University of Birmingham
University of Birmingham Research Archive, E-theses RepositoryNot a member yet
11811 research outputs found
Sort by
Authentication with what you have: improving resilience and usability
Get PDFThis thesis aims to improve the resilience and usability of authentication with what you have. I identify two problems which are pertinent to this area and present solutions to each.
The first problem concerns the remote registration of multiple authenticators. User authentication with discrete authenticators, such as YubiKeys, is becoming increasingly popular. The authenticators can be external or on-device. They work using challenge-response protocols and public key cryptography. Multiple accounts can be associated with each authenticator. Compared with other forms of authentication, this approach has advantages in security and usability. There are, however, significant limitations which persist.
In particular, if users possess only one authenticator, they lack resilience to loss and malfunction. On the other hand, if they possess multiple authenticators, they lack practical solutions to keep authenticators synchronised.
In this thesis, I present three solutions which combine the usability of a single authenticator with the resilience of multiple authenticators. I also present novel key derivation functions which are important components of the solutions. All three solutions maintain core security and privacy properties found in existing systems. Meanwhile, each solution provides additional value in different use cases. The security of the solutions is analysed using ProVerif.
The second problem concerns secret sharing without a central entity. A cryptographic secret can be shared amongst multiple players such that a subset of players must collaborate to use the secret. A central entity can be tasked to issue new shares of the secret but such an entity must be trusted and secure. This can be costly or impractical. To issue new shares in a decentralised manner, players can take two existing approaches which I call the frontloading approach [20] and the NSG approach [27].
The frontloading approach has the advantages of less communication complexity, fewer requirements to broadcast metadata, more robustness against delays or revoked decisions, and more flexibility in the choice of thresholds.
However, the frontloading approach has limitations which are not yet resolved. These limitations are addressed in this thesis. First, only a limited set of players are able to participate in issuing shares. Second, the setup stage is not fully decentralised. Players need to be provisioned with particular information before they can issue shares and an additional mechanism is required to generate this information in a decentralised manner.
To extend the ability to issue shares, I describe a protocol of multi-layered secret sharing. This includes a protocol for distributing and recombining shares without compromising the security of the shared secret. To make the frontloading approach fully decentralised, I describe a protocol of multi-layered secret sharing with multiple parties. Thus, players can generate the information required for frontloading without a central entity. These solutions may be used to improve the security and usability of secret sharing. This can be valuable for users and service providers in applications such as user authentication and threshold authorisation
Bilingualism and social cognition in young adults
Get PDFResearch on bilingual advantages has been found to extend beyond benefits in executive functions to benefits in higher levels of social cognition. The relationship between bilingualism and social cognition is complex, making it difficult to agree on whether and how bilingualism affects social cognitive abilities. However, this field continues to be explored, driven by debate and discussion, making it enter a promising period. This thesis contributes to our understanding of the effect of bilingualism on social cognitive abilities from two aspects, namely perspective-taking and social-emotional ability.
Chapter 1 introduces the effects of bilingualism, perspective-taking, and social- emotional skills. Chapter 2 reports the attempt to replicate a visuospatial perspective-taking (VPT) paradigm by Freundlieb et al. (2018). In two experiments, we did not replicate spontaneous co-representation in joint action VPT tasks. The study presented in Chapter 3 investigates whether bilingual young adults outperform their monolingual peers in VPT, including Level-1 and Level-2 VPT, independent of the effects of executive function and cross-cultural differences. The results showed that EF skills, but not individual differences in bilingualism or culture, predict VPT performance in young adults. Chapter 4 presents an individual differences study suggesting that multilingualism is negatively associated with prosocial behaviour, mediated by empathic concern. The final chapter summarises the findings, outlines the limitations of this thesis, discusses some implications for future studies, and provides a conclusion.
The thesis does not find any evidence for a bilingual advantage in VPT. More generally, it contributes to our understanding of the core mechanisms of VPT. It suggests that these core mechanisms are similar across language experience and culture. In contrast to the lack of evidence for a bilingual advantage in VPT, the findings of this thesis suggest that young adult bilinguals are less distressed and anxious and more emotionally stable, which appears to be related to less prosocial behaviour
An exploration of consumers' fashion sharing experiences
Get PDFThe purpose of this research is to explore consumer’s fashion sharing experience through the lens of identity theory. This research defines fashion sharing as a sociocultural and economic activity, allowing individuals to temporarily access fashion items. To reach the research purpose, this research adopted a qualitative research design. Specifically, 40 semi-structured online interviews with photo-elicitation and thematic data analysis were conducted.
The findings shed light on the nature of fashion sharing and its eight characteristics, which are as follows: benefit exchange, identity engagement, temporary material possession, sociality, trust, digitalisation, sustainability and de-ownership. The findings, in particular, highlight three types of benefits that people can derive from their fashion sharing practises: social benefits, utilitarian benefits, and hedonic benefits. Furthermore, this study demonstrates how individuals' sustainability concerns interact with the entire process of their fashion sharing experiences. The findings show a complex and profound relationship between fashion sharing and consumer identity. Finally, this research contributes to the development of practical implications for fashion sharing platforms/companies’ managers as well as research directions for future studies
NGO accountability and power dynamics in safeguarding: the core humanitarian standard in theory and practice in refugee camps in Sudan
Get PDFThe heightened exposure of exploitation and abuse by aid workers in 2018 resulted in watershed moment for the aid sector, in particular regarding accountability toward affected populations. Despite extensive efforts by aid providers, including establishing a range of complaint mechanisms, abuse continues and remains under-reported, leaving victims to suffer in silence. This thesis investigates NGO accountability and safeguarding failures in the humanitarian aid sector. It does so by focusing on the Core Humanitarian Standard of Quality and Accountability (CHS) and applying this to the case study of refugee camps in Sudan.
The thesis draws on in-depth qualitative research in two stages. Employing a "What’s the problem represented to be?" approach, this research first deconstructs the CHS using 42 interviews and review of 128 documents to analyse how accountability is conceptualized and framed within the Standard. It identifies a conceptual gap in the CHS, particularly in its framing of accountability and its failure to recognise and address power imbalances. Secondly, a case study of refugee camps in Sudan is developed to examine the implementation of complaint mechanisms and inter-agency coordination within the displacement context. Through 63 in-depth interviews and 7 months of follow-up correspondence, the thesis exposes the widespread SEA committed by multiple types of stakeholders and analyses dynamics of power across spaces, levels, and forms using Gaventa’s powercube approach. It also explores the responses of aid providers to encourage refugee populations to come forward with
SEA concerns.
This research identifies gaps in current complaint mechanisms and argues that, although CHS has played a role in reinforcing policy development, a lack of explicit actionable indicators on power imbalance in the Standard has contributed to its limited ability to transform the ‘closed’ space of power to a ‘claimed’ one. Leveraging my distinctive positionality as an insider practitioner-researcher, the thesis goes beyond providing academic insights to offer actionable, practical recommendations to enhance NGO accountability, contributing to a safer aid sector
Energy justice and multilevel perspective impact assessment of energy access and transition in Nigeria: a mini-grid case study
No full textThis thesis aims to advance a multi-level governance approach to a 'just' energy transition in developing countries. Using the Nigerian context as a test case and the mini-grid sub-electricity sector as case study, the thesis argues that a ‘just’ transition will not happen in developing countries despite numerous policy changes, unless the existing dominant meso-level energy regime structure is destabilised. The research reveals that the meso-level regime significantly hinders the country's current energy transition strategy, which is why policy regulations are unable to take into account various groups’ needs and strategies. This is demonstrated by the case study analysis of the impact of mini-grid projects on important Niger Delta rural communities within the Nigerian context, as well as an energy justice (EJ) and multilevel perspective (MLP) examination of the Mini-grid regulation of 2016. The thesis recognises that because the transition is made up of heterogenous actors and their interests, as well as new technologies that are foisted onto old pathways, questions regarding path dependencies and the co-dependency of sociotechnical transitions are raised. Thus, the narrative of the country's current transition is one of "new wine in old wine skins," which hinders the empowerment and security of new entrants in the energy decision making space and the blossoming of niches (RE technologies). The thesis argues that MLP and EJ frameworks are able to recognize and address marginalization’s that have occurred in the past and in the present transition, such that hinders niches. Furthermore, it contends that both frameworks can make corrections at the recognition, distribution, and procedural layers, and start multi-level governance initiatives to lessen the effects of exclusion, ultimately toppling the existing meso-level energy system of the country. The thesis concludes by offering a formalised policy approach that promotes the integration of sectoral techniques and conditions that make for the participation of all stakeholders, including non-state actors and soft law techniques, in order to ensure a successful energy transition and realisation of access goals for everyone
The effect of nuclear hormone receptor stimulation in oral epithelia
Get PDFGingivitis is a plaque-mediated, inflammatory periodontal disease of the gingival mucosa with high prevalence in the modern population. The gingival mucosa is covered by the gingival epithelium, which plays a significant role in the pathogenesis of periodontal diseases by instigating inflammatory signalling and recruiting immune cells in response to bacteria. Importantly, the gingival epithelia act as a barrier, maintaining homeostasis and preventing bacterial ingress into the deeper tissues. Gingivitis itself poses little risk to the patient but may progress to periodontitis in susceptible individuals. This is a hyperactive immune response to the plaque stimulus, leading to destruction of the deeper tissues and a loss of attachment of the tooth. This thesis aimed to study these inflammatory and barrier function responses to bacteria in vitro in monolayer cells and novel organotypic models, and then investigate the nuclear hormone receptor peroxisome proliferator activated receptor gamma (PPARγ) as an anti-inflammatory agent.
RT-qPCR, transepithelial electrical resistance and fluorescent macromolecular tracer assays were employed to identify a suitable inducer of inflammation and barrier function failure for use in successive studies. Additionally, two reporter cell lines were generated to validate PPARγ agonists in epithelial cells, with western blotting and PCR performed to identify differential expression of PPARγ tissue isoforms. Finally, a novel culture device was designed, tested and utilised to generate organotypic gingival epithelial cultures, enabling comparison of the response of monolayer and organotypic cultures to an inflammatory agent and PPARγ agonists.
Bacterial lipopolysaccharide (LPS) was shown to effectively induce pro-inflammatory cytokine expression. Treatment with a validated PPARγ agonist (GW1929) abrogated this effect, reducing the expression of pro-inflammatory cytokines and increasing anti-inflammatory cytokines. Barrier function was also significantly reduced by LPS, with this effect appearing to be partially abrogated by PPARγ treatment.
The buoyant epithelial culture device (BECD) was shown to generate stratified, differentiated gingival epithelial mimics, with minimal user input compared to alternative approaches due to a unique floating design. BECD-cultured cells showed minimal pro-inflammatory cytokine expression following LPS treatment, indicating marked differences in inflammatory signalling compared to monolayer cultures.
In conclusion, this thesis demonstrated the usage of LPS as an inducer of inflammation and barrier function failure, whilst showing that PPARγ agonists may pose significant utility in curbing inflammatory responses in gingival epithelia, with the potential to aid in the maintenance of epithelial barrier function. The efficacy of the novel BECD was also demonstrated by showing the marked difference in response between simple monolayer cultures and more complex organotypic cultures. This system may also find use in further studies of other stratified epithelial tissues
The native-like speaker myth: challenging native-like proficiency as the only measure of additional language acquisition success
Get PDFThis thesis seeks to challenge the native-like speaker myth, which consists of four assumptions about adult additional language acquisition. These four assumptions are as follows: 1) assumption of a homogenous native speaker, 2) assumption of native-like proficiency as ultimate attainment goal, 3) assumption of native-like proficiency as the only measure of success, and 4) assumption of an objective measure of additional language acquisition (ALA) success. Using a qualitative life histories approach, this study adds nuance to the notion of success and failure in adult ALA. This study consists of individual interviews of twenty-six (26) participants who began learning an additional language after the age of 12. Their interview data was analyzed primarily using a qualitative data analysis process and secondarily using corpus analysis. As a result of these multiple rounds of data analysis, four themes emerged: 1) adults learn language to connect with people, not to be like native speakers; 2) adults learn language to connect with cultures, not to be like native speakers; 3) adults can succeed at reaching or exceeding their additional language goals; and 4) adults do not always fail at ALA; instead, they have varied measures of AL success, which are not always measured by nearness to native-like proficiency. The use of the life histories approach allowed adult additional language learners to voice their own individual measures of additional language acquisition goals and measures of success. The themes that emerged from the data analysis challenged the four assumptions of the native-like speaker myth
Developing a core outcome set for twin pregnancy
Get PDFTwin pregnancy is a pregnancy with two fetusus. One in 42 babies are born a twin (1). There are multiple pathophysiological processes that cause twin pregnancy which results in different twin pregnancy types, each attributing an associated risk (2–4). Consequently, mothers and twins are at a significant increased risk of morbidity and mortality (5–7) which has resulted large body of research aiming to improve outcomes for them (8).
In order to provide strong evidence to support the clinical guidance of these patients, research is often combined in the form of meta-analysis. However, this can be hindered by the heterogeneity within outcome reporting in clinical trials. A solution to this, is the use of Core Outcome Set’s (COS). A COS is ‘an agreed standardised collection of outcomes which should be measured and reported as a minimum, in all trials for a specific clinical area’ (9) and are based on what key stakeholders (patients and medical experts) believe are essential for research. A COS for twin pregnancy will therefore standardise outcome reporting in twin pregnancy which will enable data synthesis, ensure future research remains relevant to patients and improve outcomes for mothers and twins.
COS development is broken down into the three distinct stages as defined by The COMET Initiative (9). Stage one is outcome identification, stage two is outcome consensus and stage three is COS finalisation. The aim of this research is to create the initial COS as set out in stages one and two of COS development which will lay the foundation for the final COS for twin pregnancy
An antiquity of horror: H.P. Lovecraft's classical reception
No full textThis thesis attests that the Classical reception of weird fiction pioneer Howard Phillips Lovecraft is integral to understanding his works. It puts forth that his Graeco-Roman Period of literature manifests itself in his poetry and prose as a vehicle for self-expression, and served as a tool through which Lovecraft related to the wider world. ‘An Antiquity of Horror’ contends that the famous mythopoetic megastructure known as the Cthulhu Mythos is fundamentally shaped by his relationship with Classics, exhibited through its intertextual references and inversion of traditionally mythic themes
Survival pathways supporting BRCA1 function
Get PDFThe reast ncer susceptibility protein (BRCA1) is a tumour suppressor protein that functions in the DNA damage response and in replication. In DNA double-strand break repair BRCA1 functions within the pathway homologous recombination, mainly in the regulation of DNA resection. Its roles in replication, including the protection of stalled replication forks and the suppression of single-stranded DNA (ssDNA) post-replicative gaps, are poorly understood. BRCA1 forms a heterodimeric complex with BRCA1 associated RING domain 1 (BARD1), forming an active E3 ubiquitin ligase, the cellular roles of which remain controversial. A method of further understanding the functional role(s) of BRCA1 is to investigate the pathways supporting cell survival when some of those functions are disabled.
A synthetic lethal interaction between DNA polymerase θ (Polθ) loss in BRCA1- mutated cells has been identified, yet the mechanisms underlying this relationship remain to be fully elucidated. In this thesis, we have determined that BRCA-RAD51 interactions suppress cell sensitivity to Polθ loss using Brca1 53bp1 mouse embryonic fibroblasts (MEFs) as our Brca1-mutated model. In addition, we find that RAD52 underlies the synthetic lethal relationship between Brca1/53bp1 deficiencies and Polθ depletion. We identified that Polθ limits RAD52-mediated suppression of ssDNA gap fill-in during G2/M.
We also investigated a potential ligase-defective murine allele, Bard1. Bard1 cells are proficient in homologous recombination yet form ssDNA gaps behind replication forks. We found that the Bard1 cells exhibited sensitivity to the loss of ubiquitin-specific protease 1 (USP1). These Bard1-mutant cells have provided preliminary findings surrounding the role of USP1 in DNA damage tolerance (DDT) mechanisms in our cells. Overall, the findings in this thesis increase our understanding of survival pathways supporting BRCA1 function
Data sources:
Access Repository Dashboard
Do you manage Open Research Online? Become a CORE Member to access insider analytics, issue reports and manage access to outputs from your repository in the CORE Repository Dashboard! 👇