11,402 research outputs found
Social Networks in Determining Employment and Wages: Patterns, Dynamics, and Inequality
We develop a model where agents obtain information about job opportunities through an explicitly modeled network of social contacts. We show that an improvement in the employment status of either an agent's direct or indirect contacts leads to an increase in the agent's employment probability and expected wages, in the sense of first order stochastic dominance. A similar effect results from an increase in the network contacts of an agent. In terms of dynamics and patterns, we show that employment is positively correlated across time and agents, and the same is true for wages. Moreover, unemployment exhibits persistence in the sense of duration dependence: the probability of obtaining a job decreases in the length of time that an agent has been unemployed. Finally, we examine inequality between two groups. If staying in the labor market is costly (in opportunity costs, education costs, or skills maintenance) and one group starts with a worse employment status or a smaller network, then that group's drop-out rate will be higher and their employment prospects and wages will be persistently below that of the other group.Networks, Labor Markets, Employment, Unemployment, Wages, Wage Inequality, Drop-Out Rates, Duration Dependence
Experimental Observation of Coherence and Stochastic Resonances in an Electronic Chua Circuit
Stochastic and coherence resonances appear in nonlinear systems subjected to
an external source of noise and are characterized by a maximum response at the
optimal value of the noise intensity. This paper shows experimentally that it
is possible to observe them in a chaotic system. To this end we have analysed
an electronic Chua circuit running in the chaotic regime and added noise to its
dynamics. In the case of coherence resonance, we observe an optimal periodicity
for the jumps between chaotic attractors, whereas in the case of stochastic
resonance we observe a maximum in the signal-to-noise ratio at the frequency of
an external sinusoidal perturbation.Comment: 6 page
Anticipating the response of excitable systems driven by random forcing
We study the regime of anticipated synchronization in unidirectionally
coupled model neurons subject to a common external aperiodic forcing that makes
their behavior unpredictable. We show numerically and by implementation in
analog hardware electronic circuits that, under appropriate coupling
conditions, the pulses fired by the slave neuron anticipate (i.e. predict) the
pulses fired by the master neuron. This anticipated synchronization occurs even
when the common external forcing is white noise.Comment: 12 pages (RevTex format
Genetic Effects of the Recessive Sex-Linked Lethal Gene, Tortoise, on the Prenatal Mortality of Mice
Three-frequency resonances in dynamical systems
We investigate numerically and experimentally dynamical systems having three
interacting frequencies: a discrete mapping (a circle map), an exactly solvable
model (a system of coupled ordinary differential equations), and an
experimental device (an electronic oscillator). We compare the hierarchies of
three-frequency resonances we find in each of these systems. All three show
similar qualitative behaviour, suggesting the existence of generic features in
the parameter-space organization of three-frequency resonances.Comment: See home page http://lec.ugr.es/~julya
Coherence Resonance in Chaotic Systems
We show that it is possible for chaotic systems to display the main features
of coherence resonance. In particular, we show that a Chua model, operating in
a chaotic regime and in the presence of noise, can exhibit oscillations whose
regularity is optimal for some intermediate value of the noise intensity. We
find that the power spectrum of the signal develops a peak at finite frequency
at intermediate values of the noise. These are all signatures of coherence
resonance. We also experimentally study a Chua circuit and corroborate the
above simulation results. Finally, we analyze a simple model composed of two
separate limit cycles which still exhibits coherence resonance, and show that
its behavior is qualitatively similar to that of the chaotic Chua systemComment: 4 pages (including 4 figures) LaTeX fil
Angular emission properties of a layer of rare-earth based nanophosphors embedded in one-dimensional photonic crystal coatings
The angular properties of light emitted from rare-earth based nanophosphors embedded in optical resonators built in one-dimensional photonic crystal coatings are herein investigated. Strong directional dependence of the photoluminescence spectra is found. Abrupt angular variations of the enhancement caused by the photonic structure and the extraction power are observed, in good agreement with calculated polar emission patterns. Our results confirm that the optical cavity favors the extraction of different wavelengths at different angles and that integration of nanophosphors within photonic crystals provides control over the directional emission properties that could be put into practice in phosphorescent displays.Ministerio de Ciencia e Innovación MAT2008- 02166, CSD2007-00007Junta de Andalucía FQM3579, FQM524
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