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191.
Dominique Faure Doris Lexa Jean-Michel Savéant 《Journal of Electroanalytical Chemistry》1982,140(2):269-284
The cyclic voltammetric study of vitamin B12r in DMSO shows the importance of the base-on/base-off reaction in the electrochemical reduction mechanism. Depending upon the flux of electrons flowing through the system. part of the base-on complex is reduced through prior opening of the nucleotide side-chain which gives rise to the more easily reduced DMSO-Co(II) complex. The quantitative analysis of the variations of the peak heights with the sweep rate allows the thermodynamic and kinetic characterization of the base-on/base-off reactions to be determined. DMSO thus appears as a stronger ligand toward Co(II) than water, leading to an increased participation of the base-off complex in the reduction process. The greater stability of the DMSO complex is also related to the observation that electron transfer is significantly slower than in the case of the water complex. The importance of the ligand exchange reactions in the reduction of B12r is confirmed by the effect of pyridine additions. Three complexes then participate in the reduction process, their reduction potentials lying in the order DMSO >Py >Bzm. The reduction mechanism involving the interconversion of the three complexes is described as a function of the electrode potential, the flux of electrons and the pyridine concentration. An estimation of the equilibrium and rate constants of the three ligand exchange reactions is made, based on the variations of the cyclic voltammograms with the sweep rate and the pyridine concentration. 相似文献
192.
193.
Jacques Gilbert Dominique Rousselle Charles Gansser Claude Viel 《Journal of heterocyclic chemistry》1979,16(1):7-11
A new snythesis of 6H-pyrido[4,3-b]carbazoles is described starting from substituted cyclohexanones involving the combination of Borsche's carbazole preparation and Cranwell and Saxton's ellipticine synthesis where the starting materials are easily available. The dehydrogenation step is accomplished at an early stage. In some cases (11-desmethyl ellipticines derivatives), 7H-pyrido[3,4-c]carbazoles were also obtained. 相似文献
194.
Dominique Perrin 《Mathematische Zeitschrift》1977,153(3):283-287
Sans résumé 相似文献
195.
Lise Crevier-Buchman Ollivier Laccourreye Jean-François Papon Dominique Nurit Daniel Brasnu 《Journal of voice》1997,11(2):232-237
We analyzed frequency and duration parameters of voice and speech in two men with adductor spasmodic dysphonia (SD). One was treated with botulinum toxin injection; the other received acupuncture therapy. Im provement after acupuncture therapy in terms of standard deviation of fundamental frequency, acoustic perturbation measurements, durational measurements of voice and speech, and spectrographic analysis was comparable to the results achieved with botulinum toxin injection. Voice and speech parameters were stable I year after acupuncture therapy. 相似文献
196.
J.Pierre Moeglin Bemard Gautier René Joecklé Dominique Bolmont 《Optics and Lasers in Engineering》1997,28(5):317-330
A measurement of the electrical parameters degradation of Si photodiodes irradiated by laser visible light has been performed. The laser is a Q-switched Nd:YAG, frequency doubled, operated in single pulse mode of 4 ns duration. The applied fluence levels range up to 90 J/cm2. Two kinds of irradiation process were applied: either a part of the detector active area was irradiated in single pulse mode, or a scanning of the whole detector active area was performed with successive identical pulses. It has been shown that the fluence necessary to induce significant changes (local decrease of 35%) in responsivity is several times the surface melting threshold fluence (0.5 J/cm2). Conversely, the dark current is the most sensitive parameter, increasing by about four times for high irradiation. The in-depth dopant distribution is altered by high fluence irradiation in a way that cannot be explained by simple thermal modelling. 相似文献
197.
The structure of Pb3O4 at 293 K has been refined to an R value of 0.06, using 29 neutron diffraction data obtained from a powdered sample.Oxygen atoms are displaced in the quadratic cell (space group Å and c = 6.563 Å) with respect to previous results obtained by several authors. The interatomic PbIVO and PbIIO distances are compared with those found in other lead oxides. While the oxygen octahedra around PbIV atoms are characterized by bondings a little too long, the divalent lead coordination is characterized by bondings a little too short. 相似文献
198.
Dominique Adamski-Medda Quang Trong Nguyen Edith Dellacherie 《Journal of membrane science》1981,9(3):337-342
When a protein is exposed to a ligand linked to a water soluble polymer, a macrocomplex can be formed that can be isolated from the contaminant medium by different methods such as affinity partitioning or gel filtration. Ultrafiltration technique has also been tested in the separation of trypsin and chymotrypsin using a high molecular weight dextran—p-aminobenzamidine as a macroligand. Some theoretical considerations are given in order to evaluate the performance that can be expected from this biospecific complexation—ultrafiltration technique in the separation of biological species. 相似文献
199.
Dominique Bénard 《Journal of Combinatorial Theory, Series B》1978,24(1):34-43
In this paper we compute the orientable genus of the line graph of a graph G, when G is a tree and a 2-edge connected graph, all the vertices of which have their degrees equal to 2, 3, 6, or 11 modulo 12, and either G can be imbedded with triangular faces only or G is a bipartite graph which can be imbedded with squares only as faces. In the other cases, we give an upper bound of the genus of line graphs. In this way, we solve the question of the Hamiltonian genus of the complete graph Kn, for every n ≥ 3. 相似文献
200.