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981.
Ludger A. Wessjohann Harry Wild Leonildo A. Ferreira Henri S. Schrekker 《应用有机金属化学》2016,30(8):674-679
The regioselective and diastereoselective chromium(II)‐mediated reactions of 4‐bromocrotonic acid or amides with aldehydes and ketones can proceed without the need to protect protic sites to generate the respective α‐alkenyl‐β‐hydroxy adducts, i.e. formally the addition of the α‐anion of a carboxylic acid or amide to an oxo‐compound is featured. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
982.
Bresme Fernando Vesovic Velisa Bataller Henri Croccolo Fabrizio 《The European physical journal. E, Soft matter》2019,42(11):1-6
The European Physical Journal E - The transmission and the reflection of a shock wave by one or several impurities in viscoelastic bead chains is studied in the present paper. There is only one... 相似文献
983.
Mauro Dalla Palma Davide Gaule Antonio Pimazzoni Roberto Pasqualotto Gianluigi Serianni Bernd Böswirth Henri Greuner 《Journal of Thermal Analysis and Calorimetry》2018,132(1):143-154
Carbothermic reduction of chromite in the presence of nickel as the alloying element was investigated in a wide temperature range up to 1500 °C using thermogravimetric analysis coupled with continuous off-gas analysis (TG-DSC-MS). Both isothermal and non-isothermal linear heating tests were performed for the kinetic study with the calculation of activation energies. In order to further elucidate the reduction mechanism, the reduced products were characterized by SEM–EDS and XRD. It was concluded that the reduction sequence followed a multi-stage mechanism, reflected partly by the dependency of the activation energy on the extent of reduction. With the progress of reduction, refractory oxide layers gradually formed on/close to the surface of each chromite particle, causing the shift of the rate-limiting factor from chemical control to diffusion control. The promoting effect from the addition of Ni was evident at temperatures higher than 1300 °C due to the formation of alloys of lower melting point. 相似文献
984.
Bassolé IH Lamien-Meda A Bayala B Tirogo S Franz C Novak J Nebié RC Dicko MH 《Molecules (Basel, Switzerland)》2010,15(11):7825-7839
Essential oils from leaves of Lippia multiflora, Mentha x piperita and Ocimum basilicum from Burkina Faso were analysed by GC-FID and GC-MS. Major components were p-cymene, thymol, b-caryophyllene, carvacrol and carvone for L. multiflora, menthol and iso-menthone for M. x piperita and, linalool and eugenol for O. basilicum. The essential oils and their major monoterpene alcohols were tested against nine bacterial strains using the disc diffusion and broth microdilution methods. The essential oils with high phenolic contents were the most effective antimicrobials. The checkerboard method was used to quantify the efficacy of paired combinations of essential oils and their major components. The best synergetic effects among essential oils and major components were obtained with combinations involving O. basilicum essential oil and eugenol, respectively. As phenolic components are characterized by a strong spicy aroma, this study suggests that the selection of certain combinations of EOs could help to reduce the amount of essential oils and consequently reduce any adverse sensory impact in food. 相似文献
985.
Henri Rudler Andrée Parlier Charline Denneval Patrick Herson 《Journal of fluorine chemistry》2010,131(6):738-741
The interaction of triflic anhydride with s-collidine in the presence of the (trimethylsilyl)enolether of acetophenone led to duplication products the structure of which could only be explained by the formation of CF3 radicals. 相似文献
986.
The interaction of bis(trimethylsilyl)ketene acetals with various pyridines provides a direct, general, diastereoselective access to fluorolactones via the formation of dihydropyridine-substituted carboxylic acids. These in turn reacted with selectfluor as the source of electrophilic fluorine. Whereas a discrimination of the double bonds devoid of fluorine and those bearing fluorine was observed in the case of electrophiles such as iodine, bromine and peracids, no such differentiation took place in the case of selectfluor since, besides 3,5-difluorolactones, the formation of gem-difluorolactones also took place. Moreover, the formation of two stereoisomeric fluorolactones during the lactonization of tetrahydropyridine-substituted carboxylic acids, obtained upon the interaction of (trimethylsilyl)ketene acetals with the previous lactones, could be ascribed to conformational modifications. In all the cases examined a trans, diaxial addition of the electrophile and of the carboxylate is observed. The stereochemical outcome of these reactions was assessed both by NMR spectroscopy and by X-ray crystallography. 相似文献
987.
Andrée Parlier Sandra Beaupierre Henri Rudler Louis Hamon Jean-Claude Daran 《Tetrahedron letters》2009,50(52):7274-930
In contrast to substituted 4-acetic acid 1,4-dihydropyridines, giving only δ-lactones upon intramolecular reactions, 2-substituted 1,2-dihydropyridines led, besides to δ-lactones, also to new, structurally interesting γ-lactones as the result of a bromine-induced carbon-carbon double bond ‘Umpolung’. 相似文献
988.
Thiago?Caon Betina?Giehl?Zanetti-Ramos Elenara?Lemos-Senna Eric?Cloutet Henri?Cramail Redouane?Borsali Valdir?Soldi Cláudia?Maria?Oliveira?Sim?es 《Journal of nanoparticle research》2010,12(5):1655-1665
The in vitro cytotoxicity and DNA damage evaluation of biodegradable polyurethane-based micro- and nanoparticles were carried
out on animal fibroblasts. For cytotoxicity measurement and primary DNA damage evaluation, MTT and Comet assays were used,
respectively. Different formulations were tested to evaluate the influence of chemical composition and physicochemical characteristics
of particles on cell toxicity. No inhibition of cells growth surrounding the polyurethane particles was observed. On the other
hand, a decrease of cell viability was verified when the anionic surfactant sodium dodecyl sulfate (SDS) was used as droplets
stabilizer of monomeric phase. Polyurethane nanoparticles stabilized with Tween 80 and Pluronic F68 caused minor cytotoxic
effects. These results indicated that the surface charge plays an important role on cytotoxicity. Particles synthesized from
MDI displayed a higher cytotoxicity than those synthesized from IPDI. Size and physicochemical properties of the particles
may explain the higher degree of DNA damage produced by two tested formulations. In this way, a rational choice of particles’
constituents based on their cytotoxicity and genotoxicity could be very useful for conceiving biomaterials to be used as drug
delivering systems. 相似文献
989.
Broad periodic channel waveguides, with a corrugation on their edge, exhibit a remarkable structure in their dispersion diagram, in the form of stripes of minigaps, whose hyperbolic shape is demonstrated. Around the Brillouin zone edge, the contra-directional feedback borrows the geometry of Littrow diffraction. Spontaneous emission from a large subset of modes then acquires a strong modulation. Lasing on these modes, the so-called “Littrow lasing”, offers also the lowest lasing threshold of the open resonator system. Reviewing our recent studies of this system, we discuss slow light and critical coupling phenomena: for a properly adjusted contra-directional coupling, the bands become substantially flat in a sizable area of the dispersion diagram, opening various perspectives. The band engineering tools to master these phenomena and the physical implications in other domains are briefly reviewed. 相似文献
990.
We discuss risked competitive partial equilibrium in a setting in which agents are endowed with coherent risk measures. In contrast to social planning models, we show by example that risked equilibria are not unique, even when agents’ objective functions are strictly concave. We also show that standard computational methods find only a subset of the equilibria, even with multiple starting points. 相似文献