Observed frequency-independent torque in flagellar bacterial motors optimizes space exploration

A surprising feature of many bacterial motors is the apparently conserved form of their torque-frequency relation. Experiments indicate that the torque provided by the bacterial rotary motor is approximately constant over a large range of angular speeds. This is observed in both monotrichous and peritrichous bacteria, independently of whether they are propelled by a proton flux or by a Na+ ion flux. If the relation between angular speed ω and swimming speed is linear, a ω-independent torque implies that the power spent in active motion is proportional to the instantaneous bacterial speed. Using realistic values of the relevant parameters, we show that a constant torque maximizes the volume of the region explored by a bacterium in a resource-depleted medium. Given that nutrients in the ocean are often concentrated in separate, ephemeral patches, we propose that the observed constancy of the torque may be a trait evolved to maximize bacterial survival in the ocean.Fil: Di Salvo, Mario Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; ArgentinaFil: Condat, Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentin

Los Ciclos Económicos Colombianos en el Siglo XX

A partir de una definición específica de "auge y depresión" que se acomoda a la economía colombiana se describen sus ciclos a lo largo del siglo XX y se interpretan con base en dos modelos de una pequeña economía abierta y algunos ejercicios econométricos para estimarlos.

Populist Policies in the Transition to Democracy

This paper develops a political economy model that provides an explanation as for why ruling elites in oligarquic societies may rely on income redistribution to the poor (the masses) in order to prevent them from attempting a revolution. We refer to this kind of redistribution as populist redistribution because, first it does not increase the poor’s productive capacity (human capital), and second it seeks to “buy” political support (peace) to perpetuate the elite’s control of political power. We examine the conditions under which ruling elites choose to deter the poor (by means of military repression and/or populist redistribution), to engage in a dispute with the poor for the control of political power, or, alternatively, to extend democracy. According to the results of the model populist redistribution (or military repression), if any, increases with initial wealth inequality and with the amount of redistribution that the poor can undertake under democracy, and decreases with the relative importance of a human capital externality in production. The model explains why in some cases the use of an apparently ine cient policy of populist redistribution turns out to be optimal for both groups (the ruling elite and the poor class) when the alternative is to use of military repression or default to conflict.Populism, oligarchy, democracy, conflict, inequality.

Cocaine production and trafficking : what do we know ?

The main purpose of this paper is to summarize the information currently available on cocaine production and trafficking. The paper starts by describing the available data on cocaine production and trade, the collection methodologies (if available) used by different sources, the main biases in the data, and the accuracy of different data sources. Next, it states some of the key empirical questions and hypotheses regarding cocaine production and trade and takes a first look at how well the data match these hypotheses. The paper states some of the main puzzles in the cocaine market and studies some of the possible explanations. These puzzles and empirical questions should guide future research on the key determinants of illicit drug production and trafficking. Finally, the paper studies the different policies that producer countries have adopted to fight against cocaine production and the role consumer countries play in the implementation of anti-drug policies.Health Monitoring&Evaluation,Environmental Economics&Policies,Crime and Society,Crops&Crop Management Systems,Economic Theory&Research

El Mercado Laboral Urbano: Empleo, Desempleo y Salario Real en Colombia entre 1985 y 1996

Se estimó un modelo neo-clásico del mercado laboral, con respuestas lentas o ajustes parciales, para el caso de la evolución del empleo, el desempleo transitorio (definido como la diferencia entre el desempleo total y el permanente) y el salario real en el conjunto de las siete principales ciudades colombianas entre 1985 y 1996. Los resultados son consistentes con el modelo supuesto y, en particular, muestran que el empleo es sensible al salario real y al desempleo transitorio, y recíprocamente. Además, tanto el empleo como el desempleo transitorio y el salario real dependen simultáneamente de las tres variables exógenas incorporadas en el modelo: el producto, el costo de uso del capital y la población en edad de trabajar. En equilibrio, al cual tiende el mercado según el modelo, el desempleo transitorio es nulo, así que la tasa desempleo se hace igual a la permanente.

Cocaine Production and Trafficking: What do we know?

The main purpose of this chapter is to summarize the information currently available on cocaine production and trafficking. The chapter starts by describing the available data on cocaine production and trade, the collection methodologies, (if available) used by different sources, the main biases in the data, and the accuracy of different data sources. Next, the chapter states some of the key empirical questions and hypotheses regarding cocaine production and trade and takes a first look at how well the data matches these hypotheses. Also, the chapter states some of the main puzzles in the cocaine market and studies some of the possible explanations. These puzzles and empirical questions should guide future research into our understanding of the key determinants of illicit drug production and trafficking. Finally, the chapter studies the different policies that producer countries have adopted to fight against cocaine production and the role consumer countries play in the implementation of anti-drug policies.Cocaine; Narcotraffic; War on Drugs. Classification JEL: K42; C81; H56.

Enhanced transport through desorption-mediated diffusion

We present a master equation approach to the study of the bulk-mediated surface diffusion mechanism in a three-dimensional confined domain. The proposed scheme allowed us to evaluate analytically a number of magnitudes that were used to characterize the efficiency of the bulk-mediated surface transport mechanism, for instance, the mean escape time from the domain, and the mean number of distinct visited sites on the confined domain boundary.Fil: Rojo, Félix. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; ArgentinaFil: Budde, Carlos Esteban. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Wio, Horacio Sergio. Universidad de Cantabria; España. Consejo Superior de Investigaciones Cientificas; España. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Budde, Carlos Ernesto. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentin

Unemployment Rate and the Real Wage Behavoir: A Neoclassical Hint for the Colombian Labor Market Adjustment

The colombian urban unemployment rate grew dramatically over the last six years. At the same time the real wage also had a sharp increase: The empirical evidence supports the hypothesis that an exogenous increase in the real wage was a cause of the unemployment growth. The long-run elasticity suggest that one percent increase of the real wage index increases unemployment rate something between 0.7 and 1.0 percent. Therefore it seems necessary that real wage comes back to its equilibrium path for the reduction of the unemployment rate to the natural level.Unemployment rate, real wage, cointegration, long-run elasticities.

Labor Participation of Married Women in Colombia

A pseudo-panel was built to estimate the determinants of the labor participation decision of married women between 1984 and 2000. Past participation decisions, education level, labor income taxes, children between 1 and 2 years of age, and the presence of other people unemployed at home are the main explanatory variables of married women’s labor participation in Colombia . The interest rate variable does not offer any insight into that decision.married women, labor participation, state-dependence, fertility.

The Time-Varying Long-Run Unemployment Rate: The Colombian Case

The long-run component of the Colombian unemployment rate is estimated for the last twenty years. According to the results, the main determinants of the permanent component of the unemployment rate are the real hourly wage, the non-wage labor costs and the rate of capital accumulation. Given the statistical properties of the variables, a cointegration approach was adopted.Unemployment rate, labor costs, capital accumulation, cointegration