Application of Polychlorinated Biphenyl Signatures for Environmental Fingerprinting

Chapter 2 has been produced based on the original research of Megson et al., (2013b), which was published in Science of the Total Environment (DOI: http://dx.doi.org/10.1016/j.scitotenv.2013.04.082) (presented as Appendix A). Chapter 3 is based in part on the original research of Megson et al., (2013a), which was published in the Journal of Chromatography A (DOI: http://dx.doi.org/10.1016/j.chroma.2013.10.016) (presented as Appendix B). Chapter 5 has been produced based in part on the original research of Megson et al. (2014), which was published in Chemosphere (DOI: http://dx.doi.org/10.1016/j.chemosphere.2014.04.061) (presented as Appendix D).Polychlorinated Biphenyls (PCBs) are a group of 209 ‘man-made’ chlorinated organic compounds that were widely used in the 20th century for a variety of industrial uses. PCBs were first commercially produced in the 1929 and were manufactured until the 1980s when their use was phased out due to environmental and human health risks. However, due to their widespread use and persistence they are ubiquitous in the environment and remain a contaminant of concern. The structural properties that determine the persistence of PCBs in humans were therefore elucidated by statistical analysis of data from the National Health and Nutrition Examination Survey (NHANES). PCBs with chlorine bonding in the 2,5-and 2,3,6- positions (and 2- in di- and tri-chlorinated congeners) were rapidly biotransformed and so can be classed as episodic congeners whereas PCBs with chlorine bonding in the 2,3,4-, 2,4,5-, 3,4,5-, and 2,3,4,5- positions were more resistant to biotransformation and can therefore be classed as steady state congeners. A fundamental requirement of using PCB signatures for environmental fingerprinting is an effective analytical method capable of producing high resolution signatures from biological samples. An extraction and clean-up method was developed that was successfully applied to different biological matrices (blood and tissues). A two dimensional gas chromatography with time of flight mass spectrometry (GCxGC-ToFMS) method was designed and optimised to provide a congener specific method capable of identifying 200 out of the 209 PCBs, with detection limits in human serum in the range of 1 to 10 ng g-1 lipid. The extraction and detection methods were used to determine the source of PCB contamination and age date exposure in workers at a transformer dismantling plant. A total of 84 different PCB congeners were identified in the sera of 30 workers with concentrations of the 7 indicator PCBs ranging from 1.2 - 39 μg g-1 lipid. Analysis of PCB signatures was able to distinguish recent from prolonged exposure and also identified an additional source of inhalation exposure in a subgroup of workers. Analysis of 12 different tissue types obtained from the common guillemot (Uria aalge) suggested a high degree of perpetuation between the PCB signature in different tissue types. This shows that comparative assessments can be undertaken between animals using different tissue types and that small (1 g) samples of blood can be used as a non-lethal sampling technique. The regional provenance of 25 wrecked Leach’s storm petrels (Oceanodroma leucorhoa) was also determined using PCB signatures. Results from GCxGC-ToFMS analysis revealed distinctively different PCB signatures in birds from Canada and Europe. The findings reported in this thesis enhance our understanding of PCB signatures in the environment and show how they can be used effectively to age date and identify the source of exposure in humans and animals

Screening for Intellectual Disability in Children: A Review of the Literature

BACKGROUND: Early identification of possible intellectual disability can help children and families access appropriate services and support more quickly. There has been an increasing interest in the use of screening tools for this purpose. This study reviews the literature in relation to such tools. METHODS: A literature search was carried out for English language articles from 1990 to 2009 using a range of databases. Secondary searches were carried out from references of relevant articles. RESULTS: Only one article was identified which examined the ability of an assessment to specifically identify children with a potential intellectual disability; however, no information was provided about sensitivity, specificity or cut-off points. CONCLUSIONS: There is not, as yet, a screening tool that can reliably identify children with a probable intellectual disability. Further research in this area is needed

Rapid preconditioning of data for accelerating convex hull algorithms

Given a dataset of two-dimensional points in the plane with integer coordinates, the method proposed reduces a set of n points down to a set of s points s ≤ n, such that the convex hull on the set of s points is the same as the convex hull of the original set of n points. The method is O(n). It helps any convex hull algorithm run faster. The empirical analysis of a practical case shows a percentage reduction in points of over 98%, that is reflected as a faster computation with a speedup factor of at least 4

Population change & breeding biology of the Arctic Tern (Sterna paradisaea) in Shetland 1986

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The synthesis and characterisation of water soluble polymers and biomimetic applications.

The first steps towards the long term objective of building entirely synthetic organic/inorganic composite materials in a biomimetic manner have been achieved. Following an introduction and discussion of the background to the work (Chapter 1), the syntheses and characterisation of various molecular weights of both poly(exo, exo-1,4-cyclopentenylene-5,6-ethylidene-2,3-sodium dicarboxylate) and poly(exo,endo-l,4-cyclopentenylene-5,6-ethylidene-2,3- sodium dicarboxylate) and model compounds of their repeat units have been described (Chapters 2 and 4). These compounds were used as additives in the crystallisation of CaCO(_3) from supersaturated aqueous solutions of Ca(HC0(_3))(_2) (Chapters 3 and 5). The work described in Chapter 3 showed that the diacid model compounds used as additives controlled the morphology of calcite crystals grown from supersaturated solutions of Ca(HCO(_3))(_2) over a large range of concentrations of model compound; [Ca(^2+)]: [model compound] 10 to 1000:1. The polymers of these monomers appeared to give the same type of crystal morphology as the isolated model repeat units, however, modification was observed on only one face of the CaCO(_3) crystals. This observation, and the relatively small crystal size distributions measured, indicated that the calcite crystallisation was nucleated beneath the polymer films at the truncated modified face and growth continued down into the solution