Moving Walkways, Escalators, and Elevators

We study a simple geometric model of transportation facility that consists of two points between which the travel speed is high. This elementary definition can model shuttle services, tunnels, bridges, teleportation devices, escalators or moving walkways. The travel time between a pair of points is defined as a time distance, in such a way that a customer uses the transportation facility only if it is helpful. We give algorithms for finding the optimal location of such a transportation facility, where optimality is defined with respect to the maximum travel time between two points in a given set.Comment: 16 pages. Presented at XII Encuentros de Geometria Computacional, Valladolid, Spai

Test of the Additivity Principle for Current Fluctuations in a Model of Heat Conduction

The additivity principle allows to compute the current distribution in many one-dimensional (1D) nonequilibrium systems. Using simulations, we confirm this conjecture in the 1D Kipnis-Marchioro-Presutti model of heat conduction for a wide current interval. The current distribution shows both Gaussian and non-Gaussian regimes, and obeys the Gallavotti-Cohen fluctuation theorem. We verify the existence of a well-defined temperature profile associated to a given current fluctuation. This profile is independent of the sign of the current, and this symmetry extends to higher-order profiles and spatial correlations. We also show that finite-time joint fluctuations of the current and the profile are described by the additivity functional. These results suggest the additivity hypothesis as a general and powerful tool to compute current distributions in many nonequilibrium systems.Comment: 4 pages, 4 figure

An investigation into the adjuvanticity and immunogenicity of zein microspheres being researched as drug and vaccine carriers.

We have determined whether zein microspheres could act as vaccine adjuvants i.e. increase the immune responses to co-administered immunogens. Ovalbumin (model antigen)-loaded zein microspheres, blank zein microspheres and ovalbumin solution were intramuscularly administered to mice and the sera antibody levels were determined by ELISA. Another group of mice was orally dosed with blank zein microspheres, and serum and faecal antibody levels were determined. As expected, negligible antibody titres were obtained with the ovalbumin solution. Surprisingly, intramuscular administrations of blank zein microspheres elicited high levels of serum IgG which bound to the ovalbumin antigen coated on ELISA microtitre plates. This indicated that anti-zein antibodies had been elicited by blank zein microspheres and that these antibodies were cross-reacting with ovalbumin antigen coated onto ELISA plates. Such cross-reactivity inhibited the determination of the adjuvant activity of zein microspheres, if any. Additional ELISA assays, where zein was used as the coating antigen, confirmed the generation of anti-zein antibodies by blank zein microspheres i.e. zein microspheres were immunogenic following intramuscular administration. Upon oral administration of blank zein microspheres, serum IgG levels remained low but intestinal IgA levels increased following booster doses i.e. systemic tolerance, but not mucosal tolerance, to oral zein particles was achieved. Zein microspheres were immunogenic when administered intramuscularly and orally

Reentrant Behavior of the Spinodal Curve in a Nonequilibrium Ferromagnet

The metastable behavior of a kinetic Ising--like ferromagnetic model system in which a generic type of microscopic disorder induces nonequilibrium steady states is studied by computer simulation and a mean--field approach. We pay attention, in particular, to the spinodal curve or intrinsic coercive field that separates the metastable region from the unstable one. We find that, under strong nonequilibrium conditions, this exhibits reentrant behavior as a function of temperature. That is, metastability does not happen in this regime for both low and high temperatures, but instead emerges for intermediate temperature, as a consequence of the non-linear interplay between thermal and nonequilibrium fluctuations. We argue that this behavior, which is in contrast with equilibrium phenomenology and could occur in actual impure specimens, might be related to the presence of an effective multiplicative noise in the system.Comment: 7 pages, 4 figures; Final version to appear in Phys. Rev. E; Section V has been revise

Strong Shock Waves and Nonequilibrium Response in a One-dimensional Gas: a Boltzmann Equation Approach

We investigate the nonequilibrium behavior of a one-dimensional binary fluid on the basis of Boltzmann equation, using an infinitely strong shock wave as probe. Density, velocity and temperature profiles are obtained as a function of the mixture mass ratio \mu. We show that temperature overshoots near the shock layer, and that heavy particles are denser, slower and cooler than light particles in the strong nonequilibrium region around the shock. The shock width w(\mu), which characterizes the size of this region, decreases as w(\mu) ~ \mu^{1/3} for \mu-->0. In this limit, two very different length scales control the fluid structure, with heavy particles equilibrating much faster than light ones. Hydrodynamic fields relax exponentially toward equilibrium, \phi(x) ~ exp[-x/\lambda]. The scale separation is also apparent here, with two typical scales, \lambda_1 and \lambda_2, such that \lambda_1 ~ \mu^{1/2} as \mu-->0$, while \lambda_2, which is the slow scale controlling the fluid's asymptotic relaxation, increases to a constant value in this limit. These results are discussed at the light of recent numerical studies on the nonequilibrium behavior of similar 1d binary fluids.Comment: 9 pages, 8 figs, published versio

The Simplest Piston Problem II: Inelastic Collisions

We study the dynamics of three particles in a finite interval, in which two light particles are separated by a heavy ``piston'', with elastic collisions between particles but inelastic collisions between the light particles and the interval ends. A symmetry breaking occurs in which the piston migrates near one end of the interval and performs small-amplitude periodic oscillations on a logarithmic time scale. The properties of this dissipative limit cycle can be understood simply in terms of an effective restitution coefficient picture. Many dynamical features of the three-particle system closely resemble those of the many-body inelastic piston problem.Comment: 8 pages, 7 figures, 2-column revtex4 forma