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51.
Summary The retention of 22 ring-substituted phenol derivatives on porous graphitized carbon (PGC) (eluents: acetonitrile — water and methanol — water mixtures) and on octadecylsilica (ODS) (eluents: methanol — 0.025 M KH2PO4 mixtures) was determined, and the relationship between retention and physicochemical parameters were evaluated by principal component analysis followed by two-dimensional nonlinear mapping and by cluster analysis as well as by canonical correlation analysis. Calculations proved that marked differences can be detected between the retention characteristics of PGC and ODS columns, and the electronic parameters of phenol derivatives have the highest impact on their retention. The comparison of various multivariate mathematical-statistical methods indicated that principal component analysis followed by two dimensional non-linear mapping is the most appropriate method for the evaluation of large data matrices in RP-HPLC. 相似文献
52.
The relative strength of interaction between anionic (SDS) and nonionic surfactant (octaethoxylated oleyl alcohol, GEN) and homologous series of peptides was determined by reversed-phase thin-layer chromatography (RP-TLC) carried out on alumina layers impregnated with paraffin oil. The relative strength of interaction was calculated and was correlated with the physicochemical parameters of peptides. It was established that each peptide interacted with both surfactants and with their mixture (1:1, m/m). The relative strength of interaction depended on the number of amino acid units in the peptide, side chain bulk and electronic properties and hydrophobicity of the amino acids. The impact of individual parameters highly depended on the character of surfactant. The data prove that the retention order of peptides can be modified by adding different surfactants and surfactant mixtures to the mobile phase resulting in improved separation. 相似文献
53.
Esther García 《Monatshefte für Mathematik》2005,145(3):229-238
In this work we extend to superalgebras a result of Skosyrskii [Algebra and Logic, 18 (1) (1979) 49–57, Lemma 2] relating associative and Jordan structures. As an application, we show that the Gelfand-Kirillov dimension of an associative superalgebra coincides with that of its symmetrization, and that local finiteness is equivalent in associative superalgebras and in their symmetrizations. In this situation we obtain that having zero Gelfand-Kirillov dimension is equivalent to being locally finite.Partially supported by MCYT and Fondos FEDER BFM2001-1938-C02-02, and MEC and Fondos FEDER MTM2004-06580-C02-01.Partially supported by a F.P.I. Grant (Ministerio de Ciencia y Tecnología). 相似文献
54.
Jos María Miguel del Corral Marina Gordaliza Jos-Luis Lpez Esther Del Olmo M. Angeles Castro M. Luisa Lpez 《Helvetica chimica acta》1995,78(7):1793-1796
The configuration of several keto-cyclolignans related to podophyllotoxin has been reviewed. Under basic catalysis, the configuration at the C-atom in α-position to the lactone carbonyl group in podophyllotoxone is inverted instead of the C-atom in α-position to the ketone group, as it has been reported. 相似文献
55.
A systematic approximative scheme for the solution of the Migdal's recursion formula for continuous spin systems is worked out. The new method avoids a number of problems present in the original solution given by Migdal. The critical behaviour of the two dimensional harmonic rotator model (n=2, wheren is the number of spin components) is calculated as an illustration of the method. Finally, a model for which the approximative scheme becomes exact is discussed. 相似文献
56.
57.
A family of 4n?1 parameter solutions corresponding to n monopoles is constructed by a three-dimensional “inverse scattering” method. Global regularity of the finitely separated two-monopole solution is shown. 相似文献
58.
The environmental pollutants 3,4-dimethoxybenzaldehyde (DMB) and 3,4-dimethoxyphenylacetone (DMPA) were separated and quantitatively determined in treated and untreated industrial waste waters on a porous graphitized carbon column using HPLC with diode array detection (DAD). It was established that the detector response is linear in a wide range of injected quantities for both pollutants, and the logarithm of the capacity factor depends linearly on the concentration of acetonitrile in the eluent. The relative standard deviation of the retention time, peak height and peak area was lower than 1% in the normal and lower than 3% in the lowest concentration range. Peak purity tests indicated that the method separates well DMB and DMPA from other impurities present in the waste waters. Both aerobic and anaerobic treatments markedly decreased the concentration of DMB and DMPA in industrial waters and HPLC combined with DAD proved to be an adequate analytical procedure to follow such changes. 相似文献
59.
60.
Anthony H. Jackson K. R. Nagaraja Rao N. Sim Ooi Esther Adelakun 《Tetrahedron letters》1984,25(52):6049-6050
Treatment of α-methylpyrroles with thallium (III) nitrate/Montmorillonite clay affords the corresponding α-formylpyrroles in excellent yields. 相似文献