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"Entwistle, Christopher"
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Conjugated organic and organoboron materials
A series of compounds containing one or more dimesitylboryl groups (mesityl = 2,4,6-trimethylphenyl) has been synthesised. Triarylboranes were synthesised by reaction of dimesitylfluoroborane with an appropriate lithium reagent. Dimesitylvinyl boranes were synthesised by the hydroboration of an appropriate terminal alkyne with dimesitylborane. Compounds were characterised by standard analytical techniques, and investigated by single crystal X-ray diffraction, optical, thermal and electrochemical methods. The aim of the research was to determine whether such compounds might be useful in the field of organic electronics. In addition, the compound dimesitylborane has been investigated by NMR techniques, which have shown it to exist as a monomer 一 dimer equilibrium in solution, and the structure of the dimer in the solid state has been more accurately determined using neutron diffraction.
Dissertation
Electron paramagnetic resonance as a tool to determine the sodium charge storage mechanism of hard carbon
Hard carbon is a promising negative electrode material for rechargeable sodium-ion batteries due to the ready availability of their precursors and high reversible charge storage. The reaction mechanisms that drive the sodiation properties in hard carbons and subsequent electrochemical performance are strictly linked to the characteristic slope and plateau regions observed in the voltage profile of these materials. This work shows that electron paramagnetic resonance (EPR) spectroscopy is a powerful and fast diagnostic tool to predict the extent of the charge stored in the slope and plateau regions during galvanostatic tests in hard carbon materials. EPR lineshape simulation and temperature-dependent measurements help to separate the nature of the spins in mechanochemically modified hard carbon materials synthesised at different temperatures. This proves relationships between structure modification and electrochemical signatures in the galvanostatic curves to obtain information on their sodium storage mechanism. Furthermore, through ex situ EPR studies we study the evolution of these EPR signals at different states of charge to further elucidate the storage mechanisms in these carbons. Finally, we discuss the interrelationship between EPR spectroscopy data of the hard carbon samples studied and their corresponding charging storage mechanism.
Hard carbons are considered the most suitable negative electrode materials for Na-ion batteries. Here, authors use electron paramagnetic resonance spectroscopy to determine the spin nature of mechanochemically-modified hard carbons to predict their charge storage mechanism for sodium-ion batteries.
Journal Article
Asymptotic Duration for Optimal Multiple Stopping Problems
We study the asymptotic duration of optimal stopping problems involving a sequence of independent random variables that are drawn from a known continuous distribution. These variables are observed as a sequence, where no recall of previous observations is permitted, and the objective is to form an optimal strategy to maximise the expected reward. In our previous work, we presented a methodology, borrowing techniques from applied mathematics, for obtaining asymptotic expressions for the expectation duration of the optimal stopping time where one stop is permitted. In this study, we generalise further to the case where more than one stop is permitted, with an updated objective function of maximising the expected sum of the variables chosen. We formulate a complete generalisation for an exponential family as well as the uniform distribution by utilising an inductive approach in the formulation of the stopping rule. Explicit examples are shown for common probability functions as well as simulations to verify the asymptotic calculations.
Journal Article
AN OVERVIEW OF THE 2010 HAZARDOUS WEATHER TESTBED EXPERIMENTAL FORECAST PROGRAM SPRING EXPERIMENT
The NOAA Hazardous Weather Testbed (HWT) conducts annual spring forecasting experiments organized by the Storm Prediction Center and National Severe Storms Laboratory to test and evaluate emerging scientific concepts and technologies for improved analysis and prediction of hazardous mesoscale weather. A primary goal is to accelerate the transfer of promising new scientific concepts and tools from research to operations through the use of intensive real-time experimental forecasting and evaluation activities conducted during the spring and early summer convective storm period. The 2010 NOAA/HWT Spring Forecasting Experiment (SE2010), conducted 17 May through 18 June, had a broad focus, with emphases on heavy rainfall and aviation weather, through collaboration with the Hydrometeorological Prediction Center (HPC) and the Aviation Weather Center (AWC), respectively. In addition, using the computing resources of the National Institute for Computational Sciences at the University of Tennessee, the Center for Analysis and Prediction of Storms at the University of Oklahoma provided unprecedented real-time conterminous United States (CONUS) forecasts from a multimodel Storm-Scale Ensemble Forecast (SSEF) system with 4-km grid spacing and 26 members and from a 1-km grid spacing configuration of the Weather Research and Forecasting model. Several other organizations provided additional experimental high-resolution model output. This article summarizes the activities, insights, and preliminary findings from SE2010, emphasizing the use of the SSEF system and the successful collaboration with the HPC and AWC.
Journal Article
On Asymptotics of Optimal Stopping Times
We consider optimal stopping problems, in which a sequence of independent random variables is drawn from a known continuous density. The objective of such problems is to find a procedure which maximizes the expected reward. In this analysis, we obtained asymptotic expressions for the expectation and variance of the optimal stopping time as the number of drawn variables became large. In the case of distributions with infinite upper bound, the asymptotic behaviour of these statistics depends solely on the algebraic power of the probability distribution decay rate in the upper limit. In the case of densities with finite upper bound, the asymptotic behaviour of these statistics depends on the algebraic form of the distribution near the finite upper bound. Explicit calculations are provided for several common probability density functions.
Journal Article
The value of different aspects of person-centred care: a series of discrete choice experiments in people with long-term conditions
ObjectiveTo measure the value the patients place on different aspects of person-centred care.DesignWe systematically identified four attributes of person-centred care. We then measured their value to 923 people with either chronic pain or chronic lung disease over three discrete choice experiments (DCEs) about services to support self-management. We calculated the value of each attribute for all respondents and identified groups of people with similar preferences using latent class modelling.SettingDCEs conducted online via a commercial survey company.ParticipantsAdults with either chronic pain (two DCEs, n=517 and 206, respectively) or breathlessness due to chronic respiratory disease (n=200).ResultsParticipants were more likely to choose services with higher level person-centred attributes. They most valued services that took account of a person’s current situation likelihood of selection increased by 16.9% (95% CI=15.4 to 18.3) and worked with the person on what they wanted to get from life (15.8%; 14.5 to 17.1). More personally relevant information was valued less than these (12.3%; 11.0 to 13.6). A friendly and personal communicative style was valued least (3.8%; 2.7 to 4.8). Latent class models indicated that a substantial minority of participants valued personally relevant information over the other attributes.ConclusionThis is the first study to measure the value patients place on different aspects of person-centred care. Professional training needs to emphasise the substance of clinical communication—working responsively with individuals on what matters to them—as well as the style of its delivery.
Journal Article
Ultra-stable speckle-based optical fiber sensing demonstrated on an uncrewed aerial vehicle platform
Speckle-pattern interrogation offers a route to high-resolution spectral sensing, but its uptake has been constrained by poor temporal stability under real-world conditions. Here, we introduce an ultra-stable speckle-based architecture that overcomes these limitations and enables real-time structural health monitoring of uncrewed aerial vehicles. Unlike conventional approaches that rely on large-scale, free-space passive speckle decorrelation, our system utilizes an ultra-compact speckle pattern via laser-written scattering centers in a high aspect ratio flat fiber, encapsulated within a 3D-printed polylactide housing. This architecture suppresses environmental drift and enables robust, high-fidelity interrogation of fiber Bragg gratings in dynamic aerospace conditions. The system demonstrated exceptional stability under sustained mechanical excitation, maintaining measurement integrity at ±7 G sinusoidal acceleration along the axial direction. Furthermore, in-flight validation across uncrewed aerial vehicle flight tests confirmed real-time strain interrogation in the −100–400 µε range with a standard deviation in measurement of 1.63 µε. These results mark the demonstration of stable, real-time speckle-based interrogation in flight, establishing a path toward broader deployment of specklemeters in harsh environments.
Przemyslaw Falak and colleagues report optical speckle–based fiber sensing demonstrated outside the lab on a drone under vibration and environmental disturbance. The study shows specklemeter technology can support structural monitoring of real-world aerospace systems
Journal Article