Scrap Cu-modified cast iron (CMCI) is a potent material for the reduction of 2,4-dinitrotoluene (2,4-DNT) by a surface-mediated reaction. However, the effects of operational parameters and common ions on its reduction and final rate are unknown. Results show that the 2,4-DNT reduction was significantly affected by Cu:Fe mass ratio and the optimum m(Cu:Fe) was 0.25%. The slight pH-dependent trend of 2,4-DNT reduction by CMCI was observed at pH 3 to 11, and the maximum end product, 2,4-diaminotoluene (2,4-DAT), was generated at pH 7. Dissolved oxygen (DO) in the water reduced the 2,4-DNT degradation and the formation of 2,4-DAT. CMCI effectively treated high concentrations of 2,4-DNT (60 to 150 mg L(-1)). In addition, varying the concentration of (NH4)2SO4 from 0.001 to 0.1 mol L(-1) improved the efficiency of the reduction process. The green rust-like corrosion products (GR-SO4 (2-)) were also effective for 2,4-DNT reduction, in which Na2CO3 (0.01 to 0.2 mol L(-1)) significantly inhibited this reduction. The repeated-use efficiency of CMCI was also inhibited. Moreover, 2,4-DNT and its products, such as 4A2NT, 2A4NT, and 2,4-DAT, produced mass imbalance (<35%). Hydrolysis of Fe(3+) and CO3 (2-) leading to the generation of Fe(OH)3 and conversion to FeOOH that precipitated on the surface and strongly adsorbed the products of reduction caused the inhibition of CO3 (2-). The 2,4-DNT reduction by CMCI could be described by pseudo-first-order kinetics. The operational conditions and common ions affected the 2,4-DNT reduction and its products by enhancing the corrosion of iron or accumulating a passive oxide film on the reactivity sites.
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Am J Emerg Med
January 2025
Department of Emergency Medicine, Yale University School of Medicine, New Haven, CT, USA; Center for Outcomes Research and Evaluation, Yale University, New Haven, CT, USA.
Background: This study aimed to examine how physician performance metrics are affected by the speed of other attendings (co-attendings) concurrently staffing the ED.
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Proc Natl Acad Sci U S A
January 2025
Department of Earth Sciences, Montana State University, Bozeman, MT 59717.
Climate-driven changes in high-elevation forest distribution and reductions in snow and ice cover have major implications for ecosystems and global water security. In the Greater Yellowstone Ecosystem of the Rocky Mountains (United States), recent melting of a high-elevation (3,091 m asl) ice patch exposed a mature stand of whitebark pine () trees, located ~180 m in elevation above modern treeline, that date to the mid-Holocene (c. 5,950 to 5,440 cal y BP).
View Article and Find Full Text PDFProc Natl Acad Sci U S A
January 2025
Department of Biology, Stanford University, Stanford, CA 94305.
Affordable and clean energy, eliminating poverty, and reducing inequality are important goals of the United Nations Sustainable Development Goals (SDGs). This paper examines the role of access to clean cooking fuels in promoting income growth and reducing income inequality. Using data from Chinese households, we show that a 10% increase in the adoption of clean cooking fuels would result in an increase in total annual household income of US$37 billion nationwide.
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January 2025
Department of Bioengineering, California Institute of Technology, Pasadena, CA 91125.
The diversity and heterogeneity of biomarkers has made the development of general methods for single-step quantification of analytes difficult. For individual biomarkers, electrochemical methods that detect a conformational change in an affinity binder upon analyte binding have shown promise. However, because the conformational change must operate within a nanometer-scale working distance, an entirely new sensor, with a unique conformational change, must be developed for each analyte.
View Article and Find Full Text PDFProc Natl Acad Sci U S A
January 2025
California Institute for Quantitative Biosciences, University of California, Berkeley, CA 94720.
Polysaccharide monooxygenase (PMO) catalysis involves the chemically difficult hydroxylation of unactivated C-H bonds in carbohydrates. The reaction requires reducing equivalents and will utilize either oxygen or hydrogen peroxide as a cosubstrate. Two key mechanistic questions are addressed here: 1) How does the enzyme regulate the timely and tightly controlled electron delivery to the mononuclear copper active site, especially when bound substrate occludes the active site? and 2) How does this electron delivery differ when utilizing oxygen or hydrogen peroxide as a cosubstrate? Using a computational approach, potential paths of electron transfer (ET) to the active site copper ion were identified in a representative AA9 family PMO from (PMO9E).
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