High kinetics oxygen reduction reaction (ORR) electrocatalysts under low temperature are critical and highly desired for temperature‐tolerant energy conversion and storage devices, but remain ...insufficiently investigated. Herein, oxygen vacancy‐rich porous perovskite oxide (CaMnO3) nanofibers coated with reduced graphene oxide coating (V‐CMO/rGO) are developed as the air electrode catalyst for low‐temperature and knittable Zn–air batteries. V‐CMO/rGO exhibits top‐level ORR activity among perovskite oxides and shows impressive kinetics under low temperature. Experimental and theoretical calculation results reveal that the synergistic effect between metal atoms and oxygen vacancies, as well as the accelerated kinetics and enhanced electric conductivity and mass transfer over the rGO coated nanofiber 3D network contribute to the enhanced catalytic activity. The desorption of ORR intermediate is promoted by the regulated electron filling. The V‐CMO/rGO drives knittable and flexible Zn–air batteries under a low temperature of −40 °C with high peak power density of 56 mW cm−2 and long cycle life of over 80 h. This study provides insight of kinetically active catalyst and facilitates the ZABs application in harsh environment.
The oxygen reduction reaction kinetics of a perovskite oxide is significantly promoted by a facile metal–vacancy strategy. The newly developed vacancy‐rich porous perovskite nanofibers exhibit comparable activities to the commercial Pt/C and even surpass it under low temperature. The developed catalyst can drive knittable fibrous‐type and sandwich‐type zinc–air batteries under low temperature of −40 °C with impressive performance.
Abstract
Designing novel single‐atom catalysts (SACs) supports to modulate the electronic structure is crucial to optimize the catalytic activity, but rather challenging. Herein, a general strategy ...is proposed to utilize the metalloid properties of supports to trap and stabilize single‐atoms with low‐valence states. A series of single‐atoms supported on the surface of tungsten carbide (M‐WC
x
, M=Ru, Ir, Pd) are rationally developed through a facile pyrolysis method. Benefiting from the metalloid properties of WC
x
, the single‐atoms exhibit weak coordination with surface W and C atoms, resulting in the formation of low‐valence active centers similar to metals. The unique metal‐metal interaction effectively stabilizes the low‐valence single atoms on the WC
x
surface and improves the electronic orbital energy level distribution of the active sites. As expected, the representative Ru‐WC
x
exhibits superior mass activities of 7.84 and 62.52 A mg
Ru
−1
for the hydrogen oxidation and evolution reactions (HOR/HER), respectively. In‐depth mechanistic analysis demonstrates that an ideal dual‐sites cooperative mechanism achieves a suitable adsorption balance of H
ad
and OH
ad
, resulting in an energetically favorable Volmer step. This work offers new guidance for the precise construction of highly active SACs.
Arabidopsis mutants produced by constitutive overexpression of the CRISPR/Cas9 genome editing system are usually mosaics in the T1 generation. In this study, we used egg cell-specific promoters to ...drive the expression of Cas9 and obtained non-mosaic T1 mutants for multiple target genes with high efficiency. Comparisons of 12 combinations of eight promoters and two terminators found that the efficiency of the egg cell-specific promoter-controlled CRISPR/Cas9 system depended on the presence of a suitable terminator, and the composite promoter generated by fusing two egg cell-specific promoters resulted in much higher efficiency of mutation in the T1 generation compared with the single promoters.
Natural products containing eight-membered carbocycles constitute a class of structurally intriguing and biologically important molecules such as the famous diterpenes taxol and vinigrol. Such ...natural products are being increasingly investigated because of their fascinating architectural features and potent medicinal properties. However, synthesis of natural products with cyclooctane moieties has proved to be highly challenging. This review highlights the recently completed total syntheses of natural products with eight-membered carbocycles with a focus on strategic considerations. A collection of 27 representative studies from the literature covering the decade from 2009 to 2019 is described in chronological order with relevant studies grouped together, including syntheses of the same natural product by different research groups using different strategies. Finally, a summary and outlook including a discussion of the major features of each strategy used in the syntheses are presented. This review illustrates the diversity and creativity in the elegant synthetic designs of eight-membered carbocycles. We hope this review will provide timely illumination and beneficial guidance for future synthetic efforts for organic chemists who are interested in this area.
To accelerate the application of the CRISPR/Cas9 (clustered regularly interspaced short palindromic repeats/ CRISPR-associated protein 9) system to a variety of plant species, a toolkit with ...additional plant selectable markers, more gRNA modules, and easier methods for the assembly of one or more gRNA expression cassettes is required.
We developed a CRISPR/Cas9 binary vector set based on the pGreen or pCAMBIA backbone, as well as a gRNA (guide RNA) module vector set, as a toolkit for multiplex genome editing in plants. This toolkit requires no restriction enzymes besides BsaI to generate final constructs harboring maize-codon optimized Cas9 and one or more gRNAs with high efficiency in as little as one cloning step. The toolkit was validated using maize protoplasts, transgenic maize lines, and transgenic Arabidopsis lines and was shown to exhibit high efficiency and specificity. More importantly, using this toolkit, targeted mutations of three Arabidopsis genes were detected in transgenic seedlings of the T1 generation. Moreover, the multiple-gene mutations could be inherited by the next generation.
We developed a toolkit that facilitates transient or stable expression of the CRISPR/Cas9 system in a variety of plant species, which will facilitate plant research, as it enables high efficiency generation of mutants bearing multiple gene mutations.
Neutral oxygen evolution reaction (OER) with unique reactive environments exhibits extremely slow reaction kinetics, posing significant challenges in the design of catalysts. Herein, a built‐in ...electric field between the tungstate (Ni‐FeWO4) with adjustable work function and Lewis acid WO3 is elaborately constructed to regulate asymmetric interfacial electron distribution, which promotes electron accumulation of Fe sites in the tungstate. This decelerates the rapid dissolution of Fe under the OER potentials, thereby retaining the active hydroxyl oxide with the optimized OER reaction pathway. Meanwhile, Lewis acid WO3 enhances hydroxyl adsorption near the electrode surface to improve mass transfer. As expected, the optimized Ni‐FeWO4@WO3/NF self‐supporting electrode achieves a low overpotential of 235 mV at 10 mA cm−2 in neutral media and maintains stable operation for 200 h. Furthermore, the membrane electrode assembly constructed by such self‐supporting electrode exhibits robust stability for 250 h during neutral seawater electrolysis. This work deepens the understanding of the reconstruction of OER catalysts in neutral environments and paves the way for development of the energy conversion technologies.
A built‐in electric field between Ni‐FeWO4 and WO3 simultaneously achieves the electron‐rich state of the Fe sites in tungstate and improvement of the local reaction environment to suppress Fe leaching and accelerate mass transfer during neutral water oxidation, which endows the membrane electrode assembly constructed of Ni‐FeWO4@WO3/NF with low cell voltages and robust stability for neutral seawater electrolysis.
The gut microbiota-derived metabolite, trimethylamine N-oxide (TMAO) plays an important role in cardiovascular disease (CVD). The fasting plasma TMAO was shown as a prognostic indicator of CVD ...incident in patients and raised the interest of intervention targeting gut microbiota. Here we develop a clinically applicable method called oral carnitine challenge test (OCCT) for TMAO-related therapeutic drug efforts assessment and personalising dietary guidance.
A pharmacokinetic study was performed to verify the design of OCCT protocol. The OCCT was conducted in 23 vegetarians and 34 omnivores to validate gut microbiota TMAO production capacity. The OCCT survey was integrated with gut microbiome, host genotypes, dietary records and serum biochemistry. A humanised gnotobiotic mice study was performed for translational validation.
The OCCT showed better efficacy than fasting plasma TMAO to identify TMAO producer phenotype. The omnivores exhibited a 10-fold higher OR to be high TMAO producer than vegetarians. The TMAO-associated taxa found by OCCT in this study were consistent with previous animal studies. The TMAO producer phenotypes were also reproduced in humanised gnotobiotic mice model. Besides, we found the faecal
gene was not associated with TMAO production; therefore, other key relevant microbial genes might be involved. Finally, we demonstrated the urine TMAO exhibited a strong positive correlation with plasma TMAO (r=0.92, p<0.0001) and improved the feasibility of OCCT.
The OCCT can be used to identify TMAO-producer phenotype of gut microbiota and may serve as a personal guidance in CVD prevention and treatment.
NCT02838732; Results.
Increasing awareness of climate change and food security has spawned an interest in low-carbon agriculture, an important aspect of which is the reduction of greenhouse gas emissions. As the largest ...source of agricultural emissions is fertilizer application, using a different type of fertilizer may help to mitigate greenhouse gas emissions from agriculture systems. The objectives of this study were to report a basic estimate of agricultural inputs and greenhouse gas emissions of crop production using national statistical data available for the period of 1993–2007, to compare the quantities of greenhouse gas emissions from different fertilizer types (per unit of N, P2O5, and K2O), to identify fertilizer types with the lowest emissions and the lowest costs, and to quantify the emissions gap between the lowest and actual emission scenarios, which will provide critical information for pursuing low-carbon agriculture in the future. According to available data, the use of all agricultural inputs increased during 1993–2012, resulting in an increase in not only yield but also in total greenhouse gas emissions from crop production. Not considering direct N2O emissions from the field, fertilizer-induced emissions accounted for up to 47.71% of the total greenhouse gas emissions from crop production. Therefore, lowering fertilizer-induced emissions is a priority measure that will result in low-carbon agriculture. Furthermore, ammonium bicarbonate, calcium superphosphate, and potassium chloride were found to be fertilizers with the lowest greenhouse gas emissions, and adoption of these fertilizers would result in a 49.15% reduction in fertilizer-induced emissions. This finding indicates that the judicious choice of fertilizer type would contribute to reducing greenhouse gas emissions in intensive production systems in China. Accordingly, utilizing ammonium bicarbonate, calcium superphosphate, and potassium chloride would be beneficial for greenhouse gas emission reduction and could be adopted as a good practice of low-carbon agriculture in China. This study highlights that changing to an appropriate fertilizer type could be an efficient option for mitigating greenhouse gas emissions in crop production in China.
•GHG emissions from different types of fertilizer products were compared.•The lowest emissions of the N, P, and K fertilizers were identified, respectively.•Adoption of the lowest emissions result in a 49% reduction of fertilizer emissions.
Ti−Zr alloys (oxygen content 0.42−0.54 wt.%) were prepared via powder metallurgy and hot working. The results indicate that the Ti−Zr alloys exhibit Zr-rich and Zr-lean areas with the same α-phase ...structure, and the Zr-rich area shows a slightly higher oxygen content and a much finer grain size. The Ti−Zr alloys present a good combination of high strength (σs=700−900 MPa) and total elongation (>20%), and solid solution strengthening of oxygen plays a major role. Zr does not influence much the oxygen-induced brittleness due to its high structural similarity to Ti. Therefore, the high value of 0.54 wt.% is still within the critical oxygen content for the ductile-to-brittle transition of Ti and does not degrade the ductility.
Renal tubulointerstitial fibrosis was a crucial pathological feature of diabetic nephropathy (DN), and renal tubular injury might associate with abnormal mitophagy. In this study, we investigated the ...effects and molecular mechanisms of AMPK agonist metformin on mitophagy and cellular injury in renal tubular cell under diabetic condition. The high fat diet (HFD) and streptozotocin (STZ)-induced type 2 diabetic mice model and HK-2 cells were used in this study. Metformin was administered in the drinking water (200 mg/kg/d) for 24 weeks. Renal tubulointerstitial lesions, oxidative stress and some indicators of mitophagy (e.g., LC3II, Pink1, and Parkin) were examined both in renal tissue and HK-2 cells. Additionally, compound C (an AMPK inhibitor) and Pink1 siRNA were applied to explore the molecular regulation mechanism of metformin on mitophagy. We found that the expression of p-AMPK, Pink1, Parkin, LC3II, and Atg5 in renal tissue of diabetic mice was decreased obviously. Metformin reduced the levels of serum creatinine, urine protein, and attenuated renal oxidative injury and fibrosis in HFD/STZ induced diabetic mice. In addition, Metformin reversed mitophagy dysfunction and the over-expression of NLRP3. In vitro pretreatment of HK-2 cells with AMPK inhibitor compound C or Pink1 siRNA negated the beneficial effects of metformin. Furthermore, we noted that metformin activated p-AMPK and promoted the translocation of Pink1 from the cytoplasm to mitochondria, then promoted the occurrence of mitophagy in HK-2 cells under HG/HFA ambience. Our results suggested for the first time that AMPK agonist metformin ameliorated renal oxidative stress and tubulointerstitial fibrosis in HFD/STZ-induced diabetic mice via activating mitophagy through a p-AMPK-Pink1-Parkin pathway.
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