133 research outputs found
The evolution of trilingual code-switching from infancy to school age: the shaping of trilingual competence through dynamic language dominance
This article reports on a study of the code-switches produced by two children who acquired their three languages in early childhood. We compared formal and functional aspects of their switches recorded at two different stages of their development. Of particular interest was the consideration of sociolinguistic variables that have intervened in the children’s environment. We undertook a quantitative and qualitative analysis of the children’s code-switches to ascertain the frequency of switching, the use of each of the three languages employed for switching and the linguistic complexity of the switches. We assumed that the sociolinguistic conditions that changed the linguistic landscape in which these children operated would be reflected not only in the development of each of their languages, but also in the kind of switches that they produced. We tried to establish whether it is the case that certain forms and functions of code-switches constitute a "core" of trilingual language behaviour while others are prone to change. Ultimately, our aim was to gain an insight into the specific trilingual language production processes over a given period of time that can shed light on the development and nature of trilingual competence
Cluster Persistence: a Discriminating Probe of Soap Froth Dynamics
The persistent decay of bubble clusters in coarsening two-dimensional soap
froths is measured experimentally as a function of cluster volume fraction.
Dramatically stronger decay is observed in comparison to soap froth models and
to measurements and calculations of persistence in other systems. The fraction
of individual bubbles that contain any persistent area also decays, implying
significant bubble motion and suggesting that T1 processes play an important
role in froth persistence.Comment: 5 pages, revtex, 4 eps figures. To appear in Europhys. Let
Topological correlations in soap froths
Correlation in two-dimensional soap froth is analysed with an effective
potential for the first time. Cells with equal number of sides repel (with
linear correlation) while cells with different number of sides attract (with
NON-bilinear) for nearest neighbours, which cannot be explained by the maximum
entropy argument. Also, the analysis indicates that froth is correlated up to
the third shell neighbours at least, contradicting the conventional ideas that
froth is not strongly correlated.Comment: 10 Pages LaTeX, 6 Postscript figure
Bubble kinetics in a steady-state column of aqueous foam
We measure the liquid content, the bubble speeds, and the distribution of
bubble sizes, in a vertical column of aqueous foam maintained in steady-state
by continuous bubbling of gas into a surfactant solution. Nearly round bubbles
accumulate at the solution/foam interface, and subsequently rise with constant
speed. Upon moving up the column, they become larger due to gas diffusion and
more polyhedral due to drainage. The size distribution is monodisperse near the
bottom and polydisperse near the top, but there is an unexpected range of
intermediate heights where it is bidisperse with small bubbles decorating the
junctions between larger bubbles. We explain the evolution in both bidisperse
and polydisperse regimes, using Laplace pressure differences and taking the
liquid fraction profile as a given.Comment: 7 pages, 3 figure
Glassy behaviour in a simple topological model
In this article we study a simple, purely topological, cellular model which
is allowed to evolve through a Glauber-Kawasaki process. We find a
non-thermodynamic transition to a glassy phase in which the energy (defined as
the square of the local cell topological charge) fails to reach the equilibrium
value below a characteristic temperature which is dependent on the cooling
rate. We investigate a correlation function which exhibits aging behaviour, and
follows a master curve in the stationary regime when time is rescaled by a
factor of the relaxation time t_r. This master curve can be fitted by a von
Schweidler law in the late beta-relaxation regime. The relaxation times can be
well-fitted at all temperatures by an offset Arrhenius law. A power law can be
fitted to an intermediate temperature regime; the exponent of the power law and
the von Schweidler law roughly agree with the relationship predicted by
Mode-coupling Theory. By defining a suitable response function, we find that
the fluctuation-dissipation ratio is held until sometime later than the
appearance of the plateaux; non-monotonicity of the response is observed after
this ratio is broken, a feature which has been observed in other models with
dynamics involving activated processes.Comment: 11 pages LaTeX; minor textual corrcetions, minor corrections to figs
4 & 7
Decorated vertices with 3-edged cells in 2D foams: exact solutions and properties
The energy, area and excess energy of a decorated vertex in a 2D foam are
calculated. The general shape of the vertex and its decoration are described
analytically by a reference pattern mapped by a parametric Moebius
transformation. A single parameter of control allows to describe, in a common
framework, different types of decorations, by liquid triangles or 3-sided
bubbles, and other non-conventional cells. A solution is proposed to explain
the stability threshold in the flower problem.Comment: 13 pages, 17 figure
A Phase Front Instability in Periodically Forced Oscillatory Systems
Multiplicity of phase states within frequency locked bands in periodically
forced oscillatory systems may give rise to front structures separating states
with different phases. A new front instability is found within bands where
(). Stationary fronts shifting the
oscillation phase by lose stability below a critical forcing strength and
decompose into traveling fronts each shifting the phase by . The
instability designates a transition from stationary two-phase patterns to
traveling -phase patterns
Selection of the scaling solution in a cluster coalescence model
The scaling properties of the cluster size distribution of a system of
diffusing clusters is studied in terms of a simple kinetic mean field model. It
is shown that a one parameter family of mathematically valid scaling solutions
exists. Despite this, the kinetics reaches a unique scaling solution
independent of initial conditions. This selected scaling solution is marginally
physical; i.e., it is the borderline solution between the unphysical and
physical branches of the family of solutions.Comment: 4 pages, 5 figure
Coarsening in the q-State Potts Model and the Ising Model with Globally Conserved Magnetization
We study the nonequilibrium dynamics of the -state Potts model following a
quench from the high temperature disordered phase to zero temperature. The time
dependent two-point correlation functions of the order parameter field satisfy
dynamic scaling with a length scale . In particular, the
autocorrelation function decays as . We illustrate these
properties by solving exactly the kinetic Potts model in . We then analyze
a Langevin equation of an appropriate field theory to compute these correlation
functions for general and . We establish a correspondence between the
two-point correlations of the -state Potts model and those of a kinetic
Ising model evolving with a fixed magnetization . The dynamics of this
Ising model is solved exactly in the large q limit, and in the limit of a large
number of components for the order parameter. For general and in any
dimension, we introduce a Gaussian closure approximation and calculate within
this approximation the scaling functions and the exponent . These
are in good agreement with the direct numerical simulations of the Potts model
as well as the kinetic Ising model with fixed magnetization. We also discuss
the existing and possible experimental realizations of these models.Comment: TeX, Vanilla.sty is needed. [Admin note: author contacted regarding
missing figure1 but is unable to supply, see journal version (Nov99)
Random walk on disordered networks
Random walks are studied on disordered cellular networks in 2-and
3-dimensional spaces with arbitrary curvature. The coefficients of the
evolution equation are calculated in term of the structural properties of the
cellular system. The effects of disorder and space-curvature on the diffusion
phenomena are investigated. In disordered systems the mean square displacement
displays an enhancement at short time and a lowering at long ones, with respect
to the ordered case. The asymptotic expression for the diffusion equation on
hyperbolic cellular systems relates random walk on curved lattices to
hyperbolic Brownian motion.Comment: 10 Pages, 3 Postscript figure
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