Separable energy-dependent approximation to local potentials

An extension of the single-pole separable approximation of a two-body t-matrix in which the effects of several poles are included is made. The simple form for the t-matrix derived from a single separable potential is retained. However, the separable potential is constructed using an energy-dependent superposition of the states corresponding to the various poles. The energy dependence is chosen so as to obtain the correct residue of both the on-shell and off-shell t-matrices at each of these poles, while preserving unitarity. The formalism is specialized to the case of s-wave scattering from an attractive square well. Comparison to the exact s-wave cross section gives good results.     

Heat capacity of MnBr2·4H2O near the antiferromagnetic transition temperature

Heat capacity of MnBr₂·4H₂O has been measured in the critical region around the Neel temperature. The data can be fitted, over a restricted range of |t|⩽10⁻², to the asymptotic power law. The critical exponents and the amplitudesA andA′ are not consistent with any theoretic predictions. However when scaling constraints are imposed, their values agree with the parameters of Ising model. Corrections to scaling are necessary to extend the range of the fit to |t|>10⁻². The correction terms are asymmetric giving −1·15±0·25 as the ratio of the amplitudes of the lowest order correction terms,D andD′ above and belowT _c. This value is in agreement with the recent predictions of the renormalisation group theory.     

Atomic parameters for Fe(XV) and Ni(XVII)

Transition probabilities and collision strengths are tabulated, between the fourteen lowest levels of the magnesium-like ions Fe(XV) and Ni(XVII), for use in calculations of line intensities radiated from laboratory and astrophysical plasmas.     

Application of the Poincaré-Bendixson theorem

Summary The Poincaré-Bendixson theorem is used to study the level curves of a positive definite function V(x, y), near the origin, and to obtain a short proof of the Brouwer fixed-point theorem in the plane. This will acknowledge the partial support of the authors by the National Science Foundation under Grant numbered GP 4057. This will acknowledge the partial support of the author by the U. S Army Research Office (Durham) under Grant numbered DA-ARO(D)-31-124-G-600.     

Liquid curves of eutectic system Na-K under pressure

Data on the phase diagram of Na-K under pressure is used to demonstrate that the entropy change on melting of pure Na and pure K are almost independent of pressure over a substantial range. Chemical association, involving NaK₂, is a likely explanation of the peak in the liquids curves at high pressures at a K concentration of about 2/3.     

Phase diagrams and elementary excitations

On the phase boundary separating two crystalline phases, it is shown that d(Tⁿ)/dp/_T=0=constant. The index n depends on the dominant elementary excitations, being 4,$\text{5}\text{2}$ and 2 for phonons, magnons and electronic single-particle excitations respectively.     

Levels of 209Po and 211Po populated in one-neutron stripping and pickup from 210Po

Energy levels of ²⁰⁹Po have been populated with the ²¹⁰Po(d, t)²⁰⁹Po and ²¹⁰Po(p, d)²⁰⁹Po reactions at bombarding energies of 17.0 and 17.8 MeV respectively. Fifteen levels were observed below 2.7 MeV of excitation. Energy levels of ²¹¹Po were populated with the ²¹⁰Po(d, p)²¹¹Po reaction, also at 17.0 MeV. Thirty-five levels, almost all new, were observed below 3.9 MeV of excitation. Comparison of experimental angular distributions with DWBA calculations allowed l-value assignments and extraction of spectroscopic factors for many levels. In ²⁰⁹Po the observed level structure is well described in terms of a simple particle-vibration coupling model. In ²¹¹Po the level structure is more complex and the simple model is not adequate.     

Polarographische Untersuchungen an Thallium(I)—Äthan-1,2-dithiolkomplexen

Complexation of thallium(I) with ethane-1,2-dithiol has been studied polarographically in 25% ethanol, 0.5M-NaClO₄, 0.01M-HClO₄ and 0.002% Triton X-100. Thallium in presence of ethane-1,2-dithiol, reduces reversibly at d.m.e. and the plateau current is diffusion-controlled. The successive formation of two complexes, 1∶1 and 1∶2, is indicated byDeford andHume's method. The overall changes in the thermodynamic parameters viz. ΔG, ΔH, ΔS accompanying complexation reactions have also been reported.     

Self-Gravitational Instability of a Stratified Viscous Hall-Plasma of Finite Conductivity

The hydromagnetic instability of a self-gravitating, incompressible, finitely conducting, viscous plasma of varying density has been investigated. The ambient magnetic field is assumed to be uniform and vertical. It is first shown that a variational principle characterizes the problem. The proper solutions have then been obtained, by the variational methods, for a semi-infinite plasma contained between two horizontal free boundaries. The dispersion relation has been solved numerically It is found that the growth rate of the unstable mode increases with the magnetic resistivity and with the Hall-currents while it decreases with the increasing viscosity. The influence of the effects of magnetic resistivity as well as of Hall-currents is, consequently, destabilizing on the dynamic instability of a self-gravitating stratified plasma. Viscosity has, however, a stabilizing influence on the growth rate of the disturbance.