Pozzolanic reaction of volcanic ash with hydrated lime is thought to dominate the cementing fabric\ud and durability of 2000-year-old Roman harbor concrete. Pliny the Elder, however, in first century CE\ud emphasized rock-like cementitious processes involving volcanic ash (pulvis) “that as soon as it comes\ud into contact with the waves of the sea and is submerged becomes a single stone mass (fierem unum\ud lapidem), impregnable to the waves and every day stronger” (Naturalis Historia 35.166). Pozzolanic\ud crystallization of Al-tobermorite, a rare, hydrothermal, calcium-silicate-hydrate mineral with cation\ud exchange capabilities, has been previously recognized in relict lime clasts of the concrete. Synchrotron-based\ud X-ray microdiffraction maps of cementitious microstructures in Baianus Sinus and Portus\ud Neronis submarine breakwaters and a Portus Cosanus subaerial pier now reveal that Al-tobermorite\ud also occurs in the leached perimeters of feldspar fragments, zeolitized pumice vesicles, and in situ\ud phillipsite fabrics in relict pores. Production of alkaline pore fluids through dissolution-precipitation,\ud cation-exchange and/or carbonation reactions with Campi Flegrei ash components, similar to processes\ud in altered trachytic and basaltic tuffs, created multiple pathways to post-pozzolanic phillipsite and\ud Al-tobermorite crystallization at ambient seawater and surface temperatures. Long-term chemical\ud resilience of the concrete evidently relied on water-rock interactions, as Pliny the Elder inferred. Raman\ud spectroscopic analyses of Baianus Sinus Al-tobermorite in diverse microstructural environments\ud indicate a cross-linked structure with Al3+ substitution for Si4+ in Q3\ud tetrahedral sites, and suggest\ud coupled [Al3++Na+\ud ] substitution and potential for cation exchange. The mineral fabrics provide a geoarchaeological\ud prototype for developing cementitious processes through low-temperature rock-fluid\ud interactions, subsequent to an initial phase of reaction with lime that defines the activity of natural\ud pozzolans. These processes have relevance to carbonation reactions in storage reservoirs for CO2 in\ud pyroclastic rocks, production of alkali-activated mineral cements in maritime concretes, and regenerative\ud cementitious resilience in waste encapsulations using natural volcanic pozzolans
The pyroclastic aggregate concrete of Trajan's Markets (110 CE), now Museo Fori Imperiali in Rome, has absorbed energy from seismic ground shaking and long-term foundation settlement for nearly two millenia while remaining largely intact at the structural scale. The scientific basis of this exceptional service record is explored through computed tomography of fracture surfaces and synchroton X-ray microdiffraction analyses of a reproduction of the standardized hydrated lime-volcanic ash mortar that binds decimeter-sized tuff and brick aggregate in the conglomeratic concrete. The mortar reproduction gains fracture toughness over 180 d through progressive coalescence of calcium-aluminum-silicate-hydrate (C-A-S-H) cementing binder with Ca/(Si+Al) ≈ 0.8-0.9 and crystallization of strätlingite and siliceous hydrogarnet (katoite) at ≥90 d, after pozzolanic consumption of hydrated lime was complete. Platey strät-lingite crystals toughen interfacial zones along scoria perimeters and impede macroscale propagation of crack segments. In the 1,900-y-old mortar, C-A-S-H has low Ca/(Si+Al) ≈ 0.45-0.75. Dense clusters of 2-to 30-μm strätlingite plates further reinforce interfacial zones, the weakest link of modern cement-based concrete, and the cementitious matrix. These crystals formed during long-term autogeneous reaction of dissolved calcite from lime and the alkali-rich scoriae groundmass, clay mineral (halloysite), and zeolite (phillipsite and chabazite) surface textures from the Pozzolane Rosse pyroclastic flow, erupted from the nearby Alban Hills volcano. The clastsupported conglomeratic fabric of the concrete presents further resistance to fracture propagation at the structural scale.Roman concrete | volcanic ash mortar | fracture toughness | interfacial zone | strätlingite
Rechargeable aqueous zinc‐ion batteries (ZIBs) have recently been comprehensively studied because of metal zinc (Zn) unique properties. However, the problems of metal zinc anode in ZIBs, namely, dendrite formation and side reactions, seriously shorten the cycling lifetimes and limit the coulombic efficiencies. Here, the tin (Sn) layer with a three‐dimensional nano‐channeled structure is decorated on zinc metal via a facile in situ substitution reaction, constructing the Sn modified Zn (Sn‐Zn) anode for high‐performance ZIBs. Multiscale investigation techniques, especially micro‐CT, are used to investigate the inhibition of zinc dendrites. In addition, the induction mechanism of Zn by Sn is also elaborately investigated. The designed Sn‐Zn anode can alleviate zinc dendrite growth and ensure long‐life stability. This work brings exciting new possibilities for the realization of industrial aqueous zinc‐ion batteries and provides new insights for the rational deposition of the Zn metal anodes.
Cabbage (Brassica oleracea var. capitata) is a biennial plant with strong self-incompatibility and an obligate requirement for prolonged vernalization by exposure to low temperatures to induce flowering. These characteristics significantly increase the difficulty of exploiting novel germplasm induced by physical or chemical mutagens. In this study, we report a CRISPR/Cas9 gene-editing system based on endogenous tRNA processing to induce high efficiency and inheritable mutagenesis in cabbage. Using the phytoene desaturase gene BoPDS, the S-receptor kinase gene BoSRK, and the male-sterility-associated gene BoMS1 as the target genes, multisite and multiple gene mutations were achieved using a construct with tandemly arrayed tRNA-sgRNA architecture to express multiple sgRNAs. The BoSRK3 gene mutation suppressed self-incompatibility completely, converting the self-incompatible line into a self-compatible line. In addition, the BoMS1 gene mutation produced a completely male-sterile mutant, which was highly cross compatible with its nonmutant isoline at the flowering stage as a result of a simultaneous BoSRK3 gene mutation, enabling the economic propagation of the male-sterile line through bee-mediated cross-pollination. Interestingly, higher site mutation efficiency was detected when a guide sequence was inserted into a location in the tandemly arrayed tRNA-sgRNA architecture that was distal from the upstream Pol III promoter. In addition, mutation sites were also detected in the paralogous genes of the BoPDS and BoSRK genes that had fully consistent sequences or base mismatches but beyond the “seed” region in the spacer sequence compared with the target sgRNAs. Collectively, our results demonstrate that the CRISPR/Cas9 system, coupled with an endogenous tRNA-processing system, is an efficient tool to improve cabbage traits.
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