Heavy metal contamination has caused serious threats to surrounding fragile environments and human health. While the novel microbial-induced carbonate precipitation (MICP) technology in the recent ...years has been proven effective in improving material mechanical and durability properties, the mechanisms remedying heavy metal contamination still remain unclear. In this study, the potential of applying the MICP technology to the lead remediation under the effects of urease activity and calcium source was explored. The values of OD600 corresponding to the ureolytic bacterial activity, electrical conductivity (EC), urease activity (UA) and pH were applied to monitor the degree of urea hydrolysis. Further, the carbonate precipitations that possess different speciations and cannot be distinguished through test tube experiments were reproduced using the Visual MINTEQ software package towards verifying the validity of the proposed simulations, and revealing the mechanisms affecting the lead remediation efficiency. The findings summarised in this work give deep insights into lead-contaminated site remediation engineering.
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•The potential of applying the novel biomineralisation to Pb removal is explored.•The intracellular urease and calcium source elevate the degree of urea hydrolysis.•The multilayer structure depresses the effect of Pb2+ and prevents their migration.
Herein we present a new viologen‐based radical‐containing metal–organic framework (RMOF) Gd‐IHEP‐7, which upon heating in air undergoes a single‐crystal‐to‐single‐crystal transformation to generate ...Gd‐IHEP‐8. Both RMOFs exhibit excellent air and water stability as a result of favorable radical‐radical interactions, and their long‐lifetime radicals result in wide spectral absorption in the range 200–2500 nm. Gd‐IHEP‐7 and Gd‐IHEP‐8 show excellent activity toward solar‐driven nitrogen fixation, with ammonia production rates of 128 and 220 μmol h−1 g−1, respectively. Experiments and theoretical calculations indicate that both RMOFs have similar nitrogen fixation pathways. The enhanced catalytic efficiency of Gd‐IHEP‐8 versus Gd‐IHEP‐7 is attributed to intermediates stabilized by enhanced hydrogen bonding.
A single‐crystal‐to‐single‐crystal (SCSC) transformation of stable radical‐containing MOF Gd‐IHEP‐7 generates Gd‐IHEP‐8. It is accompanied by a marked increase in efficiency of sacrificial agent‐free photocatalytic nitrogen fixation to yield NH3 from H2O and N2 under simulated solar light irradiation at ambient temperature. The NH3 production rate of 220 μmol h−1 g−1 for Gd‐IHEP‐8 is a new record for MOF photocatalysts.
ObjectiveDietary fibre has beneficial effects on energy metabolism, and the majority of studies have focused on short-chain fatty acids produced by gut microbiota. Ginseng has been reported to aid in ...body weight management, however, its mechanism of action is not yet clear. In this study, we focused on the potential modulating effect of ginseng on gut microbiota, aiming to identify specific strains and their metabolites, especially long-chain fatty acids (LCFA), which mediate the anti-obesity effects of ginseng.DesignDb/db mice were gavaged with ginseng extract (GE) and the effects of GE on gut microbiota were evaluated using 16S rDNA-based high throughput sequencing. To confirm the candidate fatty acids, untargeted metabolomics analyses of the serum and medium samples were performed.ResultsWe demonstrated that GE can induce Enterococcus faecalis, which can produce an unsaturated LCFA, myristoleic acid (MA). Our results indicate that E. faecalis and its metabolite MA can reduce adiposity by brown adipose tissue (BAT) activation and beige fat formation. In addition, the gene of E. faecalis encoding Acyl-CoA thioesterases (ACOTs) exhibited the biosynthetic potential to synthesise MA, as knockdown (KD) of the ACOT gene by CRISPR-dCas9 significantly reduced MA production. Furthermore, exogenous treatment with KD E. faecalis could not reproduce the beneficial effects of wild type E. faecalis, which work by augmenting the circulating MA levels.ConclusionsOur results demonstrated that the gut microbiota-LCFA-BAT axis plays an important role in host metabolism, which may provide a strategic advantage for the next generation of anti-obesity drug development.
Inappropriate handling of copper (Cu) and lead (Pb)-containing wastewater resulting from metallurgical and smelting industries in Northwest China encourages their migration to surrounding ...environments. Their accumulation causes damage to liver and kidney function. The electrokinetic (EK) technology is considered to be an alternative to traditional remediation technologies because of its great maneuverability. The EK remediation is accompanied by the electrode polarization and the focusing effect toward affecting removal efficiency. In this study, a nanocomposite hydrogel (NCH) electrode was proposed and applied to the EK remediation of Cu- and Pb-contaminated loess. The mechanical, adsorption capacity, adsorption kinetics, and electrochemical properties of the NCH electrode were investigated in detail, followed by microscopic analyses of Scanning Electron Microscope (SEM), Energy Dispersive X-ray Spectroscopy (EDS), and Raman spectrometer. Results showed that the enhancement of the mechanical properties of the NCH electrode was attributed to the crosslinks of graphene nanoparticles, calcium alginate, and hydrogen bonds, while the Cu or Pb adsorption by the NCH electrode was in a chemisorption manner. The second layer formation might address the increase in adsorption capacity with increasing temperature. These results highlight the relative merits of the NCH electrode and verify the potential of applying the NCH electrode to the EK remediation of Cu- and Pb-contamianted loess.
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•Hydrogen bonds promoted the crosslinked structure formation.•The surface functional groups reduced the mobility of copper and lead ions.•The non-faradaic nature of the proposed NCH electrode reduced the polarization.•The proposed NCH electrode outperformed traditional electrodes.
Reinforcing structural members and construction materials using recycled fibers has become popular in the past decades due to sustainable development concerns. The recycled fibers as soil ...reinforcement elements contribute to the increase in shear strength by distributing stresses exerted in the soil along the length of the recycled fibers. Loess, widely spread over the Chinese Loess Plateau, is featured with metastable structure, large porosity, and high water sensitivity. This study presents the results of applying the large-scale stress-controlled direct shear tests on the recycled straw fiber-reinforced loess. The formation mechanism of shearing behaviour enhancement of the loess by straw fiber inclusion is revealed. The associated strain-hardening behaviour can be manifested using the dilation angle or the difference in friction angle between the large-displacement friction angle and the peak friction angle. Further, the shear strength using the displacement-controlled direct shear tests presents good correspondence with that using the stress-controlled direct shear tests. The test results explore the potential of using the recycled straw fiber-reinforced loess to protect the fragile loess environment in the northwest of China.
Mitogen-activated protein kinase (MAPK) cascades are key signalling pathways that regulate a wide variety of cellular processes, including proliferation, differentiation, apoptosis and stress ...responses. The MAPK pathway includes three main kinases, MAPK kinase kinase, MAPK kinase and MAPK, which activate and phosphorylate downstream proteins. The extracellular signal-regulated kinases ERK1 and ERK2 are evolutionarily conserved, ubiquitous serine-threonine kinases that regulate cellular signalling under both normal and pathological conditions. ERK expression is critical for development and their hyperactivation plays a major role in cancer development and progression. The Ras/Raf/MAPK (MEK)/ERK pathway is the most important signalling cascade among all MAPK signal transduction pathways, and plays a crucial role in the survival and development of tumour cells. The present review discusses recent studies on Ras and ERK pathway members. With respect to processes downstream of ERK activation, the role of ERK in tumour proliferation, invasion and metastasis is highlighted, and the role of the ERK/MAPK signalling pathway in tumour extracellular matrix degradation and tumour angiogenesis is emphasised.
In addition to the shearing behavior of soil, the creep character is also considered crucial in determining the long-term shear strength. This especially holds true for the loess that possesses the ...metastable microstructure and is prone to landslide hazards. This study explored the potential application of straw reinforcement to enhance the shearing and creep properties of the Quaternary loess. The mechanism responsible for the straw reinforcement to elevate the peak shear strength was revealed. Furthermore, three creep characters, namely attenuating creep, non-attenuating creep, and viscous flow were identified in this study. The unreinforced and reinforced specimen behaved in a different manner under identical shear stress ratio condition. The reinforced specimen was superior in limiting the particle relative movement within the shear plane than the unreinforced specimen. The chain reaction of interparticle contact loss, accompanied with excessive viscous displacement, rapid weakening of creep resistance, and eventually accelerated creep displacement, provided an evidence for the formation mechanism of slow-moving landslide. The long-term shear strength using the isochronal stress-strain relationship may be used for optimising the design of high-fill embankment works.
Due to the monsoon climate, saline soils extensively spread over the arid or semi-arid area (e.g. NW China) and are featured with notable dissolution collapsibility and salt expandability. The ...features cause road hump and subgrade corrosion towards endangering the safety of passers. In this study, the microstructural evolution of the loess when subjected to alkaline and saline environments was investigated using a series of microscale tests, including scanning electron microscopic (SEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (SEM–EDS), and mercury intrusion porosimetry (MIP). The correspondence of the microstructural evolution with the macroscale mechanical properties using the reduced triaxial extension tests was studied. The test results showed that the alkaline and saline environments led to the microstructural evolution of the loess, involving the particle morphology, microstructural characteristics, pore distribution, and directionality of the pores. The increasing thickness of the diffuse double layer, induced by sodium sulphate, reduced the suction and deteriorated the microstructural characteristics, causing a degradation of the macroscale mechanical properties. Under sodium hydroxide conditions, a distinct transformation from granular structures to an agglomerated structure was attributed to the formation of sodium silicate, and the surface-surface connections were formed at the same time, which also indicated an enhancement of the microstructural characteristics. The enhanced microstructural characteristics contributed to the improvement in the macroscale mechanical properties. The findings of this study provide some design guideposts for preventing and mitigating the degradation of subgrade when exposed to saline environments.
The rational synthesis of single‐layer noble metal directly anchored on support materials is an elusive target to accomplish for a long time. This paper reports well‐defined single‐layer Pt (Pt‐SL) ...clusters anchored on ultrathin TiO2 nanosheets—as a new frontier in electrocatalysis. The structural evolution of Pt‐SL/TiO2 via self‐assembly of single Pt atoms (Pt‐SA) is systematically recorded. Significantly, the Pt atoms of Pt‐SL/TiO2 possess a unique electronic configuration with PtPt covalent bonds surrounded by abundant unpaired electrons. This Pt‐SL/TiO2 catalyst presents enhanced electrochemical performance toward diverse electrocatalytic reactions (such as the hydrogen evolution reaction and the oxygen reduction reaction) compared with Pt‐SA, multilayer Pt nanoclusters, and Pt nanoparticles, suggesting an efficient new type of catalyst that can be achieved by constructing single‐layer atomic clusters on supports.
Single‐layer Pt clusters, maintaining simultaneously adjacent Pt active atomic sites and PtPt covalent bonds, as a new frontier of atomic structure catalysts, are achieved by single Pt atoms self‐assembly. It exhibits unprecedented activity and stability toward diverse electrochemical reactions, such as hydrogen reduction reaction, oxygen reduction reaction, oxygen evolution reaction, and alcohol electrooxidation.
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