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We identified the perovskite oxides LaMn0.5Ni0.5O3 (L2MN), Gd0.5La0.5Mn0.5Ni0.5O3 (GLMN), and GdMn0.5Ni0.5O3 (G2MN) as candidate solar thermal chemical hydrogen (STCH) redox mediators from their density functional theory (DFT)-computed electronic and oxygen vacancy properties following a high-throughput computational screening of AA′BB′O6 compositions that are likely to form as perovskites and split water. At a thermal reduction temperature of 1350 °C and a water splitting temperature of 850 °C, the L2MN and GLMN perovskites produced ∼65 μmol g–1 of hydrogen per cycle with no phase degradation over three redox cycles at 40 mol % steam, while the G2MN perovskite did not produce STCH under these conditions. When reoxidized by exposure to a gas flow with a H2O:H2 molar ratio of 1333:1, which represents operating conditions where the thermodynamic driving force of water splitting is lowered by orders of magnitude relative to 40 mol % steam, the L2MN and GLMN perovskites each produced ∼35 μmol g–1 of hydrogen per cycle. Guided by DFT, we propose that L2MN and GLMN’s STCH activities arise from B-site cation antisite defects that facilitate oxygen vacancy formation and thus redox cycling, whereas the synthesized G2MN has few antisite defects and is therefore inactive for STCH. 

Abstract Survey teams at the El Pilar Archaeological Reserve for Maya Flora and Fauna have mapped 70 percent of its 20 km²area and revealed the extent of settlement around the city center. Large-scale civic architecture, and the distribution of smaller ceremonial groups and minor centers, reflect the wealth and power of Maya rulers presiding over the largest Classic period city in the upper Belize River area. Previous analyses suggest disparities in wealth at El Pilar were more nuanced than the elite/commoner dichotomy commonly invoked for Classic Maya society. This article works to understand wealth inequality at ancient El Pilar by computing Gini coefficients from areal and volumetric calculations of primary residential units—the class of settlement remains most likely to represent ancient households. Presentation of Gini coefficients and their potential interpretations follows a discussion of settlement classification and residential group labor investment. We conclude by contextualizing these results within prior settlement pattern analyses to explore how disparities in wealth may have been distributed across the physical and social landscape. 

Over the last two decades, science gateways have become essential tools for supporting both research and education. The SimVascular application is an open source software package providing a complete pipeline from medical image data segmentation to patient-specific blood flow simulation and analysis. With an ever-increasing user base of students, educators, clinicians, and researchers, the development group wanted a user-friendly web portal for users to run SimVascular flow simulations and to be able to support a large number of users with minimum effort and also hide complexity of using HPCs. This paper discusses how the SimVascular Science Gateway became a tool for students, educators, and researchers of all levels and continues to gather and grow a strong research community.