The overlooked role of high-valent cobalt-oxo species (Co(IV)) in the Co(II)/peroxymonosulfate (PMS) process was uncovered recently using methyl phenyl sulfoxide (PMSO) as the probe. Herein, we further interestingly found that Co(IV) could trigger hydroxyl radical (•OH) formation, resulting in the oxidized products distribution of PMSO heavily relied on the relative concentration of PMSO. More significantly, the generation of a series of 18O-labeled hydroxylated products (i.e., hydroxylated methyl phenyl sulfone, nitrobenzene and 4-nitrobenzoic acid) in H218O conclusively verified that •OH was triggered by Co(IV) species. Density functional theory calculation demonstrated that Co(IV) initiated •OH formation via oxo ligand protonation-induced valence tautomerization. Moreover, the oxidative contribution of Co(IV) and •OH on organic degradation was specifically dependent on the type and concentration of the substrate. This study provided deeper insights into the evolution pathway of •OH mediated by Co(IV) species and enriched the understandings on the collaborative oxidation mechanism in Co(IV)-involved processes.
The phenomenon of host-guest hydrogen bonding in clathrate hydrate crystal structures and its effect on physical and chemical properties have become subjects of extensive research. Hydrogen bonding has been studied for cubic (sI and sII) and hexagonal (sH) binary clathrates, while it has not been addressed for clathrate structures that exist at elevated pressures. Here, four acetone hydrate clathrates have been grown at high-pressure and low-temperature conditions. In situ single-crystal X-ray diffraction revealed that the synthesized phases possess already known trigonal (sTr), orthorhombic (sO), and tetragonal (sT) crystal structures as well as a previously unknown orthorhombic structure, so-called sO-II. Only sO and sII have previously been reported for acetone clathrates. Structural analysis suggests that acetone oxygens are hydrogen-bonded to the closest water oxygens of the host frameworks. Our discoveries show that clathrate hydrates hosting polar molecules are not as exotic as previously thought and could be stabilized at high-pressure conditions through hydrogen bonding.
Abstract Vegetation community complexity is a critical factor influencing terrestrial ecosystem stability. China, the country leading the world in vegetation greening resulting from human activities, has experienced dramatic changes in vegetation community composition during the past 30 years. However, how China's vegetation community complexity varies spatially and temporally remains unclear. Here, we examined the spatial pattern of China's vegetation community complexity and its temporal changes from the 1980s to 2015 using two vegetation maps of China as well as more than half a million field samples. Spatially, China's vegetation community complexity distribution is primarily dominated by elevation, although temperature and precipitation can be locally more influential than elevation when they become the factors limiting plant growth. Temporally, China's vegetation community complexity shows a significant decreasing trend during the past 30 years, despite the observed vegetation greening trend. Prevailing climate warming across China exhibits a significant negative correlation with the decrease in vegetation community complexity, but this correlation varies with biogeographical regions. The intensity of human activities have an overall negative influence on vegetation community complexity, but vegetation conservation and restoration efforts can have a positive effect on maintaining vegetation composition complexity, informing the critical role of vegetation management policies in achieving the sustainable development goal.
Increasing energy and environmental demands raise intensive interests on cleaner but challenging resource explorations, where unconventional tight reservoirs attract attentions due to its huge reserves but complex reservoir conditions. As commonly-used gas solvents for enhancing tight oil recovery, CO2 and N2 show their superb capabilities in each single usage, while their combinations, particularly utilizing of huff-n-puff (HnP) strategy, has been rarely investigated. In this paper, novel gas solvents, hybrid CO2-N2 gases with six molar ratios were synthesized and applied for a series of laboratory HnP tests using artificial cores. The proposed technology was specifically evaluated by analysing relevant properties, optimising production strategy, and examining the post-production residual oil saturation by means of nuclear magnetic resonance (NMR). Overall, our experiments validate the first three HnP cycles usually have higher oil recovery, while the subsequently further cycles would only be mildly beneficial. In this case, the hybrid CO2-N2 HnP simultaneously takes advantages of CO2-induced viscosity reduction and N2-induced elastic energy increase. The optimum proportion of CO2-N2 in the hybrid gas solvent is found to be 1:2, with the best HnP oil recovery of 39.0%. The NMR-assisted coreflood tests indicate largely uneven residual oil distributions. The effectivities of CO2 and N2 HnP are determined to be different in variation of pore scale in production tight oil, where the N2 HnP has better oil extraction ability in small pores.
The Devonian Antrim Shale is an unconventional biogenic gas accumulation with a technical recoverable resource of 19.9 Tcf. However, major knowledge gaps remain regarding understanding of the source rock potential, organic facies assemblages and paleo-depositional conditions of the Antrim Shale members. This work utilized Rock-Eval pyrolysis, reflected light microscopy and solid bitumen reflectance to characterize the source rock quality, organo-facies assemblages, and thermal maturity of the various Antrim Shale members at three different localities in the Michigan Basin. Results showed that the Lachine and Norwood members are richer in organic matter (up to 24 wt%) than the Upper and Paxton members (<8 wt%). Organic matter is mainly dominated by marine Type II kerogen in the black shales of the Lachine and Norwood members, and by Type II and Type II/III in the Paxton Member. Telalginite, which is represented mainly by Tasmanites and Leiosphaeridia cysts, is the dominant organic matter in the black shale members where they account for about two-thirds of the organic matter composition. Solid bitumen, which accounts for less than one-third of the organic matter composition, is second after alginite. Both alginite and solid bitumen populations decline in abundance progressively in the Upper and Paxton members at the expense of inertinite and vitrinite. The dominant organofacies groups in the studied Antrim Shale members can be assigned to the BP type B and type D/E. Organic matter maturity determined from Rock-Eval Tmax and bitumen reflectance varies from immature to marginally mature across the Michigan Basin. The results confirmed that sediment burial depth and lateral position in the basin controlled organic facies assemblages within the Antrim Shale members.
Peracetic acid (PAA) has been widely used as an alternative disinfectant in wastewater treatment, and PAA-based advanced oxidation processes (AOPs) have drawn increasing attention recently. Among the generated reactive species after PAA activation, acetylperoxyl radical (CH3CO3•) plays an important role in organic compounds degradation. However, little is known about the reaction mechanism on CH3CO3• attack due to the challenging of experimental analysis. In this study, a homogeneous PAA activation system was built up using Co(II) as an activator at neutral pH to generate CH3CO3• for phenol degradation. More importantly, reaction mechanism on CH3CO3•-driven oxidation of phenol is elucidated at the molecular level. CH3CO3• with lower electrophilicity index but much larger Waals molecular volume holds different phenol oxidation route compared with the conventional •OH. Direct evidences on CH3CO3• formation and attack mechanism are provided through integrated experimental and theoretical results, indicating that hydrogen atom abstraction (HAA) is the most favorable route in the initial step of CH3CO3•-driven phenol oxidation. HAA reaction step is found to produce phenoxy radicals with a low energy barrier of 4.78 kcal mol−1 and free energy change of -12.21 kcal mol−1. The generated phenoxy radicals will undergo further dimerization to form 4-phenoxyphenol and corresponding hydroxylated products, or react with CH3CO3• to generate catechol and hydroquinone. These results significantly promote the understanding of CH3CO3•-driven organic pollutant degradation and are useful for further development of PAA-based AOPs in environmental applications.
Neural tube defects (NTDs) are a group of common and severe congenital malformations. The PI3K-AKT signalling pathway plays a crucial role in the neural tube development. There is limited evidence concerning any possible association between aberrant methylation in PI3K-AKT signalling pathway genes and NTDs. Therefore, we aimed to investigate potential associations between aberrant methylation of PI3K-AKT pathway genes and NTDs. Methylation studies of PI3K-AKT pathway genes utilizing microarray genome-methylation data derived from neural tissues of ten NTD cases and eight non-malformed controls were performed. Targeted DNA methylation analysis was subsequently performed in an independent cohort of 73 NTD cases and 32 controls to validate the methylation levels of identified genes. siRNAs were used to pull-down the target genes in human embryonic stem cells (hESCs) to examine the effects of the aberrant expression of target genes on neural cells. As a result, 321 differentially hypermethylated CpG sites in the promoter regions of 30 PI3K-AKT pathway genes were identified in the microarray data. In target methylation analysis, CHRM1, FGF19, and ITGA7 were confirmed to be significantly hypermethylated in NTD cases and were associated with increased risk for NTDs. The down-regulation of FGF19, CHRM1, and ITGA7 impaired the formation of rosette-like cell aggregates. The down-regulation of those three genes affected the expression of PAX6, SOX2 and MAP2, implying their influence on the differentiation of neural cells. This study for the first time reported that hypermethylation of PI3K-AKT pathway genes such as CHRM1, FGF19, and ITGA7 is associated with human NTDs. Keywords: Neural tube defects,; PI3K-AKT signalling pathway; methylation.
The global pandemic of COVID-19 caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection confers great threat to public health. Human breast milk is a complex nutritional composition to nourish infants and protect them from different kinds of infectious diseases including COVID-19. Here, we identified that lactoferrin (LF), mucin1 (MUC1), and α-lactalbumin (α-LA) from human breast milk inhibit SARS-CoV-2 infection using a SARS-CoV-2 pseudovirus system and transcription and replication-competent SARS-CoV-2 virus-like-particles (trVLP). In addition, LF and MUC1 inhibited multiple steps including viral attachment, entry, and postentry replication, whereas α-LA inhibited viral attachment and entry. Importantly, LF, MUC1, and α-LA possess potent antiviral activities toward variants such as B.1.1.7 (alpha), B.1.351 (beta), P.1 (gamma), and B.1.617.1 (kappa). Taken together, our study provides evidence that human breast milk components (LF, MUC1, and α-LA) are promising antiviral and potential therapeutic candidates warranting further development for treating COVID-19.
Keywords: Biological sciences; Microbiology; Viral microbiology.
The successful preparation of immobilized nitrogen-doped carbon/cobalt @ porous spherical substrate (N-C/Co@PSS) catalyst derived from ZIF-67 was reported in this work. The oxytetracycline (OTC), tetracycline (TTC), and chlortetracycline (CTC) in the simulated wastewater were decomposed via the peroxymonosulfate (PMS) activation by N-C/Co@PSS. The degradation of TCs was initially investigated by batch-type experiments, in which ca. 100% TCs with an initial concentration of 10.0 mg L-1 can be degraded over N-C/Co@PSS + PMS system within 15 min for 30 runs’ operation. In addition, detailed non-radical dominating degradation mechanism was explored by active species capture experiments, electron spin resonance (ESR) tests and electrochemical technology. Furthermore, continuous degradation of TCs antibiotics for up to 200 h in the packed N-C/Co@PSS fixed bed reactors could be accomplished. This work provides theoretical and technical support for the application of MOFs-based catalysts in large-scale wastewater remediation.
Students need to maintain certain living conditions in order to pursue online learning at home. However, there is a lack of a scientific explanation for the extent to which students’ performance in online at-home education is influenced by living conditions. Students from 2002 low-income households in China were surveyed, and a multivariate logistic regression analysis was conducted in order to explore the impact of living conditions on online education. The results showed that, rather than computers and smartphones, broadband Internet at home can affect students’ performance in online learning. The larger the residence area, the better the children’s performance in at-home e-learning. Moreover, children living in dilapidated houses are unable to satisfactorily perform in an e-learning environment. Contrarily, children who live in families with separate rooms and tap water show better performances. Additionally, the performance will be worse in the case of unattended students. Furthermore, children from low-income and -status families in the community are often at a disadvantage in an at-home e-learning environment. Cognition regarding the connection between living conditions and online education can be crucial for the improvement of the living conditions of low-income families in order to achieve online education equity.