La tarification douanière dans un optimum de compromis

The purpose of this paper is to integrate into a general model of an open economy the study of optimal wedges on domestic and foreign transactions.While it has been customary in the literature to link the analysis of domestic taxes to the provision of public goods, the model presented here views the imposition of taxes and tariffs in the general context of internal and external monopolies. As such, the paper begins with the idea of a compromised optimality. This means essentially that a modern society, while maximizing the welfare of its members, is constrained by other internal objectives such as the fact that the State shares its monopoly power with several other economic entities (for instance employers' federations, trade-unions). Thus, the mere fact of levying taxes gives a State some monopoly power which, in a sense, is similar to that of a Cournot-type monopolist who "imposes" private taxes.On the other hand, given the possibility that a country with some monopoly power in international trade could improve its situation by imposing tariffs, the analysis lends itself to the study of tariffs and taxes in the broad context of optimal wedges. To allow for this characterization, the paper incorporates into the model of normalization. As a by-product of this, a) it establishes, in terms of generalized inverses of the Slutsky matrix, a link between domestic marginal relative revenues and foreign ones; b) it defines two concepts of optimal tariffs evaluated from f.o.b. prices and c.i.f. prices; c) it suggests some further extensions such as the analysis of transactions costs, the incorporation of market retaliations and cultural characteristics of goods

La tarification douanière dans un optimum de compromis

The purpose of this paper is to integrate into a general model of an open economy the study of optimal wedges on domestic and foreign transactions.

Mean curvature flow with triple junctions in higher space dimensions

We consider mean curvature flow of n-dimensional surface clusters. At (n-1)-dimensional triple junctions an angle condition is required which in the symmetric case reduces to the well-known 120 degree angle condition. Using a novel parametrization of evolving surface clusters and a new existence and regularity approach for parabolic equations on surface clusters we show local well-posedness by a contraction argument in parabolic Hoelder spaces.Comment: 31 pages, 2 figure

On the structure of phase transition maps for three or more coexisting phases

This paper is partly based on a lecture delivered by the author at the ERC workshop "Geometric Partial Differential Equations" held in Pisa in September 2012. What is presented here is an expanded version of that lecture.Comment: 23 pages, 6 figure

Modulation of Brain β-Endorphin Concentration by the Specific Part of the Y Chromosome in Mice

International audienceBackground: Several studies in animal models suggest a possible effect of the specific part of the Y-chromosome (Y NPAR) on brain opioid, and more specifically on brain b-endorphin (BE). In humans, male prevalence is found in autistic disorder in which observation of abnormal peripheral or central BE levels are also reported. This suggests gender differences in BE associated with genetic factors and more precisely with Y NPAR. Methodology/Principal Findings: Brain BE levels and plasma testosterone concentrations were measured in two highly inbred strains of mice, NZB/BlNJ (N) and CBA/HGnc (H), and their consomic strains for the Y NPAR. An indirect effect of the Y NPAR on brain BE level via plasma testosterone was also tested by studying the correlation between brain BE concentration and plasma testosterone concentration in eleven highly inbred strains. There was a significant and major effect (P,0.0001) of the Y NPAR in interaction with the genetic background on brain BE levels. Effect size calculated using Cohen's procedure was large (56% of the total variance). The variations of BE levels were not correlated with plasma testosterone which was also dependent of the Y NPAR. Conclusions/Significance: The contribution of Y NPAR on brain BE concentration in interaction with the genetic background is the first demonstration of Y-chromosome mediated control of brain opioid. Given that none of the genes encompassed by the Y NPAR encodes for BE or its precursor, our results suggest a contribution of the sex-determining region (Sry, carried by Y NPAR) to brain BE concentration. Indeed, the transcription of the Melanocortin 2 receptor gene (Mc2R gene, identified as the proopiomelanocortin receptor gene) depends on the presence of Sry and BE is derived directly from proopiomelanocortin. The results shed light on the sex dependent differences in brain functioning and the role of Sry in the BE system might be related to the higher frequency of autistic disorder in males

Level Set Method for the Evolution of Defect and Brane Networks

A theory for studying the dynamic scaling properties of branes and relativistic topological defect networks is presented. The theory, based on a relativistic version of the level set method, well-known in other contexts, possesses self-similar ``scaling'' solutions, for which one can calculate many quantities of interest. Here, the length and area densities of cosmic strings and domain walls are calculated in Minkowski space, and radiation, matter, and curvature-dominated FRW cosmologies with 2 and 3 space dimensions. The scaling exponents agree the naive ones based on dimensional analysis, except for cosmic strings in 3-dimensional Minkowski space, which are predicted to have a logarithmic correction to the naive scaling form. The scaling amplitudes of the length and area densities are a factor of approximately 2 lower than results from numerical simulations of classical field theories. An expression for the length density of strings in the condensed matter literature is corrected.Comment: 46pp LaTeX, revtex4(preprint), 1 eps figure, revised for publication. Note title chang

Pain Reactivity and Plasma β-Endorphin in Children and Adolescents with Autistic Disorder

International audienceBackground: Reports of reduced pain sensitivity in autism have prompted opioid theories of autism and have practical care ramifications. Our objective was to examine behavioral and physiological pain responses, plasma β-endorphin levels and their relationship in a large group of individuals with autism.Methodology/Principal Findings: The study was conducted on 73 children and adolescents with autism and 115 normal individuals matched for age, sex and pubertal stage. Behavioral pain reactivity of individuals with autism was assessed in three observational situations (parents at home, two caregivers at day-care, a nurse and child psychiatrist during blood drawing), and compared to controls during venepuncture. Plasma β-endorphin concentrations were measured by radioimmunoassay. A high proportion of individuals with autism displayed absent or reduced behavioral pain reactivity at home (68.6%), at day-care (34.2%) and during venepuncture (55.6%). Despite their high rate of absent behavioral pain reactivity during venepuncture (41.3 vs. 8.7% of controls, P<0.0001), individuals with autism displayed a significantly increased heart rate in response to venepuncture (P<0.05). Moreover, this response (Δ heart rate) was significantly greater than for controls (mean±SEM; 6.4±2.5 vs. 1.3±0.8 beats/min, P<0.05). Plasma β-endorphin levels were higher in the autistic group (P<0.001) and were positively associated with autism severity (P<0.001) and heart rate before or after venepuncture (P<0.05), but not with behavioral pain reactivity.Conclusions/Significance: The greater heart rate response to venepuncture and the elevated plasma β-endorphin found in individuals with autism reflect enhanced physiological and biological stress responses that are dissociated from observable emotional and behavioral reactions. The results suggest strongly that prior reports of reduced pain sensitivity in autism are related to a different mode of pain expression rather than to an insensitivity or endogenous analgesia, and do not support opioid theories of autism. Clinical care practice and hypotheses regarding underlying mechanisms need to assume that children with autism are sensitive to pain