16,351 results for 2010, ResearchSpace@Auckland

  • Conducting Polymer Implant for On-demand Ocular Drug Delivery

    Yasin, Muhammad Naveed (2016)

    Doctoral thesis
    The University of Auckland Library

    Introduction: Implants have become an attractive treatment option for chronic posterior eye conditions. However, a patient???s disease state and any concurrent side-effects may require a dose adjustment which is not possible with currently marketed implants. Stimuli-responsive implants present an opportunity to tailor the release of the active. They may be composed of conducting polymers (CP) such as poly(3,4-ethylenedioxythiophene) (PEDOT), a robust CP with good biocompatibility and reproducible electroactivity. This thesis investigated the fabrication of a PEDOT-based system suitable for implantation to provide stimuli-responsive ocular drug delivery. Methods: PEDOT films (non-porous and porous) were fabricated via vapour phase polymerisation (VPP) and characterised for their surface morphology, electrochemical behaviour and biocompatibility. Dexamethasone phosphate (dexP) was loaded after polymerisation as a dopant via active and passive ion-exchange. DexP release was determined in the absence and presence of an electrical stimulus. Dexamethasone base (dex) was also physically entrapped into the pores of porous PEDOT and a sealing layer was polymerized on top. PEDOT-coated cellulose membranes, replicating the PEDOT sealing layer, were also fabricated and characterised for their drug permeability using Franz-cells. Finally, a prototype implant for in-vitro evaluation was fabricated by 3D printing the casing and placing drug loaded VPP PEDOT films inside. Results and Discussion: Porous PEDOT prepared by VPP exhibited a highly porous morphology and a three-fold higher electrochemically active surface area (as determined by cyclic voltammetry) compared to non-porous PEDOT prepared by VPP. Release medium extracts from non-porous and porous PEDOT films displayed no significant cytotoxicity. The amount of dexP loading achieved via active ion-exchange was almost three-fold higher compared to passive ion-exchange. The effect of redox state over dexP release was determined where a pulse stimulus released maximum amounts of drug. A faster rate of dexP release was observed for porous compared to non-porous films. Dex was physically entrapped into the pores to increase drug loading; however, it leaked through the PEDOT sealing layer within 1 h. PEDOT-coated cellulose membranes confirmed the high permeability of these sealing layers. Therefore, the assembled prototype implant contained only dexP loaded films and exhibited a burst in drug release during in-vitro stimulation aligning well with previous dexP release where a similar burst in drug release was observed upon the application of in-vitro stimulus. Conclusion: A PEDOT-based system suitable for implantation was fabricated exhibiting a stimuli-responsive burst in drug release. However, drug loading and retention need to be further improved such as by physical entrapment and effective sealing to achieve long-term on-demand drug delivery.

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  • Tissue Oxygenation and Wound Healing in Vascular Surgery

    Chiang, Nathaniel (2015)

    Doctoral thesis
    The University of Auckland Library

    Are there simple adjuncts that can be applied in patients with peripheral vascular disease that could enhance wound healing and tissue oxygenation? Two large-scale clinical studies were conducted with the aims of targeting two stages of care, namely (i) perioperative treatments to enhance peripheral oxygenation by influencing oxygen delivery via chemical and thermal vasodilation (high-dose oxygen, a prostacyclin analogue, and extended active warming) during bypass surgery to the lower limbs, and (ii) topical negative therapy (TNP) dressings for high-risk foot wounds, such as following debridement or minor amputations in the diabetic foot. These therapies have been shown to be of benefit in other clinical settings, such as abdominal surgery and to treat abdominal wounds. How these adjuncts would help in patients with vascular disease is unknown. Mechanisms underlying the potential effects of these treatments on wound healing were assessed biochemically by quantifying hydroxyproline (a surrogate marker of collagen), growth factors, cytokines, and their respective mRNAs. Healing rates were determined by changes in wound volume over time using an innovative stereophotographic device (FastScan???). Tissue oxygenation was measured using hyperspectral technology (OxyVu???). The reliability and feasibility of using these devices was tested in clinical studies. Measurements obtained using these innovative instruments yielded excellent inter-operator and intra-operator reliability and correlated well with other methods of measurement, thus showing promise for assessment of tissue oxygenation and wound healing in clinical settings. No benefits were demonstrated in 71 patients with regard to surgical wound healing or tissue oxygenation in bypass surgery by perioperative adjunctive treatment. OxyVu identified increased tissue oxygenation in the foot in the acute phase following bypass surgery, validating its clinical use. In acute foot wounds treated with TNP, there was no significant difference in wound volume reduction at 2 weeks when compared with traditional dressings (44.2% for TNP versus 20.9% for the control; p=0.15). However, there was a trend towards an enhanced healing rate, and maximum wound depth was significantly less than that achieved using traditional dressings (36.0% for TNP versus 17.6% for the control; p=0.03). Given that no differences were found in hydroxyproline levels, growth factors, or tissue oxygenation, the benefits of TNP might involve more than merely enhanced production of granulation tissue, possibly involving mechanical (macrostrain) effects.

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  • The effect of general anaesthesia on the mammalian circadian clock and its clinical implications and potential treatment

    Ludin, Nicola (2017)

    Doctoral thesis
    The University of Auckland Library

    Patients frequently sleep poorly following an operation. This may be due, in part, to the effect of general anaesthesia on the circadian clock. The aim of this thesis was to understand the effect of general anaesthesia on the mammalian circadian clock and sleep, the relevance of this to the post-operative patient, and how these effects may be modified by intra-operative light administration. Previous data from our group???s work on the honey bee revealed that the general anaesthetic isoflurane causes phase delays of the circadian clock as a result of a shift in the expression of core circadian clock genes (cryptochrome and period). In addition, concurrent administration of light during anaesthesia in honey bees resulted in a reduction of the general anaesthesia-induced phase shift. In order to determine whether isoflurane causes robust and reproducible phase shifts in mammals, and whether these effects result from isoflurane acting directly on the suprachiasmatic nuclei (SCN), I developed a system to enable the examination of the effect of isoflurane on PER2::LUC mouse SCNs. PER2::LUC SCN tissue was cultured over eight days (n=36) and exposed to a six hour 2% isoflurane anaesthetic (or air control) after four cycles. Phase shifts and period changes were analysed using the peak expression time (acrophase) on each of the days following anaesthesia or control, compared to the days prior. Administration of a six hour isoflurane anaesthetic to SCNs between circadian times eight and 16 (CT8-CT16) resulted in an average phase delay of -6.99 hours (1.34 SEM) compared to controls at similar CTs that showed an average phase delay of only -1.33 hours (2.77 SEM, p=0.01). Neither isoflurane nor air administered at other CTs elicited significant phase shifts. The results from the SCNs and from the previous work on honey bees paved the way for a clinical trial in which I examined the efficacy of light administration in reducing anaesthesiainduced post-operative sleep and circadian disruption. I investigated this in a non-confounded patient population, kidney donors, who are hospitalised and undergo anaesthesia and surgery that they do not medically require. The work described in this thesis details the interim analysis of 20 patients (total study sample size=40) of whom 10 received phase shifting light and 10 placebo light during the operation. If humans were to respond like bees, then intra-operative bright light administration could represent a treatment strategy for combatting post-operative sleep and circadian misalignment. Actigraphy was recorded for seven pre-operative and seven post-operative days, and circadian markers (core body temperature and the urinary metabolite of melatonin, 6-sulphatoxymelatonin) were recorded for three pre-operative and three post-operative days. Subjective measures were also recorded throughout the study. Participants enrolled into the study were randomised to receive either placebo light or bright light intra-operatively. Operations occurred in the morning, the same subjective time at which anaesthesia elicited the largest phase shifts in SCNs and honey bees. All patients, irrespective of treatment group, showed disrupted sleep and circadian variables following hospitalisation, anaesthesia and surgery, with increased total sleep time and variability, and less stability. Non-parametric circadian rhythm analyses of actigraphic data showed higher interdaily stability (IS) post-operatively in those that received intra-operative bright light compared to those that received placebo light (p=0.08). Furthermore, the control group showed an average phase delay in core body temperature rhythms of -4.18 hours (1.74 SEM) compared to patients in the bright light treatment group who showed an average phase delay of -1.16 hours (0.62 SEM, p=0.07). Results from the interim analysis of the clinical trial indicate a trend towards intra-operative bright light improving sleep and circadian variables post-operatively. Having a general anaesthetic is essential for most major operations. The studies presented in this thesis show that general anaesthesia affects the mammalian (mouse) circadian clock and human circadian rhythms and sleep. In mice this occurs in a time-dependent manner which has not previously been recognised. Moreover, bright light administered intra-operatively may potentially reduce circadian and sleep disruption in the post-operative period.

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  • Nonlinear Processes in Optical Fibers and Microresonators

    Webb, Karen (2017)

    Doctoral thesis
    The University of Auckland Library

    This Thesis presents a series of experimental and numerical investigations of nonlinear frequency conversion processes in both optical fibers and microresonators. In the context of optical fibers, we consider the cascaded four-wave mixing dynamics that underlie the interaction between solitons and linear waves, while in microresonators we look in detail at the formation of optical frequency combs and their properties. We first consider the interactions between solitons and weak linear waves co-propagating in an optical fiber. Through comprehensive experiments and simulations, we demonstrate the equivalence between soliton-linear wave interactions and cascaded Bragg scattering. The observed dynamics are also interpreted in terms of fiber-optic analogues of event horizons. We also investigate cascaded four-wave mixing processes in optical fibers in the absence of weak input linear waves. Specifically, we examine the excitation of a higher-order sideband that is phasematched through the cascade, and study how the efficiency of this excitation depends on the frequency detuning between the two continuous-wave pumps that initiate the four-wave mixing process. We find that the pump separation has a significant effect on the conversion efficiency to the phasematched sideband, which we explain by treating the individual cycles of the pump beat note as independent higher-order solitons. In the study of microresonators, we quantify the coherence properties of different microres-onator frequency combs. By passing the resonator output through a delayed interferometer, the modulus of the complex degree of first order coherence can be extracted from the spectral fringes. In addition to allowing for the quantitative assessment of comb coherence across the full bandwidth, we demonstrate how this method can be used to experimentally determine the comb operating regime. Finally, we demonstrate for the first time the formation of temporal cavity solitons in silica microspheres, and experimentally verify the high coherence of the resulting frequency combs. Further experiments and numerical simulations are carried out to investigate the influence of perturbations on the generation of microresonator cavity solitons.

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  • The relationship between maternal diet and gestational diabetes mellitus: A metabolomic approach

    De Seymour, Jamie (2017)

    Doctoral thesis
    The University of Auckland Library

    Gestational diabetes mellitus (GDM) is a carbohydrate intolerance first recognised during pregnancy and is associated with serious health consequences to both mother and offspring. The best approach to reduce the adverse consequences of GDM is to prevent its development. Despite evidence suggesting a role of maternal diet in GDM development, there is little agreement on the best approach to prevent its occurrence. The observational nature of dietary research has made it difficult to determine mechanisms underlying the associations. Metabolomics, the study of low-molecular weight compounds, is an analytical approach that could be used to explore how maternal diet is associated with GDM. Aim: The aim of this thesis was to investigate the relationship between maternal diet and GDM, by exploring the effect of both diet and disease on the maternal metabolome, in a Southeast Asian multi-ethnic population (N=1,247) from Singapore (The GUSTO cohort). Method: Maternal dietary pattern analysis was conducted from 24-hr dietary recalls, to explore associations between maternal diet and GDM. The effect of GDM on metabolism was determined by metabolite profiling of maternal plasma and hair, using gas chromatography-mass spectrometry. The dietary pattern data and metabolomic data were combined to look for associations between maternal diet and GDM. A seafood-noodle-based dietary pattern, consisting of higher amounts of soup, fish and seafood products, and noodles; and lower amounts of white rice, curry-based gravy, legumes/pulses, and ethnic bread, was found to be significantly associated with a reduced likelihood of GDM (P < 0.01). Metabolite profiling of maternal hair revealed 277 metabolites, none of which were associated with GDM. Of the 219 metabolites detected in maternal plasma, 26 were associated with GDM. One metabolite, 2-hydroxybutyric acid, was significantly higher in GDM cases (P < 0.001, FDR = 7.04E-07) and could discriminate GDM outcome with higher accuracy than the model of clinical risk factors. Metabolic pathway analysis showed that a combination of the significant GDM metabolites may be linked to dysfunction in mitochondrial oxidative phosphorylation. Two plasma metabolites had a significant linear association with the seafood-noodle-based dietary pattern. However, this significance was removed after adjustment for multiple comparisons. Two significant canonical roots were derived from canonical correlation of metabolites and food groups but explained only 1% of the variation in the food groups and 4% of the variation in the metabolites, deeming them unlikely candidates as dietary biomarkers of GDM development. Conclusion: A seafood-noodle-based dietary pattern was associated with GDM in this multi-ethnic Asian cohort. The pattern was distinct from those found previously, emphasising the importance of applying caution when extrapolating dietary findings outside of the studied population. The plasma metabolome could differentiate women that developed GDM from those that did not, linking GDM to a potential dysregulation in mitochondrial function. Although the diet-metabolite associations were not strong enough to deem them clinically useful as dietary biomarkers of GDM, they highlight some interesting associations. Future work should validate these findings in early pregnancy.

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  • Calorimetry of an ultracold Bose gas and cavity quantum electrodynamics with an optical nanofibre

    Ruddell, Samuel (2017)

    Doctoral thesis
    The University of Auckland Library

    In this Thesis we present experiments involving laser cooled alkali atoms. We perform calorimetry experiments with a harmonically trapped Bose gas of 87Rb atoms. Starting from a Bose-Einstein condensate confined in an optical trap, we transfer a precise and known amount of energy to the system using one of two independent methods. Following a rethermalisation period within the trapping potential, we measure the resulting temperature of the atoms through absorption imaging. Comparisons of experimental data to various theoretical models show that the thermodynamic behaviour of the system is well described by a Hartree-Fock model for an interacting gas. In a separate experiment we have utilised a nanofibre, a section of optical fibre that has been tapered to a subwavelength diameter waist, as a tool for interfacing 133Cs atoms with the guided optical mode of the fibre through an evanescent field. The tight transverse confinement of the guided mode allows for efficient light???matter interactions at the few photon level. We enhance these interactions by forming an all-fibre ring geometry cavity containing a nanofibre section, and perform cavity quantum electrodynamics experiments with an ensemble of laser cooled caesium atoms. Due to a collective enhancement of the coupling rate by the ensemble of atoms, we observe well-resolved vacuum Rabi splitting of the cavity transmission in the weak driving limit. Additionally, we investigate the power dependence of the atom???cavity transmission on resonance, and observe saturation of the atoms at higher driving strengths. We also present a simple theoretical model to describe the behaviour of this system. Finally, modern cold atom experiments demand a high degree of control and reproducibility, which can be best provided through computer control. We present our implementation of a computer interface for the experiment, as well as various custom built hardware interfaces which are integrated into our control scheme. Our system allows for scripting of an experimental sequence, adjustment of experimental settings, and the ability to collect and analyse experimental data from a central computer.

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  • Assessing the effects of brief stimuli unrelated to reinforcement

    Bai, John (2017)

    Doctoral thesis
    The University of Auckland Library

    Reinforcers are environmental events defined by their effects on behavior. However, brief, arbitrary stimuli can also have reinforcement-like effects, despite being unrelated to food reinforcement. The present thesis explored the potential reinforcement-like effects of brief stimuli across five experiments. In Experiments 1 through 4, pigeon subjects responded for food reinforcement and brief stimulus presentations in a two-component multiple schedule. Neither baseline response rates nor resistance to change during disruption tests were systematically greater in a component with versus without brief stimulus presentations. Additionally, increasing the rate and duration of brief stimulus presentations in Experiment 4 failed to reveal reinforcement-like effects when compared directly with food. In Experiment 5, pigeons chose between independent terminal links in a concurrent-chains procedure. Across conditions, varying the location, duration, and rate of brief stimulus presentations in the terminal links had no systematic effects on preference. In contrast, varying rates of food reinforcers resulted in large and reliable shifts in preference. Therefore, the present thesis did not find any evidence that brief stimuli unrelated to food reliably increase response rates, resistance to change, or preference. These data demonstrate the value of systematic replication, and a behavioral momentum approach to assessing potential reinforcement-like effects.

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  • Automated Residential Demand-Side Management Strategies

    Croft, Aaron (2016)

    Doctoral thesis
    The University of Auckland Library

    There is growing evidence that climate change is becoming one of the major issues facing mankind within the next century. In this context, the electricity sector has been receiving increasing attention over the past decade due to the large amount of carbon it emits. Demand-side management - controlling overall power demand - has been heralded as a potential solution to this problem and while it is common in industry today, residential demand response remains elusively untapped. This is because residential electricity consumers are generally unwilling to sacrfice comfort for often meagre incentives, and the difficulty of controlling such a complex system increases its cost. This work specifically targets these barriers to adoption, proposing an entire demand- side management topology, control algorithm, and novel way of viewing controllable loads. To start, a uni ed load model is introduced which sees all controllable loads represented as batteries with time-varying power and energy values bounded by consumer comfort limits. Then, an algorithm called NES (Net Energy Stored) control is introduced that controls loads modelled in this fashion using a simple, scalable control system. The algorithm operates without making any predictions, greatly enhancing its ability to respond to unexpected events such as reserve provision, real-time pricing, unpredictable local generation, and the load profiles of diverse, human consumers. A practical system was built on low-cost microcontrollers and the algorithm was implemented thereon. A method of validating demand response algorithms is also proposed in this thesis, employing a Monte-Carlo simulation of 100 statistically representative 7-house New Zealand communities using a bottom-up load modelling tool based on large behavioural studies. Several scenarios were explored, covering electric vehicle adoption, varying allowable temperature deviation in hot water cylinders and different wind generation profiles. Then an optimal scenario operating with perfect foresight was implemented as a Mixed Integer Program and used as a benchmark. Both the optimal savings and performance of NES control varied significantly across the 100 communities and across the scenarios, notably performing very well in the most volatile scenarios. On average, NES control obtained 57.4% of the theoretical optimal savings assuming the use of existing residential loads. Increasing the allowable temperature range of hot water cylinders using a mixing valve on the output allowed NES control to extract significantly more savings relative to the uncontrolled case, extracting 68.2% of the optimal benefits if the water temperature is allowed to fluctuate between 55-85 C. At 30% electric vehicle adoption Net Energy Stored (NES) extracts 66.4% of the optimal value. Under different wind profiles NES extracts between 38.8% and 66.0%, showing its sensitivity to the timing and magnitude of wind power. Combining the extremes of all of these scenarios, NES control achieves 63.6% of the optimal results. NES performs marginally worse under a real-time pricing scheme, with 48.2% of the optimal savings extracted in the status quo situation and 56.3% with all technologies combined. Overall these results are promising because NES control does not make any predictions of load, price or wind while its benchmark is afforded `perfect foresight'. Furthermore NES control has been successfully implemented on an ultra-low-cost, ultra-low-bandwidth embedded communications system which performed almost identically over a networked control system as it did in simulation. NES control is therefore a low-cost, readily implementable solution that is well suited to the complex problem of residential demand-side management.

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  • Majority Influence in Infancy

    Anantharaman, Sweta (2017)

    Doctoral thesis
    The University of Auckland Library

    Majority influence is an integral aspect of many human societies; it is an important catalyst of learning and promotes transmission of cultural knowledge. Given the importance that majorities play in human societies, it is not surprising that young children are sensitive to information gleaned from majorities. A growing body of evidence raises the interesting, yet unexplored possibility that, like preschool-aged children and adults, infants??? behaviour might be influenced by majorities. Using a novel eye-tracking paradigm, the experiments reported across the three manuscripts examined the characteristics of, and extent to which, majorities bias infants??? behaviour in different contexts, primarily via visual attention. Chapter 2 examined whether a majority influenced 18-month-old infants' preference (i.e., looking time and behavioural preference) for two novel toys. The results across two experiments revealed that infants' visual preference for a novel toy was not influenced by the majority if they were first provided with experience with the toys, but was marginally influenced if infants received no prior experience with the toys. These experiments provided useful insights into the role that context and social cues play in guiding infants' attention. By introducing an element of ambiguity (using boxes rather than novel toys) and adding cues to boost majority salience, Chapter 3 examined whether 12- and 19-month-old infants' attention to a novel stimulus was influenced by the majority. The findings across two experiments provided the first known evidence that infants??? attention is guided by majority information at 19-, but not at 12-months of age. Further, the results indicated that infants??? attention was guided by a majority only when all majority members are shown to prefer one object to another. Finally, Chapter 4 examined the role of novel social categories and social affiliation in guiding 19- and 24-month-old infants' expectations of group members and further, whether infants' attention for novel stimuli would be biased by these expectations. The results indicated no influence on infants' attention to novel stimuli based on social categories or social affiliation across both age groups. However, looking time patterns towards events leading up to the test phase among 24-month-old infants indicated interesting trends in their understanding of groups as cohesive units. Together, the findings across the three manuscripts offer preliminary evidence of majority influence as well as the role of social cues in infants' expectations of group cohesiveness in driving visual attention early in development. Crucially, these findings suggest, to our knowledge, the first known evidence of majority bias at 19-months. Infants??? sensitivity towards the majority at the visual attention level is the likely foundation for subsequent selectivity to majority information across domains.

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  • Approaches to Describe and Quantify Uncertainty in Bio-physical Agricultural Computer Simulation Models

    Meenken, Esther (2016)

    Doctoral thesis
    The University of Auckland Library

    The objective was to explore the definition, sources, quantification, and management of uncertainty in bio-physical agricultural deterministic computer simulation models (crop models). One aim was to provide recommendations from a formalised statistical viewpoint on management of uncertainty for a small pool of crop model researchers in New Zealand. These researchers face unique issues with models that describe temperate, island-based conditions. An equally important goal was to identify ways to provide predictions complete with uncertainty bounds beyond those offered by sensitivity analysis. Given these objectives, my focus was on a single model. Section I proposes an uncertainty evaluation (UE) framework to explore how the combined components of a crop model contribute to the overall output uncertainty. Tools to curate information, diagnose the most important sources of uncertainty, and identify UE objectives have been developed. The framework links qualitative and quantitative analysis through a review of techniques for generating and analysing data from such models. Although many elements considered appear in the literature, amalgamation into a united framework is an original contribution. In Section II a detailed description of a case-study model that simulates wheat development is provided. This model provides a concrete foundation by which to demonstrate the UE framework, and illustrates the nature of crop models as constructs upon which mechanistic understanding of real-world systems continues to develop. A theoretical addition to a recent model that combines physiological and genetic characteristics of wheat is proposed based on laboratory based experimental work, reducing structural uncertainty. Finally, Section III is centred on the analysis of simulated data. In particular, it addressed the desire to provide credible intervals for state-space model estimates. This was achieved through fitting a probabilistic Bayesian hierarchical model with MCMC, a general form of data assimilation that recursively updates state predictions based on available data. Credible bounds of both an observed and a latent state variable were estimated for the case-study model. Finally, I summarise how these three sections tie together to resolve research objectives. I discuss the benefits of this research, recommendations and limitations, and propose directions for future work.

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  • Alternate motor pathways for upper limb control: Implications for noninvasive brain stimulation after stroke

    McCambridge, Alana (2016)

    Doctoral thesis
    The University of Auckland Library

    Descending pathways other than the lateral corticospinal tract may play a role in the recovery of upper limb function after stroke. Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique that has shown the potential to improve motor function of the upper limb. This thesis investigated the neurophysiological and behavioural effects of motor cortex (M1) tDCS on control of the upper limb in healthy adults and chronic stroke patients. The effects of various tDCS electrode montages on corticomotor excitability were examined, with an emphasis on the proximal upper limb. Transcranial magnetic stimulation (TMS) was used to infer corticomotor excitability of crossed, uncrossed, and transcallosal motor pathways, cervical propriospinal neurons, and intracortical inhibition in M1. The first three experiments examined the effects of dual-hemisphere tDCS on the excitability of propriospinal neurons, separate motor pathways, and upper limb coordination. Dual-hemisphere tDCS modulated subcortical excitability to cervical propriospinal neurons, and transcallosal inhibition. The electrode montage anodal tDCS (a-tDCS) was examined in two experiments with healthy adults and in the final thesis experiment with chronic stroke patients. The effects of a-tDCS varied in healthy adults. The variability of tDCS after-effects on motor evoked potentials were correlated with an individual???s preferential recruitment of early vs late indirect (I)-waves. In another experiment, it was revealed that short-interval paired-pulse TMS can be used to examine intracortical inhibition on uncrossed motor projections to the proximal upper limb. This novel TMS paradigm provides new opportunities to investigate the role of the ipsilateral M1 during movement. In the final experiment, the interhemispheric imbalance model for chronic stroke was challenged. Anodal tDCS of the contralesional M1 was hypothesised to improve motor function of chronic stroke patients that may rely on alternate motor pathways for upper limb control. Motor function of the paretic arm was positively affected by contralesional a-tDCS for patients who had greater spasticity. By identifying novel biomarkers this may help individualise tDCS protocols for future clinical trials.

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  • Tsunami Inland Structures Interaction and Impact of Floating Debris

    Shafiei Amraei, Seyedreza (2016)

    Doctoral thesis
    The University of Auckland Library

    Civil engineers have long known that large forces from tsunamis can be imposed on coastal structures. This was made obvious by the recent 2011 Japan tsunami, which also emphasised that the risk of tsunami damage is no less significant than the risk of earthquake damage. New Zealand, due to its exposed location, is also at high risk of tsunami impact by local-, regional-, and distant-source tsunamis. Although some efforts have been made to determine tsunami loads on structures, there are still discrepancies among the limited number of published design guidelines. Data on actual tsunami loads on structures are rare, hence physical modelling of the interaction between a tsunami and a structure is vital to explore the problems associated with tsunami impact, and thereby to improve the existing knowledge of tsunami engineering. This study comprises an experimental investigation of tsunami bore interaction with structures located near coastlines. Specific aims of the study were accomplished by investigation of: (1) the impact of a tsunami bore on a square prism structure having different orientations to the flow direction; (2) the impact of a tsunami bore on a cylindrical structure; (3) the effect of structure stiffness on tsunami bore impact; (4) the impact of a tsunami bore on an elevated structure, in which a square prism structure base was raised at different elevations above the ground (???base elevation???); (5) the tsunami-borne debris impact on structures through development of a new technique, utilising a smart debris device; (6) factors affecting debris impact forces. The experiments were conducted in a 14m long, 1.2m wide and 0.8m deep wave flume, separated from a reservoir using an automatic gate. The gate was designed to rapidly release water into the flume to simulate a tsunami bore. Measurements were made of the bore heights and velocities, based on which an empirical equation, with the basic form of the gravity wave velocity equation, is proposed for calculating the bore propagation velocity. For all structures, forces and moments were measured at the base of the structure, using a multi-axis load cell. For forces and pressures exerted on a square structure, a square prism with 300mm??300mm cross-section and 600mm height was made from acrylic sheets. The vertical distribution of bore induced pressure was measured on the front face of the square prism. The effect of structure orientation on the forces and pressures was investigated, with the structure???s front wall oriented at 30??, 45??, 60??, 90?? and 135?? to the flow direction. The bore induced forces were theoretically computed assuming that the total stream-wise force is due to the hydrostatic force plus the hydrodynamic force, and the upward force is due to the buoyancy only; the results were validated using the experimental data. Drag coefficients for the square prism at different orientations ranged from 1.15 to 1.65. For forces and pressures exerted on a cylindrical structure, a cylinder with 300mm outer diameter and 600mm height was made from acrylic. The vertical and angular distributions of bore induced pressure were measured on the front face of the cylindrical structure perpendicular to the flow direction, and at 30??, 45??, 60??, 90?? and 135?? to its original alignment. Similarly to the square prism, the bore induced forces were computed and validated using the experimental data, giving a drag coefficient of 0.65. For forces and pressures exerted on different structure stiffnesses, four different square prism structures, each with 300mm??300mm cross-section and 600mm height, were made from various thicknesses of acrylic sheets. Deflection of the top of the square prism structures was measured, with the deflection angles ranging from 0.01?? to 6?? with respect to the flume vertical axis. The structure deflection increased with decreasing stiffness of the structure. The vertical distribution of the pressure was not affected by varying the structure stiffness. Also, the bore induced forces measured at the structures??? bases had similar magnitudes for different stiffnesses. The results demonstrated that the bore induced pressure and forces are independent of the structure stiffness. However, this conclusion is valid only when the effect of P-delta is not significant (i.e. for small P value), and should be validated for more significant effect of P-delta (i.e. for large P value) by adding gravity load on the structure. For forces and pressures on elevated structures, the square prism structure was raised above the flume floor at base elevations of 50mm, 70mm and 90mm. Pressure exerted on the underside of the structure base was also measured and the horizontal pressure distribution was investigated. The magnitudes of the bore induced pressures on the underside of the structure base decreased with increasing base elevation. The stream-wise and upward forces due to the bore both decreased with increasing base elevation. Elevating the structure reduced the stream-wise force by up to 50% of that for a non-elevated structure. Also, the upward force for an elevated structure was significantly smaller than that for a non-elevated structure. Empirical equations are presented, to give guidance for the preliminary design of elevated structures under tsunami bore impact. For impact forces of tsunami-borne debris, an accelerometer-equipped disc-shaped smart debris device was used for direct measurement of the acceleration of the debris collision with the structure. An image processing technique was used to detect the angle of the debris at the instant of impact, and subsequently to resolve the acceleration data to horizontal and vertical directions. The measured acceleration data were converted to force using the impulse-momentum formula. The debris impact experiments were conducted for various bore velocities and various debris masses (550, 800 and 1000 g). The debris impact force was found to be a function of the debris mass, velocity, contact duration, and additional mass of entrained water. Additionally, the debris impact force was measured at the structure base, validating the results from the smart debris device. An equation was developed for the debris impact velocity, for a known distance between the location of debris pick-up by a tsunami and the structure. The debris velocity equation was validated using the experimental debris velocities obtained from integration of the measured acceleration data. For factors affecting the debris impact forces, evaluative experiments were carried out by varying debris shape (disc- and box-shaped debris), debris rigidity (rigid and deformable box-shaped debris), and structure stiffness. The results were used to modify the basic impulse-momentum formula by the addition of coefficients that take into account the added mass, the debris impact velocity, the debris shape, deformability of the debris, and stiffness of the structure. The results of this study give practitioners the ability to better analyse the tsunami bore impact on coastal structures. Most importantly, this study provides guidance for the preliminary design of structures that may be impacted by a tsunami bore, including estimation of the total stream-wise force, upward force, and floating debris impact force. Also, this study addresses a major knowledge gap in the design for tsunami impact on structures with different stiffnesses, and structures elevated above the ground.

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  • Cobalt(III) Complexes Containing Analogues of Bioactive Anticancer Compounds

    Mistry, Meet (2016)

    Doctoral thesis
    The University of Auckland Library

    Since the discovery of cisplatin as a potent anticancer agent, transition metal complexes have played a significant role in the development of new anticancer compounds. The anticancer potential of cobalt complexes has been extensively studied over the last three decades, and much time has been devoted to understanding their mechanisms of action. After understanding the Co(III)/Co(II) reduction activation mechanism, several Co(III) complexes of bioactive anticancer agents have been investigated as potential hypoxia activated prodrugs. Furthermore, after the initial use of nitrogen mustard, several bioactive compounds and their analogues have been investigated as ligands to develop hypoxia activated Co(III) complexes. This thesis describes syntheses and characterisation of Co(III) complexes that have been designed using structural analogues of bioactive anticancer compounds. Chapter 1 gives an overview of the prodrug strategy in cancer therapy, prodrug design using a trigger and an effector unit, and different mechanisms for prodrug activation. Several examples of Co(III) complexes are given, which have been investigated as potential prodrugs to target tumour hypoxia. There are three different parts to this research. Chapters 2, 3 and 4 describe the syntheses and characterisation of Co(III) complexes designed using ligands, which are structural analogues of bioactive anticancer compounds. Chapter 2 describes syntheses of dipeptide analogues of bortezomib, a proteasome inhibitor that is currently being used for the treatment for multiple myeloma. The Co(III)-dipeptide complexes were also analysed for their possible use as hypoxia activated prodrugs in Chapter 2. Chapter 3 includes the continuation to the previous investigation by Ware et al. on Co(III)-cyclen complex using 8-hydroxyquinoline (8HQ) as a model cytotoxin. Efforts were made to establish a synthetic route to introduce a porphyrin derivative into prodrug design, with the aim of improving tumour cell targeting properties of the prodrug complex. Chapter 4 describes syntheses of two polypyridyl carboxamide ligands, PDPA and MID(AMP)2, and syntheses of their Co(III) complexes. PDPA and MID(AMP)2, are structural analogues of PMAH, Py3PH2, which are carboxamide ligands containing a similar metal-binding domain as bleomycins. The experimental procedures are detailed in Chapter 5.

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  • Women Godfathers of Organised Crime: As Presented by Twenty-Three Auto/Biographies

    Tregunna, Alice (2017)

    Doctoral thesis
    The University of Auckland Library

    This thesis is guided by a grounded theoretical framework and explores the experiences presented in the auto/biographical accounts of women who have occupied management positions in illicit businesses and organised criminal networks. This project brings attention to a previously under-researched phenomenon within criminological research: the role of women as perpetrators within organised crime and not only as victims. It highlights that the current conceptualisation of organised crime as a ???male??? business is incorrect. The findings of this project demonstrate that women have occupied controlling positions for at least 150 years, across various countries and industries, and that similarities can be identified in their illicit career pathways. A narrative analysis is conducted of women's criminal career pathways in illicit business. Consideration is given to social and political factors impacting their entrance into an illicit industry and the complex process of patriarchal bargaining taking place once they have become active in organised criminal behaviours. A commonality between the women???s social position, specifically their corresponding levels of social, cultural and economic capital, and the illicit industry they initially participated in was identified. Furthermore, their reliance on gatekeepers to facilitate entrance into an illicit business and their succession within family businesses during times of crisis is discussed. This leads onto consideration of the push and pull factors experienced by the women, because of legislation and policy changes. An examination of women's experiences of abuse and utilisation of violence is conducted to produce a new theoretical model of women's criminal career pathways in organised crime. This considers the business strategies of sex and violence utilised by the women, in conjunction with their reliance on neutralisation techniques to rationalise their illicit business activities, allowing for their continued involvement in organised criminal activities. Overall, this research highlights the complex processes undertaken by women to achieve leadership positions within organised criminal networks and illicit business. The thesis contributes to criminological knowledge about women???s involvement in organised crime and the literature on gender and crime more broadly, through the analysis of the representations of women???s pathways through illicit business and organised criminal networks.

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  • He Ana, He Whakairo: Examining M??ori Belief of Place Through the Archaeological Context of Rock Art

    O'Regan, Gerard (2016)

    Doctoral thesis
    The University of Auckland Library

    There is a historical tension between archaeologically and traditionally informed M??ori perspectives in the management of M??ori archaeological heritage. A central concern is the extent to which past beliefs that M??ori held about particular places can be examined by archaeological methods and therefore factored into archaeological assessments of sites. This research investigated the extent to which such beliefs can be archaeologically recognised in two of New Zealand???s most notable rock art localities. It proposed that the way M??ori conceived of places may be archaeologically visible in the positioning of the marks they made. A multi-scalar examination of the archaeological context of the rock art localities involved re-evaluation of imagery and test excavations at rock shelters, and reviews of the surrounding archaeological, historical and land use histories. These provided an understanding of the formational processes that have resulted in the surviving archaeological record. This in turn provided the basis to assess the contexts of rock art and the extent to which spatial patterns of association indicative of past belief can be demonstrated as contributing to that formation. In a few cases where the spatial arrangements of rock art figures and other features did allow ancestral associations to be suggested and a ritual deposit to be recognised, these were considered in relation to insights of a traditional M??ori view informed by ethnographic and ethnohistorical accounts. More generally, however, preservation issues at one or more of the different spatial scales confounded the demonstration of such patterns. Comparison between the Taup?? and South Canterbury study areas demonstrate how those issues impact on the record, and how the application of current archaeological assessment practices are unlikely to provide the scope to scientifically demonstrate the role of belief in shaping that record. The tension arising from how archaeological method can factor belief into assessments of such M??ori heritage places is likely, then, to remain unresolved. Key words: M??ori, Rock art, Archaeological context, Heritage assessment, Opihi, Taup??.

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  • A Novel Biodegradable Fe-35wt.%Mn Alloy Produced via Powder Metallurgy

    Zhang, Qian (2015)

    Doctoral thesis
    The University of Auckland Library

    This doctoral project permitted to design, develop and study a degradable metallic biomaterial. Between 2011 and 2015, magnesium alloys and commercially pure iron were evaluated for their possibility for the use in biomedical areas. Their mechanical properties and degradation behaviors were not clinically well suited. Hermawan et al. investigated a series of Fe-Mn alloys via a powder metallurgical (PM) route followed by cold rolling and re-sintering cycles and found that manganese content of 35 wt% alloy was nonmagnetic and cell compatible. However, as a fully dense alloy, the degradation rate was still not satisfactory. In this doctoral project, the Fe-35wt.%Mn alloys were produced via several PM routes. This research employed three different starting powders, which were blended elemental (BE), mechanically milled (MMed) and BE powder with porogen. We aimed to develop a less dense alloy that has a higher degradation rate, suitable mechanical properties and good cell compatibility. The Fe-35Mn alloys were firstly fabricated by a simple blend-press-sinter method. Sintering temperatures and holding times were varied to investigate their influences on the microstructure evolution, densification, corrosion behavior as well as mechanical properties. The increase of sintering temperature and holding time led to the decrease of porosity level of the sintered compacts. Among these parameters, a sintering temperature of 1200??? and a holding time of 4 hours proved to be able to produce samples with a good densification level. The change of sintering temperature and time did not affect the final phase where non-ferromagnetic austenitic ?? and martensitic ?? were the main phase. A satisfactory degradation rate of 1.5 to 4 mmpy was obtained; but the mechanical strength was low. In order to enhance the mechanical properties, a mechanical milling (MMing) process was employed to obtain finer starting powder particles. The MMing parameters were investigated and ball-to-powder (B-P) ratio of 5:1 and milling time of 6 hours were identified to be able to produce the required powder. After milling, various pressing pressures using a steel die press were employed, followed by cold isostatic pressing (CIPing) at 200 MPa. Higher compaction pressure resulted in lower porosity level and CIPing further enhanced the densification. When compared with the BE powder, reducing the powder particle size via MMing had led to a decrease in porosity to 7 ~ 12%. Hence, a significant improvement of mechanical properties was then achieved. Porogen ammonium bicarbonate (NH4HCO3) particles were added to fabricate porous Fe-35Mn alloy foam which had varying degrees of porosity level. By the addition of 10 and 20 volumetric percent of NH4HCO3, the degradation rates of the Fe-35Mn samples with the introduction of the NH4HCO3 porogen were significantly accelerated when compared with the samples without NH4HCO3 addition. The electrochemical corrosion rates were ranging from ca. 2 to 8 mmpy in both 5% NaCl and SBF solutions. The proposed degradation mechanisms were uniform corrosion in addition to crevice corrosion. Iron ion release during a one-month???s dynamic corrosion was slightly higher than that of manganese. However the mechanical properties of these Fe-35Mn foams posed a limitation for the development of Fe-35Mn foams in the load-bearing applications. The stress corrosion cracking (SCC) investigation in a physiological environment followed. A slow strain rate test (SSRT) method was used in order to achieve a better understanding with regard to the stress corrosion behavior. The SCC susceptibility was sensitive to the strain rate and the testing environment. A slower strain rate and a more aggressive environment resulted in a higher SCC susceptibility. The higher density level of the sintered samples led to a reduction of SCC susceptibility. Intergranular fracture was observed on the sample surface of all tested specimens. SCC cracking was initiated from crevices and pores in both BE and MMed Fe-35Mn alloy samples. The cytocompatibility of Fe-35Mn alloys were then investigated using an indirect cell-material interaction by culturing L929 cell line in Fe and Mn ion-rich elution containing up to 1.29 and 1.12 ppm of released Fe and Mn ions. Results showed L929 mammalian cells proliferated and grew healthily in all testing extractions. It was suggested that Fe-35Mn alloys were biocompatible since no significant difference was found in the cell viability response to the material elutes. It has to be pointed out that the simple blend-press-sinter method was able to produce a Fe-35Mn alloy that met degradation requirement. MMing could increase the samples??? mechanical strength. However the strength level is still insufficient for load-bearing applications. A further investigation of optimizing the PM parameters is needed to increase mechanical strength while maintaining sufficiently fast degradation.

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  • Haemodynamic Assessment of Coronary Flow with CFD and Phase-Contrast MRI

    Beier, Susann (2015)

    Doctoral thesis
    The University of Auckland Library

    Coronary artery atherosclerosis is a major cause of morbidity and mortality worldwide. Some anatomical characteristics of coronaries may increase the likelihood of disease development, and stenting, a common treatment, has a high probability of restenosis and in-stent thrombosis. Coronary flow patterns, determined by vessel geometry and stent design and deployment, are thought to be related to adverse clinical outcomes. This thesis represents a comprehensive assessment of the relationships between flow and major coronary artery shape, and stent design and deployment. It further demonstrates the feasibility of assessing dynamically scaled coronary phantom flow with phase-contrast magnetic resonance imaging (PC-MRI). A range of idealised and patient-specific coronary artery geometries, with and without stents, were generated based on a statistical shape database from computed tomography (CT) angiograms, and micro-CT scanned benchtop deployed stents, using a computer aided drawing program. Transient flow was simulated using computational fluid dynamics (CFD). The geometries were also up-scaled, 3D printed, and incorporated into a dynamically scaled blood-analogue flow circuit for velocity acquisition with PC-MRI. The CFD results revealed little flow effect for bifurcation angle when varied in non-stented and stented idealised and patient-specific bifurcations. Flow was also computed in four patient geometries with wide shape variation, where a statistical shear stress analysis suggested that the vessel tortuosity may influence the effect of bifurcation angle. Similarly complex flow alterations were observed when systematically analysing the flow effects of major stent design features. The haemodynamic interrelations provided insights for the development of design guidelines for stent manufacture. Computational findings were validated by means of a new approach using dynamically scaled phantom flow and PC-MRI acquisition for non-invasive imaging with higher effective resolution (7-fold up-scaled geometries). The co-registered flow fields yielded good agreement (R2>0.8, magnitude error <8%) after using the PC-MRI measured inlet flow to inform the computational boundary conditions. A complementary approach of CFD and dynamically scaled PC-MRI can deliver further insights into the important haemodynamic effects of vessel shape and stent design and deployment. The results represent a potential clinical assessment tool, new considerations for stent design guidelines and deployment strategies, and a novel approach for coronary flow assessment for patient-profiling and pre-surgical planning.

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  • A Study in the Performance of Sediment Retention Ponds

    Farjood, Arash (2016)

    Doctoral thesis
    The University of Auckland Library

    This thesis describes a laboratory experimental study to investigate performance of a scale model of a sediment retention pond, with the aim of improving the understanding of the effect of physical design features on its hydraulic performance and sediment removal performance. The experiments were conducted using a 1:10 scale model of a field sediment retention pond. Several configurations of the model pond with different widths of inlet, design of outlet, and location, number and type of baffles were examined. All of the experiments were conducted at steady state condition with fixed flow rates. Tracer experiments, using Rhodamine WT tracer dye, formed the majority of the experiments, from which residence time distribution curves (RTDs) were obtained and analysed. In addition, the tracer dye was visually observed to identify the zones of short-circuiting. Sediment removal performance was evaluated for a number of pond configurations, by measuring water turbidity at the outlet. The turbidity was caused by addition of a representative sediment (silica flour) to the pond. Velocity fields were also measured for inspecting the effect of spatial velocity variations on sediment removal performance. In addition to physical modelling, a CFD technique was employed for numerical investigation of pond configurations with different length-to-width ratio and bank slopes. The results showed that reducing the width of the inlet (to 85% of pond???s width) to avoid the shallow water over the sloping side walls, and modifying the outlet to avoid disrupting the flow streamlines, both improved hydraulic performance. Installation of submerged solid baffles, and different types of porous baffles, further increased the pond???s hydraulic performance, albeit to different degrees. Sediment removal performance was also increased when baffles were incorporated. Comparison of hydraulic performance and sediment removal performance indicated a strong correlation between these two measures. In addition, the data collected from the tracer experiments were scrutinised, and a new index was developed for quantification of the hydraulic performance of ponds and wetlands. The results of CFD modelling showed that pond configurations with aspect ratio of 5:1 or larger, and (for a given aspect ratio) with a bank slope of 2:1, had higher hydraulic performances. This research is the first to extensively investigate details and locations of baffles for improving hydraulic performance of sediment retention ponds. It can provide useful information for improving the performance of ponds by altering their design. In addition, a new index was developed for ponds and wetlands, which can contribute to a more enhanced analysis of hydraulic performance in ponds and wetlands of different layouts and configurations.

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  • The genetic determinants of vigour control and precocity by pear (Pyrus communis L.) rootstocks

    Knaebel, Mareike (2016)

    Doctoral thesis
    The University of Auckland Library

    The growth habits of fruit trees have a significant influence on their efficiency in commercial production. Small tree stature allows high-density plantings and therefore more efficient land use, while minimising the length of the trees??? juvenile period means the orchard becomes profitable sooner. Vigour control and precocity are therefore two of the most important traits in commercial pear production. Dwarfing rootstocks are used to reduce the size of the scion and enable precocious flowering in many perennial cultivars. Currently there is a lack of Pyrus rootstocks that are vigour-controlling and precocity-inducing. The development of such a rootstock is a major focus in pear rootstock breeding. Marker assisted selection (MAS) could help to shorten this time consuming and costly breeding process. The aim of this PhD project was to examine the genetic determinants of vigour control and early flowering conferred to a scion by Pyrus rootstocks. A segregating population of 421 F1 seedlings from a P. communis ???Old Home??? x ???Louise Bonne de Jersey??? (OHxLBJ) cross was grafted with clonal ???Doyenne du Comice??? scions and used as the core experimental material for this project. High-density genetic maps were constructed for pear using two different high throughput genotyping tools, the Infinium?? II 9K apple/pear SNP array and the genotyping-by-sequencing (GBS) approach. QTLs influencing expression of scion vigour and precocity were detected on linkage groups (LG)5 and LG6 of OH and LG6 of LBJ. The LG5 QTL was found in the same genomic region as the dwarfing (DW1) QTL identified in the ???M9??? apple rootstock. The alignment of the QTL loci of apple and pear showed a high synteny between both loci and may help to identify candidate genes in both genera. The ease of vegetative propagation, a crucial trait for rootstock breeding, was assessed in rooting experiments and small effect QTLs were identified. These results will help to understand the genetic control of vegetative propagation in pear, and may assist in developing markers for MAS for this complex trait.

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  • A law and development perspective on services liberalisation in the Pacific Island Countries with particular reference to tourism

    Chan, Yok (2016)

    Doctoral thesis
    The University of Auckland Library

    Pacific island governments embraced the concept of reciprocal free trade agreements in the late 1990s in response to shifts in their historical relationships with their major donors and the ascendancy of neoliberal globalisation as the dominant model of development. Since then, they have placed a great deal of faith in this model as a pathway to sustainable development to generate economic growth, employment and as a means to achieve development goals such as poverty alleviation. The thesis examines whether international economic treaties and trade rules constrain development strategies and policy choices of the fourteen Pacific Island Countries (PICs). The thesis focuses on services liberalisation with special reference to tourism services, using as its analytical framework the theory of ???Three Moments??? in law and development doctrine, as advanced in 2006 by Trubek and Santos in The New Law and Economic Development: A Critical Appraisal. Using this framework, it examines the interface of two competing paradigms of development - neoliberalism and the Right to Development. The thesis also explores how the liberalisation efforts on trade in services have been rationalised and advanced at the international level through the General Agreement on Trade in Services (GATS) and at the regional level through the negotiations of regional free trade agreements such as the Economic Partnership Agreement (EPA) and the Pacific Agreement on Closer Economic Relations (PACER Plus), and the implications for policy and regulatory decisions at the national level in the PICs, especially those who are members of the World Trade Organization. The thesis supports two main conclusions. First, the prevailing neoliberal model of development, embodied in the Second Moment of Law and Development, is not appropriate for the PICs in their pursuit of sustainable development. Second, there are signs of a possible shift towards a Third Moment in the region, but this potential is constrained by the instruments of international economic law, as well as political pressure from the PICs??? key trading partners who are also major donors.

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