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61.
In this paper, the use of anisotropy of magnetic susceptibility (AMS) measurements has been investigated in order to check the sensitivity of this technique versus the flow conditions. The orientation of anisotropic magnetic particles during the flow of a polystyrene $/$ magnetite blend through a capillary rheometer has been studied. Thanks to the magnetic properties of the magnetite, AMS measurements are possible. Different values of the filler concentration, viscosity, and shear rate were used. It is shown that the AMS technique is able to detect accurately particle orientation and that sensitivity decreases when increasing the concentration of magnetite grains. In addition, the rectangular-shaped sample imposed by the rheological device does not affect measures of AMS significantly. The results give reasons to consider that the measure of AMS is an accurate and sensitive method to access the mean local rheological behavior in filled or non-filled systems containing anisotropic tracers. 相似文献
62.
The preparation of a fluorinated C-glycosidic analogue of a 2-deoxy-2-acetamido-d-altrose is described. The synthetic sequence involves the addition of a difluoroenoxysilane to a d-glucal, an epoxidation of the resulting unsaturated CF2-glycoside and a ring-opening reaction with TMSN3. An Overman rearrangement of the unsaturated intermediate is also described. 相似文献
63.
Jean-Charles Sunyé 《Journal of Geometric Analysis》2009,19(4):944-962
Let H:(M,p)→(M ′,p ′) be a formal mapping between two germs of real-analytic generic submanifolds in ? N with nonvanishing Jacobian. Assuming M to be minimal at p and M ′ holomorphically nondegenerate at p ′, we prove the convergence of the mapping H. As a consequence, we obtain a new convergence result for arbitrary formal maps between real-analytic hypersurfaces when the target does not contain any holomorphic curve. In the case when both M and M ′ are hypersurfaces, we also prove the convergence of the associated reflection function when M is assumed to be only minimal. This allows us to derive a new Artin type approximation theorem for formal maps of generic full rank. 相似文献
64.
Active flow control is a rapidly developing topic because the associated industrial applications are of immense importance, particularly for aeronautics. Among all the flow control actuators, plasma-based devices are very promising. In most cases, the plasma actuator is based on a surface dielectric barrier discharge (DBD) established between two electrodes flush mounted on both sides of a dielectric layer. In this paper, the effects of the encapsulation of the grounded electrode on the electric wind produced by a surface DBD are investigated by Pitot velocity measurements. Moreover, the current versus time is statistically analysed in order to count the number of streamers, their duration and the electrical charge they transfer. Unfortunately it was not possible to detect and separate the glow-type synchronous current because its amplitude is of the same order as noise. On one hand, the encapsulation of the grounded electrode results in an increase of the electromechanical efficiency of the surface DBD plasma actuator because the electrical power consumption is divided by two. On the other hand, statistical analysis of the discharge current versus time has shown that the encapsulation results in a decrease of the streamer number and an increase of the charge transferred by each current streamer because the duration of streamers is longer. 相似文献
65.
Sylvain Rault Yamien Effi Michel Cugnon De Sevricourt Jean-Charles Lancelot Max Robba 《Journal of heterocyclic chemistry》1983,20(1):17-21
The synthesis of pyrrolo[1,2-α]thieno[3,2-e]pyrazine and pyrrolo[1,2-α]-thieno[2,3-e]pyrazine is described. These syntheses could be achieved by intramolecular cyclization of 2- (and 3-) (1-pyrrolyl)-3- (and -2)-thienyl-amines obtained by hydrolysis of carbamates or by cleavage of the corresponding ureas. An original way giving better results was also studied via a Curtius rearrangement by reaction between the azide and aldehyde groupings. The synthesis of 2- (and -3)-2-formyl-1-pyrrolyl)-2- (and -3)-thenoylazide is described. 相似文献
66.
Bouillon A Voisin AS Robic A Lancelot JC Collot V Rault S 《The Journal of organic chemistry》2003,68(26):10178-10180
Regioselective and univocal Suzuki cross-coupling reactions performed on halopyridinyl boronic acids provide a flexible and versatile route to a multigram scale synthesis of 2,2'-dichloro-3,4'-bipyridine 14, which allows couplings with excess pyridin-3-yl boronic acid to give a new and efficient two-step rapid synthesis of nemertelline, the quaterpyridine neurotoxin isolated from a Hoplonemertine sea worm. 相似文献
67.
Strong changes in relaxation rates observed at the glass transition region are frequently explained in terms of a physical singularity of the molecular motions. We show that the unexpected trends and values for activation energy and preexponential factor of the relaxation time tau, obtained at the glass transition from the analysis of the thermally stimulated current signal, result from the use of the Arrhenius law for treating the experimental data obtained in nonstationary experimental conditions. We then demonstrate that a simple model of structural relaxation based on a time dependent configurational entropy and Adam-Gibbs relaxation time is sufficient to explain the experimental behavior, without invoking a kinetic singularity at the glass transition region. The pronounced variation of the effective activation energy appears as a dynamic signature of entropy relaxation that governs the change of relaxation time in nonstationary conditions. A connection is demonstrated between the peak of apparent activation energy measured in nonequilibrium dielectric techniques, with the overshoot of the dynamic specific heat that is obtained in calorimetry techniques. 相似文献
68.
Lepailleur A Bureau R Lemaître S Dauphin F Lancelot JC Contesse V Lenglet S Delarue C Vaudry H Rault S 《Journal of chemical information and computer sciences》2004,44(3):1148-1152
A definition of a pharmacophore for the 5-HT7 antagonists was carried out by searching the common chemical features of selective antagonists from the literature. A molecular design is described by analyzing the differences between this new pharmacophore and three other 3D serotonin pharmacophores previously described. This comparison led to the synthesis of a new series of potent 5-HT7 antagonists. 相似文献
69.
Alain Rabaron Jean-Charles Lancelot Daniel Maurne Max Robba 《Journal of heterocyclic chemistry》1979,16(1):53-55
The main nmr parameters of 1,2,4-triazino[4,5-b]indazole derivatives were measured on the basis of their 13C nmr spectral analysis compared to indazole models. 1J C-H coupling constants were studied and the correct structure of 1,2,4-triazino[4,5-b]indazoles was elucidated. 相似文献
70.
Laurent A. Decosterd Helen Stoeckli-Evans Jean-Charles Chapuis Jerome D. Msonthi Bernard Sordat Kurt Hostettmann 《Helvetica chimica acta》1989,72(3):464-471
The crude petroleum-ether extract of the root bark of Hypericum revolutum VAHL (Guttiferae) exhibited in vitro growth-inhibitory activity against the Co-115 human colon carcinoma cell line. Activity-guided fractionation of this extract resulted in the isolation of two new hyperforin derivatives 1 and 2 . The structure of 1 (hyperevolutin A) was established by X-ray analysis as the 4-hydroxy-8-exo-methyl-5,7-exo-bis(3-methylbut-2-enyl)-1-(2-methyl-1-oxopropyl)-8-endo-(4-methylpent-3-enyl)bicyclo[3.3.1]non-3-ene-2,9-dione. The structure of the homologue 2 was deduced by comparison of its UV and 1H- and 13C-NMR spectra with those of 1 . 相似文献