30 research outputs found
Adsorption on a periodically corrugated substrate
Mean field analysis of the effective interfacial Hamiltonian shows that with
increasing temperature the adsorption on a periodically corrugated substrate
can proceed in two steps: first, there is the filling transition in which the
depressions of the substrate become partially or completely filled; then there
is the wetting transition at which the substrate as a whole becomes covered
with a macroscopically thick wetting layer. The actual order and location of
both transitions are related to the wetting properties of the corresponding
planar substrate and to the form of corrugation. Certain morphological
properties of the liquid-vapor interface in the case of a saw-like corrugated
substrate are discussed analyticallyComment: 20 pages, 9 Postscript figure
Filling transition for a wedge
We study the formation and the shape of a liquid meniscus in a wedge with
opening angle which is exposed to a vapor phase. By applying a suitable
effective interface model, at liquid-vapor coexistence and at a temperature
we find a filling transition at which the height of the meniscus
becomes macroscopically large while the planar walls of the wedge far away from
its center remain nonwet up to the wetting transition occurring at
. Depending on the fluid and the substrate potential the filling
transition can be either continuous or discontinuous. In the latter case it is
accompanied by a prefilling line extending into the vapor phase of the bulk
phase diagram and describing a transition from a small to a large, but finite,
meniscus height. The filling and the prefilling transitions correspond to
nonanalyticities in the surface and line contributions to the free energy of
the fluid, respectively.Comment: 48 pages (RevTex), 14 figures (ps), submitted to PR
The problem of uniqueness in the reduced description of adsorption on the wedge-shaped substrate
In the reduced one-dimensional description of the adsorption on the
wedge-shaped substrate the mid-point interface height serves as the order
parameter. We point at the ambiguity which appears in the transfer-matrix
approach to this problem. We also propose how to avoid this problem by
introducing the appropriate order parameter.Comment: 7 pages, 4 Postscript figures, uses psfrag.sty; double reference
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Edge wetting of an Ising three-dimensional system
The effect of edge on wetting and layering transitions of a three-dimensional
spin-1/2 Ising model is investigated, in the presence of longitudinal and
surface magnetic fields, using mean field (MF) theory and Monte Carlo (MC)
simulations. For T=0, the ground state phase diagram shows that there exist
only three allowed transitions, namely: surface and bulk transition, surface
transition and bulk transition. However, there exist a surface intra-layering
temperature , above which the surface and the intra-layering surface
transitions occur. While the bulk layering and intra-layering transitions
appear above an other finite temperature . These
surface and bulk intra-layering transitions are not seen in the perfect
surfaces case.
Numerical values of and , computed by Monte Carlo
method are found to be smaller than those obtained using mean field theory.
However, the results predicted by the two methods become similar, and are
exactly those given by the ground state phase diagram, for very low
temperatures. On the other hand, the behavior of the local magnetizations as a
function of the external magnetic field, shows that the transitions are of the
first order type. and decrease when increasing the
system size and/or the surface magnetic field. In particular,
reaches the wetting temperature for sufficiently large system sizes.Comment: 11 Pages latex, 12 Figures P
Interfacial fluctuations near the critical filling transition
We propose a method to describe the short-distance behavior of an interface
fluctuating in the presence of the wedge-shaped substrate near the critical
filling transition. Two different length scales determined by the average
height of the interface at the wedge center can be identified. On one length
scale the one-dimensional approximation of Parry et al. \cite{Parry} which
allows to find the interfacial critical exponents is extracted from the full
description. On the other scale the short-distance fluctuations are analyzed by
the mean-field theory.Comment: 13 pages, 3 figure
Phase diagram for morphological transitions of wetting films on chemically structured substrates
Using an interface displacement model we calculate the shapes of thin
liquidlike films adsorbed on flat substrates containing a chemical stripe. We
determine the entire phase diagram of morphological phase transitions in these
films as function of temperature, undersaturation, and stripe widthComment: 15 pages, RevTeX, 7 Figure
Geometry dominated fluid adsorption on sculptured substrates
Experimental methods allow the shape and chemical composition of solid
surfaces to be controlled at a mesoscopic level. Exposing such structured
substrates to a gas close to coexistence with its liquid can produce quite
distinct adsorption characteristics compared to that occuring for planar
systems, which may well play an important role in developing technologies such
as super-repellent surfaces or micro-fluidics. Recent studies have concentrated
on adsorption of liquids at rough and heterogeneous substrates and the
characterisation of nanoscopic liquid films. However, the fundamental effect of
geometry has hardly been addressed. Here we show that varying the shape of the
substrate can exert a profound influence on the adsorption isotherms allowing
us to smoothly connect wetting and capillary condensation through a number of
novel and distinct examples of fluid interfacial phenomena. This opens the
possibility of tailoring the adsorption properties of solid substrates by
sculpturing their surface shape.Comment: 6 pages, 4 figure
Universality for 2D Wedge Wetting
We study 2D wedge wetting using a continuum interfacial Hamiltonian model
which is solved by transfer-matrix methods. For arbitrary binding potentials,
we are able to exactly calculate the wedge free-energy and interface height
distribution function and, thus, can completely classify all types of critical
behaviour. We show that critical filling is characterized by strongly universal
fluctuation dominated critical exponents, whilst complete filling is determined
by the geometry rather than fluctuation effects. Related phenomena for
interface depinning from defect lines in the bulk are also considered.Comment: 4 pages, 1 figur
Critical adsorption near edges
Symmetry breaking surface fields give rise to nontrivial and long-ranged
order parameter profiles for critical systems such as fluids, alloys or magnets
confined to wedges. We discuss the properties of the corresponding universal
scaling functions of the order parameter profile and the two-point correlation
function and determine the critical exponents eta_parallel and
eta_perpendicular for the so-called normal transition.Comment: 22 pages, 5 figures, accepted for publication in PR
Mediation and the Best Interests of the Child from the Child Law Perspective
What is the best interests of the child in family mediation and is mediation in the best interests of the child? In this article, I use child law and the United Nations Convention on the Rights of the Child combined with mediation theory to discuss these questions. Both mediation and the best interests of the child are open for multiple interpretations. Using facilitative and evaluative mediation theory and the legal concept ‘the best interests of the child’, I explore and compare the understandings of these concepts as they apply to family mediation. This includes a discussion of the advantages and disadvantages of facilitative as well as evaluative mediation orientations in terms of protecting the best interests of the child. Finnish court-connected family mediation is a combination of both mediation orientations, and the mediator is obliged to secure the best interests of the child. From a theoretical point of view, this seems to be a challenging combination.Peer reviewe