Open Research Exeter - University of Exeter
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A New Method of Measuring Atmospheric Refractivity
No full textThis thesis explores a new source of atmospheric refractivity information by measuring the refraction of radio transmissions broadcast by commercial aircraft. Detailed measurements of atmospheric humidity in the lower atmosphere are currently difficult and expensive to obtain. For this reason, there is interest in the development of low-cost, high-volume opportunistic technologies to acquire measurements of tropospheric humidity. The angle-of-arrival (AoA) of the 1090 MHz Automatic Dependent Surveillance-Broadcast (ADS-B) radio transmission can be measured using vertically-orientated, two-element interferometers. Atmospheric refraction is strongly influenced by changes in humidity, and refractivity observations have proved to be an effective source of humidity information for numerical weather prediction models. This thesis shows the derivation of novel inversion algorithms to retrieve refractivity structure from AoA measurements using gradient-free and adjoint-based techniques. The initial experimental results from a prototype interferometer installed on the Clee Hill weather radar tower in Shropshire, United Kingdom are shown. The inversion algorithms are applied to observational data and vertical profiles of refractivity were retrieved. The principal sources of observational uncertainties and methods to mitigate their impacts were explored through simulations and experiments. The observations obtained were significantly impacted by multipath contamination, where multiple signals from the same source mutually interfere at the receiver. Variations in atmospheric refractivity structure on mesoscale (∼10-100 km) and ∼15-minute spatial and temporal scales respectively were detected with the prototype ADS-B interferometer. The proposed technique is relatively low cost (∼€10k), requiring off the shelf equipment and making use of freely available software. The results from this thesis encourage further exploration and research into this new remote sensing technique. Future work would benefit from simulated and real assimilation experiments using observational data
Mitigating loneliness and remediating solitude: pandemic narratives from the Global South
No full textSet in the Global South context of India, this article examines how users of digital media used their platforms and devices to mitigate loneliness and create moments of solitude during the Covid-19 pandemic. Historically, experiencing loneliness has been understood as debilitating but solitude has been deemed necessary for individuality and achieving self-growth. This study, qualitative in nature, examines how users of digital media distinguished between the two and charts this engagement to examine their capabilities while using their platforms and services of choice. By adopting a longitudinal design of iterative interviews with 10 participants across age groups and demographics, our findings indicate that digital media users in the Global South repurposed their platforms and services in many ways during the pandemic but found little meaning in their online interactions. The participants, while critically reflecting on their online practices, found social media isolating, and digital media’s attempts at remediating solitude suspect
Learning Markov Processes with Latent Variables
No full textWe consider the problem of identifying the parameters of a time-homogeneous bivariate Markov chain when only one of the two variables is observable. We show that, subject to conditions that we spell out, the transition kernel and the distribution of the initial condition are uniquely recoverable (up to an arbitrary relabelling of the state space of the latent variable) from the joint distribution of four (or more) consecutive time-series observations. The result is, therefore, applicable to (short) panel data as well as to (stationary) time series data
Integrated co-simulation and Hardware-in-the-Loop testing for microgrid
No full textThis article underscores the critical necessity of practical validation through a meticulous combination of simulation and hardware experimentation. Integrating a field-programmable gate array controller with the real-time digital simulator enables robust validation via controller hardware-in-loop (CHIL) testing. This novel platform provides valuable insights into the improved performance and resilience of inverter based resources connected in the microgrid. Testing conducted with a 2.5 kW doubly fed induction generator wind turbine and a 2 kW lithium-ion battery emphasizes the importance of integrating a grid-forming controlled battery converter to maintain stable, grid-independent wind turbine operation. Unlike conventional hardware-in-the-loop (HIL) setups, this platform is further enhanced by incorporating physical power hardware elements to assess system resilience under realistic load variations and fault conditions. Key contributions include an advanced synchronization control strategy, combining modified phase-locked loop technique with PI-based presynchronization to achieve stable voltage and frequency control in grid-independent operation. This integration enables sustained standalone operation and enhances fault resilience at load connection points. The combined FPGA-RTDS platform effectively bridges theoretical models and real-world hardware, providing a reliable means of validating hardware simulations and control algorithms. Ultimately, the proposed integrated CHIL platform provides a comprehensive assessment framework, crucial for verifying microgrid reliability and resilience prior to real-world deployment
Variation of the low-mass end of the stellar initial mass function with redshift and metallicity (article)
No full textWe report the stellar mass functions obtained from 20 radiation hydrodynamical simulations of star cluster formation in 500 Msun molecular clouds with metallicities of 3, 1, 1/10 and 1/100 of the solar value, with the clouds subjected to levels of the cosmic microwave background radiation that are appropriate for star formation at redshifts z=0, 3, 5, 7, and 10. The calculations include a thermochemical model of the diffuse interstellar medium and treat dust and gas temperatures separately. We find that the stellar mass distributions obtained become increasingly bottom light as the redshift and/or metallicity are increased. Mass functions that are similar to a typical Galactic initial mass function are obtained for present-day star formation (z=0) independent of metallicity, and also for the lowest-metallicity (1/100 solar) at all redshifts up to z=10, but for higher metallicities there is a larger deficit of brown dwarfs and low-mass stars as the metallicity and redshift are increased. These effects are a result of metal-rich gas being unable to cool to as lower temperatures at higher redshift due to the warmer cosmic microwave background radiation. Based on the numerical results we provide a parameterisation that may be used to vary the stellar initial mass function with redshift and metallicity; this could be used in simulations of galaxy formation. For example, a bottom-light mass function reduces the mass-to-light ratio compared to a typical Galactic stellar initial mass function, which may reduce the estimated masses of high-redshift galaxies
The perceptual effects of signal components: black sword margins are crucial for signal size discrimination in green swordtails Xiphophorus hellerii
No full textThe signals that mediate mate choice can be complex, comprising multiple components, and understanding how complex signals evolve under sexual selection has been the focus of much study. However, open questions still remain about the role of the female’s sensory and perceptual processes in shaping the evolution of complex signals. Male green swordtails Xiphophorus hellerii have an elongated caudal fin that comprises colour, length and a black melanic margin; females prefer males with larger bodies, longer swords and complete black sword margins. Here, we used a two-choice assay to quantify female preferences for animations of courting males of different sizes with or without sword margin coloration, and found that, when a black melanic margin was present, females exhibited preferences for larger males. However, when the margin was absent, females did not show size-based mate preference, though females spent equal time assessing males in both treatments. Our results suggest that the presence/absence of the black sword margin is an important predictor of female preference, specifically a female’s ability to discriminate between potential mates of different sizes, pointing to a novel size discrimination function of black margins in animal signals, which in many species involve patterns or structures with dark edges
Association of classroom-level stressors with psychological distress in teachers
No full textBackground
Poor mental health is highly prevalent among schoolteachers. Different occupational, contextual and personal factors have been identified as sources of their psychological distress.
Aims
To explore the association of classroom-level variables with teachers’ mental health over the course of an academic year.
Methods
This study included 80 primary schoolteachers and 2075 pupils from the STARS trial conducted in England, which explored the impact of the Incredible Years Teacher Classroom Management programme. Linear regression models examined the relationships between classroom-level predictor variables and teachers’ psychological distress, as measured by the Everyday Feeling Questionnaire, at 1 and 9 months into the school year. Predictor variables included classroom size and demographic composition, amount of teaching assistant support, and pupils’ mental health, as measured by the Strengths and Difficulties Questionnaire and the Pupil Behaviour Questionnaire. Analyses were adjusted for teacher length of service and trial arm status.
Results
One month into the school year, fully adjusted analyses showed that having a classroom with a higher proportion of male pupils was associated with worse teacher mental health. None of the classroom-level stressors were associated with teacher mental health at 9 months.
Conclusions
Classroom gender balance was associated with teacher’s mental health at the beginning but not at the end of the academic year. It is important to consider classroom-level variables when developing interventions and policies for teacher mental health
The monster, Delilah and liberation in The Shape of Water
No full textThis article analyses Guillermo del Toro’s 2017 film The Shape of Water as a case study for the proposition that monsters may generate liberated, alternative ways of being. In the film, one of the main characters recounts the story of Samson and Delilah from Judges 16. I critique this biblical reception in the film using Liberative Reception Criticism and intersectional lenses. Using insights from monster theorists this examination of the film demonstrates that the monster does offer alternative ways of being which liberate those who have been oppressed and dehumanised by hegemonic patriarchy, itself constructed and perpetuated by certain biblical interpretations. The oppressive use of biblical interpretations is presented in the film as abject, while the monster is presented as potentially liberative from those oppressive legacies.</p
Anaemia, ethnicity and cancer incidence: a retrospective cohort study in primary care
No full textBACKGROUND: Haemoglobin, mean corpuscular volume (MCV), and rates of iron-deficiency anaemia (IDA) are used in primary care to investigate possible cancer symptoms, especially for gastrointestinal cancers. Underlying ethnic differences in typical test results could lead to inequalities in the diagnosis of cancer in primary care. AIM: To investigate the distribution of low haemoglobin, low MCV, and IDA, and the rate of cancer diagnosis in patients with abnormal results, by ethnic group. DESIGN AND SETTING: A retrospective cohort study using routine data collected in primary care in England was undertaken. Included patients had blood tests between 2010 and 2017, and were aged ≥40 years with no prior cancer diagnosis. METHOD: Multilevel logistic regression was used to investigate the relationship between blood test results and cancer risk for patients in different ethnic groups. RESULTS: Low haemoglobin, low MCV, and IDA were effective in identifying patients with increased cancer risk, particularly for gastrointestinal cancers. MCV was found to be a stronger cancer indicator for White patients (diagnostic odds ratio [OR] 3.84; 95% confidence interval [CI] = 3.72 to 3.96) than for Asian (OR 1.86; 95% CI = 1.64 to 2.10) or Black patients (OR 1.75; 95% CI = 1.54 to 1.99). CONCLUSION: There are some small differences in cancer risk for patients with abnormal test results, when considering patient ethnic group, especially for MCV. This is likely to be a consequence of the underlying difference in typical MCV values for patients from different ethnic groups. Further investigation is required to understand the aetiology of these differences in order to disentangle any effects on outcomes for patients with cancer.</p
Chondrocalcinosis and the haemochromatosis-linked <i>HFE</i> C282Y homozygous variant in the UK Biobank
No full textObjectivesC282Y genetic homozygosity is the main cause of the iron-overload disorder haemochromatosis. Musculoskeletal pain and arthropathy are common in haemochromatosis, but less is known about chondrocalcinosis (cartilage calcification) with the C282Y variant, especially in the community. We assessed knee chondrocalcinosis in intelligent dual-energy X-ray absorptiometer (iDXA) images from UK Biobank volunteers by HFE genotype.MethodsData were from 236 European genetic ancestry C282Y homozygotes and 236 age, sex, and body mass index (BMI)-matched controls with no C282Y alleles (48-80 years, mean 64.6, SD ±7.6). Of 472 participants, 435 had relevant left and right knee iDXA imaging. Evidence of chondrocalcinosis was assessed by an experienced reporting radiographer blind to genotype to ensure unbiased and objective evaluation. Logistic regression models were age, sex, and BMI matched.ResultsC282Y homozygotes had significantly increased odds of knee chondrocalcinosis (odds ratio [OR]: 3.79, 95% CI: 1.51-9.55, P = .005). Among males, 15.9% (14/88) of homozygotes showed chondrocalcinosis vs ConclusionsIn this community-genotyped sample, male C282Y homozygotes had markedly increased odds of knee chondrocalcinosis. Evaluation of serum ferritin levels to identify possible haemochromatosis may be justified in knee chondrocalcinosis management.</p