736 research outputs found
Recommended from our members
Computerised speechreading training for deaf children: A randomised controlled trial
Purpose: We developed and evaluated in a randomised controlled triala computerised speechreading training programme to determine a) whether it is possible to train speechreading in deaf children and b) whether speechreading training results in improvements in phonological and reading skills.Previous studies indicate a relationship between speechreading and reading skill and further suggest this relationshipmay be mediated by improved phonological representations. This is important since many deaf children find learning to read to be very challenging.
Method: Sixty-six deaf 5-7 year olds were randomised into speechreading and maths training arms. Each training programme was comprised of10 minutesessionsa day, 4 days a week for 12 weeks. Children were assessed on a battery of language and literacy measures before training, immediately after training, 3 months and 10 months after training.
Results: We found no significant benefits for participants who completed the speechreading training, compared to those who completed the maths training, on the speechreading primary outcome measure. However, significantly greater gains were observed in the speechreading training group on one of the secondary measures of speechreading. There was also some evidence of beneficial effects of the speechreading training on phonological representations, however these effects were weaker. No benefits were seen toword reading.
Conclusions: Speechreading skill is trainable in deaf children. However, to support early reading, training may need to be longer or embedded in a broader literacy programme. Nevertheless, a training tool that can improve speechreading is likely to be of great interest to professionals working with deaf children
Flow-induced compaction of a deformable porous medium.
Fluid flowing through a deformable porous medium imparts viscous drag on the solid matrix, causing it to deform. This effect is investigated theoretically and experimentally in a one-dimensional configuration. The experiments consist of the downwards flow of water through a saturated pack of small, soft, hydrogel spheres, driven by a pressure head that can be increased or decreased. As the pressure head is increased, the effective permeability of the medium decreases and, in contrast to flow through a rigid medium, the flux of water is found to increase towards a finite upper bound such that it becomes insensitive to changes in the pressure head. Measurements of the internal deformation, extracted by particle tracking, show that the medium compacts differentially, with the porosity being lower at the base than at the upper free surface. A general theoretical model is derived, and the predictions of the model give good agreement with experimental measurements from a series of experiments in which the applied pressure head is sequentially increased. However, contrary to theory, all the experimental results display a distinct and repeatable hysteresis: the flux through the material for a particular applied pressure drop is appreciably lower when the pressure has been decreased to that value compared to when it has been increased to the same value.D.R.H. was supported by a Killam Postdoctoral Fellowship and a Research Fellowship at Gonville and Caius College, Cambridge. During the experimental part of this project, J.S.N. was supported by the division of Engineering Science, University of Toronto. J.A.N. is partly supported by a Royal Society University Research Fellowship.This is the author accepted manuscript. The final version is available from the American Physical Society via http://dx.doi.org/10.1103/PhysRevE.93.02311
Ice-lens formation and geometrical supercooling in soils and other colloidal materials
We present a new, physically-intuitive model of ice-lens formation and growth
during the freezing of soils and other dense, particulate suspensions.
Motivated by experimental evidence, we consider the growth of an ice-filled
crack in a freezing soil. At low temperatures, ice in the crack exerts large
pressures on the crack walls that will eventually cause the crack to split
open. We show that the crack will then propagate across the soil to form a new
lens. The process is controlled by two factors: the cohesion of the soil, and
the geometrical supercooling of the water in the soil; a new concept introduced
to measure the energy available to form a new ice lens. When the supercooling
exceeds a critical amount (proportional to the cohesive strength of the soil) a
new ice lens forms. This condition for ice-lens formation and growth does not
appeal to any ad hoc, empirical assumptions, and explains how periodic ice
lenses can form with or without the presence of a frozen fringe. The proposed
mechanism is in good agreement with experiments, in particular explaining
ice-lens pattern formation, and surges in heave rate associated with the growth
of new lenses. Importantly for systems with no frozen fringe, ice-lens
formation and frost heave can be predicted given only the unfrozen properties
of the soil. We use our theory to estimate ice-lens growth temperatures
obtaining quantitative agreement with the limited experimental data that is
currently available. Finally we suggest experiments that might be performed in
order to verify this theory in more detail. The theory is generalizable to
complex natural-soil scenarios, and should therefore be useful in the
prediction of macroscopic frost heave rates.Comment: Submitted to PR
Axisymmetric viscous gravity currents flowing over a porous medium
We study the axisymmetric propagation of a viscous gravity current over a
deep porous medium into which it also drains. A model for the propagation and
drainage of the current is developed and solved numerically in the case of
constant input from a point source. In this case, a steady state is possible in
which drainage balances the input, and we present analytical expressions for
the resulting steady profile and radial extent. We demonstrate good agreement
between our experiments, which use a bed of vertically aligned tubes as the
porous medium, and the theoretically predicted evolution and steady state.
However, analogous experiments using glass beads as the porous medium exhibit a
variety of unexpected behaviours, including overshoot of the steady-state
radius and subsequent retreat, thus highlighting the importance of the porous
medium geometry and permeability structure in these systems.Comment: 11 pages, 6 figures, 1 tabl
Nonlinear mushy-layer convection with chimneys: stability and optimal solute fluxes
We model buoyancy-driven convection with chimneys -- channels of zero solid
fraction -- in a mushy layer formed during directional solidification of a
binary alloy in two-dimensions. A large suite of numerical simulations is
combined with scaling analysis in order to study the parametric dependence of
the flow. Stability boundaries are calculated for states of finite-amplitude
convection with chimneys, which for a narrow domain can be interpreted in terms
of a modified Rayleigh number criterion based on the domain width and
mushy-layer permeability. For solidification in a wide domain with multiple
chimneys, it has previously been hypothesised that the chimney spacing will
adjust to optimise the rate of removal of potential energy from the system. For
a wide variety of initial liquid concentration conditions, we consider the
detailed flow structure in this optimal state and derive scaling laws for how
the flow evolves as the strength of convection increases. For moderate
mushy-layer Rayleigh numbers these flow properties support a solute flux that
increases linearly with Rayleigh number. This behaviour does not persist
indefinitely, however, with porosity-dependent flow saturation resulting in
sub-linear growth of the solute flux for sufficiently large Rayleigh numbers.
Finally, we consider the influence of the porosity dependence of permeability,
with a cubic function and a Carmen-Kozeny permeability yielding qualitatively
similar system dynamics and flow profiles for the optimal states.Comment: 20 pages, 10 figures. Changes from previous version correct typos,
expand on discussion of the method including new appendix A, and minor
changes to the discussion. A modified final version has been accepted for
publication in the Journal of Fluid Mechanic
Speechreading Ability Is Related to Phonological Awareness and Single-Word Reading in Both Deaf and Hearing Children
PURPOSE: Speechreading (lipreading) is a correlate of reading ability in both deaf and hearing children. We investigated whether the relationship between speechreading and single-word reading is mediated by phonological awareness in deaf and hearing children. METHOD: In two separate studies, 66 deaf children and 138 hearing children, aged 5–8 years old, were assessed on measures of speechreading, phonological awareness, and single-word reading. We assessed the concurrent relationships between latent variables measuring speechreading, phonological awareness, and single-word reading. RESULTS: In both deaf and hearing children, there was a strong relationship between speechreading and single-word reading, which was fully mediated by phonological awareness. CONCLUSIONS: hese results are consistent with ideas from previous studies that visual speech information contributes to the development of phonological representations in both deaf and hearing children, which, in turn, support learning to read. Future longitudinal and training studies are required to establish whether these relationships reflect causal effects
Relationship between conservation biology and ecology shown through machine reading of 32,000 articles
Conservation biology was founded on the idea that efforts to save nature depend on a scientific understanding of how it works. It sought to apply ecological principles to conservation problems. We investigated whether the relationship between these fields has changed over time through machine reading the full texts of 32,000 research articles published in 16 ecology and conservation biology journals. We examined changes in research topics in both fields and how the fields have evolved from 2000 to 2014. As conservation biology matured, its focus shifted from ecology to social and political aspects of conservation. The 2 fields diverged and now occupy distinct niches in modern science. We hypothesize this pattern resulted from increasing recognition that social, economic, and political factors are critical for successful conservation and possibly from rising skepticism about the relevance of contemporary ecological theory to practical conservation
Training emergency services’ dispatchers to recognise stroke: an interrupted time-series analysis
Background: Stroke is a time-dependent medical emergency in which early presentation to specialist care reduces death and dependency. Up to 70% of all stroke patients obtain first medical contact from the Emergency Medical Services (EMS). Identifying ‘true stroke’ from an EMS call is challenging, with over 50% of strokes being misclassified.
The aim of this study was to evaluate the impact of the training package on the recognition of stroke by Emergency Medical Dispatchers (EMDs).
Methods: This study took place in an ambulance service and a hospital in England using an interrupted time-series
design. Suspected stroke patients were identified in one week blocks, every three weeks over an 18 month period,
during which time the training was implemented. Patients were included if they had a diagnosis of stroke (EMS or
hospital). The effect of the intervention on the accuracy of dispatch diagnosis was investigated using binomial
(grouped) logistic regression.
Results: In the Pre-implementation period EMDs correctly identified 63% of stroke patients; this increased to 80%
Post-implementation. This change was significant (p=0.003), reflecting an improvement in identifying stroke patients
relative to the Pre-implementation period both the During-implementation (OR=4.10 [95% CI 1.58 to 10.66]) and Post-implementation (OR=2.30 [95% CI 1.07 to 4.92]) periods. For patients with a final diagnosis of stroke who had been dispatched as stroke there was a marginally non-significant 2.8 minutes (95% CI −0.2 to 5.9 minutes, p=0.068)reduction between Pre- and Post-implementation periods from call to arrival of the ambulance at scene.
Conclusions: This is the first study to develop, implement and evaluate the impact of a training package for EMDs with
the aim of improving the recognition of stroke. Training led to a significant increase in the proportion of stroke patients dispatched as such by EMDs; a small reduction in time from call to arrival at scene by the ambulance also appeared likely. The training package has been endorsed by the UK Stroke Forum Education and Training, and is free to access on-line
Recommended from our members
CORRIGENDUM: Flow-induced morphological instability of a mushy layer Journal of Fluid Mechanics, vol. 391 (1999), pp. 337–357
- …