The carbonylation reaction represents one of the most powerful methods for the rapid build‐up of carbonyl structures and has widely applied in both academic and industry fields. Carbonylative ...difunctionalization of alkenes, which installs a unique functional group and a carbonyl group across the C−C double bonds, offers a high potential strategy for the selective synthesis of β‐substituted carbonyl compounds. The carbonylative difunctionalization of alkenes involves the formation of three σ‐bonds and two stereocenters as well as a carbonyl group in a single transformation. Careful design of the substrate and control of reaction pathway would result unexpected advantages in constructing complex structures, which are ubiquitous in natural products, pharmaceuticals and functional materials. In this Review, the important advances and contributions in carbonylative difunctionalization of alkenes are summarized based on the different reaction types, with the wish to inspire future studies and promote further developments in this field.
The main contributions in the field of first-row transition-metal-catalyzed (base-metal-catalyzed) carbonylative transformations have been summarized and discussed. The contents have been divided ...according to the electrophiles applied, followed by the different types of nucleophiles. Their reaction mechanisms and applications have been emphatically discussed.
The development of highly selective procedures is one of the core goals in organic chemistry. Among the known organic transformations, carbonylation reactions present an ideal choice for the ...preparation of carbonyl‐containing compounds. In this review, the recent achievements on the control of the selectivity for carbonylation reactions have been summarized. The effects of ligands, solvents, and bases on the selectivity are been discussed.
Control switch: The recent achievements on the control of the selectivity for carbonylation reactions have been summarized. The effects of ligands, solvents, and bases on the selectivity are discussed.
In this paper, we propose an attention pyramid method for person re-identification. Unlike conventional attention-based methods which only learn a global attention map, our attention pyramid exploits ...the attention regions in a multi-scale manner because human attention varies with different scales. Our attention pyramid imitates the process of human visual perception which tends to notice the foreground person over the cluttered background, and further focus on the specific color of the shirt with close observation. Specifically, we describe our attention pyramid by a "split-attend-merge-stack" principle. We first split the features into multiple local parts and learn the corresponding attentions. Then, we merge local attentions and stack these merged attentions with the residual connection as an attention pyramid. The proposed attention pyramid is a lightweight plug-and-play module that can be applied to off-the-shelf models. We implement our attention pyramid method in two different attention mechanisms including: channel-wise attention and spatial attention. We evaluate our method on four large-scale person re-identification benchmarks including Market-1501, DukeMTMC, CUHK03, and MSMT17. Experimental results demonstrate the superiority of our method, which outperforms the state-of-the-art methods by a large margin with limited computationa cost. Code is available at https://github.com/CHENGY12/APNet .
Infrared detection at optical communication wavelength is of great significance because of their diverse commercial and military communication applications. The layered Bi2Se3 with a narrow band gap ...of 0.3 eV is regarded as a promising candidate toward high‐performance terahertz to infrared applications. However, the controllable synthesis of large‐size ultrathin Bi2Se3 flakes remains a challenge owing to complex nucleation process and infrared telecommunication photodetectors based on Bi2Se3 flakes are rarely reported. Here, large size (submillimeter: 0.2–0.4 mm in lateral dimensions) and ultrathin (thickness: 3 nm to few nanometers) 2D Bi2Se3 flakes with high crystal quality are obtained by suppressing the nucleation density. More importantly, back‐gate field‐effect transistor based on Bi2Se3 flake exhibits an ultrahigh on/off current ratio of 106 and competitive mobility of 39.4 cm2 V−1 s−1. Moreover, excellent on/off ratio of 972.5, responsivity of 23.8 A W−1, and external quantum efficiency of 2035% are obtained from Bi2Se3‐based photodetector at 1456 nm in the E‐band of the telecommunication range. With controlled morphology and excellent photoresponse performance, the Bi2Se3 photodetector shows great potential in the optoelectronic field including communications, military, and remote sensing.
The synthesis of submillimeter atomically thin Bi2Se3 flakes via van der Waals epitaxy is presented. Impressively, the optical communication wavelength sensors based on the Bi2Se3 flakes exhibit an on/off ratio of 972.5, responsivity of 23.8 A W−1, and an external quantum efficiency of 2035% at 80 K.
Microautophagy, the non-selective lysosomal degradative process, involves direct engulfment of cytoplasmic cargo at a boundary membrane by autophagic tubes, which mediate both invagination and ...vesicle scission into the lumen. With its constitutive characteristics, microautophagy of soluble substrates can be induced by nitrogen starvation or rapamycin via regulatory signaling complex pathways. The maintenance of organellar size, membrane homeostasis, and cell survival under nitrogen restriction are the main functions of microautophagy. In addition, microautophagy is coordinated with and complements macroautophagy, chaperone-mediated autophagy, and other self-eating pathways. Three forms of selective microautophagy, including micropexophagy, piecemeal microautophagy of the nucleus, and micromitophagy, share common ground with microautophagy to some degree. As the accumulation of experimental data, the precise mechanisms that govern microautophagy are becoming more appreciated. Here, we review the microautophagic molecular machinery, its physiological functions, and relevance to human diseases, especially in diseases involving multivesicular bodies and multivesicular lysosomes.
The interaction between microglia and astrocytes significantly influences neuroinflammation. Microglia/astrocytes, part of the neurovascular unit (NVU), are activated by various brain insults. The ...local extracellular and intracellular signals determine their characteristics and switch of phenotypes. Microglia and astrocytes are activated into two polarization states: the pro-inflammatory phenotype (M1 and A1) and the anti-inflammatory phenotype (M2 and A2). During neuroinflammation, induced by stroke or lipopolysaccharides, microglia are more sensitive to pathogens, or damage; they are thus initially activated into the M1 phenotype and produce common inflammatory signals such as IL-1 and TNF-α to trigger reactive astrocytes into the A1 phenotype. These inflammatory signals can be amplified not only by the self-feedback loop of microglial activation but also by the unique anatomy structure of astrocytes. As the pathology further progresses, resulting in local environmental changes, M1-like microglia switch to the M2 phenotype, and M2 crosstalk with A2. While astrocytes communicate simultaneously with neurons and blood vessels to maintain the function of neurons and the blood-brain barrier (BBB), their subtle changes may be identified and responded by astrocytes, and possibly transferred to microglia. Although both microglia and astrocytes have different functional characteristics, they can achieve immune "optimization" through their mutual communication and cooperation in the NVU and build a cascaded immune network of amplification.
Dyes can CO do it: Organic dyes and pigments are usually applied in textile dyeing, which can be dated back to the Neolithic period. Interestingly, the possibility to use organic dyes as photoredox ...catalysts has also been noticed by organic chemists and applied in organic synthesis. Carbonylation reactions as a powerful procedure in carbonyl‐containing compound preparation have also been studied. In this manuscript, the recent achievements in using organic dyes as visible‐light sensitizers in carbonylation chemistry are summarized and discussed.
2D nonlayered materials that possess appealing properties are entering the researchers' vision. However, direct access to the 2D level of these materials is still a great challenge due to the ...instrinsic isotropic chemical bond. This work presents the initially self‐limited epitaxial growth of ultrathin nonlayered CdS flakes (as thin as 6 nm) on mica substrate with a large domain size (>40 µm) by employing In2S3 as the passivation agent. Besides, the thickness and sizes of the products could be tunable by the addition level of In2S3 amount. The growth mechanism is evidenced via experiments and theoretical calculations, which is attributed to the surface distortion effect of In–S motif and the preference of local environments for In on the CdS (0001) surface. The photodetector designed on CdS flake demonstrates a high photoswitching ratio (up to 103), a high detectivity (D* ≈ 2.71 × 109 Jones), and fast photoresponse speed (τR = 14 ms, τD = 8 ms). The as‐proposed self‐limited epitaxial growth method opens a new avenue to synthetize 2D nonlayered materials and will promote their further applications in novel optoelectronic devices.
This work presents the initially self‐limited epitaxial growth of ultrathin nonlayered CdS flakes (≈6 nm) on mica substrate with a large domain size (>40 µm) by employing In2S3 as the passivation agent. The growth mechanism is attributed to the surface distortion effect of In–S motif and the preference of local environments for In on the CdS (0001) surface.
To find potential α-glucosidase inhibitors, indolo1,2-bisoquinoline derivatives (
-
) were screened for their α-glucosidase inhibitory effects. All derivatives presented potential α-glucosidase ...inhibitory effects with IC
values of 3.44 ± 0.36~41.24 ± 0.26 μM compared to the positive control acarbose (IC
value: 640.57 ± 5.13 μM). In particular, compound
displayed the strongest anti-α-glucosidase activity, being ~186 times stronger than acarbose. Kinetic studies found that compounds
,
,
,
, and
were all reversible mix-type inhibitors. The 3D fluorescence spectra and CD spectra results revealed that the interaction between compounds
,
,
,
, and
and α-glucosidase changed the conformational changes of α-glucosidase. Molecular docking and molecular dynamics simulation results indicated the interaction between compounds and α-glucosidase. In addition, cell cytotoxicity and drug-like properties of compound
were also investigated.
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