Influence of Hydrodynamic Interactions on the Kinetics of Colloidal Particle's Adsorption

The kinetics of irreversible adsorption of spherical particles onto a flat surface is theoretically studied. Previous models, in which hydrodynamic interactions were disregarded, predicted a power-law behavior $t^{-2/3}$ for the time dependence of the coverage of the surface near saturation. Experiments, however, are in agreement with a power-law behavior of the form $t^{-1/2}$. We outline that, when hydrodynamic interactions are considered, the assymptotic behavior is found to be compatible with the experimental results in a wide region near saturation.Comment: 4 pages, 1 figures, Phys. Rev. Lett. (in press

Adsorption of colloidal particles in the presence of external field

We present a new class of sequential adsorption models in which the adsorbing particles reach the surface following an inclined direction (shadow models). Capillary electrophoresis, adsorption in the presence of a shear or on an inclined substrate are physical manifestations of these models. Numerical simulations are carried out to show how the new adsorption mechanisms are responsible for the formation of more ordered adsorbed layers and have important implications in the kinetics, in particular modifying the jamming limit.Comment: LaTex file, 3 figures available upon request, to appear in Phys.Rev.Let

Model of correlated sequential adsorption of colloidal particles

We present results of a new model of sequential adsorption in which the adsorbing particles are correlated with the particles attached to the substrate. The strength of the correlations is measured by a tunable parameter $\sigma$. The model interpolates between free ballistic adsorption in the limit $\sigma\to\infty$ and a strongly correlated phase, appearing for $\sigma\to0$ and characterized by the emergence of highly ordered structures. The phenomenon is manifested through the analysis of several magnitudes, as the jamming limit and the particle-particle correlation function. The effect of correlations in one dimension manifests in the increased tendency to particle chaining in the substrate. In two dimensions the correlations induce a percolation transition, in which a spanning cluster of connected particles appears at a certain critical value $\sigma_c$. Our study could be applicable to more general situations in which the coupling between correlations and disorder is relevant, as for example, in the presence of strong interparticle interactions.Comment: 6 pages, 8 EPS figures. Phys. Rev. E (in press

Quantum Drag Forces on a Sphere Moving Through a Rarefied Gas

As an application of quantum fluid mechanics, we consider the drag force exerted on a sphere by an ultra-dilute gas. Quantum mechanical diffraction scattering theory enters in that regime wherein the mean free path of a molecule in the gas is large compared with the sphere radius. The drag force is computed in a model specified by the ``sticking fraction'' of events in which a gaseous molecule is adsorbed by the spherical surface. Classical inelastic scattering theory is shown to be inadequate for physically reasonable sticking fraction values. The quantum mechanical scattering drag force is exhibited theoretically and compared with experimental data.Comment: 5 pages no figure

Fracture of complex metallic alloys: An atomistic study of model systems

Molecular dynamics simulations of crack propagation are performed for two extreme cases of complex metallic alloys (CMAs): In a model quasicrystal the structure is determined by clusters of atoms, whereas the model C15 Laves phase is a simple periodic stacking of a unit cell. The simulations reveal that the basic building units of the structures also govern their fracture behaviour. Atoms in the Laves phase play a comparable role to the clusters in the quasicrystal. Although the latter are not rigid units, they have to be regarded as significant physical entities.Comment: 6 pages, 4 figures, for associated avi file, see http://www.itap.physik.uni-stuttgart.de/~frohmut/MOVIES/C15.LJ.011.100.av

Basis States for Relativistic, Dynamically-Entangled Particles

In several recent papers on entanglement in relativistic quantum systems and relativistic Bell's inequalities, relativistic Bell-type two-particle states have been constructed in analogy to non-relativistic states. These constructions do not have the form suggested by relativistic invariance of the dynamics. Two relativistic formulations of Bell-type states are shown for massive particles, one using the standard Wigner spin basis and one using the helicity basis. The construction hinges on the use of Clebsch-Gordan coefficients of the Poincar\'e group to reduce the direct product of two unitary irreducible representations (UIRs) into a direct sum of UIRs.Comment: 19 pages, three tables, revte

THERMAL RADIATION FROM MAGNETIZED NEUTRON STARS: A look at the Surface of a Neutron Star.

Surface thermal emission has been detected by ROSAT from four nearby young neutron stars. Assuming black body emission, the significant pulsations of the observed light curves can be interpreted as due to large surface temperature differences produced by the effect of the crustal magnetic field on the flow of heat from the hot interior toward the cooler surface. However, the energy dependence of the modulation observed in Geminga is incompatible with blackbody emission: this effect will give us a strong constraint on models of the neutron star surface.Comment: 10 pages. tar-compressed and uuencoded postcript file. talk given at the `Jubilee Gamow Seminar', St. Petersburg, Sept. 1994

Spray-assisted polyelectrolyte multilayer buildup: from step-by-step to single-step polyelectrolyte film constructions.

The alternate deposition of polyanions and polycations on a solid substrate leads to the formation of nanometer to micrometer films called Polyelectrolyte Multilayers. This step-by-step construction of organic films constitutes a method of choice to functionalize surfaces with applications ranging from optical to bioactive coatings. The method was originally developed by dipping the substrate in the different polyelectrolyte solutions. Recent advances show that spraying the polyelectrolyte solutions onto the substrate represents an appealing alternative to dipping because it is much faster and easier to adapt at an industrial level. Multilayer deposition by spraying is thus greatly gaining in interest. Here we review the current literature on this deposition method. After a brief history of polyelectrolyte multilayers to place the spraying method in its context, we review the fundamental issues that have been addresses so far. We then give an overview the different fields where the method has been applied.journal articlereview2012 Feb 212012 01 26importe