A lattice-spring model for damage evolution in cement paste

AbstractTo understand better the fracture processes in cement-based materials, it is essential to predict the evolution of damage in cement paste. A recently proposed site-bond model is developed further to take into account the key microstructure data, such as pore size distribution, porosity, and size distribution and volume fraction of anhydrous cement grains obtained from high resolution X- ray tomography. The grains are associated with lattice sites linked by deformable bonds. The bonds are bundles of elastic-brittle springs, resisting normal and shear relative displacements between grains with potential for failure. The model length scale and thence spring constants are controlled by grain statistics. The spring failure properties are controlled by pore statistics. Macroscopic damage develops by a succession of local failures, represented by spring removal. The model is used to simulate the stress-strain response and damage in cement paste under uniaxial tensile loading. The influence of porosity on tensile strength and damage evolution is estimated in a quantitative manner. The predictions of the model are in a very good agreement with the available experimental data

Site-bond modelling of structure-failure relations in quasi-brittle media

AbstractThe non-linear behaviour of quasi-brittle media emerges from distributed micro-cracking. This is analysed conveniently by discrete lattice models. A 3D site-bond model is specialised here for materials with three-phase microstructures: stiff inclusions in a compliant matrix containing pores. The deformation behaviour is based on analytically derived relations between bond properties, length scale and macroscopic elastic constants. The microstructure-model mapping is based on size distributions and volume densities of inclusions and pores, typically obtained through analyses of 3D images. Inclusions data is used to calculate the required length scale. Pores data is used to define the failure behaviour of individual bonds. Applications of the methodology to cement-based materials and nuclear graphite are presented separately in this volume

Understanding the stigma of psychosis in ethnic minority groups: A qualitative exploration

Psychosis is a mental health difficulty which is widely stigmatized. The stigma of psychosis can lead to detrimental consequences and cause further distress. The aim of this study was to explore the experience of stigma and discrimination of psychosis from the perspective of service users from ethnic minority backgrounds. A total of 21 semistructured interviews were conducted with service users with psychosis from ethnic minority backgrounds examining their experiences of stigma from psychosis. Qualitative data were analyzed using thematic analysis. Five superordinate themes were identified, “social and cultural context of stigma,” “stigma is a family problem,” “stigma and discrimination within mental health services,” “intrapersonal impacts,” and “managing stigma within relationships.” Stigma is a significant concern for people with psychosis from an ethnic minority background. It is important that stigma and discrimination are appropriately assessed and considered within the care of people from ethnic minority backgrounds

Tate Form and Weak Coupling Limits in F-theory

We consider the weak coupling limit of F-theory in the presence of non-Abelian gauge groups implemented using the traditional ansatz coming from Tate's algorithm. We classify the types of singularities that could appear in the weak coupling limit and explain their resolution. In particular, the weak coupling limit of SU(n) gauge groups leads to an orientifold theory which suffers from conifold singulaties that do not admit a crepant resolution compatible with the orientifold involution. We present a simple resolution to this problem by introducing a new weak coupling regime that admits singularities compatible with both a crepant resolution and an orientifold symmetry. We also comment on possible applications of the new limit to model building. We finally discuss other unexpected phenomena as for example the existence of several non-equivalent directions to flow from strong to weak coupling leading to different gauge groups.Comment: 34 page

Metacognitive beliefs as psychological predictors of social functioning: An investigation with young people at risk of psychosis

Poor social functioning has been found to be present in those at risk for psychosis. This study aimed to examine metacognitive beliefs as potential predictors of structured activity (measure of social functioning) in those with an At Risk Mental State (ARMS). Regression and correlation analyses were conducted. The sample included 109 young people. Age was found to be positively correlated to structured activity. Metacognitive beliefs concerning uncontrollability and danger of worry were found to negatively predict structured activity. This was after controlling for age, gender, treatment allocation, cognitive schemas, positive symptom severity, social anxiety, and depression. Metacognitive danger items were most important. Age was the only control variable found to be an independent predictor of structured activity in the regression model, despite negative bi-variate relationships with structured activity found across three cognitive schema subscales and social anxiety. This is the first study to find that higher negative metacognitive beliefs about uncontrollability and danger predict lower social functioning in an ARMS sample, and that the perception of thoughts being dangerous was of particular importance. Psychological interventions should consider targeting this metacognitive dimension to increase social functioning. Future longitudinal research is required to strengthen findings in this area.The EDIE-2 trial was funded by the Medical Research Council (G0500264) and the Department of Health. Max Birchwood is part funded by the National Institute for Health Research through the Collaborations for Leadership in Applied Health Research and Care for West Midlands (CLAHRC-WM)

Tour guiding, organisational culture and learning: lessons from an entrepreneurial company

This paper examines the impacts of organisational culture on the learning and development of tour guides. Drawing on a case study of a small entrepreneurial tour company, the paper considers the nature of the organisation's culture, the tours it provides, including their narrative contents and the processes of organisational learning and socialisation. The paper suggests that the development of a learning culture within such an organisation may benefit from the provision of appropriate learning opportunities among the guides and facilitators who coordinate guide development