Achieving a U.S. circular economy would reduce environmental impacts and increase material independence. This article calculates maximum recycled contents (RCs) and recycling rates (RRs) in an independent U.S. steel sector, and estimates the potential to displace current imports with recycled scrap that is currently destined for landfill, hibernating stocks, or export (LHSE). A U.S. dynamic material flow analysis (1880-2100) is conducted to estimate annual steel consumption and scrap generation. The results are coupled with a linear optimization model that minimizes primary steel demand while satisfying the volumetric and compositional demands of new consumption. The compositional analysis examines only copper content because it is of greatest concern to recyclers. The best estimate is that the maximum independent RR is already constrained by copper contamination. Without interventions, this maximum RR will gradually decline throughout the century. The annual consumption to scrap availability ratio (C2SR) will decrease from around 1.4 today. Concurrently, the maximum RC rises but then plateaus below 75% as the RR falls. This highlights a conflict in the conditions for a circular economy: a C2SR approaching unity is a necessary condition for a high RC but leads to fewer opportunities for scrap contaminant dilution, which decreases the RR. Improved product design for recycling and deployment of scrap refining technologies will be needed to reach higher RCs. In 2017, the mass of U.S. scrap destined for LHSE exceeded direct steel imports. Domestic recycling of scrap exports alone could have displaced

Non-small cell lung cancer (NSCLC) is a common malignant tumor, with high morbidity and mortality. Circular RNA (circRNA) circ_0003028 was reported to be upregulated in NSCLC. This study is designed to explore the role and mechanism of circ_0003028 on NSCLC progression. In this work, circ_0003028, microRNA-1298-5p (miR-1298-5p), and glutamic oxaloacetic transaminase 2 (GOT2) level were detected by real-time quantitative polymerase chain reaction (RT-qPCR). The localization of circ_0003028 was analyzed by subcellular fractionation assay. Cell proliferation, colony number, cell cycle progression, apoptosis, migration, invasion, and angiogenesis were measured by Cell Counting Kit-8 (CCK-8), colony formation, flow cytometry, transwell, and tube formation assays. Protein levels of Beclin1, light chain 3 (LC3)-II/LC3-I, GOT2, proliferating cell nuclear antigen (PCNA) were examined by western blot assay. The binding relationship between miR-1298-5p and circ_0003028 or GOT2 was predicted by circular RNA Interactome or starbase and then verified by dual-luciferase reporter, RNA Immunoprecipitation (RIP), and RNA pull-down assays. The biological role of circ_0003028 on NSCLC tumor growth was examined by the xenograft tumor model in vivo. We reported that circ_0003028 and GOT2 were upregulated, and miR-1298-5p was decreased in NSCLC tissues and cells. Moreover, circ_0003028 knockdown curbed cell proliferative ability, migration, invasion, angiogenesis, and facilitate apoptosis and autophagy in NSCLC cells in vitro. Mechanical analysis discovered that circ_0003028 regulated GOT2 expression by sponging miR-1298-5p. Circ_0003028 silencing hindered the cell growth of NSCLC in vivo. Taken together, circ_0003028 knockdown could suppress NSCLC progression partly by regulating the miR-1298-5p/GOT2 axis, providing an underlying therapeutic target for NSCLC.

Making, driving, and disposing of U.S. light-duty vehicles (LDVs) account for 3% of global greenhouse gas emissions related to energy and processing. This study calculates future emissions and global temperature rises attributable to U.S. LDVs. We examine how 2021−2050 U.S. LDV cumulative emissions can be limited to 23.1 Gt CO 2equiv , helping to limit global warming to less than 2 °C. We vary four vehicle life cycle parameters (transport demand, sales share of alternative fuel vehicles, vehicle material recycling rates, and vehicle lifespans) in a dynamic fleet analysis to determine annual LDV sales, scrappage, and fleet compositions. We combine these data with vehicle technology and electricity emission scenarios to calculate annual production, use, and disposal emissions attributable to U.S. LDVs. Only 3% of the 1512 modeled pathways stay within the emission limit. Cumulative emissions are most sensitive to transport demand, and the speed of fleet electrification and electricity decarbonization. Increasing production of battery electric vehicles (BEVs) to 100% of sales by 2040 (at the latest) is necessary, and early retirement of internal combustion engine vehicles is beneficial. Rapid electricity decarbonization minimizes emissions from BEV use and increasingly energy-intensive vehicle production. Deploying high fuel economy vehicles can increase emissions from the production of BEV batteries and lightweight materials. Increased recycling has a small effect on these emissions because over the time period there are few postconsumer batteries and lightweight materials available for recycling. Without aggressive actions, U.S. LDVs will likely exceed the cumulative emissions budget by 2039 and contribute a further 0.02 °C to global warming by 2050, 2.7% of the remaining global 2 °C budget.

A detailed understanding of material flows is needed to target increased material efficiency and circular economy. In this article, the U.S. steel flow is modeled as a series of nodes representing processes and products. An easily updatable nonlinear least squares optimization is used to reconcile the inconsistencies across 293 collated data records on flows through and between the nodes. The data come from an integrated analysis that includes top-down estimates of steel flow from trade bodies and government statistical agencies, bottom-up estimates of the steel embedded in products based on production statistics and bills of materials, and the mass of imports and exports based on international money flow. A weighting methodology is used to consistently assign confidence scores to the data, and the optimization is used to achieve mass balance and minimize the sum of the squares of the weighted residuals. The results indicate that yield improvement efforts should focus on sheet metal forming in the car industry, which accounts for nearly half of all generated fabrication scrap. The quantity of end-of-life scrap exported and land-filled is greater than the quantity of steel products imported. Increased domestic recycling of end-of-life scrap might displace around a third of these imports.

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