More Like this

1. Hot and Heterogenous High‐ ³ He/ ⁴ He Components: New Constraints From Proto‐Iceland Plume Lavas From Baffin Island

   https://doi.org/10.1029/2019GC008654  

   Willhite, Lori N.; Jackson, Matthew G.; Blichert‐Toft, Janne; Bindeman, Ilya; Kurz, Mark D.; Halldórsson, Sæmundur A.; Harðardóttir, Sunna; Gazel, Esteban; Price, Allison A.; Byerly, Benjamin L. (December 2019, Geochemistry, Geophysics, Geosystems)

   Abstract The Icelandic hotspot has erupted basaltic magma with the highest mantle‐derived³He/⁴He over a period spanning much of the Cenozoic, from the early‐Cenozoic Baffin Island‐West Greenland flood basalt province (49.8R_A), to mid‐Miocene lavas in northwest Iceland (40.2 to 47.5R_A), to Pleistocene lavas in Iceland's neovolcanic zone (34.3R_A). The Baffin Island lavas transited through and potentially assimilated variable amounts of Precambrian continental basement. We use geochemical indicators sensitive to continental crust assimilation (Nb/Th, Ce/Pb, MgO) to identify the least crustally contaminated lavas. Four lavas, identified as “least crustally contaminated,” have high MgO (>15 wt.%), and Nb/Th and Ce/Pb that fall within the mantle range (Nb/Th = 15.6 ± 2.6, Ce/Pb = 24.3 ± 4.3). These lavas have⁸⁷Sr/⁸⁶Sr = 0.703008–0.703021,¹⁴³Nd/¹⁴⁴Nd = 0.513094–0.513128,¹⁷⁶Hf/¹⁷⁷Hf = 0.283265–0.283284,²⁰⁶Pb/²⁰⁴Pb = 17.7560–17.9375,³He/⁴He up to 39.9R_A, and mantle‐like δ¹⁸O of 5.03–5.21‰. The radiogenic isotopic compositions of the least crustally contaminated lavas are more geochemically depleted than Iceland high‐³He/⁴He lavas, a shift that cannot be explained by continental crust assimilation in the Baffin suite. Thus, we argue for the presence oftwogeochemically distinct high‐³He/⁴He components within the Iceland plume. Additionally, the least crustally contaminated primary melts from Baffin Island‐West Greenland have higher mantle potential temperatures (1510 to 1630 °C) than Siqueiros mid‐ocean ridge basalts (1300 to 1410 °C), which attests to a hot, buoyant plume origin for early Iceland plume lavas. These observations support the contention that the geochemically heterogeneous high‐³He/⁴He domain is dense, located in the deep mantle, and sampled by only the hottest plumes. 

   more » « less
2. Testing the Recycled Gabbro Hypothesis for the Origin of “Ghost Plagioclase” Melt Signatures Using ⁸⁷ Sr/ ⁸⁶ Sr of Individual Olivine‐Hosted Melt Inclusions From Hawai'i

   https://doi.org/10.1029/2020GC009260  

   Anderson, O. E.; Jackson, M. G.; Rose‐Koga, E. F.; Marske, J. P.; Peterson, M. E.; Price, A. A.; Byerly, B. L.; Reinhard, A. A. (April 2021, Geochemistry, Geophysics, Geosystems)

   Abstract Melt inclusions with large, positive Sr anomalies have been described in multiple tectonic settings, and the origins of this unusual geochemical feature are debated. Three origins have been proposed, all involving plagioclase as the source of the elevated Sr: (i) direct assimilation of plagioclase‐rich lithologies, (ii) recycled lower oceanic gabbro in the mantle source, and (iii) shallow‐level diffusive interaction between present day lower oceanic crust (i.e., plagioclase‐bearing lithologies) and the percolating melt. A “ghost plagioclase” signature (i.e., a large, positive Sr anomaly without associated high Al₂O₃) is present in melt inclusions from Mauna Loa. We present new⁸⁷Sr/⁸⁶Sr measurements of individual olivine‐hosted melt inclusions from three Hawaiian volcanoes, Mauna Loa, Loihi, and Koolau. The data set includes a Mauna Loa melt inclusion with the highest reported Sr anomaly (or highest (Sr/Ce)_N, which is 7.2) for Hawai'i. All melt inclusions have⁸⁷Sr/⁸⁶Sr values within the range reported previously for the lavas from each volcano. Critically, the⁸⁷Sr/⁸⁶Sr of the high (Sr/Ce)_Nmelt inclusion lies within the narrow range of⁸⁷Sr/⁸⁶Sr for Mauna Loa melts that lack high (Sr/Ce)_Nsignatures. Therefore, to explain the high (Sr/Ce)_Nratio of the ghost plagioclase signature using an ancient recycled gabbro, the gabbro‐infused mantle source would have had to evolve, by chance, to have the same⁸⁷Sr/⁸⁶Sr as the source of the Mauna Loa melts that lack a recycled gabbro (ghost plagioclase) signature. Alternatively, shallow‐level diffusive interactions between Mauna Loa plagioclase‐rich cumulates and a percolating mantle‐derived melt provides a simpler explanation for the presence of the high (Sr/Ce)_NMauna Loa melts. 

   more » « less
3. Comparison of Low‐Density Lipoprotein Oxidation by Hydrophilic O( ³ P)‐Precursors and Lipid‐O( ³ P)‐Precursor Conjugates

   https://doi.org/10.1111/php.13803  

   Maness, Peter F.; Cone, Grant W.; Ford, David A.; McCulla, Ryan D. (March 2023, Photochemistry and Photobiology)

   Abstract Lipid oxidation by reactive oxygen species (ROS) provide several different oxidation products that have been implicated in inflammatory responses. Ground state atomic oxygen [O(³P)] is produced by the photodeoxygenation of certain heterocyclic oxides and has a reactivity that is unique from other ROS. Due to the reactive nature of O(³P), the site of O(³P)‐generation is expected to influence the products in heterogenous solutions or environments. In this work, the oxidation of low‐density lipoprotein (LDL) by lipids with covalently bound O(³P)‐photoprecursors was compared to more hydrophilic O(³P)‐photoprecursors. Lipid oxidation products were quantified after Bligh‐Dyer extraction and pentafluorobenzyl bromide (PFB) derivatization by GC–MS. Unlike the more hydrophilic O(³P)‐photoprecursors, the oxidation of LDL during the irradiation of lipid‐(O³P)‐photoprecursor conjugates showed little quenching by the addition of the O(³P)‐scavenging sodium allyl sulfonate. This indicated that lipophilic O(³P)‐photoprecursors are expected to generate lipid oxidation products where other more hydrophilic O(³P)‐photoprecursors could be quenched by other reactive groups present in solution or the environment. 

   more » « less
4. A highly stable and conductive cerium‐doped Li ₇ P ₃ S ₁₁ glass‐ceramic electrolyte for solid‐state lithium–sulfur batteries

   https://doi.org/10.1111/jace.19712  

   Mirtaleb, Amirhossein; Wang, Ruigang (June 2024, Journal of the American Ceramic Society)

   Abstract In this report, a facile wet chemical method using acetonitrile combined with thermal annealing was used to prepare Li₂S‐P₂S₅(LPS) based glass‐ceramic electrolytes with (1 wt%, 3 wt%, and 5 wt% Ce₂S₃) and without Ce₂S₃doping. The crystal structure, ionic conductivity, and chemical stability of Li₇P₃S₁₁glass‐ceramic electrolytes were examined at varying temperatures (250–350°C). The results indicated that the highest ionic conductivity of 3.15 × 10⁻⁴S cm⁻¹for pure Li₇P₃S₁₁was observed at a temperature of 325°C. By incorporating 1 wt% Ce₂S₃and subjecting it to a heat treatment at 250°C, the glass ceramic electrolyte attained a remarkable ionic conductivity of 7.7 × 10⁻⁴(S cm⁻¹) at 25°C. Furthermore, it exhibited a stable and extensive electrochemical potential range, reaching up to 5 volts when compared to the Li/Li⁺reference electrode. By tuning the glass transition and crystallization temperature, cerium doping seems to make Li₇P₃S₁₁more chemically stable, compared to its original 70Li₂S‐30P₂S₅counterpart. According to Raman and X‐ray photoelectron spectroscopy analyses, cerium doping inhibits the decomposition of highly conductive P₂S₇^4‐(pyro‐thiophosphate) to PS₄³⁻and P₂S₆⁴⁻. Doped LPS has a greater crystallinity and more uniform microstructure than pure LPS, according to XRD, Raman spectroscopy, and scanning electron microscopy analysis. Consequently, Li₇P_2.9Ce_0.1S₁₁electrolyte shows great potential as a solid‐state electrolyte for constructing high‐performance sulfide‐based all‐solid‐state batteries. 

   more » « less
5. Truly Monodisperse Molecular Nanoparticles of Cerium Dioxide of 2.4 nm dimensions: A {Ce ₁₀₀ O ₁₆₇ } Cluster

   https://doi.org/10.1002/ange.202103110  

   Russell‐Webster, Bradley; Lopez‐Nieto, Javi; Abboud, Khalil A.; Christou, George (April 2021, Angewandte Chemie)

   Abstract Ultra‐small nanoparticles of CeO₂obtained in molecular form, so‐called molecular nanoparticles, have been limited to date to a family whose largest member is of nuclearity Ce₄₀with a {Ce₄₀O₅₈} core atom count. Herein we report that a synthetic procedure has been developed to the cation [Ce₁₀₀O₁₄₉(OH)₁₈(O₂CPh)₆₀(PhCO₂H)₁₂(H₂O)₂₀]¹⁶⁺, a member with a much higher Ce₁₀₀nuclearity and a {Ce₁₀₀O₁₆₇} core that is more akin to the smallest ceria nanoparticles. Its crystal structure reveals it to possess a 2.4 nm size and high D_2dsymmetry, and it has also allowed identification of core surface features including facet composition, the presence and location of Ce³⁺and H⁺(i.e. HO⁻) ions, and the binding modes of the ligand monolayer of benzoate, benzoic acid, and water ligands. 

   more » « less