Capillary wave dynamics on supported viscoelastic films: Single and double layers

We study the capillary wave dynamics of a single viscoelastic supported film and of a double layer of immiscible viscoelastic supported films. Using both simple scaling arguments and a continuum hydrodynamic theory, we investigate the effects of viscoelasticity and interfacial slip on the relaxation dynamics of these capillary waves. Our results account for the recent observation of a wavelength-independent decay rate for capillary waves in a supported polystyrene/brominated polystyrene double layer [X. Hu {\em et al.}, Phys. Rev. E {\bf 74}, 010602 (R) (2006)].Comment: 14 pages, 9 figure

Recruiting Lower-Income Women into Information Technology Careers: Building a Foundation for Action

This report makes the case for encouraging more low-wage women to consider careers in information technology. It assesses women's knowledge and perceptions about the IT field and establishes a framework to promote opportunities in IT. More reports like this one are available on WE's website under Media Center > Publications > Expanding Career Options

Equilibrium Bundle Size of Rodlike Polyelectrolytes with Counterion-Induced Attractive Interactions

Multivalent counterions can induce an effective attraction between like-charged rodlike polyelectrolytes, leading to the formation of polelectrolyte bundles. In this paper, we calculate the equilibrium bundle size using a simple model in which the attraction between polyelectrolytes (assumed to be pairwise additive) is treated phenomenologically. If the counterions are point-like, they almost completely neutralize the charge of the bundle, and the equilibrium bundle size diverges. When the counterions are large, however, steric and short-range electrostatic interactions prevent charge neutralization of the bundle, thus forcing the equilibrium bundle size to be finite. We also consider the possibility that increasing the number of nearest neighbors for each rod in the bundle frustrates the attractive interaction between the rods. Such a frustration leads to the formation of finite size bundles as well, even when the counterions are small.Comment: 4 pages, 2 figures; v2: typos corrected, references added, minor changes made to conten

The effect of curvature and topology on membrane hydrodynamics

We study the mobility of extended objects (rods) on a spherical liquid-liquid interface to show how this quantity is modified in a striking manner by both the curvature and the topology of the interface. We present theoretical calculations and experimental measurements of the interfacial fluid velocity field around a moving rod bound to the crowded interface of a water-in-oil droplet. By using different droplet sizes, membrane viscosities, and rod lengths, we show that the viscosity mismatch between the interior and exterior fluids leads to a suppression of the fluid flow on small droplets that cannot be captured by the flat interface predictions.Comment: 4 pages, 3 figure

Bildgebende Diagnostik der Hüftdysplasie

Zusammenfassung: Die detaillierte bildgebende Darstellung von Pathomorphologien des Hüftgelenks stellt einen wichtigen diagnostischen Baustein zur Bewertung und therapeutischen Entscheidungsfindung bei Hüftgelenkbeschwerden dar. Sowohl die konventionelle Röntgenbildgebung wie auch die Schnittbildgebung inklusive der Magnetresonanzarthrographie sind wertvolle Werkzeuge zur umfassenden diagnostischen Bewertung der Hüftgelenkmorphologie. Morphologische Abweichungen werden anhand der aktuell im Routinebetrieb zum Einsatz kommenden Techniken insbesondere im Hinblick auf die Ausprägung der Hüftgelenküberdachung im Spannungsfeld zwischen Dysplasie und femoroazetabulärem Impingement dargestellt und objektivierbare Parameter vorgestell

Mehr als Grün : Profilkatalog naturnahe Pflege

Im Projekt «Praxismodule für naturnahe Pflege» wurden Fachwissen, und Handlungsanleitungen zur Etablierung naturnaher Pflege und der Förderung der Biodiversität in urbanen Grünräumen, sowie zum schonenderen Umgang mit Ressourcen (Material, Betriebsmittel, Arbeitszeiten) vermittelt. Das Ziel des Projekts war es, durch die Förderung und Umsetzung naturnaher Pflegemassnahmen die Artenvielfalt sowie den schonenden Umgang mit Ressourcen in urbanen Grünräumen zu fördern. Im Rahmen des Projekts wurden zwei Produkte zur Förderung naturnaher Pflege von urbanen Grünräumen entwickelt: Der vorliegende Profilkatalog zur naturnahen Pflege verschiedener Grünraumprofile, sowie ein Praxishandbuch, inklusive objektbezogener Pflegeübersichtspläne und Jahrespflegeplaner. Der Profilkatalog dient der Definition der einzelnen Profile, ihrer Einordnung in das Spannungsfeld von Nutzung, Gestaltung und ökologischem Potential sowie dem Beschrieb naturnaher Pflege- und weiterer Förderungs- und Entwicklungsmassnahmen. Er ist als Nachschlagewerk und Weiterbildungsinstrument konzipiert

Polyelectrolyte Bundles

Using extensive Molecular Dynamics simulations we study the behavior of polyelectrolytes with hydrophobic side chains, which are known to form cylindrical micelles in aqueous solution. We investigate the stability of such bundles with respect to hydrophobicity, the strength of the electrostatic interaction, and the bundle size. We show that for the parameter range relevant for sulfonated poly-para-phenylenes (PPP) one finds a stable finite bundle size. In a more generic model we also show the influence of the length of the precursor oligomer on the stability of the bundles. We also point out that our model has close similarities to DNA solutions with added condensing agents, hinting to the possibility that the size of DNA aggregates is under certain circumstances thermodynamically limited.Comment: 10 pages, 8 figure

Efficiency of encounter-controlled reaction between diffusing reactants in a finite lattice: topology and boundary effects

The role of dimensionality (Euclidean versus fractal), spatial extent, boundary effects and system topology on the efficiency of diffusion-reaction processes involving two simultaneously-diffusing reactants is analyzed. We present numerically-exact values for the mean time to reaction, as gauged by the mean walklength before reactive encounter, obtained via application of the theory of finite Markov processes, and via Monte Carlo simulation. As a general rule, we conclude that for sufficiently large systems, the efficiency of diffusion-reaction processes involving two synchronously diffusing reactants (two-walker case) relative to processes in which one reactant of a pair is anchored at some point in the reaction space (one walker plus trap case) is higher, and is enhanced the lower the dimensionality of the system. This differential efficiency becomes larger with increasing system size and, for periodic systems, its asymptotic value may depend on the parity of the lattice. Imposing confining boundaries on the system enhances the differential efficiency relative to the periodic case, while decreasing the absolute efficiencies of both two-walker and one walker plus trap processes. Analytic arguments are presented to provide a rationale for the results obtained. The insights afforded by the analysis to the design of heterogeneous catalyst systems are also discussed.Comment: 15 pages, 8 figures, uses revtex4, accepted for publication in Physica