Bradford Scholars is the University of Bradford online research archive. Access is free to anyone interested in research being conducted at Bradford. In the repository you will find a range of materials from journal articles and conference papers to research reports and theses.

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  • Computational fluid dynamics modelling of unconfined gas mixing of wastewater sludge in a full scale anaerobic digester

    Dapelo, Davide; Bridgeman, John (2015-09)
    In this paper, an Euler-Lagrange model for computational fluid dynamics was used to model a full-scale gas-mixed anaerobic digester. The flow profiles, local values of non-Newtonian viscosity and average shear rate were analysed. Recommendations to enhance the effectiveness of mixing were given. In particular, the gas mixing input power can be reduced without appreciable detrimental effects on the mixing effectiveness.
  • CEOs' regulatory foci and firm-level product innovativeness in competitive environments

    Adomako, Samuel (2017-06)
    Purpose: Using arguments from the regulatory focus and upper echelons theories, this paper aims to examine the impact of a chief executive officer’s (CEO’s) regulatory foci (i.e. promotion and prevention focus) on small- and medium-sized enterprises’ (SMEs’) level of innovativeness and how these relationships are jointly moderated by intense competition. Design/methodology/approach: The empirical analysis draws on survey data gathered from 257 SMEs in Ghana. Findings: The study findings indicate that a CEO’s level of promotion focus positively affects the firm’s engagement in innovation, while a CEO’s prevention focus is negatively associated with the firm’s innovativeness. The positive association between a CEO’s promotion focus and a firm’s innovativeness is enhanced under conditions of intense competition. Additionally, the negative relationship between prevention focus and firm-level innovativeness is attenuated under intense competition. Research limitations/implications: This study relied on a single informant and also used subjective measures for the dependent variable. As such, individual respondents might have biased perspectives on firm-level product innovativeness. Future studies may use multiple informants to examine the causal links of the variables. Practical implications: The study’s findings provide managers with a deeper understanding of how to achieve superior firm-level product innovation. The understanding of this issue can promote the development and maintenance of further entrepreneurial ventures in emerging economies. Originality/value: The paper has a strong theoretical value as it pioneers research on the effect of CEOs’ regulatory foci on firm-level innovativeness in competitive environments.
  • Analytical solution of suspended sediment concentration profile: relevance of dispersive flow term in vegetated channels

    Huai, W.; Yang, L.; Guo, Yakun (2020-07)
    Simulation of the suspended sediment concentration (SSC) has great significance in predicting the sediment transport rate, vegetation growth and the river ecosystem in the vegetated open channel flows. The present study focuses on investigating the vertical SSC profile in the vegetated open channel flows. To this end, a model of the dispersive flux is proposed in which the dispersive coefficient is expressed as partitioned linear profile above or below the half height of vegetation. The double-averaging method, i.e. time-spatial average, is applied to improve the prediction accuracy of the vertical SSC profile in the vegetated open channel flows. The analytical solution of SSC in both the submerged and the emergent vegetated open channel flows is obtained by solving the vertical double-averaging sediment advection-diffusion equation. The morphological coefficient, a key factor of the dispersive coefficient, is obtained by fitting the existing experimental data. The analytically predicted SSC agrees well with the experimental measurements, indicating that the proposed model can be used to accurately predict the SSC in the vegetated open channel flows. Results show that the dispersive term can be ignored in the region without vegetation, while the dispersive term has significant effect on the vertical SSC profile within the region of vegetation. The present study demonstrates that the dispersive coefficient is closely related to the vegetation density, the vegetation structure and the stem Reynolds number, but has little relation to the flow depth. With a few exceptions, the absolute value of the dispersive coefficient decreases with the increase of the vegetation density and increases with the increase of the stem Reynolds number in the submerged vegetated open channel flows.
  • Unaltered perception of suprathreshold contrast in early glaucoma despite sensitivity loss

    Bham, H.A.; Dewsbery, S.D.; Denniss, Jonathan (2020-07)
    PURPOSE. Glaucoma raises contrast detection thresholds, but our natural visual environment is dominated by high contrast that may remain suprathreshold in early to moderate glaucoma. This study investigates the effect of glaucoma on the apparent contrast of visible stimuli. METHODS. Twenty participants with glaucoma with partial visual field defects (mean age, 72 ± 7 years) and 20 age-similar healthy controls (mean age, 70 ± 7 years) took part. Contrast detection thresholds for Gabor stimuli (SD, 0.75°) of four spatial frequencies (0.5, 1.0, 2.0, and 4.0 c/deg) were first measured at 10° eccentricity, both within and outside of visual field defects for participants with glaucoma. Subsequently, the contrast of a central Gabor was matched to that of a peripheral Gabor with contrast fixed at two times or four times the detection threshold. Data were analyzed by linear mixed modelling. RESULTS. Compared with controls, detection thresholds for participants with glaucoma were raised by 0.05 ± 0.025 (Michelson units, ± SE; P = 0.12) and by 0.141 ± 0.026 (P < 0.001) outside and within visual field defects, respectively. For reference stimuli at two times the detection contrast, matched contrast ratios (matched/reference contrast) were 0.16 ± 0.039 (P < 0.001) higher outside compared with within visual field defects in participants with glaucoma. Matched contrast ratios within visual field defects were similar to controls (mean 0.033 ± 0.066 lower; P = 0.87). For reference stimuli at four times the detection contrast, matched contrast ratios were similar across all three groups (P = 0.58). Spatial frequency had a minimal effect on matched contrast ratios. CONCLUSIONS. Despite decreased contrast sensitivity, people with glaucoma perceive the contrast of visible suprathreshold stimuli similarly to healthy controls. These results suggest possible compensation for sensitivity loss in the visual system.
  • 5C analysis of the Epidermal Differentiation Complex locus reveals distinct chromatin interaction networks between gene-rich and gene-poor TADs in skin epithelial cells

    Poterlowicz, Krzysztof; Yarker, Joanne L.; Malashchuk, Igor; Lajoie, B.R.; Mardaryev, Andrei N.; Gdula, M.R.; Sharov, A.A.; Kohwi-Shigematsu, T.; Botchkarev, Vladimir A.; Fessing, Michael Y. (2017)
    Mammalian genomes contain several dozens of large (>0.5 Mbp) lineage-specific gene loci harbouring functionally related genes. However, spatial chromatin folding, organization of the enhancer-promoter networks and their relevance to Topologically Associating Domains (TADs) in these loci remain poorly understood. TADs are principle units of the genome folding and represents the DNA regions within which DNA interacts more frequently and less frequently across the TAD boundary. Here, we used Chromatin Conformation Capture Carbon Copy (5C) technology to characterize spatial chromatin interaction network in the 3.1 Mb Epidermal Differentiation Complex (EDC) locus harbouring 61 functionally related genes that show lineage-specific activation during terminal keratinocyte differentiation in the epidermis. 5C data validated by 3D-FISH demonstrate that the EDC locus is organized into several TADs showing distinct lineage-specific chromatin interaction networks based on their transcription activity and the gene-rich or gene-poor status. Correlation of the 5C results with genome-wide studies for enhancer-specific histone modifications (H3K4me1 and H3K27ac) revealed that the majority of spatial chromatin interactions that involves the gene-rich TADs at the EDC locus in keratinocytes include both intra- and inter-TAD interaction networks, connecting gene promoters and enhancers. Compared to thymocytes in which the EDC locus is mostly transcriptionally inactive, these interactions were found to be keratinocyte-specific. In keratinocytes, the promoter-enhancer anchoring regions in the gene-rich transcriptionally active TADs are enriched for the binding of chromatin architectural proteins CTCF, Rad21 and chromatin remodeler Brg1. In contrast to gene-rich TADs, gene-poor TADs show preferential spatial contacts with each other, do not contain active enhancers and show decreased binding of CTCF, Rad21 and Brg1 in keratinocytes. Thus, spatial interactions between gene promoters and enhancers at the multi-TAD EDC locus in skin epithelial cells are cell type-specific and involve extensive contacts within TADs as well as between different gene-rich TADs, forming the framework for lineage-specific transcription.

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