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41.
Le Ngoc Xuyen Hoang Dang Lanh Ho Si Thoang J. V?lter 《Reaction Kinetics and Catalysis Letters》1989,39(2):293-298
Pt–Ni/-Al2O3 catalysts have been prepared and studied in n-hexane dehydrocyclization. The selectivity for benzene and toluene, a chain lengthening product formation was improved by Ni and correlated with its content.
Pt–Ni/-Al2O3 -. Ni . Ni , .相似文献
42.
Hoang Dang Lanh G. Lietz Ho Si Thoang J. Völter 《Reaction Kinetics and Catalysis Letters》1982,21(4):429-432
The conversion of n-hexane was studied on a Pt-Sn/Al2O3 catalyst, a PtSn alloy and on the corresponding Pt catalysts. The results indicate the same catalytic effect of tin in supported and unsupported catalysts. It is concluded that the role of tin is connected with alloy formation.
- Pt-Sn/Al2O3, PtSn Pt-. . , .相似文献
43.
44.
A highly-efficient preparative procedure for ( R, S )- and ( S, S)-pyrroHdine-2-carboxyHc acid 3,5-dioxa-4-boracyclohepta[2, 1-α ; 3,4-α′] dlnaphthalen-4-yl esters [ namely ( R, S )-BNBAP and (S, S )-BNBAP] is described and the crystal structure of (R, S )-BNBAP was obtained. The data indicate that ( R, S )-BNBAP is a spirocyclic inner borate salt with almost normal te-trahedral configuration. This structural form may be the basic reason for their high chemical, optical and thermodynamic sta-bility. 相似文献
45.
The ever-increasing travel demand has brought great challenges to the organization, operation, and management of the subway system. An accurate estimation of passenger flow distribution can help subway operators design corresponding operation plans and strategies scientifically. Although some literature has studied the problem of passenger flow distribution by analyzing the passengers’ path choice behaviors based on AFC (automated fare collection) data, few studies focus on the passenger flow distribution while considering the passenger–train matching probability, which is the key problem of passenger flow distribution. Specifically, the existing methods have not been applied to practical large-scale subway networks due to the computational complexity. To fill this research gap, this paper analyzes the relationship between passenger travel behavior and train operation in the space and time dimension and formulates the passenger–train matching probability by using multi-source data including AFC, train timetables, and network topology. Then, a reverse derivation method, which can reduce the scale of possible train combinations for passengers, is proposed to improve the computational efficiency. Simultaneously, an estimation method of passenger flow distribution is presented based on the passenger–train matching probability. Finally, two sets of experiments, including an accuracy verification experiment based on synthetic data and a comparison experiment based on real data from the Beijing subway, are conducted to verify the effectiveness of the proposed method. The calculation results show that the proposed method has a good accuracy and computational efficiency for a large-scale subway network. 相似文献
46.
47.
质子化双氧/硫杂卟啉内氢原子迁移反应的理论研究 总被引:1,自引:0,他引:1
在确定各反应体系反应物、产物稳定构象的基础上, 采用B3LYP/6-31G**方法在Gaussian 03程序下, 对质子化的双氧/硫杂卟啉的内氢迁移(IHAT)反应进行研究, 寻找并优化相应的过渡态, 比较其迁移反应速率的差异. 计算结果表明, 质子化双氧/硫杂卟啉的构象稳定性仍然是由芳香性、空间位阻、静电作用共同决定的. 质子化后的双取代体系的内氢迁移反应速率大小差异显著, 内环取代对IHAT反应速率的影响主要来源于电子效应, 而非构象变化; 且双取代对体系IHAT反应速率的影响要远大于单取代. 相似文献
48.
He Liu Mengnan An Hongyang Si Yuhang Shan Chuantao Xu Gang Hu Yunbo Xie Dongyang Liu Shujun Li Rui Qiu Chong Zhang Yuanhua Wu 《Molecules (Basel, Switzerland)》2022,27(17)
As an important microbial resource, Actinomycetes, especially Streptomyces, have important application values in medicine and biotechnology. Streptomyces fungicidicus SYH3 was isolated from soil samples in tomato-growing areas and showed good inhibitory effects on Alternaria solani in tomato. To obtain pure active compounds, SYH3 fermentation broth was subjected to XAD-16 macroporous resin and silica gel column chromatography. Combined with the repeated preparation and separation of preparative high-performance liquid chromatography (HPLC), a total of four monomer compounds were obtained after activity tracking. Compound 4 was identified as a new six-membered lactone ring compound named 6-(5-hydroxy-6-methylheptyl)-5,6-dihydro-2H-pyran-2-one by 1D and 2D nuclear magnetic resonance (NMR) data and mass spectrometry (MS). The other three active compounds belong to the cyclodipeptide, and their half maximal inhibitory concentration (IC50) values against A. solani were 43.4, 42.9, and 30.6 μg/mL, respectively. Compound 4 significantly inhibited the spore germination and induced swollen and deformed local hyphae of A. solani with an IC50 value of 24.9 μg/mL. Compound 4 also had broad-spectrum antifungal activity and had a good antifungal effect on the tested plant-pathogenic fungi. The modes of action of new compound (4) still require further investigation, representing a novel and effective anti-fungal agent for future application. 相似文献
49.
Wei Ge Chao Liu Yatao Xu Jiayao Zhang Weili Si Wenjun Wang Changjin Ou Xiaochen Dong 《Chemical science》2022,13(32):9401
Organic charge-transfer complexes (CTCs) can function as versatile second near-infrared (NIR-II) theranostic platforms to tackle complicated solid tumors, while the structure–property relationship is still an unanswered problem. To uncover the effect of molecular stacking modes on photophysical and biochemical properties, herein, five ferrocene derivatives were synthesized as electron donors and co-assembled with electron-deficient F4TCNQ to form the corresponding CTCs. The crystalline and photophysical results showed that only herringbone-aligned CTCs (named anion-radical salts, ARS NPs) possess good NIR-II absorption ability and a photothermal effect for short π–π distances (<3.24 Å) and strong π-electron delocalization in the 1D F4TCNQ anion chain. More importantly, the ARS NPs simultaneously possess ·OH generation and thiol (Cys, GSH) depletion abilities to perturb cellular redox homeostasis for ROS/LPO accumulation and enhanced ferroptosis. In vitro experiments, FcNEt-F4 NPs, and typical ARS NPs, show outstanding antitumor efficiency for the synergistic effect of NIR-II photothermal therapy and ferroptosis, which provides a new paradigm to develop versatile CTCs for anti-tumor application.Based on crystal engineering of charge transfer complexes (CTCs), ferrocene-based CTCs, with Fenton-catalyzing, biothiol-responsive and NIR-II photothermal abilities, were controllably developed and the structure–property relationship was revealed. 相似文献
50.
Qinghui He Congcong Si Zhenjiao Sun Yuhui Chen Xin Zhang 《Molecules (Basel, Switzerland)》2022,27(12)
The imbalance of intestinal microbiota can cause the accumulation of endotoxin in the main circulation system of the human body, which has a great impact on human health. Increased work and life pressure have led to a rise in the number of people falling into depression, which has also reduced their quality of life. The gut–brain axis (GBA) is closely related to the pathological basis of depression, and intestinal microbiota can improve depressive symptoms through GBA. Previous studies have proven that prebiotics can modulate intestinal microbiota and thus participate in human health regulation. We reviewed the regulatory mechanism of intestinal microbiota on depression through GBA, and discussed the effects of prebiotics, including plant polysaccharides and polyphenols on the regulation of intestinal microbiota, providing new clues for the prevention and treatment of depression. 相似文献