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排序方式: 共有140条查询结果,搜索用时 15 毫秒
91.
Qiulin Zhang Qixian Liu Ping Ning Xin Liu Lisi Xu Zhongxian Song Yankang Duan Tengfei Zhang 《Research on Chemical Intermediates》2017,43(4):2017-2032
Manganese oxide octahedral molecular sieves (OMS-2) synthesized from hydrothermal (H-OMS-2), reflux (R-OMS-2), co-precipitation (C-OMS-2), and solid phase (S-OMS-2) methods were impregnated with palladium and used for CO catalytic oxidation. Preparation methods presented an obvious effect on the morphology and catalytic activity of Pd/OMS-2 catalysts for CO oxidation. The hydrothermal synthesized OMS-2 (Pd/H-OMS-2) exhibited more ordered nanorod structure and higher crystallinity than Pd/R-OMS-2, Pd/C-OMS-2, and Pd/S-OMS-2. Further surface analysis indicated that different preparation methods of synthesizing OMS-2 and the impregnation process followed have a significant effect on the chemical states of Mn and O over the final Pd/OMS-2 products. The kinetics studies showed the trend of apparent activation energy (E a) over different catalysts: Pd/H-OMS-2 (18.19 kJ/mol) < Pd/R-OMS-2 (21.56 kJ/mol) < Pd/C-OMS-2 (22.57 kJ/mol) < Pd/S-OMS-2 (29.44 kJ/mol). Over 99 % of the CO conversion was obtained at 35 °C by the optimal Pd/H-OMS-2 catalyst. 相似文献
92.
Dr Shan Li Zhengke Li Yafen Yuan Yajun Li Lisi Zhang Prof. Dr. Yongming Wu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(4):1496-1501
A procedure for the synthesis of fluorinated imidazole derivatives from propargyl amidines has been developed. Under gold(I) catalysis, propargyl amidines were converted into 5‐fluoromethyl imidazoles in the presence of Selectfluor through a cascade cyclization/fluorination process. In contrast, imidazole‐5‐carbaldehydes were obtained in high yields when N‐iodosuccinimide (NIS) was used as the halogenating reagent. The polarity of the solvent and light had significant impact on the formation of the carbaldehydes. These transformations showed excellent functional‐group tolerance. An unfluorinated substrate with an electron‐withdrawing group also underwent aminohalogenation to give the corresponding product in good yield. Mechanistic investigation revealed the general pathways of these transformations. 相似文献
93.
Fabio?Lisi Davide?Carta Laura?Villanova Irene?Poli Dario?Buso Stefano?Costacurta Anita?J.?Hill Paolo?FalcaroEmail author 《Journal of Sol-Gel Science and Technology》2011,60(3):246-253
Functional coatings with amino groups are used in a wide range of biochemistry-related applications. A technological platform
that takes advantage of the affinity between amino-functionalized coatings and biomolecules is the DNA microarray methodology.
Reliability and reproducibility of the microarray data strongly depend on the quality of the substrate; therefore, a proper
awareness of how the storage conditions affect the amino-functionalized coatings is necessary. In this work we have studied
the influence of different relative humidity levels on amino-methyl-silane coatings prepared via sol–gel methodology. Drops
of a buffer solution containing a luminescent dye have been deposited (or spotted) on the coating; the dye molecules react with the amino-groups and leave circular luminescent marks (spots) on the substrate
surface. Shape and luminescence of the spots, as well as background signals, have been monitored using a microarray laser
scanner. With the proposed protocol we have measured the changes of these variables due to different storage conditions. FT-IR
measurements have been performed to investigate the related chemistry changes. 相似文献
94.
G. Cavallaro R. De Lisi G. Lazzara S. Milioto 《Journal of Thermal Analysis and Calorimetry》2013,112(1):383-389
Nanocomposites of poly(ethylene) glycol (PEG) 20000 filled with clay nanotubes (HNTs) were prepared. The thermal properties obtained from thermogravimetry and differential scanning calorimetry were correlated to the morphology imaged by scanning electron microscopy. Low amounts of HNTs generate compact structure while large amounts of HNTs create craters and voids. The decrease of polymer degradation temperature in the presence of large amount of nanoclay (ca. 80 wt%) is a consequence of the morphology at the mesoscale range. The thermal opposite effect observed in the HNTs low regime (up to ca. 20 wt%) is due to the gas entrapment into the nanoparticles lumen. The quantitative analysis of the PEG 20000 enthalpy of melting in the presence of HNTs allowed us to characterize the polymer adsorption onto the nanoclay surface. 相似文献
95.
96.
Dr. Guillaume Durand Samuele Lisi Dr. Corinne Ravelet Eric Dausse Prof. Eric Peyrin Dr. Jean‐Jacques Toulmé 《Angewandte Chemie (International ed. in English)》2014,53(27):6942-6945
Biosensors derived from aptamers were designed for which folding into a hairpin shape is triggered by binding of the cognate ligand. These aptamers (termed aptaswitches) thus switch between folded and unfolded states in the presence and absence of the ligand, respectively. The apical loop of the folded aptaswitch is recognized by a second hairpin called the aptakiss through loop–loop or kissing interactions, whereas the aptakiss does not bind the unfolded aptaswitch. Therefore, the formation of a kissing complex signals the presence of the ligand. Aptaswitches were designed that enable the detection of GTP and adenosine in a specific and quantitative manner by surface plasmon resonance when using a grafted aptakiss or in solution by anisotropy measurement with a fluorescently labeled aptakiss. This approach is generic and can potentially be extended to the detection of any molecule for which hairpin aptamers have been identified, as long as the apical loop is not involved in ligand binding. 相似文献
97.
Catalytic Asymmetric Hydroalkenylation of Vinylarenes: Electronic Effects of Substrates and Chiral N‐Heterocyclic Carbene Ligands 下载免费PDF全文
Prof. Dr. Chun‐Yu Ho Chun‐Wa Chan Lisi He 《Angewandte Chemie (International ed. in English)》2015,54(15):4512-4516
An asymmetric tail‐to‐tail cross‐hydroalkenylation of vinylarenes with terminal olefins was achieved by catalysis with NiH complexes bearing chiral N‐heterocyclic carbenes (NHCs). The reaction provides branched gem‐disubstituted olefins with high enantioselectivity (up to 94 % ee) and chemoselectivity (cross/homo product ratio: up to 99:1). Electronic effects of the substituents on the vinylarenes and on the N‐aryl groups of the NHC ligands, but not a π,π‐stacking mechanism, assist the steric effect and influence the outcome of the cross‐hydroalkenylation. 相似文献
98.
Irina V. Terekhova Rosario De Lisi G. Lazzara Stefania Milioto Nicola Muratore 《Journal of Thermal Analysis and Calorimetry》2008,92(1):285-290
Density and heat capacity of the water+cyclodextrin (CD), water+nicotinic acid (NA) and water+CD+NA mixtures were determined
at 298.15 K. CDs with different cavity size and alkylation were selected. From the experimental data the apparent molar properties
were calculated. Assuming the formation of inclusion complexes of 1:1 stoichiometry, these properties were modeled and provided
the stability constants of CD/NA inclusion complexes and the corresponding property change. The binding of NA with the smallest
sized α-cyclodextrin (α-CD) generates more stable complexes accompanied by the lower volume and the heat capacity changes.
These results are in agreement with earlier proposed binding mode according to which deep insertion of NA into α-CD takes
place and it is governed by the hydrophobic-hydrophilic forces. The volume and the heat capacity changes caused by the interactions
of CDs with NA were interpreted in terms of cosphere overlap model and the release of water molecules from the CD cavity due
to the NA incorporation. 相似文献
99.
针对辐射式核电磁脉冲模拟器采用TEM喇叭天线作为辐射天线时低频辐射能力有限的问题,对板型和线型两种基本形式的TEM喇叭天线进行了分析。在采用线型TEM喇叭天线以减轻模拟器重量的基础上,在天线末端采用螺旋线结构,并增加屏蔽板回路,构造了一种新型TEM喇叭天线。结果表明:与普通线型TEM喇叭天线相比,该新型天线较大地提高了低频辐射性能,可使近场波形脉宽提高7ns左右,峰值场强提高了1kV/m左右;通过增大螺旋线半径和提高螺旋线密度可以提高峰值场强,增加近场波形脉宽;通过屏蔽板回路可以降低反射波纹的波峰从而改善近场波形。 相似文献
100.
L. Kozielski M. Piechowiak D. Czekaj A. Lisińska-Czekaj G. Smalarz F. Clemens 《Phase Transitions》2013,86(11-12):1081-1088
The major problem in the production process of efficient ultrasonic transducer is the preparation of defect-free PZT fibres. A considerable amount of empirical work is presently in progress to achieve this goal of special importance for high-sensitive transducers. However, there is a lack of basic research on the detection of residual stress and defects areas in these fibres due to difficulties in mechanical examination of such flexible elements. This work presents use of the nanoindenter for material characterisation of PZT fibres of 140 µm radius obtained by extrusion method. The sudden depth-excursions during indentation on the edge of fibres have been clarified using Piezoresponse Mode Atomic Force Microscopy method and XRD measurements. The nanoindentation method proves to be the efficient tool capable to detect contribution of defects along the radius, properly estimate hardness as well as corresponding Young's modulus and concluding on structural properties of the micrometre-range ceramics fibres. 相似文献