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Contributions To Mineralogy and... 2024The aluminous calcium-ferrite type phase (CF) and new aluminous phase (NAL) are thought to hold the excess alumina produced by the decomposition of garnet in MORB...
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The aluminous calcium-ferrite type phase (CF) and new aluminous phase (NAL) are thought to hold the excess alumina produced by the decomposition of garnet in MORB compositions in the lower mantle. The respective stabilities of CF and NAL in the nepheline-spinel binary (NaAlSiO-MgAlO) are well established. However with the addition of further components the phase relations at lower mantle conditions remain unclear. Here we investigate a range of compositions around the nepheline apex of the nepheline-kalsilite-spinel compositional join (NaAlSiO-KAlSiO-MgAlO) at 28-78 GPa and 2000 K. Our experiments indicate that even small amounts of a kalsilite (KAlSiO) component dramatically impact phase relations. We find NAL to be stable up to at least 71 GPa in potassium-bearing compositions. This demonstrates the stabilizing effect of potassium on NAL, because NAL is not observed at pressures above 48 GPa on the nepheline-spinel binary. We also observe a broadening of the CF stability field to incorporate larger amounts of potassium with increasing pressure. For pressures below 50 GPa only minor amounts () of potassium are soluble in CF, whereas at 68 GPa, we find a solubility in CF of at least . This indicates that CF and NAL are suitable hosts of the alkali content of MORB compositions at lower mantle conditions. For sedimentary compositions at lower mantle pressures, we expect K-Hollandite to be stable in addition to CF and NAL for pressures of 28-48 GPa, based on our simplified compositions.
SUPPLEMENTARY INFORMATION
The online version contains supplementary material available at 10.1007/s00410-024-02129-w.
PubMed: 38686218
DOI: 10.1007/s00410-024-02129-w -
Nature Communications Apr 2024Seismic and mineralogical studies have suggested regions at Earth's core-mantle boundary may be highly enriched in FeO, reported to exhibit metallic behavior at extreme...
Seismic and mineralogical studies have suggested regions at Earth's core-mantle boundary may be highly enriched in FeO, reported to exhibit metallic behavior at extreme pressure-temperature (P-T) conditions. However, underlying electronic processes in FeO remain poorly understood. Here we explore the electronic structure of B1-FeO at extreme conditions with large-scale theoretical modeling using state-of-the-art embedded dynamical mean field theory (eDMFT). Fine sampling of the phase diagram reveals that, instead of sharp metallization, compression of FeO at high temperatures induces a gradual orbitally selective insulator-metal transition. Specifically, at P-T conditions of the lower mantle, FeO exists in an intermediate quantum critical state, characteristic of strongly correlated electronic matter. Transport in this regime, distinct from insulating or metallic behavior, is marked by incoherent diffusion of electrons in the conducting t orbital and a band gap in the e orbital, resulting in moderate electrical conductivity (~10 S/m) with modest P-T dependence as observed in experiments. Enrichment of solid FeO can thus provide a unifying explanation for independent observations of low seismic velocities and elevated electrical conductivities in heterogeneities at Earth's mantle base.
PubMed: 38658590
DOI: 10.1038/s41467-024-47489-w -
ACS Environmental Au May 2024The highly excessive uptake of cadmium (Cd) by rice plants is well known, but the transfer pathway and mechanism of Cd in the paddy system remain poorly understood....
The highly excessive uptake of cadmium (Cd) by rice plants is well known, but the transfer pathway and mechanism of Cd in the paddy system remain poorly understood. Herein, pot experiments and field investigation were systematically carried out for the first time to assess the phytoavailability of Cd and fingerprint its transfer pathway in the paddy system under different treatments (slaked lime and biochar amendments), with the aid of a pioneering Cd isotopic technique. Results unveiled that no obvious differences were displayed in the δCd of Ca(NO)-extractable and acid-soluble fractions among different treatments in pot experiments, while the δCd of the water-soluble fraction varied considerably from -0.88 to -0.27%, similar to those observed in whole rice plant [ΔCd ≈ 0 (-0.06 to -0.03%)]. It indicates that the water-soluble fraction is likely the main source of phytoavailable Cd, which further contributes to its bioaccumulation in paddy systems. However, ΔCd found in field conditions (-0.39 ± 0.05%) was quite different from those observed in pot experiments, mostly owing to additional contribution derived from atmospheric deposition. All these findings demonstrate that the precise Cd isotopic compositions can provide robust and reliable evidence to reveal different transfer pathways of Cd and its phytoavailability in paddy systems.
PubMed: 38765061
DOI: 10.1021/acsenvironau.3c00067 -
Membranes Nov 2023The lack of information on structural basis where proteins are involved, as well as the biomineralization processes of different systems such as bones, diatom frustules,...
The lack of information on structural basis where proteins are involved, as well as the biomineralization processes of different systems such as bones, diatom frustules, and eggshells, have intrigued scientists from different fields for decades. This scientific curiosity has led to the use of methodologies that help understand the mechanism involved in the formation of these complex structures. Therefore, this work focuses on the use of eggshell membranes from different species of ratites (emu and ostrich) and reptiles (two species of crocodiles) as a model to differentiate biocalcification and biosilicification by introducing calcium phosphate or silica inside the membrane fiber mantles. We performed this to obtain information about the process of eggshell formation as well as the changes that occur in the membrane during crystal formation. In order to identify and understand the early processes leading to the formation of the microstructures present in the eggshell, we decided to carry out the synthesis of silica-carbonate of calcium, barium, and strontium called biomorph in the presence of intramineral proteins. This was carried out to evaluate the influence of these proteins on the formation of specific structures. We found that the proteins on untreated membranes, present a structural growth similar to those observed in the inner part of the eggshell, while in treated membranes, the structures formed present a high similarity with those observed in the outer and intermediate part of the eggshell. Finally, a topographic and molecular analysis of the biomorphs and membranes was performed by scanning electron microscopy (SEM), Raman and Fourier-transform Infrared (FTIR) spectroscopies.
PubMed: 37999355
DOI: 10.3390/membranes13110869 -
Ultramicroscopy Mar 2024The Weighted Burgers Vector (WBV) method can extract information about dislocation types and densities present in distorted crystalline materials from electron...
The Weighted Burgers Vector (WBV) method can extract information about dislocation types and densities present in distorted crystalline materials from electron backscatter diffraction (EBSD) maps, using no assumptions about which slip systems might be present. Furthermore, high-angular resolution EBSD (HR-EBSD) uses a cross-correlation procedure to increase the angular precision of EBSD measurements by an order of magnitude compared to conventional EBSD. However, the WBV technique has not previously been applied to HR-EBSD data and therefore it remains unclear as to which low-angle substructures can be reliably characterised by WBV analysis of conventional EBSD data and which require additional HR-EBSD processing. To establish some practical examples that can be used to guide future data-acquisition strategies, we compare the output of the WBV method when applied to conventional EBSD data and HR-EBSD data collected from the most common minerals in Earth's lower crust (plagioclase feldspar) and upper mantle (olivine). The results demonstrate that HR-EBSD and WBV processing are complementary techniques. The increase in angular precision achieved with HR-EBSD processing allows low-angle (on the order of 0.1°) structures, which are obscured by noise in conventional EBSD data, to be analyzed quantitatively using the WBV method. Combining the WBV and HR-EBSD methods increases the precision of calculated WBV directions, which is essential when using information about active slip systems to infer likely deformation mechanisms from naturally deformed microstructures. This increase in precision is particularly important for low-symmetry crystals, such as plagioclase, that have a wide range of available slip systems that vary in relative activity with changing pressure, temperature and differential stress. Because WBV directions are calculated using no assumptions about which slip systems may be present, combining this technique with HR-EBSD to refine the precision of lattice orientation gradients is ideal for investigating complex natural materials with unknown deformation histories.
PubMed: 38056396
DOI: 10.1016/j.ultramic.2023.113893 -
American Heart Journal Plus :... Apr 2024Novel immune and targeted therapies approved over the past 2 decades have resulted in dramatic improvements in cancer-specific outcomes for many cancer patients....
Novel immune and targeted therapies approved over the past 2 decades have resulted in dramatic improvements in cancer-specific outcomes for many cancer patients. However, many of these agents can induce cardiovascular toxicity in a subset of patients. The field of cardio-oncology was established based on observations that anti-neoplastic chemotherapies and mantle radiation can lead to premature cardiomyopathy in cancer survivors. While conventional chemotherapy, targeted therapy, and immune therapies can all result in cardiovascular adverse events, the mechanisms, timing, and incidence of these events are inherently different. Many of these effects converge upon the coronary microvasculature to involve, through endocardial endothelial cells, a more direct effect through close proximity to cardiomyocyte with cellular communication and signaling pathways. In this review, we will provide an overview of emerging paradigms in the field of Cardio-Oncology, particularly the role of the coronary microvasculature in mediating cardiovascular toxicity of important cancer targeted and immune therapies. As the number of cancer patients treated with novel immune and targeted therapies grows exponentially and subsequently the number of long-term cancer survivors dramatically increases, it is critical that cardiologists and cardiology researchers recognize the unique potential cardiovascular toxicities of these agents.
PubMed: 38510501
DOI: 10.1016/j.ahjo.2024.100374 -
The Science of the Total Environment Mar 2024Mercury (Hg) is naturally released by volcanoes and geothermal systems, but the global flux from these natural sources is highly uncertain due to a lack of direct...
Mercury (Hg) is naturally released by volcanoes and geothermal systems, but the global flux from these natural sources is highly uncertain due to a lack of direct measurements and uncertainties with upscaling Hg/SO mass ratios to estimate Hg fluxes. The 2021 and 2022 eruptions of Fagradalsfjall volcano, southwest Iceland, provided an opportunity to measure Hg concentrations and fluxes from a hotspot/rift system using modern analytical techniques. We measured gaseous Hg and SO concentrations in the volcanic plume by near-source drone-based sampling and simultaneous downwind ground-based sampling. Mean Hg/SO was an order of magnitude higher at the downwind locations relative to near-source data. This was attributed to the elevated local background Hg at ground level (4.0 ng m) likely due to emissions from outgassing lava fields. The background-corrected plume Hg/SO mass ratio (5.6 × 10) therefore appeared conservative from the near-source to several hundred meters distant, which has important implications for the upscaling of volcanic Hg fluxes based on SO measurements. Using this ratio and the total SO flux from both eruptions, we estimate the total mass of gaseous Hg released from the 2021 and 2022 Fagradalsfjall eruptions was 46 ± 33 kg, equivalent to a flux of 0.23 ± 0.17 kg d. This is the lowest Hg flux estimate in the literature for active open-conduit volcanoes, which range from 0.6 to 12 kg d for other hotspot/rift volcanoes, and 0.5-110 kg d for arc volcanoes. Our results suggest that Icelandic volcanic systems are fed from an especially Hg-poor mantle. Furthermore, we demonstrate that the aerial near-source plume Hg measurement is feasible with a drone-based active sampling configuration that captures all gaseous and particulate Hg species, and recommend this as the preferred method for quantifying volcanic Hg emissions going forward.
PubMed: 38307278
DOI: 10.1016/j.scitotenv.2024.170457