Resistivity and magnetoresistivity of amorphous rare-earth alloys

The resistivity and magnetoresistivity of amorphous rare-earth alloys are studied starting from the general approach of Van Peski-Tinbergen and Dekker. The random axial crystal-field and the magnetic correlations between the rare-earth ions are consistently taken into account. The characteristic features of the available experimental data are explained both of the case of random ferromagnetic and antiferromagnetic order.     

Reversed-phase liquid chromatographic separation of phenolic compounds with a new derivatizing reaction

Summary A reversed-phase HPLC method for resolution of phenoic compounds is presented. A new derivatization reaction has been developed employing diazotized 4-amino-benzonitrile, which reacts also with parasubstituted phenols. The products of the reaction can be extracted in n-butanol, allowing preconcentration and clean-up steps; the extracts are very stable and show strong absorption in the visible, where many interferences are avoided. The possibility of resolution of complex mixtures is discussed with reference to the use of reversed-phase columns using octadecyl- and phenyl bonded silica.     

Aliphatic monoamines,diamines, polyamines: An HPLC method for their identification and separation by a dansylation reaction; The study of separation factors in homologous series

Summary An analytical method is presented for the identification and separation of aliphatic monoamines, diamines and polyamines. Dansyl chloride as the derivatizing agent and fluorimetric detection were employed. The behaviour of different column packings and eluent compositions was tested and compared. The interaction mechanisms of the dansylated compounds with stationary and mobile phases are discussed on the basis of the analysis of the capacity factors evaluated in the homologous series of monoamines CH₃(CH₂)_nNH₂, with n varying up to 9 and diamines NH₂(CH₂)_nNH₂, with n varying up to 12. An application of this method to a real sample is presented.     

Occurence and correlation of two non-equivalent sites for europium in EuPd3B

Mössbauer spectroscopy has been used to investigate the mechanism which affects the valence state of europium in EuPd₃B. The obtained results are interpreted in terms of a correlation between two non equivalent sites each in a fluctuating valence state.     

Simultaneous effect of salt and methanol concentrations on the hydrophobicity of some ion-pairing agents

Summary The lipophilicity (hydrophobicity) of some alkylamines and arylamines was determined with reversed-phase thin-layer chromatography using various water: methanol mixtures as eluent with and without adding salt to the system. The effect of various structural parameters of amines and that of the chromatographic conditions were assessed with stepwise regression analysis. The calculation proved that in case of alkylamines the lipophilicity does not depend linearly on the length of the alkyl chain, the effect of methanol and salt concentrations are intercorrelated and the influence of the alkyl chain branching is negligible. In case of arylamines the number of amino groups has the highest impact on the retention and the effect of methanol and salt is also intercorrelated.     

Preparation and characterization of sintered pellets and «Thick» films of Bi2Sr2Y x Ca1−x Cu2O8

Il Nuovo Cimento D - A systematic study of yttrium substitution for calcium in the high-temperature superconductor Bi2Sr2CaCu2O8 compound has been performed. The samples of Bi2Sr2Y x Ca1−x...     

Kiamycins B and C,unusual bridged angucyclinones from a marine sediment-derived Streptomyces sp.

Kiamycins B (1) and C (2), two unusual angucyclinones bearing a novel 6,12-epoxybenz[a]anthracene ring system, were isolated from the cultures of a marine sediment-derived Streptomyces sp. along with one structurally related derivative 3. Their structures and stereochemistries were determined by spectroscopic analyses, single-crystal X-ray diffraction and electronic circular dichroism (ECD) calculations.