In this thesis, we analyze volatility spillovers between crude oil and food commodities. The principal hypothesis assumes crude oil to behave as a production factor of the agricultural food commodities, thence we are looking for appropriate price effects. We mainly employ wavelet coherence and partial wavelet coherence, which provide us with valuable insight into the commodities nexus, without any strict restraints and assumptions levied on our data. Secondly, we build a DCC-GARCH model in order to model the presumed volatility spillovers. We also perform several simple benchmark analyses, in particular we test for Granger causality and we compute the Pearson correlation coefficients. Our data sample, including 10 commodities and 2 indices, covers the latest decade, significantly widening the existing contextual literature. Our results are mostly compliant with related literature, especially regarding the crude oil-fuels bundle and food commodities bundle, respectively. Considering the main research question of volatility spillovers between food commodities and crude oil, our results are indicating reasonably strong relationships with crude oil for soybeans and corn, leaving cotton and wheat rather on the verge of strong relationship and finding cattle to be completely unrelated. Main merits of the thesis...

The fiscal charges of the income tax state that if we want to consider an expense as deductible it must fulfill the causality principle, apart from that, they state rules that expenses are necessary to generate income and fulfill the criterion of reasonable expenses, majority among others.Showing that an expense is a necessity is a complicated task that in many cases will force — the person to determine that necessity — to examine internal aspects of the company, as business strategies, internal policies, etc. Apart from the analytical complexity of these topics, there will be the subjective aspect from the point of view of the outside observer.This article pretends to show the difficulty to decide if an expense is necessary or not, through the analysis of a real case where the tax system denies expenses of a taxpayer because they were not considered necessary for that kind of business. / Las normas tributarias del impuesto a la renta señalan que para que un gasto sea deducible de impuestos debe cumplirse con el principio de causalidad; además señalan dichas normas que los gastos deben ser necesarios para generar renta y cumplir con criterios de razonabilidad del gasto, generalidad, entre otros.Demostrar que un gasto es necesario es una tarea compleja que en la mayoría de los casos obligará —a la persona que quiera determinar esa necesidad— a evaluar aspectos internos de las empresas, como estrategias empresariales, políticas internas, entre otros. Además de la complejidad analítica de esos temas, subsistirá siempre el aspecto subjetivo de parte del evaluador.Este artículo propone precisamente esa dificultad en demostrar si un gasto es necesario o no, a través del análisis de un caso real donde la Administración Tributaria objeta los gastos de un contribuyente por no considerarlos necesarios para el giro del negocio.

This diploma thesis deals with a question of identification of causality between sentiment on social network Twitter and a price of specific, publicly traded stocks on New York Stock Exchange (NYSE). By a multi criteria analysis were chosen stocks of Microsoft Corporation and Apple Inc. There is constructed a model, which identifies authors messages on Twitter -- tweets and sentiment which they carry in relation to companies. Success of this model is examined by both qualitative and quantitative analysis. The thesis is trying to provide a solution to current and potential investors and management of the companies in order to take better decisions in allocating funds and managing the companies.

Submitted by Suelen Reis (suziy.ellen@gmail.com) on 2013-04-15T14:46:14Z No. of bitstreams: 1 Dissertacao Andrea Schimmentiseg.pdf: 673140 bytes, checksum: 52e682603c2b5a64359409218c25f51b (MD5) / Approved for entry into archive by Rodrigo Meirelles(rodrigomei@ufba.br) on 2013-05-29T14:44:08Z (GMT) No. of bitstreams: 1 Dissertacao Andrea Schimmentiseg.pdf: 673140 bytes, checksum: 52e682603c2b5a64359409218c25f51b (MD5) / Made available in DSpace on 2013-05-29T14:44:08Z (GMT). No. of bitstreams: 1 Dissertacao Andrea Schimmentiseg.pdf: 673140 bytes, checksum: 52e682603c2b5a64359409218c25f51b (MD5) Previous issue date: 2008 / O objetivo desta dissertação é compreender as teses de Donald Davidson acerca do lugar do mental no âmbito de uma visão fisicalista do mundo. Com seu conceito de mental, que é parte de uma teoria explicativa da vida ordinária e da ação intencional, Davidson critica a tradição reducionista. Ele afirma que a eficácia causal dos eventos mentais no mundo físico, e a autonomia destes mesmos eventos em relação às leis estritas da física, são idéias que não estão necessariamente em contradição. Neste sentido, Davidson acredita que a eficácia do pensamento e da intenção no mundo material pode conviver com a liberdade da razão em relação às leis naturais. Há causalidade mental sem reducionismo, pois a eficácia causal do mental não precisa ser suportada por leis estritas, ou por identidades entre tipos ou propriedades mentais e físicas. A visão davidsoniana do mental foi definida por alguns críticos como sendo dualista, por considerar que a irredutibilidade da intencionalidade às leis que governam o mundo natural torna o mental como um domínio autônomo. Outros críticos, ainda, sugerem que o conceito davidsoniano de mental leva ao epifenomenalismo ou ao eliminativismo, pois caracterizaria o mental como ineficaz causalmente no mundo físico. A grande contribuição de Davidson foi a sua refinada tentativa de oferecer uma teoria holística da mente e da ação, no interior da qual pensar a relação entre as nossas crenças, desejos, intenções, e as nossas ações. Neste sentido, a sua obra mostrou que a causalidade é um conceito que não pode ser excluído do conjunto dos conceitos que usamos para tentar oferecer descrições e explicações da relação entre os nossos estados mentais e nossas ações. / Salvador

L'objectif général de cette thèse est d'une part de rendre compte du traitement économétrique des phénomènes de causalité en sciences sociales et d'autre part de proposer des applications à l'étude de la causalité entre la santé et l’emploi du travail, à l’étude des décisions de retraite anticipée en relation avec la santé, la richesse et les préférences pour le futur.Pour l’analyse de la causalité santé-emploi, deux approches sont utilisées dans le cadre d’une analyse ex-post. L’approche paramétrique qui consiste en l’estimation d’un probit bivarié en panel qui inclut les valeurs retardées des variables expliquées parmi les explicatives afin de mesurer la causalité au sens de Granger entre les deux phénomènes. Le problème d’endogénéité est ainsi résolu. Les conditions initiales sont prises en compte via des équations spécifiques. Les effets individuels rendent compte de l’hétorogénéité individuelle dans l’analyse de la causalité. La seconde approche est non paramétrique et basée sur la mesure de causalité de Kullback. Elle permet de mesurer la dynamique des relations de causalité ainsi que ses déterminants.Quant à l’analyse de la décision de retraite anticipée, elle est faite grâce à un modèle structurel dynamique. Ce modèle intègre des fonctions de production et de consommation de stock de santé ainsi qu’une fonction d’utilité inter temporelle. Les conditions d’équilibre de ce modèle permettent de prédire les probabilités de retraite anticipée. / The main objective of this thesis is to investigate on the econometric treatment of causality in social sciences and to provide some applications on the establishment of causality between health condition and job status, and on the early retirement decision based on health, estate and preferences for future.To analyze the causality between health and job statuses, two approaches are used in the ex-post framework. The parametric approach involves estimating a bivariate probit panel model that includes lagged values of the dependent variables as explanatory to measure Granger causality. Thus, the problem of endogeneity is accounted for. The initial conditions are accounted for by introducing specific equations. Individual effects allow dealing with individual heterogeneity. The second approach is a nonparametric one and is based on the Kullback causality measures. This approach allows measuring the dynamic of the causal links and its determinants.For analyzing the early retirement decision, we use a dynamic structural model. This model deals with health stock production and consumption functions, and with an inter temporal utility function. The first order conditions of the model allow predicting the probabilities of early retirement.

No description available.

Made available in DSpace on 2015-12-10T14:24:25Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-03-30. Added 1 bitstream(s) on 2015-12-10T14:30:37Z : No. of bitstreams: 1 000853452.pdf: 1612990 bytes, checksum: 75c88e606a8ad7a6fce9649043e465a4 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Nesta tese apresentaremos um estudo perturbativo da Eletrodinâmica Quântica Generalizada (GQED4) via abordagem da Teoria de Perturbação Causal (TPC). Com esse propósito, primeiro faremos uma revisão dos fundamentos da TPC e, daremos uma apresentação, o suficientemente geral, para sua aplicação na GQED4. Outro ingrediente essencial, para sua aplicação, é ter uma imagem da teoria livre da Eletrodinâmica Generalizada; em particular obter os propagadores de frequência positiva e negativa. Para a obtenção desses propagadores, introduziremos a sua representação analítica, tendo como base o formalismo de Wightman. Após a classificação dos primeiros termos perturbativos, apresentaremos o espalhamento Moeller e Compton e, mostraremos a modificação do primeiro com relação à Eletrodinâmica Quântica (QED4). Calcularemos as correções radiativas a 1-loop e veremos que a normalização da polarização do vácuo segue o roteiro usual, mas na normalização da auto-energia precisaremos introduzir um novo critério naTPC, a fim de satisfazer a condição de camada de massa. Mostraremos também o comportamento regular do vértice, assim como da auto-energia. Por último, demonstraremos indutivamente as simetrias discretas, as identidades de Ward-Takahashi-Fradkin e a normalizabilidade da GQED4 / In this thesis, we will present a perturbative research of the Generalized Quantum Electrodynamics (GQED4) within the approach of the Causal Perturbation Theory (TPC). With this purpose, we first make a review of the basics ofTPC and give a complete enough theory to apply to GQED4. We need the other essential part for this objetive: the Quantum Free Field Theory of the Generalized Electrodynamics, in particular, to obtain the positive and negative frequency propagators, for which, we will introduce their analytic representations, taking as basis the Wightman Formalism. After the classification of the first perturbative terms, we will present the Moeller and Compton scattering and, show the difference with the Quantum Electrodynamicsresults. We will calculate the radiactive corrections at one-loop and, show that the vacuum polarization normalization continues the usual way but, for the electron self-enegy normalization we need to introduce a new criterion in TPC, such that fulfills the mass on-shell condition. Also, we will show the regular behavior of the vertex such as in the electronself-energy. Finally, we will demostrate inductivelly the discrete symmetries, the Ward-Takahashi-Fradkin identities and the normalizability of the GQED4 / CNPq: 141079/2010-0

Made available in DSpace on 2016-01-13T13:28:15Z (GMT). No. of bitstreams: 0 Previous issue date: 1996. Added 1 bitstream(s) on 2016-01-13T13:33:49Z : No. of bitstreams: 1 000027348.pdf: 2403793 bytes, checksum: 456178b058c50a22af1b53caee013a6d (MD5)

It is widely recognised that the construction industry has a positive role to accelerate the wheel of economic growth in any country. This research is concerned with the Libyan construction industry (LCI). Libya is a developing country which suffered from a big loss in its infrastructures and its unemployment rate increased to 30% in the middle of 2013. Regarding the importance of the construction industry through the role it has in providing infrastructure and creating employment and the poor economic condition of Libya, the rationale of this research follows the example of other nations such as Turkey, Singapore, Malaysia , and Middle East countries where the construction industry was evolved with a target to further boost up the process of economic development. The case of Libya in this regard is valid for the financial stability in the country given its oil reserves and the capacity of the country to absorb migrated skilled labour. This situation is expected to follow the fall of Gaddafi’s regime. The approach of selecting construction as providing input to economic growth follows the strong evidence of the significant role that the construction industry plays in economic growth of the country. The construction industry contributes to economic growth from the demand side and in the traditional Keynesian economy, sustainable short-run economic growth is dependent on the increased demand. For example, in the UK, construction’s 2.5% growth in the third quarter of 2013 helped the overall economy grow by 0.8% over the same period. In comparison with the other industries that contribute to the economic growth of developing countries, the construction industry is more labour-intensive while the developing countries are mostly labour-abundant. The main aim of this research is to investigate the contribution of the construction industry to economic development in order to establish a comprehensive list of recommendations and a guideline for achieving an efficient construction industry to accelerate the process of economic growth. For this aim, the first objective is to examine the causal relationship between the construction industry and gross domestic product (GDP) as a measure of the economic growth and between the construction industry and other economic sectors. To achieve the aim of this research, Granger causality tests have been conducted. The financial data about the expenditure on the construction industry in Libya and its share in the GDP of the country and the share of the other economic sectors in the GDP during 1986-2009 was provided by an authority from the Libyan construction industry. First, The Augmented Dickey Fuller (ADF) and the Philip Perron (PP) unit root tests were conducted to confirm that the tested time series are stationary. After that, to determine the existence of the long-run causal relationship between the CI and GDP, Engle-Granger co-integration test was used and, finally, vector error correction (VER) model was employed to detect the direction of the causal relationship between the two variables. The study found that in Libya, like in other countries, the relationship between the construction industry and GDP is bi-directional: GDP produces a short-term impact on the investment in the construction industry while investment in the construction industry produces a long-term impact on GDP. However, except for trade, no economic sector was found to have a causal relationship with the construction industry. According to these findings, another objective was established in this research: to identify safety and total quality management (TQM) which can play an important role in growing the efficiency of the Libyan construction industry. To achieve this objective, telephone conversations were conducted with the officials of the largest construction company in the city of Benghazi. The findings indicated that the TQM does not exist in the construction company and, although the safety department does exist, it works via strict procedures. Thus, opportunity to increase the performance of the CI in order to increase its contribution to economic growth does exist through implementation of the safety and TQM implementation in Licccbyan construction companies. The previous studies used the causal relationship just to prove specific hypotheses. The novelty of this research is to obtain benefits from the existence of the causal relationship from the CI to GDP in the long term through suggesting major issues as safety and TQM implementation to raise the performance of the CI in the current period in order to increase its contribution to the economic growth in the future.

Orientador: Bruto Max Pimentel Escoba / Banca: Josif Frenkel / Banca:Roldão da Rocha Júnior / Banca: Olivier Piguet / Banca: Alfredo Takashi Suzuki / Resumo: Nesta tese apresentaremos um estudo perturbativo da Eletrodinâmica Quântica Generalizada (GQED4) via abordagem da Teoria de Perturbação Causal (TPC). Com esse propósito, primeiro faremos uma revisão dos fundamentos da TPC e, daremos uma apresentação, o suficientemente geral, para sua aplicação na GQED4. Outro ingrediente essencial, para sua aplicação, é ter uma imagem da teoria livre da Eletrodinâmica Generalizada; em particular obter os propagadores de frequência positiva e negativa. Para a obtenção desses propagadores, introduziremos a sua representação analítica, tendo como base o formalismo de Wightman. Após a classificação dos primeiros termos perturbativos, apresentaremos o espalhamento Moeller e Compton e, mostraremos a modificação do primeiro com relação à Eletrodinâmica Quântica (QED4). Calcularemos as correções radiativas a 1-loop e veremos que a normalização da polarização do vácuo segue o roteiro usual, mas na normalização da auto-energia precisaremos introduzir um novo critério naTPC, a fim de satisfazer a condição de camada de massa. Mostraremos também o comportamento regular do vértice, assim como da auto-energia. Por último, demonstraremos indutivamente as simetrias discretas, as identidades de Ward-Takahashi-Fradkin e a normalizabilidade da GQED4 / Abstract: In this thesis, we will present a perturbative research of the Generalized Quantum Electrodynamics (GQED4) within the approach of the Causal Perturbation Theory (TPC). With this purpose, we first make a review of the basics ofTPC and give a complete enough theory to apply to GQED4. We need the other essential part for this objetive: the Quantum Free Field Theory of the Generalized Electrodynamics, in particular, to obtain the positive and negative frequency propagators, for which, we will introduce their analytic representations, taking as basis the Wightman Formalism. After the classification of the first perturbative terms, we will present the Moeller and Compton scattering and, show the difference with the Quantum Electrodynamicsresults. We will calculate the radiactive corrections at one-loop and, show that the vacuum polarization normalization continues the usual way but, for the electron self-enegy normalization we need to introduce a new criterion in TPC, such that fulfills the mass on-shell condition. Also, we will show the regular behavior of the vertex such as in the electronself-energy. Finally, we will demostrate inductivelly the discrete symmetries, the Ward-Takahashi-Fradkin identities and the normalizability of the GQED4 / Doutor