenon. Coating with neutral polyethylene oxide was found to be efficient but resulted in a very long analysis time (about 40 min). Coating with cationic poly(diallyldimethylammonium) chloride was found both to prevent analyte adsorption, reduce analysis time and alter separation selectivity. EOF measurement revealed that the highly sulfated‐γ‐CDs were strongly adsorbed on the poly(diallyldimethylammonium) chloride coating surface yielding a stable strong cathodic EOF, which considerably reduced analysis time (about 12 min). Very good repeatability of analysis was obtained (RSDmigration time<1%). 相似文献