Electric field requirements for charge packet generation and movement in XLPE

The formation of space charge packets in XLPE (Cross-linked polyethylene) tapes from unaged cable insulation has been studied utilising the pulsed electro-acoustic (PEA) technique. The 150 m thick sheets were studied under constant applied dc field of 120 kV/mm at a temperature of 20 C for a period of 48 hours. After an inception period of about 3.5 hours, during which heterocharge accumulates at the anode and increases the local field there, a sequence of positive charge packets were observed to transit the sample starting from near the anode. Calculation of the internal field showed that the packets required a field of 140 kV/mm for their initiation. Reduction of the applied field step-wise from 120 kV/mm to 80 kV/mm indicated that the charge packet would keep moving as long as the local field at its front exceeded 100 kV/mm, but with a reducing magnitude. A return to an applied field of 120 kV/mm confirmed that the local field required to initiate a new packet was in excess of 135 kV/mm. The results are discussed in terms of current theories of charge packet formation. The first packet appears to be a moving front of field ionisation. The generation of subsequent packets is governed by the field at the anode and the balance of charge injection and extraction process, which occur there. The nature of the negative charges produced at the ionisation front is not clear, but they are unlikely to be electrons

Temperature dependance of charge packet velocity in XLPE Cable peelings

The generation and transit of charge packets in 150μm thick peelings from the insulation of Medium Voltage Cables manufactured using the same XLPE batch have been investigated at a number of different temperatures. Charge packet motion was investigated in peelings taken from cables that have been electro-thermally stressed at T= 90 degrees C for 5000 hours with a Laplacian field E ≈ 20kV/mm at the location of the samples. It was found that charge packets were generated by an applied field of 120kV/mm when the internal space charge field reached 140-150kV/mm. Measurements were made in three controlled temperature environments and it was found that the transit time fitted an Arrhenius behaviour with an activation energy of ~1.2 eV. This value is similar to estimates made for the deepest traps (>1.1eV) made from the decay of space charge accumulated at lower fields of 46.67kVmm. It is also close to the activation energy for the conductivity (~1.25 eV) obtained from the dielectric spectroscopy of unpeeled cable sections at Erms ≈ 0.41 V/mm, and ~1.15eV from the dielectric spectroscopy of the peelings (E = 40V/mm). It is therefore concluded that the transit of the charge packet is associated with the trap-to-trap transport of charge carriers located in the deepest traps available. The implications of these results for the mechanism of charge packet generation is discussed

Mechanisms Underlying Weight Loss and Metabolic Improvements in Rodent Models of Bariatric Surgery

Obesity is a growing health risk with few successful treatment options and fewer still that target both obesity and obesity-associated comorbidities. Despite ongoing scientific efforts, the most effective treatment option to date was not developed from basic research but by surgeons observing outcomes in the clinic. Bariatric surgery is the most successful treatment for significant weight loss, resolution of type 2 diabetes and the prevention of future weight gain. Recent work with animal models has shed considerable light on the molecular underpinnings of the potent effects of these ‘metabolic’ surgical procedures. Here we review data from animal models and how these studies have evolved our understanding of the critical signalling systems that mediate the effects of bariatric surgery. These insights could lead to alternative therapies able to accomplish effects similar to bariatric surgery in a less invasive manner

Cooking in schools: Lessons from the UK

In the United Kingdom (UK), under successive governments, there have been many changes over the years on ‘cooking in schools’ policy, ranging from the removal of cooking from the curriculum to a promise from the current government to make cooking compulsory for all 11–14 year olds by 2011. This paper reports on the current activity around cooking in schools policy in the UK. It also looks at how previous approaches led to these activities and to changes in the school environment, and the problems associated with an un-coordinated approach to the introduction of cooking in schools

ACA chefs adopt a school: An evaluation

This document summarises an evaluation of a cooking in schools initiative called Chefs Adopt a School (CAAS) which is delivered by the Academy of Culinary Arts.1 At present, sessions are provided all over England from Cumbria to Cornwall subject to demand and resources (with a few sessions being delivered in Scotland too). Annually, 21,000 children take part in the initiative. Delivered by professional chefs, the programme aim is to teach children about food, food provenance, health, nutrition and cookery. The evaluation was informed by a rapid systematic review of the existing literature on cooking in schools. This research has been carried out at a time when cooking in schools is being put forward as a solution to improving diets and reducing obesity. It is currently the only evaluation of school cooking in the UK that measures outcomes that impact on health, such as: eating behaviour, cooking confidence and confidence asking for fruit, vegetables and ingredients at home. As such, it can inform future UK school cooking initiative interventions and evaluations. It also highlights the need to incorporate evaluation into school cooking initiatives, as findings provide valuable information necessary to fine tune an intervention. In the core programme, chefs link with local schools, usually primary, where they deliver 2-3 sessions to one year group within a school. This process is then repeated each year. Key issues covered include hygiene, healthy eating, an appreciation of food through the senses (particularly taste) and practical cooking/food preparation. The first session covers healthy eating and the sensory appreciation of food while the second and third sessions are practical

Passing networks in football: Selected Manchester United matches during the 2015-2016 season

The interactions between players during a football match can be recorded as a matrix of passes and visualised as a network diagram. The diagram provides semi-quantitative insight into the operation of the team as a whole, the functioning of units of the team (defence, midfield, attack) and the importance of individual players to team effort. In addition, in-depth quantitative analysis of patterns of team passing using network mathematics techniques has given insight into team dynamics (Clemente, Martins and Mendes, 2016) and some network parameters have been shown to be correlated with team performance in football (Clemente, Martins, Kalamaras, Wong and Mendes, 2015; Grund, 2012; Peña & Touchette, 2012). In the present study, passing networks were analysed using both informal and formal mathematical methods in an attempt to relate network parameters to the performance of an elite level team. Six national and international matches of Manchester United Football Club during the 2015-2016 season were annotated using Dartfish 10 software. The matches covered a range of team success in terms of match outcome. Account was taken of completed passes by players of the focus team, the pitch location of those passes, the context of passing in relation to opposition play and an enhanced set of match statistics. Data to be presented will relate informal and standard network measures (degree, centrality and modularity included) to match outcomes, unit performances and the influence of individual players, as supported in part by non-parametric statistics. The sensitivity of network parameters to errors in the recording of passes will be reported.This study highlights the potential and potential constraints of using network parameters in the analysis of performance of a football team

The relationship between charge distribution, charge packet formation and electroluminescence in XLPE under DC

Different reports describing the internal distribution of space charge in cross-linked polyethylene (XLPE) under DC field have been published recently. The most striking fact observed is the organization of the space charge into charge packets that cross the insulation. All models for charge packet formation imply that carrier recombination will occur. As the recombination region is potentially a luminescence one it is of interest to record the electroluminescence in this regime. This topic is addressed in this paper

The Bravyi-Kitaev transformation for quantum computation of electronic structure

Quantum simulation is an important application of future quantum computers with applications in quantum chemistry, condensed matter, and beyond. Quantum simulation of fermionic systems presents a specific challenge. The Jordan-Wigner transformation allows for representation of a fermionic operator by O(n) qubit operations. Here we develop an alternative method of simulating fermions with qubits, first proposed by Bravyi and Kitaev [S. B. Bravyi, A.Yu. Kitaev, Annals of Physics 298, 210-226 (2002)], that reduces the simulation cost to O(log n) qubit operations for one fermionic operation. We apply this new Bravyi-Kitaev transformation to the task of simulating quantum chemical Hamiltonians, and give a detailed example for the simplest possible case of molecular hydrogen in a minimal basis. We show that the quantum circuit for simulating a single Trotter time-step of the Bravyi-Kitaev derived Hamiltonian for H2 requires fewer gate applications than the equivalent circuit derived from the Jordan-Wigner transformation. Since the scaling of the Bravyi-Kitaev method is asymptotically better than the Jordan-Wigner method, this result for molecular hydrogen in a minimal basis demonstrates the superior efficiency of the Bravyi-Kitaev method for all quantum computations of electronic structure

Light-emitting diodes from polyfluorenes: characterisation and stability of performance

This thesis deals with polymer light-emitting diodes (LEDs) containing materials from the polyfluorene family, and investigates their behaviour when employed in device structures. A study of poly(9,9’-dioctylfluorene-co-bis-N,N’-(4-butylphenyl)-bis-N,N’-phenyl-1,4-phenylenediamine) (PFB) by photothermal deflection spectroscopy (PDS) shows that the polymer undergoes a doping reaction with poly(styrene sulphonic acid). This is important because the two materials are found in intimate contact in LED structures. The conditions for reaction are investigated, and it is proposed that the reacted states are directly responsible for the drive-induced degradation of LEDs containing these two materials. LEDs are studied which contain various combinations of poly(9,9’-dioctylfluorene-co-N-(4-butylphenyl)diphenylamine) (TFB) and poly(9,9’-dioctylfluorene-co-benzothiadiazole) (F8BT), using pulsed electroluminescence. A strongly morphology-dependent spike-transient is observed in the electroluminescence at turn-on, and this is investigated by numerical modelling. Although not all features of the system can be well represented in the model, the spike transient is explicitly predicted without the need to impose any special conditions. The origin of this feature is elucidated by repeatedly running the model to a range of end-points and studying the time-evolution of space-charge distributions which result. Finally, F8BT devices are considered on their own, in order to study the evolution of device performance under low-intensity electrical excitation. A phenomenon is investigated in which the quantum efficiency is dramatically increased during the early stages of driving. Ionic motions are ruled out, and the observations are attributed to the trapping of charge in the vicinity of the anode, leading to enhanced hole injection. The reverse-bias behaviour of the effect, in which a further enhancement is seen, is also examined. The analogy is made with polymer LEDs in general which increase in performance following a period of reverse bias, and it is suggested that the causes may be related

Metabolic Effects of Bariatric Surgery in Mouse Models of Circadian Disruption

Background/Objectives: Mounting evidence supports a link between circadian disruption and metabolic disease. Humans with circadian disruption (for example, night-shift workers) have an increased risk of obesity and cardiometabolic diseases compared with the non-disrupted population. However, it is unclear whether the obesity and obesity-related disorders associated with circadian disruption respond to therapeutic treatments as well as individuals with other types of obesity. Subjects/Methods: Here, we test the effectiveness of the commonly used bariatric surgical procedure, Vertical Sleeve Gastrectomy (VSG), in mouse models of genetic and environmental circadian disruption. Results: VSG led to a reduction in body weight and fat mass in both ClockΔ19 mutant and constant-light mouse models (PP\u3e0.05). Within circadian-disrupted models, VSG also led to improved glucose tolerance and lipid handling (P\u3c0.05). Conclusions: Together these data demonstrate that VSG is an effective treatment for the obesity associated with circadian disruption, and that the potent effects of bariatric surgery are orthogonal to circadian biology. However, as the effects of bariatric surgery are independent of circadian disruption, VSG cannot be considered a cure for circadian disruption. These data have important implications for circadian-disrupted obese patients. Moreover, these results reveal new information about the metabolic pathways governing the effects of bariatric surgery as well as of circadian disruption