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On the basis of a scaling hypothesis for the criticality of fluids, or fluid mixtures, held between parallel plates, we analyze the combined effects of finite wall separation and ’’symmetry breaking’’ boundary conditions at the walls (i.e., adsorption, or preferential adsorption of one component, at the surfaces). The resulting bulk (but ’’two-dimensional’’) critical point is shifted both in temperature and in density or composition (and in the conjugate field variables) by amounts described by scaling. The scaled form of the phase boundary is consistent with results from a low temperature Ising lattice gas model expansion.

Critical behavior in thin films is discussed with attention to the example of phase separation in binary fluid mixtures between parallel plates. The analyses focus on the dependence of the shift in critical temperature ΔTc, critical field, etc., on the film thickness D, and on the nature of the walls as modeled by a surface field or chemical potential h1 which acts near the walls and leads to preferential adsorption of one of the bulk phases. Mean field theory for an Ising/lattice-gas model is utilized and the resulting asymptotic scaling functions for the shifts ΔTc etc. are computed within Landau theory by analytic and numerical methods. Series analyses for simple cubic lattice Ising model films with h1=0 are used to estimate universal features of three-dimensional systems: specifically, if ξ(ΔT) is the bulk correlation length, determined, say, via scattering experiments, at ΔT=T−T∞c≳0 then the shift ratio D/ξ(‖ΔTc‖) is about 2.89 for h1=0 but 4.61 for h1→∞, compared with mean field values π and 5.0699. Crossover effects for small nonzero h1 may lead to 10%–15% errors in estimating the exponent for the decay of ΔTc with D. The relation of the theory to recent experiments and the connection with wetting phenomena are discussed briefly.

A novel concept of ‘‘surface’’ spinodal decomposition is introduced in the context of wetting and prewetting first order transitions for simple fluids in contact with a bounding wall. Qualitative and semiquantitative discussions are made within the framework of a phenomenological Landau theoretical model for semi-infinite systems with a (short-ranged) wall potential. A concept of ‘‘extended wetting’’ is also proposed, whereby even for T<TW (the wetting temperature) a macroscopically thick ‘‘wetting’’ layer can form near the wall upon rapidly quenching the solution into the coexistence region. These ideas are carried over to polymer solutions and blends near their consolute points where the characteristic time scales should be more manageable.

We present new results of Monte Carlo simulations for self-avoiding walks on randomly diluted square and simple-cubic lattices performed very close to the percolation thresholds. Our results indicate the asymptotic behavior of the walk dimension to be rather similar to the undiluted lattice even at critical dilution.

Campylobacter jejuni was isolated from stool cultures from 14 (30%) of 46 patients with Guillain-Barré syndrome and from 6 (1.2%) of 503 healthy persons, and the difference was highly significant (p < 0.0001). In addition, serological evidence of recent C. jejuni infection was found in 5 of 29 patients with negative stool cultures. Therefore, 41% of patients were associated with C. jejuni infection. Ten of 12 (83%) isolates from patients with Guillain-Barré syndrome belonged to Penner serogroup 19, which is a rare serogroup in sporadic patients with C. jejuni enteritis. In the lectin typing study, all serogroup 19 strains from patients with Guillain-Barré syndrome were shown to contain terminal beta-N-acetylglucosamine residues on their cell surface, but serogroup 19 strains from patients with enteritis were not.

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