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101.
The paper studies a codimension-4 resonant homoclinic bifurcation with one orbit flip and two inclination flips, where the resonance takes place in the tangent direction of homoclinic orbit.Local active coordinate system is introduced to construct the Poincar′e returning map, and also the associated successor functions. We prove the existence of the saddle-node bifurcation, the perioddoubling bifurcation and the homoclinic-doubling bifurcation, and also locate the corresponding 1-periodic orbit, 1-homoclinic orbit, double periodic orbits and some 2n-homoclinic orbits. 相似文献
102.
本文考虑无穷维自回归过程经验协方差函数的中偏差原理,仅对自回归过程的随机扰动项做了高斯可积性的假设,这个条件比[4]中的对数Sobolev不等式要弱很多.主要利用了m-相依随机变量的中偏差结果和Ellis-Grtner定理,推广了[6]的结果. 相似文献
103.
104.
研究了1-和2-苯基萘, 1, 1'-和2, 2'-联萘, 2, 2-二羟基-, 2, 2'-二甲氧基和-2, 2'-甲基磺酰氧基-1, 1'-联萘等七种萘衍生物和三氧化硫的磺化反应。1-苯基萘和1, 1'-联萘的磺化先发生在4位上, 第二取代位置为6和7位。2-苯基萘和2, 2'-联萘均首先得到8位磺酸取代物, 进一步磺化得到8, 4'-和8, 8'-二磺酸取代物。2, 2'-二甲氧基-1, 1'-联萘以13:87的比例得到3位和6位磺酸取代物。2, 2'-二甲磺酰氧基-1, 1'-联萘以58:42的比例得到5位和6位磺酸取代物。2, 2'-二羟基-1, 1'-联萘的等摩尔磺化得到比例为35:65的5位和6位磺酸取代物, 和大于6摩尔的SO~3反应则以62:38的比例得到5位和6位磺酸取代物。 相似文献
105.
Solution‐Liquid‐Solid Synthesis of Hexagonal Nickel Selenide Nanowire Arrays with a Nonmetal Catalyst 下载免费PDF全文
Dr. Kun Xu Hui Ding Kaicheng Jia Xiuli Lu Pengzuo Chen Tianpei Zhou Han Cheng Si Liu Prof. Changzheng Wu Prof. Yi Xie 《Angewandte Chemie (International ed. in English)》2016,55(5):1710-1713
Inorganic nanowire arrays hold great promise for next‐generation energy storage and conversion devices. Understanding the growth mechanism of nanowire arrays is of considerable interest for expanding the range of applications. Herein, we report the solution‐liquid‐solid (SLS) synthesis of hexagonal nickel selenide nanowires by using a nonmetal molecular crystal (selenium) as catalyst, which successfully brings SLS into the realm of conventional low‐temperature solution synthesis. As a proof‐of‐concept application, the NiSe nanowire array was used as a catalyst for electrochemical water oxidation. This approach offers a new possibility to design arrays of inorganic nanowires. 相似文献
106.
Dry Reforming of Methane on a Highly‐Active Ni‐CeO2 Catalyst: Effects of Metal‐Support Interactions on C−H Bond Breaking 下载免费PDF全文
B. Sc. Zongyuan Liu Dr. David C. Grinter Dr. Pablo G. Lustemberg Dr. Thuy‐Duong Nguyen‐Phan Dr. Yinghui Zhou B. Sc. Si Luo Dr. Iradwikanari Waluyo Dr. Ethan J. Crumlin Dr. Dario J. Stacchiola Prof. Jing Zhou Dr. Javier Carrasco Prof. H. Fabio Busnengo Dr. M. Verónica Ganduglia‐Pirovano Dr. Sanjaya D. Senanayake Prof. José A. Rodriguez 《Angewandte Chemie (International ed. in English)》2016,55(26):7455-7459
Ni‐CeO2 is a highly efficient, stable and non‐expensive catalyst for methane dry reforming at relative low temperatures (700 K). The active phase of the catalyst consists of small nanoparticles of nickel dispersed on partially reduced ceria. Experiments of ambient pressure XPS indicate that methane dissociates on Ni/CeO2 at temperatures as low as 300 K, generating CHx and COx species on the surface of the catalyst. Strong metal–support interactions activate Ni for the dissociation of methane. The results of density‐functional calculations show a drop in the effective barrier for methane activation from 0.9 eV on Ni(111) to only 0.15 eV on Ni/CeO2?x(111). At 700 K, under methane dry reforming conditions, no signals for adsorbed CHx or C species are detected in the C 1s XPS region. The reforming of methane proceeds in a clean and efficient way. 相似文献
107.
Dongdong Li Prof. Dr. Chaoren Shen Zhiyao Si Prof. Dr. Lu Liu 《Angewandte Chemie (International ed. in English)》2023,62(42):e202310283
An unprecedented Pd-catalyzed fluorinative bifunctionalization of aziridines and azetidines was successfully developed via regioselective C−C and C−F bond cleavage of gem-difluorocyclopropanes, leading to various β,β′-bisfluorinated amines and β,γ-bisfluorinated amines. This reaction was achieved by incorporating a 2-fluorinated allyl group and a fluorine atom scissored from gem-difluorocyclopropane in 100 % atom economy for the first time. The mechanistic investigations indicated that the reaction underwent amine attacking 2-fluorinated allyl palladium complex to generate η2-coordinated N-allyl aziridine followed by fluoride ligand transfer affording the final β- and γ-fluorinated amines. 相似文献
108.
109.
气凝胶纤维因其高外表面积和高柔韧性在能量管理系统中具有潜在应用而引起了广泛关注.但是,目前制备的气凝胶纤维力学强度较低,限制了其实际应用.为提高气凝胶纤维力学性能,在始终保持细菌纤维素(BC)纳米纤维处于湿态下,利用NaOH/尿素/硫脲复合溶剂直接低温溶解原生BC,获得透明的BC纺丝原液;通过湿法纺丝制备了BC水凝胶纤维,经过水洗和冷冻干燥后处理,制得BC气凝胶纤维.采用偏光显微镜(POM)、13C核磁共振(13C-NMR)和高级旋转流变仪研究BC在复合溶剂中的溶解过程与状态;利用全反射傅里叶变换红外吸收光谱(ATR-FTIR)、X射线衍射(XRD)和热失重(TG)研究BC溶解前后结构与性能变化;利用场发射扫描电镜(FESEM)、全自动比表面积和孔径分布分析仪、单丝强力仪对获得的BC气凝胶纤维结构与性能进行表征.结果表明,复合溶剂在?15℃条件下可以直接溶解原生湿态BC,最高溶解浓度为3 wt%;采用湿法纺丝制得高度多孔的连续BC气凝胶纤维,比表面积高达192 m^2/g且具有优异的力学性能,断裂强度和杨氏模量高达(9.36±1.68)MPa和(176±17.55)MPa,如0.4 mg BC气凝胶纤维可以支撑高于其本身质量5×10^4倍的重物. 相似文献
110.
Huiping Liu Huijuan Wang Aijun Dong Xiaoshuang Huo Huaxiang Wang Junchi Wang Jianyong Si 《Molecules (Basel, Switzerland)》2022,27(9)
Gastric cancer is considered to be one of the most common causes of cancer death worldwide due to its high recurrence and metastasis rates. The molecule 23,24-Dihydrocucurbitacin E (DHCE) is a cucurbitacin-derived tetracyclic triterpenoid compound that has anti-tumor activity, but the exact mechanism remains to be elucidated. This research aimed to explore the effects of DHCE on human gastric cancer cells and the possible mechanisms. The results showed that DHCE suppressed proliferation, migration, and invasion of gastric cancer cells, as well as induced apoptosis and G2/M phase arrest. Mechanistically, the potential targets and pathways of DHCE were predicted using database screening and verified using a molecular docking study, fluorescence staining, and Western blot. The results indicated that DHCE obviously inhibited the kinase activity of ERK2 via targeting its ATP-binding domain, destroyed F-actin microfilament, and reduced the expression levels of Ras, p-c-Raf, ERK, p-ERK, and MMP9 proteins. Collectively, our study demonstrated that DHCE suppressed gastric cancer cells’ proliferation, migration, and invasion through targeting ERK2 and disrupting the Ras/Raf/ERK/MMP9 signaling pathway. These properties make DHCE a promising candidate drug for the further design and development of novel and effective Ras/Raf/ERK/MMP9 pathway inhibitors for treating gastric cancer. 相似文献