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71.
A Beckmann Rearrangement/Friedel-Crafts strategy was utilized to prepare 5-amidotetralones in high yield. 相似文献
72.
Cecile Canlet Bing M. Fung Frederick Roussel Karine Leblanc Philippe Berdague Jean-Pierre Bayle 《Liquid crystals》2013,40(5):635-641
Mesogenic compounds containing four rings in the core usually have very high melting points. However, when two identical lateral benzyloxy groups are introduced on the same side of one of the central rings, the melting point is lowered dramatically and a large nematic range is retained. This range is affected by the bulkiness of the para-substituents in the lateral rings. Methyl groups can be introduced in the ortho- or meta-positions with a consequent decrease in the melting temperature without much affecting the nematic range. These compounds exhibit a rich solid polymorphism which is certainly related to the effect of the conformations of the lateral substituent on the molecular arrangment in the solid phase. Some preliminary NMR experiments on the nematic phase indicate that the molecular long axis coincides with the core axis, whereas the para-axis of the lateral fragment makes an angle close to the magic angle with respect to the molecular long axis. 相似文献
73.
74.
Phu T. Van Victor Bass Dan Shiwarski Frederick Lanni Jonathan Minden 《Electrophoresis》2014,35(18):2642-2655
A current challenge for proteomics is detecting proteins over the large concentration ranges found in complex biological samples such as whole‐cell extracts. Currently, no unbiased, whole‐proteome analysis scheme is capable of detecting the full range of cellular proteins. This is due in part to the limited dynamic range of the detectors used to sense proteins or peptides. We present a new technology, structured illumination (SI) gel imager, which detects fluorescently labeled proteins in electrophoretic gels over a 1 000 000‐fold concentration range. SI uses computer‐generated masks to attenuate the illumination of highly abundant proteins, allowing for long exposures of low‐abundance proteins, thus avoiding detector saturation. A series of progressively masked gel images are assembled into a single, very high dynamic range image. We demonstrate that the SI imager can detect proteins over a concentration range of approximately 1 000 000‐fold, making it a useful tool for comprehensive, unbiased proteome‐wide surveys. 相似文献
75.
Raluca‐Ioana Stefan‐van Staden Alexandrina Moscalu‐Lungu Jacobus Frederick van Staden 《Electroanalysis》2020,32(1):178-184
Three stochastic sensors based on nanodiamond (nDP) paste modified with α, β, and γ‐cyclodextrin were designed and characterized for pattern recognition of aspartame, acesulfame K and sodium cyclamate in beverages, ketchup, and biological fluids. The linear concentration ranges obtained for acesulfame K (between 1.00×10?10 mol L?1and 1.00×10?3 mol L?1), for aspartame (between 1.00×10?12 mol L?1 and 1.00×10?3 mol L?1) and for sodium cyclamate (between 4.97×10?12 mol L?1 and 4.97×10?3 mol L?1) allow their assay in biological fluids, beverages and ketchup. The lowest limits of quantification were obtained using the stochastic sensor based on γ‐CD/nDP: for acesulfame K 1.00×10?10 mol L?1, for aspartame 1.00×10?12 mol L?1 and for sodium cyclamate 4.97×10?12 mol L?1. All three stochastic sensors revealed very high values of sensitivities. The proposed method was reliable for qualitative and quantitative assay of aspartame, acesulfame K and sodium cyclamate in beverages, ketchup, and in biological fluids such as urine. 相似文献
76.
77.
Holly L. S. Salerno Frederick L. Beyer Yossef A. Elabd 《Journal of Polymer Science.Polymer Physics》2012,50(8):552-562
Robust hydroxide conducting membranes are required for long‐lasting, low‐cost solid alkaline fuel cells (AFCs). In this study, we synthesize Nafion‐based anion exchange membranes (AEMs) via amination of the Nafion precursor membrane with 1,4‐dimethylpiperazine. This initial reaction produces an AEM with covalently attached dimethylpiperazinium cations neutralized with fluoride anions, while a subsequent ion exchange reaction produces a hydroxide ion conducting membrane. These AEMs possess high thermal stability and different thermal transition temperatures compared to Nafion, while small‐angle X‐ray scattering reveals a similar ionic morphology. The hydroxide ion conductivity of the Nafion‐based AEM is fivefold lower than the proton conductivity of Nafion at 80 °C and 90% relative humidity. More importantly, the hydroxide conductivity is insensitive to drying and rehydrating the membrane, which is atypical of other AEMs with quaternary ammonium cations. The high chemical and thermal stability of this hydroxide conducting Nafion‐based AEM provides a promising alternative for AFCs. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011 相似文献
78.
We find constraints on the extent to which O??Neill??s horizontal curvature equation can be used to create positive curvature on the base space of a Riemannian submersion. In particular, we study when K. Tapp??s theorem on Riemannian submersions of compact Lie groups with bi-invariant metrics generalizes to arbitrary manifolds of non-negative curvature. 相似文献
79.
Maderna A Huertas R Hawthorne MF Luguya R Vicente MG 《Chemical communications (Cambridge, England)》2002,(16):1784-1785
A boron-rich, water-soluble porphyrin conjugate was synthesized by coupling of two carboranyl alcohols with 2-chlorophenoxyphosphorus dichloride, followed by conjugation to an amine-functionalized tetraphenyl-porphyrin via an amide linkage. 相似文献
80.