The catalytic bis‐allylation of alkynes is an important but challenging protocol to construct all‐carbon tetra‐substituted alkenes. Particularly, the catalytic unsymmetrical bis‐allylation of alkynes ...remains as an underexplored task to date. We herein report an unprecedented unsymmetrical bis‐allylation by simultaneously utilizing electrophilic trifluoromethyl alkene and nucleophilic allylboronate as the allylic reagents. With the aid of robust Ni0/NHC catalysis, valuable skipped trienes can be obtained in high regio‐ and stereo‐selectivities under mild conditions. Mechanistic studies indicate that the reaction may proceed through a β‐fluorine elimination of a nickelacycle followed by a transmetalation step with allylboronate. The present method exhibits a good tolerance of various functional groups. Besides, the skipped triene products can undergo an array of elaborate transformations, which highlights the potential applications of this strategy.
An efficient unsymmetrical bis‐allylation of alkynes has been developed by simultaneously utilizing electrophilic trifluoromethyl alkenes and nucleophilic allylboronates as the allylic reagents. With the aid of a robust Ni0/NHC catalysis, valuable skipped trienes can be obtained in high regio‐ and stereo‐selectivities under mild conditions.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Coronary atherosclerosis is a long‐term, sustained, and evolving inflammatory disease manifested with the remodeling of the coronary arteries. The purpose of this study is to explore the potential ...role of microRNA‐107 (miR‐107) in vascular endothelial cells (VECs) in coronary atherosclerosis by regulating the KRT1 gene and the Notch signaling pathway. A mouse model of coronary atherosclerosis was established. The relationship between miR‐107 and KRT1 was analyzed and verified by dual‐luciferase reporter assay. The functional role of miR‐107 in coronary atherosclerosis was determined using ectopic expression and depletion. Blood lipid levels and atherosclerotic index (AI) were measured in atherosclerotic mice. Expression pattern of miR‐107, KRT1, Notch signaling pathway, inflammatory/anti‐inflammatory factors, and endoplasmic reticulum (ER) stress‐related genes was evaluated by means of reverse transcription quantitative polymerase chain reaction, western blot analysis, and enzyme‐linked immunosorbent assay. Meanwhile, cell‐cycle distribution and cell apoptosis in VECs were assessed by flow cytometry. Atherosclerotic mice exhibited higher blood lipid levels, AI, apoptotic index, and KRT1‐positive expression as well as inhibited Notch signaling pathway when compared with normal mice. The miR‐107 was revealed to bind to KRT1; miR‐107 upregulation or KRT1 silencing resulted in reductions in blood lipid levels and AI, inhibition in cell apoptosis, inflammation, and ER stress. Restored miR‐107 or downregulated KRT1 activated the Notch signaling pathway. These results supported the notion that miR‐107‐targeted KRT1 inhibition activated the Notch pathway, thereby, protecting against the coronary atherosclerosis. Findings in this study might provide a novel biomarker for the coronary atherosclerosis treatment.
These results supported the notion that miR‐107‐targeted KRT1 inhibition activated Notch pathway, thereby, protecting against coronary atherosclerosis. Findings in this study might provide a novel biomarker for coronary atherosclerosis treatment.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
A robust and reliable grid power interface system for wind turbines using a permanent-magnet synchronous generator (PMSG) is proposed in this paper, where an integration of a generator-side ...three-switch buck-type rectifier and a grid-side Z-source inverter is employed as a bridge between the generator and the grid. The modulation strategy for the proposed topology is developed from space-vector modulation and Z-source network operation principles. Two PMSG control methods, namely, unity-power-factor control and rotor-flux-orientation control (Id = 0), are studied to establish an optimized control scheme for the generator-side three-switch buck-type rectifier. The system control scheme decouples active- and reactive-power control through voltage-oriented control and optimizes PMSG control for the grid- and generator-side converters independently. Maximum power point tracking is implemented by adjusting the shoot-through duty cycles of the Z-source network. The design considerations of the passive components are also provided. The performances and practicalities of the designed architecture have been verified by simulations and experiments.
Bridged benzazepine scaffolds, possessing unique structural and physicochemical activities, are widespread in various natural products and drugs. The construction of these skeletons often requires ...elaborate synthetic effort with low efficiency. Herein, we develop a simple and divergent approach for constructing various bridged benzazepines by a photocatalytic intermolecular dearomatization of naphthalene derivatives with readily available α‐amino acids. The bridged motif is created via a cascade sequence involving photocatalytic 1,4‐hydroaminoalkylation, alkene isomerization and cyclization. Interestingly, the diastereoselectivity can be regulated through different reaction modes in the cyclization step. Moreover, aminohydroxylation and its further bromination have also been demonstrated to access highly functionalized bridged benzazepines. Preliminary mechanistic studies have been performed to get insights into the mechanism. This method provides a divergent synthetic approach for construction of highly functionalized bridged benzazepines, which have been otherwise difficult to access.
A mild and efficient protocol is developed to convert simple aromatic substrates into value‐added and structurally complex bridged benzazepines via a photocatalytic dearomatization. The switchable diastereoselectivity could be furnished by the manipulation of base‐promoted or photoinduced intramolecular hydroamination.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Abstract
Manganese (Mn) is the third most abundant transition metal on Earth and is known for its exceptional biocompatibility. The development of novel catalytic mode for Mn is of great significance ...to advancing organic synthesis. In this study, the first manganese (Mn)‐catalyzed 2+2+2 cycloaddition of alkynes is achieved with the aid of visible‐light photoredox catalysis. Photoredox catalysis is proposed to promote the transformation by in situ reduction of high‐valent Mn(II) complex to Mn(0) species, thereby initiating the reaction. Additionally, a photooxidation‐induced reductive ellimination step is also suggested. This system is further distinguished by its notable tolerance towards both terminal and internal alkynes as counterparts of diynes.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Relativistic magnetron (RM) is a promising high-power microwave (HPM) source and major hotspot in the field of HPM research, whose advantages include high efficiency, low magnetic field, and compact ...configuration. A Formula Omitted-band RM with a novel extraction structure is presented and investigated numerically in this article. Compared with the traditional Formula Omitted-band RM with rectangular extraction slots (CRMRS), the Formula Omitted-band RM with novel extraction slots (CRMNS) has three advantages. On the one hand, mode competition is suppressed effectually, and so its operation is more stable. On the other hand, the power efficiency is enhanced. Moreover, the power capacity is enhanced, which is advantageous to increase the output power. The typical simulation results are as follows: HPM is generated with a peak power of 2.53 GW at an efficiency of 58% and a frequency of 4.3 GHz, when the voltage is 650 kV, the current is 6.7 kA, and the magnetic field is 0.347 T.
Sea cucumbers are a class of marine invertebrates and a source of food and drug. Numerous microorganisms are associated with sea cucumbers. Seventy-eight genera of bacteria belonging to 47 families ...in four phyla, and 29 genera of fungi belonging to 24 families in the phylum Ascomycota have been cultured from sea cucumbers. Sea-cucumber-associated microorganisms produce diverse secondary metabolites with various biological activities, including cytotoxic, antimicrobial, enzyme-inhibiting, and antiangiogenic activities. In this review, we present the current list of the 145 natural products from microorganisms associated with sea cucumbers, which include primarily polyketides, as well as alkaloids and terpenoids. These results indicate the potential of the microorganisms associated with sea cucumbers as sources of bioactive natural products.
The neonicotinoid pesticide, imidacloprid (IMI), is frequently detected in the environment and in foods. It is absorbed and metabolized by the intestine; however, its effects on intestinal barrier ...integrity are not well studied. We investigated whether IMI disrupts the permeability of the intestinal epithelial barrier via in vivo tests on male Wistar rats, in vitro assays using the human intestinal epithelial cell line, Caco-2, and in silico analyses. A repeated oral dose 90-day toxicity study was performed (0.06 mg/kg body weight/day). IMI exposure significantly increased intestinal permeability, which led to significantly elevated serum levels of endotoxin and inflammatory biomarkers (tumor necrosis factor-alpha and interleukin-1 beta) without any variation in body weight. Decreased transepithelial electrical resistance with increased permeability was also observed in 100 nM and 100 μM IMI-treated Caco-2 cell monolayers. Amounts of tight junction proteins in IMI-treated colon tissues and between IMI-treated Caco-2 cells were significantly lower than those of controls. Increased levels of myosin light chain phosphorylation, myosin light chain kinase (MLCK), and p65 subunit of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB p65) phosphorylation were found in IMI-exposed cells compared with control cells. Furthermore, the barrier loss caused by IMI was rescued by the MLCK inhibitor, ML-7, and cycloheximide. Pregnane X receptor (PXR, NR1I2) was inhibited by low-dose IMI treatment. In silico analysis indicated potent binding sites between PXR and IMI. Together, these data illustrate that IMI induces intestinal epithelial barrier disruption and produces an inflammatory response, involving the down-regulation of tight junctions and disturbance of the PXR-NF-κB p65-MLCK signaling pathway. The intestinal barrier disruption caused by IMI deserves attention in assessing the safety of this neonicotinoid pesticide.
Mechanism related to imidacloprid induced intestinal barrier disruption. Display omitted
•The intestinal epithelium is susceptible to oral administration of IMI.•IMI disrupts intestinal epithelial barrier by decreasing expression of tight junction proteins.•PXR inhibition by IMI triggers NF-κB-MLCK signaling to disrupt tight junctions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
A CFD-PBM coupled mathematical model was proposed to describe the bubble breakup and coalescence behavior in gas-stirred ladle based on the Eulerian-Eulerian approach. The effect of turbulence shear ...collision, bubble floating velocity difference collision and turbulence random collision on the bubble coalescence behavior were considered; the sensitivity of three typical breakup model including Luo model, Lehr model and Laakkonen model on bubble size distribution were considered. The result showed that the turbulence random collision and bubble floating velocity difference collision were the main mechanism to affect bubble coalescence behavior, while the effect of turbulence shear collision can be ignored. The bubble size distribution predicted by Lehr model was different with other two models and the measured data, because it highly predicted the bubble breakup frequency in current system. The effect of Luo model and Laakkonen model on bubble size distribution were so small that the bubble size distribution is mainly dominated by bubble coalescence behavior. Bubble-induced turbulence would affect the bubble breakup and coalescence behavior, it would promote the bubble coalescence behavior, the volume fraction of large bubbles increased significantly in this work. The size distribution predicted by the present model agree well with the measured data in the water model.
The strong interdependence between the Seebeck coefficient, the electrical and thermal conductivity makes it difficult to obtain a high thermoelectric figure of merit, ZT. It is of critical ...significance to design a novel structure that manages to decouple these parameters. Here, we combine a liquid state manipulation method for solidified Bi0.5Sb1.5Te3 alloy with subsequent melt spinning, ball milling, and spark plasma sintering processes, to construct dedicated microstructures containing plenty of 60° twin boundaries. These twin boundaries firstly scatter the very low-energy carriers and lead to an enhancement of the Seebeck coefficient. Secondly, they provide a considerable high carrier mobility, compensating the negative effect of the reduced hole concentration on the electrical conductivity. Thirdly, both experimental and calculated results demonstrate that the twin-boundary scattering dominates the conspicuous decrease of the lattice thermal conductivity. Consequently, the highest ZT value of 1.42 is achieved at 348K, which is 27% higher than that of the sample with less twin boundary treated without liquid state manipulation. The average ZT value from 300K to 400K reaches 1.34. Our particular sample processing methods enabling the twin-dominant microstructure is an efficient avenue to simultaneously optimize the thermoelectric parameters.
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•Synthesizing samples using powder sintering based on liquid state manipulation.•Generating large number of twin boundaries for Bi0.5Sb1.5Te3 alloy.•Simultaneous optimization of electrical and thermal properties due to twin boundary.•A 27% enhancement of ZT compared with twin-less sample treated without liquid state manipulation.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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