Apparatus for conducting flow electrophoresis in the substantial absence of gravity

A zero-g, constant flow electrophoretic separating apparatus is presented. The apparatus is composed a deflecting member to spread carrier fluid across a conduit, and an end wall with a valve located in the conduit past the separation electrodes from which layers of carrier and sample may be extracted. Electrode electrolyte is separated from the carrier and continually circulated and cleaned

Holder exponent spectra for human gait

The stride interval time series in normal human gait is not strictly constant, but fluctuates from step to step in a complex manner. More precisely, it has been shown that the control process for human gait is a fractal random phenomenon, that is, one with a long-term memory. Herein we study the Holder exponent spectra for the slow, normal and fast gaits of 10 young healthy men in both free and metronomically triggered conditions and establish that the stride interval time series is more complex than a monofractal phenomenon. A slightly multifractal and non-stationary time series under the three different gait conditions emerges.Comment: 23 pages, 12 figures, 9 Table

Space processing: A projection

Estimates concerning space manufacturing, which might well become the largest and most specific application of space technology by the end of the century are given. Two classes of materials are considered - electronic crystals and biologicals

Compression of thick laminated composite beams with initial impact-like damage

While the study of compression after impact of laminated composites has been under consideration for many years, the complexity of the damage initiated by low velocity impact has not lent itself to simple predictive models for compression strength. The damage modes due to non-penetrating, low velocity impact by large diameter objects can be simulated using quasi-static three-point bending. The resulting damage modes are less coupled and more easily characterized than actual impact damage modes. This study includes the compression testing of specimens with well documented initial damage states obtained from three-point bend testing. Compression strengths and failure modes were obtained for quasi-isotropic stacking sequences from 0.24 to 1.1 inches thick with both grouped and interspersed ply stacking. Initial damage prior to compression testing was divided into four classifications based on the type, extent, and location of the damage. These classifications are multiple through-thickness delaminations, isolated delamination, damage near the surface, and matrix cracks. Specimens from each classification were compared to specimens tested without initial damage in order to determine the effects of the initial damage on the final compression strength and failure modes. A finite element analysis was used to aid in the understanding and explanation of the experimental results

The effects of label design characteristics on perceptions of genetically modified food

Objective. To explore the effects on perceptions of labelling food for genetically modified content. Background: there is increasing public pressure for the compulsory labelling of genetically modified food content on all food products, and yet little is known about how the design and content of such food labels will influence product perceptions. The current research draws upon warning label research - a field in which the effect of label design manipulations on perceptions of, and responses to, potential or perceived risks is well documented. Method. Two experiments are reported that investigate how label design features influence the perception of genetically modified foods. The effects of label colour (red, blue and green), wording style (definitive vs. probabilistic and explicit vs. non-explicit) and information source (government agency, consumer group and manufacturer) on hazard perceptions and purchase intentions were measured. Results. Hazard perceptions and purchase intentions were both influenced by label design characteristics in predictable ways. Any reference to genetic modification, even if the label is stating that the product is free of genetically modified ingredients, increased hazard perception, and decreased purchase intentions, relative to a no-label condition. Conclusion. Label design effects generalise from warning label research to influence the perception of genetically modified foods in predictable ways. Application. The design of genetically modified food labels. © 2012 Copyright Taylor and Francis Group, LLC

Collective and single-particle excitations in 2D dipolar Bose gases

The Berezinskii-Kosterlitz-Thouless transition in 2D dipolar systems has been studied recently by path integral Monte Carlo (PIMC) simulations [A. Filinov et al., PRL 105, 070401 (2010)]. Here, we complement this analysis and study temperature-coupling strength dependence of the density (particle-hole) and single-particle (SP) excitation spectra both in superfluid and normal phases. The dynamic structure factor, S(q,omega), of the longitudinal excitations is rigorously reconstructed with full information on damping. The SP spectral function, A(q,omega), is worked out from the one-particle Matsubara Green's function. A stochastic optimization method is applied for reconstruction from imaginary times. In the superfluid regime sharp energy resonances are observed both in the density and SP excitations. The involved hybridization of both spectra is discussed. In contrast, in the normal phase, when there is no coupling, the density modes, beyond acoustic phonons, are significantly damped. Our results generalize previous zero temperature analyses based on variational many-body wavefunctions [F. Mazzanti et al., PRL 102, 110405 (2009), D. Hufnagl et al., PRL 107, 065303 (2011)], where the underlying physics of the excitation spectrum and the role of the condensate has not been addressed.Comment: 27 pages, 15 figures, 7 table

Spectral weight redistribution in strongly correlated bosons in optical lattices

We calculate the single-particle spectral function for the one-band Bose-Hubbard model within the random phase approximation (RPA). In the strongly correlated superfluid, in addition to the gapless phonon excitations, we find extra gapped modes which become particularly relevant near the superfluid-Mott quantum phase transition (QPT). The strength in one of the gapped modes, a precursor of the Mott phase, grows as the QPT is approached and evolves into a hole (particle) excitation in the Mott insulator depending on whether the chemical potential is above (below) the tip of the lobe. The sound velocity of the Goldstone modes remains finite when the transition is approached at a constant density, otherwise, it vanishes at the transition. It agrees well with Bogoliubov theory except close to the transition. We also calculate the spatial correlations for bosons in an inhomogeneous trapping potential creating alternating shells of Mott insulator and superfluid. Finally, we discuss the capability of the RPA approximation to correctly account for quantum fluctuations in the vicinity of the QPT.Comment: 14 pages, 12 figure

Exact results on the two-particle Green's function of a Bose-Einstein condensate

Starting from the Dyson-Beliaev and generalized Gross-Pitaevskii equations with an extra nonlocal potential, we derive an exact expression of the two-particle Green's function K for an interacting Bose-Einstein condensate in terms of unambiguously defined self-energies and vertices. The formula can be a convenient basis for approximate calculations of K. It also tells us that poles of K are not shared with (i.e. shifted from) those of the single-particle Green's function, contrary to the conclusion of previous studies.Comment: 5 pages, 2 figures, to appear in Phys. Rev.

Superfluid density and condensate fraction in the BCS-BEC crossover regime at finite temperatures

The superfluid density is a fundamental quantity describing the response to a rotation as well as in two-fluid collisional hydrodynamics. We present extensive calculations of the superfluid density \rho_s in the BCS-BEC crossover regime of a uniform superfluid Fermi gas at finite temperatures. We include strong-coupling or fluctuation effects on these quantities within a Gaussian approximation. We also incorporate the same fluctuation effects into the BCS single-particle excitations described by the superfluid order parameter \Delta and Fermi chemical potential \mu, using the Nozi\`eres and Schmitt-Rink (NSR) approximation. This treatment is shown to be necessary for consistent treatment of \rho_s over the entire BCS-BEC crossover. We also calculate the condensate fraction N_c as a function of the temperature, a quantity which is quite different from the superfluid density \rho_s. We show that the mean-field expression for the condensate fraction N_c is a good approximation even in the strong-coupling BEC regime. Our numerical results show how \rho_s and N_c depend on temperature, from the weak-coupling BCS region to the BEC region of tightly-bound Cooper pair molecules. In a companion paper by the authors (cond-mat/0609187), we derive an equivalent expression for \rho_s from the thermodynamic potential, which exhibits the role of the pairing fluctuations in a more explicit manner.Comment: 32 pages, 12 figure

Microscopic calculation of the phonon-roton branch in superfluid 4^4He

Diffusion Monte Carlo results for the phonon-roton excitation branch in bulk liquid $^4$He at zero temperature are presented. The sign problem associated to the excited wave function has been dealt both with the fixed-node approximation and the released-node technique. The upper bounds provided by the fixed-node approximation are shown to become exact when using the released-node method. An excellent agreement with experimental data is achieved both at the equilibrium and near the freezing densities.Comment: 12 pages, RevTex, 3 ps figures include