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A critical investigation of the exercise of power embedded into performance measurement systems in the higher education sector
Get PDFThis thesis was previously held under moratorium from 27th November 2019 until 27th November 2024.In order to pursue ‘business-like’ efficiency, and in keeping with ‘neoliberal-rationality’, a growing number of universities around the world have come to favour adopting PMSs (performance measurement systems) to evaluate their and their staff’s performance. This thesis is aimed at investigating how senior managers in higher education institutions implement various PMSs and how faculty members understand and feel about these PMSs. This thesis argues that PMSs are not just simple accounting technologies, but tools for management teams to use to manage and control people through the exercising of power. To complete this research, a qualitative research design and a case study were used due to the nature of this research and my interpretivist stance. A total of 35 semi-structured interviews were conducted, with interviewees from different departments with various backgrounds and job positions in a British university.
Lukes’ (2005) three dimensions of power as the lead theoretical framework was applied to analyse the power relations. Development for International Development’s (2009) political economy analysis and Cooper and Sherer’s (1984) political economy of accounting were used to identify senior managers’ real interests. Alvesson and Spicer’s (2012) functional stupidity was adopted to further explain a general status of academia in the UK.
It concludes that PMSs used by the senior managers in the case university did not create positive feelings according to the majority of faculty members. However, the PMS systems did impact on staff and they did serve to reinforce the values of senior management. The PMSs serve as a kind of media through which the senior managers can visibly and invisibly manifest different dimensions of power, and the most insidious and strongest power enables the powerful to alter the management culture. The senior managers’ political and economic interests largely determine how they utilise PMSs. The dominant contribution of the thesis is its application of the Lukes’ theoretical framework, aligned to a political economy approach to understanding the impact of PMSs in the case university. It is hoped that this thesis constructs a strong empirical foundation for future research and future researchers can be inspired by this work.In order to pursue ‘business-like’ efficiency, and in keeping with ‘neoliberal-rationality’, a growing number of universities around the world have come to favour adopting PMSs (performance measurement systems) to evaluate their and their staff’s performance. This thesis is aimed at investigating how senior managers in higher education institutions implement various PMSs and how faculty members understand and feel about these PMSs. This thesis argues that PMSs are not just simple accounting technologies, but tools for management teams to use to manage and control people through the exercising of power. To complete this research, a qualitative research design and a case study were used due to the nature of this research and my interpretivist stance. A total of 35 semi-structured interviews were conducted, with interviewees from different departments with various backgrounds and job positions in a British university.
Lukes’ (2005) three dimensions of power as the lead theoretical framework was applied to analyse the power relations. Development for International Development’s (2009) political economy analysis and Cooper and Sherer’s (1984) political economy of accounting were used to identify senior managers’ real interests. Alvesson and Spicer’s (2012) functional stupidity was adopted to further explain a general status of academia in the UK.
It concludes that PMSs used by the senior managers in the case university did not create positive feelings according to the majority of faculty members. However, the PMS systems did impact on staff and they did serve to reinforce the values of senior management. The PMSs serve as a kind of media through which the senior managers can visibly and invisibly manifest different dimensions of power, and the most insidious and strongest power enables the powerful to alter the management culture. The senior managers’ political and economic interests largely determine how they utilise PMSs. The dominant contribution of the thesis is its application of the Lukes’ theoretical framework, aligned to a political economy approach to understanding the impact of PMSs in the case university. It is hoped that this thesis constructs a strong empirical foundation for future research and future researchers can be inspired by this work
Characterisation and analysis of a corona-stabilised switch filled with environmentally-friendly gas mixtures
Get PDFTests have been completed with the intention of finding an alternative switching medium to SF6 due to environmental concerns. For this purpose, a testing procedure was designed in order to test a novel gas in pulsed power, HFO-1234ze, in mixtures with N2, used as a buffer gas. Thus, decreasing the global warming potential (GWP) of the switching medium from 23900 in SF6 to 6 in HFO-1234ze. The performance of the gas was measured in a specific corona-stabilised switch geometry, characterising triggering range and delay time experimentally, and calculating jitter.;Over the testing phase it was shown that N2/HFO-1234ze mixtures were very promising in terms of breakdown strength, with self-breakdown voltages for a 80% N2 / 20% HFO-1234ze mixture at 3 bar gauge reaching up to 32.2 kV and 36 kV for positive and negative polarity, respectively, giving an increase of 191% and 306% breakdown increase from using 100% N2. Furthermore, the triggering ranges recorded reached a maximum of 13.4 kV for positive polarity and 13.6 kV for negative polarity, giving increases of 837% and 174% compared to 100% N2. The delay time and jitter increased accordingly as the total pressure of each individual mix increased.;Von Laue statistical analysis was conducted on the delay time data, in order to estimate the relative contributions of the statistical and formative times to the overall delay time. Statistical times were found to increase slightly with pressure, with no clear polarity effect. The formative times were found to form the majority of the overall delay times, increasing with increasing pressure for both polarities.;In terms of being a viable replacement for SF6, the gas HFO-1234ze showed positive characteristics in terms of self-breakdown voltage, triggering range and delay time/jitter, in the tested geometry. Although, after testing completion, the electrodes were found to have a layer of carbon which had formed during the testing process; this requires further investigation.Tests have been completed with the intention of finding an alternative switching medium to SF6 due to environmental concerns. For this purpose, a testing procedure was designed in order to test a novel gas in pulsed power, HFO-1234ze, in mixtures with N2, used as a buffer gas. Thus, decreasing the global warming potential (GWP) of the switching medium from 23900 in SF6 to 6 in HFO-1234ze. The performance of the gas was measured in a specific corona-stabilised switch geometry, characterising triggering range and delay time experimentally, and calculating jitter.;Over the testing phase it was shown that N2/HFO-1234ze mixtures were very promising in terms of breakdown strength, with self-breakdown voltages for a 80% N2 / 20% HFO-1234ze mixture at 3 bar gauge reaching up to 32.2 kV and 36 kV for positive and negative polarity, respectively, giving an increase of 191% and 306% breakdown increase from using 100% N2. Furthermore, the triggering ranges recorded reached a maximum of 13.4 kV for positive polarity and 13.6 kV for negative polarity, giving increases of 837% and 174% compared to 100% N2. The delay time and jitter increased accordingly as the total pressure of each individual mix increased.;Von Laue statistical analysis was conducted on the delay time data, in order to estimate the relative contributions of the statistical and formative times to the overall delay time. Statistical times were found to increase slightly with pressure, with no clear polarity effect. The formative times were found to form the majority of the overall delay times, increasing with increasing pressure for both polarities.;In terms of being a viable replacement for SF6, the gas HFO-1234ze showed positive characteristics in terms of self-breakdown voltage, triggering range and delay time/jitter, in the tested geometry. Although, after testing completion, the electrodes were found to have a layer of carbon which had formed during the testing process; this requires further investigation
An oral history of domestic abuse in Scotland 1945-1992
Get PDFThis thesis was previously held under moratorium from 17th February 2020 to 17th February 2021.This thesis investigates domestic abuse in the changing socio-economic and political context of post-war Scotland. Assault on wives was a common yet under-reported crime and contemporary surveys failed to capture its true extent. Knowledge about domestic abuse comes mainly from women's aid sources dating from the 1970s. As most abused women did not contact WA services, this thesis gives voice to women who did not seek outside help over the longer post-war period and provides new insights into their reasons for this.;Twenty-six oral history narratives describing domestic abuse and criminal justice and social welfare agency responses between circa 1945 and 1992 were analysed using a newly-designed feminist theoretical framework. Continuity and change are evident in women's experiences and in agency responses. Extensive life histories reveal the resilience of patriarchal discourses and practices throughout the period with domestic abuse retaining its longstanding function of reinforcing traditional gender roles. By the 1980s, there is evidence of a shift towards public patriarchy with new legislation advancing women's social equality, improved career prospects and higher earnings. However, there is less evidence of a parallel shift away from private patriarchy as deeper, constitutive gender rules remained resistant to change. In the new socio-economic environment of the 1980s, domestic abuse retained its core function whilst evolving into new non-violent, coercive forms which extended control into women's public lives. Criminal justice and social welfare agencies remained working patriarchies, often unwilling to intervene in marital relations and hostile to abused women.;This thesis highlights the close interplay of personal and contextual factors influencing women's experiences and reporting decisions and shows that domestic abuse contributed to a patriarchal equilibrium in Scotland into the 1990s. This thesis thus makes a distinctive contribution to our understanding of the reasons for the persistence and adaptability of domestic abuse in late-twentieth-century Scotland.This thesis investigates domestic abuse in the changing socio-economic and political context of post-war Scotland. Assault on wives was a common yet under-reported crime and contemporary surveys failed to capture its true extent. Knowledge about domestic abuse comes mainly from women's aid sources dating from the 1970s. As most abused women did not contact WA services, this thesis gives voice to women who did not seek outside help over the longer post-war period and provides new insights into their reasons for this.;Twenty-six oral history narratives describing domestic abuse and criminal justice and social welfare agency responses between circa 1945 and 1992 were analysed using a newly-designed feminist theoretical framework. Continuity and change are evident in women's experiences and in agency responses. Extensive life histories reveal the resilience of patriarchal discourses and practices throughout the period with domestic abuse retaining its longstanding function of reinforcing traditional gender roles. By the 1980s, there is evidence of a shift towards public patriarchy with new legislation advancing women's social equality, improved career prospects and higher earnings. However, there is less evidence of a parallel shift away from private patriarchy as deeper, constitutive gender rules remained resistant to change. In the new socio-economic environment of the 1980s, domestic abuse retained its core function whilst evolving into new non-violent, coercive forms which extended control into women's public lives. Criminal justice and social welfare agencies remained working patriarchies, often unwilling to intervene in marital relations and hostile to abused women.;This thesis highlights the close interplay of personal and contextual factors influencing women's experiences and reporting decisions and shows that domestic abuse contributed to a patriarchal equilibrium in Scotland into the 1990s. This thesis thus makes a distinctive contribution to our understanding of the reasons for the persistence and adaptability of domestic abuse in late-twentieth-century Scotland
Observation of the impact of reactive oxygen species-inducers on the metabolomes of pulmonary artery smooth muscle cells and retinal pigment epithelial cells
Get PDFBackground: Endogenous and exogenous reactive oxygen species (ROS) inducers cause intracellular metabolic modifications leading eventually to serious diseases.Overproduction of ROS is associated with many diseases including diabetes, diabetic retinopathy and cardiovascular diseases (CVD). Exposing of different cell types to oxidative agents impair the cell redox status by primarily inducing the excessive generation of superoxide that is enzymatically converted to other forms of oxidative agents causing cell damage. The hyperglycaemia that occurs due to diabetes mellitus causes high ROS production. Identification of reliable markers that indicate metabolic alteration due to oxidative stress could enable a better understanding of many diseases in terms of diagnosis and treatment with therapeutic targets.Aim: To identify the main metabolic markers that are influenced by ROS in pulmonary artery smooth muscle cells (PASMCs) and retinal pigment epithelial cells(RPE) in-vitro. To investigate the impact of anti-oxidant agents in attenuating the modifications that may appear due to the high production of ROS. Study design and methodology: biological cell samples were prepared and collected for each of the four included studies based on the intervention of each study whether it is the impact of hyperglycaemia with or without vitamin as antioxidants and the impact of TSPO protein deletion. In the first study, PASMCs were exposed to diabetic-like conditions and either supplemented or not supplemented by anti-oxidant agents. In the following study, PASMCs were also examined under hyperglycaemia in normoxic or hypoxic conditions. In the two other following studies, we investigated the impact of oxidised low density lipoprotein (OxLDL) and hyperglycaemia on the TSPO knockout and wildtype RPE cells. All studies were carried out utilizing high-performance liquid chromatography-mass spectrometry. We used untargeted metabolic profiling to detect comprehensive metabolic alterations that occurred intracellularly due to our interventions. MzMatch software was used to identify the metabolites present;multivariate and univariate analyses were employed to determine the most reliable metabolites as biomarkers for oxidative stress.;Results: The outcomes established that high glucose influences cell proliferation and enhances oxidative stress. The general metabolomics results show the induction of carbohydrate metabolism accompanied by activation of the pentose phosphate pathway (PPP) to boost the generation of NADPH as an antioxidant product. Amino acids were also disturbed while some of them were up-regulated and some others were down-regulated. Lipids were frequently the most influenced pathway suggesting that the cell membrane was damaged by ROS induction.Purines and pyrimidines, in addition, were influenced consequently due to the changes occurring in PPP metabolism.Conclusion: These hypothesis-free metabolomics profiling studies have identified intracellular metabolites in PASMCs, and RPE cells which are differentially sensitiveto the hyperglycaemia or oxidative stress inducers and may be useful to initiate hypothesises about markers that can help to prevent or cure diseases where oxidative stress plays a role.Background: Endogenous and exogenous reactive oxygen species (ROS) inducers cause intracellular metabolic modifications leading eventually to serious diseases.Overproduction of ROS is associated with many diseases including diabetes, diabetic retinopathy and cardiovascular diseases (CVD). Exposing of different cell types to oxidative agents impair the cell redox status by primarily inducing the excessive generation of superoxide that is enzymatically converted to other forms of oxidative agents causing cell damage. The hyperglycaemia that occurs due to diabetes mellitus causes high ROS production. Identification of reliable markers that indicate metabolic alteration due to oxidative stress could enable a better understanding of many diseases in terms of diagnosis and treatment with therapeutic targets.Aim: To identify the main metabolic markers that are influenced by ROS in pulmonary artery smooth muscle cells (PASMCs) and retinal pigment epithelial cells(RPE) in-vitro. To investigate the impact of anti-oxidant agents in attenuating the modifications that may appear due to the high production of ROS. Study design and methodology: biological cell samples were prepared and collected for each of the four included studies based on the intervention of each study whether it is the impact of hyperglycaemia with or without vitamin as antioxidants and the impact of TSPO protein deletion. In the first study, PASMCs were exposed to diabetic-like conditions and either supplemented or not supplemented by anti-oxidant agents. In the following study, PASMCs were also examined under hyperglycaemia in normoxic or hypoxic conditions. In the two other following studies, we investigated the impact of oxidised low density lipoprotein (OxLDL) and hyperglycaemia on the TSPO knockout and wildtype RPE cells. All studies were carried out utilizing high-performance liquid chromatography-mass spectrometry. We used untargeted metabolic profiling to detect comprehensive metabolic alterations that occurred intracellularly due to our interventions. MzMatch software was used to identify the metabolites present;multivariate and univariate analyses were employed to determine the most reliable metabolites as biomarkers for oxidative stress.;Results: The outcomes established that high glucose influences cell proliferation and enhances oxidative stress. The general metabolomics results show the induction of carbohydrate metabolism accompanied by activation of the pentose phosphate pathway (PPP) to boost the generation of NADPH as an antioxidant product. Amino acids were also disturbed while some of them were up-regulated and some others were down-regulated. Lipids were frequently the most influenced pathway suggesting that the cell membrane was damaged by ROS induction.Purines and pyrimidines, in addition, were influenced consequently due to the changes occurring in PPP metabolism.Conclusion: These hypothesis-free metabolomics profiling studies have identified intracellular metabolites in PASMCs, and RPE cells which are differentially sensitiveto the hyperglycaemia or oxidative stress inducers and may be useful to initiate hypothesises about markers that can help to prevent or cure diseases where oxidative stress plays a role
Beastly encounters : human-animal relations in the illustrated police news and Victorian literature and culture, 1864-1901
Get PDFThis thesis was previously held under moratorium from 19/11/19 to 19/11/21This thesis examines the sensational Victorian newspaper the Illustrated Police News and its representation of human-animal relations from its inception in 1864 to the end of the Victorian era in 1901. It proposes that this critically-overlooked paper can illuminate our understanding of contemporary attitudes towards animals, providing, as it does, a popular perspective not often discussed in academic studies. -- Drawing on scholarship from animal studies, urban studies, periodical studies and literary studies, this thesis suggests the significance of this newspaper’s representation of animals and explores how this representation relates to contemporary anxieties surrounding, for example, urbanisation, criminality, degeneration, order and civility. -- The analysis is comprised of case studies, with each chapter examining the representation of human-animal relations in a different set of urban and rural spaces. The thesis moves from the private space of the home to public settings such as the street, the menagerie, the zoo and the courtroom, and finally to the controversial Victorian laboratory. In each case, the paper made important contributions to, for example, discussions of the legal status of animals, and conceptions of their potential agency and of their position in Victorian society. -- The paper’s use of genre in its dissemination of ideas is also explored, and it is situated in its literary and cultural contexts through comparisons with other contemporary periodicals and with Victorian fiction, examining particularly its use of Gothic and sensational modes. -- The thesis thus contributes to scholarly work on the representation of animals in nineteenth-century periodicals, which until now has largely focused on titles produced and read by the social elite. Often viewed as only a low and lurid title, this thesis provides the first sustained critical study of the Illustrated Police News and argues that it is a valuable resource for the study of Victorian culture.This thesis examines the sensational Victorian newspaper the Illustrated Police News and its representation of human-animal relations from its inception in 1864 to the end of the Victorian era in 1901. It proposes that this critically-overlooked paper can illuminate our understanding of contemporary attitudes towards animals, providing, as it does, a popular perspective not often discussed in academic studies. -- Drawing on scholarship from animal studies, urban studies, periodical studies and literary studies, this thesis suggests the significance of this newspaper’s representation of animals and explores how this representation relates to contemporary anxieties surrounding, for example, urbanisation, criminality, degeneration, order and civility. -- The analysis is comprised of case studies, with each chapter examining the representation of human-animal relations in a different set of urban and rural spaces. The thesis moves from the private space of the home to public settings such as the street, the menagerie, the zoo and the courtroom, and finally to the controversial Victorian laboratory. In each case, the paper made important contributions to, for example, discussions of the legal status of animals, and conceptions of their potential agency and of their position in Victorian society. -- The paper’s use of genre in its dissemination of ideas is also explored, and it is situated in its literary and cultural contexts through comparisons with other contemporary periodicals and with Victorian fiction, examining particularly its use of Gothic and sensational modes. -- The thesis thus contributes to scholarly work on the representation of animals in nineteenth-century periodicals, which until now has largely focused on titles produced and read by the social elite. Often viewed as only a low and lurid title, this thesis provides the first sustained critical study of the Illustrated Police News and argues that it is a valuable resource for the study of Victorian culture
Micro-assembly of integrated photonic devices using a high accuracy transfer printing process
Get PDFThis thesis was previously held under moratorium from 03/12/19 to 03/12/21The overall objective of this thesis is the development and implementation of a high accuracy transfer printing (TP) technique for the micro-assembly of integrated photonic devices. The method has particular relevance for the integration of hybrid photonic waveguides, and enables the production of passive/active photonic circuit technologies in a parallel and scalable manner.The initial work involves the design of an optical microscopy based absolute crosscorrelation alignment technique utilised within a custom-built TP system. Following this, the statistical characterisation of the method, with the measured absolute positional accuracy of fully fabricated devices integrated across multiple substrates is achieved. An absolute lateral alignment accuracy of ±385 nm (3σ) and rotational accuracy of ±4.8 mrad (3σ) are demonstrated. This is reported as the highest lateral alignment accuracy to date for transfer printing, lending itself a significant advantage for the micro-assembly of optical waveguiding components.Utilising the high alignment TP system, the micro-assembly of fully fabricated single-mode Si membrane micro-ring resonators on a target silicon-on-insulator (SOI) substrate is presented. The ultra-thin membrane resonators are vertically integrated with Si bus waveguides situated on a receiver SOI chip in a highly controllable manner, demonstrating variation in resonant coupling conditions with respect to the lateral coupling offset. Further to this, the TP method provides a means to produce 3D device architectures without any limiting multi-step full wafer bonding methods. By vertical assembling 3D stacked membrane devices, a 100 µm2 SOI distributed Bragg reflector (DBR) is produced taking advantage of high lateral and rotation placement accuracy. The structure exhibits a visible wavelength reflectance band in agreement with theoretical simulations.The micro-assembly of hybrid AlGaAs-on-SOI micro-disk resonators is also presented, demonstrating the highly controlled integration of pre-fabricated waveguide devices across multiple material platforms. Control over the integrated resonator's vertical and lateral coupling to the bus waveguides enables the precise and selective excitation of different mode families within the resonator cavity. By using the high accuracy TP method, the vertical micro-assembly of hybrid micro-disk resonators also allows selective mode coupling, with loaded Q-factors reaching ~40,000. The unique advantage of the assembled devices however come from the ability to perform (3) nonlinear processes on SOI without being limited by two-photon absorption and free-carrier losses. Four-wave mixing is shown with efficiency levels of -25 dB at a low input power of 2.5 mW, with a nonlinear coeffcient of 325 (Wm)-1 demonstrated.The measured nonlinearity is comparable to its monolithic silicon counterpart, whilst also detailing a clear reduction in the nonlinear losses inherent to this material platform.The overall objective of this thesis is the development and implementation of a high accuracy transfer printing (TP) technique for the micro-assembly of integrated photonic devices. The method has particular relevance for the integration of hybrid photonic waveguides, and enables the production of passive/active photonic circuit technologies in a parallel and scalable manner.The initial work involves the design of an optical microscopy based absolute crosscorrelation alignment technique utilised within a custom-built TP system. Following this, the statistical characterisation of the method, with the measured absolute positional accuracy of fully fabricated devices integrated across multiple substrates is achieved. An absolute lateral alignment accuracy of ±385 nm (3σ) and rotational accuracy of ±4.8 mrad (3σ) are demonstrated. This is reported as the highest lateral alignment accuracy to date for transfer printing, lending itself a significant advantage for the micro-assembly of optical waveguiding components.Utilising the high alignment TP system, the micro-assembly of fully fabricated single-mode Si membrane micro-ring resonators on a target silicon-on-insulator (SOI) substrate is presented. The ultra-thin membrane resonators are vertically integrated with Si bus waveguides situated on a receiver SOI chip in a highly controllable manner, demonstrating variation in resonant coupling conditions with respect to the lateral coupling offset. Further to this, the TP method provides a means to produce 3D device architectures without any limiting multi-step full wafer bonding methods. By vertical assembling 3D stacked membrane devices, a 100 µm2 SOI distributed Bragg reflector (DBR) is produced taking advantage of high lateral and rotation placement accuracy. The structure exhibits a visible wavelength reflectance band in agreement with theoretical simulations.The micro-assembly of hybrid AlGaAs-on-SOI micro-disk resonators is also presented, demonstrating the highly controlled integration of pre-fabricated waveguide devices across multiple material platforms. Control over the integrated resonator's vertical and lateral coupling to the bus waveguides enables the precise and selective excitation of different mode families within the resonator cavity. By using the high accuracy TP method, the vertical micro-assembly of hybrid micro-disk resonators also allows selective mode coupling, with loaded Q-factors reaching ~40,000. The unique advantage of the assembled devices however come from the ability to perform (3) nonlinear processes on SOI without being limited by two-photon absorption and free-carrier losses. Four-wave mixing is shown with efficiency levels of -25 dB at a low input power of 2.5 mW, with a nonlinear coeffcient of 325 (Wm)-1 demonstrated.The measured nonlinearity is comparable to its monolithic silicon counterpart, whilst also detailing a clear reduction in the nonlinear losses inherent to this material platform
Computational study of gas transport in shale at pore-scale and beyond
Get PDFUnconventional gas resources like shale are poised to enter a golden age thanks to the worldwide increased exploitation potential. Yet, the future of these resources is far from assured since it is still subject to many uncertainties, mainly with regard to gas recoverability. The macroscopic flow properties that allow the prediction of production are directly linked to the microscopic flow where underlying rarefaction effects play a major role. This is due to the pore size which is as small as a few nanometers and comparable to the mean free path. Thus, an in-depth understanding of gas transport in ultra-tight porous media is crucial for the accurate determination of flow properties in shale rocks. This thesis is a fundamental research aiming to aid and benefit shale gas exploration and development. The objective of this work is to provide useful insights for such non-equilibrium porous media flows, where the conventional fluid mechanics theory fails. Even though there are multiple heuristic permeability models in the literature, I find them unsuitable to provide reliable apparent permeability estimates since they often include simplifications of the flow mechanisms and matrix complexity. Notably, I hereby establish/prove the limitations of the accuracy of the Navier-Stokes equations to the first order of Knudsen number. We also thoroughly analyse Klinkenberg's slip factor behaviour for a wide range of gas rarefaction, utilising gas kinetic theory, for both simple and complex porous media. Moreover, using controllably random porous media, I systematically quantify the impact of numerous structural characteristics, i.e. porosity, tortuosity, specific surface area, heterogeneity and degree of anisotropy, on both intrinsic and apparent permeability.;One of the key contributions of this work is a new semi-analytical permeability formulation derived using the produced simulation results. This expression, suitable for both isotropic and anisotropic two-dimensional porous media, accounts for the aforementioned properties as well as for continuum and slip flow. The main advantage of the proposed formulation is the fact that it does not entail any experimental or numerical data as input, unlike other established models. Shale is intrinsically multiscale, thus the direct simulation of transport in all scales is not feasible. Upscaling from the pore-scale is indispensable in order to eventually obtain the essential macroscopic properties in the field-scale. For this reason, I examine well-known analytical and numerical upscaling techniques, verifying the sensitivity and accuracy of the latter ones. Studying microscale sample images, we need to consider the appearance of microfractures. The difference of the characteristic length scales between the nanopores and the microfractures requires a hybrid upscaling method such as the Brinkman approach.;The suitability of this model is extensively validated on fractured porous media of interest, especially on the grounds that the exact form of the effective viscosity is still a matter of discussion. We perform this validation comparing numerous direct simulation results with the corresponding ones from the Brinkman solution. Different values of the effective viscosity are investigated, along with a variable permeability model applied at the vicinity of the fluid-porous interface. Due to lack of an appropriate universal treatment of the transition zone of random porous media, we consider effective viscosity equal to fluid viscosity. The accuracy of the Brinkman approach is further examined using several two and three-dimensional random porous media containing fractures, as well as considering rarefied conditions. Although I find that heterogeneity and anisotropy increase the error of the effective permeability derived from the Brinkman approach, generally, the effective permeability extracted from this coarse-scale model compares favourably to its fine-scale counterpart obtained from the Stokes and Boltzmann model equations for porous media flows. Finally, I conclude that neglecting the rarefaction effects leads to a significant underestimation of the effective permeability of fractured ultra-tight porous media.Unconventional gas resources like shale are poised to enter a golden age thanks to the worldwide increased exploitation potential. Yet, the future of these resources is far from assured since it is still subject to many uncertainties, mainly with regard to gas recoverability. The macroscopic flow properties that allow the prediction of production are directly linked to the microscopic flow where underlying rarefaction effects play a major role. This is due to the pore size which is as small as a few nanometers and comparable to the mean free path. Thus, an in-depth understanding of gas transport in ultra-tight porous media is crucial for the accurate determination of flow properties in shale rocks. This thesis is a fundamental research aiming to aid and benefit shale gas exploration and development. The objective of this work is to provide useful insights for such non-equilibrium porous media flows, where the conventional fluid mechanics theory fails. Even though there are multiple heuristic permeability models in the literature, I find them unsuitable to provide reliable apparent permeability estimates since they often include simplifications of the flow mechanisms and matrix complexity. Notably, I hereby establish/prove the limitations of the accuracy of the Navier-Stokes equations to the first order of Knudsen number. We also thoroughly analyse Klinkenberg's slip factor behaviour for a wide range of gas rarefaction, utilising gas kinetic theory, for both simple and complex porous media. Moreover, using controllably random porous media, I systematically quantify the impact of numerous structural characteristics, i.e. porosity, tortuosity, specific surface area, heterogeneity and degree of anisotropy, on both intrinsic and apparent permeability.;One of the key contributions of this work is a new semi-analytical permeability formulation derived using the produced simulation results. This expression, suitable for both isotropic and anisotropic two-dimensional porous media, accounts for the aforementioned properties as well as for continuum and slip flow. The main advantage of the proposed formulation is the fact that it does not entail any experimental or numerical data as input, unlike other established models. Shale is intrinsically multiscale, thus the direct simulation of transport in all scales is not feasible. Upscaling from the pore-scale is indispensable in order to eventually obtain the essential macroscopic properties in the field-scale. For this reason, I examine well-known analytical and numerical upscaling techniques, verifying the sensitivity and accuracy of the latter ones. Studying microscale sample images, we need to consider the appearance of microfractures. The difference of the characteristic length scales between the nanopores and the microfractures requires a hybrid upscaling method such as the Brinkman approach.;The suitability of this model is extensively validated on fractured porous media of interest, especially on the grounds that the exact form of the effective viscosity is still a matter of discussion. We perform this validation comparing numerous direct simulation results with the corresponding ones from the Brinkman solution. Different values of the effective viscosity are investigated, along with a variable permeability model applied at the vicinity of the fluid-porous interface. Due to lack of an appropriate universal treatment of the transition zone of random porous media, we consider effective viscosity equal to fluid viscosity. The accuracy of the Brinkman approach is further examined using several two and three-dimensional random porous media containing fractures, as well as considering rarefied conditions. Although I find that heterogeneity and anisotropy increase the error of the effective permeability derived from the Brinkman approach, generally, the effective permeability extracted from this coarse-scale model compares favourably to its fine-scale counterpart obtained from the Stokes and Boltzmann model equations for porous media flows. Finally, I conclude that neglecting the rarefaction effects leads to a significant underestimation of the effective permeability of fractured ultra-tight porous media
Chip-scale atomic magnetometer based on free-induction-decay
Get PDFThis thesis describes the implementation of an optically pumped caesium magnetometer containing a 1:5mm thick microfabricated vapour cell with nitrogen buffer gas, operating in a free-induction-decay configuration. This allows us to monitor the free Larmor precession of the spin coherent Cs atoms by separating the pump and probe phases in the time domain. A single light pulse can sufficiently polarise the atomic sample;however, synchronous modulation of the light field actively drives the precession and maximises the induced spin coherence. Both amplitude- and frequency-modulation have been adopted producing noise floors of 3.4 pT / √Hz and 15.6 pT/√Hz, respectively,within a Nyquist limited bandwidth of 500 Hz in a bias field comparable to the Earth's (~50 μT). We investigate the magnetometers capability in reproducing time-varying magnetic signals under these conditions, including the reconstruction of a 100 pT perturbation using signal averaging.Additionally, we discuss a novel detection mode based on free-induction-decay that observes the spin precession dynamics in-the-dark using Ramsey-like pulses. This aids in suppressing the systematic effects originating from the light-atom interaction during readout, thus vastly improving the accuracy of the magnetometer whilst maintaining a sensitivity that is competitive with previous implementations. This detection technique was implemented further to measure the spin relaxation properties intrinsic to the sensor head, useful in determining the optimal buffer pressure that extends the spin lifetime and improves the sensor's sensitivity performance.This thesis describes the implementation of an optically pumped caesium magnetometer containing a 1:5mm thick microfabricated vapour cell with nitrogen buffer gas, operating in a free-induction-decay configuration. This allows us to monitor the free Larmor precession of the spin coherent Cs atoms by separating the pump and probe phases in the time domain. A single light pulse can sufficiently polarise the atomic sample;however, synchronous modulation of the light field actively drives the precession and maximises the induced spin coherence. Both amplitude- and frequency-modulation have been adopted producing noise floors of 3.4 pT / √Hz and 15.6 pT/√Hz, respectively,within a Nyquist limited bandwidth of 500 Hz in a bias field comparable to the Earth's (~50 μT). We investigate the magnetometers capability in reproducing time-varying magnetic signals under these conditions, including the reconstruction of a 100 pT perturbation using signal averaging.Additionally, we discuss a novel detection mode based on free-induction-decay that observes the spin precession dynamics in-the-dark using Ramsey-like pulses. This aids in suppressing the systematic effects originating from the light-atom interaction during readout, thus vastly improving the accuracy of the magnetometer whilst maintaining a sensitivity that is competitive with previous implementations. This detection technique was implemented further to measure the spin relaxation properties intrinsic to the sensor head, useful in determining the optimal buffer pressure that extends the spin lifetime and improves the sensor's sensitivity performance
An investigation of the neural circuitry that mediates inhibitory signalling within the lateral habenula
Get PDFPreviously held under moratorium from 3 March 2020 until 3 March 2022Background: The lateral habenula (LHb) is a brain structure which is knownto be pathologically hyperactive in depression, thus providing enhancedinhibitory input to the brains’ reward circuitry. As such, inhibition of the LHbhas an antidepressant effect, via disinhibition of the reward circuitry. However,the neural circuity which mediates inhibitory signalling within the LHb remainsto be fully described. Hence, the overarching aim of this project was to studyinhibitory signalling within the LHb, by studying the circuitry formed by neuronsexpressing one of three transgenic markers classically considered to beassociated with inhibitory neurons: Neuron-derived neurotrophic factor (Ndnf),parvalbumin (PV) and somatostatin (SOM).Methods: Circuitry was studied in vitro using patch-clamp electrophysiologyin combination with optogenetic manipulations of neurons expressing theabove molecular markers. Additionally, immunohistochemistry and confocalmicroscopy were used to assess the fraction of neurons expressing thesemarkers which were also GABAergic.Results: This work identifies three sources of inhibitory input to the LHb,arising from both local PV-positive neurons, and those in the medial dorsalthalamic nucleus; and from SOM-positive neurons in the ventral pallidum.Additionally, we find that within the LHb, these markers are not confined toexclusively inhibitory populations. Rather, we identify physiologically distinct.Background: The lateral habenula (LHb) is a brain structure which is knownto be pathologically hyperactive in depression, thus providing enhancedinhibitory input to the brains’ reward circuitry. As such, inhibition of the LHbhas an antidepressant effect, via disinhibition of the reward circuitry. However,the neural circuity which mediates inhibitory signalling within the LHb remainsto be fully described. Hence, the overarching aim of this project was to studyinhibitory signalling within the LHb, by studying the circuitry formed by neuronsexpressing one of three transgenic markers classically considered to beassociated with inhibitory neurons: Neuron-derived neurotrophic factor (Ndnf),parvalbumin (PV) and somatostatin (SOM).Methods: Circuitry was studied in vitro using patch-clamp electrophysiologyin combination with optogenetic manipulations of neurons expressing theabove molecular markers. Additionally, immunohistochemistry and confocalmicroscopy were used to assess the fraction of neurons expressing thesemarkers which were also GABAergic.Results: This work identifies three sources of inhibitory input to the LHb,arising from both local PV-positive neurons, and those in the medial dorsalthalamic nucleus; and from SOM-positive neurons in the ventral pallidum.Additionally, we find that within the LHb, these markers are not confined toexclusively inhibitory populations. Rather, we identify physiologically distinct
Iridium complexes as highly active catalysts for hydrogen isotope exchange and hydrogen borrowing processes
Get PDFOver the last several decades, the organic chemistry community has become increasingly reliant upon iridium catalysis, with applications reported across a number of research areas. In recent years, the Kerr group has developed a series of iridium complexes, which were found to be excellent catalysts for hydrogen isotope exchange and olefin hydrogenation processes. The work described within this thesis centres upon the expansion of these catalysts' reactivity in hydrogen isotope exchange, as well as the synthesis and application of a series of novel iridium complexes, designed for use in hydrogen borrowing catalysis. Chapter one focuses on the development of three efficient and selective methods for hydrogen isotope exchange. Iridium(I) catalysts previously developed within the group have been employed in the successful deuteration of N-heterocycles, which represent an important and relatively underexplored class of labelling substrates. The labelling of a large range of indole, pyrrole, and quinoline derivatives is reported, in which the regioselectivity can be controlled through careful choice of N-protecting group. Extensive practical and computational mechanistic investigations offered insight into the mechanism of indole C3 labelling, which is believed to proceed via an iridium-indoline intermediate. In chapter two, the design and synthesis of a series of novel unsymmetrical NHC ligands, functionalised with electron donating substituents, is described. The corresponding neutral iridium NHC/halide complexes were prepared, and the steric and electronic properties of the ligands were investigated using a number of techniques. These novel complexes were then tested in the catalysis of hydrogen borrowing processes. Extensive optimisation led to the development of an efficient method for the room-temperature N-alkylation of anilines. This methodology was also expanded to include the synthesis of N-heterocycles viaintramolecular C-N bond formation, albeit using more forcing conditions. Lastly, a small series of chiral NHC ligands was designed, and their corresponding iridium complexes prepared and used in a preliminary screening of asymmetric hydrogen borrowing.Over the last several decades, the organic chemistry community has become increasingly reliant upon iridium catalysis, with applications reported across a number of research areas. In recent years, the Kerr group has developed a series of iridium complexes, which were found to be excellent catalysts for hydrogen isotope exchange and olefin hydrogenation processes. The work described within this thesis centres upon the expansion of these catalysts' reactivity in hydrogen isotope exchange, as well as the synthesis and application of a series of novel iridium complexes, designed for use in hydrogen borrowing catalysis. Chapter one focuses on the development of three efficient and selective methods for hydrogen isotope exchange. Iridium(I) catalysts previously developed within the group have been employed in the successful deuteration of N-heterocycles, which represent an important and relatively underexplored class of labelling substrates. The labelling of a large range of indole, pyrrole, and quinoline derivatives is reported, in which the regioselectivity can be controlled through careful choice of N-protecting group. Extensive practical and computational mechanistic investigations offered insight into the mechanism of indole C3 labelling, which is believed to proceed via an iridium-indoline intermediate. In chapter two, the design and synthesis of a series of novel unsymmetrical NHC ligands, functionalised with electron donating substituents, is described. The corresponding neutral iridium NHC/halide complexes were prepared, and the steric and electronic properties of the ligands were investigated using a number of techniques. These novel complexes were then tested in the catalysis of hydrogen borrowing processes. Extensive optimisation led to the development of an efficient method for the room-temperature N-alkylation of anilines. This methodology was also expanded to include the synthesis of N-heterocycles viaintramolecular C-N bond formation, albeit using more forcing conditions. Lastly, a small series of chiral NHC ligands was designed, and their corresponding iridium complexes prepared and used in a preliminary screening of asymmetric hydrogen borrowing
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