Beneficial influence of nanocarbon on the aryliminopyridylnickel chloride catalyzed ethylene polymerization

A series of 1-aryliminoethylpyridine ligands (L1―L3) was synthesized by condensation of 2-acetylpyridine with 1-aminonaphthalene, 2-aminoanthracene or 1-aminopyrene, respectively. Reaction with nickel dichloride afforded the corresponding nickel (II) chloride complexes (Ni1–Ni3). All compounds were fully characterized and the molecular structures of Ni1 and Ni3 are reported. Upon activation with methylaluminoxane (MAO), all nickel complexes exhibit high activities for ethylene polymerization, producing waxes of low molecular weight and narrow polydispersity. The presence of multi-walled carbon nanotubes (MWCNTs) or few layer graphene (FLG) in the catalytic medium can lead to an increase of productivity associated to a modification of the polymer structure

Determination of Volatile Compounds of Illicium verum Hook. f. Using Simultaneous Distillation-Extraction and Solid Phase Microextraction Coupled with Gas Chromatography-Mass Spectrometry

Purpose: To determine the characteristic aromatic constituents of star anise (Illicium verum Hook. f.) and identify its main aroma compounds for sensory evaluation.Methods: The volatile compounds of star anise were prepared by simultaneous distillation-extraction (SDE) and the compounds were identified by gas chromatography-mass spectroscopy (GC-MS). The flavor compounds were confirmed by gas chromatography-olfactometry (GC-O). Their flavor dilution factor (FD) values were determined using aroma extract dilution analysis (AEDA). Finally, standard samples that meet the requirements for sensory evaluation were extracted by the solid-phase microextraction (SPME) to further validate characteristic aroma molecules.Results: Forty seven compounds were confirmed, with trans-anethole, estragole, and anisaldehyde the main aroma components. The content of trans-anethole was the highest (75.76 %), followed by linalool (1.44 %). Limonene (1.01 %) and 4’- ethoxypropiophenone (0.72 %) were the lowest.Conclusion: Combining SDE coupled with AEDA and SPME coupled with GC-MS is beneficial for identifying characteristic aroma compounds for star anise, such as trans-anethole, linalool and limonene in terms of FD value. The findings may be useful for star anise quality control in the food industry.Keywords: Aroma, Flavor dilution factor (FD value), Gas chromatography-olfactometry, Simultaneous distillation-extraction, Sensory evaluation, Star anise, Illicium verum, Trans-anethole, Linaloo, Limonen

Synthesis and characterization of 2-(2-benzhydrylnaphthyliminomethyl)pyridylnickel halides: formation of branched polyethylene

A series of 2-(2-benzhydrylnaphthyliminomethyl)pyridine derivatives (L1–L3) was prepared and used to synthesize the corresponding bis-ligated nickel(II) halide complexes (Ni1–Ni6) in good yield. The molecular structures of representative complexes, namely the bromide Ni3 and the chloride complex Ni6, were confirmed by single crystal X-ray diffraction, and revealed a distorted octahedral geometry at nickel. Upon activation with either methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), all nickel complex pre-catalysts exhibited high activities (up to 2.02 × 10⁷ g(PE) mol⁻¹(Ni) h⁻¹) towards ethylene polymerization, producing branched polyethylene of low molecular weight and narrow polydispersity. The influence of the reaction parameters and the nature of the ligands on the catalytic behavior of the title nickel complexes were investigated

2-(1-(2-Benzhydrylnaphthylimino)ethyl)pyridylnickel halides: Synthesis, characterization, and ethylene polymerization behavior

A series of 2-(1-(2-benzhydrylnaphthylimino)ethyl)pyridine derivatives (L1–L3) was synthesized and fully characterized. The organic compounds acted as bi-dentate ligands on reacting with nickel halides to afford two kinds of nickel complexes, either mononuclear bis-ligated L₂NiBr₂ (Ni1–Ni3) or chloro-bridged dinuclear L₂Ni₂Cl₄ (Ni4–Ni6) complexes. The nickel complexes were fully characterized, and the single crystal X-ray diffraction revealed for Ni2, a distorted square pyramidal geometry at nickel comprising four nitrogens of two ligands and one bromide; whereas for Ni4, a centrosymmetric dimer possessing a distorted octahedral geometry at nickel was formed by two nitrogens of one ligand, two bridging chlorides and one terminal chloride along with oxygen from methanol (solvent). When activated with diethylaluminium chloride (Et₂AlCl), all nickel complexes performed with high activities (up to 1.22 × 10⁷ g (PE) mol⁻¹(Ni) h⁻¹) towards ethylene polymerization; the obtained polyethylene possessed high branching, low molecular weight and narrow polydispersity, suggestive of a single-site active species. The effect of the polymerization parameters, including the nature of the ligands/halides on the catalytic performance is discussed

Phase- and Polarization-Controlled Two-Photon Rabi Oscillation of the Biexciton State in a Semiconductor Quantum Dot

Under a degenerate two-photon resonant excitation, the Rabi oscillation of the four-level biexciton system in a semiconductor quantum dot is theoretically investigated. The influence of the laser phases on the state manipulation is modeled and numerically calculated. Due to the interference between different excitation paths, the laser phase plays an important role and can be utilized as an alternate control knob to coherently manipulate the biexciton state. The phase control can be facilely implemented by changing the light polarization via a quarter-wave plate

A scalable P2P platform for the knowledge Grid

Abstract—The Knowledge Grid needs to operate with a scalable platform to provide large-scale intelligent services. A key function of such a platform is to efficiently support various complex queries in a dynamic large-scale network environment. This paper proposes a platform to support index-based path queries by incorporating a semantic overlay with an underlying structured P2P network that provides object location and management services. Various distributed indexing structures can be dynamically formed by publishing semantic objects as indexing nodes. Queries are forwarded along the chains of semantic object pointers to search for objects. We investigate the deployment of a scalable distributed trie index for broadcast queries on key strings, propose a decentralized load balancing method for solving the problem of uneven load distribution incurred by heterogeneity of loads and node capacities and by the distributed trie index, and give an approach for improving the availability of the semantic overlay and its trie index. Experiments demonstrate the scalability of the proposed platform. Index Terms—Peer-to-peer, semantic overlay, knowledge grid, path query, distributed trie index, load balancing, replication