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Asymmetric ketene cycloaddition is a powerful tool for chiral heterocycle synthesis, stimulating the development of innovative catalytic strategies to achieve a high level of efficiency and stereocontrol. Herein, we disclose an asymmetric cascade reaction between enynamides and α-diazoketones inspired by natural photosynthesis. The biomimic combination of visible-light photoactivation and relay gold and N-oxide catalysis allowed the facile generation and controlled assembly of two reactive intermediates, ketene and aza-o-quinone methide. This produced chiral bicyclic lactams bearing chiral all-carbon quaternary stereocenters with high efficiency and selectivity. Density functional theory calculations revealed a stepwise [4+2] cycloaddition mechanism, with the stereochemistry controlled by the amide group of the catalyst. Notably, this study presents the first example of chiral N-oxides as catalysts for asymmetric ketene cycloaddition, and demonstrates that a biomimetic cascade strategy is a promising approach to access important chiral heterocyclic scaffolds.

Catalytic asymmetric synthesis of chiral endocyclic allenes remains a challenge in allene chemistry owing to unfavored tension and complex chirality. Here, we present a new relay strategy merging Pd-catalyzed asymmetric [3+2] annulation with enyne-Cope rearrangement, providing a facile route to chiral 9-membered endocyclic allenes with high efficiency and enantioselectivity. Moreover, theoretical calculations and experimental studies were performed to illustrate the critical, but unusual Cope rearrangement that allows for the complete central-to-axial chirality transfer.

At present, the digital meter recognition is widely used in the field of power transmission and transformation, but rarely used in the petrochemical industry. This paper combines traditional image processing techniques with deep learning methods and proposes a meter recognition method based on an improved neural network model. By establishing a neural network model architecture, setting up the three convolutional layers and adding a batch normalization processing operation, the digital meters of the oil extraction platform are recognized, and the recognition rate is about 99.17%, which achieve the expectations. Through comparative research, the model constructed in this paper has a higher recognition accuracy and reflects a better recognition effect.

Networking with various healthcare devices on human body is one of the targeted applications of the IEEE 802.15.6 standard. Among those, human body communication is considered to have better performance in terms of power consumption and security for implanted and swallowable devices. Different from general applications of BAN, healthcare device network with implanted/swallowable devices requires a better understanding of the necessary time delay for the emergency messages transmission. In this article, we analyzed the delay of emergency message transmission based on IEEE802.15.6 at HBC. Both theoretical analysis and simulation were employed to calculate the average and shortest transmission delay, and also the distribution of the transmission delay at multi-user multi-UPs for slotted Aloha access protocol.

Transfer function of intra-body communication (IBC) helps the understanding of signal transmission mechanism and hints for efficient communication system design. In this paper, transfer function with phase information based on quasi-static electromagnetic (EM) field modeling for a galvanic-type IBC limb is briefly reviewed. Then the compensation factor, which is calculated by the minimum mean square error (MMSE) method, is introduced to correct the inevitable deviation in actual shapes of human limb and electrical properties of tissues. To verify the effectiveness of correction factor, the square wave response is calculated and experimentally measured. Eventually, our results demonstrate good agreement between theoretical calculation and experimental measurement.

Intra-body communication (IBC) is a short-range body based communication using the human body as the transmission medium in biomedical application. Quasi-static electric field modeling of the galvanic coupling IBC human limb channel is analyzed. Governing function can be reduced to Laplace's equation, bone and joint effects are considered as the boundary conditions. Analytical solutions of voltage distribution in the human limb from the model are obtained. Effects of human limb's properties in the model are studied. Finally, in vivo validation and calculation results are presented. Especially, the gain is greatly affected by the ratio of the thickness of muscle and bone both in calculation result and in vivo experiment.