Chain length dependence of the polymer-solvent critical point parameters

We report grand canonical Monte Carlo simulations of the critical point properties of homopolymers within the Bond Fluctuation model. By employing Configurational Bias Monte Carlo methods, chain lengths of up to N=60 monomers could be studied. For each chain length investigated, the critical point parameters were determined by matching the ordering operator distribution function to its universal fixed-point Ising form. Histogram reweighting methods were employed to increase the efficiency of this procedure. The results indicate that the scaling of the critical temperature with chain length is relatively well described by Flory theory, i.e. \Theta-T_c\sim N^{-0.5}. The critical volume fraction, on the other hand, was found to scale like \phi_c\sim N^{-0.37}, in clear disagreement with the Flory theory prediction \phi_c\sim N^{-0.5}, but in good agreement with experiment. Measurements of the chain length dependence of the end-to-end distance indicate that the chains are not collapsed at the critical point.Comment: 13 Pages Revtex, 9 epsf embedded figs. gzipped tar file. To appear in J. Chem. Phy

The Lennard-Jones-Devonshire cell model revisited

We reanalyse the cell theory of Lennard-Jones and Devonshire and find that in addition to the critical point originally reported for the 12-6 potential (and widely quoted in standard textbooks), the model exhibits a further critical point. We show that the latter is actually a more appropriate candidate for liquid-gas criticality than the original critical point.Comment: 5 pages, 3 figures, submitted to Mol. Phy

Phase behaviour of a symmetrical binary fluid mixture

We have investigated the phase behaviour of a symmetrical binary fluid mixture for the situation where the chemical potentials $\mu_1$ and $\mu_2$ of the two species differ. Attention is focused on the set of interparticle interaction strengths for which, when $\mu_1=\mu_2$, the phase diagram exhibits both a liquid-vapor critical point and a tricritical point. The corresponding phase behaviour for the case $\mu_1\ne\mu_2$ is investigated via integral-equation theory calculations within the mean spherical approximation (MSA), and grand canonical Monte Carlo (GCMC) simulations. We find that two possible subtypes of phase behaviour can occur, these being distinguished by the relationship between the critical lines in the full phase diagram in the space of temperature, density, and concentration. We present the detailed form of the phase diagram for both subtypes and compare with the results from GCMC simulations, finding good overall agreement. The scenario via which one subtype evolves into the other, is also studied, revealing interesting features.Comment: 22 pages, 13 figure

Augmented Reality in Maintenance: An information-centred design framework

Augmented Reality (AR) visualization capabilities can impact on maintenance. From enhancing performance to retrieving feedback, AR can close the information loop between maintenance information systems and the operations supported. Though, the design of AR applications is not aligned with current information systems, which prevents maintenance information to be used and improved properly. In this paper, industrial collaboration contributed to determine a framework for AR integration in maintenance systems. The framework describes information types, formats and interactions modes for AR to enhance efficiency improvements in maintenance of complex equipment. Semi-structured interviews and surveys with maintainers were conducted to determine the maintenance challenges and also to validate the framework proposed. Therefore, exposing future research in topics such as multimodal interaction, information contextualization and performance analysis to achieve the complete integration of AR in maintenance

Wetting of a symmetrical binary fluid mixture on a wall

We study the wetting behaviour of a symmetrical binary fluid below the demixing temperature at a non-selective attractive wall. Although it demixes in the bulk, a sufficiently thin liquid film remains mixed. On approaching liquid/vapour coexistence, however, the thickness of the liquid film increases and it may demix and then wet the substrate. We show that the wetting properties are determined by an interplay of the two length scales related to the density and the composition fluctuations. The problem is analysed within the framework of a generic two component Ginzburg-Landau functional (appropriate for systems with short-ranged interactions). This functional is minimized both numerically and analytically within a piecewise parabolic potential approximation. A number of novel surface transitions are found, including first order demixing and prewetting, continuous demixing, a tricritical point connecting the two regimes, or a critical end point beyond which the prewetting line separates a strongly and a weakly demixed film. Our results are supported by detailed Monte Carlo simulations of a symmetrical binary Lennard-Jones fluid at an attractive wall.Comment: submitted to Phys. Rev.

Rural homelessness : prevention practices in Wales

Homelessness is largely understood as an urban issue and so rural homelessness is to a large extent invisible in both academic literature and in policy and practice discussions, just as it is often invisible in discourses of everyday rural life. This article draws on extensive interviews with homeless service users and providers in three rural authorities in Wales to give a clearer sense of the nature and challenges of rural homelessness. The article documents and explores the very different strategies employed by those facing homelessness in the rural context, as well as those of rural local authorities providing them preventative and person-centred support. Analysis of the struggle of many rural households to remain in place, often at the cost of homelessness and lowered ability to access services, will have resonance in a range of contexts and have implications for policy makers and practitioners in rural contexts beyond Wales

Policy transfer and part 2 of the Housing Act (Wales) 2014

Part 2 of the Housing Act (Wales) 2014and its implementation has been keenly observed by governments outside of Wales, as they continue to search for policy solutions to help address the homelessness crisis.This paper examines the extent to whichthere has been policy transfer from Wales to other national contexts and thepotential for such transfer to occur in the future.It is identified that some transfer has already taken place within the UK and there is thepotentialforfuture policy transferboth within the UK and internationally. Adaptation to each of the new contexts is necessary to underpin successful transferof provisions of the Act, however, outside of the UK this will need to be more extensive and includethe introduction of a right tohousing

Self-trapping at the liquid vapor critical point

Experiments suggest that localization via self-trapping plays a central role in the behavior of equilibrated low mass particles in both liquids and in supercritical fluids. In the latter case, the behavior is dominated by the liquid-vapor critical point which is difficult to probe, both experimentally and theoretically. Here, for the first time, we present the results of path-integral computations of the characteristics of a self-trapped particle at the critical point of a Lennard-Jones fluid for a positive particle-atom scattering length. We investigate the influence of the range of the particle-atom interaction on trapping properties, and the pick-off decay rate for the case where the particle is ortho-positronium.Comment: 12 pages, 3 figures, revtex4 preprin

Evaluation of homelessness services to adults in the secure estate

This evaluation aimed to assess how changes to legislative duties towards those leaving custody since 2015 had been implemented by local authorities, prisons and probation providers; what impact the changes had on housing prison leavers; and to identify areas of good practice in meeting the housing needs of prison leavers. Chapter 1 provide some understanding the policy context for the development and implementation of the National Pathway for Homelessness Services to Adults in the Secure Estate. Chapter 2 briefly covers the existing delivery arrangements for the pathway. A background paper accompanies this report and provides more in depth exploration of both these issues. Chapter 3 describes the methodology adopted to undertake the evaluation. In turn thereafter, chapters 4, 5 and 6 respectively present the findings in relation to the operation of the National Pathway at the reception, prerelease and community stages of a prisoner’s journey into and out of custody. In Chapter 7, better practices in relation to implementing the National Pathway are discussed. Finally in chapter 8 the evaluation findings are summarised and recommendations for improving practices are identified