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En dépit de quinze années de travaux, le normalisateur comptable international, l'International Accounting Standard Board (IASB), n'a pas abouti dans sa tentative de définir une norme spécifique aux activités d'extraction. Cet échec partiel soulève la question suivante : existe-t-il un contenu informationnel propre aux actifs spécifiques et s'il existe, quelle forme communicationnelle doit-il revêtir ? L'IASB s'adressant en priorité à l'actionnaire, notre travail devait naturellement débuter par l'évaluation de ses perceptions, tout en admettant le caractère restrictif d'une telle focalisation. Mobilisant la théorie positive, en cohérence avec l'orientation marché du IASB, notre étude longitudinale est conduite sur onze ans, comprenant le prix bas du baril en 1996/1997 et sa hausse soudaine en 2004, afin de mesurer la manière dont le(s) marché(s) perçoi(ven)t les éléments comptables relatifs à l'activité d'extraction pétrolière et gazière, caractérisée par la présence d'actifs spécifiques à haute teneur stratégique, et réputés très incertains. Une revue de littérature propose une double rétrospective, d'une part, des travaux interrogeant la pertinence des divulgations de valeurs ou volumes, et d'autre part, du raisonnement par les options réelles, mis à l'épreuve dans notre dernier travail empirique. Réalisé sur une population internationale, et mesurant le lien entre les divulgations comptables spécifiques à l'activité pétrolière et gazière et la valeur de marché, notre travail examine la pertinence de ces divulgations par le prisme du modèle de Ohlson tout en proposant une solution aux problèmes de colinéarités que génèrent des variables spécifiques. / Despite a fifteen years work, the international standard setter, the International Accounting Standard Board (IASB) hasn't succeeded in its attempt to define a specific standard relative to extractive activities. This semi-failure raises the following - maybe unresolved - question : does an informational content proper to specific activities exist, and if it does, which would be its appropriate communication form ? Despite the restrictive aspect of a scope admitting that IASB's primary target is the shareholder, our work subsequently started with the evaluation of his/her perceptions. Consistent with the IASB's point of view, we mobilized the positivist theory in an eleven years longitudinal study, covering a period of low barrel prices - in 1996/1997- and the sudden raise of 2004, to study the way in which the market(s) perceive(s) the disclosures of specific items relative to oil and gas activities. The latter are characterized by the presence of specific assets, sometimes strategic, described by the standard setter as highly uncertain. A literature review offers a retrospective on previous researches questioning the value-relevance of either the volume or the value of oil and gas reserves, and on the Real Options Reasoning that is tested in our empirical work. Our examination, on a international sample, of the link between specific accounting disclosures and the market value relies on the Ohlson's model and provides us with some insights on the identification of multicollinearity as likely present when dealing with specific variables.

Made available in DSpace on 2016-08-12T19:18:26Z (GMT). No. of bitstreams: 1 JOSE TORRES FILHO 1.pdf: 620350 bytes, checksum: 5d57dd93c02e89a8a21b02484976d4cb (MD5) Previous issue date: 2008-09-16 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / The objectives of the present work were to characterize melon plant accessions collected in small farms of the Brazilian Northeast, to select traits for the grouping of accessions and cultivars of melon, to investigate the effects of the genotype x environment interaction and the environment on the grouping of accessions and cultivars and to verify the association between genetic divergence and heterosis in melon of the type Honey Dew. Two experiments were carried out to characterize and to form groups of melon accessionscollected in Northeast Brazil and another experiment was conducted to evaluate seven lines of the type Honey Dew and your hybrids. The experiments werelaid out in randomized complete blocks design with two, two and three replications, respectively. Great variation was observed among the melon accessions for all the descriptors, especially in the fruit descriptors. Variation was verified among and within botanical groups, mainly in the group Cantalupensis. Generally speaking, the accessions were prolific and productives, with fruits of intermediate to big size, with lower pulp firmness and content of soluble solids. The descriptors discard was necessary to eliminate the colinearity in the residual variance-covariance matrix. The discard of the descriptors and the grouping of the accessions were dependent of the evaluation conditions, mainly due to the year effects and the interaction accessions x years. The discarded descriptors in the evaluation were: fruit diameter and fruit mass in 2006; fruit lengthwise diameter, fruit mass and production in 2007; and weight of 100 seeds, fruit production and lengthwise diameter in the 2006-2007 joint analysis. The joint analyses, with and without discard, provided similar groupings, allowing the obtaining of five groups and discrimination between accessions and commercial cultivars. The genetic divergence was not correlated with any parameter for all the evaluated traits / Os objetivos do presente trabalho foram caracterizar acessos de meloeiro coletados em áreas de pequenos agricultores do Nordeste brasileiro, selecionar descritores para o agrupamento de acessos e cultivares, investigar os efeitos da interação genótipo x ambiente sobre o agrupamento de acessos e cultivares e verificar a associação entre divergência genética e heterose em meloeiro do tipo Honey Dew. Foram conduzidos dois experimentos para caracterizar e agrupar acessos de meloeiro coletados no Nordeste brasileiro e um terceiro experimento de avaliação de sete linhagens do tipo Honey Dew e seus híbridos. Os experimentos foram conduzidos em blocos casualizados com duas, duas e três repetições, respectivamente. Observou-se grande variação entre os acessos para todos os descritores, em especial nos descritores de fruto. Constatou-se variação entre e dentro dos grupos botânicos estudados, principalmente no grupo Cantalupensis. De um modo geral, os acessos foram prolíficos, produtivos, com frutos de tamanho intermediário a grandes, com baixa firmeza da polpa e baixo teor de sólidos solúveis. O descarte de descritores foi necessário para eliminar os problemas de colinearidade na matriz de variânciacovariância residual. O descarte dos descritores e o agrupamento dos acessos foram das condições de avaliação, principalmente devido aos efeitos de ano e da interação acessos x anos. Os descritores descartados na avaliação foram diâmetro do fruto (DF) e peso do fruto (PF), em 2006; diâmetro longitudinal (DL), peso do fruto (PF) e produção (PR), em 2007; e peso de cem sementes (PS), produção (PR) e diâmetro longitudinal (DL) na avaliação conjunta 2006-2007. As análises conjuntas, com e sem descarte, proporcionaram agrupamentos semelhantes, permitindo a obtenção de cinco grupos e a discriminação entre acessos e materiais comerciais. A divergência genética não se correlacionou com a heterose para todas as características avaliadas

Management and conservation of populations of animals requires information on where they are, why they are there, and where else they could be. These objectives are typically approached by collecting data on the animals’ use of space, relating these to prevailing environmental conditions and employing these relations to predict usage at other geographical regions. Technical advances in wildlife telemetry have accomplished manifold increases in the amount and quality of available data, creating the need for a statistical framework that can use them to make population-level inferences for habitat preference and space-use. This has been slow-in-coming because wildlife telemetry data are, by definition, spatio-temporally autocorrelated, unbalanced, presence-only observations of behaviorally complex animals, responding to a multitude of cross-correlated environmental variables. I review the evolution of techniques for the analysis of space-use and habitat preference, from simple hypothesis tests to modern modeling techniques and outline the essential features of a framework that emerges naturally from these foundations. Within this framework, I discuss eight challenges, inherent in the spatial analysis of telemetry data and, for each, I propose solutions that can work in tandem. Specifically, I propose a logistic, mixed-effects approach that uses generalized additive transformations of the environmental covariates and is fitted to a response data-set comprising the telemetry and simulated observations, under a case-control design. I apply this framework to non-trivial case-studies using data from satellite-tagged grey seals (Halichoerus grypus) foraging off the east and west coast of Scotland, and northern gannets (Morus Bassanus) from Bass Rock. I find that sea bottom depth and sediment type explain little of the variation in gannet usage, but grey seals from different regions strongly prefer coarse sediment types, the ideal burrowing habitat of sandeels, their preferred prey. The results also suggest that prey aggregation within the water column might be as important as horizontal heterogeneity. More importantly, I conclude that, despite the complex behavior of the study species, flexible empirical models can capture the environmental relationships that shape population distributions.