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Abstract-Most studies on bilateral teleoperation assume known system kinematics and only consider dynamical uncertainties. However, many practical applications involve tasks with both kinematics and dynamics uncertainties. In this paper, trilateral teleoperation systems with dual-master-single-slave framework are investigated, where a single robotic manipulator constrained by an unknown geometrical environment is controlled by dual masters. The network delay in the teleoperation system is modeled as Markov chain-based stochastic delay, then asymmetric stochastic time-varying delays, kinematics and dynamics uncertainties are all considered in the force-motion control design. First, a unified dynamical model is introduced by incorporating unknown environmental constraints. Then, by exact identification of constraint Jacobian matrix, adaptive neural network approximation method is employed, and the motion/force synchronization with time delays are achieved without persistency of excitation condition. The neural networks and parameter adaptive mechanism are combined to deal with the system uncertainties and unknown kinematics. It is shown that the system is D. Wang is with the Key Laboratory of Autonomous System and Network Control, Ministry of Education, South China University of Technology, Guangzhou, China, and also with the College of Automation Science and Engineering, South China University of Technology, Guangzhou,

Enamine catalysis is a prevalent strategy for the functionalization of aldehydes/ketones with electrophiles. Recently, the advent and development of oxidative enamine catalysis have allowed for the coupling of enamines with readily available nucleophiles under oxidative conditions, significantly expanding the domain of typical enamine catalysis. In this perspective, we summarize the recent advances in asymmetric oxidative enamine catalysis. On the basis of the oxidative strategy, these could be classified as (1) oxidation of nucleophile, (2) oxidation of enamine via single-electron transfer (SOMO catalysis), and (3) oxidation of enamine to α,β-unsaturated iminium ion, i.e. oxidative iminium catalysis. These strategies have enabled efficient oxidative functionalizations of aldehydes/ketones with various O-, N-, and C-centered nucleophiles in a highly stereocontrolled manner.

Enamines are electron-rich compounds bearing intriguing redox properties. Herein, a series of secondary enamines condensed from primary amine and β-ketocarbonyls were synthesized and their electrochemical oxidation properties were systematically studied by cyclic voltammetry. Furthermore, theoretical calculation of oxidation potentials of enamines, particularly those catalytic intermediates, was also conducted to further broaden the scope investigated. Possible structural factors on oxidation and the nature of the resulted radical cation intermediates were revealed and discussed. Correlation of redox potentials with molecular properties such as highest occupied molecular orbital energies and natural population analysis charge were explored, and there appears no simple linear correlation. On the other hand, a good correlation with Mayr's nucleophilicity parameter N was noted among a range of catalytically relevant enamines. Spin population analysis disclosed that enamine radical cations mainly exhibit the carbon-center free radical feature. Taking experimental and computation data together, a comprehensive picture about the redox property of enamines is presented, which would provide guidance in the development of oxidative enamine catalysis and transformations.

A distinctive aminocatalysis via α-imino radical is reported on the basis of SET oxidation of a secondary enamine. The combination of chiral primary amine catalysis and visible-light photoredox catalysis enables the enantioselective decarboxylative coupling of propiolic acid and β-ketocarbonyls to afford alkynylation adducts with high enantioselectivity. Mechanism studies indicate the reaction proceeds via an α-imino radical addition.

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The direct asymmetric α-benzoyloxylation of β-ketocarbonyls catalyzed by a chiral primary amine is described herein. This protocol demonstrates excellent enantioselectivity for a broad range of substrates, which allows convenient access to highly enantioenriched α-hydroxy-β-ketocarbonyls.

Plants are considered an important food and nutrition source for humans. Despite advances in plant seed metabolomics, knowledge about the genetic and molecular bases of rice seed metabolomes at different developmental stages is still limited. Here, using Zhenshan 97 (ZS97) and Minghui 63 (MH63), we performed a widely targeted metabolic profiling in seeds during grain filling, mature seeds and germinating seeds. The diversity between MH63 and ZS97 was characterized in terms of the content of metabolites and the metabolic shifting across developmental stages. Taking advantage of the ultra-high-density genetic map of a population of 210 recombinant inbred lines (RILs) derived from a cross between ZS97 and MH63, we identified 4681 putative metabolic quantitative trait loci (mQTLs) in seeds across the three stages. Further analysis of the mQTLs for the codetected metabolites across the three stages revealed that the genetic regulation of metabolite accumulation was closely related to developmental stage. Using in silico analyses, we characterized 35 candidate genes responsible for 30 structurally identified or annotated compounds, among which LOC_Os07g04970 and LOC_Os06g03990 were identified to be responsible for feruloylserotonin and L-asparagine content variation across populations, respectively. MetaboliteÀagronomic trait association and colocation between mQTLs and phenotypic quantitative trait loci (pQTLs) revealed the complexity of the metaboliteÀagronomic trait relationship and the corresponding genetic basis.