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排序方式: 共有91条查询结果,搜索用时 31 毫秒
1.
Hiba Messaoudi Fayçal Djazi Mohamed Litim Bahadır Keskin Maamar Slimane Djillali Bekhiti 《Journal of Adhesion Science and Technology》2020,34(20):2216-2244
AbstractCorrosion inhibitors based on environmentally friendly and harmless products are currently being studied and developed. The corrosion inhibition properties of caffeine (1,3,7-trimethylxanthine) on copper corrosion in aqueous chloride solution (3.5?wt.% NaCl) are analysed here using stationary and transient electrochemical methods, and a theoretical study based on density functional theory is carried out. Caffeine is a very competitive compared to the chemical inhibitors that are often used for copper protection. Electrochemical and impedance experiments reveal that the protective efficiency of caffeine reaches a value of 96% at a concentration of 10?2?mol L?1. Based on these results, the Langmuir model appears to be the best representation of the adsorption of caffeine onto the copper surface. Scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy and X-ray diffraction (XRD) were used to determine the surface morphology and the chemical composition of the copper surface in chloride media, in the absence and presence of caffeine. The results show the development of a mechanism of corrosion inhibition. In order to confirm the correlation between the inhibitory effect and the molecular structure of caffeine, quantum chemical parameters are used to calculate its electronic properties. 相似文献
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3.
Abdallah Hamze Dr. Anne Giraud Dr. Samir Messaoudi Dr. Olivier Provot Dr. Jean‐François Peyrat Prof. Jérôme Bignon Dr. Jian‐Miao Liu Dr. Joanna Wdzieczak‐Bakala Dr. Sylviane Thoret Joëlle Dubois Dr. Jean‐Daniel Brion Prof. Mouad Alami Dr. 《ChemMedChem》2009,4(11):1912-1924
The cytotoxic activities of 23 new isocombretastatin A derivatives with modifications on the B‐ring were investigated. Several compounds exhibited excellent antiproliferative activity at nanomolar concentrations against a panel of human cancer cell lines. Compounds isoFCA‐4 ( 2 e ), isoCA‐4 ( 2 k ) and isoNH2CA‐4 ( 2 s ) were the most cytotoxic, and strongly inhibited tubulin polymerization with IC50 values of 4, 2 and 1.5 μM , respectively. These derivatives were found to be 10‐fold more active than phenstatin and colchicine with respect to growth inhibition but displayed similar activities as tubulin polymerization inhibitors. In addition, cell cycle arrest in the G2/M phase and subsequent apoptosis was observed in three cancer cell lines when treated with these compounds. The disruptive effect of 2 e , 2 k and 2 s on the vessel‐like structures formed by human umbilical vein endothelial cells (HUVEC) suggest that these compounds may act as vascular disrupting agents. Both compounds 2 k and 2 s have the potential for further prodrug modification and development as vascular disrupting agents for treatment of solid tumors. 相似文献
4.
Synthesis and photovoltaic properties of mono-substituted quaterthiophenes bearing strong electron-withdrawing group 总被引:1,自引:0,他引:1
Abderrahim Yassar Christine Videlot Abdelhafid. Jaafari 《Solar Energy Materials & Solar Cells》2006,90(7-8):916-922
We report here on the synthesis and properties of a monosubstituted quaterthiophene derivative asymmetrically functionalized by an electron-withdrawing group using the palladium-catalyzed Stille's coupling reaction. The UV–vis absorption spectrum evidences a strong intramolecular charge transfer transition. Thus oligothiophenes act as electron donors and substituent group as acceptor. The diodes in which monosubstituted quaterthiophenes behave as organic semiconductors, exhibit a rectifying behavior. Photovoltaic measurements show moderate power conversion efficiency. 相似文献
5.
This paper presents the results obtained in a comparison of three neutron spectrum unfolding procedures based on the SAND, MINCHI and UNFANA computer programs. The calculations were performed with data obtained previously from measurements using the PTB Bonner sphere spectrometer and taken from the literature; the neutron dosimetry was done with the Leake rem-meter. The evaluation of some spectrum hardness quantifiers is also reported. The codes give comparable neutron spectrum results. Relative to ambient dose equivalent derived from the Bonner sphere system, as a function of the unfolding code used, the Leake calculated readings were typically 1.16 to 1.91 and 1.58 to 2.69 times larger for the environment of a transport cask with spent fuel elements (Clab) and inside the containment building of a pressurised water reactor (Ring-G), respectively, depending on the calibration fields. 相似文献
6.
Samir Messaoudi Jean‐Daniel Brion Moud Alami 《Advanced Synthesis \u0026amp; Catalysis》2010,352(10):1677-1687
An efficient copper‐catalyzed in situ C(sp2) NH2 bond formation to provide a range of 3‐aminoquinolin‐2(1H)‐ones and 3‐aminocoumarins from 3‐bromoquinolinones and 3‐bromocoumarins, respectively, has been achieved. The reaction conditions involve the use of copper powder as the catalyst, eco‐friendly ethanol as the solvent in the presence of pipecolinic acid as the ligand and ascorbic acid as the additive. The efficiency of this practical method was demonstrated in the synthesis of various anilines. 相似文献
7.
pH sensing in aqueous solutions using a MnO2 thin film electrodeposited on a glassy carbon electrode
An electrolysis technique at a constant potential was used to develop a highly reproducible and fast elaboration method of adherent manganese dioxide thin films on a glassy carbon electrode from aqueous solutions containing sulfuric acid and manganese sulfate. The resulting films were found to have a nanostructured character presumably due rather to birnessite (δ-MnO2) than to γ-MnO2, as suggested by their Raman and XRD signatures. They lead to modified electrodes that present an obvious although complex pH dependent potentiometric response. This sensor indeed showed a single slope non-Nernstian linear behaviour over the 1.5–12 pH range for increasing pH direction (“trace”), whereas a Nernstian two slopes linear behaviour was observed for decreasing pH direction (“re-trace”). Preliminary EIS experiments carried out at a pH value of 1.8 seem to reveal a sensitivity mechanism based on proton insertion process at least at highly acidic pH values. 相似文献
8.
Crack effects on gas and water permeability of concretes 总被引:6,自引:0,他引:6
The relationship between load-induced cracking and concrete permeability is studied. Ordinary concrete (OC) and high-performance concrete (HPC), including steel fiber-reinforced concrete (HPFRC), are used. Two discs, 50 mm-thick slices, cut from 110-220 mm cylindrical specimens are diametrically loaded, as for a normal splitting test. The lateral displacement, also called the crack opening displacement (COD) is monitored for each loading cycle. After unloading, gas and finally water permeability tests are both performed, using constant head permeameter, to compare the influence of the percolating fluid and the COD. Due to the wide range of measured gas flow, Klinkenberg's and Dupuit-Forcheimer's laws are applied to compute the intrinsic gas permeability. Results suggest it increases proportionally to the cube of the COD and it matches water permeability, if only the first water percolating time is considered. The roughness parameter of the cracks induced in each concrete, is compared and discussed. 相似文献
9.
Amandine Carrër Jean‐Daniel Brion Mouad Alami Samir Messaoudi 《Advanced Synthesis \u0026amp; Catalysis》2014,356(18):3821-3830
A straightforward assisted tandem palladium(II)‐ and palladium(0)‐catalyzed direct C‐3 and N‐4 arylation of quinoxalin‐2(1 H)‐ones with boronic acids and aryl halides in water as safe and cheap solvent is reported. This environmentally friendly catalytic protocol is compatible with a wide range of functional groups and allows construction of various biologically important quinoxalin‐2(1 H)‐one backbones.
10.
The transmission line matrix method permits modification of the excitation of modes in microlines. This property gives access to phase velocities by synchronisation of excitation and propagating modes. The selection of modes is possible by this synchronisation. Group velocities are deduced from frequency modulation due to geometrical dimensions variation. In another part, two methods of infinited space simulation are proposed. Applications about radiation patterns of the dipole antenna and the half dipole are given. The input impedance and the resonance frequency are calculated for a printed strip dipole. 相似文献