Review of Cultural differences and medical care.

Reviews the book "Cultural Differences and Medical Care" by Lyle Saunders (1954). This volume, based on a sociologic study of the cultural pattern of the Spanish-speaking populations of the Southwest, attempts to analyze the barriers that limit their acceptance of modern health services and medical care. According to the reviewer, this book is well written and interesting but may well fail to reach many of the readers in the medical profession for whom it might be most valuable. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The localisation model of rubber elasticity. II

Summary The effect of the spatial localization of a network chain by surrounding chains is incorporated into the chain probability distribution function and the network free energy is then calculated using the statistical mechanical formalism for constrained systems. In addition to a term having the classical Gaussian form, the resulting expression contains another term which depends on both the cross-link density of the network and the plateau modulus of the uncross-linked melt.     

Hydroxypropylmethylcellulose–anionic surfactant interactions in aqueous systems

The increase in the viscosity of an aqueous solution or gel of hydroxypropylmethylcellulose (HPMC) in the presence of an anionic surfactant is attributed to a two-step process: (a) the surfactant undergoes ion–dipole interaction with the ethereal oxygen in HPMC, in the absence or presence of water, and (b) hydrocarbon moieties in the now pendant surfactant molecules undergo hydrophobic bonding, in the presence of water, resulting in an apparent increase in the molecular weight of the HPMC. DSC of dry blends and dried gels or films confirmed HPMC–sodium lauryl sulfate interaction. Work-to-break measurements on films cast from aqueous solutions of HPMC, in the absence or presence of anionic surfactants, indicated an apparent increase in the molecular weight of HPMC in the presence of surfactants.     

Modelling the amorphous phase of a melt crystallized,semicrystalline polymer: segment distribution,chain stiffness,and deformation

The analogy between the Gambler's Ruin problem and the statistics of loops and bridges in the amorphous region of lamellar semicrystalline polymers was first recognized by Guttman et al. Results for the loop and bridge distribution compare very well with recent data from Monte Carlo calculations. However, when the molecular weight of the polymer is low, a substantial part of the amorphous region is filled by cilia and free polymer. We examined their relative importance by adapting the matrix formalism developed by DiMarzio and Rubin. The Gambler's Ruin results are recovered for high molecular weight polymer. In addition it will be shown that the effect of the temperature (chain stiffness) can be simulated by rescaling the steplength of a random walk chain. Mean field theories incorporate segment-solvent interactions and allow for non-uniform segment densities by weighting each step according to the local concentrations. Using these weighting factors, we find deformation to be controlled by energetic interactions rather than by entropy. At large strain a ‘necking’ process occurs. However, in the presence of a good solvent, the material is soft and flexible.