Polysemy advantage with abstract but not concrete words

Peer reviewed

Coal-fired Power Plants with Flexible Amine-based CCS and Co-located Wind Power: Environmental, Economic and Reliability Outcomes

Carbon Capture and Storage (CCS) technologies provide a means to significantly reduce carbon emissions from the existing fleet of fossil-fired plants, and hence can facilitate a gradual transition from conventional to more sustainable sources of electric power. This is especially relevant for coal plants that have a CO2 emission rate that is roughly two times higher than that of natural gas plants. Of the different kinds of CCS technology available, post-combustion amine based CCS is the best developed and hence more suitable for retrofitting an existing coal plant. The high costs from operating CCS could be reduced by enabling flexible operation through amine storage or allowing partial capture of CO2 during high electricity prices. This flexibility is also found to improve the power plant’s ramp capability, enabling it to offset the intermittency of renewable power sources. This thesis proposes a solution to problems associated with two promising technologies for decarbonizing the electric power system: the high costs of the energy penalty of CCS, and the intermittency and non-dispatchability of wind power. It explores the economic and technical feasibility of a hybrid system consisting of a coal plant retrofitted with a post-combustion-amine based CCS system equipped with the option to perform partial capture or amine storage, and a co-located wind farm. A techno-economic assessment of the performance of the hybrid system is carried out both from the perspective of the stakeholders (utility owners, investors, etc.) as well as that of the power system operator.

In order to perform the assessment from the perspective of the facility owners (e.g., electric power utilities, independent power producers), an optimal design and operating strategy of the hybrid system is determined for both the amine storage and partial capture configurations. A linear optimization model is developed to determine the optimal component sizes for the hybrid system and capture rates while meeting constraints on annual average emission targets of CO2, and variability of the combined power output. Results indicate that there are economic benefits of flexible operation relative to conventional CCS, and demonstrate that the hybrid system could operate as an energy storage system: providing an effective pathway for wind power integration as well as a mechanism to mute the variability of intermittent wind power.

In order to assess the performance of the hybrid system from the perspective of the system operator, a modified Unit Commitment/ Economic Dispatch model is built to consider and represent the techno-economic aspects of operation of the hybrid system within a power grid. The hybrid system is found to be effective in helping the power system meet an average CO2 emissions limit equivalent to the CO2 emission rate of a state-of-the-art natural gas plant, and to reduce power system operation costs and number of instances and magnitude of energy and reserve scarcity.

Moduli Space of (0,2) Conformal Field Theories

In this thesis we study aspects of (0,2) superconformal field theories (SCFTs), which are suitable for compactification of the heterotic string. In the first part, we study a class of (2,2) SCFTs obtained by fibering a Landau-Ginzburg (LG) orbifold CFT over a compact K\"ahler base manifold. While such models are naturally obtained as phases in a gauged linear sigma model (GLSM), our construction is independent of such an embedding. We discuss the general properties of such theories and present a technique to study the massless spectrum of the associated heterotic compactification. We test the validity of our method by applying it to hybrid phases of GLSMs and comparing spectra among the phases. In the second part, we turn to the study of the role of accidental symmetries in two-dimensional (0,2) SCFTs obtained by RG flow from (0,2) LG theories. These accidental symmetries are ubiquitous, and, unlike in the case of (2,2) theories, their identification is key to correctly identifying the IR fixed point and its properties. We develop a number of tools that help to identify such accidental symmetries in the context of (0,2) LG models and provide a conjecture for a toric structure of the SCFT moduli space in a large class of models. In the final part, we study the stability of heterotic compactifications described by (0,2) GLSMs with respect to worldsheet instanton corrections to the space-time superpotential following the work of Beasley and Witten. We show that generic models elude the vanishing theorem proved there, and may not determine supersymmetric heterotic vacua. We then construct a subclass of GLSMs for which a vanishing theorem holds.

Associates of an elevated natriuretic peptide level in stable heart failure patients:implications for targeted management

BACKGROUND: Persistently elevated natriuretic peptide (NP) levels in heart failure (HF) patients are associated with impaired prognosis. Recent work suggests that NP-guided therapy can improve outcome, but the mechanisms behind an elevated BNP remain unclear. Among the potential stimuli for NP in clinically stable patients are persistent occult fluid overload, wall stress, inflammation, fibrosis, and ischemia. The purpose of this study was to identify associates of B-type natriuretic peptide (BNP) in a stable HF population.

METHODS: In a prospective observational study of 179 stable HF patients, the association between BNP and markers of collagen metabolism, inflammation, and Doppler-echocardiographic parameters including left ventricular ejection fraction (LVEF), left atrial volume index (LAVI), and E/e prime (E/e') was measured.

RESULTS: Univariable associates of elevated BNP were age, LVEF, LAVI, E/e', creatinine, and markers of collagen turnover. In a multiple linear regression model, age, creatinine, and LVEF remained significant associates of BNP. E/e' and markers of collagen turnover had a persistent impact on BNP independent of these covariates.

CONCLUSION: Multiple variables are associated with persistently elevated BNP levels in stable HF patients. Clarification of the relative importance of NP stimuli may help refine NP-guided therapy, potentially improving outcome for this at-risk population.

Inteligência Emocional e Desempenho Académico em Estudantes do Ensino Superior

A presente investigação examina o papel da inteligêncial emocional (IE) no desempenho académico, numa amostra de 111 estudantes em frequência do ensino universitário português. No presente trabalho faz-se uma revisão bibliográfica do tema da IE e dos factores contributivos para o desempenho académico, bem como uma breve visita a outros trabalhos desenvolvidos nesta área de investigação. Para medição da IE assumiu-se o modelo misto, tendo-se avaliado as seguintes seis dimensões: 1) auto-encorajamento (uso das emoções); 2) compreensão das emoções próprias; 3) autocontrolo perante as críticas; 4)compreensão das emoções dos outros; 5) empatia e contágio emocional; 6) autocontrolo emocional (regulação das emoções). O desempenho académico foi calculado a partir das médias das classificações obtidas pelos estudantes no final do primeiro semestre do ano lectivo 2009/2010. Os resultados evidenciam que os alunos com melhores desempenhos académicos denotam níveis superiores de inteligência emocional, se bem que não foram encontradas associações significativas entre a IE e o desempenho académico, sugerindo a necessidade de mais estudos com vista ao aprofundamento desta jovem e controversa área de pesquisa. / The research investigates the role of emotional intelligence (EI)in academic achivement in a sample of 111 students that attend Portuguese universities. In this work we review the issue of EI and the factors that contibute to academic achievement, at the same time making a brief visit to other works done on this area. In order to measure EI, the mixed model was used, evaluating through the following six dimensions: 1) self-encouragement (use of emotions); 2) understanding of self emotions; 3) self-control in response to criticism; 4) understanding of emotions in others; 5) empathy and emotional contagion; 6) emotional self-control (regulation of emotions). Academic achievement was evaluated by the average of the grades obtained by the students at the end of the first semester of the academic year 2009/2010. The results show that students with better academic outcomes demonstrate higher emotional intelligence, though there were no significative associations between EI and academic achievement, suggesting the need for further studies in order to deepen this young and controversial area of research.