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At least 397 records · Page 22

Anisotropic Exchange within Decoupled Tetrahedra in the Quantum Breathing Pyrochlore Ba 3 Yb 2 Zn 5 O 11

The low energy spin excitation spectrum of the breathing pyrochlore Ba 3 Yb 2 Zn 5 O 11 has been investigated with inelastic neutron scattering. Several nearly resolution limited modes with no observable dispersion are observed at 250 mK while, at elevated temperatures, transitions between excited levels become visible. To gain deeper insight, a theoretical model of isolated Yb 3+ tetrahedra parametrized by four anisotropic exchange constants is constructed. The model reproduces the inelastic neutron scattering data, specific heat, and magnetic susceptibility with high fidelity. The fitted exchange parameters reveal a Heisenberg antiferromagnet with a very large Dzyaloshinskii-Moriya interaction. Ultimately, using this model, we predict the appearance of an unusual octupolar paramagnet at low temperatures and speculate on the development of inter-tetrahedron correlations.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

Decoupling exchange bias and coercivity enhancement in a perovskite oxide exchange spring bilayer

A wedge bilayer of epitaxial 4–8 nm La 0.7 Sr 0.3 CoO 3 (LSCO)/6-nm La 0.7 Sr 0.3 MnO 3 (LSMO), hard and soft ferromagnets (FM) respectively, was studied using soft x-ray magnetic spectroscopy to elucidate the interplay between the magnetic and electronic properties of the constituent layers. This system exhibits magnetic and electronic segregation within the LSCO layer characterized by soft FM Co 2+ ions at the interface (s-LSCO), which is biased by the underlying hard LSCO layer (h-LSCO), characterized by predominantly Co 3+ /Co 4+ FM ions. For a 5.1-nm layer, the interfacial Co 2+ ion concentration is maximized and the h-LSCO coercivity is minimized, while the opposite is true for a 7.8-nm LSCO layer. Furthermore these dual trends in Co 2+ ion concentration and h-LSCO coercivity within the LSCO serve to independently affect the exchange bias and coercivity of the soft FM layer, resulting in inverse trends between these properties that typically vary simultaneously.

36 MATERIALS SCIENCE↗

Decoupling Grain-Boundary, Grain-Interior, and Surface Recombination with Cathodoluminescence

In this work, we combine quantitative cathodoluminescence (CL) with time-resolved photoluminescence (TRPL) and numerical simulations to determine grain-boundary, grain-interior, and surface recombination parameters in standard CdTe thin films. CL intensities from thousands of grains are analyzed to accumulate statistics and chart variations with grain size. Grain-boundary contrast results for small grains indicate that the grain-boundary recombination velocity, S GB , decreases significantly with CdCl 2 treatment, but S GB is increased by subsequent Cu-diffusion. Furthermore, within a given sample, data suggests that S GB is nearly independent of grain size. The back-surface recombination velocity, S, is extracted from TRPL measurements incident on the back surface, and CL profiles are simulated to determine the grain-interior lifetime, t GI . Finally, CL intensity vs. grain size relationships are simulated to check for self-consistency of the S GB , S, and t GI values.

14 SOLAR ENERGY↗

The air mycobiome is decoupled from the soil mycobiome in the California San Joaquin Valley

Abstract Dispersal is a key force in the assembly of fungal communities and the air is the dominant route of dispersal for most fungi. Understanding the dynamics of airborne fungi is important for determining their source and for helping to prevent fungal disease. This understanding is important in the San Joaquin Valley of California, which is home to 4.2 million people and where the airborne fungus Coccidioides is responsible for the most important fungal disease of otherwise healthy humans, coccidioidomycosis. The San Joaquin Valley is the most productive agricultural region in the United States, with the principal crops grown therein susceptible to fungal pathogens. Here, we characterize the fungal community in soil and air on undeveloped and agricultural land in the San Joaquin Valley using metabarcoding of the internal transcribed spacer 2 variable region of fungal rDNA. Using 1,002 individual samples, we report one of the most extensive studies of fungi sampled simultaneously from air and soil using modern sequencing techniques. We find that the air mycobiome in the San Joaquin Valley is distinct from the soil mycobiome, and that the assemblages of airborne fungi from sites as far apart as 160 km are far more similar to one another than to the fungal communities in nearby soils. Additionally, we present evidence that airborne fungi in the San Joaquin Valley are subject to dispersal limitation and cyclical intra‐annual patterns of community composition. Our findings are broadly applicable to understanding the dispersal of airborne fungi and the taxonomic structure of airborne fungal assemblages.

59 BASIC BIOLOGICAL SCIENCES↗

Structure-based decoupling of the pro- and anti-inflammatory functions of interleukin-10

Interleukin-10 (IL-10) is an immunoregulatory cytokine with both anti-inflammatory and immunostimulatory properties and is frequently dysregulated in disease. We used a structure-based approach to deconvolute IL-10 pleiotropy by determining the structure of the IL-10 receptor (IL-10R) complex by cryo–electron microscopy at a resolution of 3.5 angstroms. The hexameric structure shows how IL-10 and IL-10Rα form a composite surface to engage the shared signaling receptor IL-10Rβ, enabling the design of partial agonists. IL-10 variants with a range of IL-10Rβ binding strengths uncovered substantial differences in response thresholds across immune cell populations, providing a means of manipulating IL-10 cell type selectivity. Some variants displayed myeloid-biased activity by suppressing macrophage activation without stimulating inflammatory CD8 + T cells, thereby uncoupling the major opposing functions of IL-10. These results provide a mechanistic blueprint for tuning the pleiotropic actions of IL-10.

60 APPLIED LIFE SCIENCES↗

Decoupling Failure Pathways in Li-O 2 Cells Operated Under Lean Electrolyte Conditions

The operation of lithium-oxygen (Li-O 2 ) batteries under lean electrolyte conditions offers higher energy density but leads to rapid degradation and short cycle life. Although cathode passivation and electrolyte decomposition occur in all regimes, we show that under lean electrolyte conditions, failure is primarily driven by progressive electrolyte consumption at the lithium/solid electrolyte interphase (SEI), rather than by irreversible cathode passivation. Poor wetting of the lithium surface results in heterogeneous SEI growth and high local current densities, which accelerate electrolyte loss and cell failure. Strategies aimed at improving interfacial stability, including optimized wetting and SEI forming additives, significantly extend cycle life without compromising energy density. Our results establish anode-electrolyte interactions as the dominant degradation mechanism under lean electrolyte conditions, and emphasize the need to engineer a stable Li/SEI interface for long-lasting Li-O 2 batteries.

Córdoba, Daniel [Argonne National Laboratory (ANL)↗