Occurrence and bioaccumulation study of PCDD and PCDF from mineral feed additives

Occurrence of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) was evaluated in sepiolite as a widely employed binder and anti-caking agent for animal feed. Also, naturally contaminated kaolinitic clay was used for comparative purposes. Since sepiolite shows remarkable adsorption properties, particular interest was paid to the extraction steps as they become critical for the final determination of these pollutants in such matrixes. Furthermore, classical Soxhlet extraction using different extracting strategies as well as acid treatment were carried out with simultaneous liquid-liquid extraction. Results obtained depended on the extraction procedure applied. Acid treatment or Soxhlet extraction using a mixture of toluene:ethanol as solvent allowed to reach the minimum requirements of recovery rates. However, Soxhlet extraction using a mixture cyclohexane:toluene as extracting solvent did not allow to comply with minimum specifications for recovery. Significant differences were obtained in TEQ units when acid treatment was applied in comparison to Soxhlet extraction. This fact can be explained because the use of drastic acid conditions allows removing strongly adsorbed analytes which can be uniquely extracted after a total destruction of the crystalline structure of sepiolite. On the contrary, Soxhlet extraction was not able to destroy the structure of sepiolite and as a consequence the PCDDs/Fs were strongly adsorbed in the internal structure of the mineral. From biological point of view the availability of these toxicants constitutes a critical aspect playing an important role in the final decision choosing particular analytical procedures. Then, acid conditions in the digestive tract should be taken into account. In this scenario, a bioaccumulation study was conducted to evaluate the transference of PCDDs/PCDFs from the sepiolite into the animal tissues when fed with feed containing sepiolite. To this end, chickens were used as a model to examine the bioavailability of PCDDs/PCDFs. Four groups of chickens were exposed through their diet to a control feed, feed with 3% w/w sepiolite as additive, feed contaminated with PCDDs/PCDFs at concentration around 2.8 pg WHO-TEQ/g and feed with 2% of a contaminated kaolinitic clay (460 pg TEQ/g mineral). Livers of the four studied groups were analyzed throughout the exposure period. Results of this trial showed that the performance of broilers was not affected by the presence of dioxins at levels tested, and chickens did not show any abnormal behaviour. Dioxins intentionally added to the diet were absorbed and accumulated in the liver in a significant manner, whereas the PCDDs/Fs from sepiolite were not available for chickens since livers from broilers fed 3% sepiolite presented similar WHO-TEQ values than those from broilers fed control diet.

The Measurement of social polarization in a multi-group context

Polarization indices presented up to now have only focused their attention on the distribution of income/wealth. However, in many circumstances income is not the only relevant dimension that might be the cause of social conflict, so it is very important to have a social polarization index able to cope with alternative dimensions. In this paper we present an axiomatic characterization of one of such indices: it has been obtained as an extension of the (income) polarization measure introduced in Duclos, Esteban and Ray (2004) to a wider domain. It turns out that the axiomatic structure introduced in that paper alone is not appropriate to obtain a fully satisfactory characterization of our measure, so additional axioms are proposed. As a byproduct, we present an alternative axiomatization of the aforementioned income polarization measure.

Leadership in collective action

We extend the model of collective action in which groups compete for a budged by endogenizing the group platform, namely the specific mixture of public/private good and the distribution of the private good to group members which can be uniform or performance-based. While the group-optimal platform contains a degree of publicness that increases in group size and divides the private benefits uniformly, a success-maximizing leader uses incentives and distorts the platform towards more private benefits - a distortion that increases with group size. In both settings we obtain the anti-Olson type result that win probability increases with group size.

nàlisi de les modificacions produïdes per llops en conjunts ossis actuals a Bialowieza i Biezcady (Polonia)

Projecte de recerca elaborat a partir d’una estada a la Université Toulouse-Le Mirail, França, entre octubre i novembre del 2006. Estudi experimental que s’emmarca en un projecte predoctoral que té com a objectius principals caracteritzar les modificacions produïdes per carnívors en conjunts ossis actuals, establir una metodologia que permeti identificar el predador o predadors que han intervingut i aplicar aquesta metodologia al registre arqueològic. S’han analitzat les modificacions produïdes per llops (Canis lupus) en conjunts ossis actuals procedents del Parc Nacional de Bialowieza y Biezcady a Polonia i que formen part de la neotafoteca amb dipòsit a la Universitat de Toulouse. L'anàlisi de les fractures i les mossegades als ossos fetes pels llops (Canis lupus) durant el consum, han revelat la important capacitat destructiva i modificadora d'aquests agents tafonòmics. Les dades obtingudes, d'aquest i altres estudis, serviran per confeccionar una metodologia vàlida per a l’estudi de la intervenció de llops en conjunts arqueològics. També serà possible crear un model del tipus de modificació que produeixen els llops. Aquest model estarà reforçat per experiments realitzats per altres investigadors i es podran aplicar als estudis tafonòmics de jaciments arqueo-paleontològics.

Model based fault diagnosis with application to an automotive engine

Report for the scientific sojourn at the University of Linköping between April to July 2007. Monitoring of the air intake system of an automotive engine is important to meet emission related legislative diagnosis requirements. During the research the problem of fault detection in the air intake system was stated as a constraint satisfaction problem over continuous domains with a big number of variables and constraints. This problem was solved using Interval-based Consistency Techniques. Interval-based consistency techniques are shown to be particularly efficient for checking the consistency of the Analytical Redundancy Relations (ARRs), dealing with uncertain measurements and parameters, and using experimental data. All experiments were performed on a four-cylinder turbo-charged spark-ignited SAAB engine located in the research laboratory at Vehicular System Group - University of Linköping.

Linking conflict to inequality and polarization

In this paper we study a behavioral model of conflict that provides a basis for choosing certain indices of dispersion as indicators for conflict. We show that the (equilibrium) level of conflict can be expressed as an (approximate) linear function of the Gini coefficient, the Herfindahl-Hirschman fractionalization index, and a specific measure of polarization due to Esteban and Ray

Government information transparency

This paper studies a model of announcements by a privately informed government about the future state of the economic activity in an economy subject to recurrent shocks and with distortions due to income taxation. Although transparent communication would ex ante be desirable, we find that even a benevolent government may ex-post be non-informative, in an attempt to countervail the tax distortion with a "second best" compensating distortion in information. This result provides a rationale for independent national statistical offices, committed to truthful communication. We also find that whether inequality in income distribution favors or harms government transparency depends on labor supply elasticity.

Redistributive taxation, public expenditure, and size of governent

We introduce a model of redistributive income taxation and public expenditure. This joint treatment permits analyzing the interdependencies between the two policies: one cannot be chosen independently of the other. Empirical evidence reveals that partisan confrontation essentially falls on expenditure policies rather than on income taxation. We examine the case in which the expenditure policy (or the size of government) is chosen by majority voting and income taxation is consistently adjusted. This adjustment consists of designing the income tax schedule that, given the expenditure policy, achieves consensus among the population. The model determines the consensus in- come tax schedule, the composition of public expenditure and the size of government. The main results are that inequality is negatively related to the size of government and to the pro-rich bias in public expenditure, and positively or negatively related to the marginal income tax, depending on substitutability between government supplied and market goods. These implications are validated using OECD data.

Work values, endogenous sentiments and redistribution

We examine the interactions between individual behavior, sentiments and the social contract in a model of rational voting over redistribution. Agents have moral "work values". Individuals' self-esteem and social consideration of others are endogenously determined comparing behaviors to moral standards. Attitudes toward redistribution depend on self-interest and social preferences. We characterize the politico-economic equilibria in which sentiments, labor supply and redistribution are determined simultaneously. The equilibria feature different degrees of "social cohesion" and redistribution depending on pre-tax income inequality. In clustered equilibria the poor are held partly responsible for their low income since they work less than the moral standard and hence redistribution is low. The paper proposes a novel explanation for the emergence of different sentiments and social contracts across countries. The predictions appear broadly in line with well-documented differences between the United States and Europe.

Strategic mass killings

Since World War II there have been about fifty episodes of large-scale mass killings of civilians and massive forced displacements. They were usually meticulously planned and independent of military goals. We provide a model where conflict onset, conflict intensity and the decision to commit mass killings are all endogenous, with two main goals: (1) to identify the key variables and situations that make mass killings more likely to occur; and (2) to distinguish conditions under which mass killings and military conflict intensity reinforce each other from situations where they are substitute modes of strategic violence. We predict that mass killings are most likely in societies with large natural resources, significant proportionality constraints for rent sharing, low productivity and low state capacity. Further, massacres are more likely in a civil than in an interstate war, as in the latter group sizes matter less for future rents. In non polarized societies there are asymmetric equilibria with only the larger group wanting to engage in massacres. In such settings the smaller group compensates for this by fighting harder in the first place. In this case we can talk of mass killings and fighting efforts to be substitutes. In contrast, in polarized societies either both or none of the groups can be ready to do mass killings in case of victory. Under the "shadow of mass killings" groups fight harder. Hence, in this case massacres and fighting are complements. We also present novel empirical results on the role of natural resources in mass killings and on what kinds of ethnic groups are most likely to be victimized in massacres and forced resettlements, using group level panel data.

Ethnicity and conflict : an empirical study

This paper examines the impact of ethnic divisions on conflict. The analysis relies on a theoretical model of conflict (Esteban and Ray, 2010) in which equilibrium conflict is shown to be accurately described by a linear function of just three distributional indices of ethnic diversity: the Gini coefficient, the Hirschman-Herfindahl fractionalization index, and a measure of polarization. Based on a dataset constructed by James Fearon and data from Ethnologue on ethno-linguistic groups and the "linguistic distances" between them, we compute the three distribution indices. Our results show that ethnic polarization is a highly significant correlate of conflict. Fractionalization is also significant in some of the statistical exercises, but the Gini coefficient never is. In particular, inter-group distances computed from language and embodied in polarization measures turn out to be extremely important correlates of ethnic conflict.

Avaluació del creixement del fong ligninolític Trametes versicolor sobre diferents suports sòlids per a l'aplicació en tractaments de bioremediació

Els fongs de podridura blanca (WRF - de l'anglès: White-rot fungi) són de gran interès en l'àmbit de la bioremediació per la seva capacitat de degradar la lignina. La lacasa, un dels enzims extracel·lulars que aquests fongs excreten per degradar la lignina, pot ser utilitzada per degradar els contamiants presents en una matriu donada. Trametes versicolor ha estat estudiat per la seva capacitat de produïr aquest enzim en rersidus agrícoles com a substrats. Un primer triatge basat en la producció de CO2, la mesura de l'activitat lacasa i la quantificació de l'ergosterol han permés seleccionar els substrats on es donava un major poder oxidatiu dels cultius inoculats amb T. versicolor. Els posteriors experiments de colonització de sòls, on es monitoritzava l'activitat lacasa i l'ergosterol, han mostrat que T. vesicolor és capaç de colonitzar sòls i que té una major activitat lacasa en condicions no estèrils. També h'ha provat, mitjançant el test ND24, que T. versicolor és capaç de degradar un contaminant emergent, el naproxè, en sòls estèrils i no estèrils esmenats amb residus agrícoles.

Ethnic and religious polarization and social conflict

In this paper we examine the link between ethnic and religious polarization and conflict using interpersonal distances for ethnic and religious attitudes obtained from the World Values Survey. We use the Duclos et al (2004) polarization index. We measure conflict by means on an index of social unrest, as well as by the standard conflict onset or incidence based on a threshold number of deaths. Our results show that taking distances into account significantly improves the quality of the fit. Our measure of polarization outperforms the measure used by Montalvo and Reynal-Querol (2005) and the fractionalization index. We also obtain that both ethnic and religious polarization are significant in explaining conflict. The results improve when we use an indicator of social unrest as the dependent variable.