Unsteady turbulent buoyant plumes

We model the unsteady evolution of turbulent buoyant plumes following temporal changes to the source conditions. The integral model is derived from radial integration of the governing equations expressing the conservation of mass, axial momentum and buoyancy. The non-uniform radial profiles of the axial velocity and density deficit in the plume are explicitly described by shape factors in the integral equations; the commonly-assumed top-hat profiles lead to shape factors equal to unity. The resultant model is hyperbolic when the momentum shape factor, determined from the radial profile of the mean axial velocity, differs from unity. The solutions of the model when source conditions are maintained at constant values retain the form of the well-established steady plume solutions. We demonstrate that the inclusion of a momentum shape factor that differs from unity leads to a well-posed integral model. Therefore, our model does not exhibit the mathematical pathologies that appear in previously proposed unsteady integral models of turbulent plumes. A stability threshold for the value of the shape factor is identified, resulting in a range of its values where the amplitude of small perturbations to the steady solutions decay with distance from the source. The hyperbolic character of the system allows the formation of discontinuities in the fields describing the plume properties during the unsteady evolution. We compute numerical solutions to illustrate the transient development following an abrupt change in the source conditions. The adjustment to the new source conditions occurs through the propagation of a pulse of fluid through the plume. The dynamics of this pulse are described by a similarity solution and, by constructing this new similarity solution, we identify three regimes in which the evolution of the transient pulse following adjustment of the source qualitatively differ.Comment: 41 pages, 16 figures, under consideration for publication in Journal of Fluid Mechanic

Agricultural spray droplet dispersion in turbulent windflow

Off-target contamination (or spray drift) during agricultural chemical application, arising from removal of small (diameter < 100 m) droplets from sprays by atmospheric or vehicle-generated cross flows, is investigated experimentally. The primary requirement for realistic wind tunnel studies is identified from background review as matching the full-scale logarithmic man velocity profile with suitable surface roughness parameters. A general calculation scheme is presented for spacing horizontal flat plates to simulate weakly-sheared mean velocity profiles. Adequate full-scale matching of logarithmic mean velocity profiles is achieved after systematic equipment modification. Comparative field and wind tunnel experiments using single nozzles show adequate agreement following the above approach, indicating that air entrained into the liquid spray stabilizes the spray to the cross flow action. Measurements within an agricultural spray in still air show that small droplets are passively transported within the entrained air field, whose characteristic turbulence length scale is too small to contribute to droplet dispersion. Wind tunnel studies employing conventional sprays show small droplet removal associated with regions where the entrained air velocity is less than the cross flow velocity, with essentially passive downwind transport. Numerical simulations of spray drift must clearly incorporate characteristics of the entrained air velocity field

Surface bound PEG-RGDS on PEG-DA hydrogels and its effects on RPE cell morphology and differentiation.

Age related macular Degeneration is a retinal condition resulting in visual impairment and central vision loss caused by dysfunction of the Bruch’s membrane and the retinal-pigmented epithelium. . A novel treatment idea proposes that these layers may be repaired through replacement using a synthetic Bruch’s membrane, such as modified poly(ethylene glycol) commonly known as PEG, allowing regrowth of the RPE layer in vivo or through inclusion of a functioning RPE layer when implanting the membrane. Modifying poly(ethylene glycol) with surface bound adhesion peptides such as RGDS provides an excellent biomaterial scaffold in which RPE cells may repopulate and regain their appropriate functions. The purpose of the proposed research is to evaluate the efficiency of the surface bound adhesion peptide, RGDS, and the effect of RGDS concentration on cellular confluency and morphology in both ARPE-19 and PRPE cell lines on modified PEG hydrogels. Using fluorescent and confocal microscopy, it was found that between 4 and 5 percent of the total coating solution was effectively bound to the hydrogel surface. Cellular morphology using immunocytochemistry staining of zonula occluden, or ZO-1, also demonstrated morphological characteristics are obtainable using visual parameters such as cell circularity. Even though differentiation was shown to be lacking when compared to fibronectin controls, the results indicate that all concentrations tested proved effective in providing optimal cellular confluency

Intelligence-Led Policing and Forces of Organizational Change in the United States

The intent of this study is to explore organisational factors that, both conceptually and operationally, facilitate or inhibit a police agency from adopting intelligence-led policing (ILP). Research to date is yet to explore organisational factors related to ILP among American law enforcement agencies. Drawing from original survey data of national law enforcement agencies as part of a 2009 US Department of Justice, National Institute of Justice-funded project, the present study incorporates force field analysis to explore factors of ILP adoption in the USA. Findings suggest state and local agencies' familiarity with the intelligence-led concept and utilisation of open source and received information appear to be driving adoption. Conversely, formal policies, lack of sufficient personnel, training and a lack of intelligence-led decision-making appear to be inhibiting change towards the ILP paradigm. It appears agency size has minimal influence on an agency's shift towards ILP. Access to necessary resources and training appear to pose a significant challenge to law enforcement. Limited resources to develop an intelligence-led approach may result in the capability going underdeveloped or taking the form of other policing practices related to available resources – such as homeland security preparedness. This research is one of the first empirical explorations of ILP adoption, especially with a national sample of state and local agencies. Further conceptual clarity of the ILP paradigm is provided and organisational factors are discussed

Prevention for a Healthier California: Investments in Disease Prevention Yield Significant Savings, Stronger Communities

Estimates how much the state and the nation could save in healthcare costs by investing in disease prevention through community programs that increase physical activity, improve nutrition, and reduce tobacco use. Provides examples of prevention efforts

Uncertainty analysis of a model of wind-blown volcanic plumes

Mathematical models of natural processes can be used as inversion tools to predict unobserved properties from measured quantities. Uncertainty in observations and model formulation impact on the efficacy of inverse modelling. We present a general methodology, history matching, that can be used to investigate the effect of observational and model uncertainty on inverse modelling studies. We demonstrate history matching on an integral model of volcanic plumes that is used to estimate source conditions from observations of the rise height of plumes during the eruptions of Eyjafjallajökull, Iceland, in 2010 and Grímsvötn, Iceland, in 2011. Sources of uncertainty are identified and quantified, and propagated through the integral plume model. A preliminary sensitivity analysis is performed to identify the uncertain model parameters that strongly influence model predictions. Model predictions are assessed against observations through an implausibility measure that rules out model inputs that are considered implausible given the quantified uncertainty. We demonstrate that the source mass flux at the volcano can be estimated from plume height observations, but the magmatic temperature, exit velocity and exsolved gas mass fraction cannot be accurately determined. Uncertainty in plume height observations and entrainment coefficients results in a large range of plausible values of the source mass flux. Our analysis shows that better constraints on entrainment coefficients for volcanic plumes and more precise observations of plume height are required to obtain tightly constrained estimates of the source mass flux

Climate change refugia for terrestrial biodiversity

AbstractWe are currently facing the likelihood of severe climate change before the close of the century. In the face of such a global driver of species loss, we urgently need to identify refugia that will shelter species from the worst impacts of climate change. This &nbsp;will be &nbsp;a critical component of successful conservation and management of our biodiversity. Despite this, little is known about how best to identify refugia in the landscape, and the practical strategies needed to identify, protect and expand refugia are just beginning to be developed. Identifying refugia that will protect most species, or large numbers of species, remains a complex and daunting endeavour due to the large variations in climatic and biotic requirements of species.&nbsp;A first step to identifying refugia for biodiversity across Australia is to locate the areas which show the least change into the future (i.e. the most environmentally stable), particularly along axes of temperature and precipitation. The second and crucial step is to identify the areas that will retain most of their biodiversity and provide opportunities for additional species to relocate to into the future. Using these approaches in this project, we take the first steps to identify refugial areas across the Australian continent under contemporary climate change scenarios. We find that the southern and eastern parts of the continent contain refugia that many species will retreat to over the next 75 years, but that the current reserve system may be inadequate to allow species to shift to and persist in these areas. Disturbingly, we also find that there is a large portion of the Australian vertebrate community for which adequate natural refugia do not appear to exist. Fine-scaled regional analyses will be required to clarify these broad findings, and we examine a number of case studies demonstrating how these regional analyses might best proceed.&nbsp;Lessons learnt across the multiple techniques employed in this study include:1. High elevation areas are important refugia.2. Tasmania and the east coast of mainland Australia contain most of the key areas for refugia into the future.3. Results are dependent on which objectives, techniques, taxonomic groups and climate scenarios are used.Please cite this report as:Reside, AE, VanDerWal, J, Phillips, B, Shoo, LP, Rosauer, DF, Anderson, BA, Welbergen, J, Moritz, C, Ferrier, S, Harwood, TD, Williams, KJ, Mackey, B, Hugh, S, Williams, SE 2013 Climate change refugia for terrestrial biodiversity: Defining areas that promote species persistence and ecosystem resilience in the face of global climate change, National Climate Change Adaptation Research Facility, Gold Coast, pp. 216We are currently facing the likelihood of severe climate change before the close of the century. In the face of such a global driver of species loss, we urgently need to identify refugia that will shelter species from the worst impacts of climate change. This &nbsp;will be &nbsp;a critical component of successful conservation and management of our biodiversity. Despite this, little is known about how best to identify refugia in the landscape, and the practical strategies needed to identify, protect and expand refugia are just beginning to be developed. Identifying refugia that will protect most species, or large numbers of species, remains a complex and daunting endeavour due to the large variations in climatic and biotic requirements of species.&nbsp;A first step to identifying refugia for biodiversity across Australia is to locate the areas which show the least change into the future (i.e. the most environmentally stable), particularly along axes of temperature and precipitation. The second and crucial step is to identify the areas that will retain most of their biodiversity and provide opportunities for additional species to relocate to into the future. Using these approaches in this project, we take the first steps to identify refugial areas across the Australian continent under contemporary climate change scenarios. We find that the southern and eastern parts of the continent contain refugia that many species will retreat to over the next 75 years, but that the current reserve system may be inadequate to allow species to shift to and persist in these areas. Disturbingly, we also find that there is a large portion of the Australian vertebrate community for which adequate natural refugia do not appear to exist. Fine-scaled regional analyses will be required to clarify these broad findings, and we examine a number of case studies demonstrating how these regional analyses might best proceed.&nbsp;Lessons learnt across the multiple techniques employed in this study include:High elevation areas are important refugia.Tasmania and the east coast of mainland Australia contain most of the key areas for refugia into the future.Results are dependent on which objectives, techniques, taxonomic groups and climate scenarios are used

Explosive expansion of a slowly decompressed magma analogue: Evidence for delayed bubble nucleation

While ascending in the plumbing system of volcanoes, magma undergoes decompression at rates spanning several orders of magnitude and set by a number of factors internal and external to the volcano. Slow decompression generally results in an effusive or mildly explosive expansion of the magma, but counterexamples of sudden switches from effusive to explosive eruptive behavior have been documented at various volcanoes worldwide. The mechanisms involved in this behavior are currently debated, in particular for basaltic magmas. Here, we explore the interplay between decompression rate and vesiculation vigor by decompressing a magma analogue obtained by dissolving pine resin into acetone in varying proportions. Analogue experiments allow direct observations of the processes of bubble nucleation and growth, flow dynamics, and fragmentation that is not currently possible with magmatic systems. Our mixtures contain solid particles, and upon decompression, nucleation of acetone bubbles is observed. We find that mixtures with a high acetone content, containing smaller and fewer solid particles, experience strong supersaturation and fragment under very slow decompressions, despite having low viscosity, while mixtures with lower acetone content, with more and larger solid particles, degas efficiently without fragmentation. We interpret our results in terms of delayed bubble nucleation due to a lack of efficient nucleation sites. We discuss how a similar mechanism might induce violent, explosive expansion in volatile‐rich and poorly crystalline low‐silica magmas, by analogy with the behavior of rhyolitic magmas

USING THE FORESTRY RECLAMATION APPROACH FOR RECLAIMED SURFACE MINELAND IN THE WESTERN GULF: EFFECTS ON PINUS TAEDA SEEDLING GROWTH AND SURVIVAL

While land reclamation efforts of surface mines have considerably increased soil stability since the implementation of SMCRA (Surface Mining Control and Reclamation Act), research suggests that resulting soil compaction hinders the productivity of forests post-mining. The Forestry Reclamation Approach (FRA) was developed to improve forest health in the Appalachian region through a five-step process that minimizes soil compaction and establishes a productive forest. The FRA has not yet been tested in the western Gulf Coastal Plain (GCP). The higher clay content of some GCP soils and the dearth of coarse fragments (e.g. cobbles, stones and boulders) may affect reclamation practices and the ability of these methods to create productive forests. Compaction caused by conventional reclamation methods in the GCP has not been studied in great detail. Thus, this study attempts to provide a comparison of two reclamation methods, the FRA low-compaction method used in the Appalachian region with that of conventional scraper-pan (scraper) methods in the GCP. This study used the FRA with common silvicultural practices of the western Gulf. The two hectare study site was installed with a randomized complete block design with three replicates comparing conventional scraper reclamation used in the region with that of an unmined control and the FRA-style low compaction treatment. Following soil reclamation, containerized loblolly pine (Pinus taeda L.) seedlings of a western Gulf provenance were hand-planted. Soil chemical and physical parameters were assessed on each treatment to determine the effect the FRA and scraper method had on resulting tree seedling growth and survival. After three growing seasons, seedlings in the FRA plots had significantly higher tree volumes than both the scraper (p=0.0139) and the control (p=0.0247) treatments. The FRA plots also had a 97% survival rate, while scraper plots had a survival of 86%. The FRA plots had significantly lower soil bulk densities than the scraper (p=0.0353) and the control (p\u3c0.0001) which likely influenced growth and survival trends. Soil nutrients were increasingly available on the FRA and scraper plots, likely due to the mixing of the soil profile when compared to the unmined control. Leaf-level water potential and gas exchange were not correlated to growth and survival and did not differ among treatments. These results suggest reclamation practices modeled after FRA methods may benefit tree growth and survival in the Western Gulf