Scale-up of oscillatory flow mixing

Oscillatory Flow Mixing is a recent development in mixing technology which has evolved over the past decade. It has a number of similarities to other mixing technologies, particularly pulsed and reciprocating plate columns, but at the laboratory scale has demonstrated a number of advantageous properties. These properties (such as control of residence time distribution, improved heat transfer and predictable mixing times) have been demonstrated at the laboratory scale for a wide range of different potential applications, but until now there has been a lack of firm understanding and research into how the technology could be scaled-up into an industrial scale process. This thesis addresses the problem of scale-up in Oscillatory Flow Mixing. It reports on a programme of experiments on geometrically scaled apparatus with the measurement of residence time distributions and flow visualisation as the principal methods of investigating the wide range of flow conditions that can be achieved by control of net flow and of oscillatory conditions. Results from these investigations are interpreted as axial dispersion coefficients and also compared with results obtained computationally using a fluid mechanics approach to simulate flow fields and the injection of inert tracers into those flow fields. Significant clarification is reported concerning the analysis of axial dispersion measurements using the diffusion model for which conflicting solutions were identified in the literature. The development of a flow visualisation technique using fluorescent dye streaklines is also reported. Using the latter technique stable manifolds in Oscillatory Flow Mixing have for the first time been experimentally observed as well as a range of other flow regimes. The study of scale-up was extended by the successful construction and investigation of an alternative reactor geometry with the potential for use in large-scale plant. From the work presented in the thesis it is concluded that Oscillatory Flow Mixing is a technology which in general lends itself readily to scaling-up from laboratory to pilot plant scale, and most probably to industrial scale. Experiments performed on small laboratory apparatus (containing less than one litre of fluid) can with confidence be used to predict mixing behaviour in much larger plant (containing hundreds of litres of fluid.

Evolutionary Divergence in Developmental Strategies and Neuromodulatory Control Systems of Two Amphibian Locomotor Networks

Attempts to understand the neural mechanisms which produce behaviour must consider both prevailing sensory cues and the central cellular and synaptic changes they direct. At each level, neuromodulation can additionally shape the final output. We have investigated neuromodulation in the developing spinal motor networks in hatchling tadpoles of two closely related amphibians, Xenopus laevis and Rana temporaria to examine the subtle differences in their behaviours that could be attributed to their evolutionary divergence. At the point of hatching, both species can swim in response to a mechanosensory stimulus, however Rana embryos often display a more forceful, non-locomotory coiling behaviour. Whilst the synaptic drive that underlies these behaviours appears similar, subtle inter-specific differences in neuronal properties shape motor outputs in different ways. For example, Rana neurons express N-methyl-D-aspartate (NMDA)/serotonin (5-HT)-dependent oscillations, not present in hatchling Xenopus and many also exhibit a prominent slow spike after-hyperpolarisation. Such properties may endow the spinal circuitry of Rana with the ability to produce a more flexible range of outputs. Finally, we compare the roles of the neuromodulators 5-HT, noradrenaline (NA) and nitric oxide (NO) in shaping motor outputs. 5-HT increases burst durations during swimming in both Xenopus and Rana, but 5-HT dramatically slows the cycle period in Rana with little effect in Xenopus. Three distinct, but presumably homologous NO-containing brainstem clusters of neurons have been described, yet the effects of NO differ between species. In Xenopus, NO slows and shortens swimming in a manner similar to NA, yet in Rana NO and NA elicit the non-rhythmic coiling pattern

The role of glucagon in health and disease

The construction of a reliable immunoassay method for glucagon has formed the basis of this thesis. The major factor in the building of a good assay was the recognition of the susceptibility of glucagon to attack by proteolytic enzymes, a fact which at first escaped the notice of earlier investigators. Trasylol, a proteolytic enzyme inhibitor, has proved to be an efficient means to prevent this enzyme degradation. The assay was able to detect as little as 20 mug. of glucagon. The application of the assay to measurement of immunoreactive glucagon (IRG) in tissues and body fluids, revealed that IRG was not only present in the pancreas but was also detected in much of the alimentary tract, mainly the small and Yarge intestines. It was apparent also that circulating IRG was derived from both enteric and pancreatic sources. Clearance studies of glucagon showed that glucagon disappeared rapidly from the body and that the liver was a major site for the degradation of glucagon. No difference in the clearances of enteric and pancreatic glucagons was noted. However immunological differences appeared to be present between the enteric and pancreatic glucagons, enteric glucagon reacting less strongly with glucagon antibody than pancreatic glucagon. When assessing the factors which might affect the release of glucagon, consideration had to be given to the factors cited above which would complicate the studies. It was realised that an assessment of factors affecting the release of glucagon from both the pancreas and gut would have to be undertaken separately. A direct assessment of factors affecting the pancreatic release of glucagon was made possible by the application of of a method for isolating the islets of Langerhans of rat pancreas. Additional use was made of dogs with venous catheters situated in pancreatic and gut veins, so that a separate measurement of IRG changes from blood draining the pancreas and gut could be made. Studies of animals in whom the pancreas was removed were also made, in order that factors affecting gut IRG release could be assessed, in the absence of the pancreas. It was realised also that studies of peripheral circulating IRG levels may fail to record changes in gut and pancreatic IRG secretion as much of the IRG would be removed in its passage through the liver. Thus many of the measurements of IRG were done in pancreatic, jejunal, colonic or portal blood prior to its passage through the liver. Wherever possible experiments were duplicated both by "in vitro" pancreatic islet studies, and "in vivo" dog or human studies, in order that observations could be confirmed by different approaches. Because of certain already established pharmacological actions of glucagon on carbohydrate metabolism, the effect of changing glucose concentrations on glucagon release was first of all studied. IRG secretion from the pancreas was found to increase during acute hypoglycaemia whereas no effect was noted on gut IRG secretion. Hyperglycaemia in contrast inhibited IRG secretion from the pancreas but once again had no effect on gut IRG secretion. Oral glucose did, however, stimulate gut IRG release but did not influence pancreatic IRG release. A study of the effect of the enteric hormones on IRG release was made, because of previous reports of the effect of these hormones on insulin release. Pancreozymin was found to exert a potent effect on both IRG and insulin release from the pancreas, although they had no effect on IRG release/ release from the gat. Secretin and gastrin did not however possess any IRG releasing properties from either gut or pancreas. It was considered probable that glucagon might be an important hormone in the control of the metabolic changes during starvation particularly through its phaimacological actions on gluconeogenesis and lipolysis. However contrary to this hypothesis, circulating levels of IRG were found to fall during starvation in human subjects. That this fall might be due to diminished pancreatic IRG secretion was suggested by the finding that the release of IRG from pancreatic islets of starved rats was also reduced. (Abstract shortened by ProQuest.)

Controlled Thiol-ene Polymer Microsphere Production Using a Low-Frequency Acoustic Excitation Coaxial Flow Method

A novel technique for the production of thiol-ene microspheres using acoustic resonance and coaxial flow is reported. The method utilizes low-frequency acoustically driven mechanical perturbations to disrupt the flow of a thiol-ene liquid jet, resulting in small thiol-ene droplets that are photochemically polymerized to yield thiol-ene microspheres. Tuning of the frequency, amplitude, and monomer solution viscosity are critical parameters impacting the diameter of the microspheres produced. Characterization by optical microscopy, scanning electron microscopy, and dynamic light scattering reveal microspheres of diameters \u3c10 mu m, with narrow particle distributions. (C) 2016 Elsevier Ltd. All rights reserved

Pipeline comparisons of convolutional neural networks for structural connectomes: predicting sex across 3,152 participants

With several initiatives well underway towards amassing large and high-quality population-based neuroimaging datasets, deep learning is set to push the boundaries of what is possible in classification and prediction in neuroimaging studies. This includes those that derive increasingly popular structural connectomes, which map out the connections (and their relative strengths) between brain regions. Here, we test different Convolutional Neural Network (CNN) models in a benchmark sex prediction task in a large sample of N=3,152 structural connectomes acquired from the UK Biobank, and compare results across different connectome processing choices. The best results (76.5% test accuracy) were achieved using Fractional Anisotropy (FA) weighted connectomes, without sparsification, and with a simple weight normalisation through division by the maximum FA value. We also confirm that for structural connectomes, a Graph CNN approach, the recently proposed BrainNetCNN, outperforms an image-based CNN

Vegetation and environmental patterns on soils derived from Hawkesbury Sandstone and Narrabeen substrata in Ku-ring-gai Chase National Park, New South Wales

[Abstract]: The vegetation patterns in the Central Coast region of New South Wales have been extensively studied with respect to single environmental variables, particularly soil nutrients. However, few data are available on the effects of multiple environmental variables. This study examines the relationships between vegetation and multiple environmental variables in natural vegetation on two underlying rock types, Hawkesbury sandstone and Narrabeen group shales and sandstones, in Ku-ring-gai Chase National Park, Sydney. Floristic composition and 17 environmental factors were characterized using duplicate 500 m2 quadrats from fifty sites representing a wide range of vegetation types. The patterns in vegetation and environmental factors were examined through multivariate analyses: indicator species analysis was used to provide an objective classification of plant community types, and the relationships between vegetation and environmental factors within the two soil types were examined through indirect and direct gradient analyses. Eleven plant communities were identified, which showed strong agreement with previous studies. The measured environmental factors showed strong correlations with vegetation patterns: within both soil types, the measured environmental variables explained approximately 32 - 35% of the variation in vegetation. No single measured environmental variable adequately described the observed gradients in vegetation; rather, vegetation gradients showed strong correlations with complex environmental gradients. These complex environmental gradients included nutrient, moisture and soil physical and site variables. These results suggest a simple 'nutrient' hypothesis regarding vegetation patterns in the Central Coast region is inadequate to explain variation in vegetation within soil types