copulaedas: An R Package for Estimation of Distribution Algorithms Based on Copulas

The use of copula-based models in EDAs (estimation of distribution algorithms) is currently an active area of research. In this context, the copulaedas package for R provides a platform where EDAs based on copulas can be implemented and studied. The package offers complete implementations of various EDAs based on copulas and vines, a group of well-known optimization problems, and utility functions to study the performance of the algorithms. Newly developed EDAs can be easily integrated into the package by extending an S4 class with generic functions for their main components. This paper presents copulaedas by providing an overview of EDAs based on copulas, a description of the implementation of the package, and an illustration of its use through examples. The examples include running the EDAs defined in the package, implementing new algorithms, and performing an empirical study to compare the behavior of different algorithms on benchmark functions and a real-world problem

On the co-existence of spot and contract markets: an analysis of quality

The possible co-existence of spot and contract market that can emerge in the presence of quality issues with a number of growers and processors in each stage is something that has largely remained an open question in the literature. This paper is an attempt to fill this void. We use a straightforward two-stage Cournot oligopoly model with specific demand and cost functions. In the first stage, processors decide simultaneously whether or not to set an incentive contract. The second stage is the stage in which growers choose their levels of quantity and quality based on the industry structure developed in the first stage. With the help of numerical simulations we conducted the study of the equilibrium structures. Our results suggest that for a wide range of number of participants in both markets, participation in both markets constitutes a Nash equilibrium for the model.Marketing,

Local government debt: an application to the Spanish case

For the last years, Europe has been subject to fiscal austerity in order to satisfy the Maastrich criteria. In this way, Spanish municipalities have been affected by new regulations and local government structure has changed. This paper is focused on the main factors that explain local government debt. In particular, budgetary information of a group of Spanish municipalities is used (1990-2000). Econometric analysis of cross section and panel data are presented. Key words:Fiscal Federalism, Local Government, debt, decentralization.

Double Sided Moral Hazard and Share Contracts in agriculture

This paper develops a double-sided moral hazard model of share contract in agriculture, with imperfect quality measurement by the agent and the principal, who contribute to the final good quality in terms of production effort and marketing effort respectively. Using this model, we analyse the implications of the share contract for quantity and quality, often ignored in previous analysis. With the help of a simulation exercise, we prove that the outcome-conditioned share generally weakens the agent´s incentive to make effort in quality input. This finding could explain the contractual evidence in some differentiated markets such as the wine market, where bottle-price conditioned contracts are rarely used.share-contract, double moral-hazard, quality, Farm Management,

The yield/quality trade-off and contractual choice

This paper provides an analysis of the choice of governance mechanism in agriculture using an integrated perspective based on agency theory. The main ways of organizing agriculture are compared: spot market and incentive contract. With the analytical development of both models, it is explored that the choice of the optimal mechanism depends on initial conditions such as uncertainty, the risk aversion of the agents or the number of competitors. Moreover, according to the predictions made by the economic literature on agrarian organization, the results support the coexistence of both governance alternatives.Crop Production/Industries,

Quality and governance mode choice: a transaction cost approach to the wine industry

We analyze the relationship between product quality and governance mode choice using the results of a survey of DOC Rioja wineries. Wineries that produce high-quality wines are more likely to vertically integrate than are wineries that produce low-quality wines. Consistent with Transaction Cost Economics, we find evidence that asset specificity and uncertainty are important determinants of vertical integration. Finally, the size of the winery is also an important factor that affects governance mode choice in viticulture.quality, governance mode choice, transaction cost, Industrial Organization,

The Quality-Quantity Trade-off in the Principal-Agent Framework

This paper uses the principal-agent theory to analytically investigate the optimal incentive-based compensation contract that a processor should offer to a grower performing efforts in quantity and quality. In this process, we contribute to the substantive literature on multi-task principal-agent models by analyzing the quality-quantity trade-off and studying the implications of such a relationship in the principal-agent framework. One striking result of these effects is that, under appropriate incentive-based grower’s compensation, the processor may encourage grower’s effort in quality without crowding out grower’s effort in quantity.quality, quantity, trade-off, incentive contract, principal-agent framework, uncertainty, Agribusiness, Agricultural and Food Policy, D86,

New Silver Nanosensor for Nickel Traces. Part II: Urinary Nickel Determination Associated to Smoking Addiction

A new fluorescence silver nanosensor assisted by surfactant has been recently synthesized and applied to ultra trace nickel determination. The methodology was validated by the standard addition method and satisfactorily applied to nickel determination in urine without previous treatment, coming from subjects with different smoking addiction levels and second hand smokers. Within-day precision was better than 0.011 CV. The reproducibility (between-days precision) was also evaluated over 3 days by performing six determinations each day with a CV of 0.025. The proposed methodology represents a promising approach in the area of biological monitoring due to its low operation cost, simplicity of instrumentation, high sampling speed and non-polluting solvents. Obtained results of urinary nickel concentration were successfully correlated with the tobacco addiction.Fil: Talio, María Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Química de San Luis. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia. Instituto de Química de San Luis; ArgentinaFil: Luconi, M. O.. Universidad Nacional de San Luis; ArgentinaFil: Fernandez, Liliana Patricia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Química de San Luis. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia. Instituto de Química de San Luis; Argentin