Browsing by Author "Rogers, Prof K."

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    Estimating and visualising imprecision in radiological emergency response assessments
    (2011-09-09) Haywood, S. M.; Healy, M. J. F.; Rogers, Prof K.
    After an accidental release of radioactivity to atmosphere, modelling assessments are needed to predict what the contamination levels are likely to be and what measures need to be taken to protect human health. These predictions will be imprecise due to lack of knowledge about the nature of the release and the weather, and also due to measurement inaccuracy. This thesis describes work to investigate this imprecision and to find better ways of including it in assessments and representing it in results. It starts by reviewing exposure pathways and the basic dose calculations in an emergency response assessment. The possible variability of key parameters in emergency dose calculations is considered, and ranges are developed for each. The imprecision typically associated with calculational endpoints is explored through a sensitivity study. This has been done using both a simple Gaussian atmospheric dispersion model and also real-time weather data in combination with a complex atmospheric dispersion model. The key parameters influencing assessment imprecision are identified. These are demonstrated to be factors relating to the release, arising from inevitable lack of knowledge in the early stages of an accident, and factors relating to meteorology and dispersion. An alternative improved approach to emergency response assessments is then outlined, which retains a simple and transparent assessment capability but which also indicates the imprecision associated with the results through incomplete knowledge. This tool uses input from real-time atmospheric dispersion and weather prediction tools. A prototype version of the tool has been created and this has been used to produce example results. The final stage of the thesis describes the use of the new tool to develop ways in which imprecise or uncertain information can be presented to decision makers. Alternative presentational techniques are demonstrated using example results.
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    Human vs non-human bone: identification and differentiation of fragmented skeletal remains using non-destructive methods
    (Cranfield University, 2018) Corrieri, B.; Marquez-Grant, Nicholas; Rogers, Prof K.
    Fragmented human and non-human bones can be found in forensic contexts, such as mass disasters, mass graves, and crime scenes, as well as in archaeological deposits. When fragmented skeletal remains are found, one of the first questions asked is whether or not the fragments are human or non- human. If none of the diagnostic features is visible, the origin of the fragments may be difficult to assess. Most of the methods currently employed to identify the origin of bone fragments, such as microscopic and biomolecular methods, are invasive and time consuming. The aim of the research presented in this thesis was to explore the potential of non-destructive procedures, such as GIS (Geographic Information System) software, morphological examination and Micro-Computed Tomography, in determining whether or not a bone fragment is human. These techniques were applied on skeletal features not commonly used for the human-nonhuman bone differentiation. Cranial suture patterns, cranial curvature and rib shaft curvature were assessed and measured using a GIS software. In addition, the morphology of the occipital condyles and the linea aspera of the femur were investigated and compared between human and non-human species. Finally, primary nutrient foramina and cross-sectional shape of long bones were analysed using micro-CT. More than 700 human and non-human bones were used; the non-human species selected are the ones whose remains are likely to be found in forensic or archaeological contexts in the United Kingdom. Most of the bone features considered and the procedures used in this study proved to be reliable for the differentiation between human and non-human fragmented bones. Blind tests performed on fragments whose human or non-human origin was not known further demonstrated the applicability and effectiveness of the methods and features explored in this study. The results of this research provide a valuable contribution to the fields of forensic anthropology, bioarchaeology, and comparative anatomy.
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    Inter-species variation in bone mineral
    (2011-02-15) Beckett, Sophie; Rogers, Prof K.
    Bone is a complex heterogeneous composite material with organic and inorganic components. The inorganic component; bone mineral, is a poorly crystalline, non-stoichiometric form of calcium hydroxylapatite. A model for the general structure and composition of bone mineral has been established within the literature. However, the nature and extent of variation in bone mineral composition and structure has, to date, been poorly understood. This situation also applies to the general response of bone mineral to heat treatment and variation in this response. This thesis presents the results of an investigation of inter-species variation in bone mineral characteristics of unheated bone and bone heated to temperatures of 600 °C and 1400 °C. Twelve different animal species were investigated, including human bone. X-ray diffraction analysis was the primary analytical technique employed. The Rietveld method of full profile fitting of diffraction data was used to quantitatively investigate characteristics of unheated and heated bone such as the weight percentages of the thermal decomposition products of bone mineral. Infrared spectroscopy, inductively coupled plasma – atomic emission spectrometry, pyrohydrolysis – ion chromatography and combustion – gas chromatography were also employed to obtain further data regarding the chemical composition of bone. Biological ii control of bone mineral composition and structure and the chemical basis for the variation observed within the results were explored. Significant inter-species variation in bone mineral composition and structure and also, the response of bone to heat treatment have been demonstrated by the results of this thesis. In particular, human bone is significantly different from bone of all other species investigated.
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    Physiochemical modifications to bone mineral
    (2016-10-05) Greenwood, Charlene; Rogers, Prof K.; Beckett, Sophie
    Bone is a complex composite material consisting of three main components: a mineral phase structurally similar to calcium hydroxyapatite (HAp), an organic matrix containing collagenous and non-collagenous proteins and, water. The complexity of bone has led to an abundance of literature across a wide range of disciplines, which have endeavoured to provide a greater understanding of this material. In particular, heated bone studies are prevalent in biomedicine where heat treatment is often used to sterilise bone material required for xeno– and allo- grafts, in forensic science where species differentiation of unknown heated bone specimens would prove invaluable and in archaeology, where heated bone material often provides information about the cooking and funeral practices of our ancestors. Unfortunately, many of these studies are largely observational and some of the processes and mechanisms associated with heated bone are largely assumed and in some instances ambiguous. Over 1000 biological and synthetic HAp specimens were utilised during this research to investigate the fundamental processes and mechanisms associated with unheated and heated bone. In particular, three controversial areas of bone research were considered: - in vivo HAp crystal size control, the relationship between the organic and mineral components of bone during heat treatment and the confounding effects of cooling on bone mineral during heat treatment. This was achieved by considering the chemical composition of unheated biological and synthetic HAp specimens, and heated bone specimens from various species including human. The results of this thesis demonstrate that an intrinsic rather than extrinsic source may be responsible for in vivo biological HAp crystal size control, a concept which has not previously be considered. The results have also shown bone mineral crystallisation during heat treatment is promoted by the organic matrix and, cooling has an impact on both crystallisation and thermal decomposition of HAp during heat treatment. This research has also questioned the use of current X-ray diffraction (XRD) refinement techniques with nanocrystalline materials such as bone, to determine crystalline size and strain. Further interpretation of the results questioned whether heated bone data is comparable between research groups, whether it was possible to create a time and temperature predictive model for heated bone and whether human bone is statistically different from other bone types when dynamically heated. Due to the fundamental nature of this research, it is expected the results will have an impact across a wide range of disciplines including biomedicine, forensic science and archaeology.
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    The production and characterisation of inorganic combinatorial libraries
    (Cranfield University, 2010-10) Karimi, O.; Rogers, Prof K.
    With the increasing demand for research into new materials, techniques which are able to produce and characterise a large number of samples rapidly are becoming indispensable. Thin film technology has the potential to improve the amount of information contained on deposited samples by creating compositionally graded libraries. Conventionally, raster scan methods are used to interrogate such libraries. The production of combinatorial samples by methods not previously employed in this role has been carried out. Both solution based electrochemical deposition and electrostatic spray vaporisation production methods have been successfully modified to produce thin film continuous compositional spread (CCS) samples. Additional samples have been produced by off-axis direct current magnetron sputtering, a method already established in the combinatorial field. Presented here is a different approach to provide high-throughput data collection and analysis of combinatorial libraries using an X-ray diffraction (XRD) probe. An extended X-ray beam was used to illuminate the polycrystalline libraries and a large area detector used to collect the data. A new partitioning algorithm has been employed to analyze the collected data and extract the crystallographic information from the illuminated area. The results of the technique have been compared with the raster scans showing that the algorithm provides reliable data equivalent to multiple point data collections with significantly increased data acquisition speed. With the new chemical libraries and other simplified samples the partitioning method has been shown to be appropriate for the analysis of both distinct composition high density chemical libraries and also CCS samples. To achieve the validation of the new method the new libraries have been illumination with the extended beam X-ray source. The resultant superimposed diffraction patterns are partitioned with the novel software and compared with conventional XRD. The resolution of the partitioning method has been shown to be in the 1 mm range when applied to CCS libraries and 1.5 mm for high density chemical libraries. For randomly orientated polycrystalline samples the d-spacing change between the partitioned data and the corresponding raster scanned data is not statistically significant. This corresponds to d-spacing determination with a precession of < 0.01 Å when used with the Bruker D8 diffractometer and our geometry.
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    Structural characterisation and in vitro behaviour of apatite coatings and powders.
    (2009-11-17T17:35:51Z) Etok , S. E.; Rogers, Prof K.; Woodman, Prof A.
    Hydroxyapatite (HAP) coatings are used in orthopaedic surgery for bone regeneration. Current methods of phase quantification of HAP coatings suffer from drawbacks. A novel methodology of quantitative phase analysis of HAP coatings has been devised and validated. This method, based on whole pattern fitting with a fundamental parameters approach, incorporates amorphous calcium phosphate (ACP) and apatite phases into structural refinements. A comparison of the structural and chemical properties of plasma sprayed (PS) and novel electrodeposited (ED) HAP coatings has been conducted. ED coatings contained less ACP and more preferred orientation than the PS coatings, although the stoichiometry was similar. In vitro investigations of PS and ED coatings in simulated body fluid and foetal calf serum revealed that both are bioactive. A carbonated apatite layer produced on the ED coatings was -0.7μm thick with a stoichiometry and chemical constituents similar to that of natural bone apatite. PS coatings produced a nanocrystalline carbonated apatite layer (-4μm). For the first time it has been possible to model crystalline HAP and nanocrystalline apatite as independent phases and obtain accurate lattice parameters for each. A positive linear correlation has been made between microstrain and the solubility of HAP and carbonated apatites. Dissolution studies have shown that the behaviour of HAP and carbonated apatite is dominated by crystallite size at low undersaturation and by crystallite size and microstrain at high undersaturation for crystallites between -30OA- 1000A. Metastable equilibrium occurred for crystallites <_400A at low undersaturation. Carbonate content did not affect the solubility or dissolution behaviour. A novel technology for coating polymeric tape with HAP for potential use in anterior cruciate ligament reconstruction has been devised. Mechanical tests have demonstrated that no adverse properties are induced by the coating technology. Cell culture studies have shown that the HAP layer is capable of enhanced attachment, proliferation and differentiation of osteoblast cells compared to uncoated tape.