Strategic behaviour in Schelling dynamics: theory and experimental evidence

In this paper we experimentally test Schelling’s (1971) segregation model and obtain the striking result of full segregation in most of the cases. In addition, we extend Schelling’s model theoretically by adding strategic behaviour and moving costs. We obtain a unique subgame perfect equilibrium in which rational agents facing moving costs may find it optimal not to move (anticipating other participants’ movements). This equilibrium is far from full segregation. We run experiments for this extended Schelling model, and find that the percentage of full segregated societies is notably reduced when the cost of moving is high, but it is not affected when it is low, relative to the baseline with costless moving. We also find that the degree of segregation depends on the distribution of strategic subjects relative of a baseline model where moving is costless

Maximum population transfer in a periodically driven two-level system

We study the dynamics of a two-level quantum system under the influence of sinusoidal driving in the intermediate frequency regime. Analyzing the Floquet quasienergy spectrum, we find combinations of the field parameters for which population transfer is optimal and takes place through a series of well defined steps of fixed duration. We also show how the corresponding evolution operator can be approximated at all times by a very simple analytical expression. We propose this model as being specially suitable for treating periodic driving at avoided crossings found in complex multi-level systems, and thus show a relevant application of our results to designing a control protocol in a realistic molecular modelComment: 7 pages, 6 figure

Optically addressable single-use microfluidic valves by laser printer lithography

We report the design, fabrication, and characterization of practical optofluidic valves fabricated using laser printer lithography. Valves are opened by directing optical energy from a solid-state laser, with similar power characterisitcs to those used in CD/DVD drives, to a spot of printed toner where localized heating melts an orifice in the polymer layer in as little as 500 ms, connecting previously isolated fluidic components or compartments. Valve functionality, response time, and laser input energy dependence of orifice size are reported for cyclo-olefin copolymer (COC) and polyethylene terephthalate (PET) films. Implementation of these optofluidic valves is demonstrated on pressure-driven and centrifugal microfluidic platforms. In addition, these “one-shot” valves comprise a continuous polymer film that hermetically isolates on-chip fluid volumes within fluidic devices using low-vapor-permeability materials; we confirmed this for a period of one month. The fabrication and integration of optofluidic valves is compatible with a range of polymer microfabrication technologies and should facilitate the development of fully integrated, reconfigurable, and automated lab-on-a-chip systems, particularly when reagents must be stored on chip for extended periods, e.g. for medical diagnostic devices, lab-on-a-chip synthetic systems, or hazardous biochemical analysis platforms

Trypanosoma brucei gambiense in domestic livestock of Kogo and Mbini foci (Equatorial Guinea).

OBJECTIVE: To evaluate Trypanosoma brucei gambiense infection in peri-domestic livestock from Kogo and Mbini foci (Equatorial Guinea) in order to investigate its possible implication in the sleeping sickness transmission cycle in these hypoendemic foci. METHODS: Samples from 698 domestic animals (goats, sheep and pigs) from trypanosomiasis-endemic localities of Kogo and Mbini foci were tested for animal trypanosomes and T. b. gambiense (group I) by species-specific polymerase chain reaction. RESULTS: Trypanosoma brucei s.l., the predominant trypanosome species, was detected in 182 (52.6%) samples from Mbini and in 127 (36.1%) samples from Kogo. T. b. gambiense was only identified in seven (2%) of the Mbini samples and one co-infection (with T. vivax) was observed. CONCLUSION: The occurrence of T. b. gambiense in peri-domestic livestock in Mbini and its absence in Kogo could explain the epidemiological differences between the two foci and could have significant implications for sleeping sickness control in Equatorial Guinea

Design and validation of a socio-emotional questionnaire for youth football players

Con el objetivo de detectar y controlar los factores socio-emocionales que influyen en la progresión del joven futbolista, se diseñó un cuestionario auto-cumplimentado de 40 ítems, agrupados en 3 dimensiones (entorno social, bienestar e inteligencia emocional). Se analizó la validez de contenido mediante la valoración de 14 expertos y la validez de constructo mediante análisis factorial. Se evaluó la fiabilidad del cuestionario, administrándolo a jóvenes futbolistas de élite (n=281) y analizando la consistencia interna por el método del Alfa de Cronbach y la fiabilidad test-retest mediante el coeficiente de correlación intraclase (CCI). El análisis factorial confirmó la existencia de 18 categorías, que en conjunto explican el 65,40% de la varianza total. El Alfa de Cronbach del cuestionario fue de 0,944 (p<0,01) y el CCI de 0,894 (p<0,01). El cuestionario reúne suficientes propiedades psicométricas como para ser considerado una herramienta válida y fiable para medir el entorno socio-emocional de jóvenes futbolistas.The objective of this study was to design a valid questionnaire to detect and manage the socio-emotional factors that influence the performance of young football players. A group of specialists designed a self-completion questionnaire of 40 items grouped into 3 dimensions. Content validity was analysed and evaluated by 14 experts and construct validity was analysed by factorial analysis. To evaluate reliability the questionnaire was administered to young elite football players, and internal consistency was analysed with Cronbach’s alpha. Test-retest reliability was assessed with the intraclass correlation coefficient (ICC). Factor analysis confirmed the existence of 18 factors, which as a whole explained 65.40% of the total variance. The Cronbach’s alpha of the questionnaire was 0.944 (p<0.01) and the ICC of the entire questionnaire was 0.894 (p<0.01). The questionnaire gathers together enough psychometric properties to be considered a valid and reliable tool for gauging the socio-emotional environment of young football players

The Poincare-Birkhoff theorem in Quantum Mechanics

Quantum manifestations of the dynamics around resonant tori in perturbed Hamiltonian systems, dictated by the Poincar\'e--Birkhoff theorem, are shown to exist. They are embedded in the interactions involving states which differ in a number of quanta equal to the order of the classical resonance. Moreover, the associated classical phase space structures are mimicked in the quasiprobability density functions and their zeros.Comment: 5 pages, 3 figures, Full resolution figures available at http://www.df.uba.ar/users/wisniaki/publications.htm

Signatures of homoclinic motion in quantum chaos

Homoclinic motion plays a key role in the organization of classical chaos in Hamiltonian systems. In this Letter, we show that it also imprints a clear signature in the corresponding quantum spectra. By numerically studying the fluctuations of the widths of wavefunctions localized along periodic orbits we reveal the existence of an oscillatory behavior, that is explained solely in terms of the primary homoclinic motion. Furthermore, our results indicate that it survives the semiclassical limit.Comment: 5 pages, 4 figure

The anatomy of urban social networks and its implications in the searchability problem

The appearance of large geolocated communication datasets has recently increased our understanding of how social networks relate to their physical space. However, many recurrently reported properties, such as the spatial clustering of network communities, have not yet been systematically tested at different scales. In this work we analyze the social network structure of over 25 million phone users from three countries at three different scales: country, provinces and cities. We consistently find that this last urban scenario presents significant differences to common knowledge about social networks. First, the emergence of a giant component in the network seems to be controlled by whether or not the network spans over the entire urban border, almost independently of the population or geographic extension of the city. Second, urban communities are much less geographically clustered than expected. These two findings shed new light on the widely-studied searchability in self-organized networks. By exhaustive simulation of decentralized search strategies we conclude that urban networks are searchable not through geographical proximity as their country-wide counterparts, but through an homophily-driven community structure

The protective effect of exercise on diabetic nephropathy : the role of histidine-containing dipeptides

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