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The authors critically examine the present theoretical understanding of the conformational rod-to-flexible chain crossover of a linear chain polymer in dilute solution with a good solvent. There is good evidence for weak universality in this crossover while strong universality seems unlikely from available evidence. In addition, this system should exhibit a second crossover from a Gaussian to an excluded volume. They present a scaling hypothesis for the behaviour of this second crossover and compare with the initial results of numerical simulations and with the experiment of Murakami et al. (1980).

The resonant part of the response of the mobility of an electron to a microwave field in liquid helium is calculated. A response with structure corresponding to the s and d resonance of order 1% of the DC mobility is expected for T

The authors consider the question of the observability of the plasmon mode in molten salts by the study of frequency moments of the dynamical structure factor Smu nu (k, omega ). They establish approximate relationships between the fourth moments and phonon frequencies in the solid which are confirmed by detailed calculations in KI. Various approximation methods for obtaining the neutron scattering function S(k, omega ) from the moments give consistent results indicating that the plasmon mode should be observable.

The authors compute the mean spin per site (Sz) using the linearised randomly dilute two-dimensional antiferromagnetic Heisenberg model developed by Thorpe and Alben. The result shows that (S- mod (Sz) mod )/S is 14-16% near the percolation concentration. Mean spins on small finite clusters in this model are in very poor agreement with exact results of (Sz)=0 for HA=0. The mean spin on the largest cluster is reasonably self-consistent but spatial inhomogeneities in (Siz) are not treated self-consistently in the model.