NAVIGATING U.S. FISHERY MANAGEMENT INTO THE 21ST CENTURY

Resource /Energy Economics and Policy,

Vortex lattices in the lowest Landau level for confined Bose-Einstein condensates

We present the results of numerical calculations of the groundstates of weakly-interacting Bose-Einstein condensates containing large numbers of vortices. Our calculations show that these groundstates appear to be close to uniform triangular vortex lattices. However, slight deviations from a uniform triangular lattice have dramatic consequences on the overall particle distribution. In particular, we demonstrate that the overall particle distribution averaged on a lengthscale large compared to the vortex lattice constant is well approximated by a Thomas-Fermi profile.Comment: 5 pages, 4 figure

On a Kelvin-Voigt Viscoelastic Wave Equation with Strong Delay

An initial-boundary value problem for a viscoelastic wave equation subject to a strong time-localized delay in a Kelvin & Voigt-type material law is considered. Transforming the equation to an abstract Cauchy problem on the extended phase space, a global well-posedness theory is established using the operator semigroup theory both in Sobolev-valued $C^{0}$- and BV-spaces. Under appropriate assumptions on the coefficients, a global exponential decay rate is obtained and the stability region in the parameter space is further explored using the Lyapunov's indirect method. The singular limit $\tau \to 0$ is further studied with the aid of the energy method. Finally, a numerical example from a real-world application in biomechanics is presented.Comment: 34 pages, 4 figures, 1 set of Matlab code

Onset of Interlayer Phase Coherence in a Bilayer Two-Dimensional Electron System: Effect of Layer Density Imbalance

Tunneling and Coulomb drag are sensitive probes of spontaneous interlayer phase coherence in bilayer two-dimensional electron systems at total Landau level filling factor $\nu_T = 1$. We find that the phase boundary between the interlayer phase coherent state and the weakly-coupled compressible phase moves to larger layer separations as the electron density distribution in the bilayer is imbalanced. The critical layer separation increases quadratically with layer density difference.Comment: 4 pages, 3 figure

Measuring the condensate fraction of rapidly rotating trapped boson systems: off-diagonal order from the density

We demonstrate a direct connection between the density profile of a system of ultra-cold trapped bosonic particles in the rapid-rotation limit and its condensate fraction. This connection can be used to probe the crossover from condensed vortex-lattice states to uncondensed quantum fluid states that occurs in rapidly rotating boson systems as the particle density decreases or the rotation frequency increases. We illustrate our proposal with a series of examples, including ones based on models of realistic finite trap systems, and comment on its application to freely expanding boson density profile measurements.Comment: 4 pages, 3 figures, version accepted for publication in Phys. Rev. Let

Spin Transition in Strongly Correlated Bilayer Two Dimensional Electron Systems

Using a combination of heat pulse and nuclear magnetic resonance techniques we demonstrate that the phase boundary separating the interlayer phase coherent quantum Hall effect at $\nu_T = 1$ in bilayer electron gases from the weakly coupled compressible phase depends upon the spin polarization of the nuclei in the host semiconductor crystal. Our results strongly suggest that, contrary to the usual assumption, the transition is attended by a change in the electronic spin polarization.Comment: 4 pages, 3 postscript figur

The Effects of a Selective and Non-Selective Organic Herbicides on Amaranthus species

The Amaranthus species has adaptive abilities that give them competitive advantages and invasive tendencies. Their high seed production, seed viability, quick growth rate, and C4 metabolism have allowed some of the species to become resistant to some types of herbicides, causing soybean, corn, and cotton crop yield losses in North America. For this investigation, different organic herbicide solutions were analyzed to determine their affects on the Amaranthus species. Different concentrations of acetic acid, eucalyptus volatile oil, and okanin were combined to test the hypothesis that the unique characteristics of each organic herbicides should safely and effectively deter Amaranthus growth, even at low concentrations. The organic herbicide cocktail significantly affected the growth rates and germination percentages of resistant A. palmeri, susceptible A. palmeri, A. viridis, and A. tricolor. Spouts died when the solution was applied daily, and seeds did not germinate after application. The solution did not have a large effect on A. hypochondriacs and A. caudatus, but most of those sprouts’ length was diminished, and growth ceased

Pattern of Reaction Diffusion Front in Laminar Flows

Autocatalytic reaction between reacted and unreacted species may propagate as solitary waves, namely at a constant front velocity and with a stationary concentration profile, resulting from a balance between molecular diffusion and chemical reaction. The effect of advective flow on the autocatalytic reaction between iodate and arsenous acid in cylindrical tubes and Hele-Shaw cells is analyzed experimentally and numerically using lattice BGK simulations. We do observe the existence of solitary waves with concentration profiles exhibiting a cusp and we delineate the eikonal and mixing regimes recently predicted.Comment: 4 pages, 3 figures. This paper report on experiments and simulations in different geometries which test the theory of Boyd Edwards on flow advection of chemical reaction front which just appears in PRL (PRL Vol 89,104501, sept2002

Composite bosons in bilayer nu = 1 system: An application of the Murthy-Shankar formalism

We calculate the dispersion of the out-of-phase mode characteristic for the bilayer nu = 1 quantum Hall system applying the version of Chern-Simons theory of Murthy and Shankar that cures the unwanted bare electron mass dependence in the low-energy description of quantum Hall systems. The obtained value for the mode when d, distance between the layers, is zero is in a good agreement with the existing pseudospin picture of the system. For d nonzero but small we find that the mode is linearly dispersing and its velocity to a good approximation depends linearly on d. This is in agreement with the Hartree-Fock calculations of the pseudospin picture that predicts a linear dependance on d, and contrary to the naive Hartree predictions with dependence on the square-root of d. We set up a formalism that enables one to consider fluctuations around the found stationary point values. In addition we address the case of imbalanced layers in the Murthy-Shankar formalism.Comment: 10 pages, 1 figur

Breaking ground in cross-cultural research on the fear of being laughed at (gelotophobia): A multi-national study involving 73 countries

The current study examines whether the fear of being laughed at (gelotophobia) can be assessed reliably and validly by means of a self-report instrument in different countries of the world. All items of the GELOPH (Ruch and Titze, GELOPH46, University of Düsseldorf, 1998; Ruch and Proyer, Swiss Journal of Psychology 67:19-27, 2008b) were translated to the local language of the collaborator (42 languages in total). In total, 22,610 participants in 93 samples from 73 countries completed the GELOPH. Across all samples the reliability of the 15-item questionnaire was high (mean alpha of .85) and in all samples the scales appeared to be unidimensional. The endorsement rates for the items ranged from 1.31% through 80.00% to a single item. Variations in the mean scores of the items were more strongly related to the culture in a country and not to the language in which the data were collected. This was also supported by a multidimensional scaling analysis with standardized mean scores of the items from the GELOPH15. This analysis identified two dimensions that further helped explaining the data (i.e., insecure vs. intense avoidant-restrictive and low vs. high suspicious tendencies towards the laughter of others). Furthermore, multiple samples derived from one country tended to be (with a few exceptions) highly similar. The study shows that gelotophobia can be assessed reliably by means of a self-report instrument in cross-cultural research. This study enables further studies of the fear of being laughed at with regard to differences in the prevalence and putative causes of gelotophobia in comparisons to different culture