CORA
Cork Open Research Archive (CORA) is UCC’s Open Access institutional repository which enables UCC researchers to make their research outputs freely available and accessible.
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Recent Submissions
Reasons why men who present with self-harm leave accident and emergency before next care recommendations: An interpretive phenomenological analysis
(The Psychological Society of Ireland, 2024-06) Moynihan, Daniel; Lambert, Sharon; Flynn, Daniel; Arensman, Ella; Cassidy, Eugene; Kinahan, James
The effect of land fragmentation on the technical inefficiency of dairy farms
(Wiley, 2020-11-14) Bradfield, Tracy; Butler, Robert; Dillon, Emma; Hennessy, Thia; Kilgarriff, Paul
Exploiting the link between land identification and farm accountancy data, we use a uniquely detailed database to conduct a robust analysis of land fragmentation and its effect on technical inefficiency on dairy farms in Ireland. Using a stochastic production frontier model, our results show that the number of parcels, the average distance between parcels and the main farm, and the portion of land separate from the main farm all increase technical inefficiency. Such inefficiency can be reduced through increased parcel area, reduced travel distances, advisory services contact, intensive practices and hired labour. Our findings support the need for policy to improve land and labour mobility, providing evidence to support incentives to promote the transfer and long-term leasing of agricultural land.
Evaluating indoor climate interventions: Balancing sustainability and health outcomes
(2024-07-07) Mishra, Asit Kumar; Wargocki, Pawel; O'Reilly, Éilis J.; Horizon 2020 Framework Programme; H2020 Marie Skłodowska-Curie Actions
SUMMARY: Over the past 20 years, we have moved from low energy buildings to sustainable buildings. With this shift, life cycle energy and emissions analysis (LCA) has taken precedence. To design buildings that are sustainable, an analysis of the resources that go into constructing and operating building needs to be complemented with an analysis of how buildings impact our life. In this work, we propose elements of building design can be optimised for occupant health and the consequent environmental impact of these benefits can be incorporated into the LCA.
INTRODUCTION: A significant portion of an energy-efficient building's embodied energy and emissions can be ascribed to its indoor conditioning system and HVAC (Shirazi and Ashuri, 2020). Sustainability modifications for buildings can also affect occupant health. To achieve global sustainability goals, a building’s energy use, emissions, as well as the impact on occupant health need to be evaluated holistically. There is a growing awareness of co-benefits of sustainable building designs that consider impact on occupant health. Yet, there is little research that includes the positive health impacts of indoor climate interventions in building performance evaluation or LCA. For example, appropriate air filtration can reduce asthma exacerbations during everyday use or cardio-respiratory hospitalizations during a wildfire. We propose that such evaluations should be part of built environment LCA to ensure optimal assessment of design alternatives.
METHODS: It is well accepted that indoor climate conditioning contributes a notable fraction of a building’s operational energy use and embodied energy. Indoor climate can also directly affect occupant performance, health, and wellbeing. These impacts have been translated into health (Asikainen et al., 2016) and economic metrics (Walker et al., 2018). We propose that LCA of indoor climate conditioning interventions consider the reduced burden of disease to provide a more comprehensive comparison of designs (Fig. 1).
RESULTS AND DISCUSSION: Taking the example of mechanical air filtration, previous studies have modelled the benefits of air filtration on hospitalizations (Fisk and Chan, 2017; MacIntosh et al., 2010), and doctor visits (Lanphear et al., 2011). These data can be combined with the LCA data from healthcare. Here, the recently developed open access, living database on healthcare LCA becomes a vital asset (Drew et al., 2022). For example, the LCA global warming potential of a portable air cleaner can be 408-670 kg CO2 equivalent (Tichá et al., 2016) while the avoidance of each asthma exacerbation, requiring a GP visit, can save ~68 kg CO2 equivalent emissions (Drew et al., 2022). Intervention effectiveness can be improved by focusing on vulnerable and susceptible populations (Fisk and Chan, 2017). A significant amount of further work is needed to ensure such analyses can be widely adopted. LCA indicators, for both the built environment component and health events, will be needed for the same or similar regions, instead of global values. Studies regarding indoor climate interventions will also need to focus on health benefits as one of the accessed outcomes.
CONCLUSIONS: As the energy and climate-change crisis evolved, our grasp of sustainability also evolved. Sustainable development goals have a planetary nature, requiring inter-sectoral cooperation. The built environment sector has a consequential impact on global energy use and emissions. We submit that this impact can be mitigated not only by constructing energy efficient buildings but also healthy buildings that influence the health sector’s energy and emission burdens.
Multiferroic investigations of Aurivillius phase thin films
(University College Cork, 2023) Colfer, Louise; Keeney, Lynette; Long, Brenda; Royal Society; Science Foundation Ireland
In recent years, the amount of data being created and processed is growing at a much faster rate than the rate of computational storage technology development. With CMOS technologies reaching their miniaturisation limits, new disruptive materials are needed to increase data storage capabilities. Technological road-maps have identified room temperature, non-volatile magnetoelectric multiferroic materials as promising candidates for memory scaling within future memory storage devices. Although multiferroic memory devices have the potential to revolutionise memory storage technologies, commercial devices successfully utilising multiferroics have not yet come to fruition. The focus of this thesis is to understand and optimise a rare example of a room temperature magnetoelectric multiferroic, Bi6TixFeyMnzO18 (B6TFMO; x = 2.80 to 3.04; Y = 1.32 to 1.52; Z = 0.54 to 0.64). Aurivillius phase materials, (Bi2O2)(An−1BnO3n+1), where ferroelectric perovskite units are interleaved between dielectric [Bi2O2]2+ layers, are flexible scaffolds for technological applications. While earlier studies indicated that B6TFMO is a promising material for future memory devices, my thesis presents significant advances in the characterisation, understanding and optimisation required towards implementing the material in fully realised devices.
In this work, correlation between the octahedral tilting and atomic-level structural distortions with functional electronic and magnetic properties of B6TFMO were determined, revealing that crystal field splitting of the Ti4+ octahedra is influenced by its position within the Aurivillius unit cell. Theoretical calculations determined that this is predominantly driven by changes in the extent of tetragonal distortion along the c-direction. Atomic scale mapping of polar displacements reveals this has a direct impact on the ferroelectric properties. Polarisation is largest towards the outer perovskite cells, correlating with an increased extent of local tetragonal distortion of octahedral geometries. Experiments demonstrate that tilting of the BO6 octahedra competes with the extent of tetragonal distortion of the TiO6 octahedra, where the degree of octahedral tilting increases towards the central layers of this Aurivillius system, where the magnetic cations preferentially partition. This work presents the first indication that octahedral tilting might be an important enabler of long-range magnetic interactions and subsequent multiferroic behaviour in B6TFMO.
Delving deeper into fundamental understandings of B6TFMO’s antipolar and magnetic behaviour, the purposeful inclusion of structural defects within the layered structure of B6TFMO and how they can impart elastic strain and electrostatic energy changes which in turn influence polar behaviour is explored. The findings show that the vicinal sapphire substrates (mis-cut angle 0.2 o to 10 o) are successful for promoting the propagation of sub-unit-cell defects and disruptions to the periodicity of the Aurivillius phases. This has a marked effect on the film morphology and ferroelectric properties. Macroscopic and local measurements show that defect, crystal grain and ferroelectric domain density increases with increasing substrate mis-cut angle. Atomic resolution polarisation mapping showed that charged domain walls alongside exotic polar vortices are facilitated by OPBs when two OPB defects are spaced 5 nm apart. This work provides insight into methods for successfully controlling defect levels and how polar vortex domain walls and charged domain walls are promoted within layered multiferroics by tailoring the underlying substrate that the film is grown on.
Moving on from vicinal sapphire surfaces, patterned sapphire with 3D domes were used to encourage the growth of the Aurivillius grains towards an upright geometry. An increased number of non-(00l) reflections were present in the B6TFMO films on patterned sapphire along with evidence from STEM imaging showing that B6TFMO grains grow along the incline of the patterned sapphire domes. With the growth of the crystal grains towards an upright geometry it would be expected that access to the major a-axis polarisation via out-of-plane measurement would be improved, however with a maximum inclination angle of 60 ° achieved with the 3D dome architectures, the out-of-plane piezoresponse of the samples remained weaker than the in-plane piezoresponse. Studies of the magnetic properties of the films demonstrated that the B6TFMO samples were ferromagnetic at room temperature. These findings provide further evidence of room temperature multiferroic behaviour in B6TFMO.
Lastly, the role of bismuth excess and substrate strain were investigated to optimise the epitaxial growth of B6TFMO via DLI-CVD. A single-step deposition method on epitaxial substrates was developed to allow the successful synthesis of continuous 45 nm thick B6TFMO films at thicknesses relevant to applications as piezoelectric actuators, sensors and energy harvesters. These films nucleated via a layer-by-layer growth mode and were found to have a strong in-plane ferroelectric response with isotropic domains. Film purity was enhanced with utilisation of epitaxial substrate with appropriate lattice match to B6TFMO and by optimising the amount of bismuth precursor used. In this work, progress was made towards the optimisation of epitaxially grown B6TFMO films, allowing greater control of film orientation and augmenting strain-induced enhancement of multiferroic properties in future data storage devices.
Overall, this research has increased understanding of the fundamental mechanisms governing the ferroelectric and ferromagnetic properties of B6TFMO. The work has elucidated some of the key requirements fundamental to the manifestation of polar topologies and has created strategies for the tailoring of novel polar topologies. This combination of new material understanding and new growth optimisation of room temperature multiferroics contributes to solving the ‘big data’ problem. Application of B6TFMO in future technologies based on ultra-high density, energy efficient memory devices, spintronic devices, multilevel resistance control (memristive and synaptic devices) and energy-efficient neuromorphic “brain inspired” devices are envisioned.
Impact of protein genotypes on milk composition and processability
(University College Cork, 2024) Gai, Nan; Kelly, Alan; O’Regan, Jonathan; Goulding, David A.; Uniacke-Lowe, Therese; Nestlé
Milk protein genotypes are associated with differences in milk yield, composition, and processability due to direct effect of their structural differences, or their indirect effects on casein micelles, as well as differences in milk composition. This study investigated the effects of β-casein (β-CN) genotypes on milk physicochemical properties, functionalities, processability (Cheddar cheese processing), and proteolytic mechanisms. Influences of β-lactoglobulin (β-lg) genotypes on heat-induced whey protein denaturation were also investigated.
The investigation of milk physicochemical properties, including gross composition, mineral content, casein micelle size, zeta potential, polydispersity index (PDI) and fat globule size distribution were initially focused on three main β-CN genotypes, A1A1, A1A2 and A2A2. No significant differences were detected on milk composition between three genotypes, and casein micelle sizes between three genotypes were similar. Better rennet coagulation properties and acid coagulation properties were determined in A1A1 milk, in comparison to A1A2 and A2A2 milk, but differences were not significant. A2A2 milk had smaller fat globule size and better stability than A1A2 and A1A1 milk against creaming.
Cheddar cheese was produced using milk with A1A1, A1A2 or A2A2 β-CN genotypes. A2A2 cheese milk had significantly poorer rennet coagulation properties compared to the other two genotypes, which caused a delay in the cutting step. A1A1 cheese had a lower protein content, while A2A2 cheese had a lower fat content compared to the other two cheeses. Protein contents in both A1A1 and A2A2 cheese whey were higher than that in A1A2 cheese whey. Ripened A1A1 cheese was the softest, and the least fracturable.
Dissociation and interfacial properties of purified A1 and A2 β-CN, obtained from milk with A1A1 and A2A2 β-CN genotypes using microfiltration (MF), were studied. A2 β-CN, on micellization, had smaller particle size than A1 β-CN, and A1 β-CN was more stable over heating and cooling than A2 β-CN. Foam stability and emulsifying ability of A2 β-CN was higher than that of A1 β-CN, while stability of emulsions produced using A1 β-CN was higher than that of A2 β-CN.
The differences between the two β-CN genetic variants A1 and A2 in terms of proteolysis in milk were determined. A2A2 milk had higher plasmin activity than A1A1 milk, and A2 β-CN was more susceptible to plasmin than A1 β-CN. Referring to the different amino acid on sequence position 67, where proline (Pro) is in A2 β-CN and histidine (His) is in A1 β-CN, His67 was determined to be more susceptible than Pro67 in hydrolysis of β-CN.
The influence of β-CN genotypes on milk characteristics was also studied for milk containing minor β-CN genotypes, A1B, A2B, A1I and A2I. Larger casein micelle size, better rennet coagulation and acid coagulation properties were associated with β-CN variant B compared to the I variant. The structural differences between the two genotypes, B and I, has also influenced their proteolysis, and the Arg122 in β-CN B variant was determined to be more sensitive to plasmin-derived proteolysis compared to the Ser122 in the I variant. In addition, the His67-Asn68 bond in the A1 and B variants was more susceptible than Pro67-Asn68 in the A2 and I variants to β-CN proteolysis driven by milk indigenous enzymes, while the activities of Ile66-His67 and Ile66-Pro67 were similar.
The effect of κ-CN genotypes was determined to have a stronger influence on milk casein micelle size and fat globule size than that of β-CN genotypes, where milk with κ-CN A had larger casein micelle and smaller fat globule size than milk with κ-CN B. The acid coagulation and rennet coagulation properties of milk containing the B variant of κ-CN were better than milk containing the A variant, which was possibly due to the effect on casein micelle size and fat globule size.
In the study of whey protein denaturation induced by heating, milk with β-lg A variant was more heat resistant than with the B variant. More denatured whey proteins with B β-lg were likely to interact with casein micelles to form insoluble aggregates compared to the A variant.
In conclusion, the findings in this study suggest that milk protein genotypes are clearly associated with milk characteristics and technological properties, and opened new, related areas such as the potential linkage between specific peptides obtained from proteolysis to milk functional properties. These findings can be used as a reference for further studies, and as guidance for milk selection when dairy products with specific characteristics are required.