Density regulation in strictly metric-free swarms

There is now experimental evidence that nearest-neighbour interactions in flocks of birds are metric free, i.e. they have no characteristic interaction length scale. However, models that involve interactions between neighbours that are assigned topologically are naturally invariant under spatial expansion, supporting a continuous reduction in density towards zero, unless additional cohesive interactions are introduced or the density is artificially controlled, e.g. via a finite system size. We propose a solution that involves a metric-free motional bias on those individuals that are topologically identified to be on an edge of the swarm. This model has only two primary control parameters, one controlling the relative strength of stochastic noise to the degree of co-alignment and another controlling the degree of the motional bias for those on the edge, relative to the tendency to co-align. We find a novel power-law scaling of the real-space density with the number of individuals N as well as a familiar order-to-disorder transition

An integrated approach to microalgae biomass generation and processing

Liquid combustible fossil fuel empowers global society, yet is a non-renewable entity with time-constrained limits to supply. Advanced generation biofuel derived from microalgae could feasibly yield more than conventional biofuel crops, utilise non-agricultural land or the sea and remediate atmospheric carbon dioxide and anthropogenic waste. However, technical and economical limits have so far prevented the successful implementation of microalgae biofuels. This thesis exemplifies how apparently disconnected technologies are able to become united in their provision for the growth and processing of microalgae. In so doing, it employs unique experimental methodology which unites inter- disciplinary themes with the proposition to cultivate and process microalgae biomass in a manner which has never been done before. The novelty of this endeavour presents a unique set of challenges, reasoning and results with implications for future creative research and investigation. The philosophical approach to conception and achievement of the laboratory work intercedes with entirely new methodology. Selected examples of such methodology follow. In chapter 3, a newly developed bio-composite gel disk was processed aligning a new design of apparatus for a geotextile puncture resistance test. In chapter 3, a novel formulation for harvesting microalgae is described. In chapter 5, a modified methodology of the preceding chapter is used to investigate seawater ion remediation via ionic and density phase separation. Chapter 6 integrates waste components from 5 different industries, namely dairy farming, anaerobic digestion, brewing, steel slag aggregates and coal power combustion with no previously known unification of such technologies in scientific literature. Chapter 7 assesses the lipid quality of biomass harvested by the novel formulation of chapter 3, before and after exposure to hydrothermal liquefaction. Chapter 8 extrapolates findings from the thesis to define an economic appraisal and suggest a cost saving process

The membrane bound phosphatidic add phosphatase from avocado

Phosphatidate Phosphatase (EC 3.1.3.4) is an important enzyme in plant lipid metabolism as it lies at a theoretical branchpoint between phospholipid and triacylglycerol biosyntheses. Since it's identification in 1955, it has received very little attention in plant lipid research. Previous studies reported in the literature have been limited to the use of crude plant cell extracts, making an accurate evaluation of the data difficult. The enzyme was characterised and purified to homogeneity from the microsomes of maturing avocado fruit, for the first time from any plant source. The novel procedure utilised detergent solubilisation in CHAPS, followed by anion exchange and Affi-Gel Blue chromatography, ammonium sulphate precipitation and Phenyl Superose chromatography. The enzyme had a subunit molecular mass, as determined by SDS-PAGE of 49kDa. Gel filtration studies revealed it was monomeric. Enzyme activity had a pH optimum of 6.0, was insensitive to N- ethylmaleimide and was stimulated by Mg(^2+). The homogenous enzyme was examined for the ability to hydrolyse sn-1,2- dioleoylglycerol-3-phosphate(PA), sn-1 -oleoylglycerol-3 -phosphate(LPA), sn-2- oleoylglycerol-3-phosphate, ceramide-1-phosphate and p-nitrophenylphosphate. All substrates were used, but the apparent V(_MAX) values for PA and LPA were considerably higher than the other substrates tested. The Michaelis-Menten kinetic model of enzyme catalysis was found to be inappropriate as the surface active enzyme was shown to be dependent on the bulk and surface concentration of the substrate in Triton X-100 mixed micelles. The surface dilution kinetic model was used to study PA and LPA hydrolysis. LPA was a better substrate and was also a potent competitive inhibitor of PA hydrolysis. Considering the specificities of the other enzymes in triacylglycerol biosynthesis, this premature dephosphorylation of LPA would prevent triacylglycerol formation. These findings possibly indicate that strict metabolic channelling is in operation with very low steady state concentrations of LPA with respect to PA, thus preventing any interaction with LPA in vivo

The Role of Projection in the Control of Bird Flocks

Swarming is a conspicuous behavioural trait observed in bird flocks, fish shoals, insect swarms and mammal herds. It is thought to improve collective awareness and offer protection from predators. Many current models involve the hypothesis that information coordinating motion is exchanged between neighbors. We argue that such local interactions alone are insufficient to explain the organization of large flocks of birds and that the mechanism for the exchange of long-ranged information necessary to control their density remains unknown. We show that large flocks self-organize to the maximum density at which a typical individual is still just able to see out of the flock in many directions. Such flocks are marginally opaque - an external observer can also just still see a substantial fraction of sky through the flock. Although seemingly intuitive we show that this need not be the case; flocks could easily be highly diffuse or entirely opaque. The emergence of marginal opacity strongly constrains how individuals interact with each other within large swarms. It also provides a mechanism for global interactions: An individual can respond to the projection of the flock that it sees. This provides for faster information transfer and hence rapid flock dynamics, another advantage over local models. From a behavioural perspective it optimizes the information available to each bird while maintaining the protection of a dense, coherent flock.Comment: PNAS early edition published online at http://www.pnas.org/cgi/doi/10.1073/pnas.140220211

A Reinforcement Learning Approach for Robotic Unloading from Visual Observations

In this work, we focus on a robotic unloading problem from visual observations, where robots are required to autonomously unload stacks of parcels using RGB-D images as their primary input source. While supervised and imitation learning have accomplished good results in these types of tasks, they heavily rely on labeled data, which are challenging to obtain in realistic scenarios. Our study aims to develop a sample efficient controller framework that can learn unloading tasks without the need for labeled data during the learning process. To tackle this challenge, we propose a hierarchical controller structure that combines a high-level decision-making module with classical motion control. The high-level module is trained using Deep Reinforcement Learning (DRL), wherein we incorporate a safety bias mechanism and design a reward function tailored to this task. Our experiments demonstrate that both these elements play a crucial role in achieving improved learning performance. Furthermore, to ensure reproducibility and establish a benchmark for future research, we provide free access to our code and simulation

Emergent behavioural phenotypes of swarming models revealed by mimicking a frustrated anti-ferromagnet

Self-propelled particle (SPP) models are often compared with animal swarms. However, the collective animal behaviour observed in experiments often leaves considerable unconstrained freedom in the structure of a proposed model. Essentially, multiple models can describe the observed behaviour of animal swarms in simple environments. To tackle this degeneracy, we study swarms of SPPs in non-trivial environments as a new approach to distinguish between candidate models. We restrict swarms of SPPs to circular (periodic) channels where they polarize in one of two directions (like spins) and permit information to pass through windows between neighbouring channels. Co-alignment between particles then couples the channels (anti-ferromagnetically) so that they tend to counter-rotate. We study channels arranged to mimic a geometrically frustrated anti-ferromagnet and show how the effects of this frustration allow us to better distinguish between SPP models. Similar experiments could therefore improve our understanding of collective motion in animals. Finally, we discuss how the spin analogy can be exploited to construct universal logic gates, and therefore swarming systems that can function as Turing machines

Changes in objectively measured BMI in children aged 4-11 years: Data from the National Child Measurement Programme

© 2015 The Author 2015. Published by Oxford University Press on behalf of Faculty of Public Health. All rights reserved. For permissions, please e-mail: [email protected]. Background This study looked at the degree of weight gain between the first (Reception) and last year (Year 6) of primary school and how weight status in Reception predicts becoming overweight/obese by Year 6. Methods A longitudinal sample of 1863 children was created using two time points (2006/7, 2012/13) from the National Child Measurement Programme (NCMP) in South Gloucestershire. T-test and logistic regression were used to test the difference between the BMI z-scores and BMI percentiles, and predict the probability of being overweight (BMI ≥ 85th) or obese (≥95th) at Year 6 based on BMI percentile in Reception. Results Of those children who were obese at Reception age, 68% were obese at Year 6. Compared with children with a BMI in the 2nd to 49th percentile range, children between the 75th and 84th percentiles of BMI at Reception age were 10 times more likely (odds ratio (OR) = 10.18, P < 0.01), and those with a BMI between the 85th and 94th percentiles were 13 times more likely (OR = 13.38, P < 0.01), to become obese by Year 6. Boys were more likely than girls to revert to a healthy weight. Conclusions This is the first study to link data from the NCMP. It provides estimates of prevalence and offers new evidence on obesity emergence and gender differences

Distributed Recycling Waste Polymer into RepRap Feedstock

Purpose – A low-cost, open source, self-replicating rapid prototyper (RepRap) has been developed, which greatly expands the potential user base of rapid prototypers. The operating cost of the RepRap can be further reduced using waste polymers as feedstock. Centralized recycling of polymers is often uneconomic and energy intensive due to transportation embodied energy. The purpose of this paper is to provide a proof of concept for high-value recycling of waste polymers at distributed creation sites. Design/methodology/approach – Previous designs of waste plastic extruders (also known as RecycleBots) were evaluated using a weighted evaluation matrix. An updated design was completed and the description and analysis of the design is presented including component summary, testing procedures, a basic life cycle analysis and extrusion results. The filament was tested for consistency of density and diameter while quantifying electricity consumption. Findings – Filament was successfully extruded at an average rate of 90 mm/min and used to print parts. The filament averaged 2.805mm diameter with 87 per cent of samples between 2.540mm and 3.081 mm. The average mass was 0.564 g/100mm length. Energy use was 0.06 kWh/m. Practical implications – The success of the RecycleBot further reduces RepRap operating costs, which enables distributed in-home, value added, plastic recycling. This has implications for municipal waste management programs, as in-home recycling could reduce cost and greenhouse gas emissions associated with waste collection and transportation, as well as the environmental impact of manufacturing custom plastic parts. Originality/value – This paper reports on the first technical evaluation of a feedstock filament for the RepRap from waste plastic material made in a distributed recycling device

Quantum gate optimisation in stoichiometric rare-earth ensembles

This thesis is an investigation into implementing quantum computing in stoichiometric rare-earth systems, with the crystal EuCl3 6D2O used as an example system. In a stoichiometric satellite system, a crystal stoichiometric in one rare-earth species is doped with a second rare-earth. The ions around a dopant experience shifts in their optical and hyperfine transition frequencies uniquely determined by their location relative to the dopant. This creates an ensemble of identical spin clusters with strong and consistent local interactions between ions in spin clusters. Ensembles of ions in the unique positions around the dopant can be used as qubits, enabling the creation of small quantum systems of 5-10 high-quality qubits for use in a small quantum processor. This thesis investigates the conditions necessary for implementation of a quantum processor in EuCl3 6D2O and other stoichiometric rare-earth systems. The primary factors explored in this thesis are the manipulation of system parameters and the implementation and optimisation of quantum gates in EuCl3 6D2O to minimise gate error. The quantum gate error of EuCl3 6D2O with Gaussian pulse shapes was first explored. It was determined that the oscillator strengths of EuCl3 6D2O are too unequal to be able to perform low error quantum operations at zero-field. The use of applied magnetic fields to manipulate the oscillator strengths and hyperfine splittings of EuCl3 6D2O was explored. It was found that broad magnetic field regions exist in which the parameters of EuCl3 6D2O can be manipulated to be closer to an ideal L system. Through the application of an 8T field, it was found that a three-qubit bit-flip error correction sequence could potentially be implemented with an error as low as 0.022. The optimisation of the optical pulses used to perform quantum gates in EuCl3 6D2O was investigated. It was determined that standard Gaussian pulses were sufficient to perform gates of a sufficiently low error for quantum error correction. Simulations of a NOT gate on an inhomogeneously broadened ensemble were performed with both a compensated pulse sequence and direct rotations. It was determined that compensated pulses do not reduce gate error over direct pulses in EuCl3 6D2O. The use of arbitrary pulse shapes was investigated and it was determined that a reduction of approximately 37% in gate error could be achieved by using optimised pulses of arbitrary shape. It was determined that the quantum gate error in europium systems is fundamentally limited by the size of the europium hyperfine splittings relative to the optical coherence time. The rare-earth species erbium and holmium were proposed for computing due to their large hyperfine structure, and it was established that there is potential for up to a 100-fold reduction in quantum gate error by moving to these host ions