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171.
Chen Miaomiao Li Weiming Xiong Huayu Wen Wei Zhang Xiuhua Wang Shengfu 《Mikrochimica acta》2017,184(9):3317-3324
Microchimica Acta - The authors describe a rapid method for the determination of 11 β 2-agonists by exploiting the color changes and fluorescence intensity changes of copper nanoclusters... 相似文献
172.
Let and denote the maximum degree and the Laplacian spectral radius of a tree , respectively. In this paper we prove that for two trees and on vertices, if and , then , and the bound “” is the best possible. We also prove that for two trees and on vertices with perfect matchings, if and , then . 相似文献
173.
174.
A phase-type geometric process repair model with spare device procurement and repairman’s multiple vacations 总被引:1,自引:0,他引:1
This paper analyzes a phase-type geometric process repair model with spare device procurement lead time and repairman’s multiple vacations. The repairman may mean here the human beings who are used to repair the failed device. When the device functions smoothly, the repairman leaves the system for a vacation, the duration of which is an exponentially distributed random variable. In vacation period, the repairman can perform other secondary jobs to make some extra profits for the system. The lifetimes and the repair times of the device are governed by phase-type distributions (PH distributions), and the condition of device following repair is not “as good as new”. After a prefixed number of repairs, the device is replaced by a new and identical one. The spare device for replacement is available only by an order and the procurement lead time for delivering the spare device also follows a PH distribution. Under these assumptions, the vector-valued Markov process governing the system is constructed, and several important performance measures are studied in transient and stationary regimes. Furthermore, employing the standard results in renewal reward process, the explicit expression of the long-run average profit rate for the system is derived. Meanwhile, the optimal maintenance policy is also numerically determined. 相似文献
175.
Maozhu Liu Mengyuan Chen Ying Luo Hong Wang Haifeng Huang Zhe Peng Miaomiao Li Huizhi Fei Wen Luo Junqing Yang 《Molecules (Basel, Switzerland)》2021,26(14)
Celastrol, a pentacyclic triterpene isolated from the traditional Chinese medicine Tripterygium wilfordii Hook. F., exhibits effectiveness in protection against multiple central nervous system (CNS) diseases such as cerebral ischemia, but its influence on lipidomics still remains unclear. Therefore, in the present study, the efficacy and potential mechanism of celastrol against cerebral ischemia/reperfusion (I/R) injury were investigated based on lipidomics. Middle cerebral artery occlusion (MCAO) followed by reperfusion was operated in mice to set up a cerebral I/R model. TTC staining and TUNEL staining were used to evaluate the therapeutic effect of celastrol. Ultra-performance liquid chromatography-tandem mass spectrometry (UPLC/MS) was employed for lipidomics analysis in ipsilateral hemisphere and plasma. Celastrol remarkably reduced cerebral infarct volume and apoptosis positive cells in tMCAO mice. Furthermore, lipidomics analysis showed that 14 common differentially expressed lipids (DELs) were identified in brain and five common DELs were identified in plasma between the Sham, tMCAO and Celastrol-treated tMCAO groups. Through enrichment analysis, sphingolipid metabolism and glycerophospholipid metabolism were demonstrated to be significantly enriched in all the comparison groups. Among the DELs, celastrol could reverse cerebral I/R injury-induced alteration of phosphatidylcholine, phosphatidylethanolamine and sulfatide, which may be responsible for the neuroprotective effect of celastrol. Our findings suggested the neuroprotection of celastrol on cerebral I/R injury may be partially associated with its regulation of lipid metabolism. 相似文献
176.
Xia Zhao Bo Yang Aoqi Wei Jianqiao Sheng Miaomiao Tian Quan Li Kui Lu 《Tetrahedron letters》2018,59(18):1719-1722
Herein, we describe the preparation of trifluoromethylthiol-substituted oxindoles by silver-mediated aryltrifluoromethylthiolation of activated alkenes, using S-trifluoromethyl 4-methylbenzenesulfonothioate as a F3CS radical source and showing that the reagent availability, mild conditions, and broad functional group compatibility of this transformation make it a viable alternative strategy of constructing Csp3SCF3 bonds. 相似文献
177.
Three cationic trisiloxane surfactants, 1-methyl-1-[bis(trimethylsiloxy)methyl]silyl-propylpyrrolidinium chloride (Si3pyCl), 1-methyl-1-[bis(triethylsiloxy)methyl]silyl-propylpyrrolidinium chloride (Et-Si3pyCl), and 1-methyl-1-[bis(vinyldimethylsiloxy)methyl]silylpropylpyrrolidinium chloride (Vi-Si3pyCl) were synthesized. The aggregation behavior of the trisiloxane surfactants with different siloxane hydrophobic groups in aqueous solution was investigated by surface tension and electrical conductivity measurements. The structures of hydrophobic groups of the trisiloxane surfactants can obviously influence their surface activities and thermodynamics. All the three cationic trisiloxane surfactants have excellent surface activity. Owing to the steric hindrance of hydrophobic groups, the CMC values increase following the order Et-Si3PyCl?<?Vi-Si3PyCl?<?Si3PyCl. The \(\Delta G_{\text{m}}^{\text{o}}\) values increase in the order Et-Si3PyCl?>?Vi-Si3PyCl?>?Si3PyCl, attributed to the decrease in the hydrophobic effect. The micellization processes of these surfactants are entropy-driven. 相似文献
178.
Shuaishuai Feng Chengtai Yan Tianhao Zhang Miaomiao Ji Ru Tao Hua Gao 《Molecules (Basel, Switzerland)》2021,26(6)
Aromatic volatile compounds are important contributors to fruit quality that vary among different cultivars. Herein, headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry was used to determine changes in volatile compounds and related gene expression patterns in “Ruixue” and “Fuji” apples (Malus domestica Borkh.) during fruit development and maturation. Volatile compounds detected in the fruit of both cultivars exhibited similar trends across different developmental stages. In the early stages of “Ruixue” fruit development (60 days after full bloom), there were fewer volatile compounds, mainly aldehydes (87.0%). During fruit maturation (180 days after full bloom), the types and amounts of volatile compounds increased, mainly including esters (37.6%), and alkenes (23.2%). The total volatile concentration, the types of major volatile compounds, and their relative content in both cultivars varied across different stages. Gene expression analysis indicated that the upregulation of MdLOX, MdAAT2, and MdADH3 was associated with increased aroma compound content, especially esters, during fruit development in both cultivars. Changes in the expression of MdArAT, MdACPD, MdADH3, MdAAT2, and MdLOX may lead to differences in volatile compounds between apple cultivars. 相似文献
179.
CHEN Zhixiao QIAN Miaomiao LIU Chang XUE Beichen YU Liyun ZHU Yanchao WANG Xiaofeng 《高等学校化学研究》2021,37(3):757-762
Rice husk ash(RHA), obtained by pyrolysis of rice husks, can be used as a potential reinforcing filler for rubber composites. In this work, ball milling in ethanol(ethanol-assisted milling) was used to hydroxylate the surface of RHA, promoting the graft modification of bis-(γ-triethoxysilylpropyl)-tetrasulfide(Si69). The obtained modified RHA(RHA-EM-Si69) was filled into the natural rubber/butadiene rubber(NR/BR) composites, and the filler-rubber interactions were enhanced. In consequence, RHA-EM-Si69 filled NR/BR composites showed overall improvement in the mechanical properties compared with RHA filled NR/BR composites. The tear strength increased from 13.37 kN/m to 34.71 kN/m, and the tensile strength increased from 1.84 MPa to 7.75 MPa. Carbon black(N774) was also used for comparison under the same conditions. This method provides a potential for promoting the value of RHA in rubber industry. 相似文献
180.
Zhang Zhijun Zhang Haoke Kang Miaomiao Li Na Wang Dong Tang Ben Zhong 《中国科学:化学(英文版)》2021,64(11):1990-1998
Science China Chemistry - Dendrimers, as the latest generation of artificial macromolecules, have aroused great attention in the field of clusteroluminescence owing to their unique structural and... 相似文献