Molecular mobility in polymer thin films

Fluorescence recovery after photobleaching was used to measure in-plane dye-probe diffusion coefficients, D, in thin films of monodisperse polystyrene supported on fused quartz substrates. The substrates were prepared with a high density of surface hydroxyl groups which interact favorably with repeat units of the polymer. The effects of temperature and film thickness were investigated, at temperatures above the bulk glass transition of the polymer, T_g, and in the range of film thicknesses from 1-10² times the radius of gyration (R_g) of individual polymer molecules. As the film thickness decreases towards R_g the value of D increases above the bulk values, with significant effects first appearing in films ≃20R_g. In the thinnest films studied, about 4R_g, the values of D lie as much as two orders over bulk values. At the same time, the temperature dependence of D becomes much weaker than in bulk. Analysis by free volume theory indicates that apparent values of both T_g and the thermal expansion coefficient for liquid state, α_L, decrease as the film thickness decreases. The possible effects of surface segregation of the dye probe are discussed

Molecular mobility in polymer thin films

Fluorescence recovery after photobleaching was used to measure in-plane dye-probe diffusion coefficients, D, in thin films of monodisperse polystyrene supported on fused quartz substrates. The substrates were prepared with a high density of surface hydroxyl groups which interact favorably with repeat units of the polymer. The effects of temperature and film thickness were investigated, at temperatures above the bulk glass transition of the polymer, T_g, and in the range of film thicknesses from 1-10² times the radius of gyration (R_g) of individual polymer molecules. As the film thickness decreases towards R_g the value of D increases above the bulk values, with significant effects first appearing in films ≃20R_g. In the thinnest films studied, about 4R_g, the values of D lie as much as two orders over bulk values. At the same time, the temperature dependence of D becomes much weaker than in bulk. Analysis by free volume theory indicates that apparent values of both T_g and the thermal expansion coefficient for liquid state, α_L, decrease as the film thickness decreases. The possible effects of surface segregation of the dye probe are discussed

Anomalous diffusion in polymers: long-time behaviour

We study the Dirichlet boundary value problem for viscoelastic diffusion in polymers. We show that its weak solutions generate a dissipative semiflow. We construct the minimal trajectory attractor and the global attractor for this problem.Comment: 13 page

Profiling strugglers in a graduate-entry medicine course at Nottingham: a retrospective case study

Background 10-15% of students struggle at some point in their medicine course. Risk factors include weaker academic qualifications, male gender, mental illness, UK ethnic minority status, and poor study skills. Recent research on an undergraduate medicine course provided a toolkit to aid early identification of students likely to struggle, who can be targeted by established support and study interventions. The present study sought to extend this work by investigating the number and characteristics of strugglers on a graduate-entry medicine (GEM) programme. Methods A retrospective study of four GEM entry cohorts (2003–6) was carried out. All students who had demonstrated unsatisfactory progress or left prematurely were included. Any information about academic, administrative, personal, or social difficulties, were extracted from their course progress files into a customised database and examined. Results 362 students were admitted to the course, and 53 (14.6%) were identified for the study, of whom 15 (4.1%) did not complete the course. Students in the study group differed from the others in having a higher proportion of 2ii first degrees, and scoring less well on GAMSAT, an aptitude test used for admission. Within the study group, it proved possible to categorise students into the same groups previously reported (struggler throughout, pre-clinical struggler, clinical struggler, health-related struggler, borderline struggler) and to identify the majority using a number of flags for early difficulties. These flags included: missed attendance, unsatisfactory attitude or behaviour, health problems, social/family problems, failure to complete immunity status checks, and attendance at academic progress committee. Conclusions Problems encountered in a graduate-entry medicine course were comparable to those reported in a corresponding undergraduate programme. A toolkit of academic and non-academic flags of difficulty can be used for early identification of many who will struggle, and could be used to target appropriate support and interventions

The Lingering Environmental Impact of Repressive Governance: The Environmental Legacy of the Apartheid Era for the New South Africa

This article aims to explore the historical link between contemporary environmental problems and the environmental, economic and political policies of the apartheid government. The analysis draws on an examination of the detrimental environmental impacts of the apartheid era and how international isolation impacted on governmental environmental management in the country, before turning attention to the way in which the ANC government has managed the South African natural and human environments in the period after 1994. The article shows that despite many important new developments since 1994, that there are high levels of continuity between the environmental management practices of the old and the new regimes. This state of affairs negatively impacts on the ability of the ANC government to provide every South African citizen with the clean and safe environment guaranteed to all within the 1996 Bill of Rights.This article also appeared unchanged as a chapter in the following edited collection: Jan Oosthoek and Barry K. Gills (eds), _The Globalization of Environmental Crisis_ (Abingdon: Routledge, 2008), pp. 109-120

Barriers to the uptake and use of feedback in the context of summative assessment

Despite calls for feedback to be incorporated in all assessments, a dichotomy exists between formative and summative assessments. When feedback is provided in a summative context, it is not always used effectively by learners. In this study we explored the reasons for this. We conducted individual interviews with 17 students who had recently received web based feedback following a summative assessment. Constant comparative analysis was conducted for recurring themes. The summative assessment culture, with a focus on avoiding failure, was a dominant and negative influence on the use of feedback. Strong emotions were prevalent throughout the period of assessment and feedback, which reinforced the focus on the need to pass, rather than excel. These affective factors were heightened by interactions with others. The influence of prior learning experiences affected expectations about achievement and the need to use feedback. The summative assessment and subsequent feedback appeared disconnected from future clinical workplace learning. Socio-cultural influences and barriers to feedback need to be understood before attempting to provide feedback after all assessments. A move away from the summative assessment culture may be needed in order to maximise the learning potential of assessments

Identifying context factors explaining physician's low performance in communication assessment: an explorative study in general practice

Contains fulltext : 97982.pdf (postprint version ) (Open Access)ABSTRACT: BACKGROUND: Communication is a key competence for health care professionals. Analysis of registrar and GP communication performance in daily practice, however, suggests a suboptimal application of communication skills. The influence of context factors could reveal why communication performance levels, on average, do not appear adequate. The context of daily practice may require different skills or specific ways of handling these skills, whereas communication skills are mostly treated as generic. So far no empirical analysis of the context has been made. Our aim was to identify context factors that could be related to GP communication. METHODS: A purposive sample of real-life videotaped GP consultations was analyzed (N = 17). As a frame of reference we chose the MAAS-Global, a widely used assessment instrument for medical communication. By inductive reasoning, we analyzed the GP behaviour in the consultation leading to poor item scores on the MAAS-Global. In these cases we looked for the presence of an intervening context factor, and how this might explain the actual GP communication behaviour. RESULTS: We reached saturation after having viewed 17 consultations. We identified 19 context factors that could potentially explain the deviation from generic recommendations on communication skills. These context factors can be categorized into doctor-related, patient-related, and consultation-related factors. CONCLUSIONS: Several context factors seem to influence doctor-patient communication, requiring the GP to apply communication skills differently from recommendations on communication. From this study we conclude that there is a need to explicitly account for context factors in the assessment of GP (and GP registrar) communication performance. The next step is to validate our findings

In-training assessment using direct observation of single-patient encounters: a literature review

We reviewed the literature on instruments for work-based assessment in single clinical encounters, such as the mini-clinical evaluation exercise (mini-CEX), and examined differences between these instruments in characteristics and feasibility, reliability, validity and educational effect. A PubMed search of the literature published before 8 January 2009 yielded 39 articles dealing with 18 different assessment instruments. One researcher extracted data on the characteristics of the instruments and two researchers extracted data on feasibility, reliability, validity and educational effect. Instruments are predominantly formative. Feasibility is generally deemed good and assessor training occurs sparsely but is considered crucial for successful implementation. Acceptable reliability can be achieved with 10 encounters. The validity of many instruments is not investigated, but the validity of the mini-CEX and the ‘clinical evaluation exercise’ is supported by strong and significant correlations with other valid assessment instruments. The evidence from the few studies on educational effects is not very convincing. The reports on clinical assessment instruments for single work-based encounters are generally positive, but supporting evidence is sparse. Feasibility of instruments seems to be good and reliability requires a minimum of 10 encounters, but no clear conclusions emerge on other aspects. Studies on assessor and learner training and studies examining effects beyond ‘happiness data’ are badly needed