Evaluating the temperature dependence of Magnox waste glass dissolution

Before vitrified waste can be safely disposed of, a comprehensive understanding of the effects of temperature on wasteform aqueous durability must be acquired. In the experiments herein, a Magnox waste glass of 25 wt.% simulant waste loading was leached in static batch experiments at 40, 70, 80 and 90 °C to investigate the Arrhenius dependence of dissolution. Results from ICP-OES/MS, EDX, SEM and XRD analyses are discussed in terms of the roles of the glass species within Magnox waste glasses. Here we show that changing the dissolution temperature changed the rate of hydrolysis relative to interdiffusion. At higher temperatures, the initial release of sodium deviated from Arrhenius-type behaviour and instead displayed an almost flat Arrhenius plot; demonstrating changes in temperature affect sodium differently to other glass species. Whilst the activation energies of the lithium and boron releases were in the range of a mixed reaction, the higher activation energy of sodium at lower temperatures combined with its non-Arrhenius behaviour suggested the dissolution processes of lithium and sodium differed. These observations were attributed to the preference of sodium to charge compensate the boron network.This work was supported by EPSRC under an Industrial CASE award (Grant Ref: EP/M507350/1) with Radioactive Waste Management Ltd

Relating Magnox and international waste glasses

Magnox and international radioactive waste glasses observe significantly different aqueous dissolution behaviours. Previously, the effects of Li on the kinetics of dissolution and B network of analogues of a complex Magnox waste glass were investigated (Li-Mg-EM). Here, an “International Simple Glass” with Li substituted for Na at two ratios (Li-ISG) was fabricated to compare the aqueous durability of Magnox and international glasses. 11B MASNMR, 23Na MAS-NMR, 6Li1H CP-NMR and SEM studies are presented. The IIIB/IVB ratio and the role of Na in the pristine glasses varied insignificantly with the Li:Na ratio. Further, the B network of Li-ISG was shown to leach congruently. Li, Na and Mg-containing secondary phases were present for Li-Mg-EM, whilst no precipitates were observed for Li-ISG. Li in ISG was shown to be detrimental but further substitution of Li improved long term aqueous durability, which was attributed to a Li-Na mixed alkali effect for Li-ISG but not Li-Mg-EM

PPM-Decay: A computational model of auditory prediction with memory decay

Statistical learning and probabilistic prediction are fundamental processes in auditory cognition. A prominent computational model of these processes is Prediction by Partial Matching (PPM), a variable-order Markov model that learns by internalizing n-grams from training sequences. However, PPM has limitations as a cognitive model: in particular, it has a perfect memory that weights all historic observations equally, which is inconsistent with memory capacity constraints and recency effects observed in human cognition. We address these limitations with PPM-Decay, a new variant of PPM that introduces a customizable memory decay kernel. In three studies—one with artificially generated sequences, one with chord sequences from Western music, and one with new behavioral data from an auditory pattern detection experiment—we show how this decay kernel improves the model’s predictive performance for sequences whose underlying statistics change over time, and enables the model to capture effects of memory constraints on auditory pattern detection. The resulting model is available in our new open-source R package, ppm (https://github.com/pmcharrison/ppm)

Assessing the effect of radioactive waste glass dissolution on early-stage radionuclide migration using simplified geological repository Monte Carlo transport models

AbstractThe vitrification of radioactive waste within glass and subsequent disposal within a geological disposal facility (GDF) requires a comprehensive understanding of the effect of glass dissolution on GDF performance. This paper aims to analyse the effect of both high-level and intermediate-level waste (HLW and ILW) glass dissolution source terms on radionuclide release into the geosphere just above the disposal vault (the ‘crown’). Radionuclide migration was simulated in GoldSim for HLW in either granite or clay host rocks with a bentonite buffer using carbon steel or copper canisters, whereas ILW simulations considered either granite or clay host rocks, in either bentonite buffer or cement backfill, using concrete or cast-iron canisters. Glass dissolution source terms were varied by coupling GoldSim and MATLAB to modify the initial, residual, and resumption dissolution rates of the glass or by applying the analytical GRAAL model to glass dissolution. HLW glass results indicate no preference of granite over clay host rocks for a given canister type but that a copper canister is preferable to steel. ILW results suggest that a granite–bentonite–cast-iron environment yields lowest crown activities with cast-iron preferable to concrete as the canister, bentonite preferable to cement as the buffer/backfill, and granite preferable to clay as the host rock. Varying glass dissolution source terms (initial, residual, and resumption dissolution rates) had an understood effect on radionuclide migration, although changes were arguably insignificant considering peak crown activity for both HLW and ILW.</jats:p

Simultaneous Consonance in Music Perception and Composition

Simultaneous consonance is a salient perceptual phenomenon corresponding to the perceived pleasantness of simultaneously sounding musical tones. Various competing theories of consonance have been proposed over the centuries, but recently a consensus has developed that simultaneous consonance is primarily driven by harmonicity perception. Here we question this view, substantiating our argument by critically reviewing historic consonance research from a broad variety of disciplines, reanalyzing consonance perception data from 4 previous behavioral studies representing more than 500 participants, and modeling three Western musical corpora representing more than 100,000 compositions. We conclude that simultaneous consonance is a composite phenomenon that derives in large part from three phenomena: interference, periodicity/harmonicity, and cultural familiarity. We formalize this conclusion with a computational model that predicts a musical chord’s simultaneous consonance from these three features, and release this model in an open-source R package, incon, alongside 15 other computational models also evaluated in this paper. We hope that this package will facilitate further psychological and musicological research into simultaneous consonance

An energy-based generative sequence model for testing sensory theories of Western harmony

The relationship between sensory consonance and Western harmony is an important topic in music theory and psychology. We introduce new methods for analysing this relationship, and apply them to large corpora representing three prominent genres of Western music: classical, popular, and jazz music. These methods centre on a generative sequence model with an exponential-family energy-based form that predicts chord sequences from continuous features. We use this model to investigate one aspect of instantaneous consonance (harmonicity) and two aspects of sequential consonance (spectral distance and voice-leading distance). Applied to our three musical genres, the results generally support the relationship between sensory consonance and harmony, but lead us to question the high importance attributed to spectral distance in the psychological literature. We anticipate that our methods will provide a useful platform for future work linking music psychology to music theory

Three-dimensional cephalometric evaluation of maxillary growth following in utero repair of cleft lip and alveolar-like defects in the mid-gestational sheep model

Objective: To evaluate maxillary growth following in utero repair of surgically created cleft lip and alveolar (CLA)-like defects by means of three-dimensional (3D) computer tomographic (CT) cephalometric analysis in the mid-gestational sheep model. Methods: In 12 sheep fetuses a unilateral CLA-like defect was created in utero (untreated control group: 4 fetuses). Four different bone grafts were used for the alveolar defect closure. After euthanasia, CT scans of the skulls of the fetuses, 3D re-constructions, and a 3D-CT cephalometric analysis were performed. Results: The comparisons between the operated and nonoperated skull sides as well as of the maxillary asymmetry among the experimental groups revealed no statistically significant differences of the 12 variables used. Conclusions: None of the surgical approaches used for the in utero correction of CLA-like defects seem to affect significantly postsurgical maxillary growth; however, when bone graft healing takes place, a tendency for almost normal maxillary growth can be observed. Copyright (c) 2006 S. Karger AG, Basel

The perceptions of undertaking a higher degree alongside orthodontic speciality training: a cross-sectional survey of British Orthodontic Society members

Introduction: In the UK, orthodontic speciality training takes place over three years full-time. In addition to the clinical training, there is an expectation that trainees undertake a higher degree. Currently, there is little evidence regarding the impact of undertaking a higher degree on specialist orthodontists. Aims: Investigate UK orthodontists' perceptions of undertaking a higher degree alongside speciality training. Materials and methods: A cross-sectional research study involving the distribution of an anonymous, descriptive, online, questionnaire-based survey between May and June 2021 via the British Orthodontic Society. Data were obtained in relation to the impact of undertaking a higher degree on the completion of speciality training, research skills, delivery of patient care and career opportunities. Results: In total, 166 questionnaires were completed (approximately 13.3% response rate). Most respondents 'agreed' or 'strongly agreed' that undertaking a higher degree had improved their scientific (77.1%) and critical appraisal skills (80.7%), job prospects (60.2%) and career opportunities (63.9%). Most respondents felt the benefits of the higher degree outweighed the associated costs (65.1%) and was a worthwhile component of training (69.3%). Conclusions: Specialist orthodontists place a high value on undertaking a higher degree. The results of this questionnaire should be of importance to stakeholders involved in the development of the orthodontic curriculum