The lithium–air battery (LAB) is envisaged as an ultimate energy storage device because of its highest theoretical specific energy among all known batteries. However, parasitic reactions bring about ...vexing issues on the efficiency and longevity of the LAB, among which the formation and decomposition of lithium carbonate Li2CO3 is of paramount importance. The discovery of Li2CO3 as the main discharge product in carbonate‐based electrolytes once brought researchers to “the end of the idyll“ in the early 2010s. In the past few years, tremendous efforts have been made to understand the formation and decomposition mechanisms of Li2CO3, as well as to conceive novel chemical/material strategies to suppress the Li2CO3 formation and to facilitate the Li2CO3 decomposition. Moreover, the study on Li2CO3 in LABs is opening up a new research field in energy technology. Considering the rapid development and innumerous emerging issues, it is timely to recapitulate the current understandings, define the ambiguities and the scientific gaps, and discuss topics of high priority for future research, which is the aim of this Minireview.
Formation and decomposition of Li2CO3: In lithium–air batteries, Li2CO3 is a major by‐product that can lead to cell dry‐out and early failure. Therefore, understanding the formation and decomposition mechanisms of Li2CO3 lays the basis for a better design of lithium–air batteries.
Content Caching at the edge of vehicular networks has been considered as a promising technology to satisfy the increasing demands of computation-intensive and latency-sensitive vehicular applications ...for intelligent transportation. The existing content caching schemes, when used in vehicular networks, face two distinct challenges: 1) Vehicles connected to an edge server keep moving, making the content popularity varying and hard to predict. 2) Cached content is easily out-of-date since each connected vehicle stays in the area of an edge server for a short duration. To address these challenges, we propose a Mobility-aware Proactive edge Caching scheme based on Federated learning (MPCF). This new scheme enables multiple vehicles to collaboratively learn a global model for predicting content popularity with the private training data distributed on local vehicles. MPCF also employs a Context-aware Adversarial AutoEncoder to predict the highly dynamic content popularity. Besides, MPCF integrates a mobility-aware cache replacement policy, which allows the network edges to add/evict contents in response to the mobility patterns and preferences of vehicles. MPCF can greatly improve cache performance, effectively protect users' privacy and significantly reduce communication costs. Experimental results demonstrate that MPCF outperforms other baseline caching schemes in terms of the cache hit ratio in vehicular edge networks.
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•Oxone induced ternary Mn2O3/Mn3O4/MnO2 was first designed under visible light.•The heterojunction achieved efficient cipro degradation under visible light.•The Mn2O3/Mn3O4/MnO2 ...exhibited reusability, stability and selectivity.•The newly-formed dual Ⅱ type heterostructure enhanced charge separation.•Holes and superoxide radicals played dominant roles in cipro degradation.
Valence state heterostructure exhibits great potential for contaminants remediation from water and wastewater with effective charge separation and little energy loss. However, the preparation process commonly shows complex with uncontrolled manner, forming undesired valence states, which hinders the advancement of valence state heterostructure. Herein, an Oxone induced strategy is established to controllably design manganese-based valence state heterostructure for the first time. A superior Mn2O3/Mn3O4/MnO2 (molar ratio of 3:1:2) photocatalyst with dual Ⅱ heterostructures was generated by Oxone (0.3 mM) induced Mn2O3 (0.2 g/L) under visible light. The Mn2O3/Mn3O4/MnO2 heterojunction achieved 95.6% removal and 63.9% mineralization of ciprofloxacin (cipro) under visible light irradiation for 40 min. The excellent catalytic performance was derived from the improved surface area, decreased isoelectric point, enhanced light absorption and efficient charge separation of the Mn2O3/Mn3O4/MnO2 heterostructure. Moreover, the radicals trapping experiment and Electron paramagnetic resonance (EPR) measurement revealed the dominant roles of holes and superoxide radicals for cipro degradation. Furthermore, the reusable Mn2O3/Mn3O4/MnO2 could remove cipro selectively with co-existing natural organic matters and inorganic ions, which exhibited high practicability in real waters. Impressively, this work provides an innovative approach for controllable design of valence state heterostructure and fabricates a promising photocatalyst towards antibiotics degradation.
Hexavalent chromium (Cr(VI)) is a widespread, toxic contaminant in the environment. Owing to the increasingly strict requirements for green production and pollution emission, Cr(VI) generation via ...Cr(III) oxidation is gradually becoming the primary source of Cr(VI) in soils and groundwater instead of direct emissions. Herein, the formation of Cr(VI) by Cr(III) oxidation in soils and groundwater is systematically reviewed. The main oxidants of Cr(III) in soils are manganese oxides (MnOx), hydrogen peroxide (H2O2), and photochemical generated radicals, which respectively dominate in aerobic, anaerobic, and surface zones of soils. In aerobic zones, dissolved Cr(III) can be oxidized on the surface of MnOx under acidic conditions (pH < 6.0), while under alkaline conditions (pH = 8.0–9.4), Mn(II)-catalyzed oxidation plays a dominant role. In anerobic zones, Mn(II) is the dominant species of Mn, thus H2O2, which is mainly produced by the serpentinization process, becomes the main oxidant involved in Cr(III) oxidation. In addition to direct oxidation, H2O2 can also indirectly oxidize Cr(III) during the catalysis of Mn(II) under alkaline conditions. In surface soils, •OH can be generated by the photolysis of Fe(OH)2+, and it can further oxidize Cr(III) to Cr(VI). Moreover, photolysis of Cr(OH)n3-n can transform Cr(III) into Cr(II), which is more active and can be further oxidized into Cr(VI) by O2. In groundwater, both MnOx and H2O2 may oxidize Cr(III) in unconfined aquifers groundwater. In confined aquifers, H2O2 becomes the main oxidant for Cr(III) under alkaline conditions. In addition to in situ oxidation, the transformations of generated Cr(VI) during migration are also reviewed.
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•The entire process of Cr(III) oxidation to Cr(VI) is reviewed.•MnOx dominate Cr(III) oxidation in aerobic zones of soils and groundwater.•MnOx oxidation involves three types: dissolved, adsorbed and catalyzed oxidation.•Cr(III) can be oxidized by photochemical pathway in surface layer of soils.•H2O2 dominates Cr(III) oxidation in confined aquifers of groundwater.
Melatonin is an ancient molecule that can be traced back to the origin of life. Melatonin's initial function was likely that as a free radical scavenger. Melatonin presumably evolved in bacteria; it ...has been measured in both α-proteobacteria and in photosynthetic cyanobacteria. In early evolution, bacteria were phagocytosed by primitive eukaryotes for their nutrient value. According to the endosymbiotic theory, the ingested bacteria eventually developed a symbiotic association with their host eukaryotes. The ingested α-proteobacteria evolved into mitochondria while cyanobacteria became chloroplasts and both organelles retained their ability to produce melatonin. Since these organelles have persisted to the present day, all species that ever existed or currently exist may have or may continue to synthesize melatonin in their mitochondria (animals and plants) and chloroplasts (plants) where it functions as an antioxidant. Melatonin's other functions, including its multiple receptors, developed later in evolution. In present day animals, via receptor-mediated means, melatonin functions in the regulation of sleep, modulation of circadian rhythms, enhancement of immunity, as a multifunctional oncostatic agent, etc., while retaining its ability to reduce oxidative stress by processes that are, in part, receptor-independent. In plants, melatonin continues to function in reducing oxidative stress as well as in promoting seed germination and growth, improving stress resistance, stimulating the immune system and modulating circadian rhythms; a single melatonin receptor has been identified in land plants where it controls stomatal closure on leaves. The melatonin synthetic pathway varies somewhat between plants and animals. The amino acid, tryptophan, is the necessary precursor of melatonin in all taxa. In animals, tryptophan is initially hydroxylated to 5-hydroxytryptophan which is then decarboxylated with the formation of serotonin. Serotonin is either acetylated to
-acetylserotonin or it is methylated to form 5-methoxytryptamine; these products are either methylated or acetylated, respectively, to produce melatonin. In plants, tryptophan is first decarboxylated to tryptamine which is then hydroxylated to form serotonin.
•A novel mZVI/AC composite synthesized by BM for Cr(VI) removal was developed.•Cr(VI) was effectively removed under acid and anaerobic conditions.•The effects of AC on mZVI activity and Cr(VI) ...removal mechanism were explored.•Inactivated mZVI/AC can be rejuvenated by BM again with a small amount of AC.
The oxide film coated on the surface of zero-valent iron (ZVI) greatly limits the reducibility of ZVI. Application of iron-based materials especially microscale or nanoscale for water treatment can be more effective when modified with activated carbon (AC). In the study, the removal efficiency of Cr(VI) was significantly enhanced by mZVI/AC composite synthesized by ball milling (BM) under acidic and anaerobic conditions, and reached 94.01% within 120 min. And BM promoted effective contact or collision between mZVI and AC, which was a necessary condition for strengthening Cr(VI) removal by mZVI/AC. By detecting pH changes and the dissolution of total iron during batch experiments, it was shown that AC enhanced the corrosion of mZVI, accompanied by consumption of H+. Tafel scans further confirmed that the corrosion of mZVI was promoted when coupled with AC. Compared with mZVI, AC enhanced the adsorption-reduction ability, and also enhanced the homogeneous reduction reaction (the role of the secondary reducing agent Fe2+) in the process of Cr(VI) removal by mZVI/AC. Based on X-ray photoelectron spectroscopy (XPS), valence analysis of chromium and 1,10-phenanthroline shielding experiments, the Cr(VI) removal mechanism by mZVI/AC was also unraveled. Furthermore, the reusability of mZVI/AC was limited by the accumulation of (hydr)oxide on its surface and the loss of surface AC, but can be easily rejuvenated by BM again with a small amount of AC. In conclusion, mZVI/AC composite synthesized by BM are a promising green material to remove Cr(VI) from wastewater.
Sulfamethoxazole (SMX), a typical sulfonamide antibiotic, has been widely detected in secondary wastewater effluents and surface waters. In this work we investigated the oxidative degradation of SMX ...by commonly used oxidants of chlorine, ozone and permanganate. Chlorine and ozone were shown to be more effective for the removal of SMX (0.05-5.0mg/L), as compared with permanganate. Higher pH enhanced the oxidation of SMX by ozone and permanganate, but decreased the removal by chlorine. Moreover, the ozonation of SMX was significantly influenced by the presence of humic acid (HA), which exhibited negligible influence on the oxidation by chlorine and permanganate. Fairly lower mineralization of SMX occurred during the oxidation reactions, with the highest dissolved organic carbon (DOC) removal of 13% (for ozone). By using LC-MS/MS, 7, 5 and 5 oxidation products were identified for chlorine, ozone and permanganate and possible transformation pathways were proposed. It was shown that different oxidants shared some common pathways, such as the cleavage of SN bond, the hydroxylation of the benzene ring, etc. On the other hand, each of the oxidants also exhibited exclusive degradation mechanisms, leading to the formation of different transformation products (TPs). This work may provide useful information for the selection of oxidants in water treatment processes.
In this work, membrane fouling behavior in a direct forward osmosis (FO) and an osmotic membrane bioreactor (OMBR) for municipal wastewater treatment was systematically investigated and compared. ...During the long-term operation, much severer flux decline was observed for the direct FO than that for the OMBR. The cake layer was found to be much thicker, together with large amounts of microorganisms growing on the membrane surface in direct FO. Interestingly, no obvious attachment of microorganisms on the membrane surface was observed in the OMBR. The fourier transform infrared spectroscopy (FTIR) and excitation emission matrices (EEM) analyses showed the polysaccharides and proteins were the dominant organic foulants in the fouling layer, and the quantity of the organic substances was also higher in direct FO than that in OMBR. Energy-dispersive X-ray (EDX) results indicated the main inorganic elements in the fouling layer were Ca, Mg, Fe and P, all of which exhibited higher relative percentages in direct FO than that in OMBR. The occurrence of higher contents of microorganisms, organic foulants and inorganic elements in the cake layer caused a higher filtration resistance for the FO membrane in the direct FO. Although more severe membrane fouling was identified in direct FO, the hydraulic and chemical cleaning was more effective on recovering the water permeability of the membrane in direct FO than that in OMBR.
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•The membrane fouling behaviors were compared between direct FO and OMBR.•Much severer flux decline was observed for direct FO than that for OMBR.•The foulants on the membrane surface were identified and quantitatively analyzed.•Large amounts of bacteria were grown on the membrane in direct FO, but not in OMBR.•Hydraulic and chemical cleaning were more effective for the direct FO than OMBR.
Gastric cancer (GC) is a malignant tumor with high incidence rate and mortality. Due to the lack of effective diagnostic indicators, most patients are diagnosed in late stage and have a poor ...prognosis. An increasing number of studies have proved that Peptidylprolyl isomerase A (PPIA) can play an oncogene role in various cancer types. However, the precise mechanism of PPIA in GC is still unclear. Herein, we analyzed the mRNA levels of PPIA in pan-cancer. The prognostic value of PPIA on GC was also evaluated using multiple databases. Additionally, the relationship between PPIA expression and clinical factors in GC was also examined. We further confirmed that PPIA expression was not affected by genetic alteration and DNA methylation. Moreover, the upstream regulator miRNA and lncRNA of PPIA were identified, which suggested that LINC10232/miRNA-204-5p/PPIA axis might act as a potential biological pathway in GC. Finally, this study revealed that PPIA was negatively correlated with immune checkpoint expression, immune cell biomarkers, and immune cell infiltration in GC.
Plant hormone candidate melatonin has been widely studied in plants under various stress conditions, such as heat, cold, salt, drought, heavy metal, and pathogen attack. Under stress, melatonin ...usually accumulates sharply by modulating its biosynthesis and metabolic pathways. Beginning from the precursor tryptophan, four consecutive enzymes mediate the biosynthesis of tryptamine or 5-hydroxytryptophan, serotonin,
-acetylserotonin or 5-methoxytryptamine, and melatonin. Then, the compound is catabolized into 2-hydroxymelatonin, cyclic-3-hydroxymelatonin, and
¹-acetyl-
²-formyl-5-methoxyknuramine through 2-oxoglutarate-dependent dioxygenase catalysis or reaction with reactive oxygen species. As an ancient and powerful antioxidant, melatonin directly scavenges ROS induced by various stress conditions. Furthermore, it confreres stress tolerance by activating the plant's antioxidant system, alleviating photosynthesis inhibition, modulating transcription factors that are involved with stress resisting, and chelating and promoting the transport of heavy metals. Melatonin is even proven to defense against pathogen attacks for the plant by activating other stress-relevant hormones, like salicylic acid, ethylene, and jasmonic acid. Intriguingly, other precursors and metabolite molecules involved with melatonin also can increase stress tolerance for plant except for unconfirmed 5-methoxytryptamine, cyclic-3-hydroxymelatonin, and
¹-acetyl-
²-formyl-5-methoxyknuramine. Therefore, the precursors and metabolites locating at the whole biosynthesis and catabolism pathway of melatonin could contribute to plant stress resistance, thus providing a new perspective for promoting plant stress tolerance.
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