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Our ability to model igneous processes depends on knowledge of the phases present. In the case of the mantle, the presence or absence of clinopyroxene in the protolith will control the productivity of the mantle as well as the trace element signature. Increasing evidence suggests that the mantle contains regions characterized by extremely depleted trace element signatures (Ti/Zr<140), consistent with a degree of melting (>20%) past the point at which clinopyroxene is exhausted. Until clinopyroxene is consumed, its relatively high partition coefficients control the trace element budget for the rare earth elements (REE) and high field strength elements (HFSE) at pressures below garnet stability. After clinopyroxene exhaustion, the geochemical evolution of subsequent melts is dependent on the trace element partitioning between orthopyroxene and melt. Therefore, understanding the degree of depletion of incompatible elements during melting of the mantle past clinopyroxene exhaustion requires accurate partition coefficients for the REE and HFSE between orthopyroxene and silicate melt for (opx-meltDREE, HFSE). However, the current experimental database for orthopyroxene/melt partitioning is compromised by inconsistencies in the number and distribution of data in temperature, pressure, and composition. We report on a series of phase equilibria and trace element partitioning experiments that aim to further our understanding of the liquidus phase relations at upper mantle conditions and to constrain the opx-meltDREE, HFSE. The starting material is a powder composed of 65% of basaltic glass from Gorda Ridge, 25% En89 Kenya enstatite, and 10% Fo90 Kilbourne Hole olivine. Experiments were conducted in a piston-cylinder press at 5, 10, 15, and 20 kbar and various temperatures for 24 hours to obtain high degrees of partial melting. Major and trace element analyses were performed on the run products to characterize their texture, mineralogical assemblage, and calculate the opx-meltDREE, HFSE. Experiments at 10 and 15 kbars produced olivine and orthopyroxene ± clinopyroxene crystals larger than 50 m which document the behavior of trace elements in low-Ca pyroxenes as a function of pressure, temperature, and degree of partial melting. Our investigation identifies the specific low-Ca pyroxene species in these experiments and discusses the improvement of analytical procedures to minimize analytical error. 

Gaussian splatting methods are emerging as a popular approach for converting multi-view image data into scene representations that allow view synthesis. In particular, there is interest in enabling view synthesis for dynamic scenes using only monocular input data---an ill-posed and challenging problem. The fast pace of work in this area has produced multiple simultaneous papers that claim to work best, which cannot all be true. In this work, we organize, benchmark, and analyze many Gaussian-splatting-based methods, providing apples-to-apples comparisons that prior works have lacked. We use multiple existing datasets and a new instructive synthetic dataset designed to isolate factors that affect reconstruction quality. We systematically categorize Gaussian splatting methods into specific motion representation types and quantify how their differences impact performance. Empirically, we find that their rank order is well-defined in synthetic data, but the complexity of real-world data currently overwhelms the differences. Furthermore, the fast rendering speed of all Gaussian-based methods comes at the cost of brittleness in optimization. We summarize our experiments into a list of findings that can help to further progress in this lively problem setting.