Impact of Baryonic astrophysics and intrinsic alignments on dark energy and neutrino constraints in cosmology

In the early 2020s, cosmology will enter an era of unprecedented precision when the next generation of large scale structure surveys begin receiving data. As a result, it is expected that stronger constraints on major features of cosmology like dark energy and massive neutrinos are forthcoming. The former could help to favour an explanation for the present accelerated expansion of the Universe, while the latter has the potential to enhance our understanding of a prominent intersection between particle physics and cosmology. However, there are many systematics that must be accounted for in parameter forecasts. One of the most prominent theoretical cases is the influence of baryonic astrophysics on large scale structure (e.g., AGN and supernova feedback, adiabatic contraction etc.) and the effect that marginalising over a limited theoretical understanding of the associated phenomena will have on forecasts. This question is one of the core concerns of this thesis. It will be applied respectively in Chapters 3, 4 and 5 to constraints on dynamical dark energy, the neutrino mass sum and a possible coupling between dark energy and dark matter. While forecasts are the primary focus here, much of this work has implications for parameter inference more broadly, and could be used to inform the direction that model building or simulation development should take in pursuit of the goal of more accurate parameter constraints. The key statistics used here to probe the growth of structure derive from the power spectrum of matter overdensities. This permits the use of both weak gravitational lensing of light from background sources by foreground objects, and galaxy clustering. The former requires accounting for the intrinsic alignments of ellipticities and shears, a systematic examined in depth for its impact on forecasts. This thesis presents Fisher analyses using weak lensing and galaxy clustering probes for parameter forecasts for a Euclid-like survey. The approach here to modelling the baryonic phenomena is to adopt a generic treatment of their global redistribution of the dark matter content in haloes, via energy transfer to their surroundings. Different baryonic effects are separated into three general but distinct categories: large scale adiabatic contraction caused by radiative cooling; high impact energy transfer from specific, localised sources; and small-scale effects that manifest as inner halo cores. I introduce the inner halo core through analytic modelling. A central tenet of this work is the use of analytic modelling, rather than numerical simulations, in capturing the relevant physics so as to circumvent computational expenses and underlying systematics associated with the latter, while retaining the useful physical insight offered by the former. Employing a maximum likelihood method, matter and weak lensing power spectra are varied around a fiducial cosmology given by Planck Collaboration et al. (2016b). For a Euclid-like survey covering 15000 sq. deg. of sky, measuring 10 redshift bins in the range 0 < z < 2 , the w0 - wa dark energy Figure of Merit is shown to experience a ~40% degradation due to the combination of baryon effects. This thesis presents a detailed analysis of the relative dark energy and baryon sensitivities over the range of available lensing modes. Ultimately, it is found that the application of cosmic microwave background (CMB) priors alleviate the baryon impact for individual errors on the dark energy parameters but the relative degradation to the Figure of Merit for the parameter space remains. A similar approach is used to address the question of whether Stage IV surveys, whilst accounting for baryons and intrinsic alignments, can make a positive detection of the neutrino mass and whether they can distinguish between the normal and inverted hierarchy of mass eigenstates. Combined forecasts from weak lensing, the CMB and galaxy clustering preclude a meaningful distinction of hierarchies but do achieve a positive detection of the mass sum, overcoming the significant degradation by factors of ~2 to that arise when marginalising over baryons for weak lensing alone. These results could be improved upon with future CMB priors on the spectral index and information from neutrinoless double beta decay to achieve a 2-σ distinction of the hierarchies. The effect of intrinsic alignments on forecasts is shown to be minimal, with constraints even experiencing mild improvements due to information from the intrinsic alignment signal. Finally, this work explores the prospects for using large scale structure to constrain the strength of a possible coupling between dark matter and a dark energy scalar field. While the growth of structure in the linear regime in this model has been well-explored, the non-linear regime is more challenging. Forecasts have been made using polynomial fits to power spectra directly. However, this thesis presents a more physically motivated approach to the problem. I show that a single parameter, the halo virial density, is responsible for describing most of the impact of the coupling on small scales. By computing the changes to the virial density in this model, a fit can be found that allows for a full physically-motivated halo model. This allows Fisher forecasts to be made for the coupling strength, including an assessment of the impact of baryons. Degradations to the coupling strength constraint of ~20% due to this systematic are found. While CMB and galaxy clustering priors notably improve the absolute errors without marginalising over baryons, when this systematic is accounted for these priors provide little improvement and the relative degradation increases. Taken as a whole, this thesis provides a comprehensive analysis of the impact of baryons and intrinsic alignments on constraints for a wide range of cosmological phenomena responsible for the accelerated expansion, the neutrino mass hierarchy and beyond ΛCDM physics coupling dark matter and dark energy. Through modified and improved approaches to halo modelling, this work demonstrates which of these phenomena are subject to the most severe degeneracies with baryonic effects. This rigorous analysis, grounded in empirically motivated parameterisations, is designed to inform optimal mitigation strategies to minimise the impact on forecasts. In turn, this provides a wide scope for making future improvements to modelling and simulations that can advance efforts to constrain cosmology still further

Octreotide in the Control of Post-Sclerotherapy Bleeding from Oesophageal Varices, Ulcers and Oesophagitis

Bleeding from oesophageal varices, oesophageal ulcers or oesophagitis is occasionally massive and difficult to control. Octreotide, a synthetic analogue of somatostin lowers portal pressure and collateral blood flow including that through varices, increases lower oesophageal sphincter pressure, and inhibits the gastric secretion of acid as well as pepsin. Our current experience suggests it is effective in controlling acute variceal haemorrhage. Therefore we have examined the efficacy of octreotide in the control of postsclerotherapy bleeding from oesophageal varices, oesophageal ulcers and oesophagitis. During the study period 77 patients experienced a significant gastrointestinal bleed (blood pressure < 100 mm Hg, pulse > 100 beats per min or the need to transfuse 2 or more units of blood to restore the haemoglobin level) following injection sclerotherapy of oesophageal varices. The source of bleeding was varices in 42 patients, oesophageal ulcers in 31 and oesophagitis in 4. All patients received a continuous intravenous infusion of octreotide (50 μg/h) for between 40–140h. If bleeding was not controlled in the first 12h after commencing octreotide hourly bolus doses (50 μg) for 24h were superimposed on the continuous infusion. Haemorrhage was successfully controlled by an infusion of octreotide in 38 of the 42 patients with bleeding from varices, in 30 of 31 patients with oesophageal ulceration, and all patients with oesophagitis. In the 1 patient with persistent bleeding from oesophageal ulceration and in 2 of the 4 with continued haemorrhage from varices, haemostasis was achieved by hourly boluses of 50 μg octreotide for 24h in addition to the continuous infusion. No major complications were associated with octreotide administration. The results of this study clearly indicate that octreotide is a safe and effective treatment for the control of severe haemorrhage after technically successful injection sclerotherapy

Collisions of Cosmic F- and D-strings

Recent work suggests that fundamental and Dirichlet strings, and their (p,q) bound states, may be observed as cosmic strings. The evolution of cosmic string networks, and therefore their observational signals, depends on what happens when two strings collide. We study this in string perturbation theory for collisions between all possible pairs of strings; different cases involve sphere, disk, and annulus amplitudes. The result also depends on the details of compactification; the dependence on ratios of scales is only logarithmic, but this is still numerically important. We study a range of models and parameters, and find that in most cases these strings can be distinguished from cosmic strings that arise as gauge theory solitons.Comment: 42 pages, 7 figures; v.2: added references, expanded discussion of reconnection in field theor

Availability, outage, and capacity of spatially correlated, Australasian free-space optical networks

Network capacity and reliability for free space optical communication (FSOC) is strongly driven by ground station availability, dominated by local cloud cover causing an outage, and how availability relations between stations produce network diversity. We combine remote sensing data and novel methods to provide a generalised framework for assessing and optimising optical ground station networks. This work is guided by an example network of eight Australian and New Zealand optical communication ground stations which would span approximately $60^\circ$ in longitude and $20^\circ$ in latitude. Utilising time-dependent cloud cover data from five satellites, we present a detailed analysis determining the availability and diversity of the network, finding the Australasian region is well-suited for an optical network with a 69% average site availability and low spatial cloud cover correlations. Employing methods from computational neuroscience, we provide a Monte Carlo method for sampling the joint probability distribution of site availabilities for an arbitrarily sized and point-wise correlated network of ground stations. Furthermore, we develop a general heuristic for site selection under availability and correlation optimisations, and combine this with orbital propagation simulations to compare the data capacity between optimised networks and the example network. We show that the example network may be capable of providing tens of terabits per day to a LEO satellite, and up to 99.97% reliability to GEO satellites. We therefore use the Australasian region to demonstrate novel, generalised tools for assessing and optimising FSOC ground station networks, and additionally, the suitability of the region for hosting such a network.Comment: Accepted in Journal of Optical Communications and Networking. 16 pages, 16 figure

Chronic Rhinosinusitis: Potential Role of Microbial Dysbiosis and Recommendations for Sampling Sites.

Chronic rhinosinusitis (CRS) is an inflammatory condition that affects up to 12% of the human population in developed countries. Previous studies examining the potential role of the sinus bacterial microbiota within CRS infections have found inconsistent results, possibly because of inconsistencies in sampling strategies. The aim of this study was to determine whether the sinus microbiome is altered in CRS and additionally if the middle meatus is a suitable representative site for sampling the sinus microbiome. Swab samples were collected from 12 healthy controls and 21 CRS patients, including all eight sinuses for CRS patients and between one and five sinuses for control subjects. The left and right middle meatus and nostril swabs were also collected. Significant differences in the sinus microbiomes between CRS and control samples were revealed using high-throughput 16S rRNA gene sequencing. The genus Escherichia was over-represented in CRS sinuses, and associations between control patients and Corynebacterium and Dolosigranulum were also identified. Comparisons of the middle meatuses between groups did not reflect these differences, and the abundance of the genus Escherichia was significantly lower at this location. Additionally, intra-patient variation was lower between sinuses than between sinus and middle meatus, which together with the above results suggests that the middle meatus is not an effective representative sampling site

Draft genome sequence of Frankia sp. strain DC12, an atypical, noninfective, ineffective isolate from Datisca cannabina

Frankia sp. strain DC12, isolated from root nodules of Datisca cannabina, is a member of the fourth lineage of Frankia, which is unable to reinfect actinorhizal plants. Here, we report its 6.88-Mbp high-quality draft genome sequence, with a G+C content of 71.92% and 5,858 candidate protein-coding genes

An intervention to improve teacher well-being support and training to support students in UK high schools (the WISE study): A cluster randomised controlled trial.

Funder: Public Health WalesFunder: Bristol City CouncilFunder: Public Health EnglandBACKGROUND: Teachers are at heightened risk of poor mental health and well-being, which is likely to impact on the support they provide to students, and student outcomes. We conducted a cluster randomised controlled trial, to test whether an intervention to improve mental health support and training for high school teachers led to improved mental health and well-being for teachers and students, compared to usual practice. We also conducted a cost evaluation of the intervention. METHODS AND FINDINGS: The intervention comprised (i) Mental Health First Aid training for teachers to support students; (ii) a mental health awareness session; and (iii) a confidential staff peer support service. In total 25 mainstream, non-fee-paying secondary schools stratified by geographical area and free school meal entitlement were randomly allocated to intervention (n = 12) or control group (n = 13) after collection of baseline measures. We analysed data using mixed-effects repeated measures models in the intention-to-treat population, adjusted for stratification variables, sex, and years of experience. The primary outcome was teacher well-being (Warwick-Edinburgh Mental Well-being Scale). Secondary outcomes were teacher depression, absence, and presenteeism, and student well-being, mental health difficulties, attendance, and attainment. Follow-up was at months 12 (T1) and 24 (T2). We collected process data to test the logic model underpinning the intervention, to aid interpretation of the findings. A total of 1,722 teachers were included in the primary analysis. Teacher well-being did not differ between groups at T2 (intervention mean well-being score 47.5, control group mean well-being score 48.4, adjusted mean difference -0.90, 95% CI -2.07 to 0.27, p = 0.130). The only effect on secondary outcomes was higher teacher-reported absence among the intervention group at T2 (intervention group median number of days absent 0, control group median number of days absent 0, ratio of geometric means 1.04, 95% CI 1.00 to 1.09, p = 0.042). Process measures indicated little change in perceived mental health support, quality of relationships, and work-related stress. The average cost of the intervention was £9,103 per school. The study's main limitations were a lack of blinding of research participants and the self-report nature of the outcome measures. CONCLUSIONS: In this study, we observed no improvements to teacher or student mental health following the intervention, possibly due to a lack of impact on key drivers of poor mental health within the school environment. Future research should focus on structural and cultural changes to the school environment, which may be more effective at improving teacher and student mental health and well-being. TRIAL REGISTRATION: www.isrctn.com ISRCTN95909211

Integrating physical activity into the treatment of depression in adults: a qualitative enquiry

Around 246 million people globally suffer from depression. Physical activity (PA) can reduce the risk of depression by 30% and is recognised as an effective treatment for mild‐to‐moderate depression (MMD). However, a high proportion of patients with MMD are currently inactive and the implementation of PA as an adherent treatment for MMD is not well understood. This study contributes to a growing body of research exploring how to support people who are experiencing MMD to increase their PA levels (i.e. initiation and maintenance). It investigated which factors individuals with MMD perceived to be important for integrating PA into the treatment of depression in adults. In‐depth interviews were carried out with individuals with MMD (N = 6), and data were analysed using thematic analysis. Two main theories of social capital that of Bourdieu and Putnam informed the discussion of findings. The initiation and maintenance of PA were linked to individual factors including health (i.e. nature of depression; comorbidities); abilities and tastes; socioeconomic status (e.g. financial position) and positive encouragement. In addition, maintenance emerged as dependent upon the choice, enjoyment, and meaningfulness of PA itself, and, for those who engaged in group PA, on social capital. PA interventions need to be personalised. This goes beyond a simple exercise prescription based on functional ability, but instead takes into account the needs, desires and capabilities of the whole person. The nature of MMD, the wider physical and socio‐economic context and the social capital that is available to the individual also need to be harnessed