Free daily newspapers: too many incentives to print?

We consider a model in which a free daily newspaper distributes news to readers and sells ad-space to advertisers, having private information about its readership. Depending on the type of readers in the market, the newspaper's may have a "plentiful and seeking" audience or a "lacking and avoiding" audience. We find that if the readers are plentiful and seeking, the newspaper prints an excessive number of copies. The rationale for this over-printing strategy lies on the newspaper's need to send a credible signal to the advertisers that there are plentiful and seeking readers in the market. When the readers are lacking and avoiding, the newspaper chooses the socially optimal tirage (does not try to cheat the advertisers).two-sided markets, asymmetric information, free press

Costly horizontal differentiation

We study the effect of quadratic differentiation costs in the Hotelling model of endogenous product differentiation. The equilibrium location choices are found to depend on the magnitude of the differentiation costs (relatively to the transportation costs supported by consumers). When the differentiation costs are low, there is maximum differentiation. When they are intermediate, there is partial differentiation, with a degree of differentiation that decreases with the differentiation costs. When they are above a certain threshold, there is no equilibrium. In any case, the socially optimal degree of differentiation is always lower than the equilibrium level. We also study the case of collusion between firms. If firms can combine locations but not prices, they locate asymmetrically when differentiation costs are high and choose maximum differentiation when they are low. When collusion extends to price setting, there is partial differentiation.Costly product differentiation, Spatial competition, Hotelling model

Linear and shared objects in concurrent programming

Tese de mestrado, Engenharia Informática (Engenharia de Software), Universidade de Lisboa, Faculdade de Ciências, 2010Although mainstream object-oriented languages, like Java, are currently able to detect and prevent many programming errors by static type-checking, common usage-related errors are not captured and signaled to programmers. In general, no (formal) support is available in these languages for ensuring that an object is used according to the protocol which the programmer had in mind when describing the behavior of a class. The file reader protocol is a simple but clarifying example: first a file must be opened, then it can be read multiple times (though not beyond the end-of-file), and finally it must be closed. As client code is not checked for protocol conformance, trying to read the file without first opening it, or when it is closed, are simple disregards caught only by runtime exceptions, assuming the language is equipped with built-in support to handle errors and exceptional events. The MOOL programming language presented in this work is an attempt to formalize object usage and access. It consists in a simple class-based object-oriented language that includes standard primitives found in most object-oriented language formalisms. Additionally, the language offers constructs that can be attached at class definitions for specifying (1) the available methods based on an object state, and (2) how methods may be called in that state – by a single client, in which case we say that the object has a linear status, or without restrictions, in which case we say it has a shared one. We refer to this abstract view that defines an object state and status the class usage type. We formalize the language syntax, the operational semantics, and a type system that enforces by static typing that methods are called only when available, and by a single client if so specified in the class usage type. We illustrate the language capabilities by encoding in MOOL the protocols of two well-known examples: the file reader and the auction system. We have built a prototype compiler to implement our ideas, and its architecture is also described. Finally, we anticipate some of the related topics which we are interested in pursuing in future work

Simple and robust tests of the quadratic break trend hypoteshis for (0), (1) and (2) time series

Mestrado em FinançasEsta tese teve como objetivo a construção de uma estatística de teste para a hipótese nula da não existência de quebra na tendência de uma série temporal unidimensional. A sua principal inovação foi o desenvolvimento de um teste robusto não só para a presença de erros I(0) e I(1) mas também para erros I(2). Para isso, construiu-se um modelo quadrático que incluiu uma variável auxiliar, com a mesma ordem, e foram propostos dois testes distintos, um para uma data de quebra conhecida e o outro para uma data de quebra desconhecida. O primeiro é uma média ponderada pelas estatísticas de teste apropriadas para o caso em que os erros são I(0), I(1) ou I(2). Esta estatística de teste tem uma distribuição normal padrão. O segundo é uma média ponderada que se obtém depois de encontrado o supremo sobre todas as possíveis datas de quebra, sujeitas a um parâmetro delimitador da amostra. Neste caso, os valores críticos foram calculados através de simulação de Monte Carlo. A metodologia de Harvey et al. (2009) foi seguida em ambos os cenários. Mais ainda, conceitos sobre convergência assintótica para processos com duas raízes unitárias foram revistos e algumas propriedades assintóticas de regressões, com uma ou duas raízes unitárias, foram derivadas. Os testes desenvolvidos têm aplicação no estudo de séries económicas e financeiras.The aim of this thesis was the construction of a test statistic for the null hypothesis of no break in trend in an univariate time series. The breakthrough was to make the test robust not only for the presence of I(0) and I(1) shocks but also for the I(2) case scenario. For this reason, a quadratic trend break model and a quadratic dummy variable were designed. The assumption of known or unknown break date motivated the construction of two separate test statistics. The former is a weighted average of the appropriate t-statistics for the case of I(0), I(1) and I(2) shocks and it was shown to have standard normal limiting distribution. The latter is a weighted average of the statistics formed as the supremum over all possible break dates, subject to a trimming parameter. In addition, the critical values for this test statistic were computed through Monte Carlo simulation. The general framework of Harvey et al. (2009) was adopted to test for the presence of a break under a known or unknown break date. At the same time, asymptotic theory for I(2) processes was reviewed and simple asymptotic properties of second and first order auto-regressions were derived. The tests can be applied to the study of financial and economic time series.info:eu-repo/semantics/publishedVersio

Aspectos do trabalho emocional estudados nas interacções entre colegas e factores facilitadores do bem-estar em Bombeiros Sapadores

Tese de mestrado, Psicologia (Psicologia dos Recursos Humanos, do Trabalho e das Organizações), Universidade de Lisboa, Faculdade de Psicologia e de Ciências da Educação, 2008O Trabalho Emocional tem sido definido como a regulação emocional necessária para expressar emoções organizacionalmente desejadas. Os estudos empíricos indicam que o trabalho é um contructo multidimensional com dimensões que têm efeitos positivos e negativos no bem-estar. No presente estudo, diferenciou-se entre os seguintes aspectos: exigências de regulação emocional: (1) a exigência para expressar emoções negativas aos colegas; (2) a exigência para expressar emoções positivas aos colegas; (3) dissonância emocional (a expressão de emoções que não estão a ser sentidas). Ao contrário da maioria dos estudos, estas exigências foram consideradas nas relações com colegas de trabalho. Os dados forma recolhidos com uma amostra de bombeiros (N = 417), constituída na sua maioria por homens. Os dados revelam que a exigência para exprimir emoções negativas aos colegas teve efeitos negativos na exaustão emocional e no cinismo. Pelo contrário, a exigência para exprimir emoções positivas aos colegas teve efeitos positivos na auto-eficácia profissional. Os indivíduos podem lidar de diversas formas com estas exigências do trabalho. As evidências empíricas sugerem que os comportamentos de coping antissociais estão relacionados com problemas de saúde. Os resultados obtidos neste estudo revelam que o coping activo e prossocial está positivamente relacionado com a auto-eficácia, e que o coping passivo e antissocial estão positivamente relacionados com o burnout. Finalmente, os resultados também indicam que o coping passivo é uma variável mediadora da relação entre as exigências para exprimir emoções negativas aos colegas e o burnout. Primeiro, esta investigação sugere que o trabalho emocional não é apenas importante nas interacções com clientes, mas também nas interacções com colegas. Segundo, demonstra que as exigências emocionais do trabalho têm simultaneamente efeitos positivos e negativos. Por último, os resultados apoiam a ideia de que existem estratégias de coping mais eficazes do que outras.Emotional work is defined as emotional regulation required to display organizationally desired emotions by the employees. Empirical studies indicate that emotional work is a multidimensional construct with dimensions having positive and negative effects on well-being. In the present study, the following aspects of emotional work were differentiated: emotional regulation requirements: (1) the requirement to display negative emotions; (2) the requirement to display positive emotions; (3) emotional dissonance (the expression of emotions that are not felt). Unlike most studies, these emotional work requirements are considered in co-workers interactions. The data was collected using a sample of firemen (N = 417), that mainly consisted of male individuals. The data showed that the requirement to display negative emotions to co-workers had negative effects on emotional exhaustion and cynicism. On the other hand, the requirement to display positive to co-workers had positive effect on professional self-efficiency. Individuals can cope in various ways with this kind of work stressors. Empirical evidence suggests that antisocial coping behaviors are more related to health problems. The results obtained in this study reveal that coping in a more prosocial form is positively related to self-efficiency, and that coping in a more passive and antisocial way is positively related to burnout. Finally, the results also have shown that passive coping is mediating variable on the relationship between requirement to display negative emotions and burnout. First, this study suggests that emotion work is not only important in client-related interactions, but also in interactions with co-workers. Second, it indicates that these emotional work requirements can have both negative effects and positive effects on well-being. Finally, the results support the idea that certain coping behaviors are more adaptive than others

Tratamento do varicocelo e impacto na infertilidade masculina

Trabalho final de mestrado integrado em Medicina área cientifica de Urologia, apresentado à Faculdade de Medicina da Universidade de CoimbraActualmente, a infertilidade é um problema em crescimento, estimando-se que a sua prevalência nos casais em idade reprodutiva seja de aproximadamente 15 %. Considera-se que o factor masculino está associado a 50% dos casos documentados. O varicocelo é uma patologia benigna e comum que atinge sensivelmente 15% da população masculina, podendo estar presente em 40% dos doentes com infertilidade. Objectivos Este artigo de revisão bibliográfica tem como objectivos expor o tratamento do varicocelo e, observar o seu potencial impacto no tratamento da infertilidade masculina. Material e Métodos O método utilizado para a elaboração deste artigo consistiu numa extensa revisão de artigos científicos originais e de revisão na Pubmed / Medline (até Novembro de 2011) em língua inglesa, usando os seguintes termos: varicocele, male infertility, varicocele treatment, varicocelectomy, percutaneous occlusion, medical treatment, semen parameters, pregnancy rates, assisted reproduction techniques, em várias combinações. Adicionalmente foram consultados livros e sites especializados na área e relevantes para a temática. Desenvolvimento A associação entre varicocelo e infertilidade masculina é conhecida desde a década de 1950, permanecendo a fisiopatologia do processo incerta. Os parâmetros seminais estão habitualmente alterados na presença de varicocelo e a oligoastenoteratozoospermia é a anormalidade mais comum. Num contexto de infertilidade conjugal, o tratamento do varicocelo tem como propósito melhorar a função testicular e os parâmetros seminais com vista ao aumento da probabilidade de concepção. Todavia, o Tratgrau em que o tratamento do varicocelo melhora as taxas de gravidez e o sucesso das técnicas de reprodução assistida, continuam a ser temas controversos. Actualmente, estão descritas duas vertentes para o tratamento do varicocelo: tratamento médico e tratamento cirúrgico, com taxas de complicações e recidiva distintas. A varicocelectomia ou a oclusão percutânea da veia espermática interna afectada, são as terapêuticas mais abordadas na literatura, e as preconizadas na maioria dos casos. Conclusão São necessários mais estudos comparativos, controlados e randomizados para uniformizar a informação dispersa por diferentes publicações, com a finalidade de se poder concluir sobre qual o melhor método para o tratamento do varicocelo e, qual o verdadeiro impacto na fertilidade de cada doente.Introduction Currently, infertility is a growing problem, and it is estimated that its prevalence among couples of reproductive age is approximately 15%. It is considered that the male factor is associated with 50% of documented and stated cases. The varicocele is a common and benign condition that affects about 15% of the men and affects 40% of the patients with infertility. Objective This literature review article aims to expose the treatment of varicocele and note its potential impact on the treatment of male infertility. Materials and Methods The method used for the preparation of this article consisted in an extensive review of original papers and reviewed articles in Pubmed / Medline (to November 2011) in English, using the following terms: varicocele, male infertility, varicocele treatment, varicocelectomy, percutaneous occlusion , medical treatment, semen parameters, pregnancy rates, assisted reproduction techniques, in several combinations. In addition, there were some consultation books and websites specialized in this area and relevant to this topic. Evolvement The association between varicocele and male infertility has been known since the 1950s, the pathophysiology of the process remains uncertain. The semen parameters are usually modified in the presence of varicocele and oligoasthenoteratozoospermia is the most common abnormality. In the context of a couple's infertility, the treatment of varicocele aims to improve testicular function and semen parameters in order to increase the probability of conception. However, the degree to which the treatment of varicocele improves pregnancy rates and the success of assisted reproduction techniques, are still controversial topics. Currently, two aspects are described for the treatment of varicocele: medical treatment and surgical treatment, with dissimilar relapse and complications rates. The varicocelectomy or percutaneous occlusion of the affected internal spermatic vein are the most addressed treatment in the therapeutic drug literature and recommended in most cases. Conclusion In order to be able to conclude about the best method for the treatment of varicocele, and what is the real impact on fertility in each patient, it would take more comparative studies, randomized and controlled to standardize the information scattered in different publication

Desidratação no idoso

Trabalho final de mestrado integrado em Medicina , área cientifica de Geriatria, apresentado á Faculdade de Medicina da Universidade de CoimbraA desidratação é o distúrbio eletrolítico mais frequente no idoso. A população idosa é mais suscetível a desidratação, não só devido às alterações fisiológicas intrínsecas da idade mas também por causas patológicas, sociais, iatrogénicas e ambientais. O diagnóstico de desidratação não é fácil, já que a clínica e exames laboratoriais perdem especificidade nesta faixa etária e podem não ser conclusivos para um diagnóstico de desidratação. Por isso, é necessário cuidado redobrado na prática clínica para que a desidratação no idoso não passe despercebida, uma vez que o diagnóstico precoce e o tratamento adequado e atempado são indispensáveis para evitar complicações. Se não for tratada, a desidratação apresenta elevadas taxas de morbilidade e mortalidade no idoso. A prevenção da desidratação, no domicílio e em unidades de cuidados, toma assim uma importância indiscutível na sociedade envelhecida dos dias de hoje. Este artigo tem como objetivo fazer uma revisão da literatura mais recente acerca da temática “desidratação no idoso”, abordando os aspetos referidos anteriormente, bastante relevantes nesta populaçãoDehydration is the most common electrolyte disorder in the elderly. The elderly population is more vulnerable to dehydration, not only because of physiological changes related to the aging process but also due to pathological, social, iatrogenic and environmental causes. Diagnosing dehydration is not easy, since clinical signs and laboratory tests are less specific in this age group and may not be conclusive to a diagnosis. Therefore, in clinical practice, it is necessary to pay double attention so that dehydration does not go unnoticed, since early diagnosis and adequate treatment are essential to avoid complications. If left untreated, dehydration presents high morbidity and mortality rates in the elderly. Preventing dehydration, at home and in care units, is incontestably important nowadays in aged societies. The main purpose of this article is to review the recent literature on the subject “dehydration in the elderly”, concerning all aspects already referred which are so pertinent to this population

Adding dependent types to class-based mutable objects

Tese de doutoramento, Informática (Ciência da Computação), Universidade de Lisboa, Faculdade de Ciências, 2018In this thesis, we present an imperative object-oriented language featuring a dependent type system designed to support class-based programming and inheritance. The system brings classes and dependent types into play so as to enable types (classes) to be refined by value parameters (indices) drawn from some constraint domain. This combination allows statically checking interesting properties of imperative programs that are impossible to check in conventional static type systems for objects. From a pragmatic point of view, this work opens the possibility to combine the scalability and modularity of object orientation with the safety provided by dependent types in the form of index refinements. These may be used to provide additional guarantees about the fields of objects, and to prevent, for example, a method call that could leave an object in a state that would violate the class invariant. One key feature is that the programmer is not required to prove equations between indices issued by types, but instead the typechecker depends on external constraint solving. From a theoretic perspective, our fundamental contribution is to formulate a system that unifies the three very different features: dependent types, mutable objects and class-based inheritance with subtyping. Our approach includes universal and existential types, as well as union types. Subtyping is induced by inheritance and quantifier instantiation. Moreover, dependent types require the system to track type varying objects, a feature missing from standard type systems in which the type is constant throughout the object’s lifetime. To ensure that an object is used correctly, aliasing is handled via a linear type discipline that enforces unique references to type varying objects. The system is decidable, provided indices are drawn from some decidable theory, and proved sound via subject reduction and progress. We also formulate a typechecking algorithm that gives a precise account of quantifier instantiation in a bidirectional style, combining type synthesis with checking. We prove that our algorithm is sound and complete. By way of example, we implement insertion and deletion for binary search trees in an imperative style, and come up with types that ensure the binary search tree invariant. To attest the relevance of the language proposed, we provide a fully functional prototype where this and other examples can be typechecked, compiled and run. The prototype can be found at http://rss.di.fc.ul.pt/tools/dol/