title: Magnetic field line random walk in models and simulations of reduced magnetohydrodynamic turbulence

authors: Snodin, A. P.

subjects: diffusion

abstract: The random walk of magnetic ﬁeld lines is examined numerically and analytically in the context of reduced magnetohydrodynamic (RMHD) turbulence, which provides a useful description of plasmas dominated by a strong mean ﬁeld, such as in the solar corona. A recently developed non-perturbative theory of magnetic ﬁeld line diffusion is compared with the diffusion coefﬁcients obtained by accurate numerical tracing of magnetic ﬁeld lines for both synthetic models and direct numerical simulations of RMHD. Statistical analysis of an ensemble of trajectories conﬁrms the applicability of the theory, which very closely matches the numerical ﬁeld line diffusion coefﬁcient as a function of distance z along the mean magnetic ﬁeld for a wide range of the Kubo number R. This theory employs Corrsin’s independence hypothesis, sometimes thought to be valid only at low R. However, the results demonstrate that it works well up to R = 10, both for a synthetic RMHD model and an RMHD simulation. The numerical results from the RMHD simulation are compared with and without phase randomization, demonstrating a clear effect of coherent structures on the ﬁeld line random walk for a very low Kubo number.

text: Magnetic field line random walk in models and simulations of reduced magnetohydrodynamic turbulence The random walk of magnetic ﬁeld lines is examined numerically and analytically in the context of reduced magnetohydrodynamic (RMHD) turbulence, which provides a useful description of plasmas dominated by a strong mean ﬁeld, such as in the solar corona. A recently developed non-perturbative theory of magnetic ﬁeld line diffusion is compared with the diffusion coefﬁcients obtained by accurate numerical tracing of magnetic ﬁeld lines for both synthetic models and direct numerical simulations of RMHD. Statistical analysis of an ensemble of trajectories conﬁrms the applicability of the theory, which very closely matches the numerical ﬁeld line diffusion coefﬁcient as a function of distance z along the mean magnetic ﬁeld for a wide range of the Kubo number R. This theory employs Corrsin’s independence hypothesis, sometimes thought to be valid only at low R. However, the results demonstrate that it works well up to R = 10, both for a synthetic RMHD model and an RMHD simulation. The numerical results from the RMHD simulation are compared with and without phase randomization, demonstrating a clear effect of coherent structures on the ﬁeld line random walk for a very low Kubo number.

year: 2013

title: Gossypol's effects on ingestive behaviour in mice: The first step in a systematic process to define gossypol's suitability for use in murine pest management

authors: Churchill, Geoff

subjects: Gossypol

abstract: Gossypol, synthesised by the cotton plant, Gossypium, causes physiological and behavioural changes in mammals, suggesting it may be suitable for murine pest management. One of the most under-studied responses to gossypol, especially in the house mouse, Mus musculus, is its effect on ingestive behaviour, with some authors reporting anorexia and others observing no effect on energy metabolism. Importantly, there has been no systematic analysis of gossypol’s effect on food intake in mice. Therefore, the goal of this thesis was to provide the initial step in defining gossypol’s effect on feeding behaviour in mice by observing their responses after exposure to precise doses of gossypol delivered via injection. Mice underwent two injection intraperitoneal (IP) paradigms; acute and chronic (11 daily injections) exposures to 0 (vehicle), 10, 30, 100 and 300 mg/kg b.wt., and 0 (vehicle) and 100 mg/kg b.wt. respectively. The intakes of bland (chow) and palatable tastants were measured during the acute exposure. An increase in chow intake was observed at 1 and 3 hr post-exposure with 300 mg/kg b.wt. dose. An increase in glucose intake was also observed in mice injected with 100 mg/kg b.wt. at 1 and 12 hr post-exposure. Neither of these hyperphagia responses showed a complementary increase in body weight. During the chronic exposure, body weight and chow intake were measured throughout the injection period and on select days of the 40 day post-exposure period. While there was no difference in food intake and body weight during the gossypol exposure, on day 10 post-exposure, food intake had increased by 50% and was still elevated on day 40, but no differences in body weight were noted. To examine whether this increase in food intake was an effect of a long-term anxiogenic response associated with a likely post-exposure malaise, several anxiety assessment tests were performed, showing no change. This thesis shows that gossypol affects feeding behaviour in mice. Interestingly, no anorexigenic effect was observed, but in fact moderate hyperphagia without changes in body weight was shown in both acute and chronic paradigms. The data from this thesis can be built upon with future studies using oral administration to develop the understanding of this important aspect of gossypol and to more precisely determine gossypol’s suitability for enhancing murine pest management.

text: Gossypol's effects on ingestive behaviour in mice: The first step in a systematic process to define gossypol's suitability for use in murine pest management Gossypol, synthesised by the cotton plant, Gossypium, causes physiological and behavioural changes in mammals, suggesting it may be suitable for murine pest management. One of the most under-studied responses to gossypol, especially in the house mouse, Mus musculus, is its effect on ingestive behaviour, with some authors reporting anorexia and others observing no effect on energy metabolism. Importantly, there has been no systematic analysis of gossypol’s effect on food intake in mice. Therefore, the goal of this thesis was to provide the initial step in defining gossypol’s effect on feeding behaviour in mice by observing their responses after exposure to precise doses of gossypol delivered via injection. Mice underwent two injection intraperitoneal (IP) paradigms; acute and chronic (11 daily injections) exposures to 0 (vehicle), 10, 30, 100 and 300 mg/kg b.wt., and 0 (vehicle) and 100 mg/kg b.wt. respectively. The intakes of bland (chow) and palatable tastants were measured during the acute exposure. An increase in chow intake was observed at 1 and 3 hr post-exposure with 300 mg/kg b.wt. dose. An increase in glucose intake was also observed in mice injected with 100 mg/kg b.wt. at 1 and 12 hr post-exposure. Neither of these hyperphagia responses showed a complementary increase in body weight. During the chronic exposure, body weight and chow intake were measured throughout the injection period and on select days of the 40 day post-exposure period. While there was no difference in food intake and body weight during the gossypol exposure, on day 10 post-exposure, food intake had increased by 50% and was still elevated on day 40, but no differences in body weight were noted. To examine whether this increase in food intake was an effect of a long-term anxiogenic response associated with a likely post-exposure malaise, several anxiety assessment tests were performed, showing no change. This thesis shows that gossypol affects feeding behaviour in mice. Interestingly, no anorexigenic effect was observed, but in fact moderate hyperphagia without changes in body weight was shown in both acute and chronic paradigms. The data from this thesis can be built upon with future studies using oral administration to develop the understanding of this important aspect of gossypol and to more precisely determine gossypol’s suitability for enhancing murine pest management.

year: 2014

title: The embodied and lived experiences of welfare and care for highly impaired, high performance para-sport athletes in Aotearoa New Zealand

authors: Lowry, Amanda

abstract: Aligning with calls in critical disability studies to bring the body and impairment into disability sport, this thesis examines the welfare and care experiences of highly impaired athletes in high-performance sport. While a focus on athlete welfare has gained some international prominence, and a duty of care is increasingly invoked as an organisational and coaching responsibility, these developments remain largely disconnected from disability.  
The research is centred around two main objectives. First, to amplify the lived and embodied experiences of highly impaired, high performance disabled athletes as they prepare for, train, and compete in sport, and those who support them. Second, to understand how sporting institutions and regulations (within the broader context of government funding and national health care provision) influence welfare and care practices for high performance disabled athletes. 
Crip methodologies and Indigenous Māori storytelling methodologies such as pūrākau centres lived experience as a site of resistance and knowledge production. Using a reflexive, qualitative approach, including semi-structured interviews, autoethnographic vignettes, and visual ethnography, I expose how impairment effects are managed in ableist sporting environments that valorise normative athlete ideals. I interviewed 11 high-performance paraathletes, seven organisational representatives and two support workers. 
The research highlights the material, emotional, and temporal labour of care in highperformance sport. Findings are organised around three core themes: the embodied labour of care, impairment effects and interdependence; the tension between crip time, care time, and performance time; the intersecting structural, institutional, and ableist barriers that shape and constrain highly impaired athletes’ participation in disability sport.  
The first theme shows how high-performance sport privileges autonomous, efficient, and normative bodies, while marginalising those whose messy, gritty embodied impairment effects demand more time, support, and interdependence. The findings bring to the fore biosocial, psycho-emotional costs of navigating care and its impact on athlete welfare. The second theme uncovers how the rhythms of highly impaired bodies disrupt the linear, clockbound time of high-performance sport, revealing the incompatibility between care time and high performance cultures. It highlights the vital yet invisible labour of support workers, ii unacknowledged in contemporary sporting discourse. The third theme addresses the barriers that highly impaired athletes face when navigating ableist institutional and organisational structures. It exposes the complexity of the ableist disability sporting landscape and the gap between duty of care rhetoric and practice. 
Ultimately, this thesis calls for a radical reimagining of disability sport, one that centres interdependence, affirms bodily difference, and addresses the structural failures that marginalise highly impaired athletes.

text: The embodied and lived experiences of welfare and care for highly impaired, high performance para-sport athletes in Aotearoa New Zealand Aligning with calls in critical disability studies to bring the body and impairment into disability sport, this thesis examines the welfare and care experiences of highly impaired athletes in high-performance sport. While a focus on athlete welfare has gained some international prominence, and a duty of care is increasingly invoked as an organisational and coaching responsibility, these developments remain largely disconnected from disability.  
The research is centred around two main objectives. First, to amplify the lived and embodied experiences of highly impaired, high performance disabled athletes as they prepare for, train, and compete in sport, and those who support them. Second, to understand how sporting institutions and regulations (within the broader context of government funding and national health care provision) influence welfare and care practices for high performance disabled athletes. 
Crip methodologies and Indigenous Māori storytelling methodologies such as pūrākau centres lived experience as a site of resistance and knowledge production. Using a reflexive, qualitative approach, including semi-structured interviews, autoethnographic vignettes, and visual ethnography, I expose how impairment effects are managed in ableist sporting environments that valorise normative athlete ideals. I interviewed 11 high-performance paraathletes, seven organisational representatives and two support workers. 
The research highlights the material, emotional, and temporal labour of care in highperformance sport. Findings are organised around three core themes: the embodied labour of care, impairment effects and interdependence; the tension between crip time, care time, and performance time; the intersecting structural, institutional, and ableist barriers that shape and constrain highly impaired athletes’ participation in disability sport.  
The first theme shows how high-performance sport privileges autonomous, efficient, and normative bodies, while marginalising those whose messy, gritty embodied impairment effects demand more time, support, and interdependence. The findings bring to the fore biosocial, psycho-emotional costs of navigating care and its impact on athlete welfare. The second theme uncovers how the rhythms of highly impaired bodies disrupt the linear, clockbound time of high-performance sport, revealing the incompatibility between care time and high performance cultures. It highlights the vital yet invisible labour of support workers, ii unacknowledged in contemporary sporting discourse. The third theme addresses the barriers that highly impaired athletes face when navigating ableist institutional and organisational structures. It exposes the complexity of the ableist disability sporting landscape and the gap between duty of care rhetoric and practice. 
Ultimately, this thesis calls for a radical reimagining of disability sport, one that centres interdependence, affirms bodily difference, and addresses the structural failures that marginalise highly impaired athletes.

year: 2025-10