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Peridynamics and its implementation in finite element framework
Get PDFPredicting crack propagation and fracture is still a challenging research area. There are various methods for this, and the finite element method (FE method) is the most popular approach. The FE method is a powerful technology that can be used across multiple problems. However, because it is based on classical continuum mechanics (CCM), there are several disadvantages. Since the governing equation of CCM is a partial differential equation with a differential term for space, it is impossible to find the exact solution of the governing equation when spatial discontinuities exist which is caused by a crack.;As an alternative approach Peridynamics is a method introduced to overcome the drawbacks of CCM. The governing equation of Peridynamics is form of an integral equation without spatial differentiation. Therefore, it is possible to analyse structures with cracks in which discontinuity in space exists.;Peridynamics is a mesh-free method in which each node interacts with other nodes in its vicinity. Because of this, researchers often use language-based programs that can easily calculate numerical values of parameters of interest. This feature make it difficult to attempt to apply peridynamics to various simulation fields. However, if a model is made by FE software based on peridynamic theory, it is possible to expand the simulation fields by utilizing functions of FE software.;In this thesis, various analyses are performed by implementing peridynamics in FE software. From the most basic isotropic material to an orthotropic plate, the simulations of the crack propagation were carried out. In addition, a peridynamic structure based on beam and plate theory were also modelled, and this model was compared with the results of the referenced papers. Furthermore, the buckling and free vibration analyses are performed for several cases to consider the effect of each parameter of the crack geometries on characteristics and stiffness of the plate.Predicting crack propagation and fracture is still a challenging research area. There are various methods for this, and the finite element method (FE method) is the most popular approach. The FE method is a powerful technology that can be used across multiple problems. However, because it is based on classical continuum mechanics (CCM), there are several disadvantages. Since the governing equation of CCM is a partial differential equation with a differential term for space, it is impossible to find the exact solution of the governing equation when spatial discontinuities exist which is caused by a crack.;As an alternative approach Peridynamics is a method introduced to overcome the drawbacks of CCM. The governing equation of Peridynamics is form of an integral equation without spatial differentiation. Therefore, it is possible to analyse structures with cracks in which discontinuity in space exists.;Peridynamics is a mesh-free method in which each node interacts with other nodes in its vicinity. Because of this, researchers often use language-based programs that can easily calculate numerical values of parameters of interest. This feature make it difficult to attempt to apply peridynamics to various simulation fields. However, if a model is made by FE software based on peridynamic theory, it is possible to expand the simulation fields by utilizing functions of FE software.;In this thesis, various analyses are performed by implementing peridynamics in FE software. From the most basic isotropic material to an orthotropic plate, the simulations of the crack propagation were carried out. In addition, a peridynamic structure based on beam and plate theory were also modelled, and this model was compared with the results of the referenced papers. Furthermore, the buckling and free vibration analyses are performed for several cases to consider the effect of each parameter of the crack geometries on characteristics and stiffness of the plate
Corporate discipline and firm financial decisions : evidence from regulatory reforms
Get PDFThis PhD thesis, comprised of 3 essays, assesses the effect of corporate discipline on corporate decisions. To do so, I focus on regulatory reforms that are aimed to improve corporate discipline. In the first two empirical studies in this thesis, I employ a setup of corporate governance reform that improves corporate discipline through internal governance in the form of board reforms and internal control mechanisms in the emerging market context of India. In my third empirical study, I exploit the staggered initiation of M&A laws in 31 countries as a plausible source of exogenous variation in the market for corporate control which improves corporate discipline through external governance and analyse the impact on corporate risk-taking. To examine whether corporate governance reform (CGR) encourages or deters risk-taking, I examine three hypotheses related to corporate governance reform and firm risk-taking my first empirical chapter. Given the theoretical tension in the literature on the effect of CGR, my study aims to answer this question in the emerging market context of India. With a battery of robustness test, I show that risk-taking offirms in emerging market increases following CGR. This empirical chapter illustrates that corporate governance reform improves corporate discipline and discourages investment conservatism that could stem from private benefits. A version of this chapter has been previously published in the Journal of Corporate Finance. Using the same setup employed in the first empirical studies, I examine the potential substitutability of corporate governance and dividend payout in my second empirical study. Using different proxies of dividend payout, I show corporate governance reform substitutes dividend payment; however, only when the reform is accompanied by the expansion of personal penalties. Consistent with the theory of adequacy of punishment, the results underscore the merit of expansion of personal liability in regulatory reforms to stimulate deterring behaviour to credibly communicate the improvement in corporate governance regime. Finally, in my third empirical study, I employ staggered changes in M&A laws as a plausible source of variation in the market for corporate control and examine the effect of these changes on firm risk-taking. Robust to a battery of robustness test, my investigation reveals a positive causal relationship between the market for corporate control and value-enhancing risk-taking. Overall, in my thesis, I conclude that improved corporate discipline in the form of regulatory reforms positively stimulate risk-taking appetite and investment of firms and has a substitutive effect on the dividend payout.This PhD thesis, comprised of 3 essays, assesses the effect of corporate discipline on corporate decisions. To do so, I focus on regulatory reforms that are aimed to improve corporate discipline. In the first two empirical studies in this thesis, I employ a setup of corporate governance reform that improves corporate discipline through internal governance in the form of board reforms and internal control mechanisms in the emerging market context of India. In my third empirical study, I exploit the staggered initiation of M&A laws in 31 countries as a plausible source of exogenous variation in the market for corporate control which improves corporate discipline through external governance and analyse the impact on corporate risk-taking. To examine whether corporate governance reform (CGR) encourages or deters risk-taking, I examine three hypotheses related to corporate governance reform and firm risk-taking my first empirical chapter. Given the theoretical tension in the literature on the effect of CGR, my study aims to answer this question in the emerging market context of India. With a battery of robustness test, I show that risk-taking offirms in emerging market increases following CGR. This empirical chapter illustrates that corporate governance reform improves corporate discipline and discourages investment conservatism that could stem from private benefits. A version of this chapter has been previously published in the Journal of Corporate Finance. Using the same setup employed in the first empirical studies, I examine the potential substitutability of corporate governance and dividend payout in my second empirical study. Using different proxies of dividend payout, I show corporate governance reform substitutes dividend payment; however, only when the reform is accompanied by the expansion of personal penalties. Consistent with the theory of adequacy of punishment, the results underscore the merit of expansion of personal liability in regulatory reforms to stimulate deterring behaviour to credibly communicate the improvement in corporate governance regime. Finally, in my third empirical study, I employ staggered changes in M&A laws as a plausible source of variation in the market for corporate control and examine the effect of these changes on firm risk-taking. Robust to a battery of robustness test, my investigation reveals a positive causal relationship between the market for corporate control and value-enhancing risk-taking. Overall, in my thesis, I conclude that improved corporate discipline in the form of regulatory reforms positively stimulate risk-taking appetite and investment of firms and has a substitutive effect on the dividend payout
The application of implementation science to the design, test and scale up of high risk medicine care bundles
Get PDFWarfarin and non-steroidal anti-inflammatory drugs (NSAIDs) result in preventable adverse effects and hospital admissions. Internationally, the community pharmacy setting is evolving to offer more patient-facing services. Therefore, the aim of this thesis was to design warfarin and NSAIDs interventions - termed 'care bundles' - and to test their implementation within the Scottish community pharmacy setting. To design the care bundles (Stage 1), consensus methods were applied.;A six-item warfarin care bundle and a six-item NSAIDs care bundle were developed, with the NSAIDs care bundle stratified into two parts: a Communication Care Bundle and a Safer Care Bundle. The second stage of this thesis evaluated their pilot implementation within 24 community pharmacies. This involved a postal questionnaire; task-analysis techniques conducted during on-site visits; and telephone interviews with patients. Stage 2 identified that the determinants of implementation success differed between the care bundles.;On-site visits to pharmacies evidenced that both care bundles penetrated well within community pharmacy practice and integrated within the dispensing process. However, the care bundles were not always delivered as intended in practice. When patients were interviewed about the warfarin care bundle, none of the warfarin patients recalled receiving a care bundle and its necessity was queried. Conversely, the NSAID participants were satisfied with their experience of the NSAIDs care bundle and it mostly had a positive impact.;Overall, these findings indicated that scale up efforts should centre on the NSAIDs care bundle. Stage 3 of this thesis informed this through active dissemination of the results to key stakeholders, which shaped the national implementation strategy for the NSAIDs Communication Care Bundle in 2018. To achieve maximal improvements in the safer use of NSAIDs, national implementation of the NSAIDs Safer Care Bundle should also be realised. Future research should explore the attainment of intended outcomes of the NSAIDs care bundles.Warfarin and non-steroidal anti-inflammatory drugs (NSAIDs) result in preventable adverse effects and hospital admissions. Internationally, the community pharmacy setting is evolving to offer more patient-facing services. Therefore, the aim of this thesis was to design warfarin and NSAIDs interventions - termed 'care bundles' - and to test their implementation within the Scottish community pharmacy setting. To design the care bundles (Stage 1), consensus methods were applied.;A six-item warfarin care bundle and a six-item NSAIDs care bundle were developed, with the NSAIDs care bundle stratified into two parts: a Communication Care Bundle and a Safer Care Bundle. The second stage of this thesis evaluated their pilot implementation within 24 community pharmacies. This involved a postal questionnaire; task-analysis techniques conducted during on-site visits; and telephone interviews with patients. Stage 2 identified that the determinants of implementation success differed between the care bundles.;On-site visits to pharmacies evidenced that both care bundles penetrated well within community pharmacy practice and integrated within the dispensing process. However, the care bundles were not always delivered as intended in practice. When patients were interviewed about the warfarin care bundle, none of the warfarin patients recalled receiving a care bundle and its necessity was queried. Conversely, the NSAID participants were satisfied with their experience of the NSAIDs care bundle and it mostly had a positive impact.;Overall, these findings indicated that scale up efforts should centre on the NSAIDs care bundle. Stage 3 of this thesis informed this through active dissemination of the results to key stakeholders, which shaped the national implementation strategy for the NSAIDs Communication Care Bundle in 2018. To achieve maximal improvements in the safer use of NSAIDs, national implementation of the NSAIDs Safer Care Bundle should also be realised. Future research should explore the attainment of intended outcomes of the NSAIDs care bundles
Experimental and numerical investigation on wave-induced loads acting on intact and damaged naval combatant vessel
Get PDFIn this study, wave-induced loads acting on an intact and damaged naval combatant vessel are investigated experimentally and numerically. Experimental tests are carried out with a double-bottom naval combatant vessel DTMB 5415, which has been widely used in benchmark studies for experimental investigation and the validation of numerical simulations. Free decay tests in roll with and without moorings are implemented in calm water, while the model is moored at the bow and stern during the tests in regular waves.;In order to investigate the performance of the intact and damaged ship in beam waves the damaged opening is located at starboard midship so that floodwater may ingress and egress from the opening from which two compartments can be flooded.;It is shown that beam waves flooding in and out from the damaged opening and the interaction between ship behaviour and water surface effect in the damaged compartments have a significant impact on ship motions and wave-induced loads acting on the ship. And it can be observed that highly nonlinear wave-induced loads can be induced on the intact and damaged ship hull in regular beam waves.;Two cases under the regular beam wave condition are investigated by CFD-based RANS method. The method is proposed to calculate wave-induced loads acting on the intact and damaged ship model. For validation of the numerical method, comparison between numerical estimation and experimental measurement shows that solution by RANS method have a generally good qualitative agreement with physical tests.In this study, wave-induced loads acting on an intact and damaged naval combatant vessel are investigated experimentally and numerically. Experimental tests are carried out with a double-bottom naval combatant vessel DTMB 5415, which has been widely used in benchmark studies for experimental investigation and the validation of numerical simulations. Free decay tests in roll with and without moorings are implemented in calm water, while the model is moored at the bow and stern during the tests in regular waves.;In order to investigate the performance of the intact and damaged ship in beam waves the damaged opening is located at starboard midship so that floodwater may ingress and egress from the opening from which two compartments can be flooded.;It is shown that beam waves flooding in and out from the damaged opening and the interaction between ship behaviour and water surface effect in the damaged compartments have a significant impact on ship motions and wave-induced loads acting on the ship. And it can be observed that highly nonlinear wave-induced loads can be induced on the intact and damaged ship hull in regular beam waves.;Two cases under the regular beam wave condition are investigated by CFD-based RANS method. The method is proposed to calculate wave-induced loads acting on the intact and damaged ship model. For validation of the numerical method, comparison between numerical estimation and experimental measurement shows that solution by RANS method have a generally good qualitative agreement with physical tests
Photophysical approaches to sensing melanoma
Get PDFThe spectroscopic/structure relationship of melanin is poorly understood which impedes the development of new biomaterials and skin cancer sensing techniques. Current methods for detecting melanoma ether lack the diagnostic capabilities or require high expense and training to use. There is a need for a melanoma diagnostic device that is both simple to use and cost-effective. The intrinsic response of eumelanin and pheomelanin with spectrophotometry, spectrofluorometry and time-correlated single photon counting were measured in order to investigate the photophysics of melanin and find a potential new technique for diagnosing melanoma that could be developed into a point-of-care device.;The optical and radiosensitising properties of gold nanorods make them attractive for biosensing applications. The toxicity of different gold nanorods, with alternative coatings, were investigated in order to establish their viability for development of a melanoma-specific biosensor. The results from the clonogenic toxicity assay and flow cytometry suggest that the gold nanorods induces long term damaging effects to the cells which hinder their viability as a biosensor.;The spectroscopic response of the sheet sensing fluorescent probe thioflavin T was measured during the formation of pheomelanin as the evidence for sheet formation in the red/yellow pigment is not as well established as the brown/black pigment, eumelanin. The increase of the dye molecule's fluorescence intensity provides strong evidence for the presence of sheet structures within pheomelanin and open up the potential use of extrinsic fluorophores as melanoma sensing probes. Successful implementation of extrinsic fluorophores could lead to investigating melanin's structure via super-resolution techniques.The spectroscopic/structure relationship of melanin is poorly understood which impedes the development of new biomaterials and skin cancer sensing techniques. Current methods for detecting melanoma ether lack the diagnostic capabilities or require high expense and training to use. There is a need for a melanoma diagnostic device that is both simple to use and cost-effective. The intrinsic response of eumelanin and pheomelanin with spectrophotometry, spectrofluorometry and time-correlated single photon counting were measured in order to investigate the photophysics of melanin and find a potential new technique for diagnosing melanoma that could be developed into a point-of-care device.;The optical and radiosensitising properties of gold nanorods make them attractive for biosensing applications. The toxicity of different gold nanorods, with alternative coatings, were investigated in order to establish their viability for development of a melanoma-specific biosensor. The results from the clonogenic toxicity assay and flow cytometry suggest that the gold nanorods induces long term damaging effects to the cells which hinder their viability as a biosensor.;The spectroscopic response of the sheet sensing fluorescent probe thioflavin T was measured during the formation of pheomelanin as the evidence for sheet formation in the red/yellow pigment is not as well established as the brown/black pigment, eumelanin. The increase of the dye molecule's fluorescence intensity provides strong evidence for the presence of sheet structures within pheomelanin and open up the potential use of extrinsic fluorophores as melanoma sensing probes. Successful implementation of extrinsic fluorophores could lead to investigating melanin's structure via super-resolution techniques
Mathematical analysis of k-path Laplacian operators on simple graphs
Get PDFA set of links and nodes are the fundamental units or components used to represent complex networks. Over the last few decades, network studies have expanded and matured, increasingly making use of complex mathematical tools. Complex networks play a significant role in the propagation of processes, which include for example the case of epidemic spreading, the diffusion process, synchronisation or the consensus process. Such dynamic processes are critically important in achieving understanding of the behaviour of complex systems at different levels of complexity - examples might be the brain and modern man-made infrastructures. Although part of the study of the diffusion of information in the dynamic processes, it is generally supposed that interactions in networks originate only from a node, spreading to its nearest neighbours, there also exist long-range interactions (LRI), which can be transmitted from a node to others not directly connected. The focus of this study is on dynamic processes on networks where nodes interact with not only their nearest neighbours but also through certain LRIs. The generalised k-path Laplacian operators (LOs) Lk, which account for the hop of a diffusive particle to its non-nearest neighbours in a graph, control this diffusive process, describing hops of nodes vi at distance k; here the distance is measured as the length of the shortest path between two nodes. In this way the introduction of the k-path LOs can facilitate conducting more precise studies of network dynamics in different applications. This thesis aims to study a generalised diffusion equation employing the transformed generalised k-path LOs for a locally finite infinite graph. This generalised diffusion equation promotes both normal and super diffusive processes on infinite graphs. Furthermore, this thesis develops a new theoretical mathematical framework for describing superdiffusion processes that use a transform of the k-path LOs defined on infinite graphs. The choice of the transform appeared to be vitally important as the probability of a long jump should be great enough. As described by other researchers the fractional diffusion equation (FDE) formed the mathematical framework employed to describe this anomalous diffusion. In this regard,it is taken that the diffusive particle is not just hopping to its nearest node but also to any other node of the network with a probability that scales according to the distance between the two places. Initially, we extend the k-path LOs above to consider a connected and locally finite infinite network with a bounded degree and investigate a number of the properties of these operators, such as their self-adjointness and boundedness. Then, three different transformations of the k-path LOs, i.e. the Laplace, Factorial and Mellin transformations as well as their properties, are studied.In addition, in order to show a number of applications of these operators and the transformed ones, the transformed k-path LOs are used to obtain a generalised diffusion process for one-dimensional and two-dimensional infinite graphs.First, the infinite path graph is studied, where it is possible to prove that when the Laplacian- and factorial-transformed operators are used in the generalised diffusion equation, the diffusive processes observed are always normal, independent of the transform parameters. It is then proven analytically that when the k-path LOs are transformed via a Mellin transform and plugged into the diffusion equation, the result is a super diffusive process for certain values of the exponent in the transform. Secondly, we generalise the results on the superdiffusive behaviour generated by transforming k-path LOs from one-dimensional graphs to 2-dimensional ones. Our attention focuses on the Abstract Cauchy problem in an infinite square lattice. A generalised diffusion equation on a square lattice corresponding to Mellin transforms of the k-path Laplacian is investigated. Similar to the one-dimensional case also for the graph embedded in two-dimensional space,we could observe superdiffusive behaviour for the Mellin transformed k-path Laplacian. In comparison to the one-dimensional case, the conclusion reached is that the asymptotic behaviour of the solution of the Cauchy problem is much subtler.A set of links and nodes are the fundamental units or components used to represent complex networks. Over the last few decades, network studies have expanded and matured, increasingly making use of complex mathematical tools. Complex networks play a significant role in the propagation of processes, which include for example the case of epidemic spreading, the diffusion process, synchronisation or the consensus process. Such dynamic processes are critically important in achieving understanding of the behaviour of complex systems at different levels of complexity - examples might be the brain and modern man-made infrastructures. Although part of the study of the diffusion of information in the dynamic processes, it is generally supposed that interactions in networks originate only from a node, spreading to its nearest neighbours, there also exist long-range interactions (LRI), which can be transmitted from a node to others not directly connected. The focus of this study is on dynamic processes on networks where nodes interact with not only their nearest neighbours but also through certain LRIs. The generalised k-path Laplacian operators (LOs) Lk, which account for the hop of a diffusive particle to its non-nearest neighbours in a graph, control this diffusive process, describing hops of nodes vi at distance k; here the distance is measured as the length of the shortest path between two nodes. In this way the introduction of the k-path LOs can facilitate conducting more precise studies of network dynamics in different applications. This thesis aims to study a generalised diffusion equation employing the transformed generalised k-path LOs for a locally finite infinite graph. This generalised diffusion equation promotes both normal and super diffusive processes on infinite graphs. Furthermore, this thesis develops a new theoretical mathematical framework for describing superdiffusion processes that use a transform of the k-path LOs defined on infinite graphs. The choice of the transform appeared to be vitally important as the probability of a long jump should be great enough. As described by other researchers the fractional diffusion equation (FDE) formed the mathematical framework employed to describe this anomalous diffusion. In this regard,it is taken that the diffusive particle is not just hopping to its nearest node but also to any other node of the network with a probability that scales according to the distance between the two places. Initially, we extend the k-path LOs above to consider a connected and locally finite infinite network with a bounded degree and investigate a number of the properties of these operators, such as their self-adjointness and boundedness. Then, three different transformations of the k-path LOs, i.e. the Laplace, Factorial and Mellin transformations as well as their properties, are studied.In addition, in order to show a number of applications of these operators and the transformed ones, the transformed k-path LOs are used to obtain a generalised diffusion process for one-dimensional and two-dimensional infinite graphs.First, the infinite path graph is studied, where it is possible to prove that when the Laplacian- and factorial-transformed operators are used in the generalised diffusion equation, the diffusive processes observed are always normal, independent of the transform parameters. It is then proven analytically that when the k-path LOs are transformed via a Mellin transform and plugged into the diffusion equation, the result is a super diffusive process for certain values of the exponent in the transform. Secondly, we generalise the results on the superdiffusive behaviour generated by transforming k-path LOs from one-dimensional graphs to 2-dimensional ones. Our attention focuses on the Abstract Cauchy problem in an infinite square lattice. A generalised diffusion equation on a square lattice corresponding to Mellin transforms of the k-path Laplacian is investigated. Similar to the one-dimensional case also for the graph embedded in two-dimensional space,we could observe superdiffusive behaviour for the Mellin transformed k-path Laplacian. In comparison to the one-dimensional case, the conclusion reached is that the asymptotic behaviour of the solution of the Cauchy problem is much subtler
Bremsstrahlung radiation and fast electron transport in laser-plasma interactions
Get PDFThis thesis reports on experimental investigations using high-intensity (> 1018W/cm2) lasers pulses to ionise and accelerate electrons from thick solid targets in order to generate a bright bremsstrahlung source. Throughout the work the focus has been, firstly, to better understand the process behind the generation of x-rays within solid target interactions and, secondly, to apply this understanding to radiography of industrial samples. Across three experimental investigations aspects of the x-ray source are addressed; in the first the spatial evolution of the x-ray source is investigated; in the second a mechanism to increase converse from laser into electrons is considered; and in the third a simple method to increase the conversion from electrons to x-rays is explored.As part of the research presented within this thesis, a novel diagnostic was developed to overcome limitations in current diagnostics that measure the spatial characteristics of the emitted x-ray source. This diagnostic was a curved foil, designed to ensure that over a large field of view the x-ray experienced a uniform transmission length - reducing the inherent uncertainty in knife edge techniques. The foil was calibrated to ensure accurate measurements at x-ray energies > 100 keV and applied throughout the research herein to characterise the emitted profile. The first experimental chapter explores the spatial characteristics of the xray profile. Using the curved foil, a two source structure was measured consistently in solid target interactions that emerges due to the recirculation of electrons. A narrow central source, and a broad secondary source. By defocusing the laser (and reducing the intensity on target) the x-ray flux produced by the small central source dominates over the secondary source and produces a sharper radiograph.;The flux of this second source was investigated through an analytical model that treated the sheath as a threshold to drive recirculation of electrons through the target. This model found good agreement with the measured results, and can be applied to predict the optimum defocus for different target materials and thicknesses.The second chapter utilises a capillary target to trap the laser light and increase the conversion into electrons, the initial concept was to invoke numerous low intensity interactions as the laser propagated through the capillary.This would, in theory, produce a high flux - low temperature electron population that in turn would produce a high flux of x-rays. However, it was found that the flux increased but the temperature remained similar to that of a solid target. PIC simulations demonstrate that the electrons experience a series of accelerations within the capillary, undergoing direct-laser-acceleration (DLA)as lateral fields emerge within the channel.The final chapter outlines a simple targetry change to confine and enhance the x-ray emission from solid targets. By using a standing wire geometry, instead of a foil target, the electron expansion is confined to the lateral extent of the wire. The resultant field that emerges on the surface of the wire is greater in magnitude than that of a foil and develops sooner into the acceleration window recirculating more of the electrons within the target. This results in a significant, 50%, increase in total x-ray flux from the same laser conditions,and an increase in imaging quality of 2:6 due to the increase in flux and the confinement of the lateral x-ray source.This thesis reports on experimental investigations using high-intensity (> 1018W/cm2) lasers pulses to ionise and accelerate electrons from thick solid targets in order to generate a bright bremsstrahlung source. Throughout the work the focus has been, firstly, to better understand the process behind the generation of x-rays within solid target interactions and, secondly, to apply this understanding to radiography of industrial samples. Across three experimental investigations aspects of the x-ray source are addressed; in the first the spatial evolution of the x-ray source is investigated; in the second a mechanism to increase converse from laser into electrons is considered; and in the third a simple method to increase the conversion from electrons to x-rays is explored.As part of the research presented within this thesis, a novel diagnostic was developed to overcome limitations in current diagnostics that measure the spatial characteristics of the emitted x-ray source. This diagnostic was a curved foil, designed to ensure that over a large field of view the x-ray experienced a uniform transmission length - reducing the inherent uncertainty in knife edge techniques. The foil was calibrated to ensure accurate measurements at x-ray energies > 100 keV and applied throughout the research herein to characterise the emitted profile. The first experimental chapter explores the spatial characteristics of the xray profile. Using the curved foil, a two source structure was measured consistently in solid target interactions that emerges due to the recirculation of electrons. A narrow central source, and a broad secondary source. By defocusing the laser (and reducing the intensity on target) the x-ray flux produced by the small central source dominates over the secondary source and produces a sharper radiograph.;The flux of this second source was investigated through an analytical model that treated the sheath as a threshold to drive recirculation of electrons through the target. This model found good agreement with the measured results, and can be applied to predict the optimum defocus for different target materials and thicknesses.The second chapter utilises a capillary target to trap the laser light and increase the conversion into electrons, the initial concept was to invoke numerous low intensity interactions as the laser propagated through the capillary.This would, in theory, produce a high flux - low temperature electron population that in turn would produce a high flux of x-rays. However, it was found that the flux increased but the temperature remained similar to that of a solid target. PIC simulations demonstrate that the electrons experience a series of accelerations within the capillary, undergoing direct-laser-acceleration (DLA)as lateral fields emerge within the channel.The final chapter outlines a simple targetry change to confine and enhance the x-ray emission from solid targets. By using a standing wire geometry, instead of a foil target, the electron expansion is confined to the lateral extent of the wire. The resultant field that emerges on the surface of the wire is greater in magnitude than that of a foil and develops sooner into the acceleration window recirculating more of the electrons within the target. This results in a significant, 50%, increase in total x-ray flux from the same laser conditions,and an increase in imaging quality of 2:6 due to the increase in flux and the confinement of the lateral x-ray source
Forensic age estimation using DNA methylation analysis
Get PDFOver the last decade, researchers have identified age-related (AR) DNAmethylation (DNAm) markers, which have outperformed all other known AR biomarkers in estimating the chronological age of individuals with high accuracy,using various tissue types. Their accuracy in age estimation has led to them being suggested as a source of intelligence for forensic investigations, to determine the age of unidentified donors of biological samples left at crime scenes. Initially, in this research, different statistical methods have been tested in order to demonstrate which one of them is optimum for the identification of AR CpG sites.The selected method was then used to identify saliva specific AR CpG markers using DNAm profiles from saliva retrieved from an online genomic repository and assayed on the Illumina Human Methylation450 BeadChip microarray. These ARCpG markers were used to build a saliva-specific age prediction model that was tested in silico on an independent saliva testing data set. They were shown to perform well in terms of age prediction, and consequently, they were further validated by targeted bisulfite sequencing of additional saliva samples, using the Illumina MiSeq® platform. Subsequently, a large cohort of 754 DNAm profiles from blood samples assayed on the newly launched Illumina Methylation EPIC®BeadChip were downloaded from an online genomic repository, in order to be tested for the first time for age association. Novel AR CpG sites were identified from both the newly added probes on this chip and from probes that were found on older platforms, however, the prediction accuracy of the blood-specific age prediction model did not improve compared to models built from the older Illumina Human Methylation platforms. Finally, a multi-tissue age prediction model that is able to predict the age across the tissues was constructed. This multi-tissue age prediction model will have potential applications in forensic science in assisting investigations to predict chronological age across different biological samples,regardless of the tissue(s) those samples are derived from.Over the last decade, researchers have identified age-related (AR) DNAmethylation (DNAm) markers, which have outperformed all other known AR biomarkers in estimating the chronological age of individuals with high accuracy,using various tissue types. Their accuracy in age estimation has led to them being suggested as a source of intelligence for forensic investigations, to determine the age of unidentified donors of biological samples left at crime scenes. Initially, in this research, different statistical methods have been tested in order to demonstrate which one of them is optimum for the identification of AR CpG sites.The selected method was then used to identify saliva specific AR CpG markers using DNAm profiles from saliva retrieved from an online genomic repository and assayed on the Illumina Human Methylation450 BeadChip microarray. These ARCpG markers were used to build a saliva-specific age prediction model that was tested in silico on an independent saliva testing data set. They were shown to perform well in terms of age prediction, and consequently, they were further validated by targeted bisulfite sequencing of additional saliva samples, using the Illumina MiSeq® platform. Subsequently, a large cohort of 754 DNAm profiles from blood samples assayed on the newly launched Illumina Methylation EPIC®BeadChip were downloaded from an online genomic repository, in order to be tested for the first time for age association. Novel AR CpG sites were identified from both the newly added probes on this chip and from probes that were found on older platforms, however, the prediction accuracy of the blood-specific age prediction model did not improve compared to models built from the older Illumina Human Methylation platforms. Finally, a multi-tissue age prediction model that is able to predict the age across the tissues was constructed. This multi-tissue age prediction model will have potential applications in forensic science in assisting investigations to predict chronological age across different biological samples,regardless of the tissue(s) those samples are derived from
Person-centred therapy and pre-therapy for people who hear voices, have unusual experiences or psychotic processes : practitioner and client perceptions of helpful and unhelpful practice and perceived client changes
Get PDFPsychotic processes may involve a wide range of experiences, including hearing voices or other hallucinations, delusions or paranoia, or unusual or disturbed thinking or behaviour. Some clients who experience psychotic processes may not be responsive to standard psychotherapy formats and can thus present challenges for therapies of all orientations. The mixed method research strategy presented in this thesis is an attempt to uncover more information regarding helpful and unhelpful practices and changes in clients who experience psychotic processes.;First, I explored UK therapists' practice with clients who have unusual experiences or 'psychotic processes' and their perceptions of helpful and unhelpful practices and changes in clients. Second, I investigated clients' perspectives on helpful and hindering factors in person-centred therapy (PCT) as well as post-therapy positive or negative changes. Third, I investigated, in detail, one case of a client with psychotic processes who received PCT, considering causal efficacy. The three related studies carried out also considered, to some degree, the context of treatments offered and other impacting factors.;The first study involved semi-structured interviews with 20 person-centred practitioners working with clients with psychotic processes. The interviews focused on what practices they had encountered that were helpful to or hindered practice with clients, as well as any positive or negative changes they had observed in clients.;In the second study, 20 adult clients who had self-identified as hearing voices, having other unusual experiences or psychotic processes were interviewed mid- or post-therapy using the Change Interview protocol (Elliott, Slatick, & Urman, 2001). Studies 1 and 2 were analysed using grounded theory (Corbin & Strauss, 2008).;The third study consisted of a hermeneutic single case efficacy design study (HSCED; Elliott, 2001) with a client who was experiencing psychotic processes and who received 22 sessions of PCT. This HSCED study involved rigorous analysis of qualitative and quantitative data gathered over the 22 therapy sessions. The data was presented to a sceptic adjudicator and formally debated in a quasi-judicial forum with five independent judges: two therapists, a carer and two experts by experience. Following integration of the results of the judgement stage, conclusions were reached regarding the possible impact of the therapy and the possibility and degree of causal efficacy.;Overall results raised themes regarding helpful or unhelpful practices and changes in clients, from the perspectives of both practitioners and clients. Results indicated that most practitioners incorporated pre-therapy and contact work into practice, with positive and sometimes surprising results. Practitioners often worked in multidisciplinary contexts with careful attention to supervision, self-care and boundaries.;They saw person-centred values and the real relationship as important. Unconditional positive regard (UPR) was the most critical condition named both by practitioners and clients in this client group, possibly because they often felt judged or diminished by those around them. Helpful practices were associated with person-centred values. Unhelpful factors included practices such as judgement and unwanted directivity, both of which deviated from the person-centred (PC) approach.;The main changes in all studies involved an increase in social abilities and positive sense of self, and an increase in specific aspects of wellbeing. There was some evidence of improvement in mood and reduction in unusual experiences.;Clients engaged in the real relationship in therapy. Studies 2 and 3 showed that most clients were evidently active agents in their own change process. Findings demonstrate that PCT can be helpful for adult clients with psychotic processes. Practice implications are discussed.;Limitations of the studies include the dual therapist-researcher relationship in the HSCED study, the homogeneity and small size of the samples, and concerns about data validity. Issues relating to measures used to ascertain changes in therapy are discussed. Results are promising and suggest that PCT can be effective for clients who experience psychotic processes, pointing to the need for further research.Psychotic processes may involve a wide range of experiences, including hearing voices or other hallucinations, delusions or paranoia, or unusual or disturbed thinking or behaviour. Some clients who experience psychotic processes may not be responsive to standard psychotherapy formats and can thus present challenges for therapies of all orientations. The mixed method research strategy presented in this thesis is an attempt to uncover more information regarding helpful and unhelpful practices and changes in clients who experience psychotic processes.;First, I explored UK therapists' practice with clients who have unusual experiences or 'psychotic processes' and their perceptions of helpful and unhelpful practices and changes in clients. Second, I investigated clients' perspectives on helpful and hindering factors in person-centred therapy (PCT) as well as post-therapy positive or negative changes. Third, I investigated, in detail, one case of a client with psychotic processes who received PCT, considering causal efficacy. The three related studies carried out also considered, to some degree, the context of treatments offered and other impacting factors.;The first study involved semi-structured interviews with 20 person-centred practitioners working with clients with psychotic processes. The interviews focused on what practices they had encountered that were helpful to or hindered practice with clients, as well as any positive or negative changes they had observed in clients.;In the second study, 20 adult clients who had self-identified as hearing voices, having other unusual experiences or psychotic processes were interviewed mid- or post-therapy using the Change Interview protocol (Elliott, Slatick, & Urman, 2001). Studies 1 and 2 were analysed using grounded theory (Corbin & Strauss, 2008).;The third study consisted of a hermeneutic single case efficacy design study (HSCED; Elliott, 2001) with a client who was experiencing psychotic processes and who received 22 sessions of PCT. This HSCED study involved rigorous analysis of qualitative and quantitative data gathered over the 22 therapy sessions. The data was presented to a sceptic adjudicator and formally debated in a quasi-judicial forum with five independent judges: two therapists, a carer and two experts by experience. Following integration of the results of the judgement stage, conclusions were reached regarding the possible impact of the therapy and the possibility and degree of causal efficacy.;Overall results raised themes regarding helpful or unhelpful practices and changes in clients, from the perspectives of both practitioners and clients. Results indicated that most practitioners incorporated pre-therapy and contact work into practice, with positive and sometimes surprising results. Practitioners often worked in multidisciplinary contexts with careful attention to supervision, self-care and boundaries.;They saw person-centred values and the real relationship as important. Unconditional positive regard (UPR) was the most critical condition named both by practitioners and clients in this client group, possibly because they often felt judged or diminished by those around them. Helpful practices were associated with person-centred values. Unhelpful factors included practices such as judgement and unwanted directivity, both of which deviated from the person-centred (PC) approach.;The main changes in all studies involved an increase in social abilities and positive sense of self, and an increase in specific aspects of wellbeing. There was some evidence of improvement in mood and reduction in unusual experiences.;Clients engaged in the real relationship in therapy. Studies 2 and 3 showed that most clients were evidently active agents in their own change process. Findings demonstrate that PCT can be helpful for adult clients with psychotic processes. Practice implications are discussed.;Limitations of the studies include the dual therapist-researcher relationship in the HSCED study, the homogeneity and small size of the samples, and concerns about data validity. Issues relating to measures used to ascertain changes in therapy are discussed. Results are promising and suggest that PCT can be effective for clients who experience psychotic processes, pointing to the need for further research
In Daedalus' workshop : technique and the dynamics of invention in organization studies
Get PDFError on front cover. Front cover reads 'In Daedalus workshop technique and the dynamics of invention in organizing studies'. Title on title page is 'In Daedalus' workshop technique and the dynamics of invention in organization studies.'This study proposes an alternative vision of organizational creativity by examining the hidden nature of technique and its role within the production of new things. Taking the figure of Daedalus as an eponym for technical activity, this study asks how technique can be understood as contributing toward creative practice. It is argued that a consideration of technique reveals the hybrid relations formed between humans and technical objects within the process of production. Such relations are found to be incompatible with current theories of organizational creativity, which fail to recognise both the role of technical objects and their attendant techniques, resulting in an incomplete account of how creative outcomes are achieved. A potential solution to this issue may be found within the theory and practice of design, which, through an appreciation of the form and content of its own process and outputs, moves away from the image of an individual creator who preconceives forms in advance of their technical implementation.;To explore these issues, this study draws upon fieldwork collected at two design-led organizations and develops the 'Dynamics of Invention': a series of guiding concepts designed to help navigate the tangled paths of creative production.This study offers four contributions to the field of process organization studies. First, it provides the resources for understanding technique from a process perspective, and highlights its value for exposing the inherently technical nature of organizational life. Second, it extends and offers a critical dialogue with process perspectives of technical action, such as Actor-Network Theory and related theories of technical assemblages. Third, it offers a critique of the dominant perspectives within the field of organizational creativity, which, without a consideration of technical activity are likely to remain the preserve of the creative individual. Finally, it offers the 'Dynamics of Invention' as a guide to creative practice, affirming the inherent technicity of creating within organizations.This study proposes an alternative vision of organizational creativity by examining the hidden nature of technique and its role within the production of new things. Taking the figure of Daedalus as an eponym for technical activity, this study asks how technique can be understood as contributing toward creative practice. It is argued that a consideration of technique reveals the hybrid relations formed between humans and technical objects within the process of production. Such relations are found to be incompatible with current theories of organizational creativity, which fail to recognise both the role of technical objects and their attendant techniques, resulting in an incomplete account of how creative outcomes are achieved. A potential solution to this issue may be found within the theory and practice of design, which, through an appreciation of the form and content of its own process and outputs, moves away from the image of an individual creator who preconceives forms in advance of their technical implementation.;To explore these issues, this study draws upon fieldwork collected at two design-led organizations and develops the 'Dynamics of Invention': a series of guiding concepts designed to help navigate the tangled paths of creative production.This study offers four contributions to the field of process organization studies. First, it provides the resources for understanding technique from a process perspective, and highlights its value for exposing the inherently technical nature of organizational life. Second, it extends and offers a critical dialogue with process perspectives of technical action, such as Actor-Network Theory and related theories of technical assemblages. Third, it offers a critique of the dominant perspectives within the field of organizational creativity, which, without a consideration of technical activity are likely to remain the preserve of the creative individual. Finally, it offers the 'Dynamics of Invention' as a guide to creative practice, affirming the inherent technicity of creating within organizations
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