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151.
Molinaro C Mowat J Gosselin F O'Shea PD Marcoux JF Angelaud R Davies IW 《The Journal of organic chemistry》2007,72(5):1856-1858
We report herein a simple, scalable, transition-metal-free approach to the synthesis of alpha-aryl methyl ketones from diazonium tetrafluoroborate salts under mild conditions. This methodology uses easily accessible and nontoxic starting material and was applied to the multi-kilogram-scale preparation of 1-(3-bromo-4-methylphenyl)propan-2-one. 相似文献
152.
Orain PY Capon JF Kervarec N Gloaguen F Pétillon F Pichon R Schollhammer P Talarmin J 《Dalton transactions (Cambridge, England : 2003)》2007,(34):3754-3756
Treatment of [Fe(2)(micro-pdt)(CO)(6)] (pdt = S(CH(2))(3)S) with 1,10-phenanthroline (phen) in refluxing toluene affords the asymmetric complex [Fe(2)(micro-pdt)(CO)(4)(phen)] (1); the protonation of with HBF(4).OEt(2) in CD(2)Cl(2) at 203 K has been monitored by (1)H NMR. 相似文献
153.
Grunert CM Goodwin HA Carbonera C Létard JF Kusz J Gütlich P 《The journal of physical chemistry. B》2007,111(24):6738-6747
[Fe(bpp)2][Pt(ox)2].H2O (with bpp=2,6-bis(pyrazol-3-yl)-pyridine and ox=oxalate) was prepared, and its spin crossover behavior was characterized. The two-step spin transition behavior changes over several cycles. The original behavior is restored when the sample is allowed to relax for a week. Furthermore, the ST exhibits a strong dependence on the heating and cooling rate. Heating the compound at 1 K/min leads to a spin transition with a third step and a second plateau at gammaHS approximately 0.8. Quenching the sample to 77 K also affects the spin transition behavior. The kinetic relaxation is followed after quenching and after light-induced excited spin state trapping experiments. 相似文献
154.
Jean-François Feller Hervé Guézénoc Hervé Bellégou Yves Grohens 《Macromolecular Symposia》2005,222(1):273-280
Conductive Polymer Composites (CPC) can be used to elaborate sensing elements able to detect solvent vapours at very low concentrations (some ppm). Our experiments have shown that combining atactic PS or syndiotactic PS to five carbon black of different specific surfaces, allows obtaining a wide range of electrical resistances and surface morphologies. The CPC films have been elaborated from solutions by spraying and spin coating, the former being more adequate to design sensitive films with tuneable electrical properties. The larger electrical responses were obtained with an initial resistance close to 104 Ω. Our sensors gave a response for very low styrene concentration (some ppm) increasing as a function of vapour concentration. 相似文献
155.
Jean-François Delmas 《Probability Theory and Related Fields》1999,114(4):505-547
We consider a super-Brownian motion X. Its canonical measures can be studied through the path-valued process called the Brownian snake. We obtain the limiting
behavior of the volume of the ɛ-neighborhood for the range of the Brownian snake, and as a consequence we derive the analogous
result for the range of super-Brownian motion and for the support of the integrated super-Brownian excursion. Then we prove
the support of X
t
is capacity-equivalent to [0, 1]2 in ℝd, d≥ 3, and the range of X, as well as the support of the integrated super-Brownian excursion are capacity-equivalent to [0, 1]4 in ℝd, d≥ 5.
Received: 7 April 1998 / Revised version: 2 October 1998 相似文献
156.
Daniel Guillon Jean-François Nierengarten Jean-Louis Gallani Jean-François Eckert Yannick Rio Maria del Pilar Carreon Blaise Dardel Robert Deschenaux 《Macromolecular Symposia》2003,192(1):63-74
Growing attention is currently devoted to large dendritic structures for applications in nanotechnology and materials science. In this respect, the incorporation of such compounds into thin ordered films appears to be an important issue. One of the most widely pursued approaches to structurally ordered dendrimer assemblies has been the preparation of Langmuir films at the air-water interface. We report on the case of a diblock globular fullerene-based dendrimer and show that peripheral substitution of the dendrimer with hydrophobic chains on one hemisphere and hydrophilic groups on the other provides the required hydrophobic/hydrophilic balance allowing the formation of stable Langmuir films. A second approach has been to consider the case of fullerene containing dendrimers terminated by mesogenic groups such as cyanobiphenyl subunits. Whatever the generation is, up to the fourth one, all these compounds exhibit a well-defined liquid crystalline smectic A phase. The molecular organisation within the smectic layers is found to be monolayered or bilayered depending on the generation. For the smallest dendrimers, the organisation is mainly governed by the size of the fullerene moiety, whereas for the higher ones, it is governed by the interactions between the terminal mesogenic groups. These two approaches appear particularly interesting for functional groups such as fullerenes, which are not well adapted to be organised in nanoscale architectures. The present study shows that fullerenes can indeed be introduced into different types of ordered structure when they have been chemically adequately modified. 相似文献
157.
Driss Laraqui Olivier Allgaier Cornelius Schönnenbeck Gontrand Leyssens Jean-François Brilhac Ricardo Lomba Clément Dumand Olivier Guézet 《Proceedings of the Combustion Institute》2019,37(3):3175-3184
This work presents a study of a magnesium/air combustion process in the context of innovative zero carbon dioxide (CO2) energy carriers for reducing global warming effects. In order to analyze more deeply the confined combustion of magnesium under fluctuating overpressure conditions (0 to 24 hPa) and the generated gaseous by-products, magnesium/air flames have been realized in a combustion chamber with a conical bluff-body as flame holder and different contraction ratios diaphragms at the exit duct. Sieved magnesium samples with two size-fractions were tested: 20–50?µm and 50–70?µm. The gaseous emissions of nitrogen oxides (NOx) and dioxygen (O2) were analyzed with on-line infrared, ultraviolet and paramagnetic analyzers. A flame pulsating behavior was clearly observed from light emission intensity (monitored by a photodiode) and pressure fluctuations (monitored by a pressure sensor); the frequencies obtained ranged between 3 and 10?Hz. The frequency of the pulsation exhibited strong dependence on the geometric configuration of the chamber: a contraction diaphragm divided by two the frequency level of the fluctuations in the studied range of maximum overpressure. Such fluctuations may probably be the consequence of periodic perturbations of the recirculation zone behind the bluff-body. These periodic perturbations are themselves caused by strong periodic overpressure variations due to stiff contraction downstream responding to gas velocity fluctuations. This feed-back-loop mechanism was considered in this study. NOx emissions produced through the thermal pathway were analyzed for equivalence ratios ranging from 0.29 to 1. The representation of NOx versus equivalence ratio exhibited a parabolic shape with a maximum for an equivalence ratio of 0.4. Moreover, NOx emissions of this metal combustor have shown a similar order of magnitude than current internal combustion engines. 相似文献
158.
159.
Alysson M. Costa Jean-François Cordeau Bernard Gendron 《Computational Optimization and Applications》2009,42(3):371-392
Solving multicommodity capacitated network design problems is a hard task that requires the use of several strategies like
relaxing some constraints and strengthening the model with valid inequalities. In this paper, we compare three sets of inequalities
that have been widely used in this context: Benders, metric and cutset inequalities. We show that Benders inequalities associated
to extreme rays are metric inequalities. We also show how to strengthen Benders inequalities associated to non-extreme rays
to obtain metric inequalities. We show that cutset inequalities are Benders inequalities, but not necessarily metric inequalities.
We give a necessary and sufficient condition for a cutset inequality to be a metric inequality. Computational experiments
show the effectiveness of strengthening Benders and cutset inequalities to obtain metric inequalities. 相似文献
160.
Huang H Hoogenboom R Leenen MA Guillet P Jonas AM Schubert US Gohy JF 《Journal of the American Chemical Society》2006,128(11):3784-3788
Microwave-assisted polymerization has been utilized to synthesize amphiphilic poly(2-ethyl-2-oxazoline-block-2-"soy alkyl"-2-oxazoline) diblock copolymers (PEtOx-PSoyOx). The amphiphilic block copolymers have been used to prepare aqueous spherical micelles consisting of a PEtOx corona and a PSoyOx core, which have been further cross-linked by UV irradiation. The morphology of these cross-linked micelles has been shown to reversibly change from spheres to short rods referred to as rice grains whenever the micelles were transferred from water into acetone, a nonselective solvent for the constituent blocks. This morphological transition has been attributed to the swelling of the slightly cross-linked PSoyOx core. 相似文献