Persistent current formation in a high-temperature Bose-Einstein condensate: an experimental test for c-field theory

Experimental stirring of a toroidally trapped Bose-Einstein condensate at high temperature generates a disordered array of quantum vortices that decays via thermal dissipation to form a macroscopic persistent current [T. W. Neely em et al. arXiv:1204.1102 (2012)]. We perform 3D numerical simulations of the experimental sequence within the Stochastic Projected Gross-Pitaevskii equation using ab initio determined reservoir parameters. We find that both damping and noise are essential for describing the dynamics of the high-temperature Bose field. The theory gives a quantitative account of the formation of a persistent current, with no fitted parameters.Comment: v2: 7 pages, 3 figures, new experimental data and numerical simulation

Suppression of Kelvon-induced decay of quantized vortices in oblate Bose-Einstein Condensates

We study the Kelvin mode excitations on a vortex line in a three-dimensional trapped Bose-Einstein condensate at finite temperature. Our stochastic Gross-Pitaevskii simulations show that the activation of these modes can be suppressed by tightening the confinement along the direction of the vortex line, leading to a strong suppression in the vortex decay rate as the system enters a regime of two-dimensional vortex dynamics. As the system approaches the condensation transition temperature we find that the vortex decay rate is strongly sensitive to dimensionality and temperature, observing a large enhancement for quasi-two-dimensional traps. Three-dimensional simulations of the recent vortex dipole decay experiment of Neely et al. [Phys. Rev. Lett. 104, 160401 (2010)] confirm two-dimensional vortex dynamics, and predict a dipole lifetime consistent with experimental observations and suppression of Kelvon-induced vortex decay in highly oblate condensates.Comment: 8 pages, 8 figure

Effects of footwear variations on three-dimensional kinematics and tibial accelerations of specific movements in American football

American football is associated with a high rate of non-contact chronic injuries. Players are able to select from both high and low cut footwear. The aim of the current investigation was to examine the influence of high and low cut American football specific footwear on tibial accelerations and three-dimensional (3D) kinematics during three sport specific movements. Twelve male American football players performed three movements, run, cut and vertical jump whilst wearing both low and high cut footwear. 3D kinematics of the lower extremities were measured using an eight-camera motion analysis system alongside tibial acceleration parameters which were obtained using a shank mounted accelerometer. Tibial acceleration and 3D kinematic differences between the different footwear were examined using either repeated measures or Friedman’s ANOVA. Tibial accelerations were significantly greater in the low cut footwear in comparison to the high cut footwear for the run and cut movements. In addition, peak ankle eversion and tibial internal rotation parameters were shown to be significantly greater in the low cut footwear in the running and cutting movement conditions. The current study indicates that the utilization of low cut American football footwear for training/performance may place American footballers at increased risk from chronic injuries

Estimating charitable giving by will bequest for Giving USA

In a typical year since 2000, Giving USA has estimated that living individuals contributed 75 percent of total charitable gifts and that estates contributed about 7 or 8 percent, with institutional donors donating the balance. The estimating procedure used for estate contributions relies extensively on amounts claimed by estate tax returns as deductions for charitable contributions. Giving USA supplements the tax return data with an estimate of giving by estates that fall below the tax filing threshold. As the estate tax filing threshold began increasing and tax rates began decreasing in 2001, a number of authors (Joulfaian 2000; Gale & Bakija; Greene and McClelland) predict declining charitable contributions from bequest gifts. With fewer estates tax returns filed, and the possibility that none will be filed after 2010, the impact of the reduced tax rates must be measured using new methods that do not rely so extensively on tax return data. Giving USA has been investigating and continues to investigate alternative methods to estimate charitable bequests that do not rely so heavily on estate tax return data. This paper reports the results of this effort and describes the bequest estimating procedure adopted for use in Giving USA beginning with the 2005 edition. This procedure incorporates survey results showing bequest amounts received at higher educational institutions and estimates charitable bequests made by estates below the federal filing threshold. The paper concludes that to track changes resulting from lowered tax rates and higher filing thresholds adequately, alternative data sources will need to be developed