We describe a 1,400 million-year old (Ma) iron formation (IF) from the Xiamaling Formation of the North China Craton. We estimate this IF to have contained at least 520 gigatons of authigenic Fe, comparable in size to many IFs of the Paleoproterozoic Era (2,500-1,600 Ma). Therefore, substantial IFs formed in the time window between 1,800 and 800 Ma, where they are generally believed to have been absent. The Xiamaling IF is of exceptionally low thermal maturity, allowing the preservation of organic biomarkers and an unprecedented view of iron-cycle dynamics during IF emplacement. We identify tetramethyl aryl isoprenoid (TMAI) biomarkers linked to anoxygenic photosynthetic bacteria and thus phototrophic Fe oxidation. Although we cannot rule out other pathways of Fe oxidation, iron and organic matter likely deposited to the sediment in a ratio similar to that expected for anoxygenic photosynthesis. Fe reduction was likely a dominant and efficient pathway of organic matter mineralization, as indicated by organic matter maturation by Rock Eval pyrolysis combined with carbon isotope analyses: Indeed, Fe reduction was seemingly as efficient as oxic respiration. Overall, this Mesoproterozoic-aged IF shows many similarities to Archean-aged (>2,500 Ma) banded IFs (BIFs), but with an exceptional state of preservation, allowing an unprecedented exploration of Fe-cycle dynamics in IF deposition.

This paper presents a systematic study on improving the performance of a 300 MW down-fired pulverizedcoal utility boiler by inclining downward the F-layer secondary air (SA). A numerical method was adopted to evaluate the effects of inclined angles on the characteristics of flow, combustion, and nitrogen oxide (NO x ) emissions in the furnace. Retrofitting was conducted to incline the F-layer SA downward with an optimal inclined angle of 25°. Full-scale experimental measurements were carried out before and after retrofitting. The results indicate that inclining downward the F-layer SA can increase the flame penetration depth and lower downward the flame center. The residence time of pulverized-coal particles increases, and the SA staging level enhances in the furnace. The boiler performance is improved with absolute increases of 3.55, 3.31, and 2.20% in boiler efficiencies and relative reductions of 28.65, 19.07, and 12.53% in NO x emissions under 300, 240, and 190 MW loads, respectively.

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The enrichment of transition metals in the brain and the dyshomeostasis of metals are thought to be important etiological factors for elderly people in a number of neurodegenerative diseases, including Alzheimer's disease (AD). However, the understanding of how biometals dynamically dysregulate in the stages of AD development, such as the exact time-dependent and site-dependent accumulation in the brain with AD progression, is still limited. Herein, by using the APP/V717I transgenic mouse model and age-matched mice as control, we offer distinctive in situ and quantitative images of metals (Cu, Fe, Zn and Ca) in brain sections by synchrotron radiation micro beam X-ray fluorescence (SR-μXRF). The images show that Fe and Ca increased with brain aging in both AD and control (CNT) mice, and Cu, Fe, Zn and Ca appeared significantly elevated in AD mice and showed an obvious age-dependent rise. Fe, Cu and Zn were obviously specifically enriched in the cortex and hippocampus, which were also the plaque-formation sensitive brain regions. Our results demonstrate that the enrichment of transition metals with age and metals' dyshomeostasis in specific regions may contribute together to the etiology and development of AD in elderly people. The XANES measurements of Cu and Fe show evidence that Cu may have redox properties in the AD brain.

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Due to the rapidly growing renewable power, the fossil fuel power plants have to be increasingly operated under large and rapid load change conditions, which can induce various challenges. This work aims to reduce NO x emissions of largescale corner-fired boilers operated at medium−low loads. The combustion characteristics and NO x emissions from a 1000 MW e corner-fired tower boiler under different loads are investigated experimentally and numerically. A new control strategy for the annular fuel air is proposed and implemented in the boiler, in which the secondary air admitted to the furnace through the air annulus around each coal nozzle tip is controlled by the boiler load, instead of being controlled by the output of the connected mill as commonly used in this kind of power plant. Both the experimental and simulation results show that the new control strategy reduces NO x emissions at the entrance of the selective catalytic reduction (SCR) system by about 20% at medium−low loads, compared to those based on the original control. The new control strategy has also been successfully applied to two other corner-fired boilers to achieve a significant NO x emission reduction at partial loads. In all three applications, no negative effect on the combustion and steam temperature characteristics of the boilers is observed.