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Minutes matter for life safety and risk exposure in Milford Sound, New Zealand
No full textThe number of people killed by rapid-onset, highly-lethal natural hazards is usually proportional to the
number of people directly exposed yet population mobility makes such exposure temporally variable.
In hazardous tourist destinations that are dominated by highly mobile transient visitors, this makes it
especially challenging to assess and manage risk. While the temporal dynamics of population exposure
have been identified as a necessary input to risk analysis, lack of data and methods means such
assessments are limited to using simplified assumptions at low temporal resolution (e.g. day-night
variations). Here we show that population can fluctuate by an order of magnitude within minutes,
meaning the timing of a hazard event could impact the number of resulting fatalities to a similar
degree. At Piopiotahi Milford Sound, we show that the population exposed to landslide-triggered
tsunami hazards had a maximum recorded change of~1000 people over a 5-min period. This increased
the modelled number of fatalities in a tsunami from 71 to 1134 within the corresponding 5-min period.
Monitoring these minute-by-minute changes longitudinally over a period of 790 days that included
New Zealand’s COVID-19 lockdown measures and their removal demonstrates that the level of
societal risk here was only acceptable during the strictest lockdown measures and has since become
increasingly unacceptable. Our approach shows that incorporating longitudinal high-resolution data
on dynamic exposure substantially improves assessment accuracy and reduces inherent uncertainty
of dynamic disaster risk, especially in popular tourist destinations and where population shifts are
frequent and significant
Novel ionic liquids for renewable and sustainable energy conversion and storage
No full textThere is an ever-growing need to increase renewable energy uptake, due to the conflict between growing energy demands and the reduction of fossil fuel use. This is necessary to mitigate the effects of climate change. Many established renewable energy approaches face limitations that impact their efficiency or practicality. This includes energy storage requirements for intermittently generated power from renewable sources, and high energy costs associated with processing, refining and storing biofuels.
Ionic liquids are a versatile class of compounds with diverse physicochemical and electrochemical characteristics that make them of interest to many industries. For example, low volatilities and high conductivities making them suitable as battery electrolytes. Alternatively, their physicochemical tunability makes them useful phase-transfer catalysts and as solvents for industrial extraction processes. This thesis investigates the utility of ionic liquids for novel renewable energy applications, specifically focussing on developing new proton-exchange membranes and separation processes for biofuel refinement. To this end, a library was synthesised using facile approaches of ion metathesis and acid base neutralisation using tetraalkylammoniums, amines, and increasingly alkylated carboxylate counterions.
Proton exchange membranes were fabricated by depositing waxy hydrophobic salts on porous polypropylene supports. Diallyldimethylammonium stearate and Aliquat 336 stearate membranes achieved comparable bulk proton transport rates to commercially available membranes, but displayed a unique mechanism of charge transfer consistent with proton hopping across bilayer-like membranes. These proton-exchange membranes are expected to find widespread applications in renewable energy technologies such as electrolysers, batteries and electrochemical carbon capture and storage systems.
Ionic liquids were screened for their ability to fractionate biofuels by co-incubation followed by gas chromatographic analysis to quantify changes in biofuel composition. Diallyldimethylammonium propionate and propylammonium propionate and were found to induce the greatest compositional changes to biofuel. The ionic liquids preferentially fractionated the smallest hydrocarbons present via selective miscibilities, resulting in a biofuel product fraction with increased energy density associated with higher proportions of large hydrocarbons. When applied in an industrial context, these ionic liquids will enable high- throughput biofuel refinement at a fraction of the time, energy and capital cost of conventional fractional distillation approaches
Anterior thalamic nuclei, medial prefrontal cortex, dorsal subiculum and memory : lesion and optogenetic manipulations.
No full textThe anterior thalamic nuclei (ATN) are a key node in a distributed network of structures that supports episodic memory. Clinical support for this comes from examples of diencephalic amnesia, such Korsakoff’s syndrome and thalamic stroke. Degenerative changes to the ATN are also among the thalamic changes associated with Alzheimer’s disease. Animal lesion studies consistently demonstrate that ATN lesions cause severe memory impairments across a range of spatial tasks. Such evidence, together with examples of changes to distal memory structures, such as decreased immediate early gene (IEG) protein expression in the retrosplenial cortex and reduced microstructural integrity of hippocampal CA1 neurons, support the view that the ATN have a critical influence on cognitive networks and episodic memory in particular. The current thesis examined the relative independent and inter-dependent impact of the ATN on memory systems, especially from the perspective of the medial prefrontal cortex (mPFC) and dorsal subiculum (dSUB). Experiment 1 provided the first direct comparison of bilateral lesions of the ATN, mPFC, and dSUB for spatial working memory and object-based episodic-like memory, associative memory, and recognition memory tasks. We replicated previous research demonstrating a severe deficit after bilateral ATN lesions compared to Sham controls on a forced-choice spatial working memory task that minimised the benefits of response strategies. Bilateral dSUB lesions and bilateral mPFC lesions produced an intermediate level of performance with the mPFC group reaching the same overall performance as Sham controls by the end of training. All experimental groups showed evidence of novel object recognition, but the object-place-context, object-in-place and object-context tasks looking at various aspects of associative memory revealed no effects in any group. Experiment 2 assessed the functional significance of ATN-mPFC pathways for cognition and memory from the perspective of a disconnection methodology. Experiment 2 did not produce evidence for an interdependent function between the ATN and the mPFC for either spatial working memory or cognitive flexibility in T-maze tasks. In contrast, bilateral ATN lesions produced a severe spatial deficit in the T-maze, and, surprisingly, a ‘shift benefit’ in a T-maze cue task of cognitive flexibility. This finding supports the involvement of the ATN in cognitive processes beyond spatial working memory. Again, all experimental groups showed evidence of novel object recognition, but the object-in-place and feature ambiguity tasks looking at associative memory and configural processing revealed no effects in any group. To examine the independent contribution of the ATN, the third Experiment used a novel experimental design in which a unilateral ATN neurotoxic lesion was combined with optogenetic inhibition, in the contralateral hemisphere, of ATN efferents within the mPFC and dSUB regions. This unilateral ATN lesion plus crossed optogenetic manipulation was unable to mimic a bilateral ATN lesion effect on spatial working memory. A novel finding was that rats with bilateral ATN lesions showed impaired spatial working memory when distracted by the visible bright light via the optic fibre stubs on their head; this effect was not found in the other groups. Overall, the thesis supports and further extends on previous research demonstrating the critical role of the ATN in a distributed memory network. The effects of ATN injury in rats is greater than that shown by dSUB lesions and especially mPFC lesions. The independent and interdependent effects of the ATN within distributed memory systems need further elucidation. It was also evident that further work is required to explain when rats are able to show associative memory in object-based tasks, including those testing episodic-like memory
Area-level socioeconomic status, greenspace, and mental health in Aotearoa New Zealand : a prospective birth cohort study
No full textMental health is shaped by upstream determinants such as area-level socioeconomic status (SES) and greenspace throughout the lifecourse. Prior research on these associations has been dominated by cross-sectional or short- to medium-term longitudinal studies. This thesis examines the lifecourse associations between area-level SES and mental health, and between greenspace and mental health. It used data from the Christchurch Health and Development Study (CHDS), comprised 1,265 individuals born in Christchurch, New Zealand, in 1977. Three mental health conditions including depression, anxiety disorders, and suicidal ideation were assessed in adolescence (ages 14–16) and during six subsequent adult waves (ages 18–40). Cohort members' residential addresses from birth to age 40 were geocoded and linked to time-series area-level SES metrics (1981–1991) and greenspace data (1985–2015) to reconstruct exposure to area-level SES in childhood and greenspace availability over the lifecourse. A range of advanced statistical methods, such as the Latent Class Growth Model and Bayesian Relevant Lifecourse Exposure Model, were employed in the data analyses. The investigated associations were comprehensively adjusted for individual, family, and area-level factors. This thesis found that transitioning from high to low area-level SES during childhood was associated with an increased risk of depression in adolescence, while living in middle SES areas in early childhood may be protective against anxiety disorders in adulthood. Additionally, greenspace availability had a beneficial effect on depression in adulthood but not in childhood. No associations were noted between greenspace availability and anxiety disorders or suicidal ideation over the lifecourse. Within a spatial lifecourse epidemiology framework, this thesis has significant implications for future research and evidence-based policymaking aimed at reducing health inequalities and promoting population health through upstream interventions. However, further research is required to confirm these findings using more sophisticated time-series environmental exposure assessments and a larger sample size
Tree Canopy Cover in Invercargill 2022
No full textResearchers at the University of Canterbury's School of Forestry assessed urban tree cover for
the 75 largest cities and towns in New Zealand¹. Each city has been sent a free, customised
report providing a baseline assessment of its tree canopy cover
Design of highly skewed rotor blades for coaxial contra-rotating UAV rotor systems.
No full textThe development of unmanned aerial vehicles (UAVs) has been gaining attention in both commercial
and research fields. They are widely utilised for various tasks, including package delivery,
environmental monitoring, and aerial photography. A critical design feature of these
modern aircraft is the arrangement of rotor blades. Coaxial contra-rotating rotor blades can be
employed due to their high thrust and small planform area, redundancy in the case of motor
failure, and potentially increased efficiency, but with the drawback of greater noise generation.
Recent research shows that skewed rotor blades can reduce noise in coaxial contra-rotating
rotor systems, though they produce less thrust than equivalent straight blades.
This research explores the design, manufacturing, and performance of coaxial contra-rotating
UAV rotor blades, focusing on skewed blade geometry. Three-dimensional (3D) printed blade
moulds facilitate the creation of the unique skewed blade shape with required precision. Prepreg
unidirectional carbon fibre is chosen as the primary material for manufacturing. Two composite
lay-up methods are investigated, with one producing higher-quality layers but resulting in
more material waste. A weight control method is implemented to minimise rotor imbalance;
however, skewed blades manufactured using the second lay-up method show inconsistencies in
pitch accuracy due to fibre irregularities.
Acoustic experiments confirm that skewed blades can effectively reduce noise in coaxial contrarotating
UAV rotor systems, with experimental measurements aligning well with analytical
predictions. Higher skew angles lead to more noise reduction but decrease total system thrust
compared to equivalent straight blades, a phenomenon not fully captured by computational
fluid dynamics (CFD) models.
Based on the conventional blade element momentum theory (BEMT), a novel adapted coaxial BEMT model is presented for aerodynamic modelling of coaxial contra-rotating UAV rotor
blades in hover, incorporating mutual rotor interactions, axial separation, and tip loss effects.
Wake contraction is evaluated using a prescribed wake model. CFD simulations were implemented
to conduct two-dimensional (2D) axisymmetric studies to validate the wake contraction
model. Comparisons with 3D CFD and experimental data show strong agreement, demonstrating
the accuracy of the conventional single-rotor BEMT model and the developed coaxial
BEMT model in accurately capturing both the wake contraction radius and the radial distributions
of aerodynamic loads. Both models were validated against literature data published for
different blade designs, showing strong agreement. The coaxial BEMT results were compared
with experimental measurements across various rotational speeds and showed good agreement.
From the CFD results, differences in thrust were observed in coaxial configurations for skewed
blades compared to straight blades, with minimal changes in axial velocity but notable variations
in radial and circumferential velocities. Overall, the developed coaxial BEMT model is
effective in capturing the trends and magnitude of the performance of coaxial contra-rotating
rotor blades at much lower set-up and computational costs than high-fidelity CFD simulations.
A coupled aeroelastic algorithm is developed to evaluate the aeroelastic behaviour of composite
coaxial rotor blades. It iteratively resolves aerodynamic loads and blade twist deformation until
convergence, enabling the evaluation of rotor aeroelastic performance. The coupled aeroelastic
model features the developed coaxial aerodynamic module based on BEMT to account for the
mutual interactions between rotors. The structural module leverages finite element analysis
(FEA) software to capture the bend-twist deflection of skewed blades. Static bend tests validate
blade stiffness. Aerodynamic tests validate the coupled aeroelastic model, confirming that
skewed geometry can significantly impact rotor blade aerodynamic performance. Additional
aeroelastic computational results demonstrate that composite lay-up methods, large skew angles,
and lower material stiffness can amplify rotor thrust due to increased aeroelastic deformation.
The presented aeroelastic model serves as an essential design tool for predicting coaxial
rotor aeroelastic performance at a low computational cost
Experiment Guam in the age of missile defence
No full textThis article argues that Guam serves as a critical testing ground for emerging US military
technologies and strategic doctrines, with particular attention to the Enhanced Integrated Air
and Missile Defense System (EIAMDS). By examining recent missile defence tests and ongoing
military projects, I highlight how Guam’s strategic significance, colonial status, and geographic
isolation can exacerbate the island’s vulnerability rather than ensuring its security. Ultimately,
I argue that Guam emerges not merely as an isolated military testbed but as a microcosm
reflecting broader geopolitical tensions, offering crucial insights into the future trajectory of
US-China competition and global security dynamics
A study of tinnitus, hyperacusis, and neural gain in the auditory brainstem and cortex in relation to temporary conductive hearing loss
No full textBackground: It is commonly believed that when there is an auditory deprivation (i.e. hearing loss), homeostatic plasticity occurs within the auditory brain to compensate for the reduction in auditory signal by increasing the neural activity, potentially leading to hearing disorders such as tinnitus and hyperacusis. The application of earplugs to create temporary conductive hearing loss has enabled researchers to investigate this homeostatic plasticity using within- subject baseline measures, rather than relying on non-tinnitus control groups. Earplug treatments have been used to investigate the changes in neural activity at the brainstem and at the cortical level via both auditory reflexes and different types of auditory evoked potentials. While reflex data tends to support the idea of a temporary increase in neural activity with temporary deprivation, electrophysiological data remain unclear. However, the electrophysiological data have been mixed, and the picture remains unclear, and there has been limited exploration of loudness perception changes, which is associated with hyperacusis. We notice that no study has attempted to capture all of these different types of measures within the same group of listeners, which formed the overarching aim of the present study.
Objectives: The objective of this study was to probe the effects of a temporary partial hearing loss at the auditory brainstem level via auditory brainstem response (ABR) and acoustic reflex thresholds (ART), and at the auditory cortical level via cortical auditory evoked potentials (CAEP) following earplug treatment. Another objective was to investigate changes to loudness sensitivity with an automated psychophysical intensity discrimination limen (IDL) test after sound deprivation.
Methods: An ABA prospective study design, consisting of a baseline condition (A1), immediately after a 48-hour unilateral earplug treatment (B), and a recovery to baseline condition (A2), was implemented on five adult participants with normal hearing. ART, ABR, CAEP, and IDL were measured for each participant at each condition (A1, B, and A2).
Results: A statistically significant reduction in ART was observed during condition B compared to baseline conditions (A1, A2). However, no significant changes were found in ABR wave V amplitudes, CAEP N1 amplitudes, or IDL following the earplug treatment.
Conclusion: The ART results support the hypothesis by demonstrating gain-related changes in neural activity. However, the absence of changes in the ABR, CAEP, and IDL suggests no alterations in neural gain, leading us to default to the null hypothesis. The reason for this remains unclear, but it is possible that the small sample size of this study limits the ability to detect significant effects, or they may have required a longer period of auditory deprivation to observe an effect. While no significant difference was detected in our ABR readings, a possible reduction in amplitude following auditory deprivation was observed, contrary to the anticipated increase in neural gain. The cause for this remains unclear, but one possibility is that the expansion of the cartilaginous ear canal may have resulted in a lower-than-expected amplitude. The ART results showed consistency with previous studies, whereas the results for auditory evoked potentials (ABR and CAEP) were more variable. Future studies could further investigate the effects of earplug treatment on reflex pathways in comparison to neural pathways. We also recommend conducting further studies with a larger sample size and a longer period of auditory deprivation