477 research outputs found

    Single-cell time-series analysis of metabolic rhythms in yeast

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    The yeast metabolic cycle (YMC) is a biological rhythm in budding yeast (Saccharomyces cerevisiae). It entails oscillations in the concentrations and redox states of intracellular metabolites, oscillations in transcript levels, temporal partitioning of biosynthesis, and, in chemostats, oscillations in oxygen consumption. Most studies on the YMC have been based on chemostat experiments, and it is unclear whether YMCs arise from interactions between cells or are generated independently by each cell. This thesis aims at characterising the YMC in single cells and its response to nutrient and genetic perturbations. Specifically, I use microfluidics to trap and separate yeast cells, then record the time-dependent intensity of flavin autofluorescence, which is a component of the YMC. Single-cell microfluidics produces a large amount of time series data. Noisy and short time series produced from biological experiments restrict the computational tools that are useful for analysis. I developed a method to filter time series, a machine learning model to classify whether time series are oscillatory, and an autocorrelation method to examine the periodicity of time series data. My experimental results show that yeast cells show oscillations in the fluorescence of flavins. Specifically, I show that in high glucose conditions, cells generate flavin oscillations asynchronously within a population, and these flavin oscillations couple with the cell division cycle. I show that cells can individually reset the phase of their flavin oscillations in response to abrupt nutrient changes, independently of the cell division cycle. I also show that deletion strains generate flavin oscillations that exhibit different behaviour from dissolved oxygen oscillations from chemostat conditions. Finally, I use flux balance analysis to address whether proteomic constraints in cellular metabolism mean that temporal partitioning of biosynthesis is advantageous for the yeast cell, and whether such partitioning explains the timing of the metabolic cycle. My results show that under proteomic constraints, it is advantageous for the cell to sequentially synthesise biomass components because doing so shortens the timescale of biomass synthesis. However, the degree of advantage of sequential over parallel biosynthesis is lower when both carbon and nitrogen sources are limiting. This thesis thus confirms autonomous generation of flavin oscillations, and suggests a model in which the YMC responds to nutrient conditions and subsequently entrains the cell division cycle. It also emphasises the possibility that subpopulations in the culture explain chemostat-based observations of the YMC. Furthermore, this thesis paves the way for using computational methods to analyse large datasets of oscillatory time series, which is useful for various fields of study beyond the YMC

    Consumption Categories, Household Attention, and Inflation Expectations: Implications for Optimal Monetary Policy

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    What in inflation measure should central banks target? This paper shows optimal monetary policy targets headline inflation if households pay limited attention to different consumption categories when forming inflation expectations. This result stands in contrast to standard rational expectations models, where optimal policy targets core inflation. The core inflation rate excludes volatile energy and food prices (non-core) from headline inflation. Using novel survey data on inflation expectations for disaggregated consumption categories, I find household expectations are disproportionately driven by beliefs about future non-core prices. I develop a sparsity-based rational inattention model to account for the empirical evidence. While forming inflation expectations, households pay attention to the volatile non-core components; the stable core inflation component receives little attention. Finally, I embed this framework into a multi-sector New Keynesian model to derive the optimal inflation target. In the model, targeting headline inflation is optimal, whereas a core inflation target would fail to stabilize the economy sufficiently

    Happiness Maximization Is a WEIRD Way of Living

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    Psychological science tends to treat subjective wellbeing and happiness synonymously. We start from the assumption that subjective wellbeing is more than being happy to ask the fundamental question: what is the ideal level of happiness? From a cross-cultural perspective, we propose that the idealization of attaining maximum levels of happiness may be especially characteristic of WEIRD (Western, Educated, Industrial, Rich, Democratic) societies, but less so for others. Searching for an explanation for why “happiness maximization” might have emerged in these societies, we turn to studies linking cultures to their eco-environmental habitat. We discuss the premise that WEIRD cultures emerged in an exceptionally benign ecological habitat, i.e., compared to other regions, they faced relatively light existential pressures. We review the influence of the Gulfstream on the North-Western European climate as a source of these comparatively benign geographical conditions. We propose that the ecological conditions in which WEIRD societies emerged afforded them a basis to endorse happiness as a value and to idealise attaining its maximum level. To provide a nomological network for “happiness maximization”, we also studied its several potential side-effects: alcohol and drug consumption and abuse, and the prevalence of mania. To evaluate our hypothesis, we re-analyse data from two large-scale studies on ideal levels of personal life satisfaction—the most common operationalization of happiness in psychology—involving respondents from 61 countries. We conclude that societies whose members seek to maximize happiness tend to be characterized as a WEIRD, and generalizing this across societies can prove problematic if adopted at the ideological and policy level

    Corporate ethical values disclosure: Evidence from Malaysian and Indonesian top companies

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    Purpose This paper aims to examine the extent of ethical values information disclosure on the top 100 Malaysian and Indonesian companies’ annual reports using coercive isomorphism under the institutional theory. Design/methodology/approach Using the content analysis, the presence or exclusion of ethical values information disclosed on 100 Malaysian and Indonesian companies’ annual reports using a newly developed Ethical Values Disclosure Index is carried out. Findings The results of the analysis found that Indonesian companies on average disclosed 31 items under study compared to 27 items disclosed by the companies in Malaysia. The results suggest that Indonesian companies are more vigilant in the code of ethics, companies policy on ethical issues, monitoring program and accountability, ethical performance, ethical infrastructure and organizational responsibility aspects, whereas their Malaysian counterparts are better in reporting governance and integrity committee or board of directors. Research limitations/implications The findings may not be applicable to other countries in the same region, nevertheless, revealed the importance of adequate ethical values disclosure in determining the level of ethical behavior. Practical implications Companies in Indonesia are coercively pressed by various influential stakeholder groups to address ethical issues. The less disclosure regarding corporate ethical behavior may indicate that unethical practices continue to be a problem in the Malaysian corporate sector. Originality/value This paper adds to the literature by examining the elements of ethical values adapted mainly from the professional bodies that regulate the accounting profession and other organizations using the institutional theory, particularly in two countries

    Essays on financial markets in Africa

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    Doutoramento em EconomiaEconomic growth in a modern economy hinges on an efficient financial sector that pools domestic savings and mobilizes foreign capital for productive investments. Absent an effective set of financial institutions, productive projects will remain unexploited. Inefficient financial institutions will have the effect of taxing productive investment and thus reducing scope for increasing the stock equipment needed to compete globally. The effect is to substantially cut growth from what would have been possible given appropriate policies and market structures. In this context, this thesis focuses on three essays analyzing the impact of financial markets in development and income inequality. First, we assessed the impact of stock market development on growth in Africa. The study uses annual data from a panel of nine countries in Africa over the period 1992–2017. Panel Vector Autoregressive econometrics technique is used in data analysis. Our main findings are that stock market development has a positive effect on economic growth. The paper also finds that when using the impulse response function, economic growth reacts to the stock market for a period of eight years and then returns to the initial level. The second essay presents evidence about the relationship between private credit, stock market indicators, income inequality and poverty, using the annual data that ranges from 1992 to 2018 on nine African economies. We applied the estimation method of Autoregressive Distributed Lag (ARDL) to model the long-run effect. In Addition, we used Dumitrescu and Hurlin Panel causality to check the direction of causality. The results of long‐run estimates show that the stock market indicators have a significant positive impact on income inequalities, but have a negative and significant impact on poverty. Further, our findings show that private credit adversely reduces income inequalities. The results also establish significant short‐run causalities among stock market indicators, private credit, income inequalities, and poverty. Lastly, we examine the relationship between financial development and economic growth in Angola for the period of Q12002 to Q42018. The results show that there is evidence of a long-run relationship between financial development and real GDP per capita, when using the Bound test approach for cointegration. Furthermore, the results of the Error Correction Model (ECM) indicate that financial development has a negative impact on GDP growth when considering credit to private and broad money as proxies for financial development. On the other hand, the degree of intermediation has a positive impact on GDP growth. The Toda–Yamamoto causality test was carried out, which indicates a unidirectional causality relationship, running from real GDP per capita to a purely financial development proxy, which shows demand-following responses. Consequently, policymakers should adopt policies that sustain the benefits of financial developments for economic growth.O crescimento econĂłmico numa economia moderna depende de um sector financeiro eficiente que reĂșna a poupança domĂ©stica e mobilize capital estrangeiro para investimentos produtivos. Sem um conjunto efetivo de instituiçÔes financeiras, os projetos produtivos permanecerĂŁo inexplorados. InstituiçÔes financeiras ineficientes terĂŁo o efeito de tributar o investimento produtivo e, assim, reduzir a margem para aumentar o estoque de equipamentos necessĂĄrios para competir globalmente. O efeito Ă© reduzir substancialmente o crescimento do que seria possĂ­vel com polĂ­ticas e estruturas de mercado apropriadas. Nesse contexto, esta tese se concentra em trĂȘs artigos que analisam o impacto dos mercados financeiros no desenvolvimento e na desigualdade de renda em África. Em primeiro lugar, avaliĂĄmos o impacto do desenvolvimento do mercado bolsista no crescimento econĂłmico em África. O estudo usa dados anuais de um painel de nove paĂ­ses da África durante o perĂ­odo de 1992 a 2017. Para a anĂĄlise dos dados foi usada a tĂ©cnica de econometria autorregressiva de vetor de painel. Nossas principais conclusĂ”es sĂŁo que o desenvolvimento do mercado de açÔes tem um efeito positivo sobre o crescimento econĂłmico. O artigo tambĂ©m constata que, ao usar a função de impulso resposta, o crescimento econĂłmico reage ao mercado de açÔes por um perĂ­odo de oito anos e depois retorna ao nĂ­vel inicial. O segundo artigo apresenta evidĂȘncias sobre a relação entre crĂ©dito privado, indicadores do mercado de açÔes, desigualdade de renda e pobreza, usando os dados anuais que variam de 1992 a 2018 em nove economias africanas. Aplicamos o mĂ©todo de estimação de Autoregressive Distributed Lag (ARDL) para modelar o efeito de longo prazo. AlĂ©m disso, usamos a causalidade do Painel de Dumitrescu e Hurlin para verificar a direção da causalidade. Os resultados das estimativas de longo prazo mostram que os indicadores do mercado de açÔes tĂȘm um impacto positivo e significativo nas desigualdades de renda, mas tĂȘm um impacto negativo e significativo na pobreza. AlĂ©m disso, nossos resultados mostram que o crĂ©dito privado reduz negativamente as desigualdades de renda. Os resultados tambĂ©m estabelecem causalidades significativas de curto prazo entre indicadores do mercado de açÔes, crĂ©dito privado, desigualdades de renda e pobreza. Por Ășltimo, examinamos a relação entre o desenvolvimento financeiro e o crescimento econĂłmico em Angola para o perĂ­odo de T12002 a T42018. Os resultados mostram que hĂĄ evidĂȘncias de uma relação de longo prazo entre o desenvolvimento financeiro e o PIB real per capita, quando se utiliza a abordagem do teste Bound para cointegração. AlĂ©m disso, os resultados do Error Correction Model (ECM) indicam que o desenvolvimento financeiro tem um impacto negativo no crescimento do PIB quando se considera o crĂ©dito ao privado e a moeda ampla como proxies do desenvolvimento financeiro. Por outro lado, o grau de intermediação tem um impacto positivo no crescimento do PIB. Foi realizado o teste de causalidade Toda–Yamamoto, que indica uma relação de causalidade unidirecional, indo do PIB real per capita a uma proxy de desenvolvimento puramente financeiro, que mostra respostas de acompanhamento da procura. Consequentemente, os formuladores de polĂ­ticas devem adotar polĂ­ticas que sustentem os benefĂ­cios dos desenvolvimentos financeiros para o crescimento econĂŽmico.info:eu-repo/semantics/publishedVersio

    Archives of the Social Sciences (Complete First Issue, 2023)

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    The issue comprises 5 scholarly publications

    GAC-MAC-SGA 2023 Sudbury Meeting: Abstracts, Volume 46

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    Examining the Relationships Between Distance Education Students’ Self-Efficacy and Their Achievement

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    This study aimed to examine the relationships between students’ self-efficacy (SSE) and students’ achievement (SA) in distance education. The instruments were administered to 100 undergraduate students in a distance university who work as migrant workers in Taiwan to gather data, while their SA scores were obtained from the university. The semi-structured interviews for 8 participants consisted of questions that showed the specific conditions of SSE and SA. The findings of this study were reported as follows: There was a significantly positive correlation between targeted SSE (overall scales and general self-efficacy) and SA. Targeted students' self-efficacy effectively predicted their achievement; besides, general self- efficacy had the most significant influence. In the qualitative findings, four themes were extracted for those students with lower self-efficacy but higher achievement—physical and emotional condition, teaching and learning strategy, positive social interaction, and intrinsic motivation. Moreover, three themes were extracted for those students with moderate or higher self-efficacy but lower achievement—more time for leisure (not hard-working), less social interaction, and external excuses. Providing effective learning environments, social interactions, and teaching and learning strategies are suggested in distance education
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