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A collective trigger for widespread planetesimal formation revealed by accretion ages
No full textThe formation of planetesimals was an integral part of the cascading series of processes that built the terrestrial planets. To illuminate planetesimal formation, here we develop a refined thermal evolution model to calculate the formation ages of meteorite parent planetesimals. This model includes chemical reactions and phase changes during heating, as well as natural variations in the proportions of the constituent phases of these planetesimals. We find that the parent bodies of non-carbonaceous (NC) and carbonaceous (CC) iron meteorites start forming at very similar times (∼0.95 Myr after calcium-aluminium-rich inclusion [CAI] formation) and occupy overlapping time windows. NC and CC chondrite parent bodies formed later during non-overlapping periods. We combine these ages with proportions of isotopic end-members we recover from mixing models to construct records of motion throughout the protoplanetary disk. These records argue that NC and CC material traversed the barrier in the disk after ∼0.95 Myr after CAI formation. The onset of this motion coincided with planetesimal formation, indicating that the phenomenon that drove motion also triggered planetesimal formation. We argue that this feature also served as the semi-permeable barrier in the disk. Although its identity is uncertain, the effects this phenomenon had on the timing of planetesimal formation and motion through the disk can now serve as constraints on models of disk evolution. Models that reproduce these effects would elucidate the nature and implications of this phenomenon, which is key to unlocking a holistic model of terrestrial planet building
Stepping into school: using the Step Model of Transition Capital to critically understand children’s transition to school
No full textThe transition to school is a very important time in children’s educational journey, as well as their families’ engagement with the community. Previous research has identified the complex interrelations of factors that influence this transition, emphasising the contextual nature of ‘eAective’ transition. In recent years, critical theoretical approaches have been utilised to highlight systemic power imbalances within transition processes, particularly for children from priority cohorts or who are experiencing vulnerability or disadvantage. While several models and guides exist for creating and evaluating transition programs, there remains a need for an accessible model that incorporates a critical theoretical approach to understanding the diversity of experiences of transition. The current paper draws upon the newly developed Step Model of Transition Capital to better understand the transition to school process experienced by four children from refugee backgrounds within Australia. The paper outlines how the Step Model can be used as a tool for critical reflection, and to examine how children and families may experience the transition to school process diAerently. The Step Model can, therefore, be used to identify risks and opportunities to better support children and families through this important period
Circular resourcing: the role of mining in a circular economy
Get PDFThe global transition towards net-zero carbon economies is driving unprecedented demand for critical minerals essential for clean energy technologies. While the circular economy (CE) concept has emerged as a promising paradigm offering pathways to reduce demand for critical energy transition minerals through approaches, such as recycling and reuse, evidence suggests that downstream-focused approaches alone cannot meet the growing mineral requirements for global decarbonisation, necessitating continued primary extraction. This thesis examines how CE approaches can be applied to mining operations to address the dual challenge of securing critical minerals while minimising societal-environmental impacts.Through three interconnected studies, this thesis broadens the scope of CE research by examining its application to the mining sector and resource-dependent regions, with a particular focus on Chile as one of the world’s leading copper and lithium producers. The first study demonstrates that recycling alone cannot meet future copper demand, a key critical energy transition mineral, highlighting the need for alternative CE strategies beyond recycling. The second study investigates how CE approaches are being applied in the Chilean mining sector, revealing both innovative practices, such as tailings valorisation, seawater use, and equipment remanufacturing, and the rebranding of existing sustainability initiatives as CE interventions. The third study examines the spatial dynamics of CE transitions in Chile’s mining territories, demonstrating how the spatial configuration of economic activities fundamentally shapes regional CE transitions.The thesis makes three key contributions to academic knowledge. First, it extends CE scholarship by demonstrating its relevance for the mining sector and by improving conceptual tools to analyse CE implementation in primary production. Second, it advances the economic geography literature by showing how territorial characteristics and spatial configurations of economic activity shape CE transitions in resource-rich regions. Third, it contributes to sustainability transitions research by demonstrating the role of place-specific factors in shaping transition pathways. Together, these contributions underline that successful CE transitions in the mining sector and its host regions depend on addressing both operational practices within firms and broader spatial dynamics, providing crucial guidance for a more sustainable resource extraction model
Numerical methods for unsteady conjugate heat transfer
Get PDFThe DPhil thesis enclosed herein addresses key challenges associated with unsteady conjugate heat transfer (CHT) modelling in the context of compressible flows. It establishes a foundation for efficient, high-fidelity simulations of coupled conduction-convection systems and provides insights into transient heat transfer dynamics that are critical to aerospace and energy applications. First, this work develops a method for generating unsteady inflow conditions in scale-resolving simulations. Most practical CHT applications involve turbulent flows, which require accurate representation of unsteady inflow conditions for capturing complex downstream flow physics. The synthetic inflow generator offers a flexible and efficient solution to this challenge. Validation against experimental data demonstrates superior performance compared to existing methods. The second contribution focuses on the simulation of unsteady CHT problems. Two primary challenges are addressed: the large disparities in time scales and length scales between solid and fluid domains. To tackle the length scale mismatch, a modal decomposition of the solid temperature field is proposed, which allows for an efficient representation of the unsteady heat conduction problem. The decomposition is coupled with a local, refined solution in the solid domain. To handle the time scale challenge, the decoupled modal equations are accelerated individually based on their respective time constants. The thesis is concluded with a study of the unsteady effects of CHT in compressible flows. The transient evolution of global flow quantities in a transonic nozzle case is monitored using simulations with different levels of fidelity. Notably, the study reveals that transient thermal drifts are governed by the ratio of thermal capacity to the Stanton number. Results show exponential decay towards steady state, with initial temperature differences dictating drift bounds but not decay rates
Learning 3D information from large image collections
Get PDFPhotos and videos, the most popular ways for us to capture the environment around us, are 2D-pixel representations that contain implicit yet rich 3D information. As 2D images are much easier to capture than 3D data, the past decade of technological advance has catalyzed the creation of image datasets that are much larger and more diverse compared to their 3D counterparts. This has led to significant improvements in 2D image recognition and generation tasks but much more limited improvements in 3D-aware computer vision problems. In this thesis, we attempt to isolate and extract 3D information from large image datasets with very little 3D data for assistance. Specifically, we explore large image-pretrained models, both for recognition and generation tasks, and focus on how we can extract three types of 3D information: 1) geometry 2) continuous movement-based attributes (e.g., camera motion, time-of-day lighting, non-rigid object motion), and 3) materials. In Chapter 3, we present 3DMiner, an end-to-end pipeline to obtain geometry from a large set of unannotated image collections. In Chapter 4, we present Continuous 3D Words, a way to extract continuous, 3D-aware motions like time-of-day illumination or camera parameters and further control them during image generation and editing. In Chapter 5, we show that generative models trained on large image datasets can implicitly extract and transfer materials from one exemplar to another image, without the need for any further finetuning. Overall, this thesis shows that, with minimal-to-none 3D data and model training, these 3D-aware attributes can be disentangled from the complex information presented in images. The resulting features are beneficial to a wide range of generation and reconstruction tasks
Devaluation, Exports, and Recovery from the Great Depression
Get PDFThis paper evaluates how a major policy shift—the suspension of the gold standard in September 1931—affected employment outcomes in interwar Britain. We use a new high-frequency industry-level dataset and difference-in-differences techniques to isolate the impact of devaluation on exporters. At the micro level, the break from gold reduced the unemployment rate by 2.7 percentage points for export-intensive industries relative to non-export industries. At the aggregate level, this effect stimulated the labor market, the fiscal outlook, and economic growth. Devaluation was therefore an important initial spark of recovery from the depths of the Great Depression
Vaccines and antimicrobial resistance: from science to policy—introduction
Get PDFVaccines for humans and animals represent an attractive means to counter the growing global pandemic of antimicrobial resistance (AMR). However, vaccines are only available against a few key bacterial pathogens, and interactions between the human and veterinary vaccine communities have been limited. In April 2024, a Royal Society Science+ Meeting on ‘Vaccines and AMR: from science to policy’ was held in London to review the science of how vaccines reduce AMR, identify research gaps in developing AMR vaccines and discuss policy in advancing development and equitable deployment of such vaccines. Taking a One Health approach, the meeting brought together clinical and veterinary experts from academia and industry, policymakers and funders, from high-income countries and from low- and middle-income countries. Articles based on presentations at the Science+ meeting, including an overall summary of the meeting, its outcomes and recommendations, are included in this issue of Philosophical Transactions of the Royal Society B. This opening article provides the background, rationale and aims of the meeting. This article is part of the Royal Society Science+ meeting issue ‘Vaccines and antimicrobial resistance: from science to policy’
Breast arterial calcifications on mammography and risk of stroke: a systematic review and meta-analysis
Get PDFBackground: Breast arterial calcifications (BAC) are commonly observed as an incidental finding on screening mammography and have been linked to cardiovascular disease. Whether BAC is independently associated with stroke risk remains uncertain. Methods: We conducted a systematic review and meta-analysis in accordance with PRISMA 2020 guidelines. PubMed, Embase, and Scopus were searched from inception to May 2024 for cohort studies evaluating the association between BAC and stroke. Eligible studies included women undergoing mammography with documented BAC status and subsequent stroke outcomes. Data on patient characteristics and vascular risk factors were extracted. Study quality was appraised using the Joanna Briggs Institute (JBI) Critical Appraisal Checklist. Random-effects meta-analyses with restricted maximum likelihood (REML) estimation were performed to pool risk ratios (RRs) and mean differences (MDs). Heterogeneity was assessed with the I2 statistic, and publication bias with Egger’s test. Results: Ten cohort studies including 52,413 women were analyzed. The presence of BAC was associated with more than a twofold increased risk of stroke (RR 2.09, 95% CI 1.58–2.75; I2 = 64.4%). This association persisted after adjustment for age, diabetes, hyperlipidemia, and menopausal status. Compared with BAC-negative women, those with BAC were significantly older (MD 7.07 years, 95% CI 5.44–8.70) and more frequently hypertensive (RR 1.48, 95% CI 1.23–1.78), diabetic (RR 1.67, 95% CI 1.38–2.02), hyperlipidemic (RR 1.27, 95% CI 1.07–1.51), and postmenopausal (RR 1.26, 95% CI 1.00–1.59). Interestingly, BAC was less common among smokers (RR 0.62, 95% CI 0.45–0.86). Egger’s test showed no evidence of publication bias (p = 0.143). Conclusion: BAC detected on screening mammography is independently associated with an increased risk of stroke, even after accounting for traditional risk factors. These findings support BAC as a promising, underutilized imaging biomarker of cerebrovascular risk in women and highlight the need for standardized reporting and prospective validation
Frequency of familial hypercholesterolaemia-causing genetic variants in the 100 000 Genomes Project cohort: whole genome sequencing analyses of 77 260 participants
Get PDFBackground: Heterozygous Familial Hypercholesterolaemia (HeFH) is caused by pathogenic variants in LDLR, APOB, APOE or PCSK9, leading to elevated low-density lipoprotein-cholesterol and increased cardiovascular risk. In the UK, HeFH affects ~1 in 288 individuals. The 100 000 Genomes Project (100KGP) generated whole genome sequencing (WGS) data from >85 000 participants recruited primarily with cancer or rare inherited disorders. We analysed WGS data to assess the prevalence and spectrum of FH-causing variants. Methods: Variants in LDLR, APOB, APOE and PCSK9 were extracted from 100KGP WGS data and annotated using expert-reviewed ClinGen curation. Demographic, ancestry and linked health records were incorporated. Analyses were restricted to unrelated individuals. Results: Among 54 818 unrelated participants, 167 were heterozygote for an FH-causing variant, giving a prevalence of 1:328 (95% CI 1:285 to 1:386). Prevalence was similar across ancestries, including African (1:388) and South Asian (1:276). Variant distribution was: LDLR 67%, APOB 26.5%, APOE 3.5% and PCSK9 3%. Two individuals carried two FH variants, consistent with homozygous FH. Among 22 442 genetic relatives, 77 also carried an FH variant. Of all variant carriers, 53% were female, mean age at recruitment was 41.3 years, with 43 younger than 18 years, and 54.3% had documented hypercholesterolaemia. Conclusions: The prevalence and gene distribution of FH-causing variants in 100KGP are consistent with UK estimates. Differences in variant spectrum across ancestries were observed; however, FH prevalence was similar. Participants who consented to the return of actionable findings were informed, providing direct clinical benefit from genomic research