Competition, efficiency and collective behavior in the "El Farol" bar model

The El Farol bar model, proposed to study the dynamics of competition of agents in a variety of contexts (W. B. Arthur, Amer. Econ. Assoc. Pap. and Proc. 84, 406 (1994)) is studied. We characterize in detail the three regions of the phase diagram (efficient, inefficient and better than random) of the simplest version of the model (D. Challet and Y.-C. Zhang, Physica A, 246, 407 (1997)). The efficient region is shown to have a rich structure, which is investigated in some detail. Changes in the payoff function enhance further the tendency of the model towards a wasteful distribution of resources.Comment: 7 pages Latex, 7 Postscript figures; changed reference, acknowledgments included. Accepted for publication in Europen Physics Journal

Influence of external information in the minority game

The influence of a fixed number of agents with the same fixed behavior on the dynamics of the minority game is studied. Alternatively, the system studied can be considered the minority game with a change in the comfort threshold away from half filling. Agents in the frustrated, non ergodic phase tend to overreact to the information provided by the fixed agents, leading not only to large fluctuations, but to deviations of the average occupancies from their optimal values. Agents which discount their impact on the market, or which use individual strategies reach equilibrium states, which, unlike in the absence of the external information provided by the fixed agents, do not give the highest payoff to the collective.Comment: 8 pages, 6 figure

Genetic characterization of uruguayan creole cattle. II. Study of its genetic variability

Animal genetic diversity is considered essential to sustain the productivity of agriculture. FAO estimates that 30 percent of livestock breeds are at risk of extinction and more than half of these breeds are found in developing countries. Previous genetic research upon American Creole Cattle (Argentina, Colombia, Venezuela, Cuba) valuate these breeds, being considered of interest to maintain and enhance livestock production. In Uruguay, limited by different geographic barriers, about 600 bovines inhabit in hard environment in areas that cannot sustain conventional farming. Aspect of Uruguayan Creole cattle is similar to that observed in certain American and Iberian breeds. Analysis of breed genetic variability involved the utilization of PCR/RFLP technology in 82 DNA samples for milk proteins (casein and lactoglobulin), amplification of 20 samples for CYP21 microsatellite and the use of protein markers such as haemoglobin in 77 animals. Inbreeding index and expected Heterocigosity considering four loci were F= 0.02 and He= 0.487. Genotypic frequency distribution was in accordance with Hardy-Weinberg equilibrium. Genetic variation estimated, reinforced by the low inbreeding index, strengthen the need of preservation of Uruguayan Creole Cattle as a domestic animal genetic resource.Se tomaron muestras de ADN por la metodología PCR/RFLP para las proteínas de la leche caseína y lactoglobulina, 20 muestras para el microsatélite CYP21 (esteroide 21-hidroxilasa) y 77 animales para hemoglobina mediante electroforesis en gel de almidón. Los índices de endogamia y de heterocigosidad correspondieron a F= 0,02 y He= 0,487. Las frecuencias genotípicas se distribuyeron de acuerdo a los valores esperados para el equilibrio H.W. El bajo índice de endogamia obtenido en los 4 loci analizados, la relación entre el número de genotipos homocigotos y heterocigotos, el alto polimorfismo que presentó el microsatélite CYP21, así como la variabilidad observada en la coloración del pelaje, permiten sugerir que, a pesar de ser ésta una reserva aislada geográficamente, ha expresado una variabilidad genética tan importante que justifica su conservación como un recurso genético de animal doméstico. La diversidad genética animal es considerada indispensable para sostener la productividad de la agricultura. La FAO estima que el 30 p.100 de las razas de ganado, corren riesgo de extinción, encontrándose más de la mitad de ellas en países en desarrollo. Antecedentes de estudios genéticos realizados en bovinos Criollos americanos (Argentina, Colombia, Venezuela, Cuba) permiten hoy, revalorizar esta raza para ser utilizada en la explotación agropecuaria. En el Uruguay, existe una reserva de alrededor de 600 animales que habita en una zona húmeda, de sierras y montes, no alterada, limitada por diferentes barreras geográficas. El aspecto morfológico de estos animales se asemeja al de ciertas poblaciones de bovinos Criollos argentinos, venezolanos, colombianos y, a ciertas razas ibéricas. Con el objetivo de estudiar la estructura genética de esta población, se analizaron 8

Multiple Independent Retroelement Insertions in the Promoter of a Stress Response Gene Have Variable Molecular and Functional Effects in Drosophila

[Abstract] Promoters are structurally and functionally diverse gene regulatory regions. The presence or absence of sequence motifs and the spacing between the motifs defines the properties of promoters. Recent alternative promoter usage analyses in Drosophila melanogaster revealed that transposable elements significantly contribute to promote diversity. In this work, we analyzed in detail one of the transposable element insertions, named FBti0019985, that has been co-opted to drive expression of CG18446, a candidate stress response gene. We analyzed strains from different natural populations and we found that besides FBti0019985, there are another eight independent transposable elements inserted in the proximal promoter region of CG18446. All nine insertions are solo-LTRs that belong to the roo family. We analyzed the sequence of the nine roo insertions and we investigated whether the different insertions were functionally equivalent by performing 5’-RACE, gene expression, and cold-stress survival experiments. We found that different insertions have different molecular and functional consequences. The exact position where the transposable elements are inserted matters, as they all showed highly conserved sequences but only two of the analyzed insertions provided alternative transcription start sites, and only the FBti0019985 insertion consistently affects CG18446 expression. The phenotypic consequences of the different insertions also vary: only FBti0019985 was associated with cold-stress tolerance. Interestingly, the only previous report of transposable elements inserting repeatedly and independently in a promoter region in D. melanogaster, were also located upstream of a stress response gene. Our results suggest that functional validation of individual structural variants is needed to resolve the complexity of insertion clusters.[Author Summary] The presence of several transposable element insertions in the promoter region of a Drosophila melanogaster gene has only been described in heat shock protein genes. In this work, we have discovered and characterized in detail several naturally occurring independent transposable element insertions in the promoter region of a cold-stress response gene in the fruitfly Drosophila melanogaster. The nine transposable element insertions described are clustered in a small 368 bp region and all belong to the same family of transposable elements: the roo family. Each individual insertion is present at relatively low population frequencies, ranging from 1% to 17%. However, the majority of strains analyzed contain one of these nine roo insertions suggesting that this region might be evolving under positive selection. Although the sequence of these insertions is highly similar, their molecular and functional consequences are different. Only one of them, FBti0019985, is associated with increased viability in nonstress and in cold-stress conditions.This work was supported by the Ministerio de Economía y Competitividad (MINECO: http://www.idi.mineco.gob.es) BFU-2011-24397 and RYC-2010-07306 to JG, and BES-2012-052999 to AU, Ministerio de Economía y Competitividad and Fondo Europeo de Desarrollo Regional (MINECO/FEDER:http://www.idi.mineco.gob.es) BFU2014-57779-P, the European Commission (https://ec.europa.eu) FP7-PEOPLE-2011-CIG-293860, the Secretaria d’Universitats i Recerca del Departament d’Economia i Coneixement de la Generalitat de Catalunya (http://agaur.gencat.cat) 2014-SGR-201 to JG, and by the Agence Nationale de la Recherche (http://www.agence-nationale-recherche.fr) ANR-14-CE02-0003 to MARdC.USD 2250 APC fee funded by the EC FP7 Post-Grant Open Access PilotPeer reviewe

A Model For The Evolution Of Assortative Mating

Many animals and plants show a correlation between the traits of the individuals in the mating pair, implying assortative mating. Given the ubiquity of assortative mating in nature, why and how it has evolved remain open questions. Here we attempt to answer these questions in those cases where the trait under assortment is the same in males and females. We consider the most favorable scenario for assortment to evolve, where the same trait is under assortment and viability selection. We find conditions for assortment to evolve using a multilocus formalism in a haploid population. Our results show how epistasis in fitness between the loci that control the focal trait is crucial for assortment to evolve. We then assume specific forms of assortment in haploids and diploids and study the limiting cases of selective and nonselective mating. We find that selection for increased assortment is weak and that where increased assortment is costly, it does not invade.Integrative Biolog

Adaptive Boolean Networks and Minority Games with Time--Dependent Capacities

In this paper we consider a network of boolean agents that compete for a limited resource. The agents play the so called Generalized Minority Game where the capacity level is allowed to vary externally. We study the properties of such a system for different values of the mean connectivity $K$ of the network, and show that the system with K=2 shows a high degree of coordination for relatively large variations of the capacity level.Comment: 4 pages, 4 figure

Statistical mechanics of the mixed majority-minority game with random external information

We study the asymptotic macroscopic properties of the mixed majority-minority game, modeling a population in which two types of heterogeneous adaptive agents, namely ``fundamentalists'' driven by differentiation and ``trend-followers'' driven by imitation, interact. The presence of a fraction f of trend-followers is shown to induce (a) a significant loss of informational efficiency with respect to a pure minority game (in particular, an efficient, unpredictable phase exists only for f<1/2), and (b) a catastrophic increase of global fluctuations for f>1/2. We solve the model by means of an approximate static (replica) theory and by a direct dynamical (generating functional) technique. The two approaches coincide and match numerical results convincingly.Comment: 19 pages, 3 figure

Microtremor Measurements in the City of Palermo, Italy: Analysis of the Correlation between Local Geology and Damage

This study presents the results of 90 seismic ambient noise measurements in Palermo, the main city of Sicily (Italy). The dataset has been processed using the horizontal-to-vertical spectral ratio (HVNSR) technique and interpreted in terms of local geology, which is characterized by the presence of alluvial sediments of two riverbeds masked by urbanization since the seventeenth century. HVNSRs show significant variations in the study area: when the transition stiff to soft is crossed, a typical spectral peak appears in the HVNSRs, mostly in the frequency band 1–2 Hz, and exceeding a factor of 3 in amplitude. Using available information on subsurface geological structure, we compute theoretical 1D and 2D transfer functions. The resonance frequencies of soft soils obtained by HVNSR are well reproduced by the fundamental frequencies from numerical modeling. The distribution of frequency peaks of HVNSR and their amplitudes are also compared with the local damage caused by historical earthquakes. Previous studies demonstrated that damage variations in Palermo were controlled more by near-surface geology than building vulnerability. A uniform vulnerability is an ideal condition to test statistical methods and their capability in seeking correlation between HVNSR and potential damage due to local geological conditions. We apply two well-established multivariate statistical methodologies (factor analysis and canonical correlation) to the HVNSR dataset and macroseismic data (damage grades of the European macroseismic scale). Through these analyses we quantify the significance of the correlation between the HVNSR peak in the low-medium frequency range (0.5–3 Hz) and the occurrence of the highest damage grades. This approach allows us (1) to estimate the threshold value in the resulting linear combination of the HVNSR amplitudes, which separates zones of light damage from zones of significant damage, and therefore (2) to improve the spatial definition of potentially high hazard zones through a denser grid of microtremor measurements

Microtremor Measurements in the City of Palermo, Italy: Analysis of the Correlation with Local Geology and Damage

This study presents the results of 90 seismic ambient noise measurements in Palermo, the main city of Sicily (Italy). The dataset has been processed using the horizontal-to-vertical spectral ratio (HVNSR) technique and interpreted in terms of local geology, which is characterized by the presence of alluvial sediments of two river-beds masked by urbanization since the 17th century. HVNSRs show significant variations in the study area: when the transition stiff-to-soft is crossed, a typical spectral peak appears in the HVNSRs, mostly in the frequency band 1 to 2 Hz, and exceeding a factor of 3 in amplitude. Using available information on sub-surface geological structure we compute theoretical 1- and 2-D transfer functions. The resonance frequencies of soft soils obtained by HVNSR are well reproduced by the fundamental frequencies from numerical modeling. The distribution of frequency peaks of HVNSR and their amplitudes are also compared with the local damage caused by historical earthquakes. Previous studies demonstrated that damage variations in Palermo were controlled more by near-surface geology than building vulnerability. A uniform vulnerability is an ideal condition to test statistical methods and their capability in seeking correlation between HVNSR and potential damage due to local geological conditions. We apply two well-established multivariate statistical methodologies (factor analysis and canonical correlation) to the HVNSR dataset and macroseismic data (damage grades of the European Macroseismic Scale). Through these analyses we quantify the significance of the correlation between the HVNSR peak in the low-medium frequency range (0.5-3 Hz) and the occurrence of the highest damage grades. This approach allows us i) to estimate the threshold value in the resulting linear combination of the HVNSR amplitudes which separates zones of light damage from zones of significant damage, and therefore ii) to improve the spatial definition of potentially high hazard zones through a denser grid of microtremor measurements