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1. Effect of Carbon Doping on CO ₂ ‐Reduction Activity of Single Cobalt Sites in Graphitic Carbon Nitride

   https://doi.org/10.1002/cnma.202100164  

   Huang, Peipei; Huang, Jiahao; Li, Junying; Zhang, Lei; He, Jie; Caputo, Christine_A; Frenkel, Anatoly_I; Li, Gonghu (June 2021, ChemNanoMat)

   Abstract Single‐atom catalysts have demonstrated interesting activity in a variety of applications. In this study, we prepared single Co²⁺sites on graphitic carbon nitride (C₃N₄), which was doped with carbon for enhanced activity in visible‐light CO₂reduction. The synthesized materials were characterized with a variety of techniques, including microscopy, X‐ray powder diffraction, UV‐vis spectroscopy, infrared spectroscopy, photoluminescence spectroscopy, and X‐ray absorption spectroscopy. Doping C₃N₄with carbon was found to have profound effect on the photocatalytic activity of the single Co²⁺sites. At relatively low levels, carbon doping enhanced the photoresponse of C₃N₄in the visible region and improved charge separation upon photoactivation, thereby enhancing the photocatalytic activity. High levels of carbon doping were found to be detrimental to the photocatalytic activity of the single Co²⁺sites by altering the structure of C₃N₄and generating defect sites responsible for charge recombination. 

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2. Amino mapping: possibility to visualize amino-N compounds in the rhizosphere of Zea Mays L.

   https://doi.org/10.1007/s00374-023-01754-0  

   Khosrozadeh, Sajedeh; Guber, Andrey; Nourbakhsh, Farshid; Khalili, Banafshe; Blagodatskaya, Evgenia (July 2023, Biology and Fertility of Soils)

   Abstract Understanding N uptake by plants, the N cycle, and their relationship to soil heterogeneity has generated a great deal of interest in the distribution of amino-N compounds in soil. Visualization of the spatial distribution of amino-N in soil can provide insights into the role of labile N in plant-microbial mechanisms of N acquisition and plant N uptake, but until now, it has remained technically challenging. Here, we describe a novel technique to visualize the amino-N distribution at the root-soil interface. The technique is based on time-lapse amino mapping (TLAM) using membranes saturated with the fluorogenic OPAME reagent ( O -phthalaldehyde and β-mercaptoethanol). OPAME in the membrane reacts with organic compounds containing a NH 2 functional group at the membrane-soil interface, generating a fluorescent product visible under UV light and detectable by a digital camera. The TLAM amino-mapping technique was applied to visualize and quantify the concentration of amino-N compounds in the rhizosphere of maize ( Zea Mays L.). A ten times greater amino-N concentration was detected in the rhizosphere compared to non-rhizosphere soil. The high content of amino-N was mainly associated with the root tips and was 3 times larger than the average amino-N content at seminal roots. The amino-N rhizosphere was 2 times broader around the root tips than around other parts of the roots. We concluded that TLAM is a promising approach for monitoring the fate of labile N in soils. However, the technique needs to be standardized for different soil types, plant species, and climate conditions to allow wider application. 

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3. Improved performance guarantees for Tukey's median

   Minsker, Stanislav; Shen, Yinan (November 2024, arXivorg)

   Is there a natural way to order data in dimension greater than one? The approach based on the notion of data depth, often associated with the name of John Tukey, is among the most popular. Tukey's depth has found applications in robust statistics, graph theory, and the study of elections and social choice. We present improved performance guarantees for empirical Tukey's median, a deepest point associated with the given sample, when the data-generating distribution is elliptically symmetric and possibly anisotropic. Some of our results remain valid in the wider class of affine equivariant estimators. As a corollary of our bounds, we show that the typical diameter of the set of all empirical Tukey's medians scales like $$o(n^{-1/2})$$ where $$n$$ is the sample size. Moreover, when the data are 2-dimensional, we prove that with high probability, the diameter is of order $$O(n^{-3/4}\log^{3/2}(n))$$. 

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4. Catalytic NH ₃ oxidation to N ₂ by hydrogen atom abstraction using a low-valent molybdenum complex

   https://doi.org/10.1039/d5cc02433a  

   Benedict, Rory J; Heiden, Zachariah M; Stephens, David N; Arulsamy, Navamoney; Mock, Michael T (June 2025, Chemical Communications)

   Fac-[(CO)₃Mo(P^tBu₂N^Ph₂)(NH₃)] catalyzed NH₃oxidation to N₂using phenoxyl radicals as H atom acceptors generating up to 88 equiv. N₂per Mo centre. 

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5. Nitrogen fixation associated with epiphytes on the seagrass Zostera marina in a temperate lagoon with moderate to high nitrogen loads

   https://doi.org/10.1007/s10533-023-01083-2  

   Marino, Roxanne; Hayn, Melanie; Howarth, Robert W.; Giblin, Anne E.; McGlathery, Karen J.; Berg, Peter (October 2023, Biogeochemistry)

   Abstract As part of a long-term study on the effects of nitrogen (N) loading in a shallow temperate lagoon, we measured rates of N₂fixation associated with seagrass (Zostera marina) epiphytes during the summer from 2005 to 2019, at two sites along a gradient from where high N groundwater enters the system (denoted SH) to a more well-flushed outer harbor (OH). The data presented here are the first such long-term N₂fixation estimates for any seagrass system and one of the very few reported for the phyllosphere in a temperate system. Mean daily N₂fixation was estimated from light and dark measurements using the acetylene reduction assay intercalibrated using both incorporation of¹⁵N₂into biomass and a novel application of the N₂:Ar method. Surprisingly, despite a large inorganic N input from a N-contaminated groundwater plume, epiphytic N₂fixation rates were moderately to very high for a seagrass system (OH site 14-year mean of 0.94 mmol N m⁻² d⁻¹), with the highest rates (2.6 mmol N m⁻² d⁻¹) measured at the more N-loaded eutrophic site (SH) where dissolved inorganic N was higher and soluble reactive phosphorus was lower than in the better-flushed OH. Over 95% of the total N₂fixation measured was in the light, suggesting the importance of cyanobacteria in the epiphyte assemblages. We observed large inter-annual variation both within and across the two study sites (range from 0.1 to 2.6 mmol N fixed m⁻²d⁻¹), which we suggest is in part related to climatic variation. We estimate that input from phyllosphere N₂fixation over the study period contributes on average an additional 20% to the total daily N load per area within the seagrass meadow. 

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