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A molecular dynamics study on cementitious materials and nanocomposites
Get PDFCementitious materials, including cement composites, are the most used construction material in the world. With the development of nanotechnology in the last several decades, the properties of cementitious materials can be significantly improved by adding nanomaterials such as nanoparticles, nanofibers, nanotubes and graphene-based materials. Graphene oxide (GO) has been widely accepted as an ideal candidate in increasing various properties of cement, i.e., strength, toughness, durability, electrical conductivity etc.;However, the strengthening mechanism and some fundamental behavior of this cementitious nanocomposite are still not very clear. Therefore, this thesis aims to carry out a comprehensive study in understanding of the micro-mechanism of GO-cement, based on the recent developed realistic atomic structure of Calcium Silicate Hydrate (C-S-H) and Molecular Dynamics (MD) method. A critical review on the state-of-the-art of the properties and nanomechanics of cementitious materials and composites as well as molecular dynamics method is provided.;The interfacial shear transfer mechanism between the GO sheet and C-S-H in the GO-cement nanocomposite is examined; also, the shear strength and shearing fracture properties are quantitatively determined. Moreover, the mechanical properties for the basic particle of C-S-H and the interfaces between the C-S-H particles, including Young's modulus, strength, fracture energy, are determined which are also affected by amount of water molecules.;The enhancing mechanism by adding GO in cement is simulated by MD method; the overall strength and fracture properties for the GO-cement composite are calculated and the cracking bridging effect is studied. Furthermore, experiments about the global mechanical properties of GO-cement are conducted by the in-situ SEM three-point bending test. The overall increase of the mechanical performance of GO-cement is confirmed. This study presents novel and comprehensive understanding of the GO-cement from nanoscale to macroscale.Cementitious materials, including cement composites, are the most used construction material in the world. With the development of nanotechnology in the last several decades, the properties of cementitious materials can be significantly improved by adding nanomaterials such as nanoparticles, nanofibers, nanotubes and graphene-based materials. Graphene oxide (GO) has been widely accepted as an ideal candidate in increasing various properties of cement, i.e., strength, toughness, durability, electrical conductivity etc.;However, the strengthening mechanism and some fundamental behavior of this cementitious nanocomposite are still not very clear. Therefore, this thesis aims to carry out a comprehensive study in understanding of the micro-mechanism of GO-cement, based on the recent developed realistic atomic structure of Calcium Silicate Hydrate (C-S-H) and Molecular Dynamics (MD) method. A critical review on the state-of-the-art of the properties and nanomechanics of cementitious materials and composites as well as molecular dynamics method is provided.;The interfacial shear transfer mechanism between the GO sheet and C-S-H in the GO-cement nanocomposite is examined; also, the shear strength and shearing fracture properties are quantitatively determined. Moreover, the mechanical properties for the basic particle of C-S-H and the interfaces between the C-S-H particles, including Young's modulus, strength, fracture energy, are determined which are also affected by amount of water molecules.;The enhancing mechanism by adding GO in cement is simulated by MD method; the overall strength and fracture properties for the GO-cement composite are calculated and the cracking bridging effect is studied. Furthermore, experiments about the global mechanical properties of GO-cement are conducted by the in-situ SEM three-point bending test. The overall increase of the mechanical performance of GO-cement is confirmed. This study presents novel and comprehensive understanding of the GO-cement from nanoscale to macroscale
Development of gold supraparticles for nanomedicine applications
No full textGold nanoparticles are widely used in bionanotechnology due to their unique optical properties and ease of surface modification with biomolecules. By assembling these gold nanoparticles into ordered structures their physiochemical properties can be fine-tuned. Gold nanoparticle assemblies have shown a remarkable increase in surface enhanced Raman signals (SERS) which can be further used for biological sensing applications. In addition, their efficient conversion of light to heat energy allows them to be promising candidates for photothermal therapies. A new method for assembling citrate capped gold nanoparticles into crystallographically aligned supraparticles is reported. These are biocompatible and have a strong SERS response. Additionally, these have been shown to convert light to heat more efficiently than their nanoparticle building blocks. Furthermore, gold nanoparticles were assembled onto a superparamagnetic iron oxide (SPION) core. These anisotropic assemblies called suprashells have a plasmon band in the near-infrared (NIR) region which makes them suitable candidates for biological applications. They also make efficient thermal transducers and promising SERS substrates due to the enhancement of signal. Finally, self-assembled structures of monomer fluorenylmethyloxycarbonyl (Fmoc) protected amino acids are used as potential templates for gold nanoparticle assemblies. Each Fmoc-amino acid assembles into its own unique structure depending on the intrinsic property of its side chain. These soft templates are used to guide the assembly of gold nanoparticles. It has been found that there is a symbiotic relationship between the gold nanoparticle and amino acid side chain which can dictate the final degree of order.Gold nanoparticles are widely used in bionanotechnology due to their unique optical properties and ease of surface modification with biomolecules. By assembling these gold nanoparticles into ordered structures their physiochemical properties can be fine-tuned. Gold nanoparticle assemblies have shown a remarkable increase in surface enhanced Raman signals (SERS) which can be further used for biological sensing applications. In addition, their efficient conversion of light to heat energy allows them to be promising candidates for photothermal therapies. A new method for assembling citrate capped gold nanoparticles into crystallographically aligned supraparticles is reported. These are biocompatible and have a strong SERS response. Additionally, these have been shown to convert light to heat more efficiently than their nanoparticle building blocks. Furthermore, gold nanoparticles were assembled onto a superparamagnetic iron oxide (SPION) core. These anisotropic assemblies called suprashells have a plasmon band in the near-infrared (NIR) region which makes them suitable candidates for biological applications. They also make efficient thermal transducers and promising SERS substrates due to the enhancement of signal. Finally, self-assembled structures of monomer fluorenylmethyloxycarbonyl (Fmoc) protected amino acids are used as potential templates for gold nanoparticle assemblies. Each Fmoc-amino acid assembles into its own unique structure depending on the intrinsic property of its side chain. These soft templates are used to guide the assembly of gold nanoparticles. It has been found that there is a symbiotic relationship between the gold nanoparticle and amino acid side chain which can dictate the final degree of order
Theoretical analysis of a fractal ultrasonic transducer using renormalisation
Get PDFTo ensure the safe operation of many safety critical structures such as nuclear plants, aircraft and oil pipelines, non-destructive imaging is employed using piezoelectric ultrasonic transducers. These sensors typically operate at a single frequency due to the restrictions imposed on their resonant behaviour by the use of a single length scale in the design. To allow these transducers to transmit and receive more complex signals it would seem logical to use a range of length scales in the design so that a wide range of resonating frequencies will result. In this thesis we derive a mathematical model to predict the operating characteristics of an ultrasound transducer that achieves this range of length scales by adopting a fractal architecture; the fractal in this case being the Sierpinski gasket. Expressions for the electrical and mechanical fields that are contained within this structure are expressed in terms of a finite element basis. A renormalisation approach is then used to calculate the key components from the discrete matrices that arise. The propagation of an ultrasonic wave in this transducer is then analyzed and used to derive expressions for the non-dimensionalised electrical impedance and the transmission and reception sensitivities as a function of the driving frequency. Comparing these key performance measures of the fractal transducer to an equivalent standard (Euclidean) design shows that the fractal devices have a significantly higher reception sensitivity and a significantly wider bandwidth.To ensure the safe operation of many safety critical structures such as nuclear plants, aircraft and oil pipelines, non-destructive imaging is employed using piezoelectric ultrasonic transducers. These sensors typically operate at a single frequency due to the restrictions imposed on their resonant behaviour by the use of a single length scale in the design. To allow these transducers to transmit and receive more complex signals it would seem logical to use a range of length scales in the design so that a wide range of resonating frequencies will result. In this thesis we derive a mathematical model to predict the operating characteristics of an ultrasound transducer that achieves this range of length scales by adopting a fractal architecture; the fractal in this case being the Sierpinski gasket. Expressions for the electrical and mechanical fields that are contained within this structure are expressed in terms of a finite element basis. A renormalisation approach is then used to calculate the key components from the discrete matrices that arise. The propagation of an ultrasonic wave in this transducer is then analyzed and used to derive expressions for the non-dimensionalised electrical impedance and the transmission and reception sensitivities as a function of the driving frequency. Comparing these key performance measures of the fractal transducer to an equivalent standard (Euclidean) design shows that the fractal devices have a significantly higher reception sensitivity and a significantly wider bandwidth
Two-tiered meta-heuristic holistic optimisation of subsea electrical networks
Get PDFHuman thirst for energy shows no signs of abating; instead global demand for electricity is projected to increase in the coming decades. If this demand is to be supplied in a sustainable manner, a rapid uptake in renewable sourced electrical energy is required. One arena that offers significant scope for increased renewable sourced generation is the offshore domain, through the offshore wind, tidal, and wave vectors. While the energy potential of the marine domain is vast, there are a number of challenges associated with deploying machines offshore to generate electricity, and transporting this energy back to population centres where it may be utilised. The deployment of a subsea electrical network to facilitate the extraction of energy from offshore renewable energy projects can be both logistically difficult and expensive. Consequently, the optimisation of such networks takes on critical importance if the marine domain is to make a significantly increased contribution towards the global electricity demand. This thesis considers the application of a two-tiered meta-heuristic optimisation approach for the holistic design of subsea electrical networks for offshore renewable energy projects; accounting for in-service costs arising from electrical losses and no-service conditions, in addition to purchase and installation costs. One current offshore wind development, Horns-Rev 1 was assessed using the optimisation framework that has been developed as part of this work. These studies demonstrate that the in-situ network at Horns-Rev 1 could have been improved upon, in terms of through-life cost minimisation while using the same design parameters, by changing the network layout. By altering the selected design parameters (voltage and frequency) the network performance, against the lifecycle cost minimisation could be further reduced. Additionally, the optimisation framework is deployed to design an optimal network for the proposed East Anglia One offshore wind park where viable solutions were identified using the projected design parameters. Again, it is shown that by altering the voltage and frequency parameters selected in the design, the through-life cost of the network solution may be improved upon relative to the assumed parameters.Human thirst for energy shows no signs of abating; instead global demand for electricity is projected to increase in the coming decades. If this demand is to be supplied in a sustainable manner, a rapid uptake in renewable sourced electrical energy is required. One arena that offers significant scope for increased renewable sourced generation is the offshore domain, through the offshore wind, tidal, and wave vectors. While the energy potential of the marine domain is vast, there are a number of challenges associated with deploying machines offshore to generate electricity, and transporting this energy back to population centres where it may be utilised. The deployment of a subsea electrical network to facilitate the extraction of energy from offshore renewable energy projects can be both logistically difficult and expensive. Consequently, the optimisation of such networks takes on critical importance if the marine domain is to make a significantly increased contribution towards the global electricity demand. This thesis considers the application of a two-tiered meta-heuristic optimisation approach for the holistic design of subsea electrical networks for offshore renewable energy projects; accounting for in-service costs arising from electrical losses and no-service conditions, in addition to purchase and installation costs. One current offshore wind development, Horns-Rev 1 was assessed using the optimisation framework that has been developed as part of this work. These studies demonstrate that the in-situ network at Horns-Rev 1 could have been improved upon, in terms of through-life cost minimisation while using the same design parameters, by changing the network layout. By altering the selected design parameters (voltage and frequency) the network performance, against the lifecycle cost minimisation could be further reduced. Additionally, the optimisation framework is deployed to design an optimal network for the proposed East Anglia One offshore wind park where viable solutions were identified using the projected design parameters. Again, it is shown that by altering the voltage and frequency parameters selected in the design, the through-life cost of the network solution may be improved upon relative to the assumed parameters
Rheological characterisation and numerical flow simulation of the human eye vitreous humour fluid
No full textIn this work, the dynamics of vitreous humour (VH) and of a range of pharmacological fluids used to replace VH in eye surgery were investigated, both experimentally and numerically. Vitreous humour is a gel-like viscoelastic material that fills the majority of the ocular globe. Age-related changes occur in the VH, and as a consequence VH becomes progressively liquefied with age, which has an impact on the corresponding rheological properties, and leads to the appearance of vitreoretinal pathologies.;The most effective treatment for such diseases is the injection of a VH substitute in the vitreous cavity. Most of the vitreous substitutes commercially available are silicone oils (SiO) and perfluorocarbon liquids (PFLC), but so far none of them proven to be used as a permanent substitute.;The results of the rheological characterisation of the VH and pharmacological fluids under shear and extensional flow conditions are presented in the first part of this thesis. Vitreous humour samples were obtained from New Zealand specimen rabbit eyes, whereas the pharmacological fluids were purchased from two different pharmaceutical companies.;Two distinct VH phases were analysed: a liquid and a gel phase. The average surface tension measured for the VH liquid phase was 47.8 mN/m, at T = 21 ± 2 °C. Steady shear experiments demonstrated that VH liquid phase has a pronounced shear-thinning behaviour. Small amplitude oscillatory shear (SAOS) experiments showed that both gel and liquid VH phases present a solid-like behaviour, which is more dominant in the gel phase, and these results were corroborated by creep experiments. Experiments with the VH liquid phase under extensional flow yielded an average relaxation time of λ = 9.7 ms, at T ≈ 37 °C.;None of the pharmacological fluids tested showed a rheological behaviour close to the VH. The PFLCs and SiO-based fluids exhibit a Newtonian behaviour, with the exception of Siluron 2000 fluid, which under extensional flow presents a relaxation time of λ = 6.8 ms, at T ≈ 20 °C. The PFLCs have viscosities close to the viscosity of water, whereas the SiO-based fluids present viscosities between 0.73 and 4.57 Pa s, at T = 37 °C.;Surface tension experiments showed that the PFLCs present lower values than the SiO-based fluids, and that the surface tension of the VH liquid phase is more than double of that measured for each of the pharmacological fluids tested. In contact with VH liquid phase from rabbit eyes, all the pharmacological fluids tested yielded interfacial tensions around 30 mN/m.;The dynamic response of VH during saccadic movements was studied numerically using the opensource software OpenFOAM®. A comparative study between the VH and pharmacological fluids was performed for a saccadic movement with an amplitude of 40°. The numerical results showed that the VH liquid and gel phases present distinct behaviour. The shear stresses at the walls for the VH gel phase are higher than those produced by the VH liquid phase.;This shows that the phase balance in VH significantly affects the flow dynamics of the biofluid. The numerical results also showed that velocity and wall shear stress (WSS) profiles are significantly different for VH and pharmacological fluids, revealing that the latter are unable to mimic accurately the VH flow behaviour in conditions such as those experienced during saccadic eye movements.;Finally, different degrees of saccadic movements were studied and the numerical results showed that, for all the fluids investigated, the momentum diffusion across the vitreous cavity and the WSS increase with the increase of the saccadic movement amplitude.;The new experimental results provided in this thesis, complemented by the dynamic behaviour computed numerically for saccadic eye movements, offer new insights for the improvement and development of new VH substitutes to be used in eye surgery, with particular focus on their mechanical functionality.In this work, the dynamics of vitreous humour (VH) and of a range of pharmacological fluids used to replace VH in eye surgery were investigated, both experimentally and numerically. Vitreous humour is a gel-like viscoelastic material that fills the majority of the ocular globe. Age-related changes occur in the VH, and as a consequence VH becomes progressively liquefied with age, which has an impact on the corresponding rheological properties, and leads to the appearance of vitreoretinal pathologies.;The most effective treatment for such diseases is the injection of a VH substitute in the vitreous cavity. Most of the vitreous substitutes commercially available are silicone oils (SiO) and perfluorocarbon liquids (PFLC), but so far none of them proven to be used as a permanent substitute.;The results of the rheological characterisation of the VH and pharmacological fluids under shear and extensional flow conditions are presented in the first part of this thesis. Vitreous humour samples were obtained from New Zealand specimen rabbit eyes, whereas the pharmacological fluids were purchased from two different pharmaceutical companies.;Two distinct VH phases were analysed: a liquid and a gel phase. The average surface tension measured for the VH liquid phase was 47.8 mN/m, at T = 21 ± 2 °C. Steady shear experiments demonstrated that VH liquid phase has a pronounced shear-thinning behaviour. Small amplitude oscillatory shear (SAOS) experiments showed that both gel and liquid VH phases present a solid-like behaviour, which is more dominant in the gel phase, and these results were corroborated by creep experiments. Experiments with the VH liquid phase under extensional flow yielded an average relaxation time of λ = 9.7 ms, at T ≈ 37 °C.;None of the pharmacological fluids tested showed a rheological behaviour close to the VH. The PFLCs and SiO-based fluids exhibit a Newtonian behaviour, with the exception of Siluron 2000 fluid, which under extensional flow presents a relaxation time of λ = 6.8 ms, at T ≈ 20 °C. The PFLCs have viscosities close to the viscosity of water, whereas the SiO-based fluids present viscosities between 0.73 and 4.57 Pa s, at T = 37 °C.;Surface tension experiments showed that the PFLCs present lower values than the SiO-based fluids, and that the surface tension of the VH liquid phase is more than double of that measured for each of the pharmacological fluids tested. In contact with VH liquid phase from rabbit eyes, all the pharmacological fluids tested yielded interfacial tensions around 30 mN/m.;The dynamic response of VH during saccadic movements was studied numerically using the opensource software OpenFOAM®. A comparative study between the VH and pharmacological fluids was performed for a saccadic movement with an amplitude of 40°. The numerical results showed that the VH liquid and gel phases present distinct behaviour. The shear stresses at the walls for the VH gel phase are higher than those produced by the VH liquid phase.;This shows that the phase balance in VH significantly affects the flow dynamics of the biofluid. The numerical results also showed that velocity and wall shear stress (WSS) profiles are significantly different for VH and pharmacological fluids, revealing that the latter are unable to mimic accurately the VH flow behaviour in conditions such as those experienced during saccadic eye movements.;Finally, different degrees of saccadic movements were studied and the numerical results showed that, for all the fluids investigated, the momentum diffusion across the vitreous cavity and the WSS increase with the increase of the saccadic movement amplitude.;The new experimental results provided in this thesis, complemented by the dynamic behaviour computed numerically for saccadic eye movements, offer new insights for the improvement and development of new VH substitutes to be used in eye surgery, with particular focus on their mechanical functionality
Trajectory generation and tracking for drone racing
Get PDFIn this thesis trajectory generation for quadrotors, a type of rotorcraft UAV (Unmanned Aerial Vehicle), is considered with two diverent methods. The first applies the Maximum Principle of optimal control to derive closed-form analytical functions that describe the translational states for two different cases of nonholonomic constraints. Parametric optimisation is used to find the trajectories. Reachable sets are found numerically and a simple obstacle avoidance method is demonstrated for both cases. The second motion planning method found trajectories with polynomial basis functions that are parametrised by an abstract function between zero and one. This virtual time domain trajectory satisfied conditions placed on the boundary derivatives and followed a sequenceof desired waypoints. A process for finding a mapping function that converts the virtual domain trajectory into one on the standard time domain is developed to minimise the trajectory time whilst ensuring the motion remained feasible by enforcing bounds on the thrust required from each rotor. An algorithm that uses additional waypoints where necessary to ensure the trajectory does not collide with the gates that define the course is developed. A method for minimising the accumulated angular acceleration of the heading angle whilst remaining within a desired tolerance of the velocity vector angle is also described. Trajectory tracking is considered by modifying an existing quadrotor tracking controller on the Special Euclidean group SE(3) to include a Linear Extended State Observer that estimates and counteracts translational disturbances. The modified controller is shown to reduce the position tracking error in the presence of square wave, sinusoidal and wind disturbances.In this thesis trajectory generation for quadrotors, a type of rotorcraft UAV (Unmanned Aerial Vehicle), is considered with two diverent methods. The first applies the Maximum Principle of optimal control to derive closed-form analytical functions that describe the translational states for two different cases of nonholonomic constraints. Parametric optimisation is used to find the trajectories. Reachable sets are found numerically and a simple obstacle avoidance method is demonstrated for both cases. The second motion planning method found trajectories with polynomial basis functions that are parametrised by an abstract function between zero and one. This virtual time domain trajectory satisfied conditions placed on the boundary derivatives and followed a sequenceof desired waypoints. A process for finding a mapping function that converts the virtual domain trajectory into one on the standard time domain is developed to minimise the trajectory time whilst ensuring the motion remained feasible by enforcing bounds on the thrust required from each rotor. An algorithm that uses additional waypoints where necessary to ensure the trajectory does not collide with the gates that define the course is developed. A method for minimising the accumulated angular acceleration of the heading angle whilst remaining within a desired tolerance of the velocity vector angle is also described. Trajectory tracking is considered by modifying an existing quadrotor tracking controller on the Special Euclidean group SE(3) to include a Linear Extended State Observer that estimates and counteracts translational disturbances. The modified controller is shown to reduce the position tracking error in the presence of square wave, sinusoidal and wind disturbances
Recycling, regenerating and reusing reinforcement glass fibres
Get PDFOver the last decades, the use of glass fibre reinforced thermosets (GRT) has become widespread and commonly used in many sectors. Currently no commercial recycling process exists for GRT and the amount of waste generated has reached an unsustainable level. The value of recycled glass fibres (RGF) is reduced significantly due to loss in strength and surface functionality during recycling. Thermal recycling processes involve decomposing the polymer matrix at elevated temperatures to recover the reinforcement fibres.;Exposing to such high temperatures degrades the strength of the fibres as well as removes the sizing on the fibre surface. The focus of this thesis is to investigate the potential for retaining and regenerating the strength and interface properties of thermally recycled glass fibres; in order to produce composites reinforced with RGF that could complete with those using virgin/pristine glass fibres.;In order to recycled GRT in-house, a lab scale thermal recycling system based on a fluidised bed reactor was initially designed and developed. To build on the already extensive research into this recycling process, this thesis aims to reduce the temperature required to recycle GRT within the fluidised bed by introducing a metal oxide catalyst to aid in the thermal decomposition of the thermosetting matrix.;This novel line of research was selected due to the potential for reducing both the energy consumption of the recycling process and thermal damage sustained by the glass fibres during recycling. Using thermogravimetric analysis it was found that copper (II) oxide (CuO) was particularly active at catalysing the thermal decomposition of epoxy, reducing the decomposition temperature by up to 125 °C.;When used within the fluidised bed recycling process, CuO facilitated recycling of glass fibre from glass fibre reinforced epoxy (GF-EP) at just 400 °C without compromising on fibre yield efficiency.;Another avenue of research in this thesis was assessing the potential of a variety of chemical treatments to regenerate the strength and surface functionality of thermally recycled glass fibres. It was found that soaking in hot NaOH solution could provide approximately a 130% increase in the strength of RGF; concluding that changes to surface morphology due to etching was the re-strengthening mechanism. The interfacial adhesion between RGF and 1) polypropylene (PP) and 2) epoxy were examined. It was found that the interfacial shear strength (IFSS) between RGF and epoxy could be fully restored by first treating the RGF in NaOH solution.;Regenerating the IFSS between RGF and PP proved more challenging despite the use of fibre sizing and PP matrix modification. GRP reinforced with RGF (with and without regeneration treatments) were prepare and mechanically characterised; however, the GRP exhibited significantly poorer mechanical properties than those prepared with virgin fibres. This drop in performance was typically attributed to a combination of 1) lower fibre strength, 2) poor fibre-polymer interfacial adhesion and 3) low fibre volume fraction within the GRP.Over the last decades, the use of glass fibre reinforced thermosets (GRT) has become widespread and commonly used in many sectors. Currently no commercial recycling process exists for GRT and the amount of waste generated has reached an unsustainable level. The value of recycled glass fibres (RGF) is reduced significantly due to loss in strength and surface functionality during recycling. Thermal recycling processes involve decomposing the polymer matrix at elevated temperatures to recover the reinforcement fibres.;Exposing to such high temperatures degrades the strength of the fibres as well as removes the sizing on the fibre surface. The focus of this thesis is to investigate the potential for retaining and regenerating the strength and interface properties of thermally recycled glass fibres; in order to produce composites reinforced with RGF that could complete with those using virgin/pristine glass fibres.;In order to recycled GRT in-house, a lab scale thermal recycling system based on a fluidised bed reactor was initially designed and developed. To build on the already extensive research into this recycling process, this thesis aims to reduce the temperature required to recycle GRT within the fluidised bed by introducing a metal oxide catalyst to aid in the thermal decomposition of the thermosetting matrix.;This novel line of research was selected due to the potential for reducing both the energy consumption of the recycling process and thermal damage sustained by the glass fibres during recycling. Using thermogravimetric analysis it was found that copper (II) oxide (CuO) was particularly active at catalysing the thermal decomposition of epoxy, reducing the decomposition temperature by up to 125 °C.;When used within the fluidised bed recycling process, CuO facilitated recycling of glass fibre from glass fibre reinforced epoxy (GF-EP) at just 400 °C without compromising on fibre yield efficiency.;Another avenue of research in this thesis was assessing the potential of a variety of chemical treatments to regenerate the strength and surface functionality of thermally recycled glass fibres. It was found that soaking in hot NaOH solution could provide approximately a 130% increase in the strength of RGF; concluding that changes to surface morphology due to etching was the re-strengthening mechanism. The interfacial adhesion between RGF and 1) polypropylene (PP) and 2) epoxy were examined. It was found that the interfacial shear strength (IFSS) between RGF and epoxy could be fully restored by first treating the RGF in NaOH solution.;Regenerating the IFSS between RGF and PP proved more challenging despite the use of fibre sizing and PP matrix modification. GRP reinforced with RGF (with and without regeneration treatments) were prepare and mechanically characterised; however, the GRP exhibited significantly poorer mechanical properties than those prepared with virgin fibres. This drop in performance was typically attributed to a combination of 1) lower fibre strength, 2) poor fibre-polymer interfacial adhesion and 3) low fibre volume fraction within the GRP
Antimicrobial stewardship in the management of sepsis in maternity hospitals - a mixed methodology study
Get PDFBackground: Sepsis is one of the leading causes of maternal mortality and morbidity. The absence of a clear diagnostic marker challenges the process of starting antibiotic therapy. Early identification and management of sepsis is essential. Thus, the sepsis six care bundle (SSCB) was introduced in the UK to improve the care of sepsis patients.;Aim: To evaluate assessment of sepsis and subsequent management including the antibiotic therapy prescribed, and to use this data as a basis of antimicrobial stewardship programme (AMSP) and quality improvement plan within maternity units.;Methods: This study was conducted within three maternity units of NHS Greater Glasgow & Clyde using a mixed methodological approach of an initial quantitative study supplemented by a qualitative study, followed by a quality improvement for further service improvement.;Results: Sepsis was diagnosed in 3% (n=89/2690) of women. There was an inconsistent clinical application of SIRS criteria to inform diagnosis. No causative pathogen was isolated from 60% of clinical specimens. Antibiotic therapy was justified in only 31 women with positive culture results. There was a limited application of AMSPs in the maternity units and midwives did not make a positive contribution, and had a low clinical threshold for initiating therapy. Only 37.1% of the 89 women diagnosed with sepsis had the identifiable SSCB sticker prominently displayed on their medical notes.;Interview findings indicate that this resulted from the absence of implementation strategies, the challenge of diagnosing sepsis and sub-optimal evaluation and review of patients post-diagnosis.;Conclusion: A specialized SSCB specifically for the obstetric population with the full contribution of the multidisciplinary team needs to be developed. Given midwives' central involvement in initial diagnosis, ongoing patient monitoring and antibiotic administration, a more midwife-centred approach to reviewing treatment is a promising way to develop AMSPs in maternity wards.Background: Sepsis is one of the leading causes of maternal mortality and morbidity. The absence of a clear diagnostic marker challenges the process of starting antibiotic therapy. Early identification and management of sepsis is essential. Thus, the sepsis six care bundle (SSCB) was introduced in the UK to improve the care of sepsis patients.;Aim: To evaluate assessment of sepsis and subsequent management including the antibiotic therapy prescribed, and to use this data as a basis of antimicrobial stewardship programme (AMSP) and quality improvement plan within maternity units.;Methods: This study was conducted within three maternity units of NHS Greater Glasgow & Clyde using a mixed methodological approach of an initial quantitative study supplemented by a qualitative study, followed by a quality improvement for further service improvement.;Results: Sepsis was diagnosed in 3% (n=89/2690) of women. There was an inconsistent clinical application of SIRS criteria to inform diagnosis. No causative pathogen was isolated from 60% of clinical specimens. Antibiotic therapy was justified in only 31 women with positive culture results. There was a limited application of AMSPs in the maternity units and midwives did not make a positive contribution, and had a low clinical threshold for initiating therapy. Only 37.1% of the 89 women diagnosed with sepsis had the identifiable SSCB sticker prominently displayed on their medical notes.;Interview findings indicate that this resulted from the absence of implementation strategies, the challenge of diagnosing sepsis and sub-optimal evaluation and review of patients post-diagnosis.;Conclusion: A specialized SSCB specifically for the obstetric population with the full contribution of the multidisciplinary team needs to be developed. Given midwives' central involvement in initial diagnosis, ongoing patient monitoring and antibiotic administration, a more midwife-centred approach to reviewing treatment is a promising way to develop AMSPs in maternity wards
Faulting, sedimentation and fluid flow at the basin margin : the north Solway fault
Get PDFFaults exert control over the formation of basins and are geometrically complex 3Dstructures. Several industries rely on characterisation of the subsurface and faults are an important component of subsurface models. Faults are poorly constrained in subsurface data sets and by necessity are approximated to planar membranes. To adequately characterise faults in 3D it is necessary to study exhumed faults in the field.The architecture of basin margin faults has received relatively little attention in the literature (Caine et al 2010 and Kristensen et al 2016 are notable exceptions). The North Solway fault is a basin margin fault exposed at the boundary of the Southern Uplands and the Solway-Northumberland trough. The fault offsets Lower Palaeozoic lithologies (basement) against Lower Carboniferous sediments. The North Solway fault is a rare example of an onshore fault with a basement footwall and sedimentary hanging wall. The fault is exposed in extensive along-strike and limited down-dip direction in a number of localities which are accessed at low tide.Field data is used to interpret the internal architecture and fault scale geometry of the North Solway fault. Sketches, descriptions and detailed mapping have been carried out and are complemented by quantitative data from scanlines, image analysis and orientation data.This study shows that the North Solway fault has a complex zig-zag plan-view geometry which has been offset by major cross faults. Simple segment linkage models are not adequate to describe the plan-view geometry of the fault. Fault throw can only be constrained to between 100m and 1500m, demonstrating the difficulty in characterising large faults. The internal architecture of the fault is shown to be a product of host lithology,deformation style, depth and fluid flow. The coupling of sedimentary processes and tectonic activity is demonstrated at the basin margin. Predictive algorithms which are used for faults within basins are not applicable in faults with a basement footwall. The textures within fault rocks such as gouge and breccias are shown to give an indication of the mechanical state of the fault at the time of deformation. Contrasting fault zone internal structures are observed where the fault is interpreted to be the result of either basement-basement faulting or basement-sedimentary faulting. The results of this study show that large basin bounding faults are highly variable in both down-dip and along-strike directions.Faults exert control over the formation of basins and are geometrically complex 3Dstructures. Several industries rely on characterisation of the subsurface and faults are an important component of subsurface models. Faults are poorly constrained in subsurface data sets and by necessity are approximated to planar membranes. To adequately characterise faults in 3D it is necessary to study exhumed faults in the field.The architecture of basin margin faults has received relatively little attention in the literature (Caine et al 2010 and Kristensen et al 2016 are notable exceptions). The North Solway fault is a basin margin fault exposed at the boundary of the Southern Uplands and the Solway-Northumberland trough. The fault offsets Lower Palaeozoic lithologies (basement) against Lower Carboniferous sediments. The North Solway fault is a rare example of an onshore fault with a basement footwall and sedimentary hanging wall. The fault is exposed in extensive along-strike and limited down-dip direction in a number of localities which are accessed at low tide.Field data is used to interpret the internal architecture and fault scale geometry of the North Solway fault. Sketches, descriptions and detailed mapping have been carried out and are complemented by quantitative data from scanlines, image analysis and orientation data.This study shows that the North Solway fault has a complex zig-zag plan-view geometry which has been offset by major cross faults. Simple segment linkage models are not adequate to describe the plan-view geometry of the fault. Fault throw can only be constrained to between 100m and 1500m, demonstrating the difficulty in characterising large faults. The internal architecture of the fault is shown to be a product of host lithology,deformation style, depth and fluid flow. The coupling of sedimentary processes and tectonic activity is demonstrated at the basin margin. Predictive algorithms which are used for faults within basins are not applicable in faults with a basement footwall. The textures within fault rocks such as gouge and breccias are shown to give an indication of the mechanical state of the fault at the time of deformation. Contrasting fault zone internal structures are observed where the fault is interpreted to be the result of either basement-basement faulting or basement-sedimentary faulting. The results of this study show that large basin bounding faults are highly variable in both down-dip and along-strike directions
Targeted and untargeted metabolomic profiling of human serum, urine and brain by liquid chromatography mass spectrometry (LC-MS)
Get PDFFour projects were undertaken in the current study to apply, and in some cases develop, metabolomic profiling methods based on LC-HRMS for application to different human biofluid and tissue samples.;In the first study concerns the potential of metabolic changes to give an indication of physical fitness. Urine samples were collected from ten physically active subjects who underwent two cycling exercise trials. Firstly, their aerobic capacity (VO2max) was determined and the second was a 45 min submaximal exercise test. One hundred and twenty urine samples were collected in total over two days at regular time intervals: on day 1 where there was no exercise intervention; on day 2 where there was an exercise session and on day 3 where there was no exercise intervention.;The metabolites affected by the exercise included a range of purine metabolites and several acyl carnitines. Some metabolites including bile acids and several amino acids were subject to diurnal variation during the rest day (day 1). Using OPLS modelling it proved possible to identify a single abundant urinary metabolite provisionally identified as oxo-aminohexanoic acid (OHA) as being strongly correlated with VO2max.;Secondly, metabolomic profiling was carried out on 53 post-mortem brain samples from subjects diagnosed with schizophrenia (S), depression (D), bipolar (B), diabetes (Di) and controls (C) in order determine whether or not there were clear metabolites distinguishing these conditions. The most important metabolites producing discrimination were the lipophilic amino acids leucine/isoleucine, proline, methionine, phenylalanine, and tyrosine; the neurotransmitters gamma-aminobutyric acid (GABA) and N-acetyl aspartyl glutamate (NAAG) and sugar metabolites sorbitol, gluconic acid, xylitol, ribitol, arabinotol, and erythritol.;For the determination of the sugar polyols it was necessary to develop and new GC-MS method. There appears some commonality between metabolic perturbations resulting from diabetes and from SDB. This study concluded that the changes in sugar alcohol levels which were quantified in physiological fluids confirm the metabolic similarity between mental illness and diabetes. This leads to the question regarding whether or not antidiabetic drugs might have a role in treating mental illness?;In a third project a reductive amination method was used in combination with hydrophilic interaction liquid chromatography and high resolution mass spectrometry to analyse the sugars in post-mortem human brain. The samples were collected from six control brain samples and eighteen samples from individuals who had suffered from schizophrenia, depression and bipolar (SDB) disorder. This method was applied to confirm the important role of sugar metabolism through evaluation of relation between the changes in sugar levels and psychiatric.;The best separation and quantification of the common hexoses (glucose, fructose, mannose and galactose) by this method was achieved when 2H5-aniline was used as a tagging agent. Additionally, it succeeded in tagging a range of other sugars including pentoses (ribose and xylose) and sugar derivatives (N-acetylneuraminic acid and glucuronic acid). The results highlighted a relationship between the increases in the levels of sugars and psychiatric disorders (SDB). This relation which matched with other studies once again supported our results project 2 suggesting that in that sugar metabolism has an important role in distinguishing the control and SDB brains.;Oxidised fatty acids have such as oxylipins and prostaglandins have profound effects on human physiology and are present a low levels in biological fluids. In project 4 a novel tagging method for the analysis of oxidised fatty acids was developed. Fatty acids give a relatively weak response in negative ion ESI-MS. In untargeted metabolomics studies, is important to obtain a good response from molecules of interest. A derivatisation method using choline as a tag to put a positive charge on the analytes succeeded for the quantification of oxidised fatty acids, especially oxylipins, in plasma samples collected from seven participants before and after taking of beetroot juice (strong anti-oxidant and a source of nitrate).;The current results concluded that this derivatisation method improved the sensitivity and selectivity of LC-MS analysis by increasing the response factors for the positively tagged oxidised fatty acids by more than 100 times in comparison to those for the untagged compounds in negative ion. There was no clear effect of beetroot juice on the levels of oxidised fatty acids in plasma.Four projects were undertaken in the current study to apply, and in some cases develop, metabolomic profiling methods based on LC-HRMS for application to different human biofluid and tissue samples.;In the first study concerns the potential of metabolic changes to give an indication of physical fitness. Urine samples were collected from ten physically active subjects who underwent two cycling exercise trials. Firstly, their aerobic capacity (VO2max) was determined and the second was a 45 min submaximal exercise test. One hundred and twenty urine samples were collected in total over two days at regular time intervals: on day 1 where there was no exercise intervention; on day 2 where there was an exercise session and on day 3 where there was no exercise intervention.;The metabolites affected by the exercise included a range of purine metabolites and several acyl carnitines. Some metabolites including bile acids and several amino acids were subject to diurnal variation during the rest day (day 1). Using OPLS modelling it proved possible to identify a single abundant urinary metabolite provisionally identified as oxo-aminohexanoic acid (OHA) as being strongly correlated with VO2max.;Secondly, metabolomic profiling was carried out on 53 post-mortem brain samples from subjects diagnosed with schizophrenia (S), depression (D), bipolar (B), diabetes (Di) and controls (C) in order determine whether or not there were clear metabolites distinguishing these conditions. The most important metabolites producing discrimination were the lipophilic amino acids leucine/isoleucine, proline, methionine, phenylalanine, and tyrosine; the neurotransmitters gamma-aminobutyric acid (GABA) and N-acetyl aspartyl glutamate (NAAG) and sugar metabolites sorbitol, gluconic acid, xylitol, ribitol, arabinotol, and erythritol.;For the determination of the sugar polyols it was necessary to develop and new GC-MS method. There appears some commonality between metabolic perturbations resulting from diabetes and from SDB. This study concluded that the changes in sugar alcohol levels which were quantified in physiological fluids confirm the metabolic similarity between mental illness and diabetes. This leads to the question regarding whether or not antidiabetic drugs might have a role in treating mental illness?;In a third project a reductive amination method was used in combination with hydrophilic interaction liquid chromatography and high resolution mass spectrometry to analyse the sugars in post-mortem human brain. The samples were collected from six control brain samples and eighteen samples from individuals who had suffered from schizophrenia, depression and bipolar (SDB) disorder. This method was applied to confirm the important role of sugar metabolism through evaluation of relation between the changes in sugar levels and psychiatric.;The best separation and quantification of the common hexoses (glucose, fructose, mannose and galactose) by this method was achieved when 2H5-aniline was used as a tagging agent. Additionally, it succeeded in tagging a range of other sugars including pentoses (ribose and xylose) and sugar derivatives (N-acetylneuraminic acid and glucuronic acid). The results highlighted a relationship between the increases in the levels of sugars and psychiatric disorders (SDB). This relation which matched with other studies once again supported our results project 2 suggesting that in that sugar metabolism has an important role in distinguishing the control and SDB brains.;Oxidised fatty acids have such as oxylipins and prostaglandins have profound effects on human physiology and are present a low levels in biological fluids. In project 4 a novel tagging method for the analysis of oxidised fatty acids was developed. Fatty acids give a relatively weak response in negative ion ESI-MS. In untargeted metabolomics studies, is important to obtain a good response from molecules of interest. A derivatisation method using choline as a tag to put a positive charge on the analytes succeeded for the quantification of oxidised fatty acids, especially oxylipins, in plasma samples collected from seven participants before and after taking of beetroot juice (strong anti-oxidant and a source of nitrate).;The current results concluded that this derivatisation method improved the sensitivity and selectivity of LC-MS analysis by increasing the response factors for the positively tagged oxidised fatty acids by more than 100 times in comparison to those for the untagged compounds in negative ion. There was no clear effect of beetroot juice on the levels of oxidised fatty acids in plasma
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