The Guianese paradox: How can the freshwater outflow from the Amazon increase the salinity of the Guianan shore?

French Guiana is notable for the extent of its rain forests, which occupy 97% of the country, and the influence of the Amazon along its shores. In fact, the shores and estuaries support a mangrove forest typical of saline conditions. This paper reports the chemical characteristics, conductivity and salinity and the stable isotopes (oxygen and deuterium) of the rivers and shores between the Cayenne area and the border with Surinam. The results show a quite homogenous freshwater pool over the country. However, the low slope of the coast, a result of the wide mud banks deposited by the Amazonian plume, have turned the mouths of the smaller rivers to the northwest, creating large salty areas where mangroves grow several kilometers inland. Despite the large amount of Amazonian water, the Guianan coast exhibits high salinity. In fact, the freshwater itself remains far from the shore, following the north Brazilian current, while only the mud plume arrives at the coast, creating this paradox

Labor Earnings Respond Differently to Income-Tax and to Payroll-Tax Reforms

We estimate the responses of gross labor earnings with respect to marginal and average net-of-tax rates in France over the period 2003-2006. We exploit a series of reforms to the income-tax and the payroll-tax schedules that affect individuals who earn less than twice the minimum wage. Our estimate for the elasticity of gross labor earnings with respect to the marginal net-of-income-tax rate is around 0.2, while we find no response to the marginal net-of-payroll-tax rate. The elasticity with respect to the average net-of-tax rates is not significant for the income-tax schedule, while it is close to -1 for the payroll-tax schedule. A plausible explanation is the existence of significant labor supply responses to the income-tax schedule, combined with a short-term rigidity of the hourly taxable wage (i.e. the gross wage minus payroll taxes), casting doubts about public finance analysis that assumes perfect competition on the labor market. Finally, the effect of the net-of-income-tax rate seems to be driven by labor supply participation decisions, in particular those of females.labor earnings, payroll tax, income tax

Global solvability of a networked integrate-and-fire model of McKean-Vlasov type

We here investigate the well-posedness of a networked integrate-and-fire model describing an infinite population of neurons which interact with one another through their common statistical distribution. The interaction is of the self-excitatory type as, at any time, the potential of a neuron increases when some of the others fire: precisely, the kick it receives is proportional to the instantaneous proportion of firing neurons at the same time. From a mathematical point of view, the coefficient of proportionality, denoted by $\alpha$, is of great importance as the resulting system is known to blow-up for large values of $\alpha$. In the current paper, we focus on the complementary regime and prove that existence and uniqueness hold for all time when $\alpha$ is small enough.Comment: Published at http://dx.doi.org/10.1214/14-AAP1044 in the Annals of Applied Probability (http://www.imstat.org/aap/) by the Institute of Mathematical Statistics (http://www.imstat.org

VR-PMS: a new approach for performance measurement and management of industrial systems

A new performance measurement and management framework based on value and risk is proposed. The proposed framework is applied to the modelling and evaluation of the a priori performance evaluation of manufacturing processes and to deciding on their alternatives. For this reason, it consistently integrates concepts relevant to objectives, activity, and risk in a single framework comprising a conceptual value/risk model, and it conceptualises the idea of value- and risk based performance management in a process context. In addition, a methodological framework is developed to provide guidelines for the decision-makers or performance evaluators of the processes. To facilitate the performance measurement and management process, this latter framework is organized in four phases: context establishment, performance modelling, performance assessment, and decision-making. Each phase of the framework is then instrumented with state of-the-art quantitative analysis tools and methods. For process design and evaluation, the deliverable of the value- and risk-based performance measurement and management system (VR-PMS) is a set of ranked solutions (i.e. alternative business processes) evaluated against the developed value and risk indicators. The proposed VR-PMS is illustrated with a case study from discrete parts manufacturing but is indeed applicable to a wide range of processes or systems

Better residential than ethnic discrimination!

Access to housing is difficult for minorities in France. An audit study we run in the Paris area showed that minority applicants do not face a strong disadvantage in the first step of the application; however, the fact that applicants come from a deprived area leads to more frequent unfavorable outcome (we call this residential discrimination as opposed to ethnic discrimination). The puzzle and paradox come from the fact that face-to-face interviews with real-estate agents in the city of Paris and the Parisian region DO NOT confirm this result. If anything, all discrimi-nation arise from ethnicity and agents dis-miss residential discrimination. Our paper, forthcoming in Urban Studies, documents this contrast between quantitative and qualitative methods and proposes interpretations

Homogenization of the linear Boltzmann equation in a domain with a periodic distribution of holes

Consider a linear Boltzmann equation posed on the Euclidian plane with a periodic system of circular holes and for particles moving at speed 1. Assuming that the holes are absorbing -- i.e. that particles falling in a hole remain trapped there forever, we discuss the homogenization limit of that equation in the case where the reciprocal number of holes per unit surface and the length of the circumference of each hole are asymptotically equivalent small quantities. We show that the mass loss rate due to particles falling into the holes is governed by a renewal equation that involves the distribution of free-path lengths for the periodic Lorentz gas. In particular, it is proved that the total mass of the particle system at time t decays exponentially fast as t tends to infinity. This is at variance with the collisionless case discussed in [Caglioti, E., Golse, F., Commun. Math. Phys. 236 (2003), pp. 199--221], where the total mass decays as Const./t as the time variable t tends to infinity.Comment: 29 pages, 1 figure, submitted; figure 1 corrected in new versio

À la recherche du locataire “idéal” : du droit aux pratiques en région parisienne

Le logement représente 18 % des dépenses annuelles totales des ménages français : c’est leur principale contrainte budgétaire [Accardo et Bugeja, 2009]. Cette contrainte s’est renforcée dans les vingt dernières années : les dépenses de logement ont augmenté en moyenne de 5,2 % par an contre 3,9 % en moyenne pour les revenus [Plateau, 2006]. Chaque année, les rapports de la fondation Abbé Pierre alertent les pouvoirs publics sur le phénomène du « mal-logement » qui touche les catégories les plus fragiles économiquement. Le logement est, selon divers sondages d’opinion, l’une des préoccupations majeures des Français.[Premier paragraphe