title: Non linear evolution of Alfvén wave in the solar atmosphere

authors: Verdini, A.

subjects: Alfvén waves

abstract: We investigate the non-linear evolution of Alfvén waves in the solar atmosphere and wind, from the photosphere out to the Earth’s orbit. Photosphere and chromosphere are modeled as isothermal layers in static equilibrium, connecting across the transition region with a corona and wind. Nonlinear coupling between waves propagating in opposite directions is modeled by a phenomenological term containing an integral turbulent length scale. Spectrum modifications remain similar to what is found in a linear analysis and some characteristic features - i.e. oscillations at higher frequencies- persist despite nonlinear interactions.

text: Non linear evolution of Alfvén wave in the solar atmosphere We investigate the non-linear evolution of Alfvén waves in the solar atmosphere and wind, from the photosphere out to the Earth’s orbit. Photosphere and chromosphere are modeled as isothermal layers in static equilibrium, connecting across the transition region with a corona and wind. Nonlinear coupling between waves propagating in opposite directions is modeled by a phenomenological term containing an integral turbulent length scale. Spectrum modifications remain similar to what is found in a linear analysis and some characteristic features - i.e. oscillations at higher frequencies- persist despite nonlinear interactions.

year: 2005

title: Crystal structure of pyruvate decarboxylase from Zymobacter palmae

authors: Buddrus, Lisa

subjects: Science & Technology

abstract: Pyruvate decarboxylase (PDC; EC 4.1.1.1) is a thiamine pyrophosphate- and Mg²⁺ ion-dependent enzyme that catalyses the non-oxidative decarboxylation of pyruvate to acetaldehyde and carbon dioxide. It is rare in bacteria, but is a key enzyme in homofermentative metabolism, where ethanol is the major product. Here, the previously unreported crystal structure of the bacterial pyruvate decarboxylase from Zymobacter palmae is presented. The crystals were shown to diffract to 2.15 Å resolution. They belonged to space group P21, with unit-cell parameters a = 204.56, b = 177.39, c = 244.55 Å and Rᵣ.ᵢ.ₘ. = 0.175 (0.714 in the highest resolution bin). The structure was solved by molecular replacement using PDB entry 2vbi as a model and the final R values were Rwₒᵣₖ = 0.186 (0.271 in the highest resolution bin) and Rfᵣₑₑ = 0.220 (0.300 in the highest resolution bin). Each of the six tetramers is a dimer of dimers, with each monomer sharing its thiamine pyrophosphate across the dimer interface, and some contain ethylene glycol mimicking the substrate pyruvate in the active site. Comparison with other bacterial PDCs shows a correlation of higher thermostability with greater tetramer interface area and number of interactions.

text: Crystal structure of pyruvate decarboxylase from Zymobacter palmae Pyruvate decarboxylase (PDC; EC 4.1.1.1) is a thiamine pyrophosphate- and Mg²⁺ ion-dependent enzyme that catalyses the non-oxidative decarboxylation of pyruvate to acetaldehyde and carbon dioxide. It is rare in bacteria, but is a key enzyme in homofermentative metabolism, where ethanol is the major product. Here, the previously unreported crystal structure of the bacterial pyruvate decarboxylase from Zymobacter palmae is presented. The crystals were shown to diffract to 2.15 Å resolution. They belonged to space group P21, with unit-cell parameters a = 204.56, b = 177.39, c = 244.55 Å and Rᵣ.ᵢ.ₘ. = 0.175 (0.714 in the highest resolution bin). The structure was solved by molecular replacement using PDB entry 2vbi as a model and the final R values were Rwₒᵣₖ = 0.186 (0.271 in the highest resolution bin) and Rfᵣₑₑ = 0.220 (0.300 in the highest resolution bin). Each of the six tetramers is a dimer of dimers, with each monomer sharing its thiamine pyrophosphate across the dimer interface, and some contain ethylene glycol mimicking the substrate pyruvate in the active site. Comparison with other bacterial PDCs shows a correlation of higher thermostability with greater tetramer interface area and number of interactions.

year: 2016

title: How learning stories shape understandings of children’s learning identities in one community of practice: A narrative inquiry

authors: Sands, Lorraine May

subjects: Narrative inquiry

abstract: Mā te mahi, ka mōhio; mā te mōhio, ka mārama; mā te mārama, ka mātau; mā te mātau, ka ora.
From hard work comes knowledge; from that knowledge comes understanding; from that understanding comes strength; from that strength comes wellbeing and life.
This thesis is a listening, dialogic investigation into ways the community of learners at Greerton Early Learning Centre considers learning stories have affected their children’s learning identities—that is, how they view themselves as learners. Aotearoa New Zealand’s early childhood curriculum, Te Whāriki, focuses on responsive, reciprocal relationships wrapped around the uniqueness and mana of each child. Learning stories—a research-based sociocultural narrative assessment approach—have been used in Aotearoa New Zealand early learning settings for over two decades to capture children’s learning while honouring the intent of Te Whāriki to nurture children’s languages, cultures, and identities. In the current climate of privatisation and neoliberalism, however, the value of learning stories is increasingly contested. This study refutes such discourses and instead navigates the value of multiple ways of knowing, meaningfully embedded in the lived experiences of children in relational communities.

This study was embedded in a narrative inquiry paradigm that sees reality as a socially mediated construction contained within stories that are told and retold across times, social contexts, and places. The study aimed to understand and document how storying children’s lived experience makes a meaningful difference to ways children view themselves as learners. Six children, their families, and their teachers were invited to reengage with selected learning stories from the children’s learning portfolios and then to rethink and retell how these learning stories contributed to their views of children’s learning identities.

The study found that learning stories have powerful effects on the ways children see themselves and on the ways those around them see the children as learners. It was clear from the data that children’s learning identities are embedded in the complex social and cultural contexts that surround them. The teachers’ long-term whanaungatanga relationships with mokopuna and whānau enabled kaiako to write learning stories that connected meaningfully with children’s wider historical, social, and cultural contexts. Insights into children’s learning from the learning stories were actively taken up by the parents and shaped the ways they saw and interacted with their children as learners. Likewise, teachers listened to stories shared from home (whether in a written learning story form or simply in the course of conversations), and these contributed to the teachers’ understandings of the children as agentic learners within sociocultural contexts. The physical folders of learning stories offered children powerful ways to maintain connections and a sense of pride in their learning achievements, linked to the people and places that surrounded those achievements.

Learning stories also enabled children to review their learning growth over time, including times when they had set goals, been supported in pursuing those goals by those around them, and had their achievements and dispositions honoured through documentation as a learning story. The process of robust engagement with crafting and reviewing their own and their colleagues’ learning stories played an important role in teachers’ ongoing professional learning. Finally, it was clear that across the whole community of practice—spanning mokopuna, whānau, and kaiako—learning stories played an important role in developing and reinforcing a shared language of learning as well as a shared understanding of the importance of children’s dispositions and working theories as the most highly valued forms of learning.

Although centred in one community, this research stands on the shoulders of many and may have resonance and implications for those in broader contexts. At a time when the usefulness and appropriateness of learning stories are increasingly contested, this study provides an important demonstration of the power of thoughtfully written learning stories and the alignment of this assessment approach with the vision and values of Te Whāriki. Further, with limited past research looking at the intersection of learning stories and children’s learning identities, this study’s rich account of this interaction in one community of practice provides a valuable contribution to the literature.

text: How learning stories shape understandings of children’s learning identities in one community of practice: A narrative inquiry Mā te mahi, ka mōhio; mā te mōhio, ka mārama; mā te mārama, ka mātau; mā te mātau, ka ora.
From hard work comes knowledge; from that knowledge comes understanding; from that understanding comes strength; from that strength comes wellbeing and life.
This thesis is a listening, dialogic investigation into ways the community of learners at Greerton Early Learning Centre considers learning stories have affected their children’s learning identities—that is, how they view themselves as learners. Aotearoa New Zealand’s early childhood curriculum, Te Whāriki, focuses on responsive, reciprocal relationships wrapped around the uniqueness and mana of each child. Learning stories—a research-based sociocultural narrative assessment approach—have been used in Aotearoa New Zealand early learning settings for over two decades to capture children’s learning while honouring the intent of Te Whāriki to nurture children’s languages, cultures, and identities. In the current climate of privatisation and neoliberalism, however, the value of learning stories is increasingly contested. This study refutes such discourses and instead navigates the value of multiple ways of knowing, meaningfully embedded in the lived experiences of children in relational communities.

This study was embedded in a narrative inquiry paradigm that sees reality as a socially mediated construction contained within stories that are told and retold across times, social contexts, and places. The study aimed to understand and document how storying children’s lived experience makes a meaningful difference to ways children view themselves as learners. Six children, their families, and their teachers were invited to reengage with selected learning stories from the children’s learning portfolios and then to rethink and retell how these learning stories contributed to their views of children’s learning identities.

The study found that learning stories have powerful effects on the ways children see themselves and on the ways those around them see the children as learners. It was clear from the data that children’s learning identities are embedded in the complex social and cultural contexts that surround them. The teachers’ long-term whanaungatanga relationships with mokopuna and whānau enabled kaiako to write learning stories that connected meaningfully with children’s wider historical, social, and cultural contexts. Insights into children’s learning from the learning stories were actively taken up by the parents and shaped the ways they saw and interacted with their children as learners. Likewise, teachers listened to stories shared from home (whether in a written learning story form or simply in the course of conversations), and these contributed to the teachers’ understandings of the children as agentic learners within sociocultural contexts. The physical folders of learning stories offered children powerful ways to maintain connections and a sense of pride in their learning achievements, linked to the people and places that surrounded those achievements.

Learning stories also enabled children to review their learning growth over time, including times when they had set goals, been supported in pursuing those goals by those around them, and had their achievements and dispositions honoured through documentation as a learning story. The process of robust engagement with crafting and reviewing their own and their colleagues’ learning stories played an important role in teachers’ ongoing professional learning. Finally, it was clear that across the whole community of practice—spanning mokopuna, whānau, and kaiako—learning stories played an important role in developing and reinforcing a shared language of learning as well as a shared understanding of the importance of children’s dispositions and working theories as the most highly valued forms of learning.

Although centred in one community, this research stands on the shoulders of many and may have resonance and implications for those in broader contexts. At a time when the usefulness and appropriateness of learning stories are increasingly contested, this study provides an important demonstration of the power of thoughtfully written learning stories and the alignment of this assessment approach with the vision and values of Te Whāriki. Further, with limited past research looking at the intersection of learning stories and children’s learning identities, this study’s rich account of this interaction in one community of practice provides a valuable contribution to the literature.

year: 2022