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111.
Dongsheng Xue Mengmeng Xu Chaoying Zheng Baochao Yang Min Hou Haibing He Shuanhu Gao 《中国化学》2019,37(2):135-139
A titanium‐promoted intramolecular photoenolization/Diels–Alder (PEDA) reaction was developed to construct the core skeleton of aromatic polycyclic terpenoids bearing an all‐carbon quaternary center on the benzylic position. Titanium(IV) isopropoxide [Ti(Oi‐Pr)4] plays a key role during the photo cycloaddition, which may help to accelerate the interaction between dienophile and the stereo‐hindered diene species as well as control the diastereoselectivity. This photolysis provides a new solution for the stereospecific formation core structures of aromatic abietane diterpenoids and sesquiterpenoids, which have multiple functional groups for the further transformations. As a synthetic application, it was successfully used in the synthesis of indolosesquiterpenoid mycoleptodiscin A. 相似文献
112.
建立了气相色谱-串联质谱(GC-MS/MS)检测肉制品中10种挥发性N-亚硝胺类化合物残留量的方法。肉制品样品经同时蒸馏萃取法(SDE)萃取,采用冷冻去脂净化法,在多反应监测模式下分析,外标法定量。结果表明,采用优化后的条件,10种挥发性N-亚硝胺类化合物在1.00~1000 μg/L范围内线性关系良好,相关系数均在0.99以上。方法的检出限(LOD,S/N=3)和定量限(LOQ,S/N=10)分别为0.01~0.02 μg/kg和0.04~0.07 μg/kg。选取3种不同类型的肉制品(火腿肠、中式香肠和腌渍腊肉),在空白样品添加水平为LOQ水平、1.0、2.0 μg/kg时,10种挥发性N-亚硝胺类化合物的平均回收率为74.8%~94.3%,相对标准偏差小于8.3%。市售3类肉制品中6种挥发性N-亚硝胺类化合物(N-亚硝基二甲胺、N-亚硝基二乙胺、N-亚硝基吡咯烷、N-亚硝基哌啶、N-亚硝基二丁胺、N-亚硝基二丙胺)均有不同程度检出,且腌渍腊肉中每种挥发性N-亚硝胺类化合物的检出值最高。该方法操作简单,萃取充分,灵敏度高,试剂用量少,可满足实验室大量样品的日常检测需求。 相似文献
113.
Longlin Zhang Mengmeng Ma Zhengyi Li Haihan Zhang Xi He Zehe Song 《Molecules (Basel, Switzerland)》2021,26(22)
L-theanine is a nonprotein amino acid found in tea leaves and has been widely used as a safe food additive in beverages or foods because of its varied bioactivities. The aim of this study was to reveal the in vitro gastrointestinal protective effects of L-theanine in DSS-induced intestinal porcine enterocyte (IPEC-J2) cell models using molecular and metabolic methods. Results showed that 2.5% dextran sulfate sodium (DSS) treatment inhibited the cell proliferation of IPEC-J2 and blocked the normal operation of the cell cycle, while L-theanine pretreatment significantly preserved these trends to exert protective effects. L-theanine pre-treatment also up-regulated the EGF, CDC2, FGF2, Rb genes and down-regulated p53, p21 proliferation-related mRNA expression in DSS-treated cells, in accompany with p53 signaling pathway inhibition. Meanwhile, metabolomics analysis revealed that L-theanine and DSS treated IPEC-J2 cells have different metabolomic profiles, with significant changes in the key metabolites involved in pyrimidine metabolism and amino acid metabolism, which play an important role in nucleotide metabolism. In summary, L-theanine has a beneficial protection in DSS-induced IPEC-J2 cells via promoting proliferation and regulating metabolism disorders. 相似文献
114.
Yanqiang Hu Yansu Shan Zhaolei Yu Haojie Sui Ting Qiu Shufang Zhang Wei Ruan Qinfeng Xu Mengmeng Jiao Dehua Wang Yunyi Wu Chuanlu Yang Feng Xu 《Journal of Energy Chemistry》2022,(1):561-567
The stability issue has become one of the main challenges for the commercialization of perovskite solar cells(PSCs).Formamidinium(FA)-based perovskites have shown great promise owing to their improved thermal and moisture stability.However,these perovskites are suffering from phase transition and separation.Here,a method of incorporating of γ-aminobutyric acid(GABA) and cesium cations into FAPbl3 is developed to improve the phase stability.It is demonstrated that the crystallinity of α-FAPbl3 phase is greatly improved and the phase transition temperature is significantly dropped.The resultant solar cell therefore obtains a champion power conversion efficiency(PCE) of 23.71%,which is one of the highest efficiencies for methylammonium-free PSCs.Furthermore,it shows an impressively enhanced stability under illumination,exhibiting the great potential of FA-based perovskites for efficient and stable solar cells. 相似文献
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Aluminum nitride (AlN) films with h〈100〉 crystalline orientation are fabricated on p-Si (100) substrates at room tempera- ture by pulsed laser deposition. The effects of laser energy density and annealing on the quality of the films are studied by x-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy. The crystalline quality of AlN films is improved considerably by increasing the laser energy density while there is increased number of farraginous particles on the surface. The annealing treatment at 600~C produces a recrystallization process in the film, characterized by the improvement of the original crystallinity, the appearance of new crystalline orientations, and the increase of the crystallites. The surface becomes rougher due to the increase of the grain size during annealing. 相似文献
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119.
Nanospheres: Full Color Emission in ZnGa2O4: Simultaneous Control of the Spherical Morphology,Luminescent, and Electric Properties via Hydrothermal Approach (Adv. Funct. Mater. 42/2014)
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120.
Yunhui Yang Mengmeng Guo Minghui Yang Zhijie Wang Ruqin Yu 《International journal of environmental analytical chemistry》2013,93(3):163-175
An amperometric pesticides inhibition biosensor has been developed and used for determination of pesticides in vegetable samples. To eliminate the interference of ascorbic acid, multilayer films of polyelectrolyte (chitosan/polystyrensulfonate) were coated on the glass carbon electrode. Then, acetylcholinesterase was immobilized on the electrode based on surface-treated nanoporous ZrO2/chitosan composite film as immobilization matrix. As a modified substrate, acetylthiocholine was hydrolysed by acetylcholinesterase and produced thiocholine which can be oxidized at +700?mV vs. SCE. Pesticides inhibit the activity of enzyme with an effect of decreasing of oxidation current. The experimental conditions were optimized. The electrode has a linear response to acetylthiocholine within 9.90?×?10?6 to 2.03?×?10?3?M. The electrode provided a linear response over a concentration range of 6.6?×?10?6 to 4.4?×?10?4?M for phoxim with a detection limit of 1.3?×?10?6?M, over a range of 1.0?×?10?8 to 5.9?×?10?7?M for malathion, and over a range of 8.6?×?10?6 to 5.2?×?10?4?M for dimethoate. This biosensor has been used to determine pesticides in a real vegetable sample. 相似文献