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61.
A metal-free acetate shift of 3-acetoxy ynamides to access α-iodo, bromo, and chloro acrylamides/acrylimides under very mild conditions is demonstrated. The inherent alkyne activation of ynamides is sufficient to ensure the α-halo acrylamides/acrylimides in high yields without the addition of a catalyst. In all cases high Z-stereoselectivity is observed. 相似文献
62.
Schlamp S Weber B Naik AD Garcia Y 《Chemical communications (Cambridge, England)》2011,47(25):7152-7154
A novel iron(II) mononuclear spin transition complex [FeL(py)(2)] displays an abrupt spin transition around 225 K accompanied by a very wide thermal hysteresis loop (~50 K) that spreads out over 100 K. Crystal structure analysis in both low-spin and high-spin states reveals a lipid layer-like arrangement of the complex molecules and provides insights into the spin switching mechanism. 相似文献
63.
Chevolot Y Zhang J Meyer A Goudot A Rouanet S Vidal S Pourceau G Cloarec JP Praly JP Souteyrand E Vasseur JJ Morvan F 《Chemical communications (Cambridge, England)》2011,47(31):8826-8828
The binding of seven multivalent glycoconjugates displaying linear or antenna-like structures and different electronic environments were evaluated towards PA-IL on a DNA-based carbohydrate microarray. The affinity can be modulated by the charge and the topology of the galactosylated derivatives. 相似文献
64.
65.
Ulrich Soupremanien Stephane Le PersonMichel Favre-Marinet Yann Bultel 《Experimental Thermal and Fluid Science》2011,35(5):797-809
This article presents experiments conducted with two single rectangular mini-channels of same hydraulic diameter (1.4 mm) and different aspect ratios for conditions of horizontal boiling flow. The Forane® 365 HX used was subcooled (ΔTsub = 15 °C) for all the boiling curves presented in the paper. Local heat transfer coefficients were measured for heat flux ranging from 25 to 62 kW m−2 and mass flux from 200 kg m−2 s−1 to 400 kg m−2 s−1. The boiling flows were observed with two different cameras (depending on the flow velocity) through a visualization window. The flow patterns in the two channels were compared for similar conditions. The results show that the boiling heat transfer coefficient and the pressure drop values are different for the two single mini-channels. For low heat flux condition, the channel with lowest aspect ratio (H/W = 0.143) has a higher heat transfer coefficient. On the other hand, for high heat flux condition, the opposite situation occurs, namely the heat transfer coefficient becomes higher for the channel with highest aspect ratio (H/W = 0.43). This is probably due to the earlier onset of dryout in the channel with lowest aspect ratio. For the two cases of heating, the pressure drop for the two-phase flow remains lower for the channel with lowest aspect ratio. These results show that the aspect ratio plays a substantial role for boiling flows in rectangular channels. As for single-phase flows, the heat transfer characteristics are significantly influenced (even though the hydraulic diameter remains the same) by this parameter. 相似文献
66.
Regio and stereoselectivity of the palladium catalyzed reduction of propargylic halides and esters is greatly influenced by the nature of the hydride donor as by the leaving group. Best results in allene formation are observed in the reduction by lithium triethyl-borohydride of mesylates and phosphates. In the former case, reaction occurs with anti displacement of the sulfonyl group. 相似文献
67.
Yann Ollivier 《Comptes Rendus Mathematique》2005,341(3):137-140
We show that random quotients of hyperbolic groups with ‘harmful’ torsion collapse at densities smaller than expected. To cite this article: Y. Ollivier, C. R. Acad. Sci. Paris, Ser. I 341 (2005). 相似文献
68.
Clayden J Foricher YJ Helliwell M Johnson P Mitjans D Vinader V 《Organic & biomolecular chemistry》2006,4(3):444-454
The orientation of a tertiary amide group adjacent to an aromatic ring may be governed by the stereochemistry of an adjacent chiral substituent. With a chiral substituent in both ortho positions, matched/mismatched pairs of isomers result. Evidence for matched stereochemistry is provided by the clean NMR spectra of single conformers, while mismatching gives poor or unexpected selectivities in the formation of chiral substituents, or mixtures of amide conformers. Attempts to use the match-mismatch effect to select for racemic pairs of enantiomeric substituents, and hence develop a "racemate-sequestering" reagent, are described, along with the use of "matching" to scavenge a single enantiomer of a diamine from material of incomplete enantiomeric purity. 相似文献
69.
Yann Civale Guglielmo Vastola Lis K. Nanver Rani Mary-Joy Jae-Ryoung Kim 《Journal of Electronic Materials》2009,38(10):2052-2062
Mechanisms governing the aluminum-mediated solid-phase epitaxy of Si on patterned crystalline Si substrates have been identified
by studying the deposited material as a function of growth conditions when varying parameters such as temperature, growth
time, and layer-stack properties. Early growth stages can be discerned as first formation of “free” Si at the Al/α-Si interface,
then diffusion of Si along the Al grain boundaries, nucleation at the Si substrate surface, nuclei rearrangement, and finally
crystal growth. The acquired understanding is applied to control the selectivity and completeness of single-crystal growth
in various sizes of contact windows to the Si substrate. 相似文献
70.
Yann?BrenierEmail author Xianglong?Duan 《Calculus of Variations and Partial Differential Equations》2018,57(5):125
Optimal transport theory has been a powerful tool for the analysis of parabolic equations viewed as gradient flows of volume forms (or, in other words, 0-currents) according to suitable transportation metrics. In this paper, we present an example of gradient flow for closed \((d-1)\)-differential forms, or, more appropriately, to closed 1-currents, which can be identified to divergence-free vector fields, in the Euclidean space \(\mathbb {R}^d\). In spite of its apparent complexity, the resulting very degenerate parabolic system is fully integrable and can be viewed, in a suitable sense, as an Eulerian version of the heat equation for loops in the Euclidean space. We analyze this system in terms of “relative entropy” and “dissipative solutions” and provide global existence and weak–strong uniqueness results. 相似文献