The majority of adenosine triphosphate (ATP) powering cellular processes in eukaryotes is produced by the mitochondrial F1Fo ATP synthase. Here, we present the atomic models of the membrane Fo domain ...and the entire mammalian (ovine) F1Fo, determined by cryo-electron microscopy. Subunits in the membrane domain are arranged in the 'proton translocation cluster' attached to the c-ring and a more distant 'hook apparatus' holding subunit e. Unexpectedly, this subunit is anchored to a lipid 'plug' capping the c-ring. We present a detailed proton translocation pathway in mammalian Fo and key inter-monomer contacts in F1Fo multimers. Cryo-EM maps of F1Fo exposed to calcium reveal a retracted subunit e and a disassembled c-ring, suggesting permeability transition pore opening. We propose a model for the permeability transition pore opening, whereby subunit e pulls the lipid plug out of the c-ring. Our structure will allow the design of drugs for many emerging applications in medicine.
•ZIF-8 can simultaneously remove 95.4% of Cu and 80.3% of norfloxacin.•Cu removal involved ion exchange with Zn.•Norfloxacin removal involved both electrostatic and π-π interactions.•Adsorption ...followed pseudo-second-order kinetics and best fit the Freundlich adsorption model.
Many wastewaters commonly contain complex mixtures of both antibiotics and heavy metals, where the simultaneous removal of these mixed contaminants is still a challenge. In this paper, ZIF-8, a metal-organic framework material, was proposed as a potential absorbent to simultaneously remove norfloxacin and copper from wastewater. Batch adsorption experiments showed that ZIF-8 could simultaneously remove 95.4% of Cu and 80.3% of norfloxacin. ZIF-8 was characterized before and after the removal of the mixed contaminants. X-ray powder diffraction (XRD) showed that ZIF-8 was synthesized successfully and maintained a stable structure after contaminant adsorption. Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) both suggested that contaminants were partially adsorbed on the surface of ZIF-8. X-ray photoelectron spectroscopy (XPS) also indicated the presence of both carboxyl and Cu on the ZIF-8 surface confirming that a mixture of contaminants was adsorbed. For both contaminants, adsorption followed pseudo-second-order kinetics and best fit the Freundlich adsorption model with correlation coefficients (R2) of 0.973 and 0.994, for copper and norfloxacin, respectively. Finally, removal mechanisms for copper and norfloxacin by ZIF-8 were proposed. For Cu, the adsorption process on ZIF-8 was mainly due to ion exchange, whereas electrostatic interactions and π-π stacking may be responsible for norfloxacin adsorption. Overall this study demonstrated that ZIF-8 was a promising material for the treatment of wastewater containing mixtures of organic and metallic contaminants.
Existing approaches to neural machine translation (NMT) generate the target language sequence token-by-token from left to right. However, this kind of unidirectional decoding framework cannot make ...full use of the target-side future contexts which can be produced in a right-to-left decoding direction, and thus suffers from the issue of unbalanced outputs. In this paper, we introduce a synchronous bidirectional–neural machine translation (SB-NMT) that predicts its outputs using left-to-right and right-to-left decoding simultaneously and interactively, in order to leverage both of the history and future information at the same time. Specifically, we first propose a new algorithm that enables synchronous bidirectional decoding in a single model. Then, we present an interactive decoding model in which left-to-right (right-to-left) generation does not only depend on its previously generated outputs, but also relies on future contexts predicted by right-to-left (left-to-right) decoding. We extensively evaluate the proposed SB-NMT model on large-scale NIST Chinese-English, WMT14 English-German, and WMT18 Russian-English translation tasks. Experimental results demonstrate that our model achieves significant improvements over the strong Transformer model by 3.92, 1.49, and 1.04 BLEU points, respectively, and obtains the state-of-the-art per- formance on Chinese-English and English- German translation tasks.
The dimensional tolerance of flexible, thin-walled aerospace parts can be violated by the excessive static deflections during milling. This paper proposes a method to predict the dimensional surface ...form errors caused by deflections of both flexible workpiece and slender end-mill in five-axis flank milling of thin-walled parts. The end-mill is modeled as a cantilevered beam. The stiffness of the thin-walled part varies as the metal is removed and the tool-part contact location changes. The time varying stiffness of the thin-walled part is predicted by an efficient structural stiffness modification method that only needs the FE model of the initial workpiece and avoids re-meshing the part at each cutter location. The cutting forces are distributed over both the cutting tool and the part in the engagement zone, and the effect of deflections on the immersion is calculated. The effect of radial runout of the tool is considered in chip thickness, hence in the cutting force prediction. Finally, the cutter and the workpiece deflections are considered to predict the surface errors left on the finished part. The proposed method has been proven in five-axis blade milling experiments.
•Dimensional form errors are predicted in five-axis flank milling of thin-walled parts.•Varying static stiffness of the flexible part is efficiently updated without re-meshing as the material is removed.•Effect of the combined tool and flexible part deflections on the cutter-workpiece engagement is considered.•The chip thickness is analytically calculated along the tool axis considering the five-axis process kinematics.•The proposed surface error prediction model is experimentally validated in five-axis flank milling of a sample blade.
NiOx hole transporting layer has been extensively studied in optoelectronic devices. In this paper, the low temperature, solution–combustion‐based method is employed to prepare the NiOx hole ...transporting layer. The resulting NiOx thin films show better quality and preferable energy alignment with perovskite thin film compared to high temperature sol–gel‐processed NiOx. With this, high‐performance perovskite solar cells are fabricated successfully with power conversion efficiency exceeding 20% using a modified two‐step prepared MA1−yFAyPbI3−xClx perovskite. This efficiency value is among the highest values for NiOx‐based devices. Various characterizations and analyses provide evidence of better film quality, enhanced charge transport and extraction, and suppressed charge recombination. Meanwhile, the device exhibits much better device stability compared to sol–gel‐processed NiOx and poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate)‐based devices.
High‐performance perovskite solar cells with a power conversion efficiency exceeding 20% have been achieved based on low temperature, solution–combustion‐processed nickel oxide hole transporting layer and modified two‐step prepared MA1−yFAyPbI3−xClx perovskite. Moreover, the unencapsulated device exhibits superior stability in ambient air conditions.
As one single cell cannot meet power and driving range requirement in an electric vehicle, the battery packs with hundreds of single cells connected in parallel and series should be constructed. The ...most significant difference between a single cell and a battery pack is cell variation. Not only does cell variation affect pack energy density and power density, but also it causes early degradation of battery and potential safety issues. The cell variation effects on battery packs are studied, which are of great significant to battery pack screening and management scheme. In this study, the description for the consistency characteristics of battery packs was first proposed and a pack model with 96 cells connected in series was established. A set of parameters are introduced to study the cell variation and their impacts on battery packs are analyzed through the battery pack capacity loss simulation and experiments. Meanwhile, the capacity loss composition of the battery pack is obtained and verified by the temperature variation experiment. The results from this research can demonstrate that the temperature, self-discharge rate and coulombic efficiency are the major affecting parameters of cell variation and indicate the dissipative cell equalization is sufficient for the battery pack.
•A battery pack model with 96 cells in series is proposed for the consistency of battery pack.•The capacity loss composition of the battery pack is obtained by simulation and experiment.•Use the battery pack available capacity as the inconsistency physical quantity.•The battery pack screening and management scheme is proposed.
Mesoporous Zn4O(−COO)6-based metal–organic frameworks (MOFs), including UMCM-1, MOF-205, MUF-7a, and the newly synthesized MOFs, termed ST-1, ST-2, ST-3, and ST-4 (ST = ShanghaiTech University), ...have been systematically investigated for ultrahigh capacity methane storage. Exceptionally, ST-2 was found to have the highest deliverable capacity of 289 cm3 STP/cm3 (567 mg/g) at 298 K and 5–200 bar, which surpasses all previously reported records held by porous materials. We illustrate that the fine-tuned mesoporosity is critical in further improving the deliverable capacities at ultrahigh pressure.
In sequence to sequence generation tasks (e.g. machine translation and abstractive summarization), inference is generally performed in a left-to-right manner to produce the result token by token. The ...neural approaches, such as LSTM and self-attention networks, are now able to make full use of all the predicted history hypotheses from left side during inference, but cannot meanwhile access any future (right side) information and usually generate unbalanced outputs (e.g. left parts are much more accurate than right ones in Chinese-English translation). In this work, we propose a synchronous bidirectional inference model to generate outputs using both left-to-right and right-to-left decoding simultaneously and interactively. First, we introduce a novel beam search algorithm that facilitates synchronous bidirectional decoding. Then, we present the core approach which enables left-to-right and right-to-left decoding to interact with each other, so as to utilize both the history and future predictions simultaneously during inference. We apply the proposed model to both LSTM and self-attention networks. Furthermore, we propose a novel fine-tuning based parameter optimization algorithm in addition to the simple two-pass strategy. The extensive experiments on machine translation and abstractive summarization demonstrate that our synchronous bidirectional inference model can achieve remarkable improvements over the strong baselines.
Transfer RNAs (tRNAs) harbor the most diverse posttranscriptional modifications. Among such modifications, those in the anticodon loop, either on nucleosides or base groups, compose over half of the ...identified posttranscriptional modifications. The derivatives of modified nucleotides and the crosstalk of different chemical modifications further add to the structural and functional complexity of tRNAs. These modifications play critical roles in maintaining anticodon loop conformation, wobble base pairing, efficient aminoacylation, and translation speed and fidelity as well as mediating various responses to different stress conditions. Posttranscriptional modifications of tRNA are catalyzed mainly by enzymes and/or cofactors encoded by nuclear genes, whose mutations are firmly connected with diverse human diseases involving genetic nervous system disorders and/or the onset of multisystem failure. In this review, we summarize recent studies about the mechanisms of tRNA modifications occurring at tRNA anticodon loops. In addition, the pathogenesis of related disease-causing mutations at these genes is briefly described.
In flank milling of thin-walled parts, the profile tolerance would usually be violated by the excessive static deformations. This paper presents a comprehensive method to compensate deformation ...errors in five-axis flank milling from the aspect of tool path optimization. Firstly, the machined surface is constructed by imprinting the predicted tool/workpiece deformations on the cutter envelope surface. Secondly, the signed distances from the sample points on the design surface to the machined surface are calculated for the machining error evaluation. Their differential increments that characterize the variation of surface errors with respect to the adjustment of tool path are then derived. On this basis, the mathematical model and algorithm for minimizing the deformation-induced surface errors are developed through slightly optimizing the shape parameters of the tool path surface. Finally, five-axis blade milling experiments are conducted to validate the effectiveness of the proposed method. The results demonstrate that the surface errors mainly caused by machining deformations in flank milling of flexible blades can be largely reduced by using the developed algorithm.
•The deformations in flank milling of blades are compensated via tool path optimization.•The machined surface is modeled by imprinting deformations on cutter envelope surface.•Machining errors are minimized by optimizing the shape parameters of tool path surface.•The tool path optimization is formulated as a MILP problem.•The proposed compensation method is experimentally validated via blade machining.
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