2,654 research outputs found

    Flood dynamics derived from video remote sensing

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    Flooding is by far the most pervasive natural hazard, with the human impacts of floods expected to worsen in the coming decades due to climate change. Hydraulic models are a key tool for understanding flood dynamics and play a pivotal role in unravelling the processes that occur during a flood event, including inundation flow patterns and velocities. In the realm of river basin dynamics, video remote sensing is emerging as a transformative tool that can offer insights into flow dynamics and thus, together with other remotely sensed data, has the potential to be deployed to estimate discharge. Moreover, the integration of video remote sensing data with hydraulic models offers a pivotal opportunity to enhance the predictive capacity of these models. Hydraulic models are traditionally built with accurate terrain, flow and bathymetric data and are often calibrated and validated using observed data to obtain meaningful and actionable model predictions. Data for accurately calibrating and validating hydraulic models are not always available, leaving the assessment of the predictive capabilities of some models deployed in flood risk management in question. Recent advances in remote sensing have heralded the availability of vast video datasets of high resolution. The parallel evolution of computing capabilities, coupled with advancements in artificial intelligence are enabling the processing of data at unprecedented scales and complexities, allowing us to glean meaningful insights into datasets that can be integrated with hydraulic models. The aims of the research presented in this thesis were twofold. The first aim was to evaluate and explore the potential applications of video from air- and space-borne platforms to comprehensively calibrate and validate two-dimensional hydraulic models. The second aim was to estimate river discharge using satellite video combined with high resolution topographic data. In the first of three empirical chapters, non-intrusive image velocimetry techniques were employed to estimate river surface velocities in a rural catchment. For the first time, a 2D hydraulicvmodel was fully calibrated and validated using velocities derived from Unpiloted Aerial Vehicle (UAV) image velocimetry approaches. This highlighted the value of these data in mitigating the limitations associated with traditional data sources used in parameterizing two-dimensional hydraulic models. This finding inspired the subsequent chapter where river surface velocities, derived using Large Scale Particle Image Velocimetry (LSPIV), and flood extents, derived using deep neural network-based segmentation, were extracted from satellite video and used to rigorously assess the skill of a two-dimensional hydraulic model. Harnessing the ability of deep neural networks to learn complex features and deliver accurate and contextually informed flood segmentation, the potential value of satellite video for validating two dimensional hydraulic model simulations is exhibited. In the final empirical chapter, the convergence of satellite video imagery and high-resolution topographical data bridges the gap between visual observations and quantitative measurements by enabling the direct extraction of velocities from video imagery, which is used to estimate river discharge. Overall, this thesis demonstrates the significant potential of emerging video-based remote sensing datasets and offers approaches for integrating these data into hydraulic modelling and discharge estimation practice. The incorporation of LSPIV techniques into flood modelling workflows signifies a methodological progression, especially in areas lacking robust data collection infrastructure. Satellite video remote sensing heralds a major step forward in our ability to observe river dynamics in real time, with potentially significant implications in the domain of flood modelling science

    Novel Acoustic Methods for Directly Monitoring Seabed Sediment Transport, Geohazards & Scour

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    In the natural environment, sediment transport processes can pose significant hazards to marine infrastructure, such as offshore wind turbines or seabed cables that carry both power onshore as well as carrying over 99% of global data. These processes are often extremely challenging to measure directly because sensors can be easily damaged by the processes themselves. It would, therefore, be highly advantageous to remotely sense and quantify sediment transport via sensors that are located outside the region of sediment transport. One way to do this is via sensors higher in the water column that detect acoustic signals emitted by sediment transport processes closer to the bed. Previous work such as Wren et al. (2015), Marineau et al. (2016), and Le Guern et al. (2021) have started to develop passive acoustic methods to record signals from sediment transport, using tools such as hydrophones and acoustic Doppler current profilers (ADCPs). Normally, ADCPs actively emit their own acoustic pulses, and their reflections are used to monitor flow velocities and concentrations. However, with modification to extend their listening times, ADCP’s can also be used to passively record acoustic signals emitted by sediment transport processes. Thus far, the potential of these passive acoustic methods have not been fully developed, and the fundamental controls that determine the type of acoustic signals produced are not yet fully understood. This PhD sought to understand what controls the nature (frequencies, strength etc) of these signals and, thus, what they can tell us about sediment transport processes (Thorne, 1985,1986,1990,2014; Rigby et al. 2016). It aims to do this using a combination of laboratory experiments (Chapter 2) and detailed fieldwork (Chapters 3 and 4) using acoustic signals passively emitted by sediment flows. In addition, the thesis includes work testing the use of active acoustic methods to monitor sediment transport processes within the natural environment, specifically seabed sediment flows (called turbidity currents) (Chapter 5). Results from this thesis found a general relationship between the strength of self-generated noise and flow speed in some types of sediment flows (Chapters 2, 3 and 4). However, the strength of this relationship changes depending on the frequency and details of the environment investigated. Field data from the Río Paraná (Chapter 3) suggested no relationship between bedload flux and acoustic signal strength, nor between acoustic signal strength and friction velocity. This is unexpected because previous research by Sime et al. (2007), Hossein and Rennie (2009), Hatcher (2017), Hay et al. (2021) and Le Guern et al. (2021) proposed links between flow speed (and bed shear stress and bedload transport) and passively detected noise strength. Passive acoustic signals generated by turbidity currents were used to monitor these flows in a set of submarine canyons, which were Bute Inlet (Canada), Monterey Canyon (offshore California), and the Congo Canyon (offshore West Africa) (Chapter 4). Noticeable variations in the level of passively detected noise between these three field sites were observed. These variations are thought to be related to the main sediment grain size present within each canyon, with lower noise being detected with an increasing mud content of the seabed. In addition, differences in noise down submarine canyons suggest that flow processes and concentration could be controlling the level of sediment-generated noise, with implications of flow field dynamics. Chapter 5 uses one of the most detailed (near-daily) series of multibeam swath bathymetry surveys yet collected, which come from within Bute Inlet, Canada, in September 2022. This unusual set of field observations is used to understand the relationship between flow evolution and the initiation mechanism of turbidity currents. For example, the Bute Inlet study supports the findings from Hizzett et al. (2018) that there is no link between the initiation mechanism and runout distance of a turbidity current. Further research is needed to improve understanding of the controls on acoustic signals in the natural environment, and to also improve our ability to use acoustic signals to monitor sediment transport in a wider range of environments, such as around offshore wind farms

    Natural and Technological Hazards in Urban Areas

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    Natural hazard events and technological accidents are separate causes of environmental impacts. Natural hazards are physical phenomena active in geological times, whereas technological hazards result from actions or facilities created by humans. In our time, combined natural and man-made hazards have been induced. Overpopulation and urban development in areas prone to natural hazards increase the impact of natural disasters worldwide. Additionally, urban areas are frequently characterized by intense industrial activity and rapid, poorly planned growth that threatens the environment and degrades the quality of life. Therefore, proper urban planning is crucial to minimize fatalities and reduce the environmental and economic impacts that accompany both natural and technological hazardous events

    Use of emerging technologies to help measure fjordic biodiversity and blue carbon: mini-manned submarines and autonomous underwater vehicle swarms

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    Meaningful protection of global oceans lags far behind that of land and has taken little consideration of climate mitigation potential to date (such as through assessment of blue carbon stocks and change). With the new emphasis on synergistic approaches to the identification and conservation of both carbon- and species- rich habitats, we need much better knowledge of the geography and status of blue carbon habitats beyond coastal wetlands. In subpolar and polar regions, some blue carbon habitats are still emerging and work as negative (mitigating) feedback on climate change, yet remain unprotected despite strong evidence of threat overlap. Scientific research expeditions are gradually increasing our understanding, but appropriate vessels are a limiting factor due to high costs and carbon footprints. Even when available such vessels cannot access all areas (e.g., remote fjords with sills) and may struggle to measure certain aspects of habitats (e.g., steep or vertical surfaces). New technologies and opportunities have advanced to aid some of these problems, and here, two of them are considered, mini-manned submersibles and autonomous underwater vehicles. These two platforms have both become much more available and affordable (through novel partnerships) while also being much more scientifically capable. This technology has the potential to reduce the carbon footprint of science and particularly aid in assessing biology and environment status and change on steep sides, such as fjord walls

    Insights into the molecular mechanisms of bacterial metabolites in the pathogenesis of autism spectrum disorder

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    Autism spectrum disorder (ASD) is a neurodevelopmental disorder usually diagnosed at early age and characterized by impairments in social behavior and communication, the presence of repetitive behavior, and deficits in learning and memory. Two of these bacterial metabolites, p-cresol sulfate (pCS) and 4-ethylphenyl sulfate (4EPS), are reported to be enhanced in feces, blood and urine of people diagnosed with ASD. Moreover, pCS and 4EPS exposure in mice induces ASD-like behavior, but the exact underlying mechanisms remain to be investigated. Many sheddases are members of the so-called ADAM family and potentially play a role in the pathogenesis of disease. In addition, the phosphatase PTEN is an important enzyme that regulates neural cell growth and survival in the brain. This thesis is focused on gaining insights into the possible molecular mechanisms of bacterial metabolites in the pathogenesis of ASD to identify potential new targets for intervention and therapy. Using an ASD mouse model and a neuroinflammation cell model, this thesis illustrates that pCS and 4EPS affect the level and function of the sheddases, ADAM10 & ADAM17, and the phosphatase, PTEN, that might be involved in the ASD-associated changes in neuroimmune responses and/or neuronal network function in the brain. In addition, this thesis further identifies that ADAM10 might be a treatment-target for ASD either through direct pharmacological inhibition or via nutritional interventions targeting bacteria that are involved in pCS and 4EPS production aimed to reduce ASD-associated detrimental symptoms

    What Makes a Habitat a Home: Understanding Settlement and Recruitment Variation in European Sea Bass, Dicentrarchus labrax

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    Sea bass stocks in the UK are in decline as a result of increased fishing pressure and variable inter-annual recruitment. Recruitment variation is driven by survival in the early life stages; therefore, nursery habitats are thought to be able to stabilize recruitment through providing optimal growth conditions for juvenile fish. A thorough understanding of the factors that drive juvenile sea bass survival is needed, however, our understanding of what constitutes quality nursery habitat for juvenile sea bass is weak, with current knowledge based almost solely on saltmarshes. Juvenile sea bass were sampled using conventional seine and fyke nets across estuarine habitats, alongside dietary DNA metabarcoding to assess their distribution diet and condition, using measures of abundance, condition, stomach fullness, and diet. To determine whether the mechanism of larvae entering estuarine nurseries is an active or passive process the vertical distribution patterns of larval sea bass were compared across tidal cycles. Finally, over-winter survival was predicted based on energy budget modelling and temperature-dependent growth experiments, based on in-situ measurements of winter temperatures. Juvenile sea bass did not differentially select high tide habitats, but saltmarshes and sand provided increased foraging success. At low tide, however, sea bass were more abundant in complex habitat with lower foraging success. Diets mainly consisted of decapods and polychaete worms across habitats, but there was evidence of increased planktivory over mud. Larval sea bass did not show evidence of flood tide transport and likely rely on passive tidal forcing to migrate into estuaries, or they are trying to retain to deeper water. According to our models, winter thermal minima resulted in complete cohort loss in all scenarios on the East coast. The results of this study suggest that multiple habitats along the estuarine mosaic are important for juvenile sea bass at some point, and that a seascape approach to management is necessary, however, winter temperatures likely present a more extreme bottleneck to recruitment

    Size Spectra as a tool to understand structures and processes of aquatic communities

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    Aquatische Gemeinschaften sind stark körpergrĂ¶ĂŸenstrukturiert mit einer exponentiellen Abnahme der HĂ€ufigkeit der Individuen mit zunehmender KörpergrĂ¶ĂŸe, die als GrĂ¶ĂŸenspektrum (SS) bezeichnet wird. KörpergrĂ¶ĂŸenbasierte AnsĂ€tze bieten eine einfache und kostengĂŒnstige Methode zur Beantwortung komplexer ökologischer Fragestellungen in aquatischer Forschung. WidersprĂŒchliche Ergebnisse zu den wichtigsten Faktoren, die GrĂ¶ĂŸenspektren beeinflussen unterstreichen jedoch die Notwendigkeit weiterer Studien. Um einige dieser widersprĂŒchlichen Schlussfolgerungen anzugehen, habe ich eine Reihe von Fragen in den Bereichen Limnologie und Korallenriffökologie untersucht. In dieser Dissertation wurden grĂ¶ĂŸenbasierte AnsĂ€tze wie SS verwendet, um zu untersuchen, (i) was die GrĂ¶ĂŸenverteilung von Zooplankton beeinflusst und ob Zooplankton-fressende Fische (topdown) oder RessourcenverfĂŒgbarkeit und Umweltbedingungen (bottom-up) die SS der Zooplanktongemeinschaft bestimmen, (ii) ob traditionelle Schleppnetze oder moderne hydroakustische Methoden Fisch-SS zuverlĂ€ssiger darstellen, und (iii) ob SS von Korallenriff- Fischgemeinschaften und die strukturelle KomplexitĂ€t der Korallen bzw. deren Beziehung zueinander sich unter verschiedenen anthropogenen Stressoren verĂ€ndert. Zuallererst konnte ich zeigen, dass weder Top-down- noch Bottom-up-KrĂ€fte stark die GrĂ¶ĂŸenverteilung der Zooplanktongemeinschaft beeinflussten. Zooplankton SS scheinen robust gegenĂŒber PrĂ€dationseffekten zu sein, aber ein empfindlicher Indikator fĂŒr die EnergieverfĂŒgbarkeit und Transfereffizienz im Nahrungsnetz des untersuchten Sees. Des Weiteren konnten meine Studien bestĂ€tigen, dass hydroakustische Methoden die SS von pelagischen Fischgemeinschaften zuverlĂ€ssig darstellen, was sie zu einer kostengĂŒnstigen und minimalinvasiven Alternative zu traditionellen Fischentnahmemethoden macht. Ich konnte jedoch kein allgemeingĂŒltiges Muster hinsichtlich der GrĂ¶ĂŸenverteilung von Korallenrifffischen und der strukturellen KomplexitĂ€t der Korallen in Beziehung zu unterschiedlichen anthropogenen Stressoren finden. Insgesamt zeigt die Dissertation das weite Anwendungsspektrum von SS, um Strukturen und Prozesse in aquatischen Gemeinschaften und Fischfangmethoden zu untersuchen. Die hohe VariabilitĂ€t von GrĂ¶ĂŸenspektren und der Einfluss von Umweltbedingungen unterstreicht weiter die Wichtigkeit, Daten ĂŒber einen langen Zeitraum einzubeziehen. DarĂŒber hinaus unterstreichen die Ergebnisse dieser Arbeit auch die Grenzen der Anwendung von SS, da fĂŒr die Beantwortung mancher ökologischer Fragestellungen artenspezifische Informationen, wie Lebensraum- und NahrungsprĂ€ferenzen benötigt werden.Aquatic communities are highly body-size structured with an exponential decline of abundance with increasing body size, which is referred to as the size spectrum (SS). The importance of body size as a principal and simplifying framework within aquatic communities, has led to a high number of theoretical and empirical studies on energy fluxes in food webs and predatorprey interactions using Size Spectra. These size-based approaches offer a rather simple and inexpensive method to answer complex ecological questions. However, conflicting findings on the key drivers of SS highlight the need for further studies. To address some of these conflicting conclusions, I investigated a range of questions within the fields of limnology and coral reef ecology. In this thesis size-based approaches such as SS were employed to explore (i) what drives zooplankton size distribution and whether zooplanktivorous fish (top-down) or resource availability and environmental condition (bottom-up) determine zooplankton community SS, (ii) whether traditional midwater trawling or modern hydroacoustic methods more reliably represent fish SS, and (iii) coral reef fish community SS and habitat structural complexity and their relationship across site-specific anthropogenic stressors. By analysing long term data, I first found that neither top-down or bottom-up forces drove the zooplankton community size distribution. Zooplankton SS seem robust against predation effects but a sensitive indicator for lake-wide energy availability and transfer efficiency in the food web. Then I found that hydroacoustic methods reliably represent pelagic fish community SS, making it a great alternative to traditional and more invasive fish removal sampling methods. Finally, I discovered that coral reef fish SS slope and structural complexity of the reef exhibited a significant negative relationship on two of the examined reef sites which are least exposed to anthropogenic disturbances. A consistent pattern of fish SS and reef complexity was missing, indicating that other environmental factors may also impact the assessed parameters. Overall, my studies show the range of applications of SS to effectively answer universal questions from trophic interactions and the importance of habitat characteristics in a community to a methodological comparison of fish sampling methods. The high variability of SS behaviour and the influence of environmental conditions further underlines the importance to include data on a large temporal scale. Community information, such as taxonomic identity and consideration of species-specific feeding and habitats preferences, for example, are still beneficial in some cases to answer ecologically questions extensively

    Development and validation of novel and quantitative MRI methods for cancer evaluation

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    Quantitative imaging biomarkers (QIB) offer the opportunity to further the evaluation of cancer at presentation as well as predict response to anti-cancer therapies before and early during treatment with the ultimate goal of truly personalised medical care and the mitigation of futile, often detrimental, therapy. Few QIBs are successfully translated into clinical practice and there is increasing recognition that rigorous methodologies and standardisation of research pipelines and techniques are required to move a theoretically useful biomarker into the clinic. To this end, I have aimed to give an overview of what I believe to be some of key elements within the research field beginning with the concept of imaging biomarkers, introducing concepts in development and validation, before providing a summary of the current and future utility of a range of quantitative MR imaging biomarkers techniques within the oncological imaging field. The original, prospective, research moves from the technical and analytical validation of a novel QIB use (T1 mapping in cancer), first in vivo qualification of this biomarker in cancer patient response assessment and prediction (sarcoma and breast cancer as well as prostate cancer separately), and then moving on to application of more established QIBs in cancer evaluation (R2*/BOLD imaging in head and neck cancer) as well as how existing MR data can be post-processed to improved cancer evaluation (further metrics derived from diffusion weighted imaging in head and neck cancer and textural analysis of existing clinical MR images utility in prostate cancer detection)

    Integrating Traditional and Close Range Photogrammetric Bathymetric Reconstructions to Enhance Predictions of Fish Abundance and Distribution on the NSW Coast

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    The physical structure of marine habitat is a key determinant of the distribution and abundance of marine biota. Photogrammetry is a new method of obtaining bathymetric reconstructions using overlapping imagery. It is associated with several potential improvements over traditional bathymetric reconstruction methods (e.g., hydroacoustic and optical remote sensing), including finer resolutions, 3D mesh surfaces, and novel metrics of structural complexity. However, the greater cost of photogrammetric data collection requires evaluation of its purported benefits to marine research. This thesis objectively assessed the potential for photogrammetry to improve predictions of marine biota abundance and distribution. Chapter 2 undertook a quantitative review and metanalysis of latest research and the relative performance of metrics. It indicated common metrics, e.g., surface-rugosity, may not always be the best performing. Chapter 3 systematically explored the relationships between metrics derived from common bathymetric reconstructions and reduced a 2,000 predictor dataset to 100 predictors, whilst maximising information captured. Metric relative performance was assessed in Chapter 4. Photogrammetric metrics contributed to 22 / 35 fish species and 10 / 15 trophic-mobility group best performing abundance models and helped explain a third more variability compared to traditional methods. Chapter 5 extrapolated (‘engineered’) broad-scale photogrammetric metrics from traditional metrics to help alleviate the cost of photogrammetry. Using an independent dataset, the variance 26 / 50 fish species distribution models was explained best when engineered photogrammetric metrics were included. These findings help confirm the purported benefits to marine research associated with photogrammetric metrics, which would likely improve predictions of the distribution and abundance of fish, and likely other marine biota, across Australia and worldwide. Engineered metrics would allow greater model performance to be translated to broad-extents required by marine spatial prioritisation, conservation and management. Notably, traditional metrics were important for some fish species and groups, and future studies should seek to combine these methods wherever possible
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