Magnetic-field dependence of dynamical vortex response in two-dimensional Josephson junction arrays and superconducting films

The dynamical vortex response of a two-dimensional array of the resistively shunted Josephson junctions in a perpendicular magnetic field is inferred from simulations. It is found that, as the magnetic field is increased at a fixed temperature, the response crosses over from normal to anomalous, and that this crossover can be characterized by a single dimensionless parameter. It is described how this crossover should be reflected in measurements of the complex impedance for Josephson junction arrays and superconducting films.Comment: 4 pages including 5 figures in two columns, final versio

Current-voltage characteristics of the two-dimensional XY model with Monte Carlo dynamics

Current-voltage characteristics and the linear resistance of the two-dimensional XY model with and without external uniform current driving are studied by Monte Carlo simulations. We apply the standard finite-size scaling analysis to get the dynamic critical exponent $z$ at various temperatures. From the comparison with the resistively-shunted junction dynamics, it is concluded that $z$ is universal in the sense that it does not depend on details of dynamics. This comparison also leads to the quantification of the time in the Monte Carlo dynamic simulation.Comment: 5 pages in two columns including 5 figures, to appear in PR

Charge Transport in the Dense Two-Dimensional Coulomb Gas

The dynamics of a globally neutral system of diffusing Coulomb charges in two dimensions, driven by an applied electric field, is studied in a wide temperature range around the Berezinskii-Kosterlitz-Thouless transition. I argue that the commonly accepted ``free particle drift'' mechanism of charge transport in this system is limited to relatively low particle densities. For higher densities, I propose a modified picture involving collective ``partner transfer'' between bound pairs. The new picture provides a natural explanation for recent experimental and numerical findings which deviate from standard theory. It also clarifies the origin of dynamical scaling in this context.Comment: 4 pages, RevTeX, 2 eps figures included; some typos corrected, final version to be published in Phys. Rev. Let

The effect of lifelong learning on men's wages

This paper develops a model of earnings and applies this to an examination of the effect of lifelong learning on men’s wages. Using data from the British Household Panel Survey, a variant of the mover–stayer model is developed in which hourly wages are either taken from a stationary distribution (movers) or closely related to the hourly wage one year earlier (stayers). Mover–stayer status is not observed, and we therefore model wages using an endogenous switching regression, estimated by maximum likelihood. Methodologically, the results support the mover–stayer characterisation since the restrictions required for the simpler specifications popular in the literature are rejected. Substantively, simulation of the estimated model shows some statistically significant effects from acquiring qualifications of a higher level than those previously held, but not from acquiring qualifications of the same level

Dynamic scaling for 2D superconductors, Josephson junction arrays and superfluids

The value of the dynamic critical exponent $z$ is studied for two-dimensional superconducting, superfluid, and Josephson Junction array systems in zero magnetic field via the Fisher-Fisher-Huse dynamic scaling. We find $z\simeq5.6\pm0.3$, a relatively large value indicative of non-diffusive dynamics. Universality of the scaling function is tested and confirmed for the thinnest samples. We discuss the validity of the dynamic scaling analysis as well as the previous studies of the Kosterlitz-Thouless-Berezinskii transition in these systems, the results of which seem to be consistent with simple diffusion ($z=2$). Further studies are discussed and encouraged.Comment: 19 pages in two-column RevTex, 8 embedded EPS figure

How many educated workers for your economy? European targets, optimal public spending, and labor market impact

This paper studies optimal taxation schemes for education in a search- matching model where the labor market is divided between a high-skill and a low-skill sector. Two public policy targets - maximizing the total employment level and optimizing the social surplus - are studied according to three different public taxation strategies. We calibrate our model using evidence from thirteen European countries, and compare our results with the target from the Europe 2020 Agenda for achievement in higher education. We show that, with current labor market char- acteristics, the target set by governments seems compatible with the social surplus maximization objective for some countries, while being too high for other countries. For all countries, maximizing employment would imply higher educational spending than that required for the social surplus to reach its maximum.info:eu-repo/semantics/publishedVersio

Prevalence of systemic immunoreactivity to Aggregatibacter actinomycetemcomitans leukotoxin in relation to the incidence of myocardial infarction

<p>Abstract</p> <p>Background</p> <p>Chronic infections and associated inflammatory markers are suggested risk factors for cardiovascular disease (CVD). The proinflammatory cytokine, interleukin (IL)-1β, is suggested to play a role in the regulation of local inflammatory responses in both CVD and periodontitis. The leukotoxin from the periodontal pathogen <it>Aggregatibacter actinomycetemcomitans </it>has recently been shown to cause abundant secretion of IL-1β from macrophages. The aim of the present study was to compare the prevalence of systemic immunoreactivity to <it>A. actinomycetemcomitans </it>leukotoxin in myocardial infarction (MI) cases (n = 532) and matched controls (n = 1,000) in a population-based case and referents study in northern Sweden.</p> <p>Methods</p> <p>Capacity to neutralize <it>A. actinomycetemcomitans </it>leukotoxin was analyzed in a bioassay with leukocytes, purified leukotoxin, and plasma. Plasma samples that inhibited lactate-dehydrogenase release from leukotoxin-lysed cells by ≥50% were classified as positive.</p> <p>Results</p> <p>Neutralizing capacity against <it>A. actinomycetemcomitans </it>leukotoxin was detected in 53.3% of the plasma samples. The ability to neutralize leukotoxin was correlated to increasing age in men (n = 1,082) but not in women (n = 450). There was no correlation between presence of systemic leukotoxin-neutralization capacity and the incidence of MI, except for women (n = 146). Women with a low neutralizing capacity had a significantly higher incidence of MI than those who had a high neutralizing capacity.</p> <p>Conclusion</p> <p>Systemic immunoreactivity against <it>A. actinomycetemcomitans </it>leukotoxin was found at a high prevalence in the analyzed population of adults from northern Sweden. The results from the present study do not support the hypothesis that systemic leukotoxin-neutralizing capacity can decrease the risk for MI.</p