Alkali metals are widely studied in various fields such as medicine and battery. However, limited by the chemical reactivity and electron/ion beam sensitivity, the intrinsic atomic structure of alkali metals and its fundamental properties are difficult to be revealed. Here, a simple and versatile method is proposed to form the alkali metals in situ inside the transmission electron microscope. Taking alkali salts as the starting materials and electron beam as the trigger, alkali metals can be obtained directly. With this method, atomic resolution imaging of lithium and sodium metal is achieved at room temperature, and the growth of alkali metals is visualized at atomic-scale with millisecond temporal resolution. Furthermore, our observations unravel the ambiguities in lithium metal growth on garnet-type solid electrolytes for lithium-metal batteries. Finally, our method enables a direct study of physical contact property of lithium metal as well as its surface passivation oxide layer, which may contribute to better understanding of lithium dendrite and solid electrolyte interphase issues in lithium ion batteries.
Drug-resistant Tuberculosis (TB) is a global public health problem. Resistance to rifampicin, the most effective drug for TB treatment, is a major growing concern. The etiological agent, Mycobacterium tuberculosis ( Mtb ), has a cluster of ATP-binding cassette (ABC) transporters which are responsible for drug resistance through active export. Here, we describe studies characterizing Mtb Rv1217c–1218c as an ABC transporter that can mediate mycobacterial resistance to rifampicin and have determined the cryo-electron microscopy structures of Rv1217c–1218c. The structures show Rv1217c–1218c has a type V exporter fold. In the absence of ATP, Rv1217c–1218c forms a periplasmic gate by two juxtaposed-membrane helices from each transmembrane domain (TMD), while the nucleotide-binding domains (NBDs) form a partially closed dimer which is held together by four salt-bridges. Adenylyl-imidodiphosphate (AMPPNP) binding induces a structural change where the NBDs become further closed to each other, which downstream translates to a closed conformation for the TMDs. AMPPNP binding results in the collapse of the outer leaflet cavity and the opening of the periplasmic gate, which was proposed to play a role in substrate export. The rifampicin-bound structure shows a hydrophobic and periplasm-facing cavity is involved in rifampicin binding. Phospholipid molecules are observed in all determined structures and form an integral part of the Rv1217c–1218c transporter system. Our results provide a structural basis for a mycobacterial ABC exporter that mediates rifampicin resistance, which can lead to different insights into combating rifampicin resistance.
Abstract The node‐based smoothed particle finite element method (NS‐PFEM) offers high computational efficiency but is numerically unstable due to possible spurious low‐energy mode in direct nodal integration (NI). Moreover, the NS‐PFEM has not been applied to hydromechanical coupled analysis. This study proposes an implicit stabilised T3 element‐based NS‐PFEM (stabilised node‐based smoothed particle finite element method [SNS‐PFEM]) for solving fully hydromechanical coupled geotechnical problems that (1) adopts the stable NI based on multiple stress points over the smooth domain to resolve the NI instability of NS‐PFEM, (2) implements the polynomial pressure projection (PPP) technique in the NI framework to cure possible spurious pore pressure oscillation in the undrained or incompressible limit and (3) expresses the NI for assembling coefficient matrices and calculating internal force in SNS‐PFEM with PPP as closed analytical expressions, guaranteeing computational accuracy and efficiency. Four classical benchmark tests (1D Terzaghi's consolidation, Mandel's problem, 2D strip footing consolidation and foundation on a vertical cut) are simulated and compared with analytical solutions or results from other numerical methods to validate the correctness and efficiency of the proposed approach. Finally, penetration of strip footing into soft soil is investigated, showing the outstanding performance the proposed approach can offer for large deformation problems. All results demonstrate that the proposed SNS‐PFEM with PPP is capable of tracking hydromechanical coupled geotechnical problems under small and large deformation with different drainage capacities.
The analysis of residential electricity consumption behavior (RECB) aims to deeply reveal the electricity consumption characteristics of customers that can be used to improve the electricity service performances from the large volume of load data. For analyzing the RECB, various clustering-based methods have been developed. However, with the dimension of power consumption data increasing, it is difficult for traditional methods to accurately identify users' power consumption patterns. To this end, this paper proposes a novel analysis method for RECB with high-dimensional data based on uniform manifold approximation and projection-criteria importance through intercriteria correlation (UMAP-CRITIC) feature optimization and sparrow search algorithm (SSA)-assisted clustering. Specifically, the high-dimensional raw data combined with load characteristics indexes are first utilized to generate low-dimensional features by UMAP-based dimension reduction theory. Secondly, the contribution weight of each reduced feature to the intrinsic information of the original data is optimized based on the CRITIC weight method, and then the data feature set of RECB identification considering feature contributions is constructed. Finally, the SSA-based k-means is employed to obtain and analyze the various RECBs. The simulation results show that the proposed method can effectively identify high-dimensional electricity consumption data and precisely extract the electricity consumption information of residents.
A strategy is proposed to induce the self-assembly process of metal ions with polyphenol in deep eutectic solvents (DESs) for the generation of metal-polyphenol network particles (MPNPs).
Recently, materials with hierarchical nanoporous architectures have been proposed to enhance the performance of alloy-type lithium-ion battery (LIB) and sodium-ion battery (SIB) anodes. However, the origin of this enhancement has not been elucidated. The present work is aimed at identifying the fundamental mechanism behind this enhanced performance using sodium storage in antimony as a model system. We have found that the amount of sodium reversibly stored in antimony is enhanced by roughly 27% when hierarchical nanoporous antimony with bimodal porosity is used as the anode instead of nanoporous antimony with unimodal porosity. Electron microscopy analysis based on energy-dispersive X-ray spectroscopy mapping and computational analysis based on Monte Carlo simulations reveal that the difference in performance originates from mass transport limitations associated with the transfer of sodium ions from the electrolyte to the bulk of antimony. Typically, in hierarchical nanoporous antimony electrodes with bimodal porosity, the diffusion of sodium ions through the bulk of the material is very favorable, resulting in full sodiation of antimony. In contrast, under similar experimental conditions (i.e., the same charge/discharge rate) nanoporous antimony with unimodal porosity is only partially sodiated. The full sodiation of hierarchical nanoporous antimony is favored by large pores, which facilitate the penetration of the electrolyte into the bulk of antimony, reducing the overall effective diffusion length inside the material. Interestingly, in terms of cycle-life, the capacities achieved in these two types of electrode architectures start to decay after 200 cycles with the same decay trend, suggesting that the hierarchical nanoporous architecture does not contribute to the cycling stability; that is, the large pores only improve the charge storage kinetics. These insights will contribute to the development of high-performance alloy-type SIB and LIB anodes.
Dealloyed nanoporous metals made of very-reactive elements have rarely been reported. Instead, reactive materials are used as sacrificial components in dealloying. The high chemical reactivity of nonprecious nanostructured metals makes them suitable for a broad range of applications such as splitting water into H2 gas and metal hydroxide. On the other hand, the same high chemical reactivity hinders the synthesis of nanostructured metals. Here we use a pH-controlled dealloying strategy to fabricate bulk nanoporous Zn with bulk dimensions in the centimeter range via the selective removal of Al from metastable face-centered cubic bulk Zn20Al80 at. % parent alloys. The corresponding bulk nanoporous Zn exhibits a hierarchical ligament/pore architecture characterized by primary ligaments and pores with an average feature size in the submicrometer range. These primary structures are made of ultrafine secondary ligaments and pores with a characteristic feature size in the range of 10–20 nm. Our bulk nanoporous Zn can split water into H2 and Zn(OH)2 at ambient temperature and pressure and continuously produce H2 at a constant rate of 0.08 mL/min per gram of Zn over 8 h. We anticipate that in this hierarchical bulk architecture, the macropores facilitate the flow of water in the bulk of the material, while the mesopores and ultrafine ligaments provide a high surface area for the reaction of water with Zn. The bulk nanoporous Zn/water system can be used for on-board or on-demand H2 applications, during which H2 is produced when needed, without prior storage of this gas compressed in cylinders as it is currently the case.
We describe full-wave single-shot computations for multi-source electromagnetic problems in both 2D and 3D using the "augmented partial factorization" method. This versatile approach bypasses unnecessary computations and avoids repetitions to achieve many orders of magnitude speed-up compared to conventional methods.
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