1,163 research outputs found
Exploring gender perceptions of student teachers using role-play
This aim of the paper is to disseminate the Deakin University Gender Project led by the author. The aim of the project was threefold: to locate the content of student teachers' gender perceptions;to find out how students represent gender in their daily lives; and, to examine the efficacy of role-play in helping students represent and critically reflect on gender-focused situations
Tuning density profiles and mobility of inhomogeneous fluids
Density profiles are the most common measure of inhomogeneous structure in
confined fluids, but their connection to transport coefficients is poorly
understood. We explore via simulation how tuning particle-wall interactions to
flatten or enhance the particle layering of a model confined fluid impacts its
self-diffusivity, viscosity, and entropy. Interestingly, interactions that
eliminate particle layering significantly reduce confined fluid mobility,
whereas those that enhance layering can have the opposite effect. Excess
entropy helps to understand and predict these trends.Comment: 5 pages, 3 figure
Impact of surface roughness on diffusion of confined fluids
Using event-driven molecular dynamics simulations, we quantify how the self
diffusivity of confined hard-sphere fluids depends on the nature of the
confining boundaries. We explore systems with featureless confining boundaries
that treat particle-boundary collisions in different ways and also various
types of physically (i.e., geometrically) rough boundaries. We show that, for
moderately dense fluids, the ratio of the self diffusivity of a rough wall
system to that of an appropriate smooth-wall reference system is a linear
function of the reciprocal wall separation, with the slope depending on the
nature of the roughness. We also discuss some simple practical ways to use this
information to predict confined hard-sphere fluid behavior in different
rough-wall systems
Composition and concentration anomalies for structure and dynamics of Gaussian-core mixtures
We report molecular dynamics simulation results for two-component fluid
mixtures of Gaussian-core particles, focusing on how tracer diffusivities and
static pair correlations depend on temperature, particle concentration, and
composition. At low particle concentrations, these systems behave like simple
atomic mixtures. However, for intermediate concentrations, the single-particle
dynamics of the two species largely decouple, giving rise to the following
anomalous trends. Increasing either the concentration of the fluid (at fixed
composition) or the mole fraction of the larger particles (at fixed particle
concentration) enhances the tracer diffusivity of the larger particles, but
decreases that of the smaller particles. In fact, at sufficiently high particle
concentrations, the larger particles exhibit higher mobility than the smaller
particles. Each of these dynamic behaviors is accompanied by a corresponding
structural trend that characterizes how either concentration or composition
affects the strength of the static pair correlations. Specifically, the dynamic
trends observed here are consistent with a single empirical scaling law that
relates an appropriately normalized tracer diffusivity to its pair-correlation
contribution to the excess entropy.Comment: 5 pages, 4 figure
Five-dimensional Nernst branes from special geometry
We construct Nernst brane solutions, that is black branes with zero entropy
density in the extremal limit, of FI-gauged minimal five-dimensional
supergravity coupled to an arbitrary number of vector multiplets. While the
scalars take specific constant values and dynamically determine the value of
the cosmological constant in terms of the FI-parameters, the metric takes the
form of a boosted AdS Schwarzschild black brane. This metric can be brought to
the Carter-Novotny-Horsky form that has previously been observed to occur in
certain limits of boosted D3-branes. By dimensional reduction to four
dimensions we recover the four-dimensional Nernst branes of arXiv:1501.07863
and show how the five-dimensional lift resolves all their UV singularities. The
dynamics of the compactification circle, which expands both in the UV and in
the IR, plays a crucial role. At asymptotic infinity, the curvature singularity
of the four-dimensional metric and the run-away behaviour of the
four-dimensional scalar combine in such a way that the lifted solution becomes
asymptotic to AdS5. Moreover, the existence of a finite chemical potential in
four dimensions is related to fact that the compactification circle has a
finite minimal value. While it is not clear immediately how to embed our
solutions into string theory, we argue that the same type of dictionary as
proposed for boosted D3-branes should apply, although with a lower amount of
supersymmetry.Comment: 59 pages, 1 figure. Revised version: references added, typos
corrected. Final version, accepted by JHEP: two references adde
Orientational correlations in confined DNA
We study how the orientational correlations of DNA confined to nanochannels
depend on the channel diameter D by means of Monte Carlo simulations and a
mean-field theory. This theory describes DNA conformations in the
experimentally relevant regime where the Flory-de Gennes theory does not apply.
We show how local correlations determine the dependence of the end-to-end
distance of the DNA molecule upon D. Tapered nanochannels provide the necessary
resolution in D to study experimentally how the extension of confined DNA
molecules depends upon D. Our experimental and theoretical results are in
qualitative agreement.Comment: Revised version including supplemental material, 7 pages, 8 figure
Cofinement, entropy, and single-particle dynamics of equilibrium hard-sphere mixtures
We use discontinuous molecular dynamics and grand-canonical transition-matrix
Monte Carlo simulations to explore how confinement between parallel hard walls
modifies the relationships between packing fraction, self-diffusivity, partial
molar excess entropy, and total excess entropy for binary hard-sphere mixtures.
To accomplish this, we introduce an efficient algorithm to calculate partial
molar excess entropies from the transition-matrix Monte Carlo simulation data.
We find that the species-dependent self-diffusivities of confined fluids are
very similar to those of the bulk mixture if compared at the same,
appropriately defined, packing fraction up to intermediate values, but then
deviate negatively from the bulk behavior at higher packing fractions. On the
other hand, the relationships between self-diffusivity and partial molar excess
entropy (or total excess entropy) observed in the bulk fluid are preserved
under confinement even at relatively high packing fractions and for different
mixture compositions. This suggests that the partial molar excess entropy,
calculable from classical density functional theories of inhomogeneous fluids,
can be used to predict some of the nontrivial dynamical behaviors of fluid
mixtures in confined environments.Comment: submitted to JC
Generalized Rosenfeld scalings for tracer diffusivities in not-so-simple fluids: Mixtures and soft particles
Rosenfeld [Phys. Rev. A 15, 2545 (1977)] noticed that casting transport
coefficients of simple monatomic, equilibrium fluids in specific dimensionless
forms makes them approximately single-valued functions of excess entropy. This
has predictive value because, while the transport coefficients of dense fluids
are difficult to estimate from first principles, excess entropy can often be
accurately predicted from liquid-state theory. Here, we use molecular
simulations to investigate whether Rosenfeld's observation is a special case of
a more general scaling law relating mobility of particles in mixtures to excess
entropy. Specifically, we study tracer diffusivities, static structure, and
thermodynamic properties of a variety of one- and two-component model fluid
systems with either additive or non-additive interactions of the hard-sphere or
Gaussian-core form. The results of the simulations demonstrate that the effects
of mixture concentration and composition, particle-size asymmetry and
additivity, and strength of the interparticle interactions in these fluids are
consistent with an empirical scaling law relating the excess entropy to a new
dimensionless (generalized Rosenfeld) form of tracer diffusivity, which we
introduce here. The dimensionless form of the tracer diffusivity follows from
knowledge of the intermolecular potential and the transport / thermodynamic
behavior of fluids in the dilute limit. The generalized Rosenfeld scaling
requires less information, and provides more accurate predictions, than either
Enskog theory or scalings based on the pair-correlation contribution to the
excess entropy. As we show, however, it also suffers from some limitations,
especially for systems that exhibit significant decoupling of individual
component tracer diffusivities.Comment: 15 pages, 10 figure
Post transition metal substituted Keggin POMs as thin film chemiresistive sensors for H2O and CO2 detection
Chemiresitive sensing allows the affordable and facile detection of small molecules such as H2O and CO2. Herein, we report a novel class of earth abundant post transition metal substituted Keggin polyoxometalates (POMs) for chemiresistive sensing applications, with conductivies up to 0.01 S cm-1 under 100% CO2 and 65% Relative Humidity (RH)
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