Prediction of chromatographic retention of metal complexes from stability constants measured by ion chromatography

Chromatographia - A theoretical model is used to predict retention times of divalent metal cations in single-column ion chromatography using one or more ligands in the eluent. Stability constants...     

End unit effect on the Tg of differentiated series of perfluoro-poly (oxymethylene-co-oxyethylene) oligomers

Twelve series of linear oligomers of four different degrees of polymerization (x_n = 8.77−41.55), having a common perfluorinated random copolymeric chain as molecular body and two equal foreign end units of one of the types listed in Table 1, have been synthesized by derivatization of base samples of one of them having a diolic---CH₂OH functionality. The glass transition temperature T_g of all the series was measured and thus examined as a function of x_n. A clear end unit effect is observed, dominantly determined in every series by chemical nature and structure of the end units, quantitatively expressed at any x_n by different positive or negative T_g deviations from the common asymptotic T_g∞ value. The results are also discussed in terms of copolymer end effect and of relation between T_g and end copolymeric composition.     

Density functionals for exchange and correlation energies: Exact conditions and comparison of approximations

A set of exact conditions is compiled for the purpose of developing and testing approximations for the exchange-correlation energy as a functional of the electron density. Special emphasis is placed upon recently developed density-scaling relationships. Commonly used generalized gradient approximations are compared against several of these conditions. A direct tabular comparison of these functionals (not of calculated properties) with one another is also made. © 1994 John Wiley & Sons, Inc.     

The external magnetic field dependence of RF splitting of57Fe hyperfine lines. NMR + Mössbauer double resonance experiment

We present the results of an experimental investigation of a RF splitting of⁵⁷Fe hyperfine lines in the regime of NMR and Mössbauer double resonance. The experiments have been performed as a function of RF field intensity and static magnetic field magnitude. The intensity of the RF components and the separation between them are extremely sensitive to the frequency and amplitude of the RF magnetic field. The RF splitting of hyperfine lines is inversely proportional to the strength of the static magnetic field.     

The lead tetraacetate oxidation of bisacylhydrazones of α-diketones: A scope re-assesment

Oxidation of the title compounds yields, besides the reported isoimides 3 and/or the amides 4 , also the imides 5 . The observed product dichotomy is considered as the result of an intramolecular nucleophilic attack on the aroyl group, of the pressumed zwitterionic intermediate 2 , by O or N present in the ambident N-aroylimine site of 2 . The results of AM1 calculations agree with the product studies and both permit the formulation of a set of rules correlating structure and selectivity.     

Distribution of magnetization in an easy-plane ferromagnet

Physics and Mathematics Division with Computational Center of the Bashkir Branch of the USSR Academy of Sciences. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 80, No. 3, pp. 470–473, September, 1989.