Returns to scale in water and sanitation: estimates for Latin America

Most countries around the world are strongly debating ways to yield more equitable access and a more efficient provision. One issue linked to efficiency is the achievement of scale economies in the industry and the optimal dimension of water and sanitation providers. Changes in the industrial structure of the sector, through mergers in highly atomized services, the breakup of very concentrated services, or the property discussion (private versus public) are major issues. These decisions have often become politicized because of the social complexity of the sector. Empirical findings of the different models reveal the existence of increasing returns to scale in Latin American water provision based on an ADERASA database (a 2005 cross section of 90 providers in 14 countries). The study of returns to scale incorporates a technical argument into the discussion because–as our study suggests–the prescription could be to agglomerate small providers.Fil: Ferro, Gustavo Adolfo. Universidad Argentina de la Empresa. Facultad de Ciencias Económicas. Instituto de Economía; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Lentini, Emilio J.. Universidad de Buenos Aires. Facultad de Ciencias Veterinarias. Centro de Estudios Transdisciplinarios del Agua; ArgentinaFil: Mercadier, Augusto C.. Universidad Argentina de la Empresa. Facultad de Ciencias Económicas. Instituto de Economía; ArgentinaFil: Romero, Carlos A.. Universidad Argentina de la Empresa. Facultad de Ciencias Económicas. Instituto de Economía; Argentin

Retornos a escala en agua y saneamiento: estimaciones para América Latina

In the whole world there are strong discussions on how to yield a more equitable access and a more efficient provision. One issue linked to efficiency is the achievement of scale economies in the industry, and the optimal dimension of water and sanitation providers. Changes in the industrial structure of the sector, through mergers in highly atomized services, the splitting of very concentrated ones, or the property discussion (private versus public) had been hotly debated in different countries. Many times, the decisions had politicized because of the social complexity of the sector. In this study, we aim to estimate the presence of returns to scale, exploiting a database of water and sanitation providers in Latin America. Public policy consequences are direct: if those returns to scale do exist, and the sector is not taking advantage of them, the agglomeration of small providers can eventually save resources which are useful to solve the coverage shortages and the insufficient access for the poor in the region. The scale economies study adds a technical argument to the discussion, because the prescription could be, as it happens to suggest the study, of the convenience of agglomerating small providers to reduce unit costs

Retornos a escala en agua y saneamiento: estimaciones para América Latina

In the whole world there are strong discussions on how to yield a more equitable access and a more efficient provision. One issue linked to efficiency is the achievement of scale economies in the industry, and the optimal dimension of water and sanitation providers. Changes in the industrial structure of the sector, through mergers in highly atomized services, the splitting of very concentrated ones, or the property discussion (private versus public) had been hotly debated in different countries. Many times, the decisions had politicized because of the social complexity of the sector. In this study, we aim to estimate the presence of returns to scale, exploiting a database of water and sanitation providers in Latin America. Public policy consequences are direct: if those returns to scale do exist, and the sector is not taking advantage of them, the agglomeration of small providers can eventually save resources which are useful to solve the coverage shortages and the insufficient access for the poor in the region. The scale economies study adds a technical argument to the discussion, because the prescription could be, as it happens to suggest the study, of the convenience of agglomerating small providers to reduce unit costs

L\'evy flights of photons in hot atomic vapours

Properties of random and fluctuating systems are often studied through the use of Gaussian distributions. However, in a number of situations, rare events have drastic consequences, which can not be explained by Gaussian statistics. Considerable efforts have thus been devoted to the study of non Gaussian fluctuations such as L\'evy statistics, generalizing the standard description of random walks. Unfortunately only macroscopic signatures, obtained by averaging over many random steps, are usually observed in physical systems. We present experimental results investigating the elementary process of anomalous diffusion of photons in hot atomic vapours. We measure the step size distribution of the random walk and show that it follows a power law characteristic of L\'evy flights.Comment: This final version is identical to the one published in Nature Physic

Eficiencia en la prestación de agua y saneamiento y su vinculación con regiones, propiedad e independencia de los prestadores en Brasil

The purpose of this paper is to assess comparative efficiency in water and sanitation sector in Brazil. We run a Sthocastic Frontier Analysis model for a panel of 127 providers, covering more than 70% of urban population of the country. We search and find an explanation for cost efficiency, and we explore its interrelations with regions, property and independence of the providers. We use a database built on the SNIS (National System of Sanitation Statistics) to run a SFA cost model. We add to the formula, environmental and institutional variables, trying to capture differences in costs and efficiency attributable to the ambience of operation. We achieve a satisfactory model, showing a modest efficiency average, and we could patterns, even not well defined. The study has policy implications, in the discussion state-run versus municipal-run, public versus private, and corporitized versus dependent providers. The optimal industrial organization of the sector can be analyzed since the efficiency perspective

Eficiencia en la prestación de agua y saneamiento y su vinculación con regiones, propiedad e independencia de los prestadores en Brasil

The purpose of this paper is to assess comparative efficiency in water and sanitation sector in Brazil. We run a Sthocastic Frontier Analysis model for a panel of 127 providers, covering more than 70% of urban population of the country. We search and find an explanation for cost efficiency, and we explore its interrelations with regions, property and independence of the providers. We use a database built on the SNIS (National System of Sanitation Statistics) to run a SFA cost model. We add to the formula, environmental and institutional variables, trying to capture differences in costs and efficiency attributable to the ambience of operation. We achieve a satisfactory model, showing a modest efficiency average, and we could patterns, even not well defined. The study has policy implications, in the discussion state-run versus municipal-run, public versus private, and corporitized versus dependent providers. The optimal industrial organization of the sector can be analyzed since the efficiency perspective

Experimental study of solubility of elemental sulphur in methane

International audienceThe chemical engineering department of LaTEP has been working for many years on theproblem of sulphur deposition especially in natural gas network [1, 2]. The solid sulphurappears immediately downstream of a pressure reduction facility. One of the hypothesesproposed to explain the solid formation, based on a thermodynamic approach, is thedesublimation of sulphur. During gas expansion, both pressure and temperature decrease.Consequently the gas may become over saturated in sulphur. Because we are below thetemperature of sulphur triple point, part of the gaseous sulphur can be transformed into solidparticles. Thus, it is important to obtain solubility data of sulphur in natural gases. Methane isthe major natural gas component. So, it is of importance to measure solubility of elementalsulphur in CH4. In this paper experimental measurements up to a pressure and temperature of30 MPA and 363.15 K are presented.The principle of the experimental pilot can be resumed following three steps: saturationof the gas with sulphur, trap of all the dissolved gaseous sulphur and finally quantification.Although the principle is simple, experimental difficulties occur at the three steps. A variablevolume equilibrium cell is used to saturate the gas with sulphur. Since sulphur solubility valueis weak in gas transport conditions, the volume of the cell is necessarily big (0.5 Litre). Thepressure of the equilibrium cell is held constant thanks to a piston during the trapping step. Anoriginal gaseous sulphur trapping method was developed. It is based on the reactiveabsorption of the gaseous sulphur with solvent. Indeed, the gas bubbles into a liquid solutionwhich traps gaseous sulphur. Finally, the solution which contains a standard is analysed bygas chromatography and sulphur is quantified. The total volume of the gas withdrawn isdetermined by a position transducer placed on the autoclave. Then, the sulphur solubilityvalue is calculated

Signatures of Le´vy flights with annealed disorder

We present theoretical and experimental results of Le´vy flights of light originating from a random walk of photons in a hot atomic vapor. In contrast to systems with quenched disorder, this system does not present any correlations between the position and the step length of the random walk. In an analytical model based on micro- scopic first principles including Doppler broadening we find anomalous Le´vy-type superdiffusion corresponding to a single-step size distribution P (x) ∝ x−(1+α), with α ≈ 1. We show that this step size distribution leads to a violation of Ohm’s law [Tdiff ∝ L−α/2 ⵬= L−1], as expected for a Le´vy walk of independent steps. Furthermore, the spatial profile of the transmitted light develops power-law tails [Tdiff(r) ∝ r−3−α]. In an experiment using a slab geometry with hot Rb vapor, we measured the total diffuse transmission Tdiff and the spatial profile of the transmitted light Tdiff(r). We obtained the microscopic Le´vy parameter α under macroscopic multiple scattering conditions paving the way to investigation of Le´vy flights in different atomic physics and astrophysics systems.We thank Dominique Delande for fruitful discussions and we acknowledge funding for N.M. and Q.B. by the french Direction Generale de l'Armement. R.P acknowledges the support of LABEX WIFI (Laboratory of Excellence ANR-10-LABX-24) within the French Program "Investments for the Future" under reference ANR-10-IDEX-0001-02 PSL*. E.J.N. and R.K. acknowledge the FCT/CNRS exchange program (441.00 CNRS)

Adult cardiac myocytes survive and remain excitable during long-term culture on synthetic supports

AbstractObjective: Cardiomyocytes can be transplanted successfully into skeletal and cardiac muscle. Our goal was to determine the feasibility of grafting cardiomyocytes onto various synthetic supports to create an excitable and viable tissue for implantation. Methods: Adult rat cardiomyocytes were cultured over an 8-week period onto different substitutes, including human glutaraldehyde-treated pericardium (n = 3), equine glutaraldehyde-treated pericardium (n = 3), polytetrafluoroethylene (n = 8), Dacron polyester (n = 16), and Vicryl polyglactin (n = 8). Results: Only the cells seeded on the Dacron survived, with the synthetic fibers colonized at 8 weeks. On the other supports, the number of myocytes progressively decreased from the first week, with their density (number of cells per square millimeter) being, after 20 days, 17 ± 2 on the polytetrafluoroethylene and 5 ± 1 on the human or equine pericardium compared with 45 ± 3 on the Dacron. After 8 weeks of culture on Dacron, the sarcomeric protein (sarcomeric α-actinin) was detected in all cells. In addition, the staining was regularly arranged and well aligned in a striated pattern. Spontaneous beating activity was obtained. Moreover, electrical stimulation of the cell preparation resulted in the generation of calcium transients, the frequency of which followed the frequency of the electrical stimulation. Conclusions: These results suggest that adult cardiac myocytes remain viable and excitable during long-term culture on a 3-dimensional Dacron support, which might constitute a new synthetic cardiac tissue. (J Thorac Cardiovasc Surg 2001;121:510-9