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Designing for "Life between buildings" : modeling the relationship between streetscape qualities and pedestrian activity in Glasgow, Scotland
No full textRising levels of physical inactivity, among other pressing urban issues, have prompted urban designers to better understand the complex relationship between the built environment and human behavior. One of the most widely-cited measures of the built environment, as it relates to human behavior, is walkability - the measure of how conducive a place is to walking and other pedestrian activity. To date, walkability has largely been characterized by macroscale measures, such as street connectivity and neighborhood density. More recently, several walking audit instruments have also been developed to measure microscale features of pedestrian environments, like the number of street trees or pieces of street furniture. Yet, both of these measures fail to capture potentially important perceptual qualities of streetscapes that urban designers have long claimed as significant factors for more active streets. However, there is a surprising lack of empirical evidence in support of these claims based on validated, objective measures of streetscape qualities.The purpose of this study was to address this gap in research by modeling the relationship between objective measures of streetscape qualities and pedestrian activity in Glasgow, Scotland. Overall, five measures of streetscape qualities - including imageability, enclosure, human scale, transparency, and complexity - were collected from over 690 street segments across the city, along with several macroscale measures of walkability and pedestrian counts. The results of this study indicated that the five objective measures of streetscape qualities added significantly (p ≤ 0.05) to the explanatory power of walkability models when controlling for standard macroscale measures of walkability. Measures of imageability and transparency, in particular, had significant (p ≤ 0.05) relationships to pedestrian activity (p = 0.02 and p = 4.60E-14 respectively). These results suggest that streetscape qualities should be considered as important variables in future, city-wide studies linking measures of the built environment to pedestrian activity.Rising levels of physical inactivity, among other pressing urban issues, have prompted urban designers to better understand the complex relationship between the built environment and human behavior. One of the most widely-cited measures of the built environment, as it relates to human behavior, is walkability - the measure of how conducive a place is to walking and other pedestrian activity. To date, walkability has largely been characterized by macroscale measures, such as street connectivity and neighborhood density. More recently, several walking audit instruments have also been developed to measure microscale features of pedestrian environments, like the number of street trees or pieces of street furniture. Yet, both of these measures fail to capture potentially important perceptual qualities of streetscapes that urban designers have long claimed as significant factors for more active streets. However, there is a surprising lack of empirical evidence in support of these claims based on validated, objective measures of streetscape qualities.The purpose of this study was to address this gap in research by modeling the relationship between objective measures of streetscape qualities and pedestrian activity in Glasgow, Scotland. Overall, five measures of streetscape qualities - including imageability, enclosure, human scale, transparency, and complexity - were collected from over 690 street segments across the city, along with several macroscale measures of walkability and pedestrian counts. The results of this study indicated that the five objective measures of streetscape qualities added significantly (p ≤ 0.05) to the explanatory power of walkability models when controlling for standard macroscale measures of walkability. Measures of imageability and transparency, in particular, had significant (p ≤ 0.05) relationships to pedestrian activity (p = 0.02 and p = 4.60E-14 respectively). These results suggest that streetscape qualities should be considered as important variables in future, city-wide studies linking measures of the built environment to pedestrian activity
A study of the biological activity of bee venom and its fractions with regard to cosmetic science and immunology
Get PDFApis mellifera venom has been used since antiquity to treat various ailments but scientific evidence to justify its therapeutic claims is incomplete. The venom has recently entered cosmetic usage as a mimetic ingredient to alleviate signs of facial aging. This study investigated the potential of bee venom (BV) as a source of cosmetic and immunomodulatory agents for use in skin anti-ageing applications and as a vaccine adjuvant, respectively. BV fractions were obtained by reversed phase preparative chromatography and characterised by LC-MS and NMR techniques. The fractions were assayed for antimicrobial and cytotoxic activities against a range of microbes (Mycobacterium marinum, Norcardia farcinia and Trypanosoma brucei brucei) and human cell lines [NCTC2544 (normal keratinocytes), PNT2A (normal epithelial cells), and HS27 (normal fibroblasts)] respectively. Immunomodulatory effects were investigated in PMA-differentiated U937 cells with and without LPS co-stimulation. The aqueous stability of the venom and its susceptibility to protease action were as-sessed by LC-MS assays. An LC-MS method was also developed and validated for the assay of BV in commercial creams using the melittin signal as an indicator of BV content. Of the 4 BV fractions (F-1 to F-4), the largest, containing melittin, showed the most activity against N. farcinia (25-50μg/mL) and T. b. brucei (0.78-1.56μg/mL), but was not very active against M. marinum (>100μg/mL). The melittin fraction (96% pure) was the most cytotoxic against keratinocytes, fibroblasts and epi-thelial cells, with IC50 ≥ 2.5-4.0μg/mL. All fractions significantly enhanced IL-1β release, while only F-4, a lipophilic fraction, enhanced TNF-α release. F-4, which was revealed through NMR elucidation to contain (Z)-9-eicosen-1-ol, produced sig-nificant inhibition of IL-6 release. Melittin in aqueous solutions of BV, but not of the melittin fraction alone, underwent a temperature-dependent spontaneous degradation within the 21Lys-22Arg-23Lys-24Arg sequence due to a serine carboxypeptidase-like activity attributed to the BV allergen, Api m9. Taken together, these results suggest that a formulation matching the 3.2-37.2ppm content of melittin assayed in commer-cial creams would be safe for skin application based on IC50 values in human cells. The immunomodulatory effects observed in U937 cells highlight the potential of BV as a possible source of vaccine adjuvants.Apis mellifera venom has been used since antiquity to treat various ailments but scientific evidence to justify its therapeutic claims is incomplete. The venom has recently entered cosmetic usage as a mimetic ingredient to alleviate signs of facial aging. This study investigated the potential of bee venom (BV) as a source of cosmetic and immunomodulatory agents for use in skin anti-ageing applications and as a vaccine adjuvant, respectively. BV fractions were obtained by reversed phase preparative chromatography and characterised by LC-MS and NMR techniques. The fractions were assayed for antimicrobial and cytotoxic activities against a range of microbes (Mycobacterium marinum, Norcardia farcinia and Trypanosoma brucei brucei) and human cell lines [NCTC2544 (normal keratinocytes), PNT2A (normal epithelial cells), and HS27 (normal fibroblasts)] respectively. Immunomodulatory effects were investigated in PMA-differentiated U937 cells with and without LPS co-stimulation. The aqueous stability of the venom and its susceptibility to protease action were as-sessed by LC-MS assays. An LC-MS method was also developed and validated for the assay of BV in commercial creams using the melittin signal as an indicator of BV content. Of the 4 BV fractions (F-1 to F-4), the largest, containing melittin, showed the most activity against N. farcinia (25-50μg/mL) and T. b. brucei (0.78-1.56μg/mL), but was not very active against M. marinum (>100μg/mL). The melittin fraction (96% pure) was the most cytotoxic against keratinocytes, fibroblasts and epi-thelial cells, with IC50 ≥ 2.5-4.0μg/mL. All fractions significantly enhanced IL-1β release, while only F-4, a lipophilic fraction, enhanced TNF-α release. F-4, which was revealed through NMR elucidation to contain (Z)-9-eicosen-1-ol, produced sig-nificant inhibition of IL-6 release. Melittin in aqueous solutions of BV, but not of the melittin fraction alone, underwent a temperature-dependent spontaneous degradation within the 21Lys-22Arg-23Lys-24Arg sequence due to a serine carboxypeptidase-like activity attributed to the BV allergen, Api m9. Taken together, these results suggest that a formulation matching the 3.2-37.2ppm content of melittin assayed in commer-cial creams would be safe for skin application based on IC50 values in human cells. The immunomodulatory effects observed in U937 cells highlight the potential of BV as a possible source of vaccine adjuvants
Health data consistency and management : case study of maternal health data in Malawi
Get PDFGood quality data is vital. It informs decision making in a wide range of sectors, at all levels. Accuracy, completeness, consistency, timeliness and standard-based are the properties of good quality data. Data which satisfies these properties is deemed fit and appropriate for its intended use. Data lacking these qualities poses challenges in operations, decision making and planning.The Millennium Development Goals (MDG), specifically MDG number 5- the reduction of maternal mortality by two-thirds between 1990 and 2015- now succeeded by Sustainable Development Goal (SDG) number 3 - has led to a significant need for reliable maternal health data. Accurate data is needed on the levels of (and trends in) maternal death in developing countries in order to address and improve maternal health and survival. The health care system in Malawi lacks vital registration systems which are rich and valuable sources of health data, including maternal health. Malawi had a health information system that did not produce reliable data, and therefore could not be used for decision making in terms of planning and management with respect to maternal health. In 1999, after reviewing the Health Management Information System (HMIS), Malawi developed a new system based on the strengths of the old system while addressing its weaknesses.This study aimed to use maternal health data to investigate management processes and procedures within the HMIS from data collection by different entities, transitioning through the hierarchy from the community to the point of use at district level. The study also assessed the consistency of the data itself as it transitioned through this hierarchy. Transitions of data were explored, and difficulties in maternal health data collection were assessed among stakeholders including community members, government health staff and non-governmental organisations (NGOs). Monthly and annual data collected and compiled by various personnel over one year, was also tested for consistency using chi-square test.The study was carried out in three phases. The first was done in the Southern Region of Malawi (Phase 1). The second one was done in three health facilities which had interventions (Phase 2) in terms of training, infrastructure and provision of resources in maternal and neonatal health. The third one was conducted in six health facilities (three with (as in Phase 2) and three without intervention (Phase 3);Ten HMIS officers and 10 data users (programme coordinators at the District Health Office (DHO)) were selected for Phase One since they were involved in data management and decision making processes respectively given the data. For Phase Two participants included 14 Secret Women, 16 Health Surveillance Assistants (HSAs), Three Village Health Committees (VHCs) and two Health Personnel. Phase Three participants included 17 Secret Women, 42 Chiefs, 40 Health Surveillance Assistants (HSAs), six Health Personnel and also one Safe Motherhood Coordinator, one Community Based Maternal and Neonatal Health Coordinator, one NGO and one HMIS Officer chosen from the District Health Office, all of whom are involved in the data management process until the data is sent to the users.Cross-tabulations, frequency tables and graphs were used to assess data management processes, procedures and problems among the personnel. Testing data uniformity was achieved using the Chi-square test of homogeneity to compare monthly data and annual data aggregates for the groups of personnel to check for data quality.The results showed that data management was compromised by problems faced by data collection personnel such as lack of transportation affecting timeliness of data submission, lack of basic needs (e.g. proper housing and low salaries for HSAs and Health Personnel) which affected their motivation to work, and lack of reporting forms and writing materials which led to data gaps and missing information. Discrepancies arose in compilation and transfer of information since some information was forgotten or not recorded during the process. Furthermore, lack of supervision coupled with lack transportation and stationary led to inconsistent, incomplete, inaccurate and unreliable data.The quantitative analysis showed that there were significant differences, thus no consistency, in the monthly and annual data for the selected variables i.e. new pregnancies, births, live births among the groups of personnel. Monthly data for maternal and neonatal deaths also showed differences among the personnel, with annual aggregates also showing differences.;Important resources such as stationary and reporting forms should be provided in good time (and in adequate numbers) to ensure that there are no data gaps. In addition, the study strongly recommends the use of eHealth/mHealth in rural communities to reduce errors and data gaps during entry, so as to increase accuracy, reliability, consistency,completeness and timeliness. It also recommends training for new officers, and refresher courses for those already in the system to instil procedures and for the purpose of review (supervision) of work that has been completed.Key words: Accuracy, Consistency, Maternal Health, Data Management, HMISGood quality data is vital. It informs decision making in a wide range of sectors, at all levels. Accuracy, completeness, consistency, timeliness and standard-based are the properties of good quality data. Data which satisfies these properties is deemed fit and appropriate for its intended use. Data lacking these qualities poses challenges in operations, decision making and planning.The Millennium Development Goals (MDG), specifically MDG number 5- the reduction of maternal mortality by two-thirds between 1990 and 2015- now succeeded by Sustainable Development Goal (SDG) number 3 - has led to a significant need for reliable maternal health data. Accurate data is needed on the levels of (and trends in) maternal death in developing countries in order to address and improve maternal health and survival. The health care system in Malawi lacks vital registration systems which are rich and valuable sources of health data, including maternal health. Malawi had a health information system that did not produce reliable data, and therefore could not be used for decision making in terms of planning and management with respect to maternal health. In 1999, after reviewing the Health Management Information System (HMIS), Malawi developed a new system based on the strengths of the old system while addressing its weaknesses.This study aimed to use maternal health data to investigate management processes and procedures within the HMIS from data collection by different entities, transitioning through the hierarchy from the community to the point of use at district level. The study also assessed the consistency of the data itself as it transitioned through this hierarchy. Transitions of data were explored, and difficulties in maternal health data collection were assessed among stakeholders including community members, government health staff and non-governmental organisations (NGOs). Monthly and annual data collected and compiled by various personnel over one year, was also tested for consistency using chi-square test.The study was carried out in three phases. The first was done in the Southern Region of Malawi (Phase 1). The second one was done in three health facilities which had interventions (Phase 2) in terms of training, infrastructure and provision of resources in maternal and neonatal health. The third one was conducted in six health facilities (three with (as in Phase 2) and three without intervention (Phase 3);Ten HMIS officers and 10 data users (programme coordinators at the District Health Office (DHO)) were selected for Phase One since they were involved in data management and decision making processes respectively given the data. For Phase Two participants included 14 Secret Women, 16 Health Surveillance Assistants (HSAs), Three Village Health Committees (VHCs) and two Health Personnel. Phase Three participants included 17 Secret Women, 42 Chiefs, 40 Health Surveillance Assistants (HSAs), six Health Personnel and also one Safe Motherhood Coordinator, one Community Based Maternal and Neonatal Health Coordinator, one NGO and one HMIS Officer chosen from the District Health Office, all of whom are involved in the data management process until the data is sent to the users.Cross-tabulations, frequency tables and graphs were used to assess data management processes, procedures and problems among the personnel. Testing data uniformity was achieved using the Chi-square test of homogeneity to compare monthly data and annual data aggregates for the groups of personnel to check for data quality.The results showed that data management was compromised by problems faced by data collection personnel such as lack of transportation affecting timeliness of data submission, lack of basic needs (e.g. proper housing and low salaries for HSAs and Health Personnel) which affected their motivation to work, and lack of reporting forms and writing materials which led to data gaps and missing information. Discrepancies arose in compilation and transfer of information since some information was forgotten or not recorded during the process. Furthermore, lack of supervision coupled with lack transportation and stationary led to inconsistent, incomplete, inaccurate and unreliable data.The quantitative analysis showed that there were significant differences, thus no consistency, in the monthly and annual data for the selected variables i.e. new pregnancies, births, live births among the groups of personnel. Monthly data for maternal and neonatal deaths also showed differences among the personnel, with annual aggregates also showing differences.;Important resources such as stationary and reporting forms should be provided in good time (and in adequate numbers) to ensure that there are no data gaps. In addition, the study strongly recommends the use of eHealth/mHealth in rural communities to reduce errors and data gaps during entry, so as to increase accuracy, reliability, consistency,completeness and timeliness. It also recommends training for new officers, and refresher courses for those already in the system to instil procedures and for the purpose of review (supervision) of work that has been completed.Key words: Accuracy, Consistency, Maternal Health, Data Management, HMI
Events prediction in electroencephalographic signals
Get PDFBrain Machine Interface (BMI) or Brain Computer Interface (BCI) technologies provide the prospect of regenerating or replacing functions lost due to motor disabilities. BCIs connect the brain to a computer which translates the electrical activity of the brain into commands used to control external devices, hence allowing people with motor disability to control their external environment through a non-muscular communication channel. A BCI operates by transforming electrophysiological signals, known as Electroencephalogram (EEG) signals, from the user into device commands under an operating protocol. The protocol initialises and defines the nature of the communication (i.e., discrete or continuous). It also determines the strategy which underpins the generation of the signals used by the system (i.e., what triggers the changes within the EEG signals). While protocols involving brisk and very constrained movements have been widely explored in BCI studies, more natural movements have barely been considered. The choice of protocols that entail non-realistic movements emanates from the generation of well understood neuronal correlates modulated by the execution of such movements, leading to a lack of freedom in the design of BCI protocols.The development of algorithms translating EEG signals into commands that control external devices,a task termed as event detection in the present research, are a central part of any BCI system. However, most of the time, complex methods are used and most event detection in BCI development is devoted to the optimisation of such methods. Furthermore, the methods require extensive training of the user, putting a mental load on the user. The present study aims to investigate simple, but powerful, event detection methods requiring minimal training and the use of a protocol involving natural movements. Scalp EEG data was recorded from nine participants using natural hand movements.In particular, self-paced reaching hand movements were considered. The data was investigated in a pseudo time frequency domain using continuous wavelet coefficients. Methods using wavelet modulus maxima, the Mahalanobis distance, and bootstrapping of the Mahalanobis distance were developed for event detection. The data was analysed over a frequency range from 0.1 Hz to 25 Hz, covering the Slow Cortical Potentials (SCP), Mu and Beta frequency bands.The results showed that the method using wavelet modulus maxima was able to predict reaching hand movements onset in the SCP, Mu and Beta frequency bands about 1 s before movement onsetand yielded an maximum average prediction rate of approximately 80%. The Mahalanolobisdistance and the bootstrap methods were able to predict reaching hand movements initiation inthe SCP band about 1 s before movement onset with a maximum prediction rate of approximately 70%. The study has demonstrated that human voluntary movements can be predicted approximatively 1 s prior to movement onset with a good prediction rate. The study may contribute to the understanding of the planning and the control of human voluntary movements. Furthermore, the present research may contribute in designing advanced assistive devices in general and in particular may contribute in improving BCI systems design. Finally, the results may encourage the use of natural movements during BCI protocols design aiming to predict movement initiation and the monitoring of the mental state of BCI users.Brain Machine Interface (BMI) or Brain Computer Interface (BCI) technologies provide the prospect of regenerating or replacing functions lost due to motor disabilities. BCIs connect the brain to a computer which translates the electrical activity of the brain into commands used to control external devices, hence allowing people with motor disability to control their external environment through a non-muscular communication channel. A BCI operates by transforming electrophysiological signals, known as Electroencephalogram (EEG) signals, from the user into device commands under an operating protocol. The protocol initialises and defines the nature of the communication (i.e., discrete or continuous). It also determines the strategy which underpins the generation of the signals used by the system (i.e., what triggers the changes within the EEG signals). While protocols involving brisk and very constrained movements have been widely explored in BCI studies, more natural movements have barely been considered. The choice of protocols that entail non-realistic movements emanates from the generation of well understood neuronal correlates modulated by the execution of such movements, leading to a lack of freedom in the design of BCI protocols.The development of algorithms translating EEG signals into commands that control external devices,a task termed as event detection in the present research, are a central part of any BCI system. However, most of the time, complex methods are used and most event detection in BCI development is devoted to the optimisation of such methods. Furthermore, the methods require extensive training of the user, putting a mental load on the user. The present study aims to investigate simple, but powerful, event detection methods requiring minimal training and the use of a protocol involving natural movements. Scalp EEG data was recorded from nine participants using natural hand movements.In particular, self-paced reaching hand movements were considered. The data was investigated in a pseudo time frequency domain using continuous wavelet coefficients. Methods using wavelet modulus maxima, the Mahalanobis distance, and bootstrapping of the Mahalanobis distance were developed for event detection. The data was analysed over a frequency range from 0.1 Hz to 25 Hz, covering the Slow Cortical Potentials (SCP), Mu and Beta frequency bands.The results showed that the method using wavelet modulus maxima was able to predict reaching hand movements onset in the SCP, Mu and Beta frequency bands about 1 s before movement onsetand yielded an maximum average prediction rate of approximately 80%. The Mahalanolobisdistance and the bootstrap methods were able to predict reaching hand movements initiation inthe SCP band about 1 s before movement onset with a maximum prediction rate of approximately 70%. The study has demonstrated that human voluntary movements can be predicted approximatively 1 s prior to movement onset with a good prediction rate. The study may contribute to the understanding of the planning and the control of human voluntary movements. Furthermore, the present research may contribute in designing advanced assistive devices in general and in particular may contribute in improving BCI systems design. Finally, the results may encourage the use of natural movements during BCI protocols design aiming to predict movement initiation and the monitoring of the mental state of BCI users
The interplay of multiple ADME mechanisms : prediction of hepatic drug-drug interactions from in vitro
Get PDFThis thesis was previously held under moratorium in Chemistry Department (GSK) from 23rd September 2014 until 14th November 2016.Rosuvastatin has poor passive membrane permeability and its uptake into the liver is mediated predominately by the transporter, Organic Anion Transporting Polypeptide 1B1 (OATP1B1). Cyclosporin A (CsA) is a potent inhibitor of a range of transporters, including OATP1B1 and clinical drug-drug interactions (DDI) have been reported with rosuvastatin. The aim of this study was to determine the uptake kinetics of rosuvastatin in human hepatocytes using a mechanistic model and to determine the inhibitory effect of CsA upon those kinetics. These data may then allow the extrapolation of in vitro to in vivo kinetics and provide an understanding of the interplay between different disposition mechanisms, with particular regard to the potential to predict DDI.This study was divided into method development and experimental phases. In the development phase, paediatric hepatocytes from a single donor were used to develop the methods. The uptake parameters (Vmax, Km,u, Pdiff,u, Fucell and CLuptake) using estradiol-17β-D-glucuronide (EG) and rosuvastatin were determined using a mechanistic two-compartment model developed by Menochet et al (2012a). The uptake of rosuvastatin was also determined using sodium free media, which prevents the efficient functioning of the uptake transporter Sodium Taurocholate Dependent Transporter (NTCP), another transporter thought to contribute to the uptake of rosuvastatin. Inhibition parameters (IC50) of the uptake of EG and rosuvastatin by CsA and rosuvastatin and rifampicin were determined.The uptake kinetic parameters of EG and rosuvastatin in the paediatric human hepatocytes were in agreement with the quoted literature values for adult human hepatocytes. The hepatocytes were robust enough to be used for method development and to plan for the future studies. The IC50 values for EG and rosuvastatin as the probe substrates using CsA and rifampicin as inhibitors were in agreement with quoted literature values and suggested a predominate role for OATP1B1 in EG and rosuvastatin uptake. In these paediatric human hepatocytes NTCP did not appear to play a role in the uptake of rosuvastatin.The paediatric human hepatocyte data were used to help define and refine the studies conducted in the experimental phase of the study. The same uptake parameters for rosuvastatin were determined in human hepatocytes from three adult donors using the mechanistic two-compartment model. The time of the incubation was extended to 60 minutes to ensure that steady state kinetics were reached. Inhibition of the uptake of rosuvastatin was determined with co- and pre-incubation of CsA and its main metabolite, AM1. The time-dependent nature of the inhibitors have been studied by ourselves, but not in human hepatocytes [Gertz et al 2012]. There did not appear to be an effect of co- versus pre-incubation of the inhibitors.The mechanistic two-compartment model was also used to determine the uptake parameters for a GSK compound, namely GSK2879552, using the same adult human hepatocytes from three adult donors. However, the hepatic uptake clearance (CLuptake) values suggested that active saturable uptake of GSK2879552 was not evident. This may explain the high variability observed between the three donors for the uptake parameters (Vmax, Km,u, Pdiff,u and Fucell) and the high coefficient of variation observed about each parameter. These data provided a useful learning with regards to understanding the limitations of the model.Rosuvastatin has poor passive membrane permeability and its uptake into the liver is mediated predominately by the transporter, Organic Anion Transporting Polypeptide 1B1 (OATP1B1). Cyclosporin A (CsA) is a potent inhibitor of a range of transporters, including OATP1B1 and clinical drug-drug interactions (DDI) have been reported with rosuvastatin. The aim of this study was to determine the uptake kinetics of rosuvastatin in human hepatocytes using a mechanistic model and to determine the inhibitory effect of CsA upon those kinetics. These data may then allow the extrapolation of in vitro to in vivo kinetics and provide an understanding of the interplay between different disposition mechanisms, with particular regard to the potential to predict DDI.This study was divided into method development and experimental phases. In the development phase, paediatric hepatocytes from a single donor were used to develop the methods. The uptake parameters (Vmax, Km,u, Pdiff,u, Fucell and CLuptake) using estradiol-17β-D-glucuronide (EG) and rosuvastatin were determined using a mechanistic two-compartment model developed by Menochet et al (2012a). The uptake of rosuvastatin was also determined using sodium free media, which prevents the efficient functioning of the uptake transporter Sodium Taurocholate Dependent Transporter (NTCP), another transporter thought to contribute to the uptake of rosuvastatin. Inhibition parameters (IC50) of the uptake of EG and rosuvastatin by CsA and rosuvastatin and rifampicin were determined.The uptake kinetic parameters of EG and rosuvastatin in the paediatric human hepatocytes were in agreement with the quoted literature values for adult human hepatocytes. The hepatocytes were robust enough to be used for method development and to plan for the future studies. The IC50 values for EG and rosuvastatin as the probe substrates using CsA and rifampicin as inhibitors were in agreement with quoted literature values and suggested a predominate role for OATP1B1 in EG and rosuvastatin uptake. In these paediatric human hepatocytes NTCP did not appear to play a role in the uptake of rosuvastatin.The paediatric human hepatocyte data were used to help define and refine the studies conducted in the experimental phase of the study. The same uptake parameters for rosuvastatin were determined in human hepatocytes from three adult donors using the mechanistic two-compartment model. The time of the incubation was extended to 60 minutes to ensure that steady state kinetics were reached. Inhibition of the uptake of rosuvastatin was determined with co- and pre-incubation of CsA and its main metabolite, AM1. The time-dependent nature of the inhibitors have been studied by ourselves, but not in human hepatocytes [Gertz et al 2012]. There did not appear to be an effect of co- versus pre-incubation of the inhibitors.The mechanistic two-compartment model was also used to determine the uptake parameters for a GSK compound, namely GSK2879552, using the same adult human hepatocytes from three adult donors. However, the hepatic uptake clearance (CLuptake) values suggested that active saturable uptake of GSK2879552 was not evident. This may explain the high variability observed between the three donors for the uptake parameters (Vmax, Km,u, Pdiff,u and Fucell) and the high coefficient of variation observed about each parameter. These data provided a useful learning with regards to understanding the limitations of the model
Simultaneous detection of multiple explosives using surface enhanced Raman scattering
Get PDFThere remains a continuing threat of terrorist/insurgent attacks on military/civilian personnel and key strategic infrastructures both within the UK mainland and in operational theatres. The development of a novel, innovative, low cost, field deployable bionanosensor, which will have the capability to detect low levels of explosive in a multiplexed fashion is required. The use of the specific interaction between small molecules and biological capture molecules such as antibodies coupled with the detection technique of surface enhanced Raman scattering (SERS) allows a 'one shot' analysis.This research makes use of antibody functionalised silver nanoparticles for the detection of the explosives TNT, RDX and PETN by surface enhanced Raman scattering (SERS). Commercially available antibodies specific for TNT and RDX have been modified to specifically orientate 'flat' on the surface of silver nanoparticles bringing the target close enough to the metal surface to allow an intrinsic SERS signal of the target molecule to be obtained. Quantitative detection of TNT and RDX explosives was achieved, with pM sensitivity demonstrated for RDX. Furthermore, TNT was detected in two different types of dirt, natural and synthetic dirt in order to mimic a more realistic matrix in which TNT would be found in the field.However, for the detection of PETN, it was required to develop a method to modify a PETN antibody in-house, to specifically orientate 'flat' on the nanoparticles surface similarly to the commercially available antibodies. This was achieved by using carbodiimide chemistry and the antibody was purified by cartridge centrifugation and HPLC. The PETN modified antibody was then functionalised onto silver nanoparticles and detection of PETN was achieved by SERS. In addition, PCA was used to allow multiplexed analysis based on unique Raman bands for the three different explosives which could be clearly identified in the SERS spectra.Finally, TNT was detected by using magnetic nanoparticles which were functionalised with a terminal amine group in combination with FITC modified TNT antibody functionalised silver nanoparticles. This assay was designed to allow for the formation of a Meisenheimer complex in the presence of TNT, between the amine functionalised magnetic nanoparticles and the TNT. Furthermore, the TNT antibody functionalised silver nanoparticles also binds to TNT, aggregating the nanoparticles. The magnetic nanoparticles were subsequently used to remove the nanoparticle assembly from the matrix, resulting in a concentrated sample on the magnet, resulting in an increase in SERS.There remains a continuing threat of terrorist/insurgent attacks on military/civilian personnel and key strategic infrastructures both within the UK mainland and in operational theatres. The development of a novel, innovative, low cost, field deployable bionanosensor, which will have the capability to detect low levels of explosive in a multiplexed fashion is required. The use of the specific interaction between small molecules and biological capture molecules such as antibodies coupled with the detection technique of surface enhanced Raman scattering (SERS) allows a 'one shot' analysis.This research makes use of antibody functionalised silver nanoparticles for the detection of the explosives TNT, RDX and PETN by surface enhanced Raman scattering (SERS). Commercially available antibodies specific for TNT and RDX have been modified to specifically orientate 'flat' on the surface of silver nanoparticles bringing the target close enough to the metal surface to allow an intrinsic SERS signal of the target molecule to be obtained. Quantitative detection of TNT and RDX explosives was achieved, with pM sensitivity demonstrated for RDX. Furthermore, TNT was detected in two different types of dirt, natural and synthetic dirt in order to mimic a more realistic matrix in which TNT would be found in the field.However, for the detection of PETN, it was required to develop a method to modify a PETN antibody in-house, to specifically orientate 'flat' on the nanoparticles surface similarly to the commercially available antibodies. This was achieved by using carbodiimide chemistry and the antibody was purified by cartridge centrifugation and HPLC. The PETN modified antibody was then functionalised onto silver nanoparticles and detection of PETN was achieved by SERS. In addition, PCA was used to allow multiplexed analysis based on unique Raman bands for the three different explosives which could be clearly identified in the SERS spectra.Finally, TNT was detected by using magnetic nanoparticles which were functionalised with a terminal amine group in combination with FITC modified TNT antibody functionalised silver nanoparticles. This assay was designed to allow for the formation of a Meisenheimer complex in the presence of TNT, between the amine functionalised magnetic nanoparticles and the TNT. Furthermore, the TNT antibody functionalised silver nanoparticles also binds to TNT, aggregating the nanoparticles. The magnetic nanoparticles were subsequently used to remove the nanoparticle assembly from the matrix, resulting in a concentrated sample on the magnet, resulting in an increase in SERS
Design and analysis of inflatable space structures
Get PDFThis thesis gives the conceptualization of inflation of inflatable membrane space structures. Although there has been little study using software simulation and the majority of documented research is based on theoretical numerical calculations. This research advanced the prior understanding of wrinkling within inflated membranes by using complex structures subjected to deformation loads. Within this thesis, a computational framework for the numerical analysis of the interaction between acting forces on the membrane and the membrane structure dynamics is presented. Moreover, in the case with thin membrane deformations, the synergy between the membrane wrinkling and structural forces has to be examined. This membrane structure-anatomical forces correlation results in a dynamic wrinkling problem, which can only be modelled easily and effectively by a simulation software that can integrate each assumption and attribute within the analysis. In the structural simulation within Abaqus FEA software, key consideration has to be given in modelling the geometric non-linearity behaviour of the membrane. By using the existing continuum expression for the virtual internal work in curvilinear coordinates. This is used to derive the modified fundamental formulation in which all subsequent analysis is established on and the initial equilibrium shape of the membrane. A critical feature of the new formulation is the prospect of adding pre-stressed forces to the membrane structure. The approach developed, established on an alteration of the material stiffness matrix to integrate the effects of wrinkling and deformation, can be utilized to calculate the behaviour of the membrane within a finite element simulation. In the wrinkling model, the state of the membrane element (taut, wrinkled or slack) is characterized by a mixed wrinkling criterion. Once it has been identified that the membrane element is wrinkled, an iterative scheme looks for the wrinkled orientation angle and the precise stress distribution, including only uni-axial tension in the wrinkle direction, is then derived. The wrinkling model has been verified and validated by contrasting the simulated conclusions with documented results for the instance of a time-independent isotropic membrane subjected to shear and axial loading. Utilizing the time integration method, a time-dependant pseudo-elastic stiffness matrix was represented and therefore, rather than calculating the convolution integral all through the Abaqus simulation, then we can calculate the behaviour of a membrane structure by superposition of a series of step by step increments in basic finite element software.;The theoretical computations from the Abaqus/Explicit analysis were compared with documented results for the shear and axial loading. The results agreed very well, assuming friction and any relativistic dynamic effects were excluded. The discrepancy between the shear loading solution is 7% while the discrepancy between the axial loading is only 5% between the Abaqus modeland the documented model. This discrepancy could be the resultant of the source of energy dissipation from the visco-elastic behaviour during the loading and unloading of forces. It can be stated that for the Kapton HN membrane, this result falls within acceptable range but to increase accuracy, the load and unloading will be carried out on a set steady amplitude to inhibit in shock effects within the model. A three-dimensional finite element model which integrates wrinkling and frictionless contact has been developed to simulate the adaptive smart cell and cylindrical membrane structure. The loading of both structures is given by a non-uniform differential inflation pressure with a continual gradient adjacent to height. The resultant solutions are computed using Abaqus/Explicit software, with an integrated user-defined material subroutine to account for elastic wrinkling deformation that administers a combined stress-strain criterion. Frictionless contact within the membrane structure is prescribed for both complex structures (Adaptive Smart Structures Model and Inflatable Beam Model) in order to prohibit the penetration of the membrane structure through itself. Both the complex inflatable membrane wrinkling models accomplish the purpose of exceptional subgrid scale performance in relation to accuracy, competency, computing hardware & software expense, complexity and the model convergence rate.;The numerical algorithm is created in general context and is flexible for a large variety of material models. For a closed membrane structure, the skew symmetric constraint parameters vanish, while the existing symmetric domain variables mirror preservation of the system. This procedure does not demand the discretization of the fluid (gas) domain or the link between coupling of fluid (gas) and membrane. As a result of this basic fact, the computation is drastically simplified. The adaptive structures model introduces a novel approach in harnessing solar power for reuse on the ground as a stable source of power. The simulations were based on the space part of the stiff structure created of hexagonal membrane cells. Simulations are carried out in Abaqus Finite Element Analysis software for simplicity & a comparison for validation purposes is tested against an experimental inflatable cell within a vacuum chamber. It was showcased that the final configuration could be achieved regardless of the packaging shape of the inflatable cell array. The inflatable beam model is comprised of two sections, the bending & buckling of the inflated beam and the post-inflation of the bent and buckled beam. Abaqus software was used to simulate the inflatable beam during each configuration utilizing the integration of a modified VUMAT subroutine. A comparison is showcased representing the importance of the integration of the VUMAT subroutine within our Abaqus model.This thesis gives the conceptualization of inflation of inflatable membrane space structures. Although there has been little study using software simulation and the majority of documented research is based on theoretical numerical calculations. This research advanced the prior understanding of wrinkling within inflated membranes by using complex structures subjected to deformation loads. Within this thesis, a computational framework for the numerical analysis of the interaction between acting forces on the membrane and the membrane structure dynamics is presented. Moreover, in the case with thin membrane deformations, the synergy between the membrane wrinkling and structural forces has to be examined. This membrane structure-anatomical forces correlation results in a dynamic wrinkling problem, which can only be modelled easily and effectively by a simulation software that can integrate each assumption and attribute within the analysis. In the structural simulation within Abaqus FEA software, key consideration has to be given in modelling the geometric non-linearity behaviour of the membrane. By using the existing continuum expression for the virtual internal work in curvilinear coordinates. This is used to derive the modified fundamental formulation in which all subsequent analysis is established on and the initial equilibrium shape of the membrane. A critical feature of the new formulation is the prospect of adding pre-stressed forces to the membrane structure. The approach developed, established on an alteration of the material stiffness matrix to integrate the effects of wrinkling and deformation, can be utilized to calculate the behaviour of the membrane within a finite element simulation. In the wrinkling model, the state of the membrane element (taut, wrinkled or slack) is characterized by a mixed wrinkling criterion. Once it has been identified that the membrane element is wrinkled, an iterative scheme looks for the wrinkled orientation angle and the precise stress distribution, including only uni-axial tension in the wrinkle direction, is then derived. The wrinkling model has been verified and validated by contrasting the simulated conclusions with documented results for the instance of a time-independent isotropic membrane subjected to shear and axial loading. Utilizing the time integration method, a time-dependant pseudo-elastic stiffness matrix was represented and therefore, rather than calculating the convolution integral all through the Abaqus simulation, then we can calculate the behaviour of a membrane structure by superposition of a series of step by step increments in basic finite element software.;The theoretical computations from the Abaqus/Explicit analysis were compared with documented results for the shear and axial loading. The results agreed very well, assuming friction and any relativistic dynamic effects were excluded. The discrepancy between the shear loading solution is 7% while the discrepancy between the axial loading is only 5% between the Abaqus modeland the documented model. This discrepancy could be the resultant of the source of energy dissipation from the visco-elastic behaviour during the loading and unloading of forces. It can be stated that for the Kapton HN membrane, this result falls within acceptable range but to increase accuracy, the load and unloading will be carried out on a set steady amplitude to inhibit in shock effects within the model. A three-dimensional finite element model which integrates wrinkling and frictionless contact has been developed to simulate the adaptive smart cell and cylindrical membrane structure. The loading of both structures is given by a non-uniform differential inflation pressure with a continual gradient adjacent to height. The resultant solutions are computed using Abaqus/Explicit software, with an integrated user-defined material subroutine to account for elastic wrinkling deformation that administers a combined stress-strain criterion. Frictionless contact within the membrane structure is prescribed for both complex structures (Adaptive Smart Structures Model and Inflatable Beam Model) in order to prohibit the penetration of the membrane structure through itself. Both the complex inflatable membrane wrinkling models accomplish the purpose of exceptional subgrid scale performance in relation to accuracy, competency, computing hardware & software expense, complexity and the model convergence rate.;The numerical algorithm is created in general context and is flexible for a large variety of material models. For a closed membrane structure, the skew symmetric constraint parameters vanish, while the existing symmetric domain variables mirror preservation of the system. This procedure does not demand the discretization of the fluid (gas) domain or the link between coupling of fluid (gas) and membrane. As a result of this basic fact, the computation is drastically simplified. The adaptive structures model introduces a novel approach in harnessing solar power for reuse on the ground as a stable source of power. The simulations were based on the space part of the stiff structure created of hexagonal membrane cells. Simulations are carried out in Abaqus Finite Element Analysis software for simplicity & a comparison for validation purposes is tested against an experimental inflatable cell within a vacuum chamber. It was showcased that the final configuration could be achieved regardless of the packaging shape of the inflatable cell array. The inflatable beam model is comprised of two sections, the bending & buckling of the inflated beam and the post-inflation of the bent and buckled beam. Abaqus software was used to simulate the inflatable beam during each configuration utilizing the integration of a modified VUMAT subroutine. A comparison is showcased representing the importance of the integration of the VUMAT subroutine within our Abaqus model
New Frontiers on Cooperative Chemistry of Rarely Employed Metals
Get PDFThis project sought to extend the concept of enhanced cooperative reactivity in bimetallic chemistry to metals beyond Mg, Zn or Al, especially, Ga and Mn.Towards new applications of trisalkylgallium in synthesis, studies on gallium NHC (N-heterocyclic carbene) chemistry afforded a novel series of normal, abnormal and anionic NHC complexes derived from Ga(CH2SiMe3)3. These complexes proved excellent platforms for accessing functionalised aNHC ligands via metallation/electrophilic interception and/or thermal isomerisation. Capitalising on these advances, a new FLP system incorporating Ga(CH2SiMe3)3 and bulky NHCs as effective Lewis acid Lewis base combinations was developed. By exploring their reactivity towards carbonyl compounds two distinct types of FLP activation processes were uncovered. Adding the FLP pair across the C=O functionality can occur, forming new C-C and Ga-O bonds, in which NHC can participate through its normal or abnormal position. Alternatively, C-H bond activation can proceed by treating enolizable ketones, or other C-H acidic substrates such as nitriles or terminal alkynes, with the same mixture;Exporting such steric incompatibility into bimetallic chemistry a new multicomponent LiTMP/GaR3 metallating mixture that works in a tandem manner has been established. Lack of co-complexation between the bulky lithium amide LiTMP and trisalkylgallium facilitates substrate deprotonation by LiTMP (the base) and anion trapping by GaR3 (the trap). Thus, introducing the concept of gallium trans-metal-trapping, for the first time formal gallation of aromatic substrates (i.e. diazines and anisole) has been accomplished.The project also developed alkali-metal manganate chemistry. A new family of homoleptic alkali-metal manganates has been prepared and characterized by X-ray crystallographic, EPR spectroscopic and SQUID magnetometric studies. Intriguing structural/synthetic/magnetic correlations were revealed in which aggregation and reactivity of different manganates were largely determined by the alkali-metal. Furthermore, addressing the issue of ill-defined manganese species participating in organic transformations, lithium manganate [(TMEDA)2Li2Mn(CH2SiMe3)4] was disclosed as an effective reagent to promote direct Mn-I exchange and homocoupling processes.This project sought to extend the concept of enhanced cooperative reactivity in bimetallic chemistry to metals beyond Mg, Zn or Al, especially, Ga and Mn.Towards new applications of trisalkylgallium in synthesis, studies on gallium NHC (N-heterocyclic carbene) chemistry afforded a novel series of normal, abnormal and anionic NHC complexes derived from Ga(CH2SiMe3)3. These complexes proved excellent platforms for accessing functionalised aNHC ligands via metallation/electrophilic interception and/or thermal isomerisation. Capitalising on these advances, a new FLP system incorporating Ga(CH2SiMe3)3 and bulky NHCs as effective Lewis acid Lewis base combinations was developed. By exploring their reactivity towards carbonyl compounds two distinct types of FLP activation processes were uncovered. Adding the FLP pair across the C=O functionality can occur, forming new C-C and Ga-O bonds, in which NHC can participate through its normal or abnormal position. Alternatively, C-H bond activation can proceed by treating enolizable ketones, or other C-H acidic substrates such as nitriles or terminal alkynes, with the same mixture;Exporting such steric incompatibility into bimetallic chemistry a new multicomponent LiTMP/GaR3 metallating mixture that works in a tandem manner has been established. Lack of co-complexation between the bulky lithium amide LiTMP and trisalkylgallium facilitates substrate deprotonation by LiTMP (the base) and anion trapping by GaR3 (the trap). Thus, introducing the concept of gallium trans-metal-trapping, for the first time formal gallation of aromatic substrates (i.e. diazines and anisole) has been accomplished.The project also developed alkali-metal manganate chemistry. A new family of homoleptic alkali-metal manganates has been prepared and characterized by X-ray crystallographic, EPR spectroscopic and SQUID magnetometric studies. Intriguing structural/synthetic/magnetic correlations were revealed in which aggregation and reactivity of different manganates were largely determined by the alkali-metal. Furthermore, addressing the issue of ill-defined manganese species participating in organic transformations, lithium manganate [(TMEDA)2Li2Mn(CH2SiMe3)4] was disclosed as an effective reagent to promote direct Mn-I exchange and homocoupling processes
Electrically-induced degradation of polyester films for photovoltaic devices
Get PDFPoly(ethylene terephthalate) (PET) is one of the most common thermoplastics that has been widely used in nearly every field all over the world. Particularly, PET is utilized as a core layer in the backsheets of photovoltaic panels to provide electrical insulation and mechanical stability.Partial discharge (PD) is localized dielectric breakdown that usually occurs in voids or air gaps within solid or liquid insulation systems. Long-term PD exposure can significantly deteriorate the system and cause final breakdown. PD is believed to be able to occur in PV backsheets under certain circumstances and this is obviously a potential risk of safe operation for the PV modules. PET, as usually being the thickest layer of the backsheet with excellent insulation properties, greatly determines the PD behaviour of the PV backsheet. Therefore a comprehensive understanding of PD-induced degradation and dielectric breakdown of PET films will be vital.In this project, various types of PET films were studied to understand how physical and chemical properties influence the PD-induced degradation and breakdown of the PET films. Efforts have endeavoured to focus on three primary aspects: morphology effect, performance additive effect and weathering effect.The main contributions of this work are: the morphology effect has been quantitatively analysed and a straightforward method was introduced to significantly improve the sample performance; great enhancement in voltage endurance has been found once the PET sample equipped with a phosphorus-based flame retardant; the weathering effect (UV and hydrolysis) on the PD-induced degradation and breakdown of PET was investigated for the first time ever.Poly(ethylene terephthalate) (PET) is one of the most common thermoplastics that has been widely used in nearly every field all over the world. Particularly, PET is utilized as a core layer in the backsheets of photovoltaic panels to provide electrical insulation and mechanical stability.Partial discharge (PD) is localized dielectric breakdown that usually occurs in voids or air gaps within solid or liquid insulation systems. Long-term PD exposure can significantly deteriorate the system and cause final breakdown. PD is believed to be able to occur in PV backsheets under certain circumstances and this is obviously a potential risk of safe operation for the PV modules. PET, as usually being the thickest layer of the backsheet with excellent insulation properties, greatly determines the PD behaviour of the PV backsheet. Therefore a comprehensive understanding of PD-induced degradation and dielectric breakdown of PET films will be vital.In this project, various types of PET films were studied to understand how physical and chemical properties influence the PD-induced degradation and breakdown of the PET films. Efforts have endeavoured to focus on three primary aspects: morphology effect, performance additive effect and weathering effect.The main contributions of this work are: the morphology effect has been quantitatively analysed and a straightforward method was introduced to significantly improve the sample performance; great enhancement in voltage endurance has been found once the PET sample equipped with a phosphorus-based flame retardant; the weathering effect (UV and hydrolysis) on the PD-induced degradation and breakdown of PET was investigated for the first time ever
Modelling offshore wind farm operation and maintenance with view to estimating the benefits of condition monitoring
Get PDFOffshore wind energy is progressing rapidly and playing an increasingly important role in electricity generation. Since the Kyoto Protocol in February 2005, Europe has been substantially increasing its installed wind capacity. Compared to onshore wind, offshore wind allows the installation of larger turbines, more extensive sites, and encounters higher wind speed with lower turbulence. On the other hand, harsh marine conditions and the limited access to the turbines are expected to increase the cost of operation and maintenance (O&M costs presently make up approximately 20-25% of the levelised total lifetime cost of a wind turbine). Efficient condition monitoring has the potential to reduce O&M costs. In the analysis of the cost effectiveness of condition monitoring, cost and operational data are crucial. Regrettably, wind farm operational data are generally kept confidential by manufacturers and wind farm operators, especially for the offshore ones.To facilitate progress, this thesis has investigated accessible SCADA and failure data from a large onshore wind farm and created a series of indirect analysis methods to overcome the data shortage including an onshore/offshore failure rate translator and a series of methods to distinguish yawing errors from wind turbine nacelle direction sensor errors. Wind turbine component reliability has been investigated by using this innovative component failure rate translation from onshore to offshore, and applies the translation technique to Failure Mode and Effect Analysis for offshore wind. An existing O&M cost model has been further developed and then compared to other available cost models. It is demonstrated that the improvements made to the model (including the data translation approach) have improved the applicability and reliability of the model. The extended cost model (called StraPCost+) has been used to establish a relationship between the effectiveness of reactive and condition-based maintenance strategies. The benchmarked cost model has then been applied to assess the O&M cost effectiveness for three offshore wind farms at different operational phases.Apart from the innovative methodologies developed, this thesis also provides detailed background and understanding of the state of the art for offshore wind technology, condition monitoring technology. The methodology of cost model developed in this thesis is presented in detail and compared with other cost models in both commercial and research domains.Offshore wind energy is progressing rapidly and playing an increasingly important role in electricity generation. Since the Kyoto Protocol in February 2005, Europe has been substantially increasing its installed wind capacity. Compared to onshore wind, offshore wind allows the installation of larger turbines, more extensive sites, and encounters higher wind speed with lower turbulence. On the other hand, harsh marine conditions and the limited access to the turbines are expected to increase the cost of operation and maintenance (O&M costs presently make up approximately 20-25% of the levelised total lifetime cost of a wind turbine). Efficient condition monitoring has the potential to reduce O&M costs. In the analysis of the cost effectiveness of condition monitoring, cost and operational data are crucial. Regrettably, wind farm operational data are generally kept confidential by manufacturers and wind farm operators, especially for the offshore ones.To facilitate progress, this thesis has investigated accessible SCADA and failure data from a large onshore wind farm and created a series of indirect analysis methods to overcome the data shortage including an onshore/offshore failure rate translator and a series of methods to distinguish yawing errors from wind turbine nacelle direction sensor errors. Wind turbine component reliability has been investigated by using this innovative component failure rate translation from onshore to offshore, and applies the translation technique to Failure Mode and Effect Analysis for offshore wind. An existing O&M cost model has been further developed and then compared to other available cost models. It is demonstrated that the improvements made to the model (including the data translation approach) have improved the applicability and reliability of the model. The extended cost model (called StraPCost+) has been used to establish a relationship between the effectiveness of reactive and condition-based maintenance strategies. The benchmarked cost model has then been applied to assess the O&M cost effectiveness for three offshore wind farms at different operational phases.Apart from the innovative methodologies developed, this thesis also provides detailed background and understanding of the state of the art for offshore wind technology, condition monitoring technology. The methodology of cost model developed in this thesis is presented in detail and compared with other cost models in both commercial and research domains
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