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  1. Free, publicly-accessible full text available July 20, 2023
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  3. Because of their enhanced quantum confinement, colloidal two-dimensional Ruddlesden–Popper (RP) perovskite nanosheets with a general formula L 2 [ABX 3 ] n −1 BX 4 stand as a promising narrow-wavelength blue-emitting nanomaterial. Despite ample studies on batch synthesis, for RP perovskites to be broadly applied, continuous synthetic routes are needed. Herein, we design and optimize a flow reactor to continuously produce high-quality n = 1 RP perovskite nanoplatelets. The effects of antisolvent composition, reactor tube length, precursor solution injection rate, and antisolvent injection rate on the morphology and optical properties of the nanoplatelets are systematically examined. Our investigation suggests that flow reactors can be employed to synthesize high-quality L 2 PbX 4 perovskite nanoplatelets ( i.e. , n = 1) at rates greater than 8 times that of batch synthesis. Mass-produced perovskite nanoplatelets promise a variety of potential applications in optoelectronics, including light emitting diodes, photodetectors, and solar cells.

    We present updated cosmological constraints from measurements of the gas mass fractions (fgas) of massive, dynamically relaxed galaxy clusters. Our new data set has greater leverage on models of dark energy, thanks to the addition of the Perseus cluster at low redshifts, two new clusters at redshifts z ≳ 1, and significantly longer observations of four clusters at 0.6 < z < 0.9. Our low-redshift (z < 0.16) fgas data, combined with the cosmic baryon fraction measured from the cosmic microwave background (CMB), imply a Hubble constant of h = 0.722 ± 0.067. Combining the full fgas data set with priors on the cosmic baryon density and the Hubble constant, we constrain the dark energy density to be ΩΛ = 0.865 ± 0.119 in non-flat Lambda cold dark matter (cosmological constant) models, and its equation of state to be $w=-1.13_{-0.20}^{+0.17}$ in flat, constant-w models, respectively 41 per cent and 29 per cent tighter than our previous work, and comparable to the best constraints available from other probes. Combining fgas, CMB, supernova, and baryon acoustic oscillation data, we also constrain models with global curvature and evolving dark energy. For the massive, relaxed clusters employed here, we find the scaling of fgas with mass to be consistent with a constant, withmore »an intrinsic scatter that corresponds to just ∼3 per cent in distance.

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  5. Deciduous shrubs are expanding across the graminoid-dominated nutrient-poor arctic tundra. Absorptive root traits of shrubs are key determinants of nutrient acquisition strategy from tundra soils, but the variations of shrub root traits within and among common shrub genera across the arctic climatic gradient are not well resolved. Consequently, the impacts of arctic shrub expansion on belowground nutrient cycling remain largely unclear. Here, we collected roots from 170 plots of three commonly distributed shrub genera ( Alnus , Betula , and Salix ) and a widespread sedge ( Eriophorum vaginatum ) along a climatic gradient in northern Alaska. Absorptive root traits that are relevant to the strategy of plant nutrient acquisition were determined. The influence of aboveground dominant vegetation cover on the standing root biomass, root productivity, vertical rooting profile, as well as the soil nitrogen (N) pool in the active soil layer was examined. We found consistent root trait variation among arctic plant genera along the sampling transect. Alnus and Betula had relatively thicker and less branched, but more frequently ectomycorrhizal colonized absorptive roots than Salix , suggesting complementarity between root efficiency and ectomycorrhizal dependence among the co-existing shrubs. Shrub-dominated plots tended to have more productive absorptive roots than sedge-dominatedmore »plots. At the northern sites, deep absorptive roots (>20 cm depth) were more frequent in birch-dominated plots. We also found shrub roots extensively proliferated into the adjacent sedge-dominated plots. The soil N pool in the active layer generally decreased from south to north but did not vary among plots dominated by different shrub or sedge genera. Our results reveal diverse nutrient acquisition strategies and belowground impacts among different arctic shrubs, suggesting that further identifying the specific shrub genera in the tundra landscape will ultimately provide better predictions of belowground dynamics across the changing arctic.« less