UCL University College London Eprints
UCL Eprints collects the work of UCL researchers and makes it freely available over the web, helping the worldwide scholarly community to discover UCL research. Institutional repositories like UCL Eprints complement the traditional academic publishing and scholarly communications processes. They raise the visibility of research and help to maximise its impact. UCL researchers are encouraged to deposit a copy of each journal article, conference paper, working paper, and any other research output, in the UCL Eprints at the earliest opportunity, ensuring that their research reaches as wide an audience as possible.
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Computer simulations reveal complex distribution of haemodynamic forces in a mouse retina model of angiogenesis - Bernabeu, MO; Franco, CA; Jones, M; Nielsen, JH; Krüger, T; Nash, RW; Groen, D; Hetherington, J; Gerhardt, H; Coveney, PV
There is currently limited understanding of the role played by haemodynamic forces on the processes governing vascular development. One of many obstacles to be overcome is being able to measure those forces, at the required resolution level, on vessels only a few micrometres thick. In the current paper, we present an in silico method for the computation of the haemodynamic forces experienced by murine retinal vasculature (a widely used vascular development animal model) beyond what is measurable experimentally. Our results show that it is possible to reconstruct high-resolution three-dimensional geometrical models directly from samples of retinal vasculature and that the...
Clinical, genetic, neurophysiological and functional study of new mutations in episodic ataxia type 1 - Tomlinson, SE; Rajakulendran, S; Tan, SV; Graves, TD; Bamiou, D-E; Labrum, RW; Giunti, P; Kullmann, DM; Hanna, MG; Schorge, S; Burke, D; Sue, CM
Background and objective Heterozygous mutations in KCNA1 cause episodic ataxia type 1 (EA1), an ion channel disorder characterised by brief paroxysms of cerebellar dysfunction and persistent neuromyotonia. This paper describes four previously unreported families with EA1, with the aim of understanding the phenotypic spectrum associated with different mutations. Methods 15 affected individuals from four families underwent clinical, genetic and neurophysiological evaluation. The functional impact of new mutations identified in the KCNA1 gene was investigated with in vitro electrophysiology and immunocytochemistry. Results Detailed clinical documentation, dating back to 1928 in one family, indicates that all patients manifested episodic ataxia of varying...
Scour development through time: modelling scour in layered - Harris, JM; Whitehouse, RJS; Porter, K; Simons, RR
This paper describes the extension of an engineering model (Harris et al., 2010) developed to predict the time evolution of scour around a monopile in uniform granular soils in the marine environment to layered granular soils. The model is capable of looking at cylindrical, square and rectangular structures. It is capable of representing both the scouring and backfilling process and has been modified to incorporate the ability to predict the effect of scouring in layered soils making use of the results from recent experimental studies into scouring in non-uniform sediment beds. Output from the model is compared with the laboratory...
Framework for the construction of a Monte Carlo simulated brain PET-MR image database - Thomas, BA; Erlandsson, K; Bousse, A; Hutton, BF; Drobnjak, I; Pedemonte, S; Ourselin, S; Vunckx, K; Reilhac-Laborde, A
Simultaneous PET-MR acquisition reduces the possibility of registration mismatch between the two modalities. This facilitates the application of techniques, either during reconstruction or post-reconstruction, that aim to improve the PET resolution by utilising structural information provided by MR. However, in order to validate such methods for brain PET-MR studies it is desirable to evaluate the performance using data where the ground truth is known. In this work, we present a framework for the production of datasets where simulations of both the PET and MR, based on real data, are generated such that reconstruction and post-reconstruction approaches can be fairly compared....
A network theory analysis of football strategies - Peña, JL; Touchette, H
We showcase in this paper the use of some tools from network theory to describe the strategy of football teams. Using passing data made available by FIFA during the 2010 World Cup, we construct for each team a weighted and directed network in which nodes correspond to players and arrows to passes. The resulting network or graph provides a direct visual inspection of a team's strategy, from which we can identify play pattern, determine hot-spots on the play and localize potential weaknesses. Using different centrality measures, we can also determine the relative importance of each player in the game, the...
Coevolving Water Infrastructures for Adaptation to Climate Change in London - Teh, T
London’s water infrastructure has coevolved over centuries and has been used as a model for water infrastructure systems in modern cities around the world. However it is a system that is stretched to limit as evidenced by the need to build a desalination plant in the Thames estuary in order to secure supplies of freshwater; and ongoing problems with sewerage overflows into aquatic environments. The system will only come under further strain in the future as the population of London increases; and climate change alters rainfall patterns. It is also a system that inherently degrades aquatic environments, preventing it from...
Bypassing the Flush - Creating New Resources - Teh, T
The flush toilet is an illogical form of sanitation from the point of view of water conservation, nutrient recovery and water pollution. Places such as London, with one of the oldest flushing toilet and sewer systems in the world, bears witness to the limits of its universal applicability through dwindling freshwater resources and polluted waterways. It is therefore important to develop new forms of sanitation infrastructure. An actor-network theory co-evolution framework is used to explore and gain insights into the co-evolution pathways for new types and paradigms of santitation in London where waterborne sanitation is currently prevalent.
Diffusion imaging with stimulated echoes: signal models and experiment design - Alexander, DC; Dyrby, TB
Purpose: Stimulated echo acquisition mode (STEAM) diffusion MRI can be advantageous over pulsed-gradient spin-echo (PGSE) for diffusion times that are long compared to $\ttwo$. It is important therefore for biomedical diffusion imaging applications at 7T and above where $\ttwo$ is short. However, imaging gradients in the STEAM sequence contribute much greater diffusion weighting than in PGSE, but are often ignored during post-processing. We demonstrate here that this can severely bias parameter estimates. Method: We present models for the STEAM signal for free and restricted diffusion that account for crusher and slice-select (butterfly) gradients to avoid such bias. The butterfly gradients...
Melting curve of face-centered-cubic nickel from first-principles calculations - Pozzo, M; Alfe, D
The melting curve of Ni up to 100 GPa has been calculated using first-principles methods based on density functional theory (DFT). We used two complementary approaches: (i) coexistence simulations with a reference system and then free-energy corrections between DFT and the reference system, and (ii) direct DFT coexistence using simulation cells including 1000 atoms. The calculated zero pressure melting temperature is slightly underestimated at 1637±10 K (experimental value is 1728 K), and at high pressure is significantly higher than recent measurements in diamond-anvil cell experiments [ Phys. Rev. B 87 054108 (2013)]. The zero pressure DFT melting slope is calculated...
Prediction of Second Neurological Attack in Patients with Clinically Isolated Syndrome Using Support Vector Machines - Wottschel, V; Alexander, DC; Chard, DT; Miller, DH; Ciccarelli, O
The aim of this study is to predict the conversion from clinically isolated syndrome to clinically definite multiple sclerosis using support vector machines. The two groups of converters and non-converters are classified using features that were calculated from baseline data of 73 patients. The data consists of standard magnetic resonance images, binary lesion masks, and clinical and demographic information. 15 features were calculated and all combinations of them were iteratively tested for their predictive capacity using polynomial kernels and radial basis functions with leave-one-out cross-validation. The accuracy of this prediction is up to 86.4% with a sensitivity and specificity in...
Hepatitis C in men who have sex with men in London - a community survey - Price, H; Gilson, R; Mercey, D; Copas, A; Johnson, A; Hart, G; Parry, J; Nardone, A
Objectives: For the last 10 years there has been an epidemic of hepatitis C virus (HCV) infection in men who have sex with men (MSM) in Europe, North America and Australia. The majority of those infected are also HIV-positive and it is unclear to what extent HIV-negative MSM are also at increased risk of infection with HCV. This study provides the first examination of the association between HIV and hepatitis C serostatus in a sample of MSM recruited in community settings. Methods: A total of 1121 participants completed a short questionnaire in 2008/2009 giving demographic and behavioural data, and donated...
Geometric models of brain white matter for microstructure imaging with diffusion MRI - Panagiotaki, E
The research presented in this thesis models the diffusion-weighted MRI signal within brain white matter tissue. We are interested in deriving descriptive microstructure indices such as white matter axon diameter and density from the observed diffusion MRI signal. The motivation is to obtain non-invasive reliable biomarkers for early diagnosis and prognosis of brain development and disease. We use both analytic and numerical models to investigate which properties of the tissue and aspects of the diffusion process affect the diffusion signal we measure. First we develop a numerical method to approximate the tissue structure as closely as possible. We construct three-dimensional...