The Superiority of Economists

In this essay, we analyze the dominant position of economics within the network of the social sciences in the United States. We begin by documenting the relative insularity of economics, using bibliometric data. Next we analyze the tight management of the field from the top down, which gives economics its characteristic hierarchical structure. Economists also distinguish themselves from other social scientists through their much better material situation (many teach in business schools, have external consulting activities), their more individualist worldviews, and their confidence in their discipline's ability to fix the world's problems. Taken together, these traits constitute what we call the superiority of economists, where economists' objective supremacy is intimately linked with their subjective sense of authority and entitlement. While this superiority has certainly fueled economists' practical involvement and their considerable influence over the economy, it has also exposed them more to conflicts of interests, political critique, even derision

Asymptotic models and curved surfaces : application to railway transportation

5 pagesInternational audienceSeveral wireless communication systems are developed for communication needs between train and ground or between trains in the railway or mass transit domains. In order to deploy these systems in specific environments, such as tunnels, straight or curved, rectangular or arch-shaped section, specific propagation models have to be developed. In this paper, we propose a method to model the radiowave propagation in straight arch-shaped tunnels by using asymptotic methods, such as ray tracing and ray launching, combined with the tessellation of the arched section. A method of interpolation of the facets normals is implemented in order to minimize the error made when using the tessellation. These results are compared to those found in the literature in order to validate our approach

WINNER model for subway tunnel at 5.8 GHz

5 pagesInternational audienceModern subways operation relies on wireless systems based on IEEE802.11x modems deployed inside tunnels. Constraints on robustness and needs for high data rates led to the use of MIMO techniques. In order to evaluate performance of MIMO systems in dynamic configurations with moving trains, it is mandatory to develop adequate dynamic channel model. In this paper, the authors present a new WINNER based model for a subway tunnel at 5.8 GHz in a representative geometric configuration with two tracks and two crossing trains and a 4x4 MIMO system. The statistical behavior of the key parameters of the new WINNER scenario are derived from the complex impulse responses obtained with a 3D ray tracing simulator and given in this paper. Five clusters are considered. The total received power and the 4x4 MIMO channel capacity are compared with the ones derived from the 3D ray tracing simulator

Utilisation des techniques MIMO pour des transmissions robustes et haut-débit en tunnels.

National audienceCe papier illustre le gain de performance potentiel apporté par l'utilisation des techniques MIMO dans le cadre des communications radio en tunnel ferroviaire. Différents schémas de transmission sont testés et évalués dans le cas de canaux faiblement puis fortement corrélés

Geology, Textural Study, Ore Genesis and Processing of the Tabuaço Tungsten Deposit (Northern Portugal)

The Tabuaço tungsten deposit (Northern Portugal) is hosted in the Cambrian Douro Group metasediments, at the northern margin of the Beira-Tabuaço granitic complex. The hosting schisto-calcareous Lower Cambrian Bateiras Formation underwent a contact metamorphism induced by the intrusion of the granitic complex. The skarnification led to the crystallisation of scheelite (CaWO4). Two different skarn facies are encountered: ‘Lower Skarn’ and ‘Main Skarn’ both corresponding to the exoskarn. The ‘Main Skarn’ is mainly composed of vesuvianite (Ca10Mg2Al4(SiO4)5(Si2O7)2(OH)4), feldspars and fluorite. Zoisite, grossular, fluorapatite and scheelite are also present, as well as malayaite and cassiterite. Scheelite is disseminated and often occurs in association with fluorite, albite and vesuvianite. The ‘Lower Skarn’ level contains predominantly diopsidic pyroxene, quartz, zoisite, grossular and feldspars. Scheelite appears both laminated and disseminated, in association with fluorite and vesuvianite in minor proportions. The ‘Main Skarn’ is located in the Garnet, Pyroxene zone, while the ‘Lower Skarn’ corresponds to the Pyroxene, Garnet zone. Pyroxene has a global hedenbergite Hd40 composition. A major phase of albitisation destabilised fluorite, scheelite, vesuvianite, garnet and pyroxene. A late stage of chloritisation is associated with the exhumation. The processing of the Tabuaço ore has been adapted to the Ca-bearing rich paragenesis and to the scheelite mean size

Modélisation de la propagation des ondes radioélectriques en tunnels courbes de section non droite

National audienceCe poster porte sur la conception et le développement d'une nouvelle technique de modélisation de la propagation d'ondes radioélectriques dans des tunnels non rectilignes de section non droite rencontrés en milieu ferroviaire pour des applications métros. Les solutions développées sous forme de modules appelés " plugin ", ont été ajoutées au noyau de l'outil de modélisation de la propagation d'ondes, RaPSor, issu des recherches menées par le laboratoire XLIM-SIC de l'Université de Poitiers. Dans ce travail, nous montrons que les techniques classiques mises en œuvre afin de modéliser la propagation des ondes en tunnel rectiligne infini de section rectangulaire, ne peuvent pas être transposées au cas des tunnels courbes de section courbe. Ainsi, nous avons développé une nouvelle méthode qui se fonde sur une représentation analytique spécifique des surfaces courbes associée à un lancer de rayons et à une optimisation originale des trajets reçus. La répartition uniforme des rayons lancés à l'émission repose sur l'utilisation de séquences quasi-aléatoires de Hammersley. Une sphère adaptative est utilisée à la réception. L'optimisation des rayons est réalisée avec la technique de minimisation de Levenberg-Marquardt. Il s'agit de minimiser la distance totale des trajets afin d'approcher les propriétés des trajets réels au sens de l'Optique Géométrique. L'ensemble des méthodes développées sont testées et validées par comparaisons avec des résultats de la littérature mais aussi avec des résultats de mesures

Evolution of structural neuroimaging biomarkers in a series of adult patients with Niemann-Pick type C under treatment

International audienceBackground: Niemann-Pick type C (NPC) disease is a lysosomal storage disorder characterized by a wide clinical spectrum and non-specific conventional magnetic resonance imaging (MRI) signs. As substrate reduction therapy with miglustat is now used in almost all patients, its efficacy and the course of the disease are sometimes difficult to evaluate. Neuroimaging biomarkers could prove useful in this matter. We first performed a retrospective analysis of volumetric and diffusion tensor imaging (DTI) data on 13 adult NPC patients compared to 13 controls of similar age and sex. Eleven NPC patients were then studied using the same neuroimaging modalities over a mean of 5 years. The NPC composite score was used to evaluate disease severity.ResultsNPC patients showed atrophy in basal ganglia – pallidum (p = 0.029), caudate nucleus (p = 0.022), putamen (p = 0.002) and thalamus (p < 0.001) – cerebral peduncles (p = 0.003) and corpus callosum (p = 0.006), compared to controls. NPC patients also displayed decreased fractional anisotropy (FA) in several regions of interest – corona radiata (p = 0.015), internal capsule (p = 0.007), corpus callosum (p = 0.032) and cingulate gyrus (p = 0.002) – as well as a broad increase in radial diffusivity (p < 0.001), compared to controls. Over time, 3 patients worsened clinically, including 2 patients who interrupted treatment, while 8 patients remained stable. With miglustat, no significant volumetric change was observed but FA improved after 2 years in the corpus callosum and the corona radiata of NPC patients (n = 4; p = 0.029) – although that was no longer observed at further time points.ConclusionThis is the first study conducted on a series of adult NPC patients using two neuroimaging modalities and followed under treatment. It confirmed that NPC patients displayed cerebral atrophy in several regions of interest compared to controls. Furthermore, miglustat showed an early effect on diffusion metrics in treated patients. DTI can detect brain microstructure alterations caused by neurometabolic dysfunction. Its potential as a biomarker in NPC shall be further evaluated in upcoming therapeutic trials

Méthodes de modélisation de la propagation en tunnels courbes

Les systèmes de communication sans fil sont déployés dans le domaine des transports guidés afin d'assurer des communications entre les trains et entre un train et l'infrastructure. Ces systèmes répondent à des besoins opérationnels pour la sécurité et le confort, tels que le contrôle-commande des trains, la gestion du trafic, la maintenance et l'information aux passagers. La prédiction de la couverture radio est donc nécessaire afin d'optimiser le déploiement des points d'accès radio et de minimiser la phase de positionnement des antennes. Ces systèmes peuvent être déployés dans des environnements complexes tels que les tunnels. Les lois usuelles de la propagation en espace libre ne sont alors plus valables et la propagation en tunnel doit être analysée spécifiquement. De plus, les tunnels peuvent être de section transversale non droite et de section longitudinale courbe. Ce papier présente une méthode de modélisation de la propagation en tunnel courbe. Elle s'appuie sur des techniques asymptotiques, et plus particulièrement sur un lancer de rayons adapté, combiné à une correction a posteriori des trajectoires calculées. La méthode est validée à l'aide de mesures dans quelques cas typiques

Ray Launching Modeling in Curved Tunnels with Rectangular or Non Rectangular Section

International audienceSeveral methods to model radio wave propagation in tunnels have been published in the literature and will be presented in this chapter with their advantages and drawbacks. Among them, only few works are dedicated to non rectangular cross section and curved tunnels. Hence, we focus on a new method recently developed. The structure of the chapter is as follows. Section 2 presents the context of the works and why deployments of wireless telecommunication systems are needed for transport applications. Existing techniques to model radio wave propagation in tunnel are presented in section 3 with their respective advantages and drawbacks. The fourth and fifth sections are respectively devoted to the design and the evaluation of a propagation prediction model for curved tunnel with a rectangular or a circular cross section. Finally, section 6 concludes and presents some perspectives to these works

Acceleration Method of Radio Propagation Simulator Based on the Ray Tracing for the Prediction of MIMO Channels in Dynamical Railway Environment.

International audienceThe 3D ray tracing method requires a detailed description of the environment and antenna characteristics. Thus, it allows us to consider all the paths between receivers and transmitters for a fixed number of electromagnetic interactions. However, the computational complexity of this method is directly connected to the number of scatterers and the electromagnetic environment interactions. Thus we proposed an optimization method allowing reducing the computation time of a railway tunnel simulation. It consists in modifying the modeling environment, by eliminating non-significant faces. The aim of our method is, in this case, to provide estimated results close to those obtained with a complete environment modeling, but in fewer computation time