Magnetic moment distributions and form factors in ferromagnetic nickel-ruthenium alloys

Using polarised neutrons, the full three-dimensional magnetic structure amplitudes in the Ni_1?c Ru _c single crystals forc = 0·027, 0·033 and 0·046 were measured. Moment density maps in various portions of the Wigner-Seitz cell were obtained. It is seen from these maps that unlike Ni-based alloys with 3d impurities, the introduction of Ru to the Ni matrix produces extensive perturbations in the diffuse moment density, giving rise to a netpositive diffuse moment which tends to increase with Ru concentration. The asphericity of the host moment at first increases and then decreases with increasing Ru content. Another significant outcome of the present study is the evidence for the reversal of the sign of the Ru moment, from negative to positive, obtained by comparing the shape of the spherical site form factors of the three-alloy concentrations with the Ni spherical form factor itself. The sign reversal of the impurity moment is confirmed by the form factor analyses. Strong local environmental effects seem to play a major role in this alloy system.     

A polarised neutron study of magnetic moment density in Cu2MnAl

A polarised neutron study of the ferromagnetic Heusler alloy Cu₂Mn_0.863Al_1.057 has been made. It has been concluded that the magnetic moment density is primarily situated on the Mn ions. On assigning the Mn-moment value, the observed magnetic form factor is found to be in good agreement with the Mn²⁺ free ion form factor calculated by Watson and Freeman. A slight asphericity has been observed in the moment density. It is estimated that there are about 3% excess 3d-electrons in the Eg states compared to spherical distribution. There is evidence of a very small positive polarisation of the Cu atoms. No appreciable conduction electron polarisation is found.     

Compressive energy of ions in ionic crystals

The possibility of writing the repulsive energy in the Born model of binary ionic crystals as a sum of two separate contributions from the two ions has been investigated. Such an approach leads to two identities, one connecting the lattice spacings of a family of ionic crystals and the other connecting their compressibilities. These identities have been tested on the alkali halide crystals over a range of pressures. The agreement is found to be quite satisfactory. Some further predictions with respect to crystals which exist as two polymorphs have also been tested. In all cases, the deviations of the experimental values from the exact identities can be traced to the fact that second neighbour repulsions in the crystals have been neglected. It is hence concluded that individual compressive energies for ions in ionic crystals is a very attractive possibility.     

Production of prompt leptons in a cluster model

Prompt lepton production in hadron collisions is explained in a cluster production model, by assuming that the clusters have a small branching ratio for decay into leptons. The production of low mass and small momentum clusters, normalized to reproduce pionization, can explain the observed large increases of e/π ratio for decreasing p_bdT at large angles and the decreasing values of ω/π with increasing x_lab near the forward direction. The present model predicts a large increase of the e/ω ratio near the forward direction as x_lab increases.     

The influence of ultrasonic waves on manganese dioxide sol in the atmosphere of nitrogen

Summary The influence of ultrasonic waves at 1 MC/sec and 225 watts/cm² power on the negatively charged manganese dioxide sol has been investigated in an atmosphere of nitrogen and thereby excluding oxygen. The stability of the sol on exposure to ultrasonic waves is affected in a similar way as in presence of air but the extent to which the sol gets unstable on exposure is less in the absence of oxygen than in its presence. The specific conductivity increases but hydrogen ion concentration remains practically constant as the time of exposure increases.

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Zusammenfassung Der Einflu? von Ultraschall (1 mHz, 225 W/cm²) auf negativ geladenes Mangandioxidsol wurde unter Stickstoff unter Ausschlu? von Sauerstoff untersucht. Die Stabilit?t des Sols ist in gleicher Weise wie bei Gegenwart von Luft ver?ndert, nur wird das Sol bei Ausschlu? von Sauerstoff weniger instabil. Die spezifische Leitf?higkeit steigt mit steigender Expositionszeit, w?hrend die Wasserstoffionenkonzentration praktisch konstant bleibt.

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The authors are thankful to the Council of Scientific and Industrial Research for the award of scholarship for this work.     

Torsional vibrations of non-uniform rotating blades with attachment flexibility

The torsional vibrations of non-uniform pretwisted rotating blades are studied by using finite element methods based on both the Rayleigh-Ritz and Galerkin formulations. The apparent differences between the matrices obtained from these formulations are explained and, as obtained by using three different orders of elements, results are presented for blades with flexibly attached roots and for a non-uniform blade representative of a bearingless rotor. A parametric study is carried out to resolve a controversy regarding the relative importance of certain terms in the equations of motion of pretwisted rotating blades. In Appendix I, an exact solution is presented for the torsional vibrations of flexibly attached rotating blades with piecewise constant inertia and elastic properties, which serves as a benchmark solution for the finite element results.     

Emission of large-p T particles inp-nucleus and nucleus-nucleus collisions

The observed dependence of the yield of highpT particles on the atomic numberA of the target and the incident energy, inp-a, a-a andp-nucleus collisions, is explained in a coherent tube model.     

Transition metal complexes of primary and secondary phosphines,part II. Some palladium(II) and platinum(II) complexes of type L3MC2

Summary The general course of reactions between [MCl₄ ]^2– (M = Pd, Pt) and primary and secondary phosphines containing phenyl, cyclohexyl, or 2-cyanoethyl groups, in polar solvents, is to yield L₃MCl₂ complexes which are probably ionic [L₃MCl]⁺Cl^– These compounds can be isolated and characterized in the solid state, but in solution they are labile, and tend to react to give phosphines plus L₂ MCI₂.     

Polybenzimidazoles. VI. Polybenzimidazoles containing aryl sulfone linkages

Four new polybenzimidazoles with aryl sulfone linkages between the recurring units have been prepared in order to study their thermal stability and solubility properties. The polymers prepared were high molecular weight materials with good thermal stability.