A novel palladium‐catalyzed three‐component reaction of phenol‐derived biaryls with N‐benzoyloxyamines and norbornadiene (NBD) has been developed for the assembly of highly functionalized ...spiroindenes. This domino process was realized through NBD‐assisted C−H amination and phenol dearomatization by forming one C−N bond and two C−C bonds in a single step. Preliminary studies indicated that asymmetric control of this transformation was feasible with chiral ligands. Moreover, the potential synthetic utility of this methodology was highlighted by a series of further transformations.
Building complexity in one step: The title reaction is realized through norbornadiene‐assisted C−H amination and phenol dearomatization by forming one C−N bond and two C−C bonds in a single step. Asymmetric control of this transformation is feasible by employing chiral ligands, and its synthetic utility was highlighted by a series of further transformations.
Machine learning algorithms are increasingly used in various remote sensing applications due to their ability to identify nonlinear correlations. Ensemble algorithms have been included in many ...practical applications to improve prediction accuracy. We provide an overview of three widely used ensemble techniques: bagging, boosting, and stacking. We first identify the underlying principles of the algorithms and present an analysis of current literature. We summarize some typical applications of ensemble algorithms, which include predicting crop yield, estimating forest structure parameters, mapping natural hazards, and spatial downscaling of climate parameters and land surface temperature. Finally, we suggest future directions for using ensemble algorithms in practical applications.
The development of cancer combination therapies, many of which rely on nanoscale theranostic agents, has received increasing attention in recent years. In this work, polyethylene glycol (PEG) ...modified mesoporous silica (MS) coated single‐walled carbon nanotubes (SWNTs) are fabricated and utilized as a multifunctional platform for imaging guided combination therapy of cancer. A model chemotherapy drug, doxorubicin (DOX), could be loaded into the mesoporous structure of the obtained SWNT@MS‐PEG nano‐carriers with high efficiency. Upon stimulation under near‐infrared (NIR) light, photothermally triggered drug release from DOX loaded SWNT@MS‐PEG is observed inside cells, resulting in a synergistic cancer cell killing effect. As revealed by both photoacoustic (PA) and magnetic resonance (MR) imaging, we further uncover efficient tumor accumulation of SWNT@MS‐PEG/DOX after intravenous injection into mice. In vivo combination therapy using this agent is further demonstrated in a mouse tumor model, achieving a remarkable synergistic anti‐tumor effect superior to that obtained by mono‐therapy. Our work presents a new type of theranostic nano‐platform, which could load therapeutic molecules with high efficiency, be responsive to external NIR stimulation, and at the same time serve as a diagnostic imaging agent.
Mesoporous silica coated single‐wall carbon nanotubes with polyethylene glycol functionalization and anti‐cancer drug loading are developed as a multifunctional theranostic platform. Upon systemic administration of such nano‐agent, combined photothermal and chemotherapy, which is under the guidance of multimodal magnetic resonance and photoacoustic imaging, is conducted on an animal tumor model, achieving a great synergistic therapeutic effect.
The synthesis of crystalline two-dimensional polymers (2DPs) with proper bandgaps and well-defined repeating units presents a great challenge to synthetic chemists. Here we report the first solution ...synthesis of a single-layer/few-layer triazine-based 2DP via trimerization of carbonitrile at the interface of dichloromethane and trifluoromethanesulfonic acid. The processable triazine-based 2DP can be assembled into mechanically strong layered free-standing films with a high specific surface area via filtration. Moreover, the highly crystalline triazine-based 2DP can function as the active semiconducting layer in a field-effect transistor via drop coating and exhibits slightly bipolar behavior with a high on/off ratio of 103 and a remarkable mobility of 0.15 cm2 V–1 s–1.
Mineral dust interacts with radiation and cloud microphysics in East Asia can affect local and regional climate. In this study, we found that the occurrences of dust storms, blowing dust, and ...floating dust over northern China has decreased 76.7%, 68.5%, and 64.5% considerably since the beginning of this century. Based on a multi-dimensional ensemble empirical mode decomposition (MEEMD) method, a steady decrease in zonal maximum wind speed (up to -0.95 m/s) in the Northern Hemisphere was largely responsible for this recent decline in dust event occurrences. Then, a new detection technique that combines multi-satellite datasets with surface observations of dust events is developed to estimate the contribution of anthropogenic dust column burden from disturbed soils to the observed total dust. It is found that the percentage of the anthropogenic dust column burdens to total mineral dust is up to 76.8% by human activities during 2007-2014 in eastern China, but only less than 9.2% near desert source regions in northwestern China. However, we note that the anthropogenic effects on the dust loading for both regions are non-negligible.
A new generation of photothermal theranostic agents is developed based on PEGylated WS2 nanosheets. Bimodal in vivo CT/photoacoustic imaging reveals strong tumor contrast after either intratumoral or ...intravenous injection of WS2‐PEG. In vivo photothermal treatment is then conducted in a mouse tumor model, achieving excellent therapeutic efficacy with complete ablation of tumors. This work promises further exploration of transition‐metal dichalcogenides for biomedical applications, such as cancer imaging and therapy.
Abstract
Quasi-solid-state Zn-air batteries are usually limited to relatively low-rate ability (<10 mA cm
−2
), which is caused in part by sluggish oxygen electrocatalysis and unstable ...electrochemical interfaces. Here we present a high-rate and robust quasi-solid-state Zn-air battery enabled by atomically dispersed cobalt sites anchored on wrinkled nitrogen doped graphene as the air cathode and a polyacrylamide organohydrogel electrolyte with its hydrogen-bond network modified by the addition of dimethyl sulfoxide. This design enables a cycling current density of 100 mA cm
−2
over 50 h at 25 °C. A low-temperature cycling stability of over 300 h (at 0.5 mA cm
−2
) with over 90% capacity retention at −60 °C and a broad temperature adaptability (−60 to 60 °C) are also demonstrated.
Insulator detection is an essential task for the safety and reliable operation of intelligent grids. Owing to insulator images including various background interferences, most traditional ...image-processing methods cannot achieve good performance. Some You Only Look Once (YOLO) networks are employed to meet the requirements of actual applications for insulator detection. To achieve a good trade-off among accuracy, running time, and memory storage, this work proposes the modified YOLO-tiny for insulator (MTI-YOLO) network for insulator detection in complex aerial images. First of all, composite insulator images are collected in common scenes and the “CCIN_detection” (Chinese Composite INsulator) dataset is constructed. Secondly, to improve the detection accuracy of different sizes of insulator, multi-scale feature detection headers, a structure of multi-scale feature fusion, and the spatial pyramid pooling (SPP) model are adopted to the MTI-YOLO network. Finally, the proposed MTI-YOLO network and the compared networks are trained and tested on the “CCIN_detection” dataset. The average precision (AP) of our proposed network is 17% and 9% higher than YOLO-tiny and YOLO-v2. Compared with YOLO-tiny and YOLO-v2, the running time of the proposed network is slightly higher. Furthermore, the memory usage of the proposed network is 25.6% and 38.9% lower than YOLO-v2 and YOLO-v3, respectively. Experimental results and analysis validate that the proposed network achieves good performance in both complex backgrounds and bright illumination conditions.
Palladium‐catalyzed alkene‐directed cross‐coupling of aryl iodide with another aryl halide through C−H arylation opens a unique avenue for unsymmetrical biaryl‐derived molecules. However, ...homo‐coupling of aryl iodides often erodes the overall synthetic efficiency. Reported herein is a highly chemoselective Pd0‐catalyzed alkyne‐directed cross‐coupling of aryl iodides with bromophenols, which was subsequently followed by phenol dearomatization to furnish a very attractive 2+2+1 spiroannulation. Notably, possible homo‐coupling of aryl iodides was not observed at all. Mechanistic studies indicated that a five‐membered aryl/vinyl palladacycle most likely accounts for promoting the key step of biaryl cross‐coupling.
Easy as 1‐2‐3: A chemoselective Pd0‐catalyzed alkyne‐directed 2+2+1 spiroannulation of aryl iodides with bromophenol derivatives has been established for the assembly of spirocycle‐embedded polycyclic frameworks. This two‐component reaction proceeds via remote C−H cleavage, biaryl cross‐coupling, and arene dearomatization.
•Graphene oxide (GO) nanosheets were prepared by oxidization and ultrasonic dispersion.•GO nanosheets can regulate forming flower-like cement hydration crystals and sharply increase its ...toughness.•The flower-like crystals were attributed to the template effect of GO naosheets.•The research provides a pathway to significantly improving the toughness of cement composites.
Graphene oxides (GOs) nanosheets were prepared by oxidization and ultrasonic dispersion. Effects of GO nanosheets on microstructure and mechanical properties of cement composites were investigated by observing shape changes of cement hydration crystals and testing mechanical strength. The results indicated that GO nanosheets can regulate formation of flower-like crystals and remarkably increase the tensile/flexural strength of the corresponding cement composites. A possible regulation mechanism was proposed and thought GO nanosheets exhibited the template effect and contributed to the formation of flower-like crystals. The research provide a new pathway to significantly improving the toughness of cement composites by a simple method.
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