1,183 results for Doctoral, 2014

  • Communicative mobility and networked mediation in transnational lifeworlds: a case study of European expatriates in Australia

    Deffner, Florian (2014)

    Doctoral thesis
    University of Otago

    Transnational lifeworlds of expatriates raise exciting questions on the use and meaning of media. Network communication, and its increased communicative connectivity, allows for a borderless communicative mobility which transforms experience and meaning by multiplying and diversifying content choices and ways of interpersonal communication. To capture the mediated transformations of expatriates’ lifeworlds, this dissertation introduces the term “networked mediation” as a descriptor for new forms of mediation emerging in the context of network communication. In the micro-perspective of the lifeworld, networked mediation comprises all forms of mediation—including their interrelation—that do not exclusively correspond to traditional ‘streamings’ of mediation, such as the strict patterns of consecutive and distinct consumptions of news in the mass media age. Therefore, networked mediation, as a multi-directional and multi-dimensional form of mediation, appears to constitute new ontological dimensions of subjective experience and meaning. The construction of more complex meaningfully lived-through mediated social realities and relations are investigated through a social-phenomenological approach illuminating the transnational communicative spaces of European expatriates in Melbourne. Results reveal new mobility cultures of communication characterized by network-based communicative internalization and communicative subjectivization. Consequently, in the case of expatriates’ transnational lifeworlds, even more complex forms of networked mediation occur as they display communicative orientations to 'dual' lifeworld attachments between home and host country. Seen from this angle, the exploration of networked mediation not only illustrates and clarifies transnational communicative spaces, but also sheds light on the complex dimensions and dynamics of contemporary cultures of mediation.

    View record details
  • 'Large letter'd as with thundering shout' : an analysis of typographic posters advertising emigration to New Zealand 1839 - 1875 : a thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Visual and Material Culture, Massey University, Wellington, New Zealand

    Thomas, Patricia Ann (2014)

    Doctoral thesis
    Massey University

    This thesis examines the role of ephemeral, typographic material in the promotion of emigration to New Zealand in the nineteenth century. It focuses on the advertising posters produced by the New Zealand Company, the Otago and Canterbury Associations, the provincial governments and Government of New Zealand. It aims to identify how advertising and typography contributed to the transfer of the promotion message from the producer to the audience in this specific historical context. For the first time a comprehensive data set of emigration posters of this period has been gathered together and examined. The posters are analysed in the context of their contemporary visual, material and print cultures, with particular reference to ephemeral printing. To account for all the historical, textual and graphic properties of the posters, the thesis develops and applies a novel, multilayered system of analysis, drawing on communication theory, social semiotic principles and Gestalt principles of composition. The posters afforded emigration promoters a visual medium for distributing audienceappropriate messages through typographic strategies. They provided promoters with the facility for fast and inexpensive messaging that was otherwise unavailable in nineteenth century communication. The thesis concludes that posters were a significant part of an early, coherent and systematic advertising campaign which utilised processes and persuasive tools that have traditionally been seen as emergent only in the late nineteenth century. This thesis establishes the value of ephemeral material and the study of graphic language when applied to the examination of historical phenomena. As well as shedding new light on these particular forms of historical design and modes of communication, it also adds a further valuable dimension to the more well-known story of nineteenth century emigration promotion by focussing on its graphic and advertising languages rather than its pictorial aspects. The investigation undertaken provides a new analytical system through which a combination of historical, ephemeral, typographic and advertising material can be examined in the future.

    View record details
  • Dynamic response of rotationally periodic structures : thesis submitted in fulfillment of the degree of Doctor of Philosophy in Engineering, Massey University, School of Engineering and Technology, February 2014

    Mubarak, Rana Noman (2014)

    Doctoral thesis
    Massey University

    Due to their structural dynamics, rotationally periodic structures (RPS) have always been an area of interest for engineers and scientists. RPS is found in almost all industries and could be as large as jet turbines to as small as hard disk drives. We come across with RPS on daily routine like washing machine tub, small gears in home appliances and brakes in automobile etc. With such an influence in our life, an RPS dynamic response to the environment is crucial to keep them working and hence is the focus of the thesis. The research involves three major responses on rotationally periodic structures (RPS) namely vibration, thermal and shock. Hard disk drives and integrally bladed rotors (IBR) has been selected as research models. On vibratory response in rotationally periodic structures, effects on structural designs and free vibrations of integrated bladed rotor (IBR) have been investigated in this research. The migration of natural frequencies is characterized through parametric studies considering changes in blade angle and blade thickness of an underlying uniform axis-symmetric rotor. Recurring coupled repeated doublet modes, defined as replica modes, have been observed in this study by characterizing blade vibrations in-phase or out-of-phase to disk vibrations. Veering and clustering of replica modes’ natural frequencies are observed with respect to the blade design parameters. Existence of replica modes has been verified via experimental studies. Fourier content for the low frequency replica component is found to be sensitive and tuneable to blade angle design. For the thermal response of RPS, structural thermal analysis of spindle disk assembly used in hard disk drives (HDDs) was adopted. With the view toward understanding the underlying physics and to minimize the corresponding repeatable run-out (RRO) of track following position error signal (PES) in high track per inch (TPI) magnetic disk drives, analytical representations of thermal expansion mismatch between disk and spindle hub structure formulated in form of operators and finite element analysis (FEA) are employed. Parametric studies with analysis taken at different operational temperatures suggested that RRO can be minimized significantly when location of spindle notch is properly located. RRO harmonics resulted from the thermal expansion mismatch and structure misalignments are studied and concluded with simple algebraic expression related to number of fasteners used in the disk-spindle assembly. On shock response of RPS, head gimbal assembly (HGA) in HDD was analysed. Experimental observation of de-bonding phenomena between head gimbal assembly (HGA) and suspension for a commercial 3.5-inch enterprise HDD under non-operational 250G shock test was performed. In this research the experimental observation and numerical finite element studies were conducted to understand the effect on the mechanical failure of HGA when it is subjected to non-operational shock in the parked position on the ramp. Different design modifications were adapted to withstand shock waves. It was observed that by changing flexure angle in HGA, shock stress can be reduced. FEA simulation results have been presented to verify the findings. The research findings in this thesis can be implemented in the industry where RPS has been widely used, as for example the new replica modes discovery in bladed rotors can also been applied on small scales like as on hard drive, where no. of blades can be replaced by no. of fasteners and the spinning hard drive will be benefited by studying its vibrations with concentration on replica modes. Furthermore, the serendipitous finding of HDD platters expansion under thermal stress can be beneficial in actually storing more data per inch as it has been recently used in TAMR (thermally assisted magnetic recording) technology. Gears, brakes, washing machines to name a few can get supported from the findings in the thesis where controlling vibrations, shock and heat is crucial.

    View record details
  • Point process models for diurnal variation rainfall data : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Statistics at Massey University, Albany (Auckland), New Zealand

    Ismail, Norazlina binti (2014)

    Doctoral thesis
    Massey University

    The theoretical basis of the point process rainfall models were developed for midlatitude rainfall that have different temporal characteristics from the tropical rainfall. The diurnal cycle, a prominent feature in the tropical rainfall, is not represented in the point process models. An extension of the point process models were developed to address the diurnal variation in rainfall. An observed indicator of the rainfall, X is added to the point process models. Two point process models, Poisson white noise (PWN) and Neyman-Scott white noise (NSWN) model were used as the main rainfall event, Y . The rainfall is modelled assuming two cases for the variable X, independent and dependent. Bernoulli trials with Markov dependence are used for the dependent assumption. To allow the model to display the diurnal variation and correlation between hours, the model was fitted to monthly rain- fall data by using the properties of two hour blocks for each month of the year. However, the main point process models were assumed the same for each of the 12 blocks, thus having only one set of point process parameters for the models for each month. There are 12 rainfall occurrence parameters and 12 Markov dependence parameters, one for each block. A total of six models were fitted to the hourly rainfall data from 1974 to 2008 taken from a rain site in Empangan Genting Klang, Malaysia. The PWN and NSWN models with X were first fitted with the assumption that the rainfall indicators are independent between the hours within the two hour block. Simulation studies showed the model does not fit the moments properties adequently. The models were then modified based on a dependence assumption between the hours within the two hour block. These models are known as the Markov X-PWN and Markov X-NSWN models. Both models improve the fit of the moment properties. However, having only one point process model to represent the rainfall events for Malaysia rainfall data was not sufficient. Since tropical rainfall consists of two types of rain, convective and stratiform, the PWN and Markov X-NSWN model were superposed to represent the two types of rainfall. A simple method by assuming non-homogenous PWN process for every two hour block did not fit well the daily diurnal variation. A comparison between the six models show that the superposed PWN and Markov X-NSWN model improved the fitting of mean, variance and autocorrelation. The superposed model was then simplified to an 8-block model to reduce the number of parameters. This modification to the point process models succeeded in describing the diurnal variation in the rainfall, but some of the models were not able to fit other properties that were not included in the parameter estimation process such as the extreme values.

    View record details
  • Comparing group-based interventions in older adults with subjective memory difficulties : a dissertation presented in partial fulfilment of the requirements for the degree of Doctorate in Clinical Psychology, Massey University, Wellington, New Zealand

    Sothieson, Veena (2014)

    Doctoral thesis
    Massey University

    The trend internationally and within New Zealand is of an increasing aging population, with numbers of those with dementia projected to increase rapidly. One way to address this issue is to consider the practical and clinical benefits of running memory intervention groups for older adults with memory difficulties/impairment. The current study intended to address some of the limitations found in memory intervention literature by (a) using a social control group as a control comparison, which has not been done before, and (b) separating out components of memory training interventions (i.e., memory strategies and lifestyle education). Therefore, the aim was to determine the extent to which receiving Memory intervention separately from a Lifestyle Education intervention would affect memory functioning in older adults with subjective memory difficulties, when compared with a social control condition. Participants for the intervention group were recruited from rest homes and retirement villages, while social control participants were community-dwelling older adults already taking part in weekly community group activities. A brief cognitive screen and subjective outcome measures were administered at baseline, post Phase 1, post Phase 2, and at six month follow-up. Quantitative and qualitative information from a total of 13 participants were analysed. Results from each of the outcome measures across the four time points indicated that there were no significant benefits of receiving Memory and/or Lifestyle Education interventions, when compared with a social control condition. However, a small sample size, non-equivalent groups, and lack of random assignment were some of the limitations which made it difficult to reach definite conclusions. Content analysis of qualitative information following intervention sessions provided some valuable considerations for running memory groups in future. In light of its limitations, the current study highlights practical considerations and recommendations for future research in this area. In particular, it identifies the value of conducting memory intervention research with older adults in residential care settings.

    View record details
  • Chicory (Cichorium intybus) and plantain (Plantago lanceolata); physiological and morphological responses to water stress, defoliation, and grazing preference with implications for the management of the Herb and Legume Mix : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Science, Massey University, Te Kunenga ki Pūrehuroa, New Zealand

    Cranston, Lydia Margaret (2014)

    Doctoral thesis
    Massey University

    Herb and legume sward mixes containing chicory (Cichorium intybus), plantain (Plantago lanceolata), red clover (Trifolium pratense) and white clover (T. repens) are being increasingly used by farmers to improve animal performance compared to perennial ryegrass and white clover swards. However, little is known about the agronomic properties of this Herb and Legume Mix. The objectives of this research were to examine key factors likely to affect the success of the Herb and Legume Mix as a perennial sward mix. This thesis included a series of glasshouse experiments, a grazing experiment (examining plant parameters and animal grazing preference) and a mowing experiment. The glasshouse experiments indicated that chicory and plantain have different strategies for coping with moisture stress. The results suggest plantain may be more productive under moderate drought due to its greater shoot mass fraction, whereas chicory may be more productive and persistent under severe drought due to its greater root mass and taproot diameter. The Herb and Legume Mix accumulated greater annual dry matter when removed under Hard grazing (post-grazing residual of 4cm) compared to Lax grazing (post-grazing residual of 8cm). Hard grazing favoured plantain growth and persistence, while Lax grazing favoured red clover growth and resulted in chicory with a larger taproot diameter. It was concluded that grazing management decisions should be determined by ensuring optimal management of chicory. Ewe lambs displayed grazing preference for species within the Herb and Legume Mix; however this varied between seasons and was affected by the species availability, vertical access and palatability. The Herb and Legume Mix had a greater herbage nutritive value than the ryegrass and white clover sward and had a more stable composition over time than pure swards of chicory and plantain under a wide range of defoliation regimes. The results suggest the Herb and Legume Mix might be a more flexible perennial forage option than pure swards of chicory and plantain. Overall the results of this thesis indicated that the Herb and Legume Mix can be successfully utilised in most New Zealand grazing systems as a perennial forage sward.

    View record details
  • Improving the response to synchronisation programmes of dairy cattle : a thesis presented in partial fulfilment of the requirement for the degree of Doctor of Philosophy in Veterinary Science at Massey University, Palmerston North, New Zealand

    Sahu, Santosh Kumar (2014)

    Doctoral thesis
    Massey University

    A gonadotrophin, prostaglandin, gonadotrophin + progesterone (GPG+P4) programme with fixed-time artificial insemination (FTAI) is the current recommended synchronisation programme for both heifers and anoestrous cows on New Zealand dairy farms. However, it is an expensive programme and a better understanding of the role of all of its components would be very useful in developing alternative cheaper programmes. The two components of the programme that are the least understood, in terms of their underlying physiological actions and how they influence the outcome of synchronisation, are the Day 0 gonadotrophin-releasing hormone (GnRH) injection and the progesterone device. Additionally it is well known that energy status has a significant impact on fertility but there is little evidence, particularly under New Zealand conditions, of how energy status affects the response to GPG-based treatments in anoestrous postpartum dairy cows. The effects of a GPG (Day 0: 100 µg GnRH, Day 7: 500 µg PGF2a, Day 9: 100 µg GnRH) programme upon follicular and luteal dynamics, ovulation synchronisation and patterns of oestradiol and progesterone secretion in postpartum anoestrous dairy cows and nulliparous dairy heifers were compared with (i) a GPG programme plus a progesterone insert from Days 0–7 (GPG+P4) and (ii) a GPG+P4 programme from which the first GnRH treatment had been omitted (P+G+P4). Interactions of each treatment with energy balance, as determined by NEFA, IGF-I and insulin concentrations, were also studied in postpartum anoestrus cattle. Finally the conception rate (CR) to fixed time AI of a GPG+P4 programme in which AI was done concurrent with the Day 9 GnRH injection (Cosynch) was compared with a progesterone + prostaglandin programme (P4+PG; Day 0–7: progesterone releasing intravaginal device, morning of Day 6: 500 µg PGF2a, afternoon of Day 9: FTAI) in heifers. The physiological effects of the GPG and the GPG+P4 programmes were similar in anoestrous dairy cows. The inclusion of the Day 0 GnRH still appeared feasible in a GPG programme for treating anoestrous cows as it led to a higher probability of a corpus luteum (CL) on Day 7. In addition, treatment response was significantly affected by the postpartum duration and negative energy balance as evidenced by the significantly higher NEFA concentrations on Days 0, 7 and 9, and a lower insulin concentration on Day 0, in cows that failed to ovulate in response to the synchronisation protocol compared with cows that did ovulate. A clear and significant relationship between NEFA concentrations and ovulation in response to all synchronisation protocols showed that, regardless of the regimen that was used to treat anoestrus, the response was moderated and limited by the degree of negative energy balance. In heifers, the removal of the progesterone-releasing device from a GPG+P4 programme had no effect on follicular dynamics or on the proportion of heifers which ovulated after either the GnRH injection on Day 0 or Day 9. Additionally, unlike the anoestrus cows, omitting the GnRH injection on Day 0 did not result in significantly delayed ovulation at the end of the programme, inasmuch as treatment with P+G+P4 was associated with earlier ovulation than GPG. Furthermore, synchronising heifers with a significantly less expensive programme (P4+PG) resulted in similar CR to synchronising with GPG+P4 (54.8% versus 52.4%, respectively) further confirming that Day 0 GnRH was not essential in heifer synchrony. In conclusion, the higher conception rate in cows treated with a GPG+P4 programme rather than a GPG programme reported previously does not seem to be modulated by the actions on follicular dynamics and improved synchronised ovulation in dairy cattle with postpartum anoestrous (or in nulliparous heifers); however, the treatment response in anoestrous cows can be significantly affected by negative energy balance. In contrast, in dairy heifers, no benefit of Day 0 GnRH or the progesterone device in a GPG+P4 programme suggests the possibility of more cost effective options (e.g. P4+PG) which can lead to a CR as high as those synchronised using a GPG+P4 programme.

    View record details
  • Measurement of true ileal phosphorus digestibility in feed ingredients for poultry : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Poultry Science at Institute of Veterinary, Animal and Biomedical Sciences (IVABS), Massey University, Palmerston North, New Zealand

    Mutucumarana, Ruvini Kamalika (2014)

    Doctoral thesis
    Massey University

    Global interest in improving the utilisation of phosphorus (P) by poultry has recently increased due to concerns over environmental pollution through excess P excretion, depletion of non-renewable inorganic phosphate deposits, and increasing price of inorganic phosphate supplements. Use of a sound criterion, preferably based on P digestibility, to assess P availability is needed to enable greater efficiency of utilisation of dietary P. No established methodology is currently available to measure the true digestible P contents in common feed ingredients for poultry. The first experiment of this thesis (Chapter 3) investigated the effects of dietary calcium (Ca) concentrations (6, 9 and 12 g/kg) on the digestibility of P, Ca, nitrogen, fat and starch in different intestinal segments and on the apparent metabolisable energy of diets in young broiler chickens. The results showed that the digestion of P and Ca was completed by upper ileum and jejunum, respectively. The site of digestion of P and nitrogen was found to shift depending on the dietary Ca concentrations. The digestibility coefficients of P in low, normal and high Ca diets at the lower ileum were determined to be 0.417, 0.379 and 0.325, respectively. The overall data showed that increasing dietary Ca concentrations negatively influenced the digestion of P, nitrogen and fat, but had no effect on those of Ca, starch and apparent metabolisable energy. The second experiment (Chapter 4) was conducted to determine endogenous losses of P and Ca in broiler chickens. The data showed that the ileal endogenous P losses in birds differed depending on the methodology employed. The ileal endogenous flow of P in birds fed P-free, gelatin-based and casein-based diets were 25, 104 and 438 mg/kg dry matter intake (DMI), respectively. Ileal endogenous flow of Ca in birds fed casein-based diet was estimated to be 321 mg/kg DMI. The next three experiments (Chapters 5, 6 and 7) investigated the potential usefulness of regression method to evaluate true ileal P digestibility of seven feed ingredients. True ileal P digestibility coefficients of maize, canola meal, wheat, sorghum, soybean meal and maize-distiller‟s dried grains with solubles for broiler chickens were determined to be 0.676, 0.469, 0.464, 0.331, 0.798 and 0.727, respectively. For plant-based ingredients, the determined true digestible P values were consistently higher than corresponding non-phytate P values (Maize, 1.72 vs. 0.75; canola meal, 4.55 vs. 2.82; wheat, 1.49 vs. 1.11; sorghum, 0.78 vs. 0.55; soybean meal, 5.16 vs. 2.15; maize-distiller‟s dried grains with solubles, 5.94 vs. 4.36 g/kg, as fed ii basis, respectively). Phytate P in maize (54.25%), soybean meal (69.7%) and maize- distiller‟s dried grains with solubles (41.5%) were well digested by broilers compared to canola meal (25.2%), wheat (18.1%) and sorghum (13.0%). True ileal P digestibility coefficients of three meat and bone meal (MBM) samples ranged from 0.420 to 0.693. Total and true digestible P contents of three MBM samples (MBM-1, MBM-2 and MBM-3) were determined to be 37.5 and 26.0; 60.2 and 36.6; and 59.8 and 25.1 g/kg, as fed basis, respectively, suggesting that P in MBM is not highly digestible. The overall data suggested that the use of regression approach to estimate true ileal P digestibility in feed ingredients has number of limitations. Overestimation as a result of using Ca- and P-deficient diets and the negative endogenous P losses observed for some ingredients (canola meal, sorghum and MBM-3) were main concerns. Negative ileal endogenous P losses were also shown to be associated with low true ileal P digestibility in these ingredients. In the final experiment (Chapter 8), two regression-based methodologies were compared for the measurement of true ileal P digestibility in maize and soybean meal. The results showed that the methodology influenced P digestibility in maize and soybean meal. The use of assay diets containing a narrow Ca:total P ratio yielded higher P digestibility for both ingredients. In this thesis research, the regression method was used to determine true ileal P digestibility of ingredients, but this approach suffers from several drawbacks. The data reported in this thesis also demonstrated that high dietary Ca concentrations were detrimental to the digestibility of nutrients, particularly of P, nitrogen and fat.

    View record details
  • E kore au e ngaro, he kakano ahau : whakapapa sharing in the context of therapy : a thesis presented in partial fulfilment of the requirements for a Doctorate in Clinical Psychology at Massey University, Wellington Campus, New Zealand

    Mitchell, Arna (2014)

    Doctoral thesis
    Massey University

    Maori experience disproportionately negative outcomes in mental health in New Zealand. The adaptation of therapeutic assessments and interventions to allow more culturally appropriate work with Maori occurs, however, little research promoting an understanding of client’s experience of these adaptations exists. One such adaptation is the sharing of whakapapa (genealogy) between therapist and client. Whakapapa sharing involves a level of therapist self disclosure not yet investigated in psychological literature. This Maori centred analogue study investigates the client’s experience of whakapapa sharing during the first session of therapy. A mixed, between and within subjects design was used, both quantitative and qualitative data were collected and analysed. 30 Maori women between the ages of 18 and 40 participated in two sessions of Acceptance and Commitment Therapy, participants were allocated to either a Whakapapa Sharing group or a Therapist Non-Disclosure group. All participants completed questionnaires measuring the therapeutic alliance, therapy expectancy, outcome of therapy and a cultural questionnaire measuring participant knowledge of their own whakapapa. Participants from the Whakapapa Sharing group also reported on their experience of the sharing. Quantitative analyses revealed no group differences in either the therapeutic relationship measure or the outcome measure. All participants from the Whakapapa Sharing group, regardless of their level of knowledge of their own whakapapa, reported the whakapapa sharing as a positive experience. Further analysis of the qualitative data revealed five main themes; the whakapapa sharing process reported to promote engagement, was perceived as important for Maori, allowed the establishment of connections between therapist and client, provided clients with information with which to form judgements about the therapist and the sharing was seen to be an equitible experience. These themes were arranged into a theoretical model, in which, all five were hypothesised to have a relationship with the power imbalance inherent between therapist and client. Whereby four of the themes were hypothesised to contribute to a decrease in the imbalance of power and the final theme was seen as a result of the decrease in the power imbalance. These tentative findings suggest that the exchange of whakapapa between a therapist and client may serve to decrease the power imbalance in the therapeutic relationship, and as such, it is an appropriate process of engagement in a therapeutic setting with Maori clients, who often experience marginalisation.

    View record details
  • The evaluation of the Transformers programme : an emotion regulation programme for people who have an intellectual disability : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Clinical Psychology at Massey University, Wellington, New Zealand

    McWilliams, Jenna Louise (2014)

    Doctoral thesis
    Massey University

    It is widely accepted that emotion regulation difficulties are common in people who have an intellectual disability. Not being able to manage their distressing emotions can lead to challenging behaviour such as verbal and physical violence and property destruction and can lead to injury, alienation, poor-self-esteem, and legal problems. Growing research suggests that people who have an intellectual disability have the ability to engage in and benefit from interventions that address their emotion regulation problems. The current thesis consists of four papers—a systematic literature review, programme description, a study regarding emotional identification, and a study about emotion regulation. The main aim of the research was to evaluate an emotion regulation programme known as Transformers that is being implemented at an intellectual disability service. Transformers is a group-based treatment programme that is run over a six-month period. Five participants with mild to moderate intellectual disability (aged 17-42 years) attended the Transformers programme and took part in the studies along with their caregivers. A single-case design was chosen to evaluate the effectiveness of the programme. Participants completed emotion recognition tasks and self-report measures of emotion regulation before, during, and after their involvement in the programme. Caregivers also rated the frequency of participants’ use of emotion regulation skills and incident reports provided insight into their ongoing behaviour. While the results showed that the Transformers programme was not effective in improving participants’ abilities to recognise emotion nonetheless participants did increase in their ability to use appropriate emotion regulation strategies and reduced the number of incidents of challenging behaviour. Overall, these preliminary findings suggest that the Transformers programme is a viable treatment option for people who have an intellectual disability who have difficulty managing their own emotions. While the findings are encouraging, it is recommended that further research be carried out using larger sample sizes and longer follow up periods to establish the effectiveness of the programme.

    View record details
  • Dietary titanium dioxide particles and intestinal health : a thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Nutritional Science at Massey University, Manawatu, New Zealand

    Riedle, Sebastian (2014)

    Doctoral thesis
    Massey University

    The purpose of this dissertation was to investigate the relationship between food-grade titanium dioxide particles and intestinal health, in particular the development of Crohn’s disease after uptake of titanium dioxide particles in intestinal lymphoid tissues. Crohn’s disease is a common form of inflammatory bowel disease. It is characterised by chronic inflammation of the gastrointestinal tract and affects approximately 1 in 1,000 people. The aetiology of Crohn’s disease is unclear, but both genetic and environmental factors are involved in the development of the disease. The gene that is most commonly associated with Crohn’s disease is the nucleotide-binding oligomerisation domain (NOD) 2 gene. The diet is one of the most likely environmental factors that have been proposed to play a role in Crohn’s disease. It has been hypothesised that uptake of titanium dioxide particles, which are used as a whitening agent in processed foods, toothpaste, and pharmaceuticals, by macrophages in intestinal lymphoid tissues negatively affects intestinal health and contributes to the development of Crohn’s disease. To investigate this hypothesis, immune cell-stimulating properties of titanium dioxide were first assessed in vitro with macrophages derived from wild-type mice and mice with a Crohn’s disease-like Nod2 gene variant. These mouse models were also used to determine particle uptake in intestinal lymphoid tissues in vivo after exposure to titanium dioxide with the diet and effects of this dietary exposure on intestinal health and urine metabolites. The results from the in vitro studies showed that titanium dioxide induced the release of the pro-inflammatory cytokine interleukin-1β. For the first time, it has been shown that accumulation of particles in intestinal lymphoid tissues was a consequence of titanium dioxide intake with the diet. However, this had no negative effects on growth performance and intestinal health of both wild-type mice and mice with a Crohn’s disease-like Nod2 gene variant. Nevertheless, differences in urine metabolite profiles between wild-type mice exposed to titanium dioxide and unexposed wild-type mice indicated that consumption of a titanium dioxide-containing diet affected the metabolism. This dissertation forms the foundation for future studies with animal models about the relationship between titanium dioxide and intestinal health.

    View record details
  • Achieving positive stepfamily relationships : negotiating fairness, forgiveness, and acceptance : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Psychology at Massey University, Wellington, New Zealand

    Falchi, Celia Noreena (2014)

    Doctoral thesis
    Massey University

    Instructional DVD (Appendix H) available with hard copy in the library

    View record details
  • Planning for a night out : local governance, power and night-time in Christchurch, New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Resource and Environmental Planning at Massey University, Turitea, Aotearoa, New Zealand

    Johnston, Karen Marie (2014)

    Doctoral thesis
    Massey University

    This research explores the changing nature of local governance and how power is exercised within Christchurch City Council’s decision-making process of its revitalisation of the Central Business District (CBD). A governmentality theoretical framework extends the scholarly debate on local government decision-making and allows for the exploration of social relations and lived realities of young people who use the night-time spaces created by the CBD revitalisation process. Three research questions structure the thesis: how is power exercised during CBD decision-making processes within Christchurch City Council?; what governmental technologies are adopted by Christchurch City Council to revitalise the CBD between 1999 and 2010?; and, what are the lived realities of the young people who use the revitalised spaces of the CBD? Christchurch, New Zealand’s second largest city, is the case study because of its recent CBD revitalisation and the significant changes to its decision-making processes. These changes impact on the way revitalisation is executed. The decision-making process of CBD revitalisation is examined through a qualitative methodology. Methods involved: document analysis; observations; individual, semi-structured interviews (with elected and non-elected local government representatives, business people, and police); and, focus-group interviews with young people who enjoy the CBD night-time entertainment spaces. There are three key research findings. First, power is simultaneously dispersed to an outside organisation and concentrated within the Council in fewer people. Particular actors have significant influence over decision-making. Second, governing at a distance occurs using technologies of a key stakeholder group followed by changes to internal Council decision-making. A post-political turn emerged where consensus is encouraged and political dissent discouraged. Third, the revitalisation project is successful in the creation of a vibrant night-time economy where young people drink and socialise. Paradoxically, these new subjects are constituted through the revitalised spaces as a problem, bringing into stark relief the conflicts between public and private interests in Christchurch’s CBD revitalisation. This research offers new possibilities for planning scholars. Governmentality allows for the critical examination of power in local governance with the explicit inclusion of the lived realities of the subjects of that governance.

    View record details
  • Effect of mechanical work on the meat used for making reformed meat products : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, Palmerston North, New Zealand

    Mohammad Rashedi, Ismail Fitry (2014)

    Doctoral thesis
    Massey University

    Tumbling, a process commonly used during production of reformed meat, applies mechanical work against the meat pieces to break down the meat structure, enhance brine absorption and extract solubilized myosin to the meat surface. The myosin acts as glue to bind meat pieces together when heated. The work done in the tumbler is currently unquantifiable and its relationships with total protein and myosin extraction and binding strength (Tensile Adhesive Strength, TAS) of two meat pieces are unknown. Much of this project was allocated to developing and evaluating an instrument called the Impact and Friction Mechanical Robot (IFMR), which is able to repeatedly apply a desired impact and to vary the rate of repeated impacts and the time gap between each impact. The degree of sample compression could also be varied. The work done as a consequence of the hitting process can be calculated for each individual hit and summed to give the total work impacted on the meat. Four groups of 20 mm3 meat cubes were prepared for the hitting treatments. One group was used as the control while the other three were pre-soaked in 0.396, 0.713 or 1.146 mol/L of brine consisting of NaCl and salts of phosphate. The meat cubes were hit so maximum impact force was 10 N with an average 0.665 s between each hit for 0, 400, 800, 1200, 1600 or 2000 hits. The exudate on the hit meat surface was scraped off and examined for total protein and myosin. The total protein extracted was not influenced by the work (p=0.764) applied on meat cubes pre-soaked in different concentrations of brine (p=0.123). Myosin extracted increased with total work done (p=0.006) on the meat and concentration of brine (p<0.001) for pre-soaking. The TAS also increased as myosin concentration increased (p=0.001). A good TAS of the meat pieces could be achieved by adequately solubilising the myosin using brine and applying sufficient total work to the meat pieces.

    View record details
  • Structure and function of the eukaryotic ADP-dependent glucokinase : a dissertation presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Biochemistry, Massey University, Manawatu, New Zealand.

    Richter, Jan Paul (2014)

    Doctoral thesis
    Massey University

    The ADP-dependent glucokinase enzymes (ADPGK) are the first new glycolytic enzymes to be discovered in over 40 years. This class of enzymes was first described in thermophilic archaea in 1994. A decade later, an ADPGK from a eukaryote was also identified and characterised. The ADPGK enzymes catalyse a phosphorylation reaction converting glucose and ADP to glucose-6-phosphate and AMP. The enzyme is well studied in extremophilic archaea, where ADPGK is part of a set of glycolytic enzymes that use ADP instead of ATP for the phosphorylation of various sugars. However, ADPGK has also been found in the genomes of mesophilic species and higher eukaryotes, suggesting that the enzyme is not necessarily an adaption to high temperatures. In eukaryotes, ADPGK has been linked to a modified glycolysis pathway that is required for T-cell activation. While crystal structures of the archaeal ADPGKs are known, no structure of a eukaryotic ADPGK had been solved before the work undertaken in this thesis. In this thesis, the kinetic analysis of a recombinant form of Homo sapiens ADPGK and the crystal structure of a truncated form of Mus musculus ADPGK are presented. Both enzymes were expressed recombinantly in E. coli and purified in soluble form. The kinetic parameters determined for H. sapiens ADPGK proved to be comparable to the mouse enzyme, which had been published earlier. In addition, the phosphoryl acceptor specificity of H. sapiens ADPGK was extensively tested by 31P-NMR, where the enzyme proved to be highly specific for Dglucose. Residues important for catalysis have been modified by site-directed mutagenesis and the variants of H. sapiens ADPGK were purified and kinetic parameters determined. A single crystal was obtained from a truncated variant of M. musculus ADPGK, which diffracted to 2.1 Å. The structure of M. musculus ADPGK could be solved by molecular replacement using the known crystal structures of the archaeal ADPGKs for initial phasing. It proved to be quite similar to the archaeal, ADPGKs, despite the low sequence identity. The combined data in this work improves our understanding of the conservation of the structure-function relationship of eukaryotic ADPGKs.

    View record details
  • Data-parallel structural optimisation in agent-based modelling : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Computer Science at Massey University, Albany, New Zealand

    Husselmann, Alwyn Visser (2014)

    Doctoral thesis
    Massey University

    AGENT-BASED MODELLING (ABM) IS PARTICULARLY SUITABLE for aiding analysis and producing insight in a range of domains where systems have constituent entities which are autonomous, interactive and situated. Decentralised control and irregular communication patterns among these make such models difficult to simulate and even more so to understand. However, the value in this methodology lies in its ability to formulate systems naturally, not only generating the desired macroscopic phenomena, but doing so in an elegant manner. With these advantages, ABM has been enjoying widespread and sustained increasing use. It is then reasonable to seek advances in the field of ABM which would improve productivity, comparability, and ease of implementation. Much work has been done towards these, notably in terms of design methodology, reporting, languages and optimisation. Three issues which remain despite these efforts concern the efficient construction, performance and calibration of agent-based models. Constructing a model involves selecting agents, their attributes, behaviours, interaction rules, and environment, but it also demands a certain level of programming ability. This learning curve stymies research effort from disciplines unrelated to computer science. It is also not clear that one methodology and software package is suitable for all circumstances. Domain-specific languages (DSLs) make development much simpler for their application area. Agent-based model simulation sometimes suffer tremendously from performance issues. Models of situations such as algal cultivation, international markets and pedestrians in dense urban areas invariably suffer from poor scaling. This puts large system sizes and temporally distant states out of reach. The advent of scientific programming on graphical processing units (GPUs) now provides inexpensive high performance, giving hope in this area. It is also important to calibrate such models. More interestingly, the problem of calibrating model structure is given particular emphasis. This ambitious task is difficult for a number of reasons, and is investigated with considerable thought in this work. In summary, the research shows that appropriate use of data-parallelism by multi-stage programming in a simple domain-specific language affords high performance, extensibility and ease of use which is capable of effective automatic model structure optimisation.

    View record details
  • Some aspects of the epidemiology of neosporosis in sheep in New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Veterinary Science at Massey University, Palmerston North, New Zealand

    Syed-Hussain, Sharifah Salmah (2014)

    Doctoral thesis
    Massey University

    Recent reports from New Zealand indicate Neospora caninum may have a role in causing reproductive problems in sheep. However, knowledge about the epidemiology of neosporosis in sheep in New Zealand is limited. Thus, the research presented in this thesis was undertaken to further understand the mode of transmission, seroprevalence, diagnosis and treatment of N. caninum in sheep in New Zealand. The initial study investigated venereal and vertical transmission. The results suggested that although N. caninum DNA can be found in the semen of experimentally infected rams (n=16), the transmission of N. caninum to ewes (n=16) via natural mating is unlikely. In a two year study, ewes inoculated prior to mating (n=25 in Year 1; n=7 in Year 2) did not have congenitally infected lambs that year (n=0/44) but did in Year 2 (n=7/11). Ewes re-inoculated on Day 120 of gestation in Year 2 (n=9) had congenitally infected lambs (n=12/12) with more severe lesions than those not re-inoculated (n=2/11) indicating that the initial inoculation did not induce protection. Ewes inoculated for the first time on Day 120 of gestation (n=12) gave birth to lambs (n=10) that were all congenitally infected. Treatment of these congenitally infected newborn lambs (n=11) with toltrazuril (20mg/kg) on Day 1, 7, 14 and 21 was not effective as determined by serology, histopathology and qPCR. An avidity ELISA assay was able to differentiate between recently and chronically infected sheep. A longitudinal study with serology on 3 farms where N. caninum infected sheep were previously identified, found an overall seroprevalence of 0.8% (n=7/880) for N. caninum antibodies. The low seroprevalence observed across selected farms did not allow a meaningful interpretation to be made about the role of neosporosis on these farms. A consistent observation was the value of using multiple diagnostic tests to detect the presence of Neospora rather than relying exclusively on any one of them. Observation of typical lesions was generally more rewarding then the detection of Neospora DNA. Overall, further work is required to fully determine if N. caninum is causing reproductive problems in sheep in New Zealand.

    View record details
  • Investigation of dothistroma needle blight development on Pinus radiata : a thesis presented in the partial fulfilment of the requirements for the degree of Doctor of Philosophy (PhD) in Microbiology and Genetics at Massey University, Manawatu, New Zealand

    Kabir, Md Shahjahan (2014)

    Doctoral thesis
    Massey University

    Dothistroma needle blight (DNB), caused by the fungi Dothistroma septosporum and Dothistroma pini, is an important foliar disease of pine species throughout the world and predictions of the future spread of this disease have been made using climate models. Although DNB infection is prevalent in many forests, attempts to achieve infection under controlled laboratory or glasshouse conditions are notoriously difficult. However, artificial infection is a very important tool for studying different aspects of plant-microbe interactions, such as pathogen life style and roles of virulence factors. D. septosporum was thought to have a hemi-biotrophic life style but this was not formally investigated in planta. The non-host selective toxin dothistromin produced by this fungus was shown not to be essential for pathogenicity but its role in pathogen virulence was unknown. The aims of this study were to improve the DNB pathogenicity assay and to use this system to test the hypotheses that D. septosporum is a hemi-biotrophic pathogen and that dothistromin plays a role in virulence. A new sporulation medium (pine needle medium with glucose) was used to obtain sufficient viable D. septosporum spores. The critical microclimatic component of leaf wetness was optimised to have a short (4-7 d) high wetness period followed by 'medium' wetness (continual misting), and using these conditions >80% needle infection was routinely achieved on Pinus radiata seedlings. A combination of microscopy, biochemical and molecular studies over a timecourse of infection of P. radiata by D. septosporum confirmed its hemi-biotrophic life style. Restricted mesophyll colonisation, shorter lesions and fewer spores from P. radiata needles infected with dothistromin-deficient mutants, compared to those with wild type D. septosporum, suggested that dothistromin has a role in virulence. Interestingly ‘green islands’ in which chlorophyll levels were maintained at higher levels than adjacent chlorotic and necrotic regions, surrounded early-appearing lesions caused by both wild-type and mutant isolates. At a later developmental stage of the lesion the green islands were still present in the mutant but appeared to be masked by the extended dothistromin-containing lesions in the wild type, which lead to the hypothesis that chloroplasts could be a site of action of dothistromin. The discovery that dothistromin is a virulence factor opens up new insights into the Dothistroma-pine interaction. This fundamental finding will be useful for management strategies for this important disease in the future.

    View record details
  • Interaction between sulfur (S) and nitrogen (N) assimilation pathways in response to S and N supply in onion (Allium cepa L.) : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Molecular Biology at Massey University, Palmerston North, New Zealand.

    Joshi, Srishti (2014)

    Doctoral thesis
    Massey University

    This thesis investigates the extent of interdependency between the sulfur (S) and nitrogen (N) assimilation pathways in the commercially important, S-accumulating, monocot species, onion CUDH2107 (Allium cepa L.), to elucidate some of the regulatory points of cross-talk between these two pathways. To test the interactions between the two pathways, a factorial S x N depletion experiment was set up. Plants were grown in short day conditions to maintain the pre-bulbing stage after which they were transferred to long day conditions to promote bulbing. At the end of the short day conditions, the plants were harvested as leaf, pseudo stem and root and at the end of the long day conditions, as leaf, bulb and roots, for each of the four treatments. The four treatments comprised of control treatment (designated C; comprising 14 mM N and 2 mM S), low S treatment (designated –S; comprising 14 mM N and 0.25 mM S), low N treatment (designated –N; comprising 3.5 mM N, 2 mM S) and coupled low S and N treatment (designated –S-N; comprising 0.25 mM S and 3.5 mM N). In terms of changes in biomass, both the root and the shoot biomass tended to be higher under the –S treatment at the bulbing stage, although these changes were only significant for the root biomass. Under the – N and the –S-N treatments, the shoot biomass was much lower when compared with the control plants at both the pre-bulbing and the bulbing stage, although no change in the root biomass was observed. The exception was at the bulbing stage under the –S-N treatment where the root biomass was significantly higher when compared with the control plants. At the transcriptional level in response to the -S treatment, the relative transcript abundance of commonly used S-starvation marker genes, AcHAST1;1LIKE1 and AcAPSR1 increased in both root and the leaf tissue and was more marked at bulbing. In contrast, transcript abundance of AcAPSK1, which marks a bifurcation in the S-assimilation pathway, decreased. At bulbing, a decrease in the relative transcript abundance of AcATPS1, AcSIR1 and AcOASTL3 in the leaf tissue and AcATPS1, AcAPSK1, AcOASTL2, AcNRT2;1LIKE1 and AcNiR1 in the root tissue was observed in response to the –S treatment. However, in response to N deprivation, under the –N as well as –S-N treatment, the transcript abundance of AcHAST1;1LIKE1 and AcAPSR1 was dramatically reduced in the roots with a significant induction in the leaf tissue at both the stages. In addition, relative transcript abundance of AcATPS1 , AcAPSK1 and AcSOX1 also increased whereas AcOASTL2, AcNR1 and AcNiR1 decreased under the –N and the –S-N treatments in the leaf tissue, at pre-bulbing. However, at bulbing, transcript levels of AcOASTL2 and AcNR1 also increased under both, the –N and the –S-N treatments. In the roots, at pre-bulbing, the relative transcript abundance of AcHAST1;1LIKE1, AcNRT2;1LIKE1 and all the down-stream reductive S and N assimilation genes investigated declined, while the transcript abundance of AcAPSK1 increased. A similar response was observed at the bulbing stage for most genes except AcSOX1 and AcOASTL3 which increased and AcOASTL1, AcOASTL2 and AcNRT2;1LIKE1 showed no change. Similar to the leaf under the –S-N treatment, the transcriptional profile of the genes investigated in the roots under the –S-N treatment also showed a dominant response to N depletion. In terms of protein accumulation and enzyme activity, AcSiR1 declined in the –S treatment but accumulated in the –N and the –S-N treatment in the leaf tissue at pre-bulbing whereas at bulbing, a decline in protein accumulation was observed under all three treatments. The AcSiR1 enzyme activity declined under the –S and the –N treatment but remained unchanged under the –S-N treatment in the leaf tissue at the pre-bulbing as well as the bulbing stage. In the roots, AcSiR1 accumulated under the –S treatment in both the stages whereas activity remained unchanged. No AcSiR1 protein could be detected under the –N treatment at both stages and in the –S-N treatment at pre-bulbing, whereas the activity increased under these treatments at both stages. Under the –S treatment in the leaf tissue, AcNiR1 accumulated slightly at both pre-bulbing and bulbing whereas the activity remained unchanged. Under the –N and the –S-N treatments, AcNiR1 declined in the leaves at pre-bulbing but accumulated at the bulbing stage. However, the activity remained unchanged at the pre-bulbing stage and was below the assay detection limit at bulbing. In the roots, the AcNiR1 accumulation response was similar to that in the leaf tissue under each treatment at both the stages, whereas the activity declined under all treatments at both stages except at the pre-bulbing stage under the –S treatment where it remained unchanged. The accumulation of a set of targeted metabolites was also compared over the four treatments. A decline in the S containing flavour precursors, including the lachrymatory factor, thiopropanal-S-oxide, was observed in all tissues in response to low S supply. However, glutathione only declined in the leaf at the bulbing stage. An effect of the –S treatment on the accumulation of N-containing metabolites was observed as an accumulation of the amino-acids in the pseudo-stem and the bulb. In contrast, a decline in the accumulation of the amino-acids and derivatives was observed in the leaf at bulbing. In response to the –N treatment, most of the N-containing metabolites declined systemically, including the N-pathway cysteine precursor, O-acetylserine and serine. Flavonol glucosides accumulated in a tissue-specific manner in the pseudostem at the pre-bulbing stage but declined in the bulb tissue. Generally, sugars accumulated systemically at both developmental stages whereas sugar phosphates accumulated only in the leaf and root tissue at the pre-bulbing stage. The lachrymatory factor thiopropanal-S-oxide, accumulated in the leaf at the pre-bulbing stage but declined at the bulbing stage in response to the –N treatment. The metabolite accumulation profile in the plants under the –S-N treatment was similar in all tissues to that of the –N treatment at both the stages. The results from the factorial experiment suggest a hierarchy of N nutrition over S nutrition in A. cepa, where the incorporation and accumulation of S metabolites as well as bulb formation is regulated by N availability. A putatively novel point of interaction between the S-assimilation and the N-assimilation pathways via sulfite reductase (AcSiR1) and nitrite reductase (AcNiR1) was also investigated. Recombinant AcSiR1 and AcNiR1 were each able to reduce both sulfite and nitrite, although with a higher specific activity for the physiological substrate in each case. Further, solid phase binding assay indicated a positive interaction between the two recombinant proteins, although this could not be confirmed by Isothermal titration calorimetry (ITC). In addition to this, in a short term S x N depletion experiment with Arabidopsis, AtSiR1 transcripts only declined in the –S-N treatment in the leaves whereas AtNiR1 transcripts declined in the –S, -N as well as –S-N treatment in wild type plants. In the roots, AtSiR1 transcripts decline in both the –N and the –S-N treatment in the roots whereas no significant change was observed in the AtNiR1 transcripts. In a sir1 T-DNA knock-down line of Arabidopsis, the AtSiR1 and the AtNiR1 transcripts did not change in response to any treatment in both leaf and the roots. Substrate redundancy between AcSiR1 and AcNiR1, in vitro, along with the other interaction studies suggest that although both AcSiR1 and AcNiR1 can reduce both substrates, the possibility of this being a direct point of cross-talk between the two pathways is not conclusively established.

    View record details
  • Probability-of-growth modelling to optimize the use of hurdle technology to achieve microbiological stability of high moisture processed cheese : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, Palmerston North, New Zealand

    Khanipour, Elham (2014)

    Doctoral thesis
    Massey University

    This thesis reports a study of the application of hurdle technology to high moisture, low acid ambient shelf-stable hot packed processed cheese analogue (PCA). Hurdle technology makes use of a combination of mild stress factors. A combination of these stress factors can be more effective in inhibiting or inactivating the growth of micro-organism than individual stress factors. The current study focused on the application of hurdle technology to inhibit the growth of the food pathogen, Clostridium botulinum (C. botulinum). This micro-organism poses a hazard for consumers and is capable of growth in low acid food (pH> 4.5). As there are difficulties in working with C. botulinum in laboratory trails, Clostridium sporogenes (C. sporogenes) was used as an analogue of C. botulinum. C. sporogenes is very similar to C. botulinum in growth characteristics but is not dangerous. The effectiveness of selected preservatives on the growth of the target micro-organism was expressed as the probability of growth and was modelled as function of the concentrations of the selected preservatives in nutrient broth. Nutrient broth was initially used as it can be easily and accurately adjusted and controlled in terms of composition, and allows more rapid growth than is observed in PCA. A combination of salt (sodium chloride), sorbic acid (in the form of potassium sorbate), nisin and lysozyme was selected as stress factor. The inhibitory effect of these preservatives was then observed in the high-moisture nutrient broth at pH 7 (the optimum condition for spore of C. sporogenes to germinate) at 37ºC for eight weeks. It was found that lysozyme did not have a significant inhibitory effect on C. sporogenes in combination with salt, potassium sorbate and nisin. Therefore, the inhibitory effect of salt, sorbic acid and nisin at two different pHs (5.5 and 7) were subsequently evaluated in the nutrient broth at 37ºC for eight weeks. The probability of growth of C. sporogenes was modelled as a function of the concentrations of these selected preservatives at each pH. The results demonstrated that a combination of salt, nisin and potassium sorbate at relatively low concentrations can be used to inhibit growth. The inhibitory effects of the preservatives were pH dependent and their inhibitory effect is higher at pH 5.5. The developed models were validated using a fresh data set. Finally, the applicability of the developed model was checked in high moisture PCA. The results showed that the developed broth model underestimated the probability of growth in the PCA. Therefore, a specific probability of growth model was developed for the PCA using the PCA instead of nutrient broth as the growth medium. This model accurately predicted the probability of growth of C. sporogenes in the PCA for given combinations of preservative concentrations. The model developed for PCA allows the relative levels of preservatives to be easily quantified without the need for time consuming and expensive experimental work. The model would have limitations in the case of strongly varying formulations, since minor changes in processed cheese formulation or its production, could significantly alter its ability to support toxin production. Therefore, the model is applicable only to PCAs that have formulations similar to that used in this study. The general approach described in this thesis could be applied in the development of other high moisture, low acid foods.

    View record details