52 research outputs found
Effects of quenched impurities on surface diffusion, spreading, and ordering of O/W(110)
We study how quenched impurities affect the surfacediffusion and ordering of strongly interactingadsorbate atoms on surfaces. To this end, we carry out Monte Carlo simulations for a lattice-gas model of O/W(110), including small concentrations of immobile impurities which block their adsorption sites. We examine the behavior of the diffusion coefficients and order parameters as a function of coverage corresponding to various ordered phases at low temperatures. The effects of impurities are examined under both equilibrium and nonequilibrium conditions, and the results are compared to recent studies on a completely clean surface. We find that even minute impurity concentrations affect the diffusion behavior considerably in equilibrium. The effects are strongest in ordered phases and close to phase boundaries, where quenched impurities lead to a reduction of order, which in turn leads to significant changes in the collective diffusion and phase behavior. As the impurity concentration is increased to a level of a few percent of the total surface area, the reduction in order becomes particularly prominent at high coverages. Further studies under nonequilibrium conditions reveal that nonequilibrium effects are strong in the absence of impurities, while for surfaces covered by impurities the nonequilibrium effects are relatively weaker.Peer reviewe
Homogeneous Bubble Nucleation driven by local hot spots: a Molecular Dynamics Study
We report a Molecular Dynamics study of homogenous bubble nucleation in a
Lennard-Jones fluid. The rate of bubble nucleation is estimated using
forward-flux sampling (FFS). We find that cavitation starts with compact
bubbles rather than with ramified structures as had been suggested by Shen and
Debenedetti (J. Chem. Phys. 111:3581, 1999). Our estimate of the
bubble-nucleation rate is higher than predicted on the basis of Classical
Nucleation Theory (CNT). Our simulations show that local temperature
fluctuations correlate strongly with subsequent bubble formation - this
mechanism is not taken into account in CNT
Academic careers and the valuation of academics. A discursive perspective on status categories and academic salaries in France as compared to the U.S., Germany and Great Britain
Academic careers are social processes which involve many members of large populations over long periods of time. This paper outlines a discursive perspective which looks into how academics are categorized in academic systems. From a discursive view, academic careers are organized by categories which can define who academics are (subjectivation) and what they are worth (valuation). The question of this paper is what institutional categorizations such as status and salaries can tell us about academic subject positions and their valuation. By comparing formal status systems and salary scales in France with those in the U.S., Great Britain and Germany, this paper reveals the constraints of institutional categorization systems on academic careers. Special attention is given to the French system of status categories which is relatively homogeneous and restricts the competitive valuation of academics between institutions. The comparison shows that academic systems such as the U.S. which are characterized by a high level of heterogeneity typically present more negotiation opportunities for the valuation of academics. From a discursive perspective, institutional categories, therefore, can reflect the ways in which academics are valuated in the inter-institutional job market, by national bureaucracies or in professional oligarchies
Lattice Boltzmann simulations of soft matter systems
This article concerns numerical simulations of the dynamics of particles
immersed in a continuum solvent. As prototypical systems, we consider colloidal
dispersions of spherical particles and solutions of uncharged polymers. After a
brief explanation of the concept of hydrodynamic interactions, we give a
general overview over the various simulation methods that have been developed
to cope with the resulting computational problems. We then focus on the
approach we have developed, which couples a system of particles to a lattice
Boltzmann model representing the solvent degrees of freedom. The standard D3Q19
lattice Boltzmann model is derived and explained in depth, followed by a
detailed discussion of complementary methods for the coupling of solvent and
solute. Colloidal dispersions are best described in terms of extended particles
with appropriate boundary conditions at the surfaces, while particles with
internal degrees of freedom are easier to simulate as an arrangement of mass
points with frictional coupling to the solvent. In both cases, particular care
has been taken to simulate thermal fluctuations in a consistent way. The
usefulness of this methodology is illustrated by studies from our own research,
where the dynamics of colloidal and polymeric systems has been investigated in
both equilibrium and nonequilibrium situations.Comment: Review article, submitted to Advances in Polymer Science. 16 figures,
76 page
Detection of serum amyloid-A concentration in the calf clinically diagnosed with pneumonia, enteritis and pneumoenteritis
The ethics of hospitality in changing journalism: A response to the rise of the anti-immigrant movement in Finnish media publicity
Evaluation of a multi-speaker system for socially assistive HRI in real scenarios
In the field of social human-robot interaction, and in particular for social assistive robotics, the capacity of recognizing the speaker’s discourse in very diverse conditions and where more than one interlocutor may be present, plays an essential role. The use of a mics. array that can be mounted in a robot supported by a voice enhancement module has been evaluated, with the goal of improving the performance of current automatic speech recognition (ASR) systems in multi-speaker conditions. An evaluation has been made of the improvement in terms of intelligibility scores that can be achieved in the operation of two off-the-shelf ASR solutions in situations that contemplate the typical scenarios where a robot with these characteristics can be found. The results have identified the conditions in which a low computational cost demand algorithm can be beneficial to improve intelligibility scores in real environments.</p
Online images and imaginings of home: the case of the QwaQwa Thaba di Mahlwa Facebook page
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