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排序方式: 共有1858条查询结果,搜索用时 31 毫秒
81.
Chung Sub Kim Oh Wook Kwon Sun Yeou Kim Sang Un Choi Ki Hyun Kim Kang Ro Lee 《Lipids》2014,49(11):1151-1159
In the course of our continuing search for bioactive constituents of Korean medicinal plants, we isolated five new oxylipins, chaenomic acid A–E ( 1 – 5 ), and six known ones ( 6 – 11 ) from the twigs of Chaenomeles sinensis. The structures of the new compounds ( 1 – 5 ) were determined by spectroscopic methods, including 1D and 2D NMR (1H and 13C NMR, 1H–1H COSY, HMQC, HMBC, and NOESY), olefin cross‐metathesis, and LC/MS analysis. The known compounds ( 6 – 11 ) were identified by comparison of their spectroscopic data and specific optical rotation with the reported data. The isolated compounds ( 1 – 11 ) were tested for their inhibitory effects on nitric oxide production in lipopolysaccharide‐activated murine microglial cells and for their cytotoxic activities against four human cancer cell lines (A549, SK‐OV‐3, A498, and HCT‐15). 相似文献
82.
This paper presents an approach for modeling with one single kinetic mechanism the chemistry of the autoignition and combustion processes inside an internal combustion engine, as well as the chemical kinetics governing the postoxidation of unburned hydrocarbons in engine exhaust gases. Therefore a new kinetic model was developed, valid over a wide range of temperatures including the negative temperature coefficient regime. The model simulates the autoignition and the oxidation of engine surrogate fuels composed of n-heptane, iso-octane, and toluene, which are sensitized by the presence of nitric oxides. The new model was obtained from previously published mechanisms for the oxidation of alkanes and toluene where the coupling reactions describing interactions between hydrocarbons and NOx were added. The mechanism was validated against a wide range of experimental data obtained in jet-stirred reactors, rapid compression machines, shock tubes, and homogeneous charge compression ignition engines. Flow rate and sensitivity analysis were performed in order to explain the low temperature chemical kinetics, especially the impact of NOx on hydrocarbon oxidation. 相似文献
83.
High activity and wide temperature window of Fe‐Cu‐SSZ‐13 in the selective catalytic reduction of NO with ammonia
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Jian Liu Daxi Wang Zhen Zhao Kai Cheng Junhua Li 《American Institute of Chemical Engineers》2015,61(11):3825-3837
Fe‐Cu‐SSZ‐13 catalysts were prepared by aqueous solution ion‐exchange method based on the one‐pot synthesized Cu‐SSZ‐13. The catalysts were applied to the selective catalytic reduction (SCR) of NO with NH3 and characterized by the means of XRD, UV‐Vis, EPR, XPS, NH3‐TPD, and so on. The selected Fe‐Cu‐SSZ‐13‐1 catalyst exhibited the high NO conversion (>90%) in the wide temperature range (225–625°C), which also showed good N2 selectivity and excellent hydrothermal stability. The results of XPS showed that the Cu and Fe species were in the internal and outer parts of the SSZ‐13 crystals, respectively. The results of UV‐Vis and EPR indicated that the monomeric Cu2+ ions coordinated to three oxygen atoms on the six‐ring sites and Fe monomers are the real active species in the NH3‐SCR reaction. Furthermore, the influence of intracrystalline mass‐transfer limitations on the Fe‐Cu‐SSZ‐13 catalysts is related to the location of active species in the SSZ‐13 crystals. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3825–3837, 2015 相似文献
84.
为了考察硫磺/石灰石自养反硝化系统的脱氮性能,并探究系统N_2O的产生和排放规律,采用均匀填充的上流式硫磺/石灰石生物滤池反应器,研究了2组HRT下,不同进水NO_3~--N浓度对系统脱氮效果的影响及N_2O的排放规律。结果表明,进水NO_3~--N浓度为(54.46±1.15)mg/L、HRT为2.5 h时,反应器容积负荷最大且对NO_3~--N去除率最高,可达99.93%,系统无NO_2~--N累积,出水N_2O低于0.86 mg/L;另外,研究发现NO_3~--N浓度随反应器高度增加而逐渐降低,N_2O浓度随着反应器下部NO_2~--N的富集逐渐增加,并随上部NO_2~--N的还原而逐渐减小;进水NO_3~--N浓度增大,N_2O累积量峰值点沿反应器高度逐渐上移,因此该系统仅能处理较低浓度NO_3~--N废水。 相似文献
85.
MnOx-Fe3O4 nanomaterials were fabricated by using the innovative scheme of pyrolyzing manganese-doped iron-based metal organic framework in inert atmosphere and exhibited extraordinary performance of NO reduction by CO (CO-SCR). Multi-technology characterizations were conducted to ascertain the properties of fabricated materials (e.g., TGA, XRD, SEM, FT-IR, XPS, BET, H2-TPR and O2-TPD). Moreover, the interaction between reactants and catalysts was ascertained by in situ FT-IR. Experimental results demonstrated that Mn was an ideal promoter for iron oxides, resulting in decrease of crystallite size, improve reducibility property, enhance the mobility and the amount of lattice O2- species, as well as strength the adsorption ability of active NO and CO to form multiple species (e.g., nitrate and carbonate). The unprecedented enhancement of CO-SCR activity over Mn-Fe nanomaterials follows the Eley-Rideal (E-R) and Langmuir-Hinshelwood (L-H) reaction pathway. 相似文献
86.
为评估差分吸收二氧化氮激光雷达中激光器的稳定性对反演浓度的影响,以NO_2的吸收谱和激光雷达方程为基础,分析了波长漂移和能量波动对距离分辨差分吸收激光雷达浓度反演带来的相对误差。采用两台Nd:YAG激光器的354.7nm波长分别泵浦两台染料激光器的方式,产生差分吸收探测所需的两个波长λon(448.10nm)和λoff(446.80nm),搭建探测大气NO_2实验系统,并就波长漂移和能量波动对NO_2浓度反演影响进行了实验验证。实验结果表明:在没有稳频条件下,当λon和λoff波长漂移≤0.005nm时,引起的浓度相对误差为≤3%;能量波动对反演浓度没有影响,但能量降低减小探测距离,当能量下降≤5%时,探测距离≤100m,实验结果与理论计算基本一致。最后,开展了大气NO_2浓度实验观测,获得实验期间水平及垂直高度0.5~3km内NO_2浓度的分布廓线,系统稳定可靠。本方法为实用化NO_2差分吸收激光雷达的设计及应用提供了理论依据及技术支持。 相似文献
87.
88.
Mikhail V. Samsonov Nikita V. Podkuychenko Asker Y. Khapchaev Eugene E. Efremov Elena V. Yanushevskaya Tatiana N. Vlasik Vadim Z. Lankin Iurii S. Stafeev Maxim V. Skulachev Marina V. Shestakova Alexander V. Vorotnikov Vladimir P. Shirinsky 《International journal of molecular sciences》2022,23(1)
Hyperlipidemia manifested by high blood levels of free fatty acids (FFA) and lipoprotein triglycerides is critical for the progression of type 2 diabetes (T2D) and its cardiovascular complications via vascular endothelial dysfunction. However, attempts to assess high FFA effects in endothelial culture often result in early cell apoptosis that poorly recapitulates a much slower pace of vascular deterioration in vivo and does not provide for the longer-term studies of endothelial lipotoxicity in vitro. Here, we report that palmitate (PA), a typical FFA, does not impair, by itself, endothelial barrier and insulin signaling in human umbilical vein endothelial cells (HUVEC), but increases NO release, reactive oxygen species (ROS) generation, and protein labeling by malondialdehyde (MDA) hallmarking oxidative stress and increased lipid peroxidation. This PA-induced stress eventually resulted in the loss of cell viability coincident with loss of insulin signaling. Supplementation with 5-aminoimidazole-4-carboxamide-riboside (AICAR) increased endothelial AMP-activated protein kinase (AMPK) activity, supported insulin signaling, and prevented the PA-induced increases in NO, ROS, and MDA, thus allowing to maintain HUVEC viability and barrier, and providing the means to study the long-term effects of high FFA levels in endothelial cultures. An upgraded cell-based model reproduces FFA-induced insulin resistance by demonstrating decreased NO production by vascular endothelium. 相似文献
89.
多壁碳纳米管的PEI修饰及NO吸附性能研究 总被引:1,自引:0,他引:1
采用CVD法以SBA-16为模板、以Fe为催化剂合成多壁碳纳米管,并对多壁碳纳米管进行羧基化,羧基化后的多壁碳纳米管分别与直链和支链结构的聚乙烯亚胺(PEI)作用.SEM、TEM及IR结果表明,羧基化后的多壁碳纳米管与PEI作用后,多壁碳纳米管表面具有酰氨基和吸附态的PEI.Ram an和XRD研究表明,PEI修饰后的多壁碳纳米管的结构并未改变.采用TG-MS对PEI修饰前后的碳纳米管进行的等温NO吸附-脱附实验表明,经支链PEI修饰的多壁碳纳米管,其NO选择性、吸附能力和吸附量较直链PEI修饰和纯化的多壁碳纳米管明显提高. 相似文献
90.
Since the discovery of perovskite-type oxides ascombustion catalysts in the 1970’s, a number of effortshave been devoted to extending this material by varyingit’s A or B site composition to synthesize the cata-lysts[1 -2]. Several preparation techniques, such asthermal decomposition of cyanide, hydroxides, metal-EDTA and the hydrothermal synthesis method, havebeen employed. Among them sol-gel method has manyadvantages such as a lower synthesis temperature andeasily doping etc[3]. At presen… 相似文献