Large numbers of earthquakes occur in subduction zones that are marked by dipping, narrow high seismic velocity slabs. The existence of these fast velocity slabs can cause serious earthquake mislocation problems that can bias estimates of seismic travel time residuals. This can affect the recovery of subducting slabs in tomography as well as introduce significant artifacts into lower mantle structure in tomography models. In order to better account for known subducting slabs, we performed a new P and S wave joint tomography inversion incorporating a three-dimensional thermal model of subducting slabs in the starting model. In addition, velocity and source locations were inverted for simultaneously. Our new P and S models feature higher-amplitude subducting slabs compared with previous global tomography results. The S to P heterogeneity ratio based on the new tomography model indicates that thermal elastic effects alone cannot explain all the heterogeneities in the lower mantle. Much of the observed abnormal S to P heterogeneity ratio can be explained by anelastic effects, the spin transition, and phase transitions of bridgmanite to post-perovskite in the lower mantle.Plain Language Summary Seismic tomography uses seismic travel time data to image deep earth velocity structure. However, it has been shown that the existence of subducting slabs can significantly bias the imaging result. In order to reduce this effect, we produced a new P and S wave tomography model that included theoretical three-dimensional subducting slab structures in the starting model. The new model has higher-amplitude subducting slabs compared with other models. Based on the new model, we conclude that it is difficult to explain the P and S velocity anomalies found in the deep mantle by temperature variations alone without invoking complex mineral phase transitions, large anelastic effects, or chemical variations. Key Points:• We developed new P and S tomography models incorporating 3-D subducting slabs • Mislocation effects caused by subducting slabs were reduced by inverting for velocity and source location simultaneously • The spin transition and the post-perovskite phase transition may explain lower mantle heterogeneitiesSupporting Information:• Supporting Information S1

Seismic tomography has revealed the existence of large-scale velocity heterogeneities in the mantle. The interpretation of seismic velocity anomalies in terms of temperature and chemical composition is nonunique. We use geodynamic observations including gravity, plate motions, dynamic topography, and excess ellipticity of the core-mantle boundary combined with seismic observations to investigate the thermo-chemical structure of the mantle through joint inversions. An outstanding issue, however, is the physical connection between mantle density anomalies and the surface geodynamic observations, which requires knowledge of the mantle viscosity structure. Here we perform joint inversions assuming different viscosity profiles and examine the dependence of the results on the viscosity. We first assume that mantle heterogeneity is due to thermal variations, which places a constraint on the relation between seismic velocity and density, and we subsequently relax the constraint to allow for potential nonthermal effects. In all of our joint inversions, a nonthermal origin of density anomalies is required to explain the geodynamic data, though the amount varies with the assumed viscosity structure. A common observation is a high-density chemical signal in the center of the large low-shear-velocity provinces at the base of the mantle resulting in a near neutral or slightly dense overall buoyancy there. Using the derived density models and their corresponding viscosity profiles, we also calculate instantaneous mantle flow fields. The predicted flow fields derived from joint inversions are generally similar but are quite different from flow fields using density models derived from a posteriori scaling of pure seismic tomography models.Plain Language Summary The origin and evolution of Earth's mantle have been long-standing fundamental questions in geosciences. We use both global seismological and geodynamical (gravity, topography, plate motions, and excess ellipticity of the core-mantle boundary) data sets to investigate whether lateral changes in mantle structure can be explained solely by temperature variations or whether the mantle must also have significant chemical variations. Our results indicate the presence of chemically distinct mantle anomalies. In particular, we find two large regions at the base of the mantle that appear to be chemically distinct with hot mantle upwellings surrounding them. We also derived several models of 3D density variations in the mantle assuming different viscosity profiles. These models were then used to predict the present-day mantle convective flow. We show that the mantle viscosity structure does not have a strong influence on the pattern of large-scale mantle flow. We find, however, that 3D density models derived by simple (1D) a posteriori scaling of tomography models obtained only from seismic data yield predictions of significantly different mantle flow.

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Four new citrinin derivatives, including two citrinin dimers and two citrinin monomer derivatives, were isolated and identified from a marine-derived fungal strain Penicillium sp. ML226 along with six known related compounds. Their structures were elucidated by spectroscopic and chemical methods. The new compounds showed modest cytotoxic activity against HepG-2 cell line and weak antimicrobial activity against Staphylococcus aureus.