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Solar Harvesting the Bright Way: Optimising Photon Multiplication with Novel Chromophores
No full textThe abundance of solar energy incident on the Earth’s surface offers immense potential for meeting current and future global energy demands. Photovoltaic cells, used for the harvesting of solar energy, are constrained by the thermodynamic Shockley-Queisser limit to a maximum of 34% efficiency. Photon multiplication offers a way to circumvent this limit by splitting a single high energy photon into two or more photons of lower energy. Singlet fission, an excitation multiplication process that occurs in some organic molecules, can be used to harness the excess energy of photons, followed by energy transfer to a quantum dot for re-emission, acting as a photon multiplication system.Singlet fission-based photon multipliers were recently developed, transferring triplets generated by singlet fission in a tetracene derivative to a lead sulfide quantum dot for emission, with a 17 ± 1% photoluminescence efficiency. Herein, we explore ways to improve this photon multiplication efficiency in a tetracene/PbS quantum dot-based system, through controlled design and synthesis of a range of novel tetracene chromophores to optimise quantum dot surface passivation. We functionalised PbS and PbS/CdS quantum dots with these novel tetracenes and measured the efficiencies of photon multiplication. We found that the addition of less tetracene to the quantum dot surface allowed efficient singlet fission without disrupting passivation. The overall photon multiplication efficiency using a PbS quantum dot emitter was found to be 36 ± 4%. The photon multiplication efficiency was further improved to 61 ± 6% with the addition of a CdS shell to aid in passivation of the emissive PbS core. As far as we are aware, these values are the highest reported singlet fission-based photon multiplication efficiencies to date.The primary limitation of current singlet fission photon multipliers is the use of quantum dots with only moderate emission efficiencies. While PbS emission efficiencies range from 10 – 70%, CsPbX3 (where X = Cl, Br or I) can reach close to 100% emission efficiency. Herein, we designed and synthesised a range of anthracene derivatives with different binding functionalities in an attempt to optimise surface functionalisation of highly emissive CsPbI3 nanocrystals. We used Stern-Volmer analysis on the synthesised anthracene derivatives and CsPbI3 nanocrystals. We found strong binding of all the anthracene derivatives, although, these systems were limited by the low (Another limitation to photon multiplication systems based on singlet fission in tetracene is the lack of absorption across the 360 – 450 nm region. Herein, we designed and synthesised two perylene- tetracene dyads to improve absorption across this region. Spectral analysis of these dyads found significant increases in absorption, without causing significant changes to the tetracene peak wavelength or shape. Energy transfer from perylene to tetracene was shown, with efficiencies estimated between 36 – 95%, demonstrating the ability for perylene sensitisation of tetracene. One of the synthesised sensitisers was then added to a tetracene/PbS quantum dot photon multiplier, both in solution and in solid state, and was found to negatively impact the emission efficiency of the PbS quantum dots in both cases.We also carried out an investigation into the unexpected solvent tuneable emission that was observed in the above perylene-tetracene dyads. We designed and synthesised two novel perylene-acene molecules for investigation into the scope of this tuneability. We performed solvent-dependent absorption and emission spectroscopy and it was found that this effect was observed across a series of perylene-tetracene molecules. This effect was extended into a perylene-pentacene dyad, offering excellent tuneability across the entire visible region. Transient absorption spectroscopy was used to investigate the mechanism of emission wavelength tuneability. It was proposed that tuneability arises from a charge separated state only accessible in more polar solvents that quickly decays once occupied.This thesis looked at optimising photon multiplication by controlling surface passivation of PbS quantum dots. This was successfully achieved, recording the highest emission efficiency of a photon multiplier to date. While photon multiplication was not able to be shown with an anthracene/perovskite nanocrystal system, energy transfer from anthracene to a nanocrystal was optimised, reaching transfer efficiencies as high as 72%. Through the synthesis of a perylene-tetracene sensitiser, we improved the absorption of tetracene through intramolecular energy transfer. Furthermore, these dyads were also used to create a novel class of tuneable dyes offering moderate emission efficiencies.</p
Population Genomic Studies Of The New Zealand Green-Lipped Mussel, Perna Canaliculus Gmelin, 1791
No full textPopulation connectivity significantly influences the spatial structure and dynamics of marine populations. Marine species, particularly those with pelagic larval stages, depend on larval dispersal for connectivity, which is driven by complex interactions between biological traits and oceanographic conditions. Understanding larval dispersal is crucial for conservation, yet challenging due to the difficulties in tracking larvae and identifying their origins. Recent advancements in genetic markers, especially single nucleotide polymorphisms (SNPs), and high-throughput sequencing technologies have enhanced our understanding of population genomics, providing detailed insights into the evolutionary processes shaping genetic variation. Integrating these genetic data with oceanographic models provides insights into larval connectivity, often highlighting the importance of local retention and recruitment for population stability. The emerging field of seascape genomics further enhances our understanding of marine population dynamics by linking genetic variation to environmental factors, revealing how oceanographic features and environmental gradients may shape genetic diversity and connectivity. This knowledge is pivotal in predicting the impacts of climate change on marine populations and in designing effective marine protected areas and conservation strategies to ensure the resilience and connectivity of marine ecosystems.This thesis explores the population genetic connectivity of a marine species, Perna canaliculus, the green-lipped mussel. This is an endemic species in New Zealand/Aotearoa found on rocky reefs and soft sediment beds across the subtidal and intertidal environments of the three main islands in the country. It is a highly valued food source for Māori and the mainstay of the aquaculture industry, where it represents the most important export species by both tonnage and dollar value. Most mussel seed used in farming comes from one site, Te Oneroa-a-Tōhe – Ninety Mile Beach (NMB), in the far north of the country, representing ~80% of the seed used (commonly known as Kaitaia spat, KS). Many attempts have been made to identify the source of KS and to describe the genetic structure of the species at both regional and national scales. Previous studies have divided the green-lipped mussel populations into northern and southern regions, separated by a pronounced genetic break located below the Cook Strait/Raukawa Moana region, at ~42⁰ S on both the east and west coasts of the northern South Island/Te Waipounamu. The low-resolution power of the genetic markers employed prevented previous research from detecting further division within these two regions, and also to locating the specific sites supplying KS to NMB.In this thesis, 37 sampling sites (1862 mussels) distributed across New Zealand/Aotearoa were used to obtain SNP markers from Next Generation Sequencing in an attempt to study the population genetic structure of the green-lipped mussel at greater resolution than previous studies. The panel of SNPs was divided into neutral (185 loci) and outlier (28 loci) to investigate the different processes influencing genetic variation in this species.At the national scale (chapter 2), the two previously characterised regions were detected, but the genetic break on the east coast was not identified due to sampling limitations and therefore the only sampling site in this coast (Christchurch/Ōtautahi, CH) was considered to be part of the major Northern mussel region. The west coast genetic break was detected, and it matched the location described for the green-lipped mussel and other marine benthic species. In addition, the inclusion of geospatial analysis enabled the identification of six genetic clusters, with five of them being a subdivision of the Northern mussel region. This new subgrouping allowed the distinction of six different regional clusters, termed: West Coast of the North Island (WCN, 13 sampling sites); Bay of Plenty (BOP, 7 sites); Wellington Harbour (WH, 1 site); North Coast of the South Island (NCS, 8 sites); West Coast of the South Island (WCS, 2 sites); and Christchurch (CH, 1 site). The patterns of genetic variation were subsequently used in seascape genomic analyses to test for associations with environmental variables. Sea surface temperature (SST), chlorophyll A concentration (ChlA), bathymetric position index broad (BPI_broad), gravel, sand and photosynthetic active radiation (PAR) were significantly correlated with genetic variation across sampling sites, suggesting that food-related variables plus temperature and current-associated habitat composition play key roles shaping the genetic diversity of the green-lipped mussel in New Zealand/Aotearoa.SNP-based analyses revealed that a representative sample of KS was part of the WCN genetic cluster, and further analyses were performed to find statistically significant differences between this sample and the rest of the genetic clusters (chapter 3). Pairwise FST estimates using both neutral and outlier SNPs revealed significant differences in allele frequencies between KS and all genetic clusters with the exception of WCN. Individual genetic assignment tests and relative migration networks further confirmed the WCN genetic cluster as the source for KS. Additional genetic tests (DAPC, Geneland, pairwise FST) were used to detect any discernible genetic structure within the WCN genetic cluster that would differentiate amongst its sampling sites to help narrow down the sources for KS. As a result, a location situated inside an estuary, Opononi Dock (OD) was discarded as potential source for KS. An additional statistical comparison between the genetic connectivity and larval connectivity output from an oceanographic model ruled out the most distant sampling site from within the WCN genetic cluster, Raglan/Whāingaroa (RG) as a relevant demographic source for KS. The KS sample is therefore most closely related to, and derived from, mussel sampling sites within the immediate region of NMB itself.The genetic break on the west coast of the South Island/Te Waipounamu was more precisely located between the NCS and WCS genetic clusters (chapter 4). A hybrid zone characterised by low interbreeding between the two mussel lineages was previously described for the green-lipped mussel, but the mechanisms and patterns of allele introgression remained elusive. In this thesis, I analysed the hybrid zone using a genomic cline approach, estimating the change of allele frequencies using a hybrid index, to elucidate patterns of introgression. The analysis suggests that the hybrid zone is situated in a context that promotes the preference of South-Western allele polymorphisms, as most of the loci exhibited a pattern of South-West to North-East introgression. In addition, the presence of F1 individuals was not detected, however F2 and backcrosses were found in up to ~45% of the mussels at some of the sites within the hybrid zone, suggesting a bottleneck in the formation of first-generation hybrid mussels. The mechanisms and factors influencing the genetic variation across the hybrid zone could not been identified, as the environmental variation obtained for the sites involved was negligible.This research represents an application of NGS-derived markers in the identification of genetic structure of one of the most important economic marine species in New Zealand/Aotearoa. The findings of high resolution spatial genetic structure can help in the delineation of management units for the green-lipped mussel and inform further sampling to locate more genetic clusters for the species. The combined multidisciplinary approach comparing genetic connectivity with oceanographic connectivity data proved to be useful in the identification, for the very first time ever, of relevant sites acting as the sources of KS. This information will be important for the New Zealand/Aotearoa government (Fisheries NZ) because it provides key scientific evidence to help develop guidelines to design effective management measures preserving these source sites against human impact and other threats. Finally, the analysis of the genetic break and hybrid zone has provided further information about its location and extent, and has shed light on the genetic composition of the mussel populations inhabiting this region.</p
Challenges and Benefits of Cat Fostering: A Focus Group Study With Volunteer Cat Fosterers in Aotearoa New Zealand
No full textCat fostering programs play a critical role in managing and supporting the health and wellbeing of stray, abandoned, or relinquished cats. Most cat fostering programs can only operate with the help of volunteer cat fosterers. Yet, there is comparatively little research on the experiences of cat fosterers. This study aimed to explore the motivations of volunteer cat fosterers, the challenges they experienced in their fostering practice, and what they perceived as the main benefits of cat fostering. We conducted focus group interviews with cat fosterers in Aotearoa New Zealand to answer our research questions. In total, 13 cat fosterers with a range of fostering experience participated in the focus groups. Data were analyzed using qualitative content analysis. The primary motivations to become cat fosterers included a general love for animals, wanting an alternative to cat ownership, and the desire to help and make a difference, which was underpinned by altruistic values. Cat fostering is an emotionally challenging role that requires significant time commitment and involves substantial responsibility, which makes it a form of high-stakes volunteerism. Despite the challenges, however, cat fosterers experienced social and emotional benefits along with the satisfaction of making a meaningful impact on their fosters' lives. These benefits fulfill the basic psychological needs of autonomy, relatedness, and competence. The findings have important implications for shelter organizations and for the recruitment, retention, and training of volunteer fosterers
Analysis of Panel Data Under Time-Inhomogeneous Markov Chains
No full textIn this slide a new approach for the analysis of panel data is presented. It is based on continuous time-inhomogeneous Markov chains with time-varying covariates dependent transition intensity. Estimation of the regression coefficients of covariates is done using maximum likelihood. Score function and observed information matrix are given explicitly in terms of tensor matrix representations. The information matrix is positive definite regardless the values of statistics of samples paths of Markov chains and the values of covariates. These appealing features allow fast convergence of the coefficient estimates using Newton-Raphson iteration with guaranteed convergence to the true values of parameters. Consistency and large sample properties are established. Numerical study confirms the accuracy of the estimates. </p
Bio-Based Self-Build Architecture: Rethinking Self-Build Practices to House Aotearoa Communities
No full textThe dissatisfaction with the quality and availability of housing in Aotearoa New Zealand may lead individuals and communities to explore self-building as an alternative method of housing. This research examines the potential of bio-based materials in self-build architecture to address the housing challenges faced by rural Aotearoa, focussing on the small coastal town of Omaui, Southland. Omaui’s unique geographical context paired with intense weather provide an opportunity to evaluate an innovative housing solution that is both resilient and contextually appropriate. The primary objective of this research is to develop a self-build framework that prioritises bio-based materials, aiming to enhance housing quality, accessibility, and buildability. Through a combination of literature research, material experimentation, digital modelling, and prototyping, this research investigates how these materials can be effectively integrated into a self-build system that is accessible to everyday New Zealanders. By contextualising this framework through two site-specific house designs, this research seeks to propose an alternative housing approach, offering practical solutions that can be adapted to diverse sites around Aotearoa. The findings contribute to the wider discourse on self-build and bio-based architecture by providing a model for addressing housing challenges through bio-based self-build methodologies.</p
Characterisation of Oxylipin Receptors in the Cnidarian-Dinoflagellate Symbiosis
No full textThe success of scleractinian corals relies on their ability to establish a symbiotic relationship with dinoflagellate algae from the family Symbiodiniaceae. These dinoflagellate symbionts reside within the host's gastrodermal cells, enclosed in a host-derived membrane known as the 'symbiosome membrane'. The symbionts can communicate with the host via molecular signalling, dampening its immune system and facilitating symbiosis establishment and homeostasis. Oxylipins, short-lived signalling molecules formed through the oxidation of polyunsaturated fatty acids, are important inflammatory regulators and may play an important signalling role in the cnidarian-dinoflagellate symbiosis through the action of specific receptors, though this has yet to be confirmed. This thesis therefore aimed to localise and quantify specific oxylipin receptors within the different tissue layers of a model cnidarian – the sea anemone ‘Aiptasia’ (Exaiptasia diaphana) - and the reef coral Acropora tenuis in response to symbiotic state, symbiont identity, thermal stress and/or life-history stage. The potential functional role of a specific oxylipin receptor in Aiptasia was then characterised further, through exposure to a pharmacological inhibitor, and the application of metabolomic and lipidomic analyses.In Chapter 2, specific antibodies were developed, and immunohistochemistry (IHC) and immunocytochemistry (ICC) used to localise and quantify four receptors: Transient Receptor Potential Cation Channel, Subfamily A, Member 1 (TRPA1); Prostaglandin E2 Receptors 2 and 4 (EP2 and EP4); and Glutamate Ionotropic Receptor Kainate Type Subunit 2 (GRIK2), in aposymbiotic anemones and symbiotic anemones hosting either the native symbiont Breviolum minutum or the non-native symbiont Durusdinium trenchii. TRPA1, EP2 and EP4 receptors are important for the signalling of the oxylipins hydroxyoctadecadienoic acid (HODEs) and prostaglandin E2 (PGE2), while GRIK2 is part of the ionotropic glutamate receptor (iGluRs) family, which help sense chemicals and pathogens in invertebrates. The receptors were found in both the gastrodermis and epidermis, and of particular interest, were further localised to the symbiosome membrane, suggesting a direct role in inter-partner signalling. However, TRPA1, EP2 and EP4 were all less abundant in the gastrodermis when it housed the native symbiont relative to the other symbiotic states, suggesting that the associated pathways are downregulated in a compatible symbiosis. GRIK2, in contrast, was upregulated in the gastrodermis and the epidermis of anemones hosting the non-native symbiont. This observationis consistent with previous suggestions that this receptor may play a role in the detection of potentially harmful microbes, especially given the reputation of D. trenchii as a nutritionally sub-optimal opportunist.In Chapter 3, IHC was used to observe how these receptors respond to thermal stress (i.e., ‘bleaching’), again using Aiptasia containing its native symbiont B. minutum. Whereas EP4 abundance did not change in response to elevated temperature, TRPA1 and EP2 increased in abundance in both the epidermis and gastrodermis, consistent with increased inflammation, symbiosis dysfunction and a potential role in the cellular bleaching cascade. GRIK2 once again behaved differently, exhibiting an initial increase in the gastrodermis and then in the whole animal in response to elevated temperature. One interpretation is that high temperature caused the native symbiont to shift from a beneficial to less beneficial state, triggering the GRIK2- mediated pathway to initiate its removal.In Chapter 4, IHC was used to localise and quantify EP2 and EP4 in the tissues of A. tenuis larvae and polyps, when in the aposymbiotic state or when hosting one of their two native dinoflagellate symbionts: Cladocopium goreaui and Durusdinium trenchii. Corals were inoculated with these symbionts and sampled at 3 and 30 days post-inoculation. EP2 and EP4 were consistently present in both the gastrodermis and epidermis. However, EP2 and EP4 abundance changed with symbiotic state, symbiont identity, coral life-stage, and time in symbiosis. D. trenchii, but not C. goreaui, was found to decrease EP2 levels in both coral larvae and polyps, as well as EP4 levels specifically in coral polyps. Conversely, C. goreaui, but not D. trenchii, reduced EP4 levels in coral larvae. These findings suggest that D. trenchii has a greater ability to modulate host immune pathways, particularly in the polyp stage. This may explain why D. trenchii frequently dominates A. tenuis polyps in the wild. Additionally, the study revealed that various coral life stages activate distinct pathways while forming symbiosis, regardless of the symbiont type.In Chapter 5, to elucidate the function of the EP4 receptor in the cnidarian-dinoflagellate symbiosis, the lipidomic and metabolomic profiles of Aiptasia and its native symbiont B. minutum were analysed before and after chemical inhibition. The host was the most affected, with several metabolites and lipids upregulated in the absence of EP4 function. Many of these upregulated molecules had possible roles in immune pathway regulation and membrane dynamics. In contrast, the symbiont fraction was only marginally affected, with some lipids involved in membrane dynamics again being upregulated. These patterns are consistent with greater cellular stress in the host than the symbiont in response to the inhibition of EP4- mediated signalling, which ultimately induces an immune response, potentially linking this pathway to homeostatic maintenance of the symbiosis.This thesis provides insights suggesting that oxylipin receptors and oxylipin signalling may contribute to inter-partner communication and homeostatic regulation of the cnidarian- dinoflagellate symbiosis, though further studies are necessary to validate these roles. Furthermore, a new pathway by which the host can identify potential pathogens and/or sub- optimal symbionts is suggested. My study augments our knowledge of the fundamental cellular mechanisms that underlie a successful cnidarian-dinoflagellate symbiosis, which is essential for developing effective tools, such as via the engineering of thermally-resistant corals (as discussed in Chapter 6), to mitigate climate change.</p
Cine ecuatoriano del siglo XXI: transnacionalismo, Buen Vivir y Ley de Cine*
No full textNo description supplie
Realities and challenges of implementing merit protection frameworks: Australian Capital Territory, Queensland and Aotearoa New Zealand
No full textMerit is a foundational principle that underpins public sector employment. This report, commissioned
by the Australia and New Zealand School of Government (ANZSOG) and the Australian Capital
Territory (ACT) government details key findings about understandings of merit, with reference to
contemporary challenges that aim to integrate suitability and diversity alongside efficiency. This
executive summary highlights key findings from the second stage of a research project. The research
was carried out by researchers at the Public Service Research Group at UNSW Canberra and
Victoria University of Wellington. It is based on interviews with 76 public servants in the ACT,
Queensland (QLD) and Aotearoa New Zealand (NZ) public sectors
Hydrogen Evolution Reaction on a Single Platinum Atom
No full textSingle-atom electrocatalysts are typically reported on in bulk scale applications (i.e. as dispersions of many individual atoms across a macroscale electrode) which represents the electrochemical activity across all single-atom electrocatalysts at once. Less is known about the fundamental workings of individual single-atom electrocatalysts. To elucidate the electrochemical activity of a single atom, this thesis presents the isolation of the hydrogen evolution reaction at a single platinum atom deposited on an electrode surface. Two important techniques were employed during the experimental work to achieve measurements at the individual atom scale: scanning electrochemical cell microscopy, and collision electrochemistry. Scanning electrochemical cell microscopy enabled the physical downsizing of the working electrode to the nanometre scale, cutting down on the background noise. The collision electrochemistry approach enabled the controlled delivery of a single Pt4+ species to be reduced to Pt0 upon collision with the electrode. The presence of Pt at the electrode acts to catalyse the hydrogen evolution reaction, amplifying the current to produce peaks that indicate the Pt4+ collision event occurred. These peaks were analysed through calculating their frequency vs Pt4+ concentration, observing their height and width as a result of the applied potential, and obtaining the hydrogen evolution reaction steady state current at a single platinum atom. A discussion surrounding how the interactions and dynamics of the Pt4+ ion during the collision event impacts the shape of the current and peaks is presented.</p
Envisaging Data Nirvana: A Delphi study of ideal data culture
No full textAbstractIn recent decades, the proliferation of data and advances in information technology have led organizations to value data more highly and aim to build a data culture that is suitable for promoting and sustaining data‐related strategic outcomes. However, what a “good” data culture comprises is often expressed abstractly and there is no consensus about how such a culture should manifest in practice. This study explores the key dimensions and attributes of an ideal data culture, as perceived by expert practitioners in large, data‐rich public sector organizations. Using a two‐stage Delphi method, we engaged with 14 data management experts from Aotearoa New Zealand to understand their views on achieving “Data Nirvana” in practice, focusing on the attributes that explain an ideal data culture. Five categories of ideal data culture are identified: strategic agility, ethical use, human centricity, capability, and controls and discipline. These are linked through two unifying themes: trust and trustworthiness, and value integration. The resulting framework for data culture comprises seven elements. The study provides insights into the aspirational potential of data and the realities of organizational data practice, contributing to a deeper understanding of data culture
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