A cobalt‐promoted electrochemical 1,2‐diarylation of alkenes with electron‐rich aromatic hydrocarbons via direct dual C−H functionalizations is described, which employs a radical relay strategy to ...produce polyaryl‐functionalized alkanes. Simply by using graphite rod cathode instead of platinum plate cathode, chemoselectivity of this radical relay strategy is shifted to the dehydrogenative 2+2+2 cycloaddition via 1,2‐diarylation, annulation, and dehydrogenation cascades leading to complex 11,12‐dihydroindolo2,3‐acarbazoles. Mechanistical studies indicate that a key step for the radical relay processes is transformations of the aromatic hydrocarbons to the aryl sp2‐hybridized carbon‐centered radicals via deprotonation of the corresponding aryl radical cation intermediates with bases.
Direct C−H functionalizations enable electrochemical diarylation of alkenes with aromatic hydrocarbons using a radical relay strategy toward polyaryl‐functionalized compounds. Chemoselectivity of the strategy relies on choice of both anode and cathode, which is shifted to the dehydogenative 2+2+2 cycloaddition of alkenes with indoles when using graphite rod as the anode and cathode.
Biodegradable plastics, as alternatives to conventional plastics, are increasingly used, but their interactions with organic pollutants are still unknown. In this study, the sorption and desorption ...behaviors on a type of biodegradable plastic−poly(butylene adipate co-terephtalate) (PBAT) were investigated, and at the same time two types of conventional plastics−polyethylene (PEc and PEv) and polystyrene (PS) were used for comparison. Phenanthrene (PHEN) was chosen as one of representative organic pollutants. Results indicated that the sorption and desorption capacities of PBAT were not only higher than those of the other types of microplastics, but also higher than those of carbonaceous geosorbents. The surface area normalized results illustrated that sorption and desorption of the microplastics were positively correlated with their abundance of rubbery subfraction. The sorption kinetic results showed that the sorption rates of PBAT and PEc were higher than PEv and PS. The effects of water chemistry factors including salinity, dissolved organic matter and Cu2+ ion on the sorption process displayed the same trend, but the degrees of influence on the four microplastics differed. The degrees of influence were mainly dependent on the abundance of rubbery subfraction for microplastics. These findings indicate that the biodegradable poly(butylene adipate co-terephtalate) microplastics are actually stronger vectors than the conventional microplastics, and crystallization characteristics of the microplastics have great influences on the vector effect.
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•Biodegradable microplastics sorbed/desorbed more PHEN than conventional ones.•Sorption/desorption capacities depended on the content of rubbery subfraction.•Plastic additives didn't alter the microplastics adsorption process.•High salinity and low DOM strengthen the sorption of PHEN onto microplastics.
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•Microplastics were found in 30 fish species from Zhanjiang mangrove wetland.•Microplastics could be detected in gills, stomach and intestine of the fishes.•Fiber was the dominant ...microplastic shape detected in fish bodies.•Polyethylene was the highly abundant polymer type in collected microplastics.
Microplastics (MPs) are widespread in marine and estuarine environments, but the contamination of MPs in mangrove wetlands is relatively unknown. Here, we quantify the presence of MPs in fish collected from Zhanjiang mangrove wetland, the largest mangrove in South China, which provide baseline data on MPs accumulation in fish in mangrove environment as the first evidence in China. MPs were found in 30 out of 32 fish species at an average abundance of 2.83 ± 1.84 items individual−1, ranged from 0.6 to 8.0 items individual−1 in each species. MPs were detected in gills, stomach and intestine, and not found in muscles and livers. Positive relationship was found between MPs abundance and body length or weight of mangrove fish. The dominant polymers identified by micro-FTIR were polyethylene, polyethylene terephthalate, polypropylene and cellophane. MPs consisted primarily of fibers and with the prominent size range of 0.02–1 mm. The body sizes, living habitats and feeding habits of fish are important factors affecting MPs accumulation in different fish species. This study revealed the wide presences of MPs in fish species within a mangrove wetland.
A new metal‐free oxidative radical 2+2+1 carbocyclization of benzene‐linked 1,n‐enynes with two C(sp3)H bonds adjacent to the same heteroatom is described. This method achieves two C(sp3)H ...oxidative functionalizations and an annulation, thus providing efficient and general access to a variety of fused five‐membered carbocyclic hydrocarbons.
An oxidative functionalization of two C(sp3)H bonds adjacent to a same heteroatom for the 2+2+1 carbocyclization with benzene‐linked 1,n‐enynes is presented. This method successfully proceeds using a radical mechanism and provides straightforward access to a variety of fused five‐membered carbocyclic hydrocarbons. TBPB=tert‐butyl perbenzoate.
Ubiquitous mobile social service allows users to interact and communicate with others at any time and place, which is different from the mobile social service in the past. It has become the mobile ...service most widely used by consumers since various mobile applications (abbreviated as “apps”) were introduced into the market. Recently, the number of elderly users of ubiquitous mobile social service aged over 60 has largely increased. However, the needs and the adoption motivations of the elderly people for this service seemed to have been neglected in the development of mobile devices or services, even in the academic research. For the purpose of understanding what factors make the elderly mobile users willing to adopt ubiquitous mobile social service, this study conducted an empirical research the integrating uses and gratification theory and the media richness theory. Totally, 226 effective questionnaires were obtained, among these questionnaires, there are 193 samples over the age of 60. The analysis results indicated that social, enjoyment and fashion motivations have influences on elderly mobile users' adoption of ubiquitous mobile social service. Furthermore, users' perceived interactive richness and apps self-efficacy also have strong influences on elderly mobile users' adoption of the service. However, the required high expenses make the elderly mobile users keep using their habitual ways to socialize with others, and therefore have a negative influence on elderly mobile users' intention to adopt ubiquitous mobile social service.
•Integrating Uses and Gratification Theory with Media Richness Theory.•Analyzing the motivations of elderly users' adoption toward mobile social service.•Except for epistemic, all the motivations have influence on elderly users' adoption.•Perceived interactive richness and self-efficacy are important for elderly users.•Users' inertia of sociality in traditional ways has negative influence on adoption.
All-aqueous printing of viscoelastic droplets (aaPVD) in yield-stress fluids is the core of an emerging voxelated bioprinting technology that enables the digital assembly of spherical bio-ink ...particles (DASP) to create functional tissue mimics. However, the mechanism of aaPVD is largely unknown. Here, by quantifying the dynamics of the whole printing process in real-time, we identify two parameters critical to aaPVD: (1) acceleration of print nozzle, and (2) droplet/nozzle diameter ratio. Moreover, we distinguish three stages associated with aaPVD: droplet generation, detachment, and relaxation. To generate a droplet of good roundness, the ink should be a highly viscous shear-thinning fluid. Using particle image velocimetry and scaling theory, we establish a universal description for the droplet displacements at various printing conditions. Along the direction of nozzle movement, the droplet displacement is determined by the detachment number, a dimensionless parameter defined as the ratio between the dragging force from the nozzle and the confinement force from the supporting matrix. Perpendicular to the direction of nozzle movement, the droplet displacement is determined by the Oldroyd number, a dimensionless parameter that describes the yielded area of the supporting matrix near the print nozzle. For a relaxed droplet, the droplet tail length is independent of droplet/nozzle diameter ratio but determined by the nozzle acceleration. We conclude that printing droplets of good fidelity requires a relatively large droplet/nozzle diameter ratio and intermediate nozzle accelerations. These ensure that the droplet is more solid-like to not flow with the nozzle to form a tadpole-like morphology and that the confinement force from the yield-stress fluid is large enough to prevent large droplet displacement. Our results provide the knowledge and tools for in situ generating and depositing highly viscoelastic droplets of good roundness at prescribed locations in 3D space, which help establish the foundational science for voxelated bioprinting.
Analogues of pixels to two-dimensional (2D) pictures, voxels – in the form of small cubes or spheres – are the basic units of three-dimensional (3D) objects. All-aqueous printing of viscoelastic droplets (aaPVD) is the core of voxelated bioprinting, an emerging technology that uses spherical bio-ink voxels as building blocks to create 3D tissue mimics. Unlike existing technologies relying on the classic Rayleigh-Plateau instability to generate droplets, aaPVD exploits previously unexplored nonlinear fluid dynamics of complex fluids to precisely manipulate viscoelastic droplets in 3D space. The developed knowledge and tools not only help advance biomanufacturing but also stimulate new research directions in soft matter and complex fluids.
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In this letter, we propose a simple yet effective unsupervised change detection approach for multitemporal synthetic aperture radar images from the perspective of clustering. This approach jointly ...exploits the robust Gabor wavelet representation and the advanced cascade clustering. First, a log-ratio image is generated from the multitemporal images. Then, to integrate contextual information in the feature extraction process, Gabor wavelets are employed to yield the representation of the log-ratio image at multiple scales and orientations, whose maximum magnitude over all orientations in each scale is concatenated to form the Gabor feature vector. Next, a cascade clustering algorithm is designed in this discriminative feature space by successively combining the first-level fuzzy c-means clustering with the second-level nearest neighbor rule. Finally, the two-level combination of the changed and unchanged results generates the final change map. Experimental results are presented to demonstrate the effectiveness of the proposed approach.
A new electrochemical intermolecular 1,2‐aminosulfonylation of alkenes with sulfinates and amines is achieved by utilizing balanced three‐component interactions and reactivity differentiation. This ...strategy can be applicable to a wide range of amines, including primary and secondary amines, thus enabling alkene aminosulfonylation for producing diverse functionalized 2‐sulfonylethan‐1‐amines without the need of additive redox catalysts, metal catalysts and chemical oxidants.
Recently, deep learning-based algorithms have been widely used for classification of hyperspectral images (HSIs) by extracting invariant and abstract features. In our conference paper presented at ...IEEE International Geoscience and Remote Sensing Symposium 2018, 1-D-capsule network (CapsNet) and 2-D-CapsNet were proposed and validated for HSI feature extraction and classification. To further improve the classification performance, the robust 3-D-CapsNet architecture is proposed in this article by following our previous work, which introduces the maximum correntropy criterion to address the noise and outliers problem, generating a robust and better generalization model. As such, discriminative features can be extracted even if some samples are corrupted more or less. In addition, a novel dual channel framework based on robust CapsNet is further proposed to fuse the hyperspectral data and light detection and ranging-derived elevation data for classification. Three widely used hyperspectral datasets are employed to demonstrate the superiority of our proposed deep learning models.
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