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

Duplex Scanning or Arteriography for Preoperative Planning of Lower Limb Revascularisation

AbstractObjective: to compare the accuracy of duplex and angiography for the planning of lower limb revascularisation.Patients and methods: Sixty limbs (82% with critical limb ischaemia) were assessed by means of duplex by one surgeon and by angiography by another in terms of the optimum inflow and outflow sites for arterial bypass. These data were then compared with the final operation performed which was used as the gold standard. Surgeons were blinded to the determinations of the other.Results: surgical plans based on duplex scan and angiography were correct in 77% (40/52) and 79% (41/52), respectively and plans based on the one imaging modality was modified by the other in only 1 and 2 instances. The diagnostic agreement between duplex scanning and arteriography was excellent (Kappa value=0.94, 95% C.I. 0.89–0.98).Conclusions: the reliability of duplex scanning is comparable to digital angiography in the preoperative planning of lower extremity arterial reconstruction. However neither exam can be considered as the gold standard because intraoperative arteriography needs to be available in a significant number of infrapopliteal procedures

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

Exploring quality-aware architectural transformations at run-time: the ENIA case

Adapting software systems at run-time is a key issue, especially when these systems consist of components used as intermediary for human-computer interaction. In this sense, model transformation techniques have a widespread acceptance as a mechanism for adapting and evolving the software architecture of such systems. However, existing model transformations often focus on functional requirements, and quality attributes are only manually considered after the transformations are done. This paper aims to improve the quality of adaptations and evolutions in component-based software systems by taking into account quality attributes within the model transformation process. To this end, we present a quality-aware transformation process using software architecture metrics to select among many alternative model transformations. Such metrics evaluate the quality attributes of an architecture. We validate the presented quality-aware transformation process in ENIA, a geographic information system whose user interfaces are based on coarsegrained components and need to be adapted at run-time

Influence of Al2O3 reinforcement on precipitation kinetic of Cu-Cr nanocomposite

In this paper, the kinetic of precipitation process in mechanically alloyed Cu-1 wt.% Cr and Cu-1 wt.% Cr/3 wt.% Al2O3 solid solution was compared using differential scanning calorimetry (DSC), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The ageing kinetics in Cu¿Cr and Cu¿Cr/Al2O3 can be described using Johnson¿Mehl¿Avrami (JMA) and Sestak¿Berggren (SB) models, respectively. These different behaviors have been discussed in details. It was found that in presence of Al2O3 reinforcement, the ageing activation energy is decreased and the overall ageing process is accelerated. This behavior is probably due to higher dislocation density previously obtained during ball milling and Al2O3¿Cu interface. TEM observations confirm that Al2O3¿Cu interface and structural defects act as a primary and secondary nucleation sites, respectively.Gobierno de España ENE 2007-67926-C02-0