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X-ray thermal diffuse scattering as a texture-robust temperature diagnostic for dynamically compressed solids
Get PDFWe present a model of x-ray thermal diffuse scattering (TDS) from a cubic polycrystal with an arbitrary crystallographic texture, based on the classic approach of Warren [B. E. Warren, Acta Crystallogr. 6, 803 (1953)]. We compare the predictions of our model with femtosecond x-ray diffraction patterns gathered from ambient and dynamically compressed rolled copper foils obtained at the High Energy Density instrument of the European X-Ray Free-Electron Laser facility and find that the texture-aware TDS model yields more accurate results than does the conventional powder model owed to Warren. Nevertheless, we further show: with sufficient angular detector coverage, the TDS signal is largely unchanged by sample orientation and in all cases strongly resembles the signal from a perfectly random powder; shot-to-shot fluctuations in the TDS signal resulting from grain-sampling statistics are at the percent level, in stark contrast to the fluctuations in the Bragg-peak intensities (which are over an order of magnitude greater); and TDS is largely unchanged even following texture evolution caused by compression-induced plastic deformation. We conclude that TDS is robust against texture variation, making it a flexible temperature diagnostic applicable just as well to off-the-shelf commercial foils as to ideal powders
A market resilient data-driven approach to option pricing
Get PDFIn this paper, we present a data-driven ensemble approach for option price prediction whose derivation is based on the no-arbitrage theory of option pricing. Using the theoretical treatment, we derive a common representation space for achieving domain adaptation. Through a specific scaling, suitable for financial time series data, we obtain a feature representation that is indistinguishable for samples coming from different domains. This provides an advantage over conventional models when predicting atypical out-of-sample test data. The success of an implementation of this idea is shown using some real market data. The root mean squared error in prediction turns out to be less than one-third of that for the benchmark model. We further report several experimental results for critically examining the predictive performance of the derived pricing models
The Matrix of Support: How to Build a Structure of Support for Meaningful Participation and Leadership in a Research Project
Get PDFThe Matrix of Support provides details of how the 'No Research About Us, Without Us: Removing Research Barriers for People with Learning Disabilities' project created a structure of support to provide the scaffolding that allowed our team members with learning disabilities to [1] contribute to the strategic direction and aims of the project, [2] inform the design of the project activities, [3] shape the delivery of the project's meetings and decision making processes, [4] prepare for the team meetings to contribute meaningfully and [5] reflect on the way the project was being run and make suggestions for changes. An evaluation of the implementation of this tool can be found in the project report. The Matrix of Support was designed by the project team in the early stages of the project to outline an agreement on how we wanted to work. We hope that teams who intend to conduct research, or conduct consultation with people with a learning disability, find the illustration of the steps we took useful to think about how to plan and cost for meaningful inclusion; because it takes time and resources if you want to get it right
Interpolation and/as Interpretation in the Early Manuscript Tradition of Dante's Commedia
No full textCritical climate geographies
Get PDFClimate change has long been a concern for geographers. Yet in recent years, the relationship between the discipline of human geography and the topic of climate change has evolved. Reflecting this, an especially vibrant area of scholarship is the consolidating field of ‘critical climate geographies’: a field that not only examines the spatial and temporal dimensions of climate change, but also the social, political, economic, and cultural structures that underpin its impacts and governance. This paper considers the present and future role of critical climate change research in geography, both within the discipline and within climate scholarship more broadly
In Silico Polymerisation and Characterisation of Auxetic Liquid Crystalline Elastomers Using Atomistic Molecular Dynamics Simulations
Get PDFUsing reactive atomistic molecular dynamics, we simulate the network formation and bulk properties of chemically identical liquid crystal elastomers (LCEs) and isotropic elastomers. The nematic elastomer is from a family of materials that have been shown to be auxetic at a molecular level. The network orientational order parameters and glass transition temperatures measured from our simulations are in strong agreement with experimental data. We reproduce, in silico, the magnitude and onset of strain-induced nematic order in isotropic simulations. Application of uniaxial strain to nematic LCE simulations causes biaxial order to emerge, as has been seen experimentally for these auxetic LCEs. At strains of ~1.0, the director reorients to be parallel to the applied strain, again as seen experimentally. The simulations shed light on the strain-induced order at a molecular level and allow insight into the individual contributions of the side-groups and crosslinker. Further, the agreement between our simulations and experimental data opens new possibilities in the computational design of high-molecular-weight liquid crystals, especially where an understanding of the properties under mechanical actuation is desired. Moreover, the simulation methodology we describe will be applicable to other combinations of orientational and/or positional order (e.g., smectics, cubics)
Modelling the calendering process of lithium-ion battery electrodes using the Discrete Element Method (DEM)
Get PDFThe electrochemical performance of a lithium-ion battery is strongly influenced by the microstructure of its electrode. A dried electrode consists of the active material (AM) particles and carbon-binder domain (CBD) phase. One of the important steps in electrode manufacturing is ‘calendering’, where a dried electrode is compressed between heated rollers to obtain a mechanically stable and uniform structure. The effect of calendering pressure on the porosity, tortuosity, and coordination number of an electrode is studied well using DEM. However, a thorough mathematical understanding of the compaction behavior of Li-ion battery electrodes remains largely unexplored.
In the present work, we aim to understand the compression behaviour of an electrode using DEM simulations. The simulation domain consists of spherical particles of varying sizes, representing the AM particles. The initial positions, shapes and sizes of the AM are obtained experimentally via XCT [1]. The domain is periodic in the lateral direction, with a moving top wall and a fixed bottom wall. Particle interactions are modelled using Edinburg elasto-plastic adhesive (EEPA) and bond-model, where the bond model captures the mechanical response of CBD phase. Simulations are performed on Altair EDEM.
It is shown that porosity and tortuosity obtained from the simulation data are well within the range of experimental values. The pressure-compression behaviour of the simulated structure closely aligns with the powder compaction behaviour described by the Kawakita equation
Assessing what matters most in older emergency department patients
Get PDFBackground
Older emergency patients have complex health needs and diverse personal priorities not captured by traditional single-disease approaches. Asking ‘what matters most’ may facilitate a more patient-centred approach. However, conceptual frameworks to document patient values have neither been implemented nor operationalised for use in the emergency department (ED).
Objective
To investigate the feasibility of asking ‘what matters most’ in the ED, assess patient priorities and determine the utility of a conceptual framework for documenting these.
Methods
Prospective, observational study in a Swiss ED with consecutive patients aged ≥65 years. Feasibility was determined as proportion of included patients to eligible patients. Patient responses were categorised using a conceptual framework consisting of 8 domains: principles, relationships, emotions, activities, abilities, possessions, medical and others. Framework evaluation included interrater reliability (IRR), time-to-abstraction rate and a questionnaire assessing utility of the framework.
Results
Asking what ‘matters most’ was feasible, including 1349 of 1625 patients (83.0%). Regarding categories of the conceptual framework, 504 patients (37.4%) reported medical issues, 297 (22.0%) relationships, 268 (19.9%) abilities and 154 (11.4%) emotions as their priority. Patients aged ≥85 years or having frailty more frequently prioritised abilities and emotions, whereas patients 65–84 years or without frailty prioritised medical issues. The framework showed substantial IRR (κ = 0.668), good time-to-abstraction rates and high ratings in the utility questionnaire.
Conclusions
Asking older people ‘what matters most’ is feasible and potentially useful in the ED setting. Applying a conceptual framework enables systematic documentation and may support patient-centred and holistic emergency care
On the rapid cooling cast solidification microstructures of Mg–Ca–Zn alloys
Get PDFThis work investigates the influence of Mg–Zn–Ca alloy compositions and rapid cooling conditions on microstructural evolution, with a focus on the formation and behaviour of intermetallic phases such as Mg
2
Ca, MgZn, and Ca
2
Mg
6
Zn
3
during solidification. To achieve this, a combination of experimental characterisation and computational modelling was employed. The Scheil model, extended to ternary alloy systems, was used to simulate micro-segregation during solidification, while a multicomponent mean-field model was applied to predict solid-state phase transformations and the evolution of second-phase particles. CALPHAD-based thermodynamic calculations were integrated to refine the prediction of segregation pathways and phase distributions under non-equilibrium conditions. The model successfully differentiates solidification paths based on alloy composition, predicting that Mg–0.8Zn–0.2Ca (wt%) first forms Mg 2 Ca phase segregation, whereas Mg–6.8Zn–0.2Ca (wt%) primarily segregates MgZn. Experimental validation using SEM–EDS characterisation confirms these predictions. Finally, intermetallic phase formation diagrams under different solidification conditions are presented, providing insights into the control of intermetallic phase formation in Mg–Zn–Ca alloys
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