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The delafossites are a class of layered metal oxides that are notable for being able to exhibit optical transparency alongside an in-plane electrical conductivity, making them promising platforms for the development of transparent conductive oxides. Pressure-induced polymorphism offers a direct method for altering the electrical and optical properties in this class, and although the copper delafossites have been studied extensively under pressure, the silver delafossites remain only partially studied. We report two new high-pressure polymorphs of silver ferrite delafossite, AgFeO2, that are stabilized above ∼6 and ∼14 GPa. In situ X-ray diffraction and vibrational spectroscopy measurements are used to examine the structural changes across the two phase transitions. The high-pressure structure between 6 and 14 GPa is assigned as a monoclinic C2/c structure that is analogous to the high-pressure phase reported for AgGaO2. Nuclear resonant forward scattering reveals no change in the spin state or valence state at the Fe3+ site up to 15.3(5) GPa. 

Abstract Vanadium (V) pollution potentially threatens human health. Here, it is found thatnsp1andnsp2,Rhizobiumsymbiosis defective mutants ofMedicago truncatula, are sensitive to V. Concentrations of phosphorus (P), iron (Fe), and sulfur (S) with V are negatively correlated in the shoots of wild‐type R108, but not in mutantnsp1andnsp2shoots. Mutations in the P transporterPHT1,PHO1, andVPTfamilies, Fe transporterIRT1, and S transporterSULTR1/3/4family confer varying degrees of V tolerance on plants. Among these gene families,MtPT1,MtZIP6,MtZIP9, andMtSULTR1; 1in R108 roots are significantly inhibited by V stress, whileMtPHO1; 2,MtVPT2, andMtVPT3are significantly induced. Overexpression ofArabidopsis thaliana VPT1orM. truncatula MtVPT3increases plant V tolerance. However, the response of these genes to V is weakened innsp1ornsp2and influenced by soil microorganisms. Mutations inNSPsreduce rhizobacterial diversity under V stress and simplify the V‐responsive operational taxonomic unit modules in co‐occurrence networks. Furthermore, R108 recruits more beneficial rhizobacteria related to V, P, Fe, and S than doesnsp1ornsp2. Thus, NSPs can modulate the accumulation and tolerance of legumes to V through P, Fe, and S transporters, ion homeostasis, and rhizobacterial community responses. 

We perform resonant Raman spectroscopy on 8◦ twisted bilayer graphene placed in an out-of-plane magnetic field. The high-quality device has narrow Landau level linewidth of less than 5 meV that enables detection of features from both electronic Raman scattering and magnetophonon resonance involving electronic transitions between the low energy Landau levels. Two magnetophonon resonances are observed, one at 4.6T in the strong coupling regime, and the other at 2.6T in the weak coupling regime. Using the measured Landau level transition energy, we analyze the renormalization of effective band velocity, whose dependence on magnetic field points to a 20% enhancement of dielectric constant due to the presence of an adjacent graphene layer, a quite prominent screening effect from a monolayer of carbon atoms in proximity. Both the Landau level transition electronic Raman and the magnetophonon resonance are gate tunable. Harnessing angular momentum conservation, we demonstrate charge tuning of electron phonon coupling strength for left and right circularly polarized G band phonons separately. 

Methane (CH4) and nitrous oxide (N2O) are major greenhouse gases that are predominantly generated by microbial activities in anoxic environments. N2O inhibition of methanogenesis has been reported, but comprehensive efforts to obtain kinetic information are lacking. Using the model methanogen Methanosarcina barkeri strain Fusaro and digester sludge-derived methanogenic enrichment cultures, we conducted growth yield and kinetic measurements and showed that micromolar concentrations of N2O suppress the growth of methanogens and CH4 production from major methanogenic substrate classes. Acetoclastic methanogenesis, estimated to account for two-thirds of the annual 1 billion metric tons of biogenic CH4, was most sensitive to N2O, with inhibitory constants (KI) in the range of 18–25 μM, followed by hydrogenotrophic (KI, 60–90 μM) and methylotrophic (KI, 110–130 μM) methanogenesis. Dissolved N2O concentrations exceeding these KI values are not uncommon in managed (i.e. fertilized soils and wastewater treatment plants) and unmanaged ecosystems. Future greenhouse gas emissions remain uncertain, particularly from critical zone environments (e.g. thawing permafrost) with large amounts of stored nitrogenous and carbonaceous materials that are experiencing unprecedented warming. Incorporating relevant feedback effects, such as the significant N2O inhibition on methanogenesis, can refine climate models and improve predictive capabilities. 

Monolayer transition metal dichalcogenide semiconductors are promising valleytronic materials. Among various quasi-particle excitations hosted by the system, the valley polarized holes are particularly interesting due to their long valley lifetime preserved by the large spin–orbit splitting and spin–valley locking in the valence band. Here we report that in the absence of any magnetic field a surprising valley splitting of exciton polarons can be induced by such valley polarized holes in monolayer WSe2. The size of the splitting is comparable to that of the Zeeman effect in a magnetic field as high as 7 T and offers a quantitative approach to extract the hole density imbalance between the two valleys. We find that the density difference can easily achieve more than 1011 per cm2, and it is tunable by gate voltage as well as optical excitation power. Our study highlights the response of exciton polarons to optical pumping and advances understanding of valley dependent phenomena in monolayer transition metal dichalcogenide. 

Preferential attachment (PA) network models have a wide range of applications in various scientific disciplines. Efficient generation of large-scale PA networks helps uncover their structural properties and facilitate the development of associated analytical methodologies. Existing software packages only provide limited functions for this purpose with restricted configurations and efficiency. We present a generic, user-friendly implementation of weighted, directed PA network generation with R package wdnet. The core algorithm is based on an efficient binary tree approach. The package further allows adding multiple edges at a time, heterogeneous reciprocal edges, and user-specified preference functions. The engine under the hood is implemented in C++. Usages of the package are illustrated with detailed explanation. A benchmark study shows that wdnet is efficient for generating general PA networks not available in other packages. In restricted settings that can be handled by existing packages, wdnet provides comparable efficiency.