Sex morphs and invasiveness of a fleshy-fruited tree in natural grasslands from Argentina

Invasiveness has usually been studied as a species-level attribute; nevertheless, phenotypic differences between individuals in a population can lead to significant variations in colonization ability. In this paper, we analyse the potential effects of sex morphs of Prunus mahaleb, a gynodioecius fleshy-fruited tree, on its invasiveness in natural grasslands in the southern Argentine Pampas. We assessed the abundance of both hermaphrodite and female plants and compared their fecundity, propagule size and germination response. We found that the females were less abundant in the invasive populations studied, apparently since the beginning of the colonization. However, our results demonstrated that at the present time females do not show any fecundity reduction, which clearly shows that P. mahaleb has established an effective interaction with generalist pollinators which compensates for the apparent disadvantage of females. Fruit set showed a wider range of variability over time in the females than in the hermaphrodites, which could be the consequence of greater susceptibility to changes in the activity of pollinators. We found no evidence of a female benefit due to reallocation of resources or better outcrossed progeny considering propagule size and germination. We discuss the relative importance of sex morphs and interactions at different stages of the invasion process.Fil: Amodeo, Martín Raúl. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Grupo de Estudios en Conservación y Manejo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Zalba, Sergio Martín. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Grupo de Estudios en Conservación y Manejo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Efficiency Measures and Regulation: An Illustration of the Gas Distribution Sector in Argentina

The paper develops a cost frontier model of gas distribution and estimates it on data for gas distribution companies of Argentina. Efficiency measures are an important tool for regulators, showing how much a firm can rise its output without using more inputs. In Argentina, the Regulatory Framework of the gas sector establishes that only firms that are efficient can earn a rate of return similar to those activities that bear comparable risk. In this context, the estimate of efficiency measures is an indispensable tool to improve regulation of the privatised utilities. The first part of the paper consists in a theoretical survey of the existent literature where we discuss recent developments in this field, paying special attention to the case of regulated utilities. Deterministic and stochastic cost frontiers are analysed, both for the cases of cross-section and panel data. In the second part, we use econometrics methods to estimate a cost frontier (deterministic and stochastic) for the gas distribution sector in Argentina. Finally, the efficiency rankings of the companies are estimated.Efficiency Measures; Gas Distribution Sector in Argentina

Methanol detection in M82

We present a multilevel study of the emission of methanol, detected for the first time in this galaxy, and discuss the origin of its emission. The high observed methanol abundance of a few 10^-9 can only be explained if injection of methanol from dust grains is taken into account. While the overall [CH3OH]/[NH3] ratio is much larger than observed towards other starbursts, the dense high excitation component shows a similar value to that found in NGC 253 and Maffei 2. Our observations suggest the molecular material in M 82 to be formed by dense warm cores, shielded from the UV radiation and similar to the molecular clouds in other starbursts, surrounded by a less dense photodissociated halo. The dense warm cores are likely the location of recent and future star formation within M 82.Comment: Accepted for publication in A&A Letter

The effect of pension rules on retirement monetary incentives with an application to pension reforms in Spain

In this work we theoretically disentangle the effects of pension provisions on a variety of financial incentives to retirement, trying to reconcile them with some key Spanish retirement patterns. We find that the "average" individual, who is never affected by any cap of contributions or benefits, has weak incentives to retire early and strong incentives to retire at the normal retirement age. Alternatively, individuals at the bottom of the wage distribution have strong incentives to retire as early as possible, because ot the interaction between age-related penalties and the minimun pension. Both findings perfectly accommodate the retirement hazard of medium and low earners respectively. In contrast, high earners (those that have their contributions capped) despite having strong incentives to retire at the Early Retirement Age, do not do so. This is because, for those workers, financial incentives are not a good proxy for the marginal utility from working. Finally, we analyze the reasons behind the failure of the 1997 reform in improving the sustainability of the Spanish public pension system

A note on the Gauge Symmetries of Unimodular Gravity

The symmetries of Unimodular Gravity are clarified somewhat.Comment: 4 pages, v2: acknowledgments correcte

El impacto de la privatización del sector eléctrico en la salud pública

Este informe utiliza información a nivel provincial en Argentina para probar la relación casual entre la distribución de electricidad y la salud. Examina el impacto de la privatización en dos medidas: incidencia en los índices de nacimientos de bajo peso y mortalidad infantil causada por envenenamiento de comida. La privatizacion mejora la cobertura del servicio que, a través del uso de refrigeradoras puede mejorar la ración nutricional. La privatización también tiene por resultado la reducción en la frecuencia de interrupciones eléctricas, y así reducir la probabilidad del envenenamiento de la comida. A pesar que la evidencia indica que la privatización reduce el índice de nacimientos de bajo peso y mortalidad infantil causados por el envenenamiento de la comida, los resultados no son lo suficientemente fuertes para enriquecer el debate de políticasrespecto a los beneficios de la privatización para el bienestar de los pobres.

Photodissociation chemistry footprints in the Starburst galaxy NGC 253

We report the first detection of PDR molecular tracers, namely HOC+, and CO+, and confirm the detection of the also PDR tracer HCO towards the starburst galaxy NGC 253, claimed to be mainly dominated by shock heating and in an earlier stage of evolution than M 82, the prototypical extragalactic PDR. Our CO+ detection suffers from significant blending to a group of transitions of 13CH3OH, tentatively detected for the first time in the extragalactic interstellar medium. These species are efficiently formed in the highly UV irradiated outer layers of molecular clouds, as observed in the late stage nuclear starburst in M 82. The molecular abundance ratios we derive for these molecules are very similar to those found in M 82. This strongly supports the idea that these molecules are tracing the PDR component associated with the starburst in the nuclear region of NGC 253. A comparison with the predictions of chemical models for PDRs shows that the observed molecular ratios are tracing the outer layers of UV illuminated clouds up to two magnitudes of visual extinction. Chemical models, which include grain formation and photodissociation of HNCO, support the scenario of a photo-dominated chemistry as an explanation to the abundances of the observed species. From this comparison we conclude that the molecular clouds in NGC 253 are more massive and with larger column densities than those in M 82, as expected from the evolutionary stage of the starbursts in both galaxies.Comment: 32 pages, 4 figures, Published in Ap