Iconography of the thruston tablet

The Thruston Tablet - also known as the Rocky Creek Tablet - is among the most interesting and unusual artifacts ever found in the American South. It consists of an irregular limestone slab 19 inches long, 14 inches high, and 1 inch thick (about the size of a cafeteria tray). One side of the tablet (which we think of today as the obverse or front) is covered with engraved designs, consisting of many human forms arranged in multiple scenes. The tablet also has engraved images on the reverse, but these are faint and less distinct. The tablet is clearly Mississippian in age and probably dates to the late thirteenth or early fourteenth centuries ad. Here we present our recent studies of the tablet\u27s imagery. We begin by reviewing past research on this object and describing our own recent investigations. We then present our analysis of the tablet\u27s iconography, a possible interpretation of its meaning, and a discussion of the tablet\u27s thematic and stylistic relationships. © 2011 by The University of Texas Press. All rights reserved

Low-cost dopant-free carbazole enamine hole-transporting materials for thermally stable perovskite solar cells

Perovskite solar cells deliver high efficiencies, but are often made from high-cost bespoke chemicals, such as the archetypical hole-conductor, 2,2′,7,7′-tetrakis(N,N-di-p-methoxy-phenylamine)-9-9′-spirobifluorene (spiro-OMeTAD). Herein, new charge-transporting carbazole-based enamine molecules are reported. The new hole conductors do not require chemical oxidation to reach high power conversion efficiencies (PCEs) when employed in n-type-intrinsic-p-type perovskite solar cells; thus, reducing the risk of moisture degrading the perovskite layer through the hydrophilicity of oxidizing additives that are typically used with conventional hole conductors. Devices made with these new undoped carbazole-based enamines achieve comparable PCEs to those employing doped spiro-OMeTAD, and greatly enhanced stability under 85 °C thermal aging; maintaining 83% of their peak efficiency after 1000 h, compared with spiro-OMeTAD-based devices that degrade to 26% of the peak PCE within 24 h. Furthermore, the carbazole-based enamines can be synthesized without the use of organometallic catalysts and complicated purification techniques, lowering the material cost by one order of magnitude compared with spiro-OMeTAD. As a result, we calculate that the overall manufacturing costs of future photovoltaic (PV) modules are reduced, making the levelized cost of electricity competitive with silicon PV modules