Towards precision measurements of large-scale structure with next-generation spectroscopic surveys

Over recent decades, spectroscopic surveys have yielded exceptional measurements of the large-scale structure of the Universe. Notably, they have measured the baryon acoustic oscillation (BAO) scale at late times, helping to develop a tightly-constrained cosmological model by complementing measurements from the cosmic microwave background. In this thesis, we focus on late-time BAO measurements from quasar (QSO) spectra. Such measurements can be made at 1<z<2 via direct QSO clustering, and at 2<z<4 via the Lyman-alpha (Lya) forest extracted from high-z QSO spectra.In the near future, the Dark Energy Spectroscopic Instrument (DESI) will continue to advance this field, increasing the quantity and quality of QSO spectra available via a host of technological improvements. In order to maximise the impact of its data, however, DESI will require major advances in analysis methods to be made. This thesis describes work to develop such methods for use in two areas of DESI’s QSO survey. First, we address the construction of optimal strategies for classifying QSO target spectra. We use data from existing surveys to demonstrate the performance of potential strategies, finding that high performance levels can be achieved using existing classification tools. Next, we present LyaCoLoRe, a package developed to produce mock Lya forest datasets from simple simulations, to be used in Lya BAO analyses. We describe the methods employed by LyaCoLoRe, and demonstrate that our mocks are suitable to be used in Lya BAO studies present and future. We then discuss applications of the classification strategies and mock datasets presented previously, as well as a method of using BAO measurements to constrain the local cosmic expansion rate, showing results from current datasets and providing forecasts for DESI. We conclude by highlighting a number of future paths which our work could follow, with particular focus on the opportunities that will emerge from DESI

Predictors of Individual-Level Innovation at Work: A Meta-Analysis

peer-reviewedNumerous narrative reviews related to innovation in work organizations have been published, yet very few quantitative reviews have been conducted. The present meta-analysis investigates the relationships between four predictor types (individual differences, motivation, job characteristics, and contextual influences) and individual-level workplace innovation. Results indicated that individual factors, characteristics of the job, and factors of the environment were moderately associated with phases of the innovation process. Implications for future research opportunities are discussed.ACCEPTEDpeer-reviewe

Developmental regulation of Foxp3 expression during ontogeny

Thymectomy of neonatal mice can result in the development of autoimmune pathology. It has been proposed that thymic output of regulatory T (T reg) cells is delayed during ontogeny and that the development of autoimmune disease in neonatally thymectomized mice is caused by the escape of self-reactive T cells before thymectomy without accompanying T reg cells. However, the kinetics of T reg cell production within the thymus during ontogeny has not been assessed. We demonstrate that the development of Foxp3-expressing T reg cells is substantially delayed relative to nonregulatory thymocytes during ontogeny. Based on our data, we speculate that induction of Foxp3 in developing thymocytes and, thus, commitment to the T reg cell lineage is facilitated by a signal largely associated with the thymic medulla

TGF-β Signaling Initiated in Dendritic Cells Instructs Suppressive Effects on Th17 Differentiation at the Site of Neuroinflammation

While the role of Transforming Growth Factor β (TGF-β) as an intrinsic pathway has been well established in driving de novo differentiation of Th17 cells, no study has directly assessed the capacity of TGF-β signaling initiated within dendritic cells (DCs) to regulate Th17 differentiation. The central finding of this study is the demonstration that Th17 cell fate during autoimmune inflammation is shaped by TGF-β extrinsic pathway via DCs. First, we provide evidence that TGF-β limits at the site of inflammation the differentiation of highly mature DCs as a means of restricting Th17 cell differentiation and controlling autoimmunity. Second, we demonstrate that TGF-β controls DC differentiation in the inflammatory site but not in the priming site. Third, we show that TGF-β controls DC numbers at a precursor level but not at a mature stage. While it is undisputable that TGF-β intrinsic pathway drives Th17 differentiation, our data provide the first evidence that TGF-β can restrict Th17 differentiation via DC suppression but such a control occurs in the site of inflammation, not at the site of priming. Such a demarcation of the role of TGF-β in DC lineage is unprecedented and holds serious implications vis-à-vis future DC-based therapeutic targets

Lack of Foxp3 function and expression in the thymic epithelium

Foxp3 is essential for the commitment of differentiating thymocytes to the regulatory CD4+ T (T reg) cell lineage. In humans and mice with a genetic Foxp3 deficiency, absence of this critical T reg cell population was suggested to be responsible for the severe autoimmune lesions. Recently, it has been proposed that in addition to T reg cells, Foxp3 is also expressed in thymic epithelial cells where it is involved in regulation of early thymocyte differentiation and is required to prevent autoimmunity. Here, we used genetic tools to demonstrate that the thymic epithelium does not express Foxp3. Furthermore, we formally showed that genetic abatement of Foxp3 in the hematopoietic compartment, i.e. in T cells, is both necessary and sufficient to induce the autoimmune lesions associated with Foxp3 loss. In contrast, deletion of a conditional Foxp3 allele in thymic epithelial cells did not result in detectable changes in thymocyte differentiation or pathology. Therefore, in mice the only known role for Foxp3 remains promotion of T reg cell differentiation within the T cell lineage, whereas there is no role for Foxp3 in thymic epithelial cells

Jamming and Stress Propagation in Particulate Matter

We present simple models of particulate materials whose mechanical integrity arises from a jamming process. We argue that such media are generically "fragile", that is, they are unable to support certain types of incremental loading without plastic rearrangement. In such models, fragility is naturally linked to the marginal stability of force chain networks (granular skeletons) within the material. Fragile matter exhibits novel mechanical responses that may be relevant to both jammed colloids and cohesionless assemblies of poured, rigid grains.Comment: LATEX, 3 Figures, elsart.cls style file, 11 page

Self-supervised vessel detection from low resolution satellite imagery

Maritime surveillance is a growing field of application for optical imaging satellites. In this paper, we aim to increase the practical effectiveness of vessel detection algorithms by developing a computationally inexpensive method that can discern vessels in low resolution optical satellite imagery. This creates an opportunity to host the algorithm on-board small, low cost nanosatellites, generating feasibility for large surveillance constellations. The presented algorithm, which is based upon a deep convolutional autoencoder utilized as an anomaly detector, was found to achieve a detection precision of 98%, and a recall of 79%. Data used to test and train the algorithm was produced by augmenting ESA Sentinel-2 imagery, reducing the resolution to mimic that of a nanosatellite’s. The results presented here are compared with comparable papers in the field, where it is demonstrated that the proposed algorithm is capable of outperforming classical techniques in terms of detection precision. For an equivalent resolution, the proposed algorithm provides a 34% increase in precision over the Constant False Alarm Rate (CFAR) technique