title: Geochemically defined space-for-time transects successfully capture microbial dynamics along lacustrine chronosequences in a polar desert

authors: Monteiro, Maria R.

subjects: Science & Technology

abstract: The space-for-time substitution approach provides a valuable empirical assessment to infer temporal effects of disturbance from spatial gradients. Applied to predict the response of different ecosystems under current climate change scenarios, it remains poorly tested in microbial ecology studies, partly due to the trophic complexity of the ecosystems typically studied. The McMurdo Dry Valleys (MDV) of Antarctica represent a trophically simple polar desert projected to experience drastic changes in water availability under current climate change scenarios. We used this ideal model system to develop and validate a microbial space-for-time sampling approach, using the variation of geochemical profiles that follow alterations in water availability and reflect past changes in the system. Our framework measured soil electrical conductivity, pH, and water activity in situ to geochemically define 17 space-for-time transects from the shores of four dynamic and two static Dry Valley lakes. We identified microbial taxa that are consistently responsive to changes in wetness in the soils and reliably associated with long-term dry or wet edaphic conditions. Comparisons between transects defined at static (open-basin) and dynamic (closed-basin) lakes highlighted the capacity for geochemically defined space-for-time gradients to identify lasting deterministic impacts of historical changes in water presence on the structure and diversity of extant microbial communities. We highlight the potential for geochemically defined space-for-time transects to resolve legacy impacts of environmental change when used in conjunction with static and dynamic scenarios, and to inform future environmental scenarios through changes in the microbial community structure, composition, and diversity.

text: Geochemically defined space-for-time transects successfully capture microbial dynamics along lacustrine chronosequences in a polar desert The space-for-time substitution approach provides a valuable empirical assessment to infer temporal effects of disturbance from spatial gradients. Applied to predict the response of different ecosystems under current climate change scenarios, it remains poorly tested in microbial ecology studies, partly due to the trophic complexity of the ecosystems typically studied. The McMurdo Dry Valleys (MDV) of Antarctica represent a trophically simple polar desert projected to experience drastic changes in water availability under current climate change scenarios. We used this ideal model system to develop and validate a microbial space-for-time sampling approach, using the variation of geochemical profiles that follow alterations in water availability and reflect past changes in the system. Our framework measured soil electrical conductivity, pH, and water activity in situ to geochemically define 17 space-for-time transects from the shores of four dynamic and two static Dry Valley lakes. We identified microbial taxa that are consistently responsive to changes in wetness in the soils and reliably associated with long-term dry or wet edaphic conditions. Comparisons between transects defined at static (open-basin) and dynamic (closed-basin) lakes highlighted the capacity for geochemically defined space-for-time gradients to identify lasting deterministic impacts of historical changes in water presence on the structure and diversity of extant microbial communities. We highlight the potential for geochemically defined space-for-time transects to resolve legacy impacts of environmental change when used in conjunction with static and dynamic scenarios, and to inform future environmental scenarios through changes in the microbial community structure, composition, and diversity.

year: 2022

title: Modelling heat transfer during chilling and freezing of packaged foods in industrial refrigeration facilities

authors: Hoang, Duy

subjects: Modelling

abstract: Industrial refrigeration equipment companies are continuously looking for ways to optimise the design of chilling and freezing tunnels in order to minimise food quality loss and increase the energy efficiency of the equipment. However, possibilities for dedicated experimental tests of the industrial operations are limited due to a large amount of food product involved while the number of design variables to be considered is high. A cost-effective alternative to experiments is numerical modelling. The main goal of this research was to simulate heat transfer of packaged food products in a chilling and freezing tunnel. Computational fluid dynamics (CFD) models were developed to improve prediction in industrial cheese chilling and chicken freezing. The industrial cheese chilling model was developed based on six blocks of agar that mimic the product arrangement and airflow pattern of a cheese chiller; while the chicken freezing model represents the first case of a CFD freezing model where the geometry was derived empirically via computed tomography scan data. The model predictions were validated by experimental temperature histories generated as part of the study. Once validated, the model was used to investigate the cooling heterogeneity and the effect of different operating conditions on the processing time. In addition to the CFD model, a simple heat transfer simulation based on the one-dimensional finite difference method was developed for industrial users. Thermal property models in the literature were also reviewed to propose the most suitable choice for thermal processing calculations.

text: Modelling heat transfer during chilling and freezing of packaged foods in industrial refrigeration facilities Industrial refrigeration equipment companies are continuously looking for ways to optimise the design of chilling and freezing tunnels in order to minimise food quality loss and increase the energy efficiency of the equipment. However, possibilities for dedicated experimental tests of the industrial operations are limited due to a large amount of food product involved while the number of design variables to be considered is high. A cost-effective alternative to experiments is numerical modelling. The main goal of this research was to simulate heat transfer of packaged food products in a chilling and freezing tunnel. Computational fluid dynamics (CFD) models were developed to improve prediction in industrial cheese chilling and chicken freezing. The industrial cheese chilling model was developed based on six blocks of agar that mimic the product arrangement and airflow pattern of a cheese chiller; while the chicken freezing model represents the first case of a CFD freezing model where the geometry was derived empirically via computed tomography scan data. The model predictions were validated by experimental temperature histories generated as part of the study. Once validated, the model was used to investigate the cooling heterogeneity and the effect of different operating conditions on the processing time. In addition to the CFD model, a simple heat transfer simulation based on the one-dimensional finite difference method was developed for industrial users. Thermal property models in the literature were also reviewed to propose the most suitable choice for thermal processing calculations.

year: 2020

title: Pākehā counsellors consider their positioning: Towards postcolonial praxis

authors: Crocket, Alastair Robert

subjects: Counselling

abstract: The challenges of achieving the potential, which the Treaty of Waitangi offers for a postcolonial present and future, have shaped life in Aotearoa New Zealand over the last four decades. This thesis draws on this history and challenge to consider the practice possibilities for Pākehā counsellors when they work with clients and colleagues of other cultures. It is strongly influenced by the Treaty of Waitangi but seeks not to be limited to a Māori/Pākehā binary. It has been undertaken in the hopes of informing developments in the practice of students seeking to qualify to work as counsellors and more experienced practitioners. The first theoretical foundation for this study is poststructuralism which is considered as a braided stream of theorizing where braids divide and unite. A Foucauldian social constructionism underlies this project, which extends to a consideration of subjectification, agency and positioning theory. This study is also intentionally postcolonial drawing on Said’s seminal works, Orientalism (1979) and Culture and Imperialism (1993) and North American and European writing about identity politics and intersectionality. It views the centring of the Treaty of Waitangi in this land as postcolonial work. These two emphases, poststructuralism and postcolonialism, provide the theoretical base for an exploration of the context of professional counselling practice in Aotearoa New Zealand. Five experienced counsellors constituted a research group who firstly discussed practising as a Pākehā counsellor and then acknowledged their hopes and fears for their practice with clients of other cultures. In later stages of the data generation the participants were invited to join in processes of discourse analysis and deconstruction which produced shifts in practice and practice identity. This study identifies two forms of praxis that might inform a counselling practice which seeks to achieve a postcolonial purpose: these are named as critical discursive praxis and critical Pākehā praxis.

text: Pākehā counsellors consider their positioning: Towards postcolonial praxis The challenges of achieving the potential, which the Treaty of Waitangi offers for a postcolonial present and future, have shaped life in Aotearoa New Zealand over the last four decades. This thesis draws on this history and challenge to consider the practice possibilities for Pākehā counsellors when they work with clients and colleagues of other cultures. It is strongly influenced by the Treaty of Waitangi but seeks not to be limited to a Māori/Pākehā binary. It has been undertaken in the hopes of informing developments in the practice of students seeking to qualify to work as counsellors and more experienced practitioners. The first theoretical foundation for this study is poststructuralism which is considered as a braided stream of theorizing where braids divide and unite. A Foucauldian social constructionism underlies this project, which extends to a consideration of subjectification, agency and positioning theory. This study is also intentionally postcolonial drawing on Said’s seminal works, Orientalism (1979) and Culture and Imperialism (1993) and North American and European writing about identity politics and intersectionality. It views the centring of the Treaty of Waitangi in this land as postcolonial work. These two emphases, poststructuralism and postcolonialism, provide the theoretical base for an exploration of the context of professional counselling practice in Aotearoa New Zealand. Five experienced counsellors constituted a research group who firstly discussed practising as a Pākehā counsellor and then acknowledged their hopes and fears for their practice with clients of other cultures. In later stages of the data generation the participants were invited to join in processes of discourse analysis and deconstruction which produced shifts in practice and practice identity. This study identifies two forms of praxis that might inform a counselling practice which seeks to achieve a postcolonial purpose: these are named as critical discursive praxis and critical Pākehā praxis.

year: 2010