Gobernabilidad democrática: logros y desafíos

En los albores de un nuevo siglo y de un nuevo milenio, la situación\ud política de América Latina es radicalmente diferente de la\ud que se vivía en la región hace más de dos décadas. En efecto, a\ud mediados de 1970, sólo en Costa Rica, Colombia y Venezuela, las\ud autoridades públicas se elegían con regularidad, mediante procesos\ud electorales abiertos y competitivos. Hoy en cambio, y pese a todas\ud sus carencias y déficit, que son muchos, la democracia es, excepto\ud en Cuba, la única forma de gobierno que se practica en la\ud región.\ud Así, entre luces y sombras, ya hace casi 30 años que América Latina\ud vive el proceso de (re)democratización más largo, extenso y\ud profundo de toda su historia. Sin embargo, este proceso aún no cubre\ud las expectativas de una ciudadanía que, realmente, anhela mayor\ud democracia, y que ello implique una mejora sustancial en sus condiciones\ud de vida. La crisis por la que atraviesan muchos de nuestros\ud países constituye un grito de alarma que nos advierte sobre el peligro\ud de dejarnos llevar por los aplausos prematuros, al tiempo que hace\ud crecer nuestra preocupación por la salud política de la democracia\ud latinoamericana, en cuanto a su arraigo, consolidación y estabilidad.\ud En este artículo, exponemos algunas de las principales características\ud del proceso democratizador en América Latina que, a nuestro\ud entender, indican cuáles son los principales desafíos imperantes en\ud la región, en su camino hacia la consolidación democrática.At the dawn of a new century and a new millennium, the political\ud situation in Latin America is radically different from what it was\ud two decades ago. In fact, in the mid 70's only Costa Rica, Colombia,\ud and Venezuela elected their public authorities regularly through\ud open and competitive elections. Today, however, and in spite of all\ud of its many shortcomings and deficiencies, democracy is the only form\ud of government found throughout the region, with the sole exception\ud of Cuba.\ud Thus, for over two decades the región has experienced, albeit with\ud periods of light and shadow, the longest, most extensive and most\ud profound process of (re)democratization of its entire history. This\ud process, however, has not fulfilled the expectations of citizens, who\ud certainly long for a greater democracy, but who also expect the system\ud to improve their living standards. The crisis currently undergoing\ud many of our countries is a wakeup call to warn us about the danger\ud of premature applause, and is the cause of growing concern\ud about the political health of democracy in Latin America in terms\ud of its entrenchment, consolidation, and durability.\ud Some of the major characteristics of this democratization process\ud are presented in this article. We point out what in our opinión are\ud the main challenges the region is faced with in its route toward the\ud consolidation of democracy

microRNAs in the Lymphatic Endothelium : Master Regulators of Lineage Plasticity and Inflammation

microRNAs (miRNAs) are highly conserved, small non-coding RNAs that regulate gene expression at the posttranscriptional level. They have crucial roles in organismal development, homeostasis, and cellular responses to pathological stress. The lymphatic system is a large vascular network that actively regulates the immune response through antigen trafficking, cytokine secretion, and inducing peripheral tolerance. Here, we review the role of miRNAs in the lymphatic endothelium with a particular focus on their role in lymphatic endothelial cell (LEC) plasticity, inflammation, and regulatory function. We highlight the lineage plasticity of LECs during inflammation and the importance of understanding the regulatory role of miRNAs in these processes. We propose that targeting miRNA expression in lymphatic endothelium can be a novel strategy in treating human pathologies associated with lymphatic dysfunction

Optimization of a landfill gas collection shutdown based on an adapted first-order decay model

Abstract: LandGEM’s equation was reformulated to include two types of refuse, fast decaying refuse (FDR) and slow decaying refuse (SDR), whose fractions and key modeling parameters k and L0 were optimized independently for three periods in the life of the Montreal-CESM landfill. Three scenarios were analyzed and compared to actual biogas collection data: (1) Two-Variable Scenario, where k and L0 were optimized for a single type of refuse; (2) Six-Variable Scenario, where three sets of k and L0 were optimized for the three periods and for a single type of refuse; and (3) Seven-Variable Scenario, whereby optimization was performed for two sets of k and L0, one associated with FDR and the second with SDR, and for the fraction of FDR during each of the three periods. Results showed that the lowest error from the error minimization technique was obtained with the Six-Variable Scenario. However, this scenario’s estimation of gas generation was found to be rather unlikely. The Seven-Variable Scenario, which allowed for considerations about changes in landfilling trends, offered a more reliable prediction tool for landfill gas generation and optimal shutdown time of the biogas collection system, when the minimum technological threshold would be attained. The methodology could potentially be applied mutatis mutandis to other landfills, by considering their specific waste disposal and gas collection histories

Restricted risk measures and robust optimization

In this paper we consider characterizations of the robust uncertainty sets associated with coherent and distortion risk measures. In this context we show that if we are willing to enforce the coherent or distortion axioms only on random variables that are affine or linear functions of the vector of random parameters, we may consider some new variants of the uncertainty sets determined by the classical characterizations. We also show that in the finite probability case these variants are simple transformations of the classical sets. Finally we present results of computational experiments that suggest that the risk measures associated with these new uncertainty sets can help mitigate estimation errors of the Conditional Value-at-Risk. Keywords: Risk management; Stochastic programming; Uncertainty modelin

Inversion of Seismic Anisotropic Parameters Using Very Fast Simulated Annealing with Application to Microseismic Event Location

The study and interpretation of hydraulically stimulated regions, such as certain unconventional hydrocarbon reservoirs (e.g. Vaca Muerta Formation, Neuquén, Argentina), requires the accurate location of the induced microseismic events. The localization is carried out by means of the analysis of the travel times of the generated compressional and shear seismic waves from the unknown event position to a set of geophones, usually located in a nearby monitoring well. The accuracy of the localization, and thus the characterization of the fracturing process, can be strongly affected by the available seismic velocity model, from which only estimates are known. Also, the underlying medium usually shows an anisotropic behavior, meaning that the velocities of the seismic waves depend on the propagation direction. Therefore, knowledge of the parameters that characterize the anisotropy and an appropriate calibration of the velocities can reduce the errors in the localization of the microseismic events. In this paper we propose a strategy to simultaneously calibrate the velocity model and invert the anisotropy parameters from three-component microseismic data. The strategy relies on the hypothesis that the subsurface is composed of a finite number of horizontal layers with weak anisotropy, a widely used approximation that requires only three anisotropy parameters per layer. The differences between the observed and the calculated travel times, for a known seismic source, are quantified by means of an appropriate objective function that turns out to be non-linear and multimodal. For this reason, we minimize it using very fast simulated annealing (VFSA), a stochastic global optimization algorithm devised to find near-optimal solutions to hard optimization problems. Tests on synthetic data show that the proposed strategy can be used to effectively calibrate the seismic velocities and to provide appropriate estimates of the anisotropy parameters in spite of the severe non-uniqueness of the inverse problem at hand. Also, the stochastic nature of VFSA allows us to obtain the uncertainties of the solutions by repeating the inversion several times. Finally, by means of a simulated microseismic location example, we show the importance of having a well calibrated model to successfully estimate the locations of the hydraulically induced events.Facultad de Ciencias Astronómicas y GeofísicasConsejo Nacional de Investigaciones Científicas y Técnica

Gobernabilidad democrática: logros y desafíos

En los albores de un nuevo siglo y de un nuevo milenio, la situación política de América Latina es radicalmente diferente de la que se vivía en la región hace más de dos décadas. En efecto, a mediados de 1970, sólo en Costa Rica, Colombia y Venezuela, las autoridades públicas se elegían con regularidad, mediante procesos electorales abiertos y competitivos. Hoy en cambio, y pese a todas sus carencias y déficit, que son muchos, la democracia es, excepto en Cuba, la única forma de gobierno que se practica en la región. Así, entre luces y sombras, ya hace casi 30 años que América Latina vive el proceso de (re)democratización más largo, extenso y profundo de toda su historia. Sin embargo, este proceso aún no cubre las expectativas de una ciudadanía que, realmente, anhela mayor democracia, y que ello implique una mejora sustancial en sus condiciones de vida. La crisis por la que atraviesan muchos de nuestros países constituye un grito de alarma que nos advierte sobre el peligro de dejarnos llevar por los aplausos prematuros, al tiempo que hace crecer nuestra preocupación por la salud política de la democracia latinoamericana, en cuanto a su arraigo, consolidación y estabilidad. En este artículo, exponemos algunas de las principales características del proceso democratizador en América Latina que, a nuestro entender, indican cuáles son los principales desafíos imperantes en la región, en su camino hacia la consolidación democrática.At the dawn of a new century and a new millennium, the political situation in Latin America is radically different from what it was two decades ago. In fact, in the mid 70's only Costa Rica, Colombia, and Venezuela elected their public authorities regularly through open and competitive elections. Today, however, and in spite of all of its many shortcomings and deficiencies, democracy is the only form of government found throughout the region, with the sole exception of Cuba. Thus, for over two decades the región has experienced, albeit with periods of light and shadow, the longest, most extensive and most profound process of (re)democratization of its entire history. This process, however, has not fulfilled the expectations of citizens, who certainly long for a greater democracy, but who also expect the system to improve their living standards. The crisis currently undergoing many of our countries is a wakeup call to warn us about the danger of premature applause, and is the cause of growing concern about the political health of democracy in Latin America in terms of its entrenchment, consolidation, and durability. Some of the major characteristics of this democratization process are presented in this article. We point out what in our opinión are the main challenges the region is faced with in its route toward the consolidation of democracy

Inversion of Seismic Anisotropic Parameters Using Very Fast Simulated Annealing with Application to Microseismic Event Location

The study and interpretation of hydraulically stimulated regions, such as certain unconventional hydrocarbon reservoirs (e.g. Vaca Muerta Formation, Neuquén, Argentina), requires the accurate location of the induced microseismic events. The localization is carried out by means of the analysis of the travel times of the generated compressional and shear seismic waves from the unknown event position to a set of geophones, usually located in a nearby monitoring well. The accuracy of the localization, and thus the characterization of the fracturing process, can be strongly affected by the available seismic velocity model, from which only estimates are known. Also, the underlying medium usually shows an anisotropic behavior, meaning that the velocities of the seismic waves depend on the propagation direction. Therefore, knowledge of the parameters that characterize the anisotropy and an appropriate calibration of the velocities can reduce the errors in the localization of the microseismic events. In this paper we propose a strategy to simultaneously calibrate the velocity model and invert the anisotropy parameters from three-component microseismic data. The strategy relies on the hypothesis that the subsurface is composed of a finite number of horizontal layers with weak anisotropy, a widely used approximation that requires only three anisotropy parameters per layer. The differences between the observed and the calculated travel times, for a known seismic source, are quantified by means of an appropriate objective function that turns out to be non-linear and multimodal. For this reason, we minimize it using very fast simulated annealing (VFSA), a stochastic global optimization algorithm devised to find near-optimal solutions to hard optimization problems. Tests on synthetic data show that the proposed strategy can be used to effectively calibrate the seismic velocities and to provide appropriate estimates of the anisotropy parameters in spite of the severe non-uniqueness of the inverse problem at hand. Also, the stochastic nature of VFSA allows us to obtain the uncertainties of the solutions by repeating the inversion several times. Finally, by means of a simulated microseismic location example, we show the importance of having a well calibrated model to successfully estimate the locations of the hydraulically induced events.Facultad de Ciencias Astronómicas y GeofísicasConsejo Nacional de Investigaciones Científicas y Técnica