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1. Comparison of Laser Ablation and Solution‐Based ICP‐MS Results for Individual Foraminifer Mg/Ca and Sr/Ca Analyses

   https://doi.org/10.1029/2020GC009254  

   Fehrenbacher, Jennifer; Marchitto, Thomas; Spero, Howard J. (December 2020, Geochemistry, Geophysics, Geosystems)

   null (Ed.)
2. Study of Thermal Insulation Nature of A2Fe2O6-δ (A and A’ = Ca, Sr)

   https://doi.org/10.19080/ETOAJ.2024.05.555671  

   Hona, Ram Krishna (January 2024, Engineering Technology Open Access Journal)

   unknown (Ed.)

   Materials with low thermal conductivity have been used in thermoelectrics, electronics, solar devices, and land base and aerospace gas turbines to prevent heat dissipation and provide safety and longevity of equipment. We report Ca2Fe2O6-δ, and Sr2Fe2O6-δ for their low thermal conductivities. These compounds are vacancy-ordered oxygen-deficient perovskites but with different vacancy arrangements. Ca2Fe2O6-δ has a brownmillerite type structure while Sr2Fe2O6-δ has a different structure. 

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3. Double-Bilayer polar nanoregions and Mn antisites in (Ca, Sr)3Mn2O7

   https://doi.org/10.1038/s41467-022-32090-w  

   Miao, Leixin; Hasin, Kishwar-E; Moradifar, Parivash; Mukherjee, Debangshu; Wang, Ke; Cheong, Sang-Wook; Nowadnick, Elizabeth A.; Alem, Nasim (August 2022, Nature Communications)

   Abstract The layered perovskite Ca₃Mn₂O₇(CMO) is a hybrid improper ferroelectric candidate proposed for room temperature multiferroicity, which also displays negative thermal expansion behavior due to a competition between coexisting polar and nonpolar phases. However, little is known about the atomic-scale structure of the polar/nonpolar phase coexistence or the underlying physics of its formation and transition. In this work, we report the direct observation of double bilayer polar nanoregions (db-PNRs) in Ca_2.9Sr_0.1Mn₂O₇using aberration-corrected scanning transmission electron microscopy (S/TEM). In-situ TEM heating experiments show that the db-PNRs can exist up to 650 °C. Electron energy loss spectroscopy (EELS) studies coupled with first-principles calculations demonstrate that the stabilization mechanism of the db-PNRs is directly related to an Mn oxidation state change (from 4+ to 2+), which is linked to the presence of Mn antisite defects. These findings open the door to manipulating phase coexistence and achieving exotic properties in hybrid improper ferroelectric. 

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4. Groundwater discharge impacts marine isotope budgets of Li, Mg, Ca, Sr, and Ba

   https://doi.org/10.1038/s41467-020-20248-3  

   Mayfield, Kimberley K.; Eisenhauer, Anton; Santiago Ramos, Danielle P.; Higgins, John A.; Horner, Tristan J.; Auro, Maureen; Magna, Tomas; Moosdorf, Nils; Charette, Matthew A.; Gonneea, Meagan Eagle; et al (December 2021, Nature Communications)

   null (Ed.)

   Abstract Groundwater-derived solute fluxes to the ocean have long been assumed static and subordinate to riverine fluxes, if not neglected entirely, in marine isotope budgets. Here we present concentration and isotope data for Li, Mg, Ca, Sr, and Ba in coastal groundwaters to constrain the importance of groundwater discharge in mediating the magnitude and isotopic composition of terrestrially derived solute fluxes to the ocean. Data were extrapolated globally using three independent volumetric estimates of groundwater discharge to coastal waters, from which we estimate that groundwater-derived solute fluxes represent, at a minimum, 5% of riverine fluxes for Li, Mg, Ca, Sr, and Ba. The isotopic compositions of the groundwater-derived Mg, Ca, and Sr fluxes are distinct from global riverine averages, while Li and Ba fluxes are isotopically indistinguishable from rivers. These differences reflect a strong dependence on coastal lithology that should be considered a priority for parameterization in Earth-system models. 

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5. Accuracy and Reproducibility of Coral Sr/Ca SIMS Timeseries in Modern and Fossil Corals

   https://doi.org/10.1029/2021GC010068  

   Sayani, Hussein R.; Cobb, Kim M.; Monteleone, Brian; Bridges, Heather (August 2022, Geochemistry, Geophysics, Geosystems)

   Abstract Coral strontium‐to‐calcium ratios (Sr/Ca) provide quantitative estimates of past sea surface temperatures (SST) that allow for the reconstruction of changes in the mean state and climate variations, such as the El Nino‐Southern Oscillation, through time. However, coral Sr/Ca ratios are highly susceptible to diagenesis, which can impart artifacts of 1–2°C that are typically on par with the tropical climate signals of interest. Microscale sampling via Secondary Ion Mass Spectrometry (SIMS) for the sampling of primary skeletal material in altered fossil corals, providing much‐needed checks on fossil coral Sr/Ca‐based paleotemperature estimates. In this study, we employ a set modern and fossil corals from Palmyra Atoll, in the central tropical Pacific, to quantify the accuracy and reproducibility of SIMS Sr/Ca analyses relative to bulk Sr/Ca analyses. In three overlapping modern coral samples, we reproduce bulk Sr/Ca estimates within ±0.3% (1σ). We demonstrate high fidelity between 3‐month smoothed SIMS coral Sr/Ca timeseries and SST (R = −0.5 to −0.8;p < 0.5). For lightly‐altered sections of a young fossil coral from the early‐20th century, SIMS Sr/Ca timeseries reproduce bulk Sr/Ca timeseries, in line with our results from modern corals. Across a moderately‐altered section of the same fossil coral, where diagenesis yields bulk Sr/Ca estimates that are 0.6 mmol too high (roughly equivalent to −6°C artifacts in SST), SIMS Sr/Ca timeseries track instrumental SST timeseries. We conclude that 3–4 SIMS analyses per month of coral growth can provide a much‐needed quantitative check on the accuracy of fossil coral Sr/Ca‐derived estimates of paleotemperature, even in moderately altered samples. 

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