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We have developed an effective organometallic‐based procedure allowing the employment of 2‐methylphenols as easily available starting materials in the synthesis of 3‐alkylbenzofuran‐2(3H)‐ones. The first step of this protocol, an anionic homologous Fries‐rearrangement, afforded 2‐(2‐ tert ‐butyldimethylsilyloxyaryl)acetamides, which were selectively metalated and monoalkylated at the benzylic position. Acidic work‐up of crude products afforded the desired heterocycles in satisfactory overall yields. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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Jean-Marc Renaud Georges Tsoupras Helen Stoeckli-Evans Raffaele Tabacchi 《Helvetica chimica acta》1989,72(6):1262-1267
The novel allenic epoxycyclohexanes 1 , and related compounds 2 and 3 have been isolated from the culture medium of Eutypa lata. Their structures were established by combination of spectroscopic and chemical techniques. Biogenetic origin and biological activity of these compounds are also discussed. 相似文献
44.
Demko MT Cheng JC Pisano AP 《Langmuir : the ACS journal of surfaces and colloids》2010,26(22):16710-16714
A novel microfluidic molding process was used to form microscale features of gold nanoparticles on polyimide, glass, and silicon substrates. This technique uses permeation pumping to pattern and concentrate a nanoparticle ink inside microfluidic channels created in a porous polymer template in contact with a substrate. The nanoparticle ink is self-concentrated in the microchannels, resulting in dense, close-packed nanoparticle features. The method allows for better control over the structure of printed features at a resolution that is comparable to inkjet printing, and is purely additive with no residual layers or etching required. The process uses low temperatures and pressures and takes place in an ambient environment. After patterning, the gold nanoparticles were sintered into continuous and conductive gold traces. 相似文献
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Dragonetti R Ianniello C Romano RA 《The Journal of the Acoustical Society of America》2011,129(2):753-764
Air-flow resistivity is a main parameter governing the acoustic behavior of porous materials for sound absorption. The international standard ISO 9053 specifies two different methods to measure the air-flow resistivity, namely a steady-state air-flow method and an alternating air-flow method. The latter is realized by the measurement of the sound pressure at 2 Hz in a small rigid volume closed partially by the test sample. This cavity is excited with a known volume-velocity sound source implemented often with a motor-driven piston oscillating with prescribed area and displacement magnitude. Measurements at 2 Hz require special instrumentation and care. The authors suggest an alternating air-flow method based on the ratio of sound pressures measured at frequencies higher than 2 Hz inside two cavities coupled through a conventional loudspeaker. The basic method showed that the imaginary part of the sound pressure ratio is useful for the evaluation of the air-flow resistance. Criteria are discussed about the choice of a frequency range suitable to perform simplified calculations with respect to the basic method. These criteria depend on the sample thickness, its nonacoustic parameters, and the measurement apparatus as well. The proposed measurement method was tested successfully with various types of acoustic materials. 相似文献
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Messenger RNA (mRNA)-based vaccines are advantageous because they can be relatively quicker and more cost efficient to manufacture compared to other traditional vaccine products. Lipid nanoparticles have three common purposes: delivery, self-adjuvanting properties, and mRNA protection. Faster vaccine development requires an efficient and fast assay to monitor mRNA purity and integrity. Microchip CE is known to be a robust technology that is capable of rapid separation. Here, we describe the development and optimization of a purity and integrity assay for mRNA-based vaccines encapsulated in lipid nanoparticles using commercial microchip-based separation. The analytical parameters of the optimized assay were assessed and the method is a stability indicating assay. 相似文献
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Raffaele Chiappinelli 《Applied mathematics and computation》2010,216(12):3772-3777
We prove upper and lower bounds on the eigenvalues (as the norm of the eigenfunction tends to zero) in bifurcation problems for a class of semilinear elliptic equations in bounded domains of RN. It is shown that these bounds are computable in terms of the eigenvalues of the associated linear equation. 相似文献