The calculations of cell dimensions of stoichiometric phases and binary and ternary solid solutions with the A15 structure

Equations that successfully reproduce the unit cell dimensions of stoichiometric (i) transition metal-transition metal (T-T) and (ii) transition metal-non-transition metal (T-B) phases with the β-Wolfram or A15 structure in terms of the diameters of the component atoms for CN 12 [J. Less-Common Metals, 81, 161 (1981)], are hear applied to binary and ternary solid solutions with the A15 structure, to discover how well and under what conditions they reproduce the observed lattice parameter variation. That in the main, they perform satisfactorily gives further credence to the model on which they are based, which shows how the various interatomic contacts within the interpenetrating icosahedra and CN 14 polyhedra of the structure, combine together in controlling the cell dimensions of the phases. The model also indicates that it is the contacts between the transition metal atoms that are paramount in controlling a. This fact leads to a specific prediction for the lattice parameter variation in transition-metal-rich solid solutions of T-B phases, which is essentially substantiated for phases of niobium.     

Reaktionen bei dem thermochemischen ZnSe-Cyclus zur Darstellung von Wasserstoff

Ohne Zusammenfassung     

Determination of substituent chemical shifts in the proton resonance spectra of the porphyrins

Reproducible proton chemical shifts in the porphyrin series are obtained when the spectrum is measured in chloroform using the zinc (II) complex of the porphyrin in the presence of an excess of pyrrolidine. This method is specifically demonstrated for the case of 2,4-dicyanodeuteroporphyrin-IX dimethyl ester which, as the free base, shows dramatic effects due to aggregation phenomena. The shifts obtained using the zinc (II) complex plus pyrrolidine method, which allow compilation of substituent chemical shifts in the porphyrin series, are shown to be the same as the less easily accessible infinite dilution shifts of the porphyrin free bases.     

A note on absorption and desorption of uranium by polyurethane foam

The separation of uranium/VI/ from solution using tri-n-octylphosphine-oxide /TOPO/ and polyurethane foam has been shown to be efficient and specific. A desorption method has been investigatied which recovers uranium and TOPO in independent fractions.     

Hartree-Fock calculations of surface-symmetry properties with finite-range forces

Complete Hartree-Fock calculations on asymmetric semi-infinite nuclear matter have been performed with a family of finite-range Gogny-type forces. For one of these forces all the computed values of the droplet-model symmetry coefficients J, L, M and Q are in good agreement with recent mass-formula fits.     

Near infrared properties of CdF2:ScF3

It is observed that heavy doping of CdF₂ with ScF₃ causes it to become semiconducting without further thermal treatment. A characteristic absorption band is induced in the near infrared which is ascribed to photoionization of impurity centers. The experimental data are in good agreement with that predicted theoretically for a Coulomb-like center.     

Crystallization of Arthrobacter sp. strain 1C N-(1-D-carboxyethyl)-L-norvaline dehydrogenase and its complex with NAD+

The novel NAD+-linked opine dehydrogenase from a soil isolate Arthrobacter sp. strain 1C belongs to an enzyme superfamily whose members exhibit quite diverse substrate specificites. Crystals of this opine dehydrogenase, obtained in the presence or absence of co-factor and substrates, have been shown to diffract to beyond 1.8 ? resolution. X-ray precession photographs have established that the crystals belong to space group P21212, with cell parameters a = 104.9, b = 80.0, c = 45.5 ? and a single subunit in the asymmetric unit. The elucidation of the three-dimensional structure of this enzyme will provide a structural framework for this novel class of dehydrogenases to enable a comparison to be made with other enzyme families and also as the basis for mutagenesis experiments directed towards the production of natural and synthetic opine-type compounds containing two chiral centres.