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A Molecular Simulation Study into the Stability of Hydrated Graphene Nanochannels used in Nanofluidics Devices
No full textGraphene-based nanochannels are a popular choice in emerging nanofluidics applications because of their tunable and nanometer-scale channels. In this work, molecular dynamics (MD) simulations were employed both to i) assess the stability of dry and hydrated graphene nanochannels and ii) elucidate the properties of water confined in these channels, using replica-scale models with 0.66 – 2.38 nm channel heights. The use of flexible nanochannel walls allows the nanochannel height to relax in response to the solvation forces arising from the confined fluid and the forces between the confining surfaces, without the need for application of arbitrarily high external pressures. Dry nanochannels were found to completely collapse if the initial nanochannel height was less than 2 nm, due to attractive van der Waals interactions between the confining graphene surfaces. However, the presence of water was found to prevent total nanochannel collapse, due to repulsive hydration forces opposing the attractive van der Waals force. For nanochannel heights less than ~1.7 nm, the confining surfaces must be relaxed to obtain accurate hydration pressures and water diffusion coefficients, by ensuring commensurability between the number of confined water layers and the channel height. For very small (~0.7 nm), hydrated channels a pressure of 231 MPa due to the van der Waals forces was obtained. In the same system, the confined water forms a mobile, liquid monolayer with a diffusion coefficient of 4.0 × 10–5 cm2 s–1, much higher than bulk liquid water. Although this finding conflicts with most classical MD simulations, which predict in-plane order and arrested dynamics, it is supported by experiments and recently published first-principles MD simulations. Classical simulations can therefore be used to predict the properties of water confined in sub-nanometre graphene channels, providing sufficiently realistic molecular models and accurate intermolecular potentials are employed
Scaling CO2 Convection in Confined Aquifers: Effects of Dispersion, Permeability Anisotropy and Geochemistry
No full textRecovering the second moment of the strain distribution from neutron Bragg edge data
No full textPoint by point strain scanning is often used to map the residual stress (strain) in engineering materials and components. However, the gauge volume and hence spatial resolution is limited by the beam defining apertures and can be anisotropic for very low and high diffraction (scattering) angles. Alternatively, wavelength resolved neutron transmission imaging has a potential to retrieve information tomographically about residual strain induced within materials through measurement in transmission of Bragg edges – crystallographic fingerprints whose locations and shapes depend on microstructure and strain distribution. In such a case the spatial resolution is determined by the geometrical blurring of the measurement setup and the detector point spread function. Mathematically, reconstruction of strain tensor field is described by the longitudinal ray transform; this transform has a non-trivial null-space, making direct inversion impossible. A combination of the longitudinal ray transform with physical constraints was used to reconstruct strain tensor fields in convex objects. To relax physical constraints and generalise reconstruction, a recently introduced concept of histogram tomography can be employed. Histogram tomography relies on our ability to resolve the distribution of strain in the beam direction, as we discuss in the paper. More specifically, Bragg edge strain tomography requires extraction of the second moment (variance about zero) of the strain distribution which has not yet been demonstrated in practice. In this paper we verify experimentally that the second moment can be reliably measured for a previously well characterised aluminium ring and plug sample. We compare experimental measurements against numerical calculation and further support our conclusions by rigorous uncertainty quantification of the estimated mean and variance of the strain distribution
ESBMC-CHERI: Towards Verification of C Programs for CHERI Platforms with ESBMC
No full textIn this paper we present ESBMC-CHERI – first bounded model checker capable of formally verifying C programs for CHERI-enabled platforms. CHERI provides run-time protection for the memory unsafe programming languages such as C/C++ at the hardware level. At the same time, it introduces new semantics to C programs, making some safe C programs cause hardware exceptions on CHERI-extended platforms. Hence, it is crucial to detect memory safety violations and compatibility issues ahead of compilation. However, there are no verification tools currently available for reasoning over CHERI-C programs. We demonstrate the work undertaken towards implementing support for CHERI-C in our state-of-the-art bounded model checker ESBMC and the plans for future work and extensive evaluation of ESBMC-CHERI. The ESBMC-CHERI demonstration and the source code are available at https://github.com/esbmc/esbmc/tree/cheri-clang
Autistic Girls and Emotionally Based School Avoidance: Supportive factors for successful re-engagement in mainstream high school
No full textSchool can be challenging for autistic girls who are at risk of internalised anxiety which can ultimately lead to school avoidance. Low attendance is acknowledged as negatively impacting on educational attainment and exacerbating mental health difficulties. Semi-structured interviews were conducted with three autistic girls aged 13-15 years from different high schools, their parent(s) and key adult. Thematic analysis identified the first phase of re-engagement is developing a trusting student-key adult relationship. This provides the foundation for social and emotional intervention. Challenges were also acknowledged and possible improvements reflected upon. These results will aid educators and researchers aiming to support the successful inclusion of autistic girls at risk of experiencing emotionally based school avoidance in mainstream high schools
Long-term antibody response following COVID-19 vaccination in patients receiving peritoneal dialysis
No full textMulti-objective QUBO Solver: Bi-objective Quadratic Assignment Problem
No full textQuantum and quantum-inspired optimisation algorithms are designed to solve problems represented in binary, quadratic and unconstrained form. Combinatorial optimisation problems are therefore often formulated as Quadratic Unconstrained Binary Optimisation Problems (QUBO) to solve them with these algorithms. Moreover, these QUBO solvers are often implemented using specialised hardware to achieve enormous speedups, e.g. Fujitsu’s Digital Annealer (DA) and D-Wave’s Quantum Annealer. However, these are single-objective solvers, while many real-world problems feature multiple conflicting objectives. Thus, a common practice when using these QUBO solvers is to scalarise such multi-objective problems into a sequence of single-objective problems. Due to design trade-offs of these solvers, formulating each scalarisation may require more time than finding a local optimum.We present the first attempt to extend the algorithm supporting a commercial QUBO solver as a multi-objective solver that is not based on scalarisation. The proposed multi-objective DA algorithm is validated on the bi-objective Quadratic Assignment Problem. We observe that algorithm performance significantly depends on the archiving strategy adopted, and that combining DA with non-scalarisation methods to optimise multiple objectives outperforms the current scalarised version of the DA in terms of final solution quality
Acceptability of reducing sedentariness using a mobile-phone application based on ‘if then’ plans for people with psychosis: a focus-group study conducted in the North West of the UK
No full textObjective: To understand the acceptability of (a) reducing sedentary-behaviour in people with psychosis using ‘if-then’ plans and (b) the proposed app content.Design: Qualitative acceptability study. Method: Three structured focus-groups and an interview were conducted with eight participants who had experience of a psychotic episode. They discussed sedentary-behaviour, being more active, critical situations in which they may be tempted to be sedentary and solutions to these (the if-then plans), and a mock-up of the mobile application. The Theoretical Framework of Acceptability (TFA) was used to analyse qualitatively the transcripts.Results: All TFA constructs were coded in each of the transcripts. The idea of reducing sedentary-behaviour was acceptable to people with psychosis, participants knew the importance of being more active, however it is not always their main priority. Likewise, the proposed content of the app was found to be acceptable, with participants already using some of the proposed solutions.Conclusion: This was the first study to use the TFA framework to assess the acceptability of an app that uses critical situations and solutions (“if-then plans”) to help reduce sedentary behaviour for people with psychosis. In this sample (male, English speaking mainly white people), participants understood the benefits of being more active. However, reducing sedentary-behaviour is not the main priority of this population and being sedentary has benefits when their mental-health is bad.<br/
Conversion of glucose to fructose over Sn and Ga-doped zeolite Y in methanol and water media
No full textIn this study, we use zeolite Y as a support for the synthesis of Sn and Ga doped zeolites aimed at the isomerization of glucose to fructose. Though these materials are inactive in water, they are active in methanol and we could ascertain a reaction pathway involving a hydride shift for the interconversion of glucose to fructose and mannose, and a Brønsted acid pathway with the formation of a methyl fructoside intermediate and its hydrolysis to fructose if water was added afterwards. By using characterizations comprising: chemisorption, XPS, XRD, HAADF-STEM and EXAFS; it was possible to demonstrate that a straightforward impregnation protocol for the preparation of our catalysts, led to Sn/Y mainly consisting of small SnO2 clusters on the external surface of the zeolite, whereas Ga/Y consisting of highly dispersed Ga species mostly inside the zeolite pores; and a catalytic activity that appears to be dominated by Brønsted acid sites
