4,245 research outputs found

    An observer principle for general relativity

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    We give a mathematical uniqueness theorem which in particular shows that symmetric tensors in general relativity are uniquely determined by their monomial functions on the light cone. Thus, for an observer to observe a tensor at an event in general relativity is to contract with the velocity vector of the observer, repeatedly to the rank of the tensor. Thus two symmetric tensors observed to be equal by all observers at a specific event are necessarily equal at that event.Comment: arXiv admin note: substantial text overlap with arXiv:0903.522

    Abductive and Consistency-Based Diagnosis Revisited: a Modeling Perspective

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    Diagnostic reasoning has been characterized logically as consistency-based reasoning or abductive reasoning. Previous analyses in the literature have shown, on the one hand, that choosing the (in general more restrictive) abductive definition may be appropriate or not, depending on the content of the knowledge base [Console&Torasso91], and, on the other hand, that, depending on the choice of the definition the same knowledge should be expressed in different form [Poole94]. Since in Model-Based Diagnosis a major problem is finding the right way of abstracting the behavior of the system to be modeled, this paper discusses the relation between modeling, and in particular abstraction in the model, and the notion of diagnosis.Comment: 5 pages, 8th Int. Workshop on Nonmonotonic Reasoning, 200

    An Exploratory Analysis of Pharmaceutical Price Disparities and Their Implications Among Six Developed Nations

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    In our study of 43 drugs, prescription drug prices in several wealthy nations (Australia, Canada, France, Germany, and the U.K.) were much lower than in the U.S. on average, well below relative per capita GDP. There was relatively little difference among the five foreign nations. All this is consistent with previous research. After separating less-unique from more unique drugs, however, important new findings emerged. Relative prices for less-unique drugs, which are subject to strong competition, were at about half the U.S. level. We suggest that this reflects the exercise of monopsony power that does not exist in the U.S., where buyers as well as sellers compete. On the other hand, relative prices for highly unique drugs tended to be approximately proportional to per capita GDP or higher. Remarkably, biotech drugs were priced at or above U.S. levels in Canada and France

    Pour une approche sociologique des risques technologiques dans la chimie

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    International audiencePoint sur une approche sociologique des risques technologiques dans la chimi

    Postgenomic Perspectives on Sex and Gender

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    This is the author accepted manuscript. The final version is available from Cambridge University Press via the link in this record.n/

    Social Reformers and Regulation: The Prohibition of Cigarettes in the U.S. and Canada

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    The apogee of anti-smoking legislation in North America was reached early in the last century. In 1903, the Canadian Parliament passed a resolution prohibiting the manufacture, importation, and sale of cigarettes. Around the same time, fifteen states in the United States banned the sale of cigarettes and thirty-five states considered prohibitory legislation. In both the United States and Canada, prohibition was part of a broad political, economic, and social coalition termed the Progressive Movement. Cigarette prohibition was special interest regulation, though not of the usual narrow neoclassical genre; it was the means by which a group of crusaders sought to alter the behavior of a much larger segment of the population. The opponents of cigarette regulation were cigarette smokers and the more organized cigarette lobby. An active Progressive Movement was the necessary condition for generating interest in prohibition, while the anti-prohibition forces played a more significant role later in the legislative process. The moral reformers' succeeded when they faced little opposition because few constituents smoked and/or no jobs were at stake because there was no cigarette industry. In other words, reform is easy when you are preaching to the converted.

    Indicateurs et risques technologiques dans la chimie

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    Cette proposition de communication s'appuie sur des enquêtes empiriques menées dans le cadre d'une recherche interdisciplinaire sur la sécurité industrielle depuis 2004 dans plusieurs entreprises françaises de la chimie. La sécurité industrielle est de fait la résultante d'interactions multiples entre des acteurs, à la fois internes et externes à l'entreprise. Que l'on songe aux interactions dans les ateliers entre opérateurs/hiérarchies intermédiaires, entre chefs d'atelier et supérieurs hiérarchiques, entre les divers départements/services de l'entreprise, enfin entre les responsables sécurité et les divers interlocuteurs externes au premier rang desquels on trouve les inspecteurs des installations classées. Des mesures sont alors faites pour attester de la sécurité en actes de l'entreprise concernée. Traduites sous formes d'indicateurs multiples qu'il conviendra de désigner, elles reviennent s'immiscer dans les interactions évoquées ci-dessus pour produire de la conformité, de la déclaration/de la non déclaration d'évènements, de la confiance de la part du régulateur etc...... On s'interrogera dans la lignée des interrogations de Denis Ségrestin sur la portée de tels indicateurs en tenant compte à la fois de la difficulté des managers confrontés à de tels chantiers, des impacts sur le travail des équipes, des interactions au sein des ateliers
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