Yang-Lee zeros and the helix-coil transition in a continuum model of polyalanine

We calculate the Yang-Lee zeros for characteristic temperatures of the helix-coil transition in a continuum model of polyalanine. The distribution of these zeros differs from predictions of the Zimm-Bragg theory and supports recent claims that polyalanine exhibits a true phase transition. New estimates for critical exponents are presented and the relation of our results to the Lee-Yang theorem is discussed.Comment: 15 pages and 5 figure

Structural transitions in biomolecules - a numerical comparison of two approaches for the study of phase transitions in small systems

We compare two recently proposed methods for the characterization of phase transitions in small systems. The usefulness of these techniques is evaluated for the case of structural transition in alanine-based peptides.Comment: Accepted for publication in Int. J. Mol. Sci., to appear in a special issue devoted to R.S. Berr

Helix Formation and Folding in an Artificial Peptide

We study the relation between $\alpha$-helix formation and folding for a simple artificial peptide, Ala$_{10}$-Gly$_5$-Ala$_{10}$. Our data rely on multicanonical Monte Carlo simulations where the interactions among all atoms are taken into account. The free-energy landscape of the peptide is evaluated for various temperatures. Our data indicate that folding of this peptide is a two-step process: in a first step two $\alpha$-helices are formed which afterwards re-arrange themselves into a U-like structure.Comment: 15 pages, with 9 eps figure

Competitive advantages as source of excess stock returns

Mestrado em FinançasThe perspectives assessment of any given company is a vital step to the efficiency of the valuation process. A correct assessment will result in the definition of assumptions that will lead to better valuation results. Wrong conclusions are frequently taken because a bad assessment was made and this is the result of the lack of a proper framework that guides the analysis of company perspectives. To solve this problem we decided to use strategic management theory and test the relation between stock returns and competitive advantages relevant for a given industry. We applied this method to the Steel Industry and tested it statistically. The results showed us that, generally, improvements in the operational efficiency, measured by the first differences in gross margin, provide excess returns. This results show us that the use of Competitive Advantages to select portfolios, in the Steel Industry, yields better than average returns.A avaliação das perspectivas para uma determinada empresa é um passo critico no processo de valorização de uma acção. Uma correcta avaliação resulta na definição de um conjunto de pressupostos que levarão a uma avaliação mais precisa. Analises erradas levam a conclusões erradas e são resultado da falta de um quadro orientador que direccione o estudo das perspectivas das empresas em causa. Para resolver este problema decidimos recorrer à teoria da gestão estratégica e testar a relação entre rendibilidades de acções e Vantagens Competitivas relevantes em determinada indústria. Aplicámos este método à Industria Siderúrgica e realizamos testes estatísticos. Os resultados mostram-nos que, na generalidade, melhorias na eficiência operacional, medida através das primeiras diferenças da margem bruta, oferece retornos acima da taxa de retorno sem risco. Estes resultados mostram-nos que a selecção de portfolios, utilizando Vantagens Competitivas, permitem-nos obter retornos acima da média