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排序方式: 共有145条查询结果,搜索用时 19 毫秒
61.
Tarik Matrab Bernadette Charleux Eva Cabet-deliry Mohamed M. Chehimi Michel Delamar 《Surface science》2007,601(11):2357-2366
Poly(n-butyl methacrylate), PBMA, chains were grafted by atom transfer radical polymerization (ATRP) from the surface of iron plates using electrochemically attached initiators based on diazonium salts providing an iron/polyphenylene/PBMA structure. This surface-initiated ATRP procedure was controlled by the addition of a small proportion of Cu++ deactivator, but in the absence of any sacrificial initiator. Combined XPS, IR and AFM experiments provide a powerful means for the characterization of the obtained complex iron/polyphenylene/PBMA layered structure. It is possible to measure the thickness of the brominated aryl structure covalently attached to iron. Concerning the PBMA brushes, their presence on the surface was confirmed by IRRAS. The brominated chain end could be traced by XPS testifying for the ATRP character of the polymerization and the thickness of the polymer brushes was determined. The controlled living ATRP character of the polymerization is confirmed through a linear correlation between the thickness of the layer and the degree of polymerization. Measurement of the grafting density of PBMA chains indicates that they are compactly packed and that, approximately, one brominated aryl chain out of two efficiently initiates ATRP. 相似文献
62.
Dr. Mei Ding Dr. Anne K. Hickey Dr. Maren Pink Prof. Joshua Telser Prof. David L. Tierney Martin Amoza Mathieu Rouzières Tarik J. Ozumerzifon Wesley A. Hoffert Prof. Matthew P. Shores Prof. Eliseo Ruiz Dr. Rodolphe Clérac Prof. Jeremy M. Smith 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(45):10625-10632
The single-molecule magnet (SMM) properties of a series of ferrocenium complexes, [Fe(η5-C5R5)2]+ (R=Me, Bn), are reported. In the presence of an applied dc field, the slow dynamics of the magnetization in [Fe(η5-C5Me5)2]BArF are revealed. Multireference quantum mechanical calculations show a large energy difference between the ground and first excited states, excluding the commonly invoked, thermally activated (Orbach-like) mechanism of relaxation. In contrast, a detailed analysis of the relaxation time highlights that both direct and Raman processes are responsible for the SMM properties. Similarly, the bulky ferrocenium complexes, [Fe(η5-C5Bn5)2]BF4 and [Fe(η5-C5Bn5)2]PF6, also exhibit magnetization slow dynamics, however an additional relaxation process is clearly detected for these analogous systems. 相似文献
63.
Muhammad Nazrul Islam Burak Aksu Mehmet Güncü Markus Gallei Metin Tulu Tarik Eren 《Journal of polymer science. Part A, Polymer chemistry》2020,58(6):872-884
Bacterial infection is a global problem, especially resistance acquired by bacteria against to antibiotics; there is urgent need for the development of antibiotics. Here, we proposed dendron-grafted polymers via ring opening metathesis polymerization (ROMP) featuring different with tailored hydrophobicity/hydrophilicity and cationic charges. Dendritic oxanorbornene derivatives were synthesized having two and six carbon linkers and their corresponding random and block copolymers were prepared having pendant pyridinium salt moieties via ROMP. In total, 12 different water-soluble dendronized cationic polymers featuring hexyl pyridinium moieties were prepared and investigated. Six carbon linker possessing triple charge density and hexyl pyridinium functionality each repeating unit copolymers exhibited high antibacterial activity against Gram-positive bacteria (S. aureus). However, all the polymers were inactive against Gram-negative bacteria (E. coli). Most of the copolymers are non-hemolytic (>HC 50 = 1,000 μg/ml). It was also observed that, there is no significant effect between block copolymers and random copolymers keeping hydrophobicity and cationic charge density constant. Zeta potential was measured to investigate the mechanism in solution via the interaction of polymers with S. aureus, while scanning electron microscope (SEM) measurements image confirms damage of the bacterial cell wall after implementation of biocidal polymer. 相似文献
64.
Marc Lachièze Rey Jean-Pierre Gazeau Eric Huguet Jacques Renaud Tarik Garidi 《International Journal of Theoretical Physics》2003,42(6):1301-1310
Current views link quantization with dynamics. The reason is that quantum mechanics or quantum field theories address to dynamical systems, i.e., particles or fields. Our point of view here breaks the link between quantization and dynamics: any (classical) physical system can be quantized. Only dynamical systems lead to dynamical quantum theories, which appear to result from the quantization of symplectic structures. 相似文献
65.
Tarik Matrab Catherine Combellas Frdric Kanoufi 《Electrochemistry communications》2008,10(9):1230-1234
The scanning electrochemical microscope (SECM) is used in the direct mode to draw patterns of a thin passivating organic layer on a gold electrode surface and to image them. The patterning is ensured by the local electrografting of the organic moieties obtained by reduction of an aryliodonium salt, as evidenced by XPS and SECM line scans. The resolution of the writing process is controlled by the charge injected. 相似文献
66.
Tarik El-Sayed Ali Magdy A. Ibrahim Somaia M. Abdel-Kariem 《Phosphorus, sulfur, and silicon and the related elements》2013,188(9):2358-2392
The synthesis of 4-oxo-4H-chromenes containing sulfur-nitrogen heterocyclic rings as well as their biological activities are reviewed. 相似文献
67.
Mohammed J. Uddin Deborah E. Daramola Ever Velasquez Tarik J. Dickens Jin Yan Emily Hammel Federico Cesano Okenwa I. Okoli 《固体物理学:研究快报》2014,8(11):898-903
An innovative hybrid QD sensitized photovoltaic carbon nanotubes microyarn has been developed using thermally‐stable and highly conductive carbon nanotubes yarns (CNYs). These CNYs are highly inter‐aligned, ultrastrong and flexible with excellent electrical conductivity, mechanical integrity and catalytic properties. The CNYs are coated with a QD‐incorporated TiO2 microfilm and intertwined with a second set of CNYs as a counter electrode (CE). The maximum photon to current conversion efficiency (ηAM1.5) achieved with prolonged‐time stability was 5.93%. These cells are capable of efficiently harvesting incident photons regardless of direction and generating photocurrents with high efficiency and operational stability.
68.
Metastasis is the main cause of cancer mortality. During this process, cancer cells dislodge from a primary tumor, enter the circulation and form secondary tumors in distal organs. It is poorly understood how these cells manage to cross the tight syncytium of endothelial cells that lines the capillaries. Such capillary transmigration would require a drastic change in cell shape. We have therefore developed a microfluidic platform to study the transmigration of cancer cells. The device consists of an array of microchannels mimicking the confined spaces encountered. A thin glass coverslip bottom allows high resolution imaging of cell dynamics. We show that nuclear deformation is a critical and rate-limiting step for transmigration of highly metastatic human breast cancer cells. Transmigration was significantly reduced following the treatment with a protein methyltransferase inhibitor, suggesting that chromatin condensation might play an important role. Since transmigration is critical for cancer metastasis, this new platform may be useful for developing improved cancer therapies. 相似文献
69.
Mounir A. I. Salem Tarik E. Ali Magda I. Marzouk 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3):336-342
Abstract The electron impact induced fragmentation reactions of 3-(4-chlorophenyl)-3,4- dihydro-2-ethoxy-2-oxido-7-methyl-2H,6H-[1,2,4]triazino[4,3-e][1,4,5,2]thiadiazaphosphin in-6-one (1), 3,7-dimethyl-2-ethoxy-2-oxido-1,2,3,4-tetrahydro-6H-[1,2,4]triazino[4,3-b][1,2,4,5]triazaphosphinin-6-one (2), and 9-amino-3,7-dimethyl-4-ethoxy-4-oxido-2,3,4,9-tetrahydro-8H-[1,2,4]triazino[3,2-c][1,2,4,5]triazaphosphinin-8-one (3) are presented and compared. The 1,2,4-triazine rings have almost identical fragmentation routes. The 1,2,4-triazine rings are rather stable relative to the phosphorus rings. Therefore, fragmentation of the phosphorus rings is more favorable for the compounds than the stable 1,2,4-triazine rings. 相似文献
70.
A three-dimensional finite-element numerical model is presented for simulation of the steady-state performance characteristics
of heat pipes. The mass, momentum and energy conservation equations are solved for the liquid and vapor flow in the entire
heat pipe domain. The calculated outer wall temperature profiles are in good agreement with the experimental data. The estimations
of the liquid and vapor pressure distributions and velocity profiles are also presented and discussed. It is shown that the
vapor flow field remains nearly symmetrical about the heat pipe centerline, even under a non-uniform heat load. The analytical
method used to predict the heat pipe capillary limit is found to be conservative. 相似文献