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The growing role of museums and community-led cultural organisations as agents of social and environmental change
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Constraining lens masses in moderately to highly magnified microlensing events from Gaia
No full textContext. Microlensing events provide a unique way to detect and measure the masses of isolated, non-luminous objects, particularly dark stellar remnants. Under certain conditions, it is possible to measure the mass of these objects using photometry alone, specifically when a microlensing light curve displays a finite source (FS) effect. This effect generally occurs in highly magnified light curves, i.e. when the source and the lens are very well aligned.Aims. In this study, we analyse Gaia Alerts and Gaia Data Release 3 datasets, identifying four moderate-to-high-magnification microlensing events without a discernible FS effect. The absence of this effect suggests a large Einstein radius, implying substantial lens masses.Methods. In each event, we constrained the FS effect, and therefore established lower limits for the angular Einstein radius and lens mass. Additionally, we used the DarkLensCode software to obtain the mass, distance, and brightness distribution for the lens based on the Galactic model.Results. Our analysis established lower mass limits of ∼0.7 M⊙ for one lens and ∼0.3 − 0.5 M⊙ for two others. A DarkLensCode analysis supports these findings, estimating lens masses in the range of ∼0.42 − 1.70 M⊙ and dark lens probabilities exceeding 80%. These results strongly indicate that the lenses are stellar remnants, such as white dwarfs or neutron stars.Conclusions. While further investigations are required to confirm the nature of these lenses, we demonstrate a straightforward yet effective approach to identifying stellar remnant candidates
Episode 3 Doctoral journeys-beyond the doctorate:Ema Ushioda
No full textDoctoral Journeys beyond the Doctorate is a podcast and academic blog series
Carbonate-associated phosphate evidence for a small inorganic phosphorus reservoir in the terminal Ediacaran ocean
No full textThe terminal Ediacaran (ca. 551–533 Ma) was characterized by profound biological innovations and environmental upheavals, in which phosphorus (P)—the ultimate limiting nutrient for marine productivity—is postulated to have played a key role. However, P availability in the terminal Ediacaran ocean remains uncertain due to the lack of an appropriate proxy record. To better reconstruct seawater P levels during this time interval, we analyzed carbonate-associated phosphate [CAP; expressed as CAP/(Ca + Mg)], a new proxy for P availability in ancient oceans, in three upper Ediacaran successions: the Nama Group (Namibia), the Shibantan Member of the Dengying Formation (Wuhe, South China), and the Algal Dolomite, Gaojiashan and Beiwan members of the Dengying Formation (Gaojiashan, South China). Our results reveal consistently low CAP/(Ca + Mg) values (range: 0.02–0.69 mmol/mol, mean: 0.13 ± 0.01 mmol/mol, 2σ, the same below) for all study sections, falling at the lower end of modern marine carbonate values. Lithofacies, carbonate oxygen isotopes, Mn/Sr and Mg/(Mg + Ca) ratios indicate possible influences from release of Fe-bound P, meteoric diagenesis, recrystallization or dolomitization. The low CAP/(Ca + Mg) values thus represent a maximum estimate for the seawater P availability. The low CAP values from two geographically separated cratons likely reflect a generally small oceanic inorganic P reservoir at least in shelves. This study provides insights into the interplay between nutrient cycling, redox dynamics, and biological evolution during one of the most pivotal transitional periods in Earth history
Insulin levels early in perimenopause inform vasomotor symptom incidence across the menopausal transition
No full textContext: Metabolic health impacts the menopausal transition. Metabolic characteristics like body mass index (BMI) affect vasomotor syndrome incidence, but the role of elevated insulin, an early marker of metabolic dysfunction, remains understudied.Objective: To determine whether midlife insulin levels are associated with vasomotor symptom incidence or reproductive hormone trajectories.Methods: Longitudinal analyses of community-based data from the Study of Women's Health Across the Nation (SWAN) were conducted. We analyzed the 704 SWAN participants (of 3302) without oophorectomy or hysterectomy who had metabolic data for age 47 and did not take insulin/medications for hyperglycemia. Mean fasting insulin at 47 was 10.117 µIU/mL (SD = 6.711), with 27.0 kg/m2 BMI (SD = 6.6); mean age of final menstrual period for these participants was 51.0 years (SD = 2.3). Main outcome measures included vasomotor symptom timings and durations, and trajectories of estradiol, follicle-stimulating hormone (FSH), and testosterone across the menopausal transition.Results: Higher insulin at 47 predicted younger onsets of hot flashes and night sweats, longer durations of hot flashes and cold sweats, and greater testosterone rise. BMI associations with vasomotor symptoms paralleled those of insulin, but BMI appeared more closely linked to slower estradiol decline and blunted FSH rise. In Cox proportional hazards models, elevated age-47 insulin was associated with increased likelihood of hot flashes; this remained significant with BMI and glucose as covariates.Conclusions: Perimenopausal fasting insulin and BMI show complementary but distinct associations with menopausal changes. Elevated insulin predicts earlier and prolonged vasomotor symptoms, and is associated with higher testosterone
Rare earth and niobium mobility at the magmatic-hydrothermal transition:Motzfeldt Sø Centre, Greenland
No full textAlkaline igneous complexes host the world’s largest deposits of rare earth elements (REE) and high field strength elements (HFSE) (e.g. Nb, Ta). The genetic models for these metals are underdeveloped, and the role hydrothermal fluids play in modifying the deposit is unclear. The Motzfeldt Sø Centre, Greenland offers an exceptional 3D slice through a collapsed roof-zone in which REE and HFSE mineralisation is found within pyrochlore-group minerals. We use textural and chemical analyses of pyrochlore to interrogate hydrothermal activity in the roof-zone, revealing a two-step model to form an REE-HFSE enriched deposit. First, magma stalls in the roof of the intrusion, accompanied by an aggressive, F-rich fluid from the cooling pluton below. Intensive hydrothermal alteration converts fluorcalciopyrochlore (P1) by adding to A-site vacancy (□) to create an Fe/□-dominated pyrochlore (P2). This liberates REEs, alkalis, and F from the pyrochlore A and Y sites. The elements form a secondary coating on the pyrochlore surfaces. Further alteration then dissolves the coating, enriching the fluid in REE, Nb, and Fe. This process forms mineralised veins containing columbite and REE-fluorcarbonates, which escape as “chimneys” in the upper-roof zone. Late-stage fluids play a key role in determining the nature of critical metal mineralisation, through reworking primary REE and Nb/Ta mineral assemblages into secondary hydrothermal phases, both proximal and distal to the primary deposit. This expands the genetic model for this deposit type, providing a robust framework for future resource exploration in alkaline mineralised roof-zone systems
Active and passive seismic surveys over the grounding zone of Eastwind Glacier, Antarctica
No full textThe grounding zone of a marine‐terminating glacier, where ice begins to float, is a key control on glacier stability and ice discharge. Seismic deployments are a powerful means of studying both the geometry and processes of grounding zones; however, these regions are frequently inaccessible and dangerous for field work, and as a result are underrepresented in field studies. We report new data sets acquired at Eastwind Glacier, Antarctica, a relatively accessible grounding zone near McMurdo Station and Scott Base, as part of the Eastwind Glacier Geophysical Surveys on Top of an Antarctic Ice Shelf Transition, EGGS on TOAST, project. These data sets comprise a deployment of three‐component seismic nodes and distributed acoustic sensing. The nodal deployment consisted of 330 nodes crossing the grounding zone, with all 330 nodes continuously recording for at least nine days, and 150 nodes recording for 19 days, in the austral summer of 2022/2023. Hammer‐and‐plate sources were recorded, with densely spaced shots along flow through the center of the array and shots located at every node. In 2023/2024, a 2.2 km fiber‐optic cable was deployed for active source imaging by distributed acoustic sensing along and across flow, immediately downstream of the grounding line, for a period of 2 hr. Analysis of active source data recorded by the nodal array locates the point of flotation within the grounding zone and provides ice thickness estimates. We present initial analyses of passive source data, including icequake detection and location, and ambient noise analysis. We expect this data set to be of significant value to provide insight into fundamental grounding zone processes and as an event‐rich cryoseismological data set on which to test novel methods of seismic analysis
Hugo Grotius:how to be (and not be) a universalist
No full textHugo Grotius’ De jure belli ac pacis libri tres was published in 1625. It was first a major statement on natural law. It soon became a foundational text within the international law, particularly around the use of force. Over time, it has become a classic in the field, due in some ways to the politics of international law but in other ways because of its profound insights. In this paper, I examine Grotius’ ‘method’ for want of a better word. His natural law argument is based not solely on appeal to Biblical or classical texts (though it certainly does that). It also looks to historical contexts in a way that brings in practice alongside of theory. While others had done this, Grotius’ ability to base his argument on both theory and practice has something to teach us in the contemporary era. I argue that Grotius provides us with a way to argue for universal values – by drawing not only on theories but on the practices that shape those theories. At the same time, the colonial legacy of Grotius’ work (brought out by Martine van Itersum’s foundational work in this area) highlights how our positionality should also caution us when making universalist claims. That is, while I argue for universal values, I recognize my location in the scholarly world, like Grotius’, is a privileged one. I will continue to make those arguments, but the lessons of Grotius’ work leads me to be cautious and humble in how and where I make those arguments
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