Topics in weak gravitational lensing

In this thesis, various topics pertaining to weak gravitational lensing and its application to cosmology and galaxy evolution are explored. The first chapter is the introduction which contains all of the background information needed to understand the rest of the thesis. Topics covered include cosmology, structure formation, the formation and evolution of galaxies, weak gravitational lensing, galaxy shape measurement, and simulations for the measurement and correction of biases in weak lensing surveys. In the second chapter of this thesis, we present an analysis of weak lensing signals around galaxy groups and clusters using the data from the Canada-France Imaging Survey (CFIS), part of the Ultraviolet Near-Infrared Optical Northern Survey (UNIONS). Lenses are selected from the Tinker group catalogue and the redMaPPer cluster catalogue, and binned by estimated halo mass and richness. The weak lensing shape distortions around groups and clusters are then fit with simple models out to the virial radius. For redMaPPer clusters, we evaluate the mass-richness relation and find good agreement with previous results using other weak lensing data sets. We make the first weak lensing measurement of the masses of galaxy groups selected from the Tinker (2020a) catalogue, finding better agreement if the cosmological parameters have a lower value of 8 ≡ (Ωm/0.3)0.58 = 0.74 ± 0.03. Additionally, we bin the groups by the colour of the central galaxy and confirm evidence for a bimodality in halo masses between groups with red and blue centrals for stellar masses > 10^11⊙. In the third chapter, we present a weak lensing analysis of satellite galaxies in galaxy group environments. We find a mean satellite mass from satellites selected from the Tinker (2020a) catalogue of log_10 = 12.5 ± 0.2. Satellite galaxies in these environments are also predicted to be tidally stripped. We place a 1 lower limit on the truncation radius of 19 h^{-1} kpc. We then attempt to measure the truncation radius as a function of their projected separation from the group centre, but find that binning the satellites reduces the strength of the signal too significantly to measure such an effect. In the final chapter of the thesis, we explore the topic of bias calibration in weak lensing surveys. A set of simulations designed to mock CFIS/UNIONS weak lensing observations is described. These simulations have a known shear applied to them, which can then attempt to be recovered via the weak lensing pipeline utilized by the survey. Initial measurements of the multiplicative and additive biases, which can be used to calibrate the shape measurements, are made

‘I stayed with my illness’: a grounded theory study of health seeking behaviour and treatment pathways of patients with obstetric fistula in Kenya

Background: Obstetric fistula classic symptoms of faecal and urinary incontinence cause women to live with social stigma, isolation, psychological trauma and lose their source of livelihoods. There is a paucity of studies on the health seeking behaviour trajectories of women with fistula illness although women live with the illness for decades before surgery. We set out to establish the complete picture of women’s health seeking behaviour using qualitative research. We sought to answer the question: what patterns of health seeking do women with obstetric fistula display in their quest for healing? Methods: We used grounded theory methodology to analyse data from narratives of women during inpatient stay after fistula surgery in 3 hospitals in Kenya. Emergent themes contributed to generation of substantive theory and a conceptual framework on the health seeking behaviour of fistula patients. Results: We recruited 121 participants aged 17 to 62 years whose treatment pathways are presented. Participants delayed health seeking, living with fistula illness after their first encounter with unresponsive hospitals. The health seeking trajectory is characterized by long episodes of staying home with illness for decades and consulting multiple actors. Staying with fistula illness entailed health seeking through seven key actions of staying home, trying home remedies, consulting with private health care providers, Non-Governmental organisations, prayer, traditional medicine and formal hospitals and clinics. Long treatment trajectories at hospital resulted from multiple hospital visits and surgeries. Seeking treatment at hospital is the most popular step for most women after recognizing fistula symptoms. Conclusions: We conclude that the formal health system is not responsive to women’s needs during fistula illness. Women suffer an illness with a chronic trajectory and seek alternative forms of care that are not ideally placed to treat fistula illness. The results suggest that a robust health system be provided with expertise and facilities to treat obstetric fistula to shorten women’s treatment pathways

The shape of dark matter haloes: results from weak lensing in the Ultraviolet Near-Infrared Optical Northern Survey (UNIONS)

Cold dark matter haloes are expected to be triaxial, and so appear elliptical in projection. We use weak gravitational lensing from the Canada-France Imaging Survey (CFIS) component of the Ultraviolet-Near Infrared Optical Northern Survey (UNIONS) to measure the ellipticity of the dark matter haloes around Luminous Red Galaxies (LRGs) from the Sloan Digital Sky Survey Data Release 7 (DR7) and from the CMASS and LOWZ samples of the Baryon Oscillation Spectroscopic Survey (BOSS), assuming their major axes are aligned with the stellar light. We find that DR7 LRGs with masses $M \sim 2.5\times10^{13} \textrm{M}_{\odot}/h$ have halo ellipticities $e=0.35\pm0.09$. Expressed as a fraction of the galaxy ellipticity, we find $f_h = 1.4\pm0.4$. For BOSS LRGs, the detection is of marginal significance: $e = 0.17\pm0.10$ and $f_h=0.1\pm0.4$. These results are in agreement with other measurements of halo ellipticity from weak lensing and, taken together with previous results, suggest an increase of halo ellipticity of $0.10\pm0.05$ per decade in halo mass. This trend agrees with the predictions from hydrodynamical simulations, which find that at higher halo masses, not only do dark matter haloes become more elliptical, but that the misalignment between major axis of the stellar light in the central galaxy and that of the dark matter decreases

Metabolic syndrome in bipolar disorder and schizophrenia: dietary and lifestyle factors compared to the general population

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106836/1/bdi12160.pd

Kepler eclipsing binary stars. VII. the catalogue of eclipsing binaries found in the entire Kepler data set

The primary Kepler Mission provided nearly continuous monitoring of ~200,000 objects with unprecedented photometric precision. We present the final catalog of eclipsing binary systems within the 105 deg2 Kepler field of view. This release incorporates the full extent of the data from the primary mission (Q0-Q17 Data Release). As a result, new systems have been added, additional false positives have been removed, ephemerides and principal parameters have been recomputed, classifications have been revised to rely on analytical models, and eclipse timing variations have been computed for each system. We identify several classes of systems including those that exhibit tertiary eclipse events, systems that show clear evidence of additional bodies, heartbeat systems, systems with changing eclipse depths, and systems exhibiting only one eclipse event over the duration of the mission. We have updated the period and galactic latitude distribution diagrams and included a catalog completeness evaluation. The total number of identified eclipsing and ellipsoidal binary systems in the Kepler field of view has increased to 2878, 1.3% of all observed Kepler targets

Computerised cognitive behavioural therapy for the treatment of depression in people with multiple sclerosis: external pilot trial

<p>Abstract</p> <p>Background</p> <p>People with multiple sclerosis (MS) are at high risk of depression. We undertook a pilot trial of computerised cognitive behavioural therapy (CCBT) for the treatment of depression in people with MS to test the feasibility of undertaking a full trial.</p> <p>Methods</p> <p>Participants with a diagnosis of MS and clinical levels of depression were recruited through out-patient clinics and postal screening questionnaires at two UK centres and randomised to CCBT or usual care. Clinical outcomes included the Beck Depression Inventory (BDI-II) and Multiple Sclerosis Impact Scale (MSIS-29) at baseline, 8 and 21 weeks. Feasibility outcomes included: recruitment rate; reasons for refusal, withdrawal and dropout; feasibility and acceptability of the proposed outcome measures; sample size estimation and variation in and preferences for service delivery.</p> <p>Results</p> <p>Twenty-four participants were recruited. The recruitment rate, calculated as the proportion of those invited to fill in a screening questionnaire who were consented into the trial, was 4.1%. Recruitment through out-patient clinics was somewhat slower than through screening questionnaire mail-out but the overall recruitment yield was similar. Of the 12 patients in the CCBT arm, 9 (75%) completed at least four, and 6 completed all 8 CCBT sessions. For completers, the median time (IQR) to complete all eight CCBT sessions was 15 (13 to 20) weeks. Participants expressed concern about the face validity of the Beck Depression Inventory II for the measurement of self-reported depression in people with MS. The MSIS-29 was the patient-reported outcome measure which participants felt best reflected their concerns. The estimated sample size for a full trial is between 180 and 390 participants. NHS partners were not delivering CCBT in community facilities and participants preferred to access CCBT at home, with no one expressing a preference for use of CCBT in an alternative location.</p> <p>Conclusions</p> <p>A definitive trial, with a recruitment window of one year, would require the participation of around 13 MS centres. This number of centres could be reduced by expanding the eligibility criteria to include either other neurological conditions or people with more severe depression. The MSIS-29 should be used as a patient-important outcome measurement.</p> <p>Trial registration</p> <p>ISRCTN: <a href="http://www.controlled-trials.com/ISRCTN81846800">ISRCTN81846800</a></p

A grounded theory of regaining normalcy and reintegration of women with obstetric fistula in Kenya

Abstract Background Obstetric fistula is a reproductive health problem causing immense suffering to 1% of women in Kenya that is formed as sequelae of prolonged obstructed labour. It is a chronic illness that disrupts women lives, causing stigma and isolation. Fistula illness often introduces a crisis in women’s life begetting feelings of shame and serious disruption to their social, psychological, physical and economic lives, in addition to dealing with moral and hygiene challenges. Currently, women undergo free of charge surgery at vesicovaginal fistula (VVF) camps held in national referral hospitals and dedicated fistula centres generating a significant pool of women who have undergone surgery and are ready to regain normal lives. Objective The purpose of this study was to explore experiences of women immersing back into communities and their return to normalcy after surgery in three VVF repair centres in Kenya. We set out to answer the question: what strategies improve obstetric fistula patients’ reintegration process? Methods We used grounded theory methodology to capture the reintegration and regaining normalcy experiences of women after surgery. Narrative interviews were held with 60 women during community follow-up visits in their homes after 6–19 months postoperatively. Grounded theory processes of theoretical sampling, repeated measurement; constant comparative coding in three stage open, axial and selective coding; memoing, reflexivity and positionality were applied. Emergent themes helped generate a grounded theory of reintegration and regaining normalcy for fistula patients. Results To regain normal healthy lives, women respond to fistula illness by seeking surgery.. After surgery, four possible outcomes of the reintegration process present; reintegration fully or partially back into their previous communities, not reintegrated or newly integrating away from previous social and family settings. The reintegration statuses point to the diversity outcomes of care for fistula patients and the necessity of tailoring treatment programs to cater for individual patient needs. Conclusion The emerging substantive theory on the process of reintegration and regaining normalcy for fistula patients is presented. The study findings have implications for fistula care, training and policy regarding women’s health, suggesting a model of care that encompasses physical, social, economic and psychological aspects of care after surgery and discharge

Additional file 1: of ‘I stayed with my illness’: a grounded theory study of health seeking behaviour and treatment pathways of patients with obstetric fistula in Kenya

Narrative guide. The set of questions used to guide the narrative interviews with the study participants. (DOCX 64 kb