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Working hours and pay: Its discourse and justification
Get PDFThe Chinese society has experienced great changes after the establishment of PRC in 1949, and especially after the economic reform in 1978. Its achievement has been an amazing success and quite unanticipated in many respects. However, inequality problems, such as the income gap between the rich and poor, rural and urban areas, eastern and western regions, are also coming up and becoming significant in the society.
Most sociological analysis of the different ways of justification, in the meanwhile, is rooted in the western values, and needs to be developed into the Chinese context.
Based on newspaper articles collected from seven Chinese newspapers over 12 years, the justification framework was studied in a Chinese context. The analysis of justification of Boltanski and Thévenot (2006) was explored through the dispute of working hours and pay in China. In this study, it was found that justifications in the Chinese society was influenced by its own culture and socialist attributes, and variations are recognised in the Chinese mode of justification compared with the Boltanski and Thévenot original work. A new logic of justification also emerged from the unique Chinese context. In the dispute, it also found that the justifications are changing over the years, and the preference of the logics varies between different actors. Moreover, this study also found a dialectical relationship between the discourse and practice of justification in the Chinese society.
The study contributes to the work of Boltanski and Thévenot (2006) by expanding it to a new context, and by identifying a new logic of justification of significance in the Chinese context
Plasma flow control in an S-shaped intake: measurement and computation
Get PDFIn modern aerospace engineering, flow control is an engineering technique that regulates fluid motion through active or passive methods to achieve specific performance objectives or optimise flow characteristics. The primary objectives typically include reducing drag, enhancing lift, suppressing flow separation, mitigating turbulence, and improving overall efficiency.
In recent years, a novel active flow control approach, known as dielectric barrier discharge (DBD) plasma flow control technology, has garnered significant attention. The DBD plasma actuator typically consists of two electrodes, with one electrode covered by a dielectric layer to limit current and prevent the occurrence of arc discharge. During operation, a high-frequency, high-voltage alternating current is applied between the two electrodes, ionising the surrounding air and generating plasma. In this process, charged particles within the plasma are accelerated under the influence of the electric field, colliding with neutral particles in the vicinity to produce a volumetric force (electrohydrodynamic force). This force enables control of the flow field. Due to its advantages, including the absence of mechanical components, rapid response, low energy consumption, and suitability for large-area deployment, DBD plasma flow control demonstrates immense potential for applications.
The relatively small magnitude of the volumetric force generated by dielectric barrier discharge significantly limits its practical applications in flow control. According to existing literature, there is a lack of theoretical foundation supporting DBD plasma actuator performance enhancement through a substantial increase in induced velocity. Therefore, this study aims to explore the potential of DBD plasma technology in broader application domains, building upon the currently known physical characteristics of DBD plasma.
Previous studies have been constrained by the limited magnitude of the volumetric force induced by DBD, leading to the selection of relatively small-scale models with simple geometries as experimental subjects. Moreover, the effectiveness of DBD actuators diminishes significantly with increasing freestream velocity, restricting their application primarily to low-speed environments. These limitations have resulted in a predominant focus on low-Reynolds-number scenarios in prior research. Under such conditions, the applicability of DBD plasma flow control in more complex flow fields remains unexplored mainly, leaving significant gaps in the existing body of research.
To address the challenges above, this study employs an S-duct model developed by NASA as the experimental subject. This duct features a complex geometric configuration and is relatively large. These characteristics enable the test model to achieve higher Reynolds numbers even in low-speed environments, providing more practical and challenging conditions for investigating the application of DBD plasma flow control in complex flow fields.
This study aims to optimise the internal flow field of an S-duct using DBD plasma flow control technology, thereby improving the airflow quality at the duct’s outlet. The research methodology integrates experimental investigations and numerical simulations. The results demonstrate that this approach offers a novel perspective for performance optimisation of S-ducts and provides valuable references for future studies on DBD plasma flow control and its applications in complex flow fields
Tribal influence on corporate governance in Nigerian firms
Get PDFPublicly listed firms are composed of different parties, with the Board of Directors (BoDs) as the primary force influencing the firms’ governance (Baysinger & Butler, 1985; Fama & Jensen, 1983a; Williamson, 1983, 1984 as cited in Hassan, Marimuthu & Satirenjit, 2015). As a result of having multiple parties on a single board, there are always divergent interests (Eisenhardt, 1989). As such, a critical challenge with governance is aligning and balancing the interests of a company’s many stakeholders, especially those represented on BoDs in multi-ethnic settings. The multiplicity of their ethnicity can create complicated, divergent interests, even within their group. The shareholders’ role in governance is to appoint directors who apply appropriate governance to ensure the parties’ interests are represented. In contrast, the BoD’s role is to act on behalf of the shareholders via their control. This control exists along with and depends on the control of other stakeholders. The question arises: Is the board members’ capacity to exercise control influenced by any tribal connections among them? Or are tribal affiliations among shareholders’ representatives and managers associated with Type 1 agency costs?
To address this question, this research initiates a review of corporate governance research, focusing on agency theory. Agency theory was chosen as a theoretical framework to explain many strengths and weaknesses of corporate governance, i.e. the structures that specify the distribution of rights and responsibilities. It also predicts the implications of relationships among various parties in controlling and directing the activities of a firm, e.g., understanding how tribal affiliations can influence a BoD’s capacity to perform its functions and reduce agency costs. First, the assumptions of agency theory are covered in the literature review. For a company with tribal ownership and/or control, agency theory predicts higher Type 1 agency costs (i.e., relating to tribal ownership and managerial control) and Type 2 agency costs (i.e., relating to tribal share ownership). However, following the data analysis, this research's empirical results contradict the negative prediction of agency theory for the predominant Nigerian tribe. Hence, alternative proximate theories like network, stewardship, and stakeholder theories as alternatives to agency theory may explain this refutation and comprehend the intricacy of interpersonal relationships within a firm
Image classification with foveated neural networks
Get PDFFoveated vision draws inspiration from the way many biological vision systems process visual information. It features space-variant resolution, concentrating high-resolution sampling in a small area known as the fovea. This approach aims to deliver the same visual acuity and field of view as uniform vision but with significantly fewer pixels. This reduction in pixel count can potentially lower the computational demands of subsequent visual processes without compromising their effectiveness in performing visual perception tasks. Despite these qualities of foveated vision, a uniform approach remains the dominant paradigm in computer vision. This thesis investigates the use of deep neural networks on foveated images, aiming to determine whether foveated vision can improve the ability of such systems to classify challenging datasets comprised of natural images.
In Chapter 1, we outline the motivations for exploring foveated vision in conjunction with deep neural networks, the research gaps, and the corresponding questions that we aim to answer through this thesis. Furthermore, we provide an overview of biological vision processes, computational models of foveated vision, and the relationship between foveated vision systems and the active vision paradigm.
In Chapter 2, we explore the application of convolutional neural networks (CNNs) to foveated images. Prior works have frequently shown that foveated sampling does not improve the accuracy of CNNs. Motivated by this observation, we analyse the implications of convolutional processing of foveated images through the lens of geometric deep learning. We hypothesise that the application of CNNs to foveated images often requires imposing a suboptimal coordinate frame for representing foveated image data, inhibiting classification accuracy. We test this hypothesis through a novel graph convolution layer that allows for coordinate frames to be freely defined. We show that the classification accuracy of a foveated CNN is highly sensitive to the choice of coordinate frame.
In Chapter 3, we expand upon the studies conducted in Chapter 2 and explore foveated CNNs in the presence of visual attention to guide the sensor. We propose a two-stage approach where a separate CNN first localises objects, informing the foveated classifier where to centre its gaze. Empirical results corroborate the findings of the previous chapter on the importance of coordinate frames. Furthermore, our novel graph convolution layer allows us to build a foveated CNN that significantly outperforms a uniform CNN under an equivalent pixel budget. Furthermore, we propose a novel foveated sensor with a parameterised sampling layout. We show the sensitivity of classification accuracy to this parameterisation and find that having smaller higher-resolution foveae for sensors with fewer pixels is favourable.
In Chapter 4, we conduct studies similar to those in Chapter 3, but in the context of non-convolutional models such as vision transformers. We propose a simple reformulation of image tokenisation to a foveated setting. We also show how the sampling layout of this method can be optimised by backpropagation using only gradients from a classification loss. We show that foveated sensing can improve the classification accuracy of these models and is increasingly beneficial as the number of total pixels in the sensor decreases. Furthermore, we explore the parameterisation of the sampling layout and how the optimal configuration is related to the properties of the data itself. We show that as the range in the scale of objects increases, it becomes increasingly beneficial to have smaller, higher resolution fovea in order to classify objects accurately at all scales.
Chapter 5 explores a sequential approach for foveated vision systems, where they can repeatedly attend to an image. For each observation, feature vectors are computed using a foveated CNN, integrated into a single representation, and used as input to a classifier. Despite using only a single dedicated convolution layer to implement attention, we show that these models can perform as well as a two-stage method where a dedicated CNN is used to perform attention. Furthermore, we show that classification accuracy increases the more times the model attends to an image and that a simple averaging approach suffices for integrating information from multiple observations. Finally, we explore an architecture based on vision transformers that maintains a memory of previous observations in all hidden layers. We show that Legendre Memory Units can effectively replace self-attention and allow such a system to run in O(1) time complexity, as opposed to self-attention’s O(N) complexity, where N is the number of previous observations.
In Chapter 6, we summarise the contributions made in this thesis in relation to the research questions we set out to answer and provide several avenues for future work that can further the field of foveated vision.
This work was supported by the Engineering and Physical Sciences Research Council, grant number 2443519, and has appeared in the following papers:
1. Killick, G., Aragon-Camarasa, G. and Siebert, J.P., 2022. Monte-Carlo Convolutions on Foveated Images. (VISAPP2022)
2. Killick, G., Henderson, P., Siebert, P. and Aragon-Camarasa, G., 2023. Foveation in the Era of Deep Learning. (BMVC2023
Absorption studies of thin-film and silicon materials for cryogenic gravitational wave detectors
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Revisiting Huangchao liqi tushi: art historical and provenance analysis of the scattered pages from a looted Qing imperial album
No full textThis dissertation presents a comprehensive exploration of the ‘biography’ of a coloured edition of a Qing imperial album, Huangchao liqi tushi (HCLQTS) 皇朝禮器圖式, or Illustrated Regulations for Ceremonial Paraphernalia of the Present (Qing) Dynasty. It traces the journey of this significant album from their creation in the Qianlong court of the 18th century, through their dispersal following the looting of the Yuanmingyuan in 1860, to their current locations in various Western museums and appearances on the art market. This research involved the meticulous gathering and examination of over 700 scattered pages found outside China or appeared on the art market, with a focus on collecting data such as the marks on the reverse sides of the pages. The study also involved an extensive survey of all relevant records, including provenance information from museum archives, publications, sales catalogues, and the Qing imperial archives.
Key findings of this dissertation include:
1. The successful reconstruction of the scattered pages back into their original 92-volume order, as recorded in the Qing archives, including the discovery of several more complete volumes with restored in-volume order.
2. A detailed clarification of the HCLQTS commissioning process, which spanned nearly three decades (1748-1775), encompassing four coloured and one printed edition. The study outlines the editing and modification journey of these editions, marking significant milestones in their development.
3. Resolution of the provenance issues of the HCLQTS, establishing that all discovered pages outside China originated from the Yuanmingyuan edition. The research identifies three key figures involved in the 1860 looting of the Qing imperial palaces: William Gordon Chalmers of 15th Punjabees (Pioneers) afterwards 23rd, John Upperton of Fane’s Horse, and Hope Grant, the commander of the British force during the second opium war.
4. An analytical discussion from both provenance and art historical perspectives, highlighting the neglected role of the rare book trade network in the late 19th-century distribution of looted Yuanmingyuan objects. The study also provides insight into the vivid and precise depiction of materials in the HCLQTS coloured illustrations, suggesting their utility as visual aids for court painting production, and challenging traditional perspectives of the HCLQTS as merely 'ideal' representations.
This dissertation not only contributes to the understanding of the HCLQTS but also opens new direction for future research in related areas of Qing Dynasty art history, rare book trade, and the provenance of Chinese artefacts in Western collections
English translation of Hongloumeng and the establishment of early British knowledge of China in the nineteenth century
No full textAbstract not currently available
Investigating the roles of FOXO3 and FOXO4 in CLL proliferation and survival
Get PDFChronic lymphocytic leukaemia is a B-cell malignancy emanating from the aberrant growth and accumulation of monoclonal lymphocytes whose origins can be traced to naïve or mature B-cell clones. A groundbreaking study revealed a heavy reliance of CLL cells on interactions with accessory cells within a ‘tumour microenvironment’ niche that drive proliferation, survival and drug resistance. As such, a core theme in the development of novel therapies has been perturbing the activity of intrinsic signalling components that are pivotal in driving these events, such as BCR and CD40 signal inhibition with the advent of BTK inhibitors (e.g. ibrutinib). Current small molecule inhibitor therapy has revolutionised CLL treatment. Even still, patient responses and suitability for treatments are highly variable, reinforcing an unmet clinical need for tailored therapeutics to treat CLL on a patient-specific basis.
Malignant cells often exploit proliferative and survival signalling components to aid their rapid, uncontrollable growth. A prime example is the PI3K-AKT-mTOR signalling axis, which is hyperactivated in most cancer contexts. This signalling axis can orchestrate proliferative and pro-survival events via downstream mTORC1/2 and AKT activity. mTOR components can promote cell growth and proliferation via a multitude of events including mTORC1-mediated translation initiation, as well as enhancing AKT activity. AKT itself can regulate the activity of several downstream substrates via phosphorylation, including FOXO transcription factors. Canonically, FOXO transcription factors mediate the expression of tumour-suppressive genes, and are negatively regulated by AKT-mediated phosphorylation and subsequent cytoplasmic sequestration. However, ever-emerging evidence (in B-cell malignancies and in the wider cancer context) suggests a bimodality to FOXO function, where they promote and/or suppress tumour progression in a context-dependent manner. Indeed, FOXO1’s tumour suppressive roles in CLL have been characterised as part of previous investigations within the group. In this work, we aimed to characterise the behaviours of the FOXO3 and FOXO4 isoforms to determine the suitability of targeting FOXO activity as a potential novel therapeutic approach in CLL.
Initially, prominent FOXO3/4 expression was demonstrated in ex vivo patient samples and in MEC1 and HG3 CLL cell lines. Further investigation revealed that, while FOXO3/4 protein and gene expression were negatively regulated by TME-associated signals (BCR ligation or CD40 activation), FOXO3/4 expression persisted in CLL cell nuclear fractions, indicative of a reliance of CLL cells on constitutive FOXO3/4 activity. Furthermore, global transcriptomic analyses of primary patient samples revealed that FOXO4 is heavily regulated by mTORC1/2-mediated signals downstream of CD40 activation, demonstrating a notable association between FOXO4 and mTOR activity in CLL. This was evidenced by tight regulation of FOXO3/4 localisation by BTK and mTOR, as well as the expression of discrete FOXO target genes downstream of CD40 activation. These findings demonstrate the complexity of FOXO biology in proliferating CLL cell populations.
To further characterise FOXO3/4 behaviour in CLL, we conducted shRNA-mediated knockdown of FOXO3 or FOXO4 in CLL cell lines (and primary patient samples: FOXO4). Here, we demonstrated an isoform-specific reliance of CLL cells on FOXO3/4; in both cases, viability and proliferative capacity were adversely affected. Cells lacking FOXO3 exhibited a loss of drug-mediated cell kill, while extensive investigation revealed that FOXO4 depletion sensitised CLL cells to multiple targeted agents including AZD8055, ibrutinib and venetoclax.
Further investigation identified that FOXO4 depletion increased CLL cell susceptibility to DNA damage, coincident with the aberrant expression of GADD45A and BCL2 family members, as well as a dysregulation of mTORC1/2 signalling components; the latter perhaps due to a lack of FOXO4-mediated SESN3 expression.
Together, these findings improve our understanding of the characteristics of FOXO transcription factors in CLL, demonstrating their ability to exhibit discrete behaviours and orchestrate distinct cellular functions. We argue that, while they are inextricably regulated by TME-associated signals and may facilitate tumour-suppressive effects, FOXO transcription factors are also required to promote CLL cell proliferation, survival and drug resistance in a context- and isoform-dependent manner. These data have the capacity to contribute to future pre-clinical investigation as well as the consideration of novel therapeutic strategies in CLL and in the wider context of malignancy
Exploring the role of substrate stiffness in endothelial senescence
Get PDFThe last two centuries have witnessed a remarkable rise in average human life expectancy, which has doubled in the most advanced countries. Cardiovascular diseases are among the leading causes of death in older adults. As the proportion of elderly people grows, the number of those affected by some form of cardiovascular disease is expected to continue increasing; hence, narrowing the gap between total and healthy lifespan becomes essential. One of the key hallmarks of ageing is cellular senescence, a stable state of cell cycle arrest. Endothelial cells are among the first to undergo senescence, and tissues with a high density of endothelial cells exhibit the highest levels of senescence. It is now widely recognised that the mechanical properties of the extracellular matrix strongly influence cellular behaviour and that these properties change with ageing. Arterial stiffness progressively increases with age, contributing to a higher risk of cardiovascular diseases. While various studies have explored the role of physical stimuli in senescence, much remains to be uncovered regarding the effect of stiffness on endothelial senescence.
We aim to address this gap by studying the role of stiffness on endothelial senescence and exploring the differences in response depending on the senescence inducer. To do so, we worked with human umbilical vein endothelial cells (HUVECs), growing them to monolayer state and inducing senescence either through treatment with the chemotherapeutic drug Doxorubicin or by passaging the cells to mimic therapy-induced senescence and replicative senescence, respectively. To assess senescence induction, we examined various hallmarks, including DNA damage, β-gal staining, cytokine secretion, cell cycle arrest, and proliferation. To evaluate the effect of substrate stiffness on the phenotype, we seeded the cells onto collagen-coated polyacrylamide hydrogels of two different stiffnesses (3 kPa and 30 kPa) as well as glass. Additionally, we analysed cellular morphology and adhesion, nuclear morphology and lamina properties, YAP nuclear translocation, and cell-cell adhesion proteins. Finally, we investigated the mechanical properties of these cells to determine their mechanical fingerprint.
In this study, we first established two effective methods for inducing senescence in HUVECs in vitro. For therapy-induced senescence using Doxorubicin, we optimised our protocol by initially testing a wide range of doses. The doses were first narrowed down based on toxicity and then further refined by assessing senescence hallmarks. For replicative senescence (RS), we first evaluated population doubling before performing the senescence assays.
Next, we produced and characterised polyacrylamide hydrogels to examine senescence markers as a function of substrate stiffness. Overall, we observed a substantial increase in senescence markers at increasing stiffness. In senescent populations on glass, we detected an increase in cell cycle arrest markers, β-gal staining, DNA damage, and cytokine secretion. RNA sequencing further revealed an upregulation of genes associated with cell-adhesion and leukocyte migration. In Doxorubicin-treated cells, the senescence-associated secretory phenotype (SASP) was more pronounced compared to RS cells, whereas the opposite was observed for p53 and DNA damage. Interestingly, on softer substrates, SASP was significantly reduced in Doxorubicin-treated cells compared to those on stiffer substrates.
To further characterise our model, we investigated how mechanosensing and mechanotransductive elements were altered by senescence in endothelial cells. In Doxorubicin-treated cells, we observed an increased aspect ratio and a larger cellular area compared to the control. The nuclear area appeared particularly enlarged, alongside increased YAP nuclear translocation. Regarding the nuclear lamina, lamin A/C invaginations were more pronounced, while lamin B intensity was reduced. Replicative senescent cells exhibited increased cellular area and stiffness. They also displayed a greater number of focal adhesions and reduced VE-cadherin and CD31 intensity. Additionally, they showed increased YAP nuclear translocation, decreased lamin B intensity, and a higher prevalence of lamin B and lamin A/C invaginations.
In summary, we propose a system for modelling endothelial senescence using two distinct methods and investigating the impact of substrates’ stiffness on senescence. We successfully modelled senescence and confirmed the detrimental effect of matrix stiffness on the senescent phenotype. Furthermore, we demonstrated that senescence not only affects cellular proliferation but also influences cellular morphology and adhesion, nuclear morphology and lamina properties, cell-cell interactions, and the mechanical fingerprint of cells. We also showed that the level of expression in the senescent markers, as well as the mechanobiology related changes, depend on the senescence inducer.
We believe this work provides an insightful overview of the impact of substrate stiffness on endothelial senescence. To the best of our knowledge, it is the first time this type of study compares two different inducers of senescence. We hope the results obtained will enable further research on the complex relationship between arterial stiffening and endothelial senescence, which may eventually help prevent cardiovascular disorders
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