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Spin crossover in iron(II) dinuclear helicates and tetranuclear cages
No full textAmongst the 151 discrete di- to poly-nuclear spin crossover (SCO) active assemblies of Fe(II) published before July 2020, only 19 are Fe(II) triply bridged dinuclear helicates (Fe2L3) and only 6 are edge bridged tetranuclear cages (Fe4L6). Brooker and coworkers have reported numerous examples of mononuclear SCO-active Fe(II) complexes of monotopic bidentate Rdpt (4-R-substituted-3,5-di(2-pyridinyl)-1,2,4-triazole) type ligands. This thesis builds on that foundation by developing new classes of ditopic Rdpt type ligands, for the self-assembly of new classes of SCO-active triply bridged dinuclear helicates (Fe2L3) and edge bridged tetranuclear tetrahedral cages (Fe4L6).
Chapter 1 starts with a brief introduction to SCO. Then the 151 SCO-active discrete di- to poly-nuclear Fe(II) architectures, from dinuclear Fe2L3 to octanuclear Fe8L12, and the ligand designs used to access them, reported before July 2020, are comprehensively reviewed, followed by selected examples of Rdpt type Fe(II) complexes from the literature. Finally, the new class of ditopic Rdpt type ligands, which feature bis-bidentate azine-triazole or azole-triazole binding pockets (Rat) and the corresponding iron(II) complexes that are targeted in this thesis, are introduced.
Chapter 2 presents the extension of our general protocol to the synthesis of the first generation of robust ditopic Rat ligands, which feature meta-phenylene linked (L2/4pym-meta) and para-phenylene linked (L2/4pym-para) bidentate azine-triazole binding pockets. The four ditopic Rat ligands enabled the assembly of two distinct supramolecular architectures, the structurally characterised pair of dinuclear helicates [FeII2Lnpym-meta3](BF4)4 and pair of tetranuclear tetrahedral cages [FeII4Lnpym-para6](BF4)8 (n = 2 and 4). Solution (UV-vis and Evans method 1H NMR spectroscopy) studies of all four complexes revealed that they remain low spin, confirming that coordination by three azine-triazole binding pockets imposes too strong a ligand field.
In order to reduce the ligand field strength, in Chapter 3, the first Rat ligands to feature azoles, not azines, in the binding pocket were accessed. A pair of monotopic azole-triazole Rat ligands (L4NMe/SIm) was synthesised by extension of our general protocol. In contrast to the low spin tris(azine-triazole) coordinated Fe(II) complexes, these new tris(azole-triazole) coordinated complexes, [Fe(L4NMeIm)3]2+ and [Fe(L4SIm)3]2+, are high spin and SCO-active, respectively, in both solid and solution. This confirmed the expected reduced ligand field strength of the azoles compared with the azine analogues.
Hence, in Chapters 4 and 5, these azole-triazole bidentate binding pockets were incorporated into a second generation of reduced ligand field ditopic Rat ligands, to enable the self-assembly of SCO-active dinuclear helicates (Chapter 4 meta-phenylene linker) and tetranuclear cages (Chapter 5 para-phenylene linker).
Specifically, in Chapter 4, five second generation ditopic bis-bidentate Rat ligands, Lazole-meta (azole: 2 and 4-imidazole, 1-methyl-4-imidazole, 4-oxazole and 4-thiazole), were prepared and shown to enable assembly of five structurally characterised SCO-active dinuclear helicates, [FeII2Lazole-meta3]4+. Variable temperature solution studies (UV-vis and Evans method NMR spectroscopy) and cyclic voltammetry studies in MeCN confirmed that all of the five helicates are SCO-active and that the choice of non-coordinated heteroatom influences the ligand field strength, SCO temperature and the redox potential of the Fe(II) centre. In general, the higher the high spin fraction present in the solution, the easier the Fe(II) centre was to oxidise. Furthermore, DOSY NMR spectroscopy was successfully used to characterise the dinuclear helicates regardless of the spin state.
Chapter 5 presents the first pair of second generation ditopic Rat ligands (L4NMeIm-para and L4SIm-para) and the self-assembly of a pair of edge-bridged tetranuclear cages, HS [FeII4L4NMeIm-para6]8+ and SCO-active [FeII4L4SIm-para6]8+. Comparison of the variable temperature solid state magnetic and MeCN solution (UV-vis and Evans method NMR spectroscopy) studies of the cages and the analogous helicates confirmed that the meta-phenylene linked ligands in the dinuclear helicates provide a stronger ligand field than the para-phenylene linked ligands do in the tetranuclear cages.
Finally, in Chapter 6, the key findings are summarised and some future directions are suggested
Determining How Chinese Consumers that Purchase Western Food Products Prioritize Food Safety Cues: A Conjoint Study on Adult Milk Powder
No full textThis study investigated how Chinese consumers prioritize cues when assessing the safety of imported milk powder. A choice-based conjoint survey was completed by 307 participants in Beijing, Shanghai, Tianjin, and Nanjing, using the internet-based software 1000minds. Important cues for consumers were “government certification logo shown on the product label/Website”; “ingredients and materials, free from preservatives and additives”; “having traceability techniques such as QR code included” and “realistic photos.” Distinct consumer segments reflecting differing trade-offs between safety cues were not detected suggesting that a single food safety communication strategy for this market may be sufficient. These findings add to extant literature by highlighting what cues give consumers the most confidence a product is safe and they provide a raft of actionable insights for government and the food industry in terms of designing and implementing effective risk or market communication strategies for Chinese consumers
The heterogeneity of women entrepreneurial spirit and the influence on strategy making
No full textAs one of the important driving forces of innovation, entrepreneurship is of vital significance to enterprises' development and strategic decision-making. However, the current research has been focusing on the broad concept of entrepreneurship or directly comparing the differences between male and female entrepreneurs, and few attentions have been paid to the heterogeneity within female entrepreneurship. Based on upper echelons theory, this study focuses on the heterogeneity of female entrepreneurship, and explores the antecedents on the development of female entrepreneurship and also the influence of different aspects of female entrepreneurship on important strategic decisions of enterprises. Based on the survey data analysis of 116 Chinese female entrepreneurs, this study finds that a harmonious family background, diversified work experience and higher educational background are conducive to the female entrepreneurship development in the aspects of humanistic care, expression and communication skills and self-control ability accordingly. The results also show that the more women entrepreneurs pay attention to humanistic care, the more likely their companies engage in corporate social responsibility activities. Female entrepreneurs with strong self-control ability tend to be more likely to promote the international diversification development of enterprises. These findings provide implications for the development of female entrepreneurship and its influence on the strategic decision-making of enterprise development
Biogeochemical cycling of trace metals in shelf regions: The importance of cross-shelf exchange
No full textMarine phytoplankton form the base of the marine food web and are fundamental to the efficiency of the ocean’s ‘biological pump’. The biological pump is especially important in the homeostasis of atmospheric CO2 levels through the sequestration of carbon into the deep ocean via organic matter production in the surface ocean that utilizes metalloprotein enzymes or intermediates. Some of these metals are present at very low concentrations in the oceans, potentially limiting phytoplankton productivity, which has a significant effect on global carbon and climate cycles.
The primary processes controlling trace metal concentrations and distributions in the ocean are a combination of external inputs and removal processes, as well as internal recycling processes. The extent of these processes varies in different oceanic regions but generally they are all prominent in shelf locations. In particular, the recent increase in meltwater input from declining sea-ice and glaciers supplies the Southern Ocean with freshwaters containing additional sources of some trace metals. During the austral spring in the Western Antarctic Peninsula region, a substantial input of Fe into shelf surface waters occurred by meltwater input and sea-ice formation, and into shelf bottom waters by non-reductive sedimentary processes. However, the characterization of distinct meltwater sources is not well constrained to differentiate the sources of Fe-enriched meltwater. High precision isotopic analysis of the conservative element uranium (U) resolved subtle variations in the 234U/238U isotope ratio (reformulated into delta-notation as δ234U) and a linear correlation between δ234U and salinity in the Dotson-Getz Trough region, West Antarctica. A three-component mixing model using δ234U and salinity of possible endmembers predicts that glacial meltwater and Antarctic stream waters are the most likely freshwater sources that, in combination with sea-ice meltwater, control the observed δ234U – salinity variations in the Dotson-Getz Trough region, potentially in other shelf regions of Antarctica as well.
The importance of intruding open ocean waters and interaction with ice shelves as a source of trace metals to high-latitude shelf regions is apparent, but the influence of shelf processes on trace metal distributions in other oceanic regions remains limited, especially in low-nutrient, stratified waters, such as those across the northeastern continental shelf of New Zealand. This continental shelf, overlain by waters of the Hauraki Gulf, is relatively narrow and temporal variation in these processes, such as localized upwelling and the extent of subsurface water intrusion, results in the observed inter-annual variability in the concentrations and distributions of trace metals across the northeast continental margin of New Zealand.
These studies demonstrate the importance of cross-shelf exchange in connecting shelf and open ocean waters, and the profound influence this has on the regional and global concentrations and distributions of trace metal micronutrients. If the current trend of climate warming continues, it will result in increased rates of ice melt and elevated water temperatures. This will likely lead to stronger stratification, weakening vertical diffusivity between the surface water layer and the water beneath the pycnocline, which could drive surface water microorganisms into (micro-) nutrient limitation, resulting in a decreased efficiency of the global biological pump
Using the Systems-Practice Framework to Understand Food Allergen Management Practices at College Catering Operations: A Qualitative Study
No full textThe number of individuals with food allergies or intolerances attending catered university residential colleges is increasing, and safe dining options are required to minimize the risk of allergic reactions and food-induced death. This qualitative research study sought to advance professional knowledge of the factors affecting allergen management practices, particularly pertaining to college foodservices. Three catered residential colleges affiliated with a major university in New Zealand were selected as research sites. The study used an ethnographic approach and systems-practice theory as a framework for data collection and organizing results. Data collection techniques included document analyses (3 hours per site), observations (6 to 8 hours per site), focus groups with foodservice workers (30 to 45 minutes per site, n¼16), and interviews with foodservice managers (45 to 90 minutes per interview, n¼5). Notes and transcripts were coded through the process of thematic analysis using NVivo for Mac software, version 11.1.1, to identify factors affecting allergen management practices. The main factors affecting allergen management practices at college foodservices included information provided by residents about dietary requirements; communication between residents and foodservice staff; systems for allergen management; attitude of foodservice staff; and college size. Detailed dietary information, effective communication with residents, sufficient resources, clarification of responsibilities, and thorough systems are required for staff to perform safe allergen management practices. Ultimately, successful implementation was predominantly determined by staff attitude. Foodservice managers are advised to identify motivators and address barriers of staff attitudes toward allergen management practices to promote successful implementation
Post-disaster housing recovery and community resilience: the case of the Canterbury earthquakes of 2010 and 2011
No full textBackground:
After a major natural disaster like the Canterbury earthquakes of 2010 and 2011, western democracies like New Zealand tend to enact top-down recovery statutes and regulations that are thought to enable a nimble response to national emergencies, save lives, and restore social order. But these statutory changes in governance not only determine the sustainability of the natural and built environments. They can also affect the wellbeing of those impacted, impairing their democratic ability to have a say and actively participate in the urban renewal processes taking place around them. What does this mean in terms of community action and resilience? This project is a case study of post-disaster housing recovery in Christchurch after the Canterbury earthquake of 2010 and 2011.
Aims:
In this qualitative study, I analysed the statutory framework governing the process of post-disaster housing recovery in Christchurch and its impact on local democracy. I also explored the role of communities and the third sector in housing and urban renewal. This aim was to contribute to the development of a critical theoretical understanding of community resilience as an inherently political concept. Community resilience is influenced by causal factors or generative mechanisms that impact upon the relations between people in a particular social context. I undertook this empirical study to develop a critical realist approach to understanding community resilience.
Methods:
I completed a narrative synthesis of textual data, derived from a thematic analysis of in-depth interviews with key informants, related policies, media, and fieldwork.
Results:
I found that a centralisation of government authority over housing recovery resulted in an erosion of democracy and representative government at a local level. This centralisation had a major impact on communities and their voice in the process of post-disaster housing recovery. Communities, however, never relented and worked tirelessly among themselves and with other social sectors to make a positive impact to post-disaster housing and urban recovery against difficult odds and stretched resources. This immense social capital and inspiring sense of community must be fostered and given the opportunity to democratically participate in the development of recovery policy as a key element of community resilience
Reframing communications that encourage individuals to reduce food waste
No full textThe waste of edible food throughout the food chain is recognised as a global issue and academic research focuses on how to encourage reductions in this waste. At the consumer level, governments are investing in communication campaigns that encourage individuals to reduce the amount of edible food discarded in their home-based activities. The specific aims of this paper were to identify causes of food waste and what experts recommend for reducing the problem, to identify gaps between information provided in food waste communication campaigns and the experts recommendations, and finally to empirically identify further gaps between individuals’ knowledge of food waste with a framework of the expert recommendations. In terms of findings, the literature review identified a range of causes and nine relevant expert recommendations for reducing this waste. An evaluation of a number of major consumer-focused communication campaigns available in Australia and New Zealand provided evidence that these campaigns were addressing some of the recommendations from experts. A subsequent qualitative investigation of household members’ knowledge of the issues of food discard showed that individuals’ understandings can be prioritised in terms of the expert recommendations and the communication messages in the campaigns. Further research is identified based on these findings
Effect of information on Chinese consumers’ perceptions and purchase intention for beverages processed by High Pressure Processing, Pulsed-Electric Field and Heat Treatment
No full textHigh Pressure Processing (HPP) and Pulsed-Electric Field (PEF) are non-thermal technologies that add value to foods by improving safety through lowering microbial loads in addition to improving the sensory properties such as color, flavor, and texture. While Heat Treatment (HT) is more widely accepted by consumers, it is a more destructive process compared to HPP and PEF. Little is known about how Chinese consumers perceive non-thermal technologies like HPP and PEF. This research aimed to understand Chinese consumer’s perceptions of non-thermal processing technologies and ways to mitigate negative perceptions. Specifically, this research sought to investigate: (a) consumers’ general knowledge of food processing technologies; (b) the effect of information on consumers’ perceptions of HT, HPP and PEF and how these perceptions influence decisions for their treated beverages; and (c) consumers’ willing-ness to pay for products processed using these technologies. Six focus groups were conducted in Hangzhou, China. When participants were provided limited and detailed technology information, six dominant consumer perceptions towards HT, HPP, and PEF emerged. Those perceptions were: (1) consumer association with the given technology, (2) trust towards the technology, (3) health, (4) food, (5) taste and quality, and (6) price. When limited information was provided, consumers were skeptical of HPP and PEF. However, the provision of detailed technology information changed participants’ attitudes towards HPP and PEF technologies and increased their stated purchase intentions for the treated products. Participants were also found to place less emphasis on the price for HPP and PEF treated beverages when detailed technology information was provided. Chinese consumers were interested in having fewer additives in their foods. Non-thermally processed foods offer this benefit. Given the change in attitudes after receiving detailed information, HPP and PEF processing technologies have potential to be widely accepted by Chinese consumers. However, to effectively promote these technologies, consumer education is needed to increase awareness of the advantages these technologies have for foods. Practical communication strategies are provided to help food manufacturers inform Chinese consumers about the benefits of these technologies
Hidden diversity of two intracellular parasites, Microsporidia and Rickettsia, in New Zealand amphipod hosts: patterns and causes
No full textIntracellular parasites, endosymbionts that are specialised to live in host cells, have evolved independently in many different lineages. Endosymbionts can be transmitted vertically and horizontally, and many of them maintain intimate associations with their hosts over space and time. For example, the mitochondrion, which is now an essential organelle in eukaryotes, is believed to have an endosymbiotic origin.
This thesis focuses on two intracellular parasite groups, Microsporidia and Rickettsia, in diverse amphipod hosts in New Zealand. Microsporidia and Rickettsia are phylogenetically distantly related, but both are ecologically and evolutionary successful in diverse groups of hosts. I aimed to understand their diversity, the factors that have shaped their current distribution, the various phylogenetic patterns they are involved in, their spatiotemporal variations and cooccurrence, and their evolutionary histories.
By starting with molecular screening of diverse amphipods collected throughout the country, I uncovered a diversity that was previously unknown in this region, a first for both groups in the Southern Hemisphere. For Microsporidia, by expanding their known geographical and host ranges, I applied phylogenetic and cophylogenetic methods to infer the evolutionary history of host-parasite associations. Based on the congruent phylogenetic and phylogeographical patterns, I provided evidence for their shared evolutionary histories.
Some vertically transmitted parasites can manipulate host reproduction, and this can have various ecological and evolutionary consequences. Certain endosymbionts are known to disrupt phylogenetic patterns of mitochondrial DNA mainly due to linkage disequilibrium. I discussed the direct and indirect impacts of Rickettsia infections on the use of mitochondrial DNA in barcoding, phylogenetic, and phylogeographical studies. Also, I explored the possible role of Rickettsia infections in accelerating host mitochondrial DNA evolution, which could result in mitonuclear discordance patterns appearing on deep time scales.
Because Microsporidia and Rickettsia share the same amphipod hosts and coexist in many populations, they may interact with each other within the same individual. I investigated spatiotemporal dynamics in the prevalence of both parasites, and tested whether infection by one parasite influences the probability of infection by the other. Although there were variations in prevalence among different sampling times and locations, there were no clear consistent patterns between the two parasites and their patterns of co-occurrence within the same individual hosts did not depart from random expectations.
Taken together, Microsporidia and Rickettsia are widespread in New Zealand amphipod hosts. It seems that both vertical and horizontal transmission have played important roles in their current distribution. The vertical transmission of endosymbionts seems to have great potential to cause profound effects on host mitochondrial DNA. However, demonstrating this will require more data from multiple systems and scales. In the future, population- to community-level studies will be especially valuable to understand the ecological interactions between hosts and parasites and among different strains/species/groups of parasites