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

Options for basing Dietary Reference Intakes (DRIs) on chronic disease endpoints: report from a joint US-/Canadian-sponsored working group.

Dietary Reference Intakes (DRIs) are used in Canada and the United States in planning and assessing diets of apparently healthy individuals and population groups. The approaches used to establish DRIs on the basis of classical nutrient deficiencies and/or toxicities have worked well. However, it has proved to be more challenging to base DRI values on chronic disease endpoints; deviations from the traditional framework were often required, and in some cases, DRI values were not established for intakes that affected chronic disease outcomes despite evidence that supported a relation. The increasing proportions of elderly citizens, the growing prevalence of chronic diseases, and the persistently high prevalence of overweight and obesity, which predispose to chronic disease, highlight the importance of understanding the impact of nutrition on chronic disease prevention and control. A multidisciplinary working group sponsored by the Canadian and US government DRI steering committees met from November 2014 to April 2016 to identify options for addressing key scientific challenges encountered in the use of chronic disease endpoints to establish reference values. The working group focused on 3 key questions: 1) What are the important evidentiary challenges for selecting and using chronic disease endpoints in future DRI reviews, 2) what intake-response models can future DRI committees consider when using chronic disease endpoints, and 3) what are the arguments for and against continuing to include chronic disease endpoints in future DRI reviews? This report outlines the range of options identified by the working group for answering these key questions, as well as the strengths and weaknesses of each option

Mycobacterium bovis Strains Causing Smear-Positive Human Tuberculosis, Southwest Ireland

Mycobacterium bovis caused 3% of human tuberculosis cases in southwest Ireland during 1998–2006. Of 11 M. bovis strains genotyped, 9 belonged to common animal spoligotypes. Seven strains were from sputum and potential sources of human-centered disease transmission. Ten-locus variable-number tandem repeat typing gave unique strain profiles and would detect disease outbreaks

Dissolution Amplification by Resonance and Cavitational Stimulation at Ultrasonic and Megasonic Frequencies

Acoustic stimulation offers a green pathway for the extraction of valuable elements such as Si, Ca, and Mg via solubilization of minerals and industrial waste materials. Prior studies have focused on the use of ultrasonic frequencies (20-40 kHz) to stimulate dissolution, but mega sonic frequencies (≥1 MHz) offer benefits such as matching of the resonance frequencies of solute particles and an increased frequency of cavitation events. Here, based on dissolution tests of a series of minerals, it is found that dissolution under resonance conditions produced dissolution enhancements between 4x-to-6x in Si-rich materials (obsidian, albite, and quartz). Cavitational collapse induced by ultrasonic stimulation was more effective for Ca- and Mg-rich carbonate precursors (calcite and dolomite), exhibiting a significant increase in the dissolution rate as the particle size was reduced (i.e. available surface area was increased), resulting in up to a 70x increase in the dissolution rate of calcite when compared to unstimulated dissolution for particles with d50\u3c 100 μm. Cavitational collapse induced by mega sonic stimulation caused a greater dissolution enhancement than ultrasonic stimulation (1.5x vs 1.3x) for amorphous class F fly ash, despite its higher Si content because the hollow particle structure was susceptible to breakage by the rapid and high number of lower-energy mega sonic cavitation events. These results are consistent with the cavitational collapse energy following a normal distribution of energy release, with more cavitation events possessing sufficient energy to break Ca-O and Mg-O bonds than Si-O bonds, the latter of which has a bond energy approximately double the others. The effectiveness of ultrasonic dissolution enhancement increased exponentially with decreasing stacking fault energy (i.e., resistance to the creation of surface faults such as pits and dislocations), while, in turn, the effectiveness of mega sonic dissolution increased linearly with the stacking fault energy. These results give new insights into the use of acoustic frequency selections for accelerating elemental release from solutes by the use of acoustic perturbation

Spatial pattern and neighbour effects on Helianthemum squamatum seedlings in a Mediterranean gypsum community

Question: Do, in a semi-arid gypsum environment, neighbours condition the spatial patterns of emergence, survival and height of Helianthemum squamatum seedlings ? Location: Vicinity of Chinchón, province of Madrid, Spain (40°11'N, 3° 35'W, 550 m a.s.l.) Methods: We evaluated the effects of neighbours on the survival and growth of naturally emerging Helianthemum seedlings in a semi-arid area during a two-year period. We followed a two-fold approach based on the use of neighbour models for seedling survival and growth and spatial point pattern analyses for seedling emergence, taking into account the germination date. Results: Seedlings appeared clumped in the vicinity of mature Helianthemum individuals. The neighbour models fitted showed that interactions with neighbours were extremely important for the survival and growth of Helianthemum seedlings. These models also suggest that the effects of neighbours on these variables vary with changes in spatial scale and in the abiotic conditions. Some species exerted negative or positive effects on Helianthemum seedlings only at certain spatial scales, and others exerted negative or positive effects at earlier stages of seedling development, but none later and vice versa. Conclusions: We suggest that the observed patterns are mainly influenced by small-scale modifications in soil conditions and microclimate created by neighbours, which change in time and space

Evaluation and Comparison of Food Records, Recalls, and Frequencies for Energy and Protein Assessment by Using Recovery Biomarkers

The food frequency questionnaire approach to dietary assessment is ubiquitous in nutritional epidemiology research. Food records and recalls provide approaches that may also be adaptable for use in large epidemiologic cohorts, if warranted by better measurement properties. The authors collected (2007–2009) a 4-day food record, three 24-hour dietary recalls, and a food frequency questionnaire from 450 postmenopausal women in the Women’s Health Initiative prospective cohort study (enrollment, 1994–1998), along with biomarkers of energy and protein consumption. Through comparison with biomarkers, the food record is shown to provide a stronger estimate of energy and protein than does the food frequency questionnaire, with 24-hour recalls mostly intermediate. Differences were smaller and nonsignificant for protein density. Food frequencies, records, and recalls were, respectively, able to “explain” 3.8%, 7.8%, and 2.8% of biomarker variation for energy; 8.4%, 22.6%, and 16.2% of biomarker variation for protein; and 6.5%, 11.0%, and 7.0% of biomarker variation for protein density. However, calibration equations that include body mass index, age, and ethnicity substantially improve these numbers to 41.7%, 44.7%, and 42.1% for energy; 20.3%, 32.7%, and 28.4% for protein; and 8.7%, 14.4%, and 10.4% for protein density. Calibration equations using any of the assessment procedures may yield suitable consumption estimates for epidemiologic study purposes

Present-day and future contribution of climate and fires to vegetation composition in the boreal forest of China

This is the final version of the article. Available from Ecological Society of America via the DOI in this recordClimate is well known as an important determinant of biogeography. Although climate is directly important for vegetation composition in the boreal forests, these ecosystems are strongly sensitive to an indirect effect of climate via fire disturbance. However, the driving balance of fire disturbance and climate on composition is poorly understood. In this study, we quantitatively analyzed their individual contributions for the boreal forests of the Heilongjiang Province, China, and their response to climate change using four warming scenarios (+1.5°, 2°, 3°, and 4°C). This study employs the statistical methods of Redundancy Analysis (RDA) and variation partitioning combined with simulation results from a SErgey VERsion Dynamic Global Vegetation Model (SEVER-DGVM), and remote sensing datasets of global land cover (GLC2000) and the third version of Global Fire Emissions Database (GFED3). Results show that the vegetation distribution for the present day is mainly determined directly by climate (35%) rather than fire (1-10.9%). However, with a future global warming of 1.5°C, local vegetation composition will be determined by fires rather than climate (36.3% > 29.3%). Above 1.5°C warming, temperature will be more important than fires in regulating vegetation distribution although other factors such as precipitation can also contribute. The spatial pattern in vegetation composition over the region, as evaluated by Moran's Eigenvector Map (MEM), has a significant impact on local vegetation coverage; for example, composition at any individual location is highly related to that in its neighborhood. It represents the largest contribution to vegetation distribution in all scenarios, but will not change the driving balance between climate and fires. Our results are highly relevant for forest and wildfires' management.This work was supported by the National Natural Science Foundation of China (31570475) and China Scholarship Council

Periprosthetic Joint Infection After Total Knee Arthroplasty With or Without Antibiotic Bone Cement.

IMPORTANCE Despite increased use of antibiotic-loaded bone cement (ALBC) in joint arthroplasty over recent decades, current evidence for prophylactic use of ALBC to reduce risk of periprosthetic joint infection (PJI) is insufficient. OBJECTIVE To compare the rate of revision attributed to PJI following primary total knee arthroplasty (TKA) using ALBC vs plain bone cement. DESIGN, SETTING, AND PARTICIPANTS This international cohort study used data from 14 national or regional joint arthroplasty registries in Australia, Denmark, Finland, Germany, Italy, New Zealand, Norway, Romania, Sweden, Switzerland, the Netherlands, the UK, and the US. The study included primary TKAs for osteoarthritis registered from January 1, 2010, to December 31, 2020, and followed-up until December 31, 2021. Data analysis was performed from April to September 2023. EXPOSURE Primary TKA with ALBC vs plain bone cement. MAIN OUTCOMES AND MEASURES The primary outcome was risk of 1-year revision for PJI. Using a distributed data network analysis method, data were harmonized, and a cumulative revision rate was calculated (1 - Kaplan-Meier), and Cox regression analyses were performed within the 10 registries using both cement types. A meta-analysis was then performed to combine all aggregated data and evaluate the risk of 1-year revision for PJI and all causes. RESULTS Among 2 168 924 TKAs included, 93% were performed with ALBC. Most TKAs were performed in female patients (59.5%) and patients aged 65 to 74 years (39.9%), fully cemented (92.2%), and in the 2015 to 2020 period (62.5%). All participating registries reported a cumulative 1-year revision rate for PJI of less than 1% following primary TKA with ALBC (range, 0.21%-0.80%) and with plain bone cement (range, 0.23%-0.70%). The meta-analyses based on adjusted Cox regression for 1 917 190 TKAs showed no statistically significant difference at 1 year in risk of revision for PJI (hazard rate ratio, 1.16; 95% CI, 0.89-1.52) or for all causes (hazard rate ratio, 1.12; 95% CI, 0.89-1.40) among TKAs performed with ALBC vs plain bone cement. CONCLUSIONS AND RELEVANCE In this study, the risk of revision for PJI was similar between ALBC and plain bone cement following primary TKA. Any additional costs of ALBC and its relative value in reducing revision risk should be considered in the context of the overall health care delivery system