Showing papers by "Lei Wang published in 2021"

Cationic intermediates assisted self-assembly two-dimensional Ti3C2T /rGO hybrid nanoflakes for advanced lithium-ion capacitors

Abstract: Two-dimensional (2D) material MXenes have been intensively concerned in energy-storage field due to these unique properties of metallic-like conductivity, good hydrophilicity and high volumetric capacity. However, the self-restocking of ultra-thin 2D materials seriously hinders these performances, which significantly inhibits the full exploitation of MXenes in the field of energy storage. To solve this issue, a strategy to prepare delaminated Ti3C2Tx (MXene) nanoflakes/reduced graphene oxide (rGO) composites is proposed using the electrostatic self-assembly between positively charged Ti3C2Tx with tetrabutylammonium ion (TBA+) modification and negatively charged graphene. The nanoflakes of Ti3C2Tx/rGO are well dispersed and arranged in a face-to-face structure to effectively alleviate the self-restacking and provide more electroactive sites for accessible of electrolyte ions. The prepared delaminated Ti3C2Tx/rGO anode shows a high reversible capacity up to 1394 mAh g−1 at a current density of 50 mA g−1. Moreover, a lithium-ion capacitor (LIC) was assembled with delaminated Ti3C2Tx/rGO anode and activated carbon (AC) cathode which can exhibit a specific capacity of 70.7 F g−1 at a current density of 0.1 A g−1 and deliver an ultrahigh energy density of 114 Wh kg−1 at a relatively high power density of 3125 W kg−1. These good electrochemical performances demonstrate the potential of delaminated Ti3C2Tx/rGO as an anode material for lithium-ion capacitors.

2,5-Bis(hydroxymethyl)furan: A new alternative to HMF for simultaneously electrocatalytic production of FDCA and H2 over CoOOH/Ni electrodes

Abstract: Simultaneous production of value-added 2,5-furandicarboxylic acid (FDCA) and H2 from the integrated 5-hydroxymethylfurfural (HMF) oxidation and hydrogen evolution reaction by electrocatalysis has drawn tremendous attention due to the significantly improved energy efficiency. However, HMF is not thermally and chemically stable enough to often cause heavy degradation, impeding its storage and industrialization. In this work, a more stable furan molecule, 2,5-bis(hydroxymethyl)furan (BHMF), was employed as the reaction substrate into the coupling system for the first time. By means of facile electrodeposition and subsequent oxidative activation, the standing CoOOH nanosheet electrocatalyst was fabricated to realize a complete BHMF conversion with 90.2 % FDCA yield and 100 % current efficiency for H2 evolution. The reaction path and apparent activation energies were therefore discussed. Scalable properties and electrochemical durability of CoOOH were evaluated in a continuous flow reactor to harvest gram-level solid FDCA, highlighting the prospect of green coupling electrolysis for industrial application.

A third dose of inactivated vaccine augments the potency, breadth, and duration of anamnestic responses against SARS-CoV-2

Abstract: Emergence of variants of concern (VOC) with altered antigenic structures and waning humoral immunity to SARS-CoV-2 are harbingers of a long pandemic. Administration of a third dose of an inactivated virus vaccine can boost the immune response. Here, we have dissected the immunogenic profiles of antibodies from 3-dose vaccinees, 2-dose vaccinees and convalescents. Better neutralization breadth to VOCs, expeditious recall and long-lasting humoral response bolster 3-dose vaccinees in warding off COVID-19. Analysis of 171 complex structures of SARS-CoV-2 neutralizing antibodies identified structure-activity correlates, revealing ultrapotent, VOCs-resistant and broad-spectrum antigenic patches. Construction of immunogenic and mutational heat maps revealed a direct relationship between “hot” immunogenic sites and areas with high mutation frequencies. Ongoing antibody somatic mutation, memory B cell clonal turnover and antibody composition changes in B cell repertoire driven by prolonged and repeated antigen stimulation confer development of monoclonal antibodies with enhanced neutralizing potency and breadth. Our findings rationalize the use of 3-dose immunization regimens for inactivated vaccines. One sentence summary A third booster dose of inactivated vaccine produces a highly sifted humoral immune response via a sustained evolution of antibodies capable of effectively neutralizing SARS-CoV-2 variants of concern.

A proof of concept for neutralizing antibody-guided vaccine design against SARS-CoV-2.

Abstract: Mutations and transient conformational movements of the receptor binding domain (RBD) that make neutralizing epitopes momentarily unavailable present immune escape routes for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). To mitigate viral escape, we developed a cocktail of neutralizing antibodies (NAbs) targeting epitopes located on different domains of spike (S) protein. Screening of a library of monoclonal antibodies generated from peripheral blood mononuclear cells of COVID-19 convalescent patients yielded potent NAbs, targeting the N-terminal domain (NTD) and RBD domain of S, effective at nM concentrations. Remarkably, a combination of RBD-targeting NAbs and NTD-binding NAbs, FC05, enhanced the neutralization potency in cell-based assays and an animal model. Results of competitive surface plasmon resonance assays and cryo-electron microscopy (cryo-EM) structures of antigen-binding fragments bound to S unveil determinants of immunogenicity. Combinations of immunogens, identified in the NTD and RBD of S, when immunized in rabbits and macaques, elicited potent protective immune responses against SARS-CoV-2. More importantly, two immunizations of this combination of NTD and RBD immunogens provided complete protection in macaques against a SARS-CoV-2 challenge, without observable antibody-dependent enhancement of infection. These results provide a proof of concept for neutralization-based immunogen design targeting SARS-CoV-2 NTD and RBD.

Double lock of a potent human therapeutic monoclonal antibody against SARS-CoV-2.

Abstract: Receptor recognition and subsequent membrane fusion are essential for the establishment of successful infection by SARS-CoV-2. Halting these steps can cure COVID-19. Here we have identified and characterized a potent human monoclonal antibody, HB27, that blocks SARS-CoV-2 attachment to its cellular receptor at sub-nM concentrations. Remarkably, HB27 can also prevent SARS-CoV-2 membrane fusion. Consequently, a single dose of HB27 conferred effective protection against SARS-CoV-2 in two established mouse models. Rhesus macaques showed no obvious adverse events when administrated with 10 times the effective dose of HB27. Cryo-EM studies on complex of SARS-CoV-2 trimeric S with HB27 Fab reveal that three Fab fragments work synergistically to occlude SARS-CoV-2 from binding to the ACE2 receptor. Binding of the antibody also restrains any further conformational changes of the receptor binding domain, possibly interfering with progression from the prefusion to the postfusion stage. These results suggest that HB27 is a promising candidate for immuno-therapies against COVID-19.

A phase I clinical trial of human embryonic stem cell-derived retinal pigment epithelial cells for early-stage Stargardt macular degeneration: 5-years' follow-up.

Abstract: Objectives To evaluate the long-term biosafety and efficacy of transplantation of human embryonic stem cells-derived retinal pigment epithelial (hESC-RPE) cells in early-stage of Stargardt macular degeneration (STGD1). Materials and methods Seven patients participated in this prospective clinical study, where they underwent a single subretinal transplantation of 1 × 105 hESC-RPE cells in one eye, whereas the fellow eye served as control. These patients were reassessed for a 60-month follow-up through systemic and ophthalmic examinations. Results None of the patients experienced adverse reactions systemically or locally, except for two who had transiently high intraocular pressure post-operation. Functional assessments demonstrated that all of the seven operated eyes had transiently increased or stable visual function 1-4 months after transplantation. At the last follow-up visit, two of the seven eyes showed visual function loss than the baseline; however, one of them showed a stable visual acuity when compared with the change of fellow eye. Obvious small high reflective foci in the RPE layer were displayed after the transplantation, and maintained until the last visit. Interestingly, three categories of patients who were classified based on autofluorescence, exhibited distinctive patterns of morphological and functional change. Conclusions Subretinal transplantation of hESC-RPE in early-stage STGD1 is safe and tolerated in the long term. Further investigation is needed for choosing proper subjects according to the multi-model image and function assessments.

Effect of horizontal resolution on the simulation of tropical cyclones in the Chinese Academy of Sciences FGOALS-f3 climate system model

Abstract: . The effects of horizontal resolution on the simulation of tropical cyclones were studied using the Chinese Academy of Sciences Flexible Global Ocean–Atmosphere–Land System Finite-Volume version 3 (FGOALS-f3) climate system model from the High-Resolution Model Intercomparison Project (HighResMIP) for the Coupled Model Intercomparison Project phase 6 (CMIP6). Both the low-resolution (about 100 km resolution) FGOALS-f3 model (FGOALS-f3-L) and the high-resolution (about 25 km resolution) FGOALS-f3 (FGOALS-f3-H) models were used to achieve the standard Tier 1 experiment required by HighResMIP. FGOALS-f3-L and FGOALS-f3-H have the same model parameterizations with the exactly the same parameters. The only differences between the two models are the horizontal resolution and the time step. The performance of FGOALS-f3-H and FGOALS-f3-L in simulating tropical cyclones was evaluated using observations. FGOALS-f3-H (25 km resolution) simulated more realistic distributions of the formation, movement and intensity of the climatology of tropical cyclones than FGOALS-f3-L at 100 km resolution. Although the number of tropical cyclones increased by about 50 % at the higher resolution and better matched the observed values in the peak month, both FGOALS-f3-L and FGOALS-f3-H appear to replicate the timing of the seasonal cycle of tropical cyclones. The simulated average and interannual variabilities of the number of tropical cyclones and the accumulated cyclone energy were both significantly improved from FGOALS-f3-L to FGOALS-f3-H over most of the ocean basins. The characteristics of tropical cyclones (e.g., the average lifetime, the wind–pressure relationship and the horizontal structure) were more realistic in the simulation using the high-resolution model. The possible physical linkage between the performance of the tropical cyclone simulation and the horizontal resolution were revealed by further analyses. The improvement in the response between the El Nino–Southern Oscillation and the number of tropical cyclones and the accumulated cyclone energy in FGOALS-f3 contributed to the realistic simulation of tropical cyclones. The genesis potential index and the vorticity, relative humidity, maximum potential intensity and the wind shear terms were used to diagnose the effects of resolution. We discuss the current insufficiencies and future directions of improvement for the simulation of tropical cyclones and the potential applications of the FGOALS-f3-H model in the subseasonal to seasonal prediction of tropical cyclones.

A new hydrodynamic interpretation of liquid metal droplet motion induced by an electrocapillary phenomenon.

Abstract: The Marangoni effect, induced by the surface tension gradient resulting from the gradient of temperature, concentration, or electric potential gradient along a surface, is commonly utilized to manipulate a droplet. It is also the reason for unique behaviors of liquid metal such as moving, breathing, and large-scale deformation under an electric field, which have aroused tremendous interest in academics. However, liquid metal droplets are usually treated as solid marbles, which neglect their fluidic features and can hardly explain some unusual phenomena, such as a droplet under a stationary electric field that moves in the opposite direction in different solutions. To better clarify these discrepancies, this study reveals that the movement of liquid metal is directly driven by viscous forces of solution rather than interfacial tension. This mechanism was determined by analyzing flow characteristics on a liquid metal surface. Additionally, experiments with liquid metal free falling in solution, liquid metal droplet movement experiments on substrates with different roughness, and liquid metal droplet movement experiments under high current density were additionally conducted to verify the theoretical interpretation. This research is instrumental for a greater understanding of the movement of liquid metal under an electric field and lays the foundation for the applications of liquid metal droplets in pumping, fluid mixing, and many other microfluidic fields.

Matrix SegNet: A Practical Deep Learning Framework for Landslide Mapping from Images of Different Areas with Different Spatial Resolutions

Abstract: Practical landslide inventory maps covering large-scale areas are essential in emergency response and geohazard analysis. Recently proposed techniques in landslide detection generally focused on landslides in pure vegetation backgrounds and image radiometric correction. There are still challenges in regard to robust methods that automatically detect landslides from images with multiple platforms and without radiometric correction. It is a significant issue in practical application. In order to detect landslides from images over different large-scale areas with different spatial resolutions, this paper proposes a two-branch Matrix SegNet to semantically segment input images by change detection. The Matrix SegNet learns landslide features in multiple scales and aspect ratios. The pre- and post- event images are captured directly from Google Earth, without radiometric correction. To evaluate the proposed framework, we conducted landslide detection in four study areas with two different spatial resolutions. Moreover, two other widely used frameworks: U-Net and SegNet, were adapted to detect landslides via the same data by change detection. The experiments show that our model improves the performance largely in terms of recall, precision, F1-score, and IOU. It is a good starting point to develop a practical, deep learning landslide detection framework for large scale application, using images from different areas, with different spatial resolutions.

Large‐scale generation of megakaryocytes from human embryonic stem cells using transgene‐free and stepwise defined suspension culture conditions

Abstract: Objectives Ex vivo engineered production of megakaryocytes (MKs) and platelets (PLTs) from human pluripotent stem cells is an alternative approach to solve shortage of donor-donated PLTs in clinics and to provide induced PLTs for transfusion. However, low production yields are observed and the generation of clinically applicable MKs and PLTs from human pluripotent stem cells without genetic modifications still needs to be improved. Materials and methods We defined an optimal, stepwise and completely xeno-free culture protocol for the generation of MKs from human embryonic stem cells (hESCs). To generate MKs from hESCs on a large scale, we improved the monolayer induction manner to define three-dimensional (3D) and sphere-like differentiation systems for MKs by using a special polystyrene CellSTACK culture chamber. Results The 3D manufacturing system could efficiently generate large numbers of MKs from hESCs within 16-18 days of continuous culturing. Each CellSTACK culture chamber could collect on an average 3.4 × 108 CD41+ MKs after a three-stage orderly induction process. MKs obtained from hESCs via 3D induction showed significant secretion of IL-8, thrombospondin-1 and MMP9. The induced cells derived from hESCs in our culture system were shown to have the characteristics of MKs as well as the function to form proPLTs and release PLTs. Furthermore, we generated clinically applicable MKs from clinical-grade hESC lines and confirmed the biosafety of these cells. Conclusions We developed a simple, stepwise, 3D and completely xeno-free/feeder-free/transgene-free induction system for the generation of MKs from hESCs. hESC-derived MKs were shown to have typical MK characteristics and PLT formation ability. This study further enhances the clinical applications of MKs or PLTs derived from pluripotent stem cells.

Modulation of winter precipitation associated with tropical cyclone of the western North Pacific by the stratospheric Quasi-Biennial oscillation

Abstract: Tropical cyclone precipitation (TCP) has increasing impacts on many coastal regions under global warming. Causes of TCP variation have been principally explored in the troposphere. This study identifies the significant modulation of the stratosphere Quasi-Biennial oscillation (QBO) on the winter TCP in the coastal regions of the western North Pacific (WNP). In the westerly QBO winter, the zonal wind vertical shear anomalies in the stratosphere strengthen (weaken) convective activities around the East China Sea (the Philippines) and cause middle-level easterly (westerly) anomalies of the middle (low) latitudes in the troposphere, leading to more (less) TC activities around the East China Sea (the Philippines). Consequently, a TCP dipole pattern can be observed. The TCP increases in East China, Korean peninsula, Japan and Russian Far East, but decreases in Indo–China Peninsula, South China and the Philippines. These results not only improve the knowledge of QBO-TCP relationship but also provide a potential indicator for the seasonal prediction of the TCP in the coastal regions of the WNP due to the high predictability of the QBO.

A Strategy of Parallel Seed-Based Image Segmentation Algorithms for Handling Massive Image Tiles over the Spark Platform

Abstract: The volume of remote sensing images continues to grow as image sources become more diversified and with increasing spatial and spectral resolution. The handling of such large-volume datasets, which exceed available CPU memory, in a timely and efficient manner is becoming a challenge for single machines. The distributed cluster provides an effective solution with strong calculation power. There has been an increasing number of big data technologies that have been adopted to deal with large images using mature parallel technology. However, since most commercial big data platforms are not specifically developed for the remote sensing field, two main issues exist in processing large images with big data platforms using a distributed cluster. On the one hand, the quantities and categories of official algorithms used to process remote sensing images in big data platforms are limited compared to large amounts of sequential algorithms. On the other hand, the sequential algorithms employed directly to process large images in parallel over a distributed cluster may lead to incomplete objects in the tile edges and the generation of large communication volumes at the shuffle stage. It is, therefore, necessary to explore the distributed strategy and adapt the sequential algorithms over the distributed cluster. In this research, we employed two seed-based image segmentation algorithms to construct a distributed strategy based on the Spark platform. The proposed strategy focuses on modifying the incomplete objects by processing border areas and reducing the communication volume to a reasonable size by limiting the auxiliary bands and the buffer size to a small range during the shuffle stage. We calculated the F-measure and execution time to evaluate the accuracy and execution efficiency. The statistical data reveal that both segmentation algorithms maintained high accuracy, as achieved in the reference image segmented in the sequential way. Moreover, generally the strategy took less execution time compared to significantly larger auxiliary bands and buffer sizes. The proposed strategy can modify incomplete objects, with execution time being twice as fast as the strategies that do not employ communication volume reduction in the distributed cluster.

Bacterial Communities Associated With Four Blooming Scyphozoan Jellyfish: Potential Species-Specific Consequences for Marine Organisms and Humans Health

Abstract: Cnidarians have large surface areas available for colonization by microbial organisms, which serve a multitude of functions in the environment. However, relatively few studies have been conducted on scyphozoan-associated microbial communities. Blooms of scyphozoan species are common worldwide and can have numerous deleterious consequences on the marine ecosystem. Four scyphozoan species, Aurelia coerulea, Cyanea nozakii, Nemopilema nomurai, and Rhopilema esculentum, form large blooms in Chinese seas. In this study, we analyzed the bacterial communities associated with these four jellyfish based on 16S rRNA gene sequencing. We found that the bacterial communities associated with each scyphozoan species were significantly different from each other and from those of the surrounding seawater. There were no significant differences between the bacterial communities associated with different body parts of the four scyphozoan jellyfish. Core bacteria in various compartments of the four scyphozoan taxa comprised 57 OTUs (Operational Taxonomic Units), dominated by genera Mycoplasma, Vibrio, Ralstonia, Tenacibaculum, Shingomonas and Phyllobacterium. FAPROTAX function prediction revealed that jellyfish could influence microbially mediated biogeochemical cycles, compound degradation and transmit pathogens in regions where they proliferate. Finally, Six genera of potentially pathogenic bacteria associated with the scyphozoans were detected: Vibrio, Mycoplasma, Ralstonia, Tenacibaculum, Nautella, and Acinetobacter. Our study suggests that blooms of these four common scyphozoans may cause jellyfish species-specific impacts on element cycling in marine ecosystems, and serve as vectors of pathogenic bacteria to threaten other marine organisms and human health.

Photochemical synthesis of 3-hydroxyphenanthro[9,10-c]furan-1(3H)-ones from α-keto acids and alkynes

Abstract: A novel and efficient method for the synthesis of 3-hydroxyphenanthro[9,10-c]furan-1(3H)-ones has been achieved from readily available α-keto acids and alkynes through photo-initiated transformation, providing a range of structurally diverse products in good to excellent yields under mild conditions. Mechanistic studies reveal that this reaction undergoes photo-induced radical addition/cyclization and hydrogen evolution cascade processes.

Unidirectional water transport on a two-dimensional hydrophilic channel with anisotropic superhydrophobic barriers

Abstract: Many creatures have a unique anisotropic structure and special wettability on their skins, presenting intriguing water transporting properties. Inspired by the biosphere, a two-dimensional titanium dioxide-based hydrophilic channel possessing anisotropic superhydrophobic barriers was synthesized. This channel demonstrates unidirectional water transporting properties. When water is injected into the channel, fluid tends to spread in a specific direction. An asymmetric spreading resistance is generated by the different interaction modes between the liquid and superhydrophobic barriers. The superhydrophobic barriers are designed as two main styles: line and curve. As for line barriers, the included angle between barrier and horizontal is the key parameter for the unidirectional water transporting ability whereas, for curve barriers, the radius is an important variable. The best design scheme for unidirectional water transporting properties could be found by varying the parameters of these two types of barriers in the channel. Overall, this study is expected to have a significant implication in the water transporting field.