title: Finite dissipation in anisotropic magnetohydrodynamic turbulence

authors: Bandyopadhyay, R.

subjects: Science & Technology

abstract: In the presence of an externally supported, mean magnetic field, a turbulent, conducting medium, such as plasma, becomes anisotropic. This mean magnetic field, which is separate from the fluctuating, turbulent part of the magnetic field, has considerable effects on the dynamics of the system. In this paper, we examine the dissipation rates for decaying incompressible magnetohydrodynamic (MHD) turbulence with an increasing Reynolds number and in the presence of a mean magnetic field of varying strength. Proceeding numerically, we find that, as the Reynolds number increases, the dissipation rate asymptotes to a finite value for each magnetic-field strength, confirming the Kármán-Howarth hypothesis as applied to MHD. The asymptotic value of the dimensionless dissipation rate is initially suppressed from the zero-mean-field value by the mean magnetic field but then approaches a constant value for higher values of the mean-field strength. Additionally, for comparison, we perform a set of two-dimensional (2DMHD) and a set of reduced MHD (RMHD) simulations. We find that the RMHD results lie very close to the values corresponding to the high-mean-field limit of the three-dimensional runs while the 2DMHD results admit distinct values far from both the zero-mean-field cases and the high-mean-field limit of the threedimensional cases. These findings provide firm underpinnings for numerous applications in space and astrophysics wherein von Kármán decay of turbulence is assumed.

text: Finite dissipation in anisotropic magnetohydrodynamic turbulence In the presence of an externally supported, mean magnetic field, a turbulent, conducting medium, such as plasma, becomes anisotropic. This mean magnetic field, which is separate from the fluctuating, turbulent part of the magnetic field, has considerable effects on the dynamics of the system. In this paper, we examine the dissipation rates for decaying incompressible magnetohydrodynamic (MHD) turbulence with an increasing Reynolds number and in the presence of a mean magnetic field of varying strength. Proceeding numerically, we find that, as the Reynolds number increases, the dissipation rate asymptotes to a finite value for each magnetic-field strength, confirming the Kármán-Howarth hypothesis as applied to MHD. The asymptotic value of the dimensionless dissipation rate is initially suppressed from the zero-mean-field value by the mean magnetic field but then approaches a constant value for higher values of the mean-field strength. Additionally, for comparison, we perform a set of two-dimensional (2DMHD) and a set of reduced MHD (RMHD) simulations. We find that the RMHD results lie very close to the values corresponding to the high-mean-field limit of the three-dimensional runs while the 2DMHD results admit distinct values far from both the zero-mean-field cases and the high-mean-field limit of the threedimensional cases. These findings provide firm underpinnings for numerous applications in space and astrophysics wherein von Kármán decay of turbulence is assumed.

year: 2018

title: Are geothermal streams important sites of nutrient uptake in an agricultural and urbanising landscape (Rotorua, New Zealand)?

authors: Hoellein, Timothy

subjects: ecosystem function

abstract: Increased nutrient loading and eutrophication are common problems for lakes globally (Carpenter et al., 1998; Smith & Schindler, 2009). New Zealand is no exception, where 30% of lakes >1 ha have very poor to extremely poor water quality (Van Bunnik et al., 2007). Many of the iconic lakes in the well-known, geothermally active Rotorua region of New Zealand exhibit the adverse affects of eutrophication, including harmful algal blooms, bottom water hypoxia, reduced clarity (Hamilton et al., 2010) and loss of aquatic biodiversity (Hamilton, 2004; Burns, Mcintosh & Scholes, 2009). These lakes are important to New Zealand both economically and culturally (Edgar, 2009).

text: Are geothermal streams important sites of nutrient uptake in an agricultural and urbanising landscape (Rotorua, New Zealand)? Increased nutrient loading and eutrophication are common problems for lakes globally (Carpenter et al., 1998; Smith & Schindler, 2009). New Zealand is no exception, where 30% of lakes >1 ha have very poor to extremely poor water quality (Van Bunnik et al., 2007). Many of the iconic lakes in the well-known, geothermally active Rotorua region of New Zealand exhibit the adverse affects of eutrophication, including harmful algal blooms, bottom water hypoxia, reduced clarity (Hamilton et al., 2010) and loss of aquatic biodiversity (Hamilton, 2004; Burns, Mcintosh & Scholes, 2009). These lakes are important to New Zealand both economically and culturally (Edgar, 2009).

year: 2012-01

title: Barriers and facilitators to Oranga Tamariki access: Wāhine voices from Te Whakaruruhau

authors: Mcleay, Ana

abstract: This thesis examines how wāhine supported by Te Whakaruruhau Waikato Women’s Refuge experience Oranga Tamariki (OT) in the context of intimate partner violence (IPV), and what barriers and facilitators shape their access to services. Within a Community-Based Participatory Research approach, influenced by Kaupapa Māori and Mana Wahine principles, qualitative data were collected through semi-structured, kanohi ki te kanohi interviews with six wāhine and kaimahi. Reflexive thematic analysis identified seven themes, grouped into two overarching clusters: barriers and facilitators to OT access. Barriers were pervasive and cumulative, encompassing relational harm, negligence, fear and risk, and cultural tokenism. Facilitators - collaborative advocacy, strengths-based practice, and procedural justice - were comparatively rare and often dependent on external supports rather than systemic provision.

Mapping these findings against Te Hā o Whānau, an access framework, revealed that barriers emerged where tikanga manaakitanga, tikanga whakawhanaungatanga, and tikanga rangatiratanga were absent, while facilitators aligned with their enactment. Te Hā o Whānau conceptualises access as a relational and culturally grounded process inseparable from wellbeing, making it both conceptually robust and uniquely suited to Aotearoa. The analysis demonstrates that OT, as currently structured, undermines whānau wellbeing through systemic practices that erode mana, restrict autonomy, and compromise safety. In the immediate term, strengthened collaborative advocacy offers some protection and support, but meaningful change requires systemic transformation.

Future research should examine how Te Hā o Whānau might be further operationalised across different service contexts and explore experiences of wāhine and whānau with OT in a variety of contexts to build a fuller understanding of access and wellbeing in child welfare.

text: Barriers and facilitators to Oranga Tamariki access: Wāhine voices from Te Whakaruruhau This thesis examines how wāhine supported by Te Whakaruruhau Waikato Women’s Refuge experience Oranga Tamariki (OT) in the context of intimate partner violence (IPV), and what barriers and facilitators shape their access to services. Within a Community-Based Participatory Research approach, influenced by Kaupapa Māori and Mana Wahine principles, qualitative data were collected through semi-structured, kanohi ki te kanohi interviews with six wāhine and kaimahi. Reflexive thematic analysis identified seven themes, grouped into two overarching clusters: barriers and facilitators to OT access. Barriers were pervasive and cumulative, encompassing relational harm, negligence, fear and risk, and cultural tokenism. Facilitators - collaborative advocacy, strengths-based practice, and procedural justice - were comparatively rare and often dependent on external supports rather than systemic provision.

Mapping these findings against Te Hā o Whānau, an access framework, revealed that barriers emerged where tikanga manaakitanga, tikanga whakawhanaungatanga, and tikanga rangatiratanga were absent, while facilitators aligned with their enactment. Te Hā o Whānau conceptualises access as a relational and culturally grounded process inseparable from wellbeing, making it both conceptually robust and uniquely suited to Aotearoa. The analysis demonstrates that OT, as currently structured, undermines whānau wellbeing through systemic practices that erode mana, restrict autonomy, and compromise safety. In the immediate term, strengthened collaborative advocacy offers some protection and support, but meaningful change requires systemic transformation.

Future research should examine how Te Hā o Whānau might be further operationalised across different service contexts and explore experiences of wāhine and whānau with OT in a variety of contexts to build a fuller understanding of access and wellbeing in child welfare.

year: 2025