Industrial production of NH
3
from N
2
and H
2
significantly relies on Haber–Bosch process, which suffers from high energy consume and CO
2
emission. As a sustainable and environmentally-benign ...alternative process, electrochemical artificial N
2
fixation at ambient conditions, however, is highly required efficient electrocatalysts. In this study, we demonstrate that hexagonal boron nitride nanosheet (h-BNNS) is able to electrochemically catalyze N
2
to NH
3
. In acidic solution, h-BNNS catalyst attains a high NH
3
formation rate of 22.4 μg·h
–1
·mg
–1
cat
. and a high Faradic efficiency of 4.7% at–0.75 V vs. reversible hydrogen electrode, with excellent stability and durability. Density functional theory calculations reveal that unsaturated boron at the edge site can activate inert N
2
molecule and significantly reduce the energy barrier for NH
3
formation.
The MXene‐supported single transition metal systems have been reported as promising electrocatalysts for hydrogen evolution reaction (HER) and carbon dioxide reduction reaction. Herein, the potential ...performance of MXene‐based catalysts was explored on nitrogen reduction reaction (NRR). Density functional theory computations are carried out to screen a series of transition metal atoms confined in a vacancy of MXene nanosheet (Mo2TiC2O2). The results reveal that the Zr, Mo, Hf, Ta, W, Re, and Os supported on defective Mo2TiC2O2 layer can significantly promote the NRR process. Among them, Zr‐doped single atom catalyst (Mo2TiC2O2‐ZrSA) possesses the lowest barrier (0.15 eV) of the potential‐determining step, as well as high selectivity over HER competition. To the best of knowledge, 0.15 eV is the lowest barrier of potential‐determining step that has been reported for NRR so far. Besides, the formation energy of Mo2TiC2O2‐ZrSA is much more negative than that of the synthesized Mo2TiC2O2‐PtSA catalyst, suggesting that the experimental preparation of Mo2TiC2O2‐ZrSA is feasible. This work thus predicts an efficient electrocatalyst for the reduction of N2 to NH3 at ambient conditions.
A series of MXene‐supported single transition metal systems are theoretically screened to explore the potential electrocatalysts for nitrogen reduction reaction. Among them, Zr‐doped single atom catalyst possesses the lowest barrier (0.15 eV) of the potential‐determining step, as well as high selectivity over hydrogen evolution. Furthermore, the simulations indicate that the designed material is stable, thus the experimental synthesis should be feasible.
We studied the mutual and relative effect of inclusion and microstructure on very high cycle fatigue (VHCF) behavior of bainite/martensite (B/M) multiphase steel by designing four combinations of ...various inclusion sizes and microstructures. Results show that the fatigue crack initiations are mostly induced by inclusions in the specimens with large inclusion size, whereas the “non-inclusion induced crack initiations” (NIICI) are observed in the specimens whose microstructure is coarse. Unlike the inclusion induced cracks that grow along the plane of maximum tensile stress, the early non-inclusion induced cracks within micro-facet propagate along the plane of maximum shear stress (i.e., Stage I crack), which is related to the strain localization in oriented B/M laths during cyclic loading. Finally, with the assistance of scanning electron microscopy, electron backscatter diffraction, 3-Dimensional surface profile, focused ion beam and transmission electron microscopy, we proposed the NIICI mechanism of coarse B/M microstructure, and found the orientation and size of coarse B/M block and blocky retained austenite (RA) are crucial microstructural factors in facilitating the formation of NIICI within VHCF regime.
The synthesis of NH3 is mainly dominated by the traditional energy-consuming Haber–Bosch process with a mass of CO2 emission. Electrochemical conversion of N2 to NH3 emerges as a carbon-free process ...for the sustainable artificial N2 reduction reaction (NRR), but requires an efficient and stable electrocatalyst. Here, we report that the Mo2C nanorod serves as an excellent NRR electrocatalyst for artificial N2 fixation to NH3 with strong durability and acceptable selectivity under ambient conditions. Such a catalyst shows a high Faradaic efficiency of 8.13% and NH3 yield of 95.1 μg h–1 mg–1 cat at −0.3 V in 0.1 M HCl, surpassing the majority of reported electrochemical conversion NRR catalysts. Density functional theory calculation was carried out to gain further insight into the catalytic mechanism involved.
Hyperspectral image (HSI) classification, due to its characteristic combination of images and spectra, has important applications in various fields through pixel-level image classification. The ...fusion of spatial–spectral features is a topic of great interest in the context of hyperspectral image classification, which typically requires selecting a larger spatial neighborhood window, potentially leading to overlaps between training and testing samples. Vision Transformer (ViTs), with their powerful global modeling abilities, have had a significant impact in the field of computer vision through various variants. In this study, an ensemble learning framework for HSI classification is proposed by integrating multiple variants of ViTs, achieving high-precision pixel-level classification. Firstly, the spatial shuffle operation was introduced to preprocess the training samples for HSI classification. By randomly shuffling operations using smaller spatial neighborhood windows, a greater potential spatial distribution of pixels can be described. Then, the training samples were transformed from a 3D cube to a 2D image, and a learning framework was built by integrating seven ViT variants. Finally, a two-level ensemble strategy was employed to achieve pixel-level classification based on the results of multiple ViT variants. Our experimental results demonstrate that the proposed ensemble learning framework achieves stable and significantly high classification accuracy on multiple publicly available HSI datasets. The proposed method also shows notable classification performance with varying numbers of training samples. Moreover, herein, it is proven that the spatial shuffle operation plays a crucial role in improving classification accuracy. By introducing superior individual classifiers, the proposed ensemble framework is expected to achieve even better classification performance.
An inverted multi-step bainitic austempering process is proposed, where a low austempering temperature step is followed by a high temperature counterpart: after austenitization, the specimens were ...cooled to the first austempering step at 260 °C for 600 s, then were raised to the second step at 360 °C and held for 1800 s. As comparison, the conventional multi-step bainitic austempering processes were carried out: the first step is at 360 °C for 1800 s, while the second step is at 260 °C for 7200 s. Through inverted multi-step bainitic austempering process, the efficacy of reducing blocky austenite is also achieved and is comparable to that obtained by conventional multi-step bainitic austempering process. But the total time used for inverted multi-step bainitic austempering treatment is reduced markedly due to accelerating bainitic ferrite formation. Furthermore, the novel heat treatment can enhance the strength of a Mn-Si-Cr-C low-alloyed steel without sacrificing ductility, which is attributed to refining austenite and bainitic ferrite blocks.
•Inverted multi-step BAT process can reduce the amount of blocky austenite.•The total time used for inverted multi-step BAT treatment is shortened.•Yield strength increases without sacrificing ductility after IBAT treatment.•The increment of yield strength is attributed to refinement of bainitic ferrite block.
Polymyxin is the "last resort" of antibiotics. The self-induced resistance to polymyxin in Gram-negative bacteria could be mediated by lipopolysaccharide (LPS) modification, which is regulated by the ...two-component system, PhoP/PhoQ.
is a common foodborne pathogen. However, PhoP/PhoQ has not been thoroughly studied in
. In this study, the functions of PhoP/PhoQ in
intrinsic resistance were investigated. The resistance of
was found to decrease with the deletion of PhoP/PhoQ. Further, PhoP/PhoQ was found to play an important role in maintaining membrane permeability, intercellular metabolism, and reducing membrane depolarization. Based on subsequent studies, the binding ability of polymyxin to
was decreased by the modification of LPS with structures, such as L-Ara4N and palmitate. Analysis of the gene transcription levels revealed that the LPS modification genes,
and
operon, were downregulated with the deletion of PhoP/PhoQ in
during exposure to polymyxin. In addition,
,
, and
were downregulated in the mutants compared with the wild-type strain. Such findings demonstrate that PhoP/PhoQ contributes to the intrinsic resistance of
toward polymyxins. LPS modification with L-Ara4N or palmitate is mainly responsible for the resistance of
to polymyxins. The transcription of genes related to LPS modification and PmrA/PmrB can be both affected by PhoP/PhoQ in
. This study adds to current knowledge regarding the role of PhoP/PhoQ in intrinsic resistance of
to polymyxin.
Two-dimensional (2D) materials are used in energy storage and conversion due to their unique electronic structure and large specific area. In this work, 2D vanadium carbide (V
2
CT
x
MXene) is ...fabricated and studied as an efficient and earth-abundant electrocatalyst for electrocatalytic N
2
reduction reaction (NRR). When tested in 0.1 M Na
2
SO
4
, such electrocatalyst achieves a large NH
3
yield rate of 12.6 μg h
–1
mg
–1
cat.
and a Faradaic efficiency of 4% at –0.7 V vs. reversible hydrogen electrode. Theoretical calculations show a low reaction barrier of 0.88 eV in the distal route for this catalyst.
Graphic Abstract
Emerging evidence shows the association between nuclear envelope and tumor progression, however, the functional contributions of specific constituents of the nuclear envelope remain largely unclear. ...We found that the expression level of transmembrane protein 201 (TMEM201), an integral inner nuclear membrane protein of unknown function, was significantly elevated in invasive breast cancer and predicted poor breast cancer prognosis. We showed that TMEM201, as a positive modulator, was both necessary and sufficient to regulate the migration and invasion of breast cancer cells in vitro and in vivo. Mechanistically, RNA-sequencing analysis and validation showed that TMEM201 deficiency inhibited epithelial-to-mesenchymal transition and transforming growth factor-β signaling. Finally, we showed that TMEM201 physically interacted with SMAD2/3 and was required for the phosphorylation of SMAD2/3, nuclear translocation and transcriptional activation of the TGFβ. Thus, we demonstrated that specific inner nuclear membrane component mediated signal-dependent transcriptional effects to control breast cancer metastasis.
Rose is recognized as an important ornamental plant worldwide, and it is also one of the most widely used flowers in gardens. At present, the improvement of rose traits is still difficult and ...uncertain, and molecular breeding can provide new ideas for the improvement of modern rose varieties. Somatic embryos are quite good receptors for genetic transformation. However, little is known about the molecular mechanisms underlying during the regeneration process of rose somatic embryos. To elucidate the molecular regulation mechanism of somatic embryo plantlet regeneration, the relationship between the differences in traits of the two different regenerated materials and the significantly differentially expressed genes (DEGs) related to phytohormone pathways in the process of regeneration were be investigated.
These representative two regenerated samples from single-piece cotyledonary somatic embryo (SPC) culture of Rosa hybrida 'John F. Kennedy', were harvested for transcriptome analysis, with the SPC explants at the initial culture (Day 0) as the control. The differentially expressed genes (DEGs) in the materials from two different types for regeneration approach (SBF type: the regeneration approach type of single bud formed from SPC explants; MBF type: the regeneration approach type of multiple buds formed from SPC explants) were be screened by means of the transcriptome sequencing technology. In this study, a total of about 396.24 million clean reads were obtained, of which 78.95-82.92% were localized to the reference genome, compared with the initial material (CK sample), there were 5594 specific genes in the material of SBF type and 6142 specific genes in the MBF type. The DEGs from the SBF type material were mainly concentrated in the biological processes of GO terms such as phytohormones, substance transport, cell differentiation, and redox reaction. The KEGG enrichment analysis revealed these DEGs were more active in ubiquinone and other terpenoid-quinone biosynthesis, fatty acid elongation, steroid biosynthesis, and glycosphingolipid biosynthesis-globo and isoglobo series. In contrast, the DEGs induced by the MBF type material were mainly associated with the biological processes such as phytohormones, phosphorylation, photosynthesis and signal transduction. According to KEGG analysis, these DEGs of MBF type were significantly enriched in the porphyrin and chlorophyll metabolism, brassinosteroid biosynthesis, carotenoid biosynthesis, and peroxisome. Furthermore, the results from the phytohormone pathways analysis showed that the auxin-responsive factor SAUR and the cell wall modifying enzyme gene XTH were upregulated for expression but the protein phosphatase gene PP2C was downregulated for expression in SBF type; the higher expression of the ethylene receptor ETR, the ethylene transduction genes EBF1/2, the transcription factor EIN3, and the ethylene-responsive transcription factor ERF1/2 were induced by MBF type.
According to the GO and KEGG analysis, it indicated the DEGs between two different regenerated materials from somatic embryos were significantly different which might be causing morphological differences. That was somatic embryos from Rosa hybrida 'John F. Kennedy' could regenerate plantlet via both classic somatic embryogenesis (seed-like germination) and organogenesis, cotyledonary somatic embryos should be considered as one kind of intermediate materials similiar to callus, rather than the indicator materials for somatic embryogenesis.
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