8,133 results for Share

  • The consequences of an innovative water quality policy

    Spicer, A.; Swaffield, Simon R.; Fairweather, John R.; Moore, Kevin

    Conference item
    Lincoln University

    This study assesses the consequences of Nitrogen Trading on the Lake Taupō catchment. It is designed to keep the agricultural sector productive as well as within environmental limits, and this makes the Lake Taupō Trading Programme unique. To date it is the only cap and trade programme in which a limit on non-point source nitrogen discharges is applied at both the watershed and the farm levels. Consequently, the Taupō case is acknowledged worldwide as an exemplar implementation of a cap and trade for water quality management. Water bodies, particularly lakes, are vulnerable to excess nutrients. The cap, in a cap and trade regime, enables an environmental goal (such as the amount of nitrate entering a lake) to be met while the trading part allows flexibility of farm management, encourages technology uptake and innovation, and allows changes that are in line with market signals. The study found that significant change has taken place since properties in the Catchment were benchmarked, and the direction of some of this change was unexpected. An important conclusion of the study is that caps on the discharge of nitrogen from farms, need to be coupled with sustained research investment into low nitrogen land uses and farm practices.

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  • 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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  • Performance of variations of the dynamic elastance model in lung mechanics

    Laufer B; Docherty PD; Knörzer A; Chiew YS; Langdon R; Moller K; Chase JG (2016)

    Journal article
    University of Canterbury Library

    © 2016 Elsevier Ltd Acute respiratory distress syndrome (ARDS) is associated with high mortality and it is a major clinical problem. A common therapy for ARDS patients is mechanical ventilation (MV). However, poorly applied MV can be potentially fatal and optimal MV settings are patient specific. Thus, choosing a good positive end expiratory pressure (PEEP)-level compromise is a clinical challenge. Physiological modeling of the lung is one way to support the selection of the optimal settings for mechanical ventilation. This research makes the reasonably well-supported assumption that optimal PEEP is in the region of minimal elastance of the lung-tissue. The first order model of pulmonary mechanics (FOM) was modified in two differing ways in order to determine the patient-specific pressure range that coincides with minimal elastance. The extensions to the FOM (multiplicative elastance correction and additive volume correction parameters) are compared and evaluated. The addition of the correction parameters ultimately improved the consistency of the modeled elastance across PEEP levels for most patients tested. The results for minimal elastance were in very similar ranges for both approaches. Although this consistency offers a partial validation of the robustness of the approaches, discernment of the optimal approach cannot be determined. Further validation across differing patient states and experimental inputs must be undertaken to determine which method is more representative of true patient physiology.

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  • How does the option of video assessment impact on student choice and grades?

    Schofield, L.; Baker, K.; Vo, D.; Pham, Truman; Lindsay, L; Han, B. (2017-12-22T13:30:22Z)

    Conference paper
    Unitec

    As digital fluency is becoming an educational priority, contemporary educators are increasingly looking at innovative means of assessment to replace or supplement more traditional approaches such as written essays or tests. Learner-generated, video-based assessment allows students to express themselves in different ways, brings the real world into assessment activities, and provides an opportunity to develop new digital and communication skills. Since 2014, The Mind Lab by Unitec has provided teachers and educators in New Zealand with a different model of professional development. Teachers and educators are able to study part time and complete a Postgraduate Certificate in Applied Practice – Digital and Collaborative Learning at a range of locations across New Zealand. Candidates can elect to work on assignments independently or collaboratively in small groups. In the first two courses candidates complete four assessments, two for each course. Assessment types for these courses include both video presentations and essays. Following anecdotal feedback from candidates about the two different assessment media, it was decided to examine what impact, if any, the medium used for assessment had on candidates’ grades. Although research indicates that video assessment is beneficial, there is minimal research into the impact of choice of media on students’ assessment outcomes. Of the four initial assessments, the first is a video, the second, an essay, and for each of the two subsequent assessments students may choose to submit either a video or an essay. We sought to investigate whether the students’ choice of medium impacted on their grades, and whether previous grades influenced the medium that students chose for subsequent assessment. We collected data from assessments of about 680 students over three consecutive intakes of the programme over a period of twelve months (November 2015 to October 2016). The findings indicate that the students’ choice of medium did not impact their grades. The choice of medium for the initial assessments also does not have a significant impact on the outcomes of subsequent assessments. The key finding is that students were not disadvantaged as a result of submitting video assessments. This may assist others in supporting and designing innovative means of assessment suitable for their students.

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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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  • Sulphate partitioning into calcite: Experimental verification of pH control and application to seasonality in speleothems

    Wynn, Peter M.; Fairchild, Ian J.; Borsato, Andrea; Spoetl, Christoph; Hartland, Adam; Baker, Andy; Frisia, Silvia; Baldini, James U.L. (2018)

    Journal article
    University of Waikato

    Carbonate-associated sulphate (CAS) is a useful carrier of palaeoenvironmental information throughout the geologic record, particularly through its stable isotope composition. However, a paucity of experimental data restricts quantitative understanding of sulphate incorporation into carbonates, and consequently CAS concentrations and their diagenetic modifications are rarely interpreted. However, in the case of calcite speleothems, the remarkably high-resolution CAS records which are obtainable via modern microanalytical techniques represent a potentially invaluable source of palaeoenvironmental information. Here, we describe the results of controlled experiments of sulphate co-precipitation with calcite in freshwater solutions where pH, saturation state, and sulphate concentration were varied independently of each other. Solution pH is confirmed as the principal control on sulphate incorporation into calcite. The relative efficiency of incorporation was calculated as a partition coefficient Dₛₒ₄=(mSO₄/mCO₃)solid/(mSO₄/mCO₃)solution. High crystal growth rates (driven by either pH or saturation state) encouraged higher values of Dₛₒ₄ because of an increasing concentration of defect sites on crystal surfaces. At low growth rates, Dₛₒ₄ was reduced due to an inferred competition between sulphate and bicarbonate at the calcite surface. These experimental results are applied to understand the incorporation of sulphate into speleothem calcite. The experimentally determined pH-dependence suggests that strong seasonal variations in cave air PCO₂ could account for annual cycles in sulphate concentration observed in stalagmites. Our new experimentally determined values of Dₛₒ₄ were compared with Dₛₒ₄ values calculated from speleothem-drip water monitoring from two caves within the Austrian and Italian Alps. At Obir cave, Austria, Dₛₒ₄ (×10⁵) varies between 11.1 (winter) and 9.0 (summer) and the corresponding figures for Ernesto cave, Italy, are 15.4 (winter) and 14.9 (summer). These values approximate predicted Dₛₒ₄ values based on our chamber experiments containing both low (2 ppm) and high (20 ppm) sulphate concentrations. Our experimental values of Dₛₒ₄ obtained at crystal growth rates typical of stalagmites, closely match those observed in other cave sites from around the world. This validates the universality of the controls behind Dₛₒ₄ and will enhance the use of speleothem CAS as a palaeoenvironmental proxy.

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  • Managing fire and biodiversity in the wildland-urban interface: A role for green firebreaks

    Curran, Timothy J.; Perry, G. L. W.; Wyse, Sarah . V.; Alam, Md

    Journal article
    Lincoln University

    In the wildland-urban interface, the imperative is often to protect life and property from destructive fires, while also conserving biodiversity. One potential tool for achieving this goal is the use of green firebreaks: strips of low flammability species planted at strategic locations to help reduce fire spread by slowing or stopping the fire front, extinguishing embers or blocking radiant heat. If comprised of native species, green firebreaks also have biodiversity benefits. Green firebreaks have been recommended for use throughout the world, including the Americas, Europe, Asia, Africa and Australasia. However, despite this widespread endorsement, there has been little empirical testing of green firebreaks, particularly with field experiments. This knowledge gap needs addressing. Green firebreaks should be considered as part of the revegetation strategy following recent extensive wildfires in places such as New Zealand and Chile.

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  • A laboratory for design-directed research. Building design scholarship and academic possibility through designing

    Abbott, Michael R.; Bowring, Jacqueline

    Journal article
    Lincoln University

    Designing is an experimental practice. Eschewing traditional concepts of designing as simply solving problems, and ideas of research as a positivist pursuit of truth, Landscope DesignLab embraces an expansive perspective of design-directed research. Using the tools of questioning, collaborating, designing, grounding and communicating, the DesignLab explores the terrains of possibility. Working within an inter-disciplinary milieu fosters strong connections, and seizes the generative possibilities of problems, questions, absences, and data.

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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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  • 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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  • 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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  • 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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