On the existence of certain generalized Moore geometries,part I

Using methods of Algebraic Graph Theory, generalized Moore geometries of type GM_m(s, t, c) with c = s + 1 are investigated. It is shown that such geometries do not exist for odd values of the diameter m exceeding 7, if st>1.     

Determination of the elementsV us andV ud of the Kobayashi-Maskawa matrix

We discuss the theoretical problems encountered in the standard evaluations of the Cabibbo angle and show that the data onK _e3 and hyperon decays require |V _us |=0.221±0.002. With this value unitary of the K-M-Matrix predicts |V _ud |=0.9753±0.0005. The ratio of pseudoscalar decay constants is found to beF _K /F _π=1.22±0.01.     

Interlaboratory studies of the determination of selected chlorobiphenyl congeners with capillary gas chromatography using splitless- and on-column injection techniques

The Community Bureau of Reference has organized a collaborative interlaboratory project to improve the analytical protocol for some specific chlorobiphenyls (CBs) within the European Community (EC). A series of test procedures were prescribed to optimize the gas chromatographic conditions for splitless and on-column injection, which substantially improved the quality of data. Important parameters included the initial column and injector temperatures and the choice of the polarity of the stationary phase. In a study with cleaned eel-fat extracts, coefficients of variation for reproducibility CV(R) ranging from 11 to 24% at the 0.04–0.3 mg/kg level per CB congener were obtained. No significant difference could be found between splitless- and on-column injection.     

Multiconfigurational perturbation theory (CASPT2) applied to the study of the low-lying singlet and triplet excited states of cyclopropene

The electronic spectrum of cyclopropene has been studied using multiconfigurational second-order perturbation theory (CASPT2) with extended ANO-type basis sets. The calculation comprises two valence states and the 3s, 3p, 3d members of the Rydberg series converging to the π and σ ionization limits. A total of twenty singlet and twenty triplet excited states have been analyzed. The results confirm the valence nature of the lowest energy singlet-singlet band and yield a conclusive assignment: the first dipole-allowed transition in cyclcopropene is due to absorption to a (σ → π*) state. The (π → π*) (V) state is interleaved among a number of Rydberg states in the most intense band of the system. The remaining spectral bands are due to Rydberg transitions of higher energy. The two lowest singlet-triplet transitions involve the same valence states. The results are in agreement with available experimental data and provide a number of new assignments of the experimental spectra.     

Analytical Study of Extracts of St John’s Wort (Hypericum perforatum), Evaluation of HPTLC Plates by Multivariate Data Analysis

JPC – Journal of Planar Chromatography – Modern TLC - HPTLC with multivariate data analysis has been used as a new means of evaluating the quality of herbal extracts. Spectral data from...