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Methane (CH4) is one of the potent greenhouse gases emitted from municipal wastewater treatment plants. The characteristics of methane emission from municipal wastewater treatment plants (WWTPs) have attracted lots of concern from related researchers. The present work investigated the source of methanogens and methane emission properties from two WWTPs in Xi’an, and one is employed in an Orbal oxidation ditch, and the other is anaerobic/anoxic/oxic (A/A/O). The measurement of specific methanogenic activity (SMA) and coenzyme F420 concentration, together with Fluorescence in situ hybridization (FISH), was used to determine the amount and activity of methanogens in two WWTPs. Additionally, a combined activated sludge model was built and predicted the growth of methanogens and other key microorganisms in the sludge. The results showed that the average CH4 emission flux from the Orbal oxidation ditch (22.74 g CH4 /(m2·d)) was much higher than that from A/A/O (9.57 g CH4/(m2·d)). The methane emission factors in the Orbal oxidation ditch and A/A/O processes were 1.18 and 0.21 g CH4 /(m3 INF), respectively. These distinct methane emission characteristics between two WWTPs are mainly attributed to the higher activity and content of methanogens, as well as the discontinuous aeration in the Orbal oxidation ditch. Additionally, dissolved oxygen concentration, water temperature, and the presence of nitrate/nitrite were also important factors that influenced methane emission. The FISH analysis showed that Methanococcus was the dominant methanogen in both WWTPs. In addition, the combined model successfully simulated the growth of methanogens in WWTPs. Methanogens in WWTPs were mainly derived from the sewer system, and the cumulative effect led to an increase in the abundance of methanogens in activated sludge. The outcomes of this study provide new insights in the prediction and management of GHG emission from WWTPs.

In aluminum alloys, the most often utilized cast Al–Si alloy system, the microstructure often needs to be improved by modification and inoculation treatment. This study comprehensively examines the impact of nanocrystals produced by Fe–B–Si amorphous alloys on the solidification behavior and microstructure of hypoeutectic Al–Si7 alloy and hypereutectic Al–Si17 alloy. The nucleation temperature of α-Al is increased and the nucleation of α-Al is easier as well as crystallization platform becomes shorter. For primary Si, the nucleation temperature is decreased and the nucleation is inhibited. The eutectic transformation is promoted and the reaction time is shortened. For α-Al, in situ nano-Fe2B can act as its heterogeneous nucleation sites and promote its nucleation. Meanwhile, the growth of α-Al dendrites is constrained by nearby grains and nanocrystals that do not participate in nucleation, therefore refining the dendrites. Furthermore, nano-Fe2B promotes the eutectic transformation and refines the eutectic microstructure. At the same time, the microstructure of the eutectic groups is refined and the distribution is more dispersed due to the confinement of finer adjacent grains and the hindrance of nanocrystals that do not participate in nucleation.

Background and Purpose: Neurotransmission and neuroinflammation are controlled by local increases in both extracellular ATP and the endocannabinoid 2‐arachidonoyl glycerol (2‐AG). While it is known that extracellular ATP stimulates 2‐AG production in cells in culture, the dynamics and molecular mechanisms that underlie this response remain poorly understood. Detection of real‐time changes in eCB levels with the genetically encoded sensor, GRABeCB2.0, can address this shortfall. Experimental Approach: 2‐AG and arachidonoylethanolamide (AEA) levels in Neuro2a (N2a) cells were measured by LC‐MS, and GRABeCB2.0 fluorescence changes were detected using live‐cell confocal microscopy and a 96‐well fluorescence plate reader. Key Results: 2‐AG and AEA increased GRABeCB2.0 fluorescence in N2a cells with EC50 values of 81 and 58 nM, respectively; both responses were reduced by the cannabinoid receptor type 1 (CB1R) antagonist SR141617 and absent in cells expressing the mutant‐GRABeCB2.0. ATP increased only 2‐AG levels in N2a cells, as measured by LC‐MS, and induced a transient increase in the GRABeCB2.0 signal within minutes primarily via activation of P2X7 receptors (P2X7R). This response was dependent on diacylglycerol lipase β activity, partially dependent on extracellular calcium and phospholipase C activity, but not controlled by the 2‐AG hydrolysing enzyme, α/β‐hydrolase domain containing 6 (ABHD6). Conclusions and Implications: Considering that P2X7R activation increases 2‐AG levels within minutes, our results show how these molecular components are mechanistically linked. The specific molecular components in these signalling systems represent potential therapeutic targets for the treatment of neurological diseases, such as chronic pain, that involve dysregulated neurotransmission and neuroinflammation. [ABSTRACT FROM AUTHOR]

Upgrading plastic wastes into high-value products via the thermochemical process is one of the most attractive topics. Although carbon nanotubes (CNTs) have been successfully synthesized from plastic pyrolysis gas over Fe-, Co-, or Ni-based catalysts, a deep discussion about the reaction mechanism was seldom mentioned in the literature. Herein, this work was intended to study the growth mechanism of CNTs from hydrocarbons on Fe–Al2O3 catalysts. C5–C7 hydrocarbons were used to synthesize CNTs in a high-temperature fixed-bed reactor, and the carbon products and cracked gas were analyzed in detail. The CNT yield was in the order of cyclohexane, cyclohexene > n-hexane > n-heptane > n-pentane, 1-hexene. It was proposed that CNT growth on Fe–Al2O3 catalysts was mainly determined by the yield and structure of six-membered cyclic species, which was tailored by the carbon chain length, C–C/C＝C bonds, and linear/cyclic structures of C5–C7 hydrocarbons. Compared with n-hexane, the six-membered rings of cyclohexane and cyclohexene promoted six-membered cyclic species formation, increasing CNT and benzene yields; the seven-membered carbon chain of n-heptane promoted methyl-six-membered cyclic species formation, decreasing CNT and benzene yields while increasing the toluene yield; the five-membered carbon chain of n-pentane and the C＝C bond of 1-hexene inhibited six-membered cyclic species formation, decreasing CNT and benzene yields. This work revealed the structure–activity relationship between C5–C7 hydrocarbons and CNT growth, which may direct the process design and optimization of CNT synthesis from plastic pyrolysis gas. [ABSTRACT FROM AUTHOR]