355 research outputs found
Influences of tailings water, sediments, macrophytes and detritus on zoobenthic community development in constructed wetlands –Results of a reciprocal transplant study
Constructed wetlands using oil sand process materials are being used by the oil sands mining corporations to reclaim the post-mining landscape. A reciprocal sediment transplant study was conducted to measure effects of sediment, water, plant cover, detritus mass and year to year variation on zoobenthic richness, density and relative abundance. Density did not change between wetlands, but the oil sand process water-affected wetland had lower richness than the reference wetland. Zoobenthic relative abundance was influenced by water type, macrophyte density and amount of accumulated detritus in sediment. Zoobenthos density was significantly positively associated with amount of plant cover and detritus combined. Sediment did not directly influence zoobenthic abundance or richness. However, its inhibition of plant percent cover caused an indirect effect
Spatial Control of Mechanical Factors: a New Design Rationale for Nerve Tissue Engineering
Peripheral nerve injuries (PNI) result from traumatic injury, surgery or repetitive compression, and are reported in 3-5% of all trauma patients. The impact ranges from severe (major loss of sensory/motor function and/or intractable neuropathic pain) to mild (some sensory and/or motor deficits) and in both cases, is devastating for the patient. PNI affect ∼1M people in Europe and the US p.a. of whom 660,000 have surgery. PNI has high healthcare, unemployment, rehabilitation, societal costs and affects mostly young people. The current surgical practice for nerve gaps >3 cm is to bridge the site of injury with a graft taken from the patient. However, this involves additional time, cost and damage to a healthy nerve, limited supply, and unsatisfactory functional recovery (50% of the cases). For these reasons, research has focused on developing artificial nerve conduits to replace grafts, but to-date those available for clinical use do not match and/or exceed the functional performance of the autograft. This project develops a rational basis for promoting neurite growth through tissue-engineered conduits for peripheral nerve repair, by exploiting the response of cells to spatial variations in mechanical properties of conduits to inform their design. This is achieved through an interdisciplinary approach, that combines in vitro experimentation with mathematical modelling. First of all, the mechanical and structural properties of RAFTStabilised collagen gels (RsC) are explored, physiologically coherent RsC stiffness gradients are fabricated and characterised as well as the neuronal response to them. Finally, a predictive framework to inform the design of nerve conduits is parameterised and tested using experimental results and literature. The use of this multidisciplinary approach can help tissue engineers in the development of novel tissue repair solutions, as well as informing mathematical models of neurite behaviour which can contribute to the design process
Flame extinctions: Critical stretch rates and sizes
The paper reports how experimental data from a fan-stirred explosion vessel have extended the boundary of the previously defined regime, within which stable premixed turbulent combustion occurs. It also defines the properties of the bordering regime of turbulent flame quenching.
The combustion regime is defined by the normalised turbulent burning velocity, U, the Karlovitz stretch factor, K, and strain rate Markstein number, Masr. The data cover hydrogen, methane, and higher hydrocarbons, at different equivalence ratios and pressures.
In contrast, the flame quench regime is defined by the mean diameters of flame kernels at quench, normalised by their laminar flame thickness, dk/δk. These values must be exceeded to initiate a propagating flame. Values of dk/δk increase with both K and Masr.
It is also shown, that the flame extinction at blow-off of non-premixed jet flames, is closely related to the observed single kernel quenching of premixed flames. With jet flames, the flow number, U*, has similarities with K. The normalised jet burner diameters, Db/δk, change with U*, in a similar fashion to the way dk/δk changes with K for premixed flames.
Finally, the way in which highly turbulent premixed flames can survive extinction by the entrainment of flame gases from a pilot flame is analysed
Rock Art Pilot Project Main Report
A report on the results of a pilot project to investigate the current state of research, conservation, management and presentation of prehistoric rock art in England commissioned by English Heritage from Archaeology Group, School of Conservation Sciences, Bournemouth Unviersity and the Institute of Archaeology, University College Londo
Recommended from our members
Electron transport in doped semiconductor nanocrystals
Electron transport through semiconductor nanocrystal (NC) systems is almost entirely understood by analogs to bulk science. The physics governing electron transport within NCs is entirely analogous to bulk semiconductors with extreme spatial constraints. In contrast, the physics of electrons conducting between NCs is understood through the physics of amorphous materials, granular metals, or bulk semiconductors, depending on the structure of the NC ensemble. Herein is an investigation of how dopant distribution engineering can be utilized to modulate near surface depletion in NC films. The dependence of NC film conductivity on dopant distribution is eliminated by surface passivation. A code to fit the optical absorption of colloidal NCs is developed to account for surface scattering, depletion, size heterogeneity, and dopant heterogeneity. This code is used to define the conduction within an individual NC. The intra-NC conduction is used as a metric to describe and define the phase diagram of NC film electron transport. Using the criteria developed here, we make metallic films in a controlled manner.
This work illustrates an overview of bulk electron transport and an introduction of NC film electron transport in Chapter 1. These descriptions will then be used to investigate the powerful capability to engineer intra-NC dopant distribution to manipulate NC film conductivity in Chapter 2. The intra-NC conductance is then investigated using a novel code to fit the optical absorption of NCs in Chapter 3. With a deep understanding of intra-NC transport, the electron transport phase diagram is constructed in Chapter 4.Chemical Engineerin
Recommended from our members
Reconstructing Population Histories in Relation to Ecology
We live in an era of significant environmental and climatic change and it has even been
suggested that the world is entering a new epoch, the ‘Anthropocene’. To understand better
how species might cope under different future climate scenarios, studies are now frequently
looking to explore how they responded to rapid environmental change in the past. Whilst
census data can capture contemporary trends, genetic approaches can infer population trends
stretching tens, or even thousands, of years back in time.
In this thesis, I first used skyline plots to infer historical demographic trends from genetic
data of a well-studied system, humans. Using this gold standard, my work revealed
detailed demographic profiles, but also identified issues relating to the way key methodological
assumptions are contravened. In Chapter 2 I present a discussion about the risk of
misinterpretation or overinterpretation in the context of Bayesian skyline plot (BSP) analysis.
Understanding that any single profile can be problematic, when moving to non-model
species, I chose to work as many species as possible. This approach exploits the recent
boom in sequencing projects that has generated a huge volume of publicly available data. By
building large, novel, multi-species datasets it becomes possible to construct profiles averaged
over many species with similar properties, such as habitat preference. The expectation is that
average profiles will prove better at capturing broad trends for the species they contain.
Collating and processing public domain data is not a trivial task. I therefore developed a
pipeline, now an R package, to access and compile sequence data for over 100 species of
bird, focusing on mitochondrial DNA (mtDNA). I found differences in the mean time of
population expansion after the ice age between bird species associated with different habitats.
However, notably, the demographic trends drawn from BSPs did not reveal a close match with
the amount of available habitat indicated by species distribution models. BSPs frequently
indicated population increases even though species’ habitat ranges were decreasing. These
results further emphasise the level of care needed when interpreting BSPs.
If genetic methods for demographic reconstruction are to be used extensively in the future,
it is important that we understand what confounding factors commonly exist in real world
populations so as to prevent misleading or inaccurate interpretations. To explore the impact of
historic range dynamics on BSPs I created a realistic spatial demographic model for a small
North American passerine, the yellow warbler (Setophaga petechia). From this I simulated
mtDNA sequences for a number of populations across the modern species’ range. With these
data I’d hoped to investigate how BSP profiles varied depending on local population history.
However, true demographic signals proved hard to capture and further work will be required
to explore my original question more fully.BBSRC DT
- …