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411.
Justin B. Diccianni Chunhua T. Hu Tianning Diao 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(39):14003-14006
The incorporation of CO2 into organometallic and organic molecules represents a sustainable way to prepare carboxylates. The mechanism of reductive carboxylation of alkyl halides has been proposed to proceed through the reduction of NiII to NiI by either Zn or Mn, followed by CO2 insertion into NiI‐alkyl species. No experimental evidence has been previously established to support the two proposed steps. Demonstrated herein is that the direct reduction of (tBu‐Xantphos)NiIIBr2 by Zn affords NiI species. (tBu‐Xantphos)NiI‐Me and (tBu‐Xantphos)NiI‐Et complexes undergo fast insertion of CO2 at 22 °C. The substantially faster rate, relative to that of NiII complexes, serves as the long‐sought‐after experimental support for the proposed mechanisms of Ni‐catalyzed carboxylation reactions. 相似文献
412.
Yiran Liang Lingxiao Wei Cunjin Yang Xiaoping Diao 《International journal of environmental analytical chemistry》2019,99(3):199-208
The dissipation and terminal residues of oryzalin in grape ecosystem under open-field condition were investigated at two different locations, Beijing and Shandong in China. Residues in field-treated samples were determined by a sample method using rapid resolution liquid chromatography triples quadrupole tandem mass spectrometry (RRLC-QqQ-MS/MS). This method showed satisfactory qualitative and quantitative performance. The mean recoveries of oryzalin at different fortification levels (0.01, 0.1 and 1 mg/kg for grape; 0.01, 0.1, 1, 10 and 30 mg/kg for soil) ranged from 88.2% to 98.8%, with the relative standard deviations ≤4.9%. The limits of detection and quantification were, respectively, 0.003 and 0.01 mg/kg. In soil, the dissipation half-lives were about 9 days and the terminal residues ranged from <0.01 to 0.58 mg/kg in both Beijing and Shandong. The concentrations of oryzalin in grapes were lower than 0.01 mg/kg in most of the samples of dissipation study and all the samples of residue study. As far as we know, this is the first study focusing on the dissipation and terminal residue of oryzalin in grape ecosystem, and no maximum residue limits (MRLs) of oryzalin in grapes were recommended by China, Codex Alimentarius Commission or European Union . Therefore, these data not only provide important information about the fate and residues of oryzalin in grape ecosystem, but also could be very useful for the establishment of the MRLs of oryzalin in grapes. 相似文献
413.
414.
A selective protocol for the synthesis of either α-ketoamides or quinoxaline derivatives under the same reaction conditions has been achieved simply by varying substitution number of amino-groups. The method features metal-free, room temperature and broad substrate scopes as well as no extra oxidant. This process applies to various substituent groups and gives products in moderate to good yield. Finally, a rational mechanism was proposed. 相似文献
415.
Yanling Wang Huan Ge Disha Wang Huan He Lu Li Yanyan Diao Zihao Shen Lili Zhu Shiliang Li Zhenjiang Zhao Honglin Li 《中国化学》2019,37(12):1259-1263
Macrocycle has attracted the attention of many researchers in the field of medicinal chemistry due to its unique advantages and good prospects, but the difficulties in drug design and synthesis of macrocycle limit its applications. In this study, a series of macrocyclic derivatives designed from anaplastic lymphoma kinase (ALK) inhibitor lorlatinib were synthesized as Janus kinase 2 (JAK2) selective inhibitors. Among them, 17f had the best inhibitory activity (IC50 = 0.177 μmol·L–1) and selectivity for JAK2 over JAK1 and JAK3, which indicated that design of the macrocyclic derivatives might be a feasible strategy for the discovery of novel selective JAK2 inhibitors. 相似文献
416.
Xiang Xu Man Jiang Diao Li Ruiduo Wang Zhaoyu Ren Jintao Bai 《Optical and Quantum Electronics》2018,50(1):39
A passively Q-switched microsecond Er-doped fiber laser at 1532 nm wavelength was demonstrated by using a ReS2-based saturable absorber. The absorber was fabricated with ReS2 by exfoliating mechanically and transferred onto a fiber end. Stable Q-switched laser pulses were observed with the shortest pulse duration of 2.1 μs, the maximum average output power of 2.48 mW, and the pulse with energy up to 38 nJ. Our experimental results suggest that ReS2 is potential for a Q-switcher near 1.55 μm wavelength. 相似文献
417.
An experimental study was conducted to investigate the heat transfer characteristic of a vertical copper plate with rectangular micro-channels. In this research, Cu/R141b nanofluids were used as the working fluid. Three different volume concentrations—0.001, 0.01, and 0.1 %—of Cu nanoparticles with an average diameter of 20 nm dispersed in R141b were prepared. Experiments were performed to measure thermal resistance of the microchannel surface under a steady operating pressure range of 0.86 × 105 Pa to 2 × 105 Pa. Thermal resistance weakened with addition of nanoparticles into the base fluid. The maximum reduction effect of the thermal resistance was 50 %, which corresponds to 0.01 % volume concentration of nanofluid at low operating pressure. The operating pressure significantly affects thermal performance of the microchannel surface. This paper also studied heat transfer characteristics for a Cu nanoparticle-coated surface with rectangular microchannels, which were produced by heating in different volume concentrations from 0.001 to 0.1 %. Nanoparticle layer on the micro-channel surface is responsible for enhanced heat transfer of nanofluids with 0.001 and 0.01 % volume concentrations. 相似文献
418.
Bo Wen Da-Ning Luo Ling-Long Zhang Xiao-Lin Li Xin Wang Liang-Liang Huang Xi Zhang Dong-Feng Diao 《Frontiers of Physics》2023,18(3):33306
Interface engineering in atomically thin transition metal dichalcogenides (TMDs) is becoming an important and powerful technique to alter their properties, enabling new optoelectronic applications and quantum devices. Interface engineering in a monolayer WSe2 sample via introduction of high-density edges of standing structured graphene nanosheets (GNs) is realized. A strong photoluminescence (PL) emission peak from intravalley and intervalley trions at about 750 nm is observed at the room temperature, which indicated the heavily p-type doping of the monolayer WSe2/thin graphene nanosheet-embedded carbon (TGNEC) film heterostructure. We also successfully triggered the emission of biexcitons (excited state biexciton) in a monolayer WSe2, via the electron trapping centers of edge quantum wells of a TGNEC film. The PL emission of a monolayer WSe2/GNEC film is quenched by capturing the photoexcited electrons to reduce the electron-hole recombination rate. This study can be an important benchmark for the extensive understanding of light–matter interaction in TMDs, and their dynamics. 相似文献
419.
Yin-Fang Wei Ho-Hua Chung Cheng-Fu Yang Kai-Huang Chen Chien-Chen Diao Chia-Hsiung Kao 《Journal of Physics and Chemistry of Solids》2008,69(4):934-940
In this study, we will develop the influences of the excess x wt% (x=0, 1, 2, and 3) Bi2O3-doped and the different fabricating process on the sintering and dielectric characteristics of 0.95 (Na0.5Bi0.5)TiO3–0.05 BaTiO3 ferroelectric ceramics with the aid of SEM and X-ray diffraction patterns, and dielectric–temperature curves. The 0.95 (Na0.5Bi0.5)TiO3–0.05 BaTiO3+x wt% Bi2O3 ceramics are fabricated by two different processes. The first process is that (Na0.5Bi0.5)TiO3 composition is calcined at 850 °C and BaTiO3 composition is calcined at 1100 °C, then the calcined (Na0.5Bi0.5)TiO3 and BaTiO3 powders are mixed in according to 0.95 (Na0.5Bi0.5)TiO3–0.05 BaTiO3+x wt% Bi2O3 compositions. The second process is that the raw materials are mixed in accordance to the 0.95 (Na0.5Bi0.5)TiO3–0.05 BaTiO3+x wt% Bi2O3 compositions and then calcining at 900 °C. The sintering process is carried out in air for 2 h from 1120 to 1240 °C. After sintering, the effects of process parameters on the dielectric characteristics will be developed by the dielectric–temperature curves. Dielectric–temperature properties are also investigated at the temperatures of 30–350 °C and at the frequencies of 10 kHz–1 MHz. 相似文献
420.