title: A reduced magnetohydrodynamic model of coronal heating in open magnetic regions driven by reflected low-frequency waves

authors: Oughton, Sean

subjects: MHD

abstract: A reduced magnetohydrodynamic (RMHD) description is employed to examine a suggestion made by W. H. Matthaeus and colleagues in 1999 that coronal heating might be sustained by a cascade of low-frequency MHD turbulence. Here RMHD simulations show that the low-frequency cascade to high transverse wavenumbers can be driven by an externally maintained flux of low-frequency propagating Alfvén waves, in combination with reflection caused by an inhomogeneous background medium. The simulations show that the suggestions made previously on the basis of a phenomenology are indeed realizable. In addition, the effect is seen to sensitively depend on the presence of reflection, as the background turbulence level needed to maintain the cascade can be sustained only when reflection is imposed. The steady level of turbulence is insensitive to the initial seed turbulence level (provided it is nonzero). Consequences of this model for realistic models of coronal heating in open field-line regions are discussed.

text: A reduced magnetohydrodynamic model of coronal heating in open magnetic regions driven by reflected low-frequency waves A reduced magnetohydrodynamic (RMHD) description is employed to examine a suggestion made by W. H. Matthaeus and colleagues in 1999 that coronal heating might be sustained by a cascade of low-frequency MHD turbulence. Here RMHD simulations show that the low-frequency cascade to high transverse wavenumbers can be driven by an externally maintained flux of low-frequency propagating Alfvén waves, in combination with reflection caused by an inhomogeneous background medium. The simulations show that the suggestions made previously on the basis of a phenomenology are indeed realizable. In addition, the effect is seen to sensitively depend on the presence of reflection, as the background turbulence level needed to maintain the cascade can be sustained only when reflection is imposed. The steady level of turbulence is insensitive to the initial seed turbulence level (provided it is nonzero). Consequences of this model for realistic models of coronal heating in open field-line regions are discussed.

year: 2001

title: Soil chronosequences and bacterial communities of the Central Transantarctic Mountains, Antarctica

authors: Scarrow, Joshua William

subjects: Antarctica

abstract: The Beardmore Glacier region of the Central Transantarctic Mountains (CTAM), approximately 600 km south of the McMurdo Dry Valleys (MDV), has been studied to a much lesser extent than the accessible MDV and other regions of the continent. The CTAM were visited in the 2010/2011 austral summer, and two concurrent studies undertaken; these are presented in the form of manuscripts for publication in peer-reviewed journals, as a thesis by publication.
Soil chronosequences in three of the largest ice-free areas (Ong Valley, Mount Achernar, and the Dominion Range), at altitudes above 1600 m along the polar plateau margin, were examined. Transects perpendicular to the current ice edge reveal a gradual increase in soil depth (from 2 cm to > 80 cm to underlying ice), weathering, horizonation, salt content, and a decrease in pH; all of these factors are consistent with increased soil development since time of deglaciation. Such fine scale variation in soil properties, previously overlooked in the CTAM region, cannot be mapped by Soil Taxonomy subgroups, as commonly utilised in Antarctic soil mapping. Patterns of soil thickness, clast abundance and soil chemistry all indicate a bi-modal form of soil development. It is proposed that the soil profile deepens by addition of englacial debris to the subsoil via the sublimation of underlying ice, and the weathering of supraglacial clasts at the soil surface.
The molecular characterization of bacterial communities in CTAM soils is the southernmost culture-independent soil survey to date. Community fingerprinting (ARISA) and 16S rRNA gene pyrosequencing demonstrated significantly different bacterial communities between eight discrete CTAM locations (5 at low altitude near the Ross Ice Shelf coast, 3 near the polar plateau > 1600 m). Abiotic environmental variables, especially those related to long-term exposure of soils to the atmosphere, correlate well with inter-site community variation. Mount Howe, the southernmost soil on the planet (87° S), harbours an extremely low biomass bacterial community, of a fundamentally different composition to all other sites. It appears that observed DNA sequences at Mount Howe are the result of atmospherically deposited bacteria, the soil being unable to support edaphic life due to extreme local climatic conditions.￼
These two studies extend previous knowledge of soil development and distribution, and microbial ecology, to the southernmost extent possible. These observations may serve as important baseline data for monitoring of this fragile system in the face of future and ongoing environmental changes.

text: Soil chronosequences and bacterial communities of the Central Transantarctic Mountains, Antarctica The Beardmore Glacier region of the Central Transantarctic Mountains (CTAM), approximately 600 km south of the McMurdo Dry Valleys (MDV), has been studied to a much lesser extent than the accessible MDV and other regions of the continent. The CTAM were visited in the 2010/2011 austral summer, and two concurrent studies undertaken; these are presented in the form of manuscripts for publication in peer-reviewed journals, as a thesis by publication.
Soil chronosequences in three of the largest ice-free areas (Ong Valley, Mount Achernar, and the Dominion Range), at altitudes above 1600 m along the polar plateau margin, were examined. Transects perpendicular to the current ice edge reveal a gradual increase in soil depth (from 2 cm to > 80 cm to underlying ice), weathering, horizonation, salt content, and a decrease in pH; all of these factors are consistent with increased soil development since time of deglaciation. Such fine scale variation in soil properties, previously overlooked in the CTAM region, cannot be mapped by Soil Taxonomy subgroups, as commonly utilised in Antarctic soil mapping. Patterns of soil thickness, clast abundance and soil chemistry all indicate a bi-modal form of soil development. It is proposed that the soil profile deepens by addition of englacial debris to the subsoil via the sublimation of underlying ice, and the weathering of supraglacial clasts at the soil surface.
The molecular characterization of bacterial communities in CTAM soils is the southernmost culture-independent soil survey to date. Community fingerprinting (ARISA) and 16S rRNA gene pyrosequencing demonstrated significantly different bacterial communities between eight discrete CTAM locations (5 at low altitude near the Ross Ice Shelf coast, 3 near the polar plateau > 1600 m). Abiotic environmental variables, especially those related to long-term exposure of soils to the atmosphere, correlate well with inter-site community variation. Mount Howe, the southernmost soil on the planet (87° S), harbours an extremely low biomass bacterial community, of a fundamentally different composition to all other sites. It appears that observed DNA sequences at Mount Howe are the result of atmospherically deposited bacteria, the soil being unable to support edaphic life due to extreme local climatic conditions.￼
These two studies extend previous knowledge of soil development and distribution, and microbial ecology, to the southernmost extent possible. These observations may serve as important baseline data for monitoring of this fragile system in the face of future and ongoing environmental changes.

year: 2013

title: Aro mai aro atu: Raising Māori-medium students' academic oral language proficiency

authors: Shandley, Rosina Mary

subjects: Māori-medium

abstract: From the early 1860s, colonial governments worked systematically to eradicate the language and culture of the indigenous people of Aotearoa / New Zealand, and, by the late 1960s, the death of the Māori language was being predicted by leading linguists. Māori leaders responded in the 1980s with language regeneration initiatives that included the birth of Māori-medium education. Today, this uniquely indigenous education system is a significant site of language learning for new generations of Māori children. In Māori-medium education, children are nurtured, educated, and loved as Māori, and they are more likely to attain educational qualifications than their Māori peers who attend English-medium schools. 

The success of Māori-medium education is achieved in the face of a raft of ongoing challenges that teachers and students confront on a daily basis. Years of language marginalisation, including the disruption to intergenerational transfer, mean Māori-medium students are required to learn the curriculum through their second and less-developed language. They have limited opportunities to hear or use the Māori language outside of the school, and this places huge pressure on teachers who are often their most significant language models. The challenge is compounded by the limited education that has been made available to teachers in relation to second-language pedagogies specifically designed for Māori-medium classrooms. The resulting situation is that Māori-medium teachers are often left struggling to find ways that they can develop students’ Māori language proficiency at the same time as their curriculum achievement so that one is not sacrificed for the other. 

This study designed and trialled pedagogies to support Māori-medium students to develop their academic oral language proficiency at the same time as their curriculum achievement. It was a mixed methods study grounded in a kaupapa Māori approach, and involved three teachers and 24 students across three separate Māori-medium schools. An Anga Putanga Ako (Curriculum Outcomes Matrix) was developed to support the students to understand what they needed to learn to progress through the writing curriculum. Teachers then learnt to share explicit learning outcomes from the Anga Putanga Ako with students before lessons and to allow them time to discuss their achievement of those outcomes in pairs at the conclusion of those lessons. Linguistic scaffolds were developed to support students’ learning conversations, including the self and peer assessment of the learning outcomes, and decisions about their curriculum achievement levels and next learning steps.

The quantitative and qualitative results of the study revealed that the confluence of the self and peer assessment practices, supported by the Anga Putanga Ako and linguistic scaffolds, improved the students’ academic oral language and accelerated their reading and writing achievement significantly beyond what is usually expected in a Māori-medium classroom in 14 weeks. The study also found that, through implementing the self and peer assessment pedagogies, teachers were able to identify ways they could develop their students’ academic language and curriculum achievement simultaneously and how these approaches could be applied across the curriculum.

It was clear from the research results that pedagogies that support second-language development and curriculum learning, such as the self and peer assessment pedagogies demonstrated in this study, need to be explicitly taught with consistency across initial and in-service teacher education programmes. This development is necessary to help ensure Māori-medium students are supported with the thinking and linguistic skills needed to contribute to the creation of new knowledge, to support or challenge the current social order as they see fit, and to continue to transfer the Māori language to new generations of mokopuna.

text: Aro mai aro atu: Raising Māori-medium students' academic oral language proficiency From the early 1860s, colonial governments worked systematically to eradicate the language and culture of the indigenous people of Aotearoa / New Zealand, and, by the late 1960s, the death of the Māori language was being predicted by leading linguists. Māori leaders responded in the 1980s with language regeneration initiatives that included the birth of Māori-medium education. Today, this uniquely indigenous education system is a significant site of language learning for new generations of Māori children. In Māori-medium education, children are nurtured, educated, and loved as Māori, and they are more likely to attain educational qualifications than their Māori peers who attend English-medium schools. 

The success of Māori-medium education is achieved in the face of a raft of ongoing challenges that teachers and students confront on a daily basis. Years of language marginalisation, including the disruption to intergenerational transfer, mean Māori-medium students are required to learn the curriculum through their second and less-developed language. They have limited opportunities to hear or use the Māori language outside of the school, and this places huge pressure on teachers who are often their most significant language models. The challenge is compounded by the limited education that has been made available to teachers in relation to second-language pedagogies specifically designed for Māori-medium classrooms. The resulting situation is that Māori-medium teachers are often left struggling to find ways that they can develop students’ Māori language proficiency at the same time as their curriculum achievement so that one is not sacrificed for the other. 

This study designed and trialled pedagogies to support Māori-medium students to develop their academic oral language proficiency at the same time as their curriculum achievement. It was a mixed methods study grounded in a kaupapa Māori approach, and involved three teachers and 24 students across three separate Māori-medium schools. An Anga Putanga Ako (Curriculum Outcomes Matrix) was developed to support the students to understand what they needed to learn to progress through the writing curriculum. Teachers then learnt to share explicit learning outcomes from the Anga Putanga Ako with students before lessons and to allow them time to discuss their achievement of those outcomes in pairs at the conclusion of those lessons. Linguistic scaffolds were developed to support students’ learning conversations, including the self and peer assessment of the learning outcomes, and decisions about their curriculum achievement levels and next learning steps.

The quantitative and qualitative results of the study revealed that the confluence of the self and peer assessment practices, supported by the Anga Putanga Ako and linguistic scaffolds, improved the students’ academic oral language and accelerated their reading and writing achievement significantly beyond what is usually expected in a Māori-medium classroom in 14 weeks. The study also found that, through implementing the self and peer assessment pedagogies, teachers were able to identify ways they could develop their students’ academic language and curriculum achievement simultaneously and how these approaches could be applied across the curriculum.

It was clear from the research results that pedagogies that support second-language development and curriculum learning, such as the self and peer assessment pedagogies demonstrated in this study, need to be explicitly taught with consistency across initial and in-service teacher education programmes. This development is necessary to help ensure Māori-medium students are supported with the thinking and linguistic skills needed to contribute to the creation of new knowledge, to support or challenge the current social order as they see fit, and to continue to transfer the Māori language to new generations of mokopuna.

year: 2022