1,318 research outputs found
Lubricated wrinkles: imposed constraints affect the dynamics of wrinkle coarsening
We study the dynamic coarsening of wrinkles in an elastic sheet that is
compressed while lying on a thin layer of viscous liquid. When the ends of the
sheet are instantaneously brought together by a small distance, viscous
resistance initially prevents the sheet from adopting a globally buckled shape.
Instead, the sheet accommodates the compression by wrinkling. Previous scaling
arguments suggested that a balance between the sheet's bending stiffness and
viscous effects lead to a wrinkle wavelength that increases with time
according to . We show that taking proper account
of the compression constraint leads to a logarithmic correction of this result,
. This correction is significant over
experimentally observable time spans, and leads us to reassess previously
published experimental data.Comment: 12 pages. Version accepted in Phys. Rev. Fluids (with small
correction to bibliography
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Automatic river quality monitoring
This thesis was submitted for the degree of Doctor of Philosophy and was awarded by Brunel University.Automatic river quality monitoring (ARQM) is potentially an important tool in water quality management for the National Rivers Authority (NRA) and similar organisations worldwide. The information produced by ARQM systems must be used in the most effective way and fully integrated with the manual monitoring effort.
The status and development of ARQM systems in the freshwater and estuarine River Thames catchment are discussed and a practical appraisal of the design, operation and maintenance requirements given. Data capture, verification and presentation methods are developed and the use of ARQM data for real time management and subsequent analysis is advocated.
Examples of data from the freshwater ARQM system are given which emphasise the variability of freshwater quality and the need for a comprehensive understanding of the behaviour of rivers before
management decisions are made. The use of ARQM data for assessing the compliance of rivers with River Quality Objectives is examined.
With respect to the tidal Thames, data processing methods to correct for the tidal movement of the waterbody are developed. ARQM data are used to highlight the principal factors affecting the water quality of the tidal Thames. The importance of the use of ARQM information in the effective management of the tidal Thames is discussed and operational examples demonstrate how it may be utilised as a basis for management decisions.
The application of ARQM to the sub-tropical environment of the River Ganges, India, is investigated. An ARQM system has been designed and prototypes are operational. Extensive site surveys were carried out and the water quality status of the Ganges is discussed. Recommendations for the improvement and future development of ARQM systems are made. The use of ARQM information and its potential for improving the management of rivers is discussed.National Rivers Authorit
Australian Aboriginal and Torres Strait Islander health information: progress, pitfalls and prospects
Despite significant developments in Aboriginal and Torres Strait Islander Health information over the last 25 years, many challenges remain. There are still uncertainties about the accuracy of estimates of the summary measure of life expectancy, and methods to estimate changes in life expectancy over time are unreliable because of changing patterns of identification. Far too little use is made of the wealth of information that is available, and formal systems for systematically using that information are often vestigial to non-existent. Available information has focussed largely on traditional biomedical topics and too little on access to, expenditure on, and availability of services required to improve health outcomes, and on the underpinning issues of social and emotional wellbeing. It is of concern that statistical artefacts may have been misrepresented as indicating real progress in key health indices. Challenges and opportunities for the future include improving the accuracy of estimation of life expectancy, provision of community level data, information on the availability and effectiveness of health services, measurement of the underpinning issues of racism, culture and social and emotional wellbeing (SEWB), enhancing the interoperability of data systems, and capacity building and mechanisms for Indigenous data governance. There is little point in having information unless it is used, and formal mechanisms for making full use of information in a proper policy/planning cycle are urgently required
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Structure variation and evolution in microphase-separated grafted diblock copolymer films
The phase behavior of grafted d-polystyrene-block-poly(methyl methacrylate) diblock copolymer films is examined, with particular focus on the effect of solvent and annealing time. It was observed that the films undergo a two-step transformation from an initially disordered state, through an ordered metastable state, to the final equilibrium configuration. It was also found that altering the solvent used to wash the films, or complete removal of the solvent prior to thermal annealing using supercritical CO2, could influence the structure of the films in the metastable state, though the final equilibrium state was unaffected. To aid in the understanding to these experimental results, a series of self-consistent field theory calculations were done on a model diblock copolymer brush containing solvent. Of the different models examined, those which contained a solvent selective for the grafted polymer block most accurately matched the observed experimental behavior. We hypothesize that the structure of the films in the metastable state results from solvent enrichment of the film near the film/substrate interface in the case of films washed with solvent or faster relaxation of the nongrafted block for supercritical CO2 treated (solvent free) films. The persistence of the metastable structures was attributed to the slow reorganization of the polymer chains in the absence of solvent
Stability of a bi-layer free film: simultaneous or individual rupture events?
We consider the stability of a long free film of liquid composed of two immiscible layers
of differing viscosities, where each layer experiences a van der Waals force between its
interfaces. We analyse the different ways the system can exhibit interfacial instability
when the liquid layers are sufficiently thin. For an excess of surfactant on one gas–liquid
interface the coupling between the layers is relatively weak and the instability manifests as
temporally separated rupture events in each layer. Conversely, in the absence of surfactant
the coupling between the layers is much stronger and the instability manifests as rupture
of both layers simultaneously. These features are consistent with recent experimental
observations
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Tim Rutherford-Johnson, Music after the Fall: Modern Composition and Culture since 1989
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