Characterizing domain mixing effects in hydrogen bond-compatibilized polymer blends

The nature and extent of phase mixing in blends of hydroxyl-functionalized polystyrene and poly(ethyl acrylate) (PS/PEA), where the driving force for mixing is hydrogen bonding, are characterized by several techniques. Small-angle x-ray scattering (SAXS) shows a reduction in average domain size with increasing functionalization level, a result also evident from scanning electron microscopy (SEM). Together, the two techniques reveal a very broad distribution of domain sizes. At high functionalization levels, both SAXS and SEM indicate a high degree of “in-domain” mixing, with little or no pure PS or PEA remaining in the blends. Mathematical modeling of dynamic mechanical thermal analysis (DMTA) data is employed to quantify this progression. Initially, mixing is primarily interfacial, but as the functionalization level increases, the mixed interphase rapidly grows to occupy the entire material. In agreement with the SAXS and SEM results, DMTA modeling shows that further increases in the functionalization level suppress the amplitude of composition variations in the sample. The onset of extensive in-domain mixing coincides with the marked changes in stress-strain behavior observed previously in these materials. © 1994 John Wiley & Sons, Inc.     

Putting Soft OR Methods to Work: Information Systems Strategy Development at Richards Bay

The development of an information systems (IS) strategy for a mineral extraction and processing plant operated by Rio Tinto Zinc (RTZ) in South Africa is described. The participative approach used was developed from soft OR and systems thinking. The aim of the Richards Bay project was to test commercially whether the Participative Information Management Strategy (PIMS) methodology could be used as a standard method to be applied to the development of an information systems strategy at any mine site. The paper describes the implementation of the process and the problems encountered. More generally it discusses the diffusion of new ideas in an international company, illustrated by the use of the participative approach for other activities including systems development. Conclusions are drawn about the value of participative approaches based on soft OR in this context.     

Inflatene,an ichthyotoxic c12 hydrocarbon from the stoloniferan soft coral clavularia inflata var. luzoniana

A new tricyclic C₁₂ hydrocarbon, inflatene (1), possessing unexpected ichthyotoxic properties, has been isolated as the major metabolite of the stoloniferan $\text{Clavularia inflata}$ var. $\text{luzoniana}$. The structure of inflatene was secured by extensive FT-NMR studies with the natural product and several key derivatives.     

Reactions involving fluoride ion. Part 40. Amines as initiators of fluoride ion catalysed reactions

Tetrakis(dimethylamino)ethene (TDAE) and trimethylamine react with anhydrous unsaturated fluorocarbons to produce, ‘in situ’, powerful fluoride- ion sources. These are used to initiate carbon- carbon bond forming reactions eg. oligomerisation and polyfluoroalkylation, and many of these reactions occur efficiently in the absence of a solvent.     

Strong-coupling approximations

Standard path-integral techniques such as instanton calculations give good answers for weak-coupling problems, but become unreliable for strong-coupling. Here we consider a method of replacing the original potential by a suitably chosen harmonic oscillator potential. Physically this is motivated by the fact that potential barriers below the level of the ground-state energy of a quantum-mechanical system have little effect. Numerically, results are good, both for quantum-mechanical problems and for massive φ⁴ field theory in 1+1 dimensions.     

On the relative efficiency of alternative modes of producing a public sector output: The case of the developmentally disabled

This paper examines the relative efficiency of alternative methods of producing care for the developmentally disabled. A linear programming framework is used to construct a production frontier which allows measurement of relative efficiency among institutions in the sample. Tests are performed to detect influential observations in the data which might result from measurement error which could distort the efficiency measures. Different types of institutions are compared in terms of average efficiency. Policy implications of the analysis are discussed in the concluding section.