7103 research outputs found
Sort by
Effect of Crotalus ruber ruber and Agkistrodon piscivorus leucostoma venoms on the dissemination of A2780 ovarian cancer cells in vitro
Get PDFOvarian cancers are the second most common female cancer in the UK. In the majority of patients there are no observable symptoms of ovarian cancer at early stage and no effective screening strategy to detect cancer before metastasis. Moreover, chemo-resistance is another problem which hinders the successful treatment of ovarian cancer. Therefore, discovery of novel anti-ovarian cancer drugs remains critically important. Snake venoms contain different proteins, peptides, enzymes and low molecular weight components that have been investigated for development of new therapies to treat many diseases including cancer. The present study was carried out to evaluate the effect of Crotalus ruber ruber and Agkistrodon piscivorus leucostoma snake venoms both from the Viperidae family on dissemination and processes of metastasis of an ovarian cancer cell line (A2870). The first part of the project involved examination of changes to cell morphology, cytotoxicity, migration, invasion and the effect of the crude venom on levels of the main integrins involved in cell adhesion. Cell morphology differences were observed with both venoms; Crotalus ruber ruber crude venom caused the cells to round up so that they were poorly spread at 1.5 and 3.1μg/ml, while, Agkistrodon piscivorus leucostoma venom caused the cells to detach from the growing surface at 0.7, 1.5, and 3.1μg/ml. An AlamarBlue® Cell Viability Assay and SYTOX®Green (nucleic acid stain) were used to test the viability of the cells following treatment and to demonstrate that the morphological alterations were not due to a cytotoxic effect, but to anti-adhesive activity. Moreover, an integrin-independent substratum (poly-Llysine)was used to determine if the venom is specific for the integrin family of adhesion molecules or not. As a result, the effect of Crotalus ruber ruber venom on adhesion was found to be specific for the integrin family of adhesion receptors, while the effect of Agkistrodon piscivorus leucostoma venom on adhesion was not specific for the integrin family. Both venoms had an inhibitory effect on migration and invasion of the cells by inhibiting α5, β1integrins (fibronectin receptor) for Crotalus ruber ruber venom and α5, β1integrins and αv integrins (fibronectin and vitronectin receptor) for Agkistrodon piscivorus leucostoma venom. The next part of the project was to semi-purify both venoms. This was achieved using gel chromatography to obtain faction 3 (F3) from Crotalus ruber ruber venom and F6 from Agkistrodon piscivorus leucostoma venom. The assays carried out with the crude venoms were repeated using the fractions instead. F3 of Crotalus ruber ruber venom and F6 of Agkistrodon piscivorus leucostoma venom were found to be the fractions that contained components responsible for the activity of the venoms. F3 had an inhibitory effect on the level of expression of α5, β1 integrins while F6 had an inhibitory effect on α5, β1 and on αv integrins. Moreover, it was proposed that F6 had hydrolytic activity against the extracellular matrix. Finally preliminary analysis was carried out on F3 and F6 using SDS-PAGE, Nanoflow HPLC Electrospray Tandem Mass Spectrometry, liquid chromatography mass spectrometry and metalloproteinase inhibitor studies to elucidate the peptides as rubelysin for F3 and leucostoma peptidase A for F6. These results suggest that rubelysin and leucostoma peptidase A have antimetastatic activity against ovarian cancer.Ovarian cancers are the second most common female cancer in the UK. In the majority of patients there are no observable symptoms of ovarian cancer at early stage and no effective screening strategy to detect cancer before metastasis. Moreover, chemo-resistance is another problem which hinders the successful treatment of ovarian cancer. Therefore, discovery of novel anti-ovarian cancer drugs remains critically important. Snake venoms contain different proteins, peptides, enzymes and low molecular weight components that have been investigated for development of new therapies to treat many diseases including cancer. The present study was carried out to evaluate the effect of Crotalus ruber ruber and Agkistrodon piscivorus leucostoma snake venoms both from the Viperidae family on dissemination and processes of metastasis of an ovarian cancer cell line (A2870). The first part of the project involved examination of changes to cell morphology, cytotoxicity, migration, invasion and the effect of the crude venom on levels of the main integrins involved in cell adhesion. Cell morphology differences were observed with both venoms; Crotalus ruber ruber crude venom caused the cells to round up so that they were poorly spread at 1.5 and 3.1μg/ml, while, Agkistrodon piscivorus leucostoma venom caused the cells to detach from the growing surface at 0.7, 1.5, and 3.1μg/ml. An AlamarBlue® Cell Viability Assay and SYTOX®Green (nucleic acid stain) were used to test the viability of the cells following treatment and to demonstrate that the morphological alterations were not due to a cytotoxic effect, but to anti-adhesive activity. Moreover, an integrin-independent substratum (poly-Llysine)was used to determine if the venom is specific for the integrin family of adhesion molecules or not. As a result, the effect of Crotalus ruber ruber venom on adhesion was found to be specific for the integrin family of adhesion receptors, while the effect of Agkistrodon piscivorus leucostoma venom on adhesion was not specific for the integrin family. Both venoms had an inhibitory effect on migration and invasion of the cells by inhibiting α5, β1integrins (fibronectin receptor) for Crotalus ruber ruber venom and α5, β1integrins and αv integrins (fibronectin and vitronectin receptor) for Agkistrodon piscivorus leucostoma venom. The next part of the project was to semi-purify both venoms. This was achieved using gel chromatography to obtain faction 3 (F3) from Crotalus ruber ruber venom and F6 from Agkistrodon piscivorus leucostoma venom. The assays carried out with the crude venoms were repeated using the fractions instead. F3 of Crotalus ruber ruber venom and F6 of Agkistrodon piscivorus leucostoma venom were found to be the fractions that contained components responsible for the activity of the venoms. F3 had an inhibitory effect on the level of expression of α5, β1 integrins while F6 had an inhibitory effect on α5, β1 and on αv integrins. Moreover, it was proposed that F6 had hydrolytic activity against the extracellular matrix. Finally preliminary analysis was carried out on F3 and F6 using SDS-PAGE, Nanoflow HPLC Electrospray Tandem Mass Spectrometry, liquid chromatography mass spectrometry and metalloproteinase inhibitor studies to elucidate the peptides as rubelysin for F3 and leucostoma peptidase A for F6. These results suggest that rubelysin and leucostoma peptidase A have antimetastatic activity against ovarian cancer
Optimisation of ozone generation using dielectric barrier discharge
Get PDFThe aims of the research include understanding the fundamental kinetics of ozone generation using dielectric barrier discharge and investigating the potential to optimize the process to improve ozone generation efficiency.The kinetics of ozone generation and its limitations are reviewed. The discharge characteristics of single filaments are investigated by analysing its equivalent circuit and the distribution of current magnitude. The parallel-plane electrode is used for the investigation of the relationship between current distribution, reduced electric field and ozone generation efficiency. The maximum ozone efficiency of the experiment is 207 g/kWh at the reduced electric field of 120 Td. With the increase of reduced electric field from 120 Td to 280 Td, the ozone generation efficiency drops to 109 g/kWh. The meshed electrode configuration was employed to optimize the ozone efficiency. The highest ozone efficiency achieved is over 330 g/kWh at ~ 100 Td which is twice higher than the commercial ozone generator. It is found that the distribution of external current amplitude using meshed electrode is narrower compared to planar plates. To further understand ozone generation kinetics, the gas discharge is generated at cryogenic temperature of -183 °C using liquid oxygen. The liquid ozone is produced and the highest ozone efficiency achieved is ~ 460 g/kWh. The ozone dissociation reactions involving atomic oxygen and free electrons and the humidity effect at cryogenic temperature of -183 °C were effectively limited.The aims of the research include understanding the fundamental kinetics of ozone generation using dielectric barrier discharge and investigating the potential to optimize the process to improve ozone generation efficiency.The kinetics of ozone generation and its limitations are reviewed. The discharge characteristics of single filaments are investigated by analysing its equivalent circuit and the distribution of current magnitude. The parallel-plane electrode is used for the investigation of the relationship between current distribution, reduced electric field and ozone generation efficiency. The maximum ozone efficiency of the experiment is 207 g/kWh at the reduced electric field of 120 Td. With the increase of reduced electric field from 120 Td to 280 Td, the ozone generation efficiency drops to 109 g/kWh. The meshed electrode configuration was employed to optimize the ozone efficiency. The highest ozone efficiency achieved is over 330 g/kWh at ~ 100 Td which is twice higher than the commercial ozone generator. It is found that the distribution of external current amplitude using meshed electrode is narrower compared to planar plates. To further understand ozone generation kinetics, the gas discharge is generated at cryogenic temperature of -183 °C using liquid oxygen. The liquid ozone is produced and the highest ozone efficiency achieved is ~ 460 g/kWh. The ozone dissociation reactions involving atomic oxygen and free electrons and the humidity effect at cryogenic temperature of -183 °C were effectively limited
Examination of IKKα inhibitors as novel anti-panceatic cancer drugs
Get PDFPancreatic cancer has a very poor prognosis, it is the fourth most common cancer worldwide in terms of mortality, and it is expected to be the second most common within a decade. Most patients with pancreatic cancer are either resistante [sic] to chemotherapy or become so, thus surgery is the only choice with a considerable chance of tumour re-growth. Therefore an alternative treatment is urgently sought. The Nuclear Factor Kappa B (NFkB) cascade is comprised of two interdependent pathways, recognized as the classical pathway or canonical NFkB pathway, which is IKKB dependent, and IKKα-dependent non-canonical or alternative NFkB pathway. Studies have linked the hyper-activation of both pathways to pancreatic tumorigenesis. IKKβ inhibitors as a class of potential drugs for anti-cancer treatment have been accompanied by a number of issues regarding toxicity. IKKα has been implicated in a number of biological processes including cancer development, therefore targeting IKKα is a new approach for the development of pancreatic cancer therapies and is examined in this thesis. In chapter three, both NFkB pathways were characterised using different agonists; LTα1β2, TNFα and FCS. LTα1β2 stimulated the IKKα -dependent non-canonical pathway, inducing phosphorylation of p100 after 4h stimulation, while the maximum activation of p52 formation was between 24 and 48h. TNFα and FCS were without effect. TNFα and LTα1β2 stimulated the canonical NFkB pathway and taken together these studies indicated the presence of a functional non-canonical pathway. In chapter four, a number of novel IKKα inhibitors generated in-house, were also examined against both the non-canonical and canonical NFkB pathways. Three different effects were observed; selective inhibition of IKKα by SU1261, SU1411, SU1349, SU1433, SU1438 and 1434. Inhibition of both IKKα and IKKβ by (SU1087, SU1432, SU1499 and SU1436) and no inhibition of either pathway (SU1392). The effect of selective IKKα inhibitors on cell cycle and growth were also examined and confirmed that IKKα has a role in proliferation of pancreatic cancer cells. In chapter five, the expression of IKKα- dependent target genes was investigated using the agonist that activates the IKKα-dependent non-canonical NFkB pathway, LTα1β2. The findings confirmed that the expression of genes (BBC3, EZH2, TNFAIP3, VCAM, MAP3K14 and SERPINB6) was likely to be regulated through this pathway. This was confirmed using IKKα selective inhibitors, which resulted in the expression of all gene subsets were reduced [sic]. Taken together these data indicate that IKKα plays a key role in the regulation of the non-canonical NFkB pathway in pancreatic cancer cells and that selective inhibition IKKα may be a new strategy for developing anti-cancer drugs.Pancreatic cancer has a very poor prognosis, it is the fourth most common cancer worldwide in terms of mortality, and it is expected to be the second most common within a decade. Most patients with pancreatic cancer are either resistante [sic] to chemotherapy or become so, thus surgery is the only choice with a considerable chance of tumour re-growth. Therefore an alternative treatment is urgently sought. The Nuclear Factor Kappa B (NFkB) cascade is comprised of two interdependent pathways, recognized as the classical pathway or canonical NFkB pathway, which is IKKB dependent, and IKKα-dependent non-canonical or alternative NFkB pathway. Studies have linked the hyper-activation of both pathways to pancreatic tumorigenesis. IKKβ inhibitors as a class of potential drugs for anti-cancer treatment have been accompanied by a number of issues regarding toxicity. IKKα has been implicated in a number of biological processes including cancer development, therefore targeting IKKα is a new approach for the development of pancreatic cancer therapies and is examined in this thesis. In chapter three, both NFkB pathways were characterised using different agonists; LTα1β2, TNFα and FCS. LTα1β2 stimulated the IKKα -dependent non-canonical pathway, inducing phosphorylation of p100 after 4h stimulation, while the maximum activation of p52 formation was between 24 and 48h. TNFα and FCS were without effect. TNFα and LTα1β2 stimulated the canonical NFkB pathway and taken together these studies indicated the presence of a functional non-canonical pathway. In chapter four, a number of novel IKKα inhibitors generated in-house, were also examined against both the non-canonical and canonical NFkB pathways. Three different effects were observed; selective inhibition of IKKα by SU1261, SU1411, SU1349, SU1433, SU1438 and 1434. Inhibition of both IKKα and IKKβ by (SU1087, SU1432, SU1499 and SU1436) and no inhibition of either pathway (SU1392). The effect of selective IKKα inhibitors on cell cycle and growth were also examined and confirmed that IKKα has a role in proliferation of pancreatic cancer cells. In chapter five, the expression of IKKα- dependent target genes was investigated using the agonist that activates the IKKα-dependent non-canonical NFkB pathway, LTα1β2. The findings confirmed that the expression of genes (BBC3, EZH2, TNFAIP3, VCAM, MAP3K14 and SERPINB6) was likely to be regulated through this pathway. This was confirmed using IKKα selective inhibitors, which resulted in the expression of all gene subsets were reduced [sic]. Taken together these data indicate that IKKα plays a key role in the regulation of the non-canonical NFkB pathway in pancreatic cancer cells and that selective inhibition IKKα may be a new strategy for developing anti-cancer drugs
Communications for CubeSat networks and fractionalised spacecraft
Get PDFThe use of low-cost CubeSats in the context of satellite formation flying appears favourable due to their small size, relatively low launch cost, short development cycle and utilisation of commercial off the shelf components. However, the task of managing complex formations using a large number of satellites in Earth orbit is not a trivial one, and is further exacerbated by low-power and processing constraints in CubeSats. With this in mind, a Field Programmable Gate Array (FPGA) based system has been developed to provide next generation on-board computing capability.;The features and functionality provided by this on-board computer, as well as the steps taken to ensure reliability, including design processes and mitigation techniques are presented in this work and compared to state of the art technology.Coupling reliable formation flying capabilities with the possibility of producing complex patterns using spacecraft will enable the potential of grouping a number of antenna elements into a cooperative structure. The key point in the exploitation of formation flying techniques for the deployment of an antenna array is that the performance of a homogeneous pattern of array elements can be matched or surpassed by fractal geometries.;This thesis analyses the Purina fractal array when utilised for beamforming. A new metric termed power concentration is introduced, which assesses the power dissipated within a cone aligned with the array's look direction, i.e. an assessment how much of the radiated power will reach a specific foot print. Using this metric the performance for beamformers of varying complexity can be compared, independent of the number of sensor elements used to form the array and across a range of frequencies. Furthermore the robustness of the array with respect to element displacement and failure is investigated.;The fractionated nature of such a satellite network and the low-power nature of the nodes motivates distributed processing when using such an array as a beamformer. By mirroring the fractal structure in the processing architecture, the proposed idea demonstrates that benefits such as strictly limited local processing capability independent of the array's dimension and local calibration can be bought at the expense of a slightly increased overall cost.The use of low-cost CubeSats in the context of satellite formation flying appears favourable due to their small size, relatively low launch cost, short development cycle and utilisation of commercial off the shelf components. However, the task of managing complex formations using a large number of satellites in Earth orbit is not a trivial one, and is further exacerbated by low-power and processing constraints in CubeSats. With this in mind, a Field Programmable Gate Array (FPGA) based system has been developed to provide next generation on-board computing capability.;The features and functionality provided by this on-board computer, as well as the steps taken to ensure reliability, including design processes and mitigation techniques are presented in this work and compared to state of the art technology.Coupling reliable formation flying capabilities with the possibility of producing complex patterns using spacecraft will enable the potential of grouping a number of antenna elements into a cooperative structure. The key point in the exploitation of formation flying techniques for the deployment of an antenna array is that the performance of a homogeneous pattern of array elements can be matched or surpassed by fractal geometries.;This thesis analyses the Purina fractal array when utilised for beamforming. A new metric termed power concentration is introduced, which assesses the power dissipated within a cone aligned with the array's look direction, i.e. an assessment how much of the radiated power will reach a specific foot print. Using this metric the performance for beamformers of varying complexity can be compared, independent of the number of sensor elements used to form the array and across a range of frequencies. Furthermore the robustness of the array with respect to element displacement and failure is investigated.;The fractionated nature of such a satellite network and the low-power nature of the nodes motivates distributed processing when using such an array as a beamformer. By mirroring the fractal structure in the processing architecture, the proposed idea demonstrates that benefits such as strictly limited local processing capability independent of the array's dimension and local calibration can be bought at the expense of a slightly increased overall cost
The effects of snake venoms as cytotoxins on selected prostate cancer cell lines
Get PDFCancer is expected to claim 9 million deaths world-wide by the year 2020. Although there has been an increase in the sophistication of current therapeutic strategies, 40% of patients are still likely to die from the disease. Novel anticancer compounds are needed. Snake venoms may represent a relevant pool for selecting candidates that may have anticancer properties. Snake venoms are complex mixtures of unexplored sources of molecules with potential use in biomedical research and drug development. Some venom molecules are of low molecular weight and might trigger anticancer responses and could have potential therapeutic applications. In this study, selected snake venoms obtained from Naja pallida, Agkistrodon piscivorus conanti and Agkistrodon contortrix laticinctus were evaluated for cytotoxicity and selectivity in vitro against a panel of prostate cancer cell lines (DU145, PC3, LNCaP) and a non-malignant prostate epithelial cell line (PNT2A). The cytotoxicity activity of each venom was initially assessed using the SYTOX Green assay. SYTOX Green is a fluorescent nucleic acid indicator dye that can be used as a marker for cell death. The whole venoms, fractions and sub-fractions of Naja pallida, Agkistrodon piscivorus conanti and Agkistrodon contortrix laticinctus were tested and found to have activity ranging that from 0.1-20μg/ml against prostate cancer cell lines using an assay based on the release of lactate dehydrogenase (LDH). Further characterization of cytotoxic activity, and chemical analysis, including High Performance Liquid Chromatography (HPLC) guided fractionation, gel filtration and ion exchange chromatography has been conducted. The investigation of the possible mode of activity of the most cytotoxic venoms, and prospects for future work and on-going isolation and identification of pure anticancer compounds have been detailed in this study. The different fractions of low molecular weight (<15kDa) were further fractionated using a C18 reverse phase HPLC column and tested for activity against the prostate cell lines. The N-terminal amino acid sequences of the first residues of active pure fractions from Naja pallida venom were P4F3-2 LKXNQLIPPFWKTXP and P4F4-1 LKXNKLIPIA YKTXPEGKNLXYK. These N-terminal sequences show homology with the group of cobra cytotoxins/ cardiotoxins from the family Elapidae and are likely to be identical to two known cytotoxins, cardiotoxin γ from N. pallida and cardiotoxin 4 from N. mossambica. Another peptide had an N-terminal sequence similar to a phospholipase A2. These peptides were tested for specific cytotoxic activities against on the cell lines by the LDH assay. Fraction P4F4 at 5 and 10μg/ml had strong cytotoxic activity on DU145 and PC3 cells, but less activity on LNCaP cells and no activity on the non-cancer PNT2A cells. The sub-fractions P4F4-1 and P4F4-2 had marked effects on PC3 cells, lesser effect on LNCaP cells and no effect on DU145 and PNT2A cells. Further characterisation is needed, but this may be the first report of cytotoxins with possibly selective anticancer cell activity isolated from the venom of red spitting cobra Naja pallida.Cancer is expected to claim 9 million deaths world-wide by the year 2020. Although there has been an increase in the sophistication of current therapeutic strategies, 40% of patients are still likely to die from the disease. Novel anticancer compounds are needed. Snake venoms may represent a relevant pool for selecting candidates that may have anticancer properties. Snake venoms are complex mixtures of unexplored sources of molecules with potential use in biomedical research and drug development. Some venom molecules are of low molecular weight and might trigger anticancer responses and could have potential therapeutic applications. In this study, selected snake venoms obtained from Naja pallida, Agkistrodon piscivorus conanti and Agkistrodon contortrix laticinctus were evaluated for cytotoxicity and selectivity in vitro against a panel of prostate cancer cell lines (DU145, PC3, LNCaP) and a non-malignant prostate epithelial cell line (PNT2A). The cytotoxicity activity of each venom was initially assessed using the SYTOX Green assay. SYTOX Green is a fluorescent nucleic acid indicator dye that can be used as a marker for cell death. The whole venoms, fractions and sub-fractions of Naja pallida, Agkistrodon piscivorus conanti and Agkistrodon contortrix laticinctus were tested and found to have activity ranging that from 0.1-20μg/ml against prostate cancer cell lines using an assay based on the release of lactate dehydrogenase (LDH). Further characterization of cytotoxic activity, and chemical analysis, including High Performance Liquid Chromatography (HPLC) guided fractionation, gel filtration and ion exchange chromatography has been conducted. The investigation of the possible mode of activity of the most cytotoxic venoms, and prospects for future work and on-going isolation and identification of pure anticancer compounds have been detailed in this study. The different fractions of low molecular weight (<15kDa) were further fractionated using a C18 reverse phase HPLC column and tested for activity against the prostate cell lines. The N-terminal amino acid sequences of the first residues of active pure fractions from Naja pallida venom were P4F3-2 LKXNQLIPPFWKTXP and P4F4-1 LKXNKLIPIA YKTXPEGKNLXYK. These N-terminal sequences show homology with the group of cobra cytotoxins/ cardiotoxins from the family Elapidae and are likely to be identical to two known cytotoxins, cardiotoxin γ from N. pallida and cardiotoxin 4 from N. mossambica. Another peptide had an N-terminal sequence similar to a phospholipase A2. These peptides were tested for specific cytotoxic activities against on the cell lines by the LDH assay. Fraction P4F4 at 5 and 10μg/ml had strong cytotoxic activity on DU145 and PC3 cells, but less activity on LNCaP cells and no activity on the non-cancer PNT2A cells. The sub-fractions P4F4-1 and P4F4-2 had marked effects on PC3 cells, lesser effect on LNCaP cells and no effect on DU145 and PNT2A cells. Further characterisation is needed, but this may be the first report of cytotoxins with possibly selective anticancer cell activity isolated from the venom of red spitting cobra Naja pallida
Novel methods for improving fault protection & health management within advanced aircraft electrical power systems
Get PDFThe more-electric aircraft (MEA) concept is widely viewed as the next evolutionary step towards enabling the industry goal of developing optimised, fuel efficient aircraft. MEA have an increased dependency on electrical energy for distribution to secondary systems and, in order to service this increased dependence, the electrical power systems (EPS) are more complex with increased voltage distribution levels, power conversion stages and safety critical components compared with their conventional counterparts. These complexities will only increase in future platforms as they further embrace the MEA concept - the migration to increasingly novel, critical and complex EPS will incur several development and integration challenges.;This thesis considers the fundamental challenge of maintaining high reliability standards within future aircraft EPS through the development of accurate and discriminative real-time protection systems which will react during fault conditions. Specifically, the thesis researches novel methods that improve real-time aircraft EPS protection and health management systems by 1) accurately diagnosing degraded faults before their progression to critical failure and 2) diagnosing faults that are difficult to detect using only conventional protection methods - in particular, series arc faults are considered.;Within future aircraft EPS, the volume of operational data is expected to significantly increase beyond that of the conventional systems; consequently, the thesis focuses on the use of data-driven, machine learning based methods, to enable these extended functionalities of the EPS protection and health management systems. The types of machine learning modelling techniques that were chosen are explained and justified. Conventional protection methods are described, including a discussion on the difficulties in using them to detect both degraded fault modes and arcing conditions. The necessity to detect these types of faults in an accurate and timely manner is also discussed.;One of the main contributions of the thesis is the proposal of the EPSmart method that can autonomously diagnose and isolate a multitude of degraded faults within an aircraft representative EPS. These degraded faults include intermittent and incipient conditions, which, in comparison to overcurrent faults, often lack the energy to be detected by conventional means. Early, and accurate, detection of these conditions will improve overall system health management and reliability and ensure safe operation of the aircraft.;Further contribution is the design of the IntelArc method that can detect series arc faults within direct current supplied systems. Accurate detection of series arc faults is extremely challenging as, despite their presence being a serious fire hazard, they result in a decrease of load current. Although methods do exist for diagnosis of series arcing, there remain challenges with regards to accurate detection across different system configurations and operating conditions. The thesis shows the potential for IntelArc to provide accurate detection across a variety of configurations and operating conditions.;While the thesis only describes the initial development of these novel methods, the significant conclusions are that application testing has shown the potential for them to enhance real-time network protection, fault tolerance and health management of aircraft EPS through detection of degraded fault and arcing conditions.The more-electric aircraft (MEA) concept is widely viewed as the next evolutionary step towards enabling the industry goal of developing optimised, fuel efficient aircraft. MEA have an increased dependency on electrical energy for distribution to secondary systems and, in order to service this increased dependence, the electrical power systems (EPS) are more complex with increased voltage distribution levels, power conversion stages and safety critical components compared with their conventional counterparts. These complexities will only increase in future platforms as they further embrace the MEA concept - the migration to increasingly novel, critical and complex EPS will incur several development and integration challenges.;This thesis considers the fundamental challenge of maintaining high reliability standards within future aircraft EPS through the development of accurate and discriminative real-time protection systems which will react during fault conditions. Specifically, the thesis researches novel methods that improve real-time aircraft EPS protection and health management systems by 1) accurately diagnosing degraded faults before their progression to critical failure and 2) diagnosing faults that are difficult to detect using only conventional protection methods - in particular, series arc faults are considered.;Within future aircraft EPS, the volume of operational data is expected to significantly increase beyond that of the conventional systems; consequently, the thesis focuses on the use of data-driven, machine learning based methods, to enable these extended functionalities of the EPS protection and health management systems. The types of machine learning modelling techniques that were chosen are explained and justified. Conventional protection methods are described, including a discussion on the difficulties in using them to detect both degraded fault modes and arcing conditions. The necessity to detect these types of faults in an accurate and timely manner is also discussed.;One of the main contributions of the thesis is the proposal of the EPSmart method that can autonomously diagnose and isolate a multitude of degraded faults within an aircraft representative EPS. These degraded faults include intermittent and incipient conditions, which, in comparison to overcurrent faults, often lack the energy to be detected by conventional means. Early, and accurate, detection of these conditions will improve overall system health management and reliability and ensure safe operation of the aircraft.;Further contribution is the design of the IntelArc method that can detect series arc faults within direct current supplied systems. Accurate detection of series arc faults is extremely challenging as, despite their presence being a serious fire hazard, they result in a decrease of load current. Although methods do exist for diagnosis of series arcing, there remain challenges with regards to accurate detection across different system configurations and operating conditions. The thesis shows the potential for IntelArc to provide accurate detection across a variety of configurations and operating conditions.;While the thesis only describes the initial development of these novel methods, the significant conclusions are that application testing has shown the potential for them to enhance real-time network protection, fault tolerance and health management of aircraft EPS through detection of degraded fault and arcing conditions
Nutrient-dependent effects of the autophagy-lysosomal inhibitor, Chloroquine, on cell death and lysosomal functionality
No full textThere is huge potential for targeting pro-survival autophagy as a cancer therapeutic strategy, but this approach has not yet been fully realised due to the complex involvement of autophagy for cancer biology. In early stages of transformation, autophagy acts as a tumour suppressor, whilst in a developed tumour, autophagy aids cancer cell survival contributing to resistance. This thesis aimed to interrogate the role of autophagy for survival in metastatic breast cancer using the 4T1 mouse mammary carcinoma model. Investigations utilised the autophagy-lysosomal inhibitor Chloroquine (CQ) since this compound is currently in clinical trials for a variety of blood and solid cancers, including breast cancer. Here, the mechanisms of CQ and furthermore, the potential of combining this drug with metabolic targeting strategies were investigated. In doing this, an unexpected resistance mechanism linking glucose metabolism and CQ was uncovered. In clonogenic assays, CQ induced cell death that cooperated with other therapeutic stressors such as ionising irradiation and PI3K-Akt inhibition. CQ and the metabolic stress of serum starvation produced cell death within 24hrs; however, unexpectedly, further glucose starvation or hexokinase inhibition fully rescued cell viability. The cytotoxic effects of CQ were found to be autophagy-independent as knockdown of ATG proteins did not mimic CQ. As the form of cell death in our model did not resemble classical caspase-dependent apoptosis or necrosis, it was hypothesised the cytotoxic effects of CQ were potentially triggering lysosome membrane permeabilisation. Indeed, CQ treatment did lead to marked lysosomal stress and enlargement, suggestive of LMP. In contrast, while CQ was still able to enter and deacidify the lysosome in glucose starved cells, it failed to induce enlargement. Our data indicate that glucose metabolic rate has a profound influence on the efficacy of CQ to target lysosomes and to induce LMP-mediated death. These effects may be reducing clinical outcomes of CQ in cancer cells with reduced glucose metabolism.There is huge potential for targeting pro-survival autophagy as a cancer therapeutic strategy, but this approach has not yet been fully realised due to the complex involvement of autophagy for cancer biology. In early stages of transformation, autophagy acts as a tumour suppressor, whilst in a developed tumour, autophagy aids cancer cell survival contributing to resistance. This thesis aimed to interrogate the role of autophagy for survival in metastatic breast cancer using the 4T1 mouse mammary carcinoma model. Investigations utilised the autophagy-lysosomal inhibitor Chloroquine (CQ) since this compound is currently in clinical trials for a variety of blood and solid cancers, including breast cancer. Here, the mechanisms of CQ and furthermore, the potential of combining this drug with metabolic targeting strategies were investigated. In doing this, an unexpected resistance mechanism linking glucose metabolism and CQ was uncovered. In clonogenic assays, CQ induced cell death that cooperated with other therapeutic stressors such as ionising irradiation and PI3K-Akt inhibition. CQ and the metabolic stress of serum starvation produced cell death within 24hrs; however, unexpectedly, further glucose starvation or hexokinase inhibition fully rescued cell viability. The cytotoxic effects of CQ were found to be autophagy-independent as knockdown of ATG proteins did not mimic CQ. As the form of cell death in our model did not resemble classical caspase-dependent apoptosis or necrosis, it was hypothesised the cytotoxic effects of CQ were potentially triggering lysosome membrane permeabilisation. Indeed, CQ treatment did lead to marked lysosomal stress and enlargement, suggestive of LMP. In contrast, while CQ was still able to enter and deacidify the lysosome in glucose starved cells, it failed to induce enlargement. Our data indicate that glucose metabolic rate has a profound influence on the efficacy of CQ to target lysosomes and to induce LMP-mediated death. These effects may be reducing clinical outcomes of CQ in cancer cells with reduced glucose metabolism
Intelligent design of microfluidic components for Newtonian and complex fluid systems
Get PDFInterest in microfluidics has increased dramatically in recent years, with applications spanning a wide range of fields. However, despite several advances, design of microfluidic devices still relies largely on trial-and-error. This thesis aims to go beyond this approach in favour of a rational design of microfluidic devices based on theoretical and numerical design rules and algorithms. More specifically, this research focuses on understanding and controlling fluid dynamics in applications involving complex non-Newtonian fluids in shear and extensional flows. Biomimetic principles and shape optimisation methods are employed to propose new designs for single-phase fluid flow. Furthermore, the single-phase numerical solver is extended to cope with two-phase systems, thus paving the way for new applications of these techniques. Focusing on shear-flows, a biomimetic principle appropriate for fully developed flows has been extended here to be applicable for non-Newtonian fluids, described by the power-law constitutive relationship. The derivation of the principle leads to a biomimetic rule that provides the appropriate dimensions for designing customised microfluidic bifurcating networks, able to generate specific wall shear-stress gradients along consecutive generations. A range of power-law fluids is examined numerically demonstrating great agreement with theoretical predictions. In terms of extensional flow, a range of shapes are proposed for designing microfluidic channels for studies related to the response of complex fluid systems under homogeneous strain-rate. Optimisation techniques are employed for finding the appropriate shapes to generate homogeneous extensional flows along the flow centre line of single stream (contraction-expansion channels) and the multi-stream designs (T-channels and flow focusing devices). The optimised geometries proposed exhibit enhanced performance compared to well defined geometrical shapes. The in-house single phase solver used in all numerical studies is upgraded here in order to solve numerically 3D-problems related to two-phase systems described by the Phase Field method. Here, the code is validated for 2D-problems only, using a range of test-cases demonstrating a very good quantitative agreement. Keywords: Non-Newtonian fluids, Shear-thinning and shear-thickening behaviour, Bifurcating networks, Biomimetics, Optimisation, Extensional flows, Two-phase systemsInterest in microfluidics has increased dramatically in recent years, with applications spanning a wide range of fields. However, despite several advances, design of microfluidic devices still relies largely on trial-and-error. This thesis aims to go beyond this approach in favour of a rational design of microfluidic devices based on theoretical and numerical design rules and algorithms. More specifically, this research focuses on understanding and controlling fluid dynamics in applications involving complex non-Newtonian fluids in shear and extensional flows. Biomimetic principles and shape optimisation methods are employed to propose new designs for single-phase fluid flow. Furthermore, the single-phase numerical solver is extended to cope with two-phase systems, thus paving the way for new applications of these techniques. Focusing on shear-flows, a biomimetic principle appropriate for fully developed flows has been extended here to be applicable for non-Newtonian fluids, described by the power-law constitutive relationship. The derivation of the principle leads to a biomimetic rule that provides the appropriate dimensions for designing customised microfluidic bifurcating networks, able to generate specific wall shear-stress gradients along consecutive generations. A range of power-law fluids is examined numerically demonstrating great agreement with theoretical predictions. In terms of extensional flow, a range of shapes are proposed for designing microfluidic channels for studies related to the response of complex fluid systems under homogeneous strain-rate. Optimisation techniques are employed for finding the appropriate shapes to generate homogeneous extensional flows along the flow centre line of single stream (contraction-expansion channels) and the multi-stream designs (T-channels and flow focusing devices). The optimised geometries proposed exhibit enhanced performance compared to well defined geometrical shapes. The in-house single phase solver used in all numerical studies is upgraded here in order to solve numerically 3D-problems related to two-phase systems described by the Phase Field method. Here, the code is validated for 2D-problems only, using a range of test-cases demonstrating a very good quantitative agreement. Keywords: Non-Newtonian fluids, Shear-thinning and shear-thickening behaviour, Bifurcating networks, Biomimetics, Optimisation, Extensional flows, Two-phase system
Electrical-field activated sintering and forming of micro-components
Get PDFThis thesis was previously held under moratorium from 11 May 2017 until 4th June 2021.As the demand for miniature products has increased significantly, so also has the need for these products to be produced in a rapid, flexible and cost efficient manner. The application of electroplasticity shows significant potential to produce the components by using powder materials. Nevertheless, previous research has shown that there are still significant challenges to be met in order to achieve increased relative densification of product samples and simplification of the processes. The process concept in this study comprises the combination of electrical-field activated sintering and forming processes. Therefore, the aims of the research were to develop the process concept for the manufacture of micro-components and to design the die sets along with other tooling for machine setup to enable the forming of micro-components from powder materials. A comprehensive literature review on micro-manufacturing, size effects, powder metallurgy and the electroplasticity process has been conducted. The development of the die sets for the process has been described, followed by a series of experiments. The FE thermal-electrical analysis was also carried out to study the heating flows of the die sets development during the process. In this research, titanium (Ti) and titanium tin alloy (90Ti10Sn) have been selected for the main powder materials tested for both vacuum and open-air process environment by using a Gleeble® 3800 testing system and Projection Welding machine respectively. Meanwhile, for the additional experiment, copper (Cu) has been selected to be tested in the open-air process environment by using a Projection Welding machine with die sets prepared by the Micro-FAST project. Based on the data collected, this efficient process has the potential to produce components with a high relative density of around 98%. Changes of the particles concerning deformation and breaking are crucial in the course of achieving the densification which differs from a conventional sintering process.As the demand for miniature products has increased significantly, so also has the need for these products to be produced in a rapid, flexible and cost efficient manner. The application of electroplasticity shows significant potential to produce the components by using powder materials. Nevertheless, previous research has shown that there are still significant challenges to be met in order to achieve increased relative densification of product samples and simplification of the processes. The process concept in this study comprises the combination of electrical-field activated sintering and forming processes. Therefore, the aims of the research were to develop the process concept for the manufacture of micro-components and to design the die sets along with other tooling for machine setup to enable the forming of micro-components from powder materials. A comprehensive literature review on micro-manufacturing, size effects, powder metallurgy and the electroplasticity process has been conducted. The development of the die sets for the process has been described, followed by a series of experiments. The FE thermal-electrical analysis was also carried out to study the heating flows of the die sets development during the process. In this research, titanium (Ti) and titanium tin alloy (90Ti10Sn) have been selected for the main powder materials tested for both vacuum and open-air process environment by using a Gleeble® 3800 testing system and Projection Welding machine respectively. Meanwhile, for the additional experiment, copper (Cu) has been selected to be tested in the open-air process environment by using a Projection Welding machine with die sets prepared by the Micro-FAST project. Based on the data collected, this efficient process has the potential to produce components with a high relative density of around 98%. Changes of the particles concerning deformation and breaking are crucial in the course of achieving the densification which differs from a conventional sintering process
Influence of impurities on the crystallisation of pharmaceutical materials
Get PDFThe major part of this thesis describes work done to investigate the organic and inorganic impurity content in metformin hydrochloride samples and their effect on induction time and nucleation kinetics. Crystallisation from solution plays a significant role in the pharmaceutical, chemical and food industry, because it is widely used as a separation and purification technique. Nucleation is the first step of crystallisation, where the extremely small species called nuclei are formed in solution. This step determines the quality of a new crystalline material, however, at present the understanding of this process is relatively poor. One of the factors affecting the nucleation pathway and kinetics is the impurity content.;Impurity control in the pharmaceutical industry should be planned at the drug design stage and carried throughout the entire drug production process. Acceptable levels for impurities in drugs are defined in official regulations released by the International Conference of Harmonisation (ICH), the United States Food and Drug Administration (FDA) and the Canadian Drug and Health Agency (CDHA). A liquid chromatography/mass spectrometry (LC/MS) method for the determination and quantification of metformin hydrochloride and five out of six known impurities was developed and validated during this project. This method was then used to determine the levels of these impurities in samples taken during the temperature stability test of metformin hydrochloride.;The results revealed that the chosen model compound was relatively stable under the chosen conditions and the levels of impurities were within the acceptable levels. A separate ion chromatography method was developed for the determination of dimethylamine. Initial experiments showed that the raw material of metformin hydrochloride contained several inorganic impurities, however, due to time limitations only ammonium sulfate was chosen as the source of sulfate ions to test their effect on nucleation rate of metformin hydrochloride. It was found that when up to 0.5 %w/w of ammonium sulfate was added to the solution it caused a decrease in nucleation rate and an increase in the average induction time.;On the other hand, addition of 1.0 %w/w of ammonium sulfate had no influence on either nucleation rate or average induction time. The unexpected loss of the impurity effect was investigated further using many analytical techniques such as Scanning Electron Microscope (SEM), Time of Flight - Secondary Ion Mass Spectrometry (ToF-SIMS), Differential Scanning Calorimetry (DSC), Dynamic Light Scattering (DLS) and Ion Chromatography (IC). The results obtained did not provide a definitive answer with regard to why the highest concentration of impurity had no effect on nucleation kinetics. It was thought the effects on induction times were due interactions between sulfate and the nucleation clusters formed during crystallisation of metformin hydrochloride, however further investigation is required.;In a separate part of this project was an investigation into whether or not a batch CoFlux reactor could be used to produce a pure polymorphic form of L-glutamic acid and whether or not enthalpy measurements were an advantage of this reactor for monitoring the crystallisation. Particles obtained from crystallisation experiments in this reactor were analysed using in-situ Raman spectrometry (for several experiments) and off-line X-Ray diffraction (XRPD), laser diffraction (LD) and microscope imaging. The results obtained in the CoFlux reactor were reproducible and a narrower particle size distribution was achieved with the improved temperature control. Enthalpy measurements were not an advantage when monitoring the crystallisation of L-glutamic acid.The major part of this thesis describes work done to investigate the organic and inorganic impurity content in metformin hydrochloride samples and their effect on induction time and nucleation kinetics. Crystallisation from solution plays a significant role in the pharmaceutical, chemical and food industry, because it is widely used as a separation and purification technique. Nucleation is the first step of crystallisation, where the extremely small species called nuclei are formed in solution. This step determines the quality of a new crystalline material, however, at present the understanding of this process is relatively poor. One of the factors affecting the nucleation pathway and kinetics is the impurity content.;Impurity control in the pharmaceutical industry should be planned at the drug design stage and carried throughout the entire drug production process. Acceptable levels for impurities in drugs are defined in official regulations released by the International Conference of Harmonisation (ICH), the United States Food and Drug Administration (FDA) and the Canadian Drug and Health Agency (CDHA). A liquid chromatography/mass spectrometry (LC/MS) method for the determination and quantification of metformin hydrochloride and five out of six known impurities was developed and validated during this project. This method was then used to determine the levels of these impurities in samples taken during the temperature stability test of metformin hydrochloride.;The results revealed that the chosen model compound was relatively stable under the chosen conditions and the levels of impurities were within the acceptable levels. A separate ion chromatography method was developed for the determination of dimethylamine. Initial experiments showed that the raw material of metformin hydrochloride contained several inorganic impurities, however, due to time limitations only ammonium sulfate was chosen as the source of sulfate ions to test their effect on nucleation rate of metformin hydrochloride. It was found that when up to 0.5 %w/w of ammonium sulfate was added to the solution it caused a decrease in nucleation rate and an increase in the average induction time.;On the other hand, addition of 1.0 %w/w of ammonium sulfate had no influence on either nucleation rate or average induction time. The unexpected loss of the impurity effect was investigated further using many analytical techniques such as Scanning Electron Microscope (SEM), Time of Flight - Secondary Ion Mass Spectrometry (ToF-SIMS), Differential Scanning Calorimetry (DSC), Dynamic Light Scattering (DLS) and Ion Chromatography (IC). The results obtained did not provide a definitive answer with regard to why the highest concentration of impurity had no effect on nucleation kinetics. It was thought the effects on induction times were due interactions between sulfate and the nucleation clusters formed during crystallisation of metformin hydrochloride, however further investigation is required.;In a separate part of this project was an investigation into whether or not a batch CoFlux reactor could be used to produce a pure polymorphic form of L-glutamic acid and whether or not enthalpy measurements were an advantage of this reactor for monitoring the crystallisation. Particles obtained from crystallisation experiments in this reactor were analysed using in-situ Raman spectrometry (for several experiments) and off-line X-Ray diffraction (XRPD), laser diffraction (LD) and microscope imaging. The results obtained in the CoFlux reactor were reproducible and a narrower particle size distribution was achieved with the improved temperature control. Enthalpy measurements were not an advantage when monitoring the crystallisation of L-glutamic acid
Access Repository Dashboard
Do you manage STAX (Strathclyde Repository)? Access insider analytics, issue reports and manage access to outputs from your repository in the CORE Repository Dashboard!