High Frequency Radio Wave Transionospheric Propagation Polarization Studies from the RRI-SuperDARN Experiment

The enhanced Polar Outflow Probe (ePOP) launched in September 2013 is the fifth Canadian satellite designed for space science observations. One of the 8 instruments it carries is the Radio Receiver Instrument (RRI) which is a passive cross-dipole radio observation instrument. The RRI detects incoming HF (High Frequency) radio waves and measures the polarization information (such as orientation angle and ellipticity angle) of the wave. Radio waves were transmitted from the Saskatoon SuperDARN (Super Dual Auroral Radar Network) radar in conjunction with RRI flybys. There have been 88 conjunctions between RRI and SuperDARN over 4 years (2014-2018). The changing polarization state of the radar signal as it propagates through the ionosphere, transionospheric propagation, is the scientific focus of this thesis. Polarization techniques are used to study and characterize the modifications to the polarization state of the transionospheric radar signal. By characterizing polarization phenomena new details of structure in the ionosphere can be observed and further understanding of HF transionospheric radio wave propagation. Of the 88 RRI-Saskatoon SuperDARN radar conjunctions, 49 flybys recorded usable data including polarization information used to characterize phenomena observed as a radio wave propagates through the ionosphere can be achieved. Magnetoionic theory of transionospheric radio wave propagation is used in this thesis to predict the phenomena observed in the RRI-Saskatoon SuperDARN radar conjunctions. Phenomena such as the Faraday rotation effect and the Voigt effect are extracted from the theory and demonstrated to occur in the Saskatoon flybys. Features in the orientation angle and ellipticity angle of the Saskatoon flybys are compared and contrasted to previously reported transionospheric observations. The Faraday rotation reversal signatures observed in the auroral region portion of the Saskatoon flybys were found to be more variable than the reversal signatures of sub-auroral events. Danskin et al. (2018) reported considerably more constant observations of the Faraday rotation reversal signatures in RRI flybys in conjunction with an HF transmitter located at Ottawa, Ontario. The Voigt effect oscillations observed were found to agree with derived magnetoionic theory. They are dependent on the rate of Faraday rotation and are observed throughout an entire RRI flyby. An interpretation of Voigt effect oscillations observations had yet to be reported in transionospheric radio wave propagation experiments before this thesis. Three distinct and consistent spikes in the ellipticity angle were observed in daytime, slewing, high-altitude flybys and such behaviour was not predicted by modelling. It is postulated that the spikes in ellipticity angle demonstrate that RRI is moving between regions of focusing and defocusing of O- and X-mode rays, or ``HF fades'' during these RRI flybys (James et al., 2006)

Ocean acidification buffers the physiological responses of the king ragworm Alitta virens to the common pollutant copper

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this recordOcean acidification (OA) has the potential to alter the bioavailability of pH sensitive metals contaminating coastal sediments, particularly copper, by changing their speciation in seawater. Hence OA may drive increased toxicity of these metals to coastal biota. Here, we demonstrate complex interactions between OA and copper on the physiology and toxicity responses of the sediment dwelling polychaete Alitta virens. Worm coelomic fluid pCO2 was not increased by exposure to OA conditions (pHNBS 7.77, pCO2 530 μatm) for 14 days, suggesting either physiological or behavioural responses to control coelomic fluid pCO2. Exposure to 0.25 μM nominal copper caused a decrease in coelomic fluid pCO2 by 43.3% and bicarbonate ions by 44.6% but paradoxically this copper-induced effect was reduced under near-future OA conditions. Hence OA appeared to ‘buffer’ the copper-induced acid-base disturbance. DNA damage was significantly increased in worms exposed to copper under ambient pCO2 conditions, rising by 11.1% compared to the worms in the no copper control, but there was no effect of OA conditions on the level of DNA damage induced by copper when exposed in combination. These interactions differ from the increased copper toxicity under OA conditions reported for several other invertebrate species. Hence this new evidence adds to the developing paradigm that species’ physiology is key in determining the interactions of these two stressors rather than it purely being driven by the changes in metal chemistry under lower seawater pH.University of Exete

Microplastics, microfibres and nanoplastics cause variable sub-lethal responses in mussels (Mytilus spp.)

We compare the toxicity of microplastics, microfibres and nanoplastics on mussels. Mussels (Mytilus spp.) were exposed to 500 ng mL-1 of 20 µm polystyrene microplastics, 10x30 µm polyamide microfibres or 50 nm polystyrene nanoplastics for 24 h or 7 days. Biomarkers of immune response, oxidative stress response, lysosomal destabilisation and genotoxic damage were measured in haemolymph, digestive gland and gills. Microplastics and microfibres were observed in the digestive glands, with significantly higher plastic concentrations after 7-days exposure (ANOVA, P<0.05). Nanoplastics had a significant effect on hyalinocyte-granulocyte ratios (ANOVA, P<0.05), indicative of a heightened immune response. SOD activity was significantly increased followed 24 h exposure to plastics (two-way ANOVA, P<0.05), but returned to normal levels after 7-days exposure. No evidence of lysosomal destabilisation or genotoxic damage was observed from any form of plastic. The study highlights how particle size is a key factor in plastic particulate toxicity

Author Correction: Boundary effects of expectation in human pain perception.

An amendment to this paper has been published and can be accessed via a link at the top of the paper

Enhancing accuracy and precision of transparent synthetic soil modelling

Over recent years non-intrusive modelling techniques have been developed to investigate soil-structure interaction problems of increasingly complex geometry. This paper concerns the development of a small-scale, 1 g, modelling technique using a transparent analogue for soil with particle image velocimetry for internal displacement measurement. Larger model geometry achieved in this research using fine-grained transparent synthetic soils has led to an increased need for rigorous photogrammetric correction techniques. A correction framework, based upon a modified version of the pinhole camera model, is presented that corrects for lens and camera movement induced errors as well as scaling from image space to object space. An additional statistical approach is also developed to enhance the system precision, by minimising the impact of increased non-coplanarity between the photogrammetry control plane and the target plane. The enhanced data correction and statistical precision is demonstrated using a case study examining the failure mechanism around a double helical screw pile installed in transparent synthetic soil representative of a soft clay

Sea urchin reproductive performance in a changing ocean: Poor males improve while good males worsen in response to ocean acidification

This is the final version. Available on open access from the Royal Society via the DOI in this recordData accessibility: The datasets supporting this article have been uploaded as part of the electronic supplementary material.Ocean acidification (OA) is predicted to be a major driver of ocean biodiversity change. At projected rates of change, sensitive marine taxa may not have time to adapt. Their persistence may depend on pre-existing inter-individual variability. We investigated individual male reproductive performance under present-day and OA conditions using two representative broadcast spawners, the sea urchins Lytechinus pictus and Heliocidaris erythrogramma. Under the non-competitive individual ejaculate scenario, we examined sperm functional parameters (e.g. swimming speed, motility) and their relationship with fertilization success under current and near-future OA conditions. Significant inter-individual differences in almost every parameter measured were identified. Importantly, we observed strong inverse relationships between individual fertilization success rate under current conditions and change in fertilization success under OA. Individuals with a high fertilization success under current conditions had reduced fertilization under OA, while individuals with a low fertilization success under current conditions improved. Change in fertilization success ranged from −67% to +114% across individuals. Our results demonstrate that while average population fertilization rates remain similar under OA and present-day conditions, the contribution by different males to the population significantly shifts, with implications for how selection will operate in a future ocean.European Union Horizon 2020Marie Curie Alumni AssociationCompany of BiologistsNSW Environmental Trus

Boundary effects of expectation in human pain perception

Funder: RCUK | Medical Research Council (MRC); doi: https://doi.org/10.13039/501100000265Funder: FONDECYT, 1161378Abstract: Perception of sensory stimulation is influenced by numerous psychological variables. One example is placebo analgesia, where expecting low pain causes a painful stimulus to feel less painful. Yet, because pain evolved to signal threats to survival, it should be maladaptive for highly-erroneous expectations to yield unrealistic pain experiences. Therefore, we hypothesised that a cue followed by a highly discrepant stimulus intensity, which generates a large prediction error, will have a weaker influence on the perception of that stimulus. To test this hypothesis we collected two independent pain-cueing datasets. The second dataset and the analysis plan were preregistered (https://osf.io/5r6z7/). Regression modelling revealed that reported pain intensities were best explained by a quartic polynomial model of the prediction error. The results indicated that the influence of cues on perceived pain decreased when stimulus intensity was very different from expectations, suggesting that prediction error size has an immediate functional role in pain perception

Sampling locality is more detectable than taxonomy or ecology in the gut microbiota of the brood-parasitic Brown-headed Cowbird (Molothrus ater)

Brown-headed Cowbirds (Molothrus ater) are the most widespread avian brood parasite in North America, laying their eggs in the nests of approximately 250 host species that raise the cowbird nestlings as their own. It is currently unknown how these heterospecific hosts influence the cowbird gut microbiota relative to other factors, such as the local environment and genetics. We test a Nature Hypothesis (positing the importance of cowbird genetics) and a Nurture Hypothesis (where the host parents are most influential to cowbird gut microbiota) using the V6 region of 16S rRNA as a microbial fingerprint of the gut from 32 cowbird samples and 16 potential hosts from nine species. We test additional hypotheses regarding the influence of the local environment and age of the birds.We found no evidence for the Nature Hypothesis and little support for the Nurture Hypothesis. Cowbird gut microbiota did not forma clade, but neither did members of the host species. Rather, the physical location, diet and age of the bird, whether cowbird or host, were the most significant categorical variables. Thus, passerine gut microbiota may be most strongly influenced by environmental factors. To put this variation in a broader context, we compared the bird data to a fecal microbiota dataset of 38 mammal species and 22 insect species. Insects were always the most variable; on some axes, we found more variation within cowbirds than across all mammals. Taken together, passerine gut microbiota may be more variable and environmentally determined than other taxonomic groups examined to date. © 2014 Hird et al