Regulation, competition and fraud: evidence from retail gas stations in Mexico

Mexican gas stations across the country buy and sell gasoline at regulated common prices. Therefore, authorities that set these prices do not take into account competition conditions of each market. In this paper we establish the effect of a regulated mark-up price as well as competition on the incentives that gas stations in Mexico have to dispense less amount of gasoline than what consumers pay for. The results of theoretical and empirical work indicate that a higher regulated mark-up price reduces the incentives of gas stations to cheat. Similarly, more intense competition among the retailers of a given market decreases the average shortage.gasoline pricing; regulation; competition; fraud

Disjointly homogeneous Banach lattices and applications

This is a survey on disjointly homogeneous Banach lattices and their applicactions. Several structural properties of this class are analyzed. In addition we show how these spaces provide a natural framework for studying the compactness of powers of operators allowing for a unified treatment of well-known results.Comment: 20 pages, to appear in Proceedings Positivity VII Conference (2013

Aprendizaje de circuitos eléctricos en el nivel polimodal : resultados de distintas aproximaciones didácticas

En este trabajo se informa sobre la enseñanza mediante Tutoriales para Física Introductoria de circuitos eléctricos simples en 2º año Polimodal de la escuela pública argentina. La experiencia se realizó en dos escuelas distintas, una estatal mixta y otra privada de mujeres. Se asignó, aleatoriamente, como población de control a otra división de la escuela estatal, donde se continuó con la enseñanza de tipo tradicional. Se utilizó como instrumento de medición un test de respuestas múltiples (DIRECT), que contiene una taxonomía, por demás completa, de concepciones alternativas y dificultades de aprendizaje sobre circuitos eléctricos. Se logró una importante mejora en el aprendizaje conceptual respecto de la enseñanza tradicional, independientemente del nivel socioeconómico, tipo de escuela y género de los alumnos. Se postula que la utilización conjunta de este tipo de estrategia educativa e instrumentos de medición provee condiciones de trabajo adecuadas para una mejora sustancial en la enseñanza de la física en casi cualquier sistema educativo.We report on teaching resistive electric circuits through Tutorials for Introductory Physics to 11th grade students at Argentina high schools. The experiment was carried out at two different schools: one public, state-run, mixed-gender institution and a confessional school only for women. The Determining and Interpreting Resistive Electric Circuits Concepts Tests (DIRECT), which contain a rather complete taxonomy of misconceptions and learning dificulties with regards to electric circuits, were used to measure conceptual learning. Our results show a very significant improvement in conceptual learning when Tutorials are used, as compared to the traditional instruction used in the control population, for students from different socio-economic backgrounds, of different gender and types of schools. We advocate that the complementary use of active learning teaching strategies, like Tutorials, and measuring instruments like DIRECT, provides the conditions for significant improvements in the teaching of physics in almost any educational system

Modelos de daño concentrados para la simulación numérica del colapso de pórticos planos

En este artículo se propone un método para el análisis no lineal de estructuras aporticadas basado en los conceptos de la Mecánica de la Degradación (Continuum Damage Mechanics). El método consiste en la introducción de un conjunto de variables internas, los índices de daño, que miden la pérdida de rigidez de cada una de las barras de la estructura. La dependencia de estas variables con respecto a la historia de deformaciones de cada barra se describe mediante las leyes de evolución de los índices de daño. El problema a resolver está constituido por las ecuaciones matriciales clásicas del cálculo de estructuras y las leyes de evolución.Peer Reviewe

Case study supermarkets and quality and safety standards for produce in Latin America

"Food safety standards that developed countries impose on developing-country exports have sometimes created a barrier to market access. But in Latin America today, the standards set by supermarkets in the region affect local producers far more than do those imposed by developed countries. Latin American farmers sell 2.5 times more to supermarkets within their own countries than they export to the rest of the world. Drawing on case studies from several Latin American countries, this brief focuses on how supermarkets in the region have gone about imposing quality and safety standards on producers of fresh fruits and vegetables for the domestic market." from TextFood safety ,food security ,Public health ,

Construction Of A Supercritical Fluid Extraction (sfe) Equipment: Validation Using Annatto And Fennel And Extract Analysis By Thin Layer Chromatography Coupled To Image

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)The present work describes setting up a laboratory unit for supercritical fluid extraction. In addition to its construction, a survey of cost was done to compare the cost of the homemade unit with that of commercial units. The equipment was validated using an extraction of annatto seeds' oil, and the extraction and fractionation of fennel oil were used to validate the two separators; for both systems, the solvent was carbon dioxide. The chemical profiles of annatto and fennel extracts were assessed using thin layer chromatography; the images of the chromatographic plates were processed using the free ImageJ software. The cost survey showed that the homemade equipment has a very low cost (similar to US$ 16,000) compared to commercial equipment. The extraction curves of annatto were similar to those obtained in the literature (yield of 3.8% oil). The separators were validated, producing both a 2.5% fraction of fennel seed extract rich in essential oils and another extract fraction composed mainly of oleoresins. The ImageJ software proved to be a low-cost tool for obtaining an initial evaluation of the chemical profile of the extracts.362210247CNPq [140287/2013-2, 301301/2010-7]Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

First record of the epizoic red seaweed Polysiphonia carettia Hollenberg in the Mediterranean Sea.

Primera cita del alga roja epizoica Polysiphonia carettia Hollenberg en el mar Mediterráneo Key words. Caretta caretta, epibionts, Mediterranean Sea, Polysiphonia carettia. Palabras claves. Caretta carom, cpibiontes, Mar Mediterráneo, Polysiphonia carettia