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An asymmetric total synthesis of cage-like indole alkaloid arborisidine is presented. The new synthetic strategy features a catalytic parallel kinetic resolution based on ambident nucleophilicity (C3/N) of indole to set the absolute configurations of the two quaternary chiral centers, and a 5-exo-trig radical cyclization to form the bridged nitrogen-containing five-membered ring.

At present, enzyme-mediated signal amplification strategies have been widely applied in photoelectrochemical (PEC) biosensing systems, while the introduction of natural enzymes onto the surface of photoelectrodes inevitably obstructs the electron transfer due to their insulating properties as proteins, leading to severe damage to photocurrent. In this work, the PdPt bimetallic nanozymes with the efficient peroxidase-like activity were used as alternatives to natural enzymes and amplified PEC biosensing signals via their efficient enzymatic reaction and remarkable enhancement in photocurrent. As a result, photoactive CdS nanorods modified with PdPt bimetallic nanozymes showed a boosted PEC performance compared with the pristine CdS nanorods due to the localized surface plasmon resonance effect and Schottky junction. On the basis of the as-prepared CdS/PdPt photoelectrode, a sensitive split-type glucose oxidase-mediated PEC immunoassay for carcinoembryonic antigen (CEA) detection was successfully constructed. Along with the sandwich immunocomplexing, the subsequently produced hydrogen peroxide (H2O2) can oxidize 4-chloro-1-naphthol into insoluble precipitates to inhibit photocurrent and simultaneously trigger the bio-etching of CdS to further restrain photocurrent signals due to the excellent peroxidase-mimicking activity of PdPt nanozymes. Owing to the synergistic signal amplification fulfilled by PdPt nanozymes, an ultrasensitive immunoassay of CEA was realized with a wider linear range from 1 to 5000 pg/mL and a low detection limit of 0.21 pg/mL, opening a new avenue for building ultrasensitive PEC biosensors with nanozymes.

Enzyme cascade reactions in biological systems can effectively improve the catalytic performances owing to their high local concentration, efficient mass transfer and reduced intermediate decomposition. However, the disadvantages of high cost, low stability, and easy inactivation limit their practical applications in harsh environments. Nanozymes as the substitutes for enzymes not only have enzyme-like activities but also possess high stability, tunable catalytic property, and high pH/temperature tolerance, which have been intensively investigated for the establishment of biomimetic catalysis systems. In this review, we first summarized the recent development of the construction and advantage of the nanozyme-involved cascade reaction system. Then, the biomedical applications of the nanozyme-enhanced biomimetic cascade catalytic systems, including biosensing, therapies and antioxidation, were highlighted in detail. Finally, current challenges and future perspectives for nanozyme-activated cascade reactions are discussed and outlooked.

Diboron(4) compounds serve as useful reagents for borylation, diboration, and reduction in organic synthesis. A variety of pyridine derivatives have been found capable of activating diboron(4) compounds, and different reaction mechanisms have been identified. 4,4'-Bipyridine was found to activate diboron(4) to form N,N'-diboryl-4,4'-bipyridinylidene in 2015, and very recently, it has been found that this transformation is crucial in the 4,4'-bipyridine-catalyzed reduction of nitroarenes by bis(neopentylglycolato)diboron (B2nep2), which features the formation of arylnitrene intermediates. However, the mechanism of N,N'-diboryl-4,4'-bipyridinylidene formation, as well as its role in the transformation of nitroarene to arylnitrene, remains unknown. In this work, we investigated the possible pathways of this intriguing transformation and discovered several important intermediates through density functional theory (DFT) calculations. An N-boryl 4,4'-bipyridyl radical was found to be a crucial intermediate in both the formation of N,N'-diboryl-4,4'-bipyridinylidene and the reduction of nitroarene. A type of single-step reaction with three stages, including a dissociation and two migration steps, was identified in the generation of nitrosobenzene and its reduction. Arylnitrene formation was found to occur on a triplet potential energy surface, and an intersystem crossing was found to be important for achieving a reasonable activation energy barrier for nitrene formation. We anticipate our work to provide deeper insights into the nature of this reaction that could facilitate further rational design of pyridine- and bipyridine-based catalysts.

Zigzag molecular belts have captured the imagination of scientists for over a half century because of their aesthetically appealing structures and tantalizing properties. One of the formidable challenges in synthesis is to circumvent the energy accumulated in the construction of strained structures. Reported herein is our theoretical study to quantify the molecular strain energies. A general exponential function equation E strain = a·n·e −n/b was obtained to estimate strain energies of both conjugated and partially hydrogenated hydrocarbon belts and their heteroatom-embedded analogs. The deformation of aromatic rings from planarity was revealed to contribute dominantly to the high strain energies. The method enabled the convenient quantification of the energetics of aromatization processes from partially hydrogenated double-stranded macrocycles, and facilitated the design and optimization of practical routes to synthesize the long-awaited zigzag molecular belts.

Design of highly active carbon nanozymes and further establishment of ultrasensitive biosensors remain a challenge. Herein, hierarchically porous carbon nanozymes with sulfur (S)/nitrogen (N) codoping (SNC) were developed. Compared with N-doped carbon (NC) nanozymes, SNC nanozymes have a smaller Michaelis-Menten constant and higher specific activities, demonstrating that the S-doping in SNC nanozymes could not only enhance their affinity toward substrates but also improve their catalytic performance. These results may be caused by the synergistic effect of heteroatoms (S and N). Because of the good enzyme-like activity, the proposed SNC nanozymes were exploited to the colorimetric detection of the total antioxidant capacity (TAC) using ascorbic acid as a typical model with a limit of detection of 0.08 mM. Because of its high sensitivity and selectivity and encouraging performance, the detection method presented practical feasibility for the TAC assay in commercial beverages. This work paves a way to design the highly active carbon nanozymes and expand their applications in the construction of high-performance biosensors.

Despite the breakthroughs of transition-metal catalysts in enzyme mimicking, fundamental investigation on the design of efficient nanozymes at the atomic scale is still required for boosting their ...

The traditional luminol-H2 O2 electrochemiluminescence (ECL) sensing platform suffers from self-decomposition of H2 O2 at room temperature, hampering its application for quantitative analysis. In this work, for the first time we employ iron single-atom catalysts (Fe-N-C SACs) as an advanced co-reactant accelerator to directly reduce the dissolved oxygen (O2 ) to reactive oxygen species (ROS). Owing to the unique electronic structure and catalytic activity of Fe-N-C SACs, large amounts of ROS are efficiently produced, which then react with the luminol anion radical and significantly amplify the luminol ECL emission. Under the optimum conditions, a Fe-N-C SACs-luminol ECL sensor for antioxidant capacity measurement was developed with a good linear range from 0.8 μm to 1.0 mm of Trolox.

High dielectric loss is one of the current obstacles to the application of dielectric materials. In this paper, we synthesized a new dielectric material, i.e., (Yb + Ta)-co-doped TiO2 dielectric material. The (Yb0.5Ta0.5)xTi1−xO2 ceramics were synthesized by the solid-state reaction method. It has been found that (Yb0.5Ta0.5)xTi1−xO2 ceramics had a dense ceramic microstructure, and (Yb0.5Ta0.5)xTi1−xO2 ceramics exhibited the rutile TiO2 structure. All (Yb0.5Ta0.5)xTi1−xO2 ceramics exhibited low dielectric loss ( 105). The optimal dielectric properties are obtained at a doping level of x = 0.05 with dielectric constant of 5.1 × 105 and dielectric loss of 0.037. Further study of the thermal stability of the dielectric properties was performed in the temperature range from − 50 to 250 ℃, which indicates that the ceramic sample with x = 0.05 co-dopant concentration maintains good dielectric properties in the temperature range from − 50 to 100 ℃. XPS shows that high dielectric properties can be explained by the electron-pinned defect-dipole mechanism.

Luminol-dissolved O2 electrochemiluminescence (ECL)-sensing platforms have been widely developed for sensitive and reliable detection, while their actual ECL mechanisms are still in controversy due to the involved multiple reactive oxygen species (ROS). Different from the structural complexity of nanomaterials, well-defined single-atom catalysts (SACs) as coreaction accelerators will provide great prospects for investigating the ECL mechanism at the atomic level. Herein, two carbon-supported nickel SACs with the active centers of Ni-N4 (Ni-N4/C) and Ni-N2O2 (Ni-N2O2/C) were synthesized as efficient coreaction accelerators to enhance the ECL signals of a luminol-dissolved O2 system. By modulating the surrounding environment of the center metal atoms, their corresponding oxygen reduction behaviors can be well controlled to selectively produce intermediate ROS, giving a great chance to study the following ECL process. According to the experimental and calculated results, the superoxide radical (O2•-) acts as the main radical for the ECL reaction and the Ni-N4/C catalyst with the four-electron pathway to activate dissolved O2 is preferential to enhance ECL emission.

Nanomaterials with enzyme-like activities, coined nanozymes, have been researched widely as they offer unparalleled advantages in terms of low cost, superior activity, and high stability. The complex structure and composition of nanozymes has led to extensive investigation of their catalytic sites at an atomic scale, and to an in-depth understanding of the biocatalysis occurring. Single-atom catalysts (SACs), characterized by atomically dispersed active sites, have provided opportunities for mimicking metalloprotease and for bridging the gap between natural enzymes and nanozymes. In this Minireview, we illustrate the unique properties of nanozymes and we discuss recent advances in the synthesis, characterization, and applications of SACs. Subsequently, we outline the impressive progress made in single-atom nanozymes and we discuss their applications in sensing, degradation of organic pollutants, and in therapeutic roles. Finally, we present the major challenges and opportunities remaining for a successful marriage of nanozymes and SACs.

Afforestation of degraded land significantly influences soil organic carbon (SOC) and total nitrogen (STN) sequestration. The interaction effects of plantation age and climate gradient on SOC and STN changes following afforestation are not well understood. In this study, five sites were selected along a precipitation gradient (410-600 mm yr(-1)) in the Loess Plateau. The SOC and STN stocks at a depth of 0-200 cm were measured in cropland and black locust (Robinia pseudoacacia L.) forests with different plantation ages, that is, young forest ( 25 years). The SOC and STN stocks in the 0- to 200-cm profiles of young forest, middle-aged forest, and cropland increased significantly with mean annual precipitation (p < .05), whereas the increasing trend of the SOC stocks of old forest was not significant, indicating an age-dependent change in the SOC and STN stocks across the precipitation gradient. The SOC stock change ( increment SOC) following afforestation increased with mean annual precipitation in young forest, but it had a decreasing trend in middle-aged and old forests. The STN stock changes ( increment STN) in the three forests were negative at most sites, and they all decreased along the precipitation gradient. There were significant positive correlations between increment SOC and increment STN (p < .01), and 1-g STN stock accumulation was accompanied by 8.40-, 6.10-, and 10.48-g SOC accumulation for young forest, middle-aged forest, and old forest, respectively. The different patterns of SOC and STN stock changes should be incorporated into soil C and N modelling and estimation.

Pd-catalyzed reactions of azides with CO to access an isocynate intermediate have been developed extensively in recent years. However, the catalytic carbonylation of sensitive acyl azides has not been reported. Herein, we report a simple Pd-catalyzed carbonylation reaction of acyl azides with broad substrate scope, high efficiency, and simple operation under mild conditions, which provides facile access to acyl ureas. In addition, a mechanistic study was carried out by both experiment and DFT calculation. Control experiments and kinetic study revealed that the real active palladium species were Pd(0). The result of kinetic study suggested that palladium catalyst, azide, and CO were all involved in the turnover-limiting step except for amine. Further DFT study suggested that an unprecedented five-membered palladacycle intermediate was the key intermediate in the carbonylation reaction.

Tin diselenide (SnSe2 ), as an anode material, has outstanding potential for use in advanced lithium-ion batteries. However, like other tin-based anodes, SnSe2 suffers from poor cycle life and low rate capability due to large volume expansion during the repeated Li+ insertion/de-insertion process. This work reports an effective and easy strategy to combine SnSe2 and carbon nanotubes (CNTs) to form a SnSe2 /CNTs hybrid nanostructure. The synthesized SnSe2 has a regular hexagonal shape with a typical 2D nanostructure and the carbon nanotubes combine well with the SnSe2 nanosheets. The hybrid nanostructure can significantly reduce the serious damage to electrodes that occurs during electrochemical cycling processes. Remarkably, the SnSe2 /CNTs electrode exhibits a high reversible specific capacity of 457.6 mA h g-1 at 0.1 C and 210.3 mA h g-1 after 100 cycles. At a cycling rate of 0.5 C, the SnSe2 /CNTs electrode can still achieve a high value of 176.5 mA h g-1 , whereas a value of 45.8 mA h g-1 is achieved for the pure SnSe2 electrode. The enhanced electrochemical performance of the SnSe2 /CNTs electrode demonstrates its great potential for use in lithium-ion batteries. Thus, this work reports a facile approach to the synthesis of SnSe2 /CNTs as a promising anode material for lithium-ion batteries.

Tin oxide (SnO2) is an attractive anode in lithium ion batteries (LIBs), but its applications have been significantly hampered by the huge volume change during the electrochemical cycling. In this work we demonstrate a rational design of crystalline SnO2 @ amorphous TiO2 core-shell nanostructures, where the crystalline SnO2 core was synthesized by a hydrothermal method and the amorphous TiO2 shell was deposited by atomic layer deposition. The SnO2@TiO2 nanostructures deliver excellent performances during the electrochemical process, having a high reversible capacity of 1259 mAh g−1 at cycling rate of 80 mA g−1, which is still up to 703 mAh g−1 after 50 cycles. The acceptable rate capacity is also revealed with 412 mAh g−1 at 400 mA g−1. The coulombic efficiency is stable at around 100% regardless of cycling rates and numbers. The electrochemical performances of the SnO2@TiO2 batteries are better than those of the SnO2 ones without TiO2 coating. In the SnO2@TiO2 nanostructures, the amorphous TiO2 shell layer can experience an isotropic stress, having the ability to evidently reduce the volume change, lattice stress and so the risk of fracture during the cycling process, which is responsible for their outstanding behaviors. The strategy provided in our study is expected to be a precious guideline for designing an ideal electrode for energy storage devices.

To develop a robust method for the detection of disease biomarkers is always the pursued goal in the field of biomedical research. Multi-modal immunoassay strategy will bring tremendous potential for the purpose. In this study, a kind of robust nanozyme-linked immunosorbent assay has been presented, which can achieve ratiometric fluorescent and colorimetric dual-modal sensing performance. Here, o-phenylenediamine (OPD) as an organic substrate can be oxidized and converted into 2,3-diaminophenazine (oxOPD) by the robust nanozyme of nanoceria with peroxidase-like properties in the present of H2O2. An exogenous fluorescence signal source of graphitic carbon nitride quantum dots (g-C3N4 QDs) is introduced, and the corresponding fluorescence can be efficiently quenched by oxOPD owing to the hydrogen bonding and π-π stacking interactions, yielding a fluorescence spectral line with dual emission peaks while only irradiated by an excitation wavelength. Meanwhile, a visible color change was derived from the oxOPD formation, which can be recorded by colorimetric method. As a proof-of-study demonstration, the detection of human cardiac troponin I was done. This method affords robust, reliable and sensitive detection performance due to the combination of the merits of ratiometric fluorescent assay and colorimetric assay. It is no doubt that our proposed approach will bring remarkable inspirations for biomedical researchers.

Improvement in the sensitivity and portability of enzyme-linked immunosorbent assay (ELISA) still faced huge challenges recently. Inspired by the nanoprecipitation process for the carrier-free nanodrug in drug delivery systems, we developed an self-assembly strategy to prepare a kind of all-inclusive allochroic 3,3',5,5'-tetramethylbenzidine (TMB) nanoparticles for developing improved ELISA (named TLISA). During the self-assembly of TMB molecules, the antibody as signal recognition units and bovine serum albumin as the stabilizing agents could be accommodated simultaneously through hydrogen-bonding and van der Waals interactions to form all-inclusive signal tags, which can avoid the complex cross-linking procedures. Due to the ultrahigh loading capacity (817 mg/g) of TMB molecules, the sensitivity of TLISA toward inflammatory biomarkers interleukin-6 was 11.82 times higher than that of conventional ELISA, which paves an avenue to develop an ultrasensitive colorimetric immunoassay.

Transpiration (Tr) is influenced by environmental factors, vegetation properties, and anthropogenic management. The effect of environmental factors on Tr are taking place from two aspects: evaporative demand (i.e., potential evapotranspiration, PET) and water supply (i.e., soil water). Soil water is one of the most important factors that limit plant transpiration in terrestrial ecosystems, especially in semi-arid and arid regions. Investigating the relationship between Tr and soil water is crucial for an improved understanding of plant survival strategies and predicting hydrological cycles and water resources under climate change. Although the relationships of soil water and Tr have been widely studied, the independent effects of soil water on Tr are difficult to separate because soil water and PET occur concurrently under natural conditions. This study carried out field observations of sapflow density, meteorological factors and soil water in a black locust (Robinia pseudoacacia) plantation in the semi-arid Loess Plateau of China. This information was used to develop a model integrating the daily PET and relative extractable soil water (REW, an index that represents the available soil water): Tr = (0.27 × PET − 0.02 × PET2 − 0.32) × (1 − e−5.70×REW). The model fitted the measured data well (R2 = 0.65 and RMSE = 0.06 mm day−1). We found that the daily Tr increased as the REW increased under varying PET levels. Additionally, the independent effects of soil water on Tr were analysed using the factorial experiment analysis method. The REW was manipulated and PET varied naturally during the measurements to separate the independent effects of the REW on Tr. The results showed that Tr increased with the REW during the study period at a rate of 0.53 mm day−1 per 0.1 REW when the REW

Protein-inorganic nanoflowers have been extensively used for sensing and biosensing applications by virtue of the signal enhancement of protein component---enzyme. Can the inorganic component of protein-inorganic nanoflowers be employed to amplify signal transducing for enzyme-free detection? In this work, a new kind of BSA-antibodies-copper phosphate hybrid nanoflowers (BSA-Ab2-Cu3(PO4)2) has been prepared by one-pot biomimetic mineralization process as signal enhancer for enzyme-free electrochemical immunoassay. C-reactive protein (CRP) has been chosen as a model biomarker. To the best of our knowledge, it is the first trial using the inorganic component---phosphate ions of BSA-Ab2-Cu3(PO4)2 for transducing electrochemical readout, which features the following advantages: (1) the three-dimensional hierarchical porous nanoflower morphology with a high specific surface area could load more antibodies, and BSA for blocking non-specific sites, greatly increasing the sensitivity of the fabricated immunosensors, (2) the Cu3(PO4)2 hybrid nanoflowers can supply a huge amount of phosphate anions to react with molybdate yielding molybdophosphate precipitates and generating redox currents for more robust enzyme-free electrochemical signal readout. The fabricated immunosensor has exhibited good detection performance with a linear range of 5 pg/mL–1 ng/mL and a limit of detection of 1.26 pg/mL. Moreover, our method has presented good feasibility for clinical sample analysis.

Soil moisture is crucial for the sustainable development of artificial forests in arid and semi-arid regions, and an accurate quantification of the influence of artificial vegetation on soil moisture has profound implications in the assessment of the ecological effects of artificial vegetation in arid and semi-arid regions. This study analyzed the variations in the soil moisture content (SMC) following the conversion of croplands into forests with Robinia pseudoacacia (RP) at different vegetation ages (5, 20, and 40 years) in the Loess Plateau and attempted to regard abandoned cropland (AL) with different restoration years (5, 20, and 40 years) as control samples to accurately quantify soil moisture depletion in the absence of RP at different ages. The results showed that the SMC of the 0–500-cm soil profile, which the zone that supports the whole growth processes for RP in the study area, was in a state of depletion, with an average water depletion of 40.75% and a maximum water depletion of 68.39%. RP mainly consumes shallow soil moisture (0–100 cm) during the early stage of afforestation, and with increases in forest age, RP mainly consumes soil moisture at increasingly deeper layers (100–500 cm). The largest soil water consumption in the presence of RP was observed at 150–180 cm. As RP forests grow, the water demand increases and shifts from the upper to deeper soil layers, and when the deeper soil water consumption reaches a certain level, the water consumption shifts upward. This phenomenon results in different degrees of drying between surface and deep soil layers over time. Abandoned cropland has a decreased influence on the SMC of the whole profile and appears to benefit water conservation at deeper soil layers in the mid-recovery period. Therefore, the vegetation succession in control plots should be considered to enhance the accuracy of the findings in future soil moisture research and afforestation practice. To maintain the sustainability of afforestation, succession should progress from less to more advanced plants (grasses-shrubs-forests), and the cultivation of shallow-rooted herbaceous plants (the main herb species in abandoned croplands) and natural restoration should be prioritized. Moreover, the ecological importance of natural restoration should be considered, the degree of blind artificial transformation should be reduced, and the strong adaptability and evolutionary ability of tree species to survive should receive proper attention.

Mobile edge computing (MEC) has shown tremendous potential as a means for computationally intensive mobile applications by partially or entirely offloading computations to a nearby server to minimize the energy consumption of user equipment (UE). However, the task of selecting an optimal set of components to offload considering the amount of data transfer as well as the latency in communication is a complex problem. In this paper, we propose a novel energy-efficient deep learning based offloading scheme (EEDOS) to train a deep learning based smart decision-making algorithm that selects an optimal set of application components based on remaining energy of UEs, energy consumption by application components, network conditions, computational load, amount of data transfer, and delays in communication. We formulate the cost function involving all aforementioned factors, obtain the cost for all possible combinations of component offloading policies, select the optimal policies over an exhaustive dataset, and train a deep learning network as an alternative for the extensive computations involved. Simulation results show that our proposed model is promising in terms of accuracy and energy consumption of UEs.

Single modal enzyme-linked immunosorbent assay (ELISA) covering colorimetric, fluorescence, and chemiluminescence techniques has been widely reported in recent years, whereas the combination of multiple signal channels in one immunosensing platform still faces huge challenges. Multimodal imaging will provide more comprehensive and precise diagnostic information by the combination of two or more imaging modalities. Inspired by this concept, we established a new kind of multimodal enzyme-linked immunosorbent assay (M-ELISA) based on the unique properties of Au@Pt nanodendrites. As a proof-of-concept demonstration, cardiac troponin I (cTnI) has been chosen as a model biomarker. Owing to the excellent photothermal effect and intrinsic peroxidase-like activity of Au@Pt nanodendrites, the concentration of cTnI can be quantificationally reflected by photothermal immunoassay, colorimetric immunoassay and ratiometric fluorescence immunoassay simultaneously. This developed M-ELISA demonstrated the good consistency with the chemiluminescence immunoassay method in clinical diagnosis for real serum samples.

Ternary PtRuCu aerogels are facilely synthesized by one-step in situ reduction. The formation of ternary PtRuCu aerogels can be completed within 2 hours owing to the accelerated gelation kinetics. Because of the unique porous architectures and synergistic effect, the optimized Pt4Ru1Cu5 aerogels exhibited good electrochemical performance for methanol oxidation reaction.

Single-atom catalysts (SACs) have emerged as one of the most competitive catalysts toward a variety of important electrochemical reactions, thanks to their maximum atom economy, unique electronic and geometric structures. However, the role of SACs supports on the catalytic performance does not receive enough research attentions. Here, we report an efficient route for synthesis of single atom Zn loading on the N-doped carbon nano-onions (ZnN/CNO). ZnN/CNO catalysts show an excellent high selectivity for CO2 electro-reduction to CO with a Faradaic efficiency of CO (FECO) up to 97% at −0.47 V (vs. reversible hydrogen electrode, RHE) and remarkable durability without activity decay. To our knowledge, ZnN/CNO is the best activity for the Zn based catalysts up to now, and superior to single atom Zn loading on the two-dimensional planar and porous structure of graphene substrate, although the graphene with larger surface area. The exact role of such carbon nano-onions (CNO) support is studied systematically by coupling characterizations and electrochemistry with density functional theory (DFT) calculations, which have attributed such good performance to the increased curvature. Such increased curvature modifies the surface charge, which then changes the adsorption energies of key intermediates, and improves the selectivity for CO generation accordingly.

The palladium-catalyzed intramolecular dearomative Heck reaction of 2,3-disubstituted indoles serves as an access to spiro-indoline products. Herein, we report an efficient construction of indoline/indolenine core stuctures via a dearomative Heck reaction of simple 2,3-disubstituted indoles with all-carbon tethers and the subsequent aza-semipinacol rearrangement. The Heck reaction features a high C2-selectivity, and the stereospecific aryl/alkyl migration selectivity has been investigated by DFT calculations. Using this method, we accomplished the formal total synthesis of

During space flight, astronauts are exposed to various influences of extreme environments and susceptible to develop depression-like behavior. Thus, this study aims to explore the molecular biological mechanism of the cause of depression-like behavior and reveal the effect of Baoyuan Jieyu Formula (BYJYF) on ameliorating depression-like behavior. Here, rats exposed to simulated long-term spaceflight composite stress (LSCS) reduced the sucrose preference rate (P0.01), and the time of forced swimming immobility and the number of climbing times were also reduced (P0.01, P0.001). Moreover, the number of neurons in the CA3 region of the hippocampus decreased ( P0.01, P0.05, P0.001), the staining became weak, and the Nissl body decreased. Antibody chip detected a total of 854 protein molecules in the hippocampus, of which 51 and 37 proteins were significantly different in the LSCS group and LSCS+BYJYF group, respectively, focusing on signaling pathways such as MAPK and neurotrophin. Western blot was used to verify the related proteins of these two pathways. Conclusively, simulated LSCS can induce depression-like behavior and neuronal damage. BYJYF can reduce neuronal apoptosis, and promote neuron survival by regulating the MAPK and the neurotrophin signaling pathway to protect neurons and combat LSCS.

Part 4: Automated Machine Learning; International audience; Solving partitioning problems in random environments is a classic and challenging task, and has numerous applications. The existing Object Migration Automaton (OMA) and its proposed enhancements, which include the Pursuit and Transitivity phenomena, can solve problems with equi-sized partitions. Currently, these solutions also include one where the partition sizes possess a Greatest Common Divisor (GCD). In this paper, we propose an OMA-based solution that can solve problems with both equally and non-equally-sized groups, without restrictions on their sizes. More specifically, our proposed approach, referred to as the Partition Size Required OMA (PSR-OMA), can solve general partitioning problems, with the only additional requirement being that the unconstrained partitions’ sizes are known a priori. The scheme is a fundamental contribution in the field of partitioning algorithms, and the numerical results presented demonstrate that PSR-OMA can solve both equi-partitioning and non-equi-partitioning problems efficiently, and is the only known solution that resolves this problem.

In this paper, the Mach Zehnder interferometer is utilized to generate a collinear dual optical path with 800-nm center wavelength, 1 kHz repetition rate, 120-fs pulse duration and an energy ratio of 1:1 to scan 6H-SiC crystal at a scanning speed of 500 μm/s, resulting in laser-induced periodic surface structure (LIPSS). From the perspective of instantaneous electron density level, variation of the period of low spatial frequency LIPSS (LSFL) with interpulse delay time and polarization angle is studied. The scanning electron microscope (SEM) characterization of the line-scanned ablation zone combined with fast Fourier transformation (FFT) spectrum analysis shows that the period of LSFL decreases with the increase of delay time, and remains stable when the delay exceeds 240 fs. Meanwhile, the period of LSFL increases with the increase of polarization angle under the same delay time, showing an anisotropy that dependent on the polarization angle. The variation trend of the maximum electron density level with delay time calculated by electron rate equation is roughly consistent with the periodic variation trend. Interaction between incident light and transient metal-like SiC surface is simulated based on finite-difference time-domain method (FDTD). The simulation results show that the surface of the sample has a periodic light field enhancement structure controlled by the transient electron density, which explains the phenomenon that the period decreases with increasing delay time. It is further confirmed that the formation of LSFL is due to the interference of incident light and surface plasmon, and the period of LSFL can be controlled by adjusting the electron density level by delay time. The periodic polarization dependence of LSFL may be related to the relative orientation change of the laser pulse front tilt (PFT) and laser polarization.

A recent trend to mitigate large-scale distributed denial-of-service (DDoS) attacks is in-network filtering, where victims can deploy traffic-filtering rules in networks other than their own. However, given multiple constraints, such as the number of rules a victim can afford to deploy, the set of rules that DDoS defense entities allow a victim to deploy, and the amount of collateral damage to limit, the selection of rules has a large impact on the efficacy of an in-network filtering solution. In this paper, we introduce a new, offer-based operational model for in-network DDoS defense and formulate the NP-hard rule selection problem for this model. We then design an algorithm that overcomes the fundamental limitations of the classical ACO framework and transform it with several key changes to make it applicable to the domain of in-network DDoS defense. Finally, we use a real-world-based Internet routing topology and two real-world DDoS traces, along with one synthetic trace that follows the attack distribution of the recent Mirai DDoS attack, to evaluate the efficacy and runtime of our algorithm against four other rule selection algorithms, and show our algorithm is near-optimal.

Multiple enzymes-induced biological cascade catalysis guides efficient and selective substrate transformations in vivo. The biomimetic cascade systems, as ingenious strategies for signal transduction and amplification, have a wide range of applications in biosensing. However, the fragile nature of enzymes greatly limits their wide applications. In this regard, metal-organic frameworks (MOFs) with porous structures, unique nano/microenvironments, and good biocompatibility have been skillfully used as carriers to immobilize enzymes for shielding them against hash surroundings and improving the catalytic efficiency. For another, nanomaterials with enzyme-like properties and brilliant stabilities (nanozymes), have been widely applied to ameliorate the low stability of the enzymes. Inheriting the abovementioned merits of MOFs, the performances of MOFs-immboilized nanozymes could be significantly enhanced. Furthermore, in addition to carriers, some MOFs can also serve as nanozymes, expanding their applications in cascade systems. Herein, recent advances in the fabrication of efficient MOFs-involving enzymes/nanozymes cascade systems and biosensing applications are highlighted. Integrating diversified signal output modes, including colorimetry, electrochemistry, fluorescence, chemiluminescence, and surface-enhanced Raman scattering, sensitive detection of various targets (including biological molecules, environmental pollutants, enzyme activities, and so on) are realized. Finally, challenges and opportunities about further constructions and applications of MOFs-involving cascade reaction systems are briefly put forward.

Generally, the photoactive materials are always tightly fixed on the photoelectrode of photoelectrochemical (PEC) sensors to produce excellent photocurrent response, while obvious and constant background currents will appear as well and then hamper the ultrasensitive sensing of target molecules. In this work, ultrasensitive detection of organophosphorus pesticides (OPs) is successfully fulfilled by using dissociable photoelectrode based on CdS nanocrystal-functionalized MnO2 nanosheets. With the assistance of acetylcholinesterase (AChE), acetylthiocholine (ATCh) is hydrolyzed into thiocholine (TCh) which can effectively etch the ultrathin MnO2 nanosheets, resulting in the dissociation of MnO2–CdS from the photoelectrode. Benefiting from the dissociation of photoactive materials, the background photocurrent induced by semiconductor itself dramatically decreases. OPs, as a specific inhibitor for AChE activity, can prevent the generation of TCh and the dissociation of MnO2 nanosheets, building a relationship between OPs concentration and photocurrent. Under the optimized test conditions, the PEC sensor for the detection of paraoxon displays a wide linear range from 0.05 to 10 ng/mL with a detection limit of 0.017 ng/mL. Furthermore, the PEC sensor shows good sensitivity, stability, and promising application in practical samples.

In water-limited areas, revegetation of abandoned croplands may lead to extensive land-use changes and considerable variations on soil carbon (C) and nitrogen (N). However, the impact of land-use patterns (i.e., the spatial combinations of different land-use types) on soil C and N variations following revegetation remains unclear. In this study, we measured soil organic carbon (SOC), total carbon (TC), and total nitrogen (TN) stocks to a depth of 200 cm in grassland (GL), shrubland (SL), young forestland (YF), and mature forestland (MF) under four land-use patterns in a catchment located in the Chinese Loess Plateau. The highest SOC, TC and TN stocks occurred in MF and the lowest was found in GL. Compared to every single land-use type, soil C and N stocks significantly increased under different land-use patterns. The highest SOC stock (6.51 kg m−2) was found in the GL-YF-SL pattern, and the highest TC stock (47.25 kg m−2) and TN stock (0.70 kg m−2) were both observed in the MF-YF pattern. SOC stocks showed significantly positive correlations with TC and TN stocks under different land-use patterns (p

Single-atom nanozymes (SAzymes), as novel nanozymes with atomically dispersed active sites, are of great importance in the development of nanozymes for their high catalytic activities, the maximum utilization efficiency of metal atoms, and the simple model of active sites. Herein, the peroxidase-like SAzymes with high-concentration Cu sites on carbon nanosheets (Cu-N-C) were synthesized through a salt-template strategy. With the densely distributed active Cu atoms (∼5.1 wt %), the Cu-N-C SAzymes exhibit remarkable activity to mimic natural peroxidase. Integrating Cu-N-C SAzymes with natural acetylcholinesterase and choline oxidase, three-enzyme-based cascade reaction system was constructed for the colorimetric detection of acetylcholine and organophosphorus pesticides. This work not only provides a strategy to synthesize SAzymes with abundant active sites but also gives some new insights for robust nanozyme biosensing systems.

Carbon materials have been widely used as nanozymes in bioapplications, attributing to their intrinsic enzyme-like activities. Nitrogen (N)-doping has been explored as a promising way to improve the activity of carbon material-based nanozymes (CMNs). However, hindered by the intricate N dopants, the real active site of N-doped CMNs (N-CMNs) has been rarely investigated, which subsequently retards the further progress of high-performance N-CMNs. Here, a series of porous N-CMNs with well-controlled N dopants were synthesized, of which the intrinsic peroxidase (POD)like activity has a positive correlation with the pyridinic N content. Density functional theory calculations also reveal that pyridinic N boosts the intrinsic POD-like activity of N-CMNs. Pyridinic-N dopant can effectively promote the first H 2 O desorption process in comparison with the graphitic and pyrrolic N, which is the key endothermic reaction during the catalytic process. Then, utilizing the optimized nanozymes with high pyridinic N content (N P -CMNs) and superior POD-like activity, a facile total antioxidant capacity (TAC) assay was developed, holding great promise in the quality assessment of medicine tablets and antioxidant food for healthcare and healthy diet.

TianQin is a proposed space gravitational-wave detection mission using circular high Earth orbits. The geocentric concept has raised questions about the disturbing effect of the nearby gravity field of the Earth-Moon system on the highly-sensitive intersatellite ranging measurements. Here we examine the issue through high precision numerical orbit simulation with detailed gravity-field models. By evaluating range accelerations between distant free-falling test masses, the study shows that the majority of the Earth-Moon's gravity disturbances are not in TianQin's detection frequency band above $10^{-4}$ Hz, and hence present no showstoppers to the mission., Comment: 7 pages, 4 figures, to match the accepted version by Phys. Rev. D

A wide range of applications in marine ecology extensively uses underwater cameras. Still, to efficiently process the vast amount of data generated, we need to develop tools that can automatically detect and recognize species captured on film. Classifying fish species from videos and images in natural environments can be challenging because of noise and variation in illumination and the surrounding habitat. In this paper, we propose a two-step deep learning approach for the detection and classification of temperate fishes without pre-filtering. The first step is to detect each single fish in an image, independent of species and sex. For this purpose, we employ the You Only Look Once (YOLO) object detection technique. In the second step, we adopt a Convolutional Neural Network (CNN) with the Squeeze-and-Excitation (SE) architecture for classifying each fish in the image without pre-filtering. We apply transfer learning to overcome the limited training samples of temperate fishes and to improve the accuracy of the classification. This is done by training the object detection model with ImageNet and the fish classifier via a public dataset (Fish4Knowledge), whereupon both the object detection and classifier are updated with temperate fishes of interest. The weights obtained from pre-training are applied to post-training as a priori. Our solution achieves the state-of-the-art accuracy of 99.27\% on the pre-training. The percentage values for accuracy on the post-training are good; 83.68\% and 87.74\% with and without image augmentation, respectively, indicating that the solution is viable with a more extensive dataset., Comment: arXiv admin note: substantial text overlap with arXiv:1904.02768

A series of Cu–SSZ-13 catalysts with the same Cu loading were prepared by different methods of incipient wetness impregnation [Cu–SSZ-13 (IWI)], ion exchange [Cu–SSZ-13 (IE)] and hydro-thermal synthesis [Cu–SSZ-13 (HTS)]. Their activity for selective catalytic reduction of nitrogen oxides (NOx) with NH3 was determined. The results show that the Cu–SSZ-13(HTS) catalyst exhibits a better ammonia selective catalytic reduction (NH3-SCR) activity compared with the other two catalysts, over which more than 90% NO conversion is obtained at 215–600 °C under the space velocity of 180,000 h−1. The characterization results reveal that the Cu–SSZ-13(HTS) catalyst possesses more amount of stable Cu2+ in the six-membered ring and high ability for NH3 and NO adsorption, leading to its high NH3-SCR activity, although this catalyst has low surface area. On the other hand, the activity of Cu–SSZ-13(IE) catalyst is almost the same as that of Cu–SSZ-13 (IWI) catalyst at the temperature lower than 400 °C, but the activity of the former is much higher than that of the latter at > 400 °C due to the high activity of Cu–SSZ-13(IWI) catalyst for NH3 oxidation. Three kinds of Cu–SSZ-13 with the same amount of Cu loading were prepared by different methods. The catalyst prepared by hydrothermal synthesis displayed the better NH3-SCR activity due to more isolated Cu2+ in six-membered ring of the CHA structure.

Evapotranspiration (ET) partitioning is crucial for understanding the impacts of ecophysiological and physical processes on water balance and plant water use strategy. Black locust (Robinia pseudoacacia) is one of the most widely planted species in the semi-arid Loess Plateau, China. The effects of its water use on stand soil water storage (S) and its water use strategy raised much concern due to soil water depletion and its growth degradation. In this study, meteorological factors, soil water content (SWC), ET components and net primary productivity (NPP) were observed in a black locust plantation during a drier (2015) and a wetter (2016) growing season. ET was 160.0 mm in 2015 and 255.0 mm in 2016, which accounted for 104.1% and 68.6% of the precipitation (P), respectively. Soil evaporation (E) accounted for the majority of ET (45.4–69.4% at monthly scale), while transpiration (T) was the smallest component of ET (9.7–28.8%). These results showed that it is E that consumed more soil water rather than T in the black locust plantation. E should be carefully considered and improved in predicting or modeling water budgets (e.g. soil water, ET partitioning and runoff) in the reforested catchments in this area. Additionally, the monthly T/ET decreased with P increasing, suggesting that black locusts could transpire water more effectively to survive under drier conditions with less P. Our study can not only improve the understanding of water budget in the reforested catchment in the semi-arid Loess Plateau but also provide the significant evidences of investigating the plant water use strategy from the point of ET partitioning.

Extreme rainstorm and the subsequent flood increasingly threaten the security of human society and ecological environment with aggravation of global climate change and anthropogenic activity in recent years. Therefore, the research on flood mitigation service (FMS) of ecosystem should be paid more attention to mitigate the risk. In this paper, we assessed FMS in the Upper Reaches of Hanjiang River (URHR), China from 2000 to 2014 using the Soil Conservation Service Curve Number (SCS-CN) model, and further simulated the future FMS under two climate scenarios (in 2020 and 2030). The results reveal that the FMS presented a fluctuating rising trend in the URHR from 2000 to 2014. The FMS in southern URHR was higher than that of northern URHR, and the change rate of FMS in the upstream of URHR (western URHR) was higher than the downstream of URHR (eastern URHR). The future FMS under scenarios of Medium-High Emissions (A2) and Medium-Low Emissions (B2) will decrease consistently. As land use/land cover changes in the URHR are negligible, we concluded that the change in FMS was mainly driven by climate change, such as storm and runoff. Our study highlights that climate scenarios analysis should be incorporated into the assessment of hydrologic-related services to facilitate regional water resources management.

In this paper, we advocate edge caching in cloud radio access networks (C-RAN) to facilitate the ever-increasing mobile multimedia services. In our framework, central offices will cooperatively allocate cloud resources to cache popular contents and satisfy user requests for those contents, so as to minimize the system costs in terms of storage, VM reconfiguration, content access latency, and content migration. However, this joint resource allocation, content placement and request routing, is nontrivial, since it needs to be continuously adjusted to accommodate system dynamics, such as user movement and content slashdot effect, while taking into account the time-correlated adjustment costs for VM reconfiguration and content migration. To this end, we build a comprehensive model to capture the key components of edge caching in C-RAN and formulate a joint optimization problem, aiming at minimizing the system costs over time and meanwhile satisfying the time-varying user requests and respecting various practical constraints (e.g., storage and bandwidth). Then, we propose a novel online approximation algorithm by resorting to the regularization, rounding, and decomposition technique, which can be proved to have a parameterized competitive ratio with a polynomial running time. Extensive trace-driven simulations corroborate the efficiency, flexibility, and lightweight of our proposed online algorithm; for instance, it achieves an empirical competitive ratio around 2 – 4 and gains over 30% improvement compared with many state-of-the-art algorithms in various system settings.

Sc 2 O 3 modified Bi 2 O 3 -ZnO films varistors with different doping ratios were prepared by Sol-gel method. The result indicated that doping of Sc 2 O 3 significantly enhance the nonlinear current-voltage ( I-V) characteristics of Bi 2 O 3 -ZnO films. The highest non-linearity was obtained for 0.4mol% Sc content with the nonlinear coefficient α = 3.7 and 301 μA in leakage current. The grain size of ZnO phase firstly increased with Sc 2 O 3 doping when the content of Sc 2 O 3 is no more than 0.2 mol%. Upon the much more doping of Sc 2 O 3 , the growth of ZnO crystal was inhibited, leading to smaller grain size. The threshold voltage V T was inversely proportional with grain size of ZnO phase. Doping oxides gathered in the grain boundary significant impact on threshold voltage and leakage current.

This study is concerned with the nonlinear dynamic characteristics of a micro-vibration fluid viscous damper used in a satellite. When a control moment gyroscope is working, it produces micro-vibrations, which is a disadvantage for imaging equipment. Taking a single-tube micro-vibration fluid viscous damper as our research subject, a nonlinear dynamic model of the micro-vibration fluid viscous damper under harmonic excitation is proposed. Then, the analytical form of the pressure gradient force is derived. Considering the entrance effect in the orifice, the nonlinear elastic force and nonlinear damping force are analyzed. The results reveal that if the entrance effect is not considered, the elastic force and damping force are linear forces. When the entrance effect is considered, the damper has a nonlinear elastic force and a nonlinear damping force. These nonlinear forces are related to the orifice length, diameter, fluid viscosity, excitation amplitude and frequency. In the low-frequency domain, the differences between the two cases are small, while in the high-frequency domain, they are considerable.

A highly efficient catalyst of a Co a Mn b O x mixed oxide prepared by the co-precipitation method was developed for the selective catalytic reduction (SCR) of NO x with ammonia. With an increase in the Mn content, the catalytic activity of the Co a Mn b O x mixed oxide exhibited a volcano-type tendency, and when Co/Mn molar ratio reached 7:3 (Co 7 Mn 3 O x ), the operation temperature for achieving >80% NO x conversion was 170 °C (116–285 °C window). The formation of spinel structured MnCo 2 O 4 is highly important, and the presence of the spinel structure in Co 7 Mn 3 O x contributes to the increase in active sites and thermal stability and promotes SO 2 and/or H 2 O resistance. In comparison with MnO x or CoO x alone, the Co a Mn b O x catalysts possess improved redox properties and more surface acid sites due to synergistic effects between the Co and Mn species. Among the Co a Mn b O x catalysts with different Co/Mn molar ratios, a higher NH 3 and NO + O 2 adsorption ability was found for the Co 7 Mn 3 O x catalyst, originating from its MnCo 2 O 4.5 phase and higher surface area, which leads to the higher activity of the Co 7 Mn 3 O x catalyst. In situ DRIFTs indicated that bridging nitrate and bidentate nitrate are the intermediate species in the NH 3 -SCR reaction, and the high NO adsorption ability and improved redox properties of the Co 7 Mn 3 O x catalyst are beneficial for the formation of nitrate species on the catalyst surface. Furthermore, NH 3 species adsorbed at Lewis acid sites taken part in SCR reaction, while the reactivity of NH 3 species adsorbed at Bronsted acid was not definitized.

The exploitation of new titanium-based coordination polymers (Ti CPs) with high crystallinity is difficult but highly desirable for their potential applications in photocatalysis. Herein, a cluster-cooperative assemble strategy is developed to synthesize Ti CPs. By utilizing various bifunctional ligands containing carboxylate acids and N-donor groups, we successfully assembled the zero-dimensional (0D) [(Ti3 O)(iPrO)8 ]2+ or [(Ti4 O2 )(iPrO)6 ]6+ clusters into one-dimensional (1D) tube-, ribbon-, or helical chain-shape architectures, two-dimensional (2D) layered structures, and a rare parallel 2D→three-dimensional (3D) polycatenation framework with various copper iodide dopants, including rhombus- or wing-shaped Cu2 I2 and tetrahedron- or ladder-shaped Cu4 I4 . The as-synthesized compounds display strong absorption in the visible region with narrow band gaps ranging from 1.70 to 2.72 eV and exhibit good photocatalytic activities in the degradation of organic pollutants.

Water oxidation is the key step in both natural and artificial photosynthesis to capture solar energy for fuel production. The design of highly efficient and stable molecular catalysts for water oxidation based on nonprecious metals is still a great challenge. In this article, the electrocatalytic oxidation of water by Na[(L4-)CoIII], where L is a substituted tetraamido macrocyclic ligand, was investigated in aqueous solution (pH 7.0). We found that Na[(L4-)CoIII] is a stable and efficient homogeneous catalyst for electrocatalytic water oxidation with 380 mV onset overpotential in 0.1 M phosphate buffer (pH 7.0). Both ligand- and metal-centered redox features are involved in the catalytic cycle. In this cycle, Na[(L4-)CoIII] was first oxidized to [(L2-)CoIIIOH] via a ligand-centered proton-coupled electron transfer process in the presence of water. After further losing an electron and a proton, the resting state, [(L2-)CoIIIOH], was converted to [(L2-)CoIV═O]. Density functional theory (DFT) calculations at the B3LYP-D3(BJ)/6-311++G(2df,2p)//B3LYP/6-31+G(d,p) level of theory confirmed the proposed catalytic cycle. According to both experimental and DFT results, phosphate-assisted water nucleophilic attack to [(L2-)CoIV═O] played a key role in O-O bond formation.

Numerous analytical techniques have been undertaken for the detection of protein biomarkers because of their extensive and significant applications in clinical diagnosis, whereas there are few strategies to develop dual-readout immunosensors to achieve more accurate results. To the best of our knowledge, inspired by smart drug delivery system (DDS), a novel pH-responsive modified enzyme-linked immunosorbent assay (ELISA) was innovatively developed for the first time, realizing dual-modal colorimetric and fluorescent detection of cardiac troponin I (cTnI). Curcumin (CUR) was elaborately selected as a reporter molecule, which played the same role of drugs in DDS based on the following considerations: (1) CUR can be used as a kind of pH indicator by the inherited allochroic effect induced by basic pH value; (2) the fluorescence of CUR can be quenched by certain nanocarriers as the acceptor because of the occurrence of fluorescence resonance energy transfer (FRET), while recovered by the stimuli of basic pH value, which can produce "signal-on" fluorescence detection. Three-dimensional MoS

The dielectric and nonlinear current–voltage properties of CaCu3Ti4−xZr x O12 (x = 0, 0.05, 0.1, 0.15 and 0.2) thin films prepared by the modified sol–gel method and annealed at 750 °C for 1 h were systematically studied. Zr doping resulted in a significant reduction in the mean grain size from 177.4 to 42.9 nm. The dielectric properties of the thin films increased significantly with the increase of Zr content from x = 0 to 0.2, indicating the importance of microstructure in controlling the dielectric properties of CaCu3Ti4−xZr x O12 thin films. A highly frequency-independent giant dielectric permittivity from 102 to 106 Hz was successfully achieved in CaCu3Ti3.8Zr0.2O12 thin film, which possessed a very high dielectric permittivity value of 7591 and a very low tanδ value of 0.023 at 1 kHz. The results indicated that reduction in the mean grain size affected the number of polarized ions per unit volume n0 (to improve e′) and the number of grain boundaries (to reduce tanδ). CaCu3Ti3.75Zr0.15O12 thin film showed the highest nonlinear coefficient (5.8) and lowest leakage current (131 μA). In addition, the relaxation mechanism based on the internal barrier layer capacitance model and the back-to-back dual Schottky barrier model were used to explain the dielectric properties and the nonlinear electrical behaviors of the samples.

Single-electron transfer is an important process in organic chemistry, in which a single-electron reductant (electron donor) acts as a key component. Compared with metal-based electron donors, organic electron donors have some unique advantages, such as tunable reduction ability and mild reaction conditions. The development of novel organic electron donors with good reduction ability together with ease of preparation is in high demand. Based on the pyridine-catalyzed radical borylation reaction developed in our laboratory, we have discovered that, the reaction system consisting of a diboron(4) compound, methoxide and a pyridine derivative could smoothly produce super electron donors in situ. Two boryl–pyridine based species, the major one being a trans-2H,2′H-[2,2′-bipyridine]-1,1′-diide borate complex and the minor one being a pyridine radical anion–borate complex, were observed and carefully characterized. These complexes were found to be organic super electron donors unprecedented in literature, and their formation mechanisms were studied by DFT calculations. The diboron/methoxide/pyridine system enables the preparation of organic super electron donors from easily accessible starting materials under mild conditions, which has the potential to be a general and practical single-electron reducing agent in organic synthesis.

The combination of small organic molecules and a base serves as a unique system for the activation carbon–halogen bonds in haloarenes by single electron transfer (SET). However, most of the molecules employed as promoters only allow for the activation of aryl iodides, and efficient activation of aryl bromides and chlorides under this mode is still rather challenging. Herein, we report the discovery of a structurally simple yet powerful promoter molecule, indoline, which exhibits unusually high activity in promoting the activation of haloarenes by SET. In the presence of t-BuOK and a trace amount of oxygen, indoline promotes the formation of aryl radicals not only from aryl iodides and bromides, but also from unactivated aryl chlorides (e.g., chlorobenzene) under relatively mild conditions. Mechanistic studies reveal the molecular basis for its high activity, for which the aromatization process plays a key role in modulating the electron transfer process.