Information Retrieval: Computational and Theoretical Aspects (Book Review)

published or submitted for publicatio

Perfectionistic concerns cognitions predict burnout in college athletes: a three-month longitudinal study

The majority of research examining the relationship between perfectionism and athlete burnout has focused on trait perfectionism, while overlooking the importance of the cognitive elements of perfectionism. Perfectionistic cognitions represent an influential cognitive bias driving perfectionistic behavior. Although perfectionistic cognitions have been shown to correlate with burnout symptoms in athletes, this body of work is very limited and does not include college athletes. In addition, it is currently unclear whether perfectionistic cognitions also predict changes in athlete burnout over time. To address these issues, we conducted a two-wave, three month longitudinal study and measured perfectionistic cognitions and burnout in a sample of 170 college athletes both at the start and end of a competitive season. In doing so, we also sought to empirically test the different models of perfectionistic cognitions that have been proposed (original, short, and multidimensional). Using cross-lagged panel models, we found that perfectionistic concerns cognitions predicted increases in burnout. The findings provide initial evidence that perfectionistic cognitions predict changes in athlete burnout over time in college athletes. Consequently, the findings have important implications for our understanding of both athlete burnout and perfectionistic cognitions

Review article: silicon carbide. Structure, properties and processing Artigo revisão: carbeto de silício, estrtutura, propriedades e processamento

In view of considerable interest in the development of liquid phase sintered structural and high-temperature ceramics on the base of silicon carbide, a comprehensive review of the data on structure, properties and the known methods of processing of silicon carbide seems timely. The most striking feature of silicon carbide is its polytypism, i.e. formation of a great number of different structural modifications without any change in composition. Although this feature of silicon carbide was extensively studied, no systematic up to date analysis was done. However, polytypism and the tendency of the polytypes to undergo structural transformations at working temperatures may lead to uncontrollable modification of the materials properties, and therefore needs to be fully understood. Furthermore, the recently developed liquid phase sintering technique for silicon carbide densification is of an undoubtful interest and the overview of the results achieved until present time may provide some guidelines for the ceramists.<br>Em vista do considerável interesse no desenvolvimento de cerâmicas estruturais e para aplicações em alta temperatura, é oportuna uma revisão quanto a estrutura, propriedades e métodos conhecidos de processamento de cerâmicas a base de carbeto de silício sinterizados via fase líquida. A característica mais interessante do carbeto de silício é o seu politipismo, isto é, a formação de um grande número modificações estruturais para uma mesma composição. Embora este fenômeno venha sendo extensivamente estudado, não se tem até o momento, uma análise sistemática do mesmo, o que seria de extrema importância, uma vez que o politipismo e a tendência à transformação estrutural destes politipos em temperaturas típicas de trabalho podem levar a incontroláveis modificações nas propriedades do material. Além disso, os recentes avanços obtidos na densificação do carbeto de silício através da técnica de sinterização na presença de fase líquida justificam uma avaliação dos resultados obtidos até o momento, que podem proporcionar alguma orientação aos profissionais da área