In this study, we have examined the lower mantle composition and mineralogy by modeling the density (ρ), bulk sound velocity (VΦ), and dlnρ/dlnVΦ profiles of candidate lower mantle minerals using literature and new experimental equation of state (EoS) results. For CaSiO3 perovskite, complimentary synchrotron X‐ray diffraction measurements in a laser‐heated diamond anvil cell were conducted up to 156 GPa between 1200 K and 2600 K to provide more reliable constraints on the thermal EoS parameters. These new experimental results as well as literature P‐V‐T data sets are systematically analyzed using an internally self‐consistent pressure scale. We have modeled ρ, VΦ, and dlnρ/dlnVΦ profiles of the lower mantle with representative pyrolitic and chondritic compositional models in which the effect of Fe spin transition in ferropericlase is also taken into account. Our modeling results show that a pyrolitic lower mantle with an aggregate mineralogy of 75 vol % bridgmanite, 17 vol % ferropericlase, and 8 vol % CaSiO3 perovskite produces ρ and VΦ profiles in better agreement with preliminary reference Earth model than a lower mantle with a chondritic composition. The modeled ρ, VΦ, and dlnρ/dlnVΦ are mainly affected by the relative ratio of bridgmanite and ferropericlase but are not sensitive to the variation of the CaSiO3 perovskite content. In addition, the spin crossover of Fe in ferropericlase can greatly raise the value of dlnρ/dlnVΦ in the middle lower mantle, which is useful in detecting the presence of ferropericlase in the region. Based on these new mineral physical constraints and radial seismic structure, our study suggests the lower mantle is pyrolitic, which is chemically indistinguishable from the upper mantle.

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Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is spreading globally, and its high transmission speed and mortality rate are severely interfering with people’s normal lives and the economy. Governments are now reopening their economies; however, the opening of theaters has been delayed, owing to their (often) crowded audiences and potentially higher infection risk. To determine whether it is safe to reopen theaters, in this study, the transport of contaminants released by an infected person in a theater hall with an overhead air supply system is analyzed numerically. The infection risks are calculated for occupants at various distances from the infected person in different directions and with/without wearing masks based on a revised Wells-Riley model, and under different supply air states and locations of the infected person. The results show that, first, the probabilities of infection in return air with filtration and all-fresh-air operations are decreased by 39.8 and 55.6%, respectively, as compared when the return air is not filtered. Second, the probabilities of infection for audiences sitting nine seats away from the infected person on the right, right-back, and back sides are 84.9–92.3%, 37.3–74.0%, and 36.3–72.0% lower, respectively, than those for audiences sitting one-seat away from the infected person. In addition, sitting in separate rows can reduce the maximum probability by 7.4–68.3%. Third, the probability of infection can be reduced by 93.7% after all the audiences wear masks with efficiencies of 75%. Fourth, the probability of infection can be controlled under a relatively safe range even though the quanta emission rate is 30 or 50 quanta/h, and even with two infected people in unfavorable seats. Thus, theaters can be safely reopened under return air filtration or all fresh air operations, and when audiences are sitting in separate seats and wearing masks.