477 research outputs found
Single-cell time-series analysis of metabolic rhythms in yeast
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
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
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 âhappiness maximizationâ 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 âhappiness maximizationâ, 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 satisfactionâthe most common operationalization of happiness in psychologyâinvolving 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
Purpose This paper aims to examine the extent of ethical values information disclosure on the top 100 Malaysian and Indonesian companiesâ 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 companiesâ 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
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 1992â2017. 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 longârun 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 shortârun 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 TodaâYamamoto 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 permanecerão 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 Ăfrica. Em
primeiro lugar, avaliĂĄmos o impacto do desenvolvimento do mercado bolsista no
crescimento econĂłmico em Ăfrica. O estudo usa dados anuais de um painel de nove
paĂses da Ăfrica durante o perĂodo de 1992 a 2017. Para a anĂĄlise dos dados foi usada a
técnica de econometria autorregressiva de vetor de painel. Nossas principais conclusÔes
são que o desenvolvimento do mercado de açÔes tem um efeito positivo sobre o
crescimento económico. O artigo também 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 método de estimação
de Autoregressive Distributed Lag (ARDL) para modelar o efeito de longo prazo. Além
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 crédito privado reduz negativamente as desigualdades de renda. Os
resultados também estabelecem causalidades significativas de curto prazo entre
indicadores do mercado de açÔes, crédito 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. Além
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 crédito
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 TodaâYamamoto, 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)
The issue comprises 5 scholarly publications
Examining the Relationships Between Distance Education Studentsâ Self-Efficacy and Their Achievement
This study aimed to examine the relationships between studentsâ self-efficacy (SSE) and studentsâ 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 achievementâphysical 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 achievementâmore 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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