The law of momentum conservation rules out many desired processes in optical microresonators. We report broadband momentum transformations of light in asymmetric whispering gallery microresonators. ...Assisted by chaotic motions, broadband light can travel between optical modes with different angular momenta within a few picoseconds. Efficient coupling from visible to near-infrared bands is demonstrated between a nanowaveguide and whispering gallery modes with quality factors exceeding 10 million. The broadband momentum transformation enhances the device conversion efficiency of the third-harmonic generation by greater than three orders of magnitude over the conventional evanescent-wave coupling. The observed broadband and fast momentum transformation could promote applications such as multicolor lasers, broadband memories, and multiwavelength optical networks.
Lithium metal is the only anode material that can enable the Li−O2 battery to realize its high theoretical energy density (≈3500 Wh kg−1). However, the inherent uncontrolled dendrite growth and ...serious corrosion limitations of lithium metal anodes make it experience fast degradation and impede the practical application of Li−O2 batteries. Herein, a multifunctional complementary LiF/F‐doped carbon gradient protection layer on a lithium metal anode by one‐step in situ reaction of molten Li with poly(tetrafluoroethylene) (PTFE) is developed. The abundant strong polar C‐F bonds in the upper carbon can not only act as Li+ capture site to pre‐uniform Li+ flux but also regulate the electron configuration of LiF to make Li+ quasi‐spontaneously diffuse from carbon to LiF surface, avoiding the strong Li+‐adhesion‐induced Li aggregation. For LiF, it can behave as fast Li+ conductor and homogenize the nucleation sites on lithium, as well as ensure firm connection with lithium. As a result, this well‐designed protection layer endows the Li metal anode with dendrite‐free plating/stripping and anticorrosion behavior both in ether‐based and carbonate ester‐based electrolytes. Even applied protected Li anodes in Li−O2 batteries, its superiority can still be maintained, making the cell achieve stable cycling performance (180 cycles).
A gradient LiF/F‐doped carbon protection layer with synergistic functions of homogenizing Li+ flux, fast Li+ diffusion ability, and low Li+ diffusion barrier is prepared by a one‐step in situ reaction to solve the challenges relating to unstable lithium anode in Li–O2 batteries, and, as a result, significantly boost the cycling stability of the Li–O2 batteries.
Large‐scale application of renewable energy and rapid development of electric vehicles have brought unprecedented demand for advanced energy‐storage/conversion technologies and equipment. ...Rechargeable zinc (Zn)–air batteries represent one of the most promising candidates because of their high energy density, safety, environmental friendliness, and low cost. The air electrode plays a key role in managing the many complex physical and chemical processes occurring on it to achieve high performance of Zn–air batteries. Herein, recent advances of air electrodes from bifunctional catalysts to architectures are summarized, and their advantages and disadvantages are discussed to underline the importance of progress in the evolution of bifunctional air electrodes. Finally, some challenges and the direction of future research are provided for the optimized design of bifunctional air electrodes to achieve high performance of rechargeable Zn–air batteries.
The air electrode plays a key role in managing a lot of complex physical and chemical processes occurring on it to achieve high performance of rechargeable Zn–air batteries. This original review briefly summarizes some recent advances of air electrodes from oxygen reduction reaction/oxygen evolution reaction bifunctional electrocatalysts to architectures and points out challenges and future research orientation for its optimized design.
Res2Net: A New Multi-Scale Backbone Architecture Gao, Shang-Hua; Cheng, Ming-Ming; Zhao, Kai ...
IEEE transactions on pattern analysis and machine intelligence,
2021-Feb.-1, 2021-Feb, 2021-2-1, 20210201, Volume:
43, Issue:
2
Journal Article
Peer reviewed
Open access
Representing features at multiple scales is of great importance for numerous vision tasks. Recent advances in backbone convolutional neural networks (CNNs) continually demonstrate stronger ...multi-scale representation ability, leading to consistent performance gains on a wide range of applications. However, most existing methods represent the multi-scale features in a layer-wise manner. In this paper, we propose a novel building block for CNNs, namely Res2Net, by constructing hierarchical residual-like connections within one single residual block. The Res2Net represents multi-scale features at a granular level and increases the range of receptive fields for each network layer. The proposed Res2Net block can be plugged into the state-of-the-art backbone CNN models, e.g., ResNet, ResNeXt, and DLA. We evaluate the Res2Net block on all these models and demonstrate consistent performance gains over baseline models on widely-used datasets, e.g., CIFAR-100 and ImageNet. Further ablation studies and experimental results on representative computer vision tasks, i.e., object detection, class activation mapping, and salient object detection, further verify the superiority of the Res2Net over the state-of-the-art baseline methods. The source code and trained models are available on https://mmcheng.net/res2net/.
Color mutation is a common, easily identifiable phenomenon in higher plants. Color mutations usually affect the photosynthetic efficiency of plants, resulting in poor growth and economic losses. ...Therefore, leaf color mutants have been unwittingly eliminated in recent years. Recently, however, with the development of society, the application of leaf color mutants has become increasingly widespread. Leaf color mutants are ideal materials for studying pigment metabolism, chloroplast development and differentiation, photosynthesis and other pathways that could also provide important information for improving varietal selection. In this review, we summarize the research on leaf color mutants, such as the functions and mechanisms of leaf color mutant-related genes, which affect chlorophyll synthesis, chlorophyll degradation, chloroplast development and anthocyanin metabolism. We also summarize two common methods for mapping and cloning related leaf color mutation genes using Map-based cloning and RNA-seq, and we discuss the existing problems and propose future research directions for leaf color mutants, which provide a reference for the study and application of leaf color mutants in the future.
Oxygen evolution: A 3D nickel foam/porous carbon/anodized nickel electrode was designed for the oxygen evolution reaction (see picture). The conductive porous carbon membrane, which is derived from a ...zeolite imidazolate framework, plays a key role as an interlayer to both protect the inner instable Ni foam and support the outermost oxygen‐evolving Ni catalyst layer.
Conspectus It is a permanent issue for modern society to develop high-energy-density, low-cost, and safe batteries to promote technological innovation and revolutionize the human lifestyle. However, ...the current popular Li-ion batteries are approaching their ceiling in energy density, and thus other battery systems with more power need to be proposed and studied to guide this revolution. Lithium–air batteries are among the candidates for next-generation batteries because of their high energy density (3500 Wh/kg). The past 20 years have witnessed rapid developments of lithium–air batteries in electrochemistry and material engineering with scientists’ collaboration from all over the world. Despite these advances, the investigation on Li–air batteries is still in its infancy, and many bottleneck problems, including fundamental and application difficulties, are waiting to be resolved. For the electrolyte, it is prone to be attacked by intermediates (LiO2, O2 –, 1O2, O2 2–) and decomposed at high voltage, accompanying side reactions that will induce cathode passivation. For the lithium anode, it can be corroded severely by H2O and the side products, thus protection methods are urgently needed. As an integrated system, the realization of high-performance Li–air batteries requires the three components to be optimized simultaneously. In this Account, we are going to summarize our progress for optimizing Li–air batteries in the past decade, including air-electrochemistry and anode optimization. Air-electrochemistry involves the interactions among electrolytes, cathodes, and air, which is a complex issue to understand. The search for stable electrolytes is first introduced because at the early age of its development, the use of incompatible Li-ion battery electrolytes leads to some misunderstandings and troubles in the advances of Li–air batteries. After finding suitable electrolytes for Li–air batteries, the fundamental research in the reaction mechanism starts to boom, and the performance has achieved great improvement. Then, air electrode engineering is introduced to give a general design principle. Examples of carbon-based cathodes and all-metal cathodes are discussed. In addition, to understand the influence of air components on Li–air batteries, the electro-activity of N2 has been tested and the role of CO2 in Li–O2/CO2 has been refreshed. Following this, the strategies for anode optimization, including constructing artificial films, introducing hydrophobic polymer electrolytes, adding electrolyte additives, and designing alloy anodes, have been discussed. Finally, we advocate researchers in this field to conduct cell level optimizations and consider their application scenarios to promote the commercialization of Li–air batteries in the near future.
Heterogeneous catalysts of inexpensive and reusable transition-metal are attractive alternatives to homogeneous catalysts; the relatively low activity of transition-metal nanoparticles has become the ...main hurdle for their practical applications. Here, the de novo design of a Mott–Schottky-type heterogeneous catalyst is reported to boost the activity of a transition-metal nanocatalyst through electron transfer at the metal/nitrogen-doped carbon interface. The Mott–Schottky catalyst of nitrogen-rich carbon-coated cobalt nanoparticles (Co@NC) was prepared through direct polycondensation of simple organic molecules and inorganic metal salts in the presence of g-C3N4 powder. The Co@NC with controllable nitrogen content and thus tunable Fermi energy and catalytic activity exhibited a high turnover frequency (TOF) value (8.12 mol methyl benzoate mol–1 Co h–1) for the direct, base-free, aerobic oxidation of benzyl alcohols to methyl benzoate; this TOF is 30-fold higher than those of the state-of-the-art transition-metal-based nanocatalysts reported in the literature. The presented efficient Mott–Schottky catalyst can trigger the synthesis of a series of alkyl esters and even diesters in high yields.
Bunge is a plant used in traditional Tibetan medicine, with reported anti-inflammatory and antioxidants effects and alleviation of myocardial ischemia reperfusion injury (MIRI). However, the ...underlying mechanism against MIRI and the phytochemical composition of
are vague. One fraction named OFF1 with anti-MIRI activity was obtained from
, and the chemical constituents were identified by ultra-high-performance liquid chromatography coupled with tandem mass spectrometry (UHPLC-MS). The potential targets and signaling pathways involved in the action of
against MIRI were predicted by network pharmacology analysis, and its molecular mechanism on MIRI was determined by in vitro assays. The results revealed that flavonoids are the dominant constituents of OFF1. A total of 92 flavonoids reported in
targeted 213 potential MIRI-associated factors, including tumor necrosis factor (TNF), prostaglandin-endoperoxide synthase 2 (PTGS2), and the NF-κB signaling pathway. The in vitro assay on H9c2 cardiomyocytes subjected to hypoxia/reoxygenation injury confirmed that the flavonoids in OFF1 reduced myocardial marker levels, apoptotic rate, and the inflammatory response triggered by oxidative stress. Moreover, OFF1 attenuated MIRI by downregulating the ROS-mediated JNK/p38MAPK/NF-κB pathway. Collectively, these findings provide novel insights into the molecular mechanism of
in alleviating MIRI, being a potential therapeutic candidate.
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