SOFT SYSTEMS

The aim of this review is to demonstrate the potential of surface forces measurement as a novel means for investigating surfaces and complex soft systems by describing our recent studies, which include cluster formation of alcohol, polyion adsorption, and polyelectrolyte brushes. 

Development of Integrated Systematic Engineering Approaches to Sustainable Resource Exploitation (e.g., life-cycle analysis, soft-systems analysis) in fields such as Mining, Forestry, and Agriculture,... 

Kirwan B., 1998a. Soft systems, hard lessons, Applied Ergonomics 31, pp. 663-678. 

Figure 3.2 Soft-systems analytical framework (adapted from [293])...

Parallels between the soft-systems analytical framework and a constrained relativism are evident when comparing Figure 3.2 with Figure 1.1(b) in Chapter 1 - reproduced as Figure 3.3 below. 

According to the soft-systems approach, actors and system constraints form the feedback loops that determine reality in terms of chemical risk and safety (see Figure 3.3). This thesis therefore considers the impact that different national actors and system constraints have on risk management processes at national and EU levels. 

The soft-systems analytical framework facilitated the comparing and contrasting of national approaches, as well as interviewee perspectives of EU decision-making and REACH. In total, the results of these processes formed the basis for proposing a framework for decision-making under REACH. 

Although soft-systems analysis provided an over-arching framework for organising and interpreting data, it was also necessary to follow a methodology to extract and validate information from the interview... 

P. Checkland and J. Scholes, Soft Systems Methodology in Action, John Wiley and Sons, Chichester, UK, 1990, p.36. 

It is useful, for reasons which are apparent in relation to movement of nanoparticles in vivo, to divide nanosystems into two types, hard and soft, although there are obviously intermediate situations. Hard systems, for example, polymeric nanoparticles and nanocapsules, nanosuspensions or nanocrystals, dendrimers, and carbon nanotubes are neither flexible nor elastic. Hard systems can block capillaries and fenestrae that have dimensions similar to the particles, whereas soft systems can deform and reform to varying degrees. Erythrocytes and many liposomes fall into this category and are thus better able to navigate capillary beds and tissue extracellular spaces. Soft systems include nanoemulsions (microemulsions) and polymeric micelles. 

We argue that the above features of star dynamics are generic for soft systems of the core-shell type for which stars serve as prototype. Support for this comes from the dynamic light scattering (DLS) investigation of large block copolymer micelles, where all three relaxation modes, i.e., cooperative, structural and selfdiffusion are observed [188]. In particular, the star model discussed above applies to core-shell particles with a small spherical core relative to the chain (shell) dimensions. For a surface number density a = f / (47i r ) the polymer layer thickness under good solvent conditions is L ... 

Fig. 18 Schematic representation of crowded soft systems (a) entangled polymers, (b) repulsive colloidal hard spheres, (c) colloidal star polymers, and (d) attractive hard spheres. The former are described by the tube model for entanglements, whereas the latter three by the general cage model for colloidal glasses...

The equilibrium softness of the ensemble is cf. Note that this is not the same as the molecular softness, large value of [Pg.106]

The volume fraction of the particles for a soft system is to be replaced by an effective volume fraction. The effective volume fraction is given by... 

The T[ value is directly related to the electron localization (system stability) and the softness is associated to the reactivity indices [68,71 [. The hard (soft) systems correspond to a high (low) stability. 

Checkland, P. (2000). Soft systems methodology A thirty year retrospective. Systems Research and Behavioral Science, 17, S11-S58. doi 10,1002/1099-1743(200011) - http //citeseerxist.psu.edu/viewdoc/ download doi=10.1.1.133.7381 rep=repl type=pdf... 

Another important feature of these polyols is their narrow MWD. Low polydispersity results in lower viscosities in both the polyol and isocyanate-terminated prepolymers. Polyol MWD has a significant effect on the mechanical and dynamic properties of polyurethane and polyurethane/urea systems. Broad-MWD polyols such as PTMEG or polyester polyols contain significant amounts of hard-segment diol, which limits their softness. Acclaim polyols contain no hard-segment diol and thus have inherent superior properties in soft systems. They can be made to approximate broad-MWD polyols such as PTMEG by incorporation of a low MW glycol. 

Polymer chains in solution form a loose coil such that two coils can interpenetrate. The resulting effective interaction potential O(lrl) is repulsive and is well approximated by a Gaussian potential of strength Oq and with a range ro which is proportional to the radius of gyration Rg. The excess free energy functional for such soft systems can be approximated by a quadratic form... 

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