Estimating local chlamydia incidence and prevalence using surveillance data

Background: Understanding patterns of chlamydia prevalence is important for addressing inequalities and planning cost-effective control programs. Population-based surveys are costly; the best data for England come from the Natsal national surveys which are only available once per decade, and are nationally representative but not powered to compare prevalence in different localities. Prevalence estimates at finer spatial and temporal scales are required. Methods: We present a method for estimating local prevalence by modeling the infection, testing and treatment processes. Prior probability distributions for parameters describing natural history and treatment-seeking behavior are informed by the literature or calibrated using national prevalence estimates. By combining them with surveillance data on numbers of chlamydia tests and diagnoses, we obtain estimates of local screening rates, incidence and prevalence. We illustrate the method by application to data from England. Results: Our estimates of national prevalence by age group agree with the Natsal-3 survey. They could be improved by additional information on the number of diagnosed cases that were asymptomatic. There is substantial local-level variation in prevalence, with more infection in deprived areas. Incidence in each sex is strongly correlated with prevalence in the other. Importantly, we find that positivity (the proportion of tests which were positive) does not provide a reliable proxy for prevalence. Conclusion: This approach provides local chlamydia prevalence estimates from surveillance data, which could inform analyses to identify and understand local prevalence patterns and assess local programs. Estimates could be more accurate if surveillance systems recorded additional information, including on symptoms

The impacts of new A8 migration in Leeds

New arrivals from Eastern Europe have made regular headlines in the popular press in recent times, not only for the unprecedented magnitude of the flows involved, but also for their impacts – positive and negative – on regions and localities up and down the country. This paper reports on a recently completed research project aimed at finding out more about A8 migrants in Leeds

‘Good relations’ among neighbours and workmates? The everyday encounters of Accession 8 migrants and established communities in urban England

Drawing on data generated in a recently completed qualitative study in a northern, English city, this paper explores the everyday social encounters of Accession 8 (A8) migrants who entered the UK following the expansion of the European Union in 2004. A number of options from permanent residence in another Member State on the one hand, to more fleeting circulatory and multiple short-term moves on the other, now exist for these new European citizens. The relatively short-term and temporary residence of some A8 migrants calls into question the focus of much UK government policy, which emphasises the need for migrants to integrate into diverse yet cohesive communities. Against this backdrop, the aim of this paper is two-fold. First, it considers the somewhat different character of A8 migration (encompassing a spectrum from permanency to temporariness) and what this means for routine experiences of mixing between new migrants and established host communities. Second, the paper explores such interactions in terms of ‘everyday encounters’ in both neighbourhood and work spaces and asks whether such spatio-temporal practices and experiences enhance or inhibit the building of ‘good relations’ in a multicultural city

The experiences of accession 8 migrants in England : motivations, work and agency

Drawing on a recently completed qualitative study in a northern English city, this paper explores motivations and experiences of Accession 8 (A8) migrants who have entered the United Kingdom following the expansion of the European Union in 2004. The paper considers commonalities and differences among the group of migrants routinely referred to as A8 migrant workers/labourers. Diversity is apparent in three particular respects: first, the motivations and forms of movement undertaken; second, their experiences of work within the UK paid labour market; and third, the extent to which the act and experience of migration offers new individual and collective opportunities and potentially opens up spaces for people to negotiate structural constraints and reconfigure aspects of their identity

Construction and analysis of causally dynamic hybrid bond graphs

Engineering systems are frequently abstracted to models with discontinuous behaviour (such as a switch or contact), and a hybrid model is one which contains continuous and discontinuous behaviours. Bond graphs are an established physical modelling method, but there are several methods for constructing switched or ‘hybrid’ bond graphs, developed for either qualitative ‘structural’ analysis or efficient numerical simulation of engineering systems. This article proposes a general hybrid bond graph suitable for both. The controlled junction is adopted as an intuitive way of modelling a discontinuity in the model structure. This element gives rise to ‘dynamic causality’ that is facilitated by a new bond graph notation. From this model, the junction structure and state equations are derived and compared to those obtained by existing methods. The proposed model includes all possible modes of operation and can be represented by a single set of equations. The controlled junctions manifest as Boolean variables in the matrices of coefficients. The method is more compact and intuitive than existing methods and dispenses with the need to derive various modes of operation from a given reference representation. Hence, a method has been developed, which can reach common usage and form a platform for further study

Influence of sediment redox conditions on uranium mobilisation during saline intrusion

This research was funded by the Natural Environment Research Council (grant NE/C506799/1: Studentship NE/H527116/1).In the UK, several coastal nuclear sites have been identified as vulnerable to future sea level rise. Legacy contamination at these sites has accumulated in sub-surface sediments at risk of future seawater inundation and intrusion. Porewater salinization, changes in pH and the influx of oxygen into sediments may impact the stability of sediment associated uranium (U). In this study, saturated column experiments were performed to compare the mobilisation of U from oxic and reduced sediments into seawater under environmentally relevant flow conditions. Uranium release profiles were independent of the initial geochemistry of the sediments. Uranium release from the sediments was kinetically controlled, showing relatively slow desorption kinetics, with release initially limited by the impact of the sediments on the pH of the seawater. Significant U release only occurred when the pH was sufficiently high for the formation of U-carbonate complexes (pHoxic 6.3; pHreduced 7.5). Uranium was more strongly bound to the reduced sediments and after 400 pore volumes of seawater flow, release was more extensive from the initially oxic (46%) compared with initially nitrate reducing (27%) and iron reducing (18%) sediments. The products of iron cycling appeared to act as a buffer limiting U mobilisation, but the on-going dissolution of the Fe-phases suggests that they did not form a permanent protective layer. © 2013 Elsevier B.V

A Kind of Affine Weighted Moment Invariants

A new kind of geometric invariants is proposed in this paper, which is called affine weighted moment invariant (AWMI). By combination of local affine differential invariants and a framework of global integral, they can more effectively extract features of images and help to increase the number of low-order invariants and to decrease the calculating cost. The experimental results show that AWMIs have good stability and distinguishability and achieve better results in image retrieval than traditional moment invariants. An extension to 3D is straightforward