Single atom catalysts (SACs) with the maximized metal atom efficiency have sparked great attention. However, it is challenging to obtain SACs with high metal loading, high catalytic activity, and ...good stability. Herein, we demonstrate a new strategy to develop a highly active and stable Ag single atom in carbon nitride (Ag‐N2C2/CN) catalyst with a unique coordination. The Ag atomic dispersion and Ag‐N2C2 configuration have been identified by aberration‐correction high‐angle‐annular‐dark‐field scanning transmission electron microscopy (AC‐HAADF‐STEM) and extended X‐ray absorption. Experiments and DFT calculations further verify that Ag‐N2C2 can reduce the H2 evolution barrier, expand the light absorption range, and improve the charge transfer of CN. As a result, the Ag‐N2C2/CN catalyst exhibits much better H2 evolution activity than the N‐coordinated Ag single atom in CN (Ag‐N4/CN), and is even superior to the Pt nanoparticle‐loaded CN (PtNP/CN). This work provides a new idea for the design and synthesis of SACs with novel configurations and excellent catalytic activity and durability.
A new Ag single atom in carbon nitride (Ag‐N2C2/CN) photocatalyst with Ag‐N2C2 configuration is developed. It affords fast charge transfer, high Ag loading, and good stability. Noteworthily, the Ag‐N2C2/CN exhibits much better hydrogen evolution activity than Ag‐N4/CN, and even superior to the platinum‐loaded CN.
Cryo‐electron microscopy (cryo‐EM) is a structural biological method that is used to determine the 3D structures of biomacromolecules. After years of development, cryo‐EM has made great achievements, ...which has led to a revolution in structural biology. In this article, the principle, characteristics, history, current situation, workflow, and common problems of cryo‐EM are systematically reviewed. In addition, the new development direction of cryo‐EM—cryo‐electron tomography (cryo‐ET), is discussed in detail. Also, cryo‐EM is prospected from the following aspects: the structural analysis of small proteins, the improvement of resolution and efficiency, and the relationship between cryo‐EM and drug development. This review is dedicated to giving readers a comprehensive understanding of the development and application of cryo‐EM, and to bringing them new insights.
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Oxygen reduction reaction (ORR) on cathode severely suffers from sluggish kinetics in zinc-air batteries. Therefore, substantial efforts have been made to prepare advanced ...electrocatalysts for facilitating the ORR. Herein, we synthesized FeCo alloyed nanocrystals entrapped in N-doped graphitic carbon nanotubes on nanosheets (FeCo-N-GCTSs) by 8-aminoquinoline coordination-induced pyrolysis, whose morphology, structures, and property were characterized in details. Impressively, the obtained FeCo-N-GCTSs catalyst showed a positive onset potential (Eonset = 1.06 V) and half-wave potential (E1/2 = 0.88 V), revealing excellent ORR activity. Further, the FeCo-N-GCTSs assembled zinc-air battery displayed the maximum power density of 133 mW cm−2 and negligible gap change in the discharge–charge voltage plot over 288 h (ca. 864 cycles) at 5 mA cm−2, outperforming the Pt/C + RuO2 based counterpart. This work provides a facile route for construction of high-efficiency, durable and low-cost nanocatalysts for the ORR in fuel cells and rechargeable Zn-air batteries.
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•FeNb2O6/3D interconnected N-doped carbon cages were synthesized by methanol-induced assembly and pyrolysis strategy.•The methanol evaporation promotes the assembly and crosslinkage ...of ZIF-8, resulting in 3D interconnected cage-like superstructure.•The 3D structure provides a spacious surface area and abundant defects for interfacial mass and electron transfer.•FeNb2O6/NICC showed excellent performances of the ORR and Zn-air battery.
Three-dimensional (3D) hollow carbon is one of advanced nanomaterials widely applied in oxygen reduction reaction (ORR). Herein, iron niobate (FeNb2O6) nanoparticles supported on metal-organic frameworks (MOFs)-derived 3D N-doped interconnected open carbon cages (FeNb2O6/NICC) were prepared by methanol induced assembly and pyrolysis strategy. During the fabrication process, the evaporation of methanol promoted the assembly and cross linkage of ZIF-8, rather than individual particles. The assembled ZIF-8 particles worked as in-situ sacrificial templates, in turn forming hierarchically interconnected open carbon cages after high-temperature pyrolysis. The as-made FeNb2O6/NICC showed a positive onset potential of 1.09 V and a half-wave potential of 0.88 V for the ORR, outperforming commercial Pt/C under the identical conditions. Later on, the as-built Zn-air battery with the FeNb2O6/NICC presented a greater power density of 100.6 mW cm−2 and durable long-cycle stability by operating for 200 h. For preparing 3D hollow carbon materials, this synthesis does not require a tedious removal process of template, which is more convenient than traditional method with silica and polystyrene spheres as templates. This work affords an exceptional example of developing 3D N-doped interconnected hollow carbon composites for energy conversion and storage devices.
This paper studies fixed-time leader-following lag consensus problem of second-order multiagent systems with input delay. Using fixed-time distributed observer, we obtain the leader's states for each ...followers. An extension of the Artstein's reducing transformation is employed to transform the delayed error system into a second-order system without time delay and a novel nonsingular terminal sliding mode protocol is proposed to achieve fixed-time consensus. The presented sliding mode controller can avoid singularity, eliminate chattering, and achieve exact convergence. It is mathematically proved that the presented protocol can achieve exact fixed-time leader-following lag consensus. Moreover, the upper bound of convergence time only depends on observer parameters, controller parameters, network parameters, and delay time, which makes it possible to determine the convergence time offline regardless of initial condition. The presented protocol is applied to coordinated lag tracking control of single-link robotic manipulators and the results validate the effectiveness of the proposed fixed-time protocol.
DNA methylation is a form of epigenetic regulation, having pivotal parts in controlling cellular expansion and expression levels within genes. Although blood DNA methylation has been studied in ...humans and other species, its prominence in cattle is largely unknown. This study aimed to methodically probe the genomic methylation map of Xinjiang brown (XJB) cattle suffering from bovine respiratory disease (BRD), consequently widening cattle blood methylome ranges. Genome-wide DNA methylation profiling of the XJB blood was investigated through whole-genome bisulfite sequencing (WGBS). Many differentially methylated regions (DMRs) obtained by comparing the cases and controls groups were found within the CG, CHG, and CHH (where H is A, T, or C) sequences (16,765, 7502, and 2656, respectively), encompassing 4334 differentially methylated genes (DMGs). Furthermore, GO/KEGG analyses showed that some DMGs were involved within immune response pathways. Combining WGBS-Seq data and existing RNA-Seq data, we identified 71 significantly differentially methylated (DMGs) and expressed (DEGs) genes (
< 0.05). Next, complementary analyses identified nine DMGs (
,
,
,
,
,
,
, and
) that might be involved in the immune response of XJB cattle infected with respiratory diseases. Although further investigations are needed to confirm their exact implication in the involved immune processes, these genes could potentially be used for a marker-assisted selection of animals resistant to BRD. This study also provides new knowledge regarding epigenetic control for the bovine respiratory immune process.
Electrochemical sensing based on conventional rigid electrodes has great restrictions for characterizing biomolecules in deformed cells or soft tissues. The recent emergence of stretchable sensors ...allows electrodes to conformally contact to curved surfaces and perfectly comply with the deformation of living cells and tissues. This provides a powerful strategy to monitor biomolecules from mechanically deformed cells, tissues, and organisms in real time, and opens up new opportunities to explore the mechanotransduction process. In this minireview, we first summarize the fabrication of stretchable electrodes with emphasis on the nanomaterial‐enabled strategies. We then describe representative applications of stretchable sensors in the real‐time monitoring of mechanically sensitive cells and tissues. Finally, we present the future possibilities and challenges of stretchable electrochemical sensing in cell, tissue, and in vivo detection.
Emerging stretchable electrodes open up new opportunities for the real‐time monitoring of biomolecule release from deformed cells, soft tissues, and organisms. In this minireview, we summarize recent advances in the fabrication of stretchable electrochemical sensors and their representative applications in cell, tissue, and in vivo detection.
The hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER) play an important role in hydrogen-based energy conversion. However, the sluggish kinetics in alkaline media has raised ...debates on the relevant mechanism, especially on the role of surface hydroxyl (OH*). With the potential-related free energy profiles obtained with density functional theory calculations, the full pH range transient kinetics simulation of HER/HOR polarization curves on Pt(111) agrees well with experimental observations. Studying model systems with varying metal–OH* binding energies confirms that the current near the HOR onset potential is contributed from the pathway through OH– rather than OH*, suggesting that OH* is unlikely an effective activity descriptor for HOR. The degree of rate control analyses reveal that, while acidic current is controlled solely by the Tafel step, alkaline current is controlled jointly by Tafel and Volmer steps, as the Volmer barrier is considerably increased in alkaline conditions. Finally, based on a model study, we draw up a scheme of reducing the overpotential of alkaline HER/HOR by accelerating the Tafel step.
Oncogene-induced cellular senescence (OIS) is a complex program that is triggered in response to aberrant activation of oncogenic signaling. Initially, OIS was thought to be a barrier to malignant ...transformation because of its suppression on cell proliferation. Later studies showed that senescence induced by oncogenes can also promote the initiation and development of cancer. The opposing effects of OIS occur through different combinations of downstream effectors as well as the interplay of senescent cells and the microenvironment, such as senescence-associated inflammation. Here, we review the common features and molecular mechanisms underlying OIS and the interaction between senescent cells and the microenvironment. We propose that targeting senescent cells may have a beneficial therapeutic effect during the treatment of cancer.
Cancer stem cells(CSCs) are a small subpopulation in cancer, have been proposed to be cancer-initiating cells, and have been shown to be responsible for chemotherapy resistance and cancer recurrence. ...The identification of CSC subpopulations inside a tumor presents a new understanding of cancer development because it implies that tumors can only be eradicated by targeting CSCs. Although advances in liver cancer detection and treatment have increased the possibility of curing the disease at early stages, unfortunately, most patients will relapse and succumb to their disease. Strategies aimed at efficiently targeting liver CSCs are becoming important for monitoring the progress of liver cancer therapy and for evaluating new therapeutic approaches. Herein, we provide a critical discussion of biological markers described in the literature regarding liver cancer stem cells and the potential of these markers to serve as therapeutic targets.
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