Growth and Pollution Convergence: Theory and Evidence

Stabilizing pollution levels in the long run is a pre-requisite for sustainable growth. We develop a neoclassical growth model with endogenous emission reduction predicting that, along optimal sustainable paths, pollution growth rates are (i) positively related to output growth (scale effect) and (ii) negatively related to emission levels (defensive effect). This dynamic law reduces to a convergence equation that is empirically tested for two major and regulated air pollutants - sulfur oxides and nitrogen oxides - with a panel of 25 European countries spanning the years 1980-2005. Traditional parametric models are rejected by the data. More flexible regression techniques confirm the existence of both the scale and the defensive effect, supporting the model predictions.Air pollution, convergence, economic growth, nonparametric regressions

Refracting profiles and generalized holodiagrams

The recently developed concept of refracting profiles and that of refraction holodiagrams are combined so that the classical Abramson holodiagrams can be generalized taking into account a wider class of wave fronts and refraction at an interface, whenever regions of caustics are avoided. These holodiagrams are obtained as envelopes of specific families of Cartesian Ovals with an appropriate parametrization. Classical and reflecting holodiagrams are particular cases of this class. Several of the properties of the classical holodiagrams are shared by their richer generalized versionsComment: 12 pages, 7 figure

El cono aluvial holoceno del Barranco de la Ballena (Las Palmas de Gran Canaria)

[Resumen] A partir del estudio y datación radiocarbónica de un corte natural en la desembocadura del barranco de la Ballena se deduce el funcionamiento del área como una charca litoral, con sedimentación predominante de finos trás una pequeña pulsación torrencial ocurrida en torno al 6200+/-60 B.P. Todo ello, junto a los escasos datos paleobotánicos disponibles, indica una morfodinámica atenuada bajo una situación de fitoestabilidad, pudiendo correlacionarse con los datos aportados por otros estudios en las islas Canarias y Africa Noroccidental.[Abstract] Starting from the study and radiocarbon dating of a cross-section in the mouth of La Ballena ravine, we have estimated the fonctioning of the area as a litoral pool, with a sedimentation mainly of silts anf clays after a brief torrential phase around the 6200+ / -60 B.P. Along with a few palaeobotanical dates indicated a poor morphodynamic activity under covered vegetation, allowing to make the correlations with other dates from the Canary Islands and Northwest Africa

Solving the brachistochrone and other variational problems with soap films

We show a method to solve the problem of the brachistochrone as well as other variational problems with the help of the soap films that are formed between two suitable surfaces. We also show the interesting connection between some variational problems of dynamics, statics, optics, and elasticity.Comment: 16 pages, 11 figures. This article, except for a small correction, has been submitted to the American Journal of Physic