63,958 results for 2000

  • An Investigation into Establishing (Motivating) Operations

    Jackson, Surrey Merryn Kate (2017)

    Doctoral thesis
    University of Waikato

    Motivating Operations (MOs) are a fundamental concept in behavioural psychology. Despite this, empirical research into MOs is lacking. The overall aim of this thesis is to contribute to the experimental literature base for MOs. Experiment 2.1 used an already published video analysis methodology to assess the morphology of food motivated pecks made to a computer screen by hens, after the hens had been trained to emit the peck using either an autoshaping or handshaping procedure. The intention of this was to then be able to use the video analysis to assess the effect of altering two MOs related to two different reinforcers (e.g., food and water) at one time, on morphology. The study showed that both methods produced similarly formed pecks despite the variability inherent in the handshaping procedure. It was then concluded it is the nature of the reinforcer that gives rise to morphology not the autoshaping procedure per se which gives rise to a particular form of elicited responses. The aim of Experiment 3.1 and 3.2 was to develop a procedure for restricting access to water in laying hens, in order to motivate them sufficiently to respond for water reinforcers. Experiment 3.1 assessed the effect that gradually decreasing time and amount of water access had on food-restricted hens’ water consumption and health. It was found that hens could be restricted to one hr access of water (restricted to the maximum amount that hens would consume when access was ad libitum) without adverse effects to health being apparent. However, when the hens were subsequently exposed to FR schedules with a low response requirement in Experiment 3.2, they did not respond consistently. This indicated that the level of restriction was insufficient to motivate responding and this finding, combined with the difficulty of obtaining ethical approval, meant that the proposed experiments utilising water deprivation as an MO had to be abandoned. Experiment 4.1 used the autoshaping paradigm to assess the acquisition of food motivated pecks to a stimulus, at two different levels of bodyweight (75% and 95%). An infra-red screen was used to analyse performance separately from learning effects by examining activity levels (location and amount of pecks). It was found that that higher numbers of effective pecks were made by hens maintained at 75% free-feeding bodyweight than hens maintained at 95% (different MO conditions). There were also higher levels of ineffective pecks in the 75% group. Experiment 5.1 investigated relative preference for stimuli correlated with different MO conditions: high deprivation (no pre-feeding), or low deprivation (pre-feeding), when subjects were maintained at either 75% or 95% of free-feeding bodyweight. The results showed that 6/10 hens demonstrated an increased preference for the stimulus paired with high deprivation conditions (no pre-feeding) when measured by log ratios of responses, and had faster response rates on this stimulus. Overall, the 75% bodyweight hens had faster response rates than the 95% hens (as in Experiment 4.1), and 8/10 hens responded faster on the stimulus that was paired with no pre-feeding. It was also found, as per Experiment 4.1, that higher numbers of effective pecks were made by hens maintained at 75% free-feeding bodyweight than hens maintained at 95% (different MO conditions). Experiments 6.1 and 6.2 extended the findings of the thesis thus far in that concurrent VI VI schedules were used to assess the effect of bodyweight and pre-feeding as MOs on steady state responding. In total 16 conditions were run exposing hens to three different VI pairs: VI-12, VI-60 (5:1); VI-20, VI-20 (1:1); and VI-60, VI-12 (1:5). Bodyweight values of 85%, 95%, 100%, and 85% with pre-feeding of 40 cc wheat delivered 40 minutes prior to experimental sessions were manipulated between hens finishing a series of the three VI pairs. It was found that 4/6 hens had higher absolute and relative response rates when bodyweight was made lower. For 3/6 of these hens, increasing bodyweight increased sensitivity as measured by the parameter a; this was more distinct when the Generalised Matching Law was applied to response rather than time locations for these hens. Frequency distributions of IRTs showed that for the hens that tended to show increasing sensitivity as bodyweights increased there were more IRTs in bins greater than 0.4 s. This was reflected on the log-survivor plots as the limbs were shallower when bodyweights were higher, indicating that more between-bout responses were occurring. It was also found that pre-feeding increased sensitivity as measured by the parameter a for all hens; this was more noticeable when the GML was applied to response rather than time allocations. Although overall response rates tended to resemble those for the 85% bodyweight condition and remain higher than the 95% and 100% bodyweight conditions, the distribution of left and right response rates showed that hens matched better to the prevailing reinforcer rates when they were pre-fed, than when they were not pre-fed. Overall, the main findings were: (1) that reducing bodyweights increased amounts of species-specific behaviour; and (2) that reducing bodyweight causes increases in response rate. These findings could explain why changes in preference for stimuli paired with high levels of deprivation are observed during SDVL procedures, and why increased sensitivity to available reinforcement at lower levels of deprivation found in studies utilising the GML have been observed in previous studies. These findings contribute to the empirical data informing the behavioural treatment of motivation and have applied implications. Reinforcement and punishment procedures such as extinction or differential reinforcement of alternative behaviours may no longer be necessary when MOs are manipulated.

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  • Spontaneous activity drives local synaptic plasticity in vivo

    Winnubst, J; Cheyne, Juliette; Niculescu, D; Lohmann, C (2015-07)

    Journal article
    The University of Auckland Library

    Spontaneous activity fine-tunes neuronal connections in the developing brain. To explore the underlying synaptic plasticity mechanisms, we monitored naturally occurring changes in spontaneous activity at individual synapses with whole-cell patch-clamp recordings and simultaneous calcium imaging in the mouse visual cortex in vivo. Analyzing activity changes across large populations of synapses revealed a simple and efficient local plasticity rule: synapses that exhibit low synchronicity with nearby neighbors ( fashion through proBDNF/p75(NTR) signaling to refine neuronal connectivity.

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  • Technical report two: Analysis of curriculum documents

    Ballantyne, N; Beddoe, Elizabeth; Hay, K; Maidment, JM; Walker, S; Ngan, L (2016)

    Report
    The University of Auckland Library

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  • Transformative aspirations and realities in Physical Education teacher education

    Ovens, Alan (2017)

    Book item
    The University of Auckland Library

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  • Field, capital and professional identity: Social work in health care

    Beddoe, Elizabeth (2017)

    Book item
    The University of Auckland Library

    This chapter explores social work identity in health settings, a significant field of practice in many parts of the world, including North America and Australasia. The influence of the French sociologist Pierre Bourdieu???s philosophical framework is explored in a consideration of professional identity. His concepts, ???field??? and ???capital??? are used to analyse the influence of power relations, utilising an additional concept of ???professional capital???. Social work may be perceived as successful in health contexts as it is not as subject to media and critical public scrutiny as children???s social work is, but health social workers still often express feelings of marginalisation (Beddoe, 2013a). In Bourdieu???s terms, social work may be viewed as a collective of ???agents??? occupying a field, playing out their roles in a ???structured social space, a field of forces??? (Bourdieu, 1998, p. 40). In such fields there may be palpable competition between actors for the accumulation of different kinds of capital and it is here perhaps that social work identity is less secure.

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  • Report on reader attitudes and behaviour

    Morris, Paula; Robertson, C (2016)

    Report
    The University of Auckland Library

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  • Technical report three: TISWEANZ Taxonomy

    Ballantyne, N; Beddoe, Elizabeth; Hay, K; Maidment, JM; Ngan, L; Walker, S (2016)

    Report
    The University of Auckland Library

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  • Report on citizenship law: New Zealand

    McMillan, K; Hood, Anna (2016)

    Report
    The University of Auckland Library

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  • Technical report one: Methods for the creation of terms for indexing social work education in Aotearoa New Zealand (TISWEANZ)

    Ballantyne, N; Beddoe, Elizabeth; Hay, K; Maidment, JM; Ngan, L; Walker, S (2016)

    Report
    The University of Auckland Library

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  • The good without the bad: Selective chelators for beryllium encapsulation

    Perera, Lakshika C (2017)

    Doctoral thesis
    The University of Auckland Library

    Beryllium is an indispensable metal. Its unmatched combination of unique properties such as extreme strength, low density and high machinability has made it vital in the automotive, nuclear, space, medical, defence sectors and other consumer industries. However, beryllium is considered the most toxic non-radioactive element on the planet. It is also a class one carcinogen and the cause of chronic beryllium disease (CBD). Surprisingly, this fact has not deterred its use in manufacturing. Therefore it is imperative that chemical agents be developed for better detection and remediation of beryllium in the environment and as therapies for individuals exposed to this element. The goal of this research was to develop strong, selective chelating agents for the encapsulation of beryllium. Furthermore a greater ex-ploration of beryllium fundamental coordination chemistry was under-taken with an investigation of binding preferences of the Be2+ cation. The introduction begins with a brief overview of beryllium solu-tion chemistry. Following this is a comprehensive review of the Be2+ coordination chemistry with an investigation into existing organic and inorganic ligands with an emphasis on hard nitrogen and oxygen donor containing ligands. This then moves on to a brief description of the selected ligand design based on the fundamental coordination prefer-ences of Be2+. The main ligand motif will be based on a di-pyridyl sca???old with selected chelating pendant groups, allowing the formation of tetradentate complexes which can form the desired six-membered chelate rings with Be2+ cations. Chapter Two explored the synthesis of a ligand based a dipyrrin pendant group. The corresponding dipyrromethane was used as the starting point. While coupling of this dipyrromethane directly on to a dipyridyl sca???old was unsuccessful, the same dipyrromethane con-taining a one pyridyl group in the form of an acyl-pyridyl unit served as a reasonably good candidate for the successful coupling of the last pyridine group. Furthermore, synthesis of a modi???ed dipyrrin ligand with the inclusion of hydrogen-bonding buttressing groups was also attempted. Chapter Three explored the synthesis of a ligand containing a mo-tif based on a hydroxy-phenyl imidazole moiety. The hydroxyphenyl imidazole moiety was synthesised and used as a starting point. The brominated analogue of the hydroxyphenyl imidazole moiety was suc-cessfully coupled to a di-pyridyl sca???old containing a nitrogen at the center sca???old position through a modi???ed Ullman type reaction. DFT studies of the ligands synthesised and preliminary complexation studies were conducted using boron and aluminium ions as safe analogues and are described in chapters Four and Five. ESI-MS studies were also used for the study of the Be-ligand complexes, allowing their synthesis on a small scale and minimising exposure to beryllium.

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  • On the analysis of quasi-periodic systems and a novel ???deterministic??? explanation of the stochastic resonance phenomenon

    Blekhman, I; Sorokin, Vladislav (2017)

    Conference item
    The University of Auckland Library

    The present paper is concerned with the analysis of quasi-periodic systems which represent an important class of dynamical systems frequently encountered in applications. The related problems appear, e.g. in the analysis of parametric amplifiers based on resonant micro- and nanoscale systems, wave propagation in nearly periodic structures and composite materials, etc. The conventional methods of linear and nonlinear dynamics, e.g. asymptotic methods and approximate approaches based on Floquet theory, often appear to be not applicable for solving such problems. The present paper addresses the application of the Oscillatory Strobodynamics approach and the Method of Varying Amplitudes for these problems with the notable effects being revealed. In particular, a novel ???deterministic??? explanation to the phenomenon of stochastic resonance is proposed.

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  • Designing graphene supercapacitor electrodes

    Farquhar, Anna K. (2017)

    Doctoral thesis
    University of Canterbury Library

    Graphene, a two-dimensional material comprised of sp2-hybridised carbon atoms, has significant potential in energy storage as an electrode material for supercapacitors. Unfortunately, strong intermolecular forces between the graphene sheets results in aggregation during assembly and use, reducing the accessible surface area and experimentally available capacitance. Prevention of aggregation during electrode assembly and cycling will allow the development of graphene materials with better energy storage capability. In this thesis work, molecular spacers grafted to few-layer graphene (FLG) were investigated as a way of preventing aggregation of the graphene sheets. Molecular spacers were grafted to FLG using three strategies: the spontaneous reaction with aryldiazonium salts, the Diels Alder reaction of an aryne, and the addition of an amine. The aryldiazonium reaction was studied using five different salts. The results indicated that at least two reaction pathways are operative for the spontaneous reaction, giving a multilayer film with both -C-C- and -N=N- linkages. Furthermore, the experimental protocol allowed the modified FLG to be collected with the film either sandwiched between the FLG and the substrate, or exposed to the electrolyte. In the sandwiched orientation two nitrophenyl reduction peaks were sometimes seen and larger surface concentrations were measured, behaviour that has not been reported previously for films grafted onto carbon materials from aryldiazonium salts. The Diels- Alder reaction, which relied on the generation of an aryne from an anthranilic acid precursor, provided an efficient route to monolayer growth. The amine addition reaction provided an alternative route modifying FLG, though a Michael-like addition or partial intercalation. Supercapacitor electrodes were assembled from aryldiazonium modified FLG using a layer-by-layer (LBL) strategy. The grafted film could efficiently separate the FLG sheets during assembly and prevent restacking during cycling, with the full surface area remaining accessible even after 20,000 galvanostatic charge discharge cycles. Furthermore, the grafted film did not diminish the total capacitance of the FLG or hinder ion movement to the surface of the sheets. To further enhance the capacitance of the FLG, pseudocapacitive metal hydroxide films were electrochemically deposited on the FLG sheets prior to LBL assembly, which enhanced the total areal capacitance of the system. This thesis work successfully developed a novel LBL protocol that allowed electrodes comprised of stacks of FLG to be assembled without diminishing the total accessible surface area and therefore capacitance of each graphene sheet, which is an essential step in the development of energy storage devices from graphene.

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  • Fire Dynamics Simulator (FDS) Pyrolysis Model Analysis of Heavy Goods Vehicle Fires in Road Tunnels

    Wang, Xiaoyun (2017)

    Doctoral thesis
    University of Canterbury Library

    Heavy goods vehicle (HGV) fires cause more serious fire safety problems than other vehicle fires in road tunnels due to the large fire size. The fire size is a critical parameter in road tunnel fire safety design and this parameter varies considerably under different environmental conditions. It is impractical to experimentally measure heat release rate (HRR) for HGV fires under different tunnel conditions because of the large experimental cost. There is a desire to use a cost-effective computational fluid dynamics (CFD) modelling method to study tunnel fires, such as fire dynamics simulator (FDS). The pyrolysis model in FDS can predict HRR based on fuel properties and environmental conditions. Therefore, the FDS pyrolysis model is adopted in this research to simulate a large-scale tunnel simulated HGV cargo experiment, which was carried out on behalf of the Land Transport Authority (LTA), Singapore. There are three major objectives in this research: to understand fuel properties for the application of the pyrolysis model; to understand influence of forced ventilation on the HRR of tunnel fires; and to assess the predictive capability of the pyrolysis model in FDS to simulate tunnel fires. The material properties of the fuels (plastic and wood) adopted in the LTA experiment are investigated. A simple hand calculation method using multiple-component schemes is proposed in this research to analyse the kinetic properties for the LTA materials through a series of material-scale experiments. Favourable FDS predictions of decomposition behaviour are obtained based on the derived kinetic properties. Following the studies of the kinetic properties, a manual optimisation process is used to determine other thermal properties for the application of the FDS pyrolysis model. The results from FDS simulations for a series of cone calorimeter experiments reveal that the use of component schemes and thermal property settings are critical in accurately predicting burning behaviour in FDS. A series of small-scale tunnel experiments are conducted which is scaled at a ratio of 1:20 on the basis of the LTA large-scale tunnel experiment. Medium density fireboard (MDF) cribs are used as fuel source to investigate the influence of forced ventilation on tunnel fires. It is found that the forced ventilation affects fire spread rate and burning efficiency which ultimately affects the peak HRR. In addition, the influence of forced ventilation on burning efficiency is affected by the crib length. A mathematical model to predict peak HRR for crib fires is proposed based on the observed influences on crib fires from these different factors. The ultimate objective is to assess the ability of the FDS pyrolysis model to predict the HRR in the small-scale and large-scale tunnel experiments. In the simulations, the decomposition reactions are described. The ventilation influences on burning efficiency are accounted for through heat of combustion. Unfortunately, FDS considerably under predicts the HRR and fire growth behaviour for both experiments. These results suggest that the FDS pyrolysis model is unable to predict fire burning behaviour for complex fuels with sufficient accuracy to be used in practical tunnel design. Overall, this research reveals an effective hand calculation method to derive kinetic properties; a manual optimisation process to determine thermal properties; a mathematical model to describe forced ventilation influence on fire size and to further estimate peak HRR for tunnel crib fires. In addition, the results from the application of FDS pyrolysis model to simulate tunnel fires reveal that the pyrolysis model is unable to accurately predict fire burning behaviour for complex fuels.

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  • Mapping the Twitter linkages between American politicians and hate groups

    Sahioun, Rania (2017)

    Masters thesis
    University of Canterbury Library

    Big Data is a growing field after social media allowed developers to collect and store data using various platforms. The present research utilises Twitter data and Apache Spark to extend and develop an easy to implement method to test a contemporary question of interest. Specifically, I focus on Donald Trump’s campaign for the President of the USA. Donald Trump’s campaign had been very controversial from the start, following his hostile views expressed toward immigrants and minorities. During this time, media pundits and the public spent much time debating whether Trump’s campaign was motivated by hate or other factors. The present work examines whether Donald Trump had unique appeal to hate groups by examining the twitter linkages between several American political leaders (Donald Trump, Hillary Clinton, Bernie Sanders, Ted Cruz, and Paul Ryan) with American hate groups. The results show that users who often retweet Donald Trump are more likely to frequently retweet American hate groups such as Neo Nazis, White Nationalists, anti-immigrant, anti-Muslim, anti-LGBT, and anti-government groups, more than any other politician. While other Republican politicians were also linked to anti-immigrant, anti-Muslim, and anti-LGBT groups, it was to a lesser extent than Trump. This data suggests Trump may have had unique appeal to American hate groups.

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  • Temporal dynamics of microbial communities in geothermal hotsprings of the Taupo Volcanic Zone

    Lowe, Caitlin Louise (2017)

    Masters thesis
    University of Waikato

    Few studies of microbial biogeography address temporal variability in physicochemical conditions and communities in geothermal environments. Here we examine the temporal variability of 43 chemical analytes, temperature and pH in association with microbial community composition of 69 water samples collected bimonthly from 12 hotsprings of the Taupo Volcanic Zone between December 2015 and October 2016. Communities and physicochemical parameters were characterized using a combination of next generation Ion Torrent sequencing (16S rRNA), UV-spectrometry, ICP-MS, FIA and gas chromatography. Using correlation association tests, significant physicochemical changes (P<0.05) were correlated with temporal variations in microbial community composition in six of the target hotsprings. Of these six hotsprings, temperature and pH were the most influential variables associated with community changes and commonly covaried with the Aquificae, Deinococcus-Thermus and Proteobacteria at four sites. Downstream effects of rainfall using rainfall and geothermal bore water datasets could be linked with physicochemical and microbial community changes during the winter months at two of these sites. This study contributes to our understanding of geothermal microbial dynamics in stable and variable geothermal environme nts, and highlights that geothermal hotsprings are not isolated from their surrounding environment.

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  • Effects of Drying Conditions on Protein Properties of Blood meal

    Damba, Chawangwa (2017)

    Masters thesis
    University of Waikato

    Blood meal is a by-product of the meat industry produced through drying of animal blood. It contains about 85 wt.% proteins. Drying has been used as a method to preserve biomaterials and involves lowering of the water activity of biomaterials. The purpose of this research was to study the drying kinetics of producing blood meal in an oven dryer, to evaluate suitable drying models for describing the drying process and to determine the effects of drying conditions on the physio-chemical properties of blood meal. Moisture content and drying rates were determined by drying coagulated blood at different temperatures (60 °C, 100 °C and 140 °C) for a constant period of 24 hours. The initial moisture content of coagulated blood was about 60.7 wt% on a wet basis. A drying temperature of 140 °C was found to be the optimal for routine moisture determination for coagulated blood as equilibrium moisture was achieved within 24 hours period. A constant drying rate period was not observed in any of the conditions tested, and the initial increasing rate period as followed by a short transition phase prior to the falling-rate period. Thus, moisture removal from the coagulated blood was governed by a diffusion-controlled process. The experimental drying data for coagulated blood was used to fit the Lewis, Page, Modified Page, Logarithmic and Henderson and Pabis models and the statistical validity of models tested were determined by non-linear regression analysis. The Page model had the highest R² (0.9999) and lowest χ² (0.0001) and RMSE values. This indicated that Page model adequately described the oven drying behaviour of coagulated blood. Blood meal samples were produced by drying coagulated blood at different temperatures (60 °C, 100 °C, 140 °C) to varying moisture contents (5 %, 10 % and 15 %). A drop penetration test using water and/or sodium dodecyl sulphate dissolved in water were used to determine the wettability of the samples produce while thermal analysis techniques such as Thermo-Gravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA) were used to investigate the thermal properties of bloodmeal. X-ray scattering was used to investigate conformational changes in blood meal proteins during drying. Drying conditions had substantial effects on both physicochemical and thermal properties of blood meal. It was established that drying temperature had a more significant effect on the wettability of blood meal than the final moisture content. However, the final moisture content had larger contribution to the thermal stability of blood meal than drying temperature. Blood meal produced at 60 °C to 15% moisture content was the most stable sample while blood meal produced at 140 °C to 10% moisture content was the least stable. Protein denaturation was observed at 92 °C to 122 °C, depending on moisture content and drying temperature. DMA results revealed that different relaxations occurred when drying coagulated blood. A dry glass transition temperature for samples was observed between 219 °C - 226.8 °C. This suggested that bound water does not act as plasticiser in blood meal. Glass transitions observed in DSC were therefore, considered more accurate and reliable for blood meal samples containing moisture. Drying of coagulated blood was observed to have drastic effect on the structural arrangement of coagulated blood in XRD. Increase in moisture content was observed to have an effect on the β-sheets structure of samples dried at 60 °C and 100 °C. Since bloodmeal produced at 60 °C and 100 °C did not show complete denaturation of proteins, future thermoplastic processing should consider blood meal produced within this temperature range for improved properties.

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  • The Accountability of New Zealand's Charities: Meeting the Needs of Charity Stakeholders through Information Disclosure

    Dimitrov, Dara Katie (2017)

    Doctoral thesis
    University of Waikato

    For decades, New Zealand’s charity sector has been able to operate, unfettered by regulation and with low levels of accountability. For this reason, gaining any information from charities about the work they do has been historically difficult, because charities have not been required to provide any reports. The New Zealand government sought to increase the accountability from the charity sector with the introduction of the Charities Act (2005) and basic reporting requirements, but ultimately, the accountability from the sector continues to be an issue. With limited charity disclosure literature in the New Zealand context, and no information disclosure practice model to guide New Zealand’s charities, the current provision and the quality of the information disclosures from charities are low, leaving the information needs of charity stakeholders unmet. The overall aim of this investigation is to improve the accountability from New Zealand’s charities by developing a charity information disclosure practice model from a charity stakeholder perspective. This was achieved by three main objectives: 1. To develop a qualitative disclosure index from the perspective of charity stakeholders 2. To assess the extent and quality of the information disclosure made by thirty registered charities 3. To make recommendations to improve the accountability by New Zealand’s charity sector To achieve this purpose, a disclosure index, which contained 136 information items was created with the assistance of 86 charity stakeholders. The index was then applied to three publications from thirty charities that were randomly selected from the Charity register. The three publications used in this investigation are the Charity register, the charity’s website and the charity’s annual report/annual review. The collected data was then quantified and analysed to determine the extent and the quality of the information disclosures from the charities. The investigation findings indicated that the current level of charity disclosures was poor both in extent and quality and that there was an information gap between the expectations of charity stakeholders and the actual disclosure practices of the charities. It was found that the top-performing information items were the mandated and the best-practice information items were either missing or inadequately disclosed. No charity within the sample managed to achieve an index score of 50%. The annual return summary found on the Charity register was the best disclosure document for both financial and non-financial information items from a charity stakeholder perspective. However, this document, along with the other publications still lacked sufficient detail to be useful for a charity stakeholder. To improve the accountability of the New Zealand’s sector, it is recommended that the New Zealand Parliament look at expanding the current annual return summary to include information items more relevant to charity stakeholders. Finally, it is recommended that the charities should be compelled to produce an annual report and use the disclosure index created by the charity stakeholders in this investigation to improve their current information disclosures.

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  • Tendency toward negative correlations for positively-skewed independent random variables

    Bardsley, W. Earl (2014)

    Journal article
    University of Waikato

    Hydrological variables often display positive skewness, with means exceeding medians. Even when two such variables are independent, there is a more than 50% chance that a bivariate random sample will yield a negative value of the Pearson product-moment linear correlation coefficient r. Simulations from inverse Gaussian distributions suggest that this effect is small and unlikely to have any effect on significance tests of r if two skewed variables are in fact independent. However, a high frequency of negative sample correlations in a multi-site hydrological study could result in an incorrect deduction that some weak but widespread physical process is in operation.

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  • Moisture Associated Microbial Communities in Antarctic Dry Valley Soils

    Anderson, Rachelle (2017)

    Masters thesis
    University of Waikato

    Climate change is having a dramatic impact on the natural environment and is one of the most imminent and important issues of the 21st century. With limited vegetation and few large terrestrial organisms, Antarctica offers a unique opportunity to understand the impact of abiotic, climatic factors on microbial ecosystems (free of many of the confounding biological variables in more complex systems). Recent in situ studies indicate that microbial communities within Antarctic soils may respond to environmental changes within far shorter time frames than originally believed. In a landmark study, Tiao et al. (2012) investigated the rate at which microbial communities responded to a unique soil modification experiment. To this end, a mummified seal carcass (dated at 250 years) was shifted from its original site in Miers Valley, to a new, geomorphically similar site in close proximity. Remarkably, increased microbial biomass, decreased biodiversity, and shifts in the microbial community composition were observed within just two summers. While the seal carcass altered the underlying soil’s nitrogen and organic carbon content, pH, and conductivity; statistical analysis revealed that none of these physicochemical changes could satisfactorily explain the changes in the microbial community. Instead the data suggest that the changes observed may have been caused by physical, abiotic factors induced by the seal carcass (i.e. increased and more stable relative humidity (RH), reduced UV exposure, and reduced daily temperature fluctuations). However, due to the un-replicated, observational nature of the study, this is merely speculation. In order to verify these findings and resolve the drivers of the microbial community changes observed, a controlled, in situ experiment was designed to replicate the abiotic effects of the seal carcass (stabilise temperature, reduce UV exposure, and increase and stabilise RH in the underlying soil). To do this, overturned or upright black and translucent plastic trays were set up on undisturbed regions of Antarctic Dry Valley soil; soil samples were taken every January for a five-year period; and Ion Torrent sequencing of 16S rRNA gene amplicons was used to assess changes in the microbial community composition and structure. However, based on RH data and visual observations of the site it would appear that the tray experiment was unknowingly set up in either a flat, low lying area where moisture accumulated; or in a subsurface water track. Due to the constant high moisture content within the soil on which the experiment was deployed, the effect of the tray treatments on the local environment (i.e. RH and temperature) was negligible. The microbial community composition in the tray treatment experiment stayed quite consistent across all years and treatments, however there was a significantly greater abundance of Cyanobacteria/ Chloroplasts in the translucent overturned (TO) treatment than in the black upright (BU) or black overturned (BO) treatments. Interestingly, the moist tray treatment soil had a greater relative abundance of Cyanobacteria/ Chloroplasts, Proteobacteria, and Bacteroidetes than the drier seal control site, in keeping with the observations of other studies investigating microbial community composition within wet environments. These findings hint at the importance of small-scale topographic factors in microbial community structure, and/or highlight the potential of using microbial community composition as a bio-indicator of hidden water tracks.

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  • Antimicrobial Peptides in Jawed and Jawless Vertebrates

    Gibbons, Olivia Robyn (2016)

    Masters thesis
    University of Waikato

    Antimicrobial peptides (AMPs) are a major part of the innate immune defence system which shows a broad spectrum of activity, defending the host against invading microbes. The aim of this work was to identify the AMPs present in yellowtail kingfish (Seriola lalandi) and pouched lamprey (Geotria australis) and use molecular techniques to fully sequence their cDNA and quantify their expression in adult individuals. Using bioinformatic approaches candidate AMP genes were ascertained from available S. lalandi and G. australis RNA-seq transcriptomic databases, obtained from various tissues. Selected AMPs were chosen to have their full cDNA sequence amplified using RACE-PCR, which were then cloned and sequenced. Complete cDNA sequences were obtained for S. lalandi hepcidin and moronecidin, whereas attempts to complete the G. australis defensin-like cDNA were unsuccessful. Comparison of the S. lalandi hepcidin and moronecidin protein sequences with proteins already characterised in other fish showed good homology and conservation of important features. In addition, specific primers were designed to examine the expression levels of S. lalandi hepcidin and moronecidin in gill, liver or spleens of three fish. Analysis showed hepcidin expression to be highest in liver tissues, whereas moronecidin expression was highest in the gills and spleens. This study provides a comprehensive overview of the AMP genes present in S. lalandi and G. australis and some initial characterisation of S. lalandi hepcidin and moronecidin, which will permit the development of future research applications. Overall, characterising AMP genes in jawed and jawless vertebrates is vital for economical and successful fish farming, while also providing possible therapeutic benefits associated with AMP research in biomedicine and disease in wild fish stocks.

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