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Investigating the use of ensemble techniques in predicting object-oriented software maintainability
Get PDFContext: Prediction of the maintainability of classes in object-oriented systems is a significant factor for software success; however, it is a challenging task. Although prior object-oriented software maintainability literature acknowledges the role of machine learning techniques as valuable predictors of potential change, the most suitable technique that consistently achieves high accuracy remains undetermined and there is no clear indication of which techniques are more appropriate.;Objective: This thesis aims to empirically investigate the capability of ensemble models to provide an increased prediction accuracy, compared with individual models, by applying them on several software maintainability datasets using different base models and analysing the impact of parameter tuning.;Method: In the first part of this thesis, a systematic review of studies related to the prediction of the maintainability of object-oriented software systems using machine learning techniques is presented. In the remaining parts of this thesis, three empirical studies were performed to evaluate and compare different homogeneous and heterogeneous ensemble models against sets of individual models for predicting software maintainability of object-oriented systems at the class level. These models were employed on 14 datasets that were extracted from the maintenance of object-oriented software systems.;Results: The systematic literature review determined 56 relevant studies and indicated that the application of ensemble models is relatively rare, thus there is a need to perform studies using these models as well as others to an extensive variety of datasets. The results obtained from three empirical studies indicate that the proposed ensemble models yield improved prediction accuracy over most of the individual models. This improvement was significant only in the third empirical study, along with a few cases in the second empirical study. In most cases, nearest neighbours or support vector regression achieved the best prediction accuracy among individual models; moreover, these models as a base model in bagging and additive regression outperformed other prediction models, along with random forest.;Conclusion: The main finding is that ensemble models are effective for predicting software maintainability and they are more accurate than some individual models; their performance may be improved by using large datasets, or parameter tuning. Also, ensemble models improve the performance of weaker base models.Context: Prediction of the maintainability of classes in object-oriented systems is a significant factor for software success; however, it is a challenging task. Although prior object-oriented software maintainability literature acknowledges the role of machine learning techniques as valuable predictors of potential change, the most suitable technique that consistently achieves high accuracy remains undetermined and there is no clear indication of which techniques are more appropriate.;Objective: This thesis aims to empirically investigate the capability of ensemble models to provide an increased prediction accuracy, compared with individual models, by applying them on several software maintainability datasets using different base models and analysing the impact of parameter tuning.;Method: In the first part of this thesis, a systematic review of studies related to the prediction of the maintainability of object-oriented software systems using machine learning techniques is presented. In the remaining parts of this thesis, three empirical studies were performed to evaluate and compare different homogeneous and heterogeneous ensemble models against sets of individual models for predicting software maintainability of object-oriented systems at the class level. These models were employed on 14 datasets that were extracted from the maintenance of object-oriented software systems.;Results: The systematic literature review determined 56 relevant studies and indicated that the application of ensemble models is relatively rare, thus there is a need to perform studies using these models as well as others to an extensive variety of datasets. The results obtained from three empirical studies indicate that the proposed ensemble models yield improved prediction accuracy over most of the individual models. This improvement was significant only in the third empirical study, along with a few cases in the second empirical study. In most cases, nearest neighbours or support vector regression achieved the best prediction accuracy among individual models; moreover, these models as a base model in bagging and additive regression outperformed other prediction models, along with random forest.;Conclusion: The main finding is that ensemble models are effective for predicting software maintainability and they are more accurate than some individual models; their performance may be improved by using large datasets, or parameter tuning. Also, ensemble models improve the performance of weaker base models
Investigation of the effects of colloidal suspension properties on spatially resolved diffuse reflectance
Get PDFMany quality attributes of pharmaceutical suspensions are directly influenced by the physical properties of constituting particles. The influence has not been explored fully as the chemical characteristics (composition/concentration) are of primary concern. Particle size distribution provides with detailed characteristics of the material population, however, it is a challenging parameter to monitor during the process, due to limitations of the available analytical techniques.;In this thesis, amethodology which analyses particle size distribution and concentration using the optical scattering properties extracted from a novel spatially and angularly resolved diffuse reflectance measurement (SAR-DRM) is proposed. This approach incorporates Mie theory and particle size distribution function, followed by Farrell's diffuse approximation to model specified reflectance signal. The developed methodology does not require a calibration model and was used to investigate three main objectives. Firstly, the sensitivity of the simulated SAR-DRM to the mode radius, distribution width and concentration of solids variations is explored.;An inversion algorithm for the measured SAR-DRM is proposed and studied on polystyrene suspensions sample sets. Lastly, the methodology is then expanded to incorporate the particle shape parameter in the form of aspect ratio. Tomy knowledge, this study is a unique attempt to directly invert SAR-DRM to obtain the particle size distribution and concentration parameters from modelled and experimental measurements as well as the first study of particle shape effect on SAR-DRM.;The simultaneous inversion of all three parameters of interest produced results comparable with reference measurements. The study provides a set of method limitations that when considered allow the optimal estimation of the parameters of interest. The results produced by the methodology developed and presented throughout this thesis suggest the great potential of using the methodology as a calibration-free tool for robust and reliable in-process analysis of pharmaceutical suspensions.Many quality attributes of pharmaceutical suspensions are directly influenced by the physical properties of constituting particles. The influence has not been explored fully as the chemical characteristics (composition/concentration) are of primary concern. Particle size distribution provides with detailed characteristics of the material population, however, it is a challenging parameter to monitor during the process, due to limitations of the available analytical techniques.;In this thesis, amethodology which analyses particle size distribution and concentration using the optical scattering properties extracted from a novel spatially and angularly resolved diffuse reflectance measurement (SAR-DRM) is proposed. This approach incorporates Mie theory and particle size distribution function, followed by Farrell's diffuse approximation to model specified reflectance signal. The developed methodology does not require a calibration model and was used to investigate three main objectives. Firstly, the sensitivity of the simulated SAR-DRM to the mode radius, distribution width and concentration of solids variations is explored.;An inversion algorithm for the measured SAR-DRM is proposed and studied on polystyrene suspensions sample sets. Lastly, the methodology is then expanded to incorporate the particle shape parameter in the form of aspect ratio. Tomy knowledge, this study is a unique attempt to directly invert SAR-DRM to obtain the particle size distribution and concentration parameters from modelled and experimental measurements as well as the first study of particle shape effect on SAR-DRM.;The simultaneous inversion of all three parameters of interest produced results comparable with reference measurements. The study provides a set of method limitations that when considered allow the optimal estimation of the parameters of interest. The results produced by the methodology developed and presented throughout this thesis suggest the great potential of using the methodology as a calibration-free tool for robust and reliable in-process analysis of pharmaceutical suspensions
A study of the toxicological properties of propolis samples from Europe and Saudi Arabia and of their biological activity against protozoa
Get PDFPropolis is a natural product collected by bees from plants to seal their hives for defence against external contamination, and a range of microorganisms and parasites including the protozoal species Crithidia. Propolis has been used as a folk medicine due to its therapeutic properties; thus, it is more likely that active components would be found in propolis rather than from random screening of plants. Ethanolic extracts of four samples from the UK (S224, S225, D6, D7), one from Poland (P) and two from Saudi Arabia (SB, T2) were profiled by high-resolution LC-MS and tested against a wide range of microorganisms including T. brucei, L. mexicana, C. fasiculata, S. aureus. Additionally, cell-based assays for cytotoxicity activities were evaluated. Several compounds were isolated, which are related to the three groups: flavonoids, phenylpropanoids and triterpenes.;In total fifteen isolated compounds were obtained as follows: twelve from the UK samples most of which were flavonoids including 3-Acetoxypinobanksin (1), 7-Methoxychrysin (2), Kaempferol (3), Pinocembrin (4), 4'-Methoxykaempferol (5), Galangin (6), Chrysin (7), Apigenin (8), Pinostrobin (9), Cinnamic acid (10), Coumaric acid cinnamyl ester (11a) and Coumaric acid benzylester (11b). Two compounds were isolated from Polish propolis namely 4', 7-Dimethoxykaempferol (12) and Naringenin 4', 7-dimethyl ether (13), and three compounds from a Saudi propolis sample: Hesperetin-7-methyl ether (14a), Sakuranetin (14b) and Lupeol (15). Both the crude extracts and isolated compounds displayed variable activity against the range of microorganisms which were tested against including S. aureus, T. brucei, C. fasiculata, T. congolense and L. mexicana. [For references see main thesis]Propolis is a natural product collected by bees from plants to seal their hives for defence against external contamination, and a range of microorganisms and parasites including the protozoal species Crithidia. Propolis has been used as a folk medicine due to its therapeutic properties; thus, it is more likely that active components would be found in propolis rather than from random screening of plants. Ethanolic extracts of four samples from the UK (S224, S225, D6, D7), one from Poland (P) and two from Saudi Arabia (SB, T2) were profiled by high-resolution LC-MS and tested against a wide range of microorganisms including T. brucei, L. mexicana, C. fasiculata, S. aureus. Additionally, cell-based assays for cytotoxicity activities were evaluated. Several compounds were isolated, which are related to the three groups: flavonoids, phenylpropanoids and triterpenes.;In total fifteen isolated compounds were obtained as follows: twelve from the UK samples most of which were flavonoids including 3-Acetoxypinobanksin (1), 7-Methoxychrysin (2), Kaempferol (3), Pinocembrin (4), 4'-Methoxykaempferol (5), Galangin (6), Chrysin (7), Apigenin (8), Pinostrobin (9), Cinnamic acid (10), Coumaric acid cinnamyl ester (11a) and Coumaric acid benzylester (11b). Two compounds were isolated from Polish propolis namely 4', 7-Dimethoxykaempferol (12) and Naringenin 4', 7-dimethyl ether (13), and three compounds from a Saudi propolis sample: Hesperetin-7-methyl ether (14a), Sakuranetin (14b) and Lupeol (15). Both the crude extracts and isolated compounds displayed variable activity against the range of microorganisms which were tested against including S. aureus, T. brucei, C. fasiculata, T. congolense and L. mexicana. [For references see main thesis
A tuneable quantum gas for matter wave interferometry and soliton experiments
No full textThe thesis reports on two strands of experiments in which we employ Bose-Einstein condensates of caesium atoms. Caesium provides favourable scattering properties due to a rich spectrum of magnetic Feshbach resonances at low fields. In particular, we take advantage of the tunability of the interaction strength to implement experiments to study matter-wave interferometry and solitons.;In a first series of experiments, we employ a magnetic levitation scheme and the tunability of caesium BEC to measure micro-g accelerations by using atomic interferometry, demonstrating free-evolution times of 1 s. We analyse the intrinsic effects of the curvature of our force field due to the magnetic levitation, and we observe the effects of a phase-shifting element in the interferometer paths.;In the second series of experiments, we exploit the tunability of our Bose-Einstein condensate to generate bright matter-wave solitons in quasi-1D geometry.We study the fundamental breathing mode frequency of a single matter-wave soliton by measuring its oscillation frequency as a function of the atom number and confinement strength and we observe signatures of the creation of secondorder solitons.;Aside from introducing some general concepts of ultra-cold atomic collisions and BECs, I also present a brief overview of the experimental apparatus. This includes details of the vacuum setup, laser cooling, magnetic field coils and diagnostic procedures, and sequence for generating BECs of caesium atoms.The thesis reports on two strands of experiments in which we employ Bose-Einstein condensates of caesium atoms. Caesium provides favourable scattering properties due to a rich spectrum of magnetic Feshbach resonances at low fields. In particular, we take advantage of the tunability of the interaction strength to implement experiments to study matter-wave interferometry and solitons.;In a first series of experiments, we employ a magnetic levitation scheme and the tunability of caesium BEC to measure micro-g accelerations by using atomic interferometry, demonstrating free-evolution times of 1 s. We analyse the intrinsic effects of the curvature of our force field due to the magnetic levitation, and we observe the effects of a phase-shifting element in the interferometer paths.;In the second series of experiments, we exploit the tunability of our Bose-Einstein condensate to generate bright matter-wave solitons in quasi-1D geometry.We study the fundamental breathing mode frequency of a single matter-wave soliton by measuring its oscillation frequency as a function of the atom number and confinement strength and we observe signatures of the creation of secondorder solitons.;Aside from introducing some general concepts of ultra-cold atomic collisions and BECs, I also present a brief overview of the experimental apparatus. This includes details of the vacuum setup, laser cooling, magnetic field coils and diagnostic procedures, and sequence for generating BECs of caesium atoms
Identification and study of the physico-chemical changes during dissolution in simulated intestinal fluids using novel techniques
Get PDFThe oral route is the preferred option for drug administration but contains the inherent issue of drug absorption from the gastro-intestinal tract (GIT) in order to elicit systemic activity. A pre-requisite for absorption is drug dissolution, which is dependent upon drug solubility and the variable milieu of GIT fluid, with poorly soluble drugs presenting a formulation and biopharmaceutical challenge. Multiple factors within GIT fluid influence solubility ranging from pH to the concentration and ratio of amphiphilic substances such as phospholipid, bile salt, monoglyceride and cholesterol.;To aid in vitro investigation, simulated intestinal fluids (SIF) covering the fasted and fed state have been developed. SIF media is complex and statistical design of experiment (DoE) investigations have revealed the range of solubility values possible within each state due to physiological variability along with the media factors and factor interactions which influence solubility. In this research a dual level, reduced experimental number (20) DoE providing three arms covering the fasted and fed states along with a combined analysis has been investigated.;The results indicate that this small scale investigation is feasible and provides solubility ranges that encompass published data in human, simulated fasted and fed fluids and published DoE results. The study also correctly identifies the major single factor or factor interactions which influence solubility but it is evident that lower significance factors are not picked up due to the lower sample number.;Moreover, several approaches were made to modify drug formulation in an aim to enhance drug solubility and dissolution including sloid dispersion and the usage of excipients. In this work, examining the effect of six representative types of excipients on solubility were examined using the design of experiment. The results indicated specific drug- excipient behavior and that each excipient will have different effect on drug solubility. Smaller molecular weight or lower concentration of excipients as mannitol for example, had no impact on solubility and or dissolution.;On the other hand, higher molecular weight and higher concentration of the excipient like chitosan for example, significantly reduced drug solubility. The results also indicated that the effect of the excipient on solubility will be dependent on the type of excipient under investigation, the concentration of the used excipient and on the media state (fasted or fed) under examination. This outcome improved the feasibility of the design to be used as a prognostic tool to examine the effect of excipients on solubility.;Finally, dissolution testing of carvedilol in presence of excipients were carried out. The results indicated that carvedilol dissolution rate were not affected in presence of lower molecular weight excipients as mannitol for example but it significantly reduced in the presence of higher molecular weight excipients as chitosan for example. Moreover, this influence of the excipient on drug dissolution were found to be due to the interaction between the excipient with the different media components and or with the drug. The results also showed that dissolution testing correlate well with the equilibrium solubility testing where, excipients that found to affect solubility showed to affect dissolution also.;These studies illustrate that these approaches therefore represent a useful initial screening tool that can guide further in depth analysis of a drug's behavior in gastrointestinal fluids and in the presence of excipients. The outputs can potentially be applied in drug formulation testing for improved bioavailability.The oral route is the preferred option for drug administration but contains the inherent issue of drug absorption from the gastro-intestinal tract (GIT) in order to elicit systemic activity. A pre-requisite for absorption is drug dissolution, which is dependent upon drug solubility and the variable milieu of GIT fluid, with poorly soluble drugs presenting a formulation and biopharmaceutical challenge. Multiple factors within GIT fluid influence solubility ranging from pH to the concentration and ratio of amphiphilic substances such as phospholipid, bile salt, monoglyceride and cholesterol.;To aid in vitro investigation, simulated intestinal fluids (SIF) covering the fasted and fed state have been developed. SIF media is complex and statistical design of experiment (DoE) investigations have revealed the range of solubility values possible within each state due to physiological variability along with the media factors and factor interactions which influence solubility. In this research a dual level, reduced experimental number (20) DoE providing three arms covering the fasted and fed states along with a combined analysis has been investigated.;The results indicate that this small scale investigation is feasible and provides solubility ranges that encompass published data in human, simulated fasted and fed fluids and published DoE results. The study also correctly identifies the major single factor or factor interactions which influence solubility but it is evident that lower significance factors are not picked up due to the lower sample number.;Moreover, several approaches were made to modify drug formulation in an aim to enhance drug solubility and dissolution including sloid dispersion and the usage of excipients. In this work, examining the effect of six representative types of excipients on solubility were examined using the design of experiment. The results indicated specific drug- excipient behavior and that each excipient will have different effect on drug solubility. Smaller molecular weight or lower concentration of excipients as mannitol for example, had no impact on solubility and or dissolution.;On the other hand, higher molecular weight and higher concentration of the excipient like chitosan for example, significantly reduced drug solubility. The results also indicated that the effect of the excipient on solubility will be dependent on the type of excipient under investigation, the concentration of the used excipient and on the media state (fasted or fed) under examination. This outcome improved the feasibility of the design to be used as a prognostic tool to examine the effect of excipients on solubility.;Finally, dissolution testing of carvedilol in presence of excipients were carried out. The results indicated that carvedilol dissolution rate were not affected in presence of lower molecular weight excipients as mannitol for example but it significantly reduced in the presence of higher molecular weight excipients as chitosan for example. Moreover, this influence of the excipient on drug dissolution were found to be due to the interaction between the excipient with the different media components and or with the drug. The results also showed that dissolution testing correlate well with the equilibrium solubility testing where, excipients that found to affect solubility showed to affect dissolution also.;These studies illustrate that these approaches therefore represent a useful initial screening tool that can guide further in depth analysis of a drug's behavior in gastrointestinal fluids and in the presence of excipients. The outputs can potentially be applied in drug formulation testing for improved bioavailability
Ownership characteristics and earnings quality : the moderating effect of institutional settings
Get PDFThis thesis was previously held under moratorium between 1 July 2020 and 1 July 2025.Ongoing debate within the corporate governance literature is inconclusive on the impact of ownership characteristics on earnings quality. The ambiguity of findings has been widely attributed to differences in institutional settings and across different
national regimes. This thesis is concerned, therefore, with how institutional settings in a number of different countries modify the link between ownership characteristics and earnings quality. It focuses on the importance of the country-level institutional context
and the extent of interplay between governance mechanisms, both within firms and between countries. Extant studies of this nature are scant and unsatisfactory, providing a research gap that this thesis aims to fill. Such evidence is helpful to regulators in designing governance regulations which help to improve the quality of financial information. By specifying and applying a contingency model, using moderating regressions, this research aims to advance, through empirical research, our understanding of how
governance mechanisms within firms and countries impact on earnings quality. It advances the literature by using both accruals and real earnings management as proxies for earnings quality, showing how the differences between them enhance, or limit, governance mechanisms. Baseline regression models are estimated at the firm level, and are used to test the direct effect of ownership characteristics on accruals and real earnings management. The work provides a quantitative analysis of panel data from 2013-2017 utilising the most recent data available at the inception of the research upon which this thesis depends. It examines secondary-source data, newly compiled from a combination of the OSIRIS and Datastream databases, from Hong Kong, Indonesia, South Korea, Malaysia, the Philippines, Singapore, Thailand, Taiwan, the United Kingdom, and the United States, thus enabling novel analysis, within and across countries, of the impact of ownership on earnings quality. Using these data, the baseline model reveals that the incentivised behaviour of owners
towards accruals and real earnings management depends upon their self-interest. This confirms predictions of agency theory, implying that alternative techniques of earnings management are likely to be used strategically, depending on the ownership characteristics of firms. Further, the results show that the same set of governance mechanisms may not limit all techniques of earnings management. Importantly, the moderating effects of country-level institutional attributes alter the earnings management incentives of owners. The results confirm institutional theory, that country-level contextual factors influence the behaviour of individuals. Further, they shed new light on the interplay effect between ownership characteristics and country level institutional settings. This research develops the governance literature, in showing how governance mechanisms within firms and countries work as an intertwined system in reality. Such findings should be of benefit to regulators in
governance design.Ongoing debate within the corporate governance literature is inconclusive on the impact of ownership characteristics on earnings quality. The ambiguity of findings has been widely attributed to differences in institutional settings and across different
national regimes. This thesis is concerned, therefore, with how institutional settings in a number of different countries modify the link between ownership characteristics and earnings quality. It focuses on the importance of the country-level institutional context
and the extent of interplay between governance mechanisms, both within firms and between countries. Extant studies of this nature are scant and unsatisfactory, providing a research gap that this thesis aims to fill. Such evidence is helpful to regulators in designing governance regulations which help to improve the quality of financial information. By specifying and applying a contingency model, using moderating regressions, this research aims to advance, through empirical research, our understanding of how
governance mechanisms within firms and countries impact on earnings quality. It advances the literature by using both accruals and real earnings management as proxies for earnings quality, showing how the differences between them enhance, or limit, governance mechanisms. Baseline regression models are estimated at the firm level, and are used to test the direct effect of ownership characteristics on accruals and real earnings management. The work provides a quantitative analysis of panel data from 2013-2017 utilising the most recent data available at the inception of the research upon which this thesis depends. It examines secondary-source data, newly compiled from a combination of the OSIRIS and Datastream databases, from Hong Kong, Indonesia, South Korea, Malaysia, the Philippines, Singapore, Thailand, Taiwan, the United Kingdom, and the United States, thus enabling novel analysis, within and across countries, of the impact of ownership on earnings quality. Using these data, the baseline model reveals that the incentivised behaviour of owners
towards accruals and real earnings management depends upon their self-interest. This confirms predictions of agency theory, implying that alternative techniques of earnings management are likely to be used strategically, depending on the ownership characteristics of firms. Further, the results show that the same set of governance mechanisms may not limit all techniques of earnings management. Importantly, the moderating effects of country-level institutional attributes alter the earnings management incentives of owners. The results confirm institutional theory, that country-level contextual factors influence the behaviour of individuals. Further, they shed new light on the interplay effect between ownership characteristics and country level institutional settings. This research develops the governance literature, in showing how governance mechanisms within firms and countries work as an intertwined system in reality. Such findings should be of benefit to regulators in
governance design
The effects of hyperglycaemia on neuronal mitochondria
No full textNeurons depend on mitochondria more than any other cell type for their growth and survival. Mitochondria are known as the main powerhouse of the cell because of their important metabolic functions. Through the processes of the electron transport chain (ETC) and oxidative phosphorylation, mitochondria convert pyruvate into adenosine triphosphate(ATP), a primary energy carrier. Mitochondria play an essential role in providing cellular energy by manufacturing ATP, buffering calcium and partaking in metabolic pathways. We hypothesised that high extracellular glucose concentration inhibits mitochondrial motility inmature primary hippocampal neurons. We did primary hippocampal cell culture, imaging and image analysis with KymoAnalyzer software to evaluate the proposed hypothesis. Neuronal cells were grown in high glucose (25 mM) or low glucose (1 mM) concentration and analysed for various parameters of mitochondrial characteristics.;When mitochondria are exposed to various concentrations of glucose, it provides more insights about their normal functions and mechanism in the cells and how dysfunction of mitochondria leads to neuron death and degeneration. Importantly, our results demonstrated that the fraction of stationary mitochondria increased and the fraction of mitochondria travelling uni-directionally either anterograde or retrograde decreased. Our study also revealed that the density of mitochondria travelling retrograde or reversing decreased and the density of stationary mitochondria increased in high glucose compared to lower glucose media. That means there was significantly difference between the parameters analysed in 25 mM and 1 mM glucose. Our findings suggest that mature primary hippocampal neurons cultured in hyperglycemic condition (25 mM) for acute period does affect mitochondrial transport.Neurons depend on mitochondria more than any other cell type for their growth and survival. Mitochondria are known as the main powerhouse of the cell because of their important metabolic functions. Through the processes of the electron transport chain (ETC) and oxidative phosphorylation, mitochondria convert pyruvate into adenosine triphosphate(ATP), a primary energy carrier. Mitochondria play an essential role in providing cellular energy by manufacturing ATP, buffering calcium and partaking in metabolic pathways. We hypothesised that high extracellular glucose concentration inhibits mitochondrial motility inmature primary hippocampal neurons. We did primary hippocampal cell culture, imaging and image analysis with KymoAnalyzer software to evaluate the proposed hypothesis. Neuronal cells were grown in high glucose (25 mM) or low glucose (1 mM) concentration and analysed for various parameters of mitochondrial characteristics.;When mitochondria are exposed to various concentrations of glucose, it provides more insights about their normal functions and mechanism in the cells and how dysfunction of mitochondria leads to neuron death and degeneration. Importantly, our results demonstrated that the fraction of stationary mitochondria increased and the fraction of mitochondria travelling uni-directionally either anterograde or retrograde decreased. Our study also revealed that the density of mitochondria travelling retrograde or reversing decreased and the density of stationary mitochondria increased in high glucose compared to lower glucose media. That means there was significantly difference between the parameters analysed in 25 mM and 1 mM glucose. Our findings suggest that mature primary hippocampal neurons cultured in hyperglycemic condition (25 mM) for acute period does affect mitochondrial transport
Modelling the thermal potential and operation of salinity gradient solar ponds
No full textAccess to freshwater is crucial for socio-economic development. In Libya, the demand for freshwater is soaring, but the supply is limited. Freshwater is intrinsically linked to energy where the paramount consideration for its sustainability is the amount of energy required to guarantee sufficient supplies of freshwater through seawater-desalination. This emphasises two paramount needs that should be promptly sought as a national priority, first stringent water conservation, and second the employment of sustainable energy sources to power desalination. Salinity Gradient Solar Pond (SGSP) can be one of a mix of technologies leading to a future based on sustainable energy. This study models the potential and operation of SGSPs as a source of thermal energy in Libya. The study makes an original contribution to knowledge by explaining the essence (when, how,and where) of the SGSP operational instability. It also investigates the optimum zone thicknesses ratio of the three different salinity zones constituting the SGSP; Upper Convective Zone (UCZ), middle Non-Convective Zone (NCZ), and Lower Convective Zone (LCZ) while implementing the double-diffusive convection (DDC) phenomenon. One-dimensional and two-dimensional numerical studies are conducted. The results indicate that SGSP has the potential to provide hot saline-water at a temperature exceeding 70°C for multi-effect desalination thermal vapour compression units which require a minimum top brine temperature of 60 - 65°C. At a SGSP thermal output of 55 W m⁻², 46.8 m² of land is required for the production of 1 m³ per day of distillate. The two-dimensional study explains the nature of the operational instability where the occurrence and expansion of convective cells at the interfaces of the NCZ due to DDC leads to instability. This study also gathered evidence on the effect of buoyancy ratio. Salt concentration differences separating the UCZ and the LCZ should be sustained at 300 kg m⁻³ to maintain stability. The optimum zone thicknesses for an average SGSP of 2 m height are 0.4, 1.2, and 0.4 meters for the UCZ, the NCZ, and the LCZ, respectively.Access to freshwater is crucial for socio-economic development. In Libya, the demand for freshwater is soaring, but the supply is limited. Freshwater is intrinsically linked to energy where the paramount consideration for its sustainability is the amount of energy required to guarantee sufficient supplies of freshwater through seawater-desalination. This emphasises two paramount needs that should be promptly sought as a national priority, first stringent water conservation, and second the employment of sustainable energy sources to power desalination. Salinity Gradient Solar Pond (SGSP) can be one of a mix of technologies leading to a future based on sustainable energy. This study models the potential and operation of SGSPs as a source of thermal energy in Libya. The study makes an original contribution to knowledge by explaining the essence (when, how,and where) of the SGSP operational instability. It also investigates the optimum zone thicknesses ratio of the three different salinity zones constituting the SGSP; Upper Convective Zone (UCZ), middle Non-Convective Zone (NCZ), and Lower Convective Zone (LCZ) while implementing the double-diffusive convection (DDC) phenomenon. One-dimensional and two-dimensional numerical studies are conducted. The results indicate that SGSP has the potential to provide hot saline-water at a temperature exceeding 70°C for multi-effect desalination thermal vapour compression units which require a minimum top brine temperature of 60 - 65°C. At a SGSP thermal output of 55 W m⁻², 46.8 m² of land is required for the production of 1 m³ per day of distillate. The two-dimensional study explains the nature of the operational instability where the occurrence and expansion of convective cells at the interfaces of the NCZ due to DDC leads to instability. This study also gathered evidence on the effect of buoyancy ratio. Salt concentration differences separating the UCZ and the LCZ should be sustained at 300 kg m⁻³ to maintain stability. The optimum zone thicknesses for an average SGSP of 2 m height are 0.4, 1.2, and 0.4 meters for the UCZ, the NCZ, and the LCZ, respectively
Assessment of novel measurement technologies for process monitoring and use of chemometric advances to facilitate their application
No full textMid-infrared (MIR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy are common laboratory techniques, but are not so widely used in process analysis. The high attenuation of MIR light inhibits the ability to locate delicate instruments away from harsh processes using long lengths of optical fibre, and the large size and cost of high-field NMR spectrometers prevent them from being easily installed in process plants. Recent advances in technology have led to the availability of miniaturised, robust MIR spectrometers and benchtop NMR spectrometers operating at low field.;The performance of a novel, robust MIR spectrometer, designed for use in process environments, was assessed for the quantitative in situ analysis of liquids and was found to be comparable to a laboratory MIR spectrometer. A reaction was then monitored using the novel spectrometer and accurate predictions of concentration could be obtained by multivariate curve resolution. This demonstrates the suitability of the spectrometer for in situ process monitoring. Calibration transfer between the two MIR spectrometers was also performed, demonstrating the ability to build a model in the laboratory for subsequent application to a process.;The instrumental stability of a low-field NMR spectrometer was evaluated, and when multiple samples were analysed, shifting of peaks and deterioration of lineshape occurred over time. To eliminate peak shift, a range of alignment methods were assessed. Alignment was successful for small peak shifts, but less effective when large peak shifts were present. However accurate predictions of concentration could still be obtained by PLS.;Calibration transfer and reference deconvolution were compared as a solution to lineshape deterioration, and the transfer of PLS models between low-field NMR spectra collected under different conditions was demonstrated. Calibration transfer was found to be more effective overall, and produced accurate predictions of concentration. These results demonstrate the suitability of low-field NMR spectroscopy for quantitative analysis.Mid-infrared (MIR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy are common laboratory techniques, but are not so widely used in process analysis. The high attenuation of MIR light inhibits the ability to locate delicate instruments away from harsh processes using long lengths of optical fibre, and the large size and cost of high-field NMR spectrometers prevent them from being easily installed in process plants. Recent advances in technology have led to the availability of miniaturised, robust MIR spectrometers and benchtop NMR spectrometers operating at low field.;The performance of a novel, robust MIR spectrometer, designed for use in process environments, was assessed for the quantitative in situ analysis of liquids and was found to be comparable to a laboratory MIR spectrometer. A reaction was then monitored using the novel spectrometer and accurate predictions of concentration could be obtained by multivariate curve resolution. This demonstrates the suitability of the spectrometer for in situ process monitoring. Calibration transfer between the two MIR spectrometers was also performed, demonstrating the ability to build a model in the laboratory for subsequent application to a process.;The instrumental stability of a low-field NMR spectrometer was evaluated, and when multiple samples were analysed, shifting of peaks and deterioration of lineshape occurred over time. To eliminate peak shift, a range of alignment methods were assessed. Alignment was successful for small peak shifts, but less effective when large peak shifts were present. However accurate predictions of concentration could still be obtained by PLS.;Calibration transfer and reference deconvolution were compared as a solution to lineshape deterioration, and the transfer of PLS models between low-field NMR spectra collected under different conditions was demonstrated. Calibration transfer was found to be more effective overall, and produced accurate predictions of concentration. These results demonstrate the suitability of low-field NMR spectroscopy for quantitative analysis
Coherent control of Rydberg atoms using sub-kHz linewidth excitation lasers
Get PDFThis thesis presents the development of a new experimental apparatus for neutral atom quantum computing with Rydberg atoms. We describe the construction and characterisation of three continuous wave lasers stabilised simultaneously on a ultrahigh finesse Ultra-low-expansion (ULE) cavity, providing long-term stability and sub-kHz linewidth lasers with a tunable offset-lock frequency as required for high fidelity quantum operations. High-resolution spectroscopy on a cloud of cold Cs atoms was achieved using electromagnetically induced transparency (EIT), in order to calibrate absolute cavity mode frequencies with respect to Rydberg transitions and determine the cavity long-term drift of ~1 Hz/s.;We have demonstrated trapping of single Cs atoms in optical tweezers and developed a high-resolution imaging system capable of sub-µm spatial resolution in the atom plane. Coherent control of atomic qubits has been achieved via fast rotations between long-lived hyperfine ground states as well as coherent Rydberg excitations towards the states 50S1/2, 69S1/2 and 81D5/2. The experiment allows us to control the atoms electric field environment and minimise stray electric fields with ~1 mV/cm sensitivity, in order to keep long ground-Rydberg coherence times.;We have observed Rydberg blockade between two atoms separated by 6 µm for both states 69S1/2 and 81D5/2, showing an almost complete suppression of the doubly excited state probability. The creation of an entangled state is deduced from the √2 collective-enhancement of the Rabi oscillations with respect to the single atom case. Our ability to perform double-atom experiment offers the opportunity to implement a proof of a principle of a cNOT mesoscopic gate based on EIT, using the Rydberg state 81D5/2 for high-fidelity operations.This thesis presents the development of a new experimental apparatus for neutral atom quantum computing with Rydberg atoms. We describe the construction and characterisation of three continuous wave lasers stabilised simultaneously on a ultrahigh finesse Ultra-low-expansion (ULE) cavity, providing long-term stability and sub-kHz linewidth lasers with a tunable offset-lock frequency as required for high fidelity quantum operations. High-resolution spectroscopy on a cloud of cold Cs atoms was achieved using electromagnetically induced transparency (EIT), in order to calibrate absolute cavity mode frequencies with respect to Rydberg transitions and determine the cavity long-term drift of ~1 Hz/s.;We have demonstrated trapping of single Cs atoms in optical tweezers and developed a high-resolution imaging system capable of sub-µm spatial resolution in the atom plane. Coherent control of atomic qubits has been achieved via fast rotations between long-lived hyperfine ground states as well as coherent Rydberg excitations towards the states 50S1/2, 69S1/2 and 81D5/2. The experiment allows us to control the atoms electric field environment and minimise stray electric fields with ~1 mV/cm sensitivity, in order to keep long ground-Rydberg coherence times.;We have observed Rydberg blockade between two atoms separated by 6 µm for both states 69S1/2 and 81D5/2, showing an almost complete suppression of the doubly excited state probability. The creation of an entangled state is deduced from the √2 collective-enhancement of the Rabi oscillations with respect to the single atom case. Our ability to perform double-atom experiment offers the opportunity to implement a proof of a principle of a cNOT mesoscopic gate based on EIT, using the Rydberg state 81D5/2 for high-fidelity operations
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