79 research outputs found
Space-time Phase Transitions in Driven Kinetically Constrained Lattice Models
Kinetically constrained models (KCMs) have been used to study and understand
the origin of glassy dynamics. Despite having trivial thermodynamic properties,
their dynamics slows down dramatically at low temperatures while displaying
dynamical heterogeneity as seen in glass forming supercooled liquids. This
dynamics has its origin in an ergodic-nonergodic first-order phase transition
between phases of distinct dynamical "activity". This is a "space-time"
transition as it corresponds to a singular change in ensembles of trajectories
of the dynamics rather than ensembles of configurations. Here we extend these
ideas to driven glassy systems by considering KCMs driven into non-equilibrium
steady states through non-conservative forces. By classifying trajectories
through their entropy production we prove that driven KCMs also display an
analogous first-order space-time transition between dynamical phases of finite
and vanishing entropy production. We also discuss how trajectories with rare
values of entropy production can be realized as typical trajectories of a
mapped system with modified forces
Phase separation in star polymer-colloid mixtures
We examine the demixing transition in star polymer-colloid mixtures for star
arm numbers f=2,6,16,32 and different star-colloid size ratios. Theoretically,
we solve the thermodynamically self-consistent Rogers-Young integral equations
for binary mixtures using three effective pair potentials obtained from direct
molecular computer simulations. The numerical results show a spinodal
instability. The demixing binodals are approximately calculated, and found to
be consistent with experimental observations.Comment: 4 pages, 4 figures, submitted to PR
Glasses in hard spheres with short-range attraction
We report a detailed experimental study of the structure and dynamics of
glassy states in hard spheres with short-range attraction. The system is a
suspension of nearly-hard-sphere colloidal particles and non-adsorbing linear
polymer which induces a depletion attraction between the particles. Observation
of crystallization reveals a re-entrant glass transition. Static light
scattering shows a continuous change in the static structure factors upon
increasing attraction. Dynamic light scattering results, which cover 11 orders
of magnitude in time, are consistent with the existence of two distinct kinds
of glasses, those dominated by inter-particle repulsion and caging, and those
dominated by attraction. Samples close to the `A3 point' predicted by mode
coupling theory for such systems show very slow, logarithmic dynamics.Comment: 22 pages, 18 figure
Macromolecular theory of solvation and structure in mixtures of colloids and polymers
The structural and thermodynamic properties of mixtures of colloidal spheres
and non-adsorbing polymer chains are studied within a novel general
two-component macromolecular liquid state approach applicable for all size
asymmetry ratios. The dilute limits, when one of the components is at infinite
dilution but the other concentrated, are presented and compared to field theory
and models which replace polymer coils with spheres. Whereas the derived
analytical results compare well, qualitatively and quantitatively, with
mean-field scaling laws where available, important differences from ``effective
sphere'' approaches are found for large polymer sizes or semi-dilute
concentrations.Comment: 23 pages, 10 figure
Constructivist learning theories and complex learning environments
Contains fulltext :
64031.pdf (publisher's version ) (Open Access
Modeling work-related learning on the basis of intentionality and developmental relatedness: A non-educational perspective
Contains fulltext :
64800_pub.pdf (publisher's version ) (Open Access)
Contains fulltext :
64800_aut.pdf (author's version ) (Open Access
Leerstrategieën, leren en verantwoordelijkheid
De oratie is opgebouwd in drie hoofdstukken. Onder 'Leren en onderwijs' wordt betoogd waarom het onderwijs moet uitgaan van een bredere visie op leren, inclusief leerstrategieën. Daarbij wordt de relatie tussen kennis en leren besproken en de vele manieren waarom mensen in hun leven leren. Onder 'Kerntaak van het onderwijs' gaat het om de belangrijke verantwoordelijkheid van onderwijs in het handhaven en steeds opnieuw vormgeven van een open, democratische en humane samenleving. Onder 'Thema's bij het opleiden van leraren' wordt, vanuit het principe van congruentie ('walk the talk'), een aantal belangrijke onderwerpen bij het opleiden van leraren besproken.
Ook uitgegeven door Coutinho, Bussum. ISBN 90 6283 454 X; www.coutinho.n
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