305 research outputs found
Properties of patchy colloidal particles close to a surface: a Monte Carlo and density functional study
We investigate the behavior of a patchy particle model close to a hard-wall
via Monte Carlo simulation and density functional theory (DFT). Two DFT
approaches, based on the homogeneous and inhomogeneous versions of Wertheim's
first order perturbation theory for the association free energy are used. We
evaluate, by simulation and theory, the equilibrium bulk phase diagram of the
fluid and analyze the surface properties for two isochores, one of which is
close to the liquid side of the gas-liquid coexistence curve. We find that the
density profile near the wall crosses over from a typical high-temperature
adsorption profile to a low-temperature desorption one, for the isochore close
to coexistence. We relate this behavior to the properties of the bulk network
liquid and find that the theoretical descriptions are reasonably accurate in
this regime. At very low temperatures, however, an almost fully bonded network
is formed, and the simulations reveal a second adsorption regime which is not
captured by DFT. We trace this failure to the neglect of orientational
correlations of the particles, which are found to exhibit surface induced
orientational order in this regime
A crítica social do teatro da juventude de Dias Gomes em Eu acuso o céu (1943)
The theatre activity of Dias Gomes has its beginning in the 1940s and lasts until the 1980s. However, the studies about his work normally consider the start of it with O Pagador de Promessas (1960). This way, Dias Gomes contribution to the modernization of Brazilian theatre in the 1940s remains less studied. At that time, Dias Gomes, despite of writing to one of the most famous actors of that time, Procópio Ferreira, brought social themes to discussion in a critical way, raising subjects as issues of black people in society, the Nazism, the terrible situation of the northeast migrants. In this paper we intend to delineate an overview of Dias Gomes production, specially through the analysis of Eu acuso o céu. A atividade teatral de Dias Gomes vai dos anos 1940 aos anos 1980. No entanto, ele costuma ser estudado a partir do sucesso de O pagador de promessas (1960). Isso faz com que sua contribuição para o início da modernização do teatro brasileiro nos anos 1940 permaneça pouco estudada. Nessa época Dias Gomes, apesar de escrever para um dos atores mais famosos da época, Procópio Ferreira, trazia temas sociais em chave crítica como a questão do negro na sociedade, o nazismo, a situação terrível dos retirantes do sertão. Neste artigo pretendemos traçar um panorama dessa produção de Dias Gomes, sem nos esquivar de suas contradições, em especial pela análise de Eu acuso o céu.  
Equilibrium self-assembly of colloids with distinct interaction sites: Thermodynamics, percolation, and cluster distribution functions
We calculate the equilibrium thermodynamic properties, percolation threshold, and cluster distribution functions for a model of associating colloids, which consists of hard spherical particles having on their surfaces three short-ranged attractive sites (sticky spots) of two different types, A and B. The thermodynamic properties are calculated using Wertheim's perturbation theory of associating fluids. This also allows us to find the onset of self-assembly, which can be quantified by the maxima of the specific heat at constant volume. The percolation threshold is derived, under the no-loop assumption, for the correlated bond model: In all cases it is two percolated phases that become identical at a critical point, when one exists. Finally, the cluster size distributions are calculated by mapping the model onto an effective model, characterized by a-state-dependent-functionality (f) over bar and unique bonding probability (p) over bar. The mapping is based on the asymptotic limit of the cluster distributions functions of the generic model and the effective parameters are defined through the requirement that the equilibrium cluster distributions of the true and effective models have the same number-averaged and weight-averaged sizes at all densities and temperatures. We also study the model numerically in the case where BB interactions are missing. In this limit, AB bonds either provide branching between A-chains (Y-junctions) if epsilon(AB)/epsilon(AA) is small, or drive the formation of a hyperbranched polymer if epsilon(AB)/epsilon(AA) is large. We find that the theoretical predictions describe quite accurately the numerical data, especially in the region where Y-junctions are present. There is fairly good agreement between theoretical and numerical results both for the thermodynamic (number of bonds and phase coexistence) and the connectivity properties of the model (cluster size distributions and percolation locus)
Hierarchical characterization of complex networks
While the majority of approaches to the characterization of complex networks
has relied on measurements considering only the immediate neighborhood of each
network node, valuable information about the network topological properties can
be obtained by considering further neighborhoods. The current work discusses on
how the concepts of hierarchical node degree and hierarchical clustering
coefficient (introduced in cond-mat/0408076), complemented by new hierarchical
measurements, can be used in order to obtain a powerful set of topological
features of complex networks. The interpretation of such measurements is
discussed, including an analytical study of the hierarchical node degree for
random networks, and the potential of the suggested measurements for the
characterization of complex networks is illustrated with respect to simulations
of random, scale-free and regular network models as well as real data
(airports, proteins and word associations). The enhanced characterization of
the connectivity provided by the set of hierarchical measurements also allows
the use of agglomerative clustering methods in order to obtain taxonomies of
relationships between nodes in a network, a possibility which is also
illustrated in the current article.Comment: 19 pages, 23 figure
The Web of Connections between Tourism Companies in Elba: Structure and Dynamics
Tourism destination networks are amongst the most complex dynamical systems,
involving a myriad of human-made and natural resources. In this work we report
a complex network-based systematic analysis of the Elba (Italy) tourism
destination network, including the characterization of its structure in terms
of a set of several traditional measurements, the investigation of its
modularity, as well as its comprehensive study in terms of the recently
reported superedges approach. In particular, structural (the number of paths of
distinct lengths between pairs of nodes, as well as the number of reachable
companies) and dynamical features (transition probabilities and the
inward/outward activations and accessibilities) are measured and analyzed,
leading to a series of important findings related to the interactions between
tourism companies. Among the several reported results, it is shown that the
type and size of the companies influence strongly their respective activations
and accessibilities, while their geographical position does not seem to matter.
It is also shown that the Elba tourism network is largely fragmented and
heterogeneous, so that it could benefit from increased integration.Comment: 13 pages, 7 figures, 5 tables. Corrected typos and added reference
Patient information leaflets (PILs) for UK randomised controlled trials : a feasibility study exploring whether they contain information to support decision making about trial participation
Peer reviewedPublisher PD
Phase diagrams of binary mixtures of patchy colloids with distinct numbers and types of patches: Theempty fluid regime
We investigate the effect of distinct bonding energies on the onset of criticality of low functionality fluid mixtures. We focus on mixtures ofparticles with two and three patches as this includes the mixture where "empty" fluids were originally reported. In addition to the number of patches, thespecies differ in the type of patches or bonding sites. For simplicity, we consider that the patches on each species are identical: one species has threepatches of type A and the other has two patches of type B. We have found a rich phase behavior with closed miscibility gaps, liquid-liquid demixing, and negative azeotropes. Liquid-liquid demixing was found to pre-empt the "empty" fluid regime, of these mixtures, when the AB bonds are weaker than the AA or BB bonds. By contrast, mixtures in this class exhibit "empty" fluid behavior when the AB bonds are stronger than at least one of the other two. Mixtureswith bonding energies epsilon(BB) = epsilon(AB) and epsilon(AA) < epsilon(BB), were found to exhibit an unusual negative azeotrope. (C) 2011 American Institute of Physics. [doi:10.1063/1.3561396
Pair contact process with a particle source
We study the phase diagram and critical behavior of the one-dimensional pair
contact process (PCP) with a particle source using cluster approximations and
extensive simulations. The source creates isolated particles only, not pairs,
and so couples not to the order parameter (the pair density) but to a
non-ordering field, whose state influences the evolution of the order
parameter. While the critical point p_c shows a singular dependence on the
source intensity, the critical exponents appear to be unaffected by the
presence of the source, except possibly for a small change in beta. In the
course of our study we obtain high-precision values for the critical exponents
of the standard PCP, confirming directed-percolation-like scaling.Comment: 15 pages, 9 figure
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