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Communication-efficient decentralized federated learning
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More than optimism and pessimism: investor emotions and stock returns
No full textThis PhD thesis seeks to advance the fields of social economics and finance, asset pricing, and behavioural finance by investigating the influence of investor psychology on asset pricing through the analysis of social media data. The research spans three empirical chapters that explore how investor emotions impact the U.S. stock market, utilising both textual and visual data from StockTwits over the period 2011 to 2022, with analysis conducted at both daily and intraday frequencies. The study is distinguished by its innovative theoretical and methodological approaches. On the theoretical front, it is one of the first to incorporate multidimensional emotion models into financial research. Methodologically, it employs advanced machine learning techniques to extract reliable emotion indicators from social media platforms. The findings from all three chapters contribute significantly to the understanding of how different emotion dimensions influence stock market dynamics, providing valuable insights for investment strategists, risk managers, and policymakers concerned with the effects of investor emotion as conveyed through social media.
The first empirical chapter focuses on the impact of various dimensions of investor emotion on stock market performance, specifically analysing user-generated content on StockTwits. Through the application of machine learning algorithms, I developed a comprehensive lexicon to construct daily indices of investor emotions, guided by the Valence-Arousal-Dominance (VAD) model by Russell and Mehrabian (1977) and Plutchick’s (2001) wheel of emotions model. The analysis reveals a counter-cyclical relationship between investor pessimism and S&P 500 index returns, marked by subsequent reversals. Furthermore, there is a statistically significant positive correlation between investor arousal and dominance with stock market returns, with emotion states characterised by high arousal and dominance exerting a strong and positive influence on equity market performance in the following trading days.
In the second empirical chapter, I introduce an innovative method to forecast intraday returns of the S&P 500 index ETF using emotion analysis of StockTwits posts. This approach combines web scraping with lexicon-based emotional analysis at 30-minute intervals. The study enhances the existing emotion lexicon by integrating specific unigrams from the Loughran and McDonald (2011) and Renault (2017) word lists using the GloVeinitiated Neural Network Mapping Method. Additionally, I assign valence, arousal, and dominance scores to frequently used emojis, aligned with the VAD model, for the first time. The empirical results demonstrate that these emotion indices positively predict intraday returns in the S&P 500, though these effects often reverse within the same trading day. Notably, the emotion impact endures through at least four subsequent 30-minute trading intervals, highlighting the significant economic implications for asset management and indicating that noise traders largely drive return predictability.
The third empirical chapter extends the analysis to examine the influence of emotion dimensions on daily returns of the S&P 500 index, incorporating the examination of images alongside traditional text and emojis. Using machine learning algorithms, I construct daily indices of emotion dimensions derived from both visual and textual content on StockTwits. The findings suggest that image-based emotion indices are robust predictors of stock market returns, even when controlling for the influence of traditional texts and emojis. Moreover, images with realistic qualities evoke stronger emotion responses after excluding cartoonish visuals, leading to a more pronounced effect on market returns. This observation highlights the amplifying role of realistic images in intensifying the emotion impact of the associated textual content.
Additional tests have been conducted across the three empirical chapters, including controls for traditional news emotions, an examination of the influence of investor emotions on size factors, and a preliminary exploration of their impact on market volatility. These tests further validate the importance of analysing investor emotions through the lens of the emotion dimension model
(Re)Constructing Chinese womanhood through UK higher education: A transnational, intersectional, and arts-based study
Get PDFThis research aims to explore Chinese women international students’ (re)construction of Chinese womanhood through UK Higher Education (UKHE). I ask two questions: 1) In what ways did participants construct Chinese womanhood through broader UKHE settings and wider transnational intersectional contexts? 2) What is the role of UKHE in participants’ construction of Chinese womanhood?
I situate these questions within the existing literature on Chinese womanhood and Chinese (women) students in international higher education. I construct a transnational intersectionality framework and adopt a life history and arts-based research approach. 56 participants participated in collage-facilitated, culturally responsive focus groups. Subsequently, 30 of them participated in timeline-facilitated life history interviews. Dialectics, intersectionality, and temporality guided my two-round data analysis.
Participants often perceived themselves as self-contradictory and discussed various contradictions in their construction of Chinese womanhood. I argue that their perception of contradictions between modern and traditional Chinese womanhood, incorporating six specific dilemmas, was shaped by the intersectionality of state neoliberalism and state heteropatriarchy through dichotomisation. Through UKHE, many participants became more aware of and resistant to the homogenisation, belittlement, restraints, and contradiction of the prescribed Chinese womanhood. They also developed towards diverse, autonomous, feminist, and integrated selfhood. Therefore, their sense of contradictions stemmed from: 1) the dichotomisation of state neoliberalism and state heteropatriarchy; 2) the conflict between their perceptions of dichotomies and their intersectional lived experiences; and 3) the tension between various restraints and their developing autonomy through UKHE.
I further conceptualise three ways in which interview participants’ autonomy can be understood in relation to heteropatriarchy and neoliberalism: neoliberal autonomy, feminist autonomy, and uncertain autonomy. These concepts seek not only to understand participants’ (re)construction of modern versus traditional womanhood but also to (re)imagine the power dynamics in their past-present-future (re)construction, where UKHE played a significant yet complex role. Specifically, some participants developed neoliberal autonomy through experiencing and internalising transnational neoliberalism and injustices, alongside their subjectification of familism-patriotism. However, many participants developed their feminist autonomy through various channels: formal education in social justice and gender; autonomous, alternative, and cooperative learning; diverse and alternative womanhood, temporalities, and politics; and transnational media.
My research grounds participants’ transformations within their social conditions to purposefully imagine alternative praxis of Chinese womanhood that transcend transnational axes of domination. For participants, this meant forging alternative ways of being beyond the dichotomy of traditional versus modern womanhood, as well as creating alternative ways of relating beyond the framework of collectives versus individuals and competition. Additionally, my research valorises the impact of UKHE on participants’ autonomy and its feminist implications, while also problematising neoliberal and (neo)colonial practices
Monitoring tidal hydrology within saltmarsh vegetation to detect current attenuation using the Mini Buoy
Get PDFCoastal zones are associated with growing populations, and with climate change increasing intensity and frequency of storms these communities are increasingly facing the threat of flooding. Saltmarshes are coastal ecosystems which are known to attenuate hydrodynamic energy thereby reducing risk for coastal populations. The incorporation of saltmarshes into coastal defence strategies is hindered by gaps in our knowledge concerning lateral saltmarsh dynamics and biophysical feedback networks. This knowledge is essential for accurately and reliably predicting the risk reduction capacity of nature-based solutions for flooding. Developing a tool for long-term hydrodynamic monitoring, quantifying the current velocity (Cv) attenuation effects of salt marsh vegetation, and understanding how plant traits can impact the Cv attenuation capacity of saltmarsh species are critical steps towards better understanding saltmarsh dynamics.
In this study, we quantified the Cv attenuation of two salt marsh species (Bolboschoenus maritimus and Phragmites australis) that are abundant in the Inner Clyde Estuary. Using a novel low-cost method (the Mini-Buoy), we monitored hydrodynamics at the edge and five meters into the vegetation at three monospecific stands of each species. Two models of the Mini Buoy (the Pendant and the B4+) were compared against each other to determine which was better suited for deployment within saltmarsh vegetation and for quantifying current attenuation. Vegetation surveys at the start, middle, and end of the growing season (May-Sep) were carried out to associate plant traits with their attenuation effect. This study found that the Pendant Mini Buoy was the better model for hydrodynamic monitoring within the vegetation canopy and for quantification of current attenuation in shallow, low-energy conditions. Also, morphological adaptations to the physical environment were observed in both B. maritimus and P. australis where slenderness of the plants increased landward of the wave-exposed seaward boundary. Between the two species, significant differences in morphology and attenuation capacity were observed. Lower stem density and FSA was consistently observed in P. australis which was also found to develop in lower hydrodynamic energy areas, suggesting that P. australis is more vulnerable to hydrodynamic forcing. Overall, B. maritimus (maximum Cv reduction of ~60%) was found to be more effective at reducing current velocities than P.australis (maximum Cv reduction of ~40%)
Papillary thyroid carcinoma in adults and children managed at the Mayo Clinic in Rochester, Minnesota
No full textNo abstract available
Challenges and opportunities for iodine prophylaxis in the UK
No full textAbstract not currently available
Thermal response of metabolic rates, feeding and growth in the corallivorous gastropod Drupella spp.
Get PDFThe corallivorous gastropod genus Drupella is known for causing large amounts of damage across Indo-Pacific reefs, yet little is known about the genus’s thermal sensitivity, limiting our ability to predict how ocean warming will affect the impact of Drupella on reefs. Combining physiological and behavioural experimentation, the current study investigated the thermal response of metabolic rate, feeding, and growth of Drupella spp. Snails collected off the coast of Moorea, French Polynesia, were held in the laboratory at one of four temperature treatments: 28 °C (annual mean), 30 °C, 32 °C (annual maximum in 2021), and 34 °C (+2 °C warming scenario, SSP2-4.5). Using intermittent flow respirometry, metabolic rates were estimated under both acute ramping and prolonged thermal exposure. During acute thermal ramping, Drupella spp. acclimated at 28 °C and 34 °C were exposed to a rapid temperature increase from 29–38 °C. Temperature was increased in 1 °C increments over 30 minutes, followed by a 30-minute measurement period at each temperature. Metabolic rate increased consistently across the thermal range tested, indicating that Drupella spp. can tolerate high shortterm temperature changes, at least under well-oxygenated laboratory conditions. In prolonged exposure, both standard metabolic rate (SMR) and routine metabolic rate (RMR) increased between 28 and 32 °C for all acclimation durations. After three days of acclimation, SMR and RMR increased between 28–32 °C by 67.3% and 39.3% respectively, but then both declined by ~30% at 34 °C, indicating metabolic suppression beyond a thermal optimum. In contrast, snails acclimated for 19–23 days showed lower increases, with SMR and RMR rising between 28–32 °C by 26.9% and 19.1% respectively, and no suppression after 32 °C. These results demonstrate that Drupella spp. can thermally acclimate, particularly in RMR, which was significantly higher at 34 °C after longer-term acclimation compared to shorter-term. The same trend was observed in SMR, however this was not statistically significant. Unlike metabolic rate, feeding and growth showed no significant effects of temperature and did not increase with metabolic demands. Although this suggests that feeding and growth may not simply rise with warming; both remained unchanged compared to lower temperatures, indicating that Drupella spp. can sustain functional performance at elevated temperatures. The combined ability to withstand acute warming up to at least 38 °C, show signs of thermal acclimation, and maintain feeding and growth under elevated temperatures, suggests high thermal resilience in Drupella spp. Thermal resilience in the corallivorous snails raises concerns that corallivory may continue during periods of reef thermal stress, when corals themselves are less resilient to damage
Feature-specific reactivation and representational geometries in the temporal structure of episodic memory retrieval
Get PDFEpisodic memory describes the ability to recall events and situations we have encountered in the past. These memories usually contain multiple elements with lots of conceptual, gist information as well as perceptual details. During perception of visual objects, perceptual and semantic features are represented at different parts along the ventral visual stream hierarchy resulting in a faster accessibility of perceptual feature information compared to semantic features. Previous research indicates that during object retrieval a reversal of this hierarchy is observable with semantic features being accessible before perceptual ones. The endeavour of the current thesis will be to evaluate this reverse stream effect of memory for its generality and robustness, for underlying cognitive components and spatio-temporal representational formats in the brain.
First, in a set of behavioral studies, feature-specific reaction times are evaluated as a measure of mapping the temporal dependencies of features within an episodic long term memory trace. Second, a detailed analysis of these feature-specific reaction time results with the help of cognitive mathematical models of decision making is presented. Third, the spatiotemporal dynamics of feature representations during the retrieval process are accessed by combining MEG, fMRI and Deep Neural Network encodings of naturalistic images using a Representational Similarity-based Fusion approach.
Results indicate that the reverse stream of feature accessibility during memory retrieval is a robust effect that generalizes over different feature dimensions, cues and attentional states. Reaction time modelling suggests that this effect is explained by differences in evidence sampling speeds from memory for perceptual and semantic features. In the fusion analysis of brain imaging data, successful retrievals showed prolonged activations of high-level areas along the visual stream compared to early visual areas and semantic, gist-like feature compared to low-level feature representations.
Together, these results provide complementary and detailed evidence for reversed hierarchical structure of an episodic long term memory trace. Further implications and future directions are discussed
Understanding employability experiences of international students in UK universities
Get PDFThe increasing number of international students in the UK raises the question about the universities’ responsibility to support those lacking the cultural and social knowledge needed to navigate employability development. The aim of this study is to investigate the international student and staff perspectives on their employability experience and the role university services play in supporting their development. This aim will be achieved by addressing four research questions: (1) what does employability mean for international students, (2) what are the facilitators and inhibitors in their employability experience, (3) to what extent can the application of an employability model enhance our understanding of the international student transition to the UK labour market, and (4) what is the responsibility of the university in international student employability from the staff perspective.
Grounded in Tomlinson’s (2017) Graduate Capital Model and Prell’s (2012) Social Network Analysis, this research perceives international students’ employability experience as a social process, which is impacted by the relations, interactions, and intercultural competencies of students and university services. As an extension of graduate capital during their studies at a UK university from the perspectives of both stakeholders, a mixed methods approach is applied to investigate the responsibility of international student’s employability development. The use of multiple data collection methods captures the ways the individuals within the university approach and develop employability. This included semi-structured staff and student interviews, and a student survey. The research findings suggest there are differing views on employability development between university staff and international students, with cultural differences causing tension. Recognising the influence of cultural diversity and social networks, this study suggests the importance of intercultural competencies between university services and international students to empower students to be independently responsible in developing their employability. An analysis of the interviews and survey provided conceptual and practical implications for university service staff and international students to continue fostering a collaborative and culturally inclusive approach to employability development. Such an approach can ensure that international students are supported in the UK labour market while maintaining their unique cultural identities
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