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81.
82.
The Diels-Alder adduct 4 of an N-protected pyrrole with dimethyl acetylenedicarboxylate can be transformed to 5 and 6 by short sequences which differenciate the two ester groups; these compounds are interesting starting materials for the synthesis of potential thromboxane A2 antagonists as well as other bio-active compounds. 相似文献
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84.
Christophe Loup Dr. Ana Tesouro Vallina Dr. Yannick Coppel Dr. Ulla Létinois Prof. Dr. Yasuo Nakabayashi Dr. Bernard Meunier Prof. Dr. Bernhard Lippert Dr. Geneviève Pratviel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(37):11420-11431
Two PtIV and two PtII complexes containing a 2,2′‐bipyridine ligand were treated with a short DNA oligonucleotide under light irradiation at 37 °C or in the dark at 37 and 50 °C. Photolysis and thermolysis of the PtIV complexes led to spontaneous reduction of the PtIV to the corresponding PtII complexes and to binding of PtII 2,2′‐bipyridine complexes to N7 of guanine. When the reduction product was [Pt(bpy)Cl2], formation of bis‐oligonucleotide adducts was observed, whereas [Pt(bpy)(MeNH2)Cl]+ gave monoadducts, with chloride ligands substituted in both cases. Neither in the dark nor under light irradiation was the reductive elimination process of these PtIV complexes accompanied by oxidative DNA damage. This work raises the question of the stability of photoactivatable PtIV complexes toward moderate heating conditions. 相似文献
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86.
This paper describes a slope scaling heuristic for solving the multicomodity capacitated fixed-charge network design problem. The heuristic integrates a Lagrangean perturbation scheme and intensification/diversification mechanisms based on a long-term memory. Although the impact of the Lagrangean perturbation mechanism on the performance of the method is minor, the intensification/diversification components of the algorithm are essential for the approach to achieve good performance. The computational results on a large set of randomly generated instances from the literature show that the proposed method is competitive with the best known heuristic approaches for the problem. Moreover, it generally provides better solutions on larger, more difficult, instances. 相似文献
87.
The extraction of injected charge carriers technique for investigation of the transport in the metal-insulator-semiconductor structures is proposed. The mobility and the amount of accumulated charge carriers are determined from extraction current transients in both, small charge and space charge limited current cases. The extraction currents transients obtained experimentally in the structures with various organic materials are demonstrated. 相似文献
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89.
St-Pierre G Chagnes A Bouchard NA Harvey PD Brossard L Ménard H 《Langmuir : the ACS journal of surfaces and colloids》2004,20(15):6365-6373
Original and versatile new materials for the electrocatalytic hydrogenation of organic compounds were designed. The materials consist of reticulated glassy carbon cathode electrodes in which the modified silica particles (average diameter 40-63 microm) were dynamically circulated. The modification of the silica surface is 2-fold. First, the silica is surface-modified using organic functions such as -OSi(CH3)2(CH2)3OCH2CH-(OH)(CH)2OH (SiO2-Diol), -OSi(CH3)2(CH2)7CH3 (SiO2-C8), and -OSi(CH3)2C6H5 (SiO2-Phenyl). Second, these silica particles were further modified by vapor phase deposition of nickel nanoaggregates (used as sites for hydrogen atoms and electric contacts with the electrode material), which does not destroy or alter the organic functionalization as demonstrated by thermogravimetric analysis-mass spectrometry and Raman, diffuse reflectance IR Fourier transform, and Auger electron spectroscopies. The new concept stems from relative adsorption and desorption properties of the organic molecules and their corresponding reduced products into the organic functionalization of the surface-modified silica. In this work, the electrocatalytic hydrogenation cyclohexanone was used to test the concept. The performances (amount of cyclohexanol vs time of generated electrolysis at constant current) are measured and compared for the various bonded organic functions of the silica surface listed above, along with the unmodified silica particles (but still containing nickel nanoaggregates) and the presence or absence of methanol in solution. The measurements of the adsorption isotherms of cyclohexanone, and the calculations of the interaction energies (MM3 force field) between the chemisorbed organic functions and the substrates, corroborate perfectly the electrocatalysis results. 相似文献
90.
The two kinds of experiments actually existing in phase conjugation and production of images by backward stimulated scatterings are explained on the basis of the holographic model. The conditions for the correct transfer of information from one wavelength to another are presented. 相似文献