4,347 research outputs found
Characterizing Pixel and Point Patterns with a Hyperuniformity Disorder Length
We introduce the concept of a hyperuniformity disorder length that controls
the variance of volume fraction fluctuations for randomly placed windows of
fixed size. In particular, fluctuations are determined by the average number of
particles within a distance from the boundary of the window. We first
compute special expectations and bounds in dimensions, and then illustrate
the range of behavior of versus window size by analyzing three
different types of simulated two-dimensional pixel pattern - where particle
positions are stored as a binary digital image in which pixels have value
zero/one if empty/contain a particle. The first are random binomial patterns,
where pixels are randomly flipped from zero to one with probability equal to
area fraction. These have long-ranged density fluctuations, and simulations
confirm the exact result . Next we consider vacancy patterns, where a
fraction of particles on a lattice are randomly removed. These also display
long-range density fluctuations, but with for small . For a
hyperuniform system with no long-range density fluctuations, we consider
Einstein patterns where each particle is independently displaced from a lattice
site by a Gaussian-distributed amount. For these, at large , approaches
a constant equal to about half the root-mean-square displacement in each
dimension. Then we turn to grayscale pixel patterns that represent simulated
arrangements of polydisperse particles, where the volume of a particle is
encoded in the value of its central pixel. And we discuss the continuum limit
of point patterns, where pixel size vanishes. In general, we thus propose to
quantify particle configurations not just by the scaling of the density
fluctuation spectrum but rather by the real-space spectrum of versus
. We call this approach Hyperuniformity Disorder Length Spectroscopy
Morphology of rain water channelization in systematically varied model sandy soils
We visualize the formation of fingered flow in dry model sandy soils under
different raining conditions using a quasi-2d experimental set-up, and
systematically determine the impact of soil grain diameter and surface wetting
property on water channelization phenomenon. The model sandy soils we use are
random closely-packed glass beads with varied diameters and surface treatments.
For hydrophilic sandy soils, our experiments show that rain water infiltrates
into a shallow top layer of soil and creates a horizontal water wetting front
that grows downward homogeneously until instabilities occur to form fingered
flows. For hydrophobic sandy soils, in contrast, we observe that rain water
ponds on the top of soil surface until the hydraulic pressure is strong enough
to overcome the capillary repellency of soil and create narrow water channels
that penetrate the soil packing. Varying the raindrop impinging speed has
little influence on water channel formation. However, varying the rain rate
causes significant changes in water infiltration depth, water channel width,
and water channel separation. At a fixed raining condition, we combine the
effects of grain diameter and surface hydrophobicity into a single parameter
and determine its influence on water infiltration depth, water channel width,
and water channel separation. We also demonstrate the efficiency of several
soil water improvement methods that relate to rain water channelization
phenomenon, including pre-wetting sandy soils at different level before
rainfall, modifying soil surface flatness, and applying superabsorbent hydrogel
particles as soil modifiers
Kinetics of Gravity-Driven Water Channels Under Steady Rainfall
We investigate the formation of fingered flow in dry granular media under
simulated rainfall using a quasi-2D experimental set-up composed of a random
close packing of mono-disperse glass beads. Using controlled experiments, we
analyze the finger instabilities that develop from the wetting front as a
function of fundamental granular (particle size) and fluid properties
(rainfall, viscosity).These finger instabilities act as precursors for water
channels, which serve as outlets for water drainage. We look into the
characteristics of the homogeneous wetting front and channel size as well as
estimate relevant time scales involved in the instability formation and the
velocity of the channel finger tip. We compare our experimental results with
that of the well-known prediction developed by Parlange and Hill [1976]. This
model is based on linear stability analysis of the growth of perturbations
arising at the interface between two immiscible fluids. Results show that in
terms of morphology, experiments agree with the proposed model. However, in
terms of kinetics we nevertheless account for another term that describes the
homogenization of the wetting front. This result shows that the manner we
introduce the fluid to a porous medium can also influence the formation of
finger instabilities.Comment: 13 pages, 7 figure
Circumstantiation: taking a broader look at circumstantial meanings
This paper argues for a view of circumstantial meaning as a region of ideational meaning that is instantiated across a range of lexicogrammatical structures: from the rank of the clausal constituent of circumstance in both directions: up to clause rank and down to below or within constituent rank (eg as Qualifier). This paper brings together and extends the work of Halliday & Matthiessen (An Introduction to Functional Grammar, 2004) on expansion and circumstantiation, and the work of Martin (English Text: System and Structure, 1992) within the discourse semantic system of ideation. Each type of circumstantial meaning is defined structurally, that is, according to rank, and semantically, according to type. Analysis of circumstantial meanings is conducted on a small corpus of four introductions to journal articles in order to demonstrate the use of viewing circumstantial meaning in this way
Considering the role of cognitive control in expert performance
© 2014, Springer Science+Business Media Dordrecht. Dreyfus and Dreyfus’ (1986) influential phenomenological analysis of skill acquisition proposes that expert performance is guided by non-cognitive responses which are fast, effortless and apparently intuitive in nature. Although this model has been criticised (e.g., by Breivik Journal of Philosophy of Sport, 34, 116–134 2007, Journal of the Philosophy of Sport, 40, 85–106 2013; Eriksen 2010; Montero Inquiry:An interdisciplinary Journal of Philosophy, 53, 105–122 2010; Montero and Evans 2011) for over-emphasising the role that intuition plays in facilitating skilled performance, it does recognise that on occasions (e.g., when performance goes awry for some reason) a form of ‘detached deliberative rationality’ may be used by experts to improve their performance. However, Dreyfus and Dreyfus (1986) see no role for calculative problem solving or deliberation (i.e., drawing on rules or mental representations) when performance is going well. In the current paper, we draw on empirical evidence, insights from athletes, and phenomenological description to argue that ‘continuous improvement’ (i.e., the phenomenon whereby certain skilled performers appear to be capable of increasing their proficiency even though they are already experts; Toner and Moran 2014) among experts is mediated by cognitive (or executive) control in three distinct sporting situations (i.e., in training, during pre-performance routines, and while engaged in on-line skill execution). We conclude by arguing that Sutton et al. Journal of the British Society for Phenomenology, 42, 78–103 (2011) ‘applying intelligence to the reflexes’ (AIR) approach may help to elucidate the process by which expert performers achieve continuous improvement through analytical/mindful behaviour during training and competition
Unexpected Effect of Internal Degrees of Freedom on Transverse Phonons in Supercooled Liquids
We show experimentally that in a supercooled liquid composed of molecules
with internal degrees of freedom the internal modes contribute to the frequency
dependent shear viscosity and damping of transverse phonons, which results in
an additional broadening of the transverse Brillouin lines. Earlier, only the
effect of internal modes on the frequency dependent bulk viscosity and damping
of longitudinal phonons was observed and explained theoretically in the limit
of weak coupling of internal degrees of freedom to translational motion. A new
theory is needed to describe this new effect. We also demonstrate, that the
contributions of structural relaxation and internal processes to the width of
the Brillouin lines can be separated by measurements under high pressure
Use of recombinant ApxIV in serodiagnosis of Actinobacillus pleuropneumoniae infections and development of an ApxIV ELISA
Actinobacillus pleuropneumoniae (App) is the etiological agent of porcine pleuropneumonia. The virulence of the fifteen serotypes of App is mainly determined by the three major RTX toxins ApxI, ApxII and ApxIII, which are secreted by the different serotypes in various combinations. A fourth RTX toxin, ApxIV, is produced by all 15 serotypes specifically during infection of pigs, but not under in vitro conditions. Pigs infected with App show specific antibodies directed against ApxIV. The analysis of sera of experimentally infected pigs revealed that ApxIV-immunoblots detected App infections in the second to third week post infection. We developed an indirect ELISA based on purified recombinant N’-terminal moiety of ApxIV that showed a specificity of 100% and a sensitivity of 93.8%
- …