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Oxidation of the sub-arc mantle driven by slab-derived fluids has been hypothesized to contribute to the formation of gold deposits in magmatic arc environments that host the majority of metal resources on Earth. However, the mechanism by which the infiltration of slab-derived fluids into the mantle wedge changes its oxidation state and affects Au enrichment remains poorly understood. Here, we present the results of a numerical model that demonstrates that slab-derived fluids introduce large amounts of sulfate (S⁶⁺) into the overlying mantle wedge that increase its oxygen fugacity by up to 3 to 4 log units relative to the pristine mantle. Our model predicts that as much as 1 wt.% of the total dissolved sulfur in slab-derived fluids reacting with mantle rocks is present as the trisulfur radical ion, S₃^–. This sulfur ligand stabilizes the aqueous Au(HS)S₃^–complex, which can transport Au concentrations of several grams per cubic meter of fluid. Such concentrations are more than three orders of magnitude higher than the average abundance of Au in the mantle. Our data thus demonstrate that an aqueous fluid phase can extract 10 to 100 times more Au than in a fluid-absent rock-melt system during mantle partial melting at redox conditions close to the sulfide-sulfate boundary. We conclude that oxidation by slab-derived fluids is the primary cause of Au mobility and enrichment in the mantle wedge and that aqueous fluid-assisted mantle melting is a prerequisite for formation of Au-rich magmatic hydrothermal and orogenic gold systems in subduction zone settings. 

The conditions for rupture of a material commonly vary from sample to sample. Of great importance to applications are the conditions for rare-event rupture, but their measurements require many sam- ples and consume much time. Here, the conditions for rare-event rupture are measured by developing a high-throughput experiment. For each run of the experiment, 1,000 samples are printed under the same nominal conditions and pulled simultaneously to the same stretch. Identifying the rupture of individual samples is automated by processing the video of the experiment. Under monotonic load, the rupture stretch for each sample is recorded. Under cyclic load, the number of cycles to rupture for each sample is also recorded. Rare-event rupture is studied by using the Weibull distribution and the peak-over-threshold method. This work reaffirms that predict- ing rare events requires large datasets. The high-throughput exper- iments enable the prediction of rare events with high accuracy and confidence. 

Biological tissues, such as heart valves and vocal cords, function through complex shapes and high fatigue resistance. Achieving both attributes with synthetic materials is hitherto an unmet challenge. Here we meet this challenge with hydrogels of heterogeneous structures. We fabricate a three-dimensional hydrogel skeleton by stereolithography and a hydrogel matrix by cast. Both the skeleton and matrix are elastic and stretchable, but the skeleton is much stiffer than the matrix, and their polymer networks entangle topologically. When such a hydrogel is stretched, the compliance of the matrix deconcentrates stress in the skeleton and amplifies fatigue resistance. We fabricate a homogeneous hydrogel and a heterogeneous hydrogel, each in the shape of a human heart valve. Subject to cyclic pressure, the former fractures in  560 cycles but the latter is intact after 50,000 cycles. Soft materials of complex shapes and high fatigue resistance open broad opportunities for applications. 

Abstract Background Brassica oleracea includes several morphologically diverse, economically important vegetable crops, such as the cauliflower and cabbage. However, genetic variants, especially large structural variants (SVs), that underlie the extreme morphological diversity of B. oleracea remain largely unexplored. Results Here we present high-quality chromosome-scale genome assemblies for two B. oleracea morphotypes, cauliflower and cabbage. Direct comparison of these two assemblies identifies ~ 120 K high-confidence SVs. Population analysis of 271 B. oleracea accessions using these SVs clearly separates different morphotypes, suggesting the association of SVs with B. oleracea intraspecific divergence. Genes affected by SVs selected between cauliflower and cabbage are enriched with functions related to response to stress and stimulus and meristem and flower development. Furthermore, genes affected by selected SVs and involved in the switch from vegetative to generative growth that defines curd initiation, inflorescence meristem proliferation for curd formation, maintenance and enlargement, are identified, providing insights into the regulatory network of curd development. Conclusions This study reveals the important roles of SVs in diversification of different morphotypes of B. oleracea , and the newly assembled genomes and the SVs provide rich resources for future research and breeding.