An observer principle for general relativity

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

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

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

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

Postgenomic Perspectives on Sex and Gender

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

Indicateurs et risques technologiques dans la chimie

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

Sparse Identification of Nonlinear Duffing Oscillator From Measurement Data

In this paper we aim to apply an adaptation of the recently developed technique of sparse identification of nonlinear dynamical systems on a Duffing experimental setup with cubic feedback of the output. The Duffing oscillator described by nonlinear differential equation which demonstrates chaotic behavior and bifurcations, has received considerable attention in recent years as it arises in many real-world engineering applications. Therefore its identification is of interest for numerous practical problems. To adopt the existing identification method to this application, the optimization process which identifies the most important terms of the model has been modified. In addition, the impact of changing the amount of regularization parameter on the mean square error of the fit has been studied. Selection of the true model is done via balancing complexity and accuracy using Pareto front analysis. This study provides considerable insight into the employment of sparse identification method on the real-world setups and the results show that the developed algorithm is capable of finding the true nonlinear model of the considered application including a nonlinear friction term.Comment: 6 pages, 8 figures, conference pape