Thermodynamic modelling of ultra-long-term durability of cementitious binders for waste immobilisation

Treatment of intermediate-level waste (ILW) generated as a by-product from nuclear power in the UK requires a long-term strategy to safely dispose of the waste. Encapsulation of ILW in a cement matrix is the current UK methodology, followed by storing the waste for potentially thousands of years in geological disposal facilities (GDFs). Understanding of the cement phase assemblage is key to predicting how these cements will behave in the long term. Thermodynamic modelling of cement hydrate phases is a powerful tool which can be used to predict the effects of cement hydration. This thesis investigates the quality of thermodynamic modelling to predict stable phase assemblages of blast furnace slag-Portland cement (BFS-PC) cements, representing UK nuclear industry practice, under conditions that are expected during the storage of encapsulated ILW. Three BFS-PC ratios (1:1, 3:1 and 9:1) were tested at different curing ages to determine the degree of hydration of the precursor materials to use as input parameters for thermodynamic modelling. Characterisation of the phase assemblages were compared to the thermodynamic modelling results to assess the robustness of the modelling approach. A solid solution model for C(-A)-S-H was used to explicitly incorporate aluminium into the C-S-H phase to more accurately portray the chemical structure in the BFS-PC system. Thermodynamic modelling was capable of accurately simulating the change in phase assemblage as curing time increased. Variation of precursor materials was effectively modelled. Temperature fluctuations are expected to occur within the GDF once the waste is stored within it. BFS-PC samples were cured for one year at 35 °C followed by periods of curing at 50 °C, 60 °C and 80 °C. Major phase changes were not observed until the curing temperature reached 60 °C, whereby hemicarbonate and ettringite destabilised. At a curing temperature of 80 °C, the sulphate and carbonate AFm and AFt phases were not observed in cement phase assemblages, however siliceous hydrogarnet was present. Two thermodynamic modelling approaches were used to simulate the effects of temperature change. It was determined that the thermodynamic simulation should not contain siliceous hydrogarnet when simulating BFS-PC hydration up to 60 °C but should contain siliceous hydrogarnet for higher temperatures. The Pitzer model used as a means to produce activity coefficients, was compared with the generalised dominant electrolyte activity model, Truesdell-Jones, to assess whether modelling of cement phases may be improved. A large ion-interaction parameter database was required to use the Pitzer model for simulating cement hydration. Solubility studies of cement phases and cement pore solution data were used as a means to compare the activity coefficient models. The more complex nature of the Pitzer model caused the simulations to require runtimes up to 18 times more than the Truesdell-Jones method. The pore solution of the BFS-PC systems was compared with the predictions from the activity coefficient models, which determined that the Pitzer model provided minimal improvement over the Truesdell-Jones method. However, the Pitzer model proved more effective for simulating higher concentration systems, therefore, the Pitzer model may be required in future modelling projects when simulating concentrated groundwater interactions with the cement wasteforms

Statin use and risk of developing diabetes: results from the Diabetes Prevention Program

Objective Several clinical trials of cardiovascular disease prevention with statins have reported increased risk of type 2 diabetes (T2DM) with statin therapy. However, participants in these studies were at relatively low risk for diabetes. Further, diabetes was often based on self-report and was not the primary outcome. It is unknown whether statins similarly modify diabetes risk in higher risk populations. Research design and methods During the Diabetes Prevention Program Outcomes Study (n=3234), the long-term follow-up to a randomized clinical trial of interventions to prevent T2DM, incident diabetes was assessed by annual 75 g oral glucose tolerance testing and semiannual fasting glucose. Lipid profile was measured annually, with statin treatment determined by a participant’s own physician outside of the protocol. Statin use was assessed at baseline and semiannual visits. Results At 10 years, the cumulative incidence of statin initiation prior to diabetes diagnosis was 33%–37% among the randomized treatment groups (p=0.36). Statin use was associated with greater diabetes risk irrespective of treatment group, with pooled HR (95% CI) for incident diabetes of 1.36 (1.17 to 1.58). This risk was not materially altered by adjustment for baseline diabetes risk factors and potential confounders related to indications for statin therapy. Conclusions In this population at high risk for diabetes, we observed significantly higher rates of diabetes with statin therapy in all three treatment groups. Confounding by indication for statin use does not appear to explain this relationship. The effect of statins to increase diabetes risk appears to extend to populations at high risk for diabetes. Trial registration number NCT00038727; Results

What are the barriers to primary prevention of type 2 diabetes in black and minority ethnic groups in the UK? A qualitative evidence synthesis.

Background: This review aimed to synthesise available qualitative evidence on barriers and facilitators to the implementation of community based lifestyle behaviour interventions to reduce the risk of diabetes in black and minority ethnic (BME) groups in the UK. Methods: A search of medical and social science databases was carried out and augmented by hand-searching of reference lists and contents of key journals. Qualitative evidence was synthesised thematically. Results: A total of 13 papers varying in design and of mainly good quality were included in the review. A limited number of intervention evaluations highlighted a lack of resources and communication between sites. A lack of understanding by providers of cultural and religious requirements, and issues relating to access to interventions for users was reported. Behaviour change was impeded by cultural and social norms, and resistance to change. There were variations in the way dietary change and physical activity was approached by different groups and contrasting practices between generations. Conclusions: Qualitative data provided insight into the ways that providers might improve or better design future interventions. Acknowledgement of the way that different groups approach lifestyle behaviours may assist acceptability of interventions

Determinants of diagnostic discordance for non-diabetic hyperglycaemia and Type 2 diabetes using paired glycated haemoglobin measurements in a large English primary care population:cross-sectional study

Aim: To investigate factors influencing diagnostic discordance for non-diabetic hyperglycaemia and Type 2 diabetes. Methods: Some 10 000 adults at increased risk of diabetes were screened with HbA1c and fasting plasma glucose (FPG). The 2208 participants with initial HbA1c ≥ 42 mmol/mol (≥ 6.0%) or FPG ≥ 6.1 mmol/l were retested after a median 40 days. We compared the first and second HbA1c results, and consequent diagnoses of non-diabetic hyperglycaemia and Type 2 diabetes, and investigated predictors of discordant diagnoses. Results: Of 1463 participants with non-diabetic hyperglycaemia and 394 with Type 2 diabetes on first testing, 28.4% and 21.1% respectively had discordant diagnoses on repeated testing. Initial diagnosis of non-diabetic hyperglycaemia and/or impaired fasting glucose according to both HbA1c and FPG criteria, or to FPG only, made reclassification as Type 2 diabetes more likely than initial classification according to HbA1c alone. Initial diagnosis of Type 2 diabetes according to both HbA1c and FPG criteria made reclassification much less likely than initial classification according to HbA1c alone. Age, and anthropometric and biological measurements independently but inconsistently predicted discordant diagnoses and changes in HbA1c. Conclusions: Diagnosis of non-diabetic hyperglycaemia or Type 2 diabetes with a single measurement of HbA1c in a screening programme for entry to diabetes prevention trials is unreliable. Diagnosis of non-diabetic hyperglycaemia and Type 2 diabetes should be confirmed by repeat testing. FPG results could help prioritise retesting. These findings do not apply to people classified as normal on a single test, who were not retested

Predicting Bulk Average Velocity with Rigid Vegetation in Open Channels Using Tree‐Based Machine Learning: A Novel Approach Using Explainable Artificial Intelligence

Predicting the bulk-average velocity (U(B)) in open channels with rigid vegetation is complicated due to the non-linear nature of the parameters. Despite their higher accuracy, existing regression models fail to highlight the feature importance or causality of the respective predictions. Therefore, we propose a method to predict U(B) and the friction factor in the surface layer (f(S)) using tree-based machine learning (ML) models (decision tree, extra tree, and XGBoost). Further, Shapley Additive exPlanation (SHAP) was used to interpret the ML predictions. The comparison emphasized that the XGBoost model is superior in predicting U(B) (R = 0.984) and f(S) (R = 0.92) relative to the existing regression models. SHAP revealed the underlying reasoning behind predictions, the dependence of predictions, and feature importance. Interestingly, SHAP adheres to what is generally observed in complex flow behavior, thus, improving trust in predictions

Deconstructing Weight Management Interventions for Young Adults: Looking Inside the Black Box of the EARLY Consortium Trials.

ObjectiveThe goal of the present study was to deconstruct the 17 treatment arms used in the Early Adult Reduction of weight through LifestYle (EARLY) weight management trials.MethodsIntervention materials were coded to reflect behavioral domains and behavior change techniques (BCTs) within those domains planned for each treatment arm. The analytical hierarchy process was employed to determine an emphasis profile of domains in each intervention.ResultsThe intervention arms used BCTs from all of the 16 domains, with an average of 29.3 BCTs per intervention arm. All 12 of the interventions included BCTs from the six domains of Goals and Planning, Feedback and Monitoring, Social Support, Shaping Knowledge, Natural Consequences, and Comparison of Outcomes; 11 of the 12 interventions shared 15 BCTs in common across those six domains.ConclusionsWeight management interventions are complex. The shared set of BCTs used in the EARLY trials may represent a core intervention that could be studied to determine the required emphases of BCTs and whether additional BCTs add to or detract from efficacy. Deconstructing interventions will aid in reproducibility and understanding of active ingredients