Hot primary melts and mantle source for the Paraná-Etendeka flood basalt province: New constraints from Al-in-olivine thermometry

Continental flood basalts (CFB) are amongst the most voluminous volcanic eruptions in Earth's history. They are rapidly emplaced, and in rare cases the thick lava piles are associated with primitive magmas that have high MgO contents. The compositions of these primitive melts are consistent with a deep-sourced, high-temperature mantle plume origin. Whilst the association of CFBs with impacting mantle plumes is widely accepted, the magnitude of the thermal anomaly is not yet resolved. The development of Al-in-olivine thermometry, however, allows the crystallisation temperature of (near-)liquidus olivine to be determined without using the composition of the co-existing melt. This provides both a robust minimum estimate of mantle temperature and a value from which potential temperature (TP) can be back-calculated. This technique has previously confirmed that crystallisation temperatures in CFB settings can be a few hundred degrees greater than those estimated for MORB, and the results hint at a diversity in crystallisation temperatures between different CFB settings

Metal–silicate partitioning of W and Mo and the role of carbon in controlling their abundances in the bulk silicate earth

The liquid metal–liquid silicate partitioning of molybdenum and tungsten during core formation must be well-constrained in order to understand the evolution of Earth and other planetary bodies, in particular because the Hf–W isotopic system is used to date early planetary evolution. The partition coefficients DMo and DW have been suggested to depend on pressure, temperature, silicate and metal compositions, although previous studies have produced varying and inconsistent models. Additionally, the high cationic charges of W and Mo in silicate melts make their partition coefficients particularly sensitive to oxygen fugacity. We combine 48 new high pressure and temperature experimental results with a comprehensive database of previous experiments to re-examine the systematics of Mo and W partitioning, and produce revised partitioning models from the large combined dataset. W partitioning is particularly sensitive to silicate and metallic melt compositions and becomes more siderophile with increasing temperature. We show that W has a 6+ oxidation state in silicate melts over the full experimental fO2 range of ΔIW −1.5 to −3.5. Mo has a 4+ oxidation state, and its partitioning is less sensitive to silicate melt composition but also depends on metallic melt composition. DMo stays approximately constant with increasing depth in Earth. Both W and Mo become more siderophile with increasing C content of the metal: we therefore performed experiments with varying C concentrations and fit epsilon interaction parameters:  = −7.03 ± 0.30 and  = −7.38 ± 0.57. W and Mo along with C are incorporated into a combined N-body accretion and core–mantle differentiation model, which already includes the major rock-forming elements as well as S, and moderately and highly siderophile elements. In this model, oxidation and volatility gradients extend through the protoplanetary disk so that Earth accretes heterogeneously. These gradients, as well as the metal–silicate equilibration pressure, are fitted using a least squares optimisation so that the model Earth-like planet reproduces the composition of the bulk silicate Earth (BSE) in terms of 17 simulated element concentrations (Mg, Fe, Si, Ni, Co, Nb, Ta, V, Cr, S, Pt, Pd, Ru, Ir, W, Mo, and C). The effects of the interaction of W and Mo with Si, S, O, and C in metal are included. Using this model with six separate terrestrial planet accretion simulations, we show that W and Mo require the early accreting Earth to be sulfur-depleted and carbon-enriched so that W and Mo are efficiently partitioned into Earth’s core and do not accumulate in the mantle. When this is the case, the produced Earth-like planets possess mantle compositions matching the BSE for all simulated elements. However, there are two distinct groups of estimates of the bulk mantle’s C abundance in the literature: low (∼100 ppm) and high (∼800 ppm), and all six models are consistent with the higher estimated carbon abundance. The low BSE C abundance would be achievable when the effects of the segregation of dispersed metal droplets produced in deep magma oceans by the disproportionation of Fe2+ to Fe3+ plus metallic Fe is included

The Composition of Melts from a Heterogeneous Mantle and the Origin of Ferropicrite: Application of a Thermodynamic Model

Evidence for chemical and lithological heterogeneity in the Earth’s convecting mantle is widely acknowledged, yet the major element signature imparted on mantle melts by this heterogeneity is still poorly resolved. In this study, a recent thermodynamic melting model is tested on a range of compositions that correspond to potential mantle lithologies (harzburgitic to pyroxenitic), to demonstrate its applicability over this compositional range, in particular for pyroxenite melting. Our results show that, despite the model’s calibration in peridotitic systems, it effectively reproduces experimental partial melt compositions for both Si-deficient and Si-excess pyroxenites. Importantly, the model accurately predicts the presence of a free silica phase at high pressures in Si-excess pyroxenites, indicating the activation of the pyroxene–garnet thermal divide. This thermal divide has a dominant control on solidus temperature, melt productivity and partial melt composition. The model is used to make new inferences on the link between mantle composition and melting behaviour. In silica-deficient and low-pressure (olivine-bearing) lithologies, melt composition is not very sensitive to source composition. Linearly varying the source composition between peridotite and basaltic pyroxenite, we find that the concentration of oxides in the melt tends to be buffered by the increased stability of more fusible phases, causing partial melts of even highly fertile lithologies to be similar to those of peridotite. An exception to this behaviour is FeO, which is elevated in partial melts of silica-deficient pyroxenite even if the bulk composition does not have a high FeO content relative to peridotite. Melt Al$_2$O$_3$ and MgO vary predominantly as a function of melting depth rather than bulk composition. We have applied the thermodynamic model to test the hypothesis that Fe-rich mantle melts such as ferropicrites are derived by partial melting of Si-deficient pyroxenite at elevated mantle potential temperatures. We show that the conspicuously high FeO in ferropicrites at a given MgO content does not require a high-Fe mantle source and is indeed best matched by model results involving around 0–20% melting of silica-deficient pyroxenite. A pyroxenite source lithology also accounts for the low CaO content of ferropicrites, whereas their characteristic low Al$_2$O$_3$ is a function of their high pressure of formation. Phanerozoic ferropicrites are exclusively located in continental flood basalt (CFB) provinces and this model of formation confirms that lithological heterogeneity (perhaps recycled oceanic crust) is present in CFB mantle sources.Natural Environment Research Council (NE/J500070/1, NE/J021539/1

General Practitioners’ Experiences of Providing Lifestyle Advice to Patients with Depression: A Qualitative Focus Group Study

Objective: Depression is an increasingly common mental health disorder in the UK, managed predominantly in the community by GPs. Emerging evidence suggests lifestyle medicine is a key component in the management of depression. We aimed to explore GPs’ experiences, attitudes, and challenges to providing lifestyle advice to patients with depression. Method: Focus groups were conducted virtually with UK GPs (May-July 2022). A topic guide facilitated the discussion and included questions on experiences, current practices, competence, challenges, and service provision. Data were analysed using template analysis. Results: ‘Supporting Effective Conversations’; ‘Willing, but Blocked from Establishing Relational Care’; ‘Working Towards Patient Empowerment’; and ‘Control Over the Prognosis’ were all elements of how individualised lifestyle advice was key to the management of depression. Establishing a doctor-patient relationship by building trust and rapport was fundamental to having effective conversations about lifestyle behaviours. Empowering patients to make positive lifestyle changes required tailoring advice using a patient-centred approach. Confidence varied across participants, depending on education, experience, type of patient, and severity of depression. Conclusions: GPs play an important role in managing depression using lifestyle medicine and a patient-centred approach. Organisational and educational changes are necessary to facilitate GPs in providing optimal care to patients with depression

Global Potato Yields Increase Under Climate Change With Adaptation and CO2 Fertilisation

The contribution of potatoes to the global food supply is increasing—consumption more than doubled in developing countries between 1960 and 2005. Understanding climate change impacts on global potato yields is therefore important for future food security. Analyses of climate change impacts on potato compared to other major crops are rare, especially at the global scale. Of two global gridded potato modeling studies published at the time of this analysis, one simulated the impacts of temperature increases on potential potato yields; the other did not simulate the impacts of farmer adaptation to climate change, which may offset negative climate change impacts on yield. These studies may therefore overestimate negative climate change impacts on yields as they do not simultaneously include CO2 fertilisation and adaptation to climate change. Here we simulate the abiotic impacts of climate change on potato to 2050 using the GLAM crop model and the ISI-MIP ensemble of global climate models. Simulations include adaptations to climate change through varying planting windows and varieties and CO2 fertilisation, unlike previous global potato modeling studies. Results show significant skill in reproducing observed national scale yields in Europe. Elsewhere, correlations are generally positive but low, primarily due to poor relationships between national scale observed yields and climate. Future climate simulations including adaptation to climate change through changing planting windows and crop varieties show that yields are expected to increase in most cases as a result of longer growing seasons and CO2 fertilisation. Average global yield increases range from 9 to 20% when including adaptation. The global average yield benefits of adaptation to climate change range from 10 to 17% across climate models. Potato agriculture is associated with lower green house gas emissions relative to other major crops and therefore can be seen as a climate smart option given projected yield increases with adaptation

The IBER study: a feasibility randomised controlled trial of imagery based emotion regulation for the treatment of anxiety in bipolar disorder

BACKGROUND: Intrusive mental imagery is associated with anxiety and mood instability within bipolar disorder and therefore represents a novel treatment target. Imagery Based Emotion Regulation (IBER) is a brief structured psychological intervention developed to enable people to use the skills required to regulate the emotional impact of these images. METHODS: Participants aged 18 and over with a diagnosis of bipolar disorder and at least a mild level of anxiety were randomly assigned (1:1) to receive IBER plus treatment as usual (IBER + TAU) or treatment as usual alone (TAU). IBER was delivered in up to 12 sessions overs 16 weeks. Clinical and health economic data were collected at baseline, end of treatment and 16-weeks follow-up. Objectives were to inform the recruitment process, timeline and sample size estimate for a definitive trial and to refine trial procedures. We also explored the impact on participant outcomes of anxiety, depression, mania, and mood stability at 16-weeks and 32-weeks follow-up. RESULTS: Fifty-seven (28: IBER + TAU, 27: TAU) participants from two sites were randomised, with 50 being recruited within the first 12 months. Forty-seven (82%) participants provided outcome data at 16 and 32-weeks follow-up. Thirty-five participants engaged in daily mood monitoring at the 32-week follow-up stage. Retention in IBER treatment was high with 27 (96%) attending ≥ 7 sessions. No study participants experienced a serious adverse event. DISCUSSION: The feasibility criteria of recruitment, outcome completion, and intervention retention were broadly achieved, indicating that imagery-focused interventions for bipolar disorder are worthy of further investigation

Global burden of human brucellosis : a systematic review of disease frequency

BACKGROUND: This report presents a systematic review of scientific literature published between 1990-2010 relating to the frequency of human brucellosis, commissioned by WHO. The objectives were to identify high quality disease incidence data to complement existing knowledge of the global disease burden and, ultimately, to contribute towards the calculation of a Disability-Adjusted Life Years (DALY) estimate for brucellosis.METHODS/PRINCIPAL FINDINGS: Thirty three databases were searched, identifying 2,385 articles relating to human brucellosis. Based on strict screening criteria, 60 studies were selected for quality assessment, of which only 29 were of sufficient quality for data analysis. Data were only available from 15 countries in the regions of Northern Africa and Middle East, Western Europe, Central and South America, Sub-Saharan Africa, and Central Asia. Half of the studies presented incidence data, six of which were longitudinal prospective studies, and half presented seroprevalence data which were converted to incidence rates. Brucellosis incidence varied widely between, and within, countries. Although study biases cannot be ruled out, demographic, occupational, and socioeconomic factors likely play a role. Aggregated data at national or regional levels do not capture these complexities of disease dynamics and, consequently, at-risk populations or areas may be overlooked. In many brucellosis-endemic countries, health systems are weak and passively-acquired official data underestimate the true disease burden.CONCLUSIONS: High quality research is essential for an accurate assessment of disease burden, particularly in Eastern Europe, the Asia-Pacific, Central and South America and Africa where data are lacking. Providing formal epidemiological and statistical training to researchers is essential for improving study quality. An integrated approach to disease surveillance involving both human health and veterinary services would allow a better understand of disease dynamics at the animal-human interface, as well as a more cost-effective utilisation of resources

A model for reactive porous transport during re-wetting of hardened concrete

A mathematical model is developed that captures the transport of liquid water in hardened concrete, as well as the chemical reactions that occur between the imbibed water and the residual calcium silicate compounds residing in the porous concrete matrix. The main hypothesis in this model is that the reaction product -- calcium silicate hydrate gel -- clogs the pores within the concrete thereby hindering water transport. Numerical simulations are employed to determine the sensitivity of the model solution to changes in various physical parameters, and compare to experimental results available in the literature.Comment: 30 page

Densification of the interlayer spacing governs the nanomechanical properties of calcium-silicate-hydrate

Calciuam-silicate-hydrate (C-S-H) is the principal binding phase in modern concrete. Molecular simulations imply that its nanoscale stiffness is 'defect-driven', i.e., dominated by crystallographic defects such as bridging site vacancies in its silicate chains. However, experimental validation of this result is difficult due to the hierarchically porous nature of C-S-H down to nanometers. Here, we integrate high pressure X-ray diffraction and atomistic simulations to correlate the anisotropic deformation of nanocrystalline C-S-H to its atomic-scale structure, which is changed by varying the Ca-to-Si molar ratio. Contrary to the 'defect-driven' hypothesis, we clearly observe stiffening of C-S-H with increasing Ca/Si in the range 0.8 ≤ Ca/Si ≤ 1.3, despite increasing numbers of vacancies in its silicate chains. The deformation of these chains along the b-axis occurs mainly through tilting of the Si-O-Si dihedral angle rather than shortening of the Si-O bond, and consequently there is no correlation between the incompressibilities of the a- and b-axes and the Ca/Si. On the contrary, the intrinsic stiffness of C-S-H solid is inversely correlated with the thickness of its interlayer space. This work provides direct experimental evidence to conduct more realistic modelling of C-S-H-based cementitious material

Minimal Holocene retreat of large tidewater glaciers in Køge Bugt, southeast Greenland

Abstract Køge Bugt, in southeast Greenland, hosts three of the largest glaciers of the Greenland Ice Sheet; these have been major contributors to ice loss in the last two decades. Despite its importance, the Holocene history of this area has not been investigated. We present a 9100 year sediment core record of glaciological and oceanographic changes from analysis of foraminiferal assemblages, the abundance of ice-rafted debris, and sortable silt grain size data. Results show that ice-rafted debris accumulated constantly throughout the core; this demonstrates that glaciers in Køge Bugt remained in tidewater settings throughout the last 9100 years. This observation constrains maximum Holocene glacier retreat here to less than 6 km from present-day positions. Retreat was minimal despite oceanic and climatic conditions during the early-Holocene that were at least as warm as the present-day. The limited Holocene retreat of glaciers in Køge Bugt was controlled by the subglacial topography of the area; the steeply sloping bed allowed glaciers here to stabilise during retreat. These findings underscore the need to account for individual glacier geometry when predicting future behaviour. We anticipate that glaciers in Køge Bugt will remain in stable configurations in the near-future, despite the predicted continuation of atmospheric and oceanic warming