15,989 results for 2010, ResearchSpace@Auckland

  • Alzheimer's disease in the human eye. Clinical tests that identify ocular and visual information processing deficit as biomarkers

    Chang, Yu-Li; Lowe, J; Ardiles, A; Lim, Julie; Grey, Angus; Robertson, K; Danesh-Meyer, Helen; Palacios, AG; Acosta Etchebarne, Monica (2014-03)

    Journal article
    The University of Auckland Library

    Alzheimer's disease (AD) is the most common form of dementia with progressive deterioration of memory and cognition. Complaints related to vision are common among AD patients. Several changes in the retina, lens, and in the vasculature have been noted in the AD eye that may be the cause of visual symptoms experienced by the AD patient. Anatomical changes have been detected within the eye before signs of cognitive impairment and memory loss are apparent. Unlike the brain, the eye is a unique organ that can be visualized noninvasively at the cellular level because of its transparent nature, which allows for inexpensive testing of biomarkers in a clinical setting. In this review, we have searched for candidate biomarkers that could enable diagnosis of AD, covering ocular neurodegeneration associated with functional tests. We explore the evidence that suggests that inexpensive, noninvasive clinical tests could be used to detect AD ocular biomarkers.

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  • OpenSolver - An open source add-in to solve linear and integer progammes in Excel

    Mason, Andrew (2012)

    Conference item
    The University of Auckland Library

    OpenSolver is an open source Excel add-in that allows spreadsheet users to solve their LP/IP models using the COIN-OR CBC solver. OpenSolver is largely compatible with the built-in Excel Solver, allowing most existing LP and IP models to be solved without change. However, OpenSolver has none of the size limitations found in Solver, and thus can solve larger models. Further, the CBC solver is often faster than the built-in Solver, and OpenSolver provides novel model construction and on-sheet visualisation capabilities. This paper describes Open- Solver???s development and features. OpenSolver can be downloaded free of charge at http://www.opensolver.org.

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  • International comparison of long term care resident dependency across four countries (1998-2009): A descriptive study

    Boyd, Michal; Bowman, C; Broad, Joanna; Connolly, Martin (2012-12)

    Journal article
    The University of Auckland Library

    Aim:??? To describe an international comparison of dependency of long-term care residents. Methods:??? All Auckland aged care residents were surveyed in 1998 and 2008 using the ???Long-Term Care in Auckland??? instrument. A large provider of residential aged care, Bupa-UK, performed a similar but separate functional survey in 2003, again in 2006 (including UK Residential Nursing Home Association facilities), and in 2009 which included Bupa facilities in Spain, New Zealand and Australia. The survey questionnaires were reconciled and functional impairment rates compared. Results:??? Of almost 90 000 residents, prevalence of dependent mobility ranged from 27 to 47%; chronic confusion, 46 to 75%; and double incontinence, 29 to 49%. Continence trends over time were mixed, chronic confusion increased, and challenging behaviour decreased. Conclusion:??? Overall functional dependency for residents is high and comparable internationally. Available trends over time indicate increasing resident dependency signifying care required for this population is considerable and possibly increasing.

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  • Life and living in advanced age: A cohort ctudy in New Zealand - Te puawaitanga o nga tapuwae kia ora tonu, LILACS NZ: Study protocol

    Hayman, Karen; Kerse, Ngaire; Dyall, Lorna; Kepa, M; Teh, Ruth; Wham, C; Wright-St Clair, V; Wiles, Janine; Keeling, S; Connolly, Martin; Wilkinson, TJ; Moyes, Simon; Broad, Joanna; Jatrana, S (2012)

    Journal article
    The University of Auckland Library

    Background The number of people of advanced age (85 years and older) is increasing and health systems may be challenged by increasing health-related needs. Recent overseas evidence suggests relatively high levels of wellbeing in this group, however little is known about people of advanced age, particularly the indigenous M??ori, in Aotearoa, New Zealand. This paper outlines the methods of the study Life and Living in Advanced Age: A Cohort Study in New Zealand. The study aimed to establish predictors of successful advanced ageing and understand the relative importance of health, frailty, cultural, social & economic factors to successful ageing for M??ori and non-M??ori in New Zealand.

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  • Sedimentology and formation of lagoonal platform reef islands in Huvadhoo Atoll, Maldives

    Liang, Yiqing (2016)

    Doctoral thesis
    The University of Auckland Library

    Sediment samples from the reef platform and island cores were collected from two lagoonal reef islands in Huvadhoo Atoll, Maldives, in order to investigate island evolution and building processes in a region where detailed sedimentary and chronology data do not yet exist. The chronostratigraphy of the study islands was resolved using sedimentary data from field samples, combined with radiocarbon ages of sediments and ground penetrating radar records of the island subsurface. Further, this study is the first to apply scanning electron microscopy and elemental mapping in the evaluation of single constituent dating of Halimeda spp. in order to investigate its suitability for inferring depositional chronology on reef islands. Chronostratigraphic results indicate that the lagoonal reef islands on Huvadhoo Atoll formed around 3000 years ago and reached their current dimensions by 350 cal yr BP. A three-phase model of island evolution was developed in relation to mid-Holocene sea-level rise, which presents the first incidence of island building over multiple phases of sea-level change in the Indian Ocean. Medium-scale (decadal) shoreline sediment redistribution identified from morphological field mapping and satellite imagery provide clues to the building processes that occurred during island evolution, and suggest frequent reworking of island sediments over the course of island building. Similar compositional properties of reef flat and island sediments suggest a reef-island link and that the study islands are still being maintained by their surrounding reefs at present. The formation of the lagoonal reef islands in Huvadhoo Atoll during various stages of sea-level change, along with the potential for shoreline adjustment and evidence of contemporary reef connectivity, suggest enhanced resilience of Maldivian reef islands in response to projected sea-level rise.

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  • Kindness Matters: Investigating the mental and physical health benefits of self-compassion in diabetes

    Friis, Anna (2016)

    Doctoral thesis
    The University of Auckland Library

    Mood disturbances among diabetes patients are both common and problematic, compounding emotional suffering and potentially leading to complications in physical health. Despite high prevalence, however, current treatment options for the management of depression are limited; evidence for psychosocial interventions that concurrently improve both psychological and physiological health metrics is sorely lacking. The work presented in the context of this thesis sought to address this deficit by investigating the mental and physical health benefits of self-compassion in diabetes patients through a series of theoretical, cross-sectional, and experimental studies. The primary aims of this programme of study were to establish: (1) whether selfcompassion predicts better mental and physical health outcomes among diabetes patients and, if so, (2) whether a self-compassion intervention improved these outcomes for patients. The first contribution (Study 1) reviewed the literature pertaining to depression and low mood among diabetes patients and presented a theoretical rationale suggesting that self-compassion is well-suited to the challenges of diabetes selfmanagement, and that enhancing this characteristic should have psychological, behavioural, and physiological benefits. Study 2, a cross-sectional study conducted primarily with Type 1 diabetes patients then tested some of these hypothesized relationships. Analysis showed (1), that diabetes-specific distress was a better predictor of HbA1c than depression and (2), that self-compassion moderated the link between diabetes-specific distress and HbA1c such that the link between distress and poorer metabolic outcomes was weakened among those with greater trait selfcompassion. In Study 3, the effects of a brief self-compassion induction on mood and motivation to undertake a common health behaviour were tested in a laboratory study among healthy participants. While the self-compassion intervention improved mood, results were not consistent with the notion that self-compassion, compared to selfcriticism, would positively improve behavioural motivation, Thus, the final study (Study 4), a randomized controlled trial, tested the effects of a more substantial and standardized ???dose??? of self-compassion training ??? mindful self-compassion. Analyses showed that the eight-week training intervention improved both psychological and physiological outcomes, with reductions in depression, distress, and HbA1c in the intervention arm; effects were sustained at three months follow-up. Taken together, these studies are the first to demonstrate that self-compassion both predicts and causes reductions in depression and diabetes-specific distress among diabetes patients while concurrently improving metabolic outcomes. The RCT provides further evidence that self-compassion is a characteristic that can be developed with training. However, while highlighting the relevance of self-compassion to a patient population that often struggles with mood issues and related complications, further work is required to understand the pathways by which benefits might be exerted; effects on behavioural motivations in the laboratory study were not clearly evident. Overall, while self-compassion may be an important clinical aid for assisting patients more effectively cope with the distress of their condition, further work is required to better understand mediating psychological, behavioural, and biological pathways.

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  • Dermal And Cellular Delivery Of An Endogenous Anti-ageing Peptide Using Niosomes

    Badenhorst, Travis (2015)

    Doctoral thesis
    The University of Auckland Library

    Aim: The overall aim of this Thesis was to investigate the physical modification by encapsulation of GHK-Cu, a hydrophilic anti-ageing peptide, with lipid based nano-vesicles to address the barriers to cutaneous and cellular delivery. The influence of the surface charge of the vesicles was particularly studied as it was hypothesized that a cationic charge within the niosomes would increase both cellular and trans-epidermal delivery. The specific objectives were to; (1) evaluate the key physicochemical properties of GHK-Cu for the eventual development of formulations for dermal delivery of this peptide, (2) develop niosomes as a nano-carrier system for GHK-Cu for the potential delivery into the skin, (3) evaluate whether niosomes could act as a potential delivery system to increase cellular absorption as well as trans-epidermal delivery, and (4) evaluate whether the biological effect of GHK-Cu can be improved through niosomal delivery, particularly with cationic niosomes. The mechanisms by which were explored. Methods: The physicochemical properties of GHK-Cu were characterized using conventional methods. High performance liquid chromatography and mass spectrometry was utilised for quantification of the parent compound and identification of degradation products. GHK-Cu was incorporated into niosomal carriers characterised by laser diffraction, transmission electron microscopy (TEM) and zeta potential analysis. Cationic niosomes were chosen and used for the experiments in this Thesis following optimization. A non-ionic niosome of the same composition was used as a reference. Human dermal fibroblasts were used for cellular uptake and intracellular trafficking investigations, imaged with confocal scanning laser microscopy (CLSM) and TEM. All trans-epidermal investigations were undertaken using ex vivo viable human skin using calcein as a fluorescent marker enabling observation with CLSM. The biological response of both niosomal delivery systems was firstly assessed using metalloproteinases (MMP-1, collagenase and MMP-2, gelatinase) and tissue inhibitors of metalloproteinases (TIMP-1 and TIMP-2) as markers in cultured primary human dermal fibroblasts. These markers were measured through their gene expression by real time quantitative polymerase chain reaction (RT-qPCR), normalised to the control. Additionally, the collagen and elastin contents was measured in fibroblast cells following GHK-Cu incubation. The Thesis culminated in a double blind placebo split face clinical trial of 40 participants to determine the effect of the encapsulated niosomal GHK-Cu on wrinkle depth and volume reduction. Results: Preformulation studies indicated GHK-Cu was freely water soluble (325.09 ?? 4.38 mg mL-1) and hydrophilic with a logD of -2.49 through -2.38 over pH 7.4 to 4.5. Decreasing the pH caused the reversible dissociation of Cu ions from GHK. This effect proceeded rapidly from pH 4.26 downwards and was primarily caused by the protonation of the imidazole and glycyl residues. Therefore at the HPLC mobile phase with a pH of 2, it was only the GHK peptide that was measured. GHK eluted at 8.02 ?? 0.10 min under isocratic conditions making it ideal for routine analysis. The LOD and LOQ were determined to be 0.55 and 1.8 ??g mL-1, respectively. The validation data, including that from mass spectrometry, proved the assay to be stability-indicating. Forced degradation studies identified hydrolysis as the main pathway of degradation, leading to the identification of three new products. The final product was verified with injections of pure histidine, a component amino acid. GHK was stable in water and in phosphate bufferered saline (0.1 M) at pH 7.4. The logD and solubility results incentivized the consideration of a lipid-based carrier system, in particular niosomes, to enhance the dermal delivery of GHK-Cu. A niosomal lipid based carrier system was subsequently developed for encapsulating GHKCu. The size, surface charge and loading efficiency of the niosomes were optimized to enhance dermal delivery. A positive charge was obtained following post-insertion of didecyldimethylammonium bromide (DDAB) into the surface of Span 60/cholesterol based niosomes. The niosomes had a final size of 225.8 ?? 7.7 nm for cationic and 193.3 ?? 5.2 nm for non-ionic niosomes. A positive surface charge of 49.4 ?? 1.2 mV was observed in cationic niosomes with a maximum entrapment efficiency of 9.7 ?? 0.2% (w/w) of GHK-Cu was achieved for both systems. Calcein, having similar physicochemical properties to GHK-Cu, was chosen for CLSM studies. The mechanism of intracellular uptake, confirmed by TEM imaging, was clathrinmediated endocytosis. This evidence was primarily supported by the size, lysosome formation and clathrin pit formation in fibroblasts. ImageJ analysis of the confocal images showed a slight increase in intensity (83 vs 79) in the cationic treated samples over the nonionic treated ones. A larger number of lysosomes were imaged in cationic niosome treated cells. Endosomal escape was determined to be by destabilisation resulting from both a cationic lipid and a surfactant interaction with the endosomal membrane without affecting the viability of the cells. This was determined using a MTT test, which resulted in all concentrations tested, except that of cationic niosomes at 10-7 M, having no detrimental effect on cell viability. CLSM images revealed that free calcein could not cross the stratum corneum. Niosomes however, both cationic and non-ionic, caused adsorption onto the surface forming a critical thermodynamic activity gradient, driving permeation into the dermis. Upon incubation with niosomes for 24 hours, fibroblasts showed greater expression of MMPs (> 2-fold, p2-fold, p1 suggesting a trend towards decreases in collagen degradation. The ratios of TIMP-2/MMP-2 were <0.005) in wrinkle volume reduction compared to both the placebo and lipophilic derivative. Wrinkle depth also improved the most, however this was only moderately significant (p=0.057). The difference in wrinkle depth and volume versus the placebo indicate the effectiveness of the cationic niosomal GHK-Cu in topical delivery. The cationic encapsulated GHK-Cu was tolerated as well as the marketed Matrixyl?? 3000 product with only one participant reacting to both. Unfortunately the non-ionic niosome formulation was not tested due to financial limitations of the company. Conclusion: GHK-Cu was effectively encapsulated into cationic and non-ionic niosomes and effectively delivered into cells and passed the epidermis with significant biological effect. The in vitro and ex vivo studies essentially proved that cationic encapsulation of GHK-Cu was marginally better than the non-ionic counterpart for intracellular and trans-epidermal delivery. This research, for the first time, found that GHK-Cu could promote the cellular expression of MMP-1, MMP-2 and their inhibitors TIMP-1, TIMP-2 in human fibroblasts, and that it is their ratios that decided the changes in their substrates, collagen and elastin content on/in the cells. The in vivo clinical evidence suggests that dermal delivery of GHKCu in cationic niosomes results in significant wrinkle volume and depth reduction with accumulative improvements.

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  • Discovery and development of imaging-capable bacterial nitroreductases and their cytotoxic prodrugs for Clostridium sporogenes based gene therapy

    Mowday, Alexandra (2015)

    Doctoral thesis
    The University of Auckland Library

    Clostridia Directed Enzyme Prodrug Therapy (CDEPT) has demonstrated anti-tumour efficacy in preclinical studies but has yet to be developed for human clinical trials. Challenges associated with stable genetic modification of the bacterial genome have recently been overcome, making CDEPT clinically feasible for the first time. The main goal of this project was to accelerate the development of nitroreductase-based CDEPT, initially by further improving nitroreductase activity with respect to PR- 104, a clinical-stage 3,5-dinitro-2-mustard prodrug. Random and site-directed mutagenesis techniques were used to optimise the E. coli NfsA polypeptide (UniProt accession P17117) for PR- 104A activation. The preferred multi residue variant #22GP (S41Y, E99G, L103M, R225P, F227S) was successfully expressed in three stable cell line models (HCT116, H1299 and C33A) and demonstrated significantly improved in vitro anti-proliferative activity with PR-104A compared to native NfsA (up to 2.3-fold), whilst retaining the ability to co-metabolise 2-nitroimidazole PET imaging substrates. In parallel, a series of PR-104A analogues were evaluated to eliminate off-mechanism aerobic metabolism by aldo-keto reductase 1C3 (AKR1C3) and to improve therapeutic activity by maximising bystander potency using 2D anti-proliferative and 3D multi-cellular layer assays for E. coli NfsA and/or AKR1C3 activity. In vivo efficacy studies on promising candidates resulted in the selection of a lead compound from each of three chemical classes; SN 34507 (an alcohol bearing 5- nitro-2-mustard phenylcarboxamide), SN 36001 (a piperazine bearing 2-nitro-4-alkylsulfone-5- mustard phenylcarboxamide) and SN 35288 (an alcohol bearing 2-nitro-4-alkylsulfone-5-mustard phenylcarboxamide). Finally, an in vivo model of CDEPT was identified. 1000mm3 H1299 xenografts treated with vascular disrupting agent DMXAA (5,6-dimethylxanthenone-4-acetic acid) produced widespread tumour necrosis and promoted colonisation of nitroreductase expressing Clostridia spores. The combination of DMXAA and Clostridia spores alone produced significant anti-tumour activity compared to untreated controls (TGD = 67%, P=0.004), but the inclusion of prodrug (PR-104) provided significant additional activity (TGD = 167%, P<0.001), validating the CDEPT concept. Successful preclinical evaluation of a transferable gene that metabolises both clinical stage PET imaging agents (for whole body vector visualisation) as well as chemotherapy prodrugs (for conditional enhancement of efficacy) is a valuable early step towards the prospect of nitroreductasearmed C. sporogenes entering clinical evaluation.

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  • Improving adherence and asthma outcomes in school aged children with asthma

    Chan, Amy (2016)

    Doctoral thesis
    The University of Auckland Library

    Asthma is one of the most common chronic conditions in children. Effective treatments are available, the most important of which are inhaled corticosteroids, which reduce morbidity and mortality. Despite the availability of effective preventive therapies, asthma control continues to be poor, primarily due to poor adherence. Interventions have been developed to improve adherence; however, changes have been modest, or not sustained. Where there have been significant increases in adherence, these have not translated to improvements in outcomes. A novel approach to adherence support is needed. Electronic monitoring devices (EMDs) have risen to prominence over the last decade, assuming an important role in adherence measurement and intervention. The ability of EMDs to provide objective, real-time data and user feedback places EMDs at the forefront of contemporary adherence interventions. This thesis discusses adherence in chronic disease, specifically asthma, and the role of EMDs in adherence promotion. Studies using EMDs to improve adherence in asthma have shown improvements in adherence, but the link to outcomes has been inconclusive. This thesis presents the main findings from a randomised controlled trial (RCT) investigating the use of an EMD in children with asthma. The results from this trial provide the first unequivocal evidence of the beneficial effects of EMDs on clinical outcomes. It provides a direction for future adherence research, focusing on the effect of EMDs on clinical outcomes, beyond adherence promotion. This thesis also presents the first performance and patient acceptability data for EMDs in children. The positive findings highlight the potential for EMDs to be used outside of the research setting, though key issues of quality control, usability and cost-effectiveness need to be addressed before EMDs can be integrated into practice. Other factors influencing adherence are also discussed. This study found associations between higher adherence and female sex, Asian ethnicity, smaller household size and a younger age at diagnosis. These findings can help identify those at risk of nonadherence to help target adherence interventions. This thesis highlights areas of knowledge growth and areas where questions remain unanswered. It provides a platform for future research, presenting new possibilities for improving medication adherence and clinical outcomes

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  • Semi-synthesis of bioactive fluorescent analogues of the cytotoxic marine alkaloid discorhabdin C

    Lam, CFC; Giddens, Anna; Chand, N; Webb, VL; Copp, Brent (2012-04-15)

    Journal article
    The University of Auckland Library

    Semi-synthetic N-13 alkylated analogues of the cytotoxic marine alkaloid discorhabdin C have been found to exhibit cytotoxicity towards tumour cell lines at comparable levels to that of the natural product. Incorporation of an ethylenediamine linker facilitated the synthesis of a variety of fluorophore-labelled probes, of which dansyl analogue 20 exhibited biological activity, providing a tool for mechanism of action and cellular localization studies. An alternative probe design was also exemplified, whereby a bioactive alkyne-terminated analogue (24) was found to undergo Huisgen 1,3-dipolar cycloaddition ???click??? reactions with fluorescent azides, enabling studies directed towards activity-based protein profiling.

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  • Clinical judgement by primary care physicians for the diagnosis of all-cause dementia or cognitive impairment in symptomatic people

    Creavin, S; Noel-Storr, A; Richard, E; Creavin, A; Cullum, Sarah; Ben-Shlomo, Y; Purdy, S (2017-02-19)

    Journal article
    The University of Auckland Library

    This is a protocol for a Cochrane Review (Diagnostic test accuracy). The objectives are as follows: To determine the accuracy of general practitioners' overall gestalt (unaided) clinical judgement for diagnosing cognitive impairment and dementia in symptomatic people presenting to primary care. There is no comparator index test. To investigate the heterogeneity of test accuracy in the included studies.

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  • A system dynamics view of safety management in small construction companies

    Guo, BHW; Yiu, Tak Wing; Gonzalez, Vicente (2015-12)

    Journal article
    The University of Auckland Library

    Due to unique characteristics of small construction companies, safety management is comprised of complex problems. This paper aims to better understand the complexity and dynamics of safety management in small construction companies. A system dynamics (SD) model was built in order to capture the causal interdependencies between factors at different system levels (regulation, organization, technical and individual) and their effects on safety outcomes. Various tests were conducted to build confidence in the model???s usefulness to understand safety problems facing small companies from a system dynamics view. A number of policies were analyzed by changing the value of parameters. The value of a system dynamics approach to safety management in small construction companies is its ability to address joint effects of multiple safety risk factors on safety performance with a systems thinking perspective. By taking into account feedback loops and non-linear relationships, such a system dynamics model provides insights into the complex causes of relatively poor safety performance of small construction companies and improvement strategies.

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  • The impact of cell ventilation on the top heat losses and fugitive emissions in an aluminium smelting cell

    Abbas, H; Taylor, Mark; Farid, Mohammed; Chen, John (2013-04-08)

    Book item
    The University of Auckland Library

    Problems associated with aluminium smelting cell ventilation, caused by leakage of fume gases through pots superstructure gaps into the potroom, are normally solved by increasing the fume suction rate (draught) above certain levels. It is also known that, fugitive emissions are associated with reducing the draught below certain critical levels. Top heat losses are increasing in smelting cells as line amperage is raised. This drives further fugitive emissions through greater buoyancy of the fume/air mixture. A quantitative understanding of the relationship between fugitive emissions, superstructure tightness, top heat loss, and cell draught is crucial in the environmental context. It is also important if this top heat loss could be recovered for re-use. This problem is studied here computationally using the ANSYS-CFX software. Possibilities to improve cell ventilation and to decrease fugitive emissions are analysed for a typical industrial cell. The computed cell emissions and temperatures are compared with measured values. The impact of draught on ventilation and heat loss is also discussed

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  • Relevance of adhesion in particulate/fibre-polymer composites and particle coated fibre yarns

    Mohan, Velram; Jayaraman, Krishnan; Bhattacharyya, Debes (2017-06)

    Book item
    The University of Auckland Library

    Functional particles or fibres when incorporated into polymeric matrices produce composites of greater density, improved electrical conductivity, and, consequently, improved mechanical behaviour at demanding operating conditions, such as high temperature and pressure. Adhesion behaviour in particulate composites and fibre-reinforced composites, together with comparison between theoretical and experimental outcomes are reviewed here. Current research outcomes with respect to electrical conductivity and in relation to the preparation of conductive wires using glass fibres and thermoplastic yarns, and surface-coated with graphene (G) using a binder (epoxy or starch) are also included. Additionally, electrical and mechanical characteristics of hybrid particulate composites involving a primary polymer, a secondary polymer, and reinforcements have been discussed. Comments have been made on the influence of adhesion phenomena in these cases.

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  • A water-model study of the ledge heat transfer in an aluminium cell

    Chen, John; Wei, CC; Ackland, AD (2013-04-08)

    Book item
    The University of Auckland Library

    A heat transfer probe was developed for studying the ledge heat transfer in a full-scale 3-D air-water model. Quantitative measurements were conducted to determine the bath/ledge heat transfer characteristics at various positions and different operating conditions. A similitude analysis was carried out to relate the measured point results to data available in the literature. A suggested range of heat transfer coefficients for the reduction cell is presented. Variation of the heat transfer were examined as a function of the anode bottom inclination, the position on the side ledge relative to the anode slot, and positions in the vertical direction. ?? 2013 The Minerals, Metals & Materials Society.

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  • Design considerations for selecting the number of point feeders in modern reduction cells

    Walker, ML; Purdie, JM; Wai-Poi, NS; Welch, BJ; Chen, John (2013-04-08)

    Book item
    The University of Auckland Library

    Point feeding systems are now installed in most modern reduction cells in preference to bar breakers. The main reason for this choice is that point feeders allow improved alumina dissolution. However complete alumina dissolution is not an explicit design criterion for selecting the size of the alumina dump or the number of feeders required. In this paper, three performance criteria for determining the number of point feeders required in a cell are investigated. These are: acceptable alumina dissolution, satisfactory mixing to avoid concentration gradients and a satisfactory rate of alumina concentration increase after anode effect. Using a combination of laboratory data and measurements from industrial cells, it is shown that the alumina dissolution requirement is likely to be the most difficult to satisfy. Complete alumina dissolution upon addition is unlikely to be achieved with the point feeder designs installed in most modern cells. ?? 2013 The Minerals, Metals & Materials Society. Published 2013 by John Wiley & Sons, Inc.

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  • The interaction between current efficiency and energy balance in aluminium reduction cells

    Stevens, FJ; Zhang, W; Taylor, Mark; Chen, John (2013-04-08)

    Book item
    The University of Auckland Library

    In aluminium reduction cells the current efficiency interacts with the energy balance through both the thermodynamics and the hydrodynamics of the reduction process. The overall enthalpy for the reduction reaction is endothermic and increases with current efficiency due to lower heat evolution from the re-oxidation reaction. Changes in current efficiency due to changed mass transfer conditions will lead to an energy deficit or surplus. This will occur predominantly in the electrolyte channels where the largest proportion of mass transfer-driven current efficiency loss occurs. Other sources of current efficiency loss such as electronic loss of faradaic current will further reduce the endothermic contribution of the reaction enthalpy and may cause localised energy surpluses. The energy balance directly affects the electrolyte temperature and composition. It also affects the volume of the liquid electrolyte and the shape and thickness of side freeze and crust, which determine the shape of the operating cavity. Bath composition and temperature determine the physical properties of the electrolyte which, along with the geometry of the flow cavity, influence the turbulence of the bubble-driven circulation and the disturbance to the electrolyte-metal interface. Both factors influence the mass transfer and hence, metal reoxidation rate. ?? 2013 The Minerals, Metals & Materials Society.

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  • Operational and control improvements in reduction lines at Aluminium Delfzijl

    Stam, MA; Taylor, Mark; Chen, John; Van Dellen, S (2013-04-08)

    Book item
    The University of Auckland Library

    Nowadays viability of smelters requires operation of cells at or beyond known performance limits. At Aldel over the last ten years the intensity of electrical energy dissipation and alumina dissolution per cubic centimeter of liquid bath have increased by 50% as production (+40%) and specific energy consumption (-6%) have improved. The cell imbalances resulting from this increased intensity must be sensed quickly and their causes corrected or removed to maintain the cells in their most efficient operating zone. This defines a new control objective for smelting relating to diagnosis of causes of abnormality in strongly interactive multivariate processes. Timely identification of these causes of variation is linked to operational practice improvement and better control decisions in reduction lines. This paper describes smelter based improvement of operational practices and control decisions using the above objective. Statistical multivariate control surfaces are presented for operating cells and identified abnormal behaviours are discussed. ?? 2013 The Minerals, Metals & Materials Society.

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  • Korea???s Growing Role(s) on the World Stage ??? South Korean Identity and Global Foreign Policy in the Early 21st Century

    Flamm, Patrick (2017)

    Doctoral thesis
    The University of Auckland Library

    South Korea is usually seen as a ???shrimp amongst whales???, a minor player with limited agency in regional and global affairs. After colonization, the Korean War, national division and decades of military rule in the 20th century, however, South Korea today contributes to international peace and security with its peacekeeping troops and has successfully promoted its ???green growth??? vision of sustainable development. The rising status of Korea begs the question about related changes in the South Korean identity or ???sense of self??? in the world. In the respective International Relations and Korean Studies literatures this question has not yet been fully addressed beyond hopes for South Korea to be a future cornerstone of the liberal international order. Further, a wide variety of ???identity??? conceptualizations has been leading to ???definitional anarchy??? as well as ???confusion and analytical ambiguity??? in the study of identity in general and South Korean international identity in particular. This thesis presents a theoretically rigorous and empirically rich approach for the inquiry into state identity through the utilization of conceptual tools from symbolic-interactionist role theory as a contribution to the research on state identity and foreign policy. By focusing on South Korean agency and domestic self-identification practices, the empirical analysis at hand is able to provide a comprehensive account of the various identity narratives and role conceptions at play in South Korea???s global engagement in peacekeeping and climate diplomacy, complementing more systemic identity approaches such as the literature on norms and socialization. It argues that in the cases of peacekeeping and climate diplomacy South Korea???s identity as an international actor has been dominated by practices of self-identification that locate the country at the brink of advanced countries, aspiring to lead the rest of the world on the basis of the Korean developmental experience, but with the overall objective to maintain national autonomy in a changing regional and global context. Finally, this study is a contribution to the Korean Studies literature on how South Korea confronts globalization on the level of identity and politics.

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  • The cardiovascular effects of preterm birth and neonatal anaemia in sheep

    Tay, Kai Yie (2016)

    Doctoral thesis
    The University of Auckland Library

    Preterm birth has been identified as a risk factor for cardiovascular disease in adulthood. The heart is in a stage of rapid development in the last trimester when preterm birth occurs. It is not known how cardiac structure and vessels remodel to enable the immature myocardium and cardiac vasculature to adapt to the haemodynamic transition at birth. We hypothesised that preterm birth would induce permanent changes in cardiac structure and function. We further hypothesised that neonatal anaemia, a common complication of prematurity which affects blood flow and thus may act as a stressor on the developing heart, would have long-term effects on autonomic cardiac regulation, cardiac blood flow (assessed via coronary conductance) and the microcirculation. Compared to lambs born at term, preterm lambs had decreased capillary-to-myocyte ratio in the myocardium, reduced muscle layer width within the left ventricular myocardium and larger cardiomyocyte cross-sectional area. Qualitative analysis of coronary blood vessels found that fetal lambs studied at term, and lambs born preterm studied at term-corrected age, have fewer branches compared to hearts of lambs born at term. However, induction of preterm birth with steroids rather than an anti-progestogen was protective for this effect. Preterm birth and neonatal anaemia resulted in greater indices of parasympathetic function (lower heart rate at rest and greater Log root mean square of successive differences between adjacent heart beatto- beat intervals (RMSSD), Log difference between adjacent R-R intervals that are greater than 50 ms (NN50) and normalized high frequency (HFnu)); however, in contrast, neonatal anaemia in term lambs resulted in greater sympathetic modulation in young adult and adult sheep. The existence of lower heart rate after vagal blockade with atropine in adult sheep born preterm with neonatal anaemia suggests that the impact of anaemia on autonomic nervous system maturation differs according to maturational stage and may be most marked on the parasympathetic nervous system. Greater maximal coronary conductance and retinal vasculature bifurcation angles were observed in adult sheep born preterm and with neonatal anaemia, indicating alteration of microcirculation architecture in both the heart and the retina. Thus, visualisation of the retina may provide a window into structural changes in the microcirculation elsewhere in the body. Findings of these studies suggest that the combination of neonatal anaemia and preterm birth may have an effect on the autonomic regulation of cardiac function, coronary blood flow and the development of the microcirculation that persists into adult life.

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