Lifetime measurements on the compound nucleus 236U by means of the shadow effect

The lifetime of the ²³⁶U nucleus is measured in the range of excitation energies E_x = 6.7–11.5 MeV by a method based on the shadow (blocking) effect. The results obtained, as well as those of an earlier measurement of the lifetime for the ²³⁹U nucleus in the range E_x = 6.4–9.1 MeV, are compared with the results of calculations based on the level density ρ(E_x) in the Fermi-gas model and on the empirical level density ρ(E)_x) calculated as a result of an analysis of(n, γ) and (n, n') cross sections. An increase of excitation energy produces a substantial reduction in the rate of decrease of the lifetime at E_x ? 7.5 MeV for both compound nuclei as compared to the theoretical dependence τ(e_x).     

Effect of doping on the absorption spectra of p-Ge

Absorption spectra recorded at 295 and 94 ° K for p-Ge samples of various concentrations are reported. There is some discrepancy between these results and those reported previously. The absorption is calculated from the approximate Kahn theoretical equations, and the results are compared with experiment. The quantitative agreement is unsatisfactory.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 6, pp. 68–72, June, 1970.     

Microscopic theory of hydrodynamic modes in a planar ferromagnet

The hydrodynamic equations for an easy-plane (planar) ferromagnet are derived by analogy with the hydrodynamics of liquid helium. The relaxation of the magnitude of an order parameter is taken into account.The derivation is based on microscopic dynamics and the nonequilibrium statistical operator method. The hydrodynamic equations are generally nonlocal in space and in time and hold for all T<T_c.Transport coefficients are expressed in terms of time correlation functions and their symmetry properties are investigated.     

Rod-climbing effect in Newtonian fluids

When a rotating rod is brought into a polymer melt or concentrated polymer solution, the meniscus climbs the rod. This spectacular rod climbing is due to the normal stresses present in the polymer fluid and is thus a purely non-Newtonian effect. A similar rod climbing of an interface between two fluids has therefore been taken as a signature that one of the fluids exhibits normal stress effects. We show here, however, that the effect can occur with simple Newtonian fluids: it occurs when a Taylor-Couette instability happens in the less viscous of the two liquids but not in the more viscous one.