title: Anomalous transport of cosmic rays in a nonlinear diffusion model

authors: Litvinenko, Yuri E.

subjects: mathematics

abstract: We investigate analytically and numerically the transport of cosmic rays following their escape from a shock or another localized acceleration site. Observed cosmic-ray distributions in the vicinity of heliospheric and astrophysical shocks imply that anomalous, superdiffusive transport plays a role in the evolution of the energetic particles. Several authors have quantitatively described the anomalous diffusion scalings, implied by the data, by solutions of a formal transport equation with fractional derivatives. Yet the physical basis of the fractional diffusion model remains uncertain. We explore an alternative model of the cosmic-ray transport: a nonlinear diffusion equation that follows from a self-consistent treatment of the resonantly interacting cosmic-ray particles and their self-generated turbulence. The nonlinear model naturally leads to superdiffusive scalings. In the presence of convection, the model yields a power-law dependence of the particle density on the distance upstream of the shock. Although the results do not refute the use of a fractional advection–diffusion equation, they indicate a viable alternative to explain the anomalous diffusion scalings of cosmic-ray particles.

text: Anomalous transport of cosmic rays in a nonlinear diffusion model We investigate analytically and numerically the transport of cosmic rays following their escape from a shock or another localized acceleration site. Observed cosmic-ray distributions in the vicinity of heliospheric and astrophysical shocks imply that anomalous, superdiffusive transport plays a role in the evolution of the energetic particles. Several authors have quantitatively described the anomalous diffusion scalings, implied by the data, by solutions of a formal transport equation with fractional derivatives. Yet the physical basis of the fractional diffusion model remains uncertain. We explore an alternative model of the cosmic-ray transport: a nonlinear diffusion equation that follows from a self-consistent treatment of the resonantly interacting cosmic-ray particles and their self-generated turbulence. The nonlinear model naturally leads to superdiffusive scalings. In the presence of convection, the model yields a power-law dependence of the particle density on the distance upstream of the shock. Although the results do not refute the use of a fractional advection–diffusion equation, they indicate a viable alternative to explain the anomalous diffusion scalings of cosmic-ray particles.

year: 2017

title: Aesthetics of the beautiful: Ideologic tensions in contemporary assessment

authors: White, Elizabeth Jayne

subjects: Education

abstract: Pedagogy is an uncertain art. Yet by its very nature, contemporary teaching and learning practice typically suggests that the expert teacher must come to know their student well enough to plan and predict for educational challenges that will expand and extend their thinking. In many countries, this process is underpinned by bureaucratic ideology that has persuasively developed an agenda for assessment as accountability for pedagogy. As a result assessment practice in these educational institutions is very public, highly accountable and heavily prescribed through curriculum documents that claim to encompass societal agendas. In some cases, such practices are even legislated. Assessment practice is now seen as integral to the pedagogical process since it is through assessment that the teacher purportedly comes to understand the learner; thus providing a rationale for the teaching approaches and strategies that are applied in order to progress learning. In this chronotopic location I suggest there is little room for uncertainty, since the quest to capture the "essence" of the learner and mould them towards societal goals is as much a political agenda of accountability as it is pedagogical.

text: Aesthetics of the beautiful: Ideologic tensions in contemporary assessment Pedagogy is an uncertain art. Yet by its very nature, contemporary teaching and learning practice typically suggests that the expert teacher must come to know their student well enough to plan and predict for educational challenges that will expand and extend their thinking. In many countries, this process is underpinned by bureaucratic ideology that has persuasively developed an agenda for assessment as accountability for pedagogy. As a result assessment practice in these educational institutions is very public, highly accountable and heavily prescribed through curriculum documents that claim to encompass societal agendas. In some cases, such practices are even legislated. Assessment practice is now seen as integral to the pedagogical process since it is through assessment that the teacher purportedly comes to understand the learner; thus providing a rationale for the teaching approaches and strategies that are applied in order to progress learning. In this chronotopic location I suggest there is little room for uncertainty, since the quest to capture the "essence" of the learner and mould them towards societal goals is as much a political agenda of accountability as it is pedagogical.

year: 2011

title: Waitangi Soda Springs alum dosing – Bioavailability of aluminium 2011-2020

authors: Ling, Nicholas

abstract: Continuous alum dosing of the Waitangi Soda Springs at Lake Rotoehu commenced in 2011 to reduce inflows of dissolved reactive phosphorus to Lake Rotoehu. Analyses of bioaccumulation in the tissues of kōura and goldfish from Lake Rotoehu were undertaken on animals collected annually since 2013 to determine the bioavailability and bioaccumulation of aluminium. Lake Rotoehu kōura and goldfish collected in 2013 showed slightly elevated aluminium concentrations in the gills indicating enhanced exposure to aluminium but little evidence for significant bioaccumulation in tissues. Concentrations in goldfish liver and gills were highest in 2016, but not significantly different to goldfish collected from Lake Rotorua in 2013 and flesh concentrations were low. Analyses of animals collected in 2020 confirm these earlier findings with no evidence of enhanced bioaccumulation of aluminium in Lake Rotoehu biota.

text: Waitangi Soda Springs alum dosing – Bioavailability of aluminium 2011-2020 Continuous alum dosing of the Waitangi Soda Springs at Lake Rotoehu commenced in 2011 to reduce inflows of dissolved reactive phosphorus to Lake Rotoehu. Analyses of bioaccumulation in the tissues of kōura and goldfish from Lake Rotoehu were undertaken on animals collected annually since 2013 to determine the bioavailability and bioaccumulation of aluminium. Lake Rotoehu kōura and goldfish collected in 2013 showed slightly elevated aluminium concentrations in the gills indicating enhanced exposure to aluminium but little evidence for significant bioaccumulation in tissues. Concentrations in goldfish liver and gills were highest in 2016, but not significantly different to goldfish collected from Lake Rotorua in 2013 and flesh concentrations were low. Analyses of animals collected in 2020 confirm these earlier findings with no evidence of enhanced bioaccumulation of aluminium in Lake Rotoehu biota.

year: 2021