title: High temperature mechanical properties of Ti-47Al-2Cr (at %) alloy produced using powder compact forging of a mechanically milled powder

authors: Nadakuduru, Vijay Navaratna

subjects: engineering

abstract: Ultrafine grained (UFG) Ti-47Al-2Cr (at %) alloy was prepared using a combination of high energy ball milling of a mixture of elemental powders to produce a Ti/Al/Cr composite powder and forging of compacts of this composite powder. The microstucture of the powder forged alloy was found to be dependent on the initial condition of the powder. The alloy produced by this method has demonstrated good formability, both in tensile and compression testings at elevated temperatures. A ductility of 80–165% in tension has been observed, while in a compression plastic strain of ~ 50% was found to be easily achievable, without causing cracking. The deformation behaviour of the particular alloy in tension and compression at elevated temperature has been discussed in detail. The results from the present investigation indicate that UFG Ti-47Al-2Cr (at %) alloy produced using powder compact forging has good formability, and is suitable precursor for near-net shaping using thermomechanical processes such as forging and superplastic forming.

text: High temperature mechanical properties of Ti-47Al-2Cr (at %) alloy produced using powder compact forging of a mechanically milled powder Ultrafine grained (UFG) Ti-47Al-2Cr (at %) alloy was prepared using a combination of high energy ball milling of a mixture of elemental powders to produce a Ti/Al/Cr composite powder and forging of compacts of this composite powder. The microstucture of the powder forged alloy was found to be dependent on the initial condition of the powder. The alloy produced by this method has demonstrated good formability, both in tensile and compression testings at elevated temperatures. A ductility of 80–165% in tension has been observed, while in a compression plastic strain of ~ 50% was found to be easily achievable, without causing cracking. The deformation behaviour of the particular alloy in tension and compression at elevated temperature has been discussed in detail. The results from the present investigation indicate that UFG Ti-47Al-2Cr (at %) alloy produced using powder compact forging has good formability, and is suitable precursor for near-net shaping using thermomechanical processes such as forging and superplastic forming.

year: 2009

title: Enzymic approach to eurythermalism of Alvinella pompejana and its Episymbionts

authors: Lee, Charles Kai-Wu

subjects: biology

abstract: The equilibrium model, which describes the influence of temperature on enzyme activity, has been established as a valid and useful tool for characterizing enzyme eurythermalism and thermophily. By introducing Keq, a temperature-dependent equilibrium constant for the interconversion between Eact, the active form of enzyme, and Einact, a reversibly inactive form of enzyme, the equilibrium model currently provides the most complete description of the enzyme-temperature relationship; its derived parameters are intrinsic and apparently universal and, being derived under reaction conditions, potentially have physiological significance. One of these parameters, Teq, correlates with host growth temperature better than enzyme stability does. The vent-dwelling annelid Alvinella pompejana has been reported as an extremely eurythermal organism, and the symbiotic complex microbial community associated with its dorsal surface is likely to experience similar environmental thermal conditions. The A. pompejana episymbiont community, predominantly composed of epsilonproteobacteria, has been analyzed metagenomically, enabling direct retrieval of genes coding for enzymes suitable for equilibrium model applications. Two such genes, coding for isopropylmalate dehydrogenase and glutamate dehydrogenase, have been isolated from the A. pompejana episymbionts, heterologously expressed, and shown by reverse transcription-quantitative PCR to be actively expressed. The equilibrium model parameters of characterized expression products suggested that enzyme eurythermalism constitutes part of the thermal adaptation strategy employed by the episymbionts. Moreover, the enzymes' thermal characteristics correspond to their predicted physiological roles and the abundance and expression of the corresponding genes. This paper demonstrates the use of the equilibrium model as part of a top-down metagenomic approach to studying temperature adaptation of uncultured organisms.

text: Enzymic approach to eurythermalism of Alvinella pompejana and its Episymbionts The equilibrium model, which describes the influence of temperature on enzyme activity, has been established as a valid and useful tool for characterizing enzyme eurythermalism and thermophily. By introducing Keq, a temperature-dependent equilibrium constant for the interconversion between Eact, the active form of enzyme, and Einact, a reversibly inactive form of enzyme, the equilibrium model currently provides the most complete description of the enzyme-temperature relationship; its derived parameters are intrinsic and apparently universal and, being derived under reaction conditions, potentially have physiological significance. One of these parameters, Teq, correlates with host growth temperature better than enzyme stability does. The vent-dwelling annelid Alvinella pompejana has been reported as an extremely eurythermal organism, and the symbiotic complex microbial community associated with its dorsal surface is likely to experience similar environmental thermal conditions. The A. pompejana episymbiont community, predominantly composed of epsilonproteobacteria, has been analyzed metagenomically, enabling direct retrieval of genes coding for enzymes suitable for equilibrium model applications. Two such genes, coding for isopropylmalate dehydrogenase and glutamate dehydrogenase, have been isolated from the A. pompejana episymbionts, heterologously expressed, and shown by reverse transcription-quantitative PCR to be actively expressed. The equilibrium model parameters of characterized expression products suggested that enzyme eurythermalism constitutes part of the thermal adaptation strategy employed by the episymbionts. Moreover, the enzymes' thermal characteristics correspond to their predicted physiological roles and the abundance and expression of the corresponding genes. This paper demonstrates the use of the equilibrium model as part of a top-down metagenomic approach to studying temperature adaptation of uncultured organisms.

year: 2007

title: Culturally-Oriented Environmental Identity Transitions: Migrant Indian Teachers in Aotearoa New Zealand Early Childhood Education

authors: Rathore, Devika

abstract: An increasingly multicultural Aotearoa New Zealand early childhood education (ECE) landscape that includes a growing number of migrant teachers forms the context for my doctoral study. In this country, respect for the natural world and kaitiakitanga are integral to the ECE bicultural curriculum framework Te Whāriki (Ministry of Education [MoE], 2017) which is grounded in Indigenous Māori worldviews that acknowledge strong spiritual connections to land and place. The natural environment is considered an integral part of the national identity and early childhood has been recognised as an important stage when Environmental and Sustainability Education should begin.   

Within the context of this superdiverse nation, a significant number of migrant teachers transfer their cultural and environmental knowledge, practice, and identity as they transition into the Aotearoa New Zealand context. This thesis explored migrant Indian teachers’ understandings of their culturally-oriented and negotiated environmental identities. I was keen to examine if the environment might hold different meanings and places in their home (Indian) and host (Aotearoa New Zealand) cultural systems.   

Through this study, insights were gained into migrant Indian teachers’ perceptions of the influence of cultural identity on their environmental identities in Aotearoa New Zealand ECE. A sociocultural theoretical perspective informed this study, drawing primarily on Sauvé’s (2009) model of personal and social development of the self in relation to other humans and the environment. Primary data for this interpretivist study were gathered through in-depth interviews with nine Indian ECE teacher participants. Interviews with their ECE setting managers/head teachers were conducted to support and supplement the teachers’ practices and experiences. The audio-recorded interview data were transcribed and examined using thematic analysis. Observations of teacher participants’ workplaces were used to provide a contextual profile for each of the nine Indian teachers. I also obtained a small number of assessment documents in the form of Learning Stories which the teachers had prepared, to analyse them for cultural and environmental themes and experiences.   

Indian teacher participants’ perceptions of their own culturally-oriented environmental identities highlighted the significance of teachers’ own early childhood environmental experiences and home cultural context influences on their environmental identities. Teacher participants’ perceptions shed light on their cultural and environmental identity transitions and acculturation process. These teachers brought their cultural and environmental identities from their home cultural context and used their cultural lens to interpret the connections between the host cultural context and environmental worldviews.   

The Indian teacher participants perceived close connections between their cultural and environmental identities. At the same time, they recognised cross-cultural connections between their culturally-oriented environmental identities and tikanga Māori (Māori ways of doing including practices, customs and rituals) and te ao Māori (the Māori world). These perceived connections were most evident through the significance of Indian philosophies of spirituality, relationships, belonging, and cultural recognition and exchange in their specific ECE contexts. These connections facilitated teachers’ cultural and environmental identity transitions and had a positive impact on their cultural and environmental teaching practices when supported within the ECE setting and by management/leadership.   

Cultural and environmental transitions for this steadily growing group of migrant teachers require further investigation to facilitate their cultural and environmental participation and acculturation into the Aotearoa New Zealand ECE context. In these ways, the existing cultural, environmental, and sustainability connections within ECE could be strengthened to foster children’s culturally-oriented environmental identities.

text: Culturally-Oriented Environmental Identity Transitions: Migrant Indian Teachers in Aotearoa New Zealand Early Childhood Education An increasingly multicultural Aotearoa New Zealand early childhood education (ECE) landscape that includes a growing number of migrant teachers forms the context for my doctoral study. In this country, respect for the natural world and kaitiakitanga are integral to the ECE bicultural curriculum framework Te Whāriki (Ministry of Education [MoE], 2017) which is grounded in Indigenous Māori worldviews that acknowledge strong spiritual connections to land and place. The natural environment is considered an integral part of the national identity and early childhood has been recognised as an important stage when Environmental and Sustainability Education should begin.   

Within the context of this superdiverse nation, a significant number of migrant teachers transfer their cultural and environmental knowledge, practice, and identity as they transition into the Aotearoa New Zealand context. This thesis explored migrant Indian teachers’ understandings of their culturally-oriented and negotiated environmental identities. I was keen to examine if the environment might hold different meanings and places in their home (Indian) and host (Aotearoa New Zealand) cultural systems.   

Through this study, insights were gained into migrant Indian teachers’ perceptions of the influence of cultural identity on their environmental identities in Aotearoa New Zealand ECE. A sociocultural theoretical perspective informed this study, drawing primarily on Sauvé’s (2009) model of personal and social development of the self in relation to other humans and the environment. Primary data for this interpretivist study were gathered through in-depth interviews with nine Indian ECE teacher participants. Interviews with their ECE setting managers/head teachers were conducted to support and supplement the teachers’ practices and experiences. The audio-recorded interview data were transcribed and examined using thematic analysis. Observations of teacher participants’ workplaces were used to provide a contextual profile for each of the nine Indian teachers. I also obtained a small number of assessment documents in the form of Learning Stories which the teachers had prepared, to analyse them for cultural and environmental themes and experiences.   

Indian teacher participants’ perceptions of their own culturally-oriented environmental identities highlighted the significance of teachers’ own early childhood environmental experiences and home cultural context influences on their environmental identities. Teacher participants’ perceptions shed light on their cultural and environmental identity transitions and acculturation process. These teachers brought their cultural and environmental identities from their home cultural context and used their cultural lens to interpret the connections between the host cultural context and environmental worldviews.   

The Indian teacher participants perceived close connections between their cultural and environmental identities. At the same time, they recognised cross-cultural connections between their culturally-oriented environmental identities and tikanga Māori (Māori ways of doing including practices, customs and rituals) and te ao Māori (the Māori world). These perceived connections were most evident through the significance of Indian philosophies of spirituality, relationships, belonging, and cultural recognition and exchange in their specific ECE contexts. These connections facilitated teachers’ cultural and environmental identity transitions and had a positive impact on their cultural and environmental teaching practices when supported within the ECE setting and by management/leadership.   

Cultural and environmental transitions for this steadily growing group of migrant teachers require further investigation to facilitate their cultural and environmental participation and acculturation into the Aotearoa New Zealand ECE context. In these ways, the existing cultural, environmental, and sustainability connections within ECE could be strengthened to foster children’s culturally-oriented environmental identities.

year: 2024